Gulf War Illness-associated increases in blood levels of interleukin 6 and C-reactive protein: biomarker evidence of inflammation

Exposure to Gulf war illness-related chemicals exacerbates alcohol-induced liver damage in rodents

Gulf War Illness (GWI) describes a series of symptoms suffered by veterans of the Gulf war, consisting of cognitive, neurological and gastrointestinal dysfunctions. Two chemicals associated with GWI are the insecticide permethrin (PER) and the nerve gas prophylactic pyridostigmine-bromide (PB). In this study we assessed the effects of PER and PB exposure on the pathology and subsequent alcohol (EtOH)-induced liver injury, and the influence of a macrophage depletor, PLX3397, on EtOH-induced liver damage in PER/PB-treated mice. Male C57BL/6 mice were injected daily with vehicle or PER/PB for 10 days, followed by 4 months recovery, then treatment with PLX3397 and a chronic-plus-single-binge EtOH challenge for 10 days. PER/PB exposure resulted in the protracted increase in liver transaminases in the serum and induced chronic low-level microvesicular steatosis and inflammation in GWI vs Naïve mice up to 4 months after cessation of exposure. Furthermore, prior exposure to PER/PB also resulted in exacerbated response to EtOH-induced liver injury, with enhanced steatosis, ductular reaction and fibrosis. The enhanced EtOH-induced liver damage in GWI-mice was attenuated by strategies designed to deplete macrophages in the liver. Taken together, these data suggest that exposure to GWI-related chemicals may alter the liver's response to subsequent ethanol exposure.

Exposing the latent phenotype of Gulf War Illness: examination of the mechanistic mediators of cognitive dysfunction

Though it has been over 30 years since the 1990-1991 Gulf War (GW), the pathophysiology of Gulf War Illness (GWI), the complex, progressive illness affecting approximately 30% of GW Veterans, has not been fully characterized. While the symptomology of GWI is broad, many symptoms can be attributed to immune and endocrine dysfunction as these critical responses appear to be dysregulated in many GWI patients. Since such dysregulation emerges in response to immune threats or stressful situations, it is unsurprising that clinical studies suggest that GWI may present with a latent phenotype. This is most often observed in studies that include an exercise challenge during which many GWI patients experience an exacerbation of symptoms. Unfortunately, very few preclinical studies include such physiological stressors when assessing their experimental models of GWI, which creates variable results that hinder the elucidation of the mechanisms mediating GWI. Thus, the purpose of this review is to highlight the clinical and preclinical findings that investigate the inflammatory component of GWI and support the concept that GWI may be characterized as having a latent phenotype. We will mainly focus on studies assessing the progressive cognitive impairments associated with GWI and emphasize the need for physiological stressors in future work to create a more unified hypothesis that can identify potential therapeutics for this patient population.

A Double-Humanized Mouse Model for Studying Host Gut Microbiome-Immune Interactions in Gulf War Illness

Unraveling the multisymptomatic Gulf War Illness (GWI) pathology and finding an effective cure have eluded researchers for decades. The chronic symptom persistence and limitations for studying the etiologies in mouse models that differ significantly from those in humans pose challenges for drug discovery and finding effective therapeutic regimens. The GWI exposome differs significantly in the study cohorts, and the above makes it difficult to recreate a model closely resembling the GWI symptom pathology. We have used a double engraftment strategy for reconstituting a human immune system coupled with human microbiome transfer to create a humanized-mouse model for GWI. Using whole-genome shotgun sequencing and blood immune cytokine enzyme linked immunosorbent assay (ELISA), we show that our double humanized mice treated with Gulf War (GW) chemicals show significantly altered gut microbiomes, similar to those reported in a Veteran cohort of GWI. The results also showed similar cytokine profiles, such as increased levels of IL-1β, IL-6, and TNF R-1, in the double humanized model, as found previously in a human cohort. Further, a novel GWI Veteran fecal microbiota transfer was used to create a second alternative model that closely resembled the microbiome and immune-system-associated pathology of a GWI Veteran. A GWI Veteran microbiota transplant in humanized mice showed a human microbiome reconstitution and a systemic inflammatory pathology, as reflected by increases in interleukins 1β, 6, 8 (IL-1β, IL-6, IL-8), tumor necrosis factor receptor 1 (TNF R-1), and endotoxemia. In conclusion, though preliminary, we report a novel in vivo model with a human microbiome reconstitution and an engrafted human immune phenotype that may help to better understand gut-immune interactions in GWI.

