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Objective: Identification of patients with high-risk asymptomatic carotid plaques remains an elusive but essential step in stroke prevention. Inflammation is a key process in plaque destabilization and a prelude to clinical sequelae. There are currently no clinical imaging tools to assess the inflammatory activity within plaques. This study characterized inflammation in atherosclerosis using dual-targeted microparticles of iron oxide (DT-MPIO) as a magnetic resonance imaging (MRI) probe., Methods: DT-MPIO were used to detect and characterize inflammatory markers, vascular cell adhesion molecule 1 (VCAM-1). and P-selectin on (1) tumor necrosis factor-α-treated cells by immunocytochemistry and (2) aortic root plaques of apolipoprotein-E deficient mice by in vivo MRI. Furthermore, apolipoprotein E-deficient mice with focal carotid plaques of different phenotypes were developed by means of periarterial cuff placement to allow in vivo molecular MRI using these probes. The association between biomarkers and the magnetic resonance signal in different contrast groups was assessed longitudinally in these models., Results: Immunocytochemistry confirmed specificity and efficacy of DT-MPIO to VCAM-1 and P-selectin. Using this in vivo molecular MRI strategy, we demonstrated (1) the DT-MPIO-induced magnetic resonance signal tracked with VCAM-1 (r = 0.69; P = .014), P-selectin (r = 0.65; P = .022), and macrophage content (r = 0.59; P = .045) within aortic root plaques and (2) high-risk inflamed plaques were distinguished from noninflamed plaques in the murine carotid artery within a practical clinical imaging time frame., Conclusions: These molecular MRI probes constitute a novel imaging tool for in vivo characterization of plaque vulnerability and inflammatory activity in atherosclerosis. Further development and translation into the clinical arena will facilitate more accurate risk stratification in carotid atherosclerotic disease in the future., (Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Highlights: [•] Atherosclerosis is an inflammatory disorder with a strong involvement of innate immunity. [•] Toll-like receptors (TLRs) are key components of the innate immune system. [•] Recent evidence suggests that TLRs elicit both protective and detrimental roles in atherosclerosis. [•] Emerging data suggests that the outcome of TLR signaling is agonist- and cell type-dependent. [•] This review aims to update and explore controversies of the role of TLRs in atherosclerosis. [ABSTRACT FROM AUTHOR]

Atherosclerosis is an inflammatory disease with a strong involvement of innate immunity. Tolllike receptors (TLRs) are the best-characterized pattern recognition receptors of the innate immune system. Almost all cell types in lesions, inflammatory leukocytes and resident vascular cells alike express TLRs. TLRs are able to sense modified lipids, enhance foam cell formation, induce leukocyte recruitment, and increase cytokine and matrix metalloproteinase production within atherosclerotic lesions. As such, TLRs represent an important link between atheroma and inflammation, making them attractive targets for the treatment of cardiovascular disease. Novel TLR-specific biologics are being developed and tested in other inflammatory diseases. This article will describe the exciting potential of TLRs as therapeutic targets for the treatment of atherosclerosis and will also highlight the potential challenges in the clinical application of TLR-based therapeutics in cardiovascular disease. INSET: Key issues. [ABSTRACT FROM AUTHOR]

Inflammation drives atherosclerosis. Both immune and resident vascular cell types are involved in the development of atherosclerotic lesions. The phenotype and function of these cells are key in determining the development of lesions. Toll-like receptors are the most characterised innate immune receptors and are responsible for the recognition of exogenous conserved motifs on pathogens, and, potentially, some endogenous molecules. Both endogenous and exogenous TLR agonists may be present in atherosclerotic plaques. Engagement of toll-like receptors on immune and resident vascular cells can affect atherogenesis as signalling downstream of these receptors can elicit proinflammatory cytokine release, lipid uptake, and foam cell formation and activate cells of the adaptive immune system. In this paper, we will describe the expression of TLRs on immune and resident vascular cells, highlight the TLR ligands that may act through TLRs on these cells, and discuss the consequences of TLR activation in atherosclerosis. [ABSTRACT FROM AUTHOR]