Prooxidant activity of transferrin and lactoferrin

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.

Lactoferrin inhibits the proliferation of IMR‑32 neuroblastoma cells even under X‑rays

Neuroblastoma is a typical solid tumor common in childhood. The present study investigated the inhibitory effects of lactoferrin on the proliferation of IMR-32 neuroblastoma cells, including under X-ray irradiation. In controlled in vitro assays, it was found that lactoferrin inhibited cell proliferation, accompanied by cell membrane disruption. Furthermore, intracellular reactive oxygen species generation increased in IMR-32 cells treated with lactoferrin, causing membrane lipid peroxidation and the leakage of lactate dehydrogenase. The IC₅₀ values for cell proliferation were ~2.0 nM for doxorubicin, 2.7 mM for dibutyryl-cAMP and 45.9 µM for lactoferrin. X-ray irradiation at 1 Gy decreased cell proliferation to ~30%, which was not restored by lactoferrin. In the Fenton reaction system with iron chloride, lactoferrin increased hydroxyl radical (OH·) formation via H₂O₂, as confirmed by electron spin resonance spectra. On the whole, the findings of the present study indicate that lactoferrin, found abundantly in milk, may help prevent or treat neuroblastoma in infants with modest efficacy, and does not exert a protective effect against X-rays.

Lactoferrin for Mental Health: Neuro-Redox Regulation and Neuroprotective Effects across the Blood-Brain Barrier with Special Reference to Neuro-COVID-19

Overall mental health depends in part on the blood-brain barrier, which regulates nutrient transfer in-and-out of the brain and its central nervous system. Lactoferrin, an innate metal-transport protein, synthesized in the substantia nigra, particularly in dopaminergic neurons and activated microglia is vital for brain physiology. Lactoferrin rapidly crosses the blood-brain barrier via receptor-mediated transcytosis and accumulates in the brain capillary endothelial cells. Lactoferrin receptors are additionally present on glioma cells, brain micro-vessels, and neurons. As a regulator of neuro-redox, microglial lactoferrin is critical for protection/repair of neurons and healthy brain function. Iron imbalance and oxidative stress are common among patients with neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease, dementia, depression, and multiple sclerosis. As an endogenous iron-chelator, lactoferrin prevents iron accumulation and dopamine depletion in Parkinson's disease patients. Oral lactoferrin supplementation could modulate the p-Akt/PTEN pathway, reduce Aβ deposition, and ameliorate cognitive decline in Alzheimer's disease. Novel lactoferrin-based nano-therapeutics have emerged as effective drug-delivery systems for clinical management of neurodegenerative disorders. Recent emergence of the Coronavirus disease-2019 (COVID-19) pandemic, initially considered a respiratory illness, demonstrated a broader virulence spectrum with the ability to cross the blood-brain barrier and inflict a plethora of neuropathological manifestations in the brain - the Neuro-COVID-19. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are widely reported in Parkinson's disease, Alzheimer's disease, dementia, and multiple sclerosis patients with aggravated clinical outcomes. Lactoferrin, credited with several neuroprotective benefits in the brain could serve as a potential adjuvant in the clinical management of Neuro-COVID-19.

SARS-CoV-2 Infection Dysregulates Host Iron (Fe)-Redox Homeostasis (Fe-R-H): Role of Fe-Redox Regulators, Ferroptosis Inhibitors, Anticoagulants, and Iron-Chelators in COVID-19 Control

