Bien qu’il ait prouvé son efficacité dans différentes espèces (lapin, porc, souris,…) ainsi que dans différents organes (rein, foie coeur, poumon,…), le Postconditionnement (PostC) peut être limité par plusieurs facteurs. Parmi les limites du Post C, on note la nécessité de son application à l’initiation de la reperfusion. L’objectif de notre travail était d’évaluer la protection induite par la Basse pression de reperfusion (BP) après un décalage temporel de son application et d’étudier les principales fonctions mitochondriales connues pour être impliquées dans la cardioprotection. Nos résultats nous ont permis de démontrer que, contrairement au PostC, la BP pouvait s’appliquer avec succès même après un décalage temporel de 10 minutes après le début de la reperfusion. Cette protection décalée est en lien avec les fonctions mitochondriales, en particulier, l’inhibition du pore de transition de perméabilité mitochondriale (PTPm). L’utilisation de la cyclosporine A (CsA), puissant inhibiteur de l’ouverture du PTPm, permet également de décaler de 10 minutes la manœuvre de protection à la reperfusion dans le modèle de coeur isolé perfusé de rat. Le PostC, comme la BP, utilise deux sources de production de NO (NOS et Xanthine oxydase reductase) pour induire la cardioprotection. Ces résultats nous semblent importants dans le sens où ils proposent une nouvelle fenêtre thérapeutique pour combattre les dégâts liés à l’ischémie/reperfusion, la BP / Although its efficacy in various species (rabbit, pig, mouse,…) and various organs (kidney, liver heart, lung), Postconditioning (PostC) can be limited by many factors such as the necessity of its application in the initiation of the reperfusion. The objective of our work was to evaluate the protection by low pressure reperfusion (LPR) with delayed intervention at reperfusion and to study the mitochondrial functions which are known to be involved in the cardioprotection. Our results showed that, contrary to PostC, LPR can protect until 10 minutes of its delayed intervention at reperfusion. This delayed protection is in correlation with mitochondrial functions, particularly, inhibition of mitochondrial transition pore (PTPm). Cyclosporine, inhibitor of PTPm, has also shown protection until 10 minutes of delayed intervention, on isolated heart rat model. PostC, like LPR, use tow sources of prodution of NO (NOS and Xanthine oxydase reductase). These results seem, to us, very important because they propose LPR as a new therapeutic window to reduce ischemia/reperfusion injury

Obesity has reached worldwide epidemic proportions and with this increased incidence of obesity, comes an increase in incidence of the comorbidities associated with obesity such as diabetes and cardiovascular disease (CVD). The underlying mechanisms which connect these diseases are still poorly understood. One system which has been shown to be up-regulated in the setting of obesity and diabetes is that of the G-protein coupled receptor-55/Lysophosphatidylinositol (GPR55/LPI). Despite being upregulated in the setting of obesity, the function of GPR55 in obesity and other disease states remains elusive. Therefore, the present study aimed to 1) investigate the role of GPR55 in obesity by characterising the phenotype of the GPR55 knockout (GPR55-/-) mouse when challenged with a high fat diet (HFD) intervention, 2) elucidate any effect of the GPR55 knockout and HFD intervention on the myocardial infarct size sustained following a period of ischaemia/reperfusion (I/R) and 3) make use of an in vitro model to elucidate the mechanisms by which changes occur in the adipose tissue of mice fed a HFD. GPR55-/- mice fed a HFD for 12-weeks gained significantly more weight in the form of fat mass, compared to wild-type (WT) controls and consequently become obese. Obese GPR55-/- mice displayed hypertrophic adipose tissue concurrent with the significant dysregulation of plasma lipids, increases in specific circulating LPI species, increased lipid deposition within the liver and a change in adipose tissue gene expression profile. These changes were not observed in GPR55-/- mice fed a standard diet or WT mice fed a HFD. Following a period of I/R, the myocardial infarct size in hearts from WT HFD fed mice was significantly smaller than in hearts from WT standard diet fed mice. This reduction in infarct size due to HFD intervention was not dependent on RISK-pathway activation and was not observed in hearts from GPR55-/- mice, therefore demonstrating that the cardio-protective effect of a HFD on infarct size is dependent on GPR55. In vitro studies using 3T3-L1 cells determined that the changes in adipose tissue gene expression of HFD fed mice was not due to enhanced stimulation with LPI or via hypoxic mechanisms. The results of these studies demonstrate that GPR55 has an anti-obesity function in vivo and also mediates the cardio-protective effect of a HFD on myocardial infarct size, through currently unknown mechanisms.

