Electroporation by nanosecond electric pulses (nsEP) is an emerging modality for tumor ablation. Here we show the efficient induction of apoptosis even by a non-toxic nsEP exposure when it is followed by a 30-min chilling on ice. This chilling itself had no impact on the survival of U-937 or HPAF-II cells, but caused more than 75% lethality in nsEP-treated cells (300 ns, 1.8-7 kV/cm, 50-700 pulses). The cell death was largely delayed by 5-23 hr and was accompanied by a 5-fold activation of caspase 3/7 (compared to nsEP without chilling) and more than 60% cleavage of poly-ADP ribose polymerase (compared to less than 5% in controls or after nsEP or chilling applied separately). When nsEP caused a transient permeabilization of 83% of cells to propidium iodide, cells placed at 37 ° C resealed in 10 min, whereas 60% of cells placed on ice remained propidium-permeable even in 30 min. The delayed membrane resealing caused cell swelling, which could be blocked by an isosmotic addition of a pore-impermeable solute (sucrose). However, the block of swelling did not prevent the delayed cell death by apoptosis. The potent enhancement of nsEP cytotoxicity by subsequent non-damaging chilling may find applications in tumor ablation therapies.
Original Publication Citation
Muratori, C., Pakhomov, A. G., Gianulis, E. C., Jensen, S. D., & Pakhomova, O. N. (2016). The cytotoxic synergy of nanosecond electric pulses and low temperature leads to apoptosis. Scientific Reports, 6, 1-9. doi: 10.1038/srep36835
Muratori, Claudia; Pakhomov, Andrei G.; Gianulis, Elena C.; Jensen, Sarah D.; and Pakhomova, Olga N., "The Cytotoxic Synergy of Nanosecond Electric Pulses and Low Temperature Leads to Apoptosis" (2016). Bioelectrics Publications. 100.
0000-0003-4950-4130 (O. Pakhomova)