Promoting podocyte protective cGMP signaling in diabetic kidney disease

肾小球足细胞在包括糖尿病在内的肾小球疾病的发病机制中起关键作用 肾病（DN）。越来越多的证据表明，cGMP信号传导具有足细胞保护作用， 肾脏疾病cGMP的产生受一氧化氮（NO）和利钠肽（NP）刺激， 心房NP（ANP）、脑NP（BNP）和C型NP（CNP）。在足细胞中， 的NP。相反，足细胞对NO的反应最低。因此，NP是cGMP的主要来源。 在足细胞中产生。NP通过与NP受体（NPR）结合诱导cGMP产生。 ANP和BNP）和NPRB（结合CNP）。NP清除受体是NP作用的一个重要调节因子 （NPRC），其结合并降解ANP、BNP和CNP。NPRC的药理学阻断抑制了 NPs对NPRC的作用，这增强了NPRA和NPRB诱导的cGMP生成。此外，NP具有直接 由于ANP受体（NPRA）的足细胞特异性敲除（KO），足细胞在体内具有保护作用 增加蛋白尿小鼠模型中的肾小球损伤。我们的初步研究发现：1.足细胞 表达NPRA、NPRB和NPRC。2. NPRC在足细胞中高度表达并显著限制cGMP 由本地可用的NP生成。3. ANP和CNP均能保护足细胞免受凋亡刺激。 足细胞特异性敲除（KO）NPRC减少1型糖尿病模型（秋田小鼠）中的白蛋白尿，5. NPRC的药理学阻断在体外和体内有效地促进足细胞保护性cGMP的产生， 和6. NPRC的药理学阻断可减少秋田小鼠的蛋白尿。根据这些观察， 我们假设NPRC阻断NPs的清除将提高局部NP水平，促进足细胞 保护cGMP信号传导并改善DKD。提出了两个具体目标。 目的1：检测DKD中足细胞特异性NPRC KO。这些研究将专门在 足细胞Subaim 1A将在秋田小鼠中研究组成型NPRC KO。子目标1B将补充子目标1A 通过研究已确诊疾病的秋田小鼠的诱导型NPRC KO。足细胞保护机制 将在KO和野生型小鼠（WT）的肾脏以及培养的足细胞中研究NP信号传导。 目的2：在秋田小鼠中检查NPRC的药理学阻断。目的2将使用ANP类似物ANP（4- 23)和AP 811通过特异性结合NPRC而不结合NPRA或NPRB来抑制NP清除， 反过来，增强NP的效果。然后我们将研究NPRC阻断对秋田小鼠的影响。Subaim 2A 将确定最有效的药物用于进一步研究（概念验证）。Subaim 2B将研究秋田小鼠， 建立疾病。因此，这些研究检查了治疗方法的转化潜力。

Glomerular podocytes play a pivotal role in the pathogenesis of glomerular diseases including diabetic nephropathy(DN). Accumulating evidence suggests that cGMP signaling has podocyte protective effects in kidney diseases. Generation of cGMP is stimulated by nitric oxide (NO) and natriuretic peptides (NPs) such as atrial NP (ANP), brain NP (BNP) and C-type NP (CNP). In podocytes, cGMP generation is potently stimulated by NPs. In contrast, podocytes are minimally responsive to NO. Thus, NPs are the predominant source cGMP generation in podocytes. NPs induce cGMP generation by binding to the NP receptors (NPRs) NPRA (binds ANP and BNP) and NPRB (binds CNP). An important regulator of NP actions is the NP clearance receptor (NPRC), which binds and degrades ANP, BNP and CNP. Pharmacologic blockade of NPRC inhibits binding of NPs to NPRC, which potentiates NPRA- and NPRB-induced cGMP generation. Moreover, NPs have direct podocyte protective actions in vivo because podocyte specific knockout (KO) of the ANP receptor (NPRA) augments glomerular injury in a proteinuric mouse model. Our preliminary studies found that: 1. Podocytes express NPRA, NPRB and NPRC. 2. NPRC is highly expressed in podocytes and significantly limits cGMP generation by locally available NPs. 3. Both ANP and CNP protect podocytes from apoptotic stimuli, 4. Podocyte specific knockout (KO) of NPRC reduces albuminuria in a model of type 1 diabetes (Akita mice), 5. Pharmacologic blockade of NPRC potently promotes podocyte protective cGMP generation in vitro and in vivo, and 6. Pharmacologic blockade of NPRC decreases albuminuria in Akita mice. Based on these observations, we hypothesized that blocking clearance of NPs by NPRC will enhance local NP levels, promote podocyte protective cGMP signaling and ameliorate DKD. Two specific aims are proposed. Aim 1: Examine podocyte specific NPRC KO in DKD. These studies will KO NPRC specifically in podocytes. Subaim 1A will study constitutive NPRC KO in Akita mice. Subaim 1B will complement subaim 1A by studying inducible NPRC KO in Akita mice with established disease. Podocyte protective mechanisms of NP signaling will be studied in kidneys of KO and wild type mice (WT), and in cultured podocytes. Aim 2: Examine pharmacologic blockade of NPRC in Akita mice. Aim 2 will use the ANP analogs ANP(4- 23) and AP811to inhibit NP clearance by specifically binding to NPRC without binding NPRA or NPRB and, in turn, enhance the effects of NPs. We will then study the effects of NPRC blockade in Akita mice. Subaim 2A will determine the most effective drug for further study (proof of concept). Subaim 2B will study Akita mice with established disease. Thus, these studies examine the translational potential of the treatment approach.