title: Leukotriene B4 activates the NADPH oxidase in eosinophils by a pertussis toxin-sensitive mechanism that is largely independent of arachidonic acid mobilization.
abstract: Experiments were designed to investigate whether leukotriene (LTB4) receptors can couple directly to phospholipase A2 (PLA2) in guinea pig eosinophils and the role of endogenous arachidonic acid (AA) in LTB4-induced activation of the NADPH oxidase. LTB4 (EC50 approximately 16 nM) and AA (EC50 approximately 6 microM) generated hydrogen peroxide (H2O2) in a concentration-dependent manner and at an equivalent maximum rate (5-6 nmol/min/10(6) cells). LTB4 stimulated PLA2 over a similar concentration range that activated the NADPH oxidase, although kinetic studies revealed that the release of [3H]AA (t1/2 approximately 2 s) preceded H2O2 generation (t1/2 > 30 s). Pretreatment of eosinophils with pertussis toxin abolished the increase in inositol(1,4,5)trisphosphate mass, [Ca2+]c, [3H]AA release, and H2O2 generation evoked by LTB4. Qualitatively identical results were obtained in eosinophils in which phospholipase C (PLC) was desensitized by 4beta-phorbol 12,13-dibutyrate with the exception that [3H]AA release was largely unaffected. Additional studies performed with the protein kinase C inhibitor, Ro 31-8220, and under conditions in which Ca2+ mobilization was abolished, provided further evidence that LTB4 released [3H]AA independently of signal molecules derived from the hydrolysis of phosphatidylinositol(4,5)bisphosphate by PLC. Pretreatment of eosinophils with the PLA2 inhibitor, mepacrine, abolished LTB4-induced [3H]AA release at a concentration that inhibited H2O2 by only 36%. Collectively, the results of this study indicate that agonism of LTB4 receptors on guinea pig eosinophils mobilizes AA by a mechanism that does not involve the activation of PLC. In addition, although LTB4 effectively stimulated PLA2, a central role for AA in the activation of the NADPH oxidase was excluded.
authors.affiliation: Thoracic Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, London, United Kingdom.
authors.forename: M A
authors.initials: MA
authors.lastname: Lindsay
authors.forename: R S
authors.initials: RS
authors.lastname: Perkins
authors.forename: P J
authors.initials: PJ
authors.lastname: Barnes
authors.forename: M A
authors.initials: MA
authors.lastname: Giembycz
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004804:Eosinophils / Q000378:metabolism*; D006168:Guinea Pigs; D007975:Leukotriene B4 / Q000378:metabolism* / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism*; D037342:Pertussis Toxin; D018102:Receptors, Leukotriene B4 / Q000378:metabolism*; D015398:Signal Transduction; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D018102:Receptors, Leukotriene B4; D010566:Virulence Factors, Bordetella; D007975:Leukotriene B4; D016718:Arachidonic Acid; D019255:NADPH Oxidases; D037342:Pertussis Toxin