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)

CDP-6-deoxy-delta 3,4-glucoseen reductase (E3), which catalyzes the reduction of the C-3 deoxygenation step during the formation of CDP-ascarylose, a 3,6-dideoxyhexose found in the lipopolysaccharide of Yersinia pseudotuberculosis, has been expressed at high level in Escherichia coli (670 times over the wild-type strain). This flavoenzyme, which also contains one plant ferredoxin type [2Fe-2S] cluster, was inactivated by 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and N-ethylmaleimide. In both cases the inactivation followed a pseudo first order kinetics. The second order rate constant for the reaction of DTNB with E3 was 0.25 mM-1 min-1 at 20 degrees C, pH 8.0. Detailed characterization of the inactivated enzyme showed that neither the flavin nor the [2Fe-2S] cluster was altered during inactivation. Since this inactivation was reversible by treating the inactivated enzyme with 1 mM D,L-dithiothreitol (DTT), it was concluded that only cysteine residues were modified during inactivation. Analysis of the inactivation using the method developed by Tsou revealed that two cysteines react with DTNB at similar rates and modification of either one is enough to impair E3's activity. Tryptic digestion of E3 labeled with N-ethyl[2,3-14C]maleimide, followed by fractionation of the digest by high performance liquid chromatography, gave two labeled peptides, both of which were separately isolated as a pair of interconvertible diastereoisomers. Sequence analysis of these labeled peptides allowed the identification of Cys-75 and Cys-296 as the reactive cysteine residues. Interestingly, the C75S and C296S mutant proteins exhibit identical physical and comparable catalytic properties as the wild-type enzyme. Since Cys-296 is a conserved residue in the NAD(P) binding domain of enzymes belonging to the same class, this residue may be involved in stabilizing the charge-transfer complex between E3 and NADH, thus facilitating hydride transfer from the nicotinamide nucleotide to flavin. A chemically modified Cys-75 which is immediately adjacent to the [2Fe-2S] center in E3 may prevent the proper juxtaposition of the redox centers and thus impede electron transfer leading to enzyme inactivation. These results may be useful for placing constraints on the peptide folding comprising the active site of E3 for electron transfer between NADH, FAD, and the [2Fe-2S] center.
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PMID:Mechanistic studies on CDP-6-deoxy-delta 3,4-glucoseen reductase: the role of cysteine residues in catalysis as probed by chemical modification and site-directed mutagenesis. 770 27

Staphylococcal enterotoxins (SE) interact with major histocompatibility complex (MHC) class II cell-surface receptors, eliciting signal transduction in antigen-presenting cells (APC). Subsequent toxin-class II complex interaction with specific T-cell receptors induces T-cell activation. We investigated the effect of niacinamide and interleukin (IL)-10 on SEB-induced responses. In a macrophage cell line, niacinamide (ED50--2mM) and IL-10 (ED50--7U/ml) inhibited interferon (IFN)-gamma-induced MHC class II expression in a dose-dependent manner. Also, niacinamide was a potent inhibitor of T-cell proliferation induced by SEB (ED50-- 1 mM) while IL-10 has minimal effects. In mice, the temporal responses of IL-1alpha, tumor necrosis factor (TNF)-alpha, IL-2, and IFN-gamma evoked by SEB were synergistically potentiated by lipopolysaccharide (LPS). Lethality occurred only when SEB was potentiated by LPS. Niacinamide or IL-10 improved survival of mice after lethal SEB challenge. Niacinamide reduced cytokine serum levels, although the pattern differed from that of IL-10. Niacinamide primarily reduced IL-2 and IFN-gamma, while IL-10 predominantly reduced IL-1alpha and TNF-alpha. The immunomodulatory effects of niacinamide observed on SEB-induced activation of APC and T-cells in vitro and in the LPS potentiated murine model for SEB-induced toxicity suggest it may have therapeutic value.
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PMID:Protective effects of niacinamide in staphylococcal enterotoxin-B-induced toxicity. 859 33

