Iron/Manganese superoxide dismutases (Fe/Mn-SODs) are metalloenzymes with highly conserved protein folds, active sites, and dimer interfaces. They protect cells against oxidative stress by catalyzing the conversion of the cytotoxic free radical superoxide to molecular oxygen and hydrogen peroxide. The majority are highly specific for the type of metal (iron or manganese) present within the active site. However, there are many key aspects of metal specificity and catalytic activity that lack a structural explanation. Computational analyses suggested that several residues are important for fine-tuning the redox potential of the metal in the active site and thereby the catalytic activity. The main objective of this thesis is to evaluate the influence of several point mutations (M27V, G73A, H75I, L80F, D150G and Q172D) and one double mutation (Q149G+G74Q)) in terms of metal specificity, catalytic activity and three-dimensional structure using the superoxide dismutase from Trichoderma reesei (TrSOD) as a model system. The corresponding genes were cloned, expressed and the resulting proteins characterized by X-ray crystallography, electron paramagnetic resonance (EPR), atomic absorption spectroscopy (AAS), dynamic light scattering (DLS) and their enzymatic activity determined. The native protein was shown to be able to use either Mn or Fe (5000 units/mg and 500 units/mg, respectively) for catalysis suggesting it to be properly classified as cambialistic. Structures for native TrSOD and the Mn-G73A, Fe-H75I, Mn-L80F, Fe-D150G and Fe-M27V, Mn-M27V mutants were solved at 2.3 Å, 2.0 Å, 2.03 Å, 2.0 Å, 1.85 Å, 1.4 Å and 1.6 Å resolution, respectively. The H75I, L80F and M27V mutations are easily accommodated by small local structural changes to the three-dimensional structure. On the other hand, the G73A mutation destabilize one of the dimer-dimer interfaces of the tetramer making it possible for two distorted tetramers to interact forming an octamer. This enzyme also lost all catalytic activity probably due to resulting exposure of the active site consistent with the observation of a sixth ligand (solvent molecule) bound to the metal in one subunit. The D150G mutant remained tetrameric but with reduced symmetry related to the rearrangement of the last helix (H9). Our results show that a large impact on activity and oligomerization of TrSOD can be generated by a single amino acids substitution in some cases and provide some insights into our understanding of the structural details associated with the metal ion specificity and oligomerization in superoxide dismutases. / Superóxido dismutases de ferro e manganês (Fe/Mn-SODs) são metaloenzimas com enovelamentos, sítios ativos e interfaces diméricas altamente conservados. Estas enzimas protegem as células contra o estresse oxidativo pela conversão do ânion superóxido em oxigênio molecular e peróxido de hidrogênio. A maioria são altamente específicas pelo tipo de metal (ferro ou manganês) presente no sítio ativo. Entretanto, existem vários aspectos críticos sobre a especificidade pelo metal e da atividade catalítica que ainda não foram explicados em termos estruturais. Análises computacionais sugerem que vários resíduos são importantes para o ajuste do potencial redox do metal no sitio ativo e, portanto, a atividade catalítica. O objetivo principal deste trabalho é avaliar a influência de mutações simples (TrSOD) (M27V, G73A, H75I, L80F, D150G e Q172D) e dupla (Q149G + G74Q) em superóxido dismutases de Trichoderma reesei em termos de especificidade pelo metal, atividade catalítica e estrutura. Os genes correspondentes foram clonados, expressos e as proteínas resultantes caracterizadas por cristalografia de raios-X, ressonância paramagnética electrónica (EPR), espectroscopia de absorção atómica (AAS), dispersão de luz dinâmica (DLS), e a atividade enzimática foi determinada. Foi mostrado que a proteína nativa é capaz de usar tanto Mn quanto Fe (5000units/mg e 500units/mg, respectivamente) para catálise sugerindo que deveria ser a classificada como enzima cambialistica. Estruturas da enzima nativa e mutantes (Mn-G73A, Fe-H75I, Mn-L80F, Fe-D150G, Fe-M27V e Mn-M27V) foram resolvidas a resoluções de 2.3 Å, 2.0 Å, 2.03 Å, 2.0 Å, 1.85 Å, 1.4 Å e 1.6 Å respetivamente. As mutações H75I, L80F e M27V são acomodadas facilmente por reajustes locais na estrutura tridimensional. Por outro lado, a mutação G73A desestabiliza uma das interfaces dímero-dímero do tetrâmero levando à formação de um octâmero feito por dois tetrâmeros distorcidos. Esta enzima também perde atividade provavelmente devido a um aumento na acessibilidade do sítio ativo, coerente com a observação de um sexto ligante (molécula de solvente) coordenando o metal em uma das subunidades. O mutante D150G continuou tetramérica mas com simetria reduzida relacionado com o rearranjo da última hélice (H9). Estes resultados mostram que, em alguns casos, uma mutação simples pode ter um impacto significativo no estado oligomérico e atividade catalítica da proteína TrSOD e fornece conhecimentos para a nossa compreensão dos detalhes estruturais associados com a especificidade de íons metálicos e oligomerização em superóxido dismutases.

