Vein grafting is a frequently used surgical intervention for cardiac revascularization. However, vein grafts display regions with intraplaque (IP) angiogenesis, which promotes atherogenesis and... Show moreVein grafting is a frequently used surgical intervention for cardiac revascularization. However, vein grafts display regions with intraplaque (IP) angiogenesis, which promotes atherogenesis and formation of unstable plaques. Graft neovessels are mainly composed of endothelial cells (ECs) that largely depend on glycolysis for migration and proliferation. In the present study, we aimed to investigate whether loss of the glycolytic flux enzyme phosphofructokinase-2/fructose-2,6-bisphosphatase 3 (PFKFB3) in ECs inhibits IP angiogenesis and as such prevents unstable plaque formation. To this end, apolipoprotein E deficient (ApoE(-/-)) mice were backcrossed to a previously generated PFKFB3(fl/fl) Cdh5(iCre) mouse strain. Animals were injected with either corn oil (ApoE(-/-)PFKFB3(fl/fl)) or tamoxifen (ApoE(-/-)PFKFB3(ECKO)), and were fed a western-type diet for 4 weeks prior to vein grafting. Hereafter, mice received a western diet for an additional 28 days and were then sacrificed for graft assessment. Size and thickness of vein graft lesions decreased by 35 and 32%, respectively, in ApoE(-/-)PFKFB3(ECKO) mice compared to controls, while stenosis diminished by 23%. Moreover, vein graft lesions in ApoE(-/-)PFKFB3(ECKO) mice showed a significant reduction in macrophage infiltration (29%), number of neovessels (62%), and hemorrhages (86%). EC-specific PFKFB3 deletion did not show obvious adverse effects or changes in general metabolism. Interestingly, RT-PCR showed an increased M2 macrophage signature in vein grafts from ApoE(-/-)PFKFB3(ECKO) mice. Altogether, EC-specific PFKFB3 gene deletion leads to a significant reduction in lesion size, IP angiogenesis, and hemorrhagic complications in vein grafts. This study demonstrates that inhibition of endothelial glycolysis is a promising therapeutic strategy to slow down plaque progression. Show less
In recent years, the study of endothelial cell (EC) metabolism has led to the discovery of novel regulatory mechanisms and potential new targets for vascular-related diseases. Despite the fact that... Show moreIn recent years, the study of endothelial cell (EC) metabolism has led to the discovery of novel regulatory mechanisms and potential new targets for vascular-related diseases. Despite the fact that ECs have readily available oxygen in the blood, they mainly generate ATP via anaerobic glycolysis rather than Krebs cycle. In the context of atherosclerosis, there has been growing interest in understanding how EC metabolism affects plaque formation and intraplaque (IP) angiogenesis, which has been identified as a contributing factor for plaque vulnerability in human atherosclerosis.Among the enzymes involved in glycolytic flux modulation, PFKFB3 plays a critical role for the proliferation and migration of ECs. PFKFB3 is upregulated in atheroprone regions of arterial vessels and in carotid plaques of patients with elevated levels of lipoprotein(a). The experimental work of this thesis focuses on PFKFB3 as a modulator of EC glycolysis and its effects on atherosclerosis progression and IP angiogenesis.In the first part of this thesis, a pharmacological study with partial glycolysis inhibitor 3PO in the context of advanced atherosclerotic plaques is described. 3PO treatment restrains IP angiogenesis and plaque frequency but it does not affect plaque size and composition in ApoE-/-Fbn1C1039G+/- mice. In addition, a 3PO-mediated reduction in plaque formation is also observed in ApoE-/- mice that develop plaques without IP neovascularization.Furthermore, EC-specific PFKFB3 deletion leads to a significant reduction in plaque size, IP angiogenesis and hemorrhagic complications in a vein graft model. These findings suggest that endothelial glycolysis inhibition may represent a new therapeutic strategy to slow down plaque progression in vein grafts.A study performed in collaboration with the University of Aberdeen is also presented in this thesis. Here the development of a new PFKFB3-targeted PET radiotracer, [18F]ZCDD083, for in vivo plaque imaging is described. The specificity of the tracer for atherosclerotic plaques is demonstrated by a combination of ex vivo autoradiography and en face Oil Red O staining. This tracer is a promising non-invasive diagnostic tool to detect rupture-prone atherosclerotic plaques,Finally, a novel imaging method for a three-dimensional reconstruction of the IP vessel network is presented. This method is based on iDISCO immunolabeling and confocal microscopy. It may represent a novel tool to investigate the causal relationship between IP angiogenesis and atherogenesis.Overall, the experimental data generated in this thesis strongly argue for a critical role of EC metabolism in the formation and progression of atherosclerosis in addition to IP angiogenesis. Show less
