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:15422

CHEBI ATP

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:0006754

GO ATP 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

WCS_7955

common ecological species Danio rerio

8090

NCBI Oryzias latipes

9606

NCBI Homo sapiens

WikiUser_28

Vertebrates

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

Decrease, Adenosine triphosphate pool

Decrease, ATP pool

Cellular

Decreased adenosine triphosphate (ATP) pool describes the loss of balance between ATP synthesis and ATP consumption, leading to reduced total ATP. As a primary form of biological energy, ATP is used by many biological processes (Bonora 2012). Decrease in ATP level normally attributes to metabolic disorders in major ATP synthetic pathways, such as mitochondrial oxidative phosphorylation, fatty acid β-oxidation, glycolysis and plant photophosphorylation.

-The ATP pool in cells or tissue can be quantified using a well-established ATP bioluminescent assay (Lemasters 1978; Wibom 1990). Assay principles: ATP can react with luciferase and luciferin from firefly and the luminescence emitted from the reaction is proportional to the ATP concentration:   ATP + D-Luciferin + O2 è Oxyluciferin + AMP + PPi + CO2 + Light -ToxCast high-throughput screening bioassays, such as “NCCT_HEK293T_CellTiterGLO” and “NIS_HEK293T_CTG_Cytotoxicity” can be used to measure this KE.

Taxonomic applicability domain This key event is in general considered applicable to all eukaryotes utilizing ATP as a direct source of energy and signaling molecule.   Life stage applicability domain This key event is considered applicable to all life stages, as all developmental stages require energy supply to maintain necessary physiological processes.   Sex applicability domain This key event is considered sex-unspecific, as both males and females use ATP as an essential energy molecule.

CL:0000000

CL cell

High Unspecific

High

Embryo

High

Juvenile

Moderate

Adult, reproductively mature

High High High High High

Bonora M, Patergnani S, Rimessi A, De Marchi E, Suski JM, Bononi A, Giorgi C, Marchi S, Missiroli S, Poletti F, Wieckowski MR, Pinton P. 2012. ATP synthesis and storage. Purinergic Signalling 8:343-357. DOI: 10.1007/s11302-012-9305-8. Lemasters JJ, Hackenbrock CR. 1978. [4] Firefly luciferase assay for ATP production by mitochondria. Methods in Enzymology. Vol 57. Academic Press, pp 36-50. Wibom R, Lundin A, Hultman E. 1990. A sensitive method for measuring ATP-formation in rat muscle mitochondria. Scandinavian Journal of Clinical and Laboratory Investigation 50:143-152. DOI: 10.1080/00365519009089146.  AOPWiki 2020-04-30T12:42:35

2021-06-14T13:40:17

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

<upstream-id>f4b29ba8-b514-44a0-b72d-af94b1f4a6e0</upstream-id> <downstream-id>2b143a7e-5d64-49ce-bd99-d2c61999c538</downstream-id>

AOPWiki 2025-10-30T04:18:44

2025-10-30T04:18:44

<upstream-id>2b143a7e-5d64-49ce-bd99-d2c61999c538</upstream-id> <downstream-id>2b342cf9-a945-4e87-9b3d-4749466a8b1a</downstream-id>

AOPWiki 2025-10-30T04:18:56

2025-10-30T04:18:56

<upstream-id>2b342cf9-a945-4e87-9b3d-4749466a8b1a</upstream-id> <downstream-id>00164ecb-eea6-4e1a-860b-a4343d7d5a6c</downstream-id> This key event relationship describes the dissipation of protonmotive force across the inner mitochondrial membrane by uncouplers (uncoupling of oxidative phosphorylation), leading to reduced total adenosine triphosphate (ATP) pool in cells or organisms.

The overall evidence supporting Relationship 2203 is considered high.

The biological plausibility of Relationship 2203 is considered high. Rationale: In eukaryotic cells, the major metabolic pathways responsible for ATP production are OXPHOS, citric acid (TCA) cycle, glycolysis and photosynthesis. Oxidative phosphorylation is much (theoretically 15-18 times) more efficient than the rest due to high energy derived from oxygen during aerobic respiration (Schmidt-Rohr 2020). As the ATP level is relatively balanced between production and consumption (Bonora 2012), ATP depletion is a plausible consequence of reduced ATP synthetic efficiency following uncoupling of OXPHOS.

