Stabilin-1 (STAB1) is a scavenger receptor expressed on alternatively activated macrophages and sinusoidal endothelial cells. Its ligands include oxidized low-density lipoprotein (LDL) and the... Show moreStabilin-1 (STAB1) is a scavenger receptor expressed on alternatively activated macrophages and sinusoidal endothelial cells. Its ligands include oxidized low-density lipoprotein (LDL) and the extracellular matrix glycoprotein SPARC and it is present in both human and murine atherosclerotic lesions. We aimed to investigate the effect of specific deletion of STAB1 in bone marrow-derived cells, including macrophages on atherosclerotic lesion formation in mice.Lethally irradiated hypercholesterolemic LDL receptor knockout mice received either wildtype (WT) or STAB1 knockout (STAB1 KO) bone marrow. Bone marrow transplanted mice were fed a Western-type diet for 9 weeks to induce atherosclerotic lesion formation. Interestingly, LDL receptor knockout mice reconstituted with STAB1 KO bone marrow showed increased body weight gain (two-way ANOVA: p < 0.001) and larger white adipocyte cell sizes (43% increase in cell area; p < 0.05) as compared to WT bone marrow transplanted mice, which correlated positively (r = 0.82; p < 0.001). This was paralleled by a significant increase in white adipose tissue relative mRNA expression levels of the adipokine leptin (+94% p < 0.05). Despite these changes, no differences in serum lipid levels, the extent of in vivo macrophage foam cell formation or circulating leukocyte concentrations were observed. Moreover, the size and composition of atherosclerotic lesions was not different between the two experimental groups. Bone marrow-specific Stabilin-1 deletion does not affect the susceptibility for atherosclerosis in mice. However, the increased body weight gain and adipocyte cell size highlight a potential role for leukocyte STAB1 in the development of metabolic disorders. Show less
Benne, N.; Duijn, J. van; Vigario, F.L.; Leboux, R.J.T.; Veelen, P. van; Kuiper, J.; ... ; Stutter, B. 2018
The E3-ligase CBL-B (Casitas B-cell lymphoma-B) is an important negative regulator of T cell activation that is also expressed in macrophages. T cells and macrophages mediate atherosclerosis, but... Show moreThe E3-ligase CBL-B (Casitas B-cell lymphoma-B) is an important negative regulator of T cell activation that is also expressed in macrophages. T cells and macrophages mediate atherosclerosis, but their regulation in this disease remains largely unknown; thus, we studied the function of CBL-B in atherogenesis.The expression of CBL-B in human atherosclerotic plaques was lower in advanced lesions compared with initial lesions and correlated inversely with necrotic core area. Twenty weeks old Cblb−/−Apoe−/− mice showed a significant increase in plaque area in the aortic arch, where initial plaques were present. In the aortic root, a site containing advanced plaques, lesion area rose by 40%, accompanied by a dramatic change in plaque phenotype. Plaques contained fewer macrophages due to increased apoptosis, larger necrotic cores, and more CD8+ T cells. Cblb−/−Apoe−/− macrophages exhibited enhanced migration and increased cytokine production and lipid uptake. Casitas B-cell lymphoma-B deficiency increased CD8+ T cell numbers, which were protected against apoptosis and regulatory T cell-mediated suppression. IFNγ and granzyme B production was enhanced in Cblb−/−Apoe−/− CD8+ T cells, which provoked macrophage killing. Depletion of CD8+ T cells in Cblb−/−Apoe−/− bone marrow chimeras rescued the phenotype, indicating that CBL-B controls atherosclerosis mainly through its function in CD8+ T cells. Casitas B-cell lymphoma-B expression in human plaques decreases during the progression of atherosclerosis. As an important regulator of immune responses in experimental atherosclerosis, CBL-B hampers macrophage recruitment and activation during initial atherosclerosis and limits CD8+ T cell activation and CD8+ T cell-mediated macrophage death in advanced atherosclerosis, thereby preventing the progression towards high-risk plaques. Show less
Cardiovascular disease is the number one cause of death worldwide. The most important risk factor for developing this disease is high cholesterol levels in the blood. Other risk factors... Show moreCardiovascular disease is the number one cause of death worldwide. The most important risk factor for developing this disease is high cholesterol levels in the blood. Other risk factors contributing to cardiovascular disease can develop in individuals which are overweight. The clinical consequences of being overweight are clustered in the medical term: metabolic syndrome. Included in the metabolic syndrome are high blood pressure, dyslipidemia and glucose intolerance. At present, most cardiovascular disease patients are treated with statins which lower blood cholesterol levels. However, this treatment is not as effective in all patients and can cause some adverse drug