Le but de notre travail était l’étude des dysfonctions artérielle et musculaire dans des modèles d’agression aiguë et chronique puis l’évaluation de l’effet de la modulation pharmacologique du stress oxydant sur les anomalies vasculaires induites. Dans le modèle aigu de choc endotoxinique chez la souris, l’administration d’albumine humaine a permis d’augmenter leur survie, d’améliorer l’hyporéactivité vasculaire et la dysfonction endothéliale grâce à des propriétés ,concentration-dépendante, anti-oxydantes, modulatrices de l’inflammation, aboutissant à une diminution de l’expression de la NOS inductible et à une amélioration fonctionnelle et quantitative de la NOS endothéliale. L’administration chronique chez le rat de ciclosporine ou d’évérolimus induit une dysfonction endothéliale caractérisée par une altération de la voie de signalisation du NO et de l’EDHF et associée à une augmentation locale du stress oxydant. Au niveau musculaire cardiaque, seul l’évérolimus induit une augmentation de radicaux libres et une diminution de la respiration mitochondriale ventriculaire droite. L’administration préventive de polyphénols a permis, une amélioration de la composante EDHF de la dysfonction endothéliale, ciclosporine-induite, via une diminution de la surexpression de la NADPH oxydase et du stress oxydant vasculaire. Ainsi, le stress oxydant est une entité commune, impliquée dans la genèse de dysfonctions vasculaire et musculaire. Sa modulation par l’administration d’albumine ou de polyphénols a permis respectivement l’amélioration de l’hyporéactivité vasculaire du choc endotoxinique et de la dysfonction endothéliale dans nos deux modèles. / The aim of this work was to study the arterial and muscular dysfunctions in two rodent models of acute and chronic injuries, then the evaluation of pharmacological evaluation of oxidative stress on vascular abnormalities induced in these models.In the acute model, a mouse endotoxic shock, human serum albumin administration improved survival, endothelial dysfunction and reduced vascular hyporeactivity thanks to its concentration-dependant , anti-oxidative and anti-inflammatory properties, leading to a decrease of inductible NOS expression and an qualitative and quantitative increase of endothelial NOS.In the chronic model, rat’s administration of ciclopsorine and everolimus induced an endothelial dysfunction characterized by alterations of both NO and EDHF pathways and associated with an in situ oxidative stress. In the cardiac muscle, an increase of reactive oxygen species and a decrease of right ventricle mitochondrial respiratory chain complexes activities was observed only with everolimus. The preventive administration of polyphenols markedly increased the blunted EDHF component, but not the NO component, of the cyclosporine-induced endothelial dysfunction by reducing NADPH oxidase over expression and oxidative vascular stress. Finally, oxidative stress is a common entity, implicated in genesis of vascular and muscular dysfunctions. Its modulation by human albumin or polyphenols administration improves respectively arterial hyporeactivity of endotoxinic shock and endothelial dysfunction in our two models.

