O endotélio reveste a parede vascular e possui função essencial na manutenção da homeostase. A célula endotelial é capaz de perceber estímulos extracelulares, como fatores químicos e mecânicos, transmitir a informação para dentro da célula e regular sua função e fenótipo. Neste sentido, investigamos os mecanismos moleculares associados as células endoteliais em dois contextos importantes de intervenções vasculares 1) nos stents farmacológicos, onde a rapamicina exerce funções antiproliferativas e pró-trombogênicas, e 2) na revascularização cardíaca por ponte de safena, onde o alto estiramento mecânico exerce grande impacto no remodelamento vascular e no fenótipo da célula endotelial. A rapamicina pertence à classe de drogas limus, bastante utilizadas nos stents farmacológicos usados no procedimento de desobstrução vascular. Além de sua função antiproliferativa, exploramos os efeitos deletérios associados a pró-trombogênese. Os dados demonstraram que a rapamicina ativa o receptor de TGF independentemente de seu ligante TGFbeta, promovendo aumento na expressão da PAI-1 (pró-trombogênica), alteração no fenótipo endotelial (Transição endotélio-mesenquimal - EndMT) e na formação de fibras de estresse. Os efeitos observados são dependentes da ativação de Smad2 e independentes da via clássica antiproliferativa por mTOR. Experimentos in vivo mostraram que o tratamento com inibidor do receptor de TGF diminui os efeitos pró-trombogênicos e a expressão de PAI-1 induzidos pela rapamicina em artérias carótidas de camundongos. A ponte de safena é um procedimento bastante utilizado na cirurgia de revascularização cardíaca e a arterialização do segmento venoso submetido ao estresse hemodinâmico arterial resulta em remodelamento vascular, que influencia o sucesso do procedimento. Nossos dados demonstram que a célula endotelial humana de veia safena humana (hSVEC), susceptível as modificações do tipo EndMT induzido quimicamente (estímulo pró-fibrótico e pró-inflamatório), não expressou o mesmo comportamento em resposta ao aumento de estiramento mecânico que ocorre durante a arterialização venosa. Entretanto, detectamos uma pronunciada redução dos filamentos de actina, modulação no padrão de ativação da cofilina e na proporção de actina glomerular (G-actina) entre citoplasma e núcleo, com redução da biodisponibilidade de NO. De modo interessante, demonstramos que a redução no filamento de actina é específica para a célula endotelial venosa, não sendo observado em células endoteliais de origem arterial de aorta e coronária. Em conjunto, os dados mostram que 1) efeitos pró-trombogênicos associados a rapamicina são mediados por ativação do receptor de TGF independente do seu ligante e da atividade antiproliferativa da droga e 2) a adaptação da célula endotelial venosa ao estiramento mecânico envolve modulação da síntese/degradação de filamentos de actina e redução na biodisponibilidade de NO. Estes novos elementos sobre o mecanismo de transdução de estímulos químicos e físicos pelo endotélio poderão ser explorados terapeuticamente para modular a plasticidade endotelial em disfunções cardiovasculares / Endothelium is the inner layer in vascular wall and displays an essential role in the maintenance of cardiovascular homeostasis. Endothelial cell senses the extracellular stimuli, such as chemical and mechanical factors, transduce and process these signals to regulate cell function and phenotype. Here, we investigated molecular underpinning of the endothelial cells under two important scenarios: 1) in drug-eluting stents, where rapamycin exerts antiproliferative and undesirable prothrombogenic functions, and 2) in vein graft bypass surgery, where increased stretch modulates vascular remodeling and endothelial cell phenotype. Rapamycin belongs to the class of limus drugs and is widely used in drug eluting stents (DES) to vascular restenosis. In addition to its antiproliferative function, we explore the deleterious effects associated with prothrombogenesis. Our data demonstrated that rapamycin activates TGF receptor independent of its ligand TGFbeta, in concert with promotion of PAI-1 expression (prothrombogenic), changes in endothelial phenotype (Endothelial to Mesenchymal Transition - EndMT) and stress fibers induction. These effects are Smad2 dependent and independent of the classical antiproliferative mTOR pathway of rapamycin. Our in vivo experiments showed that TGF receptor inhibitor treatment decreases prothrombogenic effects and PAI-1 expression induced by rapamycin in mice carotid arteries. Saphenous vein is widely used in coronary artery bypass surgery (CABG) and the vein arterialization remodeling in response to the increased stress influences graft patency. Our data demonstrated that human saphenous vein endothelial cell (hSVEC) is susceptible to chemically induced endothelial-to-mesenchymal transition (EndMT) by pro-fibrotic and pro-inflammatory stimuli. On the other hand, physical stimulus associated with high stretch failed to induce EndMT. However, we detected a pronounced decrease of actin filaments, modulation of the cofilin activation, changes in the proportion of glomerular actin (G-actin) between cytoplasm and nucleus, and reduction of NO bioavailability. Interestingly, the reduction of actin fibers by high stretch is specific to venous endothelial cell since arterial endothelial cells from aorta, and coronary artery failed to display the response. Altogether, our data show that 1) the thrombogenic effects of rapamycin are mediated by TGF receptor activation independent of its ligand and independent of the antiproliferative pathway of the drug, and 2) the adaptation of venous endothelial cell to mechanical stretch involves synthesis/degradation of actin filaments and reduced NO bioavailability. These new elements on signal transduction of endothelial cells in response to chemical and physical stimuli may be therapeutically explored to modulate endothelial plasticity in cardiovascular disorders

