1 231 116 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 2 5420 26 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 3 1177 34 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 22 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 3470 19 HYPOXIA-INDUCIBLE KDM3A ADDICTION IN MULTIPLE MYELOMA. IN MULTIPLE MYELOMA (MM), THE BONE MARROW (BM) MICROENVIRONMENT MAY CONTAIN A MYELOMA CELL FRACTION THAT HAS ACQUIRED TREATMENT RESISTANCE BY UNDERGOING AN EPIGENETIC GENE EXPRESSION CHANGE. HYPOXIC STRESS IS AN IMPORTANT FACTOR IN THE BM MICROENVIRONMENT. RECENTLY, WE DEMONSTRATED THAT MIR-210 WAS UPREGULATED IN HYPOXIA AND DOWNREGULATED IRF4, WHICH IS KNOWN AS AN ESSENTIAL FACTOR IN MYELOMA ONCOGENESIS IN NORMOXIA. IN THE STUDY, WE DEMONSTRATED THAT MYELOMA CELLS STILL SHOWED A STRONG ANTIAPOPTOTIC PHENOTYPE DESPITE IRF4 DOWNREGULATION, SUGGESTING THAT ANOTHER ANTIAPOPTOTIC FACTOR MIGHT BE INVOLVED UNDER HYPOXIC STRESS. TO DETERMINE THE FACTOR OR FACTORS, WE CONDUCTED GENE EXPRESSION ANALYSIS ON MYELOMA CELLS (PRIMARY SAMPLES AND CELL LINES) THAT WERE EXPOSED TO CHRONIC HYPOXIA AND OBSERVED UPREGULATION OF GLYCOLYTIC GENES AND GENES ENCODING H3K9 DEMETHYLASES IN MYELOMA CELLS WITH HYPOXIA. AMONG THESE, KDM3A WAS MOST SIGNIFICANTLY UPREGULATED IN ALL EXAMINED CELLS, AND ITS KNOCKDOWN INDUCED APOPTOSIS OF MYELOMA CELLS IN CHRONIC HYPOXIA. EXPRESSION OF KDM3A WAS DEPENDENT ON HIF-1ALPHA, WHICH IS A TRANSCRIPTION FACTOR SPECIFICALLY UPREGULATED IN HYPOXIA. WE FURTHER DEMONSTRATED THAT AN ESSENTIAL TARGET OF KDM3A WAS A NONCODING GENE, MALAT1, WHOSE UPREGULATION CONTRIBUTED TO ACQUISITION OF AN ANTIAPOPTOTIC PHENOTYPE BY ACCUMULATION OF HIF-1ALPHA, LEADING TO UPREGULATION OF GLYCOLYTIC GENES UNDER HYPOXIA. THIS PROCESS WAS INDEPENDENT FROM IRF4. THESE RESULTS LED US TO CONCLUDE THAT THE HYPOXIA-INDUCIBLE HIF-1ALPHA-KDM3A-MALAT1 AXIS ALSO CONTRIBUTES TO ACQUISITION OF THE ANTIAPOPTOTIC PHENOTYPE VIA UPREGULATION OF GLYCOLYSIS-PROMOTING GENES. THUS, THIS AXIS IS A PROMISING THERAPEUTIC TARGET AGAINST MYELOMA CELLS IN THE BM MICROENVIRONMENT. 