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Transferrin receptor gene expression and transferrin‐bound iron uptake are increased during postischemic rat liver reperfusion
Author(s) -
Tacchini Lorenza,
Poli Daniela Fusar,
BernelliZazzera Aldo,
Cairo Gaetano
Publication year - 2002
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1053/jhep.2002.33997
Subject(s) - transferrin receptor , transferrin , messenger rna , gene expression , ferritin , biology , downregulation and upregulation , microbiology and biotechnology , chemistry , gene , biochemistry
Iron‐catalyzed production of reactive oxygen species is a cause of liver injury after ischemia/reperfusion (I/R). The aim of the present study was to address the regulation of transferrin receptor (TfR), which mediates cellular iron uptake, during I/R. The molecular mechanisms controlling TfR gene expression in vivo during I/R of rat liver were investigated by molecular biology procedures. We also analyzed transferrin‐bound iron uptake into surviving liver slices. Increased amounts of TfR protein and messenger RNA (mRNA) were found 2 to 6 hours after reestablishment of blood supply. RNA bandshift analysis showed that iron regulatory protein (IRP) activity was decreased in the first hours of reperfusion, thus indicating that IRP‐mediated mRNA stabilization was not involved in early TfR upregulation. On the contrary, increased transcription of the TfR gene in isolated nuclei was observed during reperfusion; during the ischemic phase this was preceded by enhanced binding of hypoxia inducible factor (HIF‐1) to a DNA sequence derived from the TfR promoter. TfR2 mRNA levels were also enhanced after reperfusion. The increased expression of TfR at the cell surface resulted in increased uptake of transferrin‐bound‐iron into surviving liver slices; however, iron was not incorporated into ferritin. In conclusion, HIF‐1 mediated activation of TfR gene transcription and IRP‐mediated increase of TfR mRNA stability ensure a steady induction of TfR, and hence higher iron uptake in reperfused rat liver. TfR‐mediated entry of the metal into liver cells may represent a source of catalitically active iron, which may play a role in reperfusion damage.