Lactoferrin, the Moonlighting Protein of Innate Immunity.

Lactoferrin (Lf), a naturally occurring glycoprotein involved in innate immunity, was first discovered in bovine milk [...].

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.

Membrane Transporters Involved in Iron Trafficking: Physiological and Pathological Aspects.

Iron is an essential transition metal for its involvement in several crucial biological functions, the most notable being oxygen storage and transport. Due to its high reactivity and potential toxicity, intracellular and extracellular iron levels must be tightly regulated. This is achieved through transport systems that mediate cellular uptake and efflux both at the level of the plasma membrane and on the membranes of lysosomes, endosomes and mitochondria. Among these transport systems, the key players are ferroportin, the only known transporter mediating iron efflux from cells; DMT1, ZIP8 and ZIP14, which on the contrary, mediate iron influx into the cytoplasm, acting on the plasma membrane and on the membranes of lysosomes and endosomes; and mitoferrin, involved in iron transport into the mitochondria for heme synthesis and Fe-S cluster assembly. The focus of this review is to provide an updated view of the physiological role of these membrane proteins and of the pathologies that arise from defects of these transport systems.

Genetic Incorporation of Dansylalanine in Human Ferroportin to Probe the Alternating Access Mechanism of Iron Transport.

Ferroportin (Fpn), a member of the major facilitator superfamily (MFS) of transporters, is the only known iron exporter found in mammals and plays a crucial role in regulating cellular and systemic iron levels. MFSs take on different conformational states during the transport cycle: inward open, occluded, and outward open. However, the precise molecular mechanism of iron translocation by Fpn remains unclear, with conflicting data proposing different models. In this work, amber codon suppression was employed to introduce dansylalanine (DA), an environment-sensitive fluorescent amino acid, into specific positions of human Fpn (V46, Y54, V161, Y331) predicted to undergo major conformational changes during metal translocation. The results obtained indicate that different mutants exhibit distinct fluorescence spectra depending on the position of the fluorophore within the Fpn structure, suggesting that different local environments can be probed. Cobalt titration experiments revealed fluorescence quenching and blue-shifts of λmax in Y54DA, V161DA, and Y331DA, while V46DA exhibited increased fluorescence and blue-shift of λmax. These observations suggest metal-induced conformational transitions, interpreted in terms of shifts from an outward-open to an occluded conformation. Our study highlights the potential of genetically incorporating DA into Fpn, enabling the investigation of conformational changes using fluorescence spectroscopy. This approach holds great promise for the study of the alternating access mechanism of Fpn and advancing our understanding of the molecular basis of iron transport.

Iron Saturation Drives Lactoferrin Effects on Oxidative Stress and Neurotoxicity Induced by HIV-1 Tat.

The Trans-Activator of Transcription (Tat) of Human Immunodeficiency Virus (HIV-1) is involved in virus replication and infection and can promote oxidative stress in human astroglial cells. In response, host cells activate transcription of antioxidant genes, including a subunit of System Xc- cystine/glutamate antiporter which, in turn, can trigger glutamate-mediated excitotoxicity. Here, we present data on the efficacy of bovine Lactoferrin (bLf), both in its native (Nat-bLf) and iron-saturated (Holo-bLf) forms, in counteracting oxidative stress in U373 human astroglial cells constitutively expressing the viral protein (U373-Tat). Our results show that, dependent on iron saturation, both Nat-bLf and Holo-bLf can boost host antioxidant response by up-regulating System Xc- and the cell iron exporter Ferroportin via the Nuclear factor erythroid 2-related factor (Nrf2) pathway, thus reducing Reactive Oxygen Species (ROS)-mediated lipid peroxidation and DNA damage in astrocytes. In U373-Tat cells, both forms of bLf restore the physiological internalization of Transferrin (Tf) Receptor 1, the molecular gate for Tf-bound iron uptake. The involvement of astrocytic antioxidant response in Tat-mediated neurotoxicity was evaluated in co-cultures of U373-Tat with human neuronal SH-SY5Y cells. The results show that the Holo-bLf exacerbates Tat-induced excitotoxicity on SH-SY5Y, which is directly dependent on System-Xc- upregulation, thus highlighting the mechanistic role of iron in the biological activities of the glycoprotein.

Lactoferrin: from the structure to the functional orchestration of iron homeostasis.

