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Abstract

Actually milk lactoferrin is one multifunctional protein topromote bacterial clearance. Lactoferrin is one glycoproteins detected in the livestock milk; as camel milk containing highest amount in compared to other livestock species. Lactoferrin boosts the immune system by protecting the cells against bacterial and viral infections and inflammations. Probably the main physiological function of lactoferrin as antibacterial agent is binding to the iron, and interaction with different cellular receptors, could be great reason for the antimicrobial activity. According to studies, iron withholding capacity of lactoferrin influences the activation of immune cells and inhibits biofilm formation of pathogenic microorganism. All bacteria require iron for growth and their virulence is related to iron availability. Iron limitation in mucosal secretions, as first defense line against microorganisms hinders bacterial growth. Biofilm formation is major agent for virulence of bacteria. Lactoferrin can reduce bacterial growth, inhibit bacterial adhesion and biofilm formation; thus, it might be considered as antimicrobial therapeutic agent. Regarding the increasing resistance to antibiotics, it is necessary to explore novel antimicrobial drugs to bacterial diseases.
World Journal of Pharmaceutical Sciences
ISSN (Print): 2321-3310; ISSN (Online): 2321-3086
Available online at: http://www.wjpsonline.org/
Review Article
Address for Correspondence: Tahereh Mohammadabadi, Associate Professor, Faculty of
Animal Science and Food Technology, Agricultural Sciences and Natural Resources University
of Khuzestan, Iran; Email: mohammadabadi@asnrukh.ac.ir; t.mohammadabadi.t@gmail.com
How to Cite this Article: Tahereh Mohammadabadi. Camel Milk lactoferrin: Special agent
against bacterial infections. World J Pharm Sci 2021; 9(3): 155-159.
This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-
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© 2013-21 World J Pharm Sci
Camel Milk lactoferrin: Special agent against bacterial infections
Tahereh Mohammadabadi
Associate Professor, Faculty of Animal Science and Food Technology, Agricultural Sciences and
Natural Resources University of Khuzestan, Iran
Received: 11-01-2021 / Revised Accepted: 25-02-2021 / Published: 27-02-2021
ABSTRACT
Actually milk lactoferrin is one multifunctional protein topromote bacterial clearance.
Lactoferrin is one glycoproteins detected in the livestock milk; as camel milk containing
highest amount in compared to other livestock species. Lactoferrin boosts the immune system
by protecting the cells against bacterial and viral infections and inflammations. Probably the
main physiological function of lactoferrin as antibacterial agent is binding to the iron, and
interaction with different cellular receptors, could be great reason for the antimicrobial
activity. According to studies, iron withholding capacity of lactoferrin influences the
activation of immune cells and inhibits biofilm formation of pathogenic microorganism. All
bacteria require iron for growth and their virulence is related to iron availability. Iron
limitation in mucosal secretions, as first defense line against microorganisms hinders
bacterial growth. Biofilm formation is major agent for virulence of bacteria. Lactoferrin can
reduce bacterial growth, inhibit bacterial adhesion and biofilm formation; thus, it might be
considered as antimicrobial therapeutic agent. Regarding the increasing resistance to
antibiotics, it is necessary to explore novel antimicrobial drugs to bacterial diseases.
Key words: Camel Milk lactoferrin, anti bacterial, infections
INTRODUCTION
Actually lactoferrin works as an opsonin to induce
bacterial clearance. In addition to iron, lactoferrin
can able to bind other compounds such as
lipopolysaccharide, heparin, glycosaminoglycan’s,
DNA, or ions such as Ga3+, Mn3+, Cu2+ and Zn2+.
Probably the main physiological function of
lactoferrin as antibacterial agent is binding to the
iron, and or sequestering iron as a necessary
requirement for most bacterial pathogens. Thus
growth of a broad range of bacterial strains will be
inhibited (Janssen and Hancock, 2009).
