Ablation of PLN rescues reperfusion arrhythmias but exacerbates myocardium infarction in hearts with Ca2+/calmodulin kinase II constitutive phosphorylation of ryanodine receptors

VALVERDE CA; CIOCCI PARDO A; FELICE J; PORTIANSKY E; WEHRENS XHT; DI CARLO M; RAGONE I; CONSOLINI A; KRANIAS EG; MAZZOCCHI G; SALAS M; CELY-ORTIZ A; MOSCA S; MATTIAZZI A

CARDIOVASCULAR RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2019 vol. 115 p. 556 - 569

0008-6363

Background: Abnormal Ca2+ release from the sarcoplasmic reticulum (SR), like that produced by CaMKII-dependent phosphorylation of RyR2 at Ser2814 site, hasconsistently been linked to arrhythmogenesis and ischemia/reperfusion-induced cell death. In contrast, the role played by SR Ca2+ uptake on these diseases, remains controversial. We tested the hypothesis that an increase in SR Ca2+ uptake is able to attenuate reperfusion arrhythmias and cardiac injury associated to increased RyR2-Ser2814 phosphorylation. Methods and Results: We used WT mice, previously shown to exhibit a transient increase in RyR2-Ser2814 site phosphorylation at the onset of reperfusion; mice with constitutive pseudo-phosphorylation of RyR2 at Ser2814 (S2814D), in an attempt to exacerbate CaMKII-dependent reperfusion arrhythmias and cardiac damage, and PLNdeficient-S2814D knock-in mice (SDKO) resulting from crossbreeding S2814D with PLN deficient mice (PLNKO). At baseline, S2814D and SDKO mice had structurallynormal hearts without arrhythmias. Upon cardiac ischemia/reperfusion (I/R), PLNablation was able to prevent reperfusion arrhythmias, which were abundant in WT and S2814D hearts. In contrast, PLN ablation further increased infarct size compared to WT and S2814D hearts. Mechanistically, the enhanced SR Ca2+ sequestration evoked by PLN ablation in SDKO hearts prevented arrhythmogenic events upon reperfusion by fragmenting SR Ca2+ waves into non-propagated, non-arrhythmogenic events (miniwaves). Conversely, the increase in SR Ca2+ sequestration did not reduce but rather exacerbated I/R induced SR Ca2+ leak, as well as mitochondrial alterations, which were greatly avoided by inhibition of RyR2. These results indicate that the increase in SR Ca2+ uptake is ineffective in precluding that the enhanced SR Ca2+ leak of PLN ablated myocytes either flows into the nearby mitochondria and/or activates additionalCaMKII pathways, enabling cardiac damage. Conclusions: Our results demonstrate that increasing SR Ca2+ uptake by PLN ablation can prevent the arrhythmic events triggered by CaMKII-dependent phosphorylation of RyR2-induced-SR Ca2+ leak and underscore the benefits of increasing SERCA2a activity on SR Ca2+ triggered arrhythmias. However, it cannot prevent but rather exacerbates I/R cardiac infarct.