SEARCH · PubMed Health

Results for “Lactoferrin”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 433 records · Page 24Linked to original sources

PubMed1990

Lactoferrin-mediated formation of oxygen radicals by NADPH-cytochrome P-450 reductase system.

Superoxide generation in the NADPH oxidase reaction of NADPH-cytochrome P-450 reductase, demonstrated using the ESR spin trap, 5,5-dimethyl-1-pyrroline-1-oxide, increased on the addition of lactoferrin. The NADPH-lactoferrin reductase activity was assessed in terms of NADPH oxidation and oxygen consumption. From Lineweaver-Burk plots, the Km and Vmax for lactoferrin were estimated to be 13 microM and 0.5 S-1, respectively. The liberation of iron from lactoferrin was proven with the use of bathophenanthroline and by the demonstration of bleomycin-dependent DNA degradation; lactoferrin was reduced by the enzyme in the presence of NADPH. During the reaction, the ESR spectrum of the spin trap adduct changed from one characteristic of DMPO-OOH to that of DMPO-OH. The conversion was ascribed to the reaction of hydrogen peroxide with reduced lactoferrin.

Aerobiosis↗

PubMedDate not supplied

Use of a lactoferrin assay in the differential diagnosis of female genital tract infections and implications for the pathophysiology of bacterial vaginosis.

BACKGROUND AND OBJECTIVES: Lactoferrin has served as a marker for leukocytes (polymorphonuclear neutrophils [PMN]) in clinical specimens. GOAL: To investigate the potential of a lactoferrin latex agglutination test in the differential diagnosis of female genital infection. STUDY DESIGN: Lactoferrin was quantified in the vaginal discharge of women with genital infections. Polymorphonuclear neutrophils were added to vaginal discharge and observed over 8 hours. RESULTS: Vaginal lactoferrin titers were significantly elevated in women with trichomoniasis, candidiasis, and bacterial vaginosis (BV). Using a lactoferrin titer of > or = 1:40, the assay has a sensitivity of 79.3% and a specificity of 83.3% for the presence of trichomoniasis or bacterial vaginosis. Vaginal discharge from women with BV significantly destroyed added PMN. CONCLUSIONS: Vaginal lactoferrin determinations may provide a useful screen for inflammatory genital infections and identify individuals who require additional diagnostic evaluation. The observed absence of PMN in bacterial vaginosis may result from the destruction of PMN in vaginal discharge rather than the absence of a primary inflammatory response.

Agglutination Tests↗

PubMed1990

Lactoferrin and transferrin damage of the gram-negative outer membrane is modulated by Ca2+ and Mg2+.

Lactoferrin and transferrin have antimicrobial activity against selected Gram-negative bacteria, but the mechanism of action has not been defined. We studied the ability of lactoferrin and transferrin to damage the Gram-negative outer membrane. Lipopolysaccharide release by the proteins could be blocked by concurrent addition of Ca2+ and Mg2+. Addition of Ca2+ also blocked the ability of lactoferrin to increase the susceptibility of Escherichia coli to rifampicin. Transferrin, but not lactoferrin, increased susceptibility of Gram-negative bacteria to deoxycholate, with reversal of sensitivity occurring with exposure to Ca2+ or Mg2+. In transmission electron microscopy studies polymyxin B caused finger-like membrane projections, but no morphological alterations were seen in cells exposed to EDTA, lactoferrin or transferrin. These data provide further evidence that lactoferrin and transferrin act as membrane-active agents with the effects modulated by Ca2+ and Mg2+.

Calcium↗

PubMed1997

Iron acquisition from transferrin and lactoferrin by Pseudomonas aeruginosa pyoverdin.

Growth of Pseudomonas aeruginosa ATCC 15692 was promoted when the strain was cultured in an iron-depleted succinate medium, supplemented with transferrin at 30%, 60% and 100% and lactoferrin at 60% and 100% iron-saturation. No significant differences between cell growth and pyoverdin production were observed when transferrin iron saturation was increased from 30% to 100%; however, cell growth and pyoverdin production were strongly dependent on lactoferrin iron saturation. Lower lactoferrin iron saturation (< 30%) resulted in more pyoverdin production and reduced cell growth. Incubation of pyoverdin (1.0 microM) with 10.0 microM transferrin (30%, 60% and 100% iron-saturated) or lactoferrin (60% and 100% iron-saturated) led to quenching of pyoverdin fluorescence. Also, 24 h incubation of pyoverdin (20.0 microM) with these two proteins (20.0 microM, 30%, 60% and 100% iron-saturated transferrin and 60% and 100% iron-saturated lactoferrin) at 25 degrees C resulted in increased absorbance at 460 nm. Both the fluorescence quenching and absorbance increases were iron-saturation-dependent. Taken together, these results support the conclusion that at physiological pH, P. aeruginosa pyoverdin can acquire from partially iron-saturated transferrin or lactoferrin.

