1 4962 147 PATHOGENESIS OF PSORIATIC ARTHRITIS. PSORIATIC ARTHRITIS (PSA) IS A CHRONIC INFLAMMATORY ARTHROPATHY INVOLVING SYNOVIAL AND ENTHESEAL STRUCTURES, ASSOCIATED WITH PSORIASIS OR SIMILAR CONDITIONS. THE ETIOPATHOGENETIC MECHANISMS UNDERLYING PSA REMAIN UNCLARIFIED. THE MOST ACCREDITED HYPOTHESIS INVOLVES A COMPLEX INTERACTION AMONG GENETIC, ENVIRONMENTAL, AND IMMUNOLOGICAL FACTORS. ENVIRONMENTAL AGENTS, PARTICULARLY TRAUMA, MECHANICAL STRESS, AND SMOKE HAVE BEEN CITED AS POSSIBLE FACTORS IN TRIGGERING THE DISEASE IN GENETICALLY PREDISPOSED SUBJECTS. LIKE OTHER FORMS OF SPONDYLOARTHROPATHIES, PSA SHOWS SEVERAL GENETIC ASSOCIATIONS WITH THE MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) CLASS I ALLELES LOCATED ON CHROMOSOME 6P21.3, PARTICULARLY THE HUMAN LEUKOCYTE ANTIGEN (HLA)-B27 IN AXIAL PHENOTYPES. RECENT STUDIES HAVE DEMONSTRATED THAT THE MOST COMMON EPIGENETIC MECHANISMS THAT REGULATE GENE EXPRESSION IN PSA ARE REPRESENTED BY DNA METHYLATION, PARENT OF ORIGIN EFFECT OR GENOMIC IMPRINTING, EXPRESSION OR ACTIVITY OF EPIGENETIC MODIFYING ENZYMES, AND RNA INTERFERENCE (RNAI) BY MICRORNAS (MIRNAS). THE MECHANISMS UNDERLYING PSA PATHOGENESIS ACTIVATE THE INNATE AND ADAPTIVE IMMUNE SYSTEM AND OVEREXPRESSION OF TNF ASSOCIATED WITH AMPLIFICATION OF THE IL-23/IL-17 AXIS. IN RECENT YEARS, MORE PSA SUSCEPTIBILITY GENES AND EPIGENETIC MECHANISMS HAVE BEEN IDENTIFIED. ADVANCES IN THE KNOWLEDGE OF INNATE AND ADAPTIVE IMMUNE MECHANISMS UNDERLYING PSA HAVE CONTRIBUTED TO A BETTER UNDERSTANDING OF THE HETEROGENEOUS CLINICAL EXPRESSION OF THE DISEASE AND, THUS, TO THERAPY STRATEGIES. THE COMPLEXITY OF THE PATHOGENETIC ASPECTS INVOLVING MULTIPLE CYTOKINES, CELL LINES, AND MOLECULES NEEDS TO BE FURTHER INVESTIGATED TO ADVANCE PERSONALIZED THERAPEUTIC STRATEGIES AND TO IMPROVE OUTCOMES OF PATIENTS AFFECTED BY PSA. 2019 2 6343 45 THE ROLE OF EPIGENETICS AND IMMUNOLOGICAL IMBALANCE IN THE ETIOPATHOGENESIS OF PSORIASIS AND PSORIATIC ARTHRITIS. PSORIASIS (PS) AND PSORIATIC ARTHRITIS (PSA) REPRESENT A CLINICAL AND IMMUNOPATHOGENIC CONTINUUM, CALLED PSORIATIC DISEASE, CUMULATIVELY AFFECTING APPROXIMATELY 3% OF THE GENERAL POPULATION. PSORIATIC DISEASE IS A CHRONIC INFLAMMATORY DISORDER AFFECTING THE SKIN AND MUSCULOSKELETAL SYSTEM. THE IMMUNO-PATHOGENESIS IS CHARACTERIZED BY AN ACTIVATION OF THE TNF/IL-23/IL-17 CYTOKINE AXIS, LEADING TO AN IMMUNOLOGIC IMBALANCE OF T-CELLS RESIDENT IN ALL AFFECTED TISSUES, MAINLY ENTHESES. IN THE MAJORITY OF CASES, SKIN PS PREDATES RHEUMATOLOGICAL MANIFESTATIONS. SECONDARY TO THE HIGHER INCIDENCE AND THE AVAILABILITY OF MOUSE MODELS, THERE IS STRONGER DATA AVAILABLE ON SKIN PS, AND DATA ARE, IN MOST CASES, RELEVANT ALSO TO PSA. IN A WIDELY ACCEPTED MODEL, ENVIRONMENTAL TRIGGER FACTORS LIKE INFECTIONS OR TRAUMA ARE CAPABLE OF INITIATING AN INFLAMMATORY CASCADE, ULTIMATELY CREATING A SUSTAINED STATE OF CHRONIC INFLAMMATION IN GENETICALLY SUSCEPTIBLE INDIVIDUALS. BESIDES WELL-KNOWN GENETIC SUSCEPTIBILITY LOCI, EPIGENETIC DNA