Exposure to Gulf war illness-related chemicals exacerbates alcohol- induced liver damage in rodents

Gulf War Illness (GWI) describes a series of symptoms suffered by veterans of the Gulf war consisting of cognitive, neurological and gastrointestinal dysfunctions. Two chemicals associated with GWI are the insecticide permethrin (PER) and the nerve gas prophylactic pyridostigmine-bromide (PB). In this study we assessed the effects of PER and PB exposure on pathology and subsequent alcohol (EtOH)-induced liver injury, and the influence of a macrophage depletor, PLX3397, on EtOH-induced liver damage in PER/PB- treated mice. Male C57BL/6 mice were injected daily with vehicle or PER/PB for 10 days, followed by 4 months recovery, then treatment with PLX3397 and a chronic-plus-single-binge EtOH challenge for 10 days. PER/PB exposure resulted in the protracted increase in liver transaminases in the serum and induced chronic low-level microvesicular steatosis and inflammation in GWI vs Naïve mice up to 4 months after cessation of exposure. Furthermore, prior exposure to PER/PB also resulted in exacerbated response to EtOH-induced liver injury, with enhanced steatosis, ductular reaction and fibrosis. The enhanced EtOH-induced liver damage in GWI-mice was attenuated by strategies designed to deplete macrophages in the liver. Taken together, these data suggest that exposure to GWI-related chemicals may alter the liver's response to subsequent ethanol exposure.

Mitochondrial impairment but not peripheral inflammation predicts greater Gulf War illness severity

Gulf War illness (GWI) is an important exemplar of environmentally-triggered chronic multisymptom illness, and a potential model for accelerated aging. Inflammation is the main hypothesized mechanism for GWI, with mitochondrial impairment also proposed. No study has directly assessed mitochondrial respiratory chain function (MRCF) on muscle biopsy in veterans with GWI (VGWI). We recruited 42 participants, half VGWI, with biopsy material successfully secured in 36. Impaired MRCF indexed by complex I and II oxidative phosphorylation with glucose as a fuel source (CI&CIIOXPHOS) related significantly or borderline significantly in the predicted direction to 17 of 20 symptoms in the combined sample. Lower CI&CIIOXPHOS significantly predicted GWI severity in the combined sample and in VGWI separately, with or without adjustment for hsCRP. Higher-hsCRP (peripheral inflammation) related strongly to lower-MRCF (particularly fatty acid oxidation (FAO) indices) in VGWI, but not in controls. Despite this, whereas greater MRCF-impairment predicted greater GWI symptoms and severity, greater inflammation did not. Surprisingly, adjusted for MRCF, higher hsCRP significantly predicted lesser symptom severity in VGWI selectively. Findings comport with a hypothesis in which the increased inflammation observed in GWI is driven by FAO-defect-induced mitochondrial apoptosis. In conclusion, impaired mitochondrial function-but not peripheral inflammation-predicts greater GWI symptoms and severity.

Hormonal changes in veterans with Gulf War Illness

AIMS

Gulf War Illness (GWI) is a multi-system condition of complex etiology and pathophysiology without specific treatment. There is an overlap between the symptoms of GWI and endocrinopathies. This study aimed to identify hormonal alterations in 1990-91 Gulf War (GW) veterans and the relationship between GWI and hormonal dysregulation.

MAIN METHODS

Data from 81 GW veterans (54 with GWI and 27 controls without GWI) was analyzed in a cross-sectional, case-control observational study. Participants completed multiple questionnaires, neuropsychiatric assessments, and a comprehensive set of hormone assays including a glucagon stimulation test (GST) for adult growth hormone deficiency (AGHD) and a high-dose adrenocorticotropic hormone (ACTH) stimulation test for adrenal insufficiency.

KEY FINDINGS

The GWI group had lower quality of life and greater severity of all symptoms compared to controls. Pain intensity and pain-related interference with general activity were also higher in the GWI group. AGHD was observed in 18 of 51 veterans with GWI (35.3 %) and 2 of 26 veterans without GWI (7.7 %) (p = 0.012 for interaction). Veterans with GWI also exhibited reduced insulin-like growth factor 1 (IGF-1) levels and IGF-1 Z-scores compared to controls. One participant with GWI met the criteria for adrenal insufficiency. No significant changes were observed in other hormonal axes.

SIGNIFICANCE

The frequency of AGHD was significantly higher in veterans with GWI compared to controls. Recombinant human growth hormone replacement therapy (GHRT) may become a breakthrough therapeutic option for this subgroup. A large clinical trial is needed to evaluate the efficacy of GHRT in patients with GWI and AGHD.

