1 3337 158 HISTONE DEACETYLASE INHIBITORS PREVENT PERSISTENT HYPERSENSITIVITY IN AN OROFACIAL NEUROPATHIC PAIN MODEL. CHRONIC OROFACIAL PAIN IS A SIGNIFICANT HEALTH PROBLEM REQUIRING IDENTIFICATION OF REGULATING PROCESSES. INVOLVEMENT OF EPIGENETIC MODIFICATIONS THAT IS REPORTED FOR HINDLIMB NEUROPATHIC PAIN EXPERIMENTAL MODELS, HOWEVER, IS LESS WELL STUDIED IN CRANIAL NERVE PAIN MODELS. THREE INDEPENDENT OBSERVATIONS REPORTED HERE ARE THE (1) EPIGENETIC PROFILE IN MOUSE TRIGEMINAL GANGLIA (TG) AFTER TRIGEMINAL INFLAMMATORY COMPRESSION (TIC) NERVE INJURY MOUSE MODEL DETERMINED BY GENE EXPRESSION MICROARRAY, (2) H3K9 ACETYLATION PATTERN IN TG BY IMMUNOHISTOCHEMISTRY, AND (3) EFFICACY OF HISTONE DEACETYLASE (HDAC) INHIBITORS TO ATTENUATE DEVELOPMENT OF HYPERSENSITIVITY. AFTER TIC INJURY, IPSILATERAL WHISKER PAD MECHANICAL SENSITIZATION DEVELOPS BY DAY 3 AND PERSISTS WELL BEYOND DAY 21 IN CONTRAST TO SHAM SURGERY. GLOBAL ACETYLATION OF H3K9 DECREASES AT DAY 21 IN IPSILATERAL TG . THIRTY-FOUR GENES ARE SIGNIFICANTLY ( P < 0.05) OVEREXPRESSED IN THE IPSILATERAL TG BY AT LEAST TWO-FOLD AT EITHER 3 OR 21 DAYS POST-TRIGEMINAL INFLAMMATORY COMPRESSION INJURY. THE THREE GENES MOST OVEREXPRESSED THREE DAYS POST-TRIGEMINAL INFLAMMATORY COMPRESSION NERVE INJURY ARE NERVE REGENERATION-ASSOCIATED GENE ATF3, UP 6.8-FOLD, AND TWO OF ITS REGENERATION-ASSOCIATED GENE EFFECTOR GENES, SPRR1A AND GAL, UP 174- AND 25-FOLD, RESPECTIVELY. ALTHOUGH TRANSCRIPTION LEVELS OF 25 OF 32 GENES SIGNIFICANTLY OVEREXPRESSED THREE DAYS POST-TRIGEMINAL INFLAMMATORY COMPRESSION RETURN TO CONSTITUTIVE LEVELS BY DAY 21, THESE THREE REGENERATION-ASSOCIATED GENES REMAIN SIGNIFICANTLY OVEREXPRESSED AT THE LATER TIME POINT. ON DAY 21, WHEN TISSUES ARE HEALED, OTHER DIFFERENTIALLY EXPRESSED GENES INCLUDE 39 OF THE TOP 50 UPREGULATED AND DOWNREGULATED GENES. REMARKABLY, PREEMPTIVE MANIPULATION OF GENE EXPRESSION WITH TWO HDAC INHIBITORS (HDACI'S), SUBERANILOHYDROXAMIC ACID (SAHA) AND MS-275, REDUCES THE MAGNITUDE AND DURATION OF WHISKER PAD MECHANICAL HYPERSENSITIVITY AND PREVENTS THE DEVELOPMENT OF A PERSISTENT PAIN STATE. THESE FINDINGS SUGGEST THAT TRIGEMINAL NERVE INJURY LEADS TO EPIGENETIC MODIFICATIONS FAVORING OVEREXPRESSION OF GENES INVOLVED IN NERVE REGENERATION AND THAT MAINTAINING TRANSCRIPTIONAL HOMEOSTASIS WITH EPIGENETIC MODIFYING DRUGS COULD HELP PREVENT THE DEVELOPMENT OF PERSISTENT PAIN. 2018 2 3194 38 HDAC INHIBITORS ATTENUATE THE DEVELOPMENT OF HYPERSENSITIVITY IN MODELS OF NEUROPATHIC PAIN. HISTONE DEACETYLASE INHIBITORS (HDACIS) INTERFERE WITH THE EPIGENETIC PROCESS OF HISTONE ACETYLATION AND ARE KNOWN TO HAVE ANALGESIC PROPERTIES IN MODELS OF CHRONIC INFLAMMATORY PAIN. THE AIM OF THIS STUDY WAS TO DETERMINE WHETHER THESE COMPOUNDS COULD ALSO AFFECT NEUROPATHIC PAIN. DIFFERENT CLASS I HDACIS WERE DELIVERED INTRATHECALLY INTO RAT SPINAL CORD IN MODELS OF TRAUMATIC NERVE INJURY AND ANTIRETROVIRAL DRUG-INDUCED PERIPHERAL NEUROPATHY (STAVUDINE, D4T). MECHANICAL AND THERMAL HYPERSENSITIVITY WAS ATTENUATED BY 40% TO 50% AS A RESULT OF HDACI TREATMENT, BUT ONLY IF STARTED BEFORE ANY INSULT. THE DRUGS GLOBALLY INCREASED HISTONE ACETYLATION IN THE SPINAL CORD, BUT APPEARED TO HAVE NO MEASURABLE EFFECTS IN RELEVANT DORSAL ROOT GANGLIA IN THIS TREATMENT PARADIGM, SUGGESTING THAT ANY POTENTIAL MECHANISM SHOULD BE SOUGHT IN THE CENTRAL NERVOUS SYSTEM. MICROARRAY ANALYSIS OF DORSAL CORD RNA REVEALED THE SIGNATURE OF THE SPECIFIC COMPOUND USED (MS-275) AND SUGGESTED THAT ITS MAIN EFFECT WAS MEDIATED THROUGH HDAC1. TAKEN TOGETHER, THESE DATA SUPPORT A ROLE FOR HISTONE ACETYLATION IN THE EMERGENCE OF NEUROPATHIC PAIN. 2013 3 6461 42 TIME-COURSE PROGRESSION OF WHOLE TRANSCRIPTOME EXPRESSION CHANGES OF TRIGEMINAL GANGLIA COMPARED TO DORSAL ROOT GANGLIA IN RATS EXPOSED TO NERVE INJURY. MECHANISMS UNDERLYING NEUROPATHIC PAIN (NP) ARE COMPLEX WITH MULTIPLE GENES, THEIR INTERACTIONS, ENVIRONMENTAL AND EPIGENETIC FACTORS BEING IMPLICATED. TRANSCRIPTIONAL CHANGES IN THE TRIGEMINAL (TG) AND DORSAL ROOT (DRG) GANGLIA HAVE BEEN IMPLICATED IN THE DEVELOPMENT AND MAINTENANCE OF NP. DESPITE EFFORTS TO UNRAVEL MOLECULAR MECHANISMS OF NP, MANY REMAIN UNKNOWN. ALSO, MOST OF THE STUDIES FOCUSED ON THE SPINAL SYSTEM. ALTHOUGH THE SPINAL AND TRIGEMINAL SYSTEMS SHARE SOME OF THE MOLECULAR MECHANISMS, DIFFERENCES EXIST. WE USED RNA-SEQUENCING TECHNOLOGY TO IDENTIFY DIFFERENTIALLY EXPRESSED GENES (DEGS) IN THE TG AND DRG AT BASELINE AND 3 TIME-POINTS FOLLOWING THE INFRAORBITAL OR SCIATIC NERVE INJURIES, RESPECTIVELY. PATHWAY ANALYSIS AND COMPARISON ANALYSIS WERE PERFORMED TO IDENTIFY