Department of Molecular Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.
Department of Molecular Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland; Centro di Estudios Cientificos CECs, Valdivia, Chile.
Steroids. 2019 Nov;151:108459. doi: 10.1016/j.steroids.2019.108459. Epub 2019 Jul 19.
Basolateral membrane K channels play a key role in basal and agonist stimulated Cl transport across airway epithelial cells by generating a favourable electrical driving force for Cl efflux. The K channel sub-types and molecular mechanisms of regulation by hormones and secretagoues are still poorly understood. Here we have identified the type of K channels involved in cAMP and Ca stimulated Cl secretion and uncovered a novel anti-secretory effect of dexamethasone mediated by inhibition of basolateral membrane K channels in a human airway cell model of 16HBE14o cells commonly used for ion transport studies. Dexamethasone produced a rapid inhibition of transepithelial chloride ion secretion under steady state conditions and after stimulation with cAMP agonist (forskolin) or a Ca mobilizing agonist (ATP). Our results show three different types of K channels are targeted by dexamethasone to reduce airway secretion, namely Ca-activated secretion via KCNN4 (KCa3.1) channels and cAMP-activated secretion via KCNQ1 (Kv7.1) and KATP (Kir6.1,6.2) channels. The down-regulation of KCNN4 and KCNQ1 channel activities by dexamethasone involves rapid non-genomic activation of PKCα and PKA signalling pathways, respectively. Dexamethasone signal transduction for PKC and PKA activation was demonstrated to occur through a rapid non-genomic pathway that did not implicate the classical nuclear receptors for glucocorticoids or mineralocorticoids but occurred via a novel signalling cascade involving sequentially a G-protein coupled receptor, PKC, adenylyl cyclase Type IV, cAMP, PKA and ERK1/2 activation. The rapid, non-genomic, effects of dexamethasone on airway epithelial ion transport and cell signalling introduces a new paradigm for glucocorticoid actions in lung epithelia which may serve to augment the anti-inflammatory activity of the steroid and enhance its therapeutic potential in treating airway hypersecretion in asthma and COPD.
基底外侧膜 K 通道在气道上皮细胞的基础和激动剂刺激的 Cl 转运中发挥关键作用，通过产生有利于 Cl 外流的有利电驱动力。激素和 secretagoues 调节的 K 通道亚型和分子机制仍知之甚少。在这里，我们已经确定了参与 cAMP 和 Ca 刺激 Cl 分泌的 K 通道类型，并在常用于离子转运研究的人气道细胞模型 16HBE14o 细胞中发现了地塞米松通过抑制基底外侧膜 K 通道介导的新型抗分泌作用。地塞米松在稳态条件下和用 cAMP 激动剂（forskolin）或 Ca 动员激动剂（ATP）刺激后，迅速抑制跨上皮氯离子分泌。我们的结果表明，地塞米松靶向三种不同类型的 K 通道以减少气道分泌，即通过 KCNN4（KCa3.1）通道的 Ca 激活分泌和通过 KCNQ1（Kv7.1）和 KATP（Kir6.1,6.2）通道的 cAMP 激活分泌。地塞米松下调 KCNN4 和 KCNQ1 通道活性涉及 PKCα 和 PKA 信号通路的快速非基因组激活。地塞米松对 PKC 和 PKA 激活的信号转导被证明是通过快速的非基因组途径发生的，该途径不涉及糖皮质激素或盐皮质激素的经典核受体，而是通过涉及依次 G 蛋白偶联受体、PKC、IV 型腺苷酸环化酶、cAMP、PKA 和 ERK1/2 激活的新型信号级联发生的。地塞米松对气道上皮细胞离子转运和细胞信号的快速、非基因组作用为糖皮质激素在肺上皮细胞中的作用引入了一个新的范例，这可能有助于增强类固醇的抗炎活性并增强其在治疗哮喘和 COPD 中气道高分泌的治疗潜力。
