Neuroprotection of selenite against ischemic brain injury through negatively regulating early activation of ASK1/JNK cascade via activation of PI3K/AKT pathway

Aim: To investigate whether selenite, a known antioxidant, could decrease the activation of apoptosis signal regulating kinase 1/c-jun N-terminal kinase (ASK1/ JNK) signaling cascade in cerebral ischemia/reperfusion (I/R) by activating the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in rat hippocampi, and the neuroprotective effect of selenite against ischemic injury after 15 min of transient brain ischemia. Methods: Transient global brain ischemia was induced by 4-vessel occlusion into adult male Sprague-Dawley rats weighing 250-300 g. The rats were pretreated only with selenite (0.3 mg/kg dissolved in 0.9% saline) every 24 h for 7 d by means of intravenous injection of the tail or combined with LY2 94002 from d 5 by left cerebral ventricle injection before surgery. Results: Selenite significantly increased AKT1 activation and decreased the activation of ASK1/ JNK cascade via phosphorylating ASK1 at Ser-83 residue by AKT1 during early reperfusion after 15 min transient global brain ischemia. On the contrary, combined pretreatment of the rats with LY2 94002 (a specific PI3K inhibitor) and selenite significantly inhibited the effects solely with selenite. Conclusion: The activation of the pro-apoptotic ASK1/JNK cascade, which is closely associated with oxidative stress, could be suppressed by selenite through activating the anti-apoptotic PI3K/AKT pathway during early reperfusion after cerebral ischemia in rat hippocampi.