Triptolide protects against TGF-[beta]1-induced pulmonary fibrosis by regulating FAK/calpain signaling

• Published in: Experimental and therapeutic medicine 2019-12, Vol.18 (6), p.4781
• Main Authors: Zhang, Pingheng, Liu, Jian, Zong, Ruikai
• Format: Article
• Language: English
• Subjects: Analysis; Anti-inflammatory agents; B cells; Bone morphogenetic proteins; Calpain; Collagen; EDTA; Enzyme-linked immunosorbent assay; Fibrosis; Inflammation; Interleukins; Messenger RNA; Polymerase chain reaction; Pulmonary fibrosis; RNA; Scientific equipment industry; Transforming growth factors
• ISSN: 1792-0981
• DOI: 10.3892/etm.2019.8127

The present study aimed to investigate the mechanism of anti-proliferative, anti-inflammatory and anti-fibrotic effects of triptolide (TPL) on activated lung fibroblasts by regulating the focal adhesion kinase (FAK) and calpain signaling pathways. The HFL-1 human foetal lung fibroblast cell line was cultured in vitro and treated with 50 ng/ml transforming growth factor (TGF)-p1 for 48 h to establish the model of pulmonary fibrosis. Subsequently, the cells were divided into five groups, including a control, model, TPL, FAK inhibitor and calpeptin group. Subsequently, the proliferation of lung fibroblasts was detected using the Cell Counting Kit-8 assay. The concentration of interleukin (IL)-6 in the cell culture supernatant was examined by ELISA and the mRNA expression levels of collagen type I (ColI)[alpha] and ColIII in lung fibroblasts were quantified by reverse transcription-quantitative PCR. The protein levels of FAK, phosphorylated (p)-FAK, calpain 1 and calpain 2 were detected by western blot analysis. TGF-[beta]1 induced the proliferation of lung fibroblasts, whereas TPL inhibited this proliferation in a dose-dependent manner. TPL also decreased the TGF-[beta]1-induced production of IL-6 and reduced the upregulation of ColI[alpha], ColIII, FAK, p-FAK, and inhibited the decrease of calpain 1 and calpain 2 induced by TGF-[beta]1. In addition, the FAK inhibitor acted synergistically with TPL to decrease TGF-[beta]1-induced production of IL-6 and attenuate TGF-[beta]1-induced synthesis of ColI[alpha] and ColIII, while calpeptin had an antagonistic effect on the function of TPL. Furthermore, treatment with the FAK inhibitor and TPL markedly decreased the protein levels of FAK and p-FAK, and increased the protein expression of calpain 1 and calpain 2 in lung fibroblasts stimulated by TGF-[beta]1 to a greater extent than TPL alone, while calpeptin had an antagonistic effect on the action of TPL. In conclusion, the present study indicated that TPL protected against TGF-[beta]1-induced proliferation, inflammation and fibrosis by regulating the FAK and calpain signaling pathways. Key words: triptolide, pulmonary fibrosis, focal adhesion kinase/calpain