Activation, PPARα

117-81-7

BJQHLKABXJIVAM-UHFFFAOYNA-N

BJQHLKABXJIVAM-UHFFFAOYSA-N

Di(2-ethylhexyl) phthalate

1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester DEHP 1,2-Benzedicarboxylic acid, bis(2-ethyl-hexyl) ester 1,2-Benzenedicarboxylic acid bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid, 1,2-bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid,bis(2-ethylhexylester) Bis(2-ethylhexyl) 1,2-benzenedicarboxylate Bis(2-ethylhexyl) o-phthalate bis(2-ethylhexyl) phthalate Bis(2-ethylhexyl)phthalat Bis(2-ethylhexyl)phthalate Bisoflex 81 Bisoflex DOP Corflex 400 Di(2-ethylhexyl)phthalate Di(isooctyl) phthalate Di-2-ethylhexlphthalate Di-2-ethylhexyl phthalate DI-2-ETHYLHEXYL-PHTHALATE Diacizer DOP Diethylhexyl phthalate Dioctylphthalate DOF Ergoplast FDO Ergoplast FDO-S ETHYLHEXYL PHTHALATE Eviplast 80 Eviplast 81 Fleximel Flexol DOD Flexol DOP ftlalato de bis(2-etilhexilo) Garbeflex DOP-D 40 Good-rite GP 264 Hatco DOP Jayflex DOP Kodaflex DEHP Kodaflex DOP Monocizer DOP NSC 17069 Palatinol AH Palatinol AH-L Phtalate de Bis (Ethyle-2-Hexyle) Phtalate de bis(2-ethylhexyle) PHTHALATE, BIS(2-ETHYLHEXYL) Phthalic acid di(2-ethylhexyl) ester Phthalic acid, bis(2-ethylhexyl) ester PHTHALIC ACID, BIS(2-ETHYLHEXYL)ESTER PHTHALSAEURE-BIS-(2-AETHYLHEXYL)-ESTER Pittsburgh PX 138 Plasthall DOP Reomol D 79P Sansocizer DOP Sansocizer R 8000 Sconamoll DOP Staflex DOP Truflex DOP Vestinol AH Vinycizer 80 Vinycizer 80K Witcizer 312

DTXSID5020607

637-07-0

KNHUKKLJHYUCFP-UHFFFAOYSA-N

Clofibrate

ethyl-p-chlorophenoxyisobutyrate Propanoic acid, 2-(4-chlorophenoxy)-2-methyl-, ethyl ester 2-(p-Chlorophenoxy)-2-methylpropionic acid ethyl ester Abitrate Amotril Anparton Arteriosan Artevil Ateculon Ateriosan Atheropront Atromid S Atromidin Azionyl Bioscleran Cartagyl Claripex Claripex CPIB Clobren SF Clofibrat clofibrato Clofinit Ethyl (p-chlorophenoxy) isobutyrate Ethyl 2-(4-chlorophenoxy)-2-methylpropionate Ethyl 2-(4-chlorophenoxy)isobutyrate Ethyl 2-(p-chlorophenoxy)-2-methylpropionate Ethyl 2-(p-chlorophenoxy)isobutyrate Ethyl clofibrate Ethyl p-chlorophenoxyisobutyrate Ethyl α-(4-chlorophenoxy)isobutyrate Ethyl α-(4-chlorophenoxy)-α-methylpropionate Ethyl α-(p-chlorophenoxy)isobutyrate Ethyl α-(p-chlorophenoxy)-α-methylpropionate Hyclorate Lipavil Lipavlon Lipomid Liprinal Miscleron Misclerone Neo-Atromid Normolipol NSC 79389 p-Chlorophenoxyisobutyric acid ethyl ester Propionic acid, 2-(p-chlorophenoxy)-2-methyl-, ethyl ester Recolip Regelan Serotinex Sklerepmexe Sklerolip Skleromexe Sklero-Tablinene Ticlobran Xyduril

DTXSID3020336

3771-19-5

XJGBDJOMWKAZJS-UHFFFAOYNA-N

XJGBDJOMWKAZJS-UHFFFAOYSA-N

Nafenopin

DTXSID8020911

52214-84-3

KPSRODZRAIWAKH-UHFFFAOYNA-N

KPSRODZRAIWAKH-UHFFFAOYSA-N

Ciprofibrate

DTXSID8020331

25812-30-0

HEMJJKBWTPKOJG-UHFFFAOYSA-N

Gemfibrozil

Pentanoic acid, 5-(2,5-dimethylphenoxy)-2,2-dimethyl- 2,2-Dimethyl-5-(2,5-xylyloxy)valeric acid 5-(2,5-Dimethylphenoxy)-2,2-dimethylpentanoic acid Decrelip gemfibrozilo Gevilon Lopizid Trialmin 900 Valeric acid, 2,2-dimethyl-5-(2,5-xylyloxy)-

DTXSID0020652

41859-67-0

IIBYAHWJQTYFKB-UHFFFAOYSA-N

Bezafibrate

Propanoic acid, 2-[4-[2-[(4-chlorobenzoyl)amino]ethyl]phenoxy]-2-methyl- Befizal Benzofibrate Bezafibrat bezafibrato Bezalip Bezatol Difaterol

DTXSID3029869

49562-28-9

YMTINGFKWWXKFG-UHFFFAOYSA-N

Fenofibrate

Propanoic acid, 2-[4-(4-chlorobenzoyl)phenoxy]-2-methyl-, 1-methylethyl ester 2-[4-(4-Chlorobenzoyl)phenoxy]-2-methylpropanoic acid 1-methylethyl ester Ankebin Clorofibrate Elasterin Fenobrate Fenofibrat fenofibrato Fenogal Fenotard Isopropyl 2-[p-(p-chlorobenzoyl)phenoxy]-2-methylpropionate Lipanthyl Lipantil Lipicard Lipidil Lipidil Supra Lipirex Lipoclar Lipofene Liposit MeltDose Nolipax NSC 281319 Procetofen Procetofene Procetoken Protolipan Secalip

DTXSID2029874

79902-63-9

RYMZZMVNJRMUDD-HGQWONQESA-N

Simvastatin

Butanoic acid, 2,2-dimethyl-, (1S,3R,7S,8S,8aR)-1,2,3,7,8,8a-hexahydro-3,7-dimethyl-8-[2-[(2R,4R)-tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl]ethyl]-1-naphthalenyl ester (+)-Simvastatin Apo-Simvastatin Bestatin 20 Butanoic acid, 2,2-dimethyl-, 1,2,3,7,8,8a-hexahydro-3,7-dimethyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1-naphthalenyl ester, [1S-[1α,3α,7β,8β(2S*,4S*),8aβ]]- Cholestat Co-Simvastatin Kolestevan L 644128-000U Lipinorm Liponorm Lipovas Lodales Modutrol Nor-Vastina Novo-Simvastatin Pms-simvastatin Simastin 20 Simovil Simvastatin lactone Simvotin Sinvacor Sinvascor Sivastin Starstat 20 Synvinolin Valemia Velostatin

DTXSID0023581

51-28-5

UFBJCMHMOXMLKC-UHFFFAOYSA-N

2,4-Dinitrophenol

DNP 1,3-Dinitro-4-hydroxybenzene 1-Hydroxy-2,4-dinitrobenzene 2,4-dinitrofenol Aldifen Dinitrophenol DINITROPHENOL, 2,4- Dinofan Fenoxyl Carbon N NSC 1532 Phenol, α-dinitro- UN 1320 UN 1599 α-Dinitrophenol Phenol, 2,4-dinitro-

DTXSID0020523

87-86-5

IZUPBVBPLAPZRR-UHFFFAOYSA-N

Pentachlorophenol

PCP Phenol, pentachloro- 1-Hydroxy-2,3,4,5,6-pentachlorobenzene 1-Hydroxypentachlorobenzene Chlorophenasic acid CHLOROPHENATE Dowicide EC 7 Dura Treet II Fungifen Grundier Arbezol Lauxtol Liroprem NSC 263497 Penchlorol Pentachlorphenol Perchlorophenol Permasan Phenol, 2,3,4,5,6-pentachloro- Pole topper Pole topper fluid Preventol P Santophen 20 Satophen UN 3155 Witophen P Woodtreat A 2,3,4,5,6-Pentachlorophenol

