Blocking FOXO4 confers neuroprotection against oxidative stress and ischemia-reperfusion caused neuronal injury.

Previous studies suggest that FOXO4 facilitates inflammation and oxidative stress in non-brain tissues under stress or disease conditions, indicating that downregulation of FOXO4 may be neuroprotective in ischemia-reperfusion-induced brain injury. This possibility has not been tested in a cerebral ischemia-reperfusion context, however. Here, we exposed FOXO4 knockout (KO) primary neuronal cultures to oxidative stress or oxygen-glucose deprivation (OGD), and subjected KO mice to transient middle cerebral artery occlusion (tMCAO). We also used a structure-based approach combined with cell-based assays to identify a FOXO4 inhibitor and evaluated its effects in tMCAO-treated wild-type (WT) mice. Our results showed that FOXO4 KO reduced oxidative stress- and OGD-induced neuronal death, attenuated tMCAO-induced infarct volume, improved animal survival, decreased neurological deficits, and enhanced functional recovery compared with WT cells or mice. Immunohistochemical staining and Western blot analyses further indicated reduced neuroinflammation in the KO brain. The identified FOXO4 inhibitor Actinomycin D suppressed FOXO4 activity at a low dose, reduced brain injury, and improved functional recovery in WT mice following tMCAO. Together, these findings indicate that FOXO4 is a potential therapeutic target and that suppression of its activity may promote neuronal survival after ischemic stroke-induced brain injury.