Three-dimensional structure of lactoferrin in various functional states

Valpalf®: A New Nutraceutical Formulation Containing Bovine Lactoferrin That Exhibits Potentiated Biological Activity

As a nutraceutical, bovine lactoferrin (bLf), an iron-binding glycoprotein involved in innate immunity, is gaining elevated attention for its ability to exert pleiotropic functions and to be exceptionally tolerated even at high dosages. Some of bLf's activities, including its anti-inflammatory and antioxidant, are tightly linked to its ability to both chelate iron and enter inside the cell nucleus. Here, we present data about Valpalf®, a new formulation containing bLf, sodium citrate, and sodium bicarbonate at a molar ratio of 10-3. In the present study, Valpalf® exhibits superior iron-binding capacity, resistance to tryptic digestion, and a greater capacity to accumulate into the nucleus over time when compared to the native bLf alone. In agreement, Valpalf® effectively reduces interleukin(IL)-6 levels in lipopolysaccharide-stimulated macrophages and modulates the expression of antioxidant enzymes, such as superoxide dismutase 1 and 2, in phorbol-12-myristate-13-acetate-stimulated monocytes. Of note, this potentiated bioactivity was corroborated in a retrospective study on the treatment of anemia of inflammation in hereditary thrombophilic pregnant and non-pregnant women, demonstrating that Valpalf® improves hematological parameters and reduces serum IL-6 levels to a higher extent than bLf alone.

DNA-based molecular recognition system for lactoferrin biosensing

The paper describes the development of a novel DNA oligonucleotide-based affinity bioreceptor that binds to lactoferrin, a glycoprotein-type immunomodulator. The research was performed using surface plasmon resonance method to investigate affinity of various types of oligonucleotides to the target protein. The 72 base pair-long 5'[(TAGAGGATCAAA)AAA]4TAGAGGATCAAA3' sequence with the highest affinity to lactoferrin was selected for further investigations. Kinetic analysis of the interaction between selected DNA and lactoferrin provided rate and equilibrium constants: ka = (2.49 ± 0.03)∙104 M-1∙s-1, kd = (1.89 ± 0.02)∙10-3 s-1, KA = (0.13 ± 0.05)∙108 M-1, and KD = (7.61 ± 0.18)∙10-8 M. Thermodynamic study conducted to determine the ΔH0, ΔS0, and ΔG0 for van't Hoff characteristic in the temperature range of 291.15-305.15 K, revealed the complex formation as endothermic and entropically driven. The chosen DNA sequence's selectivity towards lactoferrin was confirmed with interferents' response constituting <3 % of the response to lactoferrin. SPR analysis justified utility of the designed DNA oligonucleotide for Lf determination, with LOD of 4.42∙10-9 M. Finally, the interaction between lactoferrin and DNA was confirmed by electrochemical impedance spectroscopy, providing the basis for further quantitative assay of lactoferrin using the developed DNA-based bioreceptor. The interactions were performed under immobilized DNA ligand conditions, thus reflecting the sensor's surface, which facilitates their transfer to other label-free biosensor technologies.

The Multifaceted Roles of Bovine Lactoferrin: Molecular Structure, Isolation Methods, Analytical Characteristics, and Biological Properties

Bovine lactoferrin (bLF) is widely known as an iron-binding glycoprotein from the transferrin family. The bLF molecule exhibits a broad spectrum of biological activity, including iron delivery, antimicrobial, antiviral, immunomodulatory, antioxidant, antitumor, and prebiotic functions, thereby making it one of the most valuable representatives for biomedical applications. Remarkably, LF functionality might completely differ in dependence on the iron saturation state and glycosylation patterns. Recently, a violently growing demand for bLF production has been observed, mostly for infant formulas, dietary supplements, and functional food formulations. Unfortunately, one of the reasons that inhibit the development of the bLF market and widespread protein implementation is related to its negligible amount in both major sources─colostrum and mature milk. This study provides a comprehensive overview of the significance of bLF research by delineating the key structural characteristics of the protein and elucidating their impact on its physicochemical and biological properties. Progress in the development of optimal isolation techniques for bLF is critically assessed, alongside the challenges that arise during its production. Furthermore, this paper presents a curated list of the most relevant instrumental techniques for the characterization of bLF. Lastly, it discusses the prospective applications and future directions for bLF-based formulations, highlighting their potential in various fields.

To Boost or to Reset: The Role of Lactoferrin in Energy Metabolism

Many pathological conditions, including obesity, diabetes, hypertension, heart disease, and cancer, are associated with abnormal metabolic states. The progressive loss of metabolic control is commonly characterized by insulin resistance, atherogenic dyslipidemia, inflammation, central obesity, and hypertension, a cluster of metabolic dysregulations usually referred to as the "metabolic syndrome". Recently, nutraceuticals have gained attention for the generalized perception that natural substances may be synonymous with health and balance, thus becoming favorable candidates for the adjuvant treatment of metabolic dysregulations. Among nutraceutical proteins, lactoferrin (Lf), an iron-binding glycoprotein of the innate immune system, has been widely recognized for its multifaceted activities and high tolerance. As this review shows, Lf can exert a dual role in human metabolism, either boosting or resetting it under physiological and pathological conditions, respectively. Lf consumption is safe and is associated with several benefits for human health, including the promotion of oral and gastrointestinal homeostasis, control of glucose and lipid metabolism, reduction of systemic inflammation, and regulation of iron absorption and balance. Overall, Lf can be recommended as a promising natural, completely non-toxic adjuvant for application as a long-term prophylaxis in the therapy for metabolic disorders, such as insulin resistance/type II diabetes and the metabolic syndrome.

Lactoferrin as a Component of Pharmaceutical Preparations: An Experimental Focus

Lactoferrin is an 80 kDa monomeric glycoprotein that exhibits multitask activities. Lactoferrin properties are of interest in the pharmaceutical field for the design of products with therapeutic potential, including nanoparticles and liposomes, among many others. In antimicrobial preparations, lactoferrin has been included either as a main bioactive component or as an enhancer of the activity and potency of first-line antibiotics. In some proposals based on nanoparticles, lactoferrin has been included in delivery systems to transport and protect drugs from enzymatic degradation in the intestine, favoring the bioavailability for the treatment of inflammatory bowel disease and colon cancer. Moreover, nanoparticles loaded with lactoferrin have been formulated as delivery systems to transport drugs for neurodegenerative diseases, which cannot cross the blood-brain barrier to enter the central nervous system. This manuscript is focused on pharmaceutical products either containing lactoferrin as the bioactive component or formulated with lactoferrin as the carrier considering its interaction with receptors expressed in tissues as targets of drugs delivered via parenteral or mucosal administration. We hope that this manuscript provides insights about the therapeutic possibilities of pharmaceutical Lf preparations with a sustainable approach that contributes to decreasing the resistance of antimicrobials and enhancing the bioavailability of first-line drugs for intestinal chronic inflammation and neurodegenerative diseases.

