Mechanisms of Adaptive and Maladaptive Responses of Renal Epithelium to Injury

摘要 人们普遍重新认识到肾上皮的重要性，而 尤其是近端小管，在慢性肾脏疾病(CKD)中既是靶点又是介体。 许多研究强调了肾小管间质损伤作为终极疾病的重要性。 肾脏疾病进展的驱动力。也有越来越多的证据表明有效的复苏 急性肾损伤(AKI)后上皮完整性对预防CKD的发展至关重要 (1)。此外，最近的研究表明，近端小管是一个重要的靶点， 糖尿病肾病的发病因素。 我们以前的研究表明，EGF受体(EGFR)的调节激活在 近端小管是AKI(3)(4)和持续性异常恢复的重要介质 EGFR活化在肾小管间质病变发展中的重要作用 高血压和糖尿病引起的纤维化(4，5)。尽管我们之前的研究已经 确定了经典的信号通路，如MEK/ERK1/2和PI-3K/AKT通路， 就在EGFR激活的下游，在这些反应的中介下，最终 介导急性损伤后再生的EGFR信号效应器和 导致肾小管间质纤维化的异常反应尚未被充分阐明。在……里面 在这方面，我们最近发现了河马/YAP途径的重要作用的证据 EGFR在糖尿病近端小管损伤中的调节作用及其在糖尿病修复中的作用 Aki(2)和初步数据)。AIMS 1和AIMS 2将利用体内研究，在基因上 修饰的小鼠和特定的药物抑制剂和体外靶向研究 依赖EGFR的近曲小管YAP的激活和功能在两者中的作用和机制 Aki(目标1)和CKD(目标2)。在目标3中，我们将使用新的近端小管模型- 定向肾小管间质纤维化研究肾小管上皮细胞与肾小管间质纤维化之间的关系 肾成纤维细胞。我们假设溶血磷脂的异常近端小管的产生 酸(LPA)在将静止的肾成纤维细胞转化为活性的过程中起着重要的旁分泌作用 肌成纤维细胞。我们还假设肾成纤维细胞依赖于有氧 糖酵解(“Warburg现象”)以及抑制这些细胞中的糖酵解将阻止 肌成纤维细胞转化和减少肾小管间质纤维化的发展。 具体目标有三个： 目的确定河马/YAP通路中EGFR激活在急性脑损伤后恢复中的作用。 肾损伤 目的2确定Hippo/YAP信号在EGFR介导的肾小管间质纤维化中的作用 目的3确定表皮生长因子受体在肌成纤维细胞转化和增殖中的作用 这些研究的最终目的是了解近端小管的生理调节。 再生与介导进展性骨质疏松症发生的病理生理机制 肾小管间质纤维化，并确定预防和治疗肾纤维化的新靶点。

Abstract There is renewed awareness of the importance of the renal epithelium generally, and the proximal tubule specifically, as both a target and a mediator in chronic kidney diseases (CKD). Numerous studies have highlighted the importance of tubulointerstitial injury as an ultimate driver of progression of kidney disease. There is also increasing evidence that effective recovery of epithelial integrity following acute kidney injury (AKI) is vital to prevent development of CKD (1). Furthermore, recent studies indicate that the proximal tubule is an important target and contributor to development of diabetic nephropathy. Our previous studies have implicated regulated activation of the EGF receptor (EGFR) in the proximal tubule as an important mediator of recovery from AKI (3) (4) and persistent aberrant EGFR activation as a significant contributor to pathologic development of tubulointerstitial fibrosis in response to hypertension and diabetes (4, 5). Although our previous studies have identified classic signaling pathways, such as the MEK/ERK1/2 and PI-3K/AKT pathways, immediately downstream of EGFR activation in mediation of these responses, the ultimate effectors of EGFR signaling that mediate the regeneration following acute injury and the aberrant responses leading to tubulointerstitial fibrosis have not been adequately elucidated. In this regard, we have recently found evidence for an important role for the HIPPO/YAP pathway in the mediation of EGFR's effects in both proximal tubule diabetic injury and in recovery from AKI (2) and preliminary data). Aims 1 and 2 will utilize in vivo studies with both genetically modified mice and specific pharmacologic inhibitors and targeted in vitro studies to elucidate roles and mechanisms of EGFR-dependent proximal tubule YAP activation and function in both AKI (Aim 1) and CKD (Aim 2). In Aim 3, we will employ novel models of proximal tubule- directed tubulointerstitial fibrosis to investigate the crosstalk between the tubule epithelium and renal fibroblasts. We hypothesize that aberrant proximal tubule production of lysophosphatidic acid (LPA) plays an important paracrine role to transform quiescent renal fibroblasts into active myofibroblasts. We also hypothesize that renal fibroblasts develop a dependence upon aerobic glycolysis (“Warburg phenomenon”) and that inhibition of glycolysis in these cells will prevent myofibroblast transformation and decrease development of tubulointerstitial fibrosis. There are three specific aims: Aim I Determine the Role of EGFR Activation of the Hippo/YAP Pathway in Recovery From Acute Kidney Injury Aim 2 Determine the Role of Hippo/YAP Signaling in EGFR-Mediated Tubulointerstitial Fibrosis Aim 3 Determine the Role of EGFR in Mediating Myofibroblast Transformation and Proliferation The ultimate goal of these studies is to understand physiologic regulation of proximal tubule regeneration and the pathophysiologic mechanisms mediating the development of progressive tubulointerstitial fibrosis and to identify new targets for prevention and treatment of renal fibrosis.