Histone h3 modifications in rat hepatic stellate cells by ethanol

The m6A methyltransferase Mettl3 deficiency attenuates hepatic stellate cell activation and liver fibrosis

Activation of hepatic stellate cells (HSCs) is a central driver of liver fibrosis. Previous investigations have identified various altered epigenetic landscapes during the cellular progression of HSC activation. N6-methyladenosine (m⁶A) is the most abundant internal RNA modification in eukaryotic cells and is dynamically regulated under various physiological and pathophysiological conditions. However, the functional role of Mettl3-mediated m⁶A in liver fibrosis remains elusive. Here, we found that the HSC-specific knockout of m⁶A methyltransferase Mettl3 suppressed HSC activation and significantly alleviated liver fibrosis. Multi-omics analysis of HSCs showed that Mettl3 depletion reduced m⁶A deposition on mRNA transcripts of Lats2 (a central player of the Hippo/YAP signaling pathway) and slowed down their degradation. Elevated Lats2 increased phosphorylation of the downstream transcription factor YAP, suppressed YAP nuclear translocation, and decreased pro-fibrotic gene expression. Overexpressing YAP mutant resistant to phosphorylation by Lats2 partially rescued the activation and pro-fibrotic gene expression of Mettl3-deficient HSCs. Our study revealed that disruption of Mettl3 in HSCs mitigated liver fibrosis by controlling the Hippo/YAP signaling pathway, providing potential therapeutic strategies to alleviate liver fibrosis by targeting epitranscriptomic machinery.

Targeting chromatin dysregulation in organ fibrosis

Fibrosis leads to destruction of organ architecture accompanied by chronic inflammation and loss of function. Fibrosis affects nearly every organ in the body and accounts for ∼45% of total deaths worldwide. Over the past decade, tremendous progress has been made in understanding the basic mechanisms leading to organ fibrosis. However, we are limited with therapeutic options and there is a significant need to develop highly effective anti-fibrotic therapies. Recent advances in sequencing technologies have advanced the burgeoning field of epigenetics towards molecular understanding at a higher resolution. Here we provide a comprehensive review of the recent advances in chromatin regulatory processes, specifically DNA methylation, post-translational modification of histones, and chromatin remodeling complexes in kidney, liver and lung fibrosis. Although this research field is young, we discuss new strategies for potential therapeutic interventions for treating organ fibrosis.

Murine Models for the Study of Fetal Alcohol Spectrum Disorders: An Overview

Prenatal alcohol exposure is associated to different physical, behavioral, cognitive, and neurological impairments collectively known as fetal alcohol spectrum disorder. The underlying mechanisms of ethanol toxicity are not completely understood. Experimental studies during human pregnancy to identify new diagnostic biomarkers are difficult to carry out beyond genetic or epigenetic analyses in biological matrices. Therefore, animal models are a useful tool to study the teratogenic effects of alcohol on the central nervous system and analyze the benefits of promising therapies. Animal models of alcohol spectrum disorder allow the analysis of key variables such as amount, timing and frequency of ethanol consumption to describe the harmful effects of prenatal alcohol exposure. In this review, we aim to synthetize neurodevelopmental disabilities in rodent fetal alcohol spectrum disorder phenotypes, considering facial dysmorphology and fetal growth restriction. We examine the different neurodevelopmental stages based on the most consistently implicated epigenetic mechanisms, cell types and molecular pathways, and assess the advantages and disadvantages of murine models in the study of fetal alcohol spectrum disorder, the different routes of alcohol administration, and alcohol consumption patterns applied to rodents. Finally, we analyze a wide range of phenotypic features to identify fetal alcohol spectrum disorder phenotypes in murine models, exploring facial dysmorphology, neurodevelopmental deficits, and growth restriction, as well as the methodologies used to evaluate behavioral and anatomical alterations produced by prenatal alcohol exposure in rodents.

Epigenetic Mechanisms of Pancreatobiliary Fibrosis

PURPOSE OF REVIEW

The goal of this manuscript is to review the current literature related to fibrogenesis in the pancreatobiliary system and how this process contributes to pancreatic and biliary diseases. In particular, we seek to define the current state of knowledge regarding the epigenetic mechanisms that govern and regulate tissue fibrosis in these organs. A better understanding of these underlying molecular events will set the stage for future epigenetic therapeutics.

RECENT FINDINGS

We highlight the significant advances that have been made in defining the pathogenesis of pancreatobiliary fibrosis as it relates to chronic pancreatitis, pancreatic cancer, and the fibro-obliterative cholangiopathies. We also review the cell types involved as well as concepts related to epithelial-mesenchymal crosstalk. Furthermore, we outline important signaling pathways (e.g., TGFβ) and diverse epigenetic processes (i.e., DNA methylation, non-coding RNAs, histone modifications, and 3D chromatin remodeling) that regulate fibrogenic gene networks in these conditions. We review a growing body of scientific evidence linking epigenetic regulatory events to fibrotic disease states in the pancreas and biliary system. Advances in this understudied area will be critical toward developing epigenetic pharmacological approaches that may lead to more effective treatments for these devastating and difficult to treat disorders.

CB1R-Mediated Activation of Caspase-3 Causes Epigenetic and Neurobehavioral Abnormalities in Postnatal Ethanol-Exposed Mice

Alcohol exposure can affect brain development, leading to long-lasting behavioral problems, including cognitive impairment, which together is defined as fetal alcohol spectrum disorder (FASD). However, the fundamental mechanisms through which this occurs are largely unknown. In this study, we report that the exposure of postnatal day 7 (P7) mice to ethanol activates caspase-3 via cannabinoid receptor type-1 (CB1R) in neonatal mice and causes a reduction in methylated DNA binding protein (MeCP2) levels. The developmental expression of MeCP2 in mice is closely correlated with synaptogenesis and neuronal maturation. It was shown that ethanol treatment of P7 mice enhanced Mecp2 mRNA levels but reduced protein levels. The genetic deletion of CB1R prevented, and administration of a CB1R antagonist before ethanol treatment of P7 mice inhibited caspase-3 activation. Additionally, it reversed the loss of MeCP2 protein, cAMP response element binding protein (CREB) activation, and activity-regulated cytoskeleton-associated protein (Arc) expression. The inhibition of caspase-3 activity prior to ethanol administration prevented ethanol-induced loss of MeCP2, CREB activation, epigenetic regulation of Arc expression, long-term potentiation (LTP), spatial memory deficits and activity-dependent impairment of several signaling molecules, including MeCP2, in adult mice. Collectively, these results reveal that the ethanol-induced CB1R-mediated activation of caspase-3 degrades the MeCP2 protein in the P7 mouse brain and causes long-lasting neurobehavioral deficits in adult mice. This CB1R-mediated instability of MeCP2 during active synaptic maturation may disrupt synaptic circuit maturation and lead to neurobehavioral abnormalities, as observed in this animal model of FASD.

