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.

Evaluation of glucagon-like peptide-1 receptor expression in nondiabetic and diabetic atherosclerotic mice using PET tracer 68Ga-NODAGA-exendin-4.

Cardiovascular effects of glucagon-like peptide-1 receptor (GLP-1R) agonist therapies are potentially mediated by anti-inflammatory effects on atherosclerosis. Our study demonstrates that 68Ga-NODAGA-exendin-4, a radioligand specifically targeting GLP-1R, detects GLP-1R expression in inflamed atherosclerotic lesions in nondiabetic and diabetic hypercholesterolemic mice. Immunofluorescence staining suggests that GLP-1R is primarily localized in M2 macrophages in lesions. This study describes a new potential tool that may have translational relevance for studies of pharmacological modification of GLP-1R signaling in atherosclerosis.

Therapeutic Antibody Against Phosphorylcholine Preserves Coronary Function and Attenuates Vascular 18F-FDG Uptake in Atherosclerotic Mice.

This study showed that treatment with a therapeutic monoclonal immunoglobulin-G1 antibody against phosphorylcholine on oxidized phospholipids preserves coronary flow reserve and attenuates atherosclerotic inflammation as determined by the uptake of 18F-fluorodeoxyglucose in atherosclerotic mice. The noninvasive imaging techniques represent translational tools to assess the efficacy of phosphorylcholine-targeted therapy on coronary artery function and atherosclerosis in clinical studies.

Effects of dipeptidyl peptidase 4 inhibition on inflammation in atherosclerosis: A 18F-fluorodeoxyglucose study of a mouse model of atherosclerosis and type 2 diabetes.

BACKGROUND AND AIMS: Dipeptidyl peptidase 4 (DPP-4) inhibitors have anti-inflammatory and atheroprotective effects. We evaluated the effects of the DPP-4 inhibitor linagliptin on atherosclerotic plaque and hepatic inflammation using histology and 2-deoxy-2-[18F]-fluoro-d-glucose (18F-FDG), a positron emission tomography tracer of inflammation, in a mouse model of hypercholesterolemia and type 2 diabetes. METHODS: Igf2/Ldlr-/-Apob100/100 mice were fed a high-fat diet (HFD) for 8 weeks and then randomly allocated to receive HFD (n = 14), or HFD with added linagliptin (n = 15) for additional 12 weeks. Five mice fed a chow diet were studied as an additional control. At the end of the study, glucose tolerance, aortic and liver uptake of 18F-FDG, and histology were studied. RESULTS: Mice in linagliptin and HFD groups had similar fasting glucose concentrations, but linagliptin improved glucose tolerance. Aortas of linagliptin and HFD groups showed advanced atherosclerotic plaques with no difference in the mean intima-to-media ratio or number of macrophages in the plaques. Autoradiography showed similar 18F-FDG uptake by atherosclerotic plaques in linagliptin and HFD groups (plaque-to-wall ratio: 1.7 ± 0.25 vs. 1.6 ± 0.21; p = 0.24). In the liver, linagliptin reduced the histologic inflammation score but had no effect on 18F-FDG uptake. Compared with chow diet, uptake of 18F-FDG was similar in the aorta, but higher in the liver after HFD. CONCLUSIONS: Linagliptin therapy improved glucose tolerance and reduced hepatic inflammation but had no effect on plaque burden or atherosclerotic inflammation, as determined by histology and 18F-FDG uptake, in atherosclerotic mice with type 2 diabetes.

Germinal Center-Derived Antibodies Promote Atherosclerosis Plaque Size and Stability.

