A nefropatia diabética (ND) é uma das principais causas de nefropatia crônica, o que torna o diabetes mellitus (DM) responsável por 44% da prevalência de doença renal crônica (DRC) no mundo. O papel do estresse oxidativo na patogênese da ND está bem estabelecido e genes pertencentes a vias pró- e antioxidantes são possíveis candidatos a conferirem susceptibilidade genética a essa e a outras complicações crônicas. Além do estresse oxidativo, o transporte intracelular de glicose, mediado por transportadores específicos, também parece exercer influência sobre a ND e outras complicações. O objetivo deste trabalho foi avaliar a associação entre ND e alguns polimorfismos de um único nucleotídeo (SNPs) em genes que codificam proteínas transportadoras de glicose (GLUT2 [SLC2A2]), proteínas pró-oxidantes (p22phox [CYBA] e NOX-2 [CYBB]) e proteínas antioxidantes (glutationa peroxidase-4 [GPX4] e catalase [CAT]) em uma coorte brasileira (n=453; 45,8% de pacientes com ND) e três coortes francesas (SURGENE [n=340; 17,7% de pacientes com ND na fase basal], GENEDIAB [n=313; 66,7% de pacientes com ND] e GENESIS [n=636; 49,7% de pacientes com ND]) de pacientes portadores de DM tipo 1. Os SNPs foram genotipados com o uso da técnica de reação em cadeia da polimerase (PCR) em tempo real e os resultados expressos em odds ratio (OR) ou hazard ratio (HR), com seus respectivos intervalos de confiança (IC), determinados em modelos ajustados de regressão logística politômica ou regressão de risco proporcional de Cox, respectivamente. A razão albumina/creatinina urinária (ACR) ou a taxa de excreção urinária de albumina (EUA) foram utilizadas para definir os estágios de ND e os pacientes foram classificados de acordo com a presença ou ausência de ND incipiente (ACR 30 - 300 mg/g de creatinina ou EUA 20 - 200 ?g/min ou 20 - 200 mg/L) e creatinina plasmática <1,7 mg/dL), ND estabilizada (ACR >300 mg/g de creatinina ou EUA > 200 ug/min ou > 200 mg/L e creatinina plasmática < 1,7 mg/dL ) ou ND avançada (ACR > 300 mg/g de creatinina ou EUA > 200 ug/min ou > 200 mg/L e creatinina plasmática > 1,7 mg/dL ou qualquer terapia de reposição renal) e também foram avaliadas associações dos SNPs com a taxa de filtração glomerular estimada (TFGe). O alelo raro A do SNP rs6610650 no gene CYBB foi associado com valores baixos de TFGe em mulheres na coorte brasileira e com a prevalência de ND estabilizada/avançada em mulheres da coorte francesa (OR 1,75; IC 95% 1,11 - 2,78; p=0,016). O alelo raro T do SNP rs713041 no gene GPX4 foi inversamente associado com a prevalência de ND estabilizada/avançada em homens na coorte brasileira (OR 0,30, IC95% 0,13 - 0,68, p=0,004) e com valores elevados de TFGe em homens na coorte francesa. O alelo raro A do SNP rs7947841 no gene CAT foi associado com a prevalência de ND incipiente (OR 2,79; IC95% 1,21 - 6,24; p=0,01) e ND estabilizada/avançada (OR 5,72; IC95% 1,62 - 22,03; p=0,007), bem como com a incidência de eventos renais, definidos como novos casos de microalbuminúria ou progressão para um estágio mais grave de ND durante o seguimento de estudo, na coorte SURGENE (HR 1,82; IC95% 1,13 - 2,81; p=0,01). O mesmo alelo de risco associou-se com a prevalência de ND incipiente (OR 3,13; IC95% 1,42 - 7,24; p=0,004) e com a incidência de insuficiência renal crônica terminal (IRCT) na coorte GENEDIAB (HR 2,11; IC95% 1,23 - 3,60; p=0,008) e com a prevalência de ND incipiente (OR 2,16; IC95% 1,14 - 4,10, p=0,02) e ND estabilizada/avançada (OR 2,71; IC95% 1,38 - 5,42; p=0,004) na coorte brasileira. O alelo raro T do SNP rs9932581 no gene CYBA foi inversamente associado com a prevalência de ND estabilizada/avançada (OR 0,60; IC95% 0,46 - 0,78; p=0,0001) e com valores mais baixos de TFGe nos pacientes de descendência europeia da coorte GENESIS/GENEDIAB. Este mesmo alelo foi associado com a incidência de eventos renais e de IRCT nas coortes SURGENE (HR 0,63; IC95% 0,46 - 0,86; p=0,003) e GENESIS/GENEDIAB (HR 0,51; IC95% 0,31 - 0,78; p=0,002), respectivamente. Entretanto