Iron overload induces hepatic iron deposition and oxidative damage in freshwater fish Megalobrama amblycephala by inhibiting ferroportin 1 gene expression.

This study investigated the effects of plasma iron overload on hepatic ferroportin 1 (fpn1) expression, iron metabolism and oxidative stress. The experiment presents the first cloning and characterization of Megalobrama amblycephala fpn1. The open reading frame (ORF) is 1689 bp, encoding a 562-amino-acid protein predicted to adopt a canonical major facilitator superfamily (MFS) fold with 12 transmembrane domains. Tissue distribution revealed the highest fpn1 expression in the liver, followed by the trunk kidney, spleen, and posterior intestine. To investigate fpn1's role in iron metabolism, a plasma iron overload model was established by tail vein injection of sterile FeSO₄ solution (1 g/L, 0.5 mL/kg body weight). Plasma iron peaked at 6 h post-injection (hpi), while hepatic iron peaked at 12 hpi (P < 0.05). Signs of hepatic oxidative stress and injury were observed, including increased plasma lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) activities (6-48 hpi), elevated hepatic malondialdehyde (MDA) content (24-72 hpi), and decreased catalase (CAT) and superoxide dismutase (SOD) activities (6-24 hpi) (P < 0.05). Iron overload significantly upregulated hepatic hepcidin (hepc), ferritin (fer) and transferrin (tf) expression (6-24 hpi), while downregulating fpn1, transferrin receptor 1 (tfr1) and divalent metal transporter 1 (dmt1) expression (6-72 hpi) (P < 0.05). This pattern suggests disrupted iron metabolism with impaired cellular iron export, enhanced storage, and suppressed uptake. Enhancing fpn1 expression or inhibiting its degradation may promote iron efflux, activate antioxidant systems, reduce tissue iron burden, and ultimately restore iron homeostasis.