1 1548 197 DNA METHYLATION IN THE DEVELOPING HIPPOCAMPUS AND AMYGDALA OF ANXIETY-PRONE VERSUS RISK-TAKING RATS. ALL ORGANISMS EXHIBIT A WIDE RANGE OF EMOTIONAL BEHAVIORS AND INTERACT WITH THE ENVIRONMENT IN DIFFERENT WAYS. SOME INDIVIDUALS MAY BE MORE QUIET AND SHY WHEREAS OTHERS ARE MORE OUTGOING AND ADVENTUROUS. THESE TEMPERAMENTAL AND PERSONALITY DIFFERENCES CAN PREDISPOSE INDIVIDUALS TO CERTAIN PSYCHOPATHOLOGIES WHICH MAY BE INFLUENCED BY GENETIC VULNERABILITY AND/OR EARLY LIFE EXPERIENCES. RODENT MODELS CAN BE USED TO RECAPITULATE EMOTIONAL REACTIVITY DIFFERENCES, AND THESE MODELS CAN, IN TURN, BE USED TO EXAMINE POTENTIAL NEUROBIOLOGICAL UNDERPINNINGS OF THESE TRAITS. THE PRESENT STUDY UTILIZES TWO STRAINS OF RATS THAT WERE SELECTIVELY BRED FOR DIFFERENCES IN NOVELTY SEEKING. HIGH NOVELTY-RESPONDING (BHR) RATS ARE VERY ACTIVE IN RESPONSE TO NOVELTY, EXHIBIT EXAGGERATED RISK-TAKING, AGGRESSION, IMPULSIVITY, AND SHOW INCREASED BEHAVIORAL RESPONSE TO COCAINE. LOW NOVELTY-RESPONDING (BLR) RATS SHOW INCREASED ANXIETY, DEPRESSIVE BEHAVIOR AND VULNERABILITY TO CHRONIC STRESS. ONE WAY IN WHICH THE BHR VERSUS BLR BEHAVIORAL PHENOTYPES MAY DIFFER IS THROUGH EPIGENETIC MODIFICATION OF DNA. DNA CAN BE MODIFIED THROUGH PROCESSES SUCH AS ACETYLATION OR METHYLATION TO EITHER ENHANCE OR SUBDUE GENE EXPRESSION. THIS STUDY EXAMINES PUTATIVE DIFFERENCES IN METHYLATION LEVELS IN THE HIPPOCAMPUS AND AMYGDALA OF DEVELOPING BHR-BLR RATS. PREVIOUS RESEARCH OBSERVED WIDESPREAD GENE EXPRESSION DIFFERENCES IN THE BLR DEVELOPING HIPPOCAMPUS, AND THE CURRENT STUDY AIMS TO BEGIN TO EXAMINE POTENTIAL EPIGENETIC FACTORS THAT MAY CONTRIBUTE TO THOSE GENE DIFFERENCES. THE AMYGDALA WAS CHOSEN BECAUSE IT IS INVOLVED IN EMOTIONAL PROCESSES, IN PART THROUGH ITS CONNECTIONS WITH THE HIPPOCAMPUS. THEREFORE, THE PRESENT STUDY USED IN SITU HYBRIDIZATION TO ASSESS THE EXPRESSION OF DNA METHYLTRANSFERASE-1 (DNMT1) MRNA IN THE HIPPOCAMPUS, AMYGDALA AND SEVERAL OTHER BRAIN AREAS OF BHR AND BLR PUPS AT THREE DEVELOPMENTAL TIME POINTS: POSTNATAL DAYS (P) 7, 14, AND 21. WE FOCUSED ON THE FIRST 3 POSTNATAL WEEKS, IN PART TO PARALLEL OUR EARLY MICROARRAY GENE EXPRESSION WORK, AND BECAUSE THIS REPRESENTS A CRITICAL PERIOD OF BRAIN DEVELOPMENT, WHICH SHAPES INDIVIDUALS' LIFELONG EMOTIONAL AND STRESS REACTIVITY. WE FOUND SIGNIFICANT DIFFERENCES IN DENTATE GYRUS AND CA3 REGIONS OF THE HIPPOCAMPUS AT P7 WITH NO DIFFERENCES SEEN AT P14 OR P21. INTERESTINGLY, WE ALSO FOUND SIGNIFICANT BHR-BLR DNMT1 DIFFERENCES AT P7 WITHIN THE LATERAL, BASOLATERAL AND MEDIAL NUCLEI OF THE AMYGDALA, WITH NO DIFFERENCE AT P14 AND P21, SUGGESTING THAT THE FIRST POSTNATAL WEEK IS A CRITICAL PERIOD FOR DNA METHYLATION DURING BRAIN DEVELOPMENT. 