Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lactoferrin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48Linked to original sources
PubMed1995

The chicken oocyte receptor for yolk precursors as a model for studying the action of receptor-associated protein and lactoferrin.

Receptor-associated protein (RAP) was originally described as a 39-kDa intracellular protein copurifying with mammalian low density lipoprotein (LDL) receptor-related protein/alpha 2-macroglobulin receptor (LRP/alpha 2MR). RAP has a high affinity for LRP/alpha 2MR and interferes with the receptor's ability to bind a variety of ligands. The laying hen expresses, in a tissue-specific manner, at least four different proteins which belong to the same family of receptors as LRP/alpha 2MR. Here we show that the chicken also produces RAP, so far thought to be expressed only in mammals. Studies on the interaction of recombinant human RAP with the LDL receptor family in the chicken revealed that RAP binds with high affinity to the abundant oocyte receptor for yolk precursors (OVR) as well as to the somatic cell-specific LRP/alpha 2MR. Significantly, RAP interacts with a lower affinity with the LDL receptor, but does not bind to the oocyte-specific form of LRP. Binding of RAP to OVR inhibits the interaction of the receptor with all known physiological ligands, i.e. the yolk precursors very low density lipoprotein, vitellogenin, and alpha 2-macroglobulin. In COS cells transfected with OVR, RAP is internalized and degraded in a concentration-dependent and saturable manner. Lactoferrin, another protein with a high affinity for mammalian LRP/alpha 2MR, also binds to OVR and abolishes its interaction with yolk precursors. Cross-competition experiments show that RAP and lactoferrin recognize sites different from those involved in yolk precursor binding. The availability of pure OVR and LDLR enable us to determine kinetic parameters for the binding of RAP and lactoferrin to these receptors by surface plasmon resonance. Taken together, our results strongly suggest that chicken OVR, which is easily accessible and highly abundant in growing oocytes, represents a superior system for studying mechanistic and structural aspects of the interaction of ligands and modulating proteins with members of the LDL receptor gene family.

Amino Acid Sequence↗
PubMed1996

Estrogen-related receptor, hERR1, modulates estrogen receptor-mediated response of human lactoferrin gene promoter.

We have shown previously that estrogen-stimulated transcription from the human lactoferrin gene in RL95-2 endometrium carcinoma cells is mediated through an imperfect estrogen response element (ERE) at the 5 -flanking region of the gene. Upstream from the ERE, a DNA sequence (-418 to -378, FP1) was selectively protected from DNase I digestion by nuclear extracts from endometrial and mammary gland cell lines. In this report, using the electrophoresis mobility shift assay, site-directed mutagenesis, and DNA methylation interference analyses, we show that three different nuclear proteins bind to the FP1 region (C1, C2, and C3 sites). The nuclear receptor, COUP-TF, binds to the C2 site. Mutations in the C1 binding region abolish C1 complex formation and reduce estrogen-dependent transcription from the lactoferrin ERE. When the imperfect ERE of the lactoferrin gene is converted to a perfect palindromic structure, the enhancing effect of the C1 binding element for estrogen responsiveness was abolished. We isolated a complementary DNA (cDNA) clone from an RL95-2 expression library that encodes the C1 site-binding protein. The encoded polypeptide maintains 99% amino acid identity with the previously described orphan nuclear receptor hERR1. A 2.2-kilobase mRNA was detected in RL95-2 cells by the newly isolated cDNA but not by the first 180 base pair of the published hERR1 sequence. By Western analysis, a major 42-kDa protein is detected in the RL95-2 nuclear extract with antibody generated against GST-hERR1 fusion protein. Finally, we show that the hERR1 interacts with the human estrogen receptor through protein-protein contacts.

Amino Acid Sequence↗
PubMed2001

Protein intermediate trapped by the simultaneous crystallization process. Crystal structure of an iron-saturated intermediate in the Fe3+ binding pathway of camel lactoferrin at 2.7 a resolution.

