1 3467 90 HYPOXIA, HIF, AND ASSOCIATED SIGNALING NETWORKS IN CHRONIC KIDNEY DISEASE. THE PATHOGENESIS OF CHRONIC KIDNEY DISEASE (CKD) IS COMPLEX AND APPARENTLY MULTIFACTORIAL. HYPOXIA OR DECREASE IN OXYGEN SUPPLY IN KIDNEY TISSUES HAS BEEN IMPLICATED IN CKD. HYPOXIA INDUCIBLE FACTORS (HIF) ARE A SMALL FAMILY OF TRANSCRIPTION FACTORS THAT ARE MAINLY RESPONSIVE TO HYPOXIA AND MEDIATE HYPOXIC RESPONSE. HIF PLAYS A CRITICAL ROLE IN RENAL FIBROSIS DURING CKD THROUGH THE MODULATION OF GENE TRANSCRIPTION, CROSSTALK WITH MULTIPLE SIGNALING PATHWAYS, EPITHELIAL-MESENCHYMAL TRANSITION, AND EPIGENETIC REGULATION. MOREOVER, HIF ALSO CONTRIBUTES TO THE DEVELOPMENT OF VARIOUS PATHOLOGICAL CONDITIONS ASSOCIATED WITH CKD, SUCH AS ANEMIA, INFLAMMATION, ABERRANT ANGIOGENESIS, AND VASCULAR CALCIFICATION. TREATMENTS TARGETING HIF AND RELATED SIGNALING PATHWAYS FOR CKD THERAPY ARE BEING DEVELOPED WITH PROMISING CLINICAL BENEFITS, ESPECIALLY FOR ANEMIA. THIS REVIEW PRESENTS AN UPDATED ANALYSIS OF HYPOXIA RESPONSE, HIF, AND THEIR ASSOCIATED SIGNALING NETWORK INVOLVED IN THE PATHOGENESIS OF CKD. 2017 2 5565 39 ROLE OF HYPOXIA IN PROGRESSIVE CHRONIC KIDNEY DISEASE AND IMPLICATIONS FOR THERAPY. PURPOSE OF REVIEW: CHRONIC HYPOXIA IN THE TUBULOINTERSTITIUM HAS BEEN RECOGNIZED AS A FINAL COMMON PATHWAY THAT LEADS TO THE DEVELOPMENT OF END-STAGE RENAL DISEASE. HYPOXIA-INDUCIBLE FACTOR (HIF), A MASTER REGULATOR OF THE ADAPTIVE RESPONSE AGAINST HYPOXIA, IS INVOLVED IN THE PATHOGENESIS OF CHRONIC KIDNEY DISEASE (CKD). THIS REVIEW FOCUSES ON HIF AND NOVEL THERAPEUTIC STRATEGIES TARGETING HIF. RECENT FINDINGS: ALTHOUGH HIF UPREGULATION IS BENEFICIAL AGAINST HYPOXIC KIDNEY INJURY, IT MAY BE HARMFUL UNDER CERTAIN PATHOLOGICAL CONDITIONS. RECENT ADVANCES IN EPIGENETIC CHANGES PROVIDE AN ADDITIONAL LAYER OF COMPLEXITY TO OUR UNDERSTANDING OF GENE REGULATION IN RESPONSE TO HYPOXIA, WHICH IS MOST LIKELY INVOLVED IN THE PROGRESSION OF CKD. ON THE BASIS OF THIS NOVEL KNOWLEDGE, THE PHARMACOLOGICAL ACTIVATION AND MODULATION OF HIF IS EMERGING AS A NOVEL THERAPEUTIC TARGET. SUMMARY: HIF PLAYS A CRUCIAL ROLE IN THE PATHOPHYSIOLOGY OF CKD. THE UNDERLYING MOLECULAR MECHANISMS, INCLUDING EPIGENETICS, HAVE BEEN THOROUGHLY INVESTIGATED. ON THE BASIS OF THE EXPERIMENTAL DATA AVAILABLE TO DATE, THE PHARMACOLOGICAL ACTIVATION OF HIF IS LIKELY A NOVEL PROMISING THERAPY FOR CKD. 2014 3 5370 28 RECENT ADVANCES IN UNDERSTANDING OF CHRONIC KIDNEY DISEASE. CHRONIC KIDNEY DISEASE (CKD) IS DEFINED AS ANY CONDITION THAT CAUSES REDUCED KIDNEY FUNCTION OVER A PERIOD OF TIME. FIBROSIS, TUBULAR ATROPHY AND INTERSTITIAL INFLAMMATION ARE THE HALLMARK OF PATHOLOGICAL FEATURES IN CKD. REGARDLESS OF INITIAL INSULT, CKD HAS SOME COMMON PATHWAYS LEADING CKD TO END-STAGE KIDNEY DISEASE, INCLUDING HYPOXIA IN THE TUBULOINTERSTITIUM AND PROTEINURIA. RECENT ADVANCES IN GENOME EDITING TECHNOLOGIES AND STEM CELL RESEARCH GIVE GREAT INSIGHTS TO UNDERSTAND THE PATHOGENESIS OF CKD, INCLUDING IDENTIFICATIONS OF THE ORIGINS OF RENAL MYOFIBROBLASTS AND TUBULAR EPITHELIAL CELLS UPON INJURY. ENVIRONMENTAL FACTORS SUCH AS HYPOXIA, OXIDATIVE STRESS, AND EPIGENETIC FACTORS IN RELATION TO CKD ARE ALSO DISCUSSED. 