scholarly journals Fast Optical Investigation of Cardiac Electrophysiology by Parallel Detection in Multiwell Plates

2021 ◽  
Vol 12 ◽  
Author(s):  
Caterina Credi ◽  
Valentina Balducci ◽  
U. Munagala ◽  
C. Cianca ◽  
S. Bigiarini ◽  
...  
Keyword(s):  
Action Potential ◽  
Cardiac Electrophysiology ◽  
Single Cells ◽  
Optical Detection ◽  
Optical Systems ◽  
Dose Titration ◽  
Optical Scheme ◽  
Optical Investigation ◽  
Parallel Detection ◽  
Multiwell Plates

Current techniques for fast characterization of cardiac electrophysiology employ optical technologies to control and monitor action potential features of single cells or cellular monolayers placed in multiwell plates. High-speed investigation capacities are commonly achieved by serially analyzing well after well employing fully automated fluorescence microscopes. Here, we describe an alternative cost-effective optical approach (MULTIPLE) that exploits high-power LED arrays to globally illuminate a culture plate and an sCMOS sensor for parallel detection of the fluorescence coming from multiple wells. MULTIPLE combines optical detection of action potentials using a red-shifted voltage-sensitive fluorescent dye (di-4-ANBDQPQ) with optical stimulation, employing optogenetic actuators, to ensure excitation of cardiomyocytes at constant rates. MULTIPLE was first characterized in terms of interwell uniformity of the illumination intensity and optical detection performance. Then, it was applied for probing action potential features in HL-1 cells (i.e., mouse atrial myocyte-like cells) stably expressing the blue light-activatable cation channel CheRiff. Under proper stimulation conditions, we were able to accurately measure action potential dynamics across a 24-well plate with variability across the whole plate of the order of 10%. The capability of MULTIPLE to detect action potential changes across a 24-well plate was demonstrated employing the selective Kv11.1 channel blocker (E-4031), in a dose titration experiment. Finally, action potential recordings were performed in spontaneous beating human induced pluripotent stem cell derived cardiomyocytes following pharmacological manipulation of their beating frequency. We believe that the simplicity of the presented optical scheme represents a valid complement to sophisticated and expensive state-of-the-art optical systems for high-throughput cardiac electrophysiological investigations.

A tale of two dogs: analyzing two models of canine ventricular electrophysiology

2007 ◽  
Vol 292 (1) ◽  
pp. H43-H55 ◽  
Author(s):  
Elizabeth M. Cherry ◽  
Flavio H. Fenton
Keyword(s):  
Action Potential ◽  
Mathematical Models ◽  
Cardiac Electrophysiology ◽  
Animal Species ◽  
Cardiac Myocyte ◽  
Ventricular Myocytes ◽  
Single Cells ◽  
Spiral Wave ◽  
Canine Models ◽  
Transmembrane Currents

The extensive development of detailed mathematical models of cardiac myocyte electrophysiology in recent years has led to a proliferation of models, including many that model the same animal species and specific region of the heart and thus would be expected to have similar properties. In this paper we review and compare two recently developed mathematical models of the electrophysiology of canine ventricular myocytes. To clarify their similarities and differences, we also present studies using them in a range of preparations from single cells to two-dimensional tissue. The models are compared with each other and with new and previously published experimental results in terms of a number of their properties, including action potential morphologies; transmembrane currents during normal heart rates and during alternans; alternans onsets, magnitudes, and cessations; and reentry dynamics of spiral waves. Action potential applets and spiral wave movies for the two canine ventricular models are available online as supplemental material. We find a number of differences between the models, including their rate dependence, alternans dynamics, and reentry stability, and a number of differences compared with experiments. Differences between models of the same species and region of the heart are not unique to these canine models. Similar differences can be found in the behavior of two models of human ventricular myocytes and of human atrial myocytes. We provide several possible explanations for the differences observed in models of the same species and region of the heart and discuss the implications for the applicability of models in addressing questions of mechanism in cardiac electrophysiology.

