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Visual event-related potentials as markers of hyperarousal in Gulf War illness: evidence against a stress-related etiology.

ABSTRACT: An exaggerated response to emotional stimuli is among the many symptoms widely reported by veterans of the 1991 Persian Gulf War. These symptomologies have been attributed to damage and dysfunction associated with deployment-related exposures. We collected event-related potential data from 22 veterans meeting Haley criteria for Gulf War (GW) Syndromes 1-3 and from 8 matched GW veteran controls, who were deployed but not symptomatic, while they performed a visual three-condition oddball task where images authenticated to be associated with the 1991 Persian Gulf War were the distractor stimuli. Hyperarousal reported by ill veterans was significantly greater than that by control veterans, but this was not paralleled by higher amplitude P3a in their ERP responses to GW-related distractor stimuli. Whereas previous studies of PTSD patients have shown higher amplitude P3b responses to target stimuli that are placed amid trauma-related nontarget stimuli, ill veterans in this study showed P3b amplitudes to target stimuli - placed amid GW-related nontarget stimuli - that were significantly lower than those of the control group. Hyperarousal scores reliably predicted P3b, but not P3a, amplitudes. Although many factors may contribute to P3b amplitude differences - most notably depression and poor sleep quality, symptoms that are prevalent in the GW syndrome groups - our findings in context of previous studies on this population are consistent with the contention that dysfunction in cholinergic and dopaminergic neurotransmitter systems, and in white matter and basal ganglia may be contributing to impairments in GW veterans.

SUBMITTER: Tillman GD

PROVIDER: S-EPMC3578115 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Visual event-related potentials as markers of hyperarousal in Gulf War illness: evidence against a stress-related etiology.

Tillman Gail D GD Calley Clifford S CS Green Timothy A TA Buhl Virginia I VI Biggs Melanie M MM Spence Jeffrey S JS Briggs Richard W RW Haley Robert W RW Kraut Michael A MA Hart John J

Psychiatry research 20121111 3

An exaggerated response to emotional stimuli is among the many symptoms widely reported by veterans of the 1991 Persian Gulf War. These symptomologies have been attributed to damage and dysfunction associated with deployment-related exposures. We collected event-related potential data from 22 veterans meeting Haley criteria for Gulf War (GW) Syndromes 1-3 and from 8 matched GW veteran controls, who were deployed but not symptomatic, while they performed a visual three-condition oddball task wher ...[more]

PMID: 23149040

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Project description:Gulf War Illness (GWI) is a complex condition that involves multiple organ systems and is characterized by an abrupt or delayed onset of persistent/relapsing symptomatology such as memory and other neurological problems, muscle and joint pain, gastrointestinal issues, hormonal imbalance, immune dysfunction and debilitating fatigue. Currently, treatment of the condition relies solely on management of symptomatology and improvement in quality of life due to a lack of knowledgeof the underlying mechanisms of disease onset and progression. An improved understanding of the key mechanisms of GWI and dysfunction within regulatory systems will lead to more objective diagnosis methods and adequate management of patients by providing targeted approaches to treatment. Disruption of DNA methylation patterns has been tied to various immune, neurological and endocrine disease states; however, the status of this epigenetic mark in GWI remains uncertain. This study aimed at identifying biomarkers of GWI by gaining knowledge on DNA methylation patterns of GWI in an effort to determine therapeutic targets of disease activity and provide insight into disease onset and progression. Methods: Genomic DNA from 10 GWI patients and 10 healthy controls [HC] (“experimental cohort”) prepared from PBMCs was analyzed with ELISA-based DNA methylation assays and Illumina MethylationEPIC microarrays. These arrays allow measuring the methylation status at 850,000 CpG sites. Methylation changes in promoter regions were separately analyzed and used as input data in ingenuity pathway analysis software to identify altered functional pathways. Relevant differentially methylated CpG sites (DMS) were validated by pyrosequencing. Results: Global DNA methylation levels using the ELISA-based assay on the DNA isolated from PBMCs of GWI patients were similar to those of HC. However, deeper evaluation using microarray-based genome-wide technology allowed detection of DMS in GWI patients with respect to HC. As an overall 10,767 CpG sites presented with differential DNA methylation levels across promoters, gene regulatory elements and within coding regions of genes. Majority of these DMS were hypermethylated in GWI patients as compared to the HC, and more than half of these sites localized to promoters and gene regulatory elements, relative to distribution of DMSin the network as a whole, indicating gene regulatory potential. Functional pathway analysis of the 776 genes with differentially methylated promoters (DMPs) fulfilling FDR≤0.2 criteriafollowing a genomic region-based approachlinks GWI to defects in at least 15 different pathways mostly related to cell signaling with a strong immune component. Conclusions: This is the first study that has explored genome-wide epigenetic changes associated with GWI using the new MethylationEPIC microarrays covering about 850,000 CpG sites; which builds on previous methylation preliminary reports. The data obtained are consistent with previous evidence for dysregulation of the immune system in GWI and suggests a role of this epigenetic modification on the DNA pathobiology of GWI. They are also consistent with previous reports showing a Th1- to Th2-mediated immune response shift in GWI in addition to altered immune system function. Future validation studies in larger cohorts of GWI patients and evaluation of the effects of these methylation patterns on gene expression regulation are granted.

