Hepatic and extrahepatic clearance of circulating human lactoferrin: an experimental study in rat

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.

Lactoferrin as a regenerative agent: The old-new panacea?

Lactoferrin (Lf) possesses various biological properties and therapeutic potentials being a perspective anti-inflammatory, antibacterial, antiviral, antioxidant, antitumor, and immunomodulatory agent. A significant body of literature has also demonstrated that Lf modulates regenerative processes in different anatomical structures, such as bone, cartilage, skin, mucosa, cornea, tendon, vasculature, and adipose tissue. Hence, this review collected and analyzed the data on the regenerative effects of Lf, as well as paid specific attention to their molecular basis. Furthermore, tissue and condition-specific activities of different Lf types as well as problems of their delivery to the targeted organs were discussed. The authors strongly hope that this review will stimulate researchers to focus on the highlighted topics thus accelerating the progress of Lf's wider clinical application.

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.

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.

Albumin fusion at the N-terminus or C-terminus of human lactoferrin leads to improved pharmacokinetics and anti-proliferative effects on cancer cell lines

Human lactoferrin (hLF), a soluble factor of the innate immune system, exhibits various biological functions and therefore has potential as a therapeutic protein. However, the clinical applications of hLF are limited by its low stability in blood. We therefore attempted to resolve this by producing recombinant hLF fused to human serum albumin (HSA). Two HSA-fused hLFs with different fusion orientations (hLF-HSA and HSA-hLF) were produced in Chinese hamster ovary (CHO) DG44 cells. hLF-HSA revealed higher thermal stability, resistance to peptic degradation, and stability during the process of cellular uptake and release in an intestinal enterocyte model (Caco-2 cells) than HSA-hLF. The lower stability of HSA-hLF is presumably due to the steric hindrance imposed by HSA fusion to the N-terminus of hLF. Both HSA fusion proteins, especially HSA-hLF, displayed improved pharmacokinetic properties despite the lower protein stability of HSA-hLF. hLF-HSA and HSA-hLF exhibited approximately 3.3- and 20.7-fold longer half-lives (64.0 and 403.6 min), respectively, than holo-rhLF (19.5 min). Both HSA fusion proteins were found to exert enhanced growth inhibition effects on cancer cells in vitro, but not normal cells. Their enhanced growth inhibitory activities were considered to be due to the synergetic effects of hLF and HSA because hLF alone or HSA alone failed to exert such an effect. Altogether, Fusion of HSA to hLF yielded superior pharmacokinetics and anti-proliferative activities against cancer cells. HSA-fused hLF is a novel candidate for further application of hLF as biopharmaceuticals for intravenous administration.

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.

Targeting of stabilized plasmid lipid particles to hepatocytes in vivo by means of coupled lactoferrin

For non-viral gene delivery we prepared stabilized plasmid lipid particles (SPLPs), to which lactoferrin (LF) was coupled as a hepatocyte specific targeting ligand. LF-SPLPs and untargeted SPLPs labeled with [3H]cholesteryloleyl-ether were injected into rats. About 87% of the LF-SPLPs were eliminated from the blood within 5 min, while 80% of untargeted SPLPs were still circulating after 2 h. Fifty-two percent of the LF-SPLPs were taken up by hepatocytes, while non-parenchymal liver cells accounted for 16% of the uptake. Despite the efficient targeting of LF-SPLPs to hepatocytes and their capacity to transfect HepG2 and COS-7 cells in vitro, expression of a reporter gene was not detected in vivo. Overall, covalent coupling of LF to SPLPs leads to massive delivery in hepatocytes after systemic administration. However, these LF-SPLPs are not able to transfect these cells in vivo.

Uptake of ingested bovine lactoferrin and its accumulation in adult mouse tissues

Lactoferrin is a glycoprotein with antimicrobial and immunoregulatory properties, which is found in milk, other external secretions, and in the secondary granules of neutrophils. The present study examined the time course of uptake and the pattern of tissue accumulation of bovine lactoferrin (bLf) following intragastric intubation of a single dose to adult naïve mice or to mice daily fed bLf for 4 weeks. Following ingestion, bLf was transferred from the intestine into peripheral blood in a form with intact molecular weight (80 kDa) and localized within 10 to 20 min after oral administration in the liver, kidneys, gall bladder, spleen, and brain of both groups of mice. Immunoreactive bLf could also be detected in the luminal contents of the stomach, small intestine and colon 1 h after intragastric intubation. Interestingly, serum and tissue accumulation of bLf was approximately 50% lower in mice chronically fed this protein than in those given only the single oral dose. Furthermore, significant levels of bLf-specific IgA and IgG antibodies as well as bLf-containing IgA- and IgG immune complexes were detected in mice chronically fed bLf but not in those fed only once. Taken together, these results indicate that bLf resists major proteolytic degradation in the intestinal lumen and is readily absorbed in an antigenic form in blood and various mouse tissues. Chronic ingestion of lactoferrin reduces its uptake, probably through mechanisms such as immune exclusion, which minimize potential harmful reactions to food products.

