Des études menées au laboratoire avaient démontré un rôle critique de l’inflammasome NLRP3 dans l’asthme allergique en réponse à l’ovalbumine en absence d’adjuvant. Mes travaux de thèse ont porté sur le rôle de NLRP3 et de la caspase-1 dans un modèle murin d’inflammation pulmonaire induite par l’allergène d’acarien HDM. Nous avons montré un rôle régulateur de la caspase-1 dépendant de l’inflammasome NLRP3 et la molécule adaptatrice ASC mais pas de l’inflammasome NLRC4. Cette régulation de la réponse allergique se caractérise par une augmentation de l’infiltration des éosinophiles, de l’hyperréactivité bronchique et de la production des cytokines de type Th2 telles que l’IL-4, l’IL-5, l’IL-13 et l’IL-33 dans les poumons. Nous avons montré que les mécanismes responsables de cette régulation sont associés à l’IL-33 produite par les macrophages et que la neutralisation de l’IL-33 par administration locale de la protéine de fusion au récepteur ST2 (muST2-Fc) atténue les caractéristiques de l’asthme allergique. Ces résultats suggèrent que l’activation de la caspase-1 réduit la production d’IL-33 in vivo et régule ainsi la réponse l’inflammation pulmonaire induite par HDM et la réponse Th2. D’autre part, nous nous sommes intéressés au rôle de la Protéine Kinase C thêta (PKC-θ) dans ce même modèle d’inflammation pulmonaire. Nous avons démontré que PKC-θ joue non seulement un rôle protecteur dans l’asthme allergique mais également un rôle critique pour la prolifération et l’activation des cellules lymphoïdes innées (ILC2). D’autre part, l’inhibition de PKC-θ in vivo par administration orale de son inhibiteur spécifique C20 (BIX02656) atténue l’inflammation pulmonaire et la production d’IL-5 et d’IL-13. Nous suggérons que PKC-θ est impliquée dans la différenciation des Th2 et des ILC2 via un mécanisme dépendant des facteurs de transcription IRF4 et NFAT-1. Au total, mes travaux de thèse mettent en exergue deux molécules IL-33 et PKC-θ qui pourraient constituer des cibles thérapeutiques potentielles. / Studies from our laboratory have shown a critical role of NLRP3 inflammasome in response to ovalbumin allergen. In the present study we investigate the role of NLRP3 and caspase-1 in a mouse model of pulmonary inflammation induced by HDM. We have shown a regulatory role of caspase-1 dependant of the NLRP3 inflammasome and the adaptator molecule ASC but not NLRC4. The regulation of the allergic response is characterized by an increase of eosinophilia, bronchial hyperreactivity and Th2 cytokines production (IL-4, IL-5, IL-13 and IL-33) in lungs. We have shown that mechanisms responsible of this regulation are associated with IL-33 production by macrophages and that neutralization of IL-33 by local administration of a fusion protein of the ST2 receptor (muST2-Fc) reduce characteristics of asthma. These results suggest that caspase-1 activation reduce IL-33 production in vivo regulating lung inflammation and Th2 response induced by HDM. Moreover, we investigate the role of the Protein Kinase C theta (PKC-θ) in allergic airway inflammation. We have demonstrated that PKC-θ plays a protective role in allergic asthma but is critical for the activation and proliferation of innate lymphoid cells (ILC2). In addition, in vivo inhibition by oral administration of PKC-θ specific inhibitor C20 (BIX02656) reduces pulmonary inflammation with IL-5 and IL-13 production. We suggest that PKC-θ is implicated in Th2 and ILC2 differenciation by a mechanism dependant on transcription factors IRF4 and NFAT-1. Finally, my thesis projects describe IL-33 and PKC-θ as potential therapeutic targets for allergic lung inflammation.

