A Interleucina 8 (IL-8) é uma quimiocina CXC angiogênica que tem papel importante no desenvolvimento e progressão de vários tumores malignos, incluindo o câncer de próstata (CaP). O polimorfismo de nucleotídeo único (SNP) -251 T/A da região promotora do gene da IL-8, relativo ao local de início da transcrição deste gene, está associado com a produção desta citocina. O efeito da IL-8 é mediado através de dois receptores de alta afinidade, CXCR1 e CXCR2. O presente estudo investigou a influência da variação dos genes IL-8 e CXCR2 na susceptibilidade e nas características clinicopatológicas do CaP em um grupo de brasileiros. Duzentos e um pacientes e 185 controles saudáveis foram selecionados neste estudo casocontrole. Amostras de sangue foram coletadas para extração de DNA; a tipagem da IL-8 -251 T/A e CXCR2 +1208 C/T foi realizada através da reação em cadeia da polimerase com sequência específica de primers (PCR-SSP), seguida pela eletroforese em gel de agarose. O risco associado entre os genótipos, a susceptibilidade do CaP e as características do tumor, foi estimado pelo odds ratio (OR), com intervalo de confiança de 95%, usando análise de regressão logística e ajustando para idade ao diagnóstico. Encontramos uma associação estatisticamente significativa entre o genótipo heterozigoto CT do gene CXCR2 +1208 e CaP. Este genótipo foi significativamente menos frequente em pacientes com estádio clínico T3-T4 comparado com T1-T2 (56.7% versus 80.5%). Nossos achados sugerem que os portadores do genótipo CT CXCR2 +1208 tiveram um efeito protetor para estádio avançado de CaP (CT versus CC: OR ajustado = 0.25; P = 0.02). Não foi encontrada associação significativa entre o polimorfismo -251 T/A da IL-8 e os parâmetros clinicopatológicos do CaP. Estes resultados indicam que o genótipo CT do CXCR2 +1208 é menos frequente em estádios avançado de CaP, sugerindo que este receptor de quimiocina tenha um papel na patogênese desta doença. / Interleukin-8 (IL-8) is an angiogenic CXC chemokine that plays an important role in both the development and progression of several human malignancies including prostate cancer (PC). A single nucleotide polymorphism (SNP) at -251 upstream of the transcriptional start site of the IL-8 gene has been shown to influence its production. The effects of IL-8 are mediated by two highly related chemokine receptors, CXCR1 and CXCR2. The present study investigated the influence of the IL-8 and CXCR2 gene variation on susceptibility and clinicopathological characteristics of PC in a group of Brazilian subjects. Two hundred and one patients and 185 healthy controls were enrolled in a case-control study. Blood was collected for DNA extraction; typing of IL-8 -251 T/A and CXCR2 +1208 C/T genes was performed by polymerase chain reaction with sequence-specific primers (PCR-SSP), followed by agarose gel electrophoresis. Risk association between the genotypes, PC susceptibility and tumor characteristics was estimated by odds ratio (OR) and 95% confidence intervals (95% CI) using logistic regression analysis, after adjusting for age at diagnosis. A significant association was found between the heterozygous CXCR2 +1208 CT genotype and PC. The CXCR2 +1208 CT genotype was significantly less frequent in patients with clinical stage T3-T4 compared to T1-T2 (56.7 versus 80.5%). Our findings suggest that carriers of the CXCR2 +1208 CT genotype had a protective effect for advanced PC (CT versus CC: adjusted OR = 0.25; P = 0.02). No association was observed between the SNP for IL-8 -251 T/A and clinicopathological parameters of PC. These results indicated that the CXCR2 +1208 CT genotype is less frequent in advanced stages of PC, suggesting that this chemokine receptor plays a role in the pathogenesis of this disease.

