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Carvedilol is mainly metabolized in the liver to O-glucuronide (O-Glu). We previously found that the glucuronidation activity of racemic carvedilol in pooled human liver microsomes (HLM) was increased, R-selectively, in the presence of amiodarone. The aim of this study was to clarify the mechanisms for the enhancing effect of amiodarone on R- and S-carvedilol glucuronidation. We evaluated O-Glu formation of R- and S-carvedilol enantiomers in a reaction mixture of HLM including 0.2% bovine serum albumin (BSA). In the absence of amiodarone, glucuronidation activity of R- and S-carvedilol for 25 min was 0.026, and 0.51 pmol/min/mg protein, and that was increased by 6.15 and 1.60-fold in the presence of 50 µM amiodarone, respectively. On the other hand, in the absence of BSA, or when BSA was replaced with human serum albumin, no enhancing effect of amiodarone on glucuronidation activity was observed, suggesting that BSA played a role in the mechanisms for the enhancement of glucuronidation activity. Unbound fraction of S-carvedilol in the reaction mixture was greater than that of R-carvedilol in the absence of amiodarone. Also, the addition of amiodarone caused a greater increase of unbound fraction of R-carvedilol than that of S-carvedilol. These results suggest that the altered protein binding by amiodarone is a key mechanism for R-selective stimulation of carvedilol glucuronidation.

Extracellular matrix components play an active role in cancer progression and prognosis. Versican, a large extracellular matrix proteoglycan, can promote cancer metastasis through facilitating cell proliferation, adhesion, migration and angiogenesis. We had previously demonstrated that amiodarone caused ectopic overexpression of similar to versican b (s-vcanb), inhibited EGFR/GSK3β/Snail signaling, and enhanced Cdh5 at the heart field of zebrafish, indicating interference with epithelial-mesenchymal transition (EMT). Since S-vcanb is homologous to mammalian versican V2 isoform, we examined the effects of amiodarone on mammalian tumor proliferation, migration, invasion and metastasis in vitro and in vivo and on EMT signaling pathways. Monolayer wound assays and extracellular matrix transwell invasion assays showed reduced migration and invasion by 15 μM amiodarone treated B16OVA, JC, 4T-1, MDA-MB-231 and MCF-7 tumor cell lines. All cancer cell lines showed reduced metastatic capabilities in vivo after treatment with amiodarone in experimental animals. Western blots revealed that EMT-related transcription factors Snail and Twist were reduced and E-cadherin was enhanced in amiodarone treated cells through an EGFR/ERK/GSK3β-dependent pathway. Immunohistochemistry showed amiodarone lead to increased expression of versican V2 isoform concomitant with reduced versican V1. Our study illustrated the role of versican v2 in EMT modulation and cancer suppression by amiodarone treatment.

Although Amiodarone, a class III antiarrhythmic drug, inhibits zebrafish cardiac valve formation, the detailed molecular pathway is still unclear. Here, we proved that Amiodarone acts as an upstream regulator, stimulating similar to versican b (s-vcanb) overexpression at zebrafish embryonic heart and promoting cdh-5 overexpression by inhibiting snail1b at atrioventricular canal (AVC), thus blocking invagination of endocardial cells and, as a result, preventing the formation of cardiac valves. A closer investigation showed that an intricate set of signaling events ultimately caused the up-regulation of cdh5. In particular, we investigated the role of EGFR signaling and the activity of Gsk3b. It was found that knockdown of EGFR signaling resulted in phenotypes similar to those of Amiodarone-treated embryos. Since the reduced phosphorylation of EGFR was rescued by knockdown of s-vcanb, it was concluded that the inhibition of EGFR activity by Amiodarone is s-vcanb-dependent. Moreover, the activity of Gsk3b, a downstream effector of EGFR, was greatly increased in both Amiodarone-treated embryos and EGFR-inhibited embryos. Therefore, it was concluded that reduced EGFR signaling induced by Amiodarone treatment results in the inhibition of Snail functions through increased Gsk3b activity, which, in turn, reduces snail1b expression, leading to the up-regulation the cdh5 at the AVC, finally resulting in defective formation of valves. This signaling cascade implicates the EGFR/Gsk3b/Snail axis as the molecular basis for the inhibition of cardiac valve formation by Amiodarone.

Dry stigmas of the Crocus sativus L. (Saffron) are well known in world as a popular flavouring and therapeutic agent. The anxiolytic, antidepressant, anticonvulsant and antiarrhythmic effects of saffron suggest that it may affect the autonomic control of the heart. This study assessed its safety on cardiac sympathovagal balance and heart rate variability in rat. Experimental groups were control, Saf50, Saf100, Saf200 (received saffron at dosages of 50 and 100 and 200 mg/kg/d, orally, respectively) and Amio (received 30 mg/mL/kg/d of amiodarone, orally, for 7 days) groups. On day 8, the frequency domain and time domain indices of animals' electrocardiograms were calculated. The heart rate decreased and RR interval increased in Saf200 and Amio groups (P<.05 vs other groups). Square root of the mean squared differences of successive RR intervals enhanced in all treated groups, however, was only significant in Amio group (P<.05). The SD1/SD2 ratio was higher in Saf200 and Amio groups. Both low-frequency (LF) and high-frequency (HF) parameters were higher, and the LF/HF ratio was non-significantly lower in treated groups. The findings suggest that saffron not only has no harmful effect on activity of cardiac autonomic nervous system, but it may improve the stability of heart sympathovagal balance in normal rat., (© 2016 John Wiley & Sons Ltd.)

In view of the reliability of the serial-shock method of measuring ventricular fibrillation threshold (VFT) in quantitatively assessing the antifibrillatory potency of many anti-arrhythmic drugs and the alarming reports of the proarrhythmic effects of several anti-arrhythmic agents, it was decided to use the above technique to study the possible interactions that may occur when anti-arrhythmic drugs from different classes are combined. Hearts isolated from New Zealand white rabbits of either sex weighing 1.5-2 kg were perfused by the Langendorff method with McEwen's solution. In six hearts, measurement of VFT was made in the absence of any drug throughout the experiments. Perfusion with either amiodarone or ibutilide produced significant, dose-dependent increase in VFT. In addition, there was no significant difference in the increase in VFT produced by the combined infusion of 1 μmol of amiodarone and 0.01 μmol of ibutilide and the summation of the increases produced by the separate infusion of these two concentrations. This is in contrast to a significant synergistic antifibrillatory effect of the combined use of lidocaine and propranolol that was reported previously. The lack of antifibrillatory interactions between amiodarone and Ibutilide may suggest the safety of combining the two drugs in the treatment of cardiac arrhythmias. However, further studies are required to establish this in the clinical setup., (© 2015 Société Française de Pharmacologie et de Thérapeutique.)

Amiodarone is a widely prescribed antiarrhythmic drug used to treat the most prevalent type of arrhythmia, atrial fibrillation (AF). At therapeutic concentrations, amiodarone alters the function of many diverse membrane proteins, which results in complex therapeutic and toxicity profiles. Other antiarrhythmics, such as dronedarone, similarly alter the function of multiple membrane proteins, suggesting that a multipronged mechanism may be beneficial for treating AF, but raising questions about how these antiarrhythmics regulate a diverse range of membrane proteins at similar concentrations. One possible mechanism is that these molecules regulate membrane protein function by altering the common environment provided by the host lipid bilayer. We took advantage of the gramicidin (gA) channels' sensitivity to changes in bilayer properties to determine whether commonly used antiarrhythmics--amiodarone, dronedarone, propranolol, and pindolol, whose pharmacological modes of action range from multi-target to specific--perturb lipid bilayer properties at therapeutic concentrations. Using a gA-based fluorescence assay, we found that amiodarone and dronedarone are potent bilayer modifiers at therapeutic concentrations; propranolol alters bilayer properties only at supratherapeutic concentration, and pindolol has little effect. Using single-channel electrophysiology, we found that amiodarone and dronedarone, but not propranolol or pindolol, increase bilayer elasticity. The overlap between therapeutic and bilayer-altering concentrations, which is observed also using plasma membrane-like lipid mixtures, underscores the need to explore the role of the bilayer in therapeutic as well as toxic effects of antiarrhythmic agents., (© 2015 Rusinova et al.)