MODIFICATIONS, WHICH ARE ASSOCIATED WITH PS DEVELOPMENT HAVE BEEN CHARACTERIZED RECENTLY AND WILL BE DISCUSSED IN THIS ARTICLE. THE CURRENT EVIDENCE IS PROMISING IN THE POSSIBILITY TO PROVIDE NEW THERAPEUTIC AVENUES AND FILL THE UNMET NEED OF PATIENTS, FOR WHOM CURRENT TREATMENTS EITHER DO NOT ALLOW THE DISEASE TO BE CONTROLLED OR MUST BE CONTINUED FOR LIFE. 2019 3 4319 38 MICRORNAS IN AXIAL SPONDYLARTHRITIS: AN OVERVIEW OF THE RECENT PROGRESSES IN THE FIELD WITH A FOCUS ON ANKYLOSING SPONDYLITIS AND PSORIATIC ARTHRITIS. PURPOSE OF REVIEW: TO HIGHLIGHT THE RECENT DISCOVERIES AND LINES OF EVIDENCE ON THE ROLE OF MICRORNAS IN ANKYLOSING SPONDYLITIS (AS) AND PSORIATIC ARTHRITIS (PSA), FOCUSING ON THEIR EXPRESSION PROFILING AND MECHANISMS OF ACTION. RECENT FINDINGS: AS AND PSA ARE CHRONIC INFLAMMATORY MUSCULOSKELETAL DISEASES WITH AXIAL MANIFESTATIONS AND REPRESENT AN EXCELLENT MODEL FOR STUDYING MICRORNAS CONTRIBUTION TO THE DISEASE PATHOGENESIS, PARTICULARLY THROUGH IMMUNOMODULATION, INFLAMMATION, AND BONE REMODELLING, OR THEIR VALUE AS CANDIDATE DIAGNOSTIC AND PROGNOSTIC BIOMARKERS. MICRORNAS ARE SINGLE-STRANDED NUCLEOTIDES ABLE TO REGULATE GENE EXPRESSION. THEY ARE A KEY COMPONENT OF THE EPIGENETIC MACHINERY, INVOLVED IN PHYSIOLOGICAL AND PATHOLOGICAL PROCESSES. THE CONTRIBUTION OF MICRORNAS IN AS AND PSA (SUCH AS MIR-29A IN REGULATING BONE METABOLISM) IS HIGHLIGHTED BY SEVERAL WORKS IN THE FIELD BUT THEIR UTILITY AS POSSIBLE MARKERS MUST BE STILL CONFIRMED, PARTICULARLY IN LARGER PATIENTS' COHORTS. 2021 4 4883 41 OVERVIEW OF THE MOLECULAR DETERMINANTS CONTRIBUTING TO THE EXPRESSION OF PSORIASIS AND PSORIATIC ARTHRITIS PHENOTYPES. PSORIASIS AND PSORIATIC ARTHRITIS ARE MULTIFACTORIAL CHRONIC DISORDERS WHOSE ETIOPATHOGENESIS ESSENTIALLY DERIVES FROM THE ALTERATION OF SEVERAL SIGNALLING PATHWAYS AND THE CO-OCCURRENCE OF GENETIC, EPIGENETIC AND NON-GENETIC SUSCEPTIBILITY FACTORS THAT ALTOGETHER AFFECT THE FUNCTIONAL AND STRUCTURAL PROPERTY OF THE SKIN. ALTHOUGH SHARED AND DIFFERENTIAL SUSCEPTIBILITY GENES AND MOLECULAR PATHWAYS ARE KNOWN TO CONTRIBUTE TO THE ONSET OF PATHOLOGICAL PHENOTYPES, FURTHER RESEARCH IS NEEDED TO DISSECT THE MOLECULAR CAUSES OF PSORIATIC DISEASE AND ITS PROGRESSION TOWARDS PSORIATIC ARTHRITIS. THIS REVIEW WILL THEREFORE BE ADDRESSED TO EXPLORE DIFFERENCES AND SIMILARITIES IN THE ETIOPATHOGENESIS AND PROGRESSION OF BOTH DISORDERS, WITH A PARTICULAR FOCUS ON GENES INVOLVED IN THE MAINTENANCE OF THE SKIN STRUCTURE AND INTEGRITY (KERATINS AND COLLAGENS), MODULATION OF PATTERNS OF RECOGNITION (THROUGH TOLL-LIKE RECEPTORS AND DECTIN-1) AND IMMUNO-INFLAMMATORY RESPONSE (BY NLRP3-DEPENDENT INFLAMMASOME) TO MICROBIAL PATHOGENS. IN ADDITION, SPECIAL EMPHASIS WILL BE GIVEN TO THE CONTRIBUTION OF EPIGENETIC ELEMENTS (METHYLATION PATTERN, NON-CODING RNAS, CHROMATIN MODIFIERS AND 3D GENOME ORGANIZATION) TO THE ETIOPATHOGENESIS AND PROGRESSION OF PSORIASIS AND PSORIATIC ARTHRITIS. THE EVIDENCE DISCUSSED IN THIS REVIEW HIGHLIGHTS HOW THE KNOWLEDGE OF PATIENTS' CLINICAL AND (EPI)GENOMIC MAKE-UP COULD BE HELPFUL FOR IMPROVING THE AVAILABLE THERAPEUTIC STRATEGIES FOR PSORIASIS AND PSORIATIC ARTHRITIS TREATMENT. 