Oncogene-induced senescence (OIS) is a fail-safe mechanism activated to halt the proliferation of cells at risk of malignant transformation. It is a cell cycle arrest program of biological changes to the cell comprising of the activation of tumour suppressor pathways, altered cellular metabolism, extensive chromatin remodelling and the activation of a senescence-associated secretory phenotype (SASP). The vast array of proteins secreted by the cells not only play a cell-autonomous role in reinforcing the senescence phenotype, but also modulate the cell's micro-environment by inducing senescence in neighbouring cells, promoting angiogenesis, and initiating an immune response through the recruitment of immune cells. To this end, senescence is a complex phenotype that has countless pathophysiological implications and understanding its molecular mechanisms of activation could prove to be fruitful for understanding its diverse functions. Components of the innate immune system have been shown to play an essential role in the development of the SASP through its processing and activation of Caspase 1 that in turn leads to activation of IL-1B. A gene set enrichment analysis of OIS cells showed significant upregulation in the Pattern Recognition Receptor (PRR) family, from the innate immune response. Hence, we explored the role of innate immune receptors in OIS. Methods and Materials IMR90 human diploid fibroblast cells, stably transfected with an oncogenic ER:RAS fusion protein undergo OIS upon treatment with 4-hydroxytamoxifen. A loss of function siRNA screen was conducted targeting components of the innate immune systems, including pattern recognition receptors. This served as a proof-of-principle screen for a larger screen of proteases and ubiquitin conjugation enzymes. Potential regulators of OIS were identified through siRNA that bypassed the proliferative arrest associated with OIS. We chose to focus on studying the role of TLR2 and TLR10 in senescence. A transcriptome analysis was carried out to identify genes regulated by these TLRs and further biological manipulation was used to confirm the mechanism through which these receptors control senescence. Results Toll-like receptor 2 (TLR2) and TLR10 have been identified as regulators of OIS. Their overexpression in IMR90 cells induces a premature form of senescence where the cells have significantly reduced proliferative activity and display senescence-associated β galactosidase activity. Moreover, the knockdown of TLR2 and TLR10 results in suppression of tumour suppressor pathway genes, reduced signaling through the pathway and blunting of the SASP. High TLR2 expression in patients with lung adenocarcinoma is associated with a higher survival rate. Concomitantly, the screening also identified Caspase 4, a critical component of non-canonical inflammasome signaling, to be regulated by TLR2 and TLR10 in OIS. A full transcriptome analysis of cells with TLR2 and TLR10 knockdown revealed serum amyloid amylase 1 (SAA1) and SAA2 are upregulated in OIS and were also confirmed to be activating ligands of TLR2. The activation of TLR2 by SAA, followed by the engagement of the non-canonical inflammasome by LPS electroporation induced senescence in proliferating IMR90 cells. Conclusion Our results suggest that the TLR2 and TLR10 act as potential tumour suppressor genes, signaling upstream of the inflammasome to initiate the production of inflammatory cytokines, and thereby the SASP. The production of the SASP develops a positive feedback loop, generating the damage-associated molecular pattern (DAMP) A-SAA that initiates an immune response signal cascade and subsequently activates senescence.

Aggregatibacter (Actinobacillus) actinomycetemcomitans is a bacterium mainly associated with aggressive forms of periodontitis. Among its virulence factors, a leukotoxin is suggested to play an important role in the pathogenicity. Periodontal infections with strains producing high levels of the leukotoxin are strongly associated with severe disease. Leukotoxin selectively kills human leukocytes and can disrupt the local defense mechanisms. Previous studies examining the role of the leukotoxin in host-parasite interactions have mainly focused on polymorphonuclear leukocytes (PMNs). In the inflamed periodontium, macrophages play a significant role in the regulation of the inflammatory reactions and the tissue breakdown and remodeling. Thus, the aim of this dissertation was to investigate death mechanisms of human macrophages exposed to leukotoxin. Human lymphocytes, PMNs, and monocytes/macrophages isolated from venous blood were exposed to purified leukotoxin or live A. actinomycetemcomitans strains producing variable levels or no leukotoxin. Different target cells were characterized by their expression of cell surface molecules. Cell death and viability were studied by examining cell membrane integrity and morphological alterations. Further, processes and cellular markers involved in apoptosis and necrosis were investigated. The expression and activation of pro-inflammatory cytokines of the leukotoxin-challenged leukocytes were examined at the mRNA and protein level. The biological activity of the secreted cytokines was investigated by testing the culture supernatants in a bone resorption assay. Additionally, different intracellular signaling pathways involved in the pro-inflammatory response from the macrophages were examined. Monocytes/macrophages were the most sensitive leukocytes for A. actinomycetemcomitans leukotoxin-induced lysis. This process in monocytes/ macrophages involved caspase-1 activation, and in addition, leukotoxin triggered abundant activation and secretion of IL-1β from these cells. The secreted IL-1β was mainly the 17 kDa bioactive protein and stimulated bone resorption. This activity could be blocked by an IL-1 receptor antagonist. When live bacteria were used, the A. actinomycetemcomitans-induced IL-1β secretion from human macrophages was mainly caused by the leukotoxin. Closer examination of the macrophages exposed to leukotoxin revealed that the induced cell death proceeded through a process that differed from classical apoptosis and necrosis. Interestingly, this process resembled a newly discovered death mechanism termed pyroptosis. The extensive leukotoxin induced IL-1β secretion did not correlate to increased levels of mRNA for IL-1β. It was mainly mediated by caspase-1 activation, since blocking it by a specific inhibitor also abolished the secretion of IL-1β. A similar pattern, but at much lower level, was seen for IL-18. In conclusion, these results show that A. actinomycetemcomitans leukotoxin induces a death process in human macrophages leading to a specific and excessive pro-inflammatory response. Our results indicate that this novel virulence mechanism of leukotoxin may play an important role in the pathogenic potential of A. actinomycetemcomitans.