The empirical support of Relationship 2203 is considered high. Rationale: The majority of relevant studies show good incidence, temporal and/or dose concordance in different organisms and cell types after exposure to known uncouplers, with relatively few exceptions. Evidence: <ul> <li>Temporal concordance: Exposure of zebrafish embryos to 0.5 µM of the classical uncoupler 2,4-DNP led to significantly uncoupling of OXPHOS after 21h, whereas significant reduction in ATP was only observed after 45h (Bestman 2015). </li> <li>Dose concordance: The uncoupler triclosan induced significant uncoupling of OXPHOS in zebrafish embryos at 15 µM, whereas higher (30 µM) concentration was required to caused significant ATP depletion  (Shim 2016).</li> <li>Dose concordance: Exposure to 1 µM of of the uncoupler CCCP led to 40% uncoupling of OXPHOS in rat RBL-2H3 cells, whereas the same magnitude of effect for ATP reduction required 1.6 µM of CCCP (Weatherly 2016).</li> <li>Dose concordance: Exposure to 10 µM of the uncoupler triclosan caused significant uncoupling of OXPHOS in rat RBL-2H3 cells, whereas significant reduction in ATP was observed at a higher concentration (30 µM)  (Weatherly 2018).</li> <li>Dose concordance: Significant effect on uncoupling of OXPHOS required  2 µM FCCP, whereas a significant reduction in ATP required 20 µM FCCP in human RD cells  (Kuruvilla 2003).</li> <li>Incidence concordance: In human colon cancer cells (SW480), exposure to 150 µM of the uncoupler flavanoid morin caused 60% reduction in MMP, whereas only around 35% decrease in ATP  (Sithara 2017).</li> <li>Incidence concordance: Exposure of rat RBL-2H3 cells to 10 µM  of the uncoupler triclosan led to 50% uncoupling of OXPHOS, whereas only 40% reduction in ATP (Weatherly 2016).</li> <li>Incidence concordance: Exposure to 5 µM of the uncoupler CCCP caused 71% uncoupling of OXPHOS, whereas only 64% reduction of ATP in human HL-60 cells (Sweet 1999).</li> <li>Incidence concordance: Exposure of human HeLa cells to 50 µM of the uncoupler CCCP for 1h led to 77% uncoupling of OXPHOS and 25% reduction in ATP (Koczor 2009).</li> <li>Incidence concordance: Exposure of the nematode Caenorhabditis elegans to 50 µM Arsenite for 1h led to approximately 45% uncoupling of OXPHOS and 20% reduction in ATP (Luz 2016).</li> </ul>

<ul> <li style="text-align:justify">A significant decrease followed by a significant increase in total ATP was observed in human RD cells during a 48h exposure to the uncoupler FCCP (Kuruvilla 2003), possibly due to the enhancement of other ATP synthetic pathways (e.g., glycolysis) as a compensatory action to impaired OXPHOS (Jose 2011</li> </ul>

The quantitative understanding of Relationship 2203 is high. Rationale: Multiple mathematical models have been developed for describing the quantitative relationships between uncoupling of OXPHOS and ATP synthesis in vertebrates (Beard 2005; Schmitz 2011; Heiske 2017; Kubo 2020). These models, however, are highly complex metabolic or systems biological models and warrant further simplification to be used for this AOP.

A regression based quantitative response-response relationship between uncoupling of OXPHOS and ATP depletion was proposed for the crustacean Daphnia magna under UVB stress (Song 2020).

<ul> <li style="text-align:justify">It is known that mild uncoupling of oxidative phosphorylation can enhance the activity of the mitochondrial electron transport chain to produce more ATP, and/or activate other ATP synthetic pathways (e.g., glycolysis) as a compensatory action to impaired OXPHOS (Jose 2011).</li> </ul>

High Unspecific

High

Embryo

High

Juvenile

High High High High

Taxonomic applicability Relationship 2203 is considered applicable to eukaryotes, as mitochondrial oxidative phosphorylation and ATP synthesis are highly conserved in these organisms. Uncoupling of oxidative phosphorylation leading to ATP depletion is a well-documented relationship in many taxa, such as human, rodents and fish.   Sex applicability Relationship 2203 is considered applicable to all genders, as mitochondrial oxidative phosphorylation and ATP synthesis are fundamental biological processes and are not sex-pecific.   Life-stage applicability Relationship 2203 is considered applicable to all life-stages, as mitochondrial oxidative phosphorylation and ATP synthesis are essential energy production processes for maintaining basic biological activities.

