Trinta e oito vacas leiteiras, 19 da raça Holandês e 19 da raça Girolando (½ e ¾), foram submetidas à elevadas temperaturas por restrição à sombra durante o período entre a ordenha da manhã e da tarde. Mensurações de temperatura retal, frequências respiratória e cardíaca e escore de ofegação, além de coletas de sangue, foram realizadas nos períodos pré ordenha. Produção de leite e características físico-químicas do mesmo foram acessadas. Durante os períodos de coleta se avaliou características ambientais com vistas a calcular um índice de temperatura e umidade (ITU). Primeiramente se buscou estabelecer diferenças em parâmetros fisiológicos, de leite e sangue de vacas com diferentes porcentagens de alelos oriundos da raça Holandesa no genoma (100, 75 e 50%) em função de aumentos no ITU. Animais puros Holandês apresentaram características que condizem com menor tolerância ao calor do que animais Girolando. Em um segundo momento se analisou o efeito do estresse térmico sobre a permeabilidade das junções firmes das células epiteliais da glândula mamária de vacas Holandês. Além disso, buscou-se perceber alterações na estabilidade do leite ao teste do álcool decorrentes de um possível aumento na permeabilidade de tais estruturas celulares. O parâmetro utilizado para aferir tal efeito foi o nível sanguíneo de lactose no plasma. Alterações lácteas foram percebidas em função de aumentos de ITU e se devem principalmente à reduções em produção de leite. Aumento nos parâmetros fisiológicos não influenciou a estabilidade do leite. Leite instável apresentou maior teor de lactose. Maior número de dias em lactação pode ser o responsável pela redução na estabilidade do leite. Percebeu-se relação inversamente proporcional entre permeabilidade das junções firmes e estabilidade do leite, porém o estado de estresse térmico, ao contrário do esperado, não apresentou influência nas células da glândula mamária. / Thirty-eight dairy cows, 19 Holstein and 19 Girolando (½ e ¾), were submitted to elevated temperatures due to shade deprivation between morning and evening milkings. Rectal temperature, heart and respiratory rates and panting score measurements, besides blood samples collection, were performed before each milking. Milk production and its physical-chemical characteristics were studied. Climatic variables were measured during data collection to calculate a temperature-humidity index (THI). Firstly, the study evaluated changes in physiological, blood and milk parameters according to the percentage of alleles derived from the Holstein breed (100, 75 and 50%) due to increases in THI. Pure Holstein cows presented characteristics that indicate lower heat tolerance than Girolando cows. Secondly, heat stress effects on mammary gland cells tight junctions permeability were evaluated in Holstein cows. Alterations in milk stability due to changes in permeability were also assessed. Plasma lactose was the parameter used to detect changes in tight junctions permeability. Modifications in milk characteristics were probably due to reduction in milk production. Increase in physiological parameters did not affect milk stability. Unstable milk samples presented higher lactose levels. Higher days in milk might be the main responsible for reductions in milk stability. There was an inversely proportional relation between tight junctions permeability and milk stability to the ethanol test, although heat stress, contradicting the expected, did not influenced mammary gland cells.

L’Insuffisance Rénale Chronique (IRC) résulte de la destruction progressive et irréversible des reins. Elle est associée à une rétention de toxines urémiques à l’origine des nombreuses complications de la maladie rénale chronique (cardiovasculaires, osseuses ou métaboliques). Nos travaux se sont focalisés sur l’impact de la dysfonction rénale et de l’urémie sur la fonction barrière de l’intestin et la motilité intestinale. Deux modèles d’IRC ont été implémentés : un modèle animal, chez la souris, par néphrectomie chimique (régime alimentaire enrichi en adénine) et un modèle cellulaire d’urémie en incubant des cellules coliques Caco-2 avec 10% de plasma de patients hémodialysés (HD). Le transit, la motilité, la perméabilité intestinale et la régulation des protéines des jonctions serrées ont été explorés. Les animaux urémiques présentent un transit gastro-intestinal ralenti et une perméabilité intestinale augmentée associés à une dérégulation de l’expression et de l’abondance des protéines des jonctions serrées dans le côlon (surexpression de la Claudine 1). La perméabilité de la monocouche cellulaire de Caco-2 incubées avec du plasma HD est significativement augmentée et est associée à une augmentation de l’expression et de l’abondance de la Claudine-1. En IRC, la motilité digestive et la fonction barrière de l’intestin sont significativement altérées. Ces dysfonctions pourraient contribuer à la production intestinale et l’absorption des toxines urémiques accélérant ainsi la progression du syndrome urémique et installant un véritable « cercle vicieux ». / Chronic Kidney Disease (CKD) result from a progressive kidney dysfunction. CKD is associated with an increase in the concentration of uremic toxins inducing CKD-associated metabolic alterations. Our work focused on the impact of renal dysfunction on gut permeability and gut motility. In vivo, CKD was induced in mice by chemical nephrectomy (adenine-enriched diet); In vitro, Caco-2 cells were incubated for 24h with 10% (v/v) of uremic plasma to mimic the uremic environment. Gastrointestinal transit time, gut motility, intestinal permeability and expression of tight junction proteins were explored. In vivo, kidney failure was associated with an impaired gastrointestinal transit and an increased intestinal permeability associated with a dysregulation of tight junction proteins (mainly claudine-1 overexpression). The Caco-2 monolayer permeability was significantly increased in cell monolayers incubated with uremic plasma. Claudine-1 expression and abundance was increased. In CKD, gut motility and gut permeability (e.g. « leaky » gut) are significantly impaired. Generally speaking, these gut dysfunctions could promote the production and the absorption of uremic toxins contributing to the uremic syndrom.

