title: Nrf2-mediated induction of cytoprotective enzymes by 15-deoxy-Delta12,14-prostaglandin J2 is attenuated by alkenal/one oxidoreductase.
abstract: NADPH-dependent alkenal/one oxidoreductase (Aor) was discovered to be highly inducible in rat liver following treatment with the cancer chemopreventive agent 3H-1, 2-dithiole-3-thione. Aor was further characterized as an Nrf2-regulated antioxidative enzyme that reduces carbon-carbon double bonds in a variety of alpha, beta-unsaturated aldehydes and ketones. 15-Deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) is a reactive membrane lipid metabolite that activates multiple pathways, including Nrf2-mediated induction of cytoprotective enzymes. Physiologically, it is postulated that 15d-PGJ2 alkylates key regulatory proteins via the electrophilic carbon centers found in two alpha, beta-unsaturated ketone moieties. This current study addresses the metabolism of 15d-PGJ2 by rat Aor (rAor) and subsequent deactivation of the Nrf2 signaling pathway by both rat and human AOR. We demonstrate that induction of NADPH-dependent quinone oxidoreductase activity by 15d-PGJ2 is markedly attenuated in mouse embryonic fibroblasts that overexpress rAor. Luciferase reporter assay and quantitative real-time PCR confirmed these findings. Concentrations required for doubling the NADPH-dependent quinone oxidoreductase response are increased from 1.8 microm in wild-type to >10 microm in rat Aor transgenic fibroblasts. 15d-PGJ2 is metabolized by recombinant rAor with a Km of 9.6 microm and k(cat) of 18.5 min(-1). The major product is 12,13-dihydro-15-deoxy-Delta12,14-prostaglandin J2 (dihydro-15d-PGJ2). The reduction of C=C by Aor yielding dihydro-15d-PGJ2 abolishes the inducibility in an antioxidant response element-driven luciferase assay. Collectively, these results demonstrate that 15d-PGJ2 can be catabolized by Aor, thereby attenuating subsequent Nrf2 signaling and possibly inflammatory and apoptotic processes also influenced by 15d-PGJ2.
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, MD, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Yu
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Egner
authors.forename: Junko
authors.initials: J
authors.lastname: Wakabayashi
authors.forename: Nobunao
authors.initials: N
authors.lastname: Wakabayashi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Kensler
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004790:Enzyme Induction; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D007155:Immunologic Factors / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D015394:Molecular Structure; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology
chemical_list: C097240:15-deoxy-delta(12,14)-prostaglandin J2; D007155:Immunologic Factors; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D000429:Alcohol Oxidoreductases; C082646:leukotriene B4 12-hydroxydehydrogenase; D016660:NAD(P)H Dehydrogenase (Quinone); D015230:Prostaglandin D2