ABSTRACT
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.
Subject(s)
Macrophages/metabolism , Matrix Metalloproteinase 8/metabolism , Tissue Inhibitor of Metalloproteinase-1/metabolism , Animals , Cell Membrane/drug effects , Cell Membrane/metabolism , Leukocyte Count/methods , Matrix Metalloproteinase 9/metabolism , Mice , Mice, Knockout , Proteolysis , Tissue Inhibitor of Metalloproteinase-2/metabolismSubject(s)
Atrial Fibrillation/surgery , Catheter Ablation/adverse effects , Embolism/etiology , Peripheral Vascular Diseases/etiology , Aged , Anticoagulants/therapeutic use , Embolism/drug therapy , Heparin/therapeutic use , Humans , Infarction/etiology , Intestinal Pseudo-Obstruction/etiology , Kidney/blood supply , Male , Peripheral Vascular Diseases/drug therapy , Warfarin/therapeutic useABSTRACT
Rapidly accumulating evidence points to the matrix metalloproteinases (MMPs) as major molecular mediators of arterial diseases. Findings from human pathological specimens, animals, and cell and molecular biology implicate matrix metalloproteinases in all stages of atherosclerosis including lesion initiation and progression and ultimately in plaque complication and triggering of thrombosis. The complex interactions within the proteolytic cascade allow multiple levels of control over these functions. This review weighs the evidence for the role of MMPs in arterial biology with particular reference to their activation in the atherosclerotic plaque.
Subject(s)
Atherosclerosis/enzymology , Muscle, Smooth, Vascular/enzymology , Peptide Hydrolases/metabolism , Enzyme Activation , Extracellular Matrix/enzymology , Extracellular Matrix/immunology , Genetic Predisposition to Disease , Humans , Inflammation , Muscle, Smooth, Vascular/immunology , Peptide Hydrolases/genetics , Polymorphism, GeneticABSTRACT
BACKGROUND: Catabolism of the extracellular matrix (ECM) contributes to vascular remodeling in health and disease. Although metalloenzymes and cysteinyl proteinases have garnered much attention in this regard, the role of serine-dependent proteinases in vascular ECM degradation during atherogenesis remains unknown. We recently discovered the presence of the metalloproteinase MMP-8, traditionally associated only with neutrophils, in atheroma-related cells. Human neutrophil elastase (NE) plays a critical role in lung disease, but the paucity of neutrophils in the atheromatous plaque has led to neglect of its potential role in vascular biology. NE can digest elastin, fibrillar and nonfibrillar collagens, and other ECM components in addition to its ability to modify lipoproteins and modulate cytokine and MMP activity. METHODS AND RESULTS: Fibrous and atheromatous plaques but not normal arteries contained NE. In particular, NE abounded in the macrophage-rich shoulders of atheromatous plaques with histological features of vulnerability. Neutrophil elastase and macrophages colocalized in such vulnerable plaques (n=7). In situ hybridization revealed NE mRNA in macrophage-rich areas, indicating local production of this enzyme. Freshly isolated blood monocytes, monocyte-derived macrophages, and vascular endothelial cells in culture produced active NE and contained NE mRNA. Monocytes produced NE constitutively, with little regulation by cytokines IL-1beta, TNF-alpha, or IFN-gamma but released it when stimulated by CD40 ligand, a cytokine found in atheroma. CONCLUSIONS: These findings point to a novel role for the serine protease, neutrophil elastase, in matrix breakdown by macrophages, a critical process in adaptive remodeling of vessels and in the pathogenesis of arterial diseases.