2018 6 3466 20 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 7 4197 25 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 8 3469 34 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 9 2800 28 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 10 2023 30 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 11 2034 17 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 12 5048 33 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 13 4746 21 NOVEL LNC RNA REGULATED BY HIF-1 INHIBITS APOPTOTIC CELL DEATH IN THE RENAL TUBULAR EPITHELIAL CELLS UNDER HYPOXIA. CHRONIC TUBULOINTERSTITIAL HYPOXIA PLAYS AN IMPORTANT ROLE AS THE FINAL COMMON PATHWAY TO END-STAGE RENAL DISEASE. HIF-1 (HYPOXIA-INDUCIBLE FACTOR-1) IS A MASTER TRANSCRIPTIONAL FACTOR UNDER HYPOXIA, REGULATING DOWNSTREAM TARGET GENES. GENOME-WIDE ANALYSIS OF HIF-1 BINDING SITES USING HIGH-THROUGHPUT SEQUENCERS HAS CLARIFIED VARIOUS KINDS OF DOWNSTREAM TARGETS AND MADE IT POSSIBLE TO DEMONSTRATE THE NOVEL ROLES OF HIF-1. OUR AIM OF THIS STUDY IS TO IDENTIFY NOVEL HIF-1 DOWNSTREAM EPIGENETIC TARGETS WHICH MAY PLAY IMPORTANT ROLES IN THE KIDNEY. IMMORTALIZED TUBULAR CELL LINES (HK2; HUMAN KIDNEY-2) AND PRIMARY CULTURED CELLS (RPTEC; RENAL PROXIMAL TUBULAR CELL LINES) WERE EXPOSED TO 1% HYPOXIA FOR 24-72 H. WE PERFORMED RNA-SEQ TO CLARIFY THE EXPRESSION OF MRNA AND LONG NON-CODING RNA (LNCRNA). WE ALSO EXAMINED CHIP-SEQ TO IDENTIFY HIF-1 BINDING SITES UNDER HYPOXIA. RNA-SEQ IDENTIFIED 44 LNCRNAS WHICH ARE UP-REGULATED UNDER HYPOXIC CONDITION IN BOTH CELLS. CHIP-SEQ ANALYSIS DEMONSTRATED THAT HIF-1 ALSO BINDS TO THE LNCRNAS UNDER HYPOXIA. THE EXPRESSION OF NOVEL LNCRNA, DARS-AS1 (ASPARTYL-TRNA SYNTHETASE ANTI-SENSE 1), IS UP-REGULATED ONLY UNDER HYPOXIA AND HIF-1 BINDS TO ITS PROMOTER REGION, WHICH INCLUDES TWO HYPOXIA-RESPONSIVE ELEMENTS. ITS EXPRESSION IS ALSO UP-REGULATED WITH COBALT CHLORIDE EXPOSURE, WHILE IT IS NOT UNDER HYPOXIA WHEN HIF-1 IS KNOCKED DOWN BY SIRNA TO CLARIFY THE BIOLOGICAL ROLES OF DARS-AS1, WE MEASURED THE ACTIVITY OF CASPASE 3/7 USING ANTI-SENSE OLIGO OF DARS-AS1. KNOCKDOWN OF DARS-AS1 DETERIORATED APOPTOTIC CELL DEATH. IN CONCLUSION, WE IDENTIFIED THE NOVEL LNCRNAS REGULATED BY HIF-1 UNDER HYPOXIA AND CLARIFIED THAT DARS-AS1 PLAYS AN IMPORTANT ROLE IN INHIBITING APOPTOTIC CELL DEATH IN RENAL TUBULAR CELLS. 