Acetylcholinesterase inhibitor exposures as an initiating factor in the development of Gulf War Illness, a chronic neuroimmune disorder in deployed veterans

Drosophila melanogaster as a model organism for screening acetylcholinesterase reactivators

The widely used insecticide chlorpyrifos (CP) is known to inhibit acetylcholinesterase (AChE) activity attributed to result in various neurological disorders and acetylcholine-dependent organ functions including heart, skeletal muscle, lung, gastrointestinal tract, and central nervous systems. Enzyme reactivators, such as oximes, are known to restore AChE activity and mitigate adverse effects. The identification of compounds that reactivate AChE constitute agents with important therapeutic beneficial effects in cases of pesticide poisoning. However, the screening of novel drugs using traditional models may raise ethical concerns. This study aimed to investigate the potential of Drosophila melanogaster as a model organism for screening AChE reactivators, with a focus on organophosphate poisoning. The efficacy of several oximes, including pralidoxime, trimedoxime, obidoxime, methoxime, HI-6, K027, and K048, against CP-induced AChE activity inhibition in D. melanogaster was determined in silico, in vitro, and in vivo experiments. Molecular docking studies indicated a strong interaction between studied oximes and the active-site gorge of AChE. Data showed that selected oximes (100 μM) are effective in the reactivation of AChE inhibited by CP (10 μM) in vitro. Finally, in vivo investigations demonstrated that selected oximes, pralidoxime and K048 (1.5 ppm), reversed the locomotor deficits, inhibition of AChE activity as well as lowered the mortality rates induced by CP (0.75 ppm). Our findings contribute to utilization of D. melanogaster as a robust model for determination of actions of identified new AChE inhibitory agents with more effective therapeutic properties that those currently in use in the clinical practice in treatment of AChE associated disorders.

Endocrine-Disrupting Chemicals, Hypothalamic Inflammation and Reproductive Outcomes: A Review of the Literature

Endocrine-disrupting chemicals (EDCs) are environmental and industrial agents that interfere with hormonal functions. EDC exposure is linked to various endocrine diseases, especially in reproduction, although the mechanisms remain unclear and effects vary among individuals. Neuroinflammation, particularly hypothalamic inflammation, is an emerging research area with implications for endocrine-related diseases like obesity. The hypothalamus plays a crucial role in regulating reproduction, and its inflammation can adversely affect reproductive health. EDCs can cross the blood-brain barrier, potentially causing hypothalamic inflammation and disrupting the reproductive axis. This review examines the existing literature on EDC-mediated hypothalamic inflammation. Our findings suggest that exposure to 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD), polychlorinated biphenyl (PCB), tributyltin (TBT), phthalates, bisphenol A (BPA), and chlorpyrifos (CPF) in animals is linked to hypothalamic inflammation, specifically affecting the hypothalamic centers of the gonadotropic axis. To our knowledge, this is the first comprehensive review on this topic, indicating hypothalamic inflammation as a possible mediator between EDC exposure and reproductive dysfunction. Further human studies are needed to develop effective prevention and treatment strategies against EDC exposure.

Inflammation and olfactory loss are associated with at least 139 medical conditions

Olfactory loss accompanies at least 139 neurological, somatic, and congenital/hereditary conditions. This observation leads to the question of whether these associations are correlations or whether they are ever causal. Temporal precedence and prospective predictive power suggest that olfactory loss is causally implicated in many medical conditions. The causal relationship between olfaction with memory dysfunction deserves particular attention because this sensory system has the only direct projection to memory centers. Mechanisms that may underlie the connections between medical conditions and olfactory loss include inflammation as well as neuroanatomical and environmental factors, and all 139 of the medical conditions listed here are also associated with inflammation. Olfactory enrichment shows efficacy for both prevention and treatment, potentially mediated by decreasing inflammation.

FDA-approved cannabidiol [Epidiolex®] alleviates Gulf War Illness-linked cognitive and mood dysfunction, hyperalgesia, neuroinflammatory signaling, and declined neurogenesis

BACKGROUND

Chronic Gulf War Illness (GWI) is characterized by cognitive and mood impairments, as well as persistent neuroinflammation and oxidative stress. This study aimed to investigate the efficacy of Epidiolex®, a Food and Drug Administration (FDA)-approved cannabidiol (CBD), in improving brain function in a rat model of chronic GWI.

METHODS

Six months after exposure to low doses of GWI-related chemicals [pyridostigmine bromide, N,N-diethyl-meta-toluamide (DEET), and permethrin (PER)] along with moderate stress, rats with chronic GWI were administered either vehicle (VEH) or CBD (20 mg/kg, oral) for 16 weeks. Neurobehavioral tests were conducted on 11 weeks after treatment initiation to evaluate the performance of rats in tasks related to associative recognition memory, object location memory, pattern separation, and sucrose preference. The effect of CBD on hyperalgesia was also examined. The brain tissues were processed for immunohistochemical and molecular studies following behavioral tests.

RESULTS

GWI rats treated with VEH exhibited impairments in all cognitive tasks and anhedonia, whereas CBD-treated GWI rats showed improvements in all cognitive tasks and no anhedonia. Additionally, CBD treatment alleviated hyperalgesia in GWI rats. Analysis of hippocampal tissues from VEH-treated rats revealed astrocyte hypertrophy and increased percentages of activated microglia presenting NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) complexes as well as elevated levels of proteins involved in NLRP3 inflammasome activation and Janus kinase/signal transducers and activators of the transcription (JAK/STAT) signaling. Furthermore, there were increased concentrations of proinflammatory and oxidative stress markers along with decreased neurogenesis. In contrast, the hippocampus from CBD-treated GWI rats displayed reduced levels of proteins mediating the activation of NLRP3 inflammasomes and JAK/STAT signaling, normalized concentrations of proinflammatory cytokines and oxidative stress markers, and improved neurogenesis. Notably, CBD treatment did not alter the concentration of endogenous cannabinoid anandamide in the hippocampus.

CONCLUSIONS

The use of an FDA-approved CBD (Epidiolex®) has been shown to effectively alleviate cognitive and mood impairments as well as hyperalgesia associated with chronic GWI. Importantly, the improvements observed in rats with chronic GWI in this study were attributed to the ability of CBD to significantly suppress signaling pathways that perpetuate chronic neuroinflammation.

Crisis in the gut: navigating gastrointestinal challenges in Gulf War Illness with bioengineering

Gulf War Illness (GWI) is characterized by a wide range of symptoms that manifests largely as gastrointestinal symptoms. Among these gastrointestinal symptoms, motility disorders are highly prevalent, presenting as chronic constipation, stomach pain, indigestion, diarrhea, and other conditions that severely impact the quality of life of GWI veterans. However, despite a high prevalence of gastrointestinal impairments among these veterans, most research attention has focused on neurological disturbances. This perspective provides a comprehensive overview of current in vivo research advancements elucidating the underlying mechanisms contributing to gastrointestinal disorders in GWI. Generally, these in vivo and in vitro models propose that neuroinflammation alters gut motility and drives the gastrointestinal symptoms reported in GWI. Additionally, this perspective highlights the potential and challenges of in vitro bioengineering models, which could be a crucial contributor to understanding and treating the pathology of gastrointestinal related-GWI.

