scholarly journals Effects of Allicin on Late Sodium Current Caused by ΔKPQ-SCN5A Mutation in HEK293 Cells

2021 ◽  
Vol 12 ◽  
Author(s):  
Yating Chen ◽  
Yun Huang ◽  
Jing Bai ◽  
Chuanbin Liu ◽  
Shanshan Ma ◽  
...  
Keyword(s):  
Steady State ◽  
Intermediate State ◽  
Sodium Current ◽  
New Drugs ◽  
Hek293 Cells ◽  
Late Sodium Current ◽  
Technology Application ◽  
Steady State Inactivation ◽  
Window Current ◽  
Scn5a Mutation

AimThe aim was to study the effect of Allitridum (Allicin) on the heterologous expression of the late sodium current on the ΔKPQ-SCN5A mutations in HEK293 cells, with a view to screening new drugs for the treatment of long QT syndrome type 3 (LQT3).Methods and ResultsThe ΔKPQ-SCN5A plasmid was transiently transferred into HEK293 cells by liposome technology and administered by extracellular perfusion, and the sodium current was recorded by whole-cell patch-clamp technology. Application of Allicin 30 μM reduced the late sodium current (INa,L) of the Nav1.5 channel current encoded by ΔKPQ-SCN5A from 1.92 ± 0.12 to 0.65 ± 0.03 pA/pF (P < 0.01, n = 15), which resulted in the decrease of INa,L/INa,P (from 0.94% ± 0.04% to 0.32% ± 0.02%). Furthermore, treatment with Allicin could move the steady-state inactivation of the channel to a more negative direction, resulting in an increase in channel inactivation at the same voltage, which reduced the increase in the window current and further increased the inactivation of the channel intermediate state. However, it had no effect on channel steady-state activation (SSA), inactivation mechanics, and recovery dynamics after inactivation. What’s more, the Nav1.5 channel protein levels of membrane in the ΔKPQ-SCN5A mutation were enhanced from 0.49% ± 0.04% to 0.76% ± 0.02% with the effect of 30 mM Allicin, close to 0.89% ± 0.02% of the WT.ConclusionAllicin reduced the late sodium current of ΔKPQ-SCN5A, whose mechanism may be related to the increase of channel steady-state inactivation (SSI) and intermediate-state inactivation (ISI) by the drug, thus reducing the window current.

scholarly journals Arachidonic acid modulation of α1H, a cloned human T-type calcium channel

2000 ◽  
Vol 278 (1) ◽  
pp. H184-H193 ◽  
Author(s):  
Yi Zhang ◽  
Leanne L. Cribbs ◽  
Jonathan Satin
Keyword(s):  
Arachidonic Acid ◽  
Steady State ◽  
Low Voltage ◽  
Specific Inhibitor ◽  
Nordihydroguaiaretic Acid ◽  
Ca Channel ◽  
Lipoxygenase Inhibitor ◽  
Inactivation Curve ◽  
Steady State Inactivation ◽  
Window Current

Arachidonic acid (AA) and the products of its metabolism are central mediators of changes in cellular excitability. We show that the recently cloned and expressed T-type or low-voltage-activated Ca channel, α1H, is modulated by external AA. AA (10 μM) causes a slow, time-dependent attenuation of α1H current. At a holding potential of −80 mV, 10 μM AA reduces peak inward α1H current by 15% in 15 min and 70% in 30 min and shifts the steady-state inactivation curve −25 mV. AA inhibition was not affected by applying the cyclooxygenase inhibitor indomethacin or the lipoxygenase inhibitor nordihydroguaiaretic acid. The epoxygenase inhibitor octadecynoic acid partially antagonized AA attenuation of α1H. The epoxygenase metabolite epoxyeicosatrienoic acid (8,9-EET) mimicked the inhibitory effect of AA on α1H peak current. A protein kinase C (PKC)-specific inhibitor (peptide fragment 19–36) only partially antagonized the AA-induced reduction of peak α1H current and the shift of the steady-state inactivation curve but had no effect on 8,9-EET-induced attenuation of current. In contrast, PKA has no role in the modulation of α1H. These results suggest that AA attenuation and shift of α1H may be mediated directly by AA. The heterologous expression of T-type Ca channels allows us to study for the first time properties of this important class of ion channel in isolation. There is a significant overlap of the steady-state activation and inactivation curves, which implies a substantial window current. The selective shift of the steady-state inactivation curve by AA reduces peak Ca current and eliminates the window current. We conclude that AA may partly mediate physiological effects such as vasodilatation via the attenuation of T-type Ca channel current and the elimination of a T-type channel steady window current.

