Made available in DSpace on 2015-07-22T20:50:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-30. Added 1 bitstream(s) on 2015-08-11T03:26:36Z : No. of bitstreams: 1 Publico-Tese%20Paloma%20Korehiza%20Maza%20versao%20final.pdf: 1568579 bytes, checksum: 8a94eab5c79046acd8162d9a949d2c36 (MD5) / Muitos patógenos são capazes de manipular a sinalização de células do hospedeiro para facilitar sua infecção. Nesta tese, demonstramos que o fungo Paracoccidioides brasiliensis promove um aumento na ativação de ERK1/2 e SFKs em células epiteliais A549 (de pulmão humano), de aproximadamente 6 e 7 vezes, respectivamente, em relação aos níveis basais. Utilizando PP2, inibidor da atividade de SFKs, e PD98059, inibidor da ativação da via ERK1/2, verificamos que a ativação de ERK1/2 é parcialmente dependente de SFKs ativadas e que provavelmente outras quinases também estão envolvidas neste evento. Além da modulação da sinalização de células do hospedeiro, diversos estudos têm demonstrado que patógenos seqüestram domínios presentes nas membranas da célula hospedeira denominados “membrane rafts”, os quais são enriquecidos em esfingolipídeos e colesterol e estão envolvidos em diversos eventos celulares, incluindo a sinalização celular. Por diferentes metodologias, como a desorganização de “membrane rafts” por drogas que extraem (metil-β- ciclodextrina, MβCD) ou que se ligam (nistatina) ao colesterol, e a localização do gangliosídeo GM1, um marcador de “membrane rafts”, utilizando a subunidade B da toxina da cólera (CTB), mostramos o envolvimento destes domínios de membranas de células epiteliais na adesão de P. brasiliensis. A partir do isolamento de membranas resistentes a detergente (DRMs) de células epiteliais após incubação com o fungo, mostramos a ativação e o deslocamento de SFKs para as frações que contêm os “membrane rafts”. Além disso, verificamos que a depleção do colesterol com MβCD inibe completamente a ativação de SFKs, corroborando a importância dos domínios de membranas para a ativação destas quinases. Os resultados apresentados nesta tese demonstram, pela primeira vez, que fungos patogênicos modulam a organização e a atividade de “membrane rafts” de células hospedeiras para o estabelecimento da infecção. / Many pathogens are able to manipulate host cell signaling in order to facilitate infection. In this thesis, we demonstrated that the fungus Paracoccidioides brasiliensis promotes an increase of ERK12 and SFK activation in A549 epithelial cells (human lung cells), by approximately 6- and 7-fold over basal levels, respectively. By using PP2, inhibitor for SFK activity, and PD98059, inhibitor for ERK1/2 activation, we verified that ERK1/2 activation is partially dependent of activated SFKs and probably other kinases are involved in this event. Besides modulation of host cell signaling, several studies have been demonstrated that pathogens hijack domains that are present in host cell membranes called membrane rafts, which are cholesterol- and sphingolipidenriched domains, that are involved in several cell events, including cell signaling. By using several approaches, such as membrane rafts disruption with cholesterolextractor (methyl-β-cyclodextrin, MβCD) or –binding (nystatin) drugs, and the localization of ganglioside GM1, a membrane raft marker, by using cholera toxin subunit B (CTB), we showed the involvement of these epithelial cell membrane domains in P. brasiliensis adhesion. By isolating detergent-resistant membrane (DRM) from epithelial cells after incubation with this fungus, we showed the activation and the dislodgment of SFKs to fractions which contain membrane rafts. Moreover, we verified that cholesteroldepletion with MβCD completely inhibits SFK activation, corroborating the importance of membrane domains in activation of these kinases.The results presented in this thesis demonstrate for the first time that pathogenic fungi may modulate the organization and activity of host cell membrane rafts for infection establishment. / TEDE / BV UNIFESP: Teses e dissertações

