Regulation of Cylooxygenase-2 in Macula Densa and cTALH

描述(申请人提供)：前列腺素调节哺乳动物肾脏的血管张力和盐和水的动态平衡，并参与调节和/或调节激素作用。环氧合酶(Prostaglandin Synthase G2/H2)是花生四烯酸代谢为前列腺素G2和前列腺素H2的限速酶，前列腺素H2是前列腺素和血栓素合成酶代谢的前体。目前认为，环氧合酶-2(COX-2)在哺乳动物肾脏致密黄斑和周围皮质粗大升支(CTAL)中高表达，参与肾素的表达和分泌调节。我们在原代培养的cTALH中的研究表明，COX-2的表达随着细胞外氯的减少而增加，这是一个依赖p38的过程。目前的提案有三个具体目标。在第一个目标中，我们将研究COX-2在致密黄斑/cTAL中表达的调节机制。我们假设，细胞外氯的减少通过细胞收缩和/或细胞内氯的减少增加了cTAL/致密斑中COX-2的表达，这将激活PLA2活性，并释放前列腺素来激活p38活性。我们进一步假设，COX-2的增加既是通过核因子-kappa B介导的转录激活，也是通过增加mRNA的稳定性。第二个特定目的是研究肾素-血管紧张素系统和一氧化氮对cTAL/致密斑COX-2表达的调节。我们假设这些激动剂通过改变氯通量从而调节p38的活性来调节COX-2的表达。第三个特定目的是研究COX-2对肾素表达的调节。在这些研究中，我们将研究前列腺素合成酶在高肾素状态下的调节，以及环氧合酶-2代谢产物和转化生长因子β2在肾素表达调节中的相互作用。我们还建议建立内皮细胞中COX-2选择性缺失的小鼠，以确定内皮产生的COX-2代谢产物在调节肾素表达和分泌中的作用。综上所述，这些研究将进一步深入了解肾皮质COX-2表达的调节机制，以及COX-2产生的代谢物在肾素-血管紧张素系统调节中的生理作用。

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.