1,720,956 research outputs found
Regulation of matrix-metalloproteinase 9 (MMP-9) in glomerular mesangial cells
No full textRemodeling of extracellular matrix (ECM) is an important physiologic feature of normal growth and development. In addition to this critical function in physiology many diseases have been associated with an imbalance of ECM synthesis and degradation. In the kidney, dysregulation of ECM turnover can lead to interstitial fibrosis, and glomerulosclerosis. The major physiologic regulators of ECM degradation in the glomerulus are the large family of zinc-dependent proteases, collectively refered to matrix metalloproteinases (MMPs). The tight regulation of most of these proteases is accomplished by different mechanisms, including the regulation of MMP gene expression, the processing and conversion of the inactive zymogen by other proteases such as serine proteases and finally the inhibition of active MMPs by endogenous inhibitors of MMPs, denoted as tissue inhibitors of metalloproteinases (TIMPs). Namely, the MMP-9 has been shown to be critically involved in the dysregulation of ECM turnover associated with severe pathologic conditions such as rheumatoid arthritis or fibrosis of lung, skin and kidney. In the present work I searched for a possible modulation of MMP-9 expression and/or activity in glomerular mesangial cells which are thought as key players of many inflammatory and non-inflammatory glomerular diseases. I found that various structurally different PPARalpha agonists such as WY-14,643, LY-171883 and fibrates potently suppress the cytokine-induced MMP-9 expression in renal MC. Furthermore, I demonstrate that the inhibition of MMP-9 expression by PPARalpha agonists was paralleled by a strong increase of cytokine-induced iNOS expression and subsequent NO formation, suggesting that PPARalpha-dependent effects on MMP-9 expression level primarily result from alterations in NO production which in turn reduces the MMP-9 mRNA half-life. Searching for the detailed mechanism of NO-dependent effects on MMP-9 mRNA stability, I found that NO either given from exogenous sources or endogenously produced increases the MMP-9 mRNA degradation by decreasing the expression of the mRNA stabilizing factor HuR. Furthermore, I demonstrate a reduction in the RNA-binding capacity of HuR containing complexes to MMP-9 ARE motifs in cells treated with NO. Since the reduction of HuR expression can be mimicked by the cGMP analog 8-Bromo-cGMP, I suggest that NO reduces in a cGMP-dependent manner the expression of HuR. Finally, I elucidated the modulatory effect of extracellular nucleotides, mainly ATP, on cytokine-triggered MMP-9 expression. Interestingly, I found that in contrast to NO, gamma-S-ATP the stable analog of ATP potently amplifies the IL-beta mediated MMP-9 expression. The increase in mRNA stability was paralleled by an increase in the nuclear-cytosolic shuttling of the mRNA stabilizing factor HuR. Furthermore, I demonstrate an increase in the RNA-binding capacity of HuR containing complexes to the 3'-UTR of MMP-9 by ATP. In summary, the data presented here may help to find new targets (posttranscriptional regulation) that could be used to manipulate or modulate the expression of not only MMP-9 but also other genes regulated on the level of mRNA stability.Umbauprozesse der Extrazellulären Matrix (ECM) spielen eine wichtige Rolle für normale Wachstums- und Entwicklungsprozesse. In der Niere kann der fehlerhafte Umsatz von ECM beispielsweise zur interstitiellen Fibrose und Glomerulosklerose führen. Zu den wichtigsten physiologischen Regulatoren des Abbaus von ECM im Glomerulus zählen die Zink-abhängigen Proteasen, die zur Familie der Matrixmetalloproteasen (MMPs) zusammengefasst werden. In der vorliegenden Arbeit untersuchte ich schwerpunktmässig nach Möglichkeiten die MMP-9 Expression und/oder MMP-Aktivität in glomerulären