Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 161-184).

L’allergie de contact est une pathologie touchant de 15 à 20 % de la population occidentale. A l’heure actuelle il n’existe aucun traitement, la seule façon efficace de prévention étant l’éviction totale des allergènes. Les tests de sensibilisation de nouvelles molécules avant leur mise sur le marché ont été réalisés sur l’animal jusqu’à l’interdiction dans le 7ème amendement à la directive Européenne concernant l’industrie cosmétique. Dans ce contexte il est primordial de développer des méthodes alternatives. Ce travail de thèse propose d’analyser la problématique de l’allergie de contact en allant de la molécule au tissu pour les allergènes réagissant par voie radicalaire :In chemico : étude de la réactivité des hydroperoxydes allyliques vis-à-vis des acides aminés par la RMNIn situ : études de radicaux issus de ces composés sur des épidermes humains reconstitués par RPEIn cellulo : étude du stress oxydant sur les cellules dendritiques et la voie de signalisation Keap1/Nrf2/ARE. / Allergic contact dermatitis is a pathology affecting 15 to 20% of the Western population. Until now no treatment exists, the prevention is the eviction of allergens. In the past, tests concerning new molecules for the market were tested on animals until the prohibition in the 7th amendment of the European directive concerning the cosmetics industry. In this context it is essential to develop alternative methods to assess the allergenic potential of chemicals.This manuscript proposes to analyze the problem of the allergic contact dermatitis from the molecule to the tissue for allergens reacting through radical mechanisms:In chemico: study of the reactivity profile of allylic hydroperoxides toward amino acids by NMRIn situ: radical intermediates formation on reconstructed human epidermis from allylic hydroperoxides by EPR In cellulo: study of the oxidative stress from allylic hydroperoxides on dendritic cells trough the Keap1/Nrf2/ARE sensor pathway.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Recent data from the literature have suggested that some Krebs cycle intermediates could act as potent antioxidant agents, both in vitro and in vivo, against a variety of pro-oxidant agents. However, the mechanism(s) involved in the antioxidant effect of Krebs cycle intermediates are not fully understood. Additionally, there are scarce data in the literature taking into account the in vitro effect of Krebs cycle intermediates during oxidative stress conditions. Thus, the aim of this study was to determine the effect of some Krebs cycle intermediates on lipid peroxidation induced in vitro by different pro-oxidant agents, and the mechanism(s) by which they act. Firstly, we investigated the effect and the mechanism(s) by which malonate and quinolinic acid modulate the thiobarbituric acid- reactive species (TBARS) production in vitro, using rat brain S1 preparations (Article 1). The present results showed that the malonate-induced TBARS production was not changed by potassium cyanide or MK-801. However, the pro-oxidant effect of quinolinic acid was significantly prevented by MK-801. In addition we found that malonate was able to form complexes with iron ions (Fe2+), but these complexes were not able to interfere with in vitro deoxyribose degradation assays. Based on the results presented, we conclude that malonate pro-oxidant activity in vitro seems to be independent of the NMDA receptors activity. Additionally, we suggest that the malonate effect, in these conditions, is due to its ability to form complexes with iron ions, thus modulating an adequate ratio Fe2+/Fe3+ that could cause an increase in free radicals generation. In contrast, the quinolinic acid effect seems to be dependent of the NMDA receptors activation. However, we can not rule out the involvement of iron ions in quinolinic acid toxicity under our assay conditions. An other objective of this study was to investigate the effect of some Krebs cycle intermediates on quinolinic acid- or iron (Fe2+)-induced TBARS production in the rat brain S1 preparations, and the mechanism(s) by which they act (Article 2). The results showed that oxaloacetate, citrate, succinate, and malate were able to significantly prevent both basal and quinolinic acid- or iron-induced TBARS production. However, α-ketoglutarate induced per se a significant increase in basal TBARS production. The addition of potassium cyanide or the heat-treatment of S1 at 100ºC during 10 min completely