L-Type Calcium Channel Inhibition Contributes to the Proarrhythmic Effects of Aconitine in Human Cardiomyocytes

Protective effect of ginsenoside Rb1 against aconitine cardiotoxicity studied by myocardial injury, action potential, and calcium signaling

Aconitine is the main active component of Aconitum plants. Although aconitine has effects that include strengthening the heart, analgesia, anti-tumor, and immune-regulating effects, aconitine has both efficacy and toxicity, especially cardiotoxicity. Severe effects can include arrhythmia and cardiac arrest, which limits the clinical application of aconitine-containing traditional Chinese medicine. Ginsenoside Rb1(Rb1) is mainly found in plants, such as ginseng and Panax notoginseng, and has cardiovascular-protective and anti-arrhythmia effects. This study aimed to investigate the detoxifying effects of Rb1 on aconitine cardiotoxicity and the electrophysiological effect of Rb1 on aconitine-induced arrhythmia in rats. Pathological analysis, myocardial enzymatic indexes, and Western blotting were used to investigate the ameliorating effect of Rb1 on aconitine cardiotoxicity. Optical mapping was used to evaluate the effect of Rb1 on action potential and calcium signaling after aconitine-induced arrhythmia. Rb1 inhibited pathological damage caused by aconitine, decreased myocardial enzyme levels, and restored the balance of apoptotic protein expression by reducing the expression of Bax and cleaved caspase 3 and increasing the expression of Bcl-2, thereby reducing myocardial damage caused by aconitine. Rb1 also reduced the increase in heart rate caused by aconitine, accelerated action potential conduction and calcium signaling, and reduced the dispersion of action potential and calcium signal conduction. Rb1 reduced the cardiotoxicity of aconitine by attenuating aconitine-induced myocardial injury and inhibiting the aconitine-induced retardation of ventricular action potential and calcium signaling in rats.

Evaluation of aconitine cardiotoxicity with a heart-on-a-particle prepared by a microfluidic device

A heart-on-a-particle model based on multicompartmental microgel is proposed to simulate the heart microenvironment and study the cardiotoxicity of drugs. The relevant microgel was fabricated by a biocompatible microfluidic-based approach, where heart function-related HL-1 and HUVEC cells were arranged in separate compartments. Finally, the mechanism of aconitine-induced heart toxicity was elucidated using mass spectrometry and molecular biotechnology.

Recurrent malignant ventricular arrhythmias and paresthesia-a mystery revealed as aconitine poisoning: a case report

BACKGROUND

We report a case of a clinical challenge lasting for 12 months, with severe and unresolved clinical features involving several medical disciplines.

CASE PRESENTATION

A 53-year-old Caucasian male, who had been previously healthy apart from a moderate renal impairment, was hospitalized 12 times during a 1-year period for a recurrent complex of neurological, cardiovascular, and gastrointestinal symptoms and signs, without any apparent etiology. On two occasions, he suffered a cardiac arrest and was successfully resuscitated. Following the first cardiac arrest, a cardiac defibrillator was inserted. During the 12th admission to our hospital, aconitine poisoning was suspected after a comprehensive multidisciplinary evaluation and confirmed by serum and urine analyses. Later, aconitine was also detected in a hair segment, indicating exposure within the symptomatic period. After the diagnosis was made, no further episodes occurred. His cardiac defibrillator was later removed, and he returned to work. A former diagnosis of epilepsy was also abandoned. Criminal intent was suspected, and his wife was sentenced to 11 years in prison for attempted murder. To make standardized assessments of the probability for aconitine poisoning as the cause of the eleven prior admissions, an "aconitine score" was established. The score is based on neurological, cardiovascular, gastrointestinal, and other clinical features reported in the literature. We also make a case for the use of hair analysis to confirm suspected poisoning cases evaluated after the resolution of clinical features.

CONCLUSION

This report illustrates the medical challenge raised by cases of covert poisoning. In patients presenting with symptoms and signs from several organ systems without apparent cause, poisoning should always be suspected. To solve such cases, insight into the effects of specific toxic agents is needed. We present an "aconitine score" that may be useful in cases of suspected aconitine poisoning.