Recent advances in cholinergic mechanisms as reactions to toxicity, stress, and neuroimmune insults

This review presents recent studies of the chemical and molecular regulators of acetylcholine (ACh) signaling and the complexity of the small molecule and RNA regulators of those mechanisms that control cholinergic functioning in health and disease. The underlying structural, neurochemical, and transcriptomic concepts, including basic and translational research and clinical studies, shed new light on how these processes inter-change under acute states, age, sex, and COVID-19 infection; all of which modulate ACh-mediated processes and inflammation in women and men and under diverse stresses. The aspect of organophosphorus (OP) compound toxicity is discussed based on the view that despite numerous studies, acetylcholinesterase (AChE) is still a vulnerable target in OP poisoning because of a lack of efficient treatment and the limitations of oxime-assisted reactivation of inhibited AChE. The over-arching purpose of this review is thus to discuss mechanisms of cholinergic signaling dysfunction caused by OP pesticides, OP nerve agents, and anti-cholinergic medications; and to highlight new therapeutic strategies to combat both the acute and chronic effects of these chemicals on the cholinergic and neuroimmune systems. Furthermore, OP toxicity was examined in view of cholinesterase inhibition and beyond in order to highlight improved small molecules and RNA therapeutic strategies and assess their predicted pitfalls to reverse the acute toxicity and long-term deleterious effects of OPs.

Gulf war toxicant-induced effects on the hippocampal dendritic arbor are reversed by treatment with a Withania somnifera extract

Gulf War Illness (GWI) is a multi-symptom disorder that manifests with fatigue, sleep disturbances, mood-cognition pathologies, and musculoskeletal symptoms. GWI affects at least 25% of the military personnel that served in Operations Desert Shield and Desert Storm from 1990 to 1991. We modeled Gulf War toxicant exposure in C57BL/6J mice by combined exposure to pyridostigmine bromide (an anti-sarin drug), chlorpyrifos (an organophosphate insecticide), and DEET (an insect repellent) for 10 days followed by oral treatment with Withania somnifera root extract for 21 days beginning at 12 weeks post-exposure. W. somnifera, commonly referred to as ashwagandha, has been used in traditional Ayurvedic medicine for centuries to improve memory and reduce inflammation, and its roots contain bioactive molecules which share functional groups with modern pain, cancer, and anti-inflammatory drugs. Previously, we observed that GWI mice displayed chronic reductions in dendritic arbor and loss of spines in granule cells of the dentate gyrus of the hippocampus at 14 weeks post-exposure. Here, we examined the effects of treatment with W. somnifera root extract on chronic dendrite and spine morphology in dentate granule cells of the mouse hippocampus following Gulf War toxicant exposure. GWI mice showed approximately 25% decreases in dendritic length (p < 0.0001) and overall dendritic spine density with significant reductions in thin and mushroom spines. GWI mice treated with the Ayurvedic W. somnifera extract exhibited dendritic lengths and spine densities near normal levels. These findings demonstrate the efficacy of the Ayurvedic treatment for neuroprotection following these toxic exposures. We hope that the extract and the neuronal processes influenced will open new avenues of research regarding treatment of Gulf War Illness and neurodegenerative disorders.

Military exposures and Gulf War illness in veterans with and without posttraumatic stress disorder

Gulf War illness (GWI) is a chronic multisymptom disorder of unknown etiology that is believed to be caused by neurotoxicant exposure experienced during deployment to the Gulf War. Posttraumatic stress disorder (PTSD) covaries with GWI and is believed to play a role in GWI symptoms. The present study examined the association between self-reported military exposures and GWI, stratified by PTSD status, in veterans from the Gulf War Era Cohort and Biorepository who were deployed to the Persian Gulf during the war. Participants self-reported current GWI and PTSD symptoms as well as military exposures (e.g., pyridostigmine [PB] pills, pesticides/insecticides, combat, chemical attacks, and oil well fires) experienced during the Gulf War. Deployed veterans' (N = 921) GWI status was ascertained using the Centers for Disease Control and Prevention definition. Individuals who met the GWI criteria were stratified by PTSD status, yielding three groups: GWI-, GWI+/PTSD-, and GWI+/PTSD+. Multivariable logistic regression, adjusted for covariates, was used to examine associations between GWI/PTSD groups and military exposures. Apart from insect bait use, the GWI+/PTSD+ group had higher odds of reporting military exposures than the GWI+/PTSD- group, adjusted odds ratio (aOR) = 2.15, 95% CI [1.30, 3.56]-aOR = 6.91, 95% CI [3.39, 14.08]. Except for PB pills, the GWI+/PTSD- group had a higher likelihood of reporting military exposures than the GWI- group, aOR = 2.03, 95% CI [1.26, 3.26]-aOR = 4.01, 95% CI [1.57, 10.25]. These findings are consistent with roles for both PTSD and military exposures in the etiology of GWI.

Cognitive decrements in 1991 Gulf War veterans: associations with Gulf War illness and neurotoxicant exposures in the Boston Biorepository, Recruitment, and Integrative Network (BBRAIN) cohorts

BACKGROUND

During deployment, veterans of the 1991 Gulf War (GW) were exposed to multiple war-related toxicants. Roughly a third of these veterans continue to exhibit neurotoxicant induced symptoms of Gulf War Illness (GWI), a multi-faceted condition that includes fatigue, pain and cognitive decrements. When studied empirically, both deployed veterans with exposures and those who meet the criteria for GWI are more likely to show deficits in the area of neuropsychological functioning. Although studies have shown cognitive impairments in small sample sizes, it is necessary to revisit these findings with larger samples and newer cohorts to see if other areas of deficit emerge with more power to detect such differences. A group of researchers and clinicians with expertise in the area of GWI have identified common data elements (CDE) for use in research samples to compare data sets. At the same time, a subgroup of researchers created a new repository to share these cognitive data and biospecimens within the GWI research community.

METHODS

The present study aimed to compare cognitive measures of attention, executive functioning, and verbal memory in a large sample of GWI cases and healthy GW veteran controls using neuropsychological tests recommended in the CDEs. We additionally subdivided samples based on the specific neurotoxicant exposures related to cognitive deficits and compared exposed versus non-exposed veterans regardless of case criteria status. The total sample utilized cognitive testing outcomes from the newly collated Boston, Biorepository, Recruitment, and Integrative Network (BBRAIN) for GWI.

