[Show abstract][Hide abstract] ABSTRACT: The implications of the neurosteroid 3α-hydroxy-5α-pregnan-20-one [allopregnanolone (Allo)] in neuropsychiatric disorders have been highlighted in several recent clinical investigations. For instance, Allo levels are decreased in the cerebrospinal fluid (CSF) of patients with posttraumatic stress disorder (PTSD) and major unipolar depression. Neurosteroidogenic antidepressants [i.e., selective brain steroidogenic stimulants (SBSSs)], including fluoxetine and analogs, correct this decrease in a manner that correlates with improved depressive symptoms. Allo positively and allosterically modulates GABA action at postsynaptic and extrasynaptic GABAA receptors. It is synthesized in both the human and rodent brain cortices by principal glutamatergic pyramidal neurons from progesterone by the sequential action of 5α-reductase type I (5α-RI), which is the rate-limiting step enzyme in Allo biosynthesis, and 3α-hydroxysteroid dehydrogenase (3α-HSD), which converts 5α-dehydroprogesterone into Allo.
We thus hypothesized that decreased CSF levels of Allo in depressed patients could reflect a brain dysfunction of 5α-RI.
In a pilot study of samples from six patients per group [six depressed patients and six nonpsychiatric subjects (NPS)], we studied the expression of 5α-RI messenger RNA (mRNA) in prefrontal cortex Brodmann's area 9 (BA9) and cerebellum from depressed patients obtained from the Maryland Brain Collection at the Maryland Psychiatric Research Center (Baltimore, MD) that were age-matched with NPS.
The levels of 5α-RI mRNA were decreased from 25 ± 5.8 in NPS to 9.1 ± 3.1 fmol/pmol neuronal specific enolase (NSE) (t1,10 = 2.7, P = 0.02) in depressed patients. These differences are absent in the cerebellum of the same patients. The levels of neurosteroids were determined in the prefrontal cortex BA9 of depressed patients obtained from the Stanley Foundation Brain Bank Neuropathology Consortium, Bethesda (MD). The BA9 levels of Allo in male depressed patients failed to reach statistical difference from the levels of NPS (1.63 ± 1.01 pg/mg, n = 8, in NPS and 0.82 ± 0.33 pg/mg, n = 5, in nontreated depressed patients). However, depressed patients who had received antidepressant treatment (three patients SSRI and one TCA) exhibited increased BA9 Allo levels (6.16 ± 2.5 pg/mg, n = 4, t1,9 = 2.4, P = 0.047) when compared with nontreated depressed patients.
Although in a small number of patients, this finding is in-line with previous reports in the field that have observed an increase of Allo levels in CSF and plasma of depressed patients following antidepressant treatment. Hence, the molecular mechanisms underlying major depression may include a GABAergic neurotransmission deficit caused by a brain Allo biosynthesis downregulation, which can be normalized by SBSSs.
[Show abstract][Hide abstract] ABSTRACT: Abstract Schizophrenia (SZ) is a heritable, non-mendelian, neurodevelopmental disorder in which epigenetic dysregulation of the brain genome plays a fundamental role in mediating the clinical manifestations and course of the disease. We recently reported that two enzymes that belong to the dynamic DNA-methylation/demethylation network -DNMT (DNA-methyltransferase) and TET (5-hydroxycytosine translocator)- are abnormally increased in cortico-limbic structures of SZ post-mortem brain suggesting a causal relationship between clinical manifestations of SZ and changes in DNA methylation and in the expression of SZ candidate genes (e.g., brain derived neurotrophic factor [BDNF], glucocorticoid receptor [GCR], glutamic acid decarboxylase67 [GAD67], reelin). Because the clinical manifestations of SZ typically begin with a prodrome followed by a first episode in adolescence with subsequent deterioration, it is obvious that the natural history of this disease cannot be studied only in post-mortem brain. Hence, the focus is currently shifting towards the feasibility of studying epigenetic molecular signatures of SZ in blood cells. Initial studies show a significant enrichment of epigenetic changes in lymphocytes in gene networks directly relevant to psychiatric disorders. Furthermore, the expression of DNA-methylating/demethylating enzymes and SZ candidate genes such as BDNF and GCR are altered in the same direction in both brain and blood lymphocytes. The coincidence of these changes in lymphocytes and brain supports the hypothesis that common environmental or genetic risk factors are operative in altering the epigenetic components involved in orchestrating transcription of specific genes in brain and peripheral tissues. The identification of DNA-methylation signatures for SZ in peripheral blood cells of subjects with genetic and clinical high risk would clearly have potential for the diagnosis of SZ early in its course and would be invaluable for initiating early intervention and individualized treatment plans.
