title: Eicosanoids in insect immunity: bacterial infection stimulates hemocytic phospholipase A2 activity in tobacco hornworms.
abstract: Intracellular phospholipase A(2) (PLA(2)) is responsible for releasing arachidonic acid from cellular phospholipids, and is thought to be the first step in eicosanoid biosynthesis. Intracellular PLA(2)s have been characterized in fat body and hemocytes from tobacco hornworms, Manduca sexta. Here we show that bacterial challenge stimulated increased PLA(2) activity in isolated hemocyte preparations, relative to control hemocyte preparations that were challenged with water. The increased activity was detected as early as 15 s post-challenge and lasted for at least 1 h. The increased activity depended on a minimum bacterial challenge dose, and was inhibited in reactions conducted in the presence of oleyoxyethylphosphorylcholine, a site-specific PLA(2) inhibitor. In independent experiments with serum prepared from whole hemolymph, we found no PLA(2) activity was secreted into serum during the first 24 h following bacterial infection. We infer that a hemocytic intracellular PLA(2) activity is increased immediately an infection is detected. The significance of this enzyme lies in its role in launching the biosynthesis of eicosanoids, which mediate cellular immune reactions to bacterial infection.
authors.affiliation: Insect Biochemical Physiology Laboratory, University of Nebraska, Lincoln 68583-0816, USA.
authors.forename: Hasan
authors.initials: H
authors.lastname: Tunaz
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Park
authors.forename: Kemal
authors.initials: K
authors.lastname: Büyükgüzel
authors.forename: Jon C
authors.initials: JC
authors.lastname: Bedick
authors.forename: A R
authors.initials: AR
authors.lastname: Nor Aliza
authors.forename: David W
authors.initials: DW
authors.lastname: Stanley
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D015777:Eicosanoids / Q000096:biosynthesis / Q000276:immunology*; D006434:Hemocytes / Q000201:enzymology / Q000378:metabolism; D006458:Hemolymph / Q000201:enzymology; D006868:Hydrolysis; D018402:Manduca / Q000201:enzymology* / Q000276:immunology* / Q000382:microbiology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016868:Serratia Infections / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D012706:Serratia marcescens; D013997:Time Factors
chemical_list: D015777:Eicosanoids; D010767:Phosphorylcholine; D016718:Arachidonic Acid; C068170:oleyloxyethylphosphorylcholine; D010741:Phospholipases A; D054467:Phospholipases A2