No abstract

Background and Aims Hepatocyte nuclear factor 4 alpha (HNF4α) is indispensable for hepatocyte differentiation and critical for maintaining liver health. Here, we demonstrate that loss of HNF4α activity is a crucial step in the pathogenesis of chronic liver diseases (CLDs) that lead to development of HCC. Approach and Results We developed an HNF4α target gene signature, which can accurately determine HNF4α activity, and performed an exhaustive in silico analysis using hierarchical and K‐means clustering, survival, and rank‐order analysis of 30 independent data sets containing over 3500 individual samples. The association of changes in HNF4α activity to CLD progression of various etiologies, including HCV‐ and HBV‐induced liver cirrhosis (LC), NAFLD/NASH, and HCC, was determined. Results revealed a step‐wise reduction in HNF4α activity with each progressive stage of pathogenesis. Cluster analysis of LC gene expression data sets using the HNF4α signature showed that loss of HNF4α activity was associated with progression of Child‐Pugh class, faster decompensation, incidence of HCC, and lower survival with and without HCC. A moderate decrease in HNF4α activity was observed in NAFLD from normal liver, but a further significant decline was observed in patients from NAFLD to NASH. In HCC, loss of HNF4α activity was associated with advanced disease, increased inflammatory changes, portal vein thrombosis, and substantially lower survival. Conclusions In conclusion, these data indicate that loss of HNF4α function is a common event in the pathogenesis of CLDs leading to HCC and is important from both diagnostic and therapeutic standpoints.

No abstract

The liver has a unique capacity to regenerate after injury in a highly orchestrated and regulated manner. Here we report that O-GlcNAcylation, an intracellular posttranslational modification (PTM) regulated by two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), is a critical termination signal for liver regeneration (LR) following partial hepatectomy (PHX). We studied liver regeneration after PHX on hepatocyte specific OGT and OGA knockout mice (OGT-KO and OGA-KO), which caused a significant decrease (OGT-KO) and increase (OGA-KO) in hepatic O-GlcNAcylation, respectively. OGA-KO mice had normal regeneration, but the OGT-KO mice exhibited substantial defects in termination of liver regeneration with increased liver injury, sustained cell proliferation resulting in significant hepatomegaly, hepatic dysplasia and appearance of small nodules at 28 days after PHX. This was accompanied by a sustained increase in expression of cyclins along with significant induction in pro-inflammatory and pro-fibrotic gene expression in the OGT-KO livers. RNA-Seq studies revealed inactivation of hepatocyte nuclear 4 alpha (HNF4α), the master regulator of hepatic differentiation and a known termination signal, in OGT-KO mice at 28 days after PHX, which was confirmed by both Western blot and IHC analysis. Furthermore, a significant decrease in HNFα target genes was observed in OGT-KO mice, indicating a lack of hepatocyte differentiation following decreased hepatic O-GlcNAcylation. Immunoprecipitation experiments revealed HNF4α is O-GlcNAcylated in normal differentiated hepatocytes. These studies show that O-GlcNAcylation plays a critical role in the termination of LR via regulation of HNF4α in hepatocytes.

Background and Aims: Overdose of acetaminophen (APAP) is the major cause of acute liver failure in the western world. We report a novel signaling interaction between hepatocyte nuclear factor 4 alpha (HNF4α) cMyc and nuclear factor erythroid 2–related factor 2 (Nrf2) during liver injury and regeneration after APAP overdose. Approach and Results: APAP-induced liver injury and regeneration were studied in male C57BL/6J (WT) mice, hepatocyte-specific HNF4α knockout mice (HNF4α-KO), and HNF4α-cMyc double knockout mice (DKO). C57BL/6J mice treated with 300 mg/kg maintained nuclear HNF4α expression and exhibited liver regeneration, resulting in recovery. However, treatment with 600-mg/kg APAP, where liver regeneration was inhibited and recovery was delayed, showed a rapid decline in HNF4α expression. HNF4α-KO mice developed significantly higher liver injury due to delayed glutathione recovery after APAP overdose. HNF4α-KO mice also exhibited significant induction of cMyc, and the deletion of cMyc in HNF4α-KO mice (DKO mice) reduced the APAP-induced liver injury. The DKO mice had significantly faster glutathione replenishment due to rapid induction in Gclc and Gclm genes. Coimmunoprecipitation and ChIP analyses revealed that HNF4α interacts with Nrf2 and affects its DNA binding. Furthermore, DKO mice showed significantly faster initiation of cell proliferation resulting in rapid liver regeneration and recovery. Conclusions: These data show that HNF4α interacts with Nrf2 and promotes glutathione replenishment aiding in recovery from APAP-induced liver injury, a process inhibited by cMyc. These studies indicate that maintaining the HNF4α function is critical for regeneration and recovery after APAP overdose.