2015 4 2614 36 EPIGENETICS: NEW QUESTIONS ON THE RESPONSE TO HYPOXIA. REDUCTION IN OXYGEN LEVELS BELOW NORMAL CONCENTRATIONS PLAYS IMPORTANT ROLES IN DIFFERENT NORMAL AND PATHOLOGICAL CONDITIONS, SUCH AS DEVELOPMENT, TUMORIGENESIS, CHRONIC KIDNEY DISEASE AND STROKE. ORGANISMS EXPOSED TO HYPOXIA TRIGGER CHANGES AT BOTH CELLULAR AND SYSTEMIC LEVELS TO RECOVER OXYGEN HOMEOSTASIS. MOST OF THESE PROCESSES ARE MEDIATED BY HYPOXIA INDUCIBLE FACTORS, HIFS, A FAMILY OF TRANSCRIPTION FACTORS THAT DIRECTLY INDUCE THE EXPRESSION OF SEVERAL HUNDRED GENES IN MAMMALIAN CELLS. ALTHOUGH DIFFERENT ASPECTS OF HIF REGULATION ARE WELL KNOWN, IT IS STILL UNCLEAR BY WHICH PRECISE MECHANISM HIFS ACTIVATE TRANSCRIPTION OF THEIR TARGET GENES. CONCOMITANTLY, HYPOXIA PROVOKES A DRAMATIC DECREASE OF GENERAL TRANSCRIPTION THAT SEEMS TO RELY IN PART ON EPIGENETIC CHANGES THROUGH A POORLY UNDERSTOOD MECHANISM. IN THIS REVIEW WE DISCUSS THE CURRENT KNOWLEDGE ON CHROMATIN CHANGES INVOLVED IN HIF DEPENDENT GENE ACTIVATION, AS WELL AS ON OTHER EPIGENETIC CHANGES, NOT NECESSARILY LINKED TO HIF THAT TAKE PLACE UNDER HYPOXIC CONDITIONS. 2011 5 4755 27 NOVEL THERAPEUTIC STRATEGY WITH HYPOXIA-INDUCIBLE FACTORS VIA REVERSIBLE EPIGENETIC REGULATION MECHANISMS IN PROGRESSIVE TUBULOINTERSTITIAL FIBROSIS. HYPOXIA-INDUCIBLE FACTOR (HIF) IS A TRANSCRIPTIONAL MASTER REGULATOR THAT TAKES CONTROL OF THE GENE EXPRESSIONS UNDER HYPOXIA. SEVERAL LINES OF EVIDENCE HAVE SHOWN THAT CHRONIC HYPOXIA IN TUBULOINTERSTITIUM RESULTS IN IRREVERSIBLE RENAL DISEASE. RECENTLY, HIF1 WAS REPORTED TO ORGANIZE A CLUSTER OF HISTONE-MODIFYING ENZYMES BY BINDING TO THEIR PROMOTER REGIONS IN VARIOUS KINDS OF CELL LINES. HOWEVER, ITS FUNCTION IN RENAL DISEASE REMAINS LARGELY UNKNOWN. WE FOCUSED ON THE EPIGENETIC REGULATION ON THE PROGRESSION OF CHRONIC KIDNEY DISEASE AND HAVE REVIEWED THE LATEST KNOWLEDGE IN THIS AREA WITH SPECIAL EMPHASIS ON THE INVOLVEMENT OF HIF. FOR EXAMPLE, A SET OF HIF1 DOWNSTREAM TARGET GENES ALSO WERE REPORTED TO BE REGULATED BY COOPERATIVE COMBINATION OF HIF1 AND HISTONE DEMETHYLASE. WE SUGGEST A NOVEL EPIGENETIC PATHWAY THAT AFFECTS THE FINAL COMMON PATHWAY TO END-STAGE RENAL DISEASE IN ADDITION TO THE TUBULOINTERSTITIAL HYPOXIA. WE EMPHASIZE THE IMPORTANCE OF FIGURING OUT THE EPIGENETIC MECHANISMS OF RENAL FAILURE TO FIND THE NOVEL THERAPEUTIC APPROACH OF CHRONIC KIDNEY DISEASE. 2013 6 2788 35 FACTORS AFFECTING THE TRANSITION OF ACUTE KIDNEY INJURY TO CHRONIC KIDNEY DISEASE: POTENTIAL MECHANISMS AND FUTURE PERSPECTIVES. ACUTE KIDNEY INJURY (AKI) IS DEFINED AS A RAPID LOSS OF KIDNEY FUNCTION CHARACTERISED BY INFLAMMATION AND CELL DEATH, ULTIMATELY LEADING TO FURTHER FUNCTIONAL AND STRUCTURAL RENAL ALTERATIONS. BASED ON EXPERIMENTAL AND EPIDEMIOLOGICAL PIECES OF EVIDENCE, AKI MAY PROGRESS TO CHRONIC KIDNEY DISEASE (CKD) EVEN AFTER A RECOVERY PERIOD DUE TO MALADAPTIVE REPAIR AND OTHER UNDERLYING MECHANISMS SUCH AS HEIGHTENED WNT SIGNALLING, OVERSTIMULATION OF THE RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM (RAAS) PATHWAY, EPIGENETIC ALTERATIONS AND INHIBITION OF HYPOXIA-INDUCIBLE FACTOR (HIF) DEPENDENT DEFENCES. IT HAS BEEN REPORTED THAT RAAS ACTIVATION SUBSEQUENT TO RENAL INSULT MEDIATES INFLAMMATORY AND FIBROTIC MECHANISMS, WHICH ARE A HALLMARK OF CKD. MOREOVER, INTERESTING EVIDENCE REGARDING THE EXPOSURE-DEPENDENT DUAL ROLE OF WNT SIGNALLING IN BOTH INJURY AND REPAIR, EPIGENETIC CHANGES UNDERLYING KIDNEY DISEASE SUGGEST A POTENTIAL THERAPEUTIC ROLE OF THESE PATHWAYS IN AKI TO CKD CONTINUUM. IN ADDITION, THE HYPOXIA-INDEPENDENT RENAL BENEFITS OF ERYTHROPOIETIN SUCH AS ANTI-APOPTOSIS AND TUBULAR REGENERATION ALSO PRESENT AN AUSPICIOUS TARGET WHICH COULD BE USEFUL IN CLINICAL SETTINGS. IN THIS REVIEW, THE SPECIFIC ROLES OF THESE PATHWAYS IN KIDNEY DISEASE, THEIR PATHOLOGICAL MECHANISMS AND THERAPEUTIC STRATEGIES ARE DISCUSSED. MOREOVER, NOTABLE REPORTS CONCERNING STEM CELL THERAPY WHICH HOLD PROMISE IN HALTING AKI-CKD CONTINUUM WILL BE ELABORATED. 