1 4618 125 NERVE INJURY-INDUCED EPIGENETIC SILENCING OF OPIOID RECEPTORS CONTROLLED BY DNMT3A IN PRIMARY AFFERENT NEURONS. OPIOIDS ARE THE GOLD STANDARD FOR PHARMACOLOGICAL TREATMENT OF NEUROPATHIC PAIN, BUT THEIR ANALGESIC EFFECTS ARE UNSATISFACTORY IN PART DUE TO NERVE INJURY-INDUCED DOWNREGULATION OF OPIOID RECEPTORS IN DORSAL ROOT GANGLIA (DRG) NEURONS. HOW NERVE INJURY DRIVES SUCH DOWNREGULATION REMAINS ELUSIVE. DNA METHYLTRANSFERASE (DNMT)-TRIGGERED DNA METHYLATION REPRESSES GENE EXPRESSION. WE SHOW HERE THAT BLOCKING THE NERVE INJURY-INDUCED INCREASE IN DRG DNMT3A (A DE NOVO DNMT) RESCUED THE EXPRESSION OF OPRM1 AND OPRK1 MRNAS AND THEIR RESPECTIVE ENCODING MU-OPIOID RECEPTOR (MOR) AND KAPPA-OPIOID RECEPTOR (KOR) PROTEINS IN THE INJURED DRG. BLOCKING THIS INCREASE ALSO PREVENTED THE NERVE INJURY-INDUCED INCREASE IN DNA METHYLATION IN THE PROMOTER AND 5'-UNTRANSLATED REGION OF THE OPRM1 GENE IN THE INJURED DRG, RESTORED MORPHINE OR LOPERAMIDE (A PERIPHERAL ACTING MOR PREFERRING AGONIST) ANALGESIC EFFECTS, AND ATTENUATED THE DEVELOPMENT OF THEIR ANALGESIC TOLERANCE UNDER NEUROPATHIC PAIN CONDITIONS. MIMICKING THIS INCREASE REDUCED THE EXPRESSION OF OPRM1 AND OPRK1 MRNAS AND THEIR CODING MOR AND KOR IN DRG AND AUGMENTED MOR-GATED NEUROTRANSMITTER RELEASE FROM THE PRIMARY AFFERENTS. MECHANISTICALLY, DNMT3A REGULATION OF OPRM1 GENE EXPRESSION REQUIRED THE METHYL-CPG-BINDING PROTEIN 1, MBD1, AS MBD1 KNOCKOUT RESULTED IN THE DECREASED BINDING OF DNMT3A TO THE OPRM1 GENE PROMOTER AND BLOCKED THE DNMT3A-TRIGGERED REPRESSION OF OPRM1 GENE EXPRESSION IN DRG NEURONS. THESE DATA SUGGEST THAT DNMT3A IS REQUIRED FOR NERVE INJURY-INDUCED AND MBD1-MEDIATED EPIGENETIC SILENCING OF THE MOR AND KOR IN THE INJURED DRG. DNMT3A INHIBITION MAY SERVE AS A PROMISING ADJUVANT THERAPY FOR OPIOID USE IN NEUROPATHIC PAIN MANAGEMENT. 2017 2 2883 62 G9A INHIBITS CREB-TRIGGERED EXPRESSION OF MU OPIOID RECEPTOR IN PRIMARY SENSORY NEURONS FOLLOWING PERIPHERAL NERVE INJURY. NEUROPATHIC PAIN, A DISTRESSING AND DEBILITATING DISORDER, IS STILL POORLY MANAGED IN CLINIC. OPIOIDS, LIKE MORPHINE, REMAIN THE MAINSTAY OF PRESCRIBED MEDICATIONS IN THE TREATMENT OF THIS DISORDER, BUT THEIR ANALGESIC EFFECTS ARE HIGHLY UNSATISFACTORY IN PART DUE TO NERVE INJURY-INDUCED REDUCTION OF OPIOID RECEPTORS IN THE FIRST-ORDER SENSORY NEURONS OF DORSAL ROOT GANGLIA. G9A IS A REPRESSOR OF GENE EXPRESSION. WE FOUND THAT NERVE INJURY-INDUCED INCREASES IN G9A AND ITS CATALYZED REPRESSIVE MARKER H3K9M2 ARE RESPONSIBLE FOR EPIGENETIC SILENCING OF OPRM1, OPRK1, AND OPRD1 GENES IN THE INJURED DORSAL ROOT GANGLIA. BLOCKING THESE INCREASES RESCUED DORSAL ROOT GANGLIA OPRM1, OPRK1, AND OPRD1 GENE EXPRESSION AND MORPHINE OR LOPERAMIDE ANALGESIA AND PREVENTED THE DEVELOPMENT OF MORPHINE OR LOPERAMIDE-INDUCED ANALGESIC TOLERANCE UNDER NEUROPATHIC PAIN CONDITIONS. CONVERSELY, MIMICKING THESE INCREASES REDUCED THE EXPRESSION OF THREE OPIOID RECEPTORS AND PROMOTED THE MU OPIOID RECEPTOR-GATED RELEASE OF PRIMARY AFFERENT NEUROTRANSMITTERS. MECHANISTICALLY, NERVE INJURY-INDUCED INCREASES IN THE BINDING ACTIVITY OF G9A AND H3K9ME2 TO THE OPRM1 GENE WERE ASSOCIATED WITH THE REDUCED BINDING OF CYCLIC AMP RESPONSE ELEMENT BINDING PROTEIN TO THE OPRM1 GENE. THESE FINDINGS SUGGEST THAT G9A PARTICIPATES IN THE NERVE INJURY-INDUCED REDUCTION OF THE OPRM1 GENE LIKELY THROUGH G9A-TRIGGERED BLOCKAGE IN THE ACCESS OF CYCLIC AMP RESPONSE ELEMENT BINDING PROTEIN TO THIS GENE. 2016 3 5574 60 ROLE OF MICRORNA-143 IN NERVE INJURY-INDUCED UPREGULATION OF DNMT3A EXPRESSION IN PRIMARY SENSORY NEURONS. PERIPHERAL NERVE INJURY INCREASED THE EXPRESSION OF THE DNA METHYLTRANSFERASE 3A (DNMT3A) MRNA AND ITS ENCODING DNMT3A PROTEIN IN INJURED DORSAL ROOT GANGLIA (DRG). THIS INCREASE IS CONSIDERED AS AN ENDOGENOUS INSTIGATOR IN NEUROPATHIC PAIN GENESIS THROUGH EPIGENETIC SILENCING OF PAIN-ASSOCIATED GENES (SUCH AS OPRM1) IN INJURED DRG. HOWEVER, HOW DRG DNMT3A IS INCREASED FOLLOWING PERIPHERAL NERVE INJURY IS STILL ELUSIVE. WE REPORTED HERE THAT PERIPHERAL NERVE INJURY CAUSED BY THE FIFTH SPINAL NERVE LIGATION (SNL) DOWNREGULATED MICRORNA (MIR)-143 EXPRESSION IN INJURED DRG. THIS DOWNREGULATION WAS REQUIRED FOR SNL-INDUCED DRG DNMT3A INCREASE AS RESCUING MIR-143 DOWNREGULATION THROUGH MICROINJECTION OF MIR-143 MIMICS INTO INJURED DRG BLOCKED THE SNL-INDUCED INCREASE IN DNMT3A AND RESTORED THE SNL-INDUCED DECREASES IN OPRM1 MRNA AND ITS ENCODING MU OPIOID