MicroRNA-485 Modulates the TGF-ß/ Smads Signaling Pathway in Chronic Asthmatic Mice by Targeting Smurf2.

BACKGROUND/AIMS: Chronic respiratory conditions continue to plague millions of people worldwide. We aimed to elucidate the detailed mechanisms of microRNA-485 (miR-485) in airway smooth muscle cell (ASMC) proliferation and apoptosis in chronic asthmatic mice. METHODS: A mouse model of chronic asthma was established. Ovalbumin was used to induce chronic asthma in the mice. The levels of transforming growth factor ß (TGF-ß), interleukin (IL)-4, IL-5, IL-13 and IL-17 in bronchoalveolar lavage fluid in mice were measured by enzyme-linked immunoassays (ELISAs). ASMCs were transfected with miR-485 mimic, miR-485 inhibitor and siRNA-Smurf2. The reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analyses were applied to detect the mRNA and protein levels of Smurf2, α-SMA, TGF-ß1 and decapentaplegic homolog (Smads). The MTT assay was utilized for cell proliferation, while flow cytometry was conducted to assess cell cycle distribution and apoptosis. RESULTS: Lower expression of miR-485 and higher expression levels of TGF-ß1, IL-4, IL-5, IL-13 and IL-17 were detected in mice with chronic asthma. Smurf2 was identified as the target gene of miR-485. Upregulation of miR-485 mimic and downregulation of Smurf2 decreased expression levels of Smurf2, α-SMA, TGF-ß1 and Smad3, inhibited cell proliferation and increased apoptosis, while contrary results were observed in ASMCs transfected with miR-485 inhibitor. CONCLUSION: Overexpressed miR-485 inhibits cell proliferation and promotes apoptosis of ASMCs through the Smurf2-mediated TGF-ß/Smads signaling pathway in mice with chronic asthma.

MicroRNA-142 Inhibits Proliferation and Promotes Apoptosis in Airway Smooth Muscle Cells During Airway Remodeling in Asthmatic Rats via the Inhibition of TGF-ß -Dependent EGFR Signaling Pathway.

BACKGROUND/AIMS: Asthma is a heterogeneous disease characterized by chronic airway inflammation resulting from airway hyper-responsiveness to diverse stimuli. In this study, we investigated whether microRNA-142 (miR-142) expression affects proliferation and apoptosis in airway smooth muscle cells (ASMCs) during airway remodeling in asthmatic rats. METHODS: Thirty six Wistar rats were randomly classified into a control group and an model group. miR-142 mimics and inhibitors were constructed, and ASMCs were transfected using liposomes according to the following groups: blank, negative control (NC), miR-142 mimics, miR-142 inhibitors, si-TGF-ß and miR-142 inhibitors + si-TGF-ß. We verified that miR-142 targets TGF-ß using a dual-luciferase reporter assay. The expression levels of miR-142, TGF-ß, EGFR and apoptosis signaling pathway-related genes were determined using RT-qPCR and western blotting. Changes in cell proliferation, cell cycle progression and apoptosis were analyzed using MTT assays and flow cytometry. RESULTS: Rats with asthma had higher expression levels of EGFR and Akt and lower miR-142 levels. miR-142 was negatively correlated with TGF-ß expression. In ASMCs, the expression of TGF-ß, EGFR, Akt, phosphorylated-Akt (p-Akt), Bcl-2 and Bcl-xl and the rate of early apoptosis were decreased while expression of Bax and p21 and the proliferation rate were elevated with the upregulation of miR-142. The opposite results were observed with the downregulation of miR-142. Finally, the proliferative rate was decreased while the apoptosis rate was increased and expression levels of EGFR, Akt, p-Akt, Bcl-2 and Bcl-xl were reduced while Bax and p21 were elevated in the ASMCs transfected with miR-142 inhibitors and si-TGF-ß. CONCLUSION: The results of our study suggest that miR-142 inhibits proliferation and promotes apoptosis in ASMCs during airway remodeling in asthmatic rats by inhibiting TGF-ß expression via a mechanism involving the EGFR signaling pathway.