Dysregulated cytokine metabolism, altered hepatic methionine metabolism and proteasome dysfunction in alcoholic liver disease

C McClain, S Barve, S Joshi‐Barve… - Alcoholism: Clinical …, 2005 - Wiley Online Library
C McClain, S Barve, S Joshi‐Barve, Z Song, I Deaciuc, T Chen, D Hill
Alcoholism: Clinical and Experimental Research, 2005Wiley Online Library
Alcoholic liver disease (ALD) remains an important complication and cause of morbidity and
mortality from alcohol abuse. Major developments in our understanding of the mechanisms
of ALD over the past decade are now being translated into new forms of therapy for this
disease process which currently has no FDA approved treatment. Cytokines are low
molecular weight mediators of cellular communication, and the pro‐inflammatory cytokine
tumor necrosis factor (TNF) has been shown to play a pivotal role in the development of …
Abstract: Alcoholic liver disease (ALD) remains an important complication and cause of morbidity and mortality from alcohol abuse. Major developments in our understanding of the mechanisms of ALD over the past decade are now being translated into new forms of therapy for this disease process which currently has no FDA approved treatment. Cytokines are low molecular weight mediators of cellular communication, and the pro‐inflammatory cytokine tumor necrosis factor (TNF) has been shown to play a pivotal role in the development of experimental ALD. Similarly, TNF levels are elevated in the serum of alcoholic hepatitis patients. Abnormal methionine metabolism is well documented in patients with ALD, with patients having elevated serum methionine levels, but low S‐adenosylmethionine levels in the liver. On the other hand, S‐adenosylhomocysteine and homocysteine levels are elevated in ALD. Recent studies have documented potential interactions between homocysteine and S‐adenosylhomocysteine with TNF in the development of ALD. Altered proteasome function also is now well documented in ALD, and decreased proteasome function can cause hepatocyte apoptosis. Recently it has been shown that decreased proteasome function can also act synergistically to enhance TNF hepatotoxicity. Hepatocytes dying of proteasome dysfunction release pro‐inflammatory cytokines such as Interleukin‐8 to cause sustained inflammation. This article reviews the interactions of cytokines, altered methionine metabolism, and proteasome dysfunction in the development of ALD.
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