RESULTS

Participants included 411 GW veterans, 312 GWI (cases) and 99 healthy veterans (controls). Veterans with GWI showed significantly poorer attention, executive functioning, learning, and short-and-long term verbal memory than those without GWI. Further, GW veterans with exposures to acetylcholinesterase inhibiting pesticides and nerve gas agents, had worse performance on executive function tasks. Veterans with exposure to oil well fires had worse performance on verbal memory and those with pyridostigmine bromide anti-nerve gas pill exposures had better verbal memory and worse performance on an attention task compared to unexposed veterans.

CONCLUSIONS

This study replicates prior results regarding the utility of the currently recommended CDEs in determining impairments in cognitive functioning in veterans with GWI in a new widely-available repository cohort and provides further evidence of cognitive decrements in GW veterans related to war-related neurotoxicant exposures.

Chemical exposures and suspected impact on Gulf War Veterans

Gulf War Illness (GWI) encompass a spectrum of maladies specific to troops deployed during the Persian Gulf War (1990-1991). There are several hypothesized factors believed to contribute to GWI, including (but not limited to) exposures to chemical agents and a foreign environment (e.g., dust, pollens, insects, and microbes). Moreover, the inherent stress associated with deployment and combat has been associated with GWI. While the etiology of GWI remains uncertain, several studies have provided strong evidence that chemical exposures, especially neurotoxicants, may be underlying factors for the development of GWI. This mini style perspective article will focus on some of the major evidence linking chemical exposures to GWI development and persistence decades after exposure.

Carbofuran pesticide toxicity to the eye

Pesticide exposure to eyes is a major source of ocular morbidities in adults and children all over the world. Carbofuran (CF), N-methyl carbamate, pesticide is most widely used as an insecticide, nematicide, and acaricide in agriculture, forestry, and gardening. Contact or ingestion of carbofuran causes high morbidity and mortality in humans and pets. Pesticides are absorbed in the eye faster than other organs of the body and damage ocular tissues very quickly. Carbofuran exposure to eye causes blurred vision, pain, loss of coordination, anti-cholinesterase activities, weakness, sweating, nausea and vomiting, abdominal pain, endocrine, reproductive, and cytotoxic effects in humans depending on amount and duration of exposure. Pesticide exposure to eye injures cornea, conjunctiva, lens, retina, and optic nerve and leads to abnormal ocular movement and vision impairment. Additionally, anticholinesterase pesticides like carbofuran are known to cause salivation, lacrimation, urination, and defecation (SLUD). Carbofuran and its two major metabolites (3-hydroxycarbofuran and 3-ketocarbofuran) are reversible inhibitors of acetylcholinesterase (AChE) which regulates acetylcholine (ACh), a neurohumoral chemical that plays an important role in corneal wound healing. The corneal epithelium contains high levels of ACh whose accumulation by AChE inhibition after CF exposure overstimulates muscarinic ACh receptors (mAChRs) and nicotinic ACh receptors (nAChRs). Hyper stimulation of mAChRs in the eye causes miosis (excessive constriction of the pupil), dacryorrhea (excessive flow of tears), or chromodacryorrhea (red tears). Recent studies reported alteration of autophagy mechanism in human cornea in vitro and ex vivo post carbofuran exposure. This review describes carbofuran toxicity to the eye with special emphasis on corneal morbidities and blindness.

Veteran-derived cerebral organoids display multifaceted pathological defects in studies on Gulf War Illness

Approximately 30% of the veterans who fought in the 1991 Gulf War (GW) suffer from a disease called Gulf War Illness (GWI), which encompasses a constellation of symptoms including cognitive deficits. A coalescence of evidence indicates that GWI was caused by low-level exposure to organophosphate pesticides and nerve agents in combination with physical stressors of the battlefield. Until recently, progress on mechanisms and therapy had been limited to rodent-based models. Using peripheral blood mononuclear cells from veterans with or without GWI, we recently developed a bank of human induced pluripotent stem cells that can be differentiated into a variety of cellular fates. With these cells, we have now generated cerebral organoids, which are three-dimensional multicellular structures that resemble the human brain. We established organoid cultures from two GW veterans, one with GWI and one without. Immunohistochemical analyses indicate that these organoids, when treated with a GW toxicant regimen consisting of the organophosphate diisopropyl fluorophosphate (a sarin analog) and cortisol (to mimic battlefield stress), display multiple indicators consistent with cognitive deficits, including increased astrocytic reactivity, enhanced phosphorylation of tau proteins, decreased microtubule stability, and impaired neurogenesis. Interestingly, some of these phenotypes were more pronounced in the organoids derived from the veteran with GWI, potentially reflecting a stronger response to the toxicants in some individuals compared to others. These results suggest that veteran-derived human cerebral organoids not only can be used as an innovative human model to uncover the cellular responses to GW toxicants but can also serve as a platform for developing personalized medicine approaches for the veterans.

Low glutamate diet improves working memory and contributes to altering BOLD response and functional connectivity within working memory networks in Gulf War Illness

Gulf War Illness is a chronic multi-symptom disorder with severe cognitive impairments which may be related to glutamate excitotoxicity and central nervous system dysfunction. The low glutamate diet has been proposed as a comprehensive intervention for Gulf War Illness. We examined the effects of the low glutamate diet on verbal working memory using a fMRI N-back task. Accuracy, whole-brain blood oxygen level dependency (BOLD) response, and task-based functional connectivity were assessed at baseline and after 1 month on the diet (N = 24). Multi-voxel pattern analysis identified regions of whole-brain BOLD pattern differences after the diet to be used as seeds for subsequent seed-to-voxel functional connectivity analyses. Verbal working memory accuracy improved after the diet (+ 13%; p = 0.006). Whole-brain BOLD signal changes were observed, revealing lower activation within regions of the frontoparietal network and default mode network after the low glutamate diet. Multi-voxel pattern analysis resulted in 3 clusters comprising parts of the frontoparietal network (clusters 1 and 2) and ventral attention network (cluster 3). The seed-to-voxel analyses identified significant functional connectivity changes post-diet for clusters 1 and 2 (peak p < 0.001, cluster FDR p < 0.05). Relative to baseline, clusters 1 and 2 had decreased functional connectivity with regions in the ventral attention and somatomotor networks. Cluster 2 also had increased functional connectivity with regions of the default mode and frontoparietal networks. These findings suggest that among veterans with Gulf War Illness, the low glutamate diet improves verbal working memory accuracy, alters BOLD response, and alters functional connectivity within two networks central to working memory.

