1 1126 150 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 2 5266 43 PROMOTED INTERACTION OF C/EBPALPHA WITH DEMETHYLATED CXCR3 GENE PROMOTER CONTRIBUTES TO NEUROPATHIC PAIN IN MICE. DNA METHYLATION HAS BEEN IMPLICATED IN THE PATHOGENESIS OF CHRONIC PAIN. HOWEVER, THE SPECIFIC GENES REGULATED BY DNA METHYLATION UNDER NEUROPATHIC PAIN CONDITION REMAIN LARGELY UNKNOWN. HERE WE INVESTIGATED HOW CHEMOKINE RECEPTOR CXCR3 IS REGULATED BY DNA METHYLATION AND HOW IT CONTRIBUTES TO NEUROPATHIC PAIN INDUCED BY SPINAL NERVE LIGATION (SNL) IN MICE. SNL INCREASED CXCR3 MRNA AND PROTEIN EXPRESSION IN THE NEURONS OF THE SPINAL CORD. MEANWHILE, THE CPG (5'-CYTOSINE-PHOSPHATE-GUANINE-3') ISLAND IN THE CXCR3 GENE PROMOTER REGION WAS DEMETHYLATED, AND THE EXPRESSION OF DNA METHYLTRANSFERASE 3B (DNMT3B) WAS DECREASED. SNL ALSO INCREASED THE BINDING OF CCAAT (CYTIDINE-CYTIDINE-ADENOSINE-ADENOSINE-THYMIDINE)/ENHANCER BINDING PROTEIN ALPHA (C/EBPALPHA) WITH CXCR3 PROMOTER AND DECREASED THE BINDING OF DNMT3B WITH CXCR3 PROMOTER IN THE SPINAL CORD. C/EBPALPHA EXPRESSION WAS INCREASED IN SPINAL NEURONS AFTER SNL, AND INHIBITION OF C/EBPALPHA BY INTRATHECAL SMALL INTERFERING RNA ATTENUATED SNL-INDUCED PAIN HYPERSENSITIVITY AND REDUCED CXCR3 EXPRESSION. FURTHERMORE, SNL-INDUCED MECHANICAL ALLODYNIA AND HEAT HYPERALGESIA WERE MARKEDLY REDUCED IN CXCR3(-/-) MICE. SPINAL INHIBITION OF CXCR3 BY SHRNA OR CXCR3 ANTAGONIST ALSO ATTENUATED ESTABLISHED NEUROPATHIC PAIN. MOREOVER, CXCL10, THE LIGAND OF CXCR3, WAS INCREASED IN SPINAL NEURONS AND ASTROCYTES AFTER SNL. SUPERFUSING SPINAL CORD SLICES WITH CXCL10 ENHANCED SPONTANEOUS EPSCS AND POTENTIATED NMDA-INDUCED AND AMPA-INDUCED CURRENTS OF LAMINA II NEURONS. FINALLY, INTRATHECAL INJECTION OF CXCL10 INDUCED CXCR3-DEPENDENT PAIN HYPERSENSITIVITY IN NAIVE MICE. COLLECTIVELY, OUR RESULTS DEMONSTRATED THAT CXCR3, INCREASED BY DNA DEMETHYLATION AND THE ENHANCED INTERACTION WITH C/EBPALPHA, CAN BE ACTIVATED BY CXCL10 TO FACILITATE EXCITATORY SYNAPTIC TRANSMISSION AND CONTRIBUTE TO THE MAINTENANCE OF NEUROPATHIC PAIN. SIGNIFICANCE STATEMENT: PERIPHERAL NERVE INJURY INDUCES CHANGES OF GENE EXPRESSION IN THE SPINAL CORD THAT MAY CONTRIBUTE TO THE PATHOGENESIS OF NEUROPATHIC PAIN. CXCR3 IS A CHEMOKINE RECEPTOR. WHETHER IT IS INVOLVED IN NEUROPATHIC PAIN AND HOW IT IS REGULATED AFTER NERVE INJURY REMAIN LARGELY UNKNOWN. OUR STUDY DEMONSTRATES THAT SPINAL NERVE LIGATION DOWNREGULATES THE EXPRESSION OF DNMT3B, WHICH MAY CAUSE DEMETHYLATION OF CXCR3 GENE PROMOTER AND FACILITATE THE BINDING OF CCAAT/ENHANCER BINDING PROTEIN ALPHA WITH CXCR3 PROMOTER AND FURTHER INCREASE CXCR3 EXPRESSION IN SPINAL NEURONS. THE UPREGULATED CXCR3 MAY CONTRIBUTE TO