Suppression of Endothelin-1 Production in Cultured Human Umbilical Vein Endothelial Cells by Heparin Fractions Separated by Strong Anion Exchange Chromatography

Heparin has been shown to lower the production/secretion of the vasoconstrictive peptide endothelin-1. Endothelin-1 production is stimulated by thrombin, and it has been proposed that heparin binds to the anion-binding exosite of thrombin, preventing it from stimulating endothelin-1 production. To further test this proposal, heparin was fractionated by strong anion exchange chromatography (QAE-Sephadex A-25) into four fractions. These fractions had anticoagulant activities that increased linearly with charge, as defined by the median salt concentration needed for elution from the column. The fractions also differed in the total number of sulfates per mole of heparin, which was dependent on the molecular mass of the fractions rather than charge density. The fractions were found to significantly differ from each other in their ability to suppress endothelin-1 production. The fraction eluting from the ion exchange column at the highest salt concentration had the greatest suppressive effect. Addition of sodium or potassium chloride to the media interfered with the ET-1 suppressive effect of unfractionated heparin, whereas lithium chloride had no effect. These data show that charge interactions between heparin and thrombin may be important in regulating the production of endothelin-1 and in regulating other thrombin-dependent functions.