title: The role of phospholipases A2 in the stimulation of neutrophil motility by cobra venoms.
abstract: Neutrophil (PMN) accumulation frequently occurs at the site of snakebite as part of the inflammatory response to envenoming. We demonstrate here that the venoms of the cobras, Naja naja and N. mossambica, and two purified venom phospholipase A(2)s (PLA(2)s) isolated from the latter venom, stimulate CD11b translocation from the PMN granule store to the plasma membrane and enhance neutrophil motility on collagen-coated surfaces. These effects were partially attenuated by the PLA(2) inhibitor, aristolochic acid, and almost completely abolished by the specific cytosolic PLA(2) inhibitor, methylarachidonylfluorophosphonate (MAFP). Annexin V and inhibitors of collagenase, cyclo-oxygenase and lipo-oxygenase, all inhibited PMN motility to a variable extent. FACS analysis and confocal microscopy showed that Annexin V interfered with binding and rapid endocytosis of the venom PLA(2). These results indicate that venom and venom PLA(2) preparations first caused a non-enzymatic stimulation of PMN leading to the activation of cytosolic PMN PLA(2) and production of arachidonate metabolites involved in stimulation of PMN degranulation and motility. The evidence suggests that venom PLA(2) then interacts with anionic phospholipids exposed on stimulated PMN, becomes endocytosed, and then contributes itself to the production of chemoattractants responsible for PMN accumulation at the site of the snakebite.
authors.affiliation: Department of Haematology, University of Liverpool, Liverpool L69 3GA, UK.
authors.forename: I Birgitta
authors.initials: IB
authors.lastname: Sundell
authors.forename: Khalil A
authors.initials: KA
authors.lastname: Aziz
authors.forename: Mirko
authors.initials: M
authors.lastname: Zuzel
authors.forename: R David G
authors.initials: RD
authors.lastname: Theakston
mesh_terms: D000818:Animals; D034341:Aristolochic Acids / Q000494:pharmacology; D039481:CD11b Antigen / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D004546:Elapid Venoms / Q000494:pharmacology*; D017815:Elapidae; D005786:Gene Expression Regulation / Q000187:drug effects; D039421:Integrin alpha2 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D034341:Aristolochic Acids; D039481:CD11b Antigen; D004546:Elapid Venoms; D039421:Integrin alpha2; D016023:Integrins; C000228:aristolochic acid I; D010741:Phospholipases A