Severe imbalance in iron metabolism among SARS-CoV-2 infected patients is prominent in every symptomatic (mild, moderate to severe) clinical phase of COVID-19. Phase-I - Hypoxia correlates with reduced O₂ transport by erythrocytes, overexpression of HIF-1α, altered mitochondrial bioenergetics with host metabolic reprogramming (HMR). Phase-II - Hyperferritinemia results from an increased iron overload, which triggers a fulminant proinflammatory response - the acute cytokine release syndrome (CRS). Elevated cytokine levels (i.e. IL6, TNFα and CRP) strongly correlates with altered ferritin/TF ratios in COVID-19 patients. Phase-III - Thromboembolism is consequential to erythrocyte dysfunction with heme release, increased prothrombin time and elevated D-dimers, cumulatively linked to severe coagulopathies with life-threatening outcomes such as ARDS, and multi-organ failure. Taken together, Fe-R-H dysregulation is implicated in every symptomatic phase of COVID-19. Fe-R-H regulators such as lactoferrin (LF), hemoxygenase-1 (HO-1), erythropoietin (EPO) and hepcidin modulators are innate bio-replenishments that sequester iron, neutralize iron-mediated free radicals, reduce oxidative stress, and improve host defense by optimizing iron metabolism. Due to its pivotal role in 'cytokine storm', ferroptosis is a potential intervention target. Ferroptosis inhibitors such as ferrostatin-1, liproxstatin-1, quercetin, and melatonin could prevent mitochondrial lipid peroxidation, up-regulate antioxidant/GSH levels and abrogate iron overload-induced apoptosis through activation of Nrf2 and HO-1 signaling pathways. Iron chelators such as heparin, deferoxamine, caffeic acid, curcumin, α-lipoic acid, and phytic acid could protect against ferroptosis and restore mitochondrial function, iron-redox potential, and rebalance Fe-R-H status. Therefore, Fe-R-H restoration is a host biomarker-driven potential combat strategy for an effective clinical and post-recovery management of COVID-19.

Questioning Established Theories and Treatment Methods Related to Iron and Other Metal Metabolic Changes, Affecting All Major Diseases and Billions of Patients

The medical and scientific literature is dominated by highly cited historical theories and findings [...].

COVID-19 during Pregnancy and Postpartum

As the COVID-19 pandemic intensified the global health crisis, the containment of SARS-CoV-2 infection in pregnancies, and the inherent risk of vertical transmission of virus from mother-to-fetus (or neonate) poses a major concern. Most COVID-19-Pregnancy patients showed mild to moderate COVID-19 pneumonia with no pregnancy loss and no congenital transmission of the virus; however, an increase in hypoxia-induced preterm deliveries was apparent. Also, the breastmilk of several mothers with COVID-19 tested negative for the virus. Taken together, the natural barrier function during pregnancy and postpartum seems to deter the SARS-CoV-2 transmission from mother-to-child. This clinical observation warrants to explore the maternal-fetal interface and identify the innate defense factors for prevention and control of COVID-19-Pregnancy. Lactoferrin (LF) is a potent antiviral iron-binding protein present in the maternal-fetal interface. In concert with immune co-factors, maternal-LF modulates chemokine release and lymphocyte migration and amplify host defense during pregnancy. LF levels during pregnancy may resolve hypertension via down-regulation of ACE2; consequently, may limit the membrane receptor access to SARS-CoV-2 for cellular entry. Furthermore, an LF-derived peptide (LRPVAA) has been shown to block ACE receptor activity in vitro. LF may also reduce viral docking and entry into host cells and limit the early phase of COVID-19 infection. An in-depth understanding of LF and other soluble mammalian milk-derived innate antiviral factors may provide insights to reduce co-morbidities and vertical transmission of SARS-CoV-2 infection and may lead to the development of effective nutraceutical supplements.

Trying to Solve the Puzzle of the Interaction of Ascorbic Acid and Iron: Redox, Chelation and Therapeutic Implications

Iron and ascorbic acid (vitamin C) are essential nutrients for the normal growth and development of humans, and their deficiency can result in serious diseases. Their interaction is of nutritional, physiological, pharmacological and toxicological interest, with major implications in health and disease. Millions of people are using pharmaceutical and nutraceutical preparations of these two nutrients, including ferrous ascorbate for the treatment of iron deficiency anaemia and ascorbate combination with deferoxamine for increasing iron excretion in iron overload. The main function and use of vitamin C is its antioxidant activity against reactive oxygen species, which are implicated in many diseases of free radical pathology, including biomolecular-, cellular- and tissue damage-related diseases, as well as cancer and ageing. Ascorbic acid and its metabolites, including the ascorbate anion and oxalate, have metal binding capacity and bind iron, copper and other metals. The biological roles of ascorbate as a vitamin are affected by metal complexation, in particular following binding with iron and copper. Ascorbate forms a complex with Fe³⁺ followed by reduction to Fe²⁺, which may potentiate free radical production. The biological and clinical activities of iron, ascorbate and the ascorbate–iron complex can also be affected by many nutrients and pharmaceutical preparations. Optimal therapeutic strategies of improved efficacy and lower toxicity could be designed for the use of ascorbate, iron and the iron–ascorbate complex in different clinical conditions based on their absorption, distribution, metabolism, excretion, toxicity (ADMET), pharmacokinetic, redox and other properties. Similar strategies could also be designed in relation to their interactions with food components and pharmaceuticals, as well as in relation to other aspects concerning personalized medicine.

