1 2885 97 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 2 2407 39 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 3 5574 48 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 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 5 1167 44 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 6 4616 44 NERVE INJURY INCREASES BRAIN-DERIVED NEUROTROPHIC FACTOR LEVELS TO SUPPRESS BK CHANNEL ACTIVITY IN PRIMARY SENSORY NEURONS. ABNORMAL HYPEREXCITABILITY OF PRIMARY SENSORY NEURONS CONTRIBUTES TO NEUROPATHIC PAIN DEVELOPMENT AFTER NERVE INJURY. NERVE INJURY PROFOUNDLY REDUCES THE EXPRESSION OF BIG CONDUCTANCE CA(2+) -ACTIVATED K(+) (BK) CHANNELS IN THE DORSAL ROOT GANGLION (DRG). HOWEVER, LITTLE IS KNOWN ABOUT HOW NERVE INJURY AFFECTS BK CHANNEL ACTIVITY IN DRG NEURONS. IN THIS STUDY, WE DETERMINED THE CHANGES IN BK CHANNEL ACTIVITY IN DRG NEURONS IN A RAT MODEL OF NEUROPATHIC PAIN AND THE CONTRIBUTION OF BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) TO REDUCED BK CHANNEL ACTIVITY. THE BK CHANNEL ACTIVITY WAS PRESENT PREDOMINANTLY IN SMALL AND MEDIUM DRG NEURONS, AND LIGATION OF L5 AND L6 SPINAL NERVES PROFOUNDLY DECREASED THE BK CURRENT DENSITY IN THESE NEURONS. BLOCKING BK CHANNELS SIGNIFICANTLY INCREASED NEURONAL EXCITABILITY IN SHAM CONTROL, BUT NOT IN NERVE-INJURED, RATS. THE BDNF CONCENTRATION IN THE DRG WAS SIGNIFICANTLY GREATER IN NERVE-INJURED RATS THAN IN CONTROL RATS. BDNF TREATMENT LARGELY REDUCED BK CURRENTS IN DRG NEURONS IN CONTROL RATS, WHICH WAS BLOCKED BY EITHER ANTI-BDNF ANTIBODY OR K252A, A TRK RECEPTOR INHIBITOR. FURTHERMORE, EITHER ANTI-BDNF ANTIBODY OR K252A REVERSED REDUCTION IN BK CURRENTS IN INJURED DRG NEURONS. BDNF TREATMENT REDUCED THE MRNA LEVELS OF BKALPHA1 SUBUNIT IN DRG NEURONS, AND ANTI-BDNF ANTIBODY ATTENUATED THE REDUCTION IN THE BKALPHA1 MRNA LEVEL IN INJURED DRG NEURONS. THESE FINDINGS SUGGEST THAT NERVE INJURY PRIMARILY DIMINISHES THE BK CHANNEL ACTIVITY IN SMALL AND MEDIUM DRG NEURONS. INCREASED BDNF LEVELS CONTRIBUTE TO REDUCED BK CHANNEL ACTIVITY IN DRG NEURONS THROUGH EPIGENETIC AND TRANSCRIPTIONAL MECHANISMS IN NEUROPATHIC PAIN. 2012 7 3332 27 HISTONE DEACETYLASE INHIBITOR-INDUCED EMERGENCE OF SYNAPTIC DELTA-OPIOID RECEPTORS AND BEHAVIORAL ANTINOCICEPTION IN PERSISTENT NEUROPATHIC PAIN. THE EFFICACY OF OPIOIDS IN PATIENTS WITH CHRONIC NEUROPATHIC PAIN REMAINS CONTROVERSIAL. ALTHOUGH ACTIVATION OF DELTA-OPIOID RECEPTORS (DORS) IN THE BRAINSTEM REDUCES INFLAMMATION-INDUCED PERSISTENT HYPERALGESIA, IT IS