The major targets in Systemic lupus erythematosus (SLE, a systemic autoimmune disease) are nuclear components (DNA, histones, ribonucleoproteins), which are mainly derived from dying cells ... Show moreThe major targets in Systemic lupus erythematosus (SLE, a systemic autoimmune disease) are nuclear components (DNA, histones, ribonucleoproteins), which are mainly derived from dying cells (apoptotic and necrotic cells). Defective clearance of dying cells by phagocytes may lead to the breakdown of peripheral tolerance and initiation of autoimmune SLE. I have investigated the role of the innate immune system in the processing of dying cells and its immunological consequences. I found that a subset of macrophages driven by M-CSF have intrinsic anti-inflammatory properties and are potent phagocytes that have the unique capacity to preferentially bind and ingest early apoptotic cells in a silent manner. I also identified that human peritoneal macrophages freshly isolated from patients on peritoneal dialysis resemble functionally the in vitro-generated M-CSF-driven macrophages. I further showed that the anti-inflammatory and pro-inflammatory macrophages co-exist but can re-differentiate towards opposing phenotype depending on the local cytokine environment. Next to the phagocyte system, I investigated the role of components of the innate immune system in the processing of dying cells. I found that one of the complement regulators called properdin, binds predominantly to late apoptotic and necrotic cells independently of C3b, resulting alternative pathway complement activation. Show less
For many years, cancer has been described as the accumulation of germinal and somatic mutations of the genome, impairing the function of tumor suppressor genes and stimulating oncogenes. Nowadays,... Show moreFor many years, cancer has been described as the accumulation of germinal and somatic mutations of the genome, impairing the function of tumor suppressor genes and stimulating oncogenes. Nowadays, it is commonly accepted that the tumor is not only a mass of malignant cells, rather than the result of a delicate network of interactions between tumor and stromal cells. Indeed, bidirectional communications between cancer cells and the surrounding microenvironment can strongly influence tumor development and progression. Stromal cells might support tumorigenesis, either via direct cell-cell contact mechanisms with tumor cells, or by releasing specific factors, including cytokines and growth factors in the surrounding extracellular matrix (ECM), with remodeling of the tumor microenvironment (TME) as a result.The aim of this thesis is to elucidate the delicate network of interactions between different TME components and tumor cells in prostate cancer (PCa) and oropharyngeal squamous cell carcinoma (OPSCC). Show less
In this thesis the role of several apoptosis regulating proteins in the development of atherosclerosis and atherosclerotic plaque stability is investigated. Apoptosis of different cell types in... Show moreIn this thesis the role of several apoptosis regulating proteins in the development of atherosclerosis and atherosclerotic plaque stability is investigated. Apoptosis of different cell types in atherosclerotic plaques, such as macrophages and smooth muscle cells may inhibit or promote plaque development or stability depending on the stage of atherosclerosis. As many of these apoptosis regulating proteins also display immune-modulating features, we have particularly investigated effects of modulation of apoptosis regulating proteins on plaque and systemic inflammation. We performed a number of studies in mouse models of atherosclerosis. First gene expression profiles of stable and unstable atherosclerotic plaques were compared in order to identify genes or pathways that are associated with plaque vulnerability. We further developed transgenic mice partially or wholly lacking genes involved in apoptosis and/or inflammation such as Bcl-2 family members and focal adhesion kinase, both systemically or in the leukocyte subset. The studies described in this thesis show amongst other things that Bim and Mcl-1, both members of the Bcl-2 family of apoptosis regulators, regulate specific cell death and inflammatory processes relevant to atherosclerosis. Show less
