Chronic ethanol feeding alters hepatocyte memory which is not altered by acute feeding

Lutein Prevents Liver Injury and Intestinal Barrier Dysfunction in Rats Subjected to Chronic Alcohol Intake

Chronic alcohol intake can affect both liver and intestinal barrier function. The goal of this investigation was to evaluate the function and mechanism of lutein administration on the chronic ethanol-induced liver and intestinal barrier damage in rats. During the 14-week experimental cycle, seventy rats were randomly divided into seven groups, with 10 rats in each group: a normal control group (Co), a control group of lutein interventions (24 mg/kg/day), an ethanol model group (Et, 8-12 mL/kg/day of 56% (v/v) ethanol), three intervention groups with lutein (12, 24 and 48 mg/kg/day) and a positive control group (DG). The results showed that liver index, ALT, AST and TG levels were increased, and SOD and GSH-Px levels were reduced in the Et group. Furthermore, alcohol intake over a long time increased the level of pro-inflammatory cytokines TNF-α and IL-1β, disrupted the intestinal barrier, and stimulated the release of LPS, causing further liver injury. In contrast, lutein interventions prevented alcohol-induced alterations in liver tissue, oxidative stress and inflammation. In addition, the protein expression of Claudin-1 and Occludin in ileal tissues was upregulated by lutein intervention. In conclusion, lutein can improve chronic alcoholic liver injury and intestinal barrier dysfunction in rats.

Epigenetics of alcohol-related liver diseases

Alcohol-related liver disease (ARLD) is a primary cause of chronic liver disease in the United States. Despite advances in the diagnosis and management of ARLD, it remains a major public health problem associated with significant morbidity and mortality, emphasising the need to adopt novel approaches to the study of ARLD and its complications. Epigenetic changes are increasingly being recognised as contributing to the pathogenesis of multiple disease states. Harnessing the power of innovative technologies for the study of epigenetics (e.g., next-generation sequencing, DNA methylation assays, histone modification profiling and computational techniques like machine learning) has resulted in a seismic shift in our understanding of the pathophysiology of ARLD. Knowledge of these techniques and advances is of paramount importance for the practicing hepatologist and researchers alike. Accordingly, in this review article we will summarise the current knowledge about alcohol-induced epigenetic alterations in the context of ARLD, including but not limited to, DNA hyper/hypo methylation, histone modifications, changes in non-coding RNA, 3D chromatin architecture and enhancer-promoter interactions. Additionally, we will discuss the state-of-the-art techniques used in the study of ARLD (e.g. single-cell sequencing). We will also highlight the epigenetic regulation of chemokines and their proinflammatory role in the context of ARLD. Lastly, we will examine the clinical applications of epigenetics in the diagnosis and management of ARLD.

The suppression of pancreatic lipase-related protein 2 ameliorates experimental hepatic fibrosis in mice

Quiescent hepatic stellate cells (HSCs) store vitamin A as lipid droplets in the cytoplasm. When activated, these cells lose vitamin A and exhibit an increased capacity for proliferation, mobility, contractility, and the synthesis of collagen and other components of the extracellular matrix. Our previous work demonstrated that the lipid hydrolytic gene pancreatic lipase-related protein 2 (mPlrp2) is involved in the hydrolysis of retinyl esters (REs) in the liver. Here, we showed that bile duct ligation (BDL)-induced liver injury triggered the conditional expression of mPlrp2 in livers and describe evidence of a strong relationship between the expression of mPlrp2 and Acta-2, a marker for activated HSCs. RNA interference targeting mPlrp2 inhibited HSC activation and ameliorated hepatic fibrosis induced by BDL in mice. Liver BDL markedly reduced the adenosine level and increased the ratio between S-adenosyl-L-methionine (SAM) and S-adenosyl-L-homocysteine (SAH). Chromatin immunoprecipitation (ChIP) analysis demonstrated an increase in trimethylated histone H3K4 at the mPlrp2 promoter in BDL mice, which was associated with the conditional expression of mPlrp2 in the liver. SAM, a well-known hepatoprotective substance, inhibited mPlrp2 expression and reduced RE hydrolysis in mice with hepatic fibrosis induced by chronic CCl4 treatment. Liver fibrosis induced by CCl4 or BDL was improved in Plrp2-/- mice. Our results reveal that mPlrp2 suppression is a potential approach for treating hepatic fibrosis.

Mechanism and Therapeutic Opportunities of Histone Modifications in Chronic Liver Disease

Chronic liver disease (CLD) represents a global health problem, accounting for the heavy burden of disability and increased health care utilization. Epigenome alterations play an important role in the occurrence and progression of CLD. Histone modifications, which include acetylation, methylation, and phosphorylation, represent an essential part of epigenetic modifications that affect the transcriptional activity of genes. Different from genetic mutations, histone modifications are plastic and reversible. They can be modulated pharmacologically without changing the DNA sequence. Thus, there might be chances to establish interventional solutions by targeting histone modifications to reverse CLD. Here we summarized the roles of histone modifications in the context of alcoholic liver disease (ALD), metabolic associated fatty liver disease (MAFLD), viral hepatitis, autoimmune liver disease, drug-induced liver injury (DILI), and liver fibrosis or cirrhosis. The potential targets of histone modifications for translation into therapeutics were also investigated. In prospect, high efficacy and low toxicity drugs that are selectively targeting histone modifications are required to completely reverse CLD and prevent the development of liver cirrhosis and malignancy.

