Extremely low frequency pulsed DC electric fields promote neutrophil extension, metabolic resonance and DNA damage when phase-matched with metabolic oscillators

Electroceutical Management of Bacterial Biofilms and Surgical Infection

Significance: In the host-microbe microenvironment, bioelectrical factors influence microbes and hosts as well as host-microbe interactions. This article discusses relevant mechanistic underpinnings of this novel paradigm. It also addresses how such knowledge may be leveraged to develop novel electroceutical solutions to manage biofilm infection. Recent Advances: Systematic review and meta-analysis of several hundred wound studies reported a 78.2% prevalence of biofilms in chronic wounds. Biofilm infection is a major cause of delayed wound healing. In the host-microbe microenvironment, bioelectrical factors influence interactions between microbes and hosts. Critical Issues: Rapid biological responses are driven by electrical signals generated by ion currents moving across cell membranes. Bacterial life, growth, and function rely on a bioelectrical milieu, which when perturbed impairs their ability to form a biofilm, a major threat to health care. Electrokinetic stability of several viral particles depend on electrostatic forces. Weak electrical field strength, otherwise safe for humans, can be anti-microbial in this context. In the host, the electric field enhanced keratinocyte migration, bolstered immune defenses, improved mitochondrial function, and demonstrated multiple other effects consistent with supporting wound healing. A deeper mechanistic understanding of bioelectrical principles will inform the design of next-generation electroceuticals. Future Directions: This is an opportune moment in time as there is a surge of interest in electroceuticals in medicine. Projected to reach $35.5 billion by 2025, electroceuticals are becoming a cynosure in the global market. The World Health Organization reports that more than 50% of surgical site infections can be antibiotic resistant. Electroceuticals offer a serious alternative.

Electrical Stimulation for Wound-Healing: Simulation on the Effect of Electrode Configurations

Endogenous electric field is known to play important roles in the wound-healing process, mainly through its effects on protein synthesis and cell migration. Many clinical studies have demonstrated that electrical stimulation (ES) with steady direct currents is beneficial to accelerating wound-healing, even though the underlying mechanisms remain unclear. In the present study, a three-dimensional finite element wound model was built to optimize the electrode configuration in ES. Four layers of the skin, stratum corneum, epidermis, dermis, and subcutis, with defined thickness and electrical properties were modeled. The main goal was to evaluate the distributions of exogenous electric fields delivered with direct current (DC) stimulation using different electrode configurations such as sizes and positions. Based on the results, some guidelines were obtained in designing the electrode configuration for applications of clinical ES.

Effect of in vivo and in vitro exposure to electrostatic field on some hematological parameters in rats

The aim of this study was to investigate the effect of the external electrostatic field (ESF) on some hematological parameters in rats. Both in vivo and in vitro experiments were carried out. In in vivo investigations, rats were exposed to ESF (200 kV/m) during short (1 h) and long periods (6 days, 6 h daily). For in vitro study, the blood of intact rats was exposed to ESF for 1 h. Blood hematology was measured using validated ABX Micros ESV 60 Veterinary Hematology Analyzer. DNA damage in blood leucocytes was detected by means of comet assay. ESF effect on blood cell count was mainly manifested in white blood cells (WBC) and platelets. Damage of WBC was shown both in vitro and in vivo despite alterations in the count. This means the observed increase in WBC count in some cases might be a result of WBC compensatory mobilization from the bone marrow. Red blood cell (RBC) count and related parameters were slightly affected by ESF. Nevertheless, alterations in the shape and size of RBC were manifested. All ESF effects were extinguished in 14 days after the end of exposure. Bioelectromagnetics. 37:513-526, 2016. © 2016 Wiley Periodicals, Inc.

