Student Research: Shengli Shi

, Environmental Toxicology (Tox), 2004
Faculty Advisor: Terrance J. Kavanagh

Effects of Enhanced Glutathione Biosynthesis on Oxidative Stress-mediated Hepatocellular Injury and Gene Expression in Mice


Abstract

Oxidative stress plays a critical role in the hepatotoxicity of tumor necrosis factor α (TNFα), a carbon tetrachloride (CCl4), and acetaminophen (APAP). Glutathione (GSH) is a major free radical scavenger and an important factor in detoxification of reactive oxygen species and xenobiotics. The rate-limiting enzyme in the synthesis of GSH is glutamate-cysteine ligase (GCL) which consists of two subunits: GCLC and GCLM. We have generated transgenic mice that conditionally express GCLC and GCLM in the liver using a mifepristone (RU486)-responsive transactivator. To test the hypothesis that enhanced GSH synthesis would prevent oxidative stress-medicated hepacellular injury, GCL transgenic mice and their non-transgenic littermate controls were treated with TNFα, CCl4, and APAP. GCLM protein levels and GCL activities were significantly increased in GCL transgenic mice with RU486 induction as revealed by Western Blotting and biochemical assay. GCL transgene induction attenuated TNFα and APAP-induced liver injury as indicated by serum ALT, histology score, and gene expression alterations. There are some common transcription responsive elements (TREs) that over-represented in genes up-regulated by the three hepatotoxicants. These results confirm the role of GSH in protection against oxidative stress. This model also provides a unique in vivo system to investigate the complicated interactions between GSH and oxidants on gene expression.

Supported by NIH grants 1P42ES04696, P30ES07033 and 1R01ES10849-02.