The oxidant hypochlorite (OCl^-), a product of the myeloperoxidase system, degrades articular cartilage proteoglycan aggregate

The myeloperoxidase-derived oxidant, hyprochlorite (OCL^-) was shown to be able to degrade proteogylcan aggregate prepared from bovine articular cartilage. Exposure of proteoglycan aggregate to OCl^- concentrations less than 10^-4 resulted in a decrease in the size of the constituent proteoglycan monomers, which were unable to reaggregate with hyaluronate due to the loss of the hyaluronic acid binding region as indicated by immunoblotting using the monoclonal 1-C-6 antibody. Analysis of the [³⁵S]-labeled core proteins by SDS / polyacrylamide electrophoresis and flurography indicated a decrease in the size of the core protein. These data suggest that concentrations of OCl^- below 10^-3 M results in the cleavage of the proteoglycan core protein in or near the hyaluronic acid binding region. The physiological consequences of these data are discussed. Exposure to higher concentrations (>10^-3) of OCl^- caused more extensive degradation of the core protein; however, there was no evidence to suggest that OCl^- cleaves glycosaminoglycan (GAG) chains.