Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Exposure of primary cultures of neonatal rat cortical astrocytes to bacterial lipopolysaccharide (LPS) results in the appearance of nitric oxide synthase (NOS) activity. The induction of NOS, which is blocked by actinomycin D, is directly related to the duration of exposure and dose of LPS, and a 2-hr pulse can induce enzyme activity. Cytosol from LPS-treated astrocyte cultures, but not from control cultures, produces a Ca(2+)-independent conversion of L-arginine to L-citrulline that can be completely blocked by the specific NOS inhibitor NG-monomethyl-L-arginine. The induced NOS activity exhibits an apparent Km of 16.5 microM for L-arginine and is dependent on NADPH, FAD, and tetrahydrobiopterin. LPS also induces NOS in C6 glioma cells and microglial cultures but not in cultured cortical neurons. The expression of NOS in astrocytes and microglial cells has been confirmed by immunocytochemical staining using an antibody to the inducible NOS of mouse macrophages and by histochemical staining for NADPH diaphorase activity. We conclude that glial cells of the central nervous system can express an inducible form of NOS similar to the inducible NOS of macrophages. Inducible NOS in glia may, by generating nitric oxide, contribute to the neuronal damage associated with cerebral ischemia and/or demyelinating diseases.
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PMID:Induction of calcium-independent nitric oxide synthase activity in primary rat glial cultures. 127 98

We have assessed the stoichiometry of the nitric oxide (NO) synthase reaction by using a novel e.p.r. technique. NO generated by crude and partially purified NO synthase from endothelial cells and Escherichia coli-lipopolysaccharide-activated macrophages was trapped by a ferrous diethyldithiocarbamate complex dispersed in yeast. The paramagnetic ferrous mononitrosyl dithiocarbamate complex formed exhibited a characteristic e.p.r. signal at g perpendicular = 2.035 and g parallel = 2.02 with a triplet hyperfine structure (hfs) at g perpendicular. NO, 3-morpholinosydnonimine and S-nitroso-L-cysteine, but not nitrite or hydroxylamine, generated a similar e.p.r. signal. NO generated by NO synthase and by SIN-1 accumulated at a constant rate for 1 h, as measured by continuous e.p.r. registration at 37 degrees C. The formation of e.p.r.-detectable NO by NO synthases was inhibited by NG-nitro-L-arginine. Incubation with [15N]NG-L-arginine caused an e.p.r. signal with doublet hfs, indicating that the nitrosyl nitrogen derived exclusively from the guanidino nitrogen. The amount of NO generated by NO synthase as measured by e.p.r. technique was compared with formation of L-[3H]citrulline from L-[3H]arginine. NO and L-citrulline were detected at a 1:1 ratio with both NO synthase preparations. GSH and thiol depletion did not significantly affect NO synthase activity, excluding S-nitrosothiols as intermediates in the NO synthase reaction. We conclude that NO fully accounts for the immediate oxygenated nitrogen species derived from the enzymic oxygenation of L-arginine.
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PMID:NO accounts completely for the oxygenated nitrogen species generated by enzymic L-arginine oxygenation. 128 8

RAW 264.7 macrophages induced with lipopolysaccharide and interferon-gamma expressed nitric oxide (NO) synthase. Approximately two-thirds of the total induced NO synthase activity was found in the cytosolic fraction, whereas one-third was associated with the particulate fraction. Both enzymes formed L-citrulline in addition to NO-like material. NO and L-citrulline formation by both enzymes were calcium-independent and inhibited by NG-nitro-L-arginine and NG-methyl-L-arginine. Transforming growth factor-beta 1 prevented the induction of both enzymes.
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PMID:Induced RAW 264.7 macrophages express soluble and particulate nitric oxide synthase: inhibition by transforming growth factor-beta. 137 63

The cytosol fraction of J774-1 murine macrophages activated with lipopolysaccharide (LPS) + interferon-gamma (IFN-gamma) was found to nitrosate a wide range of secondary and tertiary amines. The reaction was dependent on L-arginine and NADPH. The optimal pH for nitrosation was 7.2-7.3. Nitrosation was inhibited by arginine derivatives such as NG-monomethyl-L-arginine and NG-nitro-L-arginine, well-known inhibitors of nitric oxide (NO) synthase. These results indicate that nitrosation is mediated by NO synthase, which catalyzes formation of NO and L-citrulline from L-arginine. Nitrosamine formation also required oxygen and was inversely correlated with the basicity of nitrosatable amines. The nitrosation was inhibited by oxyhemoglobin, an NO trapping agent, and enhanced by superoxide dismutase, which stabilizes NO. LPS + IFN-gamma induced approximately 500-600 times greater nitrosation activity than that of non-activated macrophages. Macrophages treated with LPS alone exhibited 3-4 times greater nitrosation activity than untreated macrophages, whereas macrophages treated with IFN-gamma alone did not show enhanced nitrosation activity. A combination of the cytosols from macrophages treated with LPS alone and IFN-gamma alone did not nitrosate morpholine as rapidly as the cytosol of macrophages treated with both compounds together. The activity for forming L-citrulline and nitrite/nitrate from L-arginine was markedly induced by treatment with either LPS alone or LPS + IFN-gamma but not with IFN-gamma. Those results suggest that some other factor(s) in addition to NO synthase is involved for efficient nitrosation by the macrophage cytosol. This factor(s) was not induced in macrophages by either LPS- or IFN-gamma alone, but was induced only in the presence of the two compounds.
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PMID:L-arginine-dependent formation of N-nitrosamines by the cytosol of macrophages activated with lipopolysaccharide and interferon-gamma. 171 76