This thesis focuses on the relationship between smoking and macrophages in chronic obstructive pulmonary disease (COPD), and on treatment with inhaled corticosteroids (ICS). Macrophages play an... Show moreThis thesis focuses on the relationship between smoking and macrophages in chronic obstructive pulmonary disease (COPD), and on treatment with inhaled corticosteroids (ICS). Macrophages play an important role in COPD, and constitute a heterogeneous population with pro- (Mf1) and anti-inflammatory (Mf2) cells. This thesis evaluated YKL-40 and CD163 as markers for Mf1 and Mf2, respectively. Peripheral airways contained more CD163-positive Mf2 compared to central airways. Smoking cessation skewed the macrophage phenotype towards Mf2 in the peripheral airways, but did not influence YKL-40 levels in sputum. Whereas smoking can induce structural alterations in extracellular matrix (ECM) components in the airways, no differences in ECM components in bronchial biopsies were found between current and ex-smokers with COPD. ICS treatment attenuates lung function decline and decreases airway inflammation in a subgroup of COPD patients. However, long-term ICS treatment did not change YKL-40 levels in sputum and serum. ICS increased deposition of several ECM proteins in the airways, which was correlated with improved lung function, suggesting prevention of airway collapse. Withdrawal of ICS after long-term treatment induced a relapse in lung function decline and increased airway inflammation in bronchial biopsies and sputum, suggesting that benefits of ICS do not persist after discontinuation of ICS. Show less
Alpha1-antitrypsin is an important neutrophil elastase inhibitor that protects lung tissue from the destructive effects of neutrophil elastase released by degranulating neutrophils. In addition to... Show moreAlpha1-antitrypsin is an important neutrophil elastase inhibitor that protects lung tissue from the destructive effects of neutrophil elastase released by degranulating neutrophils. In addition to the liver, local production by macrophages and airway and alveolar epithelial cells may contribute to the formation of an anti-elastase screen in the lung. The Z mutation (E342K) of _1-antitrypsin, compromising over 95% of the _1-antitrypsin deficiency patients, causes subtle misfolding of the protein that permits polymer formation and accumulation within the endoplasmic reticulum (ER) of hepatocytes leading to plasma deficiency. This causes hepatic cirrhosis and early-onset lung emphysema. The discovery of ZZ polymers in broncho-alveolar lavage fluid and pulmonary tissue and their identification many years after liver transplantation led to the proposal that pulmonary pathology could be induced by polymers. Overexpression of Z _1-antitrypsin is known to induce polymer formation, prime cells for an exaggerated ER stress response upon a second hit and initiate NF-_B signalling. However, whether endogenous expression in primary bronchial epithelial cells and monocyte-derived macrophages has similar consequences remained unclear. This thesis concentrate on these specific questions. In addition, we focused on the ER stress response induced by P.aeruginosa as a possible second hit in _1-antitrypsin deficiency Show less
Chronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues,... Show moreChronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues, also coined metaflammation. In this context, white adipose tissue and liver-resident innate and adaptive immune cells produce proinflammatory cytokines that exacerbate inflammation and inhibit canonical insulin signaling. Among them, macrophages and dendritic cells were shown to play central roles in metaflammation, although the environmental and cellular changes dictating proinflammatory activation in the context of obesity are not fully understood. This thesis describes novel mechanisms by which macrophages and dendritic cells control metabolic homeostasis in obese mice. In addition, we show that immunomodulatory molecules derived from parasitic worm eggs promote an immune response in metabolic tissues that maintains insulin sensitivity. Finally, we describe the pleiotropic beneficial effects of a novel plant-derived nutritional supplement on metaflammation and metabolic homeostasis in obese mice. Altogether, this work may provide new leads for interventions aimed at improving immunological control of metabolic dysfunctions. Show less
Nearly one quarter of the world__s population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T... Show moreNearly one quarter of the world__s population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T helper 2 (Th2) cells. In addition to their involvement in anti-helminth immunity, recent studies have shown that components of the type 2 immune responses can have additional functions. For example, recent evidence indicates that multiple facets of the type 2 immune response can regulate tissue-specific metabolic processes and whole-body nutrient homeostasis, and protect against insulin resistance. In this work we use omega-1, a glycosylated RNase excreted from Schistsoma mansoni eggs with strong Th2-inducing capacities, to study the requirements that equip DCs for Th2 skewing. In addition, we analyse the effect of chronic S. mansoni infection and administration of S. mansoni-derived egg antigens on metabolic homeostasis in diet-induced obese mice. Elucidating how helminths generate Th2 responses and contribute to metabolic homeostasis will not only shed light on the mechanisms that promote control of parasite infection, but may provide valuable leads for the development of pharmaceutical agents for the treatment of metabolic disorders. Show less
