1 4383 147 MITOCHONDRIAL EPIGENETICS AND ENVIRONMENTAL HEALTH: MAKING A CASE FOR ENDOCRINE DISRUPTING CHEMICALS. RECENT STUDIES IMPLICATE MITOCHONDRIAL DYSFUNCTION IN THE DEVELOPMENT AND PROGRESSION OF NUMEROUS CHRONIC DISEASES, WHICH MAY BE PARTIALLY DUE TO MODIFICATIONS IN MITOCHONDRIAL DNA (MTDNA). THERE IS ALSO MOUNTING EVIDENCE THAT EPIGENETIC MODIFICATIONS TO MTDNA MAY BE AN ADDITIONAL LAYER OF REGULATION THAT CONTROLS MITOCHONDRIAL BIOGENESIS AND FUNCTION. SEVERAL ENVIRONMENTAL FACTORS (EG, SMOKING, AIR POLLUTION) HAVE BEEN ASSOCIATED WITH ALTERED MTDNA METHYLATION IN A HANDFUL OF MECHANISTIC STUDIES AND IN OBSERVATIONAL HUMAN STUDIES. HOWEVER, LITTLE IS UNDERSTOOD ABOUT OTHER ENVIRONMENTAL CONTAMINANTS THAT INDUCE MTDNA EPIGENETIC CHANGES. NUMEROUS ENVIRONMENTAL TOXICANTS ARE CLASSIFIED AS ENDOCRINE DISRUPTING CHEMICALS (EDCS). BEYOND THEIR ACTIONS ON HORMONAL PATHWAYS, EDC EXPOSURE IS ASSOCIATED WITH ELEVATED OXIDATIVE STRESS, WHICH MAY OCCUR THROUGH OR RESULT IN MITOCHONDRIAL DYSFUNCTION. ALTHOUGH ONLY A FEW STUDIES HAVE ASSESSED THE IMPACTS OF EDCS ON MTDNA METHYLATION, THE CURRENT REVIEW PROVIDES REASONS TO CONSIDER MTDNA EPIGENETIC DISRUPTION AS A MECHANISM OF ACTION OF EDCS AND REVIEWS POTENTIAL LIMITATIONS RELATED TO CURRENTLY AVAILABLE EVIDENCE. FIRST, THERE IS SUFFICIENT EVIDENCE THAT EDCS (INCLUDING BISPHENOLS AND PHTHALATES) DIRECTLY TARGET MITOCHONDRIAL FUNCTION, AND MORE DIRECT EVIDENCE IS NEEDED TO CONNECT THIS TO MTDNA METHYLATION. SECOND, THESE AND OTHER EDCS ARE POTENT MODULATORS OF NUCLEAR DNA EPIGENETICS, INCLUDING DNA METHYLATION AND HISTONE MODIFICATIONS. FINALLY, EDCS HAVE BEEN SHOWN TO DISRUPT SEVERAL MODULATORS OF MTDNA METHYLATION, INCLUDING DNA METHYLTRANSFERASES AND THE MITOCHONDRIAL TRANSCRIPTION FACTOR A/NUCLEAR RESPIRATORY FACTOR 1 PATHWAY. TAKEN TOGETHER, THESE STUDIES HIGHLIGHT THE NEED FOR FUTURE RESEARCH EVALUATING MTDNA EPIGENETIC DISRUPTION BY EDCS AND TO DETAIL SPECIFIC MECHANISMS RESPONSIBLE FOR SUCH DISRUPTIONS. 2020 2 6287 55 THE POTENTIAL ROLE OF ENVIRONMENTAL FACTORS IN MODULATING MITOCHONDRIAL DNA EPIGENETIC MARKS. MANY STUDIES IMPLICATE MITOCHONDRIAL DYSFUNCTION IN THE DEVELOPMENT AND PROGRESSION OF NUMEROUS CHRONIC DISEASES. MITOCHONDRIA ARE RESPONSIBLE FOR MOST CELLULAR ENERGY PRODUCTION, AND UNLIKE OTHER CYTOPLASMIC ORGANELLES, MITOCHONDRIA CONTAIN THEIR OWN GENOME. MOST RESEARCH TO DATE, THROUGH INVESTIGATING MITOCHONDRIAL DNA COPY NUMBER, HAS FOCUSED ON LARGER STRUCTURAL CHANGES OR ALTERATIONS TO THE ENTIRE MITOCHONDRIAL GENOME AND THEIR ROLE IN HUMAN DISEASE. USING THESE METHODS, MITOCHONDRIAL DYSFUNCTION HAS BEEN LINKED TO CANCERS, CARDIOVASCULAR DISEASE, AND METABOLIC HEALTH. HOWEVER, LIKE THE NUCLEAR GENOME, THE MITOCHONDRIAL GENOME MAY EXPERIENCE EPIGENETIC ALTERATIONS, INCLUDING DNA METHYLATION THAT MAY PARTIALLY EXPLAIN SOME OF THE HEALTH EFFECTS OF VARIOUS EXPOSURES. RECENTLY, THERE HAS BEEN A MOVEMENT TO UNDERSTAND HUMAN HEALTH AND DISEASE WITHIN THE CONTEXT OF THE EXPOSOME, WHICH AIMS TO DESCRIBE AND QUANTIFY THE ENTIRETY OF ALL EXPOSURES PEOPLE ENCOUNTER THROUGHOUT THEIR LIVES. THESE INCLUDE, AMONG OTHERS, ENVIRONMENTAL POLLUTANTS, OCCUPATIONAL EXPOSURES, HEAVY METALS, AND LIFESTYLE AND BEHAVIORAL FACTORS. IN THIS CHAPTER, WE SUMMARIZE THE CURRENT RESEARCH ON MITOCHONDRIA AND HUMAN HEALTH, PROVIDE AN OVERVIEW OF THE CURRENT KNOWLEDGE ON MITOCHONDRIAL EPIGENETICS, AND DESCRIBE THE EXPERIMENTAL AND EPIDEMIOLOGIC STUDIES THAT HAVE INVESTIGATED PARTICULAR EXPOSURES AND THEIR RELATIONSHIPS WITH MITOCHONDRIAL EPIGENETIC MODIFICATIONS. WE CONCLUDE THE CHAPTER WITH SUGGESTIONS FOR FUTURE DIRECTIONS IN EPIDEMIOLOGIC AND EXPERIMENTAL RESEARCH THAT IS NEEDED TO ADVANCE THE GROWING FIELD OF MITOCHONDRIAL EPIGENETICS. 