Aim: To explore the role of Toll-like receptor 4 (TLR4) in the injury of microglia exposed to hyperoxia.
Methods: N9 microglia (TLR4 wild type) and EOC20 microglia (TLR4 knock-out type) were exposed to 950 mL/L high oxygen respectively for different time periods to establish the high oxygen cell injury model. Expression of TLR4 mRNA and protein levels were detected by RT-PCR and Western blotting, respectively. After intervention with the antioxidant NAC (N-acetyl-L-cysteine, N-acetyl half pathway of ammonia), we detected the activity of reactive oxygen species (ROS), NF-κB and the expression of TNF-α in cellular supernatant of N9 and EOC20 microglia exposed to hyperoxia for 2, 6 h.
Results: Expression of TLR4 mRNA in N9 microglia exposed to hyperoxia increased in a time-dependent manner, meanwhile, activity of ROS, NF-κB and expression of TNF-α in microglia exposed to hyperoxia significantly increased (P<0.05), while decreased (P<0.05) after intervention with the antioxidant NAC. The activity of ROS, NF-κB and the expression of TNF-α were lower in EOC20 microglia than in N9 microglia after exposed to hyperoxia for different time periods (P<0.05).
Conclusion: TLR4 involves in the regulation of forming ROS and the release of inflammatory markers on microglia after exposed to hyperoxia.