IPF is a crippling disease that impairs gas exchange in the lung due to excessive accumulation of extra cellular matrix (ECM). IPF is thought to result from epithelial cell injury followed by aberrant wound healing. Numerous resident and recruited cell types, including lung epithelial cells, fibroblasts, activated macrophages, platelets, and lymphocytes, are known to release transforming growth factor beta (TGF-beta) in lung tissue in individuals with IPF. TGF-beta, in turn, enhances the deposition and accumulation of ECM, which leads to fibrotic lesions. To examine the molecular consequences of therapeutic application of IFN-gamma1b, we studied the effect of IFN-gamma1b on TGF-beta-modulated ECM turnover in a cellular model for IPF.
A human lung epithelial cell line (A549) was cultured in DMEM containing 10% serum, washed with PBS and serum-free medium added. After overnight incubation, cells were treated with increasing concentrations of IFN-gamma1b or left untreated, and then stimulated with 5 ng/ml TGF-beta. Both cell culture supernatant and cell lysate were collected, and ELISA assays were used to quantify secreted collagen and intracellular tissue inhibitor of metalloproteases 1, TIMP1.
Relative to untreated cells, TGF-beta induced the expression of collagen by 30% and TIMP1 by 60%. TGF-beta-induced expression of both collagen and TIMP1 was suppressed in a concentration-dependent fashion by adding IFN-gamma1b (p<0.01 for TIMP1, 0.03 for collagen). Importantly, these effects were statistically significant at the therapeutically relevant Cmax concentrations of IFN-gamma1b obtained from clinical trials.
Our results indicate that IFN-gamma1b inhibits both TGF-beta-induced collagen synthesis and TGF-beta-induced accumulation of TIMP1. Since both of these components are integral to deposition and accumulation of ECM, the likely net result may be a substantial decrease in the rate of ECM accumulation.
These results suggest that IFN-gamma1b may be beneficial in the treatment for IPF in certain patients by reducing the rate of TGF-beta-induced ECM accumulation. Further study of IFN-gamma 1b in IPF patients is warranted and may provide a means for early assessment of response to IFN-gamma1b therapy.
O. Ozes, InterMune, Inc.