1 5415 115 REGULATION OF CELLULAR IMMUNE RESPONSES IN SEPSIS BY HISTONE MODIFICATIONS. SEVERE SEPSIS, SEPTIC SHOCK, AND RELATED INFLAMMATORY SYNDROMES ARE DRIVEN BY THE ABERRANT EXPRESSION OF PROINFLAMMATORY MEDIATORS BY IMMUNE CELLS. DURING THE ACUTE PHASE OF SEPSIS, OVEREXPRESSION OF CHEMOKINES AND CYTOKINES DRIVES PHYSIOLOGICAL STRESS LEADING TO ORGAN FAILURE AND MORTALITY. FOLLOWING RECOVERY FROM SEPSIS, THE IMMUNE SYSTEM EXHIBITS PROFOUND IMMUNOSUPPRESSION, EVIDENCED BY AN INABILITY TO PRODUCE THE SAME PROINFLAMMATORY MEDIATORS THAT ARE REQUIRED FOR NORMAL RESPONSES TO INFECTIOUS MICROORGANISMS. GENE EXPRESSION IN INFLAMMATORY RESPONSES IS INFLUENCED BY THE TRANSCRIPTIONAL ACCESSIBILITY OF THE CHROMATIN, WITH HISTONE POSTTRANSLATIONAL MODIFICATIONS DETERMINING WHETHER INFLAMMATORY GENE LOCI ARE SET TO TRANSCRIPTIONALLY ACTIVE, REPRESSED, OR POISED STATES. EXPERIMENTAL EVIDENCE INDICATES THAT HISTONE MODIFICATIONS PLAY A CENTRAL ROLE IN GOVERNING THE CYTOKINE STORM OF SEVERE SEPSIS, AND THAT ABERRANT CHROMATIN MODIFICATIONS INDUCED DURING THE ACUTE PHASE OF SEPSIS MAY MEDIATE CHRONIC IMMUNOSUPPRESSION IN SEPSIS SURVIVORS. THIS REVIEW WILL FOCUS ON THE ROLE OF HISTONE MODIFICATIONS IN GOVERNING IMMUNE RESPONSES IN SEVERE SEPSIS, WITH AN EMPHASIS ON SPECIFIC LEUKOCYTE SUBSETS AND THE HISTONE MODIFICATIONS OBSERVED IN THESE CELLS DURING CHRONIC STAGES OF SEPSIS. ADDITIONALLY, THE EXPRESSION AND FUNCTION OF CHROMATIN-MODIFYING ENZYMES (CMES) WILL BE DISCUSSED IN THE CONTEXT OF SEVERE SEPSIS, AS POTENTIAL MEDIATORS OF EPIGENETIC REGULATION OF GENE EXPRESSION IN SEPSIS RESPONSES. IN SUMMARY, THIS REVIEW WILL ARGUE FOR THE USE OF CHROMATIN MODIFICATIONS AND CME EXPRESSION IN LEUKOCYTES AS POTENTIAL BIOMARKERS OF IMMUNOSUPPRESSION IN PATIENTS WITH SEVERE SEPSIS. 2017 2 4568 28 MYELOID-DERIVED SUPPRESSOR CELLS (MDSC): WHEN GOOD INTENTIONS GO AWRY. MDSC ARE A HETEROGENEOUS POPULATION OF IMMATURE MYELOID CELLS THAT ARE RELEASED BY BIOLOGICAL STRESS SUCH AS TISSUE DAMAGE AND INFLAMMATION. CONVENTIONALLY, MDSC ARE KNOWN FOR THEIR DETRIMENTAL ROLE IN CHRONIC INFLAMMATION AND NEOPLASTIC CONDITIONS. HOWEVER, THEIR INTRINSIC FUNCTIONS IN IMMUNOREGULATION, WOUND HEALING, AND ANGIOGENESIS ARE INTENDED TO PROTECT FROM OVER-REACTIVE IMMUNE RESPONSES, MAINTENANCE OF IMMUNOTOLERANCE, TISSUE REPAIR, AND HOMEOSTASIS. PARADOXICALLY, UNDER CERTAIN CONDITIONS, MDSC CAN IMPAIR PROTECTIVE IMMUNE RESPONSES AND EXACERBATE THE DISEASE. THE TRANSITION FROM PROTECTIVE TO HARMFUL MDSC IS MOST LIKELY DRIVEN BY ENVIRONMENTAL AND EPIGENETIC MECHANISMS INDUCED BY PROLONGED EXPOSURE TO UNRESOLVED INFLAMMATORY TRIGGERS. HERE, WE REVIEW SEVERAL EXAMPLES OF THE DUAL IMPACT OF MDSC IN CONDITIONS SUCH AS MATERNAL-FETAL TOLERANCE, SELF-ANTIGENS IMMUNOTOLERANCE, OBESITY-ASSOCIATED CANCER, SEPSIS AND TRAUMA. MOREOVER, WE ALSO HIGHLIGHTED THE EVIDENCE INDICATING THAT MDSC HAVE A ROLE IN COVID-19 PATHOPHYSIOLOGY. FINALLY, WE HAVE SUMMARIZED THE EVIDENCE INDICATING EPIGENETIC MECHANISMS ASSOCIATED WITH MDSC FUNCTION. 2021 3 2329 36 EPIGENETIC REGULATION OF IMMUNE CELL FUNCTIONS DURING POST-SEPTIC IMMUNOSUPPRESSION. STUDIES IN HUMANS AND ANIMAL MODELS INDICATE THAT PROFOUND IMMUNOSUPPRESSION IS ONE OF THE CHRONIC CONSEQUENCES OF SEVERE SEPSIS. THIS IMMUNE DYSFUNCTION ENCOMPASSES DEFICIENCIES IN ACTIVATION OF CELLS IN BOTH THE MYELOID AND LYMPHOID CELL LINEAGES. AS A RESULT, SURVIVORS OF SEVERE SEPSIS ARE AT RISK OF SUCCUMBING TO INFECTIONS PERPETRATED BY OPPORTUNISTIC PATHOGENS THAT ARE NORMALLY CONTROLLED BY A FULLY FUNCTIONING IMMUNE SYSTEM. RECENT STUDIES HAVE INDICATED THAT EPIGENETIC MECHANISMS MAY BE ONE DRIVING FORCE BEHIND THIS IMMUNOSUPPRESSION, THROUGH SUPPRESSION OF PROINFLAMMATORY GENE PRODUCTION AND SUBSEQUENT IMMUNE CELL ACTIVATION, PROLIFERATION AND EFFECTOR FUNCTION. A BETTER UNDERSTANDING OF EPIGENETICS AND POST-SEPTIC IMMUNOSUPPRESSION CAN IMPROVE OUR DIAGNOSTIC TOOLS AND MAY BE AN IMPORTANT POTENTIAL SOURCE OF NOVEL MOLECULAR TARGETS FOR NEW THERAPIES. THIS REVIEW WILL DISCUSS IMPORTANT PATHWAYS OF IMMUNE CELL ACTIVATION AFFECTED BY SEVERE SEPSIS, AND HIGHLIGHT PATHWAYS OF EPIGENETIC REGULATION THAT MAY BE INVOLVED IN POST-SEPTIC IMMUNOSUPPRESSION. 