DIFFERENTIALLY EXPRESSED PATHWAYS. ADDITIONALLY, UPSTREAM REGULATOR EFFECTS WERE INVESTIGATED IN THE TWO SYSTEMS. DEG (DIFFERENTIALLY EXPRESSED GENES) ANALYSES IDENTIFIED 3,225 GENES TO BE DIFFERENTIALLY EXPRESSED BETWEEN TG AND DRG IN NAIVE ANIMALS, 1,828 GENES FOUR DAYS POST INJURY, 5,644 AT DAY 8 AND 9,777 DEGS AT 21 DAYS POST INJURY. COMPARISON OF TOP ENRICHED CANONICAL PATHWAYS REVEALED THAT A NUMBER OF SIGNALING PATHWAY WAS SIGNIFICANTLY INHIBITED IN THE TG AND ACTIVATED IN THE DRG AT 21 DAYS POST INJURY. FINALLY, CORT UPSTREAM REGULATOR WAS PREDICTED TO BE INHIBITED IN THE TG WHILE EXPRESSION LEVELS OF CSF1 UPSTREAM REGULATOR WERE SIGNIFICANTLY ELEVATED IN THE DRG AT 21 DAYS POST INJURY. THIS STUDY PROVIDES A BASIS FOR FURTHER IN-DEPTH STUDIES INVESTIGATING TRANSCRIPTIONAL CHANGES, PATHWAYS, AND UPSTREAM REGULATION IN TG AND DRG IN RATS EXPOSED TO PERIPHERAL NERVE INJURIES. 2023 4 531 45 ASTROCYTE REACTIVITY FOLLOWING BLAST EXPOSURE INVOLVES ABERRANT HISTONE ACETYLATION. BLAST INDUCED NEUROTRAUMA (BINT) IS A PREVALENT INJURY WITHIN MILITARY AND CIVILIAN POPULATIONS. THE INJURY IS CHARACTERIZED BY PERSISTENT INFLAMMATION AT THE CELLULAR LEVEL WHICH MANIFESTS AS A MULTITUDE OF COGNITIVE AND FUNCTIONAL IMPAIRMENTS. EPIGENETIC REGULATION OF TRANSCRIPTION OFFERS AN IMPORTANT CONTROL MECHANISM FOR GENE EXPRESSION AND CELLULAR FUNCTION WHICH MAY UNDERLIE CHRONIC INFLAMMATION AND RESULT IN NEURODEGENERATION. WE HYPOTHESIZE THAT ALTERED HISTONE ACETYLATION PATTERNS MAY BE INVOLVED IN BLAST INDUCED INFLAMMATION AND THE CHRONIC ACTIVATION OF GLIAL CELLS. THIS STUDY AIMED TO ELUCIDATE CHANGES TO HISTONE ACETYLATION OCCURRING FOLLOWING INJURY AND THE ROLES THESE CHANGES MAY HAVE WITHIN THE PATHOLOGY. SPRAGUE DAWLEY RATS WERE SUBJECTED TO EITHER A 10 OR 17 PSI BLAST OVERPRESSURE WITHIN AN ADVANCED BLAST SIMULATOR (ABS). SHAM ANIMALS UNDERWENT THE SAME PROCEDURES WITHOUT BLAST EXPOSURE. MEMORY IMPAIRMENTS WERE MEASURED USING THE NOVEL OBJECT RECOGNITION (NOR) TEST AT 2 AND 7 DAYS POST-INJURY. TISSUES WERE COLLECTED AT 7 DAYS FOR WESTERN BLOT AND IMMUNOHISTOCHEMISTRY (IHC) ANALYSIS. SHAM ANIMALS SHOWED INTACT MEMORY AT EACH TIME POINT. THE NOVEL OBJECT DISCRIMINATION DECREASED SIGNIFICANTLY BETWEEN TWO AND 7 DAYS FOR EACH INJURY GROUP (P < 0.05). THIS IS INDICATIVE OF THE ONSET OF MEMORY IMPAIRMENT. WESTERN BLOT ANALYSIS SHOWED GLIAL FIBRILLARY ACIDIC PROTEIN (GFAP), A KNOWN MARKER OF ACTIVATED ASTROCYTES, WAS ELEVATED IN THE PREFRONTAL CORTEX (PFC) FOLLOWING BLAST EXPOSURE FOR BOTH INJURY GROUPS. ANALYSIS OF HISTONE PROTEIN EXTRACT SHOWED NO CHANGES IN THE LEVEL OF ANY TOTAL HISTONE PROTEINS WITHIN THE PFC. HOWEVER, ACETYLATION LEVELS OF HISTONE H2B, H3, AND H4 WERE DECREASED IN BOTH GROUPS (P < 0.05). CO-LOCALIZATION IMMUNOFLUORESCENCE WAS USED TO FURTHER INVESTIGATE ANY POTENTIAL CORRELATION BETWEEN DECREASED HISTONE ACETYLATION AND ASTROCYTE ACTIVATION. THESE EXPERIMENTS SHOWED A SIMILAR DECREASE IN H3 ACETYLATION IN ASTROCYTES EXPOSED TO A 17 PSI BLAST BUT NOT A 10 PSI BLAST. FURTHER INVESTIGATION OF GENE EXPRESSION BY POLYMERASE CHAIN REACTION (PCR) ARRAY, SHOWED DYSREGULATION OF SEVERAL CYTOKINE AND CYTOKINE RECEPTORS THAT ARE INVOLVED IN NEUROINFLAMMATORY PROCESSES. WE HAVE SHOWN ABERRANT HISTONE ACETYLATION PATTERNS INVOLVED IN BLAST INDUCED ASTROGLIOSIS AND COGNITIVE IMPAIRMENTS. FURTHER UNDERSTANDING OF THEIR ROLE IN THE INJURY PROGRESSION MAY LEAD TO NOVEL THERAPEUTIC TARGETS. 2016 5 2736 45 EXPLORING THE TRANSCRIPTOME OF RESIDENT SPINAL MICROGLIA AFTER COLLAGEN ANTIBODY-INDUCED ARTHRITIS. RECENT STUDIES HAVE SUGGESTED A SEXUALLY DIMORPHIC ROLE OF SPINAL GLIAL CELLS IN THE MAINTENANCE OF MECHANICAL HYPERSENSITIVITY IN RODENT MODELS OF CHRONIC PAIN. WE HAVE USED THE COLLAGEN ANTIBODY-INDUCED ARTHRITIS (CAIA) MOUSE MODEL TO EXAMINE DIFFERENCES BETWEEN MALES AND FEMALES IN THE CONTEXT OF SPINAL REGULATION OF ARTHRITIS-INDUCED PAIN. WE HAVE FOCUSED ON THE LATE PHASE OF THIS MODEL WHEN JOINT INFLAMMATION HAS RESOLVED, BUT MECHANICAL HYPERSENSITIVITY PERSISTS. ALTHOUGH THE INTENSITY OF SUBSTANCE P, CALCITONIN GENE-RELATED PEPTIDE, AND GALANIN IMMUNOREACTIVITY IN THE SPINAL CORD WAS NOT DIFFERENT FROM CONTROLS, THE INTENSITY OF MICROGLIA (IBA-1) AND ASTROCYTE (GLIAL FIBRILLARY ACIDIC PROTEIN) MARKERS WAS ELEVATED IN BOTH MALES AND FEMALES. INTRATHECAL ADMINISTRATION OF THE GLIAL INHIBITORS MINOCYCLINE AND PENTOXIFYLLINE REVERSED MECHANICAL THRESHOLDS IN MALE, BUT NOT IN FEMALE MICE. WE ISOLATED RESIDENT MICROGLIA FROM THE LUMBAR DORSAL HORNS AND OBSERVED A SIGNIFICANTLY LOWER NUMBER OF MICROGLIAL CELLS IN FEMALES BY FLOW CYTOMETRY