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 5865 43 SUPPRESSION OF HDAC2 IN SPINAL CORD ALLEVIATES MECHANICAL HYPERALGESIA AND RESTORES KCC2 EXPRESSION IN A RAT MODEL OF BONE CANCER PAIN. EPIGENETIC MODULATION PARTICIPATES IN THE MECHANISM OF MULTIPLE TYPES OF PATHOLOGICAL PAIN, SO TARGETING THE INVOLVED REGULATORS MAY BE A PROMISING STRATEGY FOR PAIN TREATMENT. OUR PREVIOUS RESEARCH IDENTIFIED THE ANALGESIC EFFECT OF THE HISTONE DEACETYLASE (HDAC) INHIBITOR TRICHOSTATIN A (TSA) ON MECHANICAL HYPERALGESIA IN A RAT MODEL OF BONE CANCER PAIN (BCP) VIA RESTORATION OF MU-OPIOID RECEPTOR (MOR) EXPRESSION. HOWEVER, THE SPECIFIC TYPES OF HDACS CONTRIBUTING TO BCP HAVE NOT BEEN EXPLORED. THE PRESENT STUDY INVESTIGATED THE EXPRESSION PATTERN OF SOME COMMON HDACS AND FOUND THAT HDAC2 WAS UP-REGULATED IN A TIME-DEPENDENT MANNER IN THE LUMBAR SPINAL CORD OF BCP RATS. TSA APPLICATION SUPPRESSED HDAC2 EXPRESSION IN CULTURED PC12 CELLS AND REVERSED THE AUGMENTED HDAC2 IN BCP RATS. AN RNA-INTERFERING STRATEGY CONFIRMED THE ESSENTIAL ROLE OF HDAC2 IN THE MODULATION OF MECHANICAL HYPERALGESIA FOLLOWING TUMOR CELL INOCULATION, AND WE FURTHER EXAMINED ITS POSSIBLE DOWNSTREAM TARGETS. NOTABLY, HDAC2 KNOCK-DOWN DID NOT RESTORE MOR EXPRESSION, BUT IT ROBUSTLY REVERSED THE DOWN-REGULATION OF POTASSIUM-CHLORIDE COTRANSPORTER 2 (KCC2). THE IMPAIRED KCC2 EXPRESSION IS A VITAL MECHANISM OF MANY TYPES OF PATHOLOGICAL PAIN. THEREFORE, OUR RESULTS DEMONSTRATED THAT HDAC2 IN SPINAL CORD CONTRIBUTED TO THE MECHANICAL HYPERALGESIA IN BCP RATS, AND THIS EFFECT MAY BE ASSOCIATED WITH KCC2 MODULATION. 2018 3 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 4 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 5 2300 48 EPIGENETIC REGULATION OF BDNF EXPRESSION IN THE PRIMARY SENSORY NEURONS AFTER PERIPHERAL NERVE INJURY: IMPLICATIONS IN THE DEVELOPMENT OF NEUROPATHIC PAIN. BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) IS KNOWN TO BE UP-REGULATED IN THE DORSAL ROOT GANGLION (DRG) AFTER PERIPHERAL NERVE INJURY, AND TO CONTRIBUTE TO NEUROPATHIC PAIN. HERE, WE FOUND THAT THERMAL HYPERALGESIA AND MECHANICAL ALLODYNIA AT DAY 7 POST-INJURY WERE INHIBITED ONLY WHEN ANTI-BDNF ANTIBODY WAS INTRATHECALLY ADMINISTRATED AT DAY 2 POST-INJURY. CONSISTENT WITH BEHAVIORAL RESULTS, WESTERN BLOT ANALYSIS SHOWED THAT THE EXPRESSION LEVELS OF BDNF PROTEIN IN THE SPINAL DORSAL HORN WERE MARKEDLY INDUCED DURING EARLY STAGE POST-INJURY. MOREOVER, THE MAXIMAL INCREASE IN BDNF MRNA EXPRESSION IN THE DRG WAS OBSERVED AT DAY 1 POST-INJURY, AND SIGNIFICANTLY ELEVATED LEVELS WERE SUSTAINED FOR AT LEAST 14 DAYS. FOUR OF FIVE BDNF MRNA TRANSCRIPTS WERE UP-REGULATED AFTER NERVE INJURY, AND THE MOST INDUCIBLE TRANSCRIPT WAS EXON I. USING A CHROMATIN IMMUNOPRECIPITATION (CHIP) ASSAY, WE FOUND THAT NERVE INJURY PROMOTES HISTONE H3 AND H4 ACETYLATION, TRANSCRIPTIONALLY ACTIVE MODIFICATIONS, AT BDNF PROMOTER I AT DAY 1 POST-INJURY, AND THE LEVELS OF HISTONE ACETYLATION REMAIN ELEVATED FOR AT LEAST 7 DAYS. TAKEN TOGETHER, OUR FINDINGS SUGGEST THAT AN INITIAL INCREASE IN BDNF EXON I EXPRESSION CONTROLLED