DTXSID7021106

3380-34-5

XEFQLINVKFYRCS-UHFFFAOYSA-N

Triclosan

5-Chloro-2-(2,4-dichlorophenoxy)phenol Phenol, 5-chloro-2-(2,4-dichlorophenoxy)- 2, 4, 4'-Trichloro-2'-hydroxydiphenylether 2,2'-Oxybis(1',5'-dichlorophenyl-5-chlorophenol) 2,4,4'-TRICHLORO-2'-HYDROXY DIPHENYLETHER 2',4',4-Trichloro-2-hydroxydiphenyl ether 2',4,4'-Trichloro-2-hydroxydiphenyl ether 2,4,4'-Trichloro-2'-hydroxydiphenyl ether 2'-Hydroxy-2,4,4'-trichlorodiphenyl ether 2-Hydroxy-2',4,4'-trichlorodiphenyl ether 3-Chloro-6-(2,4-dichlorophenoxy)phenol 4-Chloro-2-hydroxyphenyl 2,4-dichlorophenyl ether 5-Chloro-2-(2', 4'-dichlorophenoxy) phenol Aquasept Bacti-Stat soap Cansan TCH DIPHENYL ETHER, 2,4,4'-TRICHLORO-2'-HYDROXY- Irgacare MP Irgacide LP 10 Irgaguard B 1000 Irgaguard B 1325 Irgasan Irgasan CH 3565 Irgasan DP 30 Irgasan DP 300 Irgasan DP 3000 Irgasan DP 400 Irgasan PE 30 Irgasan PG 60 Microban Additive B Microban B Oletron Phenol, 5-chloro-2-(2,4-dichlorophenoxy) Phenol, 5-chloro-2-(2,4-dichlorophenoxy)-, dihydrogen phosphate Sanitized XTX Sapoderm SterZac Tinosan AM 100 Tinosan AM 110 TRICLOSAM Ultra Fresh NM 100 Ultrafresh NM-V 2 Vinyzene DP 7000 Yujiexin Zilesan UW

DTXSID5032498

518-82-1

RHMXXJGYXNZAPX-UHFFFAOYSA-N

Emodin

9,10-Anthracenedione, 1,3,8-trihydroxy-6-methyl- 1,3,8-trihidroxi-6-metilantraquinona 1,3,8-Trihydroxy-6-methyl-9,10-anthraquinone 1,3,8-Trihydroxy-6-methylanthrachinon 1,3,8-trihydroxy-6-methylanthraquinone 1,6,8-Trihydroxy-3-methylanthraquinone 3-Methyl-1,6,8-trihydroxyanthraquinone 4,5,7-Trihydroxy-2-methylanthraquinone Anthraquinone, 1,3,8-trihydroxy-6-methyl- Frangula emodin Frangulic acid NSC 408120 NSC 622947 Rheum emodin Schuttgelb

DTXSID5025231

10537-47-0

MZOPWQKISXCCTP-UHFFFAOYSA-N

Malonoben

DTXSID1042106

PR:000013056

PR peroxisome proliferator-activated receptor alpha

GO:0005739

GO mitochondrion

CHEBI:26523

CHEBI reactive oxygen species

GO:0035357

GO peroxisome proliferator activated receptor signaling pathway

GO:1901691

GO proton binding

GO:0017077

GO oxidative phosphorylation uncoupler activity

GO:0051881

GO regulation of mitochondrial membrane potential

GO:1903409

GO reactive oxygen species biosynthetic process

GO:0043114

GO regulation of vascular permeability

MP:0008762

MP embryonic lethality

D009026

MESH mortality

WIKI increased

WIKI decreased

Di(2-ethylhexyl) phthalate

2016-11-29T18:42:26

Mono(2-ethylhexyl) phthalate

2016-11-29T18:42:26

Stressor:205 pirinixic acid (WY-14,643)

2020-12-19T09:06:20

Clofibrate

2016-11-29T18:42:27

Nafenopin

2016-11-29T18:42:27

ciprofibrate

2016-11-29T18:42:27

Gemfibrozil Fibrate drug

2016-11-29T18:42:27

2020-03-31T10:24:40

PERFLUOROOCTANOIC ACID

2016-11-29T18:42:27

Bezafibrate

2016-11-29T18:42:27

Fenofibrate

2016-11-29T18:42:27

Simvastatin

2020-05-06T09:41:35

2,4-Dinitrophenol

2016-11-29T18:42:27

Carbonyl cyanide-p-trifluoromethoxyphenylhydrazone

2020-11-12T17:59:28

Carbonyl cyanide m-chlorophenyl hydrazone

2020-11-12T17:59:47

Pentachlorophenol

2020-11-12T17:59:12

Triclosan

2020-11-12T18:00:07

Emodin

2020-11-20T13:48:58

Malonoben

2020-11-27T14:43:47

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

2017-02-09T14:32:32

10116

NCBI rat

10090

NCBI mouse

WCS_9606

common toxicological species human

WCS_7955

common ecological species zebrafish

WCS_4472

common ecological species Lemna minor

WikiUser_28

Vertebrates

WikiUser_25

Wikiuser: Cyauk human and other cells in culture

WCS_35525

common ecological species crustaceans

WCS_7955

common ecological species Danio rerio

8090

NCBI Oryzias latipes

9606

NCBI Homo sapiens

Activation, PPARα

Molecular

Gene expression occurs in a coordinated fashion (Judson et al., 2012). The many observations of altered gene expression following binding of ligand to PPARα led to systematic investigations of the genomic signature that corresponds to PPARα activation (Tamura et al., 2006; Kupershmidt et al., 2010; Rosen et al., 2017; Rooney et al., 2018; Corton et al., 2020; Hill et al., 2020; Lewis et al., 2020). Specific gene with increased expression following PPARα activation include Cyp4a1, Cpt1B, and Lpl. More generally, the pathways activated include: <ul> <li>Genes involved in Metabolism of lipids and lipoproteins</li> <li>Fatty acid metabolism</li> <li>Genes involved in Fatty acid, triacylglycerol, and ketone body metabolism</li> <li>PPAR signaling pathway</li> <li>Peroxisome</li> <li>Genes involved in Cell Cycle</li> </ul> Biological state The Peroxisome Proliferator Activated receptor α (PPARα) belongs to the <a href="/wiki/index.php/Peroxisome_Proliferator_Activated_receptors_(PPARs;_NR1C)" title="Peroxisome Proliferator Activated receptors (PPARs; NR1C)">Peroxisome Proliferator Activated receptors (PPARs; NR1C)</a> steroid/thyroid/retinoid receptor superfamily of transcription factors. Biological compartments PPARα is expressed in high levels in tissues that perform significant catabolism of fatty acids (FAs), such as brown adipose tissue, liver, heart, kidney, and intestine (Michalik et al. 2006). The receptor is present also in skeletal muscle, intestine, pancreas, lung, placenta and testes (Mukherjee et al. 1997), (Schultz et al. 1999). General role in biology PPARs are activated by fatty acids and their derivatives; they are sensors of dietary lipids and are involved in lipid and carbohydrate metabolism, immune response and peroxisome proliferation (Wahli and Desvergne 1999), (Evans, Barish, & Wang, 2004). PAPRα is a also a target of hypothalamic hormone signalling and was found to play a role in embryonic development (Yessoufou and Wahli 2010). Fibrates, activators of PPARα, are commonly used to treat hypertriglyceridemia and other dyslipidemic states as they have been shown to decrease circulating lipid levels (Lefebvre et al. 2006).

