Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Crohn's disease IRGM risk alleles are associated with altered gene expression in human tissues

Crohn's disease (CD) is a chronic inflammatory gastrointestinal disorder. Genetic association studies have implicated dysregulated autophagy in CD. Among risk loci identified are a promoter single nucleotide polymorphism (SNP)( rs13361189 ) and two intragenic SNPs ( rs9637876 , rs10065172 ) in immunity-related GTPase family M ( IRGM) a gene that encodes a protein of the autophagy initiation complex. All three SNPs have been proposed to modify IRGM expression, but reports have been divergent and largely derived from cell lines. Here, analyzing RNA-Sequencing data of human tissues from the Genotype-Tissue Expression Project, we found that rs13361189 minor allele carriers had reduced IRGM expression in whole blood and terminal ileum, and upregulation in ileum of ZNF300P1, a locus adjacent to IRGM on chromosome 5q33.1 that encodes a long noncoding RNA. Whole blood and ileum from minor allele carriers had altered expression of multiple additional genes that have previously been linked to colitis and/or autophagy. Notable among these was an increase in ileum of LTF (lactoferrin), an established fecal inflammatory biomarker of CD, and in whole blood of TNF, a key cytokine in CD pathogenesis. Last, we confirmed that risk alleles at all three loci associated with increased risk for CD but not ulcerative colitis in a case-control study. Taken together, our findings suggest that genetically encoded IRGM deficiency may predispose to CD through dysregulation of inflammatory gene networks. Gene expression profiling of disease target tissues in genetically susceptible populations is a promising strategy for revealing new leads for the study of molecular pathogenesis and, potentially, for precision medicine. NEW & NOTEWORTHY Single nucleotide polymorphisms in immunity-related GTPase family M ( IRGM), a gene that encodes an autophagy initiation protein, have been linked epidemiologically to increased risk for Crohn's disease (CD). Here, we show for the first time that subjects with risk alleles at two such loci, rs13361189 and rs10065172 , have reduced IRGM expression in whole blood and terminal ileum, as well as dysregulated expression of a wide array of additional genes that regulate inflammation and autophagy.

Efficacy of Lactoferrin Oral Administration in the Treatment of Anemia and Anemia of Inflammation in Pregnant and Non-pregnant Women: An Interventional Study

The discovery of the ferroportin-hepcidin complex has led to a critical review on the treatment of anemia and anemia of inflammation (AI). Ferroportin, the only known mammalian iron exporter from cells to blood, is negatively regulated by hepcidin, a hormone peptide able to bind to ferroportin, leading to its degradation. Therefore, new efficient therapeutic interventions acting on hepcidin and ferroportin are imperative to manage anemia and AI. Bovine milk derivative lactoferrin (bLf), a glycoprotein able to chelate two ferric ions per molecule, is emerging as a natural anti-inflammatory substance able to modulate hepcidin and ferroportin synthesis through the down-regulation of interleukin-6 (IL-6). Here, an interventional study (ClinicalTrials.gov Identifier: NCT01221844) was conducted by orally administering 100 mg of 20–30% iron-saturated bLf (corresponding to 70–84 μg of elemental iron) twice a day. This treatment was compared with the Italian standard therapy, consisting in the oral administration of 329.7 mg of ferrous sulfate once a day (corresponding to 105 mg of elemental iron). Treatments were carried out on 29 anemic women with minor β-thalassemia (20 pregnant and 9 non-pregnant), 149 women with hereditary thrombophilia (HT) (70 pregnant and 79 non-pregnant) affected by AI and 20 anemic pregnant women suffering from various pathologies. In anemic pregnant and non-pregnant women with minor β-thalassemia, presenting undetectable hepcidin levels, differently from ferrous sulfate management, bLf decreased IL-6 (from 25 ± 8 to 6 ± 3 pg/ml) and increased total serum iron (TSI) (from 54 ± 17 to 80 ± 9 μg/dl). BLf was also more efficient than ferrous sulfate in AI treatment in HT pregnant and non-pregnant women by decreasing both serum IL-6 (from 89 ± 8 to 58 ± 6 pg/ml) and hepcidin (from 115 ± 23 to 65 ± 10 ng/ml), thus increasing hematological parameters, such as the number of red blood cells (RBCs), the concentration of hemoglobin, TSI and serum ferritin. BLf was also efficient in treating anemia in other pathological pregnancies. Taken together all the results, bLf, showing a greater benefit and efficacy than the standard ferrous sulfate management, can be considered as a promising compound in treating anemia and AI through its ability to down-regulate IL-6, thus restoring ferroportin-mediated iron export from cells to blood in a hepcidin-dependent or independent way.