2012 2 5465 61 RESILIENCE TO STRESS: LESSONS FROM RODENTS ABOUT NATURE VERSUS NURTURE. INDIVIDUAL DIFFERENCES IN HUMAN TEMPERAMENT INFLUENCE HOW WE RESPOND TO STRESS AND CAN CONFER VULNERABILITY (OR RESILIENCE) TO EMOTIONAL DISORDERS. FOR EXAMPLE, HIGH LEVELS OF BEHAVIORAL INHIBITION IN CHILDREN PREDICT INCREASED RISK OF MOOD AND ANXIETY DISORDERS IN LATER LIFE. THE BIOLOGICAL UNDERPINNINGS OF TEMPERAMENT ARE UNKNOWN, ALTHOUGH IMPROVED UNDERSTANDING CAN OFFER INSIGHT INTO THE PATHOGENESIS OF EMOTIONAL DISORDERS. OUR LABORATORY HAS USED A RAT MODEL OF TEMPERAMENTAL DIFFERENCES TO STUDY NEURODEVELOPMENTAL FACTORS THAT LEAD TO A HIGHLY INHIBITED, STRESS VULNERABLE PHENOTYPE. SELECTIVE BREEDING FOR HIGH VERSUS LOW BEHAVIORAL RESPONSE TO NOVELTY CREATED TWO RAT STRAINS THAT EXHIBIT DRAMATIC BEHAVIOR DIFFERENCES OVER MULTIPLE DOMAINS RELEVANT TO EMOTIONAL DISORDERS. LOW NOVELTY RESPONDER (BLR) RATS EXHIBIT HIGH LEVELS OF BEHAVIORAL INHIBITION, PASSIVE STRESS COPING, ANHEDONIA, DECREASED SOCIABILITY AND VULNERABILITY TO CHRONIC STRESS COMPARED TO HIGH NOVELTY RESPONDERS (BHRS). ON THE OTHER HAND, BHRS EXHIBIT HIGH LEVELS OF BEHAVIORAL DIS-INHIBITION, ACTIVE COPING, AND AGGRESSION. THIS REVIEW ARTICLE SUMMARIZES OUR WORK WITH THE BHR/BLR MODEL SHOWING THE DEVELOPMENTAL EMERGENCE OF THE BHR/BLR PHENOTYPES, THE ROLE THE ENVIRONMENT PLAYS IN SHAPING IT, AND THE INVOLVEMENT OF EPIGENETIC PROCESSES SUCH AS DNA METHYLATION THAT MEDIATE DIFFERENCES IN EMOTIONALITY AND STRESS REACTIVITY. 2022 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 3973 49 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 5 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 6 5199 41 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 7 990 49 CHRONIC SOCIAL STRESS INDUCES DNA METHYLATION CHANGES AT AN EVOLUTIONARY CONSERVED INTERGENIC REGION IN CHROMOSOME X. CHRONIC STRESS RESULTING FROM PROLONGED EXPOSURE TO NEGATIVE LIFE EVENTS INCREASES THE RISK OF MOOD AND ANXIETY DISORDERS. ALTHOUGH CHRONIC STRESS CAN CHANGE GENE EXPRESSION RELEVANT