Fluorescence↗

PubMed1998

Synergic antistaphylococcal properties of lactoferrin and lysozyme.

Staphylococcus epidermidis colonises a wide range of implanted prosthetic devices, but rarely contact lenses -- despite a similarity in material composition. A conceivable explanation for this anomaly is the action of the tear defences, including the constitutive proteins lactoferrin and lysozyme. Therefore this study investigated the effect of lactoferrin, lysozyme and serum on the growth of S. epidermidis isolates in artificial tear fluid. Whether supplemented with serum alone or serum with either apolactoferrin or lysozyme, this medium induced a similar, strain-variable effect. However, simultaneous addition of these proteins induced a greater bactericidal or bacteristatic effect. Of those strains killed by the concerted action of apolactoferrin and lysozyme, the absence of serum led to a further increase in the bactericidal effect, whereas strains displaying bacteriostasis were unaffected by serum. Iron saturation of lactoferrin reversed the antimicrobial synergy of apolactoferrin and lysozyme. These results show synergy between lactoferrin and lysozyme which is dependent on the iron limitation of lactoferrin. As a bactericidal mechanism, this synergy is augmented by serum, but bacteriostasis remains unaffected by serum supplemention. Thus, the combination of lysozyme and lactoferrin may partly explain the low level of contact lens colonisation by S. epidermidis in vivo.

Apoproteins↗

PubMed1997

Polymorphic sequence of Korean Native goat lactoferrin exhibiting greater antibacterial activity.

Lactoferrin, which exhibits antibacterial activity to protect infants from infectious disease, is a major component of colostrum and milk. Lactoferrin was purified from the colostrum of Korean Native goat, and the cDNA from the mammary gland mRNA of the animal was cloned and sequenced. The nucleotide sequence of the lactoferrin gene of Korean Native goat was found to differ in 15 sites from that of the goat lactoferrin gene reported earlier. This difference in nucleotide sequence resulted in six amino acid substitutions: five in the N-lobe and one in the C-lobe. The antibacterial activity of Korean Native goat lactoferrin was found to be greater than that of Sannen goat lactoferrin.

Amino Acid Substitution↗

PubMed1992

Immunoglobulins, lysozyme and lactoferrin in the teat and udder of the dry cow during endotoxin-induced inflammation.

Immunoglobulins (Ig) and antibacterial proteins like lysozyme and lactoferrin are components of the humoral defence against infections. Changes in Ig, lysozyme and lactoferrin concentrations during endotoxin-induced inflammation in the test cistern and udder quarter of the dry cow were studied. Surgical closure of the passage between teat and udder cisterns enabled studies of reactions in the teat cistern without interference of the mammary gland. After endotoxin infusion, IgG1, IgG2, lysozyme, and to some extent IgM, increased in the teats and udder quarters, and were positively correlated with changes in somatic cell counts. No significant changes were observed in IgA or lactoferrin. The origin and significance of Ig, lysozyme and lactoferrin in the bovine teat and udder are discussed. Ig probably originated both from serum and from local plasma cells, while leukocytes appeared to be the source of lysozyme during inflammation. Secretory epithelium appeared to be the source of lactoferrin. Support for this theory was the almost total absence of lactoferrin in teat cistern samples.

Animals↗

PubMed1979

Turnover of human lactoferrin in the rabbit.

Lactoferrin turnover was studied in the rabbit with 125I- and 131I-labelled human lactoferrin. Plasma lactoferrin activity showed a rapid decrease during the first 24 h, followed by a 'final slope' with a T1/2 of about 25 h. Turnover studies after transfer of plasma from one rabbit (A) 3 h after injection to another rabbit (B), showed a recovery of 100% compared to 30% in A rabbits but otherwise a similar disappearance curve. The rapid turnover was confirmed in whole body studies. Concomitantly with the initial dissapearance from the plasma, there was a marked accumulation of proteinbound activity only in the liver in both A and B rabbits. From these results, the rate of synthesis in normal man can be estimated at around 25 mg per d. The disappearance pattern and hepatic uptake are discussed in relation to knowledge about lactoferrin receptors in macrophages, asialo elimination, and fucose group recognition. Concerning the significance of lactoferrin turnover for iron metabolism it is concluded that the plasma turnover results are insufficient to explain the disturbance in iron kinetics seen in the anaemia of chronic disorders; however, it is likely that lactoferrin plays a role in iron metabolism within the extravascular space.

