Aspirin modulates interleukin-3 production: Additional explanation for the preventive effects of aspirin in antiphospholipid antibody syndrome

Objective. The granulocyte macrophage colony stimulating factors (GMCSF) and interleukin-3 (IL-3) are defined as positive signals for pregnancy, since they support the process of trophoblast invasion and expansion and induce placental growth and development. Aspirin and IL-3 were shown to be effective in preventing the manifestations of experimental antiphospholipid antibody syndrome (APS). Aspirin inhibits the activity of the enzyme cyclooxygenase in macrophages, which leads to a shift in the arachidonic acid metabolism toward the lipoxygenase pathway, and results in overproduction of leukotrienes. Our data indicated that leukotrienes are capable of stimulating IL-3 production in vitro. Our aim was to examine whether aspirin may exert its beneficial effect in APS not only by its ability to prevent thromboxane A₂ production and prostaglandin I₂ (PGI₂) formation, but also by stimulating IL-3 production. Methods. Splenocytes and macrophages from naive mice were cultured in vitro with low dose aspirin. Nordihydroguaiaretic acid (NDGA), an inhibitor of 5-lipoxygenase, was added to mixed cultures of splenocytes and macrophages containing low dose aspirin. IL-3 production was observed. Results. When splenocytes and macrophages were cultured in vitro with low dose aspirin (10 μg/nl), a marked stimulation of IL-3 production was noted. When NDGA was added to the mixed cultures of splenocytes and macrophages containing low dose aspirin, it decreased the IL-3 production. Higher doses of aspirin did not affect the cytokine production. When splenocytes were incubated without the addition of exogenous macrophages, no stimulation of IL-3 production was noted. However, when purified leukotriene B₄ or leukotriene C₄ was added, there was an increase of 71 and 261%, respectively, in the stimulation of IL-3 production (p < 0.01). These results were supported by in vivo studies, in which a higher serum IL-3 level was detected in mice fed low dose aspirin, compared to the control group and to mice fed a higher dose of aspirin. Conclusion. Aspirin acts as a potent stimulator of IL-3 through its ability to raise leukotriene production, which induces production of IL-3 both in vitro and in vivo.