A physiological model to study iron recycling in macrophages

Exp Cell Res. 2005 Oct 15;310(1):43-53. doi: 10.1016/j.yexcr.2005.07.002.

Abstract

Following erythrophagocytosis (EP) of senescent red blood cells (RBCs), heme iron is recycled to the plasma by tissue macrophages. This process is critical for mammalian iron homeostasis but remains elusive. We characterized a cellular model using artificially-aged murine RBCs and murine bone marrow-derived macrophages (BMDMs) and study mRNA and protein expression of HO-1, ferroportin and ferritin after EP. In vitro ageing of RBCs was obtained by raising intracellular calcium concentration. These RBCs exhibit several features of erythrocyte senescence including externalization of phosphatidyl-serine, specific binding and phagocytosis by BMDMs. During the first hours of EP, we observed a rapid increase of HO-1 and ferroportin mRNAs and proteins, whereas ferritin protein expression was progressively induced with no major changes in RNA levels. At later stages after EP, a different pattern of expression was observed with a net decrease of ferroportin, a sustained high level of HO-1, and a strong increase in ferritins. Taken together, these results suggest that after EP, iron is rapidly extracted from heme and exported by ferroportin. Surprisingly, the gene expression profile at late stages after EP, which is indicative of iron storage, is reminiscent of what is observed in inflammation. However, phagocytosis of artificially-aged red blood cells seems to repress the proinflammatory response of macrophages.

MeSH terms

  • Animals
  • Blotting, Western
  • Cation Transport Proteins / biosynthesis
  • Cation Transport Proteins / genetics
  • Erythrocytes / metabolism
  • Erythrocytes / physiology
  • Ferritins / genetics
  • Ferritins / metabolism
  • Fluorescent Antibody Technique
  • Heme Oxygenase (Decyclizing) / biosynthesis
  • Heme Oxygenase (Decyclizing) / genetics
  • Heme Oxygenase-1
  • Inflammation
  • Iron / metabolism*
  • Macrophages / drug effects
  • Macrophages / metabolism
  • Macrophages / physiology*
  • Membrane Proteins
  • Mice
  • Models, Biological*
  • Nitric Oxide / metabolism
  • Phagocytosis / physiology*
  • RNA, Messenger / biosynthesis
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Cation Transport Proteins
  • Membrane Proteins
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • metal transporting protein 1
  • Nitric Oxide
  • Ferritins
  • Iron
  • Heme Oxygenase (Decyclizing)
  • Heme Oxygenase-1
  • Hmox1 protein, mouse