Electromediated permeabilization of frog skeletal muscle cell membrane: Effect of voltage-gated ion channels

The Silent Threat of Hypokalemia after High Voltage Electrical Injuries: A Case Study and Review of the Literature

High-voltage electrical injuries, especially from lightning strikes, can cause life-threatening complications due to extreme temperature and voltage exposure. While burns and cardiac complications have been widely described, the documentation of metabolic imbalances, particularly hypokalemia, has not been as prevalent. This report focuses on a patient with profound transient hypokalemia following a lightning strike, alongside a review of three similar cases of transient hypokalemia from the literature. Our patient, a previously healthy young man, was struck by lightning and subsequently suffered transient hypokalemia with lower extremity sensory changes, which resolved after the normalization of serum potassium levels. While the exact underlying mechanisms of transient hypokalemia following high-voltage electrical injuries are unknown, we propose a multifactorial mechanism, which includes massive intracellular shifts of potassium due to elevated epinephrine levels and the prevention of potassium efflux through the electrical disruption of voltage-gated potassium channels. Our report underscores the importance of recognizing hypokalemia in patients with high-voltage electrical injuries and contributes to the understanding of the complex mechanisms involved. Further research is necessary to understand the connection between cellular changes induced by high-voltage exposure and their effects on metabolism, particularly in relation to hypokalemia.

A molecular dynamics study of phospholipid membrane electroporation induced by bipolar pulses with different intervals

The mechanism of changes in cell electroporation (EP) during the intervals of bipolar pulses is still unclear, and few studies have investigated the effect of the intervals at the molecular level. In this study, EP induced by bipolar pulses (BP) with different intervals was investigated using all-atom molecular dynamics simulations. Firstly, EP was formed during the positive pulses of 2 ns and 0.5 V nm^-1, then the effects of various intervals of 0, 1, 5, and 10 ns on EP evolution were investigated, and the dynamic changes of different degrees of EP induced by the following negative pulses of 2 ns and 0.5 V nm^-1 were analyzed. The elimination effect of intervals was determined and it was related to the degrees of EP and the time of intervals. At the last moment of the intervals the phospholipid membrane was classified and quantitatively defined in three states according to the degrees of EP, namely, Resealing, Destabilizing and Retaining states. These states appeared due to the combined effect of both the positive pulse and the interval, and the states represent the degrees of EP which had different responses after applying the negative pulse. These results can improve our understanding of the fundamental mechanism of BP-induced EP.

A brief overview of electroporation pulse strength-duration space: a region where additional intracellular effects are expected

Electroporation (EP) of outer cell membranes is widely used in research, biotechnology and medicine. Now intracellular effects by organelle EP are of growing interest, mainly due to nanosecond pulsed electric fields (nsPEF). For perspective, here we provide an approximate overview of EP pulse strength-duration space. This overview locates approximately some known effects and applications in strength-duration space, and includes a region where additional intracellular EP effects are expected. A feature of intracellular EP is direct, electrical redistribution of endogenous biochemicals among cellular compartments. For example, intracellular EP may initiate a multistep process for apoptosis. In this hypothesis, initial EP pulses release calcium from the endoplasmic reticulum, followed by calcium redistribution within the cytoplasm. With further EP pulses calcium penetrates mitochondrial membranes and causes changes that trigger release of cytochrome c and other death molecules. Apoptosis may therefore occur even in the presence of apoptotic inhibitors, using pulses that are smaller, but longer, than nsPEF.

Mechanisms for the intracellular manipulation of organelles by conventional electroporation

Conventional electroporation (EP) changes both the conductance and molecular permeability of the plasma membrane (PM) of cells and is a standard method for delivering both biologically active and probe molecules of a wide range of sizes into cells. However, the underlying mechanisms at the molecular and cellular levels remain controversial. Here we introduce a mathematical cell model that contains representative organelles (nucleus, endoplasmic reticulum, mitochondria) and includes a dynamic EP model, which describes formation, expansion, contraction, and destruction for the plasma and all organelle membranes. We show that conventional EP provides transient electrical pathways into the cell, sufficient to create significant intracellular fields. This emerging intracellular electrical field is a secondary effect due to EP and can cause transmembrane voltages at the organelles, which are large enough and long enough to gate organelle channels, and even sufficient, at some field strengths, for the poration of organelle membranes. This suggests an alternative to nanosecond pulsed electric fields for intracellular manipulations.

