Structure of iron saturated C-lobe of bovine lactoferrin at pH 6.8 indicates a weakening of iron coordination

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.

Influenza A-induced cystic fibrosis transmembrane conductance regulator dysfunction increases susceptibility to Streptococcus pneumoniae

Influenza A virus (IAV) infection is commonly complicated by secondary bacterial infections that lead to increased morbidity and mortality. Our recent work demonstrates that IAV disrupts airway homeostasis, leading to airway pathophysiology resembling cystic fibrosis disease through diminished cystic fibrosis transmembrane conductance regulator (CFTR) function. Here, we use human airway organotypic cultures to investigate how IAV alters the airway microenvironment to increase susceptibility to secondary infection with Streptococcus pneumoniae (Spn). We observed that IAV-induced CFTR dysfunction and airway surface liquid acidification is central to increasing susceptibility to Spn. Additionally, we observed that IAV induced profound transcriptional changes in the airway epithelium and proteomic changes in the airway surface liquid in both CFTR-dependent and -independent manners. These changes correspond to multiple diminished host defense pathways and altered airway epithelial function. Collectively, these findings highlight both the importance of CFTR function during infectious challenge and demonstrate a central role for the lung epithelium in secondary bacterial infections following IAV.

Testing Antimicrobial Properties of Human Lactoferrin-Derived Fragments

Lactoferrin, an iron-binding glycoprotein, plays a significant role in the innate immune system, with antibacterial, antivirial, antifungal, anticancer, antioxidant and immunomodulatory functions reported. It is worth emphasizing that not only the whole protein but also its derived fragments possess antimicrobial peptide (AMP) activity. Using AmpGram, a top-performing AMP classifier, we generated three novel human lactoferrin (hLF) fragments: hLF 397-412, hLF 448-464 and hLF 668-683, predicted with high probability as AMPs. For comparative studies, we included hLF 1-11, previously confirmed to kill some bacteria. With the four peptides, we treated three Gram-negative and three Gram-positive bacterial strains. Our results indicate that none of the three new lactoferrin fragments have antimicrobial properties for the bacteria tested, but hLF 1-11 was lethal against Pseudomonas aeruginosa. The addition of serine protease inhibitors with the hLF fragments did not enhance their activity, except for hLF 1-11 against P. aeruginosa, which MIC dropped from 128 to 64 µg/mL. Furthermore, we investigated the impact of EDTA with/without serine protease inhibitors and the hLF peptides on selected bacteria. We stress the importance of reporting non-AMP sequences for the development of next-generation AMP prediction models, which suffer from the lack of experimentally validated negative dataset for training and benchmarking.

Abd El-Maksoud A, M. Ambrósio F. de Gouveia G. Recent Development in Antioxidant of Milk and Its Products

Free radicals are produced in humans through natural metabolism or the external environment, such as diet. These free radicals are neutralized by the antioxidant system, whereas enzymes, for example, catalase, superoxide dismutase, and glutathione peroxidase, play an important role in preventing excessive free radicals. Food antioxidants give a good hand in enhancing the human antioxidant system; high consumption of a diet rich in natural antioxidants protects against the risk of diseases such as cardiovascular, cancer, diabetes, and obesity. Milk and its products are popular for a wide range of consumers. Milk contains casein, whey protein, lactoferrin, milk lipid and phospholipids, vitamins, and microelements, for example, selenium (Se), which have antioxidant properties. Furthermore, probiotication of milk either sweet or fermented could enhance the antioxidant capacity of milk. This chapter focuses on presenting recent review data on milk components with antioxidant activity and their health benefits, probiotics as antioxidant agents, and methods for enhancing the antioxidant capacity of dairy products. The key aim of this chapter is to focus on major strategies for enhancing the antioxidant capacity of milk and its products.

