Multiple enzymic activities of human milk lactoferrin

Viruses and Human Milk: Transmission or Protection?

Human milk (HM) is considered the best source of nutrition for infant growth and health. This nourishment is unique and changes constantly during lactation to adapt to the physiological needs of the developing infant. It is also recognized as a potential route of transmission of some viral pathogens although the presence of a virus in HM rarely leads to a disease in an infant. This intriguing paradox can be explained by considering the intrinsic antiviral properties of HM. In this comprehensive and schematically presented review, we have described what viruses have been detected in HM so far and what their potential transmission risk through breastfeeding is. We have provided a description of all the antiviral compounds of HM, along with an analysis of their demonstrated and hypothesized mechanisms of action. Finally, we have also analyzed the impact of HM pasteurization and storage methods on the detection and transmission of viruses, and on the antiviral compounds of HM. We have highlighted that there is currently a deep knowledge on the potential transmission of viral pathogens through breastfeeding and on the antiviral properties of HM. The current evidence suggests that, in most cases, it is unnecessarily to deprive an infant of this high-quality nourishment and that the continuation of breastfeeding is in the best interest of the infant and the mother.

Lactoferrin as a Human Genome “Guardian”—An Overall Point of View

Structural abnormalities causing DNA modifications of the ethene and propanoadducts can lead to mutations and permanent damage to human genetic material. Such changes may cause premature aging and cell degeneration and death as well as severe impairment of tissue and organ function. This may lead to the development of various diseases, including cancer. In response to a damage, cells have developed defense mechanisms aimed at preventing disease and repairing damaged genetic material or diverting it into apoptosis. All of the mechanisms described above are part of the repertoire of action of Lactoferrin—an endogenous protein that contains iron in its structure, which gives it numerous antibacterial, antiviral, antifungal and anticancer properties. The aim of the article is to synthetically present the new and innovative role of lactoferrin in the protection of human genetic material against internal and external damage, described by the modulation mechanisms of the cell cycle at all its levels and the mechanisms of its repair.

A review on lactoferrin as a proton pump inhibitor

Lactoferrin (Lf) is a versatile natural milk-derived protein that exhibits multiple interesting biological activities. Since it is safe for human administration and currently manufactured using low cost and well-established large-scale processes, the Lf scientific community has been devoted at dissecting its mechanisms of action towards its more rational and efficient use for various applications. Emerging literature has identified proton pumping ATPases as molecular targets of Lf in different cellular models linked to distinct activities of this natural protein. Information on this subject has not been systematically analysed before, hence herein we review the current state of art on the effect of Lf on proton pumping ATPases. Though structurally different, we propose that Lf holds a proton pump inhibitor (PPI)-like activity based on the functional resemblance with the classical inhibitors of the stomach H⁺/K⁺-ATPase. The downstream events and outcomes of the PPI-like activity of Lf, as well as its impact for the development of improved Lf applications are also discussed.

Lactoferrin supplementation for taste and smell abnormalities among patients receiving cancer chemotherapy

PURPOSE

Taste and smell abnormalities (TSA) are common in patients receiving chemotherapy and may lead to altered nutritional intake, treatment withdrawal, and impaired quality of life. Lipid peroxidation in the oral cavity is one cause of TSA. Lactoferrin (LFN), an iron-binding salivary protein, reduces production of lipid oxidation byproducts and has been shown to reduce perception of unpleasant flavors. To assess the feasibility of LFN as a treatment for TSA, we conducted pilot investigations among patients with cancer who self-reported TSA following onset of chemotherapy. The primary objective was to assess change in subjective taste and smell perception from baseline to completion of 30 days of LFN supplementation.

METHODS

Patients were treated with 750 mg LFN daily for 30 days and followed for an additional 30 days without LFN. TSA was measured via the taste and smell questionnaire (TSQ) including taste (score 0-10), smell (score 0-6), and composite scores (0-16) (0 = no TSA) at baseline, day 30, and day 60.

RESULTS

A total of 26 patients enrolled; 19 remained on study at day 30 and 17 at day 60. Baseline mean TSQ scores were 6.5 (taste), 3.1 (smell), and 9.6 (composite). By day 30, mean composite TSQ score improved by 1.7 (p = 0.018); taste and smell improved by 0.6 (p = 0.062) and 1.1 (p = 0.042), respectively. From baseline to day 60, mean composite TSQ score improved by 3.8 (p < 0.0001); taste and smell improved by 1.9 (p = 0.001) and 1.8 (p = 0.003).

CONCLUSIONS

Further evaluation of LFN is warranted to determine its value for improving self-reported TSA among patients receiving chemotherapy.

Lactoferrin may inhibit the development of cancer via its immunostimulatory and immunomodulatory activities (Review)

Lactoferrin (Lf) is secreted by ectodermal tissue and has a structure similar to that of transferrin. Although Lf seems to be multifunctional, its main function is related to the natural defense system of mammals. The present review aims to highlight the major actions of Lf, including the regulation of cell growth, the inhibition of toxic compound formation, the removal of harmful free radicals and its important role in immune response regulation. Moreover, Lf has antibacterial, antiviral, antioxidant, anticancer and anti‑inflammatory activities. In addition, the use of Lf for functionalization of drug nanocarriers, with emphasis on tumor‑targeted drug delivery, is illustrated. Such effects serve as an important theoretical basis for its future development and application. In neurodegenerative diseases and the brains of elderly people, Lf expression is markedly upregulated. Lf may exert an anti‑inflammatory effect by inhibiting the formation of hydroxyl free radicals. Through its antioxidant properties, Lf can prevent DNA damage, thereby preventing tumor formation in the central nervous system. In addition, Lf specifically activates the p53 tumor suppressor gene.

