1 1647 131 DOES THE STRESS OF LABORATORY LIFE AND EXPERIMENTATION ON ANIMALS ADVERSELY AFFECT RESEARCH DATA? A CRITICAL REVIEW. RECURRENT ACUTE AND/OR CHRONIC STRESS CAN AFFECT ALL VERTEBRATE SPECIES, AND CAN HAVE SERIOUS CONSEQUENCES. IT IS INCREASINGLY AND WIDELY APPRECIATED THAT LABORATORY ANIMALS EXPERIENCE SIGNIFICANT AND REPEATED STRESS, WHICH IS UNAVOIDABLE AND IS CAUSED BY MANY ASPECTS OF LABORATORY LIFE, SUCH AS CAPTIVITY, TRANSPORT, NOISE, HANDLING, RESTRAINT AND OTHER PROCEDURES, AS WELL AS THE EXPERIMENTAL PROCEDURES APPLIED TO THEM. SUCH STRESS IS DIFFICULT TO MITIGATE, AND LACK OF SIGNIFICANT DESENSITISATION/HABITUATION CAN RESULT IN CONSIDERABLE PSYCHOLOGICAL AND PHYSIOLOGICAL WELFARE PROBLEMS, WHICH ARE MEDIATED BY THE ACTIVATION OF VARIOUS NEUROENDOCRINE NETWORKS THAT HAVE NUMEROUS AND PERVASIVE EFFECTS. PSYCHOLOGICAL DAMAGE CAN BE REFLECTED IN STEREOTYPICAL BEHAVIOURS, INCLUDING REPETITIVE PACING AND CIRCLING, AND EVEN SELF-HARM. PHYSICAL CONSEQUENCES INCLUDE ADVERSE EFFECTS ON IMMUNE FUNCTION, INFLAMMATORY RESPONSES, METABOLISM, AND DISEASE SUSCEPTIBILITY AND PROGRESSION. FURTHER, SOME OF THESE EFFECTS ARE EPIGENETIC, AND ARE THEREFORE POTENTIALLY TRANSGENERATIONAL: THE BIOLOGY OF ANIMALS WHOSE PARENTS/GRANDPARENTS WERE WILD-CAUGHT AND/OR HAVE EXPERIENCED CHRONIC STRESS IN LABORATORIES COULD BE ALTERED, AS COMPARED TO FREE-LIVING INDIVIDUALS. IT IS ARGUED THAT THESE EFFECTS MUST HAVE CONSEQUENCES FOR THE RELIABILITY OF EXPERIMENTAL DATA AND THEIR EXTRAPOLATION TO HUMANS, AND THIS MAY NOT BE RECOGNISED SUFFICIENTLY AMONG THOSE WHO USE ANIMALS IN EXPERIMENTS. 2018 2 5810 30 STRESS & SLEEP: A RELATIONSHIP LASTING A LIFETIME. STRESS IS AN ADAPTATIVE RESPONSE AIMED AT RESTORING BODY HOMEOSTASIS. THE CLASSICAL NEUROENDOCRINE STRESS RESPONSE INVOLVING THE ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL (HPA) AXIS MODULATES MANY PHYSIOLOGICAL ASPECTS, SUCH AS THE WAKE-SLEEP CYCLE. IN THE PRESENT REVIEW, WE WILL FIRST REPORT A SERIES OF HUMAN AND RODENT STUDIES SHOWING THAT EACH ACTOR OF THE HPA AXIS HAS THE POTENTIAL TO INTERFERE WITH SLEEP HOMEOSTASIS AND, THEN, WE WILL HIGHLIGHT HOW ACUTE OR CHRONIC STRESS DIFFERENTLY MODULATES THE WAKE-SLEEP CYCLE. MOREOVER, WE WILL PRESENT NEW AND INTERESTING STUDIES DEALING WITH THE RELATIONSHIP BETWEEN SLEEP AND STRESS ON A DIFFERENT (LONGER) TIME SCALE. PARTICULARLY, WE WILL DISCUSS HOW THE EXPOSURE TO PERINATAL STRESS, PROBABLY THROUGH EPIGENETIC MODULATIONS, IS SUFFICIENT TO CAUSE PERSISTENT SLEEP DERANGEMENTS DURING ADULT LIFE. IN LIGHT OF THIS EVIDENCE, THE MAIN MESSAGE OF THE PRESENT REVIEW IS THAT THE COMPLEX RELATIONSHIP BETWEEN SLEEP AND STRESS CHANGES DRAMATICALLY ON THE BASIS OF THE TIME SCALE CONSIDERED AND, CONSEQUENTLY, "TIME" SHOULD BE CONSIDERED AS A CRITICAL FACTOR WHEN FACING THIS TOPIC. 2020 3 6853 41 [NEUROBIOLOGY OF EARLY LIFE TRAUMATIC STRESS AND TRAUMA: PROLONGED NEUROENDOCRINE DYSREGULATION AS A NEURODEVELOPMENTAL RISK FACTOR]. EARLY LIFE STRESSORS DISPLAY A HIGH UNIVERSAL PREVALENCE AND CONSTITUTE A MAJOR PUBLIC HEALTH PROBLEM WITH TWO THIRDS OF YOUTH BEING EXPOSED TO POTENTIALLY TRAUMATIC EXPERIENCES BY THE AGE OF 17. TRAUMATIC STRESS EXPOSURE DURING CRITICAL PERIODS OF DEVELOPMENT MAY HAVE ESSENTIAL AND LONG-LASTING EFFECTS ON THE PHYSICAL AND MENTAL HEALTH OF INDIVIDUALS AND REPRESENTS A DEVELOPMENTAL RISK FACTOR MEDIATING RISK FOR DISEASE. EARLY-LIFE STRESS (ELS) AND CHILDHOOD TRAUMA (CT) CAN BOTH HAVE AN IMPACT ON SENSITIVE NEURONAL BRAIN NETWORKS INVOLVED IN STRESS REACTIONS, AND COULD EXERT A PROGRAMMING EFFECT ON GLUCOCORTICOID SIGNALING LEADING TO CHRONIC HYPER- OR HYPO-ACTIVATION OF THE STRESS SYSTEM. IN ADDITION, ALTERATIONS IN EMOTIONAL AND AUTONOMIC REACTIVITY, CIRCADIAN RHYTHM DISRUPTION, FUNCTIONAL AND STRUCTURAL CHANGES IN THE BRAIN, AS WELL AS