The purpose of the thesis is to explore the role of BMP signaling in developing vertebrate midbrain. BMP signaling plays important roles in various tissues and stages of neural development to regulate cell fate, proliferation, differentiation, morphogenesis and more. We observed that several major BMPs are expressed not only at the roof plate but also the floor plate of the midbrain. This has led us to ask the role of BMP signaling in dorsal and ventral midbrain patterning. Despite ventral experiments, we found that BMP signaling does not regulate ventral cell fate specification in the midbrain. Instead BMPs profoundly influence the shape and early morphogenesis of the midbrain neural plate as it closes into a neural tube. During neural tube closure, one of the early events occurring at the ventral midline is median hinge point (MHP) formation. Failure to form MHP leads to neural tube closure defects, the 2nd most common birth defects in humans. However, the molecular mechanisms underlying MHP formation are not well known. We found that the lowest BMP signaling occurs at the MHP during early neurulation and BMP blockade is necessary and sufficient for MHP formation. Interestingly, we also demonstrated that BMP blockade directs MHP formation by regulating the apicobasal polarity pathway and this regulation may be mediated by biochemical interactions between pSMAD5 and the apical protein, PAR3. Additionally, our time-lapse data suggest that BMP blockade slows cell cycle progression by increasing duration of G1 to S transition and S phase which leads cell nuclei stay at the basal location longer. This mimics basal nuclear migration seen at the MHP where low BMP signaling occurs. Thus, we conclude that BMP signaling regulates neural tube closure via the apicobasal polarity pathway and in a cell cycle dependent manner at the ventral midline. We observed that BMP signaling is necessary and sufficient for the dorsal cell fate specification in a context-dependent manner and ventral BMP signaling affects dorsal cell fates. Taken together, we propose the idea that BMP signaling has distinct roles in different contexts. BMPs regulate tissue morphogenesis in the ventral midbrain and dorsally cell fate specification. / text

Η ηπατική εγκεφαλοπάθεια είναι ένα σύνθετο νευροψυχιατρικό σύνδρομο το οποίο εκδηλώνεται κυρίως σε συνθήκες ηπατικής κίρρωσης. Διάφορες παθολογικές και τοξικές καταστάσεις μπορεί να επηρεάσουν την ηπατική λειτουργία σε τέτοια βαθμό ώστε να προκληθεί ηπατική εγκεφαλοπάθεια. Το οξειδωτικό στρές έχει ενεπλακεί σε διάφορες μελέτες στην παθογένεση της ηπατικής εγκεφαλοπάθειας. Επιπλέον, η ανάπτυξη αυξημένου οξειδωτικού στρές υπό την επίδραση αποφρακτικού ικτέρου έχει μετρηθεί σε διάφορα όργανα πειραματοζώων, συμπεριλαμβανομένου και του εγκεφάλου. Ο σκοπός της παρούσας μελέτης ήταν να ανιχνεύσει της αλλαγές στις αποφρακτικές συνδέσεις των τριχοειδικών αγγείων του εγκεφάλου που συσχετίζονται με την οκκλουδίνη. Για να το επιτύχουμε αυτό χρησιμοποιήσαμε ένα μοντέλο απολίνωσης του κοινού χοληδόχου πόρου (BDL) σε πειραματόζωα (αρουραίους). Στο πείραμα 1 η έκφραση της οκκλουδίνης εκτιμήθηκε μέσω της μεθόδου ποσοτικοποίησης κατά Westernblot. Σε αυτό το πείραμα χρησιμοποιήθηκαν πέντε (BDL) και πέντε ψευδώς χειρουργηθέντα πειραματόζωα (sham). Τα πειραματόζωα θανατώθηκαν δέκα ημέρες μετα το χειρουργείο. Στην κατά Westernblot ποσοτικοποίηση παρατηρήθηκε μεγάλη μείωση