L’hyperglycémie et l’insulino-résistance constituent les altérations métaboliques des patients septiques associées à un pronostic défavorable, à une augmentation des dysfonctions cardiovasculaires et à une augmentation de la mortalité. Si plusieurs études démontrent quel’insulinothérapie à forte dose diminue la mortalité et prévient la dysfonction multi-organes, elle est souvent controversée car responsable d’hypoglycémies délétères. La Protéine Tyrosine Phosphatase1B (PTP1B) est un régulateur négatif de la voie de signalisation dépendante de l’insuline et de la voie de production du NO.L’idée développée dans le laboratoire est que l’inhibition de la PTP1B pourrait constituer une cible thérapeutique potentielle dans le sepsis en améliorant la sensibilité à l’insuline et ainsi les conséquences sur la fonction endothéliale et cardiaque. Bien qu’il ait été montré que la délétion génétique en PTP1B diminue la dysfonction cardiovasculaire lors du sepsis, les effets de cette délétion sur le métabolisme glucidique dans l’amélioration de la dysfonction cardiovasculaire restent méconnus et constituent l’objectif de notre travail.Dans un modèle de sepsis induit par Ligature et Perforation Caecale, nous avons pu mettre en évidence que la délétion génétique totale de PTP1B limite l’insulino-résistance induite par le sepsis,améliore la voie de signalisation dépendante de l’AMPK et la translocation des GLUT-4 et diminue l’inflammation. Ces effets s’accompagnent d’une diminution de la dysfonction endothéliale induite parle sepsis et améliore la production de NO. La délétion génétique endothéliale de PTP1B permet quant à elle une amélioration significative de la fonction endothéliale et de la sensibilité à l’insuline et au glucose.Ces travaux ont donc permis de mettre en évidence l’effet bénéfique de la délétion génétique en PTP1B dans le sepsis par amélioration de la sensibilité à l’insuline et des conséquences sur la fonction endothéliale et cardiaque. / Hyperglycemia and insulin resistance are septic metabolic alterations associated with poorprognosis, increased cardiovascular dysfunction and mortality. Several studies have demonstrated thathigh-dose insulin therapy reduces mortality and prevents multi-organ dysfunction but is controversialbecause it is often associated with deleterious hypoglycemia. Protein Tyrosine Phosphatase 1B (PTP1B)is a negative regulator of both insulin signaling and NO production.The concept developed in our laboratory is that PTP1B inhibition could be a potentialtherapeutic target in sepsis by improving both insulin sensitivity and these consequences onendothelial and cardiac function. PTP1B genetic deletion has been shown to decrease cardiovasculardysfunction in sepsis but the effects of this deletion on carbohydrate metabolism in the improvementof cardiovascular dysfunction remain unknown and constitute the objective of our work.In a sepsis model induced by Ligature and Caecal Perforation, we have demonstrated that thetotal PTP1B genetic deletion limits insulin resistance induced by sepsis, improves the AMPK signalingpathway, the GLUT-4 translocation and reduces inflammation. These effects are followed by decreasedendothelial dysfunction induced by sepsis and improves NO production. The endothelial PTP1B geneticdeletion, significantly improves endothelial function, insulin and glucose sensitivity.This work demonstrate the beneficial effect of the PTP1B genetic deletion in the sepsis byimprovement of the insulin sensibility and these consequences on endothelial and cardiac function.

Epidemiological studies have shown strong and consistent associations between exposure to air pollution and increases in morbidity and mortality. Key air pollutants that have been identified include fine particulate matter (PM) and ozone (O3), both major contributors to smog. However, there is a lack of understanding of the mechanisms involved and the relative contributions of individual pollutants. A controlled human exposure facility was used to carry out inhalation studies of concentrated ambient fine particles (CAP), O3, CAP+O3 and filtered air following a randomized design. Exposures were 2 hrs in duration at rest. Subjects included mild asthmatics and non-asthmatics. This thesis focuses on acute cardiovascular responses including blood pressure (BP), brachial artery reactivity (flow-mediated dilatation [FMD]) and markers of systemic inflammation (blood neutrophils and interleukin [IL]-6). Results showed that for CAP-containing exposures (CAP, CAP+O3) there were small but significant transient increases in diastolic BP (DBP) during exposures. Furthermore, neutrophils and IL-6 increased 1 - 3 hrs after and FMD decreased 20 hrs after CAP-containing exposures. Responses to O3 were smaller, comparable to filtered air. The data suggests that adverse responses were mainly driven by PM. The DBP increase was rapid-developing and quick to dissipate, which points to an autonomic irritant response. The magnitude of the DBP increase was strongly negatively associated with the high frequency component of heart rate variability, suggesting parasympathetic withdrawal as a mechanism. In comparison, IL-6, neutrophil and FMD responses were slower to develop, indicative of an inflammatory mechanism. An intriguing finding was that IL-6 increased 3 hrs after CAP, but not after CAP+O3. Further investigation revealed that exposure to CAP+O3 in some individuals may trigger a reflex inhibition of inspiration, decreasing their tidal volume and inhaled pollutant dose, leading to a reduction in systemic IL-6, a potential protective mechanism. Together the findings support the epidemiological evidence of adverse fine PM health effects. Many questions remain to be answered about the health effects of air pollution including a better understanding of how inhaled pollutants result in cardiovascular effects. It is hoped that the insights gained from this thesis will advance the understanding of air pollution health effects.