Bacteriostatic function of lactoferrin is due to bind
the Fe3+ ion and limiting Fe3+ for bacteria growth
and their virulence at the infection site, motility and
biofilm formation of pathogenic bacteria will be
inhibited (Gonzalez-Chavez et al., 2009).
Lactoferrin has bactericidal action due to some
Tahereh, World J Pharm Sci 2021; 9(3): 155-159
156
reasons such as direct interaction with
lipopolysaccharides of bacterial surfaces, damages
membrane of Gram-negative bacteria, increase the
membrane’s permeability, and enhances lysozyme
action and antibiotics drugs (Gonzalez-Chavez et
al., 2009). Lactoferrin effects against Gram-
positive bacteria are due to binding to anionic
molecules such as lipoteichoic acid and prevent the
attachment of these bacteria to the host cell
surfaces (Leitch and Wilcox 1999). So lactoferrin
and lysozyme exert combined effect against Gram-
positive and negative bacteria (Quiroz et al., 2013).
The effect of milk lactoferrin against pathogenic
bacteria: The antibacterial activity is the first
biological function of lactoferrin in host pre-
immune defense system. The lactoferrin of
mammalian species have been proved to inhibit the
growth of some pathogenic strains in human and/or
animal such as Escherichia coli, Salmonella
typhimurium, Shigella dysenteriae, Listeria
monocytogenes, Streptococcus spp., Vibrio
cholerae, Legionella pneumophila, Klebsiella
pneumophila, Enterococcus spp., Staphylococcus
spp., Bacillus stearothermophilus and Bacillus
subtilis (Valenti and Antonini, 2005).
Breifly the action mechanism of lactoferiin on
different types of bacteria summarized according to
Embelton et al (2013). Destabilization of micro-
organism membrane; for Gram-negatives,
lactoferrin binds to porins present on the cell
surface, release lipopolysaccharides, and increase
bacterial membrane permeability (Valenti and
Antonini, 2005). Also binding of lactoferrin to
calcium induces lipopolysaccharides release. The
membranes of gram-positive bacteria are disrupted
by binding of hydrophobic residues in the N-lobe
of lactoferrin to lipothichoic acid (Suzuki et al
2008).
Alterations of micro-organism motility;
glycosylated lactoferrin bind to bacterial adhesion
sites on bacteria and host cells and prevent bacterial
attachment. Lactoferrin binds receptors on host
cells such as glycosaminoglycan that are the entry
way for viral and bacterial pathogens. Thus
lactoferrin by competitive inhibition reduce
endocytosis of the micro-organism into host cells.
This mechanism is used by some strains of E. coli
and Staphylococcus aureus as entero invasive, even
it protects cells against viral infections (Van der
Strate et al., 2001).Iron-binding activity of
lactoferrin cause to moving of bacteria to find iron,
thus the bacterial biofilms will be disrupted.
Virulence of Pseudomonas and Burkholderia spp.,
(in cystic fibrosis) is through biofilm formation,
and the lactoferrin has protective effect due to iron
binding capacity (Van der Strate et al., 2001).
Modification of virulence factors; lactoferrin may
degrade protein virulence factors of many bacteria
through proteolysis. This proteolysis induced by
the N-lobe of lactoferrin and it’s confirmed for H.
influenza, Shigella spp. and E. coli (Ochoa and
Clearly, 2004).
Effects of lactoferrin on benefit bacteria in the
gut: It is concluded that the gut protection by the
human milk is due the presence of various
functional proteins, such as immunoglobulin A
(IgA), lactoferrin, growth factors and cytokines
(Quiroz et al., 2013). Immuno nutrients in the milk
including amino acids, fatty acids, lysozyme,
minerals such as zinc, and prebiotic
oligosaccharides which play an key role in the
maturation and health of the child´s gastrointestinal
tract (Embelton et al., 2013). Glutamine and
arginine influence gut integrity and vitamins have
basic roles in antioxidant protection. Lactoferrin
has great importance in the defense line against
gastrointestinal diseases (Embelton et al., 2013;
Quiroz et al., 2013)
The development of the intestinal micro biota in
breast-fed children is quite different from artificial
feeding. The intestinal flora pattern of breastfed
babies consisting of high percentages of
lactobacilli, especially Lactobacillus bifidus, while
babies fed with cow´s milk or formulas have
microbiota similar to the adults (Quiroz et al.,
2013).