της ποσότητας της οκκλουδίνης στα BDL πειραματόζωα σε σχέση με τα sham. Στο πείραμα 2 χρησιμοποιήθηκαν εννέα BDL και εννέα sham πειραματόζωα. Τρία πειραματόζωα από τις δύο παραπάνω ομάδες θανατώθηκαν την πρώτη, την πέμπτη και τη δέκατη μετεγχειρητική ημέρα. Τα επίπεδα οκκουδίνης σε αυτά τα πειραματόζωα συσχετιστήκαν με τις τιμές τηςinvivo μέτρησης των ελευθέρων ριζών οξυγόνο. Τα αποτελέσματα ανέδειξαν ότι η τιμή της οκκλουδίνης στα BDL ζώα ήταν σημαντικά μειωμένη σε σχέση με τα sham όλες τις χρονικές στιγμές που έγιναν οι μετρήσεις, ενώ οι χαμηλότερες τιμές καταγράφηκαν στα πειραματόζωα που παρέμειναν υπό αποφρακτικό ίκτερο για δέκα ημέρες. Επιπλέον καταδείχθη ότι η χρονικά συσχετιζόμενη μείωση των επιπέδων της οκκλουδίνης στα ενδοθηλιακά κύτταρα του εγκεφάλου συσχετίζεται με τα αυξανόμενα επίπεδα ελευθέρων ριζών οξυγόνου της ημέρες μετά το χειρουργείο, φανερώνοντας τη σχέση μεταξύ αυτών των δύο φαινομένων. Συμπερασματικά, η παρούσα μελέτη πρώτη παραθέτει στοιχεία που προτείνουν την εμπλοκή της οκκλουδίνης στην παθοφυσιολογία της ηπατικής εγκεφαλοπάθειας σε συνθήκες εξωηπατικής χολόστασης. Αυτό γίνεται μέσω της μείωσης των επιπέδων τις οκκλουδίνης στις αποφρακτικές συνδέσεις των ενδοθηλιακών κυττάρων του εγκεφάλου υπο την επίδραση του χολοστατικού ικτέρου, η οποία οδηγεί σε άρση του αιματο-εγκεφαλικού φραγμού. / Hepatic encephalopathy in a complicate neuro-psychiatric syndrome which is common under hepatic cirrhosis. Various pathological and toxic lesions can deteriorate liver function in such way, so hepatic encephalopathy can be inflicted. Oxidative stress is involved in pathogenesis of hepatic encephalopathy in several protocols. Moreover the development of increased oxidative stress in the context of obstructive cholestasis has been proven in various rats' organs including the brain. The present study aimed to detect alterations of tight junction-associated occludin in rat brain capillaries. To accomplish that we have used a rats bile duct ligation experimental model (BDL). In experiment 1, occludin expression was evaluated by Western blot analysis. In this experiment were used five BDL and five sham rats. The experimental animals were sacrificed ten days after the operation. Western blot analysis revealed significant decrease of occlidins amount in BDL rats compared to the sham rats. In experiment 2, nine BDL and nine sham animals were used. Three animals from each group were sacrificed during the first, fifth and tenth post-operate day. The results of occludin level to these animals were associated with the in vivo superoxide radical production. The results indicated that occludin level in BDL animals, as opposed to sham-operated, was significantly reduced at every time point studied, being lowest in the rats remaining on BDL condition for 10 days. Moreover, it was demonstrated that the time-dependent reduction of occludin level in the brain endothelial was significantly correlated with the time dependent increase of brain superoxide radical level, implying a relationship between these two abnormalities. In conclusion, the evidence presented herein suggests for first time the implication of occludin in pathophysiology of hepatic encephalopathy under extra-hepatic cholestasis. This phenomenon occur due to the reduce of occludin level to cerebral endothelial cells’ tight junctions under cholestatic jaundice, which drives to lift of brain-blood barrier.

