Cellular Signaling in Renal Pathophysiology

描述(申请人提供)：进行性肾脏疾病的特征是肾小球和间质细胞的增殖，循环中的炎性细胞的涌入和激活，以及细胞外基质大分子的过度产生和沉积。以前的研究已经证明了cAMP-PKA通路在调节系膜细胞(MC)增殖中的重要性，并确定了环3‘-5’核苷酸磷酸二酯酶(PDE)同工酶作为治疗急性肾损伤的药物的潜在作用。然而，目前尚不清楚PDE抑制剂是否会阻止或减缓慢性肾脏疾病的发展。需要检验的中心假设是，cAMP同工酶特异性的PDE抑制剂，通过与关键的有丝分裂、炎症和基质信号通路的负干扰，能够预防进行性肾脏疾病的发生和发展。最近的研究表明，这些关键通路是通过cAMP-PKA和转化生长因子-β1信号之间的相互作用来调节的。初步研究将确定cAMP诱导转化生长因子-β表达的机制，并将描绘cAMP和转化生长因子-β1相互作用抑制MC有丝分裂的途径(特定目标1)。在特定的目标2中，将检验PDE4抑制剂通过抑制转化生长因子-β刺激的MAPK通路(S)而抑制单核细胞趋化蛋白-1的表达，从而下调核因子-KB的假设。在具体目标3中，将确定cAMP-PKA通路在IV型胶原产生和分解代谢中的作用。CAMP激动剂能够通过下调ERK和/或p38通路来“解偶联”对升高的转化生长因子-β1水平的瘢痕反应的假说将得到检验。这些研究确定cAMP-PKA通路在MC增殖、炎症介质产生和基质产生中的作用的体内相关性将在慢性Thy1模型中建立(特定目标4)。通过仔细的半定量组织病理学分析和鉴定急性和慢性肾损伤的标志物，将有可能识别与急性肾损伤向慢性进行性肾脏疾病转变相关的不良适应信号通路，并确定PDE抑制剂在预防或改善这一过程中的作用。这些研究将揭示进行性肾脏疾病的基本机制，并可能为设计更新、更特异的药物治疗慢性肾脏疾病提供合理的基础。

DESCRIPTION (provided by applicant): Progressive renal disease is characterized by the proliferation of glomerular and interstitial cells, the influx and activation of circulating inflammatory cells, and the excessive production and deposition of extracellular matrix macromolecules. Previous studies supported by this grant have demonstrated the importance of the cAMP-PKA pathway in regulation of mesangial cell (MC) proliferation and have identified a potential role of cyclic 3'-5' nucleotide phosphodiesterase (PDE) isozymes as therapeutic agents to treat acute renal injury. However, it is not known whether PDE inhibitors will prevent the development or slow the progression of chronic renal disease. The central hypothesis to be tested is that cAMP isozyme-speciflc PDE inhibitors, through negative crosstalk with critical mitogenic, inflammatory, and matrix signaling pathways, are capable of preventing the onset and development of progressive renal disease. Recent studies have provided evidence that these critical pathways are regulated through interactions between cAMP-PKA and TGF-beta1 signaling. Initial studies will define the mechanism by which cAMP induces TGF-beta expression and will delineate pathways through which cAMP and TGF-beta1 interact to suppress MC mitogenesis (Specific Aim 1). In Specific Aim 2, the hypothesis that PDE4 inhibitors suppress MCP-1 expression through inhibition of TGF-beta-stimulated MAPK pathway(s) leading to down regulation of Nf-KB will be tested. In Specific Aim 3, the role of the cAMP-PKA pathway in collagen IV production and catabolism will be defined. The hypothesis that cAMP agonists are capable of "uncoupling" the cicatricial response to elevated TGF-beta1 levels through down regulation of the ERK and/or p38 pathways will be tested. The in vivo relevance of these studies to define the role of the cAMP-PKA pathway in MC proliferation, production of inflammatory mediators, and matrix production will be established in the chronic Thy 1 model (Specific Aim 4). Through careful semi-quantitative histopathologic analysis and identification of markers of acute and chronic renal injury, it will be possible to identify maladaptive signaling pathways that are associated with the transformation of acute injury into chronic, progressive renal disease and to define the role of PDE inhibitors in preventing or ameliorating this process. These studies will reveal insights into basic mechanisms underlying progressive renal disease and may provide the rational basis for the design of newer, more specific pharmacotherapeutic agents to treat chronic renal disease.