Lactoferrin-Conjugated Nanoparticles as New Antivirals

Lactoferrin is an iron-binding glycoprotein with multiple functions in the body. Its activity against a broad spectrum of both DNA and RNA viruses as well as the ability to modulate immune responses have made it of interest in the pharmaceutical and food industries. The mechanisms of its antiviral activity include direct binding to the viruses or its receptors or the upregulation of antiviral responses by the immune system. Recently, much effort has been devoted to the use of nanotechnology in the development of new antivirals. In this review, we focus on describing the antiviral mechanisms of lactoferrin and the possible use of nanotechnology to construct safe and effective new antiviral drugs.

Exposure of metal toxicity in Alzheimer’s disease: An extensive review

Metals serve important roles in the human body, including the maintenance of cell structure and the regulation of gene expression, the antioxidant response, and neurotransmission. High metal uptake in the nervous system is harmful because it can cause oxidative stress, disrupt mitochondrial function, and impair the activity of various enzymes. Metal accumulation can cause lifelong deterioration, including severe neurological problems. There is a strong association between accidental metal exposure and various neurodegenerative disorders, including Alzheimer’s disease (AD), the most common form of dementia that causes degeneration in the aged. Chronic exposure to various metals is a well-known environmental risk factor that has become more widespread due to the rapid pace at which human activities are releasing large amounts of metals into the environment. Consequently, humans are exposed to both biometals and heavy metals, affecting metal homeostasis at molecular and biological levels. This review highlights how these metals affect brain physiology and immunity and their roles in creating harmful proteins such as β-amyloid and tau in AD. In addition, we address findings that confirm the disruption of immune-related pathways as a significant toxicity mechanism through which metals may contribute to AD.

Diverse Mechanisms of Antimicrobial Activities of Lactoferrins, Lactoferricins, and Other Lactoferrin-Derived Peptides

Lactoferrins are an iron-binding glycoprotein that have important protective roles in the mammalian body through their numerous functions, which include antimicrobial, antitumor, anti-inflammatory, immunomodulatory, and antioxidant activities. Among these, their antimicrobial activity has been the most studied, although the mechanism behind antimicrobial activities remains to be elucidated. Thirty years ago, the first lactoferrin-derived peptide was isolated and showed higher antimicrobial activity than the native lactoferrin lactoferricin. Since then, numerous studies have investigated the antimicrobial potencies of lactoferrins, lactoferricins, and other lactoferrin-derived peptides to better understand their antimicrobial activities at the molecular level. This review defines the current antibacterial, antiviral, antifungal, and antiparasitic activities of lactoferrins, lactoferricins, and lactoferrin-derived peptides. The primary focus is on their different mechanisms of activity against bacteria, viruses, fungi, and parasites. The role of their structure, amino-acid composition, conformation, charge, hydrophobicity, and other factors that affect their mechanisms of antimicrobial activity are also reviewed.

Influence of iron binding in the structural stability and cellular internalization of bovine lactoferrin

Lactoferrin (Lf) is an iron-binding glycoprotein and a component of many external secretions with a wide diversity of functions. Structural studies are important to understand the mechanisms employed by Lf to exert so varied functions. Here, we used guanidine hydrochloride and high hydrostatic pressure to cause perturbations in the structure of bovine Lf (bLf) in apo and holo (unsaturated and iron-saturated, respectively) forms, and analyzed conformational changes by intrinsic and extrinsic fluorescence spectroscopy. Our results showed that the iron binding promotes changes on tertiary structure of bLf and increases its structural stability. In addition, we evaluated the effects of bLf structural change on the kinetics of bLf internalization in Vero cells by confocal fluorescence microscopy, and observed that the holo form was faster than the apo form. This finding may indicate that structural changes promoted by iron binding may play a key role in the intracellular traffic of bLf. Altogether, our data improve the comprehension of bLf stability and uptake, adding knowledge to its potential use as a biopharmaceutical.

Iron-Uptake Systems of Chicken-Associated Salmonella Serovars and Their Role in Colonizing the Avian Host

Iron is an essential micronutrient for most bacteria. Salmonella enterica strains, representing human and animal pathogens, have adopted several mechanisms to sequester iron from the environment depending on availability and source. Chickens act as a major reservoir for Salmonella enterica strains which can lead to outbreaks of human salmonellosis. In this review article we summarize the current understanding of the contribution of iron-uptake systems to the virulence of non-typhoidal S. enterica strains in colonizing chickens. We aim to address the gap in knowledge in this field, to help understand and define the interactions between S. enterica and these important hosts, in comparison to mammalian models.

Lactoferrin's Anti-Cancer Properties: Safety, Selectivity, and Wide Range of Action

Despite recent advances in cancer therapy, current treatments, including radiotherapy, chemotherapy, and immunotherapy, although beneficial, present attendant side effects and long-term sequelae, usually more or less affecting quality of life of the patients. Indeed, except for most of the immunotherapeutic agents, the complete lack of selectivity between normal and cancer cells for radio- and chemotherapy can make them potential antagonists of the host anti-cancer self-defense over time. Recently, the use of nutraceuticals as natural compounds corroborating anti-cancer standard therapy is emerging as a promising tool for their relative abundance, bioavailability, safety, low-cost effectiveness, and immuno-compatibility with the host. In this review, we outlined the anti-cancer properties of Lactoferrin (Lf), an iron-binding glycoprotein of the innate immune defense. Lf shows high bioavailability after oral administration, high selectivity toward cancer cells, and a wide range of molecular targets controlling tumor proliferation, survival, migration, invasion, and metastasization. Of note, Lf is able to promote or inhibit cell proliferation and migration depending on whether it acts upon normal or cancerous cells, respectively. Importantly, Lf administration is highly tolerated and does not present significant adverse effects. Moreover, Lf can prevent development or inhibit cancer growth by boosting adaptive immune response. Finally, Lf was recently found to be an ideal carrier for chemotherapeutics, even for the treatment of brain tumors due to its ability to cross the blood-brain barrier, thus globally appearing as a promising tool for cancer prevention and treatment, especially in combination therapies.

