The role of lactoferrin as an anti-inflammatory molecule

Molecular mimicry of the receptor-binding domain of the SARS-CoV-2 spike protein: from the interaction of spike-specific antibodies with transferrin and lactoferrin to the antiviral effects of human recombinant lactoferrin

The pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection involves dysregulations of iron metabolism, and although the mechanism of this pathology is not yet fully understood, correction of iron metabolism pathways seems a promising pharmacological target. The previously observed effect of inhibiting SARS-CoV-2 infection by ferristatin II, an inducer of transferrin receptor 1 (TfR1) degradation, prompted the study of competition between Spike protein and TfR1 ligands, especially lactoferrin (Lf) and transferrin (Tf). We hypothesized molecular mimicry of Spike protein as cross-reactivity of Spike-specific antibodies with Tf and Lf. Thus, strong positive correlations (R2 > 0.95) were found between the level of Spike-specific IgG antibodies present in serum samples of COVID-19-recovered and Sputnik V-vaccinated individuals and their Tf-binding activity assayed with peroxidase-labeled anti-Tf. In addition, we observed cross-reactivity of Lf-specific murine monoclonal antibody (mAb) towards the SARS-CoV-2 Spike protein. On the other hand, the interaction of mAbs produced to the receptor-binding domain (RBD) of the Spike protein with recombinant RBD protein was disrupted by Tf, Lf, soluble TfR1, anti-TfR1 aptamer, as well as by peptides RGD and GHAIYPRH. Furthermore, direct interaction of RBD protein with Lf, but not Tf, was observed, with affinity of binding estimated by KD to be 23 nM and 16 nM for apo-Lf and holo-Lf, respectively. Treatment of Vero E6 cells with apo-Lf and holo-Lf (1-4 mg/mL) significantly inhibited SARS-CoV-2 replication of both Wuhan and Delta lineages. Protective effects of Lf on different arms of SARS-CoV-2-induced pathogenesis and possible consequences of cross-reactivity of Spike-specific antibodies are discussed.

Interactions of Whey Proteins with Metal Ions

Whey proteins tend to interact with metal ions, which have implications in different fields related to human life quality. There are two impacts of such interactions: they can provide opportunities for applications in food and nutraceuticals, but may lead to analytical challenges related to their study and outcomes for food processing, storage, and food interactions. Moreover, interactions of whey proteins with metal ions are complicated, requiring deep understanding, leading to consequences, such as metalloproteins, metallocomplexes, nanoparticles, or aggregates, creating a biologically active system. To understand the phenomena of metal-protein interactions, it is important to develop analytical approaches combined with studies of changes in the biological activity and to analyze the impact of such interactions on different fields. The aim of this review was to discuss chemistry of β-lactoglobulin, α-lactalbumin, and lactotransferrin, their interactions with different metal ions, analytical techniques used to study them and the implications for food and nutraceuticals.

The Fate of Iron in The Organism and Its Regulatory Pathways

Iron is an essential element involved in many life-necessary processes. Interestingly, in mammals there is no active excretion mechanism for iron. Therefore iron kinetics has to be meticulously regulated. The most important step for regulation of iron kinetics is absorption. The absorption takes place in small intestine and it is implicated that it requires several proteins. Iron is then released from enterocytes into the circulation and delivered to the cells. Iron movement inside the cell is only partially elucidated and its traffic to mitochondia is not known. Surprisingly, the regulation of various proteins related to iron kinetics and energy metabolism at the molecular level is better described. On contrary, the complex control of iron absorption cannot be fully explicated with present knowledge.

Human lactoferrin induces asthmatic symptoms in NC/Nga mice

Lactoferrin in commercial supplements is known to exert anti‐viral and anti‐allergic effects. However, this is the first study to evaluate the induction of allergic airway inflammation in NC/Nga mice. Human lactoferrin was administered intraperitoneally with aluminum oxide for sensitization. Five days later, lactoferrin was inoculated intranasally for 5 days, and then on the 12th day, the single inoculation of lactoferrin intranasally was performed as a challenge. On the 13th day, airway hypersensitivity was assessed (AHR), a bronchoalveolar fluid (BALF) cell analysis was conducted, serum IgE and serum lactoferrin‐specific IgG and IgE levels as well as the mRNA expression levels of cytokines and chemokines in the lung were measured, and a histopathological analysis of the lung was performed. Human lactoferrin increased AHR, the number of eosinophils in BALF, serum lactoferrin‐specific IgG levels, and the mRNA levels of IL‐13, eotaxin 1, and eotaxin 2. Moreover, the accumulation of inflammatory cells around the bronchus and the immunohistochemical localization of arginase I and human lactoferrin were detected. Collectively, these results indicate that human lactoferrin induced allergic airway inflammation in mice. Therefore, the commercial use of human lactoferrin in supplements warrants more intensive study.

Iron Acquisition Mechanisms and Their Role in the Virulence of Burkholderia Species

Burkholderia is a genus within the β-Proteobacteriaceae that contains at least 90 validly named species which can be found in a diverse range of environments. A number of pathogenic species occur within the genus. These include Burkholderia cenocepacia and Burkholderia multivorans, opportunistic pathogens that can infect the lungs of patients with cystic fibrosis, and are members of the Burkholderia cepacia complex (Bcc). Burkholderia pseudomallei is also an opportunistic pathogen, but in contrast to Bcc species it causes the tropical human disease melioidosis, while its close relative Burkholderia mallei is the causative agent of glanders in horses. For these pathogens to survive within a host and cause disease they must be able to acquire iron. This chemical element is essential for nearly all living organisms due to its important role in many enzymes and metabolic processes. In the mammalian host, the amount of accessible free iron is negligible due to the low solubility of the metal ion in its higher oxidation state and the tight binding of this element by host proteins such as ferritin and lactoferrin. As with other pathogenic bacteria, Burkholderia species have evolved an array of iron acquisition mechanisms with which to capture iron from the host environment. These mechanisms include the production and utilization of siderophores and the possession of a haem uptake system. Here, we summarize the known mechanisms of iron acquisition in pathogenic Burkholderia species and discuss the evidence for their importance in the context of virulence and the establishment of infection in the host. We have also carried out an extensive bioinformatic analysis to identify which siderophores are produced by each Burkholderia species that is pathogenic to humans.

