We investigate the role of shear stress in regulating the gene expression in endothelial cells (ECs) in response to tumor necrosis factor-alpha (TNF-alpha). ECs were kept in static condition or pre- exposed to a high level (HSS, 20 dynes/cm(2)) or a low level of shear stress (LSS, 0.5 dynes/cm(2)) for 24 h, and TNF-alpha was added under static condition for 4 h. In static ECs, DNA microarray showed that TNF-alpha caused a significant increase in expression of 102 genes and a significant decrease in expression of 12 genes. Pre-shearing of ECs decreased the TNF-alpha-responsiveness of many pro-inflammatory, pro-coagulant, proliferative, and pro-apoptotic genes, whereas it increased the responsiveness of some antioxidant, anti- coagulant, and anti- apoptotic genes. LSS showed less regulatory effects than HSS on EC gene expression in response to TNF-alpha. The microarray data were confirmed by reverse-transcription polymerase chain reaction for 64 selected genes. Pre-shearing of ECs at HSS significantly inhibited the TNF-alpha-induced p65 and p50 mRNA expressions and nuclear factor-kappa B (NF-kappa B)-DNA binding activity. Inhibition of NF-kappa B activity with the p65-antisense or lactacystin under static condition blocked the expression of most of the genes that are TNF-alpha-inducible and shear stress-down-regulated. Our findings suggest that laminar shear stress serves protective functions against atherogenesis.
