P0094KLOTHO DECLINE IS ASSOCIATED WITH PRO-HYPERTROPHIC SIGNALING IN MYOCARDIUM OF NEPHRECTOMIZED SPONTANEOUSELY HYPERTENSIVE RATS (PILOT SYUDY)

Abstract

Abstract Background and Aims Klotho deficiency is suggested to be involved in cardiac complications in chronic kidney disease (CKD) through modulation of intracellular pro-hypertrophic signaling pathways. The aim of this study was to investigate the molecular mechanisms of myocardial remodeling in the settings of Klotho decline in experimental CKD. Method Systolic blood pressure (BP), myocardial mass index (MMI), serum and urinary creatinine (Cr), serum urea (Ur), inorganic phosphate (Pi), 25-hydroxyvitamin D (25OHD), parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), Klotho, myocardial Klotho, calcineurin/ NFAT and beta-catenin expression (IHC), quantitative morphometry of cardiomyocite (CM) thickness and nuclei area (hematoxylin and eosin), myocardial perivascular (PF) and interstitial fibrosis (IF), renal fibrosis (RF) (Masson’s trichrome) and Klotho expression (rKl, IHC) were analyzed in spontaneously hypertensive rats with 3/4 or 5/6 nephrectomy (Nx) and duration of experimental exposure 1 and 2 mo (Nx1, n = 9; Nx2, n = 8). Controls were sham operated (SO) animals (SO1, n = 9; SO2, n = 9). Results The experimental model was corresponded to the initial stages of CKD (Ur level was between 6.64 and 13.36 mmol/L, serum Cr increased less than 50% vs SO, RF did not exceed 22 % FOV). Serum concentration of Klotho and rKl expression decreased, while MMI, CM thickness increased in both Nx1 and Nx2 (Table). There were no differences in serum Pi, FGF23 and PTH levels in Nx1 vs SO (Table). In Nx2 Klotho decline was accompanied by the development of IF and PF, serum 25OHD decrease, Pi and FGF23 increase vs SO2 (Table). In multiple regression analyzes including SO and Nx animals rKl was independently associated with MMI (β = -0.38 ± 0.16, p = 0.026), and CM thickness (β = -0.64 ± 0.14, p <0.001). Myocardial fibrosis was associated with rKl level (IF: β = -0.87 ± 0.19, p = 0.001) and serum 25OHD (PF: β =-0.34 ± 0.15, p=0.032). According to pilot data of IHC, in Nx rat myocardium Klotho protein expression decreased, cytoplasmic calcineurin and nuclear NFAT in CM were observed (Figure), suggesting an increase in the activity of the calcineurin / NFAT signaling pathway. An intracellular redistribution of β-catenin from the cytoskeleton to the cytoplasm and nuclei were observed in CM of Nx rats (Figure), likely corresponding to increase in the activity of Wnt signaling. Conclusion Associations of CM hypertrophy, myocardial fibrosis and Klotho decline in CKD may be mediated by calcineurin / NFAT and Wnt signaling in myocardium.