Pulsed DC Electric Field-Induced Differentiation of Cortical Neural Precursor Cells

We report the differentiation of neural stem and progenitor cells solely induced by direct current (DC) pulses stimulation. Neural stem and progenitor cells in the adult mammalian brain are promising candidates for the development of therapeutic neuroregeneration strategies. The differentiation of neural stem and progenitor cells depends on various in vivo environmental factors, such as nerve growth factor and endogenous EF. In this study, we demonstrated that the morphologic and phenotypic changes of mouse neural stem and progenitor cells (mNPCs) could be induced solely by exposure to square-wave DC pulses (magnitude 300 mV/mm at frequency of 100-Hz). The DC pulse stimulation was conducted for 48 h, and the morphologic changes of mNPCs were monitored continuously. The length of primary processes and the amount of branching significantly increased after stimulation by DC pulses for 48 h. After DC pulse treatment, the mNPCs differentiated into neurons, astrocytes, and oligodendrocytes simultaneously in stem cell maintenance medium. Our results suggest that simple DC pulse treatment could control the fate of NPCs. With further studies, DC pulses may be applied to manipulate NPC differentiation and may be used for the development of therapeutic strategies that employ NPCs to treat nervous system disorders.

Galvanotactic migration of EA.Hy926 endothelial cells in a novel designed electric field bioreactor

Endogenous direct current electric fields (dcEFs) play a significant role in major biological processes such as embryogenesis, wound healing, and tissue regeneration. In this study, the galvanotaxis of human umbilical vein endothelial cell line EA.Hy926 was investigated by using a novel designed bioreactor. The physical features of the bioreactor were discussed and analyzed by both numerical simulation method and equivalent circuit model method. EA.Hy926 cells were cultured in the bioreactor for 10-24 h under 50-250 mV/mm dcEFs. Cell migration direction, distance, and velocity were recorded under an online time-lapse microscope. The effects of serum and growth factor on cell galvanotatic migration were investigated. To further explore the role of dcEFs in regulating endothelial cells, we analyzed the endothelial cell proliferation and secretion of nitric oxide (NO), endothelin-1 (ET-1) in response to dcEFs of physiological strength. Our results showed that EA.Hy926 cells had an obvious directional migration to the cathode, and the EF-directed migration was voltage dependent. The results also showed dcEFs did not affect cell proliferation, but affected the productions of NO and ET-1. Our study also showed the novel bioreactor, with a compact and planar style, makes it more convenient and more reasonable for EF stimulation experiments than earlier chamber designs.

Functional changes in human peripheral neutrophils in workers with different exposure to noxious agents

Peripheral neutrophils (PMN) are a useful model to study cell activation and to evaluate the multiple stressors' interference with signalling pathways. This study aimed to evaluate the effects of different exposure to noxious agents on PMN activity by chemiluminescence assays. Two groups of office workers were recruited: peripheral whole blood cells and isolated PMNs were analyzed, performing intra- and extra-cellular chemiluminescence evaluation to study compartmental release of radical species. The exposed group shows a higher emission in resting whole blood chemiluminescence than in controls; the intracellular chemiluminescence emission in urban employees was increased, whereas the extracellular was not affected. After stimulation, the extracellular chemiluminescence was decreased in urban employees, whereas the intracellular emission did not show differences. We hypothesize that once stimulated, exposed subjects' PMNs respond to stimuli less than unexposed: PMNs could be considered indicators of chronic exposure to noxious agents.

Calmodulin mediates DNA repair pathways involving H2AX in response to low-dose radiation exposure of RAW 264.7 macrophages

Understanding the molecular mechanisms that modulate macrophage radioresistance is necessary for the development of effective radiation therapies, as tumor-associated macrophages promote both angiogenesis and matrix remodeling that, in turn, enhance tumor metastasis. In this respect, we have identified a dose-dependent increase in the abundance (i.e., expression level) of the calcium regulatory protein calmodulin (CaM) in RAW 264.7 macrophages upon irradiation. At low doses of irradiation there are minimal changes in the abundance of other cellular proteins detected using mass spectrometry, indicating that increases in CaM levels are part of a specific radiation-dependent cellular response. CaM overexpression results in increased macrophage survival following radiation exposure, acting to diminish the sensitivity to low-dose radiation exposures. Following macrophage irradiation, increases in CaM abundance also result in an increase in the number of phosphorylated histone H2AX foci, associated with DNA repair, with no change in the extent of double-stranded DNA damage. In comparison, when nuclear factor kappaB (NFkappaB)-dependent pathways are inhibited, through the expression of a dominant-negative IkappaB construct, there is no significant increase in phosphorylated histone H2AX foci upon irradiation. These results indicate that the molecular basis for the up-regulation of histone H2AX-mediated DNA repair pathways is not the result of nonspecific NFkappaB-dependent pathways or a specific threshold of DNA damage. Rather, increases in CaM abundance act to minimize the low-dose hypersensitivity to radiation by enhancing macrophage radioresistance through processes that include the up-regulation of DNA repair pathways involving histone H2AX phosphorylation.

