The human gene encoding SCYB9B, a putative novel CXC chemokine, maps to human chromosome 4q21 like the closely related genes for MIG (SCYB9) and INP10 (SCYB10).
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Chemokine CXCL10↗
Biomedical subjects
G Werner-Felmayer
Publications and source records attributed to G Werner-Felmayer.
Tetrahydrobiopterin, cytokines, and nitric oxide synthesis.
Nitric oxide synthases require a surprisingly rich selection of cofactors to perform the conversion of L-arginine to citrulline and nitric oxide (NO): NADPH, FAD, FMN, heme and tetrahydrobiopterin. In a previous minireview in this journal we summarized work concerning the induction of tetrahydrobiopterin biosynthesis by cytokines, which yields increased intracellular tetrahydrobiopterin concentrations supporting NO formation by intact cells (P.S.E.B.M. 203:1-12). The present review updates work on the induction of tetrahydrobiopterin biosynthesis by cytokines, and summarizes recent advances in research of tetrahydrobiopterin dependence of the NO synthase reaction. Studies using recombinant NO synthases and site-directed mutations thereof have localized several amino acids critical for tetrahydrobiopterin binding, which are discussed in reference to the recently published crystal structure of the dimer of the oxygenase domain of murine inducible NO synthase with substrate and pterin. Allosteric actions of tetrahydrobiopterin on NO synthases are stabilization of dimers, stabilization of a conformation with high-spin heme iron, and support of binding of the substrate L-arginine. Since the 4-amino analog of tetrahydrobiopterin, which is a dihydropteridine reductase inhibitor, supports these allosteric actions but inhibits the enzyme activity, tetrahydrobiopterin appears to play a redox-active role in stimulating the NO synthase reaction in addition to its allosteric actions on NO synthases. Amelioration of endothelial dysfunction by tetrahydrobiopterin in animal models and in humans in vivo has been observed. It remains to be investigated, however, to what extent the role of tetrahydrobiopterin as cofactor of NO synthases contributes to these in vivo effects of tetrahydrobiopterin.
Animals↗
Human monocytoid cell lines as indicators of endotoxin: comparison with rabbit pyrogen and Limulus amoebocyte lysate assay.
The aim of this study was to develop an in vitro test system for pyrogenic substances. Three clones derived from human monocytoid cell lines, which were selected by their high sensitivity to lipopolysaccharide (LPS), were assessed for tumor necrosis factor (TNF) production. Their response to pyrogen-containing samples was compared with that in a Limulus amoebocyte lysate assay and the rabbit pyrogen test. We show here that the induction of TNF in these clones is a valid in vitro alternative to determine endotoxin in commercial preparations requiring pyrogenicity testing. Cell clones derived from Mono Mac 6 (MM6 2H8 and MM6 4B5) responded to sub-ng/ml concentrations of complete rough-strain and smooth-strain LPS, to ng/ml concentrations of diphosphoryl-lipid A, and to microgram/ml concentrations of monophosphoryl-lipid A and to detoxified LPS. Cells reacted to > or = 1 microgram/ml lipoteichoic acid by TNF production, and were relatively insensitive to toxic shock syndrome toxin-1 (TSST-1) and to muramyl dipeptide adjuvant peptide. The reaction pattern of a clone derived from THP-1 (THP-1 1G3) was in general, similar to that of the MM6 clones, except that THP-1 1G3 failed to react to diphosphoryl-lipid A. When tested on commercial samples destined for parenteral use, there was a close correlation between a sensitive Limulus amoebocyte lysate (LAL) test and the cell culture test on the one hand, and between the pyrogen test and the cell culture test on the other hand. The data suggest that this cell-based test is able to recognize pyrogens derived from gram-negative organisms in test samples with appropriate sensitivity and specificity. This test appears to be able to eliminate some of the false-positive data obtained in the LAL test.
Acetylmuramyl-Alanyl-Isoglutamine↗
Determination of tetrahydrobiopterin biosynthetic activities by high-performance liquid chromatography with fluorescence detection.
