Effect of gender on NADPH-oxidase activity, expression, and function in the cerebral circulation - Role of estrogen

Background and Purpose - This study tested whether NADPH-oxidase activity, expression, and functional effects on vascular tone are influenced by gender in the rat cerebral circulation and whether such differences are estrogen-dependent. Methods - NADPH-stimulated superoxide production by cerebral (basilar [ BA]; middle cerebral) arteries from male and female Sprague-Dawley rats was measured using lucigenin-enhanced chemiluminescence and dihydroethidium. Protein expression of Nox1, Nor2,Nox4, superoxide dismutase 1 (SOD1), SOD2, and SOD3 was measured using Western blotting. Vascular responses of BA to NADPH were assessed in a myograph. Some female rats were ovariectomized and treated with either vehicle (dimethyl sulfoxide) or 17 beta-estradiol. Results - NADPH-stimulated superoxide production by BA and middle cerebral arteries from males was approximately 2-fold greater than vessels from females. Superoxide production was virtually abolished by the NADPH-oxidase inhibitor, diphenyleneiodonium. Protein expression of Nox1 and Nox4 in BA was also higher in males than in females (2.4- and 2.8-fold, respectively), whereas Nox2, SOD1, SOD2, and SOD3 expression did not differ between genders. NADPH induced greater vasorelaxant effects in BA from males versus females (P < 0.05). The hydrogen peroxide scavenger, catalase, abolished these NADPH- induced relaxations. NADPH- stimulated superoxide production by BA from ovariectomized rats treated with vehicle was 3-fold greater than levels in intact females. Treatment of ovariectomized rats with 17 beta-estradiol decreased superoxide production (P < 0.05). NADPH- induced relaxations of BA were smaller in 17 beta-estradiol-treated than in vehicle-treated ovariectomized rats (P < 0.05). Conclusions - NADPH- oxidase activity and function are lower in cerebral arteries of female rats. These gender differences are estrogen-dependent and are associated with lower Nox1 and Nox4 expression.