Gene expression levels of matrix metalloproteinases in human atherosclerotic plaques and evaluation of radiolabeled inhibitors as imaging agents for plaque vulnerability.

Abstract

INTRODUCTION:

Atherosclerotic plaque rupture is the primary cause for myocardial infarction and stroke. During plaque progression macrophages and mast cells secrete matrix-degrading proteolytic enzymes, such as matrix metalloproteinases (MMPs). We studied levels of MMPs and tissue inhibitor of metalloproteinases-3 (TIMP-3) in relation to the characteristics of carotid plaques. We evaluated in vitro two radiolabeled probes targeting active MMPs towards non-invasive imaging of rupture-prone plaques.

METHODS:

Human carotid plaques obtained from endarterectomy were classified into stable and vulnerable by visual and histological analysis. MMP-1, MMP-2, MMP-8, MMP-9, MMP-10, MMP-12, MMP-14, TIMP-3, and CD68 levels were investigated by quantitative polymerase chain reaction. Immunohistochemistry was used to localize MMP-2 and MMP-9 with respect to CD68-expressing macrophages. Western blotting was applied to detect their active forms. A fluorine-18-labeled MMP-2/MMP-9 inhibitor and a tritiated selective MMP-9 inhibitor were evaluated by in vitro autoradiography as potential lead structures for non-invasive imaging.

RESULTS:

Gene expression levels of all MMPs and CD68 were elevated in plaques. MMP-1, MMP-9, MMP-12 and MMP-14 were significantly higher in vulnerable than stable plaques. TIMP-3 expression was highest in stable and low in vulnerable plaques. Immunohistochemistry revealed intensive staining of MMP-9 in vulnerable plaques. Western blotting confirmed presence of the active form in plaque lysates. In vitro autoradiography showed binding of both inhibitors to stable and vulnerable plaques.

CONCLUSIONS:

MMPs differed in their expression patterns among plaque phenotypes, providing possible imaging targets. The two tested MMP-2/MMP-9 and MMP-9 inhibitors may be useful to detect atherosclerotic plaques, but not the vulnerable lesions selectively.

• Authors: Adrienne Müller, Stefanie D Krämer, Romana Meletta, Katharina Beck, Svetlana V Selivanova, Zoran Rancic, Philipp A Kaufmann, Bernhard Vos, Jörg Meding, Timo Stellfeld, Tobias K Heinrich, Marcus Bauser, Joachim Hütter, Ludger M Dinkelborg, Roger Schibli, Simon M Ametamey
• Journal: Nuclear medicine and biology (Nucl Med Biol) Vol. 41 Issue 7 Pg. 562-9 (Aug 2014) ISSN: 1872-9614 [Electronic] United States
• PMID: 24853402 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier Inc. All rights reserved.

Chemical References

• Antigens, CD
• Antigens, Differentiation, Myelomonocytic
• CD68 antigen, human
• Matrix Metalloproteinase Inhibitors
• Tissue Inhibitor of Metalloproteinase-3
• Tritium
• Benzoic Acid
• Matrix Metalloproteinases

Topics

• Aged
• Aged, 80 and over
• Animals
• Antigens, CD (genetics, metabolism)
• Antigens, Differentiation, Myelomonocytic (genetics, metabolism)
• Arteries (metabolism)
• Benzoic Acid (chemistry)
• Female
• Gene Expression Regulation, Enzymologic
• Humans
• Isotope Labeling
• Macrophages (metabolism)
• Male
• Matrix Metalloproteinase Inhibitors (chemistry)
• Matrix Metalloproteinases (genetics, metabolism)
• Mice
• Middle Aged
• Molecular Imaging (methods)
• Plaque, Atherosclerotic (diagnosis, genetics, metabolism)
• Protein Transport
• Tissue Inhibitor of Metalloproteinase-3 (genetics, metabolism)
• Tritium