Heat-shock preconditioning reduces oxidative protein denaturation and ameliorates liver injury by carbon tetrachloride in rats

Abstract

Membrane lipids and cytosolic proteins are major targets of oxidative injury. This study examined the effect of heat-shock preconditioning associated with the induction of heat-shock protein 72 on liver injury, from the aspect of lipid peroxidation and protein denaturation after carbon tetrachloride (CCl4) administration in rats--one of the representative oxidative injuries. Male Wistar rats were divided into two groups, group HS (preconditioned by heat exposure) and group C (not preconditioned). Expression of HSP72 in the liver tissue was confirmed by Western blot analysis. After a 48-h recovery period, all rats were given CCl4 intragastrically. Liver damage was assessed by measuring serum liver-related enzyme levels and adenine nucleotide concentration in the liver tissue. Lipid peroxidation and protein denaturation were evaluated by measuring tiobarbituric acid reactive substances (TBARS) and by immunohistochemical staining of 4-hydroxy-2-nonenal(HNE)-modified proteins in the liver. Survival rates of the rats after CCl4 administration were also compared. Expression of HSP72 was clearly detected in group HS, but not in group C. Heat-shock preconditioning significantly improved the survival rate, suppressed the increase in liver-related enzyme levels and maintained adenosine triphosphate levels (P<0.01 each). HNE-modified proteins--denatured proteins by free radical attack--were significantly less stained in group HS than in group C (P<0.05). However, TBARS levels did not differ between groups. Because heat-shock preconditioning did not alter TBARS levels but reduced HNE-modified proteins in association with the expression of HSP72, it is suggested that HSP72 did not prevent lipid peroxidation but decreased the lipid peroxidation-induced denaturation of proteins. This seemed to be a mechanism of heat-shock preconditioning to ameliorate oxidative liver injury.