Hepatic stellate cells as key target in liver fibrosis

Progressive liver fibrosis, induced by chronic viral and metabolic disorders, leads to more than one million deaths annually via development of cirrhosis, although no antifibrotic therapy has been approved to date. Transdifferentiation (or "activation") of hepatic stellate cells is the major cellular source of matrix protein-secreting myofibroblasts, the major driver of liver fibrogenesis. Paracrine signals from injured epithelial cells, fibrotic tissue microenvironment, immune and systemic metabolic dysregulation, enteric dysbiosis, and hepatitis viral products can directly or indirectly induce stellate cell activation. Dysregulated intracellular signaling, epigenetic changes, and cellular stress response represent candidate targets to deactivate stellate cells by inducing reversion to inactivated state, cellular senescence, apoptosis, and/or clearance by immune cells. Cell type- and target-specific pharmacological intervention to therapeutically induce the deactivation will enable more effective and less toxic precision antifibrotic therapies.

Epigenetic reprogramming in liver fibrosis and cancer

Novel insights into the epigenetic control of chronic liver diseases are now emerging. Recent advances in our understanding of the critical roles of DNA methylation, histone modifications and ncRNA may now be exploited to improve management of fibrosis/cirrhosis and cancer. Furthermore, improved technologies for the detection of epigenetic markers from patients' blood and tissues will vastly improve diagnosis, treatment options and prognostic tracking. The aim of this review is to present recent findings from the field of liver epigenetics and to explore their potential for translation into therapeutics to prevent disease promoting epigenome reprogramming and reverse epigenetic changes.

WITHDRAWN: Epigenetics in Chronic Liver Disease

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Changes to histone modifications following prenatal alcohol exposure: An emerging picture

Epigenetic mechanisms are important for facilitating gene-environment interactions in many disease etiologies, including Fetal Alcohol Spectrum Disorders (FASD). Extensive research into the role of DNA methylation and miRNAs in animal models has illuminated the complex role of these mechanisms in FASD. In contrast, histone modifications have not been as well researched, due in part to being less stable than DNA methylation and less well-characterized in disease. It is now apparent that even changes in transient marks can have profound effects if they alter developmental trajectories. In addition, many histone methylations are now known to be relatively stable and can propagate themselves. As technologies and knowledge have advanced, a small group has investigated the role of histone modifications in FASD. Here, we synthesize the data on the effects of prenatal alcohol exposure (PAE) on histone modifications. Several key points are evident. AS with most alcohol-induced outcomes, timing and dosage differences yield variable effects. Nevertheless, these studies consistently find enrichment of H3K9ac, H3K27me2,3, and H3K9me2, and increased expression of histone acetyltransferases and methyltransferases. The consistency of these alterations may implicate them as key mechanisms underlying FASD. Histone modification changes do not often correlate with gene expression changes, though some important examples exist. Encouragingly, attempts to reproduce specific histone modification changes are very often successful. We comment on possible directions for future studies, focusing on further exploration of current trends, expansion of time-point and dosage regimes, and evaluation of biomarker potential.

Epigenetics and Liver Fibrosis

Liver fibrosis arises because prolonged injury combined with excessive scar deposition within hepatic parenchyma arising from overactive wound healing response mediated by activated myofibroblasts. Fibrosis is the common end point for any type of chronic liver injury including alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, and cholestatic liver diseases. Although genetic influences are important, it is epigenetic mechanisms that have been shown to orchestrate many aspects of fibrogenesis in the liver. New discoveries in the field are leading toward the development of epigenetic biomarkers and targeted therapies. This review considers epigenetic mechanisms as well as recent advances in epigenetic programming in the context of hepatic fibrosis.

Epigenetic Interactions between Alcohol and Cannabinergic Effects: Focus on Histone Modification and DNA Methylation

Epigenetic studies have led to a more profound understanding of the mechanisms involved in chronic conditions. In the case of alcohol addiction, according to the National Institute on Alcohol Abuse and Alcoholism, 16 million adults suffer from Alcohol Use Disorders (AUDs). Even though therapeutic interventions like behavioral therapy and medications to prevent relapse are currently available, no robust cure exists, which stems from the lack of understanding the mechanisms of action of alcohol and the lack of development of precision medicine approaches to treat AUDs. Another common group of addictive substance, cannabinoids, have been studied extensively to reveal they work through cannabinoid receptors. Therapeutic applications have been found for the cannabinoids and a deeper understanding of the endocannabinoid system has been gained over the years. Recent reports of cannabinergic mechanisms in AUDs has opened an exciting realm of research that seeks to elucidate the molecular mechanisms of alcohol-induced end organ diseases and hopefully provide insight into new therapeutic strategies for the treatment of AUDs. To date, several epigenetic mechanisms have been associated with alcohol and cannabinoids independently. Therefore, the scope of this review is to compile the most recent literature regarding alcohol and cannabinoids in terms of a possible epigenetic connection between the endocannabinoid system and alcohol effects. First, we will provide an overview of epigenetics, followed by an overview of alcohol and epigenetic mechanisms with an emphasis on histone modifications and DNA methylations. Then, we will provide an overview of cannabinoids and epigenetic mechanisms. Lastly, we will discuss evidence of interactions between alcohol and cannabinergic pathways and possible insights into the novel epigenetic mechanisms underlying alcohol-cannabinergic pathway activity. Finalizing the review will be a discussion of future directions and therapeutic applications.

Carcinoma-associated fibroblasts: orchestrating the composition of malignancy

The tumor stroma is no longer seen solely as physical support for mutated epithelial cells but as an important modulator and even a driver of tumorigenicity. Within the tumor stromal milieu, heterogeneous populations of fibroblast-like cells, collectively termed carcinoma-associated fibroblasts (CAFs), are key players in the multicellular, stromal-dependent alterations that contribute to malignant initiation and progression. This review focuses on novel insights into the contributions of CAFs to disease progression, emergent events leading to the generation of CAFs, identification of CAF-specific biomarkers predictive of disease outcome, and recent therapeutic approaches aimed at blunting or reverting detrimental protumorigenic phenotypes associated with CAFs.

