Mechanisms of zolpidem-induced long QT syndrome: acute inhibition of recombinant hERG K(+) channels and action potential prolongation in human cardiomyocytes derived from induced pluripotent stem cells

Tizanidine-Induced Bradycardia Without Concomitant Medications: A Case Report

A 37-year-old woman was admitted to our hospital due to a loss of consciousness. She had been taking 2 mg of tizanidine for two months to manage shoulder muscle pain at night. On admission, an electrocardiogram showed sinus bradycardia with a heart rate of 30 bpm and QT prolongation (QTc 495 msec). She had a temporary pacemaker inserted in the catheterization room, after which an improvement in her level of consciousness was observed. There were no apparent endocrine disorders or structural heart diseases. The administration was discontinued after admission, and 12 hours after admission, her heart rate normalized to a sinus rhythm of 70-100 bpm, and QTc improved to 431 msec. Therefore, she was diagnosed with tizanidine-induced bradycardia. Although reports of tizanidine-induced bradycardia are rare, tizanidine's central α2 agonistic effects can cause bradycardia, necessitating caution.

Examining the relationship between long working hours and the use of prescription sedatives among U.S. workers

OBJECTIVES

The prevalence of long working hours has been accompanied by a corresponding rise in sleep disorders. Sedative-hypnotic agents (SHAs), have been reported as the second most commonly misused drug class in the U.S. The key objective of this study was to examine the relationship between working hours on the use of sleep aids and medications with sedative properties.

METHODS

The 2010-2019 Medical Expenditure Panel Survey data was utilized. SHAs and medications with sedative related properties (MSRPs) were identified. Furthermore, we employed different regression models ranging from multivariable linear regression, Tobit regression, Heckman regression, and multivariable logistic regression, to ensure consistency, robustness, and reliability of associations.

RESULTS

Overall, a sample of 81,518 observations of full-time workers was analyzed. Working 56hours or more per week was significantly associated (p < 0.05) with an increased odds of using SHAs and MSRPs by 13% (Adjusted Odds Ratio, aOR =1.13, 95% Confidence Interval, CI=1.01:1.26) and 9% (aOR=1.09, 95% CI=1.03:1.16), respectively more than that among those who worked fewer hours. Females in our study had a higher likelihood (aOR=1.11, 95% CI=1.05:1.19) of using SHAs when compared to males. Also, professional services had the highest likelihood (aOR=1.31, 95% CI=1.14:1.50) of using SHAs.

CONCLUSION

We found that long working hours were significantly associated with an elevated use of SHAs and MSRPs among U.S. workers. Specifically, female workers and individuals working in professional services had the highest likelihood of using sleep medications.

Sleep-enhancing Effects of Phytoncide Via Behavioral, Electrophysiological, and Molecular Modeling Approaches

Sleep is indispensable for living animals to live and maintain a normal life. Due to the growing number of people suffering from sleep disorders such as insomnia, there have been increasing interests in environmentally friendly therapeutic approaches for sleep disorders to avoid any side effects of pharmacological treatment using synthetic hypnotics. It has been widely accepted that the various beneficial effects of forest, such as relieving stress and anxiety and enhancing immune system function, are caused by plant-derived products, also known as phytoncide. Recently, it has been reported that the sleep-enhancing effects of phytoncide are derived from pine trees such as (-)-α-pinene and 3-carene. These are the major constituents of pine tree that potentiate the inhibitory synaptic responses by acting as a positive modulator for GABA_A-BZD receptor. In this review, we discuss the effects of phytoncide on sleep and review the latest approaches of sleep-related behavioral assay, electrophysiological recording, and molecular modeling technique.

Late presentation of Torsades de Pointes related to fluoxetine following a multiple drug overdose

Background

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) commonly used in the treatment of depression. While most intoxications with SSRI’s have favorable outcomes and do not require interventions other than strict observation of vital signs and heart rhythm, clinicians should be aware of the life-threatening complications that may occur.

