1 5537 122 ROLE OF CALCITONIN GENE-RELATED PEPTIDE IN LIGHT-AVERSIVE BEHAVIOR: IMPLICATIONS FOR MIGRAINE. MIGRAINE IS A CHRONIC NEUROLOGICAL DISORDER CHARACTERIZED BY RECURRENT EPISODES OF SEVERE UNILATERAL THROBBING HEAD PAIN AND ASSOCIATED SYMPTOMS, SUCH AS PHOTOPHOBIA. OUR CURRENT UNDERSTANDING OF THE MECHANISMS UNDERLYING MIGRAINE HAS BEEN HAMPERED BY LIMITATIONS IN ASCERTAINING MIGRAINE SYMPTOMS IN ANIMAL MODELS. CLINICAL STUDIES HAVE ESTABLISHED THE NEUROPEPTIDE CALCITONIN GENE-RELATED PEPTIDE (CGRP) AS A KEY PLAYER IN MIGRAINE. HERE, WE ESTABLISH A GENETIC MODEL OF PHOTOPHOBIA BY ENGINEERING INCREASED SENSITIVITY TO CGRP IN MICE. THESE TRANSGENIC MICE (NESTIN/HRAMP1) DISPLAY LIGHT-AVERSIVE BEHAVIOR THAT IS GREATLY ENHANCED BY INTRACEREBROVENTRICULAR INJECTION OF CGRP AND BLOCKED BY COADMINISTRATION OF THE CGRP RECEPTOR ANTAGONIST OLCEGEPANT. THIS BEHAVIOR APPEARS TO BE AN INDICATOR OF PHOTOPHOBIA AND CANNOT BE FULLY EXPLAINED BY GROSS ABNORMALITY OF OCULAR ANATOMY OR DIFFERENCES IN GENERAL ANXIETY OR MOTOR ACTIVITY. OUR FINDINGS DEMONSTRATE THAT A SINGLE GENE, RECEPTOR ACTIVITY-MODIFYING PROTEIN 1 (RAMP1), CAN BE A MODIFIER OF PHOTOPHOBIA AND, BY EXTENSION, SUGGEST THAT GENETIC OR EPIGENETIC MODULATION OF RAMP1 LEVELS MAY CONTRIBUTE TO MIGRAINE SUSCEPTIBILITY. MOREOVER, THEY VALIDATE CGRP HYPERSENSITIVE MICE AS A TOOL FOR EXPLORING THE NEUROBIOLOGY AND NOVEL THERAPIES FOR MIGRAINE AND OTHER DISORDERS INVOLVING PHOTOPHOBIA. 2009 2 2052 32 EPIGENETIC CONNECTION OF THE CALCITONIN GENE-RELATED PEPTIDE AND ITS POTENTIAL IN MIGRAINE. THE CALCITONIN GENE-RELATED PEPTIDE (CGRP) IS IMPLICATED IN THE PATHOGENESIS OF SEVERAL PAIN-RELATED SYNDROMES, INCLUDING MIGRAINE. TARGETING CGRP AND ITS RECEPTOR BY THEIR ANTAGONISTS AND ANTIBODIES WAS A BREAKTHROUGH IN MIGRAINE THERAPY, BUT THE NEED TO IMPROVE EFFICACY AND LIMIT THE SIDE EFFECTS OF THESE DRUGS JUSTIFY FURTHER STUDIES ON THE REGULATION OF CGRP IN MIGRAINE. THE EXPRESSION OF THE CGRP ENCODING GENE, CALCA, IS MODULATED BY EPIGENETIC MODIFICATIONS, INCLUDING THE DNA METHYLATION, HISTONE MODIFICATION, AND EFFECTS OF MICRO RNAS (MIRNAS), CIRCULAR RNAS, AND LONG-CODING RNAS (LNCRNAS). ON THE OTHER HAND, CGRP CAN CHANGE THE EPIGENETIC PROFILE OF NEURONAL AND GLIAL CELLS. THE PROMOTER OF THE CALCA GENE HAS TWO CPG ISLANDS THAT MAY BE SPECIFICALLY METHYLATED IN MIGRAINE PATIENTS. DNA METHYLATION AND LNCRNAS WERE SHOWN TO PLAY A ROLE IN THE CELL-SPECIFIC ALTERNATIVE