1 1979 110 EPIGENETIC ALTERATIONS IN CHRONIC DISEASE FOCUSING ON BEHCET'S DISEASE: REVIEW. OBJECTIVE: 'EPIGENETICS' IS SPECIFIED AS THE INHERITABLE CHANGES IN GENE EXPRESSION WITH NO ALTERATIONS IN DNA SEQUENCES. EPIGENETICS IS A RAPIDLY OVERSPREADING SCIENTIFIC FIELD, AND THE STUDY OF EPIGENETIC REGULATION IN CHRONIC DISEASE IS EMERGING. THIS STUDY AIMS TO EVALUATE EPIGENETIC CHANGES INCLUDING DNA METHYLATION, HISTONE MODIFICATION, AND NON-CODING RNAS (NCRNAS) IN INFLAMMATORY DISEASE, WITH FOCUS ON BEHCET'S DISEASE. IN THIS REVIEW, FIRST WE DESCRIBE THE HISTORY AND CLASSIFICATION OF EPIGENETIC CHANGES, AND THEN THE ROLE OF EPIGENETIC ALTERATIONS IN CHRONIC DISEASES IS EXPLAINED. METHODS: SYSTEMATIC SEARCH OF MEDLINE, EMBASE, AND COCHRANE LIBRARY WAS CONDUCTED FOR ALL COMPARATIVE STUDIES SINCE 2000 TO 2015 WITH THE LIMITATIONS OF THE ENGLISH LANGUAGE. RESULTS: FOR A NOTABLE PERIOD OF TIME, RESEARCHERS HAVE MAINLY FOCUSED ON THE EPIGENETIC PATHWAYS THAT ARE INVOLVED IN THE MODULATION OF INFLAMMATORY AND ANTI-INFLAMMATORY GENES. RECENT STUDIES HAVE PROPOSED A CENTRAL ROLE FOR CHRONIC INFLAMMATION IN THE PATHOGENESIS OF CHRONIC DISEASE, INCLUDING BEHCET'S DISEASE. CONCLUSION: STUDIES HAVE BEEN REPORTED ON THE EPIGENETIC OF BD SHOWED THE ROLE OF ALTERATIONS IN THE METHYLATION LEVEL OF IRS ELEMENTS; HISTONE MODIFICATIONS SUCH AS H3K4ME27 AND H3K4ME3; UP REGULATION OF MIR-182 AND MIR-3591-3P; DOWN REGULATION OF MIR-155, MIR-638 AND MIR-4488 IN THE PATHOGENESIS OF THE DISEASE. 2017 2 6340 32 THE ROLE OF EPIGENETIC FACTORS IN PSORIASIS. PSORIASIS IS A CHRONIC, SYSTEMIC, IMMUNE-MEDIATED DISEASE WITH AN INCIDENCE OF APPROXIMATELY 2%. THE PATHOGENESIS OF THE DISEASE IS COMPLEX AND NOT YET FULLY UNDERSTOOD. GENETIC FACTORS PLAY A SIGNIFICANT ROLE IN THE PATHOGENESIS OF THE DISEASE. IN PREDISPOSED INDIVIDUALS, MULTIPLE TRIGGER FACTORS MAY CONTRIBUTE TO DISEASE ONSET AND EXACERBATIONS OF SYMPTOMS. ENVIRONMENTAL FACTORS (STRESS, INFECTIONS, CERTAIN MEDICATIONS, NICOTINISM, ALCOHOL, OBESITY) PLAY A SIGNIFICANT ROLE IN THE PATHOGENESIS OF PSORIASIS. IN ADDITION, EPIGENETIC MECHANISMS ARE CONSIDERED RESULT IN MODULATION OF INDIVIDUAL GENE EXPRESSION AND AN INCREASED LIKELIHOOD OF THE DISEASE. STUDIES HIGHLIGHT THE SIGNIFICANT ROLE OF EPIGENETIC FACTORS IN THE ETIOLOGY AND PATHOGENESIS OF PSORIASIS. EPIGENETIC MECHANISMS IN PSORIASIS INCLUDE DNA METHYLATION, HISTONE MODIFICATIONS AND NON-CODING RNAS. EPIGENETIC MECHANISMS INDUCE GENE EXPRESSION CHANGES UNDER THE INFLUENCE OF CHEMICAL MODIFICATIONS OF DNA AND HISTONES, WHICH ALTER CHROMATIN STRUCTURE AND ACTIVATE TRANSCRIPTION FACTORS OF SELECTED GENES, THUS LEADING TO TRANSLATION OF NEW MRNA WITHOUT AFFECTING THE DNA SEQUENCE. EPIGENETIC FACTORS CAN REGULATE GENE EXPRESSION AT THE TRANSCRIPTIONAL (VIA HISTONE MODIFICATION, DNA METHYLATION) AND POSTTRANSCRIPTIONAL LEVELS (VIA MICRORNAS AND LONG NON-CODING RNAS). THIS STUDY AIMS TO PRESENT AND DISCUSS THE DIFFERENT EPIGENETIC MECHANISMS IN PSORIASIS BASED ON A REVIEW OF THE AVAILABLE LITERATURE. 2021 3 2059 29 EPIGENETIC CONTROL OF GENE EXPRESSION IN THE LUNG. EPIGENETICS IS TRADITIONALLY DEFINED AS THE STUDY OF HERITABLE CHANGES IN GENE EXPRESSION CAUSED BY MECHANISMS OTHER THAN CHANGES IN THE UNDERLYING DNA SEQUENCE. THERE ARE THREE MAIN CLASSES OF EPIGENETIC MARKS--DNA METHYLATION, MODIFICATIONS OF HISTONE TAILS, AND NONCODING RNAS--EACH OF WHICH MAY BE INFLUENCED BY THE ENVIRONMENT, DIET, DISEASES, AND AGEING. IMPORTANTLY, EPIGENETIC MARKS HAVE BEEN SHOWN TO INFLUENCE IMMUNE CELL MATURATION AND ARE ASSOCIATED WITH THE RISK OF DEVELOPING VARIOUS FORMS OF CANCER, INCLUDING LUNG