1 2452 142 EPIGENETIC SUPPRESSION OF POTASSIUM-CHLORIDE CO-TRANSPORTER 2 EXPRESSION IN INFLAMMATORY PAIN INDUCED BY COMPLETE FREUND'S ADJUVANT (CFA). BACKGROUND: MULTIPLE MECHANISMS CONTRIBUTE TO THE STIMULUS-EVOKED PAIN HYPERSENSITIVITY THAT MAY BE EXPERIENCED AFTER PERIPHERAL INFLAMMATION. PERSISTENT PATHOLOGICAL STIMULI IN MANY PAIN CONDITIONS AFFECT THE EXPRESSION OF CERTAIN GENES THROUGH EPIGENETIC ALTERNATIONS. THE MAIN PURPOSE OF OUR STUDY WAS TO INVESTIGATE THE ROLE OF EPIGENETIC MODIFICATION ON POTASSIUM-CHLORIDE CO-TRANSPORTER 2 (KCC2) GENE EXPRESSION IN THE PERSISTENCE OF INFLAMMATORY PAIN. METHODS: PERSISTENT INFLAMMATORY PAIN WAS INDUCED THROUGH THE INJECTION OF COMPLETE FREUND'S ADJUVANT (CFA) IN THE LEFT HIND PAW OF RATS. ACETYL-HISTONE H3 AND H4 LEVEL WAS DETERMINED BY CHROMATIN IMMUNOPRECIPITATION IN THE SPINAL DORSAL HORN. PAIN BEHAVIOUR AND INHIBITORY SYNAPTIC FUNCTION OF SPINAL CORD WERE DETERMINED BEFORE AND AFTER CFA INJECTION. KCC2 EXPRESSION WAS DETERMINED BY REAL TIME RT-PCR AND WESTERN BLOT. INTRATHECAL KCC2 SIRNA (2 MUG PER 10 MUL PER RAT) OR HDAC INHIBITOR (10 MUG PER 10 MUL PER RAT) WAS INJECTED ONCE DAILY FOR 3 DAYS BEFORE CFA INJECTION. RESULTS: PERSISTENT INFLAMMATORY PAIN EPIGENETICALLY SUPPRESSED KCC2 EXPRESSION THROUGH HISTONE DEACETYLASE (HDAC)-MEDIATED HISTONE HYPOACETYLATION, RESULTING IN DECREASED INHIBITORY SIGNALLING EFFICACY. KCC2 KNOCK-DOWN CAUSED BY INTRATHECAL ADMINISTRATION OF KCC2 SIRNA IN NAIVE RATS REDUCED KCC2 EXPRESSION IN THE SPINAL CORD, LEADING TO SENSITIZED PAIN BEHAVIOURS AND IMPAIRED INHIBITORY SYNAPTIC TRANSMISSION IN THEIR SPINAL CORDS. MOREOVER, INTRATHECAL HDAC INHIBITOR INJECTION IN CFA RATS INCREASED KCC2 EXPRESSION, PARTIALLY RESTORING THE SPINAL INHIBITORY SYNAPTIC TRANSMISSION AND RELIEVING THE SENSITIZED PAIN BEHAVIOUR. CONCLUSION: THESE FINDINGS SUGGEST THAT THE TRANSCRIPTION OF SPINAL KCC2 IS REGULATED BY HISTONE ACETYLATION EPIGENETICALLY FOLLOWING CFA. SIGNIFICANCE: PERSISTENT PAIN SUPPRESSES KCC2 EXPRESSION THROUGH HDAC-MEDIATED HISTONE HYPOACETYLATION AND CONSEQUENTLY IMPAIRS THE INHIBITORY FUNCTION OF INHIBITORY INTERNEURONS. DRUGS SUCH AS HDAC INHIBITORS THAT SUPPRESS THE INFLUENCES OF PERSISTENT PAIN ON THE EXPRESSION OF KCC2 MAY SERVE AS A NOVEL ANALGESIC. 