BY EPIGENETIC MECHANISMS MIGHT HAVE A CRUCIAL ROLE IN THE DEVELOPMENT OF NEUROPATHIC PAIN. 2013 6 2353 49 EPIGENETIC REGULATION OF OPIOID-INDUCED HYPERALGESIA, DEPENDENCE, AND TOLERANCE IN MICE. REPEATED ADMINISTRATION OF OPIOIDS SUCH AS MORPHINE INDUCES PERSISTENT BEHAVIORAL CHANGES INCLUDING OPIOID-INDUCED HYPERALGESIA (OIH), TOLERANCE, AND PHYSICAL DEPENDENCE. IN THE CURRENT WORK WE EXPLORED HOW THE BALANCE OF HISTONE ACETYLTRANSFERASE (HAT) VERSUS HISTONE DEACETYLASE (HDAC) MIGHT REGULATE THESE MORPHINE-INDUCED CHANGES. NOCICEPTIVE THRESHOLDS, ANALGESIA, AND PHYSICAL DEPENDENCE WERE ASSESSED DURING AND FOR A PERIOD OF SEVERAL WEEKS AFTER MORPHINE EXPOSURE. TO PROBE THE ROLES OF HISTONE ACETYLATION, THE HAT INHIBITOR CURCUMIN OR A SELECTIVE HDAC INHIBITOR SUBEROYLANILIDE HYDROXAMIC ACID (SAHA) WAS ADMINISTERED DAILY TO GROUPS OF ANIMALS. HISTONE ACETYLATION IN SPINAL CORD WAS ASSESSED BY WESTERN BLOT AND IMMUNOHISTOCHEMISTRY. CONCURRENT ADMINISTRATION OF CURCUMIN WITH MORPHINE FOR 4 DAYS SIGNIFICANTLY REDUCED DEVELOPMENT OF OPIOID-INDUCED MECHANICAL ALLODYNIA, THERMAL HYPERALGESIA, TOLERANCE, AND PHYSICAL DEPENDENCE. CONVERSELY, THE HDAC INHIBITOR SAHA ENHANCED THESE RESPONSES. INTERESTINGLY, SAHA TREATMENT AFTER THE TERMINATION OF OPIOID ADMINISTRATION SUSTAINED THESE BEHAVIORAL CHANGES FOR AT LEAST 4 WEEKS. HISTONE H3 ACETYLATION IN THE DORSAL HORN OF THE SPINAL CORD WAS INCREASED AFTER CHRONIC MORPHINE TREATMENT, BUT H4 ACETYLATION WAS UNCHANGED. MOREOVER, WE OBSERVED A DECREASE IN HDAC ACTIVITY IN THE SPINAL CORDS OF MORPHINE-TREATED MICE WHILE OVERALL HAT ACTIVITY WAS UNCHANGED, SUGGESTING A SHIFT TOWARD A STATE OF ENHANCED HISTONE ACETYLATION. PERSPECTIVE: THE CURRENT STUDY INDICATES THAT EPIGENETIC MECHANISMS PLAY A CRUCIAL ROLE IN OPIOID-INDUCED LONG-LASTING NEUROPLASTICITY. THESE RESULTS PROVIDE NEW SIGHT INTO UNDERSTANDING THE MECHANISMS OF OPIOID-INDUCED NEUROPLASTICITY AND SUGGEST NEW STRATEGIES TO LIMIT OPIOID ABUSE POTENTIAL AND INCREASE THE VALUE OF THESE DRUGS AS ANALGESICS. 2013 7 2785 47 EZH2 REGULATES SPINAL NEUROINFLAMMATION IN RATS WITH NEUROPATHIC PAIN. ALTERATION IN GENE EXPRESSION ALONG THE PAIN SIGNALING PATHWAY IS A KEY MECHANISM CONTRIBUTING TO THE GENESIS OF NEUROPATHIC PAIN. ACCUMULATING STUDIES HAVE SHOWN THAT EPIGENETIC REGULATION PLAYS A CRUCIAL ROLE IN NOCICEPTIVE PROCESS IN THE SPINAL DORSAL HORN. IN THIS PRESENT STUDY, WE INVESTIGATED THE ROLE OF ENHANCER OF ZESTE HOMOLOG-2 (EZH2), A SUBUNIT OF THE POLYCOMB REPRESSIVE COMPLEX 2, IN THE SPINAL DORSAL HORN IN THE GENESIS OF NEUROPATHIC PAIN IN RATS INDUCED BY PARTIAL SCIATIC NERVE LIGATION. EZH2 IS A HISTONE METHYLTRANSFERASE, WHICH CATALYZES THE METHYLATION OF HISTONE H3 ON K27 (H3K27), RESULTING IN GENE SILENCING. WE FOUND THAT LEVELS OF EZH2 AND TRI-METHYLATED H3K27 (H3K27TM) IN THE SPINAL DORSAL HORN WERE INCREASED IN RATS WITH NEUROPATHIC PAIN ON DAY 3 AND DAY 10 POST NERVE INJURIES. EZH2 WAS PREDOMINANTLY EXPRESSED IN NEURONS IN THE SPINAL DORSAL HORN UNDER NORMAL CONDITIONS. THE NUMBER OF NEURONS WITH EZH2 EXPRESSION WAS INCREASED AFTER NERVE INJURY. MORE