Dantrolene binds to the Leu601-Cys620 region of the N-terminal domain of cardiac ryanodine receptor (RyR2), which corresponds to the Leu590-Cys609 region of the skeletal ryanodine receptor, and ...suppresses diastolic Ca2+ leakage through RyR2.
We investigated whether the chronic administration of dantrolene prevented left ventricular (LV) remodeling and ventricular tachycardia (VT) after myocardial infarction (MI) by the same mechanism with the mutation V3599K of RyR2, which indicated that the inhibition of diastolic Ca2+ leakage occurred by enhancing the binding affinity of calmodulin (CaM) to RyR2.
A left anterior descending coronary artery ligation MI model was developed in mice. Wild-type (WT) were divided into four groups: sham-operated mice (WT-Sham), sham-operated mice treated with dantrolene (WT-Sham-DAN), MI mice (WT-MI), and MI mice treated with dantrolene (WT-MI-DAN). Homozygous V3599K RyR2 knock-in (KI) mice were divided into two groups: sham-operated mice (KI-Sham) and MI mice (KI-MI). The mice were followed for 12 weeks.
Survival was significantly higher in the WT-MI-DAN (73%) and KI-MI groups (70%) than the WT-MI group (40%). Echocardiography, pathological tissue, and epinephrine-induced VT studies showed that LV remodeling and VT were prevented in the WT-MI-DAN and KI-MI groups compared to the WT-MI group. An increase in diastolic Ca2+ spark frequency and a decrease in the binding affinity of CaM to the RyR2 were observed at 12 weeks after MI in the WT-MI group, although significant improvements in these values were observed in the WT-MI-DAN and KI-MI groups.
Pharmacological or genetic stabilization of RyR2 tetrameric structure improves survival after MI by suppressing LV remodeling and proarrhythmia.
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•Dantrolene, a stabilizer of RyR2, prevented diastolic Ca2+ leakage from RyR2 by enhancing the binding affinity of calmodulin (CaM) to RyR2 in MI.•The mutation V3599K of RyR2 inhibited the diastolic Ca2+ leakage by enhancing the binding affinity of CaM to RyR2 in MI.•Pharmacological or genetic stabilization of tetrameric RyR2 improved survival after MI by suppressing LV remodeling and proarrhythmia.
Objectives We sought to investigate the effect of dantrolene, a drug generally used to treat malignant hyperthermia, on the Ca2+ release and cardiomyocyte function in failing hearts. Background The ...N-terminal (N: 1–600) and central (C: 2000–2500) domains of the ryanodine receptor (RyR) harbor many mutations associated with malignant hyperthermia in skeletal muscle RyR (RyR1) and polymorphic ventricular tachycardia in cardiac RyR (RyR2). There is strong evidence that interdomain interaction between these regions plays an important role in the mechanism of channel regulation. Methods Sarcoplasmic reticulum vesicles and cardiomyocytes were isolated from the left ventricular muscles of dogs (normal or rapid ventricular pacing for 4 weeks), for Ca2+ leak, transient, and spark assays. To assess the zipped or unzipped state of the interacting domains, the RyR was labeled fluorescently with methylcoumarin acetate in a site-directed manner. We used a quartz-crystal microbalance technique to identify the dantrolene binding site within the RyR2. Results Dantrolene specifically bound to domain 601–620 in RyR2. In the sarcoplasmic reticulum isolated from pacing-induced failing dog hearts, the defective interdomain interaction (domain unzipping) had already occurred, causing spontaneous Ca2+ leak. Dantrolene suppressed both domain unzipping and the Ca2+ leak, demonstrating identical drug concentration-dependence (IC50 = 0.3 μmol/l). In failing cardiomyocytes, both diastolic Ca2+ sparks and delayed afterdepolarization were observed frequently, but 1 μmol/l dantrolene inhibited both events. Conclusions Dantrolene corrects defective interdomain interactions within RyR2 in failing hearts, inhibits spontaneous Ca2+ leak, and in turn improves cardiomyocyte function in failing hearts. Thus, dantrolene may have a potential to treat heart failure, specifically targeting the RyR2.
