Platelet sialic acid as a potential pathogenic factor in coronary heart disease.

It was previously reported that, compared to healthy individuals, patients with coronary heart disease (CHD) exhibit a higher proportion of platelets with lower densities and higher propensity to aggregate. Reasons for this increased tendency to aggregate were unknown but appeared to be independent of the patient's age, gender, or smoking habits. Sialic acid (N-acetyl-neuraminic acid), a negatively charged sugar and constituent of many glycoproteins and gangliosides, is known to confer the bulk of negative charges to mammalian cell surfaces. These negatively charged surfaces can help cells of the bloodstream to maintain a relative distance from each other due to repulsion of the same (negative) charges. In this study, we examined whether differences in platelet sialic acid are a potential pathogenic factor in patients with coronary heart disease. Upon isolating platelets, we found a significantly higher (p < 0.05) proportion of low density platelets in patients compared to healthy controls, which is in accordance with previously published data. We found significantly less (p < 0.05) sialic acid in platelets from patients compared to the control. Most of the platelet total sialic acid was susceptible to cleavage by neuraminidase, demonstrating sialic acid to be preferably localized at the outer platelet surface. We conclude that the lower sialic acid content found in platelets from CHD patients could represent a contributing factor for the observed higher aggregability of platelets from these patients. Due to the lower sialic acid content and resulting lower negative surface charge, less repulsion between the platelets could facilitate aggregation.