2017 2 4172 40 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 3 2751 51 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 4 5328 74 PULSED RADIOFREQUENCY ATTENUATES COMPLETE FREUND'S ADJUVANT-INDUCED EPIGENETIC SUPPRESSION OF POTASSIUM CHLORIDE COTRANSPORTER 2 EXPRESSION. BACKGROUND: PULSED RADIOFREQUENCY (PRF) TREATMENT OFFERS PAIN RELIEF FOR PATIENTS SUFFERING FROM CHRONIC PAIN WHO DO NOT RESPOND WELL TO CONVENTIONAL TREATMENTS. WE TESTED WHETHER PRF TREATMENT ATTENUATED COMPLETE FREUND'S ADJUVANT (CFA)-INDUCED INFLAMMATORY PAIN. EPIGENETIC MODIFICATION OF POTASSIUM-CHLORIDE COTRANSPORTER 2 (KCC2) GENE EXPRESSION WAS EXAMINED TO ELUCIDATE THE POTENTIAL CONTRIBUTING MECHANISM. METHODS: MALE SPRAGUE-DAWLEY RATS WERE INJECTED WITH CFA INTO THE PLANTAR SURFACE OF THE LEFT HIND PAW TO INDUCE INFLAMMATION. PRF (20 MINUTES OF 500-KHZ RF PULSES, DELIVERED AT A RATE OF 2 HZ, MAXIMUM TEMPERATURE 42 MASCULINEC) WAS DELIVERED TO THE L5 AND L6 ANTERIOR PRIMARY RAMUS JUST DISTAL TO THE INTERVERTEBRAL FORAMEN OF ADULT CFA OR SALINE RATS. THE HIND PAW WITHDRAWAL THRESHOLD TO VON FREY FILAMENT STIMULI AND WITHDRAWAL LATENCY TO RADIANT HEAT WERE DETERMINED BEFORE AND AFTER CFA. ACETYL-HISTONE H3 AND H4 WAS DETERMINED BY CHROMATIN IMMUNOPRECIPITATION IN SPINAL DORSAL HORN. KCC2 EXPRESSION WAS DETERMINED BY WESTERN BLOT. INHIBITORY SYNAPTIC FUNCTION WAS EVALUATED BY PATCH CLAMP IN LAMINA II NEURONS. RESULTS: KCC2 GENE EXPRESSION WAS SUPPRESSED THROUGH HISTONE HYPOACETYLATION, RESULTING IN DECREASED EFFICACY OF GABAERGIC SIGNALING IN CFA RATS. PRF INCREASED HISTONE ACETYLATION AND KCC2 EXPRESSION, PARTIALLY RESTORED THE GABA SYNAPTIC FUNCTION, AND RELIEVED SENSITIZED PAIN BEHAVIOR. CONCLUSION: THESE FINDINGS SUGGEST THAT PRF MIGHT BE AN ALTERNATIVE THERAPY FOR INFLAMMATORY PAIN. ONE OF THE UNDERLYING MECHANISMS IS THROUGH MODIFICATION OF KCC2, WHICH IS AN IMPORTANT DETERMINANT FOR THE EFFICACY OF INHIBITORY NEUROTRANSMISSION IN THE SPINAL CORD, AND ITS EXPRESSION LEVELS ARE REGULATED BY HISTONE ACETYLATION EPIGENETICALLY FOLLOWING INFLAMMATION. 2017 5 1120 50 COMPARISON OF DIFFERENT HISTONE DEACETYLASE INHIBITORS IN ATTENUATING INFLAMMATORY PAIN IN RATS. HISTONE DEACETYLASE INHIBITORS (HDACIS), WHICH INTERFERE WITH THE EPIGENETIC PROCESS OF HISTONE ACETYLATION, HAVE SHOWN ANALGESIC EFFECTS IN ANIMAL MODELS OF PERSISTENT PAIN. THE HDAC FAMILY COMPRISES 18 GENES; HOWEVER, THE DIFFERENT EFFECTS OF DISTINCT CLASSES OF HDACIS ON PAIN RELIEF REMAIN UNCLEAR. THE AIM OF THIS STUDY WAS TO DETERMINE THE EFFICACY OF THESE HDACIS ON ATTENUATING THERMAL HYPERALGESIA IN PERSISTENT INFLAMMATORY PAIN. PERSISTENT INFLAMMATORY PAIN WAS INDUCED BY INJECTING COMPLETE FREUND'S ADJUVANT (CFA) INTO THE LEFT HIND PAW OF RATS. THEN, HDACIS TARGETING CLASS I (ENTINOSTAT (MS-275)) AND CLASS IIA (SODIUM BUTYRATE, VALPROIC ACID (VPA), AND 4-PHENYLBUTYRIC ACID (4-PBA)), OR CLASS II (SUBEROYLANILIDE HYDOXAMIC ACID (SAHA), TRICHOSTATIN A (TSA), AND DACINOSTAT (LAQ824)) WERE ADMINISTERED INTRAPERITONEALLY ONCE DAILY FOR 3 OR 4 DAYS. WE FOUND THAT THE INJECTION OF SAHA ONCE A DAY FOR 3 DAYS SIGNIFICANTLY ATTENUATED CFA-INDUCED THERMAL HYPERALGESIA FROM DAY 4 AND LASTED 7 DAYS. IN COMPARISON WITH SAHA, SUPPRESSION OF HYPERALGESIA BY 4-PBA PEAKED ON DAY 2, WHEREAS THAT BY MS-275 OCCURRED ON DAYS 5 AND 6. FATIGUE WAS A SERIOUS SIDE EFFECT SEEN WITH MS-275. THESE FINDINGS WILL BE BENEFICIAL FOR OPTIMIZING THE SELECTION OF SPECIFIC HDACIS IN MEDICAL FIELDS SUCH AS PAIN MEDICINE AND NEUROPSYCHIATRY. 2019 6 3154 39 GLUN2B/CAMKII MEDIATES CFA-INDUCED HYPERALGESIA VIA HDAC4-MODIFIED SPINAL COX2 TRANSCRIPTION. HISTONE DEACETYLASE 4 (HDAC4), WHICH ACTIVELY SHUTTLES BETWEEN THE NUCLEUS AND CYTOPLASM, IS AN ATTRACTIVE CANDIDATE FOR A REPRESSOR MECHANISM IN EPIGENETIC MODIFICATION. HOWEVER, THE POTENTIAL ROLE OF HDAC4-DEPENDENT EPIGENETICS IN THE NEURAL PLASTICITY UNDERLYING THE DEVELOPMENT OF INFLAMMATORY PAIN HAS NOT BEEN WELL ESTABLISHED. BY INJECTING COMPLETE FREUND'S ADJUVANT (CFA) INTO THE HIND-PAW OF SPRAGUE-DAWLEY RATS (200-250 G), WE FOUND ANIMALS DISPLAYED BEHAVIORAL HYPERALGESIA WAS ACCOMPANIED WITH HDAC4 PHOSPHORYLATION AND CYTOPLASMIC REDISTRIBUTION IN THE DORSAL HORN NEURONS. CYTOPLASMIC HDAC4 RETENTION LED TO ITS UNCOUPLING WITH THE COX2 PROMOTER, HENCE PROMPTING SPINAL COX2 TRANSCRIPTION AND EXPRESSION IN THE DORSAL HORN. MOREOVER, THE GLUN2B-BEARING N-METHYL-D-ASPARTATE RECEPTOR (GLUN2B-NMDAR)/CALMODULIN-DEPENDENT PROTEIN KINASE II (CAMKII) ACTED AS AN UPSTREAM CASCADE TO FACILITATE HDAC4 PHOSPHORYLATION/REDISTRIBUTION-ASSOCIATED SPINAL COX2 EXPRESSION AFTER INFLAMMATORY INSULTS. THE RESULTS OF THIS PILOT STUDY DEMONSTRATED THAT THE DEVELOPMENT AND/OR MAINTENANCE OF INFLAMMATORY PAIN INVOLVED THE SPINAL HDAC4-DEPENDENT EPIGENETIC MECHANISMS. OUR FINDINGS OPEN UP A NEW AVENUE FOR THE DEVELOPMENT OF A NOVEL MEDICAL STRATEGY FOR THE RELIEF OF INFLAMMATORY PAIN. 2018 7 3721 59 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 8 6472 43 TNFALPHA IN THE TRIGEMINAL NOCICEPTIVE SYSTEM IS CRITICAL FOR TEMPOROMANDIBULAR JOINT PAIN. PREVIOUS STUDIES HAVE SHOWN THAT TUMOR NECROSIS FACTOR ALPHA (TNFALPHA) IS SIGNIFICANTLY INCREASED IN COMPLETE FREUND'S ADJUVANT (CFA)-TREATED TEMPOROMANDIBULAR JOINT (TMJ) TISSUES. HOWEVER, IT IS UNCLEAR WHETHER TNFALPHA IN THE TRIGEMINAL NOCICEPTIVE SYSTEM CONTRIBUTES TO THE DEVELOPMENT OF TMJ PAIN. IN THE PRESENT STUDY, WE INVESTIGATED THE ROLE OF TNFALPHA IN