Multiple lines of evidence suggest that intraplaque (IP) neovascularization promotes atherosclerotic plaque growth, destabilization, and rupture. However, pharmacological inhibition of IP... Show moreMultiple lines of evidence suggest that intraplaque (IP) neovascularization promotes atherosclerotic plaque growth, destabilization, and rupture. However, pharmacological inhibition of IP neovascularization remains largely unexplored due to the limited number of animal models that develop IP neovessels and the lack of reliable methods for visualizing IP angiogenesis. Here, we applied 3D confocal microscopy with an optimized tissue-clearing process, immunolabeling-enabled three-dimensional imaging of solvent-cleared organs, to visualize IP neovessels in apolipoprotein E-deficient (ApoE(-/-)) mice carrying a heterozygous mutation (C1039+/-) in the fibrillin-1 gene. Unlike regular ApoE(-/-) mice, this mouse model is characterized by the presence of advanced plaques with evident IP neovascularization. Plaques were stained with antibodies against endothelial marker CD31 for 3 days, followed by incubation with fluorescently labeled secondary antibodies. Subsequent tissue clearing with dichloromethane (DCM)/methanol, DCM, and dibenzyl ether allowed easy visualization and 3D reconstruction of the IP vascular network while plaque morphology remained intact. Show less
Veseli, B.E.; Perrotta, P.; Wielendaele, P. van; Lambeir, A.M.; Abdali, A.; Bellosta, S.; ... ; Meyer, G.R.Y. de 2020
6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3) is a key enzyme of the glycolytic pathway, and it plays an essential role in angiogenesis. 3-(3-Pyridinyl)-1-(4-pyridinyl)-2... Show more6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3) is a key enzyme of the glycolytic pathway, and it plays an essential role in angiogenesis. 3-(3-Pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO) is frequently used as a glycolysis inhibitor and is thought to inhibit PFKFB3. However, this latter effect of 3PO has never been investigated in detail and was the aim of the present study. To demonstrate binding of 3PO to PFKFB3, we used isothermal titration calorimetry. However, 3PO did not bind to PFKFB3, even up to 750 µm, in contrast to 3 µm of AZ67, which is a potent and specific PFKFB3 inhibitor. Instead, 3PO accumulated lactic acid inside the cells, leading to a decrease in the intracellular pH and an inhibition of enzymatic reactions of the glycolytic pathway. Show less
Multiple lines of evidence suggest that intraplaque (IP) neovascularization promotes atherosclerotic plaque growth, destabilization, and rupture. However, pharmacological inhibition of IP... Show moreMultiple lines of evidence suggest that intraplaque (IP) neovascularization promotes atherosclerotic plaque growth, destabilization, and rupture. However, pharmacological inhibition of IP neovascularization remains largely unexplored due to the limited number of animal models that develop IP neovessels and the lack of reliable methods for visualizing IP angiogenesis. Here, we applied 3D confocal microscopy with an optimized tissue-clearing process, immunolabeling-enabled three-dimensional imaging of solvent-cleared organs, to visualize IP neovessels in apolipoprotein E-deficient (ApoE-/-) mice carrying a heterozygous mutation (C1039+/-) in the fibrillin-1 gene. Unlike regular ApoE-/- mice, this mouse model is characterized by the presence of advanced plaques with evident IP neovascularization. Plaques were stained with antibodies against endothelial marker CD31 for 3 days, followed by incubation with fluorescently labeled secondary antibodies. Subsequent tissue clearing with dichloromethane (DCM)/methanol, DCM, and dibenzyl ether allowed easy visualization and 3D reconstruction of the IP vascular network while plaque morphology remained intact. Show less
Perrotta, P.; Veken, B. van der; Veken, P. van der; Pintelon, I.; Roosens, L.; Adriaenssens, E.; ... ; Martinet, W. 2020