The human milk have probiotic action and
stimulate the growth of beneficial bacteria such as
bifidobacterium and lactobacilli, that protecting the
intestine by limiting the different pathogens
throuhg decreasing of the intestinal pH (Lönnerdal,
2003).
Oral administration of lactoferrin reduces bacterial
infections of the gastrointestinal tract and
promoting the proliferation and growth of bacteria
with low iron requirements such as Lactobacillus
and Bifidobacteria as beneficial strains for host
(Sherman et al., 2004). But administration of
lactoferrin as intra peritoneally, intravenously or
intramuscularly is rapidly cleared from the body of
experimental animals, that reporting little or no
protective effect against bacterial infections
(Valenti and Antonini, 2005).
The anti-bacterial mechanisms of milk
lactoferrin
Bacteriostatic activity of milk lactoferrin: All
bacteria require iron for growth and their virulence
is related to iron availability. Iron limitation in
mucosal secretions, as first defense line against
microorganisms inhibits bacterial growth (Valenti
and Antonini, 2005). The lactoferrin found in
Tahereh, World J Pharm Sci 2021; 9(3): 155-159
157
secretions is almost iron free and it tightly bind iron
Fe3+ (two Fe3+ ions per molecule), with an
affinity and stability much higher than transferrin.
The presence of apo-Lf in mucosal surfaces
maintains the iron level below required level for
microbial growth. According to studies iron
sequestration by apo-Lf can effectively inhibit the
growth of many bacterial species due to iron
deprivation and can be completely recovered after
iron supplementation (Berlutti et al., 2011).
In addition, most pathogenic bacteria can acquire
iron by means of two principal ways: secret small
iron chelators or acquiring iron directly from
transferrin and lactoferrin. Regarding to the first
system, many bacteria synthesize small iron-
chelating molecules or siderophores as microbial
virulence factors that compete with Lf for insoluble
Fe3+ ions, which bind Fe3+ ions with high affinity
and transport it into cells through a specific
membrane receptors (Orsi, 2004).
Another mechanism for iron acquisition by
pathogenic bacteria is removing of iron from hemin
that released from hemoglobin. Although
lactoferrin can efficiently compete with bacteria for
hemin iron but still many Gram-negative
pathogenic bacteria with hemin iron-acquisition
systems can acquire iron directly from transferrin
and lactoferrin by two different bacterial receptors
(Valenti and Antonini, 2005).
Bactericidal activity of milk lactoferrin
Bactericidal activity of human lactoferrin is distinct
from its iron-withholding activity. Direct binding
of lactoferrin to bacteria is though the high positive
charges of lactoferrin molecule and can easily
induce non-specific binding of lactoferrin to either
bacteria or hosts. The molecular mechanisms of
this bactericidal activity of lactoferrin, appears to
be quite similar for both Gram-negative and
positive bacteria, through damaging of bacterial
membranes (Valenti and Antonini, 2005).
In Gram-negative bacteria, lactoferrin specifically
binds to porins present on the outer membrane and
induces the release of lipopolysaccharides and
cause to increase bacterial susceptibility to osmotic
shock, lysozyme and other antibacterial molecules.
There are two ways for this case; lactoferrinis a
poly cationic molecule with high surface positive
charge in the N-lobe (Baker et al 2002). This
positive region binds to the lipid A of
lipopolysaccharides molecules on the outer
membrane of bacterial species. Also, it is proved
that lactoferrin can bind Ca2+, releasing high
amounts of lipopolysaccharides from Gram-
negative bacteria without the need of direct contact
with bacteria (Valenti and Antonini, 2005).
