En se focalisant sur l'administration de médicaments dans et vers le système nerveux central et notamment pour le traitement du glioblastome, ce travail de thèse a eu pour but la mise en place d'outils expérimentaux et l'évaluation du comportement de nanovecteurs au cours du franchissement de barrières biologiques. Trois types de nanovecteurs de taille variant entre 20 et 100nm ont été appréhendés : des nanoparticules de polysaccharide, de PLGA et des nanocapsules lipidiques (LNC). Le comportement de ces objets vis-à-vis des éléments du sang a permis de définir que le revêtement par la transferrine de nanoparticules de PLGA et l'insertion de phospholipides ou de BSA dans des nanoparticules polysaccharidiques diminuait leur reconnaissance par le système réticulo-endothélial et améliorait leur temps de résidence plasmatique. Ces modifications de surface sont également associées à une possibilité d'internalisation dans les cellules cibles F98 de gliomes influencée essentiellement par la nature lipidique ou polymérique du vecteur. L'évaluation précise du comportement cellulaire et subcellulaire des LNC dans les cellules F98 a permis de démontrer que si la nature du vecteur est impliquée notamment en ce qui concerne le recrutement de voies d'endocytoses cholestéroldépendantes, la taille, corrélée au taux de surfactant véhiculé, est également impliquée. Les LNC de 20nm sont ainsi les plus aptes à permettre l'échappement lysosomal des principes actifs véhiculés et démontrent des activités pharmacologiques renforcées notamment pour ce qui concerne la mort cellulaire induite par le paclitaxel. Ces résultats établissent donc un lien original entre le comportement subcellulaire des vecteurs et la biodisponibilité des agents anticancéreux. De nouvelles potentialités de franchissement de barrières ligand- ou taille-dépendants ont été soulignées. Ces observations renforcent donc l'intérêt d'études comparatives permettant de rationaliser l'utilisation d'un vecteur donné pour un médicament et une cible donnés. Elles démontrent également tout l'intérêt d'établir des justifications entre le comportement biologique et la pertinence thérapeutique des nanovecteurs.

<p>Tissue factor (TF) is the initiator of the coagulation cascade. Monocytes do not normally express TF, but can be induced to do so by certain stimuli. Aberrant TF expression is important in the thrombotic complications of bacterial sepsis, certain malignancies and coronary artery disease (CAD). In this thesis, regulation of monocyte TF by cytokines and by interactions with other vascular cells were studied, as well as the activation of blood cells, inflammation and coagulation in CAD patients and the association of the pro-inflammatory cytokine interleukin (IL)-6 with prognosis in unstable CAD. </p><p>In a whole blood experimental system, the anti-inflammatory cytokine IL-10 was shown to suppress lipopolysaccharide-induced TF expression in monocytes, whereas IL-4 and IL-13 did not, contrary to previous in vitro findings. Activated platelets also induced monocyte TF in whole blood in a P-selectin-dependent manner, causing a rapid surface exposure of TF independent of mRNA formation. The differentiated monocytic cell line U-937 displayed different kinetics of platelet-stimulated TF induction.</p><p>In co-culture with cytokine-activated human coronary artery endothelial cells, U-937 cells expressed TF, and also IL-6. The endothelial cells up-regulated their production of IL-10. Simvastatin, enalapril and dalteparin, all commonly used drugs in CAD treatment, suppressed TF induction but did not alter cytokine expression in co-cultures.</p><p>In unstable CAD, there was an activation of both coagulation and inflammation compared to stable CAD that coincided with an increased activation of platelets and leukocytes. Women had different patterns of cellular activation than men, indicating differences in pathogenetic mechanisms.</p><p>Plasma levels of IL-6 above 5 ng/L proved to be a strong, independent marker for increased risk of death in a 6-12 month perspective in patients with unstable CAD. This risk was significantly reduced by an early invasive strategy.</p>

<p>Cardiopulmonary bypass (CPB) is associated with inflammatory response and activation of coagulation. Heparin coating of the CPB circuit is shown to improve the biocompatibility of the surface. The biological effects of a new heparin surface, the Corline Heparin Surface (CHS), prepared according to a new principle, have been studied. </p><p>The CHS used during coronary artery bypass grafting with CPB in sixty patients prevented adhesion of cells to the extracorporeal device. The activation of inflammation, coagulation, and fibrinolysis was significantly reduced by the use of CHS. Both a reduced and an increased dose of systemic heparin in combination with the heparin-coated surface resulted in more activation of inflammation and coagulation. </p><p>Photoelectron spectroscopy studies of the molecular structure of the CHS demonstrated that a single layer of the heparin surface, equivalent to what was used in the <i>in vivo</i> studies, did not completely cover the substrate surface. Additional layer of immobilized heparin has resulted in a complete coverage. We examined the biological effects, i.e. activation of inflammation and coagulation, by CHS in one and two layers in an <i>in vitro</i>-study. The data from this study clearly demonstrated that a uniform surface coating of the CHS results in only minor activation of coagulation, inflammation and cell activation. </p><p>Monocytes do not normally express tissue factor (TF), initiator of the coagulation <i>in vivo</i>, but can be induced upon adhesion to artificial surfaces. TF is receptor for coagulation factor VIIa (FVIIa) and binding subsequently leads to formation of thrombin. Other biological effects beyond coagulation, as inflammation and angiogenesis, has recently been associated with the formation of TF·FVIIa. The TF∙FVIIa signal transduction induced an increased sensitivity to PDGF-BB-stimulated migration and an increased production of IL-8 and TNF-α in monocytes. These could be important mechanisms for continued recruitment of cells to sites of inflammation. </p>

