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

The in vivo conditions needed for the induction of nitrogen oxide synthesis by hepatocytes were determined. Hepatocytes obtained from rats injected with killed Corynebacterium parvum spontaneously produced NO2(-)+NO3- in culture and were found to contain cytosolic enzyme activity for nitrogen oxide synthesis. The enzyme activity required both L-arginine and NADPH, and was not found in hepatocytes obtained from normal rats or rats injected with lipopolysaccharide (LPS) alone. In contrast, nonparenchymal cells were stimulated to synthesize NO2(-)+NO3- by LPS. These results show the presence of inducible cytosolic enzyme activity for nitrogen oxide synthesis in hepatocytes, which is distinct from nonparenchymal cell NO. synthesis.
 ...
PMID:Inducible cytosolic enzyme activity for the production of nitrogen oxides from L-arginine in hepatocytes. 234 76

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.
 ...
PMID:Synthesis of nitrogen oxides from L-arginine by macrophage cytosol: requirement for inducible and constitutive components. 273 2

Phagocytic cells can be primed for enhanced stimulated release of superoxide anion (O2-) by exposure to a variety of biologic agents, including gamma-interferon and lipopolysaccharide. We examined the role of calcium ion in this priming, using the calcium ionophore ionomycin. Preincubation with ionomycin, 1 to 10 nM, primed human neutrophils to release up to 7-fold more O2- during stimulation with 1 microM formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe). With 160 nM phorbol myristate acetate as stimulus, ionomycin caused a doubling of O2- production in mouse peritoneal macrophages. Incubation of phagocytes with ionomycin at priming concentrations did not directly stimulate O2- release. Priming of neutrophils occurred in 1-2 min and was associated with a marked reduction in the lag time for O2- release after f-Met-Leu-Phe stimulation and with an increase in the rate of O2- production. Kinetic analysis of NADPH-dependent O2(-)-producing activity in sonicates of resting human neutrophils incubated with sodium dodecyl sulfate suggested that modification of the enzyme responsible for the respiratory burst was not responsible for priming. Priming of neutrophils with ionomycin had no apparent effect on either the activity or subcellular distribution of protein kinase C. The effect of ionomycin on the cytosolic free calcium concentration ([Ca2+]c) was assessed in neutrophils using the calcium-sensitive fluorescent dye fura-2. Ionomycin at priming concentrations caused an approximate doubling of the base-line [Ca2+]c. When neutrophils were exposed to various concentrations of ionomycin, a parallel rise in [Ca2+]c and priming was observed. A rise in [Ca2+]c of approximately 0.8 microM caused half-maximal priming. These results suggest that an increase in [Ca2+]c is not sufficient to initiate release of O2-, but they support the concept that Ca2+ can serve as a second messenger in this event.
 ...
PMID:Priming of neutrophils and macrophages for enhanced release of superoxide anion by the calcium ionophore ionomycin. Implications for regulation of the respiratory burst. 304 Jul 59

Previous studies have shown that murine macrophages immunostimulated with interferon gamma and Escherichia coli lipopolysaccharide synthesize NO2-, NO3-, and citrulline from L-arginine by oxidation of one of the two chemically equivalent guanido nitrogens. The enzymatic activity for this very unusual reaction was found in the 100,000g supernatant isolated from activated RAW 264.7 cells and was totally absent in unstimulated cells. This activity requires NADPH and L-arginine and is enhanced by Mg2+. When the subcellular fraction containing the enzyme activity was incubated with L-arginine, NADPH, and Mg2+, the formation of nitric oxide was observed. Nitric oxide formation was dependent on the presence of L-arginine and NADPH and was inhibited by the NO2-/NO3- synthesis inhibitor NG-monomethyl-L-arginine. Furthermore, when incubated with L-[guanido-15N2]arginine, the nitric oxide was 15N-labeled. The results show that nitric oxide is an intermediate in the L-arginine to NO2-, NO3-, and citrulline pathway. L-Arginine is required for the activation of macrophages to the bactericidal/tumoricidal state and suggests that nitric oxide is serving as an intracellular signal for this activation process in a manner similar to that very recently observed in endothelial cells, where nitric oxide leads to vascular smooth muscle relaxation [Palmer, R. M. J., Ashton, D. S., & Moncada, S. (1988) Nature (London) 333, 664-666].
 ...
PMID:Macrophage oxidation of L-arginine to nitrite and nitrate: nitric oxide is an intermediate. 324