STRIKINGLY, NERVE INJURY DRASTICALLY INCREASED THE NUMBER OF MICROGLIA WITH EZH2 EXPRESSION BY MORE THAN SEVENFOLD. INTRATHECAL INJECTION OF THE EZH2 INHIBITOR ATTENUATED THE DEVELOPMENT AND MAINTENANCE OF MECHANICAL AND THERMAL HYPERALGESIA IN RATS WITH NERVE INJURY. SUCH ANALGESIC EFFECTS WERE CONCURRENTLY ASSOCIATED WITH THE REDUCED LEVELS OF EZH2, H3K27TM, IBA1, GFAP, TNF-ALPHA, IL-1BETA, AND MCP-1 IN THE SPINAL DORSAL HORN IN RATS WITH NERVE INJURY. OUR RESULTS HIGHLY SUGGEST THAT TARGETING THE EZH2 SIGNALING PATHWAY COULD BE AN EFFECTIVE APPROACH FOR THE MANAGEMENT OF NEUROPATHIC PAIN. 2017 8 3832 40 INVOLVEMENT OF SPINAL SIRT1 IN DEVELOPMENT OF CHRONIC CONSTRICTION INJURY INDUCED NEUROPATHIC PAIN IN RATS. IT IS KNOWN THAT THE EPIGENETIC PROCESS OF HISTONE ACETYLATION IS INVOLVED IN THE NEUROPATHIC PAIN. THE AIM OF THIS STUDY WAS TO DETERMINE WHETHER SIRTUIN TYPE 1 (SIRT1), AN NAD(+) DEPENDENT DEACETYLASE, AFFECTED ALLODYNIA AND HYPERALGESIA IN NEUROPATHIC PAIN. THE NEUROPATHIC PAIN MODEL WAS ESTABLISHED BY LIGATURE OF THE RIGHT SCIATIC NERVE TO INDUCE CHRONIC CONSTRICTION INJURY (CCI) IN RATS. HISTONE ACETYLTRANSFERASE (HAT) ACTIVITY WAS INCREASED AND, AND HISTONE DEACETYLASE (HDAC) ACTIVITY WAS DECLINED IN TISSUE OF THE SPINAL DORSA HORN IN CCI RATES BY MEANS OF ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA). THE PERSISTENT HYPERALGESIA AND ALLODYNIA CAUSED BY CCI WERE ASSOCIATED WITH DOWNREGULATION OF SIRT1 AND UPREGULATION OF ACETYLATED-H3 (AC-H3) IN TISSUE OF THE SPINAL CORD BY WESTERN BLOT ASSAY, WHICH WAS REVERSED AFTER INTRATHECAL INJECTION OF SIRT1 AGONIST SRT1720. SRT1720 TREATMENT ACHIEVED ANALGESIC THROUGH INHIBITING THE ACETYLATION OF NUCLEAR FACTOR KAPPA B (NF-KAPPAB) AND BLOCKING THE RELEASES OF THE INFLAMMATORY FACTORS INCLUDING TUMOR NECROSIS FACTOR-ALPHA (TNF-ALPHA) AND INTERLEUKIN (IL)-6 BY MEANS OF WESTERN BLOT AND REAL-TIME QUANTITATIVE PCR (RT-PCR), RESPECTIVELY. TAKEN TOGETHER, THESE DATA SUGGEST THAT SIRT1 IN THE SPINAL CORD PLAYS AN IMPORTANT ROLE IN THE NEUROPATHIC PAIN IN THE RAT MODEL. 2018 9 3810 40 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 10 3955 36 LONG MARCH TOWARD SAFE AND EFFECTIVE ANALGESIA BY ENHANCING GENE EXPRESSION OF KCC2: FIRST STEPS TAKEN. LOW INTRANEURONAL CHLORIDE IN SPINAL CORD DORSAL HORN PAIN RELAY NEURONS IS CRITICAL FOR PHYSIOLOGIC TRANSMISSION OF PRIMARY PAIN AFFERENTS BECAUSE LOW INTRANEURONAL CHLORIDE DICTATES WHETHER GABA-ERGIC AND GLYCIN-ERGIC NEUROTRANSMISSION IS INHIBITORY. IF THE NEURONAL CHLORIDE ELEVATES TO PATHOLOGIC LEVELS, THEN SPINAL CORD PRIMARY PAIN RELAY BECOMES LEAKY AND EXHIBITS THE BEHAVIORAL HALLMARKS OF PATHOLOGIC PAIN, NAMELY HYPERSENSITIVITY AND ALLODYNIA. LOW CHLORIDE IN SPINAL CORD DORSAL HORN NEURONS IS MAINTAINED BY PROPER GENE EXPRESSION OF KCC2 AND SUSTAINED PHYSIOLOGIC FUNCTION OF THE KCC2 CHLORIDE EXTRUDING ELECTRONEUTRAL TRANSPORTER. PERIPHERAL NERVE INJURY AND OTHER FORMS OF NEURAL INJURY EVOKE GREATLY DIMINISHED KCC2 GENE EXPRESSION AND SUBSEQUENT CORRUPTION OF INHIBITORY NEUROTRANSMISSION IN THE SPINAL CORD DORSAL HORN, THUS CAUSING DERAILMENT