Allergic diseases are influenced by genetics and the environment. Maternal allergy appears to confer a higher risk for allergic sensitization than paternal allergy, suggesting an in utero influence. A decrease in particular infections or a lower exposure to microbial components during infancy is suggested to contribute to the high allergy prevalence in affluent societies. Toll-like receptors (TLR) 2 and 4 recognize peptidoglycan (PGN) and LPS respectively, are expressed on e.g. monocytes, and have been implicated in modulating the risk of IgE-sensitization. This thesis aimed to study the influence of maternal allergy and early microbial exposure on monocyte function and allergic sensitization during childhood. Blood samples from children participating in a prospective allergy cohort were used. Two-year old infants with allergic mothers had lower IL-6 production and reduced activation of the TLR-signalling intermediate p38-MAPK in response to PGN than children with non-allergic mothers. In 5-year old children, allergic disease and not maternal allergy influenced monocytic TLR2-regulation. Five-year olds who were seropositive for Epstein-Barr virus (EBV) at 2-years of age had a lower risk of persistent IgE-sensitization while EBV contraction after 2-years of age related to a higher risk of IgE-sensitization. Upon in vitro stimulation, NK cells from EBV+ 2-year olds produced lower IFN-g levels. EBV+ 2-year olds had also lower systemic IFN-g. In comparison to CD14++CD16- monocytes, CD14+CD16+ cells induced NK-cell IFN-g more potently in vitro, and EBV+ infants tended to have lower proportions of these CD14+CD16+ monocytes. This thesis highlights the importance of early-life microbial (EBV) exposure for a proper allergy-protective immunity. Also, maternal allergic heredity appears to influence monocytic microbial responses in early infancy. All these aspects relate to altered monocyte functionality, which suggest that they could have a role in allergic sensitization.

Tissue factor (TF) is the initiator of the coagulation cascade. Monocytes do not normally express TF, but can be induced to do so by certain stimuli. Aberrant TF expression is important in the thrombotic complications of bacterial sepsis, certain malignancies and coronary artery disease (CAD). In this thesis, regulation of monocyte TF by cytokines and by interactions with other vascular cells were studied, as well as the activation of blood cells, inflammation and coagulation in CAD patients and the association of the pro-inflammatory cytokine interleukin (IL)-6 with prognosis in unstable CAD. In a whole blood experimental system, the anti-inflammatory cytokine IL-10 was shown to suppress lipopolysaccharide-induced TF expression in monocytes, whereas IL-4 and IL-13 did not, contrary to previous in vitro findings. Activated platelets also induced monocyte TF in whole blood in a P-selectin-dependent manner, causing a rapid surface exposure of TF independent of mRNA formation. The differentiated monocytic cell line U-937 displayed different kinetics of platelet-stimulated TF induction. In co-culture with cytokine-activated human coronary artery endothelial cells, U-937 cells expressed TF, and also IL-6. The endothelial cells up-regulated their production of IL-10. Simvastatin, enalapril and dalteparin, all commonly used drugs in CAD treatment, suppressed TF induction but did not alter cytokine expression in co-cultures. In unstable CAD, there was an activation of both coagulation and inflammation compared to stable CAD that coincided with an increased activation of platelets and leukocytes. Women had different patterns of cellular activation than men, indicating differences in pathogenetic mechanisms. Plasma levels of IL-6 above 5 ng/L proved to be a strong, independent marker for increased risk of death in a 6-12 month perspective in patients with unstable CAD. This risk was significantly reduced by an early invasive strategy.