Role of Chronic Alcoholism Causing Cancer in Omnivores and Vegetarians through Epigenetic Modifications

One of the significant consequences of alcohol consumption is cancer formation via several contributing factors such as action of alcohol metabolites, vitamin deficiencies, and oxidative stress. All these factors have been shown to cause epigenetic modifications via DNA hypomethylation, thus forming a basis for cancer development. Several published reviews and studies were systematically reviewed. Omnivores and vegetarians differ in terms of nutritional intake and deficiencies. As folate deficiency was found to be common among the omnivores, chronic alcoholism could possibly cause damage and eventually cancer in an omnivorous individual via DNA hypomethylation due to folate deficiency. Furthermore, as niacin was found to be deficient among vegetarians, damage in vegetarian chronic alcoholics could be due to increased NADH/NAD ⁺ ratio, thus slowing alcohol metabolism in liver leading to increased alcohol and acetaldehyde which inhibit methyltransferase enzymes, eventually leading to DNA hypomethylation. Hence correcting the concerned deficiency and supplementation with S-adenosyl methionine could prove to be protective in chronic alcohol use.

Alcohol-Induced Epigenetic Changes in Cancer

Chronic, heavy alcohol consumption is associated with serious negative health effects, including the development of several cancer types. One of the pathways affected by alcohol toxicity is the one-carbon metabolism. The alcohol-induced impairment of this metabolic pathway results in epigenetic changes associated with cancer development. These epigenetic changes are induced by folate deficiency and by products of the ethanol metabolism. The changes induced by long-term heavy ethanol consumption result in elevations of homocysteine and S-adenosyl-homocysteine (SAH) and reductions in S-adenosylmethionine (SAM) and antioxidant glutathione (GSH) levels, leading to abnormal promoter gene hypermethylation, global hypomethylation, and metabolic insufficiency of antioxidant defense mechanisms. In addition, reactive oxygen species (ROS) generated during the ethanol metabolism induce alterations in DNA methylation patterns that play a critical role in cancer development. Specific epigenetic changes in esophageal, hepatic, and colorectal cancers have been detected in blood samples and proposed to be used clinically as epigenetic biomarkers for diagnosis and prognosis of these cancers. Also, genetic variants of genes involved in one-carbon metabolism and ethanol metabolism were found to modulate the relationship between alcohol-induced epigenetic changes and cancer risk. Furthermore, alcohol metabolism products have been associated with an increase in NADH levels, which lead to histone modifications and changes in gene expression that in turn influence cancer susceptibility. Chronic excessive use of alcohol also affects selected members of the family of microRNAs, and as miRNAs could act as epigenetic regulators, this may play an important role in carcinogenesis. In conclusion, targeting alcohol-induced epigenetic changes in several cancer types could make available clinical tools for the diagnosis, prognosis, and treatment of these cancers, with an important role in precision medicine.

Chronic Ethanol Consumption and Generation of Etheno-DNA Adducts in Cancer-Prone Tissues

Chronic ethanol consumption is a risk factor for several human cancers. A variety of mechanisms may contribute to this carcinogenic effect of alcohol including oxidative stress with the generation of reactive oxygen species (ROS), formed via inflammatory pathways or as byproducts of ethanol oxidation through cytochrome P4502E1 (CYP2E1). ROS may lead to lipidperoxidation (LPO) resulting in LPO-products such as 4-hydoxynonenal (4-HNE) or malondialdehyde. These compounds can react with DNA bases forming mutagenic and carcinogenic etheno-DNA adducts. Etheno-DNA adducts are generated in the liver (HepG2) cells over-expressing CYP2E1 when incubated with ethanol;and are inhibited by chlormethiazole. In liver biopsies etheno-DNA adducts correlated significantly with CYP2E1. Such a correlation was also found in the esophageal- and colorectal mucosa of alcoholics. Etheno-DNA adducts also increased in liver biopsies from patients with non alcoholic steatohepatitis (NASH). In various animal models with fatty liver either induced by high fat diets or genetically modified such as in the obese Zucker rat, CYP2E1 is induced and paralleled by high levels of etheno DNA-adducts which may be modified by additional alcohol administration. As elevation of adduct levels in NASH children were already detected at a young age, these lesions may contribute to hepatocellular cancer development later in life. Together these data strongly implicate CYP2E1 as an important mediator for etheno-DNA adduct formation, and this detrimental DNA damage may act as a driving force for malignant disease progression.

Hepatoprotective effect of grape seed oil against carbon tetrachloride induced oxidative stress in liver of γ-irradiated rat

Carbon tetrachloride (CCl4) and ionizing radiation are well known environmental pollutants that generate free radicals and induce oxidative stress. The liver is the primary and major target organ responsible for the metabolism of drugs, toxic chemicals and affected by irradiation. This study investigated the effect of grape seed oil (GSO) on acute liver injury induced by carbon tetrachloride (CCl4) in γ-irradiated rats (7Gy). CCl4-intoxicated rats exhibited an elevation of ALT, AST activities, IL-6 and TNF-α level in the serum. Further, the levels of MDA, NO, NF-κB and the gene expression of CYP2E1, iNOS and Caspase-3 were increased, and SOD, CAT, GSH-Px, GST activities and GSH content were decreased. Furthermore, silent information regulator protein 1 (SIRT1) gene expression was markedly down-regulated. Additionally, alterations of the trace elements; copper, manganese, zinc and DNA fragmentation was observed in the hepatic tissues of the intoxicated group. These effects were augmented in CCl4-intoxicated-γ-irradiated rats. However, the administration of GSO ameliorated these parameters. GSO exhibit protective effects on CCl4 induced acute liver injury in γ-irradiated rats that could be attributed to its potent antioxidant, anti-inflammatory and anti-apoptotic activities. The induction of the antioxidant enzymes activities, down-regulation of the CYP2E1, iNOS, Caspase-3 and NF-κB expression, up-regulation of the trace elements concentration levels and activation of SIRT1 gene expression are responsible for the improvement of the antioxidant and anti-inflammatory status in the hepatic tissues and could be claimed to be the hepatoprotective mechanism of GSO.

