Inhibition of IL17A Using an Affibody Molecule Attenuates Inflammation in ApoE-Deficient Mice.

The balance between pro- and anti-inflammatory cytokines released by immune and non-immune cells plays a decisive role in the progression of atherosclerosis. Interleukin (IL)-17A has been shown to accelerate atherosclerosis. In this study, we investigated the effect on pro-inflammatory mediators and atherosclerosis development of an Affibody molecule that targets IL17A. Affibody molecule neutralizing IL17A, or sham were administered in vitro to human aortic smooth muscle cells (HAoSMCs) and murine NIH/3T3 fibroblasts and in vivo to atherosclerosis-prone, hyperlipidaemic ApoE-/- mice. Levels of mediators of inflammation and development of atherosclerosis were compared between treatments. Exposure of human smooth muscle cells and murine NIH/3T3 fibroblasts in vitro to αIL-17A Affibody molecule markedly reduced IL6 and CXCL1 release in supernatants compared with sham exposure. Treatment of ApoE-/- mice with αIL-17A Affibody molecule significantly reduced plasma protein levels of CXCL1, CCL2, CCL3, HGF, PDGFB, MAP2K6, QDPR, and splenocyte mRNA levels of Ccxl1, Il6, and Ccl20 compared with sham exposure. There was no significant difference in atherosclerosis burden between the groups. In conclusion, administration of αIL17A Affibody molecule reduced levels of pro-inflammatory mediators and attenuated inflammation in ApoE-/- mice.

CD137: A checkpoint regulator involved in atherosclerosis.

Inflammation is associated with atherosclerotic plaque development and precipitation of myocardial infarction and stroke, and anti-inflammatory therapy may reduce disease severity. Costimulatory molecules are key regulators of immune cell activity and inflammation, and are associated with disease development in atherosclerosis. Accumulating evidence indicates that a costimulatory molecule of the Tumor Necrosis Factor Receptor superfamily, the checkpoint regulator CD137, promotes atherosclerosis and vascular inflammation in experimental models. In light of the burgeoning consideration of CD137-targeted therapy in the clinic, it will be important to better understand costimulator immunobiology in development of cardiovascular disease. Here, we review available data on the costimulator CD137 and its potential role in atherosclerosis.

Increased Carotid Artery Lesion Inflammation Upon Treatment With the CD137 Agonistic Antibody 2A.

BACKGROUND: Increased inflammatory activity destabilizes the atherosclerotic lesion and may lead to atherothrombosis and symptomatic cardiovascular disease. Co-stimulatory molecules, such as CD137, are key regulators of inflammation, and CD137 activity regulates inflammation in experimental atherosclerosis. Here, we hypothesized that CD137 activation promotes carotid artery inflammation and atherothrombosis.Methods and Results:In a model of inducible atherothrombosis with surgical ligation of the right carotid artery and a subsequent placement of a polyethene cuff, elevated levels of CD137 and CD137 ligand mRNA in atherothrombotic vs. non-atherothrombotic murine carotid lesions was observed. Mice treated with the CD137 agonistic antibody 2A showed signs of increased inflammation in the aorta and a higher proportion of CD8+T cells in spleen and blood. In carotid lesions of 2A-treated mice, significantly higher counts of CD8+and major histocompatibility (MHC)-class II molecule I-Ab+cells were observed. Treatment with the CD137 agonistic antibody 2A did not significantly affect the atherothrombosis frequency in 16-week-old mice in this model. CONCLUSIONS: Levels of CD137 and CD137 ligand mRNA were higher in advanced atherosclerotic disease compared to control vessels, and treatment with the CD137 agonistic antibody 2A, in a murine model for inducible atherothrombosis promoted vascular inflammation, but had no significant effect on atherothrombosis frequency at this early disease stage.

Human genetic evidence for involvement of CD137 in atherosclerosis.

Atherosclerosis is an inflammatory disease and the main cause of cardiovascular disease. Inflammation promotes plaque instability and clinical disease, such as myocardial infarction, stroke and peripheral vascular disease. Subclinical atherosclerosis begins with thickening of the arterial intimal layer, and increased intima-media thickness (IMT) in the carotid artery is a widely used measurement of subclinical atherosclerosis. Activation of CD137 (tumor necrosis factor receptor super family 9) promotes inflammation and disease development in murine atherosclerosis. CD137 is expressed in human atherosclerosis, but its role is largely unknown. This study uses a genetic approach to investigate CD137 in human atherosclerotic disease. In publicly available data on genotype and gene expression from the HapMap project, the minor T allele of rs2453021, a single nucleotide polymorphism in CD137, was significantly associated with CD137 gene expression. In the PROCARDIS and Wellcome Trust Case Control Consortium (WTCCC) cohorts of 13,029 cases and controls, no significant association was detected between the minor T allele of rs2453021 and risk for coronary artery disease or myocardial infarction. However, in the IMPROVE multicenter study of 3,418 individuals, the minor T allele of rs2453021 was associated with increased IMT of the common carotid artery (CCA), as measured by ultrasonography, with presence of plaque in CCA and with increased incidence of adverse noncardiac vascular events. Taken together, this study shows that the minor T allele of rs2453021 is associated with increased IMT in the CCA and increased risk of incident noncardiac vascular events, thus providing the first human genetic evidence for involvement of CD137 in atherosclerosis.

