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

项目摘要 慢性肾脏病（CKD）是一种公共卫生问题，会增加心血管疾病的风险， 死亡通过促进心力衰竭，心脏肥大是CKD的重要病理学，并且影响高达90% 患者达到透析的时间。血清骨源性成纤维细胞生长因子水平升高 (FGF)23是CKD常见的早期代谢并发症，与心血管疾病密切相关。 事件和死亡率。在最近的实验研究中，我们证明了在这种情况下，FGF 23可能作为 通过直接靶向心肌细胞并诱导心脏肥大来作为致病因素。我们可以证明 FGF 23可以特异性激活FGF受体亚型4（FGFR 4）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传导，其发生独立于血液中的升高 压力给予FGFR 4特异性阻断抗体减少了5/6例受试者的心脏肥大。 肾切除大鼠CKD模型，表明药物干预心肌FGF 23/FGFR 4 信号转导可能作为一种新的心脏保护治疗方法在CKD。在这里，我们将研究，如果积极的 维生素D（VitD）和可溶性klotho（sKL），两种已知具有心脏保护功能的内分泌因子， 其血清水平在CKD中显著降低， 心肌细胞中的FGF 23/FGFR 4/PLCγ/钙调神经磷酸酶/NFAT信号传导。这一假设得到了我们的支持。 初步数据显示，sKL和VitD阻断FGF 23诱导的培养心肌细胞肥大生长， 肌细胞在目的1中，我们将确定sKL和VitD的这些抑制作用是否与 FGF 23诱导的PLCγ和NFAT活性降低。我们的初步工作表明，维生素D抑制 FGFR 4/PLCγ的相互作用，我们将研究是否激活VitD受体 (VDR)可直接结合PLCγ和/或FGFR 4以阻断FGF 23处理后的PLCγ活化。Klotho是一个 FGF 23是一种跨膜蛋白，与FGFR结合并在肾脏中充当FGF 23的共受体。在这里，我们将 确定sKL是否也可以与FGF 23和/或FGFR 4相互作用，从而阻断FGF 23/FGFR 4结合， 随后的PLCγ/钙调神经磷酸酶/NFAT信号转导。事实表明， VitD或sKL在CKD啮齿动物模型中可降低心脏肥大，我们的初步数据显示，5/6 肾切除大鼠的心肌钙调神经磷酸酶/NFAT活性表明，维生素D抑制心肌钙调神经磷酸酶/NFAT活性。在目标2中，我们将 确定VitD或sKL的递送是否可以阻断5/6肾切除的FGFR 4/PLCγ/钙调神经磷酸酶/NFAT信号传导。 大鼠和减少心脏肥大。此外，我们将研究是否给予VitD或sKL， 通过表达组成性活性蛋白诱导的心脏肥大的遗传小鼠模型的建立 FGFR 4突变体形式抑制FGFR 4/PLCγ/钙调神经磷酸酶/NFAT信号传导并改善心脏形态学， 功能我们推测，通过干扰FGF 23诱导的心肌肥大，给予sKL和 维生素D可能作为一种新的治疗策略，以解决慢性肾脏病患者的心脏损伤和死亡。

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.