Leukotriene B4 stimulates human monocyte-derived dendritic cell chemotaxis

Although leukotriene B4 (LTB4) has been reported to stimulate monocytes and neutrophils, its role on dendritic cell (DC) activity has not been examined. Here, we investigated the expression of LTB4 receptor and the effect of LTB4 on human DC chemotaxis. We analyzed LTB4 receptors, BLT1 and BLT2, by using RT-PCR. DCs express BLT2 but not BLT1 mRNA. DCs were chemotactically migrated to LTB4. LTB4-induced DC chemotaxis was completely inhibited by pertussis toxin, indicating the role of Gi proteins. LTB4 induced mitogen activated protein kinase activation and Akt activation. LTB4-induced DC chemotaxis was mediated by extracellular signal-regulated protein kinase and phosphoinositide 3-kinase but not by p38 kinase. BLT2-selevite antagonist, LY255283, almost completely inhibited DC chemotaxis induced by LTB4 but not by Trp-Lys-Tyr-Met-Val-D-Met. Thus human myeloid DCs express functional BLT2 but not BLT1, suggesting a physiological role of LTB4 and BLT2 in regulating DC trafficking during induction of immune responses.