IMMUNE AND METABOLIC DYSREGULATION HAVE BEEN LATELY IDENTIFIED AS IMPORTANT RISK FACTORS FOR A CHRONICALLY IMPAIRED HOMEOSTATIC BALANCE AFTER ELS/CT. FURTHERMORE, HUMAN GENETIC BACKGROUND AND EPIGENETIC MODIFICATIONS THROUGH STRESS-RELATED GENE EXPRESSION COULD INTERACT WITH THESE ALTERATIONS AND EXPLAIN INTER-INDIVIDUAL VARIATION IN VULNERABILITY OR RESILIENCE TO STRESS. THIS NARRATIVE REVIEW PRESENTS RELEVANT EVIDENCE FROM MAINLY HUMAN RESEARCH ON THE MOST ACKNOWLEDGED NEUROBIOLOGICAL ALLOSTATIC PATHWAYS EXERTING ENDURING ADVERSE EFFECTS OF ELS/CT EVEN DECADES LATER. FUTURE STUDIES SHOULD PROSPECTIVELY INVESTIGATE POTENTIAL CONFOUNDERS, THEIR TEMPORAL SEQUENCE AND COMBINED EFFECTS AT THE BIOLOGICAL LEVEL, WHILE CONSIDERING THE POTENTIALLY DELAYED TIME-FRAME FOR THE EXPRESSION OF THEIR EFFECTS. FINALLY, SCREENING STRATEGIES FOR ELS/CT AND TRAUMA NEED TO BE IMPROVED. INFORMATION ABOUT ELS/CT HISTORY AND THE NUMBER OF ADVERSE EXPERIENCES COULD HELP TO BETTER IDENTIFY THE INDIVIDUAL RISK FOR DISEASE DEVELOPMENT, PREDICT INDIVIDUAL TREATMENT RESPONSE AND DESIGN PREVENTION STRATEGIES TO REDUCE THE NEGATIVE EFFECTS OF ELS/CT. 2023 4 421 39 ANIMAL MODELS IN EPIGENETIC RESEARCH: INSTITUTIONAL ANIMAL CARE AND USE COMMITTEE CONSIDERATIONS ACROSS THE LIFESPAN. THE RAPID EXPANSION AND EVOLUTION OF EPIGENETICS AS A CORE SCIENTIFIC DISCIPLINE HAVE RAISED NEW QUESTIONS ABOUT HOW ENDOGENOUS AND ENVIRONMENTAL FACTORS CAN INFORM THE MECHANISMS THROUGH WHICH BIOLOGICAL FORM AND FUNCTION ARE REGULATED. EXISTING AND PROPOSED ANIMAL MODELS USED FOR EPIGENETIC RESEARCH HAVE TARGETED A MYRIAD OF HEALTH AND DISEASE ENDPOINTS THAT MAY BE ACUTE, CHRONIC, AND TRANSGENERATIONAL IN NATURE. INITIATING EVENTS AND OUTCOMES MAY EXTEND ACROSS THE ENTIRE LIFESPAN TO ELICIT UNANTICIPATED PHENOTYPES THAT ARE OF PARTICULAR CONCERN TO INSTITUTIONAL ANIMAL CARE AND USE COMMITTEES (IACUCS). THE DYNAMICS AND PLASTICITY OF EPIGENETIC MECHANISMS PRODUCE EFFECTS AND CONSEQUENCES THAT ARE MANIFEST DIFFERENTIALLY WITHIN DISCREET SPATIAL AND TEMPORAL CONTEXTS, INCLUDING PRENATAL DEVELOPMENT, STEM CELLS, ASSISTED REPRODUCTIVE TECHNOLOGIES, PRODUCTION OF SEXUAL DIMORPHISMS, SENESCENCE, AND OTHERS. MANY DIETARY AND NUTRITIONAL INTERVENTIONS HAVE ALSO BEEN SHOWN TO HAVE A SIGNIFICANT IMPACT ON BIOLOGICAL FUNCTIONS AND DISEASE SUSCEPTIBILITIES THROUGH ALTERED EPIGENETIC PROGRAMMING. THE ENVIRONMENTAL, CHEMICAL, TOXIC, THERAPEUTIC, AND PSYCHOSOCIAL STRESSORS USED IN ANIMAL STUDIES TO ELICIT EPIGENETIC CHANGES CAN BECOME EXTREME AND SHOULD RAISE IACUC CONCERNS FOR THE WELL-BEING AND PROPER CARE OF ALL RESEARCH ANIMALS INVOLVED. EPIGENETICS RESEARCH IS RAPIDLY BECOMING AN INTEGRAL PART OF THE SEARCH FOR MECHANISMS IN EVERY MAJOR AREA OF BIOMEDICAL AND BEHAVIORAL RESEARCH AND WILL FOSTER THE CONTINUED DEVELOPMENT OF NEW ANIMAL MODELS. FROM THE IACUC PERSPECTIVE, CARE MUST BE TAKEN TO ACKNOWLEDGE THE PARTICULAR NEEDS AND CONCERNS CREATED BY SUPERIMPOSITION OF EPIGENETIC MECHANISMS OVER DIVERSE FIELDS OF INVESTIGATION TO ENSURE THE PROPER CARE AND USE OF ANIMALS WITHOUT IMPEDING SCIENTIFIC PROGRESS. 2012 5 1364 33 DEVELOPMENTAL NEUROENDOCRINOLOGY OF EARLY-LIFE STRESS: IMPACT ON CHILD DEVELOPMENT AND BEHAVIOR. OUR INTERNAL BALANCE, OR HOMEOSTASIS, IS THREATENED OR PERCEIVED AS THREATENED BY STRESSFUL STIMULI, THE STRESSORS. THE STRESS SYSTEM IS A HIGHLY CONSERVED SYSTEM THAT ADJUSTS HOMEOSTASIS TO THE RESTING STATE. THROUGH THE CONCURRENT ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS AND THE LOCUS COERULEUS/NOREPINEPHRINE-AUTONOMIC NERVOUS SYSTEMS, THE STRESS SYSTEM PROVIDES THE APPROPRIATE PHYSICAL AND BEHAVIORAL RESPONSES, COLLECTIVELY TERMED AS "STRESS RESPONSE", TO RESTORE HOMEOSTASIS. IF THE STRESS RESPONSE IS PROLONGED, EXCESSIVE OR EVEN INADEQUATE, SEVERAL ACUTE OR CHRONIC STRESS-RELATED