Gulf war illness inflammation reduction trial: A phase 2 randomized controlled trial of low-dose prednisone chronotherapy, effects on health-related quality of life

BACKGROUND

Gulf War illness (GWI) is a deployment-related chronic multisymptom illness impacting the health-related quality of life (HRQOL) of many U.S. Military Veterans of the 1990-91 Gulf War. A proinflammatory blood biomarker fingerprint was discovered in our initial study of GWI. This led to the hypothesis that chronic inflammation is a component of GWI pathophysiology.

OBJECTIVES

The GWI inflammation hypothesis was tested in this Phase 2 randomized controlled trial (RCT) by measuring the effects of an anti-inflammatory drug and placebo on the HRQOL of Veterans with GWI. The trial is registered at ClinicalTrials.gov, Identifier: NCT02506192.

RCT DESIGN AND METHODS

Gulf War Veterans meeting the Kansas case definition for GWI were randomized to receive either 10 mg modified-release prednisone or matching placebo. The Veterans RAND 36-Item Health Survey was used to assess HRQOL. The primary outcome was a change from baseline in the physical component summary (PCS) score, a measure of physical functioning and symptoms. A PCS increase indicates improved physical HRQOL.

RESULTS

For subjects with a baseline PCS <40, there was a 15.2% increase in the mean PCS score from 32.9±6.0 at baseline to 37.9±9.0 after 8 weeks on modified-release prednisone. Paired t-test analysis determined the change was statistically significant (p = 0.004). Eight weeks after cessation of the treatment, the mean PCS score declined to 32.7±5.8.

CONCLUSIONS

The prednisone-associated improvement in physical HRQOL supports the GWI inflammation hypothesis. Determining the efficacy of prednisone as a treatment for GWI will require a Phase 3 RCT.

Exercise-induced changes in gene expression do not mediate post exertional malaise in Gulf War illness

Background

Post-exertional malaise (PEM) is considered a characteristic feature of chronic multi-symptom illnesses (CMI) like Gulf War illness (GWI); however, its pathophysiology remains understudied. Previous investigations in other CMI populations (i.e., Myalgic Encephalomyelitis/Chronic Fatigue Syndrome) have reported associations between PEM and expression of genes coding for adrenergic, metabolic, and immune function.

Objectives

To investigate whether PEM is meditated by gene expression in Veterans with GWI.

Methods

Veterans with GWI (n = 37) and healthy control Gulf War Veterans (n = 25) provided blood samples before and after 30-min of cycling at 70% of age-predicted heart rate reserve. Relative quantification of gene expression, symptom measurements, and select cardiopulmonary parameters were compared between groups at pre-, 30 minpost-, and 24 hpost-exercise using a doubly multivariate repeated measures analysis of variance (RM-MANOVA). Mediation analyses were used to test indirect effects of changes in gene expression on symptom responses (i.e., PEM) to the standardized exercise challenge.

Results

Veterans with GWI experienced large symptom exacerbations following exercise compared to controls (Cohen's d: 1.65; p < 0.05). Expression of β -actin (ACTB), catechol-O-methyltransferase (COMT), and toll-like receptor 4 (TLR4) decreased in Veterans with GWI at 30 min (p < 0.05) and 24 h post-exercise (p < 0.05). Changes in gene expression did not mediate post-exercise symptom exacerbation in GWI (Indirect Effect Slope Coefficient: 0.06 - 0.02; 95% CI: 0.19, 0.12).

Conclusion

An acute bout of moderate intensity cycling reduced the expression of select structural, adrenergic, and immune genes in Veterans with GWI, but the pathophysiological relevance to PEM is unclear.

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.

Whole-body inhalation of nano-sized carbon black: a surrogate model of military burn pit exposure

OBJECTIVE

Chronic multisymptom illness (CMI) is an idiopathic disease affecting thousands of U.S. Veterans exposed to open-air burn pits emitting aerosolized particulate matter (PM) while serving in Central and Southwest Asia and Africa. Exposure to burn pit PM can result in profound biologic consequences including chronic fatigue, impaired cognition, and respiratory diseases. Dysregulated or unresolved inflammation is a possible underlying mechanism for CMI onset. We describe a rat model of whole-body inhalation exposure using carbon black nanoparticles (CB) as a surrogate for military burn pit-related exposure. Using this model, we measured biomarkers of inflammation in multiple tissues.

RESULTS

Male Sprague Dawley rats were exposed to CB aerosols by whole body inhalation (6 ± 0.83 mg/m3). Proinflammatory biomarkers were measured in multiple tissues including arteries, brain, lung, and plasma. Biomarkers of cardiovascular injury were also assayed in plasma. CB inhalation exposure increased CMI-related proinflammatory biomarkers such as IFN-γ and TNFα in multiple tissue samples. CB exposure also induced cardiovascular injury markers (adiponectin, MCP1, sE-Selectin, sICam-1 and TIMP1) in plasma. These findings support the validity of our animal exposure model for studies of burn pit-induced CMI. Future studies will model more complex toxicant mixtures as documented at multiple burn pit sites.