Dietary phytochemicals with anti-oxidant and pro-oxidant activities: A double-edged sword in relation to adjuvant chemotherapy and radiotherapy?

Many advances have been made in the development and introduction of new anti-cancer drugs to the clinic. However, limited attention has been paid to improving the efficacy of currently available treatments through complementary phytochemical interventions that affect cellular reactive oxygen species (ROS) levels, which are important for the etiology of certain cancers and the effectiveness of radiotherapy and some chemotherapy. In this regard, the maintenance of redox homeostasis may be influenced by the intake of anti-oxidant and pro-oxidant compounds from dietary sources. Interestingly, certain dietary phytochemicals exhibit both anti-oxidant and pro-oxidant activities, depending on their concentration and cellular microenvironment. There is evidence that concurrent administration of some dietary phytochemicals enhances the efficacy of certain cancer treatments by increasing intracellular ROS accumulation. Paradoxically, consumption of the same dietary phytochemicals under conditions that result in the scavenging of ROS might also negatively affect the outcome of ROS-dependent cancer treatments. This review discusses the potential impact of consuming dietary phytochemicals with anti-oxidant and/or pro-oxidant activities on the effectiveness of concurrent chemotherapy and/or radiotherapy in cancer patients.

Alterations in neonatal neutrophil function attributable to increased immature forms

At birth neonatal neutrophil composition differs from that of adults due to a higher number of circulating immature forms. To date only a single study has evaluated neutrophil performance based on cell maturity. For this study, we examined functional differences in chemotaxis and phagocytosis between neonatal and adult neutrophils based on cell development and labor exposure.

METHODS

Neutrophils were obtained by venipuncture from adults and cord blood from healthy term neonates delivered vaginally or by cesarean section. Transwells and the chemoattractant fMLP were used to evaluate chemotaxis. Phagocytosis assays were performed using GFP-labeled E.coli (RS218) and whole blood. Neutrophil maturation was measured by an accurate and verified flow cytometry technique using the markers CD45, CD11b, and CD16. QuantiGene Plex and Procarta immunoassays were used to determine cytokine and chemokine gene expression and protein concentration, respectively.

RESULTS

Labor exposure did not alter neonatal neutrophil function in this study. Neonatal and adult mature neutrophils performed chemotaxis and phagocytosis equally well, while immature forms showed marked impairments. Neonatal immature granulocytes, though, completed chemotaxis more proficiently than those of adults. Although cytokine and chemokine levels varied between neonatal and adult groups, no differences were detected in neonates based upon labor exposure.

CONCLUSION

Historically documented functional impairments of neonatal neutrophils may be due to the increased number of developmentally immature forms at birth rather than absolute global deficiencies.

Lactoferrin regulates an axis involving CD11b and CD49d integrins and the chemokines MIP-1α and MCP-1 in GM-CSF-treated human primary eosinophils

Eosinophils are multifunctional immune cells that contribute to innate and adaptive immune/repair responses. Lactoferrin (LF) is an iron-binding protein indicated to alter cell adhesion and immune function by receptor-mediated interactions or by participating in redox mechanisms. The eosinophil adhesion molecules, αMβ2 and α4β1, are differentially expressed following exposure to the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) and various redox agents. We hypothesized that LF can alter the function and production of proteins involved in adhesion/migration. Utilizing eosinophil peroxidase activity or fluorescent labeling adhesion assays, LF reduced GM-CSF-induced eosinophil adhesion in the presence of fibronectin or vascular adhesion molecule-1 compared with GM-CSF treatment alone. Flow cytometric analysis of eosinophil αM (CD11b) and α4 (CD49d) integrins revealed that cotreatments (24 h) with LF plus GM-CSF induced a significant increase in CD11b compared with control and GM-CSF treatments but a significant decrease in CD49d compared with control and GM-CSF treatments. These changes in CD11b and CD49d levels were significantly correlated with the increased production of chemokines (macrophage inflammatory Protein-1α, monocyte chemotactic protein-1) and an identified increase in S100A9 production. Thus, LF release at sites of inflammation may alter eosinophil recruitment/activation and possibly the progression of diseases such as cancer and asthma where significant eosinophil influx has been described.

