Abstract: Objective To observe neuroprotective effects of Ca2+/calmodulin-dependent kinase Ⅱ (CaMK Ⅱ)γ and CaMkII δ against acute neuronal ischemic reperfusion injury in mice and explore the underlying mechanism. Methods Primary cultures of brain neurons isolated from fetal mice (gestational age of 18 days) were transfected with two specific siRNAs (si-CAMK2G and si-CAMK2D) or a control sequence (si-NT). After the transfection, the cells were exposed to oxygen-glucose deprivation/reperfusion (OGD/R) conditions for 1 h followed by routine culture. The expressions of phosphatidylinositol-3-kinase/extracellular signal-regulated kinase (PI3K/Akt/Erk) signaling pathway components in the neurons were detected using immunoblotting. The expressions of the PI3K/Akt/Erk signaling pathway proteins were also detected in the brain tissues of mice receiving middle cerebral artery occlusion (MCAO) or sham operation. Results The neuronal cells transfected with si-CAMK2G showed significantly lower survival rates than those with si-NT transfection at 12, 24, 48, and 72 h after OGD/R (P<0.01), and si-CAMK2G transfection inhibited OGD/R-induced upregulation of CaMKIIγ expression. Compared to si-NT, transfection with si-CAMK2G and si-CAMK2D both significantly inhibited the expressions of PI3K/Akt/Erk signaling pathway components (P<0.01). In the mouse models of MCAO, the expressions of CaMKIIδ and CaMKIIγ were significantly increased in the brain, where activation of the PI3K/Akt/Erk signaling pathway was detected. The expression levels of CaMKIIδ, CaMKIIγ, Erk, phosphorylated Erk, Akt, and phosphorylated Akt were all significantly higher in MCAO mice than in the sham-operated mice at 24, 48, 72, and 96 h after reperfusion (P<0.05). Conclusion The neuroprotective effects of CaMKIIδ and CaMKIIγ against acute neuronal ischemic reperfusion injury are mediated probably by the PI3K/Akt/Erk pathway.

Key words: cerebral ischemia/reperfusion injury; Ca2+/calmodulin-dependent kinase Ⅱ; neuroprotection; phosphatidylinositol-3-kinase; extracellular signal-regulated kinase; signaling pathway