Objective: Intraplaque neovascularization is an important feature of unstable human atherosclerotic plaques. However, its impact on plaque formation and stability is poorly studied. Because... Show moreObjective: Intraplaque neovascularization is an important feature of unstable human atherosclerotic plaques. However, its impact on plaque formation and stability is poorly studied. Because proliferating endothelial cells generate up to 85% of their ATP from glycolysis, we investigated whether pharmacological inhibition of glycolytic flux by the small-molecule 3PO (3-[3-pyridinyl]-1-[4-pyridinyl]-2-propen-1-one) could have beneficial effects on plaque formation and composition. Approach and Results: ApoE-/- (apolipoprotein E deficient) mice treated with 3PO (50 µg/g, ip; 4×/wk, 4 weeks) showed a metabolic switch toward ketone body formation. Treatment of ApoE-/-Fbn1C1039G+/- mice with 3PO (50 µg/g, ip) either after 4 (preventive, twice/wk, 10 weeks) or 16 weeks of Western diet (curative, 4×/wk, 4 weeks) inhibited intraplaque neovascularization by 50% and 38%, respectively. Plaque formation was significantly reduced in all 3PO-treated animals. This effect was independent of intraplaque neovascularization. In vitro experiments showed that 3PO favors an anti-inflammatory M2 macrophage subtype and suppresses an M1 proinflammatory phenotype. Moreover, 3PO induced autophagy, which in turn impaired NF-κB (nuclear factor-kappa B) signaling and inhibited TNF-α (tumor necrosis factor-alpha)-mediated VCAM-1 (vascular cell adhesion molecule-1) and ICAM-1 (intercellular adhesion molecule-1) upregulation. Consistently, a preventive 3PO regimen reduced endothelial VCAM-1 expression in vivo. Furthermore, 3PO improved cardiac function in ApoE-/-Fbn1C1039G+/- mice after 10 weeks of treatment.Conclusions: Partial inhibition of glycolysis restrained intraplaque angiogenesis without affecting plaque composition. However, less plaques were formed, which was accompanied by downregulation of endothelial adhesion molecules-an event that depends on autophagy induction. Inhibition of coronary plaque formation by 3PO resulted in an overall improved cardiac function. Show less
Dominicis, C. de; Perrotta, P.; Dall'Angelo, S.; Wyffels, L.; Staelens, S.; Meyer, G.R.Y. de; Zanda, M. 2020
PFKFB3, a glycolysis-related enzyme upregulated in inflammatory conditions and angiogenesis, is an emerging target for diagnosis and therapy of atherosclerosis. The fluorinated phenoxindazole [18F... Show morePFKFB3, a glycolysis-related enzyme upregulated in inflammatory conditions and angiogenesis, is an emerging target for diagnosis and therapy of atherosclerosis. The fluorinated phenoxindazole [18F]ZCDD083was synthesized, radiolabeled in 17 ± 5% radiochemical yield and >99% radiochemical purity, and formulated for preclinical PET/CT imaging in mice. In vivo stability analysis showed no significant metabolite formation. Biodistribution studies showed high blood pool activity and slow hepatobiliary clearance. Significant activity was detected in the lung 2 h postinjection (pi) (11.0 ± 1.5%ID/g), while at 6 h pi no pulmonary background was observed. Ex vivo autoradiography at 6 h pi showed significant high uptake of [18F]ZCDD083 in the arch region and brachiocephalic artery of atherosclerotic mice, and no uptake in control mice, matching plaques distribution seen by lipid staining along with PFKFB3 expression seen by immunofluorescent staining. In vivo PET scans showed higher aortic region uptake of [18F]ZCDD083in atherosclerotic ApoE–/–Fbn1C1039G+/− than in control mice (0.78 ± 0.05 vs 0.44 ± 0.09%ID/g). [18F]ZCDD083 was detected in aortic arch and brachiocephalic artery of ApoE–/– (with moderate atherosclerosis) and ApoE–/–Fbn1C1039G+/− (with severe, advanced atherosclerosis) mice, suggesting this tracer may be useful for the noninvasive detection of atherosclerotic plaques in vivo. Show less
Vascular inflammation is present in many cardiovascular diseases, and exogenous glucocorticoids have traditionally been used as a therapy to suppress inflammation. However, recent data have shown... Show moreVascular inflammation is present in many cardiovascular diseases, and exogenous glucocorticoids have traditionally been used as a therapy to suppress inflammation. However, recent data have shown that endogenous glucocorticoids, acting through the endothelial glucocorticoid receptor, act as negative regulators of inflammation. Here, we performed ChIP for the glucocorticoid receptor, followed by next-generation sequencing in mouse endothelial cells to investigate how the endothelial glucocorticoid receptor regulates vascular inflammation. We identified a role of the Wnt signaling pathway in this setting and show that loss of the endothelial glucocorticoid receptor results in upregulation of Wnt signaling both in vitro and in vivo using our validated mouse model. Furthermore, we demonstrate glucocorticoid receptor regulation of a key gene in the Wnt pathway, Frzb, via a glucocorticoid response element gleaned from our genomic data. These results suggest a role for endothelial Wnt signaling modulation in states of vascular inflammation. Show less
