Dataset Information

Alcohol Metabolizing Enzymes, Microsomal Ethanol Oxidizing System, Cytochrome P450 2E1, Catalase, and Aldehyde Dehydrogenase in Alcohol-Associated Liver Disease.

ABSTRACT: Once ingested, most of the alcohol is metabolized in the liver by alcohol dehydrogenase to acetaldehyde. Two additional pathways of acetaldehyde generation are by microsomal ethanol oxidizing system (cytochrome P450 2E1) and catalase. Acetaldehyde can form adducts which can interfere with cellular function, leading to alcohol-induced liver injury. The variants of alcohol metabolizing genes encode enzymes with varied kinetic properties and result in the different rate of alcohol elimination and acetaldehyde generation. Allelic variants of these genes with higher enzymatic activity are believed to be able to modify susceptibility to alcohol-induced liver injury; however, the human studies on the association of these variants and alcohol-associated liver disease are inconclusive. In addition to acetaldehyde, the shift in the redox state during alcohol elimination may also link to other pathways resulting in activation of downstream signaling leading to liver injury.

SUBMITTER: Jiang Y

PROVIDER: S-EPMC7148483 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Alcohol Metabolizing Enzymes, Microsomal Ethanol Oxidizing System, Cytochrome P450 2E1, Catalase, and Aldehyde Dehydrogenase in Alcohol-Associated Liver Disease.

Jiang Yanchao Y Zhang Ting T Kusumanchi Praveen P Han Sen S Yang Zhihong Z Liangpunsakul Suthat S

Biomedicines 20200304 3

Once ingested, most of the alcohol is metabolized in the liver by alcohol dehydrogenase to acetaldehyde. Two additional pathways of acetaldehyde generation are by microsomal ethanol oxidizing system (cytochrome P450 2E1) and catalase<b>.</b> Acetaldehyde can form adducts which can interfere with cellular function, leading to alcohol-induced liver injury. The variants of alcohol metabolizing genes encode enzymes with varied kinetic properties and result in the different rate of alcohol eliminatio ...[more]

PMID: 32143280

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Project description:This study investigated the role of ethanol-inducible cytochrome P450-2E1 (CYP2E1) in enhancing CYP2E1 and other P450 proteins in extracellular vesicles (EVs) from alcohol-exposed rodents and human patients with alcoholism and their effects on oxidative hepatocyte injury. Female Fischer rats and wild-type or Cyp2e1-null mice were exposed to three oral doses of binge ethanol or dextrose control at 12-hour intervals. Plasma EV and hepatic proteins from alcohol-exposed rodents, patients with alcoholism, and their respective controls were isolated and characterized. The number of EVs and the amounts of EV CYP2E1, CYP2A, CYP1A1/2, and CYP4B proteins were markedly elevated in both patients with alcoholism and alcohol-exposed rats and mice. The number of EVs and EV P450 proteins were significantly reduced in ethanol-exposed rats fed a diet containing polyunsaturated fatty acids. The increased number of EVs and EV CYP2E1 and other P450 isoforms in alcohol-exposed wild types were significantly reduced in the corresponding Cyp2e1-null mice. EV CYP2E1 amounts depended on increased oxidative and endoplasmic reticulum (ER) stress because their levels were decreased by cotreatment with the antioxidant N-acetylcysteine or the CYP2E1 inhibitor chlormethiazole but increased by ER stress-inducer thapsigargin, which was blocked by 4-phenylbutyric acid. Furthermore, cell death rates were elevated when primary hepatocytes or human hepatoma cells were exposed to EVs from alcohol-exposed rodents and patients with alcoholism, demonstrating that EVs from alcohol-exposed rats and patients with alcoholism are functional and can promote cell death by activating the apoptosis signaling pathway, including phospho-c-Jun N-terminal kinase, proapoptotic Bax, and activated caspase-3. Conclusion: CYP2E1 has an important role in elevating EV CYP2E1 and other P450 isoforms through increased oxidative and ER stress. Elevated EV-CYP2E1 detected after withdrawal from alcohol or exposure to the CYP2E1 inducer pyrazole can be a potential biomarker for liver injury. (Hepatology Communications 2017;1:675-690).

Project description:BackgroundHepatic steatosis is an early pathology of alcohol-associated liver disease (ALD). Fatty acid-binding protein-4 (FABP4, a FABP not normally produced in the liver) is secreted by hepatocytes in ALD and stimulates hepatoma proliferation and migration. This study sought to investigate the mechanism[s] by which hepatic ethanol metabolism regulates FABP4 and steatosis.MethodsHuman hepatoma cells (HepG2/HuH7) and cells stably transfected to express cytochrome P450 2E1 (CYP2E1), were exposed to ethanol in the absence or presence of chlormethiazole (a CYP2E1-inhibitor; CMZ) and/or EX-527 (a sirtuin-1 [SIRT1] inhibitor). The culture medium was analyzed for ethanol metabolism and FABP4 protein abundance. Cells were analyzed for FABP4 mRNA expression, SIRT1 protein abundance, and neutral lipid accumulation. In parallel, cells were analyzed for forkhead box O1 [FOXO1], β-catenin, peroxisome proliferator-activated receptor-α [PPARα], and lipin-1α protein abundance in the absence or presence of ethanol and pharmacological inhibitors of the respective target proteins.ResultsCYP2E1-dependent ethanol metabolism inhibited the amount of SIRT1 protein detected, concomitant with increased FABP4 mRNA expression, FABP4 protein secretion, and neutral lipid accumulation, effects abolished by CMZ. Analysis of pathways associated with lipid oxidation revealed increased FOXO1 nuclear localization and decreased β-catenin, PPARα, and lipin-1α protein levels in CYP2E1-expressing cells in the presence of ethanol. Pharmacological inhibition of SIRT1 mimicked the effects of ethanol, while inhibition of FOXO1 abrogated the effect of ethanol on FABP4 mRNA expression, FABP4 protein secretion, and neutral lipid accumulation in CYP2E1-expressing cells. Pharmacological inhibition of β-catenin, PPARα, or lipin-1α failed to alter the effects of ethanol on FABP4 or neutral lipid accumulation.ConclusionCYP2E1-dependent ethanol metabolism inhibits SIRT1-FOXO1 signaling, which leads to increased FABP4 mRNA expression, FABP4 protein secretion, and neutral lipid accumulation. These data suggest that FABP4 released from steatotic hepatocytes could play a role in promoting tumor cell expansion in the setting of ALD and represents a potential target for therapeutic intervention.

Dataset Information

Alcohol Metabolizing Enzymes, Microsomal Ethanol Oxidizing System, Cytochrome P450 2E1, Catalase, and Aldehyde Dehydrogenase in Alcohol-Associated Liver Disease.

Publications

Alcohol Metabolizing Enzymes, Microsomal Ethanol Oxidizing System, Cytochrome P450 2E1, Catalase, and Aldehyde Dehydrogenase in Alcohol-Associated Liver Disease.

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