Binding of ligands to PPARα is measured using binding assays in vitro and in silico, whereas the information about functional activation is derived from transactivation assays (e.g. transactivation assay with reporter gene) that demonstrate functional activation of a nuclear receptor by a specific compound. Binding of agonists within the ligand-binding site of PPARs causes a conformational change of nuclear receptor that promotes binding to transcriptional co-activators. Conversely, binding of antagonists results in a conformation that favours the binding of co-repressors (Yu and Reddy 2007), (Viswakarma et al. 2010). Transactivation assays are performed using transient or stably transfected cells with the PPARα expression plasmid and a reporter plasmid, respectively. There are also other methods that have been used to measure PPARα activity, such as the Electrophoretic Mobility Shift Assay (EMSA) or commercially available PPARα transcription factor assay kits, see Table 1. The transactivation (stable transfection) assay provides the most applicable OECD Level 2 assay (i.e. In vitro assays providing mechanistic data) aimed at identifying the initiating event leading to an adverse outcome (LeBlanc, Norris, and Kloas 2011). A recent study characterized the PPARα ligand binding domain for the purpose of next-generation metabolic disease drugs (Kamata et al. 2020). The most direct measure of this MIE is microarray profiling from large gene expression databases TG-GATEs and DrugMatrix coupled with t statistical analysis of whole genome expression profiles (Svoboda et al., 2019; Igarashi et al., 2015) From these data, A gene expression signature of 131 PPARα-dependent genes was built using microarray profiles from the livers of wild-type and PPARα-null mice. A quantitative measure of this expression signature is a measure of similarity/correlation between the PPARα signature and positive and negative test sets is provided by the Running Fisher test (Corton et al., 2020; Hill et al., 2020; Kupershmidt et al., 2010; Lewis et al., 2020; Rooney et al., 2018). A gene expression signature of 131 PPARα-dependent genes was built using microarray profiles from the livers of wild-type and PPARα-null mice. A quantitative measure of this expression signature would be a measure of similarity/correlation between the PPARα signature and positive and negative test sets is provided by the Running Fisher test (Kupershmidt et al., 2010; Rooney et al., 2018; Corton et al., 2020). For all substances, MIE activation does not rise monotonically over dose or time. These fluctuations are likely due to variations in cofactor availability or access to the site of transcription (Gaillard et al., 2006; Koppen et al., 2009; Kupershmidt et al., 2010; Ong et al., 2010; Chow et al., 2011; De Vos et al., 2011; Simon et al., 2015). . <table align="left" border="1" cellpadding="1" cellspacing="1" style="height:3px; width:100px"> <caption>Measurements of PPARα Activation</caption> <thead> <tr> <th scope="row">Method/Test</th> <th scope="col">Test Principle</th> <th scope="col">Test Environment</th> <th scope="col">Test Outcome</th> <th scope="col">Assay Type/Domain</th> </tr> </thead> <tbody> <tr> <th scope="row"> molecular modelling; docking simulation </th> <td>Computational simulation of  ligand binding </td> <td>In silico</td> <td>Prediction off binding interaction </td> <td>Quantitative virtual screeings</td> </tr> <tr> <th scope="row">Scintillation proximity binding assay</th> <td>Direct binding of ligand</td> <td>In vitro</td> <td>Identifies compouds that bind to PPARα</td> <td>Qualitative in vitro screening</td> </tr> <tr> <th scope="row">PPARα reporter gene assay</th> <td>Quantify changes in in PPARα activation via a sensitive surrogate </td> <td>In vitro, Ex vivo</td> <td>Measures changes in activity of genes linked to a PPARα receptor element</td> <td>Quantitative in vitro screening</td> </tr> <tr> <th scope="row">Electrophoretic Band Shift</th> <td>determines if a protein or protein mixture will bind to a specific DNA or RNA sequence</td> <td>In vitro</td> <td>Measures cofactor binding by changes in gel mobility</td> <td>Quantitative in vitro screening</td> </tr> <tr> <th scope="row">Microarray profiling</th> <td>Develop MIE-specific sets of gene expression biomarkers</td> <td>In vivo</td> <td>Classification of PPARα biomarker genes with statistical methods</td> <td>Quantitative in vivo screening</td> </tr> </tbody> </table>

PPARα has been identified in frog (Xenopus laevis), mouse, human, rat, fish, hamster and chicken (reviewed in (Wahli and Desvergne 1999)).