FOR BEHAVIOR, MOLECULAR REGULATORS OF THIS CHANGE HAVE NOT BEEN FULLY DETERMINED. ONE PROCESS THAT COULD PLAY A ROLE IS DNA METHYLATION, AN EPIGENETIC PROCESS WHEREBY A METHYL GROUP IS ADDED ONTO NUCLEOTIDES, PREDOMINANTLY CYTOSINE IN THE CPG CONTEXT, AND WHICH CAN BE INDUCED BY CHRONIC STRESS. IT IS UNKNOWN TO WHAT EXTENT CHRONIC SOCIAL DEFEAT, A MODEL OF HUMAN SOCIAL STRESS, INFLUENCES DNA METHYLATION PATTERNS ACROSS THE GENOME. OUR STUDY ADDRESSED THIS QUESTION BY USING A TARGETED-CAPTURE APPROACH CALLED METHYL-SEQ TO INVESTIGATE DNA METHYLATION PATTERNS OF THE DENTATE GYRUS AT PUTATIVE REGULATORY REGIONS ACROSS THE MOUSE GENOME FROM MICE EXPOSED TO 14 DAYS OF SOCIAL DEFEAT. FINDINGS WERE REPLICATED IN INDEPENDENT COHORTS BY BISULFITE-PYROSEQUENCING. TWO DIFFERENTIALLY METHYLATED REGIONS (DMRS) WERE IDENTIFIED. ONE DMR WAS LOCATED AT INTRON 9 OF DROSHA, AND IT SHOWED REDUCED METHYLATION IN STRESSED MICE. THIS OBSERVATION REPLICATED IN ONE OF TWO INDEPENDENT COHORTS. A SECOND DMR WAS IDENTIFIED AT AN INTERGENIC REGION OF CHROMOSOME X, AND METHYLATION IN THIS REGION WAS INCREASED IN STRESSED MICE. THIS METHYLATION DIFFERENCE REPLICATED IN TWO INDEPENDENT COHORTS AND IN MAJOR DEPRESSIVE DISORDER (MDD) POSTMORTEM BRAINS. THESE RESULTS HIGHLIGHT A REGION NOT PREVIOUSLY KNOWN TO BE DIFFERENTIALLY METHYLATED BY CHRONIC SOCIAL DEFEAT STRESS AND WHICH MAY BE INVOLVED IN MDD. 2018 8 5467 51 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 9 5019 49 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 2445 42 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 11 3313 34 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 12 4093 46 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 13 5397 40 REDUCED LEVELS OF MIRNAS 449 AND 34 IN SPERM OF MICE AND MEN EXPOSED TO EARLY LIFE STRESS. EXPOSURE OF MALE MICE TO EARLY LIFE STRESS ALTERS THE LEVELS OF SPECIFIC SPERM MIRNAS THAT PROMOTE STRESS-ASSOCIATED BEHAVIORS IN THEIR OFFSPRING. TO BEGIN TO EVALUATE WHETHER SIMILAR PHENOMENA OCCUR IN MEN, WE SEARCHED FOR SPERM MIRNA CHANGES THAT OCCUR IN BOTH MICE AND MEN EXPOSED TO EARLY LIFE STRESSORS THAT HAVE LONG-LASTING EFFECTS. FOR MEN, WE USED THE ADVERSE CHILDHOOD EXPERIENCE (ACE) QUESTIONNAIRE. IT REVEALS THE DEGREE OF ABUSIVE AND/OR DYSFUNCTIONAL FAMILY EXPERIENCES WHEN YOUNG, WHICH INCREASES RISKS OF DEVELOPING FUTURE PSYCHOLOGICAL AND PHYSICAL