Abstract: AimTo investigate the expression of matrix metalloproteinase-9 (MMP-9) in mouse ears induced with croton oil and the inhibitory effect of dexamethasone, indomethacin and resveratrol on MMP-9 expression, and further explore the relationship between anti-inflammation and MMP-9 inhibition of these three medicines. MethodsImmuno-histochemistry was used to detect the expression of MMP-9 in mouse ears. Expression of MMP-9 in U937 cells was analyzed by gelatin zymography. ResultsMouse ear edema induced with croton oil was inhibited significantly by dexamethasone and indomethacin at the dose of 10 mg·kg^-1 and resveratrol at 50 mg·kg^-1 administered subcutaneously. The inhibitory rate was 76.2% (P<0.001), 56.7% (P<0.001) and 36.9% (P<0.001) respectively. The MMP-9 expression increased in mouse ears induced with croton oil and inhibited by dexamethasone, indomethacin and resveratrol at above doses. Gelatin zymography results showed that MMP-9 expression in U937 cells increased significantly after exposed to PMA at 1×10-8 mol·L^-1 (P<0.001); MMP-9 expression induced with phorbol myristate acetate(PMA) was inhibited by dexamethasone at 1×10-9, 1×10-7 and 1×10-5 mol·L^-1, indomethacin at 1×10-6 and 1×10-5 mol·L^-1 and resveratrol at 1×10-6 and 1×10-5 mol·L^-1. ConclusionThe inhibition of MMP-9 expression may be one of the anti-inflammatory mechanisms of dexamethasone, indomethacin and resveratrol.