Absence of BSEP (ABCB11) protects MDR2 (ABCB4) KO mice from cholestatic liver and bile duct injury through modulating the inflammatory signaling

Background Bsep KO mice are protected from acquired cholestasis by metabolic precondition with a hydrophilic bile acid (BA) pool with tetrahydroxylated bile acids (THBAs) being the most prominent BA species. We aimed to explore whether increased BA detoxification/THBAs alters inflammatory signaling, thereby improving liver injury in the Mdr2 KO mouse model of sclerosing cholangitis.

Methods Cholestatic liver injury, hepatic inflammation and fibrosis in Mdr2/Bsep DKO and Mdr2 KO mice was studied for comparison. Additionally, Mdr2 KO mice were treated with a THBA. Gene expression profiles of inflammatory/fibrotic markers were investigated by RT-PCR and Western blotting. Liver T-cell numbers were quantified by FACS. Microbiota analysis was also performed. In vitro, the impact of THBA on RORgt as well as NFkB-signaling in Jurcat cells were analyzed.

Results In contrast to Mdr2 KO, DKO mice displayed increased BA hydroxylation and lacked histological features of sclerosing cholangitis. 67 % of serum BAs in DKO mice were polyhydroxylated, with THBAs being most prominent, while Mdr2 KO mice had no such BAs. In contrast to profoundly increased gene expression of inflammatory and fibrotic markers in Mdr2 KO, no increases were seen in DKO. Increased levels of PHBAs were associated with reduced RORgt+ cells but increased FOXP3+ within the CD4+CD3+ T-cell population. Microbiota composition points also towards less inflammation in DKO vs. Mdr2 KO mice. In vitro, THBA attenuated RORgt-signaling at mRNA level in Jurcat cells. It also attenuated CDCA-induced NFkB activation in GFP-NFkB transfected Jurcat cells. THBA feeding reduced inflammatory and fibrotic genes in Mdr2 KO.

Conclusion Increased formation of THBA (due to absence of Bsep) or THBA administration represses key pro-inflammatory signals such as NFkB and RORgt in immune cells, protecting Mdr2 KO mice from cholestasis-associated inflammation and fibrosis. Therefore, THBA and their downstream targets may be a new potential treatment strategy for cholestatic liver diseases.

Publication History

Article published online:
26 May 2020