Effects of neferine on Kv4.3 channels expressed in HEK293 cells and ex vivo electrophysiology of rabbit hearts

Inhibition of Cardiac Kv4.3/KChIP2 Channels by Sulfonylurea Drug Gliquidone

The Kv4.3 channel features fast N-type inactivation and also undergoes a slow C-type inactivation. The gain-of-function mutations of Kv4.3 channels cause an inherited disease called Brugada syndrome (BrS), characterized by a shortened duration of cardiac action potential repolarization and ventricular arrhythmia. The sulfonylurea drug gliquidone, an ATP-dependent K+ channel antagonist, is widely used for the treatment of type 2 diabetes. Here, we report a novel role of gliquidone in inhibiting Kv4.3 and Kv4.3/KChIP2 channels that encode the cardiac transient outward K+ currents responsible for the initial phase of action potential repolarization. Gliquidone results in concentration-dependent inhibition of both Kv4.3 and Kv4.3/KChIP2 fast or steady-state inactivation currents with an IC50 of approximately 8 μM. Gliquidone also accelerates Kv4.3 channel inactivation and shifts the steady-state activation to a more depolarizing direction. Site-directed mutagenesis and molecular docking reveal that the residues S301 in the S4 and Y312A and L321A in the S4-S5 linker are critical for gliquidone-mediated inhibition of Kv4.3 currents, as mutating those residues to alanine significantly reduces the potency for gliquidone-mediated inhibition. Furthermore, gliquidone also inhibits a gain-of-function Kv4.3 V392I mutant identified in BrS patients in voltage- and concentration-dependent manner. Taken together, our findings demonstrate that gliquidone inhibits Kv4.3 channels by acting on the residues in the S4 and the S4-S5 linker. Therefore, gliquidone may hold repurposing potential for the therapy of Brugada syndrome. SIGNIFICANCE STATEMENT: We describe a novel role of gliquidone in inhibiting cardiac Kv4.3 currents and the channel gain-of-function mutation identified from patients with Brugada syndrome, suggesting its repurposing potential for therapy for the heart disease.

Nuciferine induces autophagy to relieve vascular cell adhesion molecule 1 activation via repressing the Akt/mTOR/AP1 signal pathway in the vascular endothelium

Pro-inflammatory factor-associated vascular cell adhesion molecule 1 (VCAM1) activation initiates cardiovascular events. This study aimed to explore the protective role of nuciferine on TNFα-induced VCAM1 activation. Nuciferine was administrated to both high-fat diet (HFD)-fed mice and the TNFα-exposed human vascular endothelial cell line. VCAM1 expression and further potential mechanism(s) were explored. Our data revealed that nuciferine intervention alleviated VCAM1 activation in response to both high-fat diet and TNFα exposure, and this protective effect was closely associated with autophagy activation since inhibiting autophagy by either genetic or pharmaceutical approaches blocked the beneficial role of nuciferine. Mechanistical studies revealed that Akt/mTOR inhibition, rather than AMPK, SIRT1, and p38 signal pathways, contributed to nuciferine-activated autophagy, which further ameliorated TNFα-induced VCAM1 via repressing AP1 activation, independent of transcriptional regulation by IRF1, p65, SP1, and GATA6. Collectively, our data uncovered a novel biological function for nuciferine in protecting VCAM1 activation, implying its potential application in improving cardiovascular events.

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.

Biologically active isoquinoline alkaloids covering 2014-2018

Isoquinoline alkaloids, an important class of N-based heterocyclic compounds, have attracted considerable attention from researchers worldwide since the early 19th century. Over the past 200 years, many compounds from this class were isolated, and most of them and their analogs possess various bioactivities. In this review, we survey the updated literature on bioactive alkaloids and highlight research achievements of this alkaloid class during the period of 2014-2018. We reviewed over 400 molecules with a broad range of bioactivities, including antitumor, antidiabetic and its complications, antibacterial, antifungal, antiviral, antiparasitic, insecticidal, anti-inflammatory, antioxidant, neuroprotective, and other activities. This review should provide new indications or directions for the discovery of new and better drugs from the original naturally occurring isoquinoline alkaloids.

