1,721,072 research outputs found
Cytoprotective activated protein C averts Nlrp3 inflammasome induced ischemia reperfusion injury via mTORC1 inhibition
Full text linkCytoprotection by activated protein C (aPC) following ischemia-reperfusion injury (IRI) is associated with apoptosis inhibition. However, IRI is hallmarked by inflammation and hence conceptually cell-death forms disjunct from immunologically silent apoptosis are more likely to be relevant. As pyroptosis, cell death resulting from inflammasome activation, is typically observed in IRI we speculated that aPC ameliorates IRI by inhibiting inflammasome activation. Here we analyzed the impact of aPC on inflammasome activity in myocardial and renal IRI. aPC treatment reduced infarct size and Nlrp3 inflammasome activation in mice. Kinetic in vivo analyses revealed that inflammasome activation preceded myocardial injury and apoptosis. The constitutively active Nlrp3A350V mutant abolished aPC’s protective effect, demonstrating that Nlrp3 suppression is required for aPC-mediated protection from IRI. In vitro aPC inhibited inflammasome activation via PAR-1 and mTORC1 signaling. Inhibiting PAR-1 signaling abolished aPC’s ability to restrict inflammasome activity and myocardial infarction, while specifically inhibiting aPC’s anticoagulant properties did not impair aPC’s effect on inflammasome activation. Targeting biased PAR-1 signaling via parmodulin-2 restricted inflammasome activation and limited myocardial IRI. aPC’s renal tissue protective effect was likewise dependent on Nlrp3 inflammasome suppression. These studies reveal that aPC protects from IRI by restricting mTORC1 dependent inflammasome activation and that mimicking biased aPC-PAR1 signaling using parmodulins may be a feasible therapeutic approach to combat IRI
Activated protein C reverses epigenetically sustained p66Shc expression in plaque-associated macrophages in diabetes mellitus
Full text linkImpaired activated protein C (aPC) generation is associated with atherosclerosis and diabetes mellitus. Diabetes-associated atherosclerosis is characterized by the hyperglycaemic memory, e.g. failure of disease improvement despite attenuation of hyperglycaemia. Therapies reversing the hyperglycaemic memory are lacking. Here we demonstrate that hyperglycaemia, but not hyperlipidaemia, induces the redox-regulator p66Shc and reactive oxygen species (ROS) in macrophages. p66Shc expression, ROS generation, and a proatherogenic phenotype are sustained despite restoring normoglycemic conditions. Inhibition of p66Shc abolishes this sustained proatherogenic phenotype, identifying p66Shc-dependent ROS in macrophages as a key mechanism conveying the hyperglycaemic memory. The p66Shc-associated hyperglycaemic memory can be reversed by aPC via protease-activated receptor-1 signalling. aPC reverses glucose-induced CpG hypomethylation within the p66Shc promoter by induction of the DNA methyltransferase-1 (DNMT1). Thus, epigenetically sustained p66Shc expression in plaque-macrophages drives the hyperglycaemic memory, which – however – can be reversed by aPC. This establishes that reversal of the hyperglycaemic memory in diabetic atherosclerosis is feasible
The regulation of endoplasmic reticulum stress by activated protein C in diabetic nephropathy
Full text linkDiabetic nephropathy is the leading cause of chronic kidney disease as well as the primary complication of diabetes worldwide. Although, the molecular function of endoplasmic reticulum (ER) stress in diabetes mellitus (DM) is well-established in the liver and the pancreas, the role of ER stress in diabetic nephropathy remained unknown when starting this project. We uncovered important pathophysiological consequences of insulin resistance and hyperglycemia towards maladaptive ER stress and its contributions to the progression of diabetic nephropathy (dNP). This study establishes causality between defective insulin signaling leading to maladaptive ER stress in podocytes and impaired kidney function in DM. Searching for potential pathways compensating for impaired insulin signaling, we identified a new role of the coagulation system. Coagulation protease signaling rescues defective insulin signaling in podocytes, thus, protecting these cells from the detrimental effects of hyperglycemia. Specifically, the coagulation protease activated protein C (aPC), known for its pleiotropic cytoprotective effects, activates the inositol-requiring enzyme 1α (IRE-1α) - spliced X-box-binding protein 1 (sXBP1) signaling arm of the adaptive unfolded protein response (UPR), restoring ER homeostasis. Insulin- and aPC-dependent signaling, despite acting through disjunct receptors, both signal through p85α/β- phosphatidylinositol 3-kinase (PI3K) to induce nuclear localization of sXBP1. Development of therapeutics that mimic aPC-signaling and restore ER homeostasis, or alterantive approaches to restore ER homeostasis in insulin resistant tissues constitute a new therapeutic approach in dNP
Biomarker zur Mortalitätsprädiktion im infarktbezogenen kardiogenen Schock
Full text linkHintergrund:
Trotz der intensiven Behandlungsmöglichkeiten im infarktbezogenen kardiogenen Schock sind hohe Mortalitätsraten (ca 40-50%) weiterhin zu beobachten. Eine Reihe klinischer, angiografischer und laborchemischer Parameter sind hinsichtlich ihrer prognostischen Aussagekraft im Einzelnen oder in kleineren Gruppen untersucht worden. Bisherige Mortalitätsprädiktionsmodelle benötigen das Einholen klinischer/anamnestischer, angiografischer und biochemischer Variablen, was zu einer erschwerten Anwendbarkeit im klinischen Alltag führt. Eine frühe und valide Risikostratifizierung ist notwendig um weitere Therapieentscheidungen zu treffen und unterschiedliche Risikopopulationen für zukünftige klinische Studien zu identifizieren.
