An Acute Porcine Phosgene Pulmonary Injury Model: Potential Biomarkers and Drug Targets
Achanta, S; Jordt, SE; Foster, MW; Clair, GCD; Lin, V; Holmes, W
Published in: American Journal of Respiratory and Critical Care Medicine
Background: Phosgene is one of the highly produced industrial gases and is an essential intermediate in polymer, pharmaceutical, and metallurgy synthesis. However, phosgene is highly toxic when inhaled. Phosgene inhalation causes delayed onset of symptoms starting 8 hours post-inhalation. While symptoms are consistent with acute respiratory distress syndrome (ARDS), pulmonary edema is the pathognomonic symptom. Due to its high propensity for toxicity, it was deployed as a chemical warfare agent during World War I. Currently, there are no mechanistic-based antidotes for treating phosgene inhalation injuries. The treatment is mainly supportive and symptomatic. As the medical countermeasures are approved through the FDA's animal rule, there is a knowledge gap in non-rodent animal models that recapitulate human phosgene inhalation injuries and detailed proteomic changes that happen in the lungs after phosgene inhalation. Methods: Sedated domestic Yorkshire swine were exposed to phosgene (40 ppm for 20 minutes) through a nose cone. Animals were recovered from sedation and observed in their home pens frequently. Animals were re-sedated at 8 or 24 hours post-phosgene exposure. Oxygenation, respiratory physiological, and pulmonary function testing parameters were recorded. At the end of the study, animals were euthanized and lung tissues were collected. Lung tissues were processed for unbiased global proteomics using previously established mass spectrometry methods and multiplex protein array assays were also performed to identify potential drug biomarkers and targets. Results: Phosgene inhalation resulted in hypoxemia and worsening of respiratory physiological parameters such as decreased compliance dynamics, and elevated airway resistance and peak inspiratory pressure. Pulmonary function testing showed decreased tolerance to increasing concentrations of nebulized methacholine concentrations. Histopathology revealed neutrophilic alveolitis, hyaline membranes, and increased septal thickness in consistent with ARDS. Unbiased global proteomics studies in phosgene-exposed lung tissues revealed >8,000 protein groups with good precision and accuracy based on quality control pool samples and internal spike-in standards. Prominent among the differentially-expressed proteins were plasma-derived and acute-phase proteins, and TGFβ activation, which were increased upon phosgene exposure. Proteins that were significantly decreased include putative cilia-expressed proteins and collagen isoforms. Conclusions: We established an acute porcine model that recapitulates human phosgene inhalation injuries and that can be utilized for testing potential medical countermeasures. Differentially expressed proteome changes may serve as potential diagnostic biomarkers and drug targets. Additional studies are warranted to develop and study extended observation porcine phosgene models.
