Downregulating Cdk5 reverses hippocampal neuron ferroptosis by regulating the AMP-activated protein kinase pathway and “M1” polarized microglia

Aberrant activation of microglia plays a crucial role in neuronal injury after ischemic stroke. Cyclin-dependent kinase 5 (Cdk5) is a serine/threonine-directed kinase that plays a significant role in neuronal damage. We investigated the role of Cdk5 in microglial activation and neuronal ferroptosis in cellular and animal models of hypoxic-ischemic neuronal injury. Treatment with the Cdk5 inhibitor (S)-roscovitine (Ros) and/or an AMPK pathway activator metformin (Met) were investigated in a middle cerebral artery occlusion/reperfusion (MCAO/R) model in C57BL/6J mice. The results showed that Ros and Met improved neurological functions, brain edema, mitigated "M1" polarization of microglia, and inhibited neuronal ferroptosis. The combination of Ros and Met had additive effects on the MCAO/R mice. Ros and Met suppressed the expression of Cdk5 and inhibited NF-κB pathway activation, whereas the AMPK inhibitor Compound C (CC) reversed the neuroprotective and anti-inflammatory effects of Ros and Met. In vitro assays revealed that Ros and Met inhibited the proinflammatory reactions of BV2 microglia and the damage and ferroptosis of HT22 cells after OGD/R stimulation; these effects were also reversed by CC. These results indicate that targeting Cdk5 and AMPK mitigated microglia-mediated neuroinflammation and reduced neuronal ferroptosis in ischemic stroke models.