Contributions
Abstract: S891
Type: Oral Presentation
Presentation during EHA23: On Saturday, June 16, 2018 from 16:00 - 16:15
Location: Room A13
Background
Nuclear Receptor Coactivator 4 (NCOA4) has been recently identified as the cargo receptor that promotes the autophagic ferritin degradation in conditions of iron deficiency (ID). Depletion of NCOA4 increases ferritin aggregates and C57Bl/6 Ncoa4-ko mice show mild microcytic anemia and increased susceptibility to ID. Previously published in vitro and ex vivo data suggest a direct role of NCOA4 in erythroid differentiation and hemoglobinization.
Aims
We will address the role of NCOA4 in response to chronic and acute iron demand and we will identify the cell type mostly affected by Ncoa4 deficiency in vivo.
Methods
The iron response has been studied in Sv129/J Ncoa4-ko and wt mice that were maintained in iron-balance (IB) or ID diet for 6 months. Complete blood count was periodically measured and the iron phenotype was evaluated at sacrifice. Ferritin degradation was also assessed ex vivo in hepatocytes and BM macrophages isolated from wt and Ncoa4-ko mice and treated with desferrioxamine.
Moreover, in order to unambiguously elucidate the function of NCOA4, we lethally irradiated Ncoa4-ko mice for transplantation of bone marrow cells (BMT) from wt and Ncoa4-ko mice, and manipulated the dietary iron content of the transplanted animals. Two months after BMT, animals were fed an ID diet for 3 months and subsequently analyzed for hematological parameters and iron content.
Results
Sv129/J Ncoa4-ko mice, that are particularly enriched in iron content, showed microcytosis without anemia. The ID diet induced slight changes in hemoglobin (Hb) levels in wt mice, but severe microcytic anemia with very low transferrin saturation in Ncoa4-ko mice. Hepatic (LIC) and splenic (SIC) iron content were reduced by ID in both genotypes. On the other hand, acute iron chelation ex vivo induced progressive ferritin degradation in wt but not in Ncoa4-ko hepatocytes and macrophages.
In the transplantation model, red blood cells count and Hb levels were comparable between mice transplanted with wt and Ncoa4-ko BM at 2 months after BMT, while mean corpuscular volume was higher in the former. The ID diet caused a more severe anemia in mice transplanted with Ncoa4-ko cells than in animals transplanted with wt cells. High SIC and ferritin levels were observed in mice transplanted with Ncoa4-ko cells, while LIC was unchanged.
Conclusion
Our results demonstrate that Sv129/J Ncoa4-ko mice, although not anemic in basal conditions, are more susceptible to iron-deficiency anemia. Their hematological phenotype is due to a defect of BM-derived cells. Ncoa4-ko BM cells are able to reconstitute almost normal Hb levels in transplanted animals and this, accompanied by a normal erythropoiesis, indicates that in vivo Ncoa4 deficiency has a limited, if any, effect on the erythroid lineage differentiation. On the contrary, the reduced iron recycling capacity of Ncoa4-ko macrophages in vivo, confirmed by ex vivo experiments, supports the role of NCOA4 in mobilizing the iron stores. Still, a prolonged ID diet leads to a substantial splenic and hepatic iron mobilization in Ncoa4-ko mice, and this suggests that other mechanisms of ferritin degradation are likely activated in chronic conditions. Therefore, to verify the role played by NCOA4 in response to acute increased iron demand in vivo, Ncoa4-ko mice are under study, exploiting an EPO based treatment protocol that induces rapid changes of iron bound transferrin, to analyse their ability to restore normal circulating iron levels after an acute erythropoietic expansion.
Session topic: 30. Iron metabolism, deficiency and overload
Keyword(s): Ferritin, Iron deficiency anemia, Iron Metabolism
Abstract: S891
Type: Oral Presentation
Presentation during EHA23: On Saturday, June 16, 2018 from 16:00 - 16:15
Location: Room A13
Background
Nuclear Receptor Coactivator 4 (NCOA4) has been recently identified as the cargo receptor that promotes the autophagic ferritin degradation in conditions of iron deficiency (ID). Depletion of NCOA4 increases ferritin aggregates and C57Bl/6 Ncoa4-ko mice show mild microcytic anemia and increased susceptibility to ID. Previously published in vitro and ex vivo data suggest a direct role of NCOA4 in erythroid differentiation and hemoglobinization.
Aims
We will address the role of NCOA4 in response to chronic and acute iron demand and we will identify the cell type mostly affected by Ncoa4 deficiency in vivo.
Methods
The iron response has been studied in Sv129/J Ncoa4-ko and wt mice that were maintained in iron-balance (IB) or ID diet for 6 months. Complete blood count was periodically measured and the iron phenotype was evaluated at sacrifice. Ferritin degradation was also assessed ex vivo in hepatocytes and BM macrophages isolated from wt and Ncoa4-ko mice and treated with desferrioxamine.
Moreover, in order to unambiguously elucidate the function of NCOA4, we lethally irradiated Ncoa4-ko mice for transplantation of bone marrow cells (BMT) from wt and Ncoa4-ko mice, and manipulated the dietary iron content of the transplanted animals. Two months after BMT, animals were fed an ID diet for 3 months and subsequently analyzed for hematological parameters and iron content.
Results
Sv129/J Ncoa4-ko mice, that are particularly enriched in iron content, showed microcytosis without anemia. The ID diet induced slight changes in hemoglobin (Hb) levels in wt mice, but severe microcytic anemia with very low transferrin saturation in Ncoa4-ko mice. Hepatic (LIC) and splenic (SIC) iron content were reduced by ID in both genotypes. On the other hand, acute iron chelation ex vivo induced progressive ferritin degradation in wt but not in Ncoa4-ko hepatocytes and macrophages.
In the transplantation model, red blood cells count and Hb levels were comparable between mice transplanted with wt and Ncoa4-ko BM at 2 months after BMT, while mean corpuscular volume was higher in the former. The ID diet caused a more severe anemia in mice transplanted with Ncoa4-ko cells than in animals transplanted with wt cells. High SIC and ferritin levels were observed in mice transplanted with Ncoa4-ko cells, while LIC was unchanged.
Conclusion
Our results demonstrate that Sv129/J Ncoa4-ko mice, although not anemic in basal conditions, are more susceptible to iron-deficiency anemia. Their hematological phenotype is due to a defect of BM-derived cells. Ncoa4-ko BM cells are able to reconstitute almost normal Hb levels in transplanted animals and this, accompanied by a normal erythropoiesis, indicates that in vivo Ncoa4 deficiency has a limited, if any, effect on the erythroid lineage differentiation. On the contrary, the reduced iron recycling capacity of Ncoa4-ko macrophages in vivo, confirmed by ex vivo experiments, supports the role of NCOA4 in mobilizing the iron stores. Still, a prolonged ID diet leads to a substantial splenic and hepatic iron mobilization in Ncoa4-ko mice, and this suggests that other mechanisms of ferritin degradation are likely activated in chronic conditions. Therefore, to verify the role played by NCOA4 in response to acute increased iron demand in vivo, Ncoa4-ko mice are under study, exploiting an EPO based treatment protocol that induces rapid changes of iron bound transferrin, to analyse their ability to restore normal circulating iron levels after an acute erythropoietic expansion.
Session topic: 30. Iron metabolism, deficiency and overload
Keyword(s): Ferritin, Iron deficiency anemia, Iron Metabolism