Thrombin regulates vascular smooth muscle cell proteoglycan synthesis via PAR 1 and multiple downstream signalling pathways

Introduction: Atherosclerosis is the underlying pathological process of most cardiovascular disease. Thrombin is a serine protease which can activate protease activated receptors (PAR) on vascular smooth muscle cells (VSMC) to elicit cellular responses that can contribute to the pathogenesis of atherosclerosis. Human atherosclerosis commences with the binding and retention of lipoproteins by the glycosaminoglycan (GAG) chains of chondroitin/dermatan sulfate proteoglycans. The potential effects of thrombin on the synthesis and structure of CS/DS proteoglycans produced by VSMCs was investigated. Materials and methods: VSMCs were derived from human internal mammary arteries. Proteoglycan synthesis was assessed by [35S]sulfate and [3H]glucosamine incorporation. Proteoglycan size was assessed by SDS-PAGE and size exclusion chromatography. Results and conclusion: Thrombin caused a dose-dependent increase in [35S]sulfate and [3H]glucosamine incorporation with maximum effects of approximately 150% at the highest doses tested. This increase was associated with increased size of biglycan and decorin assessed by SDS-PAGE. Chemically cleaved glycosaminoglycan (GAG) chains analyzed by SDS-PAGE and size exclusion chromatography were larger for proteoglycans from thrombin treated cells. VSMCs synthesize small GAGs when provided with exogenous xyloside and thrombin treatment also increased the size of the secreted xyloside GAGs.