2023 3 4805 40 OBESITY AND METABOLIC COMORBIDITIES: ENVIRONMENTAL DISEASES? OBESITY AND METABOLIC COMORBIDITIES REPRESENT INCREASING HEALTH PROBLEMS. ENDOCRINE DISRUPTING COMPOUNDS (EDCS) ARE EXOGENOUS AGENTS THAT CHANGE ENDOCRINE FUNCTION AND CAUSE ADVERSE HEALTH EFFECTS. MOST EDCS ARE SYNTHETIC CHEMICALS; SOME ARE NATURAL FOOD COMPONENTS AS PHYTOESTROGENS. PEOPLE ARE EXPOSED TO COMPLEX MIXTURES OF CHEMICALS THROUGHOUT THEIR LIVES. EDCS IMPACT HORMONE-DEPENDENT METABOLIC SYSTEMS AND BRAIN FUNCTION. LABORATORY AND HUMAN STUDIES PROVIDE COMPELLING EVIDENCE THAT HUMAN CHEMICAL CONTAMINATION CAN PLAY A ROLE IN OBESITY EPIDEMIC. CHEMICAL EXPOSURES MAY INCREASE THE RISK OF OBESITY BY ALTERING THE DIFFERENTIATION OF ADIPOCYTES. EDCS CAN ALTER METHYLATION PATTERNS AND NORMAL EPIGENETIC PROGRAMMING IN CELLS. OXIDATIVE STRESS MAY BE INDUCED BY MANY OF THESE CHEMICALS, AND ACCUMULATING EVIDENCE INDICATES THAT IT PLAYS IMPORTANT ROLES IN THE ETIOLOGY OF CHRONIC DISEASES. THE INDIVIDUAL SENSITIVITY TO CHEMICALS IS VARIABLE, DEPENDING ON ENVIRONMENT AND ABILITY TO METABOLIZE HAZARDOUS CHEMICALS. A NUMBER OF GENES, ESPECIALLY THOSE REPRESENTING ANTIOXIDANT AND DETOXIFICATION PATHWAYS, HAVE POTENTIAL APPLICATION AS BIOMARKERS OF RISK ASSESSMENT. THE POTENTIAL HEALTH EFFECTS OF COMBINED EXPOSURES MAKE THE RISK ASSESSMENT PROCESS MORE COMPLEX COMPARED TO THE ASSESSMENT OF SINGLE CHEMICALS. TECHNIQUES AND METHODS NEED TO BE FURTHER DEVELOPED TO FILL DATA GAPS AND INCREASE THE KNOWLEDGE ON HARMFUL EXPOSURE COMBINATIONS. 2013 4 6183 43 THE IMPACT OF ENVIRONMENTAL FACTORS IN INFLUENCING EPIGENETICS RELATED TO OXIDATIVE STATES IN THE CARDIOVASCULAR SYSTEM. OXIDATIVE STATES EXERT A SIGNIFICANT INFLUENCE ON A WIDE RANGE OF BIOLOGICAL AND MOLECULAR PROCESSES AND FUNCTIONS. WHEN THEIR BALANCE IS SHIFTED TOWARDS ENHANCED AMOUNTS OF FREE RADICALS, PATHOLOGICAL PHENOMENA CAN OCCUR, AS THE GENERATION OF REACTIVE OXYGEN SPECIES (ROS) IN TISSUE MICROENVIRONMENT OR IN THE SYSTEMIC CIRCULATION CAN BE DETRIMENTAL. EPIDEMIC CHRONIC DISEASES OF WESTERN SOCIETIES, SUCH AS CARDIOVASCULAR DISEASE, OBESITY, AND DIABETES CORRELATE WITH THE IMBALANCE OF REDOX HOMEOSTASIS. CURRENT ADVANCES IN OUR UNDERSTANDING OF EPIGENETICS HAVE REVEALED A PARALLEL SCENARIO SHOWING THE INFLUENCE OF OXIDATIVE STRESS AS A MAJOR REGULATOR OF EPIGENETIC GENE REGULATION VIA MODIFICATION OF DNA METHYLATION, HISTONES, AND MICRORNAS. THIS HAS PROVIDED BOTH THE BIOLOGICAL LINK AND A POTENTIAL MOLECULAR EXPLANATION BETWEEN OXIDATIVE STRESS AND CARDIOVASCULAR/METABOLIC PHENOMENA. ACCORDINGLY, IN THIS REVIEW, WE WILL PROVIDE CURRENT INSIGHTS ON THE PHYSIOLOGICAL AND PATHOLOGICAL IMPACT OF CHANGES IN OXIDATIVE STATES ON CARDIOVASCULAR DISORDERS, BY SPECIFICALLY FOCUSING ON THE INFLUENCE OF EPIGENETIC REGULATION. A SPECIAL EMPHASIS WILL HIGHLIGHT THE EFFECT ON EPIGENETIC REGULATION OF HUMAN'S CURRENT LIFE HABITS, EXTERNAL AND ENVIRONMENTAL FACTORS, INCLUDING FOOD INTAKE, TOBACCO, AIR POLLUTION, AND ANTIOXIDANT-BASED APPROACHES. ADDITIONALLY, THE STRATEGY TO QUANTIFY OXIDATIVE STATES IN HUMANS IN ORDER TO DETERMINE WHICH BIOLOGICAL MARKER COULD BEST MATCH A SUBJECT'S PROFILE WILL BE DISCUSSED. 2017 5 2282 42 EPIGENETIC REGULATION IN EXPOSOME-INDUCED TUMORIGENESIS: EMERGING ROLES OF NCRNAS. ENVIRONMENTAL FACTORS, INCLUDING POLLUTANTS AND LIFESTYLE, CONSTITUTE A SIGNIFICANT ROLE IN SEVERE, CHRONIC PATHOLOGIES WITH AN ESSENTIAL SOCIETAL, ECONOMIC BURDEN. THE MEASUREMENT OF ALL ENVIRONMENTAL EXPOSURES AND ASSESSING THEIR CORRELATION WITH EFFECTS ON INDIVIDUAL HEALTH IS DEFINED AS THE EXPOSOME, WHICH INTERACTS WITH OUR UNIQUE CHARACTERISTICS SUCH AS GENETICS, PHYSIOLOGY, AND EPIGENETICS. EPIGENETICS INVESTIGATES MODIFICATIONS IN THE EXPRESSION OF GENES THAT DO NOT DEPEND ON THE UNDERLYING DNA SEQUENCE. SOME STUDIES HAVE CONFIRMED THAT ENVIRONMENTAL FACTORS MAY PROMOTE DISEASE IN INDIVIDUALS OR SUBSEQUENT PROGENY THROUGH EPIGENETIC ALTERATIONS. VARIATIONS IN THE EPIGENETIC MACHINERY CAUSE A SPECTRUM OF DIFFERENT DISORDERS SINCE THESE MECHANISMS ARE MORE SENSITIVE TO THE ENVIRONMENT THAN THE GENOME, DUE TO THE INHERENT REVERSIBLE