title: Leukotriene B4 receptors BLT1 and BLT2: expression and function in human and murine mast cells.
abstract: Leukotriene B4 (LTB4) is a potent activator and chemoattractant for leukocytes and is implicated in several inflammatory diseases. The actions of LTB4 are mediated by two cell surface receptors, BLT1, which is predominantly expressed in peripheral blood leukocytes, and BLT2, which is expressed more ubiquitously. Recently, BLT1 expression and LTB4-dependent chemotaxis have been reported in immature mast cells (MCs). We now show the first evidence for BLT2 mRNA expression, in addition to BLT1, in murine bone marrow-derived MCs (mBMMCs) and in a human MC line (HMC-1). Protein expression of BLT1 was confirmed by mAb staining in HMC-1 cells and shown to be predominantly intracellular. Both HMC-1 cells and mBMMCs migrated to LTB4 in a dose-dependent manner in chemotaxis assays. Migration to LTB4 could be inhibited by either a BLT1- or BLT2-selective antagonist. Significant dose-dependent migration of mBMMCs also was observed to 12-(S)-hydroxyeicosotetraenoic acid, a BLT2-selective agonist, demonstrating functional BLT2 activity in these cells. Stimulation of mBMMCs with LTB4 induced transient, dose-dependent, ERK phosphorylation and changes in Akt phosphorylation. Dose-dependent ERK phosphorylation also was observed in response to 12-(S)-hydroxyeicosotetraenoic acid, indicating signaling downstream of BLT2. Pretreatment of mBMMCs with stem cell factor significantly down-regulated expression of BLT1 and BLT2 mRNA and inhibited their migration to LTB4. This study demonstrates expression of functional LTB4 receptors, both BLT1 and BLT2, in murine and human MCs and a regulatory role for stem cell factor in their expression. These receptors may mediate recruitment and accumulation of MCs in response to LTB4 production in areas of inflammation.
authors.affiliation: Alza/Johnson & Johnson Pharmaceutical Research and Development, San Diego, CA 92121, USA.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Lundeen
authors.forename: Binggang
authors.initials: B
authors.lastname: Sun
authors.forename: Lars
authors.initials: L
authors.lastname: Karlsson
authors.forename: Anne M
authors.initials: AM
authors.lastname: Fourie
mesh_terms: D000818:Animals; D001853:Bone Marrow; D002454:Cell Differentiation; D002478:Cells, Cultured; D002633:Chemotaxis; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D007975:Leukotriene B4 / Q000494:pharmacology; D008407:Mast Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000235:genetics; D018102:Receptors, Leukotriene B4 / Q000235:genetics / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000494:pharmacology
chemical_list: D015850:Interleukin-6; C513240:LTB4R protein, human; C485878:LTB4R2 protein, human; C503704:Ltb4r1 protein, mouse; C412867:Ltb4r2 protein, mouse; D012333:RNA, Messenger; D018102:Receptors, Leukotriene B4; D018048:Receptors, Purinergic P2; D019089:Stem Cell Factor; D007975:Leukotriene B4