abolished the antioxidant succinate activity, without change the effect of other Krebs cycle intermediates studied. Except for succinate, all intermediates used in this study were able to form complexes with iron (Fe2+) ions, however only oxaloacetate and α-ketoglutarate significantly prevented deoxyribose degradation induced by hydrogen peroxide. Based on the results presented, we concluded that oxaloacetate, malate, succinate, and citrate could act as antioxidants under basal, and under quinolinic acid- or iron- induced TBARS production, whereas α-ketoglutarate act as a pro-oxidant agent per se. The mechanism(s) by which citrate, malate, and oxaloacetate acts seems to be related to their ability to form complexes with iron (Fe2+) ions, thus modulating the iron redox cycle. In contrast, the succinate antioxidant effect seems to be dependent of the succinate dehydrogenase (SDH) activity. / Dados recentes na literatura têm relatado que alguns intermediários do ciclo de Krebs podem agir como potentes antioxidantes, tanto in vitro, quanto in vivo, em diversos sistemas pró-oxidantes. Porém, o(s) mecanismo(s) através dos qual(is) os intermediários do ciclo de Krebs exercem suas atividades antioxidantes não são completamente entendidas. Considerando a escassez de dados in vitro na literatura a respeito do efeito desses intermediários durante situações de estresse oxidativo, o presente trabalho tem como objetivo determinar o efeito de intermediários do ciclo de Krebs sob a peroxidação lipídica induzida por diferentes agentes pró-oxidantes in vitro, bem como investigar o(s) mecanismo(s) de ação dos mesmos. Primeiramente investigamos o efeito e o(s) mecanismo(s) pelo(s) qual(is) o malonato e o ácido quinolínico modulam a produção de espécies reativas ao ácido tiobarbitúrico (TBARS) em S1 de cérebro de ratos, in vitro (artigo 1). Os resultados obtidos mostraram um aumento na produção de TBARS induzido pelo malonato, o qual não foi modificado pela adição de cianeto de potássio, nem pelo MK-801. Por outro lado, o efeito pró-oxidante do ácido quinolínico foi significativamente prevenido pelo MK-801. Observamos ainda que o malonato foi capaz de formar complexos com íons ferrosos e que esses complexos não foram capazes de interferir nos ensaios da degradação da desoxirribose in vitro. Portanto, com base nos resultados encontrados, concluímos que o efeito pró-oxidante do malonato in vitro parece ser independente da atividade dos receptores NMDA. Os resultados sugerem que o efeito do malonato nessas condições deve-se principalmente a sua capacidade de interagir com íons ferro, modulando uma razão Fe2+/Fe3+ que favorece a geração de radicais livres. Por outro lado, o efeito do ácido quinolínico parece ser devido à ativação dos receptores NMDA. Porém, não podemos excluir a participação dos íons ferro para a toxicidade do mesmo nessas condições. Outro foco deste estudo foi investigar o efeito de alguns intermediários do ciclo de Krebs na produção de TBARS induzida por ácido quinolínico ou ferro em S1 de cérebro de ratos in vitro, bem como investigar o(s) mecanismo(s) de ação dos mesmos (artigo 2). Os resultados mostraram que o oxaloacetato, o citrato, o sucinato e o malato foram capazes de reduzir significativamente a produção de TBARS basal, bem como a induzida por ácido quinolínico ou ferro. Por outro lado, o α-cetoglutarato foi capaz de induzir per se um significativo aumento na produção de TBARS. A adição de cianeto de potássio, bem como o pré-tratamento do S1 por 10 min a 100ºC aboliram completamente o efeito antioxidante do sucinato, sem interferir significativamente no efeito dos demais intermediários estudados. Todos os intermediários estudados, exceto o sucinato, foram capazes de quelar íons ferro, porém somente o oxaloacetato e o α-cetoglutarato foram capazes de prevenir a degradação da desoxirribose induzida por peróxido de hidrogênio. Com base nos resultados obtidos, podemos concluir que o oxaloacetato, o malato o sucinato e o citrato agem como antioxidantes sob condições basais ou em presença do ácido quinolínico ou ferro, enquanto que o α-cetoglutarato age como um agente pró-oxidante per se. O mecanismo pelo qual o citrato, o malato e o oxaloacetato exercem seus efeitos antioxidantes parece ser devido à capacidade desses em interagir com íons ferro modulando o ciclo redox desse. Por outro lado, o efeito do sucinato parece ser devido à atividade da enzima succinato desidrogenase (SDH).