Effects of applied DC electric field on ligament fibroblast migration and wound healing

Applied electric fields (static and pulsing) are widely used in orthopedic practices to treat nonunions and spine fusions and have been shown to improve ligament healing in vivo. Few studies, however, have addressed the effect of electric fields (EFs) on ligament fibroblast migration and biosynthesis. In the current study, we applied static and pulsing direct current (DC) EFs to calf anterior cruciate ligament (ACL) fibroblasts. ACL fibroblasts demonstrated enhanced migration speed and perpendicular alignment to the applied EFs. The motility of ligament fibroblasts was further modulated on type I collagen. In addition, type I collagen expression increased in ACL fibroblasts after exposure to pulsing EFs. In vitro wound-healing studies showed inhibitory effects of static EFs, which were alleviated with a pulsing EF. Our results demonstrate that applied EFs augment ACL fibroblast migration and biosynthesis and provide potential mechanisms by which EFs may be used for enhancing ligament healing and repair.

Electrical stimulation of the energy metabolism in yeast cells using a planar Ti-Au-electrode interface

We report on the influence of dielectric pulse injection on the energy metabolism of yeast cells with a planar interdigitated electrode interface. The energy metabolism was measured via NADH fluorescence. The application of dielectric pulses results in a distinct decrease of the fluorescence, indicating a response of the energy metabolism of the yeast cells. The reduction of the NADH signal significantly depends on the pulse parameters, i.e., amplitude and width. Furthermore, the interface is used to detect electrical changes in the cell-electrolyte system, arising from glucose-induced oscillations in yeast cells and yeast extract, by dielectric spectroscopy at 10 kHz. These dielectric investigations revealed a beta(1)-dispersion for the system electrolyte/yeast cells as well as for the system electrolyte/yeast extract. In agreement with control measurements we obtained a glycolytic period of 45 s for yeast cells and of 11 min for yeast extract.

Effects of pulsed electric fields on DNA of human lymphocytes

The effects of pulsed electric fields of low frequency (50 Hz) on DNA of human lymphocytes were investigated. The influence of additional external factors, such as hydrogen peroxide (H2O2) and gamma-irradiation, as well as the repair efficiency in these lymphocytes, was also evaluated. The comet assay, a very sensitive and rapid method for detecting DNA damage at the single cells level was the method used. A significant amount of damage was observed after exposure to the electric fields, compared to the controls. After 2 h incubation at 37 degrees C, a proportion of damage was repaired. H2O2 and gamma-irradiation increased the damage to lymphocytes exposed to pulsed electric fields according to the dose used, while the amount of the repair was proportional to the damage.

IFN-gamma primes RAW264 macrophages and human monocytes for enhanced oxidant production in response to CpG DNA via metabolic signaling: roles of TLR9 and myeloperoxidase trafficking

