1 5199 127 PRENATAL MATERNAL STRESS IS ASSOCIATED WITH INCREASED SENSITIVITY TO NEUROPATHIC PAIN AND SEX-SPECIFIC CHANGES IN SUPRASPINAL MRNA EXPRESSION OF EPIGENETIC- AND STRESS-RELATED GENES IN ADULTHOOD. EXPOSURE TO PRENATAL MATERNAL STRESS IMPACTS ADULT BEHAVIORAL OUTCOMES AND HAS BEEN SUGGESTED AS A RISK FACTOR FOR CHRONIC PAIN. HOWEVER, THE NEUROBIOLOGICAL MECHANISMS IMPLICATED ARE NOT WELL-CHARACTERIZED. IN THIS STUDY, WE ANALYZED THE EFFECT OF A PRENATAL MATERNAL STRESS ON THE DEVELOPMENT OF NEUROPATHIC PAIN-RELATED BEHAVIOURS AND GENE EXPRESSION IN THE FRONTAL CORTEX AND HIPPOCAMPUS IN ADULT OFFSPRING FOLLOWING CHRONIC CONSTRICTION INJURY OF THE SCIATIC NERVE IN MALE AND FEMALE CD1 MICE. NERVE INJURY-INDUCED MECHANICAL HYPERSENSITIVITY WAS AMPLIFIED IN BOTH MALE AND FEMALE PRENATALLY-STRESSED OFFSPRING, SUGGESTING THAT PRENATAL STRESS EXACERBATES PAIN AFTER INJURY. ANALYSIS OF MRNA EXPRESSION OF GENES RELATED TO EPIGENETIC REGULATION AND STRESS RESPONSES IN THE FRONTAL CORTEX AND HIPPOCAMPUS, BRAIN STRUCTURES IMPLICATED IN CHRONIC PAIN, SHOWED DISTINCT SEX AND REGION-SPECIFIC PATTERNS OF DYSREGULATION. IN GENERAL, MRNA EXPRESSION WAS MOST FREQUENTLY ALTERED IN THE MALE HIPPOCAMPUS AND EFFECTS OF PRENATAL STRESS WERE MORE PREVALENT THAN EFFECTS OF NERVE INJURY IN BOTH SUPRASPINAL AREAS. THESE FINDINGS DEMONSTRATE THE IMPACT OF PRENATAL STRESS ON BEHAVIORAL SENSITIVITY TO A PAINFUL INJURY. CHANGES IN THE EXPRESSION OF EPIGENETIC- AND STRESS-RELATED GENES SUGGEST A POSSIBLE MECHANISM BY WHICH THE EARLY LIFE STRESS BECOMES EMBEDDED IN THE CENTRAL NERVOUS SYSTEM. INCREASED UNDERSTANDING OF THE INTERACTIONS AMONG EARLY-LIFE STRESS, SEX, AND PAIN MAY LEAD TO THE IDENTIFICATION OF NOVEL THERAPEUTIC TARGETS AND EPIGENETIC DRUGS FOR THE TREATMENT OF CHRONIC PAIN DISORDERS. 2020 2 5007 47 PERIPHERAL NERVE INJURY IS ASSOCIATED WITH CHRONIC, REVERSIBLE CHANGES IN GLOBAL DNA METHYLATION IN THE MOUSE PREFRONTAL CORTEX. CHANGES IN BRAIN STRUCTURE AND CORTICAL FUNCTION ARE ASSOCIATED WITH MANY CHRONIC PAIN CONDITIONS INCLUDING LOW BACK PAIN AND FIBROMYALGIA. THE MAGNITUDE OF THESE CHANGES CORRELATES WITH THE DURATION AND/OR THE INTENSITY OF CHRONIC PAIN. MOST STUDIES REPORT CHANGES IN COMMON AREAS INVOLVED IN PAIN MODULATION, INCLUDING THE PREFRONTAL CORTEX (PFC), AND PAIN-RELATED PATHOLOGICAL CHANGES IN THE PFC CAN BE REVERSED WITH EFFECTIVE TREATMENT. WHILE THE MECHANISMS UNDERLYING THESE CHANGES ARE UNKNOWN, THEY MUST BE DYNAMICALLY REGULATED. EPIGENETIC MODULATION OF GENE EXPRESSION IN RESPONSE TO EXPERIENCE AND ENVIRONMENT IS REVERSIBLE AND DYNAMIC. EPIGENETIC MODULATION BY DNA METHYLATION IS ASSOCIATED WITH ABNORMAL BEHAVIOR AND PATHOLOGICAL GENE EXPRESSION IN THE CENTRAL NERVOUS SYSTEM. DNA METHYLATION MIGHT ALSO BE INVOLVED IN MEDIATING THE PATHOLOGIES ASSOCIATED WITH CHRONIC PAIN IN THE BRAIN. WE THEREFORE TESTED A) WHETHER ALTERATIONS IN DNA METHYLATION ARE FOUND IN THE BRAIN LONG AFTER CHRONIC NEUROPATHIC PAIN IS INDUCED IN THE PERIPHERY USING THE SPARED NERVE INJURY MODAL AND B) WHETHER THESE INJURY-ASSOCIATED CHANGES ARE REVERSIBLE BY INTERVENTIONS THAT REVERSE THE PATHOLOGIES ASSOCIATED WITH CHRONIC PAIN. SIX MONTHS FOLLOWING PERIPHERAL NERVE INJURY, ABNORMAL SENSORY THRESHOLDS AND INCREASED ANXIETY WERE ACCOMPANIED BY DECREASED GLOBAL METHYLATION IN THE PFC AND THE AMYGDALA BUT NOT IN THE VISUAL CORTEX OR THE THALAMUS. ENVIRONMENTAL ENRICHMENT ATTENUATED NERVE INJURY-INDUCED HYPERSENSITIVITY AND REVERSED THE CHANGES IN GLOBAL PFC METHYLATION. FURTHERMORE, GLOBAL PFC METHYLATION CORRELATED WITH MECHANICAL AND THERMAL SENSITIVITY IN NEUROPATHIC MICE. IN SUMMARY, INDUCTION OF CHRONIC PAIN BY PERIPHERAL NERVE INJURY IS ASSOCIATED WITH EPIGENETIC CHANGES IN THE BRAIN. THESE CHANGES ARE DETECTED LONG AFTER THE ORIGINAL INJURY, AT A LONG DISTANCE FROM THE SITE OF INJURY AND ARE REVERSIBLE WITH ENVIRONMENTAL MANIPULATION. CHANGES IN BRAIN STRUCTURE AND CORTICAL FUNCTION THAT ARE ASSOCIATED WITH CHRONIC PAIN CONDITIONS MAY THEREFORE BE MEDIATED BY EPIGENETIC MECHANISMS. 