Ο αιματο-εγκεφαλικός φραγμός (ΑΕΦ) παίζει έναν καθοριστικό ρόλο στην ομοιόσταση του Κεντρικού Νευρικού Συστήματος. Οι στενοσύνδεσμοι (TJ) των ενδοθηλιακών κυττάρων των εγκεφαλικών τριχοειδών συνεισφέρουν σημαντικά στη λειτουργία του ΑΕΦ περιορίζοντας την παρακυτταρική διάχυση. Η οκλουδίνη, μια διαμεμβρανική πρωτεΐνη, αποτελεί μείζον συστατικό των TJ και παίζει σημαντικό ρόλο στη ρύθμιση της λειτουργίας τους. Το οξειδωτικό στρες αποτελεί κοινό χαρακτηριστικό πολλών νευροεκφυλιστικών και νευροφλεγμονωδών παθήσεων και η δυσλειτουργία των TJ με τη συνοδό διαταραχή του ΑΕΦ, συνδέονται με αυτό. Το αυξημένο οξειδωτικό φορτίο στα πλαίσια της αποφρακτικής χολόστασης έχει αποδειχθεί σε διάφορα όργανα αρουραίων μεταξύ των οποίων και ο εγκέφαλος. Στην παρούσα μελέτη χρησιμοποιήθηκε ένα πειραματικό μοντέλο αρουραίων με απολίνωση του χοληδόχου πόρου (BDL), για να εξεταστεί η επίδραση της χολόστασης στην εντόπιση της οκλουδίνης στο ενδοθήλιο εγκεφαλικών τριχοειδών με τη χρήση ηλεκτρονικού μικροσκοπίου. Αρσενικοί αρουραίοι Wistar χωρίστηκαν τυχαίως σε δύο ομάδες. Ομάδα Ι ψευδώς χειρουργημένοι αρουραίοι και ομάδα ΙΙ αρουραίοι που υπεβλήθησαν σε απολίνωση χοληδόχου πόρου (BDL) και οι δύο την ίδια ημέρα 0. Την 10η μετεγχειρητική ημέρα, όλα τα επιζήσαντα ζώα θυσιάστηκαν δια αποκεφαλισμού. Μετά από κατάλληλη προετοιμασία για σήμανση με ανοσοχρυσό της οκλουδίνης, δείγματα από το μετωπιαίο λοβό, το μεσεγκέφαλο και την παρεγκεφαλίδα από κάθε ομάδα παρατηρήθηκαν με ηλεκτρονικό μικροσκόπιο για διαφορές στην εντόπιση της οκλουδίνης σε σχέση με τη διενδοθηλιακή σχισμή. Τα αποτελέσματα ανέδειξαν μετακίνηση της οκλουδίνης μακριά από την περιοχή των στενοσυνδέσμων του τριχοειδικού ενδοθηλίου. Σημαντική αύξηση της απόστασης της οκλουδίνης από τη διενδοθηλιακή σχισμή παρατηρήθηκε στο μεσεγκέφαλο και στην παρεγκεφαλίδα και όχι στο μετωπιαίο λοβό, σε σχέση με την ομάδα ελέγχου (control). Τα συγκεκριμένα αποτελέσματα υπαινίσσονται μια εκλεκτική ως προς την περιοχή αποδιοργάνωση της οκλουδίνης σε απάντηση στην ηπατική δυσλειτουργία και ένα σημάδι δυσλειτουργίας των TJ με λογικό συνεπακόλουθο τη δυσλειτουργία και του ΑΕΦ. Προκαταρκτικά δεδομένα της χρήσης αντιοξειδωτικών παραγόντων, όπως η αλλοπουρινόλη, αφήνουν να διαφανεί ένας προστατευτικός ρόλος όσον αφορά τη μετατόπιση της οκλουδίνης σε BDL αρουραίους. Εν συντομία, η παρούσα πειραματική μελέτη παρουσιάζει την επίδραση του οξειδωτικού στρες, στην εντόπιση της πρωτεΐνης των στενοσυνδέσμων οκλουδίνη στο ενδοθήλιο των εγκεφαλικών τριχοειδών αγγείων σε αρουραίους με απολίνωση χοληδόχου πόρου. Για τη μελέτη χρησιμοποιήθηκαν τεχνικές ανοσοσήμανσης συνδυαζόμενες με ηλεκτρονική μικροσκοπία και παρουσιάστηκαν δεδομένα εκλεκτικής ως προς την περιοχή εγκεφαλικής δυσλειτουργίας στην ηπατική πάθηση με δυνητική συσχέτιση με τις κλινικές εκδηλώσεις της ηπατικής εγκεφαλοπάθειας. / The blood–brain barrier (BBB) plays a critical role in central nervous system homeostasis. Interendothelial tight junction (TJ) protein complexes of the brain microvasculature have a major contribution to the BBB function by limiting paracellular diffusion Occludin, a transmembrane protein, is a major component of the TJ which plays a significant role in its regulation. Oxidative stress is a major underlying cause of neurodegenerative and neuroinflammatory disorders while TJ dysfunction leading to BBB disruption is associated with it. The development of increased oxidative stress in the context of obstructive cholestasis has been proven in various rats' organs including the brain. The present study used a rat model with bile duct ligation, to examine the effect of cholestasis, to the localization of occludin in brain capillary endothelium by means of electronic microscopy. Male Wistar rats were randomly divided into Group I, rats subjected to sham operation, and Group II, rats subjected to bile duct ligation (BDL) on day 0 and on post-operative day 10 all surviving animals were sacrificed by instant decapitation. After specific treatment for immunogold labeling of occludin, samples from frontal cortex, midbrain and cerebellum from each group were observed for differences in occludin location in relation to the interendothelial cleft. The results demonstrated a dislocation of occludin away from the tight junction sites of brain endothelial cells. A significant increase of the occludin-interendothelial cleft distance was demonstrated in the midbrain and the cerebellum samples but not in the frontal cortex, compared to the control group samples. These findings imply a brain region selective derangement of occludin in response to liver disease and a sign of TJ impairment and thus, a speculated BBB dysfunction. Preliminary data of use of antioxidant agents, as allopurinol, imply a protective effect concerning the dislocation of occludin in BDL rats. In brief, this experimental study demonstrates the effect of oxidative stress, in the location of TJ protein occludin in brain capillary endothelium of BDL rats. The study used immunolabeling techniques combined with electron microscopy and presented data of region-specific brain abnormalities in liver disease with potential correlation with clinical manifestations of hepatic encephalopathy.

