Lactoferrin promotes autophagy via AMP-activated protein kinase activation through low-density lipoprotein receptor-related protein 1.

Lactoferrin (LF) is a multifunctional, iron-binding glycoprotein in mammalian secretions, such as breast milk, and has several beneficial effects for human health. However, how these effects are exerted at the cellular level is still largely unknown. In this study, we investigated the effects of LF on autophagy activity in NIH/3T3 mouse fibroblasts. LF from bovine milk was found to increase LC3-I to LC3-II conversion and LC3-positive cytosolic punctate structures because of increased autophagy flux. Knockdown of the putative LF receptor low-density receptor-related protein 1 (LRP1) completely abolished LC3 conversion in cells by LF treatment. Moreover, exposure to LF increased the phosphorylation levels of AMPK in cells, and treatment of dorsomorphin, a pharmacological inhibitor of AMPK signaling, attenuated LC3 conversion by LF. Therefore, we concluded that the beneficial effects of LF might be due to an increase of autophagy activity via AMPK signaling through the LRP1 receptor. These findings provide a novel insight into the physiological role of LF for the maintenance of cellular and tissue homeostasis.