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

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Query: EC:1.5.1.19 (NOS)
7,285 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In nitrinergic signal transduction, nitrogen oxide (NO) synthases (NOS) (EC 1.14.23) catalyze the conversion of L-arginine to L-citrulline and NO, which in turn activates soluble guanylyl cyclase. Macrophages were reported to contain a single isoform of NOS (type II, soluble, Ca(2+)-independent, 130-kDa) and only upon activation of the cells by interferon-gamma (INF) and lipopolysaccharides (LPS). By a mechanism involving L-type Ca2+ channels, calmodulin, and serine proteases, INF/LPS also induce a cytotoxic activation of macrophages. In RAW264.7 macrophages, NO release was detected upon activation of the cells by INF/LPS but also, although at a 20-fold lower level, in control cells. The latter constitutive NOS activity and NO release were Ca2+ dependent and were decreased in INF/LPS-activated RAW264.7 cells or with increasing passage number. RAW264.7 cells did not express soluble guanylyl cyclase, suggesting other target molecules for NO. In INF/LPS-activated cells, NOS activities and NO release were Ca2+ independent (type II) and coinduced with NADPH-diaphorase activities both in the soluble and in the particulate fractions. The NOS-II activities corresponded to a 130-kDa protein, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which was not recognized in a protein immunoblot with anti-NOS-I antibody. The serine protease inhibitor tosyl-lysyl chloromethyl ketone abolished the induction of NOS-II by INF/LPS, by depleting intracellular thiol pools and interfering with protein synthesis. Induction of NOS-II by INF/LPS was transcriptionally based and, for maximal enzyme activity, required increased intracellular tetrahydrobiopterin levels, intracellular Ca2+ mobilization, and activation of non-L-type Ca2+ channels but, unlike the induction of macrophage-mediated cytotoxicity, neither L-type-Ca2+ channels nor calmodulin.
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PMID:Regulation and subcellular location of nitrogen oxide synthases in RAW264.7 macrophages. 137 97

This study investigates the effects of in vivo ethanol (primed infusion, causing 170-190 mg% plasma alcohol for 12 hours) and/or LPS (12 hours after injection of E. coli LPS 1 mg/kg bw.) on the mRNA expression of inducible nitric oxide synthase (NOS II) in hepatic cells measured by competitive PCR technique, and on hepatic release of reactive nitrogen intermediates (RNI, NO2- + NO3-). Perfused livers from alcohol- or saline-infused animals did not release measurable amounts of RNI. Under these conditions small amounts of NOS II mRNA were expressed in Kupffer and endothelial cells, while it was not detectable in parenchymal cells. LPS treatment along with markedly elevating hepatic RNI release increased NOS II mRNA levels by 35- and 200-fold, in endothelial and Kupffer cells, respectively. LPS injection and alcohol infusion to the same animal decreased hepatic RNI release by about 70% and almost completely inhibited the LPS-induced, elevated NOS II mRNA in Kupffer or endothelial cells. No similar changes were observed in the parenchymal cells. These data suggest that the primary target of in vivo LPS in upregulating hepatic NO release are the nonparenchymal cells. Furthermore, alcohol inhibits the LPS-induced response which may influence immune-related hepatic function.
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PMID:Alcohol administration attenuates LPS-induced expression of inducible nitric oxide synthase in Kupffer and hepatic endothelial cells. 750 71

