The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
C F Louis - One of the best experts on this subject based on the ideXlab platform.
-
Dantrolene inhibition of ryanodine receptor Ca2+ release channels. Molecular mechanism and isoform selectivity
Journal of Biological Chemistry, 2001Co-Authors: Fangyi Zhao, C F Louis, S. R. Wayne Chen, Pin Li, Bradley R FruenAbstract:As an inhibitor of Ca(2+) release through ryanodine receptor (RYR) channels, the skeletal muscle relaxant Dantrolene has proven to be both a valuable experimental probe of intracellular Ca(2+) signaling and a lifesaving treatment for the pharmacogenetic disorder malignant hyperthermia. However, the molecular basis and specificity of the actions of Dantrolene on RYR channels have remained in question. Here we utilize [(3)H]ryanodine binding to further investigate the actions of Dantrolene on the three mammalian RYR isoforms. The inhibition of the pig skeletal muscle RYR1 by Dantrolene (10 microm) was associated with a 3-fold increase in the K(d) of [(3)H]ryanodine binding to sarcoplasmic reticulum (SR) vesicles such that Dantrolene effectively reversed the 3-fold decrease in the K(d) for [(3)H]ryanodine binding resulting from the malignant hyperthermia RYR1 Arg(615) --> Cys mutation. Dantrolene inhibition of the RYR1 was dependent on the presence of the adenine nucleotide and calmodulin and reflected a selective decrease in the apparent affinity of RYR1 activation sites for Ca(2+) relative to Mg(2+). In contrast to the RYR1 isoform, the cardiac RYR2 isoform was unaffected by Dantrolene, both in native cardiac SR vesicles and when heterologously expressed in HEK-293 cells. By comparison, the RYR3 isoform expressed in HEK-293 cells was significantly inhibited by Dantrolene, and the extent of RYR3 inhibition was similar to that displayed by the RYR1 in native SR vesicles. Our results thus indicate that both the RYR1 and the RYR3, but not the RYR2, may be targets for Dantrolene inhibition in vivo.
-
Dantrolene inhibition of sarcoplasmic reticulum ca2 release by direct and specific action at skeletal muscle ryanodine receptors
Journal of Biological Chemistry, 1997Co-Authors: Bradley R Fruen, James R Mickelson, C F LouisAbstract:Abstract The skeletal muscle relaxant Dantrolene inhibits the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca2+ release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which Dantrolene selectively affects skeletal muscle Ca2+ regulation remains to be defined. Here we provide evidence of a high-affinity, monophasic inhibition by Dantrolene of ryanodine receptor Ca2+ channel function in isolated sarcoplasmic reticulum vesicles prepared from malignant hyperthermia-susceptible and normal pig skeletal muscle. In media simulating resting myoplasm, Dantrolene increased the half-time for45Ca2+ release from both malignant hyperthermia and normal vesicles approximately 3.5-fold and inhibited sarcoplasmic reticulum vesicle [3H]ryanodine binding (K i ∼150 nm for both malignant hyperthermia and normal). Inhibition of vesicle [3H]ryanodine binding by Dantrolene was associated with a decrease in the extent of activation by both calmodulin and Ca2+. Dantrolene also inhibited [3H]ryanodine binding to purified skeletal muscle ryanodine receptor protein reconstituted into liposomes. In contrast, cardiac sarcoplasmic reticulum vesicle 45Ca2+ release and [3H]ryanodine binding were unaffected by Dantrolene. Together, these results demonstrate selective effects of Dantrolene on skeletal muscle ryanodine receptors that are consistent with the actions of Dantrolene in vivo and suggest a mechanism of action in which Dantrolene may act directly at the skeletal muscle ryanodine receptor complex to limit its activation by calmodulin and Ca2+. The potential implications of these results for understanding how Dantrolene and malignant hyperthermia mutations may affect the voltage-dependent activation of Ca2+release in intact skeletal muscle are discussed.