NEUROPATHIC PAIN BY FACILITATING CENTRAL SENSITIZATION. OUR STUDY REVEALS AN EPIGENETIC MECHANISM UNDERLYING CXCR3 EXPRESSION AND ALSO SUGGESTS THAT TARGETING THE EXPRESSION OR ACTIVATION OF CXCR3 SIGNALING MAY OFFER NEW THERAPEUTICS FOR NEUROPATHIC PAIN. 2017 3 3320 38 HISTONE ACETYLATION IN MICROGLIA CONTRIBUTES TO EXERCISE-INDUCED HYPOALGESIA IN NEUROPATHIC PAIN MODEL MICE. PHYSICAL EXERCISE CAN ATTENUATE NEUROPATHIC PAIN (NPP), BUT THE EXACT MECHANISM UNDERLYING EXERCISE-INDUCED HYPOALGESIA (EIH) REMAINS UNCLEAR. RECENT STUDIES HAVE SHOWN THAT HISTONE HYPERACETYLATION VIA PHARMACOLOGICAL INHIBITION OF HISTONE DEACETYLASES IN THE SPINAL CORD ATTENUATES NPP, AND THAT HISTONE ACETYLATION MAY LEAD TO THE PRODUCTION OF ANALGESIC FACTORS INCLUDING INTERLEUKIN 10. WE INTENDED TO CLARIFY WHETHER HISTONE ACETYLATION IN MICROGLIA IN THE SPINAL DORSAL HORN CONTRIBUTES TO EIH IN NPP MODEL MICE. C57BL/6J MICE UNDERWENT PARTIAL SCIATIC NERVE LIGATION (PSL) AND PSL- AND SHAM-RUNNER MICE RAN ON A TREADMILL AT A SPEED OF 7 M/MIN FOR 60 MIN/D, 5 DAYS PER WEEK, FROM 2 DAYS AFTER THE SURGERY. PSL-SEDENTARY MICE DEVELOPED MECHANICAL ALLODYNIA AND HEAT HYPERALGESIA, BUT SUCH BEHAVIORS WERE SIGNIFICANTLY ATTENUATED IN PSL-RUNNER MICE. IN IMMUNOFLUORESCENCE ANALYSIS, PSL SURGERY MARKEDLY INCREASED THE NUMBER OF HISTONE DEACETYLASE 1-POSITIVE/CD11B-POSITIVE MICROGLIA IN THE IPSILATERAL SUPERFICIAL DORSAL HORN, AND THEY WERE SIGNIFICANTLY DECREASED BY TREADMILL-RUNNING. MOREOVER, THE NUMBER OF MICROGLIA WITH NUCLEAR EXPRESSION OF ACETYLATED H3K9 IN THE IPSILATERAL SUPERFICIAL DORSAL HORN WAS MAINTAINED AT LOW LEVELS IN PSL-SEDENTARY MICE, BUT RUNNING EXERCISE SIGNIFICANTLY INCREASED THEM. THEREFORE, WE CONCLUDE THAT THE EPIGENETIC MODIFICATION THAT CAUSES HYPERACETYLATION OF H3K9 IN ACTIVATED MICROGLIA MAY PLAY A ROLE IN PRODUCING EIH. PERSPECTIVE: THIS ARTICLE PRESENTS THE IMPORTANCE OF EPIGENETIC MODIFICATION IN MICROGLIA IN PRODUCING EIH. THE CURRENT RESEARCH IS NOT ONLY HELPFUL FOR DEVELOPING NOVEL NONPHARMACOLOGICAL THERAPY FOR NPP, BUT WILL ALSO ENHANCE OUR UNDERSTANDING OF THE MECHANISMS AND AVAILABILITY OF EXERCISE IN OUR DAILY LIFE. 2016 4 1654 30 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 5 4906 42 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 6 4617 32 NERVE INJURY-INDUCED CHRONIC PAIN IS ASSOCIATED WITH PERSISTENT DNA METHYLATION REPROGRAMMING IN DORSAL ROOT GANGLION. NERVE INJURY-INDUCED HYPERACTIVITY OF PRIMARY SENSORY NEURONS IN THE DORSAL ROOT GANGLION (DRG) CONTRIBUTES TO CHRONIC PAIN DEVELOPMENT, BUT THE UNDERLYING EPIGENETIC MECHANISMS REMAIN POORLY UNDERSTOOD. HERE WE DETERMINED GENOME-WIDE CHANGES IN DNA METHYLATION IN THE NERVOUS