Neutrophil extravasation into tissues is an essential process required for the inflammatory response. Upon receiving an inflammatory cue, neutrophils begin accumulating on the luminal surface of the endothelium. Neutrophil recruitment is initiated by selectin-mediated tethering and rolling of neutrophils along the endothelial monolayer, followed by integrin-mediated firm adhesion. Adherent neutrophils then traverse the endothelium in a process known as transendothelial migration. The events mediating the rolling and adhesion steps are well characterised, but research into the molecular mechanisms regulating transendothelial migration is an area of intense focus. A previous study conducted in our laboratory found that the activation of endothelial extracellular signal-regulated kinase (ERK) 1/2 was required for neutrophil transmigration. Furthermore, it was found that endothelial ERK was activated in response to a soluble protein produced by fMLP- or IL-8-stimulated neutrophils. In the present study, the soluble ERK-activating neutrophil protein was identified as annexin A1, which was selected as a possible candidate following mass spectrometry analysis of proteins secreted from activated neutrophils. Annexin A1 antibodies (Abs) were found to block endothelial ERK activation induced by conditioned medium harvested from stimulated neutrophils. Annexin A1 Abs were additionally able to inhibit neutrophil transmigration across human umbilical vein endothelial cell (HUVEC) monolayers in an in vitro transmigration assay. Following the purification of recombinant annexin A1, it was demonstrated that it could activate endothelial ERK in a similar manner to neutrophil conditioned medium. Upon further investigation, ERK activation was found to be induced by a truncated form of annexin A1 present in the protein preparation rather than the full length protein. Calpain I, a calcium dependent protease that is activated upon neutrophil stimulation and is known to cleave annexin A1 within the N-terminal domain, was shown to process full length inactive recombinant annexin A1 into an unidentified product that could activate endothelial ERK. A calpain I inhibitor was also found to prevent stimulated neutrophils from secreting an ERK-activating protein, thus further suggesting a role for calpain I in this process. As full length annexin A1 has been reported to signal through the formyl peptide receptor (FPR) family, a pan-FPR antagonist was incubated with endothelial cells and was found to inhibit ERK activation induced by neutrophil conditioned medium, indicating that pro-inflammatory annexin A1 is also a FPR ligand. Endothelial projections termed “transmigratory cups” form around neutrophils during extravasation, of which ICAM-1 is a major component. Using an assay that examined transmigratory cups during neutrophil transmigration, it was found that annexin A1 Abs could inhibit neutrophil adhesion and transmigration through HUVEC monolayers by interfering with transmigratory cup formation around neutrophils, as shown by monitoring ICAM-1 during the process. Quantification of transmigrating neutrophils highlighted that the majority of neutrophils were emigrating via a transcellular pathway, which is in opposition to many in vitro studies where paracellular transmigration predominates. The results generated from this study identified a novel pro-inflammatory role for annexin A1 in neutrophil transendothelial migration. Preliminary experiments suggested that the pro-inflammatory annexin A1 responsible for endothelial ERK activation was a truncated form. Calpain I appears to be a likely candidate responsible for the generation of this uncharacterised, truncated annexin A1 product, however further experiments are required to confirm this hypothesis. Pro-inflammatory annexin A1 represents a new target for the treatment of inflammatory disorders. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374554 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2009

