Follistatin-Like 1 Promotes Bleomycin-Induced Pulmonary Fibrosis through the Transforming Growth Factor Beta 1/Mitogen-Activated Protein Kinase Signaling Pathway

• Published in: Chinese medical journal 2018-08, Vol.131 (16), p.1917-1925
• Main Authors: Jin, Yan-Kun, Li, Xiao-He, Wang, Wang, Liu, Jie, Zhang, Wei, Fang, Yin-Shan, Zhang, Zhi-Fei, Dai, Hua-Ping, Ning, Wen, Wang, Chen
• Format: Article
• Language: English
• Subjects: Animals; Antibiotics, Antineoplastic - adverse effects; Binding proteins; Bleomycin; Bleomycin - adverse effects; Cancer; Cell cycle; Cells, Cultured; Cellular signal transduction; Complications and side effects; Disease; Dosage and administration; Fibroblasts; Follistatin; Follistatin-Like 1; Mitogen-Activated Protein Kinase; Pulmonary Fibrosis; Transforming Growth Factor Beta 1; Follistatin-Related Proteins - physiology; Growth factors; Humans; Kinases; Laboratory animals; Lungs; Mice; Mice, Inbred C57BL; Mitogen-activated protein kinases; Original; p38 Mitogen-Activated Protein Kinases - drug effects; Phosphorylation; Proteins; Pulmonary fibrosis; Pulmonary Fibrosis - chemically induced; Risk factors; Rodents; Smooth muscle; Studies; Transcription factors; Transforming Growth Factor beta; Transforming Growth Factor beta1 - drug effects; Transforming Growth Factor beta1 - physiology; Transforming growth factors
• ISSN: 0366-6999; 2542-5641
• DOI: 10.4103/0366-6999.238151

Background: Follistatin-like 1 (FSTL1) is a novel profibrogenic factor that induces pulmonary fibrosis (PF) through the transforming growth factor-beta 1 (TGF-β1)/Smad signaling. Little is known about its effects on PF through the non-Smad signaling, like the mitogen-activated protein kinase (MAPK) pathway. Therefore, this study aimed to investigate the role of FSTL1 in PF through the MAPK signaling pathway and its mechanisms in lung fibrogenesis. Methods: PF was induced in Fstl1+/−and wild-type (WT) C57BL/6 mice with bleomycin. After 14 days, the mice were sacrificed, and lung tissues were stained with hematoxylin and eosin; the hydroxyproline content was measured to confirm PF. The mRNA and protein level of FSTL1 and the change of MAPK phosphorylation were measured by quantitative polymerase chain reaction and Western blotting. The effect of Fstl1 deficiency on fibroblasts differentiation was measured by Western blotting and cell immunofluorescence. MAPK signaling activation was measured by Western blotting in Fstl1+/− and WT fibroblasts treated with recombinant human FSTL1 protein. We pretreated mouse lung fibroblast cells with inhibitors of the extracellular signal-regulated kinase (ERK), p38, and Jun N-terminal kinase (JNK) signaling and analyzed their differentiation, proliferation, migration, and invasion by Western blotting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis, and transwell assays. The Student's t-test was used to compare the differences between two groups. Results: Fstl1 deficiency attenuated phosphorylation of the ERK, p38, and JNK signaling in bleomycin-induced fibrotic lung tissue 14 days after injury (0.67 ± 0.05 vs. 1.22 ± 0.03, t = 14.92, P = 0.0001; 0.41 ± 0.01 vs. 1.15 ± 0.07; t = 11.19; P = 0.0004; and 0.41 ± 0.01 vs. 1.07 ± 0.07, t = 8.92, P = 0.0009; respectively), compared with WT lungs at the same time and in primary lung fibroblasts (0.82 ± 0.01 vs. 1.01 ± 0.04, t = 4.06, P = 0.0150; 1.04 ± 0.03 vs. 1.24 ± 0.03, t = 4.44, P = 0.0100; and 0.76 ± 0.05 vs. 0.99 ± 0.05, t = 4.48, P = 0.0100; respectively), compared with TGF-β1-stimulated WT group. Recombinant human FSTL1 protein in lung fibroblasts enhanced TGF-β1-mediated phosphorylation of the ERK (1.19 ± 0.08 vs. 0.55 ± 0.04, t = 6.99, P = 0.0020), p38 (1.18 ± 0.04 vs. 0.66 ± 0.03, t = 11.20, P = 0.0020), and JNK (1.11 ± 0.01 vs. 0.84 ± 0.04, t = 6.53, P = 0.0030), compared with the TGF-β1-stimulated WT group. Fstl1-deficient fibroblasts showed reduc