Impact of gulf war toxic exposures after mild traumatic brain injury

Chemical and pharmaceutical exposures have been associated with the development of Gulf War Illness (GWI), but how these factors interact with the pathophysiology of traumatic brain injury (TBI) remains an area of study that has received little attention thus far. We studied the effects of pyridostigmine bromide (an anti-nerve agent) and permethrin (a pesticide) exposure in a mouse model of repetitive mild TBI (r-mTBI), with 5 impacts over a 9-day period, followed by Gulf War (GW) toxicant exposure for 10 days beginning 30 days after the last head injury. We then assessed the chronic behavioral and pathological sequelae 5 months after GW agent exposure. We observed that r-mTBI and GWI cumulatively affect the spatial memory of mice in the Barnes maze and result in a shift of search strategies employed by r-mTBI/GW exposed mice. GW exposure also produced anxiety-like behavior in sham animals, but r-mTBI produced disinhibition in both the vehicle and GW treated mice. Pathologically, GW exposure worsened r-mTBI dependent axonal degeneration and neuroinflammation, increased oligodendrocyte cell counts, and increased r-mTBI dependent phosphorylated tau, which was found to colocalize with oligodendrocytes in the corpus callosum. These results suggest that GW exposures may worsen TBI-related deficits. Veterans with a history of both GW chemical exposures as well as TBI may be at higher risk for worse symptoms and outcomes. Subsequent exposure to various toxic substances can influence the chronic nature of mTBI and should be considered as an etiological factor influencing mTBI recovery.

Evaluation of a Gene-Environment Interaction of PON1 and Low-Level Nerve Agent Exposure with Gulf War Illness: A Prevalence Case-Control Study Drawn from the U.S. Military Health Survey's National Population Sample

BACKGROUND

Consensus on the etiology of 1991 Gulf War illness (GWI) has been limited by lack of objective individual-level environmental exposure information and assumed recall bias.

OBJECTIVES

We investigated a prestated hypothesis of the association of GWI with a gene-environment (GxE) interaction of the paraoxonase-1 (PON1) Q192R polymorphism and low-level nerve agent exposure.

METHODS

A prevalence sample of 508 GWI cases and 508 nonpaired controls was drawn from the 8,020 participants in the U.S. Military Health Survey, a representative sample survey of military veterans who served during the Gulf War. The PON1 Q192R genotype was measured by real-time polymerase chain reaction (RT-PCR), and the serum Q and R isoenzyme activity levels were measured with PON1-specific substrates. Low-level nerve agent exposure was estimated by survey questions on having heard nerve agent alarms during deployment.

RESULTS

The GxE interaction of the Q192R genotype and hearing alarms was strongly associated with GWI on both the multiplicative [prevalence odds ratio (POR) of the interaction=3.41; 95% confidence interval (CI): 1.20, 9.72] and additive (synergy index=4.71; 95% CI: 1.82, 12.19) scales, adjusted for measured confounders. The Q192R genotype and the alarms variable were independent (adjusted POR in the controls=1.18; 95% CI: 0.81, 1.73; p=0.35), and the associations of GWI with the number of R alleles and quartiles of Q isoenzyme were monotonic. The adjusted relative excess risk due to interaction (aRERI) was 7.69 (95% CI: 2.71, 19.13). Substituting Q isoenzyme activity for the genotype in the analyses corroborated the findings. Sensitivity analyses suggested that recall bias had forced the estimate of the GxE interaction toward the null and that unmeasured confounding is unlikely to account for the findings. We found a GxE interaction involving the Q-correlated PON1 diazoxonase activity and a weak possible GxE involving the Khamisiyah plume model, but none involving the PON1 R isoenzyme activity, arylesterase activity, paraoxonase activity, butyrylcholinesterase genotypes or enzyme activity, or pyridostigmine.

DISCUSSION

Given gene-environment independence and monotonicity, the unconfounded aRERI>0 supports a mechanistic interaction. Together with the direct evidence of exposure to fallout from bombing of chemical weapon storage facilities and the extensive toxicologic evidence of biochemical protection from organophosphates by the Q isoenzyme, the findings provide strong evidence for an etiologic role of low-level nerve agent in GWI. https://doi.org/10.1289/EHP9009.

Brain-Specific Increase in Leukotriene Signaling Accompanies Chronic Neuroinflammation and Cognitive Impairment in a Model of Gulf War Illness

Persistent cognitive impairment is a primary central nervous system-related symptom in veterans afflicted with chronic Gulf War Illness (GWI). Previous studies in a rat model have revealed that cognitive dysfunction in chronic GWI is associated with neuroinflammation, typified by astrocyte hypertrophy, activated microglia, and enhanced proinflammatory cytokine levels. Studies in a mouse model of GWI have also shown upregulation of several phospholipids that serve as reservoirs of arachidonic acid, a precursor of leukotrienes (LTs). However, it is unknown whether altered LT signaling is a component of chronic neuroinflammatory conditions in GWI. Therefore, this study investigated changes in LT signaling in the brain of rats displaying significant cognitive impairments six months after exposure to GWI-related chemicals and moderate stress. The concentration of cysteinyl LTs (CysLTs), LTB4, and 5-Lipoxygenase (5-LOX), the synthesizing enzyme of LTs, were evaluated. CysLT and LTB4 concentrations were elevated in the hippocampus and the cerebral cortex, along with enhanced 5-LOX expression in neurons and microglia. Such changes were also associated with increased proinflammatory cytokine levels in the hippocampus and the cerebral cortex. Enhanced CysLT and LTB4 levels in the brain could also be gleaned from their concentrations in brain-derived extracellular vesicles in the circulating blood. The circulating blood in GWI rats displayed elevated proinflammatory cytokines with no alterations in CysLT and LTB4 concentrations. The results provide new evidence that a brain-specific increase in LT signaling is another adverse alteration that potentially contributes to the maintenance of chronic neuroinflammation in GWI. Therefore, drugs capable of modulating LT signaling may reduce neuroinflammation and improve cognitive function in GWI. Additional findings demonstrate that altered LT levels in the brain could be tracked efficiently by analyzing brain-derived EVs in the circulating blood.

Association of Gulf War Illness-Related Symptoms with Military Exposures among 1990-1991 Gulf War Veterans Evaluated at the War-Related Illness and Injury Study Center (WRIISC)