RECEPTOR (MOR) IN INJURED DRG, IMPAIRED SPINAL CORD CENTRAL SENSITIZATION AND NEUROPATHIC PAIN, AND IMPROVED MORPHINE ANALGESIC EFFECTS FOLLOWING SNL. MIMICKING SNL-INDUCED DRG MIR-143 DOWNREGULATION THROUGH DRG MICROINJECTION OF MIR143 INHIBITORS IN NAIVE RATS INCREASED THE EXPRESSION OF DNMT3A AND REDUCED THE EXPRESSION OF OPRM1 MRNA AND MOR IN INJECTED DRG AND PRODUCED NEUROPATHIC PAIN-LIKE SYMPTOMS. THESE FINDINGS SUGGEST THAT MIR-143 IS A NEGATIVE REGULATOR IN DNMT3A EXPRESSION IN THE DRG UNDER NEUROPATHIC PAIN CONDITIONS AND MAY BE A POTENTIAL TARGET FOR THERAPEUTIC MANAGEMENT OF NEUROPATHIC PAIN. 2017 4 2885 43 G9A PARTICIPATES IN NERVE INJURY-INDUCED KCNA2 DOWNREGULATION IN PRIMARY SENSORY NEURONS. NERVE INJURY-INDUCED DOWNREGULATION OF VOLTAGE-GATED POTASSIUM CHANNEL SUBUNIT KCNA2 IN THE DORSAL ROOT GANGLION (DRG) IS CRITICAL FOR DRG NEURONAL EXCITABILITY AND NEUROPATHIC PAIN GENESIS. HOWEVER, HOW NERVE INJURY CAUSES THIS DOWNREGULATION IS STILL ELUSIVE. EUCHROMATIC HISTONE-LYSINE N-METHYLTRANSFERASE 2, ALSO KNOWN AS G9A, METHYLATES HISTONE H3 ON LYSINE RESIDUE 9 TO PREDOMINANTLY PRODUCE A DYNAMIC HISTONE DIMETHYLATION, RESULTING IN CONDENSED CHROMATIN AND GENE TRANSCRIPTIONAL REPRESSION. WE SHOWED HERE THAT BLOCKING NERVE INJURY-INDUCED INCREASE IN G9A RESCUED KCNA2 MRNA AND PROTEIN EXPRESSION IN THE AXOTOMIZED DRG AND ATTENUATED THE DEVELOPMENT OF NERVE INJURY-INDUCED PAIN HYPERSENSITIVITY. MIMICKING THIS INCREASE DECREASED KCNA2 MRNA AND PROTEIN EXPRESSION, REDUCED KV CURRENT, AND INCREASED EXCITABILITY IN THE DRG NEURONS AND LED TO SPINAL CORD CENTRAL SENSITIZATION AND NEUROPATHIC PAIN-LIKE SYMPTOMS. G9A MRNA IS CO-LOCALIZED WITH KCNA2 MRNA IN THE DRG NEURONS. THESE FINDINGS INDICATE THAT G9A CONTRIBUTES TO NEUROPATHIC PAIN DEVELOPMENT THROUGH EPIGENETIC SILENCING OF KCNA2 IN THE AXOTOMIZED DRG. 2016 5 1166 54 CONTRIBUTION OF DNMT1 TO NEUROPATHIC PAIN GENESIS PARTIALLY THROUGH EPIGENETICALLY REPRESSING KCNA2 IN PRIMARY AFFERENT NEURONS. EXPRESSIONAL CHANGES OF PAIN-ASSOCIATED GENES IN PRIMARY SENSORY NEURONS OF DRG ARE CRITICAL FOR NEUROPATHIC PAIN GENESIS. DNA METHYLTRANSFERASE (DNMT)-TRIGGERED DNA METHYLATION SILENCES GENE EXPRESSION. WE SHOW HERE THAT DNMT1, A CANONICAL MAINTENANCE METHYLTRANSFERASE, ACTS AS THE DE NOVO DNMT AND IS REQUIRED FOR NEUROPATHIC PAIN GENESIS LIKELY THROUGH REPRESSING AT LEAST DRG KCNA2 GENE EXPRESSION IN MALE MICE. PERIPHERAL NERVE INJURY UPREGULATED DNMT1 EXPRESSION IN THE INJURED DRG THROUGH THE TRANSCRIPTION FACTOR CAMP RESPONSE ELEMENT BINDING PROTEIN-TRIGGERED TRANSCRIPTIONAL ACTIVATION OF DNMT1 GENE. BLOCKING THIS UPREGULATION PREVENTED NERVE INJURY-INDUCED DNA METHYLATION WITHIN THE PROMOTER AND 5'-UNTRANSLATED REGION OF KCNA2 GENE, RESCUED KCNA2 EXPRESSION AND TOTAL KV CURRENT, ATTENUATED HYPEREXCITABILITY IN THE INJURED DRG NEURONS, AND ALLEVIATED NERVE INJURY-INDUCED PAIN HYPERSENSITIVITIES. GIVEN THAT KCNA2 IS A KEY PLAYER IN NEUROPATHIC PAIN, OUR FINDINGS SUGGEST THAT DRG DNMT1 MAY BE A POTENTIAL TARGET FOR NEUROPATHIC PAIN MANAGEMENT.SIGNIFICANCE STATEMENT IN THE PRESENT STUDY, WE REPORTED THAT DNMT1, A CANONICAL DNA MAINTENANCE METHYLTRANSFERASE, IS UPREGULATED VIA THE ACTIVATION OF THE TRANSCRIPTION FACTOR CREB IN THE INJURED DRG AFTER PERIPHERAL NERVE INJURY. THIS UPREGULATION WAS RESPONSIBLE FOR NERVE INJURY-INDUCED DE NOVO DNA METHYLATION WITHIN THE PROMOTER AND 5'-UNTRANSLATED REGION OF THE KCNA2 GENE, REDUCTIONS IN KCNA2 EXPRESSION AND KV CURRENT AND INCREASES IN NEURONAL EXCITABILITY IN THE INJURED DRG. SINCE PHARMACOLOGICAL INHIBITION OR GENETIC KNOCKDOWN OF DRG DNMT1 ALLEVIATED NERVE INJURY-INDUCED PAIN HYPERSENSITIVITIES, DRG DNMT1 CONTRIBUTES TO NEUROPATHIC PAIN GENESIS PARTIALLY THROUGH REPRESSION OF DRG KCNA2 GENE EXPRESSION. 2019 6 4098 46 MBD1 CONTRIBUTES TO THE GENESIS OF ACUTE PAIN AND NEUROPATHIC PAIN BY EPIGENETIC SILENCING OF OPRM1 AND KCNA2 GENES IN PRIMARY SENSORY NEURONS. THE TRANSMISSION OF NORMAL SENSORY AND/OR ACUTE NOXIOUS INFORMATION REQUIRES INTACT EXPRESSION OF PAIN-ASSOCIATED GENES WITHIN THE PAIN PATHWAYS OF NERVOUS SYSTEM. EXPRESSIONAL CHANGES OF THESE GENES AFTER PERIPHERAL NERVE INJURY ARE ALSO CRITICAL FOR NEUROPATHIC PAIN INDUCTION AND MAINTENANCE. METHYL-CPG-BINDING DOMAIN PROTEIN 1 (MBD1), AN EPIGENETIC REPRESSOR, REGULATES GENE TRANSCRIPTIONAL ACTIVITY. WE REPORT HERE THAT MBD1 IN THE PRIMARY SENSORY NEURONS OF DRG IS CRITICAL FOR THE GENESIS OF ACUTE PAIN AND