2019 7 2195 30 EPIGENETIC MODIFICATION MECHANISMS INVOLVED IN INFLAMMATION AND FIBROSIS IN RENAL PATHOLOGY. THE GROWING INCIDENCE OF OBESITY, HYPERTENSION, AND DIABETES, COUPLED WITH THE AGING OF THE POPULATION, IS INCREASING THE PREVALENCE OF RENAL DISEASES IN OUR SOCIETY. CHRONIC KIDNEY DISEASE (CKD) IS CHARACTERIZED BY PERSISTENT INFLAMMATION, FIBROSIS, AND LOSS OF RENAL FUNCTION LEADING TO END-STAGE RENAL DISEASE. NOWADAYS, CKD TREATMENT HAS LIMITED EFFECTIVENESS UNDERSCORING THE IMPORTANCE OF THE DEVELOPMENT OF INNOVATIVE THERAPEUTIC OPTIONS. RECENT STUDIES HAVE IDENTIFIED HOW EPIGENETIC MODIFICATIONS PARTICIPATE IN THE SUSCEPTIBILITY TO CKD AND HAVE EXPLAINED HOW THE ENVIRONMENT INTERACTS WITH THE RENAL CELL EPIGENOME TO CONTRIBUTE TO RENAL DAMAGE. EPIGENETIC MECHANISMS REGULATE CRITICAL PROCESSES INVOLVED IN GENE REGULATION AND DOWNSTREAM CELLULAR RESPONSES. THE MOST RELEVANT EPIGENETIC MODIFICATIONS THAT PLAY A CRITICAL ROLE IN RENAL DAMAGE INCLUDE DNA METHYLATION, HISTONE MODIFICATIONS, AND CHANGES IN MIRNA LEVELS. IMPORTANTLY, THESE EPIGENETIC MODIFICATIONS ARE REVERSIBLE AND, THEREFORE, A SOURCE OF POTENTIAL THERAPEUTIC TARGETS. HERE, WE WILL EXPLAIN HOW EPIGENETIC MECHANISMS MAY REGULATE ESSENTIAL PROCESSES INVOLVED IN RENAL PATHOLOGY AND HIGHLIGHT SOME POSSIBLE EPIGENETIC THERAPEUTIC STRATEGIES FOR CKD TREATMENT. 2018 8 2293 33 EPIGENETIC REGULATION IN THE ACUTE KIDNEY INJURY TO CHRONIC KIDNEY DISEASE TRANSITION. EPIGENETIC MODIFICATIONS HAVE EMERGED AS A NEW, IMPORTANT CONTRIBUTOR TO GENE EXPRESSION REGULATION IN BOTH NORMAL AND PATHOPHYSIOLOGICAL CONDITIONS. EPIGENETICS HAVE BEEN STUDIED IN MANY DISEASES AND CONDITIONS SUCH AS ACUTE KIDNEY INJURY (AKI), A SYNDROME WITH A HIGH PREVALENCE THAT CARRIES A POOR PROGNOSIS WITH INCREASED MORBIDITY AND MORTALITY. IN ADDITION, IT HAS RECENTLY BEEN SHOWN THAT AKI INCREASES THE RISK FOR THE DEVELOPMENT OF CHRONIC KIDNEY DISEASE (CKD). THE SPECIFIC MOLECULAR MECHANISMS BY WHICH AKI INCREASES THE RISK OF CKD AND END STAGE RENAL DISEASE (ESRD) REMAIN UNKNOWN, ALTHOUGH THERE IS NEW EVIDENCE SUPPORTING A ROLE OF EPIGENETIC CHANGES. THE MOST STUDIED EPIGENETIC REGULATIONS IN AKI ARE CHROMATIN COMPACTION, DNA METHYLATION, AND HISTONE ACETYLATION/DEACETYLATION. THESE MODIFICATIONS PREDOMINANTLY INCREASE THE PRODUCTION OF PRO-INFLAMMATORY AND PROFIBROTIC CYTOKINES SUCH AS: MONOCYTE CHEMOATTRACTANT PROTEIN-1 (MCP-1), COMPLEMENT PROTEIN 3 (C3), TRANSFORMING GROWTH FACTOR BETA (TGF-BETA) THAT HAVE BEEN SHOWN FOR PERPETUATING INFLAMMATION, PROMOTING EPITHELIAL-TO-MESENCHYMAL TRANSITION (EMT) AND ULTIMATELY CAUSING RENAL FIBROSIS. A REVIEW OF EPIGENETIC MECHANISMS, THE PATHOPHYSIOLOGY OF AKI AND RECENT STUDIES THAT IMPLICATE EPIGENETIC MODIFICATIONS IN AKI AND IN THE TRANSITION TO CKD ARE DISCUSSED BELOW. 2015 9 4668 28 NEW INSIGHTS INTO MOLECULAR MECHANISMS OF EPIGENETIC REGULATION IN KIDNEY DISEASE. THE NUMBER OF PATIENTS WITH KIDNEY FAILURE HAS INCREASED IN RECENT YEARS. DIFFERENT FACTORS CONTRIBUTE TO THE PROGRESSION OF CHRONIC KIDNEY DISEASE, INCLUDING GLOMERULAR SCLEROSIS, ATHEROSCLEROSIS OF THE RENAL ARTERIES AND TUBULOINTERSTITIAL FIBROSIS. TUBULOINTERSTITIAL INJURY IS INDUCED BY HYPOXIA AND OTHER INFLAMMATORY SIGNALS, LEADING TO FIBROBLAST ACTIVATION. TECHNOLOGICAL ADVANCES USING HIGH-THROUGHPUT SEQUENCING HAS ENABLED THE DETERMINATION OF THE EXPRESSION PROFILE OF ALMOST ALL GENES, REVEALING THAT GENE EXPRESSION IS INTRICATELY REGULATED BY DNA METHYLATION, HISTONE MODIFICATION, CHANGES IN CHROMOSOME CONFORMATION, LONG NON-CODING RNAS AND MICRORNAS. THESE EPIGENETIC MODIFICATIONS ARE STORED AS CELLULAR EPIGENETIC MEMORY. EPIGENETIC MEMORY LEADS TO ADULT-ONSET DISEASE OR AGEING IN THE LONG TERM AND MAY POSSIBLY PLAY AN IMPORTANT ROLE IN THE KIDNEY DISEASE PROCESS. HEREIN WE EMPHASIZE THE IMPORTANCE OF CLARIFYING THE MOLECULAR MECHANISMS UNDERLYING EPIGENETIC MODIFICATIONS BECAUSE THIS MAY LEAD TO THE DEVELOPMENT OF NEW THERAPEUTIC TARGETS IN KIDNEY DISEASE. 2016 10 5420 34 REGULATION OF HYPOXIA-INDUCIBLE FACTOR IN KIDNEY DISEASE. HYPOXIA PLAYS A CRUCIAL ROLE IN THE PATHOPHYSIOLOGY OF ACUTE KIDNEY INJURY (AKI) AND PRESUMABLY ALSO CHRONIC KIDNEY DISEASE (CKD). HYPOXIA-INDUCIBLE FACTOR (HIF) IS THE MASTER TRANSCRIPTION FACTOR THAT REGULATES ADAPTIVE RESPONSES AGAINST HYPOXIA. UNDER HYPOXIC CONDITIONS, HIF ACTIVATES TARGET GENES WITH HYPOXIA-RESPONSIVE ELEMENTS IN THEIR REGULATORY REGIONS. THE HIF ISOFORMS AND REGULATORS OF HIF (I.E. PROLYL HYDROXYLASES) SHOW CELL TYPE-SPECIFIC DISTRIBUTIONS. HYPOXIA IS OBSERVED IN BOTH ISCHAEMIC AND SO-CALLED NON-ISCHAEMIC FORMS OF AKI. IN ADDITION TO THE ACUTE PHASE, HYPOXIA MAY ENSUE DURING THE RECOVERY PHASE OF AKI, POSSIBLY DUE TO THE OXYGEN-CONSUMING PROCESSES OF CELL GROWTH AND PROLIFERATION FOR REPAIR. ALTHOUGH HIF PROTECTS THE KIDNEY AGAINST AKI, INTRINSIC HIF ACTIVATION IS SUBMAXIMAL IN AKI AND FURTHER AUGMENTATION OF HIF AMELIORATES DISEASE MANIFESTATIONS. THE KIDNEY IN CKD ALSO SUFFERS FROM HYPOXIA CAUSED BY MULTIPLE MECHANISMS, INCLUDING SUSTAINED OXYGEN DEMANDS IN THE REMAINING NEPHRONS DUE TO MALADAPTIVE TUBULOGLOMERULAR FEEDBACK. WHETHER HIF IS CHRONICALLY UPREGULATED IN CKD IS CONTENTIOUS. HYPOXIA-INDUCIBLE FACTOR ACTIVATION IS A PROMISING THERAPEUTIC APPROACH TO CKD, BUT EXCESSIVE ACTIVATION OF HIF MAY BE DELETERIOUS. IT IS LIKELY THAT THERE IS A THERAPEUTIC WINDOW OF HIF ACTIVATION IN CHRONIC CONDITIONS. UNDER CERTAIN CIRCUMSTANCES, ANIMALS WITH CKD ARE PROTECTED AGAINST AKI AND THIS MAY BE EXPLAINED BY NON-PHYSIOLOGICAL HYPOXIA OF THE KIDNEY AND SUBSEQUENT HIF EXPRESSION. IN ADDITION, AN ACUTE HYPOXIC INSULT MAY INDUCE LONG-LASTING CHANGES, POSSIBLY INCLUDING EPIGENETIC MODIFICATIONS INDUCED BY HIF. THESE OBSERVATIONS SUGGEST A COMPLEX INTERACTION BETWEEN AKI AND CKD VIA HYPOXIA AND HIF ACTIVATION. 2013 11 6511 33 TRANSCRIPTION FACTORS AS THERAPEUTIC TARGETS IN CHRONIC KIDNEY DISEASE. THE GROWING NUMBER OF PATIENTS WITH CHRONIC KIDNEY DISEASE (CKD) IS RECOGNIZED AS AN EMERGING PROBLEM WORLDWIDE. RECENT STUDIES HAVE INDICATED THAT DEREGULATION OF TRANSCRIPTION FACTORS IS ASSOCIATED WITH THE ONSET OR PROGRESSION OF KIDNEY DISEASE. SEVERAL CLINICAL TRIALS INDICATED THAT REGRESSION OF CKD MAY BE FEASIBLE VIA ACTIVATION OF THE TRANSCRIPTION FACTOR NUCLEAR FACTOR ERYTHROID-2 RELATED FACTOR 2 (NRF2), WHICH SUGGESTS THAT TRANSCRIPTION FACTORS MAY BE POTENTIAL DRUG TARGETS FOR CKD. AGENTS STABILIZING HYPOXIA-INDUCIBLE