Chronic alcohol binging injures the liver and other organs by reducing NAD⁺ levels required for sirtuin's deacetylase activity

NAD(+) levels are markedly reduced when blood alcohol levels are high during binge drinking. This causes liver injury to occur because the enzymes that require NAD(+) as a cofactor such as the sirtuin de-acetylases cannot de-acetylate acetylated proteins such as acetylated histones. This prevents the epigenetic changes that regulate metabolic processes and which prevent organ injury such as fatty liver in response to alcohol abuse. Hyper acetylation of numerous regulatory proteins develops. Systemic multi-organ injury occurs when NAD(+) is reduced. For instance the Circadian clock is altered if NAD(+) is not available. Cell cycle arrest occurs due to up regulation of cell cycle inhibitors leading to DNA damage, mutations, apoptosis and tumorigenesis. NAD(+) is linked to aging in the regulation of telomere stability. NAD(+) is required for mitochondrial renewal. Alcohol dehydrogenase is present in every visceral organ in the body so that there is a systemic reduction of NAD(+) levels in all of these organs during binge drinking.

How to prevent alcoholic liver disease

Betaine supplements of alcoholic beverages are proposed to prevent the development of alcoholic liver disease in patients that abuse alcohol. This recommendation is based on the observation of studies where it has been shown in binge drinking and chronic ethanol feeding animal models that betaine prevents liver injury resulting from high blood alcohol levels. The basic observation is that betaine added to ethanol being ingested increases the elimination rate of blood alcohol, which prevents the blood alcohol levels (BALs) from reaching high levels. The mechanism of how betaine does this is postulated to be that betaine causes the increase in the elimination rate by increasing the metabolic rate which generates NAD the rate limiting cofactor of alcohol oxidation by ADH. Betaine does this most likely by supporting the methylation of norepinephrine to form epinephrine by phenylethanolamine N-methyltransferase. Epinephrine is 5 to 10-fold more active than norepinephrine in increasing the metabolic rate.

Nuclear receptor-mediated alleviation of alcoholic fatty liver by polyphenols contained in alcoholic beverages

To elucidate the effect of the polyphenols contained in alcoholic beverages on the metabolic stress induced by ethanol consumption, four groups of mice were fed for five weeks on Lieber's diet with or without ethanol, with ethanol plus ellagic acid, and with ethanol plus trans-resveratrol. Alcoholic fatty liver was observed in the group fed the ethanol diet but not in those fed the ethanol plus polyphenol diets. Liver transcriptome analysis revealed that the addition of the polyphenols suppressed the expression of the genes related to cell stress that were up-regulated by ethanol alone. Conversely, the polyphenols up-regulated the genes involved in bile acid synthesis, unsaturated fatty acid elongation, and tetrahydrofolate synthesis that were down-regulated by ethanol alone. Because parts of these genes were known to be regulated by the constitutive androstane receptor (CAR), we performed the same experiment in the CAR-deficient mice. As a result, fatty liver was observed not only in the ethanol group but also with the ethanol plus polyphenol groups. In addition, there was no segregation of the gene expression profiles among these groups. These results provide a molecular basis for the prevention of alcohol-induced stress by the polyphenols in alcoholic beverages.

Binge ethanol-induced HDAC3 down-regulates Cpt1α expression leading to hepatic steatosis and injury

BACKGROUND

Recently, we have demonstrated that acute alcohol exposure due to binge drinking leads to hepatic steatosis with the deregulation of hepatic histone deacetylase (HDAC) expression. Various class I, II, and IV HDACs were down-regulated, whereas expression of HDAC3 was solely up-regulated. Hence, in the present work, we specifically examined the mechanistic role of HDAC3 in the development of hepatic steatosis occurring in response to binge alcohol administration.

METHODS

C57BL/6 mice were gavaged 3 times with ethanol (EtOH) at a dose of 4.5 g/kg. HDAC inhibitor, Trichostatin A (TSA) was simultaneously injected intraperitoneally at a dose of 1 mg/kg. Hepatic steatosis, injury, expression of HDAC3 and carnitine palmitoyltransferase 1α (CPT1α) were evaluated. HDAC3 and histone H3 acetylation levels at the Cpt1α promoter were analyzed by chromatin immunoprecipitation (ChIP).

RESULTS

The binge EtOH-mediated increase in HDAC3 was prevented by simultaneous administration of HDAC inhibitor, TSA, which markedly attenuated hepatic steatosis and injury. Importantly, HDAC3 inhibition was able to normalize the down-regulation of Cpt1α expression. Causal role of HDAC3 in the transcriptional repression of Cpt1α was demonstrated by increased HDAC3 binding at the thyroid receptor element site in the Cpt1α distal promoter region. Further, a resultant decrease in the transcriptionally permissive histone H3 lysine 9 acetylation in the proximal promoter region near the transcriptional start site was observed. Notably, TSA treatment reduced HDAC3 binding and increased H3K9 acetylation at Cpt1α promoter leading to increased Cpt1α expression. These molecular events resulted in attenuation of binge alcohol-induced hepatic steatosis.

