Non-blocking modulation as the major mechanism of sodium channel inhibition by riluzole

ABSTRACTModulated- or guarded receptor hypothesis; Channel block or modulation; “Voltage-sensor block” or “lipophilic block” are some of the questions that arise when drug effects on sodium channels are investigated. Understanding the exact mechanism of action for individual drugs is essential, because it is one of the major factors that determine their therapeutic applicability.In this study we created a kinetic model of sodium channels, which can help us understand the modes of action for individual drugs in the context of these hypotheses. The model was constructed so that it could integrate the above hypotheses.In particular we aimed to understand the mode of action of riluzole, a neuroprotective drug with a peculiar state-dependent inhibition. In experiments the inhibition by 100μM riluzole was full within the first two milliseconds, but it was almost completely removed between 2 and 20 ms post-depolarization. This abrupt loss of inhibition could not be explained by dissociation, which was proceeding with a time constant of ~300 ms. We propose that for sodium channel inhibitors binding without blocking is possible, and riluzole predominantly inhibits by non-blocking modulation. We used lidocaine as a reference compound, and found that non-blocking modulation, although less prominent, also may play a role in its mechanism of inhibition. Non-blocking modulation may selectively inhibit cells with pathological activity patterns, therefore this property may be a good trait to investigate in the development of sodium channel inhibitor drugs.SUMMARYAlthough never actually proven, presence of sodium channel inhibitors at their binding site is assumed to prevent ion conduction. Authors provide evidence from experiments and kinetic simulations that bound riluzole permits conduction and exerts its inhibitory effect almost entirely by modulation.

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RYR2 Channel Inhibition Is the Principal Mechanism 0f Flecainide Action in CPVT

Circulation Research ◽

10.1161/circresaha.120.316819 ◽

2020 ◽

Author(s):

Dmytro O Kryshtal ◽

Daniel Blackwell ◽

Christian Egly ◽

Abigail N Smith ◽

Suzanne M Batiste ◽

...

Keyword(s):

Ventricular Tachycardia ◽

Sodium Channel ◽

Sodium Channels ◽

Antiarrhythmic Action ◽

Channel Block ◽

Principal Mechanism ◽

Channel Inhibition ◽

Ryr2 Channel ◽

Cardiac Sodium Channels

Rationale: The class Ic antiarrhythmic drug flecainide prevents ventricular tachyarrhythmia in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), a disease caused by hyperactive cardiac ryanodine receptor (RyR2) calcium (Ca) release. Although flecainide inhibits single RyR2 channels in vitro, reports have claimed that RyR2 inhibition by flecainide is not relevant for its mechanism of antiarrhythmic action and concluded that sodium channel block alone is responsible for flecainide's efficacy in CPVT. Objective: To determine whether RyR2 block independently contributes to flecainide's efficacy for suppressing spontaneous sarcoplasmic reticulum (SR) Ca release and for preventing ventricular tachycardia in vivo. Methods and Results: We synthesized N-methylated flecainide analogues (QX-FL and NM-FL) and showed that N-methylation reduces flecainide's inhibitory potency on RyR2 channels incorporated into artificial lipid bilayers. N-Methylation did not alter flecainide's inhibitory activity on human cardiac sodium channels expressed in HEK293T cells. Antiarrhythmic efficacy was tested utilizing a calsequestrin knockout (Casq2-/-) CPVT mouse model. In membrane-permeabilized Casq2-/- cardiomyocytes — lacking intact sarcolemma and devoid of sodium channel contribution — flecainide, but not its analogues, suppressed RyR2-mediated Ca release at clinically relevant concentrations. In voltage-clamped, intact Casq2-/- cardiomyocytes pretreated with tetrodotoxin (TTX) to inhibit sodium channels and isolate the effect of flecainide on RyR2, flecainide significantly reduced the frequency of spontaneous SR Ca release, while QX-FL and NM-FL did not. In vivo, flecainide effectively suppressed catecholamine-induced ventricular tachyarrhythmias in Casq2-/- mice, whereas NM-FL had no significant effect on arrhythmia burden, despite comparable sodium channel block. Conclusions: Flecainide remains an effective inhibitor of RyR2-mediated arrhythmogenic Ca release even when cardiac sodium channels are blocked. In mice with CPVT, sodium channel block alone did not prevent ventricular tachycardia. Hence, RyR2 channel inhibition likely constitutes the principal mechanism of antiarrhythmic action of flecainide in CPVT.