FACTOR (HIF), WHICH MAY BE BENEFICIAL FOR RENAL ANEMIA AND RENAL PROTECTION, ARE ALSO NOW UNDER CLINICAL TRIAL. RECENTLY, WE HAVE REPORTED THAT THE TRANSCRIPTION FACTOR KRUPPEL-LIKE FACTOR 4 (KLF4) REGULATES THE GLOMERULAR PODOCYTE EPIGENOME, AND THAT THE ANTIPROTEINURIC EFFECT OF THE RENIN(-)ANGIOTENSIN SYSTEM BLOCKADE MAY BE PARTIALLY MEDIATED BY KLF4. KLF4 IS ONE OF THE YAMANAKA FACTORS THAT INDUCES IPS CELLS AND IS REPORTED TO BE INVOLVED IN EPIGENETIC REMODELING. IN THIS ARTICLE, WE SUMMARIZE THE TRANSCRIPTION FACTORS ASSOCIATED WITH CKD AND PARTICULARLY FOCUS ON THE POSSIBILITY OF TRANSCRIPTION FACTORS BEING NOVEL DRUG TARGETS FOR CKD THROUGH EPIGENETIC MODULATION. 2018 12 5660 32 SEX-SPECIFIC EPIGENETIC PROGRAMMING IN RENAL FIBROSIS AND INFLAMMATION. THE GROWING PREVALENCE OF HYPERTENSION, HEART DISEASE, DIABETES, AND OBESITY ALONG WITH AN AGING POPULATION, IS LEADING TO HIGHER INCIDENCE OF RENAL DISEASES IN THE SOCIETY. CHRONIC KIDNEY DISEASE (CKD) IS CHARACTERIZED MAINLY BY PERSISTENT INFLAMMATION, FIBROSIS, AND GRADUAL LOSS OF RENAL FUNCTION LEADING TO RENAL FAILURE. SEX IS A KNOWN CONTRIBUTOR TO THE DIFFERENCES IN INCIDENCE AND PROGRESSION OF CKD. EPIGENETIC PROGRAMMING IS AN ESSENTIAL REGULATOR OF RENAL PHYSIOLOGY AND IS CRITICALLY INVOLVED IN THE PATHOPHYSIOLOGY OF RENAL INJURY AND FIBROSIS. EPIGENETIC SIGNALING INTEGRATES INTRINSIC AND EXTRINSIC SIGNALS ONTO THE GENOME, AND VARIOUS ENVIRONMENTAL AND HORMONAL STIMULI, INCLUDING SEX HORMONES, WHICH REGULATE GENE EXPRESSION AND DOWNSTREAM CELLULAR RESPONSES. THE MOST EXTENSIVELY STUDIED EPIGENETIC ALTERATIONS THAT PLAY A CRITICAL ROLE IN RENAL DAMAGE INCLUDE HISTONE MODIFICATIONS AND DNA METHYLATION. NOTABLY, THESE EPIGENETIC ALTERATIONS ARE REVERSIBLE, MAKING THEM CANDIDATES FOR POTENTIAL THERAPEUTIC TARGETS FOR THE TREATMENT OF RENAL DISEASES. HERE, WE WILL SUMMARIZE THE CURRENT KNOWLEDGE ON SEX-DIFFERENCES IN EPIGENETIC MODULATION OF RENAL FIBROSIS AND INFLAMMATION AND HIGHLIGHT SOME POSSIBLE EPIGENETIC THERAPEUTIC STRATEGIES FOR CKD TREATMENT. 2023 13 5988 30 TGF-BETA/SMAD AND RENAL FIBROSIS. RENAL FIBROSIS IS CHARACTERIZED BY EXCESSIVE DEPOSITION OF EXTRACELLULAR MATRIX (ECM) THAT DISRUPTS AND REPLACES FUNCTIONAL PARENCHYMA, WHICH LEADS TO ORGAN FAILURE. IT IS KNOWN AS THE MAJOR PATHOLOGICAL MECHANISM OF CHRONIC KIDNEY DISEASE (CKD). ALTHOUGH CKD HAS AN IMPACT ON NO LESS THAN 10% OF THE WORLD POPULATION, THERAPEUTIC OPTIONS ARE STILL LIMITED. REGARDLESS OF ETIOLOGY, ELEVATED TGF-BETA LEVELS ARE HIGHLY CORRELATED WITH THE ACTIVATED PRO-FIBROTIC PATHWAYS AND DISEASE PROGRESSION. TGF-BETA, THE KEY DRIVER OF RENAL FIBROSIS, IS INVOLVED IN A DYNAMIC PATHOPHYSIOLOGICAL PROCESS THAT LEADS TO CKD AND END-STAGE RENAL DISEASE (ESRD). IT IS BECOMING CLEAR THAT EPIGENETICS REGULATES RENAL PROGRAMMING, AND THEREFORE, THE DEVELOPMENT AND PROGRESSION OF RENAL DISEASE. INDEED, RECENT EVIDENCE SHOWS TGF-BETA1/SMAD SIGNALING REGULATES RENAL FIBROSIS VIA EPIGENETIC-CORRELATED MECHANISMS. THIS REVIEW FOCUSES ON THE FUNCTION OF TGF-BETA/SMADS IN RENAL FIBROGENESIS, AND THE ROLE OF EPIGENETICS AS A REGULATOR OF PRO-FIBROTIC GENE EXPRESSION. 