Rapid Component Research Articles

Electrophysiological characterization of a small molecule activator on human ether-a-go-go-related gene (hERG) potassium channel

The human ether-a-go-go-related gene (hERG) encodes the K+ channel that carries the rapid component of the delayed rectifier current in the human heart. Reduction of hERG activity induced by gene mutations or pharmacological inhibition is responsible for the type 2 form of long QT syndrome in patients which can develop into ventricular arrhythmia and sudden cardiac death. Therefore, pharmacological activation of hERG may lead to therapeutic potential for cardiac arrhythmias. In this study we characterized a small and novel compound, N-(2-(tert-butyl)phenyl)-6-(4-chlorophenyl)-4-(trifluoromethyl) nicotinamide, HW-0168, that exhibits potent activation of hERG channel with an EC50 of 0.41 ± 0.2 μM. Using whole-cell patch clamp recording of HEK293 cells stably expressed hERG channels, we found that HW-0168 dramatically increased current amplitude about 2.5 folds and slowed down current inactivation about 4 folds. HW-0168 shifted the voltage-dependent channel activation to hyperpolarizing direction about 3.7 mV and the voltage-dependent channel inactivation to depolarizing direction about 9.4 mV. In addition, recording of guinea-pig ventricular cells confirmed that HW-0168 shortened the action potential duration. In conclusion, we identified a novel hERG channel activator HW-0168 that can be used for studying the physiological role of hERG in cardiac myocytes and may be beneficial for treating long QT syndrome.

Dofetilide-Induced Microvolt T-Wave Alternans.

Dofetilide is an antiarrhythmic drug that selectively inhibits the rapid component of the delayed rectifier potassium current. The administration of dofetilide may cause ventricular arrhythmias and torsade de pointes. Electrocardiographic (ECG) microvolt T-wave alternans (TWA), an electrophysiologic phenomenon consisting in the beat-to-beat alternation of the T-wave amplitude requiring computerized algorithms to be detected, has also been associated to malignant ventricular arrhythmias. Aim of the present study was to evaluate if dofetilide induces TWA during the 24 hours following administration. The study population consisted of 22 healthy subjects ("ECG Effects of Ranolazine, Dofetilide, Verapamil, and Quinidine in Healthy Subjects" database by Physionet) to whom a 500 μg-dose of dofetilide was administered. For each subject, 10 s ECG were acquired at baseline (0.5 hour before dofetilide administration) and at 15 time points during the 24 hours following the drug administration. ECG were then processed for automatic TWA detection by correlation method. In 21 subjects out of 22, after dofetilide administration, TWA significantly increased to a peak value (median TWA values went from 6 μV at baseline to a max 32 μV; p<; 0.05), on average after 5 hours, to then come back to values closer to baseline. Thus, in healthy subjects, dofetilide increases occurrence and levels (6 times baseline value on average) of TWA in the hours following its administration.

Slope-Weighted Energy-Based Rapid Control Analysis for Hybrid Electric Vehicles

Recent studies have addressed the development of optimal control strategies for hybrid electric vehicles (HEVs). Achieving global optimality for fuel economy prediction while minimizing the computational efficiency still is a research and development challenge. This paper aims at presenting a novel technique for managing the energy flows in a power split HEV named slope-weighted energy-based rapid control analysis (SERCA). After presenting the HEV plant model and the optimal control problem, the currently most adopted energy management strategies are analyzed. The SERCA technique is then illustrated, and its operating steps are detailed. The simulation results for the considered HEV energy management strategies in the standard drive cycles subsequently indicate that the SERCA can efficiently achieve near-optimal fuel economy, while limiting the computational costs. This suggests the potential use of SERCA for rapid component sizing of HEV powertrains.

