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)

Lactoferrin is a prominent component of neutrophil secondary granules, and its blood concentration is increased in certain inflammatory diseases. In contrast to the well-described biochemical characterization of lactoferrin as an iron-binding protein, its physiologic role in the regulation of inflammation and other host defense mechanisms is unclear. In this report, we provide evidence that lactoferrin has a potent heparin-neutralizing activity during thrombin inhibition by the serine proteinase inhibitors (serpins) antithrombin and heparin co-factor II. Activated neutrophil supernatant, which contains lactoferrin and other heparin-binding proteins, could neutralize the heparin-dependent antithrombin-thrombin inhibition reaction. The addition of lactoferrin to plasma corrected the heparin-induced prolongation of blood plasma coagulation as measured by the activated partial thromboplastin time (aPTT). Treatment of whole blood with specific inflammatory mediators, fMLP, lipopolysaccharide (LPS), and tumor necrosis factor-alpha (TNF-alpha) increased the concentration of both plasma lactoferrin and platelet factor 4 while inhibiting the blood anticoagulant activity of heparin as measured by the aPTT. These results suggest that the prothrombotic sequelae of some inflammatory processes may be partly due to various agonists that release neutrophil lactoferrin, which can then neutralize glycosaminoglycan-dependent serpin-thrombin inhibition reactions.
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PMID:Neutralization of heparin activity by neutrophil lactoferrin. 781 95

The effects of bovine lactoferrin on the serum cytokine levels, induced by lipopolysaccharide (LPS) in mice, are described. Bovine lactoferrin (BLF) introduced intravenously, 24 hours before i.v. injection of 50 micrograms of LPS, significantly lowered the serum concentration of TNF-alpha. Doses of BLF lower than 100 micrograms as well as pretreatment of mice with BLF on days 6-2 or 12-2 hours before LPS challenge, were not effective. Moreover, BLF induces by itself a relatively high level of IL-6, peaking at 1 hour following injection. Pretreatment of LPS-injected mice with BLF causes, in addition, a small but statistically significant drop in IL-6 level. Human albumin, used as a control protein, did not cause any changes in the cytokine levels. The data reported herein provide a satisfactory explanation with regard to preventive activity of LF in infection.
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PMID:Lactoferrin regulates the release of tumour necrosis factor alpha and interleukin 6 in vivo. 821 78

The production of nitrate (NO3-) and nitrite (NO2-) from macrophage-derived NO was studied using EPR and spin trapping. The formation of NO3- was determined via EPR in reactions involving the iron-binding protein, lactoferrin. The formation of NO2- was determined via EPR/spin trapping in the reaction between NO2- and H2O2. Dissolved nitric oxide (NO.) was reacted with lactoferrin yielding an EPR spectrum (77 degrees K) different from the normal EPR spectrum obtained for lactoferrin, suggesting that NO. interacts with the ferric ions bound to lactoferrin forming a ferric-nitrosyl type complex. The EPR spectrum (77 degrees K) of this ferric-nitrosyl type complex was also observed in the supernatant fluid of macrophage cell suspensions following their stimulation with lipopolysaccharide (LPS). During LPS stimulation of macrophages, these cells generate NO. which in turn produces NO3- and NO2-. The ferric-nitrosyl type complex is formed in a reaction mixture containing apolactoferrin and bicarbonate following the reaction of Fe+2 with NO3-, generated from macrophage-derived NO(.), to produce Fe+3 and NO(.). Furthermore, in an acidic medium, NO2- reacts with H2O2 forming peroxynitrous acid (HOONO) which rapidly decomposes into hydroxyl radicals (.OH) and the nitrogen dioxide (NO2.) radical. In the supernatant fluid of LPS-stimulated macrophage suspensions, the production of .OH was verified by spin trapping using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as the spin trap and ethanol as the .OH scavenger. The EPR spectra corresponding to the DMPO-OH and the DMPO-hydroxyethyl adducts were identified.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nitric oxide interaction with lactoferrin and its production by macrophage cells studied by EPR and spin trapping. 828 25