Stimulation of vascular smooth muscle with bacterial lipopolysaccharide (LPS) and proinflammatory cytokines induces the expression of a distinct isoform of NO synthase (inducible NOS [iNOS]) contributing to the suppression of vascular contractility. We have obtained evidence of the involvement of an indirect pathway triggered by NO and its reaction product peroxynitrite (ONOO-) through the activation of the nuclear enzyme poly-ADP ribosyltransferase (PARS) in the pathogenesis of cellular energetic and contractile failure in vascular smooth muscle. Exposure of vascular smooth muscle cells caused DNA strand breaks, activation of PARS, depletion of NAD+, and inhibition of mitochondrial respiration. The NAD+ depletion and inhibition of mitochondrial respiration were reduced by pharmacological inhibition of PARS. Stimulation of vascular smooth muscle cells with LPS and interferon gamma (IFN-gamma) triggered the production of superoxide anion over 3 to 48 hours and NO and ONOO- over 24 to 48 hours and resulted in significant DNA strand breakage. The decrease in mitochondrial respiration in response to LPS and IFN-gamma stimulation was inhibited by the ONOO- scavenger uric acid (100 mumol/L) and by inhibitors of iNOS. The PARS inhibitors 3-aminobenzamide (1 mmol/L), nicotinamide (1 mmol/L), and PD 128763 (100 mumol/L) inhibited the reduction in cellular NAD+ and ATP and the suppression of mitochondrial respiration in response to LPS and IFN-gamma stimulation. Administration of 3-aminobenzamide also reduced PARS activation and vascular hyporeactivity of rat thoracic aortas exposed to ONOO- (300 mumol/L to 1.5 mmol/L) in vitro. 3-Aminobenzamide (10 mg/kg IP) preserved the ex vivo contractility of aortas obtained from endotoxic rats and improved survival in lethal murine endotoxic shock. These data suggest that PARS activation due to iNOS induction (1) is involved in the energetic depletion of vascular smooth muscle cells that express iNOS and (2) contributes to the pathogenesis of vascular energetic and contractile failure in endotoxic shock. Inhibition of PARS may be a novel concept of therapeutic potential in shock.
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PMID:Role of poly-ADP ribosyltransferase activation in the vascular contractile and energetic failure elicited by exogenous and endogenous nitric oxide and peroxynitrite. 863 36

Nitric oxide (NO) produced by the inducible isoform of nitric oxide synthase contributes to the hypotension and vascular hyporeactivity in shock. Nicotinamide is protective against the cytotoxic effects of exogenous and endogenous NO in vitro. We investigated the effect of nicotinamide on the cellular energetic and vascular failure in a rat model of endotoxin shock. Administration of nicotinamide to rats, starting at 1 h bacterial lipopolysaccharide, maintained higher blood pressure levels, without affecting induction of nitric oxide synthase. Nicotinamide treatment prevented the lipopolysaccharide-induced decrease in mitochondrial respiration and intracellular NAD+ levels in peritoneal macrophages and improved the contractility of the thoracic aorta ex vivo. Thus, nicotinamide protects against the delayed, NO-mediated vascular failure in endotoxic shock. Its actions are unrelated to inhibition of NO biosynthesis but may be related to inhibition of the NO-mediated activation of an energy-consuming DNA repair cycle triggered by polyADP ribose synthetase.
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PMID:Protective effects of nicotinamide against nitric oxide-mediated delayed vascular failure in endotoxic shock: potential involvement of polyADP ribosyl synthetase. 872 85