Label-free and noninvasive optical detection of the distribution of nanometer-size mitochondria in single cells

2011 ◽  
Vol 16 (6) ◽  
pp. 067003 ◽  
Author(s):  
Xuantao Su ◽  
Yuanyuan Qiu ◽  
Leah Marquez-Curtis ◽  
Manisha Gupta ◽  
Clarence E. Capjack ◽  
...  
Keyword(s):  
Single Cells ◽  
Optical Detection ◽  
Label Free ◽  
Nanometer Size

scholarly journals Contribution of two-pore K+ channels to cardiac ventricular action potential revealed using human iPSC-derived cardiomyocytes

2017 ◽  
Vol 312 (6) ◽  
pp. H1144-H1153 ◽  
Author(s):  
Sam Chai ◽  
Xiaoping Wan ◽  
Drew M. Nassal ◽  
Haiyan Liu ◽  
Christine S. Moravec ◽  
...  
Keyword(s):  
Action Potential ◽  
Expression Profile ◽  
Cardiac Electrophysiology ◽  
Human Heart ◽  
Induced Pluripotent Stem Cell ◽  
Heart Tissue ◽  
Induced Pluripotent ◽  
Interfering Rna ◽  
Human Ipsc ◽  
Physiological Systems

Two-pore K+ (K2p) channels have been described in modulating background conductance as leak channels in different physiological systems. In the heart, the expression of K2p channels is heterogeneous with equivocation regarding their functional role. Our objective was to determine the K2p expression profile and their physiological and pathophysiological contribution to cardiac electrophysiology. Induced pluripotent stem cells (iPSCs) generated from humans were differentiated into cardiomyocytes (iPSC-CMs). mRNA was isolated from these cells, commercial iPSC-CM (iCells), control human heart ventricular tissue (cHVT), and ischemic (iHF) and nonischemic heart failure tissues (niHF). We detected 10 K2p channels in the heart. Comparing quantitative PCR expression of K2p channels between human heart tissue and iPSC-CMs revealed K2p1.1, K2p2.1, K2p5.1, and K2p17.1 to be higher expressed in cHVT, whereas K2p3.1 and K2p13.1 were higher in iPSC-CMs. Notably, K2p17.1 was significantly lower in niHF tissues compared with cHVT. Action potential recordings in iCells after K2p small interfering RNA knockdown revealed prolongations in action potential depolarization at 90% repolarization for K2p2.1, K2p3.1, K2p6.1, and K2p17.1. Here, we report the expression level of 10 human K2p channels in iPSC-CMs and how they compared with cHVT. Importantly, our functional electrophysiological data in human iPSC-CMs revealed a prominent role in cardiac ventricular repolarization for four of these channels. Finally, we also identified K2p17.1 as significantly reduced in niHF tissues and K2p4.1 as reduced in niHF compared with iHF. Thus, we advance the notion that K2p channels are emerging as novel players in cardiac ventricular electrophysiology that could also be remodeled in cardiac pathology and therefore contribute to arrhythmias. NEW & NOTEWORTHY Two-pore K+ (K2p) channels are traditionally regarded as merely background leak channels in myriad physiological systems. Here, we describe the expression profile of K2p channels in human-induced pluripotent stem cell-derived cardiomyocytes and outline a salient role in cardiac repolarization and pathology for multiple K2p channels.

Abstract P309: Particulate Matter Increases Oxidative Stress And Shortens The Action Potential In IPS-derived Cardiomyocytes

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Mariana Argenziano ◽  
jiajia yang ◽  
Mariana Burgos Angulo ◽  
Thomas V McDonald
Keyword(s):  
Oxidative Stress ◽  
Particulate Matter ◽  
Action Potential ◽  
Cardiac Electrophysiology ◽  
Structural Changes ◽  
Hospital Admissions ◽  
Induced Pluripotent Stem Cell ◽  
Toxic Substances ◽  
Direct Role ◽  
Atp Production

Introduction: Air particulate matter (PM) represents one of the most critical environmental issues worldwide, causing more than 3 million deaths a year. In the US, hospital admissions due to heart failure (HF) increase by 0.8% for every 10 μg/m3 elevation in PM. However, the biological mechanisms behind the effects of PM on cardiovascular disease (CVD) remain poorly defined. Recent studies showed that PM 2.5 can translocate into the circulation, causing cumulative toxicity. With air pollution increasing due to human activity and the growing prevalence of HF, there is a critical need to understand PM's contributions to CVD to develop preventive treatments and novel therapeutic approaches. Hypothesis: We hypothesize that PM can exert its toxic effect by increasing oxidative stress and apoptosis and affecting cardiac electrophysiology. Methods: Three independent induced pluripotent stem cell lines (IPSC) were differentiated into cardiomyocytes (iCMs) and cultured for 30 days before treatment with 100 μg/ml of PM 2.5 for 48h. Experiments including immunostaining, qPCR, RNAseq and Multielectrode Array (MEA) were performed in control (CT) and PM-treated iCMs (PM). Results: Treatment with PM increased ROS and decreased ATP production (CT 9.9±1.2pmol vs PM 6.6±0.8pmol, p<0.01, n=20). Immunostaining showed mitochondrial fragmentation and increased expression of cleaved caspase3 without structural changes. Moreover, PM caused upregulation of the apoptotic markers P53 , PARP1 and CASP3, oxidative stress markers CYP1A1, CYP1B1 and MT2A, and cardiac markers CACNA1C together with downregulation of GJA1 . RNAseq analysis showed upregulation of Gene Ontology terms related to detoxification, response to toxic substances and oxidative stress. Upregulated KEGG pathways included oxidative phosphorylation, hypertrophic cardiomyopathy and dilated cardiomyopathy. MEA experiments revealed a decrease in the spike amplitude and conduction velocity, along with shortening of the action potential (APD90: CT 577±20ms vs. PM 489±16ms, p<0.05, n=20) and increased beat period irregularity (CT 3.2±0.7% vs. PM 13.1±1.6%, p<0.001, n=20). These electrophysiological changes were reversed by treatment with the antioxidant N-acetylcysteine. Conclusions: We conclude that PM plays a direct role in the development of CVD, causing an increase in oxidative stress and affecting the electrophysiology of the heart. Further functional studies in iCMs from HF patients will provide evidence of the effects of these changes on the phenotype of the disease.

