Abstract: Objective To explore whether procyanidin B2 (PCB2) regulates the P13K/Akt/Nrf2 signaling pathway to protect neurons from oxidative stress induced by cypermethrin (CYP). Methods Primary cultures of cerebral cortex neurons from C57BL/6 mice were randomly divided into 5 groups: normal control group (cultured in serum-free neurobasal-B27 medium), PCB2 treatment group (treated with 5 μg/mL PCB2 for 24 h), CYP exposure group (treated with 50 μmol/L CYP for 24 h), PCB2 pretreatment group (pretreated with 5 μg/mL PCB2 for 30 min followed by exposure to 50 μmol/L CYP for 24 h), and LY294002 treatment group (pretreated with 20 μmol/L LY294002 for 30 min before treatment with PCB2 for 30 min and then CYP for 24 h). CCK-8 assay was used to analyze the neuronal viability after the treatments. Reactive oxygen species (ROS) production in the cells was detected using the fluorescent probe DCFH-DA and flow cytometry. The changes in nuclear morphology and mitochondrial membrane potential of the cells were examined with Hoechst 33342 and JC-1 staining, respectively. Western blotting was performed to detect the protein expressions of Nrf2, HO-1, p-Akt and Akt in the cells. Results In CYP exposure group, the cells showed significantly decreased viability and mitochondrial membrane potential with obvious apoptotic morphological changes and abnormal ROS production. By comparison, the cells in PCB2 preconditioning group showed improved cell survival rate, reduced abnormalities in nuclear morphology, increased mitochondrial membrane potential, and lowered intracellular ROS production. CYP exposure caused Nrf2 nuclear translocation and up-regulated Nrf2, HO-1, p-Akt protein expressions in the cells, which were inhibited by PCB2 pretreatment. Inhibition of the P13K/Akt signaling pathway obviously neutralized the protective effect of PCB2 against CYP- induced neuronal injury. Conclusions PCB2 regulates the Nrf2/ARE signaling pathway by activating the P13K/Akt signaling pathway to protect mouse cerebral cortical neurons against oxidative injury induced by cypermethrin.

Key words: cypermethrin; procyanidin B2; neurons; P13K/Akt/Nrf2 signaling pathway