Chlamydia muridarum and Chlamydia caviae have equivalent growth rates in mouse epithelial cells but only C. muridarum replicates inside mouse macrophages, while C. caviae does not. Macrophages infected with C. muridarum or C. caviae were used to address the hypothesis that the early signaling pathways initiated during infection depend on the fate of chlamydiae in the host cell. Transmission electron microscopy of C. muridarum-infected macrophages showed intact chlamydial elementary bodies and reticulate bodies 2 h postinfection in compact vacuoles. Conversely, in macrophages infected with C. caviae, chlamydiae were observed in large phagocytic vacuoles. Furthermore, C. caviae infections failed to develop into inclusions or produce viable bacteria. Expression of proinflammatory cytokines TNFα, IL-1β and MMP13 was similar in C. caviae- or C. muridarum-infected macrophages at 3 h postinfection, indicating that chlamydial survival is not required for initiation of these responses. IL-1β secretion, dependent on inflammasome activation, occurred in C. caviae-infected macrophages despite no chlamydial growth. Conversely, IFNβ mRNA was observed only in C. muridarum- but not in C. caviae-infected macrophages. These data demonstrate that differential signaling events are initiated during a productive versus nonproductive chlamydial infection in a macrophage.

Sleep fragmentation induces acute inflammation and increases glucocorticosteroids in vertebrates. Obesity and sleep fragmentation are often concurrent pro-inflammatory conditions in patients with obstructive sleep apnea. Despite the association between the two, their simultaneous effects on immune and endocrine profiles have not been explored. In the first experiment, we investigated changes in proinflammatory (IL-1β, TNF-α) and anti-inflammatory (TGF-β1) cytokine gene expression in the periphery (liver, spleen, fat, and heart) and brain (hypothalamus, prefrontal cortex, and hippocampus) in mice exposed to various intervals of sleep fragmentation. Serum corticosterone concentration was also assessed. Sleep was disrupted in male C57BL/6J mice using an automated sleep fragmentation chamber (Lafayette Industries), which involved movement of a sweeping bar at specified intervals. Mice were exposed to bar sweeps every 20 sec (high sleep fragmentation; HSF), 120 sec (low sleep fragmentation; LSF), or the bar remained stationary (control). Trunk blood and tissue samples were collected after 24 h of SF. It was found that HSF is a potent inducer of inflammation in the periphery (IL-1β: adipose, heart, and hypothalamus), but leads to upregulation of antiinflammatory cytokines in the brain (TGF-β1: hypothalamus and hippocampus), despite elevated serum corticosterone. Due to the association between obesity and SF, this experiment was replicated in male C57BL/6J mice (lean) and ob/ob KO mice (obese) using the previously described methods. We predicted the acute inflammatory response resulting from HSF would be different for the lean and the obese mice, with the greatest cytokine gene expression levels in the OB HSF group, due to a summative effect of the pro-inflammatory conditions. Obesity was the factor that most affected cytokine gene expression profiles. Additionally, the pro- vs anti-inflammatory gene expression profile varied with tissue type. While obesity resulted in neuroinflammation (hypothalamus, prefrontal cortex, hippocampus), it led to decreases in pro-inflammatory cytokine gene expression in the periphery (spleen, fat, heart). Serum corticosterone concentration was significantly elevated due to SF, but was not affected by obesity. As a result, the obese mice likely had neuroendocrine adaptations to combat the pre-existing pro-inflammatory condition of obesity, which impacted the acute inflammatory response to sleep loss.