L'épilepsie du lobe temporal est fréquente et souvent pharmacorésistante. L'épileptogenèse est imputée à la mort neuronale, l'inflammation ou au déséquilibre de la neurotransmission. Récemment, la perméabilité vasculaire a été reconnue comme une cause de crises d'épilepsie. Dans un modèle d'épilepsie chronique, nous avons montré une angiogenèse associant vascularisation, surexpression de VEGF, perte de protéines des jonctions serrées et perméabilité de la BHE. L'observation des immunoglobulines G (IgGs) comme marqueurs de perméabilité vasculaire nous a permis de découvrir que les IgGs s'accumulent dans les neurones. Nous avons alors étudié le rôle de ces protéines dans l'épileptogenèse. Ensuite, afin de corréler la perméabilité de la BHE à l'épileptogenèse, nous avons étudié le kindling, un modèle dans lequel les crises sont induites mais pas spontanées. Nous n'avons observé aucun remaniement vasculaire, si ce n'est une dérégulation transitoire de deux protéines de jonctions serrées. La comparaison de ces deux modèles confirme la contribution de la dérégulation de la BHE dans la genèse des crises et la désigne comme une nouvelle cible thérapeutique. / Temporal lobe epilepsy is the most frequent form of pharmacoresistant epilepsies. Epileptogenesis is commonly imputed to neuronal loss, inflammation and an imbalance in neurotransmission. Now, vascular permeability was shown to participate in epileptic seizures generation. In a model of chronic epilepsy, we showed a neo-vascularisation associated with VEGF over expression, loss of tight junction proteins and BBB permeability. The use of immunoglobulins G (IgGs) as markers of permeability vascular allowed us to discover that the IgGs accumulates in neurones. We then studied the role of these proteins in epileptogenesis. Then, to correlate BBB permeability to epileptogenesis, we studied the kindling, a model in which seizures are induced but never spontaneous. We observed no vascular remodeling, except for a transient deregulation of tight junctions proteins. The comparison of these models confirms the contribution of BBB deregulation and points it as new therapeutic target.

Procyanidins (PCs) have been extensively investigated for their potential health protective activities, but the prospective bioactivities are limited by their poor bioavailability. The majority of the ingested dose remains unabsorbed and reaches the colon where extensive microbial metabolism occurs. The objectives of these studies are to better understand the roles and activities of PCs in the lower gastrointestinal tract. First, a new high-throughput Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry method was developed to efficiently analyze PCs and an extensive profile of their microbial metabolites. This method is sufficiently sensitive and effective in simultaneously extracting and measuring native PCs and their microbial metabolites in biological samples. Furthermore, administration of grape seed extract increased the expression of gut junction protein occludin and reduced levels of fecal calprotectin, which suggests an improvement of gut barrier integrity and a potential modulation of endotoxemia. Additionally, chronic supplementation of the diet with flavanols did not increase colonic tissue accumulation of PCs or their microbial metabolites over a 12 week feeding study. This was the first long-term study of its kind, and the results indicate that we still do not fully understand the outcome of ingested flavanols in the colon during chronic exposure rather than acute doses. Lastly, new understanding of the microbial metabolism of PCs in the colon has been reached by studying the colon as 4 segments, rather than as a complete unit as previous studies have done. Data show that a gradient is established along the length of the colon for both PCs and their metabolites, with PCs reaching highest concentrations within 3 h after ingestion, while metabolites reach maximum concentrations anywhere form 3-18 h after ingestion. Moreover, data indicate the progressive, step-wise degradation of PCs into small metabolites throughout the length of the colon. Overall, there is greater understanding of the colonic metabolism of dietary PCs derived from GSE and cocoa, the accumulation of these compounds, and their effect on gut permeability. Future work will build off of these novel studies, and will continue to advance the understanding of the health benefits of dietary PCs. / Ph. D.