ANALYSIS. HOWEVER, ALTHOUGH GENOME-WIDE RNA SEQUENCING RESULTS POINTED TO SEVERAL TRANSCRIPTIONAL DIFFERENCES BETWEEN MALE AND FEMALE MICROGLIA, NO CONVINCING DIFFERENCES WERE IDENTIFIED BETWEEN CONTROL AND CAIA GROUPS. TAKEN TOGETHER, THESE FINDINGS SUGGEST THAT THERE ARE SUBTLE SEX DIFFERENCES IN MICROGLIAL EXPRESSION PROFILES INDEPENDENT OF ARTHRITIS. OUR EXPERIMENTS FAILED TO IDENTIFY THE UNDERLYING MRNA CORRELATES OF MICROGLIAL ACTIONS IN THE LATE PHASE OF THE CAIA MODEL. IT IS LIKELY THAT TRANSCRIPTIONAL CHANGES ARE EITHER SUBTLE AND HIGHLY LOCALISED AND THEREFORE DIFFICULT TO IDENTIFY WITH BULK ISOLATION TECHNIQUES OR THAT OTHER FACTORS, SUCH AS CHANGES IN PROTEIN EXPRESSION OR EPIGENETIC MODIFICATIONS, ARE AT PLAY. 2019 6 2756 44 EXPRESSION OF DNA METHYLTRANSFERASES IN ADULT DORSAL ROOT GANGLIA IS CELL-TYPE SPECIFIC AND UP REGULATED IN A RODENT MODEL OF NEUROPATHIC PAIN. NEUROPATHIC PAIN IS ASSOCIATED WITH HYPEREXCITABILITY AND INTRINSIC FIRING OF DORSAL ROOT GANGLIA (DRG) NEURONS. THESE PHENOTYPICAL CHANGES CAN BE LONG LASTING, POTENTIALLY SPANNING THE ENTIRE LIFE OF ANIMAL MODELS, AND DEPEND ON ALTERED EXPRESSION OF NUMEROUS PROTEINS, INCLUDING MANY ION CHANNELS. YET, HOW DRGS MAINTAIN LONG-TERM CHANGES IN PROTEIN EXPRESSION IN NEUROPATHIC CONDITIONS REMAINS UNCLEAR. DNA METHYLATION IS A WELL-KNOWN MECHANISM OF EPIGENETIC CONTROL OF GENE EXPRESSION AND IS ACHIEVED BY THE ACTION OF THREE ENZYMES: DNA METHYLTRANSFERASE (DNMT) 1, 3A, AND 3B, WHICH HAVE BEEN STUDIED PRIMARILY DURING DEVELOPMENT. WE FIRST PERFORMED IMMUNOHISTOCHEMICAL ANALYSIS TO ASSESS WHETHER THESE ENZYMES ARE EXPRESSED IN ADULT RAT DRGS (L4-5) AND FOUND THAT DNMT1 IS EXPRESSED IN BOTH GLIA AND NEURONS, DNMT3A IS PREFERENTIALLY EXPRESSED IN GLIA AND DNMT3B IS PREFERENTIALLY EXPRESSED IN NEURONS. A RAT MODEL OF NEUROPATHIC PAIN WAS THEN USED TO DETERMINE WHETHER NERVE INJURY MAY INDUCE EPIGENETIC CHANGES IN DRGS AT MULTIPLE TIME POINTS AFTER PAIN ONSET. REAL-TIME RT PCR ANALYSIS REVEALED ROBUST AND TIME-DEPENDENT CHANGES IN DNMT TRANSCRIPT EXPRESSION IN IPSILATERAL DRGS FROM SPARED NERVE INJURY (SNI) BUT NOT SHAM RATS. INTERESTINGLY, DNMT3B TRANSCRIPT SHOWED A ROBUST UPREGULATION THAT APPEARED ALREADY 1 WEEK AFTER SURGERY AND PERSISTED AT 4 WEEKS (OUR ENDPOINT); IN CONTRAST, DNMT1 AND DNMT3A TRANSCRIPTS SHOWED ONLY MODERATE UPREGULATION THAT WAS TRANSIENT AND DID NOT APPEAR UNTIL THE SECOND WEEK. WE SUGGEST THAT DNMT REGULATION IN ADULT DRGS MAY BE A CONTRIBUTOR TO THE PAIN PHENOTYPE AND MERITS FURTHER STUDY. 2014 7 3319 38 HISTONE ACETYLATION AND HISTONE DEACETYLATION IN NEUROPATHIC PAIN: AN UNRESOLVED PUZZLE? CHRONIC PAIN IS BROADLY CLASSIFIED INTO SOMATIC, VISCERAL OR NEUROPATHIC PAIN DEPENDING UPON THE LOCATION AND EXTENT OF PAIN PERCEPTION. EVIDENCES FROM DIFFERENT ANIMAL STUDIES SUGGEST THAT INFLAMMATORY OR NEUROPATHIC PAIN IS ASSOCIATED WITH ALTERED ACETYLATION AND DEACETYLATION OF HISTONE PROTEINS, WHICH RESULT IN ABNORMAL TRANSCRIPTION OF NOCICEPTIVE PROCESSING GENES. THERE HAVE BEEN A NUMBER OF STUDIES INDICATING THAT NERVE INJURY UP-REGULATES HISTONE DEACETYLASE ENZYMES, WHICH LEADS TO INCREASED HISTONE DEACETYLATION AND INDUCE CHRONIC PAIN. TREATMENT WITH HISTONE DEACETYLASE INHIBITORS RELIEVES PAIN BY NORMALIZING NERVE INJURY-INDUCED DOWN REGULATION OF METABOTROPIC GLUTAMATE RECEPTORS, GLUTAMATE TRANSPORTERS, GLUTAMIC ACID DECARBOXYLASE 65, NEURON RESTRICTIVE SILENCER FACTOR AND SERUM AND GLUCOCORTICOID INDUCIBLE KINASE 1. ON THE OTHER HAND, A FEW STUDIES REFER TO INCREASED EXPRESSION OF HISTONE ACETYLASE ENZYMES IN RESPONSE TO NERVE INJURY THAT PROMOTES HISTONE ACETYLATION LEADING TO PAIN INDUCTION. TREATMENT WITH HISTONE ACETYL TRANSFERASE INHIBITORS HAVE BEEN REPORTED TO RELIEVE CHRONIC PAIN BY BLOCKING THE UP-REGULATION OF CHEMOKINES AND CYCLOOXYGENASE-2, THE CRITICAL FACTORS ASSOCIATED WITH HISTONE ACETYLATION-INDUCED PAIN. THE PRESENT REVIEW DESCRIBES THE DUAL ROLE OF HISTONE ACETYLATION/DEACETYLATION IN DEVELOPMENT OR ATTENUATION OF NEUROPATHIC PAIN ALONG WITH THE UNDERLYING MECHANISMS. 