Carbon tetrachloride-induced free radical mediated protein oxidation in vitro and in vivo

Trichloromethyl and trichloromethylperoxyl free radicals generated by UVC light activation of carbon tetrachloride promote the formation of protein carbonyls in chicken egg albumin in vitro. Further, UVC light itself exerts a highly significant equivalent effect of its own. The reaction was significantly blocked by Trolox but not by α-tocopherol at a concentration of 1 mM. EDTA (3 mM) partially prevented the oxidative effects of (•)CCl3 or CCl3O2(•) in proteins but not those of UV light. Rat liver microsomes in the presence of NADPH also led to the formation of carbonyl groups in microsomal proteins. That effect was significantly enhanced by the presence of CCl4 in the incubation mixture. Liver microsomes from CCl4 poisoned animals exhibited significantly increased levels of protein carbonyls at 1 and 2 h after administration but not at 3 h. These results suggest that proteins might be targets of CCl4 oxidative effects. Protein carbonyls might arise from either direct attack by (•)CCl3 or CCl3O2(•), or from 4-hydroxynonenal reaction via Michael addition with amino acids at the aldehyde double bond and retaining the carbonyl group attached to the target protein.