OBJETIVOS: determinar a relação entre parâmetros de estresse oxidativo, gravidade de sepse e resposta ao tratamento com antioxidantes. MATERIAL E MÉTODOS: foram incluídos pacientes consecutivos admitidos na UTI de um hospital terciário com o diagnóstico de sepse, sepse grave ou choque séptico. Os pacientes foram avaliados diariamente e foi coletado sangue imediatamente após a inclusão no estudo (máximo de 12h após diagnóstico de sepse). Avaliou-se os níveis séricos de substâncias reativas ao ácido tiobarbitúrico (TBARS), carbonilação de proteínas, atividade de superóxido dismutase (SOD) e catalase. Estas variáveis foram correlacionadas com desfecho e variáveis clínicas. Para determinar a relação dos parâmetros oxidativos na resposta ao tratamento, utilizamos o modelo de ligação cecal e perfuração (CLP) empregando ou não tratamento antioxidante (N-acetilcisteína mais deferoxamina). Coletou-se sangue da veia caudal 3h após a indução de sepse e correlacionou-se os parâmetros com resposta ao tratamento antibiótico e antioxidante. Para determinar se o tratamento antioxidante poderia ser retardado por 12h, em uma segunda amostra de animais coletou-se sangue da veia caudal e administrou-se ou não tratamento após 12h da indução de sepse. RESULTADOS: níveis elevados de proteínas carboniladas e de SOD no diagnóstico de sepse são relacionados com óbito por sepse nesta amostra. Estes parâmetros são correlacionados com a gravidade da doença avaliada pelos escores APACHE II e MODS. Níveis de atividade da SOD podem prever resposta ao tratamento com antioxidantes no modelo CLP, tanto 3 como 12h após a indução de sepse. CONCLUSÃO: Parâmetros oxidativos são associados com gravidade e desfecho de sepse em UTI geral, e podem prever resposta ao tratamento antioxidante em animas. / OBJECTIVE: determine the relationship between oxidative stress parameters, sepsis severity and treatment response to antioxidants. MATERIALS AND METHODS: were included consecutive patients admited on ICU at a tertiary care Hospital with sepsis, severe sepsis or septic shock. The patients were evaluated, blood samples were colected immediately after study inclusion (12h maximum after sepsis diagnosis). We determined plasma levels of thiobarbituric acid reactive species (TBARS), protein carbonyls, superoxide dismutase (SOD) and catalase activities and correlate it to clinical parameters. To determine the relation between oxidative parameters and response to antioxidant treatment we used the cecal ligation and perforation (CLP) model of sepsis, using or not antioxidants (n-acetyilcysteine plus deferoxamine) 3 or 12 hours after CLP. RESULTS: non-survivor septic patients presented higher protein carbonyls and SOD activity when compared to survivor patients. These parameters were correlated to APACHE II and MODS in our sample. In addition, plasma SOD levels predicted response to antioxidant treatment in the CLP model, both 3 and 12 houras after sepsis induction. CONCLUSION: Oxidative parameters are correlated to severity and outcome in septic patients and could predict response to antioxidant treatment in the CLP model.

