Limits...
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

PCs carrying the ΔKPQ mutation show early afterdepolarizations associated with disordered intracellular calcium cycling.Panel (A,B) Consecutive WT-PC action potentials (Panel (A)) and a representative calcium transient (Panel (B)). Panel (C,D) Consecutive action potentials from a ΔKPQ-PC (Panel (C)) and a representative calcium transient (Panel (D)) show prolonged duration, with repetitive plateau depolarizations and oscillation in calcium transient. Panel (E) Summary data showing number of cells with early afterdepolarizations and number of early afterdepolarizations for ΔKPQ-PCs compared to WT-PCs. Panel (F) Summary data showing the duration of calcium transients as assessed by time-interval to 90% Ca2+ decay (CaD90) for ΔKPQ-PCs compared to WT-PCs. *p < 0.05. For action potential experiments (panel (E)), WT-PC: N = 11, 3 animals; ΔKPQ-PC: N = 7, 3 animals. For calcium imaging experiments (panel (F)), WT-PC: N = 10, 4 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, CaD90: time-interval to 90% Ca2+ decay, EAD: early afterdepolarization.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4542521&req=5

f5: PCs carrying the ΔKPQ mutation show early afterdepolarizations associated with disordered intracellular calcium cycling.Panel (A,B) Consecutive WT-PC action potentials (Panel (A)) and a representative calcium transient (Panel (B)). Panel (C,D) Consecutive action potentials from a ΔKPQ-PC (Panel (C)) and a representative calcium transient (Panel (D)) show prolonged duration, with repetitive plateau depolarizations and oscillation in calcium transient. Panel (E) Summary data showing number of cells with early afterdepolarizations and number of early afterdepolarizations for ΔKPQ-PCs compared to WT-PCs. Panel (F) Summary data showing the duration of calcium transients as assessed by time-interval to 90% Ca2+ decay (CaD90) for ΔKPQ-PCs compared to WT-PCs. *p < 0.05. For action potential experiments (panel (E)), WT-PC: N = 11, 3 animals; ΔKPQ-PC: N = 7, 3 animals. For calcium imaging experiments (panel (F)), WT-PC: N = 10, 4 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, CaD90: time-interval to 90% Ca2+ decay, EAD: early afterdepolarization.

Mentions: Representative PC APs with EADs (ΔKPQ cell) and without EADs (WT cell) are shown in Fig. 5 (panels A and C) alongside representative intracellular calcium transients (panels B and D). In ΔKPQ-PCs, 7/7 cells exhibited at least one EAD during the drive train, compared to 0/8 ΔKPQ-VMs, 1/11 WT-PCs and 0/8 WT-VMs (p < 0.05 for ΔKPQ-PC vs. each group). In total, 114 EADs were present in ΔKPQ-PCs (N = 68 sweeps, representing on average 1.7 EADs per AP), with some sweeps showing sequential EADs during a single AP plateau (as summarized in Fig. 5E). Calcium transients in WT-PCs were of relatively short duration, without a substantial plateau phase. The long APs in ΔKPQ-PCs were associated with oscillations in the calcium transient. Corresponding to the multiple EAD events, calcium transient duration was prolonged in KPQ-PCs by nearly an order of magnitude (Fig. 5F).


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)

PCs carrying the ΔKPQ mutation show early afterdepolarizations associated with disordered intracellular calcium cycling.Panel (A,B) Consecutive WT-PC action potentials (Panel (A)) and a representative calcium transient (Panel (B)). Panel (C,D) Consecutive action potentials from a ΔKPQ-PC (Panel (C)) and a representative calcium transient (Panel (D)) show prolonged duration, with repetitive plateau depolarizations and oscillation in calcium transient. Panel (E) Summary data showing number of cells with early afterdepolarizations and number of early afterdepolarizations for ΔKPQ-PCs compared to WT-PCs. Panel (F) Summary data showing the duration of calcium transients as assessed by time-interval to 90% Ca2+ decay (CaD90) for ΔKPQ-PCs compared to WT-PCs. *p < 0.05. For action potential experiments (panel (E)), WT-PC: N = 11, 3 animals; ΔKPQ-PC: N = 7, 3 animals. For calcium imaging experiments (panel (F)), WT-PC: N = 10, 4 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, CaD90: time-interval to 90% Ca2+ decay, EAD: early afterdepolarization.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: PCs carrying the ΔKPQ mutation show early afterdepolarizations associated with disordered intracellular calcium cycling.Panel (A,B) Consecutive WT-PC action potentials (Panel (A)) and a representative calcium transient (Panel (B)). Panel (C,D) Consecutive action potentials from a ΔKPQ-PC (Panel (C)) and a representative calcium transient (Panel (D)) show prolonged duration, with repetitive plateau depolarizations and oscillation in calcium transient. Panel (E) Summary data showing number of cells with early afterdepolarizations and number of early afterdepolarizations for ΔKPQ-PCs compared to WT-PCs. Panel (F) Summary data showing the duration of calcium transients as assessed by time-interval to 90% Ca2+ decay (CaD90) for ΔKPQ-PCs compared to WT-PCs. *p < 0.05. For action potential experiments (panel (E)), WT-PC: N = 11, 3 animals; ΔKPQ-PC: N = 7, 3 animals. For calcium imaging experiments (panel (F)), WT-PC: N = 10, 4 animals; ΔKPQ-PC: N = 23, 5 animals. WT: wild type, CaD90: time-interval to 90% Ca2+ decay, EAD: early afterdepolarization.
Mentions: Representative PC APs with EADs (ΔKPQ cell) and without EADs (WT cell) are shown in Fig. 5 (panels A and C) alongside representative intracellular calcium transients (panels B and D). In ΔKPQ-PCs, 7/7 cells exhibited at least one EAD during the drive train, compared to 0/8 ΔKPQ-VMs, 1/11 WT-PCs and 0/8 WT-VMs (p < 0.05 for ΔKPQ-PC vs. each group). In total, 114 EADs were present in ΔKPQ-PCs (N = 68 sweeps, representing on average 1.7 EADs per AP), with some sweeps showing sequential EADs during a single AP plateau (as summarized in Fig. 5E). Calcium transients in WT-PCs were of relatively short duration, without a substantial plateau phase. The long APs in ΔKPQ-PCs were associated with oscillations in the calcium transient. Corresponding to the multiple EAD events, calcium transient duration was prolonged in KPQ-PCs by nearly an order of magnitude (Fig. 5F).

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