Bleomycin stimulates pro-alpha 1 (I) collagen promoter through transforming growth factor beta response element by intracellular and extracellular signaling.

The role of transforming growth factor beta as a mediator of the fibrogenic effect of bleomycin in lung has been investigated at the transcriptional level. Several constructs containing the rat pro-alpha 1 (I) collagen promoter fused to the chloramphenicol acetyltransferase gene were transfected into rat lung fibroblasts. Both bleomycin and transforming growth factor beta 1 increased promoter activity in fibroblasts transfected with constructs containing the transforming growth factor beta response element. Fibroblasts transfected with a deletion construct that lacks this response element did not respond to either bleomycin or transforming growth factor beta 1. Anti-transforming growth factor beta 1-neutralizing antibodies did not block the increase in promoter activity induced by bleomycin, suggesting intracellular signaling. Mutation of the transforming growth factor beta response element greatly reduced the bleomycin effect, which also infers intracellular signaling. In addition, plasmin added to the media greatly enhanced bleomycin stimulation of promoter activity demonstrating that transforming growth factor beta mediates the bleomycin effect through extracellular signaling.