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

项目总结 成纤维细胞生长因子23是一种磷酸调节激素，通常由骨骼产生。在慢性病 肾脏疾病(CKD)，循环中生物活性完整的FGF23(IFGF23)积聚，原因是FGF23增加 转录和FGF23失活裂解减少与心血管独立相关 死亡率。降低慢性肾脏病FGF23水平和预防不良结局的新治疗方法是 迫切需要，但目前的治疗方法并不理想。缺铁(ID)和炎症是强有力的 刺激FGF23转录和切割。在健康的小鼠中，FGF23的产生大大增加 与ID和炎症有关，但由于伴随的增加，仅观察到血清iFGF23水平的轻微增加 在FGF23切割中。MIR-122增加FGF23的切割，并在ID和 发炎。在CKD中，我们发现尽管存在ID和炎症，miR-122的表达仍然减少，FGF23 卵裂受损，ID和炎症因此导致iFGF23水平升高。我们向大家展示了 部分纠正慢性肾脏病小鼠ID或炎症成分降低FGF23转录，已更正 FGF23水平，并防止心脏病和过早死亡的发展。但是，骨骼特定 FGF23的缺失不足以完全纠正缺铁或发炎小鼠的FGF23水平，这表明 这些额外的细胞靶点会产生FGF23，以应对ID和炎症。事实上，我们发现红系 细胞和巨噬细胞也是FGF23过量的原因之一。在这个创新的提案中，我们将检验这一假设 红系和巨噬细胞系有助于增加FGF23的产生 炎症，而miR-122降低会导致健康和慢性肾脏病患者FGF23裂解受损。 在Aim1中，我们将确定FGF23是否由骨和巨噬细胞在炎症反应中产生，并通过 骨骼和红系细胞对缺铁的反应。我们将使用炎症性挑战和膳食铁 限制细胞系特异性缺失FGF23的小鼠。在AIM2中，我们将评估miR-122在 通过miR-122基因缺失和给药对FGF23切割上的ID和炎症反应的反应 小鼠体内有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， CKD中的成骨细胞、红系和巨噬细胞在遗传和药理学上的互补作用 降低CKD Col4a3KO小鼠模型中FGF23的途径我们还将使用miR-的基因缺失 122，并在CKD小鼠体内应用miR-122模拟物，以证明miR-122的治疗潜力。 122以增加CKD中FGF23的切割，并防止iFGF23水平的升高。我们将测量FGF23 水平，并评估肾脏、骨骼和心脏形态和功能的改善情况。这些创新的目标 由西北大学拥有专业知识、技能和资源的高效协作团队提供支持 这将进一步加深我们对FGF23规则的理解，并支持我们开发 改善慢性肾脏病不良结局的新疗法。

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.