-
Dantrolene inhibition of sarcoplasmic reticulum Ca2+ release by direct and specific action at skeletal muscle ryanodine receptors
Journal of Biological Chemistry, 1997Co-Authors: Bradley R Fruen, James R Mickelson, C F LouisAbstract:The skeletal muscle relaxant Dantrolene inhibits the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca2+ release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which Dantrolene selectively affects skeletal muscle Ca2+ regulation remains to be defined. Here we provide evidence of a high-affinity, monophasic inhibition by Dantrolene of ryanodine receptor Ca2+ channel function in isolated sarcoplasmic reticulum vesicles prepared from malignant hyperthermia-susceptible and normal pig skeletal muscle. In media simulating resting myoplasm, Dantrolene increased the half-time for 45Ca2+ release from both malignant hyperthermia and normal vesicles approximately 3.5-fold and inhibited sarcoplasmic reticulum vesicle [3H]ryanodine binding (Ki approximately 150 nM for both malignant hyperthermia and normal). Inhibition of vesicle [3H]ryanodine binding by Dantrolene was associated with a decrease in the extent of activation by both calmodulin and Ca2+. Dantrolene also inhibited [3H]ryanodine binding to purified skeletal muscle ryanodine receptor protein reconstituted into liposomes. In contrast, cardiac sarcoplasmic reticulum vesicle 45Ca2+ release and [3H]ryanodine binding were unaffected by Dantrolene. Together, these results demonstrate selective effects of Dantrolene on skeletal muscle ryanodine receptors that are consistent with the actions of Dantrolene in vivo and suggest a mechanism of action in which Dantrolene may act directly at the skeletal muscle ryanodine receptor complex to limit its activation by calmodulin and Ca2+. The potential implications of these results for understanding how Dantrolene and malignant hyperthermia mutations may affect the voltage-dependent activation of Ca2+ release in intact skeletal muscle are discussed.
-
Pharmacological distinction between Dantrolene and ryanodine binding sites: evidence from normal and malignant hyperthermia-susceptible porcine skeletal muscle
Biochem J, 1997Co-Authors: Sanjay S. Palnitkar, C F Louis, James R Mickelson, Jerome ParnessAbstract:Dantrolene inhibits and ryanodine stimulates calcium release from skeletal-muscle sarcoplasmic reticulum (SR), the former by an unknown mechanism, and the latter by activating the ryanodine receptor (RyR), the primary Ca2+-release channel of SR. Dantrolene is used to treat malignant hyperthermia (MH), a genetic predisposition to excessive intracellular Ca2+ release upon exposure to volatile anaesthetics. Porcine MH results from a point mutation in the SR RyR that alters the open probability of the channel, and is reflected in altered [3H]ryanodine binding parameters. Specific binding sites for [3H]Dantrolene and [3H]ryanodine co-distribute on SR that has been isolated by discontinuous sucrose gradient centrifugation. If the two drug-binding sites are functionally linked, [3H]Dantrolene binding might be affected both by pharmacological and by genetic modulators of the functional state of the RyR. Accordingly, we compared the characteristics of [3H]Dantrolene binding to porcine malignant-hyperthermia-susceptible and normal-skeletal-muscle SR, and examined the effects of RyR modulators on [3H]Dantrolene binding to these membranes. Additionally, the feasibility of separating the SR binding sites for [3H]Dantrolene and [3H]ryanodine was investigated. No significant differences in [3H]Dantrolene binding characteristics to SR membranes from the two muscle types were detected, and the Bmax ratio for [3H]Dantrolene/[3H]ryanodine was 1.4(+/-0.1):1 in both muscle types. [3H]Dantrolene binding is unaffected by the RyR modulators caffeine, ryanodine, Ruthenium Red and calmodulin, and neither Dantrolene nor azumolene have any effect on [3H]ryanodine binding. Additionally, distinct peaks of [3H]Dantrolene and [3H]ryanodine binding are detected in SR membranes fractionated by linear sucrose centrifugation, although no differences in protein patterns are detected by SDS/PAGE or Western-blot analysis. We suggest that the binding sites for these two drugs are pharmacologically distinct, and may exist on separate molecules.
Bradley R Fruen - One of the best experts on this subject based on the ideXlab platform.
-
localization of the Dantrolene binding sequence near the fk506 binding protein binding site in the three dimensional structure of the ryanodine receptor
Journal of Biological Chemistry, 2011Co-Authors: Ruiwu Wang, Bradley R Fruen, Xiaowei Zhong, Xing Meng, Andrea Koop, Xixi Tian, Peter P Jones, Terence Wagenknecht, S Wayne R ChenAbstract:Dantrolene is believed to stabilize interdomain interactions between the NH2-terminal and central regions of ryanodine receptors by binding to the NH2-terminal residues 590–609 in skeletal ryanodine receptor (RyR1) and residues 601–620 in cardiac ryanodine receptor (RyR2). To gain further insight into the structural basis of Dantrolene action, we have attempted to localize the Dantrolene-binding sequence in RyR1/RyR2 by using GFP as a structural marker and three-dimensional cryo-EM. We inserted GFP into RyR2 after residues Arg-626 and Tyr-846 to generate GFP-RyR2 fusion proteins, RyR2Arg-626-GFP and RyR2Tyr-846-GFP. Insertion of GFP after residue Arg-626 abolished the binding of a bulky GST- or cyan fluorescent protein-tagged FKBP12.6 but not the binding of a smaller, nontagged FKBP12.6, suggesting that residue Arg-626 and the Dantrolene-binding sequence are located near the FKBP12.6-binding site. Using cryo-EM, we have mapped the three-dimensional location of Tyr-846-GFP to domain 9, which is also adjacent to the FKBP12.6-binding site. To further map the three-dimensional location of the Dantrolene-binding sequence, we generated 10 FRET pairs based on four known three-dimensional locations (FKBP12.6, Ser-437-GFP, Tyr-846-GFP, and Ser-2367-GFP). Based on the FRET efficiencies of these FRET pairs and the corresponding distance relationships, we mapped the three-dimensional location of Arg-626-GFP or -cyan fluorescent protein, hence the Dantrolene-binding sequence, to domain 9 near the FKBP12.6-binding site but distant to the central region around residue Ser-2367. An allosteric mechanism by which Dantrolene stabilizes interdomain interactions between the NH2-terminal and central regions is proposed.