2011 4 4567 36 MYELOID-DERIVED SUPPRESSOR CELL FUNCTION AND EPIGENETIC EXPRESSION EVOLVES OVER TIME AFTER SURGICAL SEPSIS. BACKGROUND: SEPSIS IS AN INCREASINGLY SIGNIFICANT CHALLENGE THROUGHOUT THE WORLD AS ONE OF THE MAJOR CAUSES OF PATIENT MORBIDITY AND MORTALITY. CENTRAL TO THE HOST IMMUNOLOGIC RESPONSE TO SEPSIS IS THE INCREASE IN CIRCULATING MYELOID-DERIVED SUPPRESSOR CELLS (MDSCS), WHICH HAVE BEEN DEMONSTRATED TO BE PRESENT AND INDEPENDENTLY ASSOCIATED WITH POOR LONG-TERM CLINICAL OUTCOMES. MDSCS ARE PLASTIC CELLS AND POTENTIALLY MODIFIABLE, PARTICULARLY THROUGH EPIGENETIC INTERVENTIONS. THE OBJECTIVE OF THIS STUDY WAS TO DETERMINE HOW THE SUPPRESSIVE PHENOTYPE OF MDSCS EVOLVES AFTER SEPSIS IN SURGICAL ICU PATIENTS, AS WELL AS TO IDENTIFY EPIGENETIC DIFFERENCES IN MDSCS THAT MAY EXPLAIN THESE CHANGES. METHODS: CIRCULATING MDSCS FROM 267 SURVIVORS OF SURGICAL SEPSIS WERE PHENOTYPED AT VARIOUS INTERVALS OVER 6 WEEKS, AND HIGHLY ENRICHED MDSCS FROM 23 OF THESE SAMPLES WERE CO-CULTURED WITH CD3/CD28-STIMULATED AUTOLOGOUS T CELLS. MICRORNA EXPRESSION FROM ENRICHED MDSCS WAS ALSO IDENTIFIED. RESULTS: WE OBSERVED THAT MDSC NUMBERS REMAIN SIGNIFICANTLY ELEVATED IN HOSPITALIZED SEPSIS SURVIVORS FOR AT LEAST 6 WEEKS AFTER THEIR INFECTION. HOWEVER, ONLY MDSCS OBTAINED AT AND BEYOND 14 DAYS POST-SEPSIS SIGNIFICANTLY SUPPRESSED T LYMPHOCYTE PROLIFERATION AND IL-2 PRODUCTION. THESE SAME MDSCS DISPLAYED UNIQUE EPIGENETIC (MIRNA) EXPRESSION PATTERNS COMPARED TO EARLIER TIME POINTS. CONCLUSIONS: WE CONCLUDE THAT IN SEPSIS SURVIVORS, IMMATURE MYELOID CELL NUMBERS ARE INCREASED BUT THE IMMUNE SUPPRESSIVE FUNCTION SPECIFIC TO MDSCS DEVELOPS OVER TIME, AND THIS IS ASSOCIATED WITH A SPECIFIC EPIGENOME. THESE FINDINGS MAY EXPLAIN THE CHRONIC AND PERSISTENT IMMUNE SUPPRESSION SEEN IN THESE SUBJECTS. 2019 5 4947 28 PATERNAL SEPSIS INDUCES ALTERATIONS OF THE SPERM METHYLOME AND DAMPENS OFFSPRING IMMUNE RESPONSES-AN ANIMAL STUDY. BACKGROUND: SEPSIS REPRESENTS THE UTMOST SEVERE CONSEQUENCE OF INFECTION, INVOLVING A DYSREGULATED AND SELF-DAMAGING IMMUNE RESPONSE OF THE HOST. WHILE DIFFERENT ENVIRONMENTAL EXPOSURES LIKE CHRONIC STRESS OR MALNUTRITION HAVE BEEN WELL DESCRIBED TO REPROGRAM THE GERMLINE AND SUBSEQUENTLY OFFSPRING ATTRIBUTES, THE INTERGENERATIONAL IMPACT OF SEPSIS AS A TREMENDOUS IMMUNOLOGICAL STRESSOR HAS NOT BEEN EXAMINED YET. METHODS: POLYMICROBIAL SEPSIS IN 12-WEEK-OLD MALE C57BL/6 MICE WAS INDUCED BY CECAL LIGATION AND PUNCTURE (CLP), FOLLOWED BY A MATING OF THE MALE SURVIVORS (OR APPROPRIATE SHAM CONTROL ANIMALS) 6 WEEKS LATER WITH HEALTHY FEMALES. ALVEOLAR MACROPHAGES OF OFFSPRING ANIMALS WERE ISOLATED AND STIMULATED WITH EITHER LPS OR ZYMOSAN, AND SUPERNATANT LEVELS OF TNF-ALPHA WERE QUANTIFIED BY ELISA. FURTHERMORE, SYSTEMIC CYTOKINE RESPONSE TO INTRAPERITONEALLY INJECTED LPS WAS ASSESSED AFTER 24 H. ALSO, MORPHOLOGY, MOTILITY, AND GLOBAL DNA METHYLATION OF THE SEPSIS SURVIVORS' SPERM WAS EXAMINED. RESULTS: COMPARATIVE REDUCED REDUCTION BISULFITE SEQUENCING (RRBS) OF SPERM REVEALED CHANGES OF DNA METHYLATION (N = 381), MOST PRONOUNCED IN THE INTERGENIC GENOME AS WELL AS WITHIN INTRONS OF DEVELOPMENTALLY RELEVANT GENES. OFFSPRING OF SEPSIS FATHERS EXHIBITED A SLIGHT DECREASE IN BODY WEIGHT, WITH A MORE PRONOUNCED WEIGHT DIFFERENCE IN MALE ANIMALS (CLP VS. SHAM). MALE DESCENDANTS OF SEPSIS FATHERS, BUT NOT FEMALE DESCENDANTS, EXHIBITED LOWER PLASMA CONCENTRATIONS OF IL-6, TNF-ALPHA, AND IL-10 24 H AFTER INJECTION OF LPS. IN LINE, ONLY ALVEOLAR MACROPHAGES OF MALE DESCENDANTS OF SEPSIS FATHERS PRODUCED LESS TNF-ALPHA UPON ZYMOSAN STIMULATION COMPARED TO SHAM DESCENDANTS, WHILE LPS RESPONSES KEPT UNCHANGED. CONCLUSION: WE CAN PROVE THAT MALE-BUT SURPRISINGLY NOT FEMALE-DESCENDANTS OF POST-SEPSIS FATHERS SHOW A DAMPENED SYSTEMIC AS WELL AS PULMONARY IMMUNE RESPONSE. BASED ON THIS OBSERVATION OF AN IMMUNE HYPO-RESPONSIVITY, WE PROPOSE THAT MALE DESCENDANTS OF SEPSIS FATHERS ARE AT RISK TO DEVELOP FUNGAL AND BACTERIAL INFECTIONS AND MIGHT BENEFIT FROM THERAPEUTIC IMMUNE MODULATION. 