Cardiopulmonary bypass (CPB) is associated with inflammatory response and activation of coagulation. Heparin coating of the CPB circuit is shown to improve the biocompatibility of the surface. The biological effects of a new heparin surface, the Corline Heparin Surface (CHS), prepared according to a new principle, have been studied. The CHS used during coronary artery bypass grafting with CPB in sixty patients prevented adhesion of cells to the extracorporeal device. The activation of inflammation, coagulation, and fibrinolysis was significantly reduced by the use of CHS. Both a reduced and an increased dose of systemic heparin in combination with the heparin-coated surface resulted in more activation of inflammation and coagulation. Photoelectron spectroscopy studies of the molecular structure of the CHS demonstrated that a single layer of the heparin surface, equivalent to what was used in the in vivo studies, did not completely cover the substrate surface. Additional layer of immobilized heparin has resulted in a complete coverage. We examined the biological effects, i.e. activation of inflammation and coagulation, by CHS in one and two layers in an in vitro-study. The data from this study clearly demonstrated that a uniform surface coating of the CHS results in only minor activation of coagulation, inflammation and cell activation. Monocytes do not normally express tissue factor (TF), initiator of the coagulation in vivo, but can be induced upon adhesion to artificial surfaces. TF is receptor for coagulation factor VIIa (FVIIa) and binding subsequently leads to formation of thrombin. Other biological effects beyond coagulation, as inflammation and angiogenesis, has recently been associated with the formation of TF·FVIIa. The TF∙FVIIa signal transduction induced an increased sensitivity to PDGF-BB-stimulated migration and an increased production of IL-8 and TNF-α in monocytes. These could be important mechanisms for continued recruitment of cells to sites of inflammation.

The focus of this work was to functionally characterize the CD300e receptor expressed in human monocytes and myeloid dendritic cells and investigate the implications that receptor engagement has on their biology. We provide evidence formally supporting that CD300e functions as an activating receptor capable of regulating the innate immune response by triggering various pro- inflammatory functions including intracellular calcium mobilization, superoxide anion production, pro-inflammatory cytokine release and up-regulation of co-stimulatory molecules in myeloid cells. We also report that ligation of CD300e on the surface of monocytes results in their differentiation to functional M&#934;2-like macrophages by an autocrine mechanism that involves M-CSF and its receptor (CD115). / L'objectiu d'aquest treball ha estat caracteritzar funcionalment el receptor CD300e expressat en monòcits i cèl·lules dendrítiques mieloides humanes, així com investigar les implicacions que l'activació d'aquest receptor pot tenir en la seva biologia. Demostrem formalment que el receptor CD300e funciona com un receptor activador capaç de regular la resposta immune innata activant diverses funcions proinflamatòries, incloent la mobilització de calci intracel·lular, la producció d'anió superòxid, la secreció de citocines proinflamatòries i la inducció de molècules coestimuladores en cèl·lules mieloides. També descrivim que l'activació del receptor CD300e a la superfície dels monòcits provoca la seva diferenciació cap a macròfags funcionals del tipus M&#934;2 gràcies a un mecanisme autocrí que funciona a través del M-CSF i el seu receptor (CD115).

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Les bactéries commensales digestives jouent un rôle primordial dans l'homéostasie épithéliale et la santé de l'hôte, avec notamment un rôle modulateur du système immunitaire. Des effets bénéfiques dans le traitement des pathologies inflammatoires intestinales ont été caractérisés chez certaines souches de bactéries commensales. La compréhension de ces effets dans le maintien de l'homéostasie intestinale repose sur la connaissance des interactions entre les bactéries, l'épithélium intestinal et le système immunitaire muqueux. Streptococcus salivarius est l'un des premiers colonisateurs de la cavité buccale et du tractus digestif de l'homme. Cette bactérie a été utilisée comme modèle pour rechercher des mécanismes impliquée dans l'homéostasie.La recherche d'interactions entre des souches de l'espèce S. salivarius et les cellules humaines a été réalisée pour caractériser leurs éventuelles propriétés immunomodulatrices. Nous avons montré que les bactéries vivantes et les surnageants de cultures des souches de cette espèce modulent la réponse inflammatoire in vitro via un effet inhibiteur sur l'activation de la voie NF-B dans les cellules épithéliales intestinales (HT-29 et Caco-2) et les monocytes (THP-1). Cette modulation de l'inflammation a été confirmée par la capacité des surnageants bactériens à inhiber la sécrétion d'IL-8 par les cellules épithéliales. Ces surnageants agissent via une étape impliquant IB-, un inhibiteur du facteur NF-B. Ils inhibent la dégradation de la protéine IB- phosphorylée et diminuent ainsi la translocation nucléaire des composants NF-B. Nous avons également identifié et caractérisé un métabolite bactérien présent dans ces surnageants exerçant cette activité anti-inflammatoire. L'utilisation de ce métabolite et son isomère miment in vitro l'effet inhibiteur des surnageants sur l'activation de la voie NF-B dans les cellules épithéliales et les monocytes. Nous avons ainsi caractérisé un métabolite secrété par la bactérie commensale S. salivarius qui est capable d'inhiber une des voies centrales de signalisation impliquée dans la réponse inflammatoire intestinale. Enfin, une capacité anti-inflammatoire de S. salivarius a également été montrée dans un modèle murin d'inflammation digestive dans lequel les bactéries métaboliquement actives ont protégé les animaux de colites induites avec du TNBS. Ces travaux ouvrent la voie pour le développement d'applications thérapeutiques dans le traitement de pathologies inflammatoires de l'intestin basées sur ce composé actif ou l'utilisation de S. salivarius comme probiotique.