Thymic stromal lymphopoietin (TSLP) produced by epithelial cells acts on dendritic cells (DCs) to drive differentiation of TH2-cells, and is therefore important in allergic disease pathogenesis. However, DCs themselves make significant amounts of TSLP in response to microbial products, but little is known about the key downstream signals that induce and modulate this TSLP secretion from human DCs. We show that human monocyte derived DC (mDC) secretion of TSLP in response to Candida albicans and β-glucans requires dectin-1, Syk, NF-κB, and p38 MAPK signaling. In addition, TSLP production by mDCs is greatly enhanced by IL-1β, but not TNF-α, in contrast to epithelial cells. Furthermore, TSLP secretion is significantly increased by signals emanating from the endoplasmic reticulum (ER) stress response, specifically the unfolded protein response sensors, inositol-requiring transmembrane kinase/endonuclease 1 and protein kinase R-like ER kinase, which are activated by dectin-1 stimulation. Thus, TSLP production by mDCs requires the integration of signals from dectin-1, the IL-1 receptor, and ER stress signaling pathways. Autocrine TSLP production is likely to play a role in mDC-controlled immune responses at sites removed from epithelial cell production of the cytokine, such as lymphoid tissue.

Objective: Determine if aspirin inhibits the IL-1β-stimulated expression of inducible nitric oxide synthase (iNOS), nitric oxide (NO), and prostaglandin E2 (PGE2) in rat ovarian dispersates cultured in vitro. Design: Prospective, controlled in vitro study. Setting: Academic research laboratory. Animals: Ovaries collected from immature rats. Intervention(s): Ovaries were collected from immature rats and enzymatically dispersed. Ovarian dispersates were placed into plates containing media alone or media supplemented with IL-1β (100 U/mL) and varying concentrations of aspirin (0, 1, 3, 5 and 10 mM). Ovarian dispersates were cultured in a humidified environment of 5% CO2 in air at 37°C for 24 or 48 hours. Main Outcome Measure(s): Twenty-four- and 48-hour iNOS, nitrite (a stable metabolite of NO), and PGE2 levels were determined from ovarian dispersates cultured in vitro. Result(s): Administration of IL-1β increased nitrite and PGE2 levels over that observed in the control group after culture of ovarian dispersates for 24 and 48 hours. Aspirin dose dependently reduced the IL-1β-stimulated increase in nitrite production from ovarian dispersates after culture for 24 and 48 hours. Aspirin completely (24 hours) or dose dependently (48 hours) prevented the IL-β-stimulated increase in PGE2. Coadministration of IL-1β and aspirin (10 mM) attenuates IL-1β-stimulated iNOS expression after culture for 24 and 48 hours. Conclusion(s): Aspirin significantly inhibits the IL-1β-stimulated expression of iNOS, NO, and PGE2 in ovarian dispersates cultured in vitro.

Obesity is linked to nonalcoholic steatohepatitis. Peroxisome proliferator-activated receptor-a (PPARa) regulates lipid metabolism. Cytochrome P-450 2A5 (CYP2A5) is a potential antioxidant and CYP2A5 induction by ethanol is CYP2E1 dependent. High-fat diet (HFD)-induced obesity and steatosis are more severe in CYP2A5 knockout (cyp2a5 -/- ) mice than in wild-type mice although PPARa is elevated in cyp2a5 -/- mice. To examine why the upregulated PPARa failed to prevent the enhanced steatosis in cyp2a5 -/- mice, we abrogate the upregulated PPARa in cyp2a5 -/- mice by cross-breeding cyp2a5 -/- mice with PPARa knockout (ppara-/- ) mice to create ppara-/- /cyp2a5 -/- mice. The ppara-/- /cyp2a5 -/- mice, ppara-/- mice, and cyp2a5 -/- mice were fed HFD to induce steatosis. After HFD feeding, more severe steatosis was developed in ppara-/- /cyp2a5 -/- mice than in ppara-/- mice and cyp2a5 -/- mice. The ppara-/- /cyp2a5 -/- mice and ppara-/- mice exhibited comparable and impaired lipid metabolism. Elevated serum alanine transaminase and liver interleukin-1β, liver inflammatory cell infiltration, and foci of hepatocellular ballooning were observed in ppara-/- /cyp2a5 -/- mice but not in ppara-/- mice and cyp2a5 -/- mice. In ppara-/- /cyp2a5 -/- mice, although redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 and its target antioxidant genes were upregulated as a compensation, thioredoxin was suppressed, and phosphorylation of JNK and formation of nitrotyrosine adduct were increased. Liver glutathione was decreased, and lipid peroxidation was increased. Interestingly, inflammation and fibrosis were all observed within the clusters of lipid droplets, and these lipid droplet clusters were all located inside the area with CYP2E1-positive staining. These results suggest that HFD-induced fibrosis in ppara-/- /cyp2a5 -/- mice is associated with steatosis, and CYP2A5 interacts with PPARa to participate in regulating steatohepatitis-associated fibrosis.

