MicroRNA-29b as a Potentially Therapeutic Molecular Via Binding to SP-1 in Silica Induced EMT and Pulmonary Fibrosis

Abstract

Workers expose to crystalline silica dust could develop into silicotic fibrosis, which is characterized by diffused lung fibrosis and silicon nodules. Up to now, scholars have verified that epithelial-mesenchymal transition (EMT) is an important source of fibroblasts. During the process of EMT, epithelial and mesenchymal markers change significantly, in which transcription factors also play a vital role. Emerging evidence illustrates that microRNA-29b (miR-29b), which is one type of the non-coding small RNAs, mediates various pathogenic organ fibrotic processes by regulating the target gene transcriptionally. However, the function and mechanism of miR-29b that participates in silica-exposed pulmonary fibrosis remain unclear. In the present study, we found that silica induced EMT and pulmonary fibrosis, and the expression of miR-29b was downregulated significantly. This was performed not only in mice with silica induced EMT and MLE-12 cells treated with silica but also in the serum from workers, who had been diagnosed with the silicosis (phase I and II). In silica-induced EMT and lung fibrosis, the changes of epithelial markers (ZO-1, SP-C) and mesenchymal markers (a-SMA) were identified by RT-qPCR or Western blot, and the increasing expression of SP-1 and CTGF were also observed. Next, we fully illustrated that the down-regulation of miR-29b was associated with the up-regulation of SP-1 and CTGF by using luciferase assays. Further experiments verified that the overexpression of miR-29b inhibited silica-induced EMT in vitro. Moreover, the agomiR-29b blocked silica-induced EMT and regulated the levels of SP-1 and CTGF in mice. Our study elucidates that miR-29b have a therapeutic effect on silica induced EMT and lung fibrosis via mediation of SP-1. Funding Statement: This work was supported by grants from the National Natural Science Foundation of China (No. 81273047, 91643114, 81472958, 81703197 and 81602832) and Key Projects of Science and Technology Program by Beijing Municipal Education Commission (No. KZ201610025020). Declaration of Interests: The authors declare that there are no conflicts of interest. Ethics Approval Statement: The research program was approved by the Research Ethics Committee of Capital Medical University. All protocols were completed according to approved guidelines.