Master of Public Health / Department of Diagnostic Medicine/Pathobiology / John A. Pickrell / Beef cattle feed lots produce significant, local point source pollution of the atmosphere. The dusts generated in the CAFOs are complex mixture of fine and ultra fine particles, organic compounds, transition metals, and adsorbed toxic gases. Since each component is toxic in itself, we do not fully understand the relative importance of each component in the dust and their interactions to inducing inflammatory changes in the lung. We did extensive literature searches to understand the mechanism of dust toxicity in respiratory system. This lead to focusing on solubility of dust in lung simulant fluid, and in-vitro study of release of two common biomarkers of inflammatory processes IL-6 and IL-8 from lung epithelial cells. Various concentrations (1 to 50%) of the dust extract induced release of IL-6, and IL-8 from lung epithelial cell as indicators of pro-inflammatory changes (IL-6), and amplification and maintenance of inflammation (IL-8). IL-6 release had dose dependence; peak production was seen with 25% dust extract. IL-8 production went down as the concentration of the dust extract increased from 1% to 25%. However, 50% dust extract was cytotoxic to the cell leading to 10-15% cell viability. At non-cytotoxic concentrations for lung epithelial cells, production of IL-8 was reduced. These findings suggested that higher exposure concentration were required to initiate inflammation as indicated by IL-6 release. Lower exposure concentrations (1 and 5% extracts) were related to optimal release of IL-8 needed to amplify and maintain the inflammatory response. Inhibition of endotoxin didn't significantly change the pattern of IL-6 or IL-8 release from epithelial cells. This finding suggested that at least a portion of the mechanism by which particle induced cytokine release from the lung epithelial cells was not endotoxin dependent. Heating samples at 1200C for 5 minutes modified some of the toxic properties of the dust extracts but didn't completely detoxify it. We observed that longer incubation period was required to peak release for both IL-6 and IL-8. However, the higher concentration of sample (50% extract) found to be cytotoxic in non-heat treated sample was no longer cytotoxic and induced both IL-6 and IL-8 release from the lung epithelial cells. This result suggested that heat treatment could reduce some of the dust extract's cytotoxic properties. However, the extract's potential to induce peak cytokine release increased.

Cutaneous melanoma is a very aggressive cancer with increasing incidence. It originates from transformed pigmented skin cells (melanocytes). The main risk factor for melanoma development is exposure to UV light and repeated sunburns. In approximately 10 % of cases, melanoma occurs on hereditary basis. Patients with cutaneous melanoma diagnosed in early stages have very good prognosis, with surgical resection of the primary tumour being mostly sufficient for treatment. In contrast, the advanced melanoma stages with metastases are often progressive and refractory to conventional therapies. Cutaneous melanoma is referred to as an immunogenic tumour that is frequently infiltrated by cells of the immune system. Tumours with immune cell infiltration show better prognosis. Spontaneous regression may occur. Over the last few years, progress has been made in the treatment of melanoma using checkpoints molecules (anti-CTLA-4 and anti-PD-1) to activate patients own immune system to recognize tumour lesions. In the tumour microenvironment, cytokines play an important role, enabling communication between cells and regulation of cell proliferation and migration and thus the tumour development. Cytokines (IL-2, IFNα) can be used in adjuvant therapy of melanoma. This work analysed levels of expressed cytokines in...

LPS pretreatment of human pro-monocytic THP-1 cells induces tolerance to secondary LPS stimulation with reduced TNFα production. However, secondary stimulation with heat-killed Staphylococcus aureus (HKSa) induces priming as evidenced by augmented TNFα production. The pro-inflammatory cytokine, IFNγ, also abolishes suppression of TNFα in LPS tolerance. The effect of LPS tolerance on HKSa and IFNγ-induced inflammatory mediator production is not well defined. We hypothesized that LPS, HKSa and IFNγ differentially regulate pro-inflammatory mediators and chemokine production in LPS-induced tolerance. THP-1 cells were pretreated for 24h with LPS (100ng/ml) or LPS (100ng/ml)+IFNγ (1μg/ml). Cells were subsequently stimulated with LPS or HKSa (10μg/ml) for 24h. The production of the cytokines TNFα, IL-6, IL-1β, and GMCSF and the chemokine IL-8 were measured in supernatants. LPS and HKSa stimulated TNFα (3070±711pg/ml and 217±9pg/ml, respectively) and IL-6 (237±8.9pg/ml and 56.2±2.9pg/ml, p<0.05, n=3, respectively) in control cells compared to basal levels (<25pg/ml). LPS induced tolerance to secondary LPS stimulation as evidenced by a 90% (p<0.05, n=3) reduction in TNFα. However, LPS pretreatment induced priming to HKSa as demonstrated by increased TNFα (2.7 fold, from 217 to 580pg/ml, p<0.05, n=3). In contrast to suppressed TNFα, IL-6 production was augmented to secondary LPS stimulation (9 fold, from 237 to 2076pg/ml, p<0.01, n=3) and also primed to HKSa stimulation (62 fold, from 56 to 3470pg/ml, p<0.01, n=3). LPS induced IL-8 production and to a lesser extent IL-1β and GMCSF. LPS pretreatment did not affect secondary LPS stimulated IL-8 or IL-1β, although HKSa stimulation augmented both mediators. In addition, IFNγ pretreatment reversed LPS tolerance as evidenced by increased TNFα levels while IL-6, IL-1β, and GMCSF levels were further augmented. However, IL-8 production was not affected by IFNγ. These data support our hypothesis of differential regulation of cytokines and chemokines in gram-negative- and gram-positive-induced inflammatory events. Such changes may have implications in the pathogenesis of polymicrobial sepsis.