Taurodeoxycholate Increases the Number of Myeloid-Derived Suppressor Cells That Ameliorate Sepsis in Mice

Bile acids (BAs) control metabolism and inflammation by interacting with several receptors. Here, we report that intravenous infusion of taurodeoxycholate (TDCA) decreases serum pro-inflammatory cytokines, normalizes hypotension, protects against renal injury, and prolongs mouse survival during sepsis. TDCA increases the number of granulocytic myeloid-derived suppressor cells (MDSCLT) distinctive from MDSCs obtained without TDCA treatment (MDSCL) in the spleen of septic mice. FACS-sorted MDSCLT cells suppress T-cell proliferation and confer protection against sepsis when adoptively transferred better than MDSCL. Proteogenomic analysis indicated that TDCA controls chromatin silencing, alternative splicing, and translation of the immune proteome of MDSCLT, which increases the expression of anti-inflammatory molecules such as oncostatin, lactoferrin and CD244. TDCA also decreases the expression of pro-inflammatory molecules such as neutrophil elastase. These findings suggest that TDCA globally edits the proteome to increase the number of MDSCLT cells and affect their immune-regulatory functions to resolve systemic inflammation during sepsis.

Lactoferrin: A Critical Player in Neonatal Host Defense

Newborn infants are at a high risk for infection due to an under-developed immune system, and human milk has been shown to exhibit substantial anti-infective properties that serve to bolster neonatal defenses against multiple infections. Lactoferrin is the dominant whey protein in human milk and has been demonstrated to perform a wide array of antimicrobial and immunomodulatory functions and play a critical role in protecting the newborn infant from infection. This review summarizes data describing the structure and important functions performed by lactoferrin in protecting the neonate from infection and contributing to the maturation of the newborn innate and adaptive immune systems. We also briefly discuss clinical trials examining the utility of lactoferrin supplementation in the prevention of sepsis and necrotizing enterocolitis in newborn infants. The data reviewed provide rationale for the continuation of studies to examine the effects of lactoferrin administration on the prevention of sepsis in the neonate.

Human monocyte transcriptional profiling identifies IL-18 receptor accessory protein and lactoferrin as novel immune targets in hypertension

BACKGROUND AND PURPOSE

Monocytes play a critical role in hypertension. The purpose of our study was to use an unbiased approach to determine whether hypertensive individuals on conventional therapy exhibit an altered monocyte gene expression profile and to perform validation studies of selected genes to identify novel therapeutic targets for hypertension.

EXPERIMENTAL APPROACH

Next generation RNA sequencing identified differentially expressed genes in a small discovery cohort of normotensive and hypertensive individuals. Several of these genes were further investigated for association with hypertension in multiple validation cohorts using qRT-PCR, regression analysis, phenome-wide association study and case-control analysis of a missense polymorphism.

KEY RESULTS

We identified 60 genes that were significantly differentially expressed in hypertensive monocytes, many of which are related to IL-1β. Uni- and multivariate regression analyses of the expression of these genes with mean arterial pressure (MAP) revealed four genes that significantly correlated with MAP in normotensive and/or hypertensive individuals. Of these, lactoferrin (LTF), peptidoglycan recognition protein 1 and IL-18 receptor accessory protein (IL18RAP) remained significantly elevated in peripheral monocytes of hypertensive individuals in a separate validation cohort. Interestingly, IL18RAP expression associated with MAP in a cohort of African Americans. Furthermore, homozygosity for a missense single nucleotide polymorphism in LTF that decreases antimicrobial function and increases protein levels (rs1126478) was over-represented in patients with hypertension relative to controls (odds ratio 1.16).

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that monocytes exhibit enhanced pro-inflammatory gene expression in hypertensive individuals and identify IL18RAP and LTF as potential novel mediators of human hypertension.