SPLICING OF THE CALCA PRIMARY TRANSCRIPT. CGRP MAY BE INVOLVED IN CHANGES IN NEURAL CYTOARCHITECTURE THAT ARE CONTROLLED BY HISTONE DEACETYLASE 6 (HDAC6) AND CAN BE RELATED TO MIGRAINE. INHIBITION OF HDAC6 RESULTS IN REDUCED CORTICAL-SPREADING DEPRESSION AND A BLOCKADE OF THE CGRP RECEPTOR. CGRP LEVELS ARE ASSOCIATED WITH THE EXPRESSION OF SEVERAL MIRNAS IN PLASMA, MAKING THEM USEFUL PERIPHERAL MARKERS OF MIGRAINE. THE FUNDAMENTAL ROLE OF CGRP IN INFLAMMATORY PAIN TRANSMISSION MAY BE EPIGENETICALLY REGULATED. IN CONCLUSION, EPIGENETIC CONNECTIONS OF CGRP SHOULD BE FURTHER EXPLORED FOR EFFICIENT AND SAFE ANTIMIGRAINE THERAPY. 2022 3 6916 29 [WHAT IS MIGRAINE?]. MIGRAINE IS A MULTIFACTORIAL AND HETEROGENEOUS DISORDER. DIAGNOSTIC CRITERIA HAVE BEEN ESTABLISHED BY THE INTERNATIONAL HEADACHE SOCIETY, HOWEVER THESE ARE ONLY SUPPORTIVE IN TERMS OF DEFINITION. THE PATHOPHYSIOLOGY INVOLVES NEURONAL AND VASCULAR PHENOMENA. THE FORMER IS SUPPORTED BY THE CORTICAL SPREADING DEPRESSION BEING THE AURA CORRELATE AND BY BRAINSTEM AND HYPOTHALAMIC ACTIVATION DURING THE PAIN PHASE; THE LATTER IS SUGGESTED BY THE ASSOCIATION BETWEEN MIGRAINE AND CARDIOVASCULAR DISEASE AND FINDINGS OF PATHOLOGICAL VASOREACTIVITY AND ENDOTHELIAL DYSFUNCTION. TRIPTANS AND CALCITONIN GENE-RELATED PEPTIDE RECEPTOR ANTAGONISTS SHOW ONLY A RELATIVE MIGRAINE-SPECIFIC ACTION; UP TO 30% OF PATIENTS ARE NONRESPONDERS. DESPITE A CLEAR GENETIC COMPONENT, THE DISCOVERY OF SPECIFIC GENES FOR COMMON FORMS OF MIGRAINE REMAINS ELUSIVE. ELECTROPHYSIOLOGICAL STUDIES CONSISTENTLY INDICATE A CHARACTERISTIC "DYSHABITUATION" CONCURRING WITH CLINICAL FEATURES OF ALTERED SENSORY PERCEPTION. THE AGE- AND SEX-SPECIFIC PATTERN ALONG WITH THE EFFECT OF EXTERNAL FACTORS ON THE COURSE OF MIGRAINE ARGUE IN FAVOR OF THE INVOLVEMENT OF EPIGENETIC MECHANISMS. KNOWLEDGE ABOUT MIGRAINE IS STILL LIMITED, WHICH HAMPERS A DEFINITION. 2009 4 2176 24 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 5 6323 33 THE ROLE OF A POTENTIAL BIOMARKER IN PATIENTS WITH MIGRAINE: REVIEW AND NEW INSIGHTS. INTRODUCTION: THE SEARCH FOR AN IDEAL BIOMARKER FOR MIGRAINE HAS PERSISTED FOR A LONG TIME. THERE IS PLENTIFUL EVIDENCE OF POTENTIAL BIOMARKERS FOR MIGRAINE FOUND IN CEREBROSPINAL FLUID, BLOOD, AND SALIVA.AREAS COVERED: HEREIN, THE AUTHORS HIGHLIGHT AND DISCUSS THE MOST PROMISING CANDIDATES IN THE LITERATURE. AN ELECTRONIC SEARCH WAS PERFORMED FOR STUDIES PUBLISHED BETWEEN 2010 AND 2020 IN