During chronic inflammatory response, mono- cytes/macrophages produce 92-kDa matrix metalloproteinase-9 (MMP-9), which may contribute to their extravasation, migration and tissue remodeling. Activation of peroxisome proliferator- activated factor receptor-gamma (PPAR-gamma) has been shown to inhibit MMP-9 activity. To evaluate whether ox-LDL, a PPAR-gamma activator, inhibits PMA-induced MMP-9 expression and activity, and if so, whether CD36 and PPAR-gamma are involved in this process, we investigated the effect of ox-LDL on MMP-9 expression and activity in PMA-activated human monocytic cell line U937. PMA-induced MMP-9 expression and activity were suppressed by the treatment with ox-LDL (50 micrigram/ml) or PPAR-gamma activators such as troglitazone (5 micrometer), ciglitazone (5 micrometer), and 15d- PGJ2 (1 micrometer) for 24 h. This ox-LDL or PPAR-gamma activator-mediated inhibition of micrometer P-9 activity was diminished by the pre-treatment of cells with a blocking antibody to CD36, or PGF2a (0.3 micrometer), which is a PPAR-gamma inhibitor, as well as overexpression of a dominant-negative form of CD36. Taken together, these results suggest that ox-LDL suppresses PMA-induced MMP-9 expression and activity through CD36-mediated activation of PPAR-gamma.
Antibodies, Blocking/pharmacology ; Antigens, CD36/immunology/*physiology ; Cells, Cultured ; Chromans/pharmacology ; Gelatinase B/antagonists & inhibitors/genetics/*metabolism ; Humans ; Lipoproteins, LDL/pharmacology/*physiology ; Monocytes/drug effects/*enzymology/metabolism ; NF-kappa B/antagonists & inhibitors ; PPAR gamma/*metabolism ; Prostaglandin D2/*analogs & derivatives/pharmacology ; RNA, Messenger/analysis/metabolism ; Research Support, Non-U.S. Gov't ; Tetradecanoylphorbol Acetate/antagonists & inhibitors/pharmacology ; Thiazolidinediones/pharmacology ; Transcription, Genetic/drug effects