OF THE GATE FUNCTION FOR PAIN. HERE I REVIEW KEY DISCOVERIES THAT HAVE HELPED US UNDERSTAND THESE FUNDAMENTALS, AND FOCUS ON RECENT INSIGHTS RELATING TO THE DISCOVERY OF KCC2 GENE EXPRESSION ENHANCING COMPOUNDS VIA COMPOUND SCREENS IN NEURONS. ONE SUCH STUDY CHARACTERIZED THE KINASE INHIBITOR, KENPAULLONE, MORE IN-DEPTH, REVEALING ITS FUNCTION AS A ROBUST AND LONG-LASTING ANALGESIC IN PRECLINICAL MODELS OF NERVE INJURY AND CANCER BONE PAIN, ALSO ELUCIDATING ITS MECHANISM OF ACTION VIA GSK3BETA INHIBITION, DIMINISHING DELTA-CATENIN PHOSPHORYLATION, AND FACILITATING ITS NUCLEAR TRANSFER AND SUBSEQUENT ENHANCEMENT OF KCC2 GENE EXPRESSION BY DE-REPRESSING KAISO EPIGENETIC TRANSCRIPTIONAL REGULATOR. FUTURE DIRECTIONS RE KCC2 GENE EXPRESSION ENHANCEMENT ARE DISCUSSED, NAMELY COMBINATION WITH OTHER ANALGESICS AND ANALGESIC METHODS, SUCH AS SPINAL CORD STIMULATION AND ELECTROACUPUNCTURE, GENE THERAPY, AND LEVERAGING KCC2 GENE EXPRESSION-ENHANCING NANOMATERIALS. 2022 11 5851 48 SUBEROYLANILIDE HYDROXAMIC ACID TRIGGERS AUTOPHAGY BY INFLUENCING THE MTOR PATHWAY IN THE SPINAL DORSAL HORN IN A RAT NEUROPATHIC PAIN MODEL. HISTONE ACETYLATION LEVELS CAN BE UPREGULATED BY TREATING CELLS WITH HISTONE DEACETYLASE INHIBITORS (HDACIS), WHICH CAN INDUCE AUTOPHAGY. AUTOPHAGY FLUX IN THE SPINAL CORD OF RATS FOLLOWING THE LEFT FIFTH LUMBER SPINAL NERVE LIGATION (SNL) IS INVOLVED IN THE PROGRESSION OF NEUROPATHIC PAIN. SUBEROYLANILIDE HYDROXAMIC ACID (SAHA), ONE OF THE HDACIS CAN INTERFERE WITH THE EPIGENETIC PROCESS OF HISTONE ACETYLATION, WHICH HAS BEEN SHOWN TO EASE NEUROPATHIC PAIN. RECENT RESEARCH SUGGEST THAT SAHA CAN STIMULATE AUTOPHAGY VIA THE MAMMALIAN TARGET OF RAPAMYCIN (MTOR) PATHWAY IN SOME TYPES OF CANCER CELLS. HOWEVER, LITTLE IS KNOWN ABOUT THE ROLE OF SAHA AND AUTOPHAGY IN NEUROPATHIC PAIN AFTER NERVE INJURY. IN THE PRESENT STUDY, WE AIM TO INVESTIGATE AUTOPHAGY FLUX AND THE ROLE OF THE MTOR PATHWAY ON SPINAL CELLS AUTOPHAGY ACTIVATION IN NEUROPATHIC PAIN INDUCED BY SNL IN RATS THAT RECEIVED SAHA TREATMENT. AUTOPHAGY-RELATED PROTEINS AND MTOR OR ITS ACTIVE FORM WERE ASSESSED BY USING WESTERN BLOT, IMMUNOHISTOCHEMISTRY, DOUBLE IMMUNOFLUORESCENCE STAINING AND TRANSMISSION ELECTRON MICROSCOPY (TEM). WE FOUND THAT SAHA DECREASED THE PAW MECHANICAL WITHDRAWAL THRESHOLD (PMWT) OF THE LOWER COMPARED WITH SNL. AUTOPHAGY FLUX WAS MAINLY DISRUPTED IN THE ASTROCYTES AND NEURONAL CELLS OF THE SPINAL CORD DORSAL HORN ON POSTSURGICAL DAY 28 AND WAS REVERSED BY DAILY INTRATHECAL INJECTION OF SAHA (N = 100 NMOL/DAY OR N = 200 NMOL/DAY). SAHA ALSO DECREASED MTOR AND PHOSPHORYLATED MTOR (P-MTOR) EXPRESSION, ESPECIALLY P-MTOR EXPRESSION IN ASTROCYTES AND NEURONAL CELLS OF THE SPINAL DORSAL HORN. THESE RESULTS SUGGEST THAT SAHA ATTENUATES NEUROPATHIC PAIN AND CONTRIBUTES TO AUTOPHAGY FLUX IN ASTROCYTES AND NEURONAL CELLS OF THE SPINAL DORSAL HORN VIA THE MTOR SIGNALING PATHWAY. 