A compreensão da fisiologia e dos mecanismos moleculares da sepse tem sido foco de muitos estudos. As infecções severas, como a sepse, são responsáveis por 10% do total de mortes registradas em Unidades de Tratamento Intensivo em todo o mundo. O desfecho da sepse ocorre devido a influência de fatores ambientais e genéticos, cuja expressão de variantes genéticas suportam ou não este desfecho. Muitos mecanismos estão envolvidos na sepse, incluindo a liberação de citocinas e a ativação de neutrófilos, de monócitos e de células endoteliais. Há associação entre superprodução de óxido nítrico, produção excessiva de radicais livres, depleção de antioxidantes, e déficit energético celular. Enzimas antioxidantes endógenas como a Superóxido Dismutase, a Glutationa Peroxidase e a Catalase protegem a célula do dano oxidativo. A enzima superóxido dismutase dependente de manganês é um potente antioxidante intracelular codificada por um gene (SOD2; 6q25-2) que tem sua expressão induzida por mediadores inflamatórios tais como interleucina 1, interleucina 4, interleucina 6, Fator de Necrose Tumoral – α, lipopolisacarídeos. O gene SOD2 apresenta um polimorfismo de mutação de base C47T no exon 2, o qual resulta na substituição do resíduo 16 (Ala16Val) pertencente ao peptídeo sinal da proteína. O objetivo deste trabalho foi estudar o efeito diferencial das variantes - 9Ala e -9Val da superóxido dismutase dependente de manganês sobre as células mononucleares de sangue periférico humano (in vitro) durante um processo infeccioso (induzido por lipopolisacarídeos), investigando sua implicação: (I) na produção de Espécies Reativas; (II) na atividade e imuno-conteúdo da Superóxido Dismutase dependente de Manganês; (III) na atividade e imuno- conteúdo da Catalase; (IV) na atividade e imunoconteúdo da Glutationa Peroxidase; (V) na produção de nitrotirosina; (VI) na produção de nitrito/nitrato; (VII) na liberação de Fator de Necrose Tumoral - α; (VIII) na produção de Carboximetil-lisina; (IX) dienos conjugados; (X) no imuno-conteúdo da Poli (ADP ribose) Polimerase; (XI) no imuno-conteúdo do Receptor de Produtos Avançados de Glicação; (XII) no imuno-conteúdo da Proteína de Choque Térmico; (XIII) no imuno-conteúdo do Fator Nuclear κB; (XIV) no dano ao DNA celular; (XV) na determinação das defesas antioxidantes totais não enzimáticas. Os resultados demonstraram que o polimorfismo Ala-9Val participa na regulação do ambiente redox celular, e que o alelo 47C permite que as células no estado basal (sem lipopolisacarídeos) respondam com mais eficiência ao estresse oxidativo celular. Este alelo apesar de produzir mais espécies reativas também aumenta o mecanismo de defesa antioxidante. Porém, quando em uma doença que produza estresse oxidativo, no caso a sepse, o alelo 47C torna o ambiente intracelular pró-oxidativo podendo agravar a condição celular. Em suma, os dados aqui apresentados sugerem que o polimorfismo Ala-9Val é um alvo promissor para novos estudos com o objetivo de usar marcadores genéticos para direcionar a terapia necessária para cada paciente. / The understanding of the physiology and of molecular mechanisms of sepsis has been focus of many studies. The severe infections, as the sepsis, are responsible for 10% of total of deaths registered in Intensive Care Units all over the world. The outcome of sepsis happens due to influence of environmental and genetic factors, whose the expression of genetic variants supports or not this outcome. Many mechanisms are involved in sepsis, including the cytokines liberation and the neutrophils activation, of monocytes and of endothelial cells. There is association among overproduction of nitric oxide, excessive production of free radicals, depletion of antioxidants, and cellular energy deficit. Endogenous antioxidant enzymes as Superoxide Dismutase, Glutathione Peroxidase and Catalase protect the cell of oxidative damage. The manganese superoxide dismutase enzyme it is a potent antioxidant intracellular codified by a gene (SOD2; 6q25-2) that has her expression induced by the inflammatory mediators such as interleukin 1, interleukin 4, interleukin 6, tumor necrosis factor – α, lipopolysaccharide. The SOD2 gene presents a single-nucleotide polymorphism C47T in the exon 2, which results in the substitution of the residue 16 (Ala16 Val) belonging to the signal peptide of the protein. The aim of this work was to study the differential effect of the variants -9Ala and -9Val of manganese superoxide dismutase on the Peripheral Blood Mononuclears Cells human (in vitro) during an infectious process (induced by lipopolysaccharide), investigating her implication: (I) in the production of Reactive Species; (II) in the activity and immunocontent of Manganese Superoxide Dismutase; (III) in the activity and immunocontent of Catalase; (IV) in the activity and immunocontent of Glutathione Peroxidase; (V) in the nitrotyrosine production; (VI) in the nitrite/nitrate production; (VII) in the production of tumor necrosis factor - α; (VIII) in the production of carboxymethyl lysine; (IX) conjugated dienos; (X) in the immunocontent of the Poly (ADP-ribose) Polymerase; (XI) in the immunocontent of the Receptor for Advanced Glycation Endproducts; (XII) in the immunocontent of Heat Shock Protein; (XIII) in the immunocontent of the Nuclear Factor kappa B; (XIV) in the damage to cellular DNA; (XV) in the determination of the non-enzymatic antioxidant cellular defenses. The results demonstrated that the polymorphism Ala-9Val it participates in the regulation of the cellular redox environment, and that the 47C allele allows that the cells in the basal state (without lipopolysaccharide) they answer with more efficiency to the stress oxidative cellular. This allele in spite of producing more RS also increases the mechanism of antioxidant defense. However when in a disease that produces oxidative stress, in the case the sepsis, the 47C allele turns intracellular environmental pro-oxidative could worsen the cellular condition. In summary, the data presented here suggest that the polymorphism Ala- 9Val is a promising target for new studies with the goal of using genetic markers to guide therapy required for each patient.