Animals↗

PubMed1990

Impaired receptor binding and decrease in isoelectric point of lactoferrin after interaction with human monocytes.

The iron-binding glycoprotein lactoferrin binds to specific receptors on human monocytes as an initial step implicated in monocytic iron deposition. In this study, the properties of lactoferrin were studied after its interaction with human monocytes. Rebinding of lactoferrin to its monocytic receptor was grossly impaired and a small decrease in isoelectric point from 8.9 to 8.8 was observed. In contrast, antigenic and iron-binding properties of lactoferrin were preserved, the molecular weight by SDS-polyacrylamide gel electrophoresis was unchanged and no low-molecular fragments were detected by gel-filtration. These findings indicate that lactoferrin molecules cannot operate in a cyclic manner to deposit iron. Furthermore, these results might contribute towards explaining the complex disappearance kinetics observed for lactoferrin in plasma.

Chromatography, Gel↗

PubMed1994

Elastase and lactoferrin in gingival crevicular fluid: possible indicators of a granulocyte-associated specific host response.

Periodontitis affects a limited number of susceptible humans. The aim of this study was to determine whether there is a difference in the inflammatory reaction between patients with gingivitis and those with periodontitis. For this purpose the levels of elastase and lactoferrin were measured in gingival crevicular fluid (GCF) from three types of sites: i) inflamed sites in patients with gingivitis alone, inflamed sites both ii) with and iii) without tissue destruction in patients with periodontitis. Elastase activity, measured with a chromogenic substrate was significantly higher in the two types of sites in periodontitis patients. Lactoferrin levels, measured with ELISA were the same in the three types of sites. In vitro activation of granulocytes from healthy volunteers with Fc-receptor stimulation showed that the entire release of lactoferrin occurred immediately. In contrast, elastase release was time-dependent and continued throughout the experiment. Thus, the degranulation of the specific (lactoferrin) and azurophil granule (elastase) are under separate control and the two parameters can be combined in a ratio in order to characterize the granulocytes of a given patient. Assuming an immediate release of lactoferrin from the activated granulocytes in vivo, similar amounts of lactoferrin in the three types of sites can be regarded as reflecting similar numbers of granulocytes in the three types of sites. Consequently, a higher elastase activity in GCF from patients with periodontitis indicates a higher rate of release from the cells per se and a granulocyte-associated specific host response.

Adult↗

PubMed1993

Iron-saturated lactoferrin as a co-mitogenic substance for neonatal rat hepatocytes in primary culture.

We studied the effect of lactoferrin on DNA synthesis in neonatal rat hepatocytes in primary culture to determine if this agent acts as a mitogen in human milk. Thymidine incorporation into the DNA of cultured hepatocytes stimulated by lactoferrin in the presence of insulin and human epidermal growth factor was examined. Iron-saturated lactoferrin increased DNA synthesis of neonatal hepatocytes by 1.5 times and this potency was the same as that of insulin. It significantly enhanced the stimulatory effect of human epidermal growth factor plus insulin; DNA synthesis under these conditions was seven times that of control. Iron-free lactoferrin did not affect DNA synthesis, nor did the exogenous addition of ferric ions. The enhancement of DNA synthesis by iron-saturated lactoferrin was significant for neonatal hepatocytes, but not for adult hepatocytes. These results suggest that iron-saturated lactoferrin, which itself had low mitogenic activity, is a co-mitogenic substance for neonatal hepatocytes in vitro.

Animals↗

PubMed1981

Bactericidal activity of human lactoferrin: influence of physical conditions and metabolic state of the target microorganism.

Lactoferrin is an iron-binding protein that is bactericidal against Streptococcus mutans and several other microorganisms. In this study, the influence of several physical conditions as well as the metabolic state of S. mutans on lactoferrin susceptibility were investigated. After exposure to lactoferrin, a 15-min lag period occurred before the initiation of killing, indicating that a two-step process is involved in lactoferrin killing. Cultures harvested during the early exponential phase were very sensitive to lactoferrin, whereas cultures harvested in the early stationary phase were markedly more resistant. The rate of killing was dependent on temperature; there was no loss of viability at 2 degrees C. Killing occurred at pH 5.0 to 6.0 in water and 20 mM glycine, but did not occur at any pH in 50 mM sodium phosphate or N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer. Addition of exogenous ferrous or ferric ions did not reverse or prevent lactoferrin killing, nor did addition of 1 mM magnesium chloride.

