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)

Lipid A, the biologically active component of lipopolysaccharide, stimulated nitric oxide (NO) production by isolated rat proximal tubules (as measured by NO2- release) in a time-dependent manner. At a concentration of 50 micrograms/ml, lipid A stimulated NO2- generation and guanosine 3',5'-cyclic phosphate (cGMP) production within 5 min. Both of these effects were blocked by NG-methyl-L-arginine (L-NMMA), an inhibitor of NO synthase or by 8-(N,N'-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), an inhibitor of intracellular Ca++ release. Because an increase in NO production may be cytotoxic, we examined the cytotoxic potential of lipid A. At 90 min, lipid A (50 micrograms/ml) produced significant lactate dehydrogenase release (42 +/- 5%) compared to control (25 +/- 5%; P < .05). Both L-NMMA (1 mM) and TMB-8 (100 microM) completely protected against lipid A-induced cytotoxicity. TMB-8 but not L-NMMA inhibited the rise intracellular Ca++ concentration ([Ca++]i) in isolated proximal tubules elicited by lipid A. L-NMMA but not TMB-8 inhibited proximal tubule soluble NO synthase activity. Thus, in the proximal tubule, lipid A stimulates a rise in [Ca++]i that in turn activates constitutive NO synthase. Furthermore, these events lead ultimately to NO-dependent cytotoxicity. Therefore, these findings suggest the potential for lipopolysaccharide to have a direct impact on proximal tubule physiology and renal function in vivo and support the potential therapeutic benefits of NO synthase inhibitors in the treatment of endotoxemia.
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PMID:Nitric oxide generation by renal proximal tubules: role of nitric oxide in the cytotoxicity of lipid A. 885 80

The role of calcium in the production of tumor necrosis factor-alpha (TNF-alpha) by the lipopolysaccharide (LPS)-stimulated macrophage cell line, J774.1, was investigated. Flow cytometric measurement of intracellular calcium concentration ([Ca]i) using 2-(3,6-bis(acetyl-oxy)-2,7-dichloro-9H-xanthen-9-yl)benzoic acid (fluo-3)-loaded J774.1 cells revealed that LPS at more than 0.1 microgram/ml increased [Ca]i transiently in the presence or absence of serum, and that a mixture of a calcium chelator, ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), and a calcium release blocker from intracellular store sites, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8), inhibited the [Ca]i response induced by LPS. In concordance with this, production of TNF-alpha was inhibited by EGTA and/or TMB-8. These reagents also reduced the level of TNF-alpha mRNA significantly. These results indicate that the transient increase of [Ca]i plays a role in LPS-induced expression of TNF-alpha by the macrophage cell line.
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PMID:Role of calcium in tumor necrosis factor-alpha production by activated macrophages. 901 Jul 69

