INTRODUÇÃO: Polimiosite (PM) e Dermatomiosite (DM) são miopatias inflamatórias que se caracterizam por fraqueza, atrofia e disfunção muscular, levando a perda de capacidade funcional e de qualidade de vida. Assim, o objetivo do estudo foi avaliar se um treino de força com oclusão vascular (TF-OV) de baixa intensidade é seguro e efetivo em melhorar a força, a massa e a função muscular, além da qualidade de vida destes pacientes. MÉTODOS: Treze pacientes com PM ou DM estáveis foram submetidos a um TF-OV parcial e baixa intensidade (30% de 1RM) duas vezes por semana, por 12 semanas. Foram avaliados então as enzimas musculares, a força, a massa e a função muscular, além da qualidade de vida e as limitações para atividades diárias antes e após o protocolo de treinamento. RESULTADOS: Os pacientes apresentaram um aumento da força muscular do leg-press (19,6%, p < 0,001) e do leg-extension (25,2% p < 0,001), além de aumento da massa muscular avaliada pela área de secção transversa do quadríceps (4,57%, p =0,01). Nos testes funcionais, houve melhora do desempenho nos testes timed-stands (15,1%, p < 0,001) e timed-up-and-go (-4,5%, p=0,002). Foi observado melhora dos escores do HAQ e de todos os componentes do SF-36, além de queda significativa do VAS do médico e do paciente (p < 0,05), enquanto que as enzimas musculares permaneceram estáveis (p > 0,05). Por fim, nenhum evento adverso foi relatado. CONCLUSÃO: O TF-OV de baixa intensidade foi seguro e efetivo em melhorar a força, a massa e a função muscular, além da qualidade de vida dos pacientes com PM e DM estáveis / INTRODUCTION: Our aim was to evaluate the safety and efficacy of a low-intensity resistance training program combined with partial blood flow restriction (BFR training) in a cohort of patients with polymyositis (PM) and dermatomyositis (DM). METHODS: In total, 13 patients with PM and DM completed a 12-week twice a week low-intensity (that is, 30% onerepetition-maximum (1RM)) resistance exercise training program combined with partial blood flow restriction (BFR). Assessments of muscle strength, physical function, quadriceps cross sectional (CSA) area, health-related quality of life, and clinical and laboratory parameters were assessed at baseline and after the intervention. RESULTS: The BFR training program was effective in increasing the maximal dynamic strength in both the leg-press (19.6%, p < 0.001) and leg-extension exercises (25.2% p < 0.001), as well as in the timed-stands (15.1%, p < 0.001) and timed-up-and-go test (-4.5%, P =0.002). Quadriceps CSA was also significantly increased after the intervention (4.57%, p =0.01). Similarly, all of the components of the Short Form-36 Health Survey, the Health Assessment Questionnaire scores, and the patient- and physician reported Visual Analogue Scale were significantly improved after training (p < 0.05). Importantly, no clinical evidence or any other self-reported adverse event were found. Laboratory parameters (creatine kinase and aldolase) were also unchanged (p > 0.05) after the intervention. CONCLUSIONS: We demonstrated that a 12-week supervised low-intensity resistance training program associated with partial blood flow restriction may be safe and effective in improving muscle strength and function as well as muscle mass and health-related quality of life in patients with PM and DM