LINKED ARTICLES

This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Erythropoietin and Nrf2: key factors in the neuroprotection provided by apo-lactoferrin

Among the properties of lactoferrin (LF) are bactericidal, antianemic, immunomodulatory, antitumour, antiphlogistic effects. Previously we demonstrated its capacity to stabilize in vivo HIF-1-alpha and HIF-2-alpha, which are redox-sensitive multiaimed transcription factors. Various tissues of animals receiving recombinant human LF (rhLF) responded by expressing the HIF-1-alpha target genes, hence such proteins as erythropoietin (EPO), ceruloplasmin, etc. were synthesized in noticeable amounts. Among organs in which EPO synthesis occurred were brain, heart, spleen, liver, kidneys and lungs. Other researchers showed that EPO can act as a protectant against severe brain injury and status epilepticus in rats. Therefore, we tried rhLF as a protector against the severe neurologic disorders developed in rats, such as the rotenone-induced model of Parkinson's disease and experimental autoimmune encephalomyelitis as a model of multiple sclerosis, and observed its capacity to mitigate the grave symptoms. Moreover, an intraperitoneal injection of rhLF into mice 1 h after occlusion of the medial cerebral artery significantly diminished the necrosis area measured on the third day in the ischaemic brain. During this period EPO was synthesized in various murine tissues. It was known that EPO induces nuclear translocation of Nrf2, which, like HIF-1-alpha, is a transcription factor. In view that under conditions of hypoxia both factors demonstrate a synergistic protective effect, we suggested that LF activates the Keap1/Nrf2 signaling pathway, an important link in proliferation and differentiation of normal and malignant cells. J774 macrophages were cultured for 3 days without or in the presence of ferric and ferrous ions (RPMI-1640 and DMEM/F12, respectively). Then cells were incubated with rhLF or Deferiprone. Confocal microscopy revealed nuclear translocation of Nrf2 (the key event in Keap1/Nrf2 signaling) induced by apo-rhLF (iron-free, RPMI-1640). The reference compound Deferiprone (iron chelator) had the similar effect. Upon iron binding (in DMEM/F12) rhLF did not activate the Keap1/Nrf2 pathway. Added to J774, apo-rhLF enhanced transcription of Nrf2-dependent genes coding for glutathione S-transferase P and heme oxygenase-1. Western blotting revealed presence of Nrf2 in mice brain after 6 days of oral administration of apo-rhLF, but not Fe-rhLF or equivalent amount of PBS. Hence, apo-LF, but not holo-LF, induces the translocation of Nrf2 from cytoplasm to the nucleus, probably due to its capacity to induce EPO synthesis.

Role of lactoferrin and its receptors on biliary epithelium

Human lactoferrin is an iron-binding glycoprotein present at high concentrations in breast milk and colostrum. It is produced by many exocrine glands and widely distributed in a variety of body fluids. This protein has antimicrobial, immunomodulatory, antioxidant, and anticancer properties. Two important hLf receptors have been identified: LDL receptor related protein (LRP1), a low specificity receptor, and intelectin-1 (ITLN1), a high specificity receptor. No data are present on the role of hLf on the biliary epithelium. Our aims have been to evaluate the expression of Lf and its receptors in human and murine cholangiocytes and its effect on proliferation. Immunohistochemistry and immunofluorescence (IF) were conducted on human healthy and primary biliary cholangitis (PBC) liver samples as well as on liver samples obtained from normal and bile duct ligated (BDL) mice to evaluate the expression of Lf, LRP1 and ITLN1. Cell proliferation in vitro studies were performed on human cholangiocyte cell lines via 3-(4,5-dimetiltiazol-2-il)-2,5-diphenyltetrazolium assay as well as IF to evaluate proliferating cell nuclear antigen (PCNA) expression. Our results show that mouse and human cholangiocytes express Lf, LRP1 and ITLN1, at higher extent in cholangiocytes from BDL and PBC samples. Furthermore, the in vitro addition of bovine Lf (bLf) has a proliferative effect on human cholangiocyte cell line. The results support a proliferative role of hLf on the biliary epithelium; this pro-proliferative effect of hLf and bLf on cholangiocytes could be particularly relevant in human cholangiopathies such as PBC, characterized by cholangiocyte death and ductopenia.