NATURE OF THE EPIGENETIC LANDSCAPE. SEVERAL EPIGENETIC MECHANISMS, INCLUDING MODIFICATIONS IN DNA (E.G., METHYLATION), HISTONES, AND NONCODING RNAS CAN CHANGE GENOME EXPRESSION UNDER THE EXOGENOUS INFLUENCE. NOTABLY, THE ROLE OF LONG NONCODING RNAS IN EPIGENETIC PROCESSES HAS NOT BEEN WELL EXPLORED IN THE CONTEXT OF EXPOSOME-INDUCED TUMORIGENESIS. IN THE PRESENT REVIEW, OUR SCOPE IS TO PROVIDE RELEVANT EVIDENCE INDICATING THAT EPIGENETIC ALTERATIONS MEDIATE THOSE DETRIMENTAL EFFECTS CAUSED BY EXPOSURE TO ENVIRONMENTAL TOXICANTS, FOCUSING MAINLY ON A MULTI-STEP REGULATION BY DIVERSE NONCODING RNAS SUBTYPES. 2022 6 6034 43 THE CHALLENGE BY MULTIPLE ENVIRONMENTAL AND BIOLOGICAL FACTORS INDUCE INFLAMMATION IN AGING: THEIR ROLE IN THE PROMOTION OF CHRONIC DISEASE. THE AGING PROCESS IS DRIVEN BY MULTIPLE MECHANISMS THAT LEAD TO CHANGES IN ENERGY PRODUCTION, OXIDATIVE STRESS, HOMEOSTATIC DYSREGULATION AND EVENTUALLY TO LOSS OF FUNCTIONALITY AND INCREASED DISEASE SUSCEPTIBILITY. MOST AGED INDIVIDUALS DEVELOP CHRONIC LOW-GRADE INFLAMMATION, WHICH IS AN IMPORTANT RISK FACTOR FOR MORBIDITY, PHYSICAL AND COGNITIVE IMPAIRMENT, FRAILTY, AND DEATH. AT ANY AGE, CHRONIC INFLAMMATORY DISEASES ARE MAJOR CAUSES OF MORBIMORTALITY, AFFECTING UP TO 5-8% OF THE POPULATION OF INDUSTRIALIZED COUNTRIES. SEVERAL ENVIRONMENTAL FACTORS CAN PLAY AN IMPORTANT ROLE FOR MODIFYING THE INFLAMMATORY STATE. GENETICS ACCOUNTS FOR ONLY A SMALL FRACTION OF CHRONIC-INFLAMMATORY DISEASES, WHEREAS ENVIRONMENTAL FACTORS APPEAR TO PARTICIPATE, EITHER WITH A CAUSATIVE OR A PROMOTIONAL ROLE IN 50% TO 75% OF PATIENTS. SEVERAL OF THOSE CHANGES DEPEND ON EPIGENETIC CHANGES THAT WILL FURTHER MODIFY THE INDIVIDUAL RESPONSE TO ADDITIONAL STIMULI. THE INTERACTION BETWEEN INFLAMMATION AND THE ENVIRONMENT OFFERS IMPORTANT INSIGHTS ON AGING AND HEALTH. THESE CONDITIONS, OFTEN DEPENDING ON THE INDIVIDUAL'S SEX, APPEAR TO LEAD TO DECREASED LONGEVITY AND PHYSICAL AND COGNITIVE DECLINE. IN ADDITION TO BIOLOGICAL FACTORS, THE ENVIRONMENT IS ALSO INVOLVED IN THE GENERATION OF PSYCHOLOGICAL AND SOCIAL CONTEXT LEADING TO STRESS. POOR PSYCHOLOGICAL ENVIRONMENTS AND OTHER SOURCES OF STRESS ALSO RESULT IN INCREASED INFLAMMATION. HOWEVER, THE MECHANISMS UNDERLYING THE ROLE OF ENVIRONMENTAL AND PSYCHOSOCIAL FACTORS AND NUTRITION ON THE REGULATION OF INFLAMMATION, AND HOW THE RESPONSE ELICITED FOR THOSE FACTORS INTERACT AMONG THEM, ARE POORLY UNDERSTOOD. WHEREAS CERTAIN DELETERIOUS ENVIRONMENTAL FACTORS RESULT IN THE GENERATION OF OXIDATIVE STRESS DRIVEN BY AN INCREASED PRODUCTION OF REACTIVE OXYGEN AND NITROGEN SPECIES, ENDOPLASMIC RETICULUM STRESS, AND INFLAMMATION, OTHER FACTORS, INCLUDING NUTRITION (POLYUNSATURATED FATTY ACIDS) AND BEHAVIORAL FACTORS (EXERCISE) CONFER PROTECTION AGAINST INFLAMMATION, OXIDATIVE AND ENDOPLASMIC RETICULUM STRESS, AND THUS AMELIORATE THEIR DELETERIOUS EFFECT. HERE, WE DISCUSS PROCESSES AND MECHANISMS OF INFLAMMATION ASSOCIATED WITH ENVIRONMENTAL FACTORS AND BEHAVIOR, THEIR LINKS TO SEX AND GENDER, AND THEIR OVERALL IMPACT ON AGING. 2020 7 4460 40 MOLECULAR MECHANISMS OF ENVIRONMENTAL EXPOSURES AND HUMAN DISEASE. A SUBSTANTIAL PROPORTION OF DISEASE RISK FOR COMMON COMPLEX DISORDERS IS ATTRIBUTABLE TO ENVIRONMENTAL EXPOSURES AND POLLUTANTS. AN APPRECIATION OF HOW ENVIRONMENTAL POLLUTANTS ACT ON OUR CELLS TO PRODUCE DELETERIOUS HEALTH EFFECTS HAS LED TO ADVANCES IN OUR UNDERSTANDING OF THE MOLECULAR MECHANISMS UNDERLYING THE PATHOGENESIS OF CHRONIC DISEASES, INCLUDING CANCER AND CARDIOVASCULAR, NEURODEGENERATIVE AND RESPIRATORY DISEASES. HERE, WE DISCUSS EMERGING RESEARCH ON THE INTERPLAY OF ENVIRONMENTAL POLLUTANTS WITH THE HUMAN GENOME AND EPIGENOME. WE REVIEW EVIDENCE SHOWING THE ENVIRONMENTAL IMPACT ON GENE EXPRESSION THROUGH EPIGENETIC MODIFICATIONS, INCLUDING DNA METHYLATION, HISTONE MODIFICATION AND NON-CODING RNAS. WE ALSO HIGHLIGHT RECENT STUDIES THAT EVALUATE RECENTLY DISCOVERED MOLECULAR PROCESSES THROUGH WHICH THE ENVIRONMENT CAN EXERT ITS EFFECTS, INCLUDING EXTRACELLULAR VESICLES, THE EPITRANSCRIPTOME AND THE MITOCHONDRIAL GENOME. FINALLY, WE DISCUSS CURRENT CHALLENGES WHEN STUDYING THE EXPOSOME - THE CUMULATIVE MEASURE OF ENVIRONMENTAL INFLUENCES OVER THE LIFESPAN - AND ITS INTEGRATION INTO FUTURE ENVIRONMENTAL HEALTH RESEARCH. 