Effect of docosahexaenoic acid on microglial activation during oxygen-glucose deprivation and restoration injury

Objective To evaluate the effect of docosahexaenoic acid (DHA) on microglial activation during oxygen-glucose deprivation and restoration (OGD/R) injury. Methods N9 microglia were inoculated in 96-well culture plates at a density of 104 cells/well for 3-5 days and divided into 3 groups (n=18 each) using a random number table method: control group (group C), group OGD/R and DHA+ OGD/R group. The cells were cultured for 24 h in an incubator at 37 ℃ (95% air-5% CO2) in group C. In OGD/R and DHA groups, the culture medium was replaced by glucose-free culture medium, the cells were cultured for 12 h in an incubator at 37 ℃ (95% N2-5% CO2), and then cells were returned to the normal culture medium and cultured for 24 h in an incubator at 37 ℃ (95% air-5% CO2) to establish the OGD/R injury model. The cells in group DHA were incubated with 25 μmol/L DHA at 12 h before OGD/R. The cell viability was detected using the methyl thiazolyl tetrazolium assay, the activity of lactate dehydrogenase (LDH) was measured by using chemical colorimetric method, activated microglia were counted by immunofluorescence staining, the expression of microglia activation marker iba-1 was detected by Western blot, and the concentrations of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6) and IL-4 and IL-10 in culture medium were determined using enzyme-linked immunosorbent assay. Results Compared with the group C, the cell viability was significantly decreased, the LDH activity was increased, the number of activated microglia was increased, and the expression of iba-1 was up-regulated in OGD/R and DHA+ OGD/R groups, the concentrations of TNF-α and IL-6 were significantly increased in group OGD/R, and the concentrations of TNF-α, IL-6, IL-4 and IL-10 were significantly increased in group DHA+ OGD/R (P<0.05). Compared with group OGD/R, the cell viability was significantly increased, the LDH activity was decreased, the number of activated microglia was decreased, the expression of iba-1 was down-regulated, TNF-α and IL-6 concentrations were decreased, and IL-4 and IL-10 concentrations were increased in group DHA (P<0.05). Conclusion The mechanism by which DHA reduces OGD/R injury may be related to inhibiting activation of microglia and to reducing inflammatory responses. Key words: Docosahexaenoic acids; Reperfusion injury; Microglia