2017 14 2614 31 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 15 3633 26 INCREASE IN HDAC9 SUPPRESSES MYOBLAST DIFFERENTIATION VIA EPIGENETIC REGULATION OF AUTOPHAGY IN HYPOXIA. EXTREMELY REDUCED OXYGEN (O(2)) LEVELS ARE DETRIMENTAL TO MYOGENIC DIFFERENTIATION AND MULTINUCLEATED MYOTUBE FORMATION, AND CHRONIC EXPOSURE TO HIGH-ALTITUDE HYPOXIA HAS BEEN REPORTED TO BE AN IMPORTANT FACTOR IN SKELETAL MUSCLE ATROPHY. HOWEVER, HOW CHRONIC HYPOXIA CAUSES MUSCLE DYSFUNCTION REMAINS UNKNOWN. IN THE PRESENT STUDY, WE FOUND THAT SEVERE HYPOXIA (1% O(2)) SIGNIFICANTLY INHIBITED THE FUNCTION OF C2C12 CELLS (FROM A MYOBLAST CELL LINE). IMPORTANTLY, THE IMPAIRMENT WAS CONTINUOUSLY MANIFESTED EVEN DURING CULTURE UNDER NORMOXIC CONDITIONS FOR SEVERAL PASSAGES. MECHANISTICALLY, WE REVEALED THAT HISTONE DEACETYLASES 9 (HDAC9), A MEMBER OF THE HISTONE DEACETYLASE FAMILY, WAS SIGNIFICANTLY INCREASED IN C2C12 CELLS UNDER HYPOXIC CONDITIONS, THEREBY INHIBITING INTRACELLULAR AUTOPHAGY LEVELS BY DIRECTLY BINDING TO THE PROMOTER REGIONS OF ATG7, BECLIN1, AND LC3. THIS PHENOMENON RESULTED IN THE SEQUENTIAL DEPHOSPHORYLATION OF GSK3BETA AND INACTIVATION OF THE CANONICAL WNT PATHWAY, IMPAIRING THE FUNCTION OF THE C2C12 CELLS. TAKEN TOGETHER, OUR RESULTS SUGGEST THAT HYPOXIA-INDUCED MYOBLAST DYSFUNCTION IS DUE TO ABERRANT EPIGENETIC REGULATION OF AUTOPHAGY, AND OUR EXPERIMENTAL EVIDENCE REVEALS THE POSSIBLE MOLECULAR PATHOGENESIS RESPONSIBLE FOR SOME MUSCLE DISEASES CAUSED BY CHRONIC HYPOXIA AND SUGGESTS A POTENTIAL THERAPEUTIC OPTION. 2019 16 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 17 6702 24 VEGFA PROMOTER GENE HYPERMETHYLATION AT HIF1ALPHA BINDING SITE IS AN EARLY CONTRIBUTOR TO CKD PROGRESSION AFTER RENAL ISCHEMIA. CHRONIC HYPOXIA IS A MAJOR CONTRIBUTOR TO CHRONIC KIDNEY DISEASE (CKD) AFTER ACUTE KIDNEY INJURY (AKI). HOWEVER, THE TEMPORAL RELATION BETWEEN THE ACUTE INSULT AND MALADAPTIVE RENAL RESPONSE TO HYPOXIA REMAINS UNCLEAR. IN THIS STUDY, WE ANALYZED THE TIME-COURSE OF RENAL HEMODYNAMICS, OXIDATIVE STRESS, INFLAMMATION, AND FIBROSIS, AS WELL AS EPIGENETIC MODIFICATIONS, WITH FOCUS ON HIF1ALPHA/VEGF SIGNALING, IN THE AKI TO CKD TRANSITION. SHAM-OPERATED, RIGHT NEPHRECTOMY (UNX), AND UNX PLUS RENAL ISCHEMIA (IR + UNX) GROUPS OF RATS WERE INCLUDED AND STUDIED AT 1, 2, 3, OR 4 MONTHS. THE IR + UNX GROUP DEVELOPED CKD CHARACTERIZED BY PROGRESSIVE PROTEINURIA, RENAL DYSFUNCTION, TUBULAR PROLIFERATION, AND FIBROSIS. AT FIRST MONTH POST-ISCHEMIA, THERE WAS A TWOFOLD SIGNIFICANT INCREASE IN OXIDATIVE STRESS AND REDUCTION IN GLOBAL DNA METHYLATION THAT WAS MAINTAINED THROUGHOUT THE STUDY. HIF1ALPHA AND VEGFA EXPRESSION WERE DEPRESSED IN THE FIRST AND SECOND-MONTHS