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

Neutrophils isolated from patients with bacterial infections or stimulated in vitro with lipopolysaccharide (LPS) produce a high resolution, lipid-dominated spectrum on 1H-NMR spectroscopy (May et al, 1993. J. Infect. Dis. 168: 386-392). We have investigated the origin of this lipid signal using NMR and chemical analyses of both whole neutrophils and purified plasma membranes. Plasma membranes from neutrophils that had been stimulated with 50 microg/ml LPS exhibited the high resolution 1H-NMR signal, and contained double the triacylglycerol (TAG) content of plasma membranes isolated from resting cells. Chemical analysis of the whole cells indicated that the TAG also increased at the cellular level (1.7-fold) after stimulation with LPS. Diradylglycerol increased 2- to 3-fold in both whole cells and plasma membranes after stimulation, but was only a minor component compared with TAG. The plasma membrane protein/phospholipid ratio increased 2.6-fold, whereas cholesterol (free and esterified) was unchanged. The membranes from LPS-stimulated neutrophils exhibited increased fluidity, as judged by increased merocyanine 540 binding, consistent with a 2-fold reduction in cholesterol/phospholipid ratio. LPS induced a shift in fatty acid content of whole cell polar lipids towards more oleic acid and less palmitic acid, whereas the neutral lipid fraction contained increased amounts of palmitic and stearic acids. The TAG fraction of plasma membrane lipids contained increased amounts of palmitic acid when prepared from cells stimulated with LPS. We conclude that the 1H-NMR signal in LPS-stimulated neutrophils arises from increased amounts of plasma membrane TAG with an elevated content of palmitic acid.
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PMID:Increased saturated triacylglycerol levels in plasma membranes of human neutrophils stimulated by lipopolysaccharide. 930 Jul 78

Dihomogammalinolenic acid is derived from gammalinolenic acid, administration of which suppresses joint inflammation. It is reported here that interleukin 1beta (IL-1beta) production by human monocytes is enhanced markedly when cells are incubated 18-24 h with the polyunsaturated fatty acids dihomogammalinolenic acid (DGLA) and arachidonic acid (AA), then stimulated with lipopolysaccharide. Effects of eicosapentaenoic acid (EPA) on IL-1beta production are minimal, and palmitic acid (PA) does not influence IL-1beta production.
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PMID:Effects of unsaturated fatty acids on interleukin-1beta production by human monocytes. 941 12

A new class of outer membrane lipid (OML) was isolated from the oral spirochete Treponema denticola strain ATCC 33521 using a phenol/chloroform/light petroleum procedure normally applied for lipopolysaccharide extraction. In addition to chemical analysis, Fourier transform infrared (FTIR) spectroscopy was applied to compare the biophysical properties of OML with lipopolysaccharides (LPS) and lipoteichoic acids (LTA). Isolated OML fractions represent 1.4% of the total dry cell weight, are about 4 kDa in size, and contain 6% amino sugars, 8% neutral sugars, 14% phosphate, 35% carbazol-positive compounds, and 11% fatty acids (containing iso- and anteiso-fatty acyl chains). Rare for outer membrane lipids, OML contains no significant amount of 3-deoxy-D-manno-octulosonic acids, heptoses, and beta-hydroxy fatty acids. The fatty acyl chain composition, being similar to that of the cytoplasmic membrane, is quite heterogeneous with anteiso-pentadecanoic acid (12%), palmitic acid (51%), and iso-palmitic acid (19%) as the predominant fatty acids present. Findings of a glycerol-hexose unit and two glycerol-hexadecanoic acid fragments indicate a glycolipid membrane anchor typically found in LTA. There was also no evidence for the presence of a sphingosine-based lipid structure. The results of FTIR measurements strongly suggest that the reconstituted lipid forms normal bilayer structures (vesicles) expressing a high membrane state of order with a distinct phase transition as typical for isolated LPS. However, in contrast to LPS, OML of T. denticola has a lower Tm near 22 degreesC and a lower cooperativity of the phase transition. The results suggest a different kind of permeation barrier that is built up by this particular OML of T. denticola, which is quite different from LPS normally essential for Gram-negative bacteria.
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PMID:Evidence for a new type of outer membrane lipid in oral spirochete Treponema denticola. Functioning permeation barrier without lipopolysaccharides. 962 60

