The bovine Lactoferrin-Osteopontin complex increases proliferation of human intestinal epithelial cells by activating the PI3K/Akt signaling pathway.

ABSTRACT

Lactoferrin (LF) and osteopontin (OPN), multifunctional proteins involved in cell proliferation, can form a complex. LF binds iron, whereas OPN binds calcium. We investigated whether iron- and calcium-binding influences complex formation and the pro-proliferation property of the LF-OPN complex, and the mechanism behind this effect. LF-OPN complexes were prepared using bovine milk LF and OPN, and effects on proliferation of human intestinal epithelial cells (HIECs) were evaluated using a BrdU proliferation assay. Of the four complexes formed by apo- and holo-LF/OPN, the apo-Lf&holo-OPN complex (AH) exhibited the strongest pro-proliferative effect on HIECs, and we therefore focused on AH. AH was resistant to in vitro gastrointestinal digestion, co-localized with both LF and OPN receptors as revealed by confocal microscopy, and stimulated proliferation of HIECs by activating PI3K/Akt signaling. In conclusion, forming a LF-OPN complex may help both proteins to resist digestion and increase the capacity to promote intestinal development in infants.