Deposition of lactoferrin in fibrillar-type senile plaques in the brains of transgenic mouse models of Alzheimer's disease

We and others have previously reported that lactoferrin (LF), which acts as both an iron-binding protein and an inflammatory modulator, is strongly up-regulated in the brains of patients with Alzheimer's disease (AD). We have also studied the expression and localization of LF mRNA in the brain cortices of patients with AD. In this study, we investigated immunohistochemically the localization of LF in the brains of APP-transgenic mice, representing a model of AD. No LF immunoreactivity was detected in the brains of the wild-type mice. In the transgenic AD mice, LF deposition was detected in the brains. Double-immunofluorescence staining with antibodies directed against the amyloid-beta peptide (Abeta) and LF localized the LF depositions to amyloid deposits (senile plaques) and regions of amyloid angiopathy. Senile plaque formation precedes LF deposition in AD. In the transgenic mice aged <18 months, most of senile plaques were negative for LF. LF deposits appeared weakly at about 18 months of age in these mice. Both the intensity and number of LF-positive depositions in the transgenic mice increased with age. Double-staining for LF and thioflavin-S revealed that LF accumulated in thioflavin-S-positive, fibrillar-type senile plaques. The up-regulation of LF in the brains of both AD patients and the transgenic mouse model of AD provides evidence of an important role for LF in AD-affected brain tissues.

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.

Lactoferrin and host defense

Lactoferrin is a multifunctional member of the transferrin family of nonheme iron-binding glycoproteins. Lactoferrin is found at the mucosal surface where it functions as a prominent component of the first line of host defense against infection and inflammation. The protein is also an abundant component of the specific granules of neutrophils and can be released into the serum upon neutrophil degranulation. While the iron-binding properties were originally believed to be solely responsible for the host defense properties ascribed to lactoferrin, it is now known that other mechanisms contribute to the broad spectrum anti-infective and anti-inflammatory roles of this protein. In this article, current information on the functions and mechanism of action of lactoferrin are reviewed, with particular emphasis on the activities that contribute to this protein's role in host defense. In addition, studies demonstrating that lactoferrin inhibits allergen-induced skin inflammation in both mice and humans, most likely secondary to TNF-alpha (tumor necrosis factor alpha) production, are summarized. Collectively, these results suggest that lactoferrin functions as a key component of mammalian host defense at the mucosal surface.

Erythrocytes as targets for gamma-glutamyltranspeptidase initiated pro-oxidant reaction

Gamma-glutamyltranspeptidase (GGT) is a well known cell plasma membrane and serum circulating enzyme. In clinical chemistry, GGT is used as a marker of alcohol consumption and drug uptake. Serum GGT activity varies in hepatobiliary diseases and cancer. This enzyme is involved in glutathione (GSH) metabolism, which is generally associated with antioxidant properties. However, in recent years, findings from our group and from others showed that GGT-catalysed extracellular metabolism of GSH leads, in the presence of iron, to the generation of reactive oxygen species (ROS). It was demonstrated that those highly reactive species oxidise lipids, cell surface protein thiols or activate transcriptional factors such as Nuclear Factor kappaB (NFkappaB). The objective of the present work is to determine whether the red blood cells are targets for plasma GGT-initiated pro-oxidant reaction. The results obtained demonstrate that the GGT/GSH/iron system oxidises isolated erythrocyte membranes. A significant release of haemoglobin and a decrease of erythrocyte deformability are also observed. In addition, in vivo studies showed a relationship between plasma GGT activity and erythrocyte deformability in 20 studied subjects. In conclusion, GGT-mediated ROS production is able to oxidise erythrocytes and thus disturbs their functions.