estes resultados não foram replicados na coorte brasileira. O alelo raro T do SNP rs11924032 no gene SLC2A2 foi inversamente associado com a perda da TFGe ao logo do tempo (0,02%/ano vs 2,18%/ano para os pacientes portadores do genótipo GG; p=0,005), na coorte SURGENE. Este mesmo alelo foi inversamente associado com a incidência de IRCT nas coortes GENESIS/GENEDIAB (HR 0,53; IC95% 0,29 - 0,89; p=0,01). Os resultados observados para o gene SLC2A2 não forneceram fortes indícios para afirmarmos que este gene exerça um papel relevante no desenvolvimento da ND nos pacientes com DM tipo 1 nas coortes francesas estudadas. Em contrapartida, os SNPs nos genes que codificam as proteínas pró-oxidantes CYBA e CYBB e as proteínas antioxidantes GPX-4 e CAT foram capazes de modular o risco para doença renal em pacientes portadores de DM tipo 1, sendo que os SNPs presentes nos genes CYBB, GPX4 e CAT tiveram seus resultados replicados em coortes independentes, o que corrobora a importância destes genes e, consequentemente, do estresse oxidativo, na patogênese da ND / Diabetic nephropathy (DN) is a major cause of chronic nephropathy, with diabetes mellitus (DM) accounting for 44% of the prevalence of chronic kidney disease (CKD) in the world. The role of oxidative stress in the pathogenesis of DN is well established and genes belonging to pro- and antioxidant pathways are possible candidates to confer genetic susceptibility to this and other chronic complications. Besides oxidative stress, intracellular glucose transport mediated by specific transporters, also appears to influence DN and other complications. The aim of this study was to evaluate the association between DN and some single nucleotide polymorphisms (SNPs) present in genes encoding glucose transport proteins (GLUT2 [SLC2A2]), pro- (p22phox [CYBA] and NOX-2 [CYBB]) and antioxidants (glutathione peroxidase-4 [GPX4] and catalase [CAT]) proteins, in a Brazilian cohort [n= 453; 45.8% f patients with DN], and three French cohorts (SURGENE [n=340; 17.7% of patients with DN at baseline], GENEDIAB [n=313; 66.7% of patients with DN], and GENESIS [n=636; 49.7% of patients with DN]) of patients with type 1 DM. The SNPs were genotyped using the technique of real time polymerase chain reaction (PCR) and results expressed as odds ratio (OR) and hazard ratio (HR), with their respectively 95% confidence intervals (CI), determined by adjusted models of polytomic logistic regression and Cox proportional hazard regression, respectively. The albumin/creatinine ratio (ACR) or the urinary albumin excretion (UAE) rate were used to define the DN stages and the patients were classified according to the presence or absence of incipient DN (ACR 30 - 300 mg/g of creatinine or UAE 20 - 200 ug/min or 20 - 200 mg/L) and plasmatic creatinine < 1,7 mg/dL), established DN (ACR > 300 mg/g of creatinine or EUA > 200 ug/min or > 200 mg/L and plasmatic creatinine <1,7 mg/dL) or advanced DN (ACR >300 mg/g of creatinine or UAE > 200 ug/min or > 200 mg/L and plasmatic creatinine > 1,7 mg/dL or any renal replacement therapy). Associations for the estimated glomerular filtration rate (eGFR) were also evaluated. The rare allele A of the SNP rs6610650 in CYBB gene was associated with low values of eGFR in women in the Brazilian cohort and with the prevalence of established/advanced DN in women in the French cohort (OR 1.75, 95%CI 1.11 - 2.78, p=0.016). The rare allele T of the SNP rs713041 in GPX4 gene was inversely associated with the prevalence of established/advanced DN in men in the Brazilian cohort (OR 0.30, 95%CI 0.13 - 0.68, p=0.004) and with higher values of eGFR in men in the French cohort. The rare allele A of the SNP rs7947841 in CAT gene was associated with the prevalence of incipient DN (OR 2.79, 95%CI 1.21 - 6.24, p=0.01) and established/advanced DN (OR 5.72; 95%CI 1.62 - 22.03, p=0.007) as well as the incidence of renal events, defined as new cases of microalbuminuria or progression to a more severe stage