Este trabalho teve como objetivo analisar os efeitos fisiológicos do herbicida Paraquat, indutor de estresse oxidativo, em plantas de cana-de-açúcar (Saccharum officinarum L.). A escolha desta espécie como modelo fisiológico deste estudo deveu-se a sua importância econômica para o país, em especial para o Estado de São Paulo. O Paraquat (PQ) é um herbicida de contato que atua especificamente no Fotossistema II bloqueando o fluxo de elétrons e impedindo a redução do NADPH, aceptor final de elétrons. Como consequência, há a formação de radicais instáveis, reativos com a molécula de oxigênio (EROs), os quais causam danos em membranas, proteínas e ácidos nucleicos. A hipótese central foi a de que a atividade de peroxidase de ascorbato é mais sensível ao PQ do que a atividade de superóxido dismutase, nas mesmas condições. O experimento principal consistiu da aplicação, via pulverização foliar, de diferentes doses de PQ (0, 2, 4, 6 e 8 mM de Metil Violágeno, agente ativo), que permaneceu em contato por 24 e 48 horas. Após 18 horas de exposição, observou-se sintomas visuais de toxocidade e uma redução significativa da atividade fotossintética, medida através de parâmetros relacionados com a fluorescência da clorofila a. O nível de peroxidação de lipídeos, indicado pela concentração de TBARS, foi aumentado, indicando danos nas membranas causados pela geração de EROs. Um resultado importante foi o aumento da atividade específica de SOD (Superóxido Dismutase), primeira enzima de defesa contra EROs. Esse aumento foi gradativo com o aumento da dose e do tempo de exposição ao PQ. A isoforma mais evidente foi a SOD Cu/Zn, visualizada por atividade em gel nativo. Esta isoforma está presente preferencialmente em cloroplastos, organela alvo da ação do PQ. É importante ressaltar que mesmo em doses quase letais, a atividade desta enzima manteve-se em níveis semelhantes ao controle. Entretanto, a atividade de APX (Ascorbato Peroxidase), enzima que faz a remoção de radicais H2O2, gerados pela SOD, foi reduzida abruptamnete a partir de 4 mM PQ, apesar de ter sido observado um aumento na dose inicial (2 mM). Este fato sugere que os danos oxidativos em cana-de-açúcar tratadas com PQ podem ser causados pelo excesso de radicais H2O2. Diferente da SOD, a APX é considerada bastante susceptível a certos tipos de estresse ambiental, logo perdendo sua atividade. Analisou-se também a expressão de proteínas por SDS-PAGE e eletroforese 2-D. Em ambos resultados, foram observados diminuição na expressão de algumas proteínas ocasionada pelo tratamento com PQ. Contudo, não foi possível detectar claramente a indução de peptídeos nesse caso, provavelmente devido ao alto grau de degradação das estruturas celulares. O aumento da atividade de SOD em cloroplastos de folhas de cana-de-açúcar tratadas com PQ, deve ser mais estudado, pois esta pode ser uma enzima alvo para programas de melhoramento genético visando obtenção de plantas com resistência ao PQ e a outros herbicidas com modo de ação no sistema fotossintético. / This work had the objective to analyze physiological effects of Paraquat herbicide, an oxidative stress inductor, in sugarcane (Saccharum officinarum L.) plants. The choice to use this species as a physiological model for this study was due its recognized economical importance for our country, in special to the State of Sao Paulo. Paraquat (PQ) is a contact herbicide that acts specifically on Photosystem II by blocking the normal electron flux and the reduction reaction of NADPH, the electron acceptor molecule. As consequence, there is formation of instable radicals and highly reactive oxygen species (ROS), which cause damage to membranes, proteins and nucleic acids. The central hypothesis was that ascorbate peroxidase activity is more sensitive to PQ than the activity of superoxide dismutase in the same conditions. The main experiment consisted on the sprayed of different concentrations of PQ (0, 2, 4, 6 e 8 mM of Metil Violagen) that stayed in leaf contact for 24 and 46 hours. After 18 hours, it was observed visible symptoms of toxicity and the photosynthetic activity decreased, measured by chlorophyll a fluorescence. Also, the level of lipids peroxidation