Selon les facteurs solubles de l’environnement (cytokines), les monocytes peuvent se différencier en macrophages (Mφ) ou en cellules dendritiques. Mes travaux de thèse montrent que l’IL-34, un second ligand du M-CSF-R (c-fms ou CD115), induit la différenciation de monocytes humains en macrophages CD14+ CD163+ (IL-34-Mφ), phénotypiquement et fonctionnellement similaires aux M-CSF-Mφ et aux macrophages associés aux tumeurs (TAM) isolés du cancer de l’ovaire. Ils possèdent des propriétés immunosuppressives et diminuent la prolifération des lymphocytes T CD4+ activés. Comme les Mφ orchestrent la réponse immunitaire, j’ai évalué la capacité des M-CSF-Mφ, IL-34-Mφ et des TAM à polariser les LT CD4+ mémoires. Les résultats montrent qu’ils polarisent des LT non-Th17 mémoires en LTh17 CCR4+ CCR6+ CD161+ conventionnels exprimant ou non de l’IFN. Ce processus est médié par l’expression constitutive de l’IL-1α membranaire exprimées sur ces macrophages.Dans le but d’identifier des stratégies pour prévenir l’accumulation de ces Mφ dans le cancer, j’ai montré que (i) l’IFNγ et le GM-CSF inhibent la différenciation des M-CSF-Mφ et IL-34-Mφ et que (ii) l’IFNγ permet la réversion des M-CSF-Mφ et IL-34-Mφ en Mφ immunostimulants. En conclusion, mes travaux montrent que les M-CSF-Mφ, IL-34-Mφ et les TAM, considérés initialement comme anti-inflammatoires, induisent la génération de lymphocytes Th17 via une expression constitutive de l’IL-1α. Ce processus pourrait contribuer à maintenir, localement, une inflammation modérée nécessaire au développement tumoral. / According to the soluble factors in the environment (cytokines), monocytes differentiate into macrophages (Mϕ) or dendritic cells. This project demonstrates that IL-34, a second ligand of the M-CSF receptor (c-fms or CD115), induces the differentiation of human monocytes into CD14high CD163 high Mφ (IL-34-Mφ), phenotypically and functionally similar to M-CSF-Mφ and to tumorassociated macrophages (TAM) isolated from the ovarian cancer. They exhibit potent immunosuppressive properties and decrease the proliferation of stimulated Tcells. As Mφ orchestrate the immune response, I have evaluated the capacity of M-CSF-Mφ, IL-34-Mφ and TAM to polarize human memory CD4+ T cells. Unexpectedly, results showed that they switch non- Th17 memory CD4+ T cells into conventional CCR4+ CCR6+ CD161+ Th17 cells, expressing or not IFNγ. This process is mediated by the constitutive expression of membrane IL-1α on these Mϕ subsets. In an attempt to identify strategies to prevent an accumulation of immunomodulatory Mϕ in cancer, I have shown that (i) IFNγ and GM-CSF prevent M-CSFandIL-34-induced monocyte differentiation into immunosuppressive Mφ and (ii) that IFNγ switchesestablished M-CSF-Mφ and IL-34-Mφ into immunostimulatory Mφ. In conclusion, this study demonstrates that human MCSF- Mφ, IL-34-Mφ and TAM initially considered as antiinflammatorycells, induce in vitro Th17 cell generation via a constitutive expression of membrane IL-1α. This process may contribute to maintain locally a restrained and smoldering inflammation required for angiogenesis and metastasis in tumors.