Es ist davon auszugehen, dass Fehlfunktionen im Immunsystem mit der Ausprä-gung des Krankheitsbildes der aggressiven Parodontitis im Zusammenhang ste-hen. In dieser Arbeit sollen anhand klinischer, immunologischer und mikrobiologischer Untersuchungen ein immunologisches Risikoprofil bei Patienten mit aggressiver Parodontitis erschlossen, gegebenenfalls Unterschiede zur moderaten chronischen Parodontitis beleuchtet und explorativ Zusammenhänge zwischen immunologischen und mikrobiologischen Befunden eruiert werden. Es wurden geeignete Patienten und gesunde Probanden laut Ethikvotum rekrutiert. Die immunologischen Untersuchungen erfolgten an PBMCs unter Verwendung durchflusszytometrischer Methoden und mittels ELISpot-Assay. Mikrobiologische Untersuchungen subgingivaler Plaque wurden als klassische Kultur und 16S rRNA-Sequenzierung durchgeführt. Immundefekterkrankungen konnten bei allen Individuen ausgeschlossen werden. Im Gruppenvergleich wurde eine erhöhte Stimulierbarkeit der PBMCs von Patienten mit moderater chronischer Parodontitis bezüglich ihrer IL-1β-Freisetzung bei Inkubation mit LPS festgestellt. Des Weiteren wies diese Patientengruppe einen vergleichsweise höheren Anteil an Gedächtnis-B-Zellen auf. In der mikrobiologischen Untersuchung konnten bekannte parodontopathogene Spezies nachgewiesen und Prevotella denticola als bislang nicht explizit erwähntes Pathogen mit aggressiver Parodontitis assoziiert werden. Unsere Untersuchung weisen auf Zusammenhänge zwischen immunologischen und mikrobiologischen Befunde bezüglich einiger parodontopathogener Bakterien, wie Prevotella oralis, und Stimulierbarkeit der IL-1β-Freisetzung, B-Zelldifferenzierung und T-Zellverhältnis hin.

Cette thèse s’inscrit dans le cadre de la thématique du laboratoire de Pharmacognosie de l’UFR Santé, au sein de l’Université de Bourgogne. Elle vise essentiellement la recherche de molécules d’origine végétale issue de la biodiversité tropicale dotées d’une activité antitumorale et immuno-modulatoire dont principalement les saponines. Ce sont des glycosides triterpéniques ou stéroïdiques connus pour leurs nombreuses propriétés pharmacologiques. L’étude de 4 espèces végétales appartenant à 3 familles à savoir Dracaena marginata L., Dracaena fragrans Ker Gawl (Asparagaceae), Allium flavum L. (Amaryllidaceae) et Weigela stelzneri (Caprifoliaceae),a conduit à l’isolement et à la caractérisation de 26 glycosides naturels. Il s’agit de 22 saponines stéroïdiques parmi lesquelles 6 sont de structure nouvelle ainsi que 4 saponines triterpéniques dont 3 nouvelles. Les structures ont été élucidées principalement par l’utilisation de la RMN 2D ainsi que la spectrométrie de masse. 10 des 26 molécules isolées ont été testées en vue d’évaluer leurs activités cytotoxiques sur deux lignées cellulaires cancéreuses (SW480 et EMT-6), et 3 pour l’étude de la modulation de la production d’une cytokine pro-inflammatoire, l’interleukine IL-1β sur cellules PBMC stimulées par le LPS. Nos résultats montrent que 6 d’entre elles possèdent une activité cytotoxique modérée sur les deux lignées cancéreuses. En revanche, deux saponines triterpéniques de type oléanane exercent les plus fortes cytotoxicités sur les deux lignées cancéreuses comparées à celles des références internes (Etoposide et Methotrexate). De plus elles révèlent un important effet de modulation de la production de l’interleukine IL-1β sur cellules PBMC et de ce fait, un fort potentiel anti-inflammatoire. Des relations structure/activité ont été ainsi proposées. / This thesis was carried out in the Laboratory of Pharmacognosy, in health department of the University of Burgundy. The principal theme of this Laboratory is the research of natural compounds from tropical biodiversity, mainly saponins with antitumoral and