O Brasil possui uma imensa diversidade biológica, na qual muitos compostos bioativos podem ser encontrados e utilizados em beneficio à sociedade. No entanto, processos de degradação do ambiente e introdução de espécies exóticas têm contribuído ao conhecimento e uso limitadosde muitas plantas nativas, sendopequena a quantidade de estudos sobre sua composição química e potencial biológico. A prevenção de doenças crônicas constantemente vem sendo associada à atividade antioxidante de metabólitos secundários dos vegetais, principalmente os fenólicos. Assim, o objetivo deste trabalho foi avaliar a atividade antioxidante e composição fenólica de cinco espécies frutíferas nativas do Brasil (G. brasiliensis, E. leitonii, E. involucrata, E. brasiliensis e E. myrcianthes). Os métodos capacidade de redução do Folin-Ciocalteau, autoxidação do sistema ?-caroteno/ácido linoleico, capacidade de absorção de radicais oxigênio (ORAC), sequestro dos radicais livres DPPH e ânion superóxido foram aplicados na determinação da atividade antioxidante dos extratos etanólicos de folha, casca, semente e polpa das espécies selecionadas. As amostras demonstraram significativa atividade antioxidante e, em alguns casos, superior as frutas comumente consumidas pela população brasileira. Em geral, folhas apresentaram as maiores atividades, mas o destaque foi a semente de E. leitonii que exibiu os melhores resultados em quatro dos cinco métodos utilizados: 120,67 mg AG.g-1 na redução do reagente Folin; 7,08 Gmol Trolox.g-1 no ?-caroteno; EC50 de 0,26 mg.mL-1 e 0,07 mg.mL-1 no sequestro do ânion superóxido e DPPH, respectivamente; 514,75 Gmol Trolox.g-1 no ORAC para o qual a folha de E. involucrata obteve o maior valor (1393,3 Gmol Trolox.g-1). Os extratos das espécies nativas também demonstram efeito antioxidante contra radicais de relevância biológica, como peroxila e superóxido. Por meio de CG-EM e CLAE acoplado a arranjo de fotodiodos, os principais compostos fenólicos encontrados nos extratos vegetais foram catequina, epicatequina e ácido gálico. Este trabalho demonstrou o grande potencial antioxidante das frutíferas nativas brasileiras, evidenciando assim possível efeito positivo em sistemas biológicos. / Brazil has a great biodiversity, in which many bioactive compounds can be found and used to benefit the society. However, environmental degradation processes and introduction of exotic species have contributed to limited use and knowledge of many native plants, reflecting in few studies about chemical composition and biological potential. The prevention of chronic diseases has been constantly associated with the antioxidant activity of plants secondary metabolites, mainly the phenolics. The objective of this study was to evaluate the antioxidant activity and the phenolic composition of five Brazilian native fruitful species (G. brasiliensis, E. leitonii, E. involucrata, E. brasiliensis e E. myrcianthes). The methods of Folin-Ciocalteau reducing capacity, co-oxidation of ?-carotene/linoleic acid system, oxygen radical absorbance capacity (ORAC), DPPH and superoxide free radical scavenging were used to determine the antioxidant activity of ethanolic extracts of leaf, peel, seed and pulp of the selected species. The samples showed significant antioxidant activity and, in some cases, it was superior to fruits commonly consumed by Brazilian population. In general, leaves presented the highest activities, but the seed of E. Leitonii stood out exhibiting the best results in four of the five methods: 120.67 mg GA.g-1 in the Folin reducing; 7.08 Gmol Trolox.g-1 in the ?-carotene; EC50 of 0.26 mg.mL-1 and 0.07 mg.mL-1 in the superoxide and DPPH scavenging, respectively; 514.75 Gmol Trolox.g-1 in the ORAC, for which the E. Involucrata leaf had the highest value (1393.3 GmolTrolox.g-1). The extracts of native species also demonstrate antioxidant effect against radicals of biological relevance, such as peroxyl and superoxide. By GC-MS and HPLC coupled to a photodiode array, the major phenolic compounds found in the plant extracts were catechin, epicatechin and gallic acid. In this study, Brazilian native fruitful presented high antioxidant potential, showing a possible positive effect on biological systems.

No description available.

