Acute pulmonary response of mice to multi-wall carbon nanotubes.

Widespread use of carbon nanotubes is predicted for future and concerns have been raised about their potential health effects. The present study determined the pulmonary response of mice to multi-wall carbon nanotubes (MWCNTs). The MWCNT suspension in sterile phosphate-buffered saline (PBS) was introduced into mice lungs by oropharyngeal aspiration. Female C57Bl mice were treated with either 20 or 40 microg of MWCNTs in 40 microl PBS and control groups received equal volume of PBS. From each group, half of the mice were euthanized at day 1 and the remaining half at day 7 post treatment. Bronchoalveolar lavage (BAL) fluids, serum, and lung tissue samples were analyzed for inflammatory and oxidative stress markers. The results showed significant cellular influx by a single exposure to MWCNTs. Yields of total cells and the number of polymorphonuclear leukocytes in BAL cells were significantly elevated in MWCNT-treated mice post-treatment days 1 and 7. Analysis of cell-free BAL fluids showed significantly increased levels of total proteins, lactate dehydrogenase, tumor necrosis factor-alpha, interleukin-1beta, mucin, and surfactant protein-D (SP-D) in MWCNT-treated mice at day 1 post treatment. However, these biomarkers returned to basal levels by day 7 post exposure except mucin and SP-D. An increase in the urinary level of 8-hydroxy-2'-deoxyguanosine in mice treated with MWCNT suggested systemic oxidative stress. Western analysis of lung tissue showed decreased levels of extracellular superoxide dismutase (SOD) protein in MWCNT-treated mice but copper/zinc and manganese SOD remained unchanged. It is concluded that a single treatment of MWCNT is capable of inducing cytotoxic and inflammatory response in the lungs of mice.