Gulf War neurotoxicants and acquired cognitive and neuropsychological dysfunction

Baltimore Va Medical Center, Baltimore MD

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Abstract

? DESCRIPTION (provided by applicant): Gulf War Veterans illness (GWVI) refers to the complex of chronic symptoms that preferentially affect Veterans of the 1990-1991 Persian Gulf War, with the most debilitating symptoms being those that rob the Veteran of his or her personal identity, i.e., symptoms that affect the brain an result in acquired cognitive and neuropsychological dysfunction (AC&ND). An established concept in clinical neuroscience is that some forms of AC&ND are caused by chronic TLR4-mediated neuroinflammation. Gulf War Veterans were exposed to a specific combination of risk factors that are not usually encountered in the general population or in non-deployed military personnel, which we speculate could have been responsible for TLR4-mediated neuroinflammation leading to AC&ND. First, warfighters deployed to the Persian Gulf were exposed to many potential neurotoxicants, most importantly the classic pro-inflammatory Toll-like receptor 4 (TLR4) ligand, lipopolysaccharide (LPS). Middle East sand-dust particles contain exceptionally high levels of LPS. During sand storms, especially high levels of LPS would be delivered to the olfactory mucosa, which is increasingly recognized as a direct portal of entry into the brain. Secondly, warfighters deployed to the Persian Gulf were exposed to pyridostigmine, a long-acting acetylcholinesterase inhibitor that was used daily as prophylaxis against nerve gas. Based on new data from our laboratory, which suggest that pyridostigmine augments entry into the brain of LPS delivered to the olfactory mucosa, we speculate that the combined exposures to olfactory LPS plus oral pyridostigmine might have resulted in marked TLR4-mediated neuroinflammation leading to AC&ND typical of GWVI. OBJECTIVE: We have two specific aims (SA): In SA1, using male and female rats, we will evaluate the effect of low-dose paranasal sinus LPS, alone vs. with oral pyridostigmine, on the severity and persistence of neuroinflammation and resulting neurofunctional abnormalities. These experiments will yield a detailed characterization of our model of GWVI (olfactory LPS plus oral pyridostigmine), and will demonstrate the multiplicative role of pyridostigmine on olfactory LPS. In SA2, using our model of GWVI in male and female rats, we will evaluate the effect of treatment, after disease onset, with a PPAR? agonist, Rosiglitazone, on neuroinflammation (CSF and plasma biomarkers, and tissue inflammation), microstructural/metabolic MRI changes, and neurofunctional abnormalities. METHODS: We will use a rat model to examine the CNS effects of the neurotoxicants, low-dose paranasal sinus LPS plus oral pyridostigmine administered continuously for 4 or 8 weeks. Rats will be implanted with mini-osmotic pumps to deliver LPS into the paranasal sinus, and will have pyridostigmine in their drinking water. Neurofunctional abnormalities will be assessed using: Elevated Plus Maze, open field exploration, novel object recognition, Morris Water Maze (incremental and rapid spatial learning), tail suspension test, and forced swim test. Inflammatory cytokines in CSF and plasma will be measured using a multiplex system. Tissue neuroinflammation will be examined using immunohistochemistry. Microstructural and metabolic changes will be studied non-invasively using diffusion kurtosis imaging and proton magnetic resonance spectroscopy. Preliminary Findings: Strong preliminary data support this project. Status: This is a new project. Impact: Successful completion of this project will shed new light on the potential involvement of olfactory LPS plus oral pyridostigmine as a root cause of GWVI, and on the role of chronic indolent systemic inflammation in causing symptoms of AC&ND. Our studies provide a new direction for GWVI research, and may aid in developing novel therapies for reversing AC&ND associated with GWVI.