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Alcohol Oxidoreductases↗
Unidirectional upregulation of the synthesis of the major iron proteins, transferrin-receptor and ferritin, in HepG2 cells by the acute-phase protein alpha1-antitrypsin.
BACKGROUND/AIMS: We have previously shown that the hepatic acute-phase protein alpha1-antitrypsin (alpha1-AT) is an important mediator of changes in iron metabolism in the course of anaemia of chronic disease. Alpha1-AT profoundly reduces growth of erythroid cells by interfering with transferrin-mediated iron uptake. In the present work we investigate the effects of alpha1-AT on hepatic iron metabolism, as the liver plays a central role in body iron metabolism and in metabolic changes during acute-phase response. METHODS: The human hepatoma cell line Hep G2 was cultured in RPMI 1640+10% FCS. The effect of alpha1-AT on transferrin-receptor binding was investigated in equilibrium binding assays with 125I-transferrin. Expression of transferrin receptor was determined by saturation experiments and intracellular ferritin was measured in cell lysates after incubating cells either alone or with alpha1-AT. To determine iron regulatory protein binding activity to iron responsive elements we used gel retardation assays and Northern blot analysis was carried out to investigate transferrin receptor and ferritin mRNA expression. RESULTS: Alpha1-AT completely prevented transferrin from binding to its receptor and internalization of the transferrin-transferrin receptor complex on HepG2. In addition, alpha1-AT caused a distinct increase in iron regulatory protein binding activity to iron responsive elements, which is characteristic of iron deprivation. Normally, the synthesis of transferrin receptor and ferritin is regulated bidirectionally, but alpha1-AT promoted a unidirectional regulation. Alpha1-AT increased the synthesis of both transferrin receptor and ferritin and, moreover, increased cellular amounts of transferrin receptor mRNA and ferritin H-chain mRNA. CONCLUSIONS: The effect of alpha1-AT on transferrin receptor synthesis appears to be mediated via activation of iron responsive element binding affinity of iron regulatory protein leading to an increased stability of transferrin receptor mRNA. Changes in ferritin, however, may be related to a transcriptionally mediated, iron-independent pathway which overrides the influence of activated iron regulatory protein. These specific changes in iron metabolism are the very ones seen in the course of anaemia of chronic disease. Our results emphasize the central role of alpha1-AT as a mediator of altered iron metabolism, characteristic of anaemia of chronic disease, not only with respect to erythroid cells but also with respect to liver cells.
Cell Division↗
Colchicine derivatives inhibit neopterin production in human peripheral blood mononuclear cells (PBMC).
Colchicine is a microtubule disrupting agent, mostly used as treatment in various kinds of inflammatory diseases such as acute familial Mediterranean fever and Behcet's disease, as well as gout. In patients with familial Mediterranean fever treatment with colchicine induces a decline of urinary neopterin concentrations which indicates a decrease of cell-mediated immune activation. In this study, we investigated a potential effect of colchicine on the T cell/macrophage system in vitro. The human myelomonocytic cell line THP-1 and PBMC were treated with colchicine or the colchicine derivative, colcemide, in the presence or absence of 250 U/ml interferon-gamma (IFN-gamma) or 10 microg/ml lipopolysaccharide (LPS) for 48 h or 96 h. Colchicine and colcemide increased neopterin/protein production in unstimulated THP-1 cells, but no such effect was apparent in cells stimulated with IFN-gamma. By contrast, when PBMC were treated with colchicine or colcemide a significant reduction in neopterin formation was evident in cells without and with prestimulation by IFN-gamma or LPS. In parallel, reduced production of IFN-gamma was observed in PBMC. These data suggest that colchicine and colcemide are able to inhibit T cell activation within the cellular immune response.
Biopterins↗
Streptococcal erythrogenic toxins induce tryptophan degradation in human peripheral blood mononuclear cells.