This is the first protein intermediate obtained in the crystalline state by the simultaneous process of Fe(3+) binding and crystal nucleation and is also the first structure of an intermediate of lactoferrin in the Fe(3+) binding pathway. Lactoferrin is an iron-binding 80-kDa glycoprotein. It binds Fe(3+) very tightly in a closed interdomain cleft in both lobes. The iron-free structure of lactoferrin, on the other hand, adopts an open conformation with domains moving widely apart. These studies imply that initial Fe(3+) binding must be in the open form. The protein intermediate was crystallized by the microdialysis method. The protein solution, with a concentration of 100 mg/ml in 10 mm Tris-HCl, pH 8.0, was loaded in a capillary and dialyzed against the same buffer containing 26% (v/v) ethanol placed in a reservoir. FeCl(3) and CO(3)(2-) in excess molar ratios to that of protein in its solution were added to the reservoir buffer. The crystals appeared after some hours and grew to the optimum size within 36 h. The structure was determined by molecular replacement method and refined to final R- and R-free factors of 0.187 and 0.255, respectively. The present structure showed that the protein molecule adopts an open conformation similar to that of camel apolactoferrin. The electron density map clearly indicated the presence of two iron atoms, one in each lobe with 4-fold coordinations: two by the protein ligands of Tyr-92(433) OH and Tyr-192(526) OH and two other coordination sites occupied by oxygen atoms of bidentate CO(3)(2-) ions leading to a tetrahedral intermediate. The CO(3)(2-) anion is stabilized through hydrogen bonds with the synergistic anion-binding site Arg-121(463) and with Ser-122 Ogamma in the N-lobe and Thr-464 Ogamma in C-lobe. The third oxygen atom of CO(3)(2-) interacts with a water molecule in both lobes.

Animals↗
PubMed2002

Immunoregulatory activities of lactoferrin in the delayed type hypersensitivity in mice are mediated by a receptor with affinity to mannose.

The mannose receptor (MR) mediates clearance of pathogenic microorganisms and potentially harmful glycoproteins by recognition of the carbohydrate structures. This manuscript describes the significance of the MR in mediation of the lactoferrin (LF) effects in delayed type hypersensitivity (DTH) in mice. Here we demonstrate that the inhibitory effect of LF on the effector phase of DTH to sheep red blood cells (SRBC) was abolished by intraperitoneal (i.p.) pretreatment of mice with 50 mg of methyl-alpha-D-mannopyranoside (MMan). Also, we report that the inhibition of the effector DTH response to ovalbumin (OVA) was reversed by MMan but not by D-galactose (Gal). MMan was found to reduce the adjuvant activity of LF given together with OVA, however, did not interfere with the upstimulatory effect of the complete Freund's adjuvant. Comparative studies between bovine and human lactoferrins (BLF and HLF), revealed that the adjuvant effect of BLF was stronger than that of HLF, nevertheless, both effects were inhibited by MMan. Thus, we postulate, that MR is a primary receptor for lactoferrin in mediation of its some immunotropic activities.

Animals↗
PubMed2004

Faecal calprotectin and lactoferrin as markers of acute radiation proctitis: a pilot study of eight stool markers.

BACKGROUND: Non-invasive diagnostic tools to evaluate the severity of acute, radiation-induced proctitis are not readily available. The faecal excretion of eight markers of gut inflammation was therefore examined. Five proteins and three lipid derivates were analysed in sequential stool samples taken before and during radiation therapy. METHODS: Stool samples from 15 patients with prostate cancer scheduled for radiation therapy were examined. Pretreatment and in-treatment samples (2nd and 6th weeks) were measured by enzyme-linked immunosorbent assay (ELISA) (calprotectin, lactoferrin, transferrin, leukotriene B4, prostaglandin E2, thromboxane B2 and TNF alpha) or nephelometry (alpha 1-antitrypsin). RESULTS: Calprotectin and lactoferrin concentrations increased significantly during radiation treatment (P = 0.0005 and P = 0.019). Transferrin was detected in only 9 out of 45 samples. There were no changes in tumour necrosis factor alpha (TNF alpha), leukotriene B4, prostaglandin E2 and thromboxane B2 during treatment. alpha 1-antitrypsin could not be detected in any sample. CONCLUSIONS: This study indicates that faecal calprotectin and lactoferrin concentrations could be markers of acute, radiation-induced proctitis. Patient compliance and stability of the markers make this a promising method for clinical research. Eicosanoids could be measured in stool samples, but the concentrations did not increase with increasing radiation dose.