Ziele:
In der vorliegenden Arbeit sollte unter Einbezug einer großen Bandbreite von klinischen Parametern, sowie neuen und etablierten Biomarkern, ein Risikoscore entwickelt werden, der nur die relevantesten Prädiktoren der 30-Tage-Mortalität einschließt, um so ein einfach anzuwendendes Tool zur Risikostratifizierung zu erstellen.
Methoden:
Der Risikoscore wurde anhand von 458 Patient:innen aus der multizentrischen randomisierten CULPRIT-SHOCK Studie mittels Least Absolute Shrinkage Selection Operator (LASSO), einem penalisierten multivariaten logistischen Regressionsmodell entwickelt. Als externe Validierungskohorte dienten 163 Patient:innen der IABP-SHOCK II Studie. Die prädiktive Aussagekraft wurde in interner, intern-extern (zeitlicher) und externer Validierung durch Diskrimination (AUC, c-Statistik), Kalibration, Klinischer Nutzen (decision curve analysis) und Kaplan-Meier-Kurven analysiert. Anschließend wurde der Risikoscore mit bisherigen Prognosemodellen hinsichtlich der diskriminativen Kraft (AUC, c-Statistik) verglichen.
Ergebnisse:
Aus 58 Kandidatenvariablen (30 klinische Parameter, 28 Biomarker) wurden nur vier als relevante Prädiktoren identifiziert. Aus Cystatin C, Laktat, Interleukin-6 und NTproBNP wurde somit der CLIP Score gebildet. In der internen Validierung wurde eine AUC von 0.82 (95% CI: 0.77-0.85) erreicht, in der intern-externen (zeitlichen) Validierung eine AUC von 0.83 (95% CI 0.76 – 0.90). Die externe Validierung ergab eine AUC von 0.73 (95% CI: 0.65 – 0.80). Es zeigte sich eine gute Kalibrierung und ein großer positiver Nettobenefit im klinischen Nutzen. Der CLIP Score überragte den SAPS II risk score (0.830 95% CI 0.765-0.896 vs 0.626 95% CI 0.528-0.725; P<0.001) und den IABP-SHOCK II risk score (0.830 95% CI 0.765-0.896 vs 0.761 95% CI 0.685-0.837; P=0.03) in der intern-externen (zeitlichen) Validierungskohorte.
