Regulation of Matrix Metalloproteinase Expression in Human Vascular Smooth Muscle Cells by T Lymphocytes

Abstract

Physical disruption of an atheromatous lesion often underlies acute coronary syndromes. Matrix-degrading enzymes, eg, matrix metalloproteinases (MMPs), may cause loss in mechanical integrity of plaque tissue that favors rupture. T lymphocytes accumulate at sites where atheromata rupture, but the mechanisms by which these immune cells may contribute to plaque destabilization are unknown. This study tested the hypothesis that the T-lymphocyte surface molecule CD40 ligand (CD40L), recently localized in atherosclerotic plaques, regulates the expression of MMPs in human vascular smooth muscle cells (SMCs), the most numerous cell type in arteries. We report here that stimulated human T lymphocytes induced the expression of the matrix-degrading enzymes, ie, interstitial collagenase (MMP-1), stromelysin (MMP-3), gelatinase B (MMP-9), and activated gelatinase A (MMP-2), in human vascular SMCs by cell contact via CD40 ligation, as demonstrated by Western blot analysis, zymography, and antibody neutralization. Recombinant human CD40L (rCD40L) induced de novo synthesis of MMP-1, MMP-3, and MMP-9 on vascular SMCs and stimulated the expression of these enzymes to a greater extent than did maximally effective concentrations of tumor necrosis factor-alpha or interleukin-1beta, established agonists of MMP expression. Interferon gamma, another T-lymphocyte- derived cytokine, inhibited the induction of MMPs by rCD40L. Immunohistochemical analysis of human coronary atheromata colocalized MMP-1 and MMP-3 with CD40-positive SMCs. These results demonstrated that CD40 ligand, expressed on T lymphocytes, promoted the expression of matrix-degrading enzymes in vascular SMCs and thus established a new pathway of immune-modulated destabilization in human atheromata.

Enhanced Levels of Soluble and Membrane-Bound CD40 Ligand in Patients With Unstable Angina

“…Advanced human atheromata contain numerous T cells, and relevant to the process of plaque rupture, T cells seem to account for almost 20% of the cells in the shoulder region of a plaque. 29 These T cells are predominantly of the CD4 ϩ subset 14,29 and, interestingly, we found increased per- centages of CD4 ϩ T cells expressing CD40L only in patients with unstable angina, further supporting a role for CD4 ϩ T cells in the development of acute coronary syndromes. However, although CD40L ϩ T cells have been found within human atherosclerotic plaques and not in nonatherosclerotic human arteries, 13 forthcoming studies will have to clarify whether this increase in the numbers of CD40L ϩ T cells also exists within atherosclerotic lesions in the coronary arteries of patients with unstable angina.…”

“…7,25 Interestingly, it was recently demonstrated that both sCD40L and membrane-bound CD40L are potent inducers and activators of MMPs in macrophages and vascular SMCs but do not affect the expression of their inhibitors, tissue inhibitors of MMPs. 14,15 Furthermore, enhanced CD40L-CD40 interaction may promote thrombotic activity by enhancing tissue-factor expression in macrophages and through the direct regulation of endothelium-procoagulant activity. 15,16,26 Thus, although not specific for angina 10,12 and without being the ultimate cause of this disease, CD40 activation may lead to procoagulant responses and MMP activation which, in patients with an preexisting atherosclerotic lesion, ultimately may lead to plaque rupture and the development of an acute coronary syndrome.…”

“…15,16,26 Thus, although not specific for angina 10,12 and without being the ultimate cause of this disease, CD40 activation may lead to procoagulant responses and MMP activation which, in patients with an preexisting atherosclerotic lesion, ultimately may lead to plaque rupture and the development of an acute coronary syndrome. However, other factors not necessarily related to enhanced CD40L-CD40 interaction also seem to be involved in this process (eg, enhanced apoptosis of vascular SMCs and levels of "rupture-inhibitory" mediators such as tissue inhibitors of MMPs), 14,27 and the exact contributory role of CD40L will have to further elucidated.…”

“…These inflammatory responses, possibly mediated by sCD40L, may further promote the infiltration of activated leukocytes into the atherosclerotic lesion, which in turn, may directly activate SMCs, macrophages, and T cells inside the vessel wall. 14,15 In addition to increased levels of sCD40L, patients with unstable angina also had enhanced expression of membranebound CD40L on both CD4 ϩ and CD8 ϩ T cells in peripheral blood. Advanced human atheromata contain numerous T cells, and relevant to the process of plaque rupture, T cells seem to account for almost 20% of the cells in the shoulder region of a plaque.…”

“…14 To further elucidate the possible effects of raised sCD40L levels in patients with unstable angina, additional experiments were performed using PBMCs from 4 healthy controls. MCP-1 seems to play a pathogenic role in atherosclerosis, 21 and we hypothesized that sCD40L, known as a potent monocyte activator, 22 would enhance MCP-1 production in these cells.…”