2019 14 1487 29 DNA DAMAGE AND EPIGENETIC CHANGES IN KIDNEY DISEASES - FOCUSED ON TRANSCRIPTION FACTORS IN PODOCYTES. RECENTLY IT HAS BEEN SHOWN THAT EPIGENETIC MECHANISMS ARE INVOLVED IN INITIATION AND PROGRESSION OF CARIDIOVASCULAR AND METABOLIC DISEASES, INCLUDING DIABETES, OBESITY, ATHEROSCLEROSIS, HEART FAILURE, HYPERTENSION AND KIDNEY DISEASES. IN THESE CHRONIC DISEASES, VARIOUS EXOGENOUS AND ENDOGENOUS STRESSES CAUSE DNA DAMAGE, FOLLOWED BY DNA REPAIR PROCESS. ACCUMULATION OF DNA DAMAGES AND IMPAIRED REPAIR PROCESS CAN LEAD TO EPIGENETIC CHANGES, WHICH MAY CONTRIBUTE TO ONSET AND PROGRESSION OF DISEASES. RECENTLY WE HAVE SHOWN THAT THERAPEUTIC EFFECT OF TRANSCRIPTION FACTOR KLF4 (KRUPPEL-LIKE FACTOR 4) IN KIDNEY GLOMERULAR EPITHELIAL CELLS (PODOCYTES) ON PROTEINURIC KIDNEY DISEASES THROUGH EPIGENETIC MECHANISMS. OUR RESULT SUGGESTS THE POSSIBILITY OF TRANSCRIPTION FACTORS AS A TARGET OF SELECTIVE EPIGENETIC THERAPY. MOREOVER, WE HAVE REPORTED THAT RENIN-ANGIOTENSIN SYSTEM (RAS) BLOCKERS, WHICH ARE WIDELY PRESCRIBED FOR THE TREATMENT OF CARDIOVASCULAR DISEASES, CAN RESTORE EPIGENETIC CHANGES THROUGH KLF4 IN PART. THESE RESULTS SUGGEST THAT ACTIVATION OF RAS CAUSES EPIGENETIC CHANGES IN DISEASE STATES, AND ELUCIDATION OF THE PRECISE MECHANISM MAY LEAD TO ESTABLISHMENT OF NOVEL THERAPEUTIC TARGET OF KIDNEY DISEASES. IN THIS REVIEW WE FOCUS ON DNA DAMAGE REPAIR SYSTEM AND EPIGENETIC MODULATORS IN DISEASE STATES, AND SPECULATE A CANDIDATE FOR EPIGENETIC THERAPY OF KIDNEY DISEASES. 2016 15 6510 35 TRANSCRIPTION FACTORS AND EPIGENETIC MODULATION: ITS THERAPEUTIC IMPLICATION IN CHRONIC KIDNEY DISEASE. RECENTLY EMERGING EVIDENCE HAS SHOWN THAT EPIGENETIC MECHANISMS ARE INVOLVED IN INITIATION AND PROGRESSION OF VARIOUS DISEASES, INCLUDING KIDNEY DISEASES. IN THE PRESENT ARTICLE, WE REVIEW THE CURRENT DATA REGARDING THE ROLE OF EPIGENETIC MODULATION IN CHRONIC KIDNEY DISEASE (CKD) AND KIDNEY FIBROSIS, INCLUDING DNA METHYLATION AND HISTONE MODIFICATION. ESPECIALLY WE FOCUSED ON THE ROLE OF TRANSCRIPTION FACTORS IN EPIGENETIC MODULATION AND THE POSSIBILITY OF THERAPEUTIC TARGET OF CKD. WE HAVE RECENTLY REPORTED THAT TRANSCRIPTION FACTOR KRUPPEL-LIKE FACTOR 4 (ALSO KNOWN AS GUT-ENRICHED KRUPPEL-LIKE FACTOR) IS EXPRESSED IN KIDNEY PODOCYTES (VISCERAL EPITHELIAL CELLS) AND MODULATES PODOCYTE PHENOTYPE BY GENE-SELECTIVE EPIGENETIC CONTROL. TARGETING TRANSCRIPTION FACTORS FOR EPIGENETIC MODIFICATION MAY BE A GOOD CANDIDATE FOR REMISSION AND REGRESSION OF CKD. IT IS NECESSARY FOR THE THERAPY OF CKD WITH AN EPIGENETIC-BASED APPROACH TO INVESTIGATE ORGAN-, TISSUE-, OR GENE-SPECIFIC TREATMENT METHODS FOR REDUCTION OF SIDE EFFECTS. 2015 16 607 36 BEYOND GENETICS: EPIGENETIC CODE IN CHRONIC KIDNEY DISEASE. EPIGENETICS REFERS TO A HERITABLE CHANGE IN THE PATTERN OF GENE EXPRESSION THAT IS MEDIATED BY A MECHANISM SPECIFICALLY NOT DUE TO ALTERATIONS IN THE PRIMARY NUCLEOTIDE SEQUENCE. WELL-KNOWN EPIGENETIC MECHANISMS ENCOMPASS DNA METHYLATION, CHROMATIN REMODELING (HISTONE MODIFICATIONS), AND RNA INTERFERENCE. FUNCTIONALLY, EPIGENETICS PROVIDES AN EXTRA LAYER OF TRANSCRIPTIONAL CONTROL AND PLAYS A CRUCIAL ROLE IN NORMAL PHYSIOLOGICAL DEVELOPMENT, AS WELL AS IN PATHOLOGICAL CONDITIONS. ABERRANT DNA METHYLATION IS IMPLICATED IN IMMUNE DYSFUNCTION, INFLAMMATION, AND INSULIN RESISTANCE. EPIGENETIC CHANGES MAY BE RESPONSIBLE FOR 'METABOLIC MEMORY' AND DEVELOPMENT OF MICRO- AND MACROVASCULAR COMPLICATIONS OF DIABETES. MICRORNAS ARE CRITICAL IN THE MAINTENANCE OF GLOMERULAR HOMEOSTASIS AND HENCE RNA INTERFERENCE MAY BE IMPORTANT IN THE PROGRESSION OF RENAL DISEASE. RECENT STUDIES HAVE SHOWN THAT EPIGENETIC