Revelation of mRNAs and proteins in porcine milk exosomes by transcriptomic and proteomic analysis

Background

Milk is a complex liquid that provides nutrition to newborns. Recent reports demonstrated that milk is enriched in maternal-derived exosomes that are involved in fetal physiological and pathological conditions by transmission of exosomal mRNAs, miRNAs and proteins. Until now, there is no such research relevant to exosomal mRNAs and proteins in porcine milk, therefore, we have attempted to investigate porcine milk exosomal mRNAs and proteins using RNA-sequencing and proteomic analysis.

Results

A total of 16,304 (13,895 known and 2,409 novel mRNAs) mRNAs and 639 (571 known, 66 candidate and 2 putative proteins) proteins were identified. GO and KEGG annotation indicated that most proteins were located in the cytoplasm and participated in many immunity and disease-related pathways, and some mRNAs were closely related to metabolisms, degradation and signaling pathways. Interestingly, 19 categories of proteins were tissue-specific and detected in placenta, liver, milk, plasma and mammary. COG analysis divided the identified mRNAs and proteins into 6 and 23 categories, respectively, 18 mRNAs and 10 proteins appeared to be involved in cell cycle control, cell division and chromosome partitioning. Additionally, 14 selected mRNAs were identified by qPCR, meanwhile, 10 proteins related to immunity and cell proliferation were detected by Western blot.

Conclusions

These results provide the first insight into porcine milk exosomal mRNA and proteins, and will facilitate further research into the physiological significance of milk exosomes for infants.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1021-8) contains supplementary material, which is available to authorized users.

Invited review: Mechanisms of endotoxin neutralization by synthetic cationic compounds

A basic challenge in the treatment of septic patients in critical care units is the release of bacterial pathogenicity factors such as lipopolysaccharide (LPS, endotoxin) from the cell envelope of Gram-negative bacteria due to killing by antibiotics. LPS aggregates may interact with serum and membrane proteins such as LBP (lipopolysaccharide-binding protein) and CD14 leading to the observed strong reaction of the immune system. Thus, an effective treatment of patients infected by Gram-negative bacteria must comprise beside bacterial killing the neutralization of endotoxins. Here, data are summarized for synthetic compounds indicating the stepwise development to very effective LPS-neutralizing agents. These data include synthetic peptides, based on the endotoxin-binding domains of natural binding proteins such as lactoferrin, Limulus anti-LPS factor, NK-lysin, and cathelicidins or based on LPS sequestering polyamines. Many of these compounds could be shown to act not only in vitro, but also in vivo (e.g . in animal models of sepsis), and might be useful in future clinical trials and in sepsis therapy.

Extracellular Polyphosphate Inhibits Proliferation in an Autocrine Negative Feedback Loop in Dictyostelium discoideum

Polyphosphate is a polymer of phosphate residues linked by high energy phosphoanhydride bonds. Despite being highly conserved throughout nature, its function is poorly understood. Here we show that Dictyostelium cells accumulate extracellular polyphosphate, and this acts to inhibit proliferation at high cell densities. In shaking culture, extracellular polyphosphate concentrations increase as cell density increases, and if the concentration of polyphosphate observed at the stationary phase is added to cells at mid-log, proliferation is halted. Adding an exopolyphosphatase to cell cultures or stationary phase conditioned medium decreases polyphosphate levels and abrogates the anti-proliferative effect. The cells show saturable binding of polyphosphate, suggesting the presence of a cell surface polyphosphate receptor. Extracellular polyphosphate accumulation is potentiated by decreased nutrient levels, potentially as a means to anticipate starvation. Loss of the Dictyostelium polyphosphate kinase DdPpk1 causes intracellular polyphosphate levels to become undetectable and negatively affects fitness, cytokinesis, and germination. However, cells lacking DdPpk1 accumulate ∼50% normal levels of extracellular polyphosphate, suggesting an additional means of synthesis. We found that cells lacking inositol hexakisphosphate kinase, which is responsible for the synthesis of the inositol pyrophosphates IP7 and IP8, reach abnormally high cell densities and show decreased extracellular polyphosphate levels. Two different enzymes thus appear to mediate the synthesis of Dictyostelium extracellular polyphosphate, which is used as a signal in an autocrine negative feedback loop to regulate cell proliferation.

Detection of novel diagnostic antibodies in ankylosing spondylitis: An overview

Ankylosing spondylitis (AS) is a debilitating, chronic, rheumatic disease characterized by inflammation and new bone formation resulting in fusion of the spine and sacroiliac joints. Since early treatment is impeded by a delayed diagnosis, it is highly important to find new biomarkers that improve early diagnosis and may also contribute to a better assessment of disease activity, prognosis and therapy response in AS. Because of the absence of rheumatoid factor, AS was long assumed to have a seronegative character and antibodies are thus not considered a hallmark of the disease. However, emerging evidence suggests plasma cells and autoantibodies to be involved in the disease course. In this review, the role of B cells and antibodies in AS is discussed. Furthermore, an overview is provided of antibodies identified in AS up till now, and their diagnostic potential. Many of these antibody responses were based on small study populations and further validation is lacking. Moreover, most were identified by a hypothesis-driven approach and thus limited to antibodies against targets that are already known to be involved in AS pathogenesis. Hence, we propose an unbiased approach to identify novel diagnostic antibodies. The already successfully applied techniques cDNA phage display and serological antigen selection will be used to identify antibodies against both known and new antigen targets in AS plasma. These newly identified antibodies will enhance early diagnosis of AS and provide more insight into the underlying disease pathology, resulting in a more effective treatment strategy and eventually an improved disease outcome.

