Abstract 437: A Novel Variant Cell Cycle Related Kinase Protect Heart Against Ischemia by Promoting Cardiomyocytes Survival

Abstract

Background and objects: Our previous studies identified a novel variant of cell cycle-related kinase in heart (cardiac CCRK or cCCRK) which is different from generic CCRK found in other tissues in terms of its amino acid sequence, substrates, protein-protein interaction and tissue distribution. cCCRK has been found dramatically decreased in the failed heart tissues, while overexpress of cCCRK in cardiac myocytes in vitro protected the cells against induced cell death. Therefore, we tested the hypothesis here that cCCRK acts as a potential candidate of cell survival promotor providing cardiaoprotection in vivo upon cardiac ischemic stress. Methods and results: A cardiac specific transgenic (TG) mouse was generated with an alpha- MHC premotor in which cCCRK was overexpressed by 3.5 folds compared to wild type mice (WT). Both cCCRK TG and the litter-mated WT mice were subjected to an 45 minutes myocardial ischemia followed by an 24 hours reperfusion (IR), and the infarct size was measured by 2,3,5-Triphenyltetrazolium chloride (TTC) staining. We found that despite the similar risk area, infarct size was significantly reduced by 50% in the TG mice verse WT mice (p<0.05). The apoptosis in the adjacent area of the heart tissues measured by TUNEL was reduced by 30% in TG mice vs WT (p<0.05). Mechanistically, the survival-promoting signaling pathway, including phosphorylated extracellular-signal-regulated kinase (p-ERK), phosphorylated Mitogen-activated protein kinase/ERK kinase (p-MEK), and P21, was activated in the heart tissues from TG vs WT mice (p<0.05 vs WT). Overexpression of cCCRK in cardiac myocytes in vitro reduced chelerythrine-induced apoptosis reflected by a reduction of caspase 3 activity, this protection was abolished by the Inhibition of MEK with the treatment of its inhibitor U1206 vs vehicle controls (p<0.05 vs vehicle). Conclusion: This study demonstrated that overexpression of a variant of CCRK in heart provides protection against ischemic stress by activating survival signaling.