Stimulating monocytes/macrophages with bacterial lipopolysaccharide (LPS) results in TNF-alpha, IL-1, IL-6 and nitrite (NO2-) formation. Inhibitors of poly(ADP-ribose)polymerase inhibit release of these mediators by preventing mRNA expression indicating that ADP-ribosylation plays a crucial role in the synthesis of these mediators. Furthermore we present evidence that ADP-ribosylation is involved in modifying cellular proteins. In murine macrophages a 33 kDa cytosolic protein could be identified that in response to LPS changed its state of ADP-ribosylation, and in human monocytes we showed that the inhibitor nicotinamide prevents LPS induced phosphorylation of two cytosolic proteins of 36 kDa and 38 kDa (p36/38) LPS. Taken together these data indicate that protein modification by ADP-ribosylation may control cellular processes involved in distinct steps of monocyte/macrophage activation.
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PMID:Role of ADP-ribosylation in activated monocytes/macrophages. 919 61

Nitric oxide (NO) exerts cytotoxic effects on various cells including neuronal cells. Glial NO production, mediated via induction of inducible NO synthase (iNOS), enhances neurotoxicity associated with the N-methyl-D-aspartate (NMDA) receptor. The present study examined whether nicotinamide, an inhibitor of poly (ADP-ribose) synthetase, inhibits NO formation in primary culture of rat glial cells. Nicotinamide (5-20 mM) suppressed iNOS mRNA expression and subsequent NO formation, which were induced by the combination of interferon-gamma and lipopolysaccharide, in a dose dependent manner. In addition, high-concentration (20 mM) nicotinamide decreased mRNA of interferon regulatory factor-1, a transcription factor which plays a major role in iNOS mRNA induction. These results suggest that nicotinamide may have protective effect on glial NO-related pathologies by preventing iNOS mRNA induction.
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PMID:Nicotinamide inhibits inducible nitric oxide synthase mRNA in primary rat glial cells. 920 10

The diazaborine family of compounds have antibacterial properties against a range of gram-negative bacteria. Initially, this was thought to be due to the prevention of lipopolysaccharide synthesis. More recently, the molecular target of diazaborines has been identified as the NAD(P)H-dependent enoyl acyl carrier protein reductase (ENR), which catalyses the last reductive step of fatty acid synthase. ENR from Mycobacterium tuberculosis is the target for the front-line antituberculosis drug isoniazid. The emergence of isoniazid resistance strains of M. tuberculosis, a chronic infectious disease that already kills more people than any other infection, is currently causing great concern over the prospects for its future treatment, and it has reawakened interest in the mechanism of diazaborine action. Diazaborines only inhibit ENR in the presence of the nucleotide cofactor, and this has been explained through the analysis of the x-ray crystallographic structures of a number of Escherichia coli ENR-NAD+-diazaborine complexes that showed the formation of a covalent bond between the boron atom in the diazaborines and the 2'-hydroxyl of the nicotinamide ribose moiety that generates a noncovalently bound bisubstrate analogue. The similarities in catalytic chemistry and in the conformation of the nucleotide cofactor across the wider family of NAD(P)-dependent oxidoreductases suggest that there are generic opportunities to mimic the interactions seen here in the rational design of bisubstrate analogue inhibitors for other NAD(P)H-dependent oxidoreductases.
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PMID:Mechanism of action of diazaborines. 963 89

Inducible nitric oxide (NO) synthase (iNOS)-mediated hyperproduction of NO in airways has been reported in asthmatic patients. However, the role of NO in the pathogenesis of asthma has not yet been fully elucidated. The aim of this study was to examine whether the iNOS-derived NO affects airway microvascular leakage, one of the characteristic features of asthmatic airway inflammation. Guinea-pigs were exposed to lipopolysaccharide (LPS) (1 mg x mL(-1)) by inhalation in order to induce iNOS in the airways, and the histochemical staining of reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase activity was determined 5 h after the inhalation to confirm the iNOS induction. Airway microvascular leakage to subthreshold doses of substance P (0.3 microg x kg(-1), i.v.) was also examined in the absence and presence of an iNOS inhibitor (aminoguanidine) in LPS- or saline-exposed (control) animals using Evans blue dye and Monastral blue dye. In the LPS-exposed animals, increased NADPH-diaphorase activity was observed in the airway microvasculature compared with the control animals. Substance P caused significant airway microvascular leakage assessed by Evans blue dye in all airway levels in the LPS-exposed animals but not in the control group. This was also confirmed by Monastral blue dye extravasation. Aminoguanidine abolished this LPS-induced enhancement of plasma leakage to substance P without changing the systemic blood pressure. These results may suggest that inducible nitric oxide synthase-derived nitric oxide is capable of potentiating neurogenic plasma leakage in airways.
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PMID:Induction of nitric oxide synthase by lipopolysaccharide inhalation enhances substance P-induced microvascular leakage in guinea-pigs. 981 54