scholarly journals Phenanthrene impacts zebrafish cardiomyocyte excitability by inhibiting IKr and shortening action potential duration

2021 ◽  
Vol 153 (2) ◽  
Author(s):  
Shiva N. Kompella ◽  
Fabien Brette ◽  
Jules C. Hancox ◽  
Holly A. Shiels
Keyword(s):  
Air Pollution ◽  
Action Potential ◽  
Action Potential Duration ◽  
Cardiac Electrophysiology ◽  
Resting Membrane Potential ◽  
Dependent Manner ◽  
Polyaromatic Hydrocarbon ◽  
Premature Ventricular Contractions ◽  
Whole Cell Patch Clamp ◽  
Dose Dependent

Air pollution is an environmental hazard that is associated with cardiovascular dysfunction. Phenanthrene is a three-ringed polyaromatic hydrocarbon that is a significant component of air pollution and crude oil and has been shown to cause cardiac dysfunction in marine fishes. We investigated the cardiotoxic effects of phenanthrene in zebrafish (Danio rerio), an animal model relevant to human cardiac electrophysiology, using whole-cell patch-clamp of ventricular cardiomyocytes. First, we show that phenanthrene significantly shortened action potential duration without altering resting membrane potential or upstroke velocity (dV/dt). L-type Ca2+ current was significantly decreased by phenanthrene, consistent with the decrease in action potential duration. Phenanthrene blocked the hERG orthologue (zfERG) native current, IKr, and accelerated IKr deactivation kinetics in a dose-dependent manner. Furthermore, we show that phenanthrene significantly inhibits the protective IKr current envelope, elicited by a paired ventricular AP-like command waveform protocol. Phenanthrene had no effect on other IK. These findings demonstrate that exposure to phenanthrene shortens action potential duration, which may reduce refractoriness and increase susceptibility to certain arrhythmia triggers, such as premature ventricular contractions. These data also reveal a previously unrecognized mechanism of polyaromatic hydrocarbon cardiotoxicity on zfERG by accelerating deactivation and decreasing IKr protective current.

Effects of thyroid hormone on action potential and repolarizing currents in rat ventricular myocytes

2000 ◽  
Vol 278 (2) ◽  
pp. E302-E307 ◽  
Author(s):  
Zhuo-Qian Sun ◽  
Kaie Ojamaa ◽  
William A. Coetzee ◽  
Michael Artman ◽  
Irwin Klein
Keyword(s):  
Action Potential ◽  
Cardiac Electrophysiology ◽  
Ventricular Myocytes ◽  
Outward Current ◽  
Mechanisms Of Action ◽  
Transient Outward Current ◽  
Prolonged Action ◽  
Electrophysiological Properties ◽  
Whole Cell Patch Clamp ◽  
Prolonged Action Potential Duration

Thyroid hormones play an important role in cardiac electrophysiology through both genomic and nongenomic mechanisms of action. The effects of triiodothyronine (T3) on the electrophysiological properties of ventricular myocytes isolated from euthyroid and hypothyroid rats were studied using whole cell patch clamp techniques. Hypothyroid ventricular myocytes showed significantly prolonged action potential duration (APD90) compared with euthyroid myocytes, APD90 of 151 ± 5 vs. 51 ± 8 ms, respectively. Treatment of hypothyroid ventricular myocytes with T3 (0.1 μM) for 5 min significantly shortened APD by 24% to 115 ± 10 ms. T3 similarly shortened APD in euthyroid ventricular myocytes, but only in the presence of 4-aminopyridine (4-AP), an inhibitor of the transient outward current ( I to), which prolonged the APD by threefold. Transient outward current ( I to) was not affected by the acute application of T3 to either euthyroid or hypothyroid myocytes; however, I to density was significantly reduced in hypothyroid compared with euthyroid ventricular myocytes.

