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

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Sanna Hellberg ◽  
Heidi Liljenbäck ◽  
Olli Eskola ◽  
Veronique Morisson-Iveson ◽  
Matthew Morrison ◽  
...  
Keyword(s):  
Vessel Wall ◽  
Ex Vivo ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Positron Emission Tomography Imaging ◽  
Translocator Protein ◽  
Atherosclerotic Plaques ◽  
Third Generation ◽  
Tissue Samples ◽  
Contrast Enhanced Ct

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.

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

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3168 ◽  
Author(s):  
Max Kiugel ◽  
Sanna Hellberg ◽  
Meeri Käkelä ◽  
Heidi Liljenbäck ◽  
Tiina Saanijoki ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Tracer Uptake ◽  
Atherosclerotic Plaques ◽  
Positron Emission ◽  
Pre Treatment ◽  
Targeting Peptide ◽  
Gallium 68

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.

scholarly journals Aggregation Susceptibility of Low-Density Lipoproteins—A Novel Modifiable Biomarker of Cardiovascular Risk

2021 ◽  
Vol 10 (8) ◽  
pp. 1769
Author(s):  
Katariina Öörni ◽  
Petri T. Kovanen
Keyword(s):  
Ex Vivo ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Atherosclerotic Cardiovascular Disease ◽  
Low Density ◽  
Cholesterol Crystals ◽  
Ldl Particles ◽  
Arterial Intima ◽  
Matrix Bound ◽  
Atherosclerotic Cardiovascular Diseases

Circulating low-density lipoprotein (LDL) particles enter the arterial intima where they bind to the extracellular matrix and become modified by lipases, proteases, and oxidizing enzymes and agents. The modified LDL particles aggregate and fuse into larger matrix-bound lipid droplets and, upon generation of unesterified cholesterol, cholesterol crystals are also formed. Uptake of the aggregated/fused particles and cholesterol crystals by macrophages and smooth muscle cells induces their inflammatory activation and conversion into foam cells. In this review, we summarize the causes and consequences of LDL aggregation and describe the development and applications of an assay capable of determining the susceptibility of isolated LDL particles to aggregate when exposed to human recombinant sphingomyelinase enzyme ex vivo. Significant person-to-person differences in the aggregation susceptibility of LDL particles were observed, and such individual differences largely depended on particle lipid composition. The presence of aggregation-prone LDL in the circulation predicted future cardiovascular events in patients with atherosclerotic cardiovascular disease. We also discuss means capable of reducing LDL particles’ aggregation susceptibility that could potentially inhibit LDL aggregation in the arterial wall. Whether reductions in LDL aggregation susceptibility are associated with attenuated atherogenesis and a reduced risk of atherosclerotic cardiovascular diseases remains to be studied.

scholarly journals Targeting macrophage necroptosis for therapeutic and diagnostic interventions in atherosclerosis

2016 ◽  
Vol 2 (7) ◽  
pp. e1600224 ◽  
Author(s):  
Denuja Karunakaran ◽  
Michele Geoffrion ◽  
Lihui Wei ◽  
Wei Gan ◽  
Laura Richards ◽  
...  
Keyword(s):  
Cell Death ◽  
Molecular Mechanisms ◽  
Plaque Rupture ◽  
Ex Vivo ◽  
Density Lipoprotein ◽  
Necrotic Core ◽  
Atherosclerotic Plaques ◽  
Core Formation ◽  
Macrophage Cell ◽  
Plaque Instability

