Difference of Cell Death of Budding Yeast for Frequency Components of Pulsed Electric Field

Pulsed power technology has possibility to be able to provide a new method for tissue ablation. Applying a pulsed high electric field with nanosecond duration time onto a cancer cell can induce apoptosis into that. In this method, a frequency component of the electric field applied to the cell is an important factor. This paper focuses on the investigation of frequency characteristics of a difference of a cell death caused by applying the pulsed high electric field. The budding yeast that is a eukaryotic cell has been used as a model organism of a human cell. Difference of the cell death of the yeast for frequencies of the pulsed electric field by using molecular probes, propidium iodide, Annexin-V, and FLICA has been investigated. The frequency of the pulsed electric field was changed from 200 kHz to 70 MHz. The low frequencies, 200 kHz and 3.5 MHz, under 45 MHz yielded both necrosis and apoptosis in the cells. The electric field of frequency of 200 kHz with an intensity of 30 kV/cm only induced necrosis by breakdown in most cells. At the frequencies of 200 kHz with 16 kV/cm and 3.5 MHz, both apoptosis and necrosis occurred. The apoptotic pathway at 3.5 MHz went via caspase. At the frequency of 70 MHz, only apoptosis, not necrosis, was induced in the cells. However, the apoptosis via caspase was not dominant for the cell death. A signal for the cell death passed through other pathway of apoptosis, which was different from that of 3.5 MHz. At 45 MHz, the cell death did not occur. 45 MHz is the boundary where necrosis occurs, and the apoptotic pathway is different.