NOT EFFECTIVE UNDER PERSISTENT NEUROPATHIC PAIN CONDITIONS AND THESE CLINICAL PROBLEMS REMAIN LARGELY UNKNOWN. IN THIS STUDY, BY USING A CHRONIC CONSTRICTION INJURY (CCI) OF THE SCIATIC NERVE IN RATS, WE FOUND THAT IN THE BRAINSTEM NUCLEUS RAPHE MAGNUS (NRM), DORS EMERGED ON THE SURFACE MEMBRANE OF CENTRAL SYNAPTIC TERMINALS ON DAY 3 AFTER CCI SURGERY AND DISAPPEARED ON DAY 14. HISTONE DEACETYLASE (HDAC) INHIBITORS MICROINJECTED INTO THE NRM IN VIVO INCREASED THE LEVEL OF SYNAPTOSOMAL DOR PROTEIN AND NRM INFUSION OF DOR AGONISTS PRODUCING AN ANTINOCICEPTIVE EFFECT IN A NERVE GROWTH FACTOR (NGF) SIGNALING-DEPENDENT MANNER. IN VITRO, IN CCI RAT SLICES INCUBATED WITH HDAC INHIBITORS, DOR AGONISTS SIGNIFICANTLY INHIBITED EPSCS. THIS EFFECT WAS BLOCKED BY TYROSINE RECEPTOR KINASE A ANTAGONISTS. CHROMATIN IMMUNOPRECIPITATION ANALYSIS REVEALED THAT NRM INFUSION OF HDAC INHIBITORS IN CCI RATS INCREASED THE LEVEL OF HISTONE H4 ACETYLATION AT NGF GENE PROMOTER REGIONS. NGF WAS INFUSED INTO THE NRM OR INCUBATED CCI RAT SLICES DROVE DORS TO THE SURFACE MEMBRANE OF SYNAPTIC TERMINALS. TAKEN TOGETHER, EPIGENETIC UPREGULATION OF NGF ACTIVITY BY HDAC INHIBITORS IN THE NRM PROMOTES THE TRAFFICKING OF DORS TO PAIN-MODULATING NEURONAL SYNAPSES UNDER NEUROPATHIC PAIN CONDITIONS, LEADING TO DELTA-OPIOID ANALGESIA. THESE FINDINGS INDICATE THAT THERAPEUTIC USE OF DOR AGONISTS COMBINED WITH HDAC INHIBITORS MIGHT BE EFFECTIVE IN CHRONIC NEUROPATHIC PAIN MANAGEMENTS. 2016 8 2272 32 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 9 742 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 10 1166 43 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 11 4172 26 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 12 1654 36 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 13 3868 29 JMJD6 EXERTS FUNCTION IN NEUROPATHIC PAIN BY REGULATING NF?KAPPAB FOLLOWING PERIPHERAL NERVE INJURY IN RATS. TREATMENT OF NEUROPATHIC PAIN (NPP) CONTINUES TO BE A MAJOR CHALLENGE, AND THE UNDERLYING MECHANISMS REMAIN TO BE ELUCIDATED. PREVIOUS STUDIES HAVE DEMONSTRATED THAT HISTONE METHYLATION IS IMPORTANT IN SYNAPTIC PLASTICITY OF THE NERVOUS SYSTEM AND MAY AFFECT NUCLEAR FACTOR?KAPPAB (NF?KAPPAB) SIGNALING THROUGH EPIGENETIC MECHANISMS. THE PRESENT STUDY AIMED TO INVESTIGATE THE ROLE OF JUMONJI C DOMAIN 6 (JMJD6), A HISTONE DEMETHYLASE, IN A CHRONIC CONSTRICTION INJURY (CCI) MODEL OF NPP. ON THE THIRD DAY POST?CCI SURGERY, A JMJD6 OVEREXPRESSING LENTIVIRAL VECTOR (LV?JMJD6) WAS INTRATHECALLY INJECTED