Analysis of the reactive oxygen species sources involved in lung oxidative metabolism after acute exposure to ambient particulate matter

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

Londres

Congreso; 16th Biennial Meeting SFRRI; 2012

SFRRI

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 were also measured in isolated mitochondria. 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% increase in state 3 O2 consumption (control: 107 ± 4 ng-at O/min. mg prot. p<0.01), while no differences were found in state 4 respiration. No changes were found in H2O2 production. Regarding respiratory complexes, an increased complex II activity by 25% was observed (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. This work provides new insights to the understanding of the molecular mechanisms involving free radicals in lung oxidative damage due to exposition to ambient particles as ROFA.