<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Of the originating work:</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Jaesong Jeong and Jinhee Choi, School of Environmental Engineering, University of Seoul, Seoul, Republic of Korea</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Of the content populated in the AOP-Wiki:</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Daniel L. Villeneuve, US Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, Duluth, MN</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Travis Karschnik and John R. Frisch, General Dynamics Information Technology, Duluth, Minnesota</span></span></p>
<td>Under development: Not open for comment. Do not cite</td>
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<div id="abstract">
<h2>Abstract</h2>
<p><span style="font-size:16px"><span style="font-family:"Calibri",sans-serif">Reactive oxygen species (ROS) are derived from oxygen molecules and can occur as free radicals (ex. superoxide, hydroxyl, peroxyl) or non-radicals (ex. ozone, singlet oxygen). ROS production occurs via a variety of normal cellular process; however, in stress situations (ex. exposure to radiation, chemical or biological stressors) reactive oxygen species levels dramatically increase and cause damage to cellular components. In this Adverse Outcome Pathway (AOP) we focus on the Peroxisome proliferation-activated receptor (PPAR) response to increases in oxidative stress. Changes in activation rate of Peroxisome proliferation-activated receptors alter lipid metabolism, and decrease suppression of apoptosis. In this AOP we focus on the apoptosis response to cellular damage. Pathways leading to apoptosis, or single cell death, have traditionally been studied as both independent and simultaneous from pathways leading to necrosis, or tissue-wide cell death, with both overlap and distinct mechanisms (Elmore 2007). For the purposes of this AOP, we are characterizing cancer due to widespread cell-death, and recognize the complications in separating the related apoptosis and necrosis pathways.</span></span></p>
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<div id="background">
<h3>Background</h3>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">This Adverse Outcome Pathway focuses on the key pathways in which an established molecular disruption, increased levels of reactive oxygen species (ROS), leads to increased cancer.</span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:black">1. Support for Biological Plausibility of Key Event Relationships: Is there a mechanistic relationship between KEup and KEdown consistent with established biological knowledge?</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:#212529">Strong = Extensive understanding of the KER based on extensive previous documentation and broad acceptance.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support</span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">. Increases in reactive oxygen species (ROS) have been shown to cause a variety of cellular responses including decreased PPARgamma gene expression. </span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support</span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">. Decreased PPAR gene expression have been shown to cause an alteration of lipid metabolism. PPAR-gamma acts as a nuclear signaling element that controls the transcription of a variety of genes involved in lipid catabolism and energy production pathways.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support</span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">. Alteration of lipid metabolism have been shown to results in abnormal cell function and activity, leading to apoptosis. Alteration of lipid metabolism leads to changes in cell lipid levels, structural changes in membranes as lipids are key components, and changes in signaling pathways affecting gene and protein expression. Loss of plasma membrane integrity due to disruptions to lipid metabolism results in cellular processes identifying cells as damaged, which acts as a signal for apoptosis.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">The relationship between failure of apoptosis pathways to initiate cell death pathways and increases in cancer is broadly accepted and consistently supported across taxa.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">Extensive understanding of the relationships between events from empirical studies from a variety of taxa.</span></span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Life Stage: The life stage applicable is all life stages. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sex: Applies to both males and females.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Taxonomic: Appears to be present broadly, with representative studies including mammals (humans, lab mice, lab rats), telost fish, and invertebrates (cladocerans, mussels).</span></span></p>
<p>Support for the essentiality of the key events can be obtained from a wide diversity of taxonomic groups, with mammals (lab ice, lab rats, human cell lines), telost fish, and invertebrates (cladocerans and mussels) particularly well-studied.</p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:black">2. Essentiality of Key Events: Are downstream KEs and/or the AO prevented if an upstream KE is blocked?</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:#212529">Strong = Direct evidence from specifically designed experimental studies illustrating essentiality and direct relationship between key events.</span></span></span></span></p>
<p> </p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:#212529">Moderate = Indirect evidence from experimental studies inferring essentiality of relationship between key events due to difficulty in directly measuring at least one of key events.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support.</span></span></strong><span style="font-size:12.0pt"><span style="color:#212529"> Increased Reactive oxygen species (ROS) levels are a primary cause of decreases in PPARgamma gene expression. Evidence is available from studies of stressor exposure and resulting changes in gene expression and protein/enzyme levels.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">The PPARgamma gene family is important in controlling rate of lipid metabolism. Evidence is available from studies of stressor exposure and resulting changes in gene expression and protein/enzyme levels.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529"> Altered lipid metabolism, particularly resulting loss of plasma membrane integrity is a cause of apoptosis. Evidence is available from studies of stressor exposure and resulting changes in gene expression and protein/enzyme levels.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Moderate support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">Failure of apoptosis allows cancer cells to proliferate. </span></span><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Evidence is available from studies of stressor exposure and resulting changes in gene expression, protein/enzyme levels, and histology.</span></span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">Cancer proliferates due to a variety of stressors and breakdown of multiple celluar processes. </span></span><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Evidence is available from studies of stressor exposure and resulting changes in gene expression, protein/enzyme levels, and histology.</span></span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Moderate to strong support. </span></span></strong><span style="font-size:12.0pt"><span style="color:#212529">Direct evidence from empirical studies for most key events, with more inferential evidence rather than direct evidence for apoptosis.</span></span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Biological plausibility is high. Representative studies have been done with mammals (El Midaoui et al. 2006; Blanquicett et al. 2010; Lu et al. 2018; Jeong and Choi 2020) fish (Wang et al. 2022). </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Biological plausibility is high. Representative studies have been done with mammals (Chamorro-Garcia et al. 2018; Jeong and Choi 2020); fish (Venezia et al. 2021). For review (Tickner et al. 2001; Berger and Moller 2002; Luquet et al. 2005; Den Broeder et al. 2015).</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Biological plausibility is high. Representative studies have been done with mammals (Cadet et al. 2010, Gao et al. 2020); invertebrates (Avio et al. 2015). For review (Huang and Freter 2015).</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Biological plausibility is high. Representative studies have been done with mammals (Pavet et al. 2014; Jeong and Choi 2020). For review (Heinlein and Chang 2004; Vihervaara and Sistonen 2014).</span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:#212529">3.</span></span><span style="font-size:12.0pt"><span style="color:black"> Empirical Support for Key Event Relationship: Does empirical evidence support that a change in KEup leads to an appropriate change in KEdown?</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span style="color:#212529">Strong = Experimental evidence from exposure to toxicant shows consistent change in both events across taxa and study conditions.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="color:#212529">Strong support.</span></span></strong><span style="font-size:12.0pt"><span style="color:#212529"> Decreases in PPAR gamma expression leads to alteration of lipid metabolism, primarily by assessing lipid content and levels of energy metabolites.</span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Strong support. </span></span></span></strong><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Mechanistic studies show that failure for apoptosis to eliminate cancer cells allows increases in cancer proliferation.</span></span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Strong support. </span></span></span></strong><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Exposure from empirical studies shows consistent change in both events from a variety of taxa.</span></span></span></span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><strong><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Strong support. </span></span></span></strong><span style="font-size:12.0pt"><span style="background-color:white"><span style="color:#212529">Evidence from empirical studies shows consistent change in both events from a variety of taxa.</span></span></span></span></span></p>
