Epigenetic DNA hypermethylation of the HERP gene promoter induces down-regulation of its mRNA expression in patients with alcohol dependence

Hormones and drinking behaviour: new findings on ghrelin, insulin, leptin and volume-regulating hormones. An ESBRA Symposium report

There is growing evidence for a role of appetite-related peptides and volume-regulating hormones in alcoholism. In particular, recent evidence has suggested that hormones, such as ghrelin, insulin and leptin and volume-regulating hormones, could play a role in alcohol-seeking behaviour. The goal of this review is to discuss the results of recent preclinical and clinical investigations on this topic. The findings indicate that neuroendocrinological mechanisms are potentially involved in the neurobiology of alcohol craving. Accordingly, research on this topic could lead to possible development of new therapeutic approaches in the treatment of patients with alcohol problems.

Substance use and misuse in the aftermath of terrorism. A Bayesian meta-analysis

AIM

To conduct a comprehensive analysis of the conflicting evidence on substance use and misuse following mass traumas such as terrorist incidents.

METHODS

We reviewed and synthesized evidence from 31 population-based studies using Bayesian meta-analysis and meta-regression.

RESULTS

The majority of the studied were conducted in the aftermath of the terrorist attacks of 11 September 2001. Controlling for exposure, type of incident and time since the event occurred, 7.3% [95% credible interval (CrI) 1.1-32.5%] of a population can be expected to report increased alcohol consumption in the first 2 years following a terrorist event. There is, however, a 20% probability that the prevalence will be as high as 14%. The unadjusted prevalence of increased cigarette smoking following a terrorist event is 6.8% (95% Cr I 2.6-16.5%). Unadjusted reports of mixed drug use (including narcotics and prescription medications) was 16.3% (95% Cr I 1.3-72.5%).

CONCLUSIONS

These results underscore the potentially pervasive behavioral health effects of mass terrorism, and suggest that public health interventions may usefully consider substance use as an area of focus after such events.

Epigenetic regulation and gene expression of vasopressin and atrial natriuretic peptide in alcohol withdrawal

Disturbances of volume regulating peptides like vasopressin and atrial natriuretic peptide (ANP) have been described in early abstinent patients. Aim of the present study was to evaluate possible alterations of the promoter-related DNA methylation of the ANP and vasopressin precursor genes and the related mRNA-expression of these genes in early alcohol withdrawal. We analyzed blood samples of 57 healthy controls and of 111 patients suffering from alcohol dependence that were admitted for detoxification treatment. Promoter-related DNA methylation and mRNA-expression of vasopressin and ANP genes were assessed using real-time PCR. Vasopressin mRNA-expression was not statistically different between patients and controls. However, we found a significantly elevated promoter-related DNA methylation of the vasopressin gene in patients with alcohol dependence (Mann-Whitney U-test: Z=-2.178, p=0.029). ANP mRNA-expression was significantly elevated in alcoholic patients (Z=-6.240, p<0.001) while promoter-related DNA methylation of ANP was significantly decreased (Z=-2.282, p=0.023). Furthermore, promoter-related DNA methylation of ANP was significantly correlated to the extent of craving measured with the OCDS (r=-0.197, p=0.040). The findings of the present study show significant alterations of the mRNA-expression and promoter-related DNA methylation of vasopressin and especially ANP precursor genes in patients with alcohol dependence. Further studies focusing on longitudinal changes of epigenetic regulation and gene expression of both peptides are needed to clarify the pathophysiological role of these findings.

Elevated cannabinoid 1 receptor mRNA is linked to eating disorder related behavior and attitudes in females with eating disorders

OBJECTIVE

The endocannabinoid system is involved in the regulation of appetite, food intake and energy balance.

METHODS

To study possible differences in CB(1) and CB(2) mRNA expression in eating disorders, 20 patients with anorexia nervosa (AN), 23 with bulimia nervosa (BN) and 26 healthy women were enrolled into the trial (Homocysteine and Eating Disorders, HEaD).