CONCLUSIONS

These findings provide insights into potential epigenetic mechanisms underlying transcriptional regulation of Cpt1α in the hepatic steatosis occurring in response to binge EtOH administration.

Reversed scototaxis during withdrawal after daily-moderate, but not weekly-binge, administration of ethanol in zebrafish

Alcohol abuse can lead to severe psychological and physiological damage. Little is known, however, about the relative impact of a small, daily dose of alcohol (daily-moderate schedule) versus a large, once per week dose (weekly-binge schedule). In this study, we examined the effect of each of these schedules on behavioural measures of anxiety in zebrafish (Danio rerio). Adult wild-type zebrafish were administered either 0.2% ethanol on a daily-moderate schedule or 1.4% ethanol on a weekly-binge schedule for a period of 21 days, and then tested for scototaxis (preference for darkness) during withdrawal. Compared to a control group with no alcohol exposure, the daily-moderate group spent significantly more time on the light side of the arena (indicative of decreased anxiety) on day two of withdrawal, but not day 9 of withdrawal. The weekly-binge group was not significantly different from the control group on either day of withdrawal and showed no preference for either the light or dark zones. Our results indicate that even a small dose of alcohol on a daily basis can cause significant, though reversible, changes in behaviour.

Brief alcohol exposure alters transcription in astrocytes via the heat shock pathway

Astrocytes are critical for maintaining homeostasis in the central nervous system (CNS), and also participate in the genomic response of the brain to drugs of abuse, including alcohol. In this study, we investigated ethanol regulation of gene expression in astrocytes. A microarray screen revealed that a brief exposure of cortical astrocytes to ethanol increased the expression of a large number of genes. Among the alcohol-responsive genes (ARGs) are glial-specific immune response genes, as well as genes involved in the regulation of transcription, cell proliferation, and differentiation, and genes of the cytoskeleton and extracellular matrix. Genes involved in metabolism were also upregulated by alcohol exposure, including genes associated with oxidoreductase activity, insulin-like growth factor signaling, acetyl-CoA, and lipid metabolism. Previous microarray studies performed on ethanol-treated hepatocyte cultures and mouse liver tissue revealed the induction of almost identical classes of genes to those identified in our microarray experiments, suggesting that alcohol induces similar signaling mechanisms in the brain and liver. We found that acute ethanol exposure activated heat shock factor 1 (HSF1) in astrocytes, as demonstrated by the translocation of this transcription factor to the nucleus and the induction of a family of known HSF1-dependent genes, the heat shock proteins (Hsps). Transfection of a constitutively transcriptionally active Hsf1 construct into astrocytes induced many of the ARGs identified in our microarray study supporting the hypothesis that HSF1 transcriptional activity, as part of the heat shock cascade, may mediate the ethanol induction of these genes. These data indicate that acute ethanol exposure alters gene expression in astrocytes, in part via the activation of HSF1 and the heat shock cascade.

Epigenetic events in liver cancer resulting from alcoholic liver disease

Epigenetic mechanisms play an extensive role in the development of liver cancer (i.e., hepatocellular carcinoma [HCC]) associated with alcoholic liver disease (ALD) as well as in liver disease associated with other conditions. For example, epigenetic mechanisms, such as changes in the methylation and/or acetylation pattern of certain DNA regions or of the histone proteins around which the DNA is wrapped, contribute to the reversion of normal liver cells into progenitor and stem cells that can develop into HCC. Chronic exposure to beverage alcohol (i.e., ethanol) can induce all of these epigenetic changes. Thus, ethanol metabolism results in the formation of compounds that can cause changes in DNA methylation and interfere with other components of the normal processes regulating DNA methylation. Alcohol exposure also can alter histone acetylation/deacetylation and methylation patterns through a variety of mechanisms and signaling pathways. Alcohol also acts indirectly on another molecule called toll-like receptor 4 (TLR4) that is a key component in a crucial regulatory pathway in the cells and whose dysregulation is involved in the development of HCC. Finally, alcohol use regulates an epigenetic mechanism involving small molecules called miRNAs that control transcriptional events and the expression of genes important to ALD.

Folate, alcohol, and liver disease

Alcoholic liver disease (ALD) is typically associated with folate deficiency, which is the result of reduced dietary folate intake, intestinal malabsorption, reduced liver uptake and storage, and increased urinary folate excretion. Folate deficiency favors the progression of liver disease through mechanisms that include its effects on methionine metabolism with consequences for DNA synthesis and stability and the epigenetic regulation of gene expression involved in pathways of liver injury. This paper reviews the pathogenesis of ALD with particular focus on ethanol-induced alterations in methionine metabolism, which may act in synergy with folate deficiency to decrease antioxidant defense as well as DNA stability while regulating epigenetic mechanisms of relevant gene expressions. We also review the current evidence available on potential treatments of ALD based on correcting abnormalities in methionine metabolism and the methylation regulation of relevant gene expressions.

Early growth response-1 contributes to steatosis development after acute ethanol administration

BACKGROUND

Previous work demonstrated that the transcription factor, early growth response-1 (Egr-1), participates in the development of steatosis (fatty liver) after chronic ethanol (EtOH) administration. Here, we determined the extent to which Egr-1 is involved in fatty liver development in mice subjected to acute EtOH administration.

