SHEAR-STRESS INHIBITS APOPTOSIS OF HUMAN ENDOTHELIAL-CELLS

Physiological levels of shear stress alter the genetic program of cult ured endothelial cells and reduce endothelial cell turnover in vivo. T o test the hypothesis that shear stress interferes with programmed cel l death, apoptosis was induced in human umbilical venous endothelial c ells by growth factor withdrawal or incubation with tumor necrosis fac tor alpha (TNF alpha) for 18 h. Apoptosis was quantified by ELISA spec ific for histone-associated DNA fragments and confirmed by demonstrati ng the specific pattern of internucleosomal DNA fragmentation detected by electrophoresis and immunohistochemical staining. The TNF alpha (3 00 U/ml)-mediated increase in DNA fragmentation was completely abrogat ed by shear stress. Furthermore, shear stress dose-dependently reduced DNA fragmentation induced by growth factor withdrawal with maximal ef fect at 45 dyn/cm(2). Inhibition of the CPP32-like proteases with Ac-D EVD-CHO (100 mu T) revealed similar anti-apoptotic effects. In contras t, CPP32-independent induction of endothelial cell apoptosis by C-2-ce ramide (50 mu M) was not prevented by shear stress. Thus, we propose t hat shear stress interferes with common cell death signal transduction involving the CPP32-bke protease family and may contribute to endothe lial cell integrity by inhibition of apoptosis.