Liver iron overload in alcoholic liver disease: Crosstalk between endothelial cells and hepatocytes in iron regulation

Background and Aims Liver-secreted hepcidin is considered the systemic master switch of iron homeostasis with liver sinusoidal endothelial cells (LSECs) derived bone morphogenetic protein 6 (BMP6) and the BMP6/SMAD signaling pathway being essential for hepcidin expression. However, there are continued controversies about the strong and direct suppressive effect of iron on hepatocellular hepcidin in vitro in contrast to in vivo conditions. We here directly study the crosstalk between endothelial cells (EC) and hepatocytes and Huh7 cells using in vitro co-culture models that mimic the hepcidin signaling in vivo.

Methods Huh7 cells were direct co-cultured with ECs (HUVECs and SK hep). EC-conditioned media (CM) were also employed to culture Huh7 cells and primary mouse hepatocytes. To explore the reactions of ECs to surrounding iron, they were put under ferric ammonium citrate (FAC) and hemin. Intravenous iron injection in mice was used to study hepcidin signaling in vivo.

Results Both direct co-culture with ECs or EC-CM significantly increased hepcidin in Huh7 cells. The upstream SMAD pathway of hepcidin, including pSMAD1/5/8, SMAD1, or Id1, were induced by EC-CM. Efficient blockage of this EC-mediated hepcidin upregulation by an ALK2/3 inhibitor or BMP6 siRNA identified BMP6 as a major hepcidin regulator in this co-culture system, which highly fits the hepcidin regulation by iron in vivo. In addition, EC-derived BMP6 and hepcidin responded highly sensitive to levels of ferric iron but also heme as low as 500 nM.

Conclusion We here establish a hepatocyte-endothelial co-culture system to fully recapitulate iron regulation by hepcidin through EC-derived BMP6.

Publication History

Article published online:
26 January 2022