Beard DA. 2005. A biophysical model of the mitochondrial respiratory system and oxidative phosphorylation. PLOS Computational Biology 1:e36. DOI: 10.1371/journal.pcbi.0010036. Bestman JE, Stackley KD, Rahn JJ, Williamson TJ, Chan SS. 2015. The cellular and molecular progression of mitochondrial dysfunction induced by 2,4-dinitrophenol in developing zebrafish embryos. Differentiation 89:51-69. DOI: 10.1016/j.diff.2015.01.001. Bonora M, Patergnani S, Rimessi A, De Marchi E, Suski JM, Bononi A, Giorgi C, Marchi S, Missiroli S, Poletti F, Wieckowski MR, Pinton P. 2012. ATP synthesis and storage. Purinergic Signalling 8:343-357. DOI: 10.1007/s11302-012-9305-8. Heiske M, Letellier T, Klipp E. 2017. Comprehensive mathematical model of oxidative phosphorylation valid for physiological and pathological conditions. The FEBS Journal 284:2802-2828. DOI: <a href="https://doi.org/10.1111/febs.14151">https://doi.org/10.1111/febs.14151</a>. Jose C, Bellance N, Rossignol R. 2011. Choosing between glycolysis and oxidative phosphorylation: A tumor's dilemma? Biochimica et Biophysica Acta (BBA) - Bioenergetics 1807:552-561. DOI: <a href="https://doi.org/10.1016/j.bbabio.2010.10.012">https://doi.org/10.1016/j.bbabio.2010.10.012</a>. Koczor CA, Shokolenko IN, Boyd AK, Balk SP, Wilson GL, Ledoux SP. 2009. Mitochondrial DNA damage initiates a cell cycle arrest by a Chk2-associated mechanism in mammalian cells. J Biol Chem 284:36191-36201. DOI: 10.1074/jbc.M109.036020. Kubo S, Niina T, Takada S. 2020. Molecular dynamics simulation of proton-transfer coupled rotations in ATP synthase FO motor. Scientific Reports 10:8225. DOI: 10.1038/s41598-020-65004-1. Kuruvilla S, Qualls CW, Jr., Tyler RD, Witherspoon SM, Benavides GR, Yoon LW, Dold K, Brown RH, Sangiah S, Morgan KT. 2003. Effects of minimally toxic levels of carbonyl cyanide P-(trifluoromethoxy) phenylhydrazone (FCCP), elucidated through differential gene expression with biochemical and morphological correlations. Toxicol Sci 73:348-361. DOI: 10.1093/toxsci/kfg084. Luz AT, Godebo TR, Bhatt DP, Ilkayeva OR, Maurer LL, Hirschey MD, Meyer JN. 2016. Arsenite Uncouples Mitochondrial Respiration and Induces a Warburg-Like Effect in Caenorhabditis elegans. Toxicol Sci 154:195-195. DOI: 10.1093/toxsci/kfw185. Schmidt-Rohr K. 2020. Oxygen is the high-energy molecule powering complex multicellular life: fundamental corrections to traditional bioenergetics. ACS Omega 5:2221-2233. DOI: 10.1021/acsomega.9b03352. Schmitz JPJ, Vanlier J, van Riel NAW, Jeneson JAL. 2011. Computational modeling of mitochondrial energy transduction.  39:363-377. DOI: 10.1615/CritRevBiomedEng.v39.i5.20. 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. Sithara T, Arun KB, Syama HP, Reshmitha TR, Nisha P. 2017. Morin inhibits proliferation of SW480 colorectal cancer cells by inducing apoptosis mediated by reactive oxygen species formation and uncoupling of Warburg effect. Frontiers in Pharmacology 8. DOI: 10.3389/fphar.2017.00640. Song Y, Xie L, Lee Y, Tollefsen KE. 2020. De novo development of a quantitative adverse outcome pathway (qAOP) network for ultraviolet B (UVB) radiation using targeted laboratory tests and automated data mining. Environmental Science & Technology 54:13147-13156. DOI: 10.1021/acs.est.0c03794. Sweet S, Singh G. 1999. Changes in mitochondrial mass, membrane potential, and cellular adenosine triphosphate content during the cell cycle of human leukemic (HL-60) cells. Journal of Cellular Physiology 180:91-96. DOI: <a href="https://doi.org/10.1002/(SICI)1097-4652(199907)180:1">https://doi.org/10.1002/(SICI)1097-4652(199907)180:1</a><91::AID-JCP10>3.0.CO;2-6. Weatherly LM, Nelson AJ, Shim J, Riitano AM, Gerson ED, Hart AJ, de Juan-Sanz J, Ryan TA, Sher R, Hess ST, Gosse JA. 2018. Antimicrobial agent triclosan disrupts mitochondrial structure, revealed by super-resolution microscopy, and inhibits mast cell signaling via calcium modulation. Toxicol Appl Pharmacol 349:39-54. DOI: 10.1016/j.taap.2018.04.005. 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>. AOPWiki 2020-11-12T17:57:43