Six catalytic activities and cytotoxicity of immunoglobulin G and secretory immunoglobulin A from human milk

In the milk of healthy women, antibodies were found with different catalytic activities (abzymes), which are absent in the sera of other healthy people. Moreover, it was previously shown that DNase antibodies-abzymes of patients with autoimmune diseases are cytotoxic to cancer cells. In this work, it was first shown that IgG and secretory IgA (sIgA) do not possess embryotoxicity; they practically do not affect the development of fertilized eggs of sea urchins but demonstrate sperm toxicity. After addition to the eggs of sperm preincubated with IgG and sIgA, the number of unfertilized eggs was increased, in the case of sIgA 1.6-fold higher than that for IgG. The suppression of the growth of MCF-7 breast cancer cells by sIgA was 2.2 times more effective than with IgG antibodies. The relative enzymatic activity of milk sIgA was higher than IgG (-fold): 1.9 (DNase), 4.6 (amylase), 1.7 (peroxidase), 1.3 (protease), 3.7 [hydrolysis of poly(C)], 3.3 [hydrolysis of poly(U)], and 1.7 (oxidation of 3,3'-diaminobenzidine). One of the possible reasons for the observed difference between sIgA and IgG could be that all 6 catalytic activities of sIgA were, on average, 2.6 times higher than that for IgG. Correlation coefficients between all the relative 6 enzymatic activities of IgG and sIgA and their toxicity to sea urchin sperm and to cancer cells were calculated. Maximum correlation coefficients were observed for DNase (+0.71), protease (+0.64) activities for sIgA, as well as protease (+0.59) and RNase (+0.77) of IgG with their toxicity toward sperm. The correlation coefficients were also high between peroxidase activity (+0.85) of sIgA and poly(U) hydrolysis by IgG (+0.58) with their suppression of tumor cell growth. It has been suggested that the catalytic activities of abzymes may be important in the manifestation of their sperm toxicity and inhibition of cancer cell growth.

How Enzymes, Proteins, and Antibodies Recognize Extended DNAs; General Regularities

X-ray analysis cannot provide quantitative estimates of the relative contribution of non-specific, specific, strong, and weak contacts of extended DNA molecules to their total affinity for enzymes and proteins. The interaction of different enzymes and proteins with long DNA and RNA at the quantitative molecular level can be successfully analyzed using the method of the stepwise increase in ligand complexity (SILC). The present review summarizes the data on stepwise increase in ligand complexity (SILC) analysis of nucleic acid recognition by various enzymes-replication, restriction, integration, topoisomerization, six different repair enzymes (uracil DNA glycosylase, Fpg protein from Escherichia coli, human 8-oxoguanine-DNA glycosylase, human apurinic/apyrimidinic endonuclease, RecA protein, and DNA-ligase), and five DNA-recognizing proteins (RNA helicase, human lactoferrin, alfa-lactalbumin, human blood albumin, and IgGs against DNA). The relative contributions of structural elements of DNA fragments "covered" by globules of enzymes and proteins to the total affinity of DNA have been evaluated. Thermodynamic and catalytic factors providing discrimination of unspecific and specific DNAs by these enzymes on the stages of primary complex formation following changes in enzymes and DNAs or RNAs conformations and direct processing of the catalysis of the reactions were found. General regularities of recognition of nucleic acid by DNA-dependent enzymes, proteins, and antibodies were established.

Enzymes as a Reservoir of Host Defence Peptides

Host defence peptides (HDPs) are powerful modulators of cellular responses to various types of insults caused by pathogen agents. To date, a wide range of HDPs, from species of different kingdoms including bacteria, plant and animal with extreme diversity in structure and biological activity, have been described. Apart from a limited number of peptides ribosomally synthesized, a large number of promising and multifunctional HDPs have been identified within protein precursors, with properties not necessarily related to innate immunity, consolidating the fascinating hypothesis that proteins have a second or even multiple biological mission in the form of one or more bio-active peptides. Among these precursors, enzymes constitute certainly an interesting group, because most of them are mainly globular and characterized by a fine specific internal structure closely related to their catalytic properties and also because they are yet little considered as potential HDP releasing proteins. In this regard, the main aim of the present review is to describe a panel of HDPs, identified in all canonical classes of enzymes, and to provide a detailed description on hydrolases and their corresponding HDPs, as there seems to exist a striking link between these structurally sophisticated catalysts and their high content in cationic and amphipathic cryptic peptides.

Comparison of Trace Elements in High-Molecular-Mass Multiprotein Complex and in Female Milk from Which It Was Obtained

Background

Many biological processes are performed by different protein complexes. During the association of proteins and enzymes forming specific complexes, the latter can include ions of various metal ions, which may be important for their formation and biological function.

Objective of the Studies

However, to date in the literature there are no data on metal ions that are part of any protein complexes.

Methods

A very stable multiprotein complex (~1000±100 kDa) was separated from other proteins of nine samples of female milk by gel filtration on Sepharose 4B. The content of microelements in the stable multiprotein complex and milk was analyzed using two-jet plasma atomic emission spectrometry.