PATHOLOGIC CONDITIONS MAY DEVELOP IN CHILDHOOD, ADOLESCENCE AND ADULT LIFE. ON THE OTHER HAND, EARLY-LIFE EXPOSURE TO STRESSORS HAS BEEN RECOGNIZED AS A MAJOR CONTRIBUTING FACTOR UNDERLYING THE PATHOGENESIS OF NON-COMMUNICABLE DISORDERS, INCLUDING NEURODEVELOPMENTAL DISORDERS. ACCUMULATING EVIDENCE SUGGESTS THAT EARLY-LIFE STRESS HAS BEEN ASSOCIATED WITH AN INCREASED RISK FOR ATTENTION DEFICIT HYPERACTIVITY DISORDER AND AUTISM SPECTRUM DISORDER IN THE OFFSPRING, ALTHOUGH FINDINGS ARE STILL CONTROVERSIAL. NEVERTHELESS, AT THE MOLECULAR LEVEL, EARLY-LIFE STRESSORS ALTER THE CHEMICAL STRUCTURE OF CYTOSINES LOCAT- ED IN THE REGULATORY REGIONS OF GENES, MOSTLY THROUGH THE ADDITION OF METHYL GROUPS. THESE EPIGENETIC MODIFICATIONS RESULT IN THE SUPPRESSION OF GENE EXPRESSION WITHOUT CHANGING THE DNA SEQUENCE. IN ADDITION TO DNA METHYLATION, SEVERAL LINES OF EVIDENCE SUPPORT THE ROLE OF NON-CODING RNAS IN THE EVOLVING FIELD OF EPIGENETICS. IN THIS REVIEW ARTICLE, WE PRESENT THE ANATOMICAL AND FUNCTIONAL COMPO- NENTS OF THE STRESS SYSTEM, DISCUSS THE PROPER, IN TERMS OF QUALITY AND QUANTITY, STRESS RESPONSE, AND PROVIDE AN UPDATE ON THE IMPACT OF EARLY-LIFE STRESS ON CHILD DEVELOPMENT AND BEHAVIOR. 2023 6 1639 37 DOES EPIGENETIC 'MEMORY' OF EARLY-LIFE STRESS PREDISPOSE TO CHRONIC PAIN IN LATER LIFE? A POTENTIAL ROLE FOR THE STRESS REGULATOR FKBP5. ANIMAL BEHAVIOURS ARE AFFECTED NOT ONLY BY INHERITED GENES BUT ALSO BY ENVIRONMENTAL EXPERIENCES. FOR EXAMPLE, IN BOTH RATS AND HUMANS, STRESSFUL EARLY-LIFE EVENTS SUCH AS BEING REARED BY AN INATTENTIVE MOTHER CAN LEAVE A LASTING TRACE AND AFFECT LATER STRESS RESPONSE IN ADULT LIFE. THIS IS OWING TO A CHEMICAL TRACE LEFT ON THE CHROMATIN ATTRIBUTED TO SO-CALLED EPIGENETIC MECHANISMS. SUCH AN EPIGENETIC TRACE OFTEN HAS CONSEQUENCES, SOMETIMES LONG-LASTING, ON THE FUNCTIONING OF OUR GENES, THEREBY ALLOWING INDIVIDUALS TO RAPIDLY ADAPT TO A NEW ENVIRONMENT. ONE GENE UNDER SUCH EPIGENETIC CONTROL IS FKBP5, THE GENE THAT ENCODES THE PROTEIN FKPB51, A CRUCIAL REGULATOR OF THE STRESS AXIS AND A SIGNIFICANT DRIVER OF CHRONIC PAIN STATES. IN THIS ARTICLE, WE WILL DISCUSS THE POSSIBILITY THAT EXPOSURE TO STRESS COULD DRIVE THE SUSCEPTIBLY TO CHRONIC PAIN VIA EPIGENETIC MODIFICATIONS OF GENES WITHIN THE STRESS AXIS SUCH AS FKBP5. THE POSSIBILITY THAT SUCH MODIFICATIONS, AND THEREFORE, THE SUSCEPTIBILITY TO CHRONIC PAIN, COULD BE TRANSMITTED ACROSS GENERATIONS IN MAMMALS AND WHETHER SUCH MECHANISMS MAY BE EVOLUTIONARILY CONSERVED ACROSS PHYLA WILL ALSO BE DEBATED. THIS ARTICLE IS PART OF THE THEO MURPHY MEETING ISSUE 'EVOLUTION OF MECHANISMS AND BEHAVIOUR IMPORTANT FOR PAIN'. 2019 7 1766 36 EARLY-LIFE EXPERIENCES AND THE DEVELOPMENT OF ADULT DISEASES WITH A FOCUS ON MENTAL ILLNESS: THE HUMAN BIRTH THEORY. IN MAMMALS, EARLY ADVERSE EXPERIENCES, INCLUDING MOTHER-PUP INTERACTIONS, SHAPE THE RESPONSE OF AN INDIVIDUAL TO CHRONIC STRESS OR TO STRESS-RELATED DISEASES DURING ADULT LIFE. THIS HAS LED TO THE ELABORATION OF THE THEORY OF THE DEVELOPMENTAL ORIGINS OF HEALTH AND DISEASE, IN PARTICULAR ADULT DISEASES SUCH AS CARDIOVASCULAR AND METABOLIC DISORDERS. IN ADDITION, IN HUMANS, AS STATED BY MASSIMO FAGIOLI'S HUMAN BIRTH THEORY, BIRTH IS HEALTHY AND EQUAL FOR ALL INDIVIDUALS, SO THAT MENTAL ILLNESS DEVELOP EXCLUSIVELY IN THE POSTNATAL PERIOD BECAUSE OF THE QUALITY OF THE RELATIONSHIP IN THE FIRST YEAR OF LIFE. THUS, THIS REVIEW FOCUSES ON THE IMPORTANCE OF PROGRAMMING DURING THE EARLY DEVELOPMENTAL PERIOD ON THE MANIFESTATION OF ADULT DISEASES IN BOTH ANIMAL MODELS AND HUMANS. CONSIDERING THE OBVIOUS DIFFERENCES BETWEEN ANIMALS AND HUMANS WE CANNOT SYSTEMATICALLY MOVE FROM ANIMAL MODELS TO HUMANS. CONSEQUENTLY, IN THE FIRST PART OF THIS REVIEW, WE WILL DISCUSS HOW ANIMAL MODELS CAN BE USED TO DISSECT THE INFLUENCE OF ADVERSE