Alcohol (EtOH) intoxication remains a major factor in post-burn pathogenesis. Recent studies from our laboratory have shown that acute EtOH intoxication before burn injury results in: 1) decreased intestinal lymphoid [Peyer's patches (PP) and mesenteric lymph nodes (MLN)] T cell proliferation, IL-2 and IFN-y production;2) decreased MLN IL-12 production;3) increased PP and MLN IL-18 production;4) increased intestinal permeability;and 5) increased bacterial accumulation in MLN. Treatment of rats with Ac-YVAD- CHO, (5 mg/kg), an inhibitor of Caspase-1 (an enzyme that converts pro-IL-18 to mature IL-18), prevents the EtOH and burn-mediated decrease in MLN IFN-y production and the development of intestinal edema. These preliminary findings collectively suggest that IL-18 up-regulation together with a decrease in IL-12 production plays a role in altered intestinal immunity and barrier function following EtOH intoxication and burn injury. Previous studies have suggested that impaired intestinal barrier function and subsequent release of bacteria and their products play significant roles in post-burn pathogenesis. Therefore the overall goal of the proposed studies is to delineate mechanism responsible for impaired intestinal immunity and barrier function following EtOH intoxication and burn injury. We hypothesize that IL-18 up-regulation in the absence of IL-12 production in intestinal lymphoid organs following EtOH intoxication and burn injury results in decreased intestinal immunity and impaired barrier function. Using a rat model of acute EtOH intoxication and burn injury, studies in Specific Aim 1 will characterize the source (macrophage/dendritic cell) of altered IL-18 and IL-12 and determine whether IL-12 restitution alone by administering recombinant IL-12 or in combination with IL-18 inhibition by neutralizing anti-IL18 antibody prevents the: 1) suppression of intestinal immunity, and 2) impaired intestinal barrier function following EtOH intoxication and burn injury. Intestinal immunity will be determined by measuring PP and MLN T cell proliferation and cytokine profile (IL- 2, IFN-y, IL-4 and IL-10 production). Intestinal barrier functions will be measured by determining intestinal permeability and by quantifying translocated bacteria in MLN.
In Specific Aim 2 studies using approaches of selective decontamination of intestine with antibiotics prior to EtOH intoxication and burn injury will determine whether intestinal bacteria are critical to IL-18/IL-12-mediated alterations in intestinal immunity and barrier function. Finally, studies in Specific Aim 3 will determine whether Mitogen Activated Protein Kinase (Erk-1/2, p-38, JNK) and/or Signal Transducer and Activator Proteins (STAT-4 and -6) are involved in signaling IL-18/IL- 12-mediated suppression of PP and MLN T cell functions following EtOH intoxication and burn injury. Our studies delineating mechanism of impaired intestinal immunity and barrier function would help in designing approaches for treatment of burn patients who sustained injury under the influence of EtOH intoxication.
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