Results

The content of different elements in milk on average decreased in the order: Ca>P>Mg>Al≥Zn≥Fe>Cu >B (0.76–3500 μg/g of dry milk powder), while the content of some elements was very low (Sr>Mn>Cr>Ba>Pb>Ag>Ni>Cd, <0.03–0.5 μg/g). The content of eight elements in stable multiprotein complex was 1.2-9.6-fold higher than in milk and increased in the order: Ca≈Mg<P<Al<Fe<Pb<Ba<Cr<Cd<Zn, while content of SPC eight metals was 12.3-110-fold higher: Cu (12.3)>B (19.7)>Ag (28.7)>Ni (38)≥Sr (110).

Conclusions

The analysis of the relative content of sixteen elements in human milk and oligomeric complexes of proteins was performed for the first time. Data on the content of metals indicate that during the formation of protein which associates the increase in the content of metal ions bound with proteins of the complex can occur. Such metal ions can be important for the formation and biological function of protein complexes.

Mass Spectrometry Analysis of Changes in Human Milk N/O-Glycopatterns at Different Lactation Stages

Human milk oligosaccharides are complex carbohydrates with multibiofunctional health benefits to newborns. Human milk free oligosaccharides (HMOs) are well characterized. However, changes in the N/O-glycome during lactation are poorly reported. Herein, we qualitatively and quantitatively investigated N/O-glycome profiles and their alteration in human milk at different lactation stages. N-Glycans were mainly fucosylated and nonsialylated, nonfucosylated throughout lactation. O-Glycans mainly consisted of sialylated and nonsialylated, nonfucosylated in colostrum and transitional milk, and fucosylated and nonfucosylated, nonsialylated in mature milk. Fucosylated and sialylated N-glycans gradually decreased and increased, respectively, as lactation progressed; O-glycans showed the reverse. Interestingly, changes in HMO abundance decreased during lactation, complementing HMG N/O-glycome changes. In conclusion, temporal HMG glycosylation changes provide the groundwork for developing infant formula that is closer to breast milk at different lactation stages.

The Impact of Lactoferrin on the Growth of Intestinal Inhabitant Bacteria

Lactoferrin (Lf) is an iron-binding milk glycoprotein that promotes the growth of selected probiotic strains. The effect of Lf on the growth and diversification of intestinal microbiota may have an impact on several issues, including (i) strengthening the permeability of the epithelial cell monolayer, (ii) favoring the microbial antagonism that discourages the colonization and proliferation of enteric pathogens, (iii) enhancing the growth and maturation of cell-monolayer components and gut nerve fibers, and (iv) providing signals to balance the anti- and pro-inflammatory responses resulting in gut homeostasis. Given the beneficial role of probiotics, this contribution aims to review the current properties of bovine and human Lf and their derivatives in in vitro probiotic growth and Lf interplay with microbiota described in the piglet model. By using Lf as a component in pharmacological products, we may enable novel strategies that promote probiotic growth while conferring antimicrobial activity against multidrug-resistant microorganisms that cause life-threatening diseases, especially in neonates.

Structural and Aggregation Features of a Human κ-Casein Fragment with Antitumor and Cell-Penetrating Properties

Intrinsically disordered proteins play a central role in dynamic regulatory and assembly processes in the cell. Recently, a human κ-casein proteolytic fragment called lactaptin (8.6 kDa) was found to induce apoptosis of human breast adenocarcinoma MCF-7 and MDA-MB-231 cells with no cytotoxic activity toward normal cells. Earlier, we had designed some recombinant analogs of lactaptin and compared their biological activity. Among these analogs, RL2 has the highest antitumor activity, but the amino acid residues and secondary structures that are responsible for RL2's activity remain unclear. To elucidate the structure-activity relations of RL2, we studied the structural and aggregation features of this fairly large intrinsically disordered fragment of human milk κ-casein by a combination of physicochemical methods: NMR, paramagnetic relaxation enhancement (PRE), Electron Paramagnetic Resonance (EPR), circular dichroism, dynamic light scattering, atomic force microscopy, and a cytotoxic activity assay. It was found that in solution, RL2 exists as stand-alone monomeric particles and large aggregates. Whereas the disulfide-bonded homodimer turned out to be more prone to assembly into large aggregates, the monomer predominantly forms single particles. NMR relaxation analysis of spin-labeled RL2 showed that the RL2 N-terminal region, which is essential not only for multimerization of the peptide but also for its proapoptotic action on cancer cells, is more ordered than its C-terminal counterpart and contains a site with a propensity for α-helical secondary structure.

Cow Milk Lactoferrin Possesses Several Catalytic Activities

Lactoferrin (LF) is a Fe³⁺-binding glycoprotein, that was first recognized in milk and then in other epithelial secretions and barrier body fluids to which many different functions have been attributed to LF including protection from iron-induced lipid peroxidation, immunomodulation, cell growth regulation, DNA and RNA binding, as well as transcriptional activation, еtс. The polyfunctional physiological role of LF is still unclear, but it has been suggested to be responsible for primary defense against microbial and viral infections. It was shown previously that human milk LF possesses several enzymatic activities: DNase, RNase, ATPase, phosphatase, and amylase. Analysis of human, cow, horse, buffalo and camel LF showed a highly conserved three-dimensional (3D) structure including only detail differences in the species. Recently, it was shown that similar to human cow LF possesses DNase and RNase activities. Using different methods here we have shown for the first time that LFs from the milk of seven cows of different breeds possess high peroxidase, protease, amylase, protease, and phosphatase activities. Protease activity of cow LFs was activated by Mg²⁺ and Ca²⁺ ions. In contrast to human LFs, ATPase activity was revealed only in three of seven cow LF preparations. The discovery that LF possesses these activities may contribute to understanding the multiple physiological functions of this extremely polyfunctional protein including its protective role against microbial and viral infections.