NEUROPATHIC PAIN AS DRG MBD1-DEFICIENT MICE EXHIBIT THE REDUCED RESPONSES TO ACUTE MECHANICAL, HEAT, COLD, AND CAPSAICIN STIMULI AND THE BLUNTED NERVE INJURY-INDUCED PAIN HYPERSENSITIVITIES. FURTHERMORE, DRG OVEREXPRESSION OF MBD1 LEADS TO SPONTANEOUS PAIN AND EVOKED PAIN HYPERSENSITIVITIES IN THE WT MICE AND RESTORES ACUTE PAIN SENSITIVITIES IN THE MBD1-DEFICIENT MICE. MECHANISTICALLY, MDB1 REPRESSES OPRM1 AND KCNA2 GENE EXPRESSION BY RECRUITING DNA METHYLTRANSFERASE DNMT3A INTO THESE TWO GENE PROMOTERS IN THE DRG NEURONS. DRG MBD1 IS LIKELY A KEY PLAYER UNDER THE CONDITIONS OF ACUTE PAIN AND NEUROPATHIC PAIN.SIGNIFICANCE STATEMENT IN THE PRESENT STUDY, WE REVEALED THAT THE MICE WITH DEFICIENCY OF METHYL-CPG-BINDING DOMAIN PROTEIN 1 (MBD1), AN EPIGENETIC REPRESSOR, IN THE DRG DISPLAYED THE REDUCED RESPONSES TO ACUTE NOXIOUS STIMULI AND THE BLUNTED NEUROPATHIC PAIN. WE ALSO SHOWED THAT DRG OVEREXPRESSION OF MBD1 PRODUCED THE HYPERSENSITIVITIES TO NOXIOUS STIMULI IN THE WT MICE AND RESCUED ACUTE PAIN SENSITIVITIES IN THE MBD1-DEFICIENT MICE. WE HAVE ALSO PROVIDED THE EVIDENCE THAT MDB1 REPRESSES OPRM1 AND KCNA2 GENE EXPRESSION BY RECRUITING DNA METHYLTRANSFERASE DNMT3A INTO THESE TWO GENE PROMOTERS IN THE DRG NEURONS. DRG MBD1 MAY PARTICIPATE IN THE GENESIS OF ACUTE PAIN AND NEUROPATHIC PAIN LIKELY THROUGH REGULATING DNMT3A-CONTROLLED OPRM1 AND KCNA2 GENE EXPRESSION IN THE DRG NEURONS. 2018 7 3833 27 INVOLVEMENT OF THE DYNORPHIN/KOR SYSTEM ON THE NOCICEPTIVE, EMOTIONAL AND COGNITIVE MANIFESTATIONS OF JOINT PAIN IN MICE. JOINT PAIN IS A MAJOR CLINICAL PROBLEM MAINLY ASSOCIATED TO OSTEOARTHRITIS, AND CHARACTERIZED BY ARTICULAR CARTILAGE DEGRADATION RESULTING IN A COMPLEX CHRONIC PAIN STATE THAT INCLUDES NOCICEPTIVE, EMOTIONAL AND COGNITIVE MANIFESTATIONS. MEMORY IMPAIRMENT, DEPRESSIVE- AND ANXIETY-LIKE SYMPTOMS HAVE BEEN REPORTED TO BE ASSOCIATED WITH CHRONIC PAIN, LEADING TO A DECREASE OF LIFE QUALITY. IN THIS STUDY, WE EVALUATED THE INVOLVEMENT OF THE ENDOGENOUS DYNORPHIN/KAPPA OPIOID RECEPTOR (KOR) SYSTEM ON THE NOCICEPTIVE, EMOTIONAL, COGNITIVE, NEUROCHEMICAL AND EPIGENETIC MANIFESTATIONS OF JOINT PAIN. THE MURINE MODEL OF MONOSODIUM IODOACETATE (MIA) WAS USED TO INDUCE JOINT PAIN IN KNOCKOUT MICE FOR KOR (KOR-KO), PRODYNORPHIN (PDYN-KO) AND THEIR WILD-TYPE (WT) LITTERMATES. KOR-KO AND PDYN-KO MICE DEVELOPED MECHANICAL ALLODYNIA AFTER INTRA-ARTICULAR INJECTION OF MIA. THIS ALLODYNIA WAS SIGNIFICANTLY INCREASED IN BOTH KOR-KO AND PDYN-KO WHEN COMPARED TO WT MICE. ACCORDINGLY, BOTH MUTANTS SHOWED INCREASED MICROGLIAL ACTIVATION ON THE LUMBAR SECTION OF THE SPINAL CORD AFTER MIA. THE EMOTIONAL RESPONSES WERE EVALUATED BY MEASURING ANXIETY-LIKE BEHAVIOUR IN THE ELEVATED PLUS MAZE AND ANHEDONIA AS DEPRESSIVE-LIKE BEHAVIOUR, AND COGNITIVE ALTERATIONS IN THE OBJECT RECOGNITION PARADIGM. EMOTIONAL AND COGNITIVE IMPAIRMENTS AFTER JOINT PAIN WERE DIFFERENTLY MODIFIED IN KOR-KO AND PDYN-KO MICE. ALTERATIONS OF CORTICOTROPIN-RELEASING FACTOR (CRF) ON THE AMYGDALA AND HIPPOCAMPUS AND DOWN REGULATION OF HISTONE 3 ACETYLATION ON THE AMYGDALA SUGGEST A POSSIBLE MECHANISM TO EXPLAIN THESE EMOTIONAL AND COGNITIVE MANIFESTATIONS. OUR RESULTS REVEAL A SPECIFIC INVOLVEMENT OF THE DYNORPHIN/KOR SYSTEM ON JOINT PAIN MANIFESTATIONS THAT ARE USUALLY ASSOCIATED TO OSTEOARTHRITIS. 2017 8 4615 50 NERVE INJURY DIMINISHES OPIOID ANALGESIA THROUGH LYSINE METHYLTRANSFERASE-MEDIATED TRANSCRIPTIONAL REPRESSION OF MU-OPIOID RECEPTORS IN PRIMARY SENSORY NEURONS. THE MU-OPIOID RECEPTOR (MOR, ENCODED BY OPRM1) AGONISTS ARE THE MAINSTAY ANALGESICS FOR TREATING MODERATE TO SEVERE PAIN. NERVE INJURY CAUSES DOWN-REGULATION OF MORS IN THE DORSAL ROOT GANGLION (DRG) AND DIMINISHES THE OPIOID EFFECT ON NEUROPATHIC PAIN. HOWEVER, THE EPIGENETIC MECHANISMS UNDERLYING THE DIMINISHED MOR EXPRESSION CAUSED BY NERVE INJURY ARE NOT CLEAR. G9A (ENCODED BY EHMT2), A HISTONE 3 AT LYSINE 9 METHYLTRANSFERASE, IS A KEY CHROMATIN REGULATOR RESPONSIBLE FOR GENE SILENCING. IN THIS STUDY, WE DETERMINED THE ROLE OF G9A IN DIMINISHED MOR EXPRESSION AND OPIOID ANALGESIC EFFECTS IN ANIMAL MODELS OF NEUROPATHIC PAIN. WE FOUND THAT NERVE INJURY IN RATS INDUCED A LONG-LASTING REDUCTION IN THE EXPRESSION LEVEL OF MORS IN THE DRG BUT NOT IN THE SPINAL CORD. NERVE INJURY CONSISTENTLY INCREASED THE ENRICHMENT OF THE G9A PRODUCT HISTONE 3 AT LYSINE 9 DIMETHYLATION IN THE PROMOTER OF OPRM1 IN THE DRG. G9A INHIBITION OR SIRNA KNOCKDOWN