IN THE RATS. MECHANICAL WITHDRAWAL THRESHOLD AND THERMAL WITHDRAWAL LATENCY WERE ASSESSED PRIOR SURGERY AND ON DAYS 3, 7, 10 AND 14 POST?CCI. THE RESULTS SHOWED THAT INTRATHECAL INJECTION WITH THE LV?JMJD6 ATTENUATED CCI?INDUCED PAIN FACILITATION. THE EXPRESSION OF JMJD6 WAS LOWER FOLLOWING CCI SURGERY, AND ITS EXPRESSION WAS SIGNIFICANTLY INCREASED FOLLOWING INTRATHECAL INJECTION WITH LV?JMJD6, COMPARED WITH LEVELS IN NORMAL SALINE (NS)? AND NEGATIVE CONTROL LENTIVIRAL VECTOR (NC)?TREATED RATS. THE EXPRESSION OF SPINAL NF?KAPPAB PHOSPHORYLATED (P?)P65 SUBUNIT AND ITS DOWNSTREAM PAIN?ASSOCIATED EFFECTORS, INCLUDING INTERLEUKIN 1BETA (IL?1BETA), TUMOR NECROSIS FACTOR?ALPHA (TNF?ALPHA) AND VASCULAR ENDOTHELIAL GROWTH FACTOR (VEGF), WERE INCREASED FOLLOWING CCI SURGERY. INTRATHECAL INJECTION WITH LV?JMJD6 SUPPRESSED ACTIVATION OF THE P?P65 SUBUNIT IN CCI RATS. IN ADDITION, EXPRESSION LEVELS OF ITS DOWNSTREAM EFFECTORS IL?1BETA, TNF?ALPHA AND VEGF WERE ATTENUATED BY INTRATHECAL TREATMENT WITH LV?JMJD6, COMPARED WITH THOSE IN THE NS? AND NC?TREATED CCI RATS. FURTHERMORE, THE JMJD6? AND P65?IMMUNOREACTIVE CELLS OVERLAPPED IN THE SPINAL DORSAL HORN, HOWEVER, CO?IMMUNOPRECIPITATION SHOWED THAT JMJD6 AND THE NF?KAPPAB P65 SUBUNIT DID NOT DIRECTLY INTERACT, INDICATING OTHER FUNCTIONAL CONNECTIONS MAY EXIST BETWEEN THESE FACTORS FOLLOWING CCI SURGERY. COLLECTIVELY, THESE FINDINGS INDICATED AN IMPORTANT MECHANISM UNDERLYING THE PATHOGENESIS OF NPP. JMJD6 MAY EXERT ITS THERAPEUTIC FUNCTION IN NPP BY REGULATING NF?KAPPAB FOLLOWING CCI. 2018 14 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 15 3810 30 INTRATHECAL 5-AZACYTIDINE INHIBITS GLOBAL DNA METHYLATION AND METHYL- CPG-BINDING PROTEIN 2 EXPRESSION AND ALLEVIATES NEUROPATHIC PAIN IN RATS FOLLOWING CHRONIC CONSTRICTION INJURY. THE PATHOGENESIS OF NEUROPATHIC PAIN REMAINS LARGELY UNKNOWN. EPIGENETIC MECHANISMS MAY PLAY A MAJOR ROLE IN REGULATING EXPRESSION OF PRO- OR ANTINOCICEPTIVE GENES. DNA METHYLATION IS A MAJOR EPIGENETIC MECHANISM IN VERTEBRATES, AND METHYL- CPG-BINDING PROTEIN 2 (MECP2) IS DIRECTLY INVOLVED IN METHYLATION-MEDIATED GENE SILENCING. TO DETERMINE HOW CHANGES IN GLOBAL DNA METHYLATION AND MECP2 EXPRESSION OCCUR FOLLOWING CHRONIC CONSTRICTION INJURY (CCI) AND HOW REPRESSION OF DNA METHYLATION AFFECTS THESE CHANGES AND ATTENUATES NEUROPATHIC PAIN, WE USED INTRATHECAL 5-AZACYTIDINE, A DNA METHYLTRANSFERASE INHIBITOR, IN CCI RATS. RATS RECEIVED 0.9% SALINE OR 5-AZACYTIDINE (10MUMOL.D(-1)) VIA SPINAL INJECTION