-
Dantrolene inhibition of ryanodine receptor Ca2+ release channels. Molecular mechanism and isoform selectivity
Journal of Biological Chemistry, 2001Co-Authors: Fangyi Zhao, C F Louis, S. R. Wayne Chen, Pin Li, Bradley R FruenAbstract:As an inhibitor of Ca(2+) release through ryanodine receptor (RYR) channels, the skeletal muscle relaxant Dantrolene has proven to be both a valuable experimental probe of intracellular Ca(2+) signaling and a lifesaving treatment for the pharmacogenetic disorder malignant hyperthermia. However, the molecular basis and specificity of the actions of Dantrolene on RYR channels have remained in question. Here we utilize [(3)H]ryanodine binding to further investigate the actions of Dantrolene on the three mammalian RYR isoforms. The inhibition of the pig skeletal muscle RYR1 by Dantrolene (10 microm) was associated with a 3-fold increase in the K(d) of [(3)H]ryanodine binding to sarcoplasmic reticulum (SR) vesicles such that Dantrolene effectively reversed the 3-fold decrease in the K(d) for [(3)H]ryanodine binding resulting from the malignant hyperthermia RYR1 Arg(615) --> Cys mutation. Dantrolene inhibition of the RYR1 was dependent on the presence of the adenine nucleotide and calmodulin and reflected a selective decrease in the apparent affinity of RYR1 activation sites for Ca(2+) relative to Mg(2+). In contrast to the RYR1 isoform, the cardiac RYR2 isoform was unaffected by Dantrolene, both in native cardiac SR vesicles and when heterologously expressed in HEK-293 cells. By comparison, the RYR3 isoform expressed in HEK-293 cells was significantly inhibited by Dantrolene, and the extent of RYR3 inhibition was similar to that displayed by the RYR1 in native SR vesicles. Our results thus indicate that both the RYR1 and the RYR3, but not the RYR2, may be targets for Dantrolene inhibition in vivo.
-
Dantrolene inhibition of sarcoplasmic reticulum ca2 release by direct and specific action at skeletal muscle ryanodine receptors
Journal of Biological Chemistry, 1997Co-Authors: Bradley R Fruen, James R Mickelson, C F LouisAbstract:Abstract The skeletal muscle relaxant Dantrolene inhibits the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca2+ release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which Dantrolene selectively affects skeletal muscle Ca2+ regulation remains to be defined. Here we provide evidence of a high-affinity, monophasic inhibition by Dantrolene of ryanodine receptor Ca2+ channel function in isolated sarcoplasmic reticulum vesicles prepared from malignant hyperthermia-susceptible and normal pig skeletal muscle. In media simulating resting myoplasm, Dantrolene increased the half-time for45Ca2+ release from both malignant hyperthermia and normal vesicles approximately 3.5-fold and inhibited sarcoplasmic reticulum vesicle [3H]ryanodine binding (K i ∼150 nm for both malignant hyperthermia and normal). Inhibition of vesicle [3H]ryanodine binding by Dantrolene was associated with a decrease in the extent of activation by both calmodulin and Ca2+. Dantrolene also inhibited [3H]ryanodine binding to purified skeletal muscle ryanodine receptor protein reconstituted into liposomes. In contrast, cardiac sarcoplasmic reticulum vesicle 45Ca2+ release and [3H]ryanodine binding were unaffected by Dantrolene. Together, these results demonstrate selective effects of Dantrolene on skeletal muscle ryanodine receptors that are consistent with the actions of Dantrolene in vivo and suggest a mechanism of action in which Dantrolene may act directly at the skeletal muscle ryanodine receptor complex to limit its activation by calmodulin and Ca2+. The potential implications of these results for understanding how Dantrolene and malignant hyperthermia mutations may affect the voltage-dependent activation of Ca2+release in intact skeletal muscle are discussed.
