Apoptosis pathway in HeLa cells subjected to 5-ns and 120-ns electrical pulses

Summary form only given. Intense nanoseconds pulsed electric field (nsPEF) is a novel physical stress to organisms, and has been reported to induce various unique responses to mammalian cells, such as bleb formation, phosphatidylserine externalization, increase in calcium ion concentration¹, as well as increase in membrane permeabilization. The primary biological effect of nsPEF depends on the pulse parameters such as pulse duration, pulse amplitude, shot numbers. Electrical pulses with long duration more than 100 ns strongly influence the membrane structure or function, whereas the shorter pulses less than 10 ns are expected to affect intracellular organelles and/or proteins. However, the biological effect of short pulses remains unclear because much more energy is needed to induce apoptosis. We have investigated the mechanisms of apoptosis in HeLaS3 cells subjected to various kinds of nsPEFs. The signaling pathway, a cascade reaction of specific proteins, for apoptosis was explored by means of real-time polymerase-chain reaction (PCR) method.chain reaction (PCR) method. Here, we report the results of two kinds of pulse sequences, 100 shots of 120 ns-long 12.5 kV/cm, and 300 shots of 5 ns-long 240 kV/cm pulses. The number of pulses in each case was found to determine 50%-60% of cell death rate. There are several well-known apoptosis pathways and several organelles such as mitochondria, endoplasmic reticulum (ER) and membrane as well as cytoplasm are major venues of the reaction. Our interest is to know how apoptosis is triggered by nsPEF and how it depends on the electrical parameters, especially on the pulse duration. In the cells subjected to 120 ns-long pulses, Bcl-2 family genes in mitochondrial pathway stayed unchanged at 2 h after the exposure, whereas Ire1 gene in ER pathway were upregulated. On the other hand, in the case of 5 ns-long pulses, Bcl-2 family gene was upregulated, whereas Ire1 gene in ER pathway stayed unchanged at 2 h after the exp- sure. Our experiments elucidated the cells exposed to nsPEFs of distinct pulse duration were activated different apoptosis pathway.