Environmental inhalation exposures are inherently mixed (
gases and particles), yet regulations are still based on single toxicant exposures. While the impacts of individual components of environmental pollution have received substantial attention, the impact of inhalation co-exposures is poorly understood. Here, we mechanistically investigated
pulmonary inflammation and lung function decline after inhalation co-exposure and individual exposures to
ozone (O3) and ultrafine
carbon black (CB). Environmentally/occupationally relevant lung deposition levels in mice were achieved after inhalation of stable
aerosols with similar aerodynamic and mass median distributions. X-ray photoemission spectroscopy detected increased surface
oxygen contents on particles in co-exposure
aerosols. Compared with individual exposures, co-exposure
aerosols produced greater acellular and cellular
oxidants detected by electron paramagnetic resonance (EPR) spectroscopy, and in vivo immune-spin trapping (IST), as well as synergistically increased lavage neutrophils, lavage
proteins and
inflammation related gene/
protein expression. Co-exposure induced a significantly greater respiratory function decline compared to individual exposure. A synthetic
catalase-
superoxide dismutase mimetic (EUK-134) significantly blunted
lung inflammation and respiratory function decline confirming the role of
oxidant imbalance. We identified a significant induction of epithelial
alarmin (
thymic stromal lymphopoietin-TSLP)-dependent
interleukin-13 pathway after co-exposure, associated with increased
mucin and
interferon gene expression. We provided evidence of interactive outcomes after air pollution constituent co-exposure and identified a key mechanistic pathway that can potentially explain epidemiological observation of lung function decline after an acute peak of air pollution. Developing and studying the co-exposure scenario in a standardized and controlled fashion will enable a better mechanistic understanding of how environmental exposures result in adverse outcomes.