Membrane type 1 matrix metalloproteinase expression in human atherosclerotic plaques: evidence for activation by proinflammatory mediators.
BACKGROUND
Matrix metalloproteinases (MMPs) are expressed in atherosclerotic plaques, where in their active form, they may contribute to vascular remodeling and plaque disruption. In this study, we tested the hypothesis that membrane type 1 MMP (MT1-MMP), a novel transmembrane MMP that activates pro-MMP-2 (gelatinase A), is expressed in human atherosclerotic plaques and that its expression is regulated by proinflammatory molecules.


RESULTS
MT1-MMP expression was examined in normal and atherosclerotic human arteries by immunocytochemistry with specific antibodies. MT1-MMP expression in human saphenous vein-derived smooth muscle cells (SMCs) maintained in tissue culture was determined under basal conditions and in response to proinflammatory molecules (interleukin [IL]-1alpha, tumor necrosis factor [TNF]-alpha, and oxidized LDL [ox-LDL]) by use of Northern blot and ribonuclease protection assays for mRNA, Western blot and immunoprecipitation for protein, and gelatin zymography for catalytic activity. Medial SMCs of normal vessel wall expressed MT1-MMP. In atherosclerotic arteries, MT1-MMP expression was noted within the complex atheroma colocalizing with SMCs and macrophages (Mphi). Cultured SMCs constitutively expressed MT1-MMP mRNA and protein, which increased 2- to 4-fold over control in a time-dependent manner within 4 to 8 hours of exposure to IL-1alpha, TNF-alpha, and ox-LDL (thiobarbituric acid-reactive substances, 13.4 nmol/mg LDL protein), whereas native LDL had no effect. Flow cytometry revealed MT1-MMP expression by human monocyte-derived Mphi, which increased 3.8-fold over baseline within 6 hours after exposure to 10 ng/mL TNF-alpha.


CONCLUSIONS
This study demonstrates that MT1-MMP, an activator of pro-MMP-2, is expressed by SMCs and Mphi in human atherosclerotic plaques. Furthermore, proinflammatory molecules upregulate MT1-MMP expression in vascular SMCs and Mphi. Thus, activation of SMCs and Mphi by proinflammatory molecules may influence extracellular matrix remodeling in atherosclerosis by regulating MT1-MMP expression.
Rajavashisth
T B
TB
Atherosclerosis Research Center, Burns and Allen Research Institute, Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA. rajavashisth@cshs.org
Xu
X P
XP
Jovinge
S
S
Meisel
S
S
Xu
X O
XO
Chai
N N
NN
Fishbein
M C
MC
Kaul
S
S
Cercek
B
B
Sharifi
B
B
Shah
P K
PK
D000911:Antibodies, Monoclonal; D001161:Arteriosclerosis / Q000378:metabolism* / Q000473:pathology; D015152:Blotting, Northern; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000737:chemistry / Q000201:enzymology; D004792:Enzyme Precursors / Q000378:metabolism; D005434:Flow Cytometry; D018093:Gelatinases / Q000032:analysis / Q000096:biosynthesis / Q000276:immunology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D007375:Interleukin-1 / Q000494:pharmacology; D008074:Lipoproteins / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000494:pharmacology; D008264:Macrophages / Q000737:chemistry / Q000201:enzymology; D020778:Matrix Metalloproteinase 2; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology* / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis; D012501:Saphenous Vein / Q000166:cytology; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000032:analysis / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D004792:Enzyme Precursors; D018836:Inflammation Mediators; D007375:Interleukin-1; D008074:Lipoproteins; D008077:Lipoproteins, LDL; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C099252:oxidized low density lipoprotein; D019716:Tissue Inhibitor of Metalloproteinase-2; D018093:Gelatinases; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2