Cardiotoxicity of digitalis glycosides: roles of autonomic pathways, autacoids and ion channels

Stable Gastric Pentadecapeptide BPC 157 as Useful Cytoprotective Peptide Therapy in the Heart Disturbances, Myocardial Infarction, Heart Failure, Pulmonary Hypertension, Arrhythmias, and Thrombosis Presentation

In heart disturbances, stable gastric pentadecapeptide BPC 157 especial therapy effects combine the therapy of myocardial infarction, heart failure, pulmonary hypertension arrhythmias, and thrombosis prevention and reversal. The shared therapy effect occurred as part of its even larger cytoprotection (cardioprotection) therapy effect (direct epithelial cell protection; direct endothelium cell protection) that BPC 157 exerts as a novel cytoprotection mediator, which is native and stable in human gastric juice, as well as easily applicable. Accordingly, there is interaction with many molecular pathways, combining maintained endothelium function and maintained thrombocytes function, which counteracted thrombocytopenia in rats that underwent major vessel occlusion and deep vein thrombosis and counteracted thrombosis in all vascular studies; the coagulation pathways were not affected. These appeared as having modulatory effects on NO-system (NO-release, NOS-inhibition, NO-over-stimulation all affected), controlling vasomotor tone and the activation of the Src-Caveolin-1-eNOS pathway and modulatory effects on the prostaglandins system (BPC 157 counteracted NSAIDs toxicity, counteracted bleeding, thrombocytopenia, and in particular, leaky gut syndrome). As an essential novelty noted in the vascular studies, there was the activation of the collateral pathways. This might be the upgrading of the minor vessel to take over the function of the disabled major vessel, competing with and counteracting the Virchow triad circumstances devastatingly present, making possible the recruitment of collateral blood vessels, compensating vessel occlusion and reestablishing the blood flow or bypassing the occluded or ruptured vessel. As a part of the counteraction of the severe vessel and multiorgan failure syndrome, counteracted were the brain, lung, liver, kidney, gastrointestinal lesions, and in particular, the counteraction of the heart arrhythmias and infarction.

Boldenone Undecylenate-Mediated Hepatorenal Impairment by Oxidative Damage and Dysregulation of Heat Shock Protein 90 and Androgen Receptors Expressions: Vitamin C Preventive Role

Boldenone Undecylenate (BLD) is a synthetic derivative of testosterone and a widely used anabolic androgenic steroid. The health risk of BLD use as a pharmaceutical or dietary supplement is still underestimated and under-reported. Vitamin C (VC) has been recognized as an antioxidant with prominent hepatorenal protective effects. This study investigated the possible preventive activity of VC against BLD-induced hepatorenal damage. Forty adult male Wistar rats were classified into five groups: control, vehicle control, VC (orally given 120 mg/kg b. wt./day), BLD (intramuscularly injected 5 mg/kg b. wt./week), and BLD + VC-treated groups. The experiment continued for eight weeks. Serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured. Serum contents of total protein (TP), albumin (ALB), globulin, total cholesterol (TC), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), and very-low-density lipoprotein-cholesterol (VLDL-C) were also assayed. Urea, creatinine, and uric acid levels were determined together with sodium and potassium electrolytes measuring. Moreover, oxidative stress indicators including reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GSR) as well as malondialdehyde (MDA) levels were measured in both hepatic and renal tissues. Corresponding histological examination of renal and hepatic tissues was conducted. Besides, immunohistochemical evaluations for androgen receptors protein (AR) and heat shock protein 90 (Hsp 90) expressions were performed. BLD caused significant rises in serum ALT, AST, TP, ALB, TC, TG, LDL-C, VLDL-C, urea, creatinine, uric acid, potassium, and MDA levels. Further, BLD-injected rats showed significant declines in the serum levels of HDL-C, sodium, GSH, GPx, GST, and GSR. Besides, distinct histopathological perturbations were detected in renal and hepatic tissues of BLD-injected rats. AR and Hsp 90 immunoexpression were increased in hepatic and renal tissues. In contrast, VC significantly reversed the BLD-induced hepatorenal damage in co-treated rats but not ameliorated AR protein overexpression. VC could be an efficient preventive supplement for mitigating BLD-induced hepatorenal damage, possibly via controlling oxidative stress events.

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.

Digoxin-specific antibody fragments for the treatment of suspected Nerium oleander toxicosis in a cat

Case summary

A 6-year-old castrated male domestic shorthair cat presented for lethargy and gastrointestinal signs after possible exposure to Nerium oleander leaves. The cat developed a ventricular arrhythmia that responded positively to the administration of digoxin-specific antibody fragments. Underlying hypertrophic cardiomyopathy was also diagnosed after the development of congestive heart failure. Humane euthanasia was elected owing to a lack of significant response to continued therapy.