Digital twin aided sustainability-based lifecycle management for railway turnout systems

Railway turnouts or so-called ‘switches and crossings’ are complex systems by nature of design and construction. Railway turnouts are used to change direction of trains from one to another. They require high-quality construction and maintenance, in order to minimise rapid degradation and component failures that could result in train derailments. Due to the complexity of railway turnouts, the efficiency and effectiveness of maintenance can be improved by integrating existing practice by Building Information Modelling (BIM). This research establishes and analyses the world's first 6D BIM for life cycle management of a railway turnout system. The BIM (Level 3) has integrated 6-dimensions of field data information based on Revit-2018 and Navisworks-2018 platforms. The digital twins of a railway turnout in 3D embrace time schedule, costs and sustainability across the whole life cycle. The use of BIM for railway turnout systems has the potential to improve the overall information flow of the turnout planning and design, manufacturing pre-assembly and logistic, construction and installation, operation and management and demolition, thereby achieving better project performance and quality. Based on integrated information of railway turnout system, the 6D BIM has the ability to assess on economic, management and sustainability, and achieve a balance among them. This is the word first to demonstrate that BIM can fully deliver its essential benefits by information sharing, easing technical communication, improving design quality, reducing of design errors, accelerating implementation, speeding up work, shortening construction duration, reducing construction costs, enhancing carbon efficiency, supporting project management, and providing its owners with higher operational efficiency over the railway turnout system life-cycle. The results reveal that embodied material emission is the main contributor towards carbon footprint, especially produced during the manufacturing stage. The reconstruction stage contributes the most expensive phase of life cycle. The insight will significantly benefit the co-value creation among engineers, project managers, technicians, and senior management team.

Uncertainty in hydrological analysis of climate change: multi-parameter vs. multi-GCM ensemble predictions

The quantification of uncertainty in the ensemble-based predictions of climate change and the corresponding hydrological impact is necessary for the development of robust climate adaptation plans. Although the equifinality of hydrological modeling has been discussed for a long time, its influence on the hydrological analysis of climate change has not been studied enough to provide a definite idea about the relative contributions of uncertainty contained in both multiple general circulation models (GCMs) and multi-parameter ensembles to hydrological projections. This study demonstrated that the impact of multi-GCM ensemble uncertainty on direct runoff projections for headwater watersheds could be an order of magnitude larger than that of multi-parameter ensemble uncertainty. The finding suggests that the selection of appropriate GCMs should be much more emphasized than that of a parameter set among behavioral ones. When projecting soil moisture and groundwater, on the other hand, the hydrological modeling equifinality was more influential than the multi-GCM ensemble uncertainty. Overall, the uncertainty of GCM projections was dominant for relatively rapid hydrological components while the uncertainty of hydrological model parameterization was more significant for slow components. In addition, uncertainty in hydrological projections was much more closely associated with uncertainty in the ensemble projections of precipitation than temperature, indicating a need to pay closer attention to precipitation data for improved modeling reliability. Uncertainty in hydrological component ensemble projections showed unique responses to uncertainty in the precipitation and temperature ensembles.

Research on the Starting Characteristics and Control Law of Two Spool Turbofan Engine

A rapid and convince component characteristics extrapolation method and starting control law design method were presented in the paper. The component characteristics extrapolation method based on the relationship between flow coefficient and adiabatic pressure head coefficient in low speed region was researched, and the starting process control law of some two-spool turbofan was designed using the Virtual Power Extraction Method (VPEM). The starting characteristics was researched in both steady-state and dynamic-state models, the starting process simulation result was quick and safe, and the validity of the extrapolation method and VPEM were proved.

Sliding Wear Reliability Studies of Inconel 625 Components Manufactured by Direct Metal Deposition (DMD)

Abstract Direct Metal Deposited (DMD) specimens using Inconel 625 were tested for sliding wear and analysed for reliability. In this study, Taguchi’s experimental techniques were used to develop L9 orthogonal array using Design of Experiments (DOE). Three different process parameters, coating thickness, load and temperature were selected for manufacturing the components. Sliding wear test was carried out and wear properties was investigated. Two-parameter Weibull method was used for the reliability studies by which reliability was estimated for different wear values of the manufactured components. The distribution plot on reliability was considered as a good design for Weibull analysis. The study shows that Weibull distribution method can be used for describing the distribution of times to wear properties of rapid prototyped components using DMD for functional applications.