2018 6 4291 34 MICRORNA PROFILES IN INTESTINAL EPITHELIAL CELLS IN A MOUSE MODEL OF SEPSIS. SEPSIS IS A SYSTEMIC INFLAMMATORY DISORDER THAT LEADS TO THE DYSFUNCTION OF MULTIPLE ORGANS. IN THE INTESTINE, THE DEREGULATION OF THE EPITHELIAL BARRIER CONTRIBUTES TO THE DEVELOPMENT OF SEPSIS BY TRIGGERING CONTINUOUS EXPOSURE TO HARMFUL FACTORS. HOWEVER, SEPSIS-INDUCED EPIGENETIC CHANGES IN GENE-REGULATION NETWORKS WITHIN INTESTINAL EPITHELIAL CELLS (IECS) REMAIN UNEXPLORED. IN THIS STUDY, WE ANALYZED THE EXPRESSION PROFILE OF MICRORNAS (MIRNAS) IN IECS ISOLATED FROM A MOUSE MODEL OF SEPSIS GENERATED VIA CECAL SLURRY INJECTION. AMONG 239 MIRNAS, 14 MIRNAS WERE UPREGULATED, AND 9 MIRNAS WERE DOWNREGULATED IN THE IECS BY SEPSIS. UPREGULATED MIRNAS IN IECS FROM SEPTIC MICE, PARTICULARLY MIR-149-5P, MIR-466Q, MIR-495, AND MIR-511-3P, WERE SEEN TO EXHIBIT COMPLEX AND GLOBAL EFFECTS ON GENE REGULATION NETWORKS. INTERESTINGLY, MIR-511-3P HAS EMERGED AS A DIAGNOSTIC MARKER IN THIS SEPSIS MODEL DUE TO ITS INCREASE IN BLOOD IN ADDITION TO IECS. AS EXPECTED, MRNAS IN THE IECS WERE REMARKABLY ALTERED BY SEPSIS; SPECIFICALLY, 2248 MRNAS WERE DECREASED, WHILE 612 MRNAS WERE INCREASED. THIS QUANTITATIVE BIAS MAY BE POSSIBLY DERIVED, AT LEAST PARTLY, FROM THE DIRECT EFFECTS OF THE SEPSIS-INCREASED MIRNAS ON THE COMPREHENSIVE EXPRESSION OF MRNAS. THUS, CURRENT IN SILICO DATA INDICATE THAT THERE ARE DYNAMIC REGULATORY RESPONSES OF MIRNAS TO SEPSIS IN IECS. IN ADDITION, THE MIRNAS THAT WERE INCREASED WITH SEPSIS HAD ENRICHED DOWNSTREAM PATHWAYS INCLUDING WNT SIGNALING, WHICH IS ASSOCIATED WITH WOUND HEALING, AND FGF/FGFR SIGNALING, WHICH HAS BEEN LINKED TO CHRONIC INFLAMMATION AND FIBROSIS. THESE MODIFICATIONS IN MIRNA NETWORKS IN IECS MAY LEAD TO BOTH PRO- AND ANTI-INFLAMMATORY EFFECTS IN SEPSIS. THE FOUR MIRNAS DISCOVERED ABOVE WERE SHOWN TO PUTATIVELY TARGET LOX, PTCH1, COL22A1, FOXO1, OR HMGA2, VIA IN SILICO ANALYSIS, WHICH WERE ASSOCIATED WITH WNT OR INFLAMMATORY PATHWAYS AND SELECTED FOR FURTHER STUDY. THE EXPRESSIONS OF THESE TARGET GENES WERE DOWNREGULATED IN SEPSIS IECS, POSSIBLY THROUGH POSTTRANSCRIPTIONAL MODIFICATIONS OF THESE MIRNAS. TAKEN TOGETHER, OUR STUDY SUGGESTS THAT IECS DISPLAY A DISTINCTIVE MIRNA PROFILE WHICH IS CAPABLE OF COMPREHENSIVELY AND FUNCTIONALLY RESHAPING THE IEC-SPECIFIC MRNA LANDSCAPE IN A SEPSIS MODEL. 2023 7 6502 24 TRAINED IMMUNITY: LONG-TERM ADAPTATION IN INNATE IMMUNE RESPONSES. ADAPTIVE IMMUNE RESPONSES ARE CHARACTERIZED BY ANTIGEN SPECIFICITY AND INDUCTION OF LIFELONG IMMUNOLOGIC MEMORY. RECENTLY, IT HAS BEEN REPORTED THAT INNATE IMMUNE CELLS CAN ALSO BUILD IMMUNE MEMORY CHARACTERISTICS-A PROCESS TERMED TRAINED IMMUNITY. TRAINED IMMUNITY DESCRIBES THE PERSISTENT HYPERRESPONSIVE PHENOTYPE THAT INNATE IMMUNE CELLS CAN DEVELOP AFTER BRIEF STIMULATION. PATHOGENIC STIMULI SUCH AS MICROORGANISMS, AND ALSO ENDOGENOUS MOLECULES INCLUDING URIC ACID, OXIDIZED LDL (LOW-DENSITY LIPOPROTEIN), AND CATECHOLAMINES, ARE CAPABLE OF INDUCING MEMORY IN MONOCYTES AND MACROPHAGES. WHILE TRAINED IMMUNITY PROVIDES FAVORABLE CROSS-PROTECTION IN THE CONTEXT OF INFECTIOUS DISEASES, THE HEIGHTENED IMMUNE RESPONSE CAN BE MALADAPTIVE IN DISEASES DRIVEN BY CHRONIC SYSTEMIC INFLAMMATION, SUCH AS ATHEROSCLEROSIS. TRAINED IMMUNITY IS MAINTAINED BY DISTINCT EPIGENETIC AND METABOLIC MECHANISMS AND PERSISTS FOR AT LEAST SEVERAL MONTHS IN VIVO DUE TO REPROGRAMMING OF MYELOID PROGENITOR CELLS. ADDITIONALLY, CERTAIN NONIMMUNE CELLS ARE ALSO FOUND TO EXHIBIT TRAINED IMMUNITY CHARACTERISTICS. THUS, TRAINED IMMUNITY PRESENTS AN EXCITING FRAMEWORK TO DEVELOP NEW APPROACHES TO VACCINATION AND ALSO NOVEL PHARMACOLOGICAL TARGETS IN THE TREATMENT OF INFLAMMATORY DISEASES. 