Câncer é a principal causa de morte nos países desenvolvidos e a segunda causa de morte nos países em desenvolvimento. O trabalho de diversos grupos de pesquisa tem sugerido que os tumores estão organizados em uma hierarquia de células, na qual uma pequena fração apresenta propriedades de células-tronco. Essas células tem se mostrado resistentes à quimioterapia convencional, dependentes da sinalização do microambiente tumoral e responsivas à terapia diferenciativa. Aqui nós mostramos que butirato sódico (NaB), um inibidor de desacetilase de histonas, diminui a proliferação celular e a formação de colônias em linhagens celulares de meduoblastoma humano. Estes efeitos foram acompanhados de um aumento da expressão de RNAm Gria2, um marcador de diferenciação neuronal, em duas das três linhagens celulares testadas. A formação de neuroesferas também foi impedida com a exposição de uma linhagem crescida em meio de cultura apropriado para células-tronco e NaB. NaB se mostrou capaz de potencializar os efeitos do quimioterápico etoposídeo e do fator neurotrófico derivado de cérebro (BDNF) na inibição da viabilidade celular de meduloblastoma. Além disso, nós observamos que o tratamento com cisplatina aumenta a proporção de células-tronco tumorais (CTT), identificadas por ALDH+CD44+, em células de carcinoma de cabeça e pescoço, quando tratadas também com interleucina 6 (IL-6), uma citocina liberada pelo nicho perivascular. O mesmo tratamento promoveu a proliferação, sobrevivência e auto-renovação de CTTs in vitro ao aumentar o número de esferas em placas de baixa aderência e a expressão de Bmi-1 em western blots. A fosforilação do transdutor de sinal e ativador de transcrição 3 (STAT3), um indicativo de propriedades de CTTs, induzida por IL-6 não foi afetada pelo tratamento com cisplatina em células de HNSCC, enquanto que a indução de fosforilação de quinases reguladas por sinais extracelulares (ERK), indicativo de processo de diferenciação, por IL-6 foi parcialmente inibido por cisplatina. Células resistentes a baixas doses de cisplatina também expressaram mais Bmi-1 do que células nunca expostas ao quimioterápico. Experimentos in vivo corroboram os achados in vitro, uma vez que tumores humanos induzidos em camundongos imunocomprometidos apresentaram aumentada proporção de células ALDH+CD44+ após tratamento dos animais com cisplatina. O anticorpo contra o receptor de IL-6 foi capaz de reverter a indução de expressão de Bmi-1 por cisplatina e IL-6. Em conjunto, esses resultados sugerem que a modulação de mecanismos epigenéticos das células tumorais e de sinais provenientes do nicho tumoral são novos alvos promissores para o desenvolvimento de terapias adjuvantes contra o câncer. / Cancer is the leading cause of death in economically developed countries and the second cause of death in developing countries. Work from a number of laboratories strongly suggests that tumors are organized as a hierarchy based on a subset of cancer cells that have stem-cell properties. These cells have been shown to be resistant to conventional therapy, dependent on contextual signals within the tumor microenvironment and, to be responsive to differentiation therapy. Here we show that sodium butyrate (NaB), a histone deacetylase inhibitor, decreases cell proliferation and colony formation in human medulloblastoma cell lines. These effects were accompanied by an increased mRNA expression of Gria2, a neuronal differentiation marker, in two out of three cell lines tested. In addition, neurosphere formation was impaired by NaB exposure in a cell line submitted to stem cells proper media. NaB also may potentiate the effect of etoposide chemotherapy and BDNF (Brain-derived neurotrophic factor) on the inhibition of medulloblastoma cells viability. Moreover, we observed that cisplatin treatment increased the proportion of cancer stem cells (CSC), identified by ALDHhighCD44high cells, in head and neck squamous cell carcinoma (HNSCC), when treated together with recombinant human IL-6 (rhIL-6). The same regimen promoted proliferation, self-renewal and survival of CSC in vitro as seen by the increase in orosphere number formed in ultra-low attachment plates, and Bmi-1 expression induction in western blots. IL-6–induced signal transducer and activator of transcription 3 (STAT3) phosphorylation (indicative of stemness) was unaffected by treatment with cisplatin in HNSCC cells, whereas IL-6–induced extracellular signal-transducer kinases (ERK) phosphorylation (indicative of differentiation processes) was partially inhibited by cisplatin. Cells resistant to lower doses of cisplatin also expressed more Bmi-1. In vivo experiments corroborated in vitro findings by showing increased proportion of ALDH highCD44high cells in xenograft tumors of mice treated with cisplatin. An antibody against the receptor of IL-6 was able to revert the induction of Bmi-1 expression seen in cells treated with cisplatin plus IL-6. Taken together, these results suggest that the modulation of the epigenetic states of the cancer cell and modulation of signals provided by the niche are promising new molecular targets for the development of adjuvant therapy for cancer.