Relevance and novel information

To our knowledge, this is the first report to describe the use of digoxin-specific antibody fragments in a cat. Nerium oleander toxicosis is associated with significant morbidity and mortality, and digoxin-specific antibody fragments have been used effectively in humans and animals. The development of cardiac necrosis may have contributed to worsening arrhythmias and highlights the importance of early intervention. The use of digoxin-specific antibody fragments for suspected N oleander toxicosis in a cat resulted in a rapid response and appeared to be well tolerated.

Bufalin-induced cardiotoxicity: new findings into mechanisms

Bufalin is one of the main pharmacological and toxicological components of Venenum Bufonis and many traditional Chinese medicine preparations. The cardiotoxicity clearly limits its application to patients living in countries. Hence, an investigation of its toxicological mechanism is helpful for new drug development and treatment of the related clinical adverse reactions. We investigate the cardiotoxicity of bufalin using human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) (0.003-0.1 μmol·L^-1), human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) (0.03-0.3 μmol·L^-1) and eight human cardiac ion channel currents (0.01-100 μmol·L^-1) combined with an impedance-based bioanalytical and patch clamp method. Biphasic effect of bufalin on the contractility in hiPSC-CMs, which has been shown to strengthen myocardial contractility, accelerate conduction, and increase beating rate at the earlier stage of administration, whereas weakened myocardial contractility, abolished conduction, and ceased beating rate at the later stage of administration. Bufalin decreased the action potential duration (Action potential duration at 30%, 50% and 90% repolarization), cardiac action potential amplitude, and maximal depolarization rate and depolarized the resting membrane potential of hiPSC-CMs. Spontaneous beating rates of hiPSC-CMs were markedly increased at 0.03 μmol·L^-1, while were weakened at 0.3 μmol·L^-1 after application. Bufalin blocks I_Nav1.5 in a concentration-dependent manner with half maximal inhibitory concentration of 74.5 μmol·L^-1. Bufalin respectively increased the late sodium current and Na⁺-Ca²⁺ exchange current with a concentration for 50% of maximal effect of 2.48 and 66.06 μmol·L^-1 in hiPSC-CMs. Whereas, bufalin showed no significant effects on other cardiac ion channel currents. The enhancement of the late sodium current is one of the main mechanism for cardiotoxicity of bufalin.

Safety reassessment of cinobufotalin injection: new findings into cardiotoxicity

Cinobufotalin injection, a traditional Chinese medicine preparation, successfully used for several years, might induce cardiotoxicity. The aim of the study was to evaluate the cardiotoxicity of cinobufotalin injection and the cardiotoxicity-preventive effect of sodium phenytoin in vivo. According to the 4 × 4 Latin square design, four Beagle dogs were allocated into four dose levels of 0, 0.3, 1, and 3 g/kg in treatment phases I-IV (cinobufotalin injection) and 3 g/kg in treatment phase V (cardiotoxicity antidote). The following parameters and endpoints were assessed: clinical observations, body weight, indicators of myocardial injury, and electrocardiogram (ECG) parameters. The cinobufotalin injection-related changes were observed in clinical observations (rapid breathing pattern), indicators of myocardial injury (increased cardiac troponin I, creatine kinase isoenzymes, and aspartate aminotransferase), and ECG graphics (arrhythmia) at 3 g/kg concentration in treatment phases I-IV. The cardiotoxicity of cinobufotalin injection was attenuated by sodium phenytoin in treatment phase V. The results confirmed the cardiotoxicity of cinobufotalin injection, and they might bring information about the appropriate monitoring time points and cardiotoxicity parameters in clinical practices and shed light on the treatment of cardiovascular adverse reactions.

Acute oleander poisoning: A study of clinical profile from a tertiary care center in South India

Introduction:

Yellow oleander (Thevetia peruviana), which belongs to the Apocyanaceae family, is a common shrub seen throughout the tropics. All parts of the plant contain high concentrations of cardiac glycosides which are toxic to cardiac muscle and the autonomic nervous system. Here, we describe the clinical profile of patients with oleander poisoning and their outcomes.

Methods and Materials:

This retrospective study was conducted over a period of 12 months (March 2016 to February 2017). The data was extracted from the inpatient electronic medical records. Adult patients with a diagnosis of acute yellow oleander poisoning were included in the study. Descriptive statistics were obtained for all variables in the study and appropriate statistical tests were employed to ascertain their significance.

Results:

The study comprised 30 patients aged 30.77 ± 12.31 (mean ± SD) who presented at 12.29 ± 8.48 hours after consumption of yellow oleander. Vomiting (80%) was the most common presenting symptom. Metabolic abnormalities at presentation included hyperchloremia in 22 patients and metabolic acidosis (bicarbonate <24 mmol/L) in 29 patients. Fifteen (50%) patients had abnormal ECG, of which second-degree AV block was the commonest ECG abnormality seen in 4 (13.3%). Fifteen (50%) patients had transvenous temporary pacemaker insertion (TPI). Having a TPI significantly prolonged the duration of hospital stay (OR 1.85, 95% CI 1.06–3.21, P 0.03). The mortality in the cohort was 2 (6.7%).

