Effects of laminar shear stress on IL-8 mRNA expression in endothelial cells

This study sought to demonstrate that IL-8 expression in endothelial cells is regulated by not only chemical factors but also mechanical factors. After pretreating cultured human umbilical vein endothelial cells (HUVECs) with shear stress for different periods of time, we employed RT-PCR to assay IL-8 mRNA expression and immunocytochemical staining to detect NF-κB activation in HUVECs. The results showed: (1) IL-8 mRNA expressed little in HUVECs untreated or pretreated with low laminar shear stress for 0.5 h; IL-8 mRNA expression increased when HUVECs were pretreated with low laminar shear stress for 1 h, and it increased further when HUVECs were pretreated for 2 h; (2) the immunoreactivity of NF-κB p65 in the nuclei of HUVECs untreated or pretreated with low laminar shear stress for 0.5 h was negative, while it became weak positive in the nuclei of HUVECs pretreated with shear stress for 1 h and positive in the nuclei of HUVECs pretreated for 2 h. The findings implied that low laminar shear stress was capable of inducing IL-8 gene expression and activating NF-κB, which were both time-dependent. The induction of IL-8 gene expression by laminar shear stress is probably due to the activation of NF-κB. On these grounds we come to the conclusion that IL-8 expression induced in endothelial cells by low shear stress may play an important role in the genesis and development of both inflammation and arterioatherosclerosis.