-
Dantrolene inhibition of sarcoplasmic reticulum Ca2+ release by direct and specific action at skeletal muscle ryanodine receptors
Journal of Biological Chemistry, 1997Co-Authors: Bradley R Fruen, James R Mickelson, C F LouisAbstract:The skeletal muscle relaxant Dantrolene inhibits the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca2+ release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which Dantrolene selectively affects skeletal muscle Ca2+ regulation remains to be defined. Here we provide evidence of a high-affinity, monophasic inhibition by Dantrolene of ryanodine receptor Ca2+ channel function in isolated sarcoplasmic reticulum vesicles prepared from malignant hyperthermia-susceptible and normal pig skeletal muscle. In media simulating resting myoplasm, Dantrolene increased the half-time for 45Ca2+ release from both malignant hyperthermia and normal vesicles approximately 3.5-fold and inhibited sarcoplasmic reticulum vesicle [3H]ryanodine binding (Ki approximately 150 nM for both malignant hyperthermia and normal). Inhibition of vesicle [3H]ryanodine binding by Dantrolene was associated with a decrease in the extent of activation by both calmodulin and Ca2+. Dantrolene also inhibited [3H]ryanodine binding to purified skeletal muscle ryanodine receptor protein reconstituted into liposomes. In contrast, cardiac sarcoplasmic reticulum vesicle 45Ca2+ release and [3H]ryanodine binding were unaffected by Dantrolene. Together, these results demonstrate selective effects of Dantrolene on skeletal muscle ryanodine receptors that are consistent with the actions of Dantrolene in vivo and suggest a mechanism of action in which Dantrolene may act directly at the skeletal muscle ryanodine receptor complex to limit its activation by calmodulin and Ca2+. The potential implications of these results for understanding how Dantrolene and malignant hyperthermia mutations may affect the voltage-dependent activation of Ca2+ release in intact skeletal muscle are discussed.
Frank Wappler - One of the best experts on this subject based on the ideXlab platform.
-
Malignant hyperthermia: Current strategies for effective diagnosis and management
Expert Opinion on Orphan Drugs, 2014Co-Authors: Frank WapplerAbstract:Introduction: Malignant hyperthermia (MH) is a life-threatening, inherited disorder of skeletal muscle calcium metabolism, which is usually triggered by volatile anesthetics and succinylcholine. Mortality of the syndrome has been significantly reduced since introduction of Dantrolene. However, Dantrolene has relevant pharmacological disadvantages. Diagnosis of MH with in vitro contracture testing are the current standard, but sensitivity as well as specificity of the test procedure are not perfect. Areas covered: This review discusses and summarizes recent advances in management as well as diagnosis of MH. Special focus is directed on a new Dantrolene formulation and also on preparation of anesthesia workstations. A literature search was undertaken using several databases including Cochrane, Medline, Pubmed and Science Direct, covering materials up to November 2013. Expert opinion: In this regard, a novel nanocrystalline Dantrolene sodium suspension (DSS) was shown to be as effective as the standard Dantrolene preparation without relevant side effects. DSS has a much better solubility in water due to the nanoparticle structure and can be dissolved in small volumes of water. This enables a faster administration of Dantrolene and consequently hastens treatment of a crisis. Diagnosis of MH may be improved by recent developments in genetic mutation research, especiallyby characterization of functional effects of specific variants. (copyright) 2014 Informa UK, Ltd.
-
comparison of the therapeutic effectiveness of a Dantrolene sodium solution and a novel nanocrystalline suspension of Dantrolene sodium in malignant hyperthermia normal and susceptible pigs
European Journal of Anaesthesiology, 2011Co-Authors: Jan K Schutte, Frank Wappler, Sandra Becker, Sascha Burmester, Alexander Starosse, Daniel Lenz, Lars U Kroner, Mark U. GerbershagenAbstract:BACKGROUND AND OBJECTIVE: Stopping trigger agents and prompt administration of Dantrolene are the cornerstones of treatment of malignant hyperthermia. However, significant time is lost in treatment of the condition because of the cumbersome preparation and administration of the commercially available Dantrolene sodium for injection. A potential improvement has become available in the form of a novel nanocrystalline Dantrolene sodium suspension (DSS), which is 150 times more concentrated (50 mg ml(-1)) than the standard Dantrolene sodium solution (0.33 mg ml(-1)). The aims of this study were to measure the effects of DSS on clinical and laboratory variables in malignant hyperthermia normal pigs and to compare the therapeutic management and clinical effectiveness of DSS with standard Dantrolene sodium in a fulminant malignant hyperthermia crisis in susceptible pigs. The pig model is a well accepted method of studying the malignant hyperthermia crisis and is an ideal way to evaluate the variables of interest in this study. METHODS: Seven malignant hyperthermia normal and 10 malignant hyperthermia susceptible pigs were studied. Malignant hyperthermia susceptible pigs (body weight approximately 24 kg) were allocated to a Dantrolene sodium group or a DSS group. After induction of anaesthesia, a 22-gauge catheter was placed in an ear vein and trigger-free anaesthesia was performed. After achieving stable conditions, administration of