Stimulation of collagenase synthesis by a 20,000-dalton epithelial cytokine. Evidence for pretranslational regulation.

Certain products of cultured rabbit corneal epithelium or epidermis regulate collagenase production by rabbit corneal stromal cells. Here, we examined the effects of a 20-kDa cytokine derived from cultured epithelium on collagenase expression by normal human skin fibroblasts and by cells from recessive dystrophic epidermolysis bullosa, a disease characterized by over-production of a structurally altered collagenase. Culturing cells for 24 h in the presence of the cytokine resulted in an approximately 2-fold increase in trypsin-activatable collagenase activity paralleled by an increase in immunoreactive protein, suggesting enhanced synthesis. There was no change in the activity/immunoreactive protein, indicating a catalytically unaltered enzyme. In kinetic studies, stimulation of collagenase synthesis was first observed approximately 8 h after exposure to the epidermal cytokine. Conversely, when cells were primed with cytokine for 24 h and the stimulator was then removed, an increased rate of synthesis was seen for an additional approximately 9 h, after which the rate reverted to control levels. Since the kinetic data suggested an effect at a pretranslational level, fibroblasts cultured with 20-kDa stimulator were used to prepare mRNA. In cell-free translation total protein synthesis was unaltered; however, the cytokine caused a greater than 2-fold increase in translatable collagenase mRNA. The data suggest that this epithelial cytokine specifically modulates collagenase synthesis through transcription and that epithelial-stromal interactions are important to cutaneous connective tissue metabolism.