SYSTEM IN NEUROPATHIC PAIN. SPINAL NERVE LIGATION (SNL), BUT NOT PACLITAXEL TREATMENT, IN MALE SPRAGUE DAWLEY RATS INDUCED A CONSISTENT LOW-LEVEL HYPOMETHYLATION IN THE CPG SITES IN THE DRG DURING THE ACUTE AND CHRONIC PHASES OF NEUROPATHIC PAIN. DNA METHYLATION REMODELING IN THE DRG OCCURRED EARLY AFTER SNL AND PERSISTED FOR AT LEAST 3 WEEKS. SNL CAUSED DNA METHYLATION CHANGES AT 8% OF CPG SITES WITH PREVAILING HYPOMETHYLATION OUTSIDE OF CPG ISLANDS, IN INTRONS, INTERGENIC REGIONS, AND REPETITIVE SEQUENCES. IN CONTRAST, SNL CAUSED MORE GAINS OF METHYLATION IN THE SPINAL CORD AND PREFRONTAL CORTEX. THE DNA METHYLATION CHANGES IN THE INJURED DRGS RECAPITULATED DEVELOPMENTAL REPROGRAMMING AT THE NEONATAL STAGE. METHYLATION REPROGRAMMING WAS CORRELATED WITH INCREASED GENE EXPRESSION VARIABILITY. A DIET DEFICIENT IN METHYL DONORS INDUCED HYPOMETHYLATION AND PAIN HYPERSENSITIVITY. INTRATHECAL ADMINISTRATION OF THE DNA METHYLTRANSFERASE INHIBITOR RG108 CAUSED LONG-LASTING PAIN HYPERSENSITIVITY. DNA METHYLATION REPROGRAMMING IN THE DRG THUS CONTRIBUTES TO NERVE INJURY-INDUCED CHRONIC PAIN. RESTORING DNA METHYLATION MAY REPRESENT A NEW THERAPEUTIC APPROACH TO TREAT NEUROPATHIC PAIN.SIGNIFICANCE STATEMENT EPIGENETIC MECHANISMS ARE CRITICALLY INVOLVED IN THE TRANSITION FROM ACUTE TO CHRONIC PAIN AFTER NERVE INJURY. HOWEVER, GENOME-WIDE CHANGES IN DNA METHYLATION IN THE NERVOUS SYSTEM AND THEIR ROLES IN NEUROPATHIC PAIN DEVELOPMENT REMAIN UNCLEAR. HERE WE USED DIGITAL RESTRICTION ENZYME ANALYSIS OF METHYLATION TO QUANTITATIVELY DETERMINE GENOME-WIDE DNA METHYLATION CHANGES CAUSED BY NERVE INJURY. WE SHOWED THAT NERVE INJURY CAUSED DNA METHYLATION CHANGES AT 8% OF CPG SITES WITH PREVAILING HYPOMETHYLATION OUTSIDE OF CPG ISLANDS IN THE DORSAL ROOT GANGLION. REDUCING DNA METHYLATION INDUCED PAIN HYPERSENSITIVITY, WHEREAS INCREASING DNA METHYLATION ATTENUATED NEUROPATHIC PAIN. THESE FINDINGS EXTEND OUR UNDERSTANDING OF THE EPIGENETIC MECHANISM OF CHRONIC NEUROPATHIC PAIN AND SUGGEST NEW STRATEGIES TO TREAT NERVE INJURY-INDUCED CHRONIC PAIN. 2018 7 3955 31 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 8 4577 28 MYOSTATIN: BASIC BIOLOGY TO CLINICAL APPLICATION. MYOSTATIN IS A MEMBER OF THE TRANSFORMING GROWTH FACTOR (TGF)-BETA SUPERFAMILY. IT IS EXPRESSED BY ANIMAL AND HUMAN SKELETAL MUSCLE CELLS WHERE IT LIMITS MUSCLE GROWTH AND PROMOTES PROTEIN BREAKDOWN. ITS EFFECTS ARE INFLUENCED BY COMPLEX MECHANISMS INCLUDING TRANSCRIPTIONAL AND EPIGENETIC REGULATION AND MODULATION BY EXTRACELLULAR BINDING PROTEINS. DUE TO ITS ACTIONS IN PROMOTING MUSCLE ATROPHY AND CACHEXIA, MYOSTATIN HAS BEEN INVESTIGATED AS A PROMISING THERAPEUTIC TARGET TO COUNTERACT MUSCLE MASS LOSS