The Aryl Hydrocarbon Receptor (AhR) and the Aryl Hydrocarbon Nuclear Translocator (ARNT) play a role in mediating transcriptional responses to environmental pollutants, including the highly toxic compound 2,3,7,8-tetrachlorodibenzo -p-dioxin (TCDD) but also endogenous physiological ligands. More recent studies have also indicated that the AhR plays a role in the immune system notably in effector Th17 cells where it seems to be critical for the production of the IL-22 cytokine. It is known that AhR ligands such as dioxins can suppress CD8 T cell mediated antiviral immune responses but it is not known whether this reflects a direct role of the AhR in CD8 T cells.Accordingly, one objective of the present study was to explore AhR and ARNT expression in CD8 T cells. The initial strategy was to probe AhR and ARNT expression by western blot analysis. A second approach was to develop a mouse model that would fate mark single lymphocytes that have activated AhR signaling pathways. A third strategy was to examine the impact of deletion of AhR and ARNT on CD8 T-cell function.The data show that AhR and ARNT expression in CD8 T cells is limited to immune activated effector cells and these transcription factors are not expressed in naïve CD8 T cells. There are only low levels of AhR complexes in conventional CD8 positive cytotoxic T cells. To investigate AhR function at the single cell level we developed a mouse model to fate mark cells that have activated AhR signaling. In this model a mouse expressing Cre recombinase ‘knocked in’ to the CYP1A locus (CYP1A1Cre+/-) was backcrossed to the R26REYFP reporter mouse. In R26REYFP mice, a gene encoding EYFP is knocked into the ubiquitously expressed Rosa26 locus preceded by a loxP flanked stop sequence. CYP1A1 expression is controlled by AhR/ARNT complexes and the concept of our model was that cells that express AhR and ARNT complexes and are triggered with AhR ligands will express Cre recombinase and delete the loxP flanked stop sequence in the R26REYFP reporter locus and hence begin to express YFP.In vitro experiments demonstrated the validity of this AhR reporter model. The in vitro data reveal that expression of functional AhR/ARNT complexes occurs during Th17 and Tc17 cell differentiation but only a very low frequency of cytotoxic T cells activates the AhR. In vivo data found no evidence for AhR activation during T cell development in the thymus but show strong evidence for activation of AhR/ARNT signaling in innate lymphocytes in the gut. The ARNT transcription factor is highly expressed in cytotoxic T cells. These cells do not express functional AhR complexes, yet we considered that ARNT might play a role in CD8 T cell biology because of its ability to dimerise with the transcription factor Hif-1a. Our studies of T cells lacking ARNT expression revealed that in CD4 T cells the ARNT transcription factor regulates IL-17 and IL-22 production. In CD8 T cells we discovered that Hif-1a/ARNT signaling controls glycolysis in immune activated cells by sustaining expression of glucose transporters and multiple rate limiting glycolytic enzymes. ARNT was not required for CD8 T cell proliferation but was required for immune activated CD8 T cells to normally differentiate to express perforin and granzymes and to acquire the migratory program of effector T cells. Importantly, we discovered that Hif-1a/ARNT signaling is regulated by mTOR (mammalian target of rapamycin) thus revealing a fundamental mechanism linking nutrient sensing and transcriptional control of CD8 T-cell differentiation.

No description available.