Macrophages and monocytes are activated by CpG DNA motifs to produce NO, which is enhanced dramatically by IFN-gamma. We hypothesize that synergistic cellular responses to IFN-gamma and CpG DNA are due to cross-talk between metabolic signaling pathways of leukocytes. Adherent RAW264.7 macrophages and human monocytes exhibited NAD(P)H autofluorescence oscillation periods of approximately 20 s. IFN-gamma increased the oscillatory amplitude, which was required for CpG DNA-mediated metabolic changes. These alterations in metabolic dynamics required the appropriate combinations of murine/human TLR9 and murine/human-specific CpG DNA. Other factors that also promoted an increase in metabolic oscillatory amplitude could substitute for IFN-gamma. Because recent studies have shown that the metabolic frequency is coupled to the hexose monophosphate shunt, and the amplitude is coupled to the peroxidase cycle, we tested the hypothesis that myeloperoxidase (MPO) participates in IFN-gamma priming for oxidant production. MPO inhibitors blocked cell responses to IFN-gamma and CpG DNA. In the absence of IFN-gamma exposure, the effects of CpG DNA could be duplicated by MPO addition to cell samples. Moreover, monocytes from MPO knockout mice were metabolically unresponsive to IFN-gamma and CpG DNA. NAD(P)H frequency doubling responses due to CpG DNA were blocked by an inhibitor of the hexose monophosphate shunt. Because NAD(P)H participates in electron trafficking to NO and superoxide anions, we tested oxidant production. Although CpG DNA alone had no effect, IFN-gamma plus CpG enhanced NO and reactive oxygen metabolite release compared with IFN-gamma treatment alone. We suggest that amplitude and frequency modulation of cellular metabolic oscillations contribute to intracellular signaling synergy.

Reactive Oxygen Species (ROS): Pathogens or Sources of Vital Energy? Part 2. Bioenergetic and Bioinformational Functions of ROS

In Part 1 of the review of experimental data concerning reactive oxygen species (ROS) production and use, their indispensable role in regulation of multiple physiologic processes is examined. Part 2 considers the unique property of reactions in which ROS participates, the generation of energy of electronic excitation (EEE). Because of incessant ROS cycling, EEE is continuously produced in aerobic organisms. It may be used as an energy activator for multiple biochemical reactions and also may function as a specific signaling factor. This approach allows the perception of the beneficial effects of hydrogen peroxide, ozone, other ROS therapy, and foods rich in antioxidants. Both insufficient production of ROS and distortions in their use may cause anomalies in coordination of ROS generation and use, resulting in the deranged operation of biochemical and physiologic processes and the development of pathology.

Controversial cytogenetic observations in mammalian somatic cells exposed to extremely low frequency electromagnetic radiation: a review and future research recommendations

During the years 1990-2003, a large number of investigations were conducted using animals, cultured rodent and human cells as well as freshly collected human blood lymphocytes to determine the genotoxic potential of exposure to nonionizing radiation emitted from extremely low frequency electromagnetic fields (EMF). Among the 63 peer reviewed scientific reports, the conclusions from 29 studies (46%) did not indicate increased damage to the genetic material, as assessed from DNA strand breaks, incidence of chromosomal aberrations (CA), micronuclei (MN), and sister chromatid exchanges (SCE), in EMF exposed cells as compared with sham exposed and/or unexposed cells, while those from 14 investigations (22%) have suggested an increase in such damage in EMF exposed cells. The observations from 20 other studies (32%) were inconclusive. This study reviews the investigations published in peer reviewed scientific journals during 1990-2003 and attempts to identify probable reason(s) for the conflicting results. Recommendations are made for future research to address some of the controversial observations.

Ion channel clustering enhances weak electric field detection by neutrophils: apparent roles of SKF96365-sensitive cation channels and myeloperoxidase trafficking in cellular responses

We have tested Galvanovskis and Sandblom's prediction that ion channel clustering enhances weak electric field detection by cells as well as how the elicited signals couple to metabolic alterations. Electric field application was timed to coincide with certain known intracellular chemical oscillators (phase-matched conditions). Polarized, but not spherical, neutrophils labeled with anti-K(v)1.3, FL-DHP, and anti-TRP1, but not anti-T-type Ca(2+) channels, displayed clusters at the lamellipodium. Resonance energy transfer experiments showed that these channel pairs were in close proximity. Dose-field sensitivity studies of channel blockers suggested that K(+) and Ca(2+) channels participate in field detection, as judged by enhanced oscillatory NAD(P)H amplitudes. Further studies suggested that K(+) channel blockers act by reducing the neutrophil's membrane potential. Mibefradil and SKF93635, which block T-type Ca(2+) channels and SOCs, respectively, affected field detection at appropriate doses. Microfluorometry and high-speed imaging of indo-1-labeled neutrophils was used to examine Ca(2+) signaling. Electric fields enhanced Ca(2+) spike amplitude and triggered formation of a second traveling Ca(2+) wave. Mibefradil blocked Ca(2+) spikes and waves. Although 10 microM SKF96365 mimicked mibefradil, 7 microM SKF96365 specifically inhibited electric field-induced Ca(2+) signals, suggesting that one SKF96365-senstive site is influenced by electric fields. Although cells remained morphologically polarized, ion channel clusters at the lamellipodium and electric field sensitivity were inhibited by methyl-beta-cyclodextrin. As a result of phase-matched electric field application in the presence of ion channel clusters, myeloperoxidase (MPO) was found to traffic to the cell surface. As MPO participates in high amplitude metabolic oscillations, this suggests a link between the signaling apparatus and metabolic changes. Furthermore, electric field effects could be blocked by MPO inhibition or removal while certain electric field effects were mimicked by the addition of MPO to untreated cells. Therefore, channel clustering plays an important role in electric field detection and downstream responses of morphologically polarized neutrophils. In addition to providing new mechanistic insights concerning electric field interactions with cells, our work suggests novel methods to remotely manipulate physiological pathways.