EVENTS OCCURRING DURING THE PRENATAL AND POSTNATAL PERIODS ON THE DEVELOPMENTAL TRAJECTORIES OF THE OFFSPRING, AND IN THE SECOND PART, WE WILL DISCUSS THE ROLE OF POSTNATAL CRITICAL PERIODS ON THE DEVELOPMENT OF MENTAL DISEASES IN HUMANS. EPIGENETIC MECHANISMS THAT CAUSE REVERSIBLE MODIFICATIONS IN GENE EXPRESSION, DRIVING THE DEVELOPMENT OF A PATHOLOGICAL PHENOTYPE IN RESPONSE TO A NEGATIVE EARLY POSTNATAL ENVIRONMENT, MAY LIE AT THE CORE OF THIS PROGRAMMING, THEREBY PROVIDING POTENTIAL NEW THERAPEUTIC TARGETS. THE CONCEPT OF THE HUMAN BIRTH THEORY LEADS TO A COMPREHENSION OF THE MENTAL ILLNESS AS A PATHOLOGY OF THE HUMAN RELATIONSHIP IMMEDIATELY AFTER BIRTH AND DURING THE FIRST YEAR OF LIFE. 2017 8 6755 33 WILL WIDESPREAD SYNTHETIC OPIOID CONSUMPTION INDUCE EPIGENETIC CONSEQUENCES IN FUTURE GENERATIONS? A GROWING NUMBER OF EVIDENCE DEMONSTRATES THAT ANCESTRAL EXPOSURE TO XENOBIOTICS (POLLUTANTS, DRUGS OF ABUSE, ETC.) CAN PERTURB THE PHYSIOLOGY AND BEHAVIOR OF DESCENDANTS. BOTH MATERNAL AND PATERNAL TRANSMISSION OF PHENOTYPE ACROSS GENERATIONS HAS BEEN PROVED, DEMONSTRATING THAT PARENTAL DRUG HISTORY MAY HAVE SIGNIFICANT IMPLICATIONS FOR SUBSEQUENT GENERATIONS. IN THE LAST YEARS, THE BURDEN OF NOVEL SYNTHETIC OPIOID (NSO) CONSUMPTION, DUE TO INCREASED MEDICAL PRESCRIPTION OF PAIN MEDICATIONS AND TO EASIER ACCESSIBILITY OF THESE SUBSTANCES ON ILLEGAL MARKET, IS RAISING NEW QUESTIONS FIRST IN TERM OF PUBLIC HEALTH, BUT ALSO ABOUT THE CONSEQUENCES OF THE PARENTAL USE OF THESE DRUGS ON FUTURE GENERATIONS. BESIDES BEING ASSOCIATED TO THE NEONATAL ABSTINENCE SYNDROME, IN UTERO EXPOSURE TO OPIOIDS HAS AN IMPACT ON NEURONAL DEVELOPMENT WITH LONG-TERM REPERCUSSIONS THAT ARE POTENTIALLY TRANSMITTED TO SUBSEQUENT GENERATIONS. IN ADDITION, RECENT REPORTS SUGGEST THAT OPIOID USE EVEN BEFORE CONCEPTION INFLUENCES THE REACTIVITY TO OPIOIDS OF THE PROGENY AND THE FOLLOWING GENERATIONS, LIKELY THROUGH EPIGENETIC MECHANISMS. THIS REVIEW DESCRIBES THE CURRENT KNOWLEDGE ABOUT THE TRANSGENERATIONAL EFFECTS OF OPIOID CONSUMPTION. WE SUMMARIZE THE PRECLINICAL AND CLINICAL FINDINGS SHOWING THE IMPLICATIONS FOR THE SUBSEQUENT GENERATIONS OF PARENTAL EXPOSURE TO OPIOIDS EARLIER IN LIFE. LIMITATIONS OF THE EXISTING DATA ON NSOS AND NEW PERSPECTIVES OF THE RESEARCH ARE ALSO DISCUSSED, AS WELL AS CLINICAL AND FORENSIC CONSEQUENCES. 2018 9 5650 26 SEX DIFFERENCES IN THE DEVELOPMENT OF PHYSICAL AGGRESSION: AN INTERGENERATIONAL PERSPECTIVE AND IMPLICATIONS FOR PREVENTIVE INTERVENTIONS. THIS ARTICLE REVIEWS THE STATE OF KNOWLEDGE ON THE DEVELOPMENT OF CHRONIC PHYSICAL AGGRESSION (CPA), WITH THE AIM OF IDENTIFYING THE MOST EFFECTIVE PREVENTION STRATEGIES. WE SPECIFICALLY FOCUS ON THE EARLY DEVELOPMENT OF PHYSICAL AGGRESSION, ON SEX DIFFERENCES IN THE USE OF PHYSICAL AGGRESSION, AND ON THE TRANSMISSION OF BEHAVIOR PROBLEMS FROM ONE GENERATION TO THE OTHER. THE BODY OF RESEARCH ON THE DEVELOPMENT OF CPA FROM THE PAST THREE DECADES THAT WE REVIEW SHOWS INCREASING EVIDENCE THAT ITS PREVENTION REQUIRES A LONG-TERM BIOPSYCHOSOCIAL DEVELOPMENTAL APPROACH WHICH ALSO MUST INCLUDE AN INTERGENERATIONAL PERSPECTIVE. RECENT GENETIC AND EPIGENETIC RESEARCH HAS INDICATED THAT THERE ARE BOTH IMPORTANT GENETIC AND ENVIRONMENTAL EFFECTS ON GENE EXPRESSION WHICH START AT CONCEPTION. WE CONCLUDE THAT ONE OF THE MOST EFFECTIVE STRATEGIES TO BREAK THE INTERGENERATIONAL TRANSMISSION OF CPA INVOLVES GIVING LONG-TERM SUPPORT TO PREGNANT WOMEN WITH A HISTORY OF BEHAVIOR PROBLEMS, THEIR SPOUSE, AND THEIR OFFSPRING. 