The mechanism(s) by which alcohol causes cell injury are still not clear. A major mechanism that is a focus of considerable research is the role of lipid peroxidation and oxidative stress in alcohol toxicity. Many pathways have been suggested to play a key role on how ethanol induces """"""""oxidative stress"""""""", including mitochondrial dysfunction, activation of MAP kinases, ethanol-induced increases in cytokine formation, especially TNF1 and induction of CYP2E1. These pathways are not exclusive of each other, however, associations and interactions between them, especially under in vivo conditions, remain to be evaluated and clarified. We hypothesize that increased oxidative stress from CYP2E1 induction in vivo sensitizes hepatocytes to TNF1-induced hepatotoxicity. We propose that oxidants such as peroxynitrite, activation of MAP kinases such as JNK and/or P38 MAPK, inactivation of NF-kB and mitochondrial dysfunction are downstream mediators of the CYP2E1- TNF1 potentiated hepatotoxicity. We also hypothesize that induction of CYP2E1 plays a central role in mechanisms by which in vivo treatment with alcohol potentiates TNF1 hepatotoxicity. Since CYP2E1 and TNF1 are considered key risk factors in the development of alcoholic liver injury, possible interactions and potentiation of their actions in vivo is important to evaluate.
AIM 1 will evaluate the potentiation of TNF1-induced liver injury by induction of CYP2E1. TNF1 or saline will be administrated to either saline-treated mice with basal levels of CYP2E1, or pyrazole-treated mice with high levels of CYP2E1, and to CYP2E1-knockout mice with no CYP2E1. Various concentrations of TNF1 will be given and mice killed at various times after TNF1 challenge. We will assay for the following: Hepatotoxicity, oxidative/nitrosative stress, activation of NF-kB, activation of MAP kinases, mitochondrial dysfunction.
AIM 2 will evaluate the role of CYP2E1 in the potentiation of TNF1-induced liver injury by ethanol and to identify downstream targets for the CYP2E1-ethanol- TNF1 interactions. A binge model of alcohol intake followed by TNF1 or saline challenge will be the acute ethanol model evaluated. For chronic ethanol feeding, mice will be fed a control or an ethanol Lieber-DeCarli diet for 2, 4 or 6 weeks, followed by challenge with TNF1 (or saline). Assays similar to the above will be carried out. To prove that CYP2E1 is responsible for the potentiated injury in the pyrazole and ethanol models, CYP2E1 knockout mice and humanized CYP2E1 knockin mice will be used.
We believe that these experiments will help to clarify how two independent risk factors believed to be important for alcohol-induced liver injury, CYP2E1 and TNF1 interact to promote this liver injury, will provide clear evidence for a role for CYP2E1 in acute and chronic alcohol/ TNF1 potentiated liver injury, and help to identify downstream mediators, signaling pathways and targets of the CYP2E1-ethanol- TNF1 interactions. The latter may have potential therapeutic value. PHS 398/2590 (Rev. 09/04, Reissued 4/2006) Page Continuation Format Page
Showing the most recent 10 out of 18 publications
