Role of HSP70 in ozone preconditioning-induced reduction of hepatic ischemia-reperfusion injury in rats

Objective To evaluate the role of heat shock protein 70 (HSP70) in ozone preconditioning-induced reduction of hepatic ischemia-reperfusion (I/R) injury in rats. Methods Twenty-four pathogen-free healthy male Sprague-Dawley rats, aged 8 weeks, weighing 250-300 g, were divided into 4 groups (n=6 each) using a random number table: sham operation group (group S), group I/R, ozone preconditioning group (group OP) and HSP70 inhibitor quercetin group (group Q). Hepatic I/R injury was induced by clamping the branches of hepatic artery supplying left and middle lobes of the liver, portal vein and bile vessel for 45 min, followed by 2 h of reperfusion.In group OP, the mixture of ozone and oxygen was intraperitoneally injected at the concentration of ozone 50 μg/ml and bolus dose 1 mg/kg once a day for 5 consecutive days before operation.In group Q, quercetin 7 mg/kg was intraperitoneally injected at 1 h before injecting the mixture of ozone and oxygen.Blood samples from the abdominal aorta were collected at 2 h of reperfusion for determination of serum alanine transaminase (ALT) and aspartate transaminase (AST) activities and concentrations of interleukin-1beta (IL-1β), IL-6 and tumor necrosis factor-alpha (TNF-α) in serum (by enzyme-linked immunosorbent assay). The animals were sacrificed after blood sampling, and hepatic tissue specimens were collected for detection of activated caspase-3 expression (by Western blot) and cell apoptosis (by TUNEL). Apoptotic index (AI) was calculated. Results Compared with group S, the serum ALT and AST activities, concentrations of IL-1β, IL-6 and TNF-α in serum and AI were significantly increased, and the expression of activated caspase-3 was up-regulated in group I/R (P<0.05 or 0.01). Compared with group I/R, the serum ALT and AST activities, concentrations of IL-1β, IL-6 and TNF-α in serum and AI were significantly decreased, and the expression of activated caspase-3 was down-regulated in group OP (P<0.05 or 0.01). Compared with group OP, the serum ALT and AST activities, concentrations of IL-1β, IL-6 and TNF-α in serum and AI were significantly increased, and the expression of activated caspase-3 was up-regulated in group Q (P<0.05 or 0.01). Conclusion The mechanism by which ozone preconditioning reduces hepatic I/R injury is related to activating HSP70 and inhibiting inflammatory responses and cell apoptosis in rats. Key words: Ozone; Liver; Reperfusion injury; HSP70 heat-shock proteins