halothane was started with 0.1% and then 0.15%. Halothane was discontinued after the administration of 0.2% (malignant hyperthermia normal pigs) or when a fulminant malignant hyperthermia crisis was achieved (malignant hyperthermia susceptible pigs). After halothane was discontinued, FIO2 was set to 1.0, respiratory minute volume was doubled and sodium bicarbonate 2 mmol kg(-1) was administered. The time required to prepare and administer each formulation was measured. To simulate the administration of the substances under typical clinical conditions for a child weighing approximately 24 kg, Dantrolene sodium (5 mg kg(-1)) or DSS (5 mg kg(-1)) was prepared and injected via the intravenous 22-gauge cannula. Bolus administrations of Dantrolene sodium or DSS were repeated after 24 min. RESULTS: Arterial pH, arterial pCO2, mean arterial pressure and arterial lactate concentration remained stable during the experiment with DSS in malignant hyperthermia normal pigs. A significant decrease in cardiac index and increases in systemic vascular resistance and serum potassium concentration occurred after administration of DSS. In all malignant hyperthermia susceptible animals, the inhaled administration of halothane 0.15% led to a fulminant malignant hyperthermia crisis. The therapeutic regimens with administration of Dantrolene sodium or DSS were successful in treating the malignant hyperthermia crisis in all animals. The course of the malignant hyperthermia crisis and the therapeutic effects of Dantrolene sodium or DSS were comparable in the two groups. The time needed to prepare DSS for administration was significantly shorter (51 ± 9 s) compared to Dantrolene sodium (860 ± 202 s). The time taken to inject DSS (4 ± 2 s) was significantly shorter than for Dantrolene sodium (472 ± 51 s). CONCLUSION: The therapeutic action of DSS in a malignant hyperthermia crisis in pigs was effective and comparable to that of standard Dantrolene sodium. However, preparation and administration of DSS were significantly faster, which may offer a clinically significant advantage in the treatment of a fulminant malignant hyperthermia crisis and may result in a reduction in stress for the anaesthesia team.
-
Dantrolene a review of its pharmacology therapeutic use and new developments
Anaesthesia, 2004Co-Authors: T. Krause, M. Fiege, Mark U. Gerbershagen, Ralf Weisshorn, Frank WapplerAbstract:Human malignant hyperthermia is a life-threatening genetic sensitivity of skeletal muscles to volatile anaesthetics and depolarizing neuromuscular blocking drugs occurring during or after anaesthesia. The skeletal muscle relaxant Dantrolene is the only currently available drug for specific and effective therapy of this syndrome in man. After its introduction, the mortality of malignant hyperthermia decreased from 80% in the 1960s to < 10% today. It was soon discovered that Dantrolene depresses the intrinsic mechanisms of excitation-contraction coupling in skeletal muscle. However, its precise mechanism of action and its molecular targets are still incompletely known. Recent studies have identified the ryanodine receptor as a Dantrolene-binding site. A direct or indirect inhibition of the ryanodine receptor, the major calcium release channel of the skeletal muscle sarcoplasmic reticulum, is thought to be fundamental in the molecular action of Dantrolene in decreasing intracellular calcium concentration. Dantrolene is not only used for the treatment of malignant hyperthermia, but also in the management of neuroleptic malignant syndrome, spasticity and Ecstasy intoxication. The main disadvantage of Dantrolene is its poor water solubility, and hence difficulties are experienced in rapidly preparing intravenous solutions in emergency situations. Due to economic considerations, no other similar drugs have been introduced into routine clinical practice.
-
Dantrolene - A review of its pharmacology, therapeutic use and new developments
Anaesthesia, 2004Co-Authors: T. Krause, M. Fiege, R. WeiÃhorn, Mark U. Gerbershagen, Frank WapplerAbstract:Human malignant hyperthermia is a life-threatening genetic sensitivity of skeletal muscles to volatile anaesthetics and depolarizing neuromuscular blocking drugs occurring during or after anaesthesia. The skeletal muscle relaxant Dantrolene is the only currently available drug for specific and effective therapy of this syndrome in man. After its introduction, the mortality of malignant hyperthermia decreased from 80% in the 1960s to < 10% today. It was soon discovered that Dantrolene depresses the intrinsic mechanisms of excitation-contraction coupling in skeletal muscle. However, its precise mechanism of action and its molecular targets are still incompletely known. Recent studies have identified the ryanodine receptor as a Dantrolene-binding site. A direct or indirect inhibition of the ryanodine receptor, the major calcium release channel of the skeletal muscle sarcoplasmic reticulum, is thought to be fundamental in the molecular action of Dantrolene in decreasing intracellular calcium concentration. Dantrolene is not only used for the treatment of malignant hyperthermia, but also in the management of neuroleptic malignant syndrome, spasticity and Ecstasy intoxication. The main disadvantage of Dantrolene is its poor water solubility, and hence difficulties are experienced in rapidly preparing intravenous solutions in emergency situations. Due to economic considerations, no other similar drugs have been introduced into routine clinical practice. (copyright) 2004 Blackwell Publishing Ltd.
