TEC rescued bile metabolic dysfunction in mice with
intrahepatic cholestasis induced by ANIT or DDC
We then undertook experiments to
verify bile metabolism after TEC intervention in the CLD experimental
model.
Consistent
with previous
studies[29], ANIT
treatment alone resulted in the accumulation of bile acids in the liver
and serum of mice, and reduced the content of bile acids in feces, which
suggested that bile flow was mainly obstructed from the liver to the
intestine (Figure 3A). CLD in mice was associated with reduced hepatic
gene expression of canalicular transporters of bile salts (Bsep encoded
by Abcb11), bilirubin (Mrp2, encoded by Abcc2), and phytosterols (the
heterodimer sterolin1 and sterolin2, encoded by ABCG5 and
ABCG8)[20,
29,
30]. Concomitant with biochemical
cholestasis, mRNA expression of export transporters (Mrp2 and Bsep),
phytosterol transporters (ABCG5 and ABCG8) and uptake transporters
(Ntcp, Oatp) were significantly suppressed in mice with ANIT-induced CLD
(Figure 3B). TEC significantly decreased the bile acid pool size in the
liver and serum, and markedly increased the bile acid content in feces.
Similarly, ANIT-induced inhibition of transporters was reversed after
TEC intervention. FXR is the master regulator of bile acids transporters
(Bsep, Mrp2 and Ntcp), while LXR is an important regulator of ABCG5 and
ABCG8[20].
Therefore, western blotting analysis was performed, and the results
showed that TEC intervention restored ANIT-induced decrease in FXR and
LXR (Figure 3C).
Additionally, in 0.1% DDC-treated mice bile acids accumulated in the
liver and serum, but decreased in feces (Figure 3D). Analysis of the
expression of hepatic bile acid and phytosterol export transporters
confirmed the expected reduction of the bile acid uptake transporters
(Ntcp and Oatp), bile acid export transporters (Mrp2 and Bsep) and
phytosterol export transporters (ABCG5 and ABCG8) after 0.1% DDC
treatment (Figure 3E). Notably, TEC significantly rescued the bile acid
pool size in the liver, serum and feces. In line with this finding, TEC
improved the expression of bile acid uptake transporters (Oatp and
Ntcp), bile acid export transporters (Mrp2 and Bsep) and phytosterol
export transporters (ABCG5 and ABCG8) in 0.1% DDC fed mice. The
expression of FXR and LXR was determined by western blot analysis, and
the results showed that TEC restored DDC-induced downregulation of FXR
and LXR in mouse liver (Figure 3F).
Taken together, these results showed that TEC attenuated ANIT-induced
and DDC-induced bile metabolic dysfunction, and exerted a protective
effect on CLD.