MODIFICATIONS ORCHESTRATE THE EPITHELIAL-MESENCHYMAL TRANSITION AND EVENTUALLY FIBROSIS OF THE RENAL TISSUE. OXIDATIVE STRESS, INFLAMMATION, HYPERHOMOCYSTEINEMIA, AND UREMIC TOXINS COULD INDUCE EPIMUTATIONS IN CHRONIC KIDNEY DISEASE. EPIGENETIC ALTERATIONS ARE ASSOCIATED WITH INFLAMMATION AND CARDIOVASCULAR DISEASE IN PATIENTS WITH CHRONIC KIDNEY DISEASE. REVERSIBLE NATURE OF THE EPIGENETIC CHANGES GIVES A UNIQUE OPPORTUNITY TO HALT OR EVEN REVERSE THE DISEASE PROCESS THROUGH TARGETED THERAPEUTIC STRATEGIES. 2011 17 4463 36 MOLECULAR MECHANISMS OF HISTONE DEACETYLASES AND INHIBITORS IN RENAL FIBROSIS PROGRESSION. RENAL FIBROSIS IS A COMMON PROGRESSIVE MANIFESTATION OF CHRONIC KIDNEY DISEASE. THIS PHENOMENON OF SELF-REPAIR IN RESPONSE TO KIDNEY DAMAGE SERIOUSLY AFFECTS THE NORMAL FILTRATION FUNCTION OF THE KIDNEY. YET, THERE ARE NO SPECIFIC TREATMENTS FOR THE CONDITION, WHICH MARKS FIBROSIS AS AN IRREVERSIBLE PATHOLOGICAL SEQUELA. AS SUCH, THERE IS A PRESSING NEED TO IMPROVE OUR UNDERSTANDING OF HOW FIBROSIS DEVELOPS AT THE CELLULAR AND MOLECULAR LEVELS AND EXPLORE SPECIFIC TARGETED THERAPIES FOR THESE PATHOGENIC MECHANISMS. IT IS NOW GENERALLY ACCEPTED THAT RENAL FIBROSIS IS A PATHOLOGICAL TRANSITION MEDIATED BY EXTRACELLULAR MATRIX (ECM) DEPOSITION, ABNORMAL ACTIVATION OF MYOFIBROBLASTS, AND EPITHELIAL-MESENCHYMAL TRANSITION (EMT) OF RENAL TUBULAR EPITHELIAL CELLS UNDER THE REGULATION OF TGF-BETA. HISTONE DEACETYLASES (HDACS) APPEAR TO PLAY AN ESSENTIAL ROLE IN PROMOTING RENAL FIBROSIS THROUGH NON-HISTONE EPIGENETIC MODIFICATIONS. IN THIS REVIEW, WE SUMMARIZE THE MECHANISMS OF RENAL FIBROSIS AND THE SIGNALING PATHWAYS THAT MIGHT BE INVOLVED IN HDACS IN RENAL FIBROSIS, AND THE SPECIFIC MECHANISMS OF ACTION OF VARIOUS HDAC INHIBITORS (HDACI) IN THE ANTI-FIBROTIC PROCESS TO ELUCIDATE HDACI AS A NOVEL THERAPEUTIC TOOL TO SLOW DOWN THE PROGRESSION OF RENAL FIBROSIS. 2022 18 2193 36 EPIGENETIC MODIFICATION DRIVES ACUTE KIDNEY INJURY-TO-CHRONIC KIDNEY DISEASE PROGRESSION. ACUTE KIDNEY INJURY (AKI) IS A COMMON CLINICAL CRITICAL DISEASE. DUE TO ITS HIGH MORBIDITY, INCREASING RISK OF COMPLICATIONS, HIGH MORTALITY RATE, AND HIGH MEDICAL COSTS, IT HAS BECOME A GLOBAL CONCERN FOR HUMAN HEALTH PROBLEMS. INITIALLY, RESEARCHERS BELIEVED THAT KIDNEYS HAVE A STRONG ABILITY TO REGENERATE AND REPAIR, BUT STUDIES OVER THE PAST 20 YEARS HAVE FOUND THAT KIDNEYS DAMAGED BY AKI ARE OFTEN INCOMPLETE OR EVEN UNABLE TO REPAIR. EVEN WHEN SERUM CREATININE RETURNS TO BASELINE LEVELS, RENAL STRUCTURAL DAMAGE PERSISTS FOR A LONG TIME, LEADING TO THE DEVELOPMENT OF CHRONIC KIDNEY DISEASE (CKD). THE MECHANISM OF AKI-TO-CKD TRANSITION HAS NOT BEEN FULLY ELUCIDATED. AS AN IMPORTANT REGULATOR OF GENE EXPRESSION, EPIGENETIC MODIFICATIONS, SUCH AS HISTONE MODIFICATION, DNA METHYLATION, AND NONCODING RNAS, MAY PLAY AN IMPORTANT ROLE IN THIS PROCESS. ALTERATIONS IN EPIGENETIC MODIFICATION ARE INDUCED BY HYPOXIA, THUS PROMOTING THE EXPRESSION OF INFLAMMATORY FACTOR-RELATED GENES AND COLLAGEN SECRETION. THIS REVIEW ELABORATED THE ROLE OF EPIGENETIC MODIFICATIONS IN AKI-TO-CKD PROGRESSION, THE DIAGNOSTIC VALUE OF EPIGENETIC MODIFICATIONS BIOMARKERS IN AKI CHRONIC OUTCOME, AND THE POTENTIAL ROLE OF TARGETING EPIGENETIC MODIFICATIONS IN THE PREVENTION AND TREATMENT OF AKI TO CKD, IN ORDER TO PROVIDE IDEAS FOR THE SUBSEQUENT ESTABLISHMENT OF TARGETED THERAPEUTIC STRATEGIES TO PREVENT THE PROGRESSION OF RENAL TUBULAR-INTERSTITIAL FIBROSIS. 