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.

Alcohol and Hepatocellular Carcinoma: Adding Fuel to the Flame

“…In this regard, few data regarding the effects of alcohol on hepatocytes’ cell cycle and proliferation are available, and remain quite controversial. Classical in vitro studies performed by Clemens and co-workers [ 109 ] indicated that alcohol promotes cell cycle arrest of hepatocytes in G2/M phase and senescence via increased accumulation of the phosphorylated inactive form of the cyclin-dependent kinase, p-Cdk2, and of the cyclin dependent kinase inhibitor, p21. The augmented levels of these proteins result in a direct effect of acetaldehyde, rather than a consequence of oxidative stress.…”

Selective Killing of Cancer Cells by Nonplanar Aromatic Hydrocarbon‐Induced DNA Damage

“…The results showed that [4]helicenium significantly activated P53 and P21 in SK‐Hep1, but had no effect on HL7702 (Figure f). In addition, p‐CDC2, an important regulator in promoting G2/M phase transition, was inhibited in SK‐Hep1 after the treatment of [4]helicenium (Figure f), further implying that [4]helicenium‐treated HCC cell confronted with a problem of cell cycle progression defects. It appeared that the selective inhibition of HCC cell growth by [4]helicenium is mainly due to cell cycle arrest and cell apoptosis increment.…”

A Unifying Hypothesis Linking Hepatic Adaptations for Ethanol Metabolism to the Proinflammatory and Profibrotic Events of Alcoholic Liver Disease

“…AcAld also causes mtDNA damage, and mtDNA deletions occur in >60% of patients with alcoholic steatosis (Fromenty, et al, 1995). Progressive loss of hepatocytes signifies a failure of hepatocellular regeneration, which is otherwise extraordinary in liver, an effect that may be due to AcAld-mediated G2/M cell cycle arrest (Diehl, 2005;Scheer, et al, 2016). Compromised bioenergetics in hepatocytes with mtDepo may also contribute to failure of regeneration.…”