Nitric oxide is believed to participate in nonspecific cellular immunity. Gram negative bacterial endotoxins increase the production of reactive nitrogen intermediates (RNI) in phagocytic cells by inducing the enzyme nitric oxide synthase II (NOS II). Anti-inflammatory glucocorticoids attenuate endotoxin-induced increases in RNI. This study evaluated the effect of in vivo administration of prednisolone on Escherichia coli lipopolysaccharide endotoxin (LPS)-induced increases in plasma RNI and neutrophil mRNA for NOS II and production of RNI in the rat. We show that LPS rapidly induces mRNA for NOS II and production of RNI (NO2- and NO3- anion) in rat neutrophils within 2 hr after in vivo administration of a sublethal dose of 0.5 mg/kg, i.v. A pharmacologic dose of prednisolone (50 micrograms/kg, im) given 15 min before LPS-attenuated production of NO2- and NO3- by neutrophils and suppressed LPS-stimulated mRNA for NOS II. 3-Amino, 1,2,4-triazine inhibited NO2- and NO3- production without affecting gene expression for NOS II. These data demonstrate that LPS rapidly induces functional gene expression for NOS II and prednisolone prevents induction of NOS II activity by inhibiting transcription of its mRNA.
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PMID:Rapid induction of messenger RNA for nitric oxide synthase II in rat neutrophils in vivo by endotoxin and its suppression by prednisolone. 751 33

Nitric oxide synthase (NOS, EC 1.14.23) catalyzes the oxidation of the guanidino-nitrogen of L-arginine to form nitric oxide and L-citrulline. 2-Iminobiotin was found to be a reversible inhibitor of murine iNOS and rat n-cNOS with Ki values of 21.8 and 37.5 microM, respectively. The urea and thiourea analogs, biotin and thiobiotin, were not inhibitors of NOS, indicating that the guanidino group of 2-iminobiotin is essential for binding. 2-iminobiotin carboxy derivatives were also inhibitors of iNOS which indicates that the free carboxyl group is not required for binding. 2-Iminobiotin is a novel, potent inhibitor of NO biosynthesis and may be a useful reagent in the understanding of binding-site interactions for this important class of enzymes.
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PMID:2-Iminobiotin is an inhibitor of nitric oxide synthases. 752 56

Cognitive impairment in the absence of lesions indicative of Alzheimer's disease and other dementing conditions has long been recognized in a subgroup of patients with motor neuron disease MND), including amyotrophic lateral sclerosis. However, the mechanisms underlying this cognitive deterioration and its relationship with the relatively selective involvement of motor neurons remains elusive. We used histo- and immunocytochemical labeling methods to study the nitrogen monoxide (NO; a.k.a. nitric oxide) synthase (NOS)-/NADPH diaphorase-containing neurons (NOSN) in three patients with MND and dementia (MND+D), two patients with MND without dementia, and 19 controls that included patients with Alzheimer and non-Alzheimer dementias. Patients with MND+D, but not those with MND without dementia, exhibit numerous dystrophic perikarya and neurites throughout all sensory, motor, association, and limbic neocortices examined. Interestingly, affected NOSN appear to correspond to some subtypes (smooth stellate and spiny neurons), while other neurons containing the same molecular phenotype (such as layer I local circuit neurons and layer II granule cells) are either spared or significantly less affected. These observations indicate that cognitive impairment and dementia in MND may be due, at least in part, to a pancortical involvement of certain types of NOSN. Consequently, the elucidation of the factors that make NOSN vulnerable in MND, and the prevention or pharmacological palliation of their loss, may eventually help to prevent or ameliorate cognitive impairment in MND and may also shed some light on the nature of the insult that targets motor neurons.
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PMID:Alterations in nitrogen monoxide-synthesizing cortical neurons in amyotrophic lateral sclerosis with dementia. 855 69