In this study, IC50 shift and time-dependent inhibition (TDI) experiments were carried out to measure the ability of amiodarone (AMIO), and its circulating human metabolites, to reversibly and irreversibly inhibit CYP1A2, CYP2C9, CYP2D6, and CYP3A4 activities in human liver microsomes. The [I]u/Ki,u values were calculated and used to predict in vivo AMIO drug-drug interactions (DDIs) for pharmaceuticals metabolized by these four enzymes. Based on these values, the minor metabolite N,N-didesethylamiodarone (DDEA) is predicted to be the major cause of DDIs with xenobiotics primarily metabolized by CYP1A2, CYP2C9, or CYP3A4, while AMIO and its N-monodesethylamiodarone (MDEA) derivative are the most likely cause of interactions involving inhibition of CYP2D6 metabolism. AMIO drug interactions predicted from the reversible inhibition of the four P450 activities were found to be in good agreement with the magnitude of reported clinical DDIs with lidocaine, warfarin, metoprolol, and simvastatin. The TDI experiments showed DDEA to be a potent inactivator of CYP1A2 (KI = 0.46 μM, kinact = 0.030 minute(-1)), while MDEA was a moderate inactivator of both CYP2D6 (KI = 2.7 μM, kinact = 0.018 minute(-1)) and CYP3A4 (KI = 2.6 μM, kinact = 0.016 minute(-1)). For DDEA and MDEA, mechanism-based inactivation appears to occur through formation of a metabolic intermediate complex. Additional metabolic studies strongly suggest that CYP3A4 is the primary microsomal enzyme involved in the metabolism of AMIO to both MDEA and DDEA. In summary, these studies demonstrate both the diversity of inhibitory mechanisms with AMIO and the need to consider metabolites as the culprit in inhibitory P450-based DDIs., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)

The deregulation of autophagy is involved in liver regeneration. Here, we investigated the role of autophagy in the regulation of liver regeneration after partial hepatectomy (PHx) and the development of pharmacological interventions for improved liver regeneration after PHx. We show that autophagy was activated in the early stages of liver regeneration following 70% PHx in vivo. Moreover, amiodarone was associated with a significant enhancement of autophagy, liver growth, and hepatocyte proliferation, along with reduced liver injury and the termination of liver regeneration due to decreased transforming growth factor-β1 expression after 70% PHx. The promotion of autophagy appeared to selectively increase the removal of damaged mitochondria. We also found that Atg7 knockdown or pretreatment with chloroquine aggravated the liver injury associated with 70% PHx and reduced liver growth and hepatocyte proliferation. Finally, amiodarone improved liver regeneration, survival, and liver injury after 90% PHx. In conclusion, our results indicate that autophagy plays an important role in mouse liver regeneration and that modulating autophagy with amiodarone may be an effective method of improving liver regeneration, increasing survival, and ameliorating liver injury following PHx.

Dronedarone has been demonstrated to be harmful in patients with recent decompensated heart failure. Furthermore, a PALLAS study reported that dronedarone therapy increases mortality rates in patients with permanent atrial fibrillation. Although a pathophysiological explanation for these finding remains to be elucidated, the long term effects of dronedarone on myocardial structure and stability have been suggested. The aim of the present study was to determine whether dronedarone therapy affects left ventricular (LV) function in a chronic model of myocardial infarction (MI). An anterior MI was induced in 16 pigs. Of these animals, eight pigs were then treated with dronedarone for 1 week prior to, and 4 weeks following MI, the remaining pigs served as controls. LV angiography was performed 4 weeks after MI to determine the LV ejection fraction (LVEF). A post‑mortem magnetic resonance imaging scan of the LV was then performed on the two groups (n=6) to determine the volume and size of the induced MI. Dronedarone therapy did not affect systemic and intracardiac hemodynamic parameters or LVEF during the follow‑up assessment. Of note, dronedarone had no negative effect on the total infarct volume and size and did not induce lethal proarrhythmic effects following the induced anterior MI. Therefore, the results suggested that dronedarone did not increase the volume or size of induced anterior MI and did not affect LV performance. Thus, dronedarone therapy was observed to be safe in a porcine model of anterior MI.

The aim of this investigation was to compare the effectiveness of long-term pretreatment with amiodarone (AMIO) and its active metabolite desethylamiodarone (DEA) on arrhythmias induced by acute myocardial infarction in rats. Acute myocardial infarction was induced in conscious, male, Sprague-Dawley rats by pulling a previously inserted loose silk loop around the left main coronary artery. Long-term oral pretreatment with AMIO (30 or 100 mg·(kg body mass)(-1)·day(-1), loading dose 100 or 300 mg·kg(-1) for 3 days) or DEA (15 or 50 mg·kg(-1)·day(-1), loading dose 100 or 300 mg·kg(-1) for 3 days), was applied for 1 month before the coronary artery occlusion. Chronic oral treatment with DEA (50 mg·kg(-1)·day(-1)) resulted in a similar myocardial DEA concentration as chronic AMIO treatment (100 mg·kg(-1)·day(-1)) in rats (7.4 ± 0.7 μg·g(-1) and 8.9 ± 2.2 μg·g(-1)). Both pretreatments in the larger doses significantly improved the survival rate during the acute phase of experimental myocardial infarction (82% and 64% by AMIO and DEA, respectively, vs. 31% in controls). Our results demonstrate that chronic oral treatment with DEA resulted in similar cardiac tissue levels to that of chronic AMIO treatment, and offered an equivalent degree of antiarrhythmic effect against acute coronary artery ligation induced ventricular arrhythmias in conscious rats.

Although foamy macrophages (FMΦ) are commonly observed during nonclinical development of medicines for inhalation, there are no accepted criteria to differentiate adaptive from adverse FMΦ responses in drug safety studies. The purpose of this study was to develop a multiparameter in vitro assay strategy to differentiate and characterize different mechanisms of drug-induced FMΦ. Amiodarone, staurosporine, and poly(vinyl acetate) nanoparticles were used to induce distinct FMΦ phenotypes in J774A.1 cells, which were then compared with negative controls. Treated macrophages were evaluated for morphometry, lipid accumulation, gene expression, apoptosis, cell activation, and phagocytosis. Analysis of vacuolization (number/area vacuoles per cell) and phospholipid content revealed inducer-dependent distinctive patterns, which were confirmed by electron microscopy. In contrast to the other inducers, amiodarone increased vacuole size rather than number and resulted in phospholipid accumulation. No pronounced dysregulation of transcriptional activity or apoptosis was observed in response to sublethal concentrations of all inducers. Functionally, FMΦ induction did not affect macrophage activation by lipopolysaccharide, but it reduced phagocytic capacity, with different patterns of induction, severity, and resolution observed with the different inducers. An in vitro multiparameter assay strategy is reported that successfully differentiates and characterizes mechanisms leading to FMΦ induction by different types of agents.

