Shear Stress and Vascular Heparan Sulfate-Dependent Expression of Endothelin B Receptor

The endothelial glycocalyx (GCX) plays a crucial role in vascular health and integrity and influences many biochemical activities through mechanotransduction. Endothelin-1 (ET-1) is a potent vasodilator produced by endothelial cells (EC) and plays a significant role in many cardiovascular-related conditions, including hypertension and atherosclerosis. ET-1 binds to the endothelin B receptor (ETB) on ECs, stimulating vasodilation and to the endothelin A receptor on smooth muscle cells, stimulating vasoconstriction. Shear stress (SS) dependence of ET-1 and heparan sulfate (HS) has been shown, and reports suggest that ETB is also SS dependent. In this study, we hypothesize that GCX HS regulates the expression of ETB on the EC surface in a SS-dependent manner. Human Lung Microvascular ECs were exposed to various SS magnitudes in a parallel-plate flow chamber for 12 hours. Damaged GCX was simulated by treatment with 15mU/mL Heparinase-III during exposure to SS. Immunostaining and qPCR were used to evaluate changes in expression of ET-1, ETB, and heparan sulfate, a major GCX component. Results indicate that ETB is SS dependent, but this effect is reduced by HS degradation, indicating ETB expression may also be HS-dependent. Under SS, ET-1 synthesis increases without a corresponding rise in ET-1 protein expression, implying that post-translational regulation of ET-1 occurs independently of HS.