Rapamycin Inhibits Transforming Growth Factor β1-Induced Fibrogenesis in Primary Human Lung Fibroblasts

Purpose: The present study was designed to determine whether rapamycin could inhibit transforming growth factor beta 1 (TGF-beta 1)-induced fibrogenesis in primary lung fibroblasts, and whether the effect of inhibition would occur through the mammalian target of rapamycin (mTOR) and its downstream p70S6K pathway. Materials and Methods: Primary normal human lung fibroblasts were obtained from histological normal lung tissue of 3 patients with primary spontaneous pneumothorax. Growth arrested, synchronized fibroblasts were treated with TGF-beta 1 (10 ng/mL) and different concentrations of rapamycin (0.01, 0.1, 1, 10 ng/mL) for 24 h. We assessed m-TOR, p-mTOR, S6K1, p-S6K1 by Western blot analysis, detected type III collagen and fibronectin secreting by ELISA assay, and determined type RI collagen and fibronectin mRNA levels by real-time PCR assay. Results: Rapamycin significantly reduced TGF-beta 1-induced type III collagen and fibronectin levels, as well as type III collagen and fibronectin mRNA levels. Furthermore, we also found that TGF-beta 1-induced mTOR and p70S6K phosphorylation were significantly down-regulated by rapamycin. The mTOR/p70S6K pathway was activated through the TGF-beta 1-mediated fibrogenic response in primary human lung fibroblasts. Conclusion: These results indicate that rapamycin effectively suppresses TGF-beta 1-induced type III collagen and fibronectin levels in primary human lung fibroblasts partly through the mTOR/p70S6K pathway. Rapamycin has a potential value in the treatment of pulmonary fibrosis.