HIV infection has been shown to predispose patients to accelerated development of heart disease. One mechanism for this pathology may involve endothelial activation either by HIV itself or by its secreted proteins, gp120 (a viral envelope protein) and tat (a protein that upregulates transcription of viral genes). We have studied the effects of gp120 and tat on signaling and production of inflammatory cytokines by Human Pulmonary Artery Endothelial Cells (HPAEC). HPAEC were stimulated at varying time points with combinations of gp120, tat, and monokines (IL-1β and TNFα). Cell lysate fractions were analyzed for MAP Kinase activity and NFκB activation, and culture supernatants were assayed for inflammatory cytokines (IL-6 and IL-8). The production of IL-6 and IL-8 was significantly enhanced by tat but not by gp120. Both gp120 and tat, however, induced significant morphological changes in HPAEC. The only synergy noted was between high levels of tat and TNFα acting on the production of IL-6. When HPAEC were stimulated with IL-1β and TNFα, peak phosphorylation of p38 MAP Kinase was found at 45 minutes, while NFκB was maximally activated at two hours. Both the ERK1,2 and p38 cascades of MAP Kinase were activated by tat, and an increase in NFκB phosphorylation and translocation were noted. We conclude that the HIV tat protein could be involved in inflammatory changes in endothelium leading to the accelerated development of heart disease in HIV patients.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Les jonctions adhérentes (JA) sont nécessaires à l’élaboration d’une barrière vasculaire sélective dans laquelle la VE-cadhérine joue un rôle crucial. En effet, la VE-cadhérine est une molécule d’adhérence entrant dans la constitution des JA et présente spécifiquement au sein de l’endothélium. Lorsque la VE-cadhérine est exprimée à la surface des cellules endothéliales, l’intégrité de la barrière est préservée. En revanche, des modifications de la VE-cadhérine, comme par exemple sa phosphorylation, provoquent son internalisation, la dissociation des complexes adhésifs ou la désorganisation générale des jonctions endothéliales, défavorisant ainsi la sélectivité de la barrière. De manière générale, une perméabilité vasculaire élevée peut être observée au cours de l’activation de l’endothélium, telle que l’angiogenèse ou la réponse inflammatoire, en conditions physiologiques comme pathologiques. Par exemple, la phosphorylation de la VE-cadhérine provoquée par le facteur VEGF (vascular growth endothelial facteur) entraîne l’augmentation de la perméabilité vasculaire. En outre, une molécule pro-inflammatoire telle que l’interleukine-8 (IL-8) peut également provoquer la phosphorylation de la VE-cadhérine, aboutissant ainsi à l’augmentation de la perméabilité vasculaire. Tandis que les voies de signalisation régissant les effets pro-angiogéniques ou pro-inflammatoires du VEGF et de l’IL-8, respectivement, sont bien caractérisées, les mécanismes moléculaires sous-tendant spécifiquement l’augmentation de perméabilité endothéliale sont moins bien connus. Au cours de mon doctorat, je me suis donc attachée à examiner les interactions moléculaires entre la VE-cadhérine phosphorylée et la molécule d’échafaudage β-arrestine1, dans les cellules endothéliales humaines exposées au VEGF. J’ai également exploré la distribution de la VE-cadhérine dans les cellules endothéliales cérébrales dans un contexte tumoral, récapitulé par le sécrétome de cellules gliomateuses (GB). Mon travail a permis d’identifier la partie C-terminale (C-tail) de la β-arrestine1 qui comporte 43 acides aminés, comme une région interagissant directement avec la VE-cadhérine lorsqu’elle est phosphorylée sur le résidu S665. Cette liaison pourrait conduire alors à l’internalisation de la VE-cadhérine, lors de la stimulation par le VEGF. En outre, nous avons démontré le rôle inattendu du domaine C-tail de la β-arrestine1 dans la régulation négative de l’activité du