Lactoferrin also bind Ca2+through the carboxylate
groups of the sialic acid residues on two glycan
chains (Berlutti et al., 2004). Particularly the
binding occure to the phosphate group within the
lipid A, inducing a rigidification of the acyl chains
of lipopolysaccharides (Orsi, 2004).
Antibacterial activity related to proteolysis
In addition to bactericidal activity, lactoferrin
inhibits the growth of some bacteria such as
Shigella flexneri and E. coli through degradation of
proteins necessary for colonization of these bacteria
(Orsi, 2004; Parker et al., 2015).
Degradation of Haemophilus influenzae IgA1
protease was observed by lactoferrin. Human
lactoferrin degraded both the IgA1 protease and
Hap adhesin by serine protease like activity of the
N-lobe of lactoferrin. Lactoferrin inhibited
enteropathogenic E. coli adherence, hemolysis and
induction of actin polymerisation in Hep2 cells by
degradation of proteins A, B and D (Esp ABD) of
E. coli (Parker et al., 2015). Lactoferrin displays
proteolytic activity against some bacterial virulence
factors and decrease the pathogenicity of certain
microorganisms (Valenti and Antonini, 2005).
Massucci et al. (2004) reported that proteolytic
activity of bovine lactoferrin is similar to trypsin,
and serine protease inhibitors prevent this catalytic
activity. Interestingly, it appears less than 10% of
the lactoferrin molecules possess proteolytic
activity (Valenti and Antonini, 2005).
Lactoferrin enhances the uptake of pathogens
The presence of iron bound lactoferrin plays a vital
role in enhancing the uptake of intracellular
pathogenic bacteria such as Mycoplasma,
Mycobacterium, Chlamydia, Borrelia which can be
degraded by free radical ions or reactive oxygen
species in RBCs and macrophages (Anand et al.,
2015).
In addition, low expression of MDR was observed
by iron saturated lactoferrin. Lower drug resistance
of pathogens by increasing the sensitivity of
resistant pathogens towards drugs and retaining the
drug inside the cells works on eradication of these
bacteria. Macrophages activated and show various
metabolic activities and lead to inhibition of
pathogens through phagocytosis. These cellular
processes will be various by iron saturation levels
of lactoferrin (Parker et al., 2015).
Influence of lactoferrinon adhesion on the cell
surfaces and biofilm formation: The adhesion,
colonizing and biofilm formation of microbes on
host cell surfaces is a key step in the development
and persistence of infections. Also, the high
resistance of microbial biofilm to natural defense
Tahereh, World J Pharm Sci 2021; 9(3): 155-159
158
mechanisms and antibiotics needs to find
compounds that prevents bacterial adhesion. A
large number of Gram-positive and negative
bacteria possess specific adhesions that induce their
adhesion to epithelial cells of host (Valenti and
Antonini, 2005). Different effects of lactoferrin on
bacterial aggregation and biofilm formation have
been observed regarding to respiratory and oral
infections (Valenti and Antonini, 2005).
Singh et al. (2002) reported that lactoferrin can be
effective in the innate immunity by blocking the
biofilm development by Pseudomonas aeruginosa.
By iron binding ability, at concentrations lower
than killing or preventing the growth of bacteria,
lactoferrin induces twitching, as special form of
surface motility, then the bacteria wander across
the surface and don’t form clusters or biofilms. The
formation of biofilm is a very important step in the
colonization of the host (Orsi2004).
