46 - Heparan sulfate proteoglycans regulate aortic response to vasoactive agents

Abstract

The endothelial glycocalyx is known to regulate vascular function by sensing mechanical forces and by acting as a barrier to solute and protein transport. Its role on the regulation of vascular tone and blood pressure is incipient. Herein we sought to investigate if the genetic deletion of syndecan-1 (Sdc-1) and glypican-1 (Gpc-1) alters vascular reactivity. Male CD-1, C57BL/6, Sdc-1 knockout (Sdc-1-/-) and Gpc-1 knockout (Gpc-1-/-) mice were used. Vascular response to phenylephrine (PE, 1 nM to 0.1 µM), acetylcholine (Ach, 10 µM to 10 mM), angiotensin II (Ang II, 1 nM to 0.1 µM) was assessed in aortic rings with endothelium. The expression of p-eNOS Ser1177, eNOS, p-Akt Ser473, Akt, p-Cav-1 Tyr14 and Cav-1 were analyzed by immunoblotting. Aortic rings from Gpc-1-/- mice showed an increased maximum response to Ang II (0.21g) and preserved response to PE (0.30g) when compared to CD1 control (PE: 0.28g; Ang: 0.14g). Aortic rings from Sdc-1-/- mice showed an increased maximum response to PE (0.29g) and a decreased maximum response to Ang II (0.04g) when compared to C57BL/6 (PE: 0.13g; Ang: 0.08g). Both strains showed impaired endothelium-dependent relaxation and decreased eNOS and AKT activity. Only Sdc-1-/- showed decreased eNOS expression when compared to respective control. Gpc-1-/- showed increased p-Cav-1 Tyr14 and Cav-1 when compared to CD-1 mice. Sdc-1-/- mice had decreased p-Cav-1 Tyr14 and Cav-1 when compared to C57BL/6 mice. In addition, ROS were decreased in both Sdc-1-/- (4253.00 AU) and Gpc-1-/- (4993.20 AU) mice when compared to C57BL/6 (19166.40 AU) and CD-1 (15584.60 AU) controls. Deletion of heparan sulfate proteoglycans alter the vascular response to specific vasoactive agents by potentially redox-sensitive mechanisms. The endothelial glycocalyx may be a primary regulator of vascular tone.