Abstract: Objective To study the effect of hypoxia/reoxygenation on the the expressions of COX-2 and PGE2 in lipopolysaccharide-inducedind human periodontal ligament cells. Methods Human periodontal ligament cells were first induced by 1 μg/mL lipopolysaccharide. Then cells were divided into two experiment groups: hypoxia group and reoxygenation group. In the hypoxia group, cells were cultured in 1% O2 for 6, 12, 24, 48 h, respectively. In the re-oxygenation group, cells were first cultured under the samecondition as the hypoxia group and then returned to normoxic condition for 24 hours. The expression of COX-2 was detected by Wesrtern Blootting and PGE2 was observed by ELISA.Results The expression of COX-2 was higher in the hypoxia group compared to the control group and reached the peak at 24 h. Besides, the expression of COX-2 significantly increased in the reoxygenation group compared to the hypoxia group and the control group. The expression of PGE2 was higher than that in the hypoxia group and the control group. But there was no significant difference between the hypoxia group and the control group. Conclusions Hypoxia could influence the expression of COX-2 in lipopolysaccharide-Induced human periodontal ligament cells but does not affect the expression of PGE2. Reoxygenation could increase the expressions of COX-2 and PGE2. The hypoxia/reoxygenation condition might play an important role in periodontitis.

Key words: hypoxia/reoxygenation, lipopolysaccharide, periodontal ligament, cyclooxygenase-2, prostaglandin E2