Acute Disease↗
PubMed2002

Lactoferrin inhibits enterovirus 71 infection of human embryonal rhabdomyosarcoma cells in vitro.

Enterovirus 71 (EV71), the newest member of Enterovirudae, is notable for its etiological role in epidemics of severe neurological diseases in children. It appears to be emerging as an important virulent neurotropic enterovirus in the upcoming era of poliomyelitis eradication, whereas no effective vaccine or antiviral agents are available at this moment. Human and bovine lactoferrins, iron-binding proteins belonging to the nonimmune defense system, were assayed in vitro to assess their inhibiting capacity on the cytopathic effect of EV71 on human embryonal rhabdomyosarcoma (RD) cells. Both bovine and human lactoferrins were found to be potent inhibitors of EV71 infection (mean IC(50), 10.5-24.5 microg/mL and 103.3-185.0 microg/mL, respectively). Lactoferrin probably exerts its effect at the level of viral adsorption, since the ongoing infection could not be further inhibited after the EV71 penetrated RD cells.

Antiviral Agents↗
PubMed1999

Prediction of microbial infection and mortality in medical patients with fever: plasma procalcitonin, neutrophilic elastase-alpha1-antitrypsin, and lactoferrin compared with clinical variables.

Fever suggests the likelihood of severe microbial infection. Abnormal temperature, tachycardia, tachypnea, and abnormal white blood cell counts define the systemic inflammatory response syndrome (SIRS). In 300 hospitalized medical patients with fever, we determined clinical variables and procalcitonin, elastase-alpha1-antitrypsin, and lactoferrin levels in plasma. Of the patients, 71% had clinical infection (by clinical judgment) and 44% had microbial infection (by microbiological testing). SIRS occurred in 95%, and the 28-day mortality rate was 9%. The sensitivity for predicting microbial infection, bacteremia, and mortality was less but the specificity was greater for supranormal procalcitonin, elastase-alpha1-antitrypsin, and lactoferrin levels than for SIRS. The area under the receiver operating characteristic curve (AUC) for microbial infection was higher for procalcitonin and elastase-alpha1-antitrypsin levels than for clinical variables and lactoferrin level. The AUC for bacteremia was also higher for inflammatory factors (>0.70; P < .001) than for clinical variables. The AUC for mortality (P < .05) was 0.79 for the respiratory rate, 0.69 for elastase-alpha1-antitrypsin level, 0.65 for heart rate, 0.61 for procalcitonin level, and 0.60 for white blood cell count. In febrile medical patients, plasma procalcitonin and elastase-alpha1-antitrypsin levels may predict microbial infection and bacteremia better than (and mortality as well as) do clinical symptoms.

Adolescent↗
PubMed2006

Antioxidant and antibacterial genes are upregulated in early involution of the mouse mammary gland: sharp increase of ceruloplasmin and lactoferrin in accumulating breast milk.

The mammary gland develops mainly after birth, and shows a repeated cycle of pregnancy-triggered proliferation, differentiation for lactation, and a regressive phase after weaning known as involution. Compared to the proliferation and differentiation phases, the molecular mechanisms of involution are largely unknown. In the present study we screened genes that could play a potential role in early involution of the mouse mammary gland using fluorescent differential display followed by gene-specific reverse transcription-polymerase chain reaction. We found that five genes were upregulated more than twofold 48 h after weaning: ceruloplasmin, chemokine (CXC motif) ligand 4, epoxide hydrolase 1, lactoferrin, and properdin P factor. The products of these genes can be linked to defense against oxidative stress and/or infectious bacteria. Electrophoretic analysis and mass spectrometry of milk proteins showed that the concentrations of ceruloplasmin and lactoferrin in milk were increased fivefold and more than 38-fold, respectively, within 48 h after weaning. These increases were in contrast to the constant presence of other major proteins including albumin, caseins, transferrin, and whey acidic protein. Ceruloplasmin and lactoferrin may cooperate in the defense of the mammary gland in the postlactation period.

Amino Acid Sequence↗
PubMed1999

The effect of human lactoferrin on the MICs of doxycycline and rifampicin for Burkholderia cepacia and Pseudomonas aeruginosa strains.

