Regulation of Cylooxygenase-2 in Macula Densa and cTALH

描述（由申请人提供）：前列腺素调节哺乳动物肾脏中的血管张力以及盐和水的稳态，并参与激素作用的介导和/或调节。环氧合酶（前列腺素合酶G2/H2）是花生四烯酸代谢为前列腺素G2和随后代谢为前列腺素H2的限速酶，前列腺素H2作为前列腺素和血栓烷随后代谢的前体synthetases.lt。在哺乳动物肾脏中，参与调节肾素的表达和分泌。我们在原代培养的cTALH中的研究表明，考克斯-2表达通过p38依赖性过程响应于细胞外氯的减少而增加。目前的建议有三个具体目标。在第一个目标中，我们将研究考克斯-2在致密斑/cTAL中表达的调节机制。我们假设细胞外氯离子减少通过细胞收缩和/或细胞内氯离子减少增加cTAL/致密斑中考克斯-2的表达，这将激活PLA 2活性并释放激活p38活性的胰高血糖素。我们进一步假设，考克斯-2增加NF-κ B介导的转录激活和mRNA的稳定性增加。第二个具体目标是研究cTAL/致密斑考克斯-2表达通过肾素-血管紧张素系统和一氧化氮的调节。我们假设这些激动剂通过改变氯离子流量从而调节p38活性来调节考克斯-2的表达。第三个具体目标是研究考克斯-2对肾素表达的调节。在这些研究中，我们将研究高肾素状态下前列腺素酶的调节，并研究考克斯-2代谢物和TGF β 2在调节肾素表达中的相互作用。我们还建议开发小鼠选择性删除考克斯-2的内皮细胞，以确定内皮细胞产生的考克斯-2代谢产物的作用，在调节肾素的表达和分泌。总之，这些研究将进一步深入了解肾皮质考克斯-2表达的调节机制和考克斯-2产生的代谢产物在调节肾素-血管紧张素系统中的生理作用。

DESCRIPTION (provided by applicant): Prostaglandins regulate vascular tone and salt and water homeostasis in the mammalian kidney and are involved in the mediation and/or modulation of hormonal action. Cyclooxygenase (prostaglandin synthase G2/H2) is the rate-limiting enzyme in metabolism of arachidonic acid to prostaglandin G2 and subsequently to prostaglandin H2, which serves as precursor for subsequent metabolism by prostaglandin and thromboxane synthetases.lt is now recognized that cyclooxygenase-2 (COX-2) is highly expressed in the macula densa and surrounding cortical thick ascending limb (cTAL) of mammalian kidney and is involved in regulation of renin expression and secretion. Our studies in primary cultured cTALH have indicated that COX-2 expression is increased in response to decreased extracellular chloride by a p38 dependent process. There are three specific aims in the current proposal. In the first aim, we will examine mechanisms of regulation of COX-2 expression in macula densa/cTAL. We hypothesize that decreased extracellular chloride increases COX-2 expression in cTAL/macula densa by cell shrinkage and/or by decreases in intracellular chloride, which will activate PLA2activity and release prostaglandins that activate p38 activity. We further hypothesize that COX-2 increases both by NF-kappa B-mediated transcriptional activation and by increased mRNA stability. The second specific aim will investigate the modulation of cTAL/macula densa COX-2 expression by the renin-angiotensin system and nitric oxide. We hypothesize that these agonists modulate COX-2 expression by altering chloride flux and thereby modulating p38 activity. The third specific aim will investigate the modulation of renin expression by COX-2. In these studies, we will examine the regulation of prostaglandin synthases in high renin states and examine the interaction of COX-2 metabolites and TGF beta 2 in regulation of renin expression. We also propose to develop mice with selective deletion of COX-2 in the endothelium to determine the role of endothelial-generated COX-2 metabolites in regulation of renin expression and secretion. In summary, these studies will provide further insight into regulatory mechanisms of renal corticalCOX-2 expression and physiologic roles of COX-2-generated metabolites in regulation of the renin-angiotensin system.