CANCER. MOREOVER, THERE IS EMERGING EVIDENCE THAT THESE EPIGENETIC MARKS AFFECT GENE EXPRESSION IN THE LUNG AND ARE ASSOCIATED WITH BENIGN LUNG DISEASES, SUCH AS ASTHMA, CHRONIC OBSTRUCTIVE PULMONARY DISEASE, AND INTERSTITIAL LUNG DISEASE. TECHNOLOGICAL ADVANCES HAVE MADE IT FEASIBLE TO STUDY EPIGENETIC MARKS IN THE LUNG, AND IT IS ANTICIPATED THAT THIS KNOWLEDGE WILL ENHANCE OUR UNDERSTANDING OF THE DYNAMIC BIOLOGY IN THE LUNG AND LEAD TO THE DEVELOPMENT OF NOVEL DIAGNOSTIC AND THERAPEUTIC APPROACHES FOR OUR PATIENTS WITH LUNG DISEASE. 2011 4 2332 35 EPIGENETIC REGULATION OF INFLAMMATION IN INSULIN RESISTANCE. EPIGENETICS FOCUSES ON THE STUDY OF CHANGES IN GENE EXPRESSION BASED ON MODIFICATIONS THAT DO NOT INTERFERE WITH THE DNA SEQUENCE, SUCH AS DNA METHYLATION, POST-TRANSLATIONAL HISTONE MODIFICATION, AND NON-CODING RNA. EPIGENETIC CHANGES REGULATE THE EXPRESSION OF MANY GENES, INCLUDING INFLAMMATORY ONES. CHRONIC INFLAMMATION IS OFTEN ACCOMPANIED BY INSULIN RESISTANCE (IR), WHICH IS CHARACTERISTIC OF INTER ALIA TYPE 2 DIABETES. RECENTLY, IT HAS BEEN REPORTED THAT ALTERED EPIGENETIC SIGNATURE IN THE PROMOTER REGIONS OF INFLAMMATORY GENES MAY CONTRIBUTE TO THE DEVELOPMENT OF IR. THEREFORE, THE AIM OF THIS REVIEW IS TO PRESENT THE CURRENT STATE OF KNOWLEDGE REGARDING THE EPIGENETIC REGULATION OF INFLAMMATION IN IR. IT INCLUDES ORIGINAL PAPERS PUBLISHED FROM 2014 TO 2022. IT APPEARS THAT HYPOMETHYLATION OF THE SOCS3 GENE INCREASES THE RISK OF IR, WHILE THE ALTERATION OF H3K4ME IN THE NF-KB PROMOTER PROMOTES CHANGES IN INFLAMMATORY PHENOTYPE. FINALLY, IN HYPERGLYCEMIC STATES ASSOCIATED WITH IR, ALTERED LEVELS OF H3K4/K9M3 AND H3K9/K14AC RESULT IN INCREASED EXPRESSION OF THE INFLAMMATORY CYTOKINE IL-6. IN ADDITION, NUMEROUS MIRNAS HAVE BEEN IDENTIFIED THAT MAY BECOME A TARGET IN THE FIGHT AGAINST DISEASES RELATED TO INFLAMMATION AND IR. FUTURE STUDIES SHOULD EXAMINE THE EPIGENETIC MODIFICATIONS OF IR INFLAMMATORY MARKERS ASSOCIATED WITH ENVIRONMENTAL FACTORS. 2022 5 1518 32 DNA METHYLATION AS AN EPIGENETIC MECHANISM IN THE DEVELOPMENT OF MULTIPLE SCLEROSIS. THE EPIGENETIC MECHANISMS OF GENE EXPRESSION REGULATION ARE A GROUP OF THE KEY CELLULAR AND MOLECULAR PATHWAYS THAT LEAD TO INHERITED ALTERATIONS IN GENES' ACTIVITY WITHOUT CHANGING THEIR CODING SEQUENCE. DNA METHYLATION AT THE C5 POSITION OF CYTOSINE IN CPG DINUCLEOTIDES IS AMONGST THE CENTRAL EPIGENETIC MECHANISMS. CURRENTLY, THE NUMBER OF STUDIES THAT ARE DEVOTED TO THE IDENTIFICATION OF METHYLATION PATTERNS SPECIFIC TO MULTIPLE SCLEROSIS (MS), A SEVERE CHRONIC AUTOIMMUNE DISEASE OF THE CENTRAL NERVOUS SYSTEM, IS ON A RAPID RISE. HOWEVER, THE ISSUE OF THE CONTRIBUTION OF DNA METHYLATION TO THE DEVELOPMENT OF THE DIFFERENT CLINICAL PHENOTYPES OF THIS HIGHLY HETEROGENEOUS DISEASE HAS ONLY BEGUN TO ATTRACT THE ATTENTION OF RESEARCHERS. THIS REVIEW SUMMARIZES THE DATA ON THE MOLECULAR MECHANISMS UNDERLYING DNA METHYLATION AND THE MS RISK FACTORS THAT CAN AFFECT THE DNA METHYLATION PROFILE AND, THEREBY, MODULATE THE EXPRESSION OF THE GENES INVOLVED IN THE DISEASE'S PATHOGENESIS. THE FOCUS OF OUR ATTENTION IS CENTERED ON THE ANALYSIS OF THE PUBLISHED DATA ON THE DIFFERENTIAL METHYLATION OF DNA FROM VARIOUS BIOLOGICAL SAMPLES OF MS PATIENTS OBTAINED USING BOTH THE CANDIDATE GENE APPROACH AND HIGH-THROUGHPUT METHODS. 