Human fibroblast migration in three-dimensional collagen gel in response to noninvasive electrical stimulus. I. Characterization of induced three-dimensional cell movement

Cell adhesion and motility is one of the important biological processes involved in cell growth, differentiation, inflammatory response, and wound healing, and in engineered tissue constructs. Because cellular behaviors can be influenced by the local electrical environment within tissues, induced cell orientation, adhesion, and migration by exogenous electrical stimulus have been extensively examined on two-dimensional (2D) substrates. Similar cellular responses in 3D matrix have not been well documented, however. We have therefore used the 3D collagen gel as a model to characterize human fibroblast movement in response to noninvasive DC electrical stimulus. Cell movements were compared by plating the cells on 2D substrates and embedding them into the reconstituted 3D collagen gel. Our results indicate that 3D cell movement is regulated by both electrical stimulus strength and collagen concentration. For example, a small noninvasive electrical stimulus (0.1 V/cm) was found to be sufficient to induce 3D cell migration, and a collagen concentration of 0.58 mg/mL appeared to represent the optimal scaffold network environment. The same electrical stimulus did not induce significant 2D cell movement, however. Typical cell migration was best analyzed by assuming both directed and random movement and that, in response to an electrical stimulus of 0.1 V/cm, the cell migration rate was 0.23 microm/min and the random motility coefficient was 0.07 microm2/min. Because regulation of cell adhesion and migration is often desired in tissue engineering, the ability to apply physical stimulus and to control 3D cell movement may provide an alternative methodology for regulation of engineered tissue constructs.

Real-time control of neutrophil metabolism by very weak ultra-low frequency pulsed magnetic fields

In adherent and motile neutrophils NAD(P)H concentration, flavoprotein redox potential, and production of reactive oxygen species and nitric oxide, are all periodic and exhibit defined phase relationships to an underlying metabolic oscillation of approximately 20 s. Utilizing fluorescence microscopy, we have shown in real-time, on the single cell level, that the system is sensitive to externally applied periodically pulsed weak magnetic fields matched in frequency to the metabolic oscillation. Depending upon the phase relationship of the magnetic pulses to the metabolic oscillation, the magnetic pulses serve to either increase the amplitude of the NAD(P)H and flavoprotein oscillations, and the rate of production of reactive oxygen species and nitric oxide or, alternatively, collapse the metabolic oscillations and curtail production of reactive oxygen species and nitric oxide. Significantly, we demonstrate that the cells do not directly respond to the magnetic fields, but instead are sensitive to the electric fields which the pulsed magnetic fields induce. These weak electric fields likely tap into an endogenous signaling pathway involving calcium channels in the plasma membrane. We estimate that the threshold which induced electric fields must attain to influence cell metabolism is of the order of 10(-4) V/m.

