Mesenchymal stem cells (MSCs) have been a potential strategy in the pretreatment of pulmonary diseases, while the mechanisms of MSCs-conditioned medium (MSCs-CM) involved with microRNAs on the regulation of lung ion transport are seldom reported. We investigated the role of miR-124-5p in lipopolysaccharide-involved epithelial sodium channel (ENaC) dysfunction and explored the potential target of miR-124-5p. We observed the lower expression of miR-124-5p after the administration of MSCs-CM, and the overexpression or inhibition of miR-124-5p regulated epithelial sodium channel α-subunit (α-ENaC) expression at protein levels in mouse alveolar type 2 epithelial (AT2) cells. We confirmed that α-ENaC is one of the target genes of miR-124-5p through dual luciferase assay and Ussing chamber assay revealed that miR-124-5p inhibited amiloride-sensitive currents associated with ENaC activity in intact H441 monolayers. Our results demonstrate that miR-124-5p can decrease the expression and function of α-ENaC in alveolar epithelial cells by targeting the 3′-UTR. The involvement of MSCs-CM in lipopolysaccharide-induced acute lung injury cell model could be related to the downregulation of miR-124-5p on α-ENaC, which may provide a new target for the treatment of acute lung injury.
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Pulmonary fibrosis (PF) is the most common chronic, progressive interstitial lung disease, mainly occurring in
the elderly, with a median survival of 2-4 years after diagnosis. Its high mortality rate attributes to the delay in diagnosis
due to its generic symptoms, and more importantly, to the lack of effective treatments. MicroRNAs (miRNAs) are a class
of small non-coding RNAs that involve in many essential cellular processes, including extracellular matrix remodeling,
alveolar epithelial cell apoptosis, epithelial-mesenchymal transition, etc. We summarized the dysregulated miRNAs in
TGF-β signaling pathway-mediated PF in recent years with dual effects, such as anti-fibrotic let-7 family and pro-fibrotic
miR-21 members. Therefore, this review will set out the latest application of miRNAs to provide a new direction for PF
treatment.
BackgroundCrotonaldehyde is a highly noxious α,β-unsaturated aldehyde in cigarette smoke that causes edematous acute lung injury.ObjectiveTo understand how crotonaldehyde impairs lung function, we examined its effects on human epithelial sodium channels (ENaC), which are major contributors to alveolar fluid clearance.MethodsWe studied alveolar fluid clearance in C57 mice and ENaC activity was examined in H441 cells. Expression of α- and γ-ENaC was measured at protein and mRNA levels by western blot and real-time PCR, respectively. Intracellular ROS levels were detected by the dichlorofluorescein assay. Heterologous αβγ-ENaC activity was observed in an oocyte model.ResultsOur results showed that crotonaldehyde reduced transalveolar fluid clearance in mice. Furthermore, ENaC activity in H441 cells was inhibited by crotonaldehyde dose-dependently. Expression of α- and γ-subunits of ENaC was decreased at the protein and mRNA level in H441 cells exposed to crotonaldehyde, which was probably mediated by the increase in phosphorylated extracellular signal-regulated protein kinases 1 and 2. ROS levels increased time-dependently in cells exposed to crotonaldehyde. Heterologous αβγ-ENaC activity was rapidly eliminated by crotonaldehyde.ConclusionOur findings suggest that crotonaldehyde causes edematous acute lung injury by eliminating ENaC activity at least partly via facilitating the phosphorylation of extracellular signal-regulated protein kinases 1 and 2 signal molecules. Long-term exposure may decrease the expression of ENaC subunits and damage the cell membrane integrity, as well as increase the levels of cellular ROS products.
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