An assay for the detection of interleukin-1 synthesis inhibitors: effects of antirheumatic drugs

The monokines interleukin-1 beta and alpha (IL-1) play a central role in the connective tissue destruction of many chronic inflammatory diseases. A high capacity screening assay for the detection of inhibitors of IL-1 biosynthesis has been established. Normal human monocytes were obtained by leukapheresis and elutriation. IL-1 beta and alpha biosynthesis was stimulated with LPS, and cell-associated and secreted IL-1 beta and IL-1 alpha were measured by specific immunoassays (ELISA). The mean total IL-1 beta (cell-associated and secreted) production in 18 different donors was 11 ng/10(6) cells (range 1.2-28.8). Secreted IL-1 beta represented 31 to 86% of the total IL-1 beta. More IL-1 alpha than IL-1 beta was produced but, unlike IL-1 beta, IL-1 alpha was poorly secreted. The steroids prednisolone and dexamethasone, gold (sodium aurothiomalate) and chloroquine were potent inhibitors of the IL-1 production. Mean IC50 values of 180 nM (range 2.5 nM-1 microns), 10 microM (range 6-20 microM) and of 75 microM were found for prednisolone, gold and chloroquine, respectively. Above 5 microM, the non-steroidal anti-inflammatory compounds indomethacin and BW755C increased IL-1 beta biosynthesis. Nordihydroguaiaretic acid inhibited the level of the secreted form of IL-1 beta, but tended to increase the cell-associated level. D-Penicillamine (up to 6 mM), cyclosporin A (up to 1 microM) and methotrexate (up to 12 microM) inhibited neither cell-associated nor secreted IL-1 beta levels. This high capacity assay, which is insensitive to classical NSAIDs, may serve in the detection and characterization of new classes of anti-inflammatory compounds.