Humans↗

PubMed1982

Bactericidal activity of human lactoferrin: differentiation from the stasis of iron deprivation.

Previous studies have demonstrated a direct iron-irreversible inhibition of a variety of microorganisms by human apolactoferrin. The present study compared the bactericidal effects of lactoferrin on Streptococcus mutans with the bacteriostatic effects of iron deprivation. Growth (as determined by change in optical density) and macromolecular synthesis, as determined by incorporation of (14)C-labeled uracil, thymidine, and lysine, were inhibited by incubation of washed exponential-phase S. mutans NCTC 10449 with purified human apolactoferrin. Similarly, apolactoferrin inhibited glucose uptake and metabolism. Iron-saturated lactoferrin had no effect on bacterial growth or metabolism and was capable of serving as a source of iron in iron-depleted medium. S. mutans failed to grow, and there was no indication of macromolecular synthesis in iron-depleted partially defined medium; however, glucose metabolism continued, though at a reduced rate, and viability was retained for 72 h. There was no detectable metabolism of glucose by cells maintained for 18 h in iron-free medium. Metabolism was restored by transfer of iron-depleted S. mutans to iron-complete medium. This was in contrast to the irreversible inhibition by lactoferrin after 1 h of incubation. Inhibition could not be reversed by removal of cell surface-associated lactoferrin as detected by rhodamine isothiocyanate-labeled antilactoferrin. This inhibition of metabolism and rapid loss in viability observed with lactoferrin treatment suggest that lactoferrin has a direct bactericidal effect on S. mutans that cannot be attributed to simple iron deprivation.

Glucose↗

PubMed1987

Bacterial-lipopolysaccharide-induced release of lactoferrin from human polymorphonuclear leukocytes: role of monocyte-derived tumor necrosis factor alpha.

We have examined the role played by human peripheral blood monocytes in mediating responses of human polymorphonuclear leukocytes (PMN) to bacterial lipopolysaccharide (LPS) in vitro. When incubated with Salmonella typhimurium LPS at 37 degrees C, human PMN suspended in serum-free buffer released the specific granule constituent lactoferrin into the surrounding medium. Release of lactoferrin from PMN varied with the concentration of LPS (1 to 1,000 ng/ml) as well as with the duration of incubation (2 to 60 min) and was not accompanied by significant release of the cytoplasmic enzyme lactate dehydrogenase. LPS-induced release of lactoferrin from PMN was augmented significantly when cell suspensions were supplemented with additional monocytes and lymphocytes. Only monocytes, however, secreted significant amounts of lactoferrin-releasing activity (in a time- and concentration-dependent manner) when incubated separately with LPS. Lactoferrin-releasing activity was heat (80 degrees C for 15 min) labile, eluted after chromatography on Sephadex G-100 with an apparent molecular weight of approximately 60,000, and was inhibited by antibodies to tumor necrosis factor alpha. Thus, LPS-induced noncytotoxic release of lactoferrin from human PMN suspended in serum-free buffer is mediated, at least in part, by tumor necrosis factor alpha derived from contaminating monocytes.

Cells, Cultured↗

PubMed1988

Damage of the outer membrane of enteric gram-negative bacteria by lactoferrin and transferrin.

Many studies have shown that lactoferrin and transferrin have antimicrobial activity against gram-negative bacteria, but a mechanism of action has not been defined. We hypothesized that the iron-binding proteins could affect the gram-negative outer membrane in a manner similar to that of the chelator EDTA. The ability of lactoferrin and transferrin to release radiolabeled lipopolysaccharide (LPS) from a UDP-galactose epimerase-deficient Escherichia coli mutant and from wild-type Salmonella typhimurium strains was tested. Initial studies in barbital-acetate buffer showed that EDTA and lactoferrin cause significant release of LPS from all three strains. Further studies found that LPS release was blocked by iron saturation of lactoferrin, occurred between pH 6 and 7.5, was comparable for bacterial concentrations from 10(4) to 10(7) CFU/ml, and increased with increasing lactoferrin concentrations. Studies using Hanks balanced salt solution lacking calcium and magnesium showed that transferrin also could cause LPS release. Additionally, both lactoferrin and transferrin increased the antibacterial effect of a subinhibitory concentration of rifampin, a drug excluded by the bacterial outer membrane. This work demonstrates that these iron-binding proteins damage the gram-negative outer membrane and alter bacterial outer membrane permeability.