Journal of neurogenetics 04/2014; · 0.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by symptoms related to altered social interactions/communication and restricted and repetitive behaviors. In addition to genetic risk, epigenetic mechanisms (which include DNA methylation/demethylation) are thought to be important in the etiopathogenesis of ASD. We studied epigenetic mechanisms underlying the transcriptional regulation of candidate genes in cerebella of ASD patients, including the binding of MeCP2 (methyl CpG binding protein-2) to the glutamic acid decarboxylase 67 (GAD1), glutamic acid decarboxylase 65 (GAD2), and Reelin (RELN) promoters and gene bodies. Moreover, we performed methyl DNA immunoprecipitation (MeDIP) and hydroxymethyl DNA immunoprecipitation (hMeDIP) to measure total 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) in the same regions of these genes. The enrichment of 5-hmC and decrease in 5-mC at the GAD1 or RELN promoters detected by 5-hmC and 5-mC antibodies was confirmed by Tet-assisted bisulfite (TAB) pyrosequencing. The results showed a marked and significant increase in MeCP2 binding to the promoter regions of GAD1 and RELN, but not to the corresponding gene body regions in cerebellar cortex of ASD patients. Moreover, we detected a significant increase in TET1 expression and an enrichment in the level of 5-hmC, but not 5-mC, at the promoters of GAD1 and RELN in ASD when compared with CON. Moreover, there was increased TET1 binding to these promoter regions. These data are consistent with the hypothesis that an increase of 5-hmC (relative to 5-mC) at specific gene domains enhances the binding of MeCP2 to 5-hmC and reduces expression of the corresponding target genes in ASD cerebella.
[Show abstract][Hide abstract] ABSTRACT: Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by impaired social interactions, language deficits, as well as restrictive or repetitive behaviors. ASD is clinically heterogeneous with a complex etiopathogenesis which may be conceptualized as a dynamic interplay between heterogeneous environmental cues and predisposing genetic factors involving complex epigenetic mechanisms. Inherited and de novo copy number variants provide novel information regarding genes contributing to ASD. Epigenetic marks are stable, yet potentially reversible, chromatin modifications that alter gene expression profiles by locally changing the degree of nucleosomal compaction, thereby opening or closing promoter access to the transcriptional machinery. Here, we review progress on studies designed to provide a better understanding of how epigenetic mechanisms impact transcriptional programs operative in the brain that contribute to ASD.
International Review of Neurobiology 01/2014; 115:203-44. · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
Prenatal stress is considered a risk factor for several neurodevelopmental disorders including schizophrenia (SZ). An animal model involving restraint stress of pregnant mice suggests that prenatal stress (PRS) induces epigenetic changes in specific GABAergic and glutamatergic genes likely to be implicated in SZ including the gene for brain derived neurotrophic factor (BDNF).
Studying adult offspring of pregnant mice subjected to PRS, we explored the long-term effects of PRS on behavior and on the expression of key chromatin remodeling factors including DNA methyltransferase 1 (DNMT1), ten-eleven translocation hydroxylases (TETs), methyl CpG binding protein 2 (MeCP2), histone deacetylases (HDACs), histone methyltransferases (MLL1, SETD1, G9a and EZH1) and demethylase (LSD1) in the frontal cortex (FC) and hippocampus (HP). We also measured the expression of BDNF.