Conclusion:

In patients with yellow oleander poisoning, dyselectrolytemia with ECG abnormalities was common. TPI prolonged the duration of hospital stay. Further studies are required to know the indication for and to ascertain the effect of temporary pacing on survival.

Therapeutic effects and mechanisms of actions of Descurainia sophia

Descurainia sophia Webb ex Prantl has been used in traditional medicine globally. It has been shown that Descurainia sophia, together with many other bioactive compounds, can modulate the biological functions of various genes. We have viewed the clinical benefits and mechanisms of action of Descurainia sophia associated with its current uses and outlined potential further applications. There are many studies documenting its numerous clinical effects in cancer, respiratory, gastrointestinal, and cardiac systems. Further, Descurainia sophia has been shown to exhibit anti-inflammatory, anti-oxidative, and anthelmintic activities. The clinical studies did not indicate any significant adverse effects of Descurainia sophia, demonstrating that it is a safe and effective herbal medicine. However, more clinical studies demonstrating the therapeutic effects of Descurainia sophia are still warranted.

Subacute Toxicity of Nerium oleander Ethanolic Extract in Mice

Nerium oleander (N. oleander) is a well-known poisonous shrub that is frequently grown in gardens and public areas and contains numerous toxic compounds. The major toxic components are the cardiac glycosides oleandrin and neriin. The aim of our study was to evaluate the toxic effects of an ethanolic N. oleander leaf extract on haematological, cardiac, inflammatory, and serum biochemical parameters, as well as histopathological changes in the heart. N. oleander extract was orally administered for 14 and 30 consecutive days at doses of 100 and 200 mg of dried extract/kg of body weight in 0.5 mL of saline. The results showed significant increases in mean corpuscular volume, white blood cell counts, platelet counts, interleukins (IL-1 and IL-6), tumour necrosis factor alpha, C reactive protein, alanine aminotransferase, lactate dehydrogenase, creatine kinase and creatine kinase MB, especially at high doses. Marked pathological changes were perceived in the heart tissue. Thus, it can be concluded that exposure to N. oleander leaf extract adversely affects the heart and liver.

Grape Seed Proanthocyanidin Ameliorates Cardiac Toxicity Induced by Boldenone Undecylenate through Inhibition of NADPH Oxidase and Reduction in the Expression of NOX2 and NOX4

The effect of anabolic androgenic steroids on the cardiovascular system is poorly understood. Increased production of free radicals is coupled to the pathophysiology of many alterations within the circulatory system. The only function of the enzyme family NADPH oxidases (NOXs) is the generation of reactive oxygen species (ROS). Therefore, this study investigated the beneficial role of grape seed proanthocyanidin extract (GSPE) in ameliorating cardiac toxicity induced by the anabolic steroid Boldenone in male rats through NOX inhibition and reduction in the expression of NOX2 and NOX4. This study was conducted on forty male rats which are divided into four groups (normal control, positive control or GSPE, Boldenone, and posttreatment Boldenone with GSPE). A significant increase in relative body weight, relative heart weight, and hemodynamic parameters, as well as serum concentrations of lactate dehydrogenase, creatine kinase, creatine kinase-muscle brain, myoglobin, cholesterol, low-density lipoprotein cholesterol, risk factor 1/2, K⁺, and Cl⁻, in treated rats with Boldenone when compared with control. We also noted a significant increase in the levels of cardiac malondialdehyde, H₂O₂ generation in heart tissues, mRNA expression of NOX2 and NOX4, and immunoreactivity to proliferating cell nuclear antigen (PCNA). Posttreated rats with Boldenone and GSPE ameliorated cardiac toxicity via inhibition of NOX and a reduction in alteration of the expression of NOX2, NOX4, and PCNA induced by Boldenone. These novel insights into the antioxidative activity of GSPE should serve as a basis for the development of improved chemopreventive or therapeutic strategies for cardiac toxicity.

Usefulness of cardiotoxicity assessment using calcium transient in human induced pluripotent stem cell-derived cardiomyocytes

Monitoring dramatic changes in intracellular calcium ion levels during cardiac contraction and relaxation, known as calcium transient, in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) would be an attractive strategy for assessing compounds on cardiac contractility. In addition, as arrhythmogenic compounds are known to induce characteristic waveform changes in hiPSC-CMs, it is expected that calcium transient would allow evaluation of not only compound-induced effects on cardiac contractility, but also compound arrhythmogenic potential. Using a combination of calcium transient in hiPSC-CMs and a fast kinetic fluorescence imaging detection system, we examined in this study changes in calcium transient waveforms induced by a series of 17 compounds that include positive/negative inotropic agents as well as cardiac ion channel activators/inhibitors. We found that all positive inotropic compounds induced an increase in peak frequency and/or peak amplitude. The effects of a negative inotropic compound could clearly be detected in the presence of a β-adrenergic receptor agonist. Furthermore, most arrhythmogenic compounds raised the ratio of peak decay time to peak rise time (D/R ratio) in calcium transient waveforms. Compound concentrations at which these parameters exceeded cutoff values correlated well with systemic exposure levels at which arrhythmias were reported to be evoked. In conclusion, we believe that peak analysis of calcium transient and determination of D/R ratio are reliable methods for assessing compounds' cardiac contractility and arrhythmogenic potential, respectively. Using these approaches would allow selection of compounds with low cardiotoxic potential at the early stage of drug discovery.