Host gut resistome in Gulf War chronic multisymptom illness correlates with persistent inflammation

Chronic multisymptom illness (CMI) affects a subsection of elderly and war Veterans and is associated with systemic inflammation. Here, using a mouse model of CMI and a group of Gulf War (GW) Veterans' with CMI we show the presence of an altered host resistome. Results show that antibiotic resistance genes (ARGs) are significantly altered in the CMI group in both mice and GW Veterans when compared to control. Fecal samples from GW Veterans with persistent CMI show a significant increase of resistance to a wide class of antibiotics and exhibited an array of mobile genetic elements (MGEs) distinct from normal healthy controls. The altered resistome and gene signature is correlated with mouse serum IL-6 levels. Altered resistome in mice also is correlated strongly with intestinal inflammation, decreased synaptic plasticity, reversible with fecal microbiota transplant (FMT). The results reported might help in understanding the risks to treating hospital acquired infections in this population.

The impact of neurotoxicant exposures on posttraumatic stress disorder trajectories: The Ft. Devens Gulf War Veterans Cohort

Gulf War veterans (GWVs) were exposed to neurotoxicants, including sarin nerve gas, anti-nerve agent pills, pesticides, oil well fires, and fumes from unvented tent heaters, all of which have been associated with subsequent adverse health. Posttraumatic stress disorder (PTSD) symptoms have also been associated with GW deployment; however, associations between exposures and PTSD symptoms have not been investigated. We assessed PTSD symptom trajectories and associations with neurotoxicant exposures in Ft. Devens Cohort (FDC) veterans (N = 259) who endorsed trauma exposure during deployment and completed the PTSD Checklist at three follow-ups (1992-1993, 1997-1998, 2013-2017). Results indicate that among veterans with more severe initial PTSD symptoms, symptoms remained significantly higher across follow-ups, Bs = -1.489-1.028, whereas among those with low initial PTSD symptoms, symptom severity increased significantly over time, Bs = 1.043-10.304. Additionally, neurotoxicant exposure was associated with a significant increase in PTSD symptoms, Bs = -1.870-9.003. Significant interactions between time and exposures were observed for PTSD symptom clusters, suggesting that among participants with high initial PTSD symptom, unexposed veterans experienced symptom alleviation, whereas exposed veterans' PTSD symptoms remained high. In GWVs with low initial PTSD symptoms, both unexposed and exposed veterans experienced PTSD symptom exacerbations over time; however, this occurred at a faster rate among exposed veterans. These findings suggest that in the years following deployment, GWVs who were exposed to both traumatic events and neurotoxicants may experience more severe and chronic PTSD symptoms than those without neurotoxicant exposures.

Age differences in allostatic load among veterans: The importance of combat exposure

The current study examinedage differences in allostatic load among nonveterans, noncombat veterans, and combat veterans. Participants included 280 individuals from the Midlife Development in the United States (MIDUS) survey, including 164 veterans (n = 48 combat veterans; n = 116 noncombat veterans) and 116 nonveterans. Age differences in allostatic load were similar among nonveterans and noncombat veterans, B = 0.002, SE = .011, p = .878, with older adults showing higher levels of allostatic load than their comparatively younger counterparts. Among combat veterans, however, a different pattern emerged. In this group, levels of allostatic load were similar across age, seemingly due to higher levels of allostatic load among younger combat veterans, B = -0.029, SE = .014, p = .031, ƞ_p ²  =  .022. Results reveal the importance of considering combat exposure when examining health outcomes of military veterans, particularly in the context of age.

Induction of distinct neuroinflammatory markers and gut dysbiosis by differential pyridostigmine bromide dosing in a chronic mouse model of GWI showing persistent exercise fatigue and cognitive impairment

AIMS

To characterize neuroinflammatory and gut dysbiosis signatures that accompany exaggerated exercise fatigue and cognitive/mood deficits in a mouse model of Gulf War Illness (GWI).

METHODS

Adult male C57Bl/6N mice were exposed for 28 d (5 d/wk) to pyridostigmine bromide (P.O.) at 6.5 mg/kg/d, b.i.d. (GW1) or 8.7 mg/kg/d, q.d. (GW2); topical permethrin (1.3 mg/kg), topical N,N-diethyl-meta-toluamide (33%) and restraint stress (5 min). Animals were phenotypically evaluated as described in an accompanying article [124] and sacrificed at 6.6 months post-treatment (PT) to allow measurement of brain neuroinflammation/neuropathic pain gene expression, hippocampal glial fibrillary acidic protein, brain Interleukin-6, gut dysbiosis and serum endotoxin.