Câncer é a principal causa de morte nos países desenvolvidos e a segunda causa de morte nos países em desenvolvimento. O trabalho de diversos grupos de pesquisa tem sugerido que os tumores estão organizados em uma hierarquia de células, na qual uma pequena fração apresenta propriedades de células-tronco. Essas células tem se mostrado resistentes à quimioterapia convencional, dependentes da sinalização do microambiente tumoral e responsivas à terapia diferenciativa. Aqui nós mostramos que butirato sódico (NaB), um inibidor de desacetilase de histonas, diminui a proliferação celular e a formação de colônias em linhagens celulares de meduoblastoma humano. Estes efeitos foram acompanhados de um aumento da expressão de RNAm Gria2, um marcador de diferenciação neuronal, em duas das três linhagens celulares testadas. A formação de neuroesferas também foi impedida com a exposição de uma linhagem crescida em meio de cultura apropriado para células-tronco e NaB. NaB se mostrou capaz de potencializar os efeitos do quimioterápico etoposídeo e do fator neurotrófico derivado de cérebro (BDNF) na inibição da viabilidade celular de meduloblastoma. Além disso, nós observamos que o tratamento com cisplatina aumenta a proporção de células-tronco tumorais (CTT), identificadas por ALDH+CD44+, em células de carcinoma de cabeça e pescoço, quando tratadas também com interleucina 6 (IL-6), uma citocina liberada pelo nicho perivascular. O mesmo tratamento promoveu a proliferação, sobrevivência e auto-renovação de CTTs in vitro ao aumentar o número de esferas em placas de baixa aderência e a expressão de Bmi-1 em western blots. A fosforilação do transdutor de sinal e ativador de transcrição 3 (STAT3), um indicativo de propriedades de CTTs, induzida por IL-6 não foi afetada pelo tratamento com cisplatina em células de HNSCC, enquanto que a indução de fosforilação de quinases reguladas por sinais extracelulares (ERK), indicativo de processo de diferenciação, por IL-6 foi parcialmente inibido por cisplatina. Células resistentes a baixas doses de cisplatina também expressaram mais Bmi-1 do que células nunca expostas ao quimioterápico. Experimentos in vivo corroboram os achados in vitro, uma vez que tumores humanos induzidos em camundongos imunocomprometidos apresentaram aumentada proporção de células ALDH+CD44+ após tratamento dos animais com cisplatina. O anticorpo contra o receptor de IL-6 foi capaz de reverter a indução de expressão de Bmi-1 por cisplatina e IL-6. Em conjunto, esses resultados sugerem que a modulação de mecanismos epigenéticos das células tumorais e de sinais provenientes do nicho tumoral são novos alvos promissores para o desenvolvimento de terapias adjuvantes contra o câncer. / Cancer is the leading cause of death in economically developed countries and the second cause of death in developing countries. Work from a number of laboratories strongly suggests that tumors are organized as a hierarchy based on a subset of cancer cells that have stem-cell properties. These cells have been shown to be resistant to conventional therapy, dependent on contextual signals within the tumor microenvironment and, to be responsive to differentiation therapy. Here we show that sodium butyrate (NaB), a histone deacetylase inhibitor, decreases cell proliferation and colony formation in human medulloblastoma cell lines. These effects were accompanied by an increased mRNA expression of Gria2, a neuronal differentiation marker, in two out of three cell lines tested. In addition, neurosphere formation was impaired by NaB exposure in a cell line submitted to stem cells proper media. NaB also may potentiate the effect of etoposide chemotherapy and BDNF (Brain-derived neurotrophic factor) on the inhibition of medulloblastoma cells viability. Moreover, we observed that cisplatin treatment increased the proportion of cancer stem cells (CSC), identified by ALDHhighCD44high cells, in head and neck squamous cell carcinoma (HNSCC), when treated together with recombinant human IL-6 (rhIL-6). The same regimen promoted proliferation, self-renewal and survival of CSC in vitro as seen by the increase in orosphere number formed in ultra-low attachment plates, and Bmi-1 expression induction in western blots. IL-6–induced signal transducer and activator of transcription 3 (STAT3) phosphorylation (indicative of stemness) was unaffected by treatment with cisplatin in HNSCC cells, whereas IL-6–induced extracellular signal-transducer kinases (ERK) phosphorylation (indicative of differentiation processes) was partially inhibited by cisplatin. Cells resistant to lower doses of cisplatin also expressed more Bmi-1. In vivo experiments corroborated in vitro findings by showing increased proportion of ALDH highCD44high cells in xenograft tumors of mice treated with cisplatin. An antibody against the receptor of IL-6 was able to revert the induction of Bmi-1 expression seen in cells treated with cisplatin plus IL-6. Taken together, these results suggest that the modulation of the epigenetic states of the cancer cell and modulation of signals provided by the niche are promising new molecular targets for the development of adjuvant therapy for cancer.