Adult PRS offspring demonstrate behavioral abnormalities suggestive of SZ and molecular changes similar to SZ postmortem brain: a significant increase in DNMT1 and TET1 in the FC and HP but not in cerebellum, no changes in HDACs, histone methytransferases/demethylases or MeCP2, and a significant decrease in BDNF mRNA variants. The decrease of the corresponding BDNF transcript level was accompanied by an enrichment of 5-methylcytosine and 5-hydroxymethylcytosine at Bdnf gene regulatory regions. In addition, the expression of BDNF transcripts (IV and IX) positively correlated with social approach in both PRS and non-stressed mice.
Since patients with psychosis and PRS mice show similar epigenetic signature, PRS offspring may be a suitable model for understanding the behavioral and molecular epigenetic changes observed in SZ patients.
[Show abstract][Hide abstract] ABSTRACT: The epigenetic dysregulation of the brain genome associated with the clinical manifestations of schizophrenia (SZ) includes altered DNA promoter methylation of several candidate genes. We and others have reported that two enzymes that belong to the DNA-methylation/demethylation network pathways-DNMT1 (DNA-methyltransferase) and ten-eleven translocator-1(TET1) methylcytosine deoxygenase are abnormally increased in corticolimbic structures of SZ postmortem brain. The objective of this study was to investigate whether the expression of these components of the DNA-methylation-demethylation pathways known to be altered in the brain of SZ patients are also altered in peripheral blood lymphocytes (PBL). The data show that increases in DNMT1 and TET1 and in glucocorticoid receptor (GCortR) and brain derived neurotrophic factor (BDNF) mRNAs in PBL of SZ patients are comparable to those reported in the brain of SZ patients. The finding that the expressions of DNMT1 and TET1 are increased and SZ candidate genes such as BDNF and GCortR are altered in the same direction in both the brain and PBL together with recent studies showing highly correlated patterns of DNA methylation across the brain and blood, support the hypothesis that a common epigenetic dysregulation may be operative in the brain and peripheral tissues of SZ patients.
Schizophrenia Research 08/2013; · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Epigenetic changes are stable and long-lasting chromatin modifications that regulate genomewide and local gene activity. The addition of two methyl groups to the 9th lysine of histone 3 (H3K9me2) by histone methyltransferases (HMT) leads to a restrictive chromatin state, and thus reduced levels of gene transcription. Given the numerous reports of transcriptional down-regulation of candidate genes in schizophrenia, we tested the hypothesis that this illness can be characterized by a restrictive epigenome.
We obtained parietal cortical samples from the Stanley Foundation Neuropathology Consortium and lymphocyte samples from the University of Illinois at Chicago (UIC). In both tissues we measured mRNA expression of HMTs GLP, SETDB1 and G9a via real-time RT-PCR and H3K9me2 levels via western blot. Clinical rating scales were obtained from the UIC cohort.
A diagnosis of schizophrenia is a significant predictor for increased GLP, SETDB1 mRNA expression and H3K9me2 levels in both postmortem brain and lymphocyte samples. G9a mRNA is significantly increased in the UIC lymphocyte samples as well. Increased HMT mRNA expression is associated with worsening of specific symptoms, longer durations of illness and a family history of schizophrenia.
These data support the hypothesis of a restrictive epigenome in schizophrenia, and may associate with symptoms that are notoriously treatment resistant. The histone methyltransferases measured here are potential future therapeutic targets for small molecule pharmacology, and better patient prognosis.
