Effects of acute ethanol exposure on class I HDACs family enzymes in wild-type and BDNF(+/-) mice

[Epigenetic changes in alcohol addiction and therapeutic perspectives]

Alcohol consumption is a major public health issue. Patients with Alcohol Use Disorder (AUD) can benefit from five treatments that preferentially target membrane receptors, and whose efficacy is generally modest. However, a large body of experimental evidence points to an important role for epigenetics in the effects of alcohol consumption, and epidrugs that modify the epigenome offer an interesting alternative to current therapeutic options. This article reviews the most striking experimental evidence obtained at different ages in animal models, before comparing it with data obtained in humans and concluding on the relevance of using epidrugs. Finally, a new therapeutic option is suggested between psychedelics, recent molecules of interest, and epigenetic factors in alcohol intake.

Nociceptive behavior and central neuropeptidergic dysregulations in male and female mice of a Fabry disease animal model

Fabry disease (FD) is an X-linked inherited disorder characterized by glycosphingolipid accumulation due to deficiency of α-galactosidase A (α-Gal A) enzyme. Chronic pain and mood disorders frequently coexist in FD clinical setting, however underlying pathophysiologic mechanisms are still unclear. Here we investigated the mechanical and thermal sensitivity in α-Gal A (-/0) hemizygous male and the α-Gal A (-/-) homozygous female mice. We also characterized the gene expression of dynorphinergic, nociceptinergic and CRFergic systems, known to be involved in pain control and mood disorders, in the prefrontal cortex, amygdala and thalamus of α-Gal A (-/0) hemizygous male and the α-Gal A (-/-) homozygous female mice. Moreover, KOP receptor protein levels were evaluated in the same areas. Fabry knock-out male, but not female, mice displayed a decreased pain threshold in both mechanical and thermal tests compared to their wild type littermates. In the amygdala and prefrontal cortex, we observed a decrease of pDYN mRNA levels in males, whereas an increase was assessed in females, thus suggesting sex-related dysregulation of stress coping and pain mechanisms. Elevated mRNA levels for pDYN/KOP and CRF/CRFR1 systems were observed in male and female thalamus, a critical crossroad for both painful signals and cognitive/emotional processes. KOP receptor protein level changes assessed in the investigated areas, appeared mostly in agreement with KOP gene expression alterations. Our data suggest that α-Gal A enzyme deficiency in male and female mice is associated with distinct neuropeptide gene and protein expression dysregulations of investigated systems, possibly related to the neuroplasticity underlying the neurological features of FD.

Dysregulation of Nociceptin/Orphanin FQ and Dynorphin Systems in the Extended Amygdala of Alcohol Preferring Marchigian Sardinian (msP) Rats

Previous studies have shown that genetically selected Marchigian Sardinian alcohol-preferring (msP) rats consume excessive amounts of ethanol to self-medicate from negative moods and to relieve innate hypersensitivity to stress. This phenotype resembling a subset of alcohol use disorder (AUD) patients, appears to be linked to a dysregulation of the equilibrium between stress and antistress mechanisms in the extended amygdala. Here, comparing water and alcohol exposed msP and Wistar rats we evaluate the transcript expression of the anti-stress opioid-like peptide nociceptin/orphanin FQ (N/OFQ) and its receptor NOP as well as of dynorphin (DYN) and its cognate κ-opioid receptor (KOP). In addition, we measured the transcript levels of corticotropin-releasing factor (CRF), CRF receptor 1 (CRF1R), brain-derived neurotrophic factor (BDNF) and of the tropomyosin receptor kinase B receptor (Trk-B). Results showed an innately up-regulation of the CRFergic system, mediating negative mood and stress responses, as well as an inherent up-regulation of the anti-stress N/OFQ system, both in the amygdala (AMY) and bed nucleus of the stria terminalis (BNST) of msP rats. The up-regulation of this latter system may reflect an attempt to buffer the negative condition elicited by the hyperactivity of pro-stress mechanisms since results showed that voluntary alcohol consumption dampened N/OFQ. Alcohol exposure also reduced the expression of dynorphin and CRF transmissions in the AMY of msP rats. In the BNST, alcohol intake led to a more complex reorganization of these systems increasing receptor transcripts in msP rats, along with an increase of CRF and a decrease of N/OFQ transcripts, respectively. Moreover, mimicking the effects of alcohol in the AMY we observed that the activation of NOP receptor by intracerebroventricular administration of N/OFQ in msP rats caused an increase of BDNF and a decrease of CRF transcripts. Our study indicates that both stress and anti-stress mechanisms are dysregulated in the extended AMY of msP rats. The voluntary alcohol drinking, as well as NOP agonism, have a significant impact on neuropeptidergic systems arrangement, bringing the systems back to normalization.