METHODS

In acute studies, we treated both wild-type and Egr-1 null mice with either EtOH or phosphate-buffered saline (PBS) by gastric intubation. At various times after treatment, we harvested sera and livers and quantified endotoxin, indices of liver injury, steatosis, and hepatic Egr-1 content. In chronic studies, groups of mice were fed liquid diets containing either EtOH or isocaloric maltose-dextrin for 7 to 8 weeks.

RESULTS

Compared with controls, acute EtOH-treated mice showed a rapid, transient elevation in serum endotoxin beginning 30 minutes after treatment. One hour postgavage, livers from EtOH-treated mice exhibited a robust elevation of both Egr-1 mRNA and protein. By 3 hours postgavage, liver triglyceride increased in EtOH-treated mice as did lipid peroxidation. Acute EtOH treatment of Egr-1-null mice showed no Egr-1 expression, but these animals still developed elevated triglycerides, although significantly lower than EtOH-fed wild-type littermates. Despite showing decreased fatty liver, EtOH-treated Egr-1 null mice exhibited greater liver injury. After chronic EtOH feeding, steatosis and liver enlargement were clearly evident, but there was no indication of elevated endotoxin. Egr-1 levels in EtOH-fed mice were equal to those of pair-fed controls.

CONCLUSIONS

Acute EtOH administration induced the synthesis of Egr-1 in mouse liver. However, despite its robust increase, the transcription factor had a smaller, albeit significant, function in steatosis development after acute EtOH treatment. We propose that the rise in Egr-1 after acute EtOH is an hepatoprotective adaptation to acute liver injury from binge drinking that is triggered by EtOH metabolism and elevated levels of endotoxin.

Binge alcohol-induced microvesicular liver steatosis and injury are associated with down-regulation of hepatic Hdac 1, 7, 9, 10, 11 and up-regulation of Hdac 3

BACKGROUND

Binge, as well as chronic, alcohol consumption affects global histone acetylation leading to changes in gene expression. It is becoming increasingly evident that these histone-associated epigenetic modifications play an important role in the development of alcohol-mediated hepatic injury.

METHODS

C57BL/6 mice were gavaged 3 times (12-hour intervals) with ethanol (EtOH; 4.5 g/kg). Hepatic histone deacetylase (Hdac) mRNAs were assessed by qRT-PCR. Total HDAC activity was estimated by a colorimetric HDAC activity/inhibition assay. Histone acetylation levels were evaluated by Western blot. Liver steatosis and injury were evaluated by histopathology, plasma aminotransferase (ALT) activity, and liver triglyceride accumulation. Expression of fatty acid synthase (Fas) and carnitine palmitoyl transferase 1a (Cpt1a) was also examined. HDAC 9 association with Fas promoter was analyzed.

RESULTS

Binge alcohol exposure resulted in alterations of hepatic Hdac mRNA levels. Down-regulation of HDAC Class I (Hdac 1), Class II (Hdac 7, 9, 10), and Class IV (Hdac 11) and up-regulation of HDAC Class I (Hdac 3) gene expression were observed. Correspondent to the decrease in HDAC activity, an increase in hepatic histone acetylation was observed. These molecular events were associated with microvesicular hepatic steatosis and injury characterized by increased hepatic triglycerides (48.02 ± 3.83 vs. 19.90 ± 3.48 mg/g liver, p < 0.05) and elevated plasma ALT activity (51.98 ± 6.91 vs. 20.8 ± 0.62 U/l, p < 0.05). Hepatic steatosis was associated with an increase in FAS and a decrease in CPT1a mRNA and protein expression. Fas promoter analysis revealed that binge EtOH treatment decreased HDAC 9 occupancy at the Fas promoter resulting in its transcriptional activation.

CONCLUSIONS

Deregulation of hepatic Hdac expression likely plays a major role in the binge alcohol-induced hepatic steatosis and liver injury by affecting lipogenesis and fatty acid β-oxidation.

Treatment- and population-dependent activity patterns of behavioral and expression QTLs

Genetic control of gene expression and higher-order phenotypes is almost invariably dependent on environment and experimental conditions. We use two families of recombinant inbred strains of mice (LXS and BXD) to study treatment- and genotype-dependent control of hippocampal gene expression and behavioral phenotypes. We analyzed responses to all combinations of two experimental perturbations, ethanol and restraint stress, in both families, allowing for comparisons across 8 combinations of treatment and population. We introduce the concept of QTL activity patterns to characterize how associations between genomic loci and traits vary across treatments. We identified several significant behavioral QTLs and many expression QTLs (eQTLs). The behavioral QTLs are highly dependent on treatment and population. We classified eQTLs into three groups: cis-eQTLs (expression variation that maps to within 5 Mb of the cognate gene), syntenic trans-eQTLs (the gene and the QTL are on the same chromosome but not within 5 Mb), and non-syntenic trans-eQTLs (the gene and the QTL are on different chromosomes). We found that most non-syntenic trans-eQTLs were treatment-specific whereas both classes of syntenic eQTLs were more conserved across treatments. We also found there was a correlation between regions along the genome enriched for eQTLs and SNPs that were conserved across the LXS and BXD families. Genes with eQTLs that co-localized with the behavioral QTLs and displayed similar QTL activity patterns were identified as potential candidate genes associated with the phenotypes, yielding identification of novel genes as well as genes that have been previously associated with responses to ethanol.

Gene-selective histone H3 acetylation in the absence of increase in global histone acetylation in liver of rats chronically fed alcohol

AIMS

The aim of this study was to determine the effect of chronic ethanol feeding on acetylation of histone H3 at lysine 9 (H3-Lys9) at promoter and coding regions of genes for class I alcohol dehydrogenase (ADH I), inducible nitric oxide synthase (iNOS), Bax, p21, c-met and hepatocyte growth factor in the rat liver.