Virulent strains of the bovine opportunistic pathogen Haemophilus somnus (Histophilus somni) cause multi-systemic diseases in cattle. One of the reported virulence factors that H. somnus may use to persist in the host is resistance to intracellular killing. It is reported in this dissertation that H. somnus significantly (P <0.001) inhibited production of superoxide anion (O2-) by bovine mammary and alveolar macrophages as well as by polymorphonuclear leukocytes. Inhibition of O2- production was time- and dose-dependent and did not occur after incubation with Escherichia coli, H. influenzae, or Brucella abortus. Non-viable H. somnus, purified lipooligosaccharide (LOS), or cell-free supernatant from mid-log phase cultures did not inhibit O2- production, indicating that O2- inhibition required contact with live H. somnus. Commensal isolates of H. somnus were less capable or incapable of inhibiting macrophage O2- production compared to isolates tested from disease sites. H. somnus shares conserved epitopes in its LOS with Neisseria gonorrhoeae, N. meningitidis, and H. influenzae, and can also undergo structural phase variation of these LOS epitopes. Sialylation of the terminal galactose of H. somnus LOS is another reported virulence mechanism. Current sequencing of the genomes of H. somnus strains 2336 (pathogenic) and 129Pt (commensal) has enabled in silico identification of three open reading frames (ORFs) involved in sialylation. The ORFs-1 (hsst-I) and -2 (hsst-II) had BLASTx homology to sialyltransferases, while ORF-3 (neuAhs) had BLASTx homology to CMP-sialic acid synthetases. These ORFs were amplified by PCR and cloned into the expression vector pCWOri+. Thin layer chromatography of the hsst-I gene product showed this sialyltransferase exhibited preference for sialylation of terminal N-acetyllactosamine (LacNAc, beta-Gal-[1,4]-beta-GlcNAc-R). However, Hsst-II preferentially sialylated lacto-N-biose (LNB, beta-Gal-[1,3]-beta-GlcNAc-R). In this study, phase variation of the terminal linkage in isolate 738 from a 3 linked galactose (LNB) to a 4 linked galactose (LacNac) was demonstrated. Such variation of a glycose linkage appears to be a novel mechanism of LOS phase variation. Furthermore, the ability of sialylated strain 738 LOS vs de-sialylated strain 738 LOS to induce Toll-like receptor 4 signaling was decreased by 28%, as determined by ELISA for Macrophage Inflammatory Protein-2. Therefore, sialylated LOS may aid H. somnus to avoid host innate immunity. / Ph. D.

O consumo crônico de etanol acarreta alterações significativas das funções cardíaca e circulatória, figurando como um importante fator de risco no desenvolvimento de doenças cardiovasculares, como por exemplo a hipertensão arterial. O passo inicial para a disfunção cardiovascular associada ao etanol envolve a formação de espécies reativas de oxigênio (ERO) e redução da biodisponibilidade do óxido nítrico (NO), sendo esse processo mediado pela enzima nicotinamida adenina dinucleótido fosfato (NADPH) oxidase. Baseado nestas observações, a hipótese do estudo é a de que o consumo de etanol aumente a pressão arterial, a geração de ERO e induza a ativação de vias de sinalização redox sensíveis na vasculatura via NADPH oxidase. Portanto, o objetivo desse estudo foi investigar a participação da NADPH no aumento da pressão arterial e estresse oxidativo vascular induzidos pelo consumo crônico de etanol através de sua inibição pela apocinina. O trabalho demonstrou pela primeira vez o envolvimento do estresse oxidativo via ERO geradas pela NADPH oxidase no aumento da pressão arterial induzida pelo consumo crônico de etanol. Houve aumento da contração induzida por fenilefrina em anéis de aorta com e sem endotélio de animais tratados com etanol e foi demonstrada a participação das ERO geradas pela NADPH oxidase nesta resposta, uma vez que o tratamento com apocinina promoveu diminuição da contração observada. O tratamento com etanol aumentou a geração de ERO em tecido aórtico via NADPH oxidase, reduziu a biodisponibilidade de NO plasmático e tecidual e promoveu peroxidação lipídica, visto pela elevação dos níveis de TBARS. Também foi demonstrado que a enzima NADPH oxidase está envolvida no aumento da expressão protéica da PKC ? e SAPK/JNK induzido pelo etanol, e que o tratamento com etanol é capaz de diminuir a atividade enzimática da superóxido dismutase (SOD) e aumentar a expressão protéica especificamente da SOD2, possível resposta adaptativa ao aumento de geração de O2- via NADPH oxidase pelo etanol. Houve aumento da expressão protéica da nNOS em aorta de animais tratados com etanol, sendo esta, uma possível resposta adaptativa intrínseca às alterações promovidas pelo aumento da pressão arterial nestes animais. O tratamento com etanol não alterou os níveis aórticos de peróxido de hidrogênio (H2O2), glutationa reduzida (GSH) e atividades enzimáticas da xantina oxidase (XO), superoxido dismutase (SOD), catalase (CAT) e glutationa peroxidase (GPx). Além disso, a partir da avaliação da translocação citosol/membrana das subunidades organizadoras p47phox e Nox organizer 1 (Noxo1) e expressão protéica das subunidades catalíticas da NADPH oxidase, Nox1, Nox2 e Nox4, foi possível concluir que o aumento da expressão da Nox1 possui importante papel na modulação da geração de ERO pelo etanol, podendo participar do aumento da pressão arterial e estresse oxidativo sistêmico e vascular gerados. Portanto, a partir dos resultados obtidos, o estudo demonstrou que o consumo crônico de etanol induz o aumento da produção de ERO, resposta implicada no aumento da pressão arterial observado nos animais tratados com etanol. Além disso, o trabalho evidencia a participação da enzima Nox1/NADPH oxidase neste processo, uma vez que houve aumento da expressão protéica dessa subunidade catalítica na aorta dos animais tratados com etanol / Chronic ethanol consumption results in significant alterations in cardiac and circulatory functions, appearing as an important risk factor responsible for cardiovascular diseases such as hypertension. The initial step for cardiovascular dysfunction associated with ethanol consumption involves the generation of reactive oxygen species (ROS) and reduced bioavailability of nitric oxide (NO), processes mediated by the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Based on the mentioned observations we hypothesized that ethanol consumption increases blood pressure, ROS generation and induces activation of redox-sensitive signaling pathways in the vasculature through NADPH oxidase. Thus, here we investigated the contribution of NADPH oxidase in chronic ethanol consumption-induced hypertension and vascular oxidative stress through its inhibition by apocynin. This study demonstrated for the first time the involvement of oxidative stress via ROS derived from NADPH oxidase in increased blood pressure induced by chronic ethanol intake. The increased contractility of endothelium-intact and endothelium-denuded aortic rings from ethanol-treated rats to phenylephrine was prevented by apocynin. Ethanol consumption increased systemic and vascular oxidative stress and apocynin prevented these responses. The decrease on plasma and vascular nitrate/nitrite (NOx) levels induced by ethanol were not prevented by apocynin. Treatment with ethanol did not affect aortic levels of hydrogen peroxide (H2O2) and reduced glutathione (GSH) as well as the activity of xanthine oxidase (XO), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Ethanol-induced increased protein expression of Nox1, PKC?, nNOS, SAPK/JNK and SOD2 in the rat aorta was prevented by apocynin. No difference on the aortic expression of Nox2, Nox4, p47phox, Nox organizer 1 (Noxo1), eNOS and iNOS was detected after treatment with ethanol. Ethanol treatment did not alter the phosphorylation of SAPK/JNK, p38MAPK, ERK1/2, c-Src, Rac1 or PKC?. The major new finding of our study is that the increased vascular generation of reactive oxygen species (ROS) induced by ethanol is related to the increased vascular Nox1/NADPH oxidase expression. This mechanism is involved on the vascular dysfunction and hypertension induced by ethanol. Additionally, we conclude that ethanol consumption induces the expression of different proteins that regulate vascular contraction and growth and that NADPH oxidase-derived ROS play a role in such response

Zusammenfassung in PDF Zielstellung: Der biologische Botenstoff N ist von signifikanter Bedeutung für die Funktionsfähigkeit des Herz-Kreislauf-Systems. Pathologische Bedingungen sind oft auf eine veränderte Verfügbarkeit von N zurückzuführen. Das Verständnis der Regulierung der N-Bildung durch Endothelzellen (EC) und die nachfolgende N-Chemie im gesunden und kranken Organismus ist deshalb essentiell, jedoch längst nicht vollständig. Das Ziel dieser Dissertation war aus diesem Grund Untersuchungen zum Schutz von N vor der Wechselwirkung mit S (durch SOD-mimetische Nitroxide), sowie zum Effekt des Membranpotentials (Em) und des Zellwachstums (Proliferation) auf die Aktivität der endothelialen N Synthase (eNOS) an Kulturen von Atrium-Endothelzellen des Rindes (BAtEC). Methoden: Zum empfindlichen und spezifischen Nachweis von N wurde die ozon-vermittelte N-Chemolumineszenz (N-CL) evaluiert, modifiziert und an verschiedene in vitro Systeme angepaßt. Die N-CL wurde auf Grundlage des durch SOD hemmbaren Abbaus von N durch S als ein neuartiger Ansatz zur Bestimmung physiologisch niedriger Konzentrationen an S vorgeschlagen. Ergebnisse: Die Nitroxide -hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 3-carboxy-proxyl und 3-ethoxycar-bonyl-proxyl erhöhten die N-Konzentration durch ihre SOD-mimetische Wirkung in Modellsystemen von 3-morpholinosydnonimine (SIN-1) und Kulturen von BAtEC. Mittels ESR-Spin-Trap Untersuchungen an Lösungen von SIN-1 wurde die Bildung von H-Addukten durch Dismutierung von S bestätigt, Peroxynitrit wurde als Quelle ausgeschlossen. Modulierung