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Transendothelial migration is a key process in lymphocyte trafficking. It is known that growth hormone (GH) modulates intrathymic T cell migration and that directly or indirectly influences the biology of endothelial cells and thymocytes. In this context, we evaluated the effect of GH on the transendothelial migration of thymocytes, in the presence or absence the chemokine CXCL12. For the study, we applied the murine thymic endothelial cell line (tEnd.1) and thymocytes freshly isolated from male C57BL/6 mice aged 4-6 weeks. Through in vitro studies of transendothelial migration of thymocytes, and analyses by flow cytometry, we observed a statistically significant reduction in the numbers of transmigrated thymocytes, mainly seen for CD4+CD8+ cells, across endothelial barriers treated with GH [100 ng/ml], for 8 h. Importantly, this effect was reverted when thymocytes were treated with GH [100 ng/ml] for 1 h. Similar effects were noted in transmigration through joint action of GH and CXCL12. Despite the fact that all the CD4/CD8-defined subsets have been affected, we observed a statistically significant increase in the number of transmigrated thymocytes, mainly of CD4+CD8+ and CD4+CD8- cells, when they were treated with GH and allowed to migrate in response to CXCL12, when compared to untreated controls in response to CXCL12. We demonstrated, by real-time PCR, that GH at 100 ng/ml did not modulate the expression of VCAM-1 and CXCL12 by tEnd.1 cells treated for 8 h. Furthermore, we found by cytofluorimetric assay that GH alone did not change the membrane expression of VLA-4 and CXCR4 receptor in transmigrated thymocytes. Through joint action of GH and CXCL12, was observed increase in expression of VLA-4 on CD4-CD8+ cells from the group of GH-treated thymocytes, when compared to groups in which endothelial cells were treated. As for expression of CXCR4, we found that the GH/CXCL12 decreased the expression of this receptor on transmigrated thymocytes, mainly in CD4+CD8+ cells from the group in which the thymocytes were treated. In conclusion, our results reinforce that GH influence the thymus physiology and modulate the biology of endothelial cells and thymocytes, with differential effects in the process of endothelial transmigration of murine thymocytes. / Fundação de Amparo a Pesquisa do Estado de Alagoas / A transmigração endotelial é um processo essencial no trânsito de linfócitos. É sabido que o hormônio do crescimento (GH) está envolvido na migração intratímica de células T, e que influencia direta ou indiretamente a biologia das células endoteliais e dos timócitos. Neste contexto, avaliamos a ação do GH na migração transendotelial de timócitos, frente ou não à quimiocina CXCL12. Para o estudo, utilizamos a linhagem endotelial tEnd.1 e timócitos recém isolados de camundongos machos C57BL/6 de 4-6 semanas. Através do ensaio de transmigração endotelial in vitro de timócitos, e análise por citometria de fluxo, verificamos uma redução estatisticamente significativa no número de timócitos transmigrados, principalmente nas subpopulações CD4+CD8+, frente a barreiras endoteliais tratadas com GH [100 ng/ml], por 8 horas. Este efeito foi revertido quando os timócitos foram tratados com GH [100 ng/ml], por 1 hora. Efeitos similares na transmigração foram notados pela ação do GH frente a CXCL12. Apesar de todas as subpopulações CD4/CD8 terem sido afetadas, observamos um aumento estatisticamente significativo no número de timócitos transmigrados, principalmente das células CD4+CD8+ e CD4+CD8-, quando foram tratados com GH e colocados para migrar em presença da CXCL12, em relação ao grupo controle não tratado e em presença da quimiocina. Demonstramos, ainda, por RT-PCR, que o GH na concentração de 100 ng/ml, não modulou a expressão de VCAM-1 e CXCL12 por células tEnd.1 tratadas, por 8 horas. Além disso, verificamos por análise citofluorimétrica, que o GH sozinho não alterou a expressão dos receptores VLA-4 e CXCR4 nos timócitos transmigrados. Pela ação conjunta do GH e CXCL12, foi registrado aumento na expressão de VLA-4 sobre células CD4-CD8+ no grupo experimental em que os timócitos foram tratados com GH, quando comparamos aos grupos onde as células endoteliais foram tratadas. Quanto à expressão de CXCR4, verificamos que o GH/CXCL12 diminuiu a expressão deste receptor sobre timócitos transmigrados, principalmente em células CD4+CD8+, nos grupos experimentais em que os timócitos foram tratados. Em conclusão, nossos dados fortalecem o postulado de que o GH influencia a fisiologia do timo, e modula a biologia das células endoteliais e dos timócitos, com efeitos diferenciais no processo de transmigração endotelial de timócitos murinos.

