Oxidant-induced epithelial alarmin pathway mediates lung inflammation and functional decline following ultrafine carbon and ozone inhalation co-exposure

Abstract

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.

Transcriptomics of single dose and repeated carbon black and ozone inhalation co-exposure highlight progressive pulmonary mitochondrial dysfunction

“…These clearly point towards a tissue level change rather than just infiltration of leukocytes. These findings of increased ROS production are in line with our recently published immuno spin-trapping data which also confirmed presence of oxidants in macrophages as well as epithelial cells in the lungs after similar exposure ([ 90 ]. NOX derived ROS play an important role in regulating NLRP3 inflammasome (reviewed in [ 81 ]).…”

“…Increase H 2 O 2 levels after single exposure point towards oxidant generation being an early event followed by mitochondrial damage. Taken together with our recently published results demonstrating a key role of oxidants in lung inflammation and lung function decline through production of thymic stromal lymphopoietin further consolidates the key role of enhanced ROS production in inflammatory responses after CB + O 3 co-exposure ([ 90 ]. It is plausible to hypothesize that this ROS production led to/amplify the mitochondrial damage response that was significantly greater after multiple exposures.…”

Redox imbalance in COVID-19 pathophysiology

“…EPR spectrometry was used to measure the oxidizing potential of human serum samples using the spin probe 1-hydroxy-3-carboxymethyl-2,2,5,5-tetramethyl-pyrrolidine (CMH) (Enzo Life Science) as described previously [ 44 , 45 ]. Briefly, 0.1 mL of serum was incubated with the EPR spin probe CMH (0.2 mM) or sodium ascorbate (1 mM) for 30 min at 37 °C.…”

Whole-body inhalation of nano-sized carbon black: a surrogate model of military burn pit exposure

“…The WVU iTOX Center is fully equipped and currently performing multiple studies with mixed exposure models. Recent published work from the Hussain laboratory at WVU utilizing the mixed exposure model comprising of ozone and CB demonstrate a significantly greater decline of lung function capacity after mixed exposure compared to individual exposures [17]. Mechanistically, an oxidant mediated epithelial alarmin pathway was validated as a signaling mechanism in this model.…”

“…Combined gases and solid particles create an aerosolized particle, forming a toxic delivery system. Pulmonary deposition of such toxicants initiates an inflammatory response characterized by oxidative stress, DNA damage, macrophage activation, autonomic stimulation, cell recruitment and chemokine production [14][15][16][17]. The result is production of "pulmonary shrapnel": cellular and biochemical products that spill out of the lung and into the systemic circulation, leading to a cascade of shortand long-term biologic effects [18,19].…”