http://repub.eur.nl/res/aut/23604/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/31154/ 2011-08-05T00:00:00Z Rationale: Neovascularization is required for embryonic development and plays a central role in diseases in adults. In atherosclerosis, the role of neovascularization remains to be elucidated. In a genome-wide microarray-screen of Flk1+ angioblasts during murine embryogenesis, the v-ets erythroblastosis virus E26 oncogene homolog 2 (Ets2) transcription factor was identified as a potential angiogenic factor. Objectives: We assessed the role of Ets2 in endothelial cells during atherosclerotic lesion progression toward plaque instability. Methods and Results: In 91 patients treated for carotid artery disease, Ets2 levels showed modest correlations with capillary growth, thrombogenicity, and rising levels of tumor necrosis factor-α (TNFα), monocyte chemoattractant protein 1, and interleukin-6 in the atherosclerotic lesions. Experiments in ApoE mice, using a vulnerable plaque model, showed that Ets2 expression was increased under atherogenic conditions and was augmented specifically in the vulnerable versus stable lesions. In endothelial cell cultures, Ets2 expression and activation was responsive to the atherogenic cytokine TNFα. In the murine vulnerable plaque model, overexpression of Ets2 promoted lesion growth with neovessel formation, hemorrhaging, and plaque destabilization. In contrast, Ets2 silencing, using a lentiviral shRNA construct, promoted lesion stabilization. In vitro studies showed that Ets2 was crucial for TNFα-induced expression of monocyte chemoattractant protein 1, interleukin-6, and vascular cell adhesion molecule 1 in endothelial cells. In addition, Ets2 promoted tube formation and amplified TNFα-induced loss of vascular endothelial integrity. Evaluation in a murine retina model further validated the role of Ets2 in regulating vessel inflammation and endothelial leakage. Conclusions: We provide the first evidence for the plaque-destabilizing role of Ets2 in atherosclerosis development by induction of an intraplaque proinflammatory phenotype in endothelial cells. http://repub.eur.nl/res/pub/25580/ 2011-04-01T00:00:00Z Ras homolog enriched in brain (Rheb) couples growth factor signaling to activation of the target of rapamycin complex 1 (TORC1). To study its role in mammals, we generated a Rheb knockout mouse. In contrast to mTOR or regulatory-associated protein of mTOR (Raptor) mutants, the inner cell mass of Rheb-/-embryos differentiated normally. Nevertheless, Rheb-/-embryos died around midgestation, most likely due to impaired development of the cardiovascular system. Rheb-/-embryonic fibroblasts showed decreased TORC1 activity, were smaller, and showed impaired proliferation. Rheb heterozygosity extended the life span of tuberous sclerosis complex 1-deficient (Tsc1-/-) embryos, indicating that there is a genetic interaction between the Tsc1 and Rheb genes in mouse. http://repub.eur.nl/res/pub/27352/ 2010-05-28T00:00:00Z RATIONALE: Heme oxygenase (HO)1 is an important modulator of physiological function with cytoprotective properties. Although HO1 has previously been associated with an improved survival of the vascular allograft in rat models in response to pharmaceutical induction of HO1 the exact mechanism by which HO1 exerts it protective function remains to be elucidated. OBJECTIVE: We sought to define the role of HO1 in dendritic cells (DCs) function that governs the alloimmune response underlying the development of transplantation associated vasculopathy. METHODS AND RESULTS: Loss of HO1 in DCs or by small interfering RNA silencing resulted in major histocompatibility complex class II (MHCII) upregulation by CIITA-driven transcriptional regulation and by STAT1 (signal transducers and activators of transcription 1) phosphorylation. As a result, increased MHCII alloantigen presentation by HO1 DCs directed the primary T-cell response preferentially toward a CD4 T-cell, rather than a CD8 T-cell reaction. In a murine model for transplantation arteriosclerosis, adoptive transfer of HO1 DCs before allograft transplantation was indeed associated with pronounced intragraft CD4 T-cell infiltration and increased IgG deposition, suggestive of an accelerated development of vasculopathy toward the chronic phase. The role of HO1 in DC-mediated T cell activation