title: Discrete pathways for arachidonic acid release from tannin versus beta-glucan-stimulated rabbit alveolar macrophages.
abstract: Previously, we observed both tannin and beta-glucan to be agonists for arachidonic acid (AA) release from rabbit alveolar macrophages. Although tannin inhibited reincorporation of exogenous AA, beta-glucan had no apparent effect, suggesting separate signal transduction pathways leading to elevated AA levels. In this study alveolar macrophages were pretreated with the tyrosine phosphatase inhibitor sodium orthovanadate then stimulated with either condensed tannin or beta-glucan. Vanadate exerted opposing effects on AA release. Furthermore, vanadate reversed the ability of tannin to inhibit reacylation. Additional studies using the phospholipase A probe bis-BODIPY-C11-PC indicated that although the known phospholipase A2 activators, calcium ionophore A23187, insoluble immune complexes, and beta-glucan, generated an increase in fluorescence consistent with phospholipase A activation, tannin had no effect. These findings suggest the increase in free AA resulting from stimulation of macrophages by either tannin or beta-glucan is produced via two different mechanisms.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Foundation, Rochester, Minnesota 55905, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Kennedy
authors.forename: P J
authors.initials: PJ
authors.lastname: Bates
authors.forename: C L
authors.initials: CL
authors.lastname: Wheatley
authors.forename: M S
authors.initials: MS
authors.lastname: Rohrbach
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001992:Bronchoalveolar Lavage Fluid; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D005434:Flow Cytometry / Q000379:methods; D005456:Fluorescent Dyes; D005936:Glucans / Q000494:pharmacology*; D047348:Hydrolyzable Tannins / Q000494:pharmacology*; D007700:Kinetics; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000502:physiology*; D010713:Phosphatidylcholines; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D011817:Rabbits; D011865:Radioisotope Dilution Technique; D014638:Vanadates / Q000494:pharmacology
chemical_list: C095153:1,2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diazaindacene-3-dodecanoyl)-sn-glycero-3-phosphocholine; D002250:Carbon Radioisotopes; D005456:Fluorescent Dyes; D005936:Glucans; D047348:Hydrolyzable Tannins; D010713:Phosphatidylcholines; D016718:Arachidonic Acid; D014638:Vanadates; D010741:Phospholipases A; D054467:Phospholipases A2