Background: Amiodarone is commonly used in the acute care setting. However the acute hemodynamic and echocardiographic effect of intravenous amiodarone administered intraoperatively on right ventricular (RV) systolic and diastolic function using transesophageal echocardiography (TEE) has not been described., Methods: The study design was a randomized controlled trial in elective cardiac surgical patients undergoing valvular surgery. Patients received an intravenous loading dose of 300 mg of either amiodarone or placebo in the operating room, followed by an infusion of 15 mg/kg for two days. Hemodynamic profiles, echocardiographic measurement of RV and left ventricular (LV) dimensions, Doppler interrogation of tricuspid and mitral valve, hepatic and pulmonary venous flow combined with tissue Doppler imaging of the tricuspid and mitral valve annulus were obtained before and after bolus., Results: Although more patients in the placebo group had chronic obstructive lung disease (14 vs 6, p=0.05) and diabetes (14 vs 5; p=0.0244), there was no difference in terms of baseline hemodynamic, 2D and Doppler variables. After bolus, a significant increase in pulmonary artery pressure, central venous pressure and pulmonary vascular resistance index (p<0.05) was observed in the amiodarone group with reduction in systolic to diastolic (S/D) ratio of the hepatic (p=0.0247) and pulmonary venous (p=0.0052) velocity., Conclusion: Acute administration of amiodarone is associated with alteration in RV diastolic properties and has minimal negative inotropic effect on RV systolic function in cardiac surgical patients with valvular disease., (© The European Society of Cardiology 2014.)

Ebola virus disease (EVD) is one of the most lethal transmissible infections characterized by a high fatality rate, and a treatment has not been developed yet. Recently, it has been shown that cationic amphiphiles, among them the antiarrhythmic drug amiodarone, inhibit filovirus infection. In the present work, we investigated how amiodarone interferes with Ebola virus infection. Wild-type Sudan ebolavirus and recombinant vesicular stomatitis virus, pseudotyped with the Zaire ebolavirus glycoprotein, were used to gain further insight into the ability of amiodarone to affect Ebola virus infection. We show that amiodarone decreases Ebola virus infection at concentrations close to those found in the sera of patients treated for arrhythmias. The drug acts by interfering with the fusion of the viral envelope with the endosomal membrane. We also show that MDEA, the main amiodarone metabolite, contributes to the antiviral activity. Finally, studies with amiodarone analogues indicate that the antiviral activity is correlated with drug ability to accumulate into and interfere with the endocytic pathway. Considering that it is well tolerated, especially in the acute setting, amiodarone appears to deserve consideration for clinical use in EVD., (© FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Drug-induced QT prolongation has been reported in humans and animals. This potentially lethal effect can be induced by drugs interacting with a cardiac potassium channel, namely hERG (human ether-a go-go-related gene) leading to arrhythmia or torsade de pointes (TdP). Hence, in vitro evaluation of therapeutics for their effects on the rapid delayed rectifier current (IKr) mediated by the K(+) ion channel encoded by hERG is a valuable tool for identifying potential arrhythmic side effects during drug safety testing. Our objective was to evaluate the temperature-induced hERG channel blockade variation by human and veterinary drugs using the IonFlux 16 system. A panel of eight drugs was tested for IKr inhibition at both ambient (23 °C) and physiological (37 °C) temperatures at various concentrations using IonFlux 16, an automated patch clamp system. Our results established that both amiodarone (IC(50)  = 0.56 μM at 23 °C and 0.30 μM at 37 °C) and β-estradiol (IC(50)  = 24.72 μM at 23 °C and 8.17 μM at 37 °C) showed a dose-dependent IKr blockade with a higher blockade at 37 °C. Whereas, blockade of IKr by both ivermectin (IC(50)  = 12.52 μM at 23 °C and 24.41 μM at 37 °C) and frusemide (IC(50)  = 12.58 μM at 23 °C and 25.55 μM at 37 °C) showed a dose-dependent IKr blockade with a lower blockade at 37 °C. Gentamicin, enrofloxacin, xylazine and albendazole did not block IKr at both the assessed temperatures. Collectively, these results demonstrate that the effect of temperature variation should be taken into consideration during the evaluation of test drugs for their hERG channel blockade potential., (Copyright © 2014 John Wiley & Sons, Ltd.)

Amiodarone is an effective antiarrhythmic drug for supra­ven­tri­cular and ventricular arrhythmias. A majority of patients treated with amiodarone suffer from mild adverse events, however, serious life-threatening adverse events caused by amiodarone are also seen. This review describes the pharmacology, interac­tions, side and adverse effects of amiodarone and highlights the importance of a systematic interdisciplinary follow-up protocol for outpatients treated with amiodarone.

The antiarrhythmic agent amiodarone, a cationic amphiphilic drug, is known to induce phospholipidosis, i.e. the accumulation of phospholipids within lysosomal structures to give multi-lamellar inclusion bodies. Despite the concerns raised about phospholipidosis in the recent years, the molecular mechanisms underlying amiodarone- or other cationic amphiphilic drug-induced phospholipidosis are still under investigation. Here we demonstrated that amiodarone doses able to induce phospholiposis according to NBD-PC uptake assay (1-12 μM, 24 h) activates Transcription Factor EB (TFEB), a pivotal regulator of the autophagic pathway, in human HepG2 cells. Further evidences confirmed the effect of amiodarone on the autophagic-lysosomal system in HepG2 and BEAS-2B cells: lysosomal β-hexosaminidase isoenzymes secretion, transcriptional up-regulation of the lysosomal β-hexosaminidase α-subunit, alteration of cathepsin B, D and L intracellular maturation in a cell- and protease-specific manner. Autophagy activation was also demonstrated by increased conversion of LC3-I into LC3-II and reduced phosphorylation of the mTORC1 target S6 kinase. Besides, we provided evidence that TFEB over-expression prevents amiodarone-induced phospholipid accumulation, suggesting that this transcription factor could be a possible target to develop strategies for phospholipidosis attenuation., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Amiodarone is a benzofuran derivative that contains up to 40% of iodine. Amiodarone is used for treatment and prevention of life threatening supraventricular and ventricular tachyarrhythmias. The effects on thyroid gland vary from abnormalities in thyroid function tests to overt amiodarone induced hypothyroidism (AIH) and thyrotoxicosis (AIT). Patients with AIH are treated with L-thyroxine and may continue treatment with amiodarone. Two different forms of AIT have to be distinguished: amiodarone induced hyperthyroidism (AIT I) and thyroiditis (AIT II). AIT I is treated with antithyroid drugs, while total thyroidectomy and iodine-131 are used for definitive treatment. AIT II is treated with glucocorticoids. Patients with AIT have to stop treatment with amiodarone. Dronedarone is a less potent antiarrhythmic agent with structural and pharmacological properties similar to amiodarone. Dronedarone is devoid of iodine with fewer adverse effects and therefore it may be used in high risk patients for development of AIT or AIH.

Aims: Although sinus node modification by catheter ablation is an established therapy for the treatment of inappropriate sinus tachycardia, there is incomplete understanding of sinus node anatomy and function but also limited electroanatomical mapping data. Recently, an automatic, ultra high-resolution mapping system has been presented to accurately and quickly identify right atrial (RA) geometry and activation patterns but detailed assessment of sinus node activation has not been performed which was one aim of this study. Preclinical experiences are compared with previous sinus node mapping studies in animals and humans, and potential clinical implications for catheter ablation are discussed., Methods and Results: In anaesthetized and ventilated 14 pigs, 30 endocardial and 2 eipcardial RA maps were generated using the Rhythmia™ mapping system without complications and earliest activation sites (EAS) and sinus break-out (SBO) were determined. At baseline, EAS and SBO were located anterior to the middle (n = 6) or lower third (n = 8) of the crista terminalis exhibiting a unicentric activation pattern in all cases. Conduction pathways were directed anterior, posterior, superior, or inferior with substantial inter-individual variation in direction, pathway distance, and conduction time. Orciprenaline, propranolol, or amiodarone shifted endocardial activation with considerable variation between animals with inconsistent patterns. Multicentric activation was found in one case after orciprenaline infusion. Sequential endocardial and epicardial high-density mapping of the RA was performed in two animals and showed a high congruence of the sinus node activation in the endo- and the epicardial map., Conclusion: Ultra high-density mapping allows fast, simple, and very detailed assessment of sinus node activation. Future studies are clearly needed to evaluate novel mapping and ablation strategies for an improved understanding of sinus node disease and better outcomes., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.)

