Endogenous PGE2 up-regulates MMP-9 expression. DCs were pretreated with ibuprofen (10⁻⁵ M) for 30 minutes followed by treatment with LPS (1 μg/mL). DCs were treated with ibuprofen every 12 hours (total time in culture, 60 hours). The negative controls consisted of DCs cultured in medium (with or without ibuprofen treatment). Addition of ibuprofen to cells cultured in medium did not affect the levels of MMP-9 or -2. The positive control consisted of DCs exposed to exogenous PGE2 (10⁻⁶ M) for 24 hours. MMP-9 and MMP-2 expression was determined by real-time RT-PCR.