title: An angiotensin II type 1 receptor blocker can preserve endothelial function and attenuate brain ischemic damage in spontaneously hypertensive rats.
abstract: Hypertension reduces endothelial nitric oxide synthase (eNOS) expression and leads to endothelial dysfunction. However, few studies have demonstrated the influences of hypertension on eNOS function in the cerebral cortex. The present study investigates the influences of hypertension on endothelial function in the cerebral cortex and the protective effects of antihypertensive agents against brain ischemia through the preservation of endothelial function. Five- and ten-week-old male Wistar rats and spontaneously hypertensive rats (SHR) were used for experiments. Five-week-old SHR received olmesartan, hydralazine, or vehicle for 5 weeks in drinking water. eNOS activation in the cerebral cortex was evaluated by analyzing levels of total and Ser(1177)-phosphorylated eNOS protein by Western blot. Blood pressure of 10-week-old SHR without treatment was clearly high, and the ratio of phospho-eNOS/total eNOS protein was significantly low. Five-week treatment with olmesartan or hydralazine suppressed the elevation of blood pressure and the reduction of phosphorylated eNOS-Ser(1177) in SHR, and olmesartan was more effective in maintaining phosphorylation of eNOS-Ser(1177) than hydralazine. To assess the contribution of eNOS to maintaining cerebral blood flow (CBF), we monitored CBF by laser-Doppler flowmetry after L-N(5)-(1-iminoethyl)ornithine (L-NIO) infusion. CBF response to L-NIO was preserved in olmesartan-treated SHR but not in hydralazine-treated SHR. Furthermore, infarct volume 48 hr after transient focal brain ischemia in olmesartan-treated SHR was significantly reduced compared with vehicle-treated SHR. These findings indicate that chronic prehypertensive treatment with olmesartan could attenuate brain ischemic injury through the maintenance of endothelial function in the cerebral cortex in SHR.
authors.affiliation: Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan. oyama@medone.med.osaka-u.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Oyama
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yagita
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sasaki
authors.forename: Emi
authors.initials: E
authors.lastname: Omura-Matsuoka
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Terasaki
authors.forename: Yukio
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Saburo
authors.initials: S
authors.lastname: Sakoda
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kitagawa
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D020520:Brain Infarction / Q000209:etiology / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004195:Disease Models, Animal; D004727:Endothelium / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D020925:Hypoxia-Ischemia, Brain / Q000188:drug therapy* / Q000473:pathology*; D007093:Imidazoles / Q000494:pharmacology / Q000627:therapeutic use*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D013777:Tetrazoles / Q000494:pharmacology / Q000627:therapeutic use*; D013997:Time Factors
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D000959:Antihypertensive Agents; D007093:Imidazoles; D013777:Tetrazoles; C437965:olmesartan; D052250:Nitric Oxide Synthase Type III