2021 8 5720 36 SIRTUINS LINK INFLAMMATION AND METABOLISM. SIRTUINS (SIRT), FIRST DISCOVERED IN YEAST AS NAD+ DEPENDENT EPIGENETIC AND METABOLIC REGULATORS, HAVE COMPARABLE ACTIVITIES IN HUMAN PHYSIOLOGY AND DISEASE. MOUNTING EVIDENCE SUPPORTS THAT THE SEVEN-MEMBER MAMMALIAN SIRTUIN FAMILY (SIRT1-7) GUARD HOMEOSTASIS BY SENSING BIOENERGY NEEDS AND RESPONDING BY MAKING ALTERATIONS IN THE CELL NUTRIENTS. SIRTUINS PLAY A CRITICAL ROLE IN RESTORING HOMEOSTASIS DURING STRESS RESPONSES. INFLAMMATION IS DESIGNED TO "DEFEND AND MEND" AGAINST THE INVADING ORGANISMS. EMERGING EVIDENCE SUPPORTS THAT METABOLISM AND BIOENERGY REPROGRAMMING DIRECT THE SEQUENTIAL COURSE OF INFLAMMATION; FAILURE OF HOMEOSTASIS RETRIEVAL RESULTS IN MANY CHRONIC AND ACUTE INFLAMMATORY DISEASES. ANABOLIC GLYCOLYSIS QUICKLY INDUCED (COMPARED TO OXIDATIVE PHOSPHORYLATION) FOR ROS AND ATP GENERATION IS NEEDED FOR IMMUNE ACTIVATION TO "DEFEND" AGAINST INVADING MICROORGANISMS. LIPOLYSIS/FATTY ACID OXIDATION, ESSENTIAL FOR CELLULAR PROTECTION/HIBERNATION AND CELL SURVIVAL IN ORDER TO "MEND," LEADS TO IMMUNE REPRESSION. ACUTE/CHRONIC INFLAMMATIONS ARE LINKED TO ALTERED GLYCOLYSIS AND FATTY ACID OXIDATION, AT LEAST IN PART, BY NAD+ DEPENDENT FUNCTION OF SIRTUINS. THERAPEUTICALLY TARGETING SIRTUINS MAY PROVIDE A NEW CLASS OF INFLAMMATION AND IMMUNE REGULATORS. THIS REVIEW DISCUSSES HOW SIRTUINS INTEGRATE METABOLISM, BIOENERGETICS, AND IMMUNITY DURING INFLAMMATION AND HOW SIRTUIN-DIRECTED TREATMENT IMPROVES OUTCOME IN CHRONIC INFLAMMATORY DISEASES AND IN THE EXTREME STRESS RESPONSE OF SEPSIS. 2016 9 6452 25 THERAPIES TARGETING TRAINED IMMUNE CELLS IN INFLAMMATORY AND AUTOIMMUNE DISEASES. THE CONCEPT OF TRAINED IMMUNITY HAS RECENTLY EMERGED AS A MECHANISM CONTRIBUTING TO SEVERAL IMMUNE MEDIATED INFLAMMATORY CONDITIONS. TRAINED IMMUNITY IS DEFINED BY THE IMMUNOLOGICAL MEMORY DEVELOPED IN INNATE IMMUNE CELLS AFTER A PRIMARY NON-SPECIFIC STIMULUS THAT, IN TURN, PROMOTES A HEIGHTENED INFLAMMATORY RESPONSE UPON A SECONDARY CHALLENGE. THE MOST CHARACTERISTIC CHANGES ASSOCIATED TO THIS PROCESS INVOLVE THE REWIRING OF CELL METABOLISM AND EPIGENETIC REPROGRAMMING. UNDER PHYSIOLOGICAL CONDITIONS, THE ROLE OF TRAINED IMMUNE CELLS ENSURES A PROMPT RESPONSE. THIS ACTION IS LIMITED BY EFFECTIVE RESOLUTION OF INFLAMMATION AND TISSUE REPAIR IN ORDER TO RESTORE HOMEOSTASIS. HOWEVER, UNRESTRAINED ACTIVATION OF INNATE IMMUNE CELLS CONTRIBUTES TO THE DEVELOPMENT OF CHRONIC INFLAMMATION AND TISSUE DESTRUCTION THROUGH THE SECRETION OF INFLAMMATORY CYTOKINES, PROTEASES AND GROWTH FACTORS. THEREFORE, INTERVENTIONS AIMED AT REVERSING THE CHANGES INDUCED BY TRAINED IMMUNITY PROVIDE POTENTIAL THERAPEUTIC APPROACHES TO TREAT INFLAMMATORY AND AUTOIMMUNE DISEASES LIKE RHEUMATOID ARTHRITIS (RA). WE REVIEW CELLULAR APPROACHES THAT TARGET METABOLISM AND THE EPIGENETIC REPROGRAMMING OF DENDRITIC CELLS, MACROPHAGES, NATURAL KILLER CELLS, AND OTHER TRAINED CELLS IN THE CONTEXT OF AUTOIMMUNE INFLAMMATORY DISEASES. 