Eicosanoid regulation of hematopoiesis and hematopoietic stem and progenitor trafficking.

Hematopoietic stem cell (HSC) transplantation is a potentially curative treatment for numerous hematological malignancies. The transplant procedure as performed today takes advantage of HSC trafficking; either egress of HSC from the bone marrow to the peripheral blood, that is, mobilization, for acquisition of the hematopoietic graft, and/or trafficking of HSC from the peripheral blood to bone marrow niches in the recipient patient, that is HSC homing. Numerous studies, many of which are reviewed herein, have defined hematopoietic regulatory mechanisms mediated by the 20-carbon lipid family of eicosanoids, and recent evidence strongly supports a role for eicosanoids in regulation of hematopoietic trafficking, adding a new role whereby eicosanoids regulate hematopoiesis. Short-term exposure of HSC to the eicosanoid prostaglandin E(2) increases CXCR4 receptor expression, migration and in vivo homing of HSC. In contrast, cannabinoids reduce hematopoietic progenitor cell (HPC) CXCR4 expression and induce HPC mobilization when administered in vivo. Leukotrienes have been shown to alter CD34(+) cell adhesion, migration and regulate HSC proliferation, suggesting that eicosanoids have both opposing and complimentary roles in the regulation of hematopoiesis. As numerous FDA approved compounds regulate eicosanoid signaling or biosynthesis, the utility of eicosanoid-based therapeutic strategies to improve hematopoietic transplantation can be rapidly evaluated.