Publications by authors named "Petra Keul"

The erythrocyte S1P transporter Mfsd2b is also expressed in the heart. We hypothesized that S1P transport by Mfsd2b is involved in cardiac function. Hypertension-induced cardiac remodeling was induced by 4-weeks Angiotensin II (AngII) administration and assessed by echocardiography.

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Sphingosine-1-phosphate and its receptors (S1PRs) are involved in several diseases such as auto immunity, inflammation and cardiovascular disorders. The S1P analogue fingolimod (Gilenya®) is currently in use for the treatment of relapsing multiple sclerosis. S1PRs are also promising targets for clinical molecular imaging in vivo.

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Sphingosine-1-phosphate (S1P) plays multiple roles in bone metabolism and regeneration. Here, we have identified a novel S1P-regulated osteoanabolic mechanism functionally connecting osteoblasts (OBs) to the highly specialized bone vasculature. We demonstrate that S1P/S1PR3 signaling in OBs stimulates vascular endothelial growth factor a (VEGFa) expression and secretion to promote bone growth in an autocrine and boost osteogenic H-type differentiation of bone marrow endothelial cells in a paracrine manner.

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Red blood cells (RBC) are the major carriers of sphingosine-1-phosphate (S1P) in blood. Here we show that variations in RBC S1P content achieved by altering S1P synthesis and transport by genetic and pharmacological means regulate glucose uptake and metabolic flux. This is due to S1P-mediated activation of the catalytic protein phosphatase 2 (PP2A) subunit leading to reduction of cell-surface glucose transporters (GLUTs).

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Antiplatelet medication is standard of care in acute myocardial infarction (AMI). However, it may have obscured beneficial properties of the activated platelet secretome. We identify platelets as major source of a sphingosine-1-phosphate (S1P) burst during AMI, and find its magnitude to favorably associate with cardiovascular mortality and infarct size in STEMI patients over 12 months.

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Aims: Therapeutic options targeting post-ischaemic cardiac remodelling are sparse. The bioactive sphingolipid sphingosine-1-phosphate (S1P) reduces ischaemia/reperfusion injury. However, its impact on post-ischaemic remodelling independently of its infarct size (IS)-reducing effect is yet unknown and was addressed in this study.

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Altered plasma sphingosine-1-phosphate (S1P) concentrations are associated with clinical manifestations of atherosclerosis. However, whether long-term elevation of endogenous S1P is pro- or anti-atherogenic remains unclear. Here, we addressed the impact of permanently high S1P levels on atherosclerosis in cholesterol-fed apolipoprotein E-deficient () mice over 12 weeks.

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Article Synopsis
  • Prediction of transitions from stable coronary conditions to acute syndromes remains challenging due to factors like vascular inflammation and thrombosis, which can lead to severe heart damage.
  • A new nano-tracer platform has been developed that visually tracks signs of coronary inflammation and atherothrombosis in mice, helping to identify high-risk areas before a heart attack occurs.
  • This innovative approach could potentially be applied to monitor other diseases as well, offering significant predictive capabilities for various medical conditions.
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Aims/hypothesis: People with diabetes have an increased cardiovascular risk with an accelerated development of atherosclerosis and an elevated mortality rate after myocardial infarction. Therefore, cardioprotective effects of glucose-lowering therapies are of major importance for the pharmacotherapy of individuals with type 2 diabetes. For sodium-glucose cotransporter 2 inhibitors (SGLT2is), in addition to a reduction in blood glucose, beneficial effects on atherosclerosis, obesity, renal function and blood pressure have been observed.

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Background And Purpose: Osteoporosis is a worldwide epidemic but pharmacological agents to stimulate new bone formation are scarce. We have shown that increasing tissue levels of sphingosine-1-phosphate (S1P) by blocking its degradation by the S1P lyase has pronounced osteoanabolic effect in mouse osteoporosis models by stimulating osteoblast differentiation through the S1P receptor 2 (S1P2). However, S1P lyase inhibitors have side effects complicating potential clinical use.

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Sphingolipid and cholesterol metabolism are closely associated at the structural, biochemical, and functional levels. Although HDL-associated sphingosine-1-phosphate (S1P) contributes to several HDL functions, and S1P signaling regulates glucose and lipid metabolism, no study has addressed the involvement of S1P in cholesterol efflux. Here, we show that sphingosine kinase (Sphk) activity was induced by the LXR agonist 22(R)-hydroxycholesterol and required for the stimulation of ABCA1-mediated cholesterol efflux to apolipoprotein A-I.

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Dysfunctional HDL is associated with coronary artery disease (CAD), but its effect on inflammation in vascular smooth muscle cells (VSMCs) in atherosclerosis is unknown. We investigated the effect of healthy human HDL and CAD-HDL on TNF-α-driven inflammation in VSMCs and examined whether HDL-associated sphingosine-1-phosphate (HDL-S1P) could modulate inflammation with the aim of designing novel HDL-based anti-inflammatory strategies. Healthy human HDL, human CAD-HDL, and mouse HDL were isolated by ultracentrifugation, S1P was measured by liquid chromatography-tandem mass spectrometry, and TNF-α-induced inflammation was characterized by gene expression and analysis of NF-κB-dependent signaling.

