Epithelial Beta-catenin Signaling Improves Chronic Renal Injury

慢性肾病（CKD）是一个日益严重的公共卫生问题，影响超过10%的退伍军人， 增加了发病率和死亡率，并造成了巨大的经济负担。持续性肾小管损伤是 肾小管间质纤维化（TIF）的重要组成部分，任何病因的进展性CKD的共同特征。 生长因子如转化生长因子-β（TGF-β）和Wnt/β-连环蛋白是肿瘤生长的重要决定因素。 肾小管上皮细胞对损伤的反应Wnt/β-连环蛋白途径的各种抑制剂具有混合效应 慢性肾损伤我们使用遗传学方法来增强近端小管中β-连环蛋白的信号传导， 这导致肾损伤后CKD进展的显著改善。Wnt/β-catenin信号通路介导 在损伤和体内平衡中的作用非常不同。我们的初步数据表明，β-连环蛋白结合到 转录因子FoxO可能是损伤中改变的β-连环蛋白依赖性应答的重要介体。 该提案验证了上皮β-连环蛋白信号传导通过以下途径防止CKD进展的假设： 对炎症、氧化应激和细胞周期进程的保护作用部分依赖于 FoxO 第一个目的是研究上皮细胞β-连环蛋白信号是如何通过影响细胞的增殖来改变上皮细胞的存活的。 炎症、细胞周期和抗氧化剂产生。我们将利用基因 一种在β-连环蛋白中有突变的小鼠，这种突变的β-连环蛋白阻止了它的降解， 或者在近端小管中特异性表达，或者以强力霉素诱导的 方式我们将通过血管紧张素/单侧肾切除术或马兜铃酸诱导慢性肾损伤。我们 预期上皮β-连环蛋白活性增加的小鼠炎症减少，细胞周期改变， 进展，减少氧化应激和增加损伤后上皮存活。我们已经确定了一 基于我们的初步数据，我们发现了许多可能介导这些效应的潜在β-连环蛋白靶点。我们将 在受伤的动物模型中测量这些靶点的表达，并使用细胞凋亡检测它们如何影响细胞死亡。 培养技术 第二个目的是探讨FoxO在介导β-catenin对慢性肾损伤后的保护作用中的作用。 损伤我们将确定损伤（即氧化应激）如何改变β-连环蛋白信号促进FoxO-的方式。 介导的反应使用一个特殊的报告小鼠。我们还将交叉我们的鼠标含有活性的- 我们的小鼠在同一上皮节段中缺乏FoxO。如果你的利益- 连环蛋白活性是通过FoxO介导的，那么这种双重条件性敲除小鼠应该失去 由增强的β-连环蛋白活性赋予的保护作用（即更多的上皮细胞死亡）。此外，我们将 使用细胞培养技术来定义FoxO靶点如何改变上皮细胞对压力的反应。 该提案使用创新的遗传学方法来确定β-连环蛋白和FoxO的作用， 上皮损伤的相互作用。我们将研究这些蛋白质相互作用的几个新的目标， 通过对转录组进行测序（初步数据）。这些研究将提供有价值的临床前数据， 这些目标可能导致未来的CKD治疗。此外，这些研究将进一步加深我们对 Wnt/β-catenin信号转导和FoxO在CKD中的作用。

Chronic kidney disease (CKD) is a growing public health problem that affects more than 10% of Veterans, increases morbidity and mortality, and imposes a huge economic burden. Persistent renal tubular injury is an important component of tubulointerstitial fibrosis (TIF), the common feature of progressive CKD of any etiology. Growth factors such as transforming growth factor- (TGF-) and Wnt/-catenin are important determinants of how tubular epithelia respond to injury. Various inhibitors of the Wnt/-catenin pathway have had mixed effects on chronic renal injury. We used a genetic approach to augment -catenin signaling in the proximal tubule, and this resulted in marked improvement in CKD progression after renal injury. Wnt/-catenin signaling mediates very different actions in injury versus homeostasis. Our preliminary data suggest that -catenin binding to the transcription factor FoxO may be an important mediator of the altered -catenin-dependent responses in injury. This proposal tests the hypothesis that epithelial -catenin signaling protects against CKD progression by protective effects on inflammation, oxidative stress, and cell cycle progression in a manner partly dependent on FoxO. The first aim investigates how epithelial -catenin signaling alters epithelial survival through effects on inflammation, cell cycle, and antioxidant production using murine models of injury. We will use genetically modified mice that have a mutation in -catenin that prevents its degradation, and this mutant -catenin is either specifically expressed in the proximal tubule or present throughout the tubule in a doxycycline-inducible manner. We will induce chronic kidney injury by either angiotensin/uninephrectomy or aristolochic acid. We anticipate that mice with increased epithelial -catenin activity have reduced inflammation, altered cell cycle progression, reduced oxidative stress, and increased epithelial survival after injury. We have identified a number of potential -catenin targets that may mediate these effects based on our preliminary data. We will measure expression of these targets in the injured animal models and test how they affect cell death using cell culture techniques. The second aim explores the role of FoxO in mediating -catenin's protective effect after chronic kidney injury. We will determine how injury (i.e. oxidative stress) alters the way -catenin signals to promote FoxO- mediated responses using a special reporter mouse. We will also cross our mouse containing the active - catenin in the proximal tubule with our mouse lacking FoxO in the same epithelial segment. If the benefit of - catenin activity is mediated through FoxO, then this double conditional knockout mouse should lose the protective effect (i.e. more epithelial cell death) conferred by augmented -catenin activity. Furthermore, we will define how FoxO targets change epithelial responses to stress using cell culture techniques. This proposal uses innovative genetic approaches to determine the role of -catenin and FoxO interactions in epithelial injury. We will investigate several novel targets of these protein interactions identified by sequencing the transcriptome (preliminary data). These studies will provide valuable pre-clinical data for these targets which may lead to future therapies for CKD. In addition, these studies will further our knowledge of Wnt/-catenin signaling and the role of FoxO in CKD.