Molecular Pathogenesis of Cystic Fibrosis Liver Disease

描述(由申请人提供)：囊性纤维化(CF)(局灶性胆道纤维化导致多小叶性肝硬变)患者的肝病发生率高达43%，患病率随着年龄的增长而增加。临床表现为门静脉高压症的多小叶性肝硬变已成为CF发病和过早死亡的第三大原因，在肺部疾病得到控制的情况下，无论是否进行肺移植，肝病是最主要的死亡原因。慢性肝病的病因、机制和发病机制尚不清楚，目前熊去氧胆酸的处方没有令人信服的证据表明其疗效。在本实验室前期研究的基础上，F508和G551D小鼠模型和野生型(WT)小鼠将进行以下研究：1)利用生物物理、病理生理和物理化学方法，探讨肝胆pH、胆红素、电解质和胆脂的分泌异常；2)确定肠源性高胆红素血症的发病机制，并将其与回肠pH异常、胆盐吸收不良、肝脏胆汁pH和肝脏疾病相关联；3)阐明胆盐吸收不良是导致未结合胆红素转运体(UCB)肠肝循环的原因，重点是回肠胆盐转运体及其对低碱性pH的反应；此外，研究肠道hCFTR拯救的CF小鼠，以验证肠道缺陷的分子性质；4)成像和量化与年龄和性别相关的肝脏组织学和超微结构研究，利用透射和扫描电子显微镜结合原子发射光谱检测胆管内和胆管上皮细胞中金属胆红素的沉积，并量化UCB诱导的导管周围炎症、纤维化和闭塞性胆管炎的病理生物学；5)通过a)靶向含有去甲叉二氢叶酸的胆树以提高肝脏胆汁的pH值，b)靶向未被共价连接的D-葡萄糖基-1，4-内酯或胆酸的聚合物在远端肠道形成和吸收脐带CB，以及c)靶向使用Colesvelam盐酸盐吸收不良来防止UCB的溶解，或通过碳酸酐酶激动剂阿米洛利使管腔pH正常化，或通过用布地奈德上调ASBT活性来防治CF小鼠的慢性肝病。这些假设驱动的特定目标的分子洞察力应该提供数据、分子理解和可翻译给患有CF的人类的药物，并导致预防和治疗CF肝病的新方法。

DESCRIPTION (provided by applicant): The frequency of liver disease in humans with cystic fibrosis (CF) (focal biliary fibrosis leading to multilobular cirrhosis) ranges up to 43%, with prevalence increasing with age. Multilobular cirrhosis manifesting clinically with portal hypertension has become the third leading cause of morbidity and premature death in CF, and when pulmonary disease is controlled with or without lung transplantation, liver disease is the leading cause of death. The etiology, mechanisms and pathogenesis of CF liver disease are unknown, and currently ursodeoxycholic acid is prescribed without compelling evidence of its efficacy. Extending preliminary studies from this laboratory, the ?F508 and G551D murine models of CF and wild-type (WT) mice will be studied: 1) to explore the hepatobiliary secretory abnormalities of pH, bilirubins, electrolytes and biliary lipids utilizing biophysical, pathophysiological and physical-chemical approaches; 2) to determine the pathogenesis of enteric hyperbilirubinbilia and to correlate this with ileal pH abnormalities, bile salt malabsorption, hepatic bile pH and liver disease; 3) to elucidate the pathophysiology of bile salt malabsorption as a cause of induced enterohepatic cycling of unconjugated bilirubin (UCB), focusing on the ileal bile salt transporter and its response to less alkaline lumenal pH; in addition, to study intestinally hCFTR-rescued CF mice to verify the molecular nature of the intestinal defect; 4) to image and quantify age and gender-related liver histology and ultrastructural studies to detect deposits of metal bilirubinates intraductally and in biliary epithelial cells using transmission and scanning electron microscopy coupled with atomic emission spectroscopy, and to quantify the pathobiology of UCB-induced periductal inflammation, fibrogenesis and obliterative cholangitis; 5) to prevent and treat chronic liver disease of CF mice by a) targeting the biliary tree with norUDCA to increase pH of hepatic bile, b) targeting UCB formation and absorption in the distal gut by non-absorbed polymers with covalently linked D-glucaro-1,4-lactone or cholic acid, and c) targeting bile salt malabsorption using colesevelam HCI to prevent solubility of UCB or by normalizing the lumenal pH using amiloride, a carbonic anhydrase agonist, or by upregulating ASBT activity with budesonide. The molecular insights from these hypothesis-driven specific aims should provide data, molecular understanding and agents that are translatable to humans with CF and lead to new modalities for prevention and treatment of CF liver disease.