2017 8 345 49 ALTERED BRAIN EXPRESSION OF DNA METHYLATION AND HYDROXYMETHYLATION EPIGENETIC ENZYMES IN A RAT MODEL OF NEUROPATHIC PAIN. THE ROLE OF EPIGENETICS IN CHRONIC PAIN AT THE SUPRASPINAL LEVEL IS YET TO BE FULLY CHARACTERIZED. DNA HISTONE METHYLATION IS CRUCIALLY REGULATED BY DE NOVO METHYLTRANSFERASES (DNMT1-3) AND TEN-ELEVEN TRANSLOCATION DIOXYGENASES (TET1-3). EVIDENCE HAS SHOWN THAT METHYLATION MARKERS ARE ALTERED IN DIFFERENT CNS REGIONS RELATED TO NOCICEPTION, NAMELY THE DORSAL ROOT GANGLIA, THE SPINAL CORD, AND DIFFERENT BRAIN AREAS. DECREASED GLOBAL METHYLATION WAS FOUND IN THE DRG, THE PREFRONTAL CORTEX, AND THE AMYGDALA, WHICH WAS ASSOCIATED WITH DECREASED DNMT1/3A EXPRESSION. IN CONTRAST, INCREASED METHYLATION LEVELS AND MRNA LEVELS OF TET1 AND TET3 WERE LINKED TO AUGMENTED PAIN HYPERSENSITIVITY AND ALLODYNIA IN INFLAMMATORY AND NEUROPATHIC PAIN MODELS. SINCE EPIGENETIC MECHANISMS MAY BE RESPONSIBLE FOR THE REGULATION AND COORDINATION OF VARIOUS TRANSCRIPTIONAL MODIFICATIONS DESCRIBED IN CHRONIC PAIN STATES, WITH THIS STUDY, WE AIMED TO EVALUATE THE FUNCTIONAL ROLE OF TET1-3 AND DNMT1/3A GENES IN NEUROPATHIC PAIN IN SEVERAL BRAIN AREAS. IN A SPARED NERVE INJURY RAT MODEL OF NEUROPATHIC PAIN, 21 DAYS AFTER SURGERY, WE FOUND INCREASED TET1 EXPRESSION IN THE MEDIAL PREFRONTAL CORTEX AND DECREASED EXPRESSION IN THE CAUDATE-PUTAMEN AND THE AMYGDALA; TET2 WAS UPREGULATED IN THE MEDIAL THALAMUS; TET3 MRNA LEVELS WERE REDUCED IN THE MEDIAL PREFRONTAL CORTEX AND THE CAUDATE-PUTAMEN; AND DNMT1 WAS DOWNREGULATED IN THE CAUDATE-PUTAMEN AND THE MEDIAL THALAMUS. NO STATISTICALLY SIGNIFICANT CHANGES IN EXPRESSION WERE OBSERVED WITH DNMT3A. OUR RESULTS SUGGEST A COMPLEX FUNCTIONAL ROLE FOR THESE GENES IN DIFFERENT BRAIN AREAS IN THE CONTEXT OF NEUROPATHIC PAIN. THE NOTION OF DNA METHYLATION AND HYDROXYMETHYLATION BEING CELL-TYPE SPECIFIC AND NOT TISSUE SPECIFIC, AS WELL AS THE POSSIBILITY OF CHRONOLOGICALLY DIFFERENTIAL GENE EXPRESSION AFTER THE ESTABLISHMENT OF NEUROPATHIC OR INFLAMMATORY PAIN MODELS, OUGHT TO BE ADDRESSED IN FUTURE STUDIES. 2023 9 5007 36 PERIPHERAL NERVE INJURY IS ASSOCIATED WITH CHRONIC, REVERSIBLE CHANGES IN GLOBAL DNA METHYLATION IN THE MOUSE PREFRONTAL CORTEX. CHANGES IN BRAIN STRUCTURE AND CORTICAL FUNCTION ARE ASSOCIATED WITH MANY CHRONIC PAIN CONDITIONS INCLUDING LOW BACK PAIN AND FIBROMYALGIA. THE MAGNITUDE OF THESE CHANGES CORRELATES WITH THE DURATION AND/OR THE INTENSITY OF CHRONIC PAIN. MOST STUDIES REPORT CHANGES IN COMMON AREAS INVOLVED IN PAIN MODULATION, INCLUDING THE PREFRONTAL CORTEX (PFC), AND PAIN-RELATED PATHOLOGICAL CHANGES IN THE PFC CAN BE REVERSED WITH EFFECTIVE TREATMENT. WHILE THE MECHANISMS UNDERLYING THESE CHANGES ARE UNKNOWN, THEY MUST BE DYNAMICALLY REGULATED. EPIGENETIC MODULATION OF GENE EXPRESSION IN RESPONSE TO EXPERIENCE AND ENVIRONMENT IS REVERSIBLE AND DYNAMIC. EPIGENETIC MODULATION BY DNA METHYLATION IS ASSOCIATED WITH ABNORMAL BEHAVIOR AND PATHOLOGICAL GENE EXPRESSION IN THE CENTRAL NERVOUS SYSTEM. DNA METHYLATION MIGHT ALSO BE INVOLVED IN MEDIATING THE PATHOLOGIES ASSOCIATED WITH CHRONIC PAIN IN THE BRAIN. WE THEREFORE TESTED A) WHETHER ALTERATIONS IN DNA METHYLATION ARE FOUND IN THE BRAIN LONG AFTER CHRONIC NEUROPATHIC PAIN IS INDUCED IN THE PERIPHERY USING THE SPARED NERVE INJURY MODAL AND B) WHETHER THESE INJURY-ASSOCIATED CHANGES ARE REVERSIBLE BY INTERVENTIONS THAT REVERSE THE PATHOLOGIES ASSOCIATED WITH CHRONIC PAIN. SIX MONTHS FOLLOWING PERIPHERAL NERVE INJURY, ABNORMAL SENSORY THRESHOLDS AND INCREASED ANXIETY WERE ACCOMPANIED BY DECREASED GLOBAL METHYLATION IN THE PFC AND THE AMYGDALA BUT NOT IN THE VISUAL CORTEX OR THE THALAMUS. ENVIRONMENTAL ENRICHMENT ATTENUATED NERVE INJURY-INDUCED HYPERSENSITIVITY AND REVERSED THE CHANGES IN GLOBAL PFC METHYLATION. FURTHERMORE, GLOBAL PFC METHYLATION CORRELATED WITH MECHANICAL AND THERMAL SENSITIVITY IN NEUROPATHIC MICE. IN SUMMARY, INDUCTION OF CHRONIC PAIN BY PERIPHERAL NERVE INJURY IS ASSOCIATED WITH EPIGENETIC CHANGES IN THE BRAIN. THESE CHANGES ARE DETECTED LONG AFTER THE ORIGINAL INJURY, AT A LONG DISTANCE FROM THE SITE OF INJURY AND ARE REVERSIBLE WITH ENVIRONMENTAL MANIPULATION. CHANGES IN BRAIN STRUCTURE AND CORTICAL FUNCTION THAT ARE ASSOCIATED WITH CHRONIC PAIN CONDITIONS MAY THEREFORE BE MEDIATED BY EPIGENETIC MECHANISMS. 2013 10 2297 30 EPIGENETIC REGULATION OF ACUTE INFLAMMATORY PAIN. ACUTE PAIN IS ASSOCIATED WITH TISSUE DAMAGE, WHICH RESULTS IN THE RELEASE OF INFLAMMATORY MEDIATORS. RECENT STUDIES POINT TO THE INVOLVEMENT OF EPIGENETIC MECHANISMS (DNA METHYLATION) IN THE DEVELOPMENT OF PAIN. WE HAVE FOUND THAT DURING ACUTE INFLAMMATORY PAIN INDUCED BY THE APPLICATION OF 10% MUSTARD OIL ON THE TONGUES OF RATS, LEVELS OF DNMT3A AND 3B WERE ELEVATED MARKEDLY (36 AND 42 % RESPECTIVELY), WHEREAS THE LEVEL OF DNMT1 WAS NOT CHANGED SIGNIFICANTLY. PREVIOUS INJECTION OF XEFOCAM WITH 0,4 MG/KG DOSE DECREASED LEVELS OF DNMT3A AND 3B (25 AND 24% RESPECTIVELY). THE LEVEL OF DNMT1 WAS NOT CHANGED SIGNIFICANTLY COMPARED TO THE CONTROL GROUP. THE FINDINGS SUPPORT THE IDEA THAT INHIBITORS OF DNA-METHYLTRANSFERASES COULD BE USEFUL FOR PAIN MANAGEMENT. OUR DATA SUGGEST THAT NSAIDS (ALONE OR IN COMBINATION WITH DNMT INHIBITORS) MAY BE PROPOSED AS POSSIBLE EPIGENETIC REGULATORY AGENTS, WHICH MAY PLAY A ROLE IN EPIGENETIC MECHANISMS INDIRECTLY THROUGH ALTERING THE ACTIVITY OF INFLAMMATORY MEDIATORS INVOLVED IN PAIN DEVELOPMENT. 