Zebrafish is increasingly used to assess biological properties of chemical substances and thus is becoming a specific tool for toxicological and pharmacological studies. The effects of chemical substances on embryo survival and development are generally evaluated manually through microscopic observation by an expert and documented by several typical photographs. Here, we present a methodology to automatically classify brightfield images of wildtype zebrafish embryos according to their defects by using an image analysis approach based on supervised machine learning. We show that, compared to manual classification, automatic classification results in 90 to 100% agreement with consensus voting of biological experts in nine out of eleven considered defects in 3 days old zebrafish larvae. Automation of the analysis and classification of zebrafish embryo pictures reduces the workload and time required for the biological expert and increases the reproducibility and objectivity of this classification.

Context: Amiodarone (AMIO) is one of the most effective antiarrhythmic drugs available; however, its use is limited by a serious side effect profile, including thyroiditis. The mechanisms underlying AMIO thyroid toxicity have been elusive; thus, identification of novel approaches in order to prevent thyroiditis is essential in patients treated with AMIO., Objective: Our aim was to evaluate whether AMIO treatment could induce endoplasmic reticulum (ER) stress in human thyroid cells and the possible implications of this effect in AMIO-induced destructive thyroiditis., Results: Here we report that AMIO, but not iodine, significantly induced the expression of ER stress markers including Ig heavy chain-binding protein (BiP), phosphoeukaryotic translation initiation factor 2α (eIF2α), CCAAT/enhancer-binding protein homologous protein (CHOP) and spliced X-box binding protein-1 (XBP-1) in human thyroid ML-1 cells and human primary thyrocytes. In both experimental systems AMIO down-regulated thyroglobulin (Tg) protein but had little effect on Tg mRNA levels, suggesting a mechanism involving Tg protein degradation. Indeed, pretreatment with the specific proteasome inhibitor MG132 reversed AMIO-induced down-regulation of Tg protein levels, confirming a proteasome-dependent degradation of Tg protein. Corroborating our findings, pretreatment of ML-1 cells and human primary thyrocytes with the chemical chaperone 4-phenylbutyric acid completely prevented the effect of AMIO on both ER stress induction and Tg down-regulation., Conclusions: We identified ER stress as a novel mechanism contributing to AMIO-induced destructive thyroiditis. Our data establish that AMIO-induced ER stress impairs Tg expression via proteasome activation, providing a valuable therapeutic avenue for the treatment of AMIO-induced destructive thyroiditis.

Atrial fibrillation (AF) is a common arrhythmia associated with increased mortality and morbidity. Different studies have shown no significant difference between rhythm and rate control strategies in terms of mortality. Moreover, the use of antiarrhythmic drugs is afflicted by cardiac and extracardiac toxicity and related costs of hospitalization. Nevertheless, some patients require a rhythm-control strategy and new anti-AF agents are being sought. Only few novel agents showed promising results in term of efficacy and safety. Dronedarone and vernakalant are two of these compounds, respectively introduced for the chronic and acute rhythm control of AF. This article will review pharmacology and clinical evidence on the use of dronedarone and vernakalant and will mention currently investigated new antiarrhythmic drugs.

Background: The antiarrhythmic potential of a novel multichannel blocker CPUY102122 (CY22) was investigated in the present study., Methods: The effect of CY22 on rapid delayed rectifier potassium channel current (IKr) was studied using whole-cell patch clamp techniques in Chinese Hamster Ovary cells stably expressing human Ether-à-go-go-Related Gene. We further evaluated the antioxidant effects of CY22 and demonstrated the reversal of connexin down-regulation in the development of cardiac ventricular arrhythmias, which was produced using coronary ligation/reperfusion in rabbits. CY22 and Amiodarone were administered 30min prior to the procedure. Next, electrocardiograms were recorded, protein expression of left ventricular Connexin43 (Cx43), non-phosphorylation-Cx43 (np-Cx43), Rac-1 and gp-91[phox] were assayed using Western blot analysis, microstructural changes in the myocardium were observed and redox system activity was assayed., Results: CY22 inhibited IKr in a concentration-dependent manner with IC50 value of 2.8±0.8μmol/L. CY22 treatment significantly decreased T-wave amplitude and QTc arrhythmic scores and ameliorated the shape of the infarcted myocardium compared to the model group. CY22 decreased the serum levels of creatine kinase, lactate dehydrogenase, and myocardial levels of malondialdehyde, as well as increased superoxide dismutase activity. Cx43 expression in the left ventricle was significantly increased by CY22 treatment, which significantly decreased np-43 expression, Rac-1 activity and gp-91[phox] protein expression., Conclusions: These results indicated that CY22 has both antiarrhythmic and cardiovascular protective effects partly by blocking IKr, the production of antioxidants and protection of Cx43., (Copyright © 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.)

Dronedarone is a novel class III antiarrhythmic drug that is widely used in atrial fibrillation. It has been shown in native cardiomyocytes that dronedarone inhibits cardiac inwardly rectifying current IK1 at high concentrations, which may contribute both its antifibrillatory efficacy and its potential proarrhythmic side effects. However, the underlying mechanism has not been studied in further detail to date. In the mammalian heart, heterotetrameric assembly of Kir2.x channels is the molecular basis of IK1 current. Therefore, we studied the effects of dronedarone on wild-type and mutant Kir2.x channels in the Xenopus oocyte expression system. Dronedarone inhibited Kir2.1 currents but had no effect on Kir2.2 or Kir2.3 currents. Onset of block was slow but completely reversible upon washout. Blockade of Kir2.1 channels did not exhibit strong voltage dependence or frequency dependence. In a screening with different Kir2.1 mutants lacking specific binding sites within the cytoplasmic pore region, we found that residue E224 is essential for binding of dronedarone to Kir2.1 channels. In conclusion, direct block of Kir2.1 channel subunits by dronedarone through binding at E224 may underlie its inhibitory effects on cardiac IK1 current.

Terfenadine is a second generation histamine receptor antagonist which is widely used as a non‑sedating antihistamine to relieve allergic responses. However, terfenadine has been associated with a number of side effects on cardiac electrical activities through blocking multiple ion channels in the heart, particularly K+ channels. Previous studies have also implied that terfenadine may have a potential antiarrhythmic effect; however, the electrophysiological influence by which terfenadine exerts its antiarrhythmic action remains elusive. Based on evidence from previous studies, it was hypothesized that the antiarrhythmic effect of terfenadine may be similar to that of amiodarone. The present study aimed to examine the effect of terfenadine on the QTc interval and on experimental ventricular arrhythmia in rats by comparing with that of amiodarone. The effect of terfenadine and amiodarone on the QTc interval was evaluated by comparison of multiple electrocardiograms. Barium chloride/aconitine was intraperitoneally injected to induce ventricular arrhythmias. Normal saline was administered to control rats. In comparison with normal saline, terfenadine and amiodarone similarly dose‑dependently prolonged the QTc interval in rats. In the barium chloride/aconitine-induced ventricular arrhythmia model, terfenadine and amiodarone did not only similarly delay the onset time of arrhythmias induced by barium chloride (all P<0.05), but also increased the cumulative dosage of aconitine required to induce various arrhythmias (all P<0.05). Furthermore, the two drugs equivalently caused a significant decrease in the duration of ventricular tachycardia in comparison with the normal saline controls (all P<0.05). The present study suggested that terfenadine prolonged the QTc interval and decreased ventricular tachycardia duration. The potential protective effect of terfenadine in ventricular arrhythmia may be similar to that of amiodarone.

