Dasatinib can Impair Left Ventricular Mechanical Function But May Lack Proarrhythmic Effect: A Proposal of Non-clinical Guidance for Predicting Clinical Cardiovascular Adverse Events of Tyrosine Kinase Inhibitors.

Tyrosine kinase inhibitors are known to clinically induce various types of cardiovascular adverse events; however, it is still difficult to predict them at preclinical stage. In order to explore how to better predict such drug-induced cardiovascular adverse events, we tried to develop a new protocol by assessing acute electrophysiological, cardiohemodynamic, and cytotoxic effects of dasatinib in vivo and in vitro. Dasatinib at 0.03 and 0.3 mg/kg was intravenously administered to the halothane-anesthetized dogs for 10 min with an interval of 20 min between the dosing (n = 4). Meanwhile, that at 0.1, 0.3, and 1 µM was cumulatively applied to the human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) (n = 7). In the dogs, the low and high doses provided peak plasma concentrations of 40 ± 5 (0.08) and 615 ± 38 ng/mL (1.26 µM), respectively. The low dose decreased the heart rate, impaired the left ventricular mechanical function, and prolonged the ventricular effective refractory period. The high dose prolonged the repolarization period, induced hemorrhagic tendency, and increased plasma cardiac troponin I level in addition to enhancement of the changes observed after the low dose, whereas it neither affected the cardiac conduction nor induced ventricular arrhythmias. In the hiPSC-CMs, dasatinib prolonged the repolarization and refractory periods like in dogs, while it did not induce apoptotic or necrotic process, but that it increased the conduction speed. Clinically observed major cardiovascular adverse events of dasatinib were observed qualitatively by currently proposed assay protocol, which may become a useful guide for predicting the cardiotoxicity of new tyrosine kinase inhibitors.

Electropharmacological effects of intracellular Ca2+ handling modulator caldaret on the heart assessed in the halothane-anesthetized dogs.

We analyzed how the enhancement of net sarcoplasmic reticulum (SR) Ca2+ uptake may affect cardiac electrophysiological properties in vivo by using caldaret which can decrease SR diastolic Ca2+ leak, enhance SR Ca2+ reuptake and inhibit reverse-mode Na+/Ca2+ exchanger. Caldaret in doses of 0.5, 5 and 50 µg/kg was intravenously administered over 10 min to the halothane-anesthetized beagle dogs (n = 5), attaining pharmacologically active plasma concentration. The low and middle doses of caldaret increased the ventricular contraction, which could be explained by its on-target pharmacological activities. The high dose enhanced the sinus automaticity followed by its suppression in addition to the increase of the total peripheral resistance, which may be unfavorable for treating diastolic heart failure. The low and middle doses enhanced the atrioventricular conduction, which may have some potential for predisposing the atria to the onset of atrial fibrillation via an induction of mitral and/or tricuspid regurgitation. The middle and high doses of caldaret prolonged the ventricular effective refractory period without altering the intraventricular conduction or repolarization period, which may prevent the onset of ventricular arrhythmias. Thus, modulation of intracellular Ca2+ handling by caldaret can induce not only inotropic effect, but also various electrophysiological actions on the in situ heart.

Sunitinib does not acutely alter left ventricular systolic function, but induces diastolic dysfunction.

PURPOSE: Cancer chemotherapies have improved the prognosis of cancer patients in recent years; however, their side effects on the cardiovascular systems have emerged as a major concern in the field of both cardiology and oncology. In particular, multi-targeted tyrosine kinase inhibitors are known to induce various types of cardiovascular adverse events including hypertension, QT-interval prolongation and heart failure, but their underlying mechanisms remain elusive. To explore how to better predict such drug-induced cardiovascular adverse events, we assessed the electropharmacological effects of sunitinib using the halothane-anesthetized dogs (n = 5), while plasma concentrations of cardiac enzymes including aspartate aminotransferase, lactate dehydrogenase, creatinine kinase and cardiac troponin I  were measured. METHODS: Sunitinib was intravenously administered at 0.01 and 0.1 mg/kg for 10 min with 20 min interval. RESULTS: Sunitinib decreased the amplitude of maximum downstroke velocity of the left ventricular pressure, prolonged the isovolumic relaxation time and increased the left ventricular end-diastolic pressure in a dose-related manner without affecting the other cardiohemodynamic and electrophysiological variables. More importantly, sunitinib significantly elevated cardiac troponin I level for 30-60 min after the high dose without altering the other biomarkers. CONCLUSIONS: Monitoring of the cardiac diastolic function together with cardiac troponin I after the start of sunitinib administration may become a reliable measure to predict the onset of sunitinib-induced cardiovascular adverse events.