Providing New Insights on the Molecular Properties and Thermal Stability of Ovotransferrin and Lactoferrin

Ovotransferrin (OVT) is a multi-functional protein showing over 50% homology with Bovine lactoferrin (BLF) and human lactoferrin (HLF), which have the potential to be a substitute for lactoferrin (LF) due to the limited production of LF. To explore the substitutability of OVT, the molecular properties and thermal stability of OVT, BLF and HLF were characterized because these properties will affect the processing quality and biological activities of protein products when exposed to different processing conditions (e.g., temperature, pH, ion strength). The results showed that although obviously different isoelectric point (5.31, 9.12 and 8.75 for OVT, BLF and HLF, respectively), particle size distribution and hydrophobicity were found, they exhibited good dispersity because of high potential value. They showed an endothermic peak at 80.64 °C, 65.71 °C and 90.01 °C, respectively, and the denaturation temperature varied at different pH and ionic strength. OVT and BLF were more susceptible to heating at pH 5.0 as reflected by the decline of denaturation temperature (21.78 °C shift for OVT and 5.81 °C shift for BLF), while HLF could remain stable. Compared with BLF, OVT showed higher secondary structure stability at pH 7.0 and 9.0 with heating. For example, the α-helix content of OVT changed from 20.35% to 15.4% at pH 7.0 after heating, while that of BLF changed from 20.05% to 6.65%. The increase on fluorescence intensity and redshifts on the maximum wavelength after heating indicated the changes of tertiary structure of them. The turbidity measurements showed that the thermal aggregation degree of OVT was lower than BLF and HLF at pH 7.0 (30.98%, 59.53% and 35.66%, respectively) and pH 9.0 (4.83%, 12.80% and 39.87%, respectively). This work demonstrated the similar molecular properties and comparable thermal stability of OVT to BLF and HLF, which can offer a useful reference for the substitute of LF by OVT.

Lactoferrin: A glycoprotein that plays an active role in human health

Lactoferrin (Lf), existing widely in human and mammalian milk, is a multifunctional glycoprotein with many functions, such as immune regulation, anti-inflammation, antibacterial, antiviral, and antioxidant. These extensive functions largely attribute to its ability to chelate iron and interfere with the cellular receptors of pathogenic microorganisms and their hosts. Moreover, it is non-toxic and has good compatibility with other supplements. Thus, Lf has been widely used in food nutrition, drug carriers, biotechnology, and feed development. Although Lf has been continuously explored and studied, a more comprehensive and systematic compendium is still required. This review presents the recent advances in the structure and physicochemical properties of Lf as well as clinical studies on human diseases, with the aim of providing a reference for further research of Lf and the development of its related functional products.

The application of lactoferrin in infant formula: The past, present and future

Human milk is universally regarded as the gold standard to fulfill nutrition needs of infants. Lactoferrin (LF) is a major multiple bioactive glycoprotein in human milk but little is presented in infant formula. LF can resist digestion in the infant gastrointestinal tract and is absorbed into the bloodstream in an intact form to perform physiological functions. Evidence suggest that LF prevents pathogen infection, promotes immune system development, intestinal development, brain development and bone health, as well as ameliorates iron deficiency anemia. However, more clinical studies of LF need to be further elucidated to determine an appropriate dosage for application in infant formula. LF is sensitive to denaturation induced by processing of infant formula such as heat treatments and spay drying. Thus, further studies should be focus on maximizing the retention of LF activity in the infant formula process. This review summarizes the structural features of LF. Then the digestion, absorption and metabolism of LF in infants are discussed, followed by the function of LF for infants. Further, we summarize LF in infant formula and effects of processing of infant formula on bioactivities of LF, as well as future perspectives of LF research.

Molecular modeling of lactoferrin for food and nutraceutical applications: insights from in silico techniques

Lactoferrin is a protein, primarily found in milk that has attracted the interest of the food industries due to its health properties. Nevertheless, the instability of lactoferrin has limited its commercial application. Recent studies have focused on encapsulation to enhance the stability of lactoferrin. However, the molecular insights underlying the changes of structural properties of lactoferrin and the interaction with protectants remain poorly understood. Computational approaches have proven useful in understanding the structural properties of molecules and the key binding with other constituents. In this review, comprehensive information on the structure and function of lactoferrin and the binding with various molecules for food purposes are reviewed, with a special emphasis on the use of molecular dynamics simulations. The results demonstrate the application of modeling and simulations to determine key residues of lactoferrin responsible for its stability and interactions with other biomolecular components under various conditions, which are also associated with its functional benefits. These have also been extended into the potential creation of enhanced lactoferrin for commercial purposes. This review provides valuable strategies in designing novel nutraceuticals for food science practitioners and those who have interests in acquiring familiarity with the application of computational modeling for food and health purposes.