Epigenetic regulation of hepatic stellate cell activation and liver fibrosis

Chronic liver injury to hepatocytes or cholangiocytes, when left unmanaged, leads to the development of liver fibrosis, a condition characterized by the excessive intrahepatic deposition of extracellular matrix proteins. Activated hepatic stellate cells constitute the predominant source of extracellular matrix in fibrotic livers and their transition from a quiescent state during fibrogenesis is associated with important alterations in their transcriptional and epigenetic landscape. Areas covered: We briefly describe the processes involved in hepatic stellate cell activation and discuss our current understanding of alterations in the epigenetic landscape, i.e DNA methylation, histone modifications and the functional role of non-coding RNAs that accompany this key event in the development of chronic liver disease. Expert commentary: Although great progress has been made, our understanding of the epigenetic regulation of hepatic stellate cell activation is limited and, thus far, insufficient to allow the development of epigenetic drugs that can selectively interrupt liver fibrosis.

Epigenetics in liver disease: from biology to therapeutics

Knowledge of the fundamental epigenetic mechanisms governing gene expression and cellular phenotype are sufficiently advanced that novel insights into the epigenetic control of chronic liver disease are now emerging. Hepatologists are in the process of shedding light on the roles played by DNA methylation, histone/chromatin modifications and non-coding RNAs in specific liver pathologies. Alongside these discoveries are advances in the technologies for the detection and quantification of epigenetic biomarkers, either directly from patient tissue or from body fluids. The premise for this review is to survey the recent advances in the field of liver epigenetics and to explore their potential for translation by industry and clinical hepatologists for the design of novel therapeutics and diagnostic/prognostic biomarkers. In particular, we present findings in the context of hepatocellular carcinoma, fibrosis and non-alcoholic fatty liver disease, where there is urgent unmet need for new clinical interventions and biomarkers.

Dose-dependent alcohol-induced alterations in chromatin structure persist beyond the window of exposure and correlate with fetal alcohol syndrome birth defects

Background

In recent years, we have come to recognize that a multitude of in utero exposures have the capacity to induce the development of congenital and metabolic defects. As most of these encounters manifest their effects beyond the window of exposure, deciphering the mechanisms of teratogenesis is incredibly difficult. For many agents, altered epigenetic programming has become suspect in transmitting the lasting signature of exposure leading to dysgenesis. However, while several chemicals can perturb chromatin structure acutely, for many agents (particularly alcohol) it remains unclear if these modifications represent transient responses to exposure or heritable lesions leading to pathology.

Results

Here, we report that mice encountering an acute exposure to alcohol on gestational Day-7 exhibit significant alterations in chromatin structure (histone 3 lysine 9 dimethylation, lysine 9 acetylation, and lysine 27 trimethylation) at Day-17, and that these changes strongly correlate with the development of craniofacial and central nervous system defects. Using a neural cortical stem cell model, we find that the epigenetic changes arising as a consequence of alcohol exposure are heavily dependent on the gene under investigation, the dose of alcohol encountered, and that the signatures arising acutely differ significantly from those observed after a 4-day recovery period. Importantly, the changes observed post-recovery are consistent with those modeled in vivo, and associate with alterations in transcripts encoding multiple homeobox genes directing neurogenesis. Unexpectedly, we do not observe a correlation between alcohol-induced changes in chromatin structure and alterations in transcription. Interestingly, the majority of epigenetic changes observed occur in marks associated with repressive chromatin structure, and we identify correlative disruptions in transcripts encoding Dnmt1, Eed, Ehmt2 (G9a), EzH2, Kdm1a, Kdm4c, Setdb1, Sod3, Tet1 and Uhrf1.

Conclusions

These observations suggest that the immediate and long-term impacts of alcohol exposure on chromatin structure are distinct, and hint at the existence of a possible coordinated epigenetic response to ethanol during development. Collectively, our results indicate that alcohol-induced modifications to chromatin structure persist beyond the window of exposure, and likely contribute to the development of fetal alcohol syndrome-associated congenital abnormalities.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-015-0031-7) contains supplementary material, which is available to authorized users.

Epigenetic regulation of liver fibrosis

Fibrosis is a common and important pathology associated with progressive chronic liver diseases and underlies the development of cirrhosis and hepatocellular carcinoma. Research into the molecular regulation of fibrosis has discovered that it is under the control of a number of epigenetic mechanisms including DNA methylation, histone modifications and the activities of non-coding RNAs. A deeper understanding of how epigenetic regulators such as DNA methyltranserases, methyl-DNA binding proteins, histone modifying enzymes and regulatory RNA molecules impact on the fibrogenic process is expected to result in new biomarkers for disease progression as well as novel therapeutic targets. The aim of this mini-review is to briefly introduce the reader to the major epigenetic regulators so far identified as being implicated in fibrosis.

Alcohol consumption during gestation causes histone3 lysine9 hyperacetylation and an alternation of expression of heart development-related genes in mice

BACKGROUND

Alcohol abuse during gestation may cause congenital heart diseases (CHDs). The underlying mechanisms of alcohol-induced cardiac deformities are still not clear. Recent studies suggest that histone modification may play a crucial role in this pathological process. Moreover, our previous studies reported that ethanol could induce histone3 lysine9 (H3K9) hyperacetylation and overexpression of heart development-related genes in vitro. The aim of this study was to investigate the effect of alcohol consumption during gestation on the imbalance of H3K9 acetylation and the alternation of the expression of heart development-related genes during cardiogenesis.

METHODS

Pregnant mice were exposed to a single dose of alcohol (10 μl/g/d, 56% alcohol) by gavage every day in the morning from embryo day 7.5 (E7.5) to E15.5. Hematoxylin and eosin (H&E) staining was applied for observing the structure of the embryonic hearts. Western blotting and quantitative real-time polymerase chain reaction were used for detecting the level of H3K9 acetylation and gene expression. Histone acetyltransferase (HAT) and histone deacetylase (HDAC) activities were detected by colorimetric assay and fluorometric assay.

RESULTS

H&E staining of cardiac tissue showed abnormalities of embryonic hearts at E17.5. The level of H3K9 acetylation reached peak at E17.5 and decreased sharply to a low level at birth and maintained at low level afterward. Alcohol exposure increased H3K9 acetylation at E11.5, E14.5, E17.5, and E18.5, respectively (p < 0.05), and enhanced the expression of Gata4 in the embryonic hearts at E14.5 and E17.5, Mef2c at E14.5, and Nkx2.5 at E14.5 and E17.5, (p < 0.05) but not for Tbx5 (p > 0.05). On embryonic day 17.5, HAT activities of embryonic hearts increased significantly, however alcohol exposure did not alter HDAC activities.

CONCLUSIONS

These data indicate a time course of H3K9 acetylation change during heart development and demonstrate that alcohol exposure in utero may induce an increase of HAT activities, which results in H3K9 hyperacetylation and an increase of the expression of heart development-related genes. These findings reveal a novel epigenetic mechanism that connects the alcohol consumption during the pregnancy and the development of CHD in the fetus.

