Alcohol-induced microtubule acetylation leads to the accumulation of large, immobile lipid droplets.

Although steatosis (fatty liver) is a clinically well-described early stage of alcoholic liver disease, surprisingly little is known about how it promotes hepatotoxicity. We have shown that ethanol consumption leads to microtubule hyperacetylation that can explain ethanol-induced defects in protein trafficking. Because almost all steps of the lipid droplet life cycle are microtubule dependent and because microtubule acetylation promotes adipogenesis, we examined droplet dynamics in ethanol-treated cells.

Demethylase JMJD6 as a New Regulator of Interferon Signaling: Effects of HCV and Ethanol Metabolism.

Background & Aims: Alcohol-induced progression of hepatitis C virus (HCV) infection is related to dysfunction of innate immunity in hepatocytes. Endogenously produced interferon (IFN)α induces activation of interferon-stimulated genes (ISGs) via triggering of the Janus kinase-signal transducer and activator of transcription 1 (STAT1) pathway. This activation requires protein methyltransferase 1-regulated arginine methylation of STAT1.

Ethanol-induced steatosis involves impairment of lipophagy, associated with reduced Dynamin2 activity.

Background: Lipid droplets (LDs), the organelles central to alcoholic steatosis, are broken down by lipophagy, a specialized form of autophagy. Here, we hypothesize that ethanol administration retards lipophagy by down-regulating Dynamin 2 (Dyn2), a protein that facilitates lysosome re-formation, contributing to hepatocellular steatosis.

Methods: Primary hepatocytes were isolated from male Wistar rats fed Lieber-DeCarli control or EtOH liquid diets for 6-8 wk.

Ethanol metabolism by alcohol dehydrogenase or cytochrome P 2E1 differentially impairs hepatic protein trafficking and growth hormone signaling.

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.

Enhanced colorectal cancer metastases in the alcohol-injured liver.

Metastatic liver disease is a major cause of mortality in colorectal cancer (CRC) patients. Alcohol consumption is a noted risk factor for secondary cancers yet the role of alcoholic liver disease (ALD) in colorectal liver metastases (CRLM) is not defined. This work evaluated tumor cell colonization in the alcoholic host liver using a novel preclinical model of human CRC liver metastases.

Prolonged feeding with guanidinoacetate, a methyl group consumer, exacerbates ethanol-induced liver injury.

Aim: To investigate the hypothesis that exposure to guanidinoacetate (GAA, a potent methyl-group consumer) either alone or combined with ethanol intake for a prolonged period of time would cause more advanced liver pathology thus identifying methylation defects as the initiator and stimulator for progressive liver damage.

Methods: Adult male Wistar rats were fed the control or ethanol Lieber DeCarli diet in the absence or presence of GAA supplementation. At the end of 6 wk of the feeding regimen, various biochemical and histological analyses were conducted.

Acetaldehyde Disrupts Interferon Alpha Signaling in Hepatitis C Virus-Infected Liver Cells by Up-Regulating USP18.

Background: Alcohol consumption exacerbates the pathogenesis of hepatitis C virus (HCV) infection and worsens disease outcomes. The exact reasons are not clear yet, but they might be partially attributed to the ability of alcohol to further suppress the innate immunity. Innate immunity is known to be already decreased by HCV in liver cells.

Creatine Supplementation Does Not Prevent the Development of Alcoholic Steatosis.

Background: Alcohol-induced reduction in the hepatocellular S-adenosylmethionine (SAM):S-adenosylhomocysteine (SAH) ratio impairs the activities of many SAM-dependent methyltransferases. These impairments ultimately lead to the generation of several hallmark features of alcoholic liver injury including steatosis. Guanidinoacetate methyltransferase (GAMT) is an important enzyme that catalyzes the final reaction in the creatine biosynthetic process.

Role of apoptotic hepatocytes in HCV dissemination: regulation by acetaldehyde.

Alcohol consumption exacerbates hepatitis C virus (HCV) pathogenesis and promotes disease progression, although the mechanisms are not quite clear. We have previously observed that acetaldehyde (Ach) continuously produced by the acetaldehyde-generating system (AGS), temporarily enhanced HCV RNA levels, followed by a decrease to normal or lower levels, which corresponded to apoptosis induction. Here, we studied whether Ach-induced apoptosis caused depletion of HCV-infected cells and what role apoptotic bodies (AB) play in HCV-alcohol crosstalk.