A cartilagem articular da cabeça da mandíbula (CAM) é constituída por uma cartilagem secundária recoberta por tecido conjuntivo fibroso e, portanto, definida como fibrocartilagínea. Ela é constantemente submetida a forças de compressão e cisalhamento decorrentes da mastigação necessitando de lubrificação e capacidade de reparo. O envelhecimento é considerado um dos principais fatores para o aparecimento de alterações degenerativas nas articulações sinoviais. A lubricina é reconhecidamente um proteoglicano encontrado nas cartilagens articulares cuja função primordial é a lubrificação limítrofe. A via SMAD2, tem sido associada à capacidade de manutenção e reparo da cartilagem, e a sua fosforilação na cadeia de ligação (p-SMAD2L) foi relacionada ao aumento no tempo de fosforilação na cadeia C-terminal (p-SMAD2) e da transcrição gênica. Objetivo: Estudar as alterações morfológicas da CAM e as expressões da lubricina, p-SMAD2L e do colágeno tipo I no envelhecimento. Métodos: cortes coronais da CAM de ratos wistar com 2, 12 e 24 meses de vida foram corados pelas técnicas da hematoxilina e eosina, azul de toluidina e safranina-O. A imuno-histoquímica foi usada para detectar a localização da lubricina, p-SMAD2L e colágeno tipo I. Resultados: Notou-se modificações estruturais atribuídas ao processo natural do envelhecimento da CAM. Ainda, se verificou um aumento do colágeno tipo I nas camadas mais profundas e cartilaginificação da matriz extracelular (MEC) nas camadas superficiais. No grupo idoso, houve redução na concentração de proteoglicanos, na expressão da lubricina e na densidade e porcentagem de células p-SMAD2L. Conclusões: a CAM sofre modificações com o envelhecimento, inclusive degenerativas, e diminui sua capacidade de lubrificação e reparo em virtude da menor expressão da lubricina e p-SMAD2L. Sugere-se que a p-SMAD2L está envolvida na produção e acúmulo da lubricina na CAM / The mandibular condylar cartilage (MCC) consists of a secondary cartilage covered by fibrous connective tissue and, therefore, defined as fibrocartilage. It is constantly subjected to compression and shear forces resulting from chewing requiring lubrication and repair capability. Aging is considered one of the main factors for the appearance of degenerative changes in synovial joints. Lubricin is a proteoglycan found in articular cartilages whose primary function is boundary lubrication. SMAD2 signaling pathway has been associated with cartilage maintenance and repair, and its phosphorylation in the linker region (p-SMAD2L) was related to the increase in half-life of C-terminal phospho-SMAD2 (p-SMAD2) and gene transcription. Objective: To study the morphological alterations of MCC and the expressions of the lubricin, p-SMAD2L and type I collagen in aging. Methods: Coronal sections of the MCC from wistar rats with 2, 12 and 24 months old were stained with hematoxylin and eosin, toluidine blue and safranin-O. Immunohistochemistry were used for detection of lubricin, p-SMAD2L and type I collagen. Also, the total cell density, p-SMAD2L cells density and percentage were determined. Results: Structural modifications of the MCC related with natural aging process were observed. An increase in the expression of type I collagen in the deeper layers and \"cartilaginification\" of the extracellular matrix (ECM) in the superficial layers were detected. In the old group, it was observed a reduction in proteoglycan content, in the expression of the lubricin and in the density and percentage of positive cells for the p-SMAD2L. Conclusion: MCC undergoes structural and degenerative modifications with aging and decreases its lubrication and repair capacity due to the lower expression of the lubricin and p-SMAD2L. This study suggests that p-SMAD2L is involved in the production and accumulation of the lubricin in MCC

L’élucidation des mécanismes permettant l’optimisation de la réponse immunitaire antitumorale correspond à un enjeu majeur pour le développement de stratégies d’immunothérapie efficace. En effet, les réponses immunitaires antitumorales se traduisent rarement par l’éradication de la tumeur. Dans ce contexte, les travaux antérieurs de mon équipe ont démontré que l’interaction de l’intégrine αE(CD103)β7, souvent exprimée par les lymphocytes infiltrant la tumeur (TIL), avec son ligand E-cadhérine, à la surface des cellules tumorales épithéliales, joue un rôle majeur dans la potentialisation de l’activité lytique des cellules T en induisant la polarisation et l’exocytose des granules cytotoxiques. Nos résultats ont indiqué aussi que le TGF-β1, souvent abondant dans les tumeurs, joue un rôle déterminant dans cette induction suite à l’engagement du récepteur des cellules T. Dans ce contexte, nous avons cherché à comprendre les