Relationship between acetaldehyde levels and cell survival in ethanol-metabolizing hepatoma cells

Abstract

T he vast majority of ingested ethanol is oxidized to acetaldehyde by the hepatocytes of the liver. 1,2 It is thought that the metabolism of ethanol by hepatocytes is the reason that the liver is a target for the detrimental effects of chronic alcohol abuse. 3 Ethanol oxidation by hepatocytes results in many metabolic changes, some of which have been shown to be detrimental to cells. It has been proposed that chronic ethanol abuse promotes continual hepatocyte destruction that, in turn, stimulates abnormal hepatocyte regeneration and fibrotic scarring, which over many years results in alcoholic liver disease. Thus, alcoholic liver disease results from an eventual inability of hepatocytes to appropriately respond and regenerate in response to the toxic effects of the metabolic changes that occur during ethanol oxidation. 4 Liver regeneration is the mechanism by which cells that have been lost as a result of hepatotoxicity are replaced. It is well documented that ethanol metabolism impairs the regenerative capacity of the liver. 3,5 Therefore, it appears that ethanol oxidation not only results in hepatotoxicity, but also impairs the ability of the liver to respond to this toxic assault. The mechanism(s) by which chronic ethanol metabolism affects replication is not well understood. This is partially because the biochemical events that take place during ethanol oxidation occur simultaneously, making it difficult to attribute specific impairments to specific biochemical events.In an attempt to dissect these biochemical events, we have developed a cell-culture system with cells of hepatic origin that stably expresses alcohol dehydrogenase and efficiently metabolizes ethanol. Using these cells, we in-

Ethanol exposure inhibits hepatocyte lipophagy by inactivating the small guanosine triphosphatase Rab7

“…In the case of Rab7, the GTP‐loaded and active form of this protein exhibits a strong affinity for the RILP, an effector that promotes the recruitment of dynein–dynactin complexes to lysosomes for subsequent transport and fusion 22, 34. Accordingly, a GST‐tagged form of RILP was used in a pulldown assay to measure total Rab7 activity in EtOH‐metabolizing VA‐13 cells, a widely used HepG2 hepatoma‐derived cell line that stably expresses alcohol dehydrogenase 26, 35. An EtOH exposure of 24 hours led to a dramatic decrease in the activity of Rab7 (Fig.…”

“…All protocols were approved by the Institutional Animal Care and Use Committee at the VA Nebraska‐Western Iowa Health Care System Research Service. Adh1‐expressing VA‐13 hepatocytes26 were kindly provided by Terrence Donohue (University of Nebraska Medical Center) and cultured in Dulbecco's modified Eagle's medium containing 400 µg/mL zeocin. Glutathione S ‐transferase (GST)–Rab‐interacting lysosomal protein (RILP) was a gift from C. Bucci (University of Salente, Lecce, Italy).…”

Alcohol and smoking and subsequent risk of prostate cancer in Japanese men: The Japan Public Health Center‐based prospective study

“…Ethanol or acetaldehyde, which is a carcinogen, 24 affects cell proliferation and induces DNA damage, which may lead to malignant changes. 25,26 Furthermore, accumulating evidence suggests that prostate carcinogenesis by alcohol is mediated through increased estrogens and decreased androgens and sex hormone-biding globulin. [27][28][29][30][31][32] Results regarding the effect of smoking on prostate cancer have been inconsistent.…”

Suicide gene therapy: conversion of ethanol to acetaldehyde mediated by human beta 2 alcohol dehydrogenase

“…Acetaldehyde is a well-recognized toxin producing singlestrand DNA breaks 7 and protein adducts. 8 While not previously described as a therapeutic agent, the ability of prolonged acetaldehyde exposure to damage or inhibit cell growth in vitro [9][10][11] and in vivo is well characterized. 12 The physiological metabolism of alcohol takes place primarily within the liver where ethanol is converted to acetaldehyde, mainly via the action of alcohol dehydrogenase.…”

“…Parallel results have been reported for the human colorectal cell line Caco-2 with a 150% increase in cell doubling time following exposure to 500 mM acetaldehyde for 3 days. 16 More recent studies using plasmid-mediated transfer of ADH genes into cells with low ALDH activity have demonstrated that intracellular production of acetaldehyde reaching concentrations of up to 600 mM can result in growth inhibition 10,17,18 and induction of apoptosis. 10,19 To investigate the potential of intracellular acetaldehyde generation as a therapeutic approach, we have used the human beta 2 ADH enzyme.…”