Hydrogen sulfide (H2S) is the newest member of the gasotransmitter family and is becoming well known for its cardioprotective effects in preclinical trials. Many recent studies have shown the benefits of exogenous H2S in the setting of acute myocardial infarction (AMI) and pressure overload-induced heart failure, but current formulations are derived from inorganic salts which have shortcomings in the precision and control of release of H2S. The main objective of this thesis was to determine if the novel, orally active, slow-releasing compound, SG1002, can attenuate the severity of damage and adverse remodeling caused by ischemia/reperfusion injury through an induction of angiogenesis. A traditional sodium salt, Na2S, which has been previously shown to be cardioprotective, was used as a positive control. SG1002 improved overall left ventricular function as measured by increased ejection fraction from echocardiography and decreased QRS interval from electrocardiography compared to untreated animals following MI. SG1002 therapy was also associated with an induction of angiogenesis, which was determined through qRT-PCR, western blot, and histological methods. SG1002 increased VEGF protein levels, which was paralleled with an increase in capillary density in the infarct region. SG1002 also upregulated microRNA-126, which is thought to repress the inhibitor of VEGF, Spred-1. It is possible that this “angiomiR” plays a key role in the angiogenesis-related cardioprotection of H2S. The combination of increased pro-angiogenic factors along with greater vascular density resulting from SG1002 therapy indicates the therapeutic potential for this drug in the prevention and/or treatment of ischemic heart failure.

Der myokardiale Ischämie-Reperfusions-Schaden (IR) hat eine hohe Relevanz in der Kardiologie und Herzchirurgie. Trotz intensiver Forschung ist es bislang nicht gelungen, eine effektive Therapie des IR in den klinischen Alltag zu implementieren. Mitochondrien spielen im IR eine wichtige Rolle. Die Raman-Spektroskopie mit Laserquellen von 785 nm Wellenlänge erlaubt die nicht-invasive Analyse pathophysiologischer Prozesse in vitro in Echtzeit. Daher eignet sich die Raman-spektroskopische Analyse von Mitochondrien möglicherweise dazu, notwendige neue Einblicke in die Pathophysiologie des myokardialen IR zu gewinnen. Die vorliegende Arbeit analysierte die mitochondriale Funktion von subsarkolemmalen Mitochondrien im IR mit Hilfe bekannter Methoden. Anschließend erfolgte ein Vergleich der etablierten Methode „Clark-Elektrode“ mit der neu etablierten Raman-Spektroskopie zur Analyse der mitochondrialen Funktion im IR. / Myocardial ischemia reperfusion injury (IR) has a high relevance in cardiology and heart surgery. Despite intense research, an effective treatment of IR has to date not been implemented in clinical routine. Mitochondria play an important role in IR. Raman spectroscopy with 785 nm laser wavelength permits the non-invasive analysis of pathophysiological processes in vitro and real-time. Therefore, Raman-spectroscopic analysis of mitochondria might be able to create new necessary insights in the pathophysiology of myocardial ischemia reperfusion injury. This work analysed mitochondrial function of subsarcolemmal mitochondria in IR using well-established methods. Afterwards, a comparison of the well-established method “Clark-Elektrode” with freshly established raman spectroscopy was performed to analyse the mitochondrial function in IR.

"September 2002" Bibliography: leaves 207-230. Ch. 1. Literature review -- Ch. 2. General methods -- Ch. 3. Dietary n-3 PUFAs and reperfusion injury in isolated cardiomyocytes -- Ch. 4. The effect of dietary n-3 PUFAs on cardiomyocyte membrane fluidity, intracellular ROS and Ca 2+ levels during oxidative stress -- Ch. 5. The effect of dietary fish oil supplementation on antioxidant enzyme gene expression in rat myocardium -- Ch. 6. The effect of dietary lipids on ischaemia-reperfusion injury in rat myocardium -- Ch. 7. General discussion -- Ch. 8. Appendices. The broad aims of this thesis were to develop a cellular model for studying reperfusion injury, in order to investigate the reported protective effects of n-3 PUFAs, and to examine the underlying mechanisms associated with such protection.

