Les microglies, les cellules de l’immunité innée, résidentes du cerveau, sont impliquées dans la réponse inflammatoire cérébrale et le modelage des réseaux neuronaux au cours du développement. La perturbation de leurs activités par des stimuli environnementaux pouvant conduire à des altérations psychopathologiques, dans cette thèse, nous avons étudié le rôle des microglies dans les effets neurobiologiques et comportementaux d’un stimulus inflammatoire. Les travaux précédents ont révélé que l’administration de lipopolysaccharide (LPS), une endotoxine bactérienne, provoque des comportements de type dépressifs. Le rôle des microglies dans ces altérations a fait l’objet de la première étude de cette thèse (Chapitre 2). Afin de dépléter les microglies du cerveau, des souris adultes ont reçu par voie d’administration intra-hippocampique des liposomes contenant du clodronate, provoquant ainsi l’apoptose des microglies phagocytaires. L’administration de LPS active dans l’hippocampe la synthèse de cytokines pro-inflammatoires [interleukine (IL)-1b et facteur de nécrose tumorale (TNF)-a] et anti-inflammatoires (IL-10), et de l'indoleamine 2,3-dioxygénase, une enzyme impliquée dans le métabolisme du tryptophane aux activités pro-dépressives. La déplétion des microglies phagocytaires atténue les effets du LPS, à l’exception de l’IL-1b, dont l’expression est exacerbée. De plus, l’administration de clodronate prévient les effets du LPS sur les comportements de type dépressif. Dans leur ensemble, ces résultats ont révélé que les microglies phagocytaires sont impliquées dans les effets inflammatoires et comportementaux de type dépressif induits par le LPS. Nous avons ensuite étudié le rôle des microglies dans les effets comportementaux d’une inflammation maternelle précoce provoquée lors de la colonisation du cerveau fœtal par les microglies (Chapitres 3 & 4). Ainsi, nous avons administré au jour gestationnel (JG)9.5 du LPS à des souris gestantes et évalué la trajectoire développementale pré- et post-natale des microglies et du comportement de la progéniture (Chapitre 3). L’administration de LPS à JG9.5 provoque une réduction du pourcentage représenté par les microglies matures aux JG14.5 et 18.5 et des déficits comportementaux persistants à l’âge adulte avec un dimorphisme sexuel prononcé. Nous avons alors recherché à identifier les mécanismes moléculaires impliqués dans les effets du LPS administré à JG9.5, en étudiant la piste de l’action des cytokines inflammatoires (Chapitre 4). Pour cela, nous nous sommes focalisé sur l’IL-1b, la cytokine inflammatoire effectrice principale de l’activité microgliale. L’expression de l'IL-1b et des cytokines associées (IL-6, TNFa et IL-10) augmente dans le plasma maternel, le placenta et le cerveau fœtal, 2 et 4 heures après l’administration de LPS. Ces changements sont accompagnés d'un phénotype microglial immature à JG18.5 et d’une réduction de la population microgliale totale au jour postnatal (JPN)9. À l’âge adulte (JPN65), nous avons observé une modification morphologique de la microglie dans plusieurs structures cérébrales. Enfin, les souris adultes, prénatalement traitées au LPS, développent des altérations des comportements de type sociaux et des comportements répétitifs. Les altérations du nombre de microglies induites par le LPS sont corrélées aux troubles comportementaux, et ce, de façon spécifique en fonction du sexe des souris. Enfin, la co-administration de l'antagoniste du récepteur de l'IL-1 et de LPS chez les femelles gestantes au JG9.5 réduit, voire prévient les effets inflammatoires et comportementaux du LPS. [...] / Recent research on microglia has uncovered a multitude of activities that extends the role of these cells well beyond their traditional function as immune sentinels. The most prominent of these newly described activities is an intricate role in neuronal network remodeling notably upon environmental challenge or during brain development, the disruption of which can result in long lasting consequences relevant to several psychopathologies. We sought, in the current thesis, to identify some of the mechanisms involved. Our initial approach was to target the immune function of microglia, based on our previous findings linking systemic immunogenic challenge with lipopolysaccharide (LPS) in mice with the development of despair-like behavior/depression. Here, we