Comparing battery electric vehicle powertrains through rapid component sizing

The current transition from internal combustion engine vehicles to battery electric vehicles (BEVs) requires the development and implementation of novel design methodologies. This paper introduces an original design procedure for battery electric light vehicle powertrains based on rapid brute force optimisation. At first, a large design space is generated by sweeping the relevant design parameters, specifically the motor size, the number of gears and the transmission ratios. Analytical modelling for electric vehicle powertrains is then presented and combined with lookup tables for the actual system components. The feasible candidate designs are identified by introducing evaluation criteria for the transmission ratios according to the vehicle and electric machine data considered. Subsequently, these candidate designs are evaluated in terms of both launching performance and energy consumption by adopting an efficiency based gear-shifting strategy. Optimal designs can finally be graphically identified through a Pareto frontier analysis as effectively demonstrated in the case of four actual vehicles of different classes. The methodology introduced efficiently addresses the non-linear multidimensional optimisation problem of electric vehicle powertrain design.

Drug-Induced QT Interval Prolongation: Mechanisms, Risk Factors, Genetics and Clinical Management

Long QT syndrome LQTS characterized by prolongation of the QT interval, may occur as congenital or drug-induced forms. Drug-induced QT interval prolongation DI-QTP is closely associated with severe ventricular arrhythmias [especially torsade de pointes TdP ] and sudden cardiac death. In particular, development of DI-QTP is generally associated with multiple risk factors. Cardiac and non-cardiac drugs may cause QT interval prolongation QTP and TdP. Most of the QT-prolonging drugs act by blocking the rapid component of the delayed rectifier potassium channel whereas a smaller number of drugs act by modifying Ca2+ and Na+ currents. In addition, pharmacokinetic drug interactions are among the reasons of DI-QTP. The corrected QT interval QTc according to heart rate by Bazett’s formula is the most commonly used. Genetic susceptibility is another important issue in predicting DI-QTP and TdP risk. Silent mutations and/or polymorphisms associated with cardiac ion channels may cause a risk for DI-QTP. Firstly, for treatment, drugs that cause QTP should be stopped rapidly, electrolyte abnormalities and other pathologies should be rapidly corrected. Intravenous magnesium sulphate, overdrive pacing, isoproterenol and plasma alkalinisation via sodium bicarbonate are the main useful treatments for DI-QTP and related TdP therapy. Class 1B antiarrhythmic drugs and intravenous potassium are thought to may be effective in TdP.The purpose of this article is to review the underlying mechanisms of QTP, risk factors and genetics of DI-QTP, how to measurement of QT interval and treatment of acquired LQTS.Key-words: Drugs, QT interval, QT prolongation and torsade de pointes

Comparing battery electric vehicle powertrains through rapid component sizing

The current transition from internal combustion engine vehicles to battery electric vehicles (BEVs) requires the development and implementation of novel design methodologies. This paper introduces an original design procedure for battery electric light vehicle powertrains based on rapid brute force optimisation. At first, a large design space is generated by sweeping the relevant design parameters, specifically the motor size, the number of gears and the transmission ratios. Analytical modelling for electric vehicle powertrains is then presented and combined with lookup tables for the actual system components. The feasible candidate designs are identified by introducing evaluation criteria for the transmission ratios according to the vehicle and electric machine data considered. Subsequently, these candidate designs are evaluated in terms of both launching performance and energy consumption by adopting an efficiency based gear-shifting strategy. Optimal designs can finally be graphically identified through a Pareto frontier analysis as effectively demonstrated in the case of four actual vehicles of different classes. The methodology introduced efficiently addresses the non-linear multidimensional optimisation problem of electric vehicle powertrain design.

Interleukin-6 inhibition of hERG underlies risk for acquired long QT in cardiac and systemic inflammation.