DNA methylation cooperates with H3K9me2 at HCN4 promoter to regulate the differentiation of bone marrow mesenchymal stem cells into pacemaker-like cells

Sick sinus syndrome (SSS) is a a life-threatening disease, and biological pacemakers derived from bone marrow mesenchymal stem cells (BMSCs) have practical clinical applications. Previous studies demonstrated that epigenetics plays an important role in the differentiation of BMSCs into pacemaker-like cells. However, the underlying mechanisms remain unclear. In the present study, we investigated the role of DNA methylation and histone methylation in pacemaker cells formation and found that changes in DNA and H3K9 methylation occur in the promoter region of the pacemaker cell-specific gene HCN4. In addition, the combined addition of methylation inhibitors was able to improve the efficiency of transduction of Tbx18 in inducing the differentiation of BMSCs into pacemaker-like cells. In vitro experiments have shown that inhibition of DNA methylation and H3K9 methylation can enhance the activity of the HCN4 promoter activity, and both can affect the binding of the transcription factor NKx2.5to the HCN4 promoter region. Further research on the interaction mechanism between DNA methylation and H3K9me2 in the HCN4 promoter region revealed that the two may be coupled, and that the methylesterase G9a and DNMT1 may directly interact to bind as a complex that affects DNA methylation and H3K9me2 regulation of HCN4 transcription. In conclusion, our studies suggest that the mutual coupling of DNA and H3K9 methylation plays a critical role in regulating the differentiation of BMSCs into pacemaker-like cells from the perspective of interactions between epigenetic modifications, and combined methylation is a promising strategy to optimise pacemaker-like cells for in vitro applications.

Chinese herbal medicine for the treatment of cardiovascular diseases ─ targeting cardiac ion channels

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality, imposing an increasing global health burden. Cardiac ion channels (voltage-gated Na_V, Ca_V, K_Vs, and others) synergistically shape the cardiac action potential (AP) and control the heartbeat. Dysfunction of these channels, due to genetic mutations, transcriptional or post-translational modifications, may disturb the AP and lead to arrhythmia, a major risk for CVD patients. Although there are five classes of anti-arrhythmic drugs available, they can have varying levels of efficacies and side effects on patients, possibly due to the complex pathogenesis of arrhythmias. As an alternative treatment option, Chinese herbal remedies have shown promise in regulating cardiac ion channels and providing anti-arrhythmic effects. In this review, we first discuss the role of cardiac ion channels in maintaining normal heart function and the pathogenesis of CVD, then summarize the classification of Chinese herbal compounds, and elaborate detailed mechanisms of their efficacy in regulating cardiac ion channels and in alleviating arrhythmia and CVD. We also address current limitations and opportunities for developing new anti-CVD drugs based on Chinese herbal medicines.

Cardiac calcium regulation in human induced pluripotent stem cell cardiomyocytes: Implications for disease modeling and maturation

Human induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) are based on ground-breaking technology that has significantly impacted cardiovascular research. They provide a renewable source of human cardiomyocytes for a variety of applications including in vitro disease modeling and drug toxicity testing. Cardiac calcium regulation plays a critical role in the cardiomyocyte and is often dysregulated in cardiovascular disease. Due to the limited availability of human cardiac tissue, calcium handling and its regulation have most commonly been studied in the context of animal models. hiPSC-CMs can provide unique insights into human physiology and pathophysiology, although a remaining limitation is the relative immaturity of these cells compared to adult cardiomyocytes Therefore, this field is rapidly developing techniques to improve the maturity of hiPSC-CMs, further establishing their place in cardiovascular research. This review briefly covers the basics of cardiomyocyte calcium cycling and hiPSC technology, and will provide a detailed description of our current understanding of calcium in hiPSC-CMs.

Advances on pharmacology and toxicology of aconitine

Aconitum alkaloids are considered to be the characteristic bioactive ingredients of Aconitum species, which are widely applied to the treatment of diverse diseases, and aconitine (AC) is found in most Aconitum plants. Research evidence shows that low-dose AC has a good therapeutic potential in heart failure, myocardial infarction, neuroinflammatory diseases, rheumatic diseases, and tumors, which has become one of the hotspots in global research in recent years. However, the cardiotoxicity and neurotoxicity of AC have also attracted extensive attention. Excessive use of AC always induces ventricular tachyarrhythmia and heart arrest, even can be potentially lethal. Therefore, AC cannot simply be regarded as a good medicine or a toxicant, but its underlying curative and toxic properties remained chaos. In order to dig the unique pharmacological value of AC while preventing its toxicity, the pharmacological activities and toxic effects of AC were summarized in this paper, providing new insight into the safe and effective use of AC in clinical practice.