The presence of lactoferrin at the concentration found in cystic fibrosis (CF) sputum (0.9 g/L) reduced MICs and MBCs of doxycycline for Burkholderia cepacia and Pseudomonas aeruginosa strains. MICs for B. cepacia fell by 32- to 64-fold, from highly resistant to clinically achievable values. Rifampicin MICs for B. cepacia strains were reduced by lactoferrin and for some strains MBCs were reduced. These findings suggest new therapeutic approaches to infections and question the relevance of standard sensitivity tests for CF pathogens. Addition of lactoferrin to media for the routine sensitivity testing of CF isolates might give more relevant results.

Anti-Bacterial Agents↗
PubMed1986

Effect of the progesterone-inducible proteins human lactoferrin and chicken avidin on lymphocyte proliferation.

Lactoferrin and avidin are progesterone-inducible glycoproteins in the human and chicken reproductive tracts, respectively. The effect of these proteins on lymphocyte proliferation was studied. The results showed that both proteins suppressed Concanavalin A (Con A)-induced responses so that a 10(3)-fold higher concentration of Con A was required for an optimal response. In contrast, avidin and lactoferrin had no effect on lymphocyte proliferation induced by other mitogens, tuberculin PPD or allogeneic cells. The effect of lactoferrin and avidin on lymphocyte proliferation seem to be caused by their binding to Con A. The significance of these findings is discussed.

Animals↗
PubMed2004

Zinc, iron, copper, selenium, lactoferrin, and ferritin in human pus.

BACKGROUND: Restriction of zinc and iron available for microbial growth in tissues are well-recognized host defense mechanisms. The present studies were performed to characterize some constituents of human pus that may affect these important host defenses. METHODS: Zinc, iron, copper, calcium, and magnesium in pus were measured using an atomic absorption spectrophotometer; selenium was measured fluorometrically. Ferritin was measured with a fluorometric enzyme immunoassay, and lactoferrin was measured with a radial diffusion assay. The growth of Escherichia coli at 37 degrees C was measured in pus supernate adjusted to pH 5.5 or 7.4, in boiled supernate, or in supernate adjusted with 1.3 mM iron or 0.9 mM zinc singly or together. RESULTS: Zinc and iron concentrations in pus exceeded normal serum. Calcium and magnesium levels were 2- to 3-fold lower and higher, respectively, than normal serum values. Lactoferrin concentrations of were 880 +/- 48 microg/mL and ferritin levels were 20,726 +/- 2,667 ng/mL. Growth of an E coli strain was inhibited in pus at pH 5.5 but not at pH 7.4, and growth was enhanced by addition of iron or zinc to E coli suspended in pus at pH 6.7. CONCLUSIONS: To our knowledge, this is the first report of the zinc, iron, copper, selenium, lactoferrin, and ferritin levels of human pus. These studies provide additional insight into host defense mechanisms mediated by the restriction of the bioavailability of zinc and iron in suppurative infection.

Calcium↗
PubMed1999

Accuracy of fecal lactoferrin and other stool tests for diagnosis of invasive diarrhea at a Colombian pediatric hospital.

OBJECTIVES: Estimate under "real life" conditions the operating characteristics of several stool tests for determining whether a diarrheal episode is invasive-inflammatory. DESIGN: Determination of operating characteristics of diagnostic tests against a standard in a prospectively gathered sample. SETTING: The emergency room of the largest Social Security Pediatric Hospital in Colombia serving referred and nonreferred patients. PATIENTS: Stool samples from children attending the emergency room because of acute diarrhea (three or more loose stools per day lasting <7 days). Patients receiving antibiotics or antiparasitic medications were excluded. INTERVENTIONS: Samples were collected in sterile containers and examined immediately for protozoa, fecal leukocytes, occult blood and lactoferrin. Specimens were inoculated onto culture media for common bacterial fecal pathogens except enteroinvasive Escherichia coli and Clostridium difficile. MAIN OUTCOME MEASURE: Sensitivity, specificity and likelihood ratios of several cutoff levels for fecal lactoferrin, fecal leukocytes and occult blood. RESULTS: Stool samples from 500 infants and children with diarrhea were collected. Patients' median age was 2.66 years (range, 0.5 to 13 years), and 261 (52.2%) were males. In 155 (31%) cases enteroinvasive bacteria and/or Entamoeba histolytica were documented. Fecal leukocytes >5 had the best sensitivity (63.2%; 95% confidence interval, 55.4 to 70.5) and specificity (84.3%; 95% confidence interval, 80.2 to 87.9), although not statistically or clinically significantly different from lactoferrin. CONCLUSIONS: No single test or combination had satisfactory operating characteristics. Nevertheless the use of likelihood ratios derived here can help clinicians identify invasive-inflammatory diarrheal episodes in many instances.

