Aging is a dominant driver of atherosclerosis and induces a series of immunological alterations, called immunosenescence. Given the demographic shift towards elderly, elucidating the unknown impact... Show moreAging is a dominant driver of atherosclerosis and induces a series of immunological alterations, called immunosenescence. Given the demographic shift towards elderly, elucidating the unknown impact of aging on the immunological landscape in atherosclerosis is highly relevant. While the young Western diet-fed Ldlr-deficient (Ldlr-/-) mouse is a widely used model to study atherosclerosis, it does not reflect the gradual plaque progression in the context of an aging immune system as occurs in humans.\nHere, we show that aging promotes advanced atherosclerosis in chow diet-fed Ldlr-/- mice, with increased incidence of calcification and cholesterol crystals. We observed systemic immunosenescence, including myeloid skewing and T-cells with more extreme effector phenotypes. Using a combination of single-cell RNA-sequencing and flow cytometry on aortic leukocytes of young versus aged Ldlr-/- mice, we show age-related shifts in expression of genes involved in atherogenic processes, such as cellular activation and cytokine production. We identified age-associated cells with pro-inflammatory features, including GzmK+CD8+ T-cells and previously in atherosclerosis undefined CD11b+CD11c+T-bet+ age-associated B-cells (ABCs). ABCs of Ldlr-/- mice showed high expression of genes involved in plasma cell differentiation, co-stimulation, and antigen presentation. In vitro studies supported that ABCs are highly potent antigen-presenting cells. In cardiovascular disease patients, we confirmed the presence of these age-associated T- and B-cells in atherosclerotic plaques and blood.\nCollectively, we are the first to provide comprehensive profiling of aged immunity in atherosclerotic mice and reveal the emergence of age-associated T- and B-cells in the atherosclerotic aorta. Further research into age-associated immunity may contribute to novel diagnostic and therapeutic tools to combat cardiovascular disease. Show less
Cardiovascular diseases are still a major concern for the global health. The main underlying pathology of this disease is atherosclerosis which is characterized by the accumulation of lipids and... Show moreCardiovascular diseases are still a major concern for the global health. The main underlying pathology of this disease is atherosclerosis which is characterized by the accumulation of lipids and immune cells in the arterial wall leading to a chronic local inflammation and lesion formation. In this thesis, we aimed to (1) validate the use of zebrafish in cholesterol metabolism and atherosclerosis research, (2) study the role of certain classes of scavenger receptors in lipoprotein uptake and cholesterol-based functions, and (3) validated two immune-based potential targets for atherosclerosis. Show less
Verwilligen, R.A.F.; Mulder, L.; Araujo, P.M.; Carneiro, M.; Bussmann, J.; Hoekstra, M.; Eck, M. van 2023
Background and aims: Scavenger receptor class B1 (SCARB1) -also known as the high-density lipoprotein (HDL) receptor -is a multi-ligand scavenger receptor that is primarily expressed in liver and... Show moreBackground and aims: Scavenger receptor class B1 (SCARB1) -also known as the high-density lipoprotein (HDL) receptor -is a multi-ligand scavenger receptor that is primarily expressed in liver and steroidogenic organs. This receptor is known for its function in reverse cholesterol transport (RCT) in mammals and hence disruption leads to a massive increase in HDL cholesterol in these species. The extracellular domain of SCARB1 -which is important for cholesterol handling -is highly conserved across multiple vertebrates, except in zebrafish. Methods: To examine the functional conservation of SCARB1 among vertebrates, two stable scarb1 knockout zebrafish lines, scarb1 715delA (scarb1-1 nt) and scarb1 715_716insGG (scarb1 +2 nt), were created using CRISPR-Cas9 technology. Results: We demonstrate that, in zebrafish, SCARB1 deficiency leads to disruption of carotenoid-based pigmen-tation, reduced fertility, and a decreased larvae survival rate, whereas steroidogenesis was unaltered. The observed reduced fertility is driven by defects in female fertility (-50 %, p < 0.001). Importantly, these alter-ations were independent of changes in free (wild-type 2.4 +/- 0.2 mu g/mu l versus scarb1-/-2.0 +/- 0.1 mu g/mu l) as well as total (wild-type 4.2 +/- 0.4 mu g/mu l versus scarb1-/-4.0 +/- 0.3 mu g/mu l) plasma cholesterol levels. Uptake of HDL in the liver of scarb1- /-zebrafish larvae was reduced (-86.7 %, p < 0.001), but this coincided with reduced perfusion of the liver. No effect was observed on lipoprotein uptake in the caudal vein. SCARB1 deficient ca-naries, which also lack carotenoids in their plumage, similarly as scarb1-/-zebrafish, failed to show an increase in plasma free-and total cholesterol levels. Conclusion: Our findings suggest that the specific function of SCARB1 in maintaining plasma cholesterol could be an evolutionary novelty that became prominent in mammals, while other known functions were already present earlier during vertebrate evolution. Show less
