Ferroportin gene silencing induces iron retention and enhances ferritin synthesis in human macrophages.

Abstract

Missense mutations in the ferroportin gene (SLC11A3) result in haemochromatosis type 4 [HFE4, Online Mendelian Inheritance in Man (OMIM) reference 606069] or ferroportin disease, an autosomal dominant disorder characterized by predominantly reticuloendothelial iron accumulation. To verify whether HFE4 is caused by defective iron recycling because of loss of functionality of ferroportin, we down-regulated SLC11A gene expression in human macrophages by using small interfering RNAs (siRNAs). Transfection experiments with ferroportin siRNAs resulted in a marked reduction (about two-thirds on average) in ferroportin mRNA levels as detected by quantitative real time polymerase chain reaction. When macrophages were grown in medium supplemented with iron, cells transfected with siRNAs displayed three- to eightfold increases in staining intensities following Perls reaction. These macrophages also showed significant increases in H-ferritin content. The observation that ferroportin mRNA down-regulation to levels compatible with haplo-insufficiency causes increased iron retention and H-ferritin synthesis in cultured macrophages has important implications. First, this indicates that ferroportin levels must be finely regulated in order to maintain cellular iron homeostasis, and that both copies of SLC11A3 must function efficiently to prevent iron accumulation. Second, this observation supports the hypothesis that reticuloendothelial iron overload in patients with ferroportin disease is caused by loss-of-function mutations in the SLC11A3 gene that mainly impair macrophage iron recycling.

• Authors: Anna Gallí, Gaetano Bergamaschi, Helios Recalde, Giorgio Biasiotto, Paolo Santambrogio, Sabrina Boggi, Sonia Levi, Paolo Arosio, Mario Cazzola
• Journal: British journal of haematology (Br J Haematol) Vol. 127 Issue 5 Pg. 598-603 (Dec 2004) ISSN: 0007-1048 [Print] England
• PMID: 15566364 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cation Transport Proteins
• RNA, Messenger
• RNA, Small Interfering
• metal transporting protein 1
• Ferritins
• Iron

Topics

• Cation Transport Proteins (genetics, metabolism)
• Cells, Cultured
• Ferritins (biosynthesis)
• Gene Expression Regulation
• Gene Silencing
• Hemostasis
• Humans
• Iron (metabolism)
• Macrophages (metabolism)
• RNA, Messenger (analysis)
• RNA, Small Interfering (pharmacology)
• Reverse Transcriptase Polymerase Chain Reaction
• Transfection (methods)