Objetivos. Avaliar o papel do transplante de células hematopoiéticas (TCH) e da interleucina 6 (IL – 6) sobre vários parâmetros de estresse oxidativo em pacientes com Adrenoleucodistrofia ligada ao cromossomo X (X-ALD). Métodos. A concentração de malondialdeído (MDA), o conteúdo de carbolinas e sulfidrilas e a concentração de ácido hexacosanóico (C26:0) foram quantificados no plasma de pacientes X-ALD antes e após serem submetidos ao TCH. E, a concentração de MDA, a formação de carbonilas e a concentração de IL-6 foram quantificados em plasma e o conteúdo de glutationa reduzida (GSH) foi quantificado em eritrócitos de pacientes X-ALD com fenótipos cerebral infantil (cALD) ou assintomáticos no momento diagnóstico. Resultados. Observamos um aumento significativo na concentração de MDA em plasma de pacientes X-ALD antes e após o TCH em comparação ao grupo controle e uma redução significativa nesses valores após o transplante em comparação aos anteriores ao procedimento. Verificamos uma redução significativa no conteúdo de sulfidrilas no plasma de pacientes X-ALD antes do TCH em comparação ao grupo controle e um aumento significativo desses níveis após o TCH. Não observamos diferenças significativas no conteúdo de carbonilas no plasma de X-ALD antes e após o TCH, em comparação aos controles, apesar de observarmos uma redução significativa nesta determinação nos pacientes após o transplante em relação a antes do TCH. Os pacientes X-ALD apresentam níveis plasmáticos de C26:0 significativamente aumentados antes do TCH em comparação aos controles e, após o TCH, as concentrações de C26:0 foram reduzidas. Observamos uma correlação negativa significativa entre a medida do conteúdo de sulfidrilas e os níveis plasmáticos de C26:0 de indivíduos X-ALD antes do TCH. Também evidenciamos elevados níveis de MDA e da formação de carbonilas no plasma de pacientes cALD e assintomáticos em comparação ao grupo controle. Ainda, observamos redução significativa do conteúdo de GSH nos dois grupos testados comparados aos controles. A quantificação de IL-6 foi significativamente maior nos pacientes cALD, o que não foi observado nos pacientes assintomáticos, apesar destes mostrarem uma tendência de aumento da concentração de IL-6. Conclusões. Os resultados obtidos a partir do plasma de pacientes X-ALD antes e após o TCH demonstram que esta terapia, quando bem indicada e bem sucedida, tem alta efetividade em reduzir a concentração plasmática de C26:0 e é eficaz em reduzir a peroxidação lipídica e o dano oxidativo às proteínas nos pacientes X-ALD. Ainda, é possível relacionar o acúmulo de C26:0 e o dano oxidativo na patogênese da X-ALD. Nossos dados permitem sugerir que a lipoperoxidação e o dano oxidativo às proteínas possam de alguma forma estar envolvidos na fisiopatologia da X-ALD. Além disso, podemos presumir que, nos pacientes X-ALD assintomáticos estudados, o dano oxidativo e os aspectos inflamatórios desempenham papéis importantes na evolução e nas futuras manifestações do fenótipo neuronal. Também podemos supor que a administração de antioxidantes deve ser considerada como uma terapia adjuvante potencial para os pacientes