Aggregation of LDL with chondroitin-4-sulfate makes LDL oxidizable in the presence of water-soluble antioxidants

Abstract

The content of plasma and arterial interstitial fluid in water-soluble antioxidants makes it unlikely for low-density lipoprotein (LDL) to oxidize by the oxidation mechanisms most frequently discussed. By aggregation of LDL in the presence of chondroitin-4-sulfate (C-4-S), but not with chondroitin-6-sulfate or sphingomyelinase, a complex arises which can oxidize in the presence of 20 μM ascorbate and 300 μM urate. This oxidation sensitivity even persists after the gel-filtration of an LDL/C-4-S/Cu 2+ complex, indicating entrapment of Cu 2+ within. This corresponds well to the known ability of C-4-S to bind copper ions and is a potential mechanism by which LDL oxidation in the arterial intima is facilitated after prolonged retention by the extracellular matrix.