O conteúdo de zinco (Zn) reativo cerebral é importante para o equilíbrio da sinaptofisiologia neural. A prova disto é que um aumento nos seus níveis, após evento hipóxico-isquêmico, resulta em neurotoxicidade, o que tem estimulado o tratamento desta disfunção cerebral com quelantes de Zn, tal como o dietilditiocarabamato (DEDTC). No caso do DEDTC, o uso deste composto sobre esta disfunção deve ser analisado com cuidado, pois ele também apresenta muitos efeitos colaterais sobre o sistema nervoso central. Desta forma, para atender este propósito, é necessário antes obter uma concentração de DEDTC com menores efeitos colaterais. Por esta razão, no presente trabalho, nós decidimos usar um modelo vertebrado mais simples, tal como o peixe-zebra, o qual permitiria a triagem, em larga escala, dos efeitos de DEDTC sobre o Zn reativo. Entretanto, jamais foi mostrada a presença de Zn reativo no cérebro de peixe-zebra. Com isto, através de marcações histológicas, nós conseguimos mostrar pela primeira vez a distribuição citoarquitectônica de Zn reativo em neurônios glutamatérgicos, bem como o número desses neurônios contendo Zn no cérebro de peixe-zebra. Isto nos permitiu avaliar o efeito de diferentes concentrações de DEDTC sobre o conteúdo de Zn cerebral do peixe-zebra, o qual foi intensamente quelado por elevadas quantidades do composto, induzindo comportamentos tipo-crise. Neste mesmo estudo nós obtemos também uma concentração de DEDTC com poucos efeitos colaterais que poderia exercer neuroproteção sobre o aumento de Zn reativo induzido pela hipóxia-isquemia. Assim, após a padronização de um modelo de hipóxia em peixe-zebra, que demonstra danos relacionados à isquemia, nós testamos se essa concentração de DEDTC poderia ser neuroprotetora sobre este modelo. Contudo, DEDTC apresentou efeitos pró-oxidantes, embora ele tenha atenuado o elevado conteúdo de Zn reativo induzido pela hipóxia. Portanto, mesmo que o DEDTC tenha falhado, este modelo, agora, está apto para a triagem de outros fármacos com potencial ação sobre o alterado conteúdo de Zn reativo que ocorre em eventos hipóxicos-isquêmicos. / The content of brain reactive zinc (Zn) is important for the synaptophysiology in the central nervous system (CNS). This is evidenced in hypoxic-ischemic events, when an increase in their levels results in neurotoxicity. Consequently, this has stimulated the treatment of cerebral ischemia with Zn chelators, such as diethyldithiocarbamate (DEDTC). In the case of DEDTC, the use of this compound in this dysfunction should be examined carefully, because it also has many side effects on the (CNS). Thus, to meet this, it is necessary first to obtain a concentration of DEDTC with negligible side effects. Here, we decided to use a simpler vertebrate model, such as zebrafish, which would allow large-scale screening of DEDTC effects on reactive Zn. However, the presence of reactive Zn has never been shown in zebrafish brain. Then, using histological markers, we were able to show for the first time the cytoarchitectonic distribution of reactive Zn in glutamatergic neurons as well as the number of these neurons containing Zn in the zebrafish brain. This allowed us to evaluate the effect of different DEDTC concentrations on the brain content of Zn in zebrafish. As a result, high levels of the compound did strongly chelate the metal, inducing seizure-like behaviors. In this study we also obtained a DEDTC concentration with few side effects that could exert neuroprotection on the increased reactive Zn induced by hypoxia-ischemia. Then, after the standardization of an ischemic-sensitive model of hypoxia in zebrafish, we tested if this DEDTC concentration could be neuroprotective on this model. Nevertheless, DEDTC showed pro-oxidant effects, though it had mitigated the elevated content of reactive Zn induced hypoxia. Therefore, despite the DEDTC have failed as neuroprotective drug, this model enables the screening of other chemical agents with potential action on the increased content of reactive Zn that occurs in hypoxic-ischemic events.

