Oxygen Metabolism in the Cardiorespiratory System After an Acute Exposure to Ni-doped Nanoparticules

MAGNANI, NATALIA; MARCHINI, TIMOTEO; VANASCO, VIRGINIA; GARCÉS, MARIANA; MEBERT, ANDREA; DESIMONE, MARTIN; DIAZ, LUIS; ALVAREZ, SILVIA; EVELSON, PABLO

Chascomús, Buenos Aires

Congreso; Fourth Latin American Meeting on Biological Inorganic Chemistry; 2014

Society of Biological Inorganic Chemistry

INTRODUCTION There is strong evidence that ambient air pollution particles currently present a serious risk to human health1. Several epidemiological studies have shown an association between airborne particulate matter (PM) and aggravation of respiratory and cardiovascular diseases2. Air pollution is comprised by a wide range of chemicals and solid particles. Transition metals, are frequent PM constituents and they could play a central role in cardiopulmonary diseases mechanisms initiated by the exposure to PM1. The mechanisms of PM-health effects are believed to involve inflammation and oxidative stress3. Nickel (Ni), through the ability to initiate Fenton-like reactions, could be one of the PM constituents able to trigger cardiopulmonary diseases mechanisms. The aim of this work was to analyse the cardiovascular physiopathological mechanisms observed after an acute exposure to Ni-doped silica nanoparticles (Ni-NP), pointing out the O2 metabolism, in order to clarifying the molecular mechanisms involved. EXPERIMENTAL METHODS Ni-NP were prepared using the Stöber method. The NP hydrodynamic diameter was measured using Dynamic light scattering (DLS), and the metal content was determined by Atomic absorption spectrometry. The size and shape of NP were evaluated by transmission electron microscope (TEM). Swiss mice were intranasally instilled with 50 µL of a Ni-NP suspension (0.01; 0.05; 0.1 and 1.0 mg Ni/kg body weight) delivered in a single dose. Control group was exposed to an empty NP suspension. Lung, heart and plasma samples were collected 1 hour after exposure. TBARS content. Phospholipids oxidative damage was evaluated as TBARS content by a fluorometric assay. Tissue O2 consumption. A high-resolution respirometry was used to measured tissue cubes O2 consumption rates. KCN (4 mM) was used as a mitochondrial cytochrome oxidase inhibitor. NADPH oxidase (Nox) activity. The Lucigenin-derived chemiluminescence method was used as an indirect measurement of Nox activity. GSH, GSSG levels. To quantify reduced (GSH) and oxidized (GSSG) glutathione levels, HPLC analysis was performed. The GSH/GSSG ratio was also calculated. Results were expressed as mean values ± standard error of the mean (SEM) and represent the mean of at least 6 independent experiments. Statistical significance was considered at p˂0.05. RESULTS AND DISCUSSION NP share comparable physicochemical properties with PM as size (Control: 170 ± 2 nm; Ni-NP: 200 ± 20 nm) and shape, which was observed by TEM. Cardiopulmonary injury after PM inhalations has been suggested to be triggered by local reactive O2 species production which, in turn, could be generated from chemicals coated on the particle surface. Moreover, O2-derived free radicals may also be generated by the interaction of particle pollutants and their components, with cellular enzymes and organelles4. Tissue damage was evaluated by phospholipid oxidation. Compared to control group, every Ni-NP group showed increased TBARS content in lung (42% 0.01 mg Ni; 38% 0.05 mg Ni; 51% 0.10 mg Ni; 33% 1.00 mg Ni/kg body weight) (p˂0.001); plasma TBARS content was observed increased only in the highest assayed dose (54%; control: 9.3 ± 0.5 µM) (p˂0.001) compared with control, while no differences were observed between groups in heart phospholid oxidation. PM exposure was observed to alter not only lung but also heart O2 metabolism5,6. After the exposure to every Ni-NP dose, a significant increase in lung tissue O2 consumption was observed (35% 0.01 mg Ni; 60% 0.05 mg Ni; 45% 0.10 mg Ni; 68% 1.00 mg Ni/kg body weight) (p˂0.0001) compared with control (310 ± 20 ng-at O/min. g tissue). Non-mitochondrial O2 consumption sources were also significantly increased for the three highest assayed concentrations (89%, 95%, and 150%, respectively). Regarding total heart O2 consumption rates were decreased in every Ni group compared with control (27% 0.01 mg Ni; 30% 0.05 mg Ni; 42% 0.10 mg Ni; 37% 1.00 mg Ni/kg body weight) (p˂0.0001). Environmental agents lead to an airway inflammatory response, which includes activation and increased alveolar macrophages, which produce reactive O2 species through the assembly and activation of the Nox complex5. Lung Nox showed similar increase activity after every Ni-NP dose exposure when compared with control values (40%; p˂0.001). The GSH/GSSG rate is use to assayed tissue redox status. Lung GSSG levels were increased only in the highest Ni dose assayed, while no differences were observed in GSH levels. Therefore the GSH/GSSG rate was increased in the 1.00 mg Ni/kg body weight group (p˂0.05). CONCLUSION The use of metal coated NP was a useful approach to evaluate the effect of the metal ions present in air particles, since they are exposed in a similar way than PM. The Ni relative contribution in cardiopulmonary O2 metabolism alterations appears to be an important area of study in inflammatory conditions, triggered by PM. These findings contribute to the understanding of the cardiopulmonary O2 metabolism alterations, where oxidative stress and inflammation may play a predominant role, in association with transition metals present in environmental PM. REFERENCES 1. Nel AE., Science (2005),308:804-806 2. Dominici F. et al., JAMA (2006),295: 1127-1134 3. Alvarez S, Evelson P. Front Biosci (2007),12:964-974 4. Magnani ND et al., Biochem Biophys Res Commun (2011),412(4):667-72 5. Magnani ND et al., Toxicol Appl Pharmacol (2013),270(1):31-38. 6. Marchini T et al., Biochim Biophys Acta (2013),1830(3):2545-52 ACKNOWLEDGMENTS The authors would like to thank the University of Buenos Aires (Grant no: B413); Agencia Nacional de Promoción Científica y Tecnológica (Grant no: PICT 1574), and Consejo Nacional de Investigaciones Científicas y Técnicas (Grant no: PIP 358) for providing financial support to this project.