2020 5 2591 45 EPIGENETICS OF PSORIASIS. PSORIASIS IS A CHRONIC AND RECURRENT INFLAMMATORY SKIN DISEASE, INVOLVING THE RAPID PROLIFERATION AND ABNORMAL DIFFERENTIATION OF KERATINOCYTES AND ACTIVATION OF T CELLS. IT IS GENERALLY ACCEPTED THAT THE CENTRAL PATHOGENESIS OF PSORIASIS IS A T CELL-DOMINANT IMMUNE DISORDER AFFECTED BY MULTIPLE FACTORS INCLUDING GENETIC SUSCEPTIBILITY, ENVIRONMENTAL FACTORS, INNATE AND ADAPTIVE IMMUNE RESPONSES, ETC. HOWEVER, THE EXACT ETIOLOGY IS LARGELY UNKNOWN. IN RECENT YEARS, EPIGENETIC INVOLVEMENTS, SUCH AS THE DNA METHYLATION, CHROMATIN MODIFICATIONS, AND NONCODING RNA REGULATION ARE REPORTED TO BE CRITICAL FOR THE PATHOGENESIS OF PSORIASIS. HOWEVER, THE INTERPLAY BETWEEN THESE FACTORS HAS ONLY RECENTLY BEEN STARTED TO BE UNRAVELED. NOTABLY, INHIBITORS OF ENZYMES THAT WORK IN EPIGENETIC MODIFICATIONS, SUCH AS DNA METHYLTRANSFERASES AND HISTONE DEACETYLASES, ARE BEGINNING TO APPEAR IN THE CLINICAL SETTING TO RESTORE NORMAL EPIGENETIC PATTERNS (GENERALI ET AL. IN J AUTOIMMUN 83:51-61, 2017), PROVIDING NOVEL THERAPEUTIC POTENTIAL AS NOVEL TREATMENT TARGETS FOR PSORIASIS. INDEED, MEDICATIONS PREVIOUSLY USED TO TREAT AUTOIMMUNE DISEASES HAVE LATER BEEN DISCOVERED TO EXERT THEIR ACTION VIA EPIGENETIC MECHANISMS. HEREIN, WE REVIEW THE FINDINGS ON EPIGENETICS ASSOCIATED WITH PSORIASIS, AND DISCUSS FUTURE PERSPECTIVES IN THIS FIELD. 2020 6 6624 44 UNDERSTANDING PSORIASIS: ROLE OF MIRNAS. PSORIASIS IS A CHRONIC, IMMUNE-MEDIATED INFLAMMATORY SKIN DISEASE, WITH A MULTIFACTORIAL ETIOLOGY AND IMPORTANT IMMUNOLOGIC, GENETIC AND ENVIRONMENTAL COMPONENTS. PSORIASIS VULGARIS REPRESENTS ITS MOST COMMON FORM, WITH A VARIABLE PREVALENCE ACROSS THE GLOBE. ALTHOUGH ITS PATHOGENESIS REMAINS TO BE FULLY ELUCIDATED, A LACK OF BALANCE IN THE EPIGENETIC NETWORK HAS BEEN SHOWN TO TRIGGER CERTAIN ELEMENTS OF THIS DISEASE, POSSIBLY ALTERING ITS OUTCOME. MICRORNAS ARE SMALL NON-CODING RNA MOLECULES INVOLVED IN RNA-SILENCING AND THE POST-TRANSCRIPTIONAL REGULATION OF GENE EXPRESSION, WHICH ALSO APPEAR TO MEDIATE THE IMMUNE DYSFUNCTION IN PSORIASIS. ALTHOUGH MICRORNA RESEARCH IS A NEW FIELD IN DERMATOLOGY AND PSORIASIS, THERE IS RAPIDLY ACCUMULATING EVIDENCE FOR ITS MAJOR CONTRIBUTION IN THE PATHOGENESIS OF CHRONIC INFLAMMATORY CONDITIONS, INCLUDING PSORIASIS AND OTHER DERMATOLOGICAL DISORDERS. FURTHERMORE, CIRCULATING MIRNAS IDENTIFIED IN PATIENTS' BLOOD SAMPLES HAVE BEEN IDENTIFIED AS PROMISING BIOMARKERS OF DIAGNOSIS, PROGNOSIS OR TREATMENT RESPONSE. EXTENDED INVESTIGATIONS IN THIS FIELD ARE REQUIRED, AS UNTIL NOW, THE EXACT INVOLVEMENT OF MIRNAS IN PSORIASIS HAVE REMAINED TO BE ENTIRELY ELUCIDATED. THIS SHORT REVIEW HIGHLIGHTS A NUMBER OF THE ROLES OF MIRNAS FOUND IN DIFFERENT STAGES OF PSORIASIS. 