RESULTS

We found significantly higher levels of CB(1) receptor mRNA in the blood of patients with AN (DeltaCT: -3.9 (1.0); KW: 11.31; P=0.003) and BN (DeltaCT: -3.7 (1.7)) when compared to controls (DeltaCT: -4.6 (0.6); Dunn's test AN vs.

CONTROLS

P<0.05; BN vs.

CONTROLS

P<0.001) measured by quantitative real-time PCR. No differences were found regarding the expression of CB(2) receptor mRNA. Higher CB(1) receptor expression was associated with lower scores in several eating disorder inventory-2 (EDI-2) subscales including perfectionism, impulse regulation and drive for thinness.

CONCLUSION

Our finding of elevated CB(1)-receptor expression in AN and BN adds further evidence to the hypothesis of impaired endocannabinoid signaling in eating disorders.

Epigenetics and environmental chemicals

PURPOSE OF REVIEW

Epigenetics investigates heritable changes in gene expression occurring without changes in DNA sequence. Several epigenetic mechanisms, including DNA methylation, histone modifications, and microRNA expression, can change genome function under exogenous influence. Here, we review current evidence indicating that epigenetic alterations mediate toxicity from environmental chemicals.

RECENT FINDINGS

In-vitro, animal, and human investigations have identified several classes of environmental chemicals that modify epigenetic marks, including metals (cadmium, arsenic, nickel, chromium, and methylmercury), peroxisome proliferators (trichloroethylene, dichloroacetic acid, and TCA), air pollutants (particulate matter, black carbon, and benzene), and endocrine-disrupting/reproductive toxicants (diethylstilbestrol, bisphenol A, persistent organic pollutants, and dioxin). Most studies conducted so far have been centered on DNA methylation, whereas only a few investigations have studied environmental chemicals in relation to histone modifications and microRNA.

SUMMARY

For several exposures, it has been proved that chemicals can alter epigenetic marks, and that the same or similar epigenetic alterations can be found in patients with the disease of concern or in diseased tissues. Future prospective investigations are needed to determine whether exposed individuals develop epigenetic alterations over time and, in turn, which such alterations increase the risk of disease. Also, further research is needed to determine whether environmental epigenetic changes are transmitted transgenerationally.

Herp mRNA expression in patients classified according to Lesch's typology

Chronic alcoholism is associated with hyperhomocysteinemia. Herp (homocysteine-induced endoplasmic reticulum [ER] protein) levels are elevated as a response to ER stress prior to mitochondrial dysfunction and cell death. The Lesch classification system has been applied in many studies and has been found useful. This study was undertaken to assess Herp mRNA expression in actively drinking patients with alcoholism who were classified according to Lesch's typology. Herp mRNA expression levels were measured by quantitative PCR in the blood of 76 male alcoholic patients. Patients were classified according to Lesch's typology (type I-IV). With respect to Lesch's typology, a significant difference in Herp mRNA expression regarding the four subtypes could be shown (F[3,72]=2.83, P=.044). In a logistic regression model (dependent variable Herp dichotomized by a median-split; adjusted for age and homocysteine levels) the subtype II differed statistically significant from the others (odds ratio, 5.75; 95% confidence interval, 2.07-15.98; P=.001). Type II alcoholic patients had a statistically significant higher expression of Herp mRNA due to upregulation of the expression of this neuroprotective cell non-chaperone by toxic effects of ethanol. These findings might explain why type II patients do not express severe withdrawal symptomatology (i.e., withdrawal seizures). These findings may be useful in the understanding and treatment considerations of different subtypes of alcohol dependence.

