Aim To study the inhibitory effect of
dexamethasone and indomethacin on
matrix metalloproteinase-9 (MMP-9) and investigate
their mechanism of MMP-9 inhibition on the level of protein and mRNA. Methods U937 cells were cultured in RPMI 1640 medium with 10% fetal calf serum (FCS). After U937 cells were exposed to 1×10 -8 mol·L -1 phorbol 12-myristate 13-acetate (PMA) for 24 hours without FCS, the activity of MMP-9 in the supernatant was analyzed by gelatin zymography. The MMP-9 protein secreted from U937 in serum-free conditional media was detected by Western blot using special polyclonal antibodies. The mRNA expression of MMP-9 was investigated by RT-PCR. Results Gelatin zymography showed that MMP-9 activity in U937 cells supernatant increased significantly after exposed to 1×10 -8 mol·L -1 PMA for 24 hours without FCS. Dexamethasone at 1×10 -5 , 1×10 -7 , 1×10 -9 mol·L -1 and
indomethacin at 1×10 -5 , 1×10 -6 , 1×10 -7 mol·L -1 can inhibit this increase. Western blot showed that MMP-9 secretion from U937 cells in serum-free conditional media was increased under the same stimulating condition, Dexamethasone and indomethacin can inhibit MMP-9 secretion in U937 cells stimulated by 1×10 -8 mol·L -1 PMA and the inhibitory effect was increased as their concentration increased. RT-PCR showed that MMP-9 mRNA expression of U937 cells was also inhibited and the inhibitory effect was increased as their concentration increased. Conclusion Inhibition of MMP-9 activity may be one of the anti-inflammatory mechanisms of dexamethasone and indomethacin; the inhibition of MMP-9 activity is coherent with the inhibition of MMP-9 secretion and mRNA expression.