Ethanol metabolism by alcohol dehydrogenase or cytochrome P₄₅₀2E1 differentially impairs hepatic protein trafficking and growth hormone signaling

Abstract

The liver metabolizes alcohol using alcohol dehydrogenase (ADH) and cytochrome P 2E1 (CYP2E1). Both enzymes metabolize ethanol into acetaldehyde, but CYP2E1 activity also results in the production of reactive oxygen species (ROS) that promote oxidative stress. We have previously shown that microtubules are hyperacetylated in ethanol-treated polarized, hepatic WIF-B cells and livers from ethanol-fed rats. We have also shown that enhanced protein acetylation correlates with impaired clathrin-mediated endocytosis, constitutive secretion, and nuclear translocation and that the defects are likely mediated by acetaldehyde. However, the roles of CYP2E1-generated metabolites and ROS in microtubule acetylation and these alcohol-induced impairments have not been examined. To determine if CYP2E1-mediated alcohol metabolism is required for enhanced acetylation and the trafficking defects, we coincubated cells with ethanol and diallyl sulfide (DAS; a CYP2E1 inhibitor) or -acetyl cysteine (NAC; an antioxidant). Both agents failed to prevent microtubule hyperacetylation in ethanol-treated cells and also failed to prevent impaired secretion or clathrin-mediated endocytosis. Somewhat surprisingly, both DAS and NAC prevented impaired STAT5B nuclear translocation. Further examination of microtubule-independent steps of the pathway revealed that Jak2/STAT5B activation by growth hormone was prevented by DAS and NAC. These results were confirmed in ethanol-exposed HepG2 cells expressing only ADH or CYP2E1. Using quantitative RT-PCR, we further determined that ethanol exposure led to blunted growth hormone-mediated gene expression. In conclusion, we determined that alcohol-induced microtubule acetylation and associated defects in microtubule-dependent trafficking are mediated by ADH metabolism whereas impaired microtubule-independent Jak2/STAT5B activation is mediated by CYP2E1 activity. Impaired growth hormone-mediated signaling is observed in ethanol-exposed hepatocytes and is explained by differential effects of alcohol dehydrogenase (ADH)- and cytochrome P 2E1 (CYP2E1)-mediated ethanol metabolism on the Jak2/STAT5B pathway.

Oxidative Stress Parameters in the Liver of Growing Male Rats Receiving Various Alcoholic Beverages

“…The liver metabolizes alcohol by ADH and cytochrome P450 2E1 (CYP2E1), while both the process of metabolism and the resulting metabolites induce the production of ROS, which intensify oxidative stress [34]. However, in the present study, no differences in the level of TBARS were found in the liver of the studied groups compared with the control animals.…”

Dendropanax morbifera Leaf Polyphenolic Compounds: Optimal Extraction Using the Response Surface Method and Their Protective Effects against Alcohol-Induced Liver Damage

“…The variance analysis results showed that FRAP activity was influenced by the ethanol concentration (X1), the linear effect of extraction temperature (X3), the second-order interaction of ethanol concentration (X1 2 ), the reciprocal action of ethanol concentration and sample to solvent ratio (X12), the ethanol concentration and extraction temperature (X13), and the extraction temperature and extraction time (X34) ( Table 2). Among these, X1, X1 2 , and X13 showed largest F-value regression, and thus stronger dependency. The removal of the factors that did not influence the model led to the formation of the second-order polynomial equation given below:…”

“…Alcohol in the human body is first converted to acetaldehyde via the oxidation process, mediated by alcohol dehydrogenase (ADH) in the liver, and then converted to acetic acid via the same process, but mediated by aldehyde dehydrogenase (ALDH) [1]. The oxidation pathway used to metabolize alcohol in the liver is largely governed by three enzymes: ADH, cytochrome P450 2E1 (CYP2E1), and catalase (CAT) [2]. The reactive oxygen species (ROS) generated from excessive alcohol consumption are known to oxidize intracellular macromolecules, such as DNA, proteins, and lipids, and induce oxidative stress in the liver, causing functional damages.…”

Hesperidin promotes lysosomal biogenesis in chronically ethanol‐induced cardiotoxicity in rats: A proposed mechanisms of protection

“…Our data demonstrated that cardiac TFEB gene expression was significantly downregulated in ethanol‐fed rats compared with both control groups; this impairment in transcriptional regulation of lysosomal functioning could be indebted to the ability of ethanol metabolites to disturb protein trafficking through faulty microtubule assembly, disrupting both microtubule content and function . Furthermore, hesperidin administration resulted in significant upregulation of cardiac TFEB gene expression, thus implicating stimulation of autophagy‐lysosome machinery.…”