Nanosecond Pulsed Electric Fields (nsPEF) Induce Direct Electric Field Effects and Biological Effects on Human Colon Carcinoma Cells

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Abstract
Nanosecond pulsed electric fields (nsPEFs) are ultrashort pulses with high electric field intensity (kV/cm) and high power (megawatts), but low energy density (mJ/cc). To determine roles for p53 in response to nsPEFs, HCT116 cells (p53+/+ and p53−/−) were exposed to nsPEF and analyzed for membrane integrity, phosphatidylserine externalization, caspase activation, and cell survival. Decreasing plasma membrane effects were observed in both HCT116p53+/+ and p53−/− cells with decreasing pulse durations and/or decreasing electric fields. However, addition of ethidium homodimer-1 and Annexin-V-FITC post-pulse demonstrated greater fluorescence in p53−/− versus p53+/+ cells, suggesting a postpulse p53-dependent biological effect at the plasma membrane. Caspase activity was significantly higher than nonpulsed cells only in the p53−/− cells. HCT116 cells exhibited greater survival in response to nsPEFs than HL-60 and Jurkat cells, but survival was more evident for HCT116p53+/+ cells than for HCT116p53−/− cells. These results indicate that nsPEF effects on HCT116 cells include (1) apparent direct electric field effects, (2) biological effects that are p53-dependent and p53-independent, (3) actions on mechanisms that originate at the plasma membranes and at intracellular structures, and (4) an apparent p53 protective effect. NsPEF applications provide a means to explore intracellular structures and functions that can reveal mechanisms in health and disease.