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)

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

Since arginine is the only physiological substrate for the NO synthase reaction, regulation of arginine availability could determine the cellular rate of NO production. We investigated whether lipopolysaccharide (LPS) treatment in vivo would alter tissue expression of mRNAs for argininosuccinate synthetase (AS) and argininosuccinate lyase (AL), the net action of which is to convert citrulline to arginine. Concomitant with the induction of NO synthase mRNA, injection of LPS into the rats elicited an increase in AS and AL mRNA levels in the tissues. In contrast with modest increases in the abundance of AS and AL mRNA in lung and heart, a marked increase in levels of AS and AL mRNA in the kidney occurred. The liver, whether or not treated with LPS, contained high levels of mRNA for AS and AL which are components of the urea cycle. Findings suggest that an increase in the renal capacity to convert citrulline to arginine could play a key role in NO formation in vivo when arginine becomes limiting.
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PMID:Effect of lipopolysaccharide treatment in vivo on tissue expression of argininosuccinate synthetase and argininosuccinate lyase mRNAs: relationship to nitric oxide synthase. 757 82

Nitric oxide (NO) may be a mediator of beta-cell damage in insulin-dependent diabetes mellitus. beta-Cells express the inducible form of NO synthase (iNOS) and produce large amounts of NO upon exposure to cytokines. iNOS requires the amino acid arginine for NO formation. It has been shown in other cell types that interferon-gamma (IFN gamma) and bacterial lipopolysaccharide induce the enzyme argininosuccinate synthetase (AS), enhancing the capacity of these cells to regenerate arginine from citrulline and maintain NO production in the presence of low arginine concentrations. To characterize the messenger RNA (mRNA) expression of AS in insulin-producing cells, RINm5F cells (RIN cells) were exposed to interleukin-1 beta (IL-1 beta) or to tumor necrosis factor-alpha plus IFN gamma. After 4-6 h, there was a significant and parallel induction of AS and iNOS mRNA. IL-1 beta-induced AS and iNOS mRNA expression was prevented by an inhibitor of the activation factor NF-kappa B pyrrolidine diaminoguanidine, an inhibitor of gene transcription (actinomycin D), and a blocker of protein synthesis (cycloheximide), suggesting coregulation of AS and iNOS by cytokines. RIN cells exposed to IL-1 beta in the presence of citrulline but the absence of arginine had increased AS enzyme activity and produced NO, demonstrating that cytokine-induced AS mRNA expression is accompanied by increased AS activity. Both adult rat islets exposed to IL-1 beta and human pancreatic islets cultured in the presence of IL-1 beta, tumor necrosis factor-alpha, and IFN gamma were able to use citrulline to regenerate arginine and produce NO. Taken as a whole, the present data suggest that regulation of AS activity may play a role in modulation of NO production in both rodent and human insulin-producing cells.
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PMID:Expression of the citrulline-nitric oxide cycle in rodent and human pancreatic beta-cells: induction of argininosuccinate synthetase by cytokines. 762 52

Nitric oxide (NO) is synthesized from arginine by nitric oxide synthase (NOS), and citrulline which is generated can be recycled to arginine by argininosuccinate synthetase (AS) and argininosuccinate lyase (AL). Rats were injected with bacterial lipopolysaccharide (LPS), and expression of the inducible isoform of NOS (iNOS), AS, and AL was analyzed. In RNA blot analysis, iNOS mRNA was undetectable before the LPS treatment but was induced by LPS in the lung, heart, liver, and spleen, and less strongly in the skeletal muscle and testis. AS mRNA was induced in the lung and spleen, and AL mRNA was weakly induced in these tissues. AS and AL mRNAs were abundant in the control liver and remained unchanged after the treatment. Kinetic studies showed that iNOS mRNA increased rapidly in both spleen and lung, reached a maximum 2-5 h after the treatment, and decreased thereafter. On the other hand, AS mRNA increased more slowly and reached a maximum in 6-12 h (by about 10-fold in the spleen and 2-fold in the lung). AL mRNA in the spleen and lung increased slowly and remained high up to 24 h. In immunoblot analysis, increase of iNOS protein was evident in the lung, liver, and spleen, and there was an increase of AS protein in the lung and spleen. In immunohistochemical analysis, macrophages in the spleen that were negative for iNOS and AS before LPS treatment were strongly positive for both iNOS and AS after this treatment. As iNOS, AS, and AL were coinduced in rat tissues and cells, citrulline-arginine recycling seems to be important in NO synthesis under the conditions of stimulation.
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PMID:Coinduction of nitric oxide synthase, argininosuccinate synthetase, and argininosuccinate lyase in lipopolysaccharide-treated rats. RNA blot, immunoblot, and immunohistochemical analyses. 857 37

