Interleukin-6 inhibits voltage-gated sodium channel activity of cultured rat spinal cord neurons

ObjectiveInterleukin-6 (IL-6) is a pleiotropic proinflammatory cytokine that plays a key role in the injuries and diseases of the central nervous system (CNS). A voltage-gated Na+ channel (VGSC) is essential for the excitability and electrical properties of the neurons. However, there is still limited information on the role of IL-6 in voltage-gated sodium channels. Our study aimed to investigate the effects of IL-6 on Na+ currents in cultured spinal-cord neurons.MethodsVGSC currents were activated and recorded using whole-cell patch-clamp technique in the cultured rat spinal cord neurons. The effects of IL-6 concentration and exposure duration were examined. To determine whether any change in the number of channels in the plasma membrane can inhibit IL-6 on VGSC currents, we examined the expression of α1A (SCN1α) subunit mRNA level and protein level in the neurons before and after IL-6 induction using real-time polymerase chain reaction.ResultsWe verified that IL-6, through a receptor-mediated mechanism, suppressed Na+ currents in a time- and dose-dependent manner, but did not alter the voltage-dependent activation and inactivation. Gp130 was involved in this inhibition. Furthermore, the spike amplitude was also inhibited by IL-6 in the doses that decreased the Na+ currents.ConclusionVGSC currents are significantly inhibited by IL-6. Our findings reveal that the potential neuroprotection of IL-6 may result from the inhibitory effects on VGSC currents.

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Block of Voltage-Gated Sodium Channels by Atomoxetine in a State- and Use-dependent Manner

Frontiers in Pharmacology ◽

10.3389/fphar.2021.622489 ◽

2021 ◽

Vol 12 ◽

Author(s):

Karl Josef Föhr ◽

Ariadni Nastos ◽

Michael Fauler ◽

Thomas Zimmer ◽

Bettina Jungwirth ◽

...

Keyword(s):

Sodium Channels ◽

Heart Muscle ◽

Brain Regions ◽

Clinical Effects ◽

Dependent Manner ◽

Patch Clamp Technique ◽

Human Embryonic Kidney Cells ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

Slow Kinetics

Atomoxetine, a neuroactive drug, is approved for the treatment of attention-deficit/hyperactivity disorder (ADHD). It is primarily known as a high affinity blocker of the noradrenaline transporter, whereby its application leads to an increased level of the corresponding neurotransmitter in different brain regions. However, the concentrations used to obtain clinical effects are much higher than those which are required to block the transporter system. Thus, off-target effects are likely to occur. In this way, we previously identified atomoxetine as blocker of NMDA receptors. As many psychotropic drugs give rise to sudden death of cardiac origin, we now tested the hypothesis whether atomoxetine also interacts with voltage-gated sodium channels of heart muscle type in clinically relevant concentrations. Electrophysiological experiments were performed by means of the patch-clamp technique at human heart muscle sodium channels (hNav1.5) heterogeneously expressed in human embryonic kidney cells. Atomoxetine inhibited sodium channels in a state- and use-dependent manner. Atomoxetine had only a weak affinity for the resting state of the hNav1.5 (Kr: ∼ 120 µM). The efficacy of atomoxetine strongly increased with membrane depolarization, indicating that the inactivated state is an important target. A hallmark of this drug was its slow interaction. By use of different experimental settings, we concluded that the interaction occurs with the slow inactivated state as well as by slow kinetics with the fast-inactivated state. Half-maximal effective concentrations (2–3 µM) were well within the concentration range found in plasma of treated patients. Atomoxetine also interacted with the open channel. However, the interaction was not fast enough to accelerate the time constant of fast inactivation. Nevertheless, when using the inactivation-deficient hNav1.5_I408W_L409C_A410W mutant, we found that the persistent late current was blocked half maximal at about 3 µM atomoxetine. The interaction most probably occurred via the local anesthetic binding site. Atomoxetine inhibited sodium channels at a similar concentration as it is used for the treatment of ADHD. Due to its slow interaction and by inhibiting the late current, it potentially exerts antiarrhythmic properties.

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Block of Voltage-Gated Sodium Channels as a Potential Novel Anti-cancer Mechanism of TIC10

Frontiers in Pharmacology ◽

10.3389/fphar.2021.737637 ◽

2021 ◽

Vol 12 ◽

Author(s):

Eva Fuchs ◽

David Alexander Christian Messerer ◽

Georg Karpel-Massler ◽

Michael Fauler ◽

Thomas Zimmer ◽

...