BACKGROUND: Atherosclerosis progression is modulated by interactions with the adaptive immune system. Humoral immunity can help protect against atherosclerosis formation; however, the existence, origin, and function of putative atherogenic antibodies are controversial. How such atherosclerosis-promoting antibodies could affect the specific composition and stability of plaques, as well as the vasculature generally, remains unknown. METHODS: We addressed the overall contribution of antibodies to atherosclerosis plaque formation, composition, and stability in vivo (1) with mice that displayed a general loss of antibodies, (2) with mice that had selectively ablated germinal center-derived IgG production, or (3) through interruption of T-B-cell interactions and further studied the effects of antibody deficiency on the aorta by transcriptomics. RESULTS: Here, we demonstrate that atherosclerosis-prone mice with attenuated plasma cell function manifest reduced plaque burden, indicating that antibodies promote atherosclerotic lesion size. However, the composition of the plaque was altered in antibody-deficient mice, with an increase in lipid content and decreases in smooth muscle cells and macrophages, resulting in an experimentally validated vulnerable plaque phenotype. Furthermore, IgG antibodies enhanced smooth muscle cell proliferation in vitro in an Fc receptor-dependent manner, and antibody-deficient mice had decreased neointimal hyperplasia formation in vivo. These IgG antibodies were shown to be derived from germinal centers, and mice genetically deficient for germinal center formation had strongly reduced atherosclerosis plaque formation. mRNA sequencing of aortas revealed that antibodies are required for the sufficient expression of multiple signal-induced and growth-promoting transcription factors and that aortas undergo large-scale metabolic reprograming in their absence. Using an elastase model, we demonstrated that absence of IgG results in an increased severity of aneurysm formation. CONCLUSIONS: We propose that germinal center-derived IgG antibodies promote the size and stability of atherosclerosis plaques, through promoting arterial smooth muscle cell proliferation and maintaining the molecular identity of the aorta. These results could have implications for therapies that target B cells or B-T-cell interactions because the loss of humoral immunity leads to a smaller but less stable plaque phenotype.

Amyloid-Targeting PET Tracer [18F]Flutemetamol Accumulates in Atherosclerotic Plaques.

Atherosclerosis is characterized by the accumulation of oxidized lipids in the artery wall, which triggers an inflammatory response. Oxidized low-density lipoprotein (ox-LDL) presents amyloid-like structural properties, and different amyloid species have recently been recognized in atherosclerotic plaques. Therefore, we studied the uptake of the amyloid imaging agent [18F]Flutemetamol in atherosclerotic plaques. The binding of [18F]Flutemetamol to human carotid artery plaque was studied in vitro. In vivo uptake of the tracer was studied in hypercholesterolemic IGF-II/LDLR-/-ApoB100/100 mice and C57BL/6N controls. Tracer biodistribution was studied in vivo with PET/CT, and ex vivo by gamma counter and digital ex vivo autoradiography. The presence of amyloid, ox-LDL, and macrophages in the plaques was examined by immunohistochemistry. [18F]Flutemetamol showed specific accumulation in human carotid plaque, especially in areas positive for amyloid beta. The aortas of IGF-II/LDLR-/-ApoB100/100 mice showed large thioflavin-S-positive atherosclerotic plaques containing ox-LDL and macrophages. Autoradiography revealed 1.7-fold higher uptake in the plaques than in a lesion-free vessel wall, but no difference in aortic tissue uptake between mouse strains were observed in the in vivo PET/CT. In conclusion, [18F]Flutemetamol binds to amyloid-positive areas in human atherosclerotic plaques. Further studies are warranted to clarify the uptake mechanisms, and the potential of the tracer for in vivo imaging of atherosclerosis in patients.

Evaluation of [68Ga]Ga-DOTA-TCTP-1 for the Detection of Metalloproteinase 2/9 Expression in Mouse Atherosclerotic Plaques.