The effect of lactoferrin (Lf) on bacterial growth was tested by measuring conductance changes in the cultivation media by using a Malthus-AT system and was compared with the magnitude of 125I-labeled Lf binding in 15 clinical isolates of Escherichia coli. The binding property was inversely related to the change in bacterial metabolic rate (r = 0.91) and was directly related to the degree of bacteriostasis (r = 0.79). The magnitude of Lf-bacterium interaction showed no correlation with the MIC of Lf. In certain strains, Lf at supraoptimal levels reduced the bacteriostatic effect. Thus, the Lf concentration in the growth media was critical for the antibacterial effect. The cell envelopes of Salmonella typhimurium 395MS with smooth lipopolysaccharide (LPS) and its five isogenic rough mutants revealed 38-kDa porin proteins as peroxidase-labeled-Lf-reactive components in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (ligand blot) analysis. However, in the whole cell binding assay, parent strain 395MS demonstrated a very low interaction with 125I-Lf. On the other hand, Lf interaction gradually increased in correspondence with the decrease in LPS polysaccharide moiety in the isogenic rough mutants. Conductance measurement studies revealed that the low-level-Lf-binding (low-Lf-binding) strain 395MS with smooth LPS was relatively insusceptible to Lf, while the high-Lf-binding mutant Rd was more susceptible to Lf. These data suggested a correlation between Lf binding to porins and the Lf-mediated antimicrobial effect. The polysaccharide moiety of LPS shielded porins from the Lf interaction and concomitantly decreased the antibacterial effect.
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PMID:Relationship between antibacterial activity and porin binding of lactoferrin in Escherichia coli and Salmonella typhimurium. 838 41

Although the antimicrobial activity of lactoferrin has been well described, its mechanism of action has been poorly characterized. Recent work has indicated that in addition to binding iron, human lactoferrin damages the outer membrane of gram-negative bacteria. In this study, we determined whether bovine lactoferrin and a pepsin-derived bovine lactoferrin peptide (lactoferricin) fragment have similar activities. We found that both 20 microM bovine lactoferrin and 20 microM lactoferricin release intrinsically labeled [3H]lipopolysaccharide ([3H]LPS) from three bacterial strains, Escherichia coli CL99 1-2, Salmonella typhimurium SL696, and Salmonella montevideo SL5222. Under most conditions, more LPS is released by the peptide fragment than by whole bovine lactoferrin. In the presence of either lactoferrin or lactoferricin there is increased killing of E. coli CL99 1-2 by lysozyme. Like human lactoferrin, bovine lactoferrin and lactoferricin have the ability to bind to free intrinsically labeled [3H]LPS molecules. In addition to these effects, whereas bovine lactoferrin was at most bacteriostatic, lactoferricin demonstrated consistent bactericidal activity against gram-negative bacteria. This bactericidal effect is modulated by the cations Ca2+, Mg2+, and Fe3+ but is independent of the osmolarity of the medium. Transmission electron microscopy of bacterial cells exposed to lactoferricin show the immediate development of electron-dense "membrane blisters." These experiments offer evidence that bovine lactoferrin and lactoferricin damage the outer membrane of gram-negative bacteria. Moreover, the peptide fragment lactoferricin has direct bactericidal activity. As lactoferrin is exposed to proteolytic factors in vivo which could cleave the lactoferricin fragment, the effects of this peptide are of both mechanistic and physiologic relevance.
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PMID:Antibacterial activity of lactoferrin and a pepsin-derived lactoferrin peptide fragment. 842 97

