To analyze the interconnection between erythropoiesis and
iron metabolism, one of the issues raised in this study was to know
iron bioavailability under physiopathological conditions. Our aim was to understand the functional axis response composed of
erythropoietin (Epo)-
hepcidin-
ferroportin (FPN), when 2 dysfunctional states coexist, using an animal model of
iron overload followed by
hypoxia. FPN and
prohepcidin were assessed by immunohistochemistry using rabbit anti-mouse FPN polyclonal and
prohepcidin monoclonal antibodies. Goat-labeled
polymer -
horseradish peroxidase anti-rabbit EnVision + System (DAB) was used as the secondary antibody. Epo levels were measured by ELISA. Tissue
iron was studied by
Prussian blue iron staining. Erythropoietic response was assessed using conventional hematological tests.
Iron overload increased
prohepcidin that remained high in
hypoxia, coexisting with high levels of Epo in
hypoxia, with or without
iron overload. In
hypoxia, FPN was clearly evident in reticuloendothelial macrophages, more than in
hypoxia with
iron overload. Interestingly, duodenal FPN was clearly identified on the basolateral membrane in
hypoxia, with or without
iron overload. Our data indicate that 2 signals could induce the cell-specific response as follows: (i)
iron signal, induced
prohepcidin, which reduced reticuloendothelial FPN and reduced
iron availability; and (ii)
hypoxia signal, stimulated Epo, which affected
iron absorption by stabilizing duodenal FPN and allowed
iron supply to erythropoiesis independently of store size.