Prophylaxis with lactoferrin, a novel antimicrobial agent, in a neonatal rat model of coinfection

Lactoferrin has broad-spectrum antimicrobial activity, and the authors hypothesized that recombinant human lactoferrin (Talactoferrin alfa [TLF]) would reduce mortality and morbidity in a coinfection model. The MIC 50 (minimum inhibitory concentration required to inhibit the growth of 50% of organisms) of TLF against Candida albicans and Staphylococcus epidermidis was determined. Neonatal Wistar rats were infected with C albicans or S epidermidis or both, at doses of 2 x10(8) colony-forming units (CFUs) given subcutaneously. Rat pups in each group were randomly given TLF intraperitoneally at 40 mg/kg/dose or 300 mg/kg/dose, or saline in 0.2 mL, once a day for 4 d and were monitored for mortality, weight gain, and blood culture positivity. Trough serum levels of TLF were measured at 24, 48, 72, 96, and 144 h. MIC 50 of TLF was 30 microg/mL and 500 microg/mL for C albicans and S epidermidis, respectively. TLF prophylaxis significantly improved survival in the coinfection group at 40 mg/kg/dose (by 16.1%; P=.019) and at 300 mg/kg/dose (by 15.1%; P=.027) and in the S epidermidis group at a dose of 40 mg/kg/dose (by 18.6%; P=.04). Weight gain was not affected by TLF prophylaxis. Serum trough levels of TLF were 1000-fold lower than in vitro MIC 50. The authors conclude that lactoferrin prophylaxis significantly enhanced survival in coinfection and in the subgroup of S epidermidis infection (40 mg/kg/dose) through indirect mechanisms.

A bio-recognition device developed onto nano-crystals of carbonate apatite for cell-targeted gene delivery

The DNA delivery to mammalian cells is an essential tool for analyzing gene structure, regulation, and function. The approach holds great promise for the further development of gene therapy techniques and DNA vaccination strategies to treat and control diseases. Here, we report on the establishment of a cell-specific gene delivery and expression system by physical adsorption of a cell-recognition molecule on the nano-crystal surface of carbonate apatite. As a model, DNA/nano-particles were successfully coated with asialofetuin to facilitate uptake by hepatocyte-derived cell lines through the asialoglycoprotein receptor (ASGPr) and albumin to prevent non-specific interactions of the particles with cell-surface. The resulting composite particles with dual surface properties could accelerate DNA uptake and enhance expression to a notable extent. Nano-particles coated with transferrin in the same manner dramatically enhanced transgene expression in the corresponding receptor-bearing cells and thus our newly developed strategy represents a universal phenomenon for anchoring a bio-recognition macromolecule on the apatite crystal surface for targeted gene delivery, having immediate applications in basic research laboratories and great promise for gene therapy.

Human Apo-Lactoferrin Enhances Angiogenesis Mediated by Vascular Endothelial Growth Factor A in vivo

BACKGROUND

Lactoferrin, LF, a multifunctional iron- and heparin-binding protein, present in exocrine body secretions and leukocytes, is remarkably resistant to proteolysis. Ingested bovine iron-unsaturated LF, apo-bLF, suppresses VEGF-A-mediated angiogenesis in a previously described rat mesentery angiogenesis assay, possibly explaining, at least in part, its established anticancer effect in rats and mice.

METHODS

Using the same experimental system, we have now studied the effect of (i) ingested human apo-LF, apo-hLF, on angiogenesis mediated by VEGF-A and bFGF, (ii) ingested human iron-saturated LF, holo-hLF, on VEGF-A-mediated angiogenesis and (iii) subcutaneous continuously infused apo-hLF on VEGF-A-mediated angiogenesis.

RESULTS

Ingested holo-hLF did not affect VEGF-A-mediated angiogenesis. Ingested apo-hLF (from one and the same batch) significantly enhanced VEGF-A-mediated angiogenesis but did not affect bFGF-mediated angiogenesis. Moreover, subcutaneously infused apo-hLF also significantly stimulated VEGF-A-mediated angiogenesis.

