The effect of glutathione preconditioning on heme oxygenase-1 system established by whey protein feeding on hepatocellular injury in a rat hepatic normothermic i/r injury model

Abstract

Purpose: Oxygen radicals which are produced during reperfusion phase play a central role for hepatocellular damage during ischemia/reperfusion (I/R) injury. Antioxidant strategies appear a promising approach to prevent I/R injury. In the present study, the effect of glutathione (GSH) preconditioning established by whey protein feeding on hepatocellular injury markers was assessed in a rat hepatic normothermic I/R injury model. The interaction between intracellular GSH content and heme oxygenase-1 (HO-1) enzyme expression was also determined in order to understand the level of upgrading of HO-1 system in a high GSH content environment after preconditioning.

Material and Methods: Livers of female Sprague-Dawley rats were subjected to 45/45 minutes of normothermic I/R injury. A group of rats were fed by standard chow for a three week duration before I/R procedure (CONTROL I/R; n=16), whereas another group was fed by “whey” protein for preconditioning (WHPR I/R; n=16) during the same period. Two SHAM groups were constituted accordingly but rats were not subjected to I/R injury (STD SHAM and WHEY SHAM; n=6 in each). Following 45 minutes of reperfusion, serum transaminase levels as well as GSH, malondialdehyde (MDA) levels, apoptotic index (AI) and HO-1 gene expression in liver tissue were determined. Half of the animals in both injury groups were surveilled for a week without sampling.

Results: Intracellular GSH levels in WHEY SHAM group were significantly higher than those of STD SHAM group which indicated a successful preconditioning. Preconditioning by “whey” protein feeding prior to I/R injury (WHPR I/R) significantly ameliorated the increased levels of serum transaminase as well as liver MDA levels and Aİ in CONTROL I/R group. Survival of the rats in both injury groups were not different. “Whey” preconditioning also significantly increased GSH levels, whereas HO-1 expression was lower when compared to rats subjected to I/R injury without preconditioning.

Conclusion: Feeding with “whey” protein successfully resulted high GSH content in rat liver. Whey preconditioning ameliorated hepatic I/R injury. HO-1 enzyme seems to have a less important role in antioxidant defense system when GSH production was induced prior to I/R injury.