<p><italic>Chlamydia<italic> <italic>trachomatis<italic> remains a highly relevant clinical pathogen as it is the causative agent of the most commonly reported sexually transmitted disease in the western hemisphere, and the most common cause of infectious blindness in the developing world. As an obligate intracellular pathogen, <italic>Chlamydia<italic> employs a vast assay of virulence proteins to hijack and remodel the host cellular machinery to facilitate its growth and dissemination. Besides delivering effector proteins into the host cytoplasm via a conserved type III secretion machinery, Chlamydia encodes components of multiple secretion systems, such as type II and IV. Chapter 3 of this document describes the secretion, processing and localization of two putative autotransporters (Pls1 and Pls2) and their involvement in inclusion expansion.</p><p> </p><p>In recent years, many new chlamydial effector proteins have been described. CPAF (Chlamydial Protease-like Activity Factor) is a secreted serine protease that is emerging as a central virulence protein: it is proposed to play a central role in <italic>Chlamydia<italic> pathogenesis by cleaving proteins involved in antigen-presentation, apoptosis and cytoskeletal re-arrangements. However, the functional significance of CPAF remains elusive due to the lack of specific inhibitors and <italic>Chlamydia<italic> mutants. The body of work presented herein demonstrates that in addition to targeting host proteins, CPAF cleaves a subset of early chlamydial effector proteins, including Inc-proteins that reside on the nascent pathogenic vacuole ("inclusion"). The design and development of a CPAF-specific inhibitory peptide demonstrates that these chlamydial effector proteins are true targets of CPAF. This peptide reversed the cleavage of bacterial targets by CPAF both in an in vitro cleavage assay and during infection, indicating that these effectors are bona fide targets. Inhibition of CPAF activity also revealed that this protease regulates multiple facets of chlamydial pathogenesis. CPAF inhibition in infected epithelial cells led to the complete dismantling of the inclusion, secretion of pro-inflammatory cytokines and engagement of an inflammasome-dependent programmed cell death pathway. While fibroblasts defective in various inflammasome components were resistant to <italic>Chlamydia<italic>-induced cell death, inclusion integrity and bacterial replication was still compromised upon CPAF inhibition, indicating that loss of inclusion integrity was not a consequence of caspase-1 activation. Overall, these findings revealed that CPAF, in addition to regulating host function, directly modulates the activity of secreted effectors and early Inc-proteins. Furthermore, we establish that CPAF is an essential virulence factor that is required to maintain the integrity of the inclusion and prevent the engagement of innate immune programmed cell death pathways in infected epithelial cells. CPAF activity thus remains a compelling mechanism by which intracellular pathogens employ proteolytic events to modify the host environment.</p> / Dissertation

Lethal toxin (LeTx) of Bacillus anthracis kills murine macrophages in a caspase-1 and Nod-like-receptor-protein 1b (Nlrp1b)-dependent manner. Nlrp1b detects intoxication, and self-associates to form a macromolecular complex called the inflammasome, which activates the pro-caspase-1 zymogen. I heterologously reconstituted the Nlrp1b inflammasome in human fibroblasts to characterize the role of the FIIND domain of Nlrp1b in pro-caspase-1 activation. Amino-terminal truncation analysis of Nlrp1b revealed that Nlrp1b1100-1233, containing the CARD domain and amino-terminal 42 amino acids within the FIIND domain was the minimal region that self-associated and activated pro-caspase-1. Residues 1100EIKLQIK1106 within the FIIND domain were critical for self-association and pro-caspase-1 activation potential of Nlrp1b1100-1233, but not for binding to pro-caspase-1. Furthermore, residues 1100EIKLQIK1106 were critical for cell death and pro-caspase-1 activation potential of full-length Nlrp1b upon intoxication. These data suggest that after Nlrp1b senses intoxication, the FIIND domain promotes self-association of Nlrp1b, which activates pro-caspase-1 zymogen due to induced pro-caspase-1 proximity.

