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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

Features of action potentials recorded at 1 Hz.Panel (A) Representative VM action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (B) Representative PC action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (C) Bar graphs summarizing action potential duration measured at 50% of repolarization (APD50), 70% repolarization (APD70) and 90% repolarization (APD90). White bar: WT-VM, light gray bar: WT-PC, black bar: ΔKPQ-VM, dark gray bar: ΔKPQ-PC. *p < 0.05, **p < 0.01. WT-VM: N = 16, 6 animals; ΔKPQ-VM: N = 12, 5 animals; WT-PC: N = 16, 6 animals; ΔKPQ-PC: N = 20, 5 animals. APD: action potential duration.
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f2: Features of action potentials recorded at 1 Hz.Panel (A) Representative VM action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (B) Representative PC action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (C) Bar graphs summarizing action potential duration measured at 50% of repolarization (APD50), 70% repolarization (APD70) and 90% repolarization (APD90). White bar: WT-VM, light gray bar: WT-PC, black bar: ΔKPQ-VM, dark gray bar: ΔKPQ-PC. *p < 0.05, **p < 0.01. WT-VM: N = 16, 6 animals; ΔKPQ-VM: N = 12, 5 animals; WT-PC: N = 16, 6 animals; ΔKPQ-PC: N = 20, 5 animals. APD: action potential duration.

Mentions: APs recorded from WT-PCs were longer than those in WT-VMs, with an APD measured at 90% repolarization (APD90) of 104.3 +/− 6.8 ms versus 30.4 +/− 3.1 ms (p < 0.01). Representative APs are shown in Fig. 2A,B. ΔKPQ-VMs had longer APD90 than WT-VM (p < 0.05). ΔKPQ-PC APs were significantly longer than both WT-PC and ΔKPQ-VM APs, with an average APD90 (in cells that consistently repolarized) of 193.0 +/− 28.4 ms (p < 0.01 vs. WT-PC and p < 0.01 vs. ΔKPQ-VM). Group data for APDs at 50%, 70%, and 90% repolarization are compared for the different cell types in Fig. 2C.


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)

Features of action potentials recorded at 1 Hz.Panel (A) Representative VM action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (B) Representative PC action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (C) Bar graphs summarizing action potential duration measured at 50% of repolarization (APD50), 70% repolarization (APD70) and 90% repolarization (APD90). White bar: WT-VM, light gray bar: WT-PC, black bar: ΔKPQ-VM, dark gray bar: ΔKPQ-PC. *p < 0.05, **p < 0.01. WT-VM: N = 16, 6 animals; ΔKPQ-VM: N = 12, 5 animals; WT-PC: N = 16, 6 animals; ΔKPQ-PC: N = 20, 5 animals. APD: action potential duration.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Features of action potentials recorded at 1 Hz.Panel (A) Representative VM action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (B) Representative PC action potentials. 0 mV represented by horizontal line; gray trace: WT, black trace: ΔKPQ. Panel (C) Bar graphs summarizing action potential duration measured at 50% of repolarization (APD50), 70% repolarization (APD70) and 90% repolarization (APD90). White bar: WT-VM, light gray bar: WT-PC, black bar: ΔKPQ-VM, dark gray bar: ΔKPQ-PC. *p < 0.05, **p < 0.01. WT-VM: N = 16, 6 animals; ΔKPQ-VM: N = 12, 5 animals; WT-PC: N = 16, 6 animals; ΔKPQ-PC: N = 20, 5 animals. APD: action potential duration.
Mentions: APs recorded from WT-PCs were longer than those in WT-VMs, with an APD measured at 90% repolarization (APD90) of 104.3 +/− 6.8 ms versus 30.4 +/− 3.1 ms (p < 0.01). Representative APs are shown in Fig. 2A,B. ΔKPQ-VMs had longer APD90 than WT-VM (p < 0.05). ΔKPQ-PC APs were significantly longer than both WT-PC and ΔKPQ-VM APs, with an average APD90 (in cells that consistently repolarized) of 193.0 +/− 28.4 ms (p < 0.01 vs. WT-PC and p < 0.01 vs. ΔKPQ-VM). Group data for APDs at 50%, 70%, and 90% repolarization are compared for the different cell types in Fig. 2C.

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