The emerging roles of a novel CCCH-type zinc finger protein, ZC3H4, in silica-induced epithelial to mesenchymal transition

Background: The epithelial to mesenchymal transition (EMT) contributes to fibrosis during silicosis. Zinc finger CCCH-type containing 4 protein (ZC3H4) is a novel CCCH-type zinc finger protein that activates inflammation in pulmonary macrophages during silicosis. However, whether ZC3H4 is involved in EMT during silicosis remains unclear. In this study, we investigated the circular ZC3H4 (circZC3H4) RNA/microRNA-212 (miR-212) axis as the upstream molecular mechanism regulating ZC3H4 expression and the downstream mechanism by which ZC3H4 regulates EMT as well as its accompanying migratory characteristics. Methods: The protein levels were assessed via Western blotting and immunofluorescence staining. Scratch assays were used to analyze the increased mobility induced by silica. The CRISPR/Cas9 system and small interfering RNAs (siRNAs) were employed to analyze the regulatory mechanisms of ZC3H4 in EMT and migration changes. Results: Specific knockdown of ZC3H4 blocked EMT and migration induced by silicon dioxide (SiO2). Endoplasmic reticulum (ER) stress mediated the effects of ZC3H4 on EMT. circZC3H4 RNA served as an miR-212 sponge to regulate ZC3H4 expression, which played a pivotal role in EMT. Tissue samples from mice and patients confirmed the upregulation of ZC3H4 in alveolar epithelial cells. Conclusions: ZC3H4 may act as a novel regulator in the progression of SiO2-induced EMT, which provides a reference for further pulmonary fibrosis research.