The production of toxic, partially reduced species of oxygen is greatly enhanced in hyperoxic lungs and may eventually overwhelm the endogenous cellular capacity of antioxidant defenses resulting in lung cell damage. This kind of pulmonary injury is observed not only in experimental animals, but also in humans receiving oxygen therapy for respiratory insufficiency. Previously studies have demonstrated that augmentation of intracellular antioxidant enzyme activities [superoxide dismutase (SOD) and/or catalase] in cells or animals by treating them with liposome-encapsulated antioxidant enzymes, or exposing animals to a sublethal concentration of oxygen would provide dramatic protection to the recipient cells or animals against hyperoxic insults. In this application, a novel approach will be undertaken to further evaluate the effectiveness of each of the antioxidant enzymes in protecting lung cells from oxygen-mediated injury. Initially, five lines of transgenic mice each carrying a specific antioxidant enzyme transgene will be generated. These transgenes are being designed to be under the control of a human beta-actin promoter to insure high levels of transcription in all types of cells in animals. Additionally, mice containing a combination of two transgenes will also be obtained by mating two transgenic founder mice each bearing a different transgene. Expression of these transgenes in different tissues including the lung will be examined at both mRNA and protein levels. Immunocytochemistry will be used to identify the cellular sites, distribution and concentrations of the antioxidant enzymes in both control and exposure will be used to determine the degree of protection provided by the augmented antioxidant enzyme activities. Antioxidant enzymes are critical for cellular defense against oxidant stress. Unravelling the effectiveness of each antioxidant enzyme should help design more efficient antioxidant therapies to block or reduce oxygen- mediated lung injury. the transgenic mice generated in this study also can be used for elucidating the role of antioxidant enzymes in other diseases associated with the over-production of partially reduced oxygen species, such as some types of lung fibrosis and reperfusion injury of ischemic heart tissue.
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