title: Estrogen receptor and PI3K/Akt signaling pathway involvement in S-(-)equol-induced activation of Nrf2/ARE in endothelial cells.
abstract: S-(-)equol, a natural product of the isoflavone daidzein, has been reported to offer cytoprotective effects with respect to the cardiovascular system, but how this occurs is unclear. Interestingly, S-(-)equol is produced by the human gut, suggesting a role in physiological processes. We report that treatment of human umbilical vein endothelial cells and EA.hy926 cells with S-(-)equol induces ARE-luciferase reporter gene activity that is dose and time dependent. S-(-)equol (10-250 nM) increases nuclear factor-erythroid 2-related factor 2 (Nrf2) as well as gene products of Nrf2 target genes heme oxygenase-1 (HO-1) and NAD(P)H (nicotinamide-adenine-dinucleotide-phosphate) quinone oxidoreductase 1 (NQO1). Endothelial cells transfected with an HA-Nrf2 expression plasmid had elevated HA-Nrf2, HO-1, and NQO1 in response to S-(-)equol exposure. S-(-)equol treatment affected Nrf2 mRNA only slightly but significantly increased HO-1 and NQO1 mRNA. The pretreatment of cells with specific ER inhibitors or PI3K/Akt (ICI182,780 and LY294002) increased Nrf2, HO-1, and NQO1 protein, impaired nuclear translocation of HA-Nrf2, and decreased ARE-luciferase activity. Identical experiments were conducted with daidzein, which had effects similar to S-(-)equol. In addition, DPN treatment (an ERβ agonist) induced the ARE-luciferase reporter gene, promoting Nrf2 nuclear translocation. Cell pretreatment with an ERβ antagonist (PHTPP) impaired S-(-)equol-induced Nrf2 activation. Pre-incubation of cells followed by co-treatment with S-(-)equol significantly improved cell survival in response to H2O2 or tBHP and reduced apoptotic and TUNEL-positively-stained cells. Notably, the ability of S-(-)equol to protect against H2O2-induced cell apoptosis was attenuated in cells transfected with an siRNA against Nrf2. Thus, beneficial effects of S-(-)equol with respect to cytoprotective antioxidant gene activation may represent a novel strategy to prevent and treat cardiovascular diseases.
authors.affiliation: Research Center for Nutrition and Food Safety, The Third Military Medical University, Chongqing, PR China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.forename: Xinyu
authors.initials: X
authors.lastname: Liang
authors.forename: Linying
authors.initials: L
authors.lastname: Shi
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Junli
authors.initials: J
authors.lastname: Chen
authors.forename: Chao
authors.initials: C
authors.lastname: Kang
authors.forename: Jundong
authors.initials: J
authors.lastname: Zhu
authors.forename: Mantian
authors.initials: M
authors.lastname: Mi
mesh_terms: D002318:Cardiovascular Diseases / Q000235:genetics / Q000378:metabolism; D060754:Equol / Q000494:pharmacology*; D047629:Estrogen Receptor beta / Q000235:genetics / Q000378:metabolism*; D005260:Female; D051547:Heme Oxygenase-1 / Q000096:biosynthesis / Q000235:genetics; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000096:biosynthesis / Q000235:genetics; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D048789:Phytoestrogens / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics
chemical_list: D047629:Estrogen Receptor beta; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D016877:Oxidants; D048789:Phytoestrogens; D060754:Equol; D006861:Hydrogen Peroxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt