Abstract 1845 Effects of Oxygen on Lung Oxidant/Antioxidant Balance Poster Symposium, Sunday, 5/2

Exposure to hyperoxia alters lung development in newborn animals and humans, and inhibits cell growth in proliferating cell cultures. Oxygen-induced lung injury in premature infants during a critical period of pulmonary maturation inhibits alveolarization and may result in a permanent reduction in alveolar number, which can cause long-term pulmonary morbidity. Reactive oxygen species (ROS) are implicated as agents of cellular damage in many disease states, including pulmonary oxygen toxicity, and considerable evidence supports the role of ROS as growth-altering molecules. Glutathione (GSH)-dependant antioxidant systems protect against damage by ROS, and recycling of GSH by glutathione reductase (GR) is essential for the optimum functioning of this system. We have observed increased mitochondrial GR activities and enhanced resistance to oxidant injury by t-BuOOH in H441 cells after transient transfections with a vector (LGR) for human GR cDNA that contains a functional mitochondrial targeting signal. The present studies tested the hypothesis that enhanced mitochondrial GR activities would increase resistance to the cytostatic effects of hyperoxia. H441 cells (0.9 × 106 cells per plate) transfected with an adenoviral vector expressing LGR or a control gene (DOS), and untransfected cells (CON) were maintained in 95% or 21% oxygen for 48h. Cell growth was assessed by cell counts and by reduction of the tetrazolium dye MTT to formazan. Cells maintained in room air achieved normal growth (CON 1.98, DOS 1.91, LGR 2.0 × 106 cells per plate). Hyperoxia inhibited cell growth (CON 1.25; DOS 1.24, LGR 1.8, × 106 cells per plate, P<0.01) and the reduction of MTT (CON 29, DOS 27, LGR 16, % inhibition, P<0.01) in all cells. However, the cytostatic effects of hyperoxia were decreased in cells transfected with LGR relative to the effects in cells transfected with DOS or in untransfected cells. The mechanisms for sustaining cell growth during hyperoxia in H441 cells with enhanced GR activities are unknown, but similar effects in oxygen-dependent neonates could be highly beneficial to providing normal pulmonary outcomes.