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Title: Medical countermeasure against respiratory toxicity and acute lung injury following inhalation exposure to chemical warfare nerve agent VX

Abstract

To develop therapeutics against lung injury and respiratory toxicity following nerve agent VX exposure, we evaluated the protective efficacy of a number of potential pulmonary therapeutics. Guinea pigs were exposed to 27.03 mg/m{sup 3} of VX or saline using a microinstillation inhalation exposure technique for 4 min and then the toxicity was assessed. Exposure to this dose of VX resulted in a 24-h survival rate of 52%. There was a significant increase in bronchoalveolar lavage (BAL) protein, total cell number, and cell death. Surprisingly, direct pulmonary treatment with surfactant, liquivent, N-acetylcysteine, dexamethasone, or anti-sense syk oligonucleotides 2 min post-exposure did not significantly increase the survival rate of VX-exposed guinea pigs. Further blocking the nostrils, airway, and bronchioles, VX-induced viscous mucous secretions were exacerbated by these aerosolized treatments. To overcome these events, we developed a strategy to protect the animals by treatment with atropine. Atropine inhibits muscarinic stimulation and markedly reduces the copious airway secretion following nerve agent exposure. Indeed, post-exposure treatment with atropine methyl bromide, which does not cross the blood-brain barrier, resulted in 100% survival of VX-exposed animals. Bronchoalveolar lavage from VX-exposed and atropine-treated animals exhibited lower protein levels, cell number, and cell death compared to VX-exposed controls, indicatingmore » less lung injury. When pulmonary therapeutics were combined with atropine, significant protection to VX-exposure was observed. These results indicate that combinations of pulmonary therapeutics with atropine or drugs that inhibit mucous secretion are important for the treatment of respiratory toxicity and lung injury following VX exposure.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [3];  [4];  [2];  [3]
  1. Department of Biochemical Pharmacology/Division of Biochemistry, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910-7500 (United States) and Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814 (United States). E-mail: Madhusoodana.nambiar@na.amedd.army.mil
  2. Department of Biochemical Pharmacology/Division of Biochemistry, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910-7500 (United States)
  3. Medical Toxicology Branch /Analytical Toxicology Division, United States Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Edgewood, MD 21010-5400 (United States)
  4. Department of Pathology, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910-7500 (United States)
Publication Date:
OSTI Identifier:
20976879
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 219; Journal Issue: 2-3; Other Information: DOI: 10.1016/j.taap.2006.11.002; PII: S0041-008X(06)00413-3; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; APOPTOSIS; ATROPINE; BLOOD-BRAIN BARRIER; CENTRAL NERVOUS SYSTEM; CHEMICAL WARFARE; DEXAMETHASONE; ESTERS; FLUIDS; GUINEA PIGS; INHALATION; INJURIES; LAVAGE; LUNGS; METHYL BROMIDE; OLIGONUCLEOTIDES; PROTEINS; SECRETION; TOXICITY

Citation Formats

Nambiar, Madhusoodana P., Gordon, Richard K., Rezk, Peter E., Katos, Alexander M., Wajda, Nikolai A., Moran, Theodore S., Steele, Keith E., Doctor, Bhupendra P., and Sciuto, Alfred M. Medical countermeasure against respiratory toxicity and acute lung injury following inhalation exposure to chemical warfare nerve agent VX. United States: N. p., 2007. Web. doi:10.1016/j.taap.2006.11.002.
Nambiar, Madhusoodana P., Gordon, Richard K., Rezk, Peter E., Katos, Alexander M., Wajda, Nikolai A., Moran, Theodore S., Steele, Keith E., Doctor, Bhupendra P., & Sciuto, Alfred M. Medical countermeasure against respiratory toxicity and acute lung injury following inhalation exposure to chemical warfare nerve agent VX. United States. doi:10.1016/j.taap.2006.11.002.
