1 3710 227 INFLUENCES OF POLYCYCLIC AROMATIC HYDROCARBON ON THE EPIGENOME TOXICITY AND ITS APPLICABILITY IN HUMAN HEALTH RISK ASSESSMENT. THE EXISTENCE OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN AMBIENT AIR IS AN ESCALATING CONCERN WORLDWIDE BECAUSE OF THEIR ABILITY TO CAUSE CANCER AND INDUCE PERMANENT CHANGES IN THE GENETIC MATERIAL. GROWING EVIDENCE IMPLIES THAT DURING EARLY LIFE-SENSITIVE STAGES, THE RISK OF PROGRESSION OF ACUTE AND CHRONIC DISEASES DEPENDS ON EPIGENETIC CHANGES INITIATED BY THE INFLUENCE OF ENVIRONMENTAL CUES. SEVERAL REPORTS DECIPHERED THE RELATIONSHIP BETWEEN EXPOSURE TO ENVIRONMENTAL CHEMICALS AND EPIGENETICS, AND HAVE KNOWN TOXICANTS THAT ALTER THE EPIGENETIC STATES. AMONGST PAHS, BENZO[A]PYRENE (B[A]P) IS ACCEPTED AS A GROUP 1 CANCER-CAUSING AGENT BY THE INTERNATIONAL AGENCY FOR THE RESEARCH ON CANCER (IARC). B[A]P IS A WELL-STUDIED PRO-CARCINOGEN THAT IS METABOLICALLY ACTIVATED BY THE ARYL HYDROCARBON RECEPTOR (AHR)/CYTOCHROME P450 PATHWAY. CYTOCHROME P450 PLAYS A PIVOTAL ROLE IN THE STIMULATION STEP, WHICH IS ESSENTIAL FOR DNA ADDUCT FORMATION. ACCRUING EVIDENCE SUGGESTS THAT EPIGENETIC ALTERATIONS ASSUME A FUNDAMENTAL PART IN PAH-PROMOTED CARCINOGENESIS. THIS INTERACTION BETWEEN PAHS AND EPIGENETIC FACTORS RESULTS IN AN ALTERED PROFILE OF THESE MARKS, GLOBALLY AND LOCUS-SPECIFIC. SOME OF THE EPIGENETIC CHANGES DUE TO EXPOSURE TO PAHS LEAD TO INCREASED DISEASE SUSCEPTIBILITY AND PROGRESSION. IT IS WELL UNDERSTOOD THAT EXPOSURE TO ENVIRONMENTAL CARCINOGENS, SUCH AS PAH TRIGGERS DISEASE PATHWAYS THROUGH CHANGES IN THE GENOME. SEVERAL EVIDENCE REPORTED DUE TO THE EPIGENOME-WIDE ASSOCIATION STUDIES, THAT EARLY LIFE ADVERSE ENVIRONMENTAL EVENTS MAY TRIGGER WIDESPREAD AND PERSISTENT VARIATIONS IN TRANSCRIPTIONAL PROFILING. MOREOVER, THESE VARIATIONS RESPOND TO DNA DAMAGE AND/OR A CONSEQUENCE OF EPIGENETIC MODIFICATIONS THAT NEED FURTHER INVESTIGATION. GROWING EVIDENCE HAS ASSOCIATED PAHS WITH EPIGENETIC VARIATIONS INVOLVING ALTERATIONS IN DNA METHYLATION, HISTONE MODIFICATION, AND MICRO RNA (MIRNA) REGULATION. EPIGENETIC ALTERATIONS TO PAH EXPOSURE WERE RELATED TO CHRONIC DISEASES, SUCH AS PULMONARY DISEASE, CARDIOVASCULAR DISEASE, ENDOCRINE DISRUPTOR, NERVOUS SYSTEM DISORDER, AND CANCER. THIS HORMETIC RESPONSE GIVES A NOVEL PERCEPTION CONCERNING THE TOXICITY OF PAHS AND THE BIOLOGICAL REACTION THAT MAY BE A DISTINCT RELIANCE ON EXPOSURE. THIS REVIEW SHEDS LIGHT ON UNDERSTANDING THE LATEST EVIDENCE ABOUT HOW PAHS CAN ALTER EPIGENETIC PATTERNS AND HUMAN HEALTH. IN CONCLUSION, AS SEVERAL EPIGENETIC CHANGE MECHANISMS REMAIN UNCLEAR YET, FURTHER ANALYSES DERIVED FROM PAHS EXPOSURE MUST BE PERFORMED TO FIND NEW TARGETS AND DISEASE BIOMARKERS. IN SPITE OF THE CURRENT LIMITATIONS, NUMEROUS EVIDENCE SUPPORTS THE PERCEPTION THAT EPIGENETICS GRIPS SUBSTANTIAL POTENTIAL FOR ADVANCING OUR KNOWLEDGE ABOUT THE MOLECULAR MECHANISMS OF ENVIRONMENTAL TOXICANTS, ALSO FOR PREDICTING HEALTH-ASSOCIATED RISKS DUE TO ENVIRONMENTAL CIRCUMSTANCES EXPOSURE AND INDIVIDUAL SUSCEPTIBILITY. 