Efeitos da administração pulmonar de nanotubos de carbono em camundongos

Abstract

Carbon nanotubes (CNT) are carbon allotropes that belong to the fullerene family. Since their discovery in the 90s, applications for their usage in various fields including biology/medicine were proposed and their production notably increased. Due to their asbestos-like aspect, many questions about their safety have been raised but little information about their toxicity is available. So, the aim of this work is to study the possible toxic effects of carbon nanotubes in the lungs and to assess whether in vitro experiments can predict in vivo toxicity. For in vitro experiments, cell lineages that are present in the lungs were stimulated with single walled CNT (SWNT) 70% purity and multi walled CNT (MWNT) 95% purity in three different concentrations (1, 10 and 100 μg/mL) or with controls (negative, LPS or MSU) for 24hs. Our results showed that CNs induced production of ROS and RNS in RAW 264.7 cells measured by Griess reaction and DCFDA and DAF reduction. ELISA assay also showed that these nanomaterials could induce IL-1β but not TNFα release by THP-1 cells as well as IL-8 by A549 cells. For in vivo experiments, C57BL/6 mice were instilled intranasally with 50 μg of each compound to assess lung injury. These experiments also indicated that after only one instillation CNTs could persist in the lung for long periods, up to 30 days. BAL counts revealed that they could induce airway inflammation by the first day after instillation that was composed by a mixture of neutrophils and mononuclear cells and that this cell influx is stopped by the fifth day post instillation. At the same time, the SWNT induce neutrophil accumulation in the parenchyma meanwhile MWNT does not. ELISA assay revealed that SWNT could induce acute cytokine production in the lung parenchyma including TNFα, IL-1β, IL-6 and TGF- β1 and CCL2 and also collagen deposition, as measured by OH-proline assay. Solubilization of the CNTs with FBS improved macroscopic appearance and stability of the solutions and induced inflammation followed by fibrosis with high amount of cytokine production for both compounds. However, data is not reliable because FBS itself is able to induce persistent inflammation and cytokine production in the lungs. These results indicate that CNTs are able to interact with cells in the lungs of mice and cause inflammation and then fibrosis. Moreover, in vitro experiments do not seem to be reliable to predict lung toxicity and current effort is to standardize these in vitro experiments. Altogether, theses results indicate that CNTs are a potential inhaled biohazard for those who are directly exposed to them.