measured by the increase concentration of TBARS formation, indicate damage to cell membrane caused by the generation of ROS. An important result was the increase of SOD specific activity (superoxide dismutase) first enzyme related to defense against ROS. This gradation increase was correspondent to the exhibition period to PQ. The most evident SOD isoform by native PAGE was the SOD Cu/Zn. This isoform is located preferentially in chloroplasts, organelle target to the action of PQ. It is important to remark that even in almost lethal concentrations of PQ the chloroplast SOD activity still remains expressed beilng responsible for the removal of H2O2 generated by SOD, which was reduced abruptly after 4 mM treatment. Although, it has been observed increase with the initial dose (2 mM). This fact suggests that the oxidative damages in sugarcane treated with PQ can be caused by excess of H2O2. Differently of SOD, this enzyme is considered to be fragile to certain kinds of environmental adversities, loosing its activity Also the protein expression was analyzed by SDSPAGE and 2-D electrophoresis. In both analyses, it was observed decrease of some protein expression caused by PQ. However, it was not possible to clearly detect peptides induction in this case, probably due to the elevated level of degradation of cell structures. The increase of chloroplast SOD activity in sugarcane leaves treated with PQ should be detailed investigated since it can be a molecular target for breeding programs with the goal to obtain plants with an acquired resistance to PQ or others herbicides with model action in the photochemical system.

Previous publications from this laboratory demonstrated that administration of leukemia inhibitory factor (LIF) (125 µg/kg) to young, male Sprague-Dawley rats at 6, 24, and 48 h after middle cerebral artery occlusion (MCAO) reduced infract volume, improved sensimotor skills, and alleviated damage to white matter at 72 h after the injury. In vitro studies using cultured oligodendrocytes (OLs) showed that LIF (200 ng/ml) also protects against 24 h of oxygen-glucose deprivation through activation of Akt signaling and upregulation of the antioxidant enzymes peroxiredoxin IV and metallothionein III. Other groups have demonstrated that LIF reduces neurodegeneration in animal models of disease, but the neuroprotective mechanisms of LIF during permanent ischemia have not yet been examined. The overall hypothesis to be tested in this project is whether LIF exerts similar protective mechanisms against neurons during ischemia through increased antioxidant enzyme expression in neurons. In the first set of experiments, superoxide dismutase (SOD) activity was significantly increased in the ipsilateral hemisphere of LIF-treated rats compared to rats that received PBS treatment at 72 h after MCAO. Western blot and immunohistochemical analysis revealed that SOD3 was upregulated in brain tissue and induced specifically in cortical neurons tissue at this time point. Neurons that expressed high levels of SOD3 at 72 h after MCAO also showed high levels of phosphorylated Akt (Ser473). LIF (200 ng/ml) reduced necrotic and apoptotic cell death against 24 h of OGD as measured by lactate dehydrogenase (LDH) release and caspase-3 activation. Quantitative real-time PCR analysis showed that LIF treatment upregulated SOD3 gene expression in vitro during OGD. Treatment with 10 µM Akt Inhibitor IV and transfection with SOD3 siRNA counteracted the neuroprotective effects of LIF in vitro, showing that upregulation of SOD3 and activation of Akt signaling are necessary for LIF-mediated neuroprotection. Several transcription factors that regulated Akt-inducible genes were previously identified by this lab, including myeloid zinc finger-1 (MZF-1) and specificity protein-1 (Sp1). The goal of the second set of experiments was to determine whether LIF exerted protective actions through MZF-1 and Sp1. According to analysis with Genomatix, MZF-1 and Sp1 have multiple binding sites in the promoter for the rat SOD3 gene. Western blot analysis showed that there was a trend towards increased MZF-1 protein expression in the brains of LIF-treated rats that approached