"September 2002" / Bibliography: leaves 207-230. / x, 230 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The broad aims of this thesis were to develop a cellular model for studying reperfusion injury, in order to investigate the reported protective effects of n-3 PUFAs, and to examine the underlying mechanisms associated with such protection. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 2002

Primary graft non-function is one of the major limitations of organ transplantation increasing the risk of rejection and early graft failure. A major cause of primary non-function is ischemia reperfusion injury (IRI), an obligatory insult in transplantation. During procurement, the donor is subjected to a period of ischemia inducing the release of tissue-damaging factors such as nitric oxide and reactive oxygen species. Upon engraftment and reperfusion with the recipient blood, these ischemia-induced factors cause rapid cell death and amplification of the inflammatory response leading to further tissue damage. / CD39 is an integral vascular and immune ectonucleotidase. CD39 hydrolyses extracellular nucleotides ATP and ADP into AMP, which is then hydrolysed into adenosine by CD73. Extracellular adenosine produced by the concerted action of CD39 and CD73 has potent anti-inflammatory and anti-coagulation effects acting principally via the purinergic adenosine receptor A2a. / NKT cells have only recently been recognised and constitute an important subset of T lymphocytes that display both effector and suppressive functions. NKT cells are found in high proportion in the liver of mice and are implicated by depletion studies in protection against hepatic IRI. / We have generated mice transgenic for human CD39 (hCD39) and have shown they have an anti-coagulant phenotype. As CD39 is also critical to immune regulation we hypothesised that transgenic expression of hCD39 would modify lymphocyte development and/or function and consequently impact on ischemia reperfusion injury. / Flow cytometric analysis was used to assess the number and phenotype of lymphocytes within the thymus and in the periphery of hCD39 transgenic mice. In vitro and in vivo assays were used to test the function of CD4+ T cells and invariant NKT cells from hCD39 transgenic mice. Bone marrow adoptive transfers experiments defined the role of hCD39 expression on bone marrow progenitor cells in comparison to tissue expression. The importance of adenosine signalling through the A2a receptor was studied by crossing hCD39 transgenic mice with A2a receptor knock-out (KO) mice. The effect of hCD39 expression on ischemia reperfusion injury was evaluated in a model of murine liver transplantation / A high level of hCD39 expression in the transgenic thymus resulted in lymphocyte maturation blockade and peripheral lymphopenia of CD4+ T cells and invariant NKT cells. Both lymphocyte populations were functionally deficient. The observed phenotype resulted from the expression of hCD39 on bone marrow progenitor cells but was independent of A2a receptor signalling. Over-expression of hCD39 in transgenic livers was protective against ischemia reperfusion injury induced by cold storage and liver transplantation.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

The treatment of acute myocardial infarction (AMI) has undergone a tremendous development during the last decades, and the most important factor is probably the introduction of reperfusion therapy aimed at preventing or limiting the myocardial injury. It is of vital importance that patients with AMI are adequately monitored regarding the development of ECG changes during and after treatment to identify successful or failed reperfusion and to detect episodes of recurrent ischemia. Vectorcardiography (VCG) is one method for this purpose. This series of studies was aimed at evaluating VCG as a method for detecting reperfusion and recurrent ischemia in patients with ST-elevation AMI who were treated with different reperfusion strategies. Specific changes in the VCG during the initial treatment phase, “reperfusion peaks,” were examined in detail. The influence of the fibrinolytic system and von Willebrand factor (vWF) on successful reperfusion and subsequent AMI and death after thrombolytic treatment with streptokinase (SK) was another main objective. From the data in these studies it can be concluded that: VCG is a relevant and easily used method for ischemia-monitoring in patients with AMI. A specific sign, the reperfusion peak, is associated with vectorcardiographic signs of reperfusion. This sign is observed both in patients treated with primary coronary angioplasty and in those who are treated with fibrinolytic agents. The reperfusion peak is associated with successful reperfusion and with larger infarcts, but by itself, the parameter has little prognostic significance. The recognition of the reperfusion peak is important since it can mimic severe ischemia. In an unfortunate situation the incorrect interpretation of the VCG could lead to premature treatment decisions that might even be harmful to the patient. Streptokinase treatment of patients with AMI induced profound changes in the fibrinolytic system and vWF. A high tissue plasminogen activator (tPA) activity level (>25 U/mL) early after the start of treatment, reflecting the fibrinolytic activity obtained by the given drug, was associated with successful reperfusion. Pre-existing neutralizing antibodies to SK were found to varying degrees in the previously SK-treated patients. No association between SK-neutralizing antibodies and the result of the treatment regarding successful reperfusion as judged by VCG was seen. Pre-treatment levels of tPA activity, PAI-1 activity, PAI-1 mass-concentration and vWF had no correlation with the success of reperfusion therapy with SK or on the incidence of recurrent ischemia during the first 24 hours. Recurrent ischemia, however, was shown to be an independent risk factor for death within the first 1 year. Elevated levels of PAI-1 mass-concentration, and to some extent PAI-1 activity, after the start of SK treatment, were associated with a higher risk for death at one year, though not at five years.