Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Linköping : Univ., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Missouri--Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 100-112). Also issued on the Internet.

Thesis (Ph. D.)--University of Missouri--Columbia, 2004. / "May 2004." Typescript. Vita. Includes bibliographical references (leaves 100-112). Also issued on the Internet.

No description available.

Diss. Linköping : Univ., 2003.

La cancérogenèse gastrique est un processus d’origine multifactorielle, incluant des facteurs génétiques de l’hôte, mais aussi d’origine bactérienne et de l’environnent. Les populations humaines peuvent être exposées directement ou indirectement à des composés toxiques/génotoxiques présents dans les plantes, comme la fougère Pteridium aquilinum. Cette plante comprend une toxine, le ptaquiloside associée à des maladies graves et le développement de cancer chez les animaux. Des études épidémiologiques ont démontré une association entre l'exposition à ces fougères et l’incidence du cancer gastrique dans les populations humaines. Cependant, un autre facteur de risque majeur dans le développement du cancer gastrique est la bactérie Helicobacter pylori qui colonise l'estomac humain et induit une réponse génotoxique. Cette étude vise à caractériser l'implication biologique et moléculaire de Pteridium aquilinum et de sa toxine le ptaquiloside dans le processus de cancérogenèse gastrique et d'explorer un effet de synergie potentiel avec l'infection par H. pylori.Nous avons montré que le traitement avec des extraits de Pteridium aquilinum et le ptaquiloside diminue la viabilité cellulaire et favorise l'apoptose des cellules épithéliales gastriques. L'induction de cassures de l'ADN a été observée, exacerbée en présence de l’infection par H. pylori. Dans les cellules traitées, la protéine p53 est induite et associée à l'activation de la voie de signalisation ATR-Chk1. Cette augmentation de p53 est aussi détectée en présence des souches virulentes de H. pylori. L’induction de lésions à l’ADN par le ptaquiloside est en accord avec la dérégulation observée de l’expression d’un certain nombre de gènes impliqués dans la régulation du cycle cellulaire et la réparation de l'ADN. De plus, des souris exposées à Pteridium aquilinum, montrent des modifications histomorphologiques de la muqueuse gastrique ainsi qu’une augmentation de la prolifération cellulaire et l'induction de mutations dans le gène p53 après 7 semaines de traitement. Toutefois, bien qu’une exacerbation de la prolifération cellulaire et des lésions histologiques soient induites par un traitement chronique en association avec l'infection à H. pylori pendant 12 mois, aucune différence significative dans l'expression du gène p53 a été mise en évidence. Cependant, dans ces conditions, une modification du schéma glycophenotypique a été induite dans la muqueuse gastrique des souris. Différentes glycosyltransférases impliquées dans la biosynthèse des antigènes simples de mucines et terminaux antigènes Lewis ont été différentiellement exprimées chez les souris non-infectées et infectées, respectivement. Ces résultats sont également validés par une augmentation de l’expression de Sialyl-LewisX.De plus, des modifications des glycosyltransférases impliquées dans les étapes initiales de O-glycosylation ont été observées. Le ppGalNAcT6 a présenté une expression altérée dans un carcinome gastrique, associée à la présence de l'invasion veineuse.En conclusion, nos données confirment l’activité génotoxique de Pteridium aquilinum et du ptaquiloside sur les cellules gastriques, supportant leur rôle fondamental dans la promotion de la cancérogenèse gastrique. Cette activité est exacerbée en présence de l’infection par H. pylori, soulignant l'importance de l'interaction de ces deux facteurs de risque dans ce processus. / The multifactorial gastric carcinogenesis process encompasses host genetic susceptibility, bacterial and environmental factors. Humans can directly consume or be indirectly exposed to toxic compounds present in plants, such as the bracken fern Pteridium aquilinum. This plant has a carcinogenic toxin, ptaquiloside, and is known to cause severe health problems in animals, including cancer. Epidemiological evidence also demonstrated an association between bracken exposure and gastric cancer development in Humans. Additionally, another major etiological agent is Helicobacter pylori, a bacterium that colonizes the stomach inducing a genotoxic response in gastric cells. This study aimed to characterize the biological and molecular involvement of Pteridium aquilinum and its ptaquiloside toxin in the gastric carcinogenesis process and to evaluate the potential synergistic effect of H. pylori infection.We observed that treatment with Pteridium aquilinum extracts and ptaquiloside toxin decreased cell viability and promoted cell apoptosis in gastric epithelial cells. A genotoxic effect with induction of DNA strand breaks was noted and it was exacerbated in the presence of H. pylori infection. We further demonstrated that in treated cells a p53 accumulation occurs, controlled by the activation of the ATR-Chk1 DNA damage signalling pathway. An increased level of p53 was also detected in the presence of a H. pylori virulent strain. The contribution of ptaquiloside to this genotoxic activity was supported by the deregulation of other genes involved in DNA cell cycle regulation and DNA repair. In addition, using a mouse model exposed to Pteridium aquilinum, we detected histomorphological alterations with increased cell proliferation and induction of frameshift events in the p53 gene. However, a concomitant chronic treatment with Pteridium aquilinum and H. pylori infection did not produce significant differences in p53 gene expression.Moreover, an altered glycophenotypic pattern was induced in the gastric mucosa of mice upon Pteridium aquilinum treatment in the presence of H. pylori infection. Several glycosyltransferases involved in the biosynthesis of simple mucin-type carbohydrate antigens and terminal Lewis antigens were differently expressed in the absence and presence of H. pylori, respectively. These results were also validated by an increased expression of Sialyl-LewisX.Further alterations in glycosyltransferases involved in the initial steps of O-glycosylation were observed. The ppGalNAcT6 was shown to have a heterogeneous expression in human gastric carcinoma, associated with the presence of venous invasion.Overall, our data supports the notion that cell exposure to the genotoxic and carcinogenic Pteridium aquilinum and ptaquiloside has a fundamental role in the promotion of gastric carcinogenesis. The synergistic environment associated to H. pylori infection underlines the importance of risk factor interplay in this process. / A carcinogénese gástrica é um processo multifatorial que engloba fatores genéticos, bacterianos e ambientais. O Homem pode consumir diretamente ou ser exposto de forma indireta a compostos tóxicos presentes em plantas, como é o caso do feto vulgar Pteridium aquilinum. Esta planta tem uma toxina carcinogénica, o ptaquilosídeo, sendo conhecida a sua capacidade natural para induzir lesões neoplásicas em animais. Estudos epidemiológicos também demonstraram a existência de uma associação entre a exposição ao feto e o desenvolvimento de cancro gástrico em humanos. Outro fator etiológico importante é a Helicobacter pylori, uma bactéria que coloniza o estômago, induzindo nas células gástricas uma resposta genotóxica. Este estudo tem por objetivos caracterizar o envolvimento biológico e molecular do Pteridium aquilinum e da sua toxina, ptaquilosídeo, no processo de carcinogénese gástrica e avaliar o potencial efeito sinergístico da infeção por H. pylori.Observámos em células epiteliais gástricas que o tratamento com extratos de Pteridium aquilinum e com a toxina ptaquilosídeo, diminui a viabilidade celular e promove a apoptose. Foi demonstrado um efeito genotóxico com indução de quebras na cadeia de ADN, exacerbado pela presença da infeção por H. pylori. Demonstrámos ainda que, em células tratadas, ocorria uma acumulação de p53, controlada pela ativação da via de sinalização ATR-Chk1. Um aumento nos níveis de p53 foi igualmente detetado na presença de estirpes virulentas de H. pylori. A contribuição do ptaquilosídeo para esta atividade genotóxica foi também apoiada pela desregulação de outros genes envolvidos na regulação do ciclo celular e na reparação do ADN. Adicionalmente, usando um modelo de ratinho exposto ao Pteridium aquilinum, foram detetadas alterações histomorfológicas, bem como um aumento da proliferação celular e indução de mutações no gene p53. Contudo, um tratamento crónico com Pteridium aquilinum e infeção concomitante por H. pylori não produziu diferenças significativas na expressão do gene p53.Um padrão glicofenotípico alterado foi também observado na mucosa gástrica de ratinhos tratados com Pteridium aquilinum na presença de infeção por H. pylori. Várias glicosiltransferases envolvidas na biossíntese de antigénios simples das mucinas e antigénios terminais do tipo Lewis apresentaram uma expressão alterada, respetivamente, na ausência ou presença de H. pylori. Estes resultados foram também validados através de um aumento da expressão de Sialil-LewisX.Foram ainda observadas alterações em glicosiltransferases que estão envolvidas nas etapas iniciais de O-glicosilação. A ppGalNAcT6 apresentou uma expressão alterada em carcinomas gástricos, estando associada à presença de invasão venosa.No geral, estes dados suportam a evidência de que a exposição das células aos genotóxicos e carcinogénicos Pteridium aquilinum e ptaquilosídeo, tem um papel fundamental na promoção da carcinogénese gástrica. O ambiente sinergístico associado à infeção com H. pylori salienta a importância da interação entre os fatores de risco que dão origem a este processo.

