1 6537 110 TRANSCRIPTIONAL REGULATOR PRDM12 IS ESSENTIAL FOR HUMAN PAIN PERCEPTION. PAIN PERCEPTION HAS EVOLVED AS A WARNING MECHANISM TO ALERT ORGANISMS TO TISSUE DAMAGE AND DANGEROUS ENVIRONMENTS. IN HUMANS, HOWEVER, UNDESIRABLE, EXCESSIVE OR CHRONIC PAIN IS A COMMON AND MAJOR SOCIETAL BURDEN FOR WHICH AVAILABLE MEDICAL TREATMENTS ARE CURRENTLY SUBOPTIMAL. NEW THERAPEUTIC OPTIONS HAVE RECENTLY BEEN DERIVED FROM STUDIES OF INDIVIDUALS WITH CONGENITAL INSENSITIVITY TO PAIN (CIP). HERE WE IDENTIFIED 10 DIFFERENT HOMOZYGOUS MUTATIONS IN PRDM12 (ENCODING PRDI-BF1 AND RIZ HOMOLOGY DOMAIN-CONTAINING PROTEIN 12) IN SUBJECTS WITH CIP FROM 11 FAMILIES. PRDM PROTEINS ARE A FAMILY OF EPIGENETIC REGULATORS THAT CONTROL NEURAL SPECIFICATION AND NEUROGENESIS. WE DETERMINED THAT PRDM12 IS EXPRESSED IN NOCICEPTORS AND THEIR PROGENITORS AND PARTICIPATES IN THE DEVELOPMENT OF SENSORY NEURONS IN XENOPUS EMBRYOS. MOREOVER, CIP-ASSOCIATED MUTANTS ABROGATE THE HISTONE-MODIFYING POTENTIAL ASSOCIATED WITH WILD-TYPE PRDM12. PRDM12 EMERGES AS A KEY FACTOR IN THE ORCHESTRATION OF SENSORY NEUROGENESIS AND MAY HOLD PROMISE AS A TARGET FOR NEW PAIN THERAPEUTICS. 2015 2 5155 31 PRDM12 MODULATES PAIN-RELATED BEHAVIOR BY REMODELING GENE EXPRESSION IN MATURE NOCICEPTORS. PRDM12 IS A CONSERVED EPIGENETIC TRANSCRIPTIONAL REGULATOR THAT DISPLAYS RESTRICTED EXPRESSION IN NOCICEPTORS OF THE DEVELOPING PERIPHERAL NERVOUS SYSTEM. IN MICE, PRDM12 IS REQUIRED FOR THE DEVELOPMENT OF THE ENTIRE NOCICEPTIVE LINEAGE. IN HUMANS, PRDM12 MUTATIONS CAUSE CONGENITAL INSENSITIVITY TO PAIN, LIKELY BECAUSE OF THE LOSS OF NOCICEPTORS. PRDM12 EXPRESSION IS MAINTAINED IN MATURE NOCICEPTORS SUGGESTING A YET-TO-BE EXPLORED FUNCTIONAL ROLE IN ADULTS. USING PRDM12 INDUCIBLE CONDITIONAL KNOCKOUT MOUSE MODELS, WE REPORT THAT IN ADULT NOCICEPTORS PRDM12 IS NO LONGER REQUIRED FOR CELL SURVIVAL BUT CONTINUES TO PLAY A ROLE IN THE TRANSCRIPTIONAL CONTROL OF A NETWORK OF GENES, MANY OF THEM ENCODING ION CHANNELS AND RECEPTORS. WE FOUND THAT DISRUPTION OF PRDM12 ALTERS THE EXCITABILITY OF DORSAL ROOT GANGLION NEURONS IN CULTURE. PHENOTYPICALLY, WE OBSERVED THAT MICE LACKING PRDM12 EXHIBIT NORMAL RESPONSES TO THERMAL AND MECHANICAL NOCICEPTIVE STIMULI BUT A REDUCED RESPONSE TO CAPSAICIN AND HYPERSENSITIVITY TO FORMALIN-INDUCED INFLAMMATORY PAIN. TOGETHER, OUR DATA INDICATE THAT PRDM12 REGULATES PAIN-RELATED BEHAVIOR IN A COMPLEX WAY BY MODULATING GENE EXPRESSION IN ADULT NOCICEPTORS AND CONTROLLING THEIR EXCITABILITY. THE RESULTS ENCOURAGE FURTHER STUDIES TO ASSESS THE POTENTIAL OF PRDM12 AS A TARGET FOR ANALGESIC DEVELOPMENT. 