Effect of the FKBP51·PHLPP·Akt signal module on the phosphorylation of Akt and hippocampal neuronal injury after the cerebral ischemia/reperfusion

Abstract

Objective To investigate the effects of the FKBP51·PHLPP·AKT signal module on the phosphorylation of Akt and hippocampal neuronal injury after the cerebral ischemia / reperfusion induced neuronal death in rat hippocampus. Methods Transient(15 min)brain ischemia was induced by the four-vessel occlusion in Sprague-Dawley rats. 6 rats were used in each group. The antisense oligodeoxynucletides(AS ODN)of PHLPP2(PH domain and leucine rich repeat protein phosphatases) was used to suppress the assembly of FKBP51·PHLPP·Akt signal module by intracerebroventricular infusion once per day for 3 days before ischemia. After 6 hours reperfusion, interactions of PHLPP2 and FKBP51(FK506 binding protein 5) with Akt were detected by immunoprecipitation (IP) and the phosphorylation of Akt was detected by western blot(IB). After 5 days reperfusion, rats were perfusion-fixed with paraformaldehyde and Hematoxylin-Eosin staining was used to examine the survival number of CA1 pyramidal cells of hippocampus. Results Compared to PHLPP2 MS ODN group(1.24±0.24, 1.68±0.11, 0.58±0.01), PHLPP2 AS ODN suppressed the assembly of the FKBP51·PHLPP·Akt signaling module(1.06±0.01, 1.04±0.13), and increased the phosphorylation of Akt(0.76±0.02)(P<0.05). Furthermore, compared to PHLPP2 MS ODN group (20.1±2.5), the number of surviving neurons significantly increased in PHLPP2 AS ODN group(88.3±2.7)(P<0.05). Conclusion The increasing assembly of FKBP51·PHLPP·Akt signal module can damage CA1 pyramidal cells of hippocampus by inhibiting the phosphorylation level of Akt. Key words: Global cerebral ischemia/reperfusion; PH domain and leucine rich repeat protein phosphatases; FK506 binding protein 5; Protein kinase B