Inhibition of miR-155-5p Exerts Anti-Fibrotic Effects in Silicotic Rats by Regulating Meprin α

Abstract

Silicosis is a fatal profession-related disease linked to long term inhalation of silica. The present study aimed to determine whether meprin α, a master regulator of anti-fibrotic peptide N-acetyl-serylaspartyl-lysyl-proline (Ac-SDKP), is diminished by miR-155-5p in silicosis and control lung macrophages and fibroblasts upon activation. RAW 264.7 macrophages, primary lung fibroblasts, and mouse embryonic fibroblasts were used to evaluate the expression and function of meprin α and miR-155-5p. In vitro meprin α manipulation was performed by recombinant mouse meprin α protein, actinonin (its inhibitor), and small interfering RNA knockdown. Macrophage and fibroblast activation was assessed by western blotting, real-time PCR, matrix deposition, immunohistochemistry, and immunofluorescence staining. The roles of meprin α and miR-155-5p were also investigated in mice exposed to silica. We found that the meprin α level was stably repressed in silicotic rats.In vitro, silica decreased meprin α, and exogenous meprin α reduced activation of macrophages and fibroblasts induced by profibrotic factors. MiR-155-5p negatively regulated Mep1a by binding to the 3′ untranslated region. Treatment with anti-miR-155-5p elevated meprin α, ameliorated macrophage and fibroblast activation, and attenuated lung fibrosis in mice induced by silica. The sustained repression of meprin α and beneficial effects of its rescue by inhibition of miR-155-5p during silicosis indicate that miR-155-5p/meprin α are major regulators of silicosis. Funding Statement: This work was supported by the National Natural Science Foundation of China (No. 81472953), the Natural Science Foundation of Hebei Province (No. H20162091705), Science and Technology Research Project of Hebei Province universities (No. ZD2019077), and the Preeminence Youth Foundation of North China University of Science and Technology (JP201513). Declaration of Interests: The authors declare they have no competing interests. Ethics Approval Statement: All experimental and surgical procedures were approved (2013-038 and 2017-025) by the Ethics Committee for Animal Experimentation of North China University of Science and Technology, which complies with the US National Institutes of Health Guide for the Care and Use of Laboratory Animals.