2022 3 2993 34 GENETIC PAIN LOSS DISORDERS. GENETIC PAIN LOSS INCLUDES CONGENITAL INSENSITIVITY TO PAIN (CIP), HEREDITARY SENSORY NEUROPATHIES AND, IF AUTONOMIC NERVES ARE INVOLVED, HEREDITARY SENSORY AND AUTONOMIC NEUROPATHY (HSAN). THIS HETEROGENEOUS GROUP OF DISORDERS HIGHLIGHTS THE ESSENTIAL ROLE OF NOCICEPTION IN PROTECTING AGAINST TISSUE DAMAGE. PATIENTS WITH GENETIC PAIN LOSS HAVE RECURRENT INJURIES, BURNS AND POORLY HEALING WOUNDS AS DISEASE HALLMARKS. CIP AND HSAN ARE CAUSED BY PATHOGENIC GENETIC VARIANTS IN >20 GENES THAT LEAD TO DEVELOPMENTAL DEFECTS, NEURODEGENERATION OR ALTERED NEURONAL EXCITABILITY OF PERIPHERAL DAMAGE-SENSING NEURONS. THESE GENETIC VARIANTS LEAD TO HYPERACTIVITY OF SODIUM CHANNELS, DISTURBED HAEM METABOLISM, ALTERED CLATHRIN-MEDIATED TRANSPORT AND IMPAIRED GENE REGULATORY MECHANISMS AFFECTING EPIGENETIC MARKS, LONG NON-CODING RNAS AND REPETITIVE ELEMENTS. THERAPIES FOR PAIN LOSS DISORDERS ARE MAINLY SYMPTOMATIC BUT THE FIRST TARGETED THERAPIES ARE BEING TESTED. CONVERSELY, CHRONIC PAIN REMAINS ONE OF THE GREATEST UNRESOLVED MEDICAL CHALLENGES, AND THE GENES AND MECHANISMS ASSOCIATED WITH PAIN LOSS OFFER NEW TARGETS FOR ANALGESICS. GIVEN THE PROGRESS THAT HAS BEEN MADE, THE COMING YEARS ARE PROMISING BOTH IN TERMS OF TARGETED TREATMENTS FOR PAIN LOSS DISORDERS AND THE DEVELOPMENT OF INNOVATIVE PAIN MEDICINES BASED ON KNOWLEDGE OF THESE GENETIC DISEASES. 2022 4 6226 18 THE LINK BETWEEN EPIGENETICS, PAIN SENSITIVITY AND CHRONIC PAIN. INCREASING EVIDENCE SUGGESTS AN ASSOCIATION BETWEEN GENE EXPRESSION AND CLINICAL PAIN. EPIGENETIC MODIFICATIONS ARE THE MAIN MODULATORS OF GENE EXPRESSION OR PROTEIN TRANSLATION IN RESPONSE TO ENVIRONMENTAL STIMULI AND PATHOPHYSIOLOGICAL CONDITIONS. PRECLINICAL AND CLINICAL STUDIES INDICATE THAT EPIGENETIC MODIFICATIONS COULD ALSO IMPACT THE DEVELOPMENT OF PAIN, THE TRANSITION FROM ACUTE TO CHRONIC PAIN, AND THE MAINTENANCE HEREOF. 2022 5 2176 26 EPIGENETIC MECHANISMS OF CHRONIC PAIN. NEUROPATHIC AND INFLAMMATORY PAIN PROMOTE A LARGE NUMBER OF PERSISTING ADAPTATIONS AT THE CELLULAR AND MOLECULAR LEVEL, ALLOWING EVEN TRANSIENT TISSUE OR NERVE DAMAGE TO ELICIT CHANGES IN CELLS THAT CONTRIBUTE TO THE DEVELOPMENT OF CHRONIC PAIN AND ASSOCIATED SYMPTOMS. THERE IS EVIDENCE THAT INJURY-INDUCED CHANGES IN CHROMATIN STRUCTURE DRIVE STABLE CHANGES IN GENE EXPRESSION AND NEURAL FUNCTION, WHICH MAY CAUSE SEVERAL SYMPTOMS, INCLUDING ALLODYNIA, HYPERALGESIA, ANXIETY, AND DEPRESSION. RECENT FINDINGS ON EPIGENETIC CHANGES IN THE SPINAL CORD AND BRAIN DURING CHRONIC PAIN MAY GUIDE FUNDAMENTAL ADVANCES IN NEW TREATMENTS. HERE, WE PROVIDE A BRIEF OVERVIEW OF EPIGENETIC REGULATION IN THE NERVOUS SYSTEM AND THEN DISCUSS THE STILL-LIMITED LITERATURE THAT DIRECTLY IMPLICATES EPIGENETIC MODIFICATIONS IN CHRONIC PAIN SYNDROMES. 2015 6 6130 27 THE EPIGENETIC REGULATION OF THE OPIOID SYSTEM: NEW INDIVIDUALIZED PROMPT PREVENTION AND TREATMENT STRATEGIES. THE MOST WELL-KNOWN PHYSIOLOGICAL EFFECT ASSOCIATED WITH OPIOD SYSTEM IS THEIR EFFICACY IN PAIN REDUCTION OR ANALGESIA, ALTHOUGH THEIR EFFECT ON A VARIETY OF OTHER PHYSIOLOGICAL AND PHYSIOPHOLOGICAL FUNCTIONS HAS BECOME APPARENT IN RECENT YEARS. THIS REVIEW IS AN ATTEMPT TO CLARIFY IN MORE DETAIL THE EPIGENETIC REGULATION OF OPIOID SYSTEM TO UNDERSTAND WITH MORE PRECISION THEIR TRANSCRIPTIONAL AND POSTTRANSCRIPTIONAL REGULATION IN MULTIPLE PYISIOLOGICAL AND PHARMACOLOGICAL CONTEXTS. THE OPIOID