The proinflammatory cytokine, interleukin-1 (IL-1) is elevated in the Alzheimer's disease (AD) brain. Studies from our laboratory have demonstrated that beta-amyloid (A beta) 1-42, fibrillar A beta 1-40 and A beta 25-35 induce the release of IL-1 beta from activated THP-1 cells, a human monocyte cell line. A beta also is chemotactic for primary rodent microglia and peritoneal macrophages. We hypothesize that A beta is a chemokine and induces these responses by interaction with chemotactic receptors. If this is true, then these A beta-induced responses should be calcium-dependent and require activation of pertussis toxin-sensitive G-proteins. To test this hypothesis, THP-1 cells were grown in culture with lipopolysaccharide (LPS) and incubated with A beta 1-42 (5 muM) in the presence and absence of a calcium chelator, an inhibitor of intracellular calcium mobilization, a calcium channel blocker, or pertussis toxin, a bacterial endotoxin which uncouples G proteins from receptors by catalyzing the ADP ribosylation of cysteine near the carboxy-terminus of the alpha subunit. The media was collected and IL-1 beta present in the media was measured using an ELISA. Treatment of LPS-activated THP-1 cells with A beta 1-42 significantly elevated IL-1 beta released into the media as previously shown. Addition or ethylene glycol-bis (beta-aminothyl ether) N,N,N'N'-tetraacetic acid (EGTA) (0.5 mM), a calcium chelator, to the media blocked A beta-induced IL-1 beta release, but had no effect on LPS-activated THP-1 cell release of IL-1 beta. The presence of 3,4,5-trimethoxybenzoic acid 8-(diethyl amino)-octyl ester (TMB-8), an inhibitor of intracellular calcium mobilization, as well as nickel chloride, a non-specific calcium channel blocker, in the media also inhibited A beta-induced IL-1 release from LPS-activated THP-1 cells. IL- 1 beta release from activated THP-1 monocytes incubated with TMB-8 and nickel chloride without A beta remained at baseline values. Pretreatment of THP-1 monocytes with pertussis toxin for 4 h, followed by LPS activation and incubation with A beta, antagonized the release of IL-1 beta from these cells, but did not alter IL-1 beta release from activated THP-1 monocytes. These data suggest that A beta-induced IL-1 beta release from these cells is calcium-dependent and requires the activation of specific G-proteins. These findings are consistent with known second messengers that are activated following stimulation of chemotactic receptors.
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PMID:beta-Amyloid-induced IL-1 beta release from an activated human monocyte cell line is calcium- and G-protein-dependent. 914 72

To elucidate the cellular activation mechanisms of lipoteichoic acid (LTA) compared with those of lipopolysaccharide (LPS), a quantitatively major LTA fraction, QM-1M, was prepared from hot phenol-water extracts of Enterococcus hirae (ATCC 9790) by hydrophobic octyl-Sepharose chromatography and by ion-exchange membrane (QMA-Mem Sep 1010) chromatography as a 60% 1-propanol- and 1 M NaCl-eluted fraction. Unlike the reference Escherichia coli LPS, QM-1M did not demonstrate any ability to induce cytokines in a human whole blood culture system in this study, whereas QM-1M induced a few cytokines such as interleukin (IL)-8 and tumor necrosis factor-alpha in human monocytic THP-1 cell and human peripheral mononuclear cell (PBMC) cultures in the absence of serum. Fetal calf and human sera decreased the above cytokine induction by QM-1M in THP-1 and PBMC cultures, whereas sera increased activities of the reference LPS. IL-8 induction in the absence of serum in response to QM-1M was demonstrated to proceed through a CD14-independent pathway unlike the reference LPS.
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PMID:A lipoteichoic acid fraction of Enterococcus hirae activates cultured human monocytic cells via a CD14-independent pathway to promote cytokine production, and the activity is inhibited by serum components. 987 19

Surfactant protein (SP) A and SP-D affect numerous functions of immune cells including enhancing phagocytosis of bacteria and production of reactive species. Previous studies have shown that SP-A and SP-D bind to a variety of bacteria and to the lipopolysaccharide (LPS) components of their cell walls. In addition, purified preparations of SPs often contain endotoxin. The goals of this study were 1) to evaluate the effects of SP-A and SP-D and complexes of SPs and LPS on the production of nitric oxide metabolites by rat alveolar macrophages and 2) to evaluate methods for the removal of endotoxin with optimal recovery of SP. Incubation of SP-A or SP-D with polymyxin, 100 mM N-octyl-beta-D-glucopyranoside, and 2 mM EDTA followed by dialysis was the most effective method of those tested for reducing endotoxin levels. Commonly used storage buffers for SP-D, but not for SP-A, inhibited the detection of endotoxin. There was a correlation between the endotoxin content of the SP-A and SP-D preparations and their ability to stimulate production of nitrite by alveolar macrophages. SP-A and SP-D treated as described above to remove endotoxin did not stimulate nitrite production. These studies suggest that the functions of SP-A and SP-D are affected by endotoxin and illustrate the importance of monitoring SP preparations for endotoxin contamination.
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PMID:Effects of endotoxin on surfactant protein A and D stimulation of NO production by alveolar macrophages. 1019 63

