Hydroxyeicosanoids bind to and activate the low affinity leukotriene B-4 receptor, BLT2

Leukotriene B-4, an arachidonate metabolite, is a potent chemoattractant of leukocytes involved in various inflammatory diseases. Two G-protein-couple d receptors for leukotriene B-4 have been cloned and characterized. BLT1 (Y okomizo, T., Izumi, T., Chang, K., Takuwa, Y., and Shimizu, T. (1997) Natur e 387, 620-624) is a high affinity receptor exclusively expressed in leukoc ytes, and BLT2 (Yokomizo, T., Rate, K., Terawaki, K., Izumi, T., and Shimiz u, T. (2000) J. Exp. Med. 192, 421-432) is a low affinity receptor expresse d more ubiquitously. Here we report the binding profiles of various BLT ant agonists and eicosanoids to either BLT1 or BLT2 using the membrane fraction s of Chinese hamster ovary cells stably expressing the receptor. BLT antago nists are grouped into three classes: BLT1-specific U-75302, BLT2-specific LY255283, and BLT1/BLT2 dual-specific ZK 158252 and CP 195543. We also show that 12(S)-hydroxyeicosatetraenoic acid, 12(S)-hydroperxyeicosatetraenoic acid, and 15(S)-hydroxyeicosatetraenoic acid competed with [H-3]LTB4 bindin g to BLT2, but not BLT1, dose dependently. These eicosanoids also cause cal cium mobilization and chemotaxis through BLT2, again in contrast to BLT1. T hese findings suggest that BLT2 functions as a low affinity receptor, with broader ligand specificity for various eicosanoids, and mediates distinct b iological and pathophysiological roles from BLT1.