scholarly journals Ion channel expression and electrophysiology of singular human (primary and induced pluripotent stem cell derived) cardiomyocytes

2021 ◽  
Author(s):  
Christina Schmid ◽  
Najah Abi-Gerges ◽  
Dietmar Zellner ◽  
Georg Rast
Keyword(s):  
Ion Channels ◽  
Action Potential ◽  
Ion Channel ◽  
Single Cell ◽  
Action Potential Duration ◽  
Drug Effects ◽  
Induced Pluripotent Stem Cell ◽  
Inward Current ◽  
Beat Rate ◽  
Channel Expression

SUMMARYHuman induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and primary human cardiomyocytes are used for in vitro cardiac safety testing. hiPSC-CMs have been associated with a vast heterogeneity regarding single-cell morphology, beating behavior and action potential duration, prompting a systematic analysis of single-cell characteristics. Previously published hiPSC-CM studies revealed action potentials with nodal-, atrial- or ventricular-like morphology, although ion channel expression of singular hiPSC-CMs is not fully understood. Other studies used single-cell RNA-sequencing, however, these studies did not extensively focus on expression patterns of cardiac ion channels or failed to detect ion channel transcripts. Thus, the current study used a single-cell patch-clamp-RT-qPCR approach to get insights into single-cell electrophysiology (capacitance, action potential duration at 90% of repolarization, upstroke velocity, spontaneous beat rate, and sodium-driven fast inward current) and ion channel expression (HCN4, CACNA1G, CACNA1D, KCNA5, KCNJ4, SCN5A, KCNJ2, CACNA1D, and KCNH2), the combination of both within individual cells, and their correlations in single cardiomyocytes. We used commercially available hiPSC-CMs (iCell cardiomyocytes, atrial and ventricular Pluricytes) and primary human adult atrial and ventricular cardiomyocytes. Recordings of electrophysiological parameters revealed differences between the cell groups and variation within the hiPSC-CMs groups as well as within primary ventricular cardiomyocytes. Expression analysis on mRNA level showed no-clear-cut discrimination between primary cardiac subtypes and revealed both similarities and differences between all cell groups. Higher expression of atrial-associated ion channels in primary atrial cardiomyocytes and atrial Pluricytes compared to their ventricular counterpart indicates a successful chamber-specific hiPSC differentiation. Interpretation of correlations between the single-cell parameters was challenging, as the total data set is complex, particularly for parameters depending on multiple processes, like the spontaneous beat rate. Yet, for example, expression of SCN5A correlated well with the fast inward current amplitude for all three hiPSC-CM groups. To further enhance our understanding of the physiology and composition of the investigated hiPSC-CMs, we compared beating and non-beating cells and assessed distributions of single-cell data. Investigating the single-cell phenotypes of hiPSC-CMs revealed a combination of attributes which may be interpreted as a mixture of traits of different adult cardiac cell types: (i) nodal-related pacemaking attributes are spontaneous generation of action potentials and high HCN4 expression; and (ii) non-nodal attributes: cells have a prominent INa-driven fast inward current, a fast upstroke velocity and a high expression of SCN5A. In conclusion, the combination of nodal- and non-nodal attributes in single hiPSC-CMs may hamper the interpretation of drug effects on complex electrophysiological parameters like beat rate and action potential duration. However, the proven expression of specific ion channels enables the evaluation of drug effects on ionic currents in a more realistic environment than in recombinant systems.

scholarly journals Ion Channel and Structural Remodeling in Obesity-Mediated Atrial Fibrillation

2020 ◽  
Vol 13 (8) ◽  
Author(s):  
Mark D. McCauley ◽  
Liang Hong ◽  
Arvind Sridhar ◽  
Ambili Menon ◽  
Srikanth Perike ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Action Potential ◽  
Ion Channel ◽  
Sodium Channel ◽  
Action Potential Duration ◽  
Obese Mice ◽  
Atrial Fibrosis ◽  
Structural Remodeling ◽  
Cardiac Sodium Channel ◽  
Channel Expression