ONCE DAILY FROM DAY 3 TO DAY 14 AFTER CCI SURGERY. GLOBAL DNA METHYLATION AND MECP2 EXPRESSION INCREASED IN THE SPINAL CORD IN CCI RATS ON DAY 14 AFTER CCI SURGERY. MECHANICAL ALLODYNIA AND THERMAL HYPERALGESIA INDUCED BY CCI WERE ATTENUATED BY INTRATHECAL 5-AZACYTIDINE FROM DAY 5 TO DAY 14 AFTER CCI SURGERY. THE INCREASES IN GLOBAL DNA METHYLATION AND MECP2 EXPRESSION IN THE SPINAL CORD IN CCI RATS WERE ALSO SIGNIFICANTLY INHIBITED BY INTRATHECAL 5-AZACYTIDINE. THESE RESULTS DEMONSTRATE THAT INCREASED GLOBAL DNA METHYLATION AND MECP2 EXPRESSION IN THE SPINAL CORD AFTER NERVE DAMAGE MAY PLAY AN IMPORTANT ROLE IN NEUROPATHIC PAIN. 5-AZACYTIDINE SHOWS POTENTIAL FOR TREATING NEUROPATHIC PAIN. 2011 16 4579 23 N(6)-METHYLADENOSINE METHYLASE METTL3 CONTRIBUTES TO NEUROPATHIC PAIN BY EPIGENETIC SILENCING OF MU OPIOID RECEPTOR. WE AIMED AT EXPLORING THE ROLE AND MECHANISM OF METTL3-MEDIATED M(6)A MODIFICATION IN NEUROPATHIC PAIN. MALE SPRAGUE-DAWLEY RATS WERE RANDOMLY DIVIDED INTO FOUR GROUPS: SHAM OPERATION GROUP (SHAM GROUP), CHRONIC CONSTRICTION INJURY (CCI) OF THE SCIATIC NERVE MODEL GROUP (NPP GROUP), INTRATHECAL INJECTION OF VIRUS DOWN-REGULATED METTL3 + CCI MODEL GROUP (M3 + NPP GROUP) AND INTRATHECAL INJECTION OF NEGATIVE CONTROL VIRUS + CCI MODEL GROUP (SCR + NPP GROUP). THE M3 + NPP GROUP AND THE SCR + NPP GROUP WERE INTRATHECALLY INJECTED WITH VIRUS NINETEEN DAYS BEFORE OPERATION. THE PAW WITHDRAWAL MECHANICAL THRESHOLDS AND PAW WITHDRAWAL LATENCY WERE RESPECTIVELY RECORDED ONE DAY BEFORE OPERATION, THREE DAYS, FIVE DAYS AND SEVEN DAYS AFTER OPERATION. THE RATS WERE SACRIFICED ON THE SEVENTH DAY AFTER OPERATION, AND THEIR SPINAL CORD TISSUES WERE TAKEN. THE FROZEN SECTIONS OF RATS WERE PERFORMED TO OBSERVE THE EXPRESSION OF GREEN FLUORESCENT PROTEIN OF THE VIRUS. THE METHYLATION LEVEL OF RNA, THE PROTEIN EXPRESSION OF M(6)A-RELATED ENZYME (METTL3) AND MU OPIOID RECEPTOR (MOR) IN SPINAL CORD TISSUES OF THE FOUR GROUPS WERE MEASURED. DOWNREGULATION OF METTL3 HAD NO EFFECT ON THE OVERALL METHYLATION LEVEL OF THE SPINAL CORD, BUT IT COULD REGULATE THE METHYLATION LEVEL OF THE OPRM1 GENE RNA ENCODING MOR, PARTIALLY RESTORE THE EXPRESSION OF MOR, AND RELIEVE PAIN IN RATS. IN THE PROCESS OF NPP, METTL3 MAY INHIBIT THE EXPRESSION OF MOR BY REGULATING THE METHYLATION LEVEL OF OPRM1 GENE RNA ENCODING MOR, AND ULTIMATELY PROMOTE THE OCCURRENCE AND DEVELOPMENT OF NPP. 2023 17 4618 43 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 18 4366 29 MIRNA-23A/CXCR4 REGULATES