assintomáticos e sintomáticos afetados pela X-ALD, inclusive para aqueles submetidos ao TCH. / Objective. We aimed to evaluate the role of hematopoietic stem cell transplantation (HSCT) and interleukin 6 (IL – 6) on various parameters of oxidative stress in X-linked adrenoleukodystrophy (X-ALD) patients. Methods. Malondialdehyde (MDA), sulfhydryl, carbonyl and hexacosanoic acid (C26:0) levels were measured in plasma from X-ALD patients before and after HSCT. And, MDA, carbonyl and IL-6 levels were measured in plasma and reduced glutathione (GSH) content was measured in erythrocytes from X-ALD patients with different phenotype (asymptomatic and childhood cerebral (CCER patients) at diagnosis moment. Results. We observed increased levels of MDA in plasma from X-ALD before and after HSCT compared to control group, but there was a significant reduction in MDA values after transplantation compared to levels found before the procedure. We verified a significant decrease in sulfhydryl content in plasma of X-ALD patients before HSCT compared with the control group and we also verified a significant increase in the levels of sulfhydryl content after HSCT. No significant differences were observed in carbonyl content in plasma of X-ALD before and after HSCT, compared to controls. However, we observed a significant reduction of plasma carbonyl content from X-ALD patients after HSCT compared to before HSCT. X-ALD patients presented a significant increase of C26:0 plasma level before HSCT when compared to controls and an important reduction of C26:0 plasma concentration in X-ALD patients after HSCT when compared to before HSCT C26:0 levels. We observed an inverse significant correlation between sulfhydryl content and plasma C26:0 levels of X-ALD individuals before HSCT. We also evidenced high levels of MDA and carbonyl formation in plasma from CCER and asymptomatic patients compared to controls. Still, we observed a significant decrease of GSH content in both groups tested compared to controls. The quantification of IL-6 is significantly higher in CCER patients, which is not observed in asymptomatic patients, despite these patients show a tendency of increased concentration of IL-6. Conclusions. The results obtained from plasma of X-ALD patients before and after HSCT demonstrate that this therapy, when well indicated and successful, has high effectiveness in reducing C26:0 plasma and is effective in reducing lipid peroxidation and oxidative damage to proteins in X-ALD patients. Still, it is possible to relate the accumulation of C26:0 and oxidative damage in the pathogenesis of X-ALD. Our data also suggest that lipid peroxidation and protein damage may somehow be involved in the pathophysiology of X-ALD. Moreover, we can assume that in our asymptomatic X-ALD patients, oxidative damage and inflammatory issues seem to play an important role in the evolution and future manifestations of neuronal phenotype. We can also assume that the administration of antioxidants should be considered as a potential adjuvant therapy for asymptomatic and symptomatic patients affected by X-ALD, including those that are submitted to HSCT.

