1 5420 130 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 2 231 26 ADAPTIVE CARDIORESPIRATORY CHANGES TO CHRONIC CONTINUOUS AND INTERMITTENT HYPOXIA. THIS CHAPTER REVIEWS CARDIORESPIRATORY ADAPTATIONS TO CHRONIC HYPOXIA (CH) EXPERIENCED AT HIGH ALTITUDE AND CARDIORESPIRATORY PATHOLOGIES ELICITED BY CHRONIC INTERMITTENT HYPOXIA (CIH) OCCURRING WITH OBSTRUCTIVE SLEEP APNEA (OSA). SHORT-TERM CH INCREASES BREATHING (VENTILATORY ACCLIMATIZATION TO HYPOXIA) AND BLOOD PRESSURE (BP) THROUGH CAROTID BODY (CB) CHEMO REFLEX. HYPERPLASIA OF GLOMUS CELLS, ALTERATIONS IN ION CHANNELS, AND RECRUITMENT OF ADDITIONAL EXCITATORY MOLECULES ARE IMPLICATED IN THE HEIGHTENED CB CHEMO REFLEX BY CH. TRANSCRIPTIONAL ACTIVATION OF HYPOXIA-INDUCIBLE FACTORS (HIF-1 AND 2) IS A MAJOR MOLECULAR MECHANISM UNDERLYING RESPIRATORY ADAPTATIONS TO SHORT-TERM CH. HIGH-ALTITUDE NATIVES EXPERIENCING LONG-TERM CH EXHIBIT BLUNTED HYPOXIC VENTILATORY RESPONSE (HVR) AND REDUCED BP DUE TO DESENSITIZATION OF CB RESPONSE TO HYPOXIA AND IMPAIRED PROCESSING OF CB SENSORY INFORMATION AT THE CENTRAL NERVOUS SYSTEM. VENTILATORY CHANGES EVOKED BY LONG-TERM CH ARE NOT READILY REVERSED AFTER RETURN TO SEA LEVEL. OSA PATIENTS AND RODENTS SUBJECTED TO CIH EXHIBIT HEIGHTENED CB CHEMO REFLEX, INCREASED HYPOXIC VENTILATORY RESPONSE, AND HYPERTENSION. INCREASED GENERATION OF REACTIVE OXYGEN SPECIES (ROS) IS A MAJOR CELLULAR MECHANISM UNDERLYING CIH-INDUCED ENHANCED CB CHEMO REFLEX AND THE ENSUING CARDIORESPIRATORY PATHOLOGIES. ROS GENERATION BY CIH IS MEDIATED BY NONTRANSCRIPTIONAL, DISRUPTED HIF-1 AND HIF-2-DEPENDENT TRANSCRIPTIONS AS WELL AS EPIGENETIC MECHANISMS. 2022 3 1177 32 CONTROL OF BREATHING AND THE CIRCULATION IN HIGH-ALTITUDE MAMMALS AND BIRDS. HYPOXIA IS AN UNREMITTING STRESSOR AT HIGH ALTITUDES THAT PLACES A PREMIUM ON OXYGEN TRANSPORT BY THE RESPIRATORY AND CARDIOVASCULAR SYSTEMS. PHENOTYPIC PLASTICITY AND GENOTYPIC ADAPTATION AT VARIOUS STEPS IN THE O2 CASCADE COULD HELP OFFSET THE EFFECTS OF HYPOXIA ON CELLULAR O2 SUPPLY IN HIGH-ALTITUDE NATIVES. IN THIS REVIEW, WE WILL DISCUSS THE UNIQUE MECHANISMS BY WHICH VENTILATION, CARDIAC OUTPUT, AND BLOOD FLOW ARE CONTROLLED IN HIGH-ALTITUDE MAMMALS AND BIRDS. ACCLIMATIZATION TO HIGH ALTITUDES LEADS TO SOME CHANGES IN RESPIRATORY AND CARDIOVASCULAR CONTROL THAT INCREASE O2 TRANSPORT IN HYPOXIA (E.G., VENTILATORY ACCLIMATIZATION TO HYPOXIA). HOWEVER, ACCLIMATIZATION OR DEVELOPMENT IN HYPOXIA CAN ALSO MODIFY CARDIORESPIRATORY CONTROL IN WAYS THAT ARE MALADAPTIVE FOR O2 TRANSPORT. HYPOXIA RESPONSES THAT AROSE AS SHORT-TERM SOLUTIONS TO O2 DEPRIVATION (E.G., PERIPHERAL VASOCONSTRICTION) OR REGIONAL VARIATION IN O2 LEVELS IN THE LUNGS (I.E., HYPOXIC PULMONARY VASOCONSTRICTION) ARE DETRIMENTAL AT IN CHRONIC HIGH-ALTITUDE HYPOXIA. EVOLVED CHANGES IN CARDIORESPIRATORY CONTROL HAVE ARISEN IN MANY HIGH-ALTITUDE TAXA, INCLUDING INCREASES IN EFFECTIVE VENTILATION, ATTENUATION OF HYPOXIC PULMONARY