title: Honeybee venom secretory phospholipase A2 induces leukotriene production but not histamine release from human basophils.
abstract: The role of basophils in an anaphylactic response is well recognized but is usually masked by mast cells, which contain similar mediators for the induction of generalized vasodilatation and laryngeal constriction. The rapid onset of systemic anaphylactic symptoms, particularly in insect stings and ingested food, suggest that basophils, a circulating pool of cells containing histamine and other potent mediators such as leukotrienes, may be more involved in systemic anaphylaxis than originally thought. We wished to examine if secretory phospholipase A2, a systemic allergen found in honey bee venom (HBV-sPLA2) may activate basophils directly leading to rapid systemic mediator release. Basophils were isolated from human blood and stimulated with increasing concentrations of HBV-sPLA2. We found that physiological concentrations of HBV-sPLA2 induce rapid leukotriene C4 production from purified human basophils within 5 min, while interleukin (IL)-4 expression and production was induced at later time-points. Histamine release was not induced, signifying that HBV-sPLA2 did not induce generalized degranulation. Surface expression of CD63, CD69 and CD11b were up-regulated following HBV-sPLA2 treatment. Stimulation of basophils with anti-immunoglobulin E (IgE) following treatment with HBV-sPLA2 did not induce more leukotriene release. To investigate the mechanism of leukotriene production, 9-12 octadecadiynioc acid, a cyclooxygenase-1 (COX-1) and 15-lipoxygenase inhibitor, was used and this abrogated leukotriene production. These results indicate that HBV-sPLA2 can directly activate human basophils in vitro to induce leukotriene production.
authors.affiliation: Inflammation and Cancer Laboratory, Department of Physiology and NUS Immunology Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: F B
authors.initials: FB
authors.lastname: Mustafa
authors.forename: F S P
authors.initials: FS
authors.lastname: Ng
authors.forename: T H
authors.initials: TH
authors.lastname: Nguyen
authors.forename: L H K
authors.initials: LH
authors.lastname: Lim
mesh_terms: D000704:Analysis of Variance; D000707:Anaphylaxis / Q000276:immunology*; D001491:Basophils / Q000187:drug effects* / Q000276:immunology; D001514:Bee Venoms / Q000009:adverse effects*; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D016207:Cytokines / Q000276:immunology; D053280:Diynes / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005434:Flow Cytometry; D006636:Histamine Release; D006801:Humans; D017997:Leukotriene C4 / Q000096:biosynthesis*; D016859:Lipoxygenase Inhibitors; D054497:Phospholipases A2, Secretory / Q000009:adverse effects*; D013268:Stimulation, Chemical
chemical_list: D001514:Bee Venoms; D016861:Cyclooxygenase Inhibitors; D016207:Cytokines; D053280:Diynes; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D016859:Lipoxygenase Inhibitors; C095413:octadeca-9,12-diynoic acid; D017997:Leukotriene C4; D054497:Phospholipases A2, Secretory