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<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">For overview of the biological mechanisms involved in this AOP, see Liu et al. (2015) and Jeong and Choi (2020); their studies analyzed ToxCast in vitro assays of mammalian acute toxicity data to identify correlations between toxicity pathways and chemical stressors, providing support for the key event relationships represented here.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Avio, C.G., Gorbi, S., Milan, M., Benedetti, M., Fattorini, D., D’Errico, G., Pauletto, M., Bargelloni, L., and Regoli, F. 2015. Pollutants bioavailability and toxicological risk from microplastics to marine mussels. Environmental Pollutants 198: 211-222.</span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Berger, J. and Moller, D. 2002. The mechanisms of action of PPARS. Annual Review of Medicine 53: 409-435.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Blanquicett, C., Kang, B-Y., Ritzenthaler, J.D. Jones, D.P., and Hart, C.M. 2010. Free Radical Biology and Medicine 48: 1618-1625.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Den Broeder, M.J., Kopylova, V.A., Kamminga, L.M. Legler, J. 2015. Zebrafish as a model to study the role of peroxisome proliferating-activated receptors in adipogenesis and obesity. PPAR Research 2015: 358029.</span></span></p>
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<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Cadet, J.L., Jayanthi, S., McCoy, M.T., Beauvais, G., and Cai, N.S. 2010. Dopamine D1 receptors, regulation of gene expression in the brain, and neurogeneration. CNS Neurological Disorders - Drug Targets 9: 526-538.</span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Chamorro-Garcia, R., Shoucri, B.M., Willner, S., Kach, H., Janesick, A., and Blumberg, B. 2018. Effect of perinatal exposure to dibutyltin chloride on fat and glucose metabolism in mice, and molecular mechanisms, in vitro. Environmental Health Perspectives 126: 057006.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">El Midaoui, A., Wu, L., Wang, R., and de Champlain, J. 2006. Modulation of cardiac and aortic peroxisome proliferator-activated receptor-gamma expression by oxidative stress in chronically glucose-fed rats. American Journal of Hypertension 19: 407-412.</span></span></p>
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<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Gao, L., Xu, Z., Huang, Z., Tang, Y., Yang, D., Huang, J., He, L., Liu, M., Chen, Z., and Teng, Y. 2020. CPI-613 rewires lipid metabolism to enhance pancreatic cancer apoptosis via the AMPK-ACC signaling. 39: 73.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Heinlein, C.A. and Chang, C. 2004. Androgen receptor in prostate cancer. Endocrine Reviews 25: 276-308.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Huang, C. and Freter, C. 2015. Lipid metabolism, apoptosis and cancer therapy. International Journal of Molecular Sciences 16: 924-949.</span></span></p>
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<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Jeong, J. and Choi, J. 2019. Adverse outcome pathways potentially related to hazard identification of microplastics based on toxicity mechanisms. Chemosphere 231: 249-255.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Jeong, J. and Choi, J. 2020. Development of AOP relevant to microplastics based on toxicity mechanisms of chemical additives using ToxCast™ and deep learning models combined approach. Environment International 137:105557.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Liu, J., Mansouri, K., Judson, R.S., Martin, M.T., Hong, H., Chen, M., Xu, X., Thomas, R.S., and Shah, I. 2015. Predicting hepatoxicity using ToxCast in vitro bioactivity and chemical structure. Chemical Research in Toxicology 28: 738-751.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Lu, L., Wan, Z., Luo, T., Fu, Z., and Jin, Y. 2018. Polystyrene microplastics induce microbiota dysbiosis and hepatic lipid metabolism disorder in mice. Science of the Total Environment 631-632: 449-458.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Luquet, S., Gaudel, C., Holst, D., Lopez-Soriano, J., Jehl-Pietri, C., Fredenrich, A., and Grimaldi, P.A. 2005. Roles of PPAR delta in lipid absorption and metabolism: A new target for the treatment of type 2 diabetes. Biochimica and Biophysica Acta 1740: 313-317.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Pavet, V., Shlyakhtina, Y., He, T., Ceschin, D.G., Kohonen, P., Perala, M., Kallioniemi, O., and Gronemeyer, H. 2014. Plasminogen activator urokinase expression reveals TRAIL responsiveness and support fractional survival of cancer cells. Cell Death and Disease 5: e1043.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Tickner, J.A., Schettler, T., Guidotti, T., Mccally, M., and Rossi, M. 2001. Health risks posed by used of di-2-ethylhexyl phthalate (DEHP) in PVC medical devices: A critical review. American Journal of Industrial Medicine 39: 100-111.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Venezia, O., Islam, S., Cho, C., Timme-Laragy, A.R., and Sant, K.E. 2021. Modulation of PPAR signaling disrupts pancreas development in the zebrafish, Danio rerio. Toxicology and Applied Pharmacology 426: 115653.</span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Vihervaara, A. and Sistonen, L. 2014. HSF1 at a glance. Journal of Cell Scientce 127: 261-266.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Wang, X., Ma, Q., Chen, L. Wu, H., Chen, L.-Q., Qiao, F., Luo, Y., Zhang, M.-L., and Du, Z.-Y. 2022. Peroxisome proliferator-activated receptor gamma is essential for stress adaptation by maintaining lipid homeostatis in female fish. Biochimica et Biophysica Acta – Molecular and Cell Biology of Lipids 1867: 159162.</span></span></p>
<td><a href="/aops/383">Aop:383 - Inhibition of Angiotensin-converting enzyme 2 leading to liver fibrosis</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/382">Aop:382 - Angiotensin II type 1 receptor (AT1R) agonism leading to lung fibrosis</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/384">Aop:384 - Hyperactivation of ACE/Ang-II/AT1R axis leading to chronic kidney disease </a></td>
<td>KeyEvent</td>
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<td><a href="/aops/396">Aop:396 - Deposition of ionizing energy leads to population decline via impaired meiosis</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/409">Aop:409 - Frustrated phagocytosis leads to malignant mesothelioma</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/413">Aop:413 - Oxidation and antagonism of reduced glutathione leading to mortality via acute renal failure</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/416">Aop:416 - Aryl hydrocarbon receptor activation leading to lung cancer through IL-6 toxicity pathway</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/418">Aop:418 - Aryl hydrocarbon receptor activation leading to impaired lung function through AHR-ARNT toxicity pathway</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/386">Aop:386 - Deposition of ionizing energy leading to population decline via inhibition of photosynthesis</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/387">Aop:387 - Deposition of ionising energy leading to population decline via mitochondrial dysfunction</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/319">Aop:319 - Binding to ACE2 leading to lung fibrosis</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/451">Aop:451 - Interaction with lung resident cell membrane components leads to lung cancer</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/476">Aop:476 - Adverse Outcome Pathways diagram related to PBDEs associated male reproductive toxicity</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/492">Aop:492 - Glutathione conjugation leading to reproductive dysfunction via oxidative stress</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/497">Aop:497 - ERa inactivation alters mitochondrial functions and insulin signalling in skeletal muscle and leads to insulin resistance and metabolic syndrome</a></td>
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<td><a href="/aops/500">Aop:500 - Activation of MEK-ERK1/2 leads to deficits in learning and cognition via ROS and apoptosis</a></td>