2014 11 2253 31 EPIGENETIC MODULATION OF WNT SIGNALING CONTRIBUTES TO NEUROPATHIC PAIN IN RATS. PREVIOUS STUDIES HAVE DEMONSTRATED THAT THE WNT/BETA?CATENIN SIGNALING PATHWAY IS CRITICAL TO THE INDUCTION AND MAINTENANCE OF CHRONIC NEUROPATHIC PAIN CAUSED BY PERIPHERAL INFLAMMATION AND NERVE DAMAGE. EMERGING EVIDENCE FROM RECENT STUDIES SUGGESTS THAT EPIGENETIC MECHANISMS MAY ALSO BE CRITICAL TO THE PATHOGENESIS OF CHRONIC PAIN. THE PRESENT STUDY AIMED TO ELUCIDATE THE EPIGENETIC MECHANISMS UNDERLYING ALTERED WNT SIGNALING AND THEIR INVOLVEMENT IN CCI?INDUCED NEUROPATHIC PAIN IN RAT SCIATIC NERVES. THE RESULTS OF THE PRESENT STUDY DEMONSTRATED A SIGNIFICANT INCREASE IN THE EXPRESSION LEVELS OF WNT3A IN THE DORSAL HORN OF THE RATS WITH CCI. IN ADDITION, A SIGNIFICANT INCREASE IN HISTONE H3 ACETYLATION, AND A SIGNIFICANT DECREASE IN CYTOSINE METHYLATION IN THE PROMOTER REGION OF WNT3A WAS OBSERVED IN THE DORSAL HORN OF THE RATS WITH CCI. INTRATHECAL APPLICATION OF XAV939, WHICH ACTS AS AN INHIBITOR OF WNT SIGNALING, SIGNIFICANTLY DECREASED THE EXPRESSION LEVELS OF ACTIVE BETA?CATENIN, AND ATTENUATED THE RAT BEHAVIORAL RESPONSES TO THERMAL AND MECHANICAL PAIN STIMULI. THESE RESULTS SUGGEST THAT THE EPIGENETIC UPREGULATION OF WNT3A IN THE DORSAL HORN CONTRIBUTES TO THE MAINTENANCE OF PAIN?INDUCED BEHAVIOR IN RATS WITH CCI. 2015 12 3141 36 GLOBAL GENE EXPRESSION AND CHROMATIN ACCESSIBILITY OF THE PERIPHERAL NERVOUS SYSTEM IN ANIMAL MODELS OF PERSISTENT PAIN. BACKGROUND: EFFORTS TO UNDERSTAND GENETIC VARIABILITY INVOLVED IN AN INDIVIDUAL'S SUSCEPTIBILITY TO CHRONIC PAIN SUPPORT A ROLE FOR UPSTREAM REGULATION BY EPIGENETIC MECHANISMS. METHODS: TO EXAMINE THE TRANSCRIPTOMIC AND EPIGENETIC BASIS OF CHRONIC PAIN THAT RESIDES IN THE PERIPHERAL NERVOUS SYSTEM, WE USED RNA-SEQ AND ATAC-SEQ OF THE RAT DORSAL ROOT GANGLION (DRG) TO IDENTIFY NOVEL MOLECULAR PATHWAYS ASSOCIATED WITH PAIN HYPERSENSITIVITY IN TWO WELL-STUDIED PERSISTENT PAIN MODELS INDUCED BY CHRONIC CONSTRICTION INJURY (CCI) OF THE SCIATIC NERVE AND INTRA-PLANTAR INJECTION OF COMPLETE FREUND'S ADJUVANT (CFA) IN RATS. RESULTS: OUR RNA-SEQ STUDIES IDENTIFY A VARIETY OF BIOLOGICAL PROCESS RELATED TO SYNAPSE ORGANIZATION, MEMBRANE POTENTIAL, TRANSMEMBRANE TRANSPORT, AND ION BINDING. INTERESTINGLY, GENES THAT ENCODE TRANSCRIPTIONAL REGULATORS WERE DISPROPORTIONATELY DOWNREGULATED IN BOTH MODELS. OUR ATAC-SEQ DATA PROVIDE A COMPREHENSIVE MAP OF CHROMATIN ACCESSIBILITY CHANGES IN THE DRG. A TOTAL OF 1123 REGIONS SHOWED CHANGES IN CHROMATIN ACCESSIBILITY IN ONE OR BOTH MODELS WHEN COMPARED TO THE NAIVE AND 31 SHARED DIFFERENTIALLY ACCESSIBLE REGIONS (DAR)S. FUNCTIONAL ANNOTATION OF THE DARS IDENTIFIED DISPARATE MOLECULAR FUNCTIONS ENRICHED FOR EACH PAIN MODEL WHICH SUGGESTS THAT CHROMATIN STRUCTURE MAY BE ALTERED DIFFERENTLY FOLLOWING SCIATIC NERVE INJURY AND HIND PAW INFLAMMATION. MOTIF ANALYSIS IDENTIFIED 17 DNA SEQUENCES KNOWN TO BIND TRANSCRIPTION FACTORS IN THE CCI DARS AND 33 IN THE CFA DARS. TWO MOTIFS WERE SIGNIFICANTLY ENRICHED IN BOTH MODELS. CONCLUSIONS: OUR IMPROVED UNDERSTANDING OF THE CHANGES IN CHROMATIN ACCESSIBILITY THAT OCCUR IN CHRONIC PAIN STATES MAY IDENTIFY REGULATORY GENOMIC ELEMENTS THAT PLAY ESSENTIAL ROLES IN MODULATING GENE EXPRESSION IN THE DRG. 2021 13 6427 35 THE TRANSITION FROM ACUTE TO CHRONIC PAIN: DYNAMIC EPIGENETIC REPROGRAMMING OF THE MOUSE PREFRONTAL CORTEX UP TO 1 YEAR AFTER NERVE INJURY. CHRONIC PAIN IS ASSOCIATED WITH PERSISTENT STRUCTURAL AND FUNCTIONAL CHANGES THROUGHOUT THE NEUROAXIS, INCLUDING IN THE PREFRONTAL CORTEX (PFC). THE PFC IS IMPORTANT IN THE INTEGRATION OF SENSORY, COGNITIVE, AND EMOTIONAL INFORMATION AND IN CONDITIONED PAIN MODULATION. WE PREVIOUSLY REPORTED WIDESPREAD EPIGENETIC REPROGRAMMING IN THE PFC MANY MONTHS AFTER NERVE INJURY IN RODENTS. EPIGENETIC MODIFICATIONS, INCLUDING DNA METHYLATION, CAN DRIVE CHANGES IN GENE EXPRESSION WITHOUT MODIFYING DNA SEQUENCES. TO DATE, LITTLE IS KNOWN ABOUT EPIGENETIC DYSREGULATION AT THE ONSET OF ACUTE PAIN OR HOW IT PROGRESSES AS PAIN TRANSITIONS FROM ACUTE TO CHRONIC. WE HYPOTHESIZE THAT ACUTE PAIN AFTER INJURY RESULTS IN RAPID AND PERSISTENT EPIGENETIC REMODELLING IN THE PFC THAT EVOLVES AS PAIN BECOMES CHRONIC. WE FURTHER PROPOSE THAT UNDERSTANDING EPIGENETIC REMODELLING WILL PROVIDE INSIGHTS INTO THE MECHANISMS DRIVING