-
Dantrolene. Pharmacological and therapeutic aspects
Der Anaesthesist, 2003Co-Authors: Mark U. Gerbershagen, M. Fiege, T. Krause, K. Agarwal, Frank WapplerAbstract:Malignant hyperthermia (MH) is a genetic, potentially life-threatening disorder of the skeletal muscle presenting during or following general anaesthesia. Trigger agents are volatile anaesthetics and depolarising muscle relaxants. Dantrolene is the only available drug for effective and specific MH therapy, which reduces significantly the mortality rate. Dantrolene is a skeletal muscle relaxant that depresses the excitation-contraction coupling,however, the specificity of action remains unknown. Recent studies identified the ryanodine receptor, the calcium release channel of the sarcoplasmic reticulum, as the direct molecular target of Dantrolene. In addition to its use for MH, Dantrolene is used in other disorders such as neuroleptic malignant syndrome and spasticity. Since Dantrolene is weakly water soluble, the clinical preparation is time and manpower consuming. New agents have been synthesized, but because of economic considerations no registration for clinical usage has been realised.
James R Mickelson - One of the best experts on this subject based on the ideXlab platform.
-
Dantrolene inhibition of sarcoplasmic reticulum ca2 release by direct and specific action at skeletal muscle ryanodine receptors
Journal of Biological Chemistry, 1997Co-Authors: Bradley R Fruen, James R Mickelson, C F LouisAbstract:Abstract The skeletal muscle relaxant Dantrolene inhibits the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca2+ release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which Dantrolene selectively affects skeletal muscle Ca2+ regulation remains to be defined. Here we provide evidence of a high-affinity, monophasic inhibition by Dantrolene of ryanodine receptor Ca2+ channel function in isolated sarcoplasmic reticulum vesicles prepared from malignant hyperthermia-susceptible and normal pig skeletal muscle. In media simulating resting myoplasm, Dantrolene increased the half-time for45Ca2+ release from both malignant hyperthermia and normal vesicles approximately 3.5-fold and inhibited sarcoplasmic reticulum vesicle [3H]ryanodine binding (K i ∼150 nm for both malignant hyperthermia and normal). Inhibition of vesicle [3H]ryanodine binding by Dantrolene was associated with a decrease in the extent of activation by both calmodulin and Ca2+. Dantrolene also inhibited [3H]ryanodine binding to purified skeletal muscle ryanodine receptor protein reconstituted into liposomes. In contrast, cardiac sarcoplasmic reticulum vesicle 45Ca2+ release and [3H]ryanodine binding were unaffected by Dantrolene. Together, these results demonstrate selective effects of Dantrolene on skeletal muscle ryanodine receptors that are consistent with the actions of Dantrolene in vivo and suggest a mechanism of action in which Dantrolene may act directly at the skeletal muscle ryanodine receptor complex to limit its activation by calmodulin and Ca2+. The potential implications of these results for understanding how Dantrolene and malignant hyperthermia mutations may affect the voltage-dependent activation of Ca2+release in intact skeletal muscle are discussed.
-
Dantrolene inhibition of sarcoplasmic reticulum Ca2+ release by direct and specific action at skeletal muscle ryanodine receptors
Journal of Biological Chemistry, 1997Co-Authors: Bradley R Fruen, James R Mickelson, C F LouisAbstract:The skeletal muscle relaxant Dantrolene inhibits the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca2+ release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which Dantrolene selectively affects skeletal muscle Ca2+ regulation remains to be defined. Here we provide evidence of a high-affinity, monophasic inhibition by Dantrolene of ryanodine receptor Ca2+ channel function in isolated sarcoplasmic reticulum vesicles prepared from malignant hyperthermia-susceptible and normal pig skeletal muscle. In media simulating resting myoplasm, Dantrolene increased the half-time for 45Ca2+ release from both malignant hyperthermia and normal vesicles approximately 3.5-fold and inhibited sarcoplasmic reticulum vesicle [3H]ryanodine binding (Ki approximately 150 nM for both malignant hyperthermia and normal). Inhibition of vesicle [3H]ryanodine binding by Dantrolene was associated with a decrease in the extent of activation by both calmodulin and Ca2+. Dantrolene also inhibited [3H]ryanodine binding to purified skeletal muscle ryanodine receptor protein reconstituted into liposomes. In contrast, cardiac sarcoplasmic reticulum vesicle 45Ca2+ release and [3H]ryanodine binding were unaffected by Dantrolene. Together, these results demonstrate selective effects of Dantrolene on skeletal muscle ryanodine receptors that are consistent with the actions of Dantrolene in vivo and suggest a mechanism of action in which Dantrolene may act directly at the skeletal muscle ryanodine receptor complex to limit its activation by calmodulin and Ca2+. The potential implications of these results for understanding how Dantrolene and malignant hyperthermia mutations may affect the voltage-dependent activation of Ca2+ release in intact skeletal muscle are discussed.