2018 7 4318 34 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 8 2945 32 GENETIC AND EPIGENETIC BASIS OF PSORIASIS PATHOGENESIS. PSORIASIS IS A CHRONIC INFLAMMATORY SKIN DISEASE WHOSE PREVALENCE VARIES AMONG DIFFERENT POPULATIONS WORLDWIDE. IT IS A COMPLEX MULTI-FACTORIAL DISEASE AND THE EXACT ETIOLOGY IS LARGELY UNKNOWN. FAMILY BASED STUDIES HAVE INDICATED A GENETIC PREDISPOSITION; HOWEVER THEY CANNOT FULLY EXPLAIN THE DISEASE PATHOGENESIS. IN ADDITION TO GENETIC SUSCEPTIBILITY, ENVIRONMENTAL AS WELL AS GENDER AND AGE RELATED FACTORS WERE ALSO BEEN FOUND TO BE ASSOCIATED. RECENTLY, IMBALANCES IN EPIGENETIC NETWORKS ARE INDICATED TO BE CAUSATIVE ELEMENTS IN PSORIASIS. THE PRESENT KNOWLEDGE OF EPIGENETIC INVOLVEMENT, MAINLY THE DNA METHYLATION, CHROMATIN MODIFICATIONS AND MIRNA DEREGULATION IS SURVEYED HERE. AN INTEGRATED APPROACH CONSIDERING GENETIC AND EPIGENETIC ANOMALIES IN THE LIGHT OF IMMUNOLOGICAL NETWORK MAY EXPLORE THE PATHOGENESIS OF PSORIASIS. 2015 9 1935 39 ENVIRONMENTAL RISK FACTORS AND EPIGENETIC ALTERNATIONS IN PSORIASIS. INTRODUCTION AND OBJECTIVE: PSORIASIS ISA QUITE COMMON, CHRONIC AND IMMUNE-MEDIATED SKIN DISORDER. THE PREVALENCE OF PSORIASIS DIFFERS IN VARIOUS COUNTRIES, BUT IT IS SAID TO AFFECT 2% OF THE WORLD'S POPULATION IN GENERAL. PSORIASIS HAS MANY DIFFERENT CLINICAL FEATURES BUT ALL LESIONS HAVE THE SAME CHARACTERISTIC: ERYTHEMA, THICKENING AND SCALE, ALTHOUGH OTHER CLINICAL FEATURES ARE ALSO CONNECTED, SUCH AS PSORIATIC ARTHRITIS, OBESITY AND METABOLIC SYNDROME. ALL OF THESE MAY LEAD TO CONDITIONS IMPAIRING THE QUALITY OF LIFE. THIS REVIEW IS AN ATTEMPT TO SUMMARIZE RECENT DATA REGARDING ENVIRONMENTAL FACTORS, TOGETHER WITH EPIGENETIC MARKERS AND PROCESSES PLAYING AN IMPORTANT ROLE IN PSORIASIS. STATE OF KNOWLEDGE: MANY DIFFERENT ENVIRONMENTAL FACTORS PLAY A ROLE IN GENETICALLY PREDISPOSED PATIENTS. THIS IS CAUSES EPIGENETIC ALTERNATIONS WHICH MAY BE A LINKING PART IN THE WHOLE PROCESS. MANY STUDIES HAVE INDICATED A CONNECTION BETWEEN PSORIASIS AND VARIOUS GENES AND ANTIGENS. THE PRESENCE OF HLA-CW6 IS COMMON AS WELL A STRONG LINK BETWEEN ITS PRESENCE AND THE ONSET OF PSORIASIS BEING OBSERVED. THE MAIN ALTERNATIONS ARE DNA METHYLATION, HISTONE'S MODIFICATIONS AND THE ROLE OF MICRORNA. EXCESSIVE REACTION IS USUALLY NOT PRESENT WITHOUT A TRIGGERING FACTOR. ENVIRONMENTAL FACTORS ARE MOSTLY RATED, SUCH AS DRUGS, LIFE STYLE AND HABITS (SMOKING, ALCOHOL), DIET, PHYSICAL TRAUMA (SKIN INJURY PROVOKING KOEBNER PHENOMENON), STRESS, MICROORGANISM AND INFECTIONS. CONCLUSIONS: THE CORRELATION BETWEEN PATHOGENESIS OF PSORIASIS AND ENVIRONMENTAL RISK FACTORS, TOGETHER WITH EPIGENETIC ALTERNATIONS STILL REQUIRE MORE INVESTIGATION. EDUCATION ABOUT DIET HABITS, NUTRITION, WEIGHT LOSS AND HEALTHY LIFESTYLE SEEMS TO BE IMPORTANT DURING THE TREATMENT OF PSORIASIS. 