FULLY REVERSED MOR EXPRESSION IN THE INJURED DRG AND POTENTIATED THE MORPHINE EFFECT ON PAIN HYPERSENSITIVITY INDUCED BY NERVE INJURY. IN MICE LACKING EHMT2 IN DRG NEURONS, NERVE INJURY FAILED TO REDUCE THE EXPRESSION LEVEL OF MORS AND THE MORPHINE EFFECT. IN ADDITION, G9A INHIBITION OR EHMT2 KNOCKOUT IN DRG NEURONS NORMALIZED NERVE INJURY-INDUCED REDUCTION IN THE INHIBITORY EFFECT OF THE OPIOID ON SYNAPTIC GLUTAMATE RELEASE FROM PRIMARY AFFERENT NERVES. OUR FINDINGS INDICATE THAT G9A CONTRIBUTES CRITICALLY TO TRANSCRIPTIONAL REPRESSION OF MORS IN PRIMARY SENSORY NEURONS IN NEUROPATHIC PAIN. G9A INHIBITORS MAY BE USED TO ENHANCE THE OPIOID ANALGESIC EFFECT IN THE TREATMENT OF CHRONIC NEUROPATHIC PAIN. 2016 9 4160 60 MECP2 EPIGENETIC SILENCING OF OPRM1 GENE IN PRIMARY SENSORY NEURONS UNDER NEUROPATHIC PAIN CONDITIONS. OPIOIDS ARE THE LAST OPTION FOR THE PHARMACOLOGICAL TREATMENT OF NEUROPATHIC PAIN, BUT THEIR ANTINOCICEPTIVE EFFECTS ARE LIMITED. DECREASED MU OPIOID RECEPTOR (MOR) EXPRESSION IN THE PERIPHERAL NERVOUS SYSTEM MAY CONTRIBUTE TO THIS. HERE, WE SHOWED THAT NERVE INJURY INDUCED HYPERMETHYLATION OF THE OPRM1 GENE PROMOTER AND AN INCREASED EXPRESSION OF METHYL-CPG BINDING PROTEIN 2 (MECP2) IN INJURED DORSAL ROOT GANGLION (DRG). THE DOWNREGULATION OF MOR IN THE DRG IS CLOSELY RELATED TO THE AUGMENTATION OF MECP2, AN EPIGENETIC REPRESSOR, WHICH COULD RECRUIT HDAC1 AND BIND TO THE METHYLATED REGIONS OF THE OPRM1 GENE PROMOTER. MECP2 KNOCKDOWN RESTORED THE EXPRESSION OF MOR IN INJURED DRG AND ENHANCED THE ANALGESIC EFFECT OF MORPHINE, WHILE THE MIMICKING OF THIS INCREASE VIA THE INTRATHECAL INFUSION OF VIRAL VECTOR-MEDIATED MECP2 WAS SUFFICIENT TO REDUCE MOR IN THE DRG. MOREOVER, HDAC1 INHIBITION WITH SUBEROYLANILIDE HYDROXAMIC ACID, AN HDAC INHIBITOR, ALSO PREVENTED MOR REDUCTION IN THE DRG OF NEUROPATHIC PAIN MICE, CONTRIBUTING TO THE AUGMENTATION OF MORPHINE ANALGESIA EFFECTS. MECHANISTICALLY, UPREGULATED MECP2 PROMOTES THE BINDING OF A HIGH LEVEL OF HDCA1 TO HYPERMETHYLATED REGIONS OF THE OPRM1 GENE PROMOTER, REDUCES THE ACETYLATION OF HISTONE H3 (ACH3) LEVELS OF THE OPRM1 GENE PROMOTER, AND ATTENUATES OPRM1 TRANSCRIPTION IN INJURED DRG. THUS, UPREGULATED MECP2 AND HDAC1 IN OPRM1 GENE PROMOTER SITES, NEGATIVELY REGULATES MOR EXPRESSION IN INJURED DRG, MITIGATING THE ANALGESIC EFFECT OF THE OPIOIDS. TARGETING MECP2/HDAC1 MAY THUS PROVIDE A NEW SOLUTION FOR IMPROVING THE THERAPEUTIC EFFECT OF OPIOIDS IN A CLINICAL SETTING. 2021 10 2407 35 EPIGENETIC RESTORATION OF VOLTAGE-GATED POTASSIUM CHANNEL KV1.2 ALLEVIATES NERVE INJURY-INDUCED NEUROPATHIC PAIN. VOLTAGE-GATED POTASSIUM CHANNELS (KV) ARE IMPORTANT REGULATORS OF NEURONAL EXCITABILITY FOR ITS ROLE OF REGULATING RESTING MEMBRANE POTENTIAL AND REPOLARIZATION. RECENT STUDIES SHOW THAT KV CHANNELS PARTICIPATE IN NEUROPATHIC PAIN, BUT THE DETAILED UNDERLYING MECHANISMS ARE FAR FROM BEING CLEAR. IN THIS STUDY, WE USED SIRNA, MIR-137 AGOMIR, AND ANTAGOMIR TO REGULATE THE EXPRESSION OF KV1.2 IN SPINAL CORD AND DORSAL ROOT GANGLIA (DRG) OF NAIVE AND CHRONIC CONSTRICTION INJURY (CCI) RATS. KV CURRENTS AND NEURON EXCITABILITY IN DRG NEURONS WERE EXAMINED BY PATCH-CLAMP WHOLE-CELL RECORDING TO VERIFY THE CHANGE IN KV1.2 FUNCTION. THE RESULTS SHOWED THAT KV1.2 WAS DOWN-REGULATED IN DRG AND SPINAL DORSAL HORN (SDH) BY CCI. KNOCKDOWN OF KV1.2 BY INTRATHECALLY INJECTING KCNA2 SIRNA INDUCED SIGNIFICANT MECHANICAL AND THERMAL HYPERSENSITIVITY IN NAIVE RATS. CONCOMITANT WITH THE DOWN-REGULATION OF KV1.2 WAS AN INCREASE IN THE EXPRESSION OF THE MIR-137. THE TARGETING AND REGULATING OF MIR-137 ON KCNA2 WAS VERIFIED BY DUAL-LUCIFERASE REPORTER SYSTEM AND INTRATHECAL INJECTING MIR-137 AGOMIR. FURTHERMORE, RESCUING THE EXPRESSION OF KV1.2 IN CCI RATS, ACHIEVED THROUGH INHIBITING MIR-137, RESTORED THE ABNORMAL KV CURRENTS AND EXCITABILITY IN DRG NEURONS, AND ALLEVIATED MECHANICAL ALLODYNIA AND THERMAL HYPERALGESIA. THESE RESULTS INDICATE THAT THE MIR-137-MEDIATED KV1.2 IMPAIRMENT IS A CRUCIAL ETIOPATHOGENESIS FOR THE NERVE INJURY-INDUCED NEUROPATHIC PAIN AND CAN BE A NOVEL POTENTIAL THERAPEUTIC TARGET FOR NEUROPATHIC PAIN MANAGEMENT. 