Zusammenfassung/Schlussfolgerung:
Wir entwickelten und validierten einen reinen Biomarker Risikoscore zur Vorhersage der 30-Tage-Mortalität im infarktbezogenen kardiogenen Schock. Er stellt ein wertvolles Tool zur Unterstützung bei Entscheidungen für Therapieeskalation oder –deeskalation dar. Er kann automatisch aus vier rund um die Uhr verfügbaren Routinebiomarkern berechnet werden und übertrifft bisherige Risikoscores.:Einführung 3
1. Akuter Myokardinfarkt 3
2. Infarktbezogener kardiogener Schock 5
2.1. Definiton, Ätiologie, Epidemiologie und Klassifikation 5
2.2. Therapieansätze 8
2.3. Die CULPRIT-SHOCK Studie 10
2.4. Bisherige Biomarkeruntersuchungen 10
2.5. Bisherige Prognosemodelle 11
3. Rationale der vorliegenden Studie 14
Formatierte Publikation 15
Zusammenfassung 25
Literaturverzeichnis 28
Anlagen (Abkürzungsverzeichnis, Supplemental Materials der Publikation) 33
Darstellung des eigenen Beitrags 55
Selbstständigkeitserklärung 59
Lebenslauf 60
Publikationen 62
Danksagungen 6
Role of eosinophils in experimental autoimmune encephalomyelitis
Full text linkExperimental autoimmune encephalomyelitis (EAE) is the rodent model of multiple sclerosis (MS), a chronic autoimmune neuroinflammatory disease that has a devastating impact on various neurological functions of the patients. The hallmarks of both, MS and EAE, are neuroinflammation, demyelination and neuroaxonal degeneration. Various types of lymphoid and myeloid cells were shown to infiltrate the central nervous system and to participate in disease pathology. However, the role of eosinophil granulocytes has been less explored thus far. An early study showed that eosinophils infiltrate into the spinal cord of EAE mice and suggested their role in the disease progression. Recently, it was reported that eosinophils can play a protective role against EAE when mice are treated with an extract from helminths. Furthermore, it was shown that EAE development is not altered in mice deficient for interleukin-5, an important eosinophil pro-survival factor. Taken together, the role of eosinophils in EAE is currently unclear and needs to be investigated in detail.
In the present study, we use the active model of EAE, whereby we immunized the C57BL/6 mouse strain with MOG35-55 peptide emulsified in the complete Freund’s adjuvant, in order to study a possible contribution of eosinophils to the disease pathology. Using the flow cytometry and RT-qPCR analysis of the spinal cord, we show that eosinophils infiltrate into the tissue in the course of EAE. The infiltration is likely driven by eosinophil chemoattractants, such as eotaxin-1, as the concentration of the latter was increased in the spinal cord during EAE, as shown on mRNA and protein level.
Moreover, detailed flow cytometry analysis of spinal cord eosinophils revealed that they show signs of activation, namely an increase in CD11b and decrease in CCR-3 surface expression. Furthermore, we observed signs of degranulation of spinal cord eosinophils in EAE which was measured as a decrease of the side scatter parameter and an upregulation of CD63 surface expression. These data suggest a potential role of eosinophils in the pathology of EAE. In order to elucidate whether eosinophils are important for the disease development, eosinophil-deficient mice were subjected to EAE and the clinical development of the disease was observed. For this purpose, we used two independent models of eosinophil deficiency - ΔdblGATA1 and interleukin-5-depleted mice. ΔdblGATA1 mice are a genetically manipulated mouse strain bearing a deletion in GATA1 promoter that causes a specific depletion of eosinophils. Interestingly, clinical development of EAE was not affected in these mice when compared to their wild-type controls. As a next step, we depleted eosinophils by injecting wild-type mice with an antibody against the eosinophil pro-survival factor interleukin-5 in order to reduce eosinophil numbers in the effector phase of EAE. In accordance with the result from the experiment with ΔdblGATA1 mice, EAE progression was not altered in the eosinophil-depleted mice when compared to mice that were injected with an isotype control antibody. Further, we analyzed the neuroinflammation and demyelination in the spinal cord of
4ΔdblGATA1 mice subjected to EAE.
Specifically, the infiltration of inflammatory cell populations, including CD4 and CD8 T cells, neutrophils and macrophages, was assessed by flow cytometry. In agreement with the unchanged clinical EAE development, inflammatory cell infiltration was not affected in ΔdblGATA1 mice. Furthermore, we analyzed expression of pro-inflammatory cytokines in the spinal cord of ΔdblGATA1 mice subjected to EAE in order to better characterize the inflammatory status. No significant changes were detected further confirming that eosinophils do not contribute to neuroinflammation in EAE. Finally, we assessed the demyelination in the spinal cord of ΔdblGATA1 EAE mice using luxol fast blue staining to detect myelin. In accordance with the unaffected clinical development and inflammatory status, we did not observe any difference in the spinal cord demyelination in ΔdblGATA1 mice when compared to their wild-type littermates.
Taken together, although eosinophils infiltrate into the spinal cord of EAE mice and are activated and degranulate therein, they are dispensable for EAE development
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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