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京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第24329号 / 生博第488号 / 新制||生||65(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 野田 岳志, 教授 杉田 昌彦, 教授 垣塚 彰 / 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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It is now clear that estrogen not only modulates the differentiation and function of reproductive systems, but it also profoundly regulates the immune system of normal and autoimmune individuals. An important mechanism by which estrogen regulates the immune system is by altering the secretion and/or response to cytokines. We hypothesized that estrogen may alter the levels and/or response to IFN-g, a prototype Th1 cytokine, that plays a pivotal role in immunity against intracellular infections and in many autoimmune and inflammatory disorders. We found that estrogen treatment tended to upregulate the secretion of IFN-g protein and mRNA expression from Concanavalin-A (Con-A)-activated splenic lymphocytes. Impressively, we found that splenocytes from estrogen-treated mice when activated with Con-A also resulted in increased release of nitric oxide compared to placebo-treated mice. Furthermore, Con-A-activated splenocytes from estrogen-treated mice also had upregulated iNOS mRNA, iNOS protein, and nitric oxide-regulated COX-2 protein when compared to control mice. Blocking co-stimulatory signals mediated through interactions of CD28 and B7 molecules by using CTLA-4Ig markedly decreased not only IFN-g, but also nitric oxide, thereby implying an important role for CD28/B7 interactions in IFN-g/nitric oxide. Estrogen-induced upregulation of iNOS/nitric oxide is mediated through IFN-g since: (i) Estrogen alone did not upregulate iNOS/nitric oxide in IFN-g knockout mice; (ii) addition of rIFN-g to activated splenocytes from estrogen-treated mice further upregulated nitric oxide levels. We next investigated whether estrogen also upregulated IFN-g-inducing cytokines and select IFN-g-inducing transcription factors. Estrogen treatment resulted in increased mRNA and/or protein expression of IFN-g inducing cytokines and their receptors, including: IL-18, IL-15, IL-27, IL-12Rb2, and IL-18Rb. We also found that T-bet, a critical Th1 transcription factor, and STAT-4 phosphorylation, a key molecule in IL-12 signaling were both increased, while IRF-4, an important player in Th2 differentiation, was diminished in Con-A-activated splenocytes from mice treated with estrogen. Altogether, these studies are the first to demonstrate that estrogen regulates IFN-g-dependent iNOS and describes the potential mechanisms of how estrogen alters IFN-g-inducible genes, IFN-g inducing cytokines, and transcription factors in normal C57BL/6 mice. These studies may have profound implications to many autoimmune and inflammatory disorders, where estrogen is known to regulate the course of these diseases. Since estrogen may promote inflammatory disorders by upregulating pro-inflammatory biomolecules including IFN-g, nitric oxide, and COX-2, these studies may help in the design of therapeutic agents that regulate or block secretion and/or response to these inflammatory molecules. / Ph. D.

Les pDCs répondent aux infections virales par la production d'IFN-α. L'élimination du virus de l'hépatite C (VHC) chez plus de 50% des patients infectés par le traitement à l'IFN-alpha suggère que les pDCs jouent un rôle majeur dans le contrôle de l'infection VHC. Les pDCs exposées aux hépatocytes infectés par VHC, produisent beaucoup d'IFN-α. Néanmoins, en dépit de cette production par TLR7 par les pDCs, VHC continue à se répliquer dans le foie infecté. J'ai approfondi les connaissances des mécanismes moléculaires d'exploration des particules de VHC et des cellules infectées par le VHC par les pDCs. J'ai ciblé ma recherche sur le contact des particules de VHC avec la surface des pDCs, sur la voie de signalisation de déclenchée, sur leur effet sur la production des IFNs et des cytokines proinflammatoires et sur la différenciation cellulaire. Nos résultats suggèrent que le virus associé aux cellules signalise dans les pDCs via un mécanisme dépendant de l'endocytose et d'IRF7 mais pas de la voie NF-κB. En dépit de l'induction d'IFN-α, le VHC associé aux hépatocytes n'induit une réponse pleinement fonctionnelle des pDCs. Les particules virales de VHC inhibent, via la fixation de la glycoprotéine E2 aux CLRs, la production d'IFN-α et d'IFN-λ dans les pDCs exposées aux hépatocytes infectés par VHC et induisent dans les pDCs, une phosphorylation rapide d'Akt et Erk1/2, d'une manière similaire au crosslinking de BDCA-2 ou DCIR. Ainsi, le blocage de BDCA-2 et de DCIR avec des fragments Fab des anticorps monoclonaux préserve la capacité des pDCs à produire des IFNs de type I et III en présence des particules virales. / Plasmacytoid dendritic cells (pDCs) respond to viral infection by production of alpha interferon (IFN-alpha), proinflammatory cytokines, and cell differentiation. The elimination of hepatitis C virus (HCV) in more than 50% of infected patients by treatment with IFN-alpha suggests that pDCs play an important role in the control of HCV infection. pDCs exposed to HCV infected hepatoma cells produce large amounts of IFN-alpha. However, despite large amounts of Toll-like receptor 7-mediated IFN-α, produced by pDCs, HCV still replicates in infected liver. During my PhD training, I went into in depth to understand the molecular mecanisms used by HCV particles and HCV infected hepatocytes to explore pDCs. I focused my research on the binding of HCV particles with the pDC surface, on the triggered downstream signaling pathway, on the cellular differentiation. Our results suggest that cell-associated HCV signals in pDCs via an endocytosis-dependent mechanism and IRF7 but not via the NF-kappaB pathway. In spite of IFN-alpha induction, cell-associated HCV does not induce a full functional response of pDCs. HCV particles inhibit, via binding of E2 glycoprotein to CLRs, production of IFN-α and IFN-λ in pDCs exposed to HCV-infected hepatocytes, and induce in pDCs a rapid phosphorylation of Akt and Erk1/2, in a manner similar to the crosslinking of BDCA-2 or DCIR. Blocking of BDCA-2 and DCIR with Fab fragments of monoclonal antibodies preserves the capacity of pDCs to produce type I and III IFNs in the presence of HCV particles.