Acute Disease↗
PubMed2000

Structure of buffalo lactoferrin at 3.3 A resolution at 277 K.

The three-dimensional structure of diferric buffalo lactoferrin has been determined at 3.3 A resolution. The structure was solved by molecular replacement using the coordinates of diferric human lactoferrin as a search model and was refined by simulated annealing (X-PLOR). The final model comprises 5316 protein atoms for all 689 residues, two Fe(3+) and two CO(3)(2-) ions. The final R factor was 21.8% for 11 711 reflections in the resolution range 17.0-3.3 A. The folding of buffalo lactoferrin is essentially similar to that of the other members of the transferrin family. The significant differences are found in the dimensions of the binding cleft and the interlobe orientation. The interlobe interactions are predominantly hydrophobic in nature, thus facilitating the sliding of two lobes owing to external forces. The interdomain interactions are comparable in the N and C lobes.

Amino Acid Sequence↗
PubMed2002

Structure of a domain-opened mutant (R121D) of the human lactoferrin N-lobe refined from a merohedrally twinned crystal form.

Human lactoferrin is an iron-binding protein with a bilobal structure. Each lobe contains a high-affinity binding site for a single Fe(3+) ion and an associated CO(3)(2-) ion. Although iron binds very tightly, it can be released at low pH, with an accompanying conformational change in which the two domains move apart. The Arg121Asp (R121D) mutant of the N-lobe half-molecule of human lactoferrin was constructed in order to test whether the Asp121 side chain could substitute for the CO(3)(2-) ion at the iron-binding site. The R121D mutant protein was crystallized in its apo form as it lost iron during crystallization. The crystals were also merohedrally twinned, with a twin fraction close to 0.5. Starting from the initial molecular-replacement solution [Breyer et al. (1999), Acta Cryst. D55, 129-138], the structure has been refined at 3.0 A resolution to an R factor of 13.9% (R(free) of 19.9%). Despite the moderate resolution, the high solvent content and non-crystallographic symmetry contributed to electron-density maps of excellent quality. Weakened iron binding by the R121D mutant is explained by occlusion of the anion-binding site by the Asp side chain. The opening of the two domains in the apoR121D structure (a rotation of 54 degrees ) closely matches that of the N-lobe in full-length lactoferrin, showing that the extent of the conformational change depends on properties inherent to the N-lobe. Differences in the C-terminal portion of the N-lobe (residues 321-332) for apoR121D relative to the closed wild-type iron-bound structure point to the importance of this region in stabilizing the open form.

Amino Acid Substitution↗
PubMed1999

Structure of oxalate-substituted diferric mare lactoferrin at 2.7 A resolution.

Lactoferrin binds two Fe(3+) and two CO(2-)(3) ions with high affinity. It can also bind other metal ions and anions. In order to determine the perturbations in the environments of the binding sites in the N and C lobes and elsewhere in the protein, the crystal structure of oxalate-substituted diferric mare lactoferrin has been determined at 2.7 A resolution. The final model has a crystallographic R factor of 21.3% for all data in the resolution range 17.0-2.7 A. The substitution of an oxalate anion does not perturb the overall structure of the protein, but produces several significant changes at the metal-binding and anion-binding sites. The binding of the oxalate anion is symmetrical in both the N and C lobes, unlike in diferric dioxalate human lactoferrin, where the oxalate anion binds the metal ion symmetrically in the C lobe and asymmetrically in the N lobe.

Animals↗
PubMed2005

High-resolution diffraction from crystals of a membrane-protein complex: bacterial outer membrane protein OmpC complexed with the antibacterial eukaryotic protein lactoferrin.

