Effects of pirfenidone on transforming growth factor-beta gene expression at the transcriptional level in bleomycin hamster model of lung fibrosis

Abstract

This study was undertaken to investigate whether treatment with the antifibrotic drug pirfenidone (PD) down-regulates the bleomycin (BL)-induced overexpression of transforming growth factor (TGF)-beta gene in the lungs. Hamsters were intratracheally instilled with SA or BL (6.5 U/kg/4 ml) under anesthesia. They were fed a diet containing 0.5% PD or the same control diet (CD) without the drug 2 days before and throughout the study. After the animals were sacrificed, their lungs were appropriately processed. The BL treatment elevated the total influx of inflammatory cells, including macrophages, by severalfold at different days in bronchoalveolar lavage fluid (BALF) from hamsters in BL + CD groups, relative to the corresponding SA + CD control groups. Treatment with PD significantly (P </=.05) suppressed the influx of inflammatory cells and macrophages at day 7 in the BL + PD groups, relative to the corresponding BL + CD groups. In addition, the levels of TGF-beta in BALF from hamsters in BL + CD groups were elevated by 2.6- to 4.5-fold at different days, relative to the corresponding SA + CD groups. Treatment with PD significantly (P </=.05) reduced the TGF-beta protein in BALF from BL + PD groups at 14 and 21 days, when compared with the corresponding BL + CD groups. The intratracheal instillation of BL significantly (P </=.05) elevated the TGF-beta mRNA at 7, 14, and 21 days in BL + CD groups, relative to the corresponding SA + CD groups, and treatment with PD significantly (P </=.05) suppressed the TGF-beta gene expression in BL + PD groups at these times, when compared with the corresponding BL + CD groups. Nuclear runoff studies revealed that PD suppressed the BL-induced increase in TGF-beta gene transcription by 33%. It was concluded that one of the mechanisms for antifibrotic effect of PD is its ability to suppress the BL-induced overexpression of TGF-beta gene at the transcriptional level.