title: Epigenetic GABAergic targets in schizophrenia and bipolar disorder.
abstract: It is becoming increasingly clear that a dysfunction of the GABAergic/glutamatergic network in telencephalic brain structures may be the pathogenetic mechanism underlying psychotic symptoms in schizophrenia (SZ) and bipolar (BP) disorder patients. Data obtained in Costa's laboratory (1996-2009) suggest that this dysfunction may be mediated primarily by a downregulation in the expression of GABAergic genes (e.g., glutamic acid decarboxylase₆₇[GAD₆₇] and reelin) associated with DNA methyltransferase (DNMT)-dependent hypermethylation of their promoters. A pharmacological strategy to reduce the hypermethylation of GABAergic promoters is to administer drugs, such as the histone deacetylase (HDAC) inhibitor valproate (VPA), that induce DNA-demethylation when administered at doses that facilitate chromatin remodeling. The benefits elicited by combining VPA with antipsychotics in the treatment of BP disorder suggest that an investigation of the epigenetic interaction of these drugs is warranted. Our studies in mice suggest that when associated with VPA, clinically relevant doses of clozapine elicit a synergistic potentiation of VPA-induced GABAergic promoter demethylation. Olanzapine and quetiapine (two clozapine congeners) also facilitate chromatin remodeling but at doses higher than used clinically, whereas haloperidol and risperidone are inactive. Hence, the synergistic potentiation of VPA's action on chromatin remodeling by clozapine appears to be a unique property of the dibenzepines and is independent of their action on catecholamine or serotonin receptors. By activating DNA-demethylation, the association of clozapine or its derivatives with VPA or other more potent and selective HDAC inhibitors may be considered a promising treatment strategy for normalizing GABAergic promoter hypermethylation and the GABAergic gene expression downregulation detected in the postmortem brain of SZ and BP disorder patients. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.
authors.affiliation: Department of Psychiatry, University of Illinois at Chicago, College of Medicine, Psychiatric Institute, 1601 Taylor, Chicago, IL 60612, USA. aguidotti@psych.uic.edu
authors.forename: A
authors.initials: A
authors.lastname: Guidotti
authors.forename: J
authors.initials: J
authors.lastname: Auta
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: J M
authors.initials: JM
authors.lastname: Davis
authors.forename: E
authors.initials: E
authors.lastname: Dong
authors.forename: D P
authors.initials: DP
authors.lastname: Gavin
authors.forename: D R
authors.initials: DR
authors.lastname: Grayson
authors.forename: F
authors.initials: F
authors.lastname: Matrisciano
authors.forename: G
authors.initials: G
authors.lastname: Pinna
authors.forename: R
authors.initials: R
authors.lastname: Satta
authors.forename: R P
authors.initials: RP
authors.lastname: Sharma
authors.forename: L
authors.initials: L
authors.lastname: Tremolizzo
authors.forename: P
authors.initials: P
authors.lastname: Tueting
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use*; D001714:Bipolar Disorder / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D044127:Epigenesis, Genetic / Q000187:drug effects*; D018683:Excitatory Amino Acid Agents / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007395:Interneurons / Q000187:drug effects / Q000502:physiology; D051379:Mice; D058990:Molecular Targeted Therapy; D000091042:Reelin Protein; D012559:Schizophrenia / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000235:genetics* / Q000378:metabolism
chemical_list: D014150:Antipsychotic Agents; D018683:Excitatory Amino Acid Agents; D000091042:Reelin Protein; D005680:gamma-Aminobutyric Acid; C000717127:RELN protein, human; C000717128:Reln protein, mouse