Effect of lactoferrin on taste and smell abnormalities induced by chemotherapy: a proteome analysis

Cancer patients receiving chemotherapy often experience taste and smell abnormalities (TSA). To date, the underlying molecular mechanisms of this frequent side-effect have not been determined and effective treatments are not available. This study assessed the feasibility of lactoferrin (LF) supplementation as a treatment for TSA and investigate the related mechanisms through salivary proteome analysis. Nineteen cancer patients with established TSA following chemotherapy administration were enrolled in this study. Cancer patients and additional 12 healthy subjects took LF supplements, 3 tablets per day (250 mg per tablet), for 30 days. Saliva was collected at three timepoints: baseline, 30-day LF supplementation, and 30-day post-LF supplementation. Patient's TSA level, salivary proteome, and salivary minerals at each LF treatment stage were analyzed. High TSA level was associated with high concentration of salivary Fe and loss of critical salivary immune proteins. LF supplementation significantly decreased the concentration of salivary Fe (P = 0.025), increased the abundance (P < 0.05) of salivary α-amylase and Zn-α-2-GP, and led to an overall increase of expression (≥2-fold changes) of immune proteins including immunoglobulin heavy chain, annexin A1, and proteinase inhibitor. Abundance of α-amylase and SPLUNC2 were further increased (P < 0.05) at 30-day post-LF supplementation in cancer patients. At the same time, total TSA score was significantly reduced (P < 0.001) in chemotherapy patients. This study demonstrated the feasibility of developing lactoferrin supplementation as a treatment to reduce TSA caused by chemotherapy and improve cancer patient's oral immunity.

Iron Pathophysiology in Parkinson Diseases

The key molecular events that provoke Parkinson's disease (PD) are not fully understood. Iron deposit was found in the substantia nigra pars compacta (SNpc) of PD patients and animal models, where dopaminergic neurons degeneration occurred selectively. The mechanisms involved in disturbed iron metabolism remain unknown, however, considerable evidence indicates that iron transporters dysregulation, activation of L-type voltage-gated calcium channel (LTCC) and ATP-sensitive potassium (KATP) channels, as well as N-methyl-D-aspartate (NMDA) receptors (NMDARs) contribute to this process. There is emerging evidence on the structural links and functional modulations between iron and α-synuclein, and the key player in PD which aggregates in Lewy bodies. Iron is believed to modulate α-synuclein synthesis, post-translational modification, and aggregation. Furthermore, glia, especially activated astroglia and microglia, are involved in iron deposit in PD. Glial contributions were largely dependent on the factors they released, e.g., neurotrophic factors, pro-inflammatory factors, lactoferrin, and those undetermined. Therefore, iron chelation using iron chelators, the extracts from many natural foods with iron chelating properties, may be an effective therapy for prevention and treatment of the disease.

New Progress on the Role of Glia in Iron Metabolism and Iron-Induced Degeneration of Dopamine Neurons in Parkinson's Disease

It is now increasingly appreciated that glial cells play a critical role in the regulation of iron homeostasis. Impairment of these properties might lead to dysfunction of iron metabolism and neurodegeneration of neurons. We have previously shown that dysfunction of glia could cause iron deposit and enhance iron-induced degeneration of dopamine (DA) neurons in Parkinson’s disease (PD). There also has been a substantial growth of knowledge regarding the iron metabolism of glia and their effects on iron accumulation and degeneration of DA neurons in PD in recent years. Here, we attempt to describe the role of iron metabolism of glia and the effect of glia on iron accumulation and degeneration of DA neurons in the substantia nigra of PD. This could provide evidence to reveal the mechanisms underlying nigral iron accumulation of DA neurons in PD and provide the basis for discovering new potential therapeutic targets for PD.

Lactoferrin in a Context of Inflammation-Induced Pathology

Much progress has been achieved to elucidate the function of lactoferrin (LTF), an iron-binding glycoprotein, in the milieu of immune functionality. This review represents a unique examination of LTF toward its importance in physiologic homeostasis as related to development of disease-associated pathology. The immunomodulatory nature of this protein derives from its unique ability to "sense" the immune activation status of an organism and act accordingly. Underlying mechanisms are proposed whereby LTF controls disease states, thereby pinpointing regions of entry for LTF in maintenance of various physiological pathways to limit the magnitude of tissue damage. LTF is examined as a first line mediator in immune defense and response to pathogenic and non-pathogenic injury, as well as a molecule critical for control of oxidative cell function. Mechanisms of interaction of LTF with its receptors are examined, with a focus on protective effects via regulation of enzyme activities and reactive oxygen species production, immune deviation, and prevention of cell apoptosis. Indeed, LTF serves as a critical control point in physiologic homeostasis, functioning as a sensor of immunological performance related to pathology. Specific mediation of tissue pathophysiology is described for maintenance of intestinal integrity during endotoxemia, elicited airway inflammation due to allergens, and pulmonary damage during tuberculosis. Finally, the role of LTF to alter differentiation of adaptive immune function is examined, with specific recognition of its utility as a vaccine adjuvant to control subsequent lymphocytic reactivity. Overall, it is clear that while the ability of LTF to both sequester iron and to direct reactive oxygen intermediates is a major factor in lessening damage due to excessive inflammatory responses, further effects are apparent through direct control over development of higher order immune functions that regulate pathology due to insult and injury. This culminates in attenuation of pathological damage during inflammatory injury.

Biometal Dyshomeostasis and Toxic Metal Accumulations in the Development of Alzheimer's Disease

Biometal dyshomeostasis and toxic metal accumulation are common features in many neurodegenerative disorders, including Alzheimer’s disease (AD), Parkinson’s disease, and Huntington’s disease. The neurotoxic effects of metal imbalance are generally associated with reduced enzymatic activities, elevated protein aggregation and oxidative stress in the central nervous system, in which a cascade of events lead to cell death and neurodegeneration. Although the links between biometal imbalance and neurodegenerative disorders remain elusive, a major class of endogenous proteins involved in metal transport has been receiving increasing attention over recent decades. The abnormal expression of these proteins has been linked to biometal imbalance and to the pathogenesis of AD. Here, we present a brief overview of the physiological roles of biometals including iron, zinc, copper, manganese, magnesium and calcium, and provide a detailed description of their transporters and their synergistic involvement in the development of AD. In addition, we also review the published data relating to neurotoxic metals in AD, including aluminum, lead, cadmium, and mercury.