Neurological manifestations of electrical trauma

Some degree of neurological impairment is often found in patients following electrical injury. A wide range of neurological impairments can occur including peripheral neuropathies, chronic pain syndromes, brain injury and rarely severe paralytic syndromes. Outcome is difficult to accurately predict. The symptoms can present immediately or be delayed in onset. They can also be temporary, permanent or get progressively worse with time. The neurological impairment resulting from the current often comprises a substantial proportion of the morbidity associated with such injuries. It is known that electrical current can cause nerve injury, however, the primary etiology of such damage is yet to be elucidated. An unusual case of transient paralysis after high voltage burn associated with severe hypokalemia provides unique insight into a potential mechanism for nerve injury following electrical trauma.

Severe hypokalemia as a cause of acute transient paraplegia following electrical shock

Transient lower extremity paralysis has been previously reported following high voltage electrical injury. The following case report describes an unusual presentation of transient acute flaccid lower extremity paralysis following a high voltage electrical injury associated with profound hypokalemia and acid/base abnormalities similar to the periodic paralysis syndrome. The patient's symptoms resolved with correction of severe hypokalemia. Potential mechanisms for a metabolic neuromuscular disorder induced by electrical injury are proposed.

Dynamics of membrane sealing in transient electropermeabilization of skeletal muscle membranes

Large supraphysiologic transmembrane electrical potentials are known to alter the molecular organization of the bilayer lipid component of cell membranes, leading to ionic permeabilization or "electroporation". Typically, membrane electroporation is followed by several orders of magnitude increases in electrical conductance and diffusive permeability to low-molecular-weight solutes. Electroporation may be transient or stable depending on whether the membrane eventually seals or remains permeabilized. Factors that control sealing have not been well characterized. This paper describes the kinetics of membrane sealing following electroporation by pulses over a range of supraphysiologic potentials. The increase in membrane conductance is highly nonlinear during a -440-mV, 4-ms pulse and reaches two orders of magnitude greater than baseline. Electroporation and relaxation sealing kinetics are quite different, reflecting a significant hysteresis effect. Thus, it appears that the magnitude and duration of the field pulse are important factors in sealing.

Non-linear microscale alterations in membrane transport by electropermeabilization

The purpose of this study was to quantify the changes in cell membrane conductance in response to electropermeabilization, which may elucidate the mechanisms of tissue injury resulting from high-voltage electrical shock. A high-speed, space-clamp and voltage-clamp experimental configuration was used. The pulse parameters of an imposed transmembrane potential that are instrumental in membrane properties alteration were precisely controlled. The dynamics of the non-linear electroporation response was characterized.

Electric field-induced functional reductions in the K+ channels mainly resulted from supramembrane potential-mediated electroconformational changes

The goal of this study is to distinguish the supramembrane potential difference-induced electroconformational changes from the huge transmembrane current-induced thermal damages in the delayed rectifier K+ channels. A double Vaseline-gap voltage clamp was used to deliver shock pulses and to monitor the channel currents. Three pairs of 4-ms shock pulses were used to mimic the electric shock by a power-line frequency electric field. Each pair consists of two pulses with the same magnitude, starting from 350 to 500 mV, but with opposite polarities. The shock pulse-generated transmembrane ion flux and the responding electric energy, the Joule heating, consumed in the cell membrane, as well as the effects on the K+ channel currents, were obtained. Results showed that huge transmembrane currents are not necessary to cause damages in the K+ channel proteins. In contrast, reductions in the K+ channel currents are directly related to the field-induced supramembrane potential differences. By a comparison with the shock field-induced Joule heating effects on cell membranes, the field-induced supramembrane potential difference plays a dominant role in damaging the K+ channels, resulting in electroconformational changes in the membrane proteins. In contrast, the shock field-induced huge transmembrane currents, therefore the thermal effects, play a secondary, trivial role.