This thesis describes the role of the immune system as an important phenomenon in the most frequently occurring form of eye cancer in adults, namely in uveal melanoma. We show that the immune... Show moreThis thesis describes the role of the immune system as an important phenomenon in the most frequently occurring form of eye cancer in adults, namely in uveal melanoma. We show that the immune system can be the cause of the tumor, and also plays a role in the development of a tumor, and may be an entry for therapy. In the first chapters of this thesis, we describe the phenomenon of "an inflammatory phenotype" in uveal melanoma. It appears that when this type of cancer shows more inflammation, the survival of patients decreases. A possible explanation for this observation is that one of the key players among the immune cells, the macrophage, plays an essential role in intra-ocular tumor growth. We demonstrate this in patient material, but also in experimental studies; we are able to inhibit tumor growth when we modulate the presence of macrophages. In this thesis, we also show that the immune system can be used effectively to eradicate eye melanomas in experimental models. T cell vaccination in combination with monoclonal antibodies gave promising results for treating eye cancer. Further research has to be performed to translate this into the clinic. Show less
Uveal melanoma is a highly malignant intraocular tumor with quite homogeneous tumor tissue and a diffuse leukocytic infiltration. In contrast with many other malignancies, the presence of... Show moreUveal melanoma is a highly malignant intraocular tumor with quite homogeneous tumor tissue and a diffuse leukocytic infiltration. In contrast with many other malignancies, the presence of infiltrating macrophages and T cells is associated with a poor prognosis rather than a good one. The clear link between inflammation and this malignancy provides a paradigm for macrophage plasticity and function. Macrophages in uveal melanoma have an M2-like phenotype and are associated with the loss of one specific chromosome - monosomy 3. The central players involved in this process and discussed include macrophages, T lymphocytes, chemokines and cytokines, including the macrophage-attraction molecules. When a tumor acquires the ability to release significant amounts of macrophage-attraction molecules it causes the expansion of a population of myeloid immature cells that may not only help the tumor to suppress immune reactions but also aid in the construction of new blood vessels for tumor growth. A better understanding of the molecular basis of a local myelomonocytic cell population will bring a better understanding of the immunopathology of this disease and will lead to therapeutic interventions in uveal melanoma. This thesis focuses on the roles of the local inflammatory microenvironment in the development and progression of uveal melanoma. Show less
Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease, is a rare genetic disorder, known for its endothelial dysplasia causing vessel malformations, severe nose bleeds and... Show moreHereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease, is a rare genetic disorder, known for its endothelial dysplasia causing vessel malformations, severe nose bleeds and internal bleedings. In the majority of patients mutations are found in genes belonging to the TGFβ superfamily, causing a disbalance in the TGFβ signaling pathway by haploinsufficiency of the remaining functional protein. In this thesis we studied different aims and approaches to influence HHT1-MNC homing and differentiation to restore their contribution to tissue repair. In various experimental methods inducing ischemic and/or direct tissue damage, we aimed to improve tissue repair in the Eng+/- mice. Using DPP4 inhibition, we increased the SDF1-CXCR4 homing mechanism, to restore the impaired homing capacity of the HHT1-MNCs. Furthermore, we focused on correcting the M1/M2 differentiation in Eng+/- mice. Via use of the BMP receptor inhibitor LDN we aimed to restore the skewed BMP/TGFβ signaling; stimulating the TGFβ pathway signaling to induce M2 differentiation. We concluded that DPP4 inhibition can be used to improve the HHT1 immune system and tissue repair, and is best used in concert with other drugs or therapies that stimulate cardiac or tissue repair, like anti-coagulants or cell therapy. Show less
