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

Bonaccorsi di Patti, Maria Carmela

Cutone, Antimo

Musci, Giovanni

English

Archivio della ricerca- Università di Roma La Sapienza

Citation: Cutone, A.; Musci, G.;Bonaccorsi di Patti, M.C. Lactoferrin,the Moonlighting Protein of InnateImmunity. Int. J. Mol. Sci. 2023, 24,15888. https://doi.org/10.3390/ijms242115888Received: 26 October 2023Accepted: 30 October 2023Published: 2 November 2023Copyright: © 2023 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). International Journal of Molecular SciencesEditorialLactoferrin, the Moonlighting Protein of Innate ImmunityAntimo Cutone 1 , Giovanni Musci 1 and Maria Carmela Bonaccorsi di Patti 2,*1 Department of Biosciences and Territory, University of Molise, 86090 Pesche, Italy;antimo.cutone@unimol.it (A.C.); giovanni.musci@unimol.it (G.M.)2 Department of Biochemical Sciences, Sapienza University of Roma, 00185 Rome, Italy* Correspondence: mariacarmela.bonaccorsi@uniroma1.itLactoferrin (Lf), a naturally occurring glycoprotein involved in innate immunity, wasfirst discovered in bovine milk [1] and later purified from human milk [2]. In recentyears, Lf has become increasingly attractive to researchers from different fields due to itsmultiple functions and applications. In addition to its initially discovered antimicrobialeffects [3], Lf is currently recognized as a potent multi-target nutraceutical, endowedwith immunomodulatory [4], anti-inflammatory [5], anti-oxidant [3] and anti-cancer [6]properties. Of note, Lf shows a wide range of tolerability, being classified as a “generallyrecognized as safe” (GRAS) substance by the U.S.A. Food and Drug Administration [7] andas a dietary supplement by the European Food Safety Authority [8]. At a mechanistic level,some of the functions exerted by Lf have been related to both its iron-binding ability andits highly cationic charge, which enables it to interact with a wide repertoire of host andpathogen receptors and antigens [9,10]. However, most of its biological effects have yet tobe fully appreciated and unveiled. Moreover, Lf has recently emerged as a potent carrierfor the delivery of biologically active nanoparticles [11,12].This Special Issue, entitled “Lactoferrin, the Moonlighting Protein of Innate Immunity”,consists of five articles selected for publication.Bukowska-Ośko and colleagues reviewed the most recent studies about Lf’s ability todefend the host from DNA damage induced by chemical and biological agents [13]. Suchchanges in DNA structure and sequence can cause premature aging, cell degenerationand death, thus leading to severe tissue and organ failure [14]. Several diseases, includingcancer, have been associated with this process, so recent research has focused on promisingcompounds that can counteract/reverse these effects [15,16]. In this scenario, naturalproducts, which have evolved to prevent disease and repair damaged genetic material,are emerging as safe, well-tolerated and adjuvant substances for the maintenance of bodyhomeostasis, including genome integrity. The review by Bukowska-Ośko et al. presents thenew and innovative role of Lf in the protection of human genetic material against internaland external damage, described via cell cycle modulation mechanisms at all its levels andrepair mechanisms [13].As an ancestral guardian, the primary defense activities of Lf against pathogens andtheir sequelae have been dissected in different studies in the present Special Issue. Liand colleagues have investigated the beneficial effect of Lf administration in a model oflipopolysaccharide (LPS)-induced intestinal immune barrier damage [17]. The innate im-mune barrier of the intestinal tract plays a crucial role in human health, especially in infantsand young children who have an immature immune system [18]. First, pharmacokineticanalyses of Lf in mice intestinal tissues, stomach tissues and blood revealed the higher effi-cacy of oral gavage in improving Lf bioavailability with respect to intraperitoneal injection.In addition, through in vitro and in vivo models of infantile intestinal immune barrier dam-age, Lf was demonstrated to