The Melanocortinergic pathway inglomerular disease

摘要 蛋白尿，通常是由足细胞功能障碍或损伤引起的，是一种始终如一的发现 肾小球疾病本身就是一个长期预后的风险因素。有证据表明，多个- 任务黑素皮质素激素系统在多器官系统的应激反应中起到保护作用， 包括肾脏。黑素皮质素联合促肾上腺皮质激素诱导治疗的临床疗效 激素耐药肾病综合征的缓解表明类固醇激素非依赖性的抗蛋白尿活性 黑素皮质醇能途径。通过利用自然发生的功能丧失突变 黑素皮质素1受体(MC1R)在人和小鼠中的表达，我们最新的研究表明MC1R很可能是 对于黑素皮质素治疗的降低蛋白尿和足细胞保护作用是可有可无的。相反，我们 发现MC5R在体内和体外主要表达于肾小球足细胞，而MC5R激动剂 似乎赋予了足细胞的保护作用。在我们以前工作的基础上，这项研究将检查 MC5R介导的黑素皮质醇能通路调节足细胞损伤，探索足细胞损伤的部位和方式 行动并测试一种基于靶向治疗蛋白尿性肾小球疾病的全新策略 路径。目标1将定义和验证MC5R和MC1R在介导抗蛋白尿和 比较不同黑素皮质素对野生型MC1R-1足细胞的保护作用 阿霉素肾病或肾毒性血清性肾炎的Null和MC5R基因敲除(MC5R-/-)小鼠。这个 将在MC5R-/-中评估造血MC5R对黑素皮质素治疗有益效果的贡献 接受同基因野生型骨髓来源细胞过继移植的小鼠。此外，足细胞 MC5R的自主效应将在具有足细胞特异性MC5R重组的MC5R-/-小鼠中进行检测。目标 2将探讨MC5R信号对足细胞保护作用的机制。黑素皮质素如何 治疗影响足细胞死亡、细胞骨架解体和NF-B依赖的表达 足细胞病变介质将在有条件永生化和原代足细胞中进行评估。最重要的 MC5R的作用将使用主要的MC5R-/-足细胞和那些具有MC5R重建的足细胞来定义。研究将会 进一步研究MC5R信号的足细胞保护作用是否通过抑制磷酸化来传递 Gsk3β是MC5R信号的关键转导分子，也是多条通路的汇聚点 足细胞损伤。目的3将测试一种新型的高选择性MC5R激动剂对已建立的 阿霉素或肾毒性血清对小鼠足细胞的损伤及氨基核苷对大鼠足细胞的损伤。 黑素皮质素能信号对足细胞保护作用的机制将得到验证 在活体内。总而言之，这些研究将提供黑素皮质素能途径作用的机制观点。 在调节足细胞损伤方面，并可能为基于黑素皮质素的治疗的临床试验铺平道路，以改善 足细胞损伤，导致人蛋白尿缓解和肾小球硬化缓慢进展。

ABSTRACT Proteinuria, commonly caused by podocyte dysfunction or injury, is an invariable finding in patients with glomerular disease and is by itself a risk factor for long-term prognosis. Evidence suggests that the multi- tasking melanocortin hormone system plays a protective role in stress response in multiple organ systems, including the kidney. The clinical effectiveness of melanocortin therapy with adrenocorticotropin in inducing remission of steroid-resistant nephrotic syndrome points to a steroidogenic-independent anti-proteinuric activity of the melanocortinergic pathway. By harnessing the naturally occurring loss-of-function mutations in melanocortin 1 receptor (MC1R) in both humans and mice, our latest study demonstrated that MC1R is likely dispensable for the proteinuria-reducing and podocyte protective effect of melanocortin therapy. Rather, we found that MC5R is predominantly expressed in glomerular podocytes in vivo and in vitro, and MC5R agonists seem to confer a podocyte protective effect. Building on our previous work, this study will examine the role of the MC5R-mediated melanocortinergic pathway in regulating podocyte injury, explore the sites and modes of action and test an entirely novel strategy for treating proteinuric glomerulopathies based on targeting this pathway. Aim 1 will define and validate the role of MC5R versus MC1R in mediating the anti-proteinuric and podocyte protective effect by comparing the therapeutic efficacy of diverse melanocortins in wild-type, MC1R- null and MC5R knockout (MC5R-/-) mice with Adriamycin nephropathy or nephrotoxic serum nephritis. The contribution of hematopoietic MC5R to the beneficial effect of melanocortin therapy will be assessed in MC5R-/- mice receiving adoptive transfer of syngeneic wild-type bone marrow-derived cells. Furthermore, the podocyte autonomous effect of MC5R will be examined in MC5R-/- mice with podocyte specific MC5R reconstitution. Aim 2 will explore the mechanisms underlying the podocyte protective effect of MC5R signaling. How melanocortin treatment affects podocyte death, cytoskeleton disorganization and expression of NFB-dependent podocytopathic mediators will be assessed in conditionally immortalized and primary podocytes. The essential role of MC5R will be defined using primary MC5R-/- podocytes and those with MC5R reconstitution. Studies will further examine if the podocyte protective effect of MC5R signaling is conveyed by inhibitory phosphorylation of GSK3β, a key transducer of MC5R signaling and a point of convergence for multiple pathways involved in podocyte injury. Aim 3 will test the rescue effect of a novel and highly selective MC5R agonist on established podocyte injury elicited by Adriamycin or nephrotoxic serum in mice and by puromycin aminonucleoside in rats. The mechanisms responsible for the podocyte protective effect of melanocortinergic signaling will be validated in vivo. Collectively, these studies will provide a mechanistic view of the role of the melanocortinergic pathway in regulating podocyte injury and may pave the way for clinical trials of melanocortin based therapy to improve podocyte injury, induce proteinuria remission and slow progression of glomerulosclerosis in man.