Generation of bi-transgenic pigs overexpressing human lactoferrin and lysozyme in milk

Intensive swine production industry uses antibiotics to treat diseases and improve pig growth. This can not only cause antibiotic resistance, but can also pollute the environment or eventually affect human public health. To date, human lactoferrin (hLF) and human lysozyme (hLZ) have been known as non-adaptive but interactive antimicrobial members and could act in concert against bacteria, which contribute to host defense. Therefore, their expression in pigs might be an alternative strategy for replacing antibiotics in the pig production industry. In our study, we produced hLF and hLZ bi-transgenic pigs and assessed the milk's antibacterial ability. Integration of both transgenes was confirmed by PCR and southern blot. Both the hLF and hLZ were expressed in the mammary gland of bi-transgenic pigs, as detected by western blotting. The expression amounts were 6.5 g/L for hLF and 1.1 mg/L for hLZ using ELISA. Interestingly, pig milk containing hLF and hLZ had synergistic antimicrobial activity. Our results suggest an alternative approach for avoiding the use of antibiotics in the pig industry, which would be of great benefit to the commercial swine production.

Effects of lactoferrin on intestinal epithelial cell growth and differentiation: an in vivo and in vitro study

This study was designed to analyse the effects of human (h) and bovine lactoferrin (bLF) on the growth and differentiation of intestinal cells using the mice model supplemented with Lactoferrin (LF) and the enterocyte-like model of Caco-2 cells which spontaneously differentiate after confluency. In mice, bLF supplementation increased jejunal villus height and the expression of several intestinal brush border membrane enzymes activities. Addition of bLF or hLF to undifferentiated Caco-2 cells was able to increase cell proliferation with confluency being reached more rapidly. Moreover, when Caco-2 cells were grown in the presence of LF for 3 weeks, brush-border membrane-associated enzyme activities i.e. sucrase, alkaline phosphatase and neutral aminopeptidase, as well as the L-glutamate transporter expression were all increased indicating an increased Caco-2 cell differentiation. Accordingly, cDNA Atlas array and Western blot analysis of cell cycle proteins shown a decreased expression of Cdck2 and an increased TAF1 expression; these proteins being implicated in the regulation of numerous genes related to cellular proliferation and differentiation. These modifications were associated with an inhibition of Caco-2 cell spontaneous apoptosis. Altogether, our results indicate that LF increase in vivo and in vitro enterocyte differentiation. In addition, LF was found to increase in vitro enterocyte proliferation resulting in higher cell density in cell flasks, an effect that was likely partly due to a reduction of the cellular apoptosis. The different stimulation patterns observed for the different parameters associated with cell differentiation in relationship with specific gene regulation is discussed.

Determination of lactoferrin and immunoglobulin g in animal milks by new immunosensors

Two different immunosensors, recently developed for the determination of antibacterial proteins (lactoferrin and immunoglobulin G) in buffalo milk and in other commercial animal milks samples, were used in the present study. The aim was to propose these immunosensor methods for routine control of important diet products, such as cow and goat milks, and in particular buffalo milk. To this end we employed two different kinds of immunosensors: one for the analysis of immunoglobulin G (IgG), the other was a new amperometric immunosensor for lactoferrin analysis. Lactoferrin and IgG immunosensors were also used for the determination of lactoferrin and immunoglobulin G in buffalo milk on different days of lactation.

Lactoferrin and cancer disease prevention

Lactoferrin (LF) is an iron-binding glycoprotein that is composed of the transferrin family and is predominantly found in the products of the exocrine glands located in the gateways of the digestive, respiratory, and reproductive systems, suggesting a role in the non-specific defence against invading pathogens. Additionally, several physiological roles have been attributed to LF, namely regulation of iron homeostasis, host defence against infection and inflammation, regulation of cellular growth, and differentiation and protection against cancer development and metastasis. These findings have suggested LF's great potential therapeutic use in cancer disease prevention and/or treatment, namely as a chemopreventive agent. This review looks at the recent advances in understanding the mechanisms underlying the multifunctional roles of LF and future perspectives on its potential therapeutic applications.

The effects of lactoferrin in a rat model of catecholamine cardiotoxicity

Lactoferrin is recently under intense investigation because of its proposed several pharmacologically positive effects. Based on its iron-binding properties and its physiological presence in the human body, it may have a significant impact on pathological conditions associated with iron-catalysed reactive oxygen species (ROS). Its effect on a catecholamine model of myocardial injury, which shares several pathophysiological features with acute myocardial infarction (AMI) in humans, was examined. Male Wistar rats were randomly divided into four groups according to the received medication: control (saline), isoprenaline (ISO, 100 mg kg(-1) s.c.), bovine lactoferrin (La, 50 mg kg(-1) i.v.) or a combination of La + ISO in the above-mentioned doses. After 24 h, haemodynamic functional parameters were measured, a sample of blood was withdrawn and the heart was removed for analysis of various parameters. Lactoferrin premedication reduced some impairment caused by ISO (e.g. a stroke volume decrease, an increase in peripheral resistance and calcium overload). These positive effects were likely to have been mediated by the positive inotropic effect of lactoferrin and by inhibition of ROS formation due to chelation of free iron. The failure of lactoferrin to provide higher protection seems to be associated with the complexity of catecholamine cardiotoxicity and with its hydrophilic character.

New immunosensor for Lactoferrin determination in human milk and several pharmaceutical dairy milk products recommended for the unweaned diet

Thorough research was carried out on Lactoferrin immunosensor development. Furthermore, two different competitive procedures were used for Lactoferrin determination, in which either the antigen (Lactoferrin) or the antibody (anti-Lactoferrin) was, respectively, conjugated with horseradish peroxidase enzyme using a biotinylation process. The biotinylation of Lactoferrin and the subsequently used competition procedure for the immunosensor measurement were to get ready. Three different kinds of immunosensors were implemented, in all cases using the peroxidase enzyme as marker and hydrogen peroxide as substrate, but alternatively using as transducers one of the following sensors: (i) an amperometric electrode for H2O2, (ii) a Clark electrode and (iii) an iodide electrode. After optimizing the "competitive" measurement procedures and the transducer, the new Lactoferrin immunosensor was used for the determination of Lactoferrin content in human milk and in different types of dried milks or other dairy products, specifically produced and sold in chemist's shops to feed unweaned children in the first few months of life.