Câncer é a principal causa de morte nos países desenvolvidos e a segunda causa de morte nos países em desenvolvimento. O trabalho de diversos grupos de pesquisa tem sugerido que os tumores estão organizados em uma hierarquia de células, na qual uma pequena fração apresenta propriedades de células-tronco. Essas células tem se mostrado resistentes à quimioterapia convencional, dependentes da sinalização do microambiente tumoral e responsivas à terapia diferenciativa. Aqui nós mostramos que butirato sódico (NaB), um inibidor de desacetilase de histonas, diminui a proliferação celular e a formação de colônias em linhagens celulares de meduoblastoma humano. Estes efeitos foram acompanhados de um aumento da expressão de RNAm Gria2, um marcador de diferenciação neuronal, em duas das três linhagens celulares testadas. A formação de neuroesferas também foi impedida com a exposição de uma linhagem crescida em meio de cultura apropriado para células-tronco e NaB. NaB se mostrou capaz de potencializar os efeitos do quimioterápico etoposídeo e do fator neurotrófico derivado de cérebro (BDNF) na inibição da viabilidade celular de meduloblastoma. Além disso, nós observamos que o tratamento com cisplatina aumenta a proporção de células-tronco tumorais (CTT), identificadas por ALDH+CD44+, em células de carcinoma de cabeça e pescoço, quando tratadas também com interleucina 6 (IL-6), uma citocina liberada pelo nicho perivascular. O mesmo tratamento promoveu a proliferação, sobrevivência e auto-renovação de CTTs in vitro ao aumentar o número de esferas em placas de baixa aderência e a expressão de Bmi-1 em western blots. A fosforilação do transdutor de sinal e ativador de transcrição 3 (STAT3), um indicativo de propriedades de CTTs, induzida por IL-6 não foi afetada pelo tratamento com cisplatina em células de HNSCC, enquanto que a indução de fosforilação de quinases reguladas por sinais extracelulares (ERK), indicativo de processo de diferenciação, por IL-6 foi parcialmente inibido por cisplatina. Células resistentes a baixas doses de cisplatina também expressaram mais Bmi-1 do que células nunca expostas ao quimioterápico. Experimentos in vivo corroboram os achados in vitro, uma vez que tumores humanos induzidos em camundongos imunocomprometidos apresentaram aumentada proporção de células ALDH+CD44+ após tratamento dos animais com cisplatina. O anticorpo contra o receptor de IL-6 foi capaz de reverter a indução de expressão de Bmi-1 por cisplatina e IL-6. Em conjunto, esses resultados sugerem que a modulação de mecanismos epigenéticos das células tumorais e de sinais provenientes do nicho tumoral são novos alvos promissores para o desenvolvimento de terapias adjuvantes contra o câncer. / Cancer is the leading cause of death in economically developed countries and the second cause of death in developing countries. Work from a number of laboratories strongly suggests that tumors are organized as a hierarchy based on a subset of cancer cells that have stem-cell properties. These cells have been shown to be resistant to conventional therapy, dependent on contextual signals within the tumor microenvironment and, to be responsive to differentiation therapy. Here we show that sodium butyrate (NaB), a histone deacetylase inhibitor, decreases cell proliferation and colony formation in human medulloblastoma cell lines. These effects were accompanied by an increased mRNA expression of Gria2, a neuronal differentiation marker, in two out of three cell lines tested. In addition, neurosphere formation was impaired by NaB exposure in a cell line submitted to stem cells proper media. NaB also may potentiate the effect of etoposide chemotherapy and BDNF (Brain-derived neurotrophic factor) on the inhibition of medulloblastoma cells viability. Moreover, we observed that cisplatin treatment increased the proportion of cancer stem cells (CSC), identified by ALDHhighCD44high cells, in head and neck squamous cell carcinoma (HNSCC), when treated together with recombinant human IL-6 (rhIL-6). The same regimen promoted proliferation, self-renewal and survival of CSC in vitro as seen by the increase in orosphere number formed in ultra-low attachment plates, and Bmi-1 expression induction in western blots. IL-6–induced signal transducer and activator of transcription 3 (STAT3) phosphorylation (indicative of stemness) was unaffected by treatment with cisplatin in HNSCC cells, whereas IL-6–induced extracellular signal-transducer kinases (ERK) phosphorylation (indicative of differentiation processes) was partially inhibited by cisplatin. Cells resistant to lower doses of cisplatin also expressed more Bmi-1. In vivo experiments corroborated in vitro findings by showing increased proportion of ALDH highCD44high cells in xenograft tumors of mice treated with cisplatin. An antibody against the receptor of IL-6 was able to revert the induction of Bmi-1 expression seen in cells treated with cisplatin plus IL-6. Taken together, these results suggest that the modulation of the epigenetic states of the cancer cell and modulation of signals provided by the niche are promising new molecular targets for the development of adjuvant therapy for cancer.

