Estrogen reduces angiotensin II-induced nitric oxide synthase and NAD(P)H oxidase expression in endothelial cells

Objective-Angiotensin R (All) has been shown to increase endothelial NAD(P)H oxidase activity, which is a source of,) has been reported to have vascular superoxide anion that in turn may induce the formation of peroxynitrite. Estrogen (E,, protective effects, In this study, we hypothesized that E-2 reduces the AII-induced expression of NAD(P)H oxidase and peroxynitrite in endothelial cells. Methods and Results-Endothelial cells were cultured and stimulated with All in the absence or presence of E, 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 All 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 E-2, superoxide dismutase, or the A-H type I receptor (AT(1)R) inhibitor candesartan. Estrogen as well as superoxide dismutase also inhibited AII-induced AT(1)R expression and nitrotyrosine- staining. The effects of E-2 on the Ail responses were not inhibited by the E-2 receptor antagonist ICI-182,780. Conclusions-All stimulation of endothelial cells increases expression of NAD(P)H oxidase and NOS, which may contribute to oxidative stress, as evidenced by peroxynitrite formation. inhibits these All effects, possibly through reduced AT(1)R expression.