VASOCONSTRICTION, AND CHANGES IN CATECHOLAMINE SENSITIVITY OF THE HEART AND SYSTEMIC VASCULATURE. PARALLEL EVOLUTION OF SOME OF THESE CHANGES IN INDEPENDENT HIGHLAND LINEAGES SUPPORTS THEIR ADAPTIVE SIGNIFICANCE. MUCH LESS IS KNOWN ABOUT THE GENOMIC BASES AND POTENTIAL INTERACTIVE EFFECTS OF ADAPTATION, ACCLIMATIZATION, DEVELOPMENTAL PLASTICITY, AND TRANS-GENERATIONAL EPIGENETIC TRANSFER ON CARDIORESPIRATORY CONTROL. FUTURE WORK TO UNDERSTAND THESE VARIOUS INFLUENCES ON BREATHING AND CIRCULATION IN HIGH-ALTITUDE NATIVES WILL HELP ELUCIDATE HOW COMPLEX PHYSIOLOGICAL SYSTEMS CAN BE PUSHED TO THEIR LIMITS TO MAINTAIN CELLULAR FUNCTION IN HYPOXIA. 2015 4 3467 34 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 5 3466 36 HYPOXIA AS A KEY PLAYER IN THE AKI-TO-CKD TRANSITION. RECENT CLINICAL AND ANIMAL STUDIES HAVE SHOWN THAT ACUTE KIDNEY INJURY (AKI), EVEN IF FOLLOWED BY COMPLETE RECOVERY OF RENAL FUNCTION, CAN EVENTUALLY RESULT IN CHRONIC KIDNEY DISEASE (CKD). RENAL HYPOXIA IS EMERGING AS A KEY PLAYER IN THE PATHOPHYSIOLOGY OF THE AKI-TO-CKD TRANSITION. CAPILLARY RAREFACTION AFTER AKI EPISODES INDUCES RENAL HYPOXIA, WHICH CAN IN TURN PROFOUNDLY AFFECT TUBULAR EPITHELIAL CELLS, (MYO)FIBROBLASTS, AND INFLAMMATORY CELLS, CULMINATING IN TUBULOINTERSTITIAL FIBROSIS, I.E., PROGRESSION TO CKD. DAMAGED TUBULAR EPITHELIAL CELLS THAT FAIL TO REDIFFERENTIATE MIGHT SUPPLY A DECREASED AMOUNT OF VASCULAR ENDOTHELIAL GROWTH FACTOR AND CONTRIBUTE TO CAPILLARY RAREFACTION, THUS AGGRAVATING HYPOXIA AND FORMING A VICIOUS CYCLE. MOUNTING EVIDENCE ALSO SHOWS THAT EPIGENETIC CHANGES ARE CLOSELY RELATED TO RENAL HYPOXIA IN THE PATHOPHYSIOLOGY OF CKD PROGRESSION. ANIMAL EXPERIMENTS SUGGEST THAT TARGETING HYPOXIA IS A PROMISING STRATEGY TO BLOCK THE TRANSITION FROM AKI TO CKD. HOWEVER, THE PRECISE MECHANISMS BY WHICH HYPOXIA INDUCES THE AKI-TO-CKD TRANSITION AND BY WHICH HYPOXIA-INDUCIBLE FACTOR ACTIVATION CAN EXERT A PROTECTIVE EFFECT IN THIS CONTEXT SHOULD BE CLARIFIED IN FURTHER STUDIES. 2014 6 2023 26 EPIGENETIC CHANGES BY DNA METHYLATION IN CHRONIC AND INTERMITTENT HYPOXIA. DNA METHYLATION OF CYTOSINE RESIDUES IS A WELL-STUDIED EPIGENETIC CHANGE, WHICH REGULATES GENE TRANSCRIPTION BY ALTERING ACCESSIBILITY FOR TRANSCRIPTION FACTORS. HYPOXIA IS A PERVASIVE STIMULUS THAT AFFECTS MANY PHYSIOLOGICAL PROCESSES. THE CIRCULATORY AND RESPIRATORY SYSTEMS ADAPT TO CHRONIC SUSTAINED HYPOXIA, SUCH AS THAT ENCOUNTERED DURING A HIGH-ALTITUDE SOJOURN. MANY PEOPLE LIVING AT SEA LEVEL EXPERIENCE CHRONIC INTERMITTENT HYPOXIA (IH) DUE TO SLEEP APNEA, WHICH LEADS TO CARDIOVASCULAR AND RESPIRATORY MALADAPTATION. THIS ARTICLE PRESENTS A BRIEF UPDATE ON EMERGING EVIDENCE SUGGESTING THAT CHANGES IN DNA METHYLATION CONTRIBUTE TO PATHOLOGIES CAUSED BY CHRONIC IH AND POTENTIALLY MEDIATE ADAPTATIONS TO CHRONIC SUSTAINED HYPOXIA BY AFFECTING THE HYPOXIA-INDUCIBLE FACTOR (HIF) SIGNALING PATHWAY. 