mécanismes de régulation du gène ITGAE qui codent la sous-unité alphaE de l’intégrine CD103. Nos résultats ont montré que les facteurs transcriptionnels Smad2, Smad3 et NFAT-1 sont impliqués dans la régulation de l’expression de la sous-unité αE(CD103). En effet, une costimulation avec du TGF-β1 recombinant et un anticorps anti-CD3 d’un clone T CD103- induit l’expression de cette intégrine qui est accompagnée d’une translocation dans le noyau de Smad2, Smad3 et NFAT-1 qui sont cytoplasmiques à l’état basal. L’inhibition spécifique de ces facteurs transcriptionnels inhibe l’expression de CD103 et abroge le potentiel lytique du clone T vis à vis de sa cible tumorale autologue. De plus, nous avons identifié deux séquences régulatrices du gène ITGAE humain, un promoteur proximal et un enhancer. Par ailleurs, mon équipe a récemment montré que l’interaction de CD103 à la surface des TIL avec une molécule E-cadhérine recombinante est suffisante pour induire la polarisation des granules cytolytiques par un mécanisme dépendant de la PLC-g1 et ERK et que cette intégrine possède non seulement une fonction d’adhérence, mais aussi une fonction de costimulation du signal TCR des TIL antitumoraux. Nous avons cherché à mieux comprendre la signalisation de l’intégrine CD103, en identifiant les domaines intracytoplasmiques de la sous-unité αE impliqués dans son activation. Nous avons ainsi construit une protéine de fusion CD103-GFP et plusieurs mutants du domaine intracytoplasmique de la sous-unité αE qui ont été ensuite transfectés dans la lignée Jurkat Tag CD103-/beta7+. Nos résultats ont montré que le domaine intracytoplasmique de la chaîne alphaE n’est pas nécessaire à la reconnaissance du ligand, la E-cadhérine. Par contre, nous avons montré que ce domaine est impliqué dans le phénomène de clustering de l’intégrine et dans sa polarisation à la zone de contact avec des billes couvertes avec la E-cadhérine-Fc. Nous avons identifié un domaine de 8 acides aminés (ESIRKAQL), contenant une sérine en position 1163 potentiellement phosphorylable, et qui est indispensable pour la signalisation de l’intégrine. De plus, nos travaux ont montré que ce domaine ESIRKAQL, est nécessaire pour la phosphorylation de la ERK1/2 et PLC-g1. Ainsi, une meilleure compréhension des mécanismes moléculaires régulant les fonctions de CD103 pourrait contribuer au développement et à l’amélioration de la réponse antitumorale exercée par les CTL. / The elucidation of mechanisms for optimizing the antitumor immune response is a major challenge for the development of strategies for effective immunotherapy. Indeed, the anti-tumor immune responses rarely result in the eradication of the tumor. In this context, the previous work of my team have shown that the interaction of integrin αE(CD103)β7, often expressed by tumor infiltrating lymphocytes (TIL) with its ligand E-cadherin at the cell surface tumor epithelial cells, plays a major role in the potentiation of the lytic activity of T cells by inducing polarization and exocytosis of cytotoxic granules. Our results also indicated that TGF-β1, often abundant in tumors, plays a key role in the induction due to the commitment of the T cell receptor. In this context, we sought to understand the mechanisms regulating ITGAE gene encoding the subunit αE of integrin. Our results showed that the transcription factors Smad2, Smad3 and NFAT-1 are involved in regulating the expression of subunit αE(CD103)β7. Indeed, costimulation with recombinant TGF-β1 and anti-CD3 antibody induces on T cell clone CD103- the expression of this integrin ant the translocation into the nucleus of Smad2, Smad3 and NFAT-1 that are cytoplasmic at baseline. Specific inhibition of these transcription factors inhibits the expression of CD103 and repeals the lytic potential of cloned T with respect to the autologous tumor target. In addition, we identified two regulatory sequences of human ITGAE gene, proximal promoter and enhancer. In addition, my team has recently shown that the interaction of CD103 on the surface of TIL with a recombinant molecule E-cadherin is sufficient to induce the polarization of cytolytic granules by ERK and PLC-γ1 pathway thus this integrin has not only a function of adherence, but also a function of costimulatory signal TCR of TIL. We sought to better understand the signaling of integrin CD103, by identifying the cytoplasmic domains of the subunit αE involved in its activation. We have constructed a fusion protein CD103-GFP and several mutants of intracytoplasmic domain of the subunit αE which were then transfected into the Jurkat Tag cell line CD103-/ β7+. Our results showed that the intracytoplasmic domain of CD103 is not necessary for ligand recognition, E-cadherin. By cons, we have shown that this area is involved in the phenomenon of clustering of integrin and its polarization to the contact area with balls covered with E-cadherin-Fc. We have identified a range of 8 amino acids (ESIRKAQL) containing a potentially phosphorylatable serine in position 1163, which is essential for integrin signaling. In addition, our work has shown that this area ESIRKAQL is necessary for the phosphorylation of ERK1/2 and PLC-g1. Thus, a better understanding of the molecular mechanisms that regulate the functions of CD103 may contribute to the development and improvement of the antitumor response exerted by CTL .