Un nombre croissant de preuves suggèrent le rôle bénéfique des anthocyanes alimentaires, composés phyto-chimiques principalement présents dans les baies et les produits dérivés, sur la santé cardiovasculaire. Ces bénéfices peuvent être attribués à leur effet sur les cellules endothéliales ou les plaquettes qui sont les acteurs clés dans le développement des maladies cardiovasculaires (MCV). Cependant, les mécanismes moléculaires sous-jacents aux effets cardio-protecteurs de l'anthocyanine ne sont pas entièrement compris. L'objectif de cette thèse était d'évaluer l'effet in vitro des anthocyanines et de leurs métabolites, dans des conditions physiologiques, sur la fonction endothéliale et plaquettaire et d'identifier les mécanismes sous-jacents à leur action. Les résultats de ma thèse ont montré que le prétraitement des cellules endothéliales avec des concentrations physiologiques d'anthocyanes et de leurs métabolites circulants diminue l'adhésion des monocytes aux cellules endothéliales activées ainsi que leur migration transendothéliale qui sont les étapes initiales du développement de l'athérosclérose précédant le MCV. En accord avec ces résultats, l'analyse de l'expression génique a révélé que le traitement des cellules endothéliales avec ces molécules modulait l'expression des gènes impliqués dans la régulation de l'adhésion cellulaire, le réarrangement du cytosquelette d'actine, l'adhésion focale et la transmigration leucocytaire. Les analyses bioinformatiques de ces données ont permis d'identifier les facteurs de transcription potentiellement impliqués dans les effets nutrigénomiques observés ainsi que les protéines de signalisation cellulaire régulant leur activité. Les analyses bioinformatiques ont permit d’identifier des protéines de signalisation cellulaire auxquelles ces bioactifs peuvent se lier et potentiellement affecter leur activité entraînant modification d’activité des protéines de signalisation en aval. L’impact sur des facteurs de transcription a également été cherché et ces effets ont été confirmés par les résultats obtenus des analyses par Western blot. Les anthocyanines et leurs métabolites ont également modulé l'expression de microARN, en particulier ceux impliqués dans la régulation de la perméabilité des cellules endothéliales, contribuant ainsi aux changements observés dans la fonction endothéliale. En plus de leurs effets sur les cellules endothéliales, les résultats de mes travaux ont également montré la capacité des anthocyanes et de leurs métabolites à moduler la fonction plaquettaire en diminuant l'activation plaquettaire et leur agrégation avec les leucocytes, qui contribuent fortement au développement des MCV.En conclusion, les résultats de ma thèse ont révélé les effets positifs des anthocyanes et de leurs métabolites, aux concentrations physiologiques, sur la fonction endothéliale et plaquettaire et ont fourni de nouvelles informations sur les mécanismes sous-jacents de leurs effets cardio-protecteurs. / Increasing number of scientific evidence suggests the beneficial role of dietary anthocyanins, phytochemicals mainly present in berries and derived products, in cardiovascular health. These anthocyanin health benefits may be attributed to their effect on endothelial cells or platelets that represent the key players in the development of cardiovascular diseases (CVD). However, the exact molecular mechanisms underlying anthocyanin cardioprotective effects are not fully understood. The aim of this thesis was to investigate the effect of anthocyanins and their metabolites in vitro on endothelial and platelet function and identify the underlying mechanisms of their action using physiologically relevant conditions.Results from this thesis showed that the pretreatment of endothelial cells with physiologically relevant concentrations of circulating anthocyanins and their metabolites attenuated monocyte adhesion to activated endothelial cells as well as their transendothelial migration, which are the initial steps in the development of atherosclerosis that precede CVD. In agreement with these results, gene expression analysis revealed that the treatment of endothelial cells with these compounds modulated the expression of genes involved in regulation of cell-cell adhesion, actin cytoskeleton reorganisation, focal adhesion and leukocyte transmigration. Bioinformatics analyses of gene expression data allowed the identification of potential transcription factors involved in the observed nutrigenomic effects and cell signalling proteins regulating their activity.Molecular docking analyses further revealed cell signalling proteins to which these bioactives may bind to and potentially affect their activity and the activation of downstream signalling proteins and transcription factors, effects that were in agreement with the results of Western blot analyses. Anthocyanins and their metabolites also modulated the expression of microRNAs, especially those involved in regulation of endothelial cell permeability, contributing to the observed changes in endothelial cell function.In addition to their effects on endothelial cells, anthocyanins and their metabolites displayed the capacity to modulate platelet function by decreasing platelet activation and their aggregation with leukocytes, the processes that are important contributors to CVD development.In conclusion, results from this thesis revealed the positive effects of anthocyanins and their metabolites, at physiologically relevant concentrations, on endothelial and platelet function and provided new insights into the mechanisms underlying their cardioprotective effects.