IKKα contributes to ischemia-induced autophagy after acute cerebral ischemic injury

The function of IκB kinase α (IKKα) in the brain is largely unknown. This study examined the effects of IKKα on autophagy after cerebral ischemia.

Permanent distal middle cerebral artery occlusion (dMCAO) was conducted in C57/BL6 mice. Oxygen-glucose deprivation/reperfusion (OGD/R) was performed to mimic ischemia injury in neuro-2A (N2A) cells in vitro. Autophagy activation was assessed by detecting the ratio of microtubule-associated protein 1 light chain 3β (LC3B)-II/LC3B-I and Cyto-ID autophagic fluorescence. The infarct volume was verified by 2,3,5-triphenyltetrazolium chloride (TTC) staining and magnetic resonance imaging (MRI). Neurological functions were evaluated using the modified Garcia test. Cell death after dMCAO was confirmed with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay. To determine the role of IKKα, small interfering RNA (siRNA) was transfected into N2A cells or injected intracerebroventricularly.

IKKα and LC3B II/I expression levels were increased both in OGD/R treated N2A cells and dMCAO mice. Under the same conditions, IKKβ expression was not altered. IKKα siRNA significantly decreased the infarct volume and the apparent diffusion coefficient (ADC) related to brain edema, and promoted the neurological outcomes after dMCAO. Furthermore, inhibition of IKKα attenuated ischemia- induced the conversion of LC3B I to LC3B II both in vitro and in vivo. In addition, IKKα siRNA alleviated the formation of autophagic vacuoles and LC3 positive puncta after cerebral ischemia.

These findings indicate that IKKα, but not IKKβ, plays a critical role in ischemia-induced autophagy. Inhibition of IKKα protects the brain from ischemia injury and this may have potential benefits in stroke therapy.