PAIN-RELATED CHANGES IN THE BRAIN. EPIGENOME-WIDE ANALYSIS WAS PERFORMED IN THE MOUSE PFC 1 DAY, 2 WEEKS, 6 MONTHS, AND 1 YEAR AFTER PERIPHERAL INJURY USING THE SPARED NERVE INJURY IN MICE. SPARED NERVE INJURY RESULTED IN RAPID AND PERSISTENT CHANGES IN DNA METHYLATION, WITH ROBUST DIFFERENTIAL METHYLATION OBSERVED BETWEEN SPARED NERVE INJURY AND SHAM-OPERATED CONTROL MICE AT ALL TIME POINTS. HUNDREDS OF DIFFERENTIALLY METHYLATED GENES WERE IDENTIFIED, INCLUDING MANY WITH KNOWN FUNCTION IN PAIN. PATHWAY ANALYSIS REVEALED ENRICHMENT IN GENES RELATED TO STIMULUS RESPONSE AT EARLY TIME POINTS, IMMUNE FUNCTION AT LATER TIME POINTS, AND ACTIN AND CYTOSKELETAL REGULATION THROUGHOUT THE TIME COURSE. THESE RESULTS EMPHASIZE THE IMPORTANCE OF CONSIDERING PAIN CHRONICITY IN BOTH PAIN RESEARCH AND IN TREATMENT OPTIMIZATION. 2020 14 4173 30 MELATONIN INDUCES HISTONE HYPERACETYLATION IN THE RAT BRAIN. WE HAVE REPORTED THAT MELATONIN INDUCES HISTONE HYPERACETYLATION IN MOUSE NEURAL STEM CELLS, SUGGESTING AN EPIGENETIC ROLE FOR THIS PLEIOTROPIC HORMONE. TO SUPPORT SUCH A ROLE, IT IS NECESSARY TO DEMONSTRATE THAT MELATONIN PRODUCES SIMILAR EFFECTS IN VIVO. HISTONE ACETYLATION, FOLLOWING CHRONIC TREATMENT WITH MELATONIN (4MUG/ML IN DRINKING WATER FOR 17 DAYS), WAS EXAMINED BY WESTERN BLOTTING IN SELECTED RAT BRAIN REGIONS. MELATONIN INDUCED SIGNIFICANT INCREASES IN HISTONE H3 AND HISTONE H4 ACETYLATION IN THE HIPPOCAMPUS. HISTONE H4 WAS ALSO HYPERACETYLATED IN THE STRIATUM, BUT THERE WERE NO SIGNIFICANT CHANGES IN HISTONE H3 ACETYLATION IN THIS BRAIN REGION. NO SIGNIFICANT CHANGES IN THE ACETYLATION OF EITHER HISTONE H3 OR H4 WERE OBSERVED IN THE MIDBRAIN AND CEREBELLUM. AN EXAMINATION OF KINASE ACTIVATION, WHICH MAY BE RELATED TO THESE CHANGES, REVEALED THAT MELATONIN TREATMENT INCREASED THE LEVELS OF PHOSPHO-ERK (EXTRACELLULAR SIGNAL-REGULATED KINASE) IN THE HIPPOCAMPUS AND STRIATUM, BUT PHOSPHO-AKT (PROTEIN KINASE B) LEVELS WERE UNCHANGED. THESE FINDINGS SUGGEST THAT CHROMATIN REMODELING AND ASSOCIATED CHANGES IN THE EPIGENETIC REGULATION OF GENE EXPRESSION UNDERLIE THE MULTIPLE PHYSIOLOGICAL EFFECTS OF MELATONIN. 2013 15 1126 39 COMPLEX REGULATION OF THE REGULATOR OF SYNAPTIC PLASTICITY HISTONE DEACETYLASE 2 IN THE RODENT DORSAL HORN AFTER PERIPHERAL INJURY. HISTONE DEACETYLASES (HDACS), HDAC2 IN PARTICULAR, HAVE BEEN SHOWN TO REGULATE VARIOUS FORMS OF LEARNING AND MEMORY. SINCE COGNITIVE PROCESSES SHARE MECHANISMS WITH SPINAL NOCICEPTIVE SIGNALLING, WE DECIDED TO INVESTIGATE THE HDAC2 EXPRESSION IN THE DORSAL HORN AFTER PERIPHERAL INJURY. USING IMMUNOHISTOCHEMISTRY, WE FOUND THAT SPINAL HDAC2 WAS MAINLY SEEN IN NEURONS AND ASTROCYTES, WITH NEURONAL EXPRESSION IN NAIVE TISSUE 2.6 TIMES GREATER THAN THAT IN ASTROCYTES. CYSTEINE (S)-NITROSYLATION OF HDAC2 RELEASES HDAC2 GENE SILENCING AND IS CONTROLLED BY NITRIC OXIDE (NO). A DURATION OF 48 H AFTER INTRAPLANTAR INJECTION OF COMPLETE FREUND'S ADJUVANT, THERE WAS AN IPSILATERAL INCREASE IN THE MOST IMPORTANT NO-PRODUCING ENZYME IN PAIN STATES, NITRIC OXIDE SYNTHASE (NNOS), ACCOMPANIED BY AN INCREASE IN HDAC2 S-NITROSYLATION. MOREOVER, A SUBSET OF NNOS-POSITIVE NEURONS EXPRESSED CFOS, A KNOWN TARGET OF HDAC2, SUGGESTING THAT DEREPRESSION OF CFOS EXPRESSION FOLLOWING HDAC2 S-NITROSYLATION MIGHT OCCUR AFTER NOXIOUS STIMULATION. WE SAW NO CHANGE IN GLOBAL HDAC2 EXPRESSION IN BOTH SHORT- AND LONG-TERM PAIN STATES. HOWEVER, HDAC2 WAS INCREASED IN ASTROCYTES 7 DAYS AFTER NEUROPATHIC INJURY SUGGESTING THAT HDAC2 MIGHT INHIBIT ASTROCYTIC GENE EXPRESSION IN NEUROPATHIC PAIN STATES. ALL TOGETHER, OUR RESULTS INDICATE THAT THE EPIGENETIC REGULATION OF TRANSCRIPTIONAL PROGRAMMES IN THE DORSAL HORN AFTER INJURY IS CELL SPECIFIC. MOREOVER, THE PROMINENT ROLE OF NO IN PERSISTENT PAIN STATES SUGGESTS THAT HDAC2 S-NITROSYLATION COULD PLAY A CRUCIAL ROLE IN THE REGULATION OF GENE EXPRESSION LEADING TO HYPERSENSITIVITY. OUR MANUSCRIPT DESCRIBES FOR THE FIRST TIME THE REGULATION OF THE MEMORY REGULATOR HISTONE DEACETYLASE 2 (HDAC2) IN THE SUPERFICIAL DORSAL HORN OF ADULT RATS FOLLOWING PERIPHERAL INJURY. OUR CELL-SPECIFIC APPROACH HAS REVEALED A COMPLEX PATTERN OF EXPRESSION OF SPINAL HDAC2 THAT DEPENDS ON THE INJURY AND THE CELL TYPE, SUGGESTING A SOPHISTICATED REGULATION OF GENE EXPRESSION BY HDAC2. 