2019 12 1631 43 DNMT3A METHYLATION IN NEUROPATHIC PAIN. BACKGROUND: MU OPIOID RECEPTOR (MOR) PLAYS A CRUCIAL ROLE IN MEDIATING ANALGESIC EFFECTS OF OPIOIDS AND IS CLOSELY ASSOCIATED WITH THE PATHOLOGIES OF NEUROPATHIC PAIN. PREVIOUS STUDIES HAVE REPORTED THAT PERIPHERAL NERVE INJURY DOWNREGULATES MOR EXPRESSION, BUT THE EPIGENETIC MECHANISMS REMAIN UNKNOWN. OBJECTIVE: THEREFORE, WE INVESTIGATED DNA METHYLTRANSFERASE3A (DNMT3A) EXPRESSION OR METHYLATION CHANGES WITHIN MOR PROMOTER IN THE SPINAL CORD IN A NEUROPATHIC PAIN INDUCED BY A CHRONIC CONSTRICTION INJURY (CCI) MOUSE MODEL AND FURTHER DETERMINED WHETHER THESE INJURY-ASSOCIATED CHANGES ARE REVERSIBLE BY PHARMACOLOGICAL INTERVENTIONS. METHODS: A CCI MOUSE MODEL WAS ESTABLISHED AND TISSUE SPECIMENS OF LUMBAR SPINAL CORDS WERE COLLECTED. THE NOCICEPTION THRESHOLD WAS EVALUATED BY A MODEL HEATED 400 BASE. DNMT3A AND MOR MRNA AND PROTEIN LEVEL WERE DETECTED BY REAL-TIME-POLYMERASE CHAIN REACTION AND WESTERN BLOT, RESPECTIVELY. METHYLATION OF DNMT3A GENE WAS MEASURED BY METHYLATION-SPECIFIC PCR. RESULTS: OUR DATA SHOWED THAT CHRONIC NERVE INJURY LED TO A SIGNIFICANT UPREGULATION OF DNMT3A EXPRESSION THAT WAS ASSOCIATED WITH INCREASED METHYLATION OF MOR GENE PROMOTER AND DECREASED MOR PROTEIN EXPRESSION IN THE SPINAL CORD. INHIBITION OF DNMT3A CATALYTIC ACTIVITY WITH DNMT INHIBITOR RG108 SIGNIFICANTLY BLOCKED THE INCREASE IN METHYLATION OF THE MOR PROMOTER, AND THEN UPREGULATED MOR EXPRESSION AND ATTENUATED THERMAL HYPERALGESIA IN NEUROPATHIC PAIN MICE. CONCLUSION: THIS STUDY DEMONSTRATES THAT AN INCREASE OF DNMT3A EXPRESSION AND MOR METHYLATION EPIGENETICALLY PLAY AN IMPORTANT ROLE IN NEUROPATHIC PAIN. TARGETING DNMT3A TO THE PROMOTER OF MOR GENE BY DNMT INHIBITOR MAY BE A PROMISING APPROACH TO THE DEVELOPMENT OF NEW NEUROPATHIC PAIN THERAPY. 2017 13 4906 43 P300 EXERTS AN EPIGENETIC ROLE IN CHRONIC NEUROPATHIC PAIN THROUGH ITS ACETYLTRANSFERASE ACTIVITY IN RATS FOLLOWING CHRONIC CONSTRICTION INJURY (CCI). BACKGROUND: NEUROPATHIC PAIN IS DETRIMENTAL TO HUMAN HEALTH; HOWEVER, ITS PATHOGENESIS STILL REMAINS LARGELY UNKNOWN. OVEREXPRESSION OF PAIN-ASSOCIATED GENES AND INCREASED NOCICEPTIVE SOMATO-SENSITIVITY ARE WELL OBSERVED IN NEUROPATHIC PAIN. THE IMPORTANCE OF EPIGENETIC MECHANISMS IN REGULATING THE EXPRESSION OF PRO- OR ANTI-NOCICEPTIVE GENES HAS BEEN REVEALED BY STUDIES RECENTLY, AND WE HYPOTHESIZE THAT THE TRANSCRIPTIONAL COACTIVATOR AND THE HISTONE ACETYLTRANSFERASE E1A BINDING PROTEIN P300 (P300), AS A PART OF THE EPIGENETIC MECHANISMS OF GENE REGULATION, MAY BE INVOLVED IN THE PATHOGENESIS OF NEUROPATHIC PAIN INDUCED BY CHRONIC CONSTRICTION INJURY (CCI). TO TEST THIS HYPOTHESIS, TWO DIFFERENT APPROACHES WERE USED IN THIS STUDY: (I) DOWN-REGULATING P300 WITH SPECIFIC SMALL HAIRPIN RNA (SHRNA) AND (II) CHEMICAL INHIBITION OF P300 ACETYLTRANSFERASE ACTIVITY BY A SMALL MOLECULE INHIBITOR, C646. RESULTS: USING THE CCI RAT MODEL, WE FOUND THAT THE P300 EXPRESSION WAS INCREASED IN THE LUMBAR SPINAL CORD ON DAY 14 AFTER CCI. THE TREATMENT WITH INTRATHECAL P300 SHRNA REVERSED CCI-INDUCED MECHANICAL ALLODYNIA AND THERMAL HYPERALGESIA, AND SUPPRESSED THE EXPRESSION OF CYCLOOXYGENASE-2 (COX-2), A NEUROPATHIC PAIN-ASSOCIATED FACTOR. FURTHERMORE, C646, AN INHIBITOR OF P300 ACETYLTRANSFERASE, ALSO ATTENUATED MECHANICAL ALLODYNIA AND THERMAL HYPERALGESIA, ACCOMPANIED BY A SUPPRESSED COX-2 EXPRESSION, IN THE SPINAL CORD. CONCLUSIONS: THE RESULTS SUGGEST THAT, THROUGH ITS ACETYLTRANSFERASE ACTIVITY IN THE SPINAL CORD AFTER CCI, P300 EPIGENETICALLY PLAYS AN IMPORTANT ROLE IN NEUROPATHIC PAIN. INHIBITING P300, USING INTERFERING RNA OR C646, MAY BE A PROMISING APPROACH TO THE DEVELOPMENT OF NEW NEUROPATHIC PAIN THERAPIES. 