Abstract 44: A Slowly Inactivating Sodium Current Contributes to the Prolongation of the Action Potential in Aging Cardiomyocytes

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Kazuya Isobe ◽  
Sergio Signore ◽  
Andrea Sorrentino ◽  
João Ferreira-Martins ◽  
Mehrdad Shafaie ◽  
...  
Keyword(s):  
Qt Interval ◽  
Sodium Current ◽  
Fold Increase ◽  
Inactivation Kinetics ◽  
Patch Clamp Technique ◽  
Maximal Conductance ◽  
Late Sodium Current ◽  
Repolarization Phase ◽  
Steady State Inactivation ◽  
Old Mice

Aging is associated with alterations in the electrical properties of the heart resulting in an increased incidence of arrhythmic events and perturbation of cardiac performance. The aim of the present study was to determine whether the late sodium current (I NaL ), which presents slow inactivation kinetics, is upregulated in myocytes from old hearts contributing to the electrical remodeling of the senescent myocardium. For this purpose, the electrical profile of young (3-5 months) and old (24-30 months) C57BL6 mice was established at the organ and cellular levels. In comparison to young mice, old animals presented enlarged left ventricles and declined systolic and diastolic functions. The QRS complex and QT interval of the ECG were significantly prolonged in old animals, indicating that aging delays the electrical activation and recovery of the myocardium. The latter property was confirmed by slower repolarization phases of epicardial monophasic action potentials (AP) in old hearts, using perfused Langendorff preparations. Moreover, old hearts were more prone to develop arrhythmia by programmed electrical stimulation. By patch-clamp technique, myocytes from old mice showed a 2- and 1.7-fold increase in the time to 50% and 90% repolarization of the AP, respectively, than cells from young animals. In voltage-clamp mode, I NaL , which is operative during the repolarization phase of the AP, was 1.7-fold larger in cells obtained from old hearts with respect to young. Activation, steady state inactivation and time constants for I NaL were comparable in young and old myocytes, indicating that the enhanced late current was mediated by an increased maximal conductance. In old myocytes, blockade of I NaL with low doses of tetrodotoxin or mexiletine reduced by 24-48% the intermediate and late repolarization phases of the AP, whereas in young cells this intervention affected to a lesser extent only the late repolarization phase. Finally, administration of mexiletine in old mice shortened the QT interval by 25%, restoring ventricular electrical recovery. In conclusion, the late sodium current I NaL is upregulated with aging and contributes to the slower repolarization of the senescent myocardium.

Nitrogen narcosis and pressure reversal of anesthetic effects in node of Ranvier

1984 ◽  
Vol 246 (1) ◽  
pp. C91-C95 ◽  
Author(s):  
J. J. Kendig
Keyword(s):  
Steady State ◽  
Sodium Current ◽  
Conduction Block ◽  
Volatile Anesthetic ◽  
Inert Gases ◽  
Helium Pressure ◽  
General Anesthetic ◽  
H Infinity ◽  
Anesthetic Agents ◽  
Steady State Inactivation

To compare sodium channel block by hyperbaric nitrogen with that induced by other anesthetics and to examine the basis for pressure antagonism to anesthetic condition block, voltage clamped nodes of Ranvier were exposed to nitrogen at pressures at 1-14 atm alone and in combination with helium to a total pressure of up to 100 atm. At 7 and 14 atm nitrogen, sodium currents were reversibly depressed without accompanying changes in the current-voltage relation. The curve relating steady-state inactivation (h infinity) to voltage was shifted in the hyperpolarizing direction, as is the case with other general anesthetic agents. The time constant of inactivation (tau h) was slightly decreased at depolarized potentials. The preceding companion paper demonstrated an opposite effect of hyperbaric helium on the properties of sodium inactivation. Addition of helium pressure in the presence of nitrogen at 14 atm did not increase peak sodium current with inactivation maximally removed, but it did shift the h infinity curve back toward control levels, thus increasing sodium current at points on the slope of the curve. It is proposed that these opposing shifts in steady-state inactivation levels are the basis for pressure antagonism to anesthetic conduction block. In the case of inert gases and volatile anesthetic agents, the antagonism may be direct but has not been shown to be so. In the case of the local anesthetic benzocaine, differences in the voltage dependence of anesthetic and pressure-induced changes in tau h indicate the antagonism is indirect.