during the follow-up study, in SURGENE cohort (HR 1.82, 95%CI 1.13 - 2.81, p=0.01). The same risk allele was associated with the prevalence of incipient DN (OR 3.13, 95%CI 1.42 - 7.24, p=0.004), the incidence of end-stage renal disease (ESRD) in the cohort GENEDIAB (HR 2.11, 95%CI 1.23 - 3.60, p=0.008) and with the prevalence of incipient DN (OR 2.16, 95%CI 1.14 - 4.10, p=0.02) and established/advanced DN (OR 2.71, 95%CI 1.38 - 5.42, p=0.004) in the Brazilian cohort. The rare T allele of the SNP rs9932581 in CYBA gene was inversely associated with the prevalence of established/advanced DN (OR: 0.60, 95%CI: 0.46 - .78, p=0.0001) and associated with lower values of eGFR in patients of GENESIS/GENEDIAB cohort. The same allele was inversely associated with the incidence of renal events and ESRD in SURGENE (HR 0.63, 95%CI 0.46 - 0.86, p=0.003) and GENESIS/GENEDIAB (HR 0.51, 95%CI 0.31 - 0.78, p=0.002) cohorts. However, these results were not replicated in the Brazilian cohort. The rare T allele of the SNP rs11924032 in SLC2A2 gene was inversely associated with the loss of eGFR during the follow-up (0.02%/year vs. 2.18%/year for patients with the GG genotype, p=0.005) in the SURGENE cohort. The same allele was inversely associated with the incidence of ESRD in the GENESIS/GENEDIAB cohorts (HR 0.53, 95%CI 0.29 - 0.89, p=0.01). The results observed for the SLC2A2 gene, in this study, did not provide strong evidence to state that this gene exerts a relevant role in the development of DN in patients with type 1 DM in the studied cohorts. However, SNPs in genes encoding the pro-oxidant proteins CYBA and CYBB, and the antioxidants proteins GPX-4 and CAT were able to modulate the risk of renal disease in patients with type 1 DM. The studied SNPs in CYBB, GPX4 and CAT genes had their results replicated in independent cohorts, which confirms the importance of these genes and, hence, of the oxidative stress in the pathogenesis of DN

Estudos caracterizaram o envolvimento da PDI na modulação da geração de EROs pela Nox1 como moduladores da migração de células do músculo liso vascular (VSMC) mediados por fatores de crescimento derivados de plaqueta (PDGF). Outros estudos vêm demonstrando o envolvimento do fator de crescimento epidermal (EGFR) no remodelamento vascular, após a transativação via Angiotensina II. Entretanto o papel da PDI na ativação do EGFR via Nox1 na hipertensão arterial ainda permanece desconhecido. Objetivo foi caracterizar o papel da PDI na expressão de Nox1 dependente do EGFR durante o desenvolvimento da hipertensão arterial. Resultados demonstram um aumento da expressão de HB-EGF e ativação de ERK 1/2 na aorta de animais SHR com 8 semanas e 12 semanas de idade, e no plasma de animais SHR com 12 semanas. Ainda, a OvxPDI acarretou em um aumento na expressão gênica de Nox-1 tanto na OVXPDI quanto na forma OvxPDIMUT. Resultados mostram um novo papel da PDI na expressão gênica de Nox-1 via EGFR e a participação desta tiol oxido redutase na gênese da hipertensão arterial. / Studies characterizing the involvement of PDI in the modulation of ROS by Nox1 as modulators of cell migration of vascular smooth muscle (VSMC) mediated by growth factors derived from platelets (PDGF). Other studies have demonstrated the involvement of the epidermal growth factor receptor (EGFR) on vascular remodeling after transactivation via Angiotensin II. However the role of PDI in the activation of EGFR via Nox1 in hypertension remains unknown. Objective was to characterize the role of PDI in Nox1 dependent EGFR expression during the development of hypertension. Results show an increase of HB-EGF expression and ERK 1/2 activation in the aortic SHR at 8 weeks and 12 weeks of age, and plasma SHR at 12 weeks. Still, the OvxPDI resulted in an increase in gene expression of Nox-1 both in OVXPDI and in OvxPDIMUT way. Results show a new role of PDI in gene expression of Nox-1 via EGFR and the participation of this thiol reductase oxide in the pathogenesis of hypertension.

