Shen B Q, Widdicomb J H, Mrsny R J
Children's Hospital of Oakland Research Institute, Oakland, California 94609, USA.
Pulm Pharmacol Ther. 1999;12(3):157-64. doi: 10.1006/pupt.1999.9999.
Cystic fibrosis (CF) airway epithelial cells have a reduced cAMP-dependent Cl(-)conductance channel (CFTR) function but an increased level of amiloride-sensitive Na(+)channel (ENaC) activity. Recently, expression of the alpha -subunit of the ENaC protein complex was shown to be down-regulated by activation of the extracellular signal-regulated protein kinase (ERK) pathway. In the present study we have examined the actions of a potent regulator of the ERK pathway, recombinant human hepatocyte growth factor (rhHGF), on the function of ENaC in confluent, polarized monolayers of both primary cultures of CF airway cells and an SV40-transformed CF nasal epithelial cell line (JME CF/15). Treatment of JME/CF 15 cells with rhHGF at concentrations of 100 ng/ml and above was found to dramatically decrease the activity of amiloride-sensitive Na(+)transport. This effect required basolateral exposure of the cytokine. Addition of 100 ng/ml rhHGF to JME/CF 15 cells decreased I(eq)with a t(1/2)of;18 h, with a maximal inhibition of;90% by 36 h. By 48 h, stimulation with rhHGF induced a down-regulation of its receptor, c-met, expressed in these cells. The decrease in I(eq)of JME/CF 15 monolayers was not immediately reversed upon removal of rhHGF. Treatment with rhHGF did not appear to affect monolayer resistances nor Cl(-)currents induced by mediators such as isoproterenol, histamine or bradykinin. Studies with primary cultures of CF airway cell sheets demonstrated comparable sensitivity and time-course properties for the inhibition of amiloride-sensitive currents following rhHGF addition. These observations are consistent with the possible application of an extracellular signalling molecule, such as the cytokine HGF, to reduce the abnormally high activity of amiloride-sensitive Na(+)ion channels observed in CF airway cells.
囊性纤维化（CF）气道上皮细胞的环磷酸腺苷（cAMP）依赖性氯离子（Cl⁻）传导通道（CFTR）功能降低，但氨氯地平敏感的钠离子（Na⁺）通道（ENaC）活性水平升高。最近研究表明，细胞外信号调节蛋白激酶（ERK）途径激活可下调ENaC蛋白复合物α亚基的表达。在本研究中，我们检测了ERK途径的强效调节剂重组人肝细胞生长因子（rhHGF）对CF气道细胞原代培养物和SV40转化的CF鼻上皮细胞系（JME CF/15）汇合、极化单层中ENaC功能的作用。发现用浓度为100 ng/ml及以上的rhHGF处理JME/CF 15细胞可显著降低氨氯地平敏感的Na⁺转运活性。这种效应需要细胞因子从基底外侧暴露。向JME/CF 15细胞中添加100 ng/ml rhHGF可使I(eq)降低，t(1/2)为18小时，36小时时最大抑制率为90%。到48小时时，用rhHGF刺激可诱导这些细胞中其受体c-met的下调。去除rhHGF后，JME/CF 15单层的I(eq)降低并未立即逆转。用rhHGF处理似乎不影响单层电阻，也不影响由异丙肾上腺素、组胺或缓激肽等介质诱导的Cl⁻电流。对CF气道细胞片原代培养物的研究表明，添加rhHGF后对氨氯地平敏感电流的抑制具有相当的敏感性和时间进程特性。这些观察结果与可能应用细胞外信号分子（如细胞因子HGF）来降低CF气道细胞中观察到的氨氯地平敏感Na⁺离子通道异常高活性是一致的。
