FXR regulates liver repair after CCl4-induced toxic injury.

Liver repair is key to resuming homeostasis and preventing fibrogenesis as well as other liver diseases. Farnesoid X receptor (FXR, NR1H4) is an emerging liver metabolic regulator and cell protector. Here we show that FXR is essential to promote liver repair after carbon tetrachloride (CCl(4))-induced injury. Expression of hepatic FXR in wild-type mice was strongly suppressed by CCl(4) treatment, and bile acid homeostasis was disrupted. Liver injury was induced in both wild-type and FXR(-/-) mice by CCl(4), but FXR(-/-) mice had more severe defects in liver repair than wild-type mice. FXR(-/-) livers had a decreased peak of regenerative DNA synthesis and reduced induction of genes involved in liver regeneration. Moreover, FXR(-/-) mice displayed increased mortality and enhanced hepatocyte deaths. During the early stages of liver repair after CCl(4) treatment, we observed overproduction of TNFalpha and a strong decrease of phosphorylation and DNA-binding activity of signal transducer and activator of transcription 3 in livers from FXR(-/-) mice. Exogenous expression of a constitutively active signal transducer and activator of transcription 3 protein in FXR(-/-) liver effectively reduced hepatocyte death and liver injury after CCl(4) treatment. These results suggest that FXR is required to regulate normal liver repair by promoting regeneration and preventing cell death.