COLCHICINE HAS OPPOSITE EFFECTS ON INTERLEUKIN-1-BETA AND TUMOR-NECROSIS-FACTOR-ALPHA PRODUCTION

To study the role of microtubules in cytokine production, the effect of the microtubule depolymerizing agent colchicine on lipopolysaccharide endotoxin (LPS)-induced interleukin-1-beta (IL-1-beta) and tumor necrosis factor-alpha (TNF-alpha) release by blood monocytes and alveolar macrophages were examined. Immunofluorescence microscopy demonstrated that LPS resulted in the appearance of microtubule-containing cytoplasmic appendages and that colchicine, which resulted in microtubule disruption in monocytes, blocked appendage formation. Colchicine resulted in approximately 50% increase in LPS-induced IL-1-beta release and a 50% decrease in LPS-induced TNF-alpha release by human monocytes at all doses of LPS tested. Although colchicine resulted in a statistically significant increase in LPS-stimulated human alveolar macrophage IL-1-beta release, the increase was not as great as that observed with monocytes. Northern blot analysis suggested that the colchicine effect occurs pretranslationally because colchicine caused an increase in LPS-stimulated IL-1-beta mRNA levels and a decrease in TNF-alpha mRNA levels. These results suggest that microtubules contribute to the regulation of endotoxin-stimulated mononuclear phagocyte cytokine production and that this regulation differs significantly between IL-1-beta and TNF-alpha.