Regulation of FGF23 in Chronic Kidney Disease (CKD) by iron and inflammation

项目摘要 成纤维细胞生长因子（FGF）23是一种磷酸盐调节激素，通常由骨骼产生。慢性 肾脏疾病（CKD），由于Fgf 23增加，循环生物活性完整FGF 23（iFGF 23）蓄积 转录和FGF 23失活切割减少，与心血管疾病独立相关。 mortality.降低FGF 23水平和预防CKD不良结局的新治疗方法 迫切需要，但目前的疗法是次优的。缺铁（ID）和炎症是强大的 FGF 23转录和切割的刺激。在健康小鼠中，FGF 23的产生在应答中高度增加， 但由于伴随的增加，仅观察到血清iFGF 23水平的轻度增加。 FGF 23裂解。miR-122增加FGF 23切割，并且在响应ID时高度升高， 炎症在CKD中，我们发现，尽管ID和炎症，miR-122的表达减少，FGF 23 切割受损，因此ID和炎症导致iFGF 23水平增加。我们发现 CKD小鼠中ID或炎症组分的部分校正降低了FGF 23转录，校正 FGF 23水平和预防心脏病和过早死亡的发展。然而，骨特异性 FGF 23的缺失不足以完全纠正缺铁或发炎小鼠中的FGF 23水平，这表明 额外的细胞靶点在ID和炎症反应中产生FGF 23。事实上，我们发现红细胞 细胞和巨噬细胞也导致FGF 23过量。在这个创新的建议中，我们将测试假设 红细胞和巨噬细胞谱系有助于响应ID增加FGF 23的产生， 在健康和CKD中，较低miR-122导致FGF 23裂解受损。 在Aim 1中，我们将确定FGF 23是否由骨和巨噬细胞在炎症反应中产生，以及是否由骨和巨噬细胞在炎症反应中产生。 骨细胞和红细胞对缺铁的反应。我们将使用炎症挑战和膳食铁 在具有FGF 23的细胞谱系特异性缺失的小鼠中的限制。在Aim 2中，我们将评估miR-122在以下方面的作用： 使用miR-122的遗传缺失和施用miR-122的方法对ID和炎症对FGF 23切割的响应 小鼠中的miR-122拮抗剂。在目标3中，我们将测试靶向骨细胞的治疗潜力， 成骨细胞，红细胞和巨噬细胞在CKD，通过使用互补的遗传和药理 在CKD的Col 4a 3 KO小鼠模型中降低FGF 23的方法。我们还将使用基因缺失的miR- 122和在患有CKD的小鼠中施用miR-122模拟物以证明miR-122的治疗潜力。 122以增加CKD中的FGF 23切割并防止iFGF 23水平升高。我们将测量FGF 23 水平，并评估肾、骨和心脏形态和功能的改善。这些创新目标 得到西北大学一支拥有专业知识、技能和资源的高效协作团队的支持 这将进一步发展我们对FGF 23调控的理解，并支持我们的最终目标， 改善CKD不良结局的新疗法。

PROJECT SUMMARY Fibroblast growth factor (FGF) 23 is a phosphate regulating hormone normally produced by bone. In chronic kidney disease (CKD), accumulation of circulating bioactive intact FGF23 (iFGF23), due to increased Fgf23 transcription and decreased FGF23 de-activating cleavage, is independently associated with cardiovascular mortality. Novel therapeutic approaches to reduce FGF23 levels and prevent adverse outcomes in CKD are desperately needed but current therapies are suboptimal. Iron deficiency (ID) and inflammation are powerful stimuli of FGF23 transcription and cleavage. In healthy mice, FGF23 production is highly increased in response to ID and inflammation, but only mild increases in serum iFGF23 levels are observed due to concomitant increase in FGF23 cleavage. miR-122 increases FGF23 cleavage and is highly elevated in response to ID and inflammation. In CKD, we show that the expression of miR-122 is reduced despite ID and inflammation, FGF23 cleavage is impaired, and ID and inflammation therefore contribute to increased iFGF23 levels. We showed that partial correction of ID or inflammatory component in mice with CKD reduced FGF23 transcription, corrected FGF23 levels and prevented development of cardiac disease and premature death. However, bone-specific deletion of FGF23 was not sufficient to fully correct FGF23 levels in iron deficient or inflamed mice, suggesting that additional cell targets produce FGF23 in response to ID and inflammation. In fact, we show that erythroid cells and macrophages also contribute to FGF23 excess. In this innovative proposal, we will test the hypothesis that erythroid and macrophage cell lineage contribute to increased production of FGF23 in response to ID and inflammation, and that lower miR-122 result in impaired FGF23 cleavage in health and in CKD. In Aim1, we will determine if FGF23 is produced by bone and macrophages in response to inflammation and by bone and erythroid cells in response to iron deficiency. We will use inflammatory challenges and dietary iron restriction in mice with cell lineage specific deletion of FGF23. In Aim2, we will assess the role of miR-122 in response to ID and inflammation on FGF23 cleavage using genetic deletion of miR-122 and administration of miR-122 antagonists in mice. In Aim 3, we will test the therapeutic potential of targeting the osteocytes, pre- osteoblasts, erythroid and macrophages in CKD, by using complementary genetic and pharmacological approaches to lower FGF23 in the Col4a3KO mouse model of CKD. We will also use genetic deletion of miR- 122 and administration of a miR-122 mimetic in mice with CKD to demonstrate the therapeutic potential of miR- 122 to increase FGF23 cleavage in CKD and prevent elevations of iFGF23 levels. We will measure FGF23 levels, and assess amelioration of kidney, bone and cardiac morphology and function. These innovative aims are supported by a productive collaborative team with expertise, skills and resources at Northwestern University that will further develop our understanding of FGF23 regulation, and support our ultimate goal of developing novel therapies to improve adverse outcomes in CKD.