Abstract 12810: Postconditioning Induces Activation of cGMP/PKG Pathway and Phospholamban Phosphorylation Independently of PI3K/Akt Cascade in Rat Hearts
It has been proposed that activation of SERCA by phosphorylation of phospholamban (PLB) mediates the recovery of intracellular Ca2+ under stress situations and attenuates reperfusion injury. We assessed whether postconditioning (PoCo) causes phosphorylation of phospholamban and the implication of PI3K/Akt signaling.
Methods: Cell death (LDH release and infarct size), LVP, phosphorylation of PLB at Ser16 and Thr17, Akt and GSK-3β at different time points were measured in rat hearts submitted to 40min of ischemia and reperfusion with and without a PoCo protocol (6 cycles of 10 seconds of reperfusion and 10 seconds of reocclusion), a protocol that reduced infarct size by 48%. To exclude the possibility that the differences in phosphorylation were a mere reflection of differences between groups in cell death, hearts were reperfused with the contractile inhibitor blebbistatin, a drug effective in preventing cell death at the onset of reperfusion.
Results: PoCo and administration of a cell-permeant analog of cGMP (8-pCPT-cGMP) markedly increased phosphorylation of both pentameric and monomeric forms of Ser16 and Thr17 PLB and reduced the formation of peroxynitrite at 5 min of reperfusion, while no differences between groups were observed in Akt, eNOS and GSK-3β phosphorylated forms. In the absence of blebbistatin, blockade of cGMP synthesis with ODQ or inhibition of PKG with KT5823 abolished the cardioprotective effects of PoCo and markedly reduced the phosphorylation of PLB while inhibition of PI3K/Akt cascade with LY294002 had no effect on PoCo protection nor in PLB phosphorylation.
Conclusions: these results demonstrate that PoCo phosphorylates PLB by a mechanism dependent of cGMP/PKG pathway, independent of the IP3K/Akt cascade and probably related to increased nitric oxide availability as a result of reduced peroxynitrite formation.
- © 2011 by American Heart Association, Inc.