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)

Induction of the inducible isoform of nitric oxide synthase (iNOS) in various types of cells is implicated as the cause of septic shock. We evaluated the concentration of tetrahydrobiopterin (BH4), a cofactor of NOS, in plasma and various other tissues of rats treated with lipopolysaccharide (LPS; 10 mg/kg I.V.). The activity of GTP cyclohydrolase I (GTPCH), the first and rate-limiting enzyme in the de novo synthesis of BH4, in rat tissues was also determined. Three hours after administration of LPS, rats showed plasma levels of BH4 and NOx (NO3- and NO2-) that were elevated by 137 and 206%, respectively. GTPCH was expressed in liver and, to a lesser extent, in the lung, heart and kidney of control rats. In control rats, although a high concentration of BH4 was detected in the liver, its level was lower in lung, heart, kidney and aorta. Three hours after LPS administration, a significant increase in BH4 concentration and/or GTPCH activity was observed in all tissues examined except the liver. Our results demonstrate that the de novo synthesis of BH4 is upregulated by LPS in the rat in vivo, which may, at least in part, account for the increases in plasma level and tissue concentration of BH4 after the administration of LPS.
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PMID:Tetrahydrobiopterin and GTP cyclohydrolase I in a rat model of endotoxic shock: relation to nitric oxide synthesis. 885 74

The possibility that 5,6,7,8-tetrahydrobiopterin (BH4) biosynthesis is stimulated in glial cells by treatment with lipopolysaccharide (LPS) and tumor necrosis factor (TNF-alpha) was examined in the astrocyte-derived C6 glioma cell line. Under basal culture conditions BH4 levels were found to be at the limit of detection. Concurrent treatment with 10 micrograms/ml LPS and 50 ng/ml TNF-alpha caused a time-dependent 13-fold increase in the levels of BH4. This treatment paradigm also induced nitric oxide synthase activity, as evidenced by increased levels of nitrite, an oxidized metabolite of NO, in the culture medium. LPS and TNF-alpha treatment led to a 25-fold increase in GTPCH enzyme activity, the first and rate-limiting enzyme in BH4 synthesis, and a corresponding 23-fold increase in GTPCH protein levels. Northern blot analysis showed that increased levels of GTPCH mRNA preceded changes in GTPCH protein, GTPCH enzyme activity and BH4 levels and reached a maximal of 44-fold that was sustained for at least 48 h. These results demonstrate that LPS and TNF-alpha stimulate de-novo BH4 biosynthesis and suggest that C6 cells offer a model system for studying the molecular events that control the induction of GTPCH gene expression and BH4 synthesis in glial cells.
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PMID:Tetrahydrobiopterin biosynthesis in C6 glioma cells: induction of GTP cyclohydrolase I gene expression by lipopolysaccharide and cytokine treatment. 888 40

To investigate the interaction between endothelin (ET) and the nitric oxide system, we examined the effects of ET-1 and ET-3 on the induction of inducible nitric oxide synthase (iNOS) and guanosine triphosphate cyclohydrolase I (GTP:CHI), the rate-limiting enzyme of de novo synthesis of the cofactor tetrahydrobiopterin (BH4), in rat mesangial cells. ET-1 inhibited the nitrite accumulation induced by a combination of interleukin-1 beta, tumor necrosis factor-alpha, and lipopolysaccharide in a concentration-dependent manner. The inhibitory effect of ET-3 was less potent than that of ET-1. A selective ETA antagonist, BQ-485, and an ETA and ETB antagonist, TAK-044, abolished the inhibitory effects of ET-1, whereas the selective ETB antagonist BQ-788 had no effect on the inhibition produced by ET-1. These observations indicate that ET-1 inhibits cytokine-stimulated nitrite accumulation through the ETA receptor. Western blot analysis showed that the suppression of nitrite accumulation was accompanied by a decrease in iNOS protein. Northern blot analysis showed that ET-1 inhibited the expression of both iNOS and GTP:CHI mRNA. In conclusion, ET-1 inhibits cytokine-stimulated nitric oxide production through the ETA receptor by suppressing the expression of iNOS and GTP:CHI mRNA in rat mesangial cells.
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PMID:Endothelin-1 inhibits induction of nitric oxide synthase and GTP cyclohydrolase I in rat mesangial cells. 895 63