Abnormal mitochondrial function is common in cancer cells and activates metabolic pathways suppressed in normal tissues. Experimental and clinical studies suggest that mitochondria might serve as targets for novel anticancer therapies. We investigated whether mitochondrial metabolism-interfering agents (MMIAs) available currently in clinical practice affect cancer cell mitochondrial metabolism and synergize with chemotherapy and radiotherapy. Two cancer cell lines A549 (lung cancer) and DU145 (prostate cancer) were treated with a variety of MMIAs (metformin, nimodipine, memantine, oxytetracycline, amiodarone, and sodium azide) and their response was assessed using a resazurin reduction method and confocal microscopy. Focusing on amiodarone and metformin, we investigated their potential sensitizing effect on cancer cells when treated with ionizing radiation, cisplatin, and docetaxel. Resazurin reduction was increased by metformin and decreased by amiodarone at nontoxic concentrations. Amiodarone induced mitochondrial swelling, whereas metformin exerted no apparent effect on their morphology. Amiodarone and metformin exerted a weak radiosensitization effect on A549, whereas a synergetic activity with cisplatin and docetaxel was evident in both cell lines. It can be concluded that amiodarone and metformin, being well-established drugs in clinical practice, constitute two potential drugs for further experimental and clinical evaluation as cancer cell sensitizers to chemotherapy and radiotherapy.

Brugada syndrome predisposes individuals to ventricular arrhythmias and sudden cardiac death, in the absence of structural heart disease. The typical Brugada electrocardiogram (ECG) phenotype is often concealed in affected population, and the existing genetic testing is capable of detecting just about 20% of cases. Therefore, the diagnosis largely requires various pharmacological provocative agents like class I antiarrhythmic drugs to unmask the unique features of Brugada ECG phenotype. We report an unusual case of "unmasking" of Brugada ECG pattern with ventricular tachycardia brought out by amiodarone infusion.

Granulomatous amoebic encephalitis (GAE) is caused by two protist pathogens, Acanthamoeba spp., and Balamuthia mandrillaris. Although rare, it almost always results in death. In the present study, amoebae were treated with various combinations of clinically-approved drugs, targeting vital cellular receptors and biochemical pathways. The results revealed that among the seven different combinations tested, three proved highly effective against both Acanthamoeba castellanii as well as B. mandrillaris at a concentration of 100μM. These combinations included (i) prochlorperazine plus loperamide; (ii) prochlorperazine plus apomorphine; and (iii) procyclidine plus loperamide. In viability assays, none of the drug-treated amoebae emerged as viable trophozoites, suggesting irreversible amoebicidal effects. Four combinations of drugs tested showed varied potency against A. castellanii and B. mandrillaris at 100μM. The combination of haloperidol and loperamide was highly effective against A. castellanii at 100μM, but potent effects against B. mandrillaris were observed only at 250μM. Digoxin and amlodipine were effective against A. castellanii and B. mandrillaris at 100μM and 250μM, respectively. In contrast, the combination of apomorphine and haloperidol was effective against B. mandrillaris and A. castellanii at 100μM and 250μM, respectively. At 100μM, the combination of procyclidine and amiodarone was effective against neither A. castellanii nor B. mandrillaris. In this case, amoebicidal properties were observed at 750μM for A. castellanii, and 950μM for B. mandrillaris. As these drugs are used clinically against non-communicable diseases, the findings reported here have the potential to be tested in a clinical setting against amoebic encephalitis caused by A. castellanii and B. mandrillaris., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The pacemaker current If conducted by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels plays a critical role in the regulation of cardiac automaticity, with If density increased in hypertrophied ventricular myocytes. Amiodarone, a highly effective anti-arrhythmic agent, blocks human HCN currents and native If under normal conditions. To determine the effects of amiodarone under pathological conditions, we monitored If under after both acute (0.01, 0.1, 1, 10 and 100 μmol/L) and chronic (10 μmol/L) amiodarone treatment in ventricular myocytes from spontaneously hypertensive rats (SHR) with left ventricular hypertrophy using the whole-cell patch-clamp technique. The If current density was significantly greater in SHR ventricular myocytes than in cells from healthy normotensive control Wistar-Kyoto (WKY) rats. Acute application of amiodarone significantly decreased If density in myocytes from both SHR and WKY rats. The inhibition was concentration dependent with an IC50 of 4.9 ± 1.2 and 6.9 ± 1.3 μmol/L in myocytes from SHR and WKY rats, respectively. Amiodarone increased the activation and deactivation times of If in myocytes from SHR, although it did not alter the relationship of voltage-dependent activation and the reversal potential of If in myocytes from SHR. Chronic exposure of myocytes from SHR to amiodarone potently inhibited If and downregulated HCN2 and HCN4, the major channel subtypes underlying native If , at both the mRNA and protein level. These findings indicate that amiodarone inhibits If under hypertrophied conditions through dual mechanisms: (i) direct channel blockade of If currents; and (ii) indirect suppression via negative regulation of HCN channel gene expression. These unique properties of amiodarone may contribute to its anti-arrhythmic properties under pathological conditions., (© 2014 Wiley Publishing Asia Pty Ltd.)

Objective: Postoperative atrial fibrillation (POAF) is the most common complication after cardiac surgery, leading to increased morbidity and mortality. The aim of this preliminary study was to evaluate a novel drug delivery system for local release of amiodarone., Methods: In the current prospective study, 9 goats underwent attachment of right atrial (RA) epicardial electrodes. Alginate-based glue with amiodarone was applied to the RA of the treatment groups. Rapid atrial response (RAR) to burst pacing was assessed before application and in the third postoperative day (POD3). Average RAR frequency was defined as the average percentage of inductions resulting in RAR per animal. Myocardial and extracardiac tissue amiodarone concentrations were analyzed., Results: Differences in RAR proportions between baseline and POD3 were greater in the treatment group versus the control group (P = .034). Average RAR frequency was reduced by 34% in the treatment group (baseline: 65%; POD3: 31%), while it was increased by 11.3% in the control (baseline:43.8%; POD3: 55%). The treatment group demonstrated a greater proportion of animals meeting the success criterion of net percentage reduction in RAR frequency greater than 25% (P = .047). The average amount of total amiodarone detected in the RA was 104.4 ± 28.9 µg; the transmural concentration was linearly distributed (P < .0001). Extracardiac tissue concentrations were below the detection level., Conclusions: Local alginate-based amiodarone delivery demonstrated an RAR frequency reduction of clinical importance in response to burst pacing. The electrophysiological response was achieved while maintaining below-detection systemic drug levels. Current findings may point to the system's future applicability in reducing POAF risk in humans., (© The Author(s) 2014.)