MEDLINE, PUBMED, AND EMBASE, RELATED TO POTENTIAL BIOMARKERS IN MIGRAINE PATIENTS, FOUND IN CEREBROSPINAL FLUID, SALIVA, AND SERUM, FOCUSING ON BIOMARKERS THAT CAN BE RELATED TO TREATMENT AND CLINICAL OUTCOMES.EXPERT OPINION: AN IDEAL BIOMARKER, OR A PANEL OF BIOMARKERS, COULD REVOLUTIONIZE THE WAY WE ADDRESS AND PROPOSE TREATMENTS FOR THIS DISEASE. ONCE SEVERE PRESENTATIONS AND PHENOTYPES HAVE BEEN IDENTIFIED USING A RELIABLE BIOMARKER, PATIENTS COULD BE TREATED AT EARLIER DISEASE STAGES WITH MORE SPECIFIC MEDICATIONS. THE MOST IMPORTANT BIOMARKERS WITH THE MOST SIGNIFICANT LEVELS OF EVIDENCE COMPRISED CALCITONIN GENE-RELATED PEPTIDE (CGRP), GLUTAMATE, NERVE GROWTH FACTOR, SOME INFLAMMATORY (CRP, TNF-ALPHA, INTERLEUKINS) AND OXIDATIVE STRESS MARKERS. CGRP WAS ASSOCIATED WITH EPISODIC, CHRONIC MIGRAINE AND RESPONSE TO TREATMENT. PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE IS AN EMERGING NEUROPEPTIDE INVOLVED IN MIGRAINE DIAGNOSTICS AND SEVERITY. NEW GENETIC AND EPIGENETIC BIOMARKERS WILL BE CANDIDATES FOR FUTURE RESEARCH. 2021 6 6846 30 [MIGRAINE: IGNITION OF THE BRAIN]. ALTHOUGH OUR KNOWLEDGE OF WHICH SYSTEMS ARE ACTIVATED DURING MIGRAINE IS REASONABLY COMPLETE, WHY THE SYSTEM IS ACTIVATED REMAINS UNKNOWN. INCORPORATING THE FINDINGS OBTAINED IN STUDIES ON PAIN IN GENERAL HAS ALLOWED A MORE INTEGRATED MODEL TO BE GENERATED. ACCORDING TO THIS NEW MODEL, THERE IS AN ANATOMICAL SUBSTRATE CONSISTING IN A COMPLEX FRAMEWORK OF PAIN THAT IS MADE UP NOT ONLY OF THE TRIGEMINOVASCULAR SYSTEM (END PATHWAY) BUT OF A NUMBER OF NETWORKS THAT ARE IN TURN CONNECTED TO ONE ANOTHER, LIKE THE NEUROLIMBIC, THE ASCENDING AND DESCENDING MODULATORY SYSTEM. THIS COMPLEX NETWORK IS RESPONSIBLE FOR MODULATING AND CONVEYING NOCICEPTIVE SIGNALS. IN PATIENTS WITH MIGRAINE, HYPEREXCITABILITY OF THIS FRAMEWORK IS CONDITIONED BY GENETIC AND EPIGENETIC ALTERATIONS. EPIGENETIC CHANGES ARE CHEMICAL MODIFICATIONS AFFECTING CHROMATIN, WHICH MODULATES THE ACTIVITY OF GENES WITHOUT MODIFYING THE DNA SEQUENCE, AND WHICH ARE CAPABLE OF MODULATING THE EXPRESSION OF GENES INVOLVED IN A NUMBER OF DIFFERENT ASPECTS, SUCH AS PLASTICITY, SYSTEM EXCITABILITY, MEMORY OF PAIN OR MOODS. IN TURN, THE PRESENCE OF EXTERNAL FACTORS (SUCH AS ENVIRONMENTAL CHANGES OR ALCOHOL) AND INTERNAL FACTORS (SUCH AS HORMONES OR SLEEP DISORDERS) CONTRIBUTE TO ACTIVATE THIS LOADED ANATOMICAL SUBSTRATE, RESULTING IN THE ATTACK OF MIGRAINE. 