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<td><a href="/aops/505">Aop:505 - Reactive Oxygen Species (ROS) formation leads to cancer via inflammation pathway</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/513">Aop:513 - Reactive Oxygen (ROS) formation leads to cancer via Peroxisome proliferation-activated receptor (PPAR) pathway</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/521">Aop:521 - Essential element imbalance leads to reproductive failure via oxidative stress</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/540">Aop:540 - Oxidative Stress in the Fish Ovary Leads to Reproductive Impairment via Reduced Vitellogenin Production</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/462">Aop:462 - Activation of reactive oxygen species leading the atherosclerosis</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/299">Aop:299 - Deposition of energy leading to population decline via DNA oxidation and follicular atresia</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/311">Aop:311 - Deposition of energy leading to population decline via DNA oxidation and oocyte apoptosis</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/332">Aop:332 - Excessive reactive oxygen species leading to growth inhibition via lipid peroxidation and reduced cell growth</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/331">Aop:331 - Excessive reactive oxygen species leading to growth inhibition via lipid peroxidation and cell death</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/326">Aop:326 - Excessive reactive oxygen species leading to growth inhibition via uncoupling of oxidative phosphorylation and reduced cell proliferation</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/333">Aop:333 - Excessive reactive oxygen species leading to growth inhibition via lipid peroxidation and reduced cell proliferation</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/327">Aop:327 - Excessive reactive oxygen species production leading to mortality (1)</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/328">Aop:328 - Excessive reactive oxygen species production leading to mortality (2)</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/329">Aop:329 - Excessive reactive oxygen species production leading to mortality (3)</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/330">Aop:330 - Excessive reactive oxygen species production leading to mortality (4)</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/26">Aop:26 - Calcium-mediated neuronal ROS production and energy imbalance</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/534">Aop:534 - Succinate dehydrogenase (SDH) inhibition leads to cancer through oxidative stress</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/273">Aop:273 - Mitochondrial complex inhibition leading to liver injury</a></td>
<td>KeyEvent</td>
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<td><a href="/aops/488">Aop:488 - Increased reactive oxygen species production leading to decreased cognitive function</a></td>
<td>MolecularInitiatingEvent</td>
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<td><a href="/aops/298">Aop:298 - Increase in reactive oxygen species (ROS) leading to human treatment-resistant gastric cancer</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/27">Aop:27 - Cholestatic Liver Injury induced by Inhibition of the Bile Salt Export Pump (ABCB11)</a></td>
<td>KeyEvent</td>
</tr>
<tr>
<td><a href="/aops/511">Aop:511 - The AOP framework on ROS-mediated oxidative stress induced vascular disrupting effects </a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/207">Aop:207 - NADPH oxidase and P38 MAPK activation leading to reproductive failure in Caenorhabditis elegans</a></td>
<td>KeyEvent</td>
</tr>
<tr>
<td><a href="/aops/423">Aop:423 - Toxicological mechanisms of hepatocyte apoptosis through the PARP1 dependent cell death pathway </a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/481">Aop:481 - AOPs of amorphous silica nanoparticles: ROS-mediated oxidative stress increased respiratory dysfunction and diseases.</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/282">Aop:282 - Adverse outcome pathway on photochemical toxicity initiated by light exposure</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/569">Aop:569 - Decreased DNA methylation of FAM50B/PTCHD3 leading to IQ loss of children via PI3K-Akt pathway</a></td>
<td>KeyEvent</td>
</tr>
<tr>
<td><a href="/aops/324">Aop:324 - Excessive reactive oxygen species leading to growth inhibition via uncoupling of oxidative phosphorylation and cell death</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/325">Aop:325 - Excessive reactive oxygen species leading to growth inhibition via uncoupling of oxidative phosphorylation and reduced cell growth</a></td>
<td><a href="/aops/596">Aop:596 - Excessive reactive oxygen species leading to growth inhibition via protein oxidation and cell injury/death</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/598">Aop:598 - Excessive reactive oxygen species leading to growth inhibition via protein oxidation and reduced cell proliferation</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/599">Aop:599 - Excessive reactive oxygen species leading to growth inhibition via fatty acid oxidation and cell injury/death</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/600">Aop:600 - Excessive reactive oxygen species leading to growth inhibition via fatty acid oxidation and reduced cell growth</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/601">Aop:601 - Excessive reactive oxygen species leading to growth inhibition via fatty acid oxidation and reduced cell proliferation</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/602">Aop:602 - Excessive reactive oxygen species leading to growth inhibition via oxidative DNA damage</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/603">Aop:603 - Excessive reactive oxygen species leading to growth inhibition via protein oxidation and cell cycle disruption</a></td>
<td>MolecularInitiatingEvent</td>
</tr>
<tr>
<td><a href="/aops/608">Aop:608 - Thyroid Hormone Excess Leading to Reduced, Swimming Performance via Hypomyelination</a></td>
<td>KeyEvent</td>
</tr>
<tr>
<td><a href="/aops/613">Aop:613 - Peroxisome proliferator-activated receptor alpha activation leading to early life stage mortality via increased reactive oxygen species production</a></td>
<td>KeyEvent</td>
</tr>
<tr>
<td><a href="/aops/622">Aop:622 - Calcineurin inhibitor induced nephrotoxicity leading to kidney failure</a></td>
<p>ROS is a normal constituent found in all organisms.</p>
<p>ROS is a normal constituent found in all organisms, <em>lifestages, and sexes.</em></p>
<h4>Key Event Description</h4>
<p>Biological State: increased reactive oxygen species (ROS)</p>
<p>Biological compartment: an entire cell -- may be cytosolic, may also enter organelles.</p>
<p>Reactive oxygen species (ROS) are O2- derived molecules that can be both free radicals (e.g. superoxide, hydroxyl, peroxyl, alcoxyl) and non-radicals (hypochlorous acid, ozone and singlet oxygen) (Bedard and Krause 2007; Ozcan and Ogun 2015). ROS production occurs naturally in all kinds of tissues inside various cellular compartments, such as mitochondria and peroxisomes (Drew and Leeuwenburgh 2002; Ozcan and Ogun 2015). Furthermore, these molecules have an important function in the regulation of several biological processes – they might act as antimicrobial agents or triggers of animal gamete activation and capacitation (Goud et al. 2008; Parrish 2010; Bisht et al. 2017). <br />
<p>Reactive oxygen species (ROS) are O<sub>2</sub>- derived molecules that can be both free radicals (e.g. superoxide, hydroxyl, peroxyl, alcoxyl) and non-radicals (hypochlorous acid, ozone and singlet oxygen) (Bedard and Krause 2007; Ozcan and Ogun 2015). ROS production occurs naturally in all kinds of tissues inside various cellular compartments, such as mitochondria and peroxisomes (Drew and Leeuwenburgh 2002; Ozcan and Ogun 2015). Furthermore, these molecules have an important function in the regulation of several biological processes – they might act as antimicrobial agents or triggers of animal gamete activation and capacitation (Goud et al. 2008; Parrish 2010; Bisht et al. 2017). <br />
However, in environmental stress situations (exposure to radiation, chemicals, high temperatures) these molecules have its levels drastically increased, and overly interact with macromolecules, namely nucleic acids, proteins, carbohydrates and lipids, causing cell and tissue damage (Brieger et al. 2012; Ozcan and Ogun 2015). </p>
<div>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">Reactive oxygen species (ROS) refers to the chemical species superoxide, hydrogen peroxide, and their secondary reactive products. In the biological context, ROS are signaling molecules with important roles in cell energy metabolism, cell proliferation, and fate. Therefore, balancing ROS levels at the cellular and tissue level is an important part of many biological processes. Disbalance, mainly an increase in ROS levels, can cause cell dysfunction and irreversible cell damage.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">ROS are produced from both exogenous stressors and normal endogenous cellular processes, such as the mitochondrial electron transport chain (ETC). Inhibition of the ETC can result in the accumulation of ROS. Exposure to chemicals, heavy metal ions, or ionizing radiation can also result in increased production of ROS. Chemicals and heavy metal ions can deplete cellular antioxidants reducing the cell’s ability to control cellular ROS and resulting in the accumulation of ROS. Cellular antioxidants include glutathione (GSH), protein sulfhydryl groups, superoxide dismutase (SOD). </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">ROS are radicals, ions, or molecules that have a single unpaired electron in their outermost shell of electrons, which can be categorized into two groups: free oxygen radicals and non-radical ROS [Liou et al., 2010]. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">highly reactive lipid- or carbohydrate-derived carbonyl compounds</span></span></p>
</td>
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</tbody>
</table>
</div>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">Potential sources of ROS include NADPH oxidase, xanthine oxidase, mitochondria, nitric oxide synthase, cytochrome P450, lipoxygenase/cyclooxygenase, and monoamine oxidase [Granger et al., 2015]. ROS are generated through NADPH oxidases consisting of p47<sup>phox</sup> and p67<sup>phox</sup>. ROS are generated through xanthine oxidase activation in sepsis [Ramos et al., 2018]. Arsenic produces ROS [Zhang et al., 2011]. Mitochondria-targeted paraquat and metformin mediate ROS production [Chowdhury et al., 2020]. ROS are generated by bleomycin [Lu et al., 2010]. Radiation induces dose-dependent ROS production [Ji et al., 2019]. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">ROS are generated in the course of cellular respiration, metabolism, cell signaling, and inflammation [Dickinson and Chang 2011; Egea et al. 2017]. Hydrogen peroxide is also made by the endoplasmic reticulum in the course of protein folding. Nitric oxide (NO) is produced at the highest levels by nitric oxide synthase in endothelial cells and phagocytes. NO production is one of the main mechanisms by which phagocytes kill bacteria [Wang et al., 2017]. The other species are produced by reactions with superoxide or peroxide, or by other free radicals or enzymes.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">ROS activity is principally local. Most ROS have short half-lives, ranging from nano- to milliseconds, so diffusion is limited, while reactive nitrogen species (RNS) nitric oxide or peroxynitrite can survive long enough to diffuse across membranes [Calcerrada et al. 2011]. Consequently, local concentrations of ROS are much higher than average cellular concentrations, and signaling is typically controlled by colocalization with redox buffers [Dickinson and Chang 2011; Egea et al. 2017]. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">Although their existence is limited temporally and spatially, ROS interact with other ROS or with other nearby molecules to produce more ROS and participate in a feedback loop to amplify the ROS signal, which can increase RNS. Both ROS and RNS also move into neighboring cells, and ROS can increase intracellular ROS signaling in neighboring cells [Egea et al. 2017].</span></span></p>
<p>In the primary event, photoreactive chemicals are excited by the absorption of photon energy. The energy of the photoactivated chemicals transfer to oxygen and then generates the reactive oxygen species (ROS), including superoxide (O<sub>2</sub><sup>−</sup>) via type I reaction and singlet oxygen (<sup>1</sup>O<sub>2</sub>) via type II reaction, as principal intermediate species in phototoxic reaction (Foote, 1991, Onoue et al. , 2009).</p>
</div>
<h4>How it is Measured or Detected</h4>
<p>Photocolorimetric assays (Sharma et al. 2017; Griendling et al. 2016) or through commercial kits purchased from specialized companies.</p>
<p>Yuan, Yan, et al., (2013) described ROS monitoring by using H<sub>2</sub>-DCF-DA, a redox-sensitive fluorescent dye. Briefly, the harvested cells were incubated with H<sub>2</sub>-DCF-DA (50 µmol/L final concentration) for 30 min in the dark at 37°C. After treatment, cells were immediately washed twice, re-suspended in PBS, and analyzed on a BD-FACS Aria flow cytometry. ROS generation was based on fluorescent intensity which was recorded by excitation at 504 nm and emission at 529 nm.</p>
<p>Lipid peroxidation (LPO) can be measured as an indicator of oxidative stress damage Yen, Cheng Chien, et al., (2013).</p>
<p>Chattopadhyay, Sukumar, et al. (2002) assayed the generation of free radicals within the cells and their extracellular release in the medium by addition of yellow NBT salt solution (Park et al., 1968). Extracellular release of ROS converted NBT to a purple colored formazan. The cells were incubated with 100 ml of 1 mg/ml NBT solution for 1 h at 37 °C and the product formed was assayed at 550 nm in an Anthos 2001 plate reader. The observations of the ‘cell-free system’ were confirmed by cytological examination of parallel set of explants stained with chromogenic reactions for NO and ROS.</p>
<p> </p>
<p>On the basis of the pathogenesis of drug-induced phototoxicity, a reactive oxygen species (ROS) assay was proposed to evaluate the phototoxic risk of chemicals. The ROS assay can monitor generation of ROS, such as singlet oxygen and superoxide, from photoirradiated chemicals, and the ROS data can be used to evaluate the photoreactivity of chemicals (Onoue et al. , 2014, Onoue et al. , 2013, Onoue and Tsuda, 2006). The ROS assay is a recommended approach by guidelines to evaluate the phototoxic risk of chemicals (ICH, 2014, PCPC, 2014).</p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">Many fluorescent compounds can be used to detect ROS, some of which are specific, and others are less specific. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">・ROS can be detected by fluorescent probes such as <em>p</em>-methoxy-phenol derivative [Ashoka et al., 2020].</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">・Chemiluminescence analysis can detect the superoxide, where some probes have a wider range for detecting hydroxyl radical, hydrogen peroxide, and peroxynitrite [Fuloria et al., 2021].</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">・ROS in the blood can be detected using superparamagnetic iron oxide nanoparticles (SPION)-based biosensor [Lee et al., 2020].</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">・Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) can be detected with a colorimetric probe, which reacts with H<sub>2</sub>O<sub>2</sub> in a 1:1 stoichiometry to produce a bright pink colored product, followed by the detection with a standard colorimetric microplate reader with a filter in the 540-570 nm range.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">・The levels of ROS can be quantified using multiple-step amperometry using a stainless steel counter electrode and non-leak Ag|AgCl reference node [Flaherty et al., 2017].</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">・Singlet oxygen can be measured by monitoring the bleaching of <em>p</em>-nitrosodimethylaniline at 440 nm using a spectrophotometer with imidazole as a selective acceptor of singlet oxygen [Onoue et al., 2014].</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">Alternative methods involve the detection of redox-dependent changes to cellular constituents such as proteins, DNA, lipids, or glutathione [Dickinson and Chang 2011; Wang et al. 2013; Griendling et al. 2016]. However, these methods cannot generally distinguish between the oxidative species behind the changes and cannot provide good resolution for the kinetics of oxidative activity.</span></span></p>
</div>
<h4>References</h4>
<p>B.H. Park, S.M. Fikrig, E.M. Smithwick Infection and nitroblue tetrazolium reduction by neutrophils: a diagnostic aid Lancet, 2 (1968), pp. 532-534</p>
<p>Akai, K., et al. (2004). "Ability of ferric nitrilotriacetate complex with three pH-dependent conformations to induce lipid peroxidation." Free Radic Res. Sep;38(9):951-62. doi: 10.1080/1071576042000261945</p>
<p>Ashoka, A. H., et al. (2020). "Recent Advances in Fluorescent Probes for Detection of HOCl and HNO." ACS omega, 5(4), 1730-1742. doi:10.1021/acsomega.9b03420</p>
<p>B.H. Park, S.M. Fikrig, E.M. Smithwick Infection and nitroblue tetrazolium reduction by neutrophils: a diagnostic aid Lancet, 2 (1968), pp. 532-534</p>
<p>Bedard, Karen, and Karl-Heinz Krause. 2007. “The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology.” Physiological Reviews 87 (1): 245–313.</p>
<p>Bisht, Shilpa, Muneeb Faiq, Madhuri Tolahunase, and Rima Dada. 2017. “Oxidative Stress and Male Infertility.” Nature Reviews. Urology 14 (8): 470–85.</p>
<p>Brieger, K., S. Schiavone, F. J. Miller Jr, and K-H Krause. 2012. “Reactive Oxygen Species: From Health to Disease.” Swiss Medical Weekly 142 (August): w13659.</p>
<p>Calcerrada, P., et al. (2011). "Nitric oxide-derived oxidants with a focus on peroxynitrite: molecular targets, cellular responses and therapeutic implications." Curr Pharm Des 17(35): 3905-3932.</p>
<p>Chattopadhyay, Sukumar, et al. "Apoptosis and necrosis in developing brain cells due to arsenic toxicity and protection with antioxidants." Toxicology letters 136.1 (2002): 65-76.</p>
<p>Chowdhury, A. R., et al. (2020). "Mitochondria-targeted paraquat and metformin mediate ROS production to induce multiple pathways of retrograde signaling: A dose-dependent phenomenon." Redox Biol. doi: 10.1016/j.redox.2020.101606. PMID: 32604037; PMCID: PMC7327929.</p>
<p>Dickinson, B. C. and Chang C. J. (2011). "Chemistry and biology of reactive oxygen species in signaling or stress responses." Nature chemical biology 7(8): 504-511.</p>
<p>Drew, Barry, and Christiaan Leeuwenburgh. 2002. “Aging and the Role of Reactive Nitrogen Species.” Annals of the New York Academy of Sciences 959 (April): 66–81.</p>
<p>Egea, J., et al. (2017). "European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)." Redox biology 13: 94-162.</p>
<p>Flaherty, R. L., et al. (2017). "Glucocorticoids induce production of reactive oxygen species/reactive nitrogen species and DNA damage through an iNOS mediated pathway in breast cancer." Breast Cancer Research, 19(1), 1–13. https://doi.org/10.1186/s13058-017-0823-8</p>
<p>Foote CS. Definition of type I and type II photosensitized oxidation. Photochem Photobiol. 1991;54:659.</p>
<p>Fuloria, S., et al. (2021). "Comprehensive Review of Methodology to Detect Reactive Oxygen Species (ROS) in Mammalian Species and Establish Its Relationship with Antioxidants and Cancer." Antioxidants (Basel, Switzerland) 10(1) 128. doi:10.3390/antiox10010128</p>
<p>Go, Y. M. and Jones, D. P. (2013). "The redox proteome." J Biol Chem 288(37): 26512-26520.</p>
<p>Goud, Anuradha P., Pravin T. Goud, Michael P. Diamond, Bernard Gonik, and Husam M. Abu-Soud. 2008. “Reactive Oxygen Species and Oocyte Aging: Role of Superoxide, Hydrogen Peroxide, and Hypochlorous Acid.” Free Radical Biology & Medicine 44 (7): 1295–1304.</p>
<p>Granger, D. N. and Kvietys, P. R. (2015). "Reperfusion injury and reactive oxygen species: The evolution of a concept" Redox Biol. doi: 10.1016/j.redox.2015.08.020. PMID: 26484802; PMCID: PMC4625011.</p>
<p>Griendling, K. K., et al. (2016). "Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association." Circulation research 119(5): e39-75.</p>
<p>Griendling, Kathy K., Rhian M. Touyz, Jay L. Zweier, Sergey Dikalov, William Chilian, Yeong-Renn Chen, David G. Harrison, Aruni Bhatnagar, and American Heart Association Council on Basic Cardiovascular Sciences. 2016. “Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association.” Circulation Research 119 (5): e39–75.</p>
<p>ICH. ICH Guideline S10 Guidance on Photosafety Evaluation of Pharmaceuticals.: International Council on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use; 2014.</p>
<p>Itziou, A., et al. (2011). "In vivo and in vitro effects of metals in reactive oxygen species production, protein carbonylation, and DNA damage in land snails Eobania vermiculata." Archives of Environmental Contamination and Toxicology, 60(4), 697–707. https://doi.org/10.1007/s00244-010-9583-5</p>