UBERON:0002107

UBERON liver

CL:0000255

CL eukaryotic cell

High High High

Bhattacharya, Nandini, Jannette M Dufour, My-Nuong Vo, Janice Okita, Richard Okita, and Kwan Hee Kim. 2005. “Differential Effects of Phthalates on the Testis and the Liver.” Biology of Reproduction 72 (3) (March): 745–54. doi:10.1095/biolreprod.104.031583. Bility, Moses T, Jerry T Thompson, Richard H McKee, Raymond M David, John H Butala, John P Vanden Heuvel, and Jeffrey M Peters. 2004. “Activation of Mouse and Human Peroxisome Proliferator-Activated Receptors (PPARs) by Phthalate Monoesters.” Toxicological Sciences : An Official Journal of the Society of Toxicology 82 (1) (November): 170–82. doi:10.1093/toxsci/kfh253. Chow, C. C., Ong, K. M., Dougherty, E. J., & Simons, S. S. (2011). Inferring mechanisms from dose-response curves. Methods Enzymol, 487, 465-483. https://doi.org/10.1016/B978-0-12-381270-4.00016-0 Corton, J. C., Hill, T., Sutherland, J. J., Stevens, J. L., & Rooney, J. (2020). A Set of Six Gene Expression Biomarkers Identify Rat Liver Tumorigens in Short-Term Assays. Toxicol Sci. https://doi.org/10.1093/toxsci/kfaa101 De Vos, D., Bruggeman, F. J., Westerhoff, H. V., & Bakker, B. M. (2011). How molecular competition influences fluxes in gene expression networks. PLoS One, 6(12), e28494. https://doi.org/10.1371/journal.pone.0028494 Dufour, Jannette M, My-Nuong Vo, Nandini Bhattacharya, Janice Okita, Richard Okita, and Kwan Hee Kim. 2003. “Peroxisome Proliferators Disrupt Retinoic Acid Receptor Alpha Signaling in the Testis.” Biology of Reproduction 68 (4) (April): 1215–24. doi:10.1095/biolreprod.102.010488. Feige, Jérôme N, Laurent Gelman, Daniel Rossi, Vincent Zoete, Raphaël Métivier, Cicerone Tudor, Silvia I Anghel, et al. 2007. “The Endocrine Disruptor Monoethyl-Hexyl-Phthalate Is a Selective Peroxisome Proliferator-Activated Receptor Gamma Modulator That Promotes Adipogenesis.” The Journal of Biological Chemistry 282 (26) (June 29): 19152–66. doi:10.1074/jbc.M702724200. Gaillard, S., Grasfeder, L. L., Haeffele, C. L., Lobenhofer, E. K., Chu, T.-M., Wolfinger, R., Kazmin, D., Koves, T. R., Muoio, D. M., Chang, C.-y., & McDonnell, D. P. (2006). Receptor-selective coactivators as tools to define the biology of specific receptor-coactivator pairs. Mol Cell, 24(5), 797-803. https://doi.org/10.1016/j.molcel.2006.10.012 Hill, T., Rooney, J., Abedini, J., El-Masri, H., Wood, C. E., & Corton, J. C. (2020). Gene Expression Thresholds Derived From Short-Term Exposures Identify Rat Liver Tumorigens. Toxicol Sci. https://doi.org/10.1093/toxsci/kfaa102 Hurst, Christopher H, and David J Waxman. 2003. “Activation of PPARalpha and PPARgamma by Environmental Phthalate Monoesters.” Toxicological Sciences : An Official Journal of the Society of Toxicology 74 (2) (August): 297–308. doi:10.1093/toxsci/kfg145. Igarashi, Y., Nakatsu, N., Yamashita, T., Ono, A., Ohno, Y., Urushidani, T., & Yamada, H. (2015). Open TG-GATEs: a large-scale toxicogenomics database. Nucleic Acids Res, 43(Database issue), D921-7. https://doi.org/10.1093/nar/gku955 Kamata S, Oyama T, Saito K, Honda A, Yamamoto Y, Suda K, Ishikawa R, Itoh T, Watanabe Y, Shibata T, Uchida K, Suematsu M, Ishii I. PPARα Ligand-Binding Domain Structures with Endogenous Fatty Acids and Fibrates. iScience. 2020;23(11):101727. 10.1016/j.isci.2020.101727 Kaya, Taner, Scott C Mohr, David J Waxman, and Sandor Vajda. 2006. “Computational Screening of Phthalate Monoesters for Binding to PPARgamma.” Chemical Research in Toxicology 19 (8) (August): 999–1009. doi:10.1021/tx050301s. Koppen, A., Houtman, R., Pijnenburg, D., Jeninga, E. H., Ruijtenbeek, R., & Kalkhoven, E. (2009). Nuclear receptor-coregulator interaction profiling identifies TRIP3 as a novel peroxisome proliferator-activated receptor gamma cofactor. Mol Cell Proteomics, 8(10), 2212-2226. https://doi.org/10.1074/mcp.M900209-MCP200 Kupershmidt, I., Su, Q. J., Grewal, A., Sundaresh, S., Halperin, I., Flynn, J., Shekar, M., Wang, H., Park, J., Cui, W., Wall, G. D., Wisotzkey, R., Alag, S., Akhtari, S., & Ronaghi, M. (2010). Ontology-based meta-analysis of global collections of high-throughput public data. PLoS One, 5(9). https://doi.org/10.1371/journal.pone.0013066 Lampen, Alfonso, Susan Zimnik, and Heinz Nau. 2003. “Teratogenic Phthalate Esters and Metabolites Activate the Nuclear Receptors PPARs and Induce Differentiation of F9 Cells.” Toxicology and Applied Pharmacology 188 (1) (April): 14–23. doi:10.1016/S0041-008X(03)00014-0. Lapinskas, Paula J., Sherri Brown, Lisa M. Leesnitzer, Steven Blanchard, Cyndi Swanson, Russell C. Cattley, and J. Christopher Corton. 2005. “Role of PPARα in Mediating the Effects of Phthalates and Metabolites in the Liver.” Toxicology 207 (1): 149–163. Le Maire, Albane, Marina Grimaldi, Dominique Roecklin, Sonia Dagnino, Valérie Vivat-Hannah, Patrick Balaguer, and William Bourguet. 2009. “Activation of RXR-PPAR Heterodimers by Organotin Environmental Endocrine Disruptors.” EMBO Reports 10 (4) (April): 367–73. doi:10.1038/embor.2009.8. LeBlanc, GA, DO Norris, and W Kloas. 2011. “Detailed Review Paper State of the Science on Novel In Vitro and In Vivo Screening and Testing Methods and Endpoints for Evaluating Endocrine Disruptors” (178). Lefebvre, Philippe, Giulia Chinetti, Jean-Charles Fruchart, and Bart Staels. 2006. “Sorting out the Roles of PPAR Alpha in Energy Metabolism and Vascular Homeostasis.” The Journal of Clinical Investigation 116 (3) (March): 571–80. doi:10.1172/JCI27989. Lewis, R. W., Hill, T., & Corton, J. C. (2020). A set of six Gene expression biomarkers and their thresholds identify rat liver tumorigens in short-term assays. Toxicology, 443, 152547. https://doi.org/10.1016/j.tox.2020.152547 Maloney, Erin K., and David J. Waxman. 1999. “Trans-Activation of PPARα and PPARγ by Structurally Diverse Environmental Chemicals.” Toxicology and Applied Pharmacology 161 (2): 209–218. Michalik, Liliane, Johan Auwerx, Joel P Berger, V Krishna Chatterjee, Christopher K Glass, Frank J Gonzalez, Paul A Grimaldi, et al. 2006. “International Union of Pharmacology. LXI. Peroxisome Proliferator-Activated Receptors.” Pharmacological Reviews 58 (4) (December): 726–41. doi:10.1124/pr.58.4.5. Mukherjee, R, L Jow, G E Croston, and J R Paterniti. 1997. “Identification, Characterization, and Tissue Distribution of Human Peroxisome Proliferator-Activated Receptor (PPAR) Isoforms PPARgamma2 versus PPARgamma1 and Activation with Retinoid X Receptor Agonists and Antagonists.” The Journal of Biological Chemistry 272 (12) (March 21): 8071–6. Ong, K. M., Blackford, J. A., Kagan, B. L., Simons, S. S., & Chow, C. C. (2010). A theoretical framework for gene induction and experimental comparisons. Proc Natl Acad Sci U S A, 107(15), 7107-7112. https://doi.org/10.1073/pnas.0911095107 Rooney, J., Hill, T., Qin, C., Sistare, F. D., & Corton, J. C. (2018). Adverse outcome pathway-driven identification of rat liver tumorigens in short-term assays. Toxicol Appl Pharmacol, 356, 99-113. https://doi.org/10.1016/j.taap.2018.07.023 Schultz, R, W Yan, J Toppari, A Völkl, J A Gustafsson, and M Pelto-Huikko. 1999. “Expression of Peroxisome Proliferator-Activated Receptor Alpha Messenger Ribonucleic Acid and Protein in Human and Rat Testis.” Endocrinology 140 (7) (July): 2968–75. doi:10.1210/endo.140.7.6858. Simon, T. W., Budinsky, R. A., & Rowlands, J. C. (2015). A model for aryl hydrocarbon receptor-activated gene expression shows potency and efficacy changes and predicts squelching due to competition for transcription co-activators. PLoS One, 10(6), e0127952. https://doi.org/10.1371/journal.pone.0127952. Staels, B., J. Dallongeville, J. Auwerx, K. Schoonjans, E. Leitersdorf, and J.-C. Fruchart. 1998. “Mechanism of Action of Fibrates on Lipid and Lipoprotein Metabolism.” Circulation 98 (19) (November 10): 2088–2093. doi:10.1161/01.CIR.98.19.2088. Svoboda, D. L., Saddler, T., & Auerbach, S. S. (2019). An Overview of National Toxicology Program’s Toxicogenomic Applications: DrugMatrix and ToxFX.  In Advances in Computational Toxicology (pp. 141-157). Springer. https://link.springer.com/chapter/10.1007/978-3-030-16443-0_8 ToxCastTM Data. “ToxCastTM Data.” US Environmental Protection Agency. <a class="external free" href="http://www.epa.gov/ncct/toxcast/data.html" rel="nofollow" target="_blank">http://www.epa.gov/ncct/toxcast/data.html</a> Vanden Heuvel, John P, Jerry T Thompson, Steven R Frame, and Peter J Gillies. 2006. “Differential Activation of Nuclear Receptors by Perfluorinated Fatty Acid Analogs and Natural Fatty Acids: A Comparison of Human, Mouse, and Rat Peroxisome Proliferator-Activated Receptor-Alpha, -Beta, and -Gamma, Liver X Receptor-Beta, and Retinoid X Rec.” Toxicological Sciences : An Official Journal of the Society of Toxicology 92 (2) (August): 476–89. doi:10.1093/toxsci/kfl014. Venkata, Nagaraj Gopisetty, Jodie a Robinson, Peter J Cabot, Barbara Davis, Greg R Monteith, and Sarah J Roberts-Thomson. 2006. “Mono(2-Ethylhexyl)phthalate and Mono-N-Butyl Phthalate Activation of Peroxisome Proliferator Activated-Receptors Alpha and Gamma in Breast.” Toxicology Letters 163 (3) (June 1): 224–34. doi:10.1016/j.toxlet.2005.11.001. Viswakarma, Navin, Yuzhi Jia, Liang Bai, Aurore Vluggens, Jayme Borensztajn, Jianming Xu, and Janardan K Reddy. 2010. “Coactivators in PPAR-Regulated Gene Expression.” PPAR Research 2010 (January). doi:10.1155/2010/250126. Wahli, Walter, and B Desvergne. 1999. “Peroxisome Proliferator-Activated Receptors: Nuclear Control of Metabolism.” Endocrine Reviews 20 (5) (October): 649–88. Wu, Bin, Jie Gao, and Ming-wei Wang. 2005. “Development of a Complex Scintillation Proximity Assay for High-Throughput Screening of PPARgamma Modulators.” Acta Pharmacologica Sinica 26 (3) (March): 339–44. doi:10.1111/j.1745-7254.2005.00040.x. Xu, Chuan, Ji-An Chen, Zhiqun Qiu, Qing Zhao, Jiaohua Luo, Lan Yang, Hui Zeng, et al. 2010. “Ovotoxicity and PPAR-Mediated Aromatase Downregulation in Female Sprague-Dawley Rats Following Combined Oral Exposure to Benzo[a]pyrene and Di-(2-Ethylhexyl) Phthalate.” Toxicology Letters 199 (3) (December 15): 323–32. doi:10.1016/j.toxlet.2010.09.015. Yessoufou, a, and W Wahli. 2010. “Multifaceted Roles of Peroxisome Proliferator-Activated Receptors (PPARs) at the Cellular and Whole Organism Levels.” Swiss Medical Weekly 140 (September) (January): w13071. doi:10.4414/smw.2010.13071. Yu, Songtao, and Janardan K Reddy. 2007. “Transcription Coactivators for Peroxisome Proliferator-Activated Receptors.” Biochimica et Biophysica Acta 1771 (8) (August): 936–51. doi:10.1016/j.bbalip.2007.01.008. AOPWiki 2016-11-29T18:41:23