Human Fibroblast Migration in Three-Dimensional Collagen Gel in Response to Noninvasive Electrical Stimulus. II. Identification of Electrocoupling Molecular Mechanisms

Cell adhesion and migration is regulated by a series of coordinated and integrated molecular mechanisms. In the accompanying article (Sun et al., Tissue Eng. 10, 1548, 2004), we demonstrate and characterize the human fibroblast movement in three-dimensional (3D) collagen gel induced by non-invasive electrical stimulus. The molecular mechanisms mediating 3D cell migration in response to physical stimuli including noninvasive electrical stimulus remain to be elucidated, however. Here we report that induced human fibroblast movement in 3D collagen gel is both integrin and Ca2+ dependent. Treatment of cells with anti-integrin antibodies prevents electrically induced cell movement. More interestingly, whereas the absence of extracellular Ca2+ suppresses cell movement, inhibition of the cell surface receptor-coupled phospholipase C (PLC) completely prevents 3D cell migration, suggesting molecular association between integrin, PLC, and intracellular Ca2+. Coupling of external electrical stimulus to PLC activation appears to be the primary event required to induce cell migration, while Ca2+ influx across the plasma membrane regulates the sustained cell movement. On the basis of the rather small strength (0.1 V/cm) of electrical stimulus used in this study, activation of the electrically operated voltage-gated Ca2+ channels is unlikely, but the mechanically operated stretch-activated cation channels appear to mediate Ca2+ influx. Elucidation of the electrocoupling molecular mechanisms involved in 3D cell movement could lead to controlled and designed manipulation of 3D cell adhesion and migration.

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

High power, nanosecond pulsed electric field (nsPEF) effects have been focused on bacterial decontamination, but the impact on mammalian cells is now being revealed. During nsPEF applications, electrical pulses of 10, 60 or 300 ns durations were applied to cells using electric field amplitudes as high as 300 kV/cm. Because of the ultra-short pulse durations, the energy transferred to cells is negligible, and only non-thermal effects are observed. We investigated the genotoxicity of nsPEF on adherent and non-adherent cell lines including 10 human lines and one mouse cell line with different origin and growth characteristics. We present data examining the effects of nsPEF exposure on cell survival assessed by clonogenic formation or live cell count; DNA damage determined by the comet assay and chromosome aberrations; and cell cycle parameters by measuring the mitotic indices of exposed cells. Using each of these indicators, we observed differential effects among cell types with non-adherent cells being more sensitive to the genotoxic effects of nsPEF exposures than adherent cells. Non-adherent cultures showed a rapid decrease in cell viability (90%), induction of DNA damage, and a decrease in the number of cells reaching mitosis after one 60 ns pulse with an electric field intensity of 60 kV/cm. These effects were not observed in cells grown as adherent cultures, with the exception of the mouse 3T3 cell line, which showed survival characteristics similar to non-adherent cultures. These data suggest that nsPEF genotoxicity may be cell type specific, and therefore have potential applications in the selective removal of one cell type from another, for example, in diseased states.

Mechanism of protection of peroxidase activity by oscillatory dynamics

The peroxidase-oxidase reaction is known to involve reactive oxygen species as intermediates. These intermediates inactivate many types of biomolecules, including peroxidase itself. Previously, we have shown that oscillatory dynamics in the peroxidase-oxidase reaction seem to protect the enzyme from inactivation. It was suggested that this is due to a lower average concentration of reactive oxygen species in the oscillatory state compared to the steady state. Here, we studied the peroxidase-oxidase reaction with either 4-hydroxybenzoic acid or melatonin as cofactors. We show that the protective effect of oscillatory dynamics is present in both cases. We also found that the enzyme degradation depends on the concentration of the cofactor and on the pH of the reaction mixture. We simulated the oscillatory behaviour, including the oscillation/steady state bistability observed experimentally, using a detailed reaction scheme. The computational results confirm the hypothesis that protection is due to lower average concentrations of superoxide radical during oscillations. They also show that the shape of the oscillations changes with increasing cofactor concentration resulting in a further decrease in the average concentration of radicals. We therefore hypothesize that the protective effect of oscillatory dynamics is a general effect in this system.

