Role of Nox isoforms in angiotensin II-induced oxidative stress and endothelial dysfunction in brain

Abstract

Angiotensin II (Ang II) promotes vascular disease through several mechanisms including by producing oxidative stress and endothelial dysfunction. Although multiple potential sources of reactive oxygen species exist, the relative importance of each is unclear, particularly in individual vascular beds. In these experiments, we examined the role of NADPH oxidase (Nox1 and Nox2) in Ang II-induced endothelial dysfunction in the cerebral circulation. Treatment with Ang II (1.4 mg·kg(-1)·day(-1) for 7 days), but not vehicle, increased blood pressure in all groups. In wild-type (WT; C57Bl/6) mice, Ang II reduced dilation of the basilar artery to the endothelium-dependent agonist acetylcholine compared with vehicle but had no effect on responses in Nox2-deficient (Nox2(-/y)) mice. Ang II impaired responses to acetylcholine in Nox1 WT (Nox1(+/y)) and caused a small reduction in responses to acetylcholine in Nox1-deficient (Nox1(-/y)) mice. Ang II did not impair responses to the endothelium-independent agonists nitroprusside or papaverine in either group. In WT mice, Ang II increased basal and phorbol-dibutyrate-stimulated superoxide production in the cerebrovasculature, and these increases were abolished in Nox2(-/y) mice. Overall, these data suggest that Nox2 plays a relatively prominent role in mediating Ang II-induced oxidative stress and cerebral endothelial dysfunction, with a minor role for Nox1.

Fig. 1.

Vascular responses to acetylcholine (A; vehicle, n = 6; Ang II, n = 6), papaverine (B; vehicle, n = 6; Ang II, n = 6), nitroprusside (C; vehicle, n = 6; Ang II, n = 6), and KCl (D; vehicle, n = 6; Ang II, n = 6) in Nox2^+/y mice. All data are means ± SE. Significant difference vs. vehicle: **P < 0.01; ***P < 0.001.

Fig. 2.

Vascular responses to acetylcholine (A; vehicle, n = 6; Ang II, n = 7), papaverine (B; vehicle, n = 6; Ang II, n = 7), nitroprusside (C; vehicle, n = 6; Ang II, n = 6), and KCl (D; vehicle, n = 6; Ang II, n = 6) in Nox2^−/y mice. All data are means ± SE.

Fig. 3.

Vascular responses to acetylcholine (A; vehicle, n = 11; Ang II, n = 6), papaverine (B; vehicle, n = 11; Ang II, n = 7), nitroprusside (C; vehicle, n = 5; Ang II, n = 5), and KCl (D; vehicle, n = 9; Ang II, n = 8) in Nox1^+/y mice. All data are means ± SE. **Significant difference vs. vehicle (P < 0.01).

Fig. 4.

Vascular responses to acetylcholine (A; vehicle, n = 12; Ang II, n = 12), papaverine (B; vehicle, n = 12; Ang II, n = 12), nitroprusside (C; vehicle, n = 8; Ang II, n = 9), and KCl (D; vehicle, n = 12; Ang II, n = 12) in Nox1^−/y mice. All data are means ± SE. Significant difference vs. vehicle: *P < 0.05; **P < 0.01; ***P < 0.001.

Fig. 5.

Vascular responses to acetylcholine (A; vehicle, n = 4; Ang II, n = 5), papaverine (B; vehicle, n = 4; Ang II, n = 5), and nitroprusside (C; vehicle, n = 4; Ang II, n = 4) in eNOS^+/+ mice. **Significant difference vs. vehicle (P < 0.01).

Fig. 6.

Vascular responses to acetylcholine (A; vehicle, n = 8; Ang II, n = 8), papaverine (B; vehicle, n = 7; Ang II, n = 8), A23187 (C; vehicle, n = 7; Ang II, n = 8), and nitroprusside (D; vehicle, n = 8; Ang II, n = 8) in eNOS^−/− mice. All data are means ± SE. Significant difference vs. vehicle: **P < 0.01; ***P < 0.0001.

Fig. 7.

Superoxide levels in cerebral arteries from vehicle and Ang II-treated mice under basal conditions and in the presence of 10 μM PdB in Nox2^+/y (vehicle, n = 9; Ang II, n = 9) and Nox2^−/y mice (vehicle, n = 7; Ang II, n = 7). All data are means ± SE. *Significant difference vs. vehicle-treated basal Nox2^+/y (P < 0.05). **Significant difference vs. vehicle-treated PdBu Nox2^+/y (P < 0.05). ***Significant difference vs. Ang II-treated basal Nox2^+/y (P < 0.05). ****Significant difference vs. vehicle and Ang II-treated PdBu Nox2^+/y (P < 0.05).