Background: The expression of matrix metalloproteinases 2/9 (MMP-2/9) has been implicated in arterial remodeling and inflammation in atherosclerosis. We evaluated a gallium-68 labeled peptide for the detection of MMP-2/9 in atherosclerotic mouse aorta. Methods: We studied sixteen low-density lipoprotein receptor deficient mice (LDLR-/-ApoB100/100) kept on a Western-type diet. Distribution of intravenously-injected MMP-2/9-targeting peptide, [68Ga]Ga-DOTA-TCTP-1, was studied by combined positron emission tomography (PET) and contrast-enhanced computed tomography (CT). At 60 min post-injection, aortas were cut into cryosections for autoradiography analysis of tracer uptake, histology, and immunohistochemistry. Zymography was used to assess MMP-2/9 activation and pre-treatment with MMP-2/9 inhibitor to assess the specificity of tracer uptake. Results: Tracer uptake was not visible by in vivo PET/CT in the atherosclerotic aorta, but ex vivo autoradiography revealed 1.8 ± 0.34 times higher tracer uptake in atherosclerotic plaques than in normal vessel wall (p = 0.0029). Tracer uptake in plaques correlated strongly with the quantity of Mac-3-positive macrophages (R = 0.91, p < 0.001), but weakly with MMP-9 staining (R = 0.40, p = 0.099). Zymography showed MMP-2 activation in the aorta, and pre-treatment with MMP-2/9 inhibitor decreased tracer uptake by 55% (p = 0.0020). Conclusions: The MMP-2/9-targeting [68Ga]Ga-DOTA-TCTP-1 shows specific uptake in inflamed atherosclerotic lesions; however, a low target-to-background ratio precluded in vivo vascular imaging. Our results suggest, that the affinity of gelatinase imaging probes should be steered towards activated MMP-2, to reduce the interference of circulating enzymes on the target visualization in vivo.

Positron Emission Tomography Imaging of Macrophages in Atherosclerosis with 18F-GE-180, a Radiotracer for Translocator Protein (TSPO).

Intraplaque inflammation plays an important role in the progression of atherosclerosis. The 18 kDa translocator protein (TSPO) expression is upregulated in activated macrophages, representing a potential target to identify inflamed atherosclerotic plaques. We preclinically evaluated 18F-GE-180, a novel third-generation TSPO radioligand, in a mouse model of atherosclerosis. Methods. Nine hypercholesterolemic mice deficient in low density lipoprotein receptor and apolipoprotein B48 (LDLR-/-ApoB100/100) and six healthy C57BL/6N mice were injected with 10 MBq of 18F-GE-180. Specificity of binding was demonstrated in three LDLR-/-ApoB100/100 mice by injection of nonradioactive reference compound of 18F-GE-180 before 18F-GE-180. Dynamic 30-minute PET was performed followed by contrast-enhanced CT, and the mice were sacrificed at 60 minutes after injection. Tissue samples were obtained for ex vivo biodistribution measurements, and aortas were cut into serial cryosections for digital autoradiography. The presence of macrophages and TSPO was studied by immunohistochemistry. The 18F-GE-180 retention in plaque areas with different macrophage densities and lesion-free vessel wall were compared. Results. The LDLR-/-ApoB100/100 mice showed large, inflamed plaques in the aorta. Autoradiography revealed significantly higher 18F-GE-180 retention in macrophage-rich plaque areas than in noninflamed areas (count densities 150 ± 45 PSL/mm2 versus 51 ± 12 PSL/mm2, p < 0.001). Prominent retention in the vessel wall without plaque was also observed (220 ± 41 PSL/mm2). Blocking with nonradioactive GE-180 diminished the difference in count densities between macrophage-rich and noninflamed areas in atherosclerotic plaques and lowered the count density in vessel wall without plaque. Conclusion. 18F-GE-180 shows specific uptake in macrophage-rich areas of atherosclerotic plaques in mice. However, retention in atherosclerotic lesions does not exceed that in lesion-free vessel wall. The third-generation TSPO radioligand 18F-GE-180 did not show improved characteristics for imaging atherosclerotic plaque inflammation compared to previously studied TSPO-targeting tracers.

Effects of atorvastatin and diet interventions on atherosclerotic plaque inflammation and [18F]FDG uptake in Ldlr-/-Apob100/100 mice.