A Doença Granulomatosa Crônica é uma imunodeficiência grave e rara, na qual os quadros infecciosos por bactérias e fungos, ocorrem predominantemente nas barreiras naturais do organismo. O defeito reside em mutações em um dos componentes do sistema NADPH oxidase. O dHPLC mostrou-se mais sensível que o SSCP, sendo eficaz na detecção de alterações em 100% dos casos. Identificamos sete mutações diferentes no gene CYBB, sendo quatro delas inéditas. São elas R226X; R290X; e C537R. Dentre as mutações inéditas identificamos: T302fsX46; c.141 +5 G> T; C185R; e H222L. Identificamos a mutação V25fsX51 no gene NCF1 em duas pacientes. Estabelecemos uma correlação entre genótipo e fenótipo clínico baseado em manifestações clínicas relevantes na DGC, nos fornecendo dados importantes de cada manifestação clínica e um índice de gravidade clínica (IGC) para cada tipo de mutação. Os resultados contribuem para a construção de estratégias que permitam a identificação dos defeitos genético-moleculares relacionados à DGC. / Chronic granulomatous disease is a primary immunodeficiency characterized by recurrent and severe infections, affecting the body barriers. In these patients, phagocytes present a failure in the respiratory burst caused by a deficiency of the NADPH oxidase system, and a microbicidal defect. Mutations affecting one of the components of the NADPH oxidase system. The dHPLC proved to be more sensitive to the SSCP, being effective in detecting changes in 100% of cases. We found seven different mutations, four of which are original. Are they R226X; R290X; and C537R. Among the unpublished mutations identified: T302fsX46; c. 141 + 5 G > T; C185R; and H222L. We identify the gene mutation V25fsX51 NCF1 in two patients. We have established a correlation between genotype and phenotype clinical relevant clinical manifestations based on DGC in providing important data from each clinical and clinical severity index (CSI) for each type of mutation. The results contribute to the construction of strategies enabling the identification of molecular genetic defects related to CGD.