significantly increase the survival rate of LPS-induced primaryintestinal epithelial cells and downregulate the expression of inflammatory cytokines, suchas interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and interferon (IFN)-γ, in bothprimary intestinal epithelial cells and blood of mice. Interestingly, the beneficial effectsInt. J. Mol. Sci. 2023, 24, 15888. https://doi.org/10.3390/ijms242115888 https://www.mdpi.com/journal/ijmsInt. J. Mol. Sci. 2023, 24, 15888 2 of 4of Lf treatment were correlated with the rate of iron saturation of the glycoprotein, withhigher efficacy for Apo-Lf than for the Holo form. Next, the related immune molecularmechanism, investigated using RNA-seq assay, revealed that ELAVL1 (embryonic lethalabnormal vision Drosophila 1) is one of the key genes regulated via Lf treatment, and theELAVL1/PI3K/NF-κB pathway was shown to participate in Lf-mediated protection ofinfantile intestinal immune barrier damage. In addition, the ratio of blood CD4+/CD8+ Tcells was significantly higher in the Lf-treated mice than in the control mice. Lactoferrinwas therefore proven to alleviate LPS-induced intestinal immune barrier damage in youngmice through the regulation of ELAVL1-related immune signaling pathways, which wouldexpand the current knowledge of the functions of bioactive proteins in food within differentlevels of research, as well as benefit preclinical and clinical research in the long run [17].The antiviral activity of Lf has been widely recognized [19,20], and the recent spreadof Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), the causative agentof coronavirus disease (COVID)-19, has renewed the interest in this glycoprotein in thisfield [21]. Several in vitro [22,23] and clinical studies [24,25] have pointed out the possibleemployment of Lf, especially the bovine form, as an adjuvant of standard-of-care therapyfor COVID-19 patients [26]. In this framework, the study by Piacentini et al. was aimedat unraveling the putative interactions between human Lf (hLf), SARS-CoV-2 receptor-binding domain (RBD) and human angiotensin-converting enzyme 2 (ACE2) receptor,in order to provide a molecular basis for the reported preventive effect of Lf againstCoV-2 infection [27]. Specifically, kinetic and thermodynamic parameters of the pairwiseinteractions between the three proteins, carried out via both biolayer interferometry andlatex nanoparticle-enhanced turbidimetry, revealed that hLf was able to bind the ACE2receptor ectodomain with significantly high affinity, while no binding to the RBD wasobserved up to the maximum “physiological” concentration range of Lf. Indeed, above aconcentration of 1 µM, hLf appeared to directly interfere with RBD–ACE2 binding, bringingabout a measurable, up to 300-fold increase of the KD value relative to RBD–ACE2 complexformation [27].The protective role of Lf against pathogenic processes related to the expression ofthe sole viral proteins was also reported in the study by Ianiro and colleagues, whereiron saturation rate was found to drive bLf effects on oxidative stress and neurotoxicityinduced via HIV-1 Tat [28]. Despite tremendous advances in combined antiretroviraltherapy, the standard therapy for HIV-1 infection, HIV+ patients can experience HIV-associated neurocognitive disorders [29], mainly due to the chronic basal expression ofHIV-1 non-structural proteins, such as Tat, which can trigger neurotoxic effects, relatedto both oxidative stress induction and excitotoxicity [30,31]. BLf was found to reduceoxidative stress and oxidative damage in astrocytes expressing the Tat protein of HIV-1.Additionally, Lf restored the normal function of iron uptake in cells expressing the viralprotein. However, the effects of the glycoprotein varied depending on its iron saturation,as the Holo form was found to exacerbate Tat-induced excitotoxicity via up-regulation ofSystem Xc−, thus highlighting the utmost importance of considering Lf iron saturationwhen applied to clinical therapies, as it can dramatically influence the success or failure ofthe treatment itself [28].In this framework, the role of iron in driving Lf activities was also remarked in