immunomodulatory activities. These molecules are triterpenic or steroidic glycosides, well known for their various pharmacological activities. The study of 4 species belonging to 3 different families: Dracaena marginata L., Dracaena fragrans Ker Gawl (Asparagaceae), Allium flavum L. (Amaryllidaceae) et Weigela stelzneri (Caprifoliaceae), led to the isolation and characterization of 26 natural glycosides. Among them, 22 were steroidic saponins with 6 new structures and 4 were triterpenic saponins with 3 new structures. The spectral analysis was achieved using mainly 2D NMR and mass spectrometry. The cytotoxic activities of 10 isolated compounds were evaluated on 2 strains cancer cells (SW480 and EMT-6), and 3 compounds for studying the modulatory effect of the production of pro-inflammatory cytokine, interleukin IL-1β on PBMCs stimulated with LPS. Our results show that six of them have moderate cytotoxic activity on both cancer cell lines. However, two oleanane-type triterpene saponins exert the strongest cytotoxicity on both cancer cell lines compared to internal references (Etoposide and Methotrexate). Moreover they show a significant effect of modulating the production of interleukin IL-1β on PBMCs and thereby a strong anti-inflammatory potential. Structure / activity relationships have been proposed.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Gout is a prevalent form of inflammatory arthritis, which leads to patients poor quality of life. Acute gout attacks produce severe joint pain and inflammation associated with oxidative stress induction. This pathology is provoked by the accumulation of monosodium urate (MSU) crystals, but the underlying pain mechanisms in acute gout attacks are still poorly understood. The transient potential receptor ankyrin 1 (TRPA1) is a sensor for endogenous oxidant compounds, such as hydrogen peroxide (H2O2), found in peptidergic sensory fibers associated to inflammatory pain. The goal of this study was to explore the TRPA1 role in two models of monosodium urate (MSU) crystals-induced inflammation and nociception in rats and mice. We found that TRPA1 antagonism (HC-030031 or camphor), TRPA1 gene deletion or defunctionalization by capsaicin pretreatment of peptidergic TRPexpressing primary sensory neurons markedly decreased MSU-induced nociception and edema after intraplantar (i.pl.) or intra-articular (i.a.) injection. In addition to these neurogenic effects, MSU increased H2O2 levels in the injected tissue, an effect that was abolished by the H2O2-detoxifing, catalase enzyme. TRPA1 immunoreactivity in sciatic nerve and the levels of calcitonin gene related peptide (CGRP) in the synovial tissue were also increased by MSU. H2O2 i.pl. or i.a. injection mimicked MSU, causing nociception and edema prevented by TRPA1 antagonism. Moreover, TRPA1 blockage abrogated the increase in neutrophil infiltration and interleukin-1β elicited by MSU. Our results suggest that MSU-injection increases tissue H2O2 thereby stimulating TRPA1 on sensory nerve endings to produce inflammation and nociception. Thus, TRPA1 may be explored as a valuable target in acute gout management. / A gota é uma forma prevalente de artrite inflamatória que reduz a qualidade de vida dos pacientes. Os ataques agudos de gota produzem dor articular grave e inflamação que são associadas à produção de estresse oxidativo. Esta patologia é provocada pela deposição de cristais de urato monossódico (MSU), mas os mecanismos relacionados à dor observada nos ataques agudos de gota ainda são pouco esclarecidos. O receptor de potencial transitório anquirina 1 (TRPA1) é um sensor para compostos oxidantes, como o peróxido de hidrogênio (H2O2), encontrado em fibras sensoriais peptidérgicas e este está relacionado ao desenvolvimento de dor inflamatória. O