Cytokine induced neutrophijl mediated injury of human endothelial cells

Abstract

In an attempt to understand the pathogenesis of vascuütides we analysed how cytokine stimulation of human umbilical vein endothelial cells (HUVEC) in vitro activates the cytolytic capacity of polymorphonuclear (PMN) granulocytes. IL-l, IFN-y or TNF-a caused highly significant dose and time dependent cytolysis. Antibody blockade of ICAM-1 on HUVEC inhibited 50-70% of the cytotoxicity induced by these cytokines, whereas a Mab to E-selectin reduced 40-60% of IL-l and TNF-a, but not IFN-y, induced cytolysis. The role of nitric oxide (NO) was of notable significance since cytotoxicity achieved by the each cytokine was reduced by 65-77% by the specific NO synthase inhibitors N-monomethyl-L-arginine or nitro-L-arginine methyl ester, as well as by the scavenger of extracellular NO, oxyhemoglobin. In contrast, cytolysis induced by TNF-a was not inhibited by Superoxide dismutase or catalase (alone or in consorted action), a-1-antitrypsin, a-2-macroglobulin, or the PAF receptor antagonist WEB-2086. The possibility that high levels of IL-8, produced by HUVEC in response to TNF-a, mediated activation of PMN was not corroborated since addition of a mAb against IL-8 did not modify cytolysis. Nonetheless, TNF-a treated HUVEC conferred a transient rise of [Ca+lj in PMN, which was completly inhibited by the mAb against IL-8 but unaffected by WEB-2086. Thus, in this in vitro model of vasculitis the effect of IL-l, IFN-y and TNF-a, as potent promoters of cytokine mediated neutrophil dependent cytotoxicity for HUVEC, is a process dependent on expression of adhesion molecules and probably associated with NO produced in the system.