2020 10 4961 43 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 11 6114 47 THE EPIGENETIC CONTRIBUTION TO THE PATHOGENESIS OF PSORIASIS: RECENT ADVANCES. PSORIASIS IS DEFINED AS A CHRONIC AUTOIMMUNE DISORDER OF THE SKIN IN WHICH ABNORMAL PROLIFERATION AND DIFFERENTIATION OF KERATINOCYTES ARE BLAMED AS THE CENTRAL CULPRIT OF DISEASE ETIOPATHOGENESIS. A COMPLEX INTERPLAY BETWEEN ENVIRONMENTAL FACTORS AND GENETIC RISK FACTORS HAS BEEN SUGGESTED TO TRIGGER THE DISEASE. HOWEVER, EPIGENETIC REGULATION APPEARS TO CONNECT EXTERNAL STIMULI AND GENETIC ABNORMALITIES IN THE DEVELOPMENT OF PSORIASIS. THE DISCORDANCE IN THE PREVALENCE OF PSORIASIS BETWEEN MONOZYGOTIC TWINS AND ENVIRONMENTAL FACTORS THAT CONTRIBUTE TO ITS ONSET HAVE CAUSED A PARADIGM SHIFT REGARDING THE MECHANISMS UNDERLYING THE PATHOGENESIS OF THIS DISEASE. EPIGENETIC DYSREGULATION MAY BE INVOLVED IN ABERRANCIES OF KERATINOCYTE DIFFERENTIATION, T-CELL ACTIVATION, AND OTHER PLAUSIBLE CELLS, LEADING TO THE INITIATION AND PERPETUATION OF PSORIASIS. EPIGENETICS IS CHARACTERIZED BY HERITABLE ALTERATIONS IN THE TRANSCRIPTION OF GENES WITHOUT NUCLEOTIDE CHANGE AND IS COMMONLY CONSIDERED AT THREE LEVELS, I.E., DNA METHYLATION, HISTONE MODIFICATIONS, AND MICRORNAS. TO DATE, SCIENTIFIC EVIDENCE HAS INDICATED ABNORMAL DNA METHYLATION, HISTONE MODIFICATIONS, AND NON-CODING RNA TRANSCRIPTION IN PSORIATIC PATIENTS. IN ORDER TO REVERSE ABERRANT EPIGENETIC CHANGES IN PSORIASIS PATIENTS, SEVERAL COMPOUNDS AND DRUGS (EPI-DRUGS) HAVE BEEN DEVELOPED TO AFFECT THE MAJOR ENZYMES INVOLVED IN THE METHYLATION OF DNA, OR THE ACETYLATION OF HISTONES, WHICH AIM TO CORRECT THE ABERRANT METHYLATION AND ACETYLATION PATTERNS. A NUMBER OF CLINICAL TRIALS HAVE SUGGESTED THE THERAPEUTIC POTENTIAL OF SUCH DRUGS IN THE TREATMENT OF PSORIASIS. IN THE PRESENT REVIEW, WE ATTEMPT TO CLARIFY RECENT FINDINGS WITH RESPECT TO EPIGENETIC IRREGULARITIES IN PSORIASIS AND DISCUSS FUTURE CHALLENGES. 2023 12 6340 36 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 13 1172 43 CONTRIBUTION OF THE ENVIRONMENT, EPIGENETIC MECHANISMS AND NON-CODING RNAS IN PSORIASIS. DESPITE THE INCREASING RESEARCH AND CLINICAL INTEREST IN THE PREDISPOSITION OF PSORIASIS, A CHRONIC INFLAMMATORY SKIN DISEASE, THE MULTITUDE OF GENETIC AND ENVIRONMENTAL FACTORS INVOLVED IN ITS PATHOGENESIS REMAIN UNCLEAR. THIS COMPLEXITY IS FURTHER EXACERBATED BY THE SEVERAL CELL TYPES THAT ARE IMPLICATED IN PSORIASIS'S PROGRESSION, INCLUDING KERATINOCYTES, MELANOCYTES AND VARIOUS IMMUNE CELL TYPES. THE OBSERVED INTERACTIONS BETWEEN THE GENETIC SUBSTRATE AND THE ENVIRONMENT LEAD TO EPIGENETIC ALTERATIONS THAT DIRECTLY OR INDIRECTLY AFFECT GENE EXPRESSION. CHANGES IN DNA METHYLATION AND HISTONE MODIFICATIONS THAT ALTER DNA-BINDING SITE ACCESSIBILITY, AS WELL AS NON-CODING RNAS IMPLICATED IN THE POST-TRANSCRIPTIONAL REGULATION, ARE MECHANISMS OF GENE TRANSCRIPTIONAL ACTIVITY MODIFICATION AND THEREFORE AFFECT THE PATHWAYS INVOLVED IN THE PATHOGENESIS OF PSORIASIS. IN THIS REVIEW, WE SUMMARIZE THE RESEARCH CONDUCTED ON THE ENVIRONMENTAL FACTORS CONTRIBUTING TO THE DISEASE ONSET, EPIGENETIC MODIFICATIONS AND NON-CODING RNAS EXHIBITING DEREGULATION IN PSORIASIS, AND WE FURTHER CATEGORIZE THEM BASED ON THE UNDER-STUDY CELL TYPES. WE ALSO ASSESS THE RECENT LITERATURE CONSIDERING THERAPEUTIC APPLICATIONS TARGETING MOLECULES THAT COMPROMISE THE EPIGENOME, AS A WAY TO SUPPRESS THE INFLAMMATORY CUTANEOUS CASCADE. 