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Suppression of Central Nervous System Sodium Channels by Propofol

Anesthesiology ◽

10.1097/00000542-199908000-00026 ◽

1999 ◽

Vol 91 (2) ◽

pp. 512-520 ◽

Cited By ~ 87

Author(s):

Benno Rehberg ◽

Daniel S. Duch

Keyword(s):

Sodium Channel ◽

Sodium Channels ◽

Chinese Hamster ◽

Inhibitory Effect ◽

Ovary Cell ◽

Sodium Currents ◽

Action Potential Firing ◽

Steady State Inactivation ◽

Potential Firing ◽

Ovary Cell Line

Background Previous studies have provided evidence that clinical levels of propofol alter the functions of voltage-dependent sodium channels, thereby inhibiting synaptic release of glutamate. However, most of these experiments were conducted in the presence of sodium-channel activators, which alter channel inactivation. This study electrophysiologically characterized the interactions of propofol with unmodified sodium channels. Methods Sodium currents were measured using whole-cell patch-clamp recordings of rat brain IIa sodium channels expressed in a stably transfected Chinese hamster ovary cell line. Standard electrophysiologic protocols were used to record sodium currents in the presence or absence of externally applied propofol. Results Propofol, at concentrations achieved clinically in the brain, significantly altered sodium channel currents by two mechanisms: a voltage-independent block of peak currents and a concentration-dependent shift in steady-state inactivation to hyperpolarized potentials, leading to a voltage dependence of current suppression. The two effects combined to give an apparent concentration yielding a half-maximal inhibitory effect of 10 microM near the threshold potential of action potential firing (about -60 mV). Propofol inhibition was also use-dependent, causing a further block of sodium currents at these anesthetic concentrations. Conclusions In these experiments with pharmacologically unaltered sodium channels, propofol inhibition of currents occurred at concentrations about eight-fold above clinical plasma levels and thus at brain concentrations reached during clinical anesthesia. Therefore, the results indicate a possible role for sodium-channel suppression in propofol anesthesia.

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Cannabidiol interactions with voltage-gated sodium channels

eLife ◽

10.7554/elife.58593 ◽

2020 ◽

Vol 9 ◽

Author(s):

Lily Goodyer Sait ◽

Altin Sula ◽

Mohammad-Reza Ghovanloo ◽

David Hollingworth ◽

Peter C Ruben ◽

...

Keyword(s):

Sodium Channel ◽

Sodium Channels ◽

Neurological Diseases ◽

Pharmaceutical Drugs ◽

Voltage Gated ◽

X Ray Crystallography ◽

Ion Translocation ◽

Voltage Gated Sodium Channels ◽

Channel Inhibition ◽

Modelling Studies

Voltage-gated sodium channels are targets for a range of pharmaceutical drugs developed for the treatment of neurological diseases. Cannabidiol (CBD), the non-psychoactive compound isolated from cannabis plants, was recently approved for treatment of two types of epilepsy associated with sodium channel mutations. This study used high-resolution X-ray crystallography to demonstrate the detailed nature of the interactions between CBD and the NavMs voltage-gated sodium channel, and electrophysiology to show the functional effects of binding CBD to these channels. CBD binds at a novel site at the interface of the fenestrations and the central hydrophobic cavity of the channel. Binding at this site blocks the transmembrane-spanning sodium ion translocation pathway, providing a molecular mechanism for channel inhibition. Modelling studies suggest why the closely-related psychoactive compound tetrahydrocannabinol may not have the same effects on these channels. Finally, comparisons are made with the TRPV2 channel, also recently proposed as a target site for CBD. In summary, this study provides novel insight into a possible mechanism for CBD interactions with sodium channels.

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Cannabidiol Interactions with Voltage-Gated Sodium Channels

10.1101/2020.06.15.151720 ◽

2020 ◽

Author(s):

Lily Goodyer Sait ◽

Altin Sula ◽

David Hollingworth ◽

Benjamin J. Whalley ◽

Rohini R. Rana ◽

...

Keyword(s):

Sodium Channel ◽

Sodium Channels ◽

Neurological Diseases ◽

Pharmaceutical Drugs ◽

Voltage Gated ◽

X Ray Crystallography ◽

Ion Translocation ◽

Voltage Gated Sodium Channels ◽

Channel Inhibition ◽

Modelling Studies

AbstractVoltage-gated sodium channels are targets for a range of pharmaceutical drugs developed for treatment of neurological diseases. Cannabidiol (CBD), the non-psychoactive compound isolated from cannabis plants, was recently approved for treatment of two types of epilepsy associated with sodium channel mutations. This study used high resolution X-ray crystallography to demonstrate the detailed nature of the interactions between CBD and the NavMs voltage-gated sodium channel, showing CBD binds at a novel site at the interface of the fenestrations and the central hydrophobic cavity of the channel. Binding at this site blocks the transmembrane-spanning sodium ion translocation pathway, providing a molecular mechanism for channel inhibition. Modelling studies illuminate why the closely-related psychoactive compound THC may not bind to these channels. Finally, comparisons are made with the TRPV2 channel, also recently proposed as a target site for CBD. In summary, this study provides novel insight into a possible mechanism for CBD with sodium channels.

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Quaternary Lidocaine Derivative QX-314 Activates and Permeates Human TRPV1 and TRPA1 to Produce Inhibition of Sodium Channels and Cytotoxicity

Anesthesiology ◽

10.1097/aln.0000000000001050 ◽

2016 ◽

Vol 124 (5) ◽

pp. 1153-1165 ◽

Cited By ~ 21

Author(s):

Thomas Stueber ◽

Mirjam J. Eberhardt ◽

Christoph Hadamitzky ◽

Annette Jangra ◽

Stefan Schenk ◽

...