A CYP26B1 polymorphism enhances retinoic acid catabolism and may aggravate atherosclerosis.

All-trans retinoic acid, controlled by cytochrome P450, family 26 (CYP26) enzymes, potentially has beneficial effects in atherosclerosis treatment. This study investigates CYP26 subfamily B, polypeptide 1 (CYP26B1) in atherosclerosis and the effects of a genetic polymorphism in CYP26B1 on retinoid catabolism. We found that CYP26B1 mRNA was induced by retinoic acid in human atherosclerotic arteries, and CYP26B1 and the macrophage marker CD68 were colocalized in human atherosclerotic lesions. In mice, Cyp26B1 mRNA was higher in atherosclerotic arteries than in normal arteries. Databases were queried for nonsynonymous CYP26B1 single nucleotide polymorphisms (SNPs) and rs2241057 selected for further studies. Constructs of the CYP26B1 variants were created and used for production of purified proteins and transfection of macrophagelike cells. The minor variant catabolized retinoic acid with significantly higher efficiency, indicating that rs2241057 is functional and suggesting reduced retinoid availability in tissues with the minor variant. rs2241057 was investigated in a Stockholm Coronary Atherosclerosis Risk Factor (SCARF) subgroup. The minor allele was associated with slightly larger lesions, as determined by angiography. In summary, this study identifies the first CYP26B1 polymorphism that alters CYP26B1 capacity to metabolize retinoic acid. CYP26B1 was expressed in macrophage-rich areas of human atherosclerotic lesions, induced by retinoic acid and increased in murine atherosclerosis. Taken together, the results indicate that CYP26B1 capacity is genetically regulated and suggest that local CYP26B1 activity may influence atherosclerosis.

Activation of VPAC1 receptors aggravates early atherosclerosis in hypercholesterolemic apolipoprotein E-deficient mice.

OBJECTIVE: Vasoactive intestinal peptide (VIP) is a 28-amino acid peptide widely expressed in the body and binding three types of receptors: VPAC(1)-R, VPAC(2)-R and PAC(1)-R. Based on beneficial effects of VIP and VPAC(1)-R agonists in mouse models of several chronic inflammatory disorders, we hypothesized that activation of VIP receptors would prevent atherosclerosis development in apolipoprotein E-deficient mice. METHODS AND RESULTS: Contrary to our hypothesis, administration of a VPAC(1)-R agonist, (Ala(11,22,28))-VIP aggravated atherosclerotic lesion development in the aortic root of these mice compared to control mice. This was accompanied by a significant increase in the expression of MHC class II protein I-A(b), and suggests enhanced inflammatory activity in the vessel wall. The amount of macrophage-specific CD68 staining as well as serum cholesterol and triglyceride levels did not change as a result of the (Ala(11,22,28))-VIP treatment, i.e. the treatment resulted in significant changes in lipid accumulation in the lesions without changing the number of macrophages or systemic lipid levels. Interestingly, administration of VIP did not alter the course of the disease. CONCLUSION: Despite beneficial effects in murine models of several inflammatory disorders, VPAC(1)-R activation aggravates atherosclerotic lesion formation in apolipoprotein E-deficient mice through enhanced inflammatory activity in the vessel wall.

CD137 is expressed in human atherosclerosis and promotes development of plaque inflammation in hypercholesterolemic mice.

BACKGROUND: Atherosclerosis is a multifactorial disease in which inflammatory processes play an important role. Inflammation underlies lesion evolution at all stages, from establishment to plaque rupture and thrombosis. Costimulatory molecules of the tumor necrosis factor superfamily such as CD40/CD40L and OX40/OX40L have been implicated in atherosclerosis. METHODS AND RESULTS: This study shows that the tumor necrosis factor superfamily members CD137 and CD137 ligand (CD137L), which play a major role in several autoimmune diseases, may constitute a pathogenic pair in atherogenesis. We detected CD137 protein in human atherosclerotic lesions not only on T cells but also on endothelial cells and showed that CD137 in cultured endothelial cells and smooth muscle cells was induced by proinflammatory cytokines implicated in atherosclerosis. Activation of CD137 by CD137L induced adhesion molecule expression on endothelial cells and reduced smooth muscle cell proliferation. In addition, treatment of atherosclerosis-prone apolipoprotein E-deficient mice with a CD137 agonist caused increased inflammation. T-cell infiltration, mainly of CD8(+) cells, and expression of the murine major histocompatibility complex class II molecule I-A(b) increased significantly in atherosclerotic lesions, as did the aortic expression of proinflammatory cytokines. CONCLUSIONS: Taken together, these observations suggest that CD137-CD137L interactions in the vasculature may contribute to the progression of atherosclerosis via augmented leukocyte recruitment, increased inflammation, and development of a more disease-prone phenotype.