Digoxin: its role in contemporary medicine

Digoxin has been a key therapeutic for heart failure and atrial tachyarrhythmias for over 200 years following Withering's groundbreaking work depicting the therapeutic benefit of the common botanical foxglove in his 1785 monograph. The use of digoxin preceded any randomised evidence or even basic understanding of its mechanism of action. Over the past two decades, there has been mounting evidence further challenging the safety and efficacy of digoxin, while multiple other therapies for both heart failure and atrial tachyarrhythmias have proven to be more effective and safe. Altogether, digoxin still has an important role in contemporary pharmacotherapeutics, though its role remains controversial and should be reserved for selective patients and clinical situations, with careful attention to serum concentrations.

γ-Benzylidene digoxin derivatives synthesis and molecular modeling: Evaluation of anticancer and the Na,K-ATPase activity effect

Cardiotonic steroids (CS), natural compounds with traditional use in cardiology, have been recently suggested to exert potent anticancer effects. However, the repertoire of molecules with Na,K-ATPase activity and anticancer properties is limited. This paper describes the synthesis of 6 new digoxin derivatives substituted (on the C17-butenolide) with γ-benzylidene group and their cytotoxic effect on human fibroblast (WI-26 VA4) and cancer (HeLa and RKO) cell lines as well as their effect on Na,K-ATPase activity and expression. As digoxin, compound BD-4 was almost 100-fold more potent than the other derivatives for cytotoxicity with the three types of cells used and was also the only one able to fully inhibit the Na,K-ATPase of HeLa cells after 24h treatment. No change in the Na,K-ATPase α1 isoform protein expression was detected. On the other hand it was 30-40 fold less potent for direct Na,K-ATPase inhibition, when compared to the most potent derivatives, BD-1 and BD-3, and digoxin. The data presented here demonstrated that the anticancer effect of digoxin derivatives substituted with γ-benzylidene were not related with their inhibition of Na,K-ATPase activity or alteration of its expression, suggesting that this classical molecular mechanism of CS is not involved in the cytotoxic effect of our derivatives.

The case for induced pluripotent stem cell-derived cardiomyocytes in pharmacological screening

The current drug screening models are deficient, particularly in detecting cardiac side effects. Human stem cell-derived cardiomyocytes could aid both early cardiotoxicity detection and novel drug discovery. Work over the last decade has generated human embryonic stem cells as potentially accurate sources of human cardiomyocytes, but ethical constraints and poor efficacy in establishing cell lines limit their use. Induced pluripotent stem cells do not require the use of human embryos and have the added advantage of producing patient-specific cardiomyocytes, allowing both generic and disease- and patient-specific pharmacological screening, as well as drug development through disease modelling. A critical question is whether sufficient standards have been achieved in the reliable and reproducible generation of 'adult-like' cardiomyocytes from human fibroblast tissue to progress from validation to safe use in practice and drug discovery. This review will highlight the need for a new experimental system, assess the validity of human induced pluripotent stem cell-derived cardiomyocytes and explore what the future may hold for their use in pharmacology.

Antagonism of Cortex Periplocae extract-induced catecholamines secretion by Panax notoginseng saponins in cultured bovine adrenal medullary cells by drug combinations

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese Medicine (TCM) operates on the general principle that compatible components of different herbal decoction may work together to synergistically enhance therapeutic efficacy or reduce adverse effects. Cortex Periplocae is an herb that has been used in TCM clinics for a long time in the treatment of chronic heart failure. However, recently, the use of this herb has been restricted because of widespread abuse and misapplications. Radix Notoginseng is another herb that is used in TCM because of its protective role on cardiomyocytes. From our previous studies on these two herbs in a mouse model, we observed an increased LD50 after oral administration of Cortex Periplocae extract (CPE) and Panax notoginseng saponins (PNS) in a ratio of 1:1 compared with Cortex Periplocae extract used alone.

AIM OF THE STUDY

This study aimed to investigate whether there are mutual synergistic effects of the two herbal extracts, CPE and PNS, on catecholamines (CAs) secretion, and their possible underlying mechanism(s) for such effects.