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Peroxisome proliferator-activated receptor alpha activation leading to early life stage mortality via reduced adenosine triphosphate

PPARα activation leading to ELS mortality via reduced ATP

Agnes Aggy

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

BY-SA

2.7

This Adverse Outcome Pathway (AOP) describes the mechanistic linkage between activation of peroxisome proliferator-activated receptor alpha (PPARα) and increased mortality during early developmental stages in fish. The molecular initiating event (MIE) involves chemical activation of PPARα, leading to enhanced fatty acid β-oxidation, disrupted oxidative phosphorylation (OXPHOS) coupling, ATP depletion, loss of vascular integrity, hemopericardium, and ultimately early life stage mortality. This AOP integrates molecular, biochemical, and apical endpoints relevant to energy metabolism and cardiovascular development. It provides a mechanistically coherent framework for understanding developmental toxicity of peroxisome proliferators, including certain per- and polyfluoroalkyl substances (PFAS), and supports application of new approach methodologies (NAMs) and read-across strategies in ecological risk assessment. This AOP was developed to capture the conserved mitochondrial and metabolic perturbations following PPARα activation observed in multiple species. Peroxisome proliferators, including PFAS and phthalates, activate PPARα and induce transcriptional programs that increase β-oxidation of fatty acids. Excessive β-oxidation perturbs mitochondrial homeostasis, resulting in oxidative stress, ATP depletion, and vascular defects. These mechanisms are consistent with observed early life stage lethality in zebrafish and other fish models exposed to PPARα agonists. The AOP contributes to the expanding network of metabolism-centered AOPs and provides biological context for developmental toxicity mechanisms without relying on animal testing.

Data were identified through systematic searches of PubMed, AOP-Wiki, and OECD databases (2010–2025) using combinations of the following keywords: PPARα, fatty acid oxidation, oxidative phosphorylation, ATP depletion, vascular integrity, hemopericardium, developmental toxicity, zebrafish, PFAS, phthalate, peroxisome proliferator. Inclusion criteria required mechanistic or quantitative evidence linking key events (KEs) in vertebrate embryos or early juvenile stages. Empirical data from in vitro bioassays, zebrafish embryos, and rodent models were considered. The weight of evidence was evaluated using the OECD principles of AOP development—biological plausibility, essentiality, and empirical support.

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.

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This AOP is biologically coherent and supported by moderate-to-strong empirical data across molecular and organismal levels. The essentiality of upstream events (PPARα activation and increased β-oxidation) is well supported by experimental data using PPARα knockouts and pharmacological antagonists. Downstream events, such as decreased ATP levels, compromised vascular integrity, and hemopericardium, have been observed across diverse PPARα activators in fish embryos, indicating reproducibility. However, quantitative relationships between intermediate KEs and mortality remain incompletely defined. The AOP has moderate confidence overall and is applicable for screening-level hazard identification, read-across, and developmental toxicity prioritization. <ul> <li> Taxa: Primarily teleost fish (e.g., Danio rerio, Oryzias latipes); mechanistic plausibility extends to other vertebrates. </li> <li> Life stage: Embryonic and early larval development. </li> <li> Sex: Not sex-specific at early life stages. </li> <li> Biological systems: Liver, muscle, and cardiovascular systems. </li> </ul>

<table> <thead> <tr> <th>Key Event</th> <th>Essentiality Evidence</th> <th>Type of Evidence</th> </tr> </thead> <tbody> <tr> <td>PPARα activation (MIE)</td> <td>Knockdown or knockout of ppara in zebrafish prevents β-oxidation induction and metabolic effects following exposure to PPARα agonists.</td> <td>Direct</td> </tr> <tr> <td>Increased fatty acid β-oxidation</td> <td>Chemical inhibitors (e.g., etomoxir) of β-oxidation prevent ATP depletion and vascular effects.</td> <td>Direct</td> </tr> <tr> <td>Decreased coupling of OXPHOS</td> <td>Reduced mitochondrial efficiency and ROS generation precede ATP loss and morphological abnormalities.</td> <td>Indirect</td> </tr> <tr> <td>Decreased ATP pool</td> <td>ATP supplementation or metabolic rescue mitigates vascular and cardiac defects.</td> <td>Direct</td> </tr> <tr> <td>Decreased vascular integrity</td> <td>Vascular permeability assays correlate strongly with cardiac edema and mortality outcomes.</td> <td>Indirect</td> </tr> <tr> <td>Increased hemopericardium</td> <td>Observed consistently in PPARα agonist-exposed embryos; severity predicts mortality.</td> <td>Indirect</td> </tr> <tr> <td>Increased early life stage mortality (AO)</td> <td>Apical endpoint following cumulative mitochondrial and vascular dysfunction.</td> <td>Outcome</td> </tr> </tbody> </table>

