L-TRYPTOPHAN IN SUPRAPHYSIOLOGICAL CONCENTRATIONS STIMULATES COLLAGENASE GENE-EXPRESSION IN HUMAN SKIN FIBROBLASTS

BACKGROUND: Collagenase plays a critical role in regulating connective tissue breakdown in physiologic and pathologic processes. The express ion of collagenase is modulated by a variety of biologic and pharmacol ogic agents. L-tryptophan is an essential amino acid with diverse biol ogic effects not shared by other amino acids. EXPERIMENTAL DESIGN: In this study, we examined the effects of L-tryptophan on collagenase gen e expression in normal human skin fibroblasts using Northern hybridiza tions and transient transfection assays. RESULTS: The results indicate that L-tryptophan at supraphysiologic concentrations caused a marked increase in collagenase gene expression. The increase in collagenase m RNA levels was reversible, time- and dose-dependent, and was accompani ed by enhancement of procollagenase synthesis and secretion. Parallel accumulation of mRNA for tissue inhibitor of metalloproteinase was als o noted, whereas stromelysin mRNA levels remained undetectable. The en hancement of collagenase mRNA was specific for L-tryptophan, and was a brogated by alpha-amanitin or dexamethasone. The apparent half-life of collagenase mRNA transcripts was similar in cultures exposed to inter leukin-1 beta or L-tryptophan. In contrast to interleukin-1 beta, L-tr yptophan-induced increase in collagenase mRNA was not preceeded by exp ression of c-jun or c-fos. Transient transfection of human skin fibrob lasts with a collagenase promoter, chloramphenicol acetyl transferase construct indicated marked dose-dependent increase in promoter activit y with L-tryptophan. CONCLUSIONS: These results demonstrate that L-try ptophan in supraphysiologic concentrations is a potent inducer of coll agenase gene expression in vitro at a transcriptional level by human s kin fibroblasts.