RECEPTORS SHOW AN EPIGENETIC REGULATION AND OPIOID PEPTIDE PRECURSORS BY METHYLATION, CHROMATIN REMODELING AND MICRORNA. ALTHOUGH THE OPIOID RECEPTOR PROMOTERS HAVE SIMILARITY BETWEEN THEM, THEY USE DIFFERENT EPIGENETIC REGULATION FORMS AND THEY EXHIBIT DIFFERENT PATTERN OF EXPRESSION DURING THE CELL DIFFERENTIATION. DNA METHYLATION IS ALSO CONFIRMED IN OPIOID PEPTIDE PRECURSORS, BEING IMPORTANT FOR GENE EXPRESSION AND TISSUE SPECIFICITY. UNDERSTANDING THE EPIGENETIC BASIS OF THOSE PHYSIOLOGICAL AND PHYSIOPATHOLOGICAL PROCESESS IS ESSENTIAL FOR THE DEVELOPMENT OF INDIVIDUALIZED PROMPT PREVENTION AND TREATMENT STRATEGIES. 2015 7 6895 21 [SYSTEMIC CONTROL OF THE MOLECULAR, CELL, AND EPIGENETIC MECHANISMS OF LONG-LASTING CONSEQUENCES OF STRESS]. BASED ON M.E. LOBASHEV'S VIEWS OF THE SYSTEMIC CONTROL OF GENETIC AND CYTOGENEITC PROCESSES AND A SUBSTANTIAL EFFECT OF EXCITABILITY ON PLASTIC CHANGES IN THE CENTRAL NERVOUS SYSTEM (CNS), THE EFFECT OF PROLONGED EMOTIONAL AND PAIN STRESS (PEPS) ON THE MOLECULAR, CELL, AND EPIGENETIC MECHANISMS OF INJURY MEMORY WAS STUDIED IN RAT STRAINS BRED FOR A CERTAIN EXCITABILITY OF THE NERVOUS SYSTEM. PEPS WAS FOR THE FIRST TIME FOUND TO CAUSE LONG-LASTING (2 MONTHS) MORPHOLOGICAL ALTERATIONS OF THE CA3 REGION OF THE HIPPOCAMPUS AND TO MODIFY THE GENOME ACTIVITY OF ITS PYRAMIDAL NEURONS. THE TWO PHENOMENA WERE POTENTIATED BY A GENETICALLY DETERMINED LOW FUNCTIONAL STATE OF THE CNS. THE POST-STRESS REGULATION OF THE GENOME FUNCTION IN HIPPOCAMPAL NEURONS WAS MEDIATED BY CHANGES IN HETEROCHROMATIN CONFORMATION, ACTIVATION OF METHYL-CPG-BINDING PROTEIN (MECP2) SYNTHESIS, AND SUBSEQUENT CHANGES IN ACETYLATION OF HISTONE H4. GENETICALLY DETERMINED HIGH EXCITABILITY OF THE NERVOUS SYSTEM PROVED TO BE A RISK FACTOR THAT AFFECTS THE SPECIFICS AND TIME COURSE OF THE OBSERVED MOLECULAR, CELL, AND GENETIC TRANSFORMATIONS OF NEURONS. THE RESULTS PROVIDE FOR A BETTER UNDERSTANDING OF THE EPIGENETIC MECHANISMS OF INJURY MEMORY, WHICH FORMS A PATHOGENETIC BASIS FOR POSTTRAUMATIC STRESS DISORDER AND OTHER HUMAN PSYCHOGENIC CONDITIONS CHARACTERIZED BY A PROLONGED DURATION. 2009 8 980 23 CHRONIC PAIN: EMERGING EVIDENCE FOR THE INVOLVEMENT OF EPIGENETICS. EPIGENETIC PROCESSES, SUCH AS HISTONE MODIFICATIONS AND DNA METHYLATION, HAVE BEEN ASSOCIATED WITH MANY NEURAL FUNCTIONS INCLUDING SYNAPTIC PLASTICITY, LEARNING, AND MEMORY. HERE, WE CRITICALLY EXAMINE EMERGING EVIDENCE LINKING EPIGENETIC MECHANISMS TO THE DEVELOPMENT OR MAINTENANCE OF CHRONIC PAIN STATES. ALTHOUGH IN ITS INFANCY, RESEARCH IN THIS AREA POTENTIALLY UNIFIES SEVERAL PATHOPHYSIOLOGICAL PROCESSES UNDERPINNING ABNORMAL PAIN PROCESSING AND OPENS UP A DIFFERENT AVENUE FOR THE DEVELOPMENT OF NOVEL ANALGESICS. 