CaM Kinase II mediates maladaptive post-infarct remodeling but not acute myocardial ischemia/reperfusion injury

Calcium/calmodulin-dependent protein kinase II (CaMKII) was suggested to mediate ischemic myocardial injury and adverse cardiac remodeling. However, the specific functions of the CaMKII isoforms and splice variants in ischemia/reperfusion (I/R) injury have not been investigated yet. Thus, we studied the roles of the CaMKII isoforms and splice variants in I/R by the use of various CaMKII mutant mice. CaMKIIδC was up-regulated already one day after I/R injury but surprisingly, acute I/R injury was neither affected in CaMKIIδ-deficient mice, CaMKIIδ-deficient mice in which the splice variants CaMKIIδB and C were re-expressed nor in conditional CaMKIIδ/γ double-knockout mice (DKO). In contrast, 5 weeks after I/R, DKO mice were protected against extensive scar formation and cardiac dysfunction. Leukocyte infiltration was not altered one day but five days after I/R, explaining the late effects of CaMKII deletion on post-I/R remodeling. Other than reported before, we demonstrate that CaMKII is not critically involved in the immediate mechanisms that regulate acute I/R injury but in the process of post-infarct remodeling. We analysed 6 groups in total: 3 groups from wild-type control animals and 3 groups from CaMKII delta/gamma double-KO mice. Sham operated animals served as controls in both wild-type and KO animal groups. 2 different time points in ischia/reperfusion operated animals were investigated: 1 day and 5 days post-surgery.