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Surface-bound matrix metalloproteinase-8 on macrophages: Contributions to macrophage pericellular proteolysis and
Xiaoyun Wang1,2,3, Duo Zhang3, Quynh-Anh Fucci1
1Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
Objective:
MMP-8 binds to surface-bound tissue inhibitor of metalloproteinase-1 (TIMP-1) on PMNs to promote pericellular proteolysis during the development of inflammatory diseases associated with tissue destruction. Little is known about the biology of MMP-8 in macrophages. We tested the hypotheses that: (1) MMP-8 and TIMP-1 are also expressed on the surface of activated macrophages, (2) surface-bound MMP-8 on macrophages promotes TIMP-resistant pericellular proteolysis and macrophage migration through tissue barriers, and (3) MMP-8 binds to surface-bound TIMP-1 on macrophages.
Methods:
Surface MMP-8 and TIMP-1 levels were measured on human monocyte-derived macrophages (MDM) and/or murine macrophages using immunostaining, biotin-labeling, and substrate cleavage methods. The susceptibility of membrane-bound Mmp-8 on activated macrophages from wild-type (WT) mice to TIMPs was measured. Migration of WT and Mmp-8-/- macrophages through models of tissue barriers in vitro and the accumulation of peritoneal macrophages in WT versus Mmp-8-/- mice with sterile peritonitis was compared. Surface levels of Mmp-8 were compared on activated macrophages from WT and Timp-1-/- mice.
Results:
Lipopolysaccharides and a cluster of differentiation 40 ligand increased surface MMP-8 and/or TIMP-1 staining and surface type I collagenase activity on MDM and/or murine macrophages. Activated Mmp-8-/- macrophages degraded less type I collagen than activated WT macrophages. The surface type-I collagenase activity on WT macrophages was resistant to inhibition by Timp-1. Peritoneal macrophage accumulation was similar in WT and Mmp-8-/- mice with sterile acute peritonitis. However, Mmp-8-/- macrophages migrated less efficiently through models of tissue barriers (especially those containing type I collagen) than WT cells. Activated WT and Timp-1-/- macrophages had similar surface-bound Mmp-8 levels.
Conclusions:
MMP-8 and TIMP-1 are expressed on the surface of activated human MDM and murine macrophages, but Mmp-8 is unlikely to bind to surface-bound Timp-1 on these cells. Surface-bound MMP-8 contributes to TIMP-resistant monocyte/macrophage pericellular proteolysis and macrophage migration through collagen-containing tissue barriers.
Insights
Matrix metalloproteinase-8 (MMP-8) on activated macrophages aids tissue breakdown and migration, independent of TIMP-1 binding. This MMP-8 activity is crucial for pericellular proteolysis and navigating collagenous barriers during inflammation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Matrix metalloproteinase-8 (MMP-8) is known to bind tissue inhibitor of metalloproteinase-1 (TIMP-1) on neutrophils, facilitating pericellular proteolysis in inflammatory diseases.
- The role and regulation of MMP-8 in macrophages, particularly its surface expression and interactions, remain largely uncharacterized.
Purpose of the Study:
- To investigate the expression of MMP-8 and TIMP-1 on activated macrophages.
- To determine if surface-bound MMP-8 on macrophages mediates TIMP-resistant pericellular proteolysis and enhances migration.
- To examine the binding interaction between surface-bound MMP-8 and TIMP-1 on macrophages.
Main Methods:
- Human monocyte-derived macrophages (MDM) and murine macrophages were analyzed for surface MMP-8 and TIMP-1 using immunostaining and biotin-labeling.
- Macrophage migration through tissue barrier models and peritoneal macrophage accumulation in vivo were assessed.
- Cleavage of type I collagen by surface-bound MMP-8 and its susceptibility to TIMP-1 inhibition were measured.
Main Results:
- Activated macrophages express MMP-8 and TIMP-1 on their surface, with increased collagenase activity.
- Surface-bound MMP-8 on macrophages exhibited TIMP-1-resistant collagen degradation.
- MMP-8 deficient macrophages showed reduced migration through collagenous barriers, while peritoneal accumulation was similar.
Conclusions:
- MMP-8 and TIMP-1 are present on activated human and murine macrophages.
- Surface-bound MMP-8 contributes to TIMP-resistant pericellular proteolysis and macrophage migration, particularly through collagenous tissues.
- MMP-8 does not appear to bind to surface-bound TIMP-1 on activated macrophages.
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