Increased OPRM1 DNA methylation in lymphocytes of methadone-maintained former heroin addicts

The mu-opioid receptor is the site of action of opiates and opioids. We examined whether there are differences in cytosine:guanine (CpG) dinucleotide methylation in the OPRM1 promoter between former heroin addicts and controls. We analyzed methylation at 16 CpG dinucleotides in DNA obtained from lymphocytes of 194 Caucasian former severe heroin addicts stabilized in methadone maintenance treatment and 135 Caucasian control subjects. Direct sequencing of bisulfite-treated DNA showed that the percent methylation at two CpG sites was significantly associated with heroin addiction. The level of methylation at the -18 CpG site was 25.4% in the stabilized methadone-maintained former heroin addicts and 21.4% in controls (p=0.0035, generalized estimating equations (GEE); p=0.0077, t-test; false discovery rate (FDR)=0.048), and the level of methylation at the +84 CpG dinucleotide site was 7.4% in cases and 5.6% in controls (p=0.0095, GEE; p=0.0067, t-test; FDR=0.080). Both the -18 and the +84 CpG sites are located in potential Sp1 transcription factor-binding sites. Methylation of these CpG sites may lead to reduced OPRM1 expression in the lymphocytes of these former heroin addicts.

Prospects for epigenetic epidemiology

Epigenetic modification can mediate environmental influences on gene expression and can modulate the disease risk associated with genetic variation. Epigenetic analysis therefore holds substantial promise for identifying mechanisms through which genetic and environmental factors jointly contribute to disease risk. The spatial and temporal variance in epigenetic profile is of particular relevance for developmental epidemiology and the study of aging, including the variable age at onset for many common diseases. This review serves as a general introduction to the topic by describing epigenetic mechanisms, with a focus on DNA methylation; genetic and environmental factors that influence DNA methylation; epigenetic influences on development, aging, and disease; and current methodology for measuring epigenetic profile. Methodological considerations for epidemiologic studies that seek to include epigenetic analysis are also discussed.

Promoter specific methylation of the dopamine transporter gene is altered in alcohol dependence and associated with craving

Dopaminergic neurotransmission plays a crucial role in the genesis and maintenance of alcohol dependence. Epigenetic regulation via promoter specific DNA methylation of the dopamine transporter gene (DAT) may influence altered dopaminergic neurotransmission in alcoholism. Aim of the present study was to investigate DNA promoter methylation of DAT in early alcohol withdrawal and in relation to alcohol craving. We analyzed blood samples of 76 patients admitted for detoxification treatment and compared them to 35 healthy controls. Methylation specific quantitative real-time PCR was used to measure the promoter specific DNA methylation of the dopamine transporter. We assessed the extent of alcohol craving using the obsessive compulsive drinking scale (OCDS). Compared to healthy controls we found a significant hypermethylation of the DAT-promoter (Mann-Whitney U-test: p=0.001). Ln-transformed methylation of the DAT-promoter was negatively associated with the OCDS (linear regression: Beta=-0.275, p=0.016), particularly with the obsessive subscale (Beta=-0.300, p=0.008). Findings of the present study show that the epigenetic regulation of the DAT-promoter is altered in patients undergoing alcohol withdrawal. Furthermore, hypermethylation of the DAT-promoter may play an important role in dopaminergic neurotransmission and is associated with decreased alcohol craving.

Epigenetic and pharmacoepigenomic studies of major psychoses and potentials for therapeutics

Individuals with neuropsychiatric diseases have epigenetic programming disturbances, both in the brain, which is the primary affected organ, and in secondary tissues. Epigenetic modulations are molecular modifications made to DNA, RNA and proteins that fine-tune genotype into phenotype and do not include DNA base changes. For instance, gene-expression modulation is linked to epigenetic codes in chromatin that consist of post-replication DNA methylation and histone protein modifications (e.g., methylation, acetylation and so on), particularly in gene-promoter regions. Epigenetic coding is modulated globally, and in a gene-specific manner by environmental exposures that include nutrition, toxins, drugs and so on. Analysis of epigenetic aberrations in diseases helps to identify dysfunctional genes and pathways, establish more robust cause–effect relationships than genetic studies alone, and identify new pharmaceutical targets and drugs, including nucleic acid reagents such as inhibitory RNAs. The emerging science of pharmacoepigenomics can impact the treatment of psychiatric and other complex diseases. In fact, some therapeutics now in use target epigenetic programming. In the near future, epigenetic interventions should help stabilize affected individuals and lead to prevention strategies.

