Lactoferrin is required for early B cell development in C57BL/6 mice

Can Lactoferrin, a Natural Mammalian Milk Protein, Assist in the Battle against COVID-19?

Notwithstanding mass vaccination against specific SARS-CoV-2 variants, there is still a demand for complementary nutritional intervention strategies to fight COVID-19. The bovine milk protein lactoferrin (LF) has attracted interest of nutraceutical, food and dairy industries for its numerous properties-ranging from anti-viral and anti-microbial to immunological-making it a potential functional ingredient in a wide variety of food applications to maintain health. Importantly, bovine LF was found to exert anti-viral activities against several types of viruses, including certain SARS-CoV-2 variants. LF's potential effect on COVID-19 patients has seen a rapid increase of in vitro and in vivo studies published, resulting in a model on how LF might play a role during different phases of SARS-CoV-2 infection. Aim of this narrative review is two-fold: (1) to highlight the most relevant findings concerning LF's anti-viral, anti-microbial, iron-binding, immunomodulatory, microbiota-modulatory and intestinal barrier properties that support health of the two most affected organs in COVID-19 patients (lungs and gut), and (2) to explore the possible underlying mechanisms governing its mode of action. Thanks to its potential effects on health, bovine LF can be considered a good candidate for nutritional interventions counteracting SARS-CoV-2 infection and related COVID-19 pathogenesis.

Lactoferrin Deficiency Impairs Proliferation of Satellite Cells via Downregulating the ERK1/2 Signaling Pathway

Lactoferrin (Ltf), a naturally active glycoprotein, possesses anti-inflammatory, anti-microbial, anti-tumor, and immunomodulatory activities. Many published studies have indicated that Ltf modulates the proliferation of stem cells. However, the role of Ltf in the proliferation of satellite cells, an important cell type in muscle regeneration, has not yet been reported. Here, by using Ltf systemic knockout mice, we illustrate the role of Ltf in skeletal muscle. Results shows that Ltf deficiency impaired proliferation of satellite cells (SCs) and the regenerative capability of skeletal muscle. Mechanistic studies showed that ERK1/2 phosphorylation was significantly downregulated after Ltf deletion in SCs. Simultaneously, the cell cycle-related proteins cyclin D and CDK4 were significantly downregulated. Intervention with exogenous recombinant lactoferrin (R-Ltf) at a concentration of 1000 μg/mL promoted proliferation of SCs. In addition, intraperitoneal injection of Ltf effectively ameliorated the skeletal muscle of mice injured by 1.2% BaCl₂ solution. Our results suggest a protective effect of Ltf in the repair of skeletal muscle damage. Ltf holds promise as a novel therapeutic agent for skeletal muscle injuries.

Deficiency of Lactoferrin aggravates lipopolysaccharide-induced acute inflammation via recruitment macrophage in mice

Lactoferrin (Lf), a multiple functional natural immune protein, is widely distributed in mammalian milk and glandular secretions (bile, saliva, tears and nasal mucosal secretions, etc.). In the previous study, we found that Lf plays an anti-inflammatory and anti-tumorigenesis role in AOM/DSS (azoxymethane/dextran sulfate sodium) induced mouse colitis-associated colon cancer model. Although we found that Lf has anti-inflammatory effects in chronic inflammation, its specific role and mechanisms in acute inflammation have not been clarified. Here, we reported that the expression levels of Lf were significantly increased when the organism was infected by Gram-negative bacteria. We then explored the role and potential mechanism of Lf in lipopolysaccharide (LPS)-induced acute inflammation. In the LPS-induced acute abdominal inflammation model, Lf deficiency aggravated inflammatory response and promoted macrophage chemotaxis to the inflammation site. Lf inhibited macrophage chemotaxis by suppressing the expression of macrophage-associated chemokines Ccl2 and Ccl5. Highly activated NF-κB signaling in Lf^−/− mice was responsible for the high expression of Ccl2 and Ccl5. Our results suggested that the anti-inflammatory effect of Lf offers a new potential treatment for acute inflammatory diseases.

The Functional Role of Lactoferrin in Intestine Mucosal Immune System and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is one of the main types of intestinal inflammatory diseases with intestine mucosal immune disorder. Intestine mucosal immune system plays a remarkable and important role in the etiology and pathogenesis of IBD. Therefore, understanding the intestine mucosal immune mechanism is a key step to develop therapeutic interventions for IBD. Intestine mucosal immune system and IBD are influenced by various factors, such as inflammation, gut permeability, gut microbiota, and nutrients. Among these factors, emerging evidence show that nutrients play a key role in inflammation activation, integrity of intestinal barrier, and immune cell modulation. Lactoferrin (LF), an iron-binding glycoprotein belonging to transferrin family, is a dietary bioactive component abundantly found in mammalian milk. Notably, LF has been reported to perform diverse biological functions including antibacterial activity, anti-inflammatory activity, intestinal barrier protection, and immune cell modulation, and is involved in maintaining intestine mucosal immune homeostasis. The improved understanding of the properties of LF in intestine mucosal immune system and IBD will facilitate its application in nutrition, clinical medicine, and health. Herein, this review outlines the recent advancements on LF as a potential therapeutic intervention for IBD associated with intestine mucosal immune system dysfunction. We hope this review will provide a reference for future studies and lay a theoretical foundation for LF-based therapeutic interventions for IBD by understanding the particular effects of LF on intestine mucosal immune system.