Aspirin and sodium salicylate each inhibit to a similar extent the production of nitric oxide (NO) in the RAW 264.7 murine macrophage cell line following stimulation by either lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma). The similar potencies of aspirin and sodium salicylate indicate that acetylation of cellular macromolecules is not essential for the observed effects. The failure of added prostaglandin E2 to overcome the effects of aspirin or sodium salicylate indicates that these effects are not simply the result of inhibition of prostaglandin synthesis. The inhibition of NO production occurs irrespective of the effect of these agents on induction of nitric oxide synthase (iNOS) mRNA by LPS or IFN-gamma. Aspirin and sodium salicylate inhibit iNOS mRNA induction in LPS-stimulated cells but enhance iNOS mRNA induction in IFN-gamma-stimulated cells. In contrast, these agents consistently inhibit induction of argininosuccinate synthetase mRNA in both LPS- and IFN-gamma-stimulated cells. Concentrations of aspirin in the 3-10 mM range inhibit induced NO production and expression of iNOS protein without inhibiting induction of iNOS mRNA. Discordances between effects on NO synthesis and induction of iNOS mRNA indicate that aspirin and sodium salicylate have multiple sites of action in their effects on pathways that are involved in the production of NO by stimulated RAW 264.7 cells.
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PMID:Novel actions of aspirin and sodium salicylate: discordant effects on nitric oxide synthesis and induction of nitric oxide synthase mRNA in a murine macrophage cell line. 869 Oct 69

The presence and the possibility of induction of argininosuccinate synthetase in a glial cell line were investigated. For this purpose, antisera were produced against peptides representing partial sequences 196-222 and 337-349, respectively, of the mouse liver enzyme. Both antisera were shown to be monospecific for argininosuccinate synthetase. In Western blot experiments, immunoreactivity was found in mouse liver and brain homogenates. Only weak immunoreactivity was detectable in homogenates of cultured glioma cells, C6-BU-1. However, when the glioma cells were treated with either bacterial lipopolysaccharide, interferon-gamma, or a combination of both, argininosuccinate synthetase immunoreactivity was increased. The findings demonstrate that this enzyme is present in glial cells and is induced under conditions which stimulate persistent production of nitric oxide. The antisera will be a valuable tool for further investigations on arginine synthesis in brain as well as peripheral cells.
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PMID:Presence of argininosuccinate synthetase in glial cells as revealed by peptide-specific antisera. 904 64

Immunostimulants trigger vascular smooth muscle cells (VSMC) to express both the inducible isoform of NO synthase (iNOS) and argininosuccinate synthetase (AS). With constitutively expressed argininosuccinate lyase (AL), AS confers cells with an Arg/Cit cycle that can sustain NO production via continuous regeneration of the NOS substrate, L-arginine (Arg), from the NOS coproduct, L-citrulline (Cit). To assess whether NO synthesis can be rate-limited by Arg recycling, we tested whether AS-overexpressing cells have an enhanced capacity for immununostimulant-induced NO synthesis. Rat VSMC were stably transfected with human AS cDNA in a eukaryotic cell expression vector, driven by a strong viral promoter. AS activity in transfected VSMC exceeded that induced in untransfected cells treated for 24 h with a combination of bacterial lipopolysaccharide and interferon-gamma (LPS/IFN). AS activity was predominantly associated with membranes but was also found in cytosol. Recombinant AS was purified from cytosol and possessed a specific activity exceeding that reported for native AS. Western blotting verified the basal expression of AS antigen in membranes from untreated AS-transfected VSMC and from untransfected VSMC after 24 h exposure to LPS/IFN. Epifluorescence histochemistry revealed a punctate distribution of AS antigen in transfected cells, consistent with a predominant membrane localization. Remarkably, on a per cell basis, LPS/IFN-induced NO production was 3-4-fold greater in AS-transfected cells than untransfected VSMC. In untransfected VSMC, maximal NO production during 48 h required millimolar Arg; notably, Cit was needed at approximately 3-fold higher concentrations than Arg for a comparable NO synthesis rate. In contrast, AS-transfected VSMC utilized Arg and Cit equi-effectively and at much lower concentrations; 100 microM of either precursor supported a maximal rate of NO synthesis for 48 h. The enhanced ability of AS-transfected cells to produce NO, compared with untransfected cells, could not be ascribed to differences in iNOS protein content or LPS/IFN potency for immunoactivation. We conclude that transfection with AS provides a continuous flux of Arg which drives NO synthesis in immunoactivated VSMC. Arg regeneration by AS is rate-limiting to NO synthesis and apparently provides iNOS with a preferred cellular source of Arg. In accord with the reported "channeling" of substrates by urea cycle enzymes, we hypothesize that the Arg/Cit cycle sequesters a discrete pool of recyclable substrate that sustains high-output NO synthesis.
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PMID:Argininosuccinate synthetase overexpression in vascular smooth muscle cells potentiates immunostimulant-induced NO production. 919 76

