Background and Purpose—We tested whether gender influences cerebrovascular responses to angiotensin II (AngII) and the role(s) of Nox2.

Methods and Results—AngII-stimulated superoxide (O₂^-) production by cerebral arteries from male and female wild-type (WT) and Nox2^-/- mice was measured using lucigenin- or L-012–enhanced chemiluminescence. Hydrogen peroxide (H₂O₂) production was measured using Amplex Red fluorescence. Western Blotting was used to measure expression of Nox2, endothelial nitric oxide synthase (eNOS), angiotensin receptors (AT₁ and AT₂), and superoxide dismutases (SOD1–3). Immunofluorescence was used to localize Nox2 in middle cerebral arteries (MCA). Vascular responses to AngII were assessed in a perfusion myograph. AngII-stimulated O₂^- and H₂O₂ production by cerebral arteries from female WT mice was 75% to 85% lower than in males (P<0.05). O₂^- production was 60% lower in Nox2^-/- versus WT males (P<0.05), whereas Nox2 deletion did not affect O₂^- production in females. Expression of Nox2, eNOS, AT receptors, and SOD isoforms was similar between genders. Nox2 immunofluorescence was similarly localized in adventitial and endothelial cells of MCA from both genders. AngII elicited smaller contractions of MCA from females vs males (P<0.05). Contractions were reduced in male, but not female, Nox2^-/- mice (P<0.05). The SOD mimetic, tempol, potentiated contractions to AngII in male WT mice (P<0.05), whereas the SOD/catalase mimetic, EUK-134, virtually abolished contractions (P<0.05).

Conclusions—AngII-stimulated O₂^- and H₂O₂ production are greater in cerebral arteries from male versus female mice, and are associated with greater contractions to AngII mediated by H₂O₂. These gender differences are dependent on the expression of Nox2.