DNA electrophoretic migration patterns change after exposure of Jurkat cells to a single intense nanosecond electric pulse

Abstract

Intense nanosecond pulsed electric fields (nsPEFs) interact with cellular membranes and intracellular structures. Investigating how cells respond to nanosecond pulses is essential for a) development of biomedical applications of nsPEFs, including cancer therapy, and b) better understanding of the mechanisms underlying such bioelectrical effects. In this work, we explored relatively mild exposure conditions to provide insight into weak, reversible effects, laying a foundation for a better understanding of the interaction mechanisms and kinetics underlying nsPEF bio-effects. In particular, we report changes in the nucleus of Jurkat cells (human lymphoblastoid T cells) exposed to single pulses of 60 ns duration and 1.0, 1.5 and 2.5 MV/m amplitudes, which do not affect cell growth and viability. A dose-dependent reduction in alkaline comet-assayed DNA migration is observed immediately after nsPEF exposure, accompanied by permeabilization of the plasma membrane (YO-PRO-1 uptake). Comet assay profiles return to normal within 60 minutes after pulse delivery at the highest pulse amplitude tested, indicating that our exposure protocol affects the nucleus, modifying DNA electrophoretic migration patterns.

Figure 1. Cell growth remained unaffected after pulse exposure.

Jurkat cell growth after a single, 60 ns, 2.5 MV/m pulse. Mean ± SD of 7 independent experiments.

Figure 2. Jurkat cells plasma membrane was selectively permeabilized.

Plasma membrane permeabilization of Jurkat cells after 1 pulse, 60 ns, 2.5 MV/m, presented as representative fluorescence histograms for A) YO-PRO-1 uptake immediately (0 min) and 120 min post pulse and B) PI uptake immediately, 120 min and 180 min post pulse. C) Molecular structures and 3-D models (van der Waal's radii) of the dyes.

Figure 3. nsPEFs affect DNA migration in a dose-dependent fashion.

Dose-response for Jurkat cell DNA migration after exposure to a single, 60 ns pulse. The 75^th percentile of the distribution of exposed cells normalized to sham-exposed ones is presented for each of three independent experiments carried out at 1.0, 1.5, and 2.5 MV/m. Data refer to % DNA in the tail.

Figure 4. DNA migration pattern of Jurkat cells under nsPEFs vs MMS.

Distribution of % DNA in the tail for Jurkat cells following nsPEF exposure (Exp), sham exposure (Sham) and 2 hr exposure to 10 µM of methyl methanesulfonate (MMS). Results refer to a representative experiment carried out at 1 pulse, 2.5 MV/m, 60 ns.