TRIGEMINAL GANGLIA (TG) AND SPINAL TRIGEMINAL NUCLEUS CAUDALIS (SP5C) IN CFA-INDUCED INFLAMMATORY TMJ PAIN. INTRA-TMJ INJECTION OF CFA (10 MUL, 5 MG/ML) INDUCED INFLAMMATORY PAIN IN THE TRIGEMINAL NERVE V2- AND V3-INNERVATED SKIN AREAS OF WT MICE, WHICH WAS PRESENT ON DAY 1 AFTER CFA AND PERSISTED FOR AT LEAST 10 DAYS. TNFALPHA IN BOTH TG AND SP5C OF WT MICE WAS UPREGULATED AFTER CFA INJECTION. THE CFA-INDUCED TMJ PAIN WAS SIGNIFICANTLY INHIBITED IN TNFALPHA KO MICE. THE IMMUNOFLUORESCENCE STAINING SHOWED THAT INTRA-TMJ CFA INJECTION NOT ONLY ENHANCED CO-LOCALIZATION OF TNFALPHA WITH IBA1 (A MARKER FOR MICROGLIA) IN BOTH TG AND SP5C BUT ALSO MARKEDLY INCREASED THE EXPRESSION OF TNFALPHA IN THE SP5C NEURONS. BY THE METHYLATED DNA IMMUNOPRECIPITATION ASSAY, WE ALSO FOUND THAT DNA METHYLATION AT THE TNF GENE PROMOTER REGION IN THE TG WAS DRAMATICALLY DIMINISHED AFTER CFA INJECTION, INDICATING THAT EPIGENETIC REGULATION MAY BE INVOLVED IN THE CFA-ENHANCED TNFALPHA EXPRESSION IN OUR MODEL. OUR RESULTS SUGGEST THAT TNFALPHA IN THE TRIGEMINAL NOCICEPTIVE SYSTEM PLAYS A CRITICAL ROLE IN CFA-INDUCED INFLAMMATORY TMJ PAIN. 2019 9 5977 34 TET1-TRPV4 SIGNALING CONTRIBUTES TO BONE CANCER PAIN IN RATS. BONE CANCER PAIN (BCP) IS EXCRUCIATING FOR CANCER PATIENTS, WITH LIMITED CLINICAL TREATMENT OPTIONS AND SIGNIFICANT SIDE EFFECTS, DUE TO THE COMPLEX AND UNCLEAR PATHOGENESIS OF BONE CANCER PAIN. PERIPHERAL SENSITIZATION IN DORSAL ROOT GANGLION (DRG) NEURONS IS A RECOGNIZED CELLULAR MECHANISM FOR BONE CANCER PAIN. THE PATHOLOGICAL MECHANISM OF CHRONIC PAIN IS INCREASINGLY BEING AFFECTED BY EPIGENETIC MECHANISMS. IN THIS STUDY, WE UNBIASEDLY SHOWED THAT THE DNA HYDROXYMETHYLASE TEN-ELEVEN TRANSLOCATION 1 (TET1) EXPRESSION WAS SIGNIFICANTLY INCREASED IN THE L4-6 DRG OF BCP RATS AND TEN-ELEVEN TRANSLOCATION 2 (TET2) EXPRESSION DID NOT CHANGE SIGNIFICANTLY. NOTABLY, TET1 INHIBITION BY INTRATHECAL INJECTION OF BOBCAT339 (A TET1 INHIBITOR) EFFECTIVELY RELIEVED MECHANICAL HYPERALGESIA IN BCP RATS. PERIPHERAL SENSITIZATION IN CHRONIC PAIN RELIES ON THE ACTIVATION AND OVEREXPRESSION OF ION CHANNELS ON NEURONS. HERE, WE DEMONSTRATED THAT TRPV4, ONE OF THE TRANSIENT RECEPTOR POTENTIAL ION CHANNEL FAMILY MEMBERS, WAS SIGNIFICANTLY ELEVATED IN THE L4-6 DRG OF BCP RATS. IN ADDITION, TRPV4 INHIBITION BY INTRATHECAL INJECTION OF HC067047 (A TRPV4 INHIBITOR) ALSO SIGNIFICANTLY ATTENUATED MECHANICAL HYPERALGESIA IN BCP RATS. INTERESTINGLY, WE FOUND THAT TET1 INHIBITION DOWNREGULATED TRPV4 EXPRESSION IN THE L4-6 DRG OF BCP RATS. AS A RESULT, THESE FINDINGS SUGGESTED