Veterans with difficult-to-diagnose conditions who receive care in the Department of Veterans Affairs (VA) healthcare system can be referred for evaluation at one of three specialty VA War-Related Illness and Injury Study Centers (WRIISC). Veterans of the 1990−1991 Gulf War have long experienced excess rates of chronic symptoms associated with the condition known as Gulf War Illness (GWI), with hundreds evaluated at the WRIISC. Here we provide the first report from a cohort of 608 Gulf War Veterans seen at the WRIISC who completed questionnaires on chronic symptoms (>6 months) consistent with GWI as well as prominent exposures during Gulf War deployment. These included veterans’ reports of hearing chemical alarms/donning Military-Ordered Protective Posture Level 4 (MOPP4) gear, pesticide use, and use of pyridostigmine bromide (PB) pills as prophylaxis against the effects of nerve agents. Overall, veterans in the cohort were highly symptomatic and reported a high degree of exposures. In multivariable models, these exposures were significantly associated with moderate-to-severe chronic symptoms in neurocognitive/mood, fatigue/sleep, and pain domains. Specifically, exposure to pesticides was associated with problems with concentration and memory, problems sleeping, unrefreshing sleep, and joint pain. Use of MOPP4 was associated with light sensitivity and unrefreshing sleep and use of PB was associated with depression. We also evaluated the association of exposures with symptom summary scores based on veterans’ severity of symptoms in four domains and overall. In multivariable modeling, the pain symptom severity score was significantly associated with pesticide use (Odds ratio (OR): 4.13, 95% confidence intervals (CI): 1.78−9.57) and taking PB pills (OR: 2.28, 95% CI: 1.02−5.09), and overall symptom severity was significantly associated with use of PB pills (OR: 2.41, 95% CI: 1.01−5.75). Conclusion: Decades after deployment, Gulf War veterans referred to a VA tertiary evaluation center report a high burden of chronic symptoms, many of which were associated with reported neurotoxicant exposures during the war.

Sex-specific differences in plasma lipid profiles are associated with Gulf War Illness

Background

Nearly 250,000 veterans from the 1990–1991 Gulf War have Gulf War Illness (GWI), a condition with heterogeneous pathobiology that remains difficult to diagnose. As such, availability of blood biomarkers that reflect the underlying biology of GWI would help clinicians provide appropriate care to ill veterans. In this study, we measured blood lipids to examine the influence of sex on the association between blood lipids and GWI diagnosis.

Methods

Plasma lipid extracts from GWI (n = 100) and control (n = 45) participants were subjected to reversed-phase nano-flow liquid chromatography-mass spectrometry analysis.

Results

An influence of sex and GWI case status on plasma neutral lipid and phospholipid species was observed. Among male participants, triglycerides, diglycerides, and phosphatidylcholines were increased while cholesterol esters were decreased in GWI cases compared to controls. In female participants, ceramides were increased in GWI cases compared to controls. Among male participants, unsaturated triglycerides, phosphatidylcholine and diglycerides were increased while unsaturated cholesterol esters were lower in GWI cases compared to controls. The ratio of arachidonic acid- to docosahexaenoic acid-containing triglyceride species was increased in female and male GWI cases as compared to their sex-matched controls.

Conclusion

Differential modulation of neutral lipids and ratios of arachidonic acid to docosahexaenoic acid in male veterans with GWI suggest metabolic dysfunction and inflammation. Increases in ceramides among female veterans with GWI also suggest activation of inflammatory pathways. Future research should characterize how these lipids and their associated pathways relate to GWI pathology to identify biomarkers of the disorder.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03272-3.

Gene-Toxicant Interactions in Gulf War Illness: Differential Effects of the PON1 Genotype

About 25-35% of United States veterans who fought in the 1990-1991 Gulf War report several moderate or severe chronic systemic symptoms, defined as Gulf War illness (GWI). Thirty years later, there is little consensus on the causes or biological underpinnings of GWI. The Gulf War Era Cohort and Biorepository (GWECB) was designed to investigate genetic and environmental associations with GWI and consists of 1343 veterans. We investigate candidate gene-toxicant interactions that may be associated with GWI based on prior associations found in human and animal model studies, focusing on SNPs in or near ACHE, BCHE, and PON1 genes to replicate results from prior studies. SOD1 was also considered as a candidate gene. CDC Severe GWI, the primary outcome, was observed in 26% of the 810 deployed veterans included in this study. The interaction between the candidate SNP rs662 and pyridostigmine bromide (PB) pills was found to be associated with CDC Severe GWI. Interactions between PB pill exposure and rs3917545, rs3917550, and rs2299255, all in high linkage disequilibrium in PON1, were also associated with respiratory symptoms. These SNPs could point toward biological pathways through which GWI may develop, which could lead to biomarkers to detect GWI or to better treatment options for veterans with GWI.

The β-adrenergic receptor blocker and anti-inflammatory drug propranolol mitigates brain cytokine expression in a long-term model of Gulf War Illness

Aims:

Growing evidence suggests that Gulf War Illness (GWI) is the result of underlying neuroimmune dysfunction. For example, previously we found that several GWI-relevant organophosphate acetylcholinesterase inhibitors produce heightened neuroinflammatory responses following subchronic exposure to stress hormone as a mimic of high physiological stress. The goal of the current study was to evaluate the potential for the β-adrenergic receptor inhibitor and anti-inflammatory drug, propranolol, to treat neuroinflammation in a novel long-term mouse model of GWI.

Main methods:

Adult male C57BL/6J mice received a subchronic exposure to corticosterone (CORT) at levels mimicking high physiological stress followed by exposure to the sarin surrogate, diisopropyl fluorophosphate (DFP). These mice were then re-exposed to CORT every other week for a total of five weeks, followed by a systemic immune challenge with lipopolysaccharide (LPS). Animals receiving the propranolol treatment were given a single dose (20 mg/kg, i.p.) either four or 11 days prior to the LPS challenge. The potential anti-neuroinflammatory effects of propranolol were interrogated by analysis of cytokine mRNA expression.

Key findings:

We found that our long-term GWI model produces a primed neuroinflammatory response to subsequent immune challenge that is dependent upon GWI-relevant organophosphate exposure. Propranolol treatment abrogated the elaboration of inflammatory cytokine mRNA expression in the brain instigated in our model, having no treatment effects in non-DFP exposed groups.

Significance:

Our results indicate that propranolol may be a promising therapy for GWI with the potential to treat the underlying neuroinflammation associated with the illness.

Boston biorepository, recruitment and integrative network (BBRAIN): A resource for the Gulf War Illness scientific community

AIMS

Gulf War Illness (GWI), a chronic debilitating disorder characterized by fatigue, joint pain, cognitive, gastrointestinal, respiratory, and skin problems, is currently diagnosed by self-reported symptoms. The Boston Biorepository, Recruitment, and Integrative Network (BBRAIN) is the collaborative effort of expert Gulf War Illness (GWI) researchers who are creating objective diagnostic and pathobiological markers and recommend common data elements for GWI research.

MAIN METHODS

BBRAIN is recruiting 300 GWI cases and 200 GW veteran controls for the prospective study. Key data and biological samples from prior GWI studies are being merged and combined into retrospective datasets. They will be made available for data mining by the BBRAIN network and the GWI research community. Prospective questionnaire data include general health and chronic symptoms, demographics, measures of pain, fatigue, medical conditions, deployment and exposure histories. Available repository biospecimens include blood, plasma, serum, saliva, stool, urine, human induced pluripotent stem cells and cerebrospinal fluid.