We investigated the pathophysiological role of nitric oxide synthesized by inducible nitric oxide synthase in the brain, by injecting lipopolysaccharide directly into the rat cerebral cortex/hippocampus. The levels of nitric oxide metabolites, nitrite and nitrate, began to increase in a dose-dependent manner with a 3-h lag, and reached approximately seven-fold the basal levels 8 h after the direct injection of lipopolysaccharide (5 microg). The lipopolysaccharide-induced increase in nitrite and nitrate levels was inhibited by treatment with the specific inducible nitric oxide synthase inhibitor aminoguanidine. The protein synthesis inhibitor cycloheximide delayed the onset of the increase in nitric oxide metabolite levels, and reduced the peak levels. Lipopolysaccharide increased Ca2+-independent, but not Ca2+-dependent, nitric oxide synthase activity in the brain. Intense nicotinamide adenine dinucleotide phosphate-diaphorase activity was observed in round cells in the vicinity of the site of injection of lipopolysaccharide 8 h after the injection. Neuronal death was observed seven days after the injection of lipopolysaccharide. Spatial memory, as assessed by performance in a water maze task and spontaneous alternation behavior in a Y-maze, was significantly impaired in rats which had had previous bilateral injections of lipopolysaccharide into the hippocampus. The lipopolysaccharide-induced neuronal death and spatial memory impairments were prevented by aminoguanidine. These results suggest that direct injection of lipopolysaccharide into the brain causes an induction of inducible nitric oxide synthase in vivo. Furthermore, it is suggested that nitric oxide produced by inducible nitric oxide synthase is responsible for the lipopolysaccharide-induced brain dysfunction.
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PMID:Brain dysfunction associated with an induction of nitric oxide synthase following an intracerebral injection of lipopolysaccharide in rats. 1005 Dec 7

Endotoxin (lipopolysaccharide [LPS]) is known to induce the production of tumor necrosis factor (TNF)-alpha and the induction of manganese superoxide dismutase (MnSOD). We have recently demonstrated that induction of TNF-alpha and MnSOD by LPS is mediated through different signal transduction pathways. In the current study, we investigated the role of reactive oxygen species (ROS) in the induction of TNF-alpha and MnSOD messenger RNAs (mRNAs) in human monocytes. Hypoxia (1% O2) inhibited the production of superoxide (O2-) and the induction of MnSOD, but not TNF-alpha, mRNA. Diphenylene iodonium (DPI), a potent inhibitor of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, had no effect on LPS induction of MnSOD mRNA, whereas it markedly inhibited LPS-induced O2- production. Neither hypoxia nor DPI had any effect on LPS activation of nuclear factor (NF)-kappaB. These results suggest that (1) ROS is important in the induction of MnSOD, but not TNF-alpha, mRNA by LPS, (2) ROS from sources other than NADPH oxidase is involved in LPS induction of MnSOD mRNA, and (3) ROS-mediated LPS induction of MnSOD mRNA is independent of NF-kappaB activation.
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PMID:Differential induction of TNF-alpha and MnSOD by endotoxin: role of reactive oxygen species and NADPH oxidase. 1115 50


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