des Em (durch Veränderung der extrazellulären K + -Konzentration) beeinflußte die endotheliale N-Freisetzung; Hyperpolarisierung erhöhte, Depolarisierung verminderte die N Produktion. Inhibierung der elektrogenen Na + -K + ATPase induzierte synchrone Oszillationen der endothelialen N-Freisetzung. Die systematische Untersuchung zu EC-Wachstum/Proliferation zeigte keine Änderung der N-Produktion (in Gegenwart von SOD). Jedoch war die Menge von verfügbarem N (in der Abwesenheit von SOD) niedrig in präkonfluenten, stark proliferierenden BAtEC. Die Expression der eNOS erhöhte sich mit der Kultivierungsdauer und erreichte ein Maximum bei Konfluenz. Die relative eNOS-Aktivität (N, 2-, und L-citrulline-Produktion pro eNOS-Protein) war am größten in präkonfluenten, stark proliferierenden BAtEC. Schlußfolgerungen: Die Wechselwirkung mit S ist kritisch für die Halbwertszeit von N. Aus der durch diese Studie gezeigten Erhöhung von N in biologischen und chemischen Modellsystemen kann geschlußfolgert werden, daß Nitroxide unter Bedingungen einer S-bedingten Verminderung von verfügbarem N pharmakologische Wirksamkeit besitzen könn-ten. Untersuchungen ergaben den Nachweis zur Em-abhängigen Modulierung der endothelialen N-Freisetzung. Dies liefert eine Erklärung für die Em-bedingten Veränderungen des Gefäßto-nus, nachgewiesen während physiologischer Zellstimulierung, aber auch unter pathologischen Bedingungen. Untersuchungen zu EC-Wachstum/Proliferation lieferten den Beweis für die Ver-minderung von verfügbarem N in präkonfluenten, stark proliferierenden BAtEC durch endogen gebildetes S. Die Expremierung von eNOS war proliferationsabhängig. Die spezifische eNOS-Aktivität war in proliferierenden BAtEC erhöht (wahrscheinlich durch post-translationale Verän-derungen) und in ruhenden BAtEC erniedrigt (wahrscheinlich durch Substrat- oder Kofaktormangel). / abstract in pdf Objective: The biological messenger n is of significant importance for the functionality of the cardiovascular system. Pathological conditions are often attributed to an altered availability of n. The understanding of the regulation of n formation by endothelial cells (EC) and the concomitant chemistry of n in health and disease is therefore essential but far from being complete. The objective of this dissertation was therefore to study in culture systems of bovine atrial endothelial cells (BAtEC) the protection of n from the interaction with S by SOD-mimetic nitroxides, and the effect of the membrane potential (Em) and cell growth/proliferation on the activity of the endothelial nitric oxide synthase (eNOS). Methods: For the sensitive and specific detection of n, the ozone-mediated n chemiluminescence (n-CL) was evaluated, modified and adapted to various in vitro systems. Due to the SOD-inhibitable degradation of n by S , the n-CL was proposed as a novel approach to quantify the physiological low levels of S . Results: The nitroxides 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 3-carboxy-proxyl, and 3-ethoxycarbonyl-proxyl increased the n concentration by their SOD-mimetic action in a model system of 3-morpholinosydnonimine (SIN-1) and cultures of BAtEC. EPR spin trapping in SIN-1 solution revealed the formation of H adducts due to dismutation of S and not via decomposition of peroxynitrite. Changes in Em (by alteration of the extracellular K + concentration) affected the endothelial n release; membrane hyperpolarization increased, membrane depolarization decreased the n production. Inhibition of the electrogenic Na + -K + ATPase induced synchronous oscillations in endothelial n liberation. The systematic investigations on EC growth/proliferation showed no change in total n production (in the presence of SOD). However, the bioavailable n (in the absence of SOD) was low in preconfluent, highly proliferating BAtEC. Expression of eNOS increased with culture duration with a maximum at confluence. Relative eNOS activity (n, 2, and L-citrulline production per eNOS protein) was highest in preconfluent, highly proliferating BAtEC. Conclusions: The interaction of S is critical for the half-life of n. With the increase of n in biological and chemical model systems shown by this study, nitroxides might exert pharmacological potential under conditions of S -mediated diminution of bioavailable n. Experimental evidence was shown for the Em-dependent modulation of endothelial n formation. It supports an explanation for the Em-mediated changes of vascular tone, as demonstrated for physiological cell stimulation but also under pathological conditions. Investigations on the EC growth/proliferation provided evidence that BAtEC-derived S decreases bioavailable n in preconfluent, highly proliferating BAtEC, whereas expression of eNOS is proliferation-dependent. The specific eNOS activity is upregulated in proliferating BAtEC (probably via post-translational modifications) and down-regulated in quiescent BAtEC (probably via substrate or cofactor limitations).

