Roles of CFTR chloride channel in the pathogenesis of chronic pancreatitis

1. 我们研究了CFTR（囊性纤维化跨膜传导调节基因）突变是否与日本慢性胰腺炎有关。为了评估CFTR的功能，我们建立了一种简单且无创的方法来测量汗液中的Cl^-浓度。在25例慢性胰腺炎患者中，56%的汗液Cl^-水平超过60 mmol/L，这一水平与囊性纤维化的诊断一致。这表明，CFTR功能受损是日本约一半慢性胰腺炎的基础。在健康受试者和慢性胰腺炎患者中未发现白种人的20种主要突变。内含子8和外显子9 （TG）重复序列交界处的多态性是日本人特有的，这可能解释了慢性胰腺炎患者CFTR功能障碍的原因。为了研究HCO_3^-从胰管细胞分泌的机制，我们测量了从豚鼠胰腺分离的小叶间管细胞内HCO_3^-和Cl^-的浓度和膜电位。我们提出了一个新的模型；(a)当腔内HCO_3^-浓度低于-70 mM时，HCO_3^-的分泌由Cl^—HCO_3^-交换支持；(b)当腔内HCO_3^-浓度高于70 mM时，HCO_3^-的分泌由HCO_3^-电导介导，最有可能是cftr。CFTR和SLC26转运蛋白家族在爪蟾卵母细胞和人胚胎肾293细胞中共表达。我们发现SLC26转运体作为电致Cl^- hco_3 ^-交换体，受cftr调控。对大鼠胰腺离体胰管进行RT-PCR分析，发现AQP1在胰管细胞中表达。导管上皮的渗透性随基底外侧或管腔的改变而降低。HgCl_2的应用已知水通道中的AQP1似乎是胰腺导管上皮的主要水通道。免疫组织化学显示AQP1在大鼠导管细胞中异质表达。

1. We have investigated whether mutations of the CFTR (cystic fibrosis transmembrane conductance regulator) gene are related to chronic pancreatitis in Japanese.2. To estimate the function of CFTR, we established a simple and non-invasive method to measure Cl^- concentrations in the sweat. Of 25 patients with chronic pancreatitis, 56% had sweat Cl^- levels over 60 mmol/L, a level consistent with the diagnosis of cystic fibrosis. This suggests that the impaired CFTR function underlies about a half of chronic pancreatitis in Japanese.3. None of 20 major mutations in Caucasians were found in healthy subjects and patients with chronic pancreatitis. Polymorphisms at the junction of intron8 and exon9 (TG) repeats were unique to Japanese, which may explain CFTR dysfunction in patients with chronic pancreatitis.4. To investigate the secretory mechanism of HCO_3^- from pancreatic duct cells, we have measured intracellular concentrations of HCO_3^- and Cl^- and membrane potential in interlobular ducts isolated from guinea-pig pancreas. We proposed a new model ; (a) when the luminal HCO_3^- concentration is below-70 mM, HCO_3^- secretion is supported by Cl^--HCO_3^- exchange and (b) when the luminal HCO_3^- concentration is higher than 70 mM, it is mediated by a HCO_3^- conductance, most likely CFTR.5. CFTR and SLC26 family of transporters were co-expressed in Xenopus oocytes or HEK (Human Embryonic Kidney) 293 cells. We found that the SLC26 transporters work as electrogenic Cl^-HCO_3^- exchangers and are regulated by CFTR.6. RT-PCR analysis of isolated ducts from rat pancreas revealed the expression of AQP1 in pancreatic duct cells. The osmotic water permeability of the ductal epithelium was reduced by either basolateral or luminal. application of HgCl_2. AQP1 of the known water channels appears to be the main water pathway in pancreatic ductal epithelium. Immunohistochemistry revealed heterogeneous expression of AQP1 in rat duct cells.