Modifiers of TGF-beta1 effector function as novel therapeutic targets of pulmonary fibrosis

Pulmonary fibrosis is a fatal progressive disease with no effective therapy. Transforming growth factor (TGF)-beta1 has long been regarded as a central mediator of tissue fibrosis that involves multiple organs including skin, liver, kidney, and lung. Thus, TGF-beta1 and its signaling pathways have been attractive therapeutic targets for the development of antifibrotic drugs. However, the essential biological functions of TGF-beta1 in maintaining normal immune and cellular homeostasis significantly limit the effectiveness of TGF-beta1-directed therapeutic approaches. Thus, targeting downstream mediators or signaling molecules of TGF-beta1 could be an alternative approach that selectively inhibits TGF-beta1-stimulated fibrotic tissue response while preserving major physiological function of TGF-beta1. Recent studies from our laboratory revealed that TGF-beta1 crosstalk with epidermal growth factor receptor (EGFR) signaling by induction of amphiregulin, a ligand of EGFR, plays a critical role in the development or progression of pulmonary fibrosis. In addition, chitotriosidase, a true chitinase in humans, has been identified to have modulating capacity of TGF-beta1 signaling as a new biomarker and therapeutic target of scleroderma-associated pulmonary fibrosis. These newly identified modifiers of TGF-beta1 effector function significantly enhance the effectiveness and flexibility in targeting pulmonary fibrosis in which TGF-beta1 plays a significant role.

Rapamycin Inhibits Transforming Growth Factor beta1-Induced Fibrogenesis in Primary Human Lung Fibroblasts

PURPOSE: The present study was designed to determine whether rapamycin could inhibit transforming growth factor beta1 (TGF-beta1)-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-beta1 (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 III collagen and fibronectin mRNA levels by real-time PCR assay. RESULTS: Rapamycin significantly reduced TGF-beta1-induced type III collagen and fibronectin levels, as well as type III collagen and fibronectin mRNA levels. Furthermore, we also found that TGF-beta1-induced mTOR and p70S6K phosphorylation were significantly down-regulated by rapamycin. The mTOR/p70S6K pathway was activated through the TGF-beta1-mediated fibrogenic response in primary human lung fibroblasts. CONCLUSION: These results indicate that rapamycin effectively suppresses TGF-beta1-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.