Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Nous montrons pour la première fois qu’en plus de la MAPK ERK1/2, l’endothéline-1 (ET-1) via les récepteurs ETA et ETB active une autre MAP kinase : la p38 uniquement dans les cellules de léiomyomes utérins de rate (ELT3) mais pas dans les cellules myométriales saines. Dans les cellules ELT3, l’analyse des voies de signalisation montre que malgré les similitudes observées entre les modes d’activation des voies p38 et ERK1/2 par ET-1, celles-ci sont activées de façon indépendante l’une de l’autre. En plus, la forskoline active p38 (mais pas ERK1/2), par contre l’activation de p38 par ET-1 n’implique pas une production d’AMPc. Par ailleurs ERK1/2 et p38 coactivées par ET-1 coopèrent pour augmenter l’expression de COX2 et la production des prostaglandines E2 (PGE2) pour favoriser l’effet antiapoptotique de ET-1. De plus p38 activée par ET-1 contribue à la prolifération des léiomyomes. Nos résultats élucident les mécanismes par lesquels ET-1 contribue à la croissance des léiomyomes. / We demonstrated for the first time, that in addition to the MAPK ERK1/2, Endothelin-1 (ET-1) through ETA and ETB receptors activated another MAP kinase: p38 only in uterine leiomyoma cells (ELT3) but not in normal myometrial cells. In ELT3 cells, analysis of signaling pathways showed that, despite the similarities between the mechanisms involved in the activation of p38 and ERK1/2 pathways by ET-1, these kinases are activated independently one of another. In addition, forskolin (a cAMP inducer), activated p38 (but not ERK1/2), whereas the activation of p38 by ET-1 did not involve production cAMP. Moreover the coactivated ERK1/2 and p38 pathways by ET-1 cooperated to increase expression of COX2 and prostaglandin E2 (PGE2) production. This PGE2 like ET-1 exerted an antiapoptotic effect in ELT3 cells. Furthermore, p38 activated by ET-1 contributes to the proliferation of ELT3 leiomyoma cells. Our data highlight the mechanisms by which ET-1 could promote uterine leiomyoma growth.

Allergic diseases are influenced by genetics and the environment. Maternal allergy appears to confer a higher risk for allergic sensitization than paternal allergy, suggesting an in utero influence. A decrease in particular infections or a lower exposure to microbial components during infancy is suggested to contribute to the high allergy prevalence in affluent societies. Toll-like receptors (TLR) 2 and 4 recognize peptidoglycan (PGN) and LPS respectively, are expressed on e.g. monocytes, and have been implicated in modulating the risk of IgE-sensitization. This thesis aimed to study the influence of maternal allergy and early microbial exposure on monocyte function and allergic sensitization during childhood. Blood samples from children participating in a prospective allergy cohort were used. Two-year old infants with allergic mothers had lower IL-6 production and reduced activation of the TLR-signalling intermediate p38-MAPK in response to PGN than children with non-allergic mothers. In 5-year old children, allergic disease and not maternal allergy influenced monocytic TLR2-regulation. Five-year olds who were seropositive for Epstein-Barr virus (EBV) at 2-years of age had a lower risk of persistent IgE-sensitization while EBV contraction after 2-years of age related to a higher risk of IgE-sensitization. Upon in vitro stimulation, NK cells from EBV+ 2-year olds produced lower IFN-g levels. EBV+ 2-year olds had also lower systemic IFN-g. In comparison to CD14++CD16- monocytes, CD14+CD16+ cells induced NK-cell IFN-g more potently in vitro, and EBV+ infants tended to have lower proportions of these CD14+CD16+ monocytes. This thesis highlights the importance of early-life microbial (EBV) exposure for a proper allergy-protective immunity. Also, maternal allergic heredity appears to influence monocytic microbial responses in early infancy. All these aspects relate to altered monocyte functionality, which suggest that they could have a role in allergic sensitization.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Acute and chronic morphine administration can significantly reduce ischemia- reperfusion injury of the rat heart. However, the molecular mechanisms mediating the protective effect of morphine are not yet fully elucidated. Concurrently, there is a lack of information about the effects of the long-term action of morphine on heart tissue. Therefore, in the first part of the project, we studied the effect of long-term administration of high doses of morphine (10 mg/kg/day, 10 days) on rat heart tissue. In the second part of the project, we investigated the effect of 1 mM morphine on viability and redox state of rat cardiomyoblast cell line H9c2 that was influenced by oxidative stress elicited by exposure to 300 μM tert-butyl hydroperoxide (t-BHP). Our experiments have shown that long-term morphine administration affected neither the amount nor the affinity of myocardial β-adrenergic receptors (β-AR), but almost doubled the number of the dominant isoforms of myocardial adenylyl cyclase (AC) V/VI and led to supersensitization of AC. At the same time, proteomic analyses revealed that long-term morphine administration was associated with significant changes in the left ventricular proteome. In particular, there was an increase in the expression of heat shock proteins (HSP). Increased expression of HSP27...

No description available.