2017 7 5048 35 PHARMACOLOGICAL APPROACHES IN EITHER INTERMITTENT OR PERMANENT HYPOXIA: A TALE OF TWO EXPOSURES. HYPOXIA INDUCES SEVERAL RESPONSES AT CARDIOVASCULAR, PULMONARY AND REPRODUCTIVE LEVELS, WHICH MAY LEAD TO CHRONIC DISEASES. THIS IS RELEVANT IN HUMAN POPULATIONS EXPOSED TO HIGH ALTITUDE (HA), IN EITHER CHRONIC CONTINUOUS (PERMANENT INHABITANTS) OR INTERMITTENT FASHION (HA WORKERS, TOURISTS AND MOUNTAINEERS). IN CHILE, IT IS ESTIMATED THAT 1.000.000 PEOPLE LIVE AT HIGHLANDS AND MORE THAN 55.000 WORK IN HA SHIFTS. INITIAL RESPONSES TO HYPOXIA ARE COMPENSATORY AND INDUCE ACTIVATION OF CARDIOPROTECTIVE MECHANISMS, SUCH AS THOSE SEEN UNDER INTERMITTENT HYPOBARIC (IH) HYPOXIA, EVENTS THAT COULD MEDIATE PRECONDITIONING. HOWEVER, WHENEVER HYPOXIA IS PROLONGED, THE CHRONIC ACTIVATION OF CELLULAR RESPONSES INDUCES LONG-LASTING MODIFICATIONS THAT MAY RESULT IN ACCLIMATIZATION OR PRODUCE MALADAPTIVE CHANGES WITH INCREASE IN CARDIOVASCULAR RISK. HA EXPOSURE DURING PREGNANCY INDUCES HYPOXIA AND OXIDATIVE STRESS, WHICH IN TURN MAY PROMOTE CELLULAR RESPONSES AND EPIGENETIC MODIFICATIONS RESULTING IN SEVERE IMPAIRMENT IN GROWTH AND DEVELOPMENT. SADLY, THIS CONDITION IS ACCOMPANIED WITH AN INCREASED FETAL AND NEONATAL MORBI-MORTALITY. FURTHER, DEVELOPMENTAL HYPOXIA MAY PROGRAM CARDIO-PULMONARY CIRCULATIONS LATER IN POSTNATAL LIFE, ENDING IN VASCULAR STRUCTURAL AND FUNCTIONAL ALTERATIONS WITH AUGMENTED RISK ON PULMONARY AND CARDIOVASCULAR FAILURE. ADDITIONALLY, PERMANENT HA INHABITANTS HAVE AUGMENTED RISK AND PREVALENCE OF CHRONIC HYPOXIC PULMONARY HYPERTENSION, RIGHT VENTRICULAR HYPERTROPHY AND CARDIOPULMONARY REMODELING. SIMILAR RESPONSES ARE SEEN IN ADULTS THAT ARE INTERMITTENTLY EXPOSED TO CHRONIC HYPOXIA (CH) SUCH AS SHIFT WORKERS IN HA AREAS. THE MECHANISMS INVOLVED DETERMINING THE IMMEDIATE, SHORT AND LONG-LASTING EFFECTS ARE STILL UNCLEAR. FOR SEVERAL YEARS, THE STUDY OF THE RESPONSES TO HYPOXIC INSULTS AND PHARMACOLOGICAL TARGETS HAS BEEN THE MOTIVATION OF OUR GROUP. THIS REVIEW DESCRIBES SOME OF THE MECHANISMS UNDERLYING HYPOXIC RESPONSES AND POTENTIAL THERAPEUTIC APPROACHES WITH ANTIOXIDANTS SUCH AS MELATONIN, ASCORBATE, OMEGA 3 (OMEGA3) OR COMPOUNDS THAT INCREASE THE NITRIC OXIDE (NO) BIOAVAILABILITY. 2015 8 2034 34 EPIGENETIC CHANGES IN THE ACUTE KIDNEY INJURY-TO-CHRONIC KIDNEY DISEASE TRANSITION. PREVIOUSLY ACUTE KIDNEY INJURY (AKI) HAD BEEN BELIEVED TO BE A TRANSIENT EVENT, AND RECOVERY FROM AKI HAD BEEN THOUGHT TO LEAD TO NO CONSEQUENCES. HOWEVER, RECENT EPIDEMIOLOGICAL STUDIES HAVE SHOWN THAT EVEN IF THERE IS COMPLETE RECOVERY OF THE KIDNEY FUNCTION, AKI CAN EVENTUALLY RESULT IN CHRONIC KIDNEY DISEASE (CKD) AND EVENTUALLY IN END-STAGE KIDNEY DISEASE IN THE LONG TERM. TRANSITION OF AKI TO CKD IS MEDIATED BY MULTIPLE MECHANISMS, INCLUDING ABERRANT CELL CYCLE ARREST AND HYPOXIA. HYPOXIA OF THE KIDNEY IS INDUCED BY RAREFACTION OF THE PERITUBULAR CAPILLARIES AFTER AKI EPISODES, AND INDUCES INFLAMMATION AND FIBROSIS. IT