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 biolog ic activities, including the inhibition of collagen synthesis by derma l fibroblasts. Because some PTX activities have recently been linked t o transcription factor-mediated regulation of gene transcription, we h ave investigated if PTX acts to inhibit collagen synthesis at a transc riptional locus by measuring procollagen mRNA levels and by assaying f or the presence of an activator fo procollagen gene promoters, nuclear factor (NF)-1. The effects of another methylxanthine, pentifylline (P TF), shown herein to be a tenfold more potent inhibitor of collagen sy nthesis than PTX, and interferon-alpha, -beta, and -gamma were studied in parallel. Analysis of extracellular protein and RNA from 48-h-trea ted 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. Reduc tion of procollagen mRNA levels appeared to be dependent on new protei n synthesis, as it was prevented by treatment with cycloheximide. Assa y for the presence of nuclear NF-1 by gel mobility shift analysis show ed that extracts from interferon, PTX, and PTF-treated fibroblasts lac ked proteins recognizing the consensus DNA binding sequence for NF-1. Taken together, these observations suggest interferons and methylxanth ines may inhibit fibroblast collagen synthesis by a common mechanism r equiring new protein synthesis that suppresses procollagen gene transc ription through down-regulation of NF-1.