<p>Ji, W. O., et al. "Quantitation of the ROS production in plasma and radiation treatments of biotargets." Sci Rep. 2019 Dec 27;9(1):19837. doi: 10.1038/s41598-019-56160-0. PMID: 31882663; PMCID: PMC6934759.</p>
<p>Kruk, J. and Aboul-Enein, H. Y. (2017). "Reactive Oxygen and Nitrogen Species in Carcinogenesis: Implications of Oxidative Stress on the Progression and Development of Several Cancer Types." Mini-Reviews in Medicinal Chemistry, 17:11. doi:10.2174/1389557517666170228115324</p>
<p>Lee, D. Y., et al. (2020). "PEGylated Bilirubin-coated Iron Oxide Nanoparticles as a Biosensor for Magnetic Relaxation Switching-based ROS Detection in Whole Blood." Theranostics, 10(5), 1997-2007. doi:10.7150/thno.39662</p>
<p>Li, Z., et al. (2020). "Inhibition of MiR-25 attenuates doxorubicin-induced apoptosis, reactive oxygen species production and DNA damage by targeting pten." International Journal of Medical Sciences, 17(10), 1415–1427. https://doi.org/10.7150/ijms.41980</p>
<p>Liou, G. Y. and Storz, P. "Reactive oxygen species in cancer." Free Radic Res. 2010 May;44(5):479-96. doi:10.3109/10715761003667554. PMID: 20370557; PMCID: PMC3880197.</p>
<p>Lu, Y., et al. (2010). "Phosphatidylinositol-3-kinase/akt regulates bleomycin-induced fibroblast proliferation and collagen production." American journal of respiratory cell and molecular biology, 42(4), 432–441. https://doi.org/10.1165/rcmb.2009-0002OC</p>
<p>Onoue, S., et al. (2013). "Establishment and intra-/inter-laboratory validation of a standard protocol of reactive oxygen species assay for chemical photosafety evaluation." J Appl Toxicol. 33(11):1241-50. doi: 10.1002/jat.2776. Epub 2012 Jun 13. PMID: 22696462.</p>
<p>Onoue S, Hosoi K, Toda T, Takagi H, Osaki N, Matsumoto Y, et al. Intra-/inter-laboratory validation study on reactive oxygen species assay for chemical photosafety evaluation using two different solar simulators. Toxicology in vitro : an international journal published in association with BIBRA. 2014;28:515-23.</p>
<p>Onoue S, Hosoi K, Wakuri S, Iwase Y, Yamamoto T, Matsuoka N, et al. Establishment and intra-/inter-laboratory validation of a standard protocol of reactive oxygen species assay for chemical photosafety evaluation. Journal of applied toxicology : JAT. 2013;33:1241-50.</p>
<p>Onoue S, Kawamura K, Igarashi N, Zhou Y, Fujikawa M, Yamada H, et al. Reactive oxygen species assay-based risk assessment of drug-induced phototoxicity: classification criteria and application to drug candidates. J Pharm Biomed Anal. 2008;47:967-72.</p>
<p>Onoue S, Seto Y, Gandy G, Yamada S. Drug-induced phototoxicity; an early<em> in vitro</em> identification of phototoxic potential of new drug entities in drug discovery and development. Current drug safety. 2009;4:123-36.</p>
<p>Onoue S, Tsuda Y. Analytical studies on the prediction of photosensitive/phototoxic potential of pharmaceutical substances. Pharmaceutical research. 2006;23:156-64.</p>
<p>Ozcan, Ayla, and Metin Ogun. 2015. “Biochemistry of Reactive Oxygen and Nitrogen Species.” In Basic Principles and Clinical Significance of Oxidative Stress, edited by Sivakumar Joghi Thatha Gowder. Rijeka: IntechOpen.</p>
<p>Parrish, A. R. 2010. “2.27 - Hypoxia/Ischemia Signaling.” In Comprehensive Toxicology (Second Edition), edited by Charlene A. McQueen, 529–42. Oxford: Elsevier.</p>
<p>PCPC. PCPC 2014 safety evaluation guidelines; Chapter 7: Evaluation of Photoirritation and Photoallergy potential. Personal Care Products Council; 2014.</p>
<p>Ramos, M. F. P., et al. (2018). "Xanthine oxidase inhibitors and sepsis." Int J Immunopathol Pharmacol. 32:2058738418772210. doi:10.1177/2058738418772210</p>
<p>Ravanat, J. L., et al. (2014). "Radiation-mediated formation of complex damage to DNA: a chemical aspect overview." Br J Radiol 87(1035): 20130715.</p>
<p>Schutzendubel, A. and Polle, A. (2002). "Plant responses to abiotic stresses: heavy metal-induced oxidative stress and protection by mycorrhization." Journal of Experimental Botany, 53(372), 1351–1365. https://doi.org/10.1093/jexbot/53.372.1351</p>
<p>Seto Y, Kato M, Yamada S, Onoue S. Development of micellar reactive oxygen species assay for photosafety evaluation of poorly water-soluble chemicals. Toxicology in vitro : an international journal published in association with BIBRA. 2013;27:1838-46.</p>
<p>Sharma, Gunjan, Nishant Kumar Rana, Priya Singh, Pradeep Dubey, Daya Shankar Pandey, and Biplob Koch. 2017. “p53 Dependent Apoptosis and Cell Cycle Delay Induced by Heteroleptic Complexes in Human Cervical Cancer Cells.” Biomedicine & Pharmacotherapy = Biomedecine & Pharmacotherapie 88 (April): 218–31.</p>
<p>Silva, R., et al. (2019). "Light exposure during growth increases riboflavin production, reactive oxygen species accumulation and DNA damage in Ashbya gossypii riboflavin-overproducing strains." FEMS Yeast Research, 19(1), 1–7. https://doi.org/10.1093/femsyr/foy114</p>
<p>Tsuchiya K, et al. (2005). "Oxygen radicals photo-induced by ferric nitrilotriacetate complex." Biochim Biophys Acta. 1725(1):111-9. doi:10.1016/j.bbagen.2005.05.001</p>
<p>Wang, J., et al. (2017). "Glucocorticoids Suppress Antimicrobial Autophagy and Nitric Oxide Production and Facilitate Mycobacterial Survival in Macrophages." Scientific reports, 7(1), 982. https://doi.org/10.1038/s41598-017-01174-9</p>
<p>Wang, X., et al. (2013). "Imaging ROS signaling in cells and animals." Journal of molecular medicine 91(8): 917-927.</p>
<p>Yen, Cheng Chien, et al. "Inorganic arsenic causes cell apoptosis in mouse cerebrum through an oxidative stress-regulated signaling pathway." Archives of toxicology 85 (2011): 565-575.</p>
<p>Yuan, Yan, et al. "Cadmium-induced apoptosis in primary rat cerebral cortical neurons culture is mediated by a calcium signaling pathway." PloS one 8.5 (2013): e64330.</p>
<p>Zhang, Z., et al. (2011). "Reactive oxygen species mediate arsenic induced cell transformation and tumorigenesis through Wnt/β-catenin pathway in human colorectal adenocarcinoma DLD1 cells. " Toxicology and Applied Pharmacology, 256(2), 114-121. doi:10.1016/j.taap.2011.07.016</p>
<p><span style="font-size:16px"><span style="background-color:white"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Calibri",sans-serif"><span style="color:#212529">Life Stage: All life stages. </span></span></span></span></span></p>
<p><span style="font-size:16px"><span style="background-color:white"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Calibri",sans-serif"><span style="color:#212529">Sex: Applies to both males and females.</span></span></span></span></span></p>
<p><span style="font-size:16px"><span style="background-color:white"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Calibri",sans-serif"><span style="color:#212529">Taxonomic: Appears to be present broadly, with representative studies in mammals.</span></span></span></span></span></p>
<h4>Key Event Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">The Peroxisome Proliferator-Activated Receptors (PPAR) family of genes involved in regulation of lipid metabolism and energy pathways (Desvergne and Wahli 1999, Hihi et al. 2002, Ahmed et al. 2007). Fatty acids stimulate the expression of PPAR genes, which initiate a variety of cellular responses focused on lipid metabolism, but also inflammation and apoptosis pathways. Decreases in PPAR-gamma expression are associated with disruption of adipocyte differentiation and glucose homeostasis.</span></span></p>
<h4>How it is Measured or Detected</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Peroxisome proliferation-activated receptors are investigated by changes in gene expression and protein levels. X-ray crystallography can be used to determine molecular structure. Effects of PPAR gamma on expression of downstream genes can be investigating using metabolomics and RT-qPCR approaches. </span></span></p>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Ahmed, W., Ziouzenkova, O., Brown, J. Devchand, P. Francis, S., Kadakia, M., Kanda, T., Orasanu, G., Sharlach, M., Zandbergen, F., and Plutzky, J. 2007. PPARs and their metabolic modulation: new mechanisms for transcriptional regulation? Journal of Internal Medicine 262: 184-198.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Desvergne, B. and Wahli, W. 1999. Peroxisome proliferator-activated receptors: nuclear control of metabolism. Endocrine Reviews 20(5): 649-688.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Hihi, A.K., Michalik, L., Wahli, W. 2002. PPARs: transcriptional effectors of fatty acids and their derivatives. Cellular and Molecular Life Sciences 59: 790-798.</span></span></p>
<p><span style="font-size:16px">Life Stage: All life stages. </span></p>
<p><span style="font-size:16px">Sex: Applies to both males and females.</span></p>
<p><span style="font-size:16px">Taxonomic: Appears to be present broadly, with representative studies in mammals.</span></p>
<h4>Key Event Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Lipids are important molecules for efficient energy storage, in addition to roles as signaling molecules and basic building blocks in organisms. In addition to energy release, lipid metabolism affects the amount of stored fat. Alteration of lipid metabolism reflects a disruption of normal function, as evidenced by changes in gene expression, enzyme levels, break-down products, or fat content. Peroxisome proliferation-activated receptors pathways (and associated genes and proteins) are commonly monitored for downstream effects on lipid metabolism (Luquet et al. 2005; Den Broeder et al. 2015; Chamorro-Garcia et al. 2018; Venezia et al. 2021). </span></span></p>
