Reactive oxygen species generation mediated by NADPH oxidase and PI3K/Akt pathways contribute to invasion of Streptococcus agalactiae in human endothelial cells

BACKGROUND Streptococcus agalactiae can causes sepsis, pneumonia, and meningitis in neonates, the elderly, and immunocompromised patients. Although the virulence properties of S. agalactiae have been partially elucidated, the molecular mechanisms related to reactive oxygen species (ROS) generation in infected human endothelial cells need further investigation. OBJECTIVES This study aimed to evaluate the influence of oxidative stress in human umbilical vein endothelial cells (HUVECs) during S. agalactiae infection. METHODS ROS production during S. agalactiae-HUVEC infection was detected using the probe CM-H2DCFDA. Microfilaments labelled with phalloidin-FITC and p47phox-Alexa 546 conjugated were analysed by immunofluorescence. mRNA levels of p47phox (NADPH oxidase subunit) were assessed using Real Time qRT-PCR. The adherence and intracellular viability of S. agalactiae in HUVECs with or without pre-treatment of DPI, apocynin (NADPH oxidase inhibitors), and LY294002 (PI3K inhibitor) were evaluated by penicillin/gentamicin exclusion. Phosphorylation of p47phox and Akt activation by S. agalactiae were evaluated by immunoblotting analysis. FINDINGS Data showed increased ROS production 15 min after HUVEC infection. Real-Time qRT-PCR and western blotting performed in HUVEC infected with S. agalactiae detected alterations in mRNA levels and activation of p47phox. Pre-treatment of endothelial cells with NADPH oxidase (DPI and apocynin) and PI3K/Akt pathway (LY294002) inhibitors reduced ROS production, bacterial intracellular viability, and generation of actin stress fibres in HUVECs infected with S. agalactiae. CONCLUSIONS ROS generation via the NADPH oxidase pathway contributes to invasion of S. agalactiae in human endothelial cells accompanied by cytoskeletal reorganisation through the PI3K/Akt pathway, which provides novel evidence for the involvement of oxidative stress in S. agalactiae pathogenesis.

Mechanism for p47phox-induced reactive oxygen species increasing after oxygen therapy in premature infants / 中华实用儿科临床杂志

Objective To explore the mechanism for the increase in reactive oxygen species regulated by p47phox of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit in peripheral blood mononuclear cells (PBMCs) after oxygen therapy in premature infants.Methods According to different volume fractions of oxygen,premature infants less than 32 weeks were divided into 3 groups:fractional concentration of inspired oxygen (FiO2) ＜ 30％ was low concentration oxygen group,FiO2 between 30％ and 40％ as middle concentration oxygen group,and FiO2 ＞ 40％ as high concentration oxygen group.Premature infants less than 32 weeks without oxygen was control group.After 48 h,3 mL blood was collected via radial artery from each group,PBMCs and serum were separated.Then intracellular reactive oxygen species (ROS) by confocal laser scanning microscopy,malondialdehyde (MDA) within serum by thiobarbituric acid colorimetric,and the location and activation rate of p47phox through immunofluorescence.Results After premature infants were exposed to oxygen,as the oxygen volume fraction was increasing,ROS and MDA gradually rised.More PBMCs with p47phox translocated to membrane,then the translocation rate of p47phox also increased.Compared with the control group,ROS were significantly higher(q =4.48,6.5,16.22,all P ＜ 0.05) among the other 3 groups ; MDA significantly increased as well(q =5.08,8.22,12.76,all P ＜ 0.05) ; the activation rate of p47phox also had significant differences (x2 =134.008,P ＜ 0.05);compared with the middle concentration oxygen group,the high concentration oxygen group had higher ROS and MDA(q =15.03,4.53,all P ＜ 0.05) ; the activation rate of p47phox increased significantly(x2 =19.26,P ＜ 0.05).Conclusions After oxygen exposure,p47phox translocated to membrane may regulate the NADPH oxidase-derived ROS increase in extremely premature infants.

Caracterización molecular en pacientes con enfermedad granulomatosa crónica por deficiencia en p47 phox / Molecular characterization in patients with chronic granulomatous disease due to p47phox deficiency

El sistema NAOPH oxidasa es un complejo enzimático transportador de electrones localizado en la membrana de las células fagocíticas. De este sistema hacen parte varias proteínas; un flavocitocromo b558' el cual está conformado por una cadena b (gp91-phox) y una cadena a (p22-phox) y poral menos 3 proteínas citosólicas (p47-phox, p67- phox, p40-phox). Una alteración gen ética en cualquiera de estas proteínas causa el síndrome de Enfermedad Granulomatosa Crónica (EGC). La caracterización de las mutaciones de los pacientes con EGC ha sido fundamental para dilucidar la estructura y función de los componentes del sistema NAOPH oxidasa. En el caso de la p47-phox, se han obtenido hallazgos importantes que la hacen un modelo interesante para estudiar el mecanismo molecular involucrado en regular la expresión y función bioquímica de este sistema. En los pacientes con defecto en la p47-phox investigados hasta ahora, se ha hallado una deleción del dinucleótido GT al comienzo del exón 2 , siendo la mayoría de ellos homocigóticos para esta deleción, la cual posiblemente se debe a eventos de recombinación entre el gen p47 -phox normal y un seudogen recientemente descrito. En el diagnóstico de pacientes no homocigóticos, cualquier mutación encontrada en el análisis del ONA (gONA o cONA) puede representar un cambio sufrido por el seudogen. Por lo tanto, para la identificación precisa del defecto genético es necesario separar el gen normal del seudogen y analizar las secuencias en forma individual. Los pacientes no homocigóticos posiblemente deben tener una segunda mutación en el alelo tipo silvestre diferente a la deleción GT. De otro lado, a través de mutagénesis sitio-dirigida se pueden modificar algunos de los aminoácidos o dominios de la p47-phox, los cuales pueden ser esenciales para su funcionamiento y su relación con la EGC. Con esta metodología, es posible introducir cambios en un gen cuya secuencia es totalmente conocida, el cual es amplificado; las mutantes así generadas pueden dar información acerca de la estructura y función de los genes analizados, observando su efecto sobre la función. De esta manera se puede determinar lo importante que puede ser un cambio estructural en la función de esta proteína.