Iron is by far the most widespread and essential transition metal, possessing crucial biological functions for living systems. Despite chemical advantages, iron biology has forced organisms to face with some issues: ferric iron insolubility and ferrous-driven formation of toxic radicals. For these reasons, acquisition and transport of iron constitutes a formidable challenge for cells and organisms, which need to maintain adequate iron concentrations within a narrow range, allowing biological processes without triggering toxic effects. Higher organisms have evolved extracellular carrier proteins to acquire, transport and manage iron. In recent years, a renewed interest in iron biology has highlighted the role of iron-proteins dysregulation in the onset and/or exacerbation of different pathological conditions. However, to date, no resolutive therapy for iron disorders has been found. In this review, we outline the efficacy of Lactoferrin, a member of the transferrin family mainly secreted by exocrine glands and neutrophils, as a new emerging orchestrator of iron metabolism and homeostasis, able to counteract iron disorders associated to different pathologies, including iron deficiency and anemia of inflammation in blood, Parkinson and Alzheimer diseases in the brain and cystic fibrosis in the lung.

Collision nodal metastasis of bladder cancer and melanoma: The first reported case and literature review.

Collision metastasis is a rare phenomenon of concomitant localization of 2 or more different tumors in the same lymph node. In most cases, primary malignancies are synchronous carcinomas arising in the same organ or area of the body. A 82-year-old man presented with hematuria and acute renal failure; he had undergone dermatological consultation ten months ago because of a large deep brown skin lesion in his dorso-lumbar region, which was not excised upon patient's request. He underwent radical cystectomy with extended pelvic lymphadenectomy due to nonpapillary high-grade urothelial carcinoma, with focal squamous features, infiltrating the bladder wall and prostate gland. In one left iliac lymph node, small foci of metastatic urothelial carcinoma (positive for P63 and CK34betaE12) were close to melanoma cells (positive for HMB45). The patient refused further treatment and died of metastatic disease 12 months after cystectomy. There is no specific clinical feature for nodal collision metastasis. A polymorphic histologic appearance poses the suspect, but immunohistochemical stains are needed to define the primary tumors. Collision metastases are thought to carry a poor prognosis. Their clinical relevance is linked to the fact that the patient faces 2 different metastatic tumors that may require specific multidisciplinary approach once diagnosed as metastatic. We present, to the best of our knowledge, the first case of collision nodal metastasis from bladder cancer and melanoma, and describe its clinical and histopathological characteristics to raise awareness on this rare occurrence, which portends a poorer prognosis than each single tumor.

Lactoferrin Binding to SARS-CoV-2 Spike Glycoprotein Blocks Pseudoviral Entry and Relieves Iron Protein Dysregulation in Several In Vitro Models.

SARS-CoV-2 causes COVID-19, a predominantly pulmonary disease characterized by a burst of pro-inflammatory cytokines and an increase in free iron. The viral glycoprotein Spike mediates fusion to the host cell membrane, but its role as a virulence factor is largely unknown. Recently, the antiviral activity of lactoferrin against SARS-CoV-2 was demonstrated in vitro and shown to occur via binding to cell surface receptors, and its putative interaction with Spike was suggested by in silico analyses. We investigated the anti-SARS-CoV-2 activity of bovine and human lactoferrins in epithelial and macrophagic cells using a Spike-decorated pseudovirus. Lactoferrin inhibited pseudoviral fusion and counteracted the deleterious effects of Spike on iron and inflammatory homeostasis by restoring basal levels of iron-handling proteins and of proinflammatory cytokines IL-1ß and IL-6. Using pull-down assays, we experimentally proved for the first time that lactoferrin binds to Spike, immediately suggesting a mechanism for the observed effects. The contribution of transferrin receptor 1 to Spike-mediated cell fusion was also experimentally demonstrated. In silico analyses showed that lactoferrin interacts with transferrin receptor 1, suggesting a multifaceted mechanism of action for lactoferrin. Our results give hope for the use of bovine lactoferrin, already available as a nutraceutical, as an adjuvant to standard therapies in COVID-19.

Clinical Relevance of Subcentimetric Lymph Node Biopsy in the Diagnosis of Ocular Sarcoidosis.