A 90-day subchronic toxicology screen of genetically modified rice Lac-3 and its effects on the gut microbiota in Sprague-Dawley rats

A 90-day subchronic toxicology screen of genetically modified (GM) rice Lac-3 expressing human lactoferrin (hLF) and its effects on the gut microbiota were studied in comparison to non-GM rice fed to Sprague-Dawley (SD) rats. Three different dietary concentrations (17.5%, 35% and 70%, w/w) of the GM rice or its corresponding non-GM rice were used. Additionally, the phylotypes of gut microbiota in the control group, the 70% GM rice diet group and the 70% non-GM rice diet group on day 90 were determined by 16S rRNA sequencing. The results of the 90-day subchronic feeding study demonstrated that the GM rice Lac-3 containing human lactoferrin (LF) gene is considered as safe as the non-GM rice. The results of bacterial 16S rRNA sequencing showed that the structure of gut microbiota in the 70% GM group slightly changed when compared with the control group and the 70% non-GM group. There were no significant differences in the microbiota diversity among the three groups.

Lactoferrin is a natural inhibitor of plasminogen activation

The plasminogen system is essential for dissolution of fibrin clots, and in addition, it is involved in a wide variety of other physiological processes, including proteolytic activation of growth factors, cell migration, and removal of protein aggregates. On the other hand, uncontrolled plasminogen activation contributes to many pathological processes (e.g. tumor cells' invasion in cancer progression). Moreover, some virulent bacterial species (e.g. Streptococci or Borrelia) bind human plasminogen and hijack the host's plasminogen system to penetrate tissue barriers. Thus, the conversion of plasminogen to the active serine protease plasmin must be tightly regulated. Here, we show that human lactoferrin, an iron-binding milk glycoprotein, blocks plasminogen activation on the cell surface by direct binding to human plasminogen. We mapped the mutual binding sites to the N-terminal region of lactoferrin, encompassed also in the bioactive peptide lactoferricin, and kringle 5 of plasminogen. Finally, lactoferrin blocked tumor cell invasion in vitro and also plasminogen activation driven by Borrelia Our results explain many diverse biological properties of lactoferrin and also suggest that lactoferrin may be useful as a potential tool for therapeutic interventions to prevent both invasive malignant cells and virulent bacteria from penetrating host tissues.

Lactoferrin, chitosan and Melaleuca alternifolia-natural products that show promise in candidiasis treatment

The evolution of microorganisms resistant to many medicines has become a major challenge for the scientific community around the world. Motivated by the gravity of such a situation, the World Health Organization released a report in 2014 with the aim of providing updated information on this critical scenario. Among the most worrying microorganisms, species from the genus Candida have exhibited a high rate of resistance to antifungal drugs. Therefore, the objective of this review is to show that the use of natural products (extracts or isolated biomolecules), along with conventional antifungal therapy, can be a very promising strategy to overcome microbial multiresistance. Some promising alternatives are essential oils of Melaleuca alternifolia (mainly composed of terpinen-4-ol, a type of monoterpene), lactoferrin (a peptide isolated from milk) and chitosan (a copolymer from chitin). Such products have great potential to increase antifungal therapy efficacy, mitigate side effects and provide a wide range of action in antifungal therapy.

Human serum and milk albumins are metal-dependent DNases

It is known that that human serum albumin (HSA) and alpha-lactalbumin (LA) possess DNA-binding sites. Electrophoretically homogeneous HSA and LA containing no canonical enzymes were isolated from human sera and milk. Here we have analyzed for the first time the possibility of DNA hydrolysis by these proteins. It was shown that HSA possesses metal-dependent DNase activity, while LA cannot hydrolyze DNA. Several rigid criteria have been applied to show that DNase activity is an intrinsic property of HSA from human sera and milk. HSA preparations were inactive after their dialysis against EDTA or in the presence of EDTA, but were activated after addition of several external metal ions: Mn²⁺  > Mg²⁺  > Ca²⁺ . The best activation of HSA preparations was observed in the presence of two metal ions: Mg²⁺ +Ca²⁺  > Mn²⁺  + Ca²⁺  ≥ Mn²⁺  + Mg²⁺ . In contrast to DNases having only one pH optimum, HSA preparations demonstrated two well-pronounced optima at pH 5.7-5.9 and 6.9-7.1 as well as a weak optimum at pH 8.4-8.6. These results demonstrate the diversity of HSA in the DNA hydrolysis at various pHs and in activation by various metal cofactors. Possible reasons for the diversity of HSA preparations are discussed. © 2018 IUBMB Life, 70(6):501-510, 2018.

Selection of possible signature peptides for the detection of bovine lactoferrin in infant formulas by LC-MS/MS

An LC-MS/MS assay based on a signature peptide was developed and fully validated for the quantitation of bovine lactoferrin in infant formulas. Three unreported signature peptides were derived and identified from the tryptic peptides of bovine lactoferrin. The peptide ETTVFENLPEK was used for quantification based on assay performance. The blank matrix camel milk powder and bovine lactoferrin protein standards were mixed and spiked with stable isotope-labeled internal standard to establish a calibration curve. The established method was extensively validated by determining the linearity (R² > 0.999), sensitivity (limit of quantitation, 0.16 mg/100 g), recovery (83.1–91.6%), precision (RSD < 5.4%) and repeatability (RSD < 7.7%). To validate the applicability of the method, four different brands of infant formulas in China were analysed. The acquired contents of bovine lactoferrin were 52.60–150.56 mg/100 g.