KEY FINDINGS

Compared to GW1, GW2 showed a more intense neuroinflammatory transcriptional signature relative to sham stress controls. Interleukin-6 was elevated in GW2 and astrogliosis in hippocampal CA1 was seen in both GW groups. Beta-diversity PCoA using weighted Unifrac revealed that gut microbial communities changed after exposure to GW2 at PT188. Both GW1 and GW2 displayed systemic endotoxemia, suggesting a gut-brain mechanism underlies the neuropathological signatures. Using germ-free mice, probiotic supplementation with Lactobacillus reuteri produced less gut permeability than microbiota transplantation using GW2 feces.

SIGNIFICANCE

Our findings demonstrate that GW agents dose-dependently induce differential neuropathology and gut dysbiosis associated with cognitive, exercise fatigue and mood GWI phenotypes. Establishment of a comprehensive animal model that recapitulates multiple GWI symptom domains and neuroinflammation has significant implications for uncovering pathophysiology, improving diagnosis and treatment for GWI.

Restorative potential of (-)-epicatechin in a rat model of Gulf War illness muscle atrophy and fatigue

We examined in a rat model of Gulf War illness (GWI), the potential of (-)-epicatechin (Epi) to reverse skeletal muscle (SkM) atrophy and dysfunction, decrease mediators of inflammation and normalize metabolic perturbations. Male Wistar rats (n = 15) were provided orally with pyridostigmine bromide (PB) 1.3 mg/kg/day, permethrin (PM) 0.13 mg/kg/day (skin), DEET 40 mg/kg/day (skin) and were physically restrained for 5 min/day for 3 weeks. A one-week period ensued to fully develop the GWI-like profile followed by 2 weeks of either Epi treatment at 1 mg/kg/day by gavage (n = 8) or water (n = 7) for controls. A normal, control group (n = 15) was given vehicle and not restrained. At 6 weeks, animals were subjected to treadmill and limb strength testing followed by euthanasia. SkM and blood sampling was used for histological, biochemical and plasma pro-inflammatory cytokine and metabolomics assessments. GWI animals developed an intoxication profile characterized SkM atrophy and loss of function accompanied by increases in modulators of muscle atrophy, degradation markers and plasma pro-inflammatory cytokine levels. Treatment of GWI animals with Epi yielded either a significant partial or full normalization of the above stated indicators relative to normal controls. Plasma metabolomics revealed that metabolites linked to inflammation and SkM waste pathways were dysregulated in the GWI group whereas Epi, attenuated such changes. In conclusion, in a rat model of GWI, Epi partially reverses detrimental changes in SkM structure including modulators of atrophy, inflammation and select plasma metabolites yielding improved function.

Neuroimmune mechanisms of cognitive impairment in a mouse model of Gulf War illness

Gulf War Illness (GWI) is a chronic, multi-symptom disorder affecting approximately 30 percent of the nearly 700,000 Veterans of the 1991 Persian Gulf War. GWI-related chemical (GWIC) exposure promotes immune activation that correlates with cognitive impairment and other symptoms of GWI. However, the molecular mechanisms and signaling pathways linking GWIC to inflammation and neurological symptoms remain unclear. Here we show that acute exposure of murine macrophages to GWIC potentiates innate immune signaling and inflammatory cytokine production. Using an established mouse model of GWI, we report that neurobehavioral changes and neuroinflammation are attenuated in mice lacking the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) and NOD-, LRR- or pyrin domain-containing protein 3 (NLRP3) innate immune pathways. In addition, we report sex differences in response to GWIC, with female mice showing more pronounced cognitive impairment and hippocampal astrocyte hypertrophy. In contrast, male mice display a GWIC-dependent upregulation of proinflammatory cytokines in the plasma that is not present in female mice. Our results indicate that STING and NLRP3 are key mediators of the cognitive impairment and inflammation observed in GWI and provide important new information on sex differences in this model.

The Health of Gulf War and Gulf Era Veterans Over Time: U.S. Department of Veterans Affairs' Gulf War Longitudinal Study

OBJECTIVE

The aim of this study was to describe the self-reported physical and mental health over the course over 19 years of follow up of a population-based cohort of Gulf War and Gulf Era veterans.

METHODS

A multi-modal health survey of 6338 Gulf War and Gulf Era veterans who participated in all three waves of the longitudinal study.

RESULTS

Gulf War and Gulf War Era veterans experienced an increase in prevalence of chronic disease over time. The adjusted odds ratios suggest that Gulf War veterans not only had significantly higher odds of reporting medical conditions, but also began to report them earlier.