Lactoferrin and respiratory infections: Cystic
fibrosis (CF), is associated with alterations in the
influx and efflux of chloride and sodium ions,
results in very high concentrations of iron in
sputum (Stites et al 1998; Valenti and Antonini,
2005). Increase in iron content and inducing of
reactive oxygen species generation contribute to
lung disorders, enhances the growth and
colonization of Pseudomonas aeruginosa and
Burkholderia cepacia, as two motile Gram-
negative pathogens that are a major reason of
morbidity and mortality of CF patients. Biofilm
formation is major agent for virulence of both these
bacteria. Peptides and proteins of natural non-
immune defenses such as lactoferrin play vital role
in combating such infections. Apo-lactoferrin, by
chelating iron, inhibits P. aeruginosa adhesion and
biofilm formation (Singh et al., 2004; Valenti and
Antonini, 2005). Similarly to P. aeruginosa, free-
living forms of B. cepacia also show a noticeable
motility under iron-limiting conditions. It means,
iron availability or the addition of iron-saturated
bovine lactoferrin protective agents, and induces
aggregation of P. aeruginosaand B. cepacia into
biofilm in CF cases. The human lactoferrin
concentration increases at higher concentrations
than normal condition in infection and
inflammation processes and also it is found in
sputum of CF cases and chronic bronchitis patients
(Thompson et al., 1990).
Lactoferrin and oral infections: In human saliva,
the iron content ranges from 0.1 to 1.0 μM
depending on meals, bleeding and oral pathologies.
The physiological level of human lactoferrin in
saliva varies from 5 to 20μg/ml and it will be
reached to 60μg/ml during infections and
inflammations. Streptococcus mutans in the human
oral cavity is the principal etiological agent of
dental caries, thus adhesion and aggregation
capability of this bacteria cause to pathogenicity.
Recently, apo-bovine lactoferrin in a saliva pool
enhance S. mutans aggregates and biofilm
formation, whereas iron-saturated bovine
lactoferrin decreases aggregation and biofilm
development (Berlutti et al., 2004). Saliva of
caries-resistant patients through high aggregation
efficiency and very low adhesion-promoting
activity of these bacteria favors the clearance of
bacteria.
Apo-human bovine lactoferrin induces aggregation
of Porphyromonas gingivalis as an anaerobic
Gram-negative bacterium, which is associated with
periodontitis (Aguilera et al., 1998). However, in
these patients, the high iron concentration and the
presence of hemin and bovine lactoferrin
degradation by bacterial enzymes (Alugupalli and
Kalfas, 1996), could be responsible for the lack
activity (Valenti and Antonini, 2005).
Conclusion
Milk lactoferrin especially camel milk lactoferrin
can reduce bacterial growth, inhibit bacterial
adhesion and biofilm formation; thus, it might be
considered as antimicrobial therapeutic agent.
Lactoferrin is able to bind iron, and hinder this
nutrient for bacteria at the infection site and inhibit
the growth of these microorganisms as well as the
expression of their virulence factors. In vitro and in
vivo studies have shown that lactoferrin prevent the
attachment of certain bacteria to the host cells.
Regarding the increasing resistance to antibiotics, it
is necessary to explore novel antimicrobial drugs to
bacterial diseases.
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Lactoferrin shares many structural and functional features with serum transferrin, including an ability to bind iron very tightly, but reversibly, a highly-conserved three-dimensional structure, and essentially identical iron-binding sites. Nevertheless, lactoferrin has some unique properties that differentiate it: an ability to retain iron to much lower pH, a positively charged surface, and other surface features that give it additional functions. Here, we review the structural basis for these similarities and differences, including the importance of dynamics and conformational change, and specific interactions that regulate iron binding and release.Key words: transferrin, protein structure, dynamics, iron binding.La lactoferrine a plusieurs caractéristiques structurales et fonctionnelles identiques à celles de la transferrine sérique, tels la capacité de lier le fer très fortement, mais de façon réversible, une structure tridimensionnelle hautement conservée et des sites de liaison du fer identiques. Cependant, la lactoferrine a des propriétés exclusives qui la différencient : la capacité de retenir le fer à un pH beaucoup plus bas, une surface chargée positivement et d'autres caractéristiques de sa surface lui conférant des fonctions additionnelles. Dans cet article, nous faisons une revue des propriétés structurales à la base de ces similitudes et ces différences, incluant l'importance des changements de conformation et de la dynamique, ainsi que les interactions spécifiques qui règlent la liaison du fer et sa libération.Mots clés : transferrine, structure protéique, dynamique, liaison du fer.[Traduit par la Rédaction]
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Human lactoferrin (hLf) has been shown to interact with cells from the Caco-2 human small intestinal cell line. There currently is little information about the molecular details of its interaction. As a first step toward detailed characterization of this interaction, we used a series of Lf chimeras to analyze which part of Lf is responsible for the interaction with Caco-2 cells. Recombinant chimeric proteins consisting of segments of hLf and bovine transferrin (bTf) were produced in a baculovirus-insect cell system and purified by a combination of cation exchange chromatography and immobilized bTf antibody affinity chromatography. Each chimera was labeled with a green fluorescent dye to monitor its interaction with Caco-2 cells. Similarly, the intestinal Lf receptor (LfR), also known as intelectin, was probed with an anti-LfR antibody that was detected with a secondary antibody conjugated with a red-color fluorescent dye. The results demonstrated that chimeric proteins containing the N-lobe or the N1.1 subdomain of Lf bound as well as intact Lf to Caco-2 cells. Confocal microscopy analysis revealed that these proteins, along with the LfR, were internalized and targeted to the nucleus. These results indicate that the N1.1 subdomain of hLf is sufficient for binding, internalization, and targeting to the nucleus of Caco-2 cells.