THAT TET1 MAY CONTRIBUTE TO BONE CANCER PAIN BY UPREGULATING TRPV4 EXPRESSION IN THE L4-6 DRG OF BCP RATS AND THAT TET1 OR TRPV4 MAY BECOME THERAPEUTIC TARGETS FOR BONE CANCER PAIN. 2023 10 5574 41 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 11 742 38 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 12 6660 44 UPREGULATION OF CXCR4 THROUGH PROMOTER DEMETHYLATION CONTRIBUTES TO INFLAMMATORY HYPERALGESIA IN RATS. AIM AND METHODS: CHRONIC PAIN ASSOCIATED WITH INFLAMMATION IS A COMMON CLINICAL PROBLEM, AND THE UNDERLYING MECHANISMS YET ARE INCOMPLETELY DEFINED. DNA METHYLATION HAS BEEN IMPLICATED IN THE PATHOGENESIS OF CHRONIC PAIN. HOWEVER, THE SPECIFIC GENES REGULATED BY DNA METHYLATION UNDER INFLAMMATORY PAIN CONDITION REMAIN LARGELY UNKNOWN. HERE, WE INVESTIGATED HOW CHEMOKINE RECEPTOR CXCR4 EXPRESSION IS REGULATED BY DNA METHYLATION AND HOW IT CONTRIBUTES TO INFLAMMATORY PAIN INDUCED BY COMPLETE FREUND'S ADJUVANT (CFA) IN RATS. RESULTS: INTRAPLANTAR INJECTION OF CFA COULD NOT ONLY INDUCE SIGNIFICANT HYPERALGESIA IN RATS, BUT ALSO SIGNIFICANTLY INCREASE THE EXPRESSION OF CXCR4 MRNA AND PROTEIN IN THE DORSAL ROOT GANGLION (DRG). INTRATHECAL INJECTION OF CXCR4 ANTAGONIST AMD3100 SIGNIFICANTLY RELIEVED HYPERALGESIA IN INFLAMMATORY RATS IN A TIME- AND DOSE-DEPENDENT MANNER. BISULFITE SEQUENCING AND METHYLATION-SPECIFIC PCR DEMONSTRATE THAT CFA INJECTION LED TO A SIGNIFICANT DEMETHYLATION OF CPG ISLAND AT CXCR4 GENE PROMOTER. CONSISTENTLY, THE EXPRESSION OF DNMT3B WAS SIGNIFICANTLY DOWNREGULATED AFTER CFA INJECTION. ONLINE SOFTWARE PREDICTION REVEALS THREE BINDING SITES OF P65 IN THE CPG ISLAND OF CXCR4 GENE PROMOTER, WHICH HAS CONFIRMED BY THE CHROMATIN IMMUNOPRECIPITATION ASSAY, CFA TREATMENT SIGNIFICANTLY INCREASES THE RECRUITMENT OF P65 TO CXCR4 GENE PROMOTER. INHIBITION OF NF-KB SIGNALING USING P65 INHIBITOR PYRROLIDINE DITHIOCARBAMATE SIGNIFICANTLY PREVENTED THE INCREASES OF THE CXCR4 EXPRESSION. CONCLUSION: UPREGULATION OF CXCR4 EXPRESSION DUE TO PROMOTER DEMETHYLATION FOLLOWED BY INCREASED RECRUITMENT OF P65 TO PROMOTER OF CXCR4 GENE CONTRIBUTES TO INFLAMMATORY HYPERALGESIA. THESE FINDINGS PROVIDE A THEORETICAL BASIS FOR THE TREATMENT OF CHRONIC PAIN FROM AN EPIGENETIC PERSPECTIVE. 