The macrophage cell line RAW 264.7 when activated with Escherichia coli lipopolysaccharide and interferon-gamma synthesized nitrite (NO3-) and nitrate (NO3-). Medium change after the activation showed that L-arginine was the only amino acid essential for this synthesis. D-Arginine would not substitute for L-arginine. Other analogues that could replace L-arginine were L-homoarginine, L-arginine methyl ester, L-arginamide, and the peptide L-arginyl-L-aspartate. L-Argininic acid, L-agmatine, L-ornithine, urea, L-citrulline, and ammonia were among the nonprecursors, while L-canavanine inhibited this L-arginine-derived NO2-/NO3- synthesis. When morpholine was added to the culture medium of the activated RAW 264.7 macrophages, N-nitrosation took place, generating N-nitrosomorpholine. GC/MS experiments using L-[guanido-15N2]arginine established that the NO2-/NO3- and the nitrosyl group of N-nitrosomorpholine were derived exclusively from one or both of the terminal guanido nitrogens of arginine. Chromatographic analysis showed that the other product of the L-arginine synthesis of NO2-/NO3- was L-citrulline. The role of the respiratory burst in NO2-/NO3- synthesis was examined using the macrophage cell lines J774.16 and J774 C3C. Both cell lines synthesized similar amounts of NO2-/NO3-. However, J774 C3C cells do not produce superoxide and hence do not exhibit the respiratory burst. Additional experiments also ruled out the involvement of the respiratory burst in NO2-/NO3- synthesis.
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PMID:Macrophage synthesis of nitrite, nitrate, and N-nitrosamines: precursors and role of the respiratory burst. 281 72

Endotoxin (Escherichia coli lipopolysaccharide 0111:B4, 3 mg/kg i.v.) induced the expression of a calcium-independent nitric oxide (NO) synthase, determined after 5 h in cardiac, hepatic, pulmonary and renal tissues, as assessed by the conversion of radiolabelled L-arginine to L-citrulline. This widespread induction of NO synthase in these conscious rats was associated with microvascular injury, as assessed by the vascular leakage of radiolabelled human serum albumin. Concurrent administration of the NO synthase inhibitor. NG-nitro-L-arginine methyl ester (L-NAME, 1-5 mg/kg s.c.) with endotoxin, provoked acute vascular leakage within 2 h in the various organs. By contrast, the delayed injection of L-NAME (1-5 mg/kg s.c.) or NG-monomethyl-L-arginine (12.5-50 mg/kg s.c.) until 3 h after endotoxin challenge inhibited the subsequent microvascular leakage in these organs. These effects of NO synthase inhibitors were reversed by L-arginine (300 mg/kg s.c.) pretreatment. These results support a protective role of constitutive NO synthase in the early phase of endotoxin shock. Such actions contrast with the aggressive actions of the products of inducible NO synthase in the development of widespread microvascular injury in endotoxemic states.
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PMID:Association of microvascular leakage with induction of nitric oxide synthase: effects of nitric oxide synthase inhibitors in various organs. 749 20

We have examined the induction of nitric oxide synthase (NOS) activity in the rat astrocyte-derived C6 glioma cell line. In contrast to the previous results with primary astrocyte cultures, incubation of C6 cells with bacterial endotoxin lipopolysaccharide (LPS; 1 microgram/ml for 24 h) did not stimulate NO2 production. However, addition of either tumor necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma), cytokines that by themselves had no effect on NOS activity, imparted LPS responsiveness onto these cells in a dose-dependent manner (EC50 values of 39 ng/ml of TNF-alpha and 9.4 U/ml of IFN-gamma), and the effect of TNF-alpha could be further potentiated (twofold) by the presence of interleukin-1 beta. The simultaneous presence of TNF-alpha and IFN-gamma yielded a greater response than either cytokine alone; however, the respective EC50 values were not affected. A cytoplasmic extract from induced C6 cells catalyzed the Ca(2+)-independent conversion of L-arginine to L-citrulline, with an apparent Km of 51.2 microM, and this activity could be blocked by L-arginine analogues in the potency order amino > methyl > nitroarginine. Immunoblot analysis revealed an apparent molecular mass of 125 kDa for the NOS protein induced in C6 cells. These results indicate that the combination of LPS plus cytokines can induce NOS activity in C6 glioma cells with properties similar to those of the enzyme expressed in primary astrocyte cultures.
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PMID:Induction of nitric oxide synthase in rat C6 glioma cells. 750 14

