The function of heme-regulated eIF2alpha kinase in murine iron homeostasis and macrophage maturation.
Heme-regulated eIF2alpha kinase (HRI) plays an essential protective role in anemias of iron deficiency, erythroid protoporphyria, and beta-thalassemia. In this study, we report that HRI protein is present in murine macrophages, albeit at a lower level than in erythroid precursors. Hri-/- mice exhibited impaired macrophage maturation and a weaker antiinflammatory response with reduced cytokine production upon LPS challenge. The level of production of hepcidin, an important player in the pathogenesis of the anemia of inflammation, was significantly decreased in Hri-/- mice, accompanied by decreased splenic macrophage iron content and increased serum iron content. Hepcidin expression was also significantly lower, with a concomitant increase in serum iron in Hri-/- mice upon LPS treatment. We also demonstrated an impairment of erythrophagocytosis by Hri-/- macrophages both in vitro and in vivo under chronic hemolytic anemia, providing evidence for the role of HRI in recycling iron from senescent red blood cells. This work demonstrates that HRI deficiency attenuates hepcidin expression and iron homeostasis in mice, indicating a potential role for HRI in the anemia of inflammation.
Liu
Sijin
S
Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Suragani
Rajasekhar N V S
RN
Wang
Fudi
F
Han
Anping
A
Zhao
Wanting
W
Andrews
Nancy C
NC
Chen
Jane-Jane
JJ
D000743:Anemia, Hemolytic / Q000378:metabolism; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D064451:Hepcidins; D006706:Homeostasis; D007249:Inflammation / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010587:Phagocytosis / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013154:Spleen / Q000378:metabolism; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*
D023181:Antimicrobial Cationic Peptides; C579599:Hamp protein, mouse; D064451:Hepcidins; D008070:Lipopolysaccharides; D006418:Heme; D007501:Iron; D019892:eIF-2 Kinase