Structural characterization, in vivo toxicity and biological activity of two new pyro-type diterpenoid alkaloids derived from 3-acetylaconitine

OBJECTIVE

The transformations that occur in diterpenoid alkaloids during the process of sand frying for Chinese herbal medicine preparation have yet to be clarified. This study investigated the structural changes that take place in 3-acetylaconitine during a simulation of heat-processing and evaluated the toxicity and biological activity of the pyrolysis products.

METHODS

The diterpenoid alkaloid 3-acetylaconitine was heated at 180 °C for 15 min to simulate the process of sand frying. The pyrolysis products were separated using column chromatography, and their structures were investigated using high-resolution electrospray ionization mass spectroscopy and nuclear magnetic resonance spectroscopy. Further, in vivo cardiotoxicity and acute toxicity of 3-acetylaconitine and its pyrolysis products were compared, and the aconitine-induced arrhythmia model was employed to evaluate the antiarrhythmic effect of the pyrolysis products.

RESULTS

Two new diterpenoid alkaloids, pyroacetylaconitine and 16-epi-pyroacetylaconitine, a pair of epimers at C-16, were isolated. After comparing the structures of these compounds, possible transformation pathways were proposed. Compared with the prototype compound, 3-acetylaconitine, the cardiotoxicity and acute toxicity of the heat-transformed products were significantly decreased. In the biological activity assay, the two pyrolysis products exhibited an effective increase in ventricular premature beat latency, a reduction in the occurrence of ventricular tachycardia, as well as an increase in the rate of arrhythmia inhibition, implying strong antiarrhythmic activity.

CONCLUSION

Compared with 3-acetylaconitine, its pyrolysis products displayed lower toxicity and good antiarrhythmic effects; thus, they have potential for being developed into antiarrhythmic medicines. Please cite this article as: Wang YJ, Wang Y, Tao P. Structural characterization, in vivo toxicity and biological activity of two new pyro-type diterpenoid alkaloids derived from 3-acetylaconitine. J Integr Med. 2023; Epub ahead of print.

Investigating the efficiency and tolerability of traditional Chinese formulas combined with antiarrhythmic agents for paroxysmal atrial fibrillation: A systematic review and Bayesian network meta-analysis

BACKGROUND

The combination of antiarrhythmic drugs with traditional Chinese formulas are used treatments for the management of paroxysmal atrial fibrillation (PAF). However, the most effective treatment for PAF has yet to be been determined. A Bayesian network meta-analysis study was thus performed for comparing the relative efficacy and tolerability of different treatment alternatives.

METHODS

A comprehensive literature review of randomized controlled trials (RCTs) is performed from eight database. Maintenance rate of sinus rhythm (MRSR), p-wave dispersion (Pd), left atrium diameter (LAD), left ventricular ejection fraction (LVEF), and adverse events (AEs) were used as outcomes. We also estimated treatment rank based on the surface under the cumulative ranking curve (SUCRA). This study was performed using a Bayesian network meta-analysis with a random-effects model.

FINDINGS

After screening, 59 RCTs involving 5,543 patients and 16 treatments were included. The results showed that Shensong-Yangxin capsule (SSYX) plus amiodarone (81%) was the most effective treatment for MRSR according to the value of SUCRA, followed by Wenxin-Keli granules (WXKL) plus amiodarone (73%). Meanwhile, SSYX plus amiodarone (7%) was most likely to reduce Pd, followed by SSYX plus metoprolol (23%), WXKL plus amiodarone (26%), WXKL plus bisoprolol (27%). Furthermore, SSYX plus amiodarone (4%) was more effective in improving LAD. WXKL plus amiodarone was preferred because it had the lowest toxicity. For benefit-risk ratio, amiodarone combined with WXKL or SSYX appeared to be the best option.

CONCLUSION

Antiarrhythmic agents combined with traditional Chinese formulas had higher efficacy and lower toxicity than other treatment alternatives. This study might provide reference to help find the better treatment options for PAF.

Dantrolene reduces CaMKIIδC-mediated atrial arrhythmias

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.

Voltage-Gated Sodium Channel Blockers: Synthesis of Mexiletine Analogues and Homologues

Mexiletine is an antiarrhythmic drug belonging to IB class, acting as sodium channel blocker. Besides its well-known activity on arrhythmias, its usefulness in the treatment of myotonia, myotonic dystrophy and amyotrophic lateral sclerosis is now widely recognized. Nevertheless, it has been retired from the market in several countries because of its undesired effects. Thus, several papers were reported in the last years about analogues and homologues of mexiletine being endowed with a wider therapeutic ratio and a more selectivity of action. Some of them showed sodium channel blocking activity higher than the parent compound. It is noteworthy that mexiletine is used in therapy as a racemate even though a difference in the activities of the two enantiomers was widely demonstrated, with (-)-(R)-enantiomer being more active: this finding led several research groups to study mexiletine and its analogues and homologues in their optically active forms. This review summarizes the different synthetic routes used to obtain these compounds. They could represent an interesting starting point to new mexiletine-like compounds without common side effects related to the use of mexiletine.

