Recent experimental findings from our laboratory suggest that acute alcohol (EtOH) intoxication prior to bum injury deteriorates intestinal barrier function and increases bacterial translocation. Our proposed studies are designed to investigate the role of IL-18 in altered intestinal barrier functions following a combined insult of EtOH intoxication and burn injury. In our preliminary studies, we observed that a combined insult of EtOH intoxication and burn injury up-regulates IL-18 production in spleen and intestinal lymphoid organs (Mesenteric lymph nodes and Peyer's patches). The increase in IL-18 is accompanied by an increase in intestinal myeloperoxidase (MPO, an index of neutrophil accumulation) activity and intestinal edema. The treatment of rats at the time of injury with Ac-YVAD-CHO (5 mg/kg), an inhibitor of caspase-1 (enzyme that converts pro-IL-18, an inactive form of IL-18, to mature IL-18), prevented the increase in IL-18 production, as well as the increase in intestinal MPO activity and intestinal edema in EtOH intoxicated, burn-injured rats. ? ? These preliminary findings suggest a role for IL-18 in neutrophil accumulation and edema in intestinal tissue following EtOH intoxication and burn injury. Since neutrophils are known to cause tissue injury, it is likely that IL-18 potentiates neutrophils' ability to release oxidants (O2-) and proteases (e.g., elastase), which in turn can contribute to increased intestinal permeability and edema. Thus the overall goal of the proposed studies is to determine whether or not IL-18 influences neutrophils' tissue-damaging actions. We hypothesize that IL-18 up-regulation following a combined insult of EtOH intoxication and burn injury increases neutrophils' tissue-damaging actions via potentiating the release of O2- and elastase, and their recruitment to the intestinal tissue. The proposed hypothesis will be tested in a well-established rat model of acute EtOH intoxication and burn injury. Studies in Specific aim 1 will determine whether blocking IL-18 levels by treating animals with neutralizing anti-IL-18 antibodies or with caspase-1 inhibitor Ac-YVAD-CHO prevents neutrophils' 02- production, elastase release, and their sequestration in the intestine of rats given EtOH and burn injury.
In Specific aim 2, we will determine a) whether IL-18-mediated neutrophil sequestration in the intestine following EtOH intoxication and burn injury is a direct effect of IL-18 or is mediated via IL-18-dependent up-regulation of neutrophil chemotactic factor, CINC, and b) whether neutrophils are critical determinant of IL-18-mediated increase in intestinal permeability and edema following EtOH intoxication and burn injury. We hope that the proposed studies as outlined in this application delineating the role of IL-18 in impaired intestinal barrier function would help in designing specific therapeutic approaches for treatment of burn patients who sustained injury under the influence of EtOH intoxication. ? ? ?