2022 14 2569 36 EPIGENETICS OF ANKYLOSING SPONDYLITIS: RECENT DEVELOPMENTS. ANKYLOSING SPONDYLITIS (AS) IS A CHRONIC INFLAMMATORY AUTOIMMUNE DISEASE WHICH MAINLY AFFECTS THE SPINE, SACROILIAC JOINT AND PERIPHERAL JOINTS. TO DATE, THE EXACT CAUSES AND PATHOGENESIS OF AS STILL REMAIN UNKNOWN. IT IS CONSIDERED THAT THE PATHOGENESIS OF AS IS ASSOCIATED WITH GENETIC, INFECTION, ENVIRONMENT, IMMUNITY AND OTHER FACTORS. AMONG THEM, THE ROLE OF GENETIC FACTORS IN THE PATHOGENESIS OF AS HAS BEEN STUDIED MOST DEEPLY. HOWEVER, OVER THE PAST FEW YEARS, THE FUNCTION OF ENVIRONMENTAL PREDISPOSITION AND EPIGENETIC MODIFICATION IN THE PATHOGENESIS OF AS HAS RECEIVED EXTENSIVE ATTENTION. THIS PAPER SUMMARIZES THE RECENT PROGRESS IN THE EPIGENETICS OF AS, INCLUDING ABNORMAL EPIGENETIC MODIFICATIONS AT AS-ASSOCIATED GENOMIC LOCI, SUCH AS DNA METHYLATION, HISTONE MODIFICATION, MICRORNA, AND SO ON. IN SUMMARY, THE FINDINGS OF THIS REVIEW ATTEMPT TO EXPLAIN THE ROLE OF EPIGENETIC MODIFICATION IN THE OCCURRENCE AND DEVELOPMENT OF AS. NEVERTHELESS, THERE ARE STILL UNKNOWN AND COMPLICATED ASPECTS WORTH EXPLORING TO DEEPEN OUR UNDERSTANDING OF THE PATHOGENESIS OF AS. 2021 15 2027 38 EPIGENETIC CHANGES IN CHRONIC INFLAMMATORY DISEASES. THE NUMBER OF PEOPLE DIAGNOSED WITH CHRONIC INFLAMMATORY DISEASES HAS INCREASED NOTEWORTHY IN THE LAST 40 YEARS. SPONDYLOARTHRITIS (SPA), INFLAMMATORY BOWEL DISEASES (IBD), AND PSORIASIS ARE THE MOST FREQUENT CHRONIC INFLAMMATORY DISEASES, RESULTING FROM A COMBINATION OF GENETIC PREDISPOSITION AND ENVIRONMENTAL FACTORS. EPIGENETIC MODIFICATIONS INCLUDE DNA METHYLATION, HISTONE MODIFICATIONS, AND SMALL AND LONG NONCODING RNAS. THEY ARE INFLUENCED BY ENVIRONMENTAL EXPOSURE, LIFE-STYLE, AND AGING AND HAVE RECENTLY BEEN SHOWN TO BE ALTERED IN MANY COMPLEX DISEASES INCLUDING INFLAMMATORY DISEASES. WHILE EPIGENETIC MODIFICATIONS HAVE BEEN WELL CHARACTERIZED IN OTHER DISEASES SUCH AS CANCER AND AUTOIMMUNE DISEASES, KNOWLEDGE ON CHANGES IN INFLAMMATORY DISEASES IS LAGGING BEHIND WITH SOME DISEASE-SPECIFIC DIFFERENCES. WHILE THE DNA METHYLATION PROFILE OF DIFFERENT CELL TYPES IN PATIENTS WITH IBD HAS BEEN RELATIVELY WELL DESCRIBED, LESS IS KNOWN ON CHANGES IMPLICATED IN PSORIASIS, AND NO SYSTEMATIC GENOME-WIDE STUDIES HAVE SO FAR BEEN PERFORMED IN SPA. IN THIS CHAPTER, WE REVIEW IN DETAIL THE REPORTED CHANGES IN PATTERNS OF DNA METHYLATION AND POSTTRANSLATIONAL HISTONE MODIFICATIONS IN CHRONIC INFLAMMATORY DISEASES HIGHLIGHTING POTENTIAL CONNECTIONS BETWEEN DISEASE-ASSOCIATED PATHOPHYSIOLOGICAL CHANGES SUCH AS THE DYSBIOSIS OF THE MICROBIOME OR GENETIC VARIATIONS ASSOCIATED WITH DISEASE SUSCEPTIBILITY AND THE EPIGENOME. WE ALSO DISCUSS IMPORTANT PARAMETERS OF MEANINGFUL EPIGENETIC STUDIES SUCH AS THE USE OF WELL DEFINED, DISEASE-RELEVANT CELL POPULATIONS, AND ELUDE ON THE POTENTIAL FUTURE OF ENGINEERING OF THE EPIGENOME IN INFLAMMATORY DISEASES. 