Effects of natural phenolic compounds on the antioxidant activity of lactoferrin in liposomes and oil-in-water emulsions

The effect of natural phenolic compounds on the antioxidant and prooxidant activity of lactoferrin was studied in liposomes and oil-in-water emulsions containing iron. The antioxidants tested with lactoferrin were alpha-tocopherol, ferulic acid, coumaric acid, tyrosol, and natural phenolic extracts obtained from three different extra-virgin olive oils and olive mill wastewater. The natural extracts of olive oils and mill wastewaters were composed mainly of polyphenols and simple phenolics, respectively. Lipid oxidation at 30 degrees C was determined by the formation of hydroperoxides and fluorescent compounds resulting from oxidized lipid interactions. All phenolic compounds showed synergistic properties in reinforcing the antioxidant activity of lactoferrin in lipid systems containing iron. The highest synergistic effects were observed for the phenolic extracts rich in polyphenols of extra-virgin olive oils and lactoferrin. This synergistic effect was higher in liposomes than in emulsions.

Pulmonary defences to acute respiratory infection

Of all sites in the body, the lung is perhaps challenged by the greatest onslaught of microbial pathogens, many of which would cause lethal infections if unopposed. The immune response to respiratory infection must, therefore, be rapid and efficient. However, the respiratory tract is a fragile tissue with architecture that is finely designed for gas exchange, so that the price of excessive or inappropriate inflammatory responses may itself be very high. The first line of defence comes from barriers such as mucus and cilia, followed by a battery of mediators that constitute the innate response. These include lactoferrin, lysozyme, collectins and defensins. Activation of these molecules can lead directly to lysis of pathogens, or to destruction through opsonisation or the recruitment of inflammatory cells. The adaptive immune response includes the production of neutralising antibodies and the responses of T lymphocytes. Different populations of T lymphocytes may dramatically alter the balance between clearance of the pathogen and induction of tissue damage depending on the cytokines they secrete.

Ceruloplasmin and cardiovascular disease

Transition metal ion-mediated oxidation is a commonly used model system for studies of the chemical, structural, and functional modifications of low-density lipoprotein (LDL). The physiological relevance of studies using free metal ions is unclear and has led to an exploration of free metal ion-independent mechanisms of oxidation. We and others have investigated the role of human ceruloplasmin (Cp) in oxidative processes because it the principal copper-containing protein in serum. There is an abundance of epidemiological data that suggests that serum Cp may be an important risk factor predicting myocardial infarction and cardiovascular disease. Biochemical studies have shown that Cp is a potent catalyst of LDL oxidation in vitro. The pro-oxidant activity of Cp requires an intact structure, and a single copper atom at the surface of the protein, near His(426), is required for LDL oxidation. Under conditions where inhibitory protein (such as albumin) is present, LDL oxidation by Cp is optimal in the presence of superoxide, which reduces the surface copper atom of Cp. Cultured vascular endothelial and smooth muscle cells also oxidize LDL in the presence of Cp. Superoxide release by these cells is a critical factor regulating the rate of oxidation. Cultured monocytic cells, when activated by zymosan, can oxidize LDL, but these cells are unique in their secretion of Cp. Inhibitor studies using Cp-specific antibodies and antisense oligonucleotides show that Cp is a major contributor to LDL oxidation by these cells. The role of Cp in lipoprotein oxidation and atherosclerotic lesion progression in vivo has not been directly assessed and is an important area for future studies.

Oxidative-stress associated parameters (lactoferrin, superoxide dismutases) in serum of patients with Alzheimer's disease

In this case/control study, serum levels of oxidative stress related parameters such as Fe-binding lactoferrin (LTF), Mn- and Zn,Cu-superoxide dismutase (SOD) were determined by enzyme linked immunoassays in patients suffering from the Alzheimer's dementia as well as in non-demented controls. The Mn-SOD concentration was significantly (P<0.05, U-test) reduced in patients suffering from Alzheimer's disease if compared to non-demented controls. The other parameters investigated did not differ significantly between both groups. Our findings give evidence for the hypothesis of a disturbed free radical metabolism in Alzheimer's disease. The specificity of these results remains to be clarified. Further studies are needed to elucidate the relevance of oxidative stress in the etiopathogenesis of the Alzheimer's disease.