Objectives: Filoviruses such as Ebola virus and Marburg virus cause a severe haemorrhagic fever syndrome in humans for which there is no specific treatment. Since filoviruses use a complex route of cell entry that depends on numerous cellular factors, we hypothesized that there may be drugs already approved for human use for other indications that interfere with signal transduction or other cellular processes required for their entry and hence have anti-filoviral properties., Methods: We used authentic filoviruses and lentiviral particles pseudotyped with filoviral glycoproteins to identify and characterize such compounds., Results: We discovered that amiodarone, a multi-ion channel inhibitor and adrenoceptor antagonist, is a potent inhibitor of filovirus cell entry at concentrations that are routinely reached in human serum during anti-arrhythmic therapy. A similar effect was observed with the amiodarone-related agent dronedarone and the L-type calcium channel blocker verapamil. Inhibition by amiodarone was concentration dependent and similarly affected pseudoviruses as well as authentic filoviruses. Inhibition of filovirus entry was observed with most but not all cell types tested and was accentuated by the pre-treatment of cells, indicating a host cell-directed mechanism of action. The New World arenavirus Guanarito was also inhibited by amiodarone while the Old World arenavirus Lassa and members of the Rhabdoviridae (vesicular stomatitis virus) and Bunyaviridae (Hantaan) families were largely resistant., Conclusions: The ion channel blockers amiodarone, dronedarone and verapamil inhibit filoviral cell entry., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Amiodarone is an effective antiarrhythmic drug for supra-ven-tri-cular and ventricular arrhythmias. A majority of patients treated with amiodarone suffer from mild adverse events, however, serious life-threatening adverse events caused by amiodarone are also seen. This review describes the pharmacology, interac-tions, side and adverse effects of amiodarone and highlights the importance of a systematic interdisciplinary follow-up protocol for outpatients treated with amiodarone.

Background: Adrenaline (ADR) and vasopressin (VAS) are used as vasopressors during cardiopulmonary resuscitation. Data regarding their effects on blood-brain barrier (BBB) integrity and neuronal damage are lacking. We hypothesised that VAS given during cardiopulmonary resuscitation (CPR) after haemorrhagic circulatory arrest will preserve BBB integrity better than ADR., Methods: Twenty-one anaesthetised sexually immature male piglets (with a weight of 24.3 ± 1.3 kg) were bled 35% via femoral artery to a mean arterial blood pressure of 25 mmHg in the period of 15 min. Afterwards, the piglets were subjected to 8 min of untreated ventricular fibrillation followed by 15 min of open-chest CPR. At 9 min of circulatory arrest, piglets received amiodarone 1.0 mg/kg and hypertonic-hyperoncotic solution 4 ml/kg infusions for 20 min. At the same time, VAS 0.4 U/kg was given intravenously to the VAS group (n = 9) while the ADR group received ADR 20 μg/kg (n = 12). Internal defibrillation was attempted from 11 min of cardiac arrest to achieve restoration of spontaneous circulation. The experiment was terminated 3 h after resuscitation., Results: The intracranial pressure (ICP) in the post-resuscitation phase was significantly greater in ADR group than in VAS group. VAS group piglets exhibited a significantly smaller BBB disruption compared with ADR group. Cerebral pressure reactivity index showed that cerebral blood flow autoregulation was also better preserved in VAS group., Conclusions: Resuscitation with ADR as compared with VAS after haemorrhagic circulatory arrest increased the ICP and impaired cerebrovascular autoregulation more profoundly, as well as exerted an increased BBB disruption though no significant difference in neuronal injury was observed., (© 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.)

Background: Drug interaction studies selecting patients in a real-life setting are scarce, and most studies to date are characterized by a small sample size., Objective: To evaluate the effect of amiodarone on warfarin maintenance dose and adverse events in an anticoagulation cohort from a tertiary cardiovascular service., Methods: This study recruited 866 patients, and oral anticoagulant therapy was monitored by the prothrombin time expressed as the international normalized ratio (INR). Genotyping of CYP2C9*2, CYP2C9*3, and VKORC1 3673 polymorphisms was performed., Results: Of the 866 patients, 111 (12.8%) were taking amiodarone and warfarin simultaneously, and 514 (59.4%) reached the therapeutic target dose. The warfarin maintenance dose was significantly lower in patients simultaneously using amiodarone (23.8 ± 11.3 mg/wk) compared with other patients (29.5 ± 14.3 mg/wk; P < 0.001). Patients taking amiodarone had higher INR/current dose ratios (0.83 ± 0.04 per mg) compared with patients not using amiodarone (0.71 ± 0.02 per mg, P = 0.001). Adverse event frequency was not different between the groups (P = 0.40). No genotype effect was noted on the odds of bleeding associated with amiodarone use., Conclusions: Simultaneous use of amiodarone influences warfarin maintenance dose, but is not associated with adverse events.

The growing interest in the composition and effects of microbiota raised the question how drug pharmacokinetics could be influenced by concomitant application of probiotics. The aim of this study was to find whether probiotic E. coli strain Nissle 1917 (EcN) influences the pharmacokinetics of concomitantly taken antiarrhythmic drug amiodarone (AMI). Live bacterial suspension of probiotic EcN (or non-probiotic E. coli strain ATCC 25922) was applied orally to male Wistar rats for seven days, while a control group of rats was treated with a saline solution. On the eighth day, the amiodarone hydrochloride was administered as one single oral dose (50 mg/kg) to all rats (N = 60). After 0, 1, 2, 3, 4, 5.5, 7, 9, 14, 22, and 30 hours, blood samples were taken from the rat abdominal aorta. The plasma level of AMI and its metabolite N-desethylamiodarone (DEA) was determined using the HPLC with UV detection. Administration of EcN led to a 43% increase of AMI AUC0-30 in comparison with control samples. However, this effect was not observed if EcN was replaced by a reference non-probiotic E. coli strain. Thus, EcN administration was most probably responsible for better drug absorption from the gastrointestinal tract. Plasma levels of DEA were also increased in plasma samples from animals treated with EcN. This change was again not found in the experiment with the reference non-probiotic strain. Higher DEA levels in samples from EcN-treated rats may be explained either by better absorption of AMI and/or by an increased activity of CYP2C forms, known to participate in metabolism of this drug, after EcN administration. In this paper, it is documented that concomitantly taken probiotic EcN may modulate pharmacokinetics of a drug; in this case, it led to an increased bioavailability of AMI.

Unlabelled: In hepatocellular carcinoma (HCC), dysregulated expression of microRNA-224 (miR-224) and impaired autophagy have been reported separately. However, the relationship between them has not been explored. In this study we determined that autophagy is down-regulated and inversely correlated with miR-224 expression in hepatitis B virus (HBV)-associated HCC patient specimens. These results were confirmed in liver tumors of HBV X gene transgenic mice. Furthermore, miR-224 was preferentially recruited and degraded during autophagic progression demonstrated by real-time polymerase chain reaction and miRNA in situ hybridization electron microscopy after extraction of autophagosomes. Our in vitro study demonstrated that miR-224 played an oncogenic role in hepatoma cell migration and tumor formation through silencing its target gene Smad4. In HCC patients, the expression of low-Atg5, high-miR-224, and low-Smad4 showed significant correlation with HBV infection and a poor overall survival rate. Autophagy-mediated miR-224 degradation and liver tumor suppression were further confirmed by the autophagy inducer amiodarone and miR-224 antagonist using an orthotopic SD rat model., Conclusion: A noncanonical pathway links autophagy, miR-224, Smad4, and HBV-associated HCC. These findings open a new avenue for the treatment of HCC., (Copyright © 2013 The Authors. HEPATOLOGY published by Wiley on behalf of the American Association for the Study of Liver Diseases.)