2018 13 5018 48 PERSISTENT INFLAMMATION-INDUCED UP-REGULATION OF BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) PROMOTES SYNAPTIC DELIVERY OF ALPHA-AMINO-3-HYDROXY-5-METHYL-4-ISOXAZOLEPROPIONIC ACID RECEPTOR GLUA1 SUBUNITS IN DESCENDING PAIN MODULATORY CIRCUITS. THE ENHANCED AMPA RECEPTOR PHOSPHORYLATION AT GLUA1 SERINE 831 SITES IN THE CENTRAL PAIN-MODULATING SYSTEM PLAYS A PIVOTAL ROLE IN DESCENDING PAIN FACILITATION AFTER INFLAMMATION, BUT THE UNDERLYING MECHANISMS REMAIN UNCLEAR. WE SHOW HERE THAT, IN THE RAT BRAIN STEM, IN THE NUCLEUS RAPHE MAGNUS, WHICH IS A CRITICAL RELAY IN THE DESCENDING PAIN-MODULATING SYSTEM OF THE BRAIN, PERSISTENT INFLAMMATORY PAIN INDUCED BY COMPLETE FREUND ADJUVANT (CFA) CAN ENHANCE AMPA RECEPTOR-MEDIATED EXCITATORY POSTSYNAPTIC CURRENTS AND THE GLUA2-LACKING AMPA RECEPTOR-MEDIATED RECTIFICATION INDEX. WESTERN BLOT ANALYSIS SHOWED AN INCREASE IN GLUA1 PHOSPHORYLATION AT SER-831 BUT NOT AT SER-845. THIS WAS ACCOMPANIED BY AN INCREASE IN DISTRIBUTION OF THE SYNAPTIC GLUA1 SUBUNIT. IN PARALLEL, THE LEVEL OF HISTONE H3 ACETYLATION AT BDNF GENE PROMOTER REGIONS WAS REDUCED SIGNIFICANTLY 3 DAYS AFTER CFA INJECTION, AS INDICATED BY CHIP ASSAYS. THIS WAS CORRELATED WITH AN INCREASE IN BDNF MRNA LEVELS AND BDNF PROTEIN LEVELS. SEQUESTERING ENDOGENOUS EXTRACELLULAR BDNF WITH TRKB-IGG IN THE NUCLEUS RAPHE MAGNUS DECREASED AMPA RECEPTOR-MEDIATED SYNAPTIC TRANSMISSION AND GLUA1 PHOSPHORYLATION AT SER-831 3 DAYS AFTER CFA INJECTION. UNDER THE SAME CONDITIONS, BLOCKADE OF TRKB RECEPTOR FUNCTIONS, PHOSPHOLIPASE C, OR PKC IMPAIRED GLUA1 PHOSPHORYLATION AT SER-831 AND DECREASED EXCITATORY POSTSYNAPTIC CURRENTS MEDIATED BY GLUA2-LACKING AMPA RECEPTORS. TAKEN TOGETHER, THESE RESULTS SUGGEST THAT EPIGENETIC UP-REGULATION OF BDNF BY PERIPHERAL INFLAMMATION INDUCES GLUR1 PHOSPHORYLATION AT SER-831 SITES THROUGH ACTIVATION OF THE PHOSPHOLIPASE C-PKC SIGNALING CASCADE, LEADING TO THE TRAFFICKING OF GLUA1 TO PAIN-MODULATING NEURONAL SYNAPSES. 2014 14 1630 43 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 15 3459 38 HYPOMETHYLATION OF NERVE GROWTH FACTOR (NGF) PROMOTES BINDING OF C/EBPALPHA AND CONTRIBUTES TO INFLAMMATORY HYPERALGESIA IN RATS. BACKGROUND: CHRONIC PAIN USUALLY ACCOMPANIED BY TISSUE DAMAGE AND INFLAMMATION. HOWEVER, THE PATHOGENESIS OF CHRONIC PAIN REMAINS UNCLEAR. METHODS: WE INVESTIGATED THE ROLE OF NERVE GROWTH FACTOR (NGF) IN CHRONIC INFLAMMATORY PAIN INDUCED BY COMPLETE FREUND'S ADJUVANT (CFA), EXPLORED THE METHYLATION STATUS OF CPG ISLANDS IN THE PROMOTER REGION OF THE NGF GENE, AND CLARIFIED THE FUNCTION AND MECHANISM OF C/EBPALPHA-NGF SIGNALING PATHWAY FROM EPIGENETIC PERSPECTIVE IN THE CHRONIC INFLAMMATORY PAIN MODEL. RESULTS: CFA INDUCED SIGNIFICANT HYPERALGESIA AND CONTINUOUS UPREGULATION OF NGF MRNA AND PROTEIN LEVELS IN THE L4-6 DORSAL ROOT GANGLIONS (DRGS) IN RATS. HYPOMETHYLATION OF CPG ISLANDS OCCURRED IN THE