Neuroprotective effects of erythropoietin against sevoflurane-induced neuronal apoptosis in primary rat cortical neurons involving the EPOR-Erk1/2-Nrf2/Bach1 signal pathway

Objective: Erythropoietin (EPO)-induced activation of the EPO receptor (EPOR) against sevoflurane-induced neuronal apoptosis is an effective intervention, but the underlying mechanism is poorly understood. Previous studies have shown that alteration of the nuclear factor erythroid 2-related factor (Nrf2)/BTB-to-CNC homology 1 (Bach1) ratio by extracellular signal-related kinases (Erk) 1/2 ameliorates the oxidative stress which occurs in human macrophages. In this study, we determined whether or not EPO attenuates sevoflurane-induced neuronal apoptosis via the EPOR-Erk1/2-Nrf2/Bach1 signal pathway. Methods: Primary rat cortical neurons were exposed to 4% sevoflurane for 6 h. Neuronal viability, injury, apoptosis, and oxidative stress were assessed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), propidium iodide uptake (PI), malondialdehyde (MDA), and superoxide dismutase (SOD) assays. A real-time PCR assay was used to measure EPOR expression. Western blotting was used to assess Nrf2, Bach1, and heme oxygenase-1 (HO-1) expression. Results: Sevoflurane exposure increased cell apoptosis, injury, and MDA (P < 0.05), but decreased cell viability and the Nrf2:Bach1 ratio (P < 0.05), and down-regulated superoxide dismutase (SOD; P < 0.05), while EPO partially rescued the neurotoxicity induced by sevoflurane (P < 0.05). Inhibition of EPOR via EPO-specific monoclonal antibody or Erk1/2 phosphorylation via PD98059 reversed the protective effect of EPO (P < 0.05). Conclusion: The neuroprotective effects of EPO against sevoflurane-induced neuronal apoptosis in primary rat cortical neurons involves the EPOR-Erk1/2-Nrf2/Bach1 signal pathway. (C) 2016 Elsevier Masson SAS. All rights reserved.