Lactoferrin decreases pollen antigen-induced allergic airway inflammation in a murine model of asthma

Pollen grains contain reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and in contact with mucosal surfaces generate superoxide anion (O2*-). In the presence of iron, O2*- may be converted to more reactive oxygen radicals, such as to H2O2 and/or *OH, which may augment antigen-induced airway inflammation. The aim of the study was to examine the impact of lactoferrin (LF), an iron-binding protein, on ragweed (Ambrosia artemisiifolia) pollen extract (RWE)-induced cellular oxidative stress levels in cultured bronchial epithelial cells and accumulation of inflammatory and mucin-producing cells in airways in a mouse model of allergic airway inflammation. Results show that LF lowered RWE-induced increase in cellular reactive oxygen species (ROS) levels in bronchial epithelial cells. Most importantly, LF significantly decreased accumulation of eosinophils into airways and subepithelium of intranasally challenged, sensitized mice. LF also prevented development of mucin-producing cells. Amb a 1, the major allergenic ragweed pollen antigen lacking NADPH oxidase activity, induced low-grade airway inflammation. When administered along with glucose oxidase (G-ox), a superoxide-generating enzyme, Amb a 1 induced robust airway inflammation, which was significantly lowered by LF. Surprisingly, LF decreased also inflammation caused by Amb a 1 alone. Iron-saturated hololactoferrin had only a marginal effect on RWE-induced cellular ROS levels and RWE- or Amb a 1 plus G-ox-induced inflammation. We postulate that free iron in the airways chemically reduces O2*- to more reactive species which augment antigen-induced inflammation in a mouse model of asthma. Our results suggest the utility of LF in human allergic inflammatory disorders.

Bovine lactoferrin for Helicobacter pylori eradication: an open, randomized, multicentre study

BACKGROUND

Cure rates for eradication of Helicobacter pylori appear to be decreasing, thus more effective therapies must be identified.

AIM

To evaluate the efficacy of bovine lactoferrin in the treatment of H. pylori infection.

METHODS

In a multicentered prospective study, 402 (mean age 52.4, range 19-84 years) H. pylori-positive patients were assigned to one of three regimens: group A - esomeprazole 20 mg b.d., clarithromycin 500 mg b.d. and tinidazole 500 mg b.d. for 7 days; group B - lactoferrin 200 mg b.d. for 7 days followed by the same schedule of group A; group C - esomeprazole 20 mg b.d., clarithromycin 500 mg b.d. and tinidazole 500 mg b.d. plus lactoferrin 200 mg b.d. for 7 days.

RESULTS

Of the 402 patients, 389 completed the study. Six patients were discontinued due to side effects, one patient in group B died and six patients were lost to follow up. The eradication rate (intention-to-treat analysis) was 77% in group A (105/136), 73% in group B (97/132) and 90% in group C (120/134) (chi(2)-test P < 0.01). The incidence of side effects was 9.5% in group A, 9% in group B and 8.2% in group C (chi(2)-test P = 0.1).

CONCLUSION

This study demonstrates that bovine lactoferrin is an effective adjuvant to 7-day triple therapy for eradication of H. pylori infection.

Recombinant human lactoferrin ingestion attenuates indomethacin-induced enteropathy in vivo in healthy volunteers

OBJECTIVE

To determine whether recombinant human lactoferrin ingestion inhibits nonsteroidal antiinflammatory drugs (NSAID)-induced gastroenteropathy in vivo in healthy volunteers as a model for disorders associated with a rise in permeability of the stomach and the small intestine.

DESIGN

A randomized crossover dietary intervention.

SUBJECTS AND INTERVENTIONS

In all, 15 healthy volunteers (age 23+/-1.4 y) were tested. A sucrose and a lactulose/rhamnose (L/R) permeability test was performed to assess gastroduodenal and small intestine permeability as indicator of NSAID-induced gastroenteropathy. All subjects consumed standardized meals for 2 days. On the second day at time=-24 h each subject ingested a drink containing 5 g recombinant human lactoferrin or placebo during breakfast. At t=-9 h, subjects ingested the same drink with 75 mg of the NSAID indomethacin and after an overnight fast at t=-1 h subjects consumed the drink and 50 mg indomethacin. After 1 h, at t=0, a permeability test was performed.

RESULTS

Small intestine permeability after indomethacin and placebo was significantly higher (L/R ratio=0.036; 0.014-0.092, P<0.05) compared to the permeability observed after ingestion of indomethacin and lactoferrin (0.028; 0.015-0.056), whereas gastroduodenal permeability did not differ between the two interventions (P=0.3).

CONCLUSION

Oral recombinant human lactoferrin supplementation during a short-term indomethacin challenge reduced the NSAID-mediated increase in small intestinal permeability and hence may provide a nutritional tool in the treatment of hyperpermeability-associated disorders.

SPONSORSHIP

Grant and human recombinant lactoferrin donated from Agennix Inc., Houston, TX.

The mode of oral bovine lactoferrin administration influences mucosal and systemic immune responses in mice

Food protein intake interacts with the immune system. In earlier nutritional and immunological studies, nutrients, particularly milk whey proteins, were generally administered in soluble form and by gavage. However, orogastric intubation does not represent a natural way of ingesting nutrients such as lactoferrin (Lf). We examined how different modes of oral administration of Lf could affect the regulatory effect of this molecule on intestinal and systemic immune responses. Groups of 10 female BALB/c mice were administered Lf daily for 6 wk. To address the influence of the oral modes of administration, mice were given Lf either in solution, by gastric intubation or in the drinking water, or as a powder, by buccal deposition or in the diet. Mucosal and systemic immune responses, including specific immunoglobulin (Ig) secretion, cell proliferation, and cytokine production, were analyzed and compared with those of naïve mice given water under the same conditions or positive control mice that were administered Lf by i.m. injection. The addition of Lf to the drinking water had no visible effect on the immune status. Gastric intubation, single buccal doses, and continuous doses of Lf in the diet stimulated transient systemic and intestinal antibody responses against Lf. All of these oral modes of Lf exposure biased mucosal and systemic T-cell responses toward Thelper (Th)2-types and elevated IgA production by mucosal cells. However, the less natural gastric intubation also promoted Th1-type responses as evidenced by serum IgG(2a) antibodies and the secretion of Th1 cytokine by mucosal and systemic T cells in vitro. Thus, one should carefully consider the oral mode of administration for understanding regulation of immune responses by food proteins such as Lf.