Background: Epidemiological studies have established obesity as an independent risk factor for atrial fibrillation (AF), but the underlying pathophysiological mechanisms remain unclear. Reduced cardiac sodium channel expression is a known causal mechanism in AF. We hypothesized that obesity decreases Nav1.5 expression via enhanced oxidative stress, thus reducing I Na , and enhancing susceptibility to AF. Methods: To elucidate the underlying electrophysiological mechanisms a diet-induced obese mouse model was used. Weight, blood pressure, glucose, F 2 -isoprostanes, NOX2 (NADPH oxidase 2), and PKC (protein kinase C) were measured in obese mice and compared with lean controls. Invasive electrophysiological, immunohistochemistry, Western blotting, and patch clamping of membrane potentials was performed to evaluate the molecular and electrophysiological phenotype of atrial myocytes. Results: Pacing-induced AF in 100% of diet-induced obese mice versus 25% in controls ( P <0.01) with increased AF burden. Cardiac sodium channel expression, I Na and atrial action potential duration were reduced and potassium channel expression (Kv1.5) and current ( I Kur ) and F 2 -isoprostanes, NOX2, and PKC-α/δ expression and atrial fibrosis were significantly increased in diet-induced obese mice as compared with controls. A mitochondrial antioxidant reduced AF burden, restored I Na , I Ca,L , I Kur , action potential duration, and reversed atrial fibrosis in diet-induced obese mice as compared with controls. Conclusions: Inducible AF in obese mice is mediated, in part, by a combined effect of sodium, potassium, and calcium channel remodeling and atrial fibrosis. Mitochondrial antioxidant therapy abrogated the ion channel and structural remodeling and reversed the obesity-induced AF burden. Our findings have important implications for the management of obesity-mediated AF in patients. Graphic Abstract: A graphic abstract is available for this article.

scholarly journals Ion Channel Expression and Characterization in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Zhihan Zhao ◽  
Huan Lan ◽  
Ibrahim El-Battrawy ◽  
Xin Li ◽  
Fanis Buljubasic ◽  
...  
Keyword(s):  
Stem Cell ◽  
Ion Channels ◽  
Ion Channel ◽  
Pluripotent Stem Cell ◽  
Induced Pluripotent Stem Cell ◽  
Biological Study ◽  
Adrenergic Stimulation ◽  
Cell Therapies ◽  
Channel Expression ◽  
Induced Pluripotent

Background. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are providing new possibilities for the biological study, cell therapies, and drug discovery. However, the ion channel expression and functions as well as regulations in hiPSC-CMs still need to be fully characterized. Methods. Cardiomyocytes were derived from hiPS cells that were generated from two healthy donors. qPCR and patch clamp techniques were used for the study. Results. In addition to the reported ion channels, INa, ICa-L, ICa-T, If, INCX, IK1, Ito, IKr, IKs IKATP, IK-pH, ISK1–3, and ISK4, we detected both the expression and currents of ACh-activated (KACh) and Na+-activated (KNa) K+, volume-regulated and calcium-activated (Cl-Ca) Cl−, and TRPV channels. All the detected ion currents except IK1, IKACh, ISK, IKNa, and TRPV1 currents contribute to AP duration. Isoprenaline increased ICa-L, If, and IKs but reduced INa and INCX, without an effect on Ito, IK1, ISK1–3, IKATP, IKr, ISK4, IKNa, ICl-Ca, and ITRPV1. Carbachol alone showed no effect on the tested ion channel currents. Conclusion. Our data demonstrate that most ion channels, which are present in healthy or diseased cardiomyocytes, exist in hiPSC-CMs. Some of them contribute to action potential performance and are regulated by adrenergic stimulation.

scholarly journals Inhibition of Histone Deacetylases Induces K+ Channel Remodeling and Action Potential Prolongation in HL-1 Atrial Cardiomyocytes

2018 ◽  
Vol 49 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Patrick Lugenbiel ◽  
Katharina Govorov ◽  
Ann-Kathrin Rahm ◽  
Teresa Wieder ◽  
Dominik Gramlich ◽  
...  
Keyword(s):  
Action Potential ◽  
Ion Channel ◽  
Action Potential Duration ◽  
Histone Deacetylases ◽  
Trichostatin A ◽  
Class I ◽  
K Channel ◽  
Hdac Inhibition ◽  
Atrial Cardiomyocytes ◽  
Channel Expression