reactions. Therefore, it is essential that novel therapeutic targets for the treatment of cardiovascular disease are identified. In this thesis, potential novel therapeutic targets in cardiovascular disease and metabolic syndrome are validated. In total, three potential targets were investigated: proteoglycan 4, protein arginine methyltransferase 3 and stabilin 1. Our studies showed the involvement of two of these targets in the development of cardiovascular disease and metabolic syndrome. Moreover, our results stress (1) that cardiovascular disease and metabolic syndrome are complex, multifactorial diseases with overlapping mechanisms and (2) that integration of research into both diseases can benefit therapeutic target identification and validation. Show less
Kritikou, E.; Duijn, J. van; Nahon, J.E.; Heijden, T. van der; Bouwman, M.; Groeneveldt, C.; ... ; Bot, I. 2018
The development of atherosclerosis is tightly regulated by the innate and adaptive immune system. Communication between these two compartments occurs, among others, upon presentation of lipid... Show moreThe development of atherosclerosis is tightly regulated by the innate and adaptive immune system. Communication between these two compartments occurs, among others, upon presentation of lipid antigens to the NKT cell population by CD1d-expressing antigen-presenting cells. Recent evidence states that also mast cells express CD1d and can directly communicate with NKT cells. However, no such relationship has been reported in atherosclerosis. Here, we aimed to elucidate in vivo the CD1d-mediated interaction between mast cells and NKT cells upon atherosclerosis progression.\n mice and subsequently placed the animals on a Western-type diet for 10 weeks.\n circulating T cells.\nThis study is the first to illustrate that disruption of the CD1d communication pathway between mast cells and NKT cells aggravates atherosclerosis, through a shift towards pro-inflammatory T cell responses. This ability of mast cell action during plaque progression sheds new light on their role in atherosclerosis. Show less
Limiting the pro-inflammatory immune response is critical for the treatment of atherosclerosis. Regulatory B cells (Bregs) can modulate the immune response through interleukin-10 (IL-10). Current... Show moreLimiting the pro-inflammatory immune response is critical for the treatment of atherosclerosis. Regulatory B cells (Bregs) can modulate the immune response through interleukin-10 (IL-10). Current data regarding Bregs and atherosclerosis is scarce and conflicting.\n B cells on atherosclerosis.\n B cells on atherosclerosis.\n B cells in atherosclerosis. Show less
Atherosclerosis and the clinical consequence of cardiovascular disease remain the leading cause of death worldwide. Both an increase in cholesterol levels, as well as immune responses drive the... Show moreAtherosclerosis and the clinical consequence of cardiovascular disease remain the leading cause of death worldwide. Both an increase in cholesterol levels, as well as immune responses drive the pathogenesis of this disease. Although much is known about the role of many immune cell subsets in atherogenesis, research into the role of CD8 T cells is limited.\nBoth atheroprotective and atherogenic functions of CD8 T cells have been reported. On the one hand, the inflammatory cytokines produced by CD8 T cells exacerbate inflammatory responses, and the cytotoxic activity of these cells toward lesion-stabilizing cells such as endothelial cells drives the progression and instability of atherosclerotic lesions. On the other hand, cytotoxic activity toward antigen presenting cells and the presence of regulatory CD8 T-cell subsets dampen immunity and can limit atherosclerosis.\nHere we review the different roles of CD8 T cells in atherosclerosis and discuss possible treatment strategies targeting these cells to reduce atherosclerotic lesion burden. 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
Vos, A.; Kockelkoren, R.; Vis, J.B. de; Schouw, Y.T. van der; Schaaf, I.C. van der; Velthuis, B.K.; ... ; DUST Study Grp 2018
Phosphorylcholine (PC) is an oxidation-specific epitope present on oxidized LDL and apoptotic cells, as well as the capsular polysaccharide of Streptococcus pneumoniae. PC is bound by naturally... Show morePhosphorylcholine (PC) is an oxidation-specific epitope present on oxidized LDL and apoptotic cells, as well as the capsular polysaccharide of Streptococcus pneumoniae. PC is bound by naturally occurring IgM antibodies and low levels of anti-PC IgM are a risk factor for atherosclerosis. Active immunization of atherosclerosis-prone mice with oxidized LDL, S. pneumoniae or PC conjugated to keyhole lympet hemocyanin (PC-KLH) induces high titers of anti-PC Abs and protects from atherosclerosis. However, it is unknown if existing vaccine preparations can be exploited as preventive vaccine in atherosclerosis. Our aim was to evaluate the potential atheroprotective