Bovine Lactoferrin Inhibits Dengue Virus Infectivity by Interacting with Heparan Sulfate, Low-Density Lipoprotein Receptor, and DC-SIGN

Bovine lactoferrin (bLF) presents in milk and has been shown to inhibit several viral infections. Effective drugs are unavailable for the treatment of dengue virus (DENV) infection. In this study, we evaluated the antiviral effect of bLF against DENV infection in vivo and in vitro. Bovine LF significantly inhibited the infection of the four serotypes of DENV in Vero cells. In the time-of-drug addition test, DENV-2 infection was remarkably inhibited when bLF was added during or prior to the occurrence of virus attachment. We also revealed that bovine LF blocks binding between DENV-2 and the cellular membrane by interacting with heparan sulfate (HS), dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), and low-density lipoprotein receptors (LDLR). In addition, bLF inhibits DENV-2 infection and decreases morbidity in a suckling mouse challenge model. This study supports the finding that bLF may inhibit DENV infection by binding to the potential DENV receptors.

Bovine lactoferrin activity against Chikungunya and Zika viruses

Chikungunya (CHIKV) and Zika (ZIKV) viruses are arboviruses which have recently broken their sylvatic isolation and gone on to spread rampantly among humans in some urban areas of the world, especially in Latin America. Given the lack of effective interventions against such viruses, the aim of this work was to evaluate the antiviral potential of bovine lactoferrin (bLf) in their infections. Through viability, plaque, immunofluorescence and nucleic acid quantification assays, our data show that bLf exerts a dose-dependent strong inhibitory effect on the infection of Vero cells by the aforementioned arboviruses, reducing their infection efficiency by up to nearly 80 %, with no expressive cytotoxicity, and that such antiviral activity occurs at the levels of input and output of virus particles. These findings reveal that bLf antimicrobial properties are extendable to CHIKV and ZIKV, underlining a generic inhibition mechanism that can be explored to develop a potential strategy against their infections.

Human Milk Cells Contain Numerous miRNAs that May Change with Milk Removal and Regulate Multiple Physiological Processes

Human milk (HM) is a complex biofluid conferring nutritional, protective and developmental components for optimal infant growth. Amongst these are maternal cells, which change in response to feeding and were recently shown to be a rich source of miRNAs. We used next generation sequencing to characterize the cellular miRNA profile of HM collected before and after feeding. HM cells conserved higher miRNA content than the lipid and skim HM fractions or other body fluids, in accordance with previous studies. In total, 1467 known mature and 1996 novel miRNAs were identified, with 89 high-confidence novel miRNAs. HM cell content was higher post-feeding (p < 0.05), and was positively associated with total miRNA content (p = 0.014) and species number (p < 0.001). This coincided with upregulation of 29 known and 2 novel miRNAs, and downregulation of 4 known and 1 novel miRNAs post-feeding, but no statistically significant change in expression was found for the remaining miRNAs. These findings suggest that feeding may influence the miRNA content of HM cells. The most highly and differentially expressed miRNAs were key regulators of milk components, with potential diagnostic value in lactation performance. They are also involved in the control of body fluid balance, thirst, appetite, immune response, and development, implicating their functional significance for the infant.

Lactaptin induces p53-independent cell death associated with features of apoptosis and autophagy and delays growth of breast cancer cells in mouse xenografts

Lactaptin, the proteolytic fragment of human milk kappa-casein, induces the death of various cultured cancer cells. The mechanisms leading to cell death after lactaptin treatment have not been well characterized. In this study the in vivo and in vitro effects of a recombinant analogue of lactaptin (RL2) were examined. Following treatment with the recombinant analogue of lactaptin strong caspase -3, -7 activation was detected. As a consequence of caspase activation we observed the appearance of a sub-G1 population of cells with subdiploid DNA content. Dynamic changes in the mRNA and protein levels of apoptosis-related genes were estimated. No statistically reliable differences in p53 mRNA level or protein level were found between control and RL2-treated cells. We observed that RL2 constitutively suppressed bcl-2 mRNA expression and down regulated Bcl-2 protein expression in MDA-MB-231 cells. We demonstrated that RL2 penetrates cancer and non-transformed cells. Identification of the cellular targets of the lactaptin analogue revealed that α/β-tubulin and α-actinin-1 were RL2-bound proteins. As the alteration in cellular viability in response to protein stimulus can be realized not only by way of apoptosis but also by autophagy, we examined the implications of autophagy in RL2-dependent cell death. We also found that RL2 treatment induces LC3-processing, which is a hallmark of autophagy. The autophagy inhibitor chloroquine enhanced RL2 cytotoxicity to MDA-MB-231 cells, indicating the pro-survival effect of RL2-dependent autophagy. The antitumour potential of RL2 was investigated in vivo in mouse xenografts bearing MDA-MB-231 cells. We demonstrated that the recombinant analogue of lactaptin significantly suppressed the growth of solid tumours. Our results indicate that lactaptin could be a new molecule for the development of anticancer drugs.