Prostate cancer is the most common cancer in men, with the incidence rapidly increasing in Europe over the past two decades. Reliable biomarkers for prostate cancer are currently unavailable. Thus, there is an urgent need for improved biomarkers to diagnose prostate cancer at an early stage and to determine the best treatment options. Higher expression of transforming growth factor-β (TGFβ) has been reported in patients with aggressive cancer. TGFβ is a multifunctional cytokine that acts as a tumor suppressor during early tumor development, and as a tumor promoter at later stages of cancer. TGFβ signals through the canonical Smad or non-Smad cascade via TGFβ type II and type I receptors. The TGFβ signaling cascade is regulated by various post-translational modifications of its key components. The present investigation aimed to identify a potential function of TRAF6 in TGFβ-induced responses in prostate cancer. The first two articles of this thesis unveil the proteolytic cleavage of TGFβ type I receptor (TβRI), and the biological importance of the liberated TβRI intracellular domain (TβRI-ICD) in the nucleus. We found that tumor necrosis factor receptor-associated factor 6 (TRAF6) polyubiquitinates TβRI, which leads to cleavage of TβRI by tumor necrosis factor alpha converting enzyme (TACE) in a protein kinase C zeta (PKCζ)-dependent manner. Following ectodomain shedding, TβRI undergoes a second cleavage by presenilin 1 (PS1), which liberates TβRI-ICD. TβRI-ICD translocates to the nucleus, where it regulates its own expression as well as expression of the pro-invasive gene Snail1, thereby promoting invasion. We further found that TβRI-ICD associates with Notch intracellular domain (NICD) to drive expression of the pro-invasive gene Snail1, as well as Notch1 ligand Jag1. The third article provides evidence that TRAF6 promotes Lys63-linked polyubiquitination of TβRI at Lys178 in a TGFβ-dependent manner. TβRI polyubiquitination was found to be a prerequisite for TβRI nuclear translocation, and thus for regulation of the genes involved in cell cycle, differentiation, and invasion of prostate cancer cells. In the fourth article we investigated the role of the pro-invasive gene Snail1 in TGFβ-induced epithelial-to-mesenchymal transition (EMT) in prostate cancer cells.

A cartilagem articular da cabeça da mandíbula (CAM) é constituída por uma cartilagem secundária recoberta por tecido conjuntivo fibroso e, portanto, definida como fibrocartilagínea. Ela é constantemente submetida a forças de compressão e cisalhamento decorrentes da mastigação necessitando de lubrificação e capacidade de reparo. O envelhecimento é considerado um dos principais fatores para o aparecimento de alterações degenerativas nas articulações sinoviais. A lubricina é reconhecidamente um proteoglicano encontrado nas cartilagens articulares cuja função primordial é a lubrificação limítrofe. A via SMAD2, tem sido associada à capacidade de manutenção e reparo da cartilagem, e a sua fosforilação na cadeia de ligação (p-SMAD2L) foi relacionada ao aumento no tempo de fosforilação na cadeia C-terminal (p-SMAD2) e da transcrição gênica. Objetivo: Estudar as alterações morfológicas da CAM e as expressões da lubricina, p-SMAD2L e do colágeno tipo I no envelhecimento. Métodos: cortes coronais da CAM de ratos wistar com 2, 12 e 24 meses de vida foram corados pelas técnicas da hematoxilina e eosina, azul de toluidina e safranina-O. A imuno-histoquímica foi usada para detectar a localização da lubricina, p-SMAD2L e colágeno tipo I. Resultados: Notou-se modificações estruturais atribuídas ao processo natural do envelhecimento da CAM. Ainda, se verificou um aumento do colágeno tipo I nas camadas mais profundas e cartilaginificação da matriz extracelular (MEC) nas camadas superficiais. No grupo idoso, houve redução na concentração de proteoglicanos, na expressão da lubricina e na densidade e porcentagem de células p-SMAD2L. Conclusões: a CAM sofre modificações com o envelhecimento, inclusive degenerativas, e diminui sua capacidade de lubrificação e reparo em virtude da menor expressão da lubricina e p-SMAD2L. Sugere-se que a p-SMAD2L está envolvida na produção e acúmulo da lubricina na CAM / The mandibular condylar cartilage (MCC) consists of a secondary cartilage covered by fibrous connective tissue and, therefore, defined as fibrocartilage. It is constantly subjected to compression and shear forces resulting from chewing requiring lubrication and repair capability. Aging is considered one of the main factors for the appearance of degenerative changes in synovial joints. Lubricin is a proteoglycan found in articular cartilages whose primary function is boundary lubrication. SMAD2 signaling pathway has been associated with cartilage maintenance and repair, and its phosphorylation in the linker region (p-SMAD2L) was related to the increase in half-life of C-terminal phospho-SMAD2 (p-SMAD2) and gene transcription. Objective: To study the morphological alterations of MCC and the expressions of the lubricin, p-SMAD2L and type I collagen in aging. Methods: Coronal sections of the MCC from wistar rats with 2, 12 and 24 months old were stained with hematoxylin and eosin, toluidine blue and safranin-O. Immunohistochemistry were used for detection of lubricin, p-SMAD2L and type I collagen. Also, the total cell density, p-SMAD2L cells density and percentage were determined. Results: Structural modifications of the MCC related with natural aging process were observed. An increase in the expression of type I collagen in the deeper layers and \"cartilaginification\" of the extracellular matrix (ECM) in the superficial layers were detected. In the old group, it was observed a reduction in proteoglycan content, in the expression of the lubricin and in the density and percentage of positive cells for the p-SMAD2L. Conclusion: MCC undergoes structural and degenerative modifications with aging and decreases its lubrication and repair capacity due to the lower expression of the lubricin and p-SMAD2L. This study suggests that p-SMAD2L is involved in the production and accumulation of the lubricin in MCC

