Intracellular calcium in the treatment of polycystic kidney and liver diseases

描述(申请人提供)：常染色体隐性遗传性多囊肾病(ARPKD)是儿科实践中一种重要的遗传性疾病。ARPKD是一种新生儿和婴儿的肾脏和肝脏疾病，30%的受影响新生儿因在宫内或围产期发现肾脏过大而死亡。在存活的ARPKD患者中，随着年龄的增长，肝脏损害变得越来越严重，肝脏疾病是发病率和死亡率的主要原因。在ARPKD以及所有的多囊肝疾病中，众所周知的遗传缺陷会导致肝囊肿的形成，这些囊肿起源于胆管细胞，即排列在胆道树上的上皮细胞。由于细胞增殖、细胞-基质相互作用和液体分泌等至少三个过程的干扰，包囊进一步扩大。不同因素单独或联合作用，可影响胆管细胞增殖，促进囊壁生长。这些潜在的因素之一是细胞内钙，已知在囊肿性肾上皮细胞中细胞内钙水平降低，导致细胞去分化和过度增殖。 这项应用的总体目标是验证一种假设，即肝囊肿内的胆管细胞具有功能失调的睫状神经感觉机制，导致细胞内钙水平下降，导致cAMP介导的过度增殖表型；药物恢复正常的细胞内钙水平可以逆转过度增殖表型。为了验证这一假说，具体目标1是利用ARPKD的动物模型PCK大鼠来表征细胞内钙的失调及其对肝脏囊变的下游影响。具体目的2是评估钙离子进入通道TRPV4作为治疗靶点的潜在作用。 本应用的实验结果将为控制囊性胆管细胞增殖的机制提供新的信息，并将为多囊肝病的替代或补充治疗奠定基础。 项目简介：这项应用既将研究在肝脏中形成包囊的细胞机制，也将在ARPKD和ADPKD这两种最重要的、不可治愈的遗传性肝病的啮齿动物模型中测试抑制胆管细胞过度增殖和包囊生长的新的药理学方法。这些疾病与已知基因的突变有关，这些基因的蛋白产物在纤毛中表达，纤毛是从顶膜延伸到导管管腔的天线状细胞器。据推测，胆管细胞纤毛感觉机制的异常是肝囊肿形成的中心。

DESCRIPTION (Provided by Applicant): Autosomal recessive polycystic kidney disease (ARPKD) is an important genetic disorder in pediatric practice. ARPKD is a renal and hepatic disease in neonates and infants, and <30% of affected neonates die because of greatly enlarged kidneys detected in utero or in the perinatal period. In surviving ARPKD patients, hepatic lesions become progressively more severe with age, and liver disease is a major cause of morbidity and mortality. In ARPKD, as well as in all the polycystic liver diseases, well described genetic defects initiate formation of hepatic cysts, which arise from cholangiocytes, the epithelial cells lining the biliary tree. Cysts further expand due to disturbances in at least three processes: cell proliferation, cell-matrix interaction, and fluid secretion. Different factors, individually or in combination, could impact cholangiocyte proliferation and promote cyst growth. One of these potential factors is intracellular calcium, level of which is known to be decreased in cyst-derived kidney epithelial cells, leading to cellular dedifferentiation and hyperproliferation. The overall goal of this application is to test the hypothesis that cholangiocytes lining liver cysts have dysfunctional ciliary sensory machinery, which results in decreased levels of intracellular calcium, leading to a cAMP-mediated hyperproliferative phenotype; and that pharmacological restoration of normal intracellular calcium levels could reverse the hyperproliferative phenotype. To test this hypothesis, Specific Aim 1 is to characterize the dysregulation of intracellular calcium and its downstream effects on liver cystogenesis, using an animal model of ARPKD, the PCK rat. Specific Aim 2 is to evaluate the potential role of TRPV4, a calcium entry channel, as therapeutic target. The experimental results from the present application will provide novel information regarding the mechanisms controlling the proliferation of cyst cholangiocytes, and will produce the foundation for a plausible alternative or complementary therapeutic treatment of polycystic liver diseases. PROJECT NARRATIVE: This application will both examine the cellular mechanisms by which cysts form in the liver as well as test a new pharmacological approach to inhibit cholangiocyte hyperproliferation and cyst growth in rodent models of ARPKD and ADPKD, the two most important, incurable, genetic liver diseases. These diseases are associated with mutations in known genes, which protein products are expressed in cilia, antenna-like organelles that extend from the apical membrane into the ductal lumen. It is hypothesized that abnormalities in the sensory machinery of cholangiocyte cilia are central to hepatic cyst formation.