Nambiar, Madhusoodana P., Gordon, Richard K., Rezk, Peter E., Katos, Alexander M., Wajda, Nikolai A., Moran, Theodore S., Steele, Keith E., Doctor, Bhupendra P., and Sciuto, Alfred M. Thu . "Medical countermeasure against respiratory toxicity and acute lung injury following inhalation exposure to chemical warfare nerve agent VX". United States. doi:10.1016/j.taap.2006.11.002.
@article{osti_20976879,
title = {Medical countermeasure against respiratory toxicity and acute lung injury following inhalation exposure to chemical warfare nerve agent VX},
author = {Nambiar, Madhusoodana P. and Gordon, Richard K. and Rezk, Peter E. and Katos, Alexander M. and Wajda, Nikolai A. and Moran, Theodore S. and Steele, Keith E. and Doctor, Bhupendra P. and Sciuto, Alfred M.},
abstractNote = {To develop therapeutics against lung injury and respiratory toxicity following nerve agent VX exposure, we evaluated the protective efficacy of a number of potential pulmonary therapeutics. Guinea pigs were exposed to 27.03 mg/m{sup 3} of VX or saline using a microinstillation inhalation exposure technique for 4 min and then the toxicity was assessed. Exposure to this dose of VX resulted in a 24-h survival rate of 52%. There was a significant increase in bronchoalveolar lavage (BAL) protein, total cell number, and cell death. Surprisingly, direct pulmonary treatment with surfactant, liquivent, N-acetylcysteine, dexamethasone, or anti-sense syk oligonucleotides 2 min post-exposure did not significantly increase the survival rate of VX-exposed guinea pigs. Further blocking the nostrils, airway, and bronchioles, VX-induced viscous mucous secretions were exacerbated by these aerosolized treatments. To overcome these events, we developed a strategy to protect the animals by treatment with atropine. Atropine inhibits muscarinic stimulation and markedly reduces the copious airway secretion following nerve agent exposure. Indeed, post-exposure treatment with atropine methyl bromide, which does not cross the blood-brain barrier, resulted in 100% survival of VX-exposed animals. Bronchoalveolar lavage from VX-exposed and atropine-treated animals exhibited lower protein levels, cell number, and cell death compared to VX-exposed controls, indicating less lung injury. When pulmonary therapeutics were combined with atropine, significant protection to VX-exposure was observed. These results indicate that combinations of pulmonary therapeutics with atropine or drugs that inhibit mucous secretion are important for the treatment of respiratory toxicity and lung injury following VX exposure.},
doi = {10.1016/j.taap.2006.11.002},
journal = {Toxicology and Applied Pharmacology},
number = 2-3,
volume = 219,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Respiratory toxicity and lung injury following inhalation exposure to chemical warfare nerve agent soman was examined in guinea pigs without therapeutics to improve survival. A microinstillation inhalation exposure technique that aerosolizes the agent in the trachea was used to administer soman to anesthetized age and weight matched male guinea pigs. Animals were exposed to 280, 561, 841, and 1121 mg/m{sup 3} concentrations of soman for 4 min. Survival data showed that all saline controls and animals exposed to 280 and 561 mg/m{sup 3} soman survived, while animals exposed to 841, and 1121 mg/m{sup 3} resulted in 38% and 13% survival,more » respectively. The microinstillation inhalation exposure LCt{sub 50} for soman determined by probit analysis was 827.2 mg/m{sup 3}. A majority of the animals that died at 1121 mg/m{sup 3} developed seizures and died within 15-30 min post-exposure. There was a dose-dependent decrease in pulse rate and blood oxygen saturation of animals exposed to soman at 5-6.5 min post-exposure. Body weight loss increased with the dose of soman exposure. Bronchoalveolar lavage (BAL) fluid and blood acetylcholinesterase and butyrylcholinesterase activity was inhibited dose-dependently in soman treated groups at 24 h. BAL cells showed a dose-dependent increase in cell death and total cell counts following soman exposure. Edema by wet/dry weight ratio of the accessory lung lobe and trachea was increased slightly in soman exposed animals. An increase in total bronchoalveolar lavage fluid protein was observed in soman exposed animals at all doses. Differential cell counts of BAL and blood showed an increase in total lymphocyte counts and percentage of neutrophils. These results indicate that microinstillation inhalation exposure to soman causes respiratory toxicity and acute lung injury in guinea pigs.« less