2012 14 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 15 3194 40 HDAC INHIBITORS ATTENUATE THE DEVELOPMENT OF HYPERSENSITIVITY IN MODELS OF NEUROPATHIC PAIN. HISTONE DEACETYLASE INHIBITORS (HDACIS) INTERFERE WITH THE EPIGENETIC PROCESS OF HISTONE ACETYLATION AND ARE KNOWN TO HAVE ANALGESIC PROPERTIES IN MODELS OF CHRONIC INFLAMMATORY PAIN. THE AIM OF THIS STUDY WAS TO DETERMINE WHETHER THESE COMPOUNDS COULD ALSO AFFECT NEUROPATHIC PAIN. DIFFERENT CLASS I HDACIS WERE DELIVERED INTRATHECALLY INTO RAT SPINAL CORD IN MODELS OF TRAUMATIC NERVE INJURY AND ANTIRETROVIRAL DRUG-INDUCED PERIPHERAL NEUROPATHY (STAVUDINE, D4T). MECHANICAL AND THERMAL HYPERSENSITIVITY WAS ATTENUATED BY 40% TO 50% AS A RESULT OF HDACI TREATMENT, BUT ONLY IF STARTED BEFORE ANY INSULT. THE DRUGS GLOBALLY INCREASED HISTONE ACETYLATION IN THE SPINAL CORD, BUT APPEARED TO HAVE NO MEASURABLE EFFECTS IN RELEVANT DORSAL ROOT GANGLIA IN THIS TREATMENT PARADIGM, SUGGESTING THAT ANY POTENTIAL MECHANISM SHOULD BE SOUGHT IN THE CENTRAL NERVOUS SYSTEM. MICROARRAY ANALYSIS OF DORSAL CORD RNA REVEALED THE SIGNATURE OF THE SPECIFIC COMPOUND USED (MS-275) AND SUGGESTED THAT ITS MAIN EFFECT WAS MEDIATED THROUGH HDAC1. TAKEN TOGETHER, THESE DATA SUPPORT A ROLE FOR HISTONE ACETYLATION IN THE EMERGENCE OF NEUROPATHIC PAIN. 2013 16 2253 39 EPIGENETIC MODULATION OF WNT SIGNALING CONTRIBUTES TO NEUROPATHIC PAIN IN RATS. PREVIOUS STUDIES HAVE DEMONSTRATED THAT THE WNT/BETA?CATENIN SIGNALING PATHWAY IS CRITICAL TO THE INDUCTION AND MAINTENANCE OF CHRONIC NEUROPATHIC PAIN CAUSED BY PERIPHERAL INFLAMMATION AND NERVE DAMAGE. EMERGING EVIDENCE FROM RECENT STUDIES SUGGESTS THAT EPIGENETIC MECHANISMS MAY ALSO BE CRITICAL TO THE PATHOGENESIS OF CHRONIC PAIN. THE PRESENT STUDY AIMED TO ELUCIDATE THE EPIGENETIC MECHANISMS UNDERLYING ALTERED WNT SIGNALING AND THEIR INVOLVEMENT IN CCI?INDUCED NEUROPATHIC PAIN IN RAT SCIATIC NERVES. THE RESULTS OF THE PRESENT STUDY DEMONSTRATED A SIGNIFICANT INCREASE IN THE EXPRESSION LEVELS OF WNT3A IN THE DORSAL HORN OF THE RATS WITH CCI. IN ADDITION, A SIGNIFICANT INCREASE IN HISTONE H3 ACETYLATION, AND A SIGNIFICANT DECREASE IN CYTOSINE METHYLATION IN THE PROMOTER REGION OF WNT3A WAS OBSERVED IN THE DORSAL HORN OF THE RATS WITH CCI. INTRATHECAL APPLICATION OF XAV939, WHICH ACTS AS AN INHIBITOR OF WNT SIGNALING, SIGNIFICANTLY DECREASED THE EXPRESSION LEVELS OF ACTIVE BETA?CATENIN, AND ATTENUATED THE RAT BEHAVIORAL RESPONSES TO THERMAL AND MECHANICAL PAIN STIMULI. THESE RESULTS SUGGEST THAT THE EPIGENETIC UPREGULATION OF WNT3A IN THE DORSAL HORN CONTRIBUTES TO THE MAINTENANCE OF PAIN?INDUCED BEHAVIOR IN RATS WITH CCI. 2015 17 1126 47 COMPLEX REGULATION OF THE REGULATOR