Modulation of constitutive nitric oxide synthase, bcl-2 and Fas expression in cultured human coronary endothelial cells exposed to anoxia–reoxygenation and angiotensin II: role of AT1 receptor activation

Background: Angiotensin II (Ang II) plays a critical role in the pathophysiology of myocardial ischemia–reperfusion injury. We have recently shown that reoxygenation following a period of anoxia causes apoptosis of cultured human coronary artery endothelial cells (HCAECs). Ang II further enhances apoptosis of HCAECs via Ang II type 1 receptor (AT1R) activation. Recent studies suggest an important role of constitutive nitric oxide synthase (cNOS), Fas and bcl-2 proteins in apoptosis. This study was designed to examine the modulation of cNOS, and Fas and bcl-2 expression in HCAECs during exposure to anoxia–reoxygenation and Ang II. Methods and Results: HCAECs were exposed to anoxia–reoxygenation and Ang II. Anoxia- reoxygenation significantly decreased cNOS mRNA, protein and activity in cultured HCAECs ( P <0.05 vs. control). Anoxia–reoxygenation also caused an increase in Fas and a decrease in bcl-2 protein expression in cultured HCAECs (both P <0.05 vs. control). The presence of Ang II (0.3 μM) further enhanced these effects of anoxia–reoxygenation on cNOS, Fas and bcl-2 expression. The effects of Ang II were significantly attenuated by the AT1R inhibitor losartan (10 μM). Conclusion: During exposure of HCAECs to anoxia–reoxygenation and Ang II, AT1R activation induces important changes in cNOS mRNA, protein expression and activity, as well as bcl-2 and Fas protein expression which may have a bearing on the development of apoptosis.