1 6646 130 UP-REGULATION OF HDACS, A HARBINGER OF URAEMIC ENDOTHELIAL DYSFUNCTION, IS PREVENTED BY DEFIBROTIDE. ENDOTHELIAL DYSFUNCTION IS AN EARLIER CONTRIBUTOR TO THE DEVELOPMENT OF ATHEROSCLEROSIS IN CHRONIC KIDNEY DISEASE (CKD), IN WHICH THE ROLE OF EPIGENETIC TRIGGERS CANNOT BE RULED OUT. ENDOTHELIAL PROTECTIVE STRATEGIES, SUCH AS DEFIBROTIDE (DF), MAY BE USEFUL IN THIS SCENARIO. WE EVALUATED CHANGES INDUCED BY CKD ON ENDOTHELIAL CELL PROTEOME AND EXPLORED THE EFFECT OF DF AND THE MECHANISMS INVOLVED. HUMAN UMBILICAL CORD VEIN ENDOTHELIAL CELLS WERE EXPOSED TO SERA FROM HEALTHY DONORS (N = 20) AND PATIENTS WITH END-STAGE RENAL DISEASE ON HAEMODIALYSIS (N = 20). DIFFERENTIAL PROTEIN EXPRESSION WAS INVESTIGATED BY USING A PROTEOMIC APPROACH, WESTERN BLOT AND IMMUNOFLUORESCENCE. HDAC1 AND HDAC2 OVEREXPRESSION WAS DETECTED. INCREASED HDAC1 EXPRESSION OCCURRED AT BOTH CYTOPLASM AND NUCLEUS. THESE EFFECTS WERE DOSE-DEPENDENTLY INHIBITED BY DF. BOTH THE HDACS INHIBITOR TRICHOSTATIN A AND DF PREVENTED THE UP-REGULATION OF THE ENDOTHELIAL DYSFUNCTION MARKERS INDUCED BY THE URAEMIC MILIEU: INTERCELLULAR ADHESION MOLECULE-1, SURFACE TOLL-LIKE RECEPTOR-4, VON WILLEBRAND FACTOR AND REACTIVE OXYGEN SPECIES. MOREOVER, DF DOWN-REGULATED HDACS EXPRESSION THROUGH THE PI3/AKT SIGNALLING PATHWAY. HDACS APPEAR AS KEY MODULATORS OF THE CKD-INDUCED ENDOTHELIAL DYSFUNCTION AS SPECIFIC BLOCKADE BY TRICHOSTATIN A OR BY DF PREVENTS ENDOTHELIAL DYSFUNCTION RESPONSES TO THE CKD INSULT. MOREOVER, DF EXERTS ITS ENDOTHELIAL PROTECTIVE EFFECT BY INHIBITING HDAC UP-REGULATION LIKELY THROUGH PI3K/AKT. 2020 2 3568 33 IMPACT OF INFLAMMATION ON EPIGENETIC DNA METHYLATION - A NOVEL RISK FACTOR FOR CARDIOVASCULAR DISEASE? OBJECTIVE: THE LIFESPAN OF DIALYSIS PATIENTS IS AS SHORT AS IN PATIENTS WITH METASTATIC CANCER DISEASE, MAINLY DUE TO CARDIOVASCULAR DISEASE (CVD). DNA METHYLATION IS AN IMPORTANT CELLULAR MECHANISM MODULATING GENE EXPRESSION ASSOCIATED WITH AGEING, INFLAMMATION AND ATHEROSCLEROTIC PROCESSES. DESIGN: DNA METHYLATION WAS ANALYSED IN PERIPHERAL BLOOD LEUCOCYTES FROM THREE DIFFERENT GROUPS OF CHRONIC KIDNEY DISEASE (CKD) POPULATIONS (37 CKD STAGES 3 AND 4 PATIENTS, 98 CKD STAGE 5 PATIENTS AND 20 PREVALENT HAEMODIALYSIS PATIENTS). THIRTY-SIX HEALTHY SUBJECTS SERVED AS CONTROLS. CLINICAL CHARACTERISTICS (DIABETES MELLITUS, NUTRITIONAL STATUS AND PRESENCE OF CLINICAL CVD), INFLAMMATION AND OXIDATIVE STRESS BIOMARKERS, HOMOCYSTEINE AND GLOBAL DNA METHYLATION IN PERIPHERAL BLOOD LEUCOCYTES (DEFINED AS HPAII/MSPI RATIO BY THE LUMINOMETRIC METHYLATION ASSAY METHOD) WERE EVALUATED. CKD STAGE 5 PATIENTS (N=98) STARTING DIALYSIS TREATMENT WERE FOLLOWED FOR A PERIOD OF 36 +/- 2 MONTHS. RESULTS: INFLAMED PATIENTS HAD LOWER RATIOS OF HPAII/MSPI, INDICATING GLOBAL DNA HYPERMETHYLATION. ANALYSIS BY THE COX REGRESSION MODEL DEMONSTRATED THAT DNA HYPERMETHYLATION (HPAII/MSPI RATIO