Nontransferrin-bound iron uptake by hepatocytes is increased in the Hfe knockout mouse model of hereditary hemochromatosis.
Hereditary hemochromatosis (HH) is an iron-overload disorder caused by a C282Y mutation in the HFE gene. In HH, plasma nontransferrin-bound iron (NTBI) levels are increased and NTBI is bound mainly by citrate. The aim of this study was to examine the importance of NTBI in the pathogenesis of hepatic iron loading in Hfe knockout mice. Plasma NTBI levels were increased 2.5-fold in Hfe knockout mice compared with control mice. Total ferric citrate uptake by hepatocytes isolated from Hfe knockout mice (34.1 +/- 2.8 pmol Fe/mg protein/min) increased by 2-fold compared with control mice (17.8 +/- 2.7 pmol Fe/mg protein/min; P <.001; mean +/- SEM; n = 7). Ferrous ion chelators, bathophenanthroline disulfonate, and 2',2-bipyridine inhibited ferric citrate uptake by hepatocytes from both mouse types. Divalent metal ions inhibited ferric citrate uptake by hepatocytes, as did diferric transferrin. Divalent metal transporter 1 (DMT1) mRNA and protein expression was increased approximately 2-fold by hepatocytes from Hfe knockout mice. We conclude that NTBI uptake by hepatocytes from Hfe knockout mice contributed to hepatic iron loading. Ferric ion was reduced to ferrous ion and taken up by hepatocytes by a pathway shared with diferric transferrin. Inhibition of uptake by divalent metals and up-regulation of DMT1 expression suggested that NTBI uptake was mediated by DMT1.
Chua
Anita C G
AC
School of Medicine and Pharmacology, The University of Western Australia, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
Olynyk
John K
JK
Leedman
Peter J
PJ
Trinder
Debbie
D
D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D004195:Disease Models, Animal; D005290:Ferric Compounds / Q000493:pharmacokinetics*; D006432:Hemochromatosis / Q000235:genetics* / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D007504:Iron Radioisotopes; D033862:Iron-Binding Proteins / Q000235:genetics / Q000378:metabolism; D008345:Manganese / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010618:Phenanthrolines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D014168:Transferrin / Q000378:metabolism / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology; D000099236:Solute Carrier Family 11, Member 2
D027682:Cation Transport Proteins; D003035:Cobalt; D005290:Ferric Compounds; D007501:Iron; D007502:Iron Chelating Agents; D007504:Iron Radioisotopes; D033862:Iron-Binding Proteins; D008345:Manganese; D010618:Phenanthrolines; D012333:RNA, Messenger; D014168:Transferrin; D015032:Zinc; D000099236:Solute Carrier Family 11, Member 2; C028283:diferric transferrin; C017049:bathophenanthroline disulfonic acid; C025314:ferric citrate