2023 8 6715 42 VITAMIN A AND THE EPIGENOME. THE EPIGENETIC PHENOMENA REFER TO HERITABLE CHANGES IN GENE EXPRESSION OTHER THAN THOSE IN THE DNA SEQUENCE, SUCH AS DNA METHYLATION AND HISTONE MODIFICATIONS. MAJOR RESEARCH PROGRESS IN THE LAST FEW YEARS HAS PROVIDED FURTHER PROOF THAT ENVIRONMENTAL FACTORS, INCLUDING DIET AND NUTRITION, CAN INFLUENCE PHYSIOLOGIC AND PATHOLOGIC PROCESSES THROUGH EPIGENETIC ALTERATIONS, WHICH IN TURN INFLUENCE GENE EXPRESSION. THIS INFLUENCE IS TERMED NUTRITIONAL EPIGENETICS, AND ONE PROMINENT EXAMPLE IS THE REGULATION OF GENE TRANSCRIPTION BY VITAMIN A THROUGH INTERACTION TO ITS NUCLEAR RECEPTOR. VITAMIN A IS CRITICAL THROUGHOUT LIFE. TOGETHER WITH ITS DERIVATIVES, IT REGULATES DIVERSE PROCESSES INCLUDING REPRODUCTION, EMBRYOGENESIS, VISION, GROWTH, CELLULAR DIFFERENTIATION AND PROLIFERATION, MAINTENANCE OF EPITHELIAL CELLULAR INTEGRITY AND IMMUNE FUNCTION. HERE WE REVIEW THE EPIGENETIC ROLE OF VITAMIN A IN CANCER, STEM CELLS DIFFERENTIATION, PROLIFERATION, AND IMMUNITY. THE DATA PRESENTED HERE SHOW THAT RETINOIC ACID IS A POTENT AGENT CAPABLE OF INDUCING ALTERATIONS IN EPIGENETIC MODIFICATIONS THAT PRODUCE VARIOUS EFFECTS ON THE PHENOTYPE. MEDICAL BENEFITS OF VITAMIN A AS AN EPIGENETIC MODULATOR, ESPECIALLY WITH RESPECT TO ITS CHRONIC USE AS NUTRITIONAL SUPPLEMENT, SHOULD RELY ON OUR FURTHER UNDERSTANDING OF ITS EPIGENETIC EFFECTS DURING HEALTH AND DISEASE, AS WELL AS THROUGH DIFFERENT GENERATIONS. 2017 9 860 46 CHROMATIN MODIFICATIONS DURING REPAIR OF ENVIRONMENTAL EXPOSURE-INDUCED DNA DAMAGE: A POTENTIAL MECHANISM FOR STABLE EPIGENETIC ALTERATIONS. EXPOSURES TO ENVIRONMENTAL TOXICANTS AND TOXINS CAUSE EPIGENETIC CHANGES THAT LIKELY PLAY A ROLE IN THE DEVELOPMENT OF DISEASES ASSOCIATED WITH EXPOSURE. THE MECHANISM BEHIND THESE EXPOSURE-INDUCED EPIGENETIC CHANGES IS CURRENTLY UNKNOWN. ONE COMMONALITY BETWEEN MOST ENVIRONMENTAL EXPOSURES IS THAT THEY CAUSE DNA DAMAGE EITHER DIRECTLY OR THROUGH CAUSING AN INCREASE IN REACTIVE OXYGEN SPECIES, WHICH CAN DAMAGE DNA. LIKE TRANSCRIPTION, DNA DAMAGE REPAIR MUST OCCUR IN THE CONTEXT OF CHROMATIN REQUIRING BOTH HISTONE MODIFICATIONS AND ATP-DEPENDENT CHROMATIN REMODELING. THESE CHROMATIN CHANGES AID IN DNA DAMAGE ACCESSIBILITY AND SIGNALING. SEVERAL PROTEINS AND COMPLEXES INVOLVED IN EPIGENETIC SILENCING DURING BOTH DEVELOPMENT AND CANCER HAVE BEEN FOUND TO BE LOCALIZED TO SITES OF DNA DAMAGE. THE CHROMATIN-BASED RESPONSE TO DNA DAMAGE IS CONSIDERED A TRANSIENT EVENT, WITH CHROMATIN BEING RESTORED TO NORMAL AS DNA DAMAGE REPAIR IS COMPLETED. HOWEVER, IN INDIVIDUALS CHRONICALLY EXPOSED TO ENVIRONMENTAL TOXICANTS OR WITH CHRONIC INFLAMMATORY DISEASE, REPEATED DNA DAMAGE-INDUCED CHROMATIN REARRANGEMENT MAY ULTIMATELY LEAD TO PERMANENT EPIGENETIC ALTERATIONS. UNDERSTANDING THE MECHANISM BEHIND EXPOSURE-INDUCED EPIGENETIC CHANGES WILL ALLOW US TO DEVELOP STRATEGIES TO PREVENT OR REVERSE THESE CHANGES. THIS REVIEW FOCUSES ON EPIGENETIC CHANGES AND DNA DAMAGE INDUCED BY ENVIRONMENTAL EXPOSURES, THE CHROMATIN CHANGES THAT OCCUR AROUND SITES OF DNA DAMAGE, AND HOW THESE TRANSIENT CHROMATIN CHANGES MAY LEAD TO HERITABLE EPIGENETIC ALTERATIONS AT SITES OF CHRONIC EXPOSURE. 