2021 19 6299 31 THE PROXIMAL TUBULE IS THE PRIMARY TARGET OF INJURY AND PROGRESSION OF KIDNEY DISEASE: ROLE OF THE GLOMERULOTUBULAR JUNCTION. THERE IS AN ALARMING GLOBAL INCREASE IN THE INCIDENCE OF END-STAGE KIDNEY DISEASE, FOR WHICH EARLY BIOMARKERS AND EFFECTIVE TREATMENT OPTIONS ARE LACKING. LARGELY BASED ON THE HISTOLOGY OF THE END-STAGE KIDNEY AND ON THE MODEL OF UNILATERAL URETERAL OBSTRUCTION, CURRENT INVESTIGATION IS FOCUSED ON THE PATHOGENESIS OF RENAL INTERSTITIAL FIBROSIS AS A CENTRAL MECHANISM IN THE PROGRESSION OF CHRONIC KIDNEY DISEASE (CKD). IT IS NOW RECOGNIZED THAT CUMULATIVE EPISODES OF ACUTE KIDNEY INJURY (AKI) CAN LEAD TO CKD, AND, CONVERSELY, CKD IS A RISK FACTOR FOR AKI. BASED ON RECENT AND HISTORIC STUDIES, THIS REVIEW SHIFTS ATTENTION FROM THE GLOMERULUS AND INTERSTITIUM TO THE PROXIMAL TUBULE AS THE PRIMARY SENSOR AND EFFECTOR IN THE PROGRESSION OF CKD AS WELL AS AKI. PACKED WITH MITOCHONDRIA AND DEPENDENT ON OXIDATIVE PHOSPHORYLATION, THE PROXIMAL TUBULE IS PARTICULARLY VULNERABLE TO INJURY (OBSTRUCTIVE, ISCHEMIC, HYPOXIC, OXIDATIVE, METABOLIC), RESULTING IN CELL DEATH AND ULTIMATELY IN THE FORMATION OF ATUBULAR GLOMERULI. ANIMAL MODELS OF HUMAN GLOMERULAR AND TUBULAR DISORDERS HAVE PROVIDED EVIDENCE FOR A BROAD REPERTOIRE OF MORPHOLOGICAL AND FUNCTIONAL RESPONSES OF THE PROXIMAL TUBULE, REVEALING PROCESSES OF DEGENERATION AND REPAIR THAT MAY LEAD TO NEW THERAPEUTIC STRATEGIES. MOST PROMISING ARE STUDIES THAT ENCOMPASS THE ENTIRE LIFE CYCLE FROM FETUS TO SENESCENCE, RECOGNIZING EPIGENETIC FACTORS. THE APPLICATION OF TECHNIQUES IN MOLECULAR CHARACTERIZATION OF TUBULE SEGMENTS AND THE DEVELOPMENT OF HUMAN KIDNEY ORGANOIDS MAY PROVIDE NEW INSIGHTS INTO THE MAMMALIAN KIDNEY SUBJECTED TO STRESS OR INJURY, LEADING TO BIOMARKERS OF EARLY CKD AND NEW THERAPIES. 2016 20 5826 34 STRESS SIGNAL NETWORK BETWEEN HYPOXIA AND ER STRESS IN CHRONIC KIDNEY DISEASE. CHRONIC KIDNEY DISEASE (CKD) IS CHARACTERIZED BY AN IRREVERSIBLE DECREASE IN KIDNEY FUNCTION AND INDUCTION OF VARIOUS METABOLIC DYSFUNCTIONS. ACCUMULATED FINDINGS REVEAL THAT CHRONIC HYPOXIC STRESS AND ENDOPLASMIC RETICULUM (ER) STRESS ARE INVOLVED IN A RANGE OF PATHOGENIC CONDITIONS, INCLUDING THE PROGRESSION OF CKD. BECAUSE OF THE PRESENCE OF AN ARTERIOVENOUS OXYGEN SHUNT, THE KIDNEY IS THOUGHT TO BE SUSCEPTIBLE TO HYPOXIA. CHRONIC KIDNEY HYPOXIA IS INDUCED BY A NUMBER OF PATHOGENIC CONDITIONS, INCLUDING RENAL ISCHEMIA, REDUCED PERITUBULAR CAPILLARY, AND TUBULOINTERSTITIAL FIBROSIS. THE ER IS AN ORGANELLE WHICH HELPS MAINTAIN THE QUALITY OF PROTEINS THROUGH THE UNFOLDED PROTEIN RESPONSE (UPR) PATHWAY, AND ER DYSFUNCTION ASSOCIATED WITH MALADAPTIVE UPR ACTIVATION IS NAMED ER STRESS. ER STRESS IS REPORTED TO BE RELATED TO SOME OF THE EFFECTS OF PATHOGENESIS IN KIDNEY, PARTICULARLY IN THE PODOCYTE SLIT DIAPHRAGM AND TUBULOINTERSTITIUM. FURTHERMORE, CHRONIC HYPOXIA MEDIATES ER STRESS IN BLOOD VESSEL ENDOTHELIAL CELLS AND TUBULOINTERSTITIUM VIA SEVERAL MECHANISMS, INCLUDING OXIDATIVE STRESS, EPIGENETIC ALTERATION, LIPID METABOLISM, AND THE AKT PATHWAY. IN SUMMARY, A GROWING CONSENSUS CONSIDERS THAT THESE STRESSES INTERACT VIA COMPLICATED STRESS SIGNAL NETWORKS, WHICH LEADS TO THE EXACERBATION OF CKD (FIGURE 1). THIS STRESS SIGNAL NETWORK MIGHT BE A TARGET FOR INTERVENTIONS AIMED AT AMELIORATING CKD. 2017