Le syndrome d’apnées obstructives du sommeil (SAOS) est associé à la survenue de neuropathies optiques, en particulier la neuropathie optique ischémique antérieure aigue non artéritique (NOIAA-NA). Parmi les mécanismes d’apparition de cette neuropathie et potentiellement associés au SAOS, la dysrégulation et l’inflammation vasculaires pourraient jouer un rôle. Il n’existe aucune donnée dans la littérature sur l’effet de l’hypoxie intermittente (HI) chronique sur la fonction vasculaire de l’œil.Le but de ce travail était de développer des techniques d’évaluation de la fonction vasculaire oculaire chez le rat et de les appliquer à l’étude des conséquences vasculaires oculaires de l’HI. Ainsi, deux approches complémentaires ont été développées : 1) un prototype de fluxmètre laser Doppler (LDF) adapté au rongeur pour l’évaluation in vivo de la perfusion sanguine rétinienne et de la tête du nerf optique (TNO) et 2) le modèle d’étude de l’artère ophtalmique (AO) du rat par myographie vasculaire, in vitro.La mise au point du LDF chez le rat sain a permis de valider la pertinence du signal provenant des artères rétiniennes. A l’inverse, nos données invalident l’intérêt de la mesure au niveau de la TNO. En réponse à l’inhalation d’oxygène pur, nous observons une diminution de 17,0 ± 13,7 % de la vélocité artérielle rétinienne (VelART). Nous n’observons pas de variation significative de VelART lors d’injection intra-carotidienne d’endothéline 1 (ET-1) malgré une forte vasoconstriction des vaisseaux rétiniens. Les perspectives consistent à associer une caméra de haute résolution à un système bidirectionnel de LDF. L’étude de la réactivité de l’AO par myographie chez le rat soumis à 14 jours d’HI a mis en évidence une augmentation de la contraction à l’ET-1, associée à une augmentation de la réponse médiée par les récepteurs de type A (ETRA)et à une surexpression des ETRA au sein de l’AO. La relaxation NO-dépendante était diminuée chez le rat HI, et associée à un effet prédominant des produits vasoconstricteurs du cytochrome P450. Ces réponses étaient associées à une augmentation de la présence d’anions superoxyde dans la paroi de l’AO. Des études complémentaires sont nécessaires pour explorer les mécanismes à l’origine des ces altérations vasculaires, en particulier le rôle du stress oxydant. / Obstructive sleep apnea (OSA) has recently been associated with the occurrence of optic neuropathies, especially acute non-arteritic anterior ischemic optic neuropathy (NAION). Among the mechanisms of NAION onset potentially associated with OSA, vascular dysregulation and inflammation may play a role. There is still no data on the effect of chronic intermittent hypoxia (IH) on vascular function of the eye. The purpose of this work was to develop techniques for assessing rat ocular vascular function and apply them to the study of the ocular vascular consequences of IH. Thus, two complementary models have been developed: 1) a laser Doppler flowmeter (LDF) prototype adapted for rodents, to evaluate in vivo retinal and optic nerve head (ONH) blood perfusion and 2) in vitro model of rat ophthalmic artery (OA) study by myography. Preliminary work on healthy rat enabled us to validate the relevance of retinal arteries LDF signal, but not that of the ONH. Retinal blood velocity (VelART) dropped by 17.0 ± 13.7% in response to pure oxygen inhalation. We did not observe any significant change in VelART signal after intracarotidian endothelin 1 (ET -1) injection, despite strong vasoconstriction of retinal vessels. OA reactivity study by myography in rats exposed to a 14-day IH showed increased contraction to ET-1, associated with an increased endothelin receptor A-mediated (ETRA) response and ETRA overexpression within the AO. NO-dependent relaxation is reduced in IH rats, and associated with a shift towards vasoconstrictive effects of cytochrome P450 products. These responses were associated with an increase in superoxide anions in the OA wall. Further studies are needed to explore the underlying mechanisms of these vascular changes, particularly the role of oxidative stress. Understanding of the LDF signal is partial and should be further explored to permit application to the study of IH rat.

