Laube Mandy, Bossmann Miriam, Thome Ulrich H
Center for Pediatric Research Leipzig, Hospital for Children & Adolescents, Division of Neonatology, University of Leipzig, Leipzig, Germany.
PLoS One. 2015 Apr 24;10(4):e0124833. doi: 10.1371/journal.pone.0124833. eCollection 2015.
During fetal development, the lung is filled with fluid that is secreted by an active Cl- transport promoting lung growth. The basolateral Na+,K+,2Cl- cotransporter (NKCC1) participates in Cl- secretion. The apical Cl- channels responsible for secretion are unknown but studies suggest an involvement of the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is developmentally regulated with a high expression in early fetal development and a decline in late gestation. Perinatal lung transition is triggered by hormones that stimulate alveolar Na+ channels resulting in fluid absorption. Little is known on how hormones affect pulmonary Cl- channels. Since the rise of fetal cortisol levels correlates with the decrease in fetal CFTR expression, a causal relation may be assumed. The aim of this study was to analyze the influence of glucocorticoids on pulmonary Cl- channels. Alveolar cells from fetal and adult rats, A549 cells, bronchial Calu-3 and 16HBE14o- cells, and primary rat airway cells were studied with real-time quantitative PCR and Ussing chambers. In fetal and adult alveolar cells, glucocorticoids strongly reduced Cftr expression and channel activity, which was prevented by mifepristone. In bronchial and primary airway cells CFTR mRNA expression was also reduced, whereas channel activity was increased which was prevented by LY-294002 in Calu-3 cells. Therefore, glucocorticoids strongly reduce CFTR expression while their effect on CFTR activity depends on the physiological function of the cells. Another apical Cl- channel, anoctamin 1 showed a glucocorticoid-induced reduction of mRNA expression in alveolar cells and an increase in bronchial cells. Furthermore, voltage-gated chloride channel 5 and anoctamine 6 mRNA expression were increased in alveolar cells. NKCC1 expression was reduced by glucocorticoids in alveolar and bronchial cells alike. The results demonstrate that glucocorticoids differentially modulate pulmonary Cl- channels and are likely causing the decline of CFTR during late gestation in preparation for perinatal lung transition.
在胎儿发育过程中，肺充满了由促进肺生长的活性氯离子转运所分泌的液体。基底外侧钠钾氯共转运体（NKCC1）参与氯离子分泌。负责分泌的顶端氯离子通道尚不清楚，但研究表明囊性纤维化跨膜传导调节因子（CFTR）与之有关。CFTR在胎儿发育早期表达较高，而在妊娠后期下降，呈现发育调控。围产期肺转变由刺激肺泡钠通道导致液体吸收的激素触发。关于激素如何影响肺氯离子通道知之甚少。由于胎儿皮质醇水平的升高与胎儿CFTR表达的降低相关，因此可以假定存在因果关系。本研究的目的是分析糖皮质激素对肺氯离子通道的影响。使用实时定量PCR和尤斯灌流小室对来自胎儿和成年大鼠的肺泡细胞、A549细胞、支气管Calu-3和16HBE14o-细胞以及原代大鼠气道细胞进行了研究。在胎儿和成年肺泡细胞中，糖皮质激素强烈降低Cftr表达和通道活性，米非司酮可阻止这种作用。在支气管和原代气道细胞中，CFTR mRNA表达也降低，而通道活性增加，在Calu-3细胞中LY-294002可阻止这种增加。因此，糖皮质激素强烈降低CFTR表达，而它们对CFTR活性的影响取决于细胞的生理功能。另一种顶端氯离子通道，anoctamin 1在肺泡细胞中显示出糖皮质激素诱导的mRNA表达降低，而在支气管细胞中增加。此外，电压门控氯离子通道5和anoctamine 6的mRNA表达在肺泡细胞中增加。糖皮质激素在肺泡和支气管细胞中均降低NKCC1表达。结果表明，糖皮质激素对肺氯离子通道有不同的调节作用，可能导致妊娠后期CFTR下降，为围产期肺转变做准备。
