MicroRNA-485 Modulates the TGF-/ 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 (TGF-), 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, -SMA, TGF-1 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-1, 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, -SMA, TGF-1 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-/Smads signaling pathway in mice with chronic asthma.