2013 3 2472 42 EPIGENETIC TRANSMISSION OF THE IMPACT OF EARLY STRESS ACROSS GENERATIONS. BACKGROUND: TRAUMATIC EXPERIENCES IN EARLY LIFE ARE RISK FACTORS FOR THE DEVELOPMENT OF BEHAVIORAL AND EMOTIONAL DISORDERS. SUCH DISORDERS CAN PERSIST THROUGH ADULTHOOD AND HAVE OFTEN BEEN REPORTED TO BE TRANSMITTED ACROSS GENERATIONS. METHODS: TO INVESTIGATE THE TRANSGENERATIONAL EFFECT OF EARLY STRESS, MICE WERE EXPOSED TO CHRONIC AND UNPREDICTABLE MATERNAL SEPARATION FROM POSTNATAL DAY 1 TO 14. RESULTS: WE SHOW THAT CHRONIC AND UNPREDICTABLE MATERNAL SEPARATION INDUCES DEPRESSIVE-LIKE BEHAVIORS AND ALTERS THE BEHAVIORAL RESPONSE TO AVERSIVE ENVIRONMENTS IN THE SEPARATED ANIMALS WHEN ADULT. MOST OF THE BEHAVIORAL ALTERATIONS ARE FURTHER EXPRESSED BY THE OFFSPRING OF MALES SUBJECTED TO MATERNAL SEPARATION, DESPITE THE FACT THAT THESE MALES ARE REARED NORMALLY. CHRONIC AND UNPREDICTABLE MATERNAL SEPARATION ALSO ALTERS THE PROFILE OF DNA METHYLATION IN THE PROMOTER OF SEVERAL CANDIDATE GENES IN THE GERMLINE OF THE SEPARATED MALES. COMPARABLE CHANGES IN DNA METHYLATION ARE ALSO PRESENT IN THE BRAIN OF THE OFFSPRING AND ARE ASSOCIATED WITH ALTERED GENE EXPRESSION. CONCLUSIONS: THESE FINDINGS HIGHLIGHT THE NEGATIVE IMPACT OF EARLY STRESS ON BEHAVIORAL RESPONSES ACROSS GENERATIONS AND ON THE REGULATION OF DNA METHYLATION IN THE GERMLINE. 2010 4 6174 51 THE HIPPOCAMPUS, NEUROTROPHIC FACTORS AND DEPRESSION: POSSIBLE IMPLICATIONS FOR THE PHARMACOTHERAPY OF DEPRESSION. DEPRESSION IS A PREVALENT, HIGHLY DEBILITATING MENTAL DISORDER AFFECTING UP TO 15% OF THE POPULATION AT LEAST ONCE IN THEIR LIFETIME, WITH HUGE COSTS FOR SOCIETY. NEUROBIOLOGICAL MECHANISMS OF DEPRESSION ARE STILL NOT WELL KNOWN, ALTHOUGH THERE IS CONSENSUS ABOUT INTERPLAY BETWEEN GENETIC AND ENVIRONMENTAL FACTORS. ANTIDEPRESSANT MEDICATIONS ARE FREQUENTLY USED IN DEPRESSION, BUT AT LEAST 50% OF PATIENTS ARE POOR RESPONDERS, EVEN TO MORE RECENTLY DISCOVERED MEDICATIONS. FURTHERMORE, CLINICAL RESPONSE ONLY OCCURS FOLLOWING WEEKS TO MONTHS OF TREATMENT AND ONLY CHRONIC TREATMENT IS EFFECTIVE, SUGGESTING THAT ACTIONS BEYOND THE RAPIDLY OCCURRING EFFECT OF ENHANCING MONOAMINERGIC SYSTEMS, SUCH AS ADAPTATION OF THESE SYSTEMS, ARE RESPONSIBLE FOR THE EFFECTS OF ANTIDEPRESSANTS. RECENT STUDIES INDICATE THAT AN IMPAIRMENT OF SYNAPTIC PLASTICITY (NEUROGENESIS, AXON BRANCHING, DENDRITOGENESIS AND SYNAPTOGENESIS) IN SPECIFIC AREAS OF THE CNS, PARTICULARLY THE HIPPOCAMPUS, MAY BE A CORE FACTOR IN THE PATHOPHYSIOLOGY OF DEPRESSION. THE ABNORMAL NEURAL PLASTICITY MAY BE RELATED TO ALTERATIONS IN THE LEVELS OF NEUROTROPHIC FACTORS, NAMELY BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF), WHICH PLAY A CENTRAL ROLE IN PLASTICITY. AS BDNF IS REPRESSED BY STRESS, EPIGENETIC REGULATION OF THE BDNF GENE MAY PLAY AN IMPORTANT ROLE IN DEPRESSION. THE HIPPOCAMPUS IS SMALLER IN DEPRESSED PATIENTS, ALTHOUGH IT IS UNCLEAR WHETHER SMALLER SIZE IS A CONSEQUENCE OF DEPRESSION OR A PRE-EXISTING, VULNERABILITY MARKER FOR DEPRESSION. ENVIRONMENTAL STRESSORS TRIGGERING ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS CAUSE THE BRAIN TO BE EXPOSED TO CORTICOSTEROIDS, AFFECTING NEUROBEHAVIOURAL FUNCTIONS WITH A STRONG DOWNREGULATION OF HIPPOCAMPAL NEUROGENESIS, AND ARE A MAJOR RISK FACTOR FOR DEPRESSION. ANTIDEPRESSANT TREATMENT INCREASES BDNF LEVELS, STIMULATES NEUROGENESIS AND REVERSES THE INHIBITORY EFFECTS OF STRESS, BUT THIS EFFECT IS EVIDENT ONLY AFTER 3-4 WEEKS OF ADMINISTRATION, THE TIME COURSE FOR MATURATION OF NEW NEURONS. THE ABLATION OF HIPPOCAMPAL NEUROGENESIS BLOCKS THE BEHAVIOURAL EFFECTS OF ANTIDEPRESSANTS IN ANIMAL MODELS. THE ABOVE FINDINGS SUGGEST NEW POSSIBLE TARGETS FOR THE PHARMACOTHERAPY OF DEPRESSION SUCH AS NEUROTROPHIC FACTORS, THEIR RECEPTORS AND RELATED INTRACELLULAR SIGNALLING CASCADES; AGENTS COUNTERACTING THE EFFECTS OF STRESS ON HIPPOCAMPAL NEUROGENESIS (INCLUDING ANTAGONISTS OF CORTICOSTEROIDS, INFLAMMATORY CYTOKINES AND THEIR RECEPTORS); AND AGENTS FACILITATING THE ACTIVATION OF GENE EXPRESSION AND INCREASING THE TRANSCRIPTION OF NEUROTROPHINS IN THE BRAIN. 2011 5 6427 41 THE TRANSITION FROM ACUTE TO CHRONIC PAIN: DYNAMIC EPIGENETIC REPROGRAMMING OF THE MOUSE PREFRONTAL CORTEX UP TO 1 YEAR AFTER NERVE INJURY. CHRONIC PAIN IS ASSOCIATED WITH PERSISTENT STRUCTURAL AND FUNCTIONAL CHANGES THROUGHOUT THE NEUROAXIS, INCLUDING IN THE PREFRONTAL CORTEX (PFC). THE PFC IS IMPORTANT IN THE INTEGRATION OF SENSORY, COGNITIVE, AND EMOTIONAL INFORMATION AND IN CONDITIONED PAIN MODULATION. WE PREVIOUSLY REPORTED WIDESPREAD EPIGENETIC REPROGRAMMING IN THE PFC MANY MONTHS AFTER NERVE INJURY IN RODENTS. EPIGENETIC MODIFICATIONS, INCLUDING DNA METHYLATION, CAN DRIVE CHANGES IN GENE EXPRESSION WITHOUT MODIFYING DNA SEQUENCES. TO DATE, LITTLE IS KNOWN ABOUT EPIGENETIC DYSREGULATION AT THE ONSET OF ACUTE PAIN OR HOW IT PROGRESSES AS PAIN TRANSITIONS FROM ACUTE TO CHRONIC. WE HYPOTHESIZE THAT ACUTE PAIN AFTER INJURY RESULTS IN RAPID AND