Abnormal Calcium Handling in Atrial Fibrillation Is Linked to Changes in Cyclic AMP Dependent Signaling

• Published in: Cells (Basel, Switzerland) Vol. 10; no. 11; p. 3042
• Main Authors: Reinhardt, Franziska, Beneke, Kira, Pavlidou, Nefeli Grammatica, Conradi, Lenard, Reichenspurner, Hermann, Hove-Madsen, Leif, Molina, Cristina E.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 05.11.2021; MDPI
• Subjects: Adrenergic beta-Antagonists - pharmacology; Aged; Animals; atrial fibrillation (AF); Atrial Fibrillation - metabolism; Ca2+/calmodulin-dependent protein kinase II; Caffeine; Calcium (reticular); Calcium - metabolism; Calcium channels (L-type); Calcium Channels, L-Type - metabolism; Calcium currents; Calcium Signaling - drug effects; Calcium signalling; Calcium-binding protein; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - metabolism; Calmodulin; cAMP-dependent regulation; Cardiac arrhythmia; Carvedilol - pharmacology; Cyclic AMP; Cyclic AMP - metabolism; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic AMP-Dependent Protein Kinases - metabolism; Cytosol - drug effects; Cytosol - metabolism; Cytotoxicity; Down-regulation; Experiments; Female; Fibrillation; Fluorescence resonance energy transfer; Humans; Kinases; L-type calcium current (ICa,L); Light emitting diodes; Lymphocytes T; Male; Middle Aged; Myocytes; patch-clamp; Phosphorylation; Protein kinase A; protein kinase A (PKA); Proteins; Receptors, Adrenergic, beta - metabolism; Regulation; Sarcoplasmic reticulum; Sarcoplasmic Reticulum - drug effects; Sarcoplasmic Reticulum - metabolism; Sinuses; transient inward current (ITI); St Louis Missouri; United Kingdom > UK; United States > US; Germany; cAMP-dependent regulation; transient inward current (ITI); atrial fibrillation (AF); protein kinase A (PKA); patch-clamp; L-type calcium current (ICa,L)
• ISSN: 2073-4409; 2073-4409
• DOI: 10.3390/cells10113042

Both, the decreased L-type Ca2+ current (ICa,L) density and increased spontaneous Ca2+ release from the sarcoplasmic reticulum (SR), have been associated with atrial fibrillation (AF). In this study, we tested the hypothesis that remodeling of 3′,5′-cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) signaling is linked to these compartment-specific changes (up- or down-regulation) in Ca2+-handling. Perforated patch-clamp experiments were performed in atrial myocytes from 53 patients with AF and 104 patients in sinus rhythm (Ctl). A significantly higher frequency of transient inward currents (ITI) activated by spontaneous Ca2+ release was confirmed in myocytes from AF patients. Next, inhibition of PKA by H-89 promoted a stronger effect on the ITI frequency in these myocytes compared to myocytes from Ctl patients (7.6-fold vs. 2.5-fold reduction), while the β-agonist isoproterenol (ISO) caused a greater increase in Ctl patients (5.5-fold vs. 2.1-fold). ICa,L density was larger in myocytes from Ctl patients at baseline (p < 0.05). However, the effect of ISO on ICa,L density was only slightly stronger in AF than in Ctl myocytes (3.6-fold vs. 2.7-fold). Interestingly, a significant reduction of ICa,L and Ca2+ sparks was observed upon Ca2+/Calmodulin-dependent protein kinase II inhibition by KN-93, but this inhibition had no effect on ITI. Fluorescence resonance energy transfer (FRET) experiments showed that although AF promoted cytosolic desensitization to β-adrenergic stimulation, ISO increased cAMP to similar levels in both groups of patients in the L-type Ca2+ channel and ryanodine receptor compartments. Basal cAMP signaling also showed compartment-specific regulation by phosphodiesterases in atrial myocytes from 44 Ctl and 43 AF patients. Our results suggest that AF is associated with opposite changes in compartmentalized PKA/cAMP-dependent regulation of ICa,L (down-regulation) and ITI (up-regulation).