The impact of lactoferrin with different levels of metal saturation on the intestinal epithelial barrier function and mucosal inflammation

Translocation of bacteria, primarily Gram-negative pathogenic flora, from the intestinal lumen into the circulatory system leads to sepsis. In newborns, and especially very low birth weight infants, sepsis is a major cause of morbidity and mortality. The results of recently conducted clinical trials suggest that lactoferrin, an iron-binding protein that is abundant in mammalian colostrum and milk, may be an effective agent in preventing sepsis in newborns. However, despite numerous basic studies on lactoferrin, very little is known about how metal saturation of this protein affects a host’s health. Therefore, the main objective of this study was to elucidate how iron-depleted, iron-saturated, and manganese-saturated forms of lactoferrin regulate intestinal barrier function via interactions with epithelial cells and macrophages. For these studies, a human intestinal epithelial cell line, Caco-2, was used. In this model, none of the tested lactoferrin forms induced higher levels of apoptosis or necrosis. There was also no change in the production of tight junction proteins regardless of lactoferrin metal saturation status. None of the tested forms induced a pro-inflammatory response in Caco-2 cells or in macrophages either. However, the various lactoferrin forms did effectively inhibit the pro-inflammatory response in macrophages that were activated with lipopolysaccharide with the most potent effect observed for apolactoferrin. Lactoferrin that was not bound to its cognate receptor was able to bind and neutralize lipopolysaccharide. Lactoferrin was also able to neutralize microbial-derived antigens, thereby potentially reducing their pro-inflammatory effect. Therefore, we hypothesize that lactoferrin supplementation is a relevant strategy for preventing sepsis.

Lactoferrin from Milk: Nutraceutical and Pharmacological Properties

Lactoferrin is an iron-binding protein present in large quantities in colostrum and in breast milk, in external secretions and in polymorphonuclear leukocytes. Lactoferrin's main function is non-immune protection. Among several protective activities shown by lactoferrin, those displayed by orally administered lactoferrin are: (i) antimicrobial activity, which has been presumed due to iron deprivation, but more recently attributed also to a specific interaction with the bacterial cell wall and extended to viruses and parasites; (ii) immunomodulatory activity, with a direct effect on the development of the immune system in the newborn, together with a specific antinflammatory effects; (iii) a more recently discovered anticancer activity. It is worth noting that most of the protective activities of lactoferrin have been found, sometimes to a greater extent, also in peptides derived from limited proteolysis of lactoferrin that could be generated after lactoferrin ingestion. Lactoferrin could therefore be considered an ideal nutraceutic product because of its relatively cheap production from bovine milk and of its widely recognized tolerance after ingestion, along with its well demonstrated protective activities. The most important protective activities shown by orally administered bovine lactoferrin are reviewed in this article.

Bioactive Peptides in Milk and Dairy Products: A Review

Functionally and physiologically active peptides are produced from several food proteins during gastrointestinal digestion and fermentation of food materials with lactic acid bacteria. Once bioactive peptides (BPs) are liberated, they exhibit a wide variety of physiological functions in the human body such as gastrointestinal, cardiovascular, immune, endocrine, and nervous systems. These functionalities of the peptides in human health and physiology include antihypertensive, antimicrobial, antioxidative, antithrombotic, opioid, anti-appetizing, immunomodulatory and mineral-binding activities.

Most of the bioactivities of milk proteins are latent, being absent or incomplete in the original native protein, but full activities are manifested upon proteolytic digestion to release and activate encrypted bioactive peptides from the original protein. Bioactive peptides have been identified within the amino acid sequences of native milk proteins. Due to their physiological and physico-chemical versatility, milk peptides are regarded as greatly important components for health promoting foods or pharmaceutical applications.

Milk and colostrum of bovine and other dairy species are considered as the most important source of natural bioactive components. Over the past a few decades, major advances and developments have been achieved on the science, technology and commercial applications of bioactive components which are present naturally in the milk. Although the majority of published works are associated with the search of bioactive peptides in bovine milk samples, some of them are involved in the investigation of ovine or caprine milk. The advent of functional foods has been facilitated by increasing scientific knowledge about the metabolic and genomic effects of diet and specific dietary components on human health.

Polymorphisms in the promoter region of the bovine lactoferrin gene influence milk somatic cell score and milk production traits in Chinese Holstein cows

Lactoferrin is an iron-binding protein found in cow's milk that plays an important role in preventing mastitis caused by intramammary infection. In this study, 20 Chinese Holstein cows were selected randomly for PCR amplification and sequencing of the bovine lactoferrin gene promoter region and used for SNP discovery in the region between nucleotide positions -461 to -132. Three SNPs (-270T>C, -190G>A and -156A>G) were identified in bovine lactoferrin, then Chinese Holstein cows (n=866) were genotyped using Sequenom MassARRAY (Sequenom Inc., San Diego, CA) based on the previous SNP information in this study, and the associations between SNPs or haplotype and milk somatic cell score (SCS) and production traits were analyzed by the least squares method in the GLM procedure of SAS. SNPs -270T>C and -156A>G showed close linkage disequilibrium (r(2)=0.76). The SNP -190G>A showed a significant association with SCS, and individuals with genotype GG had higher SCS than genotypes AG and AA. Associations were found between the SNPs -270T>C and -190G>A with SCS and the milk composition. The software MatInspector revealed that these SNPs were located within several potential transcription factor binding sites, including NF-κB p50, KLF7 and SP1, and may alter gene expression, but further investigation will be required to elucidate the biological and practical relevance of these SNPs.

Effect of lactoferrin protein on red blood cells and macrophages: mechanism of parasite-host interaction

Background

Lactoferrin is a natural multifunctional protein known to have antitumor, antimicrobial, and anti-inflammatory activity. Apart from its antimicrobial effects, lactoferrin is known to boost the immune response by enhancing antioxidants. Lactoferrin exists in various forms depending on its iron saturation. The present study was done to observe the effect of lactoferrin, isolated from bovine and buffalo colostrum, on red blood cells (RBCs) and macrophages (human monocytic cell line-derived macrophages THP1 cells).

Methods

Lactoferrin obtained from both species and in different iron saturation forms were used in the present study, and treatment of host cells were given with different forms of lactoferrin at different concentrations. These treated host cells were used for various studies, including morphometric analysis, viability by MTT assay, survivin gene expression, production of reactive oxygen species, phagocytic properties, invasion assay, and Toll-like receptor-4, Toll-like receptor-9, and MDR1 expression, to investigate the interaction between lactoferrin and host cells and the possible mechanism of action with regard to parasitic infections.

