Atherosclerosis is a chronic inflammatory disease of the vasculature in which both a disturbed lipid metabolism and inflammatory immune responses against several self-antigens are involved. In this... Show moreAtherosclerosis is a chronic inflammatory disease of the vasculature in which both a disturbed lipid metabolism and inflammatory immune responses against several self-antigens are involved. In this thesis we have explored the effectiveness of DC-immunotherapy in atherosclerosis. We have used different strategies to target the immune component in different stages of atherosclerosis. First we used DCs as a vaccination strategy to induce a protective antibody response trough the injection of oxLDL-pulsed DCs or to target NKT cells by the injection of OCH-pulsed DCs. Next we assessed the potential of DC-immunotherapy in a model of established atherosclerosis. We also evaluated the effects of a disturbed TGF-_ signaling in DCs and the subsequent effects on atherosclerosis by using ApoE-/- which have a dysfunctional TGF-__ Receptor II under the CD11c promoter. Next, we were interested in the effect of foam-cell formation on the antigen-presenting capacity of DCs and macrophages. Therefore we studied the effect of oxLDL-loading on antigen uptake and antigen presentation by DCs and macrophages. Finally, by depleting or inducing Tregs we investigated the potential role of regulatory T cells in a mouse model for aneurysm formation. Show less
The studies described in this thesis focus on gene therapeutic strategies to target pathological vascular wall remodeling after PT(C)A or bypass surgery. Inflammatory processes and extracellular... Show moreThe studies described in this thesis focus on gene therapeutic strategies to target pathological vascular wall remodeling after PT(C)A or bypass surgery. Inflammatory processes and extracellular proteases, both activated by mechanical and vascular injury caused by these interventions, are thought to contribute largely to the development of post-angioplasty restenosis and vein graft disease. Therefore, viral and non-viral gene therapy techniques were used in these studies to deliver genes encoding protective as well as inhibiting proteins in order to modulate the inflammatory cascade (i.e. IL-10 and the MCP-1/CCR-2 pathway) in the first part of this thesis and the plasminogen activator and MMP-system in the second part. Finally, the expression of several involving genes was blocked locally by RNA interference techniques in the last part of this thesis. The possibilities and effects of these gene therapy applications were studied in cell cultures, in a human saphenous vein organ culture model and in two mouse models of restenosis and vein graft disease. Altogether, these studies provided more insight into the pathophysiology of post-interventional remodeling and several potential therapeutic strategies were assessed. Show less
The aim of this thesis was to explore the relation between visceral obesity and the accompanying metabolic disturbances, systemic inflammation and the atherosclerotic process. A newly developed... Show moreThe aim of this thesis was to explore the relation between visceral obesity and the accompanying metabolic disturbances, systemic inflammation and the atherosclerotic process. A newly developed magnetic resonance vessel wall imaging technique was implemented in phenotyping patients and as a therapeutic endpoint in a randomised controlled setting. A three step approach was chosen for this purpose. First, the magnetic resonance black blood vessel wall imaging technique at the magnetic field strength of 3 Tesla was developed and validated. Secondly, phenotyping of viscerally obese subjects was performed with special attention for the role of systemic inflammation and atherosclerosis. Finally, in the setting of a randomised controlled trial, the impact of reducing visceral obesity and systemic inflammation with lifestyle intervention and rosiglitazone treatment (PPARg agonist) on the progression of atherosclerosis was assessed. Show less