Ionic currents in vertebrate myelinated nerve at hyperbaric pressure

1984 ◽  
Vol 246 (1) ◽  
pp. C84-C90 ◽  
Author(s):  
J. J. Kendig
Keyword(s):  
Steady State ◽  
Sodium Current ◽  
Ionic Currents ◽  
Base Line ◽  
Myelinated Nerve ◽  
Hyperbaric Pressure ◽  
Voltage Curve ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Steady State Inactivation

To establish a base line for a study of anesthetic-pressure antagonism in axons, voltage-clamped nodes of Ranvier from amphibian sciatic nerve were subjected to pressures of 1-100 atm. Over the time of compression, there was usually an irreversible decrease in peak inward sodium current, but there was no change in peak outward sodium current or in the current-voltage relationship. The steady-state inactivation-voltage curve was shifted 5-15 mV in the depolarizing direction at 70-100 atm. The rate of rise of the sodium current was slowed, as was the time constant of inactivation (tau h). Increase in tau h was markedly voltage dependent, suggesting a selective effect of pressure on beta h, the rate constant governing development of the inactive state. The rate of development of steady-state outward potassium current was also decreased, without significant change in maximum current. The effects of pressure are qualitatively similar to, but different in detail from, those reported in squid axon and different in some details from the effects of cooling in this preparation. None of the effects can presently be related to the high-pressure nervous syndrome.

scholarly journals Inactivation of the Sodium Current in Myxicola Giant Axons

1972 ◽  
Vol 59 (6) ◽  
pp. 659-675 ◽  
Author(s):  
L. Goldman ◽  
C. L. Schauf
Keyword(s):  
Steady State ◽  
Sodium Current ◽  
Voltage Characteristic ◽  
Current Voltage Characteristic ◽  
Inactivation Curve ◽  
Giant Axons ◽  
Sodium Conductance ◽  
Current Voltage ◽  
Steady State Inactivation ◽  
The Right

Experiments were conducted on Myxicola giant axons to determine if the sodium activation and inactivation processes are coupled or independent. The main experimental approach was to examine the effects of changing test pulses on steady-state inactivation curves. Arguments were presented to show that in the presence of a residual uncompensated series resistance the interpretation of the results depends critically on the manner of conducting the experiment. Analytical and numerical calculations were presented to show that as long as test pulses are confined to an approximately linear negative conductance region of the sodium current-voltage characteristic, unambiguous interpretations can be made. When examined in the manner of Hodgkin and Huxley, inactivation in Myxicola is quantitatively similar to that described by the h variable in squid axons. However, when test pulses were increased along the linear negative region of the sodium current-voltage characteristic, steady-state inactivation curves translate to the right along the voltage axis. The shift in the inactivation curve is a linear function of the ratio of the sodium, conductance of the test pulses, showing a 5.8 mv shift for a twofold increase in conductance. An independent line of evidence indicated that the early rate of development of inactivation is a function of the rise of the sodium conductance.

scholarly journals Late Sodium Current And If Inhibition: Targets of New Antianginal Drugs

1970 ◽  
Vol 3 (2) ◽  
pp. 75-78
Author(s):  
Uzzwal Kanti Das ◽  
Syed Ali Ahsan ◽  
KMHS Sirajul Haque ◽  
Md. Khurshed Ahmed
Keyword(s):  
Sodium Current ◽  
Developed Countries ◽  
New Drugs ◽  
Late Sodium Current ◽  
Mortality And Morbidity ◽  
Cardiac Ion Channels ◽  
If Current ◽  
The Common ◽  
Antianginal Drugs ◽  
Cellular Components

Ischaemic heart disease is the common cause of mortality and morbidity in developed countries despite tremendous development in treatment in last two decades. Recently cardiac Ion Channels and other cellular components have become the target of research for new cardiovascular drugs. A number of new drugs have emerged after pre-clinical and clinical trials. Ranolazine by inhibiting late sodium current in ventricular cardiomyocytes and ibavradine by inhibiting If current in pacemaker cells have emerged as effective new antianginal drugs. Both are discussed in this review article. Key Words: Late Sodium current (IPNa), Diastolic tension, After depolarization, If current, heart rate. (University Heart Journal 2007; 3 : 75-78)