2019 10 2471 33 EPIGENETIC TRANSGENERATIONAL INHERITANCE OF ALTERED STRESS RESPONSES. ANCESTRAL ENVIRONMENTAL EXPOSURES HAVE PREVIOUSLY BEEN SHOWN TO PROMOTE EPIGENETIC TRANSGENERATIONAL INHERITANCE AND INFLUENCE ALL ASPECTS OF AN INDIVIDUAL'S LIFE HISTORY. IN ADDITION, PROXIMATE LIFE EVENTS SUCH AS CHRONIC STRESS HAVE DOCUMENTED EFFECTS ON THE DEVELOPMENT OF PHYSIOLOGICAL, NEURAL, AND BEHAVIORAL PHENOTYPES IN ADULTHOOD. WE USED A SYSTEMS BIOLOGY APPROACH TO INVESTIGATE IN MALE RATS THE INTERACTION OF THE ANCESTRAL MODIFICATIONS CARRIED TRANSGENERATIONALLY IN THE GERM LINE AND THE PROXIMATE MODIFICATIONS INVOLVING CHRONIC RESTRAINT STRESS DURING ADOLESCENCE. WE FIND THAT A SINGLE EXPOSURE TO A COMMON-USE FUNGICIDE (VINCLOZOLIN) THREE GENERATIONS REMOVED ALTERS THE PHYSIOLOGY, BEHAVIOR, METABOLIC ACTIVITY, AND TRANSCRIPTOME IN DISCRETE BRAIN NUCLEI IN DESCENDANT MALES, CAUSING THEM TO RESPOND DIFFERENTLY TO CHRONIC RESTRAINT STRESS. THIS ALTERATION OF BASELINE BRAIN DEVELOPMENT PROMOTES A CHANGE IN NEURAL GENOMIC ACTIVITY THAT CORRELATES WITH CHANGES IN PHYSIOLOGY AND BEHAVIOR, REVEALING THE INTERACTION OF GENETICS, ENVIRONMENT, AND EPIGENETIC TRANSGENERATIONAL INHERITANCE IN THE SHAPING OF THE ADULT PHENOTYPE. THIS IS AN IMPORTANT DEMONSTRATION IN AN ANIMAL THAT ANCESTRAL EXPOSURE TO AN ENVIRONMENTAL COMPOUND MODIFIES HOW DESCENDANTS OF THESE PROGENITOR INDIVIDUALS PERCEIVE AND RESPOND TO A STRESS CHALLENGE EXPERIENCED DURING THEIR OWN LIFE HISTORY. 2012 11 6119 27 THE EPIGENETIC IMPACTS OF SOCIAL STRESS: HOW DOES SOCIAL ADVERSITY BECOME BIOLOGICALLY EMBEDDED? EPIGENETIC MECHANISMS ARE IMPLICATED IN THE PROCESSES THROUGH WHICH SOCIAL STRESSORS ERODE HEALTH IN HUMANS AND OTHER ANIMALS. HERE I REVIEW PROGRESS IN ELUCIDATING THE BIOLOGICAL PATHWAYS UNDERLYING THE SOCIAL GRADIENT IN HEALTH, WITH PARTICULAR EMPHASIS ON HOW BEHAVIORAL STRESSES INFLUENCE EPIGENOMIC VARIATION LINKED TO HEALTH. THE EVIDENCE THAT EPIGENETIC CHANGES ARE INVOLVED IN EMBEDDING OF SOCIAL STATUS-LINKED CHRONIC STRESS IS REVIEWED IN THE CONTEXT OF CURRENT KNOWLEDGE ABOUT BEHAVIOR WITHIN ANIMAL DOMINANCE HIERARCHIES AND THE IMPACTS OF SOCIAL POSITION ON BEHAVIORS THAT AFFECT HEALTH. THE ROLES OF EPIGENETIC MECHANISMS IN RESPONSES TO TRAUMA AND THE EVIDENCE FOR THEIR INVOLVEMENT IN INTERGENERATIONAL TRANSMISSION OF THE BIOLOGICAL IMPACTS OF TRAUMATIC STRESS ARE ALSO CONSIDERED. TAKEN TOGETHER, THE EMERGING INSIGHTS HAVE IMPORTANT IMPLICATIONS FOR DEVELOPMENT OF STRATEGIES TO IMPROVE SOCIETAL HEALTH AND WELL-BEING. 2016 12 4996 31 PERINATAL EPIGENETIC DETERMINANTS OF COGNITIVE AND METABOLIC DISORDERS. MULTIPLE CUES FROM THE ENVIRONMENT OF OUR INDIRECT AND IMMEDIATE ANCESTORS, WHICH OFTEN PERSIST THROUGHOUT THE PRENATAL PERIOD AND ADULTHOOD, ARE SHAPING OUR PHENOTYPES THROUGH EITHER DIRECT, PARENT-TO-CHILD INFLUENCES, OR TRANSGENERATIONAL INHERITANCE. THESE EFFECTS ARE DUE TO GENE-ENVIRONMENT INTERACTIONS, WHICH ARE INTENDED TO BE A PREDICTIVE TOOL AND A MECHANISM OF QUICK ADAPTATION TO THE ENVIRONMENT, AS COMPARED WITH GENETIC VARIATIONS THAT ARE INHERITED OVER MANY GENERATIONS. IN CERTAIN CIRCUMSTANCES THE INFLUENCES INDUCED BY THE GENE-ENVIRONMENT INTERACTIONS CAN HAVE DELETERIOUS EFFECTS UPON THE HEALTH STATUS, IN THE CONTEXT OF A RADICAL CHANGE IN THE ENVIRONMENT THAT DOES NOT FIT WITH THE PREDICTED CONDITIONS, VIA EPIGENETIC ALTERATIONS. CONVERSELY THE BEST FIT TO THE EXPECTED ENVIRONMENT MIGHT HAVE A DELAYED AGING PROCESS AND A LONGER LIFE SPAN. THIS REVIEW WILL TOUCH UPON THE DEVELOPMENTAL ORIGINS OF HEALTH AND DISEASE (DOHAD) CONCEPT, WHILE DISCUSSING RECENT ADVANCES IN THE UNDERSTANDING OF METABOLIC AND COGNITIVE DISRUPTIONS, WITH A FOCUS ON EPIGENETIC FACTORS, THEIR TRANSGENERATIONAL EFFECTS, AND THE CONSEQUENCES THEY MIGHT HAVE UPON THE ONSET OF CHRONIC DISEASE AND PREMATURE EXITUS. 