Endothelial cells protect vascular smooth muscle cells from H2O2 attack.

ABSTRACT

Endothelial-dependent vascular responses are altered in ischemic acute renal failure. Oxidants formed during reperfusion of ischemic kidneys injure the renal microvasculature and prevent recovery of renal function. To determine whether endothelial cells (EC) modulate oxidant attack on vascular smooth muscle cells (VSMC), rat mesenteric artery VSMC were grown on coverslips and then coincubated with bovine pulmonary artery EC grown in wells. In the absence of EC, H2O2 caused time- and concentration-dependent increases in VSMC injury as indicated by release of [3H]adenine. In contrast, addition of EC reduced H2O2-mediated (5 mM, 1 h) VSMC adenine release from 63.8 +/- 4.5% to 28.6 +/- 2.9% (P < 0.001). The protective effect of EC did not occur when H2O2 was added to the surface of VSMC unopposed to EC and was partially reversed when EC were treated with aminotriazole to inactivate catalase (41.7 +/- 2.7%). To determine whether EC nitric oxide (NO) modified H2O2 attack on VSMC, EC were treated with N omega-nitro-L-arginine (L-NNA). The protective effect of EC was partially abrogated with L-NNA (53.8 +/- 4.3%). Treatment of EC with interleukin-1 beta (IL-1 beta) for 24 h prior to coincubation with VSMC enhanced the protective effect of EC. IL-1 beta-induced protection was reversed with L-NNA. No protection was observed when VSMC were treated with 8-bromoguanosine 3',5'-cyclic monophosphate, forskolin, or phorbol 12-myristate 13-acetate. Our conclusions are as follows. VSMC are protected by EC from luminal but not contraluminal oxidant attack. The protective effect of EC is mediated by catalase- and NO-dependent inactivation of oxidants. EC dysfunction could account for renal injury caused by oxidants formed during reperfusion of ischemic kidneys.