2020 10 2641 30 EPIGENOMIC AND TRANSCRIPTOMIC ANALYSES REVEAL DIFFERENCES BETWEEN LOW-GRADE INFLAMMATION AND SEVERE EXHAUSTION IN LPS-CHALLENGED MURINE MONOCYTES. EMERGING STUDIES SUGGEST THAT MONOCYTES CAN BE TRAINED BY BACTERIAL ENDOTOXIN TO ADOPT DISTINCT MEMORY STATES RANGING FROM LOW-GRADE INFLAMMATION TO IMMUNE EXHAUSTION. WHILE LOW-GRADE INFLAMMATION MAY CONTRIBUTE TO THE PATHOGENESIS OF CHRONIC DISEASES, EXHAUSTED MONOCYTES WITH PATHOGENIC AND IMMUNE-SUPPRESSIVE CHARACTERISTICS MAY UNDERLIE THE PATHOGENESIS OF POLYMICROBIAL SEPSIS INCLUDING COVID-19. HOWEVER, DETAILED PROCESSES BY WHICH THE DYNAMIC ADAPTION OF MONOCYTES OCCUR REMAIN POORLY UNDERSTOOD. HERE WE EXPOSED MURINE BONE-MARROW DERIVED MONOCYTES TO CHRONIC LIPOPOLYSACCHARIDE (LPS) STIMULATION AT LOW-DOSE OR HIGH-DOSE, AS WELL AS A PBS CONTROL. THE CELLS WERE PROFILED FOR GENOME-WIDE H3K27AC MODIFICATION AND GENE EXPRESSION. THE GENE EXPRESSION OF TRAM-DEFICIENT AND IRAK-M-DEFICIENT MONOCYTES WITH LPS EXPOSURE WAS ALSO ANALYZED. WE DISCOVER THAT LOW-GRADE INFLAMMATION PREFERENTIALLY UTILIZES THE TRAM-DEPENDENT PATHWAY OF TLR4 SIGNALING, AND INDUCES THE EXPRESSION OF INTERFERON RESPONSE GENES. IN CONTRAST, HIGH DOSE LPS UNIQUELY UPREGULATES EXHAUSTION SIGNATURES WITH METABOLIC AND PROLIFERATIVE PATHWAYS. THE EXTENSIVE DIFFERENCES IN THE EPIGENOMIC LANDSCAPE BETWEEN LOW-DOSE AND HIGH-DOSE CONDITIONS SUGGEST THE IMPORTANCE OF EPIGENETIC REGULATIONS IN DRIVING DIFFERENTIAL RESPONSES. OUR DATA PROVIDE POTENTIAL TARGETS FOR FUTURE MECHANISTIC OR THERAPEUTIC STUDIES. 2022 11 744 35 CANNABINOID WIN55,212-2 REPROGRAMS MONOCYTES AND MACROPHAGES TO INHIBIT LPS-INDUCED INFLAMMATION. INTRODUCTION: CHRONIC OR UNCONTROLLED ACTIVATION OF MYELOID CELLS INCLUDING MONOCYTES, MACROPHAGES AND DENDRITIC CELLS (DCS) IS A HALLMARK OF IMMUNE-MEDIATED INFLAMMATORY DISORDERS. THERE IS AN URGENT NEED FOR THE DEVELOPMENT OF NOVEL DRUGS WITH THE CAPACITY TO IMPAIR INNATE IMMUNE CELL OVERACTIVATION UNDER INFLAMMATORY CONDITIONS. COMPELLING EVIDENCE POINTED OUT CANNABINOIDS AS POTENTIAL THERAPEUTIC TOOLS WITH ANTI-INFLAMMATORY AND IMMUNOMODULATORY CAPACITY. WIN55,212-2, A NON-SELECTIVE SYNTHETIC CANNABINOID AGONIST, DISPLAYS PROTECTIVE EFFECTS IN SEVERAL INFLAMMATORY CONDITIONS BY MECHANISMS PARTIALLY DEPENDING ON THE GENERATION OF TOLEROGENIC DCS ABLE TO INDUCE FUNCTIONAL REGULATORY T CELLS (TREGS). HOWEVER, ITS IMMUNOMODULATORY CAPACITY ON OTHER MYELOID CELLS SUCH AS MONOCYTES AND MACROPHAGES REMAINS INCOMPLETELY UNDERSTOOD. METHODS: HUMAN MONOCYTE-DERIVED DCS (HMODCS) WERE DIFFERENTIATED IN THE ABSENCE (CONVENTIONAL HMODCS) OR PRESENCE OF WIN55,212-2 (WIN-HMODCS). CELLS WERE STIMULATED WITH LPS, COCULTURED WITH NAIVE T LYMPHOCYTES AND THEIR CYTOKINE PRODUCTION AND ABILITY TO INDUCE T CELL RESPONSES WERE ANALYSED BY ELISA OR FLOW CYTOMETRY. TO EVALUATE THE EFFECT OF WIN55,212-2 IN MACROPHAGE POLARIZATION, HUMAN AND MURINE MACROPHAGES WERE ACTIVATED WITH LPS OR LPS/IFNGAMMA, IN THE PRESENCE OR ABSENCE OF THE CANNABINOID. CYTOKINE, COSTIMULATORY MOLECULES AND INFLAMMASOME MARKERS WERE ASSAYED. METABOLIC AND CHROMATIN IMMUNOPRECIPITATION ASSAYS WERE ALSO PERFORMED. FINALLY, THE PROTECTIVE CAPACITY OF WIN55,212-2 WAS STUDIED IN VIVO IN BALB/C MICE AFTER INTRAPERITONEAL INJECTION WITH LPS. RESULTS: WE SHOW FOR THE FIRST TIME THAT THE DIFFERENTIATION OF HMODCS IN THE PRESENCE OF WIN55,212-2 GENERATES TOLEROGENIC WIN-HMODCS THAT ARE LESS RESPONSIVE TO LPS STIMULATION AND ABLE TO PRIME TREGS. WIN55,212-2 ALSO IMPAIRS THE PRO-INFLAMMATORY POLARIZATION OF HUMAN MACROPHAGES BY INHIBITING CYTOKINE PRODUCTION, INFLAMMASOME ACTIVATION AND RESCUING MACROPHAGES FROM PYROPTOTIC CELL DEATH. MECHANISTICALLY, WIN55,212-2 INDUCED A METABOLIC AND EPIGENETIC SHIFT IN MACROPHAGES BY DECREASING LPS-INDUCED MTORC1 SIGNALING, COMMITMENT TO GLYCOLYSIS AND ACTIVE HISTONE MARKS IN PRO-INFLAMMATORY CYTOKINE PROMOTERS. WE CONFIRMED THESE DATA IN EX VIVO LPS-STIMULATED PERITONEAL MACROPHAGES (PMPHIS), WHICH WERE ALSO SUPPORTED BY THE IN VIVO ANTI-INFLAMMATORY CAPACITY OF WIN55,212-2 IN A LPS-INDUCED SEPSIS MOUSE MODEL. CONCLUSION: OVERALL, WE SHED LIGHT INTO THE MOLECULAR MECHANISMS BY WHICH CANNABINOIDS EXERT ANTI-INFLAMMATORY PROPERTIES IN MYELOID CELLS, WHICH MIGHT WELL CONTRIBUTE TO THE FUTURE RATIONAL DESIGN OF NOVEL THERAPEUTIC STRATEGIES FOR INFLAMMATORY DISORDERS. 