Mesangiumzellen zu verändern. Mesangiumzellen gelten als Hauptakteure von glomerulären Erkrankungen mit entzündlichen- als auch nicht entzündlichen Genese. Wie ich gezeigt habe, sind unterschiedliche PPARalpha Agonisten wie beispielsweise WY-14,643, LY-171883 und Fibrate in der Lage, die Zytokin-induzierte MMP-9 Expression in Mesangiumzellen potent zu hemmen. Weiterhin konnte von mir gezeigt werden, dass die Hemmung der MMP-9 Expression durch PPARalpha Aktivatoren mit einer Steigerung der iNOS Expression und der unmittelbaren Steigerung der NO Freisetzung einhergeht. Interessanterweise konvertieren die hemmenden Effekte der PPARalpha Aktivatoren in der Gegenwart eines iNOS Hemmstoffes zu einer massiven Verstärkung der Zytokin-induzierten MMP-9 Expression was darauf hinweist, dass die PPARalpha-vermittelten Effekte in erster Linie durch Veränderungen der NO Synthese hervorgerufen werden. Auf der Suche nach dem Mechanismus der NO-vermittelten Effekte auf die MMP-9 Expression konnte ich zeigen, dass sowohl exogen zugeführtes NO als auch über eine Induktion der iNOS entstandenes NO, in der Lage ist, den Abbau von MMP-9 mRNA durch eine Expressionshemmung des mRNA Stabilitätsfaktor HuR zu beschleunigen. In einem weiteren Projekt untersuchte ich, ob extrazellulären Nukleotide in der Lage sind, einen modulierenden Einfluss auf die Zytokin-induzierte MMP-9 Expression auszuüben. Ich konnte zeigen, dass das chemisch stabilisierte ATP-Analog gamma-S ATP im Unterschied zu NO in der Lage ist, den IL- 1beta vermittelten Anstieg der MMP-9 in potenter Weise zu verstärken. Der Anstieg der mRNA Stabilität korreliert mit einer Zunahme des Transports von HuR aus dem Zellkern in das Zytoplasma. Der verstärkte Export von HuR aus dem Zellkern war verbunden mit der verstärkten RNA Bindungsaffinität von HuR-haltigen Komplexen an AU-reiche Sequenzen innerhalb des 3'-untranslatierten Bereichs (3'-UTRs) des MMP-9 Gens. Zusammenfassend könnten die vorliegende Arbeit helfen, neue (posttranskriptionellen) Ansätzen zu finden, die eine spezifische Manipulation von MMP-9 und anderen auf Ebene der mRNA Stabilität regulierten Genen, ermöglichen
Posttranslational modification of the AU-rich element binding protein HuR by protein kinase Cdelta elicits angiotensin II-induced stabilization and nuclear export of cyclooxygenase 2 mRNA
No full textThe mRNA stabilizing factor HuR is involved in the posttranscriptional regulation of many genes, including that coding for cyclooxygenase 2 (COX-2). Employing RNA interference technology and actinomycin D experiments, we demonstrate that in human mesangial cells (hMC) the amplification of cytokine-induced COX-2 by angiotensin II (AngII) occurs via a HuR-mediated increase of mRNA stability. Using COX-2 promoter constructs with different portions of the 3' untranslated region of COX-2, we found that the increase in COX-2 mRNA stability is attributable to a distal class III type of AU-rich element (ARE). Likewise, the RNA immunoprecipitation assay showed AngII-induced binding of HuR to this ARE. Using the RNA pulldown assay, we demonstrate that the AngII-caused HuR assembly with COX-2 mRNA is found in free and cytoskeleton-bound polysomes indicative of an active RNP complex. Mechanistically, the increased HuR binding to COX-2-ARE by AngII is accompanied by increased nucleocytoplasmic HuR shuttling and depends on protein kinase Cdelta (PKCdelta), which physically interacts with nuclear HuR, thereby promoting its phosphorylation. Mapping of phosphorylation sites identified serines 221 and 318 as critical target sites for PKCdelta-triggered HuR phosphorylation and AngII-induced HuR export to the cytoplasm. Posttranslational modification of HuR by PKCdelta represents an important novel mode of HuR activation implied in renal COX-2 regulation
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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