Choi, Siu Cheong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 132-148). / Abstracts in English and Chinese. / Acknowledgement --- p.i / Abstract --- p.ii / Abbreviation --- p.v / List of Figures --- p.viii / List of Tables --- p.xii / Table of Content --- p.xiii / Chapter Chapter 1: --- General Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.1.1 --- Treatment resistance in cancer --- p.1 / Chapter 1.1.1.1 --- Surgery --- p.2 / Chapter 1.1.1.2 --- Chemotherapy --- p.3 / Chapter 1.1.1.3 --- Radiotherapy --- p.3 / Chapter 1.1.1.4 --- Hormonal therapy --- p.4 / Chapter 1.1.2 --- Hypoxia/reoxygenation and its correlation with treatment resistance --- p.5 / Chapter 1.1.3 --- Aim of the study --- p.6 / Chapter Chapter 2: --- The drug sensitivity in HepG2 cells and A431 cells / Chapter 2.1 --- Introduction --- p.8 / Chapter 2.1.1 --- Treatment of cancer --- p.8 / Chapter 2.1.2 --- Drug resistance --- p.9 / Chapter 2.2 --- Materials and Methods --- p.10 / Chapter 2.2.1 --- Cell culture --- p.10 / Chapter 2.2.2 --- Drugs --- p.10 / Chapter 2.2.3 --- MTT assay --- p.11 / Chapter 2.3 --- Results --- p.12 / Chapter 2.3.1 --- The drugs to which G10HR and G20HR cells were more resistant --- p.12 / Chapter 2.3.2 --- "The drugs of which GP, G10HR and G20HR cells have similar response" --- p.12 / Chapter 2.3.3 --- The drugs to which A10HR and A20HR cells were more resistant --- p.17 / Chapter 2.3.4 --- The drugs to which A10HR and/or A20HR cells were more sensitive --- p.17 / Chapter 2.3.5 --- "The drugs which AP, A10HR and A20HR cells have similar response" --- p.18 / Chapter 2.4 --- Discussion --- p.24 / Chapter 2.4.1 --- Camptothecin and 10-hydroxy camptothecin --- p.27 / Chapter 2.4.2 --- Etoposide --- p.30 / Chapter 2.4.3 --- Hydrogen peroxide --- p.32 / Chapter 2.4.4 --- Interferons --- p.32 / Chapter 2.4.4.1 --- Interferon alpha --- p.33 / Chapter 2.4.4.2 --- Interferon gamma --- p.34 / Chapter 2.4.5 --- Methotrexate --- p.35 / Chapter 2.4.6 --- Vincristine --- p.36 / Chapter Chapter 3: --- The resistance mechanism of doxorubicin in A431 cells / Chapter 3.1 --- Introduction --- p.38 / Chapter 3.1.1 --- Chemotherapeutic resistance --- p.38 / Chapter 3.1.2 --- Tumor hypoxia --- p.39 / Chapter 3.1.3 --- Structure and function of doxorubicin --- p.39 / Chapter 3.1.4 --- Clinical use of doxorubicin --- p.40 / Chapter 3.1.5 --- Mechanisms of doxorubicin resistance --- p.41 / Chapter 3.1.6 --- Structure and function of P-glycoprotein --- p.42 / Chapter 3.1.7 --- Drug resistance contributed by P-glycoprotein and the solution --- p.43 / Chapter 3.1.8 --- Epigenetic modulation of mdr1 --- p.45 / Chapter 3.2 --- Materials and Methods --- p.47 / Chapter 3.2.1 --- Cell culture --- p.47 / Chapter 3.2.2 --- MTT assay --- p.47 / Chapter 3.2.3 --- Reverse transcription polymerase chain reaction (RT-PCR) --- p.47 / Chapter 3.2.4 --- Western blot analysis --- p.48 / Chapter 3.2.5 --- Doxorubicin efflux assay --- p.50 / Chapter 3.2.6 --- Drug sensitivity of A431 cells treated with verapamil --- p.50 / Chapter 3.2.7 --- Treatment with DNA methyltransferase inhibitor --- p.51 / Chapter 3.2.8 --- Drug sensitivity of A431 cells treated with 5-Aza-dC --- p.51 / Chapter 3.2.9 --- Methylation-specific PCR (MSP) --- p.51 / Chapter 3.2.10 --- Bisulfite genomic DNA sequencing --- p.52 / Chapter 3.3 --- Results --- p.54 / Chapter 3.3.1 --- Drug sensitivity of A431 cells to doxorubicin --- p.54 / Chapter 3.3.2 --- Expression profile of mdrl and P-glycoprotein in A431 cells --- p.54 / Chapter 3.3.3 --- Dox efflux-pump activity in A431 cells --- p.57 / Chapter 3.3.4 --- Drug sensitivity of A431 cells in the presence of verapamil --- p.59 / Chapter 3.3.5 --- Expression profile of mdrl in A431 cells in the presence of 5- Aza-dC --- p.59 / Chapter 3.3.6 --- Drug sensitivity of A431 cells in the presence of 5-Aza-dC --- p.62 / Chapter 3.3.7 --- Methylation status of mdrl promoter region --- p.64 / Chapter 3.3.8 --- Bisulfite genomic DNA sequencing of the mdrl promoter --- p.64 / Chapter 3.4 --- Discussion --- p.67 / Chapter Chapter 4: --- The resistance mechanism of cisplatin in HepG2 cells / Chapter 4.1 --- Introduction --- p.70 / Chapter 4.1.1 --- Tumor hypoxia and chemotherapeutic resistance --- p.70 / Chapter 4.1.2 --- Cisplatin and its action mechanism --- p.71 / Chapter 4.1.3 --- Mechanisms of cisplatin resistance --- p.74 / Chapter 4.1.4 --- Mismatch repair genes --- p.79 / Chapter 4.1.5 --- Epigenome and drug resistance in cancer --- p.80 / Chapter 4.2 --- Materials and Methods --- p.84 / Chapter 4.2.1 --- Cell culture --- p.84 / Chapter 4.2.2 --- MTT assay --- p.84 / Chapter 4.2.3 --- Reverse transcription polymerase chain reaction (RT-PCR) --- p.84 / Chapter 4.2.4 --- Oligonucleotide transfection --- p.85 / Chapter 4.2.5 --- Treatment with DNA methyltransferase inhibitor --- p.86 / Chapter 4.2.6 --- Drug sensitivity of HepG2 cells treated with 5-Aza-dC --- p.87 / Chapter 4.2.7 --- Treatment with histone deacetylase inhibitor --- p.87 / Chapter 4.2.8 --- Drug sensitivity of HepG2 cells treated with TSA --- p.87 / Chapter 4.3 --- Results --- p.89 / Chapter 4.3.1 --- Drug sensitivity of HepG2 cells to cisplatin --- p.89 / Chapter 4.3.2 --- Expression profile of the MMR genes in HepG2 cells --- p.89 / Chapter 4.3.3 --- Drug sensitivity of HepG2 cells to cisplatin after the knock- down of PMS2 --- p.91 / Chapter 4.3.4 --- Expression profile of MMR genes in the presence of 5-Aza-dC --- p.95 / Chapter 4.3.5 --- Drug sensitivity of HepG2 cells to cisplatin after the addition of 5-Aza-dC --- p.95 / Chapter 4.3.6 --- Expression profile of MMR genes in the presence of trichostatin A --- p.98 / Chapter 4.3.7 --- Sensitivity of HepG2 cells to cisplatin after the addition of trichostatin A --- p.98 / Chapter 4.4 --- Discussion --- p.101 / Chapter Chapter 5: --- The role of PMS2 in cisplatin-induced apoptosis / Chapter 5.1 --- Introduction --- p.105 / Chapter 5.1.1 --- Apoptosis --- p.105 / Chapter 5.1.2 --- Extrinsic pathway of apoptosis --- p.106 / Chapter 5.1.3 --- Intrinsic pathway of apoptosis --- p.106 / Chapter 5.1.4 --- Cisplatin-induced apoptosis --- p.107 / Chapter 5.1.5 --- MMR and apoptosis --- p.109 / Chapter 5.2 --- Materials and Methods --- p.111 / Chapter 5.2.1 --- Cell culture --- p.111 / Chapter 5.2.2 --- Flow cytometric analysis of apoptosis --- p.111 / Chapter 5.2.3 --- Oligonucleotide transfection --- p.111 / Chapter 5.2.4 --- Western blot analysis --- p.111 / Chapter 5.2.5 --- Drug and antibodies --- p.112 / Chapter 5.3 --- Results --- p.113 / Chapter 5.3.1 --- Cisplatin induced apoptosis --- p.113 / Chapter 5.3.2 --- Knockdown of PMS2 by siRNA --- p.113 / Chapter 5.3.3 --- Cisplatin-induced apoptosis involved caspases --- p.115 / Chapter 5.3.4 --- Protein expressions of anti-apoptotic genes --- p.119 / Chapter 5.3.5 --- Protein expressions of pro-apoptotic genes --- p.119 / Chapter 5.3.6 --- Protein expressions of apoptotic proteins after knockdown of PMS2 --- p.122 / Chapter 5.4 --- Discussion --- p.124 / Chapter Chapter 6: --- General discussion and conclusion / Chapter 6.1 --- Diverse sensitivity for hypoxia/reoxygenation treated cells to anticancer drugs --- p.128 / Chapter 6.2 --- Resistance mechanism of doxorubicin in A10HR and A20HR cells --- p.129 / Chapter 6.3 --- Resistance mechanism of cisplatin in G10HR and G20HR cells --- p.129 / Chapter 6.4 --- The role of PMS2 as a direct signaling molecule and the alteration of apoptotic proteins in cisplatin-induced apoptosis --- p.130 / Chapter 6.5 --- Future work --- p.131 / References --- p.132