was further validated by inhibition of endogenous HO1 in allograft recipients. Inhibition of HO1 in DCs aggravated transplant arteriosclerosis development, by increasing intima hyperplasia, and by activation of a CD4 T cells allograft response, mediated by MHCII upregulation. CONCLUSIONS: These findings demonstrate that HO1 plays an important role in the genetic regulation of the vascular alloimmune response elicited by DCs. http://repub.eur.nl/res/pub/27678/ 2010-04-01T00:00:00Z The immune system plays a pivotal role in initiation and progression of atherosclerosis. Monocytes and T-lymphocytes are the first cells to enter the damaged endothelium. Differentiation of monocytes into macrophages and ingestion of lipids by these macrophages turning them into foam cells is a crucial step in the development of a fatty streak, the first sign of atherosclerosis. In recent years there has been accumulating evidence for the involvement of Toll like receptor 4, a pattern recognition receptor of the innate immune system, in the pathogenesis of atherosclerosis. Different cell types present in the atherosclerotic plaque express TLR4 and several pro-atherogenic ligands have been shown to activate TLR4.The innate immune system and the TLR signaling cascade may play an important role not only in the pathogenesis of atherosclerosis, but also in plaque destabilization. In this review, we discuss the role of TLR4 in the pathogenesis of atherosclerosis and vulnerable plaque development. http://repub.eur.nl/res/pub/28310/ 2010-02-01T00:00:00Z Plaque rupture and luminal thrombosis is the most common cause of coronary occlusion that leads to acute coronary syndromes. High-risk plaques, or vulnerable plaques, are defined as lesions that are prone to rupture, also known as thin cap fibroatheroma (TCFA), or lesions prone to erosion or with calcified cores. This review will focus mainly on the vulnerable plaque, which is thought to be the precursor of the thrombogenic or ruptured plaque. Heme oxygenase 1 (HO-1) protein expression is specifically increased in lesions with a vulnerable plaque phenotype resembling TCFAs and correlates with a rise in expression levels of intimal proinflammatory markers. Data from several human and animal studies imply an important function for HO-1 in the genetic regulation of early, as well as late atherogenesis, and plaque destabilization toward a vulnerable phenotype. Although a direct association between HO-1, vulnerable plaque development, and clinical outcome is for now missing, the correlations that have been reported for HO-1 and coronary artery disease point to a possible link. http://repub.eur.nl/res/pub/35054/ 2007-12-01T00:00:00Z Wall shear stress (WSS), the frictional force between blood and endothelium, is an important determinant of vascular function. It is generally assumed that WSS remains constant at a reference value of 15 dyn/cm2. In a study of small rodents, we realized that this assumption could not be valid. This review presents an overview of recent studies in large and small animals where shear stress was measured, derived from velocity measurements or otherwise, in large vessels. The data show that large variations exist within a single species (human: variation of 2-16 N/m2). Moreover, when we compared different species at the same location within the arterial tree, an inverse relationship between animal size and wall shear stress was noted. When we related WSS to diameter, a unique relationship was derived for all species studied. This relationship could not be described by the well-known r3law of Murray, but by the r2law introduced by Zamir et al. in 1972. In summary, by comparing data from the literature, we have shown that: (i) the assumption of a physiological WSS level of ∼15 dyn/cm2for all straight vessels in the arterial tree is incorrect; (ii) WSS is not constant throughout the vascular tree; (iii) WSS varies between species; (iv) WSS is inversely related to the vessel diameter. These data support an "r2law" rather than Murray's r3law for the larger vessels in the arterial tree. http://repub.eur.nl/res/pub/35539/ 2007-03-01T00:00:00Z We previously found that low shear stress (LSS) induces atherosclerotic plaques in mice with increased lipid and matrix metalloproteinase content and decreased vascular smooth muscle and collagen content. Here, we evaluated