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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

No description available.

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

Orientador: Fabio Papes / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-24T14:16:00Z (GMT). No. of bitstreams: 1 Tolentino_FelipeThadeu_M.pdf: 9244448 bytes, checksum: deea9f7963e05d8a997d9b5a554f9708 (MD5) Previous issue date: 2014 / Resumo: O Sistema Sensorial Olfativo de mamíferos é composto por vários subsistemas na cavidade nasal. Dentre estes, destacam-se o sistema olfativo principal e o sistema olfativo acessório ou vomeronasal. O primeiro realiza a detecção geral de odores e parece participar também da detecção de algumas substâncias que levam a respostas comportamentais instintivas (feromônios), enquanto o último é especializado na detecção desta classe de semioquímicos. A detecção dos estímulos sensoriais olfativos resulta em informações importantes que dependem de vias complexas para sua interpretação e para a geração de respostas apropriadas por parte do sistema nervoso central. Existem vários pontos ainda desconhecidos sobre o funcionamento do sistema olfativo, tanto no que diz respeito aos mecanismos moleculares subjacentes à escolha dos receptores a serem expressos por um dado neurônio sensorial ¿ sendo que cada neurônio olfativo expressa apenas um receptor dentro de uma grande família multi-gênica ¿ quanto em relação ao processamento da informação sensorial em centros cerebrais superiores. Neurônios sensoriais olfativos cultivados eficientemente in vitro seriam extremamente úteis, pois poderiam ser utilizados como ferramenta para o estudo destes problemas, como a investigação da atividade das células sensoriais olfativas, possibilitando, por exemplo, uma melhor compreensão dos mecanismos genéticos e moleculares por trás da expressão dos receptores olfativos e de suas propriedades de detecção. Neste trabalho foram desenvolvidas ferramentas baseadas em vetores retrovirais com o objetivo de induzir a diferenciação celular de neurônios olfativos in vitro, utilizando uma combinação de fatores de transcrição, por meio de transdução viral em células-alvo (fibroblastos murinos). Os retrovírus produzidos foram testados e algumas combinações de fatores de transcrição foram preliminarmente testadas, sendo capazes de induzir mudanças moleculares em fibroblastos acompanhadas da expressão de marcadores de neurônios sensoriais olfativos / Abstract: The mammalian Olfactory System enables the vast majority of animal species to identify the presence and quality of food, predators, competitors, conspecifics and potential mates in the environment. Olfactory stimuli detected by sensory neurons are interpreted by brain processing pathways to generate appropriate behavioral and endocrine responses. Despite its central importance in mammalian physiology, several aspects about the biology of this sensory system remain uncharacterized. For example, it is known that each olfactory sensory neuron (OSN) in the nasal cavity expresses only one gene out of a large multi-gene family coding for receptors involved in odorant and pheromone detection. However, the molecular mechanisms behind this process of olfactory receptor gene choice are not fully understood. The study of this and many other aspects of olfaction has been made difficult by the lack of appropriate in vitro cellular models. An efficient way to obtain cultured OSNs would thus be extremely useful, enabling researchers to investigate the sensory neuron¿s activity in a controllable environment, avoiding obstacles imposed by the cellular heterogeneity found in sensory organs in vivo. In this study, we aimed at obtaining OSNs directly differentiated from mouse embryonic fibroblasts (MEF) using the forced expression of specific transcription factors via retroviral vectors. We therefore developed tools based on retroviral vectors with the objective of differentiating olfactory sensory neurons in vitro, using viral transduction in target cells (murine fibroblasts) with combinations of select transcription factors. Retroviruses were tested and some combinations of transcription factors were tested on a preliminary basis, which were capable of inducing molecular alterations on fibroblasts followed by the expression of olfactory sensory neuron markers / Mestrado / Genetica Animal e Evolução / Mestre em Genética e Biologia Molecular

The purpose of the study was to elucidate the mechanisms by which polyunsaturated fatty acids (PUFAs) prevent bone loss. MG-63 human osteoblasts and MC3T3-E1 murine osteoblasts were exposed to the n-6 PUFA arachidonic acid (AA) and the n-3 PUFA docosahexaenoic acid (DHA) as well as oestrogen (E2) and parathyroid hormone (PTH) and the effects thereof tested on a variety of biological parameters characteristic of osteoblasts. These parameters included prostaglandin E2 (PGE2) synthesis, proliferation, differentiation to mature mineralising osteoblasts as well as osteoprotegerin (OPG) and receptor activator of nuclear factor êB ligand (RANKL) secretion. Results showed that AA stimulates PGE2 production significantly in both cell lines. Stimulated PGE2 production by MC3T3-E1 cells however, was significantly higher, which might be attributed to auto-amplification by PGE2 itself in this cell line. Pre-incubation of the MG-63 cells with cyclo-oxygenase (COX)-blockers inhibited PGE2 production significantly, suggesting that both COX enzymes were involved in PGE2 synthesis. The number of functional osteoblasts is important for bone formation therefore in vitro osteoblastic cell proliferation was investigated. In contrast to the hormones E2 and PTH, both AA and DHA inhibited proliferation significantly. The AA-mediated anti-proliferative effect is possibly independent of PGE2 production, as PGE2 per se had little effect on proliferation. DHA inhibited proliferation of MG-63 cells more severely, which might be attributed to the osteosarcoma nature of the MG-63 cells. The anti-proliferative effect of these PUFAs might be attributed to modulation of cell cycle progression or anti-mitotic effects of PUFA peroxidation products. Morphological studies showed apoptotic cells after DHA exposure in MG-63 cells. There is a reciprocal relationship between reduced proliferation and the subsequent induction of cell differentiation in vitro. High basal levels of alkaline phosphatase (ALP) activity, a marker of the mature mineralising osteoblastic phenotype, were detected in MC3T3-E1 cells. Long-term exposure to AA inhibited ALP activity in these cells. This process might be PGE2-mediated. Exposure to PUFAs, however, did not compromise the ability of the MC3T3-E1 cells to differentiate to mature mineralising osteoblasts. In contrast with MC3T3-E1 cells, MG-63 cells demonstrated low basal ALP activity and were unable to differentiate to mature mineralising osteoblasts. In the absence of osteogenic-inducing supplements, PUFAs induced adipocyte-like features that might be due to the expression of high levels of PPARã in this cell line. Lipid-filled vacuoles were absent in the MC3T3-E1 cells suggesting that the MC3T3-E1 cell line may not express PPARã mRNA. The study furthermore demonstrated that PUFAs are able to modulate OPG and RANKL secretion in osteoblasts. AA inhibited OPG secretion dose-dependently in both cell lines, this could be PGE2-mediated. AA dose-dependently stimulated soluble RANKL (sRANKL) secretion in MC3T3-E1 cells thereby affecting the OPG/RANKL ratio in a negative way, supporting various reports that AA and PGE2 do cause bone resorption. No sRANKL could be detected after exposing the MC3T3-E1 cells to DHA suggesting that DHA could be protective to bone. In conclusion, contrary to in vivo evidence, this in vitro study could not indisputably demonstrate protective effects of PUFAs on the osteoblastic cell lines tested. / Thesis (PhD (Physiology))--University of Pretoria, 2006. / Physiology / unrestricted