2022 2 396 45 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 3 301 49 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 4 1970 40 EPIGENETIC ALTERATIONS AND OCCUPATIONAL EXPOSURE TO BENZENE, FIBERS, AND HEAVY METALS ASSOCIATED WITH TUMOR DEVELOPMENT (REVIEW). THE CHRONIC OCCUPATIONAL EXPOSURE TO CONTAMINANTS AND CARCINOGENS LEADS TO THE DEVELOPMENT OF CANCER. OVER THE PAST DECADES, MANY CARCINOGENS HAVE BEEN FOUND IN THE OCCUPATIONAL ENVIRONMENT AND THEIR PRESENCE IS OFTEN ASSOCIATED WITH AN INCREASED INCIDENCE OF CANCER. ACCORDING TO THE INTERNATIONAL AGENCY FOR RESEARCH ON CANCER (IARC), THE MAJORITY OF CARCINOGENS ARE CLASSIFIED AS 'PROBABLE' AND 'POSSIBLE' HUMAN CARCINOGENS, WHILE, DIRECT EVIDENCE OF CARCINOGENICITY IS PROVIDED IN EPIDEMIOLOGICAL AND EXPERIMENTAL STUDIES. ADDITIONALLY, ACCUMULATING EVIDENCE SUGGESTS THAT EPIGENETIC ALTERATIONS MAY BE EARLY INDICATORS OF GENOTOXIC AND NON-GENOTOXIC CARCINOGEN EXPOSURE. IN THE PRESENT REVIEW, THE RELATIONSHIP BETWEEN EXPOSURES TO BENZENE, MINERAL FIBERS, METALS AND EPIGENETIC ALTERATIONS ARE DISCUSSED AS THE MOST IMPORTANT CANCER RISK FACTORS DURING WORK ACTIVITIES. 2017 5 3210 48 HEALTH EFFECTS ASSOCIATED WITH PRE- AND PERINATAL EXPOSURE TO ARSENIC. INORGANIC ARSENIC IS A WELL-ESTABLISHED HUMAN CARCINOGEN, ABLE TO INDUCE GENETIC AND EPIGENETIC ALTERATIONS. MORE THAN 200 MILLION PEOPLE WORLDWIDE ARE EXPOSED TO ARSENIC CONCENTRATIONS IN DRINKING WATER EXCEEDING THE RECOMMENDED WHO THRESHOLD (10MUG/L). ADDITIONALLY, CHRONIC EXPOSURE TO LEVELS BELOW THIS THRESHOLD IS KNOWN TO RESULT IN LONG-TERM HEALTH EFFECTS IN HUMANS. THE ARSENIC-RELATED HEALTH EFFECTS IN HUMANS ARE ASSOCIATED WITH ITS BIOTRANSFORMATION PROCESS, WHEREBY THE RESULTING METABOLITES CAN INDUCE MOLECULAR DAMAGE THAT ACCUMULATES OVER TIME. THE EFFECTS DERIVED FROM THESE ALTERATIONS INCLUDE GENOMIC INSTABILITY ASSOCIATED WITH OXIDATIVE DAMAGE, ALTERATION OF GENE EXPRESSION (INCLUDING CODING AND NON-CODING RNAS), GLOBAL AND LOCALIZED EPIGENETIC REPROGRAMMING, AND HISTONE POSTTRANSLATIONAL MODIFICATIONS. THESE ALTERATIONS DIRECTLY AFFECT MOLECULAR PATHWAYS INVOLVED IN THE ONSET AND PROGRESSION OF MANY CONDITIONS THAT CAN ARISE EVEN DECADES AFTER THE EXPOSURE OCCURS. IMPORTANTLY, ARSENIC METABOLITES GENERATED DURING ITS BIOTRANSFORMATION CAN ALSO PASS THROUGH THE PLACENTAL BARRIER, RESULTING IN FETAL EXPOSURE TO THIS CARCINOGEN AT SIMILAR LEVELS TO THOSE OF THE MOTHER. AS SUCH, MORE IMMEDIATE EFFECTS OF THE ARSENIC-INDUCED MOLECULAR DAMAGE CAN BE OBSERVED AS DETRIMENTAL EFFECTS ON FETAL DEVELOPMENT, PREGNANCY, AND BIRTH OUTCOMES. IN THIS REVIEW, WE FOCUS ON THE GENETIC AND EPIGENETIC DAMAGE ASSOCIATED WITH EXPOSURE TO LOW LEVELS OF ARSENIC, PARTICULARLY THOSE AFFECTING EARLY DEVELOPMENTAL STAGES. WE ALSO PRESENT HOW THESE