L’objectif de notre travail a été de caractériser le rôle de l’IL-6 dans la différenciation des lymphocytes Tfh et des lymphocytes Th2. Les lymphocytes Tfh ont pour fonction d’aider les lymphocytes B à produire des anticorps indispensables pour nous protéger contre divers pathogènes. Les lymphocytes Th2, quant à eux, sont spécialisés dans l’élimination de parasites extracellulaires tels que les helminthes.<p>Dans un premier temps, nous avons voulu identifier les gènes dont l’expression est induite par l’IL-6, avec comme objectif une meilleure compréhension des mécanismes permettant aux lymphocytes T de se différencier en cellules Tfh.<p>Au cours de notre travail, nous avons identifié le facteur de transcription, MyoR (Myogenic Repressor) comme étant exprimé au sein des lymphocytes T helper et dont l’expression est induite par l’IL-6. Nos observations expérimentales ont démontré que le facteur MyoR n’est pas indispensable pour la différenciation des lymphocytes Tfh, ni pour leur fonction. Cependant, l’expression de l’ARNm codant pour MyoR pourrait être utilisée comme un biomarqueur des cellules Tfh in vitro ou in vivo.<p>Nous avons ensuite caractérisé la réponse immune induite in vivo par des cellules présentatrices d’antigènes issues de souris déficientes pour l’IL-6. Cette approche nous a permis de mettre en évidence le rôle immunosuppresseur de l’IL-6 sur le développement des réponses de type Th2. En effet, nous avons montré que l’injection de BMDCs (Bone Marrow derived dendritic cells) IL-6-/- dans des souris receveuses de type sauvage induisent une réponse Th2 augmentée in vivo.<p>Nos résultats suggèrent que l’inhibition de la réponse Th2 par l’IL-6 in vivo et in vitro pourrait impliquer la présence d’un ou de plusieurs miRNAs.<p>Cette inhibition pourrait être un mécanisme de rétrocontrôle afin d’éviter une exacerbation de la réponse immune Th2. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Magister Scientiae - MSc / This study shows that herbs can be effectively screened for potiential bio-activity using in vitro methods. Further studies will be needed to better explore Artemisia afra&rsquo;s effect on immunoregulation, particularly long term effects of the herb on the immune system and its effect on other disease states. / South Africa

Human cytomegalovirus (HCMV) is a ubiquitous virus of the herpes type that infects a high percentage of some populations. One of the most researched genes expressed by HCMV with close homology to human chemokine receptors is the US28 G protein-coupled receptor. Study design: This study was initiated to elucidate the intracellular signalling pathways of an inflammatory factor (IL-6) and an angiogenic factor (STAT3) triggered by the viral US28 oncogene and the presence of US28 in the HCMV viral particle. These pathways were observed by introducing the US28 gene into two human cell lines by infection with a HCMV strain that expresses the US28 gene (wild type), and two HCMV strains where the US28 gene was deleted (ÄUS28 and ÄUS28/UL33). Special attention was directed at the expression of IL-6 after promotion of the US28 gene and subsequent phosphorolation of STAT3. A new US28 antibody was validated and a method developed in an attempt to determine US28 on the viral particle. The following techniques were applied: Cell culture work, two mammalian cell lines were used, HFF’s and U373 MG. Virus stock titre determination to determine the multiplicity of infection. Protein quantitation to determine very small quantities of protein for Western blot analysis. ELISA for the quantitative determination of IL-6. Western blotting for phospho- STAT3 determination and validation of the US28 antibody. Immunocytochemistry was used for back titrations of virally infected cells. Immunofluorescence assay and use of confocal microscopic techniques was used for the location of the US28 gene in the virion and for tSTAT3 translocation to the nucleus. Conclusion: A clear increase in IL-6 secretion (495% ± 1%) was seen, and this was after only an hour in HCMV WT infected cells. From the increase in IL-6 secretion a subsequent increase in STAT3 phosphorylation was detected in the same samples. A clear link has been established between IL-6 and STAT3. A method to determine whether US28 was present in the HCMV viral particle was designed and preliminary results obtained. The results were inclusive. / Dissertation (MSc)--University of Pretoria, 2011. / Pharmacology / unrestricted

Magister Scientiae - MSc / "The aim of the study was to use in vitro human whole blood cultures to screen the water samples collected from the Eerste/Plankenbrug river system for cytotoxicity and inflammatory activity and for the first time investigate the impact on the cell- mediated and humoral immune pathways. Water samples were collected fronm the sites during the dry summer season and rainy winter season. Blood was collected from the healthy male volunteers and diluted with RPMI 1640. For cytotoxicity and inflammatory activity 2.5ul of blood for 18-20 hrs at 37 C... This study shows that waster from the Plankenbrug River is heavily polluted by contaminants from both the agricultural area and informal settlement of Kayamandi. These contaminants can be potentially immunotoxic during the summer season and they can result in inflammatory diarrheal disease and immunosuppression in exposed individuals..."

