Sepsis, a major complication following trauma, burns and/or surgery, is the leading cause of death in the intensive care unit nationwide. Balanced endothelial cell activation and subsequent immune cell recruitment are essential elements of a successful host response during infection/sepsis. By contrast, sustained endothelial cell activation and excessive immune cell influx are detrimental. Our long-term objective is to develop new therapeutic approaches to normalize endothelial cell responses during infection/sepsis. The objective of this application is to determine the effects of cholinergic activation via nicotinic acetylcholine receptor (nAChR) agonists and vagus nerve stimulation on endothelial activation and leukocyte trafficking during sepsis. Our central hypothesis is that activation of nAChRs 'blunts' endothelial cell inflammatory responses and inhibits endothelial:leukocyte interactions during sepsis to improve host outcome. This hypothesis is based on our preliminary results revealing that (a) endothelial cells express alpha7-nAChRs; (b) nAChR agonists reduce endothelial cell activation and NFkappaB nuclear translocation in vitro, (c) cholinergic stimulation inhibits endothelial cell activation and leukocyte recruitment in vivo; and (d) cholinergic agonists improve survival during experimental sepsis.
In Aim 1 we will identify the cell-associated and molecular mechanisms by which cholinergic stimulation blocks endothelial cell activation by answering these questions: Does cholinergic stimulation directly (in the absence of macrophages) inhibit endothelial cell responses and leukocyte recruitment - via alpha7-nAChRs? Does the NFkappaB pathway (or other anti-inflammatory pathways) mediate the effects of cholinergic agonists on endothelial cells? In Aim 2 we will determine the effects of cholinergic stimulation (using agonists and vagus nerve stimulation) on endothelial cell activation and leukocyte influx (within several organs) during sepsis in mice. Further studies will investigate alternative mechanisms for improved survival during sepsis following cholinergic stimulation. These proposed studies are innovative because they are the first to investigate the effects of cholinergic stimulation on endothelial cell activation and leukocyte recruitment during sepsis. Relevance to Public Health: Sepsis (or the body's inflammatory response to severe infection) is the #1 cause of death in the intensive care unit in the US, costing $16B per year. Many studies show the role of endothelial cells (cells that line all blood vessels in the body) in controlling the body's responses during sepsis/infection. Our studies show that endothelial cells express a protein (alpha7R) capable of turning 'OFF' dangerous/deadly inflammatory responses. We propose to investigate how excessive endothelial cell responses can be controlled through the alpha7R to improve survival during infection/sepsis. These studies are expected to lead to a treatment for sepsis in humans.