Background/Aims: Cardiac arrhythmias are triggered by environmental stimuli that may modulate expression of cardiac ion channels. Underlying epigenetic regulation of cardiac electrophysiology remains incompletely understood. Histone deacetylases (HDACs) control gene expression and cardiac integrity. We hypothesized that class I/II HDACs transcriptionally regulate ion channel expression and determine action potential duration (APD) in cardiac myocytes. Methods: Global class I/II HDAC inhibition was achieved by administration of trichostatin A (TSA). HDAC-mediated effects on K+ channel expression and electrophysiological function were evaluated in murine atrial cardiomyocytes (HL-1 cells) using real-time PCR, Western blot, and patch clamp analyses. Electrical tachypacing was employed to recapitulate arrhythmia-related effects on ion channel remodeling in the absence and presence of HDAC inhibition. Results: Global HDAC inhibition increased histone acetylation and prolonged APD90 in atrial cardiomyocytes compared to untreated control cells. Transcript levels of voltage-gated or inwardly rectifying K+ channels Kcnq1, Kcnj3 and Kcnj5 were significantly reduced, whereas Kcnk2, Kcnj2 and Kcnd3 mRNAs were upregulated. Ion channel remodeling was similarly observed at protein level. Short-term tachypacing did not induce significant transcriptional K+ channel remodeling. Conclusion: The present findings link class I/II HDAC activity to regulation of ion channel expression and action potential duration in atrial cardiomyocytes. Clinical implications for HDAC-based antiarrhythmic therapy and cardiac safety of HDAC inhibitors require further investigation.

scholarly journals Ion Channel Expression and Electrophysiology of Singular Human (Primary and Induced Pluripotent Stem Cell-Derived) Cardiomyocytes

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3370
Author(s):  
Christina Schmid ◽  
Najah Abi-Gerges ◽  
Michael Georg Leitner ◽  
Dietmar Zellner ◽  
Georg Rast
Keyword(s):  
Stem Cell ◽  
Single Cell ◽  
Pluripotent Stem Cell ◽  
Quantitative Polymerase Chain Reaction ◽  
Drug Effects ◽  
Induced Pluripotent Stem Cell ◽  
Ionic Currents ◽  
Human Cardiomyocytes ◽  
Ventricular Cells ◽  
Induced Pluripotent

Subtype-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are promising tools, e.g., to assess the potential of drugs to cause chronotropic effects (nodal hiPSC-CMs), atrial fibrillation (atrial hiPSC-CMs), or ventricular arrhythmias (ventricular hiPSC-CMs). We used single-cell patch-clamp reverse transcriptase-quantitative polymerase chain reaction to clarify the composition of the iCell cardiomyocyte population (Fujifilm Cellular Dynamics, Madison, WI, USA) and to compare it with atrial and ventricular Pluricytes (Ncardia, Charleroi, Belgium) and primary human atrial and ventricular cardiomyocytes. The comparison of beating and non-beating iCell cardiomyocytes did not support the presence of true nodal, atrial, and ventricular cells in this hiPSC-CM population. The comparison of atrial and ventricular Pluricytes with primary human cardiomyocytes showed trends, indicating the potential to derive more subtype-specific hiPSC-CM models using appropriate differentiation protocols. Nevertheless, the single-cell phenotypes of the majority of the hiPSC-CMs showed a combination of attributes which may be interpreted as a mixture of traits of adult cardiomyocyte subtypes: (i) nodal: spontaneous action potentials and high HCN4 expression and (ii) non-nodal: prominent INa-driven fast inward current and high expression of SCN5A. This may hamper the interpretation of the drug effects on parameters depending on a combination of ionic currents, such as beat rate. However, the proven expression of specific ion channels supports the evaluation of the drug effects on ionic currents in a more realistic cardiomyocyte environment than in recombinant non-cardiomyocyte systems.