Early changes in hepatic carbohydrate metabolism without apparent hepatocyte dysfunction were reported previously in mice infected with Listeria monocytogenes. This study was undertaken to examine possible imbalance in host regulatory mechanisms which might be responsible for these changes. Female CD-1 mice fasted 12 hr prior to the experiments were injected intraperitoneally with 10(5), 10(6), or 10(7)Listeria. Control mice received either 10(9) heat-killed Listeria or 150 mug of Salmonella typhimurium lipopolysaccharide. Hepatic glycogen, adenosine triphosphate (ATP), adenosine diphosphate (ADP), and nicotinamide adenine dinucleotide (NAD) (NAD(+), NADH, NADP(+), and NADPH) levels were assayed periodically. Activities of ATP hydrolyzing enzyme and NAD glycohydrolase were measured at various intervals after infection. Decreases in glycogen occurred as early as 10 hr after infection. Responses in the controls differed from those in infected mice. Hepatic ATP levels decreased as early as 10 hr after infection, with concomitant increases noted in ADP. Hepatic ATP hydrolyzing enzyme activity increased as the infection progressed. Decreases were noted in hepatic NAD levels, with the greatest reduction in the reduced form of NAD. Slight changes were observed after 10 hr, and greater differences were noted 20 hr after infection. The magnitude of these biochemical changes appeared to be dose-dependent. Significant increases in hepatic NAD glycohydrolase activity were noted as the infection progressed. Small but significant increases in serum inorganic phosphate were noted 10 and 20 hr after infection, with a larger increase observed 30 hr after infection. The results indicate impairment of host energy metabolism early in the course of experimental listeriosis.
 ...
PMID:Mechanisms of pathogenesis in Listeria monocytogenes infection. V. Early imbalance in host energy metabolism during experimental listeriosis. 434 93

We investigated the capacity of bacterial endotoxin (lipopolysaccharide, LPS) to modify the oxidative metabolic response to membrane stimulation of human neutrophils. Neutrophils were pretreated for 60 min with LPS, 10 ng/ml, then stimulated by exposure to fixed immune complexes, the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP), or phorbol myristate acetate. Release of superoxide anion (O-2) was up to 7-times greater in cells preincubated with LPS, depending upon the stimulus used. Consumption of oxygen and release of hydrogen peroxide (H2O2) were similarly increased, using FMLP as stimulus. The enhancement was accompanied by a reduction in lag time and an increase in the rate of the response, but the duration of the oxidative events was not changed. The molecular basis for the augmented oxidative response of LPS-pretreated cells was investigated. Preincubation with LPS at 0 degrees C prevented priming, but preincubation in the presence of cycloheximide or chelation of extracellular calcium ion did not. Neutrophils preincubated with LPS had slightly decreased numbers of binding sites and equivalent binding affinity for radiolabeled FMLP. Possible changes in the enzyme responsible for the oxidative burst were analyzed by studying NADPH-dependent generation of O-2 by particulate fractions from cells preincubated with LPS or buffer, then stimulated before cell disruption. The fraction prepared from LPS-pretreated neutrophils exhibited greater release of O-2 over a wide range of concentrations of NADPH. The calculated apparent Km for NADPH was equivalent in the two fractions, but the Vmax was increased 2.5-fold in the subcellular fraction from LPS-pretreated cells. These results suggest that LPS could increase neutrophil-mediated host defense or the tissue damage associated with endotoxemia by enhancing the generation of oxygen metabolites by neutrophils. These results also support the concept that the neutrophil is not an end-stage cell in regard to function or metabolic activity.
 ...
PMID:Priming of neutrophils for enhanced release of oxygen metabolites by bacterial lipopolysaccharide. Evidence for increased activity of the superoxide-producing enzyme. 609 75

Macrophages activated by infection or elicited by injection of lipopolysaccharide (LPS), when stimulated with phorbol myristate acetate, release greater amounts of superoxide anion (O-2) than do normal resident macrophages. This enhanced production of O-2 and of other oxygen metabolites derived from O-2 is responsible, at least in part, for the enhanced microbicidal activity of these cells. To investigate the molecular basis for the enhanced oxygen metabolite response, the kinetic parameters of the enzyme responsible for NADPH-dependent production of O-2 (NADPH oxidase) were compared in LPS-elicited and resident mouse peritoneal macrophages. Resident and LPS-elicited macrophages were stimulated with phorbol myristate acetate, disrupted by sonication, assayed for their content of NADPH, and fractionated by centrifugation. The distribution of NADPH oxidase activity among the fractions was similar in both types of macrophage. A membrane-rich 27,000 X g pellet, which had the highest specific activity for the oxidase among the various fractions, was utilized to study the kinetic parameters of the oxidase from normal and LPS macrophages. The oxidase from LPS-elicited macrophages displayed a higher Vmax and a lower Km for NADPH than did the oxidase from normal cells. LPS-elicited cells also had a higher intracellular concentration of NADPH than did normal cells. The altered Km and Vmax, combined with the higher concentration of NADPH, resulted in a 2.2- to 3.5-fold increase in the calculated velocity of the oxidase from LPS-elicited macrophages compared with that from resident macrophages. These results suggest that the enhanced oxygen metabolite response of activated macrophages is due, in part, to modification of the enzyme responsible for the production of O-2.
 ...
PMID:Activation of mouse peritoneal macrophages by lipopolysaccharide alters the kinetic parameters of the superoxide-producing NADPH oxidase. 630 77

