Injury to hepatocytes by toxicants such as ethanol and allyl alcohol is a multi-faceted process, leading to cellular dysfunction and cell death via pathways that are not clearly defined. 80me of the mechanisms proposed to contribute include glutathione depletion and subsequent oxidant stress in the cell. In addition, these toxicants alone, or in combination with other agents, may induce the production of endogenous mediators that further damage hepatocytes. S-adenosyI-L-methionine (SAMe) is a nutritional supplement that appears to have positive effects as a treatment for liver injury caused by hepatotoxicants, though its mechanisms of action are not clearly understood. SAMe is a methyl donor and a precursor for the antioxidant molecule glutathione. The intent of this proposal is to use allyl alcohol as a model for toxicant-induced hepatocyte injury, and determine the role of SAMe in attenuating the cellular damage. In addition, this laboratory has determined that allyl alcohol liver damage is augmented by the endogenous compound 15- deoxy-prostaglandin J2 (15d-PGJ2). Allyl alcohol and 15d-PGJ2 are proposed to act in an additive manner to deplete glutathione and inhibit the activation of nuclear factor (NF) kB, leading to decreased production of survival proteins and hepatooyte death. The overall hypothesis to be tested is that SAMe inhibits allyl alcohol toxicity and 15d-PGJ2 augmentation of this toxicity via stabilizing glutathione levels and establishing an oxidant balance in the cell, thus maintaining healthy mitochondda and a normalized NFkB activation status. Subcellular localization (cytosol versus mitochondda versus nucleus) of glutathione depletion may be important in determining NFkB activation and cell fate. The following specific aims will be tested: 1) SAMe inhibits glutathione depletion by allyl alcohol and 15d-PGJ2 in hepatocytes, thus decreasing cytotoxicity. 2) SAMe counteracts oxidative stress in hepatocytes due to GSH depletion caused by allyl alcohol and augmented by 15d-PGJ2, thereby maintaining a normalized NFKB activation status and decreasing cytotoxicity. 3) SAMe corrects hepatocyte mitochondrial dysfunction caused by allyl alcohol and 15d-PGJ2. 4) SAMe inhibits allyl alcohol and 15d-PGJ2-induced hepatocyte toxicity, whether cell death occurs via apoptotic or necrotic pathways. These experiments will give insight into the potential interaction of an endogenous product, 15d-PGJ2, in the complex relationship of toxicants, somatic response elements and therapeutic agents in determining liver health and cell survival. Results from these studies will increase our knowledge of the mechanism of action of an alternative medicine already in common use, SAMe, in countering the injurious actions of hepatotoxicants, with allyl alcohol as a model. Moreover, they may provide evidence for development of related therapeutic compounds.
| Maddox, Jane F; Domzalski, Alison C; Roth, Robert A et al. (2004) 15-deoxy prostaglandin J2 enhances allyl alcohol-induced toxicity in rat hepatocytes. Toxicol Sci 77:290-8 |