Polychlorinated biphenyls (PCBs) are synthetic organic chemicals that persist in the environment and are known to be carcinogenic to humans. Virtually all of the deleterious effects of PCB 126, the most potent dioxin-like PCB, are mediated by the aryl hydrocarbon receptor (AhR). By means of the common cofactor ARNT, the AhR signaling pathway can crosstalk with the hypoxia signaling pathway. Regulated by hypoxia-inducible factors (HIFs), the hypoxia pathway mediates responses to environments of reduced oxygen availability (hypoxia). This dissertation specifically examines the crosstalk and interference between these two pathways in the context of PCB 126 exposure. The results of this dissertation show that the antagonistic relationship between the AhR and hypoxia signaling pathways affects the function and responses of both AhR and HIF-1Α. We provide substantial evidence that ARNT is indeed a crucial factor in both the AhR and HIF-1Α signaling pathways. Furthermore, this dissertation examines regulatory mechanisms involved in AhR-mediated gene expression and identifies epigenetic regulation as a critical factor in AhR target gene expression. In summary, this dissertation helped to improve the understanding of mechanisms of PCB 126 toxicity. Understanding the detrimental biological effects of these ubiquitous environmental pollutants might ultimately have significant implications for human health.

Previous studies demonstrated that intravenous administration of human umbilical cord blood (HUCB) cells could improve behavioral and neurological recovery of stroked animals following middle cerebral artery occlusion (MCAO). In addition, HUCB cell recipients had less of an inflammatory response with less leukocyte infiltration. In these studies we explored how HUCB cells change the inflammatory response of neurons, astrocytes, and microglia to hypoxia/ischemia. Initiation of the inflammatory response occurs with the expression of chemokines. We determined that monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein 1alph (MIP-1a), which are upregulated in the brain early after a stroke, induce migration of HUCB cells to the site of injury. Neutralizing these chemokines with antibodies prevented migration in an in vitro migration assay. We next explored the interaction of the whole HUCB mononuclear cell fraction, as well as subpopulations from within the mononuclear fraction (T cell alone, B cell alone, and monocytes/macrophage alone) with cultures of enriched neurons, astrocytes or microglia exposed to hypoxia in an oxygen, glucose deprivation paradigm. We showed that HUCB cells increased the cell viability of neurons and astrocytes, while decreasing cell viability of microglia. There was also a change in the cytokine secretion profile from the cells exposed to HUCB cells under hypoxic conditions. These results suggested that chemokines, MCP-1 and MIP-1a increased in stroked brain, and they played an important role in recruitment of HUCB into the CNS after intravenous administration. Once inside the brain, HUCB could suppress the immune response by promoting microglial death and modulating the function of astrocytes. In addition, HUCB cells provide neuron protection against the injury caused by stroke. However, it is unlikely to contribute the effect of HUCB to a single population of HUCB.

