Abstract
Sulfotransferase 1E1 (SULT1E1, also known as estrogen sulfotransferase) plays an important role in metabolism and detoxification of many endogenous and exogenous compounds (e.g., estrogens and flavonoids). Here we aimed to assess the effects of farnesoid X receptor (FXR) activation on SULT1E1 expression, and to determine the mechanism thereof. Treatment with specific FXR agonists (i.e., GW4064 and CDCA) significantly decreased both mRNA and protein levels of SULT1E1 in HepG2 cells. This was accompanied by a decrease in the enzymatic activity. The inhibitory effect was potentiated by FXR overexpression but attenuated by FXR knockdown, confirming FXR-dependent regulation of SULT1E1. Surprisingly, direct regulation of SULT1E1 by FXR was unlikely because FXR did not bind to SULT1E1 promoter or enhancer as revealed by chromatin immunoprecipitation (ChIP). Interestingly, SULT1E1 regulation was abolished when HNF4α (hepatocyte nuclear factor 4α, a known activator of SULT1E1) was silenced, supporting a critical role for HNF4α in FXR regulation of SULT1E1. Furthermore, a combination of ChIP, luciferase reporter and co-immunoprecipitation assays showed that FXR inhibited HNF4α transactivation of SULT1E1 by suppressed binding of the co-activator PGC1α (peroxisome proliferator-activated receptor-γ coactivator 1α) to HNF4α. In conclusion, FXR transcriptionally regulates SULT1E1 through inhibition of PGC1α binding to HNF4α. Targeting the FXR-SULT1E1 axis may represent a promising approach for management of estrogen-related diseases.