KEY FINDINGS

To date, multiple datasets have been merged and combined from 15 participating study sites. These data and samples have been collated and an online request form for repository requests as well as recommended common data elements have been created. Data and biospecimen sample requests are reviewed by the BBRAIN steering committee members for approval as they are received.

SIGNIFICANCE

The BBRAIN repository network serves as a much needed resource for GWI researchers to utilize for identification and validation of objective diagnostic and pathobiological markers of the illness.

The Department of Veterans Affairs Gulf War Veterans' Illnesses Biorepository: Supporting Research on Gulf War Veterans' Illnesses

AIMS

To introduce a resource supporting research on Gulf War illness (GWI) and related disorders, the Gulf War Veterans' Illnesses Biorepository (GWVIB).

METHODS

Gulf War era veterans (GWVs) are recruited nationally and enrolled via telephone and email/postal mail. Enrolled veterans receive annual telephone and mail follow-up to collect health data until their passing. A postmortem neuropathological examination is performed, and fixed and frozen brain and spinal cord samples are banked to support research. Investigators studying GWI and related disorders may request tissue and data from the GWVIB.

RESULTS

As of September 2021, 127 GWVs from 39 states were enrolled; 60 met the criteria for GWI, and 14 met the criteria for chronic multisymptom illness (CMI). Enrollees have been followed up to six years. Postmortem tissue recoveries were performed on 14 GWVs. The most commonly found neuropathologies included amyotrophic lateral sclerosis, chronic traumatic encephalopathy, and Lewy body disease. Tissue was of good quality with an average RNA integrity number of 5.8 (SD = 1.0) and ≥4.8 in all of the cases.

DISCUSSION

The availability of health data and high-quality CNS tissue from this well-characterized GWV cohort will support research on GWI and related disorders affecting GWVs. Enrollment is ongoing.

Brain-Immune Interactions as the Basis of Gulf War Illness: Clinical Assessment and Deployment Profile of 1990-1991 Gulf War Veterans in the Gulf War Illness Consortium (GWIC) Multisite Case-Control Study

The Boston University-based Gulf War Illness Consortium (GWIC) is a multidisciplinary initiative developed to provide detailed understanding of brain and immune alterations that underlie Gulf War illness (GWI), the persistent multisymptom disorder associated with military service in the 1990–1991 Gulf War. The core GWIC case-control clinical study conducted in-depth brain and immune evaluation of 269 Gulf War veterans (223 GWI cases, 46 controls) at three U.S. sites that included clinical assessments, brain imaging, neuropsychological testing, and analyses of a broad range of immune and immunogenetic parameters. GWI cases were similar to controls on most demographic, military, and deployment characteristics although on average were two years younger, with a higher proportion of enlisted personnel vs. officers. Results of physical evaluation and routine clinical lab tests were largely normal, with few differences between GWI cases and healthy controls. However, veterans with GWI scored significantly worse than controls on standardized assessments of general health, pain, fatigue, and sleep quality and had higher rates of diagnosed conditions that included hypertension, respiratory and sinus conditions, gastrointestinal conditions, and current or lifetime depression and post-traumatic stress disorder. Among multiple deployment experiences/exposures reported by veterans, multivariable logistic regression identified just two significant GWI risk factors: extended use of skin pesticides in theater (adjusted OR = 3.25, p = 0.005) and experiencing mild traumatic brain injury during deployment (OR = 7.39, p = 0.009). Gulf War experiences associated with intense stress or trauma (e.g., participation in ground combat) were not associated with GWI. Data and samples from the GWIC project are now stored in a repository for use by GWI researchers. Future reports will present detailed findings on brain structure and function, immune function, and association of neuroimmune measures with characteristics of GWI and Gulf War service.

Dysregulation of cellular energetics in Gulf War Illness

Gulf War Illness (GWI) is estimated to have affected about one third of the Veterans who participated in the first Persian Gulf War. The symptoms of GWI include chronic neurologic impairments, chronic fatigue syndrome, as well as fibromyalgia and immune system disorders, collectively referred to as chronic multi-symptom illness. Thirty years after the war, we still do not have an effective treatment for GWI. It is necessary to understand the molecular basis of the symptoms of GWI in order to develop appropriate therapeutic strategies. Cellular energetics are critical to the maintenance of cellular homeostasis, a process that is highly dependent on intact mitochondrial function and there is significant evidence from both human studies and animal models that mitochondrial impairments may lead to GWI symptoms. The available clinical and pre-clinical data suggest that agents that improve mitochondrial function have the potential to restore cellular energetics and treat GWI. To date, the experiments conducted in animal models of GWI have mainly focused on neurobehavioral aspects of the illness. Additional studies to address the fundamental biological processes that trigger the dysregulation of cellular energetics in GWI are warranted to better understand the underlying pathology and to develop new treatment methods. This review highlights studies related to mitochondrial dysfunction observed in both GW veterans and in animal models of GWI.

Radiation exposure and mitochondrial insufficiency in chronic fatigue and immune dysfunction syndrome

Chronic fatigue and Immune Dysfunction Syndrome (CFIDS) is a heterogeneous disease that may be promoted by various environmental stressors, including viral infection, toxin uptake, and ionizing radiation exposure. Previous studies have identified mitochondrial dysfunction in CFIDS patients, including modulation of mitochondrial respiratory chain activity, deletions in the mitochondrial genome, and upregulation of reactive oxygen species (ROS). This paper focuses on radiation effects and hypothesizes that CFIDS is primarily caused by stressor-induced mitochondrial metabolic insufficiency, which results in decreased energy production and anabolic metabolites required for normal cellular metabolism. Furthermore, tissues neighbouring or distant from directly perturbed tissues compensate for this dysfunction, which causes symptoms associated with CFIDS. This hypothesis is justified by reviewing the links between radiation exposure and CFIDS, cancer, immune dysfunction, and induction of oxidative stress. Moreover, the relevance of mitochondria in cellular responses to radiation and metabolism are discussed and putative mitochondrial biomarkers for CFIDS are introduced. Implications for diagnosis are then described, including a potential urine assay and PCR test for mitochondrial genome mutations. Finally, future research needs are offered with an emphasis on where rapid progress may be made to assist the afflicted.

Differential phosphoprotein signaling in the cortex in mouse models of Gulf War Illness using corticosterone and acetylcholinesterase inhibitors

Aims

Veterans from the 1990–91 Gulf War were exposed to acetylcholinesterase inhibitors (AChEIs), and, following service, an estimated one-third began suffering from a medically unexplained, multi-symptom illness termed Gulf War Illness (GWI). Previous research has developed validated rodent models that include exposure to exogenous corticosterone (CORT) and AChEIs to simulate high stress and chemical exposures encountered in theater. This combination of exposures in mice resulted in a marked increase in neuroinflammation, which is a common symptom of veterans suffering from GWI. To further elucidate the mechanisms associated with these mouse models of GWI, an investigation into intracellular responses in the cortex were performed to characterize the early cellular signaling changes associated with this exposure-initiated neuroinflammation.