An insight into current advances on pharmacology, pharmacokinetics, toxicity and detoxification of aconitine

Aconitine is a diterpenoid alkaloid, which mainly exists in the plants of Aconitum. In the last decade, a plethora of studies on the pharmacological activities of aconitine has been conducted and demonstrated that aconitine possessed an extensive range of pharmacological activities such as anti-tumor, anti-inflammatory, analgesic, local anesthesia, and immunomodulatory effects. Pharmacokinetic studies indicated that aconitine may have the characteristics of poor bioavailability, wide distribution, and slow elimination. However, studies have also found that aconitine has toxic effects on the heart, nerves, embryos, etc. Therefore, we believe that aconitine may not be suitable for heart patients and pregnant women to treat related diseases. It is important to note that all of these pharmacological effects require further high-quality studies to determine the clinical efficacy of aconitine. This review aims to summarize the advances in pharmacological, pharmacokinetics, toxicity, and detoxification of aconitine in the last decade with an emphasis on its anti-tumor and anti-inflammatory activities, to provide researchers with the latest information and point out the limitations of relevant research at the current stage and the aspects that should be strengthened in future research.

Gallic Acid Inhibits Mesaconitine-Activated TRPV1-Channel-Induced Cardiotoxicity

Aconiti Kusnezoffii Radix (Caowu) is often combined or processed with Chebulae Fructus (Hezi) to achieve attenuation purposes in Mongolian medicine. Mesaconitine (MA), a main bioactive ingredient of Caowu, is also famous for its high cardiotoxicity while exerting good anti-inflammatory and analgesic properties. Gallic acid (GA), one of the leading chemical components in Hezi, possesses cardiac protection. This study aimed to clarify the detoxification effects of GA from Hezi on MA-induced cardiotoxicity and whether the detoxification mechanism is related to the TRPV1 channel. Cell viability was determined by methyl thiazol tetrazolium (MTT), and lactate dehydrogenase (LDH) leakage rate was determined by ELISA. Hoechst 33258, JC-1, DCFH-DA, and Fluo-3 AM staining were conducted to detect apoptosis, mitochondrial membrane potential, reactive oxygen species (ROS), and Ca2+ respectively; TRPV1 channel current was recorded by whole-cell patch-clamp technology to observe the effect of GA and MA alone or in combination on TRPV1 channel. The results showed that GA exhibited pronounced detoxification effects on MA-induced cardiotoxicity. GA significantly inhibited the MA-induced decrease in cell viability; suppressed the MA-induced LDH leakage rate, apoptosis, and the release of ROS and Ca2+; and alleviated the reduction of mitochondrial membrane potential. We found that MA-induced cardiotoxicity was significantly attenuated in H9c2 cells pretreated with the TRPV1 antagonist BCTC. In the whole-cell patch-clamp experiment, the TRPV1 channel current increase was caused by the GA and MA treatment, whereas it was reduced by the cotreatment of GA and MA. Our data demonstrate that GA in Hezi can reduce MA-induced cardiotoxicity by inhibiting intracellular Ca2+ influx, restoring mitochondrial membrane potential, and reducing apoptosis. The detoxification mechanism may be related to the desensitization of the TRPV1 channel by the combined application of MA and GA.

Wenxin Keli for the Treatment of Arrhythmia-Systems Pharmacology and In Vivo Pharmacological Assessment

This study employed a systems pharmacology approach to identify the active compounds and action mechanisms of Wenxin Keli for arrhythmia treatment. Sixty-eight components identified in vivo and in vitro by UPLC/Q-TOF-MS were considered the potential active components of Wenxin Keli. Network pharmacology further revealed 33 key targets and 75 KEGG pathways as possible pathways and targets involved in WK-mediated treatment, with the CaMKII/CNCA1C/Ca²⁺ pathway being the most significantly affected. This finding was validated using an AC-induced rat arrhythmias model. Pretreatment with Wenxin Keli reduced the malignant arrhythmias and shortened RR, PR, and the QT interval. Wenxin Keli exerted some antiarrhythmic effects by inhibiting p-CaMKII and intracellular Ca²⁺ transients and overexpressing CNCA1C. Thus, suppressing SR Ca²⁺ release and maintaining intracellular Ca²⁺ balance may be the primary mechanism of Wenxin Keli against arrhythmia. In view of the significance of CaMKII and NCX identified in this experiment, we suggest that CaMKII and NCX are essential targets for treating arrhythmias.