2021 11 6424 46 THE TRANSCRIPTION FACTOR C/EBPBETA IN THE DORSAL ROOT GANGLION CONTRIBUTES TO PERIPHERAL NERVE TRAUMA-INDUCED NOCICEPTIVE HYPERSENSITIVITY. CHANGES IN GENE TRANSCRIPTION IN THE DORSAL ROOT GANGLION (DRG) AFTER NERVE TRAUMA CONTRIBUTE TO THE GENESIS OF NEUROPATHIC PAIN. WE REPORT THAT PERIPHERAL NERVE TRAUMA CAUSED BY CHRONIC CONSTRICTION INJURY (CCI) INCREASED THE ABUNDANCE OF THE TRANSCRIPTION FACTOR C/EBPBETA (CCAAT/ENHANCER BINDING PROTEIN BETA) IN THE DRG. BLOCKING THIS INCREASE MITIGATED THE DEVELOPMENT AND MAINTENANCE OF CCI-INDUCED MECHANICAL, THERMAL, AND COLD PAIN HYPERSENSITIVITIES WITHOUT AFFECTING BASAL RESPONSES TO ACUTE PAIN AND LOCOMOTOR ACTIVITY. CONVERSELY, MIMICKING THIS INCREASE PRODUCED HYPERSENSITIVITY TO MECHANICAL, THERMAL, OR COLD PAIN. IN THE IPSILATERAL DRG, C/EBPBETA PROMOTED A DECREASE IN THE ABUNDANCE OF THE VOLTAGE-GATED POTASSIUM CHANNEL SUBUNIT KV1.2 AND MU OPIOID RECEPTOR (MOR) AT THE MRNA AND PROTEIN LEVELS, WHICH WOULD BE PREDICTED TO INCREASE EXCITABILITY IN THE IPSILATERAL DRG NEURONS AND REDUCE THE EFFICACY OF MORPHINE ANALGESIA. THESE EFFECTS REQUIRED C/EPBBETA-MEDIATED TRANSCRIPTIONAL ACTIVATION OF EHMT2 (EUCHROMATIC HISTONE-LYSINE N-METHYLTRANSFERASE 2), WHICH ENCODES G9A, AN EPIGENETIC SILENCER OF THE GENES ENCODING KV1.2 AND MOR. BLOCKING THE INCREASE IN C/EBPBETA IN THE DRG IMPROVED MORPHINE ANALGESIA AFTER CCI. THESE RESULTS SUGGEST THAT C/EBPBETA IS AN ENDOGENOUS INITIATOR OF NEUROPATHIC PAIN AND COULD BE A POTENTIAL TARGET FOR THE PREVENTION AND TREATMENT OF THIS DISORDER. 2017 12 2363 37 EPIGENETIC REGULATION OF SPINAL CORD GENE EXPRESSION CONTRIBUTES TO ENHANCED POSTOPERATIVE PAIN AND ANALGESIC TOLERANCE SUBSEQUENT TO CONTINUOUS OPIOID EXPOSURE. BACKGROUND: OPIOIDS HAVE BECOME THE MAINSTAY FOR TREATMENT OF MODERATE TO SEVERE PAIN AND ARE COMMONLY USED TO TREAT SURGICAL PAIN. WHILE OPIOID ADMINISTRATION HAS BEEN SHOWN TO CAUSE OPIOID-INDUCED HYPERALGESIA AND TOLERANCE, INTERACTIONS BETWEEN OPIOID ADMINISTRATION AND SURGERY WITH RESPECT TO THESE PROBLEMATIC ADAPTATIONS HAVE SCARCELY BEEN ADDRESSED. ACCUMULATING EVIDENCE SUGGESTS OPIOIDS AND NOCICEPTIVE SIGNALING MAY CONVERGE ON EPIGENETIC MECHANISMS IN SPINAL CORD TO ENHANCE OR PROLONG NEUROPLASTIC CHANGES. EPIGENETIC REGULATION OF BDNF (BRAIN-DERIVED NEUROTROPHIC FACTOR) AND PDYN (PRODYNORPHIN) GENES MAY BE INVOLVED. RESULTS: FOUR DAYS OF ASCENDING DOSES OF MORPHINE TREATMENT CAUSED OPIOID-INDUCED HYPERALGESIA AND REDUCED OPIOID ANALGESIC EFFICACY IN MICE. BOTH OPIOID-INDUCED HYPERALGESIA AND THE REDUCED OPIOID ANALGESIC EFFICACY WERE ENHANCED IN MICE THAT RECEIVED HINDPAW INCISIONS. THE EXPRESSION OF BDNF AND PDYN (QPCR) WAS INCREASED AFTER MORPHINE TREATMENT AND INCISION. CHROMATIN IMMUNOPRECIPITATION ASSAYS DEMONSTRATED THAT THE PDYN AND BDNF PROMOTERS WERE MORE STRONGLY ASSOCIATED WITH ACETYLATED H3K9 AFTER MORPHINE PLUS INCISION THAN IN THE MORPHINE OR INCISION ALONE GROUPS. SELECTIVE TROPOMYOSIN-RELATED KINASE B (ANA-12) AND KAPPA-OPIOID RECEPTOR (NOR-BINALTORPHIMINE) ANTAGONISTS WERE ADMINISTERED INTRATHECALLY, BOTH REDUCED HYPERALGESIA ONE OR THREE DAYS AFTER SURGERY. ADMINISTRATION OF ANA-12 OR NOR-BINALTORPHIMINE ATTENUATED THE DECREASED MORPHINE ANALGESIC EFFICACY ON DAY 1, BUT ONLY NOR-BINALTORPHIMINE WAS EFFECTIVE ON DAY 3 AFTER INCISION IN OPIOID-EXPOSED GROUP. COADMINISTRATION OF HISTONE ACETYLTRANSFERASE INHIBITOR ANACARDIC ACID DAILY WITH MORPHINE BLOCKED THE DEVELOPMENT OF OPIOID-INDUCED HYPERALGESIA AND ATTENUATED INCISION-ENHANCED HYPERALGESIA IN MORPHINE-TREATED MICE. ANACARDIC ACID HAD SIMILAR EFFECTS ON ANALGESIC TOLERANCE, SHOWING THE INVOLVEMENT OF HISTONE ACETYLATION IN THE INTERACTIONS DETECTED. CONCLUSIONS: SPINAL EPIGENETIC CHANGES INVOLVING BDNF AND PDYN MAY CONTRIBUTE TO THE ENHANCED POSTOPERATIVE NOCICEPTIVE SENSITIZATION AND ANALGESIC TOLERANCE OBSERVED AFTER CONTINUOUS OPIOID EXPOSURE. TREATMENTS BLOCKING THE EPIGENETICALLY MEDIATED UP-REGULATION OF THESE GENES OR ADMINISTRATION OF TRKB OR KAPPA-OPIOID RECEPTOR ANTAGONISTS MAY IMPROVE THE CLINICAL UTILITY OF OPIOIDS, PARTICULARLY AFTER SURGERY. 