O consumo crônico de etanol acarreta alterações significativas das funções cardíaca e circulatória, figurando como um importante fator de risco no desenvolvimento de doenças cardiovasculares, como por exemplo a hipertensão arterial. O passo inicial para a disfunção cardiovascular associada ao etanol envolve a formação de espécies reativas de oxigênio (ERO) e redução da biodisponibilidade do óxido nítrico (NO), sendo esse processo mediado pela enzima nicotinamida adenina dinucleótido fosfato (NADPH) oxidase. Baseado nestas observações, a hipótese do estudo é a de que o consumo de etanol aumente a pressão arterial, a geração de ERO e induza a ativação de vias de sinalização redox sensíveis na vasculatura via NADPH oxidase. Portanto, o objetivo desse estudo foi investigar a participação da NADPH no aumento da pressão arterial e estresse oxidativo vascular induzidos pelo consumo crônico de etanol através de sua inibição pela apocinina. O trabalho demonstrou pela primeira vez o envolvimento do estresse oxidativo via ERO geradas pela NADPH oxidase no aumento da pressão arterial induzida pelo consumo crônico de etanol. Houve aumento da contração induzida por fenilefrina em anéis de aorta com e sem endotélio de animais tratados com etanol e foi demonstrada a participação das ERO geradas pela NADPH oxidase nesta resposta, uma vez que o tratamento com apocinina promoveu diminuição da contração observada. O tratamento com etanol aumentou a geração de ERO em tecido aórtico via NADPH oxidase, reduziu a biodisponibilidade de NO plasmático e tecidual e promoveu peroxidação lipídica, visto pela elevação dos níveis de TBARS. Também foi demonstrado que a enzima NADPH oxidase está envolvida no aumento da expressão protéica da PKC ? e SAPK/JNK induzido pelo etanol, e que o tratamento com etanol é capaz de diminuir a atividade enzimática da superóxido dismutase (SOD) e aumentar a expressão protéica especificamente da SOD2, possível resposta adaptativa ao aumento de geração de O2- via NADPH oxidase pelo etanol. Houve aumento da expressão protéica da nNOS em aorta de animais tratados com etanol, sendo esta, uma possível resposta adaptativa intrínseca às alterações promovidas pelo aumento da pressão arterial nestes animais. O tratamento com etanol não alterou os níveis aórticos de peróxido de hidrogênio (H2O2), glutationa reduzida (GSH) e atividades enzimáticas da xantina oxidase (XO), superoxido dismutase (SOD), catalase (CAT) e glutationa peroxidase (GPx). Além disso, a partir da avaliação da translocação citosol/membrana das subunidades organizadoras p47phox e Nox organizer 1 (Noxo1) e expressão protéica das subunidades catalíticas da NADPH oxidase, Nox1, Nox2 e Nox4, foi possível concluir que o aumento da expressão da Nox1 possui importante papel na modulação da geração de ERO pelo etanol, podendo participar do aumento da pressão arterial e estresse oxidativo sistêmico e vascular gerados. Portanto, a partir dos resultados obtidos, o estudo demonstrou que o consumo crônico de etanol induz o aumento da produção de ERO, resposta implicada no aumento da pressão arterial observado nos animais tratados com etanol. Além disso, o trabalho evidencia a participação da enzima Nox1/NADPH oxidase neste processo, uma vez que houve aumento da expressão protéica dessa subunidade catalítica na aorta dos animais tratados com etanol / Chronic ethanol consumption results in significant alterations in cardiac and circulatory functions, appearing as an important risk factor responsible for cardiovascular diseases such as hypertension. The initial step for cardiovascular dysfunction associated with ethanol consumption involves the generation of reactive oxygen species (ROS) and reduced bioavailability of nitric oxide (NO), processes mediated by the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Based on the mentioned observations we hypothesized that ethanol consumption increases blood pressure, ROS generation and induces activation of redox-sensitive signaling pathways in the vasculature through NADPH oxidase. Thus, here we investigated the contribution of NADPH oxidase in chronic ethanol consumption-induced hypertension and vascular oxidative stress through its inhibition by apocynin. This study demonstrated for the first time the involvement of oxidative stress via ROS derived from NADPH oxidase in increased blood pressure induced by chronic ethanol intake. The increased contractility of endothelium-intact and endothelium-denuded aortic rings from ethanol-treated rats to phenylephrine was prevented by apocynin. Ethanol consumption increased systemic and vascular oxidative stress and apocynin prevented these responses. The decrease on plasma and vascular nitrate/nitrite (NOx) levels induced by ethanol were not prevented