IN EXPERIMENTAL MODELS AND PATIENTS AFFECTED BY DIFFERENT MUSCLE-WASTING CONDITIONS. MOREOVER, GROWING EVIDENCE INDICATES THAT MYOSTATIN, BEYOND TO REGULATE SKELETAL MUSCLE GROWTH, MAY HAVE A ROLE IN MANY PHYSIOLOGIC AND PATHOLOGIC PROCESSES, SUCH AS OBESITY, INSULIN RESISTANCE, CARDIOVASCULAR AND CHRONIC KIDNEY DISEASE. IN THIS CHAPTER, WE REVIEW MYOSTATIN BIOLOGY, INCLUDING INTRACELLULAR AND EXTRACELLULAR REGULATORY PATHWAYS, AND THE ROLE OF MYOSTATIN IN MODULATING PHYSIOLOGIC PROCESSES, SUCH AS MUSCLE GROWTH AND AGING. MOREOVER, WE DISCUSS THE MOST RELEVANT EXPERIMENTAL AND CLINICAL EVIDENCE SUPPORTING THE EXTRA-MUSCLE EFFECTS OF MYOSTATIN. FINALLY, WE CONSIDER THE MAIN STRATEGIES DEVELOPED AND TESTED TO INHIBIT MYOSTATIN IN CLINICAL TRIALS AND DISCUSS THE LIMITS AND FUTURE PERSPECTIVES OF THE RESEARCH ON MYOSTATIN. 2022 9 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 10 6138 30 THE ETIOLOGICAL CHANGES OF ACETYLATION IN PERIPHERAL NERVE INJURY-INDUCED NEUROPATHIC HYPERSENSITIVITY. NEUROPATHIC PAIN IS A COMMON CHRONIC PAIN CONDITION WITH MECHANISMS FAR CLEARLY BEEN ELUCIDATED. MOUNTING PRECLINICAL AND CLINICAL STUDIES HAVE SHOWN NEUROPATHIC PAIN IS HIGHLY ASSOCIATED WITH HISTONE ACETYLATION MODIFICATION, WHICH FOLLOWS EXPRESSION REGULATION OF VARIOUS PAIN-RELATED MOLECULES SUCH AS MGLUR1/5, GLUTAMATE ASPARTATE TRANSPORTER, GLUTAMATE TRANSPORTER-1, GAD65, NA(V)1.8, KV4.3, MU-OPIOID RECEPTOR, BRAIN-DERIVED NEUROTROPHIC FACTOR, AND CERTAIN CHEMOKINES. AS TWO TYPES OF PIVOTAL ENZYMES INVOLVED IN HISTONE ACETYLATION, HISTONE DEACETYLASES INDUCE HISTONE DEACETYLATION TO SILENCE GENE EXPRESSION; IN CONTRAST, HISTONE ACETYL TRANSFERASES FACILITATE HISTONE ACETYLATION TO POTENTIATE GENE TRANSCRIPTION. ACCORDINGLY, UPREGULATION OR BLOCKADE OF ACETYLATION MAY BE A PROMISING INTERVENTION DIRECTION FOR NEUROPATHIC PAIN TREATMENT. IN FACT, NUMEROUS ANIMAL STUDIES HAVE SUGGESTED VARIOUS HISTONE DEACETYLASE INHIBITORS, SIRT (CLASS III HISTONE DEACETYLASES) ACTIVATORS, AND HISTONE ACETYL TRANSFERASES INHIBITORS ARE EFFECTIVE IN NEUROPATHIC PAIN TREATMENT VIA TARGETING SPECIFIC EPIGENETIC SITES. IN THIS REVIEW, WE SUMMARIZE THE CHARACTERISTICS OF THE MOLECULES AND MECHANISMS OF NEUROPATHY-RELATED ACETYLATION, AS WELL AS THE ACETYLATION UPREGULATION AND BLOCKADE FOR NEUROPATHIC PAIN THERAPY. FINALLY, WE WILL DISCUSS THE CURRENT DRUG ADVANCES FOCUSING ON NEUROPATHY-RELATED ACETYLATION ALONG WITH THE UNDERLYING TREATMENT MECHANISMS. 