SHOULD ALSO BE NOTED THAT EPIGENETIC CHANGES ARE CLOSELY RELATED TO HYPOXIA, AND EPIGENETIC CHANGES INDUCED BY HYPOXIA, CALLED "HYPOXIC MEMORY" CAN EXPLAIN THE AKI-TO-CKD TRANSITION IN THE LONG TERM AFTER COMPLETE RECOVERY FROM THE INITIAL AKI EPISODE. TARGETING HYPOXIA AND SUBSEQUENT EPIGENETIC CHANGES ARE PROMISING STRATEGIES TO BLOCK THE TRANSITION FROM AKI TO CKD. 2017 9 2614 38 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 10 4109 29 MECHANISMS AND DRUG THERAPY OF PULMONARY HYPERTENSION AT HIGH ALTITUDE. PULMONARY VASOCONSTRICTION REPRESENTS A PHYSIOLOGICAL ADAPTIVE MECHANISM TO HIGH ALTITUDE. IF EXAGGERATED, HOWEVER, IT IS ASSOCIATED WITH IMPORTANT MORBIDITY AND MORTALITY. RECENT MECHANISTIC STUDIES USING SHORT-TERM ACUTE HIGH ALTITUDE EXPOSURE HAVE PROVIDED INSIGHT INTO THE IMPORTANCE OF DEFECTIVE VASCULAR ENDOTHELIAL AND RESPIRATORY EPITHELIAL NITRIC OXIDE (NO) SYNTHESIS, INCREASED ENDOTHELIN-1 BIOAVAILABILITY, AND OVERACTIVATION OF THE SYMPATHETIC NERVOUS SYSTEM IN CAUSING EXAGGERATED HYPOXIC PULMONARY HYPERTENSION IN HUMANS. BASED ON THESE STUDIES, DRUGS THAT INCREASE NO BIOAVAILABILITY, ATTENUATE ENDOTHELIN-1 INDUCED PULMONARY VASOCONSTRICTION, OR PREVENT EXAGGERATED SYMPATHETIC ACTIVATION HAVE BEEN SHOWN TO BE USEFUL FOR THE TREATMENT/PREVENTION OF EXAGGERATED PULMONARY HYPERTENSION DURING ACUTE SHORT-TERM HIGH ALTITUDE EXPOSURE. THE MECHANISMS UNDERPINNING CHRONIC PULMONARY HYPERTENSION IN HIGH ALTITUDE DWELLERS ARE LESS WELL UNDERSTOOD, BUT RECENT EVIDENCE SUGGESTS THAT THEY DIFFER IN SOME ASPECTS FROM THOSE INVOLVED IN SHORT-TERM ADAPTATION TO HIGH ALTITUDE. THESE DIFFERENCES HAVE CONSEQUENCES FOR THE CHOICE OF THE TREATMENT FOR CHRONIC PULMONARY HYPERTENSION AT HIGH ALTITUDE. FINALLY, RECENT DATA INDICATE THAT FETAL PROGRAMMING OF PULMONARY VASCULAR DYSFUNCTION IN OFFSPRING OF PREECLAMPSIA AND CHILDREN GENERATED BY ASSISTED REPRODUCTIVE TECHNOLOGIES REPRESENTS A NOVEL AND FREQUENT CAUSE OF PULMONARY HYPERTENSION AT HIGH ALTITUDE. IN ANIMAL MODELS OF FETAL PROGRAMMING OF HYPOXIC PULMONARY HYPERTENSION, EPIGENETIC MECHANISMS PLAY A ROLE, AND TARGETING OF THESE MECHANISMS WITH DRUGS LOWERS PULMONARY ARTERY PRESSURE. IF EPIGENETIC MECHANISMS ALSO ARE OPERATIONAL IN THE FETAL PROGRAMMING OF PULMONARY VASCULAR DYSFUNCTION IN HUMANS, SUCH DRUGS MAY BECOME NOVEL TOOLS FOR THE TREATMENT OF HYPOXIC PULMONARY HYPERTENSION. 2013 11 5565 48 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 12 4197 30 METABOLIC PROFILES IN OVINE CAROTID ARTERIES WITH DEVELOPMENTAL MATURATION AND LONG-TERM HYPOXIA. BACKGROUND: LONG-TERM HYPOXIA (LTH) IS AN IMPORTANT STRESSOR RELATED TO HEALTH AND DISEASE DURING DEVELOPMENT. AT DIFFERENT TIME POINTS FROM FETUS TO ADULT, WE ARE EXPOSED TO HYPOXIC STRESS BECAUSE OF PLACENTAL INSUFFICIENCY, HIGH-ALTITUDE RESIDENCE, SMOKING, CHRONIC ANEMIA, PULMONARY, AND HEART DISORDERS, AS WELL AS CANCERS. INTRAUTERINE HYPOXIA CAN LEAD TO FETAL GROWTH RESTRICTION