POST-ISCHEMIA, AND THEN HIF1ALPHA BUT NOT VEGFA EXPRESSION WAS RECOVERED. INTERESTINGLY, HYPERMETHYLATION OF THE VEGFA PROMOTER GENE AT THE HIF1ALPHA BINDING SITE WAS FOUND, SINCE EARLY STAGES OF THE CKD PROGRESSION. OUR FINDINGS SUGGEST THAT RENAL HYPOPERFUSION, INEFFICIENT HYPOXIC RESPONSE, INCREASED OXIDATIVE STRESS, DNA HYPOMETHYLATION, AND, VEGFA PROMOTER GENE HYPERMETHYLATION AT HIF1ALPHA BINDING SITE, ARE EARLY DETERMINANTS OF AKI-TO-CKD TRANSITION. 2021 18 5565 24 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 19 5826 26 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 20 1117 26 COMPARATIVE AND EXPERIMENTAL STUDIES ON THE GENES ALTERED BY CHRONIC HYPOXIA IN HUMAN BRAIN MICROENDOTHELIAL CELLS. BACKGROUND : HYPOXIA INDUCIBLE FACTOR 1 ALPHA (HIF1A) IS A MASTER REGULATOR OF ACUTE HYPOXIA; HOWEVER, WITH CHRONIC HYPOXIA, HIF1A LEVELS RETURN TO THE NORMOXIC LEVELS. IMPORTANTLY, THE GENES THAT ARE INVOLVED IN THE CELL SURVIVAL AND VIABILITY UNDER CHRONIC HYPOXIA ARE NOT KNOWN. THEREFORE, WE TESTED THE HYPOTHESIS THAT CHRONIC HYPOXIA LEADS TO THE UPREGULATION OF A CORE GROUP OF GENES WITH ASSOCIATED CHANGES IN THE PROMOTER DNA METHYLATION THAT MEDIATES THE CELL SURVIVAL UNDER HYPOXIA. RESULTS : WE EXAMINED THE EFFECT OF CHRONIC HYPOXIA (3 DAYS; 0.5% OXYGEN) ON HUMAN BRAIN MICRO ENDOTHELIAL CELLS (HBMEC) VIABILITY AND APOPTOSIS. HYPOXIA CAUSED A SIGNIFICANT REDUCTION IN CELL VIABILITY AND AN INCREASE IN APOPTOSIS. NEXT, WE EXAMINED CHRONIC HYPOXIA ASSOCIATED CHANGES IN TRANSCRIPTOME AND GENOME-WIDE PROMOTER METHYLATION. THE DATA OBTAINED WAS COMPARED WITH 16 OTHER MICROARRAY STUDIES ON CHRONIC HYPOXIA. NINE GENES WERE ALTERED IN RESPONSE TO CHRONIC HYPOXIA IN ALL 17 STUDIES. INTERESTINGLY, HIF1A WAS NOT ALTERED WITH CHRONIC HYPOXIA IN ANY OF THE STUDIES. FURTHERMORE, WE COMPARED OUR DATA TO THREE OTHER STUDIES THAT IDENTIFIED HIF-RESPONSIVE GENES BY VARIOUS APPROACHES. ONLY TWO GENES WERE FOUND TO BE HIF DEPENDENT. WE SILENCED EACH OF THESE 9 GENES USING CRISPR/CAS9 SYSTEM. DOWNREGULATION OF EGLN3 SIGNIFICANTLY INCREASED THE CELL DEATH UNDER CHRONIC HYPOXIA, WHEREAS DOWNREGULATION OF ERO1L, ENO2, ADRENOMEDULLIN, AND SPAG4 REDUCED THE CELL DEATH UNDER HYPOXIA. CONCLUSIONS : WE PROVIDE A CORE GROUP OF GENES THAT REGULATES CELLULAR ACCLIMATIZATION UNDER CHRONIC HYPOXIC STRESS, AND MOST OF THEM ARE HIF INDEPENDENT. 2017