Hypoxic preconditioning attenuates necroptotic neuronal death induced by global cerebral ischemia via Drp1-dependent signaling pathway mediated by CaMKII inactivation in adult rats

Hypoxic preconditioning (HPC) alleviates the selective and delayed neuronal death in the hippocampal CA1 region induced by transient global cerebral ischemia (tGCI). This type of cell death may include different programmed cell death mechanisms, namely, apoptosis and necroptosis. Although apoptotic signaling is well defined, the mechanisms that underlie neuronal necroptosis are yet to be fully elucidated. In this study, we investigated whether HPC protects neurons from cerebral ischemia-induced necroptosis. We observed that tGCI up-regulated the expression of receptor-interacting protein (RIP) 3 and increased the interaction of RIP1-RIP3 in CA1 at the early stage of reperfusion. The pretreatment with HPC or necrostatin-1 decreased the expression of RIP3 and the formation of RIP1-RIP3 after tGCI. We also found that HPC decreased the expression and the activity of caspase-8 in CA1 after tGCI, and notably, the pretreatment with Z-VAD-FMK, a pan-caspase inhibitor, did not trigger necroptosis but attenuated the tGCI-induced neuronal damage. Furthermore, we demonstrated that HPC decreased the activation of calcium-calmodulin kinase (CaMK) II and the interaction of RIP1 and CaMKII induced by tGCI. Intriguingly, the pretreatment with a CaMKs inhibitor KN-93 before tGCI resulted in significantly reduced RIP1-3 interaction and tGCI-induced neuronal damage. Finally, we ascertained that HPC prevented the dephosphorylation of dynamin-related protein 1 (Drp1)-Ser637 (serine 637) and inhibited the translocation of Drp1 to mitochondria induced by tGCI. Importantly, the treatment with a Drp1 inhibitor Mdivi-1 or necrostatin-1 before tGCI also abolished Drp1 dephosphorylation at Ser637 and mitochondrial translocation. Taken together, our results highlight that HPC attenuates necroptotic neuronal death induced by tGCI via Drp1-dependent mitochondrial signaling pathways mediated by CaMKII inactivation.Zhan, L., Lu, Z., Zhu, X., Xu, W., Li, L., Li, X., Chen, S., Sun, W., Xu, E. Hypoxic preconditioning attenuates necroptotic neuronal death induced by global cerebral ischemia via Drp1-dependent signaling pathway mediated by CaMKII inactivation in adult rats.