Angiotensin II impairs endothelial function via tyrosine phosphorylation of the endothelial nitric oxide synthase.

Proline-rich tyrosine kinase 2 (PYK2) can be activated by angiotensin II (Ang II) and reactive oxygen species. We report that in endothelial cells, Ang II enhances the tyrosine phosphorylation of endothelial NO synthase (eNOS) in an AT(1)-, H(2)O(2)-, and PYK2-dependent manner. Low concentrations (1-100 micromol/liter) of H(2)O(2) stimulated the phosphorylation of eNOS Tyr657 without affecting that of Ser1177, and attenuated basal and agonist-induced NO production. In isolated mouse aortae, 30 micromol/liter H(2)O(2) induced phosphorylation of eNOS on Tyr657 and impaired acetylcholine-induced relaxation. Endothelial overexpression of a dominant-negative PYK2 mutant protected against H(2)O(2)-induced endothelial dysfunction. Correspondingly, carotid arteries from eNOS(-/-) mice overexpressing the nonphosphorylatable eNOS Y657F mutant were also protected against H(2)O(2). In vivo, 3 wk of treatment with Ang II considerably increased levels of Tyr657-phosphorylated eNOS in the aortae of wild-type but not Nox2(y/-) mice, and this was again associated with a clear impairment in endothelium-dependent vasodilatation in the wild-type but not in the Nox2(y/-) mice. Collectively, endothelial PYK2 activation by Ang II and H(2)O(2) causes the phosphorylation of eNOS on Tyr657, attenuating NO production and endothelium-dependent vasodilatation. This mechanism may contribute to the endothelial dysfunction observed in cardiovascular diseases associated with increased activity of the renin-angiotensin system and elevated redox stress.