2021 6 2523 37 EPIGENETICS AND THE TRANSITION FROM ACUTE TO CHRONIC PAIN. OBJECTIVE: THE OBJECTIVE OF THIS STUDY WAS TO REVIEW THE EPIGENETIC MODIFICATIONS INVOLVED IN THE TRANSITION FROM ACUTE TO CHRONIC PAIN AND TO IDENTIFY POTENTIAL TARGETS FOR THE DEVELOPMENT OF NOVEL, INDIVIDUALIZED PAIN THERAPEUTICS. BACKGROUND: EPIGENETICS IS THE STUDY OF HERITABLE MODIFICATIONS IN GENE EXPRESSION AND PHENOTYPE THAT DO NOT REQUIRE A CHANGE IN GENETIC SEQUENCE TO MANIFEST THEIR EFFECTS. ENVIRONMENTAL TOXINS, MEDICATIONS, DIET, AND PSYCHOLOGICAL STRESSES CAN ALTER EPIGENETIC PROCESSES SUCH AS DNA METHYLATION, HISTONE ACETYLATION, AND RNA INTERFERENCE. AS EPIGENETIC MODIFICATIONS POTENTIALLY PLAY AN IMPORTANT ROLE IN INFLAMMATORY CYTOKINE METABOLISM, STEROID RESPONSIVENESS, AND OPIOID SENSITIVITY, THEY ARE LIKELY KEY FACTORS IN THE DEVELOPMENT OF CHRONIC PAIN. ALTHOUGH OUR KNOWLEDGE OF THE HUMAN GENETIC CODE AND DISEASE-ASSOCIATED POLYMORPHISMS HAS GROWN SIGNIFICANTLY IN THE PAST DECADE, WE HAVE NOT YET BEEN ABLE TO ELUCIDATE THE MECHANISMS THAT LEAD TO THE DEVELOPMENT OF PERSISTENT PAIN AFTER NERVE INJURY OR SURGERY. DESIGN: THIS IS A FOCUSED LITERATURE REVIEW OF EPIGENETIC SCIENCE AND ITS RELATIONSHIP TO CHRONIC PAIN. RESULTS: SIGNIFICANT LABORATORY AND CLINICAL DATA SUPPORT THE NOTION THAT EPIGENETIC MODIFICATIONS ARE AFFECTED BY THE ENVIRONMENT AND LEAD TO DIFFERENTIAL GENE EXPRESSION. SIMILAR TO MECHANISMS INVOLVED IN THE DEVELOPMENT OF CANCER, NEURODEGENERATIVE DISEASE, AND INFLAMMATORY DISORDERS, THE LITERATURE ENDORSES AN IMPORTANT POTENTIAL ROLE FOR EPIGENETICS IN CHRONIC PAIN. CONCLUSIONS: EPIGENETIC ANALYSIS MAY IDENTIFY MECHANISMS CRITICAL TO THE DEVELOPMENT OF CHRONIC PAIN AFTER INJURY, AND MAY PROVIDE NEW PATHWAYS AND TARGET MECHANISMS FOR FUTURE DRUG DEVELOPMENT AND INDIVIDUALIZED MEDICINE. 2012 7 6199 32 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 8 2279 33 EPIGENETIC REGULATION IN ALLERGIC DISEASES AND RELATED STUDIES. ASTHMA, A CHRONIC INFLAMMATORY DISORDER OF THE AIRWAY, HAS FEATURES OF BOTH HERITABILITY AS WELL AS ENVIRONMENTAL INFLUENCES WHICH CAN BE INTRODUCED IN UTERO EXPOSURES AND MODIFIED THROUGH AGING, AND THE FEATURES MAY ATTRIBUTE TO EPIGENETIC REGULATION. EPIGENETIC REGULATION EXPLAINS THE ASSOCIATION BETWEEN EARLY PRENATAL MATERNAL SMOKING AND LATER ASTHMA-RELATED OUTCOMES. EPIGENETIC MARKS (DNA METHYLATION, MODIFICATIONS OF HISTONE TAILS OR NONCODING RNAS) WORK WITH OTHER COMPONENTS OF THE CELLULAR REGULATORY MACHINERY TO CONTROL THE LEVELS OF EXPRESSED GENES, AND SEVERAL ALLERGY- AND ASTHMA-RELATED GENES HAVE BEEN FOUND TO BE SUSCEPTIBLE TO EPIGENETIC REGULATION, INCLUDING GENES IMPORTANT TO T-EFFECTOR PATHWAYS (IFN-GAMMA, INTERLEUKIN [IL] 4, IL-13, IL-17) AND T-REGULATORY PATHWAYS (FOXP3). THEREFORE, THE MECHANISM BY WHICH EPIGENETIC REGULATION CONTRIBUTES TO ALLERGIC DISEASES IS A CRITICAL ISSUE. IN THE PAST MOST PUBLISHED EXPERIMENTAL WORK, WITH FEW EXCEPTIONS, HAS ONLY COMPRISED SMALL OBSERVATIONAL STUDIES AND MODELS IN CELL SYSTEMS AND ANIMALS. HOWEVER, VERY RECENTLY EXCITING AND ELEGANT EXPERIMENTAL STUDIES AND NOVEL TRANSLATIONAL RESEARCH WORKS WERE PUBLISHED WITH NEW AND ADVANCED TECHNOLOGIES INVESTIGATING EPIGENETIC MARK ON A GENOMIC SCALE AND COMPREHENSIVE APPROACHES TO DATA ANALYSIS. INTERESTINGLY, A POTENTIAL LINK BETWEEN EXPOSURE TO ENVIRONMENTAL POLLUTANTS AND THE OCCURRENCE OF ALLERGIC DISEASES IS REVEALED RECENTLY, PARTICULAR IN DEVELOPED AND INDUSTRIALIZED COUNTRIES, AND ENDOCRINE DISRUPTING CHEMICALS (EDCS) AS ENVIRONMENTAL HORMONE MAY PLAY A KEY ROLE. THIS REVIEW ADDRESSES THE IMPORTANT QUESTION OF HOW EDCS (NONYLPHENOL, 4 OCTYLPHENOL, AND PHTHALATES) INFLUENCES ON ASTHMA-RELATED GENE EXPRESSION VIA EPIGENETIC REGULATION IN IMMUNE CELLS, AND HOW ANTI-ASTHMATIC AGENTS PROHIBIT EXPRESSION OF INFLAMMATORY GENES VIA EPIGENETIC MODIFICATION. THE DISCOVERY AND VALIDATION OF EPIGENETIC BIOMARKERS LINKING EXPOSURE TO ALLERGIC DISEASES MIGHT LEAD TO BETTER EPIGENOTYPING OF RISK, PROGNOSIS, TREATMENT PREDICTION, AND DEVELOPMENT OF NOVEL THERAPIES. 