Leukocyte trafficking-associated vascular adhesion protein 1 is expressed and functionally active in atherosclerotic plaques.

Johanna M U Silvola,Juhani Knuuti,Heidi Liljenbäck,Olli Metsälä,Antti Saraste,Helena Virtanen,Seppo Ylä-Herttuala,Mia Ståhle,Sirpa Jalkanen,Tiina Saanijoki,Pekka Saukko,Harri Hakovirta,Sanna Hellberg,Tibor Z Veres,Anne Roivainen,Matti Jauhiainen,Riikka Siitonen,Meeri Käkelä

doi:10.1038/srep35089

Abstract

Given the important role of inflammation and the potential association of the leukocyte trafficking-associated adhesion molecule vascular adhesion protein 1 (VAP-1) with atherosclerosis, this study examined whether functional VAP-1 is expressed in atherosclerotic lesions and, if so, whether it could be targeted by positron emission tomography (PET). First, immunohistochemistry revealed that VAP-1 localized to endothelial cells of intra-plaque neovessels in human carotid endarterectomy samples from patients with recent ischemic symptoms. In low-density lipoprotein receptor-deficient mice expressing only apolipoprotein B100 (LDLR−/−ApoB100/100), VAP-1 was expressed on endothelial cells lining inflamed atherosclerotic lesions; normal vessel walls in aortas of C57BL/6N control mice were VAP-1-negative. Second, we discovered that the focal uptake of VAP-1 targeting sialic acid-binding immunoglobulin-like lectin 9 based PET tracer [68Ga]DOTA-Siglec-9 in atherosclerotic plaques was associated with the density of activated macrophages (r = 0.58, P = 0.022). As a final point, we found that the inhibition of VAP-1 activity with small molecule LJP1586 decreased the density of macrophages in inflamed atherosclerotic plaques in mice. Our results suggest for the first time VAP-1 as a potential imaging target for inflamed atherosclerotic plaques, and corroborate VAP-1 inhibition as a therapeutic approach in the treatment of atherosclerosis.

Highlights

The endothelial cells lining the walls of normal vessels or the intimal layers of plaques in atherosclerotic mice showed no binding of the i.v.-injected anti-Vascular adhesion protein-1 (VAP-1) antibody
We provide evidence that VAP-1 plays a role in inflammation associated with atherosclerosis, suggesting that VAP-1 is a potential target for imaging and for anti-inflammatory therapeutics used to treat vascular inflammation
We showed that VAP-1 is expressed on the luminal surface of endothelial cells in atherosclerotic plaques in LDLR−/−ApoB100/100 mice, and we confirmed a previous report showing expression of VAP-1 in human intra-plaque neovessels[19]

Summary

Introduction

Because [18F]FDG (2-[18F]fluoro-2-deoxy-D-glucose) accumulates in macrophages, positron emission tomography (PET) with this glucose analogue is used to image vascular inflammation[12,13]. Uptake of [18F]FDG is not specific for inflammation; new imaging agents are called for. We previously developed and evaluated several imaging agents that target VAP-1 in various experimental animal models[14,15,16,17,18]. We used a phage-display method to identify a novel VAP-1-binding ligand, sialic acid-binding immunoglobulin-like lectin 9 (Siglec-9), which is expressed in activated monocytes and granulocytes. Given the important role of inflammation in atherosclerosis, the present study aimed to investigate 1) whether functionally active VAP-1 is expressed in atherosclerotic plaques, and 2) whether the new VAP-1-targeting radioligand [68Ga]DOTA-Siglec-9 can detect inflamed atherosclerotic lesions

Methods

Results

Conclusion