METHODS

Rats were fed ethanol-containing liquid diet (5%, w/v) for 1-4 weeks. The global level of acetylation of H3-Lys9 in the liver was examined by western blot analysis. The levels of mRNA for various genes were measured by real-time reverse transcriptase-polymerase chain reaction. The association of acetylated histone H3-Lys9 with the different regions of genes was monitored by chromatin immunoprecipitation assay.

RESULTS

Chronic ethanol treatment increased mRNA expression of genes for iNOS, c-jun and ADH 1. Chronic ethanol treatment did not cause increase in global acetylation of H3-Lys9, but significantly increased the association of acetylated histone H3-Lys9 in the ADH I gene, both in promoter and in coding regions. In contrast, chronic ethanol treatment did not significantly increase the association of acetylated histone H3-Lys9 with iNOS and c-jun genes.

CONCLUSION

Chronic ethanol exposure increased the gene-selective association of acetylated H3-Lys9 in the absence of global histone acetylation. Thus, not all genes expressed by ethanol are linked to transcription via histone H3 acetylation at Lys9.

Histone modifications and alcohol-induced liver disease: Are altered nutrients the missing link?

Alcoholism is a major health problem in the United States and worldwide, and alcohol remains the single most significant cause of liver-related diseases and deaths. Alcohol is known to influence nutritional status at many levels including nutrient intake, absorption, utilization, and excretion, and can lead to many nutritional disturbances and deficiencies. Nutrients can dramatically affect gene expression and alcohol-induced nutrient imbalance may be a major contributor to pathogenic gene expression in alcohol-induced liver disease (ALD). There is growing interest regarding epigenetic changes, including histone modifications that regulate gene expression during disease pathogenesis. Notably, modifications of core histones in the nucleosome regulate chromatin structure and DNA methylation, and control gene transcription. This review highlights the role of nutrient disturbances brought about during alcohol metabolism and their impact on epigenetic histone modifications that may contribute to ALD. The review is focused on four critical metabolites, namely, acetate, S-adenosylmethionine, nicotinamide adenine dinucleotide and zinc that are particularly relevant to alcohol metabolism and ALD.

Protective effect of quercetin, EGCG, catechin and betaine against oxidative stress induced by ethanol in vitro

There is a need for a nontoxic antioxidant agent to be identified which will prevent alcoholic liver disease (ALD) in alcoholic patients. We tested 4 candidate agents: quercetin, EGCG, catechin and betaine, all of which occur naturally in food. HepG2 cells overexpressing CYP2E1 were subjected to arachidonic acid, iron and 100mM ethanol with or without the antioxidant agent. All the agents prevented oxidative stress and MDA/4HNE formation induced by ethanol, except for EGCG. Catechin prevented CYP2E1 induction by ethanol. All the agents tended to down-regulate the ethanol-induced increased expression of glutathionine peroxidase 4 (GPX4). All the agents, except catechin, tended to reduce the expression of SOD2 induced by ethanol. Heat shock protein 70 was up-regulated by ethanol alone and betaine tended to prevent this. All 4 agents down-regulated the expression of Gadd45b in the presence of ethanol, which could explain the mechanism of DNA demethylation associated with the up-regulation of the gene expression observed in experimental ALD. In conclusion, the in vitro model of oxidative stress induced by ethanol provided evidence that all 4 agents tested prevented some aspect of liver cell injury caused by ethanol.

S-adenosylmethionine decreases the peak blood alcohol levels 3 h after an acute bolus of ethanol by inducing alcohol metabolizing enzymes in the liver

INTRODUCTION

An alcohol bolus causes the blood alcohol level (BAL) to peak at 1-2 h post ingestion. The ethanol elimination rate is regulated by alcohol metabolizing enzymes, primarily alcohol dehydrogenase (ADH1), acetaldehyde dehydrogenase (ALDH), and cytochrome P450 (CYP2E1). Recently, S-adenosylmethionine (SAMe) was found to reduce acute BALs 3 h after an alcohol bolus. The question, then, was: what is the mechanism involved in this reduction of BAL by feeding SAMe? To answer this question, we investigated the changes in ethanol metabolizing enzymes and the epigenetic changes that regulate the expression of these enzymes during acute binge drinking and chronic drinking.

METHODS

Rats were fed a bolus of ethanol with or without SAMe, and were sacrificed at 3 h or 12 h after the bolus.

RESULTS

RT-PCR and Western blot analyses showed that SAMe significantly induced ADH1 levels in the 3 h liver samples. However, SAMe did not affect the changes in ADH1 protein levels 12 h post bolus. Since SAMe is a methyl donor, it was postulated that the ADH1 gene expression up regulation at 3 h was due to a histone modification induced by methylation from methyl transferases. Dimethylated histone 3 lysine 4 (H3K4me2), a modification responsible for gene expression activation, was found to be significantly increased by SAMe at 3 h post bolus.

CONCLUSION

These results correlated with the low BAL found at 3 h post bolus, and support the concept that SAMe increased the gene expression to increase the elimination rate of ethanol in binge drinking by increasing H3K4me2.

Differential changes in MAP kinases, histone modifications, and liver injury in rats acutely treated with ethanol

BACKGROUND

Acute ethanol is known to affect cells and organs but the underlying molecular mechanisms are poorly explored. Recent developments highlight the potential importance of mitogen-activated protein kinases, MAPKs (i.e., ERK1/2, p38, and JNK1/2) signaling, and histone modifications (i.e., acetylation, methylation, and phosphorylation) in the actions of ethanol in hepatocytes. We have therefore investigated significance of these molecular steps in vivo using a model in which rats were acutely administered ethanol intraperitoneally (IP).