Prenatal nutritional deficiency and risk of adult schizophrenia

Converging evidence suggests that a neurodevelopmental disruption plays a role in the vulnerability to schizophrenia. The authors review evidence supporting in utero exposure to nutritional deficiency as a determinant of schizophrenia. We first describe studies demonstrating that early gestational exposure to the Dutch Hunger Winter of 1944--1945 and to a severe famine in China are each associated with an increased risk of schizophrenia in offspring. The plausibility of several candidate micronutrients as potential risk factors for schizophrenia and the biological mechanisms that may underlie these associations are then reviewed. These nutrients include folate, essential fatty acids, retinoids, vitamin D, and iron. Following this discussion, we describe the methodology and results of an epidemiologic study based on a large birth cohort that has tested the association between prenatal homocysteine, an indicator of serum folate, and schizophrenia risk. The study capitalized on the use of archived prenatal serum specimens that make it possible to obtain direct, prospective biomarkers of prenatal insults, including levels of various nutrients during pregnancy. Finally, we discuss several strategies for subjecting the prenatal nutritional hypothesis of schizophrenia to further testing. These approaches include direct assessment of additional prenatal nutritional biomarkers in relation to schizophrenia in large birth cohorts, studies of epigenetic effects of prenatal starvation, association studies of genes relevant to folate and other micronutrient deficiencies, and animal models. Given the relatively high prevalence of nutritional deficiencies during pregnancy, this work has the potential to offer substantial benefits for the prevention of schizophrenia in the population.

Epigenetic downregulation of atrial natriuretic peptide but not vasopressin mRNA expression in females with eating disorders is related to impulsivity

Disturbances of volume-regulating mechanisms have already been implicated in the pathophysiology of eating disorders like anorexia or bulimia nervosa with the peptide hormones vasopressin and atrial natriuretic peptide (ANP) being of special interest. Aim of the present study was to investigate, whether the expression of the corresponding genes was altered and if so, if these changes could be explained by epigenetic mechanisms such as DNA methylation. We analyzed blood samples of 46 women suffering from anorexia (n=22) or bulimia nervosa (n=24) as well as of 30 healthy controls. Peripheral mRNA expression and DNA methylation of the vasopressin and the ANP precursor genes were assessed using real-time PCR. We found significantly lower levels of ANP mRNA in patients with eating disorders. This downregulation was accompanied by a hypermethylation of the ANP gene promoter in the bulimic subgroup. We did not find differences regarding expression or methylation of the vasopressin gene. ANP mRNA expression was inversely associated with impaired impulse regulation. We conclude that epigenetic mechanisms may contribute to the known alterations of ANP homeostasis in women with eating disorders.

Detection of altered global DNA methylation in coronary artery disease patients

Epigenetic modifications, especially alteration in DNA methylation, are increasingly being recognized as a key factor in the pathogenesis of complex disorders, including atherosclerosis. However, there are limited data on the epigenetic changes in the coronary artery disease (CAD) patients. In the present study we evaluated the methylation status of genomic DNA from peripheral lymphocytes in a cohort of 287 individuals: 137 angiographically confirmed CAD patients and 150 controls. The differential susceptibility of genomic DNA to methylation-sensitive restriction enzymes was utilized to assess the methylation status of the genome. We observed that the genomic DNA methylation in CAD patients is significantly higher than in controls (p < 0.05). Since elevated homocysteine levels are known to be an independent risk factor for CAD and a key modulator of macromolecular methylation, we investigated the probable correlation between plasma homocysteine levels and global DNA methylation. We observed a significant positive correlation of global DNA methylation with plasma homocysteine levels in CAD patients (p = 0.001). Further, within a higher range of serum homocysteine levels (>/=12-50 muM), global DNA methylation was significantly higher in CAD patients than in controls. The alteration in genomic DNA methylation associated with cardiovascular disease per se appears to be further accentuated by higher homocysteine levels.