Verwilligen, R.A.F.; Mulder, L.; Rodenburg, F.J.; Dijke, A. van; Hoekstra, M.; Bussmann, J.; Eck, M. van 2022
BACKGROUND AND AIMS\nMETHODS\nRESULTS\nCONCLUSIONS\nScavenger receptors form a superfamily of membrane-bound receptors that bind and internalize different types of ligands, including pro... Show moreBACKGROUND AND AIMS\nMETHODS\nRESULTS\nCONCLUSIONS\nScavenger receptors form a superfamily of membrane-bound receptors that bind and internalize different types of ligands, including pro-atherogenic oxidized low-density lipoproteins (oxLDLs). In vitro studies have indicated a role for the liver sinusoidal endothelial cell receptors stabilin 1 (stab1) and 2 (stab2) in oxLDL clearance. In this study, we evaluated the potential role of stab1 and stab2 in lipoprotein uptake in zebrafish, an upcoming model for studying cholesterol metabolism and atherosclerosis.\nLipoproteins were injected in the duct of Cuvier of wild-type (ABTL) or stab1 and stab2 mutant (stab1-/-stab2-/-) zebrafish larvae at 3 days post-fertilization. To examine the effect of stabilin deficiency on lipoprotein and cholesterol metabolism, zebrafish larvae were challenged with a high cholesterol diet (HCD; 4% w/w) for 10 days.\nLipoprotein injections showed impaired uptake of both LDL and oxLDL into the vessel wall of caudal veins of stab1-/-stab2-/- zebrafish, which was paralleled by redistribution to tissue macrophages. Total body cholesterol levels did not differ between HCD-fed stab1-/-stab2-/- and ABTL zebrafish. However, stab1-/-stab2-/- larvae exhibited 1.4-fold higher mRNA expression levels of ldlra involved in (modified) LDL uptake, whereas the expression levels of scavenger receptors scarb1 and cd36 were significantly decreased.\nWe have shown that stabilins 1 and 2 have an important scavenging function for apolipoprotein B-containing lipoproteins in zebrafish and that combined deficiency of these two proteins strongly upregulates the clearance of lipoproteins by macrophages within the caudal vein. Our current study highlights the use of zebrafish as model to study lipoprotein metabolism and liver sinusoidal endothelial cell function. Show less
Signaling through the coinhibitory programmed death (PD)-1/PD-L1 pathway regulates T cell responses and can inhibit ongoing immune responses. Inflammation is a key process in the development of... Show moreSignaling through the coinhibitory programmed death (PD)-1/PD-L1 pathway regulates T cell responses and can inhibit ongoing immune responses. Inflammation is a key process in the development of atherosclerosis, the underlying cause for the majority of cardiovascular diseases. Dampening the excessive immune response that occurs during atherosclerosis progression by promoting PD-1/PD-L1 signaling may have a high therapeutic potential to limit disease burden. In this study we therefore aimed to assess whether an agonistic PD-1 antibody can diminish atherosclerosis development.Ldlr-/- mice were fed a western-type diet (WTD) while receiving 100 μg of an agonistic PD-1 antibody or control vehicle twice a week. Stimulation of the PD-1 pathway delayed the WTD-induced monocyte increase in the circulation up to 3 weeks and reduced T cell activation and proliferation. CD4+ T cell numbers in the atherosclerotic plaque were reduced upon PD-1 treatment. More specifically, we observed a 23% decrease in atherogenic IFNγ-producing splenic CD4+ T cells and a 20% decrease in cytotoxic CD8+ T cells, whereas atheroprotective IL-10 producing CD4+ T cells were increased with 47%. Furthermore, we found an increase in regulatory B cells, B1 cells and associated atheroprotective circulating oxLDL-specific IgM levels in agonistic PD-1-treated mice. This dampened immune activation following agonistic PD-1 treatment resulted in reduced atherosclerosis development (p < 0.05).Our data show that stimulation of the coinhibitory PD-1 pathway inhibits atherosclerosis development by modulation of T- and B cell responses. These data support stimulation of coinhibitory pathways as a potential therapeutic strategy to combat atherosclerosis. Show less
Zhang, Y.; Verwilligen, R.A.F.; Boer, M. de; Sijsenaar, T.J.P.; Eck, M. van; Hoekstra, M. 2021