2023 12 6494 25 TRAINED IMMUNITY AS A NOVEL THERAPEUTIC STRATEGY. RECENT STUDIES HAVE SHOWN THAT UPON CERTAIN VACCINATIONS OR INFECTIONS HUMAN INNATE IMMUNE CELLS CAN UNDERGO EXTENSIVE METABOLIC AND EPIGENETIC REPROGRAMMING, WHICH RESULTS IN ENHANCED IMMUNE RESPONSES UPON HETEROLOGOUS RE-INFECTION, A PROCESS TERMED TRAINED IMMUNITY. TRAINED IMMUNITY HAS ALSO BEEN SHOWN TO BE INAPPROPRIATELY ACTIVATED IN INFLAMMATORY DISEASES. THIS PROVIDES THE POTENTIAL FOR IDENTIFYING NOVEL THERAPEUTIC TARGETS: POTENTIATION OF TRAINED IMMUNITY COULD PROTECT FROM SECONDARY INFECTIONS AND REVERSE IMMUNOTOLERANT STATES, WHILE INHIBITION OF TRAINED IMMUNITY MIGHT REDUCE EXCESSIVE IMMUNE ACTIVATION IN CHRONIC INFLAMMATORY CONDITIONS. BY TARGETING SPECIFIC MECHANISMS OF TRAINED IMMUNITY ON EITHER IMMUNOLOGIC, METABOLIC OR EPIGENETIC LEVEL, NOVEL THERAPEUTIC APPROACHES COULD BE DEVELOPED. 2018 13 3544 28 IMMUNOMETABOLIC CONTROL OF TRAINED IMMUNITY. INNATE IMMUNE CELLS CAN ADOPT LONG-TERM INFLAMMATORY PHENOTYPES FOLLOWING BRIEF ENCOUNTERS WITH EXOGENOUS (MICROBIAL) OR ENDOGENOUS STIMULI. THIS PHENOMENON IS NAMED TRAINED IMMUNITY AND CAN IMPROVE HOST DEFENSE AGAINST (RECURRENT) INFECTIONS. IN CONTRAST, TRAINED IMMUNITY CAN ALSO BE MALADAPTIVE IN THE CONTEXT OF CHRONIC INFLAMMATORY DISORDERS, SUCH AS ATHEROSCLEROSIS. KEY TO FUTURE THERAPEUTIC EXPLOITATION OF THIS MECHANISM IS THOROUGH KNOWLEDGE OF THE MECHANISMS DRIVING TRAINED IMMUNITY, WHICH CAN BE USED AS PHARMACOLOGICAL TARGETS. THESE MECHANISMS INCLUDE PROFOUND CHANGES IN INTRACELLULAR METABOLISM, WHICH ARE CLOSELY INTERTWINED WITH EPIGENETIC REPROGRAMMING AT THE LEVEL OF HISTONE MODIFICATIONS. GLYCOLYSIS, GLUTAMINE REPLENISHMENT OF THE TRICARBOXYLIC ACID CYCLE WITH ACCUMULATION OF FUMARATE, AND THE MEVALONATE PATHWAY HAVE ALL BEEN IDENTIFIED AS CRITICAL PATHWAYS FOR TRAINED IMMUNITY IN MONOCYTES AND MACROPHAGES. IN THIS REVIEW, WE PROVIDE A STATE-OF-THE-ART OVERVIEW OF HOW THESE METABOLIC PATHWAYS INTERACT WITH EPIGENETIC PROGRAMS TO DEVELOP TRAINED IMMUNITY. 2021 14 1310 19 DEFINING TRAINED IMMUNITY AND ITS ROLE IN HEALTH AND DISEASE. IMMUNE MEMORY IS A DEFINING FEATURE OF THE ACQUIRED IMMUNE SYSTEM, BUT ACTIVATION OF THE INNATE IMMUNE SYSTEM CAN ALSO RESULT IN ENHANCED RESPONSIVENESS TO SUBSEQUENT TRIGGERS. THIS PROCESS HAS BEEN TERMED 'TRAINED IMMUNITY', A DE FACTO INNATE IMMUNE MEMORY. RESEARCH IN THE PAST DECADE HAS POINTED TO THE BROAD BENEFITS OF TRAINED IMMUNITY FOR HOST DEFENCE BUT HAS ALSO SUGGESTED POTENTIALLY DETRIMENTAL OUTCOMES IN IMMUNE-MEDIATED AND CHRONIC INFLAMMATORY DISEASES. HERE WE DEFINE 'TRAINED IMMUNITY' AS A BIOLOGICAL PROCESS AND DISCUSS THE INNATE STIMULI AND THE EPIGENETIC AND METABOLIC REPROGRAMMING EVENTS THAT SHAPE THE INDUCTION OF TRAINED IMMUNITY. 2020 15 6500 27 TRAINED IMMUNITY IN TYPE 2 IMMUNE RESPONSES. IMMUNOLOGICAL MEMORY OF INNATE IMMUNE CELLS, ALSO TERMED "TRAINED IMMUNITY", ALLOWS FOR CROSS-PROTECTION AGAINST DISTINCT PATHOGENS, BUT MAY ALSO DRIVE CHRONIC INFLAMMATION. RECENT STUDIES HAVE SHOWN THAT MEMORY RESPONSES ASSOCIATED WITH TYPE 2 IMMUNITY DO NOT SOLELY RELY ON ADAPTIVE IMMUNE CELLS, SUCH AS T- AND B CELLS, BUT ALSO INVOLVE THE INNATE IMMUNE SYSTEM AND EPITHELIAL CELLS. MEMORY RESPONSES HAVE BEEN DESCRIBED FOR MONOCYTES, MACROPHAGES AND AIRWAY EPITHELIAL CELLS OF ASTHMATIC PATIENTS AS WELL AS FOR MACROPHAGES AND GROUP 2 INNATE LYMPHOID CELLS (ILC2) FROM ALLERGEN-SENSITIZED OR HELMINTH-INFECTED MICE. THE METABOLIC AND EPIGENETIC MECHANISMS THAT MEDIATE ALLERGEN- OR HELMINTH-INDUCED REPROGRAMMING OF INNATE IMMUNE CELLS ARE ONLY BEGINNING TO BE UNCOVERED. TRAINED IMMUNITY HAS BEEN IMPLICATED IN HELMINTH-DRIVEN IMMUNE REGULATION AND ALLERGEN-SPECIFIC IMMUNOTHERAPY, SUGGESTING ITS EXPLOITATION IN FUTURE THERAPIES. HERE, WE DISCUSS RECENT ADVANCES AND KEY REMAINING QUESTIONS REGARDING THE MECHANISMS AND FUNCTIONS OF TRAINED TYPE 2 IMMUNITY IN INFECTION AND INFLAMMATION. 