Ativação do estresse oxidativo e da resposta antioxidante por ExoU de Pseudomonas aeruginosa

• Autor(a) principal: Cunha Junior, Luiz Gonzaga da
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/14358
• topic: Pseudomonas aeruginosa; ExoU; Oxidative stress; Pseudomonas aeruginosa; ExoU; Estresse oxidativo; Toxinas bacterianas; Estresse oxidativo; Pseudomonas aeruginosa; Antioxidantes; CNPQ::CIENCIAS BIOLOGICAS::MICROBIOLOGIA::MICROBIOLOGIA APLICADA

ExoU, a cytotoxin produced by the opportunistic pathogen Pseudomonas aeruginosa and translocated into the cytosol of host cells via a type III secretion system, is associated with severity of acute infections. In the present work, the effect of ExoU in the activation of oxidative stress and antioxidant response was evaluated in cultures of human respiratory epithelial cells infected with P. aeruginosa PA103 strain (producer of ExoU), or with its isogenic mutants, the ExoU-deficient PA103∆exoU or the exoU-depleted mutant complemented with an exoU gene with a site-specific mutation in the PLA2 catalytic site, PA103∆UT/S142A. Analysis of dosages of lipid hydroperoxides and isoprostanes, considered markers of oxidative stress, revealed that ExoU promoted an increase in their concentrations. It was also observed that ExoU stimulated the production of reactive oxygen species, nitric oxide and peroxynitrite in infected cells, as well as the expression of iNOS and eNOS, but not nNOS. Furthermore, ExoU was responsible for the increased activity of SOD1 and the reduced levels of GSH, but did not affect the activity of catalase or NQO1. In the in vivo model, the analysis of malondialdehyde, a byproduct of lipid peroxidation of membranes, showed increased production of this compound in the lungs of mice infected with the ExoU-producing strain compared to the lungs of mice infected with the mutant strain. Together, these results show that ExoU activates the production of reactive oxygen and nitrogen species, leading to lipid peroxidation and modulating the antioxidant defense system.