We have previously demonstrated that the anti-fibrotic effect of pirfenidone (PD) resides in its ability to downregulate procollagen (PC) I and III gene expression in the bleomycin (BL) rodent model of lung fibrosis. In this model a number of cytokines are known to be upregulated including TGF-β. It has been demonstrated that increased TGF-β mRNA accumulation and protein production are followed by increased PC gene expression. This study was conducted to test the hypothesis that the downregulation of PC gene expression by PD resides in its ability to downregulate the production of TGF-β. Hamsters were intratracheally instilled with saline or BL (5.5U/kg/5ml). The animals were fed a diet containing 0.5%PD or the same diet without the drug 2 days prior to and throughout the study. The four groups were saline-instilled fed control diet (SCD); saline-instilled fed the diet containing PD (SPD);BL-instilled fed control diet (BCD); and BL-instilled fed the diet containing PD(BPD). The animals were sacrificed at 1, 3, 5, 7, 14 and 21 days after BL-instillation. The bronchoalveolar lavage fluid (BALF) was used to analyze for various assays. The total protein in BALF supernatent was elevated at all time points in the BCD group compared to the SCD group. Treatment with PD caused a gradual reduction in the protein content at earlier time points and significantly reduced the protein content by 46% of the BCD group at 21 days. BL treatment significantly elevated the TGF-β protein content in the BALF supernatent at 3,5, 7 and 21 days by 266%, 356%, 186% and 470% of the SCD group respectively (rptly). Treatment with PD significantly reduced the TGF-β protein content at 3, 5, 7 and 21 days by 35%,40% and 25% of the BCD group rptly. The BCD group showed elevated cell counts in BALF at 3,7,14 and 21 days by 275%,348%,209% and 223% of the SCD controls rptly. Treatment with PD significantly reduced the increases in total cell counts at 3 and 7 days by 41% and 22% of the BCD groups rptly. Analysis of differential cell counts revealed that treatment with PD significantly lowered the neutrophil,macrophages and lymphocyte numbers at 3 and 7 days. We concluded that PD produces its antifibrotic action by modulating the cell-cell interactions and thus lowering TGF-β protein production which in turn downregulates PC gene expression leading to a decreased level of collagen accumulation.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology