Leukotrienes and lipoxins--new potential performers in the regulation of human myelopoiesis.

Leukotrienes and lipoxins are bioactive lipoxygenase products formed by leukocytes alone or in collaboration with other cells. While the physiological role of lipoxins remains to be clarified, accumulating evidence shows that leukotrienes are important mediators in asthma and inflammation. Consequently, recent clinical trials with leukotriene D4 receptor antagonists and 5-lipoxygenase inhibitors have demonstrated marked reduction of airway symptoms in asthmatic patients. In addition, both leukotrienes and lipoxins have been indicated as modulators of cell proliferation. This article reviews recent findings suggesting that these compounds may also participate in the regulation of human myelopoiesis. Such a role is conceivable since leukotrienes and lipoxins can be produced by bone marrow cells and potently modulate GM-CSF-induced myeloid stem cell proliferation.