PFKFB3 ameliorates ischemia-induced neuronal damage by reducing reactive oxygen species and inhibiting nuclear translocation of Cdk5.

The enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB) plays an essential role in glycolysis and in the antioxidant pathway associated with glutathione. Therefore, we investigated the effects of PFKFB3 on oxidative and ischemic damage. We synthesized a fusion protein of transactivator of transcription (Tat)-PFKFB3 to facilitate its passage into the intracellular space and examine its effects against oxidative stress induced by hydrogen peroxide (H(2)O(2)) treatment and ischemic damage caused by occlusion of the common carotid arteries for 5 min in gerbils. The Tat-PFKFB3 protein was efficiently delivered into HT22 cells in a concentration- and time-dependent manner, with higher levels observed 18 h after treatment. Furthermore, treatment with 6 µM Tat-PFKFB3 demonstrated intracellular delivery into HT22 cells, as analyzed through immunocytochemical staining. Moreover, it significantly ameliorated the reduction of cell viability induced by 200 µM H(2)O(2) treatment. Tat-PFKFB3 treatment also alleviated H(2)O(2)-induced DNA fragmentation and reactive oxygen species formation in HT22 cells. In gerbils, the intraperitoneal administration of 2 mg/kg Tat-PFKFB3 efficiently delivered the substance to all hippocampal areas, including the hippocampal CA1 region. This administration significantly mitigated ischemia-induced hyperlocomotion, long-term memory deficits, and ischemic neuronal death in the hippocampal CA1 region after ischemia. Additionally, treatment with 2 mg/kg Tat-PFKFB3 significantly ameliorated the translocation of Cdk5 from the cytosol to the nucleus in the hippocampal CA1 region 24 h after ischemia, but not in other regions. The treatment also significantly reduced reactive oxygen species formation in the CA1 region. These findings suggest that Tat-PFKFB3 reduces neuronal damage in the hippocampal CA1 region after ischemia through the reduction of Cdk5 signaling and reactive oxygen species formation. Therefore, Tat-PFKFB3 may have potential applications in reducing ischemic damage.