Increased proinflammatory interleukin-6 (IL-6) levels are associated with acquired long QT-syndrome (LQTS) in patients with systemic inflammation, leading to higher risks for life-threatening polymorphic ventricular tachycardia such as Torsades de Pointes. However, the functional and molecular mechanisms of this association are not known. In most cases of acquired LQTS, the target ion channel is the human ether-á-go-go-related gene (hERG) encoding the rapid component of the delayed rectifier K current, IKr, which plays a critical role in cardiac repolarization. Here, we tested the hypothesis that IL-6 may cause QT prolongation by suppressing IKr. Electrophysiological and biochemical assays were used to assess the impact of IL-6 on the functional expression of IKr in HEK293 cells and adult guinea-pig ventricular myocytes (AGPVM). In HEK293 cells, IL-6 alone or in combination with the soluble IL-6 receptor (IL-6R), produced a significant depression of IKr peak and tail current densities. Block of IL-6R or Janus kinase (JAK) reversed the inhibitory effects of IL-6 on IKr. In AGPVM, IL-6 prolonged action potential duration (APD) which was further prolonged in the presence of IL-6R. Similar to heterologous cells, IL-6 reduced endogenous guinea pig ERG channel mRNA and protein expression. The data are first to demonstrate that IL-6 inhibition of IKr and the resulting prolongation of APD is mediated via IL-6R and JAK pathway activation and forms the basis for the observed clinical QT interval prolongation. These novel findings may guide the development of targeted anti-arrhythmic therapeutic interventions in patients with LQTS and inflammatory disorders.

Microvascular mechanisms limiting skeletal muscle blood flow with advancing age.

Effective oxygen delivery to active muscle fibers requires that vasodilation initiated in distal arterioles, which control flow distribution and capillary perfusion, ascends the resistance network into proximal arterioles and feed arteries, which govern total blood flow into the muscle. With exercise onset, ascending vasodilation reflects initiation and conduction of hyperpolarization along endothelium from arterioles into feed arteries. Electrical coupling of endothelial cells to smooth muscle cells evokes the rapid component of ascending vasodilation, which is sustained by ensuing release of nitric oxide during elevated luminal shear stress. Concomitant sympathetic neural activation inhibits ascending vasodilation by stimulating α-adrenoreceptors on smooth muscle cells to constrict the resistance vasculature. We hypothesized that compromised muscle blood flow in advanced age reflects impaired ascending vasodilation through actions on both cell layers of the resistance network. In the gluteus maximus muscle of old (24 mo) vs. young (4 mo) male mice (corresponding to mid-60s vs. early 20s in humans) inhibition of α-adrenoreceptors in old mice restored ascending vasodilation, whereas even minimal activation of α-adrenoreceptors in young mice attenuated ascending vasodilation in the manner seen with aging. Conduction of hyperpolarization along the endothelium is impaired in old vs. young mice because of "leaky" membranes resulting from the activation of potassium channels by hydrogen peroxide released from endothelial cells. Exposing the endothelium of young mice to hydrogen peroxide recapitulates this effect of aging. Thus enhanced α-adrenoreceptor activation of smooth muscle in concert with electrically leaky endothelium restricts muscle blood flow by impairing ascending vasodilation in advanced age.

Abstract 17137: Unmasking Pathological Mechanisms of Long QT Syndrome KCNH2 H70R Variant Using Human iPSC-Cardiomyocytes

Introduction: Inherited long QT syndrome type 2 (LQT2) results from loss-of-function mutations in the KCNH2 gene encoding the hERG channel, which conducts I Kr , the rapid component of the delayed rectifier K + current. The N-terminal Per-Arnt-Sim (PAS) domain present on the hERG1a subunit, but not the hERG1b subunit, is the site of multiple LQT2-linked missense variants. The mechanism of loss of function by many of these missense PAS variants is unclear given conflicting results from different heterologous expression systems expressing hERG1a. Hypothesis: Patient-specific LQT2 human iPSC-cardiomyocytes (hiPSC-CMs) which naturally express hERG1a/1b carrying the KCNH2 H70R variant in the PAS domain will exhibit loss of I Kr associated with APD prolongation due to impaired channel protein trafficking. Methods and Results: Human iPSCs were derived from a patient carrying the LQT2-associated PAS domain mutation KCNH2 H70R, which has been reported to cause impaired hERG channel trafficking without effects on channel gating when expressed in HEK 293 cells but accelerated deactivation kinetics of I hERG when expressed in Xenopus laevis oocytes. Two clones of KCNH2 H70R and unrelated control hiPSCs (DF19-9-11T) were differentiated using monolayer-base, small molecule protocol to CMs, evaluated with whole-cell patch clamp. Action potentials from single hiPSC-CMs paced at 1Hz were prolonged in the hERG-H70R group compared to control (APD 90 439.9 ± 15.3 ms vs. 363.7 ± 29.0ms, p =0.003, H70R: n=11, control: n=9, Temp 36 ± 1°C). Voltage clamp studies showed hERG-H70R hiPSC-CMs had a significantly smaller peak tail I Kr current density (1.1 ± 0.3 vs. 2.9 ± 0.5 pA/pF, p &lt;0.001, H70R: n=11, control: n=7, Temp 36 ± 1°C). The voltage dependence of I Kr activation (V½ and k) were not affected by the mutation; however, the fast (τf) and slow (τs) deactivation time constants were significantly decreased in hERG-H70R hiPSC-CMs. Further, Western blot characterization revealed impaired trafficking of hERG-H70R channels relative to control. Conclusions: The LQT2 PAS domain variant hERG-H70R results in loss of function of I Kr by both reduced membrane trafficking and accelerated deactivation of hERG in a hiPSC-CMs model which informs therapeutic approaches.