Gastric digestion of bovine lactoferrin in vivo in adults

Lactoferrin (LF), an iron-binding glycoprotein present in milk and other endocrine and exocrine secretions, may exert a number of physiologic effects in the intestines. To study the effects of oral LF supplementation in vivo in the gastrointestinal tract, information about the gastric survival of LF in vivo is important. We tested 12 healthy volunteers (age 21 +/- 0.3 y) on 3 separate d according to a randomized, cross-over design. A test drink containing 4.5 g of bovine LF (20% iron-saturated LF; apoLF) in the presence of a gastric pH buffer (0.1 mol/L sodium citrate/citric acid; apoLFbuf), apoLF without the buffer (apoLF) or iron-saturated LF (holoLF) was administered into the stomach using nasogastric intubation. Gastric emptying rate, determined by a marker dilution technique, did not differ among any of these drinks. Gastric survival of LF, analyzed by gel permeation chromatography under denaturing conditions, was 64%, 62% and 79% after consumption of the apoLFbuf, apoLF and holoLF test drinks, respectively. Addition of the gastric pH buffer initially lowered intragastric pH because of its hydroxide buffering effect. However, it did not elevate intragastric pH over a prolonged period and thereby inhibit intragastric LF breakdown. We conclude that after oral administration, substantial amounts of apoLF and holoLF survive gastric transit.

Effects of lactoferrin on rat dermal interstitial fluid pressure (Pif) and in vitro endothelial barrier function

We recently demonstrated that intravenous (i.v.) injection of the iron-binding protein lactoferrin (Lf) followed by antilactoferrin (aLf) antibodies or iron-saturated Lf alone increased albumin extravasation in vivo in several tissues including skin. Increased driving pressure for blood-tissue exchange or direct effects of Lf on the endothelial barrier are possible mechanisms. We therefore, firstly, measured interstitial fluid pressure (Pif) in dermis of rats given 1 mg Lf i.v. followed 30 min later by aLf or saline and circulatory arrest 1 or 5 min thereafter and compared with controls. Secondly, transmonolayer passage of Evans blue labelled albumin (EB-albumin) was evaluated in porcine pulmonary artery endothelial cells exposed to iron-free or iron-saturated Lf (both 100 microg mL-1) in the absence and presence of 0.5 mM hydrogen peroxide. Pif increased significantly at 11-30 min following Lf to +2.1 +/- 0.3 and +1.7 +/- 0.2 mmHg at 11-20 and 21-30 min, respectively, compared with +0.1 +/- 0.2 mmHg before Lf (P < 0.05, n=25). Endothelial transmonolayer passage of EB-albumin during 3 h was not affected by iron-free or iron-saturated Lf neither in the absence nor presence of hydrogen peroxide that increased passage 3.5 times compared with controls. In conclusion, Lf-induced increase in albumin extravasation in rat skin is not explained by changes in Pif (because Lf raised Pif significantly) or direct effects of Lf on the endothelial barrier.

Characterisation of autoantibodies to neutrophil granule constituents among patients with reactive arthritis, rheumatoid arthritis, and ulcerative colitis

OBJECTIVE

To study the frequency and distribution of antineutrophil cytoplasmic autoantibodies (ANCA) among patients with reactive arthritis (ReA), rheumatoid arthritis (RA), and ulcerative colitis (UC) using different immunological methods.

METHODS

Fifty serum samples from patients with reactive arthritis (26 with acute disease and 24 with chronic disease-that is disease of more than one year) were analysed for ANCA with indirect immunofluorescence, enzyme linked immunosorbent assay (ELISA) with six different neutrophil granule proteins as antigens, and immunoblotting on whole neutrophil extract and extracts of azurophil and specific granules. Thirty serum samples from patients with RA and UC served as controls in ELISA and indirect immunofluorescence.

RESULTS

Sixteen per cent of patients with ReA were positive in immunofluorescence compared with 30% of patients with RA, and 70% of patients with UC. Thirty two per cent of patients with ReA were positive in ELISA. Antibodies directed against lactoferrin occurred in 20%, antibodies against bactericidal permeability increasing protein (BPI), elastase, cathepsin G, myeloperoxidase, and proteinase 3 were found in 8%, 2%, 2%, 8%, and 6%, respectively. Overall, 50% of RA sera and 53% of UC sera were positive in one or more ELISA assays, the corresponding figures for antibodies against individual antigens were for RA 7%, 3%, 0%, 13%, 47%, 17% and for UC 13%, 20%, 0%, 23%, 10%, and 17%. In immunoblotting, bands corresponding to lactoferrin and BPI were recognised in 44% and 22% of ReA sera.

CONCLUSION

Antibodies against neutrophil granule antigens are often found in patients with ReA, primarily among those with chronic disease. The different methods detect various subsets of antibodies, with immunoblotting being the most and immunofluorescence the least sensitive.

Occurrence, structure, biochemical properties and technological characteristics of lactoferrin

The structure of the iron-binding glycoprotein lactoferrin, present in milk and other exocrine secretions, has been elucidated in great detail, both the three-dimensional protein structure and the attached N-glycans. Structure-function relationships are being established. From these studies a function for lactoferrin in host defence and modulation of iron metabolism emerges. This paper describes in some detail how iron and other cations may be bound by lactoferrins from human or bovine sources and elucidates parts of the molecule that are critical for interactions with cells and biomolecules. Furthermore, the technological aspects, more specifically the heat-sensitivity, of bovine lactoferrin in different matrices are described.