The iron-binding protein lactotransferrin is present in pathologic lesions in a variety of neurodegenerative disorders: a comparative immunohistochemical analysis

Lactotransferrin is a glycoprotein that specifically binds and transports iron. This protein is also believed to transport other metals such as aluminum. Several lines of evidence indicate that iron and aluminum are involved in the pathogenesis of many dementing diseases. In this context, the analysis of the iron-binding protein distribution in the brains of patients affected by neurodegenerative disorders is of particular interest. In the present study, the distribution of lactotransferrin was analyzed by immunohistochemistry in the cerebral cortex from patients presenting with Alzheimer's disease, Down syndrome, amyotrophic lateral sclerosis/parkinsonism-dementia complex of Guam, sporadic amyotrophic lateral sclerosis, or Pick's disease. The results show that lactotransferrin accumulates in the characteristic lesions of the different pathologic conditions investigated. For instance, in Alzheimer's disease and Guamanian cases, a subpopulation of neurofibrillary tangles was intensely labeled in the hippocampal formation and inferior temporal cortex. Senile plaques and Pick bodies were also consistently labeled. These staining patterns were comparable to those obtained with antibodies to the microtubule-associated protein tau and the amyloid beta A4 protein, although generally fewer neurofibrillary tangles were positive for lactotransferrin than for tau protein. Neuronal cytoplasmic staining with lactotransferrin antibodies, was observed in a subpopulation of pyramidal neurons in normal aging, and was more pronounced in Alzheimer's disease, Guamanian cases, Pick's disease, and particularly in Down syndrome. Lactotransferrin was also strongly associated with Betz cells and other motoneurons in the primary motor cortex of control, Alzheimer's disease, Down syndrome, Guamanian and Pick's disease cases. These same lactotransferrin-immunoreactive motoneurons were severely affected in the cases with amyotrophic lateral sclerosis. It is possible that in these neurodegenerative disorders affected neurons either take up or synthesize lactotransferrin to an abnormally elevated rate. An excessive accumulation of lactotransferrin, as well as transported iron and aluminum, may lead to a cytotoxic effect resulting in the formation of intracellular lesions and neuronal death.

The role of lactoferrin as an anti-inflammatory molecule

The formation of hydroxyl radical via the iron catalyzed Haber-Weiss reaction has been implicated in phagocyte-mediated microbicidal activity and inflammatory tissue injury. The fact that neutrophils contain lactoferrin and mononuclear phagocytes have the capacity to acquire exogenous iron has suggested that iron bound to lactoferrin may influence the nature of free radical products generated by these cells. Over the years the iron-lactoferrin complex has been heralded as both a promoter and inhibitor of hydroxyl radical formation. This manuscript is intended to provide an overview of work performed to date related to this controversy and to present results of a number of preliminary studies which shed further light on the role of lactoferrin in inflammation.

Lactotransferrin immunocytochemistry in Alzheimer and normal human brain

Lactotransferrin (LF) expression was investigated immunocytochemically in postmortem brain tissues of normal controls and patients with Alzheimer's disease (AD). The antibody to LF stained some neurons weakly in young adult brains, but it stained many neurons as well as the glia of all types in elderly brains. LF expression was greatly up-regulated in both neurons and glia in affected AD tissue. It was very strongly associated with such extracellular pathological entities as diffuse and consolidated amyloid deposits and extracellular neurofibrillary tangles. In addition, it was identified in a minority of intracellular neurofibrillary tangles, neuropil threads, and degenerative neurites. LF is an iron scavenger and a complement inhibitor. Up-regulation may be a defense mechanism in AD-affected brain tissue.

Reactive nitrogen intermediates and antimicrobial activity: role of nitrite

The reactive nitrogen intermediate (RNI) nitric oxide (NO.) is formed from L-arginine by an NO. synthase and, following secondary reactions yielding additional toxic intermediates, nitrite (NO2-) and nitrate are formed. Nitrite, however, also has toxic properties. At acid pH, nitrous acid (HNO2) is bactericidal to Escherichia coli, in association with the loss of HNO2/NO2- and the uptake of oxygen, an effect which is increased by H2O2. Under conditions in which HNO2/NO2- +/- H2O2 were ineffective, the further addition of peroxidase (myeloperoxidase [MPO], eosinophil peroxidase, lactoperoxidase) or catalase resulted in bactericidal activity and the disappearance of HNO2/NO2-. Paradoxically, HNO2/NO2- also inhibited the bactericidal activity of MPO by the formation of a complex with MPO with a shift in the absorption spectrum, and by reaction with hypochlorous acid (HOCl) (the product of the chloride-supplemented MPO-H2O2 system), with loss of the bactericidal activity of HOCl and the disappearance of both HOCl and HNO2/NO2- from the reaction mixture. Thus, HNO2/NO2-, rather than being solely an end product of RNI formation, may influence antimicrobial activity either by acting alone, with H2O2, or with H2O2 and peroxidase as a source of toxic agents, or by inhibiting the peroxidase-mediated antimicrobial systems.