sought to identify immune mediators activated in microglia following a single systemic challenge with LPS (Chapter 2). These studies were conducted in adult mice in which phagocytic microglia were depleted using a single injection of liposomal clodronate in the CA3 region of the hippocampus. LPS challenge significantly upregulated the expression of both pro-inflammatory [interleukin (IL)-1b and tumor necrosis factor (TNF)-a] and anti-inflammatory (IL-10) cytokines compared to saline treated animals. In addition, LPS highly increased the expression of indoleamine 2,3-dioxygenase (IDO), an important rate limiting enzyme for metabolizing tryptophan in the brain and an established indicator of the activation of this depression mediating pathway. Clodronate-mediated depletion attenuated all of these effects apart from IL-1b expression which was further exacerbated. Behavioral assessment of the mice demonstrated a significant LPS-induced increase of immobility in the forced swim test (FST), which was prevented by clodronate. This experimental approach provided a snapshot of the role of inflammation in the development of brain dysfunction mediated by microglia. In subsequent studies (chapter 3 & 4), and in order to perform a more comprehensive, longer-term investigation of microglia activity in neurodevelopment, we utilized a prenatal infection model using LPS to activate maternal immunity at a relatively early [Gestational Day (GD)9.5] time point when microglia colonize the fetal brain to assess the impact on microglial population during development and the subsequent behavior of the progeny (Chapter 3). The results demonstrated LPS reduced the percentage of mature microglial population at GD14.5 and GD18.5 representing mid to late gestation. In addition, prenatal LPS had a significant effect on the offspring’s neonatal as well as adult behavior, with a clear divergence along sex lines in adulthood. In the final study (Chapter 4), we sought to investigate the mechanisms underlying the changes we noted in microglial development and the sexually dimorphic behavioral deficits. For this, we focused on the role played by pro-inflammatory cytokines, particularly IL-1b which represents the main effector of microglial activation following infection or injury. Detailed analysis of the expression of IL-1b and other related cytokines (IL-6, TNF-a and IL-10) revealed an increased expression of these mediators in maternal plasma, placenta and fetal brain, 2 and 4 hours after the prenatal LPS treatment. These changes were accompanied with a decreased percentage of mature microglia in the brain of embryos at GD18.5 and of total microglia population at post-natal day (PND)9. In the adult offspring (PND65), we detected an increased density and altered microglial morphology in specific higher-order structures implicated in complex behaviors, as well as altered social preference and memory and increased repetitive actions. [...]

Submitted by Alexandre Sousa (alexandre.sousa@incqs.fiocruz.br) on 2015-03-09T12:49:51Z No. of bitstreams: 1 Mestrado_Esdras.pdf: 1111555 bytes, checksum: 8a10fff93847e992405f9550e8c62e0c (MD5) / Approved for entry into archive by Alexandre Sousa (alexandre.sousa@incqs.fiocruz.br) on 2015-03-09T12:50:09Z (GMT) No. of bitstreams: 1 Mestrado_Esdras.pdf: 1111555 bytes, checksum: 8a10fff93847e992405f9550e8c62e0c (MD5) / Approved for entry into archive by Alexandre Sousa (alexandre.sousa@incqs.fiocruz.br) on 2015-03-09T12:50:22Z (GMT) No. of bitstreams: 1 Mestrado_Esdras.pdf: 1111555 bytes, checksum: 8a10fff93847e992405f9550e8c62e0c (MD5) / Made available in DSpace on 2015-03-09T12:50:22Z (GMT). No. of bitstreams: 1 Mestrado_Esdras.pdf: 1111555 bytes, checksum: 8a10fff93847e992405f9550e8c62e0c (MD5) Previous issue date: 2014 / Fundação Oswaldo Cruz. Instituto Nacional de Controle de Qualidade em Saúde. / A radiação ultravioleta pode gerar vários efeitos nocivos à saúde humana, dentre eles danos no DNA, catarata, melanoma, dentre outras malignidades. Em função desses efeitos existe a necessidade de proteger a saúde da população dos raios ultravioletas (UV) utilizando-se de cosméticos que atuem como filtros contra essa radiação. O mercado consumidor apresenta uma variedade desses filtros solares. O octil metoxi cinamato (OMC) é um deles, muito empregado em produtos cosméticos como xampus, batons, sabonetes