Chemical Characterization of Urate Hydroperoxide, A Pro-oxidant Intermediate Generated by Urate Oxidation in Inflammatory and Photoinduced Processes

Autor(es)

Patricio, Eliziane S. ^[1] ; Prado, Fernanda M. ^[1] ; da Silva, Railmara P. ^[1] ; Carvalho, Larissa A. C. ^[1] ; Prates, Marcus V. C. ^[1] ; Dadamos, Tony ^[2] ; Bertotti, Mauro ^[2] ; Di Mascio, Paolo ^[1] ; Kettle, Anthony J. ^[3] ; Meotti, Flavia C. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Bioquim, Inst Quim, BR-05508000 Sao Paulo, SP - Brazil

^[2] Univ Sao Paulo, Dept Quim, Inst Quim, BR-05508000 Sao Paulo, SP - Brazil

^[3] Univ Otago, Dept Pathol, Ctr Free Radical Res, Christchurch 8140 - New Zealand

• Tipo de documento: Artigo Científico
• Fonte: Chemical Research in Toxicology; v. 28, n. 8, p. 1556-1566, AUG 2015.
• Citações Web of Science: 10

Resumo

Urate hydroperoxide is a strong oxidant generated by the combination of urate free radical and superoxide. The formation of urate hydroperoxide as an intermediate in urate oxidation is potentially responsible for the pro-oxidant effects of urate in inflammatory disorders, protein degradation, and food decomposition. To understand the molecular mechanisms that sustain the harmful effects of urate in inflammatory and oxidative stress related conditions, we report a detailed structural characterization and reactivity of urate hydroperoxide toward biomolecules. Urate hydroperoxide was synthesized by photo-oxidation and by a myeloperoxidase/hydrogen peroxide/superoxide system. Multiple reaction monitoring (MRM) and MS3 ion fragmentation revealed that urate hydroperoxide from both sources has the same chemical structure. Urate hydroperoxide has a maximum absorption at 308 nm, epsilon(308nm) = 6.54 +/- 0.38 x 10(3) M-1 cm(-1). This peroxide decays spontaneously with a rate constant of k = 2.80 +/- 0.18 x 10(-4) s(-1) and a half-life of 41 min at 22 degrees C. Urate hydropercodde undergoes electrochemical reduction at potential values less negative than -0.5 V (versus Ag/AgCl). When incubated with taurine, histidine, tryptophan, lysine, methionine, cysteine, or glutathione, urate hydroperwdde reacted only with methionine, cysteine, and glutathione. The oxidation of these molecules occurred by a two-electron mechanism, generating the alcohol, hydroxyisourate. No adduct between cysteine or glutathione and urate hydroperoxide was detected. The second-order rate constant for the oxidation of glutathione by urate hydroperoxide was 13.7 +/- 0.8 M-1 s(-1). In conclusion, the oxidation of sulfur-containing biomolecules by urate hydroperoxide is likely to be a mechanism by which the pro-oxidant and damaging effects of urate are mediated in inflammatory and photo-oxidizing processes. (AU)

• Processo FAPESP: 11/15297-3 - Efeito do hidroperóxido de urato sobre a via da proteína dissulfeto isomerase e enzima nadph oxidase (pdi-nox) em processos inflamatórios do sistema cardiovascular
• Beneficiário: Eliziane de Souza Patricio
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 11/18106-4 - Oxidação do ácido úrico pela enzima mieloperoxidase em processos inflamatórios e as implicações sobre o sistema cardiovascular
• Beneficiário: Flavia Carla Meotti
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 13/07937-8 - Redoxoma
• Beneficiário: Ohara Augusto
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs
• Processo FAPESP: 13/02195-3 - Análise dos mecanismos pró-inflamatórios do hidroperóxido de urato sobre células do sistema imune inato: estudo sobre a via dos inflamassomas e proteínas moduladas por controle redox
• Beneficiário: Larissa Anastacio da Costa Carvalho
• Modalidade de apoio: Bolsas no Brasil - Doutorado