2016 16 4617 39 NERVE INJURY-INDUCED CHRONIC PAIN IS ASSOCIATED WITH PERSISTENT DNA METHYLATION REPROGRAMMING IN DORSAL ROOT GANGLION. NERVE INJURY-INDUCED HYPERACTIVITY OF PRIMARY SENSORY NEURONS IN THE DORSAL ROOT GANGLION (DRG) CONTRIBUTES TO CHRONIC PAIN DEVELOPMENT, BUT THE UNDERLYING EPIGENETIC MECHANISMS REMAIN POORLY UNDERSTOOD. HERE WE DETERMINED GENOME-WIDE CHANGES IN DNA METHYLATION IN THE NERVOUS SYSTEM IN NEUROPATHIC PAIN. SPINAL NERVE LIGATION (SNL), BUT NOT PACLITAXEL TREATMENT, IN MALE SPRAGUE DAWLEY RATS INDUCED A CONSISTENT LOW-LEVEL HYPOMETHYLATION IN THE CPG SITES IN THE DRG DURING THE ACUTE AND CHRONIC PHASES OF NEUROPATHIC PAIN. DNA METHYLATION REMODELING IN THE DRG OCCURRED EARLY AFTER SNL AND PERSISTED FOR AT LEAST 3 WEEKS. SNL CAUSED DNA METHYLATION CHANGES AT 8% OF CPG SITES WITH PREVAILING HYPOMETHYLATION OUTSIDE OF CPG ISLANDS, IN INTRONS, INTERGENIC REGIONS, AND REPETITIVE SEQUENCES. IN CONTRAST, SNL CAUSED MORE GAINS OF METHYLATION IN THE SPINAL CORD AND PREFRONTAL CORTEX. THE DNA METHYLATION CHANGES IN THE INJURED DRGS RECAPITULATED DEVELOPMENTAL REPROGRAMMING AT THE NEONATAL STAGE. METHYLATION REPROGRAMMING WAS CORRELATED WITH INCREASED GENE EXPRESSION VARIABILITY. A DIET DEFICIENT IN METHYL DONORS INDUCED HYPOMETHYLATION AND PAIN HYPERSENSITIVITY. INTRATHECAL ADMINISTRATION OF THE DNA METHYLTRANSFERASE INHIBITOR RG108 CAUSED LONG-LASTING PAIN HYPERSENSITIVITY. DNA METHYLATION REPROGRAMMING IN THE DRG THUS CONTRIBUTES TO NERVE INJURY-INDUCED CHRONIC PAIN. RESTORING DNA METHYLATION MAY REPRESENT A NEW THERAPEUTIC APPROACH TO TREAT NEUROPATHIC PAIN.SIGNIFICANCE STATEMENT EPIGENETIC MECHANISMS ARE CRITICALLY INVOLVED IN THE TRANSITION FROM ACUTE TO CHRONIC PAIN AFTER NERVE INJURY. HOWEVER, GENOME-WIDE CHANGES IN DNA METHYLATION IN THE NERVOUS SYSTEM AND THEIR ROLES IN NEUROPATHIC PAIN DEVELOPMENT REMAIN UNCLEAR. HERE WE USED DIGITAL RESTRICTION ENZYME ANALYSIS OF METHYLATION TO QUANTITATIVELY DETERMINE GENOME-WIDE DNA METHYLATION CHANGES CAUSED BY NERVE INJURY. WE SHOWED THAT NERVE INJURY CAUSED DNA METHYLATION CHANGES AT 8% OF CPG SITES WITH PREVAILING HYPOMETHYLATION OUTSIDE OF CPG ISLANDS IN THE DORSAL ROOT GANGLION. REDUCING DNA METHYLATION INDUCED PAIN HYPERSENSITIVITY, WHEREAS INCREASING DNA METHYLATION ATTENUATED NEUROPATHIC PAIN. THESE FINDINGS EXTEND OUR UNDERSTANDING OF THE EPIGENETIC MECHANISM OF CHRONIC NEUROPATHIC PAIN AND SUGGEST NEW STRATEGIES TO TREAT NERVE INJURY-INDUCED CHRONIC PAIN. 2018 17 3721 45 INHIBITION OF CLASS II HISTONE DEACETYLASES IN THE SPINAL CORD ATTENUATES INFLAMMATORY HYPERALGESIA. BACKGROUND: SEVERAL CLASSES OF HISTONE DEACETYLASES (HDACS) ARE EXPRESSED IN THE SPINAL CORD THAT IS A CRITICAL STRUCTURE OF THE NOCICEPTIVE PATHWAY. HDAC-REGULATED HISTONE ACETYLATION IS AN IMPORTANT COMPONENT OF CHROMATIN REMODELING LEADING TO EPIGENETIC REGULATION OF GENE TRANSCRIPTION. TO UNDERSTAND THE ROLE OF HISTONE ACETYLATION IN EPIGENETIC REGULATION OF PATHOLOGICAL PAIN, WE HAVE STUDIED THE IMPACT OF DIFFERENT CLASSES OF HDACS IN THE SPINAL CORD ON INFLAMMATORY HYPERALGESIA INDUCED BY COMPLETE FREUND'S ADJUVANT (CFA). RESULTS: WE INTRATHECALLY APPLIED INHIBITORS SPECIFIC TO DIFFERENT CLASSES OF HDACS AND EVALUATED THEIR IMPACT ON INFLAMMATORY HYPERALGESIA. PRE-INJECTED INHIBITORS TARGETING CLASS I AS WELL AS II (SAHA, TSA, LAQ824) OR IIA (VPA, 4-PB) HDACS SIGNIFICANTLY DELAYED THE THERMAL HYPERALGESIA INDUCED BY UNILATERAL CFA INJECTION IN THE HINDPAW. EXISTING HYPERALGESIA INDUCED BY CFA WAS ALSO ATTENUATED BY THE HDAC INHIBITORS (HDACIS). IN CONTRAST, THESE INHIBITORS DID NOT INTERFERE WITH THE THERMAL RESPONSE EITHER IN NAIVE ANIMALS, OR ON THE CONTRALATERAL SIDE OF INFLAMED ANIMALS. INTERESTINGLY, MS-275 THAT SPECIFICALLY INHIBITS CLASS I HDACS FAILED TO ALTER THE HYPERALGESIA ALTHOUGH IT INCREASED HISTONE 3 ACETYLATION IN THE SPINAL CORD AS SAHA DID. USING IMMUNOBLOT ANALYSIS, WE FURTHER FOUND THAT THE LEVELS OF CLASS IIA HDAC MEMBERS (HDAC4, 5, 7, 9) IN THE SPINAL DORSAL HORN WERE UPREGULATED FOLLOWING CFA INJECTION WHILE THOSE OF CLASS I HDAC MEMBERS (HDAC1, 2, 3) REMAINED STABLE OR WERE SLIGHTLY REDUCED. CONCLUSIONS: OUR DATA SUGGEST THAT ACTIVITY OF CLASS II HDACS IN THE SPINAL CORD IS CRITICAL TO THE INDUCTION AND MAINTENANCE OF INFLAMMATORY HYPERALGESIA INDUCED BY CFA, WHILE ACTIVITY OF CLASS I HDACS MAY BE UNNECESSARY. COMPARISON OF THE EFFECTS OF HDACIS SPECIFIC TO CLASS II AND IIA AS WELL AS THE EXPRESSION PATTERN OF DIFFERENT HDACS IN THE SPINAL CORD IN RESPONSE TO CFA SUGGESTS THAT THE MEMBERS OF CLASS IIA HDACS MAY BE POTENTIAL TARGETS FOR ATTENUATING PERSISTENT INFLAMMATORY PAIN. 2010 18 2353 37 EPIGENETIC REGULATION OF OPIOID-INDUCED HYPERALGESIA, DEPENDENCE, AND TOLERANCE IN MICE. REPEATED ADMINISTRATION OF OPIOIDS SUCH AS MORPHINE INDUCES PERSISTENT BEHAVIORAL CHANGES INCLUDING OPIOID-INDUCED HYPERALGESIA (OIH), TOLERANCE, AND PHYSICAL DEPENDENCE. IN THE CURRENT