PERSISTENT EPIGENETIC REMODELLING IN THE PFC THAT EVOLVES AS PAIN BECOMES CHRONIC. WE FURTHER PROPOSE THAT UNDERSTANDING EPIGENETIC REMODELLING WILL PROVIDE INSIGHTS INTO THE MECHANISMS DRIVING PAIN-RELATED CHANGES IN THE BRAIN. EPIGENOME-WIDE ANALYSIS WAS PERFORMED IN THE MOUSE PFC 1 DAY, 2 WEEKS, 6 MONTHS, AND 1 YEAR AFTER PERIPHERAL INJURY USING THE SPARED NERVE INJURY IN MICE. SPARED NERVE INJURY RESULTED IN RAPID AND PERSISTENT CHANGES IN DNA METHYLATION, WITH ROBUST DIFFERENTIAL METHYLATION OBSERVED BETWEEN SPARED NERVE INJURY AND SHAM-OPERATED CONTROL MICE AT ALL TIME POINTS. HUNDREDS OF DIFFERENTIALLY METHYLATED GENES WERE IDENTIFIED, INCLUDING MANY WITH KNOWN FUNCTION IN PAIN. PATHWAY ANALYSIS REVEALED ENRICHMENT IN GENES RELATED TO STIMULUS RESPONSE AT EARLY TIME POINTS, IMMUNE FUNCTION AT LATER TIME POINTS, AND ACTIN AND CYTOSKELETAL REGULATION THROUGHOUT THE TIME COURSE. THESE RESULTS EMPHASIZE THE IMPORTANCE OF CONSIDERING PAIN CHRONICITY IN BOTH PAIN RESEARCH AND IN TREATMENT OPTIMIZATION. 2020 6 1981 39 EPIGENETIC ALTERATIONS IN DNA AND HISTONE MODIFICATIONS CAUSED BY DEPRESSION AND ANTIDEPRESSANT DRUGS: LESSONS FROM THE RODENT MODELS. EPIGENETIC MODIFICATIONS REGULATE CHROMATIN FOLDING AND FUNCTION. EPIGENETIC MECHANISMS REGULATE TRANSCRIPTION MEDIATING EFFECTS OF VARIOUS STIMULI ON GENE EXPRESSION. THESE MECHANISMS ARE INVOLVED IN TRANSCRIPTIONAL CONTROL IN VARIOUS PHYSIOLOGICAL AND PATHOLOGICAL CONDITIONS INCLUDING NEUROPSYCHIATRIC DISORDERS AND BEHAVIORAL ABNORMALITIES SUCH AS DEPRESSION. IN RODENTS, EXPOSURE TO CHRONIC SOCIAL STRESS WAS SHOWN TO INDUCE BEHAVIORAL IMPAIRMENTS AND MEMORY/LEARNING DEFICITS THAT RESEMBLE DEPRESSIVE-LIKE PHENOTYPE IN HUMANS. THE RODENT MODELS OF CHRONIC STRESS WERE WIDELY USED TO STUDY MOLECULAR MECHANISMS OF DEPRESSION. IN THESE MODELS, EARLY EXPOSURE TO CHRONIC STRESS SUCH AS PRENATAL OR POSTNATAL STRESS INDUCES LONG-TERM HYPERACTIVE STRESS RESPONSES, BEHAVIORAL ABNORMALITIES, AND FUNCTIONAL IMPAIRMENTS IN BRAIN FUNCTION THAT PERSIST IN ADULTHOOD. FURTHERMORE, THESE ALTERATIONS CAN BE TRANSMITTED TO OFFSPRING OF CHRONICALLY STRESSED ANIMALS ACROSS SEVERAL GENERATIONS. MOLECULAR STUDIES IN ANIMAL MODELS SHOWED THAT CHRONIC STRESS INDUCES STABLE EPIGENETIC CHANGES IN SPECIFIC BRAIN REGIONS, PRIMARILY IN THE LIMBIC SYSTEM. THESE CHANGES LEAD TO LONG-LASTING ABNORMALITIES IN BEHAVIOR THAT PERSIST IN ADULTHOOD AND CAN BE TRANSMITTED TO OFFSPRING. TREATMENT WITH EPIGENETICALLY ACTIVE ANTIDEPRESSANTS DISRUPTS THE ABNORMAL STRESS-INDUCED EPIGENETIC PROGRAMMING AND PROVIDES EPIGENETIC PATTERNS THAT RESEMBLE EPIGENETIC BACKGROUND OF STRESS RESILIENT INDIVIDUALS. 2017 7 4642 37 NEURONAL PLASTICITY: A LINK BETWEEN STRESS AND MOOD DISORDERS. ALTHOUGH STRESS REPRESENTS THE MAJOR ENVIRONMENTAL ELEMENT OF SUSCEPTIBILITY FOR MOOD DISORDERS, THE RELATIONSHIP BETWEEN STRESS AND DISEASE REMAINS TO BE FULLY ESTABLISHED. IN THE PRESENT ARTICLE WE REVIEW THE EVIDENCE IN SUPPORT FOR A ROLE OF NEURONAL PLASTICITY, AND IN PARTICULAR OF NEUROTROPHIC FACTORS. EVEN THOUGH DECREASED LEVELS OF NOREPINEPHRINE AND SEROTONIN MAY UNDERLIE DEPRESSIVE SYMPTOMS, COMPELLING EVIDENCE NOW SUGGESTS THAT MOOD DISORDERS ARE CHARACTERIZED BY REDUCED NEURONAL PLASTICITY, WHICH CAN BE BROUGHT ABOUT BY EXPOSURE TO STRESS AT DIFFERENT STAGES OF LIFE. INDEED THE EXPRESSION OF NEUROTROPHIC MOLECULES, SUCH AS THE NEUROTROPHIN BDNF, IS REDUCED IN DEPRESSED SUBJECTS AS WELL AS IN EXPERIMENTAL ANIMALS EXPOSED TO ADVERSE EXPERIENCE AT EARLY STAGES OF LIFE OR AT ADULTHOOD. THESE CHANGES SHOW AN ANATOMICAL SPECIFICITY AND MIGHT BE SUSTAINED BY EPIGENETIC MECHANISMS. PHARMACOLOGICAL INTERVENTION MAY NORMALIZE SUCH DEFECTS AND IMPROVE NEURONAL FUNCTION THROUGH THE MODULATION OF THE SAME FACTORS THAT ARE DEFECTIVE IN DEPRESSION. SEVERAL STUDIES HAVE DEMONSTRATED THAT CHRONIC, BUT NOT ACUTE, ANTIDEPRESSANT TREATMENT INCREASES THE EXPRESSION OF BDNF AND MAY ENHANCE ITS LOCALIZATION AT SYNAPTIC LEVEL. ANTIDEPRESSANT TREATMENT CAN NORMALIZE DEFICITS IN NEUROTROPHIN EXPRESSION PRODUCED BY CHRONIC STRESS PARADIGMS, BUT MAY ALSO ALTER THE MODULATION OF BDNF UNDER ACUTE STRESSFUL CONDITIONS. IN SUMMARY, THERE IS GOOD AGREEMENT IN CONSIDERING NEURONAL PLASTICITY, AND THE EXPRESSION OF KEY PROTEINS SUCH AS THE NEUROTROPHIN BDNF, AS A CENTRAL PLAYER FOR THE EFFECTS OF STRESS ON BRAIN FUNCTION AND ITS IMPLICATION FOR PSYCHOPATHOLOGY. ACCORDINGLY, EFFECTIVE TREATMENTS SHOULD NOT LIMIT THEIR EFFECTS TO THE CONTROL OF NEUROTRANSMITTER AND HORMONAL DYSFUNCTIONS, BUT SHOULD BE ABLE TO NORMALIZE DEFECTIVE MECHANISMS THAT SUSTAIN THE IMPAIRMENT OF NEURONAL PLASTICITY. 