The effect of glutamine on A549 cells exposed to moderate hyperoxia

Abstract

The use of high oxygen concentrations is frequently necessary in the treatment of acute respiratory distress syndrome (ARDS) and bronchopulmonary dysplasia (BPD). High oxygen concentrations, however, are detrimental to cell growth and cell survival. Glutamine (Gln) may be protective to cells during periods of stress and recently has been shown to increase survival in A549 cells exposed to lethal concentrations of oxygen (95% O2). We found that supplemental Gln enhances cell growth in A549 cells exposed to moderate concentrations of oxygen (60% O2). We therefore evaluated the effect of moderate hyperoxia on the cell cycle distribution of A549 cells. At 48 h there was no significant difference in the cell cycle distribution between 2 mM Gln cells in 60% O2 and 2 mM cells in room air. Furthermore, 2 mM Gln cells in 60% O2 had stable protein levels of cyclin B1 consistent with ongoing cell proliferation. In contrast, at 48 h, cells not supplemented with glutamine (Gln-) in 60% O2 had evidence of growth arrest by both flow cytometry (increased percentage of G1 cells) and by decreased protein levels of cyclin B1. G1 growth arrest in the Gln- cells exposed to 60% O2 was not, however, associated with induction of p21 protein. At 72 and 96 h, Gln- cells in 60% O2, began to demonstrate a partial loss of G1 checkpoint regulation and an increase in apoptosis, indicating an increased sensitivity to oxygen toxicity. Glutathione (GSH) concentrations were then measured. 2 mM Gln cells in 60% O2 were found to have higher concentrations of GSH compared to Gln- cells in 60% O2, suggesting that Gln confers protection to the cell during exposure to hyperoxia through up-regulation of GSH. When cells in 60% O2 were given higher concentrations of Gln (5 and 10 mM), cell growth at 96 h was increased compared to cells grown in 2 mM Gln (P<0.04). Clonal survival was also increased in cells exposed 60% O2 and supplemented with higher concentrations of Gln compared to Gln- cells in 60% O2. These studies suggest that supplemental glutamine may improve cell growth and cell viability and therefore may be beneficial to the lung during exposure to moderate concentrations of supplemental oxygen.

Phosphate-activated glutaminase (GLS2), a p53-inducible regulator of glutamine metabolism and reactive oxygen species

“…Glutamine preserves total GSH levels after oxidative damage, making it a component of the cellular antioxidant defense (22). GLS2 plays a critical role by up-regulating GSH levels upon oxidative stress (23,24). Overexpression of 3×FLAG-GLS2 increased glutamine consumption and facilitated the production of glutamate detected in the culture medium of H1299 cells, thus confirming its enzymatic function to catabolize glutamine to glutamate (Fig.…”

Nutrition and the Lung

“…Since glutamine is essential for glutathione and for rapidly dividing cells, it may have a role in cell proliferation especially in the presence of high levels of oxygen [47] .…”

Antioxidants preserve macrophage phagocytosis of Pseudomonas aeruginosa during hyperoxia

“…The inhalation of supraphysiological oxygen concentrations for prolonged or even transient periods of time results in acute lung injury, which is characterized by the injury and death of pulmonary cells [6][7][8][9][10][11]. The role of hyperoxia as a potential cause of lung cell injury has been extensively characterized in alveolar epithelial [12][13][14][15][16][17] and endothelial cells [18,19]. However, only a few studies have examined it's impact on alveolar macrophages [20][21][22][23].…”