Hepatotoxicity free radical generation

The effects of chromium(III) chloride and sodium chromate(VI) on the hepatotoxicity of carbon tetrachloride exposure to mouse hepatocytes were examined by Tezuka et al. (1995). Primary cultures of mouse hepatocytes were pretreated with 10 or 100 pM chromium for 24 hours followed by exposure to 1-5 mM carbon tetrachloride for up to 1 hour. Chromium(VI) pretreatment significantly reduced the cell toxicity as well as lipid peroxidation caused by carbon tetrachloride. Chromium(III) pretreatment did not have any effect on cell toxicity. About 50% of chromium(VI) was taken up and reduced in the cells by 90% to chromium(III) within 10 minutes. The initial uptake rate of chromium(HI) into cells was greater than 500-fold less than chromium(VI), and only about 5% was absorbed. The protection against carbon tetrachloride damage by chromium(VI) was attributed to its rapid uptake and conversion to chromium(III), and it was determined that chromium(III) acts as a radical scavenger for the free radicals generated by carbon tetrachloride within the cell. Furthermore, chromium(VI) pretreatment reduced the activity of NADPH cytochrome c reductase which metabolizes carbon tetrachloride to reactive species. 

One mechanism that has been proposed to explain the hepatotoxicity of 1,1,2-trichloroethane is the generation of free radical intermediates from reactive metabolites of 1,1,2-trichloroethane (acyl chlorides). Free radicals may stimulate lipid peroxidation which, in turn, may induce liver injury (Albano et al. 1985). However, Klaassen and Plaa (1969) found no evidence of lipid peroxidation in rats given near-lethal doses of 1,1,2-trichloroethane by intraperitoneal injection. Takano and Miyazaki (1982) determined that 1,1,2-trichloroethane inhibits intracellular respiration by blocking the electron transport system from reduced nicotinamide adenine dinucleotide (NADH) to coenzyme Q (CoQ), which would deprive the cell of energy required to phosphorylate adenosine diphosphate (ADP) and thereby lead to depletion of energy stores. 

Hepatotoxicity for most chemical toxins mechanistically proceeds via free radical formation which causes OS that induces lipid peroxidation, membrane damage, and altered enzyme activities, the generation of ROS and hydrophilic toxins. Ethanol,... 

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