OF SYNAPTIC PLASTICITY HISTONE DEACETYLASE 2 IN THE RODENT DORSAL HORN AFTER PERIPHERAL INJURY. HISTONE DEACETYLASES (HDACS), HDAC2 IN PARTICULAR, HAVE BEEN SHOWN TO REGULATE VARIOUS FORMS OF LEARNING AND MEMORY. SINCE COGNITIVE PROCESSES SHARE MECHANISMS WITH SPINAL NOCICEPTIVE SIGNALLING, WE DECIDED TO INVESTIGATE THE HDAC2 EXPRESSION IN THE DORSAL HORN AFTER PERIPHERAL INJURY. USING IMMUNOHISTOCHEMISTRY, WE FOUND THAT SPINAL HDAC2 WAS MAINLY SEEN IN NEURONS AND ASTROCYTES, WITH NEURONAL EXPRESSION IN NAIVE TISSUE 2.6 TIMES GREATER THAN THAT IN ASTROCYTES. CYSTEINE (S)-NITROSYLATION OF HDAC2 RELEASES HDAC2 GENE SILENCING AND IS CONTROLLED BY NITRIC OXIDE (NO). A DURATION OF 48 H AFTER INTRAPLANTAR INJECTION OF COMPLETE FREUND'S ADJUVANT, THERE WAS AN IPSILATERAL INCREASE IN THE MOST IMPORTANT NO-PRODUCING ENZYME IN PAIN STATES, NITRIC OXIDE SYNTHASE (NNOS), ACCOMPANIED BY AN INCREASE IN HDAC2 S-NITROSYLATION. MOREOVER, A SUBSET OF NNOS-POSITIVE NEURONS EXPRESSED CFOS, A KNOWN TARGET OF HDAC2, SUGGESTING THAT DEREPRESSION OF CFOS EXPRESSION FOLLOWING HDAC2 S-NITROSYLATION MIGHT OCCUR AFTER NOXIOUS STIMULATION. WE SAW NO CHANGE IN GLOBAL HDAC2 EXPRESSION IN BOTH SHORT- AND LONG-TERM PAIN STATES. HOWEVER, HDAC2 WAS INCREASED IN ASTROCYTES 7 DAYS AFTER NEUROPATHIC INJURY SUGGESTING THAT HDAC2 MIGHT INHIBIT ASTROCYTIC GENE EXPRESSION IN NEUROPATHIC PAIN STATES. ALL TOGETHER, OUR RESULTS INDICATE THAT THE EPIGENETIC REGULATION OF TRANSCRIPTIONAL PROGRAMMES IN THE DORSAL HORN AFTER INJURY IS CELL SPECIFIC. MOREOVER, THE PROMINENT ROLE OF NO IN PERSISTENT PAIN STATES SUGGESTS THAT HDAC2 S-NITROSYLATION COULD PLAY A CRUCIAL ROLE IN THE REGULATION OF GENE EXPRESSION LEADING TO HYPERSENSITIVITY. OUR MANUSCRIPT DESCRIBES FOR THE FIRST TIME THE REGULATION OF THE MEMORY REGULATOR HISTONE DEACETYLASE 2 (HDAC2) IN THE SUPERFICIAL DORSAL HORN OF ADULT RATS FOLLOWING PERIPHERAL INJURY. OUR CELL-SPECIFIC APPROACH HAS REVEALED A COMPLEX PATTERN OF EXPRESSION OF SPINAL HDAC2 THAT DEPENDS ON THE INJURY AND THE CELL TYPE, SUGGESTING A SOPHISTICATED REGULATION OF GENE EXPRESSION BY HDAC2. 2016 18 3324 44 HISTONE DEACETYLASE 2 IS INVOLVED IN MICRO?OPIOID RECEPTOR SUPPRESSION IN THE SPINAL DORSAL HORN IN A RAT MODEL OF CHRONIC PANCREATITIS PAIN. CHRONIC PAIN OCCURS IN ~85-90% OF CHRONIC PANCREATITIS (CP) PATIENTS. HOWEVER, AS THE PATHOGENESIS OF CP PAIN REMAINS TO BE FULLY UNDERSTOOD, THE CURRENT THERAPIES FOR CP PAIN REMAIN INADEQUATE. EMERGING EVIDENCE HAS SUGGESTED THAT THE EPIGENETIC MODULATIONS OF GENES ARE INVOLVED IN CHRONIC PAIN. IN THE PRESENT STUDY, INTRAPANCREATIC TRINITROBENZENE SULFONIC ACID INFUSIONS WERE USED TO ESTABLISH A CP MODEL IN RATS. MECHANICAL ALLODYNIA WAS MEASURED WITH VON FREY FILAMENTS. IMMUNOFLUORESCENT STAINING ANALYSIS WAS USED TO OBSERVE THE EXPRESSION CHANGES OF HISTONE DEACETYLASE 2 (HDAC2) AND MICRO?OPIOID RECEPTOR (MOR), AND INTRATHECAL ADMINISTRATION OF THE SELECTIVE HDAC2 INHIBITOR AR?42 WAS USED TO ASSESS THE UNDERLYING MECHANISMS. THE EXPRESSION LEVELS OF C?JUN N?TERMINAL KINASE (JNK) IN THE THORACIC SPINAL CORD WERE DETECTED BY WESTERN