NGF GENE PROMOTER REGION AFTER CFA TREATMENT. AT THE SAME TIME, THE MIR-29B EXPRESSION LEVEL WAS SIGNIFICANTLY INCREASED, WHILE THE DNA METHYLTRANSFERASE 3B (DNMT3B) LEVEL REDUCED SIGNIFICANTLY. MOREOVER, CFA TREATMENT PROMOTED BINDING OF C/EBPALPHA TO THE NGF GENE PROMOTER REGION AND C/EBPALPHA SIRNA TREATMENT OBVIOUSLY DECREASED EXPRESSION OF NGF LEVELS AND ALSO ALLEVIATE INFLAMMATORY HYPERALGESIA SIGNIFICANTLY IN RATS. CONCLUSION: COLLECTIVELY, THE RESULTS INDICATED THAT CFA LEADS TO THE UPREGULATION OF MIR-29B LEVEL, WHICH REPRESSES THE EXPRESSION OF DNMT3B, ENHANCES THE DEMETHYLATION OF THE NGF GENE PROMOTER REGION, AND PROMOTES THE BINDING OF C/EBPALPHA WITH THE NGF GENE PROMOTER, THUS RESULTS IN THE UPREGULATION OF NGF GENE EXPRESSION AND MAINTENANCE OF CHRONIC INFLAMMATORY PAIN. 2020 16 4616 35 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 17 3332 42 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 18 6612 41 ULTRA-LOW-DOSE NALOXONE ENHANCES THE ANTINOCICEPTIVE EFFECT OF MORPHINE IN PTX-TREATED RATS: REGULATION ON GLOBAL HISTONE METHYLATION. OBJECTIVE: EPIGENETIC REPROGRAMMING MAY HAVE A POSSIBLE ROLE IN NEUROPATHIC PAIN DEVELOPMENT; THE PRESENT STUDY EXAMINED THE GLOBAL PATTERNS OF LYSINE HISTONE MODIFICATION. IN THIS SERIAL STUDY WE ANALYZED THE LEVELS OF HISTONE 3 LYSINE 4 MONOMETHYLATION, HISTONE 3 LYSINE 4 DIMETHYLATION, AND HISTONE 3 LYSINE 9 TRIMETHYLATION IN PERTUSSIS TOXIN (PTX)-INDUCED THERMAL HYPERALGESIC RAT SPINAL CORDS. METHODS: MALE WISTAR RATS IMPLANTED WITH AN INTRATHECAL CATHETER RECEIVED A SINGLE INTRATHECAL PTX (1 MUG IN 5 MUL SALINE) INJECTION. FOUR DAYS LATER, THEY WERE RANDOMLY ASSIGNED TO RECEIVE EITHER A SINGLE INJECTION OF SALINE, OR ULTRA-LOW-DOSE NALOXONE (15 NG IN 5 MUL SALINE), FOLLOWED BY MORPHINE (10 MUG IN 5 MUL SALINE) INJECTION 30 MINUTES LATER. RESULTS: THE RESULTS SHOWED THAT PTX INJECTION INDUCED THERMAL HYPERALGESIA AND SIGNIFICANT INCREASE OF GLOBAL HISTONE METHYLATION IN THE SPINAL CORDS. INTRATHECAL MORPHINE ALONE DID NOT AFFECT THE THERMAL HYPERALGESIA AND GLOBAL HISTONE METHYLATION. IN CONTRAST, INTRATHECAL ADMINISTRATION OF ULTRA-LOW-DOSE NALOXONE PLUS MORPHINE SIGNIFICANTLY ATTENUATED THE PTX-INDUCED THERMAL HYPERALGESIA AND DOWN-REGULATED THE GLOBAL HISTONE METHYLATION. CONCLUSION: THE RESULTS SUGGEST THAT ULTRA-LOW-DOSE NALOXONE MIGHT BE CLINICAL VALUABLE FOR NEUROPATHIC PAIN MANAGEMENT VIA REGULATING GLOBAL HISTONE MODIFICATION. 2012 19 2885 34 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 20 1654 35 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