Main methods

Adult male C57BL/6J mice were exposed to CORT in the drinking water (200 μg/mL) for 7 days followed by a single intraperitoneal injection of diisopropyl fluorophosphate (DFP; 4.0 mg/kg) or chlorpyrifos oxon (CPO; 8.0 mg/kg), on day 8 and euthanized 0.5, 2, and 24 h post-injection. Eleven post-translationally modified protein targets were measured using a multiplexed ELISA.

Key findings

Phosphoprotein responses were found to be exposure specific following AChEI insult, with and without CORT. Specifically, CORT + CPO exposure was found to sequentially activate several phosphoproteins involved in mitogen activated protein kinase signaling (p-MEK1/2, p-ERK1/2, and p-JNK). DFP alone similarly increased proteins in this pathway (p-RPS6, and p-JNK), but the addition of CORT ameliorated these affects.

Significance

The results of this study provide insight into differentially activated pathways depending on AChEI in these GWI models.

Epigenetic histone acetylation and Bdnf dysregulation in the hippocampus of rats exposed to repeated, low-dose diisopropylfluorophosphate

AIMS

Deployment-related exposures to organophosphate (OP) compounds are implicated for Gulf War Illness (GWI) development in First GW veterans. However, reasons for the persistence of GWI are not fully understood. Epigenetic modifications to chromatin are regulatory mechanisms that can adaptively or maladaptively respond to external stimuli. These include DNA methylation and histone acetylation. DNA methylation changes have been reported in GWI but the role of histone acetylation in GWI has been less explored, despite its importance as an epigenetic mechanism for neurological disorders.

MAIN METHODS

Male Sprague-Dawley rats were exposed to OP diisopropyl fluorophosphate (DFP, 0.5 mg/kg s.c., 5-d) and 6-m later brains were dissected for hippocampus. Western blotting, activity assays and chromatin immunoprecipitation (ChIP) were utilized for epigenetic analyses. Behavior was assessed using the Forced Swim Test (FST) and the Elevated Plus Maze (EPM).

KEY FINDINGS

We observed a significant upregulation in HDAC1 protein along with a significant increase in HDAC enzyme activity in the hippocampus of DFP rats. A locus-specific ChIP study revealed decreases in H3K9ac at the brain derived neurotrophic factor (Bdnf) promoter IV coupled with a significant decrease in BDNF protein in DFP rat hippocampus. Treatment with HDAC inhibitor valproic acid reduced HDAC activity and decreased the FST immobility time in DFP rats.

SIGNIFICANCE

Our research suggests that epigenetic alterations to histone acetylation pathways and decreased BDNF expression could represent novel mechanisms for GWI symptomatology and may provide new targets for developing effective drugs for GWI treatment.

A review of pre-clinical models for Gulf War Illness

Gulf War Illness (GWI) is a chronic multisymptomatic disorder that afflicts over 1/3rd of the 1991 GW veterans. It spans multiple bodily systems and presents itself as a syndrome exhibiting diverse symptoms including fatigue, depression, mood, and memory and concentration deficits, musculoskeletal pain and gastrointestinal distress in GW veterans. The etiology of GWI is complex and many factors, including chemical, physiological, and environmental stressors present in the GW arena, have been implicated for its development. It has been over 30 years since the end of the GW but, GWI has been persistent in suffering veterans who are also dealing with paucity of effective treatments. The multifactorial aspect of GWI along with genetic heterogeneity and lack of available data surrounding war-time exposures have proved to be challenging in developing pre-clinical models of GWI. Despite this, over a dozen GWI animal models exist in the literature. In this article, following a brief discussion of GW history, GWI definitions, and probable causes for its pathogenesis, we will expand upon various experimental models used in GWI laboratory research. These animal models will be discussed in the context of their attempts at mimicking GW-related exposures with regards to the variations in chemical combinations, doses, and frequency of exposures. We will discuss their advantages and limitations in modeling GWI followed by a discussion of behavioral and molecular findings in these models. The mechanistic data obtained from these preclinical studies have offered multiple molecular pathways including chronic inflammation, mitochondrial dysfunction, oxidative stress, lipid disturbances, calcium homeostatic alterations, changes in gut microbiota, and epigenetic modifications, amongst others for explaining GWI development and its persistence. Finally, these findings have also informed us on novel druggable targets in GWI. While, it has been difficult to conceive a single pre-clinical model that could express all the GWI signs and exhibit biological complexity reflective of the clinical presentation in GWI, animal models have been critical for identifying molecular underpinnings of GWI and evaluating treatment strategies for GWI.

Resolving whether inhalation of depleted uranium contributed to Gulf War Illness using high-sensitivity mass spectrometry

Of the hypothesized causes of Gulf War Illness (GWI), a chronic multi-symptom illness afflicting approximately 25% of military personnel deployed to the 1991 Gulf War, exposure to depleted uranium (DU) munitions has attracted international concern. Past research has not tested the potential association of GWI with inhaled DU nor used isotope mass spectrometry of sufficient sensitivity to rigorously assess prior DU exposure. We applied a standard biokinetic model to predict the urinary concentration and uranium isotopic ratios for a range of inhalation exposures. We then applied sensitive mass spectrometry capable of detecting the predicted urinary DU to 154 individuals of a population-representative sample of U.S. veterans in whom GWI had been determined by standard case definitions and DU inhalation exposures obtained by medical history. We found no difference in the ²³⁸U/²³⁵U ratio in veterans meeting the standard case definitions of GWI versus control veterans, no differences by levels of DU inhalation exposure, and no ²³⁶U associated with DU was detected. These findings show that even the highest likely levels of DU inhalation played no role in the development of GWI, leaving exposure to aerosolized organophosphate compounds (pesticides and sarin nerve agent) as the most likely cause(s) of GWI.

Sex-Based Differences in Plasma Autoantibodies to Central Nervous System Proteins in Gulf War Veterans versus Healthy and Symptomatic Controls

Veterans from the 1991 Gulf War (GW) have suffered from Gulf War illness (GWI) for nearly 30 years. This illness encompasses multiple body systems, including the central nervous system (CNS). Diagnosis and treatment of GWI is difficult because there has not been an objective diagnostic biomarker. Recently, we reported on a newly developed blood biomarker that discriminates GWI from GW healthy controls, and symptomatic controls with irritable bowel syndrome (IBS) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The present study was designed to compare levels of these biomarkers between men and women with GWI, as well as sex-specific effects in comparison to healthy GW veterans and symptomatic controls (IBS, ME/CFS). The results showed that men and women with GWI differ in 2 of 10 plasma autoantibodies, with men showing significantly elevated levels. Men and women with GWI showed significantly different levels of autoantibodies in 8 of 10 biomarkers to neuronal and glial proteins in plasma relative to controls. In summary, the present study addressed the utility of the use of plasma autoantibodies for CNS proteins to distinguish among both men and women veterans with GWI and other healthy and symptomatic control groups.