Background: Survival after out-of-hospital cardiac arrest (OHCA) remains poor. Acute coronary obstruction is a major cause of OHCA. We hypothesize that early coronary reperfusion will improve 24h-survival and neurological outcomes., Methods: Total occlusion of the mid LAD was induced by balloon inflation in 27 pigs. After 5min, VF was induced and left untreated for 8min. If return of spontaneous circulation (ROSC) was achieved within 15min (21/27 animals) of cardiopulmonary resuscitation (CPR), animals were randomized to a total of either 45min (group A) or 4h (group B) of LAD occlusion. Animals without ROSC after 15min of CPR were classified as refractory VF (group C). In those pigs, CPR was continued up to 45min of total LAD occlusion at which point reperfusion was achieved. CPR was continued until ROSC or another 10min of CPR had been performed. Primary endpoints for groups A and B were 24-h survival and cerebral performance category (CPC). Primary endpoint for group C was ROSC before or after reperfusion., Results: Early compared to late reperfusion improved survival (10/11 versus 4/10, p=0.02), mean CPC (1.4±0.7 versus 2.5±0.6, p=0.017), LVEF (43±13 versus 32±9%, p=0.01), troponin I (37±28 versus 99±12, p=0.005) and CK-MB (11±4 versus 20.1±5, p=0.031) at 24-h after ROSC. ROSC was achieved in 4/6 animals only after reperfusion in group C., Conclusions: Early reperfusion after ischemic cardiac arrest improved 24h survival rate and neurological function. In animals with refractory VF, reperfusion was necessary to achieve ROSC., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Background and Purpose: In vitro inhibitory potency (Ki )-based predictions of P-glycoprotein (P-gp)-mediated drug-drug interactions (DDIs) are hampered by the substantial variability in inhibitory potency. In this study, in vivo-based [I]/Ki values were used to predict the DDI risks of a P-gp substrate dabigatran etexilate (DABE) using physiologically based pharmacokinetic (PBPK) modelling., Experimental Approach: A baseline PBPK model was established with digoxin, a known P-gp substrate. The Km (P-gp transport) of digoxin in the baseline PBPK model was adjusted to Km (i) to fit the change of digoxin pharmacokinetics in the presence of a P-gp inhibitor. Then 'in vivo' [I]/Ki of this P-gp inhibitor was calculated using Km (i) /Km . Baseline PBPK model was developed for DABE, and the 'in vivo' [I]/Ki was incorporated into this model to simulate the static effect of P-gp inhibitor on DABE pharmacokinetics. This approach was verified by comparing the observed and the simulated DABE pharmacokinetics in the presence of five different P-gp inhibitors., Key Results: This approach accurately predicted the effects of five P-gp inhibitors on DABE pharmacokinetics (98-133% and 89-104% for the ratios of AUC and Cmax respectively). The effects of 16 other P-gp inhibitors on the pharmacokinetics of DABE were also confidently simulated., Conclusions and Implications: 'In vivo' [I]/Ki and PBPK modelling, used in combination, can accurately predict P-gp-mediated DDIs. The described framework provides a mechanistic basis for the proper design of clinical DDI studies, as well as avoiding unnecessary clinical DDI studies., (© 2013 The British Pharmacological Society.)

Although drug induced steatosis represents a mild type of hepatotoxicity it can progress into more severe non-alcoholic steatohepatitis. Current models used for safety assessment in drug development and chemical risk assessment do not accurately predict steatosis in humans. Therefore, new models need to be developed to screen compounds for steatogenic properties. We have studied the usefulness of mouse precision-cut liver slices (PCLS) as an alternative to animal testing to gain more insight into the mechanisms involved in the steatogenesis. To this end, PCLS were incubated 24 h with the model steatogenic compounds: amiodarone (AMI), valproic acid (VA), and tetracycline (TET). Transcriptome analysis using DNA microarrays was used to identify genes and processes affected by these compounds. AMI and VA upregulated lipid metabolism, whereas processes associated with extracellular matrix remodelling and inflammation were downregulated. TET downregulated mitochondrial functions, lipid metabolism, and fibrosis. Furthermore, on the basis of the transcriptomics data it was hypothesized that all three compounds affect peroxisome proliferator activated-receptor (PPAR) signaling. Application of PPAR reporter assays classified AMI and VA as PPARγ and triple PPARα/(β/δ)/γ agonist, respectively, whereas TET had no effect on any of the PPARs. Some of the differentially expressed genes were considered as potential candidate biomarkers to identify PPAR agonists (i.e. AMI and VA) or compounds impairing mitochondrial functions (i.e. TET). Finally, comparison of our findings with publicly available transcriptomics data showed that a number of processes altered in the mouse PCLS was also affected in mouse livers and human primary hepatocytes exposed to known PPAR agonists. Thus mouse PCLS are a valuable model to identify early mechanisms of action of compounds altering lipid metabolism.

Use of molecular pharmacology to reprofile older drugs discovered before the advent of recombinant technologies is a fruitful method to elucidate mechanisms of drug action, expand understanding of structure-activity relationships between drugs and receptors, and in some cases, repurpose approved drugs. The H3 histamine receptor is a G-protein-coupled receptor (GPCR) primarily expressed in the central nervous system where among many things it modulates cognitive processes, nociception, feeding and drinking behavior, and sleep/wakefulness. In binding assays and functional screens of the H3 histamine receptor, the antiarrhythmic drugs lorcainide and amiodarone were identified as potent, selective antagonists/inverse agonists of human and rat H3 histamine receptors, with relatively little or no activity at over 20 other monoamine GPCRs, including H1, H2, and H4 receptors. Potent antagonism of H3 receptors was unique to amiodarone and lorcainide of 20 antiarrhythmic drugs tested, representing six pharmacological classes. These results expand the pharmacophore of H3 histamine receptor antagonist/inverse agonists and may explain, in part, the effects of lorcainide on sleep in humans.

Dronedarone and amiodarone are cationic lipophilic benzofurans used to treat cardiac arrhythmias. They also have activity against the parasitic protozoan Trypanosoma cruzi, the causative agent of Chagas' disease. They function by disrupting intracellular Ca2+ homeostasis of the parasite and by inhibiting membrane sterol (ergosterol) biosynthesis. Amiodarone also has activity against Leishmania mexicana, suggesting that dronedarone might likewise be active against this organism. This might be of therapeutic interest, since dronedarone is thought to have fewer side effects in humans than does amiodarone. We show here that dronedarone effectively inhibits the growth of L. mexicana promastigotes in culture and, more importantly, has excellent activity against amastigotes inside infected macrophages (the clinically relevant form) without affecting the host cell, with the 50% inhibitory concentrations against amastigotes being 3 orders of magnitude lower than those obtained previously with T. cruzi amastigotes (0.65 nM versus 0.75 μM). As with amiodarone, dronedarone affects intracellular Ca2+ homeostasis in the parasite, inducing an elevation of intracellular Ca2+ levels. This is achieved by rapidly collapsing the mitochondrial membrane potential and inducing an alkalinization of acidocalcisomes at a rate that is faster than that observed with amiodarone. We also show that dronedarone inhibits parasite oxidosqualene cyclase, a key enzyme in ergosterol biosynthesis known to be vital for survival. Overall, our results suggest the possibility of repurposing dronedarone as a treatment for cutaneous, and perhaps other, leishmaniases.

Objective: To compare the acute ability of amiodarone and dronedarone (a noniodinated benzofuran derivative with a pharmacologic profile similar to amiodarone) to prevent premature ventricular contractions (PVCs) occurrence., Methods: We used an in vitro model of rabbit right ventricle mimicking the "border zone" existing between normal and ischemic/reperfused regions to test acute electrophysiological effects of dronedarone and amiodarone both at 1 and 10 μmol/L., Results: Similar to amiodarone, dronedarone affected action potential parameters with multichannel blocking properties. Dronedarone at both concentrations was equivalent to amiodarone regarding PVCs occurrence, except regarding extrasystoles occurrence during the reperfusion period (dronedarone, 10 μmol/L, was superior to amiodarone with extrasystoles incidence at 33% and 50%, respectively vs. 92% in controls, P < 0.05). Both dronedarone and amiodarone systematically induced conduction blocks during simulated ischemia (in 100% of preparations vs. 42% in controls, P < 0.05) and a marked decrease of Vmax (to 24 and 23 V/s at 10 minutes of ischemia with 1 and 10 μmol/L dronedarone versus 65 V/s in controls, P < 0.05), thus indicating class 1 antiarrhythmic effects. Both dronedarone and amiodarone at 10 μmol/L induced an increase of APD90 dispersion between normal and ischemic regions, without pro-arrhythmic effects., Conclusions: Dronedarone and amiodarone have very similar electrophysiological effects in this in vitro model of border zone and were both efficient in preventing PVCs occurrence particularly through a class 1 antiarrhythmic effect.

