Airway Obstruction Due to Bronchial Vascular Injury after Sulfur Mustard Analog Inhalation

Department of Pediatrics, University of Colorado Health Sciences Center, Denver, USA.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 12/2010; 182(11):1352-61. DOI: 10.1164/rccm.200910-1618OC
Source: PubMed


Sulfur mustard (SM) is a frequently used chemical warfare agent, even in modern history. SM inhalation causes significant respiratory tract injury, with early complications due to airway obstructive bronchial casts, akin to those seen after smoke inhalation and in single-ventricle physiology. This process with SM is poorly understood because animal models are unavailable.
To develop a rat inhalation model for airway obstruction with the SM analog 2-chloroethyl ethyl sulfide (CEES), and to investigate the pathogenesis of bronchial cast formation.
Adult rats were exposed to 0, 5, or 7.5% CEES in ethanol via nose-only aerosol inhalation (15 min). Airway microdissection and confocal microscopy were used to assess cast formation (4 and 18 h after exposure). Bronchoalveolar lavage fluid (BALF) retrieval and intravascular dye injection were done to evaluate vascular permeability.
Bronchial casts, composed of abundant fibrin and lacking mucus, occluded dependent lobar bronchi within 18 hours of CEES exposure. BALF contained elevated concentrations of IgM, protein, and fibrin. Accumulation of fibrin-rich fluid in peribronchovascular regions (4 h) preceded cast formation. Monastral blue dye leakage identified bronchial vessels as the site of leakage.
After CEES inhalation, increased permeability from damaged bronchial vessels underlying damaged airway epithelium leads to the appearance of plasma proteins in both peribronchovascular regions and BALF. The subsequent formation of fibrin-rich casts within the airways then leads to airways obstruction, causing significant morbidity and mortality acutely after exposure.