2014 9 4318 31 MICRORNAS IN ANKYLOSING SPONDYLITIS: FUNCTION, POTENTIAL AND CHALLENGES. EPIGENETIC MECHANISMS SUCH AS DNA METHYLATION, HISTONE MODIFICATIONS AND NON-CODING RNA, ARE CONSIDERED THE ESSENTIAL CONNECTION BETWEEN A DISORDER'S ONSET AND THE ENVIRONMENT, ON A PERMISSIVE GENETIC BACKGROUND. AMONG AUTOIMMUNE AND INFLAMMATORY-MEDIATED DISORDERS, ANKYLOSING SPONDYLITIS (AS), A CHRONIC ARTHRITIS OF THE SPINE, IS A VERY GOOD EXAMPLE FOR THE WEIGHT OF EPIGENETICS' CONTRIBUTION. MICRORNAS (MIRNAS) ARE SINGLE-STRANDED NUCLEOTIDES WHICH REGULATE GENE EXPRESSION AND ARE INVOLVED IN PATHOLOGICAL AND PHYSIOLOGICAL PROCESSES. IN THIS MANUSCRIPT WE PROVIDE A CLARIFICATION ON THE ROLE OF MICRORNAS IN AS, WITH A FOCUS ON THE MECHANISMS OF PATHOGENESIS. IN SPECIFIC, WE HAVE EXAMINED THE CONTRIBUTION OF MIRNAS IN THE PROCESSES OF INFLAMMATION, NEW BONE FORMATION AND T-CELL FUNCTION, AND THE PATHWAYS (I.E. WNT, BMP, TGFBETA SIGNALLING ETC.) THEY REGULATE. THE UTILITY OF MIRNAS IN BETTER UNDERSTANDING AS PATHOGENESIS IS UNDISPUTED AND THEIR UTILITY AS THERAPEUTIC OPPORTUNITY IS STRONGLY INCREASING. 2020 10 2029 27 EPIGENETIC CHANGES IN HEADACHE. INTRODUCTION: MULTIPLE FACTORS, INCLUDING BOTH GENETIC AND ENVIRONMENTAL MECHANISMS, APPEAR TO PLAY A ROLE IN THE AETIOLOGY OF HEADACHE. AN INTERESTING AREA OF STUDY IS THE POSSIBLE INVOLVEMENT OF EPIGENETIC MECHANISMS IN HEADACHE DEVELOPMENT AND THE TRANSFORMATION TO CHRONIC HEADACHE, AND THE POTENTIAL ROLE OF THESE FACTORS AS A THERAPEUTIC TARGET. METHODS: WE PERFORMED A LITERATURE REVIEW OF THE INVOLVEMENT OF DIFFERENT EPIGENETIC MECHANISMS IN HEADACHE, MAINLY USING THE MEDLINE/PUBMED DATABASE. TO THIS END, WE USED THE FOLLOWING ENGLISH SEARCH TERMS: HEADACHE, MIGRAINE, EPIGENETICS, DNA METHYLATION, HISTONES, NON-CODING RNA, AND MIRNA. RESULTS: A TOTAL OF 15 ENGLISH-LANGUAGE PUBLICATIONS RELATED TO THE ABOVE TERMS WERE OBTAINED. CONCLUSION: THERE IS LIMITED BUT CONSISTENT EVIDENCE OF THE RELATIONSHIP BETWEEN EPIGENETICS AND HEADACHE; IT IS THEREFORE ESSENTIAL TO CONTINUE RESEARCH OF EPIGENETIC CHANGES IN HEADACHE. THIS MAY HELP TO UNDERSTAND THE PATHOPHYSIOLOGY OF HEADACHE AND EVEN TO IDENTIFY CANDIDATE BIOMARKERS AND NEW, MORE EFFECTIVE, THERAPEUTIC TARGETS. 2021 11 2507 28 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 12 6013 40 THE APPLICATIONS OF DNA METHYLATION AS A BIOMARKER IN KIDNEY TRANSPLANTATION: A SYSTEMATIC REVIEW. BACKGROUND: ALTHOUGH KIDNEY TRANSPLANTATION IMPROVES PATIENT SURVIVAL AND QUALITY OF LIFE, LONG-TERM RESULTS ARE HAMPERED BY BOTH IMMUNE- AND NON-IMMUNE-MEDIATED COMPLICATIONS. CURRENT BIOMARKERS OF POST-TRANSPLANT COMPLICATIONS, SUCH AS ALLOGRAFT REJECTION, CHRONIC RENAL ALLOGRAFT DYSFUNCTION, AND CUTANEOUS SQUAMOUS CELL CARCINOMA, HAVE A SUBOPTIMAL PREDICTIVE VALUE. DNA METHYLATION IS AN EPIGENETIC MODIFICATION THAT DIRECTLY AFFECTS GENE EXPRESSION AND PLAYS AN IMPORTANT ROLE IN PROCESSES SUCH AS ISCHEMIA/REPERFUSION INJURY, FIBROSIS, AND ALLOREACTIVE IMMUNE RESPONSE. NOVEL TECHNIQUES CAN QUICKLY ASSESS THE DNA METHYLATION STATUS OF MULTIPLE LOCI IN DIFFERENT CELL TYPES, ALLOWING A DEEP AND INTERESTING STUDY OF CELLS' ACTIVITY AND FUNCTION. THEREFORE, DNA METHYLATION HAS THE POTENTIAL TO BECOME AN IMPORTANT BIOMARKER FOR PREDICTION AND MONITORING IN KIDNEY TRANSPLANTATION. PURPOSE OF THE STUDY: THE AIM OF THIS STUDY WAS TO EVALUATE THE ROLE OF DNA METHYLATION AS A POTENTIAL BIOMARKER OF GRAFT SURVIVAL AND COMPLICATIONS DEVELOPMENT IN KIDNEY TRANSPLANTATION. MATERIAL