2016 13 69 35 A MEDIAL PREFRONTAL CORTEX-NUCLEUS ACUMENS CORTICOTROPIN-RELEASING FACTOR CIRCUITRY FOR NEUROPATHIC PAIN-INCREASED SUSCEPTIBILITY TO OPIOID REWARD. RECENT STUDIES HAVE SHOWN THAT PERSISTENT PAIN FACILITATES THE RESPONSE TO MORPHINE REWARD. HOWEVER, THE CIRCUIT MECHANISM UNDERLYING THIS PROCESS REMAINS AMBIGUOUS. IN THIS STUDY, USING CHRONIC CONSTRICTION INJURY (CCI) OF THE SCIATIC NERVE IN MICE, WE FOUND THAT PERSISTENT NEUROPATHIC PAIN REDUCED THE MINIMUM NUMBER OF MORPHINE CONDITIONING SESSIONS REQUIRED TO INDUCE CONDITIONED PLACE PREFERENCE (CPP) BEHAVIOR. THIS DOSE OF MORPHINE HAD NO EFFECT ON THE PAIN THRESHOLD. IN THE MEDIAL PREFRONTAL CORTEX (MPFC), WHICH IS INVOLVED IN BOTH PAIN AND EMOTION PROCESSING, CORTICOTROPIN-RELEASING FACTOR (CRF) EXPRESSING NEURONAL ACTIVITY WAS INCREASED IN CCI MICE. CHEMOGENETIC INHIBITION OF MPFC CRF NEURONS REVERSED CCI-INDUCED MORPHINE CPP FACILITATION. FURTHERMORE, THE NUCLEUS ACUMENS (NAC) RECEIVED MPFC CRF FUNCTIONAL PROJECTIONS THAT EXERTED EXCITATORY EFFECTS ON NAC NEURONS. OPTOGENETIC INHIBITION OF MPCF NEURONAL TERMINALS OR LOCAL INFUSION OF THE CRF RECEPTOR 1 (CRFR1) ANTAGONIST IN THE NAC RESTORED THE EFFECTS OF NEUROPATHIC PAIN ON MORPHINE-INDUCED CPP BEHAVIOR, BUT NOT IN NORMAL MICE. ON A MOLECULAR LEVEL, IN CCI MICE, CRFR1 PROTEIN EXPRESSION WAS INCREASED IN THE NAC BY A HISTONE DIMETHYLTRANSFERASE G9A-MEDIATED EPIGENETIC MECHANISM. LOCAL G9A KNOCKDOWN INCREASED THE EXPRESSION OF CRFR1 AND MIMICKED CCI-INDUCED HYPERSENSITIVITY TO ACQUIRING MORPHINE CPP. TAKEN TOGETHER, THESE FINDINGS DEMONSTRATE A PREVIOUSLY UNKNOWN AND SPECIFIC MPFC CRF ENGAGEMENT OF NAC NEURONAL CIRCUITS, THE SENSITIZATION OF WHICH FACILITATES BEHAVIORAL RESPONSES TO MORPHINE REWARD IN NEUROPATHIC PAIN STATES VIA CRFR1S. 2018 14 1654 43 DORSAL ROOT GANGLIA COACTIVATOR-ASSOCIATED ARGININE METHYLTRANSFERASE 1 CONTRIBUTES TO PERIPHERAL NERVE INJURY-INDUCED PAIN HYPERSENSITIVITIES. NEUROPATHIC PAIN IS ASSOCIATED WITH GENE EXPRESSION CHANGES WITHIN THE DORSAL ROOT GANGLION (DRG) AFTER PERIPHERAL NERVE INJURY, WHICH INVOLVES EPIGENETIC MECHANISMS. COACTIVATOR-ASSOCIATED ARGININE METHYLTRANSFERASE 1 (CARM1), AN EPIGENETIC ACTIVATOR, REGULATES GENE TRANSCRIPTIONAL ACTIVITY BY PROTEIN POSTTRANSLATIONAL MODIFICATIONS. HOWEVER, WHETHER CARM1 PLAYS AN ESSENTIAL ROLE IN THE DEVELOPMENT AND MAINTENANCE OF NEUROPATHIC PAIN IS UNKNOWN. WE REPORT HERE THAT PERIPHERAL NERVE INJURY INDUCED THE UPREGULATION OF THE MRNA AND PROTEIN EXPRESSION OF CARM1 IN THE INJURED DRG, AND BLOCKING ITS EXPRESSION THROUGH SMALL INTERFERING RNA (SIRNA) IN THE INJURED DRG ATTENUATED THE DEVELOPMENT AND MAINTENANCE OF NEUROPATHIC PAIN. FURTHERMORE, PHARMACOLOGICAL INHIBITION OF CARM1 MITIGATED PERIPHERAL NERVE INJURY-INDUCED MECHANICAL ALLODYNIA AND THERMAL HYPERALGESIA. GIVEN THAT CARM1 INHIBITION OR KNOCKDOWN ATTENUATED THE INDUCTION AND MAINTENANCE OF NEUROPATHIC PAIN AFTER PERIPHERAL NERVE INJURY, OUR FINDINGS SUGGEST THAT CARM1 MAY SERVE AS A PROMISING THERAPEUTIC TARGET FOR NEUROPATHIC PAIN TREATMENT IN CLINICAL APPLICATIONS. 2018 15 2751 31 EXPRESSION OF ACETYL-HISTONE H3 AND ACETYL-HISTONE H4 IN DORSAL ROOT GANGLION AND SPINAL DORSAL HORN IN RAT CHRONIC PAIN MODELS. AIMS: HISTONE ACETYLATION AND DEACETYLATION ARE TWO HISTONE POSTTRANSLATIONAL MODIFICATIONS THAT ARE USUALLY CONTROLLED BY HISTONE ACETYLTRANSFERASES (HATS) AND HISTONE DEACETYLASES (HDACS). ALTHOUGH HATS OR HDACS INHIBITORS COULD RELIEVE PAIN HYPERSENSITIVITIES IN CHRONIC PAIN ANIMAL MODELS, IT IS NOT CLEAR ON THE EXPRESSION OF GLOBAL HISTONE ACETYLATION IN THE DORSAL ROOT GANGLION (DRG) OR SPINAL DORSAL HORN IN CHRONIC PAIN CONDITIONS. MAIN METHODS: A SPINAL NERVE LIGATION (SNL)-INDUCED NEUROPATHIC PAIN MODEL AND A COMPLETE FREUND'S ADJUVANT (CFA)-INDUCED INFLAMMATORY PAIN MODEL IN RATS WERE USED TO EXAMINE THE EXPRESSION OF TOTAL ACETYL-HISTONE H3 (ACH3) AND TOTAL ACETYL-HISTONE H4 (ACH4) BY IMMUNOFLUORESCENCE OR WESTERN BLOT. KEY FINDINGS: ACH3 AND ACH4 NOT ONLY LOCALIZED IN NEURONAL NUCLEI, BUT ALSO IN NUCLEI OF GLIAL CELLS IN THE DRG. UNILATERAL SNL INDUCED THE INCREASE OF ACH3 AND ACH4 EXPRESSION IN THE INJURED LUMBAR 5 (L5) DRG, BUT NOT IN THE UNINJURED L5 DRG OR THE SPINAL DORSAL HORN, WHILE UNILATERAL INTRAPLANTAR INJECTION OF CFA INCREASED ACH3 AND ACH4 EXPRESSION IN THE IPSILATERAL L4/5 SPINAL DORSAL HORN, BUT NOT IN THE L4/5 DRG. SIGNIFICANCE: THESE RESULTS PROVIDE MORPHOLOGICAL EVIDENCE FOR GLOBAL HISTONE ACETYLATION EXPRESSION IN THE DRG AND SPINAL CORD AND INDICATE THE DIFFERENTIAL EXPRESSION IN THE DRG AND SPINAL DORSAL HORN IN DIFFERENT CHRONIC PAIN MODELS. MORE PRECISE EPIGENETIC MECHANISMS OF HISTONE ACETYLATION ON THE TARGET GENES NEED TO BE REVEALED. 