2018 11 2300 46 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 12 2053 28 EPIGENETIC CONNECTIONS OF THE TRPA1 ION CHANNEL IN PAIN TRANSMISSION AND NEUROGENIC INFLAMMATION - A THERAPEUTIC PERSPECTIVE IN MIGRAINE? PERSISTENT REPROGRAMMING OF EPIGENETIC PATTERN LEADS TO CHANGES IN GENE EXPRESSION OBSERVED IN MANY NEUROLOGICAL DISORDERS. TRANSIENT RECEPTOR POTENTIAL CATION CHANNEL SUBFAMILY A MEMBER 1 (TRPA1), A MEMBER OF THE TRP CHANNELS SUPERFAMILY, IS ACTIVATED BY MANY MIGRAINE TRIGGERS AND EXPRESSED IN TRIGEMINAL NEURONS AND BRAIN REGIONS THAT ARE IMPORTANT IN MIGRAINE PATHOGENESIS. TRP CHANNELS CHANGE NOXIOUS STIMULI INTO PAIN SIGNALS WITH THE INVOLVEMENT OF EPIGENETIC REGULATION. THE EXPRESSION OF THE TRPA1 ENCODING GENE, TRPA1, IS MODULATED IN PAIN-RELATED SYNDROMES BY EPIGENETIC ALTERATIONS, INCLUDING DNA METHYLATION, HISTONE MODIFICATIONS, AND EFFECTS OF NON-CODING RNAS: MICRO RNAS (MIRNAS), LONG NON-CODING RNAS, AND CIRCULAR RNAS. TRPA1 MAY CHANGE EPIGENETIC PROFILE OF MANY PAIN-RELATED GENES AS IT MAY MODIFY ENZYMES RESPONSIBLE FOR EPIGENETIC MODIFICATIONS AND EXPRESSION OF NON-CODING RNAS. TRPA1 MAY INDUCE THE RELEASE OF CALCITONIN GENE RELATED PEPTIDE (CGRP), FROM TRIGEMINAL NEURONS AND DURAL TISSUE. THEREFORE, EPIGENETIC REGULATION OF TRPA1 MAY PLAY A ROLE IN EFFICACY AND SAFETY OF ANTI-MIGRAINE THERAPIES TARGETING TRP CHANNELS AND CGRP. TRPA1 IS ALSO INVOLVED IN NEUROGENIC INFLAMMATION, IMPORTANT IN MIGRAINE PATHOGENESIS. THE FUNDAMENTAL ROLE OF TRPA1 IN INFLAMMATORY PAIN TRANSMISSION MAY BE EPIGENETICALLY REGULATED. IN CONCLUSION, EPIGENETIC CONNECTIONS OF TRPA1 MAY PLAY A ROLE IN EFFICACY AND SAFETY OF ANTI-MIGRAINE THERAPY TARGETING TRP CHANNELS OR CGRP AND THEY SHOULD BE FURTHER EXPLORED FOR EFFICIENT AND SAFE ANTIMIGRAINE TREATMENT. THIS NARRATIVE/PERSPECTIVE REVIEW PRESENTS INFORMATION ON THE STRUCTURE AND FUNCTIONS OF TRPA1 AS WELL AS ROLE OF ITS EPIGENETIC CONNECTIONS IN PAIN TRANSMISSION AND POTENTIAL IN MIGRAINE THERAPY. 2023 13 5865 39 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 14 2253 26 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 15 2061 38 EPIGENETIC CONTROL OF HYPERSENSITIVITY IN CHRONIC INFLAMMATORY PAIN BY THE DE NOVO DNA METHYLTRANSFERASE DNMT3A2. CHRONIC PAIN IS A PATHOLOGICAL MANIFESTATION OF NEURONAL PLASTICITY SUPPORTED BY ALTERED GENE TRANSCRIPTION IN SPINAL CORD NEURONS THAT RESULTS IN LONG-LASTING HYPERSENSITIVITY. RECENTLY, THE CONCEPT THAT EPIGENETIC REGULATORS MIGHT BE IMPORTANT IN PATHOLOGICAL PAIN HAS EMERGED, BUT A CLEAR UNDERSTANDING OF THE MOLECULAR PLAYERS INVOLVED IN THE PROCESS IS STILL LACKING. IN THIS STUDY, WE LINKED DNMT3A2, A SYNAPTIC ACTIVITY-REGULATED DE NOVO DNA METHYLTRANSFERASE, TO CHRONIC INFLAMMATORY PAIN. WE OBSERVED THAT DNMT3A2 LEVELS ARE INCREASED IN THE SPINAL CORD OF ADULT MICE FOLLOWING PLANTAR INJECTION OF COMPLETE FREUND'S ADJUVANT, AN IN VIVO MODEL OF CHRONIC INFLAMMATORY PAIN. IN