AND METHODS: A SYSTEMATIC REVIEW OF SEVERAL DATABASES HAS BEEN CONDUCTED. THE NEWCASTLE-OTTAWA SCALE AND THE JADAD SCALE HAVE BEEN USED TO ASSESS THE RISK OF BIAS FOR OBSERVATIONAL AND RANDOMIZED STUDIES, RESPECTIVELY. RESULTS: TWENTY ARTICLES REPORTING ON DNA METHYLATION AS A BIOMARKER FOR KIDNEY TRANSPLANTATION WERE INCLUDED, ALL USING DNA METHYLATION FOR PREDICTION AND MONITORING. DNA METHYLATION PATTERN ALTERATIONS IN CELLS ISOLATED FROM DIFFERENT TISSUES, SUCH AS KIDNEY BIOPSIES, URINE, AND BLOOD, HAVE BEEN ASSOCIATED WITH ISCHEMIA-REPERFUSION INJURY AND CHRONIC RENAL ALLOGRAFT DYSFUNCTION. THESE ALTERATIONS OCCURRED IN DIFFERENT AND SPECIFIC LOCI. DNA METHYLATION STATUS HAS ALSO PROVED TO BE IMPORTANT FOR IMMUNE RESPONSE MODULATION, HAVING A CRUCIAL ROLE IN REGULATORY T CELL DEFINITION AND ACTIVITY. RESEARCH ALSO FOCUSED ON A BETTER UNDERSTANDING OF THE ROLE OF THIS EPIGENETIC MODIFICATION ASSESSMENT FOR REGULATORY T CELLS ISOLATION AND EXPANSION FOR FUTURE TOLERANCE INDUCTION-ORIENTED THERAPIES. CONCLUSIONS: STUDIES INCLUDED IN THIS REVIEW ARE HETEROGENEOUS IN STUDY DESIGN, BIOLOGICAL SAMPLES, AND OUTCOME. MORE COORDINATED INVESTIGATIONS ARE NEEDED TO AFFIRM DNA METHYLATION AS A CLINICALLY RELEVANT BIOMARKER IMPORTANT FOR PREVENTION, MONITORING, AND INTERVENTION. 2022 13 4961 33 PATHOGENESIS OF PSORIASIS IN THE "OMIC" ERA. PART II. GENETIC, GENOMIC AND EPIGENETIC CHANGES IN PSORIASIS. PSORIASIS IS A MULTIFACTORIAL DISEASE IN WHICH GENETIC, ENVIRONMENTAL AND EPIGENETIC FACTORS REGULATING GENE EXPRESSION PLAY A KEY ROLE. IN THE "GENOMIC ERA", GENOME-WIDE ASSOCIATION STUDIES TOGETHER WITH TARGET GENOTYPING PLATFORMS PERFORMED IN DIFFERENT ETHNIC POPULATIONS HAVE FOUND MORE THAN 50 GENETIC SUSCEPTIBLE MARKERS ASSOCIATED WITH THE RISK OF PSORIASIS WHICH HAVE BEEN IDENTIFIED SO FAR. UP TILL NOW, THE STRONGEST ASSOCIATION WITH THE RISK OF THE DISEASE HAS BEEN PROVED FOR HLA-C*06 GENE. THE MAJORITY OF OTHER PSORIASIS RISK SNPS ARE SITUATED NEAR THE GENES ENCODING MOLECULES INVOLVED IN ADAPTIVE AND INNATE IMMUNITY, AND SKIN BARRIER FUNCTION. MANY CONTEMPORARY STUDIES INDICATE THAT THE EPIGENETIC CHANGES: HISTONE MODIFICATION, PROMOTER METHYLATIONS, LONG NON-CODING AND MICRO-RNA HYPEREXPRESSION ARE CONSIDERED AS FACTORS CONTRIBUTING TO PSORIASIS PATHOGENESIS AS THEY REGULATE ABNORMAL KERATINOCYTE DIFFERENTIATION AND PROLIFERATION, ABERRANT KERATINOCYTES - INFLAMMATORY CELLS COMMUNICATION, NEOANGIOGENESIS AND CHRONIC INFLAMMATION. THE CIRCULATING MIRNAS DETECTED IN THE BLOOD MAY BECOME SPECIFIC MARKERS IN THE DIAGNOSIS, PROGNOSIS AND RESPONSE TO THE TREATMENT OF THE DISEASE. THE INHIBITION OF EXPRESSION IN SELECTED MIRNAS MAY BE A NEW PROMISING THERAPY OPTION FOR PATIENTS WITH PSORIASIS. 2020 14 2553 30 EPIGENETICS IN PSORIASIS: PERSPECTIVE OF DNA METHYLATION. PSORIASIS IS A CHRONIC INFLAMMATORY SKIN DISEASE CHARACTERIZED BY EXCESSIVE PROLIFERATION OF KERATINOCYTES (KCS). ONSET OF PSORIASIS IS RELATED TO GENETIC, IMMUNE AND ENVIRONMENTAL FACTORS. THE ENVIRONMENT CAN INTERACT WITH THE GENOME THROUGH EPIGENETIC MODIFICATIONS, INCLUDING DNA METHYLATION, AND THIS MODIFICATION IS INVOLVED IN THE PATHOGENESIS OF PSORIASIS. IN ADDITION TO A SKIN DISEASE, PSORIASIS IS ALSO CONSIDERED A SYSTEMIC DISEASE. WE REVIEWED THE CURRENT LITERATURE OF PSORIATIC DNA METHYLATION FOR STUDIES FROM SEVERAL ASPECTS ON THE DNA METHYLATION DISTRIBUTION PATTERNS IN DIFFERENT TISSUES/CELLS, SINGLE-NUCLEOTIDE POLYMORPHISMS, AND CANDIDATE DISEASE GENES AND IDENTIFIED TARGET GENES REGULATED BY DNA METHYLATION THAT HAVE BEEN DIRECTLY/INDIRECTLY VALIDATED. THIS REVIEW CONTRIBUTES TO A COMPREHENSIVE UNDERSTANDING OF THE IMPORTANT A ROLE THAT DNA METHYLATION PLAYS IN PSORIASIS FROM A HOLISTIC PERSPECTIVE AND WILL PROMOTE THE IMPLEMENTATION OF DNA METHYLATION IN DIAGNOSTIC AND THERAPEUTIC STRATEGIES FOR PSORIATIC PATIENTS. 