objetivo deste estudo foi avaliar o papel do receptor TRPA1 em dois modelos de inflamação e nocicepção induzidos pela administração de cristais de MSU em ratos e camundongos. Observamos que o antagonismo do receptor TRPA1 (HC-030031 ou cânfora), a deleção genética deste canal, ou ainda a indução de dessensibilização dos neurônios sensoriais que expressam os receptores TRP pelo tratamento com capsaicina reduziram marcantemente a nocicepção e edema induzido pela administração intraplantar (i.pl.) ou intra-articular (i.a.) dos cristais de MSU. Além destes efeitos neurogênicos a administração de MSU aumentou o conteúdo de H2O2 nos tecidos injetados, um efeito que foi bloqueado pela enzima catalase, e também aumentou a imunoreatividade para o receptor TRPA1 no nervo ciático e no tecido sinovial, e também os níveis do peptídeo relacionado ao gene da calcitonina (CGRP) no tecido sinovial. A administração de H2O2 por via i.pl. ou i.a. induziu efeitos semelhantes àqueles induzidos pela administração de MSU, e estes foram reduzidos pela administração de antagonistas TRPA1. Ainda, o bloqueio do receptor TRPA1 reduziu a infiltração de neutrófilos e a produção de interleucina 1β induzidas pela administração de cristais de MSU. Em conclusão, os nossos resultados sugerem que a administração dos cristais de MSU é capaz de aumentar a produção de H2O2 que então poderia estimular o receptor TRPA1 expresso em neurônios sensoriais causando nocicepção e inflamação dos tecidos. Dessa maneira, o canal TRPA1 poderia ser explorado como um alvo em potencial para o tratamento dos ataques agudos de gota.

En dehors des effets cytostatiques ou cytotoxiques sur les cellules tumorales, certaines thérapies anti-cancéreuses peuvent déclencher la mort cellulaire immunogénique, libérant les signaux de danger pour alerter le système immunitaire. Les cellules T CD8+ T (Tc1) productrices d’IFN- et spécifiques de la tumeur sont nécessaires pour le succès de la chimiothérapie et la diminution de la croissance tumorale. L’amorçage d’une réponse bénéfique Tc1 dépend de la sécrétion d'IL-1β par les cellules dendritiques confrontées à des cellules tumorales traitées avec de l’anthracycline libérant de l’ATP. Pour identifier les composants inflammatoires qui lient les réponses immunitaires innées et adaptatives, nous avons analysé l'influence de la chimiothérapie immunogène sur le microenvironnement de la tumeur. Nous avons identifié une up-régulation de gènes associés à la réponse Th1 et Th17 dans un modèle de tumeur répondant au traitement par les anthracyclines par un retard de croissance. En interférant avec les voies IFN- ou l'IL-17A, l'effet thérapeutique de la doxorubicine et l'oxaliplatine a été aboli et le vaccin à base de cellules tumorales mortes ne protège plus les souris de la réintroduction de cellules tumorales vivantes. Nous avons également découvert que des sous-populations distinctes de lymphocytes T  (V4+ et V6+) colonisent des tumeurs peu de temps après la chimiothérapie, où ils ont proliféré et sont devenus producteurs majeurs de l’IL-17 au sein de la tumeur. Nous avons constaté une forte corrélation entre la présence de lymphocytes T  producteurs d’IL-17 ( T17) et de TIL CD8+ (Tc1) dans trois modèles différents de tumeurs traitées par la chimiothérapie ou la radiothérapie. IL-17A agit sur la signalisation en amont de l'IFN- puisqu’un défaut d’expression d’IL-17RA conduit à la perte complète de la production des Tc1 spécifiques de l’antigène. La contribution des cellules  T17 (V4+ et V6+) dans l’effet bénéfique de la chimiothérapie est essentielle puisque les souris V4/6-/-. L’axe IL-1β/IL-1R, mais pas IL-23/IL-23R, est essentielle pour la production d'IL-17 par les cellules T et l’effet bénéfique de la chimiothérapie. Le transfert adoptif de lymphocytes  T