BACKGROUND: In various cells including monocytes the cytokine interferon-gamma as well as lipopolysaccharide induce indoleamine 2,3-dioxygenase which degrades tryptophan to form L-kynurenine. We addressed the question of whether the exposure of human peripheral mononuclear cells to superantigens derived from streptococci is associated with tryptophan degradation in vitro. METHODS: Peripheral blood mononuclear cells were exposed to streptococcal erythrogenic toxins A and B and a streptococcal-derived mitogen named BX. In addition, the myelomonocytic cell line THP-1 was treated with these toxin preparations. RESULTS: In peripheral blood mononuclear cells all three toxins induced tryptophan degradation. In parallel, production of interferon-gamma was found, and the tryptophan degradation could be blocked by antihuman interferon-gamma antibodies. Tryptophan degradation was not induced when the human myelocytoma cell line THP-1 was stimulated with these toxins, but there was a costimulatoty effect to interferon-gamma. CONCLUSIONS: In peripheral blood mononuclear cell culture streptococcal erythrogenic toxins are able to stimulate tryptophan degradation in humans via the induction of interferon-gamma production. There seems to be no direct effect on myelomonocytic THP-1 cells. Because some of the degradation products of tryptophan, such as quinolinic acid and kynurenic acid, are toxic, superantigen-driven degradation oftryptophan may play a role for example in the development of the toxic-shock-like syndrome associated with severe group A streptococcal infections.
Adult↗
Identification of the 4-amino analogue of tetrahydrobiopterin as a dihydropteridine reductase inhibitor and a potent pteridine antagonist of rat neuronal nitric oxide synthase.
The binding of tetrahydropteridines with 6-di- and trihydroxypropyl side chains to recombinant rat neuronal nitric oxide (NO) synthase (EC 1.14.13.39) was determined by competition with 6R-[3'-3H]-5,6,7,8-tetrahydro-L-erythro-biopterin (6R-[3'-3H]H4biopterin). Although all but one of the derivatives exhibited only poor affinities (Ki 50 microM), the 4-amino analogue of 6R-H4 biopterin was a potent antagonist of 6R-H4 biopterin binding (Ki 13.2 nM). The 4-amino analogue of 6R-H4 biopterin inhibited NO synthase stimulation by the natural cofactor 6R-H4 biopterin with an IC50 of 1 microM without affecting the basal activity observed in the absence of added 6R-H4 biopterin. Because the 4-amino analogue of 6R-H4biopterin also inhibited dihydropteridine reductase (EC 1.6.99.7; IC50 20 microM), our results support the hypothesis that redox cycling of H4 biopterin might be required for the NO synthase reaction.
Animals↗
Tumor-associated antigen 90K activates myelomonocytic cell line THP-1.
90K is a tumor-associated antigen. Using myelomonocytic cell line THP-1 we determined neopterin production and tryptophan degradation after exposure of cells to 90K in the presence and the absence of interferon-gamma. Interferon-gamma is a well known stimulus for THP-1 cells inducing e.g. neopterin production and tryptophan degradation. Treatment of cells with 50 micrograms/ml 90K induced significant neopterin formation, and the exposure of cells to 90K in addition to 100 U/ml interferon-gamma amplified neopterin production compared to the sole effect of interferon-gamma. In parallel, a significant degradation of tryptophan was observed in culture supernatants leading to the formation of kynurenine. When the cells were treated with the combination of 90K and interferon-gamma the degradation of tryptophan was further enhanced. The data demonstrate that tumor-associated antigen 90K interferes with immunocompetent target cells and is able to induce a biochemical response in monocytic cells.
Adjuvants, Immunologic↗
High-performance liquid chromatographic methods for the quantification of tetrahydrobiopterin biosynthetic enzymes.