The cytokine-inducible isoform of nitric oxide synthase (iNOS or NOS2) plays an important role in the immune response to some pathogens. Within the heart, increased activity of NOS2 in cardiac microvascular endothelial cells (CMEC) also can diminish the contractile function of adjacent cardiac myocytes. Glucocorticoids, which are known to suppress cytokine induction of NOS2 in many cell types, caused only a moderate (approximately 20%) decline in NOS2 protein content and maximal activity measured in homogenates of cytokine-treated CMEC, but almost completely inhibited synthesis of nitrogen oxides (NOx) by intact cells. To determine whether glucocorticoids were inhibiting cellular NOx production by limiting the availability of NOS co-factors or substrate, the effect of dexamethasone on tetrahydrobiopterin (BH4) and L-arginine availability in cytokine-treated CMEC was examined. Dexamethasone prevented the coordinate induction of GTP cyclohydrolase I with NOS2 after exposure to interleukin-1beta and interferon-gamma and also the increase in intracellular BH4 content in cytokine-treated CMEC. Addition of BH4 overcame dexamethasone-mediated suppression of nitrite production. Dexamethasone also prevented a cytokine-mediated increase in L-arginine uptake into CMEC by suppressing the induction of the high affinity cationic amino acid transporters CAT-1 and CAT-2B and the low affinity CAT-2A transporter. In addition, dexamethasone also inhibited cytokine induction in CMEC of argininosuccinate synthase, the rate-limiting enzyme for the de novo synthesis of arginine from citrulline. Thus, glucocorticoids regulate NOx production following cytokine exposure in cardiac microvascular endothelial cells primarily by limiting BH4 and L-arginine availability.
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PMID:Glucocorticoids regulate inducible nitric oxide synthase by inhibiting tetrahydrobiopterin synthesis and L-arginine transport. 879 25

The present studies examined the temporal sequence of inducible nitric oxide synthase (iNOS) gene expression and the cellular sources of iNOS protein and of 3-nitrotyrosine, as a marker of production of nitric oxide-derived reactive nitrogen intermediates during murine multi-stage carcinogenesis. Levels of iNOS mRNA in dorsal skin isolated from acetone-treated female Sencar mice were 2.5-fold higher than iNOS gene expression detected in cutaneous tissue isolated from Sencar mice at 1, 3, 6, 10, 16 and 22 weeks after exposure to a single topical application of 25 nmol 7,12-dimethylbenz[a]anthracene (DMBA) followed by repetitive applications of 2 microgram 17-O-tetradecanoylphorbol-13-acetate (TPA). Papillomas isolated at 16 and 22 weeks of a tumor promotion protocol also had low levels of iNOS mRNA. The diminished levels of iNOS mRNA inversely correlated with the extent of TPA-induced epidermal hyperplasia. In acetone-treated mouse skin, iNOS immunospecific antibody binding was localized to the stratum corneum and suprabasal keratinocytes. In contrast, iNOS protein was present in lower amounts and was localized to the upper-most suprabasal keratinocytes in cutaneous tissue isolated at 22 weeks following a single exposure to either 25 nmol DMBA or acetone and repetitive applications of 2 microgram TPA. At all time points examined over the 22 week time period of papilloma growth, infiltrating neutrophils within the dermis bound significant levels of anti-iNOS antibodies. The production of iNOS by neutrophils within the dermis correlated with the formation of protein nitrotyrosination within the dermal tissue, as detected by 3-nitrotyrosine-specific antibodies. The present studies indicate that NOS and reactive nitrogen intermediates, including peroxynitrite, are produced specifically by dermal neutrophils during the tumor promotion process at time points that correspond to simultaneous production of reactive oxygen intermediates. Conversely, iNOS is simultaneously down-regulated in hyperplastic epidermis and in papillomas.
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PMID:Gene expression and cellular sources of inducible nitric oxide synthase during tumor promotion. 882 34

