Functional inactivation of duodenal ferroportin by hepcidin drives iron-dependent degradation of DMT1 in lysosomes

Abstract

Abstract Hepcidin regulates systemic iron homeostasis by inhibiting iron absorption and recycling through degradation of the iron exporter ferroportin in enterocytes and macrophages. While its effects on macrophages are well characterized, ferroportin regulation in duodenal enterocytes remains less understood. Several studies suggest that duodenal ferroportin is relatively resistant to hepcidin, implying tissue-specific regulatory mechanisms. To investigate this, we used wild-type and hepcidin-deficient Hjv⁻/⁻ mice, a model of hemochromatosis. Synthetic hepcidin administration significantly reduced plasma iron and ferroportin levels in the spleen and liver. In duodenal enterocytes, hepcidin decreased ferroportin and apical divalent metal transporter 1 (DMT1) in wild-type mice. In Hjv⁻/⁻ animals, where both transporters are overexpressed, hepcidin suppressed DMT1 but not ferroportin, yet duodenal iron levels increased—indicating functional ferroportin inactivation. This DMT1 suppression was reproduced in murine intestinal organoids treated with hepcidin or iron, regardless of ferroportin degradation. Short-term high-iron diet in wild-type mice or high-dose hepcidin in Hjv⁻/⁻ mice led to duodenal iron accumulation and degradation of both transporters. Notably, DMT1 (but not ferroportin) degradation was partially rescued by the lysosomal inhibitor chloroquine. These findings demonstrate that hepcidin can degrade duodenal ferroportin under physiological expression, but higher doses are needed when it is overexpressed. Even when hepcidin fails to degrade ferroportin, it can still occlude its iron export channel, leading to intracellular iron accumulation and iron-dependent lysosomal degradation of DMT1. Thus, hepcidin controls iron absorption through dual targeting of duodenal iron transporters via distinct mechanisms: direct functional inactivation of ferroportin that indirectly triggers DMT1 degradation.