In situ use of the King-Devick eye tracking test and changes seen with sport-related concussion: saccadic and blinks counts

ABSTRACTObjectives: Sport-related concussion (SRC) can result in impaired oculomotor function. Oculomotor performance, measured utilizing the King-Devick/Eye Tracking test (K-D/ET), is reported to be able to identify sub-optimal brain function. The objectives of the study were to determine the diagnostic accuracy of the K-D/ET in identifying SRC occurring from game participation and to perform a comparative analysis on saccade and blink counts for each K-D card individually and total counts between baseline and post-concussion.Methods: Nineteen male Australian Football players were assessed on the K-D/ET test. Those suspected of having SRC secondary to a head impact were also tested.Results: Participants recorded a slower time on the third (20.2 ± 4.6 s) screen when compared with the first (p = 0.0424) and second (p = 0.0150) screens. The number of blinks was higher on the third (2.9 ± 2.9) when compared with the second (p = 0.0057) screen. There was decrease of the K-D/ET total times between pre- and post-game (p = 0.1769). Participants who sustained a head impact recorded slower mean total K-D time (p = 0.7322), fewer mean total saccades (p = 0.0112), and more mean blinks (p = 0.8678) compared with their baseline scores. The assessment of blinks was the most sensitive measure for potential SRC (0.67). The K-D/ET duration was the most specific measure for potential SRC (0.88). An increase in the number of blinks had a fair specificity of 0.69.Conclusion: The rapid number-naming component of the K-D test is an assessment tool which quantifies impairment to oculomotor function and has been validated as a diagnostic tool for SRC. The clinical usefulness of the eye tracking component of the K-D/ET test is that it may be an effective method to assess concussions with the eye tracking component serving as a measure of progression and return to play. However, more research is required at the adult and youth level.

The voltage-sensitive cardiac M2 muscarinic receptor modulates the inward rectification of the G protein-coupled, ACh-gated K+ current.

The acetylcholine (ACh)-gated inwardly rectifying K+ current (IKACh) plays a vital role in cardiac excitability by regulating heart rate variability and vulnerability to atrial arrhythmias. These crucial physiological contributions are determined principally by the inwardly rectifying nature of IKACh. Here, we investigated the relative contribution of two distinct mechanisms of IKACh inward rectification measured in atrial myocytes: a rapid component due to KACh channel block by intracellular Mg2+ and polyamines; and a time- and concentration-dependent mechanism. The time- and ACh concentration-dependent inward rectification component was eliminated when IKACh was activated by GTPγS, a compound that bypasses the muscarinic-2 receptor (M2R) and directly stimulates trimeric G proteins to open KACh channels. Moreover, the time-dependent component of IKACh inward rectification was also eliminated at ACh concentrations that saturate the receptor. These observations indicate that the time- and concentration-dependent rectification mechanism is an intrinsic property of the receptor, M2R; consistent with our previous work demonstrating that voltage-dependent conformational changes in the M2R alter the receptor affinity for ACh. Our analysis of the initial and time-dependent components of IKACh indicate that rapid Mg2+-polyamine block accounts for 60-70% of inward rectification, with M2R voltage sensitivity contributing 30-40% at sub-saturating ACh concentrations. Thus, while both inward rectification mechanisms are extrinsic to the KACh channel, to our knowledge, this is the first description of extrinsic inward rectification of ionic current attributable to an intrinsic voltage-sensitive property of a G protein-coupled receptor.

