Structural and Functional Modifications of Human Aorta Proteoglycans in Atherosclerosis

Abstract

Proteoglycans (PGs) were extracted from minced normal human aorta intima and media and adjacent atherosclerotic plaques. Samples obtained from each individual artery which showed different degrees of atherosclerotic involvement were studied separately. Comparing normal and atherosclerotic areas from the same aorta, the hexuronic acid content was always lower in the atherosclerotic minces. Atherosclerotic samples always contained a higher percentage amount of chondroitinase AC resistant material. PGs were sequentially extracted with increasing guanidine hydrochloride (GuHCl) concentrations. 0.4 M GuHCl extracted about 13% of total PGs, containing mostly chondroitin sulphate (CS), whilst 4 M GuHCl extracted about 50% of total PGs, containing CS, dermatan sulphate (DS), heparan sulphate and hyaluronic acid. PGs from atherosclerotic minces showed a higher DS amount, based on electrophoretic glycosaminoglycan (GAG) analysis. PGs extracted with 4 M GuHCl were further characterized by gel-chromatography and by CsCl density gradient centrifugation. The relative content of PGs with highest hydrodynamic size appeared to be markedly reduced in all the atherosclerotic samples. LDL/GAGs and LDL/PGs interactions were studied by affinity chromatography. GAGs obtained by papain digestion of PGs extracted from atherosclerotic areas contained a glycosaminoglycuronan interacting more strongly with human LDL than GAGs from normal areas of the same artery. The complete elution of PGs required higher NaCl concentration than GAGs. Moreover, PGs from atherosclerotic samples showed higher affinity for LDL than PGs from normal areas of the same aorta.