2018 16 1167 47 CONTRIBUTION OF DORSAL ROOT GANGLION OCTAMER TRANSCRIPTION FACTOR 1 TO NEUROPATHIC PAIN AFTER PERIPHERAL NERVE INJURY. NEUROPATHIC PAIN GENESIS IS RELATED TO GENE ALTERATIONS IN THE DORSAL ROOT GANGLION (DRG) AFTER PERIPHERAL NERVE INJURY. TRANSCRIPTION FACTORS CONTROL GENE EXPRESSION. IN THIS STUDY, WE INVESTIGATED WHETHER OCTAMER TRANSCRIPTION FACTOR 1 (OCT1), A TRANSCRIPTION FACTOR, CONTRIBUTED TO NEUROPATHIC PAIN CAUSED BY CHRONIC CONSTRICTION INJURY (CCI) OF THE SCIATIC NERVE. CHRONIC CONSTRICTION INJURY PRODUCED A TIME-DEPENDENT INCREASE IN THE LEVEL OF OCT1 PROTEIN IN THE IPSILATERAL L4/5 DRG, BUT NOT IN THE SPINAL CORD. BLOCKING THIS INCREASE THROUGH MICROINJECTION OF OCT1 SIRNA INTO THE IPSILATERAL L4/5 DRG ATTENUATED THE INITIATION AND MAINTENANCE OF CCI-INDUCED MECHANICAL ALLODYNIA, HEAT HYPERALGESIA, AND COLD ALLODYNIA AND IMPROVED MORPHINE ANALGESIA AFTER CCI, WITHOUT AFFECTING BASAL RESPONSES TO ACUTE MECHANICAL, HEAT, AND COLD STIMULI AS WELL AS LOCOMOTOR FUNCTIONS. MIMICKING THIS INCREASE THROUGH MICROINJECTION OF RECOMBINANT ADENO-ASSOCIATED VIRUS 5 HARBORING FULL-LENGTH OCT1 INTO THE UNILATERAL L4/5 DRG LED TO MARKED MECHANICAL ALLODYNIA, HEAT HYPERALGESIA, AND COLD ALLODYNIA IN NAIVE RATS. MECHANISTICALLY, OCT1 PARTICIPATED IN CCI-INDUCED INCREASES IN DNMT3A MRNA AND ITS PROTEIN AND DNMT3A-MEDIATED DECREASES IN OPRM1 AND KCNA2 MRNAS AND THEIR PROTEINS IN THE INJURED DRG. THESE FINDINGS INDICATE THAT OCT1 MAY PARTICIPATE IN NEUROPATHIC PAIN AT LEAST IN PART BY TRANSCRIPTIONALLY ACTIVATING DNMT3A AND SUBSEQUENTLY EPIGENETIC SILENCING OF OPRM1 AND KCAN2 IN THE DRG. OCT1 MAY SERVE AS A POTENTIAL TARGET FOR THERAPEUTIC TREATMENTS AGAINST NEUROPATHIC PAIN. 2019 17 1630 45 DNMT3A CONTRIBUTES TO THE DEVELOPMENT AND MAINTENANCE OF BONE CANCER PAIN BY SILENCING KV1.2 EXPRESSION IN SPINAL CORD DORSAL HORN. METASTATIC BONE TUMOR-INDUCED CHANGES IN GENE TRANSCRIPTION AND TRANSLATION IN PAIN-RELATED REGIONS OF THE NERVOUS SYSTEM MAY PARTICIPATE IN THE DEVELOPMENT AND MAINTENANCE OF BONE CANCER PAIN. EPIGENETIC MODIFICATIONS INCLUDING DNA METHYLATION REGULATE GENE TRANSCRIPTION. HERE, WE REPORT THAT INTRATHECAL INJECTION OF DECITABINE, A DNA METHYLTRANSFERASE (DNMT) INHIBITOR, DOSE DEPENDENTLY ATTENUATED THE DEVELOPMENT AND MAINTENANCE OF BONE CANCER PAIN INDUCED BY INJECTING PROSTATE CANCER CELLS INTO THE TIBIA. THE LEVEL OF THE DE NOVO DNMT3A, BUT NOT DNMT3B, TIME DEPENDENTLY INCREASED IN THE IPSILATERAL L4/5 DORSAL HORN (NOT L4/5 DORSAL ROOT GANGLION) AFTER PROSTATE CANCER CELLS INJECTION. BLOCKING THIS INCREASE THROUGH MICROINJECTION OF RECOMBINANT ADENO-ASSOCIATED VIRUS 5 (AAV5) EXPRESSING DNMT3A SHRNA INTO DORSAL HORN RESCUED PROSTATE CANCER CELLS-INDUCED DOWNREGULATION OF DORSAL HORN KV1.2 EXPRESSION AND IMPAIRED PROSTATE CANCER CELLS-INDUCED PAIN HYPERSENSITIVITY. IN TURN, MIMICKING THIS INCREASE THROUGH MICROINJECTION OF AAV5 EXPRESSING FULL-LENGTH DNMT3A INTO DORSAL HORN REDUCED DORSAL HORN KV1.2 EXPRESSION AND PRODUCED PAIN HYPERSENSITIVITY IN THE ABSENCE OF PROSTATE CANCER CELLS INJECTION. ADMINISTRATION OF NEITHER DECITABINE NOR VIRUS AFFECTED LOCOMOTOR FUNCTION AND ACUTE RESPONSES TO MECHANICAL, THERMAL, OR COLD STIMULI. GIVEN THAT DNMT3A MRNA IS CO-EXPRESSED WITH KCNA2 MRNA (ENCODING KV1.2) IN INDIVIDUAL DORSAL HORN NEURONS, OUR FINDINGS SUGGEST THAT INCREASED DORSAL HORN DNMT3A CONTRIBUTES TO BONE CANCER PAIN THROUGH SILENCING DORSAL HORN KV1.2 EXPRESSION. DNMT3A MAY REPRESENT A POTENTIAL NEW TARGET FOR CANCER PAIN MANAGEMENT. 2017 18 4172 33 MELATONIN IMPEDES TET1-DEPENDENT MGLUR5 PROMOTER DEMETHYLATION TO RELIEVE PAIN. MELATONIN (N-ACETYL-5-METHOXYTRYPTAMINE)/MT2 RECEPTOR-DEPENDENT EPIGENETIC MODIFICATION REPRESENTS A NOVEL PATHWAY IN THE TREATMENT OF NEUROPATHIC PAIN. BECAUSE SPINAL TEN-ELEVEN TRANSLOCATION METHYLCYTOSINE DIOXYGENASE 1 (TET1)-DEPENDENT EPIGENETIC DEMETHYLATION HAS RECENTLY BEEN LINKED TO PAIN HYPERSENSITIVITY, WE HYPOTHESIZED THAT MELATONIN/MT2-DEPENDENT ANALGESIA INVOLVES SPINAL TET1-DEPENDENT DEMETHYLATION. HERE, WE SHOWED THAT SPINAL TET1 GENE TRANSFER BY INTRATHECAL DELIVERY OF TET1-ENCODING VECTORS TO NAIVE RATS PRODUCED PROFOUND AND LONG-LASTING NOCICEPTIVE HYPERSENSITIVITY. IN ADDITION, ENHANCED TET1 EXPRESSION, TET1-METABOTROPIC GLUTAMATE RECEPTOR SUBTYPE 5 (MGLUR5) PROMOTER COUPLING, DEMETHYLATION AT THE MGLUR5 PROMOTER, AND MGLUR5 EXPRESSION IN DORSAL HORN NEURONS WERE OBSERVED. RATS SUBJECTED TO SPINAL NERVE LIGATION AND INTRAPLANTAR COMPLETE FREUND'S ADJUVANT INJECTION DISPLAYED TACTILE ALLODYNIA AND BEHAVIORAL HYPERALGESIA ASSOCIATED WITH SIMILAR CHANGES IN THE DORSAL HORN. NOTABLY, INTRATHECAL MELATONIN INJECTION REVERSED THE PROTEIN EXPRESSION, PROTEIN-PROMOTER COUPLING, PROMOTER DEMETHYLATION, AND PAIN HYPERSENSITIVITY INDUCED