by apocynin. Treatment with ethanol did not affect aortic levels of hydrogen peroxide (H2O2) and reduced glutathione (GSH) as well as the activity of xanthine oxidase (XO), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Ethanol-induced increased protein expression of Nox1, PKC?, nNOS, SAPK/JNK and SOD2 in the rat aorta was prevented by apocynin. No difference on the aortic expression of Nox2, Nox4, p47phox, Nox organizer 1 (Noxo1), eNOS and iNOS was detected after treatment with ethanol. Ethanol treatment did not alter the phosphorylation of SAPK/JNK, p38MAPK, ERK1/2, c-Src, Rac1 or PKC?. The major new finding of our study is that the increased vascular generation of reactive oxygen species (ROS) induced by ethanol is related to the increased vascular Nox1/NADPH oxidase expression. This mechanism is involved on the vascular dysfunction and hypertension induced by ethanol. Additionally, we conclude that ethanol consumption induces the expression of different proteins that regulate vascular contraction and growth and that NADPH oxidase-derived ROS play a role in such response

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Les dommages au nerf optique (neuropathie optique) peuvent entraîner la perte permanente de la vision ou la cécité causée par la mort des cellules ganglionnaires de la rétine (CGR). Nous avons identifié qu’une surproduction de l'anion superoxyde constitue un événement moléculaire critique précédant la mort cellulaire induite par des lésions. Récemment, Suarez-Moreira et al (JACS 131:15078, 2009) ont démontré que la vitamine B12 peut capter l’anion superoxyde aussi efficacement que l’enzyme superoxyde dismutase. La carence en vitamine B12 peut conduire à une neuropathie optique causée par des mécanismes inconnus. Nous avons étudié la relation entre la captation de superoxyde par la cyanocobalamine (forme de vitamine B12 la plus abondante) et ses propriétés neuroprotectrices dans les cellules neuronales. La cyanocobalamine aux concentrations de 10 μM et 100 μM a réduit le taux de production de superoxyde respectivement par 34% et 79% dans les essais sans-cellule. Dans les cellules RGC-5 traités avec la ménadione, les concentrations de cyanocobalamine supérieures à 10 nM ont diminué l’anion superoxyde à des valeurs similaires à celles traitées par PEG-SOD. La cyanocobalamine aux concentrations de 100 μM et 1 μM a réduit la mort des cellules RGC-5 exposées à la ménadione par 20% et 32%, respectivement. Chez les rats avec section du nerf optique unilatérale, une dose intravitréenne de 667 μM de cyanocobalamine a réduit le nombre de CGRs exposées au superoxyde. Cette dose a également augmenté le taux de survie des CGRs comparativement aux rats injectés avec la solution témoin. Ces données suggèrent que la vitamine B12 peut être un neuroprotecteur important, et sa carence nutritionnelle pourrait causer la mort de CGRs. La vitamine B12 pourrait aussi potentiellement être utilisée comme une thérapie pour ralentir la progression de la mort CGR chez les patients avec les neuropathies optiques caractérisés par une surproduction de superoxyde. / Damage to the optic nerve (optic neuropathy) can result in permanent loss of vision or blindness through retinal ganglion cell (RGC) death. Our prior work identified a burst of superoxide anion as a critical molecular event in RGCs prior to injury-induced cell death. Recently, Suarez-Moreira et al (JACS 131:15078, 2009) demonstrated that vitamin B12 scavenges superoxide as effectively as superoxide dismutase. Vitamin B12 deficiency can lead to optic neuropathy through unknown mechanisms. We investigated the relationship between superoxide scavenging by cyanocobalamin, the most abundant vitamin B12¬¬ vitamer, and its neuroprotective properties in neuronal cells. Cyanocobalamin at concentrations of 10 μM and 100 μM reduced the rate of superoxide generation by 34% and 79% in cell free assays, respectively. In menadione-treated RGC-5 cells, cyanocobalamin concentrations above 10 nM scavenged superoxide anion similar to those treated with pegylated-SOD. Cyanocobalamin at concentrations of 100 μM and 1 mM reduced RGC-5 cell death from menadione by 20% and 32%, respectively. In rats with unilateral optic nerve transection, a single intravitreal dose of 667 μM cyanocobalamin significantly reduced the number of RGCs with superoxide. This dose also increased RGC survival rate compared to rats injected with saline control. These data suggest that vitamin B¬¬12 may be an important neuroprotectant, which could cause death of RGCs when depleted in nutritional deficiency. Vitamin B12 could also potentially be used as a therapy to slow progression of RGC death in patients with optic neuropathies characterized by overproduction of superoxide.

