LncRNA MEG3 Involved in NiO NPs-Induced Pulmonary Fibrosis via Regulating TGF-beta 1-Mediated PI3K/AKT Pathway

Long noncoding RNA maternally expressed gene 3 (MEG3) involves in fibrotic diseases, but its role in nickel oxide nanoparticles (NiO NPs)-induced pulmonary fibrosis remains unclear. The present study aimed to explore the relationships among MEG3, transforming growth factor-beta 1 (TGF-beta 1) and phosphoinositide 3-kinase (PI3K)/AKT pathway in NiO NPs-induced pulmonary fibrosis. Wistar rats were intratracheally instilled with NiO NPs twice a week for 9 weeks, and human lung adenocarcinoma epithelial cells (A549 cells) were exposed to NiO NPs for 24 h. The pathological alterations and increased hydroxyproline indicated that NiO NPs caused pulmonary fibrosis in rats. The up-regulated type I collagen (Col-I) suggested that NiO NPs-induced collagen deposition in A549 cells. Meanwhile, NiO NPs could significantly down-regulate MEG3, up-regulate TGF-beta 1 and activate PI3K/AKT signaling pathway both in vivo and in vitro. However, we found that the PI3K/AKT pathway activated by NiO NPs could be suppressed by 10 mu M TGF-beta 1 inhibitor (SB431542) in A549 cells. The protein markers (Col-I, Fibronectin, and alpha-smooth muscle actin) of collagen deposition up-regulated by NiO NPs were reduced by 10 mu M PI3K inhibitor (LY294002). Furthermore, we further found that overexpressed MEG3 inhibited the expression of TGF-beta 1, resulting in the inactivation of PI3K/AKT pathway and the reduction of collagen formation. In summary, our results validated that MEG3 could arrest NiO NPs-induced pulmonary fibrosis via inhibiting TGF-beta 1-mediated PI3K/AKT pathway.