BY TET1 GENE TRANSFER, SPINAL NERVE LIGATION, AND INTRAPLANTAR COMPLETE FREUND'S ADJUVANT INJECTION. ALL THE EFFECTS CAUSED BY MELATONIN WERE BLOCKED BY PRETREATMENT WITH A MT2 RECEPTOR-SELECTIVE ANTAGONIST. IN CONCLUSION, MELATONIN RELIEVES PAIN BY IMPEDING TET1-DEPENDENT DEMETHYLATION OF MGLUR5 IN DORSAL HORN NEURONS THROUGH THE MT2 RECEPTOR. OUR FINDINGS LINK MELATONIN/MT2 SIGNALING TO TET1-DEPENDENT EPIGENETIC DEMETHYLATION OF NOCICEPTIVE GENES FOR THE FIRST TIME AND SUGGEST MELATONIN AS A PROMISING THERAPY FOR THE TREATMENT OF PAIN. 2017 19 2272 37 EPIGENETIC REDUCTION OF MIR-214-3P UPREGULATES ASTROCYTIC COLONY-STIMULATING FACTOR-1 AND CONTRIBUTES TO NEUROPATHIC PAIN INDUCED BY NERVE INJURY. EMERGING EVIDENCE HAS INDICATED THAT COLONY-STIMULATING FACTOR-1 (CSF1) MODULATES NEUROINFLAMMATION IN THE CENTRAL NERVOUS SYSTEM AND THE DEVELOPMENT OF NEUROPATHIC PAIN, WHILE THE UNDERLYING MECHANISM REMAINS UNKNOWN. HERE, WE IDENTIFIED THE INCREASED EXPRESSION OF CSF1 DERIVED FROM ACTIVATED ASTROCYTES IN THE IPSILATERAL DORSAL HORN IN RATS WITH SPINAL NERVE LIGATION (SNL). SUPPRESSION OF CSF1 EXPRESSION ALLEVIATED NEUROINFLAMMATION, NEURONAL HYPEREXCITABILITY, AND GLUTAMATERGIC RECEPTOR SUBUNIT UPREGULATION IN THE DORSAL HORN AND IMPROVED SNL-INDUCED PAIN BEHAVIOR. WE ALSO FOUND REDUCED MIR-214-3P EXPRESSION IN THE IPSILATERAL DORSAL HORN FOLLOWING AN SNL PROCEDURE; MIR-214-3P DIRECTLY BOUND TO THE 3'-UTR OF CSF1 MRNA AND NEGATIVELY REGULATED CSF1 EXPRESSION. INTRATHECAL DELIVERY OF MIR-214-3P MIMIC REVERSED THE ENHANCED EXPRESSION OF CSF1 AND ASTROCYTE OVERACTIVITY AND ALLEVIATED THE IL-6 UPREGULATION AND PAIN BEHAVIOR INDUCED BY SNL. MOREOVER, SUPPRESSION OF SPINAL MIR-214-3P INCREASED ASTROCYTE REACTIVITY, PROMOTED CSF1 AND IL-6 PRODUCTION, AND INDUCED PAIN HYPERSENSITIVITY IN NAIVE ANIMALS. FURTHERMORE, SNL INDUCED THE EXPRESSION OF DNA METHYLTRANSFERASE 3A (DNMT3A) THAT WAS ASSOCIATED WITH THE HYPERMETHYLATION OF THE MIR-214-3P PROMOTER, LEADING TO REDUCED MIR-214-3P EXPRESSION IN THE MODEL RODENTS. TREATMENT WITH THE DNMT INHIBITOR ZEBULARINE SIGNIFICANTLY REDUCED CYTOSINE METHYLATION IN THE MIR-214-3P PROMOTER; THIS REDUCED METHYLATION CONSEQUENTLY INCREASED THE EXPRESSION OF MIR-214-3P AND DECREASED THE CONTENT OF CSF1 IN THE IPSILATERAL DORSAL HORN AND, FURTHER, ATTENUATED IL-6 PRODUCTION AND PAIN BEHAVIOR IN RATS WITH SNL. TOGETHER, OUR DATA INDICATE THAT THE DNMT3A-MEDIATED EPIGENETIC SUPPRESSION OF MIR-214-3P ENHANCED CSF1 PRODUCTION IN ASTROCYTES, WHICH SUBSEQUENTLY INDUCED NEUROINFLAMMATION AND PAIN BEHAVIOR IN SNL MODEL RATS. 2020 20 742 41 CANNABINOID CB2 RECEPTORS ARE UPREGULATED VIA BIVALENT HISTONE MODIFICATIONS AND CONTROL PRIMARY AFFERENT INPUT TO THE SPINAL CORD IN NEUROPATHIC PAIN. TYPE-2 CANNABINOID RECEPTORS (CB2, ENCODED BY THE CNR2 GENE) ARE MAINLY EXPRESSED IN IMMUNE CELLS, AND CB2 AGONISTS NORMALLY HAVE NO ANALGESIC EFFECT. HOWEVER, NERVE INJURY UPREGULATES CB2 IN THE DORSAL ROOT GANGLION (DRG), FOLLOWING WHICH CB2 STIMULATION REDUCES NEUROPATHIC PAIN. IT IS UNCLEAR HOW NERVE INJURY INCREASES CB2 EXPRESSION OR HOW CB2 ACTIVITY IS TRANSFORMED IN NEUROPATHIC PAIN. IN THIS STUDY, IMMUNOBLOTTING SHOWED THAT SPINAL NERVE LIGATION (SNL) INDUCED A DELAYED AND SUSTAINED INCREASE IN CB2 EXPRESSION IN THE DRG AND DORSAL SPINAL CORD SYNAPTOSOMES. RNASCOPE IN SITU HYBRIDIZATION ALSO SHOWED THAT SNL SUBSTANTIALLY INCREASED CB2 MRNA LEVELS, MOSTLY IN MEDIUM AND LARGE DRG NEURONS. FURTHERMORE, WE FOUND THAT THE SPECIFIC CB2 AGONIST JWH-133 SIGNIFICANTLY INHIBITS THE AMPLITUDE OF DORSAL ROOT-EVOKED GLUTAMATERGIC EXCITATORY POSTSYNAPTIC CURRENTS IN SPINAL DORSAL HORN NEURONS IN SNL RATS, BUT NOT IN SHAM CONTROL RATS; INTRATHECAL INJECTION OF JWH-133 REVERSED PAIN HYPERSENSITIVITY IN SNL RATS, BUT HAD NO EFFECT IN SHAM CONTROL RATS. IN ADDITION, CHROMATIN IMMUNOPRECIPITATION-QPCR ANALYSIS SHOWED THAT SNL INCREASED ENRICHMENT OF TWO ACTIVATING HISTONE MARKS (H3K4ME3 AND H3K9AC) AND DIMINISHED OCCUPANCY OF TWO REPRESSIVE HISTONE MARKS (H3K9ME2 AND H3K27ME3) AT THE CNR2 PROMOTER IN THE DRG. IN CONTRAST, SNL HAD NO EFFECT ON DNA METHYLATION LEVELS AROUND THE CNR2 PROMOTER. OUR FINDINGS SUGGEST THAT PERIPHERAL NERVE INJURY PROMOTES CB2 EXPRESSION IN PRIMARY SENSORY NEURONS VIA EPIGENETIC BIVALENT HISTONE MODIFICATIONS AND THAT CB2 ACTIVATION REDUCES NEUROPATHIC PAIN BY ATTENUATING NOCICEPTIVE TRANSMISSION FROM PRIMARY AFFERENT NERVES TO THE SPINAL CORD. 2022