Renoprotective effect of increased PKG activity in diabetic nephropathy

描述(由申请人提供)： 糖尿病肾病是终末期肾功能衰竭最常见的单一原因，在1型和2型糖尿病患者中非常普遍。高血糖被认为在糖尿病肾病的发病机制中起关键作用。转化生长因子-2(TGF-2)是高血糖引起肾纤维化的主要效应因子。转化生长因子-2是以生物活性形式表达的，必须转化为活性形式才能诱导纤维化作用。凝血酶敏感蛋白1(TSP1)是糖尿病时转化生长因子-2激活的分子调节因子。TSP1介导的转化生长因子-2活化参与了实验性糖尿病肾病的发生发展，也参与了人类糖尿病肾病的发生发展。初步研究表明，cGMP依赖的蛋白激酶(PKG)对葡萄糖诱导的系膜细胞TSP1表达和TSP1介导的转化生长因子-2活化具有新的抑制作用，提示PKG在糖尿病肾病中具有潜在的治疗潜力。这项拟议的研究将测试，在不同的糖尿病小鼠模型中，是否通过抑制TSP1介导的转化生长因子-2的激活来通过基因或药物增加的PKG活性来防止糖尿病肾病的发生。具体目标1将确定高糖下调体外培养的肾细胞PKG活性的机制及其在葡萄糖诱导的TSP1表达、转化生长因子-2水平/活性和细胞外基质(ECM)产生中的作用。具体目的2将确定PKG活性增加是否能在体内阻止糖尿病肾病的发展。这些研究将确立PKG在糖尿病肾病发生发展中的意义。重要的是，在拟议的研究中，使用西地那非(一种cGMP特异性磷酸二酯酶5的抑制剂)来增加PKG活性是翻译的，并与人类治疗相关。西地那非是一种临床上用于治疗勃起功能障碍(ED，男性糖尿病患者的另一种并发症)和肺动脉高压(PAH)的药物。目前提出的研究将测试西地那非在不同糖尿病小鼠模型中治疗糖尿病肾病的新的潜在应用。因此，这些研究具有重要的临床意义，并将导致新的治疗方法的发展，以减轻/治疗糖尿病肾病，糖尿病的主要并发症。

DESCRIPTION (provided by applicant): Diabetic nephropathy is the single most common cause of end-stage renal failure, and is highly prevalent in both type 1 and type 2 diabetics. Hyperglycemia has been suggested to play a critical role in the pathogenesis of diabetic nephropathy. Transforming growth factor-2 (TGF-2) is a major effector leading to renal fibrosis in response to hyperglycemia. TGF-2 is expressed as a biologically inactive form and must be converted to its active form to elicit fibrogenic effects. Thrombospondin1 (TSP1) has been identified as the molecular regulator of TGF-2 activation under diabetic conditions. TSP1-mediated TGF-2 activation is involved in the development of experimental diabetic nephropathy and also plays a role in human diabetic nephropathy. Preliminary data demonstrate a novel inhibitory effect of cGMP-dependent protein kinase (PKG) on glucose-induced TSP1 expression and TSP1-mediated TGF-2 activation in mesangial cells, suggesting a therapeutic potential of PKG in diabetic nephropathy. The proposed studies will test whether genetically or pharmacologically increased PKG activity prevents the development of diabetic nephropathy through inhibition of TSP1-mediated TGF-2 activation in different diabetic mouse models. Specific Aim 1 will determine the mechanisms by which high glucose down-regulates PKG activity in kidney cells in vitro and its role in glucose-induced TSP1 expression, TGF-2 levels/activity, and extracellular matrix (ECM) production. Specific Aim 2 will determine whether increased PKG activity prevents the development of diabetic nephropathy in vivo. These studies will establish the significance of PKG in the development of diabetic nephropathy. Importantly, utilization of sildenafil (an inhibitor of cGMP specific phosphodiesterase 5) to increase PKG activity in the proposed studies is translational and relevant to human therapy. Sildenafil is a drug used to treat erectile dysfunction (ED, another diabetic complication in male patients) and pulmonary arterial hypertension (PAH) in clinic. The current proposed studies will test a novel potential application of sildenafil in the treatment of diabetic nephropathy in different diabetic mouse models. Therefore, these studies have significant clinical relevance, and will lead to the development of novel therapies to attenuate/treat diabetic nephropathy, a major complication of diabetes.