DISORDERS. FOR MALE MICE, WE USED ADOLESCENT CHRONIC SOCIAL INSTABILITY (CSI) STRESS, WHICH NOT ONLY ENHANCES SOCIABILITY DEFECTS FOR >1 YEAR, BUT ALSO ANXIETY AND DEFECTIVE SOCIABILITY IN FEMALE OFFSPRING FOR MULTIPLE GENERATIONS THROUGH THE MALE LINEAGE. HERE WE FOUND A STATISTICALLY SIGNIFICANT INVERSE CORRELATION BETWEEN LEVELS OF MULTIPLE MIRNAS OF THE MIR-449/34 FAMILY AND ACE SCORES OF CAUCASIAN MALES. REMARKABLY, WE FOUND MEMBERS OF THE SAME SPERM MIRNA FAMILY ARE ALSO REDUCED IN MICE EXPOSED TO CSI STRESS. THUS, FUTURE STUDIES SHOULD BE DESIGNED TO DIRECTLY TEST WHETHER REDUCED LEVELS OF THESE MIRNAS COULD BE USED AS UNBIASED INDICATORS OF CURRENT AND/OR EARLY LIFE EXPOSURE TO SEVERE STRESS. MOREOVER, AFTER MATING STRESSED MALE MICE, THESE SPERM MIRNA REDUCTIONS PERSIST IN BOTH EARLY EMBRYOS THROUGH AT LEAST THE MORULA STAGE AND IN SPERM OF MALES DERIVED FROM THEM, SUGGESTING THESE MIRNA CHANGES CONTRIBUTE TO TRANSMISSION OF STRESS PHENOTYPES ACROSS GENERATIONS. SINCE OFFSPRING OF MEN EXPOSED TO EARLY LIFE TRAUMA HAVE ELEVATED RISKS FOR PSYCHOLOGICAL DISORDERS, THESE FINDINGS RAISE THE POSSIBILITY THAT A PORTION OF THIS RISK MAY BE DERIVED FROM EPIGENETIC REGULATION OF THESE SPERM MIRNAS. 2018 14 6174 47 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 15 586 36 BEHAVIOURAL AND EPIGENETIC EFFECTS OF PATERNAL EXPOSURE TO CANNABINOIDS DURING ADOLESCENCE ON OFFSPRING VULNERABILITY TO STRESS. CHRONIC CANNABINOID EXPOSURE DURING ADOLESCENCE IN MALE RATS INDUCES CHRONIC COGNITIVE AND EMOTIONAL IMPAIRMENTS. HOWEVER, THE IMPACT OF THIS FORM OF EXPOSURE ON OFFSPRING VULNERABILITY TO STRESS IS UNKNOWN. THE AIM OF THIS STUDY WAS TO EVALUATE THE BEHAVIOURAL AND EPIGENETIC EFFECTS OF STRESS IN THE OFFSPRING OF MALE RATS WHOSE FATHERS WERE EXPOSED TO CANNABINOIDS DURING ADOLESCENCE. MALE ADOLESCENT OFFSPRING OF WIN55,212-2 (1.2 MG/KG) TREATED RATS WERE EXPOSED DURING ONE WEEK TO VARIABLE STRESSORS AND SUBJECTED TO BEHAVIOURAL TESTS OF ANXIETY AND EPISODIC-LIKE MEMORY, FOLLOWED BY AN ASSESSMENT OF GLOBAL DNA METHYLATION AND EXPRESSION OF DNA METHYLTRANSFERASES ENZYMES DNMT1 AND DNMT3A MRNA IN THE PREFRONTAL CORTEX. STRESS EXPOSURE INDUCED A SIGNIFICANT ANXIOGENIC-LIKE EFFECT BUT DID NOT AFFECT THE EPISODIC-LIKE MEMORY IN THE OFFSPRING OF WIN55,212-2 EXPOSED FATHERS IN COMPARISON TO THE OFFSPRING OF NON-EXPOSED FATHERS. THESE BEHAVIOURAL CHANGES