La toxine thermostable d’E.coli (STb) est une cause de diarrhée chez l’homme et l’animal. STb se lie au sulfatide, son récepteur, puis s’internalise. Dans le cytoplasme, par une cascade d’événements, STb déclenche l’ouverture des canaux ioniques permettant la sécrétion des ions et la perte d’eau menant à la diarrhée. Les jonctions serrées forment une barrière physique intercellulaire dans les cellules épithéliales intestinales, contrôlant ainsi le flux paracellulaire des ions et de l’eau. Les jonctions serrées sont affectées par divers pathogènes et par leurs toxines. À ce jour, l’effet de STb sur les jonctions serrées n’a pas été étudié. L’étude entreprise visait à explorer l’effet de STb sur les jonctions serrées et la barrière épithéliale des cellules intestinales. Des cellules épithéliales intestinales du colon humain (T84) ont été traitées pendant 24h soit avec la toxine STb purifiée soit avec une souche d’E.coli exprimant STb. La résistance transépithéliale (TER), le flux de marqueurs paracellulaires et la microscopie confocale ont été utilisés pour analyser les effets de STb sur les jonctions serrées. Les monocouches traitées par la souche E.coli exprimant STb et la toxine STb purifiée ont manifesté une forte réduction de TER (p<0.0001) parallèlement à une augmentation significative de la perméabilité paracellulaire à l’Albumine de Sérum Bovin marqué avec l’IsoThioCyanate Fluoroscéine, BSA-FITC (p<0.0001) comparativement aux cellules non traitées et aux cellules traitées par une souche d’E.coli commensale non-toxinogène. L’augmentation de la perméabilité paracellulaire induite par STb a été associée à une dissolution générale et une condensation des fibres de stress centrales des filaments d’actine. Le réarrangement des filaments d’actine a été accompagné par une redistribution et une fragmentation des protéines des jonctions serrées dont l’occludine, la claudine-1 et la Zonula Occludens-1. Les mêmes modifications on été observées après l’intoxication des cellules T84 avec un octapeptide synthétique retrouvé dans la séquence de STb correspondant à une séquence consensus de la toxine ZOT de Vibrio cholerae, impliquée dans la réorganisation des jonctions serrées. Cet effet n’a pas été observé lorsque les cellules ont été traitées avec un octapeptide synthétique comportant les mêmes acides aminés mais distribués de façon aléatoire ou avec la toxine mutée (D30V). Nos résultats montrent pour la première fois que STb induit le dysfonctionnement de la barrière épithéliale intestinale en modifiant la distribution des protéines des jonctions serrées. Ces résultats ouvrent une nouvelle voie pour la compréhension de la pathogenèse de diarrhée causée par la toxine STb. / Escherichia coli heat-stable toxin (STb) causes diarrhea in Man and animals. STb binds to sulfatide, its receptor, followed by its internalization. Inside the cytoplasm, through a cascade of events, STb triggers the opening of ion channels allowing ion secretion and water loss leading to diarrhea. Tight junctions (TJs) are well known for controlling paracellular traffic of ions and water by forming a physical intercellular barrier in epithelial cells. Some bacterial toxinz are known to affect adversibly TJs. To date, the impact of STb on TJs has not been investigated. The present study aimed to explore the effect of STb on TJs and the barrier function in intestinal epithelial cells. Human colon intestinal epithelial cells (T84) were treated for 24h with either purified STb toxin or an E. coli strains expressing STb. TransEpithelial Resistance (TER), paracellular flux marker and confocal microscopy were used to analyze the effect of STb toxin on TJs. An E. coli strains expressing STb as well as purified STb caused a significant reduction of TER (p<0.0001) parallely to an increase in paracellular permeability to BSA-FITC (p<0.0001) compared to untreated cells or a commensal non toxinogenic E.coli strain. The increased paracellular permeability induced by STb was associated with a marked general dissolution and condensation of central F-actin stress fibers. F-actin disorganisation was accompanied by redistribution and fragmentation of occludin, claudin-1 and ZO-1 (Zonula Occludens-1) proteins. These changes were also observed following intoxication of T84 cells with an 8 amino acids peptide found in the STb sequence corresponding to a consensus sequence of Vibrio cholerae Zot toxin, shown to be involved in TJs disassembly. This effect was not observed with the scramble peptide and D30V mutant. Our findings suggest that STb induces epithelial barrier dysfunction by changes in tight junction proteins that could contribute to the observed diarrhea. These results provide new insight into the diarrhea pathogenesis caused by STb.