<h4>How it is Measured or Detected</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Changes in lipid metabolism can be detected by examining organism fat content, or by examination of organs (ex. stomach, liver, intestines) for break-down products (ex. proteins) or changes in gene expression.</span></span></p>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Chamorro-Garcia, R., Shoucri, B.M., Willner, S., Kach, H., Janesick, A., and Blumberg, B. 2018. Effect of perinatal exposure to dibutyltin chloride on fat and glucose metabolism in mice, and molecular mechanisms, in vitro. Environmental Health Perspectives 126: 057006.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Den Broeder, M.J., Kopylova, V.A., Kamminga, L.M. Legler, J. 2015. Zebrafish as a model to study the role of peroxisome proliferating-activated receptors in adipogenesis and obesity. PPAR Research 2015: 358029.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Luquet, S., Gaudel, C., Holst, D., Lopez-Soriano, J., Jehl-Pietri, C., Fredenrich, A., and Grimaldi, P.A. 2005. Roles of PPAR delta in lipid absorption and metabolism: A new target for the treatment of type 2 diabetes. Biochimica and Biophysica Acta 1740: 313-317.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Venezia, O., Islam, S., Cho, C., Timme-Laragy, A.R., and Sant, K.E. 2021. Modulation of PPAR signaling disrupts pancreas development in the zebrafish, Danio rerio. Toxicology and Applied Pharmacology 426: 115653.</span></span></span></p>
<h4><a href="/events/1513">Event: 1513: General Apoptosis</a></h4>
<p>Taxonomic: appears to be present broadly among multicellular organisms.</p>
<h4>Key Event Description</h4>
<p><span style="font-size:16px"><span style="font-family:calibri,sans-serif">Apoptosis is the programmed cell death in general. This process is well regulated with a sequence of events before cell fragmentation occurs. Changes in the nucleus of a cell are the first step in apoptosis. Before that, other factors such as stress, inflammation, cell damage can induce expression or activation of signal proteins which will activate the pathway for apoptosis. Examples of proteins which are involved in apoptosis are the proteins p53, Bcl-2, JNK, and several caspases. When the first step is taken in the apoptosis process the cell will end in membrane-bounded apoptotic bodies. These bodies are cleared by macrophages or other cells where the degradation process starts within heteorphagosomes.</span></span></p>
<h4>How it is Measured or Detected</h4>
<p><span style="font-size:16px">There are several possibilities to measure and detect apoptosis, some common techniques are: </span></p>
<ul>
<li><span style="font-size:16px">The detection of </span>Lactate dehydrogenase (<span style="font-size:16px">LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) substances which are released from cells which undergo apoptosis. </span></li>
<li><span style="font-size:16px">An older but effective technique it the annexin V – affinity assay. The principle of this assay is the high affinity binding between annexin V and phosphatidylserine. In a vital cell there is a membrane lipid asymmetry where phosphatidylserine molecules are facing the cytosol. During apoptosis the membrane lipid asymmetry is lost, and the phosphatidylserine molecules are expressed in the outer membrane. When annexin-V is present in combination with Ca<sup>2+</sup> it binds with high affinity to phosphatidylserine. With a hapten label at the annexin-V this process can be detected.</span></li>
<li><span style="font-size:16px"><span style="font-family:calibri,sans-serif">Another technique is the detection of cleaved caspase-3, which could be done with western blot or enzyme-linked immunosorbent assays. </span></span></li>
<li><span style="font-size:16px"><span style="font-family:calibri,sans-serif">Cytochrome c is also a protein which is released in an early stage of apoptosis. Detection of cytochrome c can be done with metal nanoclusters which have a fluorescent probe in addition to western blot assay.</span></span></li>
</ul>
<h4>References</h4>
<p>Shtilbans, V., Wu, M. & Burstein, D. E. Evaluation of apoptosis in cytologic specimens. <em>Diagnostic Cytopathology</em> <strong>38,</strong> 685–697 (2010).</p>
<p>Wu, J., Sun, J. & Xue, Y. Involvement of JNK and P53 activation in G2/M cell cycle arrest and apoptosis induced by titanium dioxide nanoparticles in neuron cells. <em>Toxicol. Lett.</em> <strong>199,</strong> 269–276 (2010).</p>
<p>Redza-Dutordoir, M. & Averill-Bates, D. A. Activation of apoptosis signalling pathways by reactive oxygen species. <em>Biochim. Biophys. Acta - Mol. Cell Res.</em> <strong>1863,</strong> 2977–2992 (2016).</p>
<p>Lossi, L., Castagna, C. & Merighi, A. Neuronal cell death: An overview of its different forms in central and peripheral neurons. in <em>Neuronal Cell Death: Methods and Protocols</em> 1–18 (2014). doi:10.1007/978-1-4939-2152-2_1</p>
<p>Van Engeland, M., Nieland, L. J. W., Ramaekers, F. C. S., Schutte, B. & Reutelingsperger, C. P. M. Annexin V-affinity assay: A review on an apoptosis detection system based on phosphatidylserine exposure. <em>Cytometry</em> <strong>31,</strong> 1–9 (1998).</p>
<p>Shamsipur, M., Molaabasi, F., Hosseinkhani, S. & Rahmati, F. Detection of Early Stage Apoptotic Cells Based on Label-Free Cytochrome c Assay Using Bioconjugated Metal Nanoclusters as Fluorescent Probes. <em>Anal. Chem.</em> <strong>88,</strong> 2188–2197 (2016).</p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt">Life Stage:</span> All life stages. Older individuals are more likely to manifest this key event (adults > juveniles > embryos).</span></span></p>
<p><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt">Sex: A</span>pplies to both males and females.</span></span></p>
<p><span style="font-size:12.0pt"><span style="font-family:"Calibri",sans-serif">Taxonomic:</span></span><span style="font-size:11.0pt"><span style="font-family:"Calibri",sans-serif"> Appears to be present broadly, with representative studies including mammals (humans, lab mice, lab rats), teleost fish, and invertebrates (cladocerans, mussels).</span></span></p>
<h4>Key Event Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Cancer is a general key event for related diseases each exhibiting uncontrolled proliferation of abnormal cells (for review see Hanahan and Weinberg 2011). A cancer often is initially associated with a specific organ, with malignant tumors developing ability to metastasize, or travel to other areas of the body. Most cancers develop from genetic mutations in normal cells, although a minority of cancers are hereditary. Exposure to chemical stressors, radiation, tobacco smoke, or viruses can increase the likelihood that cancer will develop.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Cancer cells proliferate due to capabilities summarized by Hanahan and Weinberg (2011): </span></span></p>
<ol>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sustained proliferation signaling – by deregulating normal cell signals, cancer cells can sustain chronic proliferation.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Evading growth suppressors – by evading activities of tumor suppressor genes, cancer cells continue to proliferate.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Activating invasion and metastasis – by altering shape and attachment to cells in the extracellular matrix, cancer cells gain ability to move to other locations.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Enabling replicative immortality – by disabling senescence pathways, cancer cells have extended lifespans.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Inducing angiogenesis – by enabling neovasculature, cancer cells receive nutrients and oxygen and get rid of waste products.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Resisting cell death – by evading apotosis and necrosis defense pathways, cancer cells avoid elimination.</span></span></li>
</ol>
<h4>How it is Measured or Detected</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Most carcinogenicity studies are conducted with rodents (see OECD 2018; Zhou et al. 2023 for methods) or in-vitro with mammalian cell lines (see OECD 2023 for methods). Cancer is usually detected by biopsy or histopathological examination of tissue. Gene expression levels can also be assessed, as increased transcription of known genes have been associated with specific cancers (ex. Tumor Necrosis Factor (Pavet et al. 2014); Heat Shock Factors (Vihervaara and Sistonen 2014; Androgen Receptor (Heinlein and Chang 2004)).</span></span></p>
<h4>Regulatory Significance of the AO</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Cancer is a critical endpoint in human health risk assessment. It is embedded in regulatory frameworks for human health protection in many countries (see OSHA 2023 for examples of US regulations and European Parliament 2022 for examples of regulations in Europe).</span></span></p>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Abraha, A.M. and Ketema, E.B. 2016. Apoptotic pathways as a therapeutic target for colorectal cancer treatment. World Journal of Gastrointestinal Oncology 8 (8): 583-491</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">European Parliament. 2022. Directive 2004/37/EC of the European Parliament on the protection of workers from the risks related to exposure to carcinogens, mutagens or reprotoxic substances at work. Retrieved 3 August 2023 from http://data.europa.eu/eli/dir/2004/37/2022-04-05</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Hanahan, D. and Weinberg, R.A. 2011. Hallmarks of cancer: the next generation. Cell 144(5): 646-674.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Heinlein, C.A. and Chang, C. 2004. Androgen receptor in prostate cancer. Endocrine Reviews 25: 276-308.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">OECD. 2018. Test no. 451: OECD Guideline for the Testing of Chemicals: Carcinogenicity Studies. OECD Publishing, Paris. Retrieved 3 August 2023 from <a href="https://www.oecd.org/env/test-no-451-carcinogenicity-studies-9789264071186-en.htm" style="color:#0563c1; text-decoration:underline">https://www.oecd.org/env/test-no-451-carcinogenicity-studies-9789264071186-en.htm</a></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">OECD. 2023. Test No. 487: In Vitro Mammalian Cell Micronucleus Test, OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing, Paris. Retrieved 3 August 2023 from <a href="https://doi.org/10.1787/9789264264861-en.htm" style="color:#0563c1; text-decoration:underline">https://doi.org/10.1787/9789264264861-en.htm</a></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">OSHA. 2023. Carcinogens. Retrieved 3 August 2023 from <a href="https://www.osha.gov/carcinogens/standards" style="color:#0563c1; text-decoration:underline">https://www.osha.gov/carcinogens/standards</a></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Pavet, V., Shlyakhtina, Y., He, T., Ceschin, D.G., Kohonen, P., Perala, M., Kallioniemi, O., and Gronemeyer, H. 2014. Plasminogen activator urokinase expression reveals TRAIL responsiveness and support fractional survival of cancer cells. Cell Death and Disease 5: e1043.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Vihervaara, A. and Sistonen, L. 2014. HSF1 at a glance. Journal of Cell Scientce 127: 261-266.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Zhou, Y., Xia, J., Xu, S., She, T., Zhang, Y., Sun, Y., Wen, M., Jiang, T., Xiong, Y., and Lei, J. 2023. Experimental mouse models for translational human cancer research. Frontiers in Immunology 14: 1095388.</span></span></p>