The research described in this thesis consist of 2 parts: the first part involves studies on the influence of chemokines in cardiovascular disease. Chemokines are inflammatory proteins which play a... Show moreThe research described in this thesis consist of 2 parts: the first part involves studies on the influence of chemokines in cardiovascular disease. Chemokines are inflammatory proteins which play a pivotal role in atherosclerosis and myocardial ischemia. We identify 3 chemokines (CCL3, CCL5 and CCL18) whose levels are not only elevated during myocardial ischemia, but are also predictive of future cardiovascular events. Further studies focus on the individual role of CCL18 as well as CCL3 in atherogenesis and atherosclerotic plaque destabilization. The first is seen to recruit T-lymphocytes and the latter neutrophil granulocytes into the plaque, possibly augmenting plaque growth and destabilization. The second part focuses on the effect of gene modulation on vascular function. It start of with a study on the influence of aging in our atherosclerotic plaque mouse model. Additional genetic microarray revealed the Quaking gene as a possible modulator of atherosclerosis. This observation is further explored in studies which show a link between Quaking genetic polymorphisms and an enhanced risk of developing in-stent restenosis following percutaneous coronary intervention. This is partly mediated by disturbed vascular smooth cell function. Finally, the MEF2 gene is studied for its role in myocardial infarction as genetic mutations in the MEF2A gene are associated with enhanced risk for a myocardial infarction. In a mouse model, we show that this is primarily due to decreased endothelial cell function, leading to plaque erosion. Show less
Cardiovascular disease (CVD) is a major cause of mortality and morbidity in the Western world. CVD is mainly caused by atherosclerosis, for which dyslipidemia, characterized by high a plasma level... Show moreCardiovascular disease (CVD) is a major cause of mortality and morbidity in the Western world. CVD is mainly caused by atherosclerosis, for which dyslipidemia, characterized by high a plasma level of (very) low density lipoprotein ((V)LDL) and a low plasma level of high density lipoprotein (HDL), is a major risk factor. To reduce the risk to develop CVD, drugs aimed at correcting dyslipidemia by lowering (V)LDL are currently the first choice of treatment. Albeit that these drugs lower (V)LDL-C very efficiently (up to ~40%), and generally result in a slight increase in HDL-C, they only prevent a fraction of all cardiovascular events (~30%). Therefore new therapeutic strategies to reduce cardiovascular events more efficiently are necessary. Since HDL is has been attributed multiple protective effects in atherosclerosis by its role in reverse cholesterol transport and its anti-inflammatory and anti-oxidative properties, HDL-raising therapy is currently considered as a promising strategy to further reduce CVD risk. In this thesis, the mechanisms underlying the HDL-raising effects of the classical lipid-lowering drugs fenofibrate, atorvastatin and niacin were elucidated. Furthermore, the effects of potential novel HDL-raising strategies, including torcetrapib, PXR agonism and apoCI, on HDL metabolism were addressed. For these studies, we used the APOE*3-Leiden.CETP (E3L.CETP) transgenic mouse, a valuable model for human-like lipoprotein metabolism Show less
In summary, in this thesis it becomes clear that the intrauterine environment created by the mother during pregnancy not only has beneficial effects on the developing embryo / fetus. Although it is... Show moreIn summary, in this thesis it becomes clear that the intrauterine environment created by the mother during pregnancy not only has beneficial effects on the developing embryo / fetus. Although it is too early to draw definite conclusions, the first results of this research line show that maternal apoE-deficiency, in contrast to maternal Ldlr-deficiency, adversely affects the offspring, not only in late fetal stages but also in adult life. Our data indicate that the inflammatory status of the mother and the lack of maternal apoE itself may attribute to the increased cardiovascular disease risk observed in the adult offspring. Hypercholesterolemia and oxidative stress possibly play a more regulatory role. In a first attempt to elucidate the underlying mechanism we show that maternal apoE-deficiency leads to changes in the histone triple-methylation modifications in the vascular wall of the offspring. Thi s can be considered an important lead that needs to be investigated further. It does not mean, however, that we are close to complete elucidation of the underlying mechanism. A lot of research is needed to accomplish this and it is needed. Why? The fact that a hit so early in life exerts negative effects on cardiovascular disease risk in adulthood is worrisome. If we could succeed in elucidating the exact role of epigenetics in this process and are able to translate these data to the human situation, possibly we could reduce the incidence of cardiovascular disease. Show less