Aconitine Induces TRPV2-Mediated Ca2+ Influx through the p38 MAPK Signal and Promotes Cardiomyocyte Apoptosis

Aconitine is the main effective component of traditional Chinese medicine Aconitum, which has been proved to have severe cardiovascular toxicity. The toxic effect of aconitine on cardiomyocytes is related to intracellular calcium overload, but the mechanism remains unclear. The aim of this study was to explore the mechanism of aconitine inducing intracellular Ca²⁺ overload and promoting H9c2 cardiomyocyte apoptosis through transient receptor potential cation channel subfamily V member 2 (TRPV2). After treated with different concentrations of aconitine, the level of cell apoptosis, intracellular Ca²⁺, and expression of p-p38 MAPK and TRPV2 of H9c2 cardiomyocytes were detected. The results showed that aconitine induced Ca²⁺ influx and H9c2 cardiomyocyte apoptosis in a dose-dependent manner and promoted p38 MAPK activation as well as TRPV2 expression and plasma membrane (PM) metastasis. siTRPV2, tranilast, and SB202190 reversed intracellular Ca²⁺ overload and H9c2 cardiomyocyte apoptosis induced by aconitine. These results suggested that aconitine promoted TRPV2 expression and PM metastasis through p38 MAPK signaling, thus inducing intracellular Ca²⁺ overload and cardiomyocyte apoptosis. Furthermore, TRPV2 is a potential molecular target for the treatment of aconitine poisoning.

Risk Compounds, Preclinical Toxicity Evaluation, and Potential Mechanisms of Chinese Materia Medica-Induced Cardiotoxicity

Chinese materia medica (CMM) has been applied for the prevention and treatment of diseases for thousands of years. However, arrhythmia, myocardial ischemia, heart failure, and other cardiac adverse reactions during CMM application were gradually reported. CMM-induced cardiotoxicity has aroused widespread attention. Our review aimed to summarize the risk compounds, preclinical toxicity evaluation, and potential mechanisms of CMM-induced cardiotoxicity. All relevant articles published on the PubMed, Embase, and China National Knowledge Infrastructure (CNKI) databases for the latest twenty years were searched and manually extracted. The risk substances of CMM-induced cardiotoxicity are relatively complex. A single CMM usually contains various risk compounds, and the same risk substance may exist in various CMM. The active and risk substances in CMM may be transformed into each other under different conditions, such as drug dosage, medication methods, and body status. Generally, the risk compounds of CMM-induced cardiotoxicity can be classified into alkaloids, terpenoids, steroids, heavy metals, organic acids, toxic proteins, and peptides. Traditional evaluation methods of chemical drug-induced cardiotoxicity primarily include cardiac function monitoring, endomyocardial biopsy, myocardial zymogram, and biomarker determination. In the preclinical stage, CMM-induced cardiotoxicity should be systematically evaluated at the overall, tissue, cellular, and molecular levels, including cardiac function, histopathology, cytology, myocardial zymogram, and biomarkers. Thanks to the development of systematic biology, the higher specificity and sensitivity of biomarkers, such as genes, proteins, and metabolic small molecules, are gradually applied for evaluating CMM-induced cardiotoxicity. Previous studies on the mechanisms of CMM-induced cardiotoxicity focused on a single drug, monomer or components of CMM. The interaction among ion homeostasis (sodium, potassium, and calcium ions), oxidative damage, mitochondrial injury, apoptosis and autophagy, and metabolic disturbance is involved in CMM-induced cardiotoxicity. Clarification on the risk compounds, preclinical toxicity evaluation, and potential mechanisms of CMM-induced cardiotoxicity must be beneficial to guide new CMM development and post-marketed CMM reevaluation.

Differential effects on out-of-hospital cardiac arrest of dihydropyridines: real-world data from population-based cohorts across two European countries

AIMS

Various drugs increase the risk of out-of-hospital cardiac arrest (OHCA) in the general population by impacting cardiac ion channels, thereby causing ventricular tachycardia/fibrillation (VT/VF). Dihydropyridines block L-type calcium channels, but their association with OHCA risk is unknown. We aimed to study whether nifedipine and/or amlodipine, often-used dihydropyridines, are associated with increased OHCA risk, and how these drugs impact on cardiac electrophysiology.