Human neutrophils incubated for 1 h in vitro with 10% commercial pooled, human serum containing high levels of free fatty acids (1141 microM) displayed a distinct lipid signal, typical of triacylglycerol, in the 1H NMR spectrum. Concurrently their plasma membrane triacylglycerol mass increased 4.6-fold with a selective rise in the content of palmitic and linoleic acids. Although qualitatively similar, these effects were much greater than those observed after incubating neutrophils with 50 microg.mL-1 of lipopolysaccharide in the presence of 10% AB serum with normal free fatty acid content (345 microM, LPS/S). Incubation of neutrophils with an artificial mixture of free fatty acids at concentrations found in commercial serum, or with the fatty acid fraction isolated from commercial serum increased the 1H NMR-detectable triacylglycerol. The signal intensity of the 1H NMR-detectable triacylglycerol depended on the triacylglycerol composition, and correlated with increased membrane triacylglycerol mass. Cellular uptake of 3H-labelled palmitic or oleic acids increased in the presence of commercial serum but not with LPS/S, with little contribution in either case to the triacylglycerol pool that increased in mass. Pulse-chase experiments demonstrated that with LPS/S and commercial serum, radiolabelled palmitic acid was preferentially incorporated into triacylglycerol located in the plasma membrane. This process could occur at the plasma membrane, as cytoplasts efficiently convert exogenous fatty acids into triacylglycerol. We propose that LPS/S and serum containing high levels of free fatty acid, important in conditions of sepsis and inflammation, may facilitate the sequestration of palmitic acid into triacylglycerol by different pathways. This triacylglycerol originates from exogenous and endogenous free fatty acids, is 1H NMR-visible, and may have a role in regulating apoptosis.
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PMID:The origin of 1H NMR-visible triacylglycerol in human neutrophils. Highfatty acid environments result in preferential sequestration of palmitic acid into plasma membrane triacylglycerol. 1060 52

The structure of the lipid A from Rhizobium etli and Rhizobium leguminosarum lipopolysaccharides (LPSs) lacks phosphate and contains a galacturonosyl residue at its 4' position, an acylated 2-aminogluconate in place of the proximal glucosamine, and a very long chain omega-1 hydroxy fatty acid, 27-hydroxyoctacosanoic acid (27OHC28:0). The 27OHC28:0 moiety is common in lipid A's among members of the Rhizobiaceae and also among a number of the facultative intracellular pathogens that form chronic infections, e.g., Brucella abortus, Bartonella henselae, and Legionella pneumophila. In this paper, a mutant of R. leguminosarum was created by placing a kanamycin resistance cassette within acpXL, the gene which encodes the acyl carrier protein for 27OHC28:0. The result was an LPS containing a tetraacylated lipid A lacking 27OHC28:0. A small amount of the mutant lipid A may contain an added palmitic acid residue. The mutant is sensitive to changes in osmolarity and an increase in acidity, growth conditions that likely occur in the nodule microenvironment. In spite of the probably hostile microenvironment of the nodule, the acpXL mutant is still able to form nitrogen-fixing root nodules even though the appearance and development of nodules are delayed. Therefore, it is possible that the acpXL mutant has a host-inducible mechanism which enables it to adapt to these physiological changes.
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PMID:A Rhizobium leguminosarum AcpXL mutant produces lipopolysaccharide lacking 27-hydroxyoctacosanoic acid. 1261 48

Leptospira is the etiologic agent of leptospirosis, a bacterial zoonosis distributed worldwide. Leptospiral lipopolysaccharide is a protective immunogen, but the extensive serological diversity of leptospires has inspired a search for conserved outer membrane proteins (OMPs) that may stimulate heterologous immunity. Previously, a global analysis of leptospiral OMPs (P. A. Cullen, S. J. Cordwell, D. M. Bulach, D. A. Haake, and B. Adler, Infect. Immun. 70:2311-2318, 2002) identified pL21, a novel 21-kDa protein that is the second most abundant constituent of the Leptospira interrogans serovar Lai outer membrane proteome. In this study, we identified the gene encoding pL21 and found it to encode a putative lipoprotein; accordingly, the protein was renamed LipL21. Southern hybridization analysis revealed the presence of lipL21 in all of the pathogenic species but in none of the saprophytic species examined. Alignment of the LipL21 sequence from six strains of Leptospira revealed 96 to 100% identity. When specific polyclonal antisera to recombinant LipL21 were used, LipL21 was isolated together with other known leptospiral OMPs by both Triton X-114 extraction and sucrose density gradient membrane fractionation. All nine strains of pathogenic leptospires investigated by Western blotting, whether culture attenuated or virulent, were found to express LipL21. In contrast, the expression of LipL21 or an antigenically related protein could not be detected in nonpathogenic L. biflexa. Infected hamster sera and two of eight human leptospirosis sera tested were found to react with recombinant LipL21. Native LipL21 was found to incorporate tritiated palmitic acid, consistent with the prediction of a lipoprotein signal peptidase cleavage site. Biotinylation of the leptospiral surface resulted in selective labeling of LipL21 and the previously known OMPs LipL32 and LipL41. These findings show that LipL21 is a surface-exposed, abundant outer membrane lipoprotein that is expressed during infection and conserved among pathogenic Leptospira species.
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PMID:LipL21 is a novel surface-exposed lipoprotein of pathogenic Leptospira species. 1270 11