ALTERATIONS OCCURRING DURING EARLY LIFE CAN IMPACT THE DEVELOPMENT OF CERTAIN DISEASES IN ADULT LIFE. 2021 6 588 63 BENZENE EXPOSURE IS ASSOCIATED WITH EPIGENETIC CHANGES (REVIEW). BENZENE IS A VOLATILE AROMATIC HYDROCARBON SOLVENT AND IS KNOWN AS ONE OF THE PREDOMINANT AIR POLLUTANTS IN THE ENVIRONMENT. CHRONIC EXPOSURE TO BENZENE IS KNOWN TO CAUSE APLASTIC ANEMIA AND INCREASED RISK OF ACUTE MYELOGENOUS LEUKEMIA IN HUMANS. ALTHOUGH THE MECHANISMS BY WHICH BENZENE CAUSES TOXICITY REMAIN TO BE FULLY ELUCIDATED, IT IS WIDELY ACCEPTED THAT ITS METABOLISM IS CRUCIAL TO ITS TOXICITY, WITH INVOLVEMENT OF ONE OR MORE REACTIVE METABOLITES. NOVEL APPROACHES AIMED AT EVALUATING DIFFERENT MECHANISMS BY WHICH BENZENE CAN IMPACT ON HUMAN HEALTH BY ALTERING GENE REGULATION HAVE BEEN DEVELOPED. AMONG THESE NOVEL APPROACHES, EPIGENETICS APPEARS TO BE PROMISING. THE PRESENT REVIEW ARTICLE SUMMARIZES THE MOST IMPORTANT FINDINGS, REPORTED FROM THE LITERATURE, ON EPIGENETIC MODIFICATIONS CORRELATED TO BENZENE EXPOSURE. A COMPUTERIZED SEARCH IN PUBMED WAS PERFORMED IN NOVEMBER 2014, USING SEARCH TERMS, INCLUDING 'BENZENE', 'EPIGENETIC', 'HISTONE MODIFICATIONS', 'DNA METHYLATION' AND 'MICRORNA'. EPIDEMIOLOGICAL AND EXPERIMENTAL STUDIES HAVE DEMONSTRATED THE POTENTIAL EPIGENETIC EFFECTS OF BENZENE EXPOSURE. SEVERAL OF THE EPIGENOMIC CHANGES OBSERVED IN RESPONSE TO ENVIRONMENTAL EXPOSURES MAY BE MECHANISTICALLY ASSOCIATED WITH SUSCEPTIBILITY TO DISEASES. HOWEVER, FURTHER ELUCIDATION OF THE MECHANISMS BY WHICH BENZENE ALTERS GENE EXPRESSION MAY IMPROVE PREDICTION OF THE TOXIC POTENTIAL OF NOVEL COMPOUNDS INTRODUCED INTO THE ENVIRONMENT, AND ALLOW FOR MORE TARGETED AND APPROPRIATE DISEASE PREVENTION STRATEGIES. 2016 7 2282 54 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 8 6809 41 [EPIGENETICS IN INFLAMMATORY SYSTEMIC DISEASES]. IN ADDITION TO ANALYSIS OF THE GENETIC CODE, IN RECENT YEARS MORE AND MORE STUDIES HAVE CONCENTRATED ON CHANGES IN THE EPIGENETIC CODE. EPIGENETIC MECHANISMS DETERMINE WHICH GENES IN A CELL ARE TRANSCRIBED AND THUS FORM THE PHENOTYPE OF A CELL. THE EPIGENETIC CODE CAN BE CHANGED BY ENVIRONMENTAL INFLUENCES, WHICH ALLOWS CELLS TO ADAPT TO LONGSTANDING CHANGES IN THE ENVIRONMENT. THEREFORE, IT IS FEASIBLE TO ASSUME THAT EPIGENETIC CHANGES ARE THE MOLECULAR BASIS FOR LONG-TERM EFFECTS OF THE ENVIRONMENT ON DISEASE DEVELOPMENT. IN PARTICULAR IN TUMORS AND CHRONIC INFLAMMATORY DISEASES EPIGENETIC CHANGES WERE FOUND TO CORRELATE WITH DISEASE SEVERITY AND PROGRESSION. KNOWLEDGE ABOUT THESE EPIGENETIC CHANGES MIGHT HELP THAT EPIGENETIC MODIFICATIONS CAN BE USED IN THE FUTURE AS BIOMARKERS, PROGNOSTIC FACTORS AND THERAPEUTIC TARGETS. 