Case presentation

A 61-year-old woman presented to the emergency department after an intentional multiple drug overdose. Upon examination, she was somnolent with stable respiration and hemodynamics. Electrocardiography showed a prolonged QTc interval of 503 ms. The patient was admitted to the ICU for cardiopulmonary monitoring. During admission, the patient remained stable and showed improved neurologic function over time. After 22 h, a second ECG showed normalization of the QTc interval to 458 ms. However, 36 to 40 h after admission, our patient developed recurrent episodes of Torsades de Pointes (TdP) with loss of cardiac output, leading to cardiopulmonary resuscitation. Spontaneous circulation was restored after intravenous administration of magnesium sulphate. Retrospective serum analysis revealed fluoxetine concentrations of 2700 mcg/l.

Conclusion

Most intoxications with selective serotonin reuptake inhibitors (SSRI) have favorable outcomes and do not require medical interventions other than strict cardiopulmonary observation. However, higher doses have been associated with QTc interval prolongation, TdP, serotonin syndrome, and death. This case illustrates that life-threatening complications may occur late in the course of hospital admission. Even though overdoses with SSRI’s generally result in few fatalities, clinicians should be aware of the life-threatening clinical manifestations that may occur. Despite being an imperfect predictor of imminent TdP, continuous monitoring of cardiac rhythm is strongly recommended when either cardiac or non-cardiac symptoms are present.

Use of hypnotics and the risk of or mortality from heart disease: a meta-analysis of observational studies

BACKGROUND/AIMS

Some observational epidemiologic studies have reported conflicting results on the relationship between hypnotics use and the risk of developing and/or dying from heart disease. We investigated these associations using a meta-analysis of available literatures.

METHODS

We searched the databases PubMed and EMBASE, along with the bibliographies of relevant articles to find additional publications in February 2016.

RESULTS

Of 495 articles satisfying our initial criteria, two case-control studies and six cohort studies met our inclusion criteria and were included in the final analyses. Compared with never having used any kind of hypnotics, the odds ratio for overall use was 0.84 for risk of or mortality from heart disease (95% confidence interval, 0.79 to 0.89) in a random-effects meta-analysis of all eight studies. With respect to the geographical region, use of hypnotics was associated with a decreased risk or mortality of heart disease in Asia but not in Western countries. Among various types of sleep medications, zolpidem showed a decreased risk (-29%) of developing or dying from heart disease, but benzodiazepines were related with an increased risk (80%) of or mortality from heart disease.

CONCLUSIONS

The current meta-analysis of observational epidemiological studies suggested an evidence of association between hypnotics use and a decreased risk of heart disease.

Development and Characterization of a Scaffold-Free 3D Spheroid Model of Induced Pluripotent Stem Cell-Derived Human Cardiomyocytes

Cardiomyocytes (CMs) are terminally differentiated cells in the adult heart, and ischemia and cardiotoxic compounds can lead to cell death and irreversible decline of cardiac function. As testing platforms, isolated organs and primary cells from rodents have been the standard in research and toxicology, but there is a need for better models that more faithfully recapitulate native human biology. Hence, a new in vitro model comprising the advantages of 3D cell culture and the availability of induced pluripotent stem cells (iPSCs) of human origin was developed and characterized. Human CMs derived from iPSCs were studied in standard 2D culture and as cardiac microtissues (MTs) formed in hanging drops. Two-dimensional cultures were examined using immunofluorescence microscopy and western blotting, while the cardiac MTs were subjected to immunofluorescence, contractility, and pharmacological investigations. iPSC-derived CMs in 2D culture showed well-formed myofibrils, cell-cell contacts positive for connexin-43, and other typical cardiac proteins. The cells reacted to prohypertrophic growth factors with a substantial increase in myofibrils and sarcomeric proteins. In hanging drop cultures, iPSC-derived CMs formed spheroidal MTs within 4 days, showing a homogeneous tissue structure with well-developed myofibrils extending throughout the whole spheroid without a necrotic core. MTs showed spontaneous contractions for more than 4 weeks that were recorded by optical motion tracking, sensitive to temperature and responsive to electrical pacing. Contractile pharmacology was tested with several agents known to modulate cardiac rate and viability. Calcium transients underlay the contractile activity and were also responsive to electrical stimulation, caffeine-induced Ca(2+) release, and extracellular calcium levels. A three-dimensional culture using iPSC-derived human CMs provides an organoid human-based cellular platform that is free of necrosis and recapitulates vital cardiac functionality, thereby providing a new and promising relevant model for the evaluation and development of new therapies and detection of cardiotoxicity.

