title: Reactive oxygen species mediate phorbol ester-stimulated cAMP response in human eosinophils.
abstract: Recently, we showed that phorbol 12-myristate 13-acetate (PMA) can cause a direct, PKC-dependent, stimulation of intracellular cAMP in human eosinophils. Since PMA also stimulates the release of reactive oxygen species in these cells, we have investigated whether reactive oxygen species are involved in the cAMP response. Provided eosinophils were incubated for <20 min at 37 degrees C before stimulation, PMA potently stimulated cAMP generation that surpassed that of histamine. Pre-treatment of the cells with the NADPH oxidase inhibitors, diphenyleneiodonium (DPI) and apocynin, strongly inhibited the cAMP production induced by PMA, but not that induced by histamine. This treatment also strongly inhibited the release of superoxide anions (O(2)(-)). The cAMP response was also inhibited by pre-treatment with the specific peroxide scavenger, ebselen, but not superoxide dismutase, or NG-nitro-l-arginine methyl ester (L-NAME), thus, suggesting the possible involvement of a peroxide rather than O(2)(-) or nitric oxide (NO). These results reveal a novel involvement of intracellular reactive oxygen species in protein kinase C (PKC)-dependent stimulation of cAMP production in human eosinophils.
authors.affiliation: Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Kuwait. ezeamuzie@hsc.edu.kw
authors.forename: Charles I
authors.initials: CI
authors.lastname: Ezeamuzie
authors.forename: Najla
authors.initials: N
authors.lastname: Taslim
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000111:Acetylcysteine / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D001393:Azoles / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004804:Eosinophils / Q000187:drug effects* / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D054833:Isoindoles; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009861:Onium Compounds / Q000494:pharmacology; D016566:Organoselenium Compounds / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000098:Acetophenones; D000975:Antioxidants; D001393:Azoles; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D054833:Isoindoles; D009861:Onium Compounds; D016566:Organoselenium Compounds; D016877:Oxidants; D017382:Reactive Oxygen Species; C042986:ebselen; C016658:phorbolol myristate acetate; C007517:diphenyleneiodonium; D006632:Histamine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; C056165:acetovanillone; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; D002374:Catalase; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D019255:NADPH Oxidases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D019331:NG-Nitroarginine Methyl Ester; D000111:Acetylcysteine