Os modelos experimentais têm sido utilizados para o estudo dos mecanismos fisiopatológicos envolvidos no desenvolvimento da Doença Pulmonar Obstrutiva Crônica (DPOC). O modelo que melhor mimetiza a doença em humanos é o que utiliza a exposição à fumaça de cigarro. No entanto, a utilização deste modelo experimental requer um longo tempo de exposição (6 meses) e a lesão do parênquima obtida é considerada leve. O desequilíbrio protease/anti-protease é considerado um importante mecanismo fisiopatológico envolvido no desenvolvimento da DPOC. Desta forma, neste estudo propomos o desenvolvimento de um modelo experimental no qual associamos a instilação de elastase previamente ao início da exposição ao fumo na tentativa de obter um maior grau de lesão tecidual em um menor espaço de tempo. Para tanto, camundongos C57Bl/6 foram divididos em quatro grupos: Controle, Elastase, Fumo, Fumo/Elastase 1 dose e Fumo/Elastase 2 doses e analisados após dois meses de exposição. Os animais do grupo Fumo/Elastase 1 dose e 2 doses foram submetidos à instilação intranasal de elastase pancreática de porco (0,33UI) e expostos a fumaça de cigarro por dois meses. O grupo controle recebeu o mesmo tratamento com solução fisiológica (NaCl 0.9%). A exposição ao fumo foi feita por 30min, 2 vezes/dia, 5 dias da semana. Após dois meses, os animais foram sacrificados e observamos aumento de LM no grupo Fumo/Elastase 1 dose e 2 doses comparado aos grupos Controle e Fumo; aumento de células positivas para MAC-2 no parênquima (Fumo/Elastase 2 doses) e vias aéreas (Fumo/Elastase 1 dose e 2 doses), MMP-12 no parênquima pulmonar (Fumo/Elastase 2 doses), GP91 no parênquima (Fumo/Elastase 1 dose e 2 doses) e vias aéreas (Fumo e Fumo/Elastase 1 dose) e aumento de proporção de fibras elásticas no parênquima pulmonar do grupo Fumo/Elastase 1 dose e do grupo Fumo, caracterizando presença de enfisema pulmonar. A instilação de elastase pancreática de porco juntamente com a exposição à fumaça de cigarro aumentou a susceptibilidade ao desenvolvimento do enfisema / Experimental models have been used to study the pathophysiological mechanisms involved in the development of COPD. Cigarette Smoke exposure (CS) is considered the best model to mimetize the disease in humans. However, the CS requires a long exposure time (6 months) and the parenchymal destruction obtained is considered mild. The protease / anti - protease imbalance is considered an important pathophysiological mechanism involved in the development of COPD. Thus, in this study we propose the development of an experimental model in which we associate instillation of elastase before the start of exposure to smoke, trying to increase the parenchymal destruction degree in a shorter time. For that, C57BL / 6 mice were divided into four groups: Control, Elastase, Smoke and Smoke/Elastase 1 dose and Smoke/Elastase 2 doses and analyzed in two months after the CS exposition. The Smoke/Elastase 1 dose and 2 doses animals group received an intranasal instillation of porcine pancreatic elastase (0.33 IU) and exposed to cigarette smoke for two months. The control group received the same treatment with saline (NaCl 0.9 %). Animals were exposed to CS for 30min, 2 times / day, 5 days a week. After two months, we observed increased mean linear intercept (LM) and positive cells for MAC-2, MMP-12 and GP91 in the airways and lung parenchyma and increase of elastic fibers in the lung parenchyma characterizing the presence of pulmonary emphysema. The instillation of porcine pancreatic elastase along the exposure to cigarette smoke increased susceptibility to the development of emphysema

O sistema NADPH oxidase é um complexo enzimático gerador de superóxido. O NF-kB é um fator de transcrição envolvido no controle da expressão de diversos genes ligados à resposta inflamatória. Defeitos no eixo IL-12/23-IFN-g resultam em infecções recorrentes e à susceptibilidade mendeliana a micobacterioses, podendo diminuir a expressão do componente gp91-phox da NADPH oxidase. Estudamos qual é a relação direta do NF-kB e de defeitos no eixo IL-12/23-IFN-g na regulação dos genes CYBA, NCF1, NCF2 e NCF4 do sistema NADPH oxidase humano em células U937, células B EBV transformadas provenientes de pacientes com EDA-ID, DGC, ou de pacientes com defeitos no eixo IL-12/23-IFN-g. A expressão dos genes NCF1 e NCF2 foi diminuída em células com defeitos no eixo (IFNGR1 e INFGR2) e em células U937 IkB S32A/S36A. A expressão do gene NCF1 também foi diminuída em células EDA-ID S32I e em células EDA-ID NEMO/IKKg W420X. O NF-kB e os IFNGR1 e INFGR2 são necessários para a expressão dos genes NCF1 e NCF2 e para a ativação do sistema NADPH oxidase humano neste sistema modelo. / The NADPH oxidase system is an enzymatic complex that generates superoxide. The NF-kB is a transcriptional factor involved in the expression of several genes related to the inflammatory response. The IL-12/23-IFN-g axis defects lead to recurrent infections and to the mendelian susceptibility of mycobacterial disease (MSMD), and they can decrease the gp91-phox expression (a NADPH oxidase component). We studied the NF-kB and the IL-12/23-IFN-g axis defects consequences on the regulation of CYBA, NCF1, NCF2 and NCF4 genes of the human NADPH oxidase system in U937 cells, and in B EBV cells from patients with EDA-ID, DGC, or patients with IL-12/23-IFN-g axis defects. The NCF1 and NCF2 gene expression was decreased in IL-12/23-IFN-g axis defects cells (IFNGR1 and INFGR2) and in U937 IkB S32A/S36A cells. NCF1 gene expression was decreased in EDA-ID S32I and in EDA-ID NEMO/IKKg W420X cell lineages. The NF-kB and the IFNGR1 and INFGR2 are necessary for NCF1 and NCF2 gene expression and activation of the human NADPH oxidase in this model system.