<h2>Appendix 2</h2>
<h2>List of Key Event Relationships in the AOP</h2>
<div id="evidence_supporting_links">
<h3>List of Adjacent Key Event Relationships</h3>
<div>
<h4><a href="/relationships/3092">Relationship: 3092: Increased, Reactive oxygen species leads to Decreased, PPAR-gamma activation</a></h4>
<h4><a href="/relationships/3092">Relationship: 3092: Increase, ROS leads to Decreased, PPAR-gamma activation</a></h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Life Stage: The life stage applicable to this key event relationship is all life stages. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sex: This key event relationship applies to both males and females.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Taxonomic: This key event relationship appears to be present broadly, with representative studies including mammals (humans, lab mice, lab rats) and teleost fish.</span></span></p>
<h4>Key Event Relationship Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Oxidative stress occurs due to the accumulation of reactive oxygen species (ROS). ROS can damage DNA, lipids, and proteins (Shields et al. 2021). Superoxide dismutase is an enzyme in a common cellular defense pathway, in which superoxide dismutase converts superoxide radicals to hydrogen peroxide. When cellular defense mechanisms are unable to mitigate ROS formation from mitochondrial respiration and stressors (biological, chemical, radiation), one established pathway that is disrupted involves Peroxisome proliferation-activated receptors.</span></span></p>
<h4>Evidence Supporting this KER</h4>
<strong>Biological Plausibility</strong>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">The biological plausibility linking decreases in Peroxisome proliferation-activated receptors to reactive oxygen species (ROS) is strong. Reactive oxygen species (ROS) are produced by many normal cellular processes (ex. cellular respiration, mitochondrial electron transport, specialized enzyme reactions) and occur in multiple chemical forms (ex. superoxide anion, hydroxyl radical, hydrogen peroxide). <span style="background-color:white"><span style="color:#212529">Antioxidant enzymes play a major role in reducing reactive oxygen species (ROS) levels in cells (Ray et al. 2012) to prevent cellular damage to lipids, proteins, and DNA (Juan et al. 2021). This Key Event Relationship focuses on the disruption of Peroxisome proliferation-activated receptors gene expression due to increases in </span></span>Reactive oxygen species (ROS) level.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Male rats showed increased superoxide levels in glucose treatment but not glucose plus alpha-lipoic acid treatment, and corresponding patterns in PPAR-gamma gene expression in the treatments. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Diet exposure of 100, 1000 ug/L of 0.5, 50 um polystyrene microplastics</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Study selected stressor(s) known to elevate reactive oxygen species (ROS) levels. Male mice showed decreased gene expression of Peroxisome proliferation-activated receptor (PPAR-gamma) in blood.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Diet exposure of rosiglitazone, mitigation with N-acetylcysteine, L-carnitine, cold and heat stress, fish with PPAR-gamma mutations</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Male and female fish had increased ROS levels and corresponding decreases in PPAR-gamma expression levels</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Wang et al. (2022)</span></span></p>
</td>
</tr>
</tbody>
</table>
<p><span style="font-size:16px">1 Assumed: study selected stressor(s) known to elevate reactive oxygen species (ROS) levels, endpoints verified increased oxidative stress and disrupted pathway.</span></p>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Blanquicett, C., Kang, B-Y., Ritzenthaler, J.D. Jones, D.P., and Hart, C.M. 2010. Oxidative stress modulates PPARγ in vascular endothelial cells. Free Radical Biology and Medicine 48: 1618-1625.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">El Midaoui, A., Wu, L., Wang, R., and de Champlain, J. 2006. Modulation of cardiac and aortic peroxisome proliferator-activated receptor-gamma expression by oxidative stress in chronically glucose-fed rats. American Journal of Hypertension 19: 407-412.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="background-color:white"><span style="color:#212529">Juan, C.A., de la Lastra, J.M.P., Plou, F.J., and Lebena, E.P. 2021. The chemistry of reactive oxygen species (ROS) revisited: Outlining their role in biological macromolecules (DNA, lipids and proteins) and induced pathologies. International Journal of Molecular Sciences 22: 4642.</span></span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Lu, L., Wan, Z., Luo, T., Fu, Z., and Jin, Y. 2018. Polystyrene microplastics induce microbiota dysbiosis and hepatic lipid metabolism disorder in mice. Science of the Total Environment 631-632: 449-458.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="background-color:white"><span style="color:#212529">Ray, P.D., Huang, B.-W., and Tsuji, Y. 2012. Reactive oxygen species (ROS) homeostasis and redox regulation in cellular signalling. Cellular Signalling 24:981-990.</span></span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Life Stage: The life stage applicable to this key event relationship is all life stages. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sex: This key event relationship applies to both males and females.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Taxonomic: This key event relationship appears to be present broadly, with representative studies including mammals (humans, lab mice, lab rats) and teleost fish.</span></span></p>
<h4>Key Event Relationship Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Expression of Peroxisome proliferator-activated receptors (PPAR) family genes are closely related to different aspects of lipid metabolism, and resulting organism fat content. PPAR-alpha, PPAR-gamma, and PPAR-delta families of genes are most often discussed when considering lipid metabolism. PPAR-alpha family genes are linked to regulation of lipid metabolism, lipoprotein synthesis, and metabolism processes, while PPAR-gamma family genes are linked to the proliferation of adipose cells, and PPAR-delta family genes are linked to changes in metabolic response due to environmental change. In this Key Event Relationship, we focus on the effects of decreased expression of PPAR-gamma family genes, with altered lipid metabolism.</span></span></p>
<h4>Evidence Supporting this KER</h4>
<strong>Biological Plausibility</strong>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">The biological plausibility linking decreases in Peroxisome proliferation-activated receptors to lipid metabolism is strong. Disruption of cellular processors via stressors have been shown to decrease PPAR-gamma gene expression, with corresponding decreases in lipid metabolism and/or increases in fat content of organisms. </span></span></p>
<strong>Empirical Evidence</strong>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="background-color:white"><span style="color:#212529">For review see </span></span>Berger et al. (2002), Luquet et al. (2005), Den Broder et al. (2015). Experiments cited here have been conducted with lab mammals and with fish.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">In vitro exposure of 10e-10M to 10e-5M dibutyltin and tributyltin and 500 nm rosiglitazone and diet exposure of 50, 500 nM dibutyltin and 50 nM tributyltin.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">In human and mouse cells, as well as lab mice, increased activation of PPAR-gamma gene expression was correlated with increases in glucose levels and increased weight gain.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Diet exposure of 100, 1000 ug/L of 0.5, 50 um polystyrene microplastics</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Lu et al. (2018)</span></span></p>
</td>
</tr>
</tbody>
</table>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Berger, J. and Moller, D. 2002. The mechanisms of action of PPARS. Annual Review of Medicine 53: 409-435.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Chamorro-Garcia, R., Shoucri, B.M., Willner, S., Kach, H., Janesick, A., and Blumberg, B. 2018. Effect of perinatal exposure to dibutyltin chloride on fat and glucose metabolism in mice, and molecular mechanisms, in vitro. Environmental Health Perspectives 126(5): 057006.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Den Broeder, M.J., Kopylova, V.A., Kamminga, L.M. Legler, J. 2015. Zebrafish as a model to study the role of peroxisome proliferating-activated receptors in adipogenesis and obesity. PPAR Research 2015: 358029.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Lu, L., Wan, Z., Luo, T., Fu, Z., and Jin, Y. 2018. Polystyrene microplastics induce microbiota dysbiosis and hepatic lipid metabolism disorder in mice. Science of the Total Environment 631-632: 449-458.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Luquet, S., Gaudel, C., Holst, D., Lopez-Soriano, J., Jehl-Pietri, C., Fredenrich, A., and Grimaldi, P.A. 2005. Roles of PPAR delta in lipid absorption and metabolism: A new target for the treatment of type 2 diabetes. Biochimica and Biophysica Acta 1740: 313-317.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Venezia, O., Islam, S., Cho, C., Timme-Laragy, A.R., and Sant, K.E. 2021. Modulation of PPAR signaling disrupts pancreas development in the zebrafish, Danio rerio. Toxicology and Applied Pharmacology 426: 115653.</span></span></span></p>
