Phosphorylation of ryanodine receptors (RyR2) is a key player in the ischemia/reperfusion-induced infarct size and decrease in cardiac function

VALVERDE CA; DI CARLO MN; SAID M; WEHRENS XH; MATTIAZZI A; SALAS M

San Diego

Congreso; XXI ISHR Wolrd Congress; 2013

International Society for Heart Research

Background*     We have previously showed that CaMKII-dependent phosphorylations at the sarcoplasmic reticulum are main determinants of the detrimental effects of irreversible cardiac ischemia followed by reperfusion (I/R). The present experiments address the role of CaMKII-mediated phosphorylation of RyR2 on contractility and cardiac infarct size after I/R. The main goal of the present work is to elucidate whether RyR2 phosphorylation is a key determinant of the progression toward the post-ischemic injury mediated by CaMKII. Methods*          Experiments were performed in knock-in mice in which an alanine or aspartic acid replaces serine at RyR2-2814 residue (Ser2814A or Ser2814D, respectively), to obtain a constitutively unphosphorylated/phosphorylated Ser2814 site (Ser2814A/Ser2814D). Isolated Langendorff perfused hearts from Ser2814A, Ser2814D mice and their control WT mice, were submitted to global IR (45 min of ischemia/120min of reperfusion). Results*              Basal parameters of S2814A and Ser2814D did not differ from control hearts. In WT mice, there was a significant increase in the phosphorylation of the CaMKII-dependent Ser2814 residue of RyR2 at the onset of reperfusion, with a peak at 3 min of reperfusion (210.3±41.9% of pre-ischemic value). In Ser2814A mice, I/R induced a significant reduction in the infarct size (Ser2814A:12.6±1.2% vs. control: 25.1±2.3%) with an improvement in contractility, assessed by left ventricular developed pressure (Ser2814A: 7.2±2.0% vs. WT: 2.1±0.5% of pre-ischemic value), and a lower left ventricular end diastolic pressure during reperfusion. In contrast, Ser2814D mice showed an increased infarct size (36.9±4.5%) in comparison to WT (21.2±4.0%). This occurs in spite of the diminished SR Ca2+ content described in Ser2814D vs. WT mice (van Oort et al., 2010). Conclusion*       Our results suggest that CaMKII phosphorylation of RyR2 Ca2+ release channels at Ser2814 is main determinant of the deleterious effects of I/R injury. (Grants: PICT2008-1770, PICT2008-1795 and PICT2010-1903, Préstamo BID).