A doença granulomatosa crônica é uma imunodeficiência primária dos fagócitos causada por mutações no sistema NADPH oxidase resultando em burst oxidativo ausente ou reduzido. Nosso objetivo foi realizar uma análise genética molecular do complexo NADPH oxidase em pacientes com diagnóstico clínico de DGC. Cinqüenta e quatro pacientes com diagnóstico clínico sugestivo da DGC foram incluídos em nosso estudo. As populações de neutrófilos e monócitos foram avaliadas pela capacidade de produzir peróxido de hidrogênio por meio do teste de DHR. Dezoito pacientes apresentaram defeito no burst oxidativo, enquanto trinta e oito apresentaram produção de peróxido normal. O DNA genômico dos dezoito pacientes com burst oxidativo diminuído foi extraído, os genes da cadeia beta polipeptídica do complexo citocromo b e o factor citoplasmático de neutrófilos, foram sequenciados. Sete pacientes apresentaram diferentes mutações, tanto no gene CYBB como no NCF1. Concluímos que a combinação do teste de DHR e o sequenciamento direto são métodos eficazes para o diagnóstico genético da DGC. / Chronic granulomatous disease is a primary immunodeficiency caused by mutations in the phagocyte NADPH oxidase system resulting in absent or reduced oxidative burst. Our goal was to perform a molecular genetic analysis of complex NADPH oxidase in patients with clinical diagnosis of CGD. Fifty-four patients with a clinical diagnosis of CGD were included in our study. The populations of neutrophils and monocytes were evaluated for the ability to produce hydrogen peroxide through the DHR test. Eighteen patients had a defect in the oxidative burst, while thirty-eight had normal peroxide production. Genomic DNA of the eighteen patients with decreased oxidative burst was extracted, the genes the chain complex cytochrome beta polypeptide and the neutrophil cytoplasmic factor, were sequenced. Seven patients had different mutations, both in the CYBB gene as in NCF1. We conclude that the combination of direct sequencing and DHR test methods are effective for the genetic diagnosis of CGD.

Ce travail montre qu’une protéine non encore décrite dans les phagocytes, la PAT1 « Protein interacting with APP Tail 1 », interagit avec la partie cytosolique de la p22phox (composant du cytochrome b558 membranaire de la NADPH oxydase). Nous avons utilisé différentes approches pour montrer cette interaction : le système double hybride, la technique de GST-pull down, la microscopie confocale et la technique de co-immunoprécipitation. De plus, nous avons montré que la PAT1a recombinante augmente l’activité de la NADPH oxydase, in vitro dans un système acellulaire reconstitué, et dans les cellules intactes (monocytes et cellules COS-phox). Cette nouvelle interaction régule donc l’activation de la NADPH oxydase et la production des FRO. Par ailleurs, la liaison de PAT1 aux microtubules pourrait favoriser l’assemblage du complexe NADPH oxydase pendant son activation. Ceci pourrait conduire à l’identification de nouvelles cibles thérapeutiques qui préviennent la survenue des lésions tissulaires dans les maladies inflammatoires. / Reactive oxygen species (ROS) production by the phagocyte NADPH oxidase plays a crucial role in host defenses. NADPH oxidase is composed of the membrane flavocytochrome b558 components (p22phox and gp91phox/NOX2), and cytosolic components (p40phox, p47phox, p67phox and a small GTPase Rac1 or Rac2). In this work we identified PAT1 by double hybrid system as a potential partner of p22phox. The interaction between p22phox and PAT1a was further confirmed by in vitro GST pull-down assay, confocal microscopy and co-immunoprecipitation. Addition of recombinant PAT1a to the cell free-system enhanced NADPH oxidase activation and it’s over-expression in human monocytes and in COSphox cells increased ROS production in resting and fMLP-stimulated cells.These data clearly identify PAT1 as a novel regulator of NADPH oxidase activation in phagocytes.Inhibition of p22phox/PAT1 interaction could be used as new approach to limit ROS production by phagocytes at inflammatory sites.