2020-12-28T12:48:16

Increase, Fatty acid beta-oxidation

Increase, Fatty acid β-oxidation

Cellular

AOPWiki 2017-04-13T10:46:34

2020-12-04T15:21:51

Decrease, Coupling of oxidative phosphorylation

Decrease, Coupling of OXPHOS

Cellular

Decreased coupling of oxidative phosphorylation (OXPHOS), or uncoupling of OXPHOS, describes dissipation of protonmotive force (PMF) across the inner mitochondrial membrane (IMM) by environmental stressors. In eukaryotes, the mitochondrial electron transport chain mediates a series of redox reactions to create a PMF across the IMM. The PMF is used as energy to drive adenosine triphosphate (ATP) synthesis through phosphorylation of adenosine diphosphate (ADP). These processes are coupled and referred to as OXPHOS. A number of chemicals can dissipate the PMF, leading to uncoupling of OXPHOS. This key event describes the main outcome of the interactions between an uncoupler and the transmembrane PMF. An uncoupler can bind to a proton in the mitochondrial inter membrane space, transport the proton to the matrix side of the IMM, release the proton and move back to the inter membrane space. These processes are repeated until the transmembrane PMF is dissipated. This KE is therefore a lumped term of these processes and represents the final consequence of the interactions.

Uncoupling of oxidative phosphorylation can be indicated by reduced mitochondrial membrane potential, increased proton leak and/or increased oxygen consumption rate. <ul> <li>Mitochondrial membrane potential can be determined using ToxCast high-throughput screening bioassays such as “APR_HepG2_MitoMembPot”, “APR_Hepat_MitoFxnI”, and “APR_Mitochondrial_membrane_potential”, and the Tox21 high-throughput screening assay “tox21-mitotox-p1”.</li> <li>Mitochondrial membrane potential can also be measured using commercially available fluorescent probes such as TMRM (tetramethylrhodamine, methyl ester, perchlorate), TMRE (tetramethylrhodamine, ethyl ester, perchlorate) and JC-1 (Perry 2011).</li> <li>Proton leak and oxygen consumption rate can be measured using a high-resolution respirometry (Affourtit 2018) or a Seahorse XF analyzer (Divakaruni 2014).</li> </ul>

Taxonomic applicability domain This key event is in general considered applicable to most eukaryotes, as the mitochondrion and oxidative phosphorylation are highly conserved (Roger 2017).     Life stage applicability domain This key event is considered applicable to all life stages, as ATP synthesis by oxidative phosphorylation is an essential biological process for most living organisms.   Sex applicability domain This key event is considered sex-unspecific, as both males and females use oxidative phosphorylation as a main process to generate ATP.

CL:0000000

CL cell

High Unspecific

High

Embryo

High

Juvenile

Moderate

Adult, reproductively mature

High High High High High

Affourtit C, Wong H-S, Brand MD. 2018. Measurement of proton leak in isolated mitochondria. In Palmeira CM, Moreno AJ, eds, Mitochondrial Bioenergetics: Methods and Protocols. Springer New York, New York, NY, pp 157-170. Attene-Ramos MS, Huang R, Sakamuru S, Witt KL, Beeson GC, Shou L, Schnellmann RG, Beeson CC, Tice RR, Austin CP, Xia M. 2013. Systematic study of mitochondrial toxicity of environmental chemicals using quantitative high throughput screening. Chemical Research in Toxicology 26:1323-1332. DOI: 10.1021/tx4001754. Attene-Ramos MS, Huang RL, Michael S, Witt KL, Richard A, Tice RR, Simeonov A, Austin CP, Xia MH. 2015. Profiling of the Tox21 chemical collection for mitochondrial function to identify compounds that acutely decrease mitochondrial membrane potential. Environ Health Persp 123:49-56. DOI: 10.1289/ehp.1408642. Divakaruni AS, Paradyse A, Ferrick DA, Murphy AN, Jastroch M. 2014. Chapter Sixteen - Analysis and Interpretation of Microplate-Based Oxygen Consumption and pH Data. In Murphy AN, Chan DC, eds, Methods in Enzymology. Vol 547. Academic Press, pp 309-354. Dreier DA, Denslow ND, Martyniuk CJ. 2019. Computational in vitro toxicology uncovers chemical structures impairing mitochondrial membrane potential. J Chem Inf Model 59:702-712. DOI: 10.1021/acs.jcim.8b00433. Escher BI, Schwarzenbach RP. 2002. Mechanistic studies on baseline toxicity and uncoupling of organic compounds as a basis for modeling effective membrane concentrations in aquatic organisms. Aquatic Sciences 64:20-35. DOI: 10.1007/s00027-002-8052-2. Legradi J, Dahlberg A-K, Cenijn P, Marsh G, Asplund L, Bergman Å, Legler J. 2014. Disruption of Oxidative Phosphorylation (OXPHOS) by Hydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) Present in the Marine Environment. Environmental Science & Technology 48:14703-14711. DOI: 10.1021/es5039744. Naven RT, Swiss R, Klug-Mcleod J, Will Y, Greene N. 2012. The development of structure-activity relationships for mitochondrial dysfunction: Uncoupling of oxidative phosphorylation. Toxicol Sci 131:271-278. DOI: 10.1093/toxsci/kfs279. Perry SW, Norman JP, Barbieri J, Brown EB, Gelbard HA. 2011. Mitochondrial membrane potential probes and the proton gradient: a practical usage guide. BioTechniques 50:98-115. DOI: 10.2144/000113610. Roger AJ, Munoz-Gomez SA, Kamikawa R. 2017. The origin and diversification of mitochondria. Curr Biol 27:R1177-R1192. DOI: 10.1016/j.cub.2017.09.015. Russom CL, Bradbury SP, Broderius SJ, Hammermeister DE, Drummond RA. 1997. Predicting modes of toxic action from chemical structure: Acute toxicity in the fathead minnow (Pimephales promelas). Environ Toxicol Chem 16:948-967. DOI: <a href="https://doi.org/10.1002/etc.5620160514">https://doi.org/10.1002/etc.5620160514</a>. Schultz TW, Cronin MTD. 1997. Quantitative structure-activity relationships for weak acid respiratory uncouplers to Vibrio fisheri. Environ Toxicol Chem 16:357-360. DOI: <a href="https://doi.org/10.1002/etc.5620160235">https://doi.org/10.1002/etc.5620160235</a>. Shim J, Weatherly LM, Luc RH, Dorman MT, Neilson A, Ng R, Kim CH, Millard PJ, Gosse JA. 2016. Triclosan is a mitochondrial uncoupler in live zebrafish. J Appl Toxicol 36:1662-1667. DOI: 10.1002/jat.3311. Sugiyama Y, Shudo T, Hosokawa S, Watanabe A, Nakano M, Kakizuka A. 2019. Emodin, as a mitochondrial uncoupler, induces strong decreases in adenosine triphosphate (ATP) levels and proliferation of B16F10 cells, owing to their poor glycolytic reserve. Genes to Cells 24:569-584. DOI: <a href="https://doi.org/10.1111/gtc.12712">https://doi.org/10.1111/gtc.12712</a>. Terada H. 1990. Uncouplers of oxidative phosphorylation. Environ Health Perspect 87:213-218. DOI: 10.1289/ehp.9087213. Troger F, Delp J, Funke M, van der Stel W, Colas C, Leist M, van de Water B, Ecker GF. 2020. Identification of mitochondrial toxicants by combined in silico and in vitro studies – A structure-based view on the adverse outcome pathway. Computational Toxicology 14:100123. DOI: <a href="https://doi.org/10.1016/j.comtox.2020.100123">https://doi.org/10.1016/j.comtox.2020.100123</a>. Weatherly LM, Shim J, Hashmi HN, Kennedy RH, Hess ST, Gosse JA. 2016. Antimicrobial agent triclosan is a proton ionophore uncoupler of mitochondria in living rat and human mast cells and in primary human keratinocytes. Journal of Applied Toxicology 36:777-789. DOI: <a href="https://doi.org/10.1002/jat.3209">https://doi.org/10.1002/jat.3209</a>. Xia M, Huang R, Shi Q, Boyd WA, Zhao J, Sun N, Rice JR, Dunlap PE, Hackstadt AJ, Bridge MF, Smith MV, Dai S, Zheng W, Chu PH, Gerhold D, Witt KL, DeVito M, Freedman JH, Austin CP, Houck KA, Thomas RS, Paules RS, Tice RR, Simeonov A. 2018. Comprehensive analyses and prioritization of Tox21 10K chemicals affecting mitochondrial function by in-depth mechanistic studies. Environ Health Perspect 126:077010. DOI: 10.1289/EHP2589.  AOPWiki 2017-06-29T08:05:51

