title: 2-Methoxyestradiol, an endogenous 17β-estradiol metabolite, inhibits microglial proliferation and activation via an estrogen receptor-independent mechanism.
abstract: 17β-Estradiol (estradiol) inhibits microglia proliferation. 2-Methoxyestradiol (2-ME) is an endogenous metabolite of estradiol with little affinity for estrogen receptors (ERs). We hypothesize that 2-ME inhibits microglial proliferation and activation and contributes to estradiol's inhibitory effects on microglia. We compared the effects of estradiol, 2-hydroxyestradiol [2-OE; estradiol metabolite produced by cytochrome P450 (CYP450)], and 2-ME [formed by catechol-O-methyltransferase (COMT) acting upon 2-OE] on microglial (BV2 cells) DNA synthesis, cell proliferation, activation, and phagocytosis. 2-ME and 2-OE were approximately three- and 10-fold, respectively, more potent than estradiol in inhibiting microglia DNA synthesis. The antimitogenic effects of estradiol were reduced by pharmacological inhibitors of CYP450 and COMT. Inhibition of COMT blocked the conversion of 2-OE to 2-ME and the antimitogenic effects of 2-OE but not 2-ME. Microglia expressed ERβ and GPR30 but not ERα. 2,3-Bis(4-hydroxyphenyl)-propionitrile (ERβ agonist), but not 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (ERα agonist) or G1 (GPR30 agonist), inhibited microglial proliferation. The antiproliferative effects of estradiol, but not 2-OE or 2-ME, were partially reversed by ICI-182,780 (ERα/β antagonist) but not by 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole (ERα antagonist) or G15 (GPR30 antagonist). Lipopolysaccharide increased microglia iNOS and COX-2 expression and phagocytosing activity of microglia; these effects were inhibited by 2-ME. We conclude that in microglia, 2-ME inhibits proliferation, proinflammatory responses, and phagocytosis. 2-ME partially mediates the effects of estradiol via ER-independent mechanisms involving sequential metabolism of estradiol to 2-OE and 2-ME. 2-ME could be of potential therapeutic use in postischemic stroke injuries. Interindividual differences in estradiol metabolism might affect the individual's ability to recover from stroke.
authors.affiliation: Department of Reproductive Endocrinology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Sara A
authors.initials: SA
authors.lastname: Schaufelberger
authors.affiliation: Department of Reproductive Endocrinology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Marinella
authors.initials: M
authors.lastname: Rosselli
authors.affiliation: Department of Reproductive Endocrinology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Federica
authors.initials: F
authors.lastname: Barchiesi
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Delbert G
authors.initials: DG
authors.lastname: Gillespie
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Edwin K
authors.initials: EK
authors.lastname: Jackson
authors.affiliation: Department of Reproductive Endocrinology, University Hospital Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland; and Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania raghvendra.dubey@usz.ch.
authors.forename: Raghvendra K
authors.initials: RK
authors.lastname: Dubey
mesh_terms: D000077584:2-Methoxyestradiol; D000818:Animals; D002394:Catechol O-Methyltransferase; D065098:Catechol O-Methyltransferase Inhibitors / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects*; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis* / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology*; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects*; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D065098:Catechol O-Methyltransferase Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004967:Estrogens; D050257:Tubulin Modulators; D004958:Estradiol; D000077584:2-Methoxyestradiol; D004247:DNA; C001390:2-hydroxyestradiol; D002394:Catechol O-Methyltransferase
keywords: 17β-estradiol; 2-hydroxyestradiol; 2-methoxyestradiol; microglia; stroke