BACKGROUND AND AIMS: Uptake of the positron emission tomography (PET) tracer 2-deoxy-2-[18F]-fluoro-d- glucose ([18F]FDG) into macrophages is a sensitive marker of inflammation in atherosclerosis. To assess the anti-inflammatory effects of statins, we studied whether atorvastatin therapy reduces aortic [18F]FDG uptake in hypercholesterolemic mice deficient in low-density lipoprotein receptor (Ldlr), and expressing only apolipoprotein B-100 (Ldlr-/-Apob100/100). METHODS: Thirty-six Ldlr-/-Apob100/100 mice were fed a high-fat diet (HFD) for 12 weeks and then allocated to receive a HFD (n = 13), chow diet (Chow, n = 12), or HFD with added atorvastatin (HFD + A, n = 11), for another 12 weeks. In addition to aortic histopathology, [18F]FDG uptake was studied in vivo using PET/computed tomography (CT), and ex vivo by gamma counting of excised aorta. RESULTS: Total cholesterol levels were lower in the Chow and HFD + A groups than in the HFD group (10 ± 3.2, 23 ± 4.9 and 34 ± 9.2 mmol/l, respectively), with the Chow group also showing a lower plaque burden and lower numbers of macrophages in the lesions. Compared to the HFD group, [18F]FDG uptake in the aorta (normalized for blood) was lower in the Chow group in both in vivo (2.1 ± 0.21 vs. 1.7 ± 0.25, p = 0.018) and ex vivo (5.2 ± 2.3 vs. 2.8 ± 0.87, p = 0.011) analyses, whereas atorvastatin had no effect on uptake (2.1 ± 0.42 in vivo and 3.9 ± 1.8 ex vivo). [18F]FDG uptake correlated with plasma total cholesterol levels. CONCLUSIONS: Atorvastatin therapy did not show cholesterol-independent effects on inflammation in atherosclerotic lesions in Ldlr-/-Apob100/100 mice, as determined by histology and [18F]FDG PET, whereas a cholesterol-lowering diet intervention was effective.

Comparison of 68Ga-DOTA-Siglec-9 and 18F-Fluorodeoxyribose-Siglec-9: Inflammation Imaging and Radiation Dosimetry.

Sialic acid-binding immunoglobulin-like lectin 9 (Siglec-9) is a ligand of inflammation-inducible vascular adhesion protein-1 (VAP-1). We compared 68Ga-DOTA- and 18F-fluorodeoxyribose- (FDR-) labeled Siglec-9 motif peptides for PET imaging of inflammation. Methods. Firstly, we examined 68Ga-DOTA-Siglec-9 and 18F-FDR-Siglec-9 in rats with skin/muscle inflammation. We then studied 18F-FDR-Siglec-9 for the detection of inflamed atherosclerotic plaques in mice and compared it with previous 68Ga-DOTA-Siglec-9 results. Lastly, we estimated human radiation dosimetry from the rat data. Results. In rats, 68Ga-DOTA-Siglec-9 (SUV, 0.88 ± 0.087) and 18F-FDR-Siglec-9 (SUV, 0.77 ± 0.22) showed comparable (P = 0.29) imaging of inflammation. In atherosclerotic mice, 18F-FDR-Siglec-9 detected inflamed plaques with a target-to-background ratio (1.6 ± 0.078) similar to previously tested 68Ga-DOTA-Siglec-9 (P = 0.35). Human effective dose estimates for 68Ga-DOTA-Siglec-9 and 18F-FDR-Siglec-9 were 0.024 and 0.022 mSv/MBq, respectively. Conclusion. Both tracers are suitable for PET imaging of inflammation. The easier production and lower cost of 68Ga-DOTA-Siglec-9 present advantages over 18F-FDR-Siglec-9, indicating it as a primary choice for clinical studies.

18-kDa translocator protein ligand 18F-FEMPA: Biodistribution and uptake into atherosclerotic plaques in mice.

