title: Oxidative and nitrative modifications of enkephalins by human neutrophils: effect of nitroenkephalin on leukocyte functional responses.
abstract: Neutrophils play a major role in acute inflammation by generating reactive oxygen/nitrogen species. Opioid peptides, including enkephalins, are present at inflammation sites. Neutrophils contribute to protect against inflammatory pain by releasing opioid peptides. In this investigation, the ability of human polymorphonuclear cells to induce oxidative and nitrative modifications of Leu-enkephalin has been investigated in vitro. Activated human neutrophils mediate the oxidation of Leu-enkephalin resulting in the production of dienkephalin. In the presence of nitrite at concentrations observed during inflammatory and infectious process (10-50 μM), nitroenkephalin, a nitrated derivative of Leu-enkephalin, is additionally formed. The yield of nitroenkephalin increases with nitrite concentration and is significantly inhibited by the addition of catalase or 4-aminobenzoic acid hydrazide (ABAH), a specific inhibitor of peroxidases. These results suggest that neutrophils induce nitration of Leu-enkephalin by a mechanism that is dependent on myeloperoxidase activity and hydrogen peroxide. Oxidative/nitrative modifications of Leu-enkephalin have been also evidenced when cells were treated with the NO-donor molecule, DEANO. The nitrated enkephalin has been examined for its effect on leukocyte functional responses. The data reveal that nitroenkephalin at micromolar concentrations inhibits superoxide anion generation and degranulation of azurophilic granules of human polymorphonuclear cells. Moreover, nitroenkephalin inhibits spontaneous apoptosis of neutrophils, as evaluated by measuring caspase-3 activity. Collectively, our data indicate that the nitrated enkephalin attenuates neutrophil activation and promotes the short-term survival of these cells, suggesting a possible role of the nitrocompound in the efficiency and resolution of inflammatory processes.
authors: Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy.
authors: Elisabetta
authors: E
authors: Capuozzo
authors: Laura
authors: L
authors: Pecci
authors: Federica
authors: F
authors: Giovannitti
authors: Alessia
authors: A
authors: Baseggio Conrado
authors: Mario
authors: M
authors: Fontana
mesh_terms: D000704:Analysis of Variance; D017209:Apoptosis; D002478:Cells, Cultured; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D020536:Enzyme Activators / Q000494:pharmacology; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D018836:Inflammation Mediators / Q000494:pharmacology / Q000502:physiology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010084:Oxidation-Reduction; D026361:Reactive Nitrogen Species / Q000378:metabolism; D016897:Respiratory Burst; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D020536:Enzyme Activators; D006834:Hydrazines; D018836:Inflammation Mediators; D020030:Nitric Oxide Donors; D026361:Reactive Nitrogen Species; D013481:Superoxides; D004743:Enkephalin, Leucine; D009240:N-Formylmethionine Leucyl-Phenylalanine; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; D019255:NADPH Oxidases; D013755:Tetradecanoylphorbol Acetate