The glioma microenvironment harbors a variety of immune cells including innate immune cells such as monocytes, macrophages and microglia. Microglia are the major innate immune cells present in the... Show moreThe glioma microenvironment harbors a variety of immune cells including innate immune cells such as monocytes, macrophages and microglia. Microglia are the major innate immune cells present in the glioma microenvironment. Communication between glioma and these immune cells is crucial to maintain a tumor-promoting environment. In this thesis the role of a specific type of communication is described. In detail, the consequence of extracellular communication from glioma to the innate immune cells is studied, this includes the transferring of messages (including miRNAs) through extracellular vesicles. In addition, the changes that these cells undergo in the presence of a tumor is documented. Show less
This thesis is focused on the innate immune defence mechanisms responsible for controlling mycobacterial growth after infection. To provide a detailed description of the host__s innate immune... Show moreThis thesis is focused on the innate immune defence mechanisms responsible for controlling mycobacterial growth after infection. To provide a detailed description of the host__s innate immune response to M. marinum infection, zebrafish gene expression levels were analysed by RNA sequencing at various time points during infection and correlated with imaging data of the process of pathogenesis. We demonstrate that the scavenger receptor Marco (macrophage receptor with collagenous structure) is a key player in the rapid phagocytosis of M. marinum and we use gene expression analysis in combination with gene knockdown studies to show that it is also essential in the establishment of an initial transient pro-inflammatory response to M. marinum infection. Once phagocytosed, M. marinum is capable of avoiding killing mechanisms of the host cell and can continue to grow within macrophages. This is the period when Membrane Attack Complex/Perforin proteins are involved in killing intracellular bacteria by their pore-forming activities. We reveal the regulatory mechanisms and function of two macrophage specific genes, mpeg1 and mpeg1.2 (macrophage expressed gene 1.2). The results from this thesis complement knowledge obtained from other model organisms by providing new insights into both counteracting and supporting mechanisms underlying the innate immune response. Show less
The work described in this thesis focussed on the modes of action of maggot therapy in chronic wounds, especially related to the inflammatory phase of wound healing. For this purpose, the effect of... Show moreThe work described in this thesis focussed on the modes of action of maggot therapy in chronic wounds, especially related to the inflammatory phase of wound healing. For this purpose, the effect of maggot excretions and/or secretions on microbiological, haematological and immunological processes was investigated. The results showed that maggot excretions/secretions breakdown biofilms of both Gram-positive and Gram-negative bacteria, exposing them to the immune system, antibiotics, and ingestion and subsequent degradation by the maggots. Furthermore, proteases in maggot secretions enhance debridement by increasing the fibrinolytic activity of wound components and by degrading matrix components directly. Additionally, maggot secretions inhibit the pro-inflammatory responses of phagocytes but do not affect their ability to ingest and intracellularly kill micro-organisms. Finally, secretions induce the production of growth factors essential for angiogenesis. In conclusion, the results described in this thesis provide new insights into the modes of action of maggot therapy in chronic wounds. The success of maggot therapy may be explained by the broad spectrum of processes that are modulated by maggot secretions. Show less