2021 15 4285 33 MICRORNA EPIGENETIC SIGNATURES IN HUMAN DISEASE. MICRORNAS (MIRNAS) ARE SHORT NON-CODING RNAS THAT ACT AS IMPORTANT REGULATORS OF GENE EXPRESSION AS PART OF THE EPIGENETIC MACHINERY. IN ADDITION TO POSTTRANSCRIPTIONAL GENE SILENCING BY MIRNAS, THE EPIGENETIC MECHANISMS ALSO INCLUDE DNA METHYLATION, HISTONE MODIFICATIONS AND THEIR CROSSTALK. EPIGENETIC MODIFICATIONS WERE REPORTED TO PLAY AN IMPORTANT ROLE IN MANY DISEASE ONSETS AND PROGRESSIONS AND CAN BE USED TO EXPLAIN SEVERAL FEATURES OF COMPLEX DISEASES, SUCH AS LATE ONSET AND FLUCTUATION OF SYMPTOMS. HOWEVER, MIRNAS NOT ONLY FUNCTION AS A PART OF EPIGENETIC MACHINERY, BUT ARE ALSO EPIGENETICALLY MODIFIED BY DNA METHYLATION AND HISTONE MODIFICATION LIKE ANY OTHER PROTEIN-CODING GENE. THERE IS A STRONG CONNECTION BETWEEN EPIGENOME AND MIRNOME, AND ANY DYSREGULATION OF THIS COMPLEX SYSTEM CAN RESULT IN VARIOUS PHYSIOLOGICAL AND PATHOLOGICAL CONDITIONS. IN ADDITION, MIRNAS PLAY AN IMPORTANT ROLE IN TOXICOGENOMICS AND MAY EXPLAIN THE RELATIONSHIP BETWEEN TOXICANT EXPOSURE AND TUMORIGENESIS. THE PRESENT REVIEW PROVIDES INFORMATION ON 63 MIRNA GENES SHOWN TO BE EPIGENETICALLY REGULATED IN ASSOCIATION WITH 21 DISEASES, INCLUDING 11 CANCER TYPES: CARDIAC FIBROSIS, CARDIOVASCULAR DISEASE, PREECLAMPSIA, HIRSCHSPRUNG'S DISEASE, RHEUMATOID ARTHRITIS, SYSTEMIC SCLEROSIS, SYSTEMIC LUPUS ERYTHEMATOSUS, TEMPORAL LOBE EPILEPSY, AUTISM, PULMONARY FIBROSIS, MELANOMA, ACUTE MYELOID LEUKEMIA, CHRONIC LYMPHOCYTIC LEUKEMIA, COLORECTAL, GASTRIC, CERVICAL, OVARIAN, PROSTATE, LUNG, BREAST, AND BLADDER CANCER. THE REVIEW REVEALED THAT HSA-MIR-34A, HSA-MIR-34B, AND HSA-MIR-34C ARE THE MOST FREQUENTLY REPORTED EPIGENETICALLY DYSREGULATED MIRNAS. THERE IS A NEED TO FURTHER STUDY MOLECULAR MECHANISMS OF VARIOUS DISEASES TO BETTER UNDERSTAND THE CROSSTALK BETWEEN EPIGENETICS AND GENE EXPRESSION AND TO DEVELOP NEW THERAPEUTIC OPTIONS AND BIOMARKERS. 2016 16 2534 37 EPIGENETICS IN BIPOLAR DISORDER: A CRITICAL REVIEW OF THE LITERATURE. INTRODUCTION: BIPOLAR DISORDER (BD) IS A CHRONIC, DISABLING DISEASE CHARACTERISED BY ALTERNATE MOOD EPISODES, SWITCHING THROUGH DEPRESSIVE AND MANIC/HYPOMANIC PHASES. MOOD STABILIZERS, IN PARTICULAR LITHIUM SALTS, CONSTITUTE THE CORNERSTONE OF THE TREATMENT IN THE ACUTE PHASE AS WELL AS FOR THE PREVENTION OF RECURRENCES. THE PATHOPHYSIOLOGY OF BD AND THE MECHANISMS OF ACTION OF MOOD STABILIZERS REMAIN LARGELY UNKNOWN BUT SEVERAL PIECES OF EVIDENCE POINT TO GENE X ENVIRONMENT INTERACTIONS. EPIGENETICS, DEFINED AS THE REGULATION OF GENE EXPRESSION WITHOUT GENETIC CHANGES, COULD BE THE MOLECULAR SUBSTRATE OF THESE INTERACTIONS. IN THIS LITERATURE REVIEW, WE SUMMARIZE THE MAIN EPIGENETIC FINDINGS ASSOCIATED WITH BD AND RESPONSE TO MOOD STABILIZERS. METHODS: WE SEARCHED PUBMED, AND EMBASE DATABASES AND CLASSIFIED THE ARTICLES DEPENDING ON THE EPIGENETIC MECHANISMS (DNA METHYLATION, HISTONE MODIFICATIONS AND NON-CODING RNAS). RESULTS: WE PRESENT THE DIFFERENT EPIGENETIC MODIFICATIONS ASSOCIATED WITH BD OR WITH MOOD-STABILIZERS. THE MAJOR REPORTED MECHANISMS WERE DNA METHYLATION, HISTONE METHYLATION AND ACETYLATION, AND NON-CODING RNAS. OVERALL, THE ASSESSMENTS ARE POORLY HARMONIZED AND THE RESULTS ARE MORE LIMITED THAN IN OTHER PSYCHIATRIC DISORDERS (E.G. SCHIZOPHRENIA). HOWEVER, THE NATURE OF BD AND ITS TREATMENT OFFER EXCELLENT OPPORTUNITIES FOR EPIGENETIC RESEARCH: CLEAR IMPACT OF ENVIRONMENTAL FACTORS, CLINICAL VARIATION BETWEEN MANIC OR DEPRESSIVE EPISODES RESULTING IN POSSIBLE IDENTIFICATION OF STATE AND TRAITS BIOMARKERS, DOCUMENTED IMPACT OF MOOD-STABILIZERS ON THE EPIGENOME. CONCLUSION: EPIGENETIC IS A GROWING AND PROMISING FIELD IN BD THAT MAY SHED LIGHT ON ITS PATHOPHYSIOLOGY OR BE USEFUL AS BIOMARKERS OF RESPONSE TO MOOD-STABILIZER. 