Acute and Chronic Ethanol Administration Differentially Modulate Hepatic Autophagy and Transcription Factor EB.

Background: Chronic ethanol (EtOH) consumption decelerates the catabolism of long-lived proteins, indicating that it slows hepatic macroautophagy (hereafter called autophagy) a crucial lysosomal catabolic pathway in most eukaryotic cells. Autophagy and lysosome biogenesis are linked. Both are regulated by the transcription factor EB (TFEB).

Review: Precision Cut Liver Slices for the Evaluation of Fatty Liver and Fibrosis.

Introduction: Ethanol metabolism in the liver results in oxidative stress, altered cytokine production and fat accumulation in the liver. Thus, it is thought that the accumulation of benign fat into the liver in conjunction with a second hit leads to liver failure. However, we have recently developed the use of precision-cut liver slices (PCLSs) as an in vitro culture model in which to investigate the pathophysiology of alcohol-induced liver injury.

Acetaldehyde accelerates HCV-induced impairment of innate immunity by suppressing methylation reactions in liver cells.

Alcohol exposure worsens the course and outcomes of hepatitis C virus (HCV) infection. Activation of protective antiviral genes is induced by IFN-α signaling, which is altered in liver cells by either HCV or ethanol exposure. However, the mechanisms of the combined effects of HCV and ethanol metabolism in IFN-α signaling modulation are not well elucidated.

Hepatocyte-mediated cytotoxicity and host defense mechanisms in the alcohol-injured liver.

The consumption of alcohol is associated with many health issues including alcoholic liver disease (ALD). The natural history of ALD involves the development of steatosis, inflammation (steatohepatitis), fibrosis and cirrhosis. During the stage of steatohepatitis, the combination of inflammation and cellular damage can progress to a severe condition termed alcoholic hepatitis (AH).

Role of defective methylation reactions in ethanol-induced dysregulation of intestinal barrier integrity.

Alcoholic liver disease (ALD) is a major healthcare challenge worldwide. Emerging evidence reveals that ethanol administration disrupts the intestinal epithelial tight junction (TJ) complex; this defect allows for the paracellular translocation of gut-derived pathogenic molecules to reach the liver to cause inflammation and progressive liver injury. We have previously demonstrated a causative role of impairments in liver transmethylation reactions in the pathogenesis of ALD.

Isoaspartate, carbamoyl phosphate synthase-1, and carbonic anhydrase-III as biomarkers of liver injury.

We had previously shown that alcohol consumption can induce cellular isoaspartate protein damage via an impairment of the activity of protein isoaspartyl methyltransferase (PIMT), an enzyme that triggers repair of isoaspartate protein damage. To further investigate the mechanism of isoaspartate accumulation, hepatocytes cultured from control or 4-week ethanol-fed rats were incubated in vitro with tubercidin or adenosine. Both these agents, known to elevate intracellular S-adenosylhomocysteine levels, increased cellular isoaspartate damage over that recorded following ethanol consumption in vivo.

Alcohol, carcinoembryonic antigen processing and colorectal liver metastases.

It is well established that alcohol consumption is related to the development of alcoholic liver disease. Additionally, it is appreciated that other major health issues are associated with alcohol abuse, including colorectal cancer (CRC) and its metastatic growth to the liver. Although a correlation exists between alcohol use and the development of diseases, the search continues for a better understanding of specific mechanisms.

Malondialdehyde-acetaldehyde adducts and anti-malondialdehyde-acetaldehyde antibodies in rheumatoid arthritis.

Objective: Malondialdehyde-acetaldehyde (MAA) adducts are a product of oxidative stress associated with tolerance loss in several disease states. This study was undertaken to investigate the presence of MAA adducts and circulating anti-MAA antibodies in patients with rheumatoid arthritis (RA).

Methods: Synovial tissue from patients with RA and patients with osteoarthritis (OA) were examined for the presence of MAA-modified and citrullinated proteins.