2025-11-07T05:15:58

Increase, Reactive oxygen species

Increase, ROS

Cellular

Biological State: increased reactive oxygen species (ROS) Biological compartment: an entire cell -- may be cytosolic, may also enter organelles. 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).  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).  <div> 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. 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). 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]. <Free oxygen radicals> <div> <table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none"> <tbody> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:2px solid black; vertical-align:top; width:290px"> superoxide </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:2px solid black; vertical-align:top; width:290px"> O2·- </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> hydroxyl radical </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ·OH </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> nitric oxide </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> NO· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> organic radicals </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> R· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> peroxyl radicals </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ROO· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> alkoxyl radicals </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> RO· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> thiyl radicals </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> RS· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> sulfonyl radicals </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ROS· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> thiyl peroxyl radicals </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> RSOO· </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> disulfides </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> RSSR </td> </tr> </tbody> </table> </div> <Non-radical ROS> <div> <table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none"> <tbody> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:2px solid black; vertical-align:top; width:290px"> hydrogen peroxide </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:2px solid black; vertical-align:top; width:290px"> H2O2 </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> singlet oxygen </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> 1O2 </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ozone/trioxygen </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> O3 </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> organic hydroperoxides </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ROOH </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> hypochlorite </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ClO- </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> peroxynitrite </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> ONOO- </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> nitrosoperoxycarbonate anion </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> O=NOOCO2- </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> nitrocarbonate anion </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> O2NOCO2- </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> dinitrogen dioxide </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> N2O2 </td> </tr> <tr> <td style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> nitronium </td> <td style="border-bottom:2px solid black; border-left:none; border-right:2px solid black; border-top:none; vertical-align:top; width:290px"> NO2+ </td> </tr> <tr> <td colspan="2" style="border-bottom:2px solid black; border-left:2px solid black; border-right:2px solid black; border-top:none; vertical-align:top; width:580px"> highly reactive lipid- or carbohydrate-derived carbonyl compounds </td> </tr> </tbody> </table> </div> 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 p47phox and p67phox. 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]. 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. 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]. 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]. 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 (O2−) via type I reaction and singlet oxygen (1O2) via type II reaction, as principal intermediate species in phototoxic reaction (Foote, 1991, Onoue et al. , 2009). </div>

Photocolorimetric assays (Sharma et al. 2017; Griendling et al. 2016) or through commercial kits purchased from specialized companies. Yuan, Yan, et al., (2013) described ROS monitoring by using H2-DCF-DA, a redox-sensitive fluorescent dye. Briefly, the harvested cells were incubated with H2-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. Lipid peroxidation (LPO) can be measured as an indicator of oxidative stress damage Yen, Cheng Chien, et al., (2013). 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. 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). <div> <Direct detection> Many fluorescent compounds can be used to detect ROS, some of which are specific, and others are less specific. ・ROS can be detected by fluorescent probes such as p-methoxy-phenol derivative [Ashoka et al., 2020]. ・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]. ・ROS in the blood can be detected using superparamagnetic iron oxide nanoparticles (SPION)-based biosensor [Lee et al., 2020]. ・Hydrogen peroxide (H2O2) can be detected with a colorimetric probe, which reacts with H2O2 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. ・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]. ・Singlet oxygen can be measured by monitoring the bleaching of p-nitrosodimethylaniline at 440 nm using a spectrophotometer with imidazole as a selective acceptor of singlet oxygen [Onoue et al., 2014]. <Indirect Detection> 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. </div>

ROS is a normal constituent found in all organisms, lifestages, and sexes.

UBERON:0000062

UBERON organ

CL:0000000

CL cell

High Unspecific High Mixed

High

All life stages

High Moderate Moderate Moderate High High High

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 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 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 Bedard, Karen, and Karl-Heinz Krause. 2007. “The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology.” Physiological Reviews 87 (1): 245–313. Bisht, Shilpa, Muneeb Faiq, Madhuri Tolahunase, and Rima Dada. 2017. “Oxidative Stress and Male Infertility.” Nature Reviews. Urology 14 (8): 470–85. 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. 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. 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. 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. 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. 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. 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. 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 Foote CS. Definition of type I and type II photosensitized oxidation. Photochem Photobiol. 1991;54:659. 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 Go, Y. M. and Jones, D. P. (2013). "The redox proteome." J Biol Chem 288(37): 26512-26520. 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. 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. 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. 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. 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. 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 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. 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 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 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 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. 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 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. 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. 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. 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. Onoue S, Seto Y, Gandy G, Yamada S. Drug-induced phototoxicity; an early in vitro identification of phototoxic potential of new drug entities in drug discovery and development. Current drug safety. 2009;4:123-36. Onoue S, Tsuda Y. Analytical studies on the prediction of photosensitive/phototoxic potential of pharmaceutical substances. Pharmaceutical research. 2006;23:156-64. 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. Parrish, A. R. 2010. “2.27 - Hypoxia/Ischemia Signaling.” In Comprehensive Toxicology (Second Edition), edited by Charlene A. McQueen, 529–42. Oxford: Elsevier. PCPC. PCPC 2014 safety evaluation guidelines; Chapter 7: Evaluation of Photoirritation and Photoallergy potential. Personal Care Products Council; 2014. Ramos, M. F. P., et al. (2018). "Xanthine oxidase inhibitors and sepsis." Int J Immunopathol Pharmacol. 32:2058738418772210. doi:10.1177/2058738418772210 Ravanat, J. L., et al. (2014). "Radiation-mediated formation of complex damage to DNA: a chemical aspect overview." Br J Radiol 87(1035): 20130715. 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 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. 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. 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 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 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 Wang, X., et al. (2013). "Imaging ROS signaling in cells and animals." Journal of molecular medicine 91(8): 917-927. 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. 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. 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 AOPWiki 2016-11-29T18:41:29

2025-06-12T01:27:08

Decrease, Vascular integrity

Tissue

A decrease in vascular integrity refers to the breakdown or functional loss of endothelial barrier properties within the vasculature. Under normal conditions, endothelial cells form a continuous, semi-permeable barrier that regulates the exchange of solutes, plasma, and cells between blood and tissue compartments. This KE is characterized by disruption of tight and adherens junctions, cytoskeletal contraction, or endothelial cell death, resulting in increased vascular permeability, leakage of plasma constituents, and, in severe cases, hemorrhage or edema. In fish embryos, this manifests as pericardial edema, yolk sac swelling, or intracranial hemorrhage, often preceding hemopericardium (Event 2383). Mechanistically, decreased vascular integrity arises from ATP depletion, oxidative stress, or direct mitochondrial dysfunction in endothelial cells, consistent with perturbations observed after PPARα activation.