2013 7 6226 19 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 8 2053 30 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 9 6895 20 [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 10 6130 23 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 11 405 26 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 12 2252 35 EPIGENETIC MODULATION OF VISCERAL NOCICEPTION. EPIGENETICS IS A PROCESS THAT ALTERS GENE ACTIVITY OR PHENOTYPE WITHOUT ANY CHANGES IN THE UNDERLYING DNA SEQUENCE OR GENOTYPE. THESE BIOLOGICAL CHANGES MAY HAVE DELETERIOUS EFFECTS AND CAN LEAD TO VARIOUS HUMAN DISEASES. ONGOING RESEARCH IS CONTINUING TO ILLUMINATE THE ROLE OF EPIGENETICS IN A VARIETY OF PATHOPHYSIOLOGIC PROCESSES. SEVERAL CATEGORIES OF EPIGENETIC MECHANISMS HAVE BEEN STUDIED INCLUDING CHROMATIN REMODELING, DNA METHYLATION, HISTONE MODIFICATION, AND NON-CODING RNA MECHANISMS. THESE EPIGENETIC CHANGES CAN HAVE A LONG-TERM EFFECT ON GENE EXPRESSION WITHOUT ANY UNDERLYING CHANGES IN THE DNA SEQUENCES. THE UNDERLYING PATHOPHYSIOLOGY OF DISORDERS OF BRAIN-GUT INTERACTION AND STRESS-INDUCED VISCERAL PAIN ARE NOT FULLY UNDERSTOOD AND THE ROLE OF EPIGENETIC MECHANISMS IN THESE DISORDERS ARE STARTING TO BE BETTER UNDERSTOOD. CURRENT WORK IS UNDERWAY TO DETERMINE HOW EPIGENETICS PLAYS A ROLE IN THE NEUROBIOLOGY OF PATIENTS WITH CHRONIC VISCERAL PAIN AND HEIGHTENED VISCERAL NOCICEPTION. MORE RECENTLY, BOTH ANIMAL MODELS AND HUMAN STUDIES HAVE SHOWN HOW EPIGENETIC REGULATION MODULATES STRESS-INDUCED VISCERAL PAIN. WHILE MUCH MORE WORK IS NEEDED TO FULLY DELINEATE THE MECHANISTIC ROLE OF EPIGENETICS IN THE NEUROBIOLOGY OF CHRONIC VISCERAL NOCICEPTION, THE CURRENT STUDY BY LOUWIES ET AL., IN NEUROGASTROENTEROLOGY AND MOTILITY PROVIDES ADDITIONAL EVIDENCE SUPPORTING THE INVOLVEMENT OF EPIGENETIC ALTERATIONS IN THE CENTRAL NUCLEUS OF THE AMYGDALA IN STRESS-INDUCED VISCERAL HYPERSENSITIVITY IN RODENTS. 2022 13 4619 29 NERVE TRAUMA-CAUSED DOWNREGULATION OF OPIOID RECEPTORS IN PRIMARY AFFERENT NEURONS: MOLECULAR MECHANISMS AND POTENTIAL MANAGEMENTS. NEUROPATHIC PAIN IS THE MOST COMMON CLINICAL DISORDER DESTROYING THE QUALITY OF PATIENT LIFE AND LEADING TO A MARKED ECONOMIC AND SOCIAL BURDEN. OPIOIDS ARE STILL LAST OPTION FOR PHARMACOLOGICAL TREATMENT OF THIS DISORDER, BUT THEIR ANTINOCICEPTIVE EFFECTS ARE LIMITED IN PART DUE TO THE DOWNREGULATION OF OPIOID RECEPTORS IN THE PRIMARY AFFERENT NEURONS AFTER PERIPHERAL NERVE TRAUMA. HOW THIS DOWNREGULATION OCCURS