Taxol, an anticancer drug, has been known not only to block cell division by stabilizing microtubules but also to activate murine macrophages to express TNF-alpha, interleukin-1, and to produce nitric oxide (NO). We therefore reasoned that taxol could activate murine macrophages to generate reactive oxygen intermediates, such as superoxide anion (O2-), which are responsible for intracellular killing of pathogenic microbes. Treatment of RAW264.7 cells, murine macrophage cell line, with taxol increased phorbol ester-induced O2- production in a dose dependent manner (approximately 2 fold). In addition, taxol rapidly (< 1 hr) primed RAW264.7 cells to enhance O2- release stimulated with PMA. Taxol also enhanced stimulation of O2- production by FMLP, but not by Con A. This effect was abolished by prior treatment with both superoxide dismutase (SOD) and N-acetyl-L-cystein, a free radical scavenger. To investigate the mechanism of taxol-induced macrophage stimulation, we evaluated the ability of colchicine, a drug that inhibit tubulin polymerization, and cAMP analogues, which is known to depolymerize microtubule. Taxol-induced O2- production was inhibited by the treatment with both colchicine and DB-cAMP. Taken together, these results demonstrated that taxol provides two signals, "priming" and "enhancing", to generate superoxide anion via the stabilization of microtubules in murine RAW264.7 cells