CONCLUSION

Taken together, the data suggest that apo-hLF exerts a specific proangiogenic effect in VEGF-A-mediated angiogenesis. Clearly, human and bovine apo-LF exert opposite effects on VEGF-A-induced angiogenesis. Differences in molecular features between human and bovine LFs of possible significance for the outcome are discussed. In hypoxia, compensatory collateral circulation is mediated primarily by VEGF-A. We hypothesize that systemically administered apo-hLF may promote collateral blood vessel formation at hypoxic sites in normal tissue, thus counteracting ischemia and infarction.

The antiviral protein human lactoferrin is distributed in the body to cytomegalovirus (CMV) infection-prone cells and tissues

PURPOSE

Lactoferrin has anti-Cytomegalovirus (CMV) and -HIV properties in vitro. However, the pharmacokinetic behavior of the 80-kD protein has not been well defined. We, therefore, assessed the plasma decay and body distribution of lactoferrin after intravenous administration to freely moving rats. Furthermore, the systemic availability of lactoferrin after intraperitoneal dosing was determined.

METHODS AND RESULTS

After intravenous injection, human lactoferrin (hLF) was rapidly cleared from the plasma, but higher doses resulted in prolonged plasma levels. Immunohistochemical analysis revealed a pronounced distribution of hLF to endothelial cells in the liver whereas diffuse staining in hepatocytes indicated the presence of considerable amounts in this large cell population. This endothelial association, which also was found in other organ/tissues, including blood vessels. was confirmed by in vitro cell-binding studies. In addition, leukocytes in plasma that were infiltrated in various organs showed binding of hLF. A small fraction of hLF was transported into the lymphatic system. Western blot analysis revealed that hLF, present in the various organs. mainly consisted of an 80-kD protein. After intraperitoneal administration, small amounts of 80-kD hLF distributed to the general circulation. The bioavailability was 0.6% but increased to 3.6% after multiple administrations.

CONCLUSIONS

The affinity of hLF for endothelial cells and leukocytes, and its penetration into the lymphatic system, indicates that this protein reaches target cells and body compartments that are crucial for CMV and HIV replication. The ability to reach the blood compartment after intraperitoneal dosing offers opportunities for parenteral administration of the protein in future studies on its antiviral effects in vivo.

Antiviral activities of lactoferrin

Lactoferrin (LF) is an iron binding glycoprotein that is present in several mucosal secretions. Many biological functions have been ascribed to LF. One of the functions of LF is the transport of metals, but LF is also an important component of the non-specific immune system, since LF has antimicrobial properties against bacteria, fungi and several viruses. This review gives an overview of the present knowledge about the antiviral activities and, when possible, the antiviral modes of action of this protein. Lactoferrin displays antiviral activity against both DNA- and RNA-viruses, including rotavirus, respiratory syncytial virus, herpes viruses and HIV. The antiviral effect of LF lies in the early phase of infection. Lactoferrin prevents entry of virus in the host cell, either by blocking cellular receptors, or by direct binding to the virus particles.

Lactoferrin protects against development of hepatitis caused by sensitization of Kupffer cells by lipopolysaccharide

BALB/c mice were intravenously injected with lipopolysaccharide (LPS) (0.05 microg/g of body weight) 7 days after being primed with zymosan. Recombinant human lactoferrin (250 microg/g of body weight), intravenously administered 1 day before the injection of LPS, significantly lessened the severity of hepatitis, as assessed by levels of serum alanine transaminase compared to those seen when casein was administered. The transient rise of serum tumor necrosis factor alpha (TNF-alpha) after LPS treatment was also significantly lowered by the intravenous administration of lactoferrin, suggesting that the effect of lactoferrin was due to the suppression of TNF-alpha production. The following results indicate that the sites of action of lactoferrin for the suppression of the development of this type of hepatitis are Kupffer cells. Gadolinium chloride, a substance known to eliminate Kupffer cells, administered 1 day before LPS, inhibited the transient rise of TNF-alpha and protected against the development of hepatitis. Kupffer cells isolated from mice intraperitoneally injected with recombinant human lactoferrin became refractory to LPS. The specific interaction of recombinant human lactoferrin with the Kupffer cells was shown by a binding assay, which revealed two types of binding sites on mouse Kupffer cells. Of the two dissociation constants determined in this way, the lower dissociation constant, 0.47 x 10(-6) M, was within the range of the 50% effective doses for the suppression of TNF-alpha production. These results suggest that recombinant human lactoferrin administered to mice suppresses the production of TNF-alpha by Kupffer cells by directly associating with the binding sites on these cells.