IS NOT COMPLETELY UNDERSTOOD, BUT RECENT STUDIES HAVE DEMONSTRATED THAT PERIPHERAL NERVE TRAUMA DRIVES THE ALTERATIONS IN EPIGENETIC MODIFICATIONS (INCLUDING DNA METHYLATION, HISTONE METHYLATION AND MCIRORNAS), EXPRESSION OF TRANSCRIPTION FACTORS, POST-TRANSCRIPTIONAL MODIFICATIONS (E.G., RNA METHYLATION) AND PROTEIN TRANSLATION INITIATION IN THE NEURONS OF NERVE TRAUMA-RELATED DORSAL ROOT GANGLION (DRG) AND THAT THESE ALTERNATIONS MAY BE ASSOCIATED WITH NERVE TRAUMA-CAUSED DOWNREGULATION OF DRG OPIOID RECEPTORS. THIS REVIEW PRESENTS HOW OPIOID RECEPTORS ARE DOWNREGULATED IN THE DRG AFTER PERIPHERAL NERVE TRAUMA, SPECIFICALLY FOCUSING ON DISTINCT MOLECULAR MECHANISMS UNDERLYING TRANSCRIPTIONAL AND TRANSLATIONAL PROCESSES. THIS REVIEW ALSO DISCUSSES HOW THIS DOWNREGULATION CONTRIBUTES TO THE INDUCTION AND MAINTENANCE OF NEUROPATHIC PAIN. A DEEPER UNDERSTANDING OF THESE MOLECULAR MECHANISMS LIKELY PROVIDES A NOVEL AVENUE FOR PREVENTION AND/OR TREATMENT OF NEUROPATHIC PAIN. 2021 14 2199 27 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 15 789 39 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 16 1773 32 EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY AND ANXIETY BEHAVIOR IS REVERSED BY HISTONE DEACETYLASE INHIBITION. STRESSFUL LIFE EVENTS, ESPECIALLY IN CHILDHOOD, CAN HAVE DETRIMENTAL EFFECTS ON HEALTH AND ARE ASSOCIATED WITH A HOST OF PSYCHIATRIC AND GASTROINTESTINAL DISORDERS INCLUDING IRRITABLE BOWEL SYNDROME (IBS). EARLY-LIFE STRESS CAN BE RECAPITULATED IN ANIMALS USING THE MATERNAL SEPARATION (MS) MODEL, EXHIBITING MANY KEY PHENOTYPIC OUTCOMES INCLUDING VISCERAL HYPERSENSITIVITY AND ANXIETY-LIKE BEHAVIORS. THE MOLECULAR MECHANISMS OF MS ARE UNCLEAR, BUT RECENT STUDIES POINT TO A ROLE FOR EPIGENETICS. HISTONE ACETYLATION IS A KEY EPIGENETIC MARK THAT IS ALTERED IN NUMEROUS STRESS-RELATED DISEASE STATES. HERE, WE INVESTIGATED THE ROLE OF HISTONE ACETYLATION IN EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY. INTERESTINGLY, INCREASED NUMBER OF PAIN BEHAVIORS AND REDUCED THRESHOLD OF VISCERAL SENSATION WERE ASSOCIATED WITH ALTERATIONS IN HISTONE ACETYLATION IN THE LUMBOSACRAL SPINAL CORD, A KEY REGION IN VISCERAL PAIN PROCESSING. MOREOVER, WE ALSO INVESTIGATED WHETHER THE HISTONE DEACETYLASE (HDAC) INHIBITOR, SUBEROYLANILIDE HYDROXAMIC ACID (SAHA), COULD REVERSE EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY AND STRESS-INDUCED FECAL PELLET OUTPUT IN THE MS