METHODS AND RESULTS

We conducted a case-control study with VT/VF-documented OHCA cases with presumed cardiac cause from ongoing population-based OHCA registries in the Netherlands and Denmark, and age/sex/index date-matched non-OHCA controls (Netherlands: PHARMO Database Network, Denmark: Danish Civil Registration System). We included 2503 OHCA cases, 10 543 non-OHCA controls in Netherlands, and 8101 OHCA cases, 40 505 non-OHCA controls in Denmark. To examine drug effects on cardiac electrophysiology, we performed single-cell patch-clamp studies in human-induced pluripotent stem cell-derived cardiomyocytes. Use of high-dose nifedipine (≥60 mg/day), but not low-dose nifedipine (<60 mg/day) or amlodipine (any-dose), was associated with higher OHCA risk than non-use of dihydropyridines [Netherlands: adjusted odds ratios (ORadj) 1.45 (95% confidence interval 1.02-2.07), Denmark: 1.96 (1.18-3.25)] or use of amlodipine [Netherlands: 2.31 (1.54-3.47), Denmark: 2.20 (1.32-3.67)]. Out-of-hospital cardiac arrest risk of (high-dose) nifedipine use was not further increased in patients using nitrates, or with a history of ischaemic heart disease. Nifedipine and amlodipine blocked L-type calcium channels at similar concentrations, but, at clinically used concentrations, nifedipine caused more L-type calcium current block, resulting in more action potential shortening.

CONCLUSION

High-dose nifedipine, but not low-dose nifedipine or any-dose amlodipine, is associated with increased OHCA risk in the general population. Careful titration of nifedipine dose should be considered.

Inhibition of the INa/K and the activation of peak INa contribute to the arrhythmogenic effects of aconitine and mesaconitine in guinea pigs

Aconitine (ACO), a main active ingredient of Aconitum, is well-known for its cardiotoxicity. However, the mechanisms of toxic action of ACO remain unclear. In the current study, we investigated the cardiac effects of ACO and mesaconitine (MACO), a structurally related analog of ACO identified in Aconitum with undocumented cardiotoxicity in guinea pigs. We showed that intravenous administration of ACO or MACO (25 μg/kg) to guinea pigs caused various types of arrhythmias in electrocardiogram (ECG) recording, including ventricular premature beats (VPB), atrioventricular blockade (AVB), ventricular tachycardia (VT), and ventricular fibrillation (VF). MACO displayed more potent arrhythmogenic effect than ACO. We conducted whole-cell patch-clamp recording in isolated guinea pig ventricular myocytes, and observed that treatment with ACO (0.3, 3 μM) or MACO (0.1, 0.3 μM) depolarized the resting membrane potential (RMP) and reduced the action potential amplitude (APA) and durations (APDs) in a concentration-dependent manner. The ACO- and MACO-induced AP remodeling was largely abolished by an I_Na blocker tetrodotoxin (2 μM) and partly abolished by a specific Na⁺/K⁺ pump (NKP) blocker ouabain (0.1 μM). Furthermore, we observed that treatment with ACO or MACO attenuated NKP current (I_Na/K) and increased peak I_Na by accelerating the sodium channel activation with the EC₅₀ of 8.36 ± 1.89 and 1.33 ± 0.16 μM, respectively. Incubation of ventricular myocytes with ACO or MACO concentration-dependently increased intracellular Na⁺ and Ca²⁺ concentrations. In conclusion, the current study demonstrates strong arrhythmogenic effects of ACO and MACO resulted from increasing the peak I_Na via accelerating sodium channel activation and inhibiting the I_Na/K. These results may help to improve our understanding of cardiotoxic mechanisms of ACO and MACO, and identify potential novel therapeutic targets for Aconitum poisoning.

Cardiac efficacy and toxicity of aconitine: A new frontier for the ancient poison

Aconitine (AC) is well-known as the main toxic ingredient and active compound of Aconitum species, of which several aconites are essential herbal medicines of Traditional Chinese Medicine (TCM) and widely applied to treat diverse diseases for their excellent anti-inflammatory, analgesic, and cardiotonic effects. However, the cardiotoxicity and neurotoxicity of AC attracted a lot of attention and made it a favorite botanic poison in history. Nowadays, the narrow therapeutic window of AC limits the clinical application of AC-containing herbal medicines; overdosing on AC always induces ventricular tachyarrhythmia and heart arrest, both of which are potentially lethal. But the underlying cardiotoxic mechanisms remained chaos. Recently, beyond its cardiotoxic effects, emerging evidence shows that low doses of AC or its metabolites could generate cardioprotective effects and are necessary to aconite's clinical efficacy. Consistent with TCM's theory that even toxic substances are powerful medicines, AC thus could not be simply identified as a toxicant or a drug. To prevent cardiotoxicity while digging the unique value of AC in cardiac pharmacology, there exists a huge urge to better know the characteristic of AC being a cardiotoxic agent or a potential heart drug. Here, this article reviews the advances of AC metabolism and focuses on the latest mechanistic findings of cardiac efficacy and toxicity of this aconite alkaloid or its metabolites. We also discuss how to prevent AC-related cardiotoxicity, as well as the issues before the development of AC-based medicines that should be solved, to provide new insight into the paradoxical nature of this ancient poison.