Tetrahydrobiopterin is a cofactor in hydroxylation reactions, including phenylalanine 4-monooxygenase, tyrosine 3-monooxygenase, tryptophan 5-monooxygenase, alkyl glycol ether monooxygenase and nitric oxide synthase. Determination of its biosynthesis is carried out to diagnose inherited diseases leading to partial defects in tetrahydrobiopterin synthesis. In addition, tetrahydrobiopterin synthesis is induced by proinflammatory cytokines, and intracellular levels of tetrahydro-biopterin in many cases limit the activity of tetrahydrobiopterin-dependent reactions, such as nitric oxide synthase in intact cells. Biosynthesis of tetrahydrobiopterin from guanosine 5'-triphosphate (GTP) requires the action of three enzymes, GTP-cyclohydrolase I (E.C. 3.5.4.16), 6-pyruvoyl tetrahydropterin synthase (EC, 4.6.1.10) and sepiapterin reductase (E.C. 1.1.1.153). Methods for quantification of biopterin and related pteridines in biological matrices by HPLC and application of these for determining the activity of the three tetrahydrobiopterin biosynthetic enzymes are reviewed in this article.
Alcohol Oxidoreductases↗
Biosynthesis of nitric oxide: dependence on pteridine metabolism.
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Animals↗
Streptococcal erythrogenic toxins induce neopterin formation in human peripheral blood mononuclear cells but not in the human myelomonocytoma cell line THP-1.
We tested whether the exposure of human monocytic cells to streptococcal erythrogenic toxins A, B, C and a streptococcal-derived Mitogert BX is associated with synthesis of neopterin in vitro. Neopterin production was not induced when the human myelomono-cytoma cell line THP-1 was stimulated with these toxins, and there was only a slight co-stimulatory effect of streptococcal erythrogenic toxin A together with interferon-gamma stimulation. However, these toxins induced interferon-gamma and further neopterin production in peripheral blood mononuclear cells of three healthy individuals. This neopterin formation could be blocked by anti-human interferon-gamma. From our investigations we conclude that there is no direct effect of streptococcal erythrogenic toxins on neopterin production by monocytic cells. However, the data obtained in peripheral blood mononuclear cell culture imply that these toxins are able to stimulate neopterin production in humans via the induction of huge amounts of interferon-gamma.
Biopterins↗
Effect of neopterin and 7,8-dihydroneopterin on tumor necrosis factor-alpha induced programmed cell death.
Tumor necrosis factor-alpha and the formation of reactive oxygen intermediates are central mediators of apoptosis. Recent data indicated a role of neopterin and 7,8-dihydroneopterin in oxygen radical mediated processes. We have therefore investigated the effect of neopterin-derivatives on TNF alpha induced apoptosis of the monocyte-like cell line U937. At an elevated concentration 7,8-dihydroneopterin was found to superinduce TNF alpha mediated programmed cell death due to the formation of reactive oxygen intermediates. Our results imply that in combination with TNF alpha high concentrations of 7,8-dihydroneopterin enhances apoptosis due to oxidative stress on cells.
Acetylcysteine↗
[Neopterin as an immunodiagnostic parameter].
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Biopterins↗
2,4-Diamino-6-hydroxypyrimidine, an inhibitor of tetrahydrobiopterin synthesis, downregulates the expression of iNOS protein and mRNA in primary murine macrophages.
2,4-diamino-6-hydroxy-pyrimidine (DAHP), an inhibitor of GTP cyclohydrolase I, blocks the synthesis of tetrahydrobiopterin (BH4), which is a known cofactor of inducible nitric oxide synthase (iNOS). Previously, DAHP was shown to suppress the production of nitric oxide by cytokine-activated fibroblasts, smooth muscle cells or endothelial cells which could be attributed to its function as a cofactor antagonist. Here, we demonstrate that in interferon-gamma-activated murine peritoneal macrophages DAHP suppresses the expression of iNOS mRNA and protein in a BH4-independent manner and, thus, acts by a novel mechanism.
Amino Acid Oxidoreductases↗
Nitric oxide modulates the release of acetylcholine in the ventral striatum of the freely moving rat.
