Vascular non-protein thiols: Prooxidants or antioxidants in atherogenesis?

Abstr.-cell-mediated lipoprotein oxidation may be due to generation of non- protein thiols (NP-SH) from cystine with formation of oxidizing species. Ho wever, NP-SH, especially GSH, may also exert antioxidant effects in vitro a nd in vivo. To further investigate whether vascular NP-SH could be prooxida nts or antioxidants in atherosclerosis, we have correlated the aortic conte nt of NP-SW with that of lipoperoxides in 10 rabbits fed on a fat-enriched atherogenic diet for 9 weeks. As compared to 7 control rabbits, aortic NP-S H and lipoperoxides were significantly increased in the fat-fed animals. Th e levels of NP-SH were strongly and inversely correlated with those of lipi d peroxidation in the atherosclerotic aorta (r(s) -0.92, P < 0.0001 for thi obarbituric acid reactive substances, and r(s) -0.80, P < 0.01 for fluoresc ent damage products of lipid peroxidation). A similar trend was evident als o in the control rabbits (r(s) -0.60 for both indices of lipid peroxidation ). Thus, the present data suggest that vascular NP-SH exert significant ant ioxidant-antilipoperoxidative effects ill vivo especially in fat diet-relat ed atherogenic conditions.