Los componentes de la velocidad de denominación y su relación con la comprensión lectora en español

La velocidad de denominación es uno de los principales predictores de la lectura especialmente en ortografías transparentes como el español. Si bien ha sido consistentemente estudiada al nivel de la lectura de palabras, pocos trabajos tratan de explicar su relación con la comprensión lectora. Desde la perspectiva del análisis de los componentes de la velocidad de denominación: pausas entre ítems y tiempos de articulación; esta investigación exploró la relación entre la velocidad de denominación y la comprensión lectora en estudiantes chilenos de primero a cuarto básico. Además, evaluó si es que esta relación se explica por las habilidades en la precisión de lectura de palabras y fluidez lectora. Los resultados muestran que ambos componentes comparten una cantidad significativa de varianza con la comprensión. Sin embargo comparativamente es mayor la relación de las pausas entre ítems con la comprensión. Cuando incluimos en la relación entre la velocidad de denominación y la comprensión lectora, la precisión en la lectura de palabras y la fluidez, estas variables median la relación. Los resultados se discuten en el contexto de la velocidad de denominación como una variable relacionada con la fluidez en la lectura y la utilidad de su evaluación en el contexto escolar.

Complex aberrant splicing in the induced pluripotent stem cell–derived cardiomyocytes from a patient with long QT syndrome carrying KCNQ1-A344Aspl mutation

Long QT syndrome type 1 (LQT1) is caused by mutations in KCNQ1, which encodes the α subunit of the slow delayed rectifier potassium current channel. We previously reported that a synonymous mutation, c.1032G>A, p.A344Aspl, in KCNQ1 is most commonly identified in genotyped patients with LQT1 in Japan and the aberrant splicing was analyzed in the lymphocytes isolated from patients' blood samples. However, the mechanisms underlying the observed processes in human cardiomyocytes remain unclear. The purpose of this study was to establish and analyze patient-specific human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) model carrying KCNQ1-A344Aspl. We generated hiPSCs from the peripheral blood mononuclear cells obtained from a patient with LQT1 carrying KCNQ1-A344Aspl. Using the differentiated cardiomyocytes, we analyzed splicing variants and performed electrophysiology studies. We identified 7 aberrant RNA variants in A344Aspl hiPSC-CMs, which were more complex compared with those in peripheral lymphocytes. Multielectrode array analysis revealed that 1 μM isoproterenol significantly prolonged the duration ofthe corrected field potential in A344Aspl hiPSC-CMs ascompared with that in control hiPSC-CMs. In addition, 100nM E-4031, which inhibits the rapid component of the delayed rectifier potassium current, was shown to induce earlyafterdepolarization-like waveforms in A344Aspl hiPSC-CMs. Action potential durations (APDs) did not significantly differ between the hiPSC-CM groups. After administering 500nM isoproterenol, APDs of A344Aspl hiPSC-CMs were significantly longer than those of the controls. (R)-N-(4-(4-Methoxyphenyl)thiazol-2-yl)-1-tosylpiperidine-2-carboxamide and phenylboronic acid, slow delayed rectifier potassium current activators, ameliorated the APDs of hiPSC-CMs. We identified complex aberrant messenger RNA variants in the A344Aspl hiPSC-CM model and successfully recapitulated the clinical phenotypes of the patient with concealed LQT1. This model allows the investigation of the underlying mechanisms and development of novel therapies.

Development of a High-Throughput Flow Cytometry Assay to Monitor Defective Trafficking and Rescue of Long QT2 Mutant hERG Channels.

