Down Regulation of Hepcidin and Haemojuvelin Expression in the Hepatocyte Cell-Line HepG2 Induced by Thalassaemic Sera.

Abstract β-thalassaemia represents a group of diseases, in which ineffective erythropoiesis is accompanied by iron overload. In a mouse model of β-thalassaemia we observed that the liver expresses relatively low levels of hepcidin, which is a key factor in the regulation of iron absorption by the gut and of iron recycling by the reticuloendothelial system. We hypothesized that despite the overt iron overload, a putative plasma factor found in β-thalassaemia might suppress liver hepcidin expression. We therefore compared sera from β-thalassaemia and haemochromatosis (C282Y mutation) patients with those of healthy individuals in terms of their capacity to evoke changes in expression of key genes of iron metabolism in human HepG2 hepatoma cells. Sera from β-thalassaemia major patients evoked a major decrease in hepcidin (HAMP) and lipocalin2 (oncogene 24p3) (LCN2) expression, as well as a moderate decrease in haemojuvelin (HFE2) expression, compared to sera from healthy individuals. Significant correlation was found between the degree of downregulation of HAMP and HFE2 evoked by b-thalassaemia major sera (r=0.852, p<0.0009). Decreased HAMP expression was also found in HepG2 cells treated with sera collected from β-thalassaemia intermedia patients. In contrast, the majority of sera from hereditary haemochromatosis patients evoked an increase in HAMP expression, which correlated with their transferrin saturation (r=0.765, p<0.0099). Our results suggest that in β-thalassaemia, serum factors might override the potential effect of iron overload on HAMP expression, thereby providing an explanation for the failure to arrest excessive intestinal iron absorption.