.Ryanodine receptors are major components of the deleterious role played by CaMKII in myocardial ischemia reperfusion injury (I/R).,.

SALAS M; DI CARLO MN; SAID M; VALVERDE CA., ; KRANIAS EG; WEHRENS X., ; MATTIAZZI A

New London, NH

Congreso; Cardiac Regulatory Mechanisms Gordon Research Conference; 2012

Ryanodine receptors are major components of the deleterious role played by CaMKII in myocardial ischemia reperfusion injury (I/R).  Salas M*, Di Carlo MN.*, Said M.*, Valverde CA.*, Kranias EG^., Wehrens X.#, Mattiazzi A.*, *Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, UNLP. ^Department of Pharmacology, University of Cincinnati College of Medicine, Cincinnati, Ohio. #Department of Molecular Physiology and Biophysics, Department of Medicine (in Cardiology), Baylor College of Medicine, Houston, TX, USA   Introduction: We have previously described that activation of Ca2+-Calmodulin kinase II (CaMKII) at the onset of reperfusion has a deleterious effect in the irreversible I/R injury: Inhibition of CaMKII produced a significant decrease of infarct size, necrosis (LDH release) and apoptosis (TUNEL and Bax/Bcl-2 ratio). It was further shown that the CaMKII-dependent phosphorylations involved in this effect occurred at the sarcoplasmic reticulum (SR) (Salas et al., J Mol Cell Cardiol., 2010). We therefore hypothesized that two possible candidates for this deleterious action were Thr17 site of fosfolamban (PLN) and Ser2814 of ryanodine receptors (RyR2). Methods: To test this possibility we performed global I/R (45min/2h) in transgenic mice in which Ser2814 site of RyR2 or both phosphorylatable sites of PLN (Thr17, the CaMKII site, and Ser16, the PKA site), were mutated to alanine (Ser2814A and DM mice, respectively). Results: DM mice, showed a significant increase in infarct size (Ctrl: 20.85±4.43% vs. DM: 44.87±10.75%) with impaired contractile recovery (DM: 44.9 ±3.5 % of control).  In contrast, Ser2814A mice showed a significant reduction of the infarct area (Ctrl: 26.74±2.02 % vs. Ser2814A: 12.01±0.9%) associated with an increase in developed pressure and a decrease in diastolic pressure during reperfusion. Conclusion: The results indicate a major role of Ser2814 site of RyR2 in the deleterious effect of CaMKII in the irreversible I/R injury. In contrast, phosphorylation of Thr17 site of PLN, the only PLN site phosphorylated during reperfusion (Vittone et al., J Mol Cell Cardiol., 2002), has a beneficial effect.