The Cytoprotective and Anti-cancer Potential of Bisbenzylisoquinoline Alkaloids from Nelumbo nucifera

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Natural product therapy has been gaining therapeutic importance against various diseases, including cancer. The failure of chemotherapy due to its associated adverse effects promoted adjunct therapy with natural products. Phytochemicals exert anti-carcinogenic activities through the regulation of various cell signaling pathways such as cell survival, inflammation, apoptosis, autophagy and metastasis. The ‘small molecule-chemosensitizing agents’ from plants induce apoptosis in drug-resistant and host-immune resistant cancer cells in in vitro as well as in vivo models. For example, alkaloids from Nelumbo nucifera, liensinine, isoliensinine and neferine exert the anticancer activity through enhanced ROS generation, activation of MAP kinases, followed by induction of autophagy and apoptotic cell death. Likewise, these alkaloids also exert their cytoprotective action against cerebrovascular stroke/ischemic stroke, diabetes, and chemotherapy-induced cytotoxicity. Therefore, the present review elucidates the pharmacological activities of these bisbenzylisoquinoline alkaloids which include the cytoprotective, anticancer and chemosensitizing abilities against various diseases such as cardiovascular diseases, neurological diseases and cancer.

Nootropic effect of neferine on aluminium chloride-induced Alzheimer's disease in experimental models

Alzheimer's disease (AD) is an age-associated neurodegenerative disease, which is developed by oxidative stress and acetylcholine contraction in the synaptic cleft of the neurons. This leads to dementia, memory loss, and decrease in learning ability and orientation. In this research work, we aimed to explore the neuroprotective effect of neferine on AlCl₃ -induced AD in rats. The results of our study revealed that the increased reactive oxygen species (ROS) and nitric oxide in the hippocampus leads to the development of AD in the rats. The oral treatment of neferine done the following occurrences such as; it potentially inhibited the ROS formation and acts as a scavenging molecule by preventing the neurodegeneration. It also improved the memory and learning ability to complete the maze activity in the AD rats and significantly increased the antioxidants superoxide dismutase, catalase, and reduced glutathione in neferine treated AD rats. It aggressively declined the activity of acetylcholine esterase and Na⁺ K⁺ ATPase in the neurodegenerative rat models. The gene expression pattern of neuroinflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) were decreased in the neferine-treated rats. The neuroinflammatory proteins such as inducible nitric oxide (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor kappa β (Nf-κβ) were decreased and Nf-κβ inhibitor IKBα was increased in the neferine-treated AD rats. Finally, the histology study proved that the neferine treatment possibly prevents neurodegeneration in the hippocampus tissue of the AD models. Hence, these all findings concluded that the neferine could be a potential neuropreventive as well as neurodegenerative therapeutic compound in neurological and cognitive dysfunction.

Pharmacological benefits of neferine - A comprehensive review

This article recapitulates the existing in vitro and in vivo studies focusing on the effects of neferine-an alkaloid derivative of lotus plant, in various disease models and its effects on key signaling molecules. The review also compiles a large number of research studies that demonstrate methods for isolation and extraction, biosynthetic pathway, pharmacological activity and mode of action of neferine and their underlying mechanisms at cellular level. Neferine is a unique bis-benzylisoquinoline alkaloid that possesses a number of therapeutic effects such as anti-cancer, anti-diabetic, anti-aging, anti-microbial, anti-thrombotic, anti-arrhythmic, anti-inflammatory and even anti-HIV. It also enhances the anti-cancer properties of other anti-cancer drugs like cisplatin, adriamycin, taxol, etc. It is also reported to reverse chemo-resistance and enhance sensitivity of the cancer cells towards anti-cancer drugs. The underlying mechanisms for its activities mainly include apoptosis, autophagy and G1 arrest. Neferine protects them against the effect of drugs like cisplatin. The therapeutic properties of neferine is widely diverse, while it shows toxicity to cancer it also shows cyto-protective effects against cardio-vascular diseases, pulmonary disease, and is also effective against Alzheimer's disease and elicits anti-oxidative effect in many cellular systems. This article thus is the first ever attempt to review the therapeutic activities of neferine established in in vitro and in vivo models and to compile all the fragmented data available on the omnipotent activities of neferine.

Neferine, is not inducer but blocker for macroautophagic flux targeting on lysosome malfunction

Neferine, an alkaloid isolated from Lotus seeds, displays multiple pharmacological effects that counter cancer, oxidants, and arrhythmia. It was initially identified as a strong inducer for macroautophagy in cancer cells by suppressing AMPK/mTOR signaling. In this study, we found that autophagy signaling was inhibited in the condition of neferine treatment. Exposure to neferine resulted in the accumulation of LC3-II and an associated adaptor protein, p62/SQSTM1. Knockdown of ATG5 failed to reduce the accumulation of LC3-II induced by neferine. The electron microscopy (EM) images showed that neferine induce accumulation of multi-vesicle bodies (MVB) and failure of lysosome maturation. Moreover, exposure to neferine reduced maturation of cathepsin D and impaired the degradation of autophagic and phagocytic cargos. Rather than stimulate autophagic flux, the data indicate that neferine impaired lysosomes to block degradation within phagolysosomes.