CONCLUSIONS

The findings from this analysis suggest that Gulf War veterans are not only more likely than their non-deployed counterparts to report chronic disease, they were more likely to report it earlier.

Experimental respiratory exposure to putative Gulf War toxins promotes persistent alveolar macrophage recruitment and pulmonary inflammation

AIMS

Respiratory disorders are a prominent component of Gulf War Illness. Although much of the underlying mechanisms of Gulf War Illness remain undefined, chronic immune dysfunction is a consistent feature of this multi-symptomatic, multi-organ disorder. Alveolar macrophages represent the predominant mononuclear phagocytes of the pulmonary mucosa, orchestrating the host response to pathogens and environmental stimuli. Herein, we sought to characterize the innate immune response of the pulmonary mucosa, with a focus on macrophages, to experimental respiratory exposure to two putative Gulf War Toxins (GWTs).

MATERIALS AND METHODS

Utilizing commercially available instrumentation, we evaluated the effect of aerosolized exposure to the pesticide malathion and diesel exhaust particulate (DEP) on the immune composition and inflammatory response of the lung in FVB/N mice using multiparametric spectral cytometry, cytokine analysis, and histology.

KEY FINDINGS

Aerosolized GWTs induced gross pulmonary pathology with transient recruitment of neutrophils and sustained accumulation of alveolar macrophages to the lung for up to two weeks after exposure cessation. High-dimensional cytometry and unbiased computational analysis identified novel myeloid subsets recruited to the lung post-exposure driven by an influx of peripheral monocyte-derived progenitors. DEP and malathion, either alone or in combination, induced soluble mediators in bronchoalveolar lavage indicative of oxidative stress (PGF2α), inflammation (LTB4, TNFα, IL-12), and immunosuppression (IL-10), that were sustained or increased two weeks after exposures concluded.

SIGNIFICANCE

These findings indicate that macrophage accumulation and pulmonary inflammation induced by GWTs continue in the absence of toxin exposure and may contribute to the immunopathology of respiratory Gulf War Illness.

Exposure to Gulf War Illness-related agents leads to the development of chronic pain and fatigue

AIMS

A substantial contingent of veterans from the first Gulf War continues to suffer from a number of Gulf War-related illnesses (GWI) affecting the neurological and musculoskeletal systems; the most common symptoms include chronic pain and fatigue. Although animal models have recapitulated several aspects of cognitive impairments in GWI, the pain and fatigue symptoms have not been well documented to allow examination of potential pathogenic mechanisms.

MAIN METHODS

We used a mouse model of GWI by exposing mice repeatedly to a combination of Gulf War chemicals (pyridostigmine bromide, permethrin, DEET, and chlorpyrifos) and mild immobilization stress, followed by investigating their pain susceptibilities and fatigue symptoms. To assess whether enhanced antioxidant capacity can counter the effects of GW agents, transgenic mice overexpressing extracellular superoxide dismutase (SOD3OE) were also examined.

KEY FINDINGS

The mouse model recapitulated several aspects of the human illness, including hyperalgesia, impaired descending inhibition of pain, and increased tonic pain. There is a close association between chronic pain and fatigue in GWI patients. Consistent with this observation, the mouse model showed a significant reduction in physical endurance on the treadmill. Examination of skeletal muscles suggested reduction in mitochondrial functions may have contributed to the fatigue symptoms. Furthermore, the negative impacts of GW agents in pain susceptibilities were largely diminished in SOD3OE mice, suggesting that increased oxidative stress was associated with the emergence of these Gulf War symptoms.

SIGNIFICANCE

the mouse model will be suitable for delineating specific defects in the pain pathways and mechanisms of fatigue in GWI.

Adaptive Immune Responses Associated with the Central Nervous System Pathology of Gulf War Illness

Gulf War Illness is a multisymptomatic condition which affects 30% of veterans from the 1991 Gulf War. While there is evidence for a role of peripheral cellular and humoral adaptive immune responses in Gulf War Illness, a potential role of the adaptive immune system in the central nervous system pathology of this condition remains unknown. Furthermore, many of the clinical features of Gulf War Illness resembles those of autoimmune diseases, but the biological processes are likely different as the etiology of Gulf War Illness is linked to hazardous chemical exposures specific to the Gulf War theatre. This review discusses Gulf War chemical–induced maladaptive immune responses and a potential role of cellular and humoral immune responses that may be relevant to the central nervous system symptoms and pathology of Gulf War Illness. The discussion may stimulate investigations into adaptive immunity for developing novel therapies for Gulf War Illness.