-
Pharmacological distinction between Dantrolene and ryanodine binding sites: evidence from normal and malignant hyperthermia-susceptible porcine skeletal muscle
Biochem J, 1997Co-Authors: Sanjay S. Palnitkar, C F Louis, James R Mickelson, Jerome ParnessAbstract:Dantrolene inhibits and ryanodine stimulates calcium release from skeletal-muscle sarcoplasmic reticulum (SR), the former by an unknown mechanism, and the latter by activating the ryanodine receptor (RyR), the primary Ca2+-release channel of SR. Dantrolene is used to treat malignant hyperthermia (MH), a genetic predisposition to excessive intracellular Ca2+ release upon exposure to volatile anaesthetics. Porcine MH results from a point mutation in the SR RyR that alters the open probability of the channel, and is reflected in altered [3H]ryanodine binding parameters. Specific binding sites for [3H]Dantrolene and [3H]ryanodine co-distribute on SR that has been isolated by discontinuous sucrose gradient centrifugation. If the two drug-binding sites are functionally linked, [3H]Dantrolene binding might be affected both by pharmacological and by genetic modulators of the functional state of the RyR. Accordingly, we compared the characteristics of [3H]Dantrolene binding to porcine malignant-hyperthermia-susceptible and normal-skeletal-muscle SR, and examined the effects of RyR modulators on [3H]Dantrolene binding to these membranes. Additionally, the feasibility of separating the SR binding sites for [3H]Dantrolene and [3H]ryanodine was investigated. No significant differences in [3H]Dantrolene binding characteristics to SR membranes from the two muscle types were detected, and the Bmax ratio for [3H]Dantrolene/[3H]ryanodine was 1.4(+/-0.1):1 in both muscle types. [3H]Dantrolene binding is unaffected by the RyR modulators caffeine, ryanodine, Ruthenium Red and calmodulin, and neither Dantrolene nor azumolene have any effect on [3H]ryanodine binding. Additionally, distinct peaks of [3H]Dantrolene and [3H]ryanodine binding are detected in SR membranes fractionated by linear sucrose centrifugation, although no differences in protein patterns are detected by SDS/PAGE or Western-blot analysis. We suggest that the binding sites for these two drugs are pharmacologically distinct, and may exist on separate molecules.
Lars S Maier - One of the best experts on this subject based on the ideXlab platform.
-
Dantrolene reduces camkiiδc mediated atrial arrhythmias
Europace, 2020Co-Authors: Steffen Pabel, Julian Mustroph, Thea Stehle, Simon Lebek, Nataliya Dybkova, Andreas Keyser, Leopold Rupprecht, Stefan Wagner, Stefan Neef, Lars S MaierAbstract:Aims In atrial fibrillation (AF), an increased diastolic Ca2+ leak from the sarcoplasmic reticulum (SR) mediated by calcium/calmodulin-dependent-protein-kinaseIIδC (CaMKII) can serve as a substrate for arrhythmia induction and persistence. Dantrolene has been shown to stabilize the cardiac ryanodine-receptor. This study investigated the effects of Dantrolene on arrhythmogenesis in human and mouse atria with enhanced CaMKII activity. Methods and results Human atrial cardiomyocytes (CMs) were isolated from patients with AF. To investigate CaMKII-mediated arrhythmogenesis, atrial CMs from mice overexpressing CaMKIIδC (TG) and the respective wildtype (WT) were studied using confocal microscopy (Fluo-4), patch-clamp technique, and in vivo atrial catheter-based burst stimulations. Dantrolene potently reduced Ca2+ spark frequency (CaSpF) and diastolic SR Ca2+ leak in AF CMs. Additional CaMKII inhibition did not further reduce CaSpF or leak compared to Dantrolene alone. While the increased SR CaSpF and leak in TG mice were reduced by Dantrolene, no effects could be detected in WT. Dantrolene also potently reduced the pathologically enhanced frequency of diastolic SR Ca2+ waves in TG without having effects in WT. As an increased diastolic SR Ca2+ release can induce a depolarizing transient inward current, we could demonstrate that the incidence of afterdepolarizations in TG, but not in WT, mice was significantly diminished in the presence of Dantrolene. To translate these findings into an in vivo situation we could show that Dantrolene strongly suppressed the inducibility of AF in vivo in TG mice. Conclusion Dantrolene reduces CaMKII-mediated atrial arrhythmogenesis and may therefore constitute an interesting antiarrhythmic drug for treating patients with atrial arrhythmias driven by an enhanced CaMKII activity, such as AF.