Epidemiological studies have shown strong and consistent associations between exposure to air pollution and increases in morbidity and mortality. Key air pollutants that have been identified include fine particulate matter (PM) and ozone (O3), both major contributors to smog. However, there is a lack of understanding of the mechanisms involved and the relative contributions of individual pollutants. A controlled human exposure facility was used to carry out inhalation studies of concentrated ambient fine particles (CAP), O3, CAP+O3 and filtered air following a randomized design. Exposures were 2 hrs in duration at rest. Subjects included mild asthmatics and non-asthmatics. This thesis focuses on acute cardiovascular responses including blood pressure (BP), brachial artery reactivity (flow-mediated dilatation [FMD]) and markers of systemic inflammation (blood neutrophils and interleukin [IL]-6). Results showed that for CAP-containing exposures (CAP, CAP+O3) there were small but significant transient increases in diastolic BP (DBP) during exposures. Furthermore, neutrophils and IL-6 increased 1 - 3 hrs after and FMD decreased 20 hrs after CAP-containing exposures. Responses to O3 were smaller, comparable to filtered air. The data suggests that adverse responses were mainly driven by PM. The DBP increase was rapid-developing and quick to dissipate, which points to an autonomic irritant response. The magnitude of the DBP increase was strongly negatively associated with the high frequency component of heart rate variability, suggesting parasympathetic withdrawal as a mechanism. In comparison, IL-6, neutrophil and FMD responses were slower to develop, indicative of an inflammatory mechanism. An intriguing finding was that IL-6 increased 3 hrs after CAP, but not after CAP+O3. Further investigation revealed that exposure to CAP+O3 in some individuals may trigger a reflex inhibition of inspiration, decreasing their tidal volume and inhaled pollutant dose, leading to a reduction in systemic IL-6, a potential protective mechanism. Together the findings support the epidemiological evidence of adverse fine PM health effects. Many questions remain to be answered about the health effects of air pollution including a better understanding of how inhaled pollutants result in cardiovascular effects. It is hoped that the insights gained from this thesis will advance the understanding of air pollution health effects.

Étude de déterminants de la dysfonction vasculaire pulmonaire au cours du syndrome de détresse respiratoire aigue. La physiopathologie du syndrome de détresse respiratoire aigue (Acute Respiratory Distress Syndrome, ARDS) inclut une dysfonction vasculaire pulmonaire, résultant de phénomènes de thrombose, hyperperméabilité endothéliale, dysrégulation de la vasomotricité et remodelage. La ventilation en pression positive est un facteur aggravant. Il en résulte une augmentation des résistances vasculaires pulmonaires, à l'origine d'une hypertension pulmonaire et à risque de cœur pulmonaire aigu, associés à un pronostic péjoratif au cours de l'ARDS. Mais les déterminants de cette dysfonction vasculaire pulmonaire demeurent largement méconnus. Un modèle murin d'agression pulmonaire aigue two hit a été développé, associant une instillation orotrachéale de lipopolysaccharide bactérien à une ventilation mécanique protectrice, avec explorations physiologiques respiratoires et hémodynamiques invasives. Trois déterminants potentiels de la dysfonction vasculaire pulmonaire ont été étudiés. Dans le premier travail, nous avons établi que l'utilisation de manœuvres de recrutement alvéolaire, consistant en l'application transitoire et répétée de hauts niveaux de pression positive, limitait la dégradation de la mécanique ventilatoire mais induisait une hypertension pulmonaire. Une analyse transcriptomique pulmonaire a montré une dysrégulation d'un grand nombre de gènes impliqués dans les principales fonctions endothéliales. Dans le deuxième travail, une déficience en interleukine-6 a été montrée associée à une inflammation et un œdème pulmonaires majorés. Une élévation des résistances pulmonaires totales était aussi observée, prévenue par l'injection d'interleukine-6 