In cultured granulosa cells, interleukin-1 beta (IL-1 beta) induced a time-dependent (16-72 h) and dose-related (0.3-30 ng/ml) stimulation of nitric oxide (NO) synthase (NOS) activity, as determined by the catalytic conversion of [3H]arginine to [3H]citrulline and NO2- accumulation in the culture medium. Although FSH alone failed to stimulate NOS activity, concomitant treatment with the gonadotropin (200 ng/ ml) or the cell-permeant cAMP analog (Bu)2cAMP (0.5 mM) markedly enhanced IL-1 beta-induced NO generation in cultured granulosa cells. The effect of IL-1 beta on citrulline biosynthesis and NO2- accumulation was abrogated by the NOS inhibitor NG-methyl-L-arginine or the IL-1-receptor antagonist protein. In contrast bacterial endotoxin (lipopolysaccharide), interferon-gamma, or tumor necrosis factor-alpha, which are well known inducers of inducible NOS (iNOS) in a variety of immunocompetent and nonimmunocompetent cell types, failed to increase [3H]citrulline formation or NO2- accumulation in untreated or FSH-stimulated cells. As demonstrated by reverse transcriptase-PCR analysis, IL-1 beta-stimulated NO generation was accompanied by a time-dependent increase in messenger RNA levels for iNOS and GTP-cyclohydrolase (GTPCH), the rate-limiting step for de novo tetrahydrobiopterin (BH4) biosynthesis. Treatment with FSH augmented only GTPCH messenger RNA expression, and a more than additive GTPCH signal was observed when cells were simultaneously challenged with IL-1 beta and FSH. Treatment with the GTPCH inhibitor 2,4-diamino-6-hydroxypyrimidine prevented IL-1 beta-induced NOS activity in untreated or FSH-stimulated cells, and this inhibition was completely reversed by sepiapterin, a substrate for BH4 biosynthesis, via an alternative pterin salvage pathway present in many cell types. As BH4 is an essential cofactor for NOS catalytic activity, these observations strongly suggest that FSH-induced biosynthesis of endogenous BH4 is essential for full iNOS biosynthetic capacity in IL-1 beta-stimulated granulosa cells.
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PMID:Induction of guanosine triphosphate-cyclohydrolase by follicle-stimulating hormone enhances interleukin-1 beta-stimulated nitric oxide synthase activity in granulosa cells. 897

The amounts of messenger RNA for three enzymes, namely guanosine triphosphate (GTP) cyclohydrolase 1,6-pyruvoyltetrahydropterin synthase, and sepiapterin reductase, all of which are involved in the de novo biosynthesis of (6R)-L-erythrodihydroxypropyl-2-amino-4-hydroxy-5,6,7,8-tetrahydro pteridine (BH4) from GTP, were measured quantitatively in murine neuroblastoma cell line N1E-115 by the competitive polymerase chain reaction (PCR) technique after reverse transcription using a heterologous DNA fragment as an internal standard. Twenty-four hour activation of this cell line with 1 microg/ml lipopolysaccharide resulted in statistically significant increases in the amounts of the messages of all three enzymes. Our data suggest that lipopolysaccharide can activate the intrinsic pathway resulting in the enhanced gene expression of these three enzymes in neuron-derived cells such as N1E-115.
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PMID:Effect of lipopolysaccharide on the gene expression of the enzymes involved in tetrahydrobiopterin de novo biosynthesis in murine neuroblastoma cell line N1E-115. 946 45

It has been suggested that decreased tetrahydrobiopterin (BH4) availability may be a useful tool for limiting excessive nitric oxide (NO) formation. In order to test this hypothesis we utilised cultured astrocytes derived from the brain of the hph-1 (BH4 deficient) mouse. In response to treatment with lipopolysaccharide and interferon-gamma (LPS/gammaIFN) levels of BH4 doubled in both wild type and hph-1 astrocytes. However, levels of BH4 in hph-1 astrocytes remained only 25% of the wild type astrocytes. Nitric oxide formation, measured with an NO-electrode, was 45% less from LPS/gammaIFN stimulated hph-1 astrocytes compared with wild type stimulated astrocytes. In contrast, iNOS specific activity and iNOS protein were enhanced in hph-1 stimulated astrocytes by 40 and 60%, respectively when compared with wild type. In conclusion it appears that whilst a decrease in BH4 may limit NO release per se, the possibility and consequences of long term 'over' induction of iNOS protein requires further consideration.
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PMID:Increased inducible nitric oxide synthase protein but limited nitric oxide formation occurs in astrocytes of the hph-1 (tetrahydrobiopterin deficient) mouse. 972 34

