title: Nitroxides attenuate carrageenan-induced inflammation in rat paws by reducing neutrophil infiltration and the resulting myeloperoxidase-mediated damage.
abstract: Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) and other cyclic nitroxides have been shown to inhibit the chlorinating activity of myeloperoxidase (MPO) in vitro and in cells. To examine whether nitroxides inhibit MPO activity in vivo we selected acute carrageenan-induced inflammation on the rat paw as a model. Tempol and three more hydrophobic 4-substituted derivatives (4-azido, 4-benzenesulfonyl, and 4-(4-phenyl-1H-1,2,3-triazol-1-yl)) were synthesized, and their ability to inhibit the in vitro chlorinating activity of MPO and carrageenan-induced inflammation in rat paws was evaluated. All of the tested nitroxides inhibited the chlorinating activity of MPO in vitro with similar IC(50) values (between 1.5 and 1.8 μM). In vivo, the attenuation of carrageenan-induced inflammation showed some correlation with the lipophilicity of the nitroxide at early time points but the differences in the effects were small (<2-fold) compared with the differences in lipophilicity (>200-fold). No inhibition of MPO activity in vivo was evident because the levels of MPO activity in rat paws correlated with the levels of MPO protein. Likewise, paw edema, levels of nitrated and oxidized proteins, and levels of plasma exudation correlated with the levels of MPO protein in the paws of the animals that were untreated or treated with the nitroxides. The effects of the nitroxides in vivo were compared with those of 4-aminobenzoic hydrazide and of colchicine. Taken together, the results indicate that nitroxides attenuate carrageenan-induced inflammation mainly by reducing neutrophil migration and the resulting MPO-mediated damage. Accordingly, tempol was shown to inhibit rat neutrophil migration in vitro.
authors.affiliation: Departamento de Bioquímica and Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Raphael F
authors.initials: RF
authors.lastname: Queiroz
authors.forename: Alessandro K
authors.initials: AK
authors.lastname: Jordão
authors.forename: Anna C
authors.initials: AC
authors.lastname: Cunha
authors.forename: Vitor F
authors.initials: VF
authors.lastname: Ferreira
authors.forename: Maísa R P L
authors.initials: MR
authors.lastname: Brigagão
authors.forename: Alberto
authors.initials: A
authors.lastname: Malvezzi
authors.forename: Antonia T-do
authors.initials: AT
authors.lastname: Amaral
authors.forename: Ohara
authors.initials: O
authors.lastname: Augusto
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002351:Carrageenan; D002633:Chemotaxis / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004487:Edema / Q000139:chemically induced / Q000188:drug therapy; D054879:Halogenation / Q000187:drug effects; D007249:Inflammation / Q000139:chemically induced / Q000188:drug therapy*; D008297:Male; D020556:Neutrophil Infiltration / Q000187:drug effects* / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology; D009589:Nitrogen Oxides / Q000494:pharmacology*; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013113:Spin Labels
chemical_list: D000814:Aniline Compounds; D000975:Antioxidants; D003497:Cyclic N-Oxides; D009589:Nitrogen Oxides; D013113:Spin Labels; C034343:4-aminobenzhydrazide; D002351:Carrageenan; D009195:Peroxidase; C039900:nitroxyl; D003078:Colchicine; C001803:tempol