2012 13 678 31 BRAIN DEVELOPMENT UNDER STRESS: HYPOTHESES OF GLUCOCORTICOID ACTIONS REVISITED. ONE OF THE CONUNDRUMS IN TODAY'S STRESS RESEARCH IS WHY SOME INDIVIDUALS FLOURISH AND OTHERS PERISH UNDER SIMILAR STRESSFUL CONDITIONS. IT IS RECOGNIZED THAT THIS INDIVIDUAL VARIABILITY IN ADAPTATION TO STRESS DEPENDS ON THE OUTCOME OF THE INTERACTION OF GENETIC AND COGNITIVE/EMOTIONAL INPUTS IN WHICH GLUCOCORTICOID HORMONES AND RECEPTORS PLAY A CRUCIAL ROLE. HENCE ONE APPROACH TOWARDS UNDERSTANDING INDIVIDUAL VARIATION IN STRESS COPING IS HOW GLUCOCORTICOID ACTIONS CAN CHANGE FROM PROTECTIVE TO HARMFUL. TO ADDRESS THIS QUESTION WE FOCUS ON FOUR HYPOTHESES THAT ARE CONNECTED AND NOT MUTUAL EXCLUSIVE. FIRST, THE CLASSICAL GLUCOCORTICOID CASCADE HYPOTHESIS, IN WHICH THE INABILITY TO COPE WITH CHRONIC STRESS CAUSES A VICIOUS CYCLE OF EXCESS GLUCOCORTICOID AND DOWNREGULATION OF GLUCOCORTICOID RECEPTORS (GR) IN THE HIPPOCAMPUS TRIGGERING A FEED-FORWARD CASCADE OF DEGENERATION AND DISEASE. SECOND, THE BALANCE HYPOTHESIS, WHICH TAKES ALSO THE LIMBIC MINERALOCORTICOID RECEPTORS (MR) INTO ACCOUNT AND PROPOSES THAT AN INTEGRAL LIMBIC MR:GR IMBALANCE IS CAUSAL TO ALTERED PROCESSING OF INFORMATION IN CIRCUITS UNDERLYING FEAR, REWARD, SOCIAL BEHAVIOUR AND RESILIENCE, DYSREGULATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL (HPA) AXIS AND IMPAIRMENT OF BEHAVIOURAL ADAPTATION. THE MR:GR BALANCE IS ALTERED BY GENE VARIANTS OF THESE RECEPTOR COMPLEXES AND EXPERIENCE-RELATED FACTORS, WHICH CAN INDUCE LASTING EPIGENETIC CHANGES IN THE EXPRESSION OF THESE RECEPTORS. A PARTICULAR POTENT EPIGENETIC STIMULUS IS THE MATERNAL ENVIRONMENT WHICH IS FUNDAMENTAL FOR THE MATERNAL MEDIATION HYPOTHESIS. THE OUTCOME OF PERINATAL GENE X ENVIRONMENT INTERACTION, AND THUS OF MR:GR-MEDIATED FUNCTIONS DEPENDS HOWEVER, ON THE DEGREE OF 'MATCHING' WITH ENVIRONMENTAL DEMANDS IN LATER LIFE. THE PREDICTIVE ADAPTATION HYPOTHESIS THEREFORE PRESENTS A CONCEPTUAL FRAMEWORK TO EXAMINE THE ROLE OF GLUCOCORTICOIDS IN UNDERSTANDING INDIVIDUAL PHENOTYPIC DIFFERENCES IN STRESS-RELATED BEHAVIOURS OVER THE LIFESPAN. 2010 14 2528 26 EPIGENETICS AS A KEY LINK BETWEEN PSYCHOSOCIAL STRESS AND AGING: CONCEPTS, EVIDENCE, MECHANISMS . PSYCHOSOCIAL STRESS-ESPECIALLY WHEN CHRONIC, EXCESSIVE, OR OCCURRING EARLY IN LIFE-HAS BEEN ASSOCIATED WITH ACCELERATED AGING AND INCREASED DISEASE RISK. WITH RAPID AGING OF THE WORLD POPULATION, THE NEED TO ELUCIDATE THE UNDERLYING MECHANISMS IS PRESSING, NOW MORE SO THAN EVER. AMONG MOLECULAR MECHANISMS LINKING STRESS AND AGING, THE PRESENT ARTICLE REVIEWS EVIDENCE ON THE ROLE OF EPIGENETICS, BIOCHEMICAL PROCESSES THAT CAN BE SET INTO MOTION BY STRESSORS AND IN TURN INFLUENCE GENOMIC FUNCTION AND COMPLEX PHENOTYPES, INCLUDING AGING-RELATED OUTCOMES. THE ARTICLE FURTHER PROVIDES A CONCEPTUAL MECHANISTIC FRAMEWORK ON HOW STRESS MAY DRIVE EPIGENETIC CHANGES AT SUSCEPTIBLE GENOMIC SITES, THEREBY EXERTING SYSTEMS-LEVEL EFFECTS ON THE AGING EPIGENOME WHILE ALSO REGULATING THE EXPRESSION OF MOLECULES IMPLICATED IN AGING-RELATED PROCESSES. THIS EMERGING EVIDENCE, TOGETHER WITH WORK EXAMINING RELATED BIOLOGICAL PROCESSES, BEGINS TO SHED LIGHT ON THE EPIGENETIC AND, MORE BROADLY, MOLECULAR UNDERPINNINGS OF THE LONG-HYPOTHESIZED CONNECTION BETWEEN STRESS AND AGING. . 2019 15 1453 25 DISCOVERING HOW ENVIRONMENTAL EXPOSURES ALTER GENES COULD LEAD TO NEW TREATMENTS FOR CHRONIC ILLNESSES. EMERGING RESEARCH DEMONSTRATES THAT DIET, POLLUTION, AND OTHER ENVIRONMENTAL TRIGGERS CAN ALTER BOTH THE FUNCTION AND EXPRESSION OF HUMAN GENES AND LEAD TO A HEIGHTENED DISEASE RISK. THESE ENVIRONMENT-GENE INTERACTIONS CAN CAUSE SO-CALLED EPIGENETIC CHANGES IN GENE EXPRESSION-PATTERNS OF WHICH GENES ARE SWITCHED "ON" OR "OFF"-THAT MAY ACCOUNT FOR THE RISING MORTALITY FROM CHRONIC DISEASES IN INDUSTRIALIZED NATIONS. IN THIS PAPER, WE CALL FOR A NEW TRANSDISCIPLINARY APPROACH TO PUBLIC HEALTH THAT WOULD EXAMINE HOW ENVIRONMENTAL EXPOSURES, BOTH PHYSICAL AND SOCIAL, INFLUENCE GENE EXPRESSION AND A PERSON'S SUSCEPTIBILITY TO CHRONIC DISEASE. THIS INITIATIVE COULD LEAD TO NEW WAYS TO PREVENT AND TREAT SUCH ILLNESSES. 