SUPPRESSION OF APOPTOSIS BY NITRIC-OXIDE VIA INHIBITION OF INTERLEUKIN-1-BETA-CONVERTING ENZYME (ICE)-LIKE AND CYSTEINE PROTEASE PROTEIN (CPP)-32-LIKE PROTEASES

Physiological levels of shear stress alter the genetic programm of cul tured endothelial cells and are associated with reduced cellular turno ver rates and formation of atherosclerotic lesions in vivo. To test th e hypothesis that shear stress (15 dynes/cm(2)) interferes with progra mmed cell death, apoptosis was induced in human umbilical venous cells (HUVEC) by tumor necrosis factor-alpha (TNF-alpha). Apoptosis was qua ntified by ELISA specific for histone-associated DNA-fragments and con firmed by demonstrating the specific pattern of internucleosomal DNA-f ragmentation. TNF-alpha (300 U/ml) mediated increase of DNA-fragmentat ion was completely abrogated by shear stress (446 +/- 121% versus 57 /- 11%, P <0.05). This anti-apoptotic activity of shear stress decreas ed after pharmacological inhibition of endogenous nitric oxide (NO)-sy nthase by N-G-monomethyl-L-arginine and was completely reproduced by e xogenous NO-donors. The activation of interleukin-1 beta-converting en zyme (ICE)-like and cysteine protease protein (CPP)-32-like cysteine p roteases was required to mediate TNF-alpha-induced apoptosis of HUVEC. Endothelial-derived nitric oxide (NO) as well as exogenous NO donors inhibited TNF-alpha-induced cysteine protease activation. Inhibition o f CPP-32 enzyme activity was due to specific S-nitrosylation of Cys 16 3, a functionally essential amino acid conserved among ICE/CPP-32-like proteases. Thus, we propose that shear stress-mediated NO formation i nterferes with cell death signal transduction and may contribute to en dothelial cell integrity by inhibition of apoptosis.