Recognition of specific and nonspecific DNA by human lactoferrin

The general principles of recognition of nucleic acids by proteins are among the most exciting problems of molecular biology. Human lactoferrin (LF) is a remarkable protein possessing many independent biological functions, including interaction with DNA. In human milk, LF is a major DNase featuring two DNA-binding sites with different affinities for DNA. The mechanism of DNA recognition by LF was studied here for the first time. Electrophoretic mobility shift assay and fluorescence measurements were used to probe for interactions of the high-affinity DNA-binding site of LF with a series of model-specific and nonspecific DNA ligands, and the structural determinants of DNA recognition by LF were characterized quantitatively. The minimal ligands for this binding site were orthophosphate (K(i)  = 5 mM), deoxyribose 5'-phosphate (K(i)  = 3 mM), and different dNMPs (K(i)  = 0.56-1.6 mM). LF interacted additionally with 9-12 nucleotides or nucleotide pairs of single- and double-stranded ribo- and deoxyribooligonucleotides of different lengths and sequences, mainly through weak additive contacts with internucleoside phosphate groups. Such nonspecific interactions of LF with noncognate single- and double-stranded d(pN)(10) provided ~6 to ~7.5 orders of magnitude of the enzyme affinity for any DNA. This corresponds to the Gibbs free energy of binding (ΔG(0)) of -8.5 to -10.0 kcal/mol. Formation of specific contacts between the LF and its cognate DNA results in an increase of the DNA affinity for the enzyme by approximately 1 order of magnitude (K(d)  = 10 nM; ΔG(0)  ≈ -11.1 kcal/mol). A general function for the LF affinity for nonspecific d(pN)(n) of different sequences and lengths was obtained, giving the K(d) values comparable with the experimentally measured ones. A thermodynamic model was constructed to describe the interactions of LF with DNA.

Functional glycans and glycoconjugates in human milk

Human milk contains complex carbohydrates that are important dietary factors with multiple functions during early life. Several aspects of these glycostructures are human specific; some aspects vary between lactating women, and some change during the course of lactation. This review outlines how variability of complex glycostructures present in human milk is linked to changing infants' needs.

Lactoferrin and necrotizing enterocolitis

Lactoferrin (LF) is a multifunctional protein and a member of the transferrin family. LF and lysozyme in breast milk kill bacteria. In the stomach, pepsin digests and releases a potent peptide antibiotic called lactoferricin from native LF. The antimicrobial characteristics of LF may facilitate a healthy intestinal microbiome. LF is the major whey in human milk; its highest concentration is in colostrum. This fact highlights early feeding of colostrum and also fresh mature milk as a way to prevent necrotizing enterocolitis.

Lactoferrin a multiple bioactive protein: an overview

BACKGROUND

Lactoferrin (Lf) is an 80kDa iron-binding glycoprotein of the transferrin family. It is abundant in milk and in most biological fluids and is a cell-secreted molecule that bridges innate and adaptive immune function in mammals. Its protective effects range from anticancer, anti-inflammatory and immune modulator activities to antimicrobial activities against a large number of microorganisms. This wide range of activities is made possible by mechanisms of action involving not only the capacity of Lf to bind iron but also interactions of Lf with molecular and cellular components of both hosts and pathogens.

SCOPE OF REVIEW

This review summarizes the activities of Lf, its regulation and potential applications.

MAJOR CONCLUSIONS

The extensive uses of Lf in the treatment of various infectious diseases in animals and humans has been the driving force in Lf research however, a lot of work is required to obtain a better understanding of its activity.

GENERAL SIGNIFICANCE

The large potential applications of Lf have led scientists to develop this nutraceutical protein for use in feed, food and pharmaceutical applications. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

Recombinant lactoferrin (Lf) of Vechur cow, the critical breed of Bos indicus and the Lf gene variants

Vechur cow, categorized as a critically maintained breed by the FAO, is a unique breed of Bos indicus due to its extremely small size, less fodder intake, adaptability, easy domestication and traditional medicinal property of the milk. Lactoferrin (Lf) is an iron-binding glycoprotein that is found predominantly in the milk of mammals. The full coding region of Lf gene of Vechur cow was cloned, sequenced and expressed in a prokaryotic system. Antibacterial activity of the recombinant Lf showed suppression of bacterial growth. To the best of our knowledge this is the first time that the full coding region of Lf gene of B. indicus Vechur breed is sequenced, successfully expressed in a prokaryotic system and characterized. Comparative analysis of Lf gene sequence of five Vechur cows with B. taurus revealed 15 SNPs in the exon region associated with 11 amino acid substitutions. The amino acid arginine was noticed as a pronounced substitution and the tertiary structure analysis of the BLfV protein confirmed the positions of arginine in the β sheet region, random coil and helix region 1. Based on the recent reports on the nutritional therapies of arginine supplementation for wound healing and for cardiovascular diseases, the higher level of arginine in the lactoferrin protein of Vechur cow milk provides enormous scope for further therapeutic studies.

Discovery and development of a synthetic peptide derived from lactoferrin for clinical use

There is an urgent need to develop new antimicrobial drugs especially for combating the rise of infections caused by multi-resistant pathogens such as MRSA and VRSA. The problem of antibiotic resistant micro-organisms is expected to increase disproportionally and controlling of infections is becoming difficult because of the rapid spread of those micro-organisms. Primary therapy with classical antibiotics is becoming more ineffective. Combinational therapy of antibiotics with antimicrobial peptides (AMP's) has been suggested as an alternative approach to improve treatment outcome. Their unique mechanism of action and safety profile makes AMP's appealing candidates for simultaneous or sequential use in different cases of infections. In this review, for antimicrobial treatment the application of synthetic antimicrobial peptide hLF(1-11), derived from the first 11 amino acids of human lactoferrin is evaluated in both pre-clinical and clinical settings. Present information indicates that this derivate from lactoferrin is well tolerated in pre-clinical tests and clinical trials and thus hLF(1-11) is an interesting candidate for further exploration in various clinical indications of obscure infections, including meningitis. Another approach of using AMP's is their use in prevention of infections e.g. as coating for dental or bone implants or in biosensing applications or useful as infection specific radiopharmaceutical.