NADPH oxidase system is an enzymatic electron transport complex localized in the membrane of phagocytic cells. Several proteins belong to this system: A flavocytochrome b558, formed by a b chain (gp91.phox) and an a chain (p22.phox) and, at least, 3 cytosolic proteins (p47.phox, p67.phox and p40 phox). Genetic alteration in any of these proteins causes the syndrome of Chronic Granulomatous Disease (CGD). Characterization of mutations in patients with CGD has been fundamental to elucidate the structure and function of NADPH oxidase system ComponentS. Several findings make p47.phoX an interesting model to study the molecular mechanism involved in regulating the expreSSion and bioChemical function ofthis system. So far, in patients with p47.phoX defect a deletion of dinucleotide GT has been foUnd at the beginning of exon 2; most of them are homocygotic for this deletion which is probably due to recombinant events between normal p47.phoX gen and a recently described pseudogen. Any mutation found when diagnosing non.homocygotic patients (gDNA or cDNA) may represent a pseudogen change. Therefore, for precise identification of the genetic defect it is necessary to separate the normal gen from the pseudogen and to analyze individual sequences. Non.homocygotic patients posibly have a second mutation in the wild type allele different fron GT deletion. On the other hand, through site. oriented mutagenesis it is posible to modify some of the aminoacids or domains of p47.phoX, which may be essential for its function and relationship with CGD. With this method010gy it is possible to introduce changes in a gen whoSe sequence is thoroughly known and which is amplified; mutants So generated can give information concerning the structure and function of the analyzed genes, observing their effect on function. In this way the importance of a structural change on the function of a protein can be determined.

Calyculin A modulates activation of the NADPH-oxidase in Me2SO-differentiated HL-60 cells

Human promyelocytic leukemia cells (HL-60) have been used as a model system in which to study the effects of protein phosphatase inhibitors on NADPH-oxidase activation. Since O2- is generated by NADPH-oxidase, we examined the effect of calyculin A pretreatment on oxidase activation in response to various agonists. When Me2SO-differentiated HL-60 cells were treated with calyculin A prior to the addition of phorbol 12-myristate 13-acetate (PMA), O2- production was inhibited; however, calyculin A enhanced O2- production by N-formyl-methionyl-leucyl-phenylalanine (FMLP). The decreased O2- production seen with calyculin A pretreatment followed by PMA may be due to diminished translocation of the p47-phox and p67-phox, cytosolic components of the oxidase, and inhibition of arachidonic acid release. Interestingly calyculin A pretreatment followed by either agonist significantly enhanced mitogen-activated-protein kinase (MAPK) activity. The differential effects of pretreatment with calyculin A on subsequent oxidase stimulation elicited by FMLP or PMA provide further evidence for substantial heterogeneity in the activation of the respiratory burst.

Effect of ketamine on stimulus-induced superoxide generation and intracellular calcium in human neutrophils in vitro / 中国药理学通报

Aim To study the effect of two racemic ketamine, S(+)-ketamine and R(-)-ketamine on stimulus-induced superoxide generation and intracellular calcium in vitro. Methods The stimulus-induced superoxide generation in human neutrophils was determined by using method of cytochrome C reduction. The intracellular calcium in human neutrophils was measured by chemiluminescence with Fura-2 loading. The phosphorylation of p47phox of NADPH oxidase in neutrophils was detected by Western blotting. Results S(+)-Ket and R(-)-Ket inhibited fMLP-induced superoxide generation in neutrophils in a concentration-dependent manner. In the case of PMA, S(+)-Ket inhibited PMA-induced superoxide generation and elevation of intracellular calcium of neutrophils in a concentration-dependent manner, whereas R(-)-Ket slightly increased PMA-induced superoxide generation and elevation of intracellular calcium of neutrophils. On the other hand S(+)-Ket inhibited the phosphorytion of p47phox of NADPH oxidase subunit,which R(-)-Ket was increased. EGTA can abolished the inhibition of S(+)-Ket on PMA-induced phosphorytion of p47phox.Conclusion S(+)-Ket inhibits the phosphorylation of p47phox of NADPH oxidase subunit and the superoxide generation in human neutrophils via PKC-calcium signal pathway.