2017 16 5421 28 REGULATION OF INTERLEUKIN-23 EXPRESSION IN HEALTH AND DISEASE. INTERLEUKIN (IL)-23 PLAYS A CENTRAL ROLE IN THE ORCHESTRATION OF INFLAMMATORY RESPONSES. PRODUCED BY DENDRITIC CELLS AND MACROPHAGES, THIS CYTOKINE PROMOTES THE PROTECTION OF THE HOST AGAINST MUCOSAL PATHOGENS THROUGH THE INDUCTION OF IL-17 AND RELATED CYTOKINES BY LYMPHOID CELLS. PRECLINICAL DISEASE MODELS AND ASSOCIATION STUDIES IN HUMANS HAVE ALSO CLEARLY DEMONSTRATED THE IMPLICATION OF IL-23 SIGNALLING PATHWAY IN INFLAMMATORY DISEASES. INDEED, THIS CYTOKINE IS NOW CONSIDERED AS A MAJOR THERAPEUTIC TARGET IN IMMUNE-BASED PATHOLOGIES SUCH AS PSORIASIS, ANKYLOSING SPONDYLITIS OR CROHN'S DISEASE. FURTHERMORE, IN THE CONTEXT OF INFLAMMATION-RELATED CANCER, IL-23 IS THOUGHT TO CONTRIBUTE TO TUMORIGENESIS AND PROGRESSION TO METASTATIC DISEASE. HEREIN, WE REVIEW OUR CURRENT UNDERSTANDING OF IL-23 REGULATION AT THE TRANSCRIPTIONAL AND POST-TRANSCRIPTIONAL LEVELS. WE DISCUSS THE RELEVANCE OF THESE FINDINGS IN THE CONTEXT OF INFECTION, CHRONIC INFLAMMATION AND CANCER. 2016 17 6288 47 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 18 3039 31 GENOME ENGINEERING FOR PERSONALIZED ARTHRITIS THERAPEUTICS. ARTHRITIS REPRESENTS A FAMILY OF COMPLEX JOINT PATHOLOGIES RESPONSIBLE FOR THE MAJORITY OF MUSCULOSKELETAL CONDITIONS. NEARLY ALL DISEASES WITHIN THIS FAMILY, INCLUDING OSTEOARTHRITIS, RHEUMATOID ARTHRITIS, AND JUVENILE IDIOPATHIC ARTHRITIS, ARE CHRONIC CONDITIONS WITH FEW OR NO DISEASE-MODIFYING THERAPEUTICS AVAILABLE. ADVANCES IN GENOME ENGINEERING TECHNOLOGY, MOST RECENTLY WITH CRISPR-CAS9, HAVE REVOLUTIONIZED OUR ABILITY TO INTERROGATE AND VALIDATE GENETIC AND EPIGENETIC ELEMENTS ASSOCIATED WITH CHRONIC DISEASES SUCH AS ARTHRITIS. THESE TECHNOLOGIES, TOGETHER WITH CELL REPROGRAMMING METHODS, INCLUDING THE USE OF INDUCED PLURIPOTENT STEM CELLS, PROVIDE A PLATFORM FOR HUMAN DISEASE MODELING. WE SUMMARIZE NEW EVIDENCE FROM GENOME-WIDE ASSOCIATION STUDIES AND GENOMICS THAT SUBSTANTIATES A GENETIC BASIS FOR ARTHRITIS PATHOGENESIS. WE ALSO REVIEW THE POTENTIAL CONTRIBUTIONS OF GENOME ENGINEERING IN THE DEVELOPMENT OF NEW ARTHRITIS THERAPEUTICS. 2017 19 2294 42 EPIGENETIC REGULATION IN THE PATHOGENESIS OF SJOGREN SYNDROME AND RHEUMATOID ARTHRITIS. AUTOIMMUNE RHEUMATIC DISEASES, SUCH AS SJOGREN SYNDROME (SS) AND RHEUMATOID ARTHRITIS (RA), ARE CHARACTERIZED BY CHRONIC INFLAMMATION AND AUTOIMMUNITY, WHICH CAUSE JOINT TISSUE DAMAGE AND DESTRUCTION BY TRIGGERING REDUCED MOBILITY AND DEBILITATION IN PATIENTS WITH THESE DISEASES. INITIATION AND MAINTENANCE OF CHRONIC INFLAMMATORY STAGES ACCOUNT FOR SEVERAL MECHANISMS THAT INVOLVE IMMUNE CELLS AS KEY PLAYERS AND THE INTERACTION OF THE IMMUNE CELLS WITH OTHER TISSUES. INDEED, THE OVERLAPPING OF CERTAIN CLINICAL AND SEROLOGIC MANIFESTATIONS BETWEEN SS AND RA MAY INDICATE THAT NUMEROUS IMMUNOLOGIC-RELATED MECHANISMS ARE INVOLVED IN THE PHYSIOPATHOLOGY OF BOTH THESE DISEASES. IT IS WIDELY ACCEPTED