Antioxidant Activity of Milk and Dairy Products

The aim of the study was to present a review of literature data on the antioxidant potential of raw milk and dairy products (milk, fermented products, and cheese) and the possibility to modify its level at the milk production and processing stage. Based on the available reports, it can be concluded that the consumption of products that are a rich source of bioactive components improves the antioxidant status of the organism and reduces the risk of development of many civilization diseases. Milk and dairy products are undoubtedly rich sources of antioxidant compounds. Various methods, in particular, ABTS, FRAP, and DPPH assays, are used for the measurement of the overall antioxidant activity of milk and dairy products. Research indicates differences in the total antioxidant capacity of milk between animal species, which result from the differences in the chemical compositions of their milk. The content of antioxidant components in milk and the antioxidant potential can be modified through animal nutrition (e.g., supplementation of animal diets with various natural additives (herbal mixtures, waste from fruit and vegetable processing)). The antioxidant potential of dairy products is associated with the quality of the raw material as well as the bacterial cultures and natural plant additives used. Antioxidant peptides released during milk fermentation increase the antioxidant capacity of dairy products, and the use of probiotic strains contributes its enhancement. Investigations have shown that the antioxidant activity of dairy products can be enhanced by the addition of plant raw materials or their extracts in the production process. Natural plant additives should therefore be widely used in animal nutrition or as functional additives to dairy products.

Bioactives in bovine milk: chemistry, technology, and applications

The significance of dairy in human health and nutrition is gaining significant momentum as consumers continue to desire wholesome, nutritious foods to fulfill their health and wellness needs. Bovine milk not only consists of all the essential nutrients required for growth and development, it also provides a broad range of bioactive components that play an important role in managing human homeostasis and immune function. In recent years, milk bioactives, including α-lactalbumin, lactoferrin, glycomacropeptide, milk fat globule membrane, and milk oligosaccharides, have been intensively studied because of their unique bioactivity and functionality. Challenges for the application of these bioactive components in food and pharmaceutical formulations are associated with their isolation and purification on an industrial scale and also with their physical and chemical instability during processing, storage, and digestion. These challenges can be overcome by advanced separation techniques and sophisticated nano- or micro-encapsulation technologies. Current knowledge about the chemistry, separation, and encapsulation technology of major bioactives derived from bovine milk and their application in the food industry is reviewed here.

A Peptide Bond from the Inter-lobe Segment in the Bilobal Lactoferrin Acts as a Preferred Site for Cleavage for Serine Proteases to Generate the Perfect C-lobe: Structure of the Pepsin Hydrolyzed Lactoferrin C-lobe at 2.28 Å Resolution

C-lobe represents the C-terminal half of lactoferrin which is a bilobal 80 kDa iron binding glycoprotein. The two lobes are designated as N-lobe (Ser1-Glu333) and C-lobe (Arg344-Arg689). The N- and C-lobes are connected by a 10-residue long α-helical peptide (Thr334-Thr343). Both lobes adopt similar conformations and have identical iron binding sites. The bilobal lactoferrin was hydrolyzed in a limited proteolysis using pepsin at pH 2.0. It produced a 40 kDa and fully functional C-lobe which was purified and crystallized at pH 8.0. The structure determination revealed that the structure contained residues from Tyr342 to Arg689 representing a fully functional monoferric C-lobe. It showed that pepsin cleaved lactoferrin at the peptide bond Arg341-Tyr342 which is part of the inter-lobe decapeptide. Interestingly, the two previously determined structures of the enzymatically produced C-lobe using trypsin and proteinase K also cleaved lactoferrin at the same peptide bond Arg341-Tyr342. This was a striking result as the three enzymes, pepsin, trypsin and proteinase K have different specificity requirements and yet they cleaved the bilobal lactoferrin at the same peptide bond and generated an identical and fully functional C-lobe. This shows that the observed cleavage site in lactoferrin adopts a highly favourable conformation for proteolysis. It is noteworthy that the three enzymes with different specificities cut the protein at the same peptide bond which may be of physiological significance because the antibacterial action of lactoferrin is extended further through the C-lobe.

