Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that degrade extracellular matix (ECM) components during normal and pathogenic condition. Documented expression of MMPs contributes to tissue remodeling, atherosclerosis, and inflammatory diseases. MMPs are tight regulated by several steps including transcriptional regulation. Transcription factors, NF-？？B, Ets and activator protein (AP)-1 are reported to be involved in transcriptional regulation of MMPs. Here we demonstrated transcriptional regulations of MMP-3 in LPS-, IFN？^-, and gangliosides-activated cultured astrocytes obtained from rat brain. MMP-3 transcript and protein were increased by stimulation with LPS, IFN？^ and gangliosides. Promoter analysis revealed that sequences between -500 to start codon are important in induction of MMP-3. EMSA-based study and site-direct mutagenesis revealed that AP-1 is important in induction of MMP-3. Since three AP-1 binding sites (we described them as proximal, middle and distal, respectively according to the distances from start codon) exist in -500 promoter sites, we tested which AP-1 site is important using sequence-specific primers for EMSA. We observed that middle and distal AP-1, not proximal AP-1 are activated by all three stimulators in EMSA analysis. Further, we demonstrated that LXR activation inhibit MMP-3 transcription through interaction with AP-1.
