Following an initial rise in impedance HT-22 cells displayed a constant growth rate over time with absolute CI values proportional to the initial seeding density, caused by adherence of the cells to the bottom of the well. After treatment with glutamate, CI values began to decrease rapidly, correlating with dose-dependent glutamate-induced cell death, which was in turn confirmed by the results of MTT viability assays, as well as being consistent with the kinetics of cell death reported in mitochondrial fragmentation and AIF nuclear translocation assays. In the next step of the experiment, BI-6C9 (an inhibitor of the pro-apoptotic BH-3 protein BID) was used to prevent glutamate toxicity in HT-22 cells. BI-6C9-mediated neuroprotection was reflected in the xCELLigence System by a continued rise in CI values, demonstrating that the compound preserved cell morphology and cell survival.

As with HT-22 cells, primary rat cortical neurons showed at first an increase in CI values due to initial cellular attachment to the bottom of the well. Subsequent removal of proliferating glial cells with cytosine-arabinofuranoside caused an expected slight decrease in CI values. To monitor cell death, the primary neuronal cultures were treated with ionomycin or glutamate. Treatment with ionomycin caused a marked drop in CI correlating with the formation of pyknotic, rounded cell bodies. By comparison, cell death induced by glutamate was significantly delayed, and was reflected by a steady decline in CI values within 48 to 72 hours of treatment. These different cell death effects reflect the delayed activation of cell death signalling by glutamate compared to the more rapid loss of cell membrane integrity and necrotic cell death following ionomycin treatment.

Source : Roche