2014 10 259 43 ADVANCES IN PCOS PATHOGENESIS AND PROGRESSION-MITOCHONDRIAL MUTATIONS AND DYSFUNCTION. POLYCYSTIC OVARY SYNDROME (PCOS) IS A COMMON FEMALE ENDOCRINE DISORDER, WHICH STILL REMAINS LARGELY UNSOLVED IN TERMS OF ETIOLOGY AND PATHOGENESIS DESPITE IMPORTANT ADVANCES IN OUR UNDERSTANDING OF ITS GENETIC, EPIGENETIC, OR ENVIRONMENTAL FACTOR IMPLICATIONS. IT IS A HETEROGENEOUS DISEASE, FREQUENTLY ASSOCIATED WITH INSULIN RESISTANCE, CHRONIC INFLAMMATION, AND OXIDATIVE STRESS AND PROBABLY ACCOMPANIED WITH SUBCLINICAL CARDIOVASCULAR DISEASE (CVD) AND SOME MALIGNANT LESIONS AS WELL, SUCH AS ENDOMETRIAL CANCER. DISCREPANCIES IN THE CLINICAL PHENOTYPE AND PROGRESSION OF PCOS EXIST BETWEEN DIFFERENT POPULATION GROUPS, WHICH NUCLEAR GENETIC STUDIES HAVE SO FAR FAILED TO EXPLAIN. OVER THE LAST YEARS, MITOCHONDRIAL DYSFUNCTION HAS BEEN INCREASINGLY RECOGNIZED AS AN IMPORTANT CONTRIBUTOR TO AN ARRAY OF DISEASES. BECAUSE MITOCHONDRIA ARE UNDER THE DUAL GENETIC CONTROL OF BOTH THE MITOCHONDRIAL AND NUCLEAR GENOMES, MUTATIONS WITHIN EITHER DNA MOLECULE MAY RESULT IN DEFICIENCY IN RESPIRATORY CHAIN FUNCTION THAT LEADS TO A REDUCED ABILITY TO PRODUCE CELLULAR ADENOSINE-5'-TRIPHOSPHATE AND TO AN EXCESSIVE PRODUCTION OF REACTIVE OXYGEN SPECIES. HOWEVER, THE ASSOCIATION BETWEEN VARIANTS IN MITOCHONDRIAL GENOME, MITOCHONDRIAL DYSFUNCTION, AND PCOS HAS BEEN INVESTIGATED TO A LESSER EXTENT. MAY MUTATIONS IN MITOCHONDRIAL DNA (MTDNA) BECOME AN ADDITIONAL TARGET OF INVESTIGATIONS ON THE MISSING PCOS HERITABILITY? ARE MUTATIONS IN MTDNA IMPLICATED IN THE INITIATION AND PROGRESSION OF PCOS COMPLICATIONS, E.G., CVDS, DIABETES MELLITUS, CANCERS? 2018 11 4384 36 MITOCHONDRIAL EPIGENETICS REGULATING INFLAMMATION IN CANCER AND AGING. INFLAMMATION IS A DEFINING FACTOR IN DISEASE PROGRESSION; EPIGENETIC MODIFICATIONS OF THIS FIRST LINE OF DEFENCE PATHWAY CAN AFFECT MANY PHYSIOLOGICAL AND PATHOLOGICAL CONDITIONS, LIKE AGING AND TUMORIGENESIS. INFLAMMAGEING, ONE OF THE HALLMARKS OF AGING, REPRESENTS A CHRONIC, LOW KEY BUT A PERSISTENT INFLAMMATORY STATE. OXIDATIVE STRESS, ALTERATIONS IN MITOCHONDRIAL DNA (MTDNA) COPY NUMBER AND MIS-LOCALIZED EXTRA-MITOCHONDRIAL MTDNA ARE SUGGESTED TO DIRECTLY INDUCE VARIOUS IMMUNE RESPONSE PATHWAYS. THIS COULD ULTIMATELY PERTURB CELLULAR HOMEOSTASIS AND LEAD TO PATHOLOGICAL CONSEQUENCES. EPIGENETIC REMODELLING OF MTDNA BY DNA METHYLATION, POST-TRANSLATIONAL MODIFICATIONS OF MTDNA BINDING PROTEINS AND REGULATION OF MITOCHONDRIAL GENE EXPRESSION BY NUCLEAR DNA OR MTDNA ENCODED NON-CODING RNAS, ARE SUGGESTED TO DIRECTLY CORRELATE WITH THE ONSET AND PROGRESSION OF VARIOUS TYPES OF CANCER. MITOCHONDRIA ARE ALSO CAPABLE OF REGULATING IMMUNE RESPONSE TO VARIOUS INFECTIONS AND TISSUE DAMAGE BY PRODUCING PRO- OR ANTI-INFLAMMATORY SIGNALS. THIS OCCURS BY ALTERING THE LEVELS OF MITOCHONDRIAL METABOLITES AND REACTIVE OXYGEN SPECIES (ROS) LEVELS. SINCE MITOCHONDRIA ARE KNOWN AS THE GUARDIANS OF THE INFLAMMATORY RESPONSE, IT IS PLAUSIBLE THAT MITOCHONDRIAL EPIGENETICS MIGHT PLAY A PIVOTAL ROLE IN INFLAMMATION. HENCE, THIS REVIEW FOCUSES ON THE INTRICATE DYNAMICS OF EPIGENETIC ALTERATIONS OF INFLAMMATION, WITH EMPHASIS ON MITOCHONDRIA IN CANCER AND AGING. 2022 12 1371 43 DEVELOPMENTAL ORIGINS OF HEALTH AND DISEASE: NEW INSIGHTS. EPIDEMIOLOGICAL AND ANIMAL STUDIES SHOW THAT SMALL CHANGES IN THE DEVELOPMENTAL ENVIRONMENT CAN INDUCE PHENOTYPIC CHANGES AFFECTING AN INDIVIDUAL'S RESPONSES TO THEIR LATER ENVIRONMENT. THESE MAY ALTER THE RISK OF CHRONIC DISEASE SUCH AS METABOLIC SYNDROME OR CARDIOVASCULAR DISEASE. RECENT RESEARCH SHOWS THAT ANIMALS EXPOSED TO SUCH A MISMATCH BETWEEN PRENATAL AND POSTNATAL ENVIRONMENT DEVELOP OBESITY, REDUCED ACTIVITY, LEPTIN AND INSULIN RESISTANCE, ELEVATED BLOOD PRESSURE AND VASCULAR ENDOTHELIAL DYSFUNCTION. EPIGENETIC PROCESSES ARE INVOLVED IN SUCH EFFECTS, TARGETED TO PROMOTER REGIONS OF SPECIFIC GENES IN SPECIFIC TISSUES. SUCH FINE CONTROL OF GENE EXPRESSION SUGGESTS THAT THE MECHANISMS HAVE BEEN RETAINED THROUGH EVOLUTION THROUGH THEIR ADAPTIVE ADVANTAGE, RATHER THAN REPRESENTING EXTREME EFFECTS OF DEVELOPMENTAL DISRUPTION AKIN TO TERATOGENESIS. THERE MAY BE ADAPTIVE ADVANTAGE IN A DEVELOPMENTAL CUE INDUCING A PHENOTYPIC CHANGE IN GENERATIONS BEYOND THE IMMEDIATE PREGNANCY, AND A RANGE OF DATA THAT SUPPORT THIS CONCEPT. IN ANIMALS, EPIGENETIC EFFECTS SUCH AS DNA METHYLATION CAN BE PASSED TO SUCCESSIVE GENERATIONS. ENVIRONMENTAL TOXINS, INCLUDING ENDOCRINE DISRUPTORS, MAY INDUCE GREATER RISK OF CHRONIC DISEASE, EVEN AT LOW EXPOSURE LEVELS, IF THEY AFFECT SUCH NORMAL DEVELOPMENTAL EPIGENETIC PROCESSES. APPROPRIATE INTERVENTIONS MAY HAVE LONG-TERM MULTIGENERATIONAL EFFECTS TO REDUCE THE RISK OF CHRONIC DISEASE. 