The Role of Biologically Active Ingredients from Natural Drug Treatments for Arrhythmias in Different Mechanisms

The Effect of the Tongyang Huoxue Recipe (TYHX) on the I to/I Kur in Ischemia/Reperfusion Sinoatrial Node Cells

Background

The transient outward potassium current (I _to) and the ultrarapid delayed rectifier potassium current (I _Kur) are major potassium currents involved in the repolarization process of sinoatrial node cells (SNCs).

Methods and Results

The SNCs of neonatal rats were divided into control, ischemia/reperfusion (I/R), I/R+blank serum, and Tongyang Huoxue recipe (TYHX) serum groups. I _to and I _Kur were recorded using the whole cell patch-clamp technique, and the current-voltage (I-V), steady-state activation (SSA), steady-state inactivation (SSI), and recovery from inactivation (RFI) curves were plotted, respectively. Compared to the control group, both the peak current density and the current density at the voltage of I _to and I _Kur decreased obviously in SNCs after simulated I/R, the SSA curves moved right, and the SSI curves moved left. After TYHX was added to the extracellular solution of SNCs, both the peak current density and the current density at the voltage of I _to and I _Kur increased significantly, the SSA curves moved left, and the SSI curves moved right with a significant difference of V _1/2. The recovery from the I _Kur RFI curves was slightly restored, and the I _to curves did not change.

Conclusions

TYHX increases the peak current density, accelerates the activation, and decreases the inactivation of the I _to and I _Kur. This may be the mechanism of TYHX in shortening the action potential duration of repolarization, which accelerates spontaneous pulsation.

Neferine Protects Against Brain Damage in Permanent Cerebral Ischemic Rat Associated with Autophagy Suppression and AMPK/mTOR Regulation

Neferine is the major alkaloid compound isolated from the seed embryos of lotus. Neferine has many pharmacological effects, such as anti-inflammatory, antioxidative stress, and antiapoptotic effects, and it maintains autophagic balance. The purpose of this study was to explore the mechanism by which neferine attenuates autophagy after permanent cerebral ischemia in rats. We performed permanent cerebral ischemia in rats by middle cerebral artery occlusion (pMCAO) for 12 h with or without administration of neferine or nimodipine, a calcium (Ca²⁺) channel blocker. Neuroprotective effects were determined by evaluating the infarct volume and neurological deficits. Autophagy and its signaling pathway were determined by evaluating the expression of phosphorylated AMP-activated protein kinase alpha (AMPKα), phosphorylated mammalian target of rapamycin (mTOR), beclin-1, microtubule-associated protein 1A/1B-light chain 3 class II (LC3-II), and p62 by western blotting. Autophagosomes were evaluated by transmission electron microscopy. Neferine treatment significantly reduced infarct volumes and improved neurological deficits. Neferine significantly attenuated the upregulation of autophagy-associated proteins such as LC3-II, beclin-1, and p62 as well as autophagosome formation, all of which were induced by pMCAO. Neferine exerted remarkable protection against cerebral ischemia, possibly via the regulation of autophagy mediated by the Ca²⁺-dependent AMPK/mTOR pathway.

Impact of Dietary Factors on Brugada Syndrome and Long QT Syndrome

A healthy regime is fundamental for the prevention of cardiovascular diseases (CVD). In inherited channelopathies, such as Brugada syndrome (BrS) and Long QT syndrome (LQTS), unfortunately, sudden cardiac death could be the first sign for patients affected by these syndromes. Several known factors are used to stratify the risk of developing cardiac arrhythmias, although none are determinative. The risk factors can be affected by adjusting lifestyle habits, such as a particular diet, impacting the risk of arrhythmogenic events and mortality. To date, the importance of understanding the relationship between diet and inherited channelopathies has been underrated. Therefore, we describe herein the effects of dietary factors on the development of arrhythmia in patients affected by BrS and LQTS. Modifying the diet might not be enough to fully prevent arrhythmias, but it can help lower the risk.

A review on plants and herbal components with antiarrhythmic activities and their interaction with current cardiac drugs

This paper aimed to compile information on plants or their compounds which have experimentally shown antiarrhythmic effect and to scrutinize the efficacy and potency of them and their potential interaction with conventional cardiac drugs. Literature searches were accomplished by using numerous electronic databases, and the available knowledge on different parts of herbs and their ingredients with antiarrhythmic effects up to 2019 were identified and collected. The results indicate that 36 herbs or their derivatives can be effective in the treatment of arrhythmias, especially in animal and cellular models. They affect various ionic channels in different action potential phases. The alterations in ionic currents lead to changing in the amplitude and duration of the action potential, effective refractory period, maximum velocity, resting membrane potential, channel trafficking, or intracellular calcium concentration. The agents that prolong action potential duration and effective refractory period such as dauricine and sophocarpine seem to be more beneficial if more comprehensive studies confirm their efficacy and safety. It is noteworthy that the consumption of some herbal agents for cardiovascular (e.g. Hawthorn and Ginseng) or other (e.g. Ginseng and Licorice) therapeutic purposes may boost the pro-arrhythmogenic effect of current cardiovascular drugs such as cardiac glycosides. This study accentuates known plants or their derivatives with anti-arrhythmic effects, potential interaction with other cardiac drugs, and the possible mechanisms involved. It can assist clinicians and scientists in research and therapeutic approaches to the management of cardiac arrhythmias.

