Sepsis, following trauma/hemorrhage and ischemia/reperfusion, is a common etiology for subsequent Acute Respiratory Distress Syndrome (ARDS) and multiple organ dysfunction syndrome (MODS) and remains a leading cause of subsequent morbidity and mortality. A number of different inflammatory cells are responsible for this condition; however, it appears that the macrophage is the common central orchestrating cell underlying these conditions. It is becoming evident that this inflammatory driven signaling cascade is affected by a number of different "priming" agents, such as platelet activating factor (PAF) and oxidant stress. "Priming" does not lead to pro-inflammatory mediator production; rather it causes enhanced responsiveness by the macrophage to secondary inflammatory stimuli, such as endotoxin. The mechanism in which these "priming" agents cause this enhanced response is unknown. Therefore, the purpose of this grant is to better delineate the intracellular signaling mechanisms which are responsible for this affect. This proposal will focus on the potential role that the secondary messenger, calcium, plays during initial "priming". Although calcium flux occurs during "priming", it is unknown if and how calcium could modulate endotoxin-mediated signaling. We, therefore, hypothesis that the increase in intracellular calcium results in the activation of regulatory kinases, such as calcium/calmodulin-dependent protein kinases (CaMK), leads to enhanced endotoxin-mediated signaling. Furthermore, we hypothesis that CaMK activation leads to modulation of actin polymerization and stress fiber polymerization induced by endotoxin resulting in enhanced intracellular spatial relationships and optimal endotoxin signaling. The role of calcium and CaMK during "priming" will be investigated through the use of specific inhibitors and activators on the ability of PAF and oxidant stress to induce "priming" of endotoxin-mediated activation within the macrophage. The overall aim of this proposal is to provide further insight into potential mechanisms that serve in the activation and "priming" of the macrophage. Through an enhanced understanding of these mechanisms it is our goal that potential therapeutic targets may be discovered to regulate the inflammatory response following trauma/hemorrhage and ischemia/reperfusion.