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Previous data from the literature have shown that some Krebs cycle intermediates could act as antioxidant in several models, both in vitro and in vivo. However, the mechanism(s) involved in the antioxidant effect of Krebs cycle intermediates are not fully understood. Additionally, there are scarce data in the literature taking into account the in vitro effect of Krebs cycle intermediates during oxidative stress conditions. Thus, the aim of this study was to determine the effect of some Krebs cycle intermediates on lipid peroxidation induced in vitro by different pro-oxidant agents, and the mechanism(s) by which they act. Furthermore, it was necessary elucidate the mechanisms by which the different pro-oxidants acts under in vitro conditions. The present results showed that the malonate-induced TBARS production was not changed by potassium cyanide or MK-801. However, the pro-oxidant effect of quinolinic acid was significantly prevented by MK-801. In addition we found that both malonate and oxalate were able to form complexes with iron ions (Fe2+). Based on the presented results, we conclude that malonate pro-oxidant activity in vitro seems to be independent of the secondary excitotoxicity via indirect NMDA receptors activation. Additionally, we suggest that both the malonate and oxalate effect, in these experimental conditions, is due to its ability to form complexes with iron ions, thus modulating an adequate ratio Fe2+/Fe3+ that could cause an increase in free radicals generation. In contrast, the quinolinic acid effect seems to be dependent of the NMDA receptors activation. However, we can not rule out the involvement of iron ions in quinolinic acid toxicity under our assay conditions. Another objective of this study was to investigate the effect of some Krebs cycle intermediates against either basal or induced TBARS production, using rat brain S1 preparations and the mechanism(s) by which they act. The results showed that oxaloacetate, citrate, succinate, and malate were able to significantly prevent both basal and quinolinic acid-, iron- or malonate-induced TBARS production. On the other hand, fumarate prevented only malonate-induced TBARS production, without effect under basal conditions. However, α-ketoglutarate induced per se a significant increase in basal TBARS production. The antioxidant activity of fumarate and succinate were completely abolished when S1 was submitted to heat-treatment at 100ºC during 10 min. Likewise, potassium cyanide completely abolished the antioxidant effect of succinate. The effect of other Krebs cycle intermediates studied was unchanged with respect to heat-treatment, or cyanide. Except for succinate and fumarate, all intermediates used in this study were able to form complexes with iron (Fe2+) ions, however only oxaloacetate and α-ketoglutarate significantly prevented deoxyribose degradation induced by hydrogen peroxide. Based on the results presented, we concluded that oxaloacetate, malate, succinate, fumarate and citrate could act as antioxidants under such conditions, whereas α-ketoglutarate acts as a pro-oxidant agent per se. The mechanism(s) by which citrate, malate, and oxaloacetate acts seems to be related to their ability to form complexes with iron (Fe2+) ions, thus modulating the iron redox cycle. In contrast, the succinate and fumarate antioxidant effect seems to be dependent of the some enzymatic system. / Dados prévios da literatura têm mostrado que alguns intermediários do ciclo de Krebs podem agir como antioxidantes em diversos modelos, tanto in vitro, quanto in vivo. Porém, o(s) mecanismo(s) através dos qual(is) esses intermediários exercem suas atividades antioxidantes não são completamente entendidas. Considerando a escassez de dados na literatura a respeito do efeito dos intermediários do ciclo de Krebs durante situações de estresse oxidativo, o presente trabalho teve por objetivo determinar o efeito desses sob a peroxidação lipídica induzida por diferentes agentes pró-oxidantes in vitro, bem como investigar o(s) mecanismo(s) de ação dos mesmos. Além disso, faz-se necessário caracterizar o(s) mecanismos(s) pelo(s) qual(is) os diferentes pró-oxidantes agem nos sistemas in vitro. Os resultados dessa tese mostraram que a atividade pró-oxidante in vitro do malonato não foi modificada pela adição de cianeto de potássio, nem pelo MK-801. Por outro lado, o efeito pró-oxidante do ácido quinolínico foi significativamente prevenido pelo MK-801. Observamos ainda que o malonato, e também o oxalato foram capazes de formar complexos