Sirtuin 1 signaling and alcoholic fatty liver disease

Alcoholic fatty liver disease (AFLD) is one of the most prevalent forms of liver disease worldwide and can progress to inflammation (hepatitis), fibrosis/cirrhosis, and ultimately lead to end stage liver injury. The mechanisms, by which ethanol consumption leads to AFLD, are complicated and multiple, and remain incompletely understood. Nevertheless, understanding its pathogenesis will facilitate the development of effective pharmacological or nutritional therapies for treating human AFLD. Chronic ethanol consumption causes steatosis and inflammation in rodents or humans by disturbing several important hepatic transcriptional regulators, including AMP-activated kinase (AMPK), lipin-1, sterol regulatory element binding protein 1 (SREBP-1), PPARγ co-activator-1α (PGC-1α), and nuclear transcription factor-κB (NF-κB). Remarkably, the effects of ethanol on these regulators are mediated in whole or in part by inhibition of a central signaling molecule, sirtuin 1 (SIRT1), which is a nicotinamide adenine dinucleotide (NAD(+), NADH)-dependent class III protein deacetylase. In recent years, SIRT1 has emerged as a pivotal molecule controlling the pathways of hepatic lipid metabolism, inflammatory responses and in the development of AFLD in rodents and in humans. Ethanol-mediated SIRT1 inhibition suppresses or stimulates the activities of above described transcriptional regulators and co-regulators, thereby deregulating diverse lipid metabolism and inflammatory response pathways including lipogenesis, fatty acid β-oxidation, lipoprotein uptake and secretion and expression of pro-inflammatory cytokines in the liver. This review aims to highlight our current understanding of SIRT1 regulatory mechanisms and its response to ethanol-induced toxicity, thus, affirming significant role of SIRT1 signaling in the development of AFLD.

Alcohol directly stimulates epigenetic modifications in hepatic stellate cells

BACKGROUND & AIMS

Alcohol is a primary cause of liver disease and an important co-morbidity factor in other causes of liver disease. A common feature of progressive liver disease is fibrosis, which results from the net deposition of fibril-forming extracellular matrix (ECM). The hepatic stellate cell (HSC) is widely considered to be the major cellular source of fibrotic ECM. We determined if HSCs are responsive to direct stimulation by alcohol.

METHODS

HSCs undergoing transdifferentiation were incubated with ethanol and expression of fibrogenic genes and epigenetic regulators was measured. Mechanisms responsible for recorded changes were investigated using ChIP-Seq and bioinformatics analysis. Ethanol induced changes were confirmed using HSCs isolated from a mouse alcohol model and from ALD patient's liver and through precision cut liver slices.

RESULTS

HSCs responded to ethanol exposure by increasing profibrogenic and ECM gene expression including elastin. Ethanol induced an altered expression of multiple epigenetic regulators, indicative of a potential to modulate chromatin structure during HSC transdifferentiation. MLL1, a histone 3 lysine 4 (H3K4) methyltransferase, was induced by ethanol and recruited to the elastin gene promoter where it was associated with enriched H3K4me3, a mark of active chromatin. Chromatin immunoprecipitation sequencing (ChIPseq) revealed that ethanol has broad effects on the HSC epigenome and identified 41 gene loci at which both MML1 and its H3K4me3 mark were enriched in response to ethanol.

CONCLUSIONS

Ethanol directly influences HSC transdifferentiation by stimulating global changes in chromatin structure, resulting in the increased expression of ECM proteins. The ability of alcohol to remodel the epigenome during HSC transdifferentiation provides mechanisms for it to act as a co-morbidity factor in liver disease.

CB1-receptor knockout neonatal mice are protected against ethanol-induced impairments of DNMT1, DNMT3A, and DNA methylation

The significant consequences of ethanol use during pregnancy are neurobehavioral abnormalities involving hippocampal and neocortex malfunctions that cause learning and memory deficits collectively named fetal alcohol spectrum disorder. However, the molecular mechanisms underlying these abnormalities are still poorly understood and therefore warrant systematic research. Here, we document novel epigenetic abnormalities in the mouse model of fetal alcohol spectrum disorder. Ethanol treatment of P7 mice, which induces activation of caspase 3, impaired DNA methylation through reduced DNA methyltransferases (DNMT1 and DNMT3A) levels. Inhibition of caspase 3 activity, before ethanol treatment, rescued DNMT1, DNMT3A proteins as well as DNA methylation levels. Blockade of histone methyltransferase (G9a) activity or cannabinoid receptor type-1 (CB1R), prior to ethanol treatment, which, respectively, inhibits or prevents activation of caspase 3, rescued the DNMT1 and DNMT3A proteins and DNA methylation. No reduction of DNMT1 and DNMT3A proteins and DNA methylation was found in P7 CB1R null mice, which exhibit no ethanol-induced activation of caspase 3. Together, these data demonstrate that ethanol-induced activation of caspase 3 impairs DNA methylation through DNMT1 and DNMT3A in the neonatal mouse brain, and such impairments are absent in CB1R null mice. Epigenetic events mediated by DNA methylation may be one of the essential mechanisms of ethanol teratogenesis. Schematic mechanism of action by which ethanol impairs DNA methylation. Studies have demonstrated that ethanol has the capacity to bring epigenetic changes to contribute to the development of fetal alcohol spectrum disorder (FASD). However, the mechanisms are not well studied. P7 ethanol induces the activation of caspase 3 and impairs DNA methylation through reduced DNA methyltransferases (DNMT1 and DNMT3A) proteins (→). The inhibition or genetic ablation of cannabinoid receptor type-1 or inhibition of histone methyltransferase (G9a) by Bix (-----) or inhibition of caspase 3 activation by Q- quinoline-Val-Asp(Ome)-CH2-O-phenoxy (Q-VD-OPh) () rescue loss of DNMT1, DNMT3A as well as DNA methylation. Hence, the putative DNMT1/DNMT3A/DNA methylation mechanism may have a potential regulatory role in FASD.

Membrane-to-Nucleus Signals and Epigenetic Mechanisms for Myofibroblastic Activation and Desmoplastic Stroma: Potential Therapeutic Targets for Liver Metastasis?