  • Acute exposure guideline levels (AEGLs) have been developed for the chemical warfare agents GB, GA, GD, GF, VX, and sulfur mustard. These AEGLs were approved by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances after Federal Register publication and comment, and judged as scientifically valid by the National Research Council Committee on Toxicology Subcommittee on AEGLs. AEGLs represent general public exposure limits for durations ranging from 10 min to 8 h, and for three levels of severity (AEGL-1, AEGL-2, AEGL-3). Mild effects are possible at concentrations greater than AEGL-1, while life-threatening effects are expected at concentrationsmore » greater than AEGL-3. AEGLs can be applied to various civilian and national defense purposes, including evacuation and shelter-in-place protocols, reentry levels, protective clothing specifications, and analytical monitoring requirements. This report documents development and derivation of AEGL values for six key chemical warfare agents, and makes recommendations for their application to various potential exposure scenarios.« less
  • The highly toxic organophosphorous compound VX [O-ethyl-S-(isoporopylaminoethyl) methyl phosphonothiolate] undergoes an incomplete decontamination by conventional chemicals and thus evaporates from urban surfaces, e.g., pavement, long after the initial insult. As a consequence to these characteristics of VX, even the expected low levels should be examined for their potential to induce functional impairments including those associated with neuronal changes. In the present study, we developed an animal model for subchronic, low-dose VX exposure and evaluated its effects in rats. Animals were exposed to VX (2.25 {mu}g/kg/day, 0.05 LD{sub 50}) for three months via implanted mini osmotic pumps. The rapidly attained continuousmore » and marked whole-blood cholinesterase inhibition ({approx} 60%), fully recovered 96 h post pump removal. Under these conditions, body weight, blood count and chemistry, water maze acquisition task, sensitivity to the muscarinic agonist oxotremorine, peripheral benzodiazepine receptors density and brain morphology as demonstrated by routine histopathology, remained unchanged. However, animals treated with VX showed abnormal initial response in an Open Field test and a reduction ({approx} 30%) in the expression of the exocytotic synaptobrevin/vesicle associate membrane protein (VAMP) in hippocampal neurons. These changes could not be detected one month following termination of exposure. Our findings indicate that following a subchronic, low-level exposure to the chemical warfare agent VX some important processes might be considerably impaired. Further research should be addressed towards better understanding of its potential health ramifications and in search of optimal countermeasures.« less
  • The nerve agents, GA, GB, and VX are organophosphorus esters that form a major portion of the total agent volume contained in the U.S. stockpile of unitary chemical munitions. Congress has mandated the destruction of these agents, which is currently slated for completion in 2004. The acute, chronic, and delayed toxicity of these agents is reviewed in this analysis. The largely negative results from studies of genotoxicity, carcinogenicity, developmental, and reproductive toxicity are also presented. Nerve agents show few or delayed effects. At supralethal doses, GB can cause delayed neuropathy in antidote-protected chickens, but there is not evidence that itmore » causes this syndrome in humans at any dose. Agent VX shows no potential for inducing delayed neuropathy in any species. In view of their lack of genotoxicity, the nerve agent exposure is the extraordinarily high acute toxicity of these substances. Futhermore, acute effects of moderate exposure such as nausea, diarrhea, inability to perform simple mental tasks, and respiratory effects may render the public unable to respond adequately to emergency instructions in the unlikely event of agent release, making early warning and exposure avoidance important. Likewise, exposure or self-contamination of first responders and medical personnel must be avoided. Control limits for exposure via surface contact of drinking water are needed, as are detection methods for low levels in water or foodstuffs. 187 refs., 3 figs., 7 tabs.« less