Schizophrenia Research 06/2013; · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Recent studies suggest that protracted and excessive alcohol use induces an epigenetic dysregulation in human and rodent brains. We recently reported that DNA methylation dynamics are altered in brains of psychotic (PS) patients, including schizophrenia and bipolar disorder patients. Because PS patients are often comorbid with chronic alcohol abuse, we examined whether the altered expression of multiple members of the DNA methylation/demethylation network observed in postmortem brains of PS patients was modified in PS patients with a history of chronic alcohol abuse. METHODS: DNA-methyltransferase-1 (DNMT1) mRNA-positive neurons were counted in situ in prefrontal cortex samples obtained from the Harvard Brain Tissue Resource Center, Belmont, MA. 10-11-translocation (TETs 1, 2, 3), apolipoprotein B editing complex enzyme (APOBEC-3C), growth and DNA-damage-inducible protein 45β (GADD45β), and methyl-binding domain protein-4 (MBD4) mRNAs were measured by quantitative real-time polymerase chain reaction in inferior parietal cortical lobule samples obtained from the Stanley Foundation Neuropathology Consortium, Bethesda, MD. RESULTS: We observed an increase in DNMT1 mRNA-positive neurons in PS patients compared with non-PS subjects. In addition, there was a pronounced decrease in APOBEC-3C and a pronounced increase in GADD45β and TET1 mRNAs in PS patients with no history of alcohol abuse. In PS patients with a history of chronic alcohol abuse, the numbers of DNMT1-positive neurons were not increased significantly. Furthermore, the decrease in APOBEC-3C mRNA was less pronounced, while the increase in TET1 mRNA had a tendency to be potentiated in those PS patients that were chronic alcohol abusers. GADD45β and MBD4 mRNAs were not influenced by alcohol abuse. The effect of chronic alcohol abuse on DNA methylation/demethylation network enzymes cannot be attributed to confounding demographic variables or to the type and dose of medication used. CONCLUSIONS: Based on these results, we hypothesize that PS patients may abuse alcohol as a potential attempt at self-medication to normalize altered DNA methylation/demethylation network pathways. However, before accepting this conclusion, we need to study alterations in the DNA methylation/demethylation pathways and the DNA methylation dynamics in a substantial number of alcoholic PS and non-PS patients. Additional investigation may also be necessary to determine whether the altered DNA methylation dynamics are direct or the consequence of an indirect interaction of alcohol with the neuropathogenetic mechanisms underlying psychosis.
Alcoholism Clinical and Experimental Research 09/2012; · 3.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Major psychiatric disorders such as schizophrenia (SZ) and bipolar disorder (BP) with psychosis (BP+) express a complex symptomatology characterized by positive symptoms, negative symptoms, and cognitive impairment. Postmortem studies of human SZ and BP+ brains show considerable alterations in the transcriptome of a variety of cortical structures, including multiple mRNAs that are downregulated in both inhibitory GABAergic and excitatory pyramidal neurons compared with non-psychiatric subjects (NPS). Several reports show increased expression of DNA methyltransferases in telencephalic GABAergic neurons. Accumulating evidence suggests a critical role for altered DNA methylation processes in the pathogenesis of SZ and related psychiatric disorders. The establishment and maintenance of CpG site methylation is essential during central nervous system differentiation and this methylation has been implicated in synaptic plasticity, learning, and memory. Atypical hypermethylation of candidate gene promoters expressed in GABAergic neurons is associated with transcriptional downregulation of the corresponding mRNAs, including glutamic acid decarboxylase 67 (GAD67) and reelin (RELN). Recent reports indicate that the methylation status of promoter proximal CpG dinucleotides is in a dynamic balance between DNA methylation and DNA hydroxymethylation. Hydroxymethylation and subsequent DNA demethylation is more complex and involves additional proteins downstream of 5-hydroxymethylcytosine, including members of the base excision repair (BER) pathway. Recent advances in our understanding of altered CpG methylation, hydroxymethylation, and active DNA demethylation provide a framework for the identification of new targets, which may be exploited for the pharmacological intervention of the psychosis associated with SZ and possibly BP+.Neuropsychopharmacology Reviews advance online publication, 5 September 2012; doi:10.1038/npp.2012.125.
Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 09/2012; · 8.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human studies suggest that a variety of prenatal stressors are related to high risk for cognitive and behavioral abnormalities associated with psychiatric illness (Markham and Koenig, 2011). Recently, a downregulation in the expression of GABAergic genes (i.e., glutamic acid decarboxylase 67 and reelin) associated with DNA methyltransferase (DNMT) overexpression in GABAergic neurons has been regarded as a characteristic phenotypic component of the neuropathology of psychotic disorders (Guidotti et al., 2011). Here, we characterized mice exposed to prenatal restraint stress (PRS) in order to study neurochemical and behavioral abnormalities related to development of schizophrenia in the adult. Offspring born from non-stressed mothers (control mice) showed high levels of DNMT1 and 3a mRNA expression in the frontal cortex at birth, but these levels progressively decreased at post-natal days (PND) 7, 14, and 60. Offspring born from stressed mothers (PRS mice) showed increased levels of DNMTs compared to controls at all time-points studied including at birth and at PND 60. Using GAD67-GFP transgenic mice, we established that, in both control and PRS mice, high levels of DNMT1 and 3a were preferentially expressed in GABAergic neurons of frontal cortex and hippocampus. Importantly, the overexpression of DNMT in GABAergic neurons was associated with a decrease in reelin and GAD67 expression in PRS mice in early and adult life. PRS mice also showed an increased binding of DNMT1 and MeCP2, and an increase in 5-methylcytosine and 5-hydroxymethylcytosine in specific CpG-rich regions of the reelin and GAD67 promoters. Thus, the epigenetic changes in PRS mice are similar to changes observed in the post-mortem brains of psychiatric patients. Behaviorally, adult PRS mice showed hyperactivity and deficits in social interaction, prepulse inhibition, and fear conditioning that were corrected by administration of valproic acid (a histone deacetylase inhibitor) or clozapine (an atypical antipsychotic with DNA-demethylation activity). Taken together, these data show that prenatal stress in mice induces abnormalities in the DNA methylation network and in behaviors indicative of a schizophrenia-like phenotype. Thus, PRS mice may be a valid model for the investigation of new drugs for schizophrenia treatment targeting DNA methylation. This article is part of a Special Issue entitled 'Neurodevelopment Disorder'.
[Show abstract][Hide abstract] ABSTRACT: DNA methylation is an epigenetic regulatory mechanism commonly associated with transcriptional silencing. DNA methyltransferases (DNMTs) are a family of related proteins that both catalyze the de novo formation of 5-methylcytosine and maintain these methylation marks in cell-specific patterns in virtually all mitotic cells of the body. In the adult brain, methylation occurs in progenitor cells of the neurogenic zones and in postmitotic neurons. Of the DNMTs, DNMT1 and DNMT3a are most highly expressed in postmitotic neurons. While it has been commonly thought all postmitotic neurons and glia express DNMTs at comparable levels, the coexpression of selected DNMTs with markers of distinct neurotransmitter phenotypes has not been previously examined in detail in the mouse. To this end, we analyzed the expression of DNMT1 and DNMT3a along with GAD67 in the brains of the glutamic acid decarboxylase67-enhanced green fluorescent protein (GAD67-GFP) knockin mice. After first confirming that GFP-immunopositive neurons were also GAD67-positive, we showed that in the motor cortex, piriform cortex, striatum, CA1 region of the hippocampus, dentate gyrus, and basolateral amygdala (BLA), GFP immunofluorescence coincided with the signal corresponding to DNMT1 and DNMT3a. A detailed examination of cortical neurons, showed that ≈30% of NeuN-immunopositive neurons were also DNMT1-positive. These data do not exclude the expression of DNMT1 or DNMT3a in glutamatergic neurons and glia. However, they suggest that their expression is low compared with the levels present in GABAergic neurons.