The influence of nitric oxide on acetylcholine release in the ventral striatum was investigated by the push-pull superfusion technique in the conscious, freely moving rat. Superfusion with the nitric oxide donors S-nitroso-N-acetylpenicillamine or with 3-morpholino-sydnonimine caused a pronounced increase in striatal acetylcholine release. This effect was prevented by superfusion with tetrodotoxin. Pre-superfusion with the guanylyl cyclase inhibitor methylene blue abolished the effect of 3-morpholino-sydnonimine. Superfusion of the ventral striatum with the guanylyl cyclase inhibitor LY83583 decreased acetylcholine release by 60% of basal release, whereas the less specific guanylyl cyclase inhibitor methylene blue was ineffective in this respect. Superfusion of the ventral striatum with inhibitors of nitric oxide synthase also led to different effects on basal acetylcholine release. Superfusion with L-NG-methylarginine did not influence basal acetylcholine release, whereas superfusion with L-NG-nitroarginine or with L-NG-nitroarginine methyl ester led to a substantial decrease in acetylcholine output, the latter compound being more effective. The effect of L-NG-nitroarginine was abolished by simultaneous superfusion with L-arginine. The effects of NO donors and of LY83583 suggest that NO increases acetylcholine release, probably by a cGMP-dependent mechanism. The effectiveness of nitric oxide synthase inhibitors shows that the activity of striatal neurons is under the permanent influence of nitric oxide, that leads, via a direct or indirect mechanism, to continuous enhancement of acetylcholine release. In conclusion, our findings suggest that NO synthesized in the ventral striatum acts as an intracellular messenger which modulates acetylcholine release.
Acetylcholine↗
Serum nitrite plus nitrate in infection with human immunodeficiency virus type-1.
To get a measure of the extent of induction of nitric oxide synthase in infection with human immunodeficiency virus type-1 (HIV-1) in vivo, we estimated serum nitrite plus nitrate concentrations in 110 HIV-1 infected individuals compared to 76 blood donors. To monitor cytokine action and to measure induction of pteridine synthesis, we determined in parallel neopterin, biopterin, soluble tumor necrosis factor-alpha receptor 55 and 75, and beta 2-microglobulin. Serum nitrite plus nitrate concentrations were elevated in patients as compared to blood donor controls. In sera of patients, nitrite plus nitrate levels correlated significantly with neopterin, soluble tumor necrosis factor receptor 55 and 75, and beta 2-microglobulin. Nitrite plus nitrate levels were higher and correlations were stronger in groups of patients with lower CD4+ cell count. These results suggest that cytokine-mediated nitric oxide synthesis occurs in individuals with HIV-1 infection.
Adult↗
Detection of bacterial pyrogens on the basis of their effects on gamma interferon-mediated formation of neopterin or nitrite in cultured monocyte cell lines.
In a number of mammalian cell types, pteridine biosynthesis from guanosine 5'-triphosphate and formation of nitric oxide from L-arginine are induced by gamma interferon (IFN-gamma) and bacterial lipopolysaccharide (LPS). We assessed the possibility of using such metabolic alterations for the in vitro detection of pyrogens. Products from gram-negative and gram-positive bacteria and related synthetic compounds were tested for their potential to induce either of these pathways. Stimulation of pteridine biosynthesis was monitored as the formation of neopterin in the human myelomonocytic cell line THP-1. The formation of nitric oxide was determined as nitrite in murine J774A.1 macrophage cultures. The substances tested included toxic and detoxified parts of LPS and lipid A from Escherichia coli, Salmonella typhimurium, Salmonella minnesota, and Klebsiella pneumoniae as well as lipoteichoic acid and toxic shock syndrome toxin 1 from Staphylococcus aureus. Furthermore, two cell wall compounds from Mycobacterium tuberculosis, trehalose 6,6'-dimycolate and N-acetylmuramyl-L-alanyl-D-isoglutamine, which are active components of Freund's adjuvant, were used. When applied as a single stimulus, only the whole LPS molecule potently stimulated neopterin or nitrite formation. Lipid A and products from gram-positive bacteria were weakly active. For neopterin formation, lipid A required the presence of fetal calf serum. Besides detoxified LPS and independently from the presence of serum, all bacterial compounds tested strongly increased the effects mediated by IFN-gamma. Our results show that bacterial pyrogens can be detected by monitoring the formation of neopterin or nitrite. This may provide a basis for the development of an in vitro assay for the detection of pyrogenic contamination with the aim of replacing the currently used animal test.
Animals↗