Lactoferrin and anti-lactoferrin antibodies: effects of ironloading of lactoferrin on albumin extravasation in different tissues in rats

Lactoferrin is a cationic iron-binding protein, which is released from activated neutrophils in concert with reactive oxygen species. In vitro, lactoferrin has both anti- and proinflammatory effects; many of them dependent on iron-binding. In vivo, only iron-free lactoferrin reduced inflammatory hyperpermeability in the lung. We therefore examined whether 1 mg iron-free (Apo-Lf) or iron-saturated lactoferrin (Holo-Lf) alone or followed by anti-lactoferrin antibodies (aLf) affected permeability evaluated by extravasation of radiolabelled bovine serum albumin (CBSA) in different tissues of anaesthetized rats. Fifteen minutes after i.v. injection of Lf, aLf or saline was given and circulatory arrest was induced 20 min thereafter. Measurements were performed in control, after Apo-Lf, Holo-Lf, Apo-Lf + aLf, Holo-Lf + aLf and aLf alone (n=6-8 in each group). No intergroup differences were found for plasma volume and haematocrit at the start and end of the 37 min extravasation period or for total tissue water in any of the six different tissues studied, excluding larger transcapillary fluid shifts. However, increases in CBSA were seen without differences in tissue intravascular volume. Iron-free lactoferrin and aLf alone did not change CBSA significantly. Iron-saturated lactoferrin significantly increased CBSA in skin (neck), trachea and left ventricle of the heart to 249 +/- 9, 284 +/- 16 and 160 +/- 7% of control, respectively. When followed by aLf, both Apo- and Holo-Lf increased CBSA significantly in four and five of the tissues studied, respectively. However, no significant effect was seen for Holo-Lf + aLf compared with Holo-Lf alone. In conclusion, iron-saturated, but not iron-free lactoferrin increased CBSA, whereas antilactoferrin increased CBSA compared with lactoferrin alone only when following iron-free lactoferrin.

Milk and dairy products in cancer prevention: focus on bovine lactoferrin

Milk and dairy products constitute an important part of the western style diet. A large number of epidemiological studies have been conducted to determine effects of consumption on cancer development but the data are largely equivocal, presumably reflecting the different included components. It has been proposed that whereas fats in general could promote tumor development, individual milk fats like conjugated linoleic acid could exert inhibitory effects. There is also considerable evidence that calcium in milk products protects against colon cancer, while promoting in the prostate through suppression of circulating levels of 1,25-dihydroxyvitamin D3. Whey protein may also be beneficial, as shown by both animal and human studies, and experimental data have demonstrated that the major component bovine lactoferrin (bLF), inhibits colon carcinogenesis in the post-initiation stage in male F344 rats treated with azoxymethane (AOM) without any overt toxicity. The incidence of adenocarcinomas in the groups receiving 2% and 0.2% bLF were thus 15% and 25%, respectively, in contrast to the 57.5% control value (P<0.01 and P<0.05, respectively). Results in other animal models have provided further indications that bLF might find application as a natural ingredient of milk with potential for chemoprevention of colon and other cancers.

Chemopreventive effect of bovine lactoferrin on 4-nitroquinoline 1-oxide-induced tongue carcinogenesis in male F344 rats

The modifying effects of dietary feeding of bovine lactoferrin (bLF) on tongue carcinogenesis initiated with 4-nitroquinoline 1-oxide (4-NQO) were investigated in male F344 rats. The activities of phase II detoxifying enzymes, glutathione S-transferase (GST) and quinone reductase (QR), polyamine content and ornithine decarboxylase (ODC) activity in the tongue were also examined for mechanistic analysis of possible modifying effects of bLF on carcinogenesis. At 7 weeks of age, all animals except those treated with bLF alone and untreated rats were given 20 ppm 4-NQO in drinking water for 8 weeks to induce tongue neoplasms. Starting 7 days before 4-NQO exposure, experimental groups were fed experimental diets containing bLF (0.2% and 2%) for 10 weeks ("initiation feeding"). Starting 1 week after the cessation of exposure to 4-NQO, the other experimental groups given 4-NQO and a basal diet were fed the experimental diets for 22 weeks ("postinitiation feeding"). At week 32, the incidence and multiplicity of tongue neoplasms in the "initiation feeding" groups of 0.2% and 2% bLF and the "post-initiation feeding" group of 0.2% bLF were lower than those of the 4-NQO alone group, but without statistical significance. However, "post-initiation feeding" of 2% bLF caused a significant reduction in the incidence (20% vs. 55%, P=0.02418) and multiplicity (0.25+/-0.54 vs. 0.70+/-0.71, P<0.05) of tongue squamous cell carcinoma (by 64%, P=0.02418). bLF treatment elevated liver and tongue GST activities and liver QR activity. The "post-initiation feeding" with 2% bLF significantly decreased QR activity, proliferating cell nulcear antigen-positive index and ODC activity in the tongue. In addition, feeding with bLF decreased tongue polyamine content. These results suggest that bLF, when given at the 2% dose level during the post-initiation phase, exerts chemopreventive action against tongue tumorigenesis through modification of cell proliferation activity and/or the activities of detoxifying enzymes.

Tumor necrosis factor-alpha increases lactoferrin transcytosis through the blood-brain barrier

Lactoferrin (Lf) is an iron-binding protein involved in host defense against infection and severe inflammation, which accumulates in the brain during neurodegenerative disorders. Prior to determining Lf function in pathological brain tissues, we investigated its transport through the blood-brain barrier (BBB) in inflammatory conditions. For this purpose, we used a reconstituted BBB model consisting of the coculture of bovine brain capillary endothelial cells (BBCECs) and astrocytes in the presence of tumor necrosis factor-alpha (TNF-alpha). As TNF-alpha can be either synthesized by brain glial cells or present in circulating blood, BBCECs were exposed to this cytokine at their luminal or abluminal side. We have been able to demonstrate that in the presence of TNF-alpha, whatever the type of exposure, BBCECs were activated and Lf transport through the activated BBCECs was markedly increased. Lf was recovered intact at the abluminal side of the cells, suggesting that increased Lf accumulation may occur in immune-mediated pathophysiology. This process was transient as 20 h later, cells were in a resting state and Lf transendothelial traffic was back to normal. The enhancement of Lf transcytosis seems not to involve the up-regulation of the Lf receptor but rather an increase in the rate of transendothelial transport.

Lactoferrin: a multifunctional glycoprotein

Lactoferrin is an iron-binding glycoprotein found in milk, exocrine secretions of mammals, and in secondary granules from polymorphonuclear neutrophils. This review describes the wide spectrum of functions ascribed to lactoferrin, with special emphasis on the antimicrobial properties of this protein, and its derived peptides.