2014 9 1324 56 DEOXYRIBONUCLEIC ACID (DNA) METHYLATION IN CHILDREN EXPOSED TO AIR POLLUTION: A POSSIBLE MECHANISM UNDERLYING RESPIRATORY HEALTH EFFECTS DEVELOPMENT. AIR POLLUTION IS A SUBSTANTIAL ENVIRONMENTAL THREAT TO CHILDREN AND ACTS AS ACUTE AND CHRONIC DISEASE RISK FACTORS ALIKE. SEVERAL STUDIES HAVE PREVIOUSLY EVALUATED EPIGENETIC MODIFICATIONS CONCERNING ITS EXPOSURE ACROSS VARIOUS LIFE STAGES. HOWEVER, FINDINGS ON EPIGENETIC MODIFICATIONS AS THE CONSEQUENCES OF AIR POLLUTION DURING CHILDHOOD ARE RATHER MINIMAL. THIS REVIEW EVALUATED HIGHLY RELEVANT STUDIES IN THE FIELD TO ANALYZE THE EXISTING LITERATURE REGARDING EXPOSURE TO AIR POLLUTION, WITH A FOCUS ON EPIGENETIC ALTERATIONS DURING CHILDHOOD AND THEIR CONNECTIONS WITH RESPIRATORY HEALTH EFFECTS. THE SEARCH WAS CONDUCTED USING READILY AVAILABLE ELECTRONIC DATABASES (PUBMED AND SCIENCEDIRECT) TO SCREEN FOR CHILDREN'S STUDIES ON EPIGENETIC MECHANISMS FOLLOWING EITHER PRE- OR POST-NATAL EXPOSURE TO AIR POLLUTANTS. STUDIES RELEVANT ENOUGH AND MATCHED THE PREDETERMINED CRITERIA WERE CHOSEN TO BE REVIEWED. NON-ENGLISH ARTICLES AND STUDIES THAT DID NOT REPORT BOTH AIR MONITORING AND EPIGENETIC OUTCOMES IN THE SAME ARTICLE WERE EXCLUDED. THE REVIEW FOUND THAT EPIGENETIC CHANGES HAVE BEEN LINKED WITH EXPOSURE TO AIR POLLUTANTS DURING EARLY LIFE WITH EVIDENCE AND REPORTS OF HOW THEY MAY DEREGULATE THE EPIGENOME BALANCE, THUS INDUCING DISEASE PROGRESSION IN THE FUTURE. EPIGENETIC STUDIES EVOLVE AS A PROMISING NEW APPROACH IN DECIPHERING THE UNDERLYING IMPACTS OF AIR POLLUTION ON DEOXYRIBONUCLEIC ACID (DNA) DUE TO LINKS ESTABLISHED BETWEEN SOME OF THESE EPIGENETIC MECHANISMS AND ILLNESSES. 2021 10 266 60 ADVERSE OUTCOME PATHWAYS FOR IONIZING RADIATION AND BREAST CANCER INVOLVE DIRECT AND INDIRECT DNA DAMAGE, OXIDATIVE STRESS, INFLAMMATION, GENOMIC INSTABILITY, AND INTERACTION WITH HORMONAL REGULATION OF THE BREAST. KNOWLEDGE ABOUT ESTABLISHED BREAST CARCINOGENS CAN SUPPORT IMPROVED AND MODERNIZED TOXICOLOGICAL TESTING METHODS BY IDENTIFYING KEY MECHANISTIC EVENTS. IONIZING RADIATION (IR) INCREASES THE RISK OF BREAST CANCER, ESPECIALLY FOR WOMEN AND FOR EXPOSURE AT YOUNGER AGES, AND EVIDENCE OVERALL SUPPORTS A LINEAR DOSE-RESPONSE RELATIONSHIP. WE USED THE ADVERSE OUTCOME PATHWAY (AOP) FRAMEWORK TO OUTLINE AND EVALUATE THE EVIDENCE LINKING IONIZING RADIATION WITH BREAST CANCER FROM MOLECULAR INITIATING EVENTS TO THE ADVERSE OUTCOME THROUGH INTERMEDIATE KEY EVENTS, CREATING A QUALITATIVE AOP. WE IDENTIFIED KEY EVENTS BASED ON REVIEW ARTICLES, SEARCHED PUBMED FOR RECENT LITERATURE ON KEY EVENTS AND IR, AND IDENTIFIED ADDITIONAL PAPERS USING REFERENCES. WE MANUALLY CURATED PUBLICATIONS AND EVALUATED DATA QUALITY. IONIZING RADIATION DIRECTLY AND INDIRECTLY CAUSES DNA DAMAGE AND INCREASES PRODUCTION OF REACTIVE OXYGEN AND NITROGEN SPECIES (RONS). RONS LEAD TO DNA DAMAGE AND EPIGENETIC CHANGES LEADING TO MUTATIONS AND GENOMIC INSTABILITY (GI). PROLIFERATION AMPLIFIES THE EFFECTS OF DNA DAMAGE AND MUTATIONS LEADING TO THE AO OF BREAST CANCER. SEPARATELY, RONS AND DNA DAMAGE ALSO INCREASE INFLAMMATION. INFLAMMATION CONTRIBUTES TO DIRECT AND INDIRECT EFFECTS (EFFECTS