Promoter-wide hypermethylation of the ribosomal RNA gene promoter in the suicide brain

BACKGROUND

Alterations in gene expression in the suicide brain have been reported and for several genes DNA methylation as an epigenetic regulator is thought to play a role. rRNA genes, that encode ribosomal RNA, are the backbone of the protein synthesis machinery and levels of rRNA gene promoter methylation determine rRNA transcription.

METHODOLOGY/PRINCIPAL FINDINGS

We test here by sodium bisulfite mapping of the rRNA promoter and quantitative real-time PCR of rRNA expression the hypothesis that epigenetic differences in critical loci in the brain are involved in the pathophysiology of suicide. Suicide subjects in this study were selected for a history of early childhood neglect/abuse, which is associated with decreased hippocampal volume and cognitive impairments. rRNA was significantly hypermethylated throughout the promoter and 5' regulatory region in the brain of suicide subjects, consistent with reduced rRNA expression in the hippocampus. This difference in rRNA methylation was not evident in the cerebellum and occurred in the absence of genome-wide changes in methylation, as assessed by nearest neighbor.

CONCLUSIONS/SIGNIFICANCE

This is the first study to show aberrant regulation of the protein synthesis machinery in the suicide brain. The data implicate the epigenetic modulation of rRNA in the pathophysiology of suicide.

Global DNA methylation is influenced by smoking behaviour

The level of epigenetic DNA methylation is an important factor in the pathogenesis of various human diseases. As smoking may influence DNA methylation, we investigated the effect of smoking habits on global DNA methylation in 298 genomic DNA samples (73 fathers, 69 mothers and 156 offspring). We did not find a direct effect of smoking on global DNA methylation. However, there was an association of the offspring's DNA methylation with paternal DNA methylation that was strongest if both had never smoked (R2corr=0.41, Beta=0.68, p=0.02) and completely vanished if the offspring smoked or had ever smoked. These findings suggest an association between smoking behaviour and global DNA methylation, which may be of importance for a wide range of diseases.

Reduced MeCP2 expression is frequent in autism frontal cortex and correlates with aberrant MECP2 promoter methylation

Mutations in MECP2, encoding methyl CpG binding protein 2 (MeCP2), cause most cases of Rett syndrome (RTT), an X-linked neurodevelopmental disorder. Both RTT and autism are "pervasive developmental disorders" and share a loss of social, cognitive and language skills and a gain in repetitive stereotyped behavior, following apparently normal perinatal development. Although MECP2 coding mutations are a rare cause of autism, MeCP2 expression defects were previously found in autism brain. To further study the role of MeCP2 in autism spectrum disorders (ASDs), we determined the frequency of MeCP2 expression defects in brain samples from autism and other ASDs. We also tested the hypotheses that MECP2 promoter mutations or aberrant promoter methylation correlate with reduced expression in cases of idiopathic autism. MeCP2 immunofluorescence in autism and other neurodevelopmental disorders was quantified by laser scanning cytometry and compared with control postmortem cerebral cortex samples on a large tissue microarray. A significant reduction in MeCP2 expression compared to age-matched controls was found in 11/14 autism (79%), 9/9 RTT (100%), 4/4 Angelman syndrome (100%), 3/4 Prader-Willi syndrome (75%), 3/5 Down syndrome (60%), and 2/2 attention deficit hyperactivity disorder (100%) frontal cortex samples. One autism female was heterozygous for a rare MECP2 promoter variant that correlated with reduced MeCP2 expression. A more frequent occurrence was significantly increased MECP2 promoter methylation in autism male frontal cortex compared to controls. Furthermore, percent promoter methylation of MECP2 significantly correlated with reduced MeCP2 protein expression. These results suggest that both genetic and epigenetic defects lead to reduced MeCP2 expression and may be important in the complex etiology of autism.