Cancer-associated fibroblasts (CAFs), the most abundant cells in the tumor microenvironment (TME), are a key source of the extracellular matrix (ECM) that constitutes the desmoplastic stroma. Through remodeling of the reactive tumor stroma and paracrine actions, CAFs regulate cancer initiation, progression, and metastasis, as well as tumor resistance to therapies. The CAFs found in stroma-rich primary hepatocellular carcinomas (HCC) and liver metastases of primary cancers of other organs predominantly originate from hepatic stellate cells (HSTC), which are pericytes associated with hepatic sinusoids. During tumor invasion, HSTCs transdifferentiate into myofibroblasts in response to paracrine signals emanating from either tumor cells or a heterogeneous cell population within the hepatic tumor microenvironment. Mechanistically, HSTC-to-myofibroblast transdifferentiation, also known as, HSTC activation, requires cell surface receptor activation, intracellular signal transduction, gene transcription, and epigenetic signals, which combined ultimately modulate distinct gene expression profiles that give rise to and maintain a new phenotype. The current review defines a paradigm that explains how HSTCs are activated into CAFs to promote liver metastasis. Furthermore, a focus on the most relevant intracellular signaling networks and epigenetic mechanisms that control HSTC activation is provided. Finally, we discuss the feasibility of targeting CAF/activated HSTCs, in isolation or in conjunction with targeting cancer cells, which constitutes a promising and viable therapeutic approach for the treatment of primary stroma-rich liver cancers and liver metastasis.

Long-term effects of chromatin remodeling and DNA damage in stem cells induced by environmental and dietary agents

The presence of histones acts as a barrier to protein access; thus chromatin remodeling must occur for essential processes such as transcription and replication. In conjunction with histone modifications, DNA methylation plays critical roles in gene silencing through chromatin remodeling. Chromatin remodeling is also interconnected with the DNA damage response, maintenance of stem cell properties, and cell differentiation programs. Chromatin modifications have increasingly been shown to produce long-lasting alterations in chromatin structure and transcription. Recent studies have shown environmental exposures in utero have the potential to alter normal developmental signaling networks, physiologic responses, and disease susceptibility later in life during a process known as developmental reprogramming. In this review we discuss the long-term impact of exposure to environmental compounds, the chromatin modifications that they induce, and the differentiation and developmental programs of multiple stem and progenitor cell types altered by exposure. The main focus is to highlight agents present in the human lifestyle that have the potential to promote epigenetic changes that impact developmental programs of specific cell types, may promote tumorigenesis through altering epigenetic marks, and may be transgenerational, for example, those able to be transmitted through multiple cell divisions.

Alcohol-induced epigenetic alterations to developmentally crucial genes regulating neural stemness and differentiation

BACKGROUND

From studies using a diverse range of model organisms, we now acknowledge that epigenetic changes to chromatin structure provide a plausible link between environmental teratogens and alterations in gene expression leading to disease. Observations from a number of independent laboratories indicate that ethanol (EtOH) has the capacity to act as a powerful epigenetic disruptor and potentially derail the coordinated processes of cellular differentiation. In this study, we sought to examine whether primary neurospheres cultured under conditions maintaining stemness were susceptible to alcohol-induced alterations in the histone code. We focused our studies on trimethylated histone 3 lysine 4 and trimethylated histone 3 lysine 27, as these are 2 of the most prominent posttranslational histone modifications regulating stem cell maintenance and neural differentiation.

METHODS

Primary neurosphere cultures were maintained under conditions promoting the stem cell state and treated with EtOH for 5 days. Control and EtOH-treated cellular extracts were examined using a combination of quantitative RT-PCR and chromatin immunoprecipitation techniques.

RESULTS

We find that the regulatory regions of genes controlling both neural precursor cell identity and processes of differentiation exhibited significant declines in the enrichment of the chromatin marks examined. Despite these widespread changes in chromatin structure, only a small subset of genes including Dlx2, Fabp7, Nestin, Olig2, and Pax6 displayed EtOH-induced alterations in transcription. Unexpectedly, the majority of chromatin-modifying enzymes examined including members of the Polycomb Repressive Complex displayed minimal changes in expression and localization. Only transcripts encoding Dnmt1, Uhrf1, Ehmt1, Ash2 l, Wdr5, and Kdm1b exhibited significant differences.

CONCLUSIONS

Our results indicate that primary neurospheres maintained as stem cells in vitro are susceptible to alcohol-induced perturbation of the histone code and errors in the epigenetic program. These observations indicate that alterations to chromatin structure may represent a crucial component of alcohol teratogenesis and progress toward a better understanding of the developmental origins of fetal alcohol spectrum disorders.

Alcohol and epigenetic changes: summary of the 2011 Alcohol and Immunology Research Interest Group (AIRIG) meeting

On November 18, 2011, the 16th annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held at Loyola University Medical Center in Maywood, Illinois. The focus of this year's meeting was alcohol's effect on epigenetic changes and possible outcomes induced by these changes. Two sessions, which consisted of talks from invited speakers as well as presentations of selected abstracts, were held in addition to a poster session. Participants presented information on alcohol-induced alterations in histone modifications and gene expression along with immunologic responses to alcohol. Speakers shared new research specifically on histone deacetylase enzyme expression and modifications due to alcohol and the downstream effect of these modifications may have on gene expression and tissue damage. Additional studies suggested that alcohol exacerbates inflammation when combined with other insults such as infection, trauma, inhalation injury, and disease.

Inhibition of histone acetylation by curcumin reduces alcohol-induced expression of heart development-related transcription factors in cardiac progenitor cells

Alcohol exposure during pregnancy may cause congenital heart disease (CHD). In our previous studies, we found that alcohol selectively increased acetylation of histone H3 at lysine 9 (H3K9) and enhanced the expression of heart development-related genes in cardiac progenitor cells. The objective of this study is to investigate the protective effects of histone acetyltransferases (HATs) inhibitor, curcumin, on histone hyperacetylation and the over-expression of heart development genes induced by alcohol. Western blot analysis was employed to detect the acetylation levels of histone H3K9 and real-time PCR was applied to measure the expressions of heart development-related transcription factors, GATA4, Mef2c and Tbx5 (GMT). Our results showed that alcohol increased the acetylation of H3K9 by 2.76-fold (P<0.05) and significantly enhanced the expression of GATA4 and Mef2c (P<0.05). When cells were treated with alcohol plus 25 μM curcumin, the hyperacetylation of H3K9 and over-expression of GATA4 and Mef2c by alcohol was reversed. These data indicate that curcumin can correct the over-expression of cardiac genes by reversing the alcohol induced hyperacetylation of histone H3 at lysine 9 in cardiac progenitor cells, suggesting that curcumin is protective against alcohol-induced cardiac gene over-expression that may result in heart malformations.