2011 16 5829 29 STRESS, PSYCHIATRIC DISORDERS, MOLECULAR TARGETS, AND MORE. MENTAL HEALTH IS CENTRAL TO NORMAL HEALTH OUTCOMES. A WIDELY ACCEPTED THEORY IS THAT CHRONIC PERSISTENT STRESS DURING ADULTHOOD AS WELL AS DURING EARLY LIFE TRIGGERS ONSET OF NEUROPSYCHIATRIC AILMENTS. HOWEVER, QUESTIONS RELATED TO HOW THAT OCCURS, AND WHY ARE SOME INDIVIDUALS RESISTANT TO STRESS WHILE OTHERS ARE NOT, REMAIN UNANSWERED. AN INTEGRATED, MULTISYSTEMIC STRESS RESPONSE INVOLVING NEUROINFLAMMATORY, NEUROENDOCRINE, EPIGENETIC AND METABOLIC CASCADES HAVE BEEN SUGGESTED TO HAVE CAUSATIVE LINKS. SEVERAL THEORIES HAVE BEEN PROPOSED OVER THE YEARS TO CONCEPTUALIZE THIS LINK INCLUDING THE CYTOKINE HYPOTHESIS, THE ENDOCRINE HYPOTHESIS, THE OXIDATIVE STRESS HYPOTHESIS AND THE OXIDO-NEUROINFLAMMATION HYPOTHESIS. THE DATA DISCUSSED IN THIS REVIEW DESCRIBES POTENTIAL BIOCHEMICAL BASIS OF THE LINK BETWEEN STRESS, AND STRESS-INDUCED NEURONAL, BEHAVIORAL AND EMOTIONAL DEFICITS, PROVIDING INSIGHTS INTO POTENTIALLY NOVEL DRUG TARGETS. 2019 17 2000 32 EPIGENETIC AND NON-CODING REGULATION OF ALCOHOL ABUSE AND ADDICTION. ALCOHOL USE DISORDER IS A CHRONIC DEBILITATED CONDITION ADVERSELY AFFECTING THE LIVES OF MILLIONS OF INDIVIDUALS THROUGHOUT THE MODERN WORLD. INDIVIDUALS SUFFERING FROM AN ALCOHOL USE DISORDER DIAGNOSIS FREQUENTLY HAVE SERIOUS COOCCURRING CONDITIONS, WHICH OFTEN FURTHER EXACERBATES PROBLEMATIC DRINKING BEHAVIOR. COMPREHENDING THE BIOCHEMICAL PROCESSES UNDERLYING THE PROGRESSION AND PERPETUATION OF DISEASE IS ESSENTIAL FOR MITIGATING MALADAPTIVE BEHAVIOR IN ORDER TO RESTORE BOTH PHYSIOLOGICAL AND PSYCHOLOGICAL HEALTH. THE RANGE OF CELLULAR AND BIOLOGICAL SYSTEMS CONTRIBUTING TO, AND AFFECTED BY, ALCOHOL USE DISORDER AND OTHER COMORBID DISORDERS NECESSITATES A FUNDAMENTAL GRASP OF INTRICATE FUNCTIONAL RELATIONSHIPS THAT GOVERN MOLECULAR BIOLOGY. EPIGENETIC FACTORS ARE RECOGNIZED AS ESSENTIAL MEDIATORS OF CELLULAR BEHAVIOR, ORCHESTRATING A SYMPHONY OF GENE EXPRESSION CHANGES WITHIN MULTICELLULAR ENVIRONMENTS THAT ARE ULTIMATELY RESPONSIBLE FOR DIRECTING HUMAN BEHAVIOR. UNDERSTANDING THE EPIGENETIC AND TRANSCRIPTIONAL REGULATORY MECHANISMS INVOLVED IN THE PATHOGENESIS OF DISEASE IS IMPORTANT FOR IMPROVING AVAILABLE PHARMACOTHERAPIES AND REDUCING THE INCIDENCE OF ALCOHOL ABUSE AND COOCCURRING CONDITIONS. 2021 18 2521 33 EPIGENETICS AND THE INTERNATIONAL CLASSIFICATION OF FUNCTIONING, DISABILITY AND HEALTH MODEL: BRIDGING NATURE, NURTURE, AND PATIENT-CENTERED POPULATION HEALTH. EPIGENETIC PROCESSES ENABLE ENVIRONMENTAL INPUTS SUCH AS DIET, EXERCISE, AND HEALTH BEHAVIORS TO REVERSIBLY TAG DNA WITH CHEMICAL "MARKS" THAT INCREASE OR DECREASE THE EXPRESSION OF AN INDIVIDUAL'S GENETIC TEMPLATE. OVER TIME, EPIGENETIC ADAPTATIONS ENABLE THE EFFECTS OF HEALTHY OR UNHEALTHY STRESSES TO BECOME STABLY EXPRESSED IN THE TISSUE OF AN ORGANISM, WITH IMPORTANT CONSEQUENCES FOR HEALTH AND DISEASE. NEW RESEARCH INDICATES THAT SEEMINGLY NON-BIOLOGICAL FACTORS SUCH AS SOCIAL STRESS, POVERTY, AND CHILDHOOD HARDSHIP INITIATE EPIGENETIC ADAPTATIONS IN GENE PATHWAYS THAT GOVERN INFLAMMATION AND IMMUNITY, TWO OF THE GREATEST CONTRIBUTORS TO CHRONIC DISEASES SUCH AS DIABETES AND OBESITY. EPIGENETIC PROCESSES THEREFORE PROVIDE A BIOLOGICAL BRIDGE BETWEEN THE GENOME-AN INDIVIDUAL'S GENETIC INHERITANCE-AND THE SOCIAL DETERMINANTS OF HEALTH-THE CONDITIONS IN WHICH THEY ARE BORN, GROW, LIVE, WORK, AND AGE. THIS PERSPECTIVE PAPER ARGUES THAT PHYSICAL THERAPY CLINICIANS, RESEARCHERS, AND EDUCATORS CAN USE THE THEORETICAL FRAMEWORK PROVIDED BY THE INTERNATIONAL CLASSIFICATION OF FUNCTIONING, DISABILITY, AND HEALTH (ICF MODEL) TO HARMONIZE NEW DISCOVERIES FROM BOTH PUBLIC HEALTH RESEARCH AND MEDICALLY FOCUSED GENOMIC RESEARCH. THE ICF MODEL LIKEWISE CAPTURES