PURPOSE: To evaluate the clinical relevance of subcentimetric lymph node biopsy via mediastinoscopy in patients with presumed ocular sarcoidosis (OS). METHODS: Retrospective study of consecutive patients who underwent biopsy via mediastinoscopy for suspected OS. The biopsy outcomes and clinical features of patients with subcentimetric nodes and of those with lymph nodes >1 cm were compared. RESULTS: A total of 67 patients with presumed OS were included. Forty-two patients (63%) had lymph nodes ≥1 cm in diameter, while 25(37%) showed subcentimetric lymph nodes. Biopsy was consistent with sarcoidosis in 83% of patients with lymph nodes ≥1 cm and in 76% of patients with subcentimetric lymph nodes (p = .60). Patients with OS who had subcentimetric lymph nodes had less lymphopenia (p = .01), lower lysozyme values (p = .03) and a longer diagnostic delay compared to those with larger lymph nodes. CONCLUSIONS: The biopsy of subcentimetric lymph nodes via mediastinoscopy may provide a histological diagnosis and reduce diagnostic delay.

Production of Recombinant Human Ceruloplasmin: Improvements and Perspectives.

The ferroxidase ceruloplasmin (CP) plays a crucial role in iron homeostasis in vertebrates together with the iron exporter ferroportin. Mutations in the CP gene give rise to aceruloplasminemia, a rare neurodegenerative disease for which no cure is available. Many aspects of the (patho)physiology of CP are still unclear and would benefit from the availability of recombinant protein for structural and functional studies. Furthermore, recombinant CP could be evaluated for enzyme replacement therapy for the treatment of aceruloplasminemia. We report the production and preliminary characterization of high-quality recombinant human CP in glycoengineered Pichia pastoris SuperMan5. A modified yeast strain lacking the endogenous ferroxidase has been generated and employed as host for heterologous expression of the secreted isoform of human CP. Highly pure biologically active protein has been obtained by an improved two-step purification procedure. Glycan analysis indicates that predominant glycoforms HexNAc2Hex8 and HexNAc2Hex11 are found at Asn119, Asn378, and Asn743, three of the canonical four N-glycosylation sites of human CP. The availability of high-quality recombinant human CP represents a significant advancement in the field of CP biology. However, productivity needs to be increased and further careful glycoengineering of the SM5 strain is mandatory in order to evaluate the possible therapeutic use of the recombinant protein for enzyme replacement therapy of aceruloplasminemia patients.

Histological Remission in Ulcerative Colitis in Deep Remission under Treatment with Adalimumab.

BACKGROUND AND AIMS: Histological remission (HR) has been recently demonstrated as the last therapeutic goal in ulcerative colitis (UC), but it is unknown whether and how it may occur. Our aim was to assess the histology during the follow-up of an UC population in deep remission under treatment with adalimumab (ADA). METHODS: We performed a retrospective study on 22 UC patients who were in deep remission and followed-up while receiving therapy with ADA. Colonoscopy in those patients was performed every year. Four-quadrant biopsies every 10 cm were obtained during each colonoscopy and assessed by hematoxylin and eosin stain. Histological activity was classified using the Geboes scale. RESULTS: A total of 22 patients were enrolled in the study. The mean follow-up of those patients was 28±7 months, and 2,592 biopsy specimens in total were taken during 108 colonoscopies performed during the follow-up. At the beginning of the follow-up, histological inflammation was found in 15/22 (68.2%) of patients in deep remissio while receiving maintenance ADA therapy, 8/22 (36.4%) of them with Geboes score ≥3.1. At the end of the follow-up, when patients were still in deep remission while receiving maintenance ADA therapy, only 4 patients (18.2%) had at least one biopsy specimen with evidence of any histological inflammation during the follow-up; only two patients (9.1%) had Geboes score ≥3.1. CONCLUSIONS: Our study shows for the first time that UC patients in deep remission under ADA may reach HR, but it seems slower than other clinical or endoscopic goals.

Biophysical characterization of the complex between the iron-responsive transcription factor Fep1 and DNA.