Molecular evolution of the transferrin family and associated receptors

BACKGROUND

In vertebrates, serum transferrins are essential iron transporters that have bind and release Fe(III) in response to receptor binding and changes in pH. Some family members such as lactoferrin and melanotransferrin can also bind iron while others have lost this ability and have gained other functions, e.g., inhibitor of carbonic anhydrase (mammals), saxiphilin (frogs) and otolith matrix protein 1 (fish).

SCOPE OF REVIEW

This article provides an overview of the known transferrin family members and their associated receptors and interacting partners.

MAJOR CONCLUSIONS

The number of transferrin genes has proliferated as a result of multiple duplication events, and the resulting paralogs have developed a wide array of new functions. Some homologs in the most primitive metazoan groups resemble both serum and melanotransferrins, but the major yolk proteins show considerable divergence from the rest of the family. Among the transferrin receptors, the lack of TFR2 in birds and reptiles, and the lack of any TFR homologs among the insects draw attention to the differences in iron transport and regulation in those groups.

GENERAL SIGNIFICANCE

The transferrin family members are important because of their clinical significance, interesting biochemical properties, and evolutionary history. More work is needed to better understand the functions and evolution of the non-vertebrate family members. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

Lactoferrin in human tumours: immunohistochemical investigations during more than 25 years

Lactoferrin (LF) is an iron-binding glycoprotein of the transferrin family, today known to have multifunctional physiological activities. In humans, under normal conditions, LF has been found in blood, mucosal secretions, gastrointestinal fluids, urine and mostly in milk and colostrum. The first pioneering immunohistochemical report about LF distribution in human tissues dated in 1978; successively, many studies have been performed to analyze the LF immunohistochemical pattern in different normal and neoplastic tissues. In this review, we present data from literature concerning the evidence of LF in tumors together with those by us obtained during more than 25 years; the immunohistochemical applications to human neoplastic tissues have been done to investigate the LF pathogenetic role as well as its activity in cancer. After a systematic analysis of LF immunoreactivity in different human districts, a possible explanation for its presence and function has been modulated for each site or tissue, according to experimental evidences obtained either by in vivo as well as by in vitro studies.

New concepts of microbial translocation in the neonatal intestine: mechanisms and prevention

Bacterial translocation from the gastrointestinal tract is an important pathway initiating late-onset sepsis and necrotizing enterocolitis in very low-birth-weight infants. The emerging intestinal microbiota, nascent intestinal epithelia, naive immunity, and suboptimal nutrition (lack of breast milk) have roles in facilitating bacterial translocation. Feeding lactoferrin, probiotics, or prebiotics has presented exciting possibilities to prevent bacterial translocation in preterm infants, and clinical trials will identify the most safe and efficacious prevention and treatment strategies.

Recombinant analogs of a novel milk pro-apoptotic peptide, lactaptin, and their effect on cultured human cells

We recently isolated and characterized a human milk peptide, lactaptin, which induced apoptosis of cultured human MCF-7 cells. Lactaptin was identified as a proteolytic fragment of human kappa-casein. Here, we generated two recombinant analogs of the peptide, RL1 and RL2, containing truncated and complete amino acid sequences of lactaptin, respectively. Analogs were produced in E.coli, purified and assayed for biological activity on cultured human MCF-7 cells. RL1 was shown to induce only a small decrease in cell viability, whereas RL2 lowered the viability of MCF-7 cells by 60%. This reduction in MCF-7 cell viability was associated with apoptosis, which was indicated by phosphatidilserine externalization and caspase-7 activation. The viability of A549 and Hep-2 cells was also reduced by RL2, albeit to a lesser degree than seen with MCF-7 cells; this reduced viability was not accompanied by apoptosis. Non-malignant human mesenchymal stem cells (MSC) were completely resistant to RL2 action.

DNA, oligosaccharides, and mononucleotides stimulate oligomerization of human lactoferrin

Using small-angle X-ray scattering (SAXS), light scattering (LS), and soft laser ablation we have shown that lactoferrin (LF) in solution at neutral pH is oligomerized in the absence of salt or at physiological salt concentrations. The level of oligomerization depends on the concentration of LF, KCl or NaCl, and on the duration of the protein storage in solution. At the concentrations comparable with those in human milk (1-6 mg/ml), the average radius of gyration (R(g)) values of LF can attain 400-480 A, while fresh solution of previously lyophylized LF demonstrate a lower average R(g) (50-100 A), and R(g) value characterizing the LF monomer formed at 1 M NaCl is 26.7 A. The addition of oligonucleotides, oligosaccharides, or mononucleotides to LF in the presence or in the absence of KCl with different level of initial oligomerization accelerates the oligomerization rate and increases the R(g) values up to approximately 600-700 A, which correspond to associates containing ten or more protein molecules. During gel filtration on Sepharose 4B, high-degree LF oligomers dissociate nearly completely forming different degraded complexes, but in some cases it is possible to reveal small amount of a decamer. A possible role for oligomerization of LF, a highly polyfunctional protein, for its different biological activities is discussed.