2022 16 3732 28 INNATE IMMUNE MEMORY AND THE HOST RESPONSE TO INFECTION. UNLIKE THE ADAPTIVE IMMUNE SYSTEM, THE INNATE IMMUNE SYSTEM HAS CLASSICALLY BEEN CHARACTERIZED AS BEING DEVOID OF MEMORY FUNCTIONS. HOWEVER, RECENT RESEARCH SHOWS THAT INNATE MYELOID AND LYMPHOID CELLS HAVE THE ABILITY TO RETAIN MEMORY OF PRIOR PATHOGEN EXPOSURE AND BECOME PRIMED TO ELICIT A ROBUST, BROAD-SPECTRUM RESPONSE TO SUBSEQUENT INFECTION. THIS PHENOMENON HAS BEEN TERMED INNATE IMMUNE MEMORY OR TRAINED IMMUNITY. INNATE IMMUNE MEMORY IS INDUCED VIA ACTIVATION OF PATTERN RECOGNITION RECEPTORS AND THE ACTIONS OF CYTOKINES ON HEMATOPOIETIC PROGENITORS AND STEM CELLS IN BONE MARROW AND INNATE LEUKOCYTES IN THE PERIPHERY. THE TRAINED PHENOTYPE IS INDUCED AND SUSTAINED VIA EPIGENETIC MODIFICATIONS THAT REPROGRAM TRANSCRIPTIONAL PATTERNS AND METABOLISM. THESE MODIFICATIONS AUGMENT ANTIMICROBIAL FUNCTIONS, SUCH AS LEUKOCYTE EXPANSION, CHEMOTAXIS, PHAGOCYTOSIS, AND MICROBIAL KILLING, TO FACILITATE AN AUGMENTED HOST RESPONSE TO INFECTION. ALTERNATIVELY, INNATE IMMUNE MEMORY MAY CONTRIBUTE TO THE PATHOGENESIS OF CHRONIC DISEASES, SUCH AS ATHEROSCLEROSIS AND ALZHEIMER'S DISEASE. 2022 17 6503 21 TRAINED IMMUNITY: REPROGRAMMING INNATE IMMUNITY IN HEALTH AND DISEASE. TRADITIONALLY, THE INNATE AND ADAPTIVE IMMUNE SYSTEMS ARE DIFFERENTIATED BY THEIR SPECIFICITY AND MEMORY CAPACITY. IN RECENT YEARS, HOWEVER, THIS PARADIGM HAS SHIFTED: CELLS OF THE INNATE IMMUNE SYSTEM APPEAR TO BE ABLE TO GAIN MEMORY CHARACTERISTICS AFTER TRANSIENT STIMULATION, RESULTING IN AN ENHANCED RESPONSE UPON SECONDARY CHALLENGE. THIS PHENOMENON HAS BEEN CALLED TRAINED IMMUNITY. TRAINED IMMUNITY IS CHARACTERIZED BY NONSPECIFIC INCREASED RESPONSIVENESS, MEDIATED VIA EXTENSIVE METABOLIC AND EPIGENETIC REPROGRAMMING. TRAINED IMMUNITY EXPLAINS THE HETEROLOGOUS EFFECTS OF VACCINES, WHICH RESULT IN INCREASED PROTECTION AGAINST SECONDARY INFECTIONS. HOWEVER, IN CHRONIC INFLAMMATORY CONDITIONS, TRAINED IMMUNITY CAN INDUCE MALADAPTIVE EFFECTS AND CONTRIBUTE TO HYPERINFLAMMATION AND PROGRESSION OF CARDIOVASCULAR DISEASE, AUTOINFLAMMATORY SYNDROMES, AND NEUROINFLAMMATION. IN THIS REVIEW WE SUMMARIZE THE CURRENT STATE OF THE FIELD OF TRAINED IMMUNITY, ITS MECHANISMS, AND ITS ROLES IN BOTH HEALTH AND DISEASE. 2021 18 1323 32 DENDRITIC CELLS IN SYSTEMIC LUPUS ERYTHEMATOSUS: FROM PATHOGENESIS TO THERAPEUTIC APPLICATIONS. SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) IS A SEVERE CHRONIC SYSTEMIC AUTOIMMUNE DISEASE CAUSED BY COMPLICATED INTERACTIONS AMONG GENETIC, EPIGENETIC, AND IMMUNOLOGICAL FACTORS. DENDRITIC CELLS (DCS), AS THE MOST IMPORTANT ANTIGEN-PRESENTING CELLS, PLAY PIVOTAL ROLES IN BOTH TRIGGERING PATHOGENIC AUTOIMMUNE RESPONSES, AND ALSO MAINTAINING IMMUNE TOLERANCE. DISTINCT DC SUBSETS ARE ENDOWED WITH DIVERSIFIED PHENOTYPIC AND FUNCTIONAL CHARACTERISTICS, AND PLAY VARIABLE ROLES IN SHAPING IMMUNITY AND TOLERANCE DURING THE DEVELOPMENT OF SLE. ABNORMAL ACTIVATION OR DISABLED TOLERANCE OF DCS NOT ONLY TRIGGERS ABERRANT PRODUCTION OF INFLAMMATORY MEDIATORS AND TYPE I INTERFERONS LEADING TO PATHOGENIC INNATE IMMUNITY AND AUTOINFLAMMATION, BUT ALSO CAUSES AN IMBALANCE OF EFFECTOR VERSUS REGULATORY T CELL RESPONSES AND SUSTAINED PRODUCTION OF AUTO-ANTIBODIES FROM B CELLS, LEADING TO CONTINUOUSLY AMPLIFIED AUTOIMMUNE PATHOGENESIS IN SLE. OVER THE PAST DECADE, SIGNIFICANT PROGRESS HAS BEEN MADE IN REVEALING THE CHANGES OF DC ACCUMULATION OR FUNCTION IN SLE, AND HOW THE FUNCTIONAL DYSREGULATIONS OF DCS CONTRIBUTE TO THE PATHOLOGICAL INFLAMMATION OF SLE, LEADING TO BREAKTHROUGHS IN DC-BASED THERAPEUTICS IN THE TREATMENT OF SLE. IN THIS REVIEW, WE REVIEW THE RECENT ADVANCES IN THE ACTIVATION AND FUNCTION OF THE MAJOR DC SUBSETS IN THE PATHOGENESIS