Fep1 is an iron-responsive GATA-type transcriptional repressor present in numerous fungi. The DNA-binding domain of this protein is characterized by the presence of two zinc fingers of the Cys2-Cys2 type and a Cys-X5-Cys-X8-Cys-X2-Cys motif located between the two zinc fingers, that is involved in binding of a [2Fe-2S] cluster. In this work, biophysical characterization of the DNA-binding domain of Pichia pastoris Fep1 and of the complex of the protein with cognate DNA has been undertaken. The results obtained by analytical ultracentrifugation sedimentation velocity, small-angle X-ray scattering and differential scanning calorimetry indicate that Fep1 is a natively unstructured protein that is able to bind DNA forming 1:1 and 2:1 complexes more compact than the individual partners. Complex formation takes place independently of the presence of a stoichiometric [2Fe-2S] cluster, suggesting that the cluster may play a role in recruiting other protein(s) required for regulation of transcription in response to changes in intracellular iron levels.

Lactoferrin and oral pathologies: a therapeutic treatment.

The oral cavity is a non-uniform, extraordinary environment characterized by mucosal, epithelial, abiotic surfaces and secretions as saliva. Aerobic and anaerobic commensal and pathogenic microorganisms colonize the tongue, teeth, jowl, gingiva, and periodontium. Commensals exert an important role in host defenses, while pathogenic microorganisms can nullify this protective function causing oral and systemic diseases. Every day, 750-1000 mL of saliva, containing several host defense constituents including lactoferrin (Lf), are secreted and swallowed. Lf is a multifunctional iron-chelating cationic glycoprotein of innate immunity. Depending on, or regardless of its iron-binding ability, Lf exerts bacteriostatic, bactericidal, antibiofilm, antioxidant, antiadhesive, anti-invasive, and anti-inflammatory activities. Here, we report the protective role of Lf in different oral pathologies, such as xerostomia, halitosis, alveolar or maxillary bone damage, gingivitis, periodontitis, and black stain. Unlike antibiotic therapy, which is ineffective against bacteria that are within a biofilm, adherent, or intracellular, the topical administration of Lf, through its simultaneous activity against microbial replication, biofilms, adhesion, and invasiveness, as well as inflammation, has been proven to be efficient in the treatment of all known oral pathologies without any adverse effects.

Lactoferrin in the Prevention and Treatment of Intestinal Inflammatory Pathologies Associated with Colorectal Cancer Development.

The connection between inflammation and cancer is well-established and supported by genetic, pharmacological and epidemiological data. The inflammatory bowel diseases (IBDs), including Crohn's disease and ulcerative colitis, have been described as important promoters for colorectal cancer development. Risk factors include environmental and food-borne mutagens, dysbalance of intestinal microbiome composition and chronic intestinal inflammation, with loss of intestinal epithelial barrier and enhanced cell proliferation rate. Therapies aimed at shutting down mucosal inflammatory response represent the foundation for IBDs treatment. However, when applied for long periods, they can alter the immune system and promote microbiome dysbiosis and carcinogenesis. Therefore, it is imperative to find new safe substances acting as both potent anti-inflammatory and anti-pathogen agents. Lactoferrin (Lf), an iron-binding glycoprotein essential in innate immunity, is generally recognized as safe and used as food supplement due to its multifunctionality. Lf possesses a wide range of immunomodulatory and anti-inflammatory properties against different aseptic and septic inflammatory pathologies, including IBDs. Moreover, Lf exerts anti-adhesive, anti-invasive and anti-survival activities against several microbial pathogens that colonize intestinal mucosa of IBDs patients. This review focuses on those activities of Lf potentially useful for the prevention/treatment of intestinal inflammatory pathologies associated with colorectal cancer development.

Dynamical Behavior of the Human Ferroportin Homologue from Bdellovibrio bacteriovorus: Insight into the Ligand Recognition Mechanism.

Members of the major facilitator superfamily of transporters (MFS) play an essential role in many physiological processes such as development, neurotransmission, and signaling. Aberrant functions of MFS proteins are associated with several diseases, including cancer, schizophrenia, epilepsy, amyotrophic lateral sclerosis and Alzheimer's disease. MFS transporters are also involved in multidrug resistance in bacteria and fungi. The structures of most MFS members, especially those of members with significant physiological relevance, are yet to be solved. The lack of structural and functional information impedes our detailed understanding, and thus the pharmacological targeting, of these transporters. To improve our knowledge on the mechanistic principles governing the function of MSF members, molecular dynamics (MD) simulations were performed on the inward-facing and outward-facing crystal structures of the human ferroportin homologue from the Gram-negative bacterium Bdellovibrio bacteriovorus (BdFpn). Several simulations with an excess of iron ions were also performed to explore the relationship between the protein's dynamics and the ligand recognition mechanism. The results reinforce the existence of the alternating-access mechanism already described for other MFS members. In addition, the reorganization of salt bridges, some of which are conserved in several MFS members, appears to be a key molecular event facilitating the conformational change of the transporter.