The cellular sites of H2O2 formation in phagocytizing granulocytes have been identified with cerium chloride. A precipitate was visible in phagosomes and on plasma membranes from intact normal cells in the presence of either 0.71 mM NADH or NADPH. X-ray microanalysis permitted identification of cerium deposition within the phagosomes even in the absence of reduced pyridine nucleotides. Catalase ablated the formation of the reaction product. Intact granulocytes obtained from subjects receiving 1600 units of vitamin E daily for 2 weeks exhibited reaction product in the presence of NADH but not NADPH. Intact cells from subjects treated with vitamin E demonstrated diminished numbers of phagocytic vesicles containing reaction product. During phagocytosis the granulocytes treated with vitamin E consumed oxygen but exhibited significantly reduced rates of hydrogen-peroxide-dependent glucose-1-14C oxidation to 14CO2. Isolated phagocytic vesicles obtained from granulocytes after ingestion of opsonized lipopolysaccharide-paraffin oil droplets contained reaction product when exposed to 0.71 mM NADPH. No reaction product was evident at 0.71 mM NADH but was evident at 2.0 mM NADH. Isolated phagocytic vesicles from the granulocytes of subjects receiving vitamin E exhibited reaction product only in the presence of NADH. These observations suggest that vitamin E interferes with the electron transport chain apparently required for the oxidation of NADPH to form H2O2 in the phagocytizing granulocyte.
 ...
PMID:Vitamin E--a selective inhibitor of the NADPH oxidoreductase enzyme system in human granulocytes. 661 42

1. Bacterial endotoxin, a soluble lipopolysaccharide, has been studied to ascertain its effects in vivo and in vitro on the hepatic drug-metabolizing enzymes of adult male and female rats. 2. 24 h after a single 1 X 0 or 2 X 0 mg/kg i.p. dose of endotoxin, hexobarbital sleeping time was significantly increased in adult male rats. Significant inhibition of liver microsomal cytochrome P-450 occurred after 6 h and continued only until 24 h after endotoxin administration, while injection of inactivated endotoxin did not result in any significant decrease of hepatic mixed-function oxidase enzymes or cytochrome P-450. In contrast, rho-nitrophenol-UDP-glucuronyltransferase enzyme activity was unaffected by these levels of endotoxin. 3. Electron-microscopic examination of rat liver hepatocytes did not reveal any significant change in ultrastructure 24 h after a single i.p. dose of endotoxin. 4. Endotoxin failed to depress the phenobarbitone- or 3-methylcholanthrene-induced forms of cytochrome P-450 and the dependent mono-oxygenase enzymes. Simultaneous administration of phenobarbital and endotoxin resulted in 100% mortality of rats. Combination of 3-methylcholanthrene and endotoxin did not block the induction of cytochrome P-448 or dependent benzo[a]pyrene hydroxylase activity. 5. Addition of endotoxin in vitro resulted in significant inhibition of hepatic microsomal cytochrome P-450 and aminopyrine N-demethylase activity only on preincubation with an NADPH-generating system supplemented with EDTA.
 ...
PMID:Effects of endotoxin upon rat hepatic microsomal drug metabolism in vivo and in vitro. 713 99

Nitric oxide synthase produces NO, citrulline, water, and NADP at the expense of arginine, NADPH, and dioxygen. While citrulline has been considered to be an inert by-product of the high output inducible isoform of NO synthase (iNOS), we show here that immunostimulants induce a metabolic pathway in vascular smooth muscle cells, which enables them to regenerate arginine from citrulline. Regeneration of arginine from citrulline is accomplished by two urea cycle enzymes: arginino-succinate synthetase (AS) and argininosuccinate lyase (AL). Whereas AL is constitutive to vascular smooth muscle cells, AS mRNA and enzyme activity is markedly induced in cells by treatment with bacterial lipopolysaccharide (LPS). The induction of AS mRNA and activity by LPS follows a time course which mirrors that for iNOS but lags 1-2 h behind. As shown for iNOS, interferon-gamma does not itself induce AS but is synergistic with LPS. AS induction is suppressed by glucocorticoids, actinomycin D, and, to a lesser extent, cycloheximide. On the other hand, AS induction is unaffected by an excess of citrulline or the inhibitor of iNOS, N omega-methyl-L-arginine. Our results show the urea cycle enzymes AS and AL confer cells with the capacity to produce NO without a need for exogenous arginine. In conjunction with NOS, citric acid cycle enzymes that covert fumarate to oxaloacetate (fumarase and malate dehydrogenase) and oxaloacetate to aspartate (aspartate transaminase), AS and AL form a novel arginine-citrulline cycle that enables high output NO production by cells.
 ...
PMID:Argininosuccinate synthetase mRNA and activity are induced by immunostimulants in vascular smooth muscle. Role in the regeneration or arginine for nitric oxide synthesis. 751 85


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>