A superexpressão de receptores HER-2 é anormalidade celular de grande relevância clínica no câncer de mama. Ela ocorre em aproximadamente 30% de carcinomas de mama incluindo lesões pré-neoplásicas e malignas, e está associada a prognóstico desfavorável. A hiperativação dos receptores HER-2, consequência natural de sua superexpressão, promove proliferação celular aberrante e tumorigênese. Admite-se que a ativação e envio de sinais via HER-2 possa acontecer quando estes receptores se encontram em compartimentos específicos da membrana celular, os lipid rafts. Assim, um número maior de HER-2 poderia implicar em maior quantidade de lipis rafts. Para testar essa hipótese, usamos modelo de transformação oncogênica que nos permitiu avaliar, especificamente, os efeitos da superexpressão de HER-2 e identificar a quantidade de lipid rafts. Para isso utilizamos a linhagem celular HB4a, derivada de célula epitelial luminal do tecido mamário humano normal com baixa expressão de HER-2; e a linhagem HB4aC5.2, um clone derivado da HB4a, que superexpressa receptores HER-2. Nas células HB4aC5.2, a superexpressão de HER-2 foi acompanhada pelo aumento dos lipid rafts na membrana celular, bem como, hiperativação de sinais de sobrevivência, proliferação (aumento da ativação de proteínas Akt e Erk1/2, respectivamente), e taxa de proliferação celular duas vezes mais rápida que a linhagem normal HB4a. Adicionalmente, a superexpressão de HER-2 foi associada com aumento da lipogênese celular (fenótipo lipogênico), dependente do aumento de ativação da enzima FASN e da superexpressão de DEPTOR. A FASN é responsável pela síntese de palmitato, utilizado para formação de lipid rafts. A superexpressão de DEPTOR, por modular a atividade transcricional de PPAR?, pode evitar a lipotoxicidade do excesso de palmitato. Além disso, DEPTOR, por sua capacidade em reduzir atividade do complexo mTORC1, contribui para sobrevivência celular dependente da proteína Akt. Em continuidade, consideramos, como segunda hipótese, que a desestruturação de lipid rafts poderia influenciar negativamente a ativação dos receptores HER-2. Para isso tratamos, as mesmas linhagens celulares anteriormente descritas, com ácido docosaexaenoico (DHA), um tipo de ácido graxo ômega-3. Nossos resultados mostraram que, nas células HB4aC5.2, o tratamento com DHA desestruturou os lipid rafts, inibiu a sinalização iniciada pelos receptores HER-2 ( diminuição da ativação das proteínas Akt, Erk1/2, FASN, atividade transcricional de PPAR? e expressão de DEPTOR) e reverteu o fenótipo lipogênico. Adiciona-se que essas modificações celulares e moleculares foram acompanhadas por indução significativa de morte e apoptose. As mesmas alterações não foram observadas nas células normais HB4a. Em conclusão, o presente estudo reforça a associação entre a presença de HER-2 e lipid rafts. Adicionalmente aponta que a desestruturação de lipid rafts por DHA reduz a sinalização de HER-2. Por fim, sugere que distúrbios em lipid rafts, induzidos por DHA, possam representar ferramenta útil no controle da sinalização aberrante deflagrada pelos receptores HER-2, e aponta potencial terapêutico na suplementação de DHA para quimioprevenção e tratamento do câncer de mama HER-2 positivo. / HER-2 receptor overexpression is a cellular abnormality of great clinical significance in breast cancer. It is described in approximately 30% of breast carcinomas, including preneoplasic and malignant lesions, and is associated with poor prognosis. Hyperactivation of HER-2 receptors, a natural consequence of its overexpression, promotes aberrant cell proliferation and tumorigenesis. For signal activation and transduction to occur, HER-2 must be localized in specific compartments in the cell membrane: the lipid rafts. Therefore, we hypothesize that a greater number of HER-2 receptors could indicate a greater quantity of lipid rafts. To test this, we used an oncogenic transformation model that specifically allowed assessment of the effects of HER-2 overexpression and identification of the quantity of lipid rafts: an HB4a cell line derived from normal human breast tissue luminal epithelial cells with low HER-2 expression, and an HB4aC5.2 cell line, a clone derived from HB4a that overexpresses HER-2 receptors. In the HB4aC5.2 cells, HER-2 overexpression was accompanied by an increase in lipid rafts in cell membranes as well as hyperactivation of survival signals, proliferation (increased activation of the proteins Akt and ERK1/2, respectively), and an increased rate of proliferation, compared to the normal HB4a line. In addition, HER-2 overexpression was associated with increased cellular lipogenesis (lipogenic phenotype), dependent on the increased activation of the FASN enzyme and the overexpression of DEPTOR. FASN is responsible for the synthesis of palmitate, used to synthesize lipid rafts. Overexpression of DEPTOR by modulating