Influence of oral administration mode on the efficacy of commercial bovine Lactoferrin against iron and inflammatory homeostasis disorders.

Milk derivative bovine Lactoferrin (bLf), a multifunctional glycoprotein available in large quantities and recognized as safe, possesses high homology and identical functions with human Lactoferrin. There are numerous food supplements containing bLf which, however, can vary in its purity, integrity and, consequently, functionality. Here, we report on a clinical trial where bLf (100 mg two times/day) was orally administered before (Arm A) or during meals (Arm B) to pregnant women with hereditary thrombophilia and suffering from anemia of inflammation. A significant increase of the number of red blood cells (RBCs), hemoglobin (Hb), total serum iron (TSI) and serum ferritin (sFtn) levels, along with a significant decrease of interleukin-6 were detected after 30 days in Arm A, but not in Arm B, thus letting us to hypothesize that bLf inefficacy could be related to its degradation by digestive proteases. To verify this hypothesis, bLf was incubated in gastric juice collected before or after meals. An undigested or a digested profile was observed when bLf was incubated in gastric juice sampled before or after meals, respectively. These results can explain the beneficial effect observed when bLf is administered under fasting conditions, i.e. in the absence of active proteases.

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.

Native and iron-saturated bovine lactoferrin differently hinder migration in a model of human glioblastoma by reverting epithelial-to-mesenchymal transition-like process and inhibiting interleukin-6/STAT3 axis.

Glioblastoma, the most lethal form of brain cancer, is characterized by fast growth, migration and invasion of the surrounding parenchyma, with epithelial-to-mesenchymal transition (EMT)-like process being mostly responsible for tumour spreading and dissemination. A number of actors, including cadherins, vimentin, transcriptional factors such as SNAIL, play critical roles in the EMT process. The interleukin (IL)-6/STAT3 axis has been related to enhanced glioblastoma's migration and invasion abilities as well. Here, we present data on the differential effects of native and iron-saturated bovine lactoferrin (bLf), an iron-chelating glycoprotein of the innate immune response, in inhibiting migration in a human glioblastoma cell line. Through a wound healing assay, we found that bLf was able to partially or completely hinder cell migration, depending on its iron saturation rate. At a molecular level, bLf down-regulated both SNAIL and vimentin expression, while inducing a notable increase in cadherins' levels and inhibiting IL-6/STAT3 axis. Again, these effects positively correlated to bLf iron-saturation state, with the Holo-form resulting more efficient than the native one. Overall, our data suggest that bLf could represent a novel and efficient adjuvant treatment for glioblastoma's standard therapeutic approaches.

Bovine Lactoferrin Pre-Treatment Induces Intracellular Killing of AIEC LF82 and Reduces Bacteria-Induced DNA Damage in Differentiated Human Enterocytes.

LF82, a prototype of adherent-invasive E. coli (AIEC), is able to adhere to, invade, survive and replicate into intestinal epithelial cells. LF82 is able to enhance either its adhesion and invasion by up-regulating carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM-6), the main cell surface molecule for bacterial adhesion, and its intracellular survival by inducing host DNA damage, thus blocking the cellular cycle. Lactoferrin (Lf) is a multifunctional cationic glycoprotein of natural immunity, exerting an anti-invasive activity against LF82 when added to Caco-2 cells at the moment of infection. Here, the infection of 12 h Lf pre-treated Caco-2 cells was carried out at a time of 0 or 3 or 10 h after Lf removal from culture medium. The effect of Lf pre-treatment on LF82 invasiveness, survival, cell DNA damage, CEACAM-6 expression, apoptosis induction, as well as on Lf subcellular localization, has been evaluated. Lf, even if removed from culture medium, reduced LF82 invasion and survival as well as bacteria-induced DNA damage in Caco-2 cells independently from induction of apoptosis, modulation of CEACAM-6 expression and Lf sub-cellular localization. At our knowledge, this is the first study showing that the sole Lf pre-treatment can activate protective intracellular pathways, reducing LF82 invasiveness, intracellular survival and cell-DNA damages.