BACKGROUND: Radioligands of 18-kDa translocator protein (TSPO) expressed on activated macrophages are a potential approach for imaging of inflammation in atherosclerosis. We evaluated a novel TSPO-targeted tracer 18F-FEMPA for the detection of atherosclerotic plaque inflammation in mice. METHODS AND RESULTS: The distribution kinetics of 18F-FEMPA was evaluated by in vivo PET/CT imaging. 18F-FEMPA uptake was compared in atherosclerotic (LDLR-/-ApoB100/100, n = 10) and healthy mice (C57BL/6 N, n = 7) ex vivo at twenty minutes post-injection. Biodistribution was analyzed from harvested tissue samples, and aortas were sectioned for autoradiography. Aortas of LDLR-/-ApoB100/100 mice showed large, macrophage-rich atherosclerotic plaques. In vivo, 18F-FEMPA showed rapid blood clearance but no difference in aortic uptake between atherosclerotic and healthy mice. In the mice studied ex vivo at 20 minutes post-injection, quantification of radioactivity in the whole aorta showed 1.3-fold higher 18F-FEMPA accumulation in atherosclerotic than healthy mice (P = .028). Autoradiography showed higher tracer uptake in plaque areas with high macrophage content as compared with areas of no macrophages (count densities 190 ± 54 vs 40 ± 13 PSL/mm2, P < .001), but the uptake in the plaques was not higher than in the normal vessel wall (230 ± 78 PSL/mm2). In vitro blocking showed specific accumulation in mouse and human atherosclerotic plaques. Immunohistochemistry confirmed co-localization of TSPO and macrophages. CONCLUSIONS: 18F-FEMPA shows rapid blood clearance and uptake in the mouse aorta. Uptake in atherosclerotic plaques correlated with the amount of macrophages, but did not exceed that in the normal vessel wall.

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

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.

Type 2 diabetes enhances arterial uptake of choline in atherosclerotic mice: an imaging study with positron emission tomography tracer ¹8F-fluoromethylcholine.

BACKGROUND: Diabetes is a risk factor for atherosclerosis associated with oxidative stress, inflammation and cell proliferation. The purpose of this study was to evaluate arterial choline uptake and its relationship to atherosclerotic inflammation in diabetic and non-diabetic hypercholesterolemic mice. METHODS: Low-density lipoprotein-receptor deficient mice expressing only apolipoprotein B100, with or without type 2 diabetes caused by pancreatic overexpression of insulin-like growth factor II (IGF-II/LDLR(-/-)ApoB(100/100) and LDLR(-/-)ApoB(100/100)) were studied. Distribution kinetics of choline analogue (18)F-fluoromethylcholine ((18)F-FMCH) was assessed in vivo by positron emission tomography (PET) imaging. Then, aortic uptakes of (18)F-FMCH and glucose analogue (18)F-fluorodeoxyglucose ((18)F-FDG), were assessed ex vivo by gamma counting and autoradiography of tissue sections. The (18)F-FMCH uptake in atherosclerotic plaques was further compared with macrophage infiltration and the plasma levels of cytokines and metabolic markers. RESULTS: The aortas of all hypercholesterolemic mice showed large, macrophage-rich atherosclerotic plaques. The plaque burden and densities of macrophage subtypes were similar in diabetic and non-diabetic animals. The blood clearance of (18)F-FMCH was rapid. Both the absolute (18)F-FMCH uptake in the aorta and the aorta-to-blood uptake ratio were higher in diabetic than in non-diabetic mice. In autoradiography, the highest (18)F-FMCH uptake co-localized with macrophage-rich atherosclerotic plaques. (18)F-FMCH uptake in plaques correlated with levels of total cholesterol, insulin, C-peptide and leptin. In comparison with (18)F-FDG, (18)F-FMCH provided similar or higher plaque-to-background ratios in diabetic mice. CONCLUSIONS: Type 2 diabetes enhances the uptake of choline that reflects inflammation in atherosclerotic plaques in mice. PET tracer (18)F-FMCH is a potential tool to study vascular inflammation associated with diabetes.

Comparison of Somatostatin Receptor 2-Targeting PET Tracers in the Detection of Mouse Atherosclerotic Plaques.