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    • "To test this hypothesis, a TRPA1-expressing HEK293 cell line and the alkylating agent 2-chloroethyl- ethylsulfide (CEES) were used. The monoalkylating agent CEES was used as a well-established surrogate for SM (Veress et al. 2010), while proof-of-concept experiments using SM and lung epithelial cells were also conducted. "
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    ABSTRACT: The transient receptor potential ankyrin 1 (TRPA1) cation channel is expressed in different tissues including skin, lung and neuronal tissue. Recent reports identified TRPA1 as a sensor for noxious substances, implicating a functional role in the molecular toxicology. TRPA1 is activated by various potentially harmful electrophilic substances. The chemical warfare agent sulfur mustard (SM) is a highly reactive alkylating agent that binds to numerous biological targets. Although SM is known for almost 200 years, detailed knowledge about the pathophysiology resulting from exposure is lacking. A specific therapy is not available. In this study, we investigated whether the alkylating agent 2-chloroethyl-ethylsulfide (CEES, a model substance for SM-promoted effects) and SM are able to activate TRPA1 channels. CEES induced a marked increase in the intracellular calcium concentration ([Ca(2+)]i) in TRPA1-expressing but not in TRPA1-negative cells. The TRP-channel blocker AP18 diminished the CEES-induced calcium influx. HEK293 cells permanently expressing TRPA1 were more sensitive toward cytotoxic effects of CEES compared with wild-type cells. At low CEES concentrations, CEES-induced cytotoxicity was prevented by AP18. Proof-of-concept experiments using SM resulted in a pronounced increase in [Ca(2+)]i in HEK293-A1-E cells. Human A549 lung epithelial cells, which express TRPA1 endogenously, reacted with a transient calcium influx in response to CEES exposure. The CEES-dependent calcium response was diminished by AP18. In summary, our results demonstrate that alkylating agents are able to activate TRPA1. Inhibition of TRPA1 counteracted cellular toxicity and could thus represent a feasible approach to mitigate SM-induced cell damage.
    Full-text · Article · Nov 2014 · Archive für Toxikologie
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    • "The most common late complication of SM inhalation is respiratory tract injury. There are about 100,000 surviving victims who were exposed to chemical warfare agents in Iran, many with permanent pulmonary disabilities such as bronchiolitis obliterans.[234567] "
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    ABSTRACT: Statins have anti-inflammatory effects in patients with chronic obstructive pulmonary disease (COPD). This study designed to evaluate the effects of atorvastatin on serum highly sensitive C-reactive protein (hs-CRP) and pulmonary function in sulfur mustard exposed patients with COPD. Fifty patients with chronic obstructive pulmonary disease due to sulfur mustard and high serum hs-CRP entered in this study. Participants were randomized to receive 40 mg atorvastatin or placebo in a double-blind clinical trial. Forty-five patients completed the study (n = 23 atorvastatin and n = 22 placebo). Pulse oximetry (SpO2), pulmonary function test (PFT), and 6 min walk distance test (6MWD) was measured. COPD assessment test (CAT) and St. George's respiratory questionnaire (SGRQ) were also completed by patients at the beginning of trial and after 9 weeks of prescription of 40 mg/day atorvastatin or placebo. At fourth week, SpO2, PFT, and 6MWD were again measured. After 9 weeks serum hs-CRP was re-measured. There was no significant difference between atorvastatin and the placebo group in SpO2, FEV1, and 6MWD after fourth week (P = 0.79, P = 0.12, P = 0.12, respectively). The difference between baseline and ninth week was calculated for two groups of trial and control in term of serum hs-CRP, SpO2, FEV1, and 6MWD. Significant improvement was not observed between two groups in above mentioned variables (P = 0.35, P = 0.28, P = 0.94, P = 0.43, respectively). However, the quality of life was improved by administration of atorvastatin using the CAT score (P < 0.001) and SGRQ total score (P = 0.004). Atorvastatin does not alter serum hs-CRP and lung functions but may improve quality of life in SM-injured patients with COPD.
    Full-text · Article · Feb 2014 · Journal of research in medical sciences
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    • "As previously reported, CEES inhalation caused vascular leak into airways (Veress et al., 2010). We sought to determine if anticoagulant administration would increase such leak due to CEES injury. "
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    ABSTRACT: Unlabelled: Sulfur mustard (SM) inhalation causes airway injury, with enhanced vascular permeability, coagulation, and airway obstruction. The objective of this study was to determine whether recombinant tissue factor pathway inhibitor (TFPI) could inhibit this pathogenic sequence. Methods: Rats were exposed to the SM analog 2-chloroethyl ethyl sulfide (CEES) via nose-only aerosol inhalation. One hour later, TFPI (1.5mg/kg) in vehicle, or vehicle alone, was instilled into the trachea. Arterial O2 saturation was monitored using pulse oximetry. Twelve hours after exposure, animals were euthanized and bronchoalveolar lavage fluid (BALF) and plasma were analyzed for prothrombin, thrombin-antithrombin complex (TAT), active plasminogen activator inhibitor-1 (PAI-1) levels, and fluid fibrinolytic capacity. Lung steady-state PAI-1 mRNA was measured by RT-PCR analysis. Airway-capillary leak was estimated by BALF protein and IgM, and by pleural fluid measurement. In additional animals, airway cast formation was assessed by microdissection and immunohistochemical detection of airway fibrin. Results: Airway obstruction in the form of fibrin-containing casts was evident in central conducting airways of rats receiving CEES. TFPI decreased cast formation, and limited severe hypoxemia. Findings of reduced prothrombin consumption, and lower TAT complexes in BALF, demonstrated that TFPI acted to limit thrombin activation in airways. TFPI, however, did not appreciably affect CEES-induced airway protein leak, PAI-1 mRNA induction, or inhibition of the fibrinolytic activity present in airway surface liquid. Conclusions: Intratracheal administration of TFPI limits airway obstruction, improves gas exchange, and prevents mortality in rats with sulfur mustard-analog-induced acute lung injury.
    Full-text · Article · May 2013 · Toxicology and Applied Pharmacology
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