Characterisation of hepcidin response to holotransferrin treatment in CHO TRVb-1 cells

Iron elevates mesenchymal and metastatic biomarkers in HepG2 cells

Liver iron excess is observed in several chronic liver diseases and is associated with the development of hepatocellular carcinoma (HCC). However, apart from oxidative stress, other cellular mechanisms by which excess iron may mediate/increase HCC predisposition/progression are not known. HCC pathology involves epithelial to mesenchymal transition (EMT), the basis of cancer phenotype acquisition. Here, the effect of excess iron (holo-transferrin 0–2 g/L for 24 and 48 h) on EMT biomarkers in the liver-derived HepG2 cells was investigated. Holo-transferrin substantially increased intracellular iron. Unexpectedly, mRNA and protein expression of the epithelial marker E-cadherin either remained unaltered or increased. The mRNA and protein levels of metastasis marker N-cadherin and mesenchymal marker vimentin increased significantly. While the mRNA expression of EMT transcription factors SNAI1 and SNAI2 increased and decreased, respectively after 24 h, both factors increased after 48 h. The mRNA expression of TGF-β (EMT-inducer) showed no significant alterations. In conclusion, data showed direct link between iron and EMT. Iron elevated mesenchymal and metastatic biomarkers in HepG2 cells without concomitant decrement in the epithelial marker E-cadherin and altered the expression of the key EMT-mediating transcription factors. Such studies can help identify molecular targets to devise iron-related adjunctive therapies to ameliorate HCC pathophysiology.

Hepcidin secretion was not directly proportional to intracellular iron-loading in recombinant-TfR1 HepG2 cells: short communication

Hepcidin is the master regulator of systemic iron homeostasis and its dysregulation is observed in several chronic liver diseases. Unlike the extracellular iron-sensing mechanisms, the intracellular iron-sensing mechanisms in the hepatocytes that lead to hepcidin induction and secretion are incompletely understood. Here, we aimed to understand the direct role of intracellular iron-loading on hepcidin mRNA and peptide secretion using our previously characterised recombinant HepG2 cells that over-express the cell-surface iron-importer protein transferrin receptor-1. Gene expression of hepcidin (HAMP) was determined by real-time PCR. Intracellular iron levels and secreted hepcidin peptide levels were measured by ferrozine assay and immunoassay, respectively. These measurements were compared in the recombinant and wild-type HepG2 cells under basal conditions at 30 min, 2 h, 4 h and 24 h. Data showed that in the recombinant cells, intracellular iron content was higher than wild-type cells at 30 min (3.1-fold, p < 0.01), 2 h (4.6-fold, p < 0.01), 4 h (4.6-fold, p < 0.01) and 24 h (1.9-fold, p < 0.01). Hepcidin (HAMP) mRNA expression was higher than wild-type cells at 30 min (5.9-fold; p = 0.05) and 24 h (6.1-fold; p < 0.03), but at 4 h, the expression was lower than that in wild-type cells (p < 0.05). However, hepcidin secretion levels in the recombinant cells were similar to those in wild-type cells at all time-points, except at 4 h, when the level was lower than wild-type cells (p < 0.01). High intracellular iron in recombinant HepG2 cells did not proportionally increase hepcidin peptide secretion. This suggests a limited role of elevated intracellular iron in hepcidin secretion.

HFE mRNA expression is responsive to intracellular and extracellular iron loading: short communication

In liver hepatocytes, the HFE gene regulates cellular and systemic iron homeostasis by modulating cellular iron-uptake and producing the iron-hormone hepcidin in response to systemic iron elevation. However, the mechanism of iron-sensing in hepatocytes remain enigmatic. Therefore, to study the effect of iron on HFE and hepcidin (HAMP) expressions under distinct extracellular and intracellular iron-loading, we examined the effect of holotransferrin treatment (1, 2, 5 and 8 g/L for 6 h) on intracellular iron levels, and mRNA expressions of HFE and HAMP in wild-type HepG2 and previously characterized iron-loaded recombinant-TfR1 HepG2 cells. Gene expression was analyzed by real-time PCR and intracellular iron was measured by ferrozine assay. Data showed that in the wild-type cells, where intracellular iron content remained unchanged, HFE expression remained unaltered at low holotransferrin treatments but was upregulated upon 5 g/L (p < 0.04) and 8 g/L (p = 0.05) treatments. HAMP expression showed alternating elevations and increased upon 1 g/L (p < 0.05) and 5 g/L (p < 0.05). However, in the recombinant cells that showed higher intracellular iron levels than wild-type cells, HFE and HAMP expressions were elevated only at low 1 g/L treatment (p < 0.03) and were repressed at 2 g/L treatment (p < 0.03). Under holotransferrin-untreated conditions, the iron-loaded recombinant cells showed higher expressions of HFE (p < 0.03) and HAMP (p = 0.05) than wild-type cells. HFE mRNA was independently elevated by extracellular and intracellular iron-excess. Thus, it may be involved in sensing both, extracellular and intracellular iron. Repression of HAMP expression under simultaneous intracellular and extracellular iron-loading resembles non-hereditary iron-excess pathologies.