effect of Prevenar®, a clinical-grade pneumococcal vaccine.Male apolipoprotein E-/-,mice (n=10 per group) were injected subcutaneously with 50μl Prevenar® (diluted 1:10 in PBS) at 8 and 12 weeks of age. PC-KLH and PBS were used as positive and negative controls, respectively. Mice were fed regular chow for the entire study. Serum anti-PC Abs were analyzed at baseline and 15 days after the second injection. After 20 weeks serum lipid levels were measured and atherosclerotic lesion size was quantified in the aortic root.Both vaccination with Prevenar® and PC-KLH induced high titers of anti-PC IgM and IgG Abs and resulted in reduced atherosclerosis compared to PBS injected mice (figure) despite similar serum cholesterol levels.The amount of residual PC in Prevenar® is sufficient to elicit atheroprotective anti-PC responses in apoE-/- mice. Since Prevenar® is already used in humans, its potential to prevent atherosclerosis and/or slow down atherosclerosis progression could readily be tested in clinical trials. Show less
Snip, O.S.C.; Hoekstra, M.; Zhao, Y.; Calpe-Berdiel, L.; Vulve, J.; Carles Escola-Gil, J.; ... ; Eck, M. van 2018
Various studies have shown that leukocyteATP-binding cassette transporter A1 (ABCA1) is an anti-atherogenic factor. It has long been assumed that the increased atherosclerosis susceptibility... Show moreVarious studies have shown that leukocyteATP-binding cassette transporter A1 (ABCA1) is an anti-atherogenic factor. It has long been assumed that the increased atherosclerosis susceptibility observed in leukocyte ABCA1 deficient hyperlipidemic mice was due to an accelerated foam cell formation. However, several studies have suggested that leukocyte ABCA1 may also have a beneficial effect on systemic inflammation. In this study we aim to determine the effect of leukocyte ABCA1 deficiency on atherosclerosis susceptibility in mice that are apolipoprotein A1 (apoA1) deficient.To determine the impact of leukocyte ABCA1 on atherosclerosis outcome, lethally irradiated low-density lipoprotein receptorknock-out (sKO) mice or LDLr/apoA1 double KO (dKO) mice were reconstituted with either ABCA1 KO or wild-type bone marrow. All four groups of chimeric mice were fed a Western-type diet for 6 weeks to induce atherosclerotic lesion development.Leukocyte ABCA1 deficiency in dKO mice resulted in 50-70% larger lesions in the aortic root than those observed in both sKO mice transplanted with ABCA1 KO bone marrow and dKO mice transplanted with wild-type bone marrow. Furthermore, total leukocyte numbers in blood were generally higher in mice lacking apoA1 as compared to those containing apoA1-carrying HDL particles. Two way ANOVA on the different white blood cell sub-populations suggested that the apoA1 deficiency-associated increase in total leukocyte counts was driven by an increase in the number of lymphocytes (P<0.001) and, to a minor extent, monocytes (P<0.01).This study shows that reduced systemic inflammation and increased reverse cholesterol transport together drive macrophage ABCA1-mediated protection against atherosclerosis. Show less
Proteoglycan 4 (Prg4) has a high structural similarity with the established atherosclerosis-modulating proteoglycan versican, but its role in atherogenesis is still unknown. Therefore, the impact... Show moreProteoglycan 4 (Prg4) has a high structural similarity with the established atherosclerosis-modulating proteoglycan versican, but its role in atherogenesis is still unknown. Therefore, the impact of Prg4 deficiency on macrophage function in vitro and atherosclerosis susceptibility in vivo was investigated.The presence and localization of Prg4 was studied in atherosclerotic lesions. Furthermore, the effect of Prg4 deficiency on macrophage foam cell formation, cholesterol efflux and lipopolysaccharide (LPS) response was determined. Finally, susceptibility for atherosclerotic lesion formation was investigated in bone marrow-specific Prg4 knockout (KO) mice.Prg4 mRNA expression was induced 91-fold (p<0.001) in murine initial atherosclerotic lesions and Prg4 protein co-localized with human lesional macrophages. Murine Prg4 KO macrophages showed increased foam cell formation (+2.1-fold, p<0.01). In parallel, the expression of the cholesterol efflux genes ATP-binding cassette transporter A1 and scavenger receptor type B1 was lower (-35%, p<0.05;-40%, p<0.05) in Prg4 KO macrophages. This translated into an impaired cholesterol efflux to high-density lipoprotein (-13%, p<0.001) and apolipoprotein A1 (-8%, p<0.05). Furthermore, Prg4 KO macrophages showed an impaired LPS-induced rise in TNFα secretion as compared to wild-type controls (-31%, p<0.001), indicating a reduced inflammatory response. Combined, these pro- and anti-atherogenic effects did not translate into a significant difference in atherosclerotic lesion formation upon bone marrow-specific deletion of Prg4 in low-density lipoprotein receptor KO mice.Prg4 is present in macrophages in both murine and human atherosclerotic lesions and critically influences macrophage function, but deletion of Prg4 in bone marrow-derived cells does not affect atherosclerotic lesion development. Show less