Effect of intracellular and extracellular acidosis on sodium current in ventricular myocytes

1995 ◽  
Vol 268 (4) ◽  
pp. H1749-H1756 ◽  
Author(s):  
C. L. Watson ◽  
M. R. Gold
Keyword(s):  
Steady State ◽  
Time Course ◽  
Ventricular Myocytes ◽  
Sodium Current ◽  
Essential Element ◽  
Neonatal Rat ◽  
Cardiac Conduction ◽  
Inactivation Kinetics ◽  
Extracellular Acidosis ◽  
Steady State Inactivation

Conduction slowing is an essential element in the generation of ischemic ventricular arrhythmias and is determined in part by the inward Na+ current (INa). Because intracellular acidosis is an early consequence of ischemia, we hypothesized that lowering intracellular pH (pHi) would reduce or kinetically modulate INa and thus affect cardiac conduction. To test this hypothesis, the whole cell patch-clamp method was used to measure INa in neonatal rat ventricular myocytes exposed to varying extracellular pH (pHo 6.4–7.4), while perfusing the cells with acidic solutions (pHi 6.2–7.2). With simultaneous acidification of pHo and pHi there was a progressive increase in time to peak current, a 31% decrease in peak INa (298 +/- 18 to 206 +/- 16 pA/pF), and a complex slowing of inactivation kinetics. At the most extreme levels of acidification, there was a 5-mV hyperpolarizing shift in steady-state inactivation and a 6-mV depolarizing shift in activation. Independent changes of pHo and pHi indicate that the reduction of peak INa is a function of pHo. However, steady-state inactivation is modulated by pHi. The time course of activation and inactivation appears to depend on both pHo and pHi. We conclude that both intracellular and extracellular acidosis are significant but distinct modulators of INa amplitude and kinetics in cardiac myocytes.

scholarly journals Modal Gating of Human CaV2.1 (P/Q-type) Calcium Channels

2004 ◽  
Vol 124 (5) ◽  
pp. 445-461 ◽  
Author(s):  
Siro Luvisetto ◽  
Tommaso Fellin ◽  
Michele Spagnolo ◽  
Bruno Hivert ◽  
Paul F. Brust ◽  
...  
Keyword(s):  
Steady State ◽  
Calcium Channels ◽  
Voltage Dependence ◽  
Hek293 Cells ◽  
Fast Mode ◽  
Β Subunit ◽  
Slow Mode ◽  
Open Probability ◽  
Steady State Inactivation ◽  
Modal Gating

The single channel gating properties of human CaV2.1 (P/Q-type) calcium channels and their modulation by the auxiliary β1b, β2e, β3a, and β4a subunits were investigated with cell-attached patch-clamp recordings on HEK293 cells stably expressing human CaV2.1 channels. These calcium channels showed a complex modal gating, which is described in this and the following paper (Fellin, T., S. Luvisetto, M. Spagnolo, and D. Pietrobon. 2004. J. Gen. Physiol. 124:463–474). Here, we report the characterization of two modes of gating of human CaV2.1 channels, the slow mode and the fast mode. A channel in the two gating modes differs in mean closed times and latency to first opening (both longer in the slow mode), in voltage dependence of the open probability (larger depolarizations are necessary to open the channel in the slow mode), in kinetics of inactivation (slower in the slow mode), and voltage dependence of steady-state inactivation (occurring at less negative voltages in the slow mode). CaV2.1 channels containing any of the four β subtypes can gate in either the slow or the fast mode, with only minor differences in the rate constants of the transitions between closed and open states within each mode. In both modes, CaV2.1 channels display different rates of inactivation and different steady-state inactivation depending on the β subtype. The type of β subunit also modulates the relative occurrence of the slow and the fast gating mode of CaV2.1 channels; β3a promotes the fast mode, whereas β4a promotes the slow mode. The prevailing mode of gating of CaV2.1 channels lacking a β subunit is a gating mode in which the channel shows shorter mean open times, longer mean closed times, longer first latency, a much larger fraction of nulls, and activates at more positive voltages than in either the fast or slow mode.

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