WERE SUBSEQUENT TO A SIGNIFICANT INCREASE IN GLOBAL DNA METHYLATION AND DNMT1 AND DNMTA3 TRANSCRIPTION IN THE PREFRONTAL CORTEX. THESE DATA SUGGEST THAT THE DELETERIOUS EFFECT OF CHRONIC EXPOSURE TO CANNABINOIDS DURING ADOLESCENCE ARE NOT LIMITED TO THE EXPOSED INDIVIDUALS BUT MAY INCREASE THE VULNERABILITY TO STRESS-INDUCED ANXIETY IN THE OFFSPRING AND ALTER THEIR EPIGENETIC PROGRAMMING. 2019 16 5219 47 PREVIOUS HISTORY OF CHRONIC STRESS CHANGES THE TRANSCRIPTIONAL RESPONSE TO GLUCOCORTICOID CHALLENGE IN THE DENTATE GYRUS REGION OF THE MALE RAT HIPPOCAMPUS. CHRONIC STRESS IS A RISK FACTOR FOR SEVERAL NEUROPSYCHIATRIC DISEASES, SUCH AS DEPRESSION AND PSYCHOSIS. IN RESPONSE TO STRESS GLUCOCORTICOIDS (GCS) ARE SECRETED THAT BIND TO MINERALOCORTICOID AND GLUCOCORTICOID RECEPTORS, LIGAND-ACTIVATED TRANSCRIPTION FACTORS THAT REGULATE THE TRANSCRIPTION OF GENE NETWORKS IN THE BRAIN NECESSARY FOR COPING WITH STRESS, RECOVERY, AND ADAPTATION. CHRONIC STRESS PARTICULARLY AFFECTS THE DENTATE GYRUS (DG) SUBREGION OF THE HIPPOCAMPUS, CAUSING SEVERAL FUNCTIONAL AND MORPHOLOGICAL CHANGES WITH CONSEQUENCES FOR LEARNING AND MEMORY, WHICH ARE LIKELY ADAPTIVE BUT AT THE SAME TIME MAKE DG NEURONS MORE VULNERABLE TO SUBSEQUENT CHALLENGES. THE AIM OF THIS STUDY WAS TO INVESTIGATE THE TRANSCRIPTIONAL RESPONSE OF DG NEURONS TO A GC CHALLENGE IN MALE RATS PREVIOUSLY EXPOSED TO CHRONIC RESTRAINT STRESS (CRS). AN INTRIGUING FINDING OF THE CURRENT STUDY WAS THAT HAVING A HISTORY OF CRS HAD PROFOUND CONSEQUENCES FOR THE SUBSEQUENT RESPONSE TO ACUTE GC CHALLENGE, DIFFERENTIALLY AFFECTING THE EXPRESSION OF SEVERAL HUNDREDS OF GENES IN THE DG COMPARED WITH CHALLENGED NONSTRESSED CONTROL ANIMALS. THIS ENDURING EFFECT OF PREVIOUS STRESS EXPOSURE SUGGESTS THAT EPIGENETIC PROCESSES MAY BE INVOLVED. IN LINE WITH THIS, CRS INDEED AFFECTED THE EXPRESSION OF SEVERAL GENES INVOLVED IN CHROMATIN STRUCTURE AND EPIGENETIC PROCESSES, INCLUDING ASF1, ASH1L, HIST1H3F, AND TP63. THE DATA PRESENTED HERE INDICATE THAT CRS ALTERS THE TRANSCRIPTIONAL RESPONSE TO A SUBSEQUENT GC INJECTION. WE PROPOSE THAT THIS ALTERED TRANSCRIPTIONAL POTENTIAL FORMS PART OF THE MOLECULAR MECHANISM UNDERLYING THE ENHANCED VULNERABILITY FOR STRESS-RELATED DISORDERS LIKE DEPRESSION CAUSED BY CHRONIC STRESS. 