Down Regulation Of Glutathione S‐Transferase‐Pi Is Involved In The Pathogenesis Of Alcohol‐Induced Liver Injury

Background Alcohol‐associated liver disease (ALD) remains a major cause of morbidity and mortality in the United States and worldwide. The pathogenic mechanisms of ALD are not fully understood and there is no FDA approved therapy. Several mechanisms are known to be involved in the pathogenesis of ALD, including ethanol metabolism–associated lipid peroxidation, glutathione (GSH) depletion and oxidative stress. Protection against oxidative damage, particularly certain oxidant species and lipid peroxidation derived toxic aldehydes, is mediated by GSH conjugation, which can occur spontaneously or be facilitated by the glutathione S‐transferase (GST) enzymes. In this study, we investigated the role of GST‐Pi (GSTP) in experimental ALD using GSTP null mice. Methods We used the chronic binge alcohol feeding (10+1) murine model of ALD to examine the role of GSTP in wild type C57Bl/6 (WT) mice and GSTP knockout mice (GSTPKO). Serum was analyzed by routine biochemical assays to measure AST and ALT as markers of liver injury. Liver tissue was analyzed by real‐time PCR, Western blotting and immunostaining to assess lipid metabolism, hepatic peroxidation, ER stress, apoptosis and injury. Results Alcohol consumption significantly reduced hepatic GSTP in mRNA and protein levels in WT mice. H istological analysis of H&E or Oil Red O stained liver tissue sections showed increased hepatic steatosis in GSTPKO mice compared to WT, with a concomitant decrease in the expression of Cpt1, the rate limiting enzyme of fatty acid oxidation. Further, GSTPKO mice had a significant increase in the alcohol‐induced hepatic oxidative stress and accumulation of acrolein and 4‐hydroxynonenal. Real‐time PCR and liver tissue immunofluorescence staining revealed that deficiency of GSTP was associated with endoplasmic reticulum (ER) stress, and consequently, increased hepatocyte apoptosis and liver injury as measured by TUNEL staining and serum ALT and AST. Conclusions This study indicates that down regulation of hepatic GSTP plays an important role in alcohol‐induced hepatic steatosis, oxidative and ER stress, apoptosis and injury during the development of ALD. Strategies to upregulate or induce GSTP may have therapeutic potential in attenuating ALD.