MATERIALS AND METHODS

CPE and PNS were quantified by the LC-MS/MS method. HPLC-ECD was used to determine the CAs secreted into the medium by bovine adrenal medulla cells (BAMCs) and calcium influx was measured using a Calcium 4 reagent kit.

RESULTS

We found that the stimulatory effect of CPE on CAs secretion was inhibited when used together with PNS. For a better clarification of the different constituents of the extracts, a quantitative analysis was carried out. Periplocin was found to be the main active component of CPE valued as 0.99% and saponins were the principal constituents of PNS. These results also showed that CPE increased the secretion of CAs in a dose-dependent manner while the actions of PNS were seen to be inhibitory. Periplocin monomer of CPE could be implicated for the actions of CPE since it plays the role of increasing the ACh-induced CAs secretion in a calcium-dependent manner. We therefore conclude that; CPE and PNS exert antagonistic effects in regulating the concentration of intracellular calcium.

CONCLUSIONS

PNS inhibits CPE-induced CAs secretion by suppressing calcium influx in bovine adrenal medulla cells while periplocin, one of the main components of CPE has the same secretagogue effect as CPE.

Potassium channel activators differentially modulate the effect of sodium channel blockade on cardiac conduction

AIMS

Diminished repolarization reserve contributes to the arrhythmogenic substrate in many disease states. Pharmacological activation of K(+) channels has been suggested as a potential antiarrhythmic therapy in such conditions. Having previously demonstrated that I(K1) and I(Kr) can modulate cardiac conduction, we tested here the effects of pharmacological I(KATP) and I(Ks) activation on cardiac conduction and its dependence on the sodium current (I(Na)).

METHODS AND RESULTS

Bath electrocardiograms (ECGs) recorded from Langendorff-perfused guinea pig ventricles revealed QRS prolongation during I(KATP) activation by pinacidil but not during I(Ks) activation by R-L3 relative to control. In contrast, when I(Na) was partially blocked by flecainide, R-L3 but not pinacidil prolonged the QRS relative to flecainide alone. Conduction velocity (θ) was quantified by optical mapping during epicardial pacing. Both longitudinal (θ(L)) and transverse (θ(T)) θ were reduced by pinacidil (by 10 ± 1 and 9 ± 3%, respectively) and R-L3 (by 11 ± 2% and 15 ± 4%, respectively). Flecainide decreased θ(L) by 33 ± 4% and θ(T) by 36 ± 5%. Whereas pinacidil did not further slow θ relative to flecainide alone, R-L3 decreased both θ(L) and θ(T).

CONCLUSION

Pharmacological activation of I(KATP) and I(Ks) slows cardiac conduction; however, they demonstrate diverse effects on θ dependence on I(Na) blockade. These findings may have significant implications for the use of K(+) channel activators as antiarrhythmic drugs and for patients with Na(+) channel abnormalities or being treated with Na(+) channel blockers.

Coordinated regulation of murine cardiomyocyte contractility by nanomolar (-)-epigallocatechin-3-gallate, the major green tea catechin

Green tea polyphenolic catechins exhibit biological activity in a wide variety of cell types. Although reports in the lay and scientific literature suggest therapeutic potential for improving cardiovascular health, the underlying molecular mechanisms of action remain unclear. Previous studies have implicated a wide range of molecular targets in cardiac muscle for the major green tea catechin, (-)-epigallocatechin-3-gallate (EGCG), but effects were observed only at micromolar concentrations of unclear clinical relevance. Here, we report that nanomolar concentrations of EGCG significantly enhance contractility of intact murine myocytes by increasing electrically evoked Ca(2+) transients, sarcoplasmic reticulum (SR) Ca(2+) content, and ryanodine receptor type 2 (RyR2) channel open probability. Voltage-clamp experiments demonstrate that 10 nM EGCG significantly inhibits the Na(+)-Ca(2+) exchanger. Of importance, other Na(+) and Ca(2+) handling proteins such as Ca(2+)-ATPase, Na(+)-H(+) exchanger, and Na(+)-K(+)-ATPase were not affected by EGCG ≤ 1 μM. Thus, nanomolar EGCG increases contractility in intact myocytes by coordinately modulating SR Ca(2+) loading, RyR2-mediated Ca(2+) release, and Na(+)-Ca(2+) exchange. Inhibition of Na(+)-K(+)-ATPase activity probably contributes to the positive inotropic effects observed at EGCG concentrations >1 μM. These newly recognized actions of nanomolar and micromolar EGCG should be considered when the therapeutic and toxicological potential of green tea supplementation is evaluated and may provide a novel therapeutic strategy for improving contractile function in heart failure.