2012 9 2354 23 EPIGENETIC REGULATION OF PERSISTENT PAIN. PERSISTENT OR CHRONIC PAIN IS TIGHTLY ASSOCIATED WITH VARIOUS ENVIRONMENTAL CHANGES AND LINKED TO ABNORMAL GENE EXPRESSION WITHIN CELLS PROCESSING NOCICEPTIVE SIGNALING. EPIGENETIC REGULATION GOVERNS GENE EXPRESSION IN RESPONSE TO ENVIRONMENTAL CUES. RECENT ANIMAL MODEL AND CLINICAL STUDIES INDICATE THAT EPIGENETIC REGULATION PLAYS AN IMPORTANT ROLE IN THE DEVELOPMENT OR MAINTENANCE OF PERSISTENT PAIN AND POSSIBLY THE TRANSITION OF ACUTE PAIN TO CHRONIC PAIN, THUS SHEDDING LIGHT IN A DIRECTION FOR DEVELOPMENT OF NEW THERAPEUTICS FOR PERSISTENT PAIN. 2015 10 405 23 ANALYSIS OF EPIGENETIC MECHANISMS REGULATING OPIOID RECEPTOR GENE TRANSCRIPTION. OPIOID DRUGS ARE GENERALLY USED FOR MODERATE AND SEVERE PAIN REDUCTIONS WHICH ACT THROUGH OPIOID RECEPTORS. STUDIES ON TRANSCRIPTIONAL REGULATION OF OPIOID RECEPTORS ARE STILL INVALUABLE BECAUSE NOT ONLY TRANSCRIPTION IS THE FIRST STEP TO PRODUCE PROTEIN PRODUCTS IN CELLS, BUT THE RECEPTOR TRANSCRIPTION LEVELS ALSO AFFECT THE PAIN REDUCTION BY OPIOIDS, AS OBSERVED IN STUDIES OF HETEROZYGOUS OPIOID RECEPTOR KNOCKOUT MICE.THERE ARE GROWING EVIDENCES THAT EPIGENETIC REGULATION HAS PLAYED SIGNIFICANT ROLES IN TRANSCRIPTIONAL REGULATION OF GENES, INCLUDING OPIOID RECEPTORS. IN GENERAL, EPIGENETIC MECHANISMS INCLUDE THREE MAIN REGULATORY FACTORS: DNA METHYLATION, CHROMATIN MODIFICATION, AND NONCODING RNAS (SUCH AS MICRORNA). FROM PREVIOUS STUDIES OF OURS AND OTHERS ON OPIOID RECEPTORS, THOSE EPIGENETIC FACTORS WERE CLEARLY INVOLVED IN REGULATING OPIOID RECEPTOR EXPRESSION IN VIVO AND IN VITRO. IN THIS CHAPTER, AMONG THOSE THREE TECHNIQUES WE DESCRIBE MORE DETAILS OF DNA METHYLATION METHODS BECAUSE OF EMERGING CONCEPTS OF DNA METHYLATION WITH THE RECENT DISCOVERY OF 5-HYDROXYMETHYLCYTOSINE CONVERTING ENZYME, TET1. ANOTHER ANALYTICAL METHOD OF THE EPIGENETIC FACTORS, CHROMATIN MODIFICATION, WILL BE DESCRIBED BRIEFLY AND INFORMATION OF ANALYZING NONCODING RNAS IS BRIEFLY MENTIONED IN SUBHEADING 1. 2015 11 4036 22 MACROPHAGE EPIGENETIC MEMORIES OF EARLY LIFE INJURY DRIVE NEONATAL NOCICEPTIVE PRIMING. THE DEVELOPING PERIPHERAL NERVOUS AND IMMUNE SYSTEMS ARE FUNCTIONALLY DISTINCT FROM ADULTS. THESE SYSTEMS ARE VULNERABLE TO EFFECTS OF EARLY LIFE INJURY WHICH CAN INFLUENCE OUTCOMES RELATED TO NOCICEPTION FOLLOWING SUBSEQUENT INJURY LATER IN LIFE (I.E. "NEONATAL NOCICEPTIVE PRIMING"). THE UNDERPINNINGS OF THIS PHENOMENON ARE LARGELY UNKNOWN, ALTHOUGH MACROPHAGES CAN BE EPIGENETICALLY TRAINED BY INJURY. WE FOUND THAT MACROPHAGES ARE BOTH NECESSARY AND PARTIALLY SUFFICIENT TO DRIVE NEONATAL NOCICEPTIVE PRIMING POSSIBLY DUE TO A LONG-LASTING EPIGENETIC REMODELING OF PERIPHERAL MACROPHAGES. THE P75 NEUROTROPHIC FACTOR RECEPTOR (NTR) WAS OBSERVED TO BE AN IMPORTANT EFFECTOR IN REGULATING NEONATAL NOCICEPTIVE PRIMING. P75NTR MODULATES THE INFLAMMATORY PROFILE AND RESPONSES OF RODENT AND HUMAN MACROPHAGES. THIS "PAIN MEMORY" WAS ABLE TO BE TRANSFERRED TO A NAIVE HOST TO ALTER SEX-SPECIFIC PAIN-RELATED BEHAVIORS. THIS STUDY REVEALS A NOVEL MECHANISM BY WHICH ACUTE POST-SURGICAL PAIN MAY TRANSITION TO CHRONIC PAIN IN CHILDREN. 