In macrophages and other cell types, bacterial lipopolysaccharide and certain cytokines stimulate nitric oxide (NO) production via expression of the inducible isoform of nitric oxide synthase (NOS). Citrulline, which is the coproduct of NOS-catalyzed metabolism of arginine, can be recycled to arginine by the action of argininosuccinate synthetase and argininosuccinate lyase, which are present at high levels in hepatocytes and renal tubular cells but normally at very low levels in other cell types such as macrophages. The present study demonstrates that lipopolysaccharide and interferon-gamma, which induce NOS in the murine macrophage cell line RAW 264.7, also coinduce activity and mRNA for argininosuccinate synthetase, which is limiting for arginine synthesis. Argininosuccinate lyase activity and mRNA abundance are unaffected. Induction of argininosuccinate synthetase is not blocked by NG-monomethyl-L-arginine, a potent inhibitor of NOS, indicating that argininosuccinate synthetase induction is not the consequence of depleting cellular arginine levels by NOS. Because plasma levels of arginine are limiting for NO synthesis, enhanced cellular capacity to regenerate arginine from citrulline could play a significant role in regulating NO production, especially under conditions where the inducible isoform of NOS is expressed.
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PMID:Coinduction of nitric oxide synthase and argininosuccinate synthetase in a murine macrophage cell line. Implications for regulation of nitric oxide production. 750 6

1. Effects of dexamethasone on induction of nitric oxide (NO) synthase and L-arginine transport by lipopolysaccharide (LPS) were examined in a murine cultured macrophage cell line J774. Metabolism of L-arginine to L-citrulline and subsequent changes in intracellular amino acids pools were correlated with changes in nitrite production. 2. Despite a high intracellular concentration of arginine in activated J774 cells, LPS (1 microgram ml-1, 8 h) induced a 2.4 fold increase in arginine transport. Treatment of cells with cycloheximide (1 microgram ml-1) inhibited the time-dependent (1-8 h) induction of NO synthase and arginine transport mediated by LPS. 3. Induction of NO synthase by LPS (1 microgram ml-1, 24 h) alone was accompanied by a marked increase in arginine utilisation leading to decreased intracellular arginine levels and elevated intracellular and extracellular L-citrulline levels. These changes were further enhanced in the presence of interferon-gamma (IFN-gamma, 100 units ml-1, 24 h). 4. Dexamethasone (1 microM) abolished the increases in both nitrite and citrulline production induced by LPS alone but only partially reversed the combined effects of LPS and IFN-gamma. In contrast, treatment of cells with dexamethasone (10 microM) had no effect on the LPS-mediated induction of arginine transport or the decrease in intracellular arginine concentration. 5. We conclude that induction of arginine transporter activity in LPS-stimulated J774 cells involves de novo synthesis of carrier proteins, which increases transport of exogenous arginine during enhanced NO production. Moreover, the intracellular signalling pathways mediating induction of arginine transport and of NO synthase by LPS in activated macrophages diverge, since only the latter is sensitive to dexamethasone.
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PMID:Selective inhibition by dexamethasone of induction of NO synthase, but not of induction of L-arginine transport, in activated murine macrophage J774 cells. 750 26

Cytokine-inducible nitric oxide (NO) production has been implicated in the pathogenesis of septic shock. The present study was designed to determine which cytokines induce expression of the NO synthase gene in rat aortic vascular smooth muscle cells (VSMC) in vitro and whether NO synthase gene expression is inducible in vivo. NO synthase mRNA appeared after 4-h exposure to interleukin-1 beta (IL-1 beta), and levels continued to increase up to 24 h. Levels of NO synthase transcripts were greatest in VSMC treated with IL-1 beta (1 nM), lower in VSMC treated with Escherichia coli lipopolysaccharide (LPS; 100 micrograms/ml), and just detectable in VSMC treated with tumor necrosis factor-alpha (TNF-alpha; 1 nM). IL-1 beta, TNF-alpha, and LPS each induced NO synthase activity, assessed by release of nitrite, conversion of L-arginine to L-citrulline, and increased levels of guanosine 3',5'-cyclic monophosphate, whereas IL-2, IL-6, and interferon-gamma were ineffective. IL-1 beta was more potent and effective than TNF-alpha; however, submaximal concentrations of TNF-alpha acted synergistically with IL-1 beta to induce NO synthase gene expression and activity. Inducible NO synthase mRNA was present in aorta from rats 6 h after treatment with LPS (5 mg/kg), but not at 24 h. Synergistic activation of NO synthase gene expression in VSMC by IL-1 beta and TNF-alpha may contribute to hypotension in sepsis.
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PMID:Interleukin-1 beta and tumor necrosis factor-alpha synergistically induce NO synthase in rat vascular smooth muscle cells. 751 63


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