THE EFFECT OF CORNEA PROTEOGLYCANS ON LIPOSOME PEROXIDATION

Proteoglycans (PGs) from bovine cornea showed a protective effect on l iposome peroxidation induced by Fe2+. Both chondroitin sulfate, dermat an sulfate-containing PG (CS,DS-PG) and keratan sulfate-containing PG (KS-PG) inhibited thiobarbituric acid-reactive substance formation whe n incubated with liposomes and Fe2+, CS,DS-PG being more effective tha n KS-PG. The native structure of PGs contributed markedly to antioxida nt activity. Papain digestion of core protein reduced the protective e ffect of CS,DS-PG, whereas it abolished completely that of KS-PG. Appa rently, only hexuronate-containing glycosaminoglycan (GAG) chains may exert a significant antioxidant activity and this was confirmed using standard GAGs. Quasielastic laser light scattering was used to evaluat e the structural consequence of peroxidative damage induced by Fenton reagent on liposomes. After exposure to the free-radical-generating sy stem, a bimodal distribution of liposomes was observed, probably depen ding on the loss of native structure and fragmentation. Both CS,DS-PG and KS-PG prevented liposome breakdown. Again, free KS chains were ine ffective against liposome damage, whereas DS and CS maintained the nor mal distribution of liposome size, These data support the hypothesis t hat PGs may represent part of the antioxidant mechanisms of organisms and suggest that modifications of PG content and/or composition might affect tissue sensitivity to oxidative stress. (C) 1996 Academic Press , Inc.