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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytosols prepared from murine peritoneal macrophages and the RAW 264 macrophage cell line catalyzed conversion of L-arginine to the labile vaso-relaxant nitric oxide and its accumulating endproducts, nitrite and nitrate. This activity required previous exposure of the cells to interferon-gamma and bacterial lipopolysaccharide. Nitrogen oxide synthetase activity was characterized further using nitrite + nitrate production as an indicator of the synthesis of all three nitrogen oxides. Nitrogen oxide synthetase activity was heat-sensitive, NADPH-dependent, and exhibited substrate stereospecificity. The nitrite + nitrate formation was proportional to time and concentration of cytosol. However, dilution decreased the specific activity, suggesting a cofactor requirement in addition to NADPH. Specific activity was restored by addition of cytosol from non-activated macrophages, which itself did not make nitric oxide. Both high and low molecular weight fractions of control macrophage cytosol were required to restore activity of cytosol from activated macrophages that had been either diluted or partially purified. Thus, the enzymatic system involved in nitric oxide synthesis by murine macrophages consists of at least one inducible and two constitutive components.
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PMID:Synthesis of nitrogen oxides from L-arginine by macrophage cytosol: requirement for inducible and constitutive components. 273 2

Nitric Oxide (NO) has been implicated in the pathologic vasodilation of sepsis. Because NO can be measured in the exhaled gas of animals and humans, we hypothesized that increases in exhaled NO would occur in a septic model. Using a blinded design, 10 male Sprague-Dawley rats (300 to 400 g) were anesthetized, paralyzed, tracheotomized, and randomized (5/group) to receive an intravenous injection of either lipopolysaccharide (LPS) (Salmonella typhosa, 20 mg/kg) or placebo (equal volume of saline). Thereafter, exhaled gas was collected and measurements of NO concentration were made using chemiluminescence every 20 min for 300 min during ventilation (RR 40 breaths/min, VT 3 ml; PEEP 0, FIO2 0.21). Another group of 10 animals (5 LPS; 5 control) were treated in the same fashion and then killed at 240 min and an arterial blood sample obtained for blood gas and TNF alpha determinations. Pressure volume (PV) curves were constructed and lungs removed, preserved, and submitted for histologic evaluation. LPS-treated rats had lower mean arterial pressures than the control group, p < 0.0001. No significant differences in static lung compliance and PV curves were found in the two groups. TNF alpha levels were greater in the LPS group (1.40 +/- 0.24 ng/ml) versus control group (0.09 +/- 0.04 ng/ml), p < 0.001. By contrast to the control group, exhaled NO concentration rose in all LPS-treated rats at approximately 100 min and at about 160 min reached a plateau that was 6 times greater than control levels (p < 0.0001). There was greater interstitial, airspace, and total lung injury in the LPS group (p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Increased nitric oxide in exhaled gas as an early marker of lung inflammation in a model of sepsis. 753 2

The roles of nitric oxide derived from either the constitutive endothelial NO synthase (eNOS or NOS3) or the inducible NOS (iNOS or NOS2) in hepatic injury during endotoxemia remain controversial. To investigate this further, rats received a bolus of lipopolysaccharide (LPS) following implantation of osmotic pumps containing one of two nonselective NOS inhibitors (NMA or NAME), one of two inducible NOS inhibitors (NIL or AG), or saline. The inhibitors were infused continuously into the liver via the portal vein. Treatment of LPS-injected rats with NMA and NAME resulted in 106 and 227% increases, respectively, in circulating hepatic enzyme levels compared to LPS-treated control rats. In contrast, infusion of the iNOS-selective inhibitors had no effect on the LPS-induced hepatic necrosis. In rats receiving NAME, LPS induced greater neutrophil infiltration and ICAM-1 expression than in the LPS + saline group, whereas NIL infusion did not. The increased hepatic necrosis and PMN infiltration in the LPS + NAME group was partially prevented by a simultaneous infusion of a liver-selective NO donor. Inhibition of PMN accumulation using an anti-ICAM-1 antibody or by PMN depletion using vinblastine pretreatment, however, did not reverse the increased necrosis with NAME infusion during endotoxemia. In contrast to the assessment for necrosis, increased apoptosis was observed in the livers of LPS-treated rats receiving infusions of either NAME or NIL, but not with LPS alone. These data indicate that NO produced by eNOS may be adequate to prevent necrosis by a mechanism independent of PMN, while induced NO appears to prevent apoptosis.
Nitric Oxide 1997 Oct
PMID:Differential effects of nonselective nitric oxide synthase (NOS) and selective inducible NOS inhibition on hepatic necrosis, apoptosis, ICAM-1 expression, and neutrophil accumulation during endotoxemia. 944 11