2021 17 4228 23 METHYLATION OF INFLAMMATORY CELLS IN LUNG DISEASES. THIS CHAPTER OVERVIEWS ROLES OF DNA METHYLATION IN INFLAMMATORY CELL BIOLOGY WITH THE FOCUSES ON LYMPHOCYTES AND MACROPHAGES/MONOCYTES IN LUNG DISEASES, ALTHOUGH THE MOLECULAR MECHANISMS BY WHICH TARGET GENES ARE METHYLATED AND REGULATED IN LUNG DISEASES REMAIN UNCLEAR. MOST OF EPIGENETIC STUDIES ON DNA METHYLATION OF TARGET GENES IN LUNG DISEASES MAINLY DEMONSTRATED THE CORRELATION OF DNA METHYLATION OF TARGET GENES WITH THE LEVELS OF OTHER CORRESPONDING FACTORS, WITH THE SPECIFICITY OF CLINICAL PHENOMES, AND WITH THE SEVERITY OF LUNG DISEASES. THERE IS AN URGENT NEED TO IDENTIFY AND VALIDATE THE SPECIFICITY AND REGULATORY MECHANISMS OF INFLAMMATORY CELL EPIGENETICS IN DEPTH. THE EPIGENETIC HETEROGENEITY AMONG DIFFERENT SUBSETS OF T CELLS AND AMONG PROMOTERS OR NON-PROMOTERS OF TARGET GENES SHOULD BE FURTHERMORE CLARIFIED IN ACUTE OR CHRONIC LUNG DISEASES AND CANCERS. THE HYPER/HYPO-METHYLATION AND MODIFICATIONS OF CHROMOSOL AND EXTRACHROMOSOMAL DNA MAY RESULT IN ALTERNATIONS IN PROTEINS WITHIN INFLAMMATORY CELLS, WHICH CAN BE IDENTIFIED AS DISEASE-SPECIFIC BIOMARKERS AND THERAPEUTIC TARGETS. 2020 18 528 36 ASTHMA EPIGENETICS. ASTHMA IS THE MOST COMMON CHRONIC DISEASE OF CHILDHOOD, AND A GROWING BODY OF EVIDENCE INDICATES THAT EPIGENETIC VARIATIONS MAY MEDIATE THE EFFECTS OF ENVIRONMENTAL EXPOSURES ON THE DEVELOPMENT AND NATURAL HISTORY OF ASTHMA. EPIGENETICS IS THE STUDY OF MITOTICALLY OR MEIOTICALLY HERITABLE CHANGES IN GENE EXPRESSION THAT OCCUR WITHOUT DIRECTLY ALTERING THE DNA SEQUENCE. DNA METHYLATION, HISTONE MODIFICATIONS AND MICRORNAS ARE MAJOR EPIGENETIC VARIATIONS IN HUMANS THAT ARE CURRENTLY BEING INVESTIGATED FOR ASTHMA ETIOLOGY AND NATURAL HISTORY. DNA METHYLATION RESULTS FROM ADDITION OF A METHYL GROUP TO THE 5 POSITION OF A CYTOSINE RING AND OCCURS ALMOST EXCLUSIVELY ON A CYTOSINE IN A CPG DINUCLEOTIDE. HISTONE MODIFICATIONS INVOLVE POSTTRANSLATIONAL MODIFICATIONS SUCH AS ACETYLATION, METHYLATION, PHOSPHORYLATION AND UBIQUITINATION ON THE TAILS OF CORE HISTONES. MICRORNAS ARE SHORT ~22 NUCLEOTIDE LONG, NON-CODING, SINGLE-STRANDED RNAS THAT BINDS TO COMPLEMENTARY SEQUENCES IN THE TARGET MRNAS, USUALLY RESULTING IN GENE SILENCING. WHILE MANY STUDIES HAVE DOCUMENTED RELATIONSHIPS OF ENVIRONMENTAL EXPOSURES THAT HAVE BEEN IMPLICATED IN ASTHMA ETIOLOGY WITH EPIGENETIC ALTERATIONS, TO DATE, FEW STUDIES HAVE DIRECTLY LINKED EPIGENETIC VARIATIONS WITH ASTHMA DEVELOPMENT. THERE ARE SEVERAL METHODOLOGICAL CHALLENGES IN STUDYING THE EPIGENETICS OF ASTHMA. IN THIS CHAPTER, THE INFLUENCE OF EPIGENETIC VARIATIONS ON ASTHMA PATHOPHYSIOLOGY, METHODOLOGICAL CONCERNS IN CONDUCTING EPIGENETIC RESEARCH AND FUTURE DIRECTION OF ASTHMA EPIGENETICS RESEARCH ARE DISCUSSED. 