Project description:BACKGROUND:Gulf War Illness (GWI) remains a serious health consequence for at least 11,000 veterans of the first Gulf War in the early 1990s. Our understanding of the health consequences that resulted remains inadequate, and this is of great concern with another deployment to the same theater of operations occurring now. Chronic immune cell dysfunction and activation have been demonstrated in patients with GWI, although the literature is not uniform. We exposed GWI patients and matched controls to an exercise challenge to explore differences in immune cell function measured by classic immune assays and gene expression profiling. METHODS:This pilot study enrolled 9 GWI cases identified from the Department of Veterans Affairs GWI registry, and 11 sedentary control veterans who had not been deployed to the Persian Gulf and were matched to cases by sex, body mass index (BMI) and age. We measured peripheral blood cell numbers, NK cytotoxicity, cytokines and expression levels of 20,000 genes immediately before, immediately after and 4 hours following a standard bicycle ergometer exercise challenge. RESULTS:A repeated-measures analysis of variance revealed statistically significant differences for three NK cell subsets and NK cytotoxicity between cases and controls (p < 0.05). Linear regression analysis correlating NK cell numbers to the gene expression profiles showed high correlation of genes associated with NK cell function, serving as a biologic validation of both the in vitro assays and the microarray platform. Intracellular perforin levels in NK and CD8 T-cells trended lower and showed a flatter profile in GWI cases than controls, as did the expression levels of the perforin gene PRF1. Genes distinguishing cases from controls were associated with the glucocorticoid signaling pathway. CONCLUSION:GWI patients demonstrated impaired immune function as demonstrated by decreased NK cytotoxicity and altered gene expression associated with NK cell function. Pro-inflammatory cytokines, T-cell ratios, and dysregulated mediators of the stress response (including salivary cortisol) were also altered in GWI cases compared to control subjects. An interesting and potentially important observation was that the exercise challenge augments these differences, with the most significant effects observed immediately after the stressor, possibly implicating some block in the NK and CD8 T-cells ability to respond to "stress-mediated activation". This has positive implications for the development of laboratory diagnostic tests for this syndrome and provides a paradigm for exploration of the immuno-physiological mechanisms that are operating in GWI, and similar complex syndromes. Our results do not necessarily elucidate the cause of GWI, but they do reveal a role for immune cell dysfunction in sustaining illness.

Dataset Information

Visual event-related potentials as markers of hyperarousal in Gulf War illness: evidence against a stress-related etiology.

Publications

Visual event-related potentials as markers of hyperarousal in Gulf War illness: evidence against a stress-related etiology.

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