The ability of lactoferrin (Lf), an iron-binding glycoprotein that is also called lactotransferrin, to bind lipopolysaccharide (LPS) may be relevant to some of its biological properties. A knowledge of the LPS-binding site on Lf may help to explain the mechanism of its involvement in host defence. Our report reveals the presence of two Escherichia coli 055B5 LPS-binding sites on human Lf (hLf): a high-affinity binding site (Kd 3.6 +/- 1 nM) and a low-affinity binding site (Kd 390 +/- 20 nM). Bovine Lf (bLf), which shares about 70% amino acid sequence identity with hLf, exhibits the same behaviour towards LPS. Like hLf, bLf also contains a low- and a high-affinity LPS-binding site. The Kd value (4.5 +/- 2 nM) corresponding to the high-affinity binding site is similar to that obtained for hLf. Different LPS-binding sites for human serum transferrin have been suggested, as this protein, which is known to bind bacterial endotoxin, produced only 12% inhibition of hLf-LPS interaction. Binding and competitive binding experiments performed with the N-tryptic fragment (residues 4-283), the C-tryptic fragment (residues 284-692) and the N2-glycopeptide (residues 91-255) isolated from hLf have demonstrated that the high-affinity binding site is located in the N-terminal domain I of hLf, and the low-affinity binding site is present in the C-terminal lobe. The inhibition of hLf-LPS interaction by a synthetic octadecapeptide corresponding to residues 20-37 of hLf and lactoferricin B (residues 17-41), a proteolytic fragment from bLf, revealed the importance of the 28-34 loop region of hLf and the homologous region of bLf for LPS binding. Direct evidence that this amino acid sequence is involved in the high-affinity binding to LPS was demonstrated by assays carried out with EGS-loop hLf, a recombinant hLf mutated at residues 28-34.
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PMID:Lactoferrin-lipopolysaccharide interaction: involvement of the 28-34 loop region of human lactoferrin in the high-affinity binding to Escherichia coli 055B5 lipopolysaccharide. 855 29

Human milk is in several ways anti-inflammatory. This study investigates whether or not human milk lactoferrin (LF) in comparison with bovine LF can affect the IL-6 release from human cells. Human, as well as bovine, LF and a bactericidal pepsin-derived fragment of bovine LF (lactoferricin B) were found to suppress the IL-6 response in a monocytic cell line (THP-1) when stimulated by lipopolysaccharide (LPS). The suppression of bovine LF was similar to or higher than that of human LF. Lactoferricin B was the strongest inhibitor of the LPS-induced IL-6 response. A time-dependence regarding the inhibitory capacity of LF was found. For human LF, the strongest inhibition was observed when added 15-30 min after the addition of LPS. Addition of LF before the LPS induced an approximately 45% reduction of the IL-6 response. The results suggest an anti-inflammatory activity of both human and bovine LF, and of the LF fragment lactoferricin B through their suppressive effects on the cytokine release.
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PMID:Lactoferrin or a fragment thereof inhibits the endotoxin-induced interleukin-6 response in human monocytic cells. 882 74

Human lactoferrin (hLF) is an iron-binding protein involved in host defense against infection and severe inflammation. Transgenic mice were produced harboring either hLF cDNA or genomic hLF sequences fused to regulatory elements of the bovine alphaS1 casein gene. Recombinant hLF expressed in the milk of transgenic mice (transgenic hLF) was compared with natural (human milk-derived) hLF. Immunological identity of the two forms was shown by double antibody immunoassays and the absence of an anti-hLF antibody response in transgenic mice on hyperimmunization with natural hLF. Mono S cation-exchange chromatography and N-terminal protein sequencing of transgenic and natural hLF revealed identical cationicity and N-terminal sequences. SDS-polyacrylamide gel electrophoresis and absorbance measurements of purified transgenic hLF showed this protein was 90% saturated with iron, whereas natural hLF is only 3% saturated. The pH-mediated release of iron from transgenic hLF was not different from that of iron-saturated natural hLF. Unsaturated transgenic hLF could be completely resaturated upon addition of iron. Slight differences in mobility between transgenic and natural hLF on SDS-polyacrylamide gel electrophoresis were abolished by enzymatic deglycosylation. Binding of transgenic and natural hLF to a range of ligands, including bacterial lipopolysaccharide, heparin, single-stranded DNA, Cibacron blue FG 3A, and lectins, was not different. Based on these observations, we anticipate that (unsaturated) rhLF and natural hLF will exert similar, if not identical, antibacterial and anti-inflammatory activity in vivo.
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PMID:Characterization of recombinant human lactoferrin secreted in milk of transgenic mice. 907 16