MODEL. SIGNIFICANTLY, SAHA REVERSED BOTH OF THESE PARAMETERS. TAKEN TOGETHER, THESE DATA DESCRIBE, FOR THE FIRST TIME, A KEY ROLE OF HISTONE ACETYLATION IN THE PATHOPHYSIOLOGY OF EARLY-LIFE STRESS-INDUCED VISCERAL HYPERSENSITIVITY IN A WELL-ESTABLISHED MODEL OF IBS. THESE FINDINGS WILL INFORM NEW RESEARCH AIMED AT THE DEVELOPMENT OF NOVEL PHARMACEUTICAL APPROACHES TARGETING THE EPIGENETIC MACHINERY FOR NOVEL ANTI-IBS DRUGS. 2015 17 2194 34 EPIGENETIC MODIFICATION IN NEUROPATHIC PAIN. NEUROPATHIC PAIN IS CHARACTERIZED BY COMPLICATED COMBINATION OF POSITIVE (E.G., HYPERALGESIA AND ALLODYNIA) AND NEGATIVE (E.G., HYPOESTHESIA AND HYPOALGESIA) SYMPTOMS, AND IS OFTEN REFRACTORY TO CONVENTIONAL PHARMACOLOGICAL AGENTS, INCLUDING MORPHINE. ALTHOUGH THE MOLECULAR MECHANISMS FOR POSITIVE SYMPTOMS ARE EXTENSIVELY STUDIED, THOSE FOR NEGATIVE SYMPTOMS ARE POORLY UNDERSTOOD. THERE IS CONVINCING EVIDENCE THAT ALTERED GENE EXPRESSION WITHIN PERIPHERAL AND CENTRAL NERVOUS SYSTEMS IS A KEY MECHANISM FOR NEUROPATHIC PAIN; HOWEVER, ITS TRANSCRIPTIONAL MECHANISMS ARE POORLY UNDERSTOOD. EPIGENETIC MODIFICATIONS, SUCH AS DNA METHYLATION AND HISTONE MODIFICATIONS (E.G., ACETYLATION, METHYLATION, AND PHOSPHORYLATION), ARE KNOWN TO CAUSE STABLE GENE EXPRESSION VIA CHROMATIN REMODELING. THESE MECHANISMS HAVE A ROLE NOT ONLY IN THE DETERMINATION OF DEVELOPMENTAL CELL FATES, BUT ALSO IN THE PHYSIOLOGICAL AND PATHOLOGICAL PROCESSES IN NERVOUS SYSTEM. MOREOVER, EPIGENETIC THERAPIES USING EPIGENETIC MODIFYING COMPOUNDS ARE PROGRESSIVELY ADVANCED IN THE TREATMENTS OF DIVERSE DISEASES, INCLUDING CANCER AND NEUROLOGICAL DISEASES. IMPORTANTLY, THERE IS EMERGING EVIDENCE THAT A VARIETY OF GENES UNDERGO EPIGENETIC REGULATION VIA DNA METHYLATION AND HISTONE MODIFICATIONS WITHIN PERIPHERAL AND CENTRAL NERVOUS SYSTEMS, THEREBY CONTRIBUTING TO THE ALTERATIONS IN BOTH PAIN SENSITIVITY AND PHARMACOLOGICAL EFFICACY IN NEUROPATHIC PAIN. IN THIS REVIEW, WE WILL HIGHLIGHT THE EPIGENETIC GENE REGULATION UNDERLYING NEUROPATHIC PAIN, ESPECIALLY FOCUSING ON THE NEGATIVE SYMPTOMS. MOREOVER, WE WILL DISCUSS WHETHER EPIGENETIC MECHANISMS CAN SERVE AS A POTENTIAL TARGET TO TREAT NEUROPATHIC PAIN. 2015 18 2310 32 EPIGENETIC REGULATION OF CHRONIC PAIN. CHRONIC PAIN ARISING FROM PERIPHERAL INFLAMMATION AND TISSUE OR NERVE INJURY IS A COMMON CLINICAL SYMPTOM. ALTHOUGH INTENSIVE RESEARCH ON THE NEUROBIOLOGICAL MECHANISMS OF CHRONIC PAIN HAS BEEN CARRIED OUT DURING PREVIOUS