Endothelin-1 activates ETA receptors on human vascular smooth muscle cells to yield proteoglycans with increased binding to LDL

ObjectiveLipid retention in the vessel wall by glycosaminoglycan (GAG) chains on chondroitin/dermatan sulfate proteoglycans synthesized by vascular smooth muscle cells (VSMC) have recently been established as an early event in human coronary artery atherosclerosis. GAG structure can be altered by growth factors resulting in enhanced binding to low density lipoprotein (LDL). The aim of this study was to determine if proteoglycans produced by endothelin-1 treated VSMCs had increased binding to human LDL, to examine the effect of endothelin-1 on the synthesis and structure of proteoglycans and to elucidate the signalling pathway.Methods and resultsEndothelin-1 stimulated an increase in [35S]sulfate and [3H]glucosamine incorporation into proteoglycans produced by human VSMC. The increase was due to an increase in GAG chain size assessed by SDS-PAGE and size exclusion chromatography. Increased radiolabel incorporation was inhibited by an ETA but not an ETB receptor antagonist. Endothelin-1 stimulated an increase in the 6:4 position sulfation ratio on the disaccharides of the GAG chains, an effect that was blocked by bosentan. The EGF receptor antagonist AG1478 did not affect the increase in GAG size mediated by endothelin-1. Inhibition of protein kinase C (PKC) with GF109203X or down regulation by PMA pre-treatment attenuated the effect of endothelin-1 on GAG synthesis.ConclusionThese data demonstrate that endothelin-1 stimulates changes in GAG chain structure that increase binding to LDL. This action of endothelin-1 may represent a new target for the prevention of lipid binding within the vascular wall and the associated complications resulting from this interaction.