In vivo (fish embryos): <ul> <li> Fluorescent tracer leakage assay (microangiography): Injection of high-molecular-weight FITC- or TexasRed-dextran into circulation followed by time-lapse imaging to quantify extravasation. <ul> <li> Quantitative metric: Extravasation index (EI = F_extravascular / F_intravascular), leakage rate constant (kₗₑₐₖ), or % fluorescence outside vessels. </li> </ul> </li> <li> Evans Blue / sulforhodamine B uptake: Quantitative dye extraction or imaging to measure plasma leakage. </li> <li> Pericardial or tissue edema scoring: Morphometric assessment of pericardial area or edema volume using image analysis. </li> <li> Hemorrhage frequency or severity index: % embryos showing localized bleeding, particularly near the heart or brain. </li> </ul> In vitro (endothelial models): <ul> <li> Trans-Endothelial Electrical Resistance (TEER): Measures ionic conductance across endothelial monolayers; expressed as % decrease from baseline (Ω·cm²). </li> <li> Macromolecular permeability (Papp): Apparent permeability coefficient using fluorescent dextrans in Transwell systems. </li> <li> Immunostaining of junctional markers: Quantification of VE-cadherin or ZO-1 continuity index (proportion of intact junction length). </li> </ul>

The KE applies broadly to vertebrates with closed circulatory systems, particularly during vascular development. Evidence is strongest for teleost fish embryos, where vascular permeability and integrity can be directly visualized in vivo. Mechanistic conservation of endothelial junctional signaling (VE-cadherin, claudin-5, occludin) supports extrapolation to mammals, including humans. Most sensitive life stages: embryonic and early larval. Applicable to both sexes.

UBERON:0001981

UBERON blood vessel

Not Specified Unspecific

High

Embryo

Moderate

Juvenile

High Moderate Moderate

AOPWiki 2025-10-29T17:07:24

2025-11-07T05:42:38

Increase, Hemopericardium

Organ

AOPWiki 2025-10-29T17:05:33

2025-10-29T17:05:33

Increase, Early Life Stage Mortality

Individual

Increased early life stage mortality refers to an increase in the number of individuals dying in an experimental replicate group or in a population over a specific period of time. In Birds: Early life stage mortality occurs at any stage in development prior to birth/hatch and is considered embryolethal. In Fishes: Early Life Stage Mortality refers to death prior to yolk sac adsorption and swim-up.

In birds it may be identified as failure to hatch or lack of movement within the egg when candled; heartbeat monitors are available for identifying viable avian and reptillian eggs (ex. Avitronic's Buddy monitor). In mammals, stillborn or mummified offspring, or an increased rate of resorptions early in pregnancy are all considered embryolethal, and can be detected using ultra-high frequency ultrasound (30-70 MHz; a.k.a. ultrasound biomicroscopy) (Flores et al. 2014). In fishes, mortality is typically measured by observation. Lack of any heart beat, gill movement, and body movement are typical signs of death used in the evaluation of mortality.

All members of the subphylum vertebrata are susceptible to early life stage death (Weinstein 1999).

High Unspecific

High

Embryo

High

Foetal

High

Development

High

1. Flores, L.E., Hildebrandt, T.B., Kuhl, A.A., and Drews, B. (2014) Early detection and staging of spontaneous embryo resorption by ultrasound biomicroscopy in murine pregnancy. Reproductive Biology and Endocrinology 12(38). DOI: 10.1186/1477-7827-12-38 2. Weinstein, B. M. (1999). What guides early embryonic blood vessel formation? Dev. Dyn. 215(1), 2-11. Doering, J.A.; Giesy, J.P.; Wiseman S.; Hecker, M. (2013). Predicting the sensivity of fishes to dioxin-like compounds: possible role of the aryl hydrocarbon receptor (AhR) ligand binding domain. Environmental Science and Pollution Research. 20 (3), 1219-1224. AOPWiki 2016-11-29T18:41:28

2018-03-22T10:23:28

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AOPWiki 2025-10-30T04:18:44

2025-10-30T04:18:44

<upstream-id>27f05058-9c55-45e5-8490-9ab912ad3743</upstream-id> <downstream-id>5a6d88fa-9551-4269-8b45-ed946c2694be</downstream-id>

AOPWiki 2025-10-30T04:18:56

2025-10-30T04:18:56

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AOPWiki 2025-02-25T11:13:29

2025-02-25T11:13:29

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AOPWiki 2025-10-30T04:28:24

2025-10-30T04:28:24

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AOPWiki 2025-10-30T04:19:29

2025-10-30T04:19:29

<upstream-id>7746924d-79b8-4848-8144-5bb260e0b213</upstream-id> <downstream-id>fdb6b827-7558-496e-b54c-9e2652c5edc1</downstream-id>

AOPWiki 2025-10-30T04:19:36

2025-10-30T04:19:36

Peroxisome proliferator-activated receptor alpha activation leading to early life stage mortality via increased reactive oxygen species production

PPARα activation leading to ELS mortality via ROS

Allie Always

You Song Norwegian Institute for Water Research (NIVA), Oslo, Norway

BY-SA

2.7

This Adverse Outcome Pathway (AOP) describes the mechanistic sequence linking activation of peroxisome proliferator-activated receptor alpha (PPARα) to early life stage mortality in aquatic vertebrates. Activation of PPARα increases fatty acid β-oxidation, which disrupts oxidative phosphorylation (OXPHOS) coupling and elevates reactive oxygen species (ROS) production. The resulting mitochondrial dysfunction and oxidative stress decrease vascular integrity, induce hemopericardium, and culminate in early developmental mortality. The AOP integrates well-established molecular mechanisms of energy metabolism with observable developmental endpoints in fish embryos. It provides a biologically coherent framework to assess developmental toxicity of PPARα agonists, including per- and polyfluoroalkyl substances (PFAS) and fibrates, supporting new approach methodologies (NAMs), read-across, and next-generation risk assessment applications. The AOP was developed to capture the conserved mitochondrial and oxidative stress mechanisms underlying developmental toxicity following PPARα activation. Chemicals such as PFAS, phthalates, and fibrates activate PPARα, enhancing fatty acid oxidation and increasing ROS generation. Disruption of mitochondrial coupling and energy depletion leads to vascular leakage and cardiac defects that contribute to embryo lethality. This AOP builds on existing AOPs describing PPARα activation (Event 227) and oxidative stress (Event 1115) to form a metabolism-centered AOP network relevant to fish early life stages.

A systematic evidence-gathering strategy was applied to identify and evaluate studies linking key events (KEs) and key event relationships (KERs): <ul> <li> Databases searched: PubMed, AOP-Wiki, OECD AOP-KB, Web of Science (2010–2025). </li> <li> Search terms: PPARα activation, β-oxidation, OXPHOS, ROS, ATP depletion, vascular integrity, hemopericardium, mortality, zebrafish, PFAS, fibrate. </li> <li> Inclusion criteria: Experimental or mechanistic studies demonstrating sequential or causal linkage between KEs, preferably with dose–response or temporal concordance data. </li> <li> Approach: Literature screening and expert evaluation to identify essentiality, biological plausibility, and empirical support consistent with OECD AOP development guidelines (2018). </li> </ul>

Fibrates are ligands of PPARα (Staels et al. 1998). Phthalates MHEP (CAS 4376-20-9) directly binds in vitro to PPARα (Lapinskas et al. 2005) and activates this receptor in transactivation assays PPARα (Lapinskas et al. 2005), (Maloney and Waxman 1999), (Hurst and Waxman 2003), (Bility et al. 2004), (Lampen, Zimnik, and Nau 2003), (Venkata et al. 2006) ]. DEHP (CAS 117-81-7) has not been found to bind and activate PPARα (Lapinskas et al. 2005), (Maloney and Waxman 1999). However, the recent studies shown activation of PPARα (ToxCastTM Data). Notably, PPARα are responsive to DEHP in vitro as they are translocated to the nucleus (in primary Sertoli cells) (Dufour et al. 2003), (Bhattacharya et al. 2005). Expression of PPARα [mRNA and protein] has been reported to be also modulated by phthtalates: (to be up-regulated in vivo upon DEHP treatment (Xu et al. 2010) and down-regulated by Diisobutyl phthalate (DiBP) (Boberg et al. 2008)). Perfluorooctanoic Acid (PFOA) is known to activate PPARα (Vanden Heuvel et al. 2006). Organotin Tributyltin (TBT) activates all three heterodimers of PPAR with RXR, primarily through its interaction with RXR (le Maire et al. 2009)