Atherosclerotic cardiovascular disease is a metabolic and inflammatory disorder. In vitro studies have suggested that protein arginine methyltransferase 4 (PRMT4) may act as a transcriptional... Show moreAtherosclerotic cardiovascular disease is a metabolic and inflammatory disorder. In vitro studies have suggested that protein arginine methyltransferase 4 (PRMT4) may act as a transcriptional coactivator to modulate inflammatory and metabolic processes. Here we investigated the potential anti-atherogenic effect of PRMT4 inhibitor TP-064 in vivo.\nMale apolipoprotein E knockout mice fed a high cholesterol/high fat Western-type diet were intraperitoneally injected three times a week with 2.5 mg/kg (low dose) or 10 mg/kg (high dose) TP-064 or with DMSO control.\nTP-064 induced a dose-dependent decrease in lipopolysaccharide-induced ex vivo blood monocyte Tnfα secretion (p < 0.05 for trend) in the context of unchanged blood monocyte concentrations and neutrophilia induction (p < 0.01 for trend). A dose-dependent decrease in gonadal white adipose tissue expression levels of PPARγ target genes was detected, which translated into a reduced body weight gain after high dose TP-064 treatment (p < 0.05). TP-064 treatment also dose-dependently downregulated gene expression of the glycogen metabolism related protein G6pc in the liver (p < 0.001 for trend). In addition, a trend towards lower plasma insulin and higher blood glucose levels was observed, which was paralleled by a reduction in hepatic mRNA expression levels of the insulin-responsive genes Fasn (-55%; p < 0.001) and Gck (-47%; p < 0.001) in high dose-treated mice. Plasma triglyceride levels were reduced by high dose TP-064 treatment (-30%; p < 0.05). However, no change was observed in the size or composition of aortic root atherosclerotic lesions.\nThe PRMT4 inhibitor TP-064 impacts both inflammatory and metabolic processes without changing atherosclerosis susceptibility of male apolipoprotein E knockout mice. Show less
Verwilligen, R.A.F.; Bussmann, J.; Eck, M. van 2020
Atherosclerosis, the main underlying cause of cardiovascular disease and related morbidities, is a multifactorial disease in which liver endothelial cells and macrophages have shown to play an... Show moreAtherosclerosis, the main underlying cause of cardiovascular disease and related morbidities, is a multifactorial disease in which liver endothelial cells and macrophages have shown to play an important role. Recently, it has been demonstrated that oxidized phospholipids in oxidized LDL (oxLDL) are pro-inflammatory and pro-atherogenic in hypercholesterolaemic mice. Multiple scavenger receptors are known for oxLDL. They form a superfamily of membrane bound receptors that bind and internalize different types of ligands including other modified lipoproteins, endogenous proteins and pathogens. Several studies, including a microarray study of our research group, have already identified scavenger receptors stabilin-1 and -2 (STAB1 and STAB2) as a risk factor for atherosclerosis, and therefore as potential targets for treatment. An upcoming and powerful model organism to study early atherogenesis and that allows non-invasive cell tracking studies is the zebrafish. Recent studies have demonstrated the possibility to induce (early) atherosclerosis in zebrafish.We have used Crispr/Cas9 mutagenesis to generate zebrafish stab1 and stab2 mutants.Our results show that oxLDL clearance by zebrafish scavenger endothelial cells (homologous to liver sinusoidal endothelial cells) is diminished in stab2 zebrafish mutants and is absent in stab1/2 double mutants. In stabilin mutants, macrophage oxLDL uptake is increased, suggesting a protective role for stabilins in foam cell formation.To study this further, we are currently performing an atherosclerosis study to examine foam cell formation and vascular lipid accumulation in stabilin mutant zebrafish. Show less
Sluis, R.J. van der; Depuydt, M.A.C.; Verwilligen, R.A.F.; Hoekstra, M.; Eck, M. van 2019
Apolipoprotein E (APOE) deficient mice exhibit unexplained hypercorticosteronemia. Given that APOE is also produced locally within the adrenals, we evaluated the effect of adrenal-specific APOE... Show moreApolipoprotein E (APOE) deficient mice exhibit unexplained hypercorticosteronemia. Given that APOE is also produced locally within the adrenals, we evaluated the effect of adrenal-specific APOE deficiency on the glucocorticoid function. Hereto, one adrenal containing or lacking APOE was transplanted into adrenalectomized wild-type mice. Adrenal APOE deficiency did not impact adrenal total cholesterol levels. Importantly, the ability of the two adrenal types to produce glucocorticoids was also not different as judged from the similar plasma corticosterone levels. Adrenal mRNA expression levels of HMG-CoA reductase and the LDL receptor were decreased by respectively 72% (p < 0.01) and 65% (p = 0.07), suggesting that cholesterol acquisition pathways were inhibited to possibly compensate the lack of APOE. In support, a parallel increase in the expression level of the cholesterol accumulation-associated ER stress marker CHOP was detected (+117%; p < 0.05). In conclusion, our studies show that elimination of adrenocortical APOE production does not impact glucocorticoid output in wild-type mice. Show less
