Fullerene Carbon Nanoparticles Inhibit Macrophage Response to a Viral Stimulus

Carbon nanoparticles are the natural product of combustion, therefore making it easy to encounter them on a daily basis.   Carbon nanoparticles are generated with various structures; fullerene and nanotubes are the most common with fullerenes being the more abundant species.  When inhaled, macrophages (MΦ) are the first line of defense they come across before they can enter the blood stream.  We hypothesized that MΦ ability to respond effectively to a viral mimic will be altered upon pre-treatment with black carbon (BC, fullerene) and multi-walled carbon nanotubes (MWCNT).  To test this, a murine MΦ cell line (RAW 264.7) and primary bone marrow-derived MΦs faced an acute pre-exposure to the nanoparticles.  Following a 24 hour treatment, the cells were re-treated with the carbon nanoparticles along with polyinosinic:polycytidylic acid (Poly: IC), a mimic for viral double stranded RNA . Cellular viability, levels of nitric oxide production and the amount of tumor necrosis alpha (TNFα) released by the cells were assessed. MWCNT pre-treatment showed no significant effects on MΦ responses.  BC pre-treatment caused a decrease in MΦ viability and significantly increased nitric oxide production in both primary and RAW cells when stimulated with Poly:IC.  The data demonstrates that effects of carbon nanoparticles on MΦ function is dependent on structure and that pre-exposure to these materials can detrimentally affect MΦ response to virus.  Thus, inhaling this carbon material poses a serious threat against our health as lung cells are unable to fend them off, making our bodies vulnerable to infections.