Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 212-224). Also available in electronic version. Access restricted to campus users.

Severe Acute Pancreatitis (SAP) is the rapid onset of inflammation within the pancreatic organ. Unlike the milder form of this illness, SAP is associated with a high mortality and morbidity. No significant reduction in the outcomes of this disease has been made since the implementation of organ supportive management over two decades ago. This is due to difficulties in distinguishing between the milder form of the disease in the early period of the onset of symptoms when clinical intervention is most likely to prevent complications and death. Clinical equipoise exists in the management of one of these complications, namely Abdominal Compartment Syndrome (ACS) as the conventional management of surgery runs contrary to published evidence showing early abdominal surgery deteriorates clinical outcomes. Aims: Validation of the potential use of the Early Warning Score (EWS) as a predictor of SAP. Evaluation of the evidence for recombinant human protein C (Xigris™) in the early treatment of SAP. Determination of the safety profile of Xigris™ when given early in SAP. To determine if surgical management of ACS in SAP is of significant benefit compared to conventional management alone. Methods: Four studies were performed: A prospective observational study assessing the median EWS of patients admitted with acute pancreatitis; a systematic review of published evidence reporting the use of Xigris™ in SAP; a prospective cohort study using a 24 hour infusion of Xigris™ early in patients diagnosed with SAP and a pilot randomized controlled trial of targeted decompression in patients with ACS complicating SAP. Results: The highest EWS values for 130 patients with acute pancreatitis within the first 3 days of admission were not shown to have significant sensitivity and specificity in predicting an unfavourable outcome. A review of the published literature between from January 1985 to January 2011 supported the further investigation of Xigris™ as a treatment for SAP. No significant adverse events or differences in outcomes were evident in 19 patients who received a 24-hour infusion of Xigris™ early in SAP compared to matched historical controls. 22 patients were screened for the development of ACS. No patient developed ACS and consequently no randomization to either treatment arm was possible. Conclusion: With the recent advent of an updated classification system for the severity of acute pancreatitis, further prospective evaluation of the use of EWS in clinical practice is warranted. The results of the Phase 1 clinical trial of Xigris™ didnot reveal significant safety issues that might preclude the further investigation of Xigris™ as a specific therapy early in the onset of SAP. The absence of ACS inpatients with SAP lends support to a theory that ACS may be an epiphenomenon in the course of SAP.

Sepsis has been defined as a systemic response to an infection. With an incidence of 3 per 1000 population per year or about 750 000 cases a year, this syndrome ranks as the 10th leading cause of death in the United States (1). Increasing severity of sepsis correlates with increasing mortality, which rises from 30-40% for severe sepsis up to 40-60% for septic shock. This thesis examines the effectiveness of adjunctive therapies, including activated protein C, hypercapnia and acidosis, and sodium selenite, in a clinically relevant ovine model of septic shock. The results from these studies can provide valuable information for future clinical trials on sepsis.<p>This thesis is divided into four sections: 1) sepsis overview; 2) an autologous fecal peritonitis model in sheep and its evaluation; 3) the series of studies on adjunctive therapeutics; and 4) ongoing studies and future perspective.<p>In the first section, a broad overview gives a rough introduction to delineate many aspects of sepsis syndrome such as terminology, etiology, epidemiology, pathophysiology and current guidelines for management. Hemodynamics in sepsis are especially elaborated since these are major observations throughout the studies presented later.<p>In the second section, the general characteristics of the sepsis models used in this thesis are elucidated. Data on hemodynamics, lung mechanics, gas exchange, etc. are presented to feature the ovine peritonitis model. The results of laboratory examinations for hematology, coagulation, bacteriology, biochemistry and hormonology are also presented. And then, I review currently used sepsis models with regards to their advantages and disadvantages.<p>The third section discusses three studies with their objectives, the methods used, the major findings, and the potential clinical implications.<p>9<p>1) Beneficial effects of recombinant human activated protein C in experimental septic shock. Activated protein C has a multitude of beneficial effects in severe sepsis and septic shock, including anti-inflammation, anti-coagulation, profibrinolysis, anti-apoptosis and endothelial protection. A clinical Phase III trial demonstrated that the administration of recombinant human activated protein C improved survival in patients with severe sepsis. However, doubts on the protective effects of activated protein C have persisted and been refueled by the recently published negative trials in less severely ill patients and in children. In the light of these ambiguities and uncertainties, we reinvestigated the effects of activated protein C in experimental septic shock.<p>2) Acute hypercapnia improves indices of tissue oxygenation more than dobutamine in septic shock. Hepercapnia has been found to possess beneficial effects in diverse acute inflammatory states independent of protective lung mechanics. To prove the hypothesis that acute hypercapnia has similar or superior hemodynamic effects to those of a dobutamine infusion, which may be particularly relevant in the presence of hemodynamic instability associated with respiratory failure, we investigated the effects of hypercapnia, which induced by inspiring extrinsic carbon dioxide in experimental septic shock.<p>3) High bolus dose of sodium selenite prolongs survival in an ovine model of septic shock. Selenite has both pro- and anti-oxidant effects. The administration of high dose sodium selenite may improve survival in septic shock patients. The benefit may be greater with the administration of a bolus (to achieve higher concentrations) rather than a continuous infusion. To test this hypothesis, we examined the effects of a high dose bolus administration of sodium selenite in experimental septic shock.<p>The fourth and final section talks about currently ongoing studies and offers some perspective on future direction. / Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

Initiation of transcription is a major step in the regulation of gene expression. A dominant theme in regulation of gene expression lies in understanding the mechanism involved in selective expression of the genes in response to external or internal stimuli. Gene regulatory proteins bind DNA at specific sites either cognate to the promoters they act upon or at a distance, thereby exerting their effect by turning on (activation) or turning off (repression) the genes. Response of these factors to the environmental signals is further achieved by the DNA binding affinity of the transcription factors that can be modulated by small ligands, concentrations of which may fluctuate in response to nutrient availability and stress. Bacteriophages achieve a high degree of efficiency in gene expression by evolving elegant strategies of transcriptional control. mom gene of enterobacteriophage Mu serves as an excellent model to understand this elaborate regulation of gene expression. The gene encodes a unique DNA modification function that confers an anti-restriction phenotype to the phage genome. Though dispensable for phage growth, it is fascinating in two respects (i) a novel modification; (ii) regulation follows a complex scheme without precedence in prokaryotes. mom is the last gene to be expressed during the phage lytic life cycle. Premature expression of the gene is deleterious to both host and phage and hence it is under a complex regulatory network. Dam methylase, a host encoded protein acts as a positive regulator of gene expression, an example where methylation has been shown to play a positive role in regulating tranascription. OxyR, another host encoded protein negatively regulates mom gene expression. Dam methylation prevents the binding OxyR to its site located in the mom regulatory region. The regulatory interplay also involves two phage encoded proteins. C, a middle gene product is essential for transcriptional switch from middle to late genes and Com, a late gene product, for enhancing translation of mom mRNA. Thus, C and Com serve as transcriptional and translational activators of mom gene expression. Pmom is a weak promoter with both -10 and -35 elements away from consensus and a sub-optimal 19 bp spacer element encompassing a stretch of 6T residues that act as negative elements. ‘T stretch’ is known to induce a kink in the DNA. The sub-optimal spacer region makes the promoter elements out of phase and RNAP by itself cannot bind at mom promoter. C protein exerts its effect in activation in a multistep mechanism. The protein binds DNA as a dimer overlapping the promoter and unwinds the DNA, realigning the promoter elements, thus recruiting the RNAP. In the next step, it enhances the promoter clearance by the enzyme, thus enhancing the rate of productive transcription. With this prevailing knowledge on C mediated mom gene expression, the present thesis work describes the experiments carried out to further understand the molecular mechanism of second step activation at Pmom. Genetic and biochemical analysis were carried out to identify the interacting surface of C protein on RNAP. Subsequently, studies have been extended to understand the C mediated transactivation at other late promoters- lys, I, P, which encode for the lysis and morphogenetic functions of the phage. Finally, Mg2+ coordinating residues in C protein were identified to decipher the ligand induced conformational changes in the activator protein required for its transactivator function. Chapter I, a general introduction to the thesis, deals with the detailed discussion on gene expression and its regulatory mechanisms. RNA polymerase (RNAP) being the central molecule of gene expression (transcription) its organization and assembly are discussed. With the availability of the high resolution crystal structures of bacterial RNAP, an in-depth review on RNAP structure in terms of its potential regulatory targets, conformational changes associated with the formation of a functional holoenzyme, and during its transition from initiation to elongation processes have been described. Regulation of transcription with an emphasis on activation mechanism, ligand mediated allosteric transitions in regulatory proteins and the polymerase-activator interactions are discussed citing a few examples. The chapter concludes by introducing bacteriophage Mu and mom gene and its regulation by C. The objectives of the thesis form the concluding section of the chapter. Activators are capable of resurrecting defective promoters in response to cellular demands. The unusual, multistep activation of mom promoter (Pmom) by C protein involves activator mediated promoter unwinding to recruit RNA Polymerase (RNAP) and subsequent enhanced promoter clearance of the enzyme. The first step of transactivation is an interaction independent step, while the later might involve a transient interaction between C and one of the subunits of RNAP. Previous studies pointed out β′ subunit to be the most probable interaction partner. Chapter II comprises the genetic and biochemical studies carried out to confirm this observation. Employing a genetic screen mutations in rpoC gene (encoding the β′ subunit of RNAP), were isolated which result in the defective RNAP. The mutant RNAPs were assayed for their C specific activity by in vivo transactivation assays. Such mutants have been purified and characterized to understand their effect at different steps of C mediated mom gene expression during transcription initiation. The mutant RNAP had normal transcription activity with typical σ70 promoters but exhibited reduced productive transcription and enhanced abortive initiation on C-dependent Pmom. Experiments carried out to probe the interaction between C and mutant RNAP revealed that the physical interaction per se is not disrupted between the two proteins. Post C-mediated recruitment of RNAP to the promoter, transient interactions between the two proteins appears to induce subtle conformational changes in RNAP leading to an enhanced promoter clearance. Transactiavtor protein C is essential for the expression of other late genes lys, I, P apart from mom during the phage life cycle. Although the mechanism of multistep activation at Pmom has been elucidated, little is known on the transactivation from lys, I and P promoters. Chapter III includes studies carried out to understand the process of activation at these promoters. Owing to the differences in their C-binding site and promoter architecture it was important to investigate the differential effect of C, if any at lys, I , P promoters compared to that at Pmom. Activators in prokaryotes are shown to stimulate different steps of transcription initiation pathway ranging from the polymerase binding to the promoters to the post recruitment steps of isomerization and promoter clearance. Effect of C at different steps of transcription initiation pathway was analysed. The results indicate that C is absolutely essential for transcription from lys, I and P promoters similar to mom. However, at these promoters C exerts its effect at the step of Isomerisation from closed complex to open complex formation. Thus, C acts at a single step here and the mode of activation is different from that observed at Pmom. C dimer binds DNA with high affinity and sequence specificity, to an interrupted palindromic sequence overlapping the -35 element of mom promoter. Mg2+ mediated conformational transitions in C protein are essential for its DNA binding and transactivation functions. Chapter IV deals with the identification of the Mg2+ coordinating residues in C protein. Primary sequence analyses lead to the identification of a putative metal coordinating motif (EXDXD) towards the N-terminus of the protein. These residues were subjected to site directed mutagenesis to infer their role in Mg2+ coordination, its associated allosteric transition required for specific interaction with DNA. Mutants showed an altered Mg2+ induced conformation, compromised DNA binding and reduced levels of transcription activation when compared to C protein. Though Mg2+ is widely used in various DNA transaction reactions, this study provides the first insights on the importance of metal-ion induced allosteric transitions in regulating transcription factor function.

Effective management of acute pancreatitis has for centuries eluded mankind. The disease has a wide spectrum of presentation; the milder form is usually a self limiting condition, whereas the severe form presents as a highly morbid and frequently lethal attack. The ability to predict disease progression on admission would aid in the comprehensive and multidisciplinary management of patients. The perfect predictor of disease progression has been an elusive factor hindering the management of the disease. On systematically reviewing literature and identifying appropriate biochemical markers in predicting progression of acute pancreatitis, the ideal predictor would be a combination of biochemical, clinical and contemporary organ dysfunction scoring systems. Early prediction of disease progression however, is important in the better management of the disease. The pathophysiological changes of acinar cell injury and death are the earliest events that occur in acute pancreatitis. Identification of potential pharmacological interventions offered through valuable insight in to experimental and clinical acute pancreatitis may lead on to the development of various natural and synthetic potential disease modifiers. Green Tea Extracts (GTE) consumed in many parts of the world has been examined as a potential therapeutic medication. Experimental results have demonstrated the effect of GTE on the oxidative pathway significantly ameliorating the effects of pancreatic injury. The various green tea catechins especially Epigallocatechin-3- gallate (EGCG) can perhaps be useful lead compounds for new drug discovery. With no specific targeted therapy for severe acute pancreatitis at present, various medications have been tested. The possibility of targeting initial acinar cell injury may not be a feasible option as patient presentation and management would usually be after this phase. As the disease progresses, severe acute pancreatitis is characterised by inflammation and necrosis. The hypothesis of preserving pancreatic parenchymal microvascular patency and thus ameliorating pancreatic injury through the early administration of recombinant human Activated Protein C (rhAPC) has identified a potential treatment for acute pancreatitis. rhAPC converted from its inactive precursor, protein C, by thrombin acts through fibrinolysis and inhibition of thrombosis. Studies on rhAPC in experimental acute pancreatitis examined the modulation of rhAPC on inflammatory markers, morphology, microvascular thrombosis and apoptosis. The encouraging results from initial experimental work helped set up the Phase 2 clinical trial of administering rhAPC early on in severe acute pancreatitis. Prior to taking this significant step from bench to bed side, the variation in functional protein C levels with the severity of the disease was examined as a precursor to the Phase 2 trial.

No description available.

Les mutations du gène codant pour la protéine C (SP-C) du surfactant pulmonaire (SFTPC) sont à l’origine de pathologies interstitielles chroniques du nourrisson, de l’enfant mais également de l’adulte. Une importante hétérogénéité phénotypique est cependant observée, y compris au sein d’une même famille. Par un épissage alternatif, le gène SFTPC permet la synthèse de deux isoformes du précurseur protéique de SP-C (proSP-C) pour aboutir à la protéine mature après plusieurs modifications post-traductionnelles. Les conséquences des mutations de SFTPC sur l'homéostasie du surfactant ne sont pas clairement élucidées, mais il semble que le mauvais repliement de la protéine soit une caractéristique commune. A l’issue de nos travaux antérieurs, nous avons mis en évidence un effet de certaines mutations et de polymorphismes sur l’épissage de SFTPC faisant ainsi varier significativement l’expression de chacune des deux isoformes protéiques, sans qu’à l’heure actuelle nous ne connaissions le rôle de chacune dans la synthèse de la protéine SP-C mature. Notre projet, s’inscrivant dans la continuité de mon master 2, a pour but de mieux comprendre les mécanismes physiopathologiques pré et post-transcriptionnels associés aux variations de SFTPC et leurs conséquences sur le développement des pneumopathies interstitielles. Le premier axe de notre projet repose sur l’étude in vitro (lignées cellulaires) et in vivo (modèle murin, ARN des patients) des variations de chacun des isoformes. Dans un second axe, nous souhaitons poursuivre l'étude de facteurs pouvant influencer le phénotype des patients porteurs de mutations du gène SFTPC, qu'ils soient d'origine externes (infections virales et bactériennes ou environnementaux comme le tabac) ou génétique. Collectivement, ces études nous permettrons de fournir une signature moléculaire pour cette maladie et d’identifier de nouvelles cibles thérapeutiques afin d’en améliorer le pronostic mais également la prise en charge et la qualité de vie des patients. / Surfactant pathologies linked to mutations in the SFTPC gene, via autosomal dominant transmission, are most commonly associated with diffuse interstitial diseases in infants, children and adults, and may also be responsible for acute respiratory distress syndrome in newborns. They are most often accompanied by a high morbidity and mortality rate, thus rendering early diagnosis essential for ideal intervention and support. Mutations in the SFTPC gene lead to alveolar and intracellular accumulation of an abnormal form of the precursor protein SP-C (ProSP-C), which is responsible for the resulting tissue damage. However, the pathophysiological mechanisms are not yet completely deciphered. The gene encodes two isoforms of ProSP-C from three alternative transcripts. The expression level of each is currently unknown and the vast majority of studies evaluating the effect of mutations are performed on only one isoform. Incidentally, our preliminary results on the analysis of RNA extracted from bronchoalveolar washing, both from control subjects and patients harboring a mutation, show that the all three SFTPC transcripts are expressed and that the presence of a mutation is associated with a variation in the expression levels of the transcripts. The aim of my project is to study the expression level of SFTPC transcripts and ProSP-C isoforms from the heterologous expression of the SFTPC gene (exons and introns) in cell lines. I will beanalyzing the post-translational maturation profile of these pro-proteins and evaluating the effect of the mutations on their expression and maturation in both our cellular models and in vivo with two Knock-in mice models.A better understanding of the pathophysiology of genetic abnormalities associated with mutations in the SFTPC gene will not only greatly contribute to earlier management of patients, but also it will help in modifying the progression of lung injury and its prognosis.

Enterohemorrhagic E. coli (EHEC) infection is a leading cause of acute kidney failure in otherwise healthy children, and a leading cause of foodborne illness with an outsized economic impact from outbreaks. EHEC secrete two Shiga-like toxins (Stx1 and Stx2) which are AB5 holotoxins that inhibit protein synthesis in cells expressing the toxin receptor Gb3. Infection with EHEC typically begins with a diarrheal prodrome that can progress in 5-15% of cases to hemolytic uremic syndrome (HUS), a clinical diagnosis characterized by thrombocytopenia, hemolytic anemia, and thrombotic microangiopathy. Historically, strains of EHEC expressing Stx2 have been associated with more severe disease. We hypothesized that tissue injury due to the toxins leads to the release of damage-associated molecular patterns (DAMPs), which act through inflammatory receptors to promote the endothelial dysfunction that drives this disease alongside the inciting Shiga toxins. Here we demonstrate that two well-characterized DAMPs, extracellular histones and HMGB1, are produced in two different mouse models when Stx2 is present; one model represents challenge with the toxin alone, and the second model introduces toxin through secretion with a lysogenized bacterium, C. rodentium, mimicking EHEC colonization. We investigate whether Stx1, Stx2, or histones affect the endothelial expression of well-characterized members of the protein C pathway, namely the endothelial protein C receptor (ECPR), protease-activated receptor 1 (PAR1), and thrombomodulin (TM), on human aortic (HAEC) and human renal glomerular endothelial cells (HRGEC). We show that Stx and/or histones reduce endothelial expression of these anti-coagulant molecules and histones dramatically increase expression of pro-thrombotic PAR-1. These changes lead to physiologically important decreases in activated protein C (APC), a critical anti-coagulant and cytoprotective molecule. Finally, we demonstrate that histones exacerbate thrombin's barrier-disruptive effects on the endothelium, and prevent APC's protective effects. These data provide novel mechanistic insight into the endothelial dysfunction that characterizes HUS and also provide a new perspective on systemic consequences of the bacterial Shiga toxins that might drive organ injury in susceptible patients.