The role of iron in the pathogenesis of COVID-19 and possible treatment with lactoferrin and other iron chelators

Iron overload is increasingly implicated as a contributor to the pathogenesis of COVID-19. Indeed, several of the manifestations of COVID-19, such as inflammation, hypercoagulation, hyperferritinemia, and immune dysfunction are also reminiscent of iron overload. Although iron is essential for all living cells, free unbound iron, resulting from iron dysregulation and overload, is very reactive and potentially toxic due to its role in the generation of reactive oxygen species (ROS). ROS react with and damage cellular lipids, nucleic acids, and proteins, with consequent activation of either acute or chronic inflammatory processes implicated in multiple clinical conditions. Moreover, iron-catalyzed lipid damage exerts a direct causative effect on the newly discovered nonapoptotic cell death known as ferroptosis. Unlike apoptosis, ferroptosis is immunogenic and not only leads to amplified cell death but also promotes a series of reactions associated with inflammation. Iron chelators are generally safe and are proven to protect patients in clinical conditions characterized by iron overload. There is also an abundance of evidence that iron chelators possess antiviral activities. Furthermore, the naturally occurring iron chelator lactoferrin (Lf) exerts immunomodulatory as well as anti-inflammatory effects and can bind to several receptors used by coronaviruses thereby blocking their entry into host cells. Iron chelators may consequently be of high therapeutic value during the present COVID-19 pandemic.

Lactoferrin: an overview of its main functions, immunomodulatory and antimicrobial role, and clinical significance

Lactoferrin (LF), a glycoprotein found in mucosal secretions, is characterized by a wide range of functions, including immunomodulatory and anti-inflammatory activities. Moreover, several investigations confirmed that LF displays high effectiveness against multiple bacteria and viruses and may be regarded as a potential inhibitor of enveloped viruses, such as presently prevailing SARS-CoV-2. In our review, we discuss available studies about LF functions and bioavailability of different LF forms in in vitro and in vivo models. Moreover, we characterize the potential benefits and side effects of LF use; we also briefly summarize the latest clinical trials examining LF application. Finally, we point potential role of LF in inflammatory bowel disease and indicate its use as a marker for disease severity.

In Silico Discovery of JMJD6 Inhibitors for Cancer Treatment

The 2-oxoglutarate (2OG)-dependent oxygenase JMJD6 is emerging as a potential anticancer target, but its inhibitors have not been reported so far. In this study, we reported an in silico protocol to discover JMJD6 inhibitors targeting the druggable 2OG-binding site. Following this protocol, one compound, which we named as WL12, was found to be able to inhibit JMJD6 enzymatic activity and JMJD6-dependent cell proliferation. To our best knowledge, this is the first case in drug discovery targeting JMJD6.

Research and development on lactoferrin and its derivatives in China from 2011–2015

Lactoferrin (Lf), a multifunctional glycoprotein, is an important antimicrobial and immune regulatory protein present in neutrophils and most exocrine secretions of mammals. Lactoferricin (Lfcin) is located in the N-terminal region of this protein. In this review, the current state of research into Lf and Lfcin in China is described. Searching with HistCite software in Web Sci located 118 papers published by Chinese researchers from 2011–2015, making China one of the top 3 producers of Lf research and development in the world. The biological functions of Lf and Lfcin are discussed, including antibacterial, antiviral, antifungal, anticarcinogenic, and anti-inflammatory activities; targeted drug delivery, induction of neurocyte, osteoblast, and tenocyte growth, and possible mechanisms of action. The preparation and heterologous expression of Lf in animals, bacteria, and yeast are discussed in detail. Five Lf-related food additive factories and 9 Lf-related health food production companies are certified by the China Food and Drug Administration (CFDA). The latest progress in the generation of transgenic livestock in China, the safety of the use of transgenic animals, and future prospects for the uses of Lf and Lfcin are also covered.

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.