The main objective: To provide mechanistic insight into the role of brain cholinergic pathways in the central cholinergic regulation of the systemic inflammatory response during endotoxemia and polymicrobial sepsis. Background: The pathophysiology of sepsis and other inflammatory disorders is critically mediated by dysregulated innate immune responses and abnormally elevated cytokine levels, which are important experimental therapeutic targets. Sepsis and post-sepsis morbidity may also be associated with abnormalities in the brain cholinergic system. Our recent findings demonstrate the critical role of cholinergic activation in the brain in reducing systemic levels of the pro-inflammatory cytokines tumor necrosis factor (TNF) and high mobility group box1 (HMGB1) and improving survival during lethal inflammation. We have demonstrated that M1 receptor agonists suppress cytokine responses and improve survival during endotoxemia and this anti- inflammatory function is mediated through brain muscarinic receptors. We have also recently shown that galantamine, a centrally-acting acetylcholinesterase (AChE) inhibitor suppresses systemic TNF levels and improves survival in endotoxemia through brain muscarinic receptor-dependent signaling. We have shown that the anti-inflammatory effect of galantamine is mediated through the efferent vagus nerve-based cholinergic anti-inflammatory pathway. This pathway is a major brain-to immune communication circuit. Activation of the cholinergic anti-inflammatory pathway, which mediates the brain-dependent anti-inflammatory effect of galantamine, also suppresses HMGB1 levels and improves survival in experimental sepsis. These findings reveal an important contribution of brain cholinergic signaling to the modulation of inflammation. We hypothesize that there is a correlation between the levels of cholinergic muscarinic receptor-mediated activation in the brain and the systemic inflammatory response. This hypothesis will be tested by the following 2 aims: (SA#1) Delineate the role of brain pathways in the cholinergic regulation of the inflammatory response during endotoxemia. We will perform selective lesions of neurons of two major brain cholinergic pathways the basal forebrain cholinergic system (BFCS), and the mesopontine cholinergic system (MCS) in rats. Then, animals will be treated with galantamine and subjected to endotoxemia to evaluate the effects of selective brain cholinergic dysfunction on TNF, other cytokines, and organ injury and the magnitude of galantamine anti-inflammatory efficacy. (SA#2) Evaluate the brain cholinergic regulation of the inflammatory response during cecal ligation and puncture (CLP)-induced polymicrobial sepsis. We will perform lesions of brain cholinergic BFCS and MCS neurons in rats and will subject animals to CLP to evaluate the impact of specific cholinergic denervations on the levels of HMGB1, other cytokines, organ injury and survival in this model of polymicrobial sepsis. The effect of galantamine on the systemic cytokine response and survival and its dependence on specific brain dysfunction will be evaluated in therapeutic settings.
The proposed study will examine the role of the brain cholinergic system in controlling the release of cytokines that mediate lethal inflammation. The results generated from this study will advance our understanding of the regulation of pathological mechanisms in sepsis and other devastating inflammatory diseases, which in turn may provide a rationale/platform for the design of novel and efficient treatments.
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