From Mycobacterium tuberculosis, a serologically specific polysaccharide was purified. It contained mannose, arabinose, and a trace of glucose. It was not active in hemagglutination (HA) reaction. Partial acylation of the polysaccharide was carried out with palmitoylchloride, and the synthetic lipopolysaccharide contained 15.1 per cent of esterified palmitic acid. The synthetic lipopolysaccharide had hemagglutination activity and 0.5 microg was able to sensitize 1 ml of 2 per cent erythrocyte suspension; it had the same activity as the natural antigenic lipopolysaccharide. The same antibody in the antiserum was involved in the hemagglutination reaction with both the synthetic and natural lipopolysaccharides. The sensitizing activity of the synthetic lipopolysaccharide was completely neutralized by cholesterol. Model experiments showed that the lipid moiety of hemagglutination antigen was essential for the sensitization of erythrocytes. The mechanism of the hemagglutination reaction is discussed.
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PMID:A SYNTHETIC ACYL POLYSACCHARIDE AND THE HEMAGGLUTINATION ACTIVITY. 1417 89

Insect cellular immune reactions to bacterial infection include nodule formation. Eicosanoids mediate several cellular actions in the nodulation process, including formation of hemocyte microaggregates, an early step. In previous work, we reported that isolated hemocytes produce and secrete eicosanoids that influence hemocyte behavior in response to bacterial challenge. We also reported that microaggregate formation in response to challenge was mediated by prostaglandins (PGs), but not by products of the lipoxygenase (LOX) pathways. In this paper we describe experiments designed to test the idea that exposing isolated hemocytes to lipopolysaccharide (LPS) evokes formation of hemocyte microaggregates and this cellular action is mediated by PGs. Results show that isolated hemocyte preparations challenged with LPS formed more hemocyte microaggregates than unchallenged preparations (6.9x10(3) microaggregates/ml hemolymph vs. 2.5x10(3) microaggregates/ml hemolymph). LPS challenge stimulated formation of hemocyte microaggregates in a dose dependent manner. Experimental groups pretreated with cyclooxygenase inhibitors produced fewer hemocyte microaggregates in response to LPS challenge than untreated control groups. The formation of hemocyte microaggregates was not influenced by LOX inhibitors. Furthermore, the influence of dexamethasone was reversed by supplementing the experimental groups with the eicosanoid precursor fatty acid molecule, arachidonic acid and PGH(2). Palmitic acid, which is not substrate for eicosanoid biosynthesis, did not reverse the effects of dexamethasone on the formation of microaggregates. The LOX product 5(S)hydroperoxyeicosa-6E,8Z,11Z,14Z-tetraenoic acid also did not reverse the effects of dexamethasone. These results are consistent with similar investigations performed with bacterial suspensions. We infer that isolated hemocyte preparations recognize and react to LPS by forming microaggregates and this reaction is mediated by PGs, but not products of the LOX pathway.
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PMID:Lipopolysaccharide evokes microaggregation reactions in hemocytes isolated from tobacco hornworms, Manduca sexta. 1512 2

