Effect of ethanol on tumor necrosis factor signaling during liver regeneration.
OBJECTIVE
The liver has tremendous regenerative capacity but can be damaged by toxins, such as ethanol (EtOH). It has long been known that EtOH inhibits liver regeneration. Recent work demonstrates that the proinflammatory cytokine, tumor necrosis factor ( (TNF), is required for normal liver regeneration, as well as for EtOH-related liver damage. Therefore, it is conceivable that EtOH promotes liver damage by altering TNF signal transduction in such a way that proliferative signals are aborted and death signals predominate.


METHODS
Anti-TNF antibodies were used to characterize the TNF signals that are induced in the regenerating liver after two-thirds (partial) hepatectomy (PH) in normal mice and rats. Then, these TNF-regulated processes were evaluated in animals that had been fed nutritionally replete, EtOH-containing diets for several weeks before PH.


RESULTS
During normal liver regeneration, TNF induces potentially dangerous responses, such as increased mitochondrial ROS production, but also promotes the activation of several factors, including NF kappa B, Jun N-terminal Kinase (JNK), and various mitochondrial membrane proteins, which are likely to permit hepatocytes to survive apoptotic and oxidant stress. Previous EtOH exposure inhibits the normal regenerative induction of NF kappa B and JNK.


CONCLUSIONS
These finding are consistent with the possibility that potential hepatotoxins compromise the balanced induction of toxic and trophic signals by TNF.
Diehl
A M
AM
Johns Hopkins University, Baltimore, Maryland 21205, USA. amdiehl@jhmi.edu
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D004789:Enzyme Activation; D000431:Ethanol / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D019254:Genes, bcl-2; D048031:JNK Mitogen-Activated Protein Kinases; D008115:Liver Regeneration; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D015398:Signal Transduction / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D016328:NF-kappa B; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D000431:Ethanol; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases