CaMKIIδ subtypes differentially regulate infarct formation following ex vivo myocardial ischemia/reperfusion through NF-κB and TNF-α

Deletion of Ca2+/calmodulin-dependent protein kinase II delta (CaMKIIδ) has been shown to protect against in vivo ischemia/reperfusion (I/R) injury. It remains unclearwhich CaMKIIδ isoformsand downstreammechanisms are responsible for the salutary effects of CaMKIIδ gene deletion. In this study we sought to compare the roles of the CaMKIIδB and CaMKIIδC subtypes and the mechanisms by which they contribute to ex vivo I/R damage. WT, CaMKIIδKO, and mice expressing only CaMKIIδB or δCwere subjectedto ex vivo global ischemia for 25min follow- ed by reperfusion. Infarct formationwas assessed at 60 min reperfusion by triphenyl tetrazoliumchloride (TTC) staining. Deletion of CaMKIIδ conferred significant protection from ex vivo I/R. Re-expression of CaMKIIδC in the CaMKIIδKO background reversed this effect and exacerbated myocardial damage and dysfunction following I/R, while re-expression ofCaMKIIδBwas protective. Selective activation of CaMKIIδC in response to I/Rwas evident in a subcellular fraction enriched for cytosolic/membrane proteins. Further studies demonstrated differential regu- lation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and tumor necrosis fac- tor alpha (TNF-α) expression by CaMKIIδB and CaMKIIδC. Selective activation of CaMKIIδCwas also observed and associated with NF-κB activation in neonatal rat ventricular myocytes (NRVMs) subjected to oxidative stress. Pharmacological inhibition of NF-κB or TNF-α significantly ameliorated infarct formation in WT mice and those that re-express CaMKIIδC, demonstrating distinct roles for CaMKIIδ subtypes in I/R and implicating acute activation of CaMKIIδC and NF-κB in the pathogenesis of reperfusion injury.