thestudy by Lian and colleagues in which, as a natural defense agent in ocular wellness [32,33],Lf was explored as a promising tool in the treatment of myopia in a murine model [34]. Micewere given different forms of Lf, such as native Lf, Holo Lf and digested Lf, for 3 weeksbefore inducing myopia with minus lenses. The results showed that mice given digestedLf or Holo-Lf had a less elongated axial length and thinned choroid compared with thosegiven native-Lf. Gene expression analysis also showed that the groups given Lf, both innative and Holo forms, and its derivatives had lower levels of certain cytokines, such asIL-8 and TNF-α, and growth factors, such as vascular endothelial growth factor (VEGF),associated with myopia, compared with the PBS-treated group. The authors concludethat oral administration of digested Lf can suppress myopia more effectively than theInt. J. Mol. Sci. 2023, 24, 15888 3 of 4administration of native-Lf. Additionally, Holo-Lf can suppress choroidal thinning moreeffectively than native-Lf with low saturation, again confirming the primary role of themetal in Lf biological functions.This Special Issue was effective in bringing together new and promising studies in thelactoferrin field, emphasizing the potential application of this natural product in currentand future research as an effective alternative or complement to standard therapy.Author Contributions: All authors have read and agreed to the published version of the manuscript.Conflicts of Interest: The authors declare no conflict of interest.References1. Sorensen, M.; Sorensen, S. The Proteins in Whey. Compte Rendu Trav. Lab. Carlsberg Ser. Chim. 1939, 23, 55–99.2. Johanson, B. Isolation of an iron-containing red protein from human milk. Acta. Chem. Scand. 1960, 14, 510–512. [CrossRef]3. Valenti, P.; Antonini, G. Lactoferrin: An important host defence against microbial and viral attack. Cell. Mol. Life Sci. 2005, 62,2576–2587. [CrossRef]4. Legrand, D. Lactoferrin, a key molecule in immune and inflammatory processes. Biochem. Cell Biol. 2012, 90, 252–268. [CrossRef][PubMed]5. Kruzel, M.L.; Zimecki, M.; Actor, J.K. Lactoferrin in a Context of Inflammation-Induced Pathology. Front. Immunol. 2017, 8, 1438.[CrossRef] [PubMed]6. Superti, F. Lactoferrin from Bovine Milk: A Protective Companion for Life. Nutrients 2020, 12, 2562. [CrossRef]7. U.S. FDA. GRN 000465 Cow’s Milk-Derived Lactoferrin; Morinaga Milk Industry Co., Ltd.: Tokyo, Japan; U.S. Food and DrugAdministration (U.S. FDA), Center for Food Safety & Applied Nutrition (CFSAN), Office of Food Additive Safety: Silver Spring,MD, USA, 2014. Available online: https://www.accessdata.fda.gov/scripts/fdcc/index.cfm?set=GRASNotices&id=465 (accessedon 27 October 2023).8. European Food Safety Authority. Scientific opinion on bovine lactoferrin. EFSA J. 2012, 10, 2701. [CrossRef]9. Suzuki, Y.A.; Lopez, V.; Lönnerdal, B. Mammalian lactoferrin receptors: Structure and function. Cell. Mol. Life Sci. 2005, 62,2560–2575. [CrossRef]10. Latorre, D.; Puddu, P.; Valenti, P.; Gessani, S. Reciprocal Interactions between Lactoferrin and Bacterial Endotoxins and Their Rolein the Regulation of the Immune Response. Toxins 2010, 2, 54–68. [CrossRef]11. Sabra, S.; Agwa, M.M. Lactoferrin, a unique molecule with diverse therapeutical and nanotechnological applications. Int. J. Biol.Macromol. 2020, 164, 1046–1060. [CrossRef]12. Elzoghby, A.O.; Abdelmoneem, M.A.; Hassanin, I.A.; Abd Elwakil, M.M.; Elnaggar, M.A.; Mokhtar, S.; Fang, J.Y.; Elkhodairy,K.A. Lactoferrin, a multi-functional glycoprotein: Active therapeutic, drug nanocarrier & targeting ligand. Biomaterials 2020, 263,120355. [CrossRef]13. Bukowska-Ośko, I.; Sulejczak, D.; Kaczyńska, K.; Kleczkowska, P.; Kramkowski, K.; Popiel, M.; Wietrak, E.; Kowalczyk, P.Lactoferrin as a Human Genome “Guardian”—An Overall Point of View. Int. J. Mol. Sci. 2022, 23, 5248. 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Lactoferrin, the moonlighting protein of innate immunity

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

Lactoferrin, the moonlighting protein of innate immunity

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