BMP6 treatment compensates for the molecular defect and ameliorates hemochromatosis in Hfe knockout mice.

Background & Aims: Abnormal hepcidin regulation is central to the pathogenesis of HFE hemochromatosis. Hepatic bone morphogenetic protein 6 (BMP6)-SMAD signaling is a main regulatory mechanism controlling hepcidin expression, and this pathway was recently shown to be impaired in Hfe knockout (Hfe(-/-)) mice. To more definitively determine whether HFE regulates hepcidin expression through an interaction with the BMP6-SMAD signaling pathway, we investigated whether hepatic Hfe overexpression activates the BMP6-SMAD pathway to induce hepcidin expression. We then investigated whether excess exogenous BMP6 administration overcomes the BMP6-SMAD signaling impairment and ameliorates hemochromatosis in Hfe(-/-) mice.

Methods: The BMP6-SMAD pathway and the effects of neutralizing BMP6 antibody were examined in Hfe transgenic mice (Hfe Tg) compared with wild-type (WT) mice. Hfe(-/-) and WT mice were treated with exogenous BMP6 and analyzed for hepcidin expression and iron parameters.

Results: Hfe Tg mice exhibited hepcidin excess and iron deficiency anemia. Hfe Tg mice also exhibited increased hepatic BMP6-SMAD target gene expression compared with WT mice, whereas anti-BMP6 antibody administration to Hfe Tg mice improved the hepcidin excess and iron deficiency. In Hfe(-/-) mice, supraphysiologic doses of exogenous BMP6 improved hepcidin deficiency, reduced serum iron, and redistributed tissue iron to appropriate storage sites.

Conclusions: HFE interacts with the BMP6-SMAD signaling pathway to regulate hepcidin expression, but HFE is not necessary for hepcidin induction by BMP6. Exogenous BMP6 treatment in mice compensates for the molecular defect underlying Hfe hemochromatosis, and BMP6-like agonists may have a role as an alternative therapeutic strategy for this disease.