LPS dosage-dependently regulates FOXA2 expression through NFkB signaling and thus determining BSEP expression in ACLF

Background & Aims Apical ABC-transporter BSEP/ABCB11 is in charge of bile acid delivery. Loss of BSEP in end-stage liver disease such as acute-on-chronic liver failure (ACLF) leads to severe cholestasis and poor prognosis. Our previous study shows that transcription factor FOXA2 replaces FXR to control BSEP expression in ACLF. As a sepsis-like syndrome, ACLF patients usually suffer from severe bacterial infection. In this study, we scrutinize how LPS influences apical BSEP expression through modulating FOXA2.

Methods We investigated 18 ACLF patients, 13 receiving liver transplantation (LTx) and 5 recovered. BSEP and FOXA2 were examined in liver tissues by immunohistochemistry. LPS effects on FOXA2 and BSEP expression were investigated in cultured hepatocytes and in mice.

Results Recovered ACLF patients display apical BSEP expression in hepatocytes. In those receiving LTx, 3 patients lacking BSEP expression show more severe disease. Compared with irreversible patients possessing BSEP, the patients who lost apical BSEP demonstrated higher serum total bilirubin concentration, higher international normalized ratio and Model for End-stage Liver Disease score. 15 patients who maintained apical BSEP expressed robust FOXA2 in hepatocytes. ChIP assays confirmed that FOXA2 initiated ABCB11 transcription through binding to the gene promoter in primary human and mouse hepatocytes. Foxa2 and Bsep expression was induced with 2-5 mg/mL LPS in hepatocytes. Knockdown of Foxa2 by RNAi abolished LPS-induced Bsep expression. ChIP assays showed that LPS increased binding activity of Foxa2 to the bsep gene promoter. ChIP analyses further revealed that LPS treatment led to binding of p65, a NFkB signaling protein, to the foxa2 gene promoter. When hepatocytes were treated by p65 nuclear translocation inhibitor JSH23, p65 binding to the foxa2 gene promoter was blocked and expression of Foxa2 and Bsep were inhibited. Interestingly, high concentrations of LPS (20mg/mL) inhibited Foxa2 nuclear translocation and induced high levels of p-Foxa2, which resulted in inhibition of BSEP expression. Consistent with the in vitro observation, regulation of nuclear FOXA2 and BSEP expression in hepatocytes by LPS is dosage dependent in mice

Conclusions LPS dosage-dependently regulates FOXA2 expression through NFkB signaling and thus determining BSEP expression in severe inflammatory diseases, such as ACLF.

Publikationsverlauf

Artikel online veröffentlicht:
04. Januar 2021