PPAR? transcriptional activity, may avoid lipotoxicity from excess palmitate. Moreover, DEPTOR, with its ability to reduce mTORC1 complex activity, contributes to cell survival dependent on Akt. To continue, we considered as a second hypothesis that the disruption of lipid rafts could negatively influence HER-2 receptor activation. For this, we treated the same cell lines described above with docosahexaenoic acid (DHA), a omega-3 fatty acid. Our results showed that in HB4aC5.2 cells DHA treatment disrupted the lipid rafts, inhibited signaling initiated by HER-2 receptors (reduced activation of Akt, ERK1/2, and FASN proteins, PPAR? transcriptional activity, and DEPTOR expression) and reversed the lipogenic phenotype. In addition, these cellular and molecular changes were accompanied by a significant induction of apoptosis and death. The same changes were not observed in normal HB4a cells. In conclusion, the present study reinforces the association between HER-2 presence and lipid rafts. It also indicates that the disruption of lipid rafts by DHA reduces HER-2 signaling. Finally, it suggests that DHA-induced disturbances in lipid rafts may represent a useful tool in controlling aberrant signaling triggered by HER-2 receptors, and indicate therapeutic potential in DHA supplementation for chemoprevention and treatment of HER-2 positive breast cancer.

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Dans le cerveau, les astrocytes sont les cellules gliales les plus abondantes et elles jouent divers rôles, y compris le maintien des synapses tripartites et la régulation du débit sanguin cérébral (DSC). Le monoxyde d’azote (NO) est une molécule de signal endogène qui a un impact sur la régulation de l'activité synaptique et du DSC. Des études antérieures ont démontré que le NO est produit dans les cellules endothéliales et les neurones par la synthase du monoxyde d’azote endothéliale (eNOS) et neuronale (nNOS), respectivement. Cependant, la source de production de NO dans les astrocytes reste incertaine. Par conséquent, nous proposons que la voie de signalisation NOS constitutive puisse coexister dans les astrocytes et puisse être activée par différents neurotransmetteurs. L'objectif de cette thèse est d'identifier les sources et les activateurs de la production de NO dans les astrocytes corticaux de la souris. L'identification des isoformes constitutives de NOS effectuée au moyen de la microscopie électronique et d'immunohistochimie a révélé l’expression des eNOS et nNOS dans les astrocytes. Des préparations de culture d'astrocytes et de tranches de cerveau marquées avec du diacétate de 4-amino-5-méthylamino-2',7'-difluorescéine (DAF-FM), un indicateur de NO perméable aux cellules qui devient imperméable une fois à l’intérieur ont été réalisées. Cette fonctionnalité a été mise à profit pour évaluer la production de NO exclusivement dans les astrocytes en utilisant la microscopie confocale à uni- et multi-photons. De plus, des agonistes cholinergiques ou glutamatergiques qui ont la capacité d’augmenter la concentration de Ca2+ intracellulaire peuvent induire une production du NO in vitro et ex vivo dans les astrocytes, qui est supprimée en présence de l'inhibiteur de NOS non sélectif, L-NG -Nitro-arginine. Fait intéressant, la réponse NO à l’acétylcholine était absente chez les souris eNOS-/-, tandis que l'acide trans-1-aminocyclopentane-1,3-dicarboxylique (t-ACPD) a peu affecté la production de NO chez les souris nNOS-/-. Ces résultats impliquent que les eNOS et nNOS astrocytaires peuvent être déclenchés par des cascades d'activation distinctes (cholinergique et glutamatergique métabotrope). En outre, les études sur la mobilisation cytosolique du Ca2+ indiquent l'importance du réticulum endoplasmique comme réservoir de Ca2+ pour la production de NO, et suggèrent aussi une voie de signalisation astrocytaire qui, une fois activée par le t- ACPD, provoque l'efflux de Ca2+ médié par le récepteur à la ryanodine, qui à son tour active les nNOS adjacents et conduit à la production de NO. Par ailleurs, la superfusion de préparations in vitro et ex vivo avec du N-Méthyl-D-aspartate (NMDA) a provoqué une augmentation du NO tant dans les souris eNOS-/- que nNOS-/-, ce qui indique l'implication des eNOS et nNOS astrocytaires. La production de NO a été atténuée par l'inhibition du complexe PSD-95 / nNOS ce qui suggère que le récepteur NMDA astrocytaire rend fonctionnelle la cassette de signalisation NR2B/PSD-95/nNOS. En