L'épilepsie est une maladie neurologique chronique caractérisée par des crises spontanées et récurrentes. Les crises sont générées par un déséquilibre dans le fonctionnement des neurotransmetteurs et des canaux ioniques qui contrôlent l'excitabilité. L'épileptogenèse est majoritairement associée à des pertes neuronales, une gliose, une inflammation plus ou moins importants. Un tiers des patients deviennent réfractaires. Récemment, plusieurs équipes ont montré une association entre les épilepsies focales pharmacorésistantes et la rupture de la barrière hémato-encéphalique (BHE). De plus, une implication du système immunitaire ainsi qu'une cause auto-immune de l'épilepsie ont été suggérées. Dans cette thèse, nous avons observé dans le tissu de patients atteints d'épilepsie pharmacorésistante du lobe temporal (ELT), des fuites d'Immunoglobulines G (IgG) dans le parenchyme et leur accumulation dans les neurones présentant des signes de neurodégénérescence. Le récepteur d'IgG de grande affinité FcyRI est surexprimé sur les cellules ayant une morphologie de type microglie/ macrophages, tandis que le récepteur de faible affinité FcyRIII et le récepteur inhibiteur FcγRII sont moins présents. Dans ce même tissu nous avons noté que les protéines du complément C3c et C5b9 sont exprimées. Ensuite, nous avons étudié si le modèle murin d'épilepsie focale induite par injection intra-amygdalienne de kaïnate reproduit la physiopathologie de l'ELT associée à une rupture de la BHE. ZO-1, la principale protéine des jonctions serrées, présente un marquage discontinu indiquant que la BHE a été affectée. Nous avons remarqué des fuites d'IgGs et d'albumine ainsi que leur accumulation dans le parenchyme coïncidant avec la survenue des crises. La présence d‘IgG dans l'épilepsie pourrait également avoir une cause auto-immune. Nous avons utilisé des puces à protéines pour identifier des antigènes qui induisent une réponse immunitaire, dans le plasma des patients atteints d'ELT, Nous avons sélectionné 19 auto-anticorps spécifiques qui peuvent servir de potentiels biomarqueurs diagnostiques L'ensemble de ces résultats suggère que les fuites d'IgG sont associées à une déficience neuronale, conduisant à des changements immunologiques dans le foyer épileptique qui participent à la pathogénèse de l'ELT. Nous pensons qu'une meilleure interprétation des profils de ces auto-anticorps pourrait offrir de nouvelles perspectives thérapeutiques. / Epilepsy is a chronic neurologic disorder characterized by recurrent unprovoked seizures. Seizures are generated by an imbalance in the functioning of neurotransmitters and ion channels that control excitability. Epileptogenesis is mostly associated with neuronal loss, gliosis, and inflammation more or less important. A third of patients become drug refractory. Recently, several teams have shown an association between drug-resistant focal epilepsy and disruption of the blood-brain barrier (BBB). In addition, a possible role of the immune system and an autoimmune nature in epilepsy has been suggested. In this thesis, in the tissue of patients with drug-resistant temporal lobe epilepsy (TLE), leakage of immunoglobulin G (IgG) into the parenchyma and IgG accumulation in neurons with attendant signs of neurodegeneration was observed. In addition, the high affinity IgG receptor, FcγRI was expressed on microglia/macrophage shaped cells. The expression of the low affinity IgG receptor, FcγRIII and the inhibitory IgG receptor, FcγRII was decreased. In the same tissue the complement proteins C3c and C5b9 were present on astrocyte/ microglia and macrophage/ microglia shaped cells respectively. Then, we evaluated whether the mouse model of focal epilepsy induced by intra-amygdala microinjection of kainic acid reproduced a pathophysiology of TLE associated with BBB impairment. ZO-1, the main tight junction protein presented discontinuous staining indicating that BBB was affected. Both IgG and albumin extravasations from blood vessels were noted and its parenchymal accumulation was concomitant with seizure occurrence. Another hypothesis of IgG presence in epilepsy incriminates an auto-immune cause. Protein microarray technology was used for identification in pooled plasma samples, of antigens that bind plasma antibody from TLE patients. 19 potential autoantibodies were identified as potential diagnostic biomarkers. Together, these observations suggest that IgG leakage is associated with neuronal impairment, leading to immunological changes in epileptic focus involved in the pathogenesis of TLE. A better interpretation of the profiles of these autoantibodies could offer new therapeutic and diagnostic perspectives.

