Novel neurotrophic therapies in an optimized mouse model of GWVI

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DESCRIPTION (provided by applicant): The etiology and pathophysiology of Gulf War Veterans' Illness (GWVI) remain poorly understood and treatments are lacking. Most studies suggest that GWVI may be the result of exposure to drugs designed to protect military personnel from a chemical warfare attack and from insects. These drugs include: 1) pyridostigmine bromide (PB) - a reversible inhibitor of acetylcholinesterase (AChE) - that prevents nerve agents, such as sarin, from inhibiting AChE permanently; 2) permethrin (PET) - an insecticide whose mechanism of action is to block neuronal sodium channels; and 3) DEET - an insect repellent. These drugs target the nervous system and in particular, via the inhibition of AChE, the cholinergic system. Although these drugs are safe at the doses given to GW personnel, it has been hypothesized that their combination together with the stress encountered during the GW deployment may have contributed collectively to generate the multi-symptom disease, GWVI. This has been tested in toxin/stress animal models with considerable success. Recent landmark studies performed on GW Veterans and non-deployed Veterans indicate that pathophysiology of GWVI involves abnormalities in the function of the cholinergic parasympathetic system. Moreover, cognitive and sleep disturbances that characterize GWVI are consistent with a dysfunction of the basal forebrain cholinergic neurons (BFCN) whose normal activity is central to the processes of memory, attention and sleep. Together the data point to the possibility that the GW-associated exposure to the above-listed drugs and to stress caused a long-term dysfunction of cholinergic neurons within central nervous system (CNS). Therefore it would be desirable to design treatment modalities that could restore the normal functioning of cholinergic neurons and their targets in patients with GWVI. One strategy to accomplish this goal would be to use trophic factors that support neuronal viability and function. Specifically brain derived neurotrophic facto (BDNF) that signals via its receptor, TrkB. The central parasympathetic neurons and BFCN express TrkB. BDNF increases BFCN survival and elevates their cholinergic marker expression in cell culture and it is necessary for postnatal maturation of BFCN in vivo. BDNF prevents axotomy-induced degeneration and loss of cholinergic marker expression in BFCN in rats. However, BDNF does not cross the blood-brain barrier (BBB). 7,8-dihydroxyflavone (7,8-DHF) is a potent and selective TrkB agonist that readily enters the brain. Beneficial effects of 7,8-DHF have been reported in models of PTSD, PD, AD and Rett syndrome. We found that 7,8-DHF is effective in mouse models of ALS and AD. The overall goal of the proposed studies is to test the hypothesis that administration of 7,8-DHF and/or moderate exercise (MEX) - interventions known to generate a trophic neuronal environment - will cause a recovery of brain function in a mouse model of GWVI optimized for the studies of cholinergic neurons. Specifically, we will use the CHGFP transgenic mouse line that expresses the green fluorescent protein (GFP) exclusively in cholinergic cells. This permits the purification of these cells by fluorescence-activated cell sorting (FACS) and facilitates their visualization with microscopic imaging techniques. These mice will be exposed to the GWVI- associated drug combination (PB/PET/DEET) together with restraint stress, and then to our therapeutic regimens (i.e. 7,8-DHF and/or MEX) that will be employed immediately after the exposure, or after a delay of 4 weeks to treat an established illness. These studies incorporate principles of rational pharmacology and behavioral evaluation combined with state-of- the-art MR imaging and spectroscopy, physiological telemetry as well as neuropathological, neurochemical and gene-analytic techniques to define the therapeutic benefits of a novel neurotrophic compound that crosses the BBB as well as a non-pharmacological treatment modality in a unique GWVI mouse model. In addition, our studies will contribute to our understanding of the basic biology of cholinergic neurons and their role in GWVI and further characterize a novel animal model for future use to test therapeutics relevant to patients with GWVI.