A role for neuroimmune signaling in a rat model of Gulf War Illness-related pain

More than a quarter of veterans of the 1990-1991 Persian Gulf War suffer from Gulf War Illness (GWI), a chronic, multi-symptom illness that commonly includes musculoskeletal pain. Exposure to a range of toxic chemicals, including sarin nerve agent, are a suspected root cause of GWI. Moreover, such chemical exposures induce a neuroinflammatory response in rodents, which has been linked to several GWI symptoms in rodents and veterans with GWI. To date, a neuroinflammatory basis for pain associated with GWI has not been investigated. Here, we evaluated development of nociceptive hypersensitivity in a model of GWI. Male Sprague Dawley rats were treated with corticosterone in the drinking water for 7 days, to mimic high physiological stress, followed by a single injection of the sarin nerve agent surrogate, diisopropyl fluorophosphate. These exposures alone were insufficient to induce allodynia. However, an additional sub-threshold challenge (a single intramuscular injection of pH 4 saline) induced long-lasting, bilateral allodynia. Such allodynia was associated with elevation of markers for activated microglia/macrophages (CD11b) and astrocytes/satellite glia (GFAP) in the lumbar dorsal spinal cord and dorsal root ganglia (DRG). Additionally, Toll-like receptor 4 (TLR4) mRNA was elevated in the lumbar dorsal spinal cord, while IL-1β and IL-6 were elevated in the lumbar dorsal spinal cord, DRG, and gastrocnemius muscle. Demonstrating a casual role for such neuroinflammatory signaling, allodynia was reversed by treatment with either minocycline, the TLR4 inhibitor (+)-naltrexone, or IL-10 plasmid DNA. Together, these results point to a role for neuroinflammation in male rats in the model of musculoskeletal pain related to GWI. Therapies that alleviate persistent immune dysregulation may be a strategy to treat pain and other symptoms of GWI.

Calcium Hypothesis of Gulf War Illness: Role of Calcium Ions in Neurological Morbidities in a DFP-Based Rat Model for Gulf War Illness

Gulf War Illness (GWI) refers to a multi-system disorder that afflicts approximately 30% of First Gulf War (GW) veterans. Amongst the symptoms exhibited, mood and memory impairment are commonly reported by GW veterans. Exposure to organophosphate (OP) compounds which target the cholinergic system is considered a leading cause for GWI symptoms. It is hypothesized that chronic OP-based war-time stimulation of cholinergic signaling led to recruitment of excitatory glutamatergic signaling and other downstream signaling cascades leading to neuronal injury, neuroinflammation, generation of reactive oxygen species, oxidative stress, and mitochondrial damage within the central nervous system. These findings have been observed in both experimental models and GWI veterans. In this context the role of calcium (Ca2+) signaling in GWI has come to the forefront. Here we present our Ca2+ hypothesis of GWI that suggests sustained neuronal Ca2+ elevations serve as a molecular trigger for pathological synaptic plasticity that has allowed for the persistence of GWI symptoms. Subsequently we discuss that therapeutic targeting of Ca2+ homeostatic mechanisms provides novel targets for effective treatment of GWI-related neurological signs in our rodent model.

Pyridostigmine bromide exposure creates chronic, underlying neuroimmune disruption in the gastrointestinal tract and brain that alters responses to palmitoylethanolamide in a mouse model of Gulf War Illness

Gulf War Illness (GWI) is a chronic multisymptom illness that includes gastrointestinal disorders. Although the exact etiology of GWI is unknown, exposure to the drug pyridostigmine bromide (PB) is considered a major factor. Exposure to PB drives enteric neuroinflammation, promotes immunosuppression, and alters physiological functions of the colon in the short term but whether exposure to PB is sufficient to promote long term dysfunction is not known. Here, we tested whether exposure to PB is sufficient to drive long term changes that reflect GWI, and whether the endogenous anti-inflammatory mediator palmitoylethanolamide (PEA) is sufficient to reduce the detrimental effects of PB in the gut and brain of mice. Exposure to PB alone was not sufficient to cause major changes in neuromuscular transmission but did drive major changes by altering the effects of PEA. Calcium imaging data show that the mechanisms responsible include a shift in receptor signaling mediated by TRPV1, endocannabinoids, and peroxisome proliferator-activated receptors alpha (PPARα). Additional mechanisms include the development of glial reactivity and changes in enteric neurochemical coding and survival. PB and PEA caused major shifts in pro-inflammatory cytokines/chemokines in the brain and colon that persisted up to 5 months following exposure. Many of the effects of PB and PEA exhibit significant sex differences. Together, these results highlight novel mechanisms whereby PB promotes long-lasting changes in nervous system and immune function by inducing occult neuroplasticity that is revealed by subsequent exposure to unrelated drugs in a sex dependent manner.

Gulf War Illness: Mechanisms Underlying Brain Dysfunction and Promising Therapeutic Strategies

Gulf War Illness (GWI), a chronic multisymptom health problem, afflicts ~30% of veterans served in the first GW. Impaired brain function is among the most significant symptoms of GWI, which is typified by persistent cognitive and mood impairments, concentration problems, headaches, chronic fatigue, and musculoskeletal pain. This review aims to discuss findings from animal prototypes and veterans with GWI on mechanisms underlying its pathophysiology and emerging therapeutic strategies for alleviating brain dysfunction in GWI. Animal model studies have linked brain impairments to incessantly elevated oxidative stress, chronic inflammation, inhibitory interneuron loss, altered lipid metabolism and peroxisomes, mitochondrial dysfunction, modified expression of genes relevant to cognitive function, and waned hippocampal neurogenesis. Furthermore, the involvement of systemic alterations such as the increased intensity of reactive oxygen species and proinflammatory cytokines in the blood, transformed gut microbiome, and activation of the adaptive immune response have received consideration. Investigations in veterans have suggested that brain dysfunction in GWI is linked to chronic activation of the executive control network, impaired functional connectivity, altered blood flow, persistent inflammation, and changes in miRNA levels. Lack of protective alleles from Class II HLA genes, the altered concentration of phospholipid species and proinflammatory factors in the circulating blood have also been suggested as other aiding factors. While some drugs or combination therapies have shown promise for alleviating symptoms in clinical trials, larger double-blind, placebo-controlled trials are needed to validate such findings. Based on improvements seen in animal models of GWI, several antioxidants and anti-inflammatory compounds are currently being tested in clinical trials. However, reliable blood biomarkers that facilitate an appropriate screening of veterans for brain pathology need to be discovered. A liquid biopsy approach involving analysis of brain-derived extracellular vesicles in the blood appears efficient for discerning the extent of neuropathology both before and during clinical trials.