2023 12 5288 20 PROSPECTS FOR EPIGENETIC COMPOUNDS IN THE TREATMENT OF AUTOIMMUNE DISEASE. THERE IS GROWING EVIDENCE FOR A ROLE FOR EPIGENETIC MECHANISMS IN THE DEVELOPMENT OF AUTOIMMUNE DISEASES. IN MOST CASES OFAUTOIMMUNE DISEASE THE PRECISE EPIGENETIC MECHANISM INVOLVED REMAINS TO BE RESOLVED, HOWEVER DNA HYPOMETHYLATION ACCOMPANIED BY HYPOACETYLATION OFHISTONE H3/H4 IS COMMONLY OBSERVED. DUE TO THE REVERSIBLE NATURE OF EPIGENETIC MARKS THEIR MAINTENANCE ENZYMES SUCH AS DNA METHYLTRANSFERASES (DNMTS), HISTONE DEACETYLASES (HDACS) AND HISTONE LYSINE METHYLTRANSFERASES (HKMT) ARE ATTRACTIVE DRUG TARGETS. SMALL MOLECULE INHIBITORS OF HISTONE MODIFICATION AND DNA METHYLATION MAINTENANCE ARE INCREASINGLY BECOMING AVAILABLE AND WILL BE USEFUL CHEMICAL BIOLOGICAL TOOLS TO DISSECT EPIGENETIC MECHANISMS IN THESE DISEASES. HOWEVER, ALTHOUGH EPIGENETIC THERAPIES USED IN CANCER TREATMENT ARE A PROMISING STARTING POINT FOR THE EXPLORATION OF AUTOIMMUNE DISEASE TREATMENT, THERE IS A REQUIREMENT FOR MORE SPECIFIC AND LESS TOXIC AGENTS FOR THESE CHRONIC DISEASES OR FOR USE AS CHEMOPREVENTATIVE AGENTS. 2011 13 6802 19 [EPIGENETIC MECHANISMS IN MODELS OF CHRONIC PAIN - A TARGET FOR NOVEL THERAPY?]. EVIDENCE OF EPIGENETICS' ROLE IN PAIN RESPONSE IS ACCUMULATING IN RECENT YEARS. TIGHTLY REGULATED EPIGENETIC ALTERATIONS ON DNA AND HISTONES IN THE SENSORY CIRCUIT SHAPE THE PHYSIOLOGICAL RESPONSE TO INJURY. ALTERING THOSE EPIGENETIC PROCESSES HINDERS THERAPEUTIC POTENTIAL IN PAIN. THIS REVIEW PROVIDES AN OVERVIEW OF EPIGENOMIC MODIFICATION IN THE DEVELOPMENT OF CHRONIC PAIN, AND SUMMARIZES THE THERAPEUTIC POTENTIAL TO ALTER EPIGENETIC PROCESSES. 2018 14 2199 22 EPIGENETIC MODIFICATION OF DRG NEURONAL GENE EXPRESSION SUBSEQUENT TO NERVE INJURY: ETIOLOGICAL CONTRIBUTION TO COMPLEX REGIONAL PAIN SYNDROMES (PART II). CUMULATING EVIDENCE INDICATED THAT NERVE INJURY-ASSOCIATED CELLULAR AND MOLECULAR CHANGES PLAY AN ESSENTIAL ROLE IN CONTRIBUTING TO THE DEVELOPMENT OF PATHOLOGICAL PAIN, AND MORE RECENT FINDINGS IMPLICATED THE CRITICAL ROLE OF EPIGENETIC MECHANISMS IN PAIN-RELATED SENSITIZATION IN THE DRG SUBSEQUENT TO NERVE INJURY. IN THIS PART OF THE DYAD REVIEW (PART II), WE REVIEWED AND PAID SPECIAL ATTENTION ON THE ETIOLOGICAL CONTRIBUTION OF DGR GENE EXPRESSION MODULATED BY EPIGENETIC MECHANISMS OF CRPS. AS ESSENTIAL EFFECTORS TO DIFFERENT MOLECULAR ACTIVATION, WE FIRST DISCUSSED THE ACTIVATION OF VARIOUS SIGNALING PATHWAYS THAT SUBSEQUENTLY FROM NERVE INJURY, AND IN FURTHER ILLUSTRATED THE FUNDAMENTAL AND FUNCTIONAL UNDERPINNINGS OF NERVE INJURY-INDUCED PAIN, IN WHICH WE ARGUED FOR THE POTENTIAL EPIGENETIC MECHANISMS IN RESPONSE TO SENSITIZING STIMULI OR INJURY. THEREFORE, UNDERSTANDING THE SPECIFIC MEDIATING FACTORS THAT INFLUENCE INDIVIDUAL EPIGENETIC DIFFERENCES CONTRIBUTING TO PAIN SENSITIVITY AND RESPONSIVENESS TO ANALGESICS POSSESSES CRUCIAL CLINICAL IMPLICATIONS. 