conclusion, nos résultats démontrent que : i) les astrocytes corticaux expriment à la fois eNOS et nNOS; ii) la nNOS cytosolique colocalise avec les récepteurs 2 et 3 de la ryanodine, alors que les nNOS membranaires colocalisent avec le récepteur NMDA contenant le NR2B; iii) la stimulation neuronale a la capacité d'induire la production de NO par les eNOS et nNOS astrocytaires par des voies de signalisation différentes; iv) l'activation des nNOS cytosoliques nécessite une activation des récepteurs à la ryanodine. Collectivement, ces données suggèrent une production de NO compartimentée et spécifique après une stimulation neuronale probablement dans le but de réguler finement et de façon polarisée les fonctions astrocytaires. Ce travail fournit un nouvel aperçu des conséquences physiologiques pour les fonctions neuronales et vasculaires et améliore notre compréhension de la fonction NO astrocytaire dans le cerveau. / In the brain, astrocytes are the most abundant glial cells and play various roles including maintenance of tripartite synapses and regulation of CBF. An endogenous signal molecule that has a potential to have an effect on regulation of both synaptic activity and CBF is nitric oxide (NO). Previous studies have demonstrated that NO is produced in endothelial cells and neurons by endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS), respectively. However, the source of NO production in astrocyte remains uncertain. Therefore, we propose that constitutive NOS signalling pathways may exist in astrocyte and can be activated by different neurotransmitters. The aim of this thesis is to identify the sources and activators of NO production in mouse cortical astrocytes. Identification of constitutive NOS isoforms done by means of electron microscopy and immunohistochemistry revealed the expression of both eNOS and nNOS in astrocytes. All preparations were performed in astrocyte cultures and brain slice preparations labeled with 4- amino-5-methylamino-2',7'-difluorescein (DAF-FM) diacetate, a cell-permeant NO indicator that becomes cell-impermeable once inside cells. Therefore, I took advantage of this feature to evaluate NO production exclusively in astrocytes using single and multi-photon confocal microscopy. We then tested whether cholinergic and glutamatergic agonists that have the capacity to increase intracellular Ca2+ concentration can induce an increase in astrocytic NO. Both in vitro and ex vivo, NO production levels indicate that cholinergic and glutamatergic stimulations can induce astrocytic NO increases, which was abolished by the non-selective NOS inhibitor L- NG -Nitro-arginine. Moreover, the NO response to ACh was absent in eNOS-/- mice, while trans-1-aminocyclopentane-1,3-dicarboxylic acid (t-ACPD) barely affected NO production in nNOS-/- mice. These results imply that astrocytic eNOS and nNOS can be triggered discretely by distinct activation cascades (cholinergic and metabotropic glutamatergic). Furthermore, studies on cytosolic Ca2+ mobilization point out the importance of the endoplasmic reticulum (ER) Ca2+ as key in the mechanism of NO production, and suggests a signalling pathway that t-ACPD causes IP3Rs to elicit RyRs-mediated Ca2+ efflux, which in turn, activates adjacent nNOS and leads to NO production. Furthermore, superfusion of in vitro and ex vivo preparations with N-Methyl-D-aspartate (NMDA) evoked an increase in NO in eNOS-/- and nNOS-/- mice. The NO production was attenuated through removal of PSD-95/nNOS complex. This result posits that astrocytic NMDA receptor may comprise the functional NR2B/PSD- 95/nNOS signalling cassette. In conclusion, our findings demonstrate that: i) cortical astrocytes express both eNOS and nNOS; ii) nNOS colocalizes with ryanodine receptor 2 and 3, whereas membrane nNOS colocalizes with NR2B-containing NMDA receptor; iii) neuronal stimulation has the capacity of inducing eNOS- and nNOS-produced NO in astrocytes via different activation signalling; iv) activation of cytosolic nNOS requires the activation of ryanodine receptors. Collectively, these data suggest a compartmentalized and specific NO production following neuronal stimulation probably for a fine and polarized regulation of astrocytic functions. This work provides new insight into physiological consequences for neuronal and vascular functions and ameliorates our understanding of astrocytic NO function in the brain.

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