Abstract: AimTo study the effect of proanthocyanidins on the COX-2 enzyme activity and COX-2 protein expression in LPS-induced RAW264.7 cells.MethodsAfter being pretreated with different concentrations of proanthocyanidins for 30 min, and then 1 mg·L^-1 LPS for 9 h, the effect of proanthocyanidins on the activity of COX-2 enzyme in RAW264.7 cells was analysed by radioimmunoassay(RIA).After being pretreated with different concentrations of proanthocyanidins for 30 min, and then 1 mg·L^-1 LPS for 9 h, the effects of proanthocyanidins on the expressions of COX-2 mRNA and protein in RAW264.7 cells were analysed by RT-PCR and Western blotting.ResultsThe activity of COX-2 enzyme was not inhibited by proanthocyanidins (0.8, 4 and 20 mg·L^-1, P>005 vs LPS group), but the activity of COX-2 enzyme was significantly inhibited by 10 μmol·L^-1 NS-398 (P<001 vs LPS group).The expression of COX-2 mRNA was inhibited by proanthocyanidins (0.8, 4 and 20 mg·L^-1).The expression of COX-2 protein was inhibited by proanthocyanidins (4 and 20 mg·L^-1).Conclusion Proanthocyanidins had no effect on the activity of COX-2 enzyme in LPS-induced RAW264.7 cells.Proanthocyanidins inhibited significantly the expression of COX-2 mRNA and protein in LPS-induced RAW2647 cells.