The effect of preconception paternal alcohol exposure on epigenetic remodeling of the h19 and rasgrf1 imprinting control regions in mouse offspring

Imprinted loci play a critical role in fetal development. Their expression is often regulated by CCCTC-binding factor (CTCF) protein binding at imprinting control regions (ICRs). Prenatal alcohol exposure has been shown to reduce global DNA methylation in the developing mouse fetus. This study explored the effect of preconception paternal alcohol exposure on DNA methylation at two paternally methylated ICRs (H19 and Rasgrf1) in the sperm of exposed males and somatic DNA of sired offspring. Significant reductions at the H19 CTCF 1 (p = 0.0027) and CTCF 2 (p = 0.0009) binding sites were observed in the offspring of ethanol-treated sires, which was significantly correlated with reduced weight at postnatal days 35–42 (p < 0.05). As birth weight was unaffected and growth was only delayed during the postnatal weaning period, with subsequent re-convergence, we hypothesize that this may be the result of a mental deficit causing delayed establishment of independent feeding following weaning and would explain why this effect is transient. No difference in DNA methylation was observed in the sperm of alcohol-exposed males, indicating that the transmission of the epigenetic signal at conception is not due to altered methylation, but may be the result of an RNA-mediated mechanism or altered chromatin remodeling.

The redox basis of epigenetic modifications: from mechanisms to functional consequences

Epigenetic modifications represent mechanisms by which cells may effectively translate multiple signaling inputs into phenotypic outputs. Recent research is revealing that redox metabolism is an increasingly important determinant of epigenetic control that may have significant ramifications in both human health and disease. Numerous characterized epigenetic marks, including histone methylation, acetylation, and ADP-ribosylation, as well as DNA methylation, have direct linkages to central metabolism through critical redox intermediates such as NAD(+), S-adenosyl methionine, and 2-oxoglutarate. Fluctuations in these intermediates caused by both normal and pathologic stimuli may thus have direct effects on epigenetic signaling that lead to measurable changes in gene expression. In this comprehensive review, we present surveys of both metabolism-sensitive epigenetic enzymes and the metabolic processes that may play a role in their regulation. To close, we provide a series of clinically relevant illustrations of the communication between metabolism and epigenetics in the pathogenesis of cardiovascular disease, Alzheimer disease, cancer, and environmental toxicity. We anticipate that the regulatory mechanisms described herein will play an increasingly large role in our understanding of human health and disease as epigenetics research progresses.

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.

Pathogenesis of liver fibrosis

Liver fibrosis is a major cause of morbidity and mortality worldwide due to chronic viral hepatitis and, more recently, from fatty liver disease associated with obesity. Hepatic stellate cell activation represents a critical event in fibrosis because these cells become the primary source of extracellular matrix in liver upon injury. Use of cell-culture and animal models has expanded our understanding of the mechanisms underlying stellate cell activation and has shed new light on genetic regulation, the contribution of immune signaling, and the potential reversibility of the disease. As pathways of fibrogenesis are increasingly clarified, the key challenge will be translating new advances into the development of antifibrotic therapies for patients with chronic liver disease.

Ethanol and its metabolites induce histone lysine 9 acetylation and an alteration of the expression of heart development-related genes in cardiac progenitor cells

Alcohol exposure during pregnancy may cause congenital heart disease (CHD), but the underlying mechanisms are not clear. Recent evidence suggests that ethanol and its metabolites can selectively increase histone H3 acetylation at lysine 9 (H3AcK9) residue in rat hepatocytes. This may be a mechanism by which ethanol alters gene expression. The goal of current study is to investigate the effect of ethanol and its metabolites on H3AcK9 acetylation and the mRNA expression of heart development-related genes (GATA4, Mef2c, and Tbx5) in cardiac progenitor cells. We used mitochondrial activity (MTT) assay to assess the viability of cardiac progenitor cells. Western blotting and real-time PCR were employed to determine H3AcK9 acetylation and gene expression. Low levels of ethanol (50 mM), acetaldehyde (4 mM), and acetate (4 mM) had no effect on cell proliferation. However, high concentrations of ethanol (200 mM), acetaldehyde (12 mM), and acetate (16 mM) reduced cell viability by 30%, respectively (P < 0.05). Low levels of ethanol and acetate increased the acetylation of H3 lysine 9 by 2.4- and 2.2-fold, respectively (P < 0.05), but did not significantly change the expression of the heart development-related genes. High concentrations of ethanol and acetate increased H3 lysine 9 acetylation by 5.3- and 5.6-fold, respectively (P < 0.05). Moreover, high levels of ethanol and acetate significantly augmented the expression of GATA4 and Mef2c. Conversely, acetaldehyde (4 or 12 mM) had little effect on H3 lysine 9 acetylation or the expression of the heart development-related genes. Our studies demonstrate that high levels of ethanol or its metabolites induce H3AcK9 acetylation and impair cardiac progenitor cells. The altered histone H3 acetylation at lysine 9 has an important impact on the expression of the heart development-related genes, which may be one of the mechanisms underlying the alcohol-induced CHD.

Epigenetic regulation of the endothelial nitric oxide synthase gene in persistent pulmonary hypertension of the newborn rat

OBJECTIVE

Persistent pulmonary hypertension of the newborn (PPHN) is a major clinical problem. Nitric oxide produced by endothelial nitric oxide synthase (eNOS) in endothelial cells plays an important role in the pathogenesis of PPHN. The eNOS expression in endothelial cells is controlled by epigenetic regulation. The aim of this study was to investigate the epigenetic regulatory mechanisms of the eNOS gene in PPHN.

METHODS

The rat model of PPHN was induced by hypoxia and indomethacin. Pulmonary vascular endothelial cells were isolated from the fetal rat lungs by magnetic-activated cell sorting. Chromatin immunoprecipitation and bisulfite sequencing methods were used to analyze epigenetic regulation.

RESULTS

The levels of acetylated histone H3 and acetylated histone H4 at the proximal promoter of the eNOS gene in pulmonary vascular endothelial cells from PPHN were significantly higher than those from the control group (P < 0.01, respectively). Total methylation percentage of the eNOS gene promoter in PPHN rat was slightly lower than that of control, but there was no statistically significant difference between the two groups (24.7 ± 2.0 vs. 27.3 ± 2.3%, P = 0.408). These changes of epigenetic modifications at the eNOS gene promoter were consistent with increased levels of eNOS mRNA and protein in PPHN.

CONCLUSION

The increased expression of eNOS in PPHN was associated with epigenetic regulation.