Therapy for HIV often can make pharmacologic management of comorbidities challenging since many antiretroviral agents significantly modulate drug metabolism pathways. Amiodarone is commonly used to control cardiac arrhythmias; however, it is recognized as having a narrow therapeutic window with potential for significant drug toxicity. Amiodarone is metabolized by CYP3A4, CYP2C8 and CYP1A1 to an active metabolite and therefore may be affected by comedications that modulate these isoenzymes. Since amiodarone is frequently associated with toxicity, the Heart Rhythm Society (formerly the North American Society of Pacing and Electrophysiology) developed guidelines to minimize the potential for adverse events. However, recommendations for the management of situations where amiodarone must be given with a drug that significantly affects its metabolism are lacking. This paper will discuss our experience with a case of concurrent amiodarone and antiretroviral therapy, as well as provide a review of interactions that may lead to toxicity or potential treatment failure with amiodarone. Primary literature was identified through Medline (1946 to May 2013) and Embase (1980 to May 2013), using the following terms: amiodarone, antiretroviral, HIV, cytochrome P450 and drug interaction. Case reports, studies of xenobiotic interactions with amiodarone in healthy volunteers, and in vitro studies that investigated metabolic pathways of amiodarone were reviewed. Although clinical data was limited, several cases support the finding that potent inhibitors or inducers of cytochrome P450 may lead to amiodarone toxicity or lack of therapeutic effect, respectively. As well, several case reports, in vitro data and clinical investigations have associated some of the antiretrovirals with QT prolongation, which may result in additive cardiotoxicity in patients also receiving amiodarone. Therefore, to manage situations where amiodarone must be used with concurrent interacting antiretrovirals, we recommend a monitoring plan that follows the Heart Rhythm Society guidelines, however with the addition of serial therapeutic drug level monitoring and frequent electrocardiography to minimize potential toxicity and successfully manage both conditions.

Background/aims: Cardiac action potential duration (APD) is regulated by heart rate, leading to the trans-membrane movement of inorganic ions. Whether the alteration of heart rate can affect the expression of transient receptor potential canonical channels (TRPCs), further studies should be made. We investigated the changes of APD at different stimulus frequencies and their influences on the expression of TRPCs in rabbit ventricular myocardium., Methods: Monophasic action potential (MAP) was recorded by contact electrode technique in different programmed stimulus frequencies on rabbit ventricular epicardium in vivo, and the expression of TRPCs was detected using RT-PCR and Western blot., Results: At the frequency range of 4.5-7.5 Hz, APD gradually shortened with the increase of stimulus frequency, showing the property of significant frequency dependence in rabbit ventricular myocardium in vivo. Compared with 4.5 Hz group, TRPC3 mRNA and protein expression increased in 6 Hz and 7.5 Hz groups by way of frequency dependence. Both amiodarone (AM) and neferine (Nef) could prolongate APD and showed characters of frequency independence at the designed frequency. In contrast with 4.5 Hz control group, it was Nef treatment group rather than AM treatment group that could obviously increase the expression of TRPC3 mRNA and protein., Conclusions: At the frequency range of 4.5-7.5 Hz, frequency-dependent shortening of APD was associated with the expression of TRPC3. AM and Nef exhibited frequency-independent lengthening of the APD. Nef may prolong APD via the increasement of TRPC3., (© 2014 S. Karger AG, Basel.)

HCV (hepatitis C virus) infection affects an estimated 180 million people in the world's population. Adverse effects occur frequently with current standard treatment of interferon and ribavirin, while resistance of new direct anti-viral agents, NS3 protease inhibitors, is a major concern because of their single anti-HCV mechanism against the viral factor. New anti-viral agents are needed to resolve the problems. Amiodarone, an anti-arrhythmic drug, has recently been shown to inhibit HCV infection in vitro. The detailed mechanism has yet to be clarified. The aim of the present study was to elucidate the molecular mechanism of the inhibitory effect of amiodarone on HCV life cycle. The effect of amiodarone on HCV life cycle was investigated in Huh-7.5.1 cells with HCVcc (cell culture-derived HCV), HCVpp (HCV pseudoviral particles), sub-genomic replicons, IRES (internal ribosomal entry site)-mediated translation assay, and intracellular and extracellular infectivity assays. The administration of amiodarone appeared to inhibit HCV entry independent of genotypes, which was attributed to the down-regulation of CD81 receptor expression. The inhibitory effect of amiodarone also manifested in the HCV assembly step, via the suppression of MTP (microsomal triacylglycerol transfer protein) activity. Amiodarone revealed no effects on HCV replication and translation. With the host factor-targeting characteristics, amiodarone may be an attractive agent for the treatment of HCV infection.

Dronedarone is a relatively new antiarrhythmic drug approved for paroxysmal or persistent atrial fibrillation. Dronedarone can inhibit P-glycoprotein-mediated digoxin clearance and increase steady-state digoxin level 2.5 times. It is important to closely monitor plasma digoxin levels or administer a lower loading dose of digoxin in patients taking dronedarone concomitantly. We report a case of digoxin toxicity in a patient taking concomitant dronedarone as a result of interaction between digoxin and dronedarone.

Background: Large animal models serve as a critical link in the translation of basic science to clinical practice. However, large animal models of myocardial infarction (MI), especially large size MI, have been associated with high mortality because of arrhythmia. The prophylactic effect of amiodarone and lidocaine were retrospectively reviewed in our ovine MI model., Materials and Methods: A total of 114 Dorset hybrid sheep with 25%-30% MI were included in the present study. The sheep were prophylactically treated with amiodarone plus lidocaine before ligation of the four to six coronary artery branches supplying the apex of the heart (arrhythmia prevention [AP] group, n = 45) and with epinephrine (shock prevention [SP] group, n = 49), respectively. The sheep without prophylactic treatment (no prevention [NP] group, n = 20) were used as the control group. The incidence of arrhythmia requiring treatment, mortality due to arrhythmia, hemodynamics, and arterial blood gas values during surgery were analyzed in these three groups., Results: No significant difference was found in infarct size among the three groups. The incidence of arrhythmia requiring treatment was significantly decreased in the AP group compared with that in the NP or SP groups (4.4% for AP versus 35% for NP and 45% for SP groups; P < 0.05). The mortality due to lethal arrhythmia was 2.2% in the AP group, significantly lower than that in the NP group (15%) or SP group (18.4%). Other than the heart rate, no significant differences were found in the hemodynamic data between the AP and NP groups. Metabolic acidosis was not observed in any group, as indicated by the pH and lactate values., Conclusions: Prophylactic amiodarone plus lidocaine decreased the mortality due to lethal arrhythmia after acute MI in our sheep model without significant negative effects on the hemodynamics. However, epinephrine improved the hemodynamics but also increased the mortality due to lethal arrhythmia. Thus, prophylactic amiodarone plus lidocaine is recommended to improve the stability in a large MI animal model., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Cruzipain (Cz) is the major cystein protease of the protozoan Trypanosoma cruzi , etiological agent of Chagas disease. From a 163 compound data set, a 2D-classifier capable of identifying Cz inhibitors was obtained and applied in a virtual screening campaign on the DrugBank database, which compiles FDA-approved and investigational drugs. Fifty-four approved drugs were selected as candidates, four of which were acquired and tested on Cz and T. cruzi epimastigotes. Among them, the antiparkinsonian and antidiabetic drug bromocriptine and the antiarrhythmic amiodarone showed dose-dependent inhibition of Cz and antiproliferative activity on the parasite.