PENTOXIFYLLINE, PENTIFYLLINE, AND INTERFERONS DECREASE TYPE-I AND TYPE-III PROCOLLAGEN MESSENGER-RNA LEVELS IN DERMAL FIBROBLASTS - EVIDENCE FOR MEDIATION BY NUCLEAR FACTOR-1 DOWN-REGULATION

Pentoxifylline (PTX) is a methylxanthine that exhibits multiple biologic activities, including the inhibition of collagen synthesis by dermal fibroblasts. Because some PTX activities have recently been linked to transcription factor-mediated regulation of gene transcription, we have investigated if PTX acts to inhibit collagen synthesis at a transcriptional locus by measuring procollagen mRNA levels and by assaying for the presence of an activator fo procollagen gene promoters, nuclear factor (NF)-1. The effects of another methylxanthine, pentifylline (PTF), shown herein to be a tenfold more potent inhibitor of collagen synthesis than PTX, and interferon-alpha, -beta, and -gamma were studied in parallel. Analysis of extracellular protein and RNA from 48-h-treated fibroblasts showed that PTX, PTF, and interferons decreased alpha 1(I), alpha 2(I), and alpha 1(III) procollagens by reducing the steady-state levels of the corresponding procollagen mRNA transcripts. Reduction of procollagen mRNA levels appeared to be dependent on new protein synthesis, as it was prevented by treatment with cycloheximide. Assay for the presence of nuclear NF-1 by gel mobility shift analysis showed that extracts from interferon, PTX, and PTF-treated fibroblasts lacked proteins recognizing the consensus DNA binding sequence for NF-1. Taken together, these observations suggest interferons and methylxanthines may inhibit fibroblast collagen synthesis by a common mechanism requiring new protein synthesis that suppresses procollagen gene transcription through down-regulation of NF-1.