IN CELLS NOT DIRECTLY REACHED BY IR) VIA POSITIVE FEEDBACK TO RONS AND DNA DAMAGE, AND SEPARATELY INCREASES PROLIFERATION AND BREAST CANCER THROUGH PRO-CARCINOGENIC EFFECTS ON CELLS AND TISSUE. FOR EXAMPLE, GENE EXPRESSION CHANGES ALTER INFLAMMATORY MEDIATORS, RESULTING IN IMPROVED SURVIVAL AND GROWTH OF CANCER CELLS AND A MORE HOSPITABLE TISSUE ENVIRONMENT. ALL OF THESE EVENTS OVERLAP AT MULTIPLE POINTS WITH EVENTS CHARACTERISTIC OF "BACKGROUND" INDUCTION OF BREAST CARCINOGENESIS, INCLUDING HORMONE-RESPONSIVE PROLIFERATION, OXIDATIVE ACTIVITY, AND DNA DAMAGE. THESE OVERLAPS MAKE THE BREAST PARTICULARLY SUSCEPTIBLE TO IONIZING RADIATION AND REINFORCE THAT THESE BIOLOGICAL ACTIVITIES ARE IMPORTANT CHARACTERISTICS OF CARCINOGENS. AGENTS THAT INCREASE THESE BIOLOGICAL PROCESSES SHOULD BE CONSIDERED POTENTIAL BREAST CARCINOGENS, AND PREDICTIVE METHODS ARE NEEDED TO IDENTIFY CHEMICALS THAT INCREASE THESE PROCESSES. TECHNIQUES ARE AVAILABLE TO MEASURE RONS, DNA DAMAGE AND MUTATION, CELL PROLIFERATION, AND SOME INFLAMMATORY PROTEINS OR PROCESSES. IMPROVED ASSAYS ARE NEEDED TO MEASURE GI AND CHRONIC INFLAMMATION, AS WELL AS THE INTERACTION WITH HORMONALLY DRIVEN DEVELOPMENT AND PROLIFERATION. SEVERAL METHODS MEASURE DIVERSE EPIGENETIC CHANGES, BUT IT IS NOT CLEAR WHICH CHANGES ARE RELEVANT TO BREAST CANCER. IN ADDITION, MOST TOXICOLOGICAL ASSAYS ARE NOT CONDUCTED IN MAMMARY TISSUE, AND SO IT IS A PRIORITY TO EVALUATE IF RESULTS FROM OTHER TISSUES ARE GENERALIZABLE TO BREAST, OR TO CONDUCT ASSAYS IN BREAST TISSUE. DEVELOPING AND APPLYING THESE ASSAYS TO IDENTIFY EXPOSURES OF CONCERN WILL FACILITATE EFFORTS TO REDUCE SUBSEQUENT BREAST CANCER RISK. 2020 11 738 43 CANCER SUSCEPTIBILITY: EPIGENETIC MANIFESTATION OF ENVIRONMENTAL EXPOSURES. CANCER IS A DISEASE THAT RESULTS FROM BOTH GENETIC AND EPIGENETIC CHANGES. DISCORDANT PHENOTYPES AND VARYING INCIDENCES OF COMPLEX DISEASES SUCH AS CANCER IN MONOZYGOTIC TWINS AS WELL AS GENETICALLY IDENTICAL LABORATORY ANIMALS HAVE LONG BEEN ATTRIBUTED TO DIFFERENCES IN ENVIRONMENTAL EXPOSURES. ACCUMULATING EVIDENCE INDICATES, HOWEVER, THAT DISPARITIES IN GENE EXPRESSION RESULTING FROM VARIABLE MODIFICATIONS IN DNA METHYLATION AND CHROMATIN STRUCTURE IN RESPONSE TO THE ENVIRONMENT ALSO PLAY A ROLE IN DIFFERENTIAL SUSCEPTIBILITY TO DISEASE. DESPITE A GROWING CONSENSUS ON THE IMPORTANCE OF EPIGENETICS IN THE ETIOLOGY OF CHRONIC HUMAN DISEASES, THE GENES MOST PRONE TO EPIGENETIC DYSREGULATION ARE INCOMPLETELY DEFINED. MOREOVER, NEITHER THE ENVIRONMENTAL AGENTS MOST STRONGLY AFFECTING THE EPIGENOME NOR THE CRITICAL WINDOWS OF VULNERABILITY TO ENVIRONMENTALLY INDUCED EPIGENETIC ALTERATIONS ARE ADEQUATELY CHARACTERIZED. THESE MAJOR DEFICITS IN KNOWLEDGE MARKEDLY IMPAIR OUR ABILITY TO UNDERSTAND FULLY THE ETIOLOGY OF CANCER AND THE IMPORTANCE OF THE EPIGENOME IN DIAGNOSING AND PREVENTING THIS DEVASTATING DISEASE. 