Nerve agents are a class of organophosphorus compounds (OPs) that blocks communication between nerves and organs. Because of their acute neurotoxicity, it is extremely difficult to rescue the victims after exposure. Numerous efforts have been devoted to search for an effective prophylactic nerve agent bioscavenger to prevent the deleterious effects of these compounds. However, low scavenging efficiency, unfavorable pharmacokinetics, and immunological problems have hampered the development of effective drugs. Here, we report the development and testing of a nanoparticle-based nerve agent bioscavenger (nanoscavenger) that showed long-term protection against OP intoxication in rodents. The nanoscavenger, which catalytically breaks down toxic OP compounds, showed a good pharmacokinetic profile and negligible immune response in a rat model of OP intoxication. In vivo administration of the nanoscavenger before or after OP exposure in animal models demonstrated protective and therapeutic efficacy. In a guinea pig model, a single prophylactic administration of the nanoscavenger effectively prevented lethality after multiple sarin exposures over a 1-week period. Our results suggest that the prophylactic administration of the nanoscavenger might be effective in preventing the toxic effects of OP exposure in humans.
O-Isobutyl S-[2-(diethylamino)ethyl]methylphosphonothioate (VR) is a structural isomer of a more widely known chemical warfare agent O-ethyl S-[2(diisopropylamino)ethyl]methylphosphonothioate (VX). VR has the potential of being used as military threat/sabotage/terrorist agent. The development of a sound medical countermeasure will undoubtedly enhance not only our medical readiness and ability in VR casualty management, but also our defense posture against the deployment of VR in both combat and politically volatile environments. Acute exposure to a lethal dose of VR has been shown to cause cholinergic hyperfunction, incapacitation, seizures, convulsions, cardiorespiratory depression and death. In this study, pharmacological antagonism of VR-induced cardiorespiratory failure and lethality was investigated in guinea pigs chronically instrumented for concurrent recordings of electrocorticogram, diaphragmatic EMG, Lead II ECG, heart rate and neck skeletal muscle EMG. Thirty (30) min prior to intoxication with a 2 x LD50 dose of VR (22.6 micrograms/kg, s.c.), animals were pretreated with pyridostigmine (0.026 mg/kg, i.m.). Immediately after VR intoxication, animals were given pralidoxime chloride (2-PAM; 25 mg/kg, i.m.) and atropine sulfate (2, 8 or 16 mg/kg, i.m.). In animals that displayed seizures and convulsions, diazepam (5 mg/kg, i.m.) was administered 10 min following the onset of epileptiform activities. Responses to pretreatment/therapy modality were evaluated at 24 h post-VR. All animals survived the 2 x LD50 VR challenge. With the exception of an increased heart rate in response to atropine, the myocardial and diaphragmatic (respiratory) activity profiles appeared normal throughout the course of intoxication and recovery. Animals receiving 2 mg/kg atropine all developed fasciculations, seizures, signs of excessive mucoid/salivary secretion, and needed diazepam adjunct therapy. One-half (50%) of the animals receiving 8 mg/kg atropine developed seizure activities and were given diazepam, whereas the other half only showed a brief period of increase in CNS excitability. No fasciculations, seizures or convulsions were noted in animals receiving 16 mg/kg atropine. In summary, although lethality can be prevented with the pretreatment/therapy modality containing 2 mg/kg atropine and diazepam adjunct, a complete CNS and cardiorespiratory recovery from 2 x LD50 of VR requires a minimum of 8 mg/kg atropine.
Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of infomiation, including suggestions for reduang this burden to Department of Defense Washington Headquarters Services, Directorate for Infomiation Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington. VA 22202-4302 Respondents should be aware tdat notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply v^ith a collection of infomiation if it does not display a cunently valid OMB control number. PLEASE DO NOT RETURN YOUR FORIW TO THE ABOVE ADDRESS.