<p>Transforming growth factor-β (TGF-β) is a member of a large superfamily of cytokines which participate in many different types of cellular processes, such as growth inhibition, cell migration, differentiation, cell adhesion, wound healing and immunosuppression. Alterations of TGF-β superfamily signalling results in several different disorders, including bone disease, vascular disease and cancer. The TGF-β signalling pathways involve several different proteins, such as the Smad proteins, which upon receptor activation are translocated to the nucleus, where they affect transcriptional responses. </p><p>The actin cytoskeleton is an organised network of filaments with a highly dynamic structure, which is under a continuous reconstruction to control the morphology, survival, growth and motility of eukaryotic cells. The members of the family of small GTP-binding proteins have been shown to be important regulators of the actin cytoskeleton.</p><p>TGF-β was found to induce short term as well as long term actin reorganisation in prostate cancer cells. The short term response included membrane ruffling, and required signalling by the small GTPases Cdc42 and Rho as well as, the involvement of the mitogen-activated protein kinases p38 (p38 MAPK). The long term response included formation of stress fibers and required a cooperation between Smad and Rho GTPase signalling pathways involving the Rho-associated coiled-coil-containing protein kinase 1 (ROCK1). </p><p>The TGF-β-induced activation of Cdc42 was, furthermore, shown to require the inhibitory Smad7 and p38 MAP kinase, via a PI3K-dependent pathway. Mixed lineage kinase 3 (MLK3), a mediator downstream of Cdc42, was necessary for the Cdc42-dependent actin filament reorganisation.</p><p>Apoptosis is an important and carefully regulated process in human development and disease, which allows the multicellular organisms to remove cells that are in excess or potentially dangerous. TGF-β family members can induce apoptosis in many different cell types, in the presence or absence of other growth factors. Smad7 had previously been shown to be necessary for TGF-β-induced apoptosis of epithelial cells. We could show that Smad7 is required for TGF-β-induced activation of the TGF-β activated kinase 1 (TAK1)-mitogen-activated protein kinase kinase 3 (MKK3)-p38 MAPK pathway, which subsequently leads to apoptosis in prostate cancer cells.</p><p>Members of the lymphoid enhancer factor-1/T-cell factor (LEF1/TCF) family of transcription factors have, together with β-catenin, been shown to be nuclear effectors in the Wnt-signalling pathway. We investigated a possible cross-talk between the TGF-β and Wnt signalling pathways. We found that TGF-β, in a Smad7-dependent manner induced a nuclear accumulation of β-catenin and enhanced the transcriptional activity of β-catenin and the induction of the downstream target gene <i>c-myc</i>. Since β-catenin and c-Myc has been shown to promote apoptosis, our results suggests the possibility that β-catenin contributes to TGF-β-induced apoptosis</p>

Transforming growth factor-β (TGF-β) is a member of a large superfamily of cytokines which participate in many different types of cellular processes, such as growth inhibition, cell migration, differentiation, cell adhesion, wound healing and immunosuppression. Alterations of TGF-β superfamily signalling results in several different disorders, including bone disease, vascular disease and cancer. The TGF-β signalling pathways involve several different proteins, such as the Smad proteins, which upon receptor activation are translocated to the nucleus, where they affect transcriptional responses. The actin cytoskeleton is an organised network of filaments with a highly dynamic structure, which is under a continuous reconstruction to control the morphology, survival, growth and motility of eukaryotic cells. The members of the family of small GTP-binding proteins have been shown to be important regulators of the actin cytoskeleton. TGF-β was found to induce short term as well as long term actin reorganisation in prostate cancer cells. The short term response included membrane ruffling, and required signalling by the small GTPases Cdc42 and Rho as well as, the involvement of the mitogen-activated protein kinases p38 (p38 MAPK). The long term response included formation of stress fibers and required a cooperation between Smad and Rho GTPase signalling pathways involving the Rho-associated coiled-coil-containing protein kinase 1 (ROCK1). The TGF-β-induced activation of Cdc42 was, furthermore, shown to require the inhibitory Smad7 and p38 MAP kinase, via a PI3K-dependent pathway. Mixed lineage kinase 3 (MLK3), a mediator downstream of Cdc42, was necessary for the Cdc42-dependent actin filament reorganisation. Apoptosis is an important and carefully regulated process in human development and disease, which allows the multicellular organisms to remove cells that are in excess or potentially dangerous. TGF-β family members can induce apoptosis in many different cell types, in the presence or absence of other growth factors. Smad7 had previously been shown to be necessary for TGF-β-induced apoptosis of epithelial cells. We could show that Smad7 is required for TGF-β-induced activation of the TGF-β activated kinase 1 (TAK1)-mitogen-activated protein kinase kinase 3 (MKK3)-p38 MAPK pathway, which subsequently leads to apoptosis in prostate cancer cells. Members of the lymphoid enhancer factor-1/T-cell factor (LEF1/TCF) family of transcription factors have, together with β-catenin, been shown to be nuclear effectors in the Wnt-signalling pathway. We investigated a possible cross-talk between the TGF-β and Wnt signalling pathways. We found that TGF-β, in a Smad7-dependent manner induced a nuclear accumulation of β-catenin and enhanced the transcriptional activity of β-catenin and the induction of the downstream target gene c-myc. Since β-catenin and c-Myc has been shown to promote apoptosis, our results suggests the possibility that β-catenin contributes to TGF-β-induced apoptosis