Ion Channel and Structural Remodeling in Obesity-Mediated Atrial Fibrillation

BACKGROUND

Epidemiological studies have established obesity as an independent risk factor for atrial fibrillation (AF), but the underlying pathophysiological mechanisms remain unclear. Reduced cardiac sodium channel expression is a known causal mechanism in AF. We hypothesized that obesity decreases Nav1.5 expression via enhanced oxidative stress, thus reducing INa, and enhancing susceptibility to AF.

METHODS

To elucidate the underlying electrophysiological mechanisms a diet-induced obese mouse model was used. Weight, blood pressure, glucose, F2-isoprostanes, NOX2 (NADPH oxidase 2), and PKC (protein kinase C) were measured in obese mice and compared with lean controls. Invasive electrophysiological, immunohistochemistry, Western blotting, and patch clamping of membrane potentials was performed to evaluate the molecular and electrophysiological phenotype of atrial myocytes.

RESULTS

Pacing-induced AF in 100% of diet-induced obese mice versus 25% in controls (P<0.01) with increased AF burden. Cardiac sodium channel expression, INa and atrial action potential duration were reduced and potassium channel expression (Kv1.5) and current (IKur) and F2-isoprostanes, NOX2, and PKC-α/δ expression and atrial fibrosis were significantly increased in diet-induced obese mice as compared with controls. A mitochondrial antioxidant reduced AF burden, restored INa, ICa,L, IKur, action potential duration, and reversed atrial fibrosis in diet-induced obese mice as compared with controls.

CONCLUSIONS

Inducible AF in obese mice is mediated, in part, by a combined effect of sodium, potassium, and calcium channel remodeling and atrial fibrosis. Mitochondrial antioxidant therapy abrogated the ion channel and structural remodeling and reversed the obesity-induced AF burden. Our findings have important implications for the management of obesity-mediated AF in patients. Graphic Abstract: A graphic abstract is available for this article.

Regulation of beta adrenoceptor-mediated myocardial contraction and calcium dynamics by the G protein-coupled estrogen receptor 1

The G protein-coupled estrogen receptor 1 (GPER) produces cardioprotective effects. However, the underlying mechanisms are not well understood. We aimed to investigate the role of GPER in β adrenoceptor-mediated cardiac contraction and myocardial signaling. In anesthetized animals, intrajugular administration of isoproterenol produces a rapid and sustained rise in left ventricular pressure (LVP) and increases ectopic contractions. Administration of the GPER agonist G-1 during the plateau phase of isoproterenol-induced LVP increase rapidly restores LVP to baseline levels and reduces the frequency of ectopic contractions. In freshly isolated cardiomyocytes, isoproterenol potentiates electrically induced peak currents of L-type Ca²⁺ channels (LTCC) and increases the potential sensitivity of their inactivation. Coadministration of G-1 prevents isoproterenol-induced potentiation of peak LTCC currents and makes channels more sensitive to being inactivated compared to isoproterenol alone. Isoproterenol treatment of cardiomyocytes without electrical stimulation triggers slow-rising Ca²⁺ signals that are inhibited by the β₁AR antagonist metoprolol but not by β₂AR antagonist ICI-118551. G-1 pretreatment dose-dependently suppresses isoproterenol-induced total Ca²⁺ signals and the amplitude and frequency of the intrinsic Ca²⁺ oscillatory deflections. Pretreatment with the GPER antagonist G-36 produces opposite effects, dose-dependently increasing these signals. ISO promotes robust phosphorylation of Ca_v1.2 channels at Ser1928. G-1 pretreatment inhibits isoproterenol-stimulated phosphorylation of Ca_v1.2 at Ser1928, while G-36 pretreatment enhances this signal. Our data indicate that GPER functions as an intrinsic component of β₁AR signaling to moderate myocardial Ca²⁺ dynamics and contraction.