Abnormal vascular physiology and precipitating inflammatory pathways underlie many different diseases, including hemorrhage, stroke, vascular dementia and even cancer. Pluripotent stem cells (PSCs)... Show moreAbnormal vascular physiology and precipitating inflammatory pathways underlie many different diseases, including hemorrhage, stroke, vascular dementia and even cancer. Pluripotent stem cells (PSCs) can now be derived by reprogramming from any individual so that it is possible in principle to derive all somatic cells of the human body that would normally be difficult to access. In this thesis, I studied the derivation of myeloid cells from human induced pluripotent stem cells (hiPSCs) to model the inflammatory component of vascular disease and characterized the development path of hiPSC-derived endothelial cells (hiPSC-ECs) which form the vascular walls. Functional defects in either of these cell types can cause or exacerbate vascular disease. I then used these cell types to gain insight into the mechanisms underlying two genetic diseases: Hereditary Hemorrhagic Telangiectasia (HHT) which is caused by mutations in a gene called Endoglin expressed on cells of the vascular wall and inflammatory macrophages, and a vascular tumor called Pseudomyogenic hemangioendothelioma (PHE) in which endothelial cells are thought to be the tumor cell of origin. I developed new differentiation protocols to generate inflammatory cells from hiPSC, characterized these cells functionally and used Next-Generation Sequencing and bioinformatic analysis to gain insight into the molecular pathways controlling development of one particular type of endothelial cells from hiPSC and the underlying tumorigenic mechanisms of PHE. Show less
Transplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation... Show moreTransplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation of the complement system, part of our innate immune system, plays a local role. We reviewed that properdin, the only known positive regulator of the complement system, was detected in serum, plasma and urine from patients with various complement-mediated renal diseases. In protocol biopsies obtained 10 days after transplantation, properdin was found deposited in addition to complement activation markers. Next, we showed that dendritic cells secrete properdin and a decrease in properdin levels during dendritic cell- T-cell interaction resulted in reduced T-cell proliferation and activation. We also showed that properdin is able to bind to surfaces of both viable and dead cells, contributing to complement activation. Macrophages can also produce properdin and negative regulators factor H and its splice variant FHL-1. Increasing knowledge on complement factor production by other cells than hepatocytes, including immune cells, hints towards a local role of the complement system in various processes. These findings contribute to a better understanding of the local role of the complement system and are important for the applications of (new) complement-inhibiting drugs. Show less
Atherosclerosis is one of the primary causes of cardiovascular disease; the number one cause of death in the western society. Atherosclerotic plaque formation is a dynamic multi-cellular process... Show moreAtherosclerosis is one of the primary causes of cardiovascular disease; the number one cause of death in the western society. Atherosclerotic plaque formation is a dynamic multi-cellular process where regulation of different genes essentially determines the activity of the different cell types involved. Gene expression is regulated, amongst others, by epigenetic processes. Epigenetic mechanisms change the accessibility of the DNA sequence and is thought to form a link between environmental factors and gene expression. Epigenetics may therefor play an important role in atherosclerosis pathology. The research described in this thesis evaluated the role of epigenetic regulation on various aspects of atherosclerosis pathology. It was found that the epigenetic H3K27Me3-mark was reduced in later stages of the disease. Monocytes differentiating into dendritic cells and macrophages (an important process in atherosclerosis pathology) showed higher transcription of the epigenetic regulatory gene KMT1c. Specifically blocking this gene resulted in reduction of DC-SIGN (a dendritic cell specific molecule) expression. By specifically blocking other epigenetic proteins, CCR5 (a molecule important to monocyte migration) was re-expressed on cells which did not express CCR5. This shows that epigenetic regulation is an important process in atherosclerosis pathology and might prove to be novel pharmacological target for treatment of atherosclerosis. Show less