Atherosclerosis results from maladaptive inflammation driven primarily by macrophages, whose recruitment and proliferation drive plaque progression. In advanced plaques, macrophage death contributes centrally to the formation of plaque necrosis, which underlies the instability that promotes plaque rupture and myocardial infarction. Hence, targeting macrophage cell death pathways may offer promise for the stabilization of vulnerable plaques. Necroptosis is a recently discovered pathway of programmed cell necrosis regulated by RIP3 and MLKL kinases that, in contrast to apoptosis, induces a proinflammatory state. We show herein that necroptotic cell death is activated in human advanced atherosclerotic plaques and can be targeted in experimental atherosclerosis for both therapeutic and diagnostic interventions. In humans with unstable carotid atherosclerosis, expression of RIP3 and MLKL is increased, and MLKL phosphorylation, a key step in the commitment to necroptosis, is detected in advanced atheromas. Investigation of the molecular mechanisms underlying necroptosis showed that atherogenic forms of low-density lipoprotein increase RIP3 and MLKL transcription and phosphorylation—two critical steps in the execution of necroptosis. Using a radiotracer developed with the necroptosis inhibitor necrostatin-1 (Nec-1), we show that 123I-Nec-1 localizes specifically to atherosclerotic plaques in Apoe−/− mice, and its uptake is tightly correlated to lesion areas by ex vivo nuclear imaging. Furthermore, treatment of Apoe−/− mice with established atherosclerosis with Nec-1 reduced lesion size and markers of plaque instability, including necrotic core formation. Collectively, our findings offer molecular insight into the mechanisms of macrophage cell death that drive necrotic core formation in atherosclerosis and suggest that this pathway can be used as both a diagnostic and therapeutic tool for the treatment of unstable atherosclerosis.

scholarly journals Sea Buckthorn and Grape Antioxidant Effects in Hyperlipidemic Rats: Relationship with the Atorvastatin Therapy

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Erieg A. Mohamed ◽  
Despina M. Bordean ◽  
Isidora Radulov ◽  
Răzvan F. Moruzi ◽  
Călin I. Hulea ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Sea Buckthorn ◽  
Cellular Damage ◽  
Tissue Samples ◽  
Grape Extract ◽  
Atorvastatin Therapy ◽  
Liver And Kidney ◽  
And Control

Background. Medications to reduce oxidative stress are preventing cellular damage associated with hyperlipidemia. In this regard, statins (e.g., atorvastatin) act primarily by decrease in low-density lipoprotein-c but, in the last decade, hepatotoxicity, associated with liver injuries in the next months after treatments’ initiation, was reported. In this case, associated phytotherapy can be a solution. Purpose. To investigate the antioxidant potential and response to free radicals, in the case of hyperlipidemic rats treated with atorvastatin. Sea buckthorn (Hippophae rhamnoides) and a grape extract (antioxivita) efficiency in the oxidative stress were investigated, also being ascertained the rats’ organs cytoarchitecture. Methods. Eighty-four hyperlipidemic Wistar rats were divided into seven groups and orally treated as follows: ATS, atorvastatin (20 mg/kg·bw); ATS + Hr, atorvastatin + H. rhamnoides; ATS + Aox, atorvastatin + grape extract; Hr, H. rhamnoides; and Aox, grape extract (both as 100 mg/kg·bw). HFD and Control received high fat diet and normal fodder only. After two and six months, respectively, rats were euthanized and the heart, liver, and kidneys were gathered. The tissue samples were prepared by homogenization of 0.5 g tissue, in ethanol, kept for 48 hours at 4°C–10°C and then filtered, in order to assess organs’ cytoarchitecture and the TAC’s values (by using cupric ion reducing antioxidant capacity (CUPRAC) assay). The test tubes were incubated, at room temperature, for 30 minutes, and then analyzed using a spectrophotometer at 450–650 nm. Results. The statistics (ANOVA) revealed that sea buckthorn diminished notably (p<0.001) the oxidative stress in the heart, liver, and kidney. After six months, the TAC’s reduced levels for the heart were significant (p<0.001) in ATS + Aox. In the case of histology, the liver’s cytoarchitecture in ATS revealed abnormal cytoarchitecture. In ATS + Hr, ATS + Aox, Hr, and Aox, cell regeneration improved in different stages, especially for ATS + Hr and ATS + Aox, in comparison with HFD, which exhibited fat degeneration. Kidney’s cytoarchitecture revealed cellular healing, especially in ATS + Hr and ATS + Aox.

