THE CYTOKINE-PROTEASE CONNECTION - IDENTIFICATION OF A 96-KD THP-1 GELATINASE AND REGULATION BY INTERLEUKIN-1 AND CYTOKINE INDUCERS

The induction of proteolytic enzymes is an important mechanism in the migration of monocytes into tissues and body fluids. The monocytic cell line THP-1 was used as a model system to study the production of a particular gelatinase. Upon stimulation with phorbol myristate acetate (PMA) the cells differentiated to the adherent phenotype and produced significant amounts of a 96-kD gelatinase in a dose-dependent way. The secretion rate was maximal between 12 and 24 h after induction. Study of gelatinase mRNA steady state levels showed that the synthesis of THP-1 gelatinase is regulated by PMA at transcriptional or posttranscriptional levels. Stimulation of signal transduction pathways with other substances, including calcium ionophore A 23187, dibutyryl cyclic AMP, and dexamethasone, were ineffective in inducing gelatinase mRNA or enzyme activity. However, THP-1 cells were responsive to the cytokine interleukin (IL)-1β, to bacterial lipopolysaccharide (LPS), and the lectin concanavalin A (Con A), the kinetics of gelatinase induction being similar to those of induction by PMA. The THP-1 cells did not synthesize and/or secrete detectable levels of IL-6 after stimulation with PMA, Con A, LPS, or IL-1β. The 96-kD monocytic THP-1 gelatinase was shown to be a neutral metalloproteinase that cross-reacted with hepatoma-derived and neutrophil gelatinases in immunoprecipitation experiments. The active enzyme produced by THP-1 cells consistently showed, however, a molecular mass different from that of normal granulocyte-, monocyte-, and tumor cell-derived gelatinases. The THP-1 enzyme was therefore purified to homogeneity by substrate affinity chromatography, and its amino-terminal amino acid sequence was determined and compared to those of known gelatinases. The terminus was identical to that of the 92-kD gelatinase from fibrosarcoma cells but was eight residues longer than that of the gelatinase from normal human blood granulocytes and monocytes. The activity of the gelatinase was also found to be regulated at the extracellular level by simultaneous production and secretion of the tissue inhibitor of metalloproteases (TIMP-1) by the THP-1 cells. This inhibitor was copurified and unequivocally identified by amino-terminal sequence analysis. © 1991.