Article
Lactoferrin and lysozyme are proteins found in high concentrations on mucosal surfaces, and they have activities potentially important for the modulation of inflammation. To investigate whether these proteins might contribute to the modulation of the intraluminal airway inflammation associated with chronic bronchitis, lactoferrin and lysozyme were measured in bronchoalveolar lavage (BAL) fluid from 22 subjects with chronic bronchitis and, for comparison, with 10 symptom-free smokers and 16 normal subjects. As a further control, transferrin, a protein structurally homologous to lactoferrin but not known to arise in airway epithelial cells, was also measured. BAL was performed by sequentially instilling and retrieving five 20 ml aliquots of normal saline solution into each of three sites. Analyzing the first aliquots separately from the later four provided fluid that was enriched for airway contents. The concentration of lactoferrin (11.83 +/- 2.86 micrograms/ml vs 0.68 +/- 0.18 micrograms/ml, p less than 0.00001), and lysozyme (6.75 +/- 1.51 micrograms/ml vs 0.52 +/- 0.09 microgram/ml, p less than 0.00001), but not transferrin (3.22 +/- 0.38 microgram/ml vs 2.68 +/- 0.24 micrograms/ml, p = 0.55) was higher in the bronchial sample lavage fluid, suggesting an airway origin for lactoferrin and lysozyme. In subjects with chronic bronchitis, bronchial sample lactoferrin (23.1 +/- 0.5 micrograms/ml) and lysozyme (12.6 +/- 3.5 micrograms/ml) were elevated compared with the normal subjects' lactoferrin (1.9 +/- 0.5 micrograms/ml, p less than 0.0001) and lysozyme (0.77 +/- 0.22 microgram/ml, p less than 0.0001) and the symptom-free smokers' lactoferrin (4.1 +/- 0.8 micrograms/ml, p = 0.005) and lysozyme (4.9 +/- 1.3 micrograms/ml, p = 0.02). Transferrin concentrations did not demonstrate the same relationships. Finally, when the content of bronchial sample lactoferrin and lysozyme were compared with the content of bronchial sample neutrophils, poor correlations were found, which may imply an airway epithelial origin for the two proteins. Thus lactoferrin and lysozyme appear to arise in the lower respiratory tract within the airways and their levels are elevated in association with chronic bronchitis. This suggests that lactoferrin and lysozyme may contribute to the modulation of airway inflammation in chronic bronchitis.