scholarly journals Potent lipoprotein(a) lowering following apolipoprotein(a) antisense treatment reduces the pro-inflammatory activation of circulating monocytes in patients with elevated lipoprotein(a)

2020 ◽  
Vol 41 (24) ◽  
pp. 2262-2271 ◽  
Author(s):  
Lotte C A Stiekema ◽  
Koen H M Prange ◽  
Renate M Hoogeveen ◽  
Simone L Verweij ◽  
Jeffrey Kroon ◽  
...  
Keyword(s):  
Gene Expression ◽  
Ex Vivo ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cvd Risk ◽  
Inflammatory Gene Expression ◽  
Lipoprotein A ◽  
Inflammatory Gene ◽  
Apolipoprotein A ◽  
Inflammatory Activation

Abstract Aims Elevated lipoprotein(a) [Lp(a)] is strongly associated with an increased cardiovascular disease (CVD) risk. We previously reported that pro-inflammatory activation of circulating monocytes is a potential mechanism by which Lp(a) mediates CVD. Since potent Lp(a)-lowering therapies are emerging, it is of interest whether patients with elevated Lp(a) experience beneficial anti-inflammatory effects following large reductions in Lp(a). Methods and results Using transcriptome analysis, we show that circulating monocytes of healthy individuals with elevated Lp(a), as well as CVD patients with increased Lp(a) levels, both have a pro-inflammatory gene expression profile. The effect of Lp(a)-lowering on gene expression and function of monocytes was addressed in two local sub-studies, including 14 CVD patients with elevated Lp(a) who received apolipoprotein(a) [apo(a)] antisense (AKCEA-APO(a)-LRx) (NCT03070782), as well as 18 patients with elevated Lp(a) who received proprotein convertase subtilisin/kexin type 9 antibody (PCSK9ab) treatment (NCT02729025). AKCEA-APO(a)-LRx lowered Lp(a) by 47% and reduced the pro-inflammatory gene expression in monocytes of CVD patients with elevated Lp(a), which coincided with a functional reduction in transendothelial migration capacity of monocytes ex vivo (−17%, P &lt; 0.001). In contrast, PCSK9ab treatment lowered Lp(a) by 16% and did not alter transcriptome nor functional properties of monocytes, despite an additional reduction of 65% in low-density lipoprotein cholesterol (LDL-C). Conclusion Potent Lp(a)-lowering following AKCEA-APO(a)-LRx, but not modest Lp(a)-lowering combined with LDL-C reduction following PCSK9ab treatment, reduced the pro-inflammatory state of circulating monocytes in patients with elevated Lp(a). These ex vivo data support a beneficial effect of large Lp(a) reductions in patients with elevated Lp(a).

scholarly journals Acute estrogen exposure does not affect basal very low-density lipoprotein–triglyceride production or oxidation in postmenopausal women

2010 ◽  
Vol 163 (3) ◽  
pp. 421-426 ◽  
Author(s):  
Lars C Gormsen ◽  
Christian Høst ◽  
Britta Eilersen Hjerrild ◽  
Claus H Gravholt ◽  
Søren Nielsen
Keyword(s):  
Single Dose ◽  
Postmenopausal Women ◽  
Ex Vivo ◽  
Hormone Replacement ◽  
Low Density Lipoprotein ◽  
Detection Threshold ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Estrogen Exposure

