Cellular Pre-Adaptation to the High O Concentration Used in Standard Cell Culture Confers Resistance to Subsequent HO-Induced Cell Death.

The addition of hydrogen peroxide (HO) to cultured cells is widely used as a method to modulate redox-regulated cellular pathways, including the induction of programmed cell death in cell culture experiments and the testing of pro- and antioxidant compounds. Here, we assessed the effect on the cellular response to HO of pre-adapting squamous cell carcinoma cells (A431) to the standard cell culture oxygenation of 18.6% O, compared to cells pre-adapted to a physiological skin O concentration (3.0% O). We showed that cells pre-adapted to 18.6% O resisted HO-induced cell death compared to cells pre-adapted to 3.0% O for 96 h prior to treatment with HO. Moreover, the enzymatic activities of catalase and glutathione reductase, as well as the protein expression levels of catalase, were higher in cells pre-adapted to 18.6% O compared to cells pre-adapted to 3.0% O HO-resistant cells, pre-adapted to 18.6% O, exhibited increased nuclear Nrf-2 levels. It is concluded that A431 cells pre-adapted to standard cell culture oxygenation conditions resist HO-induced cell death. This effect may be related to their heightened activation of Nrf-2.