Analysis of proarrhythmic potential of an atypical antipsychotic drug paliperidone in the halothane-anesthetized dogs.

Fatal cases with the use of atypical antipsychotic drug paliperidone have been reported; however, there was no clinical report describing paliperidone-induced torsade de pointes. In this study we assessed its electropharmacological effects together with its proarrhythmic potential in intravenous doses of 0.03, 0.3 and 3 mg/kg using the halothane-anesthetized dogs (n = 5), which could provide approximately 2, 20 and 200 times higher peak plasma drug concentrations than its therapeutic level, respectively. Paliperidone exerted potent vasodilator effect resulting in hypotension, which may be largely explained by its α1-adrenoceptor blocking action. In vivo electrophysiological results suggest that paliperidone may inhibit human ether-à-go-go-related gene K+ channel in a dose-related manner and modestly suppress Na+ channel in the in situ heart. The high dose of paliperidone may have some potential to induce early afterdepolarization that can trigger lethal ventricular arrhythmias, whereas the low and middle doses lack such proarrhythmic possibility, indicating that at least 20 times higher plasma concentration may be considered to be safe.

Assessment of the Anti-anginal Effect of Tetramethylpyrazine Using Vasopressin-Induced Angina Model Rats.

Intravenous tetramethylpyrazine has been widely used in China as a complementary and/or alternative medicine to treat patients with ischemic heart disease. We assessed the anti-anginal effect of tetramethylpyrazine (10 mg/kg, intravenously (i.v.), n=6) in comparison with that of its vehicle, saline (1 mL/kg, i.v., n=6), using vasopressin-induced angina model rats. First, Donryu rats were anesthetized with pentobarbital sodium (60 mg/kg, intraperitoneally (i.p.)), and the surface lead I electrocardiogram was continuously monitored. Administration of vasopressin (0.5 IU/kg, i.v.) to the rats depressed the S-wave level of the electrocardiogram, indicating the onset of subendocardial ischemia. However, pretreatment with tetramethylpyrazine suppressed the vasopressin-induced depression of the S-wave level, which was not observed following pretreatment with its vehicle alone (saline), suggesting that tetramethylpyrazine ameliorated the vasopressin-induced subendocardial ischemia in vivo. These results may provide experimental evidence for the empirically known clinical efficacy of tetramethylpyrazine against ischemic heart disease, and could provide clues to better understanding its in vivo mechanism of action.

Electropharmacological effects of amantadine on cardiovascular system assessed with J-Tpeak and Tpeak-Tend analysis in the halothane-anesthetized beagle dogs.

Since amantadine-induced long QT syndrome has been clinically reported, we investigated its electropharmacological effects to estimate the extent of proarrhythmic risk by using the halothane-anesthetized beagle dogs (n = 4). Amantadine in doses of 0.1, 1 and 10 mg/kg was infused over 10 min with a pause of 20 min under the monitoring of multiple cardiovascular variables. J-Tpeak and Tpeak-Tend were separately measured on the lead II electrocardiogram to precisely analyze the net balance between inward and outward current modifications by amantadine. The low dose increased the ventricular contractile force, but suppressed the intraventricular conduction. The middle dose prolonged the QT interval besides enhancing the changes induced by the low dose. The high dose increased the mean blood pressure, left ventricular end-diastolic pressure and total peripheral resistance, and accelerated the atrioventricular nodal conduction, but decreased the cardiac output besides enhancing the changes induced by the middle dose. A reverse use-dependence was confirmed in the repolarization delay. Amantadine hardly affected the J-Tpeak, but prolonged the Tpeak-Tend. Amantadine can be considered to stimulate Ca(2+) channel but inhibit Na(+) and K(+) channels in the in situ heart. J-Tpeak and Tpeak-Tend analysis suggests that amantadine may possess modest risk for arrhythmia.