2013 17 2021 40 EPIGENETIC CHANGES ASSOCIATED WITH DIFFERENT TYPES OF STRESSORS AND SUICIDE. STRESS IS ASSOCIATED WITH VARIOUS EPIGENETIC CHANGES. SOME STRESS-INDUCED EPIGENETIC CHANGES ARE HIGHLY DYNAMIC, WHEREAS OTHERS ARE ASSOCIATED WITH LASTING MARKS ON THE EPIGENOME. IN OUR STUDY, A COMPREHENSIVE NARRATIVE REVIEW OF THE LITERATURE WAS PERFORMED BY INVESTIGATING THE EPIGENETIC CHANGES THAT OCCUR WITH ACUTE STRESS, CHRONIC STRESS, EARLY CHILDHOOD STRESS, AND TRAUMATIC STRESS EXPOSURES, ALONG WITH EXAMINING THOSE OBSERVED IN POST-MORTEM BRAINS OR BLOOD SAMPLES OF SUICIDE COMPLETERS AND ATTEMPTERS. IN ADDITION, THE TRANSGENERATIONAL EFFECTS OF THESE CHANGES ARE REPORTED. FOR ALL TYPES OF STRESS STUDIES EXAMINED, THE GENES NR3C1, OXTR, SLC6A4, AND BDNF REPRODUCIBLY SHOWED EPIGENETIC CHANGES, WITH SOME MODIFICATIONS OBSERVED TO BE PASSED DOWN TO SUBSEQUENT GENERATIONS FOLLOWING STRESS EXPOSURES. THE AFOREMENTIONED GENES ARE KNOWN TO BE INVOLVED IN NEURONAL DEVELOPMENT AND HORMONAL REGULATION AND ARE ALL ASSOCIATED WITH SUSCEPTIBILITY TO MENTAL HEALTH DISORDERS INCLUDING DEPRESSION, ANXIETY, PERSONALITY DISORDERS, AND PTSD (POST-TRAUMATIC STRESS DISORDER). FURTHER RESEARCH IS WARRANTED IN ORDER TO DETERMINE THE SCOPE OF EPIGENETIC ACTIONABLE TARGETS IN INDIVIDUALS SUFFERING FROM THE LONG-LASTING EFFECTS OF STRESSFUL EXPERIENCES. 2023 18 1981 41 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 19 1466 34 DISTINCT ACTIONS OF ANCESTRAL VINCLOZOLIN AND JUVENILE STRESS ON NEURAL GENE EXPRESSION IN THE MALE RAT. EXPOSURE TO THE ENDOCRINE DISRUPTING CHEMICAL VINCLOZOLIN DURING GESTATION OF AN F0 GENERATION AND/OR CHRONIC RESTRAINT STRESS DURING ADOLESCENCE OF THE F3 DESCENDANTS AFFECTS BEHAVIOR, PHYSIOLOGY, AND GENE EXPRESSION IN THE BRAIN. GENES RELATED TO THE NETWORKS OF GROWTH FACTORS, SIGNALING PEPTIDES, AND RECEPTORS, STEROID HORMONE RECEPTORS AND ENZYMES, AND EPIGENETIC RELATED FACTORS WERE MEASURED USING QUANTITATIVE POLYMERASE CHAIN REACTION VIA TAQMAN LOW DENSITY ARRAYS TARGETING 48 GENES IN THE CENTRAL AMYGDALOID NUCLEUS, MEDIAL AMYGDALOID NUCLEUS, MEDIAL PREOPTIC AREA (MPOA), LATERAL HYPOTHALAMUS (LH), AND THE VENTROMEDIAL NUCLEUS OF THE HYPOTHALAMUS. WE FOUND THAT GROWTH FACTORS ARE PARTICULARLY VULNERABLE TO ANCESTRAL EXPOSURE IN THE CENTRAL AND MEDIAL AMYGDALA; RESTRAINT STRESS DURING ADOLESCENCE AFFECTED NEURAL GROWTH FACTORS IN THE MEDIAL AMYGDALA. SIGNALING PEPTIDES WERE AFFECTED BY BOTH ANCESTRAL EXPOSURE AND STRESS DURING ADOLESCENCE