</div>
<div>
<h4><a href="/relationships/3094">Relationship: 3094: Alteration, lipid metabolism leads to General Apoptosis</a></h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Life Stage: The life stage applicable to this key event relationship is all life stages. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sex: This key event relationship applies to both males and females.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Taxonomic: This key event relationship appears to be present broadly, with representative studies on mammals (humans, lab mice, lab rats).</span></span></p>
<h4>Key Event Relationship Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Alteration of lipid metabolism leads to changes in cell lipid levels, structural changes in membranes (lipids are key components), and changes in signaling pathways affecting gene and protein expression (Huang and Freter, 2015). Loss of plasma membrane integrity due to disruptions to lipid metabolism results in cellular processes identifying cells as damaged, triggering apoptosis pathways. Oxidation of fatty acids can lead to increases of reactive oxygen species (ROS), creating an additional stress disrupting the cellular environment. As lipids represent a diverse class of molecules, and the basic building blocks for many biologically important compounds, disruption of lipid function will eventually lead to damaged cells and cell death via apoptosis.</span></span></p>
<h4>Evidence Supporting this KER</h4>
<strong>Biological Plausibility</strong>
<p><span style="font-size:11.0pt"><span style="font-family:"Calibri",sans-serif">The biological plausibility linking alterations in lipid metabolism to apoptosis is moderate. Disruption of lipid metabolism via stressors has been shown to lead to apoptosis, particularly through resulting loss of plasma membrane integrity.</span></span></p>
<strong>Empirical Evidence</strong>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">See Huang and Freter (2015) for review of the relationship between lipid metabolism and apoptosis.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">In rats, methamphetamine exposure induced expression genes that control lipid metabolism and apoptosis.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Aquatic exposure of 0.5, 5, 50 ug/L of <100, 100-1000 um polyethylene and polystyrene microplastics</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Mussels showed altered gene expression of genes associated with lipid metabolism and apoptosis.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Avio et al. (2015)</span></span></p>
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</tr>
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</table>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Avio, C.G., Gorbi, S., Milan, M., Benedetti, M., Fattorini, D., D’Errico, G., Pauletto, M., Bargelloni, L., and Regoli, F. 2015. Pollutants bioavailability and toxicological risk from microplastics to marine mussels. Environmental Pollutants 198: 211-222.</span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif"><span style="color:black">Cadet, J.L., Jayanthi, S., McCoy, M.T., Beauvais, G., and Cai, N.S. 2010. Dopamine D1 receptors, regulation of gene expression in the brain, and neurogeneration. CNS Neurological Disorders - Drug Targets 9: 526-538.</span></span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Gao, L., Xu, Z., Huang, Z., Tang, Y., Yang, D., Huang, J., He, L., Liu, M., Chen, Z., and Teng, Y. 2020. CPI-613 rewires lipid metabolism to enhance pancreatic cancer apoptosis via the AMPK-ACC signaling. 39: 73.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Huang, C. and Freter, C. 2015. Lipid metabolism, apoptosis and cancer therapy. International Journal of Molecular Sciences 16: 924-949.</span></span></p>
</div>
<div>
<h4><a href="/relationships/2977">Relationship: 2977: General Apoptosis leads to Increase, Cancer</a></h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Life Stage: The life stage applicable to this key event relationship is all life stages. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sex: This key event relationship applies to both males and females.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Taxonomic: This key event relationship appears to be present broadly, with representative studies focused in mammals (humans, lab mice, lab rats).</span></span></p>
<h4>Key Event Relationship Description</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Cancer is a general key event for related diseases each exhibiting uncontrolled proliferation of abnormal cells (for review see Hanahan and Weinberg 2011). A cancer often is initially associated with a specific organ, with malignant tumors developing ability to metastasize, or travel to other areas of the body. Most cancers develop from genetic mutations in normal cells; in this key event relationship we are focusing on disruption of apoptosis and necrosis pathways, leading to cancer. Exposure to chemical stressors, radiation, tobacco smoke, or viruses can increase the likelihood that cancer will develop. Pathways leading to apoptosis, or single cell death, have traditionally been studied as both independent and simultaneous from pathways leading to necrosis, or tissue-wide cell death, with both overlap and distinct mechanisms (Elmore 2007). For the purposes of this key event relationship, we are characterizing cancer due to widespread cell-death. </span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Cancer cells proliferate due to capabilities summarized by Hanahan and Weinberg (2011): </span></span></p>
<ol>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Sustained proliferation signaling – by deregulating normal cell signals, cancer cells can sustain chronic proliferation.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Evading growth suppressors – by evading activities of tumor suppressor genes, cancer cells continue to proliferate.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Activating invasion and metastasis – by altering shape and attachment to cells in the extracellular matrix, cancer cells gain ability to move to other locations.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Enabling replicative immortality – by disabling senescence pathways, cancer cells have extended lifespans.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Inducing angiogenesis – by enabling neovasculature, cancer cells receive nutrients and oxygen and get rid of waste products.</span></span></li>
<li><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Resisting cell death – by evading apotosis and necrosis defense pathways, cancer cells avoid elimination.</span></span></li>
</ol>
<h4>Evidence Supporting this KER</h4>
<strong>Biological Plausibility</strong>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">The biological plausibility linking cancer to avoidance of apoptosis is strong. Apoptosis is a series of related pathways that eliminate abnormal cells. </span></span><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Cancer cells proliferate due to evasion of cellular defenses (apoptosis pathways) and tissue-level defenses (necrosis pathways). Specific modifications to cancer cells that enable proliferation rather than elimination are listed under the Key Event Relationship Description. For review see:</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">1. Heinlein and Chang (2004): Role of androgen receptor in apoptosis, loss of androgen pathway function resulting in increases in mammalian prostate cancer.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">2. Hanahan and Weinberg (2011): Biological capabilities gained by cancer cell to enable proliferation of tumor cells and evasion of normal regulating mechanisms of apoptosis and necrosis pathways in mammals.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">3. Pavet et al. (2014): Role of tumor necrosis factor-related apoptosis-inducing ligandin to induce apoptosis in mammalian cells and reduce incidence of cancer.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">4. Vihervaara and Sistonen (2014): Role of increased rate of transcription of heat shock factor 1 in mammalian cancer cells enhancing survival and metastasis, as well as evasion of cellular defenses.</span></span></p>
<strong>Empirical Evidence</strong>
<p>References cited by Jeong and Choi (2020) are review articles and gene expression studies. Empirical studies linking apoptosis to cancer were not provided.</p>
<h4>References</h4>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Elmore, S. 2007. Apoptosis: A Review of Programmed Cell Death. Toxicologic pathology 35 (4): 495-516.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Hanahan, D. and Weinberg, R.A. 2011. Hallmarks of cancer: the next generation. Cell 144(5): 646-674.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Heinlein, C.A. and Chang, C. 2004. Androgen receptor in prostate cancer. Endocrine Reviews 25: 276-308.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Pavet, V., Shlyakhtina, Y., He, T., Ceschin, D.G., Kohonen, P., Perala, M., Kallioniemi, O., and Gronemeyer, H. 2014. Plasminogen activator urokinase expression reveals TRAIL responsiveness and support fractional survival of cancer cells. Cell Death and Disease 5: e1043.</span></span></p>
<p><span style="font-size:16px"><span style="font-family:Calibri,sans-serif">Vihervaara, A. and Sistonen, L. 2014. HSF1 at a glance. Journal of Cell Scientce 127: 261-266.</span></span></p>