AND LONG-TERM SEQUELAE SUCH AS COGNITIVE IMPAIRMENTS, HYPERTENSION, CARDIOVASCULAR DISORDERS, DIABETES, AND SCHIZOPHRENIA. SIMILARLY, PROLONGED HYPOXIC EXPOSURE DURING ADULT LIFE CAN LEAD TO ACUTE MOUNTAIN SICKNESS, CHRONIC FATIGUE, CHRONIC HEADACHE, COGNITIVE IMPAIRMENT, ACUTE CEREBRAL AND/OR PULMONARY EDEMA, AND DEATH. AIM: LTH ALSO CAN LEAD TO ALTERATION IN METABOLITES SUCH AS FUMARATE, 2-OXOGLUTARATE, MALATE, AND LACTATE, WHICH ARE LINKED TO EPIGENETIC REGULATION OF GENE EXPRESSION. IMPORTANTLY, DURING THE INTRAUTERINE LIFE, A FETUS IS UNDER A RELATIVE HYPOXIC ENVIRONMENT, AS COMPARED TO NEWBORN OR ADULT. THUS, THE CHANGES IN GENE EXPRESSION WITH DEVELOPMENT FROM FETUS TO NEWBORN TO ADULT MAY BE AS A CONSEQUENCE OF UNDERLYING CHANGES IN THE METABOLIC PROFILE BECAUSE OF THE HYPOXIC ENVIRONMENT ALONG WITH DEVELOPMENTAL MATURATION. TO EXAMINE THIS POSSIBILITY, WE EXAMINED THE METABOLIC PROFILE IN CAROTID ARTERIES FROM NEAR-TERM FETUS, NEWBORN, AND ADULT SHEEP IN BOTH NORMOXIC AND LONG-TERM HYPOXIC ACCLIMATIZED GROUPS. RESULTS: OUR RESULTS DEMONSTRATE THAT LTH DIFFERENTIALLY REGULATED GLUCOSE METABOLISM, MITOCHONDRIAL METABOLISM, NICOTINAMIDE COFACTOR METABOLISM, OXIDATIVE STRESS AND ANTIOXIDANTS, MEMBRANE LIPID HYDROLYSIS, AND FREE FATTY ACID METABOLISM, EACH OF WHICH MAY PLAY A ROLE IN GENETIC-EPIGENETIC REGULATION. 2015 13 5826 36 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 14 2800 43 FEEDBACK REGULATORS OF HYPOXIA-INDUCIBLE FACTORS AND THEIR ROLE IN CANCER BIOLOGY. MALIGNANT TUMORS ARE CHARACTERIZED BY REGIONS OF LOW OXYGEN CONCENTRATION (HYPOXIA). THE HYPOXIC TUMOR MICROENVIRONMENT CONTRIBUTES TO TUMOR PROGRESSION BY ACTIVATING A SET OF ADAPTIVE RESPONSES VIA THE KEY TRANSCRIPTIONAL REGULATORS HIF-1ALPHA AND HIF-2ALPHA. THESE FACTORS HAVE BEEN TRADITIONALLY LINKED TO AN AGGRESSIVE TUMOR PHENOTYPE BY PROMOTING PROCESSES ESSENTIAL FOR TUMOR GROWTH, SUCH AS ANGIOGENESIS, GLYCOLYSIS, METASTASIS AND INVASION, AS WELL AS DIFFERENTIATION AND SELF RENEWAL. NOTABLY, THE COMPLEX HIF PATHWAY ALSO INITIATES ANTI-TUMORIGENIC MECHANISMS THAT LEAD TO CELL CYCLE ARREST OR CELL DEATH, INDICATING THE NEED FOR A STRINGENT CONTROL OF THE EXTENT AND THE DIRECTION OF THE HYPOXIA RESPONSE. THE IMPORTANCE OF THIS CONTROL FOR TUMOR CELL SURVIVAL IS ILLUSTRATED BY THE INTRICATE REGULATION OF HIF ACTIVITY AT THE MRNA, PROTEIN AND EPIGENETIC LEVEL BY A COMPLEX NETWORK OF POSITIVE AND NEGATIVE FEEDBACK REGULATORS. WE PROPOSE THAT THESE FEEDBACK REGULATORS HELP TO FLEXIBLY ADJUST AND ADAPT HIF ACTIVATED RESPONSES TO THE FLUCTUATING OXYGEN CONCENTRATIONS WITHIN TUMORS DURING ACUTE AND CHRONIC HYPOXIA AND TO CURTAIL THE TUMOR-SUPPRESSING COMPONENTS OF THE HIF PATHWAY. MOREOVER, FEEDBACK REGULATION OF HIF INDUCES A SWITCH FROM HIF-1ALPHA TO HIF-2ALPHA DRIVEN RESPONSES UNDER CHRONIC HYPOXIA WHICH MAY HAVE ESSENTIAL FUNCTIONS IN THE REGULATION OF TUMOR CELL DIFFERENTIATION AND TUMOR STEM CELL MAINTENANCE. GIVEN THEIR CENTRAL ROLE IN CANCER BIOLOGY, HIF FEEDBACK REGULATORS MAY REPRESENT AN ATTRACTIVE AND NOVEL ANTI-TUMOR THERAPY TARGET TO OVERCOME CELL DEATH RESISTANCE IN TUMORS. 