PURPOSE: Rupture-prone atherosclerotic plaques are characterized by accumulation of macrophages, which have shown to express somatostatin type 2 receptors. We aimed to investigate whether somatostatin receptor-targeting positron emission tomography (PET) tracers, [(68)Ga]DOTANOC, [(18)F]FDR-NOC, and [(68)Ga]DOTATATE, can detect inflamed atherosclerotic plaques. PROCEDURES: Atherosclerotic IGF-II/LDLR(-/-)ApoB(100/100) mice were studied in vivo and ex vivo for tracer uptake into atherosclerotic plaques. Furthermore, [(68)Ga]DOTANOC and [(68)Ga]DOTATATE were compared in a head-to-head setting for in vivo PET/X-ray computed tomography (CT) imaging characteristics. RESULTS: Ex vivo uptake of [(68)Ga]DOTANOC and [(68)Ga]DOTATATE in the aorta was higher in atherosclerotic mice compared to control C57Bl/6N mice, while the aortic uptake of [(18)F]FDR-NOC showed no genotype difference. Unlike [(18)F]FDR-NOC, [(68)Ga]DOTANOC and [(68)Ga]DOTATATE showed preferential binding to atherosclerotic plaques with plaque-to-wall ratio of 1.7 ± 0.3 and 2.1 ± 0.5, respectively. However, the aortic uptake and aorta-to-blood ratio of [(68)Ga]DOTANOC were higher compared to [(68)Ga]DOTATATE in in vivo PET/CT imaging. CONCLUSION: Our results demonstrate superior applicability for [(68)Ga]DOTANOC and [(68)Ga]DOTATATE in the detection of atherosclerotic plaques compared to [(18)F]FDR-NOC.

Pharmacological activation of the melanocortin system limits plaque inflammation and ameliorates vascular dysfunction in atherosclerotic mice.

OBJECTIVE: Melanocortin peptides have been shown to elicit anti-inflammatory actions and to promote vascular endothelial function by activating type 1 and 3 melanocortin receptors. Here, we addressed whether these favorable properties of melanocortins could reduce atherosclerotic plaque inflammation and improve vasoreactivity in atherosclerotic mice. APPROACH AND RESULTS: Low-density lipoprotein receptor-deficient mice expressing only apolipoprotein B100 were fed a high-fat diet for 8 or 16 weeks and treated with either vehicle or a stable melanocortin analog, melanotan II (MT-II, 0.3 mg/kg per day, 4 weeks). We determined plaque uptake of fluorine-18-labeled fluorodeoxyglucose as a surrogate marker for atherosclerotic plaque inflammation and vascular function of the aorta by ex vivo analyses. MT-II had no effect on body weight or composition, or plasma cholesterol levels in atherosclerotic mice. Without attenuating atherosclerotic lesion size or lesional macrophage accumulation, MT-II treatment reduced fluorine-18-labeled fluorodeoxyglucose uptake in the atherosclerotic plaques. Resident macrophages in the lesions of MT-II-treated mice were polarized toward the anti-inflammatory M2 phenotype. Systemic inflammation was also attenuated by MT-II intervention as evidenced by decreased plasma levels of proinflammatory cytokines. In terms of aortic vasoreactivity, MT-II-treated mice showed enhanced endothelium-dependent relaxations, as well as promotion of vascular sensitivity to nitric oxide-mediated vasodilation, which were markedly impaired in control mice after prolonged duration of diet exposure. CONCLUSIONS: The present study demonstrates that pharmacological activation of the melanocortin system has therapeutic benefits in pre-established atherosclerosis by limiting plaque inflammation and promoting vascular endothelial function, which may provide a novel therapeutic approach for atherosclerosis.

VEGF-B-induced vascular growth leads to metabolic reprogramming and ischemia resistance in the heart.