peut rétablir l'efficacité de la chimiothérapie dans le modèle de souris IL-17A-/- et améliorer l'effet de la chimiothérapie chez la souris wt, s'ils conservent l'expression de l'IL-1R et de l'IL-17A. Nos résultats suggèrent l’existence d’un axe fonctionnel: DC (IL-1β) → cellules T (IL-17) → Tc1 (IFN-), déclenché par la chimiothérapie induisant la mort des cellules tumorales, phénomène essentiel pour une réponse thérapeutique favorable. Pour renforcer la réponse immunitaire, nous essayons de combiner la chimiothérapie « immunogène » avec le vaccin anti-tumoral en présence d’adjuvants (poly (A:U), l'agoniste de TLR3).Ce type de thérapie séquentielle combinée, appelé VCT, pourrait retarder considérablement la croissance des tumeurs, voire l’éradiquer complètement et établir une protection spécifique à long terme. Pour décortiquer l'effet de la poly (A:U) sur le système immunitaire et sur les cellules tumorales exprimant le TLR3, nous avons effectué un traitement VCT chez la souris nude, TRIF-/- et les souris présentant une diminution de l’expression de TRIF au niveau des cellules tumorales. Ainsi l'effet anti-tumoral de VCT requiert les lymphocytes T et la voie de signalisation TRIF intacte au niveau de l'hôte et des cellules tumorales. Le traitement poly (A:U) peut induire un niveau élevé de production de certaines chimiokines associées à la réponse de type Th1 (CCL5 et CXCL10 ) par les cellules tumorales in vitro et in vivo, ce qui peut influencer négativement et positivement les résultats thérapeutiques. Le découplage de l’action de CCL5 et de XCL10, pourrait améliorer le traitement par la VCT. Notre étude souligne ainsi le rôle des facteurs inflammatoires dérivés de la tumeur et de l’hôte dans la régulation de la réponse immunitaire anti-tumorale. / Besides exerting cytostatic or cytotoxic effects on tumor cells, some anti-cancer therapies (anthracyclines, oxaliplatin, X-Rays) could trigger an immunogenic cell death modality, releasing danger signals to alert immune system. We have shown that tumor-specific IFN- producing CD8+ T cells (Tc1) are mandatory for the success of chemotherapy to prevent tumor outgrowth. Priming of Tc1 response depends on IL-1β secretion by DC confronted with anthracycline-treated tumor cells releasing ATP. To identify the inflammatory components which link innate and cognate immune responses, we analyzed the influence of immunogenic chemotherapy on tumor microenvironment. We found an upregulated Th1- and Th17-related gene expression pattern in growth-retarded tumor after anthracycline treatment. By interfering with IFN- or IL-17A pathways, therapeutic effect of doxorubicin and oxaliplatin was abolished and dying tumor cell-based vaccine lost its efficacy to protect mice from live tumor cell rechallenge. Interestingly, we discovered that distinct subsets of  T lymphocytes (V4+ and V6+) colonized tumors shortly after chemotherapy, where they proliferated and became the dominant IL-17 producers within tumor beds. In three tumor models treated with chemotherapy or radiotherapy, a strong correlation between the presence of IL-17-producing  T ( T17) and IFN--producing CD8+ TIL (Tc1) was discovered. IL-17A signaling acts as upstream of IFN- since defect in IL-17RA led to complete loss of antigen specific Tc1 priming. The contribution of  T17 cells (V4+ and V6+) to chemotherapy is critical as V4/6-/- mice showed reduced sensitivity to chemotherapy and vaccination. Also, tumor infiltrating  T17 and Tc1 cells were reduced to basal level in this strain. IL-1β/IL-1R, but not IL-23/IL-23R, is pivotal for IL-17 production by  T cells and the success of chemotherapy. Importantly, adoptive transfer of  T cells could restore the efficacy of chemotherapy in IL-17A-/- mice and ameliorate the effect of chemotherapy in wild