significance. Immunohistochemical analysis and quantitative real-time PCR showed a significant in vitro upregulation in MZF-1 expression among LIF-treated neurons compared to PBS-treated neurons. Sp1 gene expression was not changed by LIF treatment, but there was a trend towards increased protein expression. In addition, there was a significant correlation between Sp1 and MZF-1 among brain samples from LIF-treated rats but not PBS-treated or sham rats at 72 h after MCAO. Immunohistochemical analysis revealed that Sp1 and MZF-1 co-localized with neuronal nuclei and SOD3 at 72 h after MCAO. Neurons that were transfected with MZF-1 or Sp1 siRNA following isolation did not show a significant decrease in LDH release after 24 h OGD that was observed among neurons transfected with scrambled siRNA. These data demonstrate that Sp1 and MZF-1 are involved with the neuroprotective signaling of LIF under ischemia. This laboratory has demonstrated that LIF activates transcription of protective genes and increases the activity of transcription factors through modulation of intracellular signaling. However, the upstream signaling mechanisms of LIF during ischemia had not previously been investigated. Previous investigators found that the LIF-specific subunit of the heterodimeric LIF receptor (LIFR) is induced by CNS injury. Western blot analysis was used to determine whether LIFR was induced in the brain and the spleen, which plays a role in the peripheral immune response, after MCAO. According to these results, LIF treatment significantly upregulates LIF in the brain compared to PBS treatment or sham injury at 72 h after MCAO. Genomatix analysis of the LIFR promoter region revealed a binding site for Sp1, which is one of the transcription factors responsible for neuroprotection by LIF. At this same time point, splenic LIFR expression is significantly reduced after MCAO compared to sham injury. LIF treatment did not significantly increase LIFR expression, but did significantly increase spleen size compared to PBS treatment at 72 h after MCAO. Although there was a trend towards increased LIFR expression in the spleen from 24 h to 72 h after MCAO, this increase was not statistically significant. However, there was a significant positive correlation between spleen weight and LIFR expression among rats euthanized 24-72 h after MCAO/sham injury. In addition, there was a significant negative correlation between LIFR expression in the brain and the spleen weight, thus showing that LIFR is upregulated following the splenic response. According to findings from other groups, JAK1 has been shown to associate with the heterodimeric LIF receptor (LIFR/gp130) and directly activate PI3K/Akt signaling. To test whether JAK1 contributes neuroprotection during ischemia, cultured neurons were treated with several concentrations (2.5-50 nM) of GLPG0634, a JAK1-specific inhibitor prior to 24 h of OGD. With the exception of the 2.5 nM concentration, all concentrations of GLPG0634 significantly decreased LDH release compared to DMSO treatment, with the 5 nM concentration having the most potent effect on reducing cytotoxicity. However, the 5 nM concentration had no significant did not significantly reduce LDH release compared to DMSO treatment under 24 h of normoxic conditions. These results indicate that JAK1 activity is primarily detrimental to neurons during ischemia. Although it is possible that LIF signaling activates JAK1, it is unlikely that JAK1 is responsible for LIF-mediated neuroprotection during ischemia. The results of these experiments allowed us to determine several molecular mechanisms for LIF-mediated neuroprotection. LIF, which binds to its heterodimeric receptor, activates Akt signaling during ischemia. The transcription factors Sp1 and MZF-1, which are located downstream of Akt, bind to the promoter of the SOD3 gene. In addition, Sp1 also regulates the LIFR gene. SOD3 upregulation increases total SOD activity, which decreases apoptotic and necrotic cell death during apoptosis. Due to its ability to promote antioxidant expression and survival signaling in multiple neural cell types, LIF shows promise as a novel treatment for permanent focal cerebral ischemia.