2010 15 4138 37 MECHANISMS OF MICROGLIAL ACTIVATION IN MODELS OF INFLAMMATION AND HYPOXIA: IMPLICATIONS FOR CHRONIC INTERMITTENT HYPOXIA. CHRONIC INTERMITTENT HYPOXIA (CIH) IS A HALLMARK OF SLEEP APNOEA, A CONDITION ASSOCIATED WITH DIVERSE CLINICAL DISORDERS. CIH AND SLEEP APNOEA ARE CHARACTERIZED BY INCREASED REACTIVE OXYGEN SPECIES FORMATION, PERIPHERAL AND CNS INFLAMMATION, NEURONAL DEATH AND NEUROCOGNITIVE DEFICITS. FEW STUDIES HAVE EXAMINED THE ROLE OF MICROGLIA, THE RESIDENT CNS IMMUNE CELLS, IN MODELS OF CIH. THUS, LITTLE IS KNOWN CONCERNING THEIR DIRECT CONTRIBUTIONS TO NEUROPATHOLOGY OR THE CELLULAR MECHANISMS REGULATING THEIR ACTIVITIES DURING OR FOLLOWING PATHOLOGICAL CIH. IN THIS REVIEW, WE IDENTIFY GAPS IN KNOWLEDGE REGARDING CIH-INDUCED MICROGLIAL ACTIVATION, AND PROPOSE MECHANISMS BASED ON DATA FROM RELATED MODELS OF HYPOXIA AND/OR HYPOXIA-REOXYGENATION. CIH MAY DIRECTLY AFFECT MICROGLIA, OR MAY HAVE INDIRECT EFFECTS VIA THE PERIPHERY OR OTHER CNS CELLS. PERIPHERAL INFLAMMATION MAY INDIRECTLY ACTIVATE MICROGLIA VIA ENTRY OF PRO-INFLAMMATORY MOLECULES INTO THE CNS, AND/OR ACTIVATION OF VAGAL AFFERENTS THAT TRIGGER CNS INFLAMMATION. CIH-INDUCED RELEASE OF DAMAGE-ASSOCIATED MOLECULAR PATTERNS FROM INJURED CNS CELLS MAY ALSO ACTIVATE MICROGLIA VIA INTERACTIONS WITH PATTERN RECOGNITION RECEPTORS EXPRESSED ON MICROGLIA. FOR EXAMPLE, TOLL-LIKE RECEPTORS ACTIVATE MITOGEN-ACTIVATED PROTEIN KINASE/TRANSCRIPTION FACTOR PATHWAYS REQUIRED FOR MICROGLIAL INFLAMMATORY GENE EXPRESSION. ALTHOUGH EPIGENETIC EFFECTS FROM CIH HAVE NOT YET BEEN STUDIED IN MICROGLIA, POTENTIAL EPIGENETIC MECHANISMS IN MICROGLIAL REGULATION ARE DISCUSSED, INCLUDING MICRORNAS, HISTONE MODIFICATIONS AND DNA METHYLATION. EPIGENETIC EFFECTS CAN OCCUR DURING CIH, OR LONG AFTER IT HAS ENDED. A BETTER UNDERSTANDING OF CIH EFFECTS ON MICROGLIAL ACTIVITIES MAY BE IMPORTANT TO REVERSE CIH-INDUCED NEUROPATHOLOGY IN PATIENTS WITH SLEEP DISORDERED BREATHING. 2016 16 6543 25 TRANSCRIPTOME REMODELING IN HYPOXIC INFLAMMATION. HYPOXIA IS AN INTEGRAL COMPONENT OF THE INFLAMED TISSUE MICROENVIRONMENT. TODAY, THE INFLUENCE OF HYPOXIA ON THE NATURAL EVOLUTION OF INFLAMMATORY RESPONSES IS WIDELY ACCEPTED; HOWEVER, MANY MOLECULAR AND CELLULAR MECHANISMS MEDIATING THIS RELATIONSHIP REMAIN TO BE CLARIFIED. HYPOXIC STRESS AFFECTS SEVERAL INDEPENDENT TRANSCRIPTIONAL REGULATORS RELATED TO INFLAMMATION IN WHICH HIF-1 AND NF-KAPPAB PLAY CENTRAL ROLES. TRANSCRIPTION FACTORS INTERACT WITH BOTH HATS AND HDACS, WHICH ARE COMPONENTS OF LARGE MULTIPROTEIN CO-REGULATORY COMPLEXES. THIS REVIEW SUMMARIZES THE CURRENT KNOWLEDGE ON HYPOXIA-RESPONSIVE TRANSCRIPTIONAL PATHWAYS IN INFLAMMATION AND THEIR IMPORTANCE IN THE ETIOLOGY OF CHRONIC INFLAMMATORY DISEASES, WITH THE PRIMARY FOCUS ON TRANSCRIPTIONAL CO-REGULATORS AND HISTONE MODIFICATIONS IN DEFINING GENE-SPECIFIC TRANSCRIPTIONAL RESPONSES IN HYPOXIA, AND ON THE RECENT PROGRESS IN THE UNDERSTANDING OF HYPOXIA-MEDIATED EPIGENETIC REPROGRAMMING. FURTHERMORE, THIS REVIEW DISCUSSES THE MOLECULAR CROSS-TALK BETWEEN GLUCOCORTICOID ANTI-INFLAMMATORY PATHWAYS AND HYPOXIA. 