Mechanical and electrophysiological effects of a hydroxyphenyl-substituted tetrahydroisoquinoline, SL-1, on isolated rat cardiac tissues

1995 ◽  
Vol 73 (11) ◽  
pp. 1651-1660 ◽  
Author(s):  
Gwo-Jyh Chang ◽  
Ming-Jai Su ◽  
Pei-Hong Lee ◽  
Shoei-Sheng Lee ◽  
Karin Chiung-Sheue Liu
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Positive Inotropic Effect ◽  
Ventricular Myocytes ◽  
Inotropic Effect ◽  
Dependent Manner ◽  
Cardiac Tissues ◽  
Inward Current ◽  
Adrenoceptor Antagonist ◽  
Isolated Rat

The mechanisms of the positive inotropic action of a new synthetic tetrahydroisoquinoline compound, SL-1, were investigated in isolated rat cardiac tissues and ventricular myocytes. SL-1 produced a rapidly developing, concentration-dependent positive inotropic response in both atrial and ventricular muscles and a negative chronotropic effect in spontaneously beating right atria. The positive inotropic effect was not prevented by pretreatment with reserpine (3 mg/kg) or the α-adrenoceptor antagonist prazosin (1 μM), but was suppressed by either the β-adrenoceptor antagonist atenolol (3 μM) or the K+ channel blocker 4-aminopyridine (4AP, 1 mM). In the whole-cell recording study, SL-1 increased the plateau level and prolonged the action potential duration in a concentration-dependent manner and decreased the maximum upstroke velocity [Formula: see text] and amplitude of the action potential in isolated rat ventricular myocytes stimulated at 1.0 Hz. On the other hand, SL-1 had little effect on the resting membrane potential, although it caused a slight decrease at higher concentrations. Voltage clamp experiments revealed that the increase of action potential plateau and prolongation of action potential duration were associated with an increase of Ca2+ inward current (ICa) via the activation of β-adrenoceptors and a prominent inhibition of 4AP-sensitive transient outward K+ current (Ito) with an IC50 of 3.9 μM. Currents through the inward rectifier K+ channel (IKl) were also reduced. The inhibition of Ito is characterized by a reduction in peak amplitude and a marked acceleration of current decay but without changes on the voltage dependence of steady-state inactivation. In addition to the inhibition of K+ currents, SL-1 also inhibited the Na+ inward current (INa) with an IC50 of 5.4 μM, which was correlated with the decrease of [Formula: see text]. We conclude that the positive inotropic effect of SL-1 may be due to an increase in Ca2+ current mediated via partial activation of β-adrenoceptors and an inhibition of K+ outward currents and the subsequent prolongation of action potentials.Key words: SL-1, tetrahydroisoquinoline, inotropic and chronotropic action, action potential, Na+, Ca2+, and K+ currents.

scholarly journals Plasma membrane ion channels and epithelial to mesenchymal transition in cancer cells

2016 ◽  
Vol 23 (11) ◽  
pp. R517-R525 ◽  
Author(s):  
Iman Azimi ◽  
Gregory R Monteith
Keyword(s):  
Plasma Membrane ◽  
Ion Channels ◽  
Ion Channel ◽  
Cancer Cells ◽  
Epithelial To Mesenchymal Transition ◽  
Therapeutic Resistance ◽  
Therapeutic Approaches ◽  
Mesenchymal Transition ◽  
Pharmacological Modulation ◽  
Channel Expression

A variety of studies have suggested that epithelial to mesenchymal transition (EMT) may be important in the progression of cancer in patients through metastasis and/or therapeutic resistance. A number of pathways have been investigated in EMT in cancer cells. Recently, changes in plasma membrane ion channel expression as a consequence of EMT have been reported. Other studies have identified specific ion channels able to regulate aspects of EMT induction. The utility of plasma membrane ion channels as targets for pharmacological modulation make them attractive for therapeutic approaches to target EMT. In this review, we provide an overview of some of the key plasma membrane ion channel types and highlight some of the studies that are beginning to define changes in plasma membrane ion channels as a consequence of EMT and also their possible roles in EMT induction.

scholarly journals Co-expression of calcium channels and delayed rectifier potassium channels protects the heart from proarrhythmic events

2019 ◽  
Author(s):  
Sara Ballouz ◽  
Melissa M Mangala ◽  
Matthew D Perry ◽  
Stewart Heitmann ◽  
Jesse A Gillis ◽  
...  
Keyword(s):  
Ion Channel ◽  
Cardiac Electrophysiology ◽  
Meta Analysis ◽  
Surrogate Marker ◽  
Induced Pluripotent Stem Cell ◽  
Delayed Rectifier ◽  
Cardiac Electrical Activity ◽  
Channel Expression ◽  
Induced Pluripotent ◽  
Electrical Signaling

