Bossmann Miriam, Ackermann Benjamin W, Thome Ulrich H, Laube Mandy
Center for Pediatric Research Leipzig, Division of Neonatology, University of Leipzig, 04103 Leipzig, Germany.
Int J Mol Sci. 2017 Aug 19;18(8):1807. doi: 10.3390/ijms18081807.
Impairment of mucociliary clearance with reduced airway fluid secretion leads to chronically inflamed airways. Cystic fibrosis transmembrane conductance regulator (CFTR) is crucially involved in airway fluid secretion and dexamethasone (dexa) has previously been shown to elevate CFTR activity in airway epithelial cells. However, the pathway by which dexa increases CFTR activity is largely unknown. We aimed to determine whether the increase of CFTR activity by dexa is achieved by non-genomic signaling and hypothesized that the phosphoinositide 3-kinase (PI3K) pathway is involved in CFTR stimulation. Primary rat airway epithelial cells and human bronchial submucosal gland-derived Calu-3 cells were analyzed in Ussing chambers and kinase activation was determined by Western blots. Results demonstrated a critical involvement of PI3K and protein kinase B (AKT) signaling in the dexa-induced increase of CFTR activity, while serum and glucocorticoid dependent kinase 1 (SGK1) activity was not essential. We further demonstrated a reduced neural precursor cell expressed, developmentally downregulated 4-like (NEDD4L) ubiquitin E3 ligase activity induced by dexa, possibly responsible for the elevated CFTR activity. Finally, increases of CFTR activity by dexa were demonstrated within 30 min accompanied by rapid activation of AKT. In conclusion, dexa induces a rapid stimulation of CFTR activity which depends on PI3K/AKT signaling in airway epithelial cells. Glucocorticoids might thus represent, in addition to their immunomodulatory actions, a therapeutic strategy to rapidly increase airway fluid secretion.
气道液体分泌减少导致的黏液纤毛清除功能受损会引发气道慢性炎症。囊性纤维化跨膜传导调节因子（CFTR）在气道液体分泌中起关键作用，先前已证明地塞米松（dexa）可提高气道上皮细胞中的CFTR活性。然而，dexa增加CFTR活性的途径在很大程度上尚不清楚。我们旨在确定dexa对CFTR活性的增加是否通过非基因组信号传导实现，并假设磷酸肌醇3激酶（PI3K）途径参与CFTR的刺激。在尤斯灌流小室中分析原代大鼠气道上皮细胞和人支气管黏膜下腺来源的Calu-3细胞，并通过蛋白质印迹法测定激酶激活情况。结果表明PI3K和蛋白激酶B（AKT）信号传导在dexa诱导的CFTR活性增加中起关键作用，而血清和糖皮质激素依赖性激酶1（SGK1）活性并非必需。我们进一步证明dexa诱导神经前体细胞表达、发育下调4样（NEDD4L）泛素E3连接酶活性降低，这可能是CFTR活性升高的原因。最后，dexa在30分钟内即可增加CFTR活性，并伴有AKT的快速激活。总之，dexa可快速刺激CFTR活性，这依赖于气道上皮细胞中的PI3K/AKT信号传导。因此，糖皮质激素除了具有免疫调节作用外，可能还代表一种快速增加气道液体分泌的治疗策略。