Current non-invasive detection of coronary artery disease (CAD) is based on demonstration of ischemia using stress-rest imaging: this is an indirect way of identifying CAD by demonstration of the... Show moreCurrent non-invasive detection of coronary artery disease (CAD) is based on demonstration of ischemia using stress-rest imaging: this is an indirect way of identifying CAD by demonstration of the hemodynamic consequences rather than direct visualization of the obstructive lesions in the coronary arteries. Multi-slice computed tomography (MSCT) has recently emerged as an extremely rapidly developing non-invasive imaging modality, which allows anatomical imaging of the coronary arteries, or non-invasive coronary angiography. In addition, total plaque burden, plaque morphology and (to some extent) plaque constitution can be assessed by MSCT. The technique also provides information on resting left ventricular systolic function, and possibly resting perfusion. Ideally, stress function and perfusion should also be evaluated, since this would allow detection of ischemia and would complete the picture on CAD. However, this is not routinely performed, since sequential acquisitions are associated with high radiation doses and thus pose a limitation for cardiovascular applications of MSCT. It is anticipated that, with reduction in radiation, MSCT may become an important player in the diagnostic and prognostic workup of patients with known or suspected CAD. Show less
In this thesis we aimed to expand our knowledge on the pathophysiological aspects of the metabolic syndrome in transgenic mice. The metabolic syndrome involves multiple aspects and has a major... Show moreIn this thesis we aimed to expand our knowledge on the pathophysiological aspects of the metabolic syndrome in transgenic mice. The metabolic syndrome involves multiple aspects and has a major impact on cardiovascular diseases. In the first part of thesis the role of PAI-1 in the development of insulin resistance will addressed. This part will also focus on the mechanism of plasma PAI-1 clearance. In the second part of this thesis, the roles of LRP in atherosclerosis and LPL activity in lipid metabolism are addressed. In this thesis we showed the PAI-1 catabolism is facilitated by a RAP-sensitive mechanism other than LRP, LDLR and VLDLR. The increased plasma PAI-1 levels observed in insulin resistance and obesity is not explained by impaired clearance of PAI-1. The increased plasma PAI-1 levels might be an epiphenomenon of the chronic inflammatory state of insulin resistance or obesity. Furthermore, alternative pathways other than the traditional lipoprotein receptors are involved in the regulation of plasma cholesterol and triglyceride levels. The development of atherosclerosis is multi-factorial in which the balance between the antiand pro-inflammatory processes plays a central role. Macrophage LRP might be one of the features that control this balance. Inflammation not only promotes to the development of atherosclerosis, but might also be involved in the processes that restore the damaged vascular wall. Show less
Atherosclerosis, the predominantly underlying pathology of cardiovascular events, is the consequence of lipid deposition in the arterial wall, mostly as consequence of high levels of serum... Show moreAtherosclerosis, the predominantly underlying pathology of cardiovascular events, is the consequence of lipid deposition in the arterial wall, mostly as consequence of high levels of serum cholesterol. Treatment of atherosclerosis is mainly focused at the reduction of cholesterol levels by lipid lowering medication, such as statins. Despite the use of statins and prophylactic treatments, such as a reduction in blood pressure and a reduction in risk factors to prevent atherosclerosis, cardiovascular disease is still the major cause of death in the Western world.1-3 As the struggle against atherosclerosis continues and its prevalence is increasing in the world, it is pivotal to find new targets for implementing new strategies against atherosclerosis. Inflammation is considered to be a major component in the process of atherosclerosis and is involved in initiation, progression and destabilization of the atherosclerotic lesion. Although the beneficial effects of statins on atherosclerosis may partly be ascribed to their anti-inflammatory properties, relatively little is known about the exact mechanism and contribution of different inflammatory cells and products in atherosclerosis. The aim of this thesis was to further elucidate the contribution of various components of the inflammatory response in atherosclerosis and thereby finding new intervention points to reduce the incidence and the consequences of atherosclerosis. Show less