Background:An association between atrial high-rate episode (AHRE) and stroke has been reported, although data for the Asian population are limited. This study aimed to investigate the role of AHRE in ...ischemic and major bleeding events in patients who underwent a cardiac implantable electronic device (CIED) procedure.Methods and Results:This single-center historical cohort study included 710 patients (age: 78±11 years, 374 women) who underwent a CIED-related procedure between October 2009 and September 2019 at Shimane Prefectural Central Hospital (median follow-up period: 4.5 2.5, 7 years, 3439 person-years). Based on the maximum AHRE burden, patients were divided into: (1) <6 min; (2) ≥6 min to 24-h; and (3) ≥24-h groups. The cumulative incidence of ischemic (ischemic stroke, systemic embolism, and transient ischemic attack) and major bleeding (≥3 Bleeding Academic Research Consortium bleeding criteria) events after the procedure were compared. Uni- and multivariate analyses were performed to identify factors associated with these events. The incidence of both events increased with the rising AHRE burden, being significantly higher in the ≥24-h group than in the <6 min group. Multivariate analysis found age ≥85 years to be the only independent factor associated with both events.Conclusions:Longer AHRE duration is associated with a high number of major bleeding and ischemic events. Monitoring these bleeding risks is mandatory when clinicians are considering anticoagulation therapy for such patients.
Increased endoplasmic reticulum (ER) stress is strongly associated with the phenotypic switching of vascular smooth muscle cells (VSMCs) in atherosclerosis. Depletion of the ER Ca2+ content is one of ...the leading causes of increased ER stress in VSMCs. The ryanodine receptor (RyR) is a major Ca2+ release channel in the sarcoplasmic reticulum membrane. Calmodulin (CaM), which binds to RyR (CaM-RyR), stabilizes the closed state of RyR in the resting state in normal cells. Defective CaM-RyR interactions can cause abnormal Ca2+ leakage through RyR, resulting in decreased Ca2+ content, indicating that defective CaM-RyR interactions may be a cause of increased ER stress. Herein, we used a mouse VSMCs to assess whether CaM-RyR plays a pivotal role in VSMCs phenotypic switching, which is caused by ER stress, and whether dantrolene, which enhances the binding affinity of CaM to RyR, affects VSMCs phenotypic switching.
Tunicamycin was used to mimic ER stress in vitro. Tunicamycin-induced ER stress caused CaM to dissociate from the RyR and translocate to the nucleus, which stimulated phenotypic switching through the activation of MEF2 and KLF5. Dantrolene suppressed tunicamycin-induced apoptosis, ER stress (restoring ER Ca2+ content), and phenotypic switching of VSMCs. Suramin, which directly unbinds CaM from RyR, promoted nuclear CaM accumulation with parallel VSMCs phenotypic switching, and dantrolene prevented these effects.
We observed that ER stress causes CaM translocation to the nucleus and drives the phenotypic switching of VSMCs. Thus, restoration of the binding affinity of CaM to RyR may be a therapeutic target for atherosclerosis.
•Tunicamycin-induced ER stress promotes cell death by causing apoptosis, but this tunicamycin-driven apoptosis can be inhibited by dantrolene.•Dantrolene suppresses the expression of GRP78 and CHOP by restoring the ER Ca2+ content.•Tunicamycin-induced ER stress promotes MEF2 and KLF5 expression in the nucleus, which promotes the phenotypic switching of VSMCs, but dantrolene reduces the nuclear MEF2 and KLF5 expressions, suggesting that dantrolene prevents the phenotypic switching of VSMCs.•Tunicamycin-induced ER stress reduces the CaM-RyR binding and accelerates the translocation of CaM to the nucleus.•Direct displacement of CaM from RyR by suramin promotes both the nuclear accumulation of CaM and the nuclear expression of KLF5, leading to the phenotypic switching of VSMCs.•Treatment with dantrolene suppresses the formation of atherosclerotic plaque in ApoE−/− mice.
Sudden cardiac death (SCD) is the major cause of death in cardiac sarcoidosis (CS). We aimed to identify the prognostic markers for sustained ventricular tachycardia (sVT) and SCD in patients with ...CS.
We performed a prospective observational cohort study for patients with CS diagnosed according to the Japanese or Heart Rhythm Society guidelines between June 2008 and March 2020 in our hospital. The primary endpoint was a composite of the first sVT and SCD. The levels of urinary 8-hydroxy-2'-deoxyguanosine (U-8-OHdG), a marker of oxidative DNA damage that reflects the inflammatory activity of CS, other biomarkers, and indices of cardiac function and renal function were measured on admission.
Eighty-nine consecutive patients with CS were enrolled; 28 patients with no abnormal
F-fluorodeoxyglucose (
F-FDG) accumulation in the heart were excluded and 61 patients with abnormal
F-FDG accumulation were followed up for a median of 46 months (IQR: 20-84). During the follow-up period, 15 of 61 patients showed sVT (n=12) or SCD (n=3). A Cox proportional hazard model showed that U-8-OHdG concentration and presence of ventricular aneurysm (VA) were independent predictors of first sVT/SCD. The cut-off U-8-OHdG concentration for predicting first sVT/SCD was 14.9 ng/mg·Cr. Patients with U-8-OHdG concentration ≥14.9 ng/mg·Cr and VA showed a significantly increased risk of sVT/SCD.
