Smoke inhalation is a major cause of morbidity and mortality in fire- related injuries causing at least 20,000 fatalities per year. A delayed- onset noncardiogenic pulmonary edema frequently develops in fire victims with smoke inhalation. This phenomenon is not caused by heat, but by chemical toxins in smoke that appear to indirectly cause cell injury by the release of secondary messengers. The metabolites of the arachidonic cascade are one group of secondary messengers involved in smoke induced acute long injury. We hypothesize that activation of enzymes in the arachidonic acid cascade, especially the family of phospholipase A2 (PLA2) and leukotriene A4(LTA4) hydrolase mediate acute lung injury in smoke inhalation through production of these secondary messengers. Gene therapy offers a unique approach to inhibiting LTA4 hydrolase or individual members of the PLA2 family such as cytosolic or secretory PLA2 for which there are not selective pharmacologic inhibitors. Manipulation of these key enzymes through gene therapy will help delineate their role in acute lung injury and may well lead to new therapeutic options. To test hypothesis, a rat model showing a dose response lung injury to smoke inhalation will be used. The production of these key enzymes will be manipulated by gene therapy. Plasmids which overexpress the genes encoding cytosolic or secretory PLA2 or LTA4 hydrolase will be complexed with liposomes and delivered to the lung by tracheal insufflation. At various times after delivery to the lung the levels of these enzymes as well as their metabolites will be measured in bronchoalveolar lavage fluid. The dose response to smoke induced acute lung injury will be assessed in animals that overexpress these genes by measurement of pulmonary hemodynamics and extravascular lung water, and examination of histology. Finally acute lung injury will be studied in animals in which these enzymes will be downregulated by antisense-based inhibitors. These antisense genes will be complexed with liposomes and delivered to the lung prior to smoke inhalation and at various times after smoke inhalation to determine their therapeutic effect(s).
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