Results

The mechanism of interaction between host cells and lactoferrin have shown various aspects of gene expression and cellular activity depending on the degree of iron saturation of lactoferrin. A significant increase (P<0.05) in production of reactive oxygen species, phagocytic activity, and Toll-like receptor expression was observed in host cells incubated with iron-saturated lactoferrin when compared with an untreated control group. However, there was no significant (P>0.05) change in percentage viability in the different groups of host cells treated, and no downregulation of survivin gene expression was found at 48 hours post-incubation. Upregulation of the Toll-like receptor and downregulation of the P-gp gene confirmed the immunomodulatory potential of lactoferrin protein.

Conclusion

The present study details the interaction between lactoferrin and parasite host cells, ie, RBCs and macrophages, using various cellular processes and expression studies. The study reveals the possible mechanism of action against various intracellular pathogens such as Toxoplasma, Plasmodium, Leishmania, Trypanosoma, and Mycobacterium. The presence of iron in lactoferrin plays an important role in enhancing the various activities taking place inside these cells. This work provides a lot of information about targeting lactoferrin against many parasitic infections which can rule out the exact pathways for inhibition of diseases caused by intracellular microbes mainly targeting RBCs and macrophages for their survival. Therefore, this initial study can serve as a baseline for further evaluation of the mechanism of action of lactoferrin against parasitic diseases, which is not fully understood to date.

The protective effect of lactoferrin on ventral mesencephalon neurons against MPP + is not connected with its iron binding ability

Lactoferrin (Lf) can bind to lactoferrin receptor (LfR), leading to iron transport through the plasma membrane. Besides iron transportation, Lf also has antioxidant and anti-inflammatory properties. In the brain, Lf is only synthesized by activated microglia. LfR is present in blood vessels and nigral dopaminergic neurons. Both nigral iron accumulation and microglia activation is believed to be involved in Parkinson’s disease (PD), moreover, increased Lf and LfR in dopaminergic neurons were found in PD cases and MPTP-intoxicated mice. How iron influences microglia to release Lf? Does Lf tend to transport iron to dopaminergic neurons leading to cell death or to protect dopaminergic neuron from neurotoxin? In this study, we observed that iron increased Lf synthesis in activated microglia. In ventral mesencephalon neurons, both iron-free Lf (apo-Lf) and iron-saturated Lf (holo-Lf) exerted neuroprotective effects against MPP⁺ by mechanisms, believed to enhance the mitochondrial transmembrane potential, improve Cu/Zn-superoxide dismutase activity, increase Bcl-2 expression. Although apo-Lf but not holo-Lf chelated cellular iron, there was no difference between the two types of Lf in the neuroprotection. Our data indicate that iron overload increases the activated microglia releasing Lf. Lf plays protective role on ventral mesencephalon neurons against MPP⁺, which is iron-chelating independent.

Potential lactoferrin activity against pathogenic viruses

Lactoferrin (LF) is an 80-kDa globular glycoprotein with high affinity for metal ions, particularly for iron. This protein possesses many biological functions, including the binding and release of iron and serves as one of the important components of the innate immune system, where it acts as a potent inhibitor of several pathogens. LF has efficacious antibacterial and antiviral activities against a wide range of Gram-positive and Gram-negative bacteria and against both naked and enveloped DNA and RNA viruses. In its antiviral pursuit, LF acts predominantly at the acute phase of the viral infection or even at the intracellular stage, as in hepatitis C virus infection. LF inhibits the entry of viral particles into host cells, either by direct attachment to the viral particles or by blocking their cellular receptors. This wide range of activities may be attributed to the capacity of LF to bind iron and its ability to interfere with the cellular receptors of both hosts and pathogenic microbes.

Peptide inhibitors against herpes simplex virus infections

Herpes simplex virus (HSV) is a significant human pathogen causing mucocutaneous lesions primarily in the oral or genital mucosa. Although acyclovir (ACV) and related nucleoside analogs provide successful treatment, HSV remains highly prevalent worldwide and is a major cofactor for the spread of human immunodeficiency virus. Encephalitis, meningitis, and blinding keratitis are among the most severe diseases caused by HSV. ACV resistance poses an important problem for immunocompromised patients and highlights the need for new safe and effective agents; therefore, the development of novel strategies to eradicate HSV is a global public health priority. Despite the continued global epidemic of HSV and extensive research, there have been few major breakthroughs in the treatment or prevention of the virus since the introduction of ACV in the 1980s. A therapeutic strategy at the moment not fully addressed is the use of small peptide molecules. These can be either modeled on viral proteins or derived from antimicrobial peptides. Any peptide that interrupts protein-protein or viral protein-host cell membrane interactions is potentially a novel antiviral drug and may be a useful tool for elucidating the mechanisms of viral entry. This review summarizes current knowledge and strategies in the development of synthetic and natural peptides to inhibit HSV infectivity.

LF immunomodulatory strategies: mastering bacterial endotoxin1This article is part of a Special Issue entitled Lactoferrin and has undergone the Journal's usual peer review process

Lactoferrin (LF), an iron-binding glycoprotein expressed in most biological fluids, represents a major component of mammalian innate immune system. The multiple activities of LF rely not only on its capacity to bind iron but also to interact with molecular and cellular components of both the host and pathogens. LF can bind and sequester lipopolysaccharide thus preventing proinflammatory pathway activation, sepsis, and tissue damage. However, the interplay between LF and lipopolysaccharide is complex and may lead to different outcomes including both the suppression of inflammatory response and immune activation. Understanding the molecular basis and the functional consequences of this complex interaction is critically relevant in the development of LF-based therapeutic interventions in humans.