2007 12 6199 54 THE IMPORTANCE OF EPIGENETICS IN THE DEVELOPMENT OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE. IT IS GENERALLY ACCEPTED THAT GENETIC PREDISPOSITION PLAYS A ROLE IN COPD DEVELOPMENT IN SUSCEPTIBLE INDIVIDUALS. THEREFORE, MANY CANDIDATE GENES THAT COULD BE LINKED TO THE DEVELOPMENT OF DISEASE HAVE BEEN EXAMINED IN COPD. HOWEVER, INCONSISTENT RESULTS IN DIFFERENT STUDY POPULATIONS OFTEN LIMIT THIS APPROACH, SUGGESTING THAT NOT ONLY GENETICS, BUT ALSO OTHER FACTORS, MAY BE CONTRIBUTED TO THE SUSCEPTIBILITY TO COPD. EPIGENETIC MECHANISMS CAN AFFECT THE TRANSCRIPTIONAL ACTIVITY OF SPECIFIC GENES, AT DIFFERENT POINTS IN TIME, AND IN DIFFERENT ORGANS. MOREOVER, THESE MECHANISMS CAN HAVE AN EFFECT ON PEOPLE'S HEALTH. RECENTLY, THERE IS EMERGING EVIDENCE SUPPORTING A ROLE OF EPIGENETICS FOR THE REGULATION OF INFLAMMATORY GENES IN DISEASES SUCH AS ASTHMA AND COPD. MOREOVER, RECENT STUDIES SUGGEST THAT THE CURRENTLY USED TREATMENTS INCLUDING CORTICOSTEROIDS MAY WORK THROUGH EPIGENETIC MECHANISMS. EPIGENETIC REGULATION CAN BE REPROGRAMMED, POTENTIALLY AFFECTING THE RISK, AETIOLOGY AND TREATMENT OF VARIOUS DISEASE STATES. THE EPIGENETICALLY INFLUENCED PHENOTYPE COULD BE REVERSED WITH DEMETHYLATING OR DEACETYLATING AGENTS, CONSISTENT WITH EPIGENETIC PLASTICITY. THE POSTNATAL REVERSIBILITY OF THESE METHYLATION OR ACETYLATION EVENTS MAY THEREFORE PROVIDE GOOD OPPORTUNITIES FOR INTERVENTION. THE RECOGNITION OF THE ROLE OF GENETIC AND EPIGENETIC MECHANISMS IN THE DEVELOPMENT OF COPD MAY IDENTIFY NOVEL TARGETS THAT HATCH NEW THERAPIES FOR PATIENTS WITH COPD. 2011 13 3106 48 GENOMICS AND THE RESPIRATORY EFFECTS OF AIR POLLUTION EXPOSURE. ADVERSE HEALTH EFFECTS FROM AIR POLLUTANTS REMAIN IMPORTANT, DESPITE IMPROVEMENT IN AIR QUALITY IN THE PAST FEW DECADES. THE EXACT MECHANISMS OF LUNG INJURY FROM EXPOSURE TO AIR POLLUTANTS ARE NOT YET FULLY UNDERSTOOD. STUDYING THE GENOME (E.G. SINGLE-NUCLEOTIDE POLYMORPHISMS (SNP) ), EPIGENOME (E.G. METHYLATION OF GENES), TRANSCRIPTOME (MRNA EXPRESSION) AND MICRORNAOME (MICRORNA EXPRESSION) HAS THE POTENTIAL TO IMPROVE OUR UNDERSTANDING OF THE ADVERSE EFFECTS OF AIR POLLUTANTS. GENOME-WIDE ASSOCIATION STUDIES OF SNP HAVE DETECTED SNP ASSOCIATED WITH RESPIRATORY PHENOTYPES; HOWEVER, TO DATE, ONLY CANDIDATE GENE STUDIES OF AIR POLLUTION EXPOSURE HAVE BEEN PERFORMED. CHANGES IN EPIGENETIC PROCESSES, SUCH DNA METHYLATION THAT LEADS TO GENE SILENCING WITHOUT ALTERING THE DNA SEQUENCE, OCCUR WITH AIR POLLUTANT EXPOSURE, ESPECIALLY GLOBAL AND GENE-SPECIFIC METHYLATION CHANGES. RESPIRATORY CELL LINE AND ANIMAL MODELS DEMONSTRATE DISTINCT GENE EXPRESSION SIGNATURES IN THE TRANSCRIPTOME, ARISING FROM EXPOSURE TO PARTICULATE MATTER OR OZONE. PARTICULATE MATTER AND OTHER ENVIRONMENTAL TOXINS ALTER EXPRESSION OF MICRORNA, WHICH ARE SHORT NON-CODING RNA THAT REGULATE GENE EXPRESSION. WHILE IT IS CLEARLY IMPORTANT TO CONTAIN RISING LEVELS OF AIR POLLUTION, STRATEGIES ALSO NEED TO BE DEVELOPED TO MINIMIZE THE DAMAGING EFFECTS OF AIR POLLUTANT EXPOSURE ON THE LUNG, ESPECIALLY FOR PATIENTS WITH CHRONIC LUNG DISEASE AND FOR PEOPLE AT RISK OF FUTURE LUNG DISEASE. CAREFUL STUDY OF GENOMIC RESPONSES WILL IMPROVE OUR UNDERSTANDING OF MECHANISMS OF LUNG INJURY FROM AIR POLLUTION AND ENABLE FUTURE CLINICAL TESTING OF INTERVENTIONS AGAINST THE TOXIC EFFECTS OF AIR POLLUTANTS. 