Estimating the risk of drug-induced proarrhythmia using human induced pluripotent stem cell-derived cardiomyocytes

Improved in vitro systems for predicting drug-induced toxicity are needed in the pharmaceutical and biotechnology industries to decrease late-stage drug attrition. One unmet need is an early screen for cardiotoxicity, which accounts for about one third of safety-based withdrawn pharmaceuticals. Herein, the first published report of a high-throughput functional assay employing a monolayer of beating human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is described, detailing a model that accurately detects drug-induced cardiac abnormalities. Using 96-well plates with interdigitated electrode arrays that assess impedance, the rhythmic, synchronous contractions of the iPSC-CMs were detected. Treatment of the iPSC-CMs with 28 different compounds with known cardiac effects resulted in compound-specific changes in the beat rate and/or the amplitude of the impedance measurement. Changes in impedance for the compounds tested were comparable with the results from a related technology, electric field potential assessment obtained from microelectrode arrays. Using the results from the set of compounds, an index of drug-induced arrhythmias was calculated, enabling the determination of a drug's proarrhythmic potential. This system of interrogating human cardiac function in vitro opens new opportunities for predicting cardiac toxicity and studying cardiac biology.

Interactions between verapamil and digoxin in Langendorff-perfused rat hearts: the role of inhibition of P-glycoprotein in the heart

P-glycoprotein (P-gp) is expressed in tumour cells as well as normal tissues including heart. Modulation of P-gp transport in vivo may lead to increased drug penetrance to tissues with resulting increases in toxicity. We aimed to investigate the effects of P-gp on the isolated heart by digoxin infusion in the absence and presence of verapamil. The study was performed in Langendorff isolated perfused rat hearts. After a 20 min. stabilisation period with Tyrode Buffer, digoxin (125 μg/5 mL) was infused for 10 min. in the control group (n = 7). The same dose of digoxin was infused during perfusion with verapamil (1 nm) containing Tyrode Buffer (n = 8) in the study group. Outflow concentration and cardiac parameters of digoxin were measured at frequent intervals for 40 min. AUEC((0-40 min)) for left ventricular developed pressure was significantly increased in the presence of verapamil (4260 ± 39.37 mmHg min versus 4607 ± 98.09 mmHg min; 95% CI -587.7 to -105.8; p = 0.0083). The significant increases in left ventricular developed pressure were at 20, 25, 30, 35 and 40 min. AUC((0-40 min)) value for outflow digoxin concentration-time curve was significantly lower in the presence of verapamil. Verapamil increased the positive inotropic effect of digoxin, probably through the inhibition of P-gp, which effluxes digoxin out of cardiac cells.

Inhibition of methyldigoxin-induced arrhythmias by pentadecapeptide BPC 157: a relation with NO-system

Pentadecapeptide BPC 157 (GEPPPGKPADDAGLV, MW 1419) reversed congestive heart failure and various arrhythmias, influenced the NO-system and showed no proarrhythmic effect. In therapy analogy, we challenged rats with digitalis, to show attenuation by BPC 157 and the relation between the NO-system and digitalis toxicity. (i). BPC 157 prophylactic effect. Development of cumulative intravenous digitalis toxicity, BPC 157 (50 microg, 10 microg, 10 ng/kg applied intravenously immediately before a methyldigoxin increment regimen (2.0/1.5/1.5/1.0 mg/kg at 15 min-intervals, total dose 6.0 mg/kg/45 min)) reduced the number of ventricular premature beats, prolonged the time before onset of ventricular tachycardia, reduced ventricular tachycardia and AV-block duration (microg-regimes) or reduced mainly the AV-block duration (ng-regimen). (ii). BPC 157 therapy. Advanced methyldigoxin toxicity (6.0 mg/kg i.v. bolus). BPC 157 applied at the 20th second of the grade 3 AV-block shortened AV-blocks, mitigated a further digitalis toxicity course. Ventricular tachycardias were either avoided (50 microg), or markedly reduced (10 microg, 10 ng). Fatal outcome was either avoided (50 microg), reduced (10 microg), or only delayed (10 ng) (iii) BPC 157, L-NAME, l-arginine, L-NAME+l-arginine application. L-NAME-application (5 mg/kg i.p.) aggravated methyldigoxin-arrhythmias. l-arginine (200 mg/kg i.p.) alone had no effect but blunted L-NAME-exaggeration (L-NAME+l-arginine). In this respect, BPC 157 (50 microg/kg i.p.) was prophylactically and therapeutically more effective: the antagonism of L-NAME with BPC 157 produced an effect similar to BPC 157 alone. In conclusion, digitalis-induced arrhythmias in rats could be prevented and counteracted by pentadecapeptide BPC 157, mainly through an interaction with the NO-system.

