Sheer stress reduces protease activated receptor-1 expression in human endothelial cells

Shear stress has been shown to regulate several genes involved in the throm botic and proliferative functions of endothelial cells. Thrombin receptor ( protease-activated receptor-1: PAR-1) increases at sites of vascular injury , which suggests an important role for PAR-1 in vascular diseases. However, the effect of shear stress on PAR-1 expression has not been previously stu died. This work investigates effects of shear stress on PAR-1 gene expressi on in both human umbilical vein endothelial cells (HUVECs) and microvascula r endothelial cells (HMECs). Cells were exposed to different shear stresses using a parallel plate flow system. Northern blot and flow cytometry analy sis showed that shear stress downregulated PAR-1 messenger RNA (mRNA) and p rotein levels in both HUVECs and HMECs but with different thresholds. Furth ermore, shear-reduced PAR-1 mRNA was due to a decrease of transcription rat e, not increased mRNA degradation. Postshear stress release of endothelin-l in response to thrombin was reduced in HUVECs and HMECs. Moreover, inhibit ors of potential signaling pathways applied during shear stress indicated m ediation of the shear-decreased PAR-1 expression by protein kinases. In con clusion, shear stress exposure reduces PAR-1 gene expression in HMECs and H UVECs through a mechanism dependent in part on protein kinases, leading to altered endothelial cell functional responses to thrombin. (C) 2001 Biomedi cal Engineering Society.