Lipid A, the biologically active component of lipopolysaccharide, initiates a specific cytotoxic signaling cascade in the renal proximal tubule that involves a rapid release of intracellular calcium, the activation of nitric oxide synthase (NOS) and NO production. Superoxide (O2-) generation is also a component of this cascade and both NO and O2- are required for the development of oxidant stress and cytotoxicity. Here we examined whether NOS activity was responsible for O2- generation. In renal proximal tubules isolated from the rat, the NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA) but not D-NMMA blocked lipid A (50 microg/ml)-stimulated O2- generation as measured by the reduction of cytochrome c during a 30-min incubation period. When L-arginine (2 mM) was added to the tubule suspensions, O2- generation was significantly inhibited, while NO2- (a marker of NO generation) was significantly increased. The addition of L-arginine also reduced lipid A-stimulated malondialdehyde formation at 30 min (a marker of lipid peroxidation) and lactate dehydrogenase release at 90 min (a marker of cell death). Thus, lipid A-stimulated the generation of both NO and O2- via NOS activation. Furthermore, increasing L-arginine availability shifted NOS activity toward NO generation and reduced oxidant injury. These results offer an explanation of why scavengers of NO or oxygen radicals ameliorate endotoxin-induced acute renal failure in vivo.
Nitric Oxide 1997 Oct
PMID:Superoxide generation by renal proximal tubule nitric oxide synthase. 944 14

In genetic hemochromatosis (GH), iron overload affects mainly parenchymal cells, whereas little iron is found in reticuloendothelial (RE) cells. We previously found that RE cells from GH patients had an inappropriately high activity of iron regulatory protein (IRP), the key regulator of intracellular iron homeostasis. Elevated IRP should reflect a reduction of the iron pool, possibly because of a failure to retain iron. A defect in iron handling by RE cells that results in a lack of feedback regulation of intestinal absorption might be the basic abnormality in GH. To further investigate the capacity of iron retention in RE cells of GH patients, we used inflammation as a model system as it is characterized by a block of iron release from macrophages. We analyzed the iron status of RE cells by assaying IRP activity and ferritin content after 4, 8, and 24 hours of incubation with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). RNA-bandshift assays showed that in monocytes and macrophages from 16 control subjects, IRP activity was transiently elevated 4 hours after treatment with LPS and IFN-gamma but remarkably downregulated thereafter. Treatment with NO donors produced the same effects whereas an inducible Nitric Oxide Synthase (iNOS) inhibitor prevented them, which suggests that the NO pathway was involved. Decreased IRP activity was also found in monocytes from eight patients with inflammation. Interestingly, no late decrease of IRP activity was detected in cytokine-treated RE cells from 12 GH patients. Ferritin content was increased 24 hours after treatment in monocytes from normal subjects but not in monocytes from GH patients. The lack of downregulation of IRP activity under inflammatory conditions seems to confirm that the control of iron release from RE cells is defective in GH.
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PMID:Response of monocyte iron regulatory protein activity to inflammation: abnormal behavior in genetic hemochromatosis. 951 58