La mutagénèse dirigée et la transfection stable dans le modèle cellulaire X-CGD PLB-985 ont été utilisées pour étudier les mécanismes moléculaires du dysfonctionnement de l'oxydase dans 3 cas de CGD-X+ (H303N /P304R, D500G, L505R), 1 cas de X–-CGD (S193F) et le rôle de 2 domaines de Nox2 191TSSTKTIRRS200 et 484DESQANHFAVHHDEEKD500. Les mutations H303N, P304R et D500G inhibent l'assemblage et l'activité de l'oxydase. La mutation L505R diminue partiellement l'affinité de Nox2 pour NADPH et son interaction avec p67phox in vitro. Cependant cet acide aminé n'est impliqué dans la fixation directe du NADPH. La boucle D et la région (484-504) sont essentielles à l'activité oxydase. Seule la région C-terminale est impliquée dans l'assemblage de l'oxydase et le transfert électronique du NADPH vers FAD. La boucle D des Nox1/3/4 est fonctionnelle pour l'activité oxidase de Nox2. Le modèle-3D de la partie C-terminale de Nox2 confirme l'importance de l'hélice-alpha dans l'activation du complexe oxydase.

Plant programmed cell death (PCD) is an essential process in plant-pathogen interactions. Importantly, PCD can have contrasting effects on the outcome depending on context. For example, plant PCD in plant-biotroph interactions is clearly beneficial to plants, whereas it could be detrimental to plants in plant-necrotroph interactions. Sclerotinia sclerotiorum is an agriculturally and economically important necrotrophic pathogen. Previous studies have shown that S. sclerotiorum secretes oxalic acid (OA) to enhance Sclerotinia virulence by various mechanisms including induction of PCD in plants. A recent study has also shown that reactive oxygen species (ROS) generation correlates with induction of PCD during disease development. These studies focus on links between ROS, oxalate, and PCD, and how they impact S. sclerotiorum disease development. I examined the involvement of ROS in pathogenic development of S. sclerotiorum. I identified and functionally characterized two predicted S. sclerotiorum NADPH oxidases (Nox1 and Nox2) by RNAi. Both nox genes appear to have roles in sclerotial development, while only Nox1-silenced mutants showed reduced virulence. Interestingly, the reduced virulence of the Nox1-silenced mutant correlated with decreased production of OA in the mutant. This observation suggests that regulation of ROS by S. sclerotiorum Nox1 may be linked to OA. The next study details the phenotype of plants inoculated with an S. sclerotiorum oxalate deficient mutant (A2), which showed restricted growth at the infected site. This response resembles the hypersensitive response (HR), and is associated with plant resistance responses including cell wall strengthening, plant oxidative burst, and induction of defensin genes. Conversely, leaves infected with wild type showed unrestricted spreading of cell death and were not associated with these resistant responses. Furthermore, previous work had shown that a Caenorhabditis elegans anti-apoptotic gene (ced-9) conferred resistance to wild type S. sclerotiorum, while this gene had negligible effects on the phenotype of plant leaves inoculated with A2 mutants. These findings suggest that HR-like cell death by A2 and PCD by wild type S. sclerotiorum may be regulated by different pathways. As a whole, these results reveal the importance of ROS, oxalate, and PCD in Sclerotinia disease development as well as the significance of interplay between them. These studies contribute to the understanding of the underlying mechanisms of Sclerotinia disease.