Epigenetic alterations of the dopaminergic system in major psychiatric disorders

Although there is evidence to link schizophrenia (SCZ) and bipolar disorder (BD) to genetic and environmental factors, specific individual or groups of genes/factors causative of the disease have been elusive to the research community. An understanding of the molecular aberrations that cause these mental illnesses requires comprehensive approaches that examine both genetic and epigenetic factors. Because of the overwhelming evidence for the role of environmental factors in the disease presentation, our initial approach involved deciphering how epigenetic changes resulting from promoter DNA methylation affect gene expression in SCZ and BD. Apparently, the central reversible but covalent epigenetic modification to DNA is derived from methylation of the cytosine residues that is potentially heritable and can affect gene expression and downstream activities. Environmental factors can influence DNA methylation patterns and hence alter gene expression. Such changes can be especially problematic in individuals with genetic susceptibilities to specific diseases. Recent reports from our laboratory provided compelling evidence that both hyper- and hypo-DNA methylation changes of the regulatory regions play critical roles in defining the altered functionality of genes in major psychiatric disorders such as SCZ and BD. In this chapter, we outline the technical details of the methods that could help to expand this line of research to assist with compiling the differential methylation-mediated epigenetic alterations that are responsible for the pathogenesis of SCZ, BD, and other mental diseases. We use the genes of the extended dopaminergic (DAergic) system such as membrane-bound catechol-O-methyltransferase (MB-COMT), monoamine oxidase A (MAOA), dopamine transporter 1 (DAT1), tyrosine hydroxylase (TH), dopamine (DA) receptors1 and 2 (DRD1/2), and related genes (e.g., reelin [RELN] and brain-derived neurotrophic factor [BDNF]) to illustrate the associations between differential promoter DNA methylations and disease phenotype. It is our hope that comprehensive analyses of the DAergic system as the prototype could provide the impetus and molecular basis to uncover early markers for diagnosis, help in the understanding of differences in disease severity in individuals with similar or identical genetic makeup, and assist with the identification of novel targets for therapeutic applications.

Metals and neurotoxicology

Metals are ubiquitous and play a critical role in neurobiology. Transition metals are important because they alter the redox state of the physical environment. Biologically, transition metals catalyze redox reactions that are critical to cellular respiration, chemical detoxification, metabolism, and even neurotransmitter synthesis. Many metals are both nutrients and neurotoxicants, such as iron, zinc, copper, and manganese. Other metals, such as lead and cadmium, are metabolized similarly to these metals, particularly iron. Iron metabolism and genes that regulate iron metabolism may be the key to understanding metal toxicity. Finally, recent evidence demonstrates that early life exposures may program later life and adult disease phenotypes via processes of epigenetics. Parallel work in metals demonstrates that epigenetics may be a critical pathway by which metals produce health effects.

Hyperhomocysteinemia due to cystathionine beta synthase deficiency induces dysregulation of genes involved in hepatic lipid homeostasis in mice

BACKGROUND/AIMS

Cystathionine beta synthase (CBS) deficiency leads to severe hyperhomocysteinemia, which confers diverse clinical manifestations, notably fatty liver. Recently, abnormal lipid metabolism has been demonstrated in CBS-deficient mice, a murine model of severe hyperhomocysteinemia. To gain further insights into effects of CBS deficiency on hepatic cholesterol metabolism, the expression of hepatic genes involved in biosynthesis, uptake and efflux was determined in CBS-deficient mice.

METHODS

Gene expression analysis was performed on liver of CBS-deficient mice using quantitative real-time PCR.