2008 13 4382 39 MITOCHONDRIAL EPIGENETICS AND ENVIRONMENTAL EXPOSURE. THE RISING TOLL OF CHRONIC AND DEBILITATING DISEASES BROUGHT ABOUT BY THE EXPOSURE TO AN EVER EXPANDING NUMBER OF ENVIRONMENTAL POLLUTANTS AND SOCIO-ECONOMIC FACTORS IS CALLING FOR ACTION. THE UNDERSTANDING OF THE MOLECULAR MECHANISMS BEHIND THE EFFECTS OF ENVIRONMENTAL EXPOSURES CAN LEAD TO THE DEVELOPMENT OF BIOMARKERS THAT CAN SUPPORT THE PUBLIC HEALTH FIELDS OF BOTH EARLY DIAGNOSIS AND INTERVENTION TO LIMIT THE BURDEN OF ENVIRONMENTAL DISEASES. THE STUDY OF MITOCHONDRIAL EPIGENETICS CARRIES HIGH HOPES TO PROVIDE IMPORTANT BIOMARKERS OF EXPOSURE AND DISEASE. MITOCHONDRIA ARE IN FACT ON THE FRONTLINE OF THE CELLULAR RESPONSE TO THE ENVIRONMENT. MODIFICATIONS OF THE EPIGENETIC FACTORS REGULATING THE MITOCHONDRIAL ACTIVITY ARE EMERGING AS INFORMATIVE TOOLS THAT CAN EFFECTIVELY REPORT ON THE EFFECTS OF THE ENVIRONMENT ON THE PHENOTYPE. HERE, WE WILL DISCUSS THE EMERGING FIELD OF MITOCHONDRIAL EPIGENETICS. THIS REVIEW DESCRIBES THE MAIN EPIGENETIC PHENOMENA THAT MODIFY THE ACTIVITY OF THE MITOCHONDRIAL DNA INCLUDING DNA METHYLATION, LONG AND SHORT NON-CODING RNAS. WE WILL DISCUSS THE UNIQUE PATTERN OF MITOCHONDRIAL DNA METHYLATION, DESCRIBE THE CHALLENGES OF CORRECTLY MEASURING IT, AND REPORT ON THE EXISTING STUDIES THAT HAVE ANALYSED THE CORRELATION BETWEEN ENVIRONMENTAL EXPOSURES AND MITOCHONDRIAL DNA METHYLATION. FINALLY, WE PROVIDE A BRIEF ACCOUNT OF THE THERAPEUTIC APPROACHES TARGETING MITOCHONDRIA CURRENTLY UNDER CONSIDERATION. 2016 14 301 44 AIR POLLUTION ASSOCIATED EPIGENETIC MODIFICATIONS: TRANSGENERATIONAL INHERITANCE AND UNDERLYING MOLECULAR MECHANISMS. AIR POLLUTION IS ONE OF THE LEADING CAUSES OF DEATHS IN SOUTHEAST ASIAN COUNTRIES INCLUDING INDIA. EXPOSURE TO AIR POLLUTANTS AFFECTS VITAL CELLULAR MECHANISMS AND IS INTIMATELY LINKED WITH THE ETIOLOGY OF A NUMBER OF CHRONIC DISEASES. EARLIER WORK FROM OUR LABORATORY HAS SHOWN THAT AIRBORNE PARTICULATE MATTER DISTURBS THE MITOCHONDRIAL MACHINERY AND CAUSES SIGNIFICANT DAMAGE TO THE EPIGENOME. MITOCHONDRIAL REACTIVE OXYGEN SPECIES POSSESS THE ABILITY TO TRIGGER REDOX-SENSITIVE SIGNALING MECHANISMS AND INDUCE IRREVERSIBLE EPIGENOMIC CHANGES. THE ELECTROPHILIC NATURE OF REACTIVE METABOLITES CAN DIRECTLY RESULT IN DEPROTONATION OF CYTOSINE AT C-5 POSITION OR INTERFERE WITH THE DNA METHYLTRANSFERASES ACTIVITY TO CAUSE ALTERATIONS IN DNA METHYLATION. IN ADDITION, IT ALSO PERTURBS LEVEL OF CELLULAR METABOLITES CRITICALLY INVOLVED IN DIFFERENT EPIGENETIC PROCESSES LIKE ACETYLATION AND METHYLATION OF HISTONE CODE AND DNA HYPO OR HYPERMETHYLATION. INTERESTINGLY, THESE MODIFICATIONS MAY PERSIST THROUGH DOWNSTREAM GENERATIONS AND RESULT IN THE TRANSGENERATIONAL EPIGENOMIC INHERITANCE. THIS PHENOMENON OF SUBSEQUENT TRANSFER OF EPIGENETIC MODIFICATIONS IS MAINLY ASSOCIATED WITH THE GERM CELLS AND RELIES ON THE GERMLINE STABILITY OF THE EPIGENETIC STATES. OVERALL, THE RECENT LITERATURE SUPPORTS, AND ARGUABLY STRENGTHENS, THE CONTENTION THAT AIR POLLUTION MIGHT CONTRIBUTE TO TRANSMISSION OF EPIMUTATIONS FROM GAMETES TO ZYGOTES BY INVOLVING MITOCHONDRIAL DNA, PARENTAL ALLELE IMPRINTING, HISTONE WITHHOLDING AND NON-CODING RNAS. HOWEVER, LARGER PROSPECTIVE STUDIES USING INNOVATIVE, INTEGRATED EPIGENOME-WIDE METABOLOMIC STRATEGY ARE HIGHLY WARRANTED TO ASSESS THE AIR POLLUTION INDUCED TRANSGENERATIONAL EPIGENETIC INHERITANCE AND ASSOCIATED HUMAN HEALTH EFFECTS. 