Les espèces réactives de l'oxygène ou ROS sont des molécules dérivées de l'oxygène produites " de manière professionnelle " par les NADPH oxydases (NOX). Ces enzymes utilisent l'oxygène comme accepteur d'électrons afin de les transférer à travers les membranes. Le produit de cette réaction est l'anion superoxyde. La famille des NADPH oxydases est composée chez l'Homme de 7 membres : NOX1, NOX2, NOX3, NOX4, NOX5, DUOX1 et DUOX2. Bien que les structures des différentes isoformes des NOX soient très homologues, leurs mécanismes d'activation et leurs distributions tissulaires, cellulaires et subcellulaires et en conséquence, leurs fonctions physiologiques sont très différents. Leurs rôles physiologiques mais aussi pathologiques ont été très souvent déterminés à l'aide de modèles murins transgéniques. Le travail présenté dans cette thèse a eu pour but de déterminer deux nouveaux rôles de NOX1 dans des pathologies humaines : l'hypertension artérielle et le syndrome de détresse respiratoire. Dans un second temps, nous avons également évalué le rôle anti-inflammatoire de NOX2 en utilisant comme modèle des souris déficientes en Nox2. NOX1 a été impliqué dans l'hypertension artérielle induite par l'angiotensine II. Dans cette étude, il a été démontré que les ROS générés par NOX1 sont impliqués dans la formation des anévrysmes aortiques induits par l'angiotensine II, en régulant l'activité des métallo-protéases ainsi que la fibrose. L'activation de NOX1 par l'angiotensine II via son récepteur AT1 est un phénomène bien connu. Nous avons démontré que NOX1 est capable également de réguler la présence du récepteur AT1 à la membrane plasmique. Ces données font de NOX1 une cible thérapeutique de plus en plus importante dans l'hypertension artérielle ainsi que dans les anévrysmes aortiques. Le syndrome de détresse respiratoire des prématurés est caractérisé par une immaturité pulmonaire nécessitant une ventilation mécanique et de fortes concentrations d'oxygène. Les poumons soumis alors à des conditions d'hyperoxie vont être exposés à des concentrations importantes de ROS favorisant et exacerbant les lésions pulmonaires. Lors de cette étude, nous avons démontré à l'aide de souris déficientes en Nox1 que cette NADPH oxydase uniquement est impliquée dans la génération des ROS au niveau des cellules épithéliales et endothéliales pulmonaires induite par l'hyperoxie. NOX1 est à nouveau une cible potentielle thérapeutique lors des syndromes respiratoires des prématurés particulièrement sensibles aux fortes concentrations de ROS. La maladie granulomateuse septique ou CGD est un syndrome d'immunodéficience dû à la présence de mutations essentiellement de gp91phox, gène codant pour NOX2. En conséquence, les patients atteints de CGD souffrent d'infections récurrentes mettant en jeu leur pronostic vital. Associées à ces infections, des réactions inflammatoires exacerbées sont observées et ont un impact sur la morbidité. Dans cette étude, nous avons déterminé qu'une des origines possibles de l'inflammation en l'absence de NOX2 est le beta-glycan. Ces polymères de glucose, composés majoritaires de la paroi des champignons, induisent une inflammation qui ne peut se résoudre en l'absence de NOX2. Mais bien que l'hyperinflammation observée dans un modèle inflammatoire cutané chez les souris déficientes en Nox2 soit associée à de fortes quantités de TNF-alpha, l'augmentation de cette cytokine pro-inflammatoire n'est pas le principal médiateur les lésions inflammatoires induites par les beta-glycans et l'absence de Nox2. Le traitement des patients CGD par des bloqueurs du TNF-alpha ne semblent donc pas recommandés. D'un autre côté, il semble que les molécules capables de bloquer les effets des beta-glycans sont à considérer comme des cibles potentielles pour la recherche de molécules anti-inflammatoires spécifiques et le développement de nouvelles stratégies thérapeutiques et préventives pour les patients CGD.