SHEAR-STRESS INHIBITS H2O2-INDUCED APOPTOSIS OF HUMAN ENDOTHELIAL-CELLS BY MODULATION OF THE GLUTATHIONE REDOX CYCLE AND NITRIC-OXIDE SYNTHASE

Physiological levels of shear stress reduce endothelial cell turnover and exert a potent antiatherosclerotic effect. Here we demonstrate tha t oxidative stress-induced apoptosis of human endothelial cells was in hibited by shear stress (15 dynes/cm(2)). incubation with H2O2 (200 mu mol/L) for 18 hours induced apoptosis of human umbilical venous endot helial cells as demonstrated by an enzyme-linked immunosorbent assay s pecific for histone-associated DNA fragments and visual analysis of fl uorescence-stained nuclei. Sheer stress-mediated inhibition of apoptos is was partially prevented by pharmacological inhibition of glutathion e (GSH) biosynthesis with buthionine sulfoximine (BSO) or nitric oxide (NO) synthase with N-G-monomethyl-L-arginine (LNMA), whereas inhibiti on of catalase by aminotriazol did not affect the inhibitory action of shear stress. Combined inhibition of NO synthase and GSH biosynthesis completely reversed the protective effect of sheer stress. suggesting that bath NO synthase and the GSH redox cycle system are involved in the apoptosis-suppressing effect of sheer stress. Similar results were obtained when apoptosis was stimulated by tumor necrosis factor alpha (TNF alpha). To gain further insights into the interference of shear stress with apoptosis signal transduction, we measured caspase-3-like activity, a cysteine protease that has been shown to play a predominan t role in the cell death effector pathway. Indeed, shear stress preven ted the activation of caspase-3-like activity induced by H2O2 or TNF a lpha. The inhibitory effect of shear stress was prevented by LNMA and BSO. suggesting that the reduction of oxidative flux by shear stress p revents the activation of caspase-like proteases and thereby inhibits apoptotic cell death in human endothelial cells.