Isolation of cell-free DNA from plasma by chromatography on short monolithic columns and quantification of non-apoptotic fragments by real-time polymerase chain reaction

Human plasma is an important medical substance and a raw material for production of various therapeutics. During blood sampling, storage and processing, genomic DNA is released into plasma from nucleated blood cells that are damaged in the course of the procedure. In order to determine the concentration of contaminating DNA in plasma, we developed a method for DNA isolation by using anion-exchange chromatography on a BIA Separations CIM (convective interaction media) diethylaminoethyl column. DNA was quantified by SYBR Green based real-time polymerase chain reaction. The concentration of cell-free, non-apoptotic DNA in plasma ranged between 0.06 and 22.5 ng/ml. As substantial volumes of plasma or whole blood are administered directly into the vascular system, a recipient is exposed to high amounts of cell-free DNA, several orders of magnitude higher than the amount found in other biologicals.

Pre-germinated brown rice could enhance maternal mental health and immunity during lactation

BACKGROUND

Rice is a dietary staple worldwide, especially pre-germinated brown rice has recently been widely served in Japan because of its abundant nutrition. Relationship between lactation and pre-germinated brown rice has attracted interest in terms of mental health and immunity.

AIM OF THE STUDY

To demonstrate that Japanese foods are beneficial for psychosomatic health, the effects of pre-germinated brown rice on the mental status and immunological features during lactation were investigated.

METHODS

Forty-one breast-feeding mothers were recruited, and randomly divided into two groups. One group took pre-germinated brown rice and the other white rice (control) as their staple diet for 2 weeks. The Profile of Mood States (POMS) and salivary amylase activity as psychological indices and secretory IgA (s-IgA) and lactoferrin (LTF) in breast milk as immunological indices were determined before and after dietary intervention, and changes were investigated.

RESULTS

In the psychological assessment, the scores of depression, anger-hostility, and fatigue were decreased on POMS analysis in the pre-germinated brown rice diet group, resulting in a significant decrease in total mood disturbance (TMD). The salivary amylase activity measurement suggested that resistance to stress was increased in the pre-germinated brown rice diet group. On the immunological assessment, the s-IgA level was significantly increased in the pre-germinated brown rice diet group.

CONCLUSION

We have shown that pre-germinated brown rice may have beneficial effects on psychosomatic health.

Immunochemical assay for deoxyribonuclease activity in body fluids

We have developed two microtiter plate assays to quantify the deoxyribonuclease activity in biological fluids. Both assays are based on hydrolysis of biotinylated and fluorescein-labeled DNA substrates, with subsequent immunochemical detection of non-digested DNA. The assay based on hydrolysis of 974 bp PCR product labeled with biotinylated forward and fluorescein-labeled reverse primers is more sensitive (0.05 U/ml) and convenient for quantifying the DNase activity in biological fluids than the assay based on hydrolysis of double-labeled 20 bp oligonucleotide. The DNase activity in urine and blood plasma of healthy donors was measured using the PCR product-based assay. Urine samples revealed greater activity, 1.49+/-1.41 U/ml; blood plasma DNase I-like activity was 0.36+/-0.20 U/ml. DNase II-like activity was not detected in the plasma samples. The data obtained confirm that DNase I-like enzymes are responsible for the majority of deoxyribonuclease activity in blood plasma.

Antimicrobial peptides and proteins, exercise and innate mucosal immunity

This review examines the question of whether exercise can be used as an experimental model to further our understanding of innate antimicrobial peptides and proteins (AMPs) and their role in susceptibility to infection at mucosal surfaces. There is strong evidence to suggest that AMPs, in combination with cellular and physical factors, play an important role in preventing infection. Although AMPs act directly on microorganisms, there is increasing recognition that they also exert their protective effect via immunomodulatory mechanisms, especially in noninflammatory conditions. Further studies that manipulate physiologically relevant concentrations of AMPs are required to shed light on the role they play in reducing susceptibility to infection. Evidence shows that in various form prolonged and/or exhaustive exercise is a potent modulator of the immune system, which can either sharpen or blunt the immune response to pathogens. The intensity and duration of exercise can be readily controlled in experimental settings to manipulate the degree of physical stress. This would allow for an investigation into a potential dose–response effect between exercise and AMPs. In addition, the use of controlled exercise could provide an experimental model by which to examine whether changes in the concentration of AMPs alters susceptibility to illness.

Effect of fish skin mucus on the soluble proteome of Vibrio salmonicida analysed by 2-D gel electrophoresis and tandem mass spectrometry

Vibrio salmonicida is the causative agent of cold-water vibriosis in farmed marine fish species. Adherence of pathogenic bacteria to mucosal surfaces is considered to be the first steps in the infective processes, and proteins involved are regarded as virulence factors. The global protein expression profile of V. salmonicida, grown with and without the presence of fish skin mucus in the synthetic media, was compared. Increased levels of proteins involved in motility, oxidative stress responses, and general stress responses were demonstrated as an effect of growth in the presence of mucus compared to non-mucus containing media. Enhanced levels of the flagellar proteins FlaC, FlaD and FlaE indicate increased motility capacity, while enhanced levels of the heat shock protein DnaK and the chaperonin GroEL indicate a general stress response. In addition, we observed that peroxidases, TPx.Grx and AhpC, involved in the oxidative stress responses, were induced by mucus proteins. The addition of mucus to the culture medium did not significantly alter the growth rate of V. salmonicida. An analysis of mucus proteins suggests that the mucus layer harbours a protein species that potentially possesses catalytic activity against DNA, and a protein with iron chelating activity. This study represents the first V. salmonicida proteomic analysis, and provides specific insight into the proteins necessary for the bacteria to challenge the skin mucus barrier of the fish.