Atherosclerosis is a multifactorial disease of the large arteries and the leading cause of morbidity and mortality in industrialized countries. There is ample evidence that hypercholesterolemia (i... Show moreAtherosclerosis is a multifactorial disease of the large arteries and the leading cause of morbidity and mortality in industrialized countries. There is ample evidence that hypercholesterolemia (i.e. elevated plasma levels apo-B-containing lipoproteins) is a major causative factor in atherogenesis. It is equally clear that atherogenesis has an inflammatory component which is thought to drive the progression of the disease. However, while the lipid component in atherosclerosis development is relatively well-understood, the origin and exact contribution of the inflammatory component remains largely unknown. The aim of this thesis is to further define and delineate the contribution of the inflammatory component to the atherosclerotic process and to elucidate the link between cholesterol and inflammation in atherosclerotic lesion formation and progression. The studies of this thesis show that, besides plasma cholesterol, inflammation contributes to a substantial extent to atherogenesis. Intervention strategies directed at lowering apoB-containing lipoproteins and reducing inflammation may therefore be more effective than current lipid-lowering strategies. Direct experimental evidence for this assumption mainly comes from animal experiments as described in this thesis. Human intervention studies are necessary to evaluate whether these findings can also be translated to the human situation. Show less
Scheuring van een vaatwandvernauwing (plaque) kan ertoe leiden dat materiaal vanuit deze plaques in direct contact komt met de bloedsomloop wat de bloedstolling kan activeren met als mogelijk... Show moreScheuring van een vaatwandvernauwing (plaque) kan ertoe leiden dat materiaal vanuit deze plaques in direct contact komt met de bloedsomloop wat de bloedstolling kan activeren met als mogelijk gevolg bloedvatafsluiting en hartinfarct. Vooral vetten zoals het lysofosfatidaat (LPA) in deze plaques zijn verantwoordelijk voor het in gang zetten van de bloedstolling. In dit project werd het mechanisme achter de LPA accumulatie in de plaque en de effecten van LPA op plaquestabiliteit onderzocht. Expressie analyse heeft aangetoond dat verschillende sleutelfactoren in de aanmaak, afbraak van LPA gedurende de plaqueontwikkeling toe- of afnemen en dat dit gepaard gaat met een netto ophoping van LPA in de plaque. Analyse van de vetsamenstelling van muizenplaques liet zien dat ook in ons muizenmodel voor hart- en vaatziekten LPA ophoping plaatsvindt en wel in dezelfde mate als in humane plaques. Bovendien hebben we een studie uitgevoerd naar het effect van LPA op atherosclerose in een muizenstam met een verhoogd cholesterol gehalte. Zowel toediening via de buikholte als lokale toediening van LPA ter plekke van de plaque blijkt te leiden tot een verslechtering van de plaquestabiliteit en zelfs tot bloedingen in de plaque, waarbij dit laatste mogelijk is terug te voeren op een verhoogde activering van mestcellen in het vaatweefsel. Dit blijkt ook uit het feit dat de effecten omkeerbaar zijn bij toediening van een remmer van mestcel activatie. Daarnaast werd een studie uitgevoerd naar de effecten van een op LPA gelijkend vetmolecuul, sfingosine 1-phosphate (S1P). Verhoging van de S1P concentratie door afwezigheid van een afbraakenzym voor S1P of toediening van een synthetische analoog van S1P, FTY720, bleek de plaqueontwikkeling aanzienlijk af te remmen door een selectieve onderdrukking van het immuunsysteem. Bij afwezigheid van het S1P afbraakenzym werd ook verlaging in cholesterolconcentratie in het bloed geconstateerd. Concluderend kunnen wij stellen dat LPA kan worden beschouwd als een overwegend pro-atherogeen, en S1P als een voornamelijk anti-atherogeen lipide. Verlaging van LPA en verhoging van S1P kan dus leiden tot een effectieve therapeutische benadering ter vermindering van instabiele atherosclerotische plaque vorming. Show less