com íons ferrosos. Portanto, com base nos resultados encontrados, concluímos que o efeito pró-oxidante do malonato in vitro parece ser independente da excitotoxicidade secundária, conseqüência da ativação indireta dos receptores NMDA. Os resultados sugerem que o efeito do malonato e do oxalato nessas condições experimentais deve-se principalmente a sua capacidade de interagir com íons ferro, modulando uma razão Fe2+/Fe3+ que favorece a geração de radicais livres. Por outro lado, o efeito do ácido quinolínico parece ser devido à ativação dos receptores NMDA. Porém, não podemos excluir a participação dos íons ferro para a toxicidade do mesmo nessas condições. Outro foco deste estudo foi investigar o efeito de alguns intermediários do ciclo de Krebs na produção de TBARS basal ou induzida por diferentes pró-oxidantes em S1 de cérebro de ratos in vitro, bem como investigar o(s) mecanismo(s) de ação dos mesmos. Os resultados mostraram que o oxaloacetato, o citrato, o sucinato e o malato foram capazes de reduzir significativamente a produção de TBARS basal, bem como a induzida por ácido quinolínico, ferro ou malonato. O fumarato, por sua vez, teve efeito antioxidante somente sobre a produção de TBARS induzida. Por outro lado, o α-cetoglutarato foi capaz de induzir per se um significativo aumento na produção de TBARS. O efeito antioxidante do fumarato e do sucinato foi completamente abolido quando o S1 foi submetido a um prétratamento por 10 min a 100ºC, enquanto que o efeito dos demais intermediários permaneceu inalterado. Da mesma forma, a adição de cianeto de potássio aboliu completamente o efeito antioxidante do sucinato sem interferir significativamente no efeito dos demais intermediários estudados. Todos os intermediários estudados, exceto o sucinato e o fumarato, foram capazes de quelar íons ferro, porém somente o oxaloacetato e o α- cetoglutarato foram capazes de prevenir a degradação da desoxirribose induzida por peróxido de hidrogênio. Com base nos resultados obtidos, podemos concluir que o oxaloacetato, o malato, o sucinato, o fumarato e o citrato agem como antioxidantes sob determinadas condições, enquanto que o α-cetoglutarato age como um agente pró-oxidante per se. O mecanismo pelo qual o citrato, o malato e o oxaloacetato exercem seus efeitos antioxidantes parece ser devido à capacidade desses em interagir com íons ferro modulando o ciclo redox desse. Por outro lado, o efeito do sucinato e do fumarato parece ser devido a alguma atividade enzimática.

L'objectif de la thèse est de mieux comprendre les mécanismes de dégradation photocatalytique se produisant sous air ou sous azote en étudiant la disparition, la minéralisation et les produits intermédiaires d'une molécule simple l'acide acétique. Les réactions sont réalisées sous ces deux atmosphères afin de se placer dans des conditions de dépollution ou de génération d'énergie. L'étude est réalisée en phase gazeuse et sous flux en prenant comme molécule organique une molécule simple l'acide acétique. Dans un premier temps nous avons étudié la dégradation de l'acide acétique en utilisant le photocatalyseur de référence, TiO2 P25. Quel que soit le flux gazeux de réaction, air ou N2, nous avons montré que la réaction de décarboxylation est la première étape de la disparition de l'acide acétique. Cependant, le sort du groupe méthyle dépend du gaz porteur et du débit molaire (en d'autres termes de la concentration du polluant en phase gazeuse). Le mécanisme de dégradation se produisant à la surface du photocatalyseur est alors représenté pour expliquer l'importance de ce mécanisme comparé à celui faisant intervenir les radicaux hydroxyles. La schématisation du mécanisme inclut la régénération du photocatalyseur et la formation possible de H2O2, lequel a été observé dans la littérature. Il est également noté que la sélectivité d'éthane observé sous flux d'air augmente avec la concentration en polluant et correspond à la réaction de deux radicaux méthyl. Comme précédemment la formation de ce composé en surface du TiO2 est proposée. L'étude des produits de dégradation de l'acide acétique marqué par du carbone 13 sur le groupe carbonyle (CH313COOH) suggère que l'acétone et l'acétaldéhyde ne proviennent pas de la réduction du groupe carboxylique. Dans une seconde étape l'impact du flux photonique et de l'humidité en présence de TiO2 P25 et l'effet de différents TiO2 commerciaux sur la conversion et plus particulièrement la distribution des produits intermédiaires ont été étudiés. La comparaison de