OF SLE AS WELL AS THE THERAPEUTIC POTENTIAL OF TARGETING DC SUBSET OR STATUS AGAINST SLE. 2022 19 3734 30 INNATE IMMUNE MEMORY IN MONOCYTES AND MACROPHAGES: THE POTENTIAL THERAPEUTIC STRATEGIES FOR ATHEROSCLEROSIS. ATHEROSCLEROSIS IS A COMPLEX METABOLIC DISEASE CHARACTERIZED BY THE DYSFUNCTION OF LIPID METABOLISM AND CHRONIC INFLAMMATION IN THE INTIMAL SPACE OF THE VESSEL. AS THE MOST ABUNDANT INNATE IMMUNE CELLS, MONOCYTE-DERIVED MACROPHAGES PLAY A PIVOTAL ROLE IN THE INFLAMMATORY RESPONSE, CHOLESTEROL METABOLISM, AND FOAM CELL FORMATION. IN RECENT DECADES, IT HAS BEEN DEMONSTRATED THAT MONOCYTES AND MACROPHAGES CAN ESTABLISH INNATE IMMUNE MEMORY (ALSO TERMED TRAINED IMMUNITY) VIA ENDOGENOUS AND EXOGENOUS ATHEROGENIC STIMULI AND EXHIBIT A LONG-LASTING PROINFLAMMATORY PHENOTYPE. THE IMPORTANT CELLULAR METABOLISM PROCESSES, INCLUDING GLYCOLYSIS, OXIDATIVE PHOSPHORYLATION (OXPHOS), THE TRICARBOXYLIC ACID (TCA) CYCLE, FATTY ACID SYNTHESIS, AND CHOLESTEROL SYNTHESIS, ARE REPROGRAMMED. TRAINED MONOCYTES/MACROPHAGES WITH INNATE IMMUNE MEMORY CAN BE PERSISTENTLY HYPERACTIVATED AND CAN UNDERGO EXTENSIVE EPIGENETIC REWIRING, WHICH CONTRIBUTES TO THE PATHOPHYSIOLOGICAL DEVELOPMENT OF ATHEROSCLEROSIS VIA INCREASED PROINFLAMMATORY CYTOKINE PRODUCTION AND LIPID ACCUMULATION. HERE, WE PROVIDE AN OVERVIEW OF THE REGULATION OF CELLULAR METABOLIC PROCESSES AND EPIGENETIC MODIFICATIONS OF INNATE IMMUNE MEMORY IN MONOCYTES/MACROPHAGES AS WELL AS THE POTENTIAL ENDOGENOUS AND EXOGENOUS STIMULATIONS INVOLVED IN THE PROGRESSION OF ATHEROSCLEROSIS THAT HAVE BEEN REPORTED RECENTLY. THESE ELUCIDATIONS MIGHT BE BENEFICIAL FOR FURTHER UNDERSTANDING INNATE IMMUNE MEMORY AND THE DEVELOPMENT OF THERAPEUTIC STRATEGIES FOR INFLAMMATORY DISEASES AND ATHEROSCLEROSIS. 2022 20 5489 35 REVERSING POST-INFECTIOUS EPIGENETIC-MEDIATED IMMUNE SUPPRESSION. THE IMMUNE RESPONSE MUST BALANCE THE PRO-INFLAMMATORY, CELL-MEDIATED CYTOTOXICITY WITH THE ANTI-INFLAMMATORY AND WOUND REPAIR RESPONSE. EPIGENETIC MECHANISMS MEDIATE THIS BALANCE AND LIMIT HOST IMMUNITY FROM INDUCING EXUBERANT COLLATERAL DAMAGE TO HOST TISSUE AFTER SEVERE AND CHRONIC INFECTIONS. HOWEVER, FOLLOWING TREATMENT FOR THESE INFECTIONS, INCLUDING SEPSIS, PNEUMONIA, HEPATITIS B, HEPATITIS C, HIV, TUBERCULOSIS (TB) OR SCHISTOSOMIASIS, DETRIMENTAL EPIGENETIC SCARS PERSIST, AND RESULT IN LONG-LASTING IMMUNE SUPPRESSION. THIS IS HYPOTHESIZED TO BE ONE OF THE CONTRIBUTING MECHANISMS EXPLAINING WHY SURVIVORS OF INFECTION HAVE INCREASED ALL-CAUSE MORTALITY AND INCREASED RATES OF UNRELATED SECONDARY INFECTIONS. THE MECHANISMS THAT INDUCE EPIGENETIC-MEDIATED IMMUNE SUPPRESSION HAVE BEEN DEMONSTRATED IN-VITRO AND IN ANIMAL MODELS. MODULATION OF THE AMP-ACTIVATED PROTEIN KINASE (AMPK)-MAMMALIAN TARGET OF RAPAMYCIN (MTOR), NUCLEAR FACTOR OF ACTIVATED T CELLS (NFAT) OR NUCLEAR RECEPTOR (NR4A) PATHWAYS IS ABLE TO BLOCK OR REVERSE THE DEVELOPMENT OF DETRIMENTAL EPIGENETIC SCARS. SIMILARLY, DRUGS THAT DIRECTLY MODIFY EPIGENETIC ENZYMES, SUCH AS THOSE THAT INHIBIT HISTONE DEACETYLASES (HDAC) INHIBITORS, DNA HYPOMETHYLATING AGENTS OR MODIFIERS OF THE NUCLEOSOME REMODELING AND DNA METHYLATION (NURD) COMPLEX OR POLYCOMB REPRESSIVE COMPLEX (PRC) HAVE DEMONSTRATED CAPACITY TO RESTORE HOST IMMUNITY IN THE SETTING OF CANCER-, LCMV- OR MURINE SEPSIS-INDUCED EPIGENETIC-MEDIATED IMMUNE SUPPRESSION. A THIRD CLINICALLY FEASIBLE STRATEGY FOR REVERSING DETRIMENTAL EPIGENETIC SCARS INCLUDES BIOENGINEERING APPROACHES TO EITHER DIRECTLY REVERSE THE DETRIMENTAL EPIGENETIC MARKS OR TO MODIFY THE EPIGENETIC ENZYMES OR TRANSCRIPTION FACTORS THAT INDUCE DETRIMENTAL EPIGENETIC SCARS. EACH OF THESE APPROACHES, ALONE OR IN COMBINATION, HAVE ABLATED OR REVERSED DETRIMENTAL EPIGENETIC MARKS IN IN-VITRO OR IN ANIMAL MODELS; TRANSLATIONAL STUDIES ARE NOW REQUIRED TO EVALUATE CLINICAL APPLICABILITY. 2021