scholarly journals Bond graph modelling of the cardiac action potential: implications for drift and non-unique steady states

2018 ◽  
Vol 474 (2214) ◽  
pp. 20180106 ◽  
Author(s):  
Michael Pan ◽  
Peter J. Gawthrop ◽  
Kenneth Tran ◽  
Joseph Cursons ◽  
Edmund J. Crampin
Keyword(s):  
Action Potential ◽  
Conservation Laws ◽  
Cardiac Electrophysiology ◽  
Bond Graph ◽  
Steady States ◽  
Cardiac Action Potential ◽  
Bond Graphs ◽  
Charge Conservation ◽  
Cardiac Action ◽  
Wide Range

Mathematical models of cardiac action potentials have become increasingly important in the study of heart disease and pharmacology, but concerns linger over their robustness during long periods of simulation, in particular due to issues such as model drift and non-unique steady states. Previous studies have linked these to violation of conservation laws, but only explored those issues with respect to charge conservation in specific models. Here, we propose a general and systematic method of identifying conservation laws hidden in models of cardiac electrophysiology by using bond graphs, and develop a bond graph model of the cardiac action potential to study long-term behaviour. Bond graphs provide an explicit energy-based framework for modelling physical systems, which makes them well suited for examining conservation within electrophysiological models. We find that the charge conservation laws derived in previous studies are examples of the more general concept of a ‘conserved moiety’. Conserved moieties explain model drift and non-unique steady states, generalizing the results from previous studies. The bond graph approach provides a rigorous method to check for drift and non-unique steady states in a wide range of cardiac action potential models, and can be extended to examine behaviours of other excitable systems.

scholarly journals Optical mapping of the electrical activity of isolated adult zebrafish hearts: acute effects of temperature

2014 ◽  
Vol 306 (11) ◽  
pp. R823-R836 ◽  
Author(s):  
Eric Lin ◽  
Amanda Ribeiro ◽  
Weiguang Ding ◽  
Leif Hove-Madsen ◽  
Marinko V. Sarunic ◽  
...  
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Cardiac Electrophysiology ◽  
Optical Mapping ◽  
Cooling System ◽  
Effect Of Temperature ◽  
Adult Zebrafish ◽  
Depth Analysis ◽  
Zebrafish Heart ◽  
Av Delay

The zebrafish ( Danio rerio) has emerged as an important model for developmental cardiovascular (CV) biology; however, little is known about the cardiac function of the adult zebrafish enabling it to be used as a model of teleost CV biology. Here, we describe electrophysiological parameters, such as heart rate (HR), action potential duration (APD), and atrioventricular (AV) delay, in the zebrafish heart over a range of physiological temperatures (18–28°C). Hearts were isolated and incubated in a potentiometric dye, RH-237, enabling electrical activity assessment in several distinct regions of the heart simultaneously. Integration of a rapid thermoelectric cooling system facilitated the investigation of acute changes in temperature on critical electrophysiological parameters in the zebrafish heart. While intrinsic HR varied considerably between fish, the ex vivo preparation exhibited impressively stable HRs and sinus rhythm for more than 5 h, with a mean HR of 158 ± 9 bpm (means ± SE; n = 20) at 28°C. Atrial and ventricular APDs at 50% repolarization (APD50) were 33 ± 1 ms and 98 ± 2 ms, respectively. Excitation originated in the atrium, and there was an AV delay of 61 ± 3 ms prior to activation of the ventricle at 28°C. APD and AV delay varied between hearts beating at unique HRs; however, APD and AV delay did not appear to be statistically dependent on intrinsic basal HR, likely due to the innate beat-to-beat variability within each heart. As hearts were cooled to 18°C (by 1°C increments), HR decreased by ∼40%, and atrial and ventricular APD50 increased by a factor of ∼3 and 2, respectively. The increase in APD with cooling was disproportionate at different levels of repolarization, indicating unique temperature sensitivities for ion currents at different phases of the action potential. The effect of temperature was more apparent at lower levels of repolarization and, as a whole, the atrial APD was the cardiac parameter most affected by acute temperature change. In conclusion, this study describes a preparation enabling the in-depth analysis of transmembrane potential dynamics in whole zebrafish hearts. Because the zebrafish offers some critical advantages over the murine model for cardiac electrophysiology, optical mapping studies utilizing zebrafish offer insightful information into the understanding and treatment of human cardiac arrhythmias, as well as serving as a model for other teleosts.