Serine protease PrtA from Streptococcus pneumoniae plays a role in the killing of S. pneumoniae by apolactoferrin

It is known that apolactoferrin, the iron-free form of human lactoferrin, can kill many species of bacteria, including Streptococcus pneumoniae. Lactoferricin, an N-terminal peptide of apolactoferrin, and fragments of it are even more bactericidal than apolactoferrin. In this study we found that apolactoferrin must be cleaved by a serine protease in order for it to kill pneumococci. The serine protease inhibitors were able to block killing by apolactoferrin but did not block killing by a lactoferrin-derived peptide. Thus, the killing of pneumococci by apolactoferrin appears to require a protease to release a lactoferricin-like peptide(s). Incubation of apolactoferrin with growing pneumococci resulted in a 12-kDa reduction in its molecular mass, of which about 7 to 8 kDa of the reduction was protease dependent. Capsular type 2 and 19F strains with mutations in the gene encoding the major cell wall-associated serine protease, prtA, lost much of their ability to degrade apolactoferrin and were relatively resistant to killing by apolactoferrin (P < 0.001). Recombinant PrtA was also able to cleave apolactoferrin, reducing its mass by about 8 kDa, and greatly enhance the killing activity of the solution containing the apolactoferrin and its cleavage products. Mass spectroscopy revealed that PrtA makes a major cut between amino acids 78 and 79 of human lactoferrin, removing the N-terminal end of the molecule (about 8.6 kDa). The simplest interpretation of these data is that the mechanism by which apolactoferrin kills Streptococcus pneumoniae requires the release of a lactoferricin-like peptide(s) and that it is this peptide(s), and not the intact apolactoferrin, which kills pneumococci.

Sortase anchored proteins of Streptococcus uberis play major roles in the pathogenesis of bovine mastitis in dairy cattle

Streptococcus uberis, strain 0140J, contains a single copy sortase A (srtA), encoding a transamidase capable of covalently anchoring specific proteins to peptidoglycan. Unlike the wild-type, an isogenic mutant carrying an inactivating ISS1 insertion within srtA was only able to infect the bovine mammary gland in a transient fashion. For the first 24 h post challenge, the srtA mutant colonised at a similar rate and number to the wild type strain, but unlike the wild type did not subsequently colonise in higher numbers. Similar levels of host cell infiltration were detected in response to infection with both strains, but only in those mammary quarters infected with the wild type strain were clinical signs of disease evident. Mutants that failed to express individual sortase substrate proteins (sub0135, sub0145, sub0207, sub0241, sub0826, sub0888, sub1095, sub1154, sub1370, and sub1730) were isolated and their virulence determined in the same challenge model. This revealed that mutants lacking sub0145, sub1095 and sub1154 were attenuated in cattle. These data demonstrate that a number of sortase anchored proteins each play a distinct, non-redundant and important role in pathogenesis of S. uberis infection within the lactating bovine mammary gland.

Contribution of bovine lactoferrin inter-lobe region to iron binding stability and antimicrobial activity against Staphylococcus aureus

The investigation of the recombinant bovine lactoferrin-derived antimicrobial protein (rBLfA) demonstrates that the inter-lobe region of bovine lactoferrin contributes to iron binding stability and antimicrobial activity against Staphylococcus aureus. rBLfA containing N-lobe (amino acid residues 1-333) and inter-lobe region (residues 334-344) was expressed in Pichia pastoris at shaking flask and fermentor level. The recombinant intact bovine lactoferrin (rBLf) and N-lobe (rBLfN) were expressed in the same system as control. The physical-chemical parameters of rBLfA, rBLfN and rBLf including amino acid residues, molecular weight, isoelectric point, net positive charge and instability index were computed and compared. The simulated tertiary structure and the calculated surface net charge showed that rBLfA maintained original structure and exhibited a higher cationic feature than rBLf and rBLfN. The three proteins showed different iron binding stability and antimicrobial activity. rBLfA released iron in the pH range of 7.0-3.5, whereas rBLfN lost its iron over the pH range of 7.0-4.0 and iron release from rBLf occurred in the pH range of 5.5-3.0. However, the minimum inhibition concentration of rBLfA against S. aureus ATCC25923 was 6.5 micromol/L, compared with 12.5 and 25 micromol/L that of rBLfN and rBLf, respectively. These results revealed that S. aureus was more sensitive to rBLfA than rBLfN and rBLf. It appeared that the strong cationic character of inter-lobe region related positively to the higher anti-S. aureus activity.

Expression and localization of lactotransferrin messenger RNA in the cortex of Alzheimer's disease

We and others have previously reported that lactotransferrin (LF), acting both as an iron-binding protein and inflammatory modulator, is greatly up-regulated in the brain of patients with Alzheimer's disease (AD). However, it remains unknown which type of cells express LF in the brain of AD. In this study, therefore, we investigated the expression and localization of LF messenger RNA (mRNA) in the cerebral cortex of AD and control cases using real-time polymerase chain reaction (PCR) and in situ hybridization histochemistry. Real-time PCR demonstrated that LF mRNA expression in the cortex of AD cases was significantly greater than that in control cases. LF mRNA-positive granules were observed in the cortex by in situ hybridization histochemistry, and the number of positive granules was increased in AD cases compared to controls. The double staining technique of LF mRNA in situ hybridisation and D-related human leukocyte antigen (HLA-DR) immunohistochemistry revealed that positive granules were localized in a subpopulation of HLA-DR-positive reactive microglia. In addition, LF mRNA-positive granules were observed in some cells that were negative for HLA-DR. These cells were also negative for CD4 and CD8 but positive for leukocyte common antigen (CD45RB), suggesting they were monocytes/macrophages. These results indicate that reactive microglia in the cerebral cortex and monocytes/macrophages infiltrating from the circulation might be responsible for synthesizing LF in AD brain.

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.

Inhibition of HBV infection by bovine lactoferrin and iron-, zinc-saturated lactoferrin

In this study, we investigated the effect of bovine lactoferrin (BLf), lactoferrin hydrolysate, or iron-, zinc-saturated lactoferrin on hepatitis B virus (HBV)-infected HepG2 cells. Fluorescent quantitative polymerase chain reaction (FQ-PCR) was used to quantify HBV-DNA copies. BLf, iron- or zinc-saturated lactoferrin significantly inhibited the amplification of HBV-DNA in a dose-dependent manner in HBV-infected HepG2 cells. However, the inhibitive effect of lactoferrin hydrolysate on HBV-DNA copies was insignificant. These findings suggest that BLf inhibits the function of HBV by integrated structure. In conclusion, BLf, iron- or zinc-saturated BLf is one of the candidates for anti-HBV reagents in treatment of patients with hepatitis.

