A Chronic Longitudinal Characterization of Neurobehavioral and Neuropathological Cognitive Impairment in a Mouse Model of Gulf War Agent Exposure.

Zuchra Zakirova,Lauren Horne,Fiona Crawford,Laila Abdullah,Samira Hassan,Ghania Ait-Ghezala,Gogce Crynen,Venkatarajan Mathura

doi:10.3389/fnint.2015.00071

Abstract

Gulf War Illness (GWI) is a chronic multisymptom illness with a central nervous system component that includes memory impairment as well as neurological and musculoskeletal deficits. Previous studies have shown that in the First Persian Gulf War conflict (1990–1991) exposure to Gulf War (GW) agents, such as pyridostigmine bromide (PB) and permethrin (PER), were key contributors to the etiology of GWI. For this study, we used our previously established mouse model of GW agent exposure (10 days PB+PER) and undertook an extensive lifelong neurobehavioral characterization of the mice from 11 days to 22.5 months post exposure in order to address the persistence and chronicity of effects suffered by the current GWI patient population, 24 years post-exposure. Mice were evaluated using a battery of neurobehavioral testing paradigms, including Open Field Test (OFT), Elevated Plus Maze (EPM), Three Chamber Testing, Radial Arm Water Maze (RAWM), and Barnes Maze (BM) Test. We also carried out neuropathological analyses at 22.5 months post exposure to GW agents after the final behavioral testing. Our results demonstrate that PB+PER exposed mice exhibit neurobehavioral deficits beginning at the 13 months post exposure time point and continuing trends through the 22.5 month post exposure time point. Furthermore, neuropathological changes, including an increase in GFAP staining in the cerebral cortices of exposed mice, were noted 22.5 months post exposure. Thus, the persistent neuroinflammation evident in our model presents a platform with which to identify novel biological pathways, correlating with emergent outcomes that may be amenable to therapeutic targeting. Furthermore, in this work we confirmed our previous findings that GW agent exposure causes neuropathological changes, and have presented novel data which demonstrate increased disinhibition, and lack of social preference in PB+PER exposed mice at 13 months after exposure. We also extended upon our previous work to cover the lifespan of the laboratory mouse using a battery of neurobehavioral techniques.

Highlights

IntroductionIn a different study using isolated perfused porcine skin flaps, pyridostigmine bromide (PB) administration was shown to dampen the protective inflammatory response normally stimulated by topical exposure to either permethrin or DEET, by down-regulating the production of interleukin 8 and prostaglandin E2 (MonteiroRiviere et al, 2003; Binns et al, 2008)
While we agree that investigation into the effects of different doses of Gulf War (GW) agents in different preclinical models is critical in order to fully capture the heterogeneity of exposure and to recapitulate the clinical presentation seen in veterans with Gulf War Illness (GWI), the doses for pyridostigmine bromide (PB) and PER used in this study are approximately less than one fifth and less than half of the reported LD50 dose for mice, respectively (Williamson et al, 1989; Chaney et al, 2002)and are relevant to modeling GWI disease pathophysiology
Elevated Plus Maze (EPM) testing revealed that there were no differences between PB+PER exposed and control mice when examining cumulative distance traveled (F = 0.33, DF = 1, p = 0.57) and velocity (F = 0.34, DF = 1, p = 0.57; Figures 2G,H, respectively), indicating that these parameters were not influencing entry behavior

Summary

Introduction

In a different study using isolated perfused porcine skin flaps, PB administration was shown to dampen the protective inflammatory response normally stimulated by topical exposure to either permethrin or DEET, by down-regulating the production of interleukin 8 and prostaglandin E2 (MonteiroRiviere et al, 2003; Binns et al, 2008) Other chemicals such as depleted uranium, exposure to low levels of nerve gas agents including soman, sarin, and mustard gas, multiple vaccination regimes, as well as vaccinations against anthrax and botulinum, that may contribute to the etiology of GWI have been proposed (Mahan et al, 2005; Binns et al, 2008; Shoenfeld and Agmon-Levin, 2011; Brimfield, 2012; Speed et al, 2012; Haley and Tuite, 2013; Tuite and Haley, 2013). These agents were chosen as they are amenable for experimental animal modeling in a laboratory setting, with the plan to model acute exposures to GW agents and follow the consequences of these exposures chronically

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