Physico-chemical properties influence the functions and efficacy of commercial bovine lactoferrins

Human and bovine lactoferrin (hLf and bLf) are multifunctional iron-binding glycoprotein constitutively synthesized and secreted by glandular epithelial cells and by neutrophils following induction. HLf and bLf possess very high similarity of sequence. Therefore, most of the in vitro and in vivo studies are carried out with commercial bLf (cbLf), available in large quantities and recognized by Food and Drug Administration (FDA, USA) as a safe substance. Physico-chemical heterogeneity of different cbLf preparations influences their effectiveness. CbLf iron-saturation affects thermal stability and resistance to proteolysis. Moreover, other metal ions such as Al(III), Cu(II), Mg(II), Mn(II), Zn(II) are chelated by cbLf, even if at lower affinity than Fe(III). Ca(II) is also sequestered by the carboxylate groups of sialic acid present on glycan chains of cbLf thus provoking the release of LPS, contributing to bactericidal activity. Similarly to more than 50% of eukaryotic proteins, cbLf possesses five N-glycosylation sites, also contributing to the resistance to proteolysis and, putatively, to the protection of intestinal mucosa from pathogens. CbLfs possess several functions as anti-microbial, anti-biofilm, anti-adhesive, anti-invasive and anti-inflammatory activities. They are also relevant modulators of iron and inflammatory homeostasis. However, the efficacy of cbLfs in exerting several functions can be erratic mainly depending from integrity, degree of iron and other metal ions saturation, N-glycosylation sites and chains, desialylated forms, Ca(II) sequestration, presence of contaminants and finally the ability to enter inside nucleus.

Role of Lactobacilli and Lactoferrin in the Mucosal Cervicovaginal Defense

The innate defense system of the female mucosal genital tract involves a close and complex interaction among the healthy vaginal microbiota, different cells, and various proteins that protect the host from pathogens. Vaginal lactobacilli and lactoferrin represent two essential actors in the vaginal environment. Lactobacilli represent the dominant bacterial species able to prevent facultative and obligate anaerobes outnumber in vaginal microbiota maintaining healthy microbial homeostasis. Several mechanisms underlie the protection exerted by lactobacilli: competition for nutrients and tissue adherence, reduction of the vaginal pH, modulation of immunity, and production of bioactive compounds. Among bioactive factors of cervicovaginal mucosa, lactoferrin, an iron-binding cationic glycoprotein, is a multifunctional glycoprotein with antibacterial, antifungal, antiviral, and antiparasitic activities, recently emerging as an important modulator of inflammation. Lactobacilli and lactoferrin are largely under the influence of female hormones and of paracrine production of various cytokines. Lactoferrin is strongly increased in lower genital tract mucosal fluid of women affected by Neisseria gonorrheae, Chlamydia trachomatis, and Trichomonas vaginalis infections promoting both innate and adaptive immune responses. In vaginal dysbiosis characterized by low amounts of vaginal lactobacilli and increased levels of endogenous anaerobic bacteria, the increase in lactoferrin could act as an immune modulator assuming the role normally played by the healthy microbiota in vaginal mucosa. Then lactoferrin and lactobacilli may be considered as biomarkers of altered microbial homeostasis at vaginal level. Considering the shortage of effective treatments to counteract recurrent and/or antibiotic-resistant bacterial infections, the intravaginal administration of lactobacilli and lactoferrin could be a novel efficient therapeutic strategy and a valuable tool to restore mucosal immune homeostasis.