Early life exposure to hypercaloric diet impairs eating behavior during weaning: The role of BDNF signaling and astrocyte marks

Literature shows that gestational and/or lactational exposure to hypercaloric diets induces long term effects on eating behavior and the involvement of neurochemical mechanisms. We hypothesized that the effects of hypercaloric diets in early development phases can precede an overweight or an obesity status. The aim of the present study was to evaluate the impact of gestational and lactational exposure to cafeteria diet on eating behavior and neurochemical parameters, BDNF signaling, epigenetic and astrocyte marks in the hippocampus and olfactory bulb during the weaning phase. Pregnant female rats were randomized between standard and cafeteria diet, the respective diet was maintained through the lactational period. The framework of feeding pattern, meal, and its microstructure, was observed in postnatal day 20. Exposure to cafeteria diet increased the number of meals, associated with a lower first inter-meal interval and higher consumption in both genders, without any changes in body weight. Diet exposure also reduced the number of grooming, a behavior typically found at the end of meals. Hypercaloric diet exposure reduced BDNF levels in the olfactory bulb and hippocampus from rats of both sexes and increased the content of the TrkB receptor in hippocampi. It was observed an increase in HDAC5 levels, an epigenetic mark. Still, early exposure to the hypercaloric diet reduced hippocampal GFAP and PPARγ levels, without any effect on NeuN content, indicating that alterations in astrocytes can precede those neuronal outcomes. Our results showed that changes in interrelated neurochemical signaling, BDNF, and astrocyte marks, induced by hypercaloric diet in early stages of development may be related to impairment in the temporal distribution of eating pattern and consequent amounts of consumed food during the weaning phase.

Memory and plasticity impairment after binge drinking in adolescent rat hippocampus: GluN2A/GluN2B NMDA receptor subunits imbalance through HDAC2

Ethanol (EtOH) induces cognitive impairment through modulation of synaptic plasticity notably in the hippocampus. The cellular mechanism(s) of these EtOH effects may range from synaptic signaling modulation to alterations of the epigenome. Previously, we reported that two binge-like exposures to EtOH (3 g/kg, ip, 9 h apart) in adolescent rats abolished long-term synaptic depression (LTD) in hippocampus slices, induced learning deficits, and increased N-methyl-d-aspartate (NMDA) receptor signaling through its GluN2B subunit after 48 hours. Here, we tested the hypothesis of EtOH-induced epigenetic alterations leading to modulation of GluN2B and GluN2A NMDA receptor subunits. Forty-two days old rats were treated with EtOH or the histone deacetylase inhibitor (HDACi) sodium butyrate (NaB, 600 mg/kg, ip) injected alone or 30 minutes before EtOH. After 48 hours, learning was tested with novel object recognition while synaptic plasticity and the role of GluN2A and GluN2B subunits in NMDA-fEPSP were measured in CA1 field of hippocampus slices. LTD and memory were impaired 48 hours after EtOH and NMDA-fEPSP analysis unraveled changes in the GluN2A/GluN2B balance. These results were associated with an increase in histone deacetylase (HDAC) activity and HDAC2 mRNA and protein while Ac-H4K12 labelling was decreased. EtOH increases expression of HDAC2 and mRNA level for GluN2B subunit (but not GluN2A), while HDAC2 modulates the promoter of the gene encoding GluN2B. Interestingly, NaB pretreatment prevented all the cellular and memory-impairing effects of EtOH. In conclusion, the memory-impairing effects of two binge-like EtOH exposure involve NMDA receptor-dependent LTD deficits due to a GluN2A/GluN2B imbalance resulting from changes in GluN2B expression induced by HDAC2.

How alcohol drinking affects our genes: an epigenetic point of view

This work highlights recent studies in epigenetic mechanisms that play a role in alcoholism, which is a complex multifactorial disorder. There is a large body of evidence showing that alcohol can modify gene expression through epigenetic processes, namely DNA methylation and nucleosomal remodeling via histone modifications. In that regard, chronic exposure to ethanol modifies DNA and histone methylation, histone acetylation, and microRNA expression. The alcohol-mediated chromatin remodeling in the brain promotes the transition from use to abuse and addiction. Unravelling the multiplex pattern of molecular modifications induced by ethanol could support the development of new therapies for alcoholism and drug addiction targeting epigenetic processes.

