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Purkinje Cells as Sources of Arrhythmias in Long QT Syndrome Type 3.

Iyer V, Roman-Campos D, Sampson KJ, Kang G, Fishman GI, Kass RS - Sci Rep (2015)

Bottom Line: Isolated ventricular myocytes (VMs) (EGFP(-)) and PCs (EGFP(+)) from wild type and ΔKPQ mutant hearts were compared using the whole-cell patch clamp technique and microfluorimetry of calcium transients.Marked prolongation of action potential duration of ΔKPQ-PCs was seen compared to ΔKPQ-VMs. ΔKPQ-PCs, but not ΔKPQ-VMs, exhibited frequent early afterdepolarizations, which corresponded to repetitive oscillations of intracellular calcium.We present the first direct experimental evidence that PCs are uniquely sensitive to LQT3 mutations, displaying electrophysiological behavior that is highly pro-arrhythmic.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Columbia University Medical Center, New York, NY.

ABSTRACT
Long QT syndrome (LQTS) is characterized by ventricular arrhythmias and sudden cardiac death. Purkinje cells (PC) within the specialized cardiac conduction system have unique electrophysiological properties that we hypothesize may produce the primary sources of arrhythmia in heritable LQTS. LQTS type 3 (LQT3) transgenic mice harboring the ΔKPQ(+/-) mutation were crossed with Contactin2-EGFP BAC transgenic mice, which express a fluorescent reporter gene within the Purkinje fiber network. Isolated ventricular myocytes (VMs) (EGFP(-)) and PCs (EGFP(+)) from wild type and ΔKPQ mutant hearts were compared using the whole-cell patch clamp technique and microfluorimetry of calcium transients. Increased late sodium current was seen in ΔKPQ-PCs and ΔKPQ-VMs, with larger density in ΔKPQ-PCs. Marked prolongation of action potential duration of ΔKPQ-PCs was seen compared to ΔKPQ-VMs. ΔKPQ-PCs, but not ΔKPQ-VMs, exhibited frequent early afterdepolarizations, which corresponded to repetitive oscillations of intracellular calcium. Abnormalities in cell repolarization were reversed with exposure to mexiletine. We present the first direct experimental evidence that PCs are uniquely sensitive to LQT3 mutations, displaying electrophysiological behavior that is highly pro-arrhythmic.

No MeSH data available.


Related in: MedlinePlus

Representative cells and voltage-clamp recordings for VM and PCs.Panel (A) Photomicrograph of isolated PC and VM; the green fluorescent cell expresses Cntn2-EGFP and represents a typical PC, and the cell without fluorescence represents a typical VM. Panels (B,C) Representative whole cell currents recorded for a step pulse (200 ms at −10 mV; pulse frequency, 0.5 Hz) from VMs (panel (B)) and PCs (panel (C), peak currents are off scale). Gray trace represents a control cell, and black trace represents a ΔKPQ cell. Panels (D,E) Bar graphs summarizing absolute magnitude of INaL (INa measured at 200 ms) normalized by cell capacitance. *p < 0.05 for WT vs ΔKPQ. WT-VM: N = 15, 5 animals; ΔKPQ-VM: N = 17, 5 animals; WT-PC: N = 15, 5 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, VM: ventricular myocyte, PC: Purkinje cell.
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f1: Representative cells and voltage-clamp recordings for VM and PCs.Panel (A) Photomicrograph of isolated PC and VM; the green fluorescent cell expresses Cntn2-EGFP and represents a typical PC, and the cell without fluorescence represents a typical VM. Panels (B,C) Representative whole cell currents recorded for a step pulse (200 ms at −10 mV; pulse frequency, 0.5 Hz) from VMs (panel (B)) and PCs (panel (C), peak currents are off scale). Gray trace represents a control cell, and black trace represents a ΔKPQ cell. Panels (D,E) Bar graphs summarizing absolute magnitude of INaL (INa measured at 200 ms) normalized by cell capacitance. *p < 0.05 for WT vs ΔKPQ. WT-VM: N = 15, 5 animals; ΔKPQ-VM: N = 17, 5 animals; WT-PC: N = 15, 5 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, VM: ventricular myocyte, PC: Purkinje cell.

Mentions: Mouse PCs were easily identified via green fluorescence and morphological differences (Fig. 1A), and had lower capacitance than VMs (corresponding to lesser surface area of the longer, thinner “spindle” shape reported in PCs from mice15), measuring on average 53.9 ± 15.8 pF versus 136.4 ± 44.7 pF (p < 0.01).