2019 15 4273 51 MICROBIOTA AND EPIGENETICS: HEALTH IMPACT. EPIGENETIC CHANGES ASSOCIATED WITH DISEASE DEVELOPMENT AND PROGRESSIONS ARE OF INCREASING IMPORTANCE BECAUSE OF THEIR POTENTIAL DIAGNOSTIC AND THERAPEUTIC APPLICATIONS. SEVERAL EPIGENETIC CHANGES ASSOCIATED WITH CHRONIC METABOLIC DISORDERS HAVE BEEN STUDIED IN VARIOUS DISEASES. EPIGENETIC CHANGES ARE MOSTLY MODULATED BY ENVIRONMENTAL FACTORS, INCLUDING THE HUMAN MICROBIOTA LIVING IN DIFFERENT PARTS OF OUR BODIES. THE MICROBIAL STRUCTURAL COMPONENTS AND THE MICROBIALLY DERIVED METABOLITES DIRECTLY INTERACT WITH HOST CELLS, THEREBY MAINTAINING HOMEOSTASIS. MICROBIOME DYSBIOSIS, ON THE OTHER HAND, IS KNOWN TO PRODUCE ELEVATED LEVELS OF DISEASE-LINKED METABOLITES, WHICH MAY DIRECTLY AFFECT A HOST METABOLIC PATHWAY OR INDUCE EPIGENETIC CHANGES THAT CAN LEAD TO DISEASE DEVELOPMENT. DESPITE THEIR IMPORTANT ROLE IN HOST PHYSIOLOGY AND SIGNAL TRANSDUCTION, THERE HAS BEEN LITTLE RESEARCH INTO THE MECHANICS AND PATHWAYS ASSOCIATED WITH EPIGENETIC MODIFICATIONS. THIS CHAPTER FOCUSES ON THE RELATIONSHIP BETWEEN MICROBES AND THEIR EPIGENETIC EFFECTS IN DISEASED PATHOLOGY, AS WELL AS ON THE REGULATION AND METABOLISM OF THE DIETARY OPTIONS AVAILABLE TO THE MICROBES. FURTHERMORE, THIS CHAPTER ALSO PROVIDES A PROSPECTIVE LINK BETWEEN THESE TWO IMPORTANT PHENOMENA, TERMED "MICROBIOME AND EPIGENETICS." 2023 16 396 44 AN UPDATE ON EPIGENETICS AND CHILDHOOD RESPIRATORY DISEASES. EPIGENETIC MECHANISMS, DEFINED AS CHANGES IN PHENOTYPE OR GENE EXPRESSION CAUSED BY MECHANISMS OTHER THAN CHANGES IN THE UNDERLYING DNA SEQUENCE, HAVE BEEN PROPOSED TO CONSTITUTE A LINK BETWEEN GENETIC AND ENVIRONMENTAL FACTORS THAT AFFECT COMPLEX DISEASES. RECENT STUDIES SHOW THAT DNA METHYLATION, ONE OF THE KEY EPIGENETIC MECHANISMS, IS ALTERED IN CHILDREN EXPOSED TO AIR POLLUTANTS AND ENVIRONMENTAL TOBACCO SMOKE EARLY IN LIFE. SEVERAL CANDIDATE GENE STUDIES ON EPIGENETICS HAVE BEEN PUBLISHED TO DATE, BUT IT IS ONLY RECENTLY THAT GLOBAL METHYLATION ANALYSES HAVE BEEN PERFORMED FOR RESPIRATORY DISORDERS SUCH AS ASTHMA AND CHRONIC OBSTRUCTIVE PULMONARY DISEASE. HOWEVER, LARGE-SCALE STUDIES WITH ADEQUATE POWER ARE YET TO BE PRESENTED IN CHILDREN, AND IMPLICATIONS FOR CLINICAL USE REMAIN TO BE EVALUATED. IN THIS REVIEW, WE SUMMARIZE THE RECENT ADVANCES IN EPIGENETICS AND RESPIRATORY DISORDERS IN CHILDREN, WITH A MAIN FOCUS ON METHODOLOGICAL CHALLENGES AND ANALYSES RELATED TO PHENOTYPE AND EXPOSURE USING GLOBAL METHYLATION APPROACHES. 2014 17 6812 33 [EPIGENETICS, INTERFACE BETWEEN ENVIRONMENT AND GENES: ROLE IN COMPLEX DISEASES]. EPIGENETICS IS THE STUDY OF HERITABLE CHANGES IN GENE EXPRESSION OR CELLULAR PHENOTYPE CAUSED BY MECHANISMS OTHER THAN CHANGES IN THE UNDERLYING DNA SEQUENCE. EPIGENETICS IS ONE OF THE MAJOR MECHANISMS EXPLAINING THE "DEVELOPMENTAL ORIGIN OF HEALTH AND DISEASES" (DOHAD). BESIDES GENETIC BACKGROUND INHERITED FROM PARENTS, WHICH CONFERS SUSCEPTIBILITY TO CERTAIN PATHOLOGIES, EPIGENETIC CHANGES CONSTITUTE THE MEMORY OF PREVIOUS EVENTS, EITHER POSITIVE OR NEGATIVE, ALONG THE LIFE CYCLE, INCLUDING AT THE IN UTERO STAGE. THE LATER EXPOSITION TO HOSTILE ENVIRONMENT MAY REVEAL SUCH SUSCEPTIBILITY, WITH THE DEVELOPMENT OF VARIOUS PATHOLOGIES, AMONG THEM NUMEROUS CHRONIC COMPLEX DISEASES. THE DEMONSTRATION OF SUCH A SEQUENCE OF EVENTS HAS BEEN SHOWN FOR METABOLIC DISEASES AS OBESITY, METABOLIC SYNDROME AND TYPE 2 DIABETES, CARDIOVASCULAR DISEASE AND CANCER. IN CONTRAST TO GENETIC PREDISPOSITION, WHICH IS IRREVERSIBLE, EPIGENETIC CHANGES ARE POTENTIALLY REVERSIBLE, THUS GIVING TARGETS NOT ONLY FOR PREVENTION, BUT POSSIBLY ALSO FOR THE TREATMENT OF CERTAIN COMPLEX DISEASES. 