INTRODUÇÃO: Isquemia e reperfusão (I/R) intestinal podem ocorrer em cirurgias vasculares e abdominais, trauma, choque, grandes queimados e transplante intestinal. O órgão funciona como barreira contra agressores externos, e uma vez lesionado, sofre aumento da permeabilidade, que permite a passagem de mediadores inflamatórios e bactérias, causando sepse, inflamação sistêmica e disfunção de múltiplos órgãos, que é a maior causa de morte em unidades de terapia intensiva cirúrgica. O diazóxido tem mecanismo de ação semelhante ao pré-condicionamento isquêmico, e demonstrou proteção em I/R de diversos órgãos. De forma semelhante, em cenário de isquemia e reperfusão intestinal, supomos que ele desempenharia função protetora no intestino, através do pré-condicionamento farmacológico, e em órgãos distantes, exercendo o pré-condicionamento remoto. OBJETIVOS: Avaliar os efeitos do diazóxido em intestino, fígado e coração de ratos submetidos a uma hora de isquemia e doze horas de reperfusão intestinal. MÉTODOS: 32 ratos machos Wistar divididos em três grupos, Sham (n=6); Salina (n=13) submetido a uma hora de isquemia e doze horas de reperfusão intestinal, tendo recebido soro fisiológico; Diazóxido (n=13) submetido a I/R e diazóxido. O modelo de I/R incluiu laparotomia mediana e clampeamento da artéria mesentérica superior. No soro, estudamos citocinas, AST, ALT, troponina e IFABP. Em amostras de intestino e fígado, quantificamos a expressão gênica de citocinas e COX-2. No intestino foi estudada ainda a expressão de proteínas ligadas a barreira intestinal (tight junctions): ZO-1, ocludina e JAM-A. Realizamos preparações histológicas em hematoxiina e eosina de intestino, fígado e coração. RESULTADOS: Evidenciamos redução de expressão de IL-6 intestinal, redução de IL-10 hepática, além de menor expressão de COX-2 intestinal e de ZO-1. IL-6 tem níveis associados a dano da barreira intestinal, assim como COX-2. A menor expressão de ZO-1 indica menor esforço de reparação, proporcional ao grau de lesão em modelos não letais de dano tecidual. CONCLUSÃO: O diazóxido exerce efeito protetor sobre o intestino de ratos após uma hora de isquemia e doze horas de reperfusão, porém não foi possível demonstrar efeito protetor sobre fígado ou coração / INTRODUCTION: Intestinal ischemia and reperfusion can occur in great vascular and abdominal surgeries, trauma, shock, great burns and intestinal transplantation. Since the organ works as a barrier against external threats, and once damaged, permeability increases, which permits passage of bacteria and inflammatory mediators, causing sepsis, systemic inflammation and multiple organ dysfunction, the greatest death cause in surgical intensive care units. Diazoxide has similar mechanisms to ischemic preconditioning, and proved benefit during I/R in several tissues. Similarly, in an intestinal ischemia-reperfusion situation, we suppose it can protect intestine with pharmacological preconditioning, and remote organs, with remote preconditioning. OBJECTIVE: To evaluate diazoxide effects over intestine, liver and heart of rats submitted to one-hour ischemia and twelve-hour reperfusion of intestine. METHODS: 32 male Wistar rats divided in three groups, Sham (n=6); Saline (n=13) submitted to one hour of intestinal ischemia and 12 hours of reperfusion and 0.9% saline; Diazoxide (n=13), submitted I/R and diazoxide. I/R model included median laparotomy and superior mesenteric artery clamping. In blood, we studied cytokines, TGO, TGP, troponin and IFABP. In intestine and liver, we quantified genic expression. Of cytokines and COX-2. In intestine, we also studied expression of tight junctions proteins. Also, histologic analysis in hematoxilin-eosin for intestine, liver and heart. RESULTS: We found lower expression of intestinal IL-6, hepatic IL-10, and lower levels of intestinal COX-2 and ZO-1. IL-6 high levels are associated with intestinal barrier lesion, as for COX-2. Lower levels of ZO-1 correlate with minor repair effort, proportional to lesion grade in non-letal models of damage. CONCLUSION: Diazoxide exerts protective effect over intestine of rats submitted to one hour of ischemia and twelve hours of intestinal reperfusion, but no effect was demonstrated over liver and heart