Improvements in medical care over recent decades have increased the number of premature and low birth weight infants that survive hypoxic-ischemic (H-I) insults. Because there is a rising incidence in diseases associated with these events, it is critical to develop effective therapies to treat the various resulting neuropathies. Extracellular matrix constitutes the majority of brain parenchyma. Lecticans and matrix-degrading proteases including ADAMTSs (a disintegrin and metalloproteinase with thrombospondin repeats) and matrix metalloproteinases (MMPs) exert effects on cell viability and may be associated with either protective or destructive processes after H-I. Both ADAMTSs (Cross et al. 2006; Tian et al. 2007) and MMPs (del Zoppo et al. 2007; Gu et al. 2005; Rosenberg et al. 2001) have been associated with pathological states in brain, yet the relative contributions of lecticans, ADAMTSs and MMPs to inflammation and cell death remain unknown. In the present study, the first series of experiments were conducted to characterize cellular damage and neuroinflammation in the postnatal day 7 rat after exposure to H-I, and to determine if cell death and inflammation were associated with alterations in lectican expression. Data showed that reduced brevican expression occurred 4 days after H-I in lesioned hippocampus. Additionally, reduced versican expression in white matter was concomitant with pre-OL cell death at this endpoint. In contrast, both lecticans were elevated at later endpoints (14, 21 days) that were associated with increased neuroinflammation and cavitary infarction. These data suggest that lectican loss is associated with cell death at the early endpoint, whereas increased lectican deposition over time likely leads to glial scar formation and a reduced capacity for neuroplasticity. Two subsequent series of experiments were conducted to determine the relative contributions of matrix-degrading proteases to injury, and whether proteolytic activity was associated with neuroinflammatory events. The first objective was to determine whether treatment with AG3340, a selective inhibitor of gelatin-degrading MMPs, or the anti-inflammatory compound minocycline, could provide neuroprotection when administered at a delayed time point after insult, and to compare the efficacy of AG3340 with that of the well-known anti-inflammatory compound minocycline. Data showed that both compounds effectively dampened the recruitment of microglia/macrophages to the lesion site when administered 24 hrs after H-I. These effects were associated with reduced neurodegeneration, indicating that these compounds neuroprotect at a clinically relevant time point. The final series of experiments tested whether these compounds could neuroprotect in an ex vivo model of oxygen glucose deprivation (OGD) that lacks peripheral immune cell involvement, thus providing insight into the relative contributions of resident microglia and gelatinase activity to the inflammatory sequelae. Results showed that both compounds blocked the OGD-induced increase in gelatinase activity and were neuroprotective in the absence of peripheral immune cells. Taken together, these data indicate that resident microglia contribute to H-I injury through gelatinase activation. Thus, the present study demonstrates that gelatin-degrading MMPs are important targets to consider when developing therapies to combat neonatal H-I injury.

L’angiogenèse, indispensable à la mise en place d’un réseau vasculaire fonctionnel, est au cœur des stratégies thérapeutiques des pathologies ischémiques. L’hypoxie, caractérisant ces tissus ischémiques, est un stimulus majeur de l’angiogenèse, en induisant l’expression de facteurs de croissance tels que le VEGF et de protéines de la matrice extracellulaire endothéliale. Nous avons identifié la protéine ANGPTL4, comme une cible majeure de l’hypoxie et ayant des effets opposés au VEGF sur la perméabilité vasculaire. Le but de cette thèse a consisté en l’analyse du rôle d’ANGPTL4 sur la formation de capillaire et l’organisation des jonctions adhérentes dans un contexte dépendant du VEGF. J’ai démontré que le VEGF stimule la formation d’un dense réseau capillaire 3D alors qu’ANGPTL4 induit la formation de capillaires étroits et peu ramifiés. ANGPTL4 réduit la taille du réseau de capillaire induit par le VEGF en limitant le nombre de bourgeons, de branchements et la largeur des capillaires. ANGPTL4 renforce l’intégrité des capillaires formés en présence de VEGF en préservant des jonctions adhérentes stables. J’ai démontré qu’ANGPTL4 limite les processus de migration 3D et de prolifération induits par le VEGF. L’analyse de la voie de signalisation VEGF/ANGPTL4 a montré une potentialisation par ANGPTL4 de la phosphorylation Y1175 