NEUROPATHIC PAIN VIA DIRECTLY TARGETING TXNIP/NLRP3 INFLAMMASOME AXIS. BACKGROUND: CHEMOKINE CXC RECEPTOR 4 (CXCR4) IN SPINAL GLIAL CELLS HAS BEEN IMPLICATED IN NEUROPATHIC PAIN. HOWEVER, THE REGULATORY CASCADES OF CXCR4 IN NEUROPATHIC PAIN REMAIN ELUSIVE. HERE, WE INVESTIGATED THE FUNCTIONAL REGULATORY ROLE OF MIRNAS IN THE PAIN PROCESS AND ITS INTERPLAY WITH CXCR4 AND ITS DOWNSTREAM SIGNALING. METHODS: MIRNAS AND CXCR4 AND ITS DOWNSTREAM SIGNALING MOLECULES WERE MEASURED IN THE SPINAL CORDS OF MICE WITH SCIATIC NERVE INJURY VIA PARTIAL SCIATIC NERVE LIGATION (PSNL). IMMUNOBLOTTING, IMMUNOFLUORESCENCE, IMMUNOPRECIPITATION, AND MAMMAL TWO-HYBRID AND BEHAVIORAL TESTS WERE USED TO EXPLORE THE DOWNSTREAM CXCR4-DEPENDENT SIGNALING PATHWAY. RESULTS: CXCR4 EXPRESSION INCREASED IN SPINAL GLIAL CELLS OF MICE WITH PSNL-INDUCED NEUROPATHIC PAIN. BLOCKING CXCR4 ALLEVIATED THE PAIN BEHAVIOR; CONTRARILY, OVEREXPRESSING CXCR4 INDUCED PAIN HYPERSENSITIVITY. MICRORNA-23A-3P (MIR-23A) DIRECTLY BOUNDS TO 3' UTR OF CXCR4 MRNA. PSNL-INDUCED NEUROPATHIC PAIN SIGNIFICANTLY REDUCED MRNA EXPRESSION OF MIR-23A. OVEREXPRESSION OF MIR-23A BY INTRATHECAL INJECTION OF MIR-23A MIMICS OR LENTIVIRUS REDUCED SPINAL CXCR4 AND PREVENTED PSNL-INDUCED NEUROPATHIC PAIN. IN CONTRAST, KNOCKDOWN OF MIR-23A BY INTRATHECAL INJECTION OF MIR-23A INHIBITOR OR LENTIVIRUS INDUCED PAIN-LIKE BEHAVIOR, WHICH WAS REDUCED BY CXCR4 INHIBITION. ADDITIONALLY, MIR-23A KNOCKDOWN OR CXCR4 OVEREXPRESSION IN NAIVE MICE COULD INCREASE THE THIOREDOXIN-INTERACTING PROTEIN (TXNIP), WHICH WAS ASSOCIATED WITH INDUCTION OF NOD-LIKE RECEPTOR PROTEIN 3 (NLRP3) INFLAMMASOME. INDEED, CXCR4 AND TXNIP WERE CO-EXPRESSED. THE MAMMAL TWO-HYBRID ASSAY REVEALED THE DIRECT INTERACTION BETWEEN CXCR4 AND TXNIP, WHICH WAS INCREASED IN THE SPINAL CORD OF PSNL MICE. IN PARTICULAR, INHIBITION OF TXNIP REVERSED PAIN BEHAVIOR ELICITED BY PSNL, MIR-23A KNOCKDOWN, OR CXCR4 OVEREXPRESSION. MOREOVER, MIR-23A OVEREXPRESSION OR CXCR4 KNOCKDOWN INHIBITED THE INCREASE OF TXNIP AND NLRP3 INFLAMMASOME IN PSNL MICE. CONCLUSIONS: MIR-23A, BY DIRECTLY TARGETING CXCR4, REGULATES NEUROPATHIC PAIN VIA TXNIP/NLRP3 INFLAMMASOME AXIS IN SPINAL GLIAL CELLS. EPIGENETIC INTERVENTIONS AGAINST MIR-23A, CXCR4, OR TXNIP MAY POTENTIALLY SERVE AS NOVEL THERAPEUTIC AVENUES IN TREATING PERIPHERAL NERVE INJURY-INDUCED NOCICEPTIVE HYPERSENSITIVITY. 2018 19 4615 47 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 20 1630 42 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