The Journal of Comparative Neurology 12/2011; 520(9):1951-64. · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Prenatal exposure to restraint stress causes long-lasting changes in neuroplasticity that likely reflect pathological modifications triggered by early-life stress. We found that the offspring of dams exposed to repeated episodes of restraint stress during pregnancy (here named 'prenatal restraint stress mice' or 'PRS mice') developed a schizophrenia-like phenotype, characterized by a decreased expression of brain-derived neurotrophic factor and glutamic acid decarboxylase 67, an increased expression of type-1 DNA methyl transferase (DNMT1) in the frontal cortex, and a deficit in social interaction, locomotor activity, and prepulse inhibition. PRS mice also showed a marked decrease in metabotropic glutamate 2 (mGlu2) and mGlu3 receptor mRNA and protein levels in the frontal cortex, which was manifested at birth and persisted in adult life. This decrease was associated with an increased binding of DNMT1 to CpG-rich regions of mGlu2 and mGlu3 receptor promoters and an increased binding of MeCP2 to the mGlu2 receptor promoter. Systemic treatment with the selective mGlu2/3 receptor agonist LY379268 (0.5 mg/kg, i.p., twice daily for 5 days), corrected all the biochemical and behavioral abnormalities shown in PRS mice. Our data show for the first time that PRS induces a schizophrenia-like phenotype in mice, and suggest that epigenetic changes in mGlu2 and mGlu3 receptors lie at the core of the pathological programming induced by early-life stress.
Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 11/2011; 37(4):929-38. · 8.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aberrant neocortical DNA methylation has been suggested to be a pathophysiological contributor to psychotic disorders. Recently, a growth arrest and DNA-damage-inducible, beta (GADD45b) protein-coordinated DNA demethylation pathway, utilizing cytidine deaminases and thymidine glycosylases, has been identified in the brain. We measured expression of several members of this pathway in parietal cortical samples from the Stanley Foundation Neuropathology Consortium (SFNC) cohort. We find an increase in GADD45b mRNA and protein in patients with psychosis. In immunohistochemistry experiments using samples from the Harvard Brain Tissue Resource Center, we report an increased number of GADD45b-stained cells in prefrontal cortical layers II, III, and V in psychotic patients. Brain-derived neurotrophic factor IX (BDNF IXabcd) was selected as a readout gene to determine the effects of GADD45b expression and promoter binding. We find that there is less GADD45b binding to the BDNF IXabcd promoter in psychotic subjects. Further, there is reduced BDNF IXabcd mRNA expression, and an increase in 5-methylcytosine and 5-hydroxymethylcytosine at its promoter. On the basis of these results, we conclude that GADD45b may be increased in psychosis compensatory to its inability to access gene promoter regions.
Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 11/2011; 37(2):531-42. · 8.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sponsored by the New York Academy of Sciences and with support from the National Institute of Mental Health, the Life Technologies Foundation, and the Josiah Macy Jr. Foundation, "Advancing Drug Discovery for Schizophrenia" was held March 9-11 at the New York Academy of Sciences in New York City. The meeting, comprising individual talks and panel discussions, highlighted basic, clinical, and translational research approaches, all of which contribute to the overarching goal of enhancing the pharmaceutical armamentarium for treating schizophrenia. This report surveys work by the vanguard of schizophrenia research in such topics as genetic and epigenetic approaches; small molecule therapeutics; and the relationships between target genes, neuronal function, and symptoms of schizophrenia.