The research presented in this thesis focuses on the molecular design of an oxidation-sensitive nanocarrier and its enzyme conjugate with a view of their application in the field of biomaterials. I have polarised our attention on a specific class of polymers, the polysulfides, for their environmental responsiveness (towards oxidising substances, a condition often associated with inflammatory reactions), interesting physico-chemical properties, ease of the preparation and multiple possibilities for further modifications and bioconjugations, which are perfectly suitable for the development as systems for drug delivery applications. In this work we firstly have focused on the synthesis of amphiphilic poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) block copolymers by employing vinyl sulfone as the functional group to link the blocks and modify the end of the PEG. This study was followed by an investigation of the macromolecular interchange and payload exchange of the formed polymeric micelles to understand the 'co-formulation' events, employing fluorophores (dansyl groups) and quenchers (dabsyl groups) either as terminal groups in macroamphiphiles or as encapsulated hydrophobic payloads. In another part of the work, I have developed a micellar system with which simultaneously to two of the most important ROS: superoxide and hydrogen peroxide, for inflammation-responsive drug release. The system is composed of superoxide dismutase (SOD) conjugated to oxidation-sensitive amphiphilic polysulfide/PEG block copolymers; the conjugate combines the SOD reactivity towards superoxide with that of hydrophobic thioethers towards hydrogen peroxide. Specifically, here we have demonstrated how this hybrid system can efficiently convert superoxide into hydrogen peroxide, which is then 'mopped-up' by the polysulfides. This mode of operation is functionally analogous to the SOD/catalase combination, with the advantage of being based on a single and more stable system.

Aging and disease processes may be due to deleterious and irreversible changes produced by free radical reactions. The enzyme copper-zinc superoxide dismutase (CuZn SOD; superoxide: superoxide oxidoreductase, EC 1.15.1.1) performs a protective function by scavenging superoxide radicals. In order to determine whether additional SOD activity affects longevity and oxygen metabolism in Drosophila, our approach was to clone the Sod gene and introduce additional copies of the gene back into the genome via P element mediated transformation. The effects of increased SOD activity on Drosophila life span and oxygen free radical metabolism were investigated. The CuZn SOD cDNA and gene were cloned from Drosophila melanogaster. The sequence of the Sod cDNA and gene revealed an additional C-terminal triplet coding for valine not found in the mature SOD protein. The nucleotide sequence of the coding region has 56% and 57% identity when compared to the corresponding human and rat Sod genes, respectively. A probe of the cloned gene hybridizes to position 68A4-9 on Drosophila polytene chromosomes. In wild-type Drosophila the Sod cDNA hybridizes to a 0.7-0.8 kb transcript which is greatly diminished in a SOD 'null' mutant that produces only 3.5% of the SOD protein. A 1.8 kb EcoRI gene fragment containing the Sod gene was cloned into the P vector pUChsneo and microinjected into Drosophila embryos. Five transformed lines, each of which contain an additional copy of the Sod gene at different chromosomal sites were constructed. The chromosomal positions of the transposed Sod sequence were determined by in situ hybridization of the Sod gene to salivary gland polytene chromosomes. Analysis of RNA from the transformed flies revealed that the transposed Sod gene was expressed. The range of SOD activity for the five transformed lines was 131% to 170% of the value of wild-type. There was good correlation between the amount of Sod mRNA and the level of SOD activity in the transformed lines. Increased SOD levels in the transformed lines did not confer greater resistance to paraquat-generated superoxide radicals, nor increase their lifespan. The SOD 'null' mutant with 3.5% of the wild-type SOD activity was hypersensitive to paraquat when compared to wild-type, whereas the heterozygous SOD deficiency Df(3L)1xd⁹/TM3SbSer with 50% of the wild-type SOD activity was not. Mutants lacking SOD are dramatically impaired in oxygen metabolism and a few percent of wild-type activity appears to provide significant protection against superoxide, while 50% of the wild-type levels confers essentially the same resistance as wild-type. Despite the observation that the SOD activities found in a wide range of animals correlates directly with their longevity, Drosophila melanogaster appears to be well protected against the toxic effects of oxygen by its native levels of SOD. / Arts, Faculty of / Philosophy, Department of / Graduate