Alcohol-induced defects in hepatic transcytosis may be explained by impaired dynein function.

Alcoholic liver disease has been clinically well described, but the molecular mechanisms leading to hepatotoxicity have not been fully elucidated. Previously, we determined that microtubules are hyperacetylated and more stable in ethanol-treated WIF-B cells, VL-17A cells, liver slices, and in livers from ethanol-fed rats. From our recent studies, we believe that these modifications can explain alcohol-induced defects in microtubule motor-dependent protein trafficking including nuclear translocation of a subset of transcription factors.

Increased methylation demand exacerbates ethanol-induced liver injury.

We previously reported that chronic ethanol intake lowers hepatocellular S-adenosylmethionine to S-adenosylhomocysteine ratio and significantly impairs many liver methylation reactions. One such reaction, catalyzed by guanidinoacetate methyltransferase (GAMT), is a major consumer of methyl groups and utilizes as much as 40% of the SAM-derived groups to convert guanidinoacetate (GAA) to creatine. The exposure to methyl-group consuming compounds has substantially increased over the past decade that puts additional stresses on the cellular methylation potential.

Alcohol consumption decreases rat hepatic creatine biosynthesis via altered guanidinoacetate methyltransferase activity.

Background: We have previously shown that decreased S-adenosylmethionine (SAM):S-adenosylhomocysteine (SAH) ratio generated in livers of alcohol-fed rats can impair the activities of many SAM-dependent methyltransferases. One such methyltransferase is guanidinoacetate methyltransferase (GAMT) that catalyzes the last step of creatine synthesis. As GAMT is the major utilizer of SAM, the purpose of the study was to examine the effects of ethanol (EtOH) on liver creatine levels and GAMT activity.

Rab GTPases associate with isolated lipid droplets (LDs) and show altered content after ethanol administration: potential role in alcohol-impaired LD metabolism.

Background: Alcoholic liver disease is manifested by the presence of fatty liver, primarily due to accumulation of hepatocellular lipid droplets (LDs). The presence of membrane-trafficking proteins (e.g.

Relaxin decreases the severity of established hepatic fibrosis in mice.

Background & Aims: Hepatic fibrosis is characterized by excess collagen deposition, decreased extracellular matrix degradation and activation of the hepatic stellate cells. The hormone relaxin has shown promise in the treatment of fibrosis in a number of tissues, but the effect of relaxin on established hepatic fibrosis is unknown. The aim of this study was to determine the effect of relaxin on an in vivo model after establishing hepatic fibrosis

Methods: Male mice were made fibrotic by carbon tetrachloride treatment for 4 weeks, followed by treatment with two doses of relaxin (25 or 75 μg/kg/day) or vehicle for 4 weeks, with continued administration of carbon tetrachloride.

Susceptibility to T cell-mediated liver injury is enhanced in asialoglycoprotein receptor-deficient mice.

T cell activation and associated pro-inflammatory cytokine production is a pathological feature of inflammatory liver disease. It is also known that liver injury is associated with marked impairments in the function of many hepatic proteins including a hepatocyte-specific binding protein, the asialoglycoprotein receptor (ASGPR). Recently, it has been suggested that hepatic ASGPRs may play an important role in the physiological regulation of T lymphocytes, leading to our hypothesis that ASGPR defects correlate with inflammatory-mediated events in liver diseases.

Multilevel regulation of autophagosome content by ethanol oxidation in HepG2 cells.

Acute and chronic ethanol administration increase autophagic vacuole (i.e., autophagosome; AV) content in liver cells.

Hepatic microtubule acetylation and stability induced by chronic alcohol exposure impair nuclear translocation of STAT3 and STAT5B, but not Smad2/3.

Although alcoholic liver disease is clinically well described, the molecular basis for alcohol-induced hepatotoxicity is not well understood. Previously, we found that alcohol exposure led to increased microtubule acetylation and stability in polarized, hepatic WIF-B cells and in livers from ethanol-fed rats. Because microtubules are known to regulate transcription factor nuclear translocation and dynamic microtubules are required for translocation of at least a subset of these factors, we examined whether alcohol-induced microtubule acetylation and stability impair nuclear translocation.