NADPH oxidase activity

There are various angiotensin II-dependent pathways of NADPH oxidase activation. Xie et al. [116] have found that angiotensin II induced the stimulation of osteopontin, an extracellular matrix protein, in cardiac microvascular endothelial... 

Aspirin (acetylsalicylic acid) (Figure 29.21) is a widely applied drug for reducing ischemic cardiovascular events in patients with coronary artery disease, hypertension, or at cardiovascular risk. It is believed that the main protective function of aspirin is the inhibition of cyclooxygenase however, it has been recently proposed that aspirin may possess additional antioxidant activity [348]. It was found that long-term aspirin treatment of normotensive and hypertensive rats resulted in a decrease in vascular superoxide production by the inhibition of NADPH oxidase activity. 

Sengelpv, H., Nielson, M. H., Borregaard, N. (1992). Separation of human neutrophil plasma membrane from vesicles containing alkaline phosphatase and NADPH oxidase activity by free flow electrophoresis. J. Biol. Chem. 267,14912-17. 

Hence, this assay is an extremely useful and selective assay to measure O2 secretion. Because of this selectivity and because it measures the initial product of O2 reduction, it is often used as the method of choice to detect NADPH oxidase activity. It is suitable for semi-automation because assays can be performed in 96-well microtitre plates (using ELISA plate readers with a suitable filter), or cytochrome c reduction can be detected using simple spectrophotometers. The assay, however, is not suitable for measuring O2 that may be generated intracellularly within activated neutrophils. 

Abo, A., Boyhan, A., West, I., Thrasher, A. J., Segal, A. W. (1992). Reconstitution of neutrophil NADPH oxidase activity in the cell-free system by four components p67-phox, p47-phox, p2lracl, and cytochrome b.245. J. Biol. Chem. 267, 16767-70. 

Eklund, E. A., Marshall, M Gibbs, J. B Crean, C. D Gabig, T. G. (1991). Resolution of a low molecular weight G protein in neutrophil cytosol required for NADPH oxidase activation and reconstitution by recombinant Krev-1 protein. J. Biol. Chem. 266, 13964-70. 

Figure 6.20. Role of phospholipase D in NADPH oxidase activation. In (a) neimophils were preincubated with [3H]-alkyl-lyso-PAF (5 /iCi/ml) for 60 nun at 37 C. The cells were then washed twice with RPMI 1640 medium and finally resuspended at 2 x 10 cells/ ml in the presence ( ) and absence ( ) of 100 mM ethanol. The cells were then stimulated with 1 pM fMet-Leu-Phe and, at time intervals,aliquots were removed for analysis ofphos-phatidic acid ( ) and phosphatidylethanol ( ) by thin layer chromatography (TLC). In (b), neutrophils were incubated in the presence and absence of 10 mM butanol, and luminol chemiluminescence (10 jUM, final concentration of luminol) was measured after stimulation by 1 jUM fMet-Leu-Phe. Source Experiment of Gordon Lowe and Fiona Watson.

Gabig, T. G., Eklund, E. A., Potter, G. B., Dykes, J. R., II (1990). A neutrophil GTP-binding protein that regulates cellfree NADPH oxidase activation is located in the cytosolic fraction. J. Immunol. 145,945-51. 

The role of the Na+/H+ antiporter in human neutrophil NADPH-oxidase activation. J. Leuk. Biol. 43,183-6. 

Disulfoton induced the liver MFO system in animals (Stevens et al. 1973). In the same study, exposure to disulfoton orally for 3 days also increased ethylmorphine N-demethylase and NADPH oxidase activities, but had no effect on NADPH cytochrome c reductase. Thus, the induction of the MFO system required repeated dosing with relatively high doses. Furthermore, these changes are not specific for disulfoton exposure, and these subtle liver effects require invasive techniques in humans to obtain liver tissue for performance of these enzyme assays. 

An alternative model to explain the destruction of pathogens within phagosomes has been proposed based on the effects of NADPH oxidase activity on ion distribution. Transfer of electrons into the vacuole and the simultaneous consumption of protons... 

The O2 formed by NADPH oxidase activity can rapidly be converted into H2O2 and other toxic species that destroy microorganisms and impart injury to surrounding host tissue. The most direct evidence for the role of NADPH oxidase in host defense has come from studies of patients who have genetic defects in NADPH oxidase activity (chronic granulomatous disease). Chronic granulomatous disease patients suffer from recurrent, severe bacterial infections, which are often fatal in early childhood. 

CN188 Lopes, L. R., F. R. Laurindo, J. Mancini-Filho, R. Curi, and P. Sannomiya. NADPH-oxidase activity and lipid peroxidation in neutrophils from rats fed fat-rich diets. Cell Biochem Funct 1999 17(1) 57-64. 

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