Lung oxygen metabolism after and acute exposure to ambient particles

MAGNANI, NATALIA; MARCHINI, TIMOTEO; TASAT, DEBORAH; ALVAREZ, SILVIA; EVELSON, PABLO

Sao Paulo

Congreso; Free Radicals Brazil 2011; 2011

SFRBM-South American Group

Reactive oxygen species are able to initiate molecular mechanisms leading to lung oxidative damage due to particulate matter exposure. The aim of this work was to study the O2 metabolism in mice lung after an acute exposure to ambient particles (ROFA) by intranasal instillation (1.00 mg/kg body). Oxygen consumption by tissue cubes was determined by a polarographic technique. As main sources of oxygen uptake, we assessed NADPH oxidase activity in homogenates, following the superoxide anion (O2.-) production and NADPH consumption, and mitochondrial O2 consumption. Respiratory complexes activity and H2O2 production were also measured in isolated mitochondria by spectrophotometric and fluorometric assays respectively. Measurements were made 1 h after instillation. ROFA exposure showed a 66% increased tissue O2 consumption (control: 225 ± 7 ng-at O/min. g tissue p<0.01). O2 uptake inhibition by KCN in ROFA group was found to be 45%, while for control group was 59%. NADPH oxidase activity showed similar increases through both assays, O2.- production (25%) (control: 0.72 ± 0.02 AU/mg prot. p<0.01), and NADPH consumption (32%) (control: 0.82 ± 0.09 nmol NADPH/min. mg prot. p<0.01) after particle instillation. After ROFA exposure, mitochondria showed a 33% increased in state 3 O2 consumption (control: 107 ± 4 ng-at O/min. mg prot. p<0.01), no differences in state 4, no significant differences in H2O2 production, and increased complex II activity by 25% (control: 14.1 ± 0.74 nmol /min. mg prot. p<0.01). Our data shows that increased tissue O2 consumption is caused by increased mitochondria O2 uptake, through a higher complex II activity, and an augmented NADPH oxidase activity, due to an inflammatory response.