Conformational changes in bovine lactoferrin induced by slow or fast temperature increases

Lactoferrin (LF) is an iron-binding protein present in several secreted substances, such as milk, and has broad antimicrobial and physiological properties. Because high temperatures may affect protein stability and its functional properties, we investigated the effect of heat on bovine LF structure and stability. The effects of temperatures used during the pasteurization process on LF and its relationship to protein functionality were studied. Conformational changes were monitored using spectroscopic techniques, such as circular dichroism (CD) and fluorescence spectroscopy. The CD data at 70°C showed that LF's secondary structure is drastically and irreversibly affected when the temperature is gradually increased. The same effect is observed when the temperature is gradually raised from 25°C to 105°C and changes are monitored by tryptophan fluorescence emission. We also verified the effects of simulating the pasteurization process; LF remained well structured during the entire process and this result was not time-dependent. Owing to preservation of the secondary structure with changes in the tertiary structure, we thus believe that pasteurization might cause LF to change into an intermediate partially folded state. A better understanding of heat stability is important for the use of LF as a bioactive component in food.

IsdA protects Staphylococcus aureus against the bactericidal protease activity of apolactoferrin

An important facet of the Staphylococcus aureus host-pathogen interaction is the ability of the invading bacterium to evade host innate defenses, particularly the cocktail of host antimicrobial peptides. In this work, we showed that IsdA, a surface protein of S. aureus which is required for nasal colonization, binds to lactoferrin, the most abundant antistaphylococcal polypeptide in human nasal secretions. The presence of IsdA on the surface of S. aureus confers resistance to killing by lactoferrin. In addition, the bactericidal activity of lactoferrin was inhibited by addition of phenylmethylsulfonyl fluoride, implicating the serine protease activity of lactoferrin in the killing of S. aureus. Recombinant IsdA was a competitive inhibitor of lactoferrin protease activity. Reciprocally, antibody reactive to IsdA enhanced killing of S. aureus. Thus, IsdA can protect S. aureus against lactoferrin and acts as a protease inhibitor.

Utilization of lactoferrin to fight antibiotic-resistant mammary gland pathogens

The widespread use of antibiotics has lead to the increased presence of pathogens that are less susceptible to their antibacterial effect. Lactoferrin (Lf) is naturally produced by the mammary gland. Lactoferrin is the main whey protein in human milk and is also present in cow's milk but at a much lower concentration than in human milk. This protein appears to have many biological functions, including antibacterial and antiinflammatory activities. The best-known effect of Lf is to bind iron that is essential for bacterial growth. However, the cationic nature of this protein also appears to be important for the antimicrobial activity of this protein. Lactoferrin has a weak antibacterial effect when used alone, but interestingly, Lf appears much more effective when used at low concentration in combination with several antibiotics. The most striking observation is that Lf increases the inhibitory activity of penicillin up to 4-fold in most penicillin-susceptible Staphylococcus aureus strains, whereas this increase was 4- to 16-fold in penicillin-resistant strains. Indeed, Lf reduces beta-lactamase activity in S. aureus strains producing this enzyme. Transcription of beta-lactamase gene is dramatically repressed in the presence of Lf. We evaluated the efficacy of intramammary treatments containing penicillin G or bovine Lf (bLf), or both, to cure chronic mastitis caused by a clinical isolate of S. aureus highly resistant to beta-lactam antibiotics. In a first trial, mastitis was induced in lactating cows by injecting a low dose of S. aureus through the teat canal of all quarters. Bacterial cure rate was null for control quarters, 11.1% for bLf, 9.1% for penicillin, and 45.5% for the combination of bLf and penicillin. A second trial was undertaken to investigate the effect of an extended therapy on chronic mastitis acquired in a previous lactation. Quarters were treated with 100,000 IU of penicillin G with or without 250 mg of bLf for 7 d. Bacterial cure rate was greater for the bLf + penicillin combination (33.3%) compared with penicillin alone (12.5%). In conclusion, bLf added to penicillin is an effective combination for the treatment of stable S. aureus infections resistant to beta-lactam antibiotics.

Transcriptional profiling of Mycoplasma hyopneumoniae during iron depletion using microarrays

Mycoplasma hyopneumoniae, the causative agent of swine enzootic pneumonia and a major component of the porcine respiratory disease complex, continues to confound swine producers despite control programmes worldwide. The disease is chronic and self-limiting, but the host is subject to immunopathological changes that potentiate respiratory disease associated with other pathogens. The response of M. hyopneumoniae to environmental stress is of interest because of its relevance to virulence mechanisms in other bacterial pathogens. One of these stressors, iron deprivation, is a prominent feature of the host innate immune response, and most certainly impacts growth of mycoplasmas in vivo. To study this, microarray technology was applied to the transcriptome analysis of M. hyopneumoniae during iron deprivation. An array consisting of 632 of the 698 ORFs in the genome was used to compare the mRNA isolated from organisms grown under normal laboratory conditions with that from organisms subjected to iron deprivation with the chelator 2,2'-dipyridyl. This analysis identified 27 genes that were either up- or down-regulated in response to low-iron growth conditions (P<0.01), with an estimated false discovery rate below 10 %. These included genes encoding transport proteins, enzymes involved in energy metabolism, and components of the translation process. Ten of the 27 identified genes had no assigned function. These studies indicate that M. hyopneumoniae can respond to changes in environmental conditions, but the mechanism employed remains unknown.

Milk biologically active components as nutraceuticals: review

Milk contains components that provide critical nutritive elements, immunological protection, and biologically active substances to both neonates and adults. Milk proteins are currently the main source of a range of biologically active peptides. Concentrates of these peptides are potential health-enhancing nutraceuticals for food and pharmaceutical applications. Several bioactive peptides may be used as nutraceuticals, for example, in the treatment of diarrhea, hypertension, thrombosis, dental diseases, as well as mineral malabsorption, and immunodeficiency. Minor whey proteins, such as lactoferrin, lactoperoxidase, lysozyme, and immunoglobulins, are considered antimicrobial proteins. Milk also contains some natural bioactive substances. These include oligosaccharides, fucosylated oligosaccharides, hormones, growth factors, mucin, gangliosides, and endogenous peptides, which are present in milk at secretion. Most of the claimed physiological properties of milk bioactive components have been carried out in vitro or in animal model systems, and these hypothesized properties remain to be proven in humans. Whether these milk bioactive components will replace drugs entirely in the immediate future is still unclear, but the increasing appreciation of "drug foods" or nutraceuticals plays a complementary rather than a substitutional role to the synthetic pharmacological drugs.

Modelling of anti-HSV activity of lactoferricin analogues using amino acid descriptors

Herpes simplex virus (HSV) causes a number of diseases and new therapies are being pursued vigorously. Earlier studies have shown that modified peptides based on lactoferricins reduce HSV-1 and HSV-2 infection, and structure-activity studies indicate that the anti-viral activity correlates with the binding affinity for heparan sulphate and chondroitin sulphate. In this study it is shown that theoretically derived amino acid descriptors can be used to model the anti-viral activity of peptides, as well as other peptide properties, even more accurately.

