The Role of Cyclooxygenase-2 in Podocyte Injury in Diabetic Nephropathy

描述(由申请人提供)： 项目摘要/摘要足细胞是终末期肾病(ESRD)肾小球疾病发生发展过程中损伤的主要靶细胞。在进展性肾损伤模型中，肾脏环氧合酶-2(COX-2)的表达增加，选择性COX-2抑制剂在肾切除、糖尿病和盐敏性高血压模型中减少蛋白尿，延缓进行性肾损伤。然而，抑制前列腺素合成可以改善进行性肾损伤的机制仍不确定。我们认为，足细胞中COX-2的局部表达易导致进行性肾小球损伤。我们和其他人已经证明在进行性肾小球损伤模型中足细胞中COX-2的表达选择性增加，并发现足细胞中COX-2的过度表达使肾小球对阿霉素肾病易感。然而，足细胞COX-2上调的机制以及损伤对足细胞功能的潜在作用仍不完全清楚。我们假设足细胞增多的COX-2会产生与局部足细胞RAS相互作用的代谢物，使足细胞在肾脏受损时容易受到进一步的损伤。这些研究的目的是研究前列腺素在糖尿病肾病发展过程中作为足细胞损伤的介体和/或调节物的潜在作用。我们提出两个相辅相成的具体目标。在特定的目标I中，我们将使用基因工程小鼠，选择性地在足细胞中过表达COX-2或具有COX-2的基因缺失，来研究COX-2的表达变化在糖尿病肾病中足细胞损伤中的作用。我们还将利用特定前列腺素受体基因缺失的小鼠来确定哪种前列腺素(S)介导足细胞损伤，并将阐明糖尿病肾病发展过程中足细胞环氧合酶-2和局部足细胞肾素-血管紧张素系统(RAS)之间的相互作用。在特定的目的II中，我们将使用野生型小鼠的条件永生化小鼠足细胞、足细胞中高表达COX-2或COX-2表达缺失的转基因小鼠的足细胞，在体外研究COX-2增加足细胞损伤的机制。我们将研究高糖对以下方面的影响：1)导致足细胞COX-2表达增加的信号；2)COX-2表达变化对分化的足细胞结构和功能的影响；以及3)足细胞COX-2作为足细胞ROS产生增加的介质所起的作用。虽然COX-2抑制剂可以有效改善动物模型中的肾脏损伤，但由于认识到它们可能促进血栓形成血管损伤和升高血压，因此无法在进展性肾脏疾病患者中使用它们。确定哪些前列腺素介导了肾小球损伤并确定了它们的损伤机制，可能有助于开发潜在副作用较少的治疗策略。

DESCRIPTION (provided by applicant): Project Summary/Abstract The podocyte is the primary glomerular cell targeted for injury during the development and progression of glomerular diseases that eventuate in end stage renal disease (ESRD). Renal expression of cyclooxygenase-2 (COX-2) increases in models of progressive renal injury, and selective COX-2 inhibitors decrease proteinuria and retard progressive renal injury in models of renal ablation, diabetes and salt- sensitive hypertension. However, the mechanisms by which inhibition of prostaglandin synthesis can ameliorate progressive renal injury remain undetermined. We propose that local expression of COX-2 in podocytes predisposes to progressive glomerular injury. We and others have demonstrated a selective increase of COX-2 expression in podocytes in models of progressive glomerular injury and found that over- expression of COX-2 in podocytes renders the glomerulus susceptible to adriamycin nephropathy. However, the mechanisms underlying COX-2 up-regulation in podocytes and potential roles in podocyte function in response to injury remain incompletely understood. We hypothesize increased podocyte COX-2 generates metabolites that interact with the local podocyte RAS, predisposing the podocyte to further injury in response to renal insults. The goal of these studies is to examine the potential role of prostaglandins as mediators and/or modulators of podocyte injury during the development of diabetic nephropathy. We propose two complementary specific aims. In Specific Aim I, we will investigate the role of altered COX-2 expression in podocyte injury during diabetic nephropathy in vivo, using genetically engineered mice that either selectively overexpress COX-2 or have genetic deletion of COX-2 in podocytes. We will also utilize mice with genetic deletions of specific prostanoid receptors to determine which prostaglandin(s) mediate podocyte injury and will elucidate interactions between podocyte COX-2 and the local podocyte renin-angiotensin system (RAS) during the development of diabetic nephropathy. In Specific Aim II, we will investigate the mechanisms by which COX-2 increases podocyte injury in response to high glucose in vitro using conditionally immortalized mouse podocytes from wild type mice, from the transgenic mice overexpressing COX-2 or null for COX-2 expression in podocytes. We will investigate the effects of high glucose on 1) the signals leading to increased podocyte COX-2 expression; 2) the effects of alterations in COX-2 expression on structure and function of differentiated podocytes in response to high glucose; and 3) the role of podocyte COX-2 as a mediator of increased production of ROS in podocytes. Although COX-2 inhibitors effectively ameliorate renal injury in animal models, the awareness of their potential to promote thrombotic vascular injury and to raise blood pressure preclude their clinical use in patients with progressive renal disease. Identification of which prostaglandins mediate glomerular injury and the determination of their mechanisms of injury may allow the development of therapeutic strategies with fewer potential side effects.