Estrogen reduces angiotensin II-induced nitric oxide synthase and NAD(P)H oxidase expression in endothelial cells.
OBJECTIVE
Angiotensin II (AII) has been shown to increase endothelial NAD(P)H oxidase activity, which is a source of superoxide anion that in turn may induce the formation of peroxynitrite. Estrogen (E2) has been reported to have vascular protective effects. In this study, we hypothesized that E2 reduces the AII-induced expression of NAD(P)H oxidase and peroxynitrite in endothelial cells.


RESULTS
Endothelial cells were cultured and stimulated with AII in the absence or presence of E2. Western blots were used to assess nitric oxide synthase (NOS) and NAD(P)H oxidase expression. Immunofluorescence of nitrotyrosine provided evidence of peroxynitrite formation. Our data indicate that AII increased the expression of endothelial NOS, inducible NOS, and NAD(P)H oxidase in a dose-dependent manner, which was attenuated by incubation with either E2, superoxide dismutase, or the AII type 1 receptor (AT1R) inhibitor candesartan. Estrogen as well as superoxide dismutase also inhibited AII-induced AT(1)R expression and nitrotyrosine staining. The effects of E2 on the AII responses were not inhibited by the E2 receptor antagonist ICI-182,780.


CONCLUSIONS
AII stimulation of endothelial cells increases expression of NAD(P)H oxidase and NOS, which may contribute to oxidative stress, as evidenced by peroxynitrite formation. E2 inhibits these AII effects, possibly through reduced AT1R expression.
Gragasin
Ferrante S
FS
Department of Obstetrics & Gynecology, Perinatal Research Centre, University of Alberta, Edmonton, Alberta, Canada.
Xu
Yi
Y
Arenas
Ivan A
IA
Kainth
Neelam
N
Davidge
Sandra T
ST
D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002196:Capillaries / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D002417:Cattle; D002460:Cell Line; D003331:Coronary Vessels / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004790:Enzyme Induction / Q000187:drug effects / Q000502:physiology; D004958:Estradiol / Q000494:pharmacology / Q000502:physiology*; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis*; D019255:NADPH Oxidases; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II; D030421:Peroxynitrous Acid / Q000096:biosynthesis / Q000378:metabolism
D000804:Angiotensin II; D030421:Peroxynitrous Acid; D004958:Estradiol; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases