The mortality from septic shock is approximately 50%. Most patients die from the ensuing multi-organ dysfunction syndrome rather than the acute septic inflammatory process per se. The aetiology of the organ dysfunction is unknown. A characteristic phenomenon of an increasing severity of sepsis is a decrease in tissue oxygen extraction with a decrease (relative and/or absolute) in tissue oxygen consumption. Two theories have been advanced to explain this observed decrease in oxygen extraction. Traditionally, this has been ascribed to micro vascular shunting of blood away from nutrient capillaries. However, findings in both patients and animal models have demonstrated a raised tissue PO2, suggesting that the oxygen is available to cells but cannot be metabolised, i.e. a state of dysoxia. As mitochondria account for over 90% of total oxygen consumption, in the process of oxidative phosphorylation, it has been hypothesised that sepsis results in an inhibition of the mitochondrial enzymes involved in this process. If severe, this would be expected to lead to energy failure in the organs and, possibly, to initiation of apoptotic or necrotic cell death. Marked over-production of the intercellular messenger nitric oxide is a characteristic feature of sepsis; the mitochondrial damage theory has been given additional credence by the discovery that nitric oxide and its derivative, peroxynitrite, can inhibit or permanently damage mitochondrial enzymes involved in the oxidative phosphorylation pathway. The work leading to this thesis has demonstrated that sepsis is associated with an increase in nitric oxide production, a reduction in antioxidant protection, respiratory chain enzyme inhibition, and a depletion in tissue ATP levels. These changes were shown in both skeletal muscle biopsies obtained from critically ill patients in septic shock, and in skeletal muscle and liver biopsies obtained from a long-term septic rat model. These changes correlated with the severity of disease and eventual outcome. These findings thus demonstrate a mechanism that is present in both 'non-vital' and 'vital' organs, and across species. These findings may be epiphenomenal and causation needs to be definitively demonstrated. However, this work does suggest that mitochondrial dysfunction could be an important pathophysiological mechanism underlying sepsis-induced organ failure.

No description available.

Sepsis is the leading cause of mortality in non-coronary intensive care units and its incidence is set to rise. Despite advances in patient care, novel therapeutic interventions (with the exception of activated protein C) have failed to demonstrate benefit in clinical trials. High density lipoprotein has been widely reported to possess immunomodulatory properties and has been shown to be beneficial in animal models of systemic inflammation and sepsis. This thesis investigates the hypothesis that lysophospholipids, which are derivatives of high density lipoprotein, and other lipoproteins, display similar immunomodulatory properties. I have administered Gram-negative (lipopolysaccharide) or Gram-positive (peptidoglycan and lipoteichoic acid) cell wall components in anaesthetised rats to cause shock, organ injury/dysfunction and systemic inflammation. Subsequently, I have investigated the effects of various lysophospholipids in these models. I have demonstrated that therapeutic administration of lysophosphatidylcholine (LPC) dose-dependently attenuates the organ injury/dysfunction caused by administration of lipopolysaccharide. Furthermore, I have shown that LPC is also protective in a model of systemic inflammation caused by eo-administration of peptidoglycan and lipoteichoic acid. Lastly, I have reported that the beneficial effects of LPC discovered here can be demonstrated with an LPC derived from a natural source or with synthetic LPC. In addition, I have found that both saturated and unsaturated lysophosphatidic acid (LP A) significantly reduces the organ injury associated with systemic inflammation associated with endotoxic shock. The observed beneficial effects of LP A are dependant on acyl chain saturation, as saturated LP A only activates specific G-protein coupled receptors, while unsaturated LP A activates both G-protein coupled receptors and peroxisome proliferator-activated receptor-y. Finally, I have established that sphingosylphosphorylcholine attenuates the organ injury/dysfunction caused by administration of lipopolysaccharide. These beneficial effects were associated with potent anti-inflammatory effects, which include the reduction in the formation of pro-inflammatory cytokines, adhesion molecules, COX- 2 and iNOS expression and the recruitment of neutrophils.

Background: Sepsis may be modelled in vivo using lipopolysaccharide (LPS) to cause microvascular disturbances including macromolecular leak and leucocyte adhesion. Such changes may be due to an altered balance of eNOS and iNOS. Statins are widely used to lower cholesterol. Recently evidence indicates statins may exert pleiotropic effects, possibly restoring physiological levels of eNOS and iNOS.

No description available.

No description available.

Le sepsis, état pathologique lié à une réaction inflammatoire systémique suite à une infection, est lapremière cause de mortalité dans les unités de réanimation médicale et de soins intensifs hospitaliers.Parmi les pistes thérapeutiques envisagées, l’hypothermie est un bon candidat. En effet, l’hypothermiemodérée induite augmente la durée de survie de rats septiques. Ce travail avait pour objectifd’apporter des éléments permettant de comprendre et d’identifier les mécanismes responsables decet effet bénéfique. Pour cela, différentes fonctions couramment affectées lors du sepsis(inflammation, stress oxydant, défaillance rénale, capacités de transport de l’oxygène par le sang etéquilibre acide-base) ont été étudiées sur des rats septiques en hypothermie modérée (34°C). Lesrésultats obtenus révèlent que l’hypothermie modérée ralentit de manière significative la production decytokines pro-inflammatoires et tend à exercer une diminution de la production radicalaire systémiquechez les rats septiques. L’apparition de l’acidose métabolique et la défaillance rénale sont égalementretardées. Enfin, alors que le sepsis en normothermie conduit à une diminution de la coopérativité etde l’affinité de l’hémoglobine pour l’oxygène, synonymes d’une adaptation face à des modificationspotentiellement délétères, en hypothermie modérée, ces paramètres ne sont pas modifiés. Cesrésultats concourent à penser que l’hypothermie modérée en ralentissant l’évolution du sepsis permetd’augmenter la durée de survie des rats septiques. Ainsi, l’hypothermie pourrait constituer une pistepour traiter les patients atteints de sepsis sévère dans le but de temporiser l’inflammation et decontrôler l’agression retardant ainsi les défaillances d’organes. / Despite numerous studies over the past twenty years, sepsis, a pathologic state related to a systemicinflammatory response following infection, remains the main cause of death in intensive care units.Among the therapeutic approaches proposed, hypothermia is a good candidate. Indeed, mild inducedhypothermia increased the survival duration of septic rats. This work aimed to provide elements tounderstand and identify the mechanisms responsible for this beneficial effect. Consequently, variousfunctions commonly affected during sepsis (inflammation, oxidative stress, renal failure, oxygen bloodcapacity and acid-base balance) were studied on septic rats maintained in mild induced hypothermia(34°C). The results showed that mild hypothermia significantly slows the cytokine proinflammatoryproduction and tends to exert a decrease in the radical systemic production of septic rats. Theappearance of metabolic acidosis and renal failure are also delayed. Finally, while in normothermiasepsis led to a decrease in the cooperativity and oxygen haemoglobin affinity, synonymous of anadaptation when faced with potential deleterious changes, in mild hypothermia, these parameters arenot modified. These results suggest that by reducing the development of sepsis, mild inducedhypothermia increases the survival duration of septic rats. Thus, hypothermia may be an option fortreating patients with severe sepsis by stalling inflammation and controlling aggression, therebydelaying organ failure.

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The unlimited replicative potential of cells is one of the hallmarks of cancer. Telomeres, DNA structures found at the ends of chromosomes have attracted a great deal of interest in recent years as potential anti-cancer drug targets since they play an important role in cancer cell immortality. The repetitive TTAGGG sequences of telomeres are complexed to a group of six indispensible proteins, one of which is the protection of telomeres 1 (POT1) protein. This specialised protein binds to a ten nucleotide single stranded DNA sequence at the ends of chromosomes and plays an important role in telomere capping and length regulation. It has recently been proposed that the key function of POT1 is to suppress a potent DNA damage response at telomeres thereby protecting chromosome tips from being recognised as sites of DNA damage. Deletion of POT1 from telomeres in a variety of organisms including humans results in cytogenetic aberrations, senescence and cell death. These results indicate that POT1 is an integral telomere end-protection protein which is necessary for continued cellular proliferation and therefore POT1 is becoming a promising new target in cancer. Using a structure-based approach, several small molecule inhibitors of POT1 have been designed to affect telomere integrity by disrupting the binding interaction of human POT1 with its target DNA sequence thereby driving cancer cells into senescence/apoptosis. Using a range of computational tools, a suitable drug binding pocket in POT1 has been identified and the de novo design of a specific class of POT1 inhibitor was completed. Using this novel scaffold, a small focussed library of hit-like compounds were synthesised and screened in a new POT1 fluorescence polarisation displacement assay developed by scientists at the University of Nottingham. In total, over 90 small molecule inhibitors based on two different scaffolds: pyrido[1,2-a]pyrimidines and sulfathiazoles have been synthesized with some inhibitors effectively decreasing POT1-DNA binding between 10-54% at 100μM ligand concentration. The biological results have established that electron-withdrawing substituents on the pendent phenyl ring of the pyrimidine core are essential for strong binding. These results have the potential to guide future development of improved lead compounds as therapeutics for the treatment of cancer.

Le choc septique est la principale cause de mortalité dans les services de réanimation. Les glucocorticoïdes (GC) et la protéine C activée (APC) sont deux traitements adjuvants recommandés au cours du choc septique. Ce travail a pour objectif d'évaluer l'impact de la combinaison d'APC et des GC sur les paramètres hémodynamiques et la survie. Le sepsis expérimental se caractérise par une hypotension artérielle avec acidose lactique et une hyporéactivité vasculaire. L'administration de Dexa et/ou d'APC permet de diminuer les taux de lactates, d'interleukines et de nitrate/nitrite. Chez les groupes traités, la contraction est améliorée ainsi que la relaxation vasculaire des aortes et des artères mésentériques. L'administration d'APC et de Dexa, seul ou en association, entraine une diminution de l'expression induite d'iNOS et la restauration de la voie Akt. La combinaison APC et Dexa améliore le temps de survie de façon synergique. Nos résultats suggèrent que l'APC et les GC devraient être réévalués en association dans le traitement du choc septique / Sepsis remains the major cause of death in intensive care units. International guidelines for management of severe sepsis and septic shock recommend both stress-dose steroid therapy and recombinant activated protein C (APC). The aims of the present study were to compare the effects of APC and dexamethasone (Dexa) alone as well as in combination in resuscitated septic shock on survival, hemodynamics, and vascular reactivity. Sepsis was associated with a decrease in mean arterial pressure, elevation in plasma lactate and nitrite/nitrate concentration. Administration of APC, Dexa, and their combination improve arterial pressure and decrease lactate and nitrite/nitrate concentration. Both APC and Dexa improved arterial contractility and endothelial dysfunction resulting from septic shock in rats. The expression of iNOS was significantly reduced by the administration of Dexa, APC, and combination therapy. All treatments restore the Akt pathway. Moreover, their combination increased the length of survival. These findings suggest that APC and glucocorticoids should be further re-evaluated in combination in septic shock