Tachyarrhythmias and neurologic complications

Tachyarrhythmias are abnormal heart rhythms with a ventricular rate of 100 or more beats per minute. These rhythms are classified as either narrow or wide-complex tachycardia with further subdivision into regular or irregular rhythm. Patients are frequently symptomatic presenting with palpitations, diaphoresis, dyspnea, chest pain, dizziness, and syncope. Sudden cardiac death may occur with certain arrhythmias. Recognizing tachyarrhythmia and understanding its management is important as a wide spectrum of neurologic complications have been associated with such arrhythmias. The purpose of this chapter is to provide a comprehensive overview on the neurologic complications of tachyarrhythmias, neurologic adverse events of antiarrhythmic interventions, and neurologic conditions that can precipitate tachyarrhythmia.

Atrial arrhythmias in chronic lung disease-associated pulmonary hypertension

Atrial arrhythmias are common during episodes of acute respiratory failure in patients with chronic lung disease-associated pulmonary hypertension. Expert opinion suggests that management of atrial arrhythmias in patients with pulmonary hypertension should aim to restore sinus rhythm. This is clinically challenging in pulmonary hypertension patients with coexisting chronic lung disease, as there is controversy on the use of rhythm control agents; generally, in regard to either their pulmonary toxicity profile or the lack of evidence supporting their use. Rate control methods are largely focused on the use of beta blockers and calcium channel blockers. Concerns regarding their use involve their negative inotropic properties in cor pulmonale, the risk of bronchospasm associated with beta blockers, and the potential for ventilation/perfusion mismatching associated with calcium channel blockers. While digoxin has been associated with promising outcomes during acute right ventricular failure, there is limited evidence to suggest its routine use. Electrical cardioversion is associated with a high failure rate and it frequently requires multiple attempts. Radiofrequency catheter ablation is a more definitive approach, but concerns surrounding mechanical ventilation and sedation limit its applicability in decompensated pulmonary hypertension. Individual approaches are needed to address atrial arrhythmia management during acute episodes of respiratory failure.

Management of paroxysmal atrial flutter that occurred in an outpatient prior to dental surgery: a case report

Background

It is essential to accomplish the appropriate emergency care particularly in patients undergoing stressful dento-oral surgical procedures. Atrial flutter may be induced by sympathetic hypertonia due to excessive mental and physical stress. There is no report regarding dental care in patients with atrial flutter. Herein, we describe a rare case of the antiarrhythmic management in an outpatient who presented with an electrocardiographic finding of paroxysmal atrial flutter before the initiation of the dento-oral surgical procedure.

Case presentation

A 60-year-old male patient was scheduled for a dental extraction. He had a history of angina pectoris, diabetes mellitus, and paroxysmal atrial fibrillation with medication. The preoperative electrocardiogram (ECG) revealed left ventricular hypertrophy and ST-T segment abnormality. Immediately before the dental extraction, II-lead ECG revealed atrial flutter; however, he complained of few subjective symptoms, such as precordial discomfort or palpitation. Observing the vital signs, ECG findings, and the general condition of the patient, low dose diltiazem was immediately administered by continuous infusion in order to control the heart rate and prevent atrial flutter-induced supraventricular tachyarrhythmia. Special attention was paid to prevent any critical cardiovascular condition under a preparation of intravenous disopyramide and verapamil and a defibrillator. The intravenous administration of diltiazem progressively restored the sinus rhythm after converting atrial flutter into atrial fibrillation, resulting in the prevention of tachycardia, and then was found to be appropriate as a prophylactic therapy of tachyarrhythmia.

Conclusions

The present case suggests that it is possible to successfully manage some of such patients using our method during dento-oral surgery which is likely to be associated with mental and physical stress. Therefore, it is essential to accomplish an initial emergency care in parallel to the differential diagnosis of unforeseen serious medical conditions or paroxysmal arrhythmia such as atrial flutter.

[Catheter ablation of ventricular tachycardia : Clinical outcome]

Catheter-based ablation of ventricular tachycardia (VT) is increasingly used in clinical practice. The reported success rates are especially high in idiopathic VT. In randomized controlled clinical trials like VANISH, ablation of scar-associated VT was superior in terms of mortality when compared to antiarrhythmic therapy. Treatment at experienced centers, e.g., using state-of-the-art electroanatomical mapping systems, is a promising option for these complex and often multimorbid patients.

