Modulation of constitutive nitric oxide synthase, bcl-2 and Fas expressionin 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 pathophysi ology of myocardial ischemia-reperfusion injury. We have recently shown tha t reoxygenation following a period of anoxia causes apoptosis of cultured h uman coronary artery endothelial cells (HCAECs). Ang II further enhances ap optosis of HCAECs via Ang II type 1 receptor (AT1R) activation. Recent stud ies suggest an important role of constitutive nitric oxide synthase (cNOS), Fas and bcl-2 proteins in apoptosis. This study was designed to examine th e modulation of cNOS, and Fas and bcl-2 expression in HCAECs during exposur e to anoxia-reoxygenation and Ang II. Methods and Results: HCAECs were expo sed to anoxia-reoxygenation and Ang II. Anoxia- reoxygenation significantly decreased cNOS mRNA, protein and activity in cultured HCAECs (P<0.05 vs. c ontrol). 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 mu M) 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 mu M). Conclus ion: During exposure of HCAECs to anoxia-reoxygenation and Ang II, AT1R act ivation induces important changes in cNOS mRNA, protein expression and acti vity, as well as bcl-2 and Fas protein expression which may have a bearing on the development of apoptosis. (C) 1999 Elsevier Science B.V. All rights reserved.