METHODS

Ethanol was administered IP (3.5 gm/kg body weight) to 12-week-old male Sprague-Dawley rats. Liver was subsequently removed at 1 and 4 hours. Serum was used for alcohol and ALT assays. At the time of the removal of liver, small portions of each liver were formalin-fixed and stained with hematoxylin and eosin (H&E) and used for light microscopy. Western blot analysis was carried out with specific primary antibodies for various parameters.

RESULTS

There were clear differences at 1 and 4 hours in blood ethanol, ALT, steatosis, and cleaved caspase 3. Apoptosis at 1 hour was followed by necrosis at 4 hours. Acute alcohol elicited a marked increase in the phosphorylation of ERK1/2 and moderate increases in the phosphorylation of p38 MAPK and JNK. Temporally different phosphorylation of histone H3 at ser-10 and ser-28 occurred and acetylation of histone H3 at lys 9 increased progressively.

CONCLUSIONS

There were distinct differences in the behavior of the activation of the 3 MAP kinases and histone modifications after acute short exposure of liver to ethanol in vivo. Although all 3 MAPKs were rapidly activated at 1 hour, the necrosis, occurring at 4 hours, correlated to sustained activation of ERK1/2. Transient activation of p38 is associated with rapid phosphorylation of histone H3, whereas prolonged activation of ERK1/2 is correlated to persistent histone H3 acetylation.

Gene expression modifications in the liver caused by binge drinking and S-adenosylmethionine feeding. The role of epigenetic changes

Chronic ethanol ingestion, achieved by feeding ethanol at a constant rate using intragastric tube feeding, alters the expression of genes in the liver. This is done by epigenetic mechanisms, which depend on the blood alcohol levels at the time of killing. However, acute bolus feeding of ethanol changes gene expression without lasting epigenetic changes. This occurs with histone 3 methylation and acetylation modifications. The gene expression response to an acute bolus of ethanol might be modified by feeding S-adenosylmethionine (SAMe), a methyl donor. In the present study, rats were given a bolus of ethanol (6 g/kg body weight (bw), SAMe (1 g/kg bw), ethanol + SAMe, or isocaloric glucose. The group of rats (n = 3) were killed at 3 and 12 h post bolus, and gene microarray analysis was performed on their liver cells. SAMe reduced the 3 h blood ethanol levels and increased the ALT levels at 3 h. Venn diagrams showed that alcohol changed the expression of 646 genes at 3 h post bolus and 586 genes at 12 h. SAMe changed the expression of 1,012 genes when fed with ethanol 3 h post ethanol bolus and 554 genes at 12 h post ethanol bolus. SAMe alone changed the expression of 1,751 genes at 3 h and 1,398 at 12 h. There were more changes in gene expression at 3 h than at 12 h post ethanol when ethanol alone was compared to the dextrose control. The same was true when SAMe was compared to SAMe + ethanol. Ethanol up regulated gene expression in most functional pathways at 3 h. However, when SAMe was fed with ethanol at 3 h, most pathways were down regulated. At 12 h, however, when ethanol was fed, the pathways were half up regulated and half down regulated. The same was true when SAMe + ethanol was fed. The expression of epigenetically important genes, such as BHMT and Foxn3, was up regulated 3 h post alcohol bolus. At 3 h, SAMe down regulated the expression of genes, such as BHMT, Mat2a, Jun, Tnfrs9, Ahcy 1, Tgfbr1 and 2, and Pcaf. At 12 h, the insulin signaling pathways were half down regulated by ethanol, which was partly prevented by SAMe. The MAPK pathway was up regulated by ethanol, but SAMe did not prevent this. In conclusion, profound changes in gene expression evolved between 3 h and 12 post ethanol bolus. SAMe down regulated these changes in gene expression at 3 h, and less so at 12 h.

The effects of betaine treatment on rats fed an acute bolus of ethanol at 3 and 12 h post bolus: a microarray analysis

Betaine, a methyl donor active in methionine metabolism, is effective in preventing and reversing experimental alcohol liver disease. The metabolic and molecular biologic mechanisms involved in this prevention are only partially known. To further investigate how betaine modifies the effects of ethanol on the liver, rats were given an acute ethanol bolus with or without betaine and the results were compared to isocaloric dextrose-fed controls. Livers were subjected to microarray analysis, and functional pathways and individual gene expression changes were analyzed. Experimental groups were compared by Venn diagrams showing that both ethanol and betaine caused a change in the expression of a large number of genes indicating that the changes were global. The bio-informatic analysis showed that all the KEGG functional pathways were affected and mainly down regulated at 3 h post bolus when ethanol plus betaine were compared with ethanol-fed rats. The most profound effect of betaine was on the metabolic pathways both at 3 and 12 h post bolus. At 3 h, the changes in gene expression were mostly down regulated, but at 12 h, the changes were regulated equally up and down. This hypothesis-driven analysis showed that the effects of betaine on the effects of ethanol were partly transient.