O endotélio reveste a parede vascular e possui função essencial na manutenção da homeostase. A célula endotelial é capaz de perceber estímulos extracelulares, como fatores químicos e mecânicos, transmitir a informação para dentro da célula e regular sua função e fenótipo. Neste sentido, investigamos os mecanismos moleculares associados as células endoteliais em dois contextos importantes de intervenções vasculares 1) nos stents farmacológicos, onde a rapamicina exerce funções antiproliferativas e pró-trombogênicas, e 2) na revascularização cardíaca por ponte de safena, onde o alto estiramento mecânico exerce grande impacto no remodelamento vascular e no fenótipo da célula endotelial. A rapamicina pertence à classe de drogas limus, bastante utilizadas nos stents farmacológicos usados no procedimento de desobstrução vascular. Além de sua função antiproliferativa, exploramos os efeitos deletérios associados a pró-trombogênese. Os dados demonstraram que a rapamicina ativa o receptor de TGF independentemente de seu ligante TGFbeta, promovendo aumento na expressão da PAI-1 (pró-trombogênica), alteração no fenótipo endotelial (Transição endotélio-mesenquimal - EndMT) e na formação de fibras de estresse. Os efeitos observados são dependentes da ativação de Smad2 e independentes da via clássica antiproliferativa por mTOR. Experimentos in vivo mostraram que o tratamento com inibidor do receptor de TGF diminui os efeitos pró-trombogênicos e a expressão de PAI-1 induzidos pela rapamicina em artérias carótidas de camundongos. A ponte de safena é um procedimento bastante utilizado na cirurgia de revascularização cardíaca e a arterialização do segmento venoso submetido ao estresse hemodinâmico arterial resulta em remodelamento vascular, que influencia o sucesso do procedimento. Nossos dados demonstram que a célula endotelial humana de veia safena humana (hSVEC), susceptível as modificações do tipo EndMT induzido quimicamente (estímulo pró-fibrótico e pró-inflamatório), não expressou o mesmo comportamento em resposta ao aumento de estiramento mecânico que ocorre durante a arterialização venosa. Entretanto, detectamos uma pronunciada redução dos filamentos de actina, modulação no padrão de ativação da cofilina e na proporção de actina glomerular (G-actina) entre citoplasma e núcleo, com redução da biodisponibilidade de NO. De modo interessante, demonstramos que a redução no filamento de actina é específica para a célula endotelial venosa, não sendo observado em células endoteliais de origem arterial de aorta e coronária. Em conjunto, os dados mostram que 1) efeitos pró-trombogênicos associados a rapamicina são mediados por ativação do receptor de TGF independente do seu ligante e da atividade antiproliferativa da droga e 2) a adaptação da célula endotelial venosa ao estiramento mecânico envolve modulação da síntese/degradação de filamentos de actina e redução na biodisponibilidade de NO. Estes novos elementos sobre o mecanismo de transdução de estímulos químicos e físicos pelo endotélio poderão ser explorados terapeuticamente para modular a plasticidade endotelial em disfunções cardiovasculares / Endothelium is the inner layer in vascular wall and displays an essential role in the maintenance of cardiovascular homeostasis. Endothelial cell senses the extracellular stimuli, such as chemical and mechanical factors, transduce and process these signals to regulate cell function and phenotype. Here, we investigated molecular underpinning of the endothelial cells under two important scenarios: 1) in drug-eluting stents, where rapamycin exerts antiproliferative and undesirable prothrombogenic functions, and 2) in vein graft bypass surgery, where increased stretch modulates vascular remodeling and endothelial cell phenotype. Rapamycin belongs to the class of limus drugs and is widely used in drug eluting stents (DES) to vascular restenosis. In addition to its antiproliferative function, we explore the deleterious effects associated with prothrombogenesis. Our data demonstrated that rapamycin activates TGF receptor independent of its ligand TGFbeta, in concert with promotion of PAI-1 expression (prothrombogenic), changes in endothelial phenotype (Endothelial to Mesenchymal Transition - EndMT) and stress fibers induction. These effects are Smad2 dependent and independent of the classical antiproliferative mTOR pathway of rapamycin. Our in vivo experiments showed that TGF receptor inhibitor treatment decreases prothrombogenic effects and PAI-1 expression induced by rapamycin in mice carotid arteries. Saphenous vein is widely used in coronary artery bypass surgery (CABG) and the vein arterialization remodeling in response to the increased stress influences graft patency. Our data demonstrated that human saphenous vein endothelial cell (hSVEC) is susceptible to chemically induced endothelial-to-mesenchymal transition (EndMT) by pro-fibrotic and pro-inflammatory stimuli. On the other hand, physical stimulus associated with high stretch failed to induce EndMT. However, we detected a pronounced decrease of actin filaments, modulation of the cofilin activation, changes in the proportion of glomerular actin (G-actin) between cytoplasm and nucleus, and reduction of NO bioavailability. Interestingly, the reduction of actin fibers by high stretch is specific to venous endothelial cell since arterial endothelial cells from aorta, and coronary artery failed to display the response. Altogether, our data show that 1) the thrombogenic effects of rapamycin are mediated by TGF receptor activation independent of its ligand and independent of the antiproliferative pathway of the drug, and 2) the adaptation of venous endothelial cell to mechanical stretch involves synthesis/degradation of actin filaments and reduced NO bioavailability. These new elements on signal transduction of endothelial cells in response to chemical and physical stimuli may be therapeutically explored to modulate endothelial plasticity in cardiovascular disorders