AbstractCardiac electrical activity is controlled by the carefully orchestrated activity of more than a dozen different ion conductances. Yet, there is considerable variability in cardiac ion channel expression levels both within and between subjects. In this study we tested the hypothesis that variations in ion channel expression between individuals are not random but rather there are modules of co-expressed genes and that these modules make electrical signaling in the heart more robust.Meta-analysis of 3653 public RNA-Seq datasets identified a strong correlation between expression of CACNA1C (L-type calcium current, ICaL) and KCNH2 (rapid delayed rectifier K+ current, IKr), which was verified in mRNA extracted from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). In silico modeling, validated with functional measurements in hiPSC-CM, indicates that the co-expression of CACNA1C and KCNH2 limits the variability in action potential duration and reduces susceptibility to early afterdepolarizations, a surrogate marker for pro-arrhythmia.Impact StatementCoexpressed levels of potassium and calcium ion channel genes in the heart encode more robust cardiac electrophysiology and provide insights into genetic basis of arrhythmic risk

Abstract MP110: Inhibition of the Unfolded Protein Response Reduces Arrhythmic Risk After Myocardial Infarction

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Man Liu ◽  
Hong Liu ◽  
Preethy Parthiban ◽  
guangbin shi ◽  
Gyeoung-Jin Kang ◽  
...  
Keyword(s):  
Ion Channels ◽  
Action Potential ◽  
Ion Channel ◽  
Unfolded Protein Response ◽  
Coronary Artery Ligation ◽  
Unfolded Protein ◽  
Cardiac Ion Channels ◽  
Increased Risk ◽  
The Unfolded Protein Response ◽  
Protein Response

Background: Ischemic cardiomyopathy is associated with an increased risk of sudden death, activation of the unfolded protein response (UPR), and reductions in multiple cardiac ion channels and transporters. When activated, the protein kinase-like ER kinase (PERK) arm of the unfolded protein response (UPR) reduces protein translation and abundance. We hypothesize that inhibition of PERK could prevent cardiac ion channel downregulation and reduce arrhythmic risk after myocardial infarct (MI). Methods: The MI mouse model was induced by a left anterior descending coronary artery ligation. Pharmacological inhibition of PERK was achieved with a specific inhibitor, GSK2606414. Genetic inhibition of PERK was achieved by cardiac-specific PERK knockout in C57BL/6J mice (PERKKO). Echocardiography, telemetry, and electrophysiological measurements were performed to monitor cardiac function and arrhythmias. Results: Three weeks after surgery, the wild type MI mice exhibited decreased ejection fraction (EF%), ventricular tachycardia (VT) and prolonged QTc intervals. The UPR effectors (phospho-PERK, phospho-IRE1, and ATF6N) were elevated significantly (1.7- to 5.9-fold) at protein levels, and all major cardiac ion channels showed decreased protein expression in MI hearts. MI cardiomyocytes showed decreased currents for all major channels (I Na , I CaL , I to , I K1 , and I Kur : 60±6%, 53±9%, 27±6%, 55±7%, and 40±7% of sham, respectively, P<0.05 vs. sham) with significantly prolonged action potential duration (APD 90 : 291±43 ms of MI vs. 100±12 ms of sham, P<0.05) and decreased maximum upstroke velocity (dV/dt max : 95±4 V/s of MI vs. 132±6 ms of sham, P<0.05) of the action potential phase 0. GSK treatment restored I Na and I to , shortened APD, and increased dV/dt max . PERKKO mice exhibited reduced electrical remodeling in response to MI with shortened QTc intervals, less VT episodes, and higher survival rates. Conclusion: PERK is activated during MI and contributes to arrhythmic risk by downregulation of select cardiac ion channels. PERK inhibition prevented these changes and reduced arrhythmic risk. These results suggest that ion channel downregulation during MI is a fundamental arrhythmic mechanism and maintaining ion channel levels is antiarrhythmic.

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