2012 14 1938 66 EPIDEMIOLOGIC EVIDENCE FOR ASSOCIATION BETWEEN ADVERSE ENVIRONMENTAL EXPOSURES IN EARLY LIFE AND EPIGENETIC VARIATION: A POTENTIAL LINK TO DISEASE SUSCEPTIBILITY? A GROWING BODY OF EVIDENCE SUGGESTS THAT THE RISK OF DEVELOPMENT AND PROGRESSION OF A VARIETY OF HUMAN CHRONIC DISEASES DEPENDS ON EPIGENETIC MODIFICATIONS TRIGGERED BY ENVIRONMENTAL CUES DURING EARLY LIFE SENSITIVE STAGES. EXPOSURES TO ENVIRONMENTAL FACTORS SUCH AS ADVERSE NUTRITIONAL, PSYCHOLOGICAL, AND SOCIAL CONDITIONS, AS WELL AS POLLUTANTS AND SUBSTANCE ABUSE IN EARLY LIFE, HAVE BEEN SHOWN TO BE IMPORTANT DETERMINANTS OF EPIGENETIC PROGRAMMING OF CHRONIC PATHOLOGICAL CONDITIONS IN HUMAN POPULATIONS. OVER THE PAST YEARS, IT HAS BECOME INCREASINGLY CLEAR DUE TO THE EPIGENOME-WIDE ASSOCIATION STUDIES (EWASS) THAT EARLY LIFE ADVERSE ENVIRONMENTAL EVENTS MAY TRIGGER WIDESPREAD AND PERSISTENT ALTERATIONS IN TRANSCRIPTIONAL PROFILING. SEVERAL CANDIDATE GENES HAVE BEEN IDENTIFIED UNDERLYING THESE ASSOCIATIONS. IN THIS CONTEXT, DNA METHYLATION IS THE MOST INTENSIVELY STUDIED EPIGENETIC PHENOMENON. IN THIS REVIEW, THE CLINICAL AND EPIDEMIOLOGICAL EVIDENCE FOR THE ROLE OF EPIGENETIC FACTORS IN MEDIATING THE LINK BETWEEN EARLY LIFE EXPERIENCES AND LONG-TERM HEALTH OUTCOMES ARE SUMMARIZED. 2015 15 3848 42 IS EPIGENETICS AN IMPORTANT LINK BETWEEN EARLY LIFE EVENTS AND ADULT DISEASE? BACKGROUND: EPIGENETIC MECHANISMS PROVIDE ONE POTENTIAL EXPLANATION FOR HOW ENVIRONMENTAL INFLUENCES IN EARLY LIFE CAUSE LONG-TERM CHANGES IN CHRONIC DISEASE SUSCEPTIBILITY. WHEREAS EPIGENETIC DYSREGULATION IS INCREASINGLY IMPLICATED IN VARIOUS RARE DEVELOPMENTAL SYNDROMES AND CANCER, THE ROLE OF EPIGENETICS IN COMPLEX CHRONIC DISEASES, SUCH AS CARDIOVASCULAR DISEASE, TYPE 2 DIABETES AND OBESITY, REMAINS LARGELY UNCHARACTERIZED. EXTENSIVE WORK IN ANIMAL MODELS IS REQUIRED TO DEVELOP SPECIFIC HYPOTHESES THAT CAN BE PRACTICABLY TESTED IN HUMANS. ANIMAL MODELS: WE HAVE DEVELOPED A MOUSE MODEL SHOWING THAT METHYL DONOR SUPPLEMENTATION PREVENTS TRANSGENERATIONAL AMPLIFICATION OF OBESITY, SUGGESTING A ROLE FOR DNA METHYLATION IN THE DEVELOPMENTAL ESTABLISHMENT OF BODY WEIGHT REGULATION. CONCLUSIONS: COUPLING SUCH MODELS WITH RECENTLY DEVELOPED EPIGENOMIC TECHNOLOGIES SHOULD ULTIMATELY ENABLE US TO DETERMINE IF EPIGENETICS IS AN IMPORTANT LINK BETWEEN EARLY LIFE EVENTS AND ADULT DISEASE. 