Management of yellow oleander poisoning

BACKGROUND

Poisoning due to deliberate self-harm with the seeds of yellow oleander (Thevetia peruviana) results in significant morbidity and mortality each year in South Asia. Yellow oleander seeds contain highly toxic cardiac glycosides including thevetins A and B and neriifolin. A wide variety of bradyarrhythmias and tachyarrhythmias occur following ingestion. Important epidemiological and clinical differences exist between poisoning due to yellow oleander and digoxin; yellow oleander poisoning is commonly seen in younger patients without preexisting illness or comorbidity. Assessment and initial management. Initial assessment and management is similar to other poisonings. No definite criteria are available for risk stratification. Continuous ECG monitoring for at least 24 h is necessary to detect arrhythmias; longer monitoring is appropriate in patients with severe poisoning. Supportive care. Correction of dehydration with normal saline is necessary, and antiemetics are used to control severe vomiting. Electrolytes. Hypokalemia worsens toxicity due to digitalis glycosides, and hyperkalemia is life-threatening. Both must be corrected. Hyperkalemia is due to extracellular shift of potassium rather than an increase in total body potassium and is best treated with insulin-dextrose infusion. Intravenous calcium increases the risk of cardiac arrhythmias and is not recommended in treating hyperkalemia. Oral or rectal administration of sodium polystyrene sulfonate resin may result in hypokalemia when used together with digoxin-specific antibody fragments. Unlike digoxin toxicity, serum magnesium concentrations are less likely to be affected in yellow oleander poisoning. The effect of magnesium concentrations on toxicity and outcome is not known. Hypomagnesaemia should be corrected as it can worsen cardiac glycoside toxicity. Gastric decontamination. The place of emesis induction and gastric lavage has not been investigated, although they are used in practice. Gastric decontamination by the use of single dose and multiple doses of activated charcoal has been evaluated in two randomized controlled trials, with contradictory results. Methodological differences (severity of poisoning in recruited patients, duration of treatment, compliance) between the two trials, together with differences in mortality rates in control groups, have led to much controversy. No firm recommendation for or against the use of multiple doses of activated charcoal can be made at present, and further studies are needed. Single-dose activated charcoal is probably beneficial. Activated charcoal is clearly safe. Arrhythmia management. Bradyarrhythmias are commonly managed with atropine, isoprenaline, and temporary cardiac pacing in severe cases, although without trial evidence of survival benefit, or adequate evaluation of possible risks. Accelerating the heart rate with atropine or beta-adrenergic agents theoretically increases the risk of tachyarrhythmias, and it has been claimed that atropine increases tachyarrhythmic deaths. Further studies are required. Tachyarrhythmias have a poor prognosis and are more difficult to treat. Lidocaine is the preferred antiarrhythmic; the role of intravenous magnesium is uncertain. Digoxin-specific antibody fragments. Digoxin-specific antibody fragments are effective in reverting life-threatening cardiac arrhythmias; prospective observational studies show a beneficial effect on mortality. High cost and lack of availability limit the widespread use of digoxin-specific antibody fragments in developing countries.

CONCLUSIONS

Digoxin-specific antibody fragments remain the only proven therapy for yellow oleander poisoning. Further studies are needed to determine the place of activated charcoal, the benefits or risks of atropine and isoprenaline, the place and choice of antiarrhythmics, and the effect of intravenous magnesium in yellow oleander poisoning.

Pharmacological profile of the new inotropic agent AT-11

Although there are many classes of drugs, including cardiac glycosides, sympathomimetic inotropes, beta-adrenergic antagonists, angiotensin-converting enzyme inhibitors (ACE inhibitors) and spironolactone etc. used for the treatment of heart failure, the morbidity and mortality rates of patients after these treatments are not ameliorated. Chronic administration of Sympathomimetic inotropes also increased the arrhythmogenic effects. Consequently, improvement of treatment for heart failure remains a major medical challenge for the coming years. In this present experiment, the novel Na(+)-K(+) ATPase inhibitor AT-11 was characterized for its inotropic and toxic properties. Comparing AT-11 with ouabain, we found that AT-11 concentration-dependently increased contractility in guinea pig heart preparations, and the safety index of AT-11 was better than ouabain in vitro. In the in vivo study, AT-11 was also safer than ouabain at the equieffective dose. Moreover, AT-11 slowed heart rate more than ouabain did. This may be due to a larger AT-11-induced increase in vagal reflex than with ouabain and an indirect decrease in sympathetic tone to prevent Ca(2+) overload.

Cardiotonic steroids on the road to anti-cancer therapy

The sodium pump, Na(+)/K(+)-ATPase, could be an important target for the development of anti-cancer drugs as it serves as a versatile signal transducer, it is a key player in cell adhesion and its aberrant expression and activity are implicated in the development and progression of different cancers. Cardiotonic steroids, known ligands of the sodium pump have been widely used for the treatment of heart failure. However, early epidemiological evaluations and subsequent demonstration of anti-cancer activity in vitro and in vivo have indicated the possibility of developing this class of compound as chemotherapeutic agents in oncology. Their development to date as anti-cancer agents has however been impaired by a narrow therapeutic margin resulting from their potential to induce cardiovascular side-effects. The review will thus discuss (i) sodium pump structure, function, expression in diverse cancers and its chemical targeting and that of its sub-units, (ii) reported in vitro and in vivo anti-cancer activity of cardiotonic steroids, (iii) managing the toxicity of these compounds and the limitations of existing preclinical models to adequately predict the cardiotoxic potential of new molecules in man and (iv) the potential of chemical modification to reduce the cardiovascular side-effects and improve the anti-cancer activity of new molecules.

