Effects of ACE-inhibition on redox status and expression of P-selectin of endothelial cells subjected to oxidative stress

Redox stress during post-ischemic reperfusion may be the prime signal for processes leading to myocardial remodelling and hypertrophy. Nitric oxide (NO) is antioxidative, and adhesive for neutrophils (PMN) and antiproliferative. Thus, enhancing endothelial production of NO, eg by inhibiting breakdown of endogenous bradykinin via angiotensin converting enzyme (ACE), could be beneficial. The effect of cilazaprilat (CILA, 10 muM), an ACE inhibitor, on redox status, expression of the adhesion molecule P-selectin, and PMN adhesion under conditions of oxidative stress was investigated in cultured human umbilical vein endothelial cells (HUVECs). Incubation of the cells with H2O2 (0.1 and 1mM) for 15 min served as oxidative stimulus. The intra- and extracellular concentrations of reduced and oxidized glutathione (GSH and GSSG) were measured by HPLC as indicators of endothelial redox status. Expression of P-selectin was measured by flow cytometry. Furthermore, fim leukocyte adhesion to HUVECs was assessed. In controls, the intracellular ration GSH/GSSG averaged 47 and dropped to 30 after incubation with 0.1 mM H2O2. The ratio declined to 6.5 with 1 mM H2O2. CILA blocked the effects of 0.1 mM H2O2, but was ineffective against 1mM peroxide. The extracellular ration did not discriminate between 0.1 and 1mM H2O2, falling from 18 to 1 in both situations. P-selectin expression rose from 100% (control) to 146% after 1 mM H2O2 without CILA, but only to 114% in the presence of CILA. PMN adhesion was enhanced from about 1600 PMN per microwell (control) to 4300/well by 1 mM H2O2. CILA had no significant effect on adhesion (3900 PMN/well). Exposure of HUVECs to 0.1 mM H2O2 affected neither P-selectin expression nor PMN adhesion. Consequently, ACE inhibition can mitigate mild (0.1 mM H2O2) but not more severe redox stress in HUVECs. Irrespectively, CILA reduced the upregulation of P-selectin at the higher H2O2 concentration, indicating that this process is regulated independently of the cellular redox status. The firm adhesion of PMN to HUVECs was independent of P-selectin expression.