Changes in the structure and functional activity of porin, a protein from Yersinia pseudotuberculosis, resulting from the removal of lipopolysaccharide (LPS) normally bound with the protein were studied. The treatment of LPS-containing porin with a 30% SDS solution led to an LPS-free protein that, according to the SDS-PAGE, remained to be a trimer. It was shown by CD and UV spectroscopies and intrinsic protein fluorescence that the removal of LPS caused only conformational changes in the porin secondary and tertiary structures. The LPS-free porin folded into a completely beta-structured protein aggregate. The bilayer lipid membrane technique showed that the pore-forming activity of the LPS-free porin decreased, and its concentration should be increased by two orders of magnitude to achieve the same effect. Incubation of the LPS-free porin with LPS led to a porin-LPS complex and affected the character of the protein functional activity. The treatment of the LPS-free porin by octyl glucoside, a nonionic detergent, resulted in the restoration of the protein pore-forming activity. It was suggested that the LPS and detergent provide a definite protein conformation necessary for its functioning.
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PMID:[Effect of a lipopolysaccharide on the conformational state and functional activity of a Yersinia pseudotuberculosis porin]. 1049 99

The two NOD-derived T cell clones, BDC-2.5 and BDC-6.9, are CD4+, Vbeta4+, islet-specific, and diabetogenic. These two T cell clones show different response patterns to whole islet cell antigen, but were found to respond to the same fraction isolated from beta granule membranes. The clones were used to follow the antigenic activity in the biochemical purification of a beta cell membrane detergent lysate subjected to HPLC anion exchange (IEX) and size exclusion chromatography (SEC). Antigenic activity could be retained after lysis in only one detergent (octyl-beta-glucoside) among several tested. In order to detect solubilized antigen, beta membrane proteins were covalently linked to microlatex beads prior to being added to T cell proliferation assays, a technique that eliminated detergent toxicity and resulted in increased assay sensitivity. To purify the antigen, membrane proteins were absorbed onto an anion exchange column and after elution using a salt gradient, activity for the clones was found in a fraction containing 0.15-0.2 M NaCl. Subsequent analysis of this material by size exclusion chromatography provided an apparent molecular weight of the antigen to be between 50 and 80 kDa. Further attempts to purify the protein by SDS-PAGE resulted in loss of antigenic activity. It is possible that the elusive nature of this protein is a clue to its importance as an autoantigen.
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PMID:Biochemical characterization of a beta cell membrane fraction antigenic for autoreactive T cell clones. 1088 61

Surfactant protein A (SP-A) is thought to play a role in the modulation of lung inflammation during acute respiratory distress syndrome (ARDS). However, SP-A has been reported both to stimulate and to inhibit the proinflammatory activity of pulmonary macrophages (Mphi). Because of the interspecies differences and heterogeneity of Mphi subpopulations used may have influenced previous controversial results, in this study, we investigated the effect of human SP-A on the production of cytokines and other inflammatory mediators by two well-defined subpopulations of human pulmonary Mphi. Surfactant and both alveolar (aMphi) and interstitial (iMphi) macrophages were obtained from multiple organ donor lungs by bronchoalveolar lavage and enzymatic digestion. Donors with either recent history of tobacco smoking, more than 72 h on mechanical ventilation, or any radiological pulmonary infiltrate were discarded. SP-A was purified from isolated surfactant using sequential butanol and octyl glucoside extractions. After 24-h preculture, purified Mphi were cultured for 24 h in the presence or absence of LPS (10 microg/mL), SP-A (50 microg/mL), and combinations. Nitric oxide and carbon monoxide (CO) generation (pmol/microg protein), cell cGMP content (pmol/microg protein), and tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1, and IL-6 release to the medium (pg/microg protein) were determined. SP-A inhibited the lipopolysaccharide (LPS)-induced TNFalpha response of both interstitial and alveolar human Mphi, as well as the IL-1 response in iMphi. The SP-A effect on TNFalpha production could be mediated by a suppression in the LPS-induced increase in intracellular cGMP. In iMphi but not in aMphi, SP-A also inhibited the LPS-induced IL-1 secretion and CO generation. These data lend further credit to a physiological function of SP-A in regulating alveolar host defense and inflammation by suggesting a fundamental role of this apoprotein in limiting excessive proinflammatory cytokine release in pulmonary Mphi during ARDS.
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PMID:Effect of surfactant protein A (SP-A) on the production of cytokines by human pulmonary macrophages. 1102 47

