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R. Yanai, Y. Liu, J.-A. Ko, T. Nishida; Hyperoxia Induces Apoptosis and Akt Activation in Human Corneal Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2711.
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Ambient oxygen (O2) affects the metabolism and other functions of corneal epithelial cells. The effects of changes in O2 concentration on apoptosis and activation of the protein kinase Akt in cultured corneal epithelial cells were investigated.
Simian virus 40-transformed human corneal epithelial (HCE) cells were maintained at 37°C in a humidified incubator containing 5% CO2 and 95% room air. For experiments, HCE cells were cultured at 37°C in multigas incubators containing 5% CO2 and either 1, 21, or 60% O2 plus 94, 74, or 35% N2, respectively. Cell lysis was quantified by measurement of the release of lactate dehydrogenase. Apoptosis was evaluated by immunoblot analysis of the active (cleaved) form of caspase 7 as well as by flow cytometric analysis of cells stained with annexin V and propidium iodide. The phosphorylation (activation) of Akt was detected by immunoblot analysis.
The release of lactate dehydrogenase was markedly greater for HCE cells cultured under 60% O2 than for those cultured under 1 or 21% O2. The abundance of the cleaved form of caspase 7 and the number of cells positive for annexin V staining were also substantially greater for HCE cells cultured under 60% O2 than for those cultured under 1 or 21% O2. Phosphorylation of Akt was detected only in the cells exposed to 60% O2.
A high concentration (60%) of O2 induced apoptosis in human corneal epithelial cells. The anti-apoptotic protein Akt was also activated in cells exposed to the high concentration of O2, possibly reflecting a protective response to oxygen toxicity.
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