recombinante et au moins partiellement attribuable à une dysrégulation de la vasomotricité pulmonaire impliquant la voie des nitric oxide synthases. Dans le troisième travail, nous avons comparé des souris adultes jeunes et d'âge mature et illustré une gravité âge-dépendante, caractérisée par une inflammation systémique et pulmonaire et une fuite alvéolocapillaire accrues, ainsi qu'un dosage bronchoalvéolaire d'angiopoiétine 2 élevé, suggérant une atteinte endothéliale sévère. Nos résultats pourraient contribuer à l'identification de nouvelles voies thérapeutiques ciblant la microvascularisation pulmonaire au cours de l'ARDS. Mots clés: syndrome de détresse respiratoire aigue, ventilation mécanique, hypertension pulmonaire, dysfonction vasculaire pulmonaire, vieillissement, interleukine-6, manœuvre de recrutement. / Study of factors determining the pulmonary vascular dysfunction during acute respiratory distress syndrome.The pathophysiology of the acute respiratory distress syndrome (ARDS) includes a pulmonary vascular dysfunction, which is attributable to thrombosis, endothelial hyperpermeability, dysregulation of the pulmonary vasomotor tone and remodeling. Positive pressure ventilation is an exacerbating factor. The result is an increase in the pulmonary vascular resistances, which lead to an acute pulmonary hypertension and may cause acute cor pulmonale, both associated with an altered prognosis during ARDS. But the factors determining the pulmonary vascular dysfunction are poorly known. A murine model of two hit acute lung injury, combining an orotracheal aspiration of bacterial lipopolysaccharide to a protective mechanical ventilation, with physiological respiratory and invasive hemodynamic monitoring. Three factors which might determine pulmonary vascular dysfunction were studied. In the first work, we established that the use of alveolar recruitment maneuvers, consisting in a transient and repetitive application of high positive pressure level, minimized the alteration of lung mechanics but induced a pulmonary hypertension. A transcriptomic lung analysis showed a dysregulation of many genes involved in main endothelial functions. In the second work, a interleukin-6 deficiency was shown to be associated with higher pulmonary inflammation and edema. An increase in total pulmonary resistances was also observed, but prevented with a human recombinant interleukin-6 treatment and at least partially attributed to a nitric oxide synthase-dependent dysregulation of the pulmonary vasoreactivity. In the third work, we compared young adult and mature adult mice and we observed an age-dependent severity, including a higher systemic and pulmonary inflammation, a higher alveolocapillary leak and a higher bronchoalveolar angiopoietin 2, suggestive for a severe endothelial injury. Our results might contribute to identify new therapeutic pathways targeting pulmonary microvessels during ARDS.Key words: acute respiratory distress syndrome, mechanical ventilation, pulmonary hypertension, pulmonary vascular dysfunction, aging, interleukin-6, recruitment maneuvers.

Functional vasodilation in arterioles is impaired with chronic ischemia. We sought to examine the impact of chronic ischemia and age on skeletal muscle resistance artery function. To examine the impact of chronic ischemia, the femoral artery was resected from young (2-3mo) and adult (6-7mo) mice and the profunda femoris artery diameter was measured at rest and following gracilis muscle contraction 14 days later using intravital microscopy. Functional vasodilation was significantly impaired in ischemic mice (14.4±4.6% vs. 137.8±14.3%, p<0.0001 n=8) and non-ischemic adult mice (103.0±9.4% vs. 137.8±14.3%, p=0.05 n=10). In order to analyze the cellular mechanisms of the impairment, a protocol was developed to apply pharmacological agents to the experimental preparation while maintaining tissue homeostasis. Endothelial and smooth muscle dependent vasodilation were impaired with ischemia, 39.6 ± 13.6% vs. 80.5 ± 11.4% and 43.0 ± 11.7% vs. 85.1 ± 10.5%, respectively. From this data, it can be supported that smooth muscle dysfunction is the reason for the observed impairment in arterial vasodilation.