Inhibitory effects of three bisbenzylisoquinoline alkaloids on lipopolysaccharide-induced microglial activation

Three bisbenzylisoquinoline alkaloids (liensinine, neferine, and isoliensinine) inhibit lipopolysaccharide-induced microglial activation.

Inhibitory effects of hesperetin on Nav1.5 channels stably expressed in HEK 293 cells and on the voltage-gated cardiac sodium current in human atrial myocytes

AIM

Voltage-gated sodium channels composed of a pore-forming α subunit and auxiliary β subunits are responsible for the upstroke of the action potential in cardiac myocytes. The pore-forming subunit of the cardiac sodium channel Nav1.5, which is encoded by SCN5A, is the main ion channel that conducts the voltage-gated cardiac sodium current (I_Na) in cardiac cells. The current study sought to investigate the inhibitory effects of hesperetin on human cardiac Nav1.5 channels stably expressed in human embryonic kidney 293 (HEK 293) cells and on the voltage-gated cardiac sodium current (I_Na) in human atrial myocytes.

METHODS

The effects of hesperetin on human cardiac Nav1.5 channels expressed in HEK 293 cells and on cardiac Na⁺ currents in human atrial myocytes were examined through whole-cell patch-clamp techniques.

RESULTS

Nav1.5 currents were potently and reversibly suppressed in a concentration- and voltage-dependent manner by hesperetin, which exhibited an IC₅₀ of 62.99 μmol/L. Hesperetin significantly and negatively shifted the voltage-dependent activation and inactivation curves. Hesperetin also markedly decelerated Nav1.5 current inactivation and slowed the recovery from Nav1.5 channel inactivation. The hesperetin-dependent blockage of Nav1.5 currents was frequency-dependent. Hesperetin also potently and reversibly inhibited Na⁺ current (I_Na) in human atrial myocytes, consistently with its effects on Nav1.5 currents in HEK 293 cells.

CONCLUSION

Hesperetin is a potent inhibitor of I_Na in human atrial myocytes and Nav1.5 channels expressed in human embryonic kidney 293 cells. Hesperetin probably functions by blocking the open state and the inactivated state of these channels.

Quantitative ethnomedicinal survey of medicinal plants given for cardiometabolic diseases by the non-institutionally trained siddha practitioners of Tiruvallur district, Tamil Nadu, India

ETHNOBOTANICAL RELEVANCE

The burden of cardiometabolic diseases such as dyslipidemia, hyperglycemia, hypertension, visceral obesity and atherosclerotic cardiovascular diseases and the use of traditional medicine for the management of such diseases are high in India; hence there is a need to document and analyze such therapies.

AIM OF THE STUDY

This study documented and analyzed the medicinal plants prescribed for cardiometabolic diseases by the non-institutionally trained siddha practitioners of Tiruvallur district of Tamil Nadu, India.

METHODOLOGY

The field survey was conducted between December 2014 to November 2015. Successive free listing assisted with field-walks was used to interview the informants. After assessing the sampling sufficiency using rarefaction curve analysis, indices such as Informant Consensus Factor (Fic) and Index of Agreement on Remedies (IAR) were calculated for the data. The indicators of informant's medicinal plant knowledge such as Shannon's index, equitability index, etc., were regressed with the demographic profile of the informants.

RESULTS

For this study 70 non-institutionally trained Siddha medical practitioners were approached; the data from 36 practitioners who were treating cardiometabolic diseases were documented. This study recorded the use of 188 species which were used to prepare 368 formulations to treat illnesses categorized under cardiometabolic diseases. In this, 53.04% claims were singletons. Regression analysis showed that single species dominance was reduced and the diversity of medicinal plants was increased with the increase in the age and experience. Increase in the years of formal education increased the equitability in the uses. The plants such as Nelumbo nucifera Gaertn. (cardiovascular diseases), Allium sativum L. (dyslipidemia), Cuminum cyminum L. (hypertension), Macrotyloma uniflorum Verdc. (obesity) and Azadirachta indica A. Juss. (type 2 diabetes) were the highly cited medicinal plants.

CONCLUSION

This survey has identified the plants most commonly used by Siddha practitioners of Tiruvallur district, Tamil Nadu, India for cardiometabolic diseases. The prevalence of chronic, non-communicable metabolic illnesses such as type 2 diabetes, hypertension and obesity are increasing worldwide due to the rapid changes in the lifestyle. These ailments require a life-long care and in such instances, people tend to use complementary therapies in most cases, alongside with conventional therapies. In view of the high use of traditional therapies for treating cardiometabolic illnesses, this study supports the need for more research to evaluate the potential benefits of the treatments and to identify any safety concern.