Effect of hypothermia on polarization of microglia and TLR4/NF-κB signaling pathway during oxygen-glucose deprivation/restoration / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the effect of hypothermia on the polarization of microglia and TLR4/NF-κB signaling pathway during oxygen-glucose deprivation/restoration (OGD/R).Methods:BV2 microglia were cultured in vitro and divided into 3 groups ( n=18 each) using the random number table method: control group (group C), group OGD/R and OGD/R plus hypothermia group (group OGD/R+ HT). Group C was cultured normally for 24 h. In group OGD/R, the cells were exposed to 5% CO 2-1% O 2 at 37 ℃ for 2 h in a glucose-free medium, followed by restoration of glucose and oxygen for 24 h. In group OGD/R+ HT, the high-glucose medium was replaced with a glucose-free medium, the cells were exposed to 5% CO 2-1% O 2 for 2 h in a 33 ℃ cryostat, followed by restoration of glucose and oxygen for 24 h. The cell survival rate was measured by CCK-8 assay.The expression of M1 microglia markers CD32 and iNOS protein and mRNA and M2 microglia markers CD206 and Arg-1 and mRNA was detected by immunofluorescence and real-time quantitative polymerase chain reaction.The expression of TLR-4 and NF-κB in cells was detected by Western blot, and the expression of TLR4 and NF-κB mRNA in cells was detected by real-time quantitative polymerase chain reaction.The concentrations of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β) and interleukin 10 (IL-10) in the cell supernatant were detected by enzyme-linked immunosorbent assay. Results:Compared with group C, the cell survival rate was significantly decreased, the expression of CD32, iNOS, CD206, Arg-1, TLR4 and NF-κB protein and mRNA was up-regulated, and the concentrations of TNF-α, IL-1β and IL-10 in supernatant were increased in OGD/R and OGD/R+ HT groups ( P<0.05). Compared with group OGD/R, the cell survival rate was significantly increased, the expression of CD32, iNOS, TLR4 and NF-κB protein and mRNA was down-regulated, the expression of CD206 and Arg-1 protein and mRNA was up-regulated, the concentrations of TNF-α and IL-1β in supernatant were decreased, and the concentration of IL-10 was increased in group OGD/R+ HT ( P<0.05). Conclusions:Hypothermia can significantly inhibit microglia polarization toward M1 phenotype, increase microglia polarization toward M2 phenotype and inhibit the development of inflammatory responses during OGD/R, and the mechanism may be related to inhibition of TLR4/NF-κB signaling pathway.