promoteur de la VE-cadhérine. Ceci se traduit par une réduction des niveaux d’expression de la VE-cadhérine, contribuant ainsi à l’affaiblissement de la barrière endothéliale en réponse au VEGF. En outre, nous avons voulu évaluer l’effet des différents facteurs secrétés par le GB sur la perméabilité vasculaire. L’étude du sécrétome du GB a révélé une production abondante et majoritaire d’IL-8, qui provoque l’internalisation de la VE-cadhérine et la désorganisation des jonctions endothéliales. En plus de son action sur la perméabilité, l’IL-8 favorise la tubulogenèse des cellules endothéliales cérébrales. En conclusion, nous avons mis en évidence un rôle nouveau de la β-arrestine1 dans la régulation de la VE-cadhérine dans les cellules endothéliales humaines. Nous avons également démontré que la sécrétion d’IL-8 par le GB entraîne le remodelage des jonctions de la VE-cadhérine et conduit à une perte de la fonction de barrière des cellules endothéliales cérébrales. L’ensemble de nos résultats a donc permis d’améliorer nos connaissances des mécanismes moléculaires modulant la perméabilité endothéliale. / VE-cadherin is a major adhesion molecule composing endothelial adherens junctions (AJ), which ensure selectivity of the endothelial barrier. Stabilization of the VE-cadherin complex at the surface of endothelial cells plays a pivotal role in the maintenance of vascular homeostasis. Conversely, the disorganization or internalisation of VE-cadherin is a frequent consequence of VE-cadherin modifications (e.g phosphorylation), which promotes in turn vascular permeability. In general, vascular leakage can be observed in both physiological and pathological conditions. Indeed, VE-cadherin phosphorylation caused by pro-angiogenic and pro-permeability factors, among which vascular endothelial growth factor (VEGF) is the prototype, occurs during physiological angiogenesis, as well as tumour-associated angiogenesis. Besides, pro-inflammatory molecules, such as interleukin-8 (IL-8) can also participate in the phosphorylation of VE-cadherin and thereby promote vascular permeability. To best characterise VE-cadherin-mediated increase in vascular permeability under physiological VEGF challenge, we notably investigated the molecular interactions between serine (S665) phosphorylated VE-cadherin and the scaffolding molecule β-arrestin. We also studied the distribution of VE-cadherin in brain endothelial cells under pathological conditions, as provided by the secretome of glioblastoma (GB) brain tumour cells. My work allows the identification of a 43 amino-acid sequence within the C-terminus tail of β-arrestin1 (C-tail) that can directly bind to (S665) phosphorylated VE-cadherin and further triggers its internalisation upon VEGF stimulation. Moreover, we demonstrated the unexpected role of β-arrestin1 C-tail in the down-regulation of the VE-cadherin promoter activity, which results in reduction of VE-cadherin RNA and protein levels, thus contributing to the endothelial barrier properties. Furthermore, in order to evaluate the effects of tumour-secreted factors on the hyper-permeability associated with the tumour microenvironment, we explored the composition and function of the GB secretome on brain endothelial cells. We found that abundant secretion of IL-8 by GB cells causes VE-cadherin-mediated endothelial junction disorganization. Moreover, IL-8 promotes both brain endothelial cell permeability and tubulogenesis. In conclusion, we established a new role for β-arrestin1 in the control of VE-cadherin-based junctions in human endothelial cells. Likewise, we demonstrated that tumour cell-released IL-8 chemokine provokes VE-cadherin-dependent junction remodelling and thereby increases the permeability of human brain endothelial cells. Our results reinforce the central role of VE-cadherin in the modulation of the vascular barrier function in physiological and pathological conditions.

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