Characterization of the infection-responsive bovine lactoferrin promoter

The concentration of lactoferrin in bovine milk is dramatically increased in response to infection. The high levels of lactoferrin may have a role in the prevention of microbial infection of the mammary gland. However, molecular mechanisms of how the lactoferrin gene is regulated in the mammary gland in response to infection remain unknown. In this study, we isolated and characterized the 5' flanking region of the bovine lactoferrin gene. An 8.2 kilobase (kb) fragment of the bovine lactoferrin gene, containing 4.4 kb of 5' flanking region, exon 1, intron 1, and exon 2, was isolated from a bovine genomic library on two overlapping bacterial artificial chromosome (BAC) clones. Sequence analysis of the isolated lactoferrin gene revealed that the promoter region contains a high GC content, a non-canonical TATA box, multiple stimulating protein 1 (SP1)/GC elements, and other putative binding sites for transcription factors including nuclear factor-kappaB (NF-kappaB), activator protein 1 (AP1), signal transducer and activator of transcriptions 3 and 5 (STAT3 and STAT5), and steroid hormone receptors. To demonstrate that the isolated promoter is functional, 4.4 kb of 5' flanking region was inserted upstream from the firefly luciferase gene and the chimeric construct was transiently transfected into murine mammary epithelial cells. Transfection studies showed that the basal promoter activity is quite potent, being similar in strength to that of the simian virus 40 (SV40) promoter/enhancer. In addition, a 24-h treatment with Escherichia coli lipopolysaccharide (LPS) significantly stimulated its activity up to 2.3-fold in a dose-dependent manner. Furthermore, promoter deletion analysis indicated that the sequence up to -543 was sufficient for basal activity, whereas the sequence up to -1029 was required for maximal basal activity. The basal activity of the promoter is affected by both positive regulatory regions (-2462/-1879 and -1029/-75) and a negative regulatory region (-1407/-1029). LPS-responsive regions of the promoter were localized to the region from -1029 to -543 containing one STAT3 site and two NF-kappaB sites, and the region from -4355 to -2462 containing three AP1 sites and six NF-kappaB sites. Taken together, our findings suggested that the lactoferrin promoter responds to infection via the NF-kappaB pathway.

Anti-complement effects of lactoferrin-derived peptides

Lactoferrin is an important biological molecule with many functions such as modulation of the inflammatory response, iron metabolism and antimicrobial defense. One effect of lactoferrin is the inhibition of the classical complement pathway. This study reports that antimicrobial peptides derived from the N-terminal region from both human and bovine lactoferrin, lactoferricin H and lactoferricin B, respectively, inhibit the classical complement pathway. No inhibitory effect of these peptides was observed on the alternative complement pathway in an AP50 assay. However, lactoferricin B reduced the inhibitory properties of serum against Escherichia coli in a concentration dependent manner. These results suggest that the N-terminal region of lactoferrin is the important part in the inhibition of complement activation and that these peptides possess other important properties than their antimicrobial effect.

Effect of bovine lactoferrin on a transmissible AIDS-like disease in mice

The effect of bovine lactoferrin (bLF) was examined on an AIDS-like disease (ALD) in mice. Induction of disease was achieved by inoculation with infected cell-free plasma from diseased mice to uninfected ones. The effect of treatment with bLF was investigated when administered simultaneously with the virus, 20 days prior to infection, or 20 days after infection. Animals underwent clinical surveillance and enumeration of white blood cells (WBC) and lymphocytes, as well as fluorescent staining of CD4 and CD8 bearing cells. Simultaneous administration of bLF and virus did not affect the pattern of ALD progress along the course of the experiment. Pretreatment with bLF prior to virus inoculation abolished on day 21 the detrimental effect of viral infection that lasted for two months. An opposite outcome was observed when bLF was administered 20 days after the virus. It seems that bLF had played a preventive role for a restricted period of time. However, an adverse response was elicited when bLF was administered 20 days after viral infection.

Spectral studies on aluminum ion binding to the ligands with phenolic group(s): implications for the differences between N- and C-terminal binding sites of human serum apotransferrin

Both the binding and releasing of ferric ions in C-, and N-terminal binding sites of human serum transferrin are different. To understand the difference here the interactions of aluminum with the ligands containing phenolic group(s), including 8-hydroxyquinoline, salicylic acid, N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, N,N'-ethylenebis[2-(o-hydroxyphenolic)glycine], and human serum apotransferrin, respectively, are investigated by using UV difference and fluorescence spectra methods in 0.1 M N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid at pH 7.4. Aluminum binding produces a UV difference peak near 235 nm that is characteristic of phenolic groups binding to aluminum. The peak at 235 nm has been used to determine conditional binding constants of log K(Al-HBED)=8.88+/-0.74 and log K(Al-EHPG)=9.38+/-0.03. However, the effects of aluminum binding on the fluorescence intensity of N,N'-ethylenebis[2-(o-hydroxyphenolic)glycine], salicylic acid and N,N'-di(2-hydroxybenzyl) ethylenediamine-N,N'-diacetic acid, 8-hydroxyquinoline are disparate, the former showing a decrease and the latter an increase. At pH 7.4, there is N cdots, three dots, centered H-O type intramolecular hydrogen bond in 8-hydroxyquinoline, N,N'-di(2-hydroxybenzyl) ethylenediamine-N,N'-diacetic acid and O cdots, three dots, centered H-O type intramolecular hydrogen bond in salicylic acid, N,N'-ethylenebis[2-(o-hydroxyphenolic)glycine]. The effects of salts on the fluorescence intensity of the ligands containing phenolic group(s) show that fluorescence emission increases with the breaking of an N cdots, three dots, centered H-O type intramolecular hydrogen bond and fluorescence emission decreases with the breaking of an O cdots, three dots, centered H-O type intramolecular hydrogen bond. Fluorescence titrations of apotransferrin and both forms of monoferric transferrin with aluminum indicated that there is O cdots, three dots, centered H-O type intramolecular hydrogen bonds for the phenolic groups of Tyr426 and Tyr517 in the C-terminal binding site. While N cdots, three dots, centered H-O type intramolecular hydrogen bonds are found for the phenolic groups of Tyr95 and Tyr188 in the N-terminal binding site.