Heart Failure Enhanced Pulmonary Vein Arrhythmogenesis and Dysregulated Sodium and Calcium Homeostasis with Increased Calcium Sparks
ABSTRACT Late sodium currents and intracellular Ca(2+) (Ca(2+) (i)) dynamics play an important role in arrhythmogenesis of pulmonary vein (PV) and heart failure (HF). It is not clear whether HF enhances PV arrhythmogenesis through modulation of Ca(2+) homeostasis and increased late sodium currents. The aim of this study was to investigate the sodium and calcium homeostasis in PV cardiomyocytes with HF. METHODS AND RESULTS: Whole-cell patch clamp was used to investigate the action potentials and ionic currents in isolated rabbit single PV cardiomyocytes with and without rapid pacing induced HF. The Ca(2+) (i) dynamics were evaluated through fluorescence and confocal microscopy. As compared to control PV cardiomyocytes (n = 18), HF PV cardiomyocytes (n = 13) had a higher incidence of delayed afterdepolarization (45% vs 13%, P < 0.05) and faster spontaneous activity (3.0 ± 0.2 vs 2.1 ± 0.2 Hz, P < 0.05). HF PV cardiomyocytes had increased late Na(+) currents, Na(+) /Ca(2+) exchanger currents, and transient inward currents, but had decreased Na(+) currents or L-type calcium currents. HF PV cardiomyocytes with pacemaker activity had larger Ca(2+) (i) transients (R410/485, 0.18 ± 0.04 vs 0.11 ± 0.02, P < 0.05), and sarcoplasmic reticulum Ca(2+) stores. Moreover, HF PV cardiomyocytes with pacemaker activity (n = 18) had higher incidence (95% vs 70%, P < 0.05), frequency (7.8 ± 3.1 vs 2.3 ± 1.2 spark/mm/s, P < 0.05), amplitude (F/F(0) , 3.2 ± 0.8 vs 1.9 ± 0.5, P < 0.05), and longer decay time (65 ± 3 vs 48 ± 4 ms, P < 0.05) of Ca(2+) sparks than control PV cardiomyocytes with pacemaker activity (n = 18). CONCLUSIONS: Dysregulated sodium and calcium homeostasis, and enhanced calcium sparks promote arrhythmogenesis of PV cardiomyocytes in HF, which may play an important role in the development of atrial fibrillation.
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ABSTRACT: Ectopic foci originating from the pulmonary veins (PVs) have been suggested as the underlying cause for generating atrial arrhythmias that include atrial fibrillation (AF). Recent experimental findings indicate two types of PV cells: pacemaking and non-pacemaking. In this study, we have developed two mathematical models for human PV cardiomyocytes with and without pacemaking activities. The models were reconstructed by modifying an existing model of the human right atrium to incorporate extant experimental data on the electrical differences between the two cell types. Differences in their action potential (AP) profiles and automaticity were reproduced by the models, which can be attributed to the observed differences in the current densities of I(NCX), I(to), I(Na) and I(Ca-L), as well as the difference in the channel kinetics of I(Ca-L) and inclusion of the I(f) and I(Ca-T) currents in the pacemaking cells. The developed models provide a useful tool suitable for studying the substrates for generating AF.Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:199-202. DOI:10.1109/EMBC.2012.6345905
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ABSTRACT: Background: This study aimed to investigate the mechanism by which colchicine suppresses atrial fibrillation (AF) in a rabbit heart failure (HF) model. Methods and results: HF was induced by coronary ligation. Using the Langendorff perfusion system, monophasic action potentials were recorded in =the left atrial appendage (LAA) of normal rabbits (n = 6) and HF rabbits (n = 6) treated with colchicine (100 mu M) followed by colchicine (100 mu M) plus paclitaxel (5 RIM). Collagen content and mRNA and protein expression of ion channels through the PI3K/AKT/eNOS signaling pathway were evaluated in LAA of normal rabbits (n = 6) and HF rabbits treated with vehicle (n =6) or colchicine (n = 6) intraperitoneal injection for 2 clays. Colchicine decreased action potential duration (74.1 +/- 2.6 vs 91.8 +/- 3.3 ms, P < 0.001), effective refractory period, and maximum slope of the restitution curve in HF LAA. However, these effects were reversed by paclitaxel. The incidence of early afterdepolarizations, delayed afterdepolarizations, and AF inducibility was significantly lower after colchicine perfusion than at baseline or after colchicine plus paclitaxel perfusion. Cardiac function increased and LA fibrosis decreased after colchicine treatment, mRNA and protein expression of Kir2.1, Kv1.4, Kv1.5, Kv7.1, Cav1.2, and SERCA2a were upregulated after colchicine treatment, as was mRNA expression of PI3K, AKT, and eNOS. Conclusion: Colchicine regulates ion channel gene expression and activates the PI3K/AKT/eNOS signaling pathway in HF rabbits, which may reverse atrial remodeling and suppress AF.International Journal of Cardiology 08/2014; 176(3). DOI:10.1016/j.ijcard.2014.07.069 · 6.18 Impact Factor
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ABSTRACT: Geranylgeranylacetone (GGA) has been reported up-regulating heat shock protein (HSP) expression, and protecting against atrial remodeling. This study aimed to investigate the effects of GGA on atrial electrophysiology and inducibility of atrial fibrillation (AF) in heart failure (HF) model. HF rabbits were created 4weeks after coronary artery ligation. Monophasic action potential recordings and multielectrode array were used to record the electrophysiological characteristics of left atrium (LA) in normal, or HF rabbits with (HF-GGA) and without (HF-control) oral administration of GGA (200mg/kg, 24h before experiments). The mRNA and protein expressions of ionic channels were measured by Western blot and PCR. HF-GGA LA (n=10), similar to normal LA (n=10) had a shorter action potential duration (APD) and effective refractory period than HF-control LA (n=10). HF-GGA LA had less triggered activity and APD alternans (20% vs. 100%, P=0.001), lower maxima slope of restitution curve of APD (0.94±0.04 vs.1.69±0.04, P<0.001), and less inducibility of AF (50% vs. 100%, P=0.033) than HF-control LA. HF-GGA LA had a shorter activation time and higher conduction velocity than HF-control LA. HF-GGA LA had a higher mRNA expression of Cav1.2, Nav1.5, Kir2.1, Kv1.4, Kv7.1, Kv11.1, sarcoplasmic reticulum Ca(2+)-ATPase, and higher phosphorylation of phospholamban than HF-control LA. GGA decreases triggered activity, dispersion of APD and inducibility of AF in failing heart through induction of HSP, and modulation of ionic channels and calcium homeostasis.International journal of cardiology 07/2013; 168(4). DOI:10.1016/j.ijcard.2013.06.072 · 6.18 Impact Factor