Sialic acid moieties on surface glycoproteins protect endothelial cells from proteolytic damage.

The importance of the glycocalyx in controlling responses to proteinases was studied by enzymic removal of sialic acids from the luminal surface of arterial endothelium. In the perfused rat aorta collagenase induced cell detachment in greater numbers from the desialylated than from the untreated endothelium. Neuraminidase treatment increased by three-fold prostacyclin synthesis by the vessel wall in respons to thrombin. The supernatant from activated human neutrophils, containing elastolytic activity, when perfused together with neuraminidase enhanced and prolonged sialic acid release induced by neuraminidase alone. Thus the effects of different proteinases on various endothelial cell functions are potentiated by removal of surface sialic acid residues.