-
Dantrolene reduces CaMKIIδC-mediated atrial arrhythmias.
Europace, 2020Co-Authors: Steffen Pabel, Julian Mustroph, Thea Stehle, Simon Lebek, Nataliya Dybkova, Andreas Keyser, Leopold Rupprecht, Stefan Wagner, Stefan Neef, Lars S MaierAbstract:AIMS: In atrial fibrillation (AF), an increased diastolic Ca2+ leak from the sarcoplasmic reticulum (SR) mediated by calcium/calmodulin-dependent-protein-kinaseIIδC (CaMKII) can serve as a substrate for arrhythmia induction and persistence. Dantrolene has been shown to stabilize the cardiac ryanodine-receptor. This study investigated the effects of Dantrolene on arrhythmogenesis in human and mouse atria with enhanced CaMKII activity. METHODS AND RESULTS: Human atrial cardiomyocytes (CMs) were isolated from patients with AF. To investigate CaMKII-mediated arrhythmogenesis, atrial CMs from mice overexpressing CaMKIIδC (TG) and the respective wildtype (WT) were studied using confocal microscopy (Fluo-4), patch-clamp technique, and in vivo atrial catheter-based burst stimulations. Dantrolene potently reduced Ca2+ spark frequency (CaSpF) and diastolic SR Ca2+ leak in AF CMs. Additional CaMKII inhibition did not further reduce CaSpF or leak compared to Dantrolene alone. While the increased SR CaSpF and leak in TG mice were reduced by Dantrolene, no effects could be detected in WT. Dantrolene also potently reduced the pathologically enhanced frequency of diastolic SR Ca2+ waves in TG without having effects in WT. As an increased diastolic SR Ca2+ release can induce a depolarizing transient inward current, we could demonstrate that the incidence of afterdepolarizations in TG, but not in WT, mice was significantly diminished in the presence of Dantrolene. To translate these findings into an in vivo situation we could show that Dantrolene strongly suppressed the inducibility of AF in vivo in TG mice. CONCLUSION: Dantrolene reduces CaMKII-mediated atrial arrhythmogenesis and may therefore constitute an interesting antiarrhythmic drug for treating patients with atrial arrhythmias driven by an enhanced CaMKII activity, such as AF.
-
antiarrhythmic effects of Dantrolene in human diseased cardiomyocytes
Heart Rhythm, 2017Co-Authors: Nico Hartmann, Steffen Pabel, Jonas Herting, Felix Schatter, Andre Renner, J Gummert, Hanna Schotola, Bernhard C Danner, Lars S Maier, Norbert FreyAbstract:Background Cardiac type 2 ryanodine receptors (RyR 2 s) play a pivotal role in cellular electrophysiology and contractility. Increased RyR 2 -mediated diastolic sarcoplasmic reticulum (SR) Ca 2+ release is linked to heart failure (HF) and arrhythmias. Dantrolene, a drug used for the treatment of malignant hyperthermia, is known to stabilize RyRs in skeletal muscle. Objective The purpose of this study was to investigate the effects of Dantrolene on arrhythmogenic triggers and contractile function in human atrial fibrillation (AF) and HF cardiomyocytes (CM). Methods Human CM were isolated from either patients with HF (ventricular) or patients with AF (atrial), and Ca 2+ imaging, patch-clamp, or muscle strip experiments were performed. Results After exposure to Dantrolene, human atrial AF and left ventricular HF CM showed significant reductions in proarrhythmic SR Ca 2+ spark frequency and diastolic SR Ca 2+ leak. Moreover, Dantrolene decreased the frequency of Ca 2+ waves and spontaneous Ca 2+ transients in HF CM. Patch-clamp experiments revealed that Dantrolene significantly suppressed delayed afterdepolarizations in HF and AF CM. Importantly, Dantrolene had no effect on action potential duration in AF or in HF CM. In addition, Dantrolene had neutral effects on contractile force of human isometrically twitching ventricular HF trabeculae. Conclusion Our study showed that Dantrolene beneficially influenced disrupted SR Ca 2+ homeostasis in human HF and AF CM. Cellular arrhythmogenic triggers were potently suppressed by Dantrolene, whereas action potential duration and contractility were not affected. As a clinically approved drug for the treatment of malignant hyperthermia, Dantrolene may be a potential antiarrhythmic drug for patients with rhythm disorders and merits further clinical investigation.