Das Surfactant-Protein C (SP-C) moduliert die Rheologie der Liquor cerebrospinalis (CSF). Während des Alterns geht sein abnehmender Spiegel mit einer erhöhten Belastung durch Läsionen der weißen Substanz einher. Pulmonale SP-C-Zwischenprodukte, die die BRICHOS-Domäne enthalten, verhindern Proteinfehlfaltung in der Lunge. So könnten zerebrale SP-C-Zwischenprodukte der zerebralen β-Amyloidose, einem Kennzeichen der Alzheimer-Krankheit, entgegenwirken. Es fehlen jedoch Daten über die molekulare Neuroanatomie von SP-C und seine Veränderungen in Wildtyp- und triple-transgenen (3xTg) Mäusen, die wesentliche Elemente der AD-Neuropathologie aufweisen. In dieser Studie wurden daher SP-C-haltige Strukturen im Vorderhirn von Mäusen und ihre räumlichen Beziehungen zu vaskulären, glialen und neuronalen Komponenten der neurovaskulären Einheit untersucht. Durch Fluoreszenzmarkierung wurde neuronales SP-C in der medialen Habenula, dem Indusium griseum und dem Hippocampus nachgewiesen. Die Glia-Gegenfärbung zeigte Astrozyten im Corpus callosum, die SP-C und S100β gemeinsam exprimieren. Insbesondere waren perineuronale Netze mit SP-C im Nucleus reticularis thalami, im lateralen Hypothalamus und im retrosplenialen Kortex assoziiert. Im Hippocampus älterer 3xTg-Mäuse wurden neben AD-ähnlichen Läsionen vermehrt punktförmige Ablagerungen gefunden, die SP-C und Reelin enthielten, aber keine BRICHOS-Immunreaktivität aufwiesen. Wildtyp- und 3xTg-Mäuse zeigten eine altersabhängige Zunahme solcher Ablagerungen, die bei etwa 24 Monate alten 3xTg-Mäusen deutlich ausgeprägt war. Die SP-C-Konzentrationen in den intra- und extrazellulären Kompartimenten jeder Gruppe zeigten eine umgekehrte Korrelation zwischen SP-C und Reelin, wobei insbesondere bei 3xTg-Mäusen eine altersabhängige Abnahme von SP-C und eine Zunahme von Reelin zu beobachten war. Zusammenfassend lässt sich sagen, dass extrazelluläres SP-C als Modulator der glymphatischen Clearance und potenzieller Ligand von PNs während des Alterns bei 3xTg-Mäusen abnimmt.:Inhaltsverzeichnis 1. Einführung...........................................................................................................1 2. Grundlagen .........................................................................................................4 2.1 Alzheimersche Erkrankung ...............................................................................4 2.2 Glymphatisches System....................................................................................6 2.3 Surfactant-Protein C..........................................................................................8 3. Zielsetzung..........................................................................................................12 4. Material und Methoden .......................................................................................13 4.1 Versuchstiere ....................................................................................................13 4.2 Gewebeaufbereitung für die Histochemie .........................................................14 4.3 Immunhistochemische Färbungen ....................................................................14 4.4 SP-C, gliale und neurovaskuläre Marker............................................................15 4.5 Doppelfärbungen in Kombination mit der Cy2-Markierung von SP-C................16 4.6 Mikroskopie und Bildgebung ..............................................................................17 4.7 Semiquantifizierung der SP-C-Ablagerungen im Hippokampus ........................18 4.8 Biochemische Analyse des SP-C- und Reelin-Gehalts in Mäusehirnen.............19 4.9 Statistische Auswertung der ELISA-Ergebnisse.................................................20 5. Ergebnisse ...........................................................................................................22 5.1 Qualitative Analyse der SP-C-Verteilung im Vorderhirn von Mäusen.................22 5.2 Semiquantitative Auswertung hippokampaler SP-C-Ablagerungen ..................39 5.3 Quantitative Analyse des SP-C- und Reelin-Gehalts in Mäusehirnen...............41 6. Diskussion............................................................................................................52 6.1 Technische Betrachtungen.................................................................................52 6.2 SP-C bei Drainage und Amyloidogenese ..........................................................53 6.3 SP-C und gliale Marker .....................................................................................55 6.4 SP-C und perineuronale Netze .........................................................................56 7. Zusammenfassung der Arbeit .............................................................................58 8. Literaturverzeichnis..............................................................................................63 Erklärung über die eigenständige Abfassung der Arbeit..........................................80 Lebenslauf................................................................................................................81 Danksagung ............................................................................................................83