2012 18 3837 35 IONIZING RADIATION-INDUCED OXIDATIVE STRESS, EPIGENETIC CHANGES AND GENOMIC INSTABILITY: THE PIVOTAL ROLE OF MITOCHONDRIA. PURPOSE: TO REVIEW THE DATA CONCERNING THE ROLE OF ENDOGENOUSLY GENERATED REACTIVE OXYGEN SPECIES (ROS) IN THE NON-TARGETED IONIZING RADIATION (IR) EFFECTS AND IN DETERMINATION OF THE CELL POPULATION'S FATE, BOTH EARLY AFTER EXPOSURE AND AFTER MANY GENERATIONS. CONCLUSIONS: THE SHORT-TERM AS WELL AS CHRONIC OXIDATIVE STRESS RESPONSES MAINLY ARE PRODUCED DUE TO ROS GENERATION BY THE ELECTRON TRANSPORT CHAIN (ETC) OF THE MITOCHONDRIA AND BY THE CYTOPLASMIC NADPH OXIDASES. WHETHER THE INDUCTION OF THE OXIDATIVE STRESS AND ITS CONSEQUENCES OCCUR OR ARE HAMPERED IN A SINGLE CELL LARGELY DEPENDS ON THE INTERACTION BETWEEN THE NUCLEUS AND THE CELLULAR POPULATION OF SEVERAL HUNDRED OR THOUSANDS OF MITOCHONDRIA THAT ARE GENETICALLY HETEROGENEOUS. HIGH INTRA-MITOCHONDRIAL ROS LEVEL IS DAMAGING THE MITOCHONDRIAL (MT) DNA AND ITS MUTATIONS AFFECT THE EPIGENETIC CONTROL MECHANISMS OF THE NUCLEAR (N) DNA, BY DECREASING THE ACTIVITY OF METHYLTRANSFERASES AND THUS, CAUSING GLOBAL DNA HYPOMETHYLATION. THESE CHANGES ARE TRANSMITTED TO THE PROGENY OF THE IRRADIATED CELLS. THE CHRONIC OXIDATIVE STRESS IS THE MAIN CAUSE OF THE LATE POST-RADIATION EFFECTS, INCLUDING CANCER, AND THIS MAKES IT AN IMPORTANT ADVERSE EFFECT OF EXPOSURE TO IR AND A TARGET FOR RADIOLOGICAL PROTECTION. 2015 19 1919 36 ENVIRONMENTAL ENDOCRINE DISRUPTORS: NEW DIABETOGENS? THE PREVALENCE OF TYPE-2 DIABETES HAS DRAMATICALLY INCREASED WORLDWIDE DURING THE LAST FEW DECADES. WHILE LIFESTYLE FACTORS (SEDENTARINESS, NOXIOUS FOOD), TOGETHER WITH GENETIC SUSCEPTIBILITY, ARE WELL-KNOWN ACTORS, THERE IS ACCUMULATING EVIDENCE SUGGESTING THAT ENDOCRINE DISRUPTING CHEMICALS (EDCS) MAY ALSO PLAY A PATHOPHYSIOLOGICAL ROLE IN THE OCCURRENCE OF METABOLIC DISEASES. BOTH EXPERIMENTAL AND EPIDEMIOLOGICAL EVIDENCE SUPPORT A ROLE FOR EARLY AND CHRONIC EXPOSURE TO LOW DOSES OF CHEMICAL POLLUTANTS WITH ENDOCRINE AND METABOLIC DISRUPTING EFFECTS. MOST ARE PRESENT IN THE FOOD CHAIN AND ACCUMULATE IN THE FAT MASS AFTER ABSORPTION. IN RODENTS, BISPHENOL A STIMULATES SYNTHESIS AND SECRETION OF PANCREATIC BETA CELLS AND DISTURBS INSULIN SIGNALING IN LIVER, MUSCLE AND ADIPOSE TISSUE THROUGH EPIGENETIC CHANGES LEADING TO INSULIN RESISTANCE AND BETA CELL IMPAIRMENT. IN HUMANS, EPIDEMIOLOGICAL REPORTS SHOW STATISTICAL LINK BETWEEN EXPOSURE TO PESTICIDES, POLYCHLORINATED BISPHENYLS, BISPHENOL A, PHTHALATES, DIOXINS OR AROMATIC POLYCYCLIC HYDROCARBIDES OR HEAVY METALS AND DT2 AFTER ACUTE ACCIDENTAL RELEASES OR EARLY IN LIFE AND/OR CHRONIC, LOW DOSES EXPOSURE. MORE PROSPECTIVE, LONGITUDINAL STUDIES ARE NEEDED TO DETERMINE THE IMPORTANCE OF SUCH ENVIRONMENTAL RISK FACTORS. 2017 20 4626 47 NEURODEVELOPMENTAL DISORDERS AND ENVIRONMENTAL TOXICANTS: EPIGENETICS AS AN UNDERLYING MECHANISM. THE INCREASING PREVALENCE OF NEURODEVELOPMENTAL DISORDERS, ESPECIALLY AUTISM SPECTRUM DISORDERS (ASD) AND ATTENTION DEFICIT HYPERACTIVITY DISORDER (ADHD), CALLS FOR MORE RESEARCH INTO THE IDENTIFICATION OF ETIOLOGIC AND RISK FACTORS. THE DEVELOPMENTAL ORIGIN OF HEALTH AND DISEASE (DOHAD) HYPOTHESIZES THAT THE ENVIRONMENT DURING FETAL AND CHILDHOOD DEVELOPMENT AFFECTS THE RISK FOR MANY CHRONIC DISEASES IN LATER STAGES OF LIFE, INCLUDING NEURODEVELOPMENTAL DISORDERS. EPIGENETICS, A TERM DESCRIBING MECHANISMS THAT CAUSE CHANGES IN THE CHROMOSOME STATE WITHOUT AFFECTING DNA SEQUENCES, IS SUGGESTED TO BE THE UNDERLYING MECHANISM, ACCORDING TO THE DOHAD HYPOTHESIS. MOREOVER, MANY NEURODEVELOPMENTAL DISORDERS ARE ALSO RELATED TO EPIGENETIC ABNORMALITIES. EXPERIMENTAL AND EPIDEMIOLOGICAL STUDIES SUGGEST THAT EXPOSURE TO PRENATAL ENVIRONMENTAL TOXICANTS IS ASSOCIATED WITH NEURODEVELOPMENTAL DISORDERS. IN ADDITION, THERE IS ALSO EVIDENCE THAT ENVIRONMENTAL TOXICANTS CAN RESULT IN EPIGENETIC ALTERATIONS, NOTABLY DNA METHYLATION. IN THIS REVIEW, WE FIRST FOCUS ON THE RELATIONSHIP BETWEEN NEURODEVELOPMENTAL DISORDERS AND ENVIRONMENTAL TOXICANTS, IN PARTICULAR MATERNAL SMOKING, PLASTIC-DERIVED CHEMICALS (BISPHENOL A AND PHTHALATES), PERSISTENT ORGANIC POLLUTANTS, AND HEAVY METALS. WE THEN REVIEW STUDIES SHOWING THE EPIGENETIC EFFECTS OF THOSE ENVIRONMENTAL FACTORS IN HUMANS THAT MAY AFFECT NORMAL NEURODEVELOPMENT. 2017