Role of BK Channel in Chronic Kidney Disease

项目摘要 慢性肾脏疾病(CKD)影响着2600-3000万美国成年人，仍然是一个主要的公共卫生问题 (1；2)。肾纤维化是几乎所有类型慢性肾脏病的必然结果，而不考虑潜在的原因。 病因，并导致进行性肾功能衰竭和终末期肾病(ESRD)(1)。因此，防止 肾脏纤维化可能反过来阻止CKD和ESRD的进展。虽然有令人信服的文学作品 提出了许多治疗肾纤维化的潜在靶点，但很少有进展到最初的阶段 临床试验阶段(3；4)，没有一项在治疗肾纤维化方面显示有效(4)。因此，它是 继续发现和测试肾脏纤维化的新的潜在治疗靶点至关重要。 单侧输尿管梗阻(UUO)是一种常见的肾纤维化实验模型。 转化生长因子-β(转化生长因子-β)亚型是一种多功能细胞因子，在 在大多数(如果不是全部)形式的CKD中推动纤维化(5)。大钾(BK)通道(也称为大钾、大钾或大钾 SLO1通道)是K+通道，可能是在肾纤维化中发挥重要作用的一个新靶点。BK 通道由独立起通道作用的α亚基(BKα)、β亚基(β1-4)和 γ亚基(6；7)。最近的一项研究报道，BK通道β1亚单位缺陷会加剧血管 高脂饮食肥胖小鼠的纤维化和重塑，表明BKα敏感性和活性降低 由β-1缺乏引起的(8)导致血管纤维化(9)。我们有令人信服的初步证据表明 第一次，BKα在肾纤维化中也发挥了关键作用。而BKα基因敲除(KO)小鼠 对于UUO后出现更严重的纤维化(图1)，使用BK通道开放剂进行预治疗， BMS191011(Sigma-Aldrich，SML0866)可以激活BK通道(10)，保护小鼠不发育 野生型(WT)UUO小鼠的肾脏纤维化(图2)通过抑制转化生长因子-β1信号通路(图3-4)。 提示BK通道在肾纤维化的发生发展中起重要作用。 因此，阐明BK通道在肾纤维化发病机制中的作用机制是 极其重要的临床意义。我们的总体假设是BK通道缺陷容易发生 通过激活转化生长因子-β信号通路在肾纤维化小鼠模型中实现肾纤维化。在这 应用程序我们将提出三个具体目标来检验我们的总体假设： 具体目的1：验证BK通道在肾纤维化发生发展中的作用 不同的肾纤维化小鼠模型。 特定目标2：研究BK介导的发育的分子机制 肾脏纤维化的症状。 具体目标3：通过检查BK的表达水平来翻译实验结果 与CKD患者肾脏纤维化的严重程度相关。 SA3.1。确定BK表达水平是否与肾脏纤维化的严重程度定量相关 CKD合并糖尿病肾病和局灶节段性肾小球硬化患者的肾活检标本 (FSGS)。 阐明BK介导的肾纤维化发展的分子机制将 为BK经络是否可用作潜在的治疗靶点提供新的见解 CKD患者，防止他们发展为终末期肾病。

Project Summary Chronic kidney disease (CKD) affects 26–30 million U.S. adults and remains a major public health problem (1; 2). Renal fibrosis is the inevitable consequence of almost every type of CKD regardless of underlying etiology, and leads to progressive renal failure and end-stage of renal disease (ESRD) (1). Thus, preventing renal fibrosis may in turn prevent progression of CKD and ESRD. While there is compelling literature suggesting many potential therapeutic targets for treating renal fibrosis, very few have advanced to the initial phase of clinical trials (3; 4), and none have shown efficacy in the treatment of renal fibrosis (4). Thus, it is crucial to continue to discover and test novel potential therapeutic targets for renal fibrosis. Unilateral ureteral obstruction (UUO) is a common and well-validated renal fibrosis experimental model. Transforming growth factor-beta (TGF-β) isoforms are multifunctional cytokines that play a central role in driving fibrosis in most, if not all, forms of CKD (5). Big potassium (BK) channels (also called Big-K, Maxi-K or Slo1 channels) are K+ channels and may be one novel target that plays a major role in renal fibrosis. BK channels consist of the α-subunit (BKα), which functions as a channel independently, β-subunits (β1-4), and the γ-subunit (6; 7). A recent study reported that BK channel β1-subunit deficiency exacerbates vascular fibrosis and remodeling in high-fat fed obesity mice, suggesting that reduced BKα sensitivity and activity caused by β1 deficiency (8) leads to vascular fibrosis (9). We have compelling preliminary evidence that shows for the first time that BKα also plays a critical role in renal fibrosis. While BKα knockout (KO) mice were prone to developing more severe fibrosis after UUO (Figure 1), pre-treatment with the BK channel opener, BMS191011 (Sigma-Aldrich, SML0866), that can activate BK channels (10), protected mice from developing renal fibrosis in wild-type (WT) UUO mice (Figure 2) by suppressing TGF-β1 signaling pathway (Figures 3-4). These data suggest that the BK channel plays an important role in the development of renal fibrosis. Thus, elucidating the mechanisms underlying the role of BK channel in the pathogenesis of renal fibrosis is of utmost clinical importance. Our overall hypothesis is that BK channel deficiency is prone to developing renal fibrosis via activating the TGF-β signaling pathway in renal fibrotic mouse models. In this application we will propose three specific aims to test our overall hypothesis: Specific Aim 1: To validate the role of the BK channels in the development of renal fibrosis in different renal fibrosis mouse models. Specific Aim 2: To investigate the molecular mechanisms underlying the BK-mediated development of renal fibrosis. Specific Aim 3: To translate the experimental findings by examining whether BK expression levels are correlated with the severity of renal fibrosis in CKD patients. SA3.1. Determine whether BK expression levels are quantifiably correlated to the severity of renal fibrosis in kidney biopsy samples from CKD patients with diabetic nephropathy and focal segmental glomerulosclerosis (FSGS). Elucidation of the molecular mechanisms underlying the BK-mediated development of renal fibrosis will provide novel insights into whether BK channels can be utilized as a potential therapeutic target for treating CKD patients and preventing them from progressing to ESRD.