Therapeutic efficacy of catalpol against apoptosis in cardiomyocytes derived from human induced pluripotent stem cells

Cardiac arrhythmia is an irregular heart rhythm that can lead to serious heart conditions and various organ disorders, and may cause sudden cardiac death. Catalpol belongs to the iridoid glycoside family and is highly abundant in Rehmannia glutinosa Libosch. The study included five groups such as group I (normal control), group II (treatment control), group III (low-dose treatment), group IV (medium-dose treatment) and group V (high-dose treatment). We investigated the therapeutic effects of catalpol on cardiac arrhythmia in human-induced pluripotent stem cells (iPSCs). Cell viability, lactate dehydrogenase (LDH) levels, lipid peroxidation, antioxidant activity, and caspase-3 and caspase-9 activities and protein levels were measured in normal control, treatment control, and treated (1, 10, and 100 µM) iPSC groups. Compared with the treatment control group, catalpol supplementation (1, 10, and 100 µM) increased iPSC cell viability by 7.5, 27.3, and 65.8%, respectively; reduced the LDH levels by 10.4, 31.3, and 75.2%, respectively; and reduced the lipid peroxidation levels by 7.7, 33.0, and 62.6%, respectively. The antioxidant levels were significantly higher in the treatment control group than in the normal control group. Catalpol (100 µM) reduced the caspase-3 and caspase-9 activities by more than 30% and increased expression of the corresponding proteins by more than 50%. These findings suggest that the naturally occurring iridoid glycoside catalpol is effective against aconitine-induced cardiac arrhythmia in iPSCs.

Nerol Attenuates Ouabain-Induced Arrhythmias

Nerol (C₁₀H₁₈O) is a monoterpene found in many essential oils, such as lemon balm and hop. In this study, we explored the contractile and electrophysiological properties of nerol and demonstrated its antiarrhythmic effects in guinea pig heart preparation. Nerol effects were evaluated on atrial and ventricular tissue contractility, electrocardiogram (ECG), voltage-dependent L-type Ca²⁺ current (I_Ca,L), and ouabain-triggered arrhythmias. Overall our results revealed that by increasing concentrations of nerol (from 0.001 to 30 mM) there was a significant decrease in left atrium contractile force. This effect was completely and rapidly reversible after washing out (~ 2 min). Nerol (at 3 mM concentration) decreased the left atrium positive inotropic response evoked by adding up CaCl₂ in the extracellular medium. Interestingly, when using a lower concentration of nerol (30 μM), it was not possible to clearly observe any significant ECG signal alterations but a small reduction of ventricular contractility was observed. In addition, 300 μM nerol promoted a significant decrease on the cardiac rate and contractility. Important to note is the fact that in isolated cardiomyocytes, peak I_Ca,L was reduced by 58.9 ± 6.31% after perfusing 300 μM nerol (n=7, p<0.05). Nerol, at 30 and 300 μM, delayed the time of onset of ouabain-triggered arrhythmias and provoked a decrease in the diastolic tension induced by the presence of ouabain (50 μM). Furthermore, nerol preincubation significantly attenuated arrhythmia severity index without changes in the positive inotropism elicited by ouabain exposure. Taken all together, we may be able to conclude that nerol primarily by reducing Ca²⁺ influx through L-type Ca²⁺ channel blockade lessened the severity of ouabain-triggered arrhythmias in mammalian heart.

Disease Modifiers of Inherited SCN5A Channelopathy

To date, a large number of mutations in SCN5A, the gene encoding the pore-forming α-subunit of the primary cardiac Na⁺ channel (Na_V1.5), have been found in patients presenting with a wide range of ECG abnormalities and cardiac syndromes. Although these mutations all affect the same Na_V1.5 channel, the associated cardiac syndromes each display distinct phenotypical and biophysical characteristics. Variable disease expressivity has also been reported, where one particular mutation in SCN5A may lead to either one particular symptom, a range of various clinical signs, or no symptoms at all, even within one single family. Additionally, disease severity may vary considerably between patients carrying the same mutation. The exact reasons are unknown, but evidence is increasing that various cardiac and non-cardiac conditions can influence the expressivity and severity of inherited SCN5A channelopathies. In this review, we provide a summary of identified disease entities caused by SCN5A mutations, and give an overview of co-morbidities and other (non)-genetic factors which may modify SCN5A channelopathies. A comprehensive knowledge of these modulatory factors is not only essential for a complete understanding of the diverse clinical phenotypes associated with SCN5A mutations, but also for successful development of effective risk stratification and (alternative) treatment paradigms.