25 Using Advanced in Vitro Approaches to Elucidate the Differential Toxicity of Nitrogen Dioxide and Particulate Matter in Ambient Air Pollution

Abstract

Ambient nitrogen dioxide (NO2) and particulate matter (PM) concentrations are often found to be proportional, such that inhalation of one pollutant is expected to be accompanied by the inhalation of the other. Epidemiological evidence consistently demonstrates the health burdens associated with the inhalation of NO2 and PM, though has difficulty deciphering the inhalation hazard of either pollutant individually. Airway models can be exposed to NO2 and PM separately or as a co-exposure in vitro, allowing mechanisms of toxicity to be elucidated. Herein, NCI-H441 cells were exposed to either 780 ng/cm2 Printex 90 carbon black (CB) (a surrogate model of PM) using a VitroCell Cloud12, 5 ppm NO2 (within a modified Coy hypoxic cabinet) or a combination of NO2+CB over 24 hours. Cytotoxicity was not altered by NO2 or CB (trypan blue exclusion assay), however CB, and to a lesser extent CB+NO2 exposure resulted in a non-significant increase in membrane permeability (p>0.05). qPCR revealed no alterations in expression of superoxide dismutase 1 (SOD1) for any exposure condition. Both CB and NO2 exposures resulted in significantly increased IL6 and IL8 release (ELISA) (p<0.05), although co-exposure of the two pollutants did not augment the detected IL6 or IL8 levels. These data indicate NO2 and CB produce an inflammatory response in this model, though little evidence suggests that NO2 and CB act in an additive or synergistic manner via this pathway. Additional work remains ongoing to establish the mechanisms of toxicity utilising an anatomically relevant triple cell co-culture of the alveolar epithelial barrier.