Immunolocalization of Ferroportin in Healthy and Anemic Mice

Abstract

S U M M A R Y Ferroportin (FPN), the only iron exporter identified to date, participates in iron release from enterocytes and macrophages, regulating its absorption and recycling. We used a murine model of experimental hemolytic anemia to study adaptive changes in the localization of FPN in duodenum, liver, and spleen. FPN was assessed by IHC in healthy and anemic mice using rabbit anti-mouse FPN polyclonal antibodies. Goat-labeled polymer-horseradish peroxidase anti-rabbit Envision1System (DAB) was used as secondary antibody. Tissue iron was studied by Prussian blue iron staining. Anemia evolution and erythropoietic recovery was assessed using conventional hematological tests. Healthy mice showed mainly supranuclear expression of FPN in enterocytes and a weak basolateral expression, whereas in anemic mice, the expression was detected mainly at the basolateral membrane (days 4 and 5). Red pulp macrophages of healthy mice showed FPN-hemosiderin colocalization. In the liver of healthy mice, FPN was mainly cytoplasmic, whereas in anemic mice, it was redistributed to the cell membrane. Our findings clearly show that anemia induces adaptive changes in FPN expression, contributing to anemia restoration by increasing available iron. FPN expression in the membrane is the main pathway of iron release. Our data indicate that iron homeostasis in vivo is maintained through the coordinated expression of this iron exporter in both intestinal and phagocytic cells. (J Histochem Cytochem 57:9-16, 2009)

Increased Ferroportin-1 Expression and Rapid Splenic Iron Loss Occur with Anemia Caused by Salmonella enterica Serovar Typhimurium Infection in Mice

“…The spleen is the predominant site for iron storage in mice (29,30), and splenic iron is stored in tissue macrophages (30). We previously reported reduced tissue iron histochemical staining in resistant (Sv129S6 and C57/BL6 Nramp1 G169 ) mice infected with S. Typhimurium that became acutely anemic; Prussian blue staining of ferric iron in the spleen was scored at 3 to 4ϩ (on a scale of 0 to 4) in red pulp reticuloendothelial cells of control mice compared to 0 to 1ϩ in infected mice (7,8).…”

“…Splenic macrophages are the major iron storage site in mice (30). To establish whether the finding of decreased splenic iron in infected mice reflected decreased numbers of splenic macrophages, we quantified phagocytes in the spleen by flow cytometry with cell-type-specific markers.…”

“…Macrophages of the reticuloendothelial system express the iron exporter Fpn1 to regulate cellular iron levels (18,30). To establish whether increased Fpn1 expression by tissue macrophages could suggest a mechanism by which tissue iron is decreased following infection, we performed Fpn1 immunohistochemistry on the spleens and livers of infected and control mice.…”

Reverse overshot water-wheel retroendocytosis of Apo Transferrin extrudes cellular iron

“…The model proposed for this process involves Fe extrusion from cells through the classic cell surface ferroportin pump, followed by rapid chelation of the externalized Fe into apotransferrin (Sheokand et al, 2014). These findings still cannot explain as to how the vast majority of cells that lack ferroportin on their surface are able to extrude excess of the metal ions (D'Anna et al, 2009;Donovan et al, 2005), and the possibility that GAPDH utilizes an alternative method to remove Fe from cells in a surface-ferroportinindependent manner cannot be ruled out. In the current study, using different primary cell types and cell lines that lack surface ferroportin, we demonstrate that surface GAPDH recruited upon Fe accumulation is able to not only capture but to also internalize apotransferrin into cells to chelate Fe intracellularly.…”

Modelo Animal de Anemia Inducida por Flebotomía Crónica: Relación Funcional Entre Hierro y Eritropoyesis

“…Dependiendo de los requerimientos erit ropoyéticos, el hierro ferroso puede ser exportado a la circulación a través del exportador ferroportina (FPN) (9). En contraste con las múltiples vías de ingreso celular, el exportador FPN constituye el único mecanismo de egreso utilizado por todos los tipos celulares que exportan Fe.…”