Interleukin-6 receptor superantagonist Sant7 inhibits TGF-β-induced proliferation of human lung fibroblasts

Objectives: Both interleukin-6 (IL-6) and transforming growth factor-beta (TGF-beta) are crucially involved in fibrotic events that characterize interstitial lung diseases (ILD). Therefore, the aim of this study was to investigate in primary cultures of normal and fibrotic human lung fibroblasts (HLF), exposed to either IL-6 or TGF-beta 1, the effects on phosphorylation of mitogen-activated protein kinases (MAPK) and cell growth of IL-6 signalling inhibition, performed by the IL-6 receptor superantagonist Sant7.Materials and methods: MAPK phosphorylation was detected by Western blotting, HLF viability and proliferation were evaluated using the trypan blue staining and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, respectively. Results: Sant7, at a concentration of 1 mu g/mL, was capable of significantly inhibiting HLF proliferation and MAPK phosphorylation induced by cell exposure to IL-6 (100 ng/mL) or TGF-beta 1 (10 ng/mL), whose actions were more evident in fibrotic cells. Conclusions: These findings suggest that, in HLFs derived from patients with ILDs, the proliferative mechanisms activated by TGF-beta 1 are at least in part mediated by an increased release of IL-6, leading to phosphorylation-dependent MAPK activation. Such preliminary findings may thus open new therapeutic perspectives for fibrogenic ILDs, based on inhibition of signal transduction pathways stimulated by the IL-6 receptor.