In the past years, our group has made several observations suggesting that blood cells behave differently and when stimulated, release different levels of cytokines, depending on which anticoagulant the blood has been drawn into. The aim of this study was therefore to compare the effect of the four anticoagulants EDTA, citrate, heparin and hirudin on monocyte, neutrophil (PMN), and platelet function in human whole blood. Human whole blood was employed as an ex vivo model of cytokine production and protein secretion, and lipopolysaccharide (LPS) induced tissue factor (TF) activity in monocytes and LPS induced tumor necrosis factor alpha (TNF alpha) release were chosen as parameters of monocyte activation. Platelet factor 4 (PF4) secretion and LPS induced lactoferrin release were chosen as parameters of platelet and PMN activation, respectively. When human whole blood was stimulated with 5 ng/ml LPS for 2 h, TF activity in monocytes isolated from EDTA blood was found to be 2.9 mU/10(6) cells, whereas TF activity in monocytes isolated from citrated, heparinized and hirudinized blood was 14.7, 24.7 and 28.5 mU/10(6) cells, respectively. TNF alpha concentrations in platelet poor plasma (PPP) isolated from whole blood stimulated with 5 ng/ml LPS for 2 h was increased with 200, 400 and 350% in citrated, heparinized and hirudinized blood respectively, as compared to EDTA blood. Next, the effect of the anticoagulant on PMN secretion was measured. PPP isolated from whole blood incubated with 5 ng/ml LPS for 90 min contained 1170 ng/ml (EDTA blood), 2880 ng/ml (citrated blood), 4220 ng/ml (heparinized blood), and 5520 ng/ml lactoferrin (hirudinized blood). When studying the platelet parameter PF4, whole blood was incubated without any stimuli for 60 min, and we found that heparin PPP contained 1180 ng/ml PF4, while hirudin PPP contained 469 ng/ml, citrate PPP 440 ng/ml, and EDTA PPP 217 ng/ml PF4, respectively. Finally, the low molecular weight heparin compound Fragmin had no enhancing effect on PF4 levels in whole blood. It is concluded that the anticoagulant used in in vitro experiments has a large influence on the parameters measured.
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PMID:Modulation of blood cell activation by four commonly used anticoagulants. 913 44

To determine the role of tumor necrosis factor (TNF) in lipopolysaccharide (LPS)-induced inflammation, 12 healthy subjects received an intravenous injection with LPS (2 ng/kg) preceded by infusion of either a recombinant human dimeric TNF receptor type II-IgG fusion protein (TNFR:Fc; 6 mg/m2; n = 6) or vehicle (n = 6) from -30 minutes to directly before LPS injection. LPS elicited a transient increase in plasma TNF activity, peaking after 1.5 hours (219 +/- 42 pg/mL; P < .05). Infusion of TNFR:Fc completely neutralized endogenous TNF activity. LPS administration was associated with an early activation of fibrinolysis (plasma concentrations of tissue-type plasminogen activator, plasminogen activator activity, and plasmin-alpha2-antiplasmin complexes), followed by inhibition (plasma plasminogen activator inhibitor type I), changes that were completely prevented by TNFR:Fc. By contrast, TNFR:Fc did not influence LPS-induced activation of coagulation (plasma levels of prothrombin fragment F1 + 2 and thrombin-antithrombin III complexes). TNFR:Fc strongly inhibited endothelial cell activation (plasma levels of soluble E-selectin), modestly reduced neutrophil responses (neutrophilia and plasma concentrations of elastase-alpha1-antitrypsin complexes and lactoferrin), but did not affect the release of secretory phospholipase A2 or lipopolysaccharide-binding protein (P > .05). Infusion of TNFR:Fc only (without LPS) in another 6 normal subjects did not induce any inflammatory response. These data indicate that TNF is involved in only some inflammatory responses to intravenous LPS in humans.
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PMID:Effect of a recombinant dimeric tumor necrosis factor receptor on inflammatory responses to intravenous endotoxin in normal humans. 916 Jun 78


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