Cell Division↗

PubMed1993

Transferrin and lactoferrin undergo proteolytic cleavage in the Pseudomonas aeruginosa-infected lungs of patients with cystic fibrosis.

Bacterium- and neutrophil-derived proteases have been suggested to contribute to tissue injury at sites of Pseudomonas aeruginosa infection. Pseudomonas elastase cleavage of transferrin enhances in vitro iron removal from this protein by the P. aeruginosa siderophore pyoverdin. This cleavage also generates new iron chelates which, in contrast to iron bound to transferrin, are able to catalyze formation of the highly cytotoxic hydroxyl radical from neutrophil-derived superoxide and hydrogen peroxide via the Haber-Weiss reaction. In order to determine whether this cleavage occurs in vivo, a chemiluminescence immunoblot system was developed to detect the presence of proteolysis products of transferrin or the related iron-binding protein, lactoferrin. Using this immunoblot system, we detected transferrin and lactoferrin cleavage products in bronchoalveolar lavage (BAL) samples from 21 of 22 and 20 of 21 cystic fibrosis (CF) patients, respectively. Three of eleven and two of nine BAL samples from individuals with other forms of chronic inflammatory lung disease had transferrin and lactoferrin cleavage products, respectively. Each patient in whom such products were detected was also infected with P. aeruginosa. No such products were detected in normal individuals. In the CF patients, there was no clear correlation between the extent of transferrin or lactoferrin cleavage and BAL neutrophil or P. aeruginosa concentration or the disease status of the patient. In contrast, in the non-CF patients with chronic inflammatory lung disease, transferrin and lactoferrin cleavage products were detected only in those BAL samples which contained the greatest concentration of both neutrophils and P. aeruginosa. These data provide evidence that P. aeruginosa- and/or human-derived protease cleavage of transferrin and lactoferrin occurs in vivo in the airways of individuals with CF and other forms of chronic lung disease, suggesting that this process could contribute to P. aeruginosa-associated lung injury in these patients.

Adult↗

PubMed1997

Identification, characterization, and immunogenicity of the lactoferrin-binding protein from Helicobacter pylori.

Iron acquisition plays an important role in bacterial virulence. Different studies have been initiated to define the mechanism by which Helicobacter pylori acquires iron. We had previously demonstrated that human lactoferrin (HLf) supported full growth of the bacteria in media lacking other iron sources. The ability of H. pylori to use HLf as an iron source had been found to be dependent on cell-to-protein contact. Since lactoferrin has been found in significant amounts in human stomach resection specimens from patients with superficial or atrophic gastritis, the iron uptake of H. pylori via a specific HLf receptor may play a major role in the virulence of H. pylori infection. In this study, by using affinity chromatography with biotinylated HLf and streptavidin-agarose, we identified a 70-kDa lactoferrin-binding protein (Lbp) from outer membrane proteins of H. pylori. This Lbp was only present when H. pylori was grown in an iron-starved medium, suggesting that it serves in iron uptake. Direct binding assays with increasing concentrations of biotinylated HLf demonstrated that the lactoferrin interaction with the outer membrane of H. pylori grown in iron-restricted medium was saturable. Competitive binding experiments with bovine and human lactoferrin and with transferrin of horse, bovine, and human origin indicated that this Lbp appeared highly specific for HLf. A number of other studies have focused on the importance of transferrin and lactoferrin receptors in pathogenic bacteria and their specificity with the host species. This observation might explain the very strict human specificity of H. pylori.

Bacterial Outer Membrane Proteins↗

PubMed2003

Lactoferrin impairs type III secretory system function in enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) is an important cause of infant diarrhea in developing countries. EPEC uses a type III secretory system to deliver effector proteins into the host cell. These proteins cause the characteristic attaching and effacing lesion on enterocytes. Lactoferrin, a glycoprotein present in human milk, inhibits EPEC adherence to mammalian cells. To determine the effect of lactoferrin on the initial host cell attachment step that is mediated by the type III secretory system, we focused on EPEC-induced actin polymerization in HEp2 cells, on the hemolytic activity, and on measurement of E. coli secreted proteins A, B, and D (EspABD). Lactoferrin blocked EPEC-mediated actin polymerization in HEp2 cells and blocked EPEC-induced hemolysis. The mechanism of this inhibition was lactoferrin-mediated degradation of secreted proteins necessary for bacterial contact and pore formation, particularly EspB. The proteolytic effect of lactoferrin was prevented by serine protease inhibitors. This disruption of the type III secretory system implies that lactoferrin could provide broad cross protection against the enteropathogens that share this mechanism.

Actins↗