Die Störung der intestinalen Mikrozirkulation gilt als ein kardinaler Mechanismus für die Entwicklung des Multiorganversagens bei Sepsis. Da das Intestinum für mikrozirkulatorische Studien klinisch kaum zugänglich ist, wurden die Auswirkungen einer Therapie mit den antioxidativen Substanzen Oxypurinol und U-74389G (Lazaroid) bzw. den vasoaktiven Substanzen Iloprost (Prostacyclin-Analogon) und Dopexamin auf die intestinale Mikrozirkulation und die systemische Mediatorfreisetzung in einem Tiermodell mit moderater und hoher Endotoxin-Belastung untersucht. Die intravitalmikroskopische Untersuchung der Kapillarperfusion in der Muskularisschicht bei Endotoxinämie erbrachte eine Verbesserung durch Oxypurinol- und Dopexamingabe. Die Perfusion der Mukosa konnte vor allem durch eine Iloprostapplikation gesteigert werden. Die Endotoxin-induzierte, intestinale Leukozytenadhärenz wurde insbesondere durch die Behandlung mit den antioxidativen Substanzen vermindert. Beide therapeutischen Optionen bewirkten eine ca. 60 %ige Reduktion der initialen Tumornekrosefaktor-alpha-Freisetzung in der Versuchsreihe mit der niedrigeren Endotoxin-Dosis. Parallel dazu konnte anhand von Malondialdehyd-Analysen gezeigt werden, dass Oxypurinol und U-74389G wirksam die intestinale, Radikal-induzierte Lipidperoxidation verringerten. Der intestinale mikrovaskuläre Blutfluss konnte durch beide vasoaktiven Substanzen - sowohl bei moderater als auch bei erhöhter Endotoxin-Dosierung - signifikant gesteigert werden. Die Ergebnisse beider Teilstudien bestätigten, dass sowohl reaktive Sauerstoffspezies als auch eine inadäquate Perfusion in der Mikrozirkulation wesentliche pathogenetische Faktoren bei Endotoxinämie bzw. Sepsis darstellen und entsprechende Therapieformen indiziert und effektiv sind. Eine kombinierte Gabe beider Substanzklassen erscheint daher sinnvoll und sollte in weiteren tierexperimentellen und klinischen Studien evaluiert werden. / The disturbance of the intestinal microcirculation is regarded as a pivotal mechanism in the development of multiorgan failure related to sepsis. Since the intestine is clinically not accessible for microcirculatory studies, the effects of a therapy with the antioxidants oxypurinol and U-74389G (lazaroid) as well as the vasoactive substances iloprost (a prostacyclin analogue) and dopexamine on the intestinal microcirculation and the systemic mediator release was studied in an animal model with moderate and high endotoxin challenge. The intravital microscopic examination of the capillary perfusion in the muscularis layer of the intestine during endotoxemia revealed an improvement by administration of oxypurinol and dopexamine. The perfusion of the mucosa could be increased by iloprost administration. The amount of the endotoxin induced, intestinal leukocyte adherence was especially decreased by the treatment with the antioxidants. Both therapeutic options caused a 60 % reduction in the initial tumor necrosis factor-alpha-release in the experiments with the lower endotoxin dose. Malondialdehyde analyses showed that oxypurinol and U-74389G reduced effectively the intestinal, radical-induced lipid peroxidation. The intestinal microvascular blood flow could be significantly increased by both vasoactive substances - as well as with moderately than also with elevated endotoxin-dosage. The results of the study confirmed that both reactive oxygen-species as well as an inadequate perfusion in the microcirculation represent essential pathogenetic factors during endotoxemia as well as sepsis and index corresponding therapy-forms and participates effective. A combined offering both substance-classes appears therefore meaningfully and should be evaluated in further experimental and clinical studies.

Inflammatory bowel diseases, (IBD), are a group of chronic disorders of the gastro-intestinal tract, and include Crohn’s disease (CD) and Ulcerative Colitis (UC). The pathogenesis is not known, but involves at least in part a loss of tolerance towards the commensal colonic microbiota. In this thesis, we show in animal models of CD and UC that the colonic mucosal blood flow increased compared to healthy animals. This blood flow increase is due to an up regulation of endothelial nitric oxide synthase (NOS). Further, we show in the UC model that the thickness of the firmly adherent colonic mucus layer increased compared to healthy animals. This increase is due to an up regulation of inducible NOS in the epithelium. Both the blood flow and mucus thickness increase appear to be protective mechanisms.  We demonstrate that the firmly adherent colonic mucus layer acts as a partial barrier towards luminal bacteria. In the UC model, this barrier is destroyed, causing increased bacterial translocation. The adhesion molecule P-selectin was up regulated in the UC model, leading to increased interactions between leukocytes and the endothelium, but also increased interactions between platelets and the endothelium. This indicates that not only leukocytes, but also platelets are involved in colonic inflammation. The addition of the probiotic bacterial strain Lactobacillus reuteri prevented disease by normalizing P-selectin levels and endothelial interactions with leukocytes and platelets. Lactobacillus reuteri also decreased bacterial translocation over the epithelium. In summary, this thesis highlights the importance of colonic barrier functions, and investigates the role of the microbiota in experimental IBD.