Les accidents vasculaires cérébraux (AVC) sont considérés comme la pathologie neurologique la plus sévère en termes de mortalité et d’infirmité. Ils touchent plus de 140 000 personnes chaque année. L’AVC ischémique, qui représente 80% des AVC, est causé par l’occlusion localisée d’un vaisseau conduisant à un arrêt de l’apport en oxygène et en glucose au cerveau. Il est ainsi responsable de déficits moteurs, sensitifs et cognitifs qui peuvent gravement compromettre l’autonomie et la qualité de vie des patients. Les patients qui ont subi un AVC ischémique développent notamment une atrophie musculaire qui se produit principalement dans le membre parétique, mais aussi dans une moindre mesure dans le membre non parétique. Toutefois, les mécanismes moléculaires à l’origine de cette atrophie musculaire sont méconnus. Dans une première étude, l’objectif a été d’identifier les déterminants moléculaires mis en jeu dans l’atrophie musculaire induite par une ischémie cérébrale. Pour répondre à cet objectif, les travaux ont été menés sur un modèle d'ischémie cérébrale chez la souris qui consiste en l’occlusion de l'artère cérébrale moyenne par un monofilament en nylon. Nous avons montré que l’ischémie cérébrale entraînait, 3 jours après son induction, une atrophie musculaire des muscles quadriceps, soleus et tibialis anterior du côté parétique. Cette atrophie musculaire était associée à des déficits moteurs touchant l’équilibre, la coordination, la force musculaire, la posture ou la marche. Au niveau moléculaire, nous avons reporté un déséquilibre de la balance entre la synthèse et la dégradation des protéines musculaires en faveur d’une augmentation de la dégradation dans les muscles parétique et non parétique des souris ischémiées. Nous avons notamment montré que l’expression de la myostatine, un régulateur négatif majeur de la masse musculaire, était significativement augmentée. Dans une seconde étude, l’objectif a été d’identifier une cible d’intervention thérapeutique pour préserver la masse musculaire suite à une ischémie cérébrale. Au vu des résultats obtenus dans la première étude, nous avons ciblé la myostatine. Nous avons montré que l’inhibition de la myostatine entraînait, une meilleure récupération du poids de corps et du poids de divers muscles, 15 jours après une ischémie cérébrale. De plus, l’inhibition de la myostatine tendait à améliorer le comportement moteur des souris ischémiées (équilibre, coordination, force musculaire). En revanche, nous n’avons reporté aucune variation majeure des niveaux en ARNm ou protéines d’acteurs impliqués dans les voies de signalisation Akt/mTOR, Smad2/3, ubiquitine-protéasome et autophagie-lysosome, 15 jours après une ischémie cérébrale. Ces données préliminaires suggèrent que l’inhibition pharmacologique de la myostatine pourrait représenter une stratégie thérapeutique efficace pour limiter la perte de masse musculaire suite à une ischémie cérébrale / Strokes are considered as the most severe neurological disease in terms of mortality and disability. The incidence of stroke in France is estimated at 140 000. Ischemic stroke, which represents about 80% of strokes occur as a result of an obstruction of a blood vessel supplying blood to the brain. Motor, cognitive and sensory deficits are common impacts of stroke and can seriously compromise the autonomy and patient quality of life. Ischemic stroke leads to muscle atrophy, wich occurs primarily in the paretic limb, but also to a lesser extent in the nonparetic limb. However, the molecular mechanisms of muscle atrophy is unknown. In a first study, the purpose was to identify the molecular determinants involved in skeletal muscle atrophy following cerebral ischemia. To meet this objective, the work was carried out on a mouse model of cerebral ischemia, which involves the occlusion of the middle cerebral artery (MCAO) with a nylon monofilament. We have shown that cerebral ischemia leads to skeletal muscle atrophy of quadriceps, soleus and tibialis anterior muscles of the paretic side, 3 days after MCAO. This muscular atrophy was associated with motor deficits in the balance, coordination, muscle strength, posture and walking. From a molecular point of view, we reported an imbalance between the rates of synthesis and degradation of muscle protein, in favour of protein degradation in both paretic and nonparetic muscles. In particular, we showed that the expression of myostatin, a master negative regulator of skeletal muscle mass was significantly increased. In a second study, the purpose was to identify a target for therapeutic intervention in order to maintain muscle mass following cerebral ischemia. In view of the results obtained in the first study, we targeted the myostatin. Our results show that myostatin inhibition increases body weight and muscle mass recovery, 15 days after cerebral ischemia. In addition, myostatin inhibition tends to improve motor behavior (balance, coordination, strength). From a molecular point of view, we reported no major change in mRNA or protein level of actors involved in Akt/mTOR, Smad2/3, autophagy-lysosome and ubiquitin-proteasome pathways, involved in the control of muscle mass, 15 days after cerebral ischemia. These preliminary results strongly suggest that pharmacological inhibitors of myostatin may provide significant therapeutic benefit for muscle atrophy following cerebral ischemia

