Role of Nrf2/HO-1 signaling pathway in dexmedetomidine-induced reduction of oxygen-glucose deprivation and restoration injury to microglia / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of nuclear factor erythroid 2-related factor/ heme oxygenase-1 (Nrf2/HO-1) signaling pathway in dexmedetomidine-induced reduction of oxygen-glucose deprivation and restoration (OGD/R) injury to microglia.Methods:BV-2 microglia were cultured in high-glucose DMEM culture medium supplemented with 10% fetal bovine serum in an normal culture incubator at 37 ℃ (5%CO 2-21%O 2-74 %N 2). The cells were seeded in 96-well plates at a density of 1.5×10 4 cells/ml (200 μl/well) or 6-well plates at a density of 2×10 5 cells/ml (2 ml/well) and divided into 5 groups ( n=30 each) using a random number table method: control group (group C), dexmedetomidine group (group D), group OGD/R, OGD/R+ dexmedetomidine group (group OGD/R+ D) and OGD/R+ dexmedetomidine+ ML385 group (group OGD/R+ D+ ML). The cells in group C were continuously cultured in a normal culture incubator for 26 h. In group D, dexmedetomidine at the final concentration of 10 μmol/L was added, cells were incubated for 2 h, and then were continuously incubated in a normal culture incubator for 26 h. In OGD/R, OGD/R+ D and OGD/R+ D+ ML groups, the culture medium was replaced with glucose-free DMEM culture medium, cells were cultured for 2 h in an incubator at 37 ℃ (5%CO 2-1%O 2-94 %N 2), the culture medium was replaced with high-glucose DMEM culture medium containing 10% fetal bovine serum and then the cells were cultured for 24 h in a normal incubator.Dexmedetomidine at the final concentration of 10 μmol/L was added at 2 h before OGD in OGD/R+ D and OGD/R+ D+ ML groups.Nrf-2 inhibitor ML385 at the final concentration of 4 μmol/L was added at 30 min before dexmedetomidine was added in group OGD/R+ D+ ML.Cells in 6 wells in each group were selected randomly for assessment of cell viability (by methyl thiazolyl tetrazolium assay) and apoptosis (using flow cytometry), and for determination of the concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 in the supernatant (using enzyme-linked immunosorbent assay), the expression of Nrf2 in nucleus, Nrf2 and HO-1(by Western blot ) and the expression of HO-1 mRNA (by real-time polymerase chain reaction). Results:Compared with group C, the cell viability was significantly decreased, cell apoptosis rate and concentrations of TNF-α, IL-6 and IL-10 in the supernatant were increased, and the expression of Nrf2 in nucleus, Nrf2, HO-1 and its mRNA was up-regulated in OGD/R and OGD/R+ D groups ( P<0.05), and no significant change was found in each parameter mentioned above in group D ( P>0.05). Compared with group OGD/R, the cell viability and IL-10 in the supernatant concentration were significantly increased, cell apoptosis rate and concentrations of TNF-α and IL-6 in the supernatant were decreased and the expression of Nrf2 in nucleus, Nrf2, HO-1 and its mRNA was up-regulated in group OGD/R+ D ( P<0.05), and no significant changes were found in the parameters mentioned above in group OGD/R+ D+ ML ( P>0.05). Compared with group OGD/R+ D, the cell viability and concentration of IL-10 in the supernatant were significantly decreased, cell apoptosis rate and concentrations of TNF-α and IL-6 in the supernatant were increased and the expression of Nrf2 in nucleus, Nrf2, HO-1 and its mRNA was down-regulated in group OGD/R+ D+ ML ( P<0.05). Conclusion:The mechanism by which dexmedetomidine alleviates OGD/R injury to microglia may be related to promoting the activation of Nrf2/HO-1 signaling pathway and inhibition of inflammatory responses.