Matrix Metalloproteinase-8 Promotes Vascular Smooth Muscle Cell Proliferation and Neointima Formation

Abstract

T he pathogenesis of postangioplasty restenosis involves migration and proliferation of vascular smooth muscle cells (VSMCs), which constitute a major component of postangioplasty neointimal lesions.1-4 VSMC migration and proliferation are regulated by growth factors, adhesion molecules, proteases, and intracellular proteins. Among them, the cadherin-β-catenin complex and its cognate intracellular pathway have been increasingly appreciated as important regulators of these processes. 5-8Matrix metalloproteinase-8 (MMP8) was once thought to be produced exclusively by polymorphonuclear leukocytes, but more recent studies have shown that various other cell types including stem/progenitor cells express this protease.9 Compared with some other members of the MMP family, MMP8 has been less investigated for its proteolytic substrates and biological roles. Herman et al 10 were the first to reveal that VSMCs, endothelial cells, and macrophages in atherosclerotic plaques express MMP8. Subsequently other investigators showed a correlation between increased MMP8 expression and rapid atherosclerotic lesion progression.11,12 A causal role of MMP8 in atherosclerosis development was demonstrated by our recent study, which showed that in apolipoprotein E (apoE)-deficient mice fed a Western diet for 12 weeks, MMP8 knockout resulted in a significant reduction of atherosclerotic lesions with decreased macrophage and VSMC contents. 13 The study also revealed a role of MMP8 in vascular recruitment of leukocytes, 13 providing a mechanistic explanation for the effect of MMP8 knockout on macrophage content in atherosclerotic lesions.In the present study, we sought to investigate whether MMP8 also plays a role in neointima formation after vessel © 2013 American Heart Association, Inc. Objective-We investigated the role of matrix metalloproteinase-8 (MMP8) in neointima formation and in vascular smooth muscle cell (VSMC) migration and proliferation. Approach and Results-After carotid artery wire injuring, MMP8-/-/apoE -/-mice had fewer proliferating cells in neointimal lesions and smaller lesion sizes. Ex vivo assays comparing VSMCs isolated from MMP8 knockout and wild-type mice showed that MMP8 knockout decreased proliferation and migration. Proteomics analysis revealed that a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) had lower concentrations in MMP8 knockout VSMC culture media than in MMP8 wild-type VSMC culture media. Western blot, flow cytometric, and immunocytochemical analyses showed that MMP8 knockout VSMCs contained more pro-ADAM10 but less mature ADAM10, more N-cadherin, and β-catenin in the plasma membrane but less β-catenin in the nucleus and less cyclin D1. Treatment of MMP8 wildtype VSMCs with an ADAM10 inhibitor, GI254023X, or siRNA knockdown of ADAM10 in MMP8 wild-type VSMCs inhibited proliferation and migration, increased N-cadherin and β-catenin in the plasma membrane, reduced β-catenin in the nucleus, and decreased cyclin D1 expression. Incubation of MMP8 knockout VSMCs with a recombinant ADAM...

Genetic and Pharmacologic Inhibition of the Neutrophil Elastase Inhibits Experimental Atherosclerosis

“…The vascular tree and heart were carefully isolated and the atherosclerotic lesions were characterized as described in previous studies 13, 14, 16. Briefly, after euthanization, the aorta, from heart to the level below the iliac bifurcation, was extensively exposed.…”

A Novel Role of Matrix Metalloproteinase-8 in Macrophage Differentiation and Polarization

“…The finding of the present study that MMP8 promotes M2-M polarization seems at odds with the finding that MMP8 promotes atherosclerosis, because inflammation plays an important role in atherogenesis and because M2-M are anti-inflammatory. However, athero- genesis also involves a number of other cell types, and previous studies have indicated that MMP8 can promote atherosclerosis partly via its influences on migration and proliferation of stem/ progenitor cells (19), smooth muscle cells (17), and endothelial cells (18), as well as leukocyte recruitment (11). Thus, it appears that MMP8 can influence atherosclerosis via multiple mechanisms.…”

“…However, it is now known that various other types of cells also express this protease. Studies have shown that MMP8 can modulate the behavior and function of several cell types including neutrophils (14,15), eosinophils (16), smooth muscle cells (17), endothelial cells (18), and stem/progenitor cells (19), underlain by its proteolytic activity on matrix and non-matrix proteins. Furthermore, studies have shown that MMP8 is involved in a number of pathological conditions including atherosclerosis (11,19), acute hepatitis (20), acute lung injury (14), airway inflammation (16), and cancers (21).…”

Putative targeting of matrix metalloproteinase-8 in atherosclerosis

“…In vitro experiments showed that by cleaving and thereby activating latent ADAM10, MMP8 activated an ADAM10/N-cadherin/ β-catenin mediated pathway that enhanced vascular smooth muscle cell migration and proliferation (Xiao et al, 2014) (Figs. 1 and 2).…”