2014 15 5130 29 POSTTRANSCRIPTIONAL GENE REGULATION: NOVEL PATHWAYS FOR GLUCOCORTICOIDS' ANTI-INFLAMMATORY ACTION. POSTTRANSCRIPTIONAL GENE REGULATION (PTR) IS A FUNDAMENTAL BIOLOGICAL PROCESS THAT INTEGRATES WITH THE MASTER TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION, IN WAYS THAT ONLY IN THE LAST DECADE HAVE BEEN INCREASINGLY UNDERSTOOD [1, 2]. WHILE EPIGENETIC AND TRANSCRIPTIONAL EVENTS SHAPE CELL RESPONSE QUALITATIVELY, DECIDING THE PATTERN OF GENE EXPRESSION TO 'SWITCH ON OR OFF' IN RESPONSE TO ENDOGENOUS OR ENVIRONMENTAL TRIGGERS, THE KEY TASK OF PTR IS TO ACT AS A 'RHEOSTAT' AND RAPIDLY ADAPT THE CELLULAR RESPONSE BY PROVIDING THE APPROPRIATE AMPLITUDE AND TIMING TO THE PROTEIN EXPRESSION PATTERNS [3, 4]. THE PIVOTAL ROLE OF THIS MECHANISM COMES TO THE FOREFRONT IN INFLAMMATORY AND IMMUNE RESPONSE, WHERE THE CHANGES IN AMPLITUDE AND DURATION IN THE EXPRESSION OF DANGEROUS AND PROTECTIVE GENES ARE IN DELICATE BALANCE, AND ARE CRITICAL IN DETERMINING EITHER THE SUCCESSFUL RESOLUTION OF THE IMMUNE RESPONSE OR ITS CHRONIC OVEREXPRESSION [5]. THIS BRIEF REVIEW INTRODUCES MEMBERS OF THE MAIN CLASSES OF MOLECULES MEDIATING THE CYTOPLASMIC ARM OF GENE REGULATION, NAMELY RNA-BINDING PROTEINS AND MICRO-RNA (MIRNA), AND SUMMARIZES EXPERIMENTAL DATA THAT UNDERSCORE THE ROLE OF THESE MOLECULES IN THE PATHOPHYSIOLOGY OF CHRONIC INFLAMMATION, AS WELL AS THEIR PROMISING VALUE AS MECHANISMS CONVEYING THE ANTI-INFLAMMATORY EFFECT OF SYNTHETIC GLUCOCORTICOIDS. 2012 16 1688 26 DUAL BET/HDAC INHIBITION TO RELIEVE NEUROPATHIC PAIN: RECENT ADVANCES, PERSPECTIVES, AND FUTURE OPPORTUNITIES. DESPITE THE INTENSE RESEARCH ON DEVELOPING NEW THERAPIES FOR NEUROPATHIC PAIN STATES, AVAILABLE TREATMENTS HAVE LIMITED EFFICACY AND UNFAVORABLE SAFETY PROFILES. EPIGENETIC ALTERATIONS HAVE A GREAT INFLUENCE ON THE DEVELOPMENT OF CANCER AND NEUROLOGICAL DISEASES, AS WELL AS NEUROPATHIC PAIN. HISTONE ACETYLATION HAS PREVAILED AS ONE OF THE WELL INVESTIGATED EPIGENETIC MODIFICATIONS IN THESE DISEASES. ALTERED SPINAL ACTIVITY OF HISTONE DEACETYLASE (HDAC) AND BROMO AND EXTRA TERMINAL DOMAIN (BET) HAVE BEEN DESCRIBED IN NEUROPATHIC PAIN MODELS AND RESTORATION OF THESE ABERRANT EPIGENETIC MODIFICATIONS SHOWED PAIN-RELIEVING ACTIVITY. OVER THE LAST DECADES HDACS AND BETS HAVE BEEN THE FOCUS OF DRUG DISCOVERY STUDIES, LEADING TO THE DEVELOPMENT OF NUMEROUS SMALL-MOLECULE INHIBITORS. CLINICAL TRIALS TO EVALUATE THEIR ANTICANCER ACTIVITY SHOWED GOOD EFFICACY BUT RAISED TOXICITY CONCERNS THAT LIMITED TRANSLATION TO THE CLINIC. TO MAXIMIZE ACTIVITY AND MINIMIZE TOXICITY, THESE COMPOUNDS CAN BE APPLIED IN COMBINATION OF SUB-MAXIMAL DOSES TO PRODUCE ADDITIVE OR SYNERGISTIC INTERACTIONS (COMBINATION THERAPY). RECENTLY, OF PARTICULAR INTEREST, DUAL BET/HDAC INHIBITORS (MULTI-TARGET DRUGS) HAVE BEEN DEVELOPED TO ASSURE SIMULTANEOUS MODULATION OF BET AND HDAC ACTIVITY BY A SINGLE MOLECULE. THIS REVIEW WILL SUMMARIZE THE MOST RECENT ADVANCES WITH THESE STRATEGIES, DESCRIBING ADVANTAGES AND LIMITATIONS OF SINGLE DRUG TREATMENT VS COMBINATION REGIMENS. THIS REVIEW WILL ALSO PROVIDE A FOCUS ON DUAL BET/HDAC DRUG DISCOVERY INVESTIGATIONS AS FUTURE THERAPEUTIC OPPORTUNITY FOR HUMAN THERAPY OF NEUROPATHIC PAIN. 2021 17 1686 36 DRUGGING THE PAIN EPIGENOME. MORE THAN 20% OF