2009 8 1790 41 EFFECT OF CHRONIC MILD STRESS ON HIPPOCAMPAL TRANSCRIPTOME IN MICE SELECTED FOR HIGH AND LOW STRESS-INDUCED ANALGESIA AND DISPLAYING DIFFERENT EMOTIONAL BEHAVIORS. THERE IS INCREASING EVIDENCE THAT MOOD DISORDERS MAY DERIVE FROM THE IMPACT OF ENVIRONMENTAL PRESSURE ON GENETICALLY SUSCEPTIBLE INDIVIDUALS. STRESS-INDUCED HIPPOCAMPAL PLASTICITY HAS BEEN IMPLICATED IN DEPRESSION. WE STUDIED HIPPOCAMPAL TRANSCRIPTOMES IN STRAINS OF MICE THAT DISPLAY HIGH (HA) AND LOW (LA) SWIM STRESS-INDUCED ANALGESIA AND THAT DIFFER IN EMOTIONAL BEHAVIORS AND RESPONSES TO DIFFERENT CLASSES OF ANTIDEPRESSANTS. CHRONIC MILD STRESS (CMS) AFFECTED EXPRESSION OF A NUMBER OF GENES COMMON FOR BOTH STRAINS. CMS ALSO PRODUCED STRAIN SPECIFIC CHANGES IN EXPRESSION SUGGESTING THAT HIPPOCAMPAL RESPONSES TO STRESS DEPEND ON GENOTYPE. CONSIDERABLY LARGER NUMBER OF GENES, BIOLOGICAL PROCESSES, MOLECULAR FUNCTIONS, BIOCHEMICAL PATHWAYS, AND GENE NETWORKS WERE AFFECTED BY CMS IN LA THAN IN HA MICE. THE RESULTS SUGGEST THAT POTENTIAL DRUG TARGETS AGAINST DETRIMENTAL EFFECTS OF STRESS INCLUDE GLUTAMATE TRANSPORTERS, AND CHOLINERGIC, CHOLECYSTOKININ (CCK), GLUCOCORTICOIDS, AND THYROID HORMONES RECEPTORS. FURTHERMORE, SOME BIOLOGICAL PROCESSES EVOKED BY STRESS AND DIFFERENT BETWEEN THE STRAINS, SUCH AS APOPTOSIS, NEUROGENESIS AND CHROMATIN MODIFICATIONS, MAY BE RESPONSIBLE FOR THE LONG-TERM, IRREVERSIBLE EFFECTS OF STRESS AND SUGGEST A ROLE FOR EPIGENETIC REGULATION OF MOOD RELATED STRESS RESPONSES. 2011 9 5019 43 PERSISTENT INFLAMMATORY PAIN IS LINKED WITH ANXIETY-LIKE BEHAVIORS, INCREASED BLOOD CORTICOSTERONE, AND REDUCED GLOBAL DNA METHYLATION IN THE RAT AMYGDALA. CHRONIC PAIN INCREASES THE RISK OF DEVELOPING ANXIETY, WITH LIMBIC AREAS BEING LIKELY NEUROLOGICAL SUBSTRATES. DESPITE HIGH CLINICAL RELEVANCE, LITTLE IS KNOWN ABOUT THE PRECISE BEHAVIORAL, HORMONAL, AND BRAIN NEUROPLASTIC CORRELATES OF ANXIETY IN THE CONTEXT OF PERSISTENT PAIN. PREVIOUS STUDIES HAVE SHOWN THAT DECREASED NOCICEPTIVE THRESHOLDS IN CHRONIC PAIN MODELS ARE PARALLELED BY ANXIETY-LIKE BEHAVIOR IN RATS, BUT THERE ARE CONFLICTING IDEAS REGARDING ITS EFFECTS ON THE STRESS RESPONSE AND CIRCULATING CORTICOSTERONE LEVELS. EVEN LESS IS KNOWN ABOUT THE MOLECULAR MECHANISMS THROUGH WHICH THE BRAIN ENCODES PAIN-RELATED ANXIETY. THIS STUDY EXAMINES HOW PERSISTENT INFLAMMATORY PAIN IN A RAT MODEL WOULD IMPACT ANXIETY-LIKE BEHAVIORS AND CORTICOSTERONE RELEASE, AND WHETHER THESE CHANGES WOULD BE REFLECTED IN LEVELS OF GLOBAL DNA METHYLATION IN BRAIN AREAS INVOLVED IN STRESS REGULATION. COMPLETE FREUND'S ADJUVANT (CFA) OR SALINE WAS ADMINISTERED IN THE RIGHT HINDPAW OF ADULT MALE WISTAR RATS. BEHAVIORAL TESTING INCLUDED THE MEASUREMENT OF NOCICEPTIVE THRESHOLDS (DIGITAL ANESTHESIOMETER), MOTOR FUNCTION (OPEN FIELD TEST), AND ANXIETY-LIKE BEHAVIORS (ELEVATED PLUS MAZE AND THE DARK-LIGHT BOX TEST). CORTICOSTERONE WAS MEASURED VIA RADIOIMMUNOASSAY. GLOBAL DNA METHYLATION (ENZYME IMMUNOASSAY) AS WELL AS DNMT3A LEVELS (WESTERN BLOTTING) WERE QUANTIFIED IN THE AMYGDALA, PREFRONTAL CORTEX, AND VENTRAL HIPPOCAMPUS. CFA ADMINISTRATION RESULTED IN PERSISTENT REDUCTION IN NOCICEPTIVE THRESHOLD IN THE ABSENCE OF LOCOMOTOR ABNORMALITIES. INCREASED ANXIETY-LIKE BEHAVIORS WERE OBSERVED IN THE ELEVATED PLUS MAZE AND WERE ACCOMPANIED BY INCREASED BLOOD CORTICOSTERONE LEVELS 10 DAYS AFTER PAIN INDUCTION. GLOBAL DNA METHYLATION WAS DECREASED IN THE AMYGDALA, WITH NO CHANGES IN DNMT3A ABUNDANCE IN ANY OF THE REGIONS EXAMINED. PERSISTENT INFLAMMATORY PAIN PROMOTES ANXIETY -LIKE BEHAVIORS, HPA AXIS ACTIVATION, AND EPIGENETIC REGULATION THROUGH DNA METHYLATION IN THE AMYGDALA. THESE FINDINGS DESCRIBE A MOLECULAR MECHANISM THAT LINKS PAIN AND STRESS IN A WELL-CHARACTERIZED RODENT MODEL. 