Anti-lactoferrin antibodies and other types of anti-neutrophil cytoplasmic antibodies (ANCA) in reactive arthritis and ankylosing spondylitis

Fifty-five serum samples from patients with reactive arthritis (ReA), 40 from patients with ankylosing spondylitis (AS) and three from patients with chronic sacroiliac joint arthritis were analysed for the presence of ANCA of IgG class by means of enzyme immunosorbent assay using lactoferrin (Lf), myeloperoxidase (MPO) and antigen extracted from azurophil granules ('alpha-antigen') containing proteinase 3 (PR3) as substrate. IgG-ANCA were found in 31 (56%) patients with ReA. Twenty-three (42%) had anti-Lf antibodies, nine (16%) had anti-MPO and eight (15%) had anti-alpha-antigen antibodies, none of which reacted with PR3. Only six (14%) AS or sacroiliac joint arthritis patients had ANCA (P < 0.001). Three (7%) had anti-Lf, two (5%) anti-MPO and two (5%) anti-alpha-antigen antibodies. Yersinia and Salmonella bacteria were separated by SDS-PAGE and blots were incubated with serum from rabbits immunized with human Lf. The hyperimmune serum recognized a band of 78 kD from both bacteria which was not seen when preimmune serum was used. The reaction to the 78-kD antigen could be completely inhibited when anti-Lf antibodies were absorbed on Lf coupled to cyanogen bromide-activated Sepharose, possibly indicating cross-reacting epitopes in Lf and enterobacterial antigen.

Formation of reactive oxygen species by the contracting diaphragm is PLA(2) dependent

Recent work indicates that respiratory muscles generate superoxide radicals during contraction (M. B. Reid, K. E. Haack, K. M. Francik, P. A. Volberg, L. Kabzik, and M. S. West. J. Appl. Physiol. 73: 1797-1804, 1992). The intracellular pathways involved in this process are, however, unknown. The purpose of the present study was to test the hypothesis that contraction-related formation of reactive oxygen species (ROS) by skeletal muscle is linked to activation of the 14-kDa isoform of phospholipase A(2) (PLA(2)). Studies were performed by using an in vitro hemidiaphragm preparation submerged in an organ bath, and formation of ROS in muscles was assessed by using a recently described fluorescent indicator technique. We examined ROS formation in resting and contracting muscle preparations and then determined whether contraction-related ROS generation could be altered by administration of various PLA(2) inhibitors: manoalide and aristolochic acid, both inhibitors of 14-kDa PLA(2); arachidonyltrifluoromethyl ketone (AACOCF(3)), an inhibitor of 85-kDa PLA(2); and haloenol lactone suicide substrate (HELSS), an inhibitor of calcium-independent PLA(2). We found 1) little ROS formation [2.0 +/- 0.8 (SE) ng/mg] in noncontracting control diaphragms, 2) a high level of ROS (20.0 +/- 2.0 ng/mg) in electrically stimulated contracting diaphragms (trains of 20-Hz stimuli for 10 min, train rate 0.25 s(-1)), 3) near-complete suppression of ROS generation in manoalide (3.0 +/- 0.5 ng/mg, P < 0. 001)- and aristolochic acid-treated contracting diaphragms (4.0 +/- 1.0 ng/mg, P < 0.001), and 4) no effect of AACOCF(3) or HELSS on ROS formation in contracting diaphragm. During in vitro studies examining fluorescent measurement of ROS formation in response to a hypoxanthine/xanthine oxidase superoxide-generating solution, manoalide, aristolochic acid, AACOCF(3), and HELSS had no effect on signal intensity. These data indicate that ROS formation by contracting diaphragm muscle can be suppressed by the administration of inhibitors of the 14-kDa isoform of PLA(2) and suggest that this enzyme plays a critical role in modulating ROS formation during muscle contraction.

Lactoferrin: a multifunctional glycoprotein involved in the modulation of the inflammatory process

Lactoferrin is an iron-binding glycoprotein found in exocrine secretions of mammals and released from neutrophilic granules during inflammation. This review describes the biological roles of lactoferrin in host defence. Secreted lactoferrin exerts antimicrobial action either by chelation of iron or by destabilization of bacterial membranes. Furthermore, lactoferrin modulates the inflammatory process, mainly by preventing the release of cytokines from monocytes and by regulating the proliferation and differentiation of immune cells. Some of these activities are related to the ability of lactoferrin to bind lipopolysaccharides (LPS) with high affinity. Indeed, recent in vitro studies indicate that lactoferrin is able to compete with the LPS-binding protein for LPS binding and therefore to prevent the transfer of LPS to CD14 present at the surface of monocytes. Moreover, the prophylactic properties of lactoferrin against septicemia in vivo have been demonstrated. Taken as a whole, these observations strongly suggest that lactoferrin is one of the key molecules which modulate the inflammatory response.

Inhibitory effects of bovine lactoferrin on intestinal polyposis in the Apc(Min) mouse

Chemopreventive effects of bovine lactoferrin (bLF), previously shown to strongly inhibit intestinal carcinogenesis in rats (K. Sekine, E. Watanabe, J. Nakamura, N. Takasuka, D.J. Kim, M. Asamoto, V. Krutovskikh, T.H. Baba, T. Ota, M.A. Moore, M. Masuda, H. Sugimoto, H. Nishino, T. Kakizoe, H. Tsuda, Inhibition of azoxymethane-initiated colon tumor by bovine lactoferrin administration in F344 rats, Jpn. J. Cancer Res. 88 (1997) 523-526; K. Sekine, Y. Ushida, T. Kuhara, M. Iigo, H. Baba-Toriyama, M.A. Moore, M. Murakoshi, Y. Satomi, H. Nishino, T. Kakizoe, H. Tsuda, Inhibition of initiation and early stage development of aberrant crypt foci and enhanced natural killer activity in male rats administered bovine lactoferrin concomitantly with azoxymethane, Cancer Lett. 121 (1997) 211-216), on spontaneous intestinal polyp development were assessed in the ApcMin mouse, a model for both familial adenomatous polyposis and sporadic colon cancers. In the experiment, 54 mice at 6 weeks of age were given 2% bLF (15 mice), 0.2% bLF (15 mice) and AIN-93G (24 mice) as basal diet ad libitum for 8 weeks. An overall tendency for a reduction in the total number of polyps in the small intestine was evident in the bLF-treated animals, along with significant suppression in the jejunum at the 2% dose (P < 0.05, 68% of the control). In addition, body growth suppression, presumed to be due to anemia and/or intussusception as a consequence of numerous polyps in the intestine, was alleviated. No toxic effects were observed in the intestinal epithelium. Although not as obvious as observed for the rat case, the data suggest that bLF may be a chemopreventor of intestinal polyposis.