Angiogenic growth factors have recently been linked to tissue metabolism. We have used genetic gain- and loss-of function models to elucidate the effects and mechanisms of action of vascular endothelial growth factor-B (VEGF-B) in the heart. A cardiomyocyte-specific VEGF-B transgene induced an expanded coronary arterial tree and reprogramming of cardiomyocyte metabolism. This was associated with protection against myocardial infarction and preservation of mitochondrial complex I function upon ischemia-reperfusion. VEGF-B increased VEGF signals via VEGF receptor-2 to activate Erk1/2, which resulted in vascular growth. Akt and mTORC1 pathways were upregulated and AMPK downregulated, readjusting cardiomyocyte metabolic pathways to favor glucose oxidation and macromolecular biosynthesis. However, contrasting with a previous theory, there was no difference in fatty acid uptake by the heart between the VEGF-B transgenic, gene-targeted or wildtype rats. Importantly, we also show that VEGF-B expression is reduced in human heart disease. Our data indicate that VEGF-B could be used to increase the coronary vasculature and to reprogram myocardial metabolism to improve cardiac function in ischemic heart disease.

Epitope specificity and IgG subclass distribution of autoantibodies to cardiac troponin.

BACKGROUND: Autoantibodies to cardiac troponins (cTnAAbs) can interfere with the measurement of cardiac troponin I (cTnI) by immunoassays for the diagnosis of myocardial infarction. Therefore, we determined the cTnI binding sites and IgG subclasses of circulating cTnAAbs. METHODS: We studied epitope specificity with sandwich-type immunoassays by measuring the recovery of troponin complex added to 10 cTnAAb-negative and 10 cTnAAb-positive sera from healthy volunteers. To study the IgG subclasses, we analyzed admission and 3-month follow-up sera from chest pain patients with a reference assay measuring total IgG (14 cTnAAb negative and 14 cTnAAb positive at 3 months) and with 4 subclass-specific assays measuring exclusively IgG subclasses 1-4. RESULTS: Mean recoveries of troponin complex in cTnAAb-positive samples for single cTnI epitopes ranged from 37% to 211%, being lowest for the cTnI midfragment (aa 30-110). However, the lowest sample-specific recoveries, 4%-92%, showed that none of the studied epitopes completely escaped the cTnAAb-related interference. Eight chest pain patients of the cTnAAb-positive group became positive between sampling points, and according to all 5 cTnAAb assays, specific signals were generally higher at follow-up. IgG4, with the highest prevalence, was detected in 68% of samples in the cTnAAb-positive group. CONCLUSIONS: IgG subclass studies confirm that cTnAAb formation may be triggered/boosted in acute cardiac events. This new information about the epitope specificity of cTnAAbs should be used to reevaluate existing recommendations regarding use of midfragment epitopes in cTnI assays. To circumvent the negative interference of the highly heterogeneous cTnAAbs, use of 3 or more unconventionally selected epitopes should be considered.

Uptake of 11C-choline in mouse atherosclerotic plaques.

UNLABELLED: The purpose of this study was to explore the feasibility of (11)C-choline in the assessment of the degree of inflammation in atherosclerotic plaques. METHODS: Uptake of (11)C-choline was studied ex vivo in tissue samples and aortic sections excised from 6 atherosclerotic mice deficient for both low-density lipoprotein receptor and apolipoprotein B48 (LDLR(-/-)ApoB(100/100)) and 5 control mice. The autoradiographs were compared with the immunohistology of the arterial sites. RESULTS: The uptake of (11)C-choline (percentage of the injected activity per gram of tissue) in the atherosclerotic aortas of the LDLR(-/-)ApoB(100/100) mice was significantly higher (1.9-fold, P = 0.0016) than that in the aortas of the control mice. The autoradiography analysis showed significantly higher uptake of (11)C-choline in the plaques than in healthy vessel wall (mean ratio, 2.3 +/- 0.6; P = 0.014), prominently in inflamed plaques, compared with noninflamed plaque areas. CONCLUSION: We observed a high (11)C-choline uptake in the aortic plaques of atherosclerotic mice. Our data suggest that macrophages may be responsible for the uptake of (11)C-choline in the plaques.