2014 19 1508 38 DNA METHYLATION AND MRNA AND MICRORNA EXPRESSION OF SLE CD4+ T CELLS CORRELATE WITH DISEASE PHENOTYPE. SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) IS AN AUTOIMMUNE DISEASE WELL KNOWN FOR ITS CLINICAL HETEROGENEITY, AND ITS ETIOLOGY SECONDARY TO A CROSS-TALK INVOLVING GENETIC PREDISPOSITION AND ENVIRONMENTAL STIMULI. ALTHOUGH GENOME-WIDE ANALYSIS HAS CONTRIBUTED GREATLY TO OUR UNDERSTANDING OF THE GENETIC BASIS OF SLE, THERE IS INCREASING EVIDENCE FOR A ROLE OF EPIGENETICS. INDEED, RECENT DATA HAVE DEMONSTRATED THAT IN PATIENTS WITH SLE, THERE ARE STRIKING ALTERATIONS OF DNA METHYLATION, HISTONE MODIFICATIONS, AND DEREGULATED MICRORNA EXPRESSION, THE SUM OF WHICH CONTRIBUTE TO OVER-EXPRESSION OF SELECT AUTOIMMUNE-RELATED GENES AND LOSS OF TOLERANCE. TO ADDRESS THIS ISSUE AT THE LEVEL OF CLINICAL PHENOTYPE, WE PERFORMED DNA METHYLATION, MRNA AND MICRORNA EXPRESSION SCREENING USING HIGH-THROUGHPUT SEQUENCING OF PURIFIED CD4+ T CELLS FROM PATIENTS WITH SLE, COMPARED TO AGE AND SEX MATCHED CONTROLS. IN PARTICULAR, WE STUDIED 42 PATIENTS WITH SLE AND DIVIDED THIS GROUP INTO THREE CLINICAL PHENOTYPES: A) THE PRESENCE OF SKIN LESIONS WITHOUT SIGNS OF SYSTEMIC PATHOLOGY; B) SKIN LESIONS BUT ALSO CHRONIC RENAL PATHOLOGY; AND C) SKIN LESIONS, CHRONIC RENAL PATHOLOGY AND POLYARTICULAR DISEASE. INTERESTINGLY, AND AS EXPECTED, SEQUENCING DATA REVEALED CHANGES IN DNA METHYLATION IN SLE COMPARED TO CONTROLS. HOWEVER, AND MORE IMPORTANTLY, ALTHOUGH THERE WERE COMMON METHYLATION CHANGES FOUND IN ALL GROUPS OF SLE COMPARED TO CONTROLS, THERE WAS SPECIFIC DNA METHYLATION CHANGES THAT CORRELATED WITH CLINICAL PHENOTYPE. THESE INCLUDED CHANGES IN THE NOVEL KEY TARGET GENES NLRP2, CD300LB AND S1PR3, AS WELL AS CHANGES IN THE CRITICAL PATHWAYS, INCLUDING THE ADHERENS JUNCTION AND LEUKOCYTE TRANSENDOTHELIAL MIGRATION. WE ALSO NOTED THAT A SIGNIFICANT PROPORTION OF GENES UNDERGOING DNA METHYLATION CHANGES WERE INVERSELY CORRELATED WITH GENE EXPRESSION AND THAT MIRNA SCREENING REVEALED THE EXISTENCE OF SUBSETS WITH CHANGES IN EXPRESSION. INTEGRATED ANALYSIS OF THIS DATA HIGHLIGHTS SPECIFIC SETS OF MIRNAS CONTROLLED BY DNA METHYLATION, AND GENES THAT ARE ALTERED BY METHYLATION AND TARGETED BY MIRNAS. IN CONCLUSION, OUR FINDINGS SUGGEST SELECT EPIGENETIC MECHANISMS THAT CONTRIBUTE TO CLINICAL PHENOTYPES AND FURTHER SHED LIGHT ON A NEW VENUE FOR BASIC SLE RESEARCH. 2014 20 6288 37 THE POTENTIAL ROLE OF EPIGENETIC MODIFICATIONS ON DIFFERENT FACETS IN THE PERIODONTAL PATHOGENESIS. PERIODONTITIS IS A CHRONIC INFLAMMATORY DISEASE THAT AFFECTS THE SUPPORTING STRUCTURES OF TEETH. IN THE LITERATURE, THE ASSOCIATION BETWEEN THE PATHOGENICITY OF BACTERIA AND ENVIRONMENTAL FACTORS IN THIS REGARD HAVE BEEN EXTENSIVELY EXAMINED. IN THE PRESENT STUDY, WE WILL SHED LIGHT ON THE POTENTIAL ROLE THAT EPIGENETIC CHANGE CAN PLAY ON DIFFERENT FACETS OF ITS PROCESS, MORE PARTICULARLY THE MODIFICATIONS CONCERNING THE GENES INVOLVED IN INFLAMMATION, DEFENSE, AND IMMUNE SYSTEMS. SINCE THE 1960S, THE ROLE OF GENETIC VARIANTS IN THE ONSET AND SEVERITY OF PERIODONTAL DISEASE HAS BEEN WIDELY DEMONSTRATED. THESE MAKE SOME PEOPLE MORE SUSCEPTIBLE TO DEVELOPING IT THAN OTHERS. IT HAS BEEN DOCUMENTED THAT THE WIDE VARIATION IN ITS FREQUENCY FOR VARIOUS RACIAL AND ETHNIC POPULATIONS IS DUE PRIMARILY TO THE COMPLEX INTERPLAY AMONG GENETIC FACTORS WITH THOSE AFFECTING THE ENVIRONMENT AND THE DEMOGRAPHY. IN MOLECULAR BIOLOGY, EPIGENETIC MODIFICATIONS ARE DEFINED AS ANY CHANGE IN THE PROMOTER FOR THE CPG ISLANDS, IN THE STRUCTURE OF THE HISTONE PROTEIN, AS WELL AS POST-TRANSLATIONAL REGULATION BY MICRORNAS (MIRNAS), BEING KNOWN TO CONTRIBUTE TO THE ALTERATION IN GENE EXPRESSION FOR COMPLEX MULTIFACTORIAL DISEASES SUCH AS PERIODONTITIS. THE KEY ROLE OF EPIGENETIC MODIFICATION IS TO UNDERSTAND THE MECHANISM INVOLVED IN THE GENE-ENVIRONMENT INTERACTION, AND THE DEVELOPMENT OF PERIODONTITIS IS NOW THE SUBJECT OF MORE AND MORE STUDIES THAT ATTEMPT TO IDENTIFY WHICH FACTORS ARE STIMULATING IT, BUT ALSO AFFECT THE REDUCED RESPONSE TO THERAPY. 2023