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Mécanismes cellulaires et moléculaires de la susceptibilité à l'infection au cours de la bronchopneumopathie chronique obstructive (BPCO) / Cellular and molecular mechanisms of susceptibility to infection in chronic obstructive pulmonary disease (COPD)Koné, Bachirou 26 September 2017 (has links)
La BPCO se traduit rapidement par l'apparition d'une susceptibilité aux infections liées aux atteintes des mécanismes de défense du poumon. Les travaux antérieurs de l’équipe montrent qu'une altération de la réponse IL-17/IL-22 et de la fonction des cellules dendritiques (DC) participe au développement de l’exacerbation de la BPCO par les bactéries. Les mécanismes responsables de ce défaut de réponse ne sont pas élucidés. Au cours de cette thèse, nous nous sommes intéressés aux points suivants :1-Mécanismes cellulaires responsables du défaut de production d'IL-17 et d'IL-22 au cours de l'infection.Les cellules présentatrices d'antigène (APC) et en particulier, les DC jouent un rôle essentiel dans la réponse antimicrobienne, par leur fonction de phagocytes et par l’activation et la polarisation de cellules immunitaires innées et adaptatives. Sur des modèles murins d’exacerbation de la BPCO par Streptococcus pneumoniae ou Haemophilus influenzae non typable (NTHi), nous avons réalisé des tris de macrophages, DC et monocytes inflammatoires du poumon par cytométrie en flux. Ces analyses montrent que les cellules APC pulmonaires présentent des altérations fonctionnelles aboutissant à une limitation de leur capacité à polariser la réponse Th17 de Lymphocytes T CD4+. Une analyse transcriptomique est également effectuée sur les ARN des APC triées afin de préciser les altérations fonctionnelles de ces cellules par rapport aux souris contrôles.2-Rôle des cytokines IL-20 dans la susceptibilité à l'infection et l'exacerbation de la BPCO Myles et al ont montré en 2013 que les cytokines IL-20 (IL-19, IL-20 et IL-24) jouent un rôle délétère dans la réponse immunitaire cutanée contre Staphylococcus aureus par un mécanisme impliquant une inhibition indirecte d’IL-17 produite par les cellules T. La fonction des DC peut être affecté par l'environnement cytokinique. Comme les cytokines IL-20 sont surexprimées chez les souris BPCO, notre objectif a été de définir leur rôle au cours de l'exacerbation de la BPCO et l'impact de ces cytokines sur les DC dans ce contexte.Dans notre modèle d’exacerbation de la BPCO, nous avons bloqué cette voie en neutralisant l'IL-20RB qui est commune aux 2 récepteurs de ces cytokines afin d’étudier leur impact sur l'exacerbation et sur la réponse immune associée, notamment la réponse IL-17/IL-22. En parallèle, nous avons analysé la modulation de la fonction des DC humaines par ces cytokines dans un contexte d'infection bactérienne. Nos résultats montrent que le traitement avec l'anticorps bloquant anti-IL-20RB permet de bloquer le développement de l'exacerbation de la BPCO en diminuant la charge bactérienne et l'inflammation associée. Cet effet est associé à une diminution importante de la mobilisation des DC dans le poumon mais sans affecter sur la réponse IL-17/IL-22. In vitro, les cytokines IL-20 sont produites par les DC dans un contexte infectieux. De plus, ces cytokines sont capables de diminuer l'activation des ces cellules par les bactéries et de réduire leur capacité à activer les Lymphocytes T dans ce contexte.3-Capacité d'un immunostimulant à restaurer la réponse IL-17/IL-22, et à limiter le développement de l'exacerbation.L’utilisation d’immunostimulant dont la flagelline (agoniste du TLR-5, principale composante du flagelle bactérien) est souvent proposé comment pouvant promouvoir la réponse immunitaire des muqueuses et en particulier la réponse IL-17/IL-22. Nous avons analysé la capacité de cet agoniste du TLR-5 à améliorer la réponse à S. pneumoniae et NTHi dans notre modèle d’exacerbation de la BPCO.Le traitement par la flagelline permet de limiter les conséquences de l'infection bactérienne chez les souris BPCO en diminuant l'inflammation et les lésions pulmonaires associées. L'effet de ce ligand de TLR est au moins en partie dépendant de la production d'IL-22._A terme, ces données permettent d'envisager de nouvelles options thérapeutiques pour le traitement des exacerbations de la BPCO. / Patients with COPD often presented a susceptibility to respiratory infections. Previous works in our lab have showed that a defect of IL-17/IL-22 response and an altered dendritic cell (DC) function is involved in COPD exacerbation with bacteria. However, the mechanism responsible for this defect is not elucidated yet. In order to better define these mechanisms and to develop new therapeutic approaches against COPD exacerbation, we focused on the following points during this PhD project:1-Cellular mechanisms responsible of the defect of IL-17 and IL-22 production during infection in COPD.Antigen presenting cells (APC) particularly, DC are essential in antimicrobial immune response since they are professional phagocytes able to engulf and kill bacteria, but also by their essential role in the polarization of innate and adaptive immune responses. We worked on COPD exacerbation mice model infected with Streptococcus pneumoniae or Nontypeable Haemophilus influenzae (NTHi). APC including macrophages, DC and inflammatory monocytes were sorted by flow cytometry for phenotype and functional analysis. We found an altered function of these lung APC showing limited capacity of Th17 polarization. Transcriptional analysis on total RNA from sorted APC is performed to decipher the mechanisms involved in this functional alteration regarding to control mice.2-The role of IL-20 cytokines in the susceptibility to infection during COPD exacerbation.Myles et al showed in 2013 that IL-20 cytokines (IL-19, IL-20 and IL-24) are deleterious in skin immune response against Staphylococcus aureus. Indeed, these IL-20 cytokines indirectly inhibited IL-17 produced by T cells. The function of DC is also controlled by the presence of cytokines in the microenvironment. Because IL-20 cytokines are overexpressed in COPD, we aimed to determine their role during COPD exacerbation and the impact on DC.We used IL-20RB (common subunits of the 2 receptors) neutralizing antibodies to blocked IL-20 cytokines in COPD exacerbation mice model. We analyzed the impact of this treatment on the immune response, more particularly IL-17/IL-22 response. In addition, we analyzed the modulation of human monocyte derived DC (MDDC) function by IL-20 cytokines in the context of bacterial infection.Our results shows that treatment with IL-20 RB neutralizing antibodies limited COPD exacerbation by reducing the bacterial burden and the associated inflammatory response. This process was associated to reduced number of DC in the lung without impacting IL-17 and IL-22 production. In vitro, MDDC produced IL-20 cytokines upon bacterial infection. Additionally, these cytokines impaired MDDC activation following bacterial infection, which was associated to a reduced capacity of MDDC to activate T lymphocytes.3-The possibility to restore IL-17 and IL-22 response with immuno-stimulants in order to limit the development of COPD exacerbation.Flagellin (a TLR-5 agonist, the main component of bacterial flagellum) is an immuno-stimulant often used to promote mucosal immune response. This activity is related to its ability to promote IL-17 and IL-22 production. In this PhD work, we analyzed the capacity of this TLR-5 agonist to improve the immune response during S. pneumoniae and NTHi infection in COPD exacerbation mice model.Flagellin treatment reduced the bacterial burden and limited the consequences of bacterial infection in COPD mice, by lowering the inflammation and the associated lung remodeling. We also found that the immunomodulatory effect of flagellin was at least partially IL-22 dependent.Finally, these data allow to identify new therapeutic tools potentially useful for the treatment of COPD exacerbations.
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Dynamics of Cilia and Flagella / Bewegung von Zilien und GeißelnHilfinger, Andreas 14 January 2006 (has links) (PDF)
Cilia and flagella are hair-like appendages of eukaryotic cells. They are actively bending structures that exhibit regular beat patterns and thereby play an important role in many different circumstances where motion on a cellular level is required. Most dramatic is the effect of nodal cilia whose vortical motion leads to a fluid flow that is directly responsible for establishing the left-right axis during embryological development in many vertebrate species, but examples range from the propulsion of single cells, such as the swimming of sperm, to the transport of mucus along epithelial cells, e.g. in the ciliated trachea. Cilia and flagella contain an evolutionary highly conserved structure called the axoneme, whose characteristic architecture is based on a cylindrical arrangement of elastic filaments (microtubules). In the presence of a chemical fuel (ATP), molecular motors (dynein) exert shear forces between neighbouring microtubules, leading to a bending of the axoneme through structural constraints. We address the following two questions: How can these organelles generate regular oscillatory beat patterns in the absence of a biochemical signal regulating the activity of the force generating elements? And how can the beat patterns be so different for apparently very similar structures? We present a theoretical description of the axonemal structure as an actively bending elastic cylinder, and show that in such a system bending waves emerge from a non-oscillatory state via a dynamic instability. The corresponding beat patterns are solutions to a set of coupled partial differential equations presented herein.
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Dynamics of Cilia and FlagellaHilfinger, Andreas 07 February 2006 (has links)
Cilia and flagella are hair-like appendages of eukaryotic cells. They are actively bending structures that exhibit regular beat patterns and thereby play an important role in many different circumstances where motion on a cellular level is required. Most dramatic is the effect of nodal cilia whose vortical motion leads to a fluid flow that is directly responsible for establishing the left-right axis during embryological development in many vertebrate species, but examples range from the propulsion of single cells, such as the swimming of sperm, to the transport of mucus along epithelial cells, e.g. in the ciliated trachea. Cilia and flagella contain an evolutionary highly conserved structure called the axoneme, whose characteristic architecture is based on a cylindrical arrangement of elastic filaments (microtubules). In the presence of a chemical fuel (ATP), molecular motors (dynein) exert shear forces between neighbouring microtubules, leading to a bending of the axoneme through structural constraints. We address the following two questions: How can these organelles generate regular oscillatory beat patterns in the absence of a biochemical signal regulating the activity of the force generating elements? And how can the beat patterns be so different for apparently very similar structures? We present a theoretical description of the axonemal structure as an actively bending elastic cylinder, and show that in such a system bending waves emerge from a non-oscillatory state via a dynamic instability. The corresponding beat patterns are solutions to a set of coupled partial differential equations presented herein.
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