Hagiwara Teruki, Yoshida Shigeru, Hidaka Yuji
a Department of Life Science, Faculty of Science and Engineering , Kindai University , Higashi-Osaka , Osaka , Japan.
Exp Lung Res. 2017 Apr;43(3):150-157. doi: 10.1080/01902148.2017.1321064. Epub 2017 May 30.
The concentration-sensitive sodium channel (Na) is expressed in alveolar type II epithelial cells and pulmonary microvascular endothelial cells in mouse lungs. We recently reported that Na contributes to amiloride-insensitive sodium transport in mouse lungs (Respiratory Physiology & Neurobiology, 2016). However, details regarding its physiological role in the lung remain unknown. To examine whether Na is involved in alveolar fluid clearance during an acute lung injury (ALI), we analyzed the relationship between Na gene expression in the lung and the development of pulmonary edema in lipopolysaccharide (LPS)-induced ALI mice.
LPS-induced ALI mice were prepared by the intratracheal administration of LPS. Bronchoalveolar lavage (BAL) neutrophils and lung water content (LWCs) were used as a marker of ALI and pulmonary edema, respectively. Na protein production in the lung was detected by immunoblotting and immunofluorescence. The gene expressions of Na and the epithelial sodium channel (ENaC) of LPS-induced ALI mice were examined by quantitative RT-PCR over a time course of 14 days.
The BAL neutrophil count increased until day 2 after LPS administration and had nearly recovered by day 6. LWCs in LPS-induced mice gradually increased until day 8 and had recovered by day 14. The expression of the Na protein in the lungs of LPS-induced mice dramatically decreased from day 2 to day 6, but recovered by day 8. The mRNA expression of Na decreased in the lung, as well as those for α-, β-, and γ-ENaC during ALI. Thus, Na expression is suppressed during the development stage of pulmonary edema and then recovers in the convalescent phase.
Our results suggest that suppression of the gene expression of Na is involved in the development of pulmonary edema in ALI.
浓度敏感钠通道（Na）在小鼠肺脏的Ⅱ型肺泡上皮细胞和肺微血管内皮细胞中表达。我们最近报道，Na参与小鼠肺脏中对阿米洛利不敏感的钠转运（《呼吸生理学与神经生物学》，2016年）。然而，其在肺脏中的生理作用细节仍不清楚。为了研究Na是否参与急性肺损伤（ALI）期间的肺泡液体清除，我们分析了肺中Na基因表达与脂多糖（LPS）诱导的ALI小鼠肺水肿发展之间的关系。
通过气管内给予LPS制备LPS诱导的ALI小鼠。支气管肺泡灌洗（BAL）中性粒细胞和肺含水量（LWC）分别用作ALI和肺水肿的标志物。通过免疫印迹和免疫荧光检测肺中Na蛋白的产生。通过定量RT-PCR在14天的时间过程中检测LPS诱导的ALI小鼠的Na和上皮钠通道（ENaC）的基因表达。
BAL中性粒细胞计数在LPS给药后第2天之前增加，并在第6天几乎恢复。LPS诱导的小鼠中的LWC在第8天之前逐渐增加，并在第14天恢复。LPS诱导的小鼠肺中Na蛋白的表达从第2天到第6天急剧下降，但在第8天恢复。在ALI期间，肺中Na的mRNA表达以及α-、β-和γ-ENaC的mRNA表达均下降。因此，Na表达在肺水肿的发展阶段受到抑制，然后在恢复期恢复。
我们的结果表明，Na基因表达的抑制参与了ALI中肺水肿的发展。