The major objective of this experiment was to determine whether the bovine placenta could be stimulated to secrete progesterone, since the bovine placenta secretes little progesterone when the corpus luteum is functional. Secondly, we wanted to determine whether reported abortifacients or progesterone or estrogen receptor antagonists affected bovine placental prostaglandin secretion. The ovine placenta secretes half of the circulating progesterone at day 90 of pregnancy and PGE2 appears to regulate ovine placental progesterone secretion. Calcium has been reported to regulate placental progesterone secretion in cattle. Diced 186-245-day placental slice explants from six Brahman and six Angus cows were incubated in vitro at 39.5 degrees C under 95% air: 5% CO2 at pH 7.2 in 5 ml of M-199 for 1 h in the absence of treatments and for 4 and 8 h in the presence of treatments. Treatments were: vehicle; R24571; compound 48/80; IP3; PGE2; CaCl2; cyclosporin A; lipopolysaccharide (endotoxin) from Salmonella abortus equi., enteriditis, and typhimurium; monensin; ionomycin; arachidonic acid; mimosine; palmitic acid; progesterone, androstenedione; estradiol-17beta; A23187; RU-486; or MER-25. Jugular and uterine venous plasma and culture media were analyzed for progesterone, PGE2 and PGF2alpha by radioimmunoassay (RIA). Plasma hormone data were analyzed by a One-Way Analysis of Variance (ANOVA). Hormone data in culture media were analyzed for breed and treatment effects by a Factorial Design (2 breeds, 2-range of days, 21 treatments) for ANOVA (2 x 2 x 21). Since hormone data secreted by placental tissue in vitro did not differ (P > or = 0.05) by breed or range of days of pregnancy, data were pooled and analyzed by a One-Way ANOVA. Concentrations of PGE2 in uterine venous blood were two-fold greater (P < or = 0.05) in Angus than Brahman cows. PGE2 and PGF2alpha in vehicle controls increased from 4 to 8h (P < or = 0.05), but not progesterone (P > or = 0.05) Progesterone in culture media treated with RU-486 increased (P < or = 0.05) at 4 and 8 h compared to vehicle controls and was not affected by other treatments (P > or = 0.05). Concentrations of PGE2 in media at 4 and 8 h were lower (P < or = 0.05) when compared to controls except treatment with PGE2 at 4 and 8h and RU-486 at 8h (P > or = 0.05). PGF2alpha was increased (P < or = 0.05) by RU-486 at 8h and no other treatment affected PGF2alpha at 4 or 8 h (P < or = 0.05). In conclusion, modulators of cellular calcium signalling pathways given alone do not affect bovine placental progesterone secretion at the days studied and progesterone receptor-mediated events appear to suppress placental progesterone, PGF2alpha, and PGE2 secretion in cattle. In addition, PGE2 does not appear to regulate bovine placental progesterone secretion when the corpus luteum is functional and bacterial endotoxin does not appear to affect bovine placental secretion of PGF2alpha or PGE2.
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PMID:Do calcium-mediated cellular signalling pathways, prostaglandin E2 (PGE2), estrogen or progesterone receptor antagonists, or bacterial endotoxins affect bovine placental function in vitro? 1528 56

A number of cell types express inducible nitric-oxide synthase (NOS2) in response to exogenous insults such as bacterial lipopolysaccharide or proinflammatory cytokines. Although it has been known for some time that the N-terminal end of NOS2 suffers a post-translational modification, its exact identification has remained elusive. Using radioactive fatty acids, we show herein that NOS2 becomes thioacylated at Cys-3 with palmitic acid. Site-directed mutagenesis of this single residue results in the absence of the radiolabel incorporation. Acylation of NOS2 is completely indispensable for intracellular sorting and .NO synthesis. In fact, a C3S mutant of NOS2 is completely inactive and accumulates to intracellular membranes that almost totally co-localize with the Golgi marker beta-cop. Likewise, low concentrations of the palmitoylation blocking agents 2-Br-palmitate or 8-Br-palmitate severely affected the .NO synthesis of both NOS2 induced in muscular myotubes and transfected NOS2. However, unlike endothelial NOS, palmitoylation of inducible NOS is not involved in its targeting to caveolae. We have created 16 NOS2-GFP chimeras to inspect the effect of the neighboring residues of Cys-3 on the degree of palmitoylation. In this regard, the hydrophobic residue Pro-4 and the basic residue Lys-6 seem to be indispensable for palmitoylation. In addition, agents that block the endoplasmic reticulum to Golgi transit such as brefeldin A and monensin drastically reduced NOS2 activity leading to its accumulation in perinuclear areas. In summary, palmitoylation of NOS2 at Cys-3 is required for both its activity and proper intracellular localization.
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PMID:Palmitoylation of inducible nitric-oxide synthase at Cys-3 is required for proper intracellular traffic and nitric oxide synthesis. 1548 46


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