Résumé : Les ostéosarcomes sont des tumeurs malignes osseuses primaires qui affectent principalement les enfants et les adolescents. Les thérapies utilisées depuis les 30 dernières années n'ont malheureusement eu que très peu d'effet sur la survie des patients. Ce projet de doctorat évalue deux stratégies pour contrer certaines dérégulations des cellules d'ostéosarcome humain. La première consiste à abolir leur résistance à l'apoptose avec un alcaloïde d'origine végétale. La seconde consiste à accroître leur différenciation ou à réduire leur prolifération en utilisant des protéines morphogénétiques osseuses (BMPs) et leurs peptides dérivés (pBMPs). La première partie de ce doctorat s'intéresse donc au comportement et à la régulation des cellules d'ostéosarcome en comparaison avec celui des cellules osseuses normales afin d'identifier des cibles potentielles. Elle met l'accent sur trois caractéristiques de l'ostéosarcome: la résistance à l'apoptose, la prolifération incontrôlée des cellules et leur différenciation défectueuse. La sanguinarine, un alcaloïde d'origine végétale, est déjà utilisée pour traiter plusieurs types de cancers (sein et colon). Cet alcaloïde a été choisi pour vaincre la résistance à l'apoptose des cellules d'ostéosarcome. La sanguinarine a éradiqué les deux lignées cellulaires humaines d'ostéosarcome, MG-63 et SaOS-2, d'une manière dépendante du temps et de la dose. Les deux lignées cellulaires se distinguent par des états de différenciation et des taux de prolifération différents. L'alcaloïde induit l'apoptose par les voies extrinsèque et intrinsèque en activant les caspases-8 et -9. La sanguinarine semble agir sur les cellules d'ostéosarcome en fonction de leur potentiel tumorigène. La BMP-2, la BMP-9 et leurs peptides dérivés, pBMP-2 et pBMP-9, ont été utilisés pour contrer la différenciation défectueuse ou la prolifération incontrôlée des cellules d'ostéosarcome. La BMP-2, la BMP-9 et le pBMP-9 activent la phosphorylation des Smads dans les deux lignées cellulaires MG-63 et SaOS-2. Le pBMP-2 n'a eu aucun effet sur ces cellules d'ostéosarcome. Alors que le pBMP-9 agit sur la voie canonique des BMPs, il n'a cependant eu aucun effet significatif sur l'expression des gènes des marqueurs ostéogéniques à 6h. La BMP-2 induit essentiellement la phosphorylation de ERK 112, tandis que la BMP-9 et le pBMP-9 activent la voie p38. De plus, un inhibiteur de MEK1 bloque complètement l'augmentation de la phosphorylation de ERK1/2 induite par la BMP-2 et renforce la phosphorylation de la p38 en présence de BMP-9 ou du pBMP-9. Le traitement avec la BMP-2 ou la BMP-9 et l'inhibiteur MEKI augmente l'expression de gènes codant pour des marqueurs ostéogéniques précoces dans les cellules SaOS-2, tout en inhibant la croissance des cellules MG-63. Ainsi, la sanguinarine ou les BMPs en combinaison avec un inhibiteur MEKI pourraient donner lieu à un traitement anti-cancéreux prometteur. D'autres expériences sont néanmoins nécessaires pour déterminer leurs effets sur les cellules souches cancéreuses. // Abstract : Osteosarcomas are malignant primary bone tumours that normally occur in children and adolescents. Currently used therapies have not measurably improved patient survival rates over the last 30 years. This doctoral research evaluates two strategies for overcoming the major features of osteosarcoma cells. One is to abolish their resistance to apoptosis with a plant-derived alkaloid. The other is to block their defective differentiation or uncontrolled proliferation with bone morphogenetic proteins (BMPs) and peptides derived from them (pBMPs). The first part of this thesis compares the behaviour and regulation of osteosarcoma cells and normal bone cells to identify potential targets. It focuses on three features of osteosarcoma: resistance to apoptosis, uncontrolled cell proliferation, and defective cell differentiation. The plant-derived alkaloid, sanguinarine, is already used to treat several cancers (breast and colon). It was selected to overcome the resistance of osteosarcoma cells to apoptosis. Sanguinarine killed both MG-63 and SaOS-2 human osteosarcoma cells in a time- and dose-dependent manner. These two cell lines have different differentiation states and proliferate at different rates. The alkaloid induces apoptosis through the extrinsic and intrinsic pathways, activating both caspases-8 and -9. Sanguinarine seems to act on osteosarcoma cells depending on their tumourigenic potential. BMP-2, BMP-9, and their derived peptides, pBMP-2 and pBMP-9, were used to overcome the defective differentiation or uncontrolled proliferation of osteosarcoma cells. BMP-2, BMP-9, and pBMP-9 activated the phosphorylation of Smad in both MG-63 and SaOS-2 cells. pBMP-2 had no effect on osteosarcoma cells. While pBMP-9 acted on the canonical BMP pathway, it had no significant effect on the expression of genes encoding osteogenic markers at 6h. BMP-2 mainly increased the phosphorylation of ERK1 /2, while BMP-9 and pBMP-9 activated the p38 pathway. A MEKI inhibitor completely blocked the BMP-2-triggered increase in ERK1/2 phosphorylation and enhanced the phosphorylation of p38 induced by BMP-9 or pBMP-9. Treatment with BMP-2 or BMP-9 and MEKI inhibitor increased the the expression of genes encoding osteogenic markers in SaOS-2 cells, while inhibiting the growth of MG-63 cells. Thus, sanguinarine or BMPs plus a MEK I inhibitor could give rise to a promising anti-cancer treatment. Further experiments are now required to determine their effect on cancer stem cells.