Lethal toxin (LeTx) of Bacillus anthracis kills murine macrophages in a caspase-1 and Nod-like-receptor-protein 1b (Nlrp1b)-dependent manner. Nlrp1b detects intoxication, and self-associates to form a macromolecular complex called the inflammasome, which activates the pro-caspase-1 zymogen. I heterologously reconstituted the Nlrp1b inflammasome in human fibroblasts to characterize the role of the FIIND domain of Nlrp1b in pro-caspase-1 activation. Amino-terminal truncation analysis of Nlrp1b revealed that Nlrp1b1100-1233, containing the CARD domain and amino-terminal 42 amino acids within the FIIND domain was the minimal region that self-associated and activated pro-caspase-1. Residues 1100EIKLQIK1106 within the FIIND domain were critical for self-association and pro-caspase-1 activation potential of Nlrp1b1100-1233, but not for binding to pro-caspase-1. Furthermore, residues 1100EIKLQIK1106 were critical for cell death and pro-caspase-1 activation potential of full-length Nlrp1b upon intoxication. These data suggest that after Nlrp1b senses intoxication, the FIIND domain promotes self-association of Nlrp1b, which activates pro-caspase-1 zymogen due to induced pro-caspase-1 proximity.

Le cancer du côlon reste un problème majeur de santé publique puisqu’il constitue en France en 2013 le deuxième cancer en termes de mortalité. La chirurgie, la radiothérapie et les traitements par chimiothérapies classiques secondés par les thérapeutiques ciblées ne constituent pas toujours un arsenal efficace mettant ainsi en évidence la nécessité de trouver de nouvelles cibles thérapeutiques.Dans ce contexte, nous avons étudié la possibilité soit d’utiliser de nouvelles thérapeutiques (ligands du récepteur Liver X Receptor (LXR)), soit d’améliorer les conditions de traitements classiques (chimiothérapie intrapéritonéale hyperthermique (CHIP)) ainsi que le rôle de la caspase-1 dans ces événements.Nous avons d’abord démontré que les agonistes de LXR, un récepteur nucléaire aux oxystérols, pouvaient activer une mort de type pyroptotique dans les cellules cancéreuses coliques en permettant la construction de l’inflammasome et le clivage de la caspase-1. De plus, nous soulignons le potentiel thérapeutique des agonistes de LXR, puisque nous mettons en évidence une perte de localisation nucléaire du récepteur LXRβ dans les cellules tumorales coliques par rapport aux cellules épithéliales saines qui ne sont pas sensibles à la cytotoxicité des ligands de LXR.Nous démontrons également que la caspase-1 pourrait aussi avoir un rôle dans un modèle in vitro de CHIP lorsque celle-ci associe l’oxaliplatine à l’hypotonie. Cette technique chirurgicale utilisée pour des patients atteints de carcinose péritonéale consiste en l’infusion de chimiothérapie dans la cavité abdominale à 42°C pendant un temps variant généralement de 30 à 60 minutes. Même si cette procédure a permis l’augmentation de la survie chez des patients au pronostic vital sombre, les résultats de notre modélisation in vitro montrent que l’efficacité de la CHIP pourrait être améliorée. / Colon cancer is a major public health matter because it has reached the second rank of cancer mortality in 2013 in France. Surgery, radiotherapy and standard chemotherapies helped by targeted therapies are not often efficient enough, underlying the need of using new therapies.Against this background, we have studied the possibilities to use new therapies (Liver X Receptor (LXR) ligands) or to improve classical treatment conditions (hyperthermic intraperitoneal chemotherapy (HIPC)) and the implication of caspase-1.We have first demonstrated that the nuclear receptor (LXR) agonists can induce pyroptotic cell death of colon cancer cell lines by inflammasome activation and subsequent caspase-1 cleavage. Moreover LXR agonists can act as a targeted therapy because we show that nuclear localization of LXRβ in normal colon cells turns into a cytoplasmic expression in colon tumor cells leading LXRβ ready to induce pyroptosis by its agonists.We also demonstrated that caspase-1 could have an implication in an in vitro model of HIPC when it associates oxaliplatin and hypotony. This surgery procedure used for patients suffering from peritoneal carcinomatosis involves a 42°C chemotherapy bath inside the abdominal cavity during 30 to 60 minutes. Although HIPC has increased global survival of patients with poor prognosis, the results of our study indicates that HIPC combining oxaliplatin and hypotony could significantly improve the procedure efficacy.

京都大学 / 0048 / 新制・課程博士 / 博士(生命科学) / 甲第20782号 / 生博第388号 / 新制||生||51(附属図書館) / 京都大学大学院生命科学研究科統合生命科学専攻 / (主査)教授 藤田 尚志, 教授 朝長 啓造, 教授 永尾 雅哉 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

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