iNOS REGULATION OF INFLAMMATION IN SHOCK

The consequences of traumatic shock include systemic inflammation associated with organ damage and dysfunction. These responses are initiated, in part, by intracellular changes that occur during hemorrhagic shock (HS) as well as events initiated at the time of resuscitation from HS. The over-arching hypothesis of the center is that changes in gene expression occur during shock that control the post-resuscitation inflammatory response and contribute to the organ dysfunction and damage. The focused hypothesis of this Project is that the inducible nitric oxide synthase (iNOS) is up-regulated during shock and that NO, in combination with superoxide, activates redox-sensitive signaling pathways. We have already shown that iNOS is up-regulated in clinical and experimental shock. Furthermore, we have conclusive evidence that iNOS-generated NO activates NF-kappaB and increases IL-6 expression and PMN accumulation in tissues (liver, lungs, and gut) following resuscitation. Because cyclooxygenase-2 (COX-2) is also up-regulated during shock and NO activates COX-2, we also postulated that NO/COX- 2 interaction contributes to the post-resuscitation inflammatory changes. Under AIM I, we will determine the mechanisms of the up-regulation of iNOS and COX-2 during hemorrhagic shock. A number of likely mechanisms will be pursued, including the roles of catecholamines, hypoxia, gut microbial products, macrophage activation products, PMN, and mast cells in iNOS and COX-2 expression in the liver. Under AIM II, we will determine how induced NO promotes the inflammatory response during resuscitated hemorrhagic shock. These experiments will focus on the relative roles of NO, superoxide, and peroxynitrite activation of NF- kappaB, expression of IL-6, and accumulation of PMN. The contribution of NO/COX-2 interaction with be established. The signaling pathways leading to NF-kappaB will be investigated with a focus on Ras and MAP kinase activation by NO. Almost all of the studies will be carried out in collaboration with Bauer, Fink, or Pitt to correlate our observations with studies on other organ systems and responses. By identifying the pathways leading to iNOS expression and NO-mediated signaling, we can devise strategies to limit organ damage and dysfunction in severely injured patients.