Hoekstra, M.; Geerling, J.J.; Jiskoot, W.; Eck, M. van 2018
Atherosclerotic changes of the carotid artery are associated with elevated cardiovascular risk. Non-invasive imaging studies of the artery can provide information on the presence or absence of... Show moreAtherosclerotic changes of the carotid artery are associated with elevated cardiovascular risk. Non-invasive imaging studies of the artery can provide information on the presence or absence of abnormalities. Although the techniques are extensively used in clinical research their implementation in common practice is not widespread. In this thesis the potential benefits and challenges of carotid imaging in clinical practice are studied. Ultrasound and magnetic resonance imaging are the two modalities of interest. The findings suggest that ultrasound can be performed by the clinician in a routine outpatient setting. Clinicians are able to detect atherosclerotic plaques but not intima-media thickness. Plaques are highly prevalent in asymptomatic primary prevention patients. Magnetic resonance imaging is a new highly reproducible modality but requires further clinical validation. Its utility in individual patient risk assessment is unclear and ultrasound validity cannot be extrapolated to magnetic resonance. The use of a combination of the two imaging modalities may allow for estimation of the lamina adventitia in vivo. Finally, interpretation of the imaging parameters must be done in conjunction with all cardiovascular risk factors and treatment decision should not be based on imaging results alone. Show less
The most important risk factor for atherosclerotic cardiovascular disease is increased levels of LDL-C. Statins have long been the most potent LDL-C lowering drugs on the market. However,... Show moreThe most important risk factor for atherosclerotic cardiovascular disease is increased levels of LDL-C. Statins have long been the most potent LDL-C lowering drugs on the market. However, statin treatment is complicated by the fact that a considerable number of patients is unable to tolerate full therapeutic doses, or can be classified as statin low or non-responders. In >25% of patients at (very) high risk for cardiovascular disease, statin efficacy is too limited to achieve current guideline-mandated LDL-C target goals, and aggressive statin therapy decreases relative risk for ASCD by only 30-35%, leaving an unacceptable residual relative risk of 65-70% for life-threatening events. It is clear that on-treatment LDL-C levels and on-treatment measures of systemic inflammation are of equal importance in this residual risk. Both for residual cholesterol risk and residual inflammatory risk, effective drug therapy has been lacking for decades. In this thesis, we describe the first clinical studies with novel compounds based on increased LDL-C levels and inflammation (including the required methodology), and present the methodology that may be useful to develop future compounds based on dysfunctional endothelial barrier function resulting in subendothelial cholesterol accumulation and subsequent atheroma formation. Show less
Within this thesis, several diseases central in the field of cardiovascular disease will be outlined. First, the central dogma of molecular biology, RNA biology in general, RNA (alternative... Show moreWithin this thesis, several diseases central in the field of cardiovascular disease will be outlined. First, the central dogma of molecular biology, RNA biology in general, RNA (alternative)splicing and the role of RNA-binding proteins within these processes will be discussed to enhance the accessibility to non-molecular biologists. Subsequently, the current literature and insights into the RNA-binding protein Quaking will be outlined. Thereafter, a brief summary of the role of many distinct RNA-binding proteins (RBPs) in the cardiovascular system is provided, detailing their importance in the heart and cells of the blood vessels. This review provides some historical and biological perspectives, while simultaneously highlighting many recent advances in our understanding of RBP function in cardiovascular health and disease. By harnessing established and novel techniques, including RNA-sequencing, this thesis will describe the role of Quaking in vascular stenosis, atherosclerosis, inflammation and endothelial barrier function. Collectively, Quaking can be described as a genome-wide governor of RNA-processing that results in the proper translation into functional proteins. This thesis describes which RNA transcripts are under control of Quaking, which alternative transcripts are being generated through modulation by Quaking, while also describing the unique role for this protein in health and cardiovascular and renal disease. Show less