Transforming growth factor-β1 (TGFβ1) is a mediator of the fibrotic response through activation of quiescent cardiac fibroblasts to hypersynthetic myofibroblasts. Scleraxis (Scx) is a pro-fibrotic transcription factor that is induced by TGFβ1-3 and works synergistically with Smads to promote collagen expression. Ski is a negative regulator of TGFβ/Smad signaling through its interactions with Smad proteins at the promoter region of TGFβ regulated genes. To date, no studies have examined the direct DNA:protein transcriptional mechanisms that regulate Scx expression by TGFβ1-3 or Ski, nor the mechanisms that govern Ski expression by Scx. We hypothesize that Ski and Scx regulate one another, and form a negative feedback loop that represses gene expression and is a central regulator of the fibrotic response in cardiac myofibroblasts. Primary adult rat cardiac myofibroblasts were isolated via retrograde Langendorff perfusion. First passage (P1) cells were infected with adenovirus encoding HA-Ski, HA-Scx, or LacZ at the time of plating. Twenty-four hours later, cells were harvested for Western blot, quantitative real-time PCR (qPCR), and electrophoretic gel shift assays (EMSA). NIH-3T3 or Cos7 cells were transfected with equal quantities of plasmid DNA for 24 hours prior to harvesting for luciferase, qPCR, and EMSA analysis. Ski overexpression in P1 myofibroblasts resulted in a reduction in both Scx mRNA and protein levels. Overexpression of Scx had no effect on Ski expression. Luciferase reporter assays demonstrated that Scx was induced by TGFβ1 treatment in a concentration dependent manner. However, ectopic Smad2/3 expression was unable to transactivate the Scx promoter in a luciferase reporter assay. Inhibition of p44/42-MAPK signaling modestly counteracted the effect of TGFβ1 on Scx expression. Scx had no effect on Ski promoter expression, however, both tumor necrosis factor-α (TNFα) and p65 expression repressed the Ski promoter and correlated with reduced Ski mRNA levels. We conclude that Ski is a repressor of Scx and that Scx expression is partially mediated through a Smad-independent, p44/42-MAPK pathway in cardiac myofibroblasts. Furthermore, this study proposes a role for TNFα/p65 NF-κΒ signaling in the regulation of Ski gene expression in the cardiac myofibroblast. / October 2016

Long interspersed nuclear element-1 (L1) is a genetic element that mobilizes throughout the mammalian genome via retrotransposition and damages host DNA via mutational insertions, chromosomal rearrangements, and reprogramming of gene expression. The cellular mechanisms responsible for aberrant L1 expression during cancer pathogenesis are unclear. Previously, we have shown that L1 reactivation in several human cell lines is dependent upon the activation of aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor member of the PAS superfamily of proteins. We also showed that ectopic expression of L1 reprograms the HepG2 genome leading to epithelial-to-mesenchymal transition (EMT). Here we present evidence that reactivation of L1 and modulation of EMT in HepG2 cells by the AhR ligand benzo(a)pyrene (BaP) is effected through the canonical TGF-β1 signaling pathway. BaP increased TGF-β1 mRNA, SMAD2 phosphorylation and decreased expression of E-Cadherin. The functional relevance of these interactions and the involvement of TGFBR1/ALK5 and SMAD2/3 were confirmed by siRNA interference. Furthermore, expression of L1-encoded ORF1p was positively correlated with the activation of TGF-β1 signaling in human hepatocarcinoma samples at various stages of malignant progression. These results indicate that ligand-mediated AhR activation regulates L1 via canonical TGF-β1 signaling and raise important questions about the molecular etiology of human hepatocarcinomas.