Prevailing Effects of Ibutilide on Fast Delayed Rectifier K+ Channel

Effects of ibutilide, a class III antiarrhythmic drug, on delayed rectifier potassium currents (I_K) in freshly isolated guinea pig ventricular myocytes were studied. Experiments were performed using the whole-cell configuration of patch-clamp technique under blockade of L-type calcium currents (Cav1). Ibutilide at concentrations ranging between 10 nM and 100 µM inhibited I_Kr in dose-dependent manner with a half maximal effective concentration of 2.03 ± 0.74 µM (n = 5-10). The amplitude of tail currents activated by prepulse to + 20 mV was decreased from 253 ± 52 to 130 ± 25 pA (n = 8, p < 0.01) in the presence of 1 µM ibutilide. The envelope test revealed time-dependent changes in ratio of I_K-tail/ΔI_K during 0.2-2 s pulse durations in the absence of drug. With ibutilide, regardless of pulse duration, a relatively constant ratio was estimated, indicative of predominant involvement of I_Kr component. The slow I_Ks persisted to greater extent even at 100 μM ibutilide revealing a distinguishable selectivity toward the I_Kr component.

Cardiac Therapeutics in Horses

Many cardiac therapeutics lack significant evidence of benefit in the horse, and in many cases their use is based on extrapolation of evidence from other species. In recent years there has been a push to develop a better understanding of both the pharmacodynamics and pharmacokinetics of these drugs. Recent data have described the use of antiarrhythmic agents including sotalol, flecainide, and amiodarone. Data about the use of ACE inhibitors in the management of congestive heart failure are encouraging and support their use in certain cases, wheras evidence for other medicines, such as pimobendan, remain speculative.

Nano-scale drug delivery systems for antiarrhythmic agents

Arrhythmia means the heart is beating too fast, too slow, or with an irregular pattern. Due to the side effects and low bioavailability of many antiarrhythmic drugs, nano-encapsulation has been widely used for their targeted delivery. Lipid nanocapsules, nano liposomes, nano niosomes, solid lipid nanoparticles and polymeric nanoparticles are common nano-carriers used for this purpose. The aim of this article is to summarize some of nano systems used for the specific delivery of antiarrhythmic agents to target tissues. At first, nanotechnology and its applications in drug delivery are described in brief. Then, some information on arrhythmias and antiarrhythmic drugs are provided. Finally, the nano drug delivery systems are explained and examples of their applications in encapsulation of antiarrhythmic drugs are presented.

Intravenous Sotalol: An Under Used Treatment Strategy

The pharmacologic treatment of arrhythmias has seen little advance over the past few years. Physicians treating life threatening or hemodynamically destabilizing arrhythmias depend almost entirely on intravenous (IV) amiodarone. This is regrettable due to the multiple toxicities of amiodarone and its long half-life. Once administered, it is a therapeutic commitment to long-term therapy. Given the very long terminal elimination half-life, treatment with amiodarone may interfere with baseline electrophysiologic studies and ablation procedures. Additionally, the side effect profile can be consequential, even with brief periods of treatment. Currently, sotalol, like amiodarone, is available in both IV and oral formulations, facilitating their use in emergency situations. IV sotalol has a rapid onset of action with linear pharmacokinetics. While sotalol's efficacy has mostly been evaluated in small clinical trials, 2 recent meta-analysis have been informative as to the utility of sotalol. Sotalol has similar efficacy as amiodarone, but has much more favorable adverse event profile. IV sotalol has been underutilized and could offer advantage in the treatment of AF for rate and rhythm control, as well in the pediatrics for treatment of supraventricular arrhythmias often resistant to other therapies.

A Focus on the Synthesis and Pharmacokinetics of Tocainide and its Analogues

Tocainide is an antiarrhythmic agent belonging to class IB that was primarily used for suppression of symptomatic ventricular arrhythmias. Tocainide was also reported to relieve pain such as tic douloureux, trigemina neuralgia in humans and tinnitus. Significant antinociception, as assayed on the hot-plate test, was observed after intraperitoneal injection of tocainide, too. By the mid-1980s tocainide was emerging as a more consistently effective treatment for myotonic disorders. Numerous reports of serious adverse reactions led to the use of tocainide being discontinued, even though research on tocainide and its analogues, endowed with a better pharmacological profile, is still in progress for their potential usefulness in the treatment of myotonias. This review is focused on the description of the different synthetic routes to racemic and optically active tocainide developed in the last decades, as well as analytical studies regarding enantioseparation methods. Finally, some analogues of tocainide reported in the literature, most of which with pharmacological studies, have been mentioned.

Antiarrhythmic effects of interleukin 1 inhibition after myocardial infarction

BACKGROUND

Interleukin 1β (IL-1β) is a key regulator of the inflammatory response after myocardial infarction (MI) by modulating immune cell recruitment, cytokine production, and extracellular matrix turnover. Elevated levels of IL-1β are associated with adverse remodeling, and inhibition of IL-1 signaling after MI results in improved contractile function.

