Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.6.3.1 (NADPH oxidase)
11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Superoxide (O-2) and nitric oxide (NO) act to kill invading microbes in phagocytes. In macrophages NO is synthesized by inducible nitric oxide synthase (iNOS, NOS 2) from L-arginine (L-Arg) and oxygen; however, O-2 was thought to be produced mainly by NADPH oxidase. Electron paramagnetic resonance (EPR) spin trapping experiments performed in murine macrophages demonstrate a novel pathway of O-2 generation. It was observed that depletion of cytosolic L-Arg triggers O-2 generation from iNOS. This iNOS-mediated O-2 generation was blocked by the NOS inhibitor N-nitro-L-arginine methyl ester or by L-Arg, but not by the noninhibitory enantiomer N-nitro-D-arginine methyl ester. In L-Arg-depleted macrophages iNOS generates both O-2 and NO that interact to form the potent oxidant peroxynitrite (ONOO-), which was detected by luminol luminescence and whose formation was blocked by superoxide dismutase, urate, or L-Arg. This iNOS-derived ONOO- resulted in nitrotyrosine formation, and this was inhibited by iNOS blockade. iNOS-mediated O-2 and ONOO- increased the antibacterial activity of macrophages. Thus, with reduced L-Arg availability iNOS produces O-2 and ONOO- that modulate macrophage function. Due to the existence of L-Arg depletion in inflammation, iNOS-mediated O-2 and ONOO- may occur and contribute to cytostatic/cytotoxic actions of macrophages.
...
PMID:Superoxide and peroxynitrite generation from inducible nitric oxide synthase in macrophages. 919 73

Superoxide anion (O2-) plays a key role in the endogenous suppression of endothelium-derived nitric oxide (NO) bioactivity and has been implicated in the development of hypertension. In previous studies, we found that O2- is produced predominantly in the adventitia of isolated rabbit aorta and acts as a barrier to NO. In the present studies, we characterize the enzyme responsible for O2- production in the adventitia and show that this enzyme is a constitutively active NADPH oxidase with similar composition as the phagocyte NADPH oxidase. Constitutive O2--generating activity was localized to aortic adventitial fibroblasts and was enhanced by the potent vasoconstrictor angiotensin II. Immunohistochemistry of aortic sections demonstrated the presence of p22(phox), gp91(phox), p47(phox), and p67(phox) localized exclusively in rabbit aortic adventitia, coincident with the site of staining for O2- production. Furthermore, immunodepletion of p67(phox) from adventitial fibroblast particulates resulted in the loss of NADPH oxidase activity, which could be restored by the addition of recombinant p67(phox). Further study into the regulation of this adventitial source of O2- is important in elucidating the mechanisms regulating the bioactivity of NO and may contribute to our understanding of the pathogenesis of hypertension.
...
PMID:Localization of a constitutively active, phagocyte-like NADPH oxidase in rabbit aortic adventitia: enhancement by angiotensin II. 940 39

The effects of nitric oxide (NO) on superoxide (O-2) generation of the NADPH oxidase in pig neutrophils were studied. NO dose-dependently suppressed O-2 generation of both neutrophil NADPH oxidase and reconstituted NADPH oxidase. Effects of NO on NADPH-binding site and the redox centers including FAD and low spin heme in cytochrome b558 and the electron transfer rates from NADPH to heme via FAD were examined under anaerobic conditions. Both reaction rates and the Km value for NADPH were unchanged by NO. Visible and EPR spectra of cytochrome b558 showed that the structure of heme was unchanged by NO, indicating that NO does not affect the redox centers of the oxidase. In reconstituted NADPH oxidase system, NO did not inhibit O-2 generation of the oxidase when added after activation. The addition of NO to the membrane component or the cytosol component inhibited the activity by 24.0 +/- 5.3 or 37.4 +/- 7.1%, respectively. The addition of NO during the activation process or to the cytosol component simultaneously with myristate inhibited the activity by 74.0 +/- 5.2 or 70.0 +/- 8.3%, respectively, suggesting that cytosol protein(s) treated with myristate becomes susceptible to NO. Peroxynitrite did not interfere with O-2 generation.
...
PMID:Nitric oxide inactivates NADPH oxidase in pig neutrophils by inhibiting its assembling process. 940 51