DECADES, THIS DISORDER IS STILL POORLY MANAGED BY CURRENT DRUGS SUCH AS OPIOIDS AND NONSTEROIDAL ANTI-INFLAMMATORY DRUGS. INFLAMMATION, TISSUE INJURY AND/OR NERVE INJURY-INDUCED CHANGES IN GENE EXPRESSION IN SENSORY NEURONS OF THE DORSAL ROOT GANGLION, SPINAL CORD DORSAL HORN AND PAIN-ASSOCIATED BRAIN REGIONS ARE THOUGHT TO PARTICIPATE IN CHRONIC PAIN GENESIS; HOWEVER, HOW THESE CHANGES OCCUR IS STILL ELUSIVE. EPIGENETIC MODIFICATIONS INCLUDING DNA METHYLATION AND COVALENT HISTONE MODIFICATIONS CONTROL GENE EXPRESSION. RECENT STUDIES HAVE SHOWN THAT PERIPHERAL NOXIOUS STIMULATION CHANGES DNA METHYLATION AND HISTONE MODIFICATIONS AND THAT THESE CHANGES MAY BE RELATED TO THE INDUCTION OF PAIN HYPERSENSITIVITY UNDER CHRONIC PAIN CONDITIONS. THIS REVIEW SUMMARIZES THE CURRENT KNOWLEDGE AND PROGRESS IN EPIGENETIC RESEARCH IN CHRONIC PAIN AND DISCUSSES THE POTENTIAL ROLE OF EPIGENETIC MODIFICATIONS AS THERAPEUTIC ANTINOCICEPTIVE TARGETS IN THIS DISORDER. 2015 19 2119 26 EPIGENETIC HISTONE MODIFICATION REGULATES DEVELOPMENTAL LEAD EXPOSURE INDUCED HYPERACTIVITY IN RATS. LEAD (PB) EXPOSURE WAS COMMONLY CONSIDERED AS A HIGH ENVIRONMENTAL RISK FACTOR FOR THE DEVELOPMENT OF ATTENTION-DEFICIT/HYPERACTIVITY DISORDER (ADHD). HOWEVER, THE MOLECULAR BASIS OF THIS PATHOLOGICAL PROCESS STILL REMAINS ELUSIVE. IN LIGHT OF THE ROLE OF EPIGENETICS IN MODULATING THE NEUROLOGICAL DISEASE AND THE CAUSATIVE ENVIRONMENT, THE ALTERATIONS OF HISTONE MODIFICATIONS IN THE HIPPOCAMPUS OF RATS EXPOSED BY VARIOUS DOSES OF LEAD, ALONG WITH CONCOMITANT BEHAVIORAL DEFICITS, WERE INVESTIGATED IN THIS STUDY. ACCORDING TO THE FREE AND FORCED OPEN FIELD TEST, THERE SHOWED THAT IN A DOSAGE-DEPENDENT MANNER, LEAD EXPOSURE COULD RESULT IN THE INCREASED LOCOMOTOR ACTIVITY OF RATS, THAT IS, HYPERACTIVITY: A SUBTYPE OF ADHD. WESTERN BLOTTING ASSAYS REVEALED THAT THE LEVELS OF HISTONE ACETYLATION INCREASED SIGNIFICANTLY IN THE HIPPOCAMPUS BY CHRONIC LEAD EXPOSURE, WHILE NO DRAMATIC CHANGES WERE DETECTED IN TERMS OF EXPRESSION YIELDS OF ADHD-RELATED DOPAMINERGIC PROTEINS, INDICATING THAT HISTONE ACETYLATION PLAYS ESSENTIAL ROLES IN THIS TOXICANT-INVOLVED PATHOGENESIS. IN ADDITION, THE INCREASED LEVEL OF HISTONE ACETYLATION MIGHT BE ATTRIBUTED TO THE ENZYMATIC ACTIVITY OF P300, A TYPICAL HISTONE ACETYLTRANSFERASE, AS THE TRANSCRIPTIONAL LEVEL OF P300 WAS SIGNIFICANTLY INCREASED UPON HIGHER-DOSE PB EXPOSURE. IN SUMMARY, THIS STUDY FIRST DISCOVERED THE EPIGENETIC MECHANISM BRIDGING THE ENVIRONMENTAL INFLUENCE (PB) AND THE DISEASE ITSELF (ADHD) IN THE HISTONE MODIFICATION LEVEL, PAVING THE WAY FOR THE COMPREHENSIVE UNDERSTANDING OF ADHD'S ETIOLOGY AND IN FURTHER STEPS, ESTABLISHING THE THERAPY STRATEGY OF THIS WIDESPREAD NEUROLOGICAL DISORDER. 