Modeling inherited cardiac disorders

Advances in the understanding and treatment of cardiac disorders have been thwarted by the inability to study beating human cardiac cells in vitro. Induced pluripotent stem cells (iPSCs) bypass this hurdle by enabling the creation of patient-specific iPSC-derived cardiomyocytes (iPSC-CMs). These cells provide a unique platform to study cardiac diseases in vitro, especially hereditary cardiac conditions. To date, iPSC-CMs have been used to successfully model arrhythmic disorders, showing excellent recapitulation of cardiac channel function and electrophysiologic features of long QT syndrome types 1, 2, 3, and 8, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Similarly, iPSC-CM models of dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) have shown robust correlation of predicted morphologic, contractile, and electrical phenotypes. In addition, iPSC-CMs have shown some features of the respective phenotypes for arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), LEOPARD syndrome, Pompe's disease, and Friedriech's ataxia. In this review, we examine the progress of utilizing iPSC-CMs as a model for cardiac conditions and analyze the potential for the platform in furthering the biology and treatment of cardiac disorders.  

HERG K+ channel-dependent apoptosis and cell cycle arrest in human glioblastoma cells

Glioblastoma (GB) is associated with poor patient survival owing to uncontrolled tumor proliferation and resistance to apoptosis. Human ether-a-go-go-related gene K⁺ channels (hERG; Kv11.1, KCNH2) are expressed in multiple cancer cells including GB and control cell proliferation and death. We hypothesized that pharmacological targeting of hERG protein would inhibit tumor growth by inducing apoptosis of GB cells. The small molecule hERG ligand doxazosin induced concentration-dependent apoptosis of human LNT-229 (EC₅₀ = 35 µM) and U87MG (EC₅₀ = 29 µM) GB cells, accompanied by cell cycle arrest in the G0/G1 phase. Apoptosis was associated with 64% reduction of hERG protein. HERG suppression via siRNA-mediated knock down mimicked pro-apoptotic effects of doxazosin. Antagonism of doxazosin binding by the non-apoptotic hERG ligand terazosin resulted in rescue of protein expression and in increased survival of GB cells. At the molecular level doxazosin-dependent apoptosis was characterized by activation of pro-apoptotic factors (phospho-erythropoietin-producing human hepatocellular carcinoma receptor tyrosine kinase A2, phospho-p38 mitogen-activated protein kinase, growth arrest and DNA damage inducible gene 153, cleaved caspases 9, 7, and 3), and by inactivation of anti-apoptotic poly-ADP-ribose-polymerase, respectively. In summary, this work identifies doxazosin as small molecule compound that promotes apoptosis and exerts anti-proliferative effects in human GB cells. Suppression of hERG protein is a crucial molecular event in GB cell apoptosis. Doxazosin and future derivatives are proposed as novel options for more effective GB treatment.

High-content assays for hepatotoxicity using induced pluripotent stem cell-derived cells

Development of predictive in vitro assays for early toxicity evaluation is extremely important for improving the drug development process and reducing drug attrition rates during clinical development. High-content imaging-based in vitro toxicity assays are emerging as efficient tools for safety and efficacy testing to improve drug development efficiency. In this report we have used an induced pluripotent stem cell (iPSC)-derived hepatocyte cell model having a primary tissue-like phenotype, unlimited availability, and the potential to compare cells from different individuals. We examined a number of assays and phenotypic markers and developed automated screening methods for assessing multiparameter readouts of general and mechanism-specific hepatotoxicity. Endpoints assessed were cell viability, nuclear shape, average and integrated cell area, mitochondrial membrane potential, phospholipid accumulation, cytoskeleton integrity, and apoptosis. We assayed compounds with known mechanisms of toxicity and also evaluated a diverse hepatotoxicity library of 240 compounds. We conclude that high-content automated screening assays using iPSC-derived hepatocytes are feasible, provide information about mechanisms of toxicity, and can facilitate the safety assessment of drugs and chemicals.