<h4>Biological Plausibility</h4> High. The pathway aligns with well-characterized PPARα-mediated transcriptional regulation of energy metabolism. Excessive β-oxidation generates ROS and perturbs mitochondrial homeostasis, leading to ATP depletion and vascular collapse, consistent with observed early life stage mortality. <h4>Empirical Support</h4> Moderate. Numerous studies report coherent concentration–response relationships between upstream and downstream KEs. Zebrafish embryos exposed to PFAS (e.g., HFPO-DA, PFOA) or fibrates (e.g., clofibrate) exhibit transcriptional activation of ppara target genes, mitochondrial dysfunction, hemopericardium, and mortality. <h4>Quantitative Understanding</h4> Low to moderate. While dose–response data exist for individual KEs, quantitative linkage functions (KERs) are not yet formalized. The AOP can be qualitatively modeled but lacks a complete mathematical framework.

<table> <thead> <tr> <th>Modulating Factor (MF)</th> <th>Influence or Outcome</th> <th>KER(s) Involved</th> </tr> </thead> <tbody> <tr> <td>Energy/nutrient availability</td> <td>Limited glucose or lipid substrates reduce β-oxidation flux and lower ATP depletion severity; conversely, high lipid load enhances PPARα activation and downstream metabolic disruption.</td> <td>PPARα activation (increase) → Fatty acid β-oxidation (increase); β-oxidation (increase) → Coupling of OXPHOS (decrease)</td> </tr> <tr> <td>Antioxidant capacity</td> <td>Elevated antioxidant defenses (e.g., glutathione, SOD, catalase) buffer ROS generated by excessive β-oxidation and OXPHOS uncoupling, mitigating ATP loss and vascular effects.</td> <td>Coupling of OXPHOS (decrease) → ATP pool (decrease); ATP pool (decrease) → Vascular integrity (decrease)</td> </tr> <tr> <td>Oxygen availability</td> <td>Hypoxia limits oxidative metabolism, reducing ROS formation and ATP depletion; hyperoxia or increased oxygen tension enhances oxidative damage and mitochondrial uncoupling.</td> <td>Coupling of OXPHOS (decrease) → ATP pool (decrease)</td> </tr> <tr> <td>Temperature</td> <td>Elevated temperature accelerates mitochondrial respiration and energy turnover, intensifying ATP depletion and vascular damage.</td> <td>β-oxidation (increase) → OXPHOS coupling (decrease); ATP pool (decrease) → Vascular integrity (decrease)</td> </tr> <tr> <td>Developmental stage</td> <td>Early embryos are more vulnerable due to higher energy demand and immature mitochondrial and antioxidant systems.</td> <td>ATP pool (decrease) → Vascular integrity (decrease); Vascular integrity (decrease) → Hemopericardium (increase)</td> </tr> <tr> <td>Mitochondrial density and efficiency</td> <td>Tissues with high mitochondrial density (heart, liver, muscle) show more pronounced energy depletion and structural defects.</td> <td>OXPHOS coupling (decrease) → ATP pool (decrease); ATP pool (decrease) → Vascular integrity (decrease)</td> </tr> <tr> <td>Chemical lipophilicity</td> <td>Lipophilic compounds bioaccumulate in lipid-rich embryonic ti</td> <td> </td> </tr> </tbody> </table>

Limited quantitative KERs available. Correlative evidence suggests that ≥40–50% reduction in ATP levels is associated with severe vascular leakage and increased mortality probability.

<ul> <li> Supports read-across of PPARα-activating chemicals (e.g., PFAS, fibrates, phthalates). </li> <li> Enables in vitro-to-in vivo extrapolation through metabolic biomarkers (e.g., β-oxidation gene expression, ATP depletion). </li> <li> Applicable to screening-level developmental toxicity assessments in non-animal frameworks (e.g., NGRA, IATA). </li> <li> May inform adverse outcome network linkages with hepatic steatosis and mitochondrial dysfunction AOPs. </li> </ul>

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