title: Activation of estrogen receptor-α and of angiotensin-converting enzyme 2 suppresses ischemic brain damage in oophorectomized rats.
abstract: Like the angiotensin II type 1 receptor blocker, endogenous estrogen (17β-estradiol) is neuroprotective against cerebral ischemia; its effects are thought to be mediated by estrogen receptors (ERs). To verify the role of ERs and the brain renin-angiotensin system in estrogen-deficient rats with ischemia induced by middle cerebral artery occlusion, we compared rats subjected to oophorectomy (OVX(+)) with sham-oophorectomized rats (OVX(-)) and OVX(+) rats treated with 0.3 or 3.0 mg/kg of olmesartan for 2 weeks before middle cerebral artery occlusion. Independent of the blood pressure, the cortical infarct volume was larger in OVX(+) than in OVX(-) rats. It was smaller in olmesartan-pretreated OVX(+) rats. The expression of ERα in the peri-infarct region was correlated with the reduction of cortical infarct but not that of ERβ or G protein-coupled estrogen receptor. Olmesartan prevented ERα downregulation in the cortical peri-infarct area, without affecting ERβ or G protein-coupled estrogen receptor. Olmesartan also increased mRNA expression of angiotensin-converting enzyme 2, Bcl-2, and Bcl-xL and reduced angiotensin II and cleaved caspase 3. These effects were augmented by olmesartan and abolished by the ER inhibitor. In OVX(+) rats treated with the ERα agonist alone, the infarct size was decreased, and the neuroprotective genes were upregulated. These findings suggest that the transactivation of neuroprotective genes and the reduction in brain angiotensin II are ERα dependent and that this may augment neuroprotection together with an angiotensin II type 1 receptor blockade by olmesartan. We present the new insight that the activation of ERα independent of estrogen contributes at least partly to limiting cerebral ischemic damage.
authors.affiliation: Department of Neurosurgery, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan. s_kenji1032@yahoo.co.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Shimada
authors.forename: Keiko T
authors.initials: KT
authors.lastname: Kitazato
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kinouchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Yagi
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Tada
authors.forename: Junichiro
authors.initials: J
authors.lastname: Satomi
authors.forename: Teruyoshi
authors.initials: T
authors.lastname: Kageji
authors.forename: Shinji
authors.initials: S
authors.lastname: Nagahiro
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000085962:Angiotensin-Converting Enzyme 2; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D053148:Caspase 3 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology*; D007150:Immunohistochemistry; D010052:Ovariectomy; D007703:Peptidyl-Dipeptidase A / Q000235:genetics / Q000378:metabolism*; D010636:Phenols; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011945:Receptors, Angiotensin / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013777:Tetrazoles / Q000494:pharmacology*; D018631:ras Proteins / Q000378:metabolism
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D047628:Estrogen Receptor alpha; D007093:Imidazoles; D010636:Phenols; D011720:Pyrazoles; D011945:Receptors, Angiotensin; D013777:Tetrazoles; C486184:4,4',4''-(4-propyl-((1)H)-pyrazole-1,3,5-triyl) tris-phenol; D000804:Angiotensin II; C437965:olmesartan; D007703:Peptidyl-Dipeptidase A; C000705329:Ace2 protein, rat; D000085962:Angiotensin-Converting Enzyme 2; D053148:Caspase 3; D018631:ras Proteins