The alpha1 subunit of the sodium pump could represent a novel target to combat non-small cell lung cancers

With an overall 5 year survival rate as low as 15% for non-small cell lung cancer (NSCLC), even with surgical intervention and the use of newer molecules in adjuvant chemotherapy, there is an urgent need for new biological targets and associated novel anti-cancer agents. The present study was undertaken to evaluate the potential of the Na(+)/K(+)-ATPase alpha1 subunit as a novel target in NSCLC and revealed that alpha1 expression is markedly higher in a significant proportion of NSCLC clinical samples compared to normal lung tissue. Furthermore, reduction in alpha1 expression in A549 NSCLC cells by anti-alpha1 siRNA resulted in markedly impaired proliferation and migration of these cancer cells. Finally, of three cardenolides investigated, UNBS1450, which is known to bind to Na(+)/K(+)-ATPase and displays potent anti-tumour activity in vivo in experimental models of human NSCLCs, is the most potent inhibitor of Na(+)/K(+)-ATPase isozymes (alpha1beta1, alpha2beta1 and alpha3beta1), most strikingly of alpha1beta1. This was reflected in the compound's more potent anti-proliferative activity in all NSCLC cell lines evaluated (A549, Cal-12T, NCI-H727 and A427); the first three of which over-express alpha1. The marked impairment in A549 NSCLC cell proliferation and migration, and resulting similar morphology following anti-alpha1 siRNA or UNBS1450 treatment, was associated with features of abnormal cytokinesis, mediated in the case of UNBS1450 by disorganization of the actin cytoskeleton. Collectively these data strongly suggest that targeting the Na(+)/K(+)-ATPase alpha1 using specific cardenolides could represent a novel means to combat certain NSCLCs.

Antidiarrhoeal and antimicrobial activities of Emilia coccinea (Sims) G. Don extracts

Emilia coccinea (Sims) G. Don is reported to possess a number of medicinal properties including antidiarrhoeal and antimicrobial activities. The antidiarrhoeal effects of both methanol and aqueous extracts of the leaves of Emilia coccinea were studied in rats against castor oil-induced diarrhoea at the doses of 200, 400 and 600 mg/kg body weight. The methanol extract, and to a lesser extent the aqueous extract, significantly prolonged the time for diarrhoeal induction; it reduced the frequency of diarrhoea episodes and decreased the propulsion of charcoal meal through the gastrointestinal tract in a dose dependent manner. The aqueous extract did not have any antimicrobial activity at the tested concentration (5 mg/ml), but the methanol extract was most active on Escherichia coli. These results may support the fact that this plant is used traditionally to cure diarrhoea.

Comparison of digitalis-related adverse events in hospitalized men and women in Italy: An observational study

BACKGROUND

A higher mortality rate in women than in men treated with digitalis has been described. We hypothesized that this result could be due in part to an increased susceptibility of women to adverse events (AEs) from digitalis.

OBJECTIVE

The aim of this study was to compare the incidence of AEs related to digitalis in women and men.

METHODS

This was an observational study conducted in geriatrics and internal medicine acute-care wards located throughout Italy. We used the data of the Gruppo Italiano di Farmacoepidemiologia nell'Anziano (Italian Group of Pharmacoepidemiology in the Elderly), a collaborative study group on drug use and adverse drug reactions in hospitalized adults that performed 6 different surveys between 1988 and 1998. Adults who were taking digitalis at the time of admission or during the hospital stay were studied, with no other inclusion or exclusion criteria. The proportion of AEs to digitalis diagnosed at the time of admission or during the hospital stay was compared in men and women. Information on AEs was collected using a structured questionnaire at admission and during the hospital stay. A logistic regression model was used to evaluate the association between sex and AE(s) to digitalis, corrected for potential confounding variables.

RESULTS

The total sample size was 9626 patients. Women received a higher weight-adjusted dose of digitalis compared with men (0.0027 mg/kg per day vs 0.0025 mg/kg per day; P < 0.001). Overall, 199 AEs to digitalis were diagnosed. Women were more likely than men to suffer from an AE to digitalis (odds ratio, 1.51; 95% CI, 1.12-2.02). This finding was confirmed after correction for dose of digitalis, age, physical and cognitive impairment, atrial fibrillation, chronic obstructive pulmonary disease, glomerular filtration rate, and use of amiodarone, beta-blockers, nondihydropyridine calcium channel blockers, and potassium-sparing diuretics (odds ratio, 1.58; 95% CI, 1.01-2.48).

CONCLUSIONS

In this sample of hospitalized adults in Italy, we found a higher incidence of AEs to digitalis in women than in men.