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Sphingosine-1-phosphate (S1P) signaling influences bone metabolism, but its therapeutic potential in bone disorders has remained unexplored. We show that raising S1P levels in adult mice through conditionally deleting or pharmacologically inhibiting S1P lyase, the sole enzyme responsible for irreversibly degrading S1P, markedly increased bone formation, mass and strength and substantially decreased white adipose tissue. S1P signaling through S1P potently stimulated osteoblastogenesis at the expense of adipogenesis by inversely regulating osterix and PPAR-γ, and it simultaneously inhibited osteoclastogenesis by inducing osteoprotegerin through newly discovered p38-GSK3β-β-catenin and WNT5A-LRP5 pathways.

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The hepatocyte nuclear factor (HNF) family regulates complex networks of metabolism and organ development. Human mutations in its prototypical member HNF1A cause maturity-onset diabetes of the young (MODY) type 3. In this study, we identified an important role for HNF1A in the preservation of erythrocyte membrane integrity, calcium homeostasis, and osmotic resistance through an as-yet unrecognized link of HNF1A to sphingolipid homeostasis.

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Background: Cardiovascular magnetic resonance with gadolinium-based contrast agents has established as gold standard for tissue characterization after myocardial infarction (MI). Beyond accurate diagnosis, the value of cardiovascular magnetic resonance to predict the outcome after MI has yet to be substantiated.

Methods And Results: Recent cardiovascular magnetic resonance approaches were systematically compared for quantification of tissue injury and functional impairment after MI using murine models with permanent left anterior descending coronary artery ligation (n=14) or 50 minutes ischemia/reperfusion (n=13).

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Objective: Sphingosine-1-Phosphate (S1P) is a bioactive sphingolipid with important functions in immunity, inflammation and cardiovascular biology. S1P is associated with prevalence and severity of coronary artery disease and myocardial infarction. However, its relevance in ischemic cardiomyopathy is unknown.

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Article Synopsis
  • Sphingosine-1-phosphate (S1P) and its receptor 1 (S1P1) are crucial for heart cell function and protecting against heart injury, but the specific role of S1P1 in living organisms was not well understood.
  • Deleting S1P1 in heart cells of mice led to heart disease, poor treatment response, and early death, revealing that S1P1 is essential for regulating calcium levels in these cells.
  • The study highlighted that S1P1 also affects heart muscle contraction and relaxation, interacts with key proteins, and is necessary for the heart's natural defense mechanisms, suggesting new ways to treat heart conditions.
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The hepatocyte NF (HNF) family of transcription factors regulates the complex gene networks involved in lipid, carbohydrate, and protein metabolism. In humans, HNF1A mutations cause maturity onset of diabetes in the young type 3, whereas murine HNF6 participates in fetal liver B lymphopoiesis. In this study, we have identified a crucial role for the prototypical member of the family HNF1A in adult bone marrow B lymphopoiesis.

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The sphingosine-1-phosphate receptor type 1 (S1P1) is involved in fundamental biological processes such as regulation of immune cell trafficking, vascular barrier function and angiogenesis. This Letter presents multistep syntheses of various fluorine substituted 12-aryl analogues of the drug fingolimod (FTY720) and a seven-steps route to 2-amino-17,17-difluoro-2-(hydroxymethyl)heptadecan-1-ol. In vitro and in vivo tests proved all these compounds as potent S1P1 receptor agonists.

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Background: Sphingosine-1-phosphate (S1P) is a constituent of high-density lipoproteins (HDL) that contributes to their beneficial effects. We have shown decreased HDL-S1P in coronary artery disease (CAD) but its functional relevance remains unclear.

Objectives: This study investigated the functional consequences of reduced HDL-S1P content in CAD and tested if increasing it may improve or restore HDL function.

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Sphingosine-1-phosphate (S1P) participates in inflammation; however, its role in leukocyte rolling is still unclear. Here we use intravital microscopy in inflamed mouse cremaster muscle venules and human endothelial cells to show that S1P contributes to P-selectin-dependent leukocyte rolling through endothelial S1P receptor 3 (S1P3) and Gαq, PLCβ and Ca(2+). Intra-arterial S1P administration increases leukocyte rolling, while S1P3 deficiency or inhibition dramatically reduces it.

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Sphingosine-1-phosphate (S1P) is a lysophospholipid that evokes a variety of biological responses via stimulation of a set of cognate G-protein coupled receptors (GPCRs): S1P1-S1P5. S1P and its receptors (S1PRs) play important roles in the immune, cardiovascular, and central nervous systems and have also been implicated in carcinogenesis. Recently, the S1P analogue Fingolimod (FTY720) has been approved for the treatment of patients with relapsing multiple sclerosis.

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Sphingosine-1-phosphate (S1P) influences various fundamental biological processes by interacting with a family of five G protein-coupled receptors (S1P1-5). FTY720, a sphingosine analogue, which was approved for treatment of relapsing forms of multiple sclerosis, is phosphorylated in vivo and acts as an agonist of four of the five S1P receptor subtypes. Starting from these lead structures we developed new agonists for the S1P1 receptor.

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Sphingosine-1-phosphate (S1P) receptors play major roles in cardiovascular, immunological and neurological diseases. The recent approval of the sphingolipid drug Fingolimod (Gilenya®), a sphingosine-1-phosphate agonist for relapsing multiple sclerosis, in 2010 exemplifies the potential for targeting sphingolipids for the treatment of human disorders. Moreover, non-invasive in vivo imaging of S1P receptors that are not available till now would contribute to the understanding of their role in specific pathologies and is therefore of preclinical interest.

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