L’analyse métalloprotéomique est un nouveau champ d’étude qui couple la détermination du protéome et l’identification, localisation et spéciation des éléments inorganiques complexés aux protéines. La faible concentration de ces hétéroéléments et la labilité possible de ceux-ci nécessite la mise en place d’outils de chimie analytique permettant une séparation des protéines à grande résolution, sans modifier la liaison protéine-hétéroélément, et une spéciation des protéines avec une technique bénéficiant d’une faible limite de détection. L’objet de cette étude est la mise en place de tels protocoles pour une application sur deux systèmes protéiques, modèles représentant les deux principales interactions métal-protéine : formation de complexes métalliques ou de liaisons covalentes. Dans une première partie, nous avons étudié la superoxyde dismutase à cuivre et zinc (CuZnSOD), protéine dont des formes mutantes sont impliquées dans une maladie neurodégénérative, la sclérose latérale amyotrophique. Les isoformes de point isoélectrique de CuZnSOD sauvage et mutante, séparées sur gel d’électrophorèse, ont été analysées par spectroscopie d’absorption des rayons X (XAS). Une analyse XAS sur des protéines séparées sur gel d’électrophorèse a ainsi pour la première fois été menée. Le traitement des spectres obtenus au seuil du Zn révèle la faisabilité de cette technique et celui au seuil du Cu met notamment en évidence des différences d’état d’oxydation Cu(I) et Cu(II) entre les isoformes. Dans une seconde partie, nous avons étudié la métabolisation de l’arsenic dans le cadre de la cancérogénicité de ce métalloïde. Les protéines extraites de cellules hépatiques exposées à l’arsenic ont été séparées par électrophorèse sur gel et chromatographie en phase liquide. L’analyse des échantillons obtenus par spectrométrie de masse a mis en évidence trois espèces protéiques complexant l’arsenic. / Metalloproteomic is a new discipline which ally proteome determination and the identification, location and speciation of inorganic elements bound to proteins. The low concentration of these heteroelements and sometimes their non-covalent binding to proteins need to set up analytical tools enabling the protein separation at high resolution, without any modification of the bond protein-heteroelement, and the protein speciation with a technique presenting a low detection limit. The aim of this study is to set up such protocols on two proteic systems, depicting the two main protein-heteroelement interactions: forming of metallic complexes or covalent bonds. First, we studied copper, zinc superoxide dismutase (CuZnSOD), mutants of this protein being involved in a neurodegenerative disease, the amyotrophic lateral sclerosis. Isoelectric point isoforms of wild-type and mutant CuZnSOD, separated on electrophoresis gel, were analyzed using X-ray Absorption Spectroscopy (XAS). XAS experiments on proteins separated on electrophoresis gel were performed for the first time. Data analysis at Zn K-edge demonstrated the feasibility of this technique and the ones at the Cu K-edge highlighted oxidation states Cu(I) et Cu(II) differences between isoforms. Second, we studied arsenic metabolisation to understand its carcinogenicity. Proteins extracted from hepatic cells exposed to arsenic were separated using gel electrophoresis and liquid chromatography. Samples analysis using mass spectrometry highlighted three proteic species which bind arsenic.

Superoxide dismutase is an enzyme which scavenges superoxide radicals and is thought to be a longevity determinant, as there exists a positive correlation between superoxide dismutase concentration and maximum life span potential. The cytosolic CuZn superoxide dismutase in D. melanogaster has been purified and sequenced, but the gene has not been cloned. However, when it is available the CuZn SOD gene may be reintroduced into the Drosophila genome via the P-element transformation system so its effects on the life span potential of Drosophila may be studied. This study describes attempts to clone the CuZn SOD gene from D. melanogaster using two mixed sequence oligonucleotide probes. The SI probe corresponds to amino acids 43-48 of the protein sequence and contains 128 different oligonucleotide sequences representing all possible codon combinations predicted from the amino acid sequence. The GT3 probe is targeted to amino acids 90-95 of the protein. In this probe, deoxyguanosine was placed in positions where all four nucleotides may occur to decrease probe heterogeneity. The probes were used to screen D. melanogaster Canton-S and Oregon-R genomic lambda libraries. Three positive clones isolated from the Canton-S library had identical nucleotide sequence in the GT3 probe binding region, and sequencing of the probe binding site revealed that one member of the GT3 probe had formed a 15 bp duplex with the phage DNA. Screening of the Oregon-R library produced four clones which hybridized with both GT3 and S1 probes. When these phage DNA were hybridized to polytene chromosomes by in situ hybridization, none mapped to 68AB on the third chromosome, the location of the CuZn SOD gene. These results suggest that modification of the classical strategy used in this study is necessary, and implications on probe design are discussed. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

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