Purkinje Cells as Sources of Arrhythmias in Long QT Syndrome Type 3.

Iyer V, Roman-Campos D, Sampson KJ, Kang G, Fishman GI, Kass RS - Sci Rep (2015)

Representative cells and voltage-clamp recordings for VM and PCs.Panel (A) Photomicrograph of isolated PC and VM; the green fluorescent cell expresses Cntn2-EGFP and represents a typical PC, and the cell without fluorescence represents a typical VM. Panels (B,C) Representative whole cell currents recorded for a step pulse (200 ms at −10 mV; pulse frequency, 0.5 Hz) from VMs (panel (B)) and PCs (panel (C), peak currents are off scale). Gray trace represents a control cell, and black trace represents a ΔKPQ cell. Panels (D,E) Bar graphs summarizing absolute magnitude of INaL (INa measured at 200 ms) normalized by cell capacitance. *p < 0.05 for WT vs ΔKPQ. WT-VM: N = 15, 5 animals; ΔKPQ-VM: N = 17, 5 animals; WT-PC: N = 15, 5 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, VM: ventricular myocyte, PC: Purkinje cell.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542521&req=5

f1: Representative cells and voltage-clamp recordings for VM and PCs.Panel (A) Photomicrograph of isolated PC and VM; the green fluorescent cell expresses Cntn2-EGFP and represents a typical PC, and the cell without fluorescence represents a typical VM. Panels (B,C) Representative whole cell currents recorded for a step pulse (200 ms at −10 mV; pulse frequency, 0.5 Hz) from VMs (panel (B)) and PCs (panel (C), peak currents are off scale). Gray trace represents a control cell, and black trace represents a ΔKPQ cell. Panels (D,E) Bar graphs summarizing absolute magnitude of INaL (INa measured at 200 ms) normalized by cell capacitance. *p < 0.05 for WT vs ΔKPQ. WT-VM: N = 15, 5 animals; ΔKPQ-VM: N = 17, 5 animals; WT-PC: N = 15, 5 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, VM: ventricular myocyte, PC: Purkinje cell.
Mentions: Mouse PCs were easily identified via green fluorescence and morphological differences (Fig. 1A), and had lower capacitance than VMs (corresponding to lesser surface area of the longer, thinner “spindle” shape reported in PCs from mice15), measuring on average 53.9 ± 15.8 pF versus 136.4 ± 44.7 pF (p < 0.01).

Bottom Line: Isolated ventricular myocytes (VMs) (EGFP(-)) and PCs (EGFP(+)) from wild type and ΔKPQ mutant hearts were compared using the whole-cell patch clamp technique and microfluorimetry of calcium transients.Marked prolongation of action potential duration of ΔKPQ-PCs was seen compared to ΔKPQ-VMs. ΔKPQ-PCs, but not ΔKPQ-VMs, exhibited frequent early afterdepolarizations, which corresponded to repetitive oscillations of intracellular calcium.We present the first direct experimental evidence that PCs are uniquely sensitive to LQT3 mutations, displaying electrophysiological behavior that is highly pro-arrhythmic.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Columbia University Medical Center, New York, NY.

ABSTRACT
Long QT syndrome (LQTS) is characterized by ventricular arrhythmias and sudden cardiac death. Purkinje cells (PC) within the specialized cardiac conduction system have unique electrophysiological properties that we hypothesize may produce the primary sources of arrhythmia in heritable LQTS. LQTS type 3 (LQT3) transgenic mice harboring the ΔKPQ(+/-) mutation were crossed with Contactin2-EGFP BAC transgenic mice, which express a fluorescent reporter gene within the Purkinje fiber network. Isolated ventricular myocytes (VMs) (EGFP(-)) and PCs (EGFP(+)) from wild type and ΔKPQ mutant hearts were compared using the whole-cell patch clamp technique and microfluorimetry of calcium transients. Increased late sodium current was seen in ΔKPQ-PCs and ΔKPQ-VMs, with larger density in ΔKPQ-PCs. Marked prolongation of action potential duration of ΔKPQ-PCs was seen compared to ΔKPQ-VMs. ΔKPQ-PCs, but not ΔKPQ-VMs, exhibited frequent early afterdepolarizations, which corresponded to repetitive oscillations of intracellular calcium. Abnormalities in cell repolarization were reversed with exposure to mexiletine. We present the first direct experimental evidence that PCs are uniquely sensitive to LQT3 mutations, displaying electrophysiological behavior that is highly pro-arrhythmic.

No MeSH data available.


Related in: MedlinePlus