ContextLong-term hormone replacement therapy (HRT) with estradiol (E2) is associated with an altered lipid profile including unfavorable increases in triglyceride (TG) concentrations and augmented hepatic very low-density lipoprotein (VLDL)–TG production. There are indications that this effect of estrogens may be immediate.ObjectiveTo study thein vivoeffect of a single dose of E2on VLDL–TG kinetics and oxidation in humans.MethodsEight healthy, postmenopausal women were given a single dose of either placebo or E2(4 mg) orally. VLDL–TG kinetics was assessed by a 240-min primed-continuous infusion ofex vivolabeled [1-14C]triolein-labeled VLDL. Fractional and absolute VLDL–TG oxidation was determined by hyamin trapping of exhaled14C label. Indirect calorimetry provided measurements of lipid oxidation.ResultsAdministration of 4 mg of E2orally rapidly increased plasma E2concentrations from below detection threshold to premenopausal levels. Free fatty acids (FFA) and TG concentrations were unaltered. No immediate effect was observed on either VLDL–TG production (placebo versus E2): 20.0±12.4 vs 24.1±10.7 μmol/min,P=0.33; VLDL–TG oxidation: 12.3±10.9 vs 12.6±5.6 μmol/min,P=0.93); or VLDL–TG clearance rates: 51.4±16.8 vs 64.9±28.8 ml/min,P=0.34).ConclusionsShort-term E2elevation does not affect VLDL–TG production, oxidation, or clearance in humans. We therefore propose that HRT-associated dyslipidemia has a gradual rather than immediate onset.

Development of Nanoparticle Probes for In Vivo Imaging of Atherosclerotic Plaques

2012 ◽  
Author(s):  
Zihao Zhang ◽  
Sheng Tong ◽  
Gang Bao
Keyword(s):  
Surface Defects ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Necrotic Core ◽  
Intraplaque Hemorrhage ◽  
Atherosclerotic Plaques ◽  
Nanoparticle Probes ◽  
Arterial Lumen ◽  
Inflammatory Macrophage

Atherosclerosis, the formation of fatty plaques in the arterial lumen, is mediated by inflammatory macrophage infiltration in the lesion and ingestion of low-density lipoprotein (LDL), forming foam cells. Its progression will likely form a large necrotic core and fibrotic cap surface defects. The resulting intraplaque hemorrhage causes red blood cell infiltration and hemoglobin abundance, which oxidizes LDL to form cholesterol crystal aggregates (1). Hemorrhagic plaques could rupture and form artery-blocking emboli. Thus, it is critical to develop a tool to detect and locate unstable hemorrhagic plaques in live specimens.

scholarly journals SUMO2 regulates vascular endothelial function and oxidative stress in mice

2019 ◽  
Vol 317 (6) ◽  
pp. H1292-H1300 ◽  
Author(s):  
Young-Rae Kim ◽  
Julia S. Jacobs ◽  
Qiuxia Li ◽  
Ravinder Reddy Gaddam ◽  
Ajit Vikram ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Endothelial Function ◽  
Vascular Function ◽  
Ex Vivo ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Vascular Endothelial ◽  
Vascular Endothelial Function ◽  
Density Lipoprotein Receptor ◽  
Vascular Oxidative Stress

SUMOylation is a posttranslational modification of lysine residues. Modification of proteins by small ubiquitin-like modifiers (SUMO)1, -2, and -3 can achieve varied, and often unique, physiological and pathological effects. We looked for SUMO2-specific effects on vascular endothelial function. SUMO2 expression was upregulated in the aortic endothelium of hypercholesterolemic low-density lipoprotein receptor-deficient mice and was responsible for impairment of endothelium-dependent vasorelaxation in these mice. Moreover, overexpression of SUMO2 in aortas ex vivo, in cultured endothelial cells, and transgenically in the endothelium of mice increased vascular oxidative stress and impaired endothelium-dependent vasorelaxation. Conversely, inhibition of SUMO2 impaired physiological endothelium-dependent vasorelaxation in normocholesterolemic mice. These findings indicate that while endogenous SUMO2 is important in maintenance of normal endothelium-dependent vascular function, its upregulation impairs vascular homeostasis and contributes to hypercholesterolemia-induced endothelial dysfunction. NEW & NOTEWORTHY Sumoylation is known to impair vascular function; however, the role of specific SUMOs in the regulation of vascular function is not known. Using multiple complementary approaches, we show that hyper-SUMO2ylation impairs vascular endothelial function and increases vascular oxidative stress, whereas endogenous SUMO2 is essential for maintenance of normal physiological function of the vascular endothelium.

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