Nitric oxide (NO) is synthesized from arginine by nitric-oxide synthase (NOS), and citrulline that is generated can be recycled to arginine by argininosuccinate synthase (AS) and argininosuccinate lyase (AL). Rats were injected with bacterial lipopolysaccharide (LPS) and expression of the inducible isoform of NOS (iNOS), AS and AL was analysed. In RNA blot analysis, iNOS mRNA was induced by LPS in the lung, heart, liver and spleen, and less strongly in the skeletal muscle and testis. AS and AL mRNAs were induced in the lung and spleen. Kinetic studies showed that iNOS mRNA increased rapidly in both spleen and lung, reached a maximum 2-5 h after the treatment, and decreased thereafter. On the other hand, AS mRNA increased more slowly and reached a maximum in 6-12 h (by about 10-fold in the spleen and 2-fold in the lung). AL mRNA in the spleen and lung increased slowly and remained high up to 24 h. In immunohistochemical analysis, macrophages in the spleen that were negative for iNOS and AS before LPS treatment were strongly positive for both iNOS and AS after this treatment. As iNOS, AS and AL were co-induced in rat tissues and cells, citrulline-arginine recycling seems to be important in NO synthesis under the conditions of stimulation. Arginine is a common substrate of NOS and arginase. Rat peritoneal macrophages were cultured in the presence of LPS and expression of iNOS and livertype arginase (arginase I) was analysed. mRNAs for iNOS and arginase I were induced by LPS in a dose-dependent manner. iNOS mRNA appeared 2 h after LPS treatment and increased up to a near-maximum at 8-12 h. On the other hand, arginase I mRNA began to increase after 4 h with a lag time and reached a maximum at 12 h. Immunoblot analysis showed that iNOS and arginase I proteins were also induced. Induction of iNOS and arginase I mRNAs were also observed in LPS-injected rats in vivo. Thus, arginase I appears to have an important role in downregulating NO synthesis in murine macrophages by decreasing the availability of arginine. A cDNA for human arginase II, an arginase isozyme, was isolated. A polypeptide of 354 amino acid residues including the putative NH2-terminal presequence for mitochondrial import was predicted. It was 59% identical with arginase I. mRNA for human arginase II was present in the kidney and other tissues but was not detected in the liver. Arginase II mRNA was co-induced with iNOS mRNA in murine macrophage-like RAW 264.7 cells by LPS. This induction was enhanced by dexamethasone and dibutyrul cAMP, and was prevented by interferon-gamma. These results indicate that NO synthesis is regulated by arginine-synthesizing and -degrading enzymes in a complicated manner.
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PMID:Regulation of the urea cycle enzyme genes in nitric oxide synthesis. 968 45

An antiserum raised against the peptide representing the partial sequence 196-222 of mouse liver argininosuccinate synthetase (ASS) was used to detect and localize the enzyme in cells of neural primary cultures. No ASS immunoreactivity was detected by Western blotting in homogenates of mouse pure astroglial cultures and rat astroglia-rich cultures. However, when the cultures had been treated with bacterial lipopolysaccharide, interferon-gamma, or a combination of both, ASS immunoreactivity was disclosed. Immunocytochemical examination of rat astroglia-rich cultures revealed a colocalization of ASS with the astroglial marker glial fibrillary acidic protein (GFAP) in many cells. However, there were some GFAP-positive cells showing no specific staining for ASS, and vice versa. Colocalization of ASS with the inducible isoform of nitric oxide synthase in the same cell was shown only occasionally; nitric oxide synthase was predominantly expressed in microglial cells. In rat neuron-rich primary cultures astroglial cells as well as neurons expressed ASS. Cells of mouse pure astroglial cultures were able to synthesize arginine and, consequently, nitric oxide from citrulline, but not from ornithine. The findings demonstrate that ASS is expressed in astroglial cells under conditions that stimulate long-lasting production of nitric oxide; a functional role of this enzyme in the latter process is implicated.
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PMID:Argininosuccinate synthetase: localization in astrocytes and role in the production of glial nitric oxide. 981 23

Arginase exists in two isoforms, the hepatic (arginase I) and extrahepatic types (arginase II). Arginase I is markedly induced in rat peritoneal macrophages and rat tissues in vivo by bacterial lipopolysaccharide (LPS). In contrast, both arginase I and arginase II are induced in LPS-activated mouse peritoneal macrophages. In the present study, expression of arginase isoforms and related enzymes was studied in mouse tissues in vivo and in peritoneal macrophages with RNA blot and immunoblot analyses and enzyme assay. When mice were injected intraperitoneally with LPS, inducible nitric oxide synthase (iNOS) and arginase II were induced early in the lung and spleen. mRNAs for argininosuccinate synthase (AS) and ornithine decarboxylase (ODC) were also induced early. In comparison, arginase I was induced later in the lung. Early induction of iNOS, arginase II, AS, ODC, and cationic amino acid transporter 2 and late induction of arginase I were observed in LPS-activated peritoneal macrophages. These results indicate that the genes for the two arginase isoforms are regulated differentially. Possible roles of the arginase isoforms in the regulation of nitric oxide production and in polyamine synthesis are discussed.
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PMID:Regulation of the genes for arginase isoforms and related enzymes in mouse macrophages by lipopolysaccharide. 1040 34


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