2022 10 377 36 AN EPIGENETIC HYPOTHESIS FOR THE GENOMIC MEMORY OF PAIN. CHRONIC PAIN IS ACCOMPANIED WITH LONG-TERM SENSORY, AFFECTIVE AND COGNITIVE DISTURBANCES. WHAT ARE THE MECHANISMS THAT MEDIATE THE LONG-TERM CONSEQUENCES OF PAINFUL EXPERIENCES AND EMBED THEM IN THE GENOME? WE HYPOTHESIZE THAT ALTERATIONS IN DNA METHYLATION, AN ENZYMATIC COVALENT MODIFICATION OF CYTOSINE BASES IN DNA, SERVE AS A "GENOMIC" MEMORY OF PAIN IN THE ADULT CORTEX. DNA METHYLATION IS AN EPIGENETIC MECHANISM FOR LONG-TERM REGULATION OF GENE EXPRESSION. NEURONAL PLASTICITY AT THE NEUROANATOMICAL, FUNCTIONAL, MORPHOLOGICAL, PHYSIOLOGICAL AND MOLECULAR LEVELS HAS BEEN DEMONSTRATED THROUGHOUT THE NEUROAXIS IN RESPONSE TO PERSISTENT PAIN, INCLUDING IN THE ADULT PREFRONTAL CORTEX (PFC). WE HAVE PREVIOUSLY REPORTED WIDESPREAD CHANGES IN GENE EXPRESSION AND DNA METHYLATION IN THE PFC MANY MONTHS FOLLOWING PERIPHERAL NERVE INJURY. IN SUPPORT OF THIS HYPOTHESIS, WE SHOW HERE THAT UP-REGULATION OF A GENE INVOLVED WITH SYNAPTIC FUNCTION, SYNAPTOTAGMIN II (SYT2), IN THE PFC IN A CHRONIC PAIN MODEL IS ASSOCIATED WITH LONG-TERM CHANGES IN DNA METHYLATION. THE CHALLENGES OF UNDERSTANDING THE CONTRIBUTIONS OF EPIGENETIC MECHANISMS SUCH AS DNA METHYLATION WITHIN THE PFC TO PAIN CHRONICITY AND THEIR THERAPEUTIC IMPLICATIONS ARE DISCUSSED. 2015 11 4093 37 MATERNAL SEPARATION FOLLOWED BY CHRONIC MILD STRESS IN ADULTHOOD IS ASSOCIATED WITH CONCERTED EPIGENETIC REGULATION OF AP-1 COMPLEX GENES. DEPRESSION IS ONE OF THE MOST PREVALENT MENTAL DISEASES WORLDWIDE. PATIENTS WITH PSYCHIATRIC DISEASES OFTEN HAVE A HISTORY OF CHILDHOOD NEGLECT, INDICATING THAT EARLY-LIFE EXPERIENCES PREDISPOSE TO PSYCHIATRIC DISEASES IN ADULTHOOD. TWO STRONG MODELS WERE USED IN THE PRESENT STUDY: THE MATERNAL SEPARATION/EARLY DEPRIVATION MODEL (MS) AND THE CHRONIC MILD STRESS MODEL (CMS). IN BOTH MODELS, WE FOUND CHANGES IN THE EXPRESSION OF A NUMBER OF GENES SUCH AS CREB AND NPY. STRIKINGLY, THERE WAS A CLEAR REGULATION OF EXPRESSION OF FOUR GENES INVOLVED IN THE AP-1 COMPLEX: C-FOS, C-JUN, FOSB, AND JUN-B. INTERESTINGLY, DIFFERENT EXPRESSION LEVELS WERE OBSERVED DEPENDING ON THE MODEL, WHEREAS THE COMBINATION OF THE MODELS RESULTED IN A NORMAL LEVEL OF GENE EXPRESSION. THE EFFECTS OF MS AND CMS ON GENE EXPRESSION WERE ASSOCIATED WITH DISTINCT HISTONE METHYLATION/ACETYLATION PATTERNS OF ALL FOUR GENES. THE EPIGENETIC CHANGES, LIKE GENE EXPRESSION, WERE ALSO DEPENDENT ON THE SPECIFIC STRESSOR OR THEIR COMBINATION. THE OBTAINED RESULTS SUGGEST THAT SINGLE LIFE EVENTS LEAVE A MARK ON GENE EXPRESSION AND THE EPIGENETIC SIGNATURE OF GENE PROMOTERS, BUT A COMBINATION OF DIFFERENT STRESSORS AT DIFFERENT LIFE STAGES CAN FURTHER CHANGE GENE EXPRESSION THROUGH EPIGENETIC FACTORS, POSSIBLY CAUSING THE LONG-LASTING ADVERSE EFFECTS OF STRESS. 2021 12 5645 40 SEX DEPENDENT ALTERATION OF EPIGENETIC MARKS AFTER CHRONIC MORPHINE TREATMENT IN MICE ORGANS. EPIGENETIC MARKS MAY BE ALSO AFFECTED BY SEVERAL FACTORS, SUCH AS AGE, LIFESTYLE, EARLY LIFE EXPERIENCES AND EXPOSURE TO CHEMICALS OR DRUGS, SUCH AS OPIOIDS. PREVIOUS STUDIES HAVE FOCUSED ON HOW MORPHINE EPIGENETICALLY REGULATES DIFFERENT REGIONS OF THE BRAIN THAT ARE IMPLICATED IN TOLERANCE, DEPENDENCE AND OTHER PSYCHIATRIC DISORDERS MORE RELATED TO THE PHYSIO-PATHOLOGICAL EFFECTS OF OPIOIDS. NEVERTHELESS, A SIGNIFICANT KNOWLEDGE GAP REMAINS REGARDING THE EFFECT OF CHRONIC TREATMENT ON OTHER ORGANS AND BIOLOGICAL SYSTEMS. THEREFORE, THE AIM OF THIS WORK IS TO INCREASE OUR KNOWLEDGE ABOUT THE IMPACT OF CHRONIC MORPHINE EXPOSURE ON DNA METHYLATION AND HISTONE MODIFICATION LEVELS IN EACH OF THE ORGANS OF MALE AND FEMALE MODEL MICE IN VIVO. OUR RESULTS REVEAL, FOR THE FIRST TIME, THAT CHRONIC MORPHINE TREATMENT INDUCED CHANGES IN DNA METHYLATION/HYDROXYMETHYLATION AND HISTONE MODIFICATION IN-VIVO AT THE SYSTEMIC LEVEL, REVEALING A POTENTIAL PHYSIOLOGICAL EFFECT ON THE REGULATION OF GENE EXPRESSION. NOTABLY, MORPHINE-INDUCED EPIGENETIC MODIFICATION OCCURS IN A SEX-DEPENDENT MANNER, REVEALING THE EXISTENCE OF DIFFERENT UNDERLYING MECHANISMS OF EPIGENETIC MODIFICATION IN MALE AND FEMALE MICE. 2021 13 3973 42 LONG-TERM BEHAVIORAL AND NEUROENDOCRINE ALTERATIONS FOLLOWING CHRONIC SOCIAL STRESS IN MICE: IMPLICATIONS FOR STRESS-RELATED DISORDERS. THE PERIOD OF ADOLESCENCE IS CHARACTERIZED BY A HIGH VULNERABILITY TO STRESS AND TRAUMA, WHICH MIGHT RESULT IN LONG-LASTING CONSEQUENCES AND AN INCREASED RISK TO DEVELOP PSYCHIATRIC DISORDERS. USING A RECENTLY DEVELOPED MOUSE MODEL FOR CHRONIC SOCIAL STRESS DURING ADOLESCENCE, WE STUDIED PERSISTENT NEUROENDOCRINE AND BEHAVIORAL EFFECTS OF CHRONIC SOCIAL STRESS OBTAINED 12 MONTHS AFTER CESSATION OF THE STRESSOR. AS A REFERENCE, WE INVESTIGATED IMMEDIATE EFFECTS OF CHRONIC STRESS EXPOSURE OBTAINED AT THE END OF THE CHRONIC STRESS PERIOD. IMMEDIATELY AFTER THE 7 WEEK CHRONIC STRESS PERIOD STRESSED ANIMALS SHOW SIGNIFICANTLY INCREASED ADRENAL WEIGHTS, DECREASED THYMUS WEIGHT, INCREASED BASAL CORTICOSTERONE SECRETION AND A FLATTENED CIRCADIAN RHYTHM. FURTHERMORE, STRESSED ANIMALS DISPLAY AN INCREASED ANXIETY-LIKE BEHAVIOR IN