Tetrahydrobiopterin (BH4) is one of the cofactors of nitric oxide synthase (NOS), and the synthesis of BH4 is induced as well as inducible NOS (iNOS) by lipopolysaccharide (LPS) and/or cytokines. BH4 has a protective effect against the cytotoxicity induced by nitric oxide (NO) and/or reactive oxygen species in various types of cells. The purpose of this study was to examine whether or not an excess of BH4 is present during the production of NO by iNOS in LPS-treated de-endothelialized rat aorta. Addition of LPS (10 microg/ml) to the aorta bath solution caused L-arginine (L-Arg)-induced relaxation from 1.5 hr after the addition of LPS in de-endothelialized rat aorta pre-contracted with 30 mM KCl. The L-Arg-induced relaxation was prevented by NOS inhibitors. BH4 content also increased from 3 hr after the addition of LPS. mRNAs of iNOS and GTP cyclohydrolase I (GTPCH), a rate-limiting enzyme of BH4 synthesis, were increased from 1.5 hr after addition of LPS. Although the expression of iNOS and GTPCH mRNAs was observed in the media, the expression levels in the media were much lower than those in the adventitia. Ten millimolar 2,4-diamino-6-hydroxypyrimidine (DAHP), an inhibitor of GTPCH, strongly reduced L-Arg-induced relaxation, and decreased BH4 content to below the basal level in LPS-treated aorta, whereas 0.5 mM DAHP reduced the LPS-induced increase in BH4 content to the basal level but did not affect L-Arg-induced relaxation. The inhibition of L-Arg-induced relaxation by 10 mM DAHP was overcome by the addition of BH4 (10 microM). These results suggest that although BH4 is essential for NO production from iNOS, the increase in BH4 content above the basal level is not needed for eliciting L-Arg-induced relaxation by the treatment with LPS. Thus, an excess amount of BH4 may be synthesized during NO production by iNOS in LPS-treated rat aorta.
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PMID:Presence of excess tetrahydrobiopterin during nitric oxide production from inducible nitric oxide synthase in LPS-treated rat aorta. 1062 66

Among the enzymes involved in the system for catecholamine biosynthesis, GTP cyclohydrolase I (GCH) contributes to the system as the first and rate-limiting enzyme for the de novo biosynthesis of tetrahydrobiopterin (BH4), which is the cofactor for tyrosine hydroxylase (TH). Therefore, we investigated whether the endotoxemia caused by an intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) can modulate BH4 production in the norepinephrine nuclei, i.e. the locus ceruleus (LC; A6) and central caudal pons (A5), in C3H/HeN mice and whether such a change in BH4, if any, can result in the modification of norepinephrine production in these nuclei. After a 5-microg i.p. injection of LPS, the protein expression of GCH and TH in both nuclei was examined by immunohistochemistry. The staining intensity of GCH-positive cells increased at 6 h, whereas no significant change in the staining intensity of TH-positive cells was detected. Next, we measured the contents of BH4, norepinephrine, and its metabolites 4-hydroxy-3-methoxyphenylglycol (MHPG) and DL-4-hydroxy-3-methoxymandelic acid (VMA) in these nuclei after LPS i.p. injection. The BH4 content increased to a statistically significant level at 2 and 4 h after the injection. The contents of MHPG and VMA also showed a time-course similar to that of BH4. These data can be rationalized to indicate that an increased supply of BH4 in the LC increased TH activity and resulted in an increase in norepinephrine production rate at the site. This is the first report that sheds light on BH4 as a molecule that intervenes during endotoxemia to increase norepinephrine production rate in the LC.
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PMID:Expression of GTP cyclohydrolase I in murine locus ceruleus is enhanced by peripheral administration of lipopolysaccharide. 1116 86