Effect of lactoferrin on the phagocytic activity of polymorphonuclear leucocytes isolated from blood of patients with autoimmune diseases and Staphylococcus aureus allergy

Phagocytic number (PN) and phagocytic index (PI) of neutrophils isolated from blood of patients with autoimmune diseases, allergy to Staphylococcus aureus and from blood of healthy individuals were examined. Our results concerning the influence of lactoferrin (Lf); (6.7 mg/l) on the PI of PMN showed that: 1) Lf enhances reliable PI of PMN at the 30-th minute starting the phagocytic reaction in patients with autoimmune disease in an active stage, in blood donors treated as healthy with the presence of autoantibodies, in patients with autoimmune diseases and proved autoantibodies against tissue, cell antigens and collagen, 2) Lf influences non-significantly PI of PMN in patients with autoimmune collagen diseases in remission, 3) Lf increases PI of PMN with 19% only in 58% from the assessed patients with Staphylococcus aureus, and 4) Lf decreases non-significantly PI of PMN in the healthy controls. Our studies on the effect of Lf on the phagocytic activity of PMN suggest that Lf has stronger effect on the PN compared to the PI: 1) Lf enhances with 86% the PN in patients with Staphylococcus aureus, 2) Lf increases PN of PMN in all of the assessed patients with autoimmune collagen diseases in active stage (mean with 72%), and 3) Lf increases PN of PMN in 4 from the 5 investigated healthy controls (mean with 22%). Our results show a "corrective" effect of Lf on the phagocytic functions in the investigated groups of patients. The possible mechanisms, by which Lf increases PN and PI of neutrophils, is discussed: 1) they may concern the antioxidative properties of Lf to block the iron ions in their catalytic inactive form or to take part as ferric-Lf in an oxidative-reduction processes on the plasma membrane and controlling transmembrane transport systems, 2) Lf decreases the negative surface charge and thus enhances the adherent ability of the PMN. Probably to this stimulated adherent ability dues the increased ingestion of bacteria in the presence of Lf, and 3) The "changed" membrane of PMN may have higher number receptors for Lf to bind more molecules of exogenous Lf. The increase of Lf binding which enhances the adherence and aggregation of neutrophils, facilitates the phagocytosis.

Hepatic and extrahepatic clearance of circulating human lactoferrin: an experimental study in rat

Lactoferrin, unlabelled or 125I-labelled by 2 different methods, was given intravenously to rats. Blood, tissue and liver cell radioactivity was measured. Both of the radiolabelled preparations were eliminated by the liver, and some deposited extrahepatically. One preparation formed large aggregates--here 90% of the hepatic uptake occurred in the Kupffer cells. The other preparation, consisting mostly of protein monomers but also dimers/oligomers/microaggregates, was taken up by hepatocytes (63% of total liver uptake), liver endothelial cells (22%) and Kupffer cells (15%). On a per cell volume basis, lactoferrin uptake was much more efficient by nonparenchymal cells compared to hepatocytes, which explains why immunomorphological staining only revealed lactoferrin in the nonparenchymal liver cells. The study demonstrates that radio-iodination of lactoferrin can affect its properties and handling, which may be important regarding contradictory reports on hepatic lactoferrin uptake. We conclude that both hepatocytes and nonparenchymal liver cells are involved in the blood clearance of lactoferrin, probably to a great extent owing to nonspecific mechanisms. Extrahepatic deposition and exposure (for instance on vessel walls/glomeruli) suggests that lactoferrin can be available to circulating anti-lactoferrin autoantibodies in autoimmune disease.

The protective effects of lactoferrin feeding against endotoxin lethal shock in germfree piglets

The unique germfree, colostrum-deprived, immunologically "virgin" piglet model was used to evaluate the ability of lactoferrin (LF) to protect against lethal shock induced by intravenously administered endotoxin. Piglets were fed LF or bovine serum albumin (BSA) prior to challenge with intravenous Escherichia coli lipopolysaccharide (LPS), and temperature, clinical symptoms, and mortality were tracked for 48 h following LPS administration. Prefeeding with LF resulted in a significant decrease in piglet mortality compared to feeding with BSA (16.7 versus 73.7% mortality, P < 0.001). Protection against the LPS challenge by LF was also correlated with both resistance to induction of hypothermia by endotoxin and an overall increase in wellness, as quantified by a toxicity score developed for these studies. In vitro studies using a flow cytometric assay system demonstrated that LPS binding to porcine monocytes was inhibited by LF in a dose-dependent fashion, suggesting that the mechanism of LF action in vivo may be inhibition of LPS binding to monocytes/macrophages and, in turn, prevention of induction of monocyte/macrophage-derived inflammatory-toxic cytokines.

Iron overload in patients with chronic hepatitis C: a clinicopathologic study

Recent studies suggest that increased hepatic iron may impair the response to interferon therapy in patients with chronic hepatitis C. We reviewed the records and liver biopsies of 72 patients with chronic hepatitis C to determine the prevalence of iron overload and to evaluate whether there is a correlation between serum and hepatic iron concentrations and activity of liver disease. Patients with other causes of liver disease or iron overload were excluded. Necroinflammatory activity and fibrosis were evaluated using modified Knodell score. Hepatic iron was assessed using Brissot's grading system. Increased serum iron and ferritin levels were found in 29% and 43% patients, respectively. Hepatic iron grades 0, I, II, III, and IV were present in 37%, 35%, 25%, 3%, and 0% of patients, respectively. A significant correlation was found between hepatic iron grade and serum ferritin (P = .0001). There was no correlation between hepatic iron grade and histological activity index or fibrosis score. In summary, we found a high proportion of patients with chronic hepatitis C had mild to moderate increase in hepatic iron content even when patients with alcoholism and recurrent transfusions were excluded. However, very few patients had severely increased iron load.