PRIMARILY IN HYPOTHALAMIC NUCLEI. STEROID HORMONE RECEPTORS AND ENZYMES WERE STRONGLY AFFECTED BY RESTRAINT STRESS IN THE MPOA. EPIGENETIC RELATED GENES WERE AFFECTED BY STRESS IN THE VENTROMEDIAL NUCLEUS AND BY BOTH ANCESTRAL EXPOSURE AND STRESS DURING ADOLESCENCE INDEPENDENTLY IN THE CENTRAL AMYGDALA. IT IS NOTEWORTHY THAT THE LH SHOWED NO EFFECTS OF EITHER MANIPULATION. GENE EXPRESSION IS DISCUSSED IN THE CONTEXT OF BEHAVIORAL AND PHYSIOLOGICAL MEASURES PREVIOUSLY PUBLISHED. 2015 20 578 40 BEHAVIOR, BDNF AND EPIGENETIC MECHANISMS IN RESPONSE TO SOCIAL ISOLATION AND SOCIAL SUPPORT IN MIDDLE AGED RATS EXPOSED TO CHRONIC STRESS. SOCIAL DEPRIVATION CAN BE STRESSFUL FOR GROUP-LIVING MAMMALS. ON THE OTHER HAND, AN AMAZING RESPONSE OF THESE ANIMALS TO STRESS IS SEEKING SOCIAL CONTACT TO GIVE AND RECEIVE JOINT PROTECTION IN THREATENING SITUATIONS. WE EXPLORED THE EFFECTS OF SOCIAL ISOLATION AND SOCIAL SUPPORT ON EPIGENETIC AND BEHAVIORAL RESPONSES TO CHRONIC STRESS. MORE SPECIFICALLY, WE INVESTIGATED THE BEHAVIORAL RESPONSES, CORTICOSTERONE LEVELS, BDNF GENE EXPRESSION, AND MARKERS OF HIPPOCAMPAL EPIGENETIC ALTERATIONS (LEVELS OF H3K9 ACETYLATION AND METHYLATION, H3K27 METHYLATION, HDAC5, DNMT1, AND DNMT3A GENE EXPRESSIONS) IN MIDDLE-AGED ADULT RATS MAINTAINED IN DIFFERENT HOUSING CONDITIONS (ISOLATION OR ACCOMPANIED HOUSING) AND EXPOSED TO THE CHRONIC UNPREDICTABLE STRESS PROTOCOL (CUS). ISOLATION WAS ASSOCIATED WITH DECREASED BASAL LEVELS OF CORTICOSTERONE, IMPAIRED LONG-TERM MEMORY, AND DECREASED EXPRESSION OF THE BDNF GENE, BESIDES ALTERING THE BALANCE OF H3K9 FROM ACETYLATION TO METHYLATION AND INCREASING THE DNMT1 GENE EXPRESSION. THE CUS PROTOCOL DECREASED H3K9 ACETYLATION, BESIDES INCREASING H3K27 METHYLATION AND DNMT1 GENE EXPRESSION, BUT HAD NO SIGNIFICANT EFFECTS ON MEMORY AND BDNF GENE EXPRESSION. INTERESTINGLY, THE EFFECTS OF CUS ON CORTICOSTERONE AND HDAC5 GENE EXPRESSION WERE SEEN ONLY IN ISOLATED ANIMALS, WHEREAS THE EFFECTS OF CUS ON DNMT1 GENE EXPRESSION WERE MORE PRONOUNCED IN ISOLATED THAN ACCOMPANIED ANIMALS. IN CONCLUSION, SOCIAL ISOLATION IN MIDDLE AGE SHOWED BROADER EFFECTS THAN CHRONIC UNPREDICTABLE STRESS ON BEHAVIORAL AND EPIGENETIC ALTERATIONS POTENTIALLY ASSOCIATED WITH DECREASED BDNF EXPRESSION. MOREOVER, SOCIAL SUPPORT PREVENTED THE ADVERSE EFFECTS OF CUS ON HPA AXIS FUNCTIONING, HDAC5, AND DNMT1 GENE EXPRESSIONS. 2023