The cyclic pattern of blood alcohol levels during continuous ethanol feeding in rats: the effect of feeding S-adenosylmethionine

S-adenosylmethionine (SAMe), the major methyl donor for DNA and histone methylation was fed with ethanol for 1month in order to modify the effects of ethanol on rat liver. The following parameters were studied to determine the effects of SAMe; liver histology, the blood alcohol cycle (BAL), changes in gene expression mined from microarray analysis, changes in histone methylation, changes in liver SAMe levels and its metabolites and ADH. SAMe changed the type of fatty liver, reduced liver ALT levels and prevented the BAL cycle caused by intragastric ethanol feeding. Microarray analysis showed that SAMe feeding prevented most of the changes in gene expression induced by ethanol feeding, presumably by inducing H3K27me3 and gene silencing. H3K27me3 was significantly increased by SAMe with or without ethanol feeding. It is concluded that SAMe feeding stabilized global gene expression so that the changes in gene expression involved in the blood alcohol cycle were prevented.

Epigenetic regulation of hepatic endoplasmic reticulum stress pathways in the ethanol-fed cystathionine beta synthase-deficient mouse

We tested the hypothesis that the pathogenesis of alcoholic liver injury is mediated by epigenetic changes in regulatory genes that result from the induction of aberrant methionine metabolism by ethanol feeding. Five-month-old cystathionine beta synthase heterozygous and wild-type C57BL/6J littermate mice were fed liquid control or ethanol diets by intragastric infusion for 4 weeks. Both ethanol-fed groups showed typical histopathology of alcoholic steatohepatitis, with reduction in liver S-adenosylmethionine (SAM), elevation in liver S-adenosylhomocysteine (SAH), and reduction in the SAM/SAH ratio with interactions of ethanol and genotype effects. Hepatic endoplasmic reticulum stress signals including glucose-regulated protein-78 (GRP78), activating transcription factor 4, growth arrest and DNA damage-inducible gene 153 (GADD153), caspase 12, and transcription factor sterol response element binding protein-1c (SREBP-1c) were up-regulated in ethanol-fed mice with genotype interactions and negative correlations with the SAM/SAH ratio. Immunohistochemical staining showed reduction in trimethylated histone H3 lysine-9 (3meH3K9) protein levels in centrilobular regions in both ethanol groups, with no changes in trimethylated histone H3 lysine-4 levels. The chromatin immunoprecipitation assay revealed a decrease in levels of suppressor chromatin marker 3meH3K9 in the promoter regions of GRP78, SREBP-1c, and GADD153 in ethanol-treated heterozygous cystathionine beta synthase mice. The messenger RNA expression of the histone H3K9 methyltransferase EHMT2 (G9a) was selectively decreased in ethanol-fed mice.

CONCLUSION

The pathogenesis of alcoholic steatohepatitis is mediated in part through the effects of altered methionine metabolism on epigenetic regulation of pathways of endoplasmic reticulum stress relating to apoptosis and lipogenesis.

Adipocyte accumulation of long-chain fatty acids in obesity is multifactorial, resulting from increased fatty acid uptake and decreased activity of genes involved in fat utilization

BACKGROUND

The obesity epidemic causes significant morbidity and mortality. Knowledge of cellular function and gene expression in obese adipose tissue will yield insights into obesity pathogenesis and suggest therapeutic targets. The aim of this work is to study the processes determining fat accumulation in adipose tissue from obese patients.

METHODS

Omental fat was collected from two cohorts of obese bariatric surgery patients and sex-matched normal-weight donors. Isolated adipocytes were compared for cell size, volume, and long-chain fatty acid (LCFA) uptake. Omental fat RNAs were screened by 10K microarray (cohort 1: three obese, three normal) or Whole Genome microarray (cohort 2: seven obese, four normal). Statistical differences in gene and pathway expression were identified in cohort 1 using the GeneSifter Software (Geospiza) with key results confirmed in cohort 2 samples by microarray, quantitative real-time polymerase chain reaction, and pathway analysis.

RESULTS

Obese omental adipocytes had increased surface area, volume, and V (max) for saturable LCFA uptake. Dodecenoyl-coenzyme A delta isomerase, central to LCFA metabolism, was approximately 1.6-fold underexpressed in obese fat in cohorts 1 and 2. Additionally, the Kyoto Encyclopedia of Genes and Genomics pathway analysis identified oxidative phosphorylation and fatty acid metabolism pathways as having coordinate, nonrandom downregulation of gene expression in both cohorts.

CONCLUSIONS

In obese omental fat, saturable adipocyte LCFA uptake was greater than in controls, and expression of key genes involved in lipolysis, beta-oxidation, and metabolism of fatty acids was reduced. Thus, both increased uptake and reduced metabolism of LCFAs contribute to the accumulation of LCFAs in obese adipocytes.

Nuclear effects of ethanol-induced proteasome inhibition in liver cells

Alcohol ingestion causes alteration in several cellular mechanisms, and leads to inflammation, apoptosis, immunological response defects, and fibrosis. These phenomena are associated with significant changes in the epigenetic mechanisms, and subsequently, to liver cell memory. The ubiquitin-proteasome pathway is one of the vital pathways in the cell that becomes dysfunctionial as a result of chronic ethanol consumption. Inhibition of the proteasome activity in the nucleus causes changes in the turnover of transcriptional factors, histone modifying enzymes, and therefore, affects epigenetic mechanisms. Alcohol consumption has been associated with an increase in histone acetylation and a decrease in histone methylation, which leads to gene expression changes. DNA and histone modifications that result from ethanol-induced proteasome inhibition are key players in regulating gene expression, especially genes involved in the cell cycle, immunological responses, and metabolism of ethanol. The present review highlights the consequences of ethanol-induced proteasome inhibition in the nucleus of liver cells that are chronically exposed to ethanol.