Effects of pirfenidone on procollagen gene expression at the transcriptional level in bleomycin hamster model of lung fibrosis

A time course study was carried out to elucidate the mechanisms for antifib rotic effect of pirfenidone (PD). Hamsters were intratracheally (i.t.) inst illed with saline (SA) or bleomycin (BL) (7.5 units/kg/5 ml). The animals w ere fed a diet containing 0.5% PD or the same control diet (CD) without the drug 2 days before and throughout the study. The animals were sacrificed a t various times after instillation. The lung hydroxyproline level in BL + C D groups was gradually increased and peaked at 21 days to 181% of the SA CD control. The BL + PD-treated groups showed a gradual decrease in their l ung collagen content, showing a maximum reduction of 40% at day 21. The lun g malondialdehyde levels of the BL + CD groups were increased by several-fo ld of the corresponding SA + CD groups at various times. The lung prolyl hy droxylase (PH) activities in the BL + CD groups were also increased by seve ral-fold of the corresponding SA + CD groups at these time points. The hams ters in the BL + PD showed a gradual decrease in the lung malondialdehyde l evels from 10 to 21 days compared with their corresponding BL + CD groups. Treatment with PD also reduced the lung PH activities in the BL + PD groups compared with the corresponding BL + CD groups. However, PD failed to mani fest any direct inhibitory effect on PH activity in vitro. BL treatment inc reased the lung procollagen I and III gene expressions in the BL + CD group s by several-fold at varying times compared with the corresponding SA + CD, and treatment with PD in the BL + PD groups significantly down-regulated t he BL-induced overexpression of these genes. Studies evaluating the regulat ion of these genes at the transcriptional level revealed PD significantly r educed the transcription of PC I at 14 days. Our results indicate that the antifibrotic effect of PD was partly due to suppression of the BL-induced i nflammatory events and partly due to down-regulation of BL-induced overexpr ession of lung procollagen I and III genes.