líquidos entre outros, produtos esses que são comercializados no Brasil. Diversos estudos têm apontado a presença dele em fluidos biológicos como sangue, urina e leite materno humano, assim como sua presença na água e em tecidos de diversos animais. A literatura tem o demonstrado como potencial desregulador da tireóide. Em humanos, alterações na função tireoideana durante períodos críticos do desenvolvimento podem gerar comprometimentos como hiperatividade, problemas motores e déficit de memória e aprendizagem. Por isso,o presente trabalho visa avaliar se a exposição ao OMC no período lactacional é capaz de induzir a desregulação tireoideana e alterações neurocomportamentais em ratos. Para alcançar tal objetivo ratos de ambos os sexos foram sexados e divididos nos dois gruposde exposição no dia pós-natal1 (PN), óleo de milho ou OMC. Os roedores receberam diariamente uma dose deOMC na concentração de 500 mg/kg/dia do PN5 ao PN22. No PN23, dia do desmame, metade dos animais foi eutanasiada, o sangue coletado para dosagem de tiroxina total (T4) e coleta do timo e baço. Aqueles que não foram eutanasiados seguiram até a vida adulta para serem submetidos a testes comportamentais. A exposição dos roedores ao OMC durante o período lactacional reduziuT4 total. Além disso, este grupoapresentou menor ganho de peso no período lactacional que foi revertido após o desmamebem como atraso na abertura de olhos. A análise do timo e baçomostrou diminuição do peso relativo, sem alterar o número de células. No labirinto em cruz elevado o número de entradas nos braços abertos foi significativamente maior. No campo vazado observamos que os animais OMC deslocaram-se significativamente mais. Não observamos alterações cognitivas no labirinto aquático de Morris. Portanto o filtro solar em questão causou várias alterações nodesenvolvimento, sistema imune, comportamento e hormônio tireoideano. Tais alterações servem de alerta parao uso de OMC em infantes expostos em períodos críticos do desenvolvimento. / The ultraviolet radiation may induce several adverse effects for human health, as well damage in DNA, cataract, immunosupression, melanoma and others malignancies. Because these effects is necessary to protect the population health of ultravioleta (UV) using cosmetics that act like filters against this radiation. The consumption market show a variety of these sunscreens. The octyl methoxy cinnamate (OMC) is one these, at organic sunscreens that protects against UV radiation widely used in personal care products such as sunscreens, shampoos, lipstick, liquid soap and others products that are commercialy avaiable. The problem is that studies display the OMC presence in biologics fluids such as blood, urine and human breast milk beyond presence in water and all food chain. This have worried researchers in whole world because several works shows that OMC is a potencial disruptor the thyroid axis. It’swellknew that disturbances in the thyroidaxisduring critical period of development may cause hyperactivity, motor disorders and déficit in memory and learning. This present work a into evaluate if the thyroid disruptor induced by administration of OMC in rats in lactacional period cause neurobehavioral alterations. In this context, pups were separated and divided in two exposition groups in post natal day 1 (PN), corn oil or OMC. The rodents received daily one dose of OMC at 500 mg/kg/day at PN5 until PN22. In PN23, day of weaning, part of animals were euthanasied for to collect of blood for total T4 dosage and organs collets such as brain, pituitary, hypothalamo, thyroid, liver, thymus and spleen. Those that don’t were euthanasied lead until adult life for submited behavioral tests. The exposition of rodents OMC during lactacional period decreasedtotal T4. Moreover, this group display decresead weight gain in lactacional period that were reverted after weaning. The OMC administration delayed total open eyes of animals. Plus this were observed decresead in relative weight of thymus and spleen without change the total number of cells this organs. And in behavioral tests, the OMC rodents visited more times the open arms in elevated plus maze, deslocated more in hole board and no exibited cognitives changes in Morris water maze. This alterations alert for the use of OMC in infants exposure in criticals periods of neurodevelopment.