du VEGFR2, impliqué dans l’internalisation de VEGFR2. En conclusion, ce modèle révèle un effet d’ANGPTL4 dépendant du contexte 3D, qui stimule les processus d’angiogenèse en absence de VEGF et qui contrecarre la morphogenèse induite par le VEGF en renforçant l’intégrité des jonctions adhérentes et en régulant la signalisation en aval du VEGFR2. / Angiogenesis, by promoting new functional capillaries, is a main target of therapeutic strategies of ischemic pathologies. Ischemic tissues are characterized by hypoxic environment, which stimulates angiogenesis by inducing expression and secretion of growth factors such as VEGF and by remodeling endothelial extracellular matrix. Our team identified ANGPTL4 as a hypoxia-induced target and characterized its counteracting effect on VEGF-induced vascular permeability. This PhD study therefore aimed to decipher the role of ANGPTL4 on angiogenesis, capillary architecture and adherens junction (VE-cadherin) organization in a VEGF-dependent context. I demonstrated that VEGF induced formation of branched capillaries forming a dense 3D network while ANGPTL4 enhanced the formation of unbranched and tight capillaries. Remarkably, ANGPTL4 reduces VEGF-induced angiogenesis, by limiting branching and widening of the capillaries. Furthermore, ANGPTL4 regulates the local VE-cadherin patterning during the sprouting process by maintaining lateral linear structures and limiting the VEGF-induced formations involved in the migratory capacities. I demonstrated that ANGPTL4 limited VEGF-induced 3D endothelial cell migration and proliferation. Analysis of VEGF/ANGPTL4 signaling pathway pointed out that ANGPTL4 enhanced phosphorylation of Y1175 VEGFR2, known to enhance internalization of VEGFR2. In conclusion, this study modeled the 3D context-dependent effect of ANGPTL4 that stimulates angiogenesis in absence of VEGF whereas it counteracts VEGF-induced endothelial morphogenesis by regulating VEGFR2 trafficking and strengthening adherens junctions.

Mastitis, the inflammation of the mammary gland by bacterial infection, is one of the costliest diseases to the dairy industry primarily due to a loss in milk production. The aim of this study was to investigate the mechanisms underlying reduced milk production during mastitis. We hypothesized that bacterial endotoxin induces cell apoptosis, oxidative stress and increases hypoxia while inhibiting milk gene expression in the mammary gland. To test this hypothesis, mice were bred to pregnancy, and 3 days post-partum the left and right sides of the 4th pair of mammary glands were alternately injected with either the endotoxin liposaccharide (LPS, E. coli 055:B5, 100 ul of 0.2 mg/ml) or sterile PBS through the teat meatus. At 10.5 and 22.5 h post-injection, pimonidazole HCl, a hypoxyprobe, was injected intraperitoneally. At 12 or 24 h after the LPS injection, the fourth glands were individually collected (n=8 pairs) and analyzed for hypoxia, gene expression and oxidative stress. LPS treatment induced mammary gland inflammation as shown by increases in inflammatory cytokine expression (P < 0.001) and neutrophil recruitment at 12 and 24 h. LPS promoted cell apoptosis in a transient manner; an abundance of cleaved caspase 3 was evident only at 12 h after LPS challenge (P = 0.02). Increased H2O2 content was seen at 12 h (P < 0.001) but decreased dramatically after 24 h of LPS treatment (P < 0.001). Total antioxidative capacity tended to decrease at both 12 and 24 h (P = 0.067 and 0.061, respectively). In agreement with these findings, LPS activated Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidative signaling in the mammary gland, demonstrated by increased expression of its target gene Nqo1 at 12 h (P = 0.05) and xCT at 24 h (P = 0.076). Hypoxyprobe staining, indicative of hypoxia, was greater in the alveoli of PBS-treated glands than LPS-treated glands at both 12 and 24 h. This suggests oxygen tension rises in response to LPS treatment. Conversely, milk expression genes, β-casein gene (CSN2) and α-lactalbumin (LALBA), were inhibited by LPS treatment across time. Expression of α-S1 casein (CSN1S1) mRNA increased with LPS treatment at 24 h, but protein expression was reduced at this same time point (P < 0.05). In summary, intramammary LPS challenge incurs inflammation, augments cell apoptosis, induces oxidative stress and activation of the Nrf2 antioxidation pathway, increases oxygen tension, and inhibits milk protein expression in the mammary gland. This study provides functional insight into mechanisms of reduced milk production during mastitis and provides possible approaches to combat reduction in milk production, such as enhancing the Nrf2-antioxidative signaling pathway and reducing inhibition of milk protein expression.