Hepatic HDAC3 Regulates Systemic Iron Homeostasis and Ferroptosis via the Hippo Signaling Pathway

Histone deacetylases (HDACs) are epigenetic regulators that play an important role in determining cell fate and maintaining cellular homeostasis. However, whether and how HDACs regulate iron metabolism and ferroptosis (an iron-dependent form of cell death) remain unclear. Here, the putative role of hepatic HDACs in regulating iron metabolism and ferroptosis was investigated using genetic mouse models. Mice lacking Hdac3 expression in the liver (Hdac3-LKO mice) have significantly reduced hepatic Hamp mRNA (encoding the peptide hormone hepcidin) and altered iron homeostasis. Transcription profiling of Hdac3-LKO mice suggests that the Hippo signaling pathway may be downstream of Hdac3. Moreover, using a Hippo pathway inhibitor and overexpressing the transcriptional regulator Yap (Yes-associated protein) significantly reduced Hamp mRNA levels. Using a promoter reporter assay, we then identified 2 Yap-binding repressor sites within the human HAMP promoter region. We also found that inhibiting Hdac3 led to increased translocation of Yap to the nucleus, suggesting activation of Yap. Notably, knock-in mice expressing a constitutively active form of Yap (Yap K342M) phenocopied the altered hepcidin levels observed in Hdac3-LKO mice. Mechanistically, we show that iron-overload-induced ferroptosis underlies the liver injury that develops in Hdac3-LKO mice, and knocking down Yap expression in Hdac3-LKO mice reduces both iron-overload-and ferroptosis-induced liver injury. These results provide compelling evidence supporting the notion that HDAC3 regulates iron homeostasis via the Hippo/Yap pathway and may serve as a target for reducing ferroptosis in iron-overload-related diseases.