Antifibrotic effect of interferon gamma in silicosis model of rat

This study presents the antifibrotic effect of interferon gamma (IFN-gamma,) in silicosis of rats. Wistar rats were received saline or 20 mg of quartz by intratracheal instillation. The next day after instillation, silicosis model of rats were daily treated IFN-gamma (1.0 x 10(5) units/rat) or saline by intramuscular route. At 1 month or 2 months after instillation, rats were sacrificed to determine hydroxyproline content and observe the change of fibrosis and expression of interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) in the lung of rats. The hydroxyproline content of IFN-gamma treated groups was significantly lower than that of quartz groups (P < 0.05). At I month after instillation, there were Stage II and II+ of silicotic nodules in quartz group; however, in IFN-gamma treated group only cellular nodules (Stage I) were observed. At 2 months after instillation, there was Stage II+ and III of silicotic nodules in quartz group. In IFN-gamma treated group Stage 11 was found. The expressions of IL-4 (2.19 +/- 0.90, 0.61 +/- 0.22, respectively) and TGF-beta1 (1.37 +/- 0.31, 1.76 +/- 0.72, respectively) in IFN-gamma treated groups were significantly lower than those in quartz groups (IL-4: 3.33 +/- 1.27, 1.99 +/- 0.80; TGF-beta1 1: 3.67 +/- 0.63, 4.90 +/- 1.11, respectively; P < 0.05 or P < 0.01). It may be concluded that the decreased expression of IL-4 and TGF-beta1 may be associated with decreased hydroxyproline synthesis, which then results in decreased lung fibrosis. (C) 2004 Elsevier Ireland Ltd. All rights reserved.