Article
The degradation of human lactoferrin by putative periodontopathogenic bacteria was examined. Fragments of lactoferrin were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and measured by densitometry. The degradation of lactoferrin was more extensive by Porphyromonas gingivalis and Capnocytophaga sputigena, slow by Capnocytophaga ochracea, Actinobacillus actinomycetemcomitans and Prevotella intermedia, and very slow or absent by Prevotella nigrescens, Campylobacter rectus, Campylobacter sputorum, Fusobacterium nucleatum ssp. nucleatum, Capnocytophaga gingivalis, Bacteroides forsythus and Peptostreptococcus micros. All strains of P. gingivalis tested degraded lactoferrin. The degradation was sensitive to protease inhibitors, cystatin C and albumin. The degradation by C. sputigena was not affected by the protease inhibitors and the detected lactoferrin fragments exhibited electrophoretic mobilities similar to those ascribed to deglycosylated forms of lactoferrin. Furthermore a weak or absent reactivity of these fragments with sialic acid-specific lectin suggested that they are desialylated. The present data indicate that certain bacteria colonizing the periodontal pocket can degrade lactoferrin. The presence of other human proteins as specific inhibitors and/or as substrate competitors may counteract this degradation process.
Article
The antimicrobial effect of lactoferrin (apoLf) on the oral, black-pigmented anaerobes Porphyromonas gingivalis, Prevotella intermedia and P. nitrescens has been studied. ApoLf did not kill any of these species but it did inhibit the growth of P. gingivalis, while iron-saturated Lf (FeLf) had no effect. The other two species were unaffected by apoLf. This growth inhibitory effect of apoLf could not be explained on the basis of chelation of inorganic iron, since growth of P. gingivalis occurred in the presence of ethylenediamine di-o-hydroxyphenylacetic acid provided haemin was added. Both apoLf and FeLf reduced haemin uptake by all three species and caused the release of cell-bound haemin in a dose-dependent manner. In addition, haemin reduced the binding of both apoLf and FeLf to P. intermedia and P. nigrescens but stimulated the binding of Lf by P. gingivalis. These data suggest that Lf forms complexes with haemin in solution and competes for the binding of haemin to certain cell receptors, possibly lipopolysaccharides, but this is not sufficient to inhibit growth of the bacteria. P. gingivalis appears to bind Lf-haemin complexes, as well as haemin alone, which may facilitate access of the Lf to the outer and cytoplasmic membranes of P. gingivalis, so disrupting function.
Article
Extracellular free iron, or iron bound to ferritin, may promote oxidative injury and bacterial growth in airways of patients with chronic airway inflammation due to cystic fibrosis (CF) or chronic bronchitis (CB). In this study, we assessed sputum content of total iron, ferritin, and transferrin in patients with CF or CB as well as sputum from normal subjects with acute airway inflammation caused by viral upper respiratory tract infections (URTIs). Spontaneously produced sputum was obtained from 33 subjects, including 10 subjects with CF, 18 subjects with CB (10 acute exacerbations, 8 with stable CB), and 5 subjects with URTIs (control subjects). After lysing and dilution, total iron concentrations were determined by controlled coulometry, ferritin was measured by radioimmunoassay, and transferrin was measured by enzyme-linked immunosorbent assay. Iron was not present in detectable amounts in control sputums, but ferritin was present (6+/-2 ng/mg protein, mean+/-SE), as was transferrin (2.37+/-0.44 microg/mg). Compared with control subjects, concentrations of iron in sputum were increased in patient groups with higher amounts in CF patients (242+/-47 ng/mg, p<0.01) than CB patients with acute exacerbations or patients with stable CB (98+/-50 and 42+/-12 ng/mg, p<0.05 for both). Ferritin content of sputum was also increased in each group, with CF patients (113+/-22 ng/mg, p<0.001) higher than CB patients (acute, 45+/-10 ng/mg; stable, 87+/-24 ng/mg; p<0.01 for both). Compared with control subjects, sputum transferrin was decreased in CF patients (1.09+/-0.40 microg/mg, p<0.05), but not CB patients. These findings indicate there are increased airway concentrations of total iron and ferritin-bound iron in patients with CB and, to a greater extent, in patients with CF. Particularly in CF patients who also demonstrated decreased airway concentrations of transferrin, ferritin-bound iron in airways may promote oxidative injury and enhance bacterial growth.