Effect of the low glutamate diet on inflammatory cytokines in veterans with Gulf War Illness (GWI): A pilot study

AIM

To examine the effects of the low glutamate diet on inflammatory cytokines in veterans with Gulf War Illness (GWI).

MAIN METHODS

Forty veterans with GWI were recruited from across the country. Anthropometric measurements and blood samples were collected at baseline and after one month on the low glutamate diet. Dietary adherence was measured with a glutamate food frequency questionnaire (FFQ). Inflammatory cytokines (IL-1β, IL-6, IFN-γ, and TNF-α) were measured in pre- and post-diet serum (N = 34). Improvement was defined as being "much" or "very much" improved on the patient global impression of change scale (PGIC), or as having ≥30% of their symptoms remit. Correlations of the FFQ and the cytokines were calculated, followed by multivariable linear regression for significant findings. Mann Whitney U tests were used to compare cytokine levels according to improvement on the diet, and then logistic regression was used to estimate the association after adjustment for potential confounders. Classification trees were also produced to determine the ability of change in the inflammatory cytokines to predict improvement on the diet.

KEY FINDINGS

Dietary adherence was significantly associated with reduction in TNF-α, and PGIC improvement was significantly associated with reduced IL-1β, after adjustment for potential confounders. Classification trees demonstrated that IL-1β, TNF-α, and IL-6 can predict improvement on the diet with 76.5% accuracy.

SIGNIFICANCE

Findings suggest that the low glutamate diet may be able to reduce systemic inflammation in veterans with GWI.

Minocycline alleviates Gulf War Illness rats via altering gut microbiome, attenuating neuroinflammation and enhancing hippocampal neurogenesis

Accumulating evidences suggest that deficits in neurogenesis, chronic inflammation and gut microbiome dysregulation contribute to the pathophysiology of Gulf War Illness (GWI). Minocycline has been demonstrated to be a potent neuroprotective agent and could regulate neuroinflammation. The present study intends to investigate whether the treatment of minocycline maintains better cognition and mood function in a rat model of GWI and the potential mechanism. Rats received 28 days of GWI-related chemical exposure and restraint stress, along with daily minocycline or vehicle treatment. Cognitive and mood function, neuroinflammation, neurogenesis and gut microbiota were detected. We found that minocycline treatment induces better cognitive and mood function in the GWI rat model, as indicated by open-field test, elevated plus maze test, novel object recognition test and forced swim test. Moreover, minocycline treatment reversed the altered gut microbiome, neuroinflammation and the decreased hippocampal neurogenesis of rats with GWI. Taken together, our study indicated that minocycline treatment exerts better cognitive and mood function in GWI rat model, which is possibly related to gut microbiota remodeling, restrained inflammation and enhanced hippocampal neurogenesis. These results may establish minocycline as a potential prophylactic or therapeutic agent for the treatment of GWI.

Biological measures and diagnostic tools for Gulf War Illness - A systematic review

AIMS

Gulf War Illness (GWI) is a chronic multisymptom illness with debated etiology and pathophysiology. This systematic review catalogues studies of validated biological tests for diagnosing GWI and of associations between biological measures and GWI for their promise as biomarkers.

MAIN METHODS

We searched multiple sources through February 2020 for studies of diagnostic tests of GWI and of associations between biological measures and GWI. We abstracted data on study design, demographics, and outcomes. We assessed the risk of bias of included studies.

KEY FINDINGS

We did not identify any studies validating tests of biomarkers that distinguish cases of GWI from non-cases. We included the best-fitting studies, 32 completed and 24 ongoing or unpublished studies, of associations between GWI and biological measures. The less well-fitting studies (n = 77) were included in a Supplementary Table. Most studies were of the central nervous and immune systems and indicated a significant association of the biological measure with GWI case status. Biological measures were heterogeneous across studies.

SIGNIFICANCE

Our review indicates that there are no existing validated biological tests to determine GWI case status. Many studies have assessed the potential association between a variety of biological measures and GWI, the majority of which pertain to the immune and central nervous systems. More importantly, while most studies indicated a significant association between biological measures and GWI case status, the biological measures across studies were extremely heterogeneous. Due to the heterogeneity, the focus of the review is to map out what has been examined, rather than synthesize information.

Cognitive behavioral therapy for insomnia in veterans with gulf war illness: Results from a randomized controlled trial

Aims:

To examine whether cognitive behavioral therapy for insomnia (CBT-I), delivered by telephone, improves sleep and non-sleep symptoms of Gulf War Illness (GWI).

