Clare M. Dollery

Matrix Metalloproteinases and Cardiovascular Disease

The vessel wall is an integrated functional component of the circulatory system that is continually remodeling in response to hemodynamic conditions and disease states. The endothelium releases locally active mediators, such as nitric oxide and endothelin, which have immediate vasoactive properties and longer-term trophic effects on the medial SMCs. Vascular tone and compliance are determined by these SMCs, which not only actively control wall tension but also synthesize the major structural components of the vessel wall: collagens types I, III, IV, and V, elastin, proteoglycans, and glycoproteins. These components interact to form a complex network that gives blood vessels their elastic physical characteristics. Continual mechanical stresses will cause weakening of the vessel wall if the structural integrity and physical properties of the matrix are not maintained. The matrix composition determines not only the physical elastic properties of the vessel wall but also its cellular components via stored growth factors in the matrix and growth factor activation by MMPs. The matrix, therefore, rather than being merely a system of scaffolding for the surrounding cells, is a dynamic structure that is central to the control of vascular remodeling. Connective tissue repair and remodeling to maintain matrix integrity involves the synthesis and removal of these proteins, a process that depends on the action of a range of proteases and their inhibitors. Evidence suggests that there are two systems that predominate and interact to achieve homeostasis within the vessel wall: the plasminogen activator-plasmin system and the MMPs. This review focuses on discussing the increasing evidence that supports a role for enzymes of the MMP family in the pathogenesis of atherosclerosis and postangioplasty restenosis. MMPs are a family of Zn2+- and Ca2+-dependent enzymes, which are important in the resorption of extracellular matrices in both normal physiological processes and pathological states. Nine …

Association of Angiotensin-Converting Enzyme Gene I/D Polymorphism With Change in Left Ventricular Mass in Response to Physical Training

BACKGROUND The absence (deletion allele [D]) of a 287-base pair marker in the ACE gene is associated with higher ACE levels than its presence (insertion allele [I]). If renin-angiotensin systems regulate left ventricular (LV) growth, then individuals of DD genotype might show a greater hypertrophic response than those of II genotype. We tested this hypothesis by studying exercise-induced LV hypertrophy. METHODS AND RESULTS Echocardiographically determined LV dimensions and mass (n=140), electrocardiographically determined LV mass and frequency of LV hypertrophy (LVH) (n=121), and plasma brain natriuretic peptide (BNP) levels (n=49) were compared at the start and end of a 10-week physical training period in male Caucasian military recruits. Septal and posterior wall thicknesses increased with training, and LV mass increased by 18% (all P<.0001). Response magnitude was strongly associated with ACE genotype: mean LV mass altered by +2.0, +38.5, and +42.3 g in II, ID and DD, respectively (P<.0001). The prevalence of electrocardiographically defined LVH rose significantly only among those of DD genotype (from 6 of 24 before training to 11 of 24 after training, P<.01). Plasma brain natriuretic peptide levels rose by 56.0 and 11.5 pg/mL for DD and II, respectively (P<.001). CONCLUSIONS Exercise-induced LV growth in young males is strongly associated with the ACE I/D polymorphism.

Neutrophil elastase in human atherosclerotic plaques: Production by macrophages

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-1&bgr;, TNF-&agr;, or IFN-&ggr; 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.

Expression of Tissue Inhibitor of Matrix Metalloproteinases 1 by Use of an Adenoviral Vector Inhibits Smooth Muscle Cell Migration and Reduces Neointimal Hyperplasia in the Rat Model of Vascular Balloon Injury

BACKGROUND Cell migration is a major contributor to injury-induced neointimal hyperplasia and depends on alteration of the proteolytic balance within the arterial wall toward matrix breakdown. This is partly mediated by the matrix metalloproteinases (MMPs) and their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). METHODS AND RESULTS An increase in expression of biologically active and immunoreactive TIMP-1 was seen in vitro after infection of rat smooth muscle cells (SMCs) with Av1.TIMP1 (an adenoviral vector containing the human TIMP1 cDNA). Infection of rat SMCs with Av1.TIMP1 reduced migration in vitro by 27% compared with control virus-infected cells (37.6+/-4.34 versus 51+/-5.01 cells per high-power field, P<0.05). The adenoviral vector was delivered to the injured rat carotid artery, and 4 days later, immunoreactive protein was identified and migration of SMCs reduced by 60% (5.2+/-0. 5 versus 12.8+/-1.5 cells per section, P<0.05, n=5). Neointimal area 14 days after injury showed a 30% reduction in the animals receiving the Av1.TIMP1 virus compared with controls (0.09+/-0.01 versus 0. 14+/-0.01 mm2, P=0.02, n=14). CONCLUSIONS The response to arterial balloon injury involves MMP-dependent SMC migration and can be attenuated in vivo by the transmural expression of TIMP-1 by adenoviral gene transfer.

TIMP-4 Is Regulated by Vascular Injury in Rats

Abstract—The role of basement membrane–degrading matrix metalloproteinases (MMPs) in enabling vascular smooth muscle cell migration after vascular injury has been established in several animal models. In contrast, the role of their native inhibitors, the tissue inhibitors of matrix metalloproteinases (TIMPs), has remained unproven despite frequent coregulation of MMPs and TIMPs in other disease states. We have investigated the time course of expression and localization of TIMP-4 in rat carotid arteries 6 hours, 24 hours, 3 days, 7 days, and 14 days after balloon injury by in situ hybridization, immunohistochemistry, and Western blot analysis. TIMP-4 protein was present in the adventitia of injured carotid arteries from 24 hours after injury. At 7 and 14 days after injury, widespread immunostaining for TIMP-4 was observed throughout the neointima, media, and adventitia of injured arteries. Western blot analysis confirmed the quantitative increase in TIMP-4 protein at 7 and 14 days. In situ hybridization de...