Positive and Negative Regulation of Human Hepatic Hydroxysteroid Sulfotransferase (SULT2A1) Gene Transcription by Rifampicin: Roles of Hepatocyte Nuclear Factor 4α and Pregnane X Receptor

Abstract

The effects of rifampicin treatment on SULT2A1 mRNA expression were evaluated in 23 preparations of primary cultured human hepatocytes. In contrast to the consistently occurring induction of CYP3A4, a prototypical pregnane X receptor (PXR) target gene, rifampicin treatment increased SULT2A1 mRNA levels in 12 of the hepatocyte preparations, but it produced little change or even suppression in the others. Transient transfection of HepG2 cells with a series of reporter constructs implicated two SULT2A1 5Ј-flanking regions as containing rifampicin-responsive information. Each of these regions contained a hepatocyte nuclear factor 4 (HNF4) binding site (at nucleotide [nt] Ϫ6160 and Ϫ54), as demonstrated by in vitro binding and site-directed mutagenesis. HNF4␣ bound to the HNF4-54 region of the endogenous SULT2A1 gene, as indicated by chromatin immunoprecipitation. Cotransfection of HepG2 cells with pregnane X receptor (PXR) dose-dependently suppressed reporter expression from SULT2A1 constructs containing the HNF4 sites, and rifampicin treatment augmented the suppression. Rifampicin treatment concentration-dependently suppressed SULT2A1 reporter expression at the same concentrations that progressively induced expression from a PXR-responsive CYP3A4 reporter, whereas higher rifampicin concentrations reversed the SULT2A1 suppression. The suppressive effect of rifampicin was diminished, whereas the activating effect was augmented, in HepG2 cells with RNA interference-mediated PXR knockdown. These results suggest that HNF4␣ plays a central role in the control of SULT2A1 transcription and that rifampicin-liganded PXR suppresses SULT2A1 expression by interfering with HNF4␣ activity. By contrast, the rifampicin-inducible SULT2A1 expression that occurs in many human hepatocyte preparations seems to be mediated through a PXR-independent mechanism.

Molecular Mechanisms and Therapeutic Targets in Steatosis and Steatohepatitis

“…HNF4␣ controls the expression of genes involved in glucose, lipid, and xenobiotic metabolism and is involved in the regulation of developmental processes of the liver as well as in later events of hepatocellular differentiation (Schrem et al, 2002). Target genes of HNF4␣ are the nuclear transcription factors HNF1␣, PXR, and CAR and genes such as aldolase B, apolipoproteins, L-fatty acid binding protein, Cyp7a1, the rate-limiting step in bile acid biosynthesis, as well as other genes involved in xenobiotic and lipid as well as carbohydrate metabolism (Fang et al, 2007;Onica et al, 2008). HNF4␣ is post-transcriptionally regulated, and specificity and affinity to DNA is either lowered or enhanced by phosphorylation at serine, threonine, and tyrosine residues via respective kinases (e.g., p38 kinase, PKA) (Schrem et al, 2002;Xu et al, 2007).…”

Human Pregnane X Receptor Activation and CYP3A4/CYP2B6 Induction by 2,3-Oxidosqualene:Lanosterol Cyclase Inhibition

“…Although there was considerable variability in the magnitude of Ro 48-8071-mediated CYP3A4/CYP2B6 induction among hepatocyte culture preparations, this variability was consistent with that observed with other inducers. For example, when 23 preparations of primary cultured human hepatocytes were treated with rifampicin, we observed CYP3A4 mRNA levels to increase from 1.6-to 436-fold (Fang et al, 2007). In most preparations, the magnitude of CYP3A4 mRNA induction that was produced by Ro 48-8071 treatment was lower than that produced by rifampicin treatment.…”

Transcriptional Regulation of Cytosolic Sulfotransferase 1C2 by Intermediates of the Cholesterol Biosynthetic Pathway in Primary Cultured Rat Hepatocytes

“…For example, SULT2A1 has high sulfonating activity toward the secondary bile acid lithocholic acid (Huang et al, 2010). VDR and PXR are activated by lithocholate and regulate the transcription of SULT2A1 (Makishima et al, 2002;Echchgadda et al, 2004;Fang et al, 2007). Additionally, LXR regulates the expression of SULT2A1 and 2B1b (Jiang et al, 2005;Ou et al, 2014), and several oxysterols that are ligands for LXR are also sulfonated by these enzymes (Fuda et al, 2007;Cook et al, 2009).…”