Ouweneel, A.B.; Verwilligen, R.A.F.; Eck, M. van 2019
Atherothrombotic events such as myocardial infarction and ischemic stroke are a major cause of morbidity and mortality worldwide. Understanding the molecular and cellular mechanisms of... Show moreAtherothrombotic events such as myocardial infarction and ischemic stroke are a major cause of morbidity and mortality worldwide. Understanding the molecular and cellular mechanisms of atherosclerotic plaque destabilization or erosion, and developing new therapeutics to prevent acute cardiovascular events is important for vascular biology research and clinical cardiovascular medicine. However, basic research on plaque destabilization, rupture and erosion is hampered by the lack of appropriate animal models of atherothrombosis. Unprovoked atherothrombosis is very scarce in commonly used mouse models for atherosclerosis, the low-density lipoprotein receptor knockout and apolipoprotein E knockout mice. Therefore, specific interventions are required to induce atherothrombosis in these models. Two strategies can be employed to induce atherothrombosis: 1) plaque destabilization and 2) induction of blood hypercoagulability. Although the individual strategies yield atherothrombosis at low incidence, it appears that the combination of both plaque destabilization and an increase in blood coagulability is the most promising strategy to induce atherothrombosis on a larger scale. In this review, we summarize the recent developments on mouse models for the investigation of atherothrombosis. Show less
Sluis, R.J. van der; Verwilligen, R.A.F.; Lendvai, Z.; Wever, R.; Hoekstra, M.; Eck, M. van 2018
Although studies in mice have suggested that lesion regression is feasible, the underlying mechanisms remain largely unknown. Here we determined the impact of high-density lipoprotein (HDL) on... Show moreAlthough studies in mice have suggested that lesion regression is feasible, the underlying mechanisms remain largely unknown. Here we determined the impact of high-density lipoprotein (HDL) on atherosclerosis regression outcome.\nAtherosclerotic lesion dynamics were studied upon bone marrow transplantation-mediated re-introduction of apolipoprotein E (Apoe) in Apoe knockout mice. Probucol was used to pharmacologically deplete HDL.\n for controls: p < 0.05).\nWe have shown that probucol-induced HDL deficiency impairs the ability of established lesions to regress in response to reversal of the genetic hypercholesterolemia in Apoe knockout mice. Our studies thus highlight a crucial role for HDL in the process of atherosclerosis regression. Show less
Ouweneel, A.B.; Heestermans, M.; Verwilligen, R.A.F.; Gijbels, M.J.J.; Reitsma, P.H.; Eck, M. van; Vlijmen, B.J.M. van 2017
Murine atherosclerosis models do not spontaneously develop atherothrombotic complications. We investigated whether disruption of natural anticoagulation allows preexisting atherosclerotic plaques... Show moreMurine atherosclerosis models do not spontaneously develop atherothrombotic complications. We investigated whether disruption of natural anticoagulation allows preexisting atherosclerotic plaques to progress toward an atherothrombotic phenotype. Mice featured clots in the left atrium of the heart. Our findings indicate that small interfering RNA-mediated silencing of protein C in apolipoprotein E-deficient mice creates a condition that allows the occurrence of spontaneous atherothrombosis, albeit at a low incidence. Lowering natural anticoagulation in atherosclerosis models may help to discover factors that increase atherothrombotic complications. Show less
Ouweneel, A.B.; Heestermans, M.; Verwilligen, R.A.F.; Eck, M. van; Vlijmen, B.J.M. van 2016
Objectives: Studies on atherothrombosis, a major cause of cardiovascularevents, are hampered by the lack of animal models spontaneously developingatherothrombosis. Major underlying problems are the... Show moreObjectives: Studies on atherothrombosis, a major cause of cardiovascularevents, are hampered by the lack of animal models spontaneously developingatherothrombosis. Major underlying problems are the stability ofthe atherosclerotic plaques, combined with the strong plasma anticoagulantactivity. We hypothesized that inhibition of the anticoagulant systemby silencing of protein C (Proc) may cause murine atherosclerotic plaquesto become prone to atherothrombosis. Show less