Differential effects in cells exposed to ultra-short, high intensity electric fields: cell survival, DNA damage, and cell cycle analysis

Garner

Biochemical and Biophysical Research Communications

et al. 2007

Nanosecond electric pulses generate nanopores in the interior membranes of cells and modulate cellular functions. Here, we used confocal microscopy and flow cytometry to observe Smith antigen antibody (Y12) binding to nuclear speckles, known as small nuclear ribonucleoprotein particles (snRNPs) or intrachromatin granule clusters (IGCs), in Jurkat cells following one or five 10 ns, 150 kV/cm pulses. Using confocal microscopy and flow cytometry, we observed changes in nuclear speckle labeling that suggested a disruption of pre-messenger RNA splicing mechanisms. Pulse exposure increased the nuclear speckled substructures by 2.5-fold above basal levels while the propidium iodide (PI) uptake in pulsed cells was unchanged. The resulting nuclear speckle changes were also cell cycle dependent. These findings suggest that 10 ns pulses directly influenced nuclear processes, such as the changes in the nuclear RNA-protein complexes. Published by Elsevier Inc.Keywords: Nucleus; Nuclear speckles; Small nuclear ribonucleoprotein particles/intrachromatin granule clusters; Intracellular electromanipulation; Nanosecond electric pulsesWe have been exploring a new nanosecond (ns) time domain in cell biology. When cells are exposed to intense (50-300 kV/cm) pulsed electric fields (PEFs) with rise times faster than the time it takes for charges on the plasma membrane to redistribute, the electric field can penetrate into the interior of the cell and organelles. If these fields exceed the breakdown threshold of these membranes, nanopores will form in the organelle membranes [1,2]. To better understand the mechanism involved, mathematical models for the cellular electropermeabilization due to nsPEFs have been developed [3,4]. The resulting changes in cellular structures and functions differ significantly from traditional electroporation [microseconod to millisecond pulsed electric fields (PEFs)] [1,5,6]. Increased permeabilization of the plasma membrane, typically demonstrated by measuring propidium iodide (PI) uptake, due to nsPEFs was delayed compared to traditional electroporation [5,6], indicating that it was an indirect effect. These nsPEFs 0006-291X/$ -see front matter Published by Elsevier Inc.

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 96%

mentioning

confidence: 99%

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Nanosecond electric pulses penetrate the nucleus and enhance speckle formation

Garner

Biochemical and Biophysical Research Communications

et al. 2007

“…(1) Using a comet assay, Stacey et al [24] found that ten 60 ns pulses of 60 kV/cm caused a rapid 2.6-fold increase in the mean image length of DNA electrophoresis tracks in Jurkat cell extracts and a 1.6-fold increase in the comet assay from HL60 cell extracts. In both cases, this was a very significant change (p < 0.001).…”

Section: Previously Reported Changes In Dna Post-nspefmentioning

confidence: 99%

Nanosecond pulsed electric fields cause melanomas to self-destruct

Nuccitelli

Pliquett

Biochemical and Biophysical Research Communications

et al. 2006

464

250

We have discovered a new, drug-free therapy for treating solid skin tumors. Pulsed electric fields greater than 20 kV/cm with rise times of 30 ns and durations of 300 ns penetrate into the interior of tumor cells and cause tumor cell nuclei to rapidly shrink and tumor blood flow to stop. Melanomas shrink by 90% within two weeks following a cumulative field exposure time of 120 μs. A second treatment at this time can result in complete remission. This new technique provides a highly localized targeting of tumor cells with only minor effects on overlying skin. Each pulse deposits 0.2 J and 100 pulses increase the temperature of the treated region by only 3 °C, ten degrees lower than the minimum temperature for hyperthermia effects. KeywordsSkin cancer; Cancer therapy; Tumor; Pulsed electric fields; Pyknosis; Inhibiting angiogenesis; DNA; Nucleus Electric fields have been employed in several different types of cancer therapy. Some of these involve radiofrequency or microwave devices that heat the tumor to greater than 43 °C to kill the cells via hyperthermia [1,2]. Others use pulsed electric fields to permeabilize the tumor cells to allow the introduction of toxic drugs or DNA [3][4][5]. We have discovered that ultrashort electrical pulses can be used as a purely electrical cancer therapy that kills tumors without hyperthermia or drugs. Previous work from this laboratory found that fibrosarcoma tumors treated in vivo with ten 300 ns pulses exhibited a reduced growth rate compared to control tumors in the same animal [6]. Here, we report that when melanoma tumors are treated with four hundred of these pulses, tumors shrink by 90% within two weeks and a subsequent treatment can result in complete remission.The main characteristics of these nanosecond pulsed electric fields (nsPEF) are their low energy that leads to very little heat production and their ability to penetrate into the cell to permeabilize intracellular organelles [7,8] and release calcium [9][10][11] from the endoplasmic reticulum [11]. They provide a new approach for physically targeting intracellular organelles with many applications, including the initiation of apoptosis in cultured cells [12][13][14] and tumors [6], enhancement of gene transfection efficiency [13,14], and inhibiting tumor growth [6]. During the past year, we have treated over 300 murine melanomas in 120 mice with 40 kV/cm electric field pulses 300 ns in duration with dramatic results. Every tumor exposed to 400 such pulses exhibits rapid pyknosis and reduced blood flow and shrinks by an average of 90% within two The efficacy of this nsPEF treatment depends on two separate electric field parameters: pulse duration and amplitude. The effect of pulse duration can be understood by considering the process of membrane charging when the cell is placed in an electric field. Ions in the cell interior will respond to the electric field by moving in the field direction and charging the highly resistive membrane until they experience no further force. By definition this will only occur ...

Electrotherapies for Glioblastoma

et al. 2021

Non-thermal, intermediate frequency (100-500 kHz) electrotherapies present a unique therapeutic strategy to treat malignant neoplasms. Here, pulsed electric fields (PEFs) which induce reversible or irreversible electroporation (IRE) and tumour-treating fields (TTFs) are reviewed highlighting the foundations, advances, and considerations of each method when applied to glioblastoma (GBM). Several biological aspects of GBM that contribute to treatment complexity (heterogeneity, recurrence, resistance, and blood-brain barrier(BBB)) and electrophysiological traits which are suggested to promote glioma progression are described. Particularly, the biological responses at the cellular and molecular level to specific parameters of the electrical stimuli are discussed offering ways to compare these parameters despite the lack of a universally adopted physical description. Reviewing the literature, a disconnect is found between electrotherapy techniques and how they target the biological complexities of GBM that make treatment difficult in the first place. An attempt is made to bridge the interdisciplinary gap by mapping biological characteristics to different methods of electrotherapy, suggesting important future research topics and directions in both understanding and treating GBM. To the authors' knowledge, this is the first paper that attempts an in-tandem assessment of the biological effects of different aspects of intermediate frequency electrotherapy methods, thus offering possible strategies toward GBM treatment.