Plasma lactoferrin as a marker of infection in elderly individuals

To assess lactoferrin as a marker of infection, plasma lactoferrin (LF) levels were determined in elderly in patients with infection and compared with age- and sex-matched healthy and hospital controls and young healthy blood donors. The median LF level in infection (800 ng/mL) was significantly higher than in healthy elderly living in old people's home (300 ng/mL) or elderly hospital controls (298 ng/mL) (p less than 0.01 in each case). Plasma LF correlated significantly with elastase alpha-1-proteinase inhibitor complex (EPIC) (Rs = 0.8, p less than 0.01) and C-reactive protein (CRP) (Rs = 0.45, p less than 0.02), but not with erythrocyte sedimentation rate (ESR) or white blood cell counts. We conclude that plasma LF, like CRP and EPIC, is a marker of infection in elderly individuals.

Bactericidal effect of Fe2+, ceruloplasmin, and phosphate

Fe2+, when combined with ceruloplasmin or phosphate, was bactericidal to Escherichia coli at pH 5.0, and when Fe2+, ceruloplasmin, and phosphate were combined, a bactericidal effect was observed under conditions, i.e., short incubation period, in which Fe2+ plus ceruloplasmin and Fe2+ plus phosphate were ineffective. Bactericidal activity increased with the ceruloplasmin or phosphate concentration to a maximum and then decreased as their concentration was further increased. Fe2+ was oxidized in the presence of ceruloplasmin, phosphate, or, in particular, a combination of the two. A bactericidal effect was observed when there was only a partial loss of Fe2+, with more extensive oxidation resulting in a loss of bactericidal activity. The bactericidal effect of Fe2+ plus ceruloplasmin and/or phosphate was unaffected by catalase or superoxide dismutase and was not associated with iodination. Fe-EDTA was also bactericidal at an Fe2+: EDTA molar ratio of 1:0.5, where Fe2+ was partially oxidized. However, in contrast to Fe2+ plus ceruloplasmin and/or phosphate, bactericidal activity was inhibited by catalase and was associated with iodination. Combinations of Fe2+ and Fe3+ were not bactericidal under the conditions employed. A requirement for Fe2+ plus either a product of Fe2+ oxidation or an iron ceruloplasmin and/or phosphate chelate for bactericidal activity is proposed.

Identification and purification of transferrin- and lactoferrin-binding proteins of Bordetella pertussis and Bordetella bronchiseptica

Bordetella pertussis and Bordetella bronchiseptica were both able to grow in iron-deficient medium when supplemented with iron-saturated human lactoferrin or transferrin but not with human apotransferrin. Direct contact between the transferrins and the Bordetella cells did not appear to be required for growth but considerably improved the growth of the organisms. Analysis of B. pertussis and B. bronchiseptica whole-cell lysates from cultures carried out in iron-deficient or iron-replete media revealed iron-repressible proteins (IRPs) of 27 kDa in B. pertussis and of 30, 32, 73.5, and 79.5 kDa in B. bronchiseptica. Iron-inducible proteins of 16, 23.5, 36.5, and 92.5 kDa and of 17, 23.5, 70, 84, and 91 kDa were also identified in B. pertussis and B. bronchiseptica, respectively. By use of affinity chromatography with iron-saturated human lactoferrin or transferrin as ligands, the 27- and 32-kDa IRPs from B. pertussis and B. bronchiseptica, respectively, were specifically isolated. By using iron-chelated affinity columns, we showed that these proteins exhibit an affinity for iron. Cell fractionation experiments indicated that both of these proteins are probably associated with the outer membrane. Growth of the organisms under modulating conditions showed that the production of these IRPs is not under the genetic transcriptional control of vir or bvg, the general virulence regulon in Bordetella spp.