Keyword(s):

Sodium Channel ◽

Sodium Channels ◽

Transient Receptor Potential ◽

Sodium Current ◽

Receptor Potential ◽

Transient Receptor Potential Vanilloid ◽

Viable Cells ◽

Channel Inhibition ◽

Transient Receptor ◽

Human Isoforms

Abstract Background The relatively membrane-impermeable lidocaine derivative QX-314 has been reported to permeate the ion channels transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential cation channel, subfamily A, member 1 (TRPA1) to induce a selective inhibition of sensory neurons. This approach is effective in rodents, but it also seems to be associated with neurotoxicity. The authors examined whether the human isoforms of TRPV1 and TRPA1 allow intracellular entry of QX-314 to mediate sodium channel inhibition and cytotoxicity. Methods Human embryonic kidney 293 (HEK-293) cells expressing wild-type or mutant human (h) TRPV1 or TRPA1 constructs as well as the sodium channel Nav1.7 were investigated by means of patch clamp and ratiometric calcium imaging. Cytotoxicity was examined by flow cytometry. Results Activation of hTRPA1 by carvacrol and hTRPV1 by capsaicin produced a QX-314–independent reduction of sodium current amplitudes. However, permeation of QX-314 through hTRPV1 or hTRPA1 was evident by a concentration-dependent, use-dependent inhibition of Nav1.7 activated at 10 Hz. Five and 30 mM QX-314 activated hTRPV1 via mechanisms involving the intracellular vanilloid-binding domain and hTRPA1 via unknown mechanisms independent of intracellular cysteins. Expression of hTRPV1, but not hTRPA1, was associated with a QX-314–induced cytotoxicity (viable cells 48 ± 5% after 30 mM QX-314) that was ameliorated by the TRPV1 antagonist 4-(3-chloro-2-pyridinyl)-N-[4-(1,1-dimethylethyl)phenyl]-1-piperazinecarboxamide (viable cells 81 ± 5%). Conclusions The study data demonstrate that QX-314 directly activates and permeates the human isoforms of TRPV1 and TRPA1 to induce inhibition of sodium channels, but also a TRPV1-dependent cytotoxicity. These results warrant further validation of this approach in more intact preparations and may be valuable for the development of this concept into clinical practice.

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Indoxacarb, metaflumizone, and other sodium channel inhibitor insecticides: Mechanism and site of action on mammalian voltage-gated sodium channels

Pesticide Biochemistry and Physiology ◽

10.1016/j.pestbp.2013.03.004 ◽

2013 ◽

Vol 106 (3) ◽

pp. 101-112 ◽

Cited By ~ 25

Author(s):

Richard T. von Stein ◽

Kristopher S. Silver ◽

David M. Soderlund

Keyword(s):

Sodium Channel ◽

Sodium Channels ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

Site Of Action

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Effect of guaianolides in the meiosis reinitiation of amphibian oocytes

Zygote ◽

10.1017/s0967199416000265 ◽

2016 ◽

Vol 25 (1) ◽

pp. 10-16 ◽

Cited By ~ 2

Author(s):

J. Zapata-Martínez ◽

G. Sánchez-Toranzo ◽

F. Chaín ◽

C.A.N. Catalán ◽

M.I. Bühler

Keyword(s):

Biological Activities ◽

Wide Spectrum ◽

Sesquiterpene Lactones ◽

Inhibitory Effect ◽

Biological Molecules ◽

Plant Metabolites ◽

Major Mechanism ◽

Bufo Arenarum ◽

Asteraceae Family

SummarySesquiterpene lactones (STLs) are a large and structurally diverse group of plant metabolites generally found in the Asteraceae family. STLs exhibit a wide spectrum of biological activities and it is generally accepted that their major mechanism of action is the alkylation of the thiol groups of biological molecules. The guaianolides is one of various groups of STLs. Anti-tumour and anti-migraine effects, an allergenic agent, an inhibitor of smooth muscle cells and of meristematic cell proliferation are only a few of the most commonly reported activities of STLs. In amphibians, fully grown ovarian oocytes are arrested at the beginning of meiosis I. Under stimulus with progesterone, this meiotic arrest is released and meiosis progresses to metaphase II, a process known as oocyte maturation. There are previous records of the inhibitory effect of dehydroleucodin (DhL), a guaianolide lactone, on the progression of meiosis. It has been also shown that DhL and its 11,13-dihydroderivative (2H-DhL; a mixture of epimers at C-11) act as blockers of the resumption of meiosis in fully grown ovarian oocytes from the amphibian Rhinella arenarum (formerly classified as Bufo arenarum). The aim of this study was to analyze the effect of four closely related guaianolides, i.e., DhL, achillin, desacetoxymatricarin and estafietin as possible inhibitors of meiosis in oocytes of amphibians in vitro and discuss some structure–activity relationships. It was found that the inhibitory effect on meiosis resumption is greater when the lactone has two potentially reactive centres, either a α,β–α′,β′-diunsaturated cyclopentanone moiety or an epoxide group plus an exo-methylene-γ-lactone function.

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