Air pollution accounts for more than 7 million premature deaths worldwide. Using ultrafine carbon black (CB) and ozone (O3) as a model for an environmental co-exposure scenario, the dose response relationships in acute pulmonary injury and inflammation were determined by generating, characterizing, and comparing stable concentrations of CB aerosols (2.5, 5.0, 10.0mg/m3), O3 (0.5, 1.0, 2.0ppm) with mixture CB+O3 (2.5+0.5, 5.0+1.0, 10.0+2.0). C57BL6 male mice were exposed for 3hours by whole body inhalation and acute toxicity determined after 24h. CB itself did not cause any alteration, however, a dose response in pulmonary injury/inflammation was observed with O3 and CB+O3. This increase in response with mixtures was not dependent on the uptake but due to enhanced reactivity of the particles. Benchmark dose modeling showed several-fold increase in potency with CB+O3 compared to CB or O3 alone. Principal component analysis provided insight into response relationships between various doses and treatments. There was a significant correlation in lung responses with charge-based size distribution, total/alveolar deposition, oxidant generation and antioxidant depletion potential. Lung tissue gene/protein response demonstrated distinct patterns that are better predicted by either particle dose/aerosol responses (IL-1, KC, TGF-) or particle reactivity (TSLP, IL13, IL-6). Hierarchical clustering showed a distinct signature with high dose and a similarity in mRNA expression pattern of low and medium doses of CB+O3. In conclusion, we demonstrate that the biological outcomes from CB+O3 co-exposure are significantly greater than individual exposures over a range of aerosol concentrations and aerosol characteristics can predict biological outcome.

Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CB(ox)) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CB(ox) particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CB(ox) particles. Treatment with CB(ox) demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CB(ox)-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CB(ox) particles and established the role of macrophage-released chemical mediators in endothelial damage.

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 (O(3)) 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.

Pulmonary exposure to multi-walled carbon nanotubes (MWCNT) disrupts peripheral microvascular function. Thrombospondin-1 (TSP-1) is highly expressed during lung injury and has been shown to alter microvascular reactivity. It is unclear exactly how TSP-1 exerts effects on vascular function, but we hypothesized that the TSP-1 receptor CD47 may mediate changes in vasodilation.Wildtype (WT) or CD47 knockout (CD47 KO) C57B6/J-background animals were exposed to 50 microg of MWCNT or saline control via pharyngeal aspiration. Twenty-four hours post-exposure, intravital microscopy was performed to assess arteriolar dilation and venular leukocyte adhesion and rolling. To assess tissue redox status, electron paramagnetic resonance and NOx measurements were performed, while inflammatory biomarkers were measured via multiplex assay.Vasodilation was impaired in the WT+MWCNT group compared to control (57+/-9% vs 90+/-2% relaxation), while CD47 KO animals showed no impairment (108+/-8% relaxation). Venular leukocyte adhesion and rolling increased by > 2-fold, while the CD47 KO group showed no change. Application of the antioxidant apocynin rescued normal leukocyte activity in the WT+MWCNT group. Lung and plasma NOx were reduced in the WT+MWCNT group by 47% and 32%, respectively, while the CD47 KO groups were unchanged from control. Some inflammatory cytokines were increased in the CD47+MWCNT group only.In conclusion, TSP-1 is an important ligand mediating MWCNT-induced microvascular dysfunction, and CD47 is a component of this dysregulation. CD47 activation likely disrupts nitric oxide (*NO) signaling and promotes leukocyte-endothelial interactions. Impaired *NO production, signaling, and bioavailability is linked to a variety of cardiovascular diseases in which TSP-1/CD47 may play an important role.