TGF-beta enhances alcohol dependent hepatocyte damage via down-regulation of alcohol dehydrogenase I.
OBJECTIVE
Adverse alcohol effects in the liver involve oxidative metabolism, fat deposition and release of fibrogenic mediators, including TGF-beta. The work presents an assessment of liver damaging cross-talk between ethanol and TGF-beta in hepatocytes.


METHODS
To investigate TGF-beta effects on hepatocytes, microarray analyses were performed and validated by qRT-PCR, Western blot analysis and immunohistochemistry. The cellular state was determined by assessing lactate dehydrogenase, cellular glutathione, reactive oxygen species, lipid peroxidation and neutral lipid deposition. RNA interference was used for gene silencing in vitro.


RESULTS
TGF-beta is induced in mouse livers after chronic ethanol insult, enhances ethanol induced oxidative stress and toxicity towards cultured hepatocytes plus induces lipid-, oxidative stress metabolism- and fibrogenesis-gene expression signatures. Interestingly, TGF-beta down-regulates alcohol metabolizing enzyme Adh1 mRNA in cultured hepatocytes and liver tissue from TGF-beta transgenic mice via the ALK5/Smad2/3 signalling branch, with Smad7 as a potent negative regulator. ADH1 deficiency is a determining factor for the increased lipid accumulation and Cyp2E1 dependent toxicity in liver cells upon alcohol challenge. Further, ADH1 expression was decreased during liver damage in an intragastric ethanol infusion mouse model.


CONCLUSIONS
In the presence of ethanol, TGF-beta displays pro-steatotic action in hepatocytes via decreasing ADH1 expression. Low ADH1 levels are correlated with enhanced hepatocyte damage upon chronic alcohol consumption by favoring secondary metabolic pathways.
Ciuclan
Loredana
L
Molecular Hepatology-Alcohol Dependent Diseases, II. Medical Clinic, Faculty of Medicine at Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, Mannheim, Germany.
Ehnert
Sabrina
S
Ilkavets
Iryna
I
Weng
Hong-Lei
HL
Gaitantzi
Haristi
H
Tsukamoto
Hidekazu
H
Ueberham
Elke
E
Meindl-Beinker
Nadja M
NM
Singer
Manfred V
MV
Breitkopf
Katja
K
Dooley
Steven
S
D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D056486:Chemical and Drug Induced Liver Injury / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology*; D000431:Ethanol / Q000009:adverse effects*; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology; D050356:Lipid Metabolism / Q000502:physiology; D015227:Lipid Peroxidation / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018384:Oxidative Stress / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051906:Smad7 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D018125:Receptors, Transforming Growth Factor beta; D051906:Smad7 Protein; C497807:Smad7 protein, mouse; D016212:Transforming Growth Factor beta; D000431:Ethanol; D000426:Alcohol Dehydrogenase; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625842:Tgfbr1 protein, mouse