type host, provided that they retain the expression of IL-1R and IL-17A. Our research suggest a DC (IL-1β) →  T cells (IL-17) → Tc1 (IFN-) immune axis triggered by chemotherapy-induced dying tumor cells, which is critical for the favorable therapeutic response. To boost the immune system, we try to combine immunogenic chemotherapy with tumor vaccine in the presence of TLR3 agonist Poly (A:U). This sequential combined therapy, which we named VCT, could significantly retard tumor growth or even completely eradicate tumor and establish long-term protection against rechallenge in highly tumorigenic models. To dissect the effect of Poly (A:U) on immune system and that on TLR3 expressing-tumor cells, we performed VCT treatment in nude mice, TRIF-/- mice and with TRIF-silencing tumors. Interestingly, our results suggested that anti-tumor effect of VCT required T cells and intact TRIF signaling pathway at the level of the host and that of tumor cells. Poly (A:U) treatment could induce high level of CCL5 and CXCL10 production from tumor cells both in vitro and in vivo, which could negatively and positively influence the therapeutic outcome. By uncoupling the effect of CCL5 from that of CXCL10, the VCT treatment can be ameliorated. Our study emphasizes that both tumor and host derived inflammatory factors participate in regulating anti-tumor response. We also highlight that therapeutic application of TLR agonists can be optimized through regulating the profile of chemokines and their downstream signaling events.

Dans la première partie de ma thèse, nous avons étudié le rôle de la TSLP, une cytokine produite par les kératinocytes, dans la mélanogenèse. Nous avons montré que l'expression de TSLP était induite dans l'épiderme de la peau atteinte de mélanome chez la souris et l'humain. Notre resulats indiquent que la TSLP murine joue un rôle dans la croissance de la tumeur et que ce rôle s'exerçait via les cellules immunitaires. Nos résultats suggèrent l'existence d'un dialogue entre les cellules du mélanome, les kératinocytes et les cellules immunitaires jouant un rôle important dans la croissance et la métastase du mélanome. Dans la seconde partie, nous avons exploré les cytokines produites dans le contexte de la dermatite atopique et leur rôle dans l'initiation de l'asthme. Nous avons trouvé que TSLP est différemment impliquée dans la sensibilisation allergique épicutanée et dermocutanée, et nous avons identifiée l'IL-1β comme un acteur majeur dans la marche atopique. Cette étude expose de nouvelles approches pour le développement de stratégies pour prévenir ou stopper la marche atopique. / My PhD thesis aimed at studying skin inflammatory responses under two pathogenic contexts, melanoma and atopic march. In the first part, we studied the role of keratinocyte-produced cytokine TSLP in melanomagenesis. We showed that TSLP expression was induced in skin epidermis of both mouse and human melanoma. We further provided evidence that TSLP played a tumor-promoting role by ablating or overexpressing TSLP in mouse melanoma, and that such role of TSLP was mediated through immune cells. Our results suggest that a crosstalk between melanoma cells, epidermal keratinocytes and immune cells plays an important role for melanoma growth and metastasis. In the second part, we explored the cytokine factors derived from atopic dermatitis (AD) in driving the asthma. By using an innovative laser-assistant microporation system, we established novel atopic march mouse models. We found that TSLP was differentially implicated in allergen epicutaneous or dermacutaneous sensitization, and further identified IL-1β as an important player in atopic march. This study adds new insight into the development of potential strategies for preventing or stopping the atopic march.