THE ELEVATED PLUS MAZE AND THE NOVELTY-INDUCED SUPPRESSION OF FEEDING TEST. HIPPOCAMPAL MINERALOCORTICOID RECEPTOR (MR) AND THE GLUCOCORTICOID RECEPTOR (GR) MRNA LEVELS WERE SIGNIFICANTLY DECREASED. TO INVESTIGATE PERSISTENT CONSEQUENCES OF THIS EARLY STRESSFUL EXPERIENCE, THE SAME PARAMETERS WERE ASSESSED IN AGED MICE 12 MONTHS AFTER THE CESSATION OF THE STRESSOR. INTERESTINGLY, WE STILL FOUND DIFFERENCES BETWEEN FORMERLY STRESSED AND CONTROL MICE IN IMPORTANT STRESS-RELATED PARAMETERS. MR EXPRESSION LEVELS WERE SIGNIFICANTLY LOWER IN STRESSED ANIMALS, SUGGESTING LASTING, POSSIBLY EPIGENETIC ALTERATIONS IN GENE EXPRESSION REGULATION. FURTHERMORE, WE OBSERVED LONG-TERM BEHAVIORAL ALTERATIONS IN ANIMALS STRESSED DURING ADOLESCENCE. THUS, WE COULD DEMONSTRATE THAT CHRONIC STRESS EXPOSURE DURING A CRUCIAL DEVELOPMENTAL TIME PERIOD RESULTS IN LONG-TERM, PERSISTENT EFFECTS ON PHYSIOLOGICAL AND BEHAVIORAL PARAMETERS THROUGHOUT LIFE, WHICH MAY CONTRIBUTE TO AN ENHANCED VULNERABILITY TO STRESS-INDUCED DISEASES. 2008 14 3313 39 HIPPOCAMPAL BDNF IN PHYSIOLOGICAL CONDITIONS AND SOCIAL ISOLATION. EXPOSURE OF AN ORGANISM TO CHRONIC PSYCHOSOCIAL STRESS MAY AFFECT BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) EXPRESSION THAT HAS BEEN IMPLICATED IN THE ETIOLOGY OF PSYCHIATRIC DISORDERS, SUCH AS DEPRESSION. GIVEN THAT DEPRESSION IN HUMANS HAS BEEN LINKED WITH SOCIAL STRESS, THE CHRONIC SOCIAL STRESS PARADIGMS FOR MODELING PSYCHIATRIC DISORDERS IN ANIMALS HAVE THUS BEEN DEVELOPED. CHRONIC SOCIAL ISOLATION IN ANIMAL MODELS GENERALLY CAUSES CHANGES IN HYPOTHALAMIC-PITUITARY-ADRENAL AXIS FUNCTIONING, ASSOCIATED WITH ANXIETY- AND DEPRESSIVE-LIKE BEHAVIORS. ALSO, THIS CHRONIC STRESS CAUSES DOWNREGULATION OF BDNF PROTEIN AND MRNA IN THE HIPPOCAMPUS, A STRESS-SENSITIVE BRAIN REGION CLOSELY RELATED TO THE PATHOPHYSIOLOGY OF DEPRESSION. IN THIS REVIEW, WE DISCUSS THE CURRENT KNOWLEDGE REGARDING THE STRUCTURE, FUNCTION, INTRACELLULAR SIGNALING, INTER-INDIVIDUAL DIFFERENCES AND EPIGENETIC REGULATION OF BDNF IN BOTH PHYSIOLOGICAL CONDITIONS AND DEPRESSION AND CHANGES IN CORTICOSTERONE LEVELS, AS A MARKER OF STRESS RESPONSE. SINCE BDNF LEVELS ARE AGE DEPENDENT IN HUMANS AND RODENTS, THIS REVIEW WILL ALSO HIGHLIGHT THE EFFECTS OF ADOLESCENT AND ADULT CHRONIC SOCIAL ISOLATION MODELS OF BOTH GENDERS ON THE BDNF EXPRESSION. 2017 15 5818 35 STRESS AND TRAUMA: BDNF CONTROL OF DENDRITIC-SPINE FORMATION AND REGRESSION. CHRONIC RESTRAINT STRESS LEADS TO INCREASES IN BRAIN DERIVED NEUROTROPHIC FACTOR (BDNF) MRNA AND PROTEIN IN SOME REGIONS OF THE BRAIN, E.G. THE BASAL LATERAL AMYGDALA (BLA) BUT DECREASES IN OTHER REGIONS SUCH AS THE CA3 REGION OF THE HIPPOCAMPUS AND DENDRITIC SPINE DENSITY INCREASES OR DECREASES IN LINE WITH THESE CHANGES IN BDNF. GIVEN THE POWERFUL INFLUENCE THAT BDNF HAS ON DENDRITIC SPINE GROWTH, THESE OBSERVATIONS SUGGEST THAT THE FUNDAMENTAL REASON FOR THE DIRECTION AND EXTENT OF CHANGES IN DENDRITIC SPINE DENSITY IN A PARTICULAR REGION OF THE BRAIN UNDER STRESS IS DUE TO THE CHANGES IN BDNF THERE. THE MOST LIKELY CAUSE OF THESE CHANGES IS PROVIDED BY THE STRESS INITIATED RELEASE OF STEROIDS, WHICH READILY ENTER NEURONS AND ALTER GENE EXPRESSION, FOR EXAMPLE THAT OF BDNF. OF PARTICULAR INTEREST IS HOW GLUCOCORTICOIDS AND MINERALOCORTICOIDS TEND TO HAVE OPPOSITE EFFECTS ON BDNF GENE EXPRESSION OFFERING THE POSSIBILITY THAT DIFFERENCES IN THE DISTRIBUTION OF THEIR RECEPTORS AND OF THEIR DOWNSTREAM EFFECTS MIGHT PROVIDE A BASIS FOR THE DIFFERENTIAL TRANSCRIPTION OF THE BDNF GENES. ALTERNATIVELY, DIFFERENCES IN THE EXTENT OF METHYLATION AND ACETYLATION IN THE EPIGENETIC CONTROL OF BDNF TRANSCRIPTION ARE POSSIBLE IN DIFFERENT PARTS OF THE BRAIN FOLLOWING STRESS. ALTHOUGH PRESENT EVIDENCE POINTS TO CHANGES IN BDNF TRANSCRIPTION BEING THE MAJOR CAUSAL AGENT FOR THE CHANGES IN SPINE DENSITY IN DIFFERENT PARTS OF THE BRAIN FOLLOWING STRESS, STEROIDS HAVE SIGNIFICANT EFFECTS ON DOWNSTREAM PATHWAYS FROM THE TRKB RECEPTOR ONCE IT IS ACTED UPON BY BDNF, INCLUDING THOSE THAT MODULATE THE DENSITY OF DENDRITIC SPINES. FINALLY, ALTHOUGH GLUCOCORTICOIDS PLAY A CANONICAL ROLE IN DETERMINING BDNF MODULATION OF DENDRITIC SPINES, RECENT STUDIES HAVE SHOWN A ROLE FOR CORTICOTROPHIN RELEASING FACTOR (CRF) IN THIS REGARD. THERE IS CONSIDERABLE IMPROVEMENT IN THE EXTENT OF CHANGES IN SPINE SIZE AND DENSITY IN RODENTS WITH FOREBRAIN SPECIFIC KNOCKOUT OF CRF RECEPTOR 1 (CRFR1) EVEN WHEN THE GLUCOCORTICOID PATHWAYS ARE LEFT INTACT. IT SEEMS THEN THAT CRF DOES HAVE A ROLE TO PLAY IN DETERMINING BDNF CONTROL OF DENDRITIC SPINES. 