OBJECTIVE

The goal of this study was to determine whether IL-1 signaling also contributes to post-MI arrhythmogenesis.

METHODS

MI was created in 2 murine models of elevated inflammation: atherosclerotic on the Western diet or wild-type with a subseptic dose of lipopolysaccharide. The role of IL-1β was assessed with the IL-1 receptor antagonist anakinra (10 mg/(kg·d), starting 24 hours post-MI).

RESULTS

In vivo and ex vivo molecular imaging showed reduced myocardial inflammation after a 4-day course of anakinra treatment, despite no change in infarct size. At day 5 post-MI, high-speed optical mapping of transmembrane potential and intracellular Ca²⁺ in isolated hearts revealed that IL-1β inhibition improved conduction velocity, reduced action potential duration dispersion, improved intracellular Ca²⁺ handling, decreased transmembrane potential and Ca²⁺ alternans magnitude, and reduced spontaneous and inducible ventricular arrhythmias. These functional improvements were linked to increased expression of connexin 43 and sarcoplasmic reticulum Ca²⁺-ATPase.

CONCLUSION

This study revealed a novel mechanism for IL-1β in contributing to defective excitation-contraction coupling and arrhythmogenesis in the post-MI heart. Our results suggest that inhibition of IL-1 signaling post-MI may represent a novel antiarrhythmic therapy.

Is the acetylcholine-regulated inwardly rectifying potassium current a viable antiarrhythmic target? Translational discrepancies of AZD2927 and A7071 in dogs and humans

AIMS

We aimed at examining the acetylcholine-dependent inward-rectifier current (IKAch) as a target for the management of atrial fibrillation (AF).

METHODS AND RESULTS

The investigative agents AZD2927 and A7071 concentration-dependently blocked IKACh in vitro with minimal off-target activity. In anaesthetized dogs (n = 17) subjected to 8 weeks of rapid atrial pacing (RAP), the left atrial effective refractory period (LAERP) was maximally increased by 50 ± 7.4 and 50 ± 4.8 ms following infusion of AZD2927 and A7071. Ventricular refractoriness and the QT interval were unaltered. During sustained AF, both drugs significantly reduced AF frequency and effectively restored sinus rhythm. AZD2927 successfully restored sinus rhythm at 10/10 conversion attempts and A7071 at 14/14 attempts, whereas saline converted 4/17 episodes only (P<0.001 vs. AZD2927 and A7071). In atrial flutter patients (n = 18) undergoing an invasive investigation, AZD2927 did not change LAERP, the paced QT interval, or ventricular refractoriness when compared with placebo. To address the discrepancy on LAERP by IKACh blockade in man and dog and the hypothesis that atrial electrical remodelling is a prerequisite for IKACh blockade being efficient, six dogs were studied after 8 weeks of RAP followed by sinus rhythm for 4 weeks to reverse electrical remodelling. In these dogs, both AZD2927 and A7071 were as effective in increasing LAERP as in the dogs studied immediately after the 8-week RAP period.

CONCLUSION

Based on the present series of experiments, an important role of IKACh in human atrial electrophysiology, as well as its potential as a viable target for effective management of AF, may be questioned.

Potent and use-dependent block of cardiac sodium channels by U-50,488H, a benzeneacetamide kappa opioid receptor agonist

OBJECTIVES

To determine whether the kappa opioid receptor agonist U-50,488H, a benzacetamide derivative of the cyclo-hexane-1,2-diamine analgesics, may be a useful molecular probe to define the structural requirements of this class of drugs for cardiac sodium channel blockade.

ANIMALS AND METHODS

The electrophysiological effects of U-50,488H were compared with those of lidocaine, a clinically used class Ib antiarrhythmic agent, in rat heart sodium currents expressed in Xenopus laevis oocytes by using two-electrode voltage clamp.

RESULTS

Both U-50,488H and lidocaine produced a concentration-dependent tonic block of sodium current, but U-50,488H was approximately fourfold more potent than lidocaine. Both drugs produced a hyperpolarizing shift in the voltage dependence of sodium channel inactivation and both delayed recovery from inactivation. Both drugs exhibited use-dependent block, but U-50,488H showed a 1.8-fold increase in potency compared with lidocaine at a high frequency of stimulation (30 Hz).

CONCLUSIONS

The more potent tonic and use-dependent block of cardiac sodium channels by U-50,488H suggests that structural features of this molecule may provide it with a greater ability to block the channel. An understanding of these structural features may provide information needed in the development of novel arylacetamide-based antiarrhythmic drugs and insight into possible mechanisms describing channel block, resulting in a highly efficacious antiarrhythmic action in the heart.