Acetate, the key modulator of inflammatory responses in acute alcoholic hepatitis

Acute alcoholic hepatitis is characterized by disproportionate macrophage inflammatory cytokine responses to bacterial lipopolysaccharide. Lack of knowledge of the underlying mechanism has limited progress toward effective therapy. We postulated a novel mechanism by which ethanol increases histone acetylation, increasing proinflammatory gene transcription and cytokine synthesis. Cytokine responses to lipopolysaccharide in a human macrophage cell line cultured in 86 mM ethanol, 1 mM acetate, and normal media were measured by multiplex immunoassay. Changes in histone acetylation were determined by immunofluorescence microscopy and chromatin immunoprecipitation on presentation. The effect of ethanol and acetate on acetyl-coenzyme A (acetyl-coA) synthetases, which convert acetate to acetyl-coA, the substrate for histone acetylation, was determined by quantitative reverse-transcription polymerase chain reaction and immunoblotting. Knockdown of acetyl-coA synthetases by short hairpin RNA (shRNA) was used to determine their role in ethanol's enhancement of the inflammatory cytokine response. Ethanol-exposed macrophages developed enhanced interleukin 6 (IL6), IL8, and tumor necrosis factor alpha responses to lipopolysaccharide with time-dependent increases in histone acetylation that could be prevented by inhibition of ethanol metabolism. Chromatin immunoprecipitation confirmed increased histone acetylation at promoter regions of specific cytokine genes. The effect of ethanol was reproduced by incubation with acetate, the principal hepatic metabolite of ethanol, and both ethanol and acetate reduced histone deacetylase activity and up-regulated acetyl-coA synthetases. Knockdown of the acetyl-coA synthetases abrogated the effect of ethanol on cytokine production.

CONCLUSION

Synthesis of metabolically available acetyl-coA from acetate is critical to the increased acetylation of proinflammatory gene histones and consequent enhancement of the inflammatory response in ethanol-exposed macrophages. This mechanism is a potential therapeutic target in acute alcoholic hepatitis.

Maternal ethanol consumption alters the epigenotype and the phenotype of offspring in a mouse model

Recent studies have shown that exposure to some nutritional supplements and chemicals in utero can affect the epigenome of the developing mouse embryo, resulting in adult disease. Our hypothesis is that epigenetics is also involved in the gestational programming of adult phenotype by alcohol. We have developed a model of gestational ethanol exposure in the mouse based on maternal ad libitum ingestion of 10% (v/v) ethanol between gestational days 0.5-8.5 and observed changes in the expression of an epigenetically-sensitive allele, Agouti viable yellow (A(vy)), in the offspring. We found that exposure to ethanol increases the probability of transcriptional silencing at this locus, resulting in more mice with an agouti-colored coat. As expected, transcriptional silencing correlated with hypermethylation at A(vy). This demonstrates, for the first time, that ethanol can affect adult phenotype by altering the epigenotype of the early embryo. Interestingly, we also detected postnatal growth restriction and craniofacial dysmorphology reminiscent of fetal alcohol syndrome, in congenic a/a siblings of the A(vy) mice. These findings suggest that moderate ethanol exposure in utero is capable of inducing changes in the expression of genes other than A(vy), a conclusion supported by our genome-wide analysis of gene expression in these mice. In addition, offspring of female mice given free access to 10% (v/v) ethanol for four days per week for ten weeks prior to conception also showed increased transcriptional silencing of the A(vy) allele. Our work raises the possibility of a role for epigenetics in the etiology of fetal alcohol spectrum disorders, and it provides a mouse model that will be a useful resource in the continued efforts to understand the consequences of gestational alcohol exposure at the molecular level.

Chronic ethanol consumption induces global hepatic protein hyperacetylation

BACKGROUND

Although the clinical manifestations of alcoholic liver disease are well described, little is known about the molecular basis for liver injury. Recent studies have indicated that chronic alcohol consumption leads to the lysine-hyperacetylation of several hepatic proteins, and this list is growing quickly.

METHODS

To identify other hyperacetylated proteins in ethanol-fed livers, we chose a proteomics approach. Cytosolic and membrane proteins (excluding nuclei) were separated on 2D gels, transferred to PVDF and immunoblotted with antibodies specific for acetylated lysine residues. Hyperacetylated proteins were selected for trypsin digestion and mass spectrometric analysis.

RESULTS

In all, 40 proteins were identified, 11 of which are known acetylated proteins. Remarkably, the vast majority of hyperacetylated membrane proteins were mitochondrial residents. Hyperacetylated cytosolic proteins ranged in function from metabolism to cytoskeletal support. Notably, 3 key anti-oxidant proteins were identified whose activities are impaired in ethanol-treated cells. We confirmed that the anti-oxidant enzyme, glutathione peroxidase 1, actin and cortactin are hyperacetylated in ethanol-treated livers.

CONCLUSIONS

Alcohol-induced hyperacetylation of multiple proteins may contribute to the development of liver injury. The abundance of acetylated mitochondrial proteins further suggests that this modification is important in regulating liver metabolism and when perturbed, may contribute to the progression of a variety of metabolic diseases.

Cathepsins B and D drive hepatic stellate cell proliferation and promote their fibrogenic potential

Cathepsins have been best characterized in tumorigenesis and cell death and implicated in liver fibrosis; however, whether cathepsins directly regulate hepatic stellate cell (HSC) activation and proliferation, hence modulating their fibrogenic potential, is largely unknown. Here, we show that expression of cathepsin B (CtsB) and cathepsin D (CtsD) is negligible in quiescent HSCs but parallels the increase of alpha-smooth muscle actin and transforming growth factor-beta during in vitro mouse HSC activation. Both cathepsins are necessary for HSC transdifferentiation into myofibroblasts, because their silencing or inhibition decreased HSC proliferation and the expression of phenotypic markers of HSC activation, with similar results observed with the human HSC cell line LX2. CtsB inhibition blunted AKT phosphorylation in activated HSCs in response to platelet-derived growth factor. Moreover, during in vivo liver fibrogenesis caused by CCl(4) administration, CtsB expression increased in HSCs but not in hepatocytes, and its inactivation mitigated CCl(4)-induced inflammation, HSC activation, and collagen deposition.

CONCLUSION

These findings support a critical role for cathepsins in HSC activation, suggesting that the antagonism of cathepsins in HSCs may be of relevance for the treatment of liver fibrosis.

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.

Alcohol-induced protein hyperacetylation: Mechanisms and consequences

Although the clinical manifestations of alcoholic liver disease are well-described, little is known about the molecular basis of liver injury. Recent studies have indicated that ethanol exposure induces global protein hyperacetylation. This reversible, post-translational modification on the epsilon-amino groups of lysine residues has been shown to modulate multiple, diverse cellular processes ranging from transcriptional activation to microtubule stability. Thus, alcohol-induced protein hyperacetylation likely leads to major physiological consequences that contribute to alcohol-induced hepatotoxicity. Lysine acetylation is controlled by the activities of two opposing enzymes, histone acetyltransferases and histone deacetylases. Currently, efforts are aimed at determining which enzymes are responsible for the increased acetylation of specific substrates. However, the greater challenge will be to determine the physiological ramifications of protein hyperacetylation and how they might contribute to the progression of liver disease. In this review, we will first list and discuss the proteins known to be hyperacetylated in the presence of ethanol. We will then describe what is known about the mechanisms leading to increased protein acetylation and how hyperacetylation may perturb hepatic function.