Master of Science / Department of Biology / Sherry D. Fleming / Helicobacter is a common intestinal pathogen of most laboratory mice from both commercial and academic sources worldwide. Not previously thought to have an effect, recent evidence indicates Helicobacter infection alters cytokine, chemokine, and gene expression in the stomach, intestine, and colon. Though the in vivo cell types responsible for these changes are currently unknown, in vitro results suggest macrophages are the likely source. In addition to detection and elimination of pathogens, intestinal macrophages play a role in maintaining homeostasis. By altering gene expression and cytokine production in the microenvironment, we hypothesized that Helicobacter infection altered the phenotype and inflammatory response of submucosal intestinal macrophages. To test this hypothesis, we examined macrophages within whole mounts of intestinal muscle as well as isolated macrophages from Helicobacter-infected or uninfected mouse intestine. Macrophages from the intestinal muscle of Helicobacter-infected mice showed increased expression of F4/80 and CD11b, altered gene expression, and increased phagocytosis when compared to macrophages from uninfected mice. Infection also altered the macrophage response to stimuli. Macrophages from infected mice produced significantly lower concentrations of cytokines, chemokines, and PGE[subscript]2 in response to stimulation with either IFN and LPS or IL-4 and IC. These data support our hypothesis demonstrating that the intestinal muscle macrophage phenotype, function, and response to stimulation are altered by Helicobacter infection both in vivo and in vitro.