U-8-OHdG and presence of VA were powerful predictors of first sVT/SCD in patients with CS, facilitating the stratification of cardiac events and providing relevant information about the substrates of ventricular tachycardia.
Dantrolene is a ryanodine receptor blocker that is used clinically for treatment of malignant hyperthermia. This study was conducted using murine aortic vascular smooth muscle cells (MOVAS) and a ...mouse arterial injury model to investigate the inhibitory effect of dantrolene on smooth muscle cell proliferation and migration.
We investigated whether dantrolene suppressed platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell proliferation and migration in vitro. The effect of dantrolene on smooth muscle phenotype was evaluated using immunostaining. In addition, smooth muscle cell proliferation and phenotype switching were tested by applying dantrolene around blood vessels using a mouse arterial injury model. Dantrolene inhibited PDGF-induced cell proliferation and migration of MOVAS. Dantrolene also inhibited the switch from contractile to synthetic phenotype both in vitro and in vivo.
Dantrolene is effective at inhibiting vascular smooth muscle cell proliferation, migration, and neointimal formation following arterial injury in mice.
•Dantrolene inhibits PDGF induced smooth muscle cell proliferation.•Dantrolene inhibits PDGF induced smooth muscle cell migration.•These effects are via inhibiting phenotype switch of smooth muscle cells.
The study aimed to investigate predictive factors associated with outcome six months after mild to moderate aneurysmal subarachnoid hemorrhage (SAH).
We divided 136 patients (51 men and 85 women) ...after SAH (Hunt & Kosnik H&K grade I to III) into groups with good and poor outcome according to scores on the modified Rankin Scale (mRS) at six months after SAH onset: good outcome (mRS score, 0–1; n = 105) and poor outcome (mRS score, 2–6; n = 31). At admission, we assessed age, sex, H&K grade, and Fisher grade, and one month after aneurysmal SAH, we evaluated aneurysm location, treatment modality (coil embolization, clipping, or no surgical treatment), proportion of patients who underwent shunt placement, proportion of patients with delayed cerebral ischemia, and scores on neuropsychological tests (Mini-Mental State Examination, Raven’s Colored Progressive Matrices, Kana-hiroi Test, Trail Making Test, and Rey-Osterrieth Complex Figure Test, immediate recall).
H&K grade was associated with outcome (χ2 = 6.220, P = 0.005), and a significantly higher proportion of the good outcome group had an H&K grade II (P = 0.025). The good outcome group had significantly better scores on the Mini-Mental State Examination (U = 1251, P = 0.045), Raven’s Colored Progressive Matrices (U = 1224, P = 0.036), and Trail Making Test parts A (U = 1238, P = 0.043) and B (U = 1247, P = 0.048). However, we found no significant intergroup differences in the other patient demographic and disease characteristics, including age, treatment modality, and delayed cerebral ischemia, or in the other neuropsychological assessments. Binary logistic regression analysis identified H&K grade I and II as predictive factors associated with good outcome.
Besides severity at admission as indicated by H&K grade, neuropsychological tests explicitly performed one month after mild to moderate aneurysmal SAH may help nursing staff to predict patient outcome, including possible symptoms after discharge.
Right ventricular (RV) dysfunction and its associated arrhythmias are recognized as important determinants of the prognosis of pulmonary arterial hypertension (PAH).
Here, we aimed to investigate ...whether direct pharmacological intervention in the RV muscle with dantrolene (DAN), a stabilizer of the cardiac ryanodine receptor (RyR2), has a protective effect against RV dysfunction and arrhythmia in a monocrotaline (MCT)-induced PAH rat model.
Male 8-week-old Sprague-Dawley rats were injected with MCT for the induction of PAH. Induction of ventricular tachycardia (VT) by catecholamines was also evaluated in association with RyR2-mediated Ca
release properties in isolated cardiomyocytes. A pulmonary artery-banding model has also been established to assess the independent effects of chronic pressure overload on RV morphology and function.
In the MCT-induced PAH rat model, RV hypertrophy, dilation, and functional decline were observed, with a survival rate of 0% 2 months after MCT induction. In contrast, chronic DAN treatment improved all these RV parameters and increased survival by 80%. Chronic DAN treatment also prevented the dissociation of calmodulin from RyR2, thereby inhibiting Ca
sparks and spontaneous Ca
transients in MCT-induced hypertrophied RV cardiomyocytes. Epinephrine induced VT in more than 50% of rats with MCT-induced PAH, but complete suppression of VT was achieved by chronic DAN treatment.
Stabilization of RyR2 by DAN has potential as a new therapeutic agent against the development of RV dysfunction and fatal arrhythmia associated with PAH.
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