L’ozone est un des polluants présents dans l’air que nous respirons. Les pics de ce polluant entrainent une augmentation des hospitalisations et des cas d’exacerbations d’asthme allergique. L’objectif de ce travail est d’étudier plus en détails les mécanismes inflammatoires mis en place après exposition à l’ozone. Cette étude s’est déroulée en trois axes, les deux premiers traitant du rôle de deux alarmines, l’IL-33 et l’IL-1α et le troisième se focalisant sur AhR, un récepteur impliqué dans la réponse à de nombreux polluants. Pour ce faire, des souris ont été exposées à l’ozone selon deux modèles, l’un aigu et l’autre chronique, puis les paramètres inflammatoires, le dommage tissulaire et les difficultés respiratoires ont été évalués. Nous montrons ici qu’une exposition aigüe à l’ozone induit la libération de molécules comme l’IL-33 et l’IL-1α. L’IL-33 agit au niveau de la barrière épithéliale, où elle permet l’expression et le maintien des jonctions serrées, qui sont augmentées en réponse à la pollution à l’ozone. L’IL-33 régule également l’infiltration des neutrophiles, alors que l’IL-1α l’induit. Ensuite nous avons montré que le récepteur AhR est activé après exposition chronique à l’ozone. AhR semble réguler la production de cytokines telles que l’IL-17A et l’IL-22 et ainsi protège d’une trop forte réponse inflammatoire. Pour conclure, nous avons montré que la production d’IL-33 et l’activation du récepteur AhR étaient nécessaires pour contrôler l’inflammation induite par l’ozone, alors que la production d’IL-1α l’induisait. Cette étude aura permis de mettre en évidence de potentielles cibles thérapeutiques pour soulager les maux provoqués par la pollution. / Ozone is a common ambient air polluant. Ozone peaks induce increase of asthma exacerbation, respiratory distress, emergencies and hospital admissions. The aim of this thesis project is to dissect inflammatory mechanisms induced after ozone exposure. This study is conducted according three axes, the first two dealing with the roles of two alarmines, IL-1α and IL-33 and the third is focused on the role of aryl hydrocarbon receptor (AhR), a receptor involved in several pollutant responses. Acute and chronic experimental models of ozone exposure were used to evaluate inflammatory parameters in lung, tissue damage and airway hyperresponsiveness. Here we show that acute ozone exposure induces IL-1α and IL-33 release. IL-33 acts on lung epithelial barrier, allowing the expression and maintenance of tight junctions induced after ozone exposure. Moreover, IL-33 represses neutrophils infiltration while IL-1α induces it. Furthermore we show that AhR is activated after chronic ozone exposure. AhR regulates cytokines production such as IL-17A and IL-22 and plays a protective role against higher inflammation. Overall, IL-33 production and AhR activation are necessary to control ozone-induced inflammation, in contrast to IL-1α. These findings highlight potential therapeutic targets for the treatment of lung inflammation following ozone exposure.

Interactome of IL-1α N-terminal domain Cytokines are highly effective mediators produced by various cell types within and outside of the immune system with the aim to influence the orientation, intensity, and duration of the immune response and inflammatory process. Their biological effects mediated through binding the high-affinity membrane receptors and triggering the signal transduction pathway are usually well defined. However, as it is more and more frequently observed, in addition to the exocrine function, some cytokines may show intracrine effects. For this type of cytokines, the term "dual function cytokines" has been adopted. One of these cytokines is Interleukin-1α, in which the recent research has concentrated on determining its intracellular functions. The intracellular function of interleukin-1α has not been clearly defined so far. However, apart from the absence of the conventional hydrophobic sequence, its existence is supported by the fact that the N-terminal peptide included in its precursor is highly conserved and contains nuclear localization signal. The aim of this work is to define the conditions of localization of the interleukin-1α N- terminal domain in different cellular compartments and to study proteins potentially interacting with it using fluorescent microscopy. Key words:...

Dysregulated wound healing is commonly associated with excessive fibrosis. Connective tissue growth factor (CTGF/CCN2) is characteristically overexpressed in fibrotic diseases and stimulated by transforming growth factor-β (TGF-β) in dermal fibroblasts. Reepithelialisation and epidermal wound coverage counteract excessive scar formation. We have previously shown that interleukin-1α (IL-1α) derived from keratinocytes conteracts TGF-β-stimulated CTGF-expression. The aim of this thesis was to further explore the effects of keratinocytes and IL-1α on gene and protein expression, as well as pathways, in TGF-β stimulated fibroblasts. Fibroblasts were studied in vitro by conventional two dimensional cell culture models and in a three dimensional keratinocyte-fibroblast organotypic skin culture model. The results showed that IL-1 suppresses basal and TGF-β-induced CTGF mRNA and protein, involving a possible TAK1 mechanism. Keratinocytes regulate the expression of fibroblast genes important for the turnover of the extracellular matrix. Most of the genes analysed (11/13) were regulated by TGF-β and counter regulated by keratinocytes. The overall results support a view that keratinocytes regulate fibroblasts to act catabolically (anti-fibrotic) on the extracellular matrix. Transcriptional microarray and gene set enrichment analysis showed that antagonizing effects of IL-1α on TGF-β were much more prominent than the synergistic effects. The most confident of these pathways was the interferon signaling, which were inhibited by TGF-β and activated by IL-1α. A proteomics study confirmed that IL-1α preferentially conteracts TGF-β effects. Six new fibroblast proteins involved in synthesis/ regulation were identified, being regulated by TGF-β and antagonized by IL-1α. Pathway analysis confirmed counter-regulation of interferon signaling by the two cytokines. These findings have implications for understanding the role of fibroblasts for inflammatory responses and development of fibrosis in the skin.