2010 17 3469 43 HYPOXIA-INDUCIBLE HISTONE LYSINE DEMETHYLASES: IMPACT ON THE AGING PROCESS AND AGE-RELATED DISEASES. HYPOXIA IS AN ENVIRONMENTAL STRESS AT HIGH ALTITUDE AND UNDERGROUND CONDITIONS BUT IT IS ALSO PRESENT IN MANY CHRONIC AGE-RELATED DISEASES, WHERE BLOOD FLOW INTO TISSUES IS IMPAIRED. THE OXYGEN-SENSING SYSTEM STIMULATES GENE EXPRESSION PROTECTING TISSUES AGAINST HYPOXIC INSULTS. HYPOXIA STABILIZES THE EXPRESSION OF HYPOXIA-INDUCIBLE TRANSCRIPTION FACTOR-1ALPHA (HIF-1ALPHA), WHICH CONTROLS THE EXPRESSION OF HUNDREDS OF SURVIVAL GENES RELATED TO E.G. ENHANCED ENERGY METABOLISM AND AUTOPHAGY. MOREOVER, MANY STRESS-RELATED SIGNALING MECHANISMS, SUCH AS OXIDATIVE STRESS AND ENERGY METABOLIC DISTURBANCES, AS WELL AS THE SIGNALING CASCADES VIA CERAMIDE, MTOR, NF-KAPPAB, AND TGF-BETA PATHWAYS, CAN ALSO INDUCE THE EXPRESSION OF HIF-1ALPHA PROTEIN TO FACILITATE CELL SURVIVAL IN NORMOXIA. HYPOXIA IS LINKED TO PROMINENT EPIGENETIC CHANGES IN CHROMATIN LANDSCAPE. SCREENING STUDIES HAVE INDICATED THAT THE STABILIZATION OF HIF-1ALPHA INCREASES THE EXPRESSION OF DISTINCT HISTONE LYSINE DEMETHYLASES (KDM). HIF-1ALPHA STIMULATES THE EXPRESSION OF KDM3A, KDM4B, KDM4C, AND KDM6B, WHICH ENHANCE GENE TRANSCRIPTION BY DEMETHYLATING H3K9 AND H3K27 SITES (REPRESSIVE EPIGENETIC MARKS). IN ADDITION, HIF-1ALPHA INDUCES THE EXPRESSION OF KDM2B AND KDM5B, WHICH REPRESS TRANSCRIPTION BY DEMETHYLATING H3K4ME2,3 SITES (ACTIVATING MARKS). HYPOXIA-INDUCIBLE KDMS SUPPORT LOCALLY THE GENE TRANSCRIPTION INDUCED BY HIF-1ALPHA, ALTHOUGH THEY CAN ALSO CONTROL GENOME-WIDE CHROMATIN LANDSCAPE, ESPECIALLY KDMS WHICH DEMETHYLATE H3K9 AND H3K27 SITES. THESE EPIGENETIC MARKS HAVE IMPORTANT ROLE IN THE CONTROL OF HETEROCHROMATIN SEGMENTS AND 3D FOLDING OF CHROMOSOMES, AS WELL AS THE GENETIC LOCI REGULATING CELL TYPE COMMITMENT, PROLIFERATION, AND CELLULAR SENESCENCE, E.G. THE INK4 BOX. A CHRONIC STIMULATION OF HIF-1ALPHA CAN PROVOKE TISSUE FIBROSIS AND CELLULAR SENESCENCE, WHICH BOTH ARE INCREASINGLY PRESENT WITH AGING AND AGE-RELATED DISEASES. WE WILL REVIEW THE REGULATION OF HIF-1ALPHA-DEPENDENT INDUCTION OF KDMS AND CLARIFY THEIR ROLE IN PATHOLOGICAL PROCESSES EMPHASIZING THAT LONG-TERM STRESS-RELATED INSULTS CAN IMPAIR THE MAINTENANCE OF CHROMATIN LANDSCAPE AND PROVOKE CELLULAR SENESCENCE AND TISSUE FIBROSIS ASSOCIATED WITH AGING AND AGE-RELATED DISEASES. 