2014 16 2445 30 EPIGENETIC STATUS OF GDNF IN THE VENTRAL STRIATUM DETERMINES SUSCEPTIBILITY AND ADAPTATION TO DAILY STRESSFUL EVENTS. STRESSFUL EVENTS DURING ADULTHOOD ARE POTENT ADVERSE ENVIRONMENTAL FACTORS THAT CAN PREDISPOSE INDIVIDUALS TO PSYCHIATRIC DISORDERS, INCLUDING DEPRESSION; HOWEVER, MANY INDIVIDUALS EXPOSED TO STRESSFUL EVENTS CAN ADAPT AND FUNCTION NORMALLY. WHILE STRESS VULNERABILITY MAY INFLUENCE DEPRESSION, THE MOLECULAR MECHANISMS UNDERLYING THE SUSCEPTIBILITY AND ADAPTATION TO CHRONIC STRESS WITHIN THE BRAIN ARE POORLY UNDERSTOOD. IN THIS STUDY, TWO GENETICALLY DISTINCT MOUSE STRAINS THAT EXHIBIT DIFFERENT BEHAVIORAL RESPONSES TO CHRONIC STRESS WERE USED TO DEMONSTRATE HOW THE DIFFERENTIAL EPIGENETIC STATUS OF THE GLIAL CELL-DERIVED NEUROTROPHIC FACTOR (GDNF) GENE IN THE VENTRAL STRIATUM MODULATES SUSCEPTIBILITY AND ADAPTATION TO CHRONIC STRESS. OUR RESULTS SUGGEST THAT THE HISTONE MODIFICATIONS AND DNA METHYLATION OF THE GDNF PROMOTER HAVE CRUCIAL ROLES IN THE CONTROL OF BEHAVIORAL RESPONSES TO CHRONIC STRESS. OUR DATA PROVIDE INSIGHTS INTO THESE MECHANISMS, SUGGESTING THAT EPIGENETIC MODIFICATIONS OF GDNF, ALONG WITH GENETIC AND ENVIRONMENTAL FACTORS, CONTRIBUTE TO BEHAVIORAL RESPONSES TO STRESS. 2011 17 4276 37 MICROGLIA FROM OFFSPRING OF DAMS WITH ALLERGIC ASTHMA EXHIBIT EPIGENOMIC ALTERATIONS IN GENES DYSREGULATED IN AUTISM. DYSREGULATION IN IMMUNE RESPONSES DURING PREGNANCY INCREASES THE RISK OF A HAVING A CHILD WITH AN AUTISM SPECTRUM DISORDER (ASD). ASTHMA IS ONE OF THE MOST COMMON CHRONIC DISEASES AMONG PREGNANT WOMEN, AND SYMPTOMS OFTEN WORSEN DURING PREGNANCY. WE RECENTLY DEVELOPED A MOUSE MODEL OF MATERNAL ALLERGIC ASTHMA (MAA) THAT INDUCES CHANGES IN SOCIABILITY, REPETITIVE, AND PERSEVERATIVE BEHAVIORS IN THE OFFSPRING. SINCE EPIGENETIC CHANGES HELP A STATIC GENOME ADAPT TO THE MATERNAL ENVIRONMENT, ACTIVATION OF THE IMMUNE SYSTEM MAY EPIGENETICALLY ALTER FETAL MICROGLIA, THE BRAIN'S RESIDENT IMMUNE CELLS. WE THEREFORE TESTED THE HYPOTHESIS THAT EPIGENOMIC ALTERATIONS TO MICROGLIA MAY BE INVOLVED IN BEHAVIORAL ABNORMALITIES OBSERVED IN MAA OFFSPRING. WE USED THE GENOME-WIDE APPROACHES OF WHOLE GENOME BISULFITE SEQUENCING TO EXAMINE DNA METHYLATION AND RNA SEQUENCING TO EXAMINE GENE EXPRESSION IN MICROGLIA FROM JUVENILE MAA OFFSPRING. DIFFERENTIALLY METHYLATED REGIONS WERE ENRICHED FOR IMMUNE SIGNALING PATHWAYS AND IMPORTANT MICROGLIAL DEVELOPMENTAL TRANSCRIPTION FACTOR BINDING MOTIFS. DIFFERENTIAL EXPRESSION ANALYSIS IDENTIFIED GENES INVOLVED IN CONTROLLING MICROGLIAL SENSITIVITY TO THE ENVIRONMENT AND SHAPING NEURONAL CONNECTIONS IN THE DEVELOPING BRAIN. DIFFERENTIALLY EXPRESSED GENES SIGNIFICANTLY OVERLAPPED GENES WITH ALTERED EXPRESSION IN HUMAN ASD CORTEX, SUPPORTING A ROLE FOR MICROGLIA IN THE PATHOGENESIS OF ASD. 2018 18 291 34 AGING AND STRESS: PAST HYPOTHESES, PRESENT APPROACHES AND PERSPECTIVES. BRAIN AGING HAS BEEN SUGGESTED TO BE CONDITIONED BY AN EXCESSIVE GLUCOCORTIOID SECRETION LEADING TO DAMAGES ON BRAIN AREAS INVOLVED NOT ONLY IN COGNITIVE AND EMOTIONAL PROCESSES BUT ALSO IN THE CONTROL OF THE ACTIVITY OF THE HYPOTHALAMIC-PITUITARY ADRENAL AXIS. THIS REVIEW DESCRIBES SOME OF THE HYPOTHESIS THAT TRY TO EXPLAIN THE RELATION BETWEEN THE DYSREGULATION OF THE STRESS RESPONSE AND BRAIN AGING, FOCUSING ON CORTICOSTERONE BUT ALSO ON NEUROTRANSMISSION IN THE HIPPOCAMPUS, THE PREFRONTAL CORTEX AND THE AMYGDALA. MOREOVER, DIFFERENT MOLECULAR FACTORS CAN ACCOUNT FOR AN ENHANCED VULNERABILITY OF THE AGED BRAIN TO STRESS EXPOSURE, SPECIALLY FOR RESILIENCE. AMONG THEM, GOOD CANDIDATES COULD BE THOSE MECHANISMS DETERMINING THE LEVELS OF CORTICOSTERONE IN THE BRAIN, SEVERAL MOLECULES DOWNSTREAM GLUCOCORTICOID RECEPTOR ACTIVATION (IE: HEAT SHOCK PROTEINS, BAG-1) OR EVEN THE EPIGENETIC PROGRAMMING OF THE HPA AXIS IN EARLY STAGES. IN CONCLUSION, GENETIC AND ENVIRONMENTAL FACTORS (EARLY LIFE STRESS, CHRONIC STRESS DURING ADULTHOOD) CAN PRODUCE AN ENHANCED VULNERABILITY AND A REDUCED RESILIENCE OF THE BRAIN TO SUBSEQUENT STRESS EXPOSURES OR TO METABOLIC CHALLENGES LEADING, IN TURN, TO AN UNSUCCESSFUL AGING OF THE BRAIN. HOWEVER, RESULTS OBTAINED WITH THE USE OF THE ENVIRONMENTAL ENRICHMENT MODEL IN ANIMALS, ADDED TO SEVERAL RESULTS IN HUMANS ALSO DESCRIBED IN THIS REVIEW SUGGEST THAT POSITIVE ENVIRONMENTAL FACTORS (COGNITIVE-DEMANDING TASKS OR PHYSICAL EXERCISE) CAN HELP TO MAINTAIN NEURONAL PLASTICITY DURING AGING AND TO PROTECT THE BRAIN AGAINST THE DAMAGING EFFECTS OF STRESS EXPOSURE. 