Work described in this thesis was aimed to further understand the role of macrophages in acute cellular rejection of transplanted kidneys, and perform a pre-clinical assessment of the localization... Show moreWork described in this thesis was aimed to further understand the role of macrophages in acute cellular rejection of transplanted kidneys, and perform a pre-clinical assessment of the localization and efficacy of liposomal prednisolone. First, we explored the role of anti-inflammatory macrophages in the onset of acute cellular rejection using human biopsy samples. Here, we discovered that the presence of high levels of CD163+ macrophages was associated with a lower risk of rejection, in a population of patients with a high rate of delayed graft function. Subsequently, we identified the ability of liposomal prednisolone to target macrophages in the kidney using in vitro models of human macrophages, and their ability to accumulate in inflamed kidney tissue in vivo rat models of ischemia reperfusion injury in the kidney. Finally, we evaluated the treatment efficacy of liposomal prednisolone in a mouse model of cellular rejection following kidney transplantation. Here, we were able to show an improved efficacy of liposomal prednisolone in treating rejection, when compared to treatment with free prednisolone. Show less
De resultaten beschreven in dit proefschrift verschaffen nieuwe inzichten in verschillende aspecten van de behandeling van inflammatoire darmziekten. Uit grote studies is gebleken dat mutaties in... Show moreDe resultaten beschreven in dit proefschrift verschaffen nieuwe inzichten in verschillende aspecten van de behandeling van inflammatoire darmziekten. Uit grote studies is gebleken dat mutaties in genen die betrokken zijn bij het autofagie proces (autophagos: __zelf-eten__), geassocieerd zijn met de ziekte van Crohn. In dit proefschrift wordt beschreven hoe deze mutatie in dendritische cellen leidt tot hyperactivatie van het immuunsysteem. Dit mechanisme kan mogelijk een nieuw aangrijpingspunt verschaffen voor nieuwe therapie voor pati_nten die een mutatie hebben in dit gen. Anti-tumor-necrosis-factor-alpha (anti-TNF_) therapie neemt een steeds belangrijkere plaats in in de behandeling van IBD; het werkingsmechanisme is echter niet geheel duidelijk. In dit proefschrift wordt beschreven hoe regulatoire macrophagen met immuunsuppressieve en wondgenezende eigenschappen ge_nduceerd worden door anti-TNF_ therapie. Dit werkingsmechanisme kan nieuwe aangrijpingspunten verschaffen voor toekomstige therapie_n. Tevens wordt in dit proefschrift een experimentele behandeling van Crohn met mesenchymale stamcellen (MSCs) beschreven. Deze behandeling is haalbaar en veilig gebleken, hetgeen aanleiding geeft tot verder onderzoek naar de effectiviteit van MSCs in de behandeling van Crohn. Tot slot werd het v__rkomen van kwaadaardige lymfomen onderzocht in IBD pati_nten in Nederland. Deze lymfomen bleken niet vaker voor te komen in de totale groep IBD pati_nten vergeleken met gezonde mensen, wel werd een verhoogde incidentie gezien in bepaalde leeftijdsgroepen. Daarnaast bleek het ontstaan van een EBV positief lymfoom (epstein Barr virus) sterk geassocieerd te zijn met het gebruik van azathioprine, een ander immuunsuppressieve therapie. Samenvattend beschrijft dit proefschrift verschillende aspecten van IBD therapie, en worden nieuwe inzichten en aangrijpinspunten verschaft Show less
In this thesis the aim was to study immune cell interactions at the maternal-fetal interface to understand the role for immune cells during healthy pregnancy development an pregnancy complications.... Show moreIn this thesis the aim was to study immune cell interactions at the maternal-fetal interface to understand the role for immune cells during healthy pregnancy development an pregnancy complications. Specifically in cases of recurrent pregnancy loss and chronic histiocytic intervillositis. Show less
The aim of this thesis was to investigate the expression, and function of genes associated with remodelling and regeneration in the zebrafish model species. Here, we studied the role of cell... Show moreThe aim of this thesis was to investigate the expression, and function of genes associated with remodelling and regeneration in the zebrafish model species. Here, we studied the role of cell populations, defined by their expression of markers, in bone regeneration and remodelling in zebrafish embryos and adult zebrafish scales. We used mesoporous silica nanoparticles to carry cytokines, known to activate hematopoietic cells into osteoclasts, into tissues of the living embryo. We further investigated the role of genes such as matrix metalloproteinases in regeneration of adult zebrafish scales. These genes are known to be involved in matrix degradation and have been found to be expressed in mammalian osteoclasts. We studied both by in situ hybridisation and immunocytochemistry the presence of mononucleated and multinucleated mmp-9 positive cells on the episquamal side of adult zebrafish scales. Finally we studied the regeneration of the caudal fin of zebrafish embryos with a special emphasis on the effect of glucocorticoids on regeneration and wound healing. Glucocorticoids in this case mimic stress conditions in the embryos, thus helping understand the effect of early exposure to stress on wound healing and tissue Remodelling. Show less