Crystals of the complex formed between the outer membrane protein OmpC from Escherichia coli and the eukaryotic antibacterial protein lactoferrin from Camelus dromedarius (camel) have been obtained using a detergent environment. Initial data processing suggests that the crystals belong to the hexagonal space group P6, with unit-cell parameters a = b = 116.3, c = 152.4 A, alpha = beta = 90, gamma = 120 degrees. This indicated a Matthews coefficient (VM) of 3.3 A3 Da(-1), corresponding to a possible molecular complex involving four molecules of lactoferrin and two porin trimers in the unit cell (4832 amino acids; 533.8 kDa) with 63% solvent content. A complete set of diffraction data was collected to 3 A resolution at 100 K. Structure determination by molecular replacement is in progress. Structural study of this first surface-exposed membrane-protein complex with an antibacterial protein will provide insights into the mechanism of action of OmpC as well as lactoferrin.

Animals↗
PubMed1991

Lactoferrin-inducible monocyte cytotoxicity for K562 cells and decay of natural killer lymphocyte cytotoxicity.

Monocyte-enriched and lymphocyte-enriched fractions of peripheral blood from three healthy volunteers were obtained by percoll density gradient centrifugation. The cytotoxic activity of each fraction against 51Cr-labelled K562 cells was quantified in a 2-h assay using freshly isolated cells of each fraction and cells of each fraction which had been incubated with and without lactoferrin in complete medium for 18 h before performing the assay. We have thereby shown that cytotoxicity was not demonstrable in the lymphocyte fraction (containing 7.3 +/- 2% large granular lymphocytes) after 18 h in medium, whereas the cytotoxicity of the monocyte fraction (containing 3 +/- 0.4% large granular lymphocytes) was still significantly increased (P less than or equal to 0.01) and that lactoferrin had no effect on lymphocyte fraction cytotoxicity while producing an 11-fold increase in the cytotoxicity of the monocyte fraction. It is therefore possible to perform a relatively simple test of monocyte cytotoxicity using lactoferrin as a stimulant in a 2-h 51Cr-labelled K562 assay system by allowing 18 h to elapse for lymphocyte natural killer cytotoxicity to decay.

Cell Separation↗
PubMed1992

Characterization of the chylomicron-remnant-recognition sites on parenchymal and Kupffer cells of rat liver. Selective inhibition of parenchymal cell recognition by lactoferrin.

Upon injection of chylomicrons into rats, chylomicron remnants are predominantly taken up by parenchymal cells, with a limited contribution (8.6% of the injected dose) by Kupffer cells. In vitro storage of partially processed chylomicron remnants for only 24 h leads, after in vivo injection, to an avid recognition by Kupffer cells (uptake up to 80% of the total liver-associated radioactivity). Lactoferrin greatly reduces the liver uptake of chylomicron remnants, which appears to be the consequence of a specific inhibition of the uptake by parenchymal cells. Kupffer-cell uptake is not influenced by lactoferrin. In vitro studies with isolated parenchymal and Kupffer cells show that both contain a specific recognition site for chylomicron remnants. The Kupffer-cell recognition site differs in several ways from the recognition site on parenchymal cells as follows. (a) The maximum level of binding is 3.7-fold higher/mg cell protein than with parenchymal cells. (b) Binding of chylomicron remnants is partially dependent on the presence of calcium, while binding to parenchymal cells is not. (c) beta-Migrating very-low-density lipoprotein is a less effective competitor for chylomicron-remnant binding to Kupffer cells compared to parenchymal cells. (d) Lactoferrin leaves Kupffer-cell binding uninfluenced, while it greatly reduces binding of chylomicron remnants to parenchymal cells. The properties of chylomicron-remnant recognition by parenchymal cells are consistent with apolipoprotein E being the determinant for recognition. It can be concluded that the chylomicron-remnant recognition site on Kupffer cells possesses properties which are distinct from the recognition site on parenchymal cells. It might be suggested that partially processed chylomicron remnants are specifically sensitive to a modification, which induces an avid interaction with the Kupffer cells. The recognition site for (modified) chylomicron remnants on Kupffer cells might function as a protection system against the occurrence of these potential atherogenic chylomicron-remnant particles in the blood.

Animals↗