ADULTS WORLDWIDE EXPERIENCE DIFFERENT TYPES OF CHRONIC PAIN, WHICH ARE FREQUENTLY ASSOCIATED WITH SEVERAL COMORBIDITIES AND A DECREASE IN QUALITY OF LIFE. SEVERAL APPROVED PAINKILLERS ARE AVAILABLE, BUT CURRENT ANALGESICS ARE OFTEN HAMPERED BY INSUFFICIENT EFFICACY AND/OR SEVERE ADVERSE EFFECTS. CONSEQUENTLY, NOVEL STRATEGIES FOR SAFE, HIGHLY EFFICACIOUS TREATMENTS ARE HIGHLY DESIRABLE, PARTICULARLY FOR CHRONIC PAIN. EPIGENETIC MECHANISMS SUCH AS DNA METHYLATION, HISTONE MODIFICATIONS AND MICRORNAS (MIRNAS) STRONGLY AFFECT THE REGULATION OF GENE EXPRESSION, POTENTIALLY FOR LONG PERIODS OVER YEARS OR EVEN GENERATIONS, AND HAVE BEEN ASSOCIATED WITH PATHOPHYSIOLOGICAL PAIN. SEVERAL STUDIES, MOSTLY IN ANIMALS, REVEALED THAT INHIBITORS OF DNA METHYLATION, ACTIVATORS AND INHIBITORS OF HISTONE MODIFICATION AND MODULATORS OF MIRNAS REVERSE A NUMBER OF PATHOLOGICAL CHANGES IN THE PAIN EPIGENOME, WHICH ARE ASSOCIATED WITH ALTERED EXPRESSION OF PAIN-RELEVANT GENES. THIS EPIGENETIC MODULATION MIGHT THEN REDUCE THE NOCICEPTIVE RESPONSE AND PROVIDE NOVEL THERAPEUTIC OPTIONS FOR ANALGESIC THERAPY OF CHRONIC PAIN STATES. HOWEVER, A NUMBER OF CHALLENGES, SUCH AS NONSPECIFIC EFFECTS AND POOR DELIVERY TO TARGET CELLS AND TISSUES, HINDER THE RAPID DEVELOPMENT OF SUCH ANALGESICS. IN THIS REVIEW, WE CRITICALLY SUMMARIZE DATA ON EPIGENETICS AND PAIN, FOCUSING ON CHALLENGES IN CLINICAL DEVELOPMENT AS WELL AS POSSIBLE NEW APPROACHES TO THE DRUG MODULATION OF THE PAIN EPIGENOME. 2017 18 5347 28 RARBETA AGONIST DRUG (C286) DEMONSTRATES EFFICACY IN A PRE-CLINICAL NEUROPATHIC PAIN MODEL RESTORING MULTIPLE PATHWAYS VIA DNA REPAIR MECHANISMS. NEUROPATHIC PAIN (NP) IS ASSOCIATED WITH PROFOUND GENE EXPRESSION ALTERATIONS WITHIN THE NOCICEPTIVE SYSTEM. DNA MECHANISMS, SUCH AS EPIGENETIC REMODELING AND REPAIR PATHWAYS HAVE BEEN IMPLICATED IN NP. HERE WE HAVE USED A RAT MODEL OF PERIPHERAL NERVE INJURY TO STUDY THE EFFECT OF A RECENTLY DEVELOPED RARBETA AGONIST, C286, CURRENTLY UNDER CLINICAL RESEARCH, IN NP. A 4-WEEK TREATMENT INITIATED 2 DAYS AFTER THE INJURY NORMALIZED PAIN SENSATION. GENOME-WIDE AND PATHWAY ENRICHMENT ANALYSIS SHOWED THAT MULTIPLE MECHANISMS PERSISTENTLY ALTERED IN THE SPINAL CORD WERE RESTORED TO PREINJURY LEVELS BY THE AGONIST. CONCOMITANT UPREGULATION OF DNA REPAIR PROTEINS, ATM AND BRCA1, THE LATTER BEING REQUIRED FOR C286-MEDIATED PAIN MODULATION, SUGGESTS THAT EARLY DNA REPAIR MAY BE IMPORTANT TO PREVENT PHENOTYPIC EPIGENETIC IMPRINTS IN NP. THUS, C286 IS A PROMISING DRUG CANDIDATE FOR NEUROPATHIC PAIN AND DNA REPAIR MECHANISMS MAY BE USEFUL THERAPEUTIC TARGETS TO EXPLORE. 