Syntheses and Biological Evaluation of Novel Hydroxamic Acid Derivatives Containing Purine Moiety as Histone Deacetylase Inhibitors

The novel hydroxamates containing purine scaffold were designed, synthesized and screened for their biological activities as histone deacetylase (HDAC) inhibitors. Some of them exhibited excellent acti-HDACs activities and antiproliferative activities, the most promising compound was 7m'. Western blot analysis indicated the compounds 7f', 7l', 7m', 7o' could increase histone H3 acetylation levels in HCT116 and K562 cell lines, and 7m' increased the level of acetyl histone H3 in a dose-dependent manner, which is similar to the behavior of suberoylanilide hydroxamic acid (SAHA). Molecular docking study revealed that the conformation of 7m' in the active site of HDAC2 was similar to positive drug SAHA, which were oriented with the hydroxamic acid towards the catalytic center and formed metal binding with zinc ion.

Age-related alterations in histone deacetylase expression in Purkinje neurons of ethanol-fed rats

Ethanol and age-induced pathologies of the Purkinje neuron (PN) may result from histone deacetylases (HDACs), enzymes which repress transcription through coiling of the DNA. The purposes of this study were to investigate expression patterns of Class 1 and IIa HDACs in PN and the effects of aging and alcohol on the density of HDACs and histone acetylation in PN. Ninety, eight month old rats (30/diet) were fed a liquid ethanol, liquid control, or rat chow diet for 10, 20, or 40weeks (30/treatment duration). Double immunocytochemical labeling on tissue sections from these rats used antibodies against HDAC isoforms or acetylated histones, and calbindin, a marker for PN. Fluorescent intensities were also measured. Results showed a significant age but not an alcohol-related decrease in the densities of HDACs 2, 3, and 7. In contrast, there were age related-increases in the densities of phosphorylated form of HDAC (4, 5, 7) PN and in PN nuclei expressing HDAC 7. There were also a trend towards ethanol-induced inhibition of acetylation as the density of AH2b PN nuclei and AH3 and AH2b fluorescent intensity was significantly lower in the EF compared to the PF rats. This study presents unique data concerning which HDACs are commonly expressed in PN and indicates that aging rather than lengthy alcohol expression alters expression of the HDACs studied here. These results also suggest that lengthy ethanol consumption may inhibit histone deacetylation in PN.

Epigenetic mechanisms of alcoholism and stress-related disorders

Stress-related disorders, such as anxiety, early life stress, and posttraumatic stress disorder appear to be important factors in promoting alcoholism, as alcohol consumption can temporarily attenuate the negative affective symptoms of these disorders. Several molecules involved in signaling pathways may contribute to the neuroadaptation induced during alcohol dependence and stress disorders, and among these, brain-derived neurotrophic factor (BDNF), corticotropin releasing factor (CRF), neuropeptide Y (NPY) and opioid peptides (i.e., nociceptin and dynorphin) are involved in the interaction of stress and alcohol. In fact, alterations in the expression and function of these molecules have been associated with the pathophysiology of stress-related disorders and alcoholism. In recent years, various studies have focused on the epigenetic mechanisms that regulate chromatin architecture, thereby modifying gene expression. Interestingly, epigenetic modifications in specific brain regions have been shown to be associated with the neurobiology of psychiatric disorders, including alcoholism and stress. In particular, the enzymes responsible for chromatin remodeling (i.e., histone deacetylases and methyltransferases, DNA methyltransferases) have been identified as common molecular mechanisms for the interaction of stress and alcohol and have become promising therapeutic targets to treat or prevent alcoholism and associated emotional disorders.

Ethanol downregulates N-acyl phosphatidylethanolamine-phospholipase D expression in BV2 microglial cells via epigenetic mechanisms

Excessive ethanol drinking has deleterious effects on the brain. However, the effects of alcohol on microglia, the main mediator of the brain's innate immune response remain poorly understood. On the other hand, the endocannabinoid system plays a fundamental role in regulating microglial reactivity and function. Here we studied the effects of acute ethanol exposure to murine BV2 microglial cells on N-acyl phosphatidylethanolamine-phospholipase D (NAPE-PLD), a major synthesizing enzyme of anandamide and other N-acylethanolamines. We found that ethanol downregulated microglial NAPE-PLD expression by activating cAMP/PKA and ERK1/2. These signaling pathways converged on increased phosphorylation of CREB. Moreover, ethanol induced and increase in histone acetyltransferase activity which led to higher levels of acetylation of histone H3. Taken together, our results suggest that ethanol actions on microglial NAPE-PLD expression might involve epigenetic mechanisms.