VIVO KNOCKDOWN OF DNMT3A2 EXPRESSION IN DORSAL HORN NEURONS BLUNTED THE INDUCTION OF GENES TRIGGERED BY COMPLETE FREUND'S ADJUVANT INJECTION. AMONG THE GENES WHOSE TRANSCRIPTION WAS FOUND TO BE INFLUENCED BY DNMT3A2 EXPRESSION IN THE SPINAL CORD IS PTGS2, ENCODING FOR COX-2, A PRIME MEDIATOR OF PAIN PROCESSING. LOWERING THE LEVELS OF DNMT3A2 PREVENTED THE ESTABLISHMENT OF LONG-LASTING INFLAMMATORY HYPERSENSITIVITY. THESE RESULTS IDENTIFY DNMT3A2 AS AN IMPORTANT EPIGENETIC REGULATOR NEEDED FOR THE ESTABLISHMENT OF CENTRAL SENSITIZATION. TARGETING EXPRESSION OR FUNCTION OF DNMT3A2 MAY BE SUITABLE FOR THE TREATMENT OF CHRONIC PAIN. 2019 16 2272 36 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 17 2452 47 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 18 2756 41 EXPRESSION OF DNA METHYLTRANSFERASES IN ADULT DORSAL ROOT GANGLIA IS CELL-TYPE SPECIFIC AND UP REGULATED IN A RODENT MODEL OF NEUROPATHIC PAIN. NEUROPATHIC PAIN IS ASSOCIATED WITH HYPEREXCITABILITY AND INTRINSIC FIRING OF DORSAL ROOT GANGLIA (DRG) NEURONS. THESE PHENOTYPICAL CHANGES CAN BE LONG LASTING, POTENTIALLY SPANNING THE ENTIRE LIFE OF ANIMAL MODELS, AND DEPEND ON ALTERED EXPRESSION OF NUMEROUS PROTEINS, INCLUDING MANY ION CHANNELS. YET, HOW DRGS MAINTAIN LONG-TERM CHANGES IN PROTEIN EXPRESSION IN NEUROPATHIC CONDITIONS REMAINS UNCLEAR. DNA METHYLATION IS A WELL-KNOWN MECHANISM OF EPIGENETIC CONTROL OF GENE EXPRESSION AND IS ACHIEVED BY THE ACTION OF THREE ENZYMES: DNA METHYLTRANSFERASE (DNMT) 1, 3A, AND 3B, WHICH HAVE BEEN STUDIED PRIMARILY DURING DEVELOPMENT. WE FIRST PERFORMED IMMUNOHISTOCHEMICAL ANALYSIS TO ASSESS WHETHER THESE ENZYMES ARE EXPRESSED IN ADULT RAT DRGS (L4-5) AND FOUND THAT DNMT1 IS EXPRESSED IN BOTH GLIA AND NEURONS, DNMT3A IS PREFERENTIALLY EXPRESSED IN GLIA AND DNMT3B IS PREFERENTIALLY EXPRESSED IN NEURONS. A RAT MODEL OF NEUROPATHIC PAIN WAS THEN USED TO DETERMINE WHETHER NERVE INJURY MAY INDUCE EPIGENETIC CHANGES IN DRGS AT MULTIPLE TIME POINTS AFTER PAIN ONSET. REAL-TIME RT PCR ANALYSIS REVEALED ROBUST AND TIME-DEPENDENT CHANGES IN DNMT TRANSCRIPT EXPRESSION IN IPSILATERAL DRGS FROM SPARED NERVE INJURY (SNI) BUT NOT SHAM RATS. INTERESTINGLY, DNMT3B TRANSCRIPT SHOWED A ROBUST UPREGULATION THAT APPEARED ALREADY 1 WEEK AFTER SURGERY AND PERSISTED AT 4 WEEKS (OUR ENDPOINT); IN CONTRAST, DNMT1 AND DNMT3A TRANSCRIPTS SHOWED ONLY MODERATE UPREGULATION THAT WAS TRANSIENT AND DID NOT APPEAR UNTIL THE SECOND WEEK. WE SUGGEST THAT DNMT REGULATION IN ADULT DRGS MAY BE A CONTRIBUTOR TO THE PAIN PHENOTYPE AND MERITS FURTHER STUDY. 2014 19 1630 34 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 20 3721 49 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