In response to bacterial endotoxin (lipopolysaccharide, LPS) monocytes synthesize and express on their surface tissue factor (TF) which triggers the blood coagulation cascade. Since LPS stimulates active oxygen species production by these cells, we investigated the roles of superoxide anion and nitric oxide in the induction of TF in human blood monocytes. Scavengers of reactive oxygen intermediates such as N-acetyl cysteine or pyrrolidine dithiocarbamate were able to block TF induction. In addition, inhibition of NADPH oxidase and/or NO synthase which are major sources of active oxygen species in phagocytes also blocked TF induction. The restoration of TF expression, in monocytes treated with inhibitors of reactive oxygen production, by N,N'-dimethyl-gamma, gamma'-dipyridylium dichloride and/or sodium nitrosylpentacyanoferrate (III), which generate respectively O2- and NO, suggests that these two radicals participate in the induction of TF at the surface of blood monocytes stimulated by LPS.
...
PMID:Role of oxygen radicals in tissue factor induction by endotoxin in blood monocytes. 948 74

Interleukin-1 beta (IL-1) is implicated in cartilage destruction in arthritis through promotion of matrix metalloproteinase production. Upregulation of collagenase gene expression by IL-1 is known to require the transactivators Fos and Jun. Recently, reactive oxygen species (ROS) have been suggested to act as intracellular signaling molecules mediating the biological effects of cytokines. Here, we demonstrated ROS production by IL-1-stimulated bovine chondrocytes and that neutralizing ROS activity by the potent antioxidant, N-acetylcysteine, or inhibiting endogenous ROS production by diphenyleneiodonium (DPI), significantly attenuated IL-1-induced c-fos and collagenase gene expression. The inhibitory effect of DPI implicates enzymes such as NADPH oxidase in the endogenous production of ROS. Chondrocytes were also found to produce nitric oxide (NO) upon IL-1 stimulation. That NO may mediate part of the inducing effects of IL-1 was supported by the observation that L-NG-monomethylarginine, a NO synthase inhibitor, partially inhibited IL-1-regulated collagenase expression. Moreover, treatment of chondrocytes with the NO-producing agent, S-nitroso-N-acetylpenicillamine, was sufficient to induce collagenase mRNA levels. In summary, our results suggest that ROS released in response to IL-1 may function as second messengers transducing extracellular stimuli to their targets in the nucleus, leading to augmentation of gene expression.
...
PMID:Interleukin-1 beta induction of c-fos and collagenase expression in articular chondrocytes: involvement of reactive oxygen species. 951 43

Nitric oxide (NO.) has a complex role in the inflammatory response. In this study, we modified the levels of endogenous NO. in vivo in an acute model of inflammation and evaluated the interactions between NO. and superoxide anion (O2-.) produced by polymorphonuclear leukocytes (PMNs) accumulated in the inflamed area. We injected phosphate-buffered saline (control group), 6 mumol of L-N5-(1-iminoethyl)ornithine (L-NIO group), or 6 mumol of L-arginine (L-arginine group) into the granuloma pouch induced by carrageenan in rats. NO2- plus NO3- (indicative of NO. generation) was 188 nmol in the exudate of the control group, but it decreased in the L-NIO group (P < 0.05) and increased in the L-arginine group (P < 0.05). When PMNs from treated rats were incubated in vitro, the production of superoxide anion (O2-.) decreased by approximately 46% in the L-arginine group. Furthermore, O2-. was inhibited in PMNs when L-arginine was added to the incubation medium before phorbol 12-myristate 13-acetate stimulation but not when added simultaneously. Our results suggest a protective role for NO. in inflammation, through the inactivation of NADPH oxidase and the consequent impairment of O2-. production for cell-mediated injury.
...
PMID:Nitric oxide inhibits superoxide production by inflammatory polymorphonuclear leukocytes. 953 Jan 15

