1,4-Naphthoquinone Induces FcRn Protein Expression and Albumin Recycling in Human THP-1 Cells

[Image: see text] The neonatal Fc receptor (FcRn) has been established as a major factor in regulating the metabolism of albumin and IgG in humans by protecting them from intracellular degradation after they are endocytosed into cells. We assume that increasing the levels of endogenous FcRn proteins in cells would be beneficial to enhance the recycling of these molecules. In this study, we identify the compound 1,4-naphthoquinone as an efficient stimulator of FcRn protein expression in human THP-1 monocytic cells with potency at the submicromolar range. Also, the compound increased the subcellular localization of FcRn to the endocytic recycling compartment and enhanced human serum albumin recycling in the PMA-induced THP-1 cells. These results suggest that 1,4-naphthoquinone stimulates FcRn expression and activity in human monocytic cells in vitro and it could open a new avenue for designing cotreatment agents to enhance the efficacy of biological treatments such as albumin-conjugated drugs in vivo.