THAT EPIGENETIC PATHWAYS PLAY AN ESSENTIAL ROLE IN THE DEVELOPMENT AND FUNCTION OF THE IMMUNE SYSTEM. ALTHOUGH MANY PUBLISHED STUDIES HAVE ATTEMPTED TO ELUCIDATE THE RELATION BETWEEN EPIGENETIC MODIFICATIONS (E.G. DNA METHYLATION, HISTONE POST-TRANSLATIONAL MODIFICATIONS, MIRNAS) AND AUTOIMMUNE DISORDERS, THE CONTRIBUTION OF EPIGENETIC REGULATION TO THE PATHOGENESIS OF SS AND RA IS AT PRESENT POORLY UNDERSTOOD. THIS REVIEW ATTEMPTS TO SHED LIGHT FROM A CRITICAL POINT OF VIEW ON THE IDENTIFICATION OF THE MOST RELEVANT EPIGENETIC MECHANISMS RELATED TO RA AND SS BY EXPLAINING INTRICATE REGULATORY PROCESSES AND PHENOTYPIC FEATURES OF BOTH AUTOIMMUNE DISEASES. MOREOVER, WE POINT OUT SOME EPIGENETIC MARKERS WHICH CAN BE USED TO MONITOR THE INFLAMMATION STATUS AND THE DYSREGULATED IMMUNITY IN SS AND RA. FINALLY, WE DISCUSS THE INCONVENIENCE OF USING EPIGENETIC DATA OBTAINED FROM BULK IMMUNE CELL POPULATIONS INSTEAD SPECIFIC IMMUNE CELL SUBPOPULATIONS. 2019 20 6202 51 THE INFLAMMATORY RESPONSE IN PSORIASIS: A COMPREHENSIVE REVIEW. PSORIASIS IS A CHRONIC INFLAMMATORY AUTOIMMUNE DISEASE CHARACTERIZED BY AN EXCESSIVELY ABERRANT HYPERPROLIFERATION OF KERATINOCYTES. THE PATHOGENESIS OF PSORIASIS IS COMPLEX AND THE EXACT MECHANISM REMAINS ELUSIVE. HOWEVER, PSORIASIS IS THOUGHT TO RESULT FROM A COMBINATION OF GENETIC, EPIGENETIC, AND ENVIRONMENTAL INFLUENCES. RECENT STUDIES HAVE IDENTIFIED THAT EPIGENETIC FACTORS INCLUDING DYSREGULATED DNA METHYLATION LEVELS, ABNORMAL HISTONE MODIFICATION AND MICRORNAS EXPRESSIONS ARE INVOLVED IN THE DEVELOPMENT OF PSORIASIS. THE INTERPLAY OF IMMUNE CELLS AND CYTOKINES IS ANOTHER CRITICAL FACTOR IN THE PATHOGENESIS OF PSORIASIS. THESE FACTORS OR PATHWAYS INCLUDE TH1/TH2 HOMEOSTASIS, THE TH17/TREG BALANCE AND THE IL-23/TH17 AXIS. TH17 IS BELIEVED PARTICULARLY IMPORTANT IN PSORIASIS DUE TO ITS PRO-INFLAMMATORY EFFECTS AND ITS INVOLVEMENT IN AN INTEGRATED INFLAMMATORY LOOP WITH DENDRITIC CELLS AND KERATINOCYTES, CONTRIBUTING TO AN OVERPRODUCTION OF ANTIMICROBIAL PEPTIDES, INFLAMMATORY CYTOKINES, AND CHEMOKINES THAT LEADS TO AMPLIFICATION OF THE IMMUNE RESPONSE. IN ADDITION, OTHER PATHWAYS AND SIGNALING MOLECULES HAVE BEEN FOUND TO BE INVOLVED, INCLUDING TH9, TH22, REGULATORY T CELLS, GAMMADELTA T CELLS, CD8(+) T CELLS, AND THEIR RELATED CYTOKINES. UNDERSTANDING THE PATHOGENESIS OF PSORIASIS WILL ALLOW US TO DEVELOP INCREASINGLY EFFICIENT TARGETED TREATMENT BY BLOCKING RELEVANT INFLAMMATORY SIGNALING PATHWAYS AND MOLECULES. THERE IS NO CURE FOR PSORIASIS AT THE PRESENT TIME, AND MUCH OF THE TREATMENT INVOLVES MANAGING THE SYMPTOMS. THE BIOLOGICS, WHILE LACKING THE ADVERSE EFFECTS ASSOCIATED WITH SOME OF THE TRADITIONAL MEDICATIONS SUCH AS CORTICOSTEROIDS AND METHOTREXATE, HAVE THEIR OWN SET OF SIDE EFFECTS, WHICH MAY INCLUDE REACTIVATION OF LATENT INFECTIONS. SIGNIFICANT CHALLENGES REMAIN IN DEVELOPING SAFE AND EFFICACIOUS NOVEL TARGETED THERAPIES THAT DEPEND ON A BETTER UNDERSTANDING OF THE IMMUNOLOGICAL DYSFUNCTION IN PSORIASIS. 2016