2014 20 2214 34 EPIGENETIC MODIFICATIONS ASSOCIATED TO NEUROINFLAMMATION AND NEUROPATHIC PAIN AFTER NEURAL TRAUMA. ACCUMULATING EVIDENCE SUGGESTS THAT EPIGENETIC ALTERATIONS LIE BEHIND THE INDUCTION AND MAINTENANCE OF NEUROPATHIC PAIN. NEUROPATHIC PAIN IS USUALLY A CHRONIC CONDITION CAUSED BY A LESION, OR PATHOLOGICAL CHANGE, WITHIN THE NERVOUS SYSTEM. NEUROPATHIC PAIN APPEARS FREQUENTLY AFTER NERVE AND SPINAL CORD INJURIES OR DISEASES, PRODUCING A DEBILITATION OF THE PATIENT AND A DECREASE OF THE QUALITY OF LIFE. AT THE CELLULAR LEVEL, NEUROPATHIC PAIN IS THE RESULT OF NEURONAL PLASTICITY SHAPED BY AN INCREASE IN THE SENSITIVITY AND EXCITABILITY OF SENSORY NEURONS OF THE CENTRAL AND PERIPHERAL NERVOUS SYSTEM. ONE OF THE MECHANISMS THOUGHT TO CONTRIBUTE TO HYPEREXCITABILITY AND THEREFORE TO THE ONTOGENY OF NEUROPATHIC PAIN IS THE ALTERED EXPRESSION, TRAFFICKING, AND FUNCTIONING OF RECEPTORS AND ION CHANNELS EXPRESSED BY PRIMARY SENSORY NEURONS. BESIDES, NEURONAL AND GLIAL CELLS, SUCH AS MICROGLIA AND ASTROCYTES, TOGETHER WITH BLOOD BORNE MACROPHAGES, PLAY A CRITICAL ROLE IN THE INDUCTION AND MAINTENANCE OF NEUROPATHIC PAIN BY RELEASING POWERFUL NEUROMODULATORS SUCH AS PRO-INFLAMMATORY CYTOKINES AND CHEMOKINES, WHICH ENHANCE NEURONAL EXCITABILITY. ALTERED GENE EXPRESSION OF NEURONAL RECEPTORS, ION CHANNELS, AND PRO-INFLAMMATORY CYTOKINES AND CHEMOKINES, HAVE BEEN ASSOCIATED TO EPIGENETIC ADAPTATIONS OF THE INJURED TISSUE. WITHIN THIS REVIEW, WE DISCUSS THE INVOLVEMENT OF THESE EPIGENETIC CHANGES, INCLUDING HISTONE MODIFICATIONS, DNA METHYLATION, NON-CODING RNAS, AND ALTERATION OF CHROMATIN MODIFIERS, THAT HAVE BEEN SHOWN TO TRIGGER MODIFICATION OF NOCICEPTION AFTER NEURAL LESIONS. IN PARTICULAR, THE FUNCTION ON THESE PROCESSES OF EZH2, JMJD3, MECP2, SEVERAL HISTONE DEACETYLASES (HDACS) AND HISTONE ACETYL TRANSFERASES (HATS), G9A, DNMT, REST AND DIVERSE NON-CODING RNAS, ARE DESCRIBED. DESPITE THE EFFORT ON DEVELOPING NEW THERAPIES, CURRENT TREATMENTS HAVE ONLY PRODUCED LIMITED RELIEF OF THIS PAIN IN A PORTION OF PATIENTS. THUS, THE PRESENT REVIEW AIMS TO CONTRIBUTE TO FIND NOVEL TARGETS FOR CHRONIC NEUROPATHIC PAIN TREATMENT. 2018