Relationships between the Toxicities of Radix Aconiti Lateralis Preparata (Fuzi) and the Toxicokinetics of Its Main Diester-Diterpenoid Alkaloids

The processed lateral root of Aconitum carmichaelii Deb (Aconiti Radix lateralis praeparata or Fuzi) is a potent traditional herbal medicine extensively used in treatment of cardiovascular diseases, rheumatism arthritis, and bronchitis in many Asian countries. Although Fuzi has promising therapeutic effects, its toxicities are frequently observed. Three main C₁₉-diester-diterpenoid alkaloids (DDAs) are believed to be the principal toxins of the herb. Although toxicokinetic profiles of the toxic DDAs have already been examined in several studies, they have seldom been correlated with the toxicities of Fuzi. The current article aimed to investigate the relationship between the up-to-date toxicokinetic data of the toxic DDAs and the existing evidence of the toxic effects of Fuzi. Relationships between the cardiac toxicity and the plasma and heart concentration of DDAs in mice and rats were established. Based on our findings, clinical monitoring of the plasma concentrations of DDAs of Fuzi is recommended to prevent potential cardiac toxicities. Additionally, caution with respect to potential hepatic and renal toxicity induced by Fuzi should be exercised. In addition, further analyses focusing on the preclinical tissue distribution profile of DDAs and on the long-term toxicokinetic-toxicity correlation of DDAs are warranted for a better understanding of the toxic mechanisms and safer use of Fuzi.

Protective effect of berberine on aconite‑induced myocardial injury and the associated mechanisms

Aconitum plants, which have analgesic, diuretic and anti-inflammatory effects, have been widely used to treat various types of disease. However, the apparent toxicity of Aconitum-derived agents, particularly in the cardiovascular system, has largely limited their clinical use. Thus, the present study investigated whether berberine (Ber), an isoquinoline alkaloid, may reduce myocardial injury induced by aconitine (AC) in rats and the underlying mechanisms. Rats (n=40) were randomly divided into four groups: Control, Chuan-wu and Chuan-wu + Ber (8 and 16 mg/kg doses). Electrocardiograms (ECG) of the rats were recorded and serum biomarkers of cardiac function [lactate dehydrogenase (LDH), creatine kinase (CK) and CK-MB] were assayed. Histopathological changes were assessed using myocardial tissue sectioning and hematoxylin and eosin staining. Additionally, the effects of Ber on AC-induced arrhythmias in rats were observed. The changes in ECG following AC perfusion were observed, and the types and onset time of arrhythmias were analyzed. Furthermore, the effects of Ber and AC on papillary muscle action potentials were observed. The results suggested that Ber ameliorated myocardial injury induced by Chuan-wu, which was indicated by reduced arrhythmias and decreased LDH, CK and CK-MB levels in serum. Furthermore, histological damage, including dilation of small veins and congestion, was also markedly attenuated by Ber. In addition, the occurrence of arrhythmias was significantly delayed, and the dosage of AC required to induce arrhythmias was also increased by Ber pretreatment. Additionally, AC-induced changes in action potential amplitude, duration of 30% repolarization and duration of 90% repolarization in the papillary muscle were attenuated by Ber. All of these results indicate that Ber had a preventive effect on acute myocardial injury induced by Chuan-wu and arrhythmias caused by AC, which may be associated with the inhibition of delayed depolarization and triggered activity caused by AC. Thus, combination treatment of Ber with Aconitum plants may be a novel strategy to prevent AC-induced myocardial injury in clinical practice.

Aconitine-induced cardiac arrhythmia in human induced pluripotent stem cell-derived cardiomyocytes

Pre-clinical evaluation of cardiac dysfunction is important for assessing the safety of traditional or novel medicines due to the universality of potential drug-induced heart failure and irreversible arrhythmia. Aconitine (ACO), a traditionally used anti-pyretic, analgesic and anti-rheumatic drug, has been reported to have arrhythmogenic effects. In the present study, the Real-Time Cellular Analysis Cardio system was applied to evaluate the arrhythmogenic effects of ACO in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The results indicated that ACO is capable of increasing the frequency and decreasing the amplitude of hiPSC-CM contraction in a dose- and time-dependent manner. ACO at 0.25 µM increased the beating rate of hiPSC-CMs by 3.7-fold within 30 min, while 3.0 µM of ACO increased the beating rate by 7.3-fold. The present study also evaluated the potential pro-apoptotic effects of ACO by using caspase-3 and caspase-9 kits. To the best of our knowledge, the present study was the first to record the ACO-induced cardiac arrhythmia of hiPSC-CMsin real-time. The results also indicate that ACO-induced cell death is mediated, at least in part, by caspase-dependent apoptotic pathways.

