Pulmonary toxicity following inhalation exposure to VX in anesthetized rats: Possible roles for compromised immunity and oxidative stress-induced lung injury

Abstract

The nerve agent VX is one of the most deadly threat agents available in weapons stockpiles for intentional release. While mostly considered a percutaneous toxicant, it can be fatal when aerosolized. The objective of this study was to investigate toxic responses in the lung up to two weeks following a single 10-minute exposure to inhaled VX. Anesthetized rats were exposed singly and only once to VX. The nebulization rate in this system was 0.2–0.3 ml per minute with the delivery of a consistent particle size of 2.1 µm. Following exposure, all rats were removed from the ventilator and allowed to recover in the glovebox for 10–15 minutes. Results showed that inhaled VX altered several respiratory parameters and caused increased lung resistance up to 6 h post-exposure (PE). There was a trending increase in SOD and xanthine oxidoreductase (XOR) activities, both of which are indicative of oxidative stress. Based on increased lung tissue p38 signaling, MAP kinase expression was activated after VX exposure. IL-6 expression was also increased at 6 h post-inhalation for the 31.6 mg/m³ exposed group. Innate survival response mechanisms in rats may be present due to increased lung tissue mRNA AChE expression 6 h after exposure. Immunohistochemistry showed reduced staining for surfactant D and increased expression of iNOS, indicating that the activation of ^•NO precursor pathways. Bronchoalveloar lavage fluid (BALF) results from 1 h to 2 weeks PE show that inflammatory cells are highly active as evidenced by the increased production of cytokines and chemokines. This is the first study linking VX-induced lung injury to a possible innate survival amplification of AChE and possibly compromised immune function. These results could supplement medical treatment strategies with regard to therapeutic approaches against VX inhalational challenge.

Keywords:

• VX nerve agent
• inhalation
• lung toxicity
• oxidative stress
• immunotoxicity

Acknowledgements

This study was supported by the Defense Threat Reduction Agency of the Department of Defense Agency project 3.F0009 07 RC C & CBM.RESP.01.10.RC.007. We would also like to thank Drs. Larry Mitcheltree and Tony Alves for their expertise in reading pathology and Dr. Robert Kan and Thuy Dao for their superb immunohistochemistry technical assistance. In addition, we would wish to express our gratitude for the expert technical assistance of Jennifer Collins, Ashley M. Rodriguez, Ms Brittany Benjamin, Jannitt Simmons, and Ms. Alicia Witriol. We would also wish to thank Mr. James Abraham for his graphical expertise on this project. We also thank Adriana M. Jones, Nathan A. Jones and Joshua M. Novak for their support.

Declaration of interest

The experimental protocol was approved by the Animal Care and Use Committee at the United States Army Medical Research Institute of Chemical Defense and all procedures were conducted in accordance with the principles stated in the Guide for the Care and Use of Laboratory Animals and the Animal Welfare Act of 1966 (P.L. 89-544), as amended. The views expressed in this manuscript are those of the author(s) and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.