Catecol e catecolaminas foram ensaiados sobre as atividades NADPH e NADH oxidásica dos microssomos. Quantidades catalíticas de adrenalina aumentam de duas a três vezes a velocidade de oxidação do NADPH, após um pequeno período de indução. O efeito da adrenalina é suprimido pela superóxido dismutase, se a enzima é adicionada antes de iniciada a reação. O efeito catalítico é atribuído a dois produtos de oxidação da adrenalina pelo íon superóxido; à quinona, produto de oxidação de dois elétrons e ao adrenocromo, produto de oxidação de quatro elétrons. Provavelmente, o adrenocromo reoxida a NADPH citocromo c redutase, e a quinona formada reage com oxigênio, regenerando adrenocromo. A adrenalina não mostrou qualquer efeito sobre a atividade NADH oxidásica, nem sobre a atividade NADPH oxidásica, estimulada por menadiona. Provavelmente, durante estes processos, dois elétrons são transferidos simultaneamente ao oxigênio. Catecol e catecolaminas duplicam a velocidade de oxidação do NADH em presença de quantidades catalíticas de NADH-citocromo b5 redutase e citocromo b5. Este resultado sugere a formação do íon superóxido, durante a autoxidação do citocromo b5. Catecol e p-hidroquinona promovem, cataliticamente, a oxidação da oxihemoglobina e oximioglobina à forma ferri. A velocidade de oxidação da oxihemoglobina mostra dependência de primeira ordem em relação à concentração de hemeproteína e de meia ordem em relação ao difenol ; contudo a altas concentrações dos catalisadores observa-se saturação, com valores de Vmáx similares para ambos os difenóis. É proposto que uma quinona , inicialmente formada, oxida a oxihemeproteína com liberação de oxigênio; por sua vez, a semiquinona oxida uma segunda molécula de oxihemeproteína, sendo que o oxigênio ligado recebe dois elétrons. Exceto para o caso da oximioglobina, que é mais reativa, a forma reduzida do catalisador deve estar presente para se opor ao desaparecimento da semiquinona por dismutação. Desde que se observa a liberação de oxigênio, esperada para a formação de água, o sistema pode ser considerado modelo de oxidase terminal. Infere-se tentativamente, que a oxihemoglobina tem estrutura HbFe2+ ...O2, e que a velocidade da oxidação catalisada é limitada pela velocidade de produção da verdadeira forma reativa, a estrutura ferri-superóxido, HbFe3+...O-2. / Catechol and catecholamines have been assayed upon the microsomal NADPH and NADH oxidase activities. Adrenaline shows a catalytic effect on the NADPH oxidation characterized by a small lag. The two-to three fold increase in rate can be supressed by dismutase if the enzyme is added before superoxide the reaction begins. The catalytic effect is ascribed to two products of adrenaline oxidation by the superoxide ion; to the quinone, the two electron oxidation product, and to the adrenochrome, the four electron oxidation product. Presumably, the adrenochrome reoxidizes the NADPH-cytochrome c reductase, and the formed quinone reacts with oxygen and regenerates the adrenochrome. Adrenaline neither changed, the NADH oxidase activity nor the menadione-stimulated NADPH oxidase activity. Presumably in these processes, two electrons are simultaneously transferred to the oxygen. Catechol and catecholamines doubled the rate of autoxidation of NADH in the presence of catalytic amounts of NADH-cytochrome b5 reductase and cytochrome b5 This result suggests superoxide ion formation in the autoxidation of the cytochrome. Catechol and p-hydroquinone catalytically promote the oxidation of oxyhemoglobin and oxymyoglobin to the ferri-form. Kinetic data for oxyhemoglobin oxidation indicates a first-order dependence upon the hemoprotein concentration and half-order dependence upon diphenol; however at high catalyst concentration, saturation is observed with similar Vmax values for both diphenols despite the difference in reactivity. It is proposed that initially formed quinone oxidizes the hemoprotein with oxygen release; in turn the semiquinone oxidizes a second molecule of hemoprotein and regenerates the quinone, with the bound oxygen acquiring two electrons. Except for the more reactive oxymyoglobin, the reduced form of the catalyst must be present to oppose semiquinone disappearance by dismutation, Since the expected release of 02 for water formation is observed, the system may be considered a model for terminal oxidase. It is tentatively inferred that oxyhemoglobin has the structure HbFe2+...02 and that the rate of the catalyzed oxidation is limited by the rate of generation of the true reacting form, the superoxide ferri structure, HbFe3+...0-2.

