Exposure to multiwalled carbon nanotubes and allergen promotes early- and late-phase increases in airway resistance in mice.

The facilitating effects of multiwalled carbon nanotubes (MWCNT) on allergic asthma have not been sufficiently examined, although MWCNT appear to significantly increase the risk of health problems from occupational or environmental exposure. In this study, we examined whether sensitization by the combination of MWCNT with ovalbumin (OVA) promotes allergic asthmatic responses. BALB/c mice administered vehicle, MWCNT, OVA, or MWCNT+OVA through an intranasal route were challenged with OVA intratracheally four times. In the MWCNT+OVA group, the fourth challenge caused not only early- but also late-phase increases in airway resistance, although these responses were not observed in the vehicle, MWCNT, or OVA group; furthermore, the extents of the early and late responses were comparable to those in mice systemically sensitized with OVA+alum. Sensitization with MWCNT and OVA promoted airway inflammation and goblet cell hyperplasia in the lung compared with the vehicle, MWCNT or OVA group. In addition, adjuvant activity for OVA-specific immunoglobulin E (IgE), IgG1, and IgG2a production in serum and increased levels of interleukin-4 (IL-4), IL-5, IL-13, and IL-17 in the lung tissue were observed. In conclusion, these results suggest that exposure to MWCNT and antigen can induce a biphasic increase in airway resistance, airway inflammation, goblet cell hyperplasia, and the production of antigen-specific antibodies. This study highlights the risk of exposure to a combination of MWCNT with antigen.