O vírus linfotrópico de células T humanas do tipo 1 (HTLV-1) é o agente etiológico de duas principais manifestações clínicas, a mielopatia associada ao HTLV-1/paraparesia espástica tropical (HAM/TSP) e a leucemia/linfoma de células T do adulto (ATLL). O desenvolvimento de HAM/TSP, uma doença neuroinflamatória crônica é relacionada a uma complexa interação entre vírus e resposta imunológica do hospedeiro. A expressão do gene viral tax desempenha um papel importante na patogênese da HAM/TSP pela ativação de diversos genes celulares, incluindo genes das citocinas inflamatórias IFN-? e TNF- Recentemente, os exossomos surgiram como um importante fator na comunicação célula-célula contribuindo em diversos processos celulares, inclusive na modulação do sistema imunológico. Considerando o potencial papel dos exossomos na imunomodulação e no processo inflamatório, o objetivo deste trabalho foi avaliar se os exossomos produzidos por células infectadas pelo HTLV-1 carreiam moléculas virais e se poderiam participar dos processos de imunomodulação e inflamação crônica observados na HAM/TSP. Os exossomos foram isolados de células infectadas pelo HTLV-1 da linhagem celular C8166, avaliados quanto à presença de RNAm viral tax e testados quanto à capacidade de ativar células mononucleares do sangue periférico (PBMC) à indução de resposta inflamatória. Neste trabalho, foi observado que, após a exposição de PBMC aos exossomos contendo RNAm viral tax, a expressão da citocina inflamatória IFN-? foi aumentada em linfócitos T CD4+ e CD8+ quando comparado ao grupo não exposto aos exossomos. Foi observado um pequeno aumento de TNF-? no grupo exposto aos exossomos. Não houve diferença na expressão das citocinas IL-4, perforina e granzima B. Tomados em conjunto, estes resultados sugerem que exossomos contendo tax isolados de células infectadas pelo HTLV-1 induzem a produção de citocinas inflamatórias ativam a resposta imunológica de padrão Th1, e não Th2. Estes achados podem contribuir na elucidação do papel dos exossomos na infecção pelo HTLV-1 e nos estudos relacionados à patogênese da HAM/TSP e à resposta inflamatória envolvendo a apresentação clínica desta doença. / Human T-cell lymphotropic virus type 1 (HTLV-1) is the etiological agent of HTLV-1 associated myelopathy/tropical paraparesis spastic (HAM/TSP) and adult T-cell leukemia/lymphoma (ATLL). The development of HAM/TSP, a chronic neuroinflammatory disease, is correlated to a complex host-virus dynamic immune response interaction. Tax expression plays an important role in HAM/TSP pathogenesis by activating various cellular genes, including the cytokines IFN-? and TNF-?. Exosomes have emerged as an important factor of cell-to-cell communication contributing to diverse cellular processes, including immune modulation. Considering the potential role of exosomes in modulating the immune response and inflammation, the main objective of this study was to examine if HTLV-1-infected cells produce exosomes can carry viral tax mRNA, and if they can can participate in the chronic inflammation observed in patients with HAM/TSP. Exosomes were isolated from HTLV-1-infected cell line culture, evaluated for the tax mRNA presence and tested for the ability to activate peripheral mononuclear cells (PBMC) in inducing an inflammatory immune response. We observed that the proinflammatory cytokine IFN-? was upregulated in CD4 and CD8 T-cells after treatment of the PBMC with Tax carrying exosomes compared to the negative control. The expression of TNF-? was slightly upregulated. IL-4, Granzyme B and Perforin did not show alterations. Taken together, these results suggest that exosomes carrying Tax isolated from HTLV-1-infected cells might induce the production of proinflammatory cytokines and activate T helper (Th)1, and not Th2, immune response. This study may have important impact on the studies involving the pathogenesis of HAM-TSP and the inflammatory response involved in the clinical presentation of the disease.