BLOTTING, AND THE MRNA EXPRESSION LEVELS OF INTERLEUKIN (IL)1?BETA, IL?6 AND TUMOR NECROSIS FACTOR (TNF)?ALPHA WERE DETECTED BY REVERSE TRANSCRIPTION?QUANTITATIVE POLYMERASE CHAIN REACTION. THE RESULTS DEMONSTRATED THAT HDAC2 EXPRESSION WAS UPREGULATED DURING THE COURSE OF CP INDUCTION, WHILE MOR ACTIVITY IN THE THORACIC SPINAL DORSAL HORN WAS SIGNIFICANTLY SUPPRESSED. INTRATHECAL INFUSION OF AR?42 SIGNIFICANTLY ATTENUATED CP?INDUCED MECHANICAL ALLODYNIA, WITH RESCUED MOR ACTIVITY. ADDITIONALLY, HDAC2 FACILITATED THE RELEASE OF INFLAMMATORY CYTOKINES, INCLUDING IL?1BETA, IL?6 AND TNF?ALPHA. THESE RESULTS SUGGESTED THAT THE UNDERLYING MECHANISMS OF HDAC2 REGULATING MOR ACTIVITY UNDER CP INDUCTION MAY OCCUR VIA PROMOTING THE RELEASE OF INFLAMMATORY CYTOKINES, THUS ACTIVATING THE JNK SIGNALING PATHWAY. THE PRESENT STUDY SUGGESTED THAT THE EPIGENETIC?REGULATED DISTURBANCE OF MOR IS DEPENDENT ON THE ENDOGENOUS ANALGESIA SYSTEM IN CP, WHICH MAY A PROVIDE NOVEL THERAPEUTIC STRATEGY FOR TREATING PAIN IN CP. 2018 19 1320 39 DEMETHYLATION REGULATION OF BDNF GENE EXPRESSION IN DORSAL ROOT GANGLION NEURONS IS IMPLICATED IN OPIOID-INDUCED PAIN HYPERSENSITIVITY IN RATS. REPEATED ADMINISTRATION OF MORPHINE MAY RESULT IN OPIOID-INDUCED HYPERSENSITIVITY (OIH), WHICH INVOLVES ALTERED EXPRESSION OF NUMEROUS GENES, INCLUDING BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) IN DORSAL ROOT GANGLION (DRG) NEURONS. YET, IT REMAINS UNCLEAR HOW BDNF EXPRESSION IS INCREASED IN DRG NEURONS AFTER REPEATED MORPHINE TREATMENT. DNA METHYLATION IS AN IMPORTANT MECHANISM OF EPIGENETIC CONTROL OF GENE EXPRESSION. IN THE CURRENT STUDY, WE HYPOTHESIZED THAT THE DEMETHYLATION REGULATION OF CERTAIN BDNF GENE PROMOTERS IN DRG NEURONS MAY CONTRIBUTE TO THE DEVELOPMENT OF OIH. REAL-TIME RT-PCR WAS USED TO ASSESS CHANGES IN THE MRNA TRANSCRIPTION LEVELS OF MAJOR BDNF EXONS INCLUDING EXON I, II, IV, VI, AS WELL AS TOTAL BDNF MRNA IN DRGS FROM RATS AFTER REPEATED MORPHINE ADMINISTRATION. THE LEVELS OF EXON IV AND TOTAL BDNF MRNA WERE SIGNIFICANTLY UPREGULATED BY REPEATED MORPHINE ADMINISTRATION, AS COMPARED TO THAT IN SALINE CONTROL GROUP. FURTHER, ELISA ARRAY AND IMMUNOCYTOCHEMISTRY STUDY REVEALED A ROBUST UPREGULATION OF BDNF PROTEIN EXPRESSION IN DRG NEURONS AFTER REPEATED MORPHINE EXPOSURE. CORRESPONDINGLY, THE METHYLATION LEVELS OF BDNF EXON IV PROMOTER SHOWED A SIGNIFICANT DOWNREGULATION BY MORPHINE TREATMENT. IMPORTANTLY, INTRATHECAL ADMINISTRATION OF A BDNF ANTIBODY, BUT NOT CONTROL IGG, SIGNIFICANTLY INHIBITED MECHANICAL HYPERSENSITIVITY THAT DEVELOPED IN RATS AFTER REPEATED MORPHINE TREATMENT. CONVERSELY, INTRATHECAL ADMINISTRATION OF AN INHIBITOR OF DNA METHYLATION, 5-AZA-2'-DEOXYCYTIDINE (5-AZA-DC) MARKEDLY UPREGULATED THE BDNF PROTEIN EXPRESSION IN DRG NEURONS AND ENHANCED THE MECHANICAL ALLODYNIA AFTER REPEATED MORPHINE EXPOSURE. TOGETHER, OUR FINDINGS SUGGEST THAT DEMETHYLATION REGULATION OF BDNF GENE PROMOTER MAY BE IMPLICATED IN THE DEVELOPMENT OF OIH THROUGH EPIGENETIC CONTROL OF BDNF EXPRESSION IN DRG NEURONS. 2016 20 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