Beneficial and Adverse Effects of Electro-acupuncture Assessed in the Canine Chronic Atrio-ventricular Block Model Having Severe Hypertension and Chronic Heart Failure.

Regarding the effects of electro-acupuncture for severe hypertension, we assessed its acute cardiovascular consequences with 4 subjects of the chronic atrioventricular block dogs having severe hypertension and chronic heart failure. The electro-acupuncture consisting of 2 mA at 2 Hz frequency was carried out for 30 min at Renying (ST-9) and Taichong (LR-3) every other day. Seven sessions were performed within 2 weeks. In the 1st and 7th sessions, the animals were anesthetized with pentobarbital to analyze the effects of the electro-acupuncture on cardiovascular variables. No significant change was detected in any of the basal control values of the cardiohemodynamic or electrophysiological variables between the 1st and 7th sessions. During the 1st session, electo-acupuncture produced a peak increase in mean blood pressure by 8.7% at 35 min (p < 0.05), whereas during the 7th session the peak increase was 6.5% at 35 min (p = 0.06). There was no significant change in the cardiac output, total peripheral resistance, a product of the heart rate and systolic blood pressure (= double product) reflecting myocardial oxygen consumption, QRS width or QT interval during the electrical stimulation in the 1st or 7th session. The results suggest that electroacupuncture may not exert lethal adverse effect except the vasopressor response, but that it can decrease the treatment-induced sympathetic response including vasopressor reaction and tachycardia. Since electro-acupuncture may have some potential to induce hypertensive crisis at the beginning, clinicians have to pay attention on its use for patients with hypertension.

Common parameters of acupuncture for the treatment of hypertension used in animal models.

Hypertension is associated with at least 7.6 million annual deaths worldwide. While pharmacotherapy may provide good control for blood pressure, it sometimes induces adverse effects. Meanwhile, acupuncture has been used for the treatment of cardiovascular diseases, such as hypertension, coronary artery disease, and stroke, but its mechanisms of actions remain poorly understood. The efficacy of acupuncture depends on multiple constituent elements including acupoints, manipulation skills, and implementation programs, which are termed as acupuncture prescription. This review summarized the previous information of experimental use of acupuncture on animals including species, hypertension models, acupoints selection, acupoint location, stimulation protocols, and evaluation of effectiveness to provide useful guidance for researchers when performing acupuncture in animal experiments.

Possible effects of inhibition of IKr and IKs on field-potential waveforms in the human iPS cell-derived cardiomyocytes sheet.

In order to investigate how IKr and IKs inhibitions affect waveforms of the field potential in the human iPS cell-derived cardiomyocytes sheet, we analyzed the effects of E-4031 and chromanol 293B on the maximum upslope and peak amplitude of its second wave (n = 7 for each drug). E-4031 in 10-100 nM as well as chromanol 293B in 3-30 µM prolonged the field-potential duration, whereas E-4031 decreased the upslope in 10-100 nM and amplitude at 100 nM, which was not observed by chromanol 293B. Thus, the decrease of the upslope can be used as a supplemental marker of drug-induced IKr inhibition.

Cardiohemodynamic and electrophysiological effects of a selective EP4 receptor agonist ONO--AE1--329 in the halothane-anesthetized dogs.

