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Chemokine stimulation of monocyte matrix metalloproteinase-9 requires endogenous TNF-alpha
Stephen C Robinson1, Kate A Scott, Frances R Balkwill
1ICRF Translational Oncology Laboratory, Bart's and the London Queen Mary School of Dentistry, Charterhouse Square, London, EC1M 6BQ, GB. s.c.robinson@icrf.icnet.uk
Abstract:
Leukocyte extravasation into tissues is a multi-step process culminating in the migration of cells through the basement membrane. This requires the production of matrix-degrading enzymes, in particular matrix metalloproteinases (MMP). We investigated the role of chemokines in regulating MMP production in the monocytic cell line THP-1 and in peripheral blood monocytes (PBM). The CC chemokines CCL2 (MCP-1), CCL3 (MIP-1alpha), and CCL5 (RANTES) stimulated the release of monocyte MMP-9 protein in a bell-shaped dose-dependent manner. The increase in MMP-9 protein detected at 24 h was due to de novo synthesis, confirmed by Northern blotting, with MMP-9 mRNA detectable at 6-8 h. Autocrine TNF-alpha was necessary for chemokine stimulation of MMP-9. Chemokines increased TNF-alpha mRNA levels and protein release in monocytes and THP-1 cells, and neutralizing anti-TNF-alpha antibodies inhibited CCL2-induced MMP-9 release. Furthermore, the broad spectrum MMP inhibitor BB 2516, which inhibits TNF-alpha release, abrogated CCL2- and CCL5-induced MMP-9 release in both THP-1 cells and freshly isolated monocytes. Monocyte production of MMP is of major importance in the pathology of cancer, asthma, and rheumatoid arthritis. An understanding of the mechanisms by which these MMP are produced may lead to novel therapies to modulate extravasation of leukocytes in disease.
Insights
Chemokines like CCL2 stimulate monocyte matrix metalloproteinase-9 (MMP-9) production via TNF-alpha, crucial for leukocyte extravasation in diseases.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Leukocyte extravasation requires matrix-degrading enzymes, particularly matrix metalloproteinases (MMPs).
- Monocyte production of MMPs is implicated in inflammatory diseases like cancer, asthma, and rheumatoid arthritis.
Purpose of the Study:
- To investigate the role of CC chemokines in regulating MMP production in monocytes.
- To elucidate the signaling pathways involved in chemokine-induced MMP release.
Main Methods:
- Utilized THP-1 monocytic cells and peripheral blood monocytes (PBM).
- Stimulated cells with CC chemokines (CCL2, CCL3, CCL5) and assessed MMP-9 protein and mRNA levels.
- Investigated the role of autocrine TNF-alpha using neutralizing antibodies and an MMP inhibitor (BB 2516).
Main Results:
- CC chemokines induced MMP-9 release in a bell-shaped dose-dependent manner.
- MMP-9 production resulted from de novo synthesis, with increased mRNA levels preceding protein release.
- Autocrine TNF-alpha was essential for chemokine-mediated MMP-9 induction, as confirmed by antibody neutralization and MMP inhibitor studies.
Conclusions:
- Chemokines regulate monocyte MMP-9 production through an autocrine TNF-alpha-dependent pathway.
- Understanding these mechanisms may offer novel therapeutic targets for diseases involving leukocyte extravasation.