Miceand other small rodent animal models are known to have greater resistance tointoxication by the organophosphorus (OP) nerve agents sarin, soman, andcyclosarin than do humans and non‐human primates. This resistance has beendirectly attributed to the presence of carboxylesterase in the blood plasma of these animals. Carboxylesterase acts asan endogenous bioscavenger and is not found in the blood plasma of humans andnon‐human primates. To create an improved small animal model of nerve agentintoxication, the gene encoding serum carboxylesterase (Es1) in C57BL/6 mice was deleted to generate a transgenic strain of mice (Es1 KO) that no longer expresses this protein. In contrast with previousgenetic modification efforts to remove other endogenous bioscavenger enzymes frommice, the median lethal dose for several OP nerve agents in Es1 KO mice was significantly lower than that in wild type control mice. Physiological and behavioral characterizations of these mice have been conducted in an effort to determine their suitability as a small animal model for OP nerve agentintoxication.Removal of serum carboxylesterasere presents one piece of a gestalt in vivo model not only for predicting human OP nerve agent susceptibility but also for testing medical countermeasures for that intoxication. One of the primary molecular targets of many current and novel OP countermeasures isacetylcholinesterase (AChE), the enzyme which hydrolyzes the neurotransmitter acetylcholineto terminate nerve signaling. When the active site of this enzyme is covalently inhibited by OP nerve agents, the resulting cholinergic crisis can quickly result in death. Several countermeasures have been developed which act directly upon inhibited AChE to remove the OP nerve agent and restore enzyme activity. While AChE is found in all species, significant biochemical differences resulting from species‐specific amino acid variations have been observed in a variety of in vitro experiments. Efforts to quantify these differences using in vitro models have been undertaken in this study.Support or Funding Information*This research was supported in part by an appointment to the Postgraduate Research Participation Program at the U.S. Army Medical Research Institute of Chemical Defense administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the U. S. Army Medical Research and Materiel Command. 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 (National Research Council, 2011), and the Animal Welfare Act of 1966 (P.L. 89‐544), as amended. This research was supported by the Defense Threat Reduction Agency – Joint Science and Technology Office, Medical S&T Division. The views expressed in this abstract 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.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
There are many variables to consider when optimizing a polymerase chainreaction (PCR) assay for a specific gene—from methods of DNA extraction to choosing an effective combination of primers. A multiplex PCR assay analyzing two genes in the same reaction may require additional optimization. The objective of this experiment was to optimize a single PCR assay to effectively genotype C57BL/6 transgenic mouse strains in which two genes have been modified. By removing a portion of the Es1 gene, the expression of serum carboxylesterase was interrupted, resulting in serum carboxylesterase knock out (Es1 KO) mice. In another location, the gene expressing mouse acetylcholinesterase was replaced by a gene expressing human acetylcholinesterase, resulting in a human acetylcholinesterase knock in (AChEKI) mouse strain. There are several possible genotypes for each mouse strain: for Es1 KO mice the possibilities are wild type (WT +/+), knock out (KO −/−), or heterozygous (Het +/−), and for AChEKI mice the possibilities are human (H/H), mouse (M/M), or heterozygous (M/H). Optimization of the PCR genotyping assays for these strains was achieved by altering the method of DNA extraction, annealing temperatures, and testing multiple primer sets. Initially, DNA was extracted from mouse fecal matter, but this method was later determined to produce unreliable results in the subsequent PCR assays. DNA extracted from tail tissue was found to be much more reliable. Utilizing tail tissue DNA, a single pair of primers was found that could differentiate WT, KO, and Het alleles in the Es1 KO strain. The optimal annealing temperature for these primers was determined using a temperature gradient experiment. Primers for genotyping the AChE KI strain were selected and optimized in a similar manner. Finally, a multiplex PCR assay was developed allowing for the simultaneous determination of the genotype of both genes in mice.Support or Funding Information*This research was supported in part by an appointment to the Postgraduate Research Participation Program at the U.S. Army Medical Research Institute of Chemical Defense administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the U. S. Army Medical Research and Materiel Command.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 (National Research Council, 2011), and the Animal Welfare Act of 1966 (P.L. 89‐544), as amended.Threat Reduction Agency – Joint Science and Technology Office, Medical S&T Division.The views expressed in this abstract 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.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.