2011 19 5467 44 RESILIENT PHENOTYPE IN CHRONIC MILD STRESS PARADIGM IS ASSOCIATED WITH ALTERED EXPRESSION LEVELS OF MIR-18A-5P AND SEROTONIN 5-HT(1A) RECEPTOR IN DORSAL PART OF THE HIPPOCAMPUS. DISTURBED SEROTONERGIC SIGNALING IN THE HIPPOCAMPUS OBSERVED IN MANY INDIVIDUALS VULNERABLE TO STRESS HAS BEEN SUGGESTED AS ONE OF THE PRIMARY FACTORS CONTRIBUTING TO THE DEVELOPMENT OF DEPRESSION. HOWEVER, LITTLE IS KNOWN ABOUT THE PHYSIOLOGY OF THE BRAIN IN THE RESILIENT PHENOTYPE. RESILIENT SUBJECTS MAINTAIN A POSITIVE MOOD AND PSYCHOLOGICAL BALANCE DESPITE BEING UNDER THE STRESS INFLUENCE. IN OUR STUDY, WE GENERATED STRESS-VULNERABLE AND RESILIENT RATS BY USING A CHRONIC MILD STRESS (CMS) PARADIGM. USING DIFFERENT MOLECULAR APPROACHES, WE REVEALED THAT RESILIENT ANIMALS EXHIBITED A SIGNIFICANTLY DECREASED EXPRESSION LEVEL OF MIR-18A-5P AND, IN THE SAME TIME, AN ELEVATED LEVEL OF 5-HT1AR IN DORSAL, BUT NOT VENTRAL, PART OF THE HIPPOCAMPUS. DESCRIBED BIOCHEMICAL CHANGES WERE NOT OBSERVED IN ANIMALS BEHAVIORALLY VULNERABLE TO STRESS. FURTHER, IN VITRO ANALYSIS SHOWED THAT MIR-18A-5P MAY BE A NEGATIVE EPIGENETIC REGULATOR OF 5-HT1AR SINCE THE TREATMENT OF ADULT HIPPOCAMPAL NEURONS WITH MIR-18A-5P MIMIC SIGNIFICANTLY LOWERED THE EXPRESSION LEVEL OF MRNA ENCODING 5-HT1AR. MOREOVER, BIOINFORMATIC ANALYSIS OF POTENTIAL TARGET GENES EXPRESSED IN THE HIPPOCAMPUS AND BEING REGULATED BY MIR-18A-5P SHOWED THAT THIS MICRORNA MAY REGULATE BIOLOGICAL PROCESSES, SUCH AS AXONOGENESIS, WHICH ARE IMPORTANT IN THE FUNCTIONING OF THE HIPPOCAMPUS IN BOTH RATS AND HUMANS. ALL THESE MOLECULAR FEATURES MAY CONTRIBUTE TO SEROTONERGIC HOMEOSTATIC BALANCE AT THE LEVEL OF SEROTONIN TURNOVER OBSERVED IN HIPPOCAMPI OF RESILIENT BUT NOT STRESS-VULNERABLE RATS. DELINEATION OF FURTHER MOLECULAR AND BIOCHEMICAL MARKERS UNDERLYING RESILIENCE TO STRESS MAY CONTRIBUTE TO THE DEVELOPMENT OF NEW ANTIDEPRESSANT STRATEGIES WHICH WILL RESTORE RESILIENT PHENOTYPE IN DEPRESSED PATIENTS. 2019 20 5709 46 SIRT1 DECREASES EMOTIONAL PAIN VULNERABILITY WITH ASSOCIATED CAMKIIALPHA DEACETYLATION IN CENTRAL AMYGDALA. EMOTIONAL DISORDERS ARE COMMON COMORBID CONDITIONS THAT FURTHER EXACERBATE THE SEVERITY AND CHRONICITY OF CHRONIC PAIN. HOWEVER, INDIVIDUALS SHOW CONSIDERABLE VULNERABILITY TO THE DEVELOPMENT OF CHRONIC PAIN UNDER SIMILAR PAIN CONDITIONS. IN THIS STUDY ON MALE RAT AND MOUSE MODELS OF CHRONIC NEUROPATHIC PAIN, WE IDENTIFY THE HISTONE DEACETYLASE SIRTUIN 1 (SIRT1) IN CENTRAL AMYGDALA AS A KEY EPIGENETIC REGULATOR THAT CONTROLS THE DEVELOPMENT OF COMORBID EMOTIONAL DISORDERS UNDERLYING THE INDIVIDUAL VULNERABILITY TO CHRONIC PAIN. WE FOUND THAT ANIMALS THAT WERE VULNERABLE TO DEVELOPING BEHAVIORS OF ANXIETY AND DEPRESSION UNDER THE PAIN CONDITION DISPLAYED REDUCED SIRT1 PROTEIN LEVELS IN CENTRAL AMYGDALA, BUT NOT THOSE ANIMALS RESISTANT TO THE EMOTIONAL DISORDERS. VIRAL OVEREXPRESSION OF LOCAL SIRT1 REVERSED THIS VULNERABILITY, BUT VIRAL KNOCKDOWN OF LOCAL SIRT1 MIMICKED THE PAIN EFFECT, ELICITING THE PAIN VULNERABILITY IN PAIN-FREE ANIMALS. THE SIRT1 ACTION WAS ASSOCIATED WITH CAMKIIALPHA DOWNREGULATION AND DEACETYLATION OF HISTONE H3 LYSINE 9 AT THE CAMKIIALPHA PROMOTER. THESE RESULTS SUGGEST THAT, BY TRANSCRIPTIONAL REPRESSION OF CAMKIIALPHA IN CENTRAL AMYGDALA, SIRT1 FUNCTIONS TO GUARD AGAINST THE EMOTIONAL PAIN VULNERABILITY UNDER CHRONIC PAIN CONDITIONS. THIS STUDY INDICATES THAT SIRT1 MAY SERVE AS A POTENTIAL THERAPEUTIC MOLECULE FOR INDIVIDUALIZED TREATMENT OF CHRONIC PAIN WITH VULNERABLE EMOTIONAL DISORDERS.SIGNIFICANCE STATEMENT CHRONIC PAIN IS A PREVALENT NEUROLOGICAL DISEASE WITH NO EFFECTIVE TREATMENT AT PRESENT. PAIN PATIENTS DISPLAY CONSIDERABLY VARIABLE VULNERABILITY TO DEVELOPING CHRONIC PAIN, INDICATING INDIVIDUAL-BASED MOLECULAR MECHANISMS UNDERLYING THE PAIN VULNERABILITY, WHICH IS HARDLY ADDRESSED IN CURRENT PRECLINICAL RESEARCH. IN THIS STUDY, WE HAVE IDENTIFIED THE HISTONE DEACETYLASE SIRTUIN 1 (SIRT1) AS A KEY REGULATOR THAT CONTROLS THIS PAIN VULNERABILITY. THIS STUDY REVEALS THAT THE SIRT1-CAMKIIAALPHA PATHWAY IN CENTRAL AMYGDALA ACTS AS AN EPIGENETIC MECHANISM THAT GUARDS AGAINST THE DEVELOPMENT OF COMORBID EMOTIONAL DISORDERS UNDER CHRONIC PAIN, AND THAT ITS DYSFUNCTION CAUSES INCREASED VULNERABILITY TO THE DEVELOPMENT OF CHRONIC PAIN. THESE FINDINGS SUGGEST THAT SIRT1 ACTIVATORS MAY BE USED IN A NOVEL THERAPEUTIC APPROACH FOR INDIVIDUAL-BASED TREATMENT OF CHRONIC PAIN. 2020