The role of endothelial glycocalyx components in mechanotransduction of fluid shear stress

The surface of endothelial cells is decorated with a wide variety of membrane-bound macromolecules that constitute the glycocalyx. These include glycoproteins bearing acidic oligosaccharides with terminal sialic acids (SA), and proteoglycans with their associated glycosaminoglycan that include: heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA). In this study, enzymes were used to selectively degrade glycocalyx components from the surface of bovine aortic endothelial cells and the effects of these alterations on fluid shear-induced nitric oxide (NO) and prostacyclin (PGI₂) production were determined. Depletion of HS, HA, and SA, but not CS, blocked shear-induced NO production. Surprisingly, the same enzyme depletions that blocked NO production had no influence on shear-induced PGI₂ production. The results may be interpreted in terms of a glypican-caveolae-eNOS mechanism for shear-induced NO transduction, with PGI₂ being transduced in basal adhesion plaques that sense the same reaction stress whether the glycocalyx is intact or not.