No description available.

L’activateur tissulaire du plasminogène (tPA) est une sérine protéase qui est synthétisée principalementpar les cellules endothéliales des vaisseaux. Initialement découvert dans le compartiment vasculaire où sa fonctionprincipale est de participer à la fibrinolyse, le tPA est aussi exprimé dans le parenchyme cérébral par plusieurstypes cellulaires comme les neurones ou les oligodendrocytes. Le tPA est impliqué dans de nombreuses fonctionscérébrales comme la plasticité synaptique ou encore la potentialisation glutamatergique. Le tPA est aussi un acteurclé de la neuroinflammation. Il active la microglie et participe à l’ouverture de la barrière hémato-encéphalique pardes effets de type cytokine et via son domaine protéase en générant de la plasmine à partir du plasminogène. Uneactivité plus importante du tPA est retrouvée dans le liquide céphalorachidien des patients atteints de sclérose enplaques (SEP). De plus, le tPA possède des aspects délétères dans son modèle murin, l’encéphalomyélite autoimmune expérimentale (EAE). Dans le but de mieux comprendre le rôle du tPA dans la physiopathologie de l’EAE,nous nous sommes intéressés à son implication dans la réponse immunitaire pendant la maladie. Nos donnéesmontrent que les animaux tPA-/- ont des scores cliniques moins importants que les animaux WT pendant une EAE.Les nombres absolus de LT CD4+, de microglie activée et de macrophages infiltrés, ainsi que de cellulesdendritiques sont moins importants dans le parenchyme spinal des animaux tPA-/- en comparaison avec lesanimaux WT. En lien avec ces observations in vivo, le tPA augmente in vitro l’activation et la prolifération des LTainsi que la sécrétion d’IL-6 par un mécanisme dépendant du domaine protéase et de la génération de plasmine.Dans des expériences in vitro en collaboration avec l’équipe du Dr Diego Clemente, le tPA induit l’augmentation del’expression des molécules du CMH de classe II et des molécules de costimulation à la surface des cellulesdendritiques et des macrophages par un effet de type cytokine, suggérant une capacité plus importante pour cescellules à présenter des antigènes en présence de tPA. Notre étude apporte une meilleure compréhension du rôledu tPA dans la réponse immunitaire pendant l’EAE et ouvre de nouvelles perspectives dans l’étude de l’axe tPA/plasmine dans la physiopathologie de la maladie. / Tissue plasminogen activator (tPA) is a serine protease, mainly synthesized by endothelial cells of vessels.Initially discovered in the vascular compartment where its main function is to participate to fibrinolysis, tPA is alsopresent in the cerebral parenchyma, and expressed by several cell types like neurons or oligodendrocytes. tPA isinvolved in many physiological brain functions such as synaptic plasticity or glutamatergic potentiation. tPA is alsoa main actor of neuroinflammation. It activates microglia and participates in the opening of the blood-brain barrier(BBB) by cytokine-like effects and via its protease domain and plasmin generation from plasminogen. Interestingly,tPA activity is more important in cerebrospinal fluid of multiple sclerosis (MS) patients. In addition, tPA revealsdeleterious aspects in experimental autoimmune encephalomyelitis (EAE), the mouse model of MS. In order tobetter understand the role of tPA in EAE physiopathology, we focused on its involvement in the immune responseduring disease. tPA-/- EAE animals present less severe clinical scores than WT animals. Our results indicate alsothat absolute numbers of CD4 + T cells, activated microglia and infiltrated macrophages, as well as dendritic cellsare less important in the spinal parenchyma of tPA-/-. In connection with these in vivo observations, our in vitro datashow that tPA increases activation and proliferation of T cells, as well as IL-6 secretion by a protease-dependentmechanism and plasmin generation. In experiments in collaboration with Dr Diego Clemente's team, our data showthat tPA increases the expression of MHC class II and costimulatory molecules on the surface of dendritic cells andmacrophages in vitro by a cytokine-like effect, suggesting a more important ability for these cells to present antigenswith tPA. Our study provides a better understanding of the role of tPA in immune response during EAE, and opensup new perspectives in the study of the tPA / plasmin axis in the physiopathology of the disease.