2019 19 2551 31 EPIGENETICS IN PAIN AND ANALGESIA: AN IMMINENT RESEARCH FIELD. HERITABLE PHENOTYPES RESULTING FROM ENVIRONMENT-CAUSED CHANGES IN A CHROMOSOME WITHOUT ALTERATIONS IN THE DNA SEQUENCE ARE INCREASINGLY RECOGNIZED AS A BASIS OF PERSONALIZED THERAPY. EPIGENETIC MECHANISMS INCLUDE COVALENT MODIFICATIONS OF THE DNA (METHYLATION) OR OF THE DNA-PACKAGING HISTONES (E.G., DEACETYLATION OR PHOSPHORYLATION). IN ADDITION, REGULATORY NON-CODING RNA MOLECULES (MICRO-RNAS) EXERT EPIGENETIC ACTIONS. THIS LEADS TO DISRUPTION OR OTHERWISE MODIFIED EXPRESSION OF GENES. ENVIRONMENTAL INFLUENCES SUCH AS NUTRITIONAL FACTORS, EXPOSURE TO CHEMICALS OR DRUGS, BUT ALSO SOCIAL FACTORS APPEAR TO EXERT EPIGENETIC ACTIONS. HISTONE MODIFICATIONS AND DNA METHYLATION ARE ASSOCIATED WITH THE SUBJECT'S AGE. EPIGENETIC MECHANISMS CAN SILENCE THE EXPRESSION OF PRO- OR ANTINOCICEPTIVE GENES. TO THE EPIGENETIC CONTROL OF NOCICEPTION ADDS ITS CONTROL OF THE PHARMACODYNAMICS OR PHARMACOKINETICS OF ANALGESICS BY EPIGENETIC CONTROL OF DRUG TARGETS AND ANALGESICS METABOLIZING ENZYMES. ALTHOUGH EPIGENETICS-BASED STRATEGIES FOR PAIN THERAPY ARE NOT YET AVAILABLE, EXPERIMENTS IN RODENTS SUGGEST THAT RNA INTERFERENCE MAY BECOME A NEW THERAPY APPROACH FOR NEUROPATHIC AND OTHER PAIN. ANOTHER EPIGENETIC APPROACH TO ANALGESIC TREATMENT EMPLOYS INHIBITORS OF HISTONE DEACETYLASE THAT ACT ON THE EPIGENOME BY INDIRECTLY REMODELING THE SPATIAL CONFORMATION OF THE CHROMATIN. FINALLY, EPIGENETIC TECHNIQUES SUCH AS RNA INTERFERENCE HAVE BEEN EMPLOYED IN PAIN RESEARCH TO PROOF THE CONTRIBUTION OF CERTAIN PROTEINS TO NOCICEPTION. THUS, THE NEW FIELD OF EPIGENETICS BECOMES INCREASINGLY USED IN RESEARCH AND MANAGEMENT OF PAIN AND WILL COMPLEMENT GENETICS. THIS ARTICLE INTRODUCES EPIGENETICS TO PAIN AND SUMMARIZES THE CURRENT AND FUTURE UTILITY. 2011 20 789 30 CELLULAR AND MOLECULAR MECHANISMS DRIVING NEUROPATHIC PAIN: RECENT ADVANCEMENTS AND CHALLENGES. CURRENT PHARMACOTHERAPEUTICS FOR NEUROPATHIC PAIN OFFER ONLY SYMPTOMATIC RELIEF WITHOUT TREATING THE UNDERLYING PATHOPHYSIOLOGY. ADDITIONALLY, THEY ARE ASSOCIATED WITH VARIOUS DOSE-LIMITING SIDE EFFECTS. PAIN RESEARCH IN THE PAST FEW DECADES HAS REVOLVED AROUND THE ROLE OF OXIDATIVE-NITROSATIVE STRESS, PROTEIN KINASES, GLIAL CELL ACTIVATION, AND INFLAMMATORY SIGNALING CASCADES BUT HAS FAILED TO PRODUCE SPECIFIC AND EFFECTIVE THERAPIES. AREAS COVERED: THIS REVIEW FOCUSES ON RECENT ADVANCES IN CELLULAR AND MOLECULAR MECHANISMS OF NEUROPATHIC PAIN THAT MAY BE TRANSLATED INTO FUTURE THERAPIES. WE DISCUSS EMERGING TARGETS SUCH AS WNT SIGNALING MECHANISMS, THE TETRAHYDROBIOPTERIN PATHWAY, MRG RECEPTORS, ENDOGENOUS LIPID MEDIATORS, MICRO-RNAS AND THEIR ROLES IN PAIN REGULATION. RECENT EVIDENCE IS ALSO PRESENTED REGARDING GENETIC AND EPIGENETIC MECHANISMS OF PAIN MODULATION. EXPERT OPINION: DURING CHRONIC NEUROPATHIC PAIN, MALADAPTATION OCCURS IN THE PERIPHERAL AND CENTRAL NERVOUS SYSTEMS, INCLUDING A SHIFT IN MICROGLIAL PHENOTYPE FROM A SURVEILLANCE STATE TO AN ACTIVATED STATE. MICROGLIAL ACTIVATION LEADS TO AN ALTERED EXPRESSION OF CELL SURFACE PROTEINS, GROWTH FACTORS, AND INTRACELLULAR SIGNALING MOLECULES THAT CONTRIBUTE TO DEVELOPMENT OF A NEUROINFLAMMATORY CASCADE AND CHRONIC PAIN SENSITIZATION. SPECIFIC TARGETING OF THESE CELLULAR AND MOLECULAR MECHANISMS MAY PROVIDE THE KEY TO DEVELOPMENT OF EFFECTIVE NEUROPATHIC PAIN THERAPIES THAT HAVE MINIMAL SIDE EFFECTS. 2018