Poor early life stage survival is an endpoint of major relevance to environmental regulators, as it is likely to lead to population decline.  Early-life stage, acute and chronic test guidelines have been established by the Organisation for Economic Co-operation and Development (OECD), U.S. Environmental Protection Agency (EPA) and Environment and Climate Change Canada (ECCC), and are currently used in risk assessments to set limits for safe exposures.  Aquatic test guidlines are most prevalent and include OECD210, OECD229, EPA850.1400 and ECCC  EPS 1/RM/28 for fish and OECD241 for frogs.

adjacent

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Not Specified adjacent

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Not Specified adjacent

Not Specified

Not Specified Unspecific

Not Specified

Embryo

Not Specified

Juvenile

Not Specified

The AOP demonstrates strong biological plausibility, particularly for the upstream molecular and cellular events. Empirical support is robust for PPARα activation, β-oxidation increase, and ROS formation, which are consistently observed across multiple vertebrate species and chemical stressors. Empirical evidence linking oxidative stress to vascular and cardiac outcomes is moderate but reproducible. Quantitative understanding of the relationships between intermediate and apical events is developing, with growing omics and imaging datasets supporting semi-quantitative modeling. The AOP has moderate to high overall confidence and is suitable for screening-level hazard identification and mechanistic read-across. <table> <thead> <tr> <th>Aspect</th> <th>Applicability</th> </tr> </thead> <tbody> <tr> <td>Taxa</td> <td>Teleost fish (e.g., Danio rerio, Oryzias latipes); mechanistic conservation across vertebrates.</td> </tr> <tr> <td>Life stage</td> <td>Embryonic and early larval development.</td> </tr> <tr> <td>Sex</td> <td>Non-sex-specific (early life stage).</td> </tr> <tr> <td>Biological systems</td> <td>Liver (metabolic activation), mitochondria (energy homeostasis), and cardiovascular system (vascular integrity).</td> </tr> </tbody> </table>

<table> <thead> <tr> <th>Key Event</th> <th>Essentiality Evidence</th> <th>Type of Evidence</th> </tr> </thead> <tbody> <tr> <td>Event 227: PPARα activation (MIE)</td> <td>Knockdown or knockout of ppara in zebrafish blocks β-oxidation induction and oxidative stress after exposure to PPARα agonists.</td> <td>Direct</td> </tr> <tr> <td>Event 1312: Fatty acid β-oxidation (Increase)</td> <td>Inhibition of β-oxidation (e.g., by etomoxir) reduces ROS formation and prevents cardiac toxicity.</td> <td>Direct</td> </tr> <tr> <td>Event 1446: Coupling of OXPHOS (Decrease)</td> <td>Reduced mitochondrial membrane potential and respiratory coupling precede ROS accumulation and ATP depletion.</td> <td>Direct</td> </tr> <tr> <td>Event 1115: ROS (Increase)</td> <td>ROS scavengers (e.g., N-acetylcysteine) or antioxidants mitigate vascular and cardiac damage, supporting causality.</td> <td>Direct</td> </tr> <tr> <td>Event 2384: Vascular integrity (Decrease)</td> <td>Vascular permeability assays correlate with ROS burden and cardiac edema severity.</td> <td>Indirect</td> </tr> <tr> <td>Event 2383: Hemopericardium (Increase)</td> <td>Reversible upon antioxidant treatment or metabolic rescue.</td> <td>Indirect</td> </tr> <tr> <td>Event 947: Early life stage mortality (Increase)</td> <td>Occurs downstream of cumulative mitochondrial and vascular dysfunction.</td> <td>Outcome</td> </tr> </tbody> </table>

<h4>Biological Plausibility</h4> High. The mechanistic sequence aligns with established mitochondrial physiology: excessive fatty acid oxidation leads to electron leakage from the respiratory chain, ROS formation, oxidative damage to vascular endothelium, and developmental cardiac failure. The sequence has strong mechanistic coherence across vertebrates. <h4>Empirical Support</h4> Moderate to high. Multiple independent studies in zebrafish embryos and mammalian hepatocytes demonstrate: <ul> <li> PPARα activation induces β-oxidation genes (acox1, cpt1a, echs1). </li> <li> OXPHOS uncoupling and ROS increase within 24–48 hours of exposure. </li> <li> ROS elevation precedes vascular collapse and hemopericardium in fish embryos. </li> <li> Temporal and dose concordance between intermediate and apical events is well supported. </li> </ul> <h4>Quantitative Understanding</h4> Moderate. Dose–response data exist for several KEs, including ROS induction and mortality. Transcriptomic and metabolomic data enable modeling of upstream relationships, but quantitative linkage between oxidative stress and vascular integrity remains semi-quantitative.

<table> <thead> <tr> <th>Modulating Factor (MF)</th> <th>Influence or Outcome</th> <th>KER(s) Involved</th> </tr> </thead> <tbody> <tr> <td>Antioxidant capacity</td> <td>High antioxidant levels (e.g., glutathione, superoxide dismutase, catalase) can buffer ROS accumulation, mitigating oxidative stress and reducing vascular and cardiac toxicity.</td> <td>ROS (increase) → Vascular integrity (decrease); ROS (increase) → Hemopericardium (increase)</td> </tr> <tr> <td>Oxygen availability</td> <td>Hypoxic or low-oxygen conditions decrease mitochondrial ROS generation, attenuating downstream vascular effects, while hyperoxia enhances ROS formation and vascular damage.</td> <td>OXPHOS coupling (decrease) → ROS (increase)</td> </tr> <tr> <td>Nutritional and metabolic status</td> <td>Lipid-rich diets or high energy reserves enhance fatty acid β-oxidation and PPARα activation, increasing ROS and developmental toxicity risk.</td> <td>PPARα activation (increase) → Fatty acid β-oxidation (increase); β-oxidation (increase) → OXPHOS coupling (decrease)</td> </tr> <tr> <td>Temperature</td> <td>Elevated temperature increases metabolic rate and mitochondrial respiration, enhancing ROS production and sensitivity to mitochondrial uncoupling.</td> <td>OXPHOS coupling (decrease) → ROS (increase)</td> </tr> <tr> <td>Chemical lipophilicity</td> <td>Highly lipophilic compounds bioaccumulate in lipid-rich tissues, leading to stronger PPARα activation and more pronounced metabolic and oxidative effects.</td> <td>PPARα activation (increase) → β-oxidation (increase)</td> </tr> <tr> <td>Developmental stage</td> <td>Early embryonic stages are more susceptible due to immature antioxidant defenses and higher mitochondrial activity.</td> <td>ROS (increase) → Vascular integrity (decrease); Vascular integrity (decrease) → Hemopericardium (increase)</td> </tr> <tr> <td>Mitochondrial density and activity</td> <td>Tissues with high mitochondrial content (e.g., heart, liver) are more vulnerable to OXPHOS disruption and oxidative injury.</td> <td>OXPHOS coupling (decrease) → ROS (increase); ROS (increase) → Vascular integrity (decrease)</td> </tr> <tr> <td>Exposure duration and timing</td> <td>Prolonged or early developmental exposures amplify cumulative ROS burden and downstream damage, while short, late exposures may be reversible.</td> <td>Across all KERs—temporal accumulation enhances downstream outcomes</td> </tr> <tr> <td>Chemical co-exposure (e.g., PPARγ or CAR agonists)</td> <td>May synergistically amplify or modulate PPARα-driven metabolic changes and oxidative stress.</td> <td>PPARα activation (increase) → downstream metabolic and ROS pathways</td> </tr> </tbody> </table>

While no fully parameterized quantitative AOP model exists, several dose–response relationships are established: <ul> <li> ROS levels above ~2× baseline associate with mitochondrial uncoupling and decreased ATP. </li> <li> A ≥40% reduction in ATP or mitochondrial potential predicts vascular leakage onset. </li> <li> Hemopericardium incidence correlates with ROS intensity and exposure concentration (e.g., EC50 ~50–100 µM PFOA-equivalents). </li> </ul>

<ul> <li> Supports chemical read-across and prioritization of PPARα agonists for developmental toxicity screening. </li> <li> Provides mechanistic context for non-animal test methods assessing mitochondrial and oxidative stress pathways. </li> <li> Applicable for Adverse Outcome Network integration with hepatic steatosis and mitochondrial dysfunction AOPs. </li> <li> Facilitates NGRA and IATA development focused on energy metabolism perturbation and oxidative stress biomarkers. </li> </ul>

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