Copper repletion enhances apical iron uptake and transepithelial iron transport by Caco-2 cells.
The influence of copper status on Caco-2 cell apical iron uptake and transepithelial transport was examined. Cells grown for 7-8 days in media supplemented with 1 microM CuCl(2) had 10-fold higher cellular levels of copper compared with control. Copper supplementation did not affect the integrity of differentiated Caco-2 cell monolayers grown on microporous membranes. Copper-repleted cells displayed increased uptake of iron as well as increased transport of iron across the cell monolayer. Northern blot analysis revealed that expression of the apical iron transporter divalent metal transporter-1 (DMT1), the basolateral transporter ferroportin-1 (Fpn1), and the putative ferroxidase hephaestin (Heph) was upregulated by copper supplementation, whereas the recently identified ferrireductase duodenal cytochrome b (Dcytb) was not. These results suggest that DMT1, Fpn1, and Heph are involved in the iron uptake process modulated by copper status. Although a clear role for Dcytb was not identified, an apical surface ferrireductase was modulated by copper status, suggesting that its function also contributes to the enhanced iron uptake by copper-repleted cells. A model is proposed wherein copper promotes iron depletion of intestinal Caco-2 cells, creating a deficiency state that induces upregulation of iron transport factors.
Han
Okhee
O
Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA.
Wessling-Resnick
Marianne
M
D001692:Biological Transport / Q000187:drug effects; D015152:Blotting, Northern; D018938:Caco-2 Cells; D027682:Cation Transport Proteins / Q000235:genetics; D002454:Cell Differentiation; D003300:Copper / Q000378:metabolism*; D003470:Culture Media; D003573:Cytochrome b Group / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism*; D038181:FMN Reductase; D015870:Gene Expression; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007504:Iron Radioisotopes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics; D000098742:Ferroportin
D027682:Cation Transport Proteins; D003470:Culture Media; D003573:Cytochrome b Group; C492164:HEPH protein, human; D007504:Iron Radioisotopes; D008565:Membrane Proteins; D000098742:Ferroportin; D003300:Copper; D007501:Iron; D010088:Oxidoreductases; D038181:FMN Reductase; D009247:NADH, NADPH Oxidoreductases; C422926:CYBRD1 protein, human; C023903:ferric citrate iron reductase