Singh Saurav, Grabner Alexander, Yanucil Christopher, Schramm Karla, Czaya Brian, Krick Stefanie, Czaja Mark J, Bartz Rene, Abraham Reimar, Di Marco Giovana S, Brand Marcus, Wolf Myles, Faul Christian
Katz Family Drug Discovery Center, Division of Nephrology and Hypertension, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, Florida, USA; Department of Cell Biology and Anatomy, University of Miami Leonard M. Miller School of Medicine, Miami, Florida, USA.
Katz Family Drug Discovery Center, Division of Nephrology and Hypertension, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, Florida, USA.
Kidney Int. 2016 Nov;90(5):985-996. doi: 10.1016/j.kint.2016.05.019. Epub 2016 Jul 22.
Patients with chronic kidney disease (CKD) develop increased levels of the phosphate-regulating hormone, fibroblast growth factor (FGF) 23, that are associated with a higher risk of mortality. Increases in inflammatory markers are another common feature that predicts poor clinical outcomes. Elevated FGF23 is associated with higher circulating levels of inflammatory cytokines in CKD, which can stimulate osteocyte production of FGF23. Here, we studied whether FGF23 can directly stimulate hepatic production of inflammatory cytokines in the absence of α-klotho, an FGF23 coreceptor in the kidney that is not expressed by hepatocytes. By activating FGF receptor isoform 4 (FGFR4), FGF23 stimulated calcineurin signaling in cultured hepatocytes, which increased the expression and secretion of inflammatory cytokines, including C-reactive protein. Elevating serum FGF23 levels increased hepatic and circulating levels of C-reactive protein in wild-type mice, but not in FGFR4 knockout mice. Administration of an isoform-specific FGFR4 blocking antibody reduced hepatic and circulating levels of C-reactive protein in the 5/6 nephrectomy rat model of CKD. Thus, FGF23 can directly stimulate hepatic secretion of inflammatory cytokines. Our findings indicate a novel mechanism of chronic inflammation in patients with CKD and suggest that FGFR4 blockade might have therapeutic anti-inflammatory effects in CKD.
慢性肾脏病(CKD)患者体内调节磷酸盐的激素——成纤维细胞生长因子(FGF)23水平升高,这与更高的死亡风险相关。炎症标志物升高是另一个预示临床预后不良的常见特征。CKD患者中,FGF23升高与循环中炎症细胞因子水平升高有关,而炎症细胞因子可刺激骨细胞产生FGF23。在此,我们研究了在缺乏α-klotho(一种肾脏中的FGF23共受体,肝细胞不表达)的情况下,FGF23是否能直接刺激肝脏产生炎症细胞因子。通过激活FGF受体亚型4(FGFR4),FGF23刺激了培养肝细胞中的钙调神经磷酸酶信号传导,从而增加了包括C反应蛋白在内的炎症细胞因子的表达和分泌。提高野生型小鼠血清FGF23水平会增加肝脏和循环中C反应蛋白的水平,但在FGFR4基因敲除小鼠中则不会。在CKD的5/6肾切除大鼠模型中,给予亚型特异性FGFR4阻断抗体可降低肝脏和循环中C反应蛋白的水平。因此,FGF23可直接刺激肝脏分泌炎症细胞因子。我们的研究结果揭示了CKD患者慢性炎症的一种新机制,并表明阻断FGFR4可能对CKD具有治疗性抗炎作用。