Annals of the New York Academy of Sciences 10/2011; 1236:30-43. · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The clinical use of diazepam or midazolam to control organophosphate (OP) nerve agent-induced seizure activity is limited by their unwanted effects including sedation, amnesia, withdrawal, and anticonvulsant tolerance. Imidazenil is an imidazo-benzodiazepine derivative with high intrinsic efficacy and selectivity for α2-, α3-, and α5- but low intrinsic efficacy for α1-containing GABA(A) receptors. We have previously shown that imidazenil is more efficacious than diazepam at protecting rats and mice from diisopropyl fluorophosphate (DFP)-induced seizures and neuronal damage without producing sedation. In the present study, we compared the tolerance liability of imidazenil and diazepam to attenuate the seizure activity and neurotoxic effects of DFP. Rats received protracted (14 days) oral treatment with increasing doses of imidazenil (1-4 mg/kg), diazepam (5-20 mg/kg), or vehicle. Eighteen hours after the last dose of the protracted treatment schedule, rats were tested for anticonvulsant tolerance after a 30 min pretreatment with a single test dose of imidazenil (0.5 mg/kg) or diazepam (5 mg/kg) prior to a DFP challenge (1.5 mg/kg). The anticonvulsant (modified Racine score scale) and neuroprotective (fluoro-jade B staining) effects of diazepam were significantly reduced in protracted diazepam-treated animals whereas the effects of imidazenil were not altered in protracted imidazenil-treated animals. The present findings indicate that protracted imidazenil treatment does not produce tolerance to its protective action against the neurotoxic effects of OP exposure.
[Show abstract][Hide abstract] ABSTRACT: Activation of group II metabotropic glutamate receptors (mGlu2 and -3 receptors) has shown a potential antipsychotic activity, yet the underlying mechanism is only partially known. Altered epigenetic mechanisms contribute to the pathogenesis of schizophrenia and currently used medications exert chromatin remodeling effects. Here, we show that systemic injection of the brain-permeant mGlu2/3 receptor agonist (-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY379268; 0.3-1 mg/kg i.p.) increased the mRNA and protein levels of growth arrest and DNA damage 45-β (Gadd45-β), a molecular player of DNA demethylation, in the mouse frontal cortex and hippocampus. Induction of Gadd45-β by LY379268 was abrogated by the mGlu2/3 receptor antagonist (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495; 1 mg/kg i.p.). Treatment with LY379268 also increased the amount of Gadd45-β bound to specific promoter regions of reelin, brain-derived neurotrophic factor (BDNF), and glutamate decarboxylase-67 (GAD67). We directly assessed gene promoter methylation in control mice and in mice pretreated for 7 days with the methylating agent methionine (750 mg/kg i.p.). Both single and repeated injections with LY379268 reduce cytosine methylation in the promoters of the three genes, although the effect on the GAD67 was significant only in response to repeated injections. Single and repeated treatment with LY379268 could also reverse the defect in social interaction seen in mice pretreated with methionine. The action of LY379268 on Gadd45-β was mimicked by valproate and clozapine but not haloperidol. These findings show that pharmacological activation of mGlu2/3 receptors has a strong impact on the epigenetic regulation of genes that have been linked to the pathophysiology of schizophrenia.
[Show abstract][Hide abstract] ABSTRACT: In 1996, Dr. Costa was invited by Prof. Boris Astrachan, Chairman of the Department of Psychiatry at the University of Illinois at Chicago, to direct the research of the "Psychiatric Institute, Department of Psychiatry, School of Medicine, at the University of Illinois at Chicago." He was asked to develop a seminal research program on psychiatric disorders. Viewed in retrospect, Dr. Costa met and surpassed the challenge, as was usual for him. To elucidate the molecular mechanisms whereby nurture (epigenetic factors) and nature (genetic factors) interact to cause major psychiatric disorders was at the center of Dr. Costa's mission for the last 15 years of his research at the Psychiatric Institute. The challenge for Dr. Costa and his colleagues (Auta, Caruncho, Davis, Grayson, Guidotti, Impagnatiello, Kiedrowski, Larson, Manev, Pappas, Pesold, Pinna, Sharma, Smalheiser, Sugaya, Tueting, Veldic [1-111]) had always been to find new ways to prevent and treat psychiatric disorders with pharmacological agents that failed to have major unwanted side effects. In this list, we have quoted the first authors of the papers pertaining to the field of research highlighted in the title. As you know, Dr. Costa was an eclectic scientist and in his 15 years of studies at UIC, he touched many other aspects of neuroscience research that are not discussed in this overview.
