Toxic species of oxygen are generated by processes within lung cells or are formed in the extracellular milieu of the lung. Exposure of lung tissue to reactive oxygen species may induce cellular damage and, ultimately, respiratory distress. Enzymatic protection against such activated oxygen-based destruction is partially provided by catalase and superoxide dismutase (SOD). Mouse strain Csb possesses the only known nonhuman mammalian genetic variant of the catalase structural gene that produces a relatively diminished expression of catalase in the lung. This provides a unique probe to study the regulatory mechanisms active in normal lung catalase gene (Csa) expression. To understand the relationship between genetic variability of antioxidant gene expression and oxygen radical-induced respiratory distress, the molecular basis of the Csb-catalase mutation will first be determined, and lung regulatory mechanism(s) influenced by this genetic perturbation will be analyzed. In vitro translation and in vivo turnover studies of lung catalase mRNA and protein, will identify lung-specific control processes influenced by this mutation. Sequence analyses of catalase Csa and Csb cDNAs will identify any nucleotide differences between these lung mRNAs. To identify specific nucleotide sequences that produce Csb lung acatalasemia, recombinant expression plasmids containing hybrid catalase encoding molecules (Csa/Csb) will be tested for their ability to rescue acatalasemic fibroblasts from H2O2 toxicity. Hyperoxia will be used to induce oxidative stress to estimate the incidence, degree, and mechanisms of catalase and SOD induction in Csa and Csb lung tissue. Influence of lung maturational level and variability of gene expression of survival rates after oxidative stress will be evaluated. To identify regulatory sequences that may influence catalase gene expression in murine lung tissue, genomic catalase clones of 5'-noncoding sequences will be isolated and putative controlling regions tested for inductive capabilities. Results from this study will not only identify molecular regulatory processes which modulate lung antioxidant enzyme levels, but also provide an aspect of the molecular basis for susceptibility to the adult respiratory distress syndrome.
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