Nitric oxide synthase (NOS) catalyzes the NADPH- and O2-dependent conversion of L-arginine to nitric oxide (NO) and citrulline; three isoforms, the neuronal (nNOS), endothelial, and inducible, have been identified. Because overproduction of NO is known to contribute to several pathophysiological conditions, NOS inhibitors are of interest as potential therapeutic agents. Inhibitors that are potent, mechanism-based, and relatively selective for the NOS isoform causing pathology are of particular interest. In the present studies we report that vinyl-L-NIO (N5-(1-imino-3-butenyl)-L-ornithine; L-VNIO) binds to and inhibits nNOS in competition with L-arginine (Ki = 100 nM); binding is accompanied by a type I optical difference spectrum consistent with binding near the heme cofactor without interaction as a sixth axial heme ligand. Such binding is fully reversible. However, in the presence of NADPH and O2, L-VNIO irreversibly inactivates nNOS (kinact = 0.078 min-1; KI = 90 nM); inactivation is Ca2+/calmodulin-dependent. The cytochrome c reduction activity of the enzyme is not affected by such treatment, but the L-arginine-independent NADPH oxidase activity of nNOS is lost in parallel with the overall activity. Spectral analyses establish that the nNOS heme cofactor is lost or modified by L-VNIO-mediated mechanism-based inactivation of the enzyme. The inducible isoform of NOS is not inactivated by L-VNIO, and the endothelial isoform requires 20-fold higher concentrations to attain approximately 75% of the rate of inactivation seen with nNOS. Among the NOS inactivating L-arginine derivatives, L-VNIO is the most potent and nNOS-selective reported to date.
...
PMID:N5-(1-Imino-3-butenyl)-L-ornithine. A neuronal isoform selective mechanism-based inactivator of nitric oxide synthase. 953 69

The purpose of this study was to determine whether superoxide anion is produced endogenously in the rat aortic adventitia and whether sufficient superoxide anion is produced to interfere with the response of the rat aorta to nitric oxide. Relaxation was measured in rings of the rat thoracic aorta, which were oriented so that the adventitial or luminal surface could be preferentially exposed to nitric oxide or sodium nitroprusside. To accomplish this, the rings were mounted (1) with the adventitia facing outward, (2) with the adventitia facing inward after inverting, or (3) with the adventitia facing outward after inverting twice (to control for the inverting procedure). The relaxation to nitric oxide, but not to sodium nitroprusside, was less in rings with the adventitia facing outward compared with those in which it faced inward. In contrast, the response to nitric oxide via either surface was similar when extracellular superoxide anion was scavenged with superoxide dismutase. Incubation of rings with nitro blue tetrazolium (NBT) resulted in blue formazan staining of the adventitia, and lucigenin chemiluminescence was significantly greater when detected from the adventitial compared with the intimal aspect of the artery. The reduction of NBT in intact aortic rings was 30+/-2 pmol x min(-1) x mg(-1) and was significantly decreased by superoxide dismutase to 19+/-2 pmol x min(-1) x mg(-1) and by a synthetic superoxide dismutase mimic, Euk-8, to 11+/-2 pmol x min(-1) x mg(-1). The NADPH oxidase inhibitor, diphenyleneiodonium, decreased NBT reduction to 9+/-1 pmol x min(-1) x mg(-1), whereas inhibitors of xanthine oxidase, mitochondrial oxidases, and nitric oxide synthase were ineffective. Immunohistochemical staining indicated the localization of NADPH oxidase proteins gp91phox, p22phox, p47phox, and p67phox almost exclusively in the adventitia of the rat aorta with no substantial staining in the media. These results indicate that NADPH oxidase located in the adventitia of rat thoracic aorta generates sufficient extracellular superoxide anion to constitute a barrier capable of inactivating nitric oxide. This study suggests that adventitial superoxide anion can play a role in the pathophysiology of the arterial wall.
...
PMID:Superoxide anion from the adventitia of the rat thoracic aorta inactivates nitric oxide. 956 41