Long QT Syndrome (LQTS) is an acquired or inherited disorder characterized by prolonged QT interval, exertion-triggered arrhythmias, and sudden cardiac death. One of the most prevalent hereditary LQTS subtypes, LQT2, results from loss-of-function mutations in the hERG channel, which conducts IKr, the rapid component of the delayed rectifier K+ current, critical for cardiac repolarization. The majority of LQT2 mutations result in Class 2 deficits characterized by impaired maturation and trafficking of hERG channels. Here, we have developed a high-throughput flow cytometric assay to analyze the surface and total expression of wild-type (WT) and mutant hERG channels with single-cell resolution. To test our method, we focused on 16 LQT2 mutations in the hERG Per-Arnt-Sim (PAS) domain that were previously studied via a widely used biochemical approach that compares levels of 135-kDa immature and 155-kDa fully glycosylated hERG protein to infer surface expression. We confirmed that LQT2 mutants expressed in HEK293 cells displayed a decreased surface density compared to WT hERG, and were differentially rescued by low temperature. However, we also uncovered some notable differences from the findings obtained via the biochemical approach. In particular, three mutations (N33T, R56Q, and A57P) with apparent WT-like hERG glycosylation patterns displayed up to 50% decreased surface expression. Furthermore, despite WT-like levels of complex glycosylation, these mutants have impaired forward trafficking, and exhibit varying half-lives at the cell surface. The results highlight utility of the surface labeling/flow cytometry approach to quantitatively assess trafficking deficiencies associated with LQT2 mutations, to discern underlying mechanisms, and to report on interventions that rescue deficits in hERG surface expression.

Ciprofloxacin, an antibiotic with cardiac actions on isolated rat hearts

Context: Ciprofloxacin is the most commonly used fluoroquinolone and is prescribed as the antibiotic of choice in the treatment of several microbial infections. Some clinical reports have suggested that ciprofloxacin may induce QT-interval prolongation and Torsades de Pointes arrhythmias. This drug is a weak inhibitor of a rapid component of the cardiac delayed rectifier potassium current IKr, but there are few electrophysiological data available to assess whether ciprofloxacin has the potency to provoke QT prolongation and subsequent Torsades de Pointes arrhythmias. Aims: To evaluate the effect of ciprofloxacin on the contractile and electrical activity of isolated rat hearts. Methods: The Langendorff technique was performed in rat hearts, and the effects of ciprofloxacin (0.001 - 100 μM) were measured on the cardiac force of contraction and on the RR, QRS and QTc intervals. The arrhythmogenic potential and the ventricular fibrillation threshold were evaluated with ciprofloxacin. Results: Ciprofloxacin decreased the force of contraction of all hearts studied, in a concentration-dependent manner. The estimated IC50 for the inotropic negative effect was 0.15 ± 0.04 μM. Ciprofloxacin significantly prolonged the QRS complex, QTc and RR interval. Significant arrhythmic effects with ciprofloxacin were shown and the ventricular fibrillation threshold was decreased. Conclusions: These results suggest that ciprofloxacin exerted effects on cardiac Na+, K+ and Ca2+ channels. The actions of ciprofloxacin require further studies at the cellular level. These conclusions may account for clinical data that have been reported previously.

Inhibition of aldose-reductase-2 by a benzofuroxane derivative bf-5m increases the expression of kcne1, kcnq1 in high glucose cultured H9c2 cardiac cells and sudden cardiac death.

Long QT syndrome (LQTS) is characterized by prolonged QT interval, leading to sudden cardiac death. Hyperglycemia is an important risk factor for LQTS, inhibiting the cardiac rapid component delayed rectifier K+ current (Iks), responsible for QT interval. We previously showed that the new ALR2 inhibitor BF-5m supplies cardioprotection from QT prolongation induced by high glucose concentration in the medium, reducing QT interval prolongation and preserving morphology. Here we investigated the effects of BF-5m on cell cytotoxicity and viability in H9c2 cells, and on cellular potassium ion channels expression.H9c2 cells were grown in medium with high glucose and high glucose plus the BF-5m by assessing the cytotoxic effects and the cell survival rate. In addition, KCNE1 and KCNQ1 expression in plasma and mitochondrial membranes were monitored. Also, the expression levels of miR-1 proved to suppress KCNQ1 and KCNE1, were analyzed.BF-5m treatment reduced the cytotoxic effects of high glucose on H9c2 cells by increasing cell survival rate and improving H9c2 morphology. Plasmatic KCNE1 and KCNQ1 expression levels were restored by BF-5m in H9c2 exposed to high glucose, down-regulating miR-1.These results suggest that BF-5m exerts cardioprotection from high glucose in rat heart ventricle H9c2 cells exposed to high glucose.