Emerging role of epigenetics in the actions of alcohol

This review deals with the recent developments on the epigenetic effects of ethanol. A large body of data have come from studies in liver and in neuronal systems and involve post-translational modifications in histones and methylations in DNA. Ethanol causes site selective acetylation, methylation, and phosphorylation in histone. With respect to methylations the methyl group donating system involving S-adenosyl methionine appears to play a central role. There is contrasting effect of acetylation versus methylation on the same site of histone, as it relates to the transcriptional activation. Epigenetic memory also appears to correlate with liver pathology and Mallory body formation. Experimental evidence supports transcriptional regulation of genes in the CNS by DNA methylations. These studies are contributing towards a better understanding of a novel epigenetic regulation of gene expression in the context of alcohol. The critical steps and the enzymes (e.g., histone acetyltransferase, histone deacetylase, DNA methyltransferase) responsible for the epigenetic modifications are prime targets for intense investigation. The emerging data are also beginning to offer novel insight towards defining the molecular actions of ethanol and may contribute to potential therapeutic targets at the nucleosomal level. These epigenetic studies have opened up a new avenue of investigation in the alcohol field.

Mammalian sirtuin 1 is involved in the protective action of dietary saturated fat against alcoholic fatty liver in mice

This study was undertaken to elucidate the mechanism underlying the protective effect of a high saturated fat (HSF) diet against the development of alcoholic fatty liver in mice. We tested the effects of a HSF diet on the ethanol-mediated increase in hepatic sterol regulatory element binding protein 1 (SREBP-1) activity. Thirty-two male mice were divided into 4 groups and fed liquid diets consisting of either a high polyunsaturated fat (40% of energy from corn oil) or a HSF (40% of energy from cocoa butter) diet with or without ethanol for 4 wk. In the ethanol-containing diets, ethanol was substituted for an equivalent amount of carbohydrate to provide 27.5% of the total energy. Control mice were pair-fed the same volume of liquid diets as the ethanol-fed mice. The HSF diet suppressed the increase in mature SREBP-1 protein and prevented increased mRNA of the SREBP-1-regulated lipogenic enzymes in the ethanol-fed mice (P < 0.05). Sirtuins 1 (SIRT1), a NAD+-dependent class III histone deacetylase, was upregulated by ethanol administration in mice fed the HSF diet (P < 0.05). The HSF diet blocked histone H3 at lysine 9 (lys9) hyperacetylation and attenuated association of acetylated histone H3-Lys9 with the promoters of mitochondrial glycerol-3-phosphate acyltransferase and stearoyl-CoA desaturase 1 in the livers of the ethanol-fed mice. These results suggest that the protective effects of HSF diet against the development of alcoholic liver steatosis may occur via regulation of the hepatic SIRT1-SREBP-1-histone H3 axis, suppressing the expression of genes encoding lipogenic enzymes and slowing the synthesis of hepatic fatty acids.

Epigenetic regulation of hepatic stellate cell activation

Activation of hepatic stellate cells (HSC) to a myofibroblast-like phenotype is the pivotal event in liver fibrosis. In uninjured liver, HSC are quiescent and non-dividing, but upon liver injury these cells undergo a dramatic change in phenotype which generates activated myofibroblast-like HSC. The change in phenotype is underpinned by a global change in gene expression with hundreds of genes being up- or downregulated. Molecular events that orchestrate changes in gene expression take place at the level of chromatin packaging which is altered through three main processes: histone modifications, DNA methylation, and silencing by non-coding RNAs. The present review focuses on the epigenetic regulation of HSC activation.

Epigenetic effects of ethanol on liver and gastrointestinal injury

Alcohol consumption causes cellular injury. Recent developments indicate that ethanol induces epigenetic alterations, particularly acetylation, methylation of histones, and hypo- and hypermethylation of DNA. This has opened up a new area of interest in ethanol research and is providing novel insight into actions of ethanol at the nucleosomal level in relation to gene expression and patho-physiological consequences. The epigenetic effects are mainly attributable to ethanol metabolic stress (Emess), generated by the oxidative and non-oxidative metabolism of ethanol, and dysregulation of methionine metabolism. Epigenetic changes are important in ethanol-induced hepatic steatosis, fibrosis, carcinoma and gastrointestinal injury. This editorial highlights these new advances and its future potential.

Acute in vivo effect of ethanol (binge drinking) on histone H3 modifications in rat tissues

AIMS

To investigate the effect of acute in vivo administration of ethanol on acetylation or methylation of histone H3 at lysine9 in different tissues in rat.

METHODS

Ethanol was injected into the stomach of Sprague-Dawley rats (8-weeks-old) using blunt tipped needle. The rats were divided into three groups based on ethanol exposure times (1, 3, and 12 h). Each group was compared with water-injected control group. The tissues from 14 different organs were removed. We essentially used similar type of protocol, tissue homogenization method, and sucrose density gradient centrifugation for isolation of nuclei with only minor modifications for some organs. Histone was isolated from the nuclei using acid extraction method. Acetylation of histone H3 at lysine9 (Ac-H3-lys9) and methylation of histone H3 at lysine9 (Me-H3-lys9) were analysed by western blotting.

RESULTS

Effect of ethanol on Ac-H3-lys9 was investigated in 11 out of 14 rat tissues. In liver, we observed an increase in Ac-H3-lys9 with maximal increase of approximately 6-fold after 12 h exposure. Lung also showed approximately 3-fold increase. In spleen, ethanol-induced Ac-H3-lys9 in all three ethanol-treated groups with similar increase (1.5- to 1.6-fold). Testes showed significant increase (3-fold increase) of Ac-H3-lys9 only at 1 h ethanol exposure. Ethanol had no affect on Ac-H3-lys9 in other tissues: kidney, brain, heart, stomach, colorectum, pancreas, and vessels. Ethanol had little effect on Me-H3-lys9 in all rat tissues examined.

CONCLUSIONS

After in vivo administration of ethanol, analogous to binge drinking condition, the acetylations of H3-lys9 in rat tissues are not universal but tissue-specific events with different patterns of responses. Ac-H3-Lys9 in liver, lung, and spleen were significantly affected and it was demonstrated that ethanol causes this epigenetic alteration in rat tissues selectively.