Inhibition of Cultured Bovine Aortic Smooth Muscle Cell Proliferation by Colominic Acid

Colominic acid (CA) is an alpha2,8-linked polymer of sialic acid, originally isolated from capsular Escherichia coli K1. Since inhibition of arterial smooth muscle cell hyperplasia is one of the effective strategies to prevent atherosclerosis, we investigated the effect of CA, purified as an alpha2,8-linked homopolymer of N-acetylneuraminic acid, on the proliferation of bovine aortic smooth muscle cells in culture. The results demonstrate that CA inhibits the proliferation of the cells without nonspecific cell damage. Sulfation did not modify the inhibitory effect of CA. Specifically, the inhibitory effect of sulfated CA was almost equal to that of CA in vascular smooth muscle cell proliferation. On the other hand, it was suggested that the inhibition of the proliferation by CA is in a degree similar to that by heparin but weaker than that by sodium/calcium-spirulans, known sulfated polysaccharides as the potent inhibitor of vascular smooth muscle cells. The present data suggest that CA with or without sulfate groups can be an origin of beneficial agents that prevents atherosclerosis through a moderate inhibition of arterial smooth muscle cell proliferation.

Induction of synthesis of a large heparan sulfate proteoglycan, perlecan, by thrombin in cultured human coronary smooth muscle cells

The accumulation of extracellular matrix components such as proteoglycans is a hallmark of an atherosclerotic lesion. A large heparan sulfate proteoglycan, perlecan, dramatically increases in the advanced lesion, and vascular smooth muscle cells are the cell type responsible for the accumulation. In this study, we investigated the effects of thrombin on the proteoglycan synthesis in cultured human coronary smooth muscle cells to determine the interrelationship between the accumulation of proteoglycans and the procoagulant state of blood in atherosclerosis. The cells were metabolically labeled with [(35)S]sulfate or (35)S-labeled amino acids in the presence of thrombin, and the labeled proteoglycans were characterized by Sepharose CL-4B molecular sieve chromatography and DEAE-Sephacel ion-exchange chromatography. The glycosaminoglycan M(r) and composition were analyzed by Sepharose CL-6B chromatography, and the core protein M(r) was determined by SDS-polyacrylamide gel electrophoresis before and after digestion with chondroitinase ABC or papain. The results indicate that thrombin increases the cell layer-associated heparan sulfate proteoglycan with a core protein size of approximately 400 kDa without any change in the length of the glycosaminoglycan chains when the cell density is high. The heparan sulfate proteoglycan was identified as perlecan by Western blot analysis. In addition, quantitative reverse transcription-polymerase chain reaction showed that thrombin elevated the steady-state level of perlecan mRNA but not that of versican, decorin, and syndecan-1 mRNAs, although that of biglycan mRNA was moderately elevated. Furthermore, the percentage of disaccharide units that compose perlecan heparan sulfate chains remained unaffected by thrombin. Therefore, it is suggested that thrombin induces the perlecan core protein synthesis without influencing the formation of the heparan sulfate chains in human coronary smooth muscle cells at a high cell density. The regulation of proteoglycan synthesis by thrombin may be involved in the accumulation of perlecan in advanced lesions of atherosclerosis.