scholarly journals Effect of activation sequence on transmural patterns of repolarization and action potential duration in rabbit ventricular myocardium

2010 ◽  
Vol 299 (6) ◽  
pp. H1812-H1822 ◽  
Author(s):  
Rachel C. Myles ◽  
Olivier Bernus ◽  
Francis L. Burton ◽  
Stuart M. Cobbe ◽  
Godfrey L. Smith
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Single Cells ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Isolated Cells ◽  
Electrophysiological Properties ◽  
Relative Contribution ◽  
Rabbit Ventricular Myocardium ◽  
Transmural Heterogeneity

Although transmural heterogeneity of action potential duration (APD) is established in single cells isolated from different tissue layers, the extent to which it produces transmural gradients of repolarization in electrotonically coupled ventricular myocardium remains controversial. The purpose of this study was to examine the relative contribution of intrinsic cellular gradients of APD and electrotonic influences to transmural repolarization in rabbit ventricular myocardium. Transmural optical mapping was performed in left ventricular wedge preparations from eight rabbits. Transmural patterns of activation, repolarization, and APD were recorded during endocardial and epicardial stimulation. Experimental results were compared with modeled data during variations in electrotonic coupling. A transmural gradient of APD was evident during endocardial stimulation, which reflected differences previously seen in isolated cells, with the longest APD at the endocardium and the shortest at the epicardium (endo: 165 ± 5 vs. epi: 147 ± 4 ms; P < 0.05). During epicardial stimulation, this gradient reversed (epi: 162 ± 4 vs. endo: 148 ± 6 ms; P < 0.05). In both activation sequences, transmural repolarization followed activation and APD shortened along the activation path such that significant transmural gradients of repolarization did not occur. This correlation between transmural activation time and APD was recapitulated in simulations and varied with changes in intercellular coupling, confirming that it is mediated by electrotonic current flow between cells. These data suggest that electrotonic influences are important in determining the transmural repolarization sequence in rabbit ventricular myocardium and that they are sufficient to overcome intrinsic differences in the electrophysiological properties of the cells across the ventricular wall.

Changes in cytosolic calcium monitored by inward currents during action potentials in guinea-pig ventricular cells

1989 ◽  
Vol 238 (1291) ◽  
pp. 171-188 ◽  
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Voltage Clamp ◽  
Action Potentials ◽  
Single Cells ◽  
Calcium Transient ◽  
Cytosolic Calcium ◽  
Time To Peak ◽  
Ventricular Cells ◽  
In Cells

Action potentials were recorded from single cells isolated from guinea-pig ventricular muscle. Contraction was measured with an optical technique. Tail currents thought to be activated by cytosolic calcium were recorded when action potentials were interrupted by application of a voltage-clamp. A family of tail currents was recorded by interrupting the action potential at various times after the upstroke. The envelope of tail current amplitudes was taken as an index of changes in cytosoli calcium. Con­sistent with this interpretation, tail currents were negligible following intracellular loading with the calcium chelator BAPTA to suppress calcium transients. The cytosolic calcium transient estimated from the envelope of tails reached a peak approximately 50 ms after the upstroke of the action potential, and fell close to diastolic levels before repolarization was com­plete; 10 mM caffeine delayed the time to peak contraction, and caused a prolongation of the cytosolic calcium transient estimated from the envelope of tail currents. Caffeine also induced the appearance of a distinct late plateau phase of the action potential. Intracellular BAPTA suppressed the late plateau, contraction and tail currents in cells exposed to caffeine. Exposure to caffeine increased the time constant for decay of tail currents (from approximately 35 to 70 ms). When action potentials were greatly abbreviated by interruption with a voltage-clamp, a pro­gressive decline occurred in the subsequent three contractions and tail currents. There was a progressive reversal of these effects over four responses when the full action potential duration was restored. None of these effects was observed in cells exposed to caffeine. Calcium-activated tail currents appear to be a useful qualitative index of changes in cytosolic calcium. The observations are consistent with the suggestion that cytosolic calcium is reduced during the plateau by a combination of calcium extrusion through Na–Ca exchange and calcium uptake into caffeine-sensitive stores. It also appears that reduction of stores loading during abbreviated action potentials reduces subsequent contraction in cells not exposed to caffeine.

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