Mein Ziel war es, genetische Faktoren in C. elegans zu identifizieren, die eine Rolle bei induzierter Transdifferenzierung durch Missexpression des Transkriptionsfaktors (TF) HLH-1, welcher das Wurmhomolog des myogenen bHLH TF MyoD ist, spielen. Ich entwickelte hierzu einen semiautomatischen Hochdurchsatz-Vorwärtsgenetik-Screen, indem ich EMS Mutagenese mit dem Biosorter-System (Union Biometrica) kombinierte. Mit diesem Ansatz ist es mir gelungen, die Mutante bar18 zu isolieren, die eine Anhäufung an Muskelzellkernen um den posterioren Teil des Pharynx zeigt. Ich identifizierte den mutierten Lokus, indem ich das gesamte Genom sequenzierte und charakterisierte den mutanten Phänotyp im Detail. Zusätzlich war ich bei der Charakterisierung von Faktoren, die das Umprogrammieren zu neuronalen Zellen in C. elegans verhindern, beteiligt. Dabei stand der sogenannte FACT-Komplex im Focus, welcher mittels eines genom-weiten RNAi-Screen in unserer Arbeitsgruppe identifiziert wurde. Interessanterweise ist eine der FACT-Komplex-Untereinheiten, spt-16, das parentale Gen zu dem bislang nicht charakterisierten Pseudogen F55A3.7. Eine putative Null-Mutante von F55A3.7, in Kombination mit ubiquitärer Überexpression von CHE-1, zeigte einen Keimzellen-zu-Neuronen Transdifferenzierungsphänotyp ähnlich dem Phänotypen, der nach dem Knock-down der FACT-Komponente hmg-3 beobachtet wird. Unseres Wissens nach ist dies das erste Beispiel einen Pseudogens, dessen Knock-down dazu führt, dass ein bestimmtes Gewebe durch einen terminalen Selektor-TF reprogrammiert werden kann, dessen Expression unter normalen Konditionen dies nicht zur Folge hätte. Aufgrund dieser Einzigartigkeit, habe ich das Pseudogen F55A3.7 charakterisiert und außerdem versucht, einen Mechanismus zu finden, wie F55A3.7 die Keimbahnidentität schützt. / My aim was to identify and characterize genetic factors in C. elegans that play a role in induced transdifferentiation by mis-expressing the transcription factor (TF) HLH-1, which is the worm homolog of the myogenic bHLH TF MyoD. For this, I developed a semi-automated high-throughput forward genetic screen combining EMS mutagenesis with the Biosorter system (Union Biometrica). When mis-expressed, HLH-1 induces muscle fate in early embryonic cells, but terminally differentiated cells are resistant to HLH-1-induced direct reprogramming. In order to identify mechanisms that antagonize HLH-1-induced reprogramming, I used a transgenic line allowing ectopic expression of hlh-1 in combination with a reporter for muscle fate. Using this approach, I isolated the mutant bar18, showing an accumulation of muscle cell nuclei around the posterior pharyngeal bulb. I identified the mutated locus using whole genome sequencing and characterized the identified gene and the mutant phenotype further. Additionally, I was also involved in characterizing the FACT complex, which was identified through a whole-genome RNAi screen conducted by my colleague Ena Kolundžić. This reverse genetic screen aimed at identifying factors that play a role in induced transdifferentiation by mis-expressing the TF CHE-1, a Zn-finger TF essential for terminal differentiation of glutamatergic ASE neurons. Interestingly, one of the FACT complex members, spt-16, is the parental gene of a previously uncharacterized pseudogene named F55A3.7. A putative null mutant of F55A3.7, combined with broad overexpression of CHE-1, showed a germ cells to neurons transdifferentiation phenotype. To our knowledge, this is the first example of a pseudogene whose depletion leads to the permissiveness of a certain tissue to be reprogrammed when challenged by a terminal selector TF. Due to this uniqueness, I characterized the pseudogene F55A3.7 and tried to find a potential mechanism for how F55A3.7 safeguards germline identity.