WORK WE EXPLORED HOW THE BALANCE OF HISTONE ACETYLTRANSFERASE (HAT) VERSUS HISTONE DEACETYLASE (HDAC) MIGHT REGULATE THESE MORPHINE-INDUCED CHANGES. NOCICEPTIVE THRESHOLDS, ANALGESIA, AND PHYSICAL DEPENDENCE WERE ASSESSED DURING AND FOR A PERIOD OF SEVERAL WEEKS AFTER MORPHINE EXPOSURE. TO PROBE THE ROLES OF HISTONE ACETYLATION, THE HAT INHIBITOR CURCUMIN OR A SELECTIVE HDAC INHIBITOR SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) WAS ADMINISTERED DAILY TO GROUPS OF ANIMALS. HISTONE ACETYLATION IN SPINAL CORD WAS ASSESSED BY WESTERN BLOT AND IMMUNOHISTOCHEMISTRY. CONCURRENT ADMINISTRATION OF CURCUMIN WITH MORPHINE FOR 4 DAYS SIGNIFICANTLY REDUCED DEVELOPMENT OF OPIOID-INDUCED MECHANICAL ALLODYNIA, THERMAL HYPERALGESIA, TOLERANCE, AND PHYSICAL DEPENDENCE. CONVERSELY, THE HDAC INHIBITOR SAHA ENHANCED THESE RESPONSES. INTERESTINGLY, SAHA TREATMENT AFTER THE TERMINATION OF OPIOID ADMINISTRATION SUSTAINED THESE BEHAVIORAL CHANGES FOR AT LEAST 4 WEEKS. HISTONE H3 ACETYLATION IN THE DORSAL HORN OF THE SPINAL CORD WAS INCREASED AFTER CHRONIC MORPHINE TREATMENT, BUT H4 ACETYLATION WAS UNCHANGED. MOREOVER, WE OBSERVED A DECREASE IN HDAC ACTIVITY IN THE SPINAL CORDS OF MORPHINE-TREATED MICE WHILE OVERALL HAT ACTIVITY WAS UNCHANGED, SUGGESTING A SHIFT TOWARD A STATE OF ENHANCED HISTONE ACETYLATION. PERSPECTIVE: THE CURRENT STUDY INDICATES THAT EPIGENETIC MECHANISMS PLAY A CRUCIAL ROLE IN OPIOID-INDUCED LONG-LASTING NEUROPLASTICITY. THESE RESULTS PROVIDE NEW SIGHT INTO UNDERSTANDING THE MECHANISMS OF OPIOID-INDUCED NEUROPLASTICITY AND SUGGEST NEW STRATEGIES TO LIMIT OPIOID ABUSE POTENTIAL AND INCREASE THE VALUE OF THESE DRUGS AS ANALGESICS. 2013 19 2061 31 EPIGENETIC CONTROL OF HYPERSENSITIVITY IN CHRONIC INFLAMMATORY PAIN BY THE DE NOVO DNA METHYLTRANSFERASE DNMT3A2. CHRONIC PAIN IS A PATHOLOGICAL MANIFESTATION OF NEURONAL PLASTICITY SUPPORTED BY ALTERED GENE TRANSCRIPTION IN SPINAL CORD NEURONS THAT RESULTS IN LONG-LASTING HYPERSENSITIVITY. RECENTLY, THE CONCEPT THAT EPIGENETIC REGULATORS MIGHT BE IMPORTANT IN PATHOLOGICAL PAIN HAS EMERGED, BUT A CLEAR UNDERSTANDING OF THE MOLECULAR PLAYERS INVOLVED IN THE PROCESS IS STILL LACKING. IN THIS STUDY, WE LINKED DNMT3A2, A SYNAPTIC ACTIVITY-REGULATED DE NOVO DNA METHYLTRANSFERASE, TO CHRONIC INFLAMMATORY PAIN. WE OBSERVED THAT DNMT3A2 LEVELS ARE INCREASED IN THE SPINAL CORD OF ADULT MICE FOLLOWING PLANTAR INJECTION OF COMPLETE FREUND'S ADJUVANT, AN IN VIVO MODEL OF CHRONIC INFLAMMATORY PAIN. IN VIVO KNOCKDOWN OF DNMT3A2 EXPRESSION IN DORSAL HORN NEURONS BLUNTED THE INDUCTION OF GENES TRIGGERED BY COMPLETE FREUND'S ADJUVANT INJECTION. AMONG THE GENES WHOSE TRANSCRIPTION WAS FOUND TO BE INFLUENCED BY DNMT3A2 EXPRESSION IN THE SPINAL CORD IS PTGS2, ENCODING FOR COX-2, A PRIME MEDIATOR OF PAIN PROCESSING. LOWERING THE LEVELS OF DNMT3A2 PREVENTED THE ESTABLISHMENT OF LONG-LASTING INFLAMMATORY HYPERSENSITIVITY. THESE RESULTS IDENTIFY DNMT3A2 AS AN IMPORTANT EPIGENETIC REGULATOR NEEDED FOR THE ESTABLISHMENT OF CENTRAL SENSITIZATION. TARGETING EXPRESSION OR FUNCTION OF DNMT3A2 MAY BE SUITABLE FOR THE TREATMENT OF CHRONIC PAIN. 2019 20 2300 42 EPIGENETIC REGULATION OF BDNF EXPRESSION IN THE PRIMARY SENSORY NEURONS AFTER PERIPHERAL NERVE INJURY: IMPLICATIONS IN THE DEVELOPMENT OF NEUROPATHIC PAIN. BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) IS KNOWN TO BE UP-REGULATED IN THE DORSAL ROOT GANGLION (DRG) AFTER PERIPHERAL NERVE INJURY, AND TO CONTRIBUTE TO NEUROPATHIC PAIN. HERE, WE FOUND THAT THERMAL HYPERALGESIA AND MECHANICAL ALLODYNIA AT DAY 7 POST-INJURY WERE INHIBITED ONLY WHEN ANTI-BDNF ANTIBODY WAS INTRATHECALLY ADMINISTRATED AT DAY 2 POST-INJURY. CONSISTENT WITH BEHAVIORAL RESULTS, WESTERN BLOT ANALYSIS SHOWED THAT THE EXPRESSION LEVELS OF BDNF PROTEIN IN THE SPINAL DORSAL HORN WERE MARKEDLY INDUCED DURING EARLY STAGE POST-INJURY. MOREOVER, THE MAXIMAL INCREASE IN BDNF MRNA EXPRESSION IN THE DRG WAS OBSERVED AT DAY 1 POST-INJURY, AND SIGNIFICANTLY ELEVATED LEVELS WERE SUSTAINED FOR AT LEAST 14 DAYS. FOUR OF FIVE BDNF MRNA TRANSCRIPTS WERE UP-REGULATED AFTER NERVE INJURY, AND THE MOST INDUCIBLE TRANSCRIPT WAS EXON I. USING A CHROMATIN IMMUNOPRECIPITATION (CHIP) ASSAY, WE FOUND THAT NERVE INJURY PROMOTES HISTONE H3 AND H4 ACETYLATION, TRANSCRIPTIONALLY ACTIVE MODIFICATIONS, AT BDNF PROMOTER I AT DAY 1 POST-INJURY, AND THE LEVELS OF HISTONE ACETYLATION REMAIN ELEVATED FOR AT LEAST 7 DAYS. TAKEN TOGETHER, OUR FINDINGS SUGGEST THAT AN INITIAL INCREASE IN BDNF EXON I EXPRESSION CONTROLLED BY EPIGENETIC MECHANISMS MIGHT HAVE A CRUCIAL ROLE IN THE DEVELOPMENT OF NEUROPATHIC PAIN. 2013