Luteolin Alleviates Acute Lung Injury In Mice By Upregulating Epithelial Sodium Channels

Objective:Acute lung injury(ALI)is a clinically common respiratory disease without effective treatment.One of the characteristics of ALI is severe pulmonary edema,which is closely related to alveolar fluid clearance.Enhance of alveolar fluid clearance contributes to the relief of pulmonary edema.The epithelial sodium channels(ENaC)located in the lung epithelial cells are responsible for the transmembrane transport of Na~+,which is particularly important for maintaining the water-salt transport balance of the lung.Increasing the expression of ENaC on the lung epithelial cell membrane can serve as a point for the treatment of ALI.Luteolin(Lut)is a flavonoid compound with various pharmacological activities and has the potential to treat respiratory diseases such as ALI.We speculate that Lut may alleviate ALI by up-regulating ENaC activity.This research aims to explore the effects of Lut on ENaC and the relative mechanisms.Methods:1.The effect of Lut on lung clearance in mice was investigated by using mouse lung wet-dry ratio experiment and mouse alveolar fluid clearance test.2.The effect of Lut on the morphology of lung tissue in ALI model mice was demonstrated by HE staining experiment.3.The techology of Western Blot,qRT-PCR and membrane protein extraction was used to detect the effects of Lut on mouse lung tissue and human lung epithelial cell line H441 ENaC total protein,mRNA,and membrane protein expression.4.The effect of Lut on the short-circuit current of H441 monolayer cells was analyzed by Ussing chamber technique.5.ELISA was used to study the effect of Lut on the expression of cGMP in serum and lung tissues of mice.6.cGMP and PI3K inhibitors was used to verify whether Lut affects the expression of ENaC membrane proteins in H441 cells through the cGMP/PI3K pathway.Results:1.Lut could reduce the lung wet-to-dry ratio of ALI model mice,improve lung pathological changes and increase the alveolar fluid clearance of mice.2.The decrease of amiloride-sensitive current in H441 monolayer cells induced by LPS could be reversed by Lut.3.Lut could increase mRNA,the total and membrane protein expression of ENaC of mouse lung tissue,increase the total and membrane protein expression of ENaC of H441 cell in ALI.4.cGMP expression was increased by Lut in serum and lung tissues of ALI model mice.5.After the addition of cGMP and PI3K inhibitors,the effect of Lut on upregulation of expression of ENaC membrane protein disappeared.Conclusions:Lut could alleviate ALI in mice by upregulation of ENaC through cGMP/PI3K pathway.