l'efficacité de différents TiO2 commerciaux a été discutée en considérant la présence de phase rutile, la nature des espèces actives, la surface spécifique de TiO2, le nombre de groupes OH à la surface des catalyseurs, la présence d'impuretés et la porosité des matériaux. Notre étude s'est ensuite focalisée sur la détermination de l'efficacité d'échantillons de TiO2 modifiés par ajout d'or afin d'améliorer la séparation des charges et ainsi la dégradation de polluant en présence d'air ou la formation de produit en présence de flux d'azote. Deux séries de Au/TiO2 avec les mêmes charges d'or (~ 0,16% en poids) ont été préparées par les deux méthodes: pyrolyse laser et pyrolyse par pulvérisation de flamme (Au-TiO2 LP et Au-TiO2 FSP). Les résultats ont montré que la présence d'or améliore l'activité photocatalytique dans l'air dans le cas des échantillons préparés par pyrolyse laser alors qu'aucun effet n'est observé avec les catalyseurs préparés par pyrolyse à flamme (FSP). Ce résultat s'explique en considérant la taille des nanoparticules d'or plus petite dans le cas des échantillons obtenus par pyrolyse laser. L'effet inverse est observé sous atmosphère de N2, la présence d'or diminue de plus de moitié la dégradation de l'acide acétique mais favorise la formation d'éthane. Ce résultat est discuté en considérant la présence d'or sous forme cationique. Malheureusement, par XPS, il n'a pas été possible d'observer d'or probablement dû à sa faible quantité. L'impact du dopage à l'azote de TiO2 LP et Au-TiO2 LP a également été étudié. Ce dopage diminue l'efficacité de cet échantillon. Finalement des études préliminaires ont été conduite d'une part sur l'efficacité de textile lumineux photocatalytique pour dégrader l'acide acétique afin d'améliorer les rendements quantiques et d'autre part sur les efficacités de catalyseurs Ag/TiO2 lesquels, outre diminué la pollution organique permettrait également l'inactivation des microorganismes / The objective of the thesis is to better understand the mechanisms of photocatalytic degradation occurring under air or under nitrogen by studying the disappearance, mineralization and intermediate products of a simple molecule acetic acid. The reactions are carried out under these two atmospheres in gas phase and dynamic mode in order to place themselves under conditions of depollution or of energy generation. Firstly, we studied the degradation of acetic acid using the reference photocatalyst, TiO2 P25. Regardless of the atmosphere, air or N2, we have shown that the decarboxylation reaction is the first step in the disappearance of acetic acid. However, the fate of the methyl group depends on the carrier gas and the molar flow rate (in other words, the concentration of the pollutant in the gas phase). The mechanism of degradation occurring on the surface of the photocatalyst is then represented to explain the importance of this mechanism compared to that involving the hydroxyl radicals. The schematization of the mechanism includes the regeneration of the photocatalyst and the possible formation of H2O2, which has been observed in the literature. The study of the degradation products of acetic acid labelled with carbon 13 on the carbonyl group (CH313COOH) suggests that acetone and acetaldehyde do not result from the reduction of the carboxylic group. In a second step, the impact of photonic flux and moisture in the presence of TiO2 P25 as well as the effect of different commercial TiO2 on the conversion and more particularly the distribution of the intermediate products have been studied. Comparison of the effectiveness of different commercial TiO2s was discussed by considering the presence of rutile phase, the nature of the active species, the specific surface area of TiO2, the number of OH groups on the surface of the catalysts, the presence of impurities and the porosity of the materials

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For the first time, successful synthesis of an unknown class of compounds, 3-azido-2H-azirines, which are implicated as highly reactive intermediates in the thermolysis of the corresponding 1,1-diazidoethenes, has been performed. These elusive heterocycles have been detected and characterised by low-temperature NMR and in situ IR spectroscopy. Even the parent compound, 3-azido-2H-azirine, has been observed via low-temperature photolysis of 1,1-diazidoethene, as a highly reactive species with a half-life period of only 12 min at −40 °C. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.