Vitamin D and soluble Klotho inhibit FGF23-mediated cardiac hypertrophy in Chronic Kidney Disease

项目总结 慢性肾脏疾病(CKD)是一个公共卫生问题，它增加了心血管疾病和 死亡。通过促进心力衰竭，心肌肥厚是慢性肾脏病的一种重要病理改变，影响高达90% 当患者达到透析时。血清骨源性成纤维细胞生长因子水平升高 (成纤维细胞生长因子)23是慢性肾脏病常见的早期代谢并发症，与心血管疾病密切相关 事件和死亡。在最近的实验研究中，我们证明了在这种情况下，FGF23可能起到 直接靶向心肌细胞并诱导心肌肥大的致病因子。我们可以证明这一点 FGF23可以特异性地激活成纤维细胞生长因子受体亚型4(FGFR4)和随后的PLCγ/钙调神经磷酸酶/NFAT 导致心肌细胞肥大生长的信号不受血液中浓度的影响 压力。应用FGFR4特异性封闭抗体可减少5/6心肌肥厚 肾切除大鼠慢性肾功能不全模型，提示药物干预心肌FGF23/FGFR4 信号转导可能成为慢性肾脏病心脏保护治疗的一种新途径。在这里，我们将学习是否活跃 维生素D(VitD)和可溶性Klotho(SKL)，这两种已知具有心脏保护功能的内分泌因子和 其血清水平在CKD时显著降低，通过阻断其抗肥大作用 FGF23/FGFR4/PLCγ/CaN/NFAT在心肌细胞中的信号转导。这一假设得到了我们的 SKL和VitD阻断FGF23诱导的培养心脏肥大的初步数据 肌细胞。在目标1中，我们将确定SKL和VitD的这些抑制作用是否与 FGF23诱导的PLCγ和NFAT活性降低。我们的初步工作表明，维生素D可以抑制 在FGF23刺激的心肌细胞中FGFR4/PLCγ的相互作用，我们将研究是否激活VitD受体 经FGF23处理后，VdR可直接结合PLCγ和/或FGFR4来阻断PLCγ的激活。Klotho是一种 与FGFRs结合的跨膜蛋白，在肾脏中作为FGF23的共同受体。在这里，我们将 确定SKL是否也可以与FGF23和/或FGFR4相互作用，从而阻止FGF23/FGFR4结合和 随后的PLCγ/钙调神经磷酸酶/非胰岛素样生长因子在心肌细胞中的信号转导。事实表明，管理…… 在CKD的啮齿动物模型中，维生素D或SKL可减少心肌肥厚，我们的初步数据为5/6 肾切除大鼠表明VitD抑制心肌钙调神经磷酸酶/NFAT活性。在目标2中，我们将 确定维生素D或SKL能否阻断5/6肾切除后FGFR4/PLCγ/钙调神经磷酸酶/NFAT信号转导 并能减轻大鼠心肌肥厚。此外，我们将研究维生素D或SKL是否适用于 一种成分活性基因表达诱导的小鼠心肌肥厚遗传模型的建立 FGFR4突变型，抑制FGFR4/PLCγ/钙调神经磷酸酶/NFAT信号转导，改善心脏形态和心脏功能 功能。我们推测，通过干预FGF23诱导的心肌肥厚，SKL和 维生素D可作为治疗慢性肾脏病患者心脏损伤和死亡的新策略。

PROJECT SUMMARY Chronic kidney disease (CKD) is a public health problem that increases the risk of cardiovascular disease and death. By promoting heart failure, cardiac hypertrophy is an important pathology in CKD and affects up to 90% of patients by the time they reach dialysis. Elevated serum levels of bone-derived fibroblast growth factor (FGF) 23 are a common, early metabolic complication of CKD that is strongly associated with cardiovascular events and mortality. In recent experimental studies, we demonstrated that in this context, FGF23 might act as a causal factor by directly targeting cardiac myocytes and inducing cardiac hypertrophy. We could show that FGF23 can specifically activate FGF receptor isoform 4 (FGFR4) and subsequent PLCγ/calcineurin/NFAT signaling leading to hypertrophic growth of cardiac myocytes that occurs independently of elevations in blood pressure. Administration of an FGFR4-specific blocking antibody reduced cardiac hypertrophy in the 5/6 nephrectomy rat model of CKD, suggesting that pharmacological interference with myocardial FGF23/FGFR4 signaling might serve as a novel cardio-protective therapeutic approach in CKD. Here, we will study if active vitamin D (VitD) and soluble klotho (sKL), two endocrine factors with known cardio-protective functions and whose serum levels are significantly reduced in CKD, confer their anti-hypertrophic actions by blocking FGF23/FGFR4/PLCγ/calcineurin/NFAT signaling in cardiac myocytes. This hypothesis is supported by our preliminary data showing that sKL and VitD block FGF23-induced hypertrophic growth of cultured cardiac myocytes. In Aim 1, we will determine if these inhibitory actions of sKL and VitD are associated with a reduction in FGF23-induced PLCγ and NFAT activity. Our preliminary work indicates that VitD inhibits the FGFR4/PLCγ interaction in FGF23-stimulated cardiac myocytes, and we will study if activated VitD receptor (VDR) can directly bind PLCγ and/or FGFR4 to block PLCγ activation post FGF23 treatment. Klotho is a transmembrane protein that binds to FGFRs and acts as co-receptor for FGF23 in the kidney. Here, we will determine if sKL can also interact with FGF23 and/or FGFR4 thereby blocking FGF23/FGFR4 binding and subsequent PLCγ/calcineurin/NFAT signaling in cardiac myocytes. It has been shown that administration of VitD or sKL in rodent models of CKD reduces cardiac hypertrophy, and our preliminary data in 5/6 nephrectomized rats indicates that VitD inhibits myocardial calcineurin/NFAT activity. In Aim 2, we will determine if delivery of VitD or sKL can block FGFR4/PLCγ/calcineurin/NFAT signaling in 5/6 nephrectomized rats and reduce cardiac hypertrophy. Furthermore, we will study if administration of VitD or sKL to an established genetic mouse model for cardiac hypertrophy induced by expression of a constitutively active FGFR4 mutant form, inhibits FGFR4/PLCγ/calcineurin/NFAT signaling and improves cardiac morphology and function. We postulate that by interfering with FGF23-induced cardiac hypertrophy, administration of sKL and VitD might serve as a novel therapeutic strategy to tackle cardiac injury and death in patients with CKD.