Pharmacological Research 06/2011; 64(4):344-9. · 4.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: One of the more consistent findings observed in post mortem tissue from schizophrenia (SZ) patients is that the genes encoding
reelin and glutamate decarboxylase 67 (GAD67 or GAD1) are downregulated in cortex and other brain regions. Reelin is important for cortical migration during development and for
synaptic plasticity and memory acquisition in the adult. GAD1 is one of two enzymes that synthesize the inhibitory neurotransmitter
GABA in the central nervous system. Those neurons that make GABA are GABAergic and they serve a role in dampening excitatory
neurotransmission throughout the brain. In addition, reports also show that NMDA receptor subunit expression and excitatory
neurotransmission are reduced in cortical GABA neurons of SZ patients. Conditional knockout mice in which the NR1 subunit
of the NMDA receptor is selectively reduced in GABA neurons of the brain show a downregulation of GAD67 and parvalbumin (PV) mRNAs and also exhibit behaviors characteristic of SZ. These findings allow us to conceptually integrate two major schools
of thought regarding the neurotransmitter deficit responsible for the symptoms of this psychiatric disorder. That is, if reduced
glutamatergic neurotransmission occurs on GABAergic interneurons, the net effect would be reduced GABA output impacting the
neuronal synchronization of pyramidal cell firing. Since it has also been shown that in GABAergic neurons, the mRNA encoding
DNA methyltransferase 1 (DNMT1) is increased in SZ patients, this and other data suggest an epigenetic mechanism by which certain genes may be selectively
downregulated contributing to SZ symptomatology. We propose that enzymes that methylate DNA and selectively reduce gene expression
are hyperactive in patients with SZ and that this may be related to the pathogenesis of the disease. Here, we discuss these
concepts in more detail and present our integrated view of synaptic transmission in SZ.
KeywordsCortex-DNA methylation-Gamma-aminobutyric acid (GABA)-Gene expression-Schizophrenia
[Show abstract][Hide abstract] ABSTRACT: Nicotine improves cognitive performance and attention in both experimental animals and in human subjects, including patients affected by neuropsychiatric disorders. However, the specific molecular mechanisms underlying nicotine-induced behavioral changes remain unclear. We have recently shown in mice that repeated injections of nicotine, which achieve plasma concentrations comparable to those reported in high cigarette smokers, result in an epigenetically induced increase of glutamic acid decarboxylase 67 (GAD(67)) expression. Here we explored the impact of synthetic α(4)β(2) and α(7) nAChR agonists on GABAergic epigenetic parameters. Varenicline (VAR), a high-affinity partial agonist at α(4)β(2) and a lower affinity full agonist at α(7) neuronal nAChR, injected in doses of 1-5 mg/kg/s.c. twice daily for 5 days, elicited a 30-40% decrease of cortical DNA methyltransferase (DNMT)1 mRNA and an increased expression of GAD(67) mRNA and protein. This upregulation of GAD(67) was abolished by the nAChR antagonist mecamylamine. Furthermore, the level of MeCP(2) binding to GAD(67) promoters was significantly reduced following VAR administration. This effect was abolished when VAR was administered with mecamylamine. Similar effects on cortical DNMT1 and GAD(67) expression were obtained after administration of A-85380, an agonist that binds to α(4)β(2) but has negligible affinity for α(3)β(4) or α(7) subtypes containing nAChR. In contrast, PNU-282987, an agonist of the homomeric α(7) nAChR, failed to decrease cortical DNMT1 mRNA or to induce GAD(67) expression. The present study suggests that the α(4)β(2) nAChR agonists may be better suited to control the epigenetic alterations of GABAergic neurons in schizophrenia than the α(7) nAChR agonists.
Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 03/2011; 36(7):1366-74. · 8.68 Impact Factor