2009 16 6287 53 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 17 3404 56 HOW EPIGENETICS IMPACTS ON HUMAN DISEASES. EPIGENETICS IS A RAPIDLY GROWING FIELD OF BIOLOGY THAT STUDIES THE CHANGES IN GENE EXPRESSION THAT ARE NOT DUE TO ALTERATIONS IN THE DNA SEQUENCE BUT RATHER THE CHEMICAL MODIFICATIONS OF DNA AND ITS ASSOCIATED PROTEINS. EPIGENETIC MECHANISMS CAN PROFOUNDLY INFLUENCE GENE EXPRESSION, CELL DIFFERENTIATION, TISSUE DEVELOPMENT, AND DISEASE SUSCEPTIBILITY. UNDERSTANDING EPIGENETIC CHANGES IS ESSENTIAL TO ELUCIDATE THE MECHANISMS UNDERLYING THE INCREASINGLY RECOGNIZED ROLE OF ENVIRONMENTAL AND LIFESTYLE FACTORS IN HEALTH AND DISEASE AND THE INTERGENERATIONAL TRANSMISSION OF PHENOTYPES. RECENT STUDIES SUGGEST EPIGENETICS MAY BE CRITICAL IN VARIOUS DISEASES, FROM CARDIOVASCULAR DISEASE AND CANCER TO NEURODEVELOPMENTAL AND NEURODEGENERATIVE DISORDERS. EPIGENETIC MODIFICATIONS ARE POTENTIALLY REVERSIBLE AND COULD PROVIDE NEW THERAPEUTIC AVENUES FOR TREATING THESE DISEASES USING EPIGENETIC MODULATORS. MOREOVER, EPIGENETICS PROVIDE INSIGHT INTO DISEASE PATHOGENESIS AND BIOMARKERS FOR DISEASE DIAGNOSIS AND RISK STRATIFICATION. NEVERTHELESS, EPIGENETIC INTERVENTIONS HAVE THE POTENTIAL FOR UNINTENDED CONSEQUENCES AND MAY POTENTIALLY LEAD TO INCREASED RISKS OF UNEXPECTED OUTCOMES, SUCH AS ADVERSE DRUG REACTIONS, DEVELOPMENTAL ABNORMALITIES, AND CANCER. THEREFORE, RIGOROUS STUDIES ARE ESSENTIAL TO MINIMIZE THE RISKS ASSOCIATED WITH EPIGENETIC THERAPIES AND TO DEVELOP SAFE AND EFFECTIVE INTERVENTIONS FOR IMPROVING HUMAN HEALTH. THIS ARTICLE PROVIDES A SYNTHETIC AND HISTORICAL VIEW OF THE ORIGIN OF EPIGENETICS AND SOME OF THE MOST RELEVANT ACHIEVEMENTS. 2023 18 2507 44 EPIGENETICS AND OBESITY: THE DEVIL IS IN THE DETAILS. OBESITY IS A COMPLEX DISEASE WITH MULTIPLE WELL-DEFINED RISK FACTORS. NEVERTHELESS, SUSCEPTIBILITY TO OBESITY AND ITS SEQUELAE WITHIN OBESOGENIC ENVIRONMENTS VARIES GREATLY FROM ONE PERSON TO THE NEXT, SUGGESTING A ROLE FOR GENE X ENVIRONMENT INTERACTIONS IN THE ETIOLOGY OF THE DISORDER. EPIGENETIC REGULATION OF THE HUMAN GENOME PROVIDES A PUTATIVE MECHANISM BY WHICH SPECIFIC ENVIRONMENTAL EXPOSURES CONVEY RISK FOR OBESITY AND OTHER HUMAN DISEASES AND IS ONE POSSIBLE MECHANISM THAT UNDERLIES THE GENE X ENVIRONMENT/TREATMENT INTERACTIONS OBSERVED IN EPIDEMIOLOGICAL STUDIES AND CLINICAL TRIALS. A STUDY PUBLISHED IN BMC MEDICINE THIS MONTH BY WANG ET AL. REPORTS ON AN EXAMINATION OF DNA METHYLATION IN PERIPHERAL BLOOD LEUKOCYTES OF LEAN AND OBESE ADOLESCENTS, COMPARING METHYLATION PATTERNS BETWEEN THE TWO GROUPS. THE AUTHORS IDENTIFIED TWO GENES THAT WERE DIFFERENTIALLY METHYLATED, BOTH OF WHICH HAVE ROLES IN IMMUNE FUNCTION. HERE WE OVERVIEW THE FINDINGS FROM THIS STUDY IN THE CONTEXT OF THOSE EMERGING FROM OTHER RECENT GENETIC AND EPIGENETIC STUDIES, DISCUSS THE STRENGTHS AND WEAKNESSES OF THE STUDY AND SPECULATE ON THE FUTURE OF EPIGENETICS IN CHRONIC DISEASE RESEARCH. 2010 19 6812 38 [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 20 860 54 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