Late INa increases diastolic SR-Ca2+-leak in atrial myocardium by activating PKA and CaMKII

TY - JOUR

T1 - Late INa increases diastolic SR-Ca2+-leak in atrial myocardium by activating PKA and CaMKII

AU - Fischer, Thomas H

AU - Herting, Jonas

AU - Mason, Fleur E

AU - Hartmann, Nico

AU - Watanabe, Saera

AU - Nikolaev, Viacheslav O

AU - Sprenger, Julia U

AU - Fan, Peidong

AU - Yao, Lina

AU - Popov, Aron-Frederik

AU - Danner, Bernhard C

AU - Schöndube, Friedrich

AU - Belardinelli, Luiz

AU - Hasenfuss, Gerd

AU - Maier, Lars S

AU - Sossalla, Samuel

N1 - © The Author 2015. Published by Oxford University Press on behalf of the European Society of Cardiology.

PY - 2015/7/1

Y1 - 2015/7/1

N2 - AIMS: Enhanced cardiac late Na current (late INa) and increased sarcoplasmic reticulum (SR)-Ca(2+)-leak are both highly arrhythmogenic. This study seeks to identify signalling pathways interconnecting late INa and SR-Ca(2+)-leak in atrial cardiomyocytes (CMs).METHODS AND RESULTS: In murine atrial CMs, SR-Ca(2+)-leak was increased by the late INa enhancer Anemonia sulcata toxin II (ATX-II). An inhibition of Ca(2+)/calmodulin-dependent protein kinase II (Autocamide-2-related inhibitory peptide), protein kinase A (H89), or late INa (Ranolazine or Tetrodotoxin) all prevented ATX-II-dependent SR-Ca(2+)-leak. The SR-Ca(2+)-leak induction by ATX-II was not detected when either the Na(+)/Ca(2+) exchanger was inhibited (KBR) or in CaMKIIδc-knockout mice. FRET measurements revealed increased cAMP levels upon ATX-II stimulation, which could be prevented by inhibition of adenylyl cyclases (ACs) 5 and 6 (NKY 80) but not by inhibition of phosphodiesterases (IBMX), suggesting PKA activation via an AC-dependent increase of cAMP levels. Western blots showed late INa-dependent hyperphosphorylation of CaMKII as well as PKA target sites at ryanodine receptor type-2 (-S2814 and -S2808) and phospholamban (-Thr17, -S16). Enhancement of late INa did not alter Ca(2+)-transient amplitude or SR-Ca(2+)-load. However, upon late INa activation and simultaneous CaMKII inhibition, Ca(2+)-transient amplitude and SR-Ca(2+)-load were increased, whereas PKA inhibition reduced Ca(2+)-transient amplitude and load and additionally slowed Ca(2+) elimination. In atrial CMs from patients with atrial fibrillation, inhibition of late INa, CaMKII, or PKA reduced the SR-Ca(2+)-leak.CONCLUSION: Late INa exerts distinct effects on Ca(2+) homeostasis in atrial myocardium through activation of CaMKII and PKA. Inhibition of late INa represents a potential approach to attenuate CaMKII activation and decreases SR-Ca(2+)-leak in atrial rhythm disorders. The interconnection with the cAMP/PKA system further increases the antiarrhythmic potential of late INa inhibition.

AB - AIMS: Enhanced cardiac late Na current (late INa) and increased sarcoplasmic reticulum (SR)-Ca(2+)-leak are both highly arrhythmogenic. This study seeks to identify signalling pathways interconnecting late INa and SR-Ca(2+)-leak in atrial cardiomyocytes (CMs).METHODS AND RESULTS: In murine atrial CMs, SR-Ca(2+)-leak was increased by the late INa enhancer Anemonia sulcata toxin II (ATX-II). An inhibition of Ca(2+)/calmodulin-dependent protein kinase II (Autocamide-2-related inhibitory peptide), protein kinase A (H89), or late INa (Ranolazine or Tetrodotoxin) all prevented ATX-II-dependent SR-Ca(2+)-leak. The SR-Ca(2+)-leak induction by ATX-II was not detected when either the Na(+)/Ca(2+) exchanger was inhibited (KBR) or in CaMKIIδc-knockout mice. FRET measurements revealed increased cAMP levels upon ATX-II stimulation, which could be prevented by inhibition of adenylyl cyclases (ACs) 5 and 6 (NKY 80) but not by inhibition of phosphodiesterases (IBMX), suggesting PKA activation via an AC-dependent increase of cAMP levels. Western blots showed late INa-dependent hyperphosphorylation of CaMKII as well as PKA target sites at ryanodine receptor type-2 (-S2814 and -S2808) and phospholamban (-Thr17, -S16). Enhancement of late INa did not alter Ca(2+)-transient amplitude or SR-Ca(2+)-load. However, upon late INa activation and simultaneous CaMKII inhibition, Ca(2+)-transient amplitude and SR-Ca(2+)-load were increased, whereas PKA inhibition reduced Ca(2+)-transient amplitude and load and additionally slowed Ca(2+) elimination. In atrial CMs from patients with atrial fibrillation, inhibition of late INa, CaMKII, or PKA reduced the SR-Ca(2+)-leak.CONCLUSION: Late INa exerts distinct effects on Ca(2+) homeostasis in atrial myocardium through activation of CaMKII and PKA. Inhibition of late INa represents a potential approach to attenuate CaMKII activation and decreases SR-Ca(2+)-leak in atrial rhythm disorders. The interconnection with the cAMP/PKA system further increases the antiarrhythmic potential of late INa inhibition.

U2 - 10.1093/cvr/cvv153

DO - 10.1093/cvr/cvv153

M3 - SCORING: Journal article

C2 - 25990311

VL - 107

SP - 184

EP - 196

JO - CARDIOVASC RES

JF - CARDIOVASC RES

SN - 0008-6363

IS - 1

ER -