Main methods:

Eighty-five Gulf War veterans (21 women, mean age: 54 years, range 46–72 years) who met the Kansas GWI case definition, the Centers for Disease Control and Prevention (CDC) case definition for Chronic Multisymptom Illness (CMI), and research diagnostic criteria for insomnia disorder were randomly assigned to CBT-I or monitor-only wait list control. Eight weekly sessions of individual CBT-I were administered via telephone by Ph.D. level psychologists to study participants. Outcome measures included pre-, mid-, and post-treatment assessments of GWI and insomnia symptoms, subjective sleep quality, and continuous sleep monitoring with diary. Outcomes were re-assessed 6-months post-treatment in participants randomized to CBT-I.

Key findings:

Compared to wait list, CBT-I produced significant improvements in overall GWI symptom severity, individual measures of fatigue, cognitive dysfunction, depression and anxiety, insomnia severity, subjective sleep quality, and sleep diary outcome measures. The beneficial effects of CBT-I on overall GWI symptom severity and most individual GWI symptom measures were maintained 6-months after treatment.

Significance:

GWI symptoms have historically been difficult to treat. Because CBT-I, which is associated with low stigma and is increasingly readily available to veterans, improved both sleep and non-sleep symptoms of GWI, these results suggest that a comprehensive approach to the treatment of GWI should include behavioral sleep interventions.

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.

Using Plasma Autoantibodies of Central Nervous System Proteins to Distinguish Veterans with Gulf War Illness from Healthy and Symptomatic Controls

For the past 30 years, there has been a lack of objective tools for diagnosing Gulf War Illness (GWI), which is largely characterized by central nervous system (CNS) symptoms emerging from 1991 Gulf War (GW) veterans. In a recent preliminary study, we reported the presence of autoantibodies against CNS proteins in the blood of veterans with GWI, suggesting a potential objective biomarker for the disorder. Now, we report the results of a larger, confirmatory study of these objective biomarkers in 171 veterans with GWI compared to 60 healthy GW veteran controls and 85 symptomatic civilian controls (n = 50 myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and n = 35 irritable bowel syndrome (IBS)). Specifically, we compared plasma markers of CNS autoantibodies for diagnostic characteristics of the four groups (GWI, GW controls, ME/CFS, IBS). For veterans with GWI, the results showed statistically increased levels of nine of the ten autoantibodies against neuronal "tubulin, neurofilament protein (NFP), Microtubule Associated Protein-2 (MAP-2), Microtubule Associated Protein-Tau (Tau), alpha synuclein (α-syn), calcium calmodulin kinase II (CaMKII)" and glial proteins "Glial Fibrillary Acidic Protein (GFAP), Myelin Associated Glycoprotein (MAG), Myelin Basic Protein (MBP), S100B" compared to healthy GW controls as well as civilians with ME/CFS and IBS. Next, we summed all of the means of the CNS autoantibodies for each group into a new index score called the Neurodegeneration Index (NDI). The NDI was calculated for each tested group and showed veterans with GWI had statistically significantly higher NDI values than all three control groups. The present study confirmed the utility of the use of plasma autoantibodies for CNS proteins to distinguish among veterans with GWI and other healthy and symptomatic control groups.

The Innate Immune System and Inflammatory Priming: Potential Mechanistic Factors in Mood Disorders and Gulf War Illness

Gulf War Illness is a chronic multisystem disorder affecting approximately a third of the Veterans of the Gulf War, manifesting with physical and mental health symptoms such as cognitive impairment, neurological abnormalities, and dysregulation of mood. Among the leading theories into the etiology of this multisystem disorder is environmental exposure to the various neurotoxins encountered in the Gulf Theatre, including organophosphates, nerve agents, pyridostigmine bromide, smoke from oil well fires, and depleted uranium. The relationship of toxin exposure and the pathogenesis of Gulf War Illness converges on the innate immune system: a nonspecific form of immunity ubiquitous in nature that acts to respond to both exogenous and endogenous insults. Activation of the innate immune system results in inflammation mediated by the release of cytokines. Cytokine mediated neuroinflammation has been demonstrated in a number of psychiatric conditions and may help explain the larger than expected population of Gulf War Veterans afflicted with a mood disorder. Several of the environmental toxins encountered by soldiers during the first Gulf War have been shown to cause upregulation of inflammatory mediators after chronic exposure, even at low levels. This act of inflammatory priming, by which repeated exposure to chronic subthreshold insults elicits robust responses, even after an extended period of latency, is integral in the connection of Gulf War Illness and comorbid mood disorders. Further developing the understanding of the relationship between environmental toxin exposure, innate immune activation, and pathogenesis of disease in the Gulf War Veterans population, may yield novel therapeutic targets, and a greater understanding of disease pathology and subsequently prevention.