Antirotaviral potential of lactoferrin from different origin: effect of thermal and high pressure treatments

Rotaviral gastroenteritis causes a high rate of infant mortality and severe healthcare implications worldwide. Several studies have pointed out that human milk and dairy fractions, such as whey and buttermilk, possess antirotaviral activity. This activity has been mainly associated with glycoproteins, among them lactoferrin (LF). Thermal treatments are necessary to provide microbiological safety and extend the shelf life of milk products, though they may diminish their biological value. High hydrostatic pressure (HHP) treatment is a non-thermal method that causes lower degradation of food components than other treatments. Thus, the main objective of this study was to prove the antirotaviral activity of LFs from different origin and to evaluate the effect of several thermal and HHP treatments on that activity. LF exerted a high antirotaviral activity, regardless of its origin. Native LFs from bovine, ovine, swine and camel milk, and the human recombinant forms, at 1 mg/mL, showed neutralizing values in the range 87.5-98.6%, while human LF neutralized 58.2%. Iron saturation of bovine LF did not modify its antirotaviral activity. Results revealed interspecies differences in LFs heat susceptibility. Thus, pasteurization at 63 °C for 30 min led to a decrease of 60.1, 44.5, 87.1, 3.8 and 8% of neutralizing activity for human, bovine, swine, ovine and camel LFs, respectively. Pasteurization at 75 °C for 20 s was less harmful to the activity of LFs, with losses ranging from 0 to 13.8%. HHP treatment at 600 MPa for 15 min did not cause any significant decrease in the neutralizing activity of LFs.

Insights into Natural Products in Inflammation

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The ferroportin-ceruloplasmin system and the mammalian iron homeostasis machine: regulatory pathways and the role of lactoferrin

In the last 20 years, several new genes and proteins involved in iron metabolism in eukaryotes, particularly related to pathological states both in animal models and in humans have been identified, and we are now starting to unveil at the molecular level the mechanisms of iron absorption, the regulation of iron transport and the homeostatic balancing processes. In this review, we will briefly outline the general scheme of iron metabolism in humans and then focus our attention on the cellular iron export system formed by the permease ferroportin and the ferroxidase ceruloplasmin. We will finally summarize data on the role of the iron binding protein lactoferrin on the regulation of the ferroportin/ceruloplasmin couple and of other proteins involved in iron homeostasis in inflamed human macrophages.

Antibacterial and immunomodulatory activities of bovine lactoferrin against Escherichia coli O157:H7 infections in cattle

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a zoonotic pathogen that causes food-borne disease in humans ranging from watery diarrhea to bloody diarrhea and severe hemorrhagic colitis, renal failure and hemolytic uremic syndrome. Cattle, the most important source of E. coli O157:H7 transmission to humans, harbor the bacteria in their gastrointestinal tract without showing clinical symptoms. Prevention of E. coli O157:H7 infections in ruminants could diminish the public health risk. However, there is no specific treatment available nor a vaccine or a therapeutic agent which completely prevents E. coli O157:H7 infections in cattle. This paper provides an overview of latest research data on eradicating enterohemorrhagic E. coli O157:H7 in ruminants by use of bovine lactoferrin administration. The article provides insights into the anti-microbial and immunomodulatory activities of bovine lactoferrin against E. coli O157:H7 infections in cattle.

Efficacy of bovine lactoferrin in the post-surgical treatment of patients suffering from bisphosphonate-related osteonecrosis of the jaws: an open-label study

Osteonecrosis of the jaws is an emerging pathological condition characterized by un-exposure or exposure of the necrotic bone, independently from the etiology. This term is usually referred to medication-related osteonecrosis of the jaws due to severe adverse reaction to certain medicines, as bisphosphonates, used for the treatment of cancer and osteoporosis. The management of patients with Bisphosphonate-Related Osteonecrosis of the Jaws (BRONJ) remains challenging because surgical and medical interventions may not eradicate this pathology. The goal of treatment of patients at risk of developing BRONJ or of those who have active disease is the preservation of quality of life by controlling pain, managing infection, and preventing the development of new areas of necrosis. The treatment of osteonecrosis consists in the surgical removal of necrotic bone followed by antibiotic therapy and application of sterile greasy gauze until the wound closure. The classical medical treatment has been compared with the innovative one consisting in the application of sterile greasy gauze soaked with bovine lactoferrin (bLf) after surgery. Here, for the first time, bLf efficacy on wound repair in subjects suffering from BRONJ with the progressive destruction of bone in the mandible or maxilla has been demonstrated. The positive results consist in a significant shorter time of wound closure (1 or 2 weeks) compared to that observed with classical surgical treatment (2-3 months). These promising results are an interesting tool for the innovative treatment of this pathology and for increasing the quality of life of these patients.