Alveolar macrophages (AMs) constitute an important first line of host defense against infection in the lung, and NO is an essential component of the microbicidal activity of cytokine-activated macrophages. Previously we studied the respiratory burst, protein kinase C activity, and NO generation in tumor necrosis factor (TNF) and lipopolysaccharide (LPS)-treated AMs and gender differences in phagocytosis in ethanol (EtOH)-intoxicated rats. Now we have investigated NO production by AMs in EtOH plus LPS-treated male and female rats. Rats were infused iv with EtOH for 3 h to a blood level of approximately 180 mg/dl. At 90 min of infusion, Escherichia coli LPS (750 microg/kg) was injected i.v. Controls received saline (SAL) + LPS. AMs were isolated by bronchoalveolar lavage and cultured for 20 h in the absence and presence of LPS, interferon-y (IFN), and LPS + IFN. Nitrite was determined in the medium and was taken as an index of NO production. EtOH alone resulted in no significant differences compared with SAL infusion. LPS treatment caused a decrease in basal and an increase in LPS and IFN-stimulated generation of NO in males and females. EtOH + LPS treatment vs EtOH showed no significant differences. There are gender differences in both spontaneous and in vitro stimulated NO production by AMs. AMs of female rats treated with SAL + LPS released significantly more NO spontaneously than AMs of equally treated male rats. Cells of SAL + LPS-treated male rats activated in vitro by LPS and IFN-gamma produced significantly greater amounts of NO than AMs of female rats. These differences in activated induction of NO production were abrogated by ethanol treatment.
Nitric Oxide 1997 Feb
PMID:Gender differences in nitric oxide production by alveolar macrophages in ethanol plus lipopolysaccharide-treated rats. 970 Oct 42

The inducible human cationic amino acid transporter hCAT-2B was expressed in Xenopus laevis oocytes, and this system was used to test the effect of several NO synthase (NOS) inhibitors and/or L-arginine analogues on L-arginine transport by this y+ carrier. L-NG-Methyl-L-arginine (L-NMA), asymmetrical L-NG, NG-dimethyl-L-arginine (L-ADMA), L-N5-(1-iminoethyl)-ornithine (L-NIO), L-NG-nitro-L-arginine (L-NNA), and L-NG-nitro-L-arginine methyl ester (L-NAME) all inhibited the inducible NOS II extracted from RAW 264.7 macrophages induced with bacterial lipopolysaccharide. L-NMA, L-ADMA, and L-NIO also competed with L-arginine for transport by hCAT-2B, whereas L-NNA and L-NAME did not. The two L-arginine analogues, symmetrical NG, NG-dimethyl-L-arginine (L-SDMA) and alpha-amino-delta-isothioureidovaleric acid (AITV), as well as L-lysine, did not block enzymatic activity of NOS II, but did compete for L-arginine transport mediated by hCAT-2B. L-Lysine and L-SDMA were transported efficiently by hCAT-2B and exchanged against intracellular L-arginine, resulting in an L-arginine depletion of the cells. AITV was a much poorer substrate of hCAT-2B and had only little effect on intracellular L-arginine concentrations. These data indicate that substrate recognition differs markedly between the inducible L-arginine transporter hCAT-2B and the inducible NOS II, with different L-arginine analogues having affinity to only one or both of these proteins.
Nitric Oxide 1997 Feb
PMID:Interference of L-arginine analogues with L-arginine transport mediated by the y+ carrier hCAT-2B. 970 Oct 46