Tetrahydrobiopterin (BH4) has been shown to be required for dimerization and acquisition of nitric oxide (NO) generating capacity by nitric oxide synthase (NOS). In the present study we have investigated the hypothesis that BH4 may affect NOS activity through a novel mechanism-namely, modulating arginine transport in rat cardiac myocytes. Cardiac myocytes have been previously shown to express cationic amino acid transport proteins (y+ system) CAT-1 and CAT-2. Increasing extracellular BH4 concentrations up to 0.5 mmol/L augments arginine transport in 1 mmol/L arginine media (no BH4, 558 +/- 42 fmol arginine/microg protein/min; 0.1 mmol/L BH4, 580 +/- 11 fmol arginine/microg protein/min; 0.5 mmol/L BH4, 944 +/- 71* fmol arginine/microg protein/min; 1.0 mmol/L BH4, 983+/-84* fmol arginine/microg protein/min, n = 4; *: P <.05 vs no BH4). Treating the cells with lipopolysaccharide (LPS) (10 microg/mL) significantly augmented arginine transport only in the presence of BH4 (no BH4, 600 +/- 33 fmol arginine/microg protein/min; 0.1 mmol/L BH4, 691 +/- 29*dagger fmol arginine/microg protein/min; 0.5 mmol/L BH4, 1123 +/- 32*dagger fmol arginine/microg protein/min; 1.0 mmol/L BH4, 1296 +/- 42*dagger fmol arginine/microg protein/min, n = 4; *: P <.01 vs no BH4, dagger: P <.05 vs no LPS). The administration of biopterin, sodium nitroprusside (NO donor), 2,4-diamino-6-hydroxy-pyrimidine (inhibitor of BH4 synthesis), and sepiapterin (the precursor of de novo synthesis of BH4) to unstimulated cells had no effect on arginine uptake values. Using reverse trancriptase-polymerase chain reaction, we next studied the steady state levels for CAT-1 and CAT-2 mRNA. Incubation with BH4 significantly increased CAT-2 mRNA expression in a concentration-dependent manner in 0.1, 0.5, and 1 mmol/L BH4, respectively. Northern blotting analysis further confirmed this observation. We also found that in the presence of BH4 in these concentrations, CAT-1 mRNA expression was abolished. We suggest that BH4 augments intracellular arginine availability by modulating CAT-2 mRNA expression and suggest that its presence is required for the LPS effect on trans-membrane arginine traffic.
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PMID:Tetrahydrobiopterin augments arginine transport in rat cardiac myocytes through modulation of CAT-2 mRNA. 1132 33

The aim of the present study was to characterize the increase in tetrahydrobiopterin (BH4), which is a cofactor for nitric oxide synthase (NOS), by carboxy-PTIO, a scavenger of nitric oxide (NO), in vascular endothelial cells. BH4 level was determined by oxidation under acidic conditions as biopterin. Addition of lipopolysaccharide (LPS) to endothelial cells increased mRNA levels of inducible NOS (iNOS) and GTP-cyclohydrolase I (GTPCH), which is a rate-limiting enzyme for BH4 synthesis, and the biopterin level. NOS inhibitors, NO-donors and L-arginine, a substrate of NOS, did not affect the increase in the biopterin level induced by LPS, suggesting that BH4 synthesis is unlikely to be modulated by NO produced by iNOS during LPS treatment. However, carboxy-PTIO increased the biopterin level in the absence and the presence of LPS. Carboxy-PTIO did not affect the expression of GTPCH mRNA level. Moreover, 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTPCH, inhibited only about 30% of the carboxy-PTIO-induced increase in the biopterin level. Whereas, N-acetylserotonin, an inhibitor of sepiapterin reductase, strongly inhibited the increase in biopterin level. Carboxy-PTIO inhibited the accumulation of pterin, a decomposition product of BH4 in endothelial cells. These findings suggest that carboxy-PTIO accumulates BH4 under basal and LPS-treated conditions in vascular endothelial cells due to both inhibition of the decomposition of BH4 to pterin and activation of the salvage pathway of BH4 synthesis via sepiapterin reductase.
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PMID:Carboxy-PTIO increases the tetrahydrobiopterin level in mouse brain microvascular endothelial cells. 1167 98


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