Objective

2

To investigate the effects of bear bile on intrahepatic cholestasis and its underlying mechanisms via the farnesoid X receptor （FXR）/transient receptor potential （TRP） pathway.

Methods

2

Forty male C57BL/6J mice were randomly divided into a control group， model group， positive drug group ［obeticholic acid （OCA） 30 mg/kg， gavage］， and bear bile high- and low-dose groups （36 and 9 mg/kg， respectively， gavage）， with eight mice in each group. On day 5 of administration， all groups except the control group were intragastrically administered α-naphthyl isothiocyanate （ANIT， 80 mg/kg） to establish an intrahepatic cholestasis model. Samples were collected 2 days after modeling. Liver histopathological changes were observed by hematoxylin-eosin （HE） staining. Serum levels of aspartate aminotransferase （AST）， alanine aminotransferase （ALT）， total bile acids （TBA）， and total bilirubin （TBIL） were measured. Real-time quantitative polymerase chain reaction was used to detect the expression of genes related to bile acid synthesis ［cytochrome P450 family 27 subfamily A member 1 （CYP27A1）］， transport ［multidrug resistance-associated proteins 3 and 4 （MRP3， MRP4）］， excretion ［bile salt export pump （BSEP）］， inflammatory mediators ［interleukin-6 （IL-6）， interleukin-1β （IL-1β）， tumor necrosis factor-α （TNF-α）， nuclear factor-κB （NF-κB）］， antioxidant stress ［nuclear factor erythroid 2-related factor 2 （NRF2）， glutamate-cysteine ligase catalytic subunit （GCLC）］， and TRP ion channels ［transient receptor potential ankyrin 1 （TRPA1）， transient receptor potential vanilloid 1 （TRPV1）］ in mouse liver tissue.

Results

2

Compared with the control group， mice in the model group showed obvious histopathological liver damage， characterized by marked inflammatory cell infiltration， focal vacuolar

degeneration and necrosis of hepatocytes， and loosened connective tissue. Serum biochemical indices of cholestasis were significantly increased （

P

<

0.05）. The mRNA expression levels of small heterodimer partner （SHP）， MRP3， MRP4， IL-6， IL-1β， TNF-α， NF-κB， TRPA1， and TRPV1 were significantly upregulated （

P

<

0.05）， while FXR， CYP27A1， NRF2， and GCLC mRNA levels were significantly downregulated （

P

<

0.05）. No significant difference was observed in BSEP mRNA expression （

P

>

0.05）. Compared with the model group， mice in the bear bile high- and low-dose groups showed reduced inflammatory cell infiltration， fewer vacuolated and necrotic cells， less nuclear pyknosis， and alleviated pathological damage to liver tissue structure. Serum biochemical indices of cholestasis were significantly decreased （

P

<

0.05）. The mRNA expression levels of MRP3， MRP4， IL-6， IL-1β， TNF-α， NF-κB， TRPA1， and TRPV1 were significantly downregulated （

P

<

0.05）， while FXR， SHP， BSEP， CYP27A1， NRF2， and GCLC mRNA expression levels were significantly upregulated （

P

<

0.05）.

Conclusion

2

Bear bile can improve ANIT-induced intrahepatic cholestasis in mice through multiple targets. On the one hand， it activates FXR and upregulates BSEP to promote bile acid excretion while inhibiting CYP27A1 to reduce intrahepatic bile acid synthesis， thereby directly regulating bile acid homeostasis. On the other hand， it exerts hepatoprotective effects by activating TRPA1/TRPV1 and alleviating oxidative stress and inflammatory responses.