RESULTS

We found that CBS-deficiency in liver mice significantly increases expression of genes induced by endoplasmic reticulum stress and genes that regulate the expression of enzymes required for cholesterol and fatty acid biosynthesis and uptake, notably the scavenger receptor class B type I (SR-BI), concomitant with overexpression of SR-BI at the protein level. Moreover, we also found increased mRNA levels of ABCG5, ABCG8, ABCG1 and ABCA1, which play important roles in reverse cholesterol transport, associated with an upregulation of liver X receptors and a downregulation of the peroxisome proliferators-activated receptor alpha.

CONCLUSIONS

We found that several ATP-binding cassette transporters and nuclear hormone receptors involved in liver lipid homeostasis are differentially expressed in liver of CBS-deficient mice.

Hypomethylation of MB-COMT promoter is a major risk factor for schizophrenia and bipolar disorder

The variability in phenotypic presentations and the lack of consistency of genetic associations in mental illnesses remain a major challenge in molecular psychiatry. Recently, it has become increasingly clear that altered promoter DNA methylation could play a critical role in mediating differential regulation of genes and in facilitating short-term adaptation in response to the environment. Here, we report the investigation of the differential activity of membrane-bound catechol-O-methyltransferase (MB-COMT) due to altered promoter methylation and the nature of the contribution of COMT Val158Met polymorphism as risk factors for schizophrenia and bipolar disorder by analyzing 115 post-mortem brain samples from the frontal lobe. These studies are the first to reveal that the MB-COMT promoter DNA is frequently hypomethylated in schizophrenia and bipolar disorder patients, compared with the controls (methylation rate: 26 and 29 versus 60%; P=0.004 and 0.008, respectively), particularly in the left frontal lobes (methylation rate: 29 and 30 versus 81%; P=0.003 and 0.002, respectively). Quantitative gene-expression analyses showed a corresponding increase in transcript levels of MB-COMT in schizophrenia and bipolar disorder patients compared with the controls (P=0.02) with an accompanying inverse correlation between MB-COMT and DRD1 expression. Furthermore, there was a tendency for the enrichment of the Val allele of the COMT Val158Met polymorphism with MB-COMT hypomethylation in the patients. These findings suggest that MB-COMT over-expression due to promoter hypomethylation and/or hyperactive allele of COMT may increase dopamine degradation in the frontal lobe providing a molecular basis for the shared symptoms of schizophrenia and bipolar disorder.

Homocysteine regulates expression of Herp by DNA methylation involving the AARE and CREB binding sites

Herp (homocysteine-induced endoplasmic reticulum protein) is an ER-resident membrane protein, which has a ubiquitin-like domain at its N-terminus. Expression of Herp protein is up-regulated in response to ER stress, including homocysteine. Herp stabilizes neuronal Ca(2+) homeostasis and is involved in improving the balance of the folding capacity and protein loading in the ER. In patients with alcoholism, we observed a significant decrease in Herp mRNA expression, and an increase of Herp promoter DNA methylation, which was associated with elevated homocysteine levels. Therefore, we studied the mechanism of Herp CpG islands regulation by luciferase assays and mRNA analysis in neuronal SH-SY5Y (human neuroblastoma cell line) and HEK 293T (human embryonic kidney 293T) cells. Acute homocysteine treatment caused transient demethylation of the Herp promoter and an increase in Herp mRNA level. Global DNA methylation was increased over the following 48 h period. We identified the transcription factor binding site AARE (amino acid response element) by mutational analysis involved in Herp induction in SH-SY5Y cells, and the more significant role of the CREB binding site (cyclic AMP response element-binding protein) compared to AARE in HEK 293T cells. Stimulation with SAM (S-adenosyl methionine) and homocysteine led to an increase in Herp promoter methylation, which correlated to an acute decrease in luciferase expression in SAM, but not in homocysteine stimulated cells. Complete methylation of the CpG islands resulted in suppressed gene expression.

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.