In the present study, we investigated the effects and mechanisms of a novel potent antioxidant, octyl caffeate, on the induction of iNOS expression by lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) in cultured primary rat aortic smooth muscle cells (RASMCs) in vitro and LPS-induced hypotension in vivo. Octyl caffeate (0.1-1.0 microM) exerted a concentration-dependent inhibition of iron-catalyzed lipid peroxidation in rat brain homogenates. Furthermore, octyl caffeate (20, 50, and 100 microM) concentration-dependently diminished the initial rate of superoxide-induced NBT reduction and the enzymatic activity of xanthine oxidase. It also concentration-dependently (1-50 microM) inhibited the NO production, iNOS protein and messenger RNA expressions upon stimulation by LPS (100 microg/mL)/IFN-gamma (100U/mL) in RASMCs. In addition, we found that octyl caffeate did not significantly affect IkappaBalpha degradation stimulated by LPS/IFN-gamma in RASMCs. On the other hand, octyl caffeate (10 and 50 microM) significantly suppressed activation of c-Jun-N-terminal kinase and extracellular signal-regulated kinase. Moreover, octyl caffeate (10mg/kg, i.v.) significantly inhibited the fall in mean arterial pressure stimulated by LPS (7.5mg/kg) in rats. In conclusion, we demonstrate that a novel potent antioxidant, octyl caffeate, significantly ameliorates circulatory failure of endotoxemia in vivo by a mechanism involving suppression of iNOS expression through inactivation of mitogen-activated protein kinases in RASMCs.
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PMID:A novel antioxidant, octyl caffeate, suppression of LPS/IFN-gamma-induced inducible nitric oxide synthase gene expression in rat aortic smooth muscle cells. 1269 79

Salmonella enterica serovar Typhimurium remodels the lipid A component of lipopolysaccharide, a major component of the outer membrane, to survive within animals. The activation of the sensor kinase PhoQ in host environments increases the synthesis of enzymes that deacylate, palmitoylate, hydroxylate, and attach aminoarabinose to lipid A, also known as endotoxin. These modifications promote bacterial resistance to antimicrobial peptides and reduce the host recognition of lipid A by Toll-like receptor 4. The Salmonella lipid A 3-O-deacylase, PagL, is an outer membrane protein whose expression is regulated by PhoQ. In S. enterica serovar Typhimurium strains that had the ability to add aminoarabinose to lipid A, 3-O-deacylated lipid A species were not detected, despite the PhoQ induction of PagL protein expression. In contrast, strains defective for the aminoarabinose modification of lipid A demonstrated in vivo PagL activity, indicating that this membrane modification inhibited PagL's enzymatic activity. Since not all lipid A molecules are modified with aminoarabinose upon PhoQ activation, these results cannot be ascribed to the substrate specificity of PagL. PagL-dependent deacylation was detected in sonically disrupted membranes and membranes treated with the nonionic detergent n-octyl-beta-d-glucopyranoside, suggesting that perturbation of the intact outer membrane releases PagL from posttranslational inhibition by aminoarabinose-containing membranes. Taken together, these results suggest that PagL enzymatic deacylation is posttranslationally inhibited by membrane environments, which either sequester PagL from its substrate or alter its conformation.
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PMID:Inhibition of Salmonella enterica serovar Typhimurium lipopolysaccharide deacylation by aminoarabinose membrane modification. 1577 88


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