A model of the oscillatory metabolism of activated neutrophils

We present a two-compartment model to explain the oscillatory behavior observed experimentally in activated neutrophils. Our model is based mainly on the peroxidase-oxidase reaction catalyzed by myeloperoxidase with melatonin as a cofactor and NADPH oxidase, a major protein in the phagosome membrane of the leukocyte. The model predicts that after activation of a neutrophil, an increase in the activity of the hexose monophosphate shunt and the delivery of myeloperoxidase into the phagosome results in oscillations in oxygen and NAD(P)H concentration. The period of oscillation changes from >200 s to 10-30 s. The model is consistent with previously reported oscillations in cell metabolism and oxidant production. Key features and predictions of the model were confirmed experimentally. The requirement of the hexose monophosphate pathway for 10 s oscillations was verified using 6-aminonicotinamide and dexamethasone, which are inhibitors of glucose-6-phosphate dehydrogenase. The role of the NADPH oxidase in promoting oscillations was confirmed by dose-response studies of the effect of diphenylene iodonium, an inhibitor of the NADPH oxidase. Moreover, the model predicted an increase in the amplitude of NADPH oscillations in the presence of melatonin, which was confirmed experimentally. Successful computer modeling of complex chemical dynamics within cells and their chemical perturbation will enhance our ability to identify new antiinflammatory compounds.

Pulsed DC electric fields couple to natural NAD(P)H oscillations in HT-1080 fibrosarcoma cells

Previously, we have demonstrated that NAD(P)H levels in neutrophils and macrophages are oscillatory. We have also found that weak ultra low frequency AC or pulsed DC electric fields can resonate with, and increase the amplitude of, NAD(P)H oscillations in these cells. For these cells, increased NAD(P)H amplitudes directly signal changes in behavior in the absence of cytokines or chemotactic factors. Here, we have studied the effect of pulsed DC electric fields on HT-1080 fibrosarcoma cells. As in neutrophils and macrophages, NAD(P)H levels oscillate. We find that weak (~10(-)(5) V/m), but properly phased DC (pulsed) electric fields, resonate with NAD(P)H oscillations in polarized and migratory, but not spherical, HT-1080 cells. In this instance, electric field resonance signals an increase in HT-1080 pericellular proteolytic activity. Electric field resonance also triggers an immediate increase in the production of reactive oxygen metabolites. Under resonance conditions, we find evidence of DNA damage in HT-1080 cells in as little as 5 minutes. Thus the ability of external electric fields to effect cell function and physiology by acting on NAD(P)H oscillations is not restricted to cells of the hematopoietic lineage, but may be a universal property of many, if not all polarized and migratory eukaryotic cells.

Dissipative metabolic patterns respond during neutrophil transmembrane signaling

Self-organization is a common theme in biology. One mechanism of self-organization is the creation of chemical patterns by the diffusion of chemical reactants and their nonlinear interactions. We have recently observed sustained unidirectional traveling chemical redox [NAD(P)H - NAD(P)(+)] waves within living polarized neutrophils. The present study shows that an intracellular metabolic wave responds to formyl peptide receptor agonists, but not antagonists, by splitting into two waves traveling in opposite directions along a cell's long axis. Similar effects were noted with other neutrophil-activating substances. Moreover, when cells were exposed to an N-formyl-methionyl-leucyl-phenylalanine (FMLP) gradient whose source was perpendicular to the cell's long axis, cell metabolism was locally perturbed with reorientation of the pattern in a direction perpendicular to the initial cellular axis. Thus, extracellular activating signals and the signals' spatial cues are translated into distinct intracellular dissipative structures.

Interferon-gamma and sinusoidal electric fields signal by modulating NAD(P)H oscillations in polarized neutrophils

Metabolic activity in eukaryotic cells is known to naturally oscillate. We have recently observed a 20-s period NAD(P)H oscillation in neutrophils and other polarized cells. Here we show that when polarized human neutrophils are exposed to interferon-gamma or to ultra-low-frequency electric fields with periods double that of the NAD(P)H oscillation, the amplitude of the NAD(P)H oscillations increases. Furthermore, increases in NAD(P)H amplitude, whether mediated by interferon-gamma or by an oscillating electric field, signals increased production of reactive oxygen metabolites. Hence, amplitude modulation of NAD(P)H oscillations suggests a novel signaling mechanism in polarized cells.