title: The Involvement of Acetaldehyde in Ethanol-Induced Cell Cycle Impairment.
abstract: BACKGROUND
  Hepatocytes metabolize the vast majority of ingested ethanol. This metabolic activity results in hepatic toxicity and impairs the ability of hepatocytes to replicate. Previous work by our group has shown that ethanol metabolism results in a G2/M cell cycle arrest. The intent of these studies was to discern the roles of acetaldehyde and reactive oxygen, two of the major by-products of ethanol metabolism, in the G2/M cell cycle arrest.
  
  
  METHODS
  To investigate the role of ethanol metabolites in the cell cycle arrest, VA-13 and VL-17A cells were used. These are recombinant Hep G2 cells that express alcohol dehydrogenase or alcohol dehydrogenase and cytochrome P450 2E1, respectively. Cells were cultured with or without ethanol, lacking or containing the antioxidants N-acetylcysteine (NAC) or trolox, for three days. Cellular accumulation was monitored by the DNA content of the cultures. The accumulation of the cyclin-dependent kinase, Cdc2 in the inactive phosphorylated form (p-Cdc2) and the cyclin-dependent kinase inhibitor p21 were determined by immunoblot analysis.
  
  
  RESULTS
  Cultures maintained in the presence of ethanol demonstrated a G2/M cell cycle arrest that was associated with a reduction in DNA content and increased levels of p-Cdc2 and p21, compared with cells cultured in its absence. Inclusion of antioxidants in the ethanol containing media was unable to rescue the cells from the cell cycle arrest or these ethanol metabolism-mediated effects. Additionally, culturing the cells in the presence of acetaldehyde alone resulted in increased levels of p-Cdc2 and p21.
  
  
  CONCLUSIONS
  Acetaldehyde produced during ethanol oxidation has a major role in the ethanol metabolism-mediated G2/M cell cycle arrest, and the concurrent accumulation of p21 and p-Cdc2. Although reactive oxygen species are thought to have a significant role in ethanol-induced hepatocellular damage, they may have a less important role in the inability of hepatocytes to replace dead or damaged cells.
authors.affiliation: Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68105, USA. Scheer77@aol.com.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Scheer
authors.affiliation: Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68105, USA. km0308@hotmail.com.|Nebraska and Western Iowa Veterans Administration Medical Center, University of Nebraska Medical Center, Omaha, NE 68105, USA. km0308@hotmail.com.
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Schneider
authors.affiliation: Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68105, USA. rochelle.finnigan@yahoo.com.
authors.forename: Rochelle L
authors.initials: RL
authors.lastname: Finnigan
authors.affiliation: Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68105, USA. epmaloney@gmail.com.
authors.forename: Eamon P
authors.initials: EP
authors.lastname: Maloney
authors.affiliation: Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68105, USA. wellsma@gmail.com.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wells
authors.affiliation: Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68105, USA. dclemens@unmc.edu.|Nebraska and Western Iowa Veterans Administration Medical Center, University of Nebraska Medical Center, Omaha, NE 68105, USA. dclemens@unmc.edu.|Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, NE 68105, USA. dclemens@unmc.edu.
authors.forename: Dahn L
authors.initials: DL
authors.lastname: Clemens
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism / Q000633:toxicity*; D000111:Acetylcysteine / Q000494:pharmacology; D000426:Alcohol Dehydrogenase / Q000378:metabolism; D000975:Antioxidants / Q000494:pharmacology; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002460:Cell Line; D002839:Chromans / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D000431:Ethanol / Q000633:toxicity*; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D056945:Hep G2 Cells; D006801:Humans; D015151:Immunoblotting; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002839:Chromans; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017382:Reactive Oxygen Species; D000431:Ethanol; D000426:Alcohol Dehydrogenase; D016203:CDC2 Protein Kinase; D000079:Acetaldehyde; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; D000111:Acetylcysteine
keywords: acetaldehyde; cell cycle arrest; cyclin-dependent kinase inhibitors; cyclin-dependent kinases; ethanol metabolism