During the innate immune response, excessive release of reactive oxygen species (ROS) from sequestered phagocytes and activated resident macrophages represents the predominant component of oxidative stress in the liver and other tissues. The consequence of oxidative stress is determined by the status and adaptive changes of antioxidant pathways. In this review, we present evidence that the synchronized response of hepatic sinusoidal endothelial cells, the primary sites of phagocyte attachment, plays an important role in defense against phagocyte-derived ROS. An essential component of the metabolic adaptation of hepatic sinusoidal cells to lipopolysaccharide (LPS)-induced oxidative stress is the stimulated expression of glucose-6-phosphate dehydrogenase (G6PD), the key enzyme of the pentose cycle (hexose monophosphate shunt, HMS). All major ROS-metabolic enzymes, i.e., glutathione peroxidase, glutathione reductase, catalase, superoxide dismutases, NADPH oxidase, and nitric oxide synthase, directly or indirectly depend on NADPH, which is produced in the HMS in these cells. The functional significance of up-regulated HMS within a particular cell type depends on the accompanying adaptive changes in ROS-metabolizing enzymes. In LPS-activated Kupffer cells, the elevated expression of glucose transporter GLUT1 and G6PD mainly serves primed production of superoxide anion, hydrogen peroxide, and nitric oxide. In sinusoidal endothelial cells, the LPS-induced response pattern of glucose- and ROS-metabolizing enzymes results in elevated ROS detoxifying capacity. The described studies also suggest the existence of an intercellular oxidant balance between pro-oxidant Kupffer cells and antioxidant endothelial cells in the hepatic micro-environment. Maintenance of the intercellular oxidant/antioxidant balance between phagocytes and endothelial cells may represent an important mechanism protecting the hepatic parenchyma against exogenous oxidative stress during the inflammatory response.
...
PMID:Endotoxemia, pentose cycle, and the oxidant/antioxidant balance in the hepatic sinusoid. 958 96

When differentiated into mature macrophages by the combination of all-trans retinoic acid and 1,25-dihydroxyvitamin D3, the human promonocytic cell lines U937 and THP-1 expressed inducible nitric oxide synthase (iNOS) transcripts. During their differentiation, the cells acquired the capacity to produce not only superoxide anion (O2.-) but also nitric oxide (.NO) in response to IgG (or IgE)-opsonized zymosan. The inhibitors of the iNOS pathway, aminoguanidine and NG-monomethyl-L-arginine (L-NMMA), suppressed the production of .NO and enhanced the steady-state concentration of O2.- determined. Conversely, superoxide dismutase (SOD) scavenged the O2.- released and increased the .NO-derived nitrite concentration detected. These data suggested a possible interaction between O2.- and .NO. In differentiated U937 (or THP-1) cells, IgG or IgE-opsonized zymosan induced a strong time-dependent luminol-dependent chemiluminescence (LDCL), which was abrogated by SOD and partially inhibited by aminoguanidine or L-NMMA. Since the iNOS inhibitors did not directly scavenge O2.-, LDCL determination in the presence or absence of SOD and/or iNOS inhibitors demonstrated a concomitant production of O2.- and .NO. These radicals induced the formation of a .NO-derived product(s), probably peroxynitrite (ONOO-), which was required to elicit maximal LDCL. Finally, LDCL measurement provided a convenient tool to characterize iNOS triggering and demonstrated an interaction between NADPH oxidase and iNOS products in human macrophagic cells phagocytizing opsonized-zymosan. These findings show that in activated macrophages, iNOS activity can be involved in LDCL and support the debated hypothesis of iNOS participation to the microbicidal activity of human macrophages.
...
PMID:Nitric oxide production in human macrophagic cells phagocytizing opsonized zymosan: direct characterization by measurement of the luminol dependent chemiluminescence. 964 94


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---