Cardiovascular effects of a highly selective prostaglandin E2 type 4 (EP4) receptor agonist ONO-AE1-329 were assessed with the halothane-anesthetized dogs (n=6). ONO-AE1-329 was intravenously infused in three escalating doses of 0.3, 1 and 3ng/kg/min for 10min with a pause of 20min between the doses. The low dose of 0.3ng/kg/min significantly increased maximum upstroke velocity of left ventricular pressure by 18% at 20min, indicating increase of ventricular contractility. The middle dose of 1ng/kg/min significantly decreased total peripheral resistance by 24% and left ventricular end-diastolic pressure by 32% at 10min, indicating dilation of arteriolar resistance vessels and venous capacitance ones, respectively; and increased cardiac output by 25% at 10min in addition to the change induced by the low dose. The high dose of 3ng/kg/min increased heart rate by 34% at 10min; decreased mean blood pressure by 14% at 10min and atrioventricular nodal conduction time by 13% at 5min; and shortened left ventricular systolic period by 8% at 10min and electromechanical coupling defined as an interval from completion of repolarization to the start of ventricular diastole by 39% at 10min in addition to the changes induced by the middle dose. No significant change was detected in a ventricular repolarization period. These results indicate that ONO-AE1-329 may possess a similar cardiovascular profile to typical phosphodiesterase 3 inhibitors as an inodilator, and suggest that EP4 receptor stimulation can become an alternative strategy for the treatment of congestive heart failure.

Assessment of testing methods for drug-induced repolarization delay and arrhythmias in an iPS cell-derived cardiomyocyte sheet: multi-site validation study.

A prospective comparison study across 3 independent research laboratories of a pure IKr blocker E-4031 was conducted by using the same batch of human iPS cell-derived cardiomyocytes in order to verify the utility and reliability of our original standard protocol. Field potential waveforms were recorded with a multi-electrode array system to measure the inter-spike interval and field potential duration. The effects of E-4031 at concentrations of 1 to 100 nM were sequentially examined every 10 min. In each facility, E-4031 significantly prolonged the field potential duration corrected by Fridericia's formula and caused early afterdepolarizations occasionally resulting in triggered activities, whereas it tended to decrease the rate of spontaneous contraction. These results were qualitatively and quantitatively consistent with previous non-clinical in vitro and in vivo studies as well as clinical reports. There were inter-facility differences in some absolute values of the results, which were not observed when the values were normalized as percentage change. Information described in this paper may serve as a guide when predicting the drug-induced repolarization delay and arrhythmias with this new technology of stem cells.

The antipsychotic and antiemetic drug prochlorperazine delays the ventricular repolarization of the in situ canine heart.

Electropharmacological effect of the antipsychotic and antiemetic drug prochlorperazine was assessed using the halothane-anesthetized in vivo canine model (n = 5). Up to 10 times higher than the clinically relevant doses of prochlorperazine (< or = 3 mg/kg, i.v.) did not induce cardiohemodynamic collapse in the model. Meanwhile, clinically relevant to supratherapeutic doses (0.3 - 3 mg/kg, i.v.) prolonged the ventricular repolarization period in a dose-related and reverse-use dependent manner that could become proarrhythmic substrates. Thus, caution has to be paid on the use of prochlorperazine particularly for patients with risks of the elevated plasma drug concentration, compromised cardiac repolarization, and/or frequent ventricular premature beats.

Electropharmacological effects of a spironolactone derivative, potassium canrenoate, assessed in the halothane-anesthetized canine model.

While aldosterone receptor blockers improve survival of patients with congestive heart failure, spironolactone and its derivatives were recently shown to block ether-a-go-go-related gene (HERG) channels and native IKs and IKr currents in guinea pig ventricular myocytes. In this study, we examined in vivo electropharmacological effects of an active derivative of spironolactone, potassium canrenoate, using a halothane-anesthetized canine model. Potassium canrenoate was intravenously administered in three doses of 1, 10, and 100 mg/kg per 10 min with a pause of 20 min between doses (n = 5). The low dose hardly affected any of the cardiovascular parameters. The middle dose, a clinically recommended daily maximum i.v. dose, slightly inhibited the intraventricular conduction. The high dose decreased the heart rate, ventricular contraction and blood pressure, delayed the atrioventricular and intraventricular conduction, and prolonged the ventricular repolarization and refractory period. Increment in the refractoriness by the high dose was greater than that in the repolarization, resulting in the reduction of ventricular electrical vulnerability. This unique electrophysiological profile of potassium canrenoate may in part contribute to the favorable clinical results, whereas caution has to be paid on the cardiohemodynamic actions, particularly for patients with risk of elevated plasma drug concentration.