Rat C6 glioma cells were stably transfected with a human cDNA encoding heat shock protein (HSP)70. Immunostaining revealed the presence of largely cytosolic HSP70 in C6-hsp70 cells, but not in control (vector transfected) C6-pTK cells. Induction of nitric oxide synthase (NOS-2) expression in C6-hsp70 cells, assessed by nitrite accumulation, was significantly reduced compared to control C6-pTK cells (25+/-8% of control cell induction, P < 0.005), when induced with a maximally stimulatory combination of bacterial endotoxin lipopolysaccharide (LPS) plus a mixture of three cytokines ("CM:" TNF-alpha, IL1-beta, and IFN-gamma). Immunostaining for the transcription factor NFkappaB p65 subunit revealed decreased cytokine-dependent nuclear uptake in HSP70 expressing cells compared to control cells. Activation of C6 cell NFkappaB by LPS plus CM required IkappaB degradation by the 20S proteasome, since NOS-2 expression was blocked by a selective proteasome inhibitor. In parental C6 cells, the presence of LPS plus CM caused a rapid (within 30 min) decrease in inhibitory IkappaB-alpha protein levels, and this loss was abolished by prior heat shock of the cells. In contrast, IkappaB-alpha levels in transfected cells were not modified by the expression of HSP70. These results demonstrate that constitutive HSP70 expression in glial cells can reduce NOS-2 induction, presumably due to inhibition of NFkappaB nuclear uptake. Furthermore, whereas prevention of decreases in IkappaB-alpha can account for the suppressive effects of heat shock, the results suggest that HSP70 blocks NOS-2 induction by interfering at a later step in the NFkappaB activation pathway.
Nitric Oxide 1997 Apr
PMID:Suppression of glial nitric oxide synthase induction by heat shock: effects on proteolytic degradation of IkappaB-alpha. 970 Oct 55

The effect of lipopolysaccharide (LPS) treatment on noradrenergic responses elicited by electrical field stimulation (EFS) was investigated in the rabbit anococcygeus muscle. In the absence of LPS, EFS-induced contractions were enhanced and nitrergic relaxations were inhibited by NG-nitro-L-arginine (L-NOARG) but not by NG-monomethyl-L-arginine (L-NMMA). Administration of L-NMMA prior to L-NOARG inhibited the enhancement of EFS-induced contractions by L-NOARG and reversed the inhibitory effect of L-NOARG on nitrergic relaxations. Treatment with LPS induced a time-dependent loss of phenylephrine-induced tone which was inhibited by cycloheximide, dexamethasone, L-NMMA, or L-NOARG. Treatment of the anococcygeus muscle with LPS also resulted in a time-dependent loss in the magnitude of EFS-induced contractions and an increase in the delay of onset of contractions. These effects were reversible by pretreatment with cycloheximide or by treatment with L-NMMA. These results suggest that LPS induces a loss of tone and of noradrenergic responses through expression of the inducible NO synthase in the rabbit anococcygeus muscle. L-NMMA blocks these effects but does not affect nitrergic transmission, while L-NOARG is active against both.
Nitric Oxide 1997 Jun
PMID:Modulation of noradrenergic responses by nitric oxide from inducible nitric oxide synthase. 970 81

Liver cells can produce nitric oxide from L-arginine through either constitutive NO synthase or inducible NO synthase (NOS) detected after in vivo or in vitro treatment with cytokines and/or lipopolysaccharide (LPS). The effects of NO on liver cells are associated with protein synthesis and mitochondrial electron transfer inhibition. L-Arginine is also the precursor of L-ornithine and polyamines. The latter are considered to be protective in the liver in several experimental models. The aim of the present work was to test the effects of polyamines on LPS-inducible NOS activity in rat liver cytosol using the test of radioactive L-citrulline synthesis from L-[guanido-14C]arginine. The three polyamines inhibited inducible NO synthase activity with the following hierarchy: spermine > spermidine approximately equal to putrescine. The 0.5 mM spermine was found to inhibit 50% of inducible NO synthase activity. The present data suggest an inhibitory interrelationship in the liver between two metabolites derived from the common precursor L-arginine.
Nitric Oxide 1997 Jun
PMID:Polyamines inhibit lipopolysaccharide-induced nitric oxide synthase activity in rat liver cytosol. 970 89


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