The regulatory role of NF-κB in autophagy-like cell death after focal cerebral ischemia in mice

• Autophagy contributes to brain damage after focal ischemia in the barrel cortex.
• The autophagic cell death increases in adult NF-κB p50 knockout mice.
• The autophagic damage involves neuronal and vascular cells.
• A reduction of Akt-mTOR signaling may contribute to the autophagy activity.

Autophagy may contribute to ischemia-induced cell death in the brain, but the regulation of autophagic cell death is largely unknown. Nuclear factor kappa B (NF-κB) is a regulator of apoptosis in cerebral ischemia. We examined the hypothesis that autophagy-like cell death could contribute to ischemia-induced brain damage and the process was regulated by NF-κB. In adult wild-type (WT) and NF-κB p50 knockout (p50−/−) mice, focal ischemia in the barrel cortex was induced by ligation of distal branches of the middle cerebral artery. Twelve to 24 h later, autophagic activity increased as indicated by enhanced expression of Beclin-1 and LC3 in the ischemic core and/or penumbra regions. This increased autophagy contributed to cell injury, evidenced by terminal deoxynucleotidyltransferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) co-staining and a protective effect achieved by the autophagy inhibitor 3-methyladenine. The number of Beclin-1/TUNEL-positive cells was significantly more in p50−/− mice than in WT mice. Neuronal and vascular cell death, as determined by TUNEL-positive cells co-staining with NeuN or Collagen IV, was more abundant in p50−/− mice. Immunostaining of the endothelial cell tight junction marker occludin revealed more damage to the blood–brain barrier in p50−/− mice. Western blotting of the peri-infarct tissue showed a reduction of Akt-the mammalian target of rapamycin (mTOR) signaling in p50−/− mice after ischemia. These findings provide the first evidence that cerebral ischemia induced autophagy-like injury is regulated by the NF-κB pathway, which may suggest potential treatments for ischemic stroke.