Endothelial homeostasis is controlled by blood components and mechanical forces, including wall shear stress (WSS). In response to shear stress, endothelial cells (EC) release ATP, a regulator of vascular function. Pannexin1 (Panx1) is a transmembrane channel known for its involvement in ATP release from multiple cell types.

To study the expression of Panx1 in response to WSS and its role in the endothelium.

Human Umbilical Vein Endothelial Cells (HUVECs) were submitted to physiological high laminar shear stress (HLSS) and atheroprone shear oscillatory shear stress (OSS) for 48h using an orbital shaker. Panx1 mRNA and protein levels were determined by qPCR and Western blot. A WSS modifying cast was placed around the carotid artery of Apolipoprotein E-deficient (Apoe-/-) mice. Panx1 was detected by en face immunofluorescence.

Panx1 protein was increased in HUVECs exposed to OSS compared with HLSS. Moreover, carotid artery regions exposed to OSS showed more Panx1 immunofluorescence than regions exposed to HLSS. In silico analysis of the promotor of Panx1 revealed binding sites for the WSS-sensitive transcription factors NFkB and CREB. However, no changes were observed in Panx1, NFkB and CREB mRNA levels in HUVECs exposed to OSS or HLSS, suggesting that the increased Panx1 level under OSS may be due to decreased Panx1 degradation rather than to increased synthesis. Using cyclohexamide treatment for various periods up to 48h, preliminary data showed that the half-life of Panx1 protein in HUVECs is about 18h.

Endothelial Panx1 protein expression is increased in response to OSS. Absence of OSS effects on Panx1, NFkB and CREB mRNA demonstrated that the upregulation of Panx1 protein is not due to transcriptional effects of OSS. Future experiments aim to understand the role of proteasomal degradation and autophagy pathways on endothelial Panx1 levels under OSS and HLSS.