The nitric-oxide synthase (NOS; EC 1.14.13.39) reaction is formulated as a partially tetrahydrobiopterin (H4Bip)-dependent 5-electron oxidation of a terminal guanidino nitrogen of L-arginine (Arg) associated with stoichiometric consumption of dioxygen (O2) and 1.5 mol of NADPH to form L-citrulline (Cit) and nitric oxide (.NO). Analysis of NOS activity has relied largely on indirect methods such as quantification of nitrite/nitrate or the coproduct Cit; we therefore sought to directly quantify .NO formation from purified NOS. However, by two independent methods, NOS did not yield detectable .NO unless superoxide dismutase (SOD; EC 1.15.1.1) was present. In the presence of H4Bip, internal .NO standards were only partially recovered and the dismutation of superoxide (O2-.), which otherwise scavenges. .NO to yield ONOO-, was a plausible mechanism of action of SOD. Under these conditions, a reaction between NADPH and ONOO- resulted in considerable overestimation of enzymatic NADPH consumption. SOD lowered the NADPH:Cit stoichiometry to 0.8-1.1, suggesting either that additional reducing equivalents besides NADPH are required to explain Arg oxidation to .NO or that .NO was not primarily formed. The latter was supported by an additional set of experiments in the absence of H4Bip. Here, recovery of internal .NO standards was unaffected. Thus, a second activity of SOD, the conversion of nitroxyl (NO-) to .NO, was a more likely mechanism of action of SOD. Detection of NOS-derived nitrous oxide (N2O) and hydroxylamine (NH2OH), which cannot arise from .NO decomposition, was consistent with formation of an .NO precursor molecule such as NO-. When, in the presence of SOD, glutathione was added, S-nitrosoglutathione was detected. Our results indicate that .NO is not the primary reaction product of NOS-catalyzed Arg turnover and an alternative reaction mechanism and stoichiometry have to be taken into account.
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PMID:No .NO from NO synthase. 896 79

The effect of oxidized starch (OS) which contained 15% of COOH groups and its nitroether (NOS) with 4% of nitrogen on coagulation properties of rat blood was studied in vitro and in vivo. The results of the study in vitro showed that OS did not affect the function of the coagulation system. In contrast to OS, a dose-dependent increase in prothrombin-, thrombin time, and activated partial thromboplastin time was observed for NOS. The activity of the components of the internal coagulation pathway changed when the NOS concentration reached 0.1 mg/ml. At a concentration of 0.6 mg/ml and higher this compound affect the external pathway and final stage of coagulation. According to the efficiency (in vitro) of the influence on the thrombine time I mg/ml NOS corresponded to 0.2 U/ml of heparine. The anticoagulant effect of NOS was also observed in vivo along with reliable changes in thromboplastin and thrombin time. Antithrombin activity of plasma remained the same. Standard test was negative and indicated to the absence of fibrin monomers. The pronounced anticoagulant effect of NOS in the experiments in vitro and quick response in the experiments in vivo make it possible to consider this compound as anticoagulant of direct action.
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PMID:[The anticoagulant action of the nitric acid ester of oxidized starch]. 897 59

The active site topologies of neuronal (nNOS), endothelial (eNOS), and inducible (iNOS) nitric-oxide synthases heterologously expressed in Escherichia coli have been examined using three aryldiazene (Ar-N=NH) probes. The topological information derives from (a) the rate and extent of aryl-iron complex formation in the presence and absence of tetrahydrobiopterin (H4B), Ca2+-dependent calmodulin (CaM), and L-arginine, and (b) the N-phenylprotoporphyrin IX regioisomer ratios obtained upon migration of the phenyl of the phenyl-iron complex to the heme nitrogen atoms. The N-phenylprotoporphyrin ratios indicate that the three NOS isoforms have related active site topologies with unencumbered space above all four pyrrole rings but particularly above pyrrole ring D. H4B binds directly above the heme pyrrole ring D or causes a conformational change that constricts that region, because H4B markedly decreases phenyl migration to pyrrole ring D. Small CaM-dependent changes in the nNOS N-phenylporphyrin isomer pattern are consistent with a conformational link between the CaM and heme sites in this protein. The ceiling height directly above the heme iron atom differs among the isoforms and is lower than in the P450 enzymes because only nNOS and iNOS react with 2-naphthyldiazene, and none of the isoforms reacts with p-biphenyldiazene. L-Arg blocks access to the heme iron atom in all three NOS isoforms and nearly suppresses the phenyldiazene reaction. The data indicate that topological differences, including differences in the size of the active site, are superimposed on the structural similarities among the NOS active sites.
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PMID:Active site topologies and cofactor-mediated conformational changes of nitric-oxide synthases. 904 46


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