Keyword(s):

Tumor Cells ◽

Sodium Channels ◽

Tumor Therapy ◽

Kinetic Studies ◽

Dependent Manner ◽

Patch Clamp Technique ◽

Voltage Gated ◽

Beneficial Effects ◽

Voltage Gated Sodium Channels ◽

Anti Cancer

Background: Tumor therapeutics are aimed to affect tumor cells selectively while sparing healthy ones. For this purpose, a huge variety of different drugs are in use. Recently, also blockers of voltage-gated sodium channels (VGSCs) have been recognized to possess potentially beneficial effects in tumor therapy. As these channels are a frequent target of numerous drugs, we hypothesized that currently used tumor therapeutics might have the potential to block VGSCs in addition to their classical anti-cancer activity. In the present work, we have analyzed the imipridone TIC10, which belongs to a novel class of anti-cancer compounds, for its potency to interact with VGSCs.Methods: Electrophysiological experiments were performed by means of the patch-clamp technique using heterologously expressed human heart muscle sodium channels (hNav1.5), which are among the most common subtypes of VGSCs occurring in tumor cells.Results: TIC10 angular inhibited the hNav1.5 channel in a state- but not use-dependent manner. The affinity for the resting state was weak with an extrapolated Kr of about 600 μM. TIC10 most probably did not interact with fast inactivation. In protocols for slow inactivation, a half-maximal inhibition occurred around 2 µM. This observation was confirmed by kinetic studies indicating that the interaction occurred with a slow time constant. Furthermore, TIC10 also interacted with the open channel with an affinity of approximately 4 µM. The binding site for local anesthetics or a closely related site is suggested as a possible target as the affinity for the well-characterized F1760K mutant was reduced more than 20-fold compared to wild type. Among the analyzed derivatives, ONC212 was similarly effective as TIC10 angular, while TIC10 linear more selectively interacted with the different states.Conclusion: The inhibition of VGSCs at low micromolar concentrations might add to the anti-tumor properties of TIC10.

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Na+ Entry Through AMPA Receptors Results in Voltage-Gated K+ Channel Blockade in Cultured Rat Spinal Cord Motoneurons

Journal of Neurophysiology ◽

10.1152/jn.2002.88.2.965 ◽

2002 ◽

Vol 88 (2) ◽

pp. 965-972 ◽

Cited By ~ 11

Author(s):

P. Van Damme ◽

L. Van den Bosch ◽

E. Van Houtte ◽

J. Eggermont ◽

G. Callewaert ◽

...

Keyword(s):

Spinal Cord ◽

Ampa Receptor ◽

Ampa Receptors ◽

Outward Current ◽

Equilibrium Potential ◽

Inward Rectification ◽

Delayed Rectifier ◽

Rat Spinal Cord ◽

Patch Clamp Technique ◽

Voltage Gated

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor currents, evoked with the agonist kainate, were studied with the gramicidin perforated-patch-clamp technique in cultured rat spinal cord motoneurons. Kainate-induced currents could be blocked by the AMPA receptor antagonist LY 300164 and displayed an apparent strong inward rectification. This inward rectification was not a genuine property of AMPA receptor currents but was a result of a concomitant decrease in outward current at potentials positive to −40.5 ± 1.3 mV. The AMPA receptor current itself was nearly linear (rectification index 0.91). The kainate-inhibited outward current had a reversal potential close to the estimated K+equilibrium potential and was blocked by 30 mM tetraethylammonium. When voltage steps were applied, it was found that kainate inhibited both the delayed rectifier K+ current KV and the transient outward K+ current, KA. The kainate-induced inhibition of K+ currents was dependent on ion flux through the AMPA receptor, because no change in the membrane conductance was noticed in the presence of LY 300164. Removing extracellular Ca2+ had no effect, whereas replacing extracellular Na+ or clamping the membrane close to the estimated Na+equilibrium potential during kainate application attenuated the inhibition of the K+ current. Sustained Na+ influx induced by application of the Na+ ionophore monensin could mimic the effect of kainate on K+ conductance. These findings demonstrate that Na+ influx through AMPA receptors results in blockade of voltage-gated K+channels.

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