HEAT-SHOCK OF HUMAN SYNOVIAL AND DERMAL FIBROBLASTS INDUCES DELAYED UP-REGULATION OF COLLAGENASE-GENE EXPRESSION

We investigated the effect of heat shock on the expression of the coll agenase gene in normal human synovial and dermal fibroblasts. Heat sho ck (42-44 degrees C for 1 h) caused a marked increase in heat-shock pr otein 70 (HSP-70) mRNA levels, followed by a delayed increase in colla genase mRNA levels, in both cell types. Pretreatment with cycloheximid e had no effect on the heat-shock-induced increase in HSP-70 mRNA expr ession, but abrogated the induction of collagenase mRNA during the rec overy. To study the mechanisms of collagenase-gene induction by heat s hock, the transcriptional activity of a collagenase-promoter-driven ch loramphenicol acetyltransferase (CAT) reporter gene was examined in tr ansient transfection experiments. Heat shock was followed by a > 2-fol d increase in CAT activity driven by a 3.8 kb fragment of the collagen ase promoter, or by a construct containing an AP-1 binding site. A mut ation in the AP-1 binding site abolished the effect of heat shock. Ele ctrophoretic-mobility-shift assays revealed a marked increase in DNA-b inding activity specific for the AP-1 binding site in nuclear extracts prepared from synovial fibroblasts recovering from heat shock. These results indicate that heat shock causes a delayed increase in collagen ase-gene expression in human fibroblasts, and suggests that this stimu lation involves, at least in part, transcriptional activation through an AP-1 binding site. Heat shock appears to initiate a programme of ce llular events resulting in collagenase-gene expression, and therefore may contribute to connective-tissue degradation in disease states.