the role of chemokines in this process, using an extravascular device inducing regions of LSS, high shear stress, and oscillatory shear stress (OSS) in the carotid artery. One week of shear stress alterations induced expression of IFN-γ-inducible protein-10 (IP-10) exclusively in the LSS region, whereas monocyte chemoattractant protein-1 (MCP-1) and the mouse homolog of growth-regulated oncogene α (GRO-α) were equally upregulated in both LSS and OSS regions. After 3 weeks, GRO-α and IP-10 were specifically upregulated in LSS regions. After 9 weeks, lesions with thinner fibrous caps and larger necrotic cores were found in the LSS region compared with the OSS region. Equal levels of MCP-1 expression were observed in both regions, while expression of fractalkine was found in the LSS region only. Blockage of fractalkine inhibited plaque growth and resulted in striking differences in plaque composition in the LSS region. We conclude that LSS or OSS triggers expression of chemokines involved in atherogenesis. Fractalkine upregulation is critically important for the composition of LSS-induced atherosclerotic lesions. http://repub.eur.nl/res/pub/35615/ 2007-02-01T00:00:00Z BACKGROUND - Atherosclerosis is considered an inflammatory disease. Recent studies provided evidence for a predominant upstream location of plaque inflammation. The present study introduces a novel technique that evaluates the underlying mechanism of this spatial organization. METHODS AND RESULTS - In hypercholesterolemic rabbits, atherosclerosis of the infrarenal aorta was induced by a combination of endothelial denudation and a high-cholesterol diet (2% cholesterol for 2 months). At the time of death, aortic vessel segments were dissected and reconstructed with a new technique that preserved the original intravascular ultrasound-derived lumen geometry. This enabled us to study the spatial relation of histological markers like macrophages, smooth muscle cells, lipids, gelatinolytic activity, and oxidized low-density lipoprotein. Results showed a predominant upstream localization of macrophages and gelatinase activity. Colocalization studies indicated that gelatinase activity was associated with macrophages and smooth muscle cells. Further analysis revealed that this was caused by subsets of smooth muscle cells and macrophages, which were associated with oxidized low-density lipoprotein accumulation. CONCLUSIONS - Upstream localization of a vulnerable plaque phenotype is probably due to an accumulation of oxidized low-density lipoprotein, which activates/induces subsets of smooth muscle cells and macrophages to gelatinase production. http://repub.eur.nl/res/pub/8455/ 2004-01-01T00:00:00Z BACKGROUND: Childhood acute lymphoblastic leukemia (ALL) is curable with chemotherapy in approximately 80 percent of patients. However, the cause of treatment failure in the remaining 20 percent of patients is largely unknown. METHODS: We tested leukemia cells from 173 children for sensitivity in vitro to prednisolone, vincristine, asparaginase, and daunorubicin. The cells were then subjected to an assessment of gene expression with the use of 14,500 probe sets to identify differentially expressed genes in drug-sensitive and drug-resistant ALL. Gene-expression patterns that differed according to sensitivity or resistance to the four drugs were compared with treatment outcome in the original 173 patients and an independent cohort of 98 children treated with the same drugs at another institution. RESULTS: We identified sets of differentially expressed genes in B-lineage ALL that were sensitive or resistant to prednisolone (33 genes), vincristine (40 genes), asparaginase (35 genes), or daunorubicin (20 genes). A combined gene-expression score of resistance to the four drugs, as compared with sensitivity to the four, was significantly and independently related to treatment outcome in a multivariate analysis (hazard ratio for relapse, 3.0; P=0.027). Results were confirmed in an independent population of patients treated with the same medications (hazard ratio for relapse, 11.85; P=0.019). Of the 124 genes identified, 121 have not previously been associated with resistance to the four drugs we tested. CONCLUSIONS: Differential expression of a relatively small number of genes is associated with drug resistance and treatment outcome in childhood ALL.