Bradycardia and Hypotension from Improper Use of Aconite Root: A Case Report and Brief Review

Background: Adverse reactions associated with Chinese herbal medicines (CHMs) are usually the result of unpredictable active/toxic ingredients, inaccurate or mistaken beliefs, or poor supervision. The herb that most commonly induces severe adverse effects in Hong Kong and China is aconite root. More than 200 species of Aconitum plants are used for medicinal purposes, with aconite roots producing analgesic, anti-inflammatory, cardiotonic, and anti-tumor effects. The active components are alkaloids; these can be toxic, but CHM processing methods lower their toxicity and increase the pharmacological efficacy. However, aconite poisoning can result from inadequate decoction time or exceeding the recommended dose. Case Report: Here we report the case of a 92-year-old woman who presented with life-threatening bradycardia and hypotension. This started 1 h after she inappropriately consumed a herbal decoction containing Fuzi for mood fluctuation and health maintenance; Fuzi, an aconite root, has known cardiotoxicity. Electrocardiography showed supraventricular abnormalities, including sinus bradycardia and low-amplitude P waves. After an infusion of normal saline and inotropic agents for 25 h, the clinical manifestations subsided, her sinus rhythm returned to normal, and she was discharged. At follow-up 2 weeks later, she was in good health and had ceased taking any CHM. Conclusions: Standardized processing methods, stringent regulations, and cooperation between health professions can ensure medication safety and establish a fully-fledged operating process for these valuable drugs. We hope this report will help establish correct attitudes toward CHM and will assist Traditional Chinese Medicine practitioners to become more familiar with Aconitum plants.

Recurrent Ventricular Arrhythmia Caused by Ingestion of Aconitum (Monkshood) Flowers

We report the case of a patient who presented with respiratory failure, recurrent ventricular fibrillation, ventricular arrhythmias, and hypotension after an intentional ingestion of aconite flowers. Significant ingestion of this plant can produce life-threatening cardio- and neurotoxicity that may require evacuation from the wilderness to a medical facility capable of advanced treatment and intensive care monitoring.

Research progress of aconitine toxicity and forensic analysis of aconitine poisoning

Chinese herbal medicines have been extensively used in China and other countries for centuries. Aconitine, a diterpenoid alkaloid extracted from Aconitum plants, has anti-inflammatory and analgesic activities, but can also induce severe arrhythmia and neurotoxicity. Aconitine poisoning accidents caused by misuse, suicide, or homicide have been reported in recent years. In China, fatal aconitine poisoning can occasionally happen on account of accidental ingestion of some wild plants or consumption of herbal decoction made from the roots of Aconitum plants. However, it is rather difficult for forensic experts to find the specific results in present forensic autopsy of aconitine-induced death. To further clarify its potential risk following the widespread application of aconitine, toxicological characteristics and pharmacokinetics of aconitine are reviewed. Moreover, gastrointestinal, neurological, and cardiovascular symptoms were observed frequently in aconitine poisoning cases. In addition, the review also aims at providing some convincing evidences for forensic experts to identify unexplained death with postmortem examination.

Identification of Na+/K+-ATPase inhibition-independent proarrhythmic ionic mechanisms of cardiac glycosides

The current study explored the Na⁺/K⁺-ATPase (NKA) inhibition-independent proarrhythmic mechanisms of cardiac glycosides (CGs) which are well-known NKA inhibitors. With the cytosolic Ca²⁺ chelated by EGTA and BAPTA or extracellular Ca²⁺ replaced by Ba²⁺, effects of bufadienolides (bufalin (BF) and cinobufagin (CBG)) and cardenolides (ouabain (Oua) and pecilocerin A (PEA)) on the L-type calcium current (I_Ca,L) were recorded in heterologous expression Cav1.2-CHO cells and human embryonic stem cell-derived cardiomyocytes (hESC-CMs). BF and CBG demonstrated a concentration-dependent (0.1 to 100 µM) I_Ca,L inhibition (maximal ≥50%) without and with the NKA activity blocked by 10 µM Oua. BF significantly shortened the action potential duration at 1.0 µM and shortened the extracellular field potential duration at 0.01~1.0 µM. On the other hand, BF and CBG at 100 µM demonstrated a strong inhibition (≥40%) of the rapidly activating component of the delayed rectifier K⁺ current (I_Kr) in heterologous expression HEK293 cells and prolonged the APD of the heart of day-3 Zebrafish larva with disrupted rhythmic contractions. Moreover, hESC-CMs treated with BF (10 nM) for 24 hours showed moderate yet significant prolongation in APD90. In conclusion, our data indicate that CGs particularly bufadienolides possess cytosolic [Ca²⁺]_i- and NKA inhibition- independent proarrhythmic potential through I_Ca,L and I_Kr inhibitions.