La surexploitation des ressources de la planète est aujourd’hui une problématique de premier ordre, et fait du remplacement des sources non renouvelables, d'énergie et de matières premières, l’un des défis majeurs du XXIe siècle. Dans cet objectif, les lignines, par leur disponibilité et leur biocompatibilité, apparaissent comme l’une des alternatives aux ressources fossiles. C’est dans ce contexte que le Laboratoire PEIRENE a décidé de mener ce travail de thèse portant sur le développement de nouveaux matériaux photosensibles à base de lignines modifiées. Dans ce but, trois lignines d’origines différentes ont été acétylées. Leur étude par spectroscopie RPE a révélé que le blocage de leurs fonctions antioxydantes augmente considérablement la quantité d’espèces réactives de l’oxygène qu’elles sont capables de générer sous irradiation lumineuse, permettant ainsi d’envisager l’utilisation de ce biopolymère modifié dans de nombreux domaines tels que le traitement photodynamique antimicrobien. Afin de les rendre hydrodispersibles et d’élargir ainsi leur champ d’applications, ces matériaux aux propriétés prometteuses ont été mis sous forme de nanoparticules puis, leur comportement photosensible a été lui aussi évalué par spectroscopie RPE. Il a ainsi été démontré qu’une fois dispersées dans l’eau sous la forme de nanoparticules, les lignines acétylées étaient toujours capables de produire de l’oxygène singulet sous irradiation lumineuse. Cette activité, qui n’a pas encore été reportée dans la littérature à notre connaissance, reste cependant assez restreinte et nécessite donc d’être améliorée. Afin d’élargir le domaine du spectre solaire permettant leur activation, un photosensibilisateur a par ailleurs été associé à ces nano-objets par encapsulation et par greffage covalent. L’ensemble des résultats découlant de ces travaux permettent d’envisager le développement de systèmes à base de nanoparticules de lignines acétylées dans de nombreux domaines, notamment pharmaceutique et phytosanitaire. / The overexploitation of the planet's resources is nowadays a major problem and makes the replacement of non-renewable sources of energy and raw materials, one of the major challenges of the XXIe century. For this purpose, lignins, by their availability and their biocompatibility, appear as one of the alternatives to fossil resourcesIn this context, the PEIRENE Laboratory decided to carry out this PhD work on the development of new photosensitive materials based on modified lignins. For this purpose, three lignins from different origin were acetylated. Their study by EPR spectroscopy revealed that blocking their antioxidant functions considerably increases the quantity of reactive oxygen species they are able to generate under light irradiation. Thus it is possible to envisage the use of this modified biopolymer in many areas such as antimicrobial photodynamic therapy. In order to make them water-dispersible and thus to widen their field of applications, these materials with promising properties were put in the form of nanoparticles. Their photosensitive behavior has been also valuated by EPR spectroscopy. It has been demonstrated that once dispersed in water in the form of nanoparticles, the acetylated lignins were still capable of producing singlet oxygen under light irradiation. This activity, which has not yet been reported in the literature to our knowledge, however, remains quite limited and therefore needs to be improved. In order to widen the range of the solar spectrum allowing their activation, a photosensitizer has also been associated with these nano-objects by encapsulation and covalent grafting. The results of these studies make possible to envisage the development of systems based on acetylated lignins nanoparticles in in many field, in particular pharmaceutical and phytosanitary.