THE ESSENTIAL ROLE PLAYED BY PHYSICAL ACTIVITY AND EXERCISE, WHICH INITIATE POWERFUL AND WIDESPREAD EPIGENETIC ADAPTATIONS THAT PROMOTE HEALTH AND FUNCTIONING. IN THIS PROPOSED FRAMEWORK, EPIGENETIC PROCESSES TRANSDUCE THE EFFECTS OF THE SOCIAL DETERMINANTS OF HEALTH AND BEHAVIORS SUCH AS EXERCISE INTO STABLE BIOLOGICAL ADAPTATIONS THAT AFFECT AN INDIVIDUAL'S DAILY ACTIVITIES AND THEIR PARTICIPATION IN SOCIAL ROLES. BY HARMONIZING "NATURE" AND "NURTURE," PHYSICAL THERAPISTS CAN APPROACH PATIENT CARE WITH A MORE INTEGRATED PERSPECTIVE, CAPITALIZING ON NOVEL DISCOVERIES IN PRECISION MEDICINE, REHABILITATION SCIENCE, AND IN POPULATION-LEVEL RESEARCH. AS THE EXPERTS IN PHYSICAL ACTIVITY AND EXERCISE, PHYSICAL THERAPISTS ARE IDEALLY POSITIONED TO DRIVE PROGRESS IN THE NEW ERA OF PATIENT-CENTERED POPULATION HEALTH CARE. 2022 19 2586 28 EPIGENETICS OF PAIN MEDIATORS. PURPOSE OF REVIEW: THE FIELD OF EPIGENETICS CONTINUES ITS INFLUENTIAL RISE AS A MEANS TO BETTER UNDERSTAND AN ORGANISM'S UNIQUE DEVELOPMENTAL IDENTITY OVER A LIFESPAN. WHEREAS A GENOME IS CONSTANT AND UNCHANGING, AN EPIGENOME IS DYNAMIC AND ALTERABLE. EPIGENETIC CHANGES ARE IN RESPONSE TO INNUMERABLE INTERNAL AND EXTERNAL INFLUENCES INCLUDING ENVIRONMENTAL CHANGES SUCH AS DIET, EXERCISE, DISEASE, TOXINS, AND STRESS. EPIGENETICS IS OF PARTICULAR INTEREST IN THE MEDICAL RESEARCH COMMUNITY BOTH FOR THE POTENTIAL TO CAUSE DISEASE AND AS A TARGET FOR THERAPEUTIC INTERVENTIONS. THIS ARTICLE PROVIDES A SUCCINCT EXPLANATION OF THE POTENTIAL FOR EPIGENETICS TO INFLUENCE THE UNDERSTANDING OF PAIN AS WELL AS A REVIEW OF RELEVANT RESEARCH ON THE TOPIC. RECENT FINDINGS: STUDIES ON EPIGENETICS AND PAIN REMAIN LARGELY PRECLINICAL AND INVESTIGATE THE THEORETICAL ABILITY OF EPIGENETICS TO ALTER THE NOCICEPTIVE PATHWAYS BOTH IN THE PERIPHERY AND CENTRALLY. SIGNIFICANT EVIDENCE NOW EXISTS FOR THE ABILITY OF EPIGENETICS TO MODIFY BROADLY CATEGORIZED PAIN TYPES, INCLUDING INFLAMMATORY, NEUROPATHIC, VISCERAL, AND CANCER RELATED. SUMMARY: BOTH PATIENTS AND PROVIDERS RECOGNIZE THAT NOVEL MEDICATIONS FOR THE TREATMENT OF BOTH ACUTE AND CHRONIC PAIN CONDITIONS ARE SORELY NEEDED. THE UNDERSTANDING OF EPIGENETICS AND ITS INFLUENCE ON NOCICEPTION REMAINS IN RELATIVE INFANCY BUT EARLY EVIDENCE IS STRONG FOR POTENTIAL THERAPEUTIC BENEFITS TO TREAT THESE CONDITIONS. 2018 20 3418 26 HUMAN HEALTH CONSEQUENCES OF ENVIRONMENTALLY-MODULATED GENE EXPRESSION: POTENTIAL ROLES OF ELF-EMF INDUCED EPIGENETIC VERSUS MUTAGENIC MECHANISMS OF DISEASE. IN ORDER TO DETERMINE IF THERE MIGHT BE BIOLOGICAL AND HEALTH CONSEQUENCES AFTER EXPOSURES TO EXTREMELY-LOW FREQUENCY ELECTROMAGNETIC FIELDS (ELF-EMF), EITHER EXPERIMENTALLY OR EPIDEMIOLOGICALLY, MECHANISTIC UNDERSTANDING OF THE POTENTIAL MEANS BY WHICH ANY ENVIRONMENTAL AGENT CAN AFFECT CELLS IN A MULTICELLULAR ORGANISM HAS TO BE REVIEWED. THE GOAL OF THIS LIMITED REVIEW IS TO DEMONSTRATE THAT, WHILE THE PREVAILING PARADIGM OF THE ENVIRONMENTALLY-INDUCED ACUTE AND CHRONIC DISEASES INVOLVES EITHER CELL KILLING (CYTOTOXICITY) OR GENE/CHROMOSOME MUTATIONS (GENOTOXICITY), ALTERATION OF THE EXPRESSION OF GENETIC INFORMATION AT THE TRANSCRIPTIONAL (TURNING GENES "ON" OR "OFF"), TRANSLATIONAL (STABILIZING OR DE-STABILIZING THE GENETIC MESSAGE), OR POSTTRANSLATIONAL (ALTERING THE GENE PRODUCT OR PROTEIN) LEVELS HAS THE POTENTIAL TO CONTRIBUTE TO VARIOUS DISEASES. THIS LATTER MECHANISM, "EPIGENETIC" TOXICITY, UNLIKE THE FORMER TWO WHICH ARE IRREVERSIBLE, IS CHARACTERIZED BY THRESHOLD-LIKE ACTION, MULTIPLE BIOCHEMICAL PATHWAYS AND CHRONIC, REGULAR EXPOSURES TO BE EFFECTIVE. ULTIMATELY, EPIGENETIC TOXICANTS AFFECT ONE OF FOUR POTENTIAL CELL STATES, NAMELY ALTERATION OF CELL PROLIFERATION, CELL DIFFERENTIATION, PROGRAMMED CELL DEATH (APOPTOSIS) OR ADAPTIVE RESPONSES OF DIFFERENTIATED CELLS. 2000