INDUCTION OF HUMAN ENDOTHELIAL-CELL APOPTOSIS REQUIRES BOTH HEAT-SHOCK AND OXIDATIVE STRESS RESPONSES

Endothelial cell (EC) death may play an important role in the developm ent of increased vascular permeability and capillary leak syndrome dur ing systemic inflammatory response syndrome. However, the mode of EC d eath and the mechanisms involved remain unclear. In this study we empl oyed the proinflammatory mediators lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF-alpha), the chemical reagent sodium arsenit e, and heat shock to trigger the stress gene responses. Human ECs were used as surrogates of the microvasculature to test the hypothesis tha t the induction of the heat shock response and the oxidative stress re sponse might combine to induce apoptosis rather than necrosis in human ECs. Sodium arsenite at 80-320 mu M, which induced heat shock protein 72 (HSP72) expression and reactive oxygen intermediate (ROI) generati on in ECs, resulted in EC apoptosis. TNF-alpha alone (5-75 ng/ml) incr eased EC ROI generation but did not induce EC apoptosis. Heat shock al one (42 degrees C, 45 min) or sodium arsenite (40 mu M) alone, each of which induced HSP72 expression, did not result in EC apoptosis. Howev er, the combination of TNF-alpha with heat shock or 40 mu M sodium ars enite led to EC apoptosis as HSP72 expression and ROI were induced. Fu rthermore, sodium arsenite (80 mu M) in the presence of antioxidants f ailed to induce EC apoptosis. Apoptotic ECs also exhibited functional disturbances as represented by the depression of intercellular adhesio n molecule-1 expression as well as the disruption of FC monolayer inte grity. These results indicate that the simultaneous induction of a hea t shock response and an oxidative stress response is responsible for h uman EC apoptosis.