2016 18 2738 29 EXPOSOMES TO EXOSOMES: EXOSOMES AS TOOLS TO STUDY EPIGENETIC ADAPTIVE MECHANISMS IN HIGH-ALTITUDE HUMANS. HUMANS ON EARTH INHABIT A WIDE RANGE OF ENVIRONMENTAL CONDITIONS AND SOME ENVIRONMENTS ARE MORE CHALLENGING FOR HUMAN SURVIVAL THAN OTHERS. HOWEVER, MANY LIVING BEINGS, INCLUDING HUMANS, HAVE DEVELOPED ADAPTIVE MECHANISMS TO LIVE IN SUCH INHOSPITABLE, HARSH ENVIRONMENTS. AMONG DIFFERENT DIFFICULT ENVIRONMENTS, HIGH-ALTITUDE LIVING IS ESPECIALLY DEMANDING BECAUSE OF DIMINISHED PARTIAL PRESSURE OF OXYGEN AND RESULTING CHRONIC HYPOBARIC HYPOXIA. THIS RESULTS IN POOR BLOOD OXYGENATION AND REDUCES AEROBIC OXIDATIVE RESPIRATION IN THE MITOCHONDRIA, LEADING TO INCREASED REACTIVE OXYGEN SPECIES GENERATION AND ACTIVATION OF HYPOXIA-INDUCIBLE GENE EXPRESSION. GENETIC MECHANISMS IN THE ADAPTATION TO HIGH ALTITUDE IS WELL-STUDIED, BUT THERE ARE ONLY LIMITED STUDIES REGARDING THE ROLE OF EPIGENETIC MECHANISMS. THE PURPOSE OF THIS REVIEW IS TO UNDERSTAND THE EPIGENETIC MECHANISMS BEHIND HIGH-ALTITUDE ADAPTIVE AND MALADAPTIVE PHENOTYPES. HYPOBARIC HYPOXIA IS A FORM OF CELLULAR HYPOXIA, WHICH IS SIMILAR TO THE ONE SUFFERED BY CRITICALLY-ILL HYPOXEMIA PATIENTS. THUS, UNDERSTANDING THE ADAPTIVE EPIGENETIC SIGNALS OPERATING IN IN HIGH-ALTITUDE ADJUSTED INDIGENOUS POPULATIONS MAY HELP IN THERAPEUTICALLY MODULATING SIGNALING PATHWAYS IN HYPOXEMIA PATIENTS BY COPYING THE MOST SUCCESSFUL EPIGENOTYPE. IN ADDITION, WE HAVE SUMMARIZED THE CURRENT INFORMATION ABOUT EXOSOMES IN HYPOXIA RESEARCH AND PROSPECTS TO USE THEM AS DIAGNOSTIC TOOLS TO STUDY THE EPIGENOME OF HIGH-ALTITUDE ADAPTED HEALTHY OR MALADAPTED INDIVIDUALS. 2021 19 3428 29 HUMANS AT HIGH ALTITUDE: HYPOXIA AND FETAL GROWTH. HIGH-ALTITUDE STUDIES OFFER INSIGHT INTO THE EVOLUTIONARY PROCESSES AND PHYSIOLOGICAL MECHANISMS AFFECTING THE EARLY PHASES OF THE HUMAN LIFESPAN. CHRONIC HYPOXIA SLOWS FETAL GROWTH AND REDUCES THE PREGNANCY-ASSOCIATED RISE IN UTERINE ARTERY (UA) BLOOD FLOW. MULTIGENERATIONAL VS. SHORTER-TERM HIGH-ALTITUDE RESIDENTS ARE PROTECTED FROM THE ALTITUDE-ASSOCIATED REDUCTIONS IN UA FLOW AND FETAL GROWTH. PRESENTLY UNKNOWN IS WHETHER THIS FETAL-GROWTH PROTECTION IS DUE TO THE GREATER DELIVERY OR METABOLISM OF OXYGEN, GLUCOSE OR OTHER SUBSTRATES OR TO OTHER CONSIDERATIONS SUCH AS MECHANICAL FACTORS PROTECTING FRAGILE FETAL VILLI, THE CREATION OF A RESERVE PROTECTING AGAINST ISCHEMIA/REPERFUSION INJURY, OR IMPROVED PLACENTAL O(2) TRANSFER AS THE RESULT OF NARROWING THE A-V O(2) DIFFERENCE AND RAISING UTERINE P(V)O(2). PLACENTAL GROWTH AND DEVELOPMENT APPEAR TO BE NORMAL OR MODIFIED AT HIGH ALTITUDE IN WAYS LIKELY TO BENEFIT DIFFUSION. MUCH REMAINS TO BE LEARNED CONCERNING THE EFFECTS OF CHRONIC HYPOXIA ON EMBRYONIC DEVELOPMENT. FURTHER RESEARCH IS REQUIRED FOR IDENTIFYING THE FETOPLACENTAL AND MATERNAL MECHANISMS RESPONSIBLE FOR TRANSFORMING THE MATERNAL VASCULATURE AND REGULATING UA BLOOD FLOW AND FETAL GROWTH. GENOMIC AS WELL AS EPIGENETIC STUDIES ARE OPENING NEW AVENUES OF INVESTIGATION THAT CAN YIELD INSIGHTS INTO THE BASIC PATHWAYS AND EVOLUTIONARY PROCESSES INVOLVED. 2011 20 4755 38 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