Effect of geniposidic acid on SHP-LRH-1 signaling pathway in cholestasis rats

Abstract

To explore the effect of geniposidic acid (GPA) on the signal pathway of small heterodimer dimer receptor (SHP) and liver receptor homologue 1 (LRH-1) in cholestasis rats induced by alpha-naphthalene isothiocyanate (ANIT). Methods: Fifty SD rats were randomly divided into five groups: a blank group, an ANIT group, an ANIT+GPA (100 mg/kg) group, an ANIT+GPA (50 mg/kg) group, and an ANIT+GPA (25 mg/kg) group (n=10 in each group). The GPA were intragastrically given to rats for 10 days, and the control group and the ANIT group were given normal saline. At the eighth day of administration, all rats except the blank group were given 65 mg/kg ANIT once until the tenth day. After the last administration, serum total cholesterol (TC), triglyceride (TG) and total bile acids (TBA) were measured. The primary hepatocytes (RPH) were isolated from normal rats and cultured. The cells were divided into a blank group, an ANIT (40 μmol/L) group, an ANIT (40 μmol/L)+GPA (4.00 mmol/L) group (A4.00G group), an ANIT (40 μmol/L)+GPA (1.00 mmol/L) group (A1.00G group), and an ANIT (40 μmol/L)+GPA (0.25 mmol/L) group (A0.25G group). The mRNA transcription levels of SHP and cholesterol 7 alpha hydroxylase (CYP7A1) in RPH were detected by real-time-PCR, and the protein levels of SHP and CYP7a1 were detected by Western blotting. In the LRH-1 silence experiment, the RPH were divided into a blank group, a negative transfection group, a siRNA-LRH group (ZR group), a siRNA-LRH+GPA (4.00 mmol/L) group (ZR4.00G group), a siRNA-LRH+GPA (1.00 mmol/L) group (ZR1.00G group) and a siRNA-LRH+GPA (0.25 mmol/L) group (ZR0.25G group). The protein and mRNA levels of SHP, CYP7a1, LRH-1 were detected. In the over-expression experiment, the RPH were also divided into a blank group, a negative transfection group, a LRH-1 over-expression plasmid group (OE group), a LRH-1 over-expression plasmid+GPA (4.00 mmol/L) group (OE4.00G group), a LRH-1 over-expression plasmid+GPA (1.00 mmol/L) group (OE1.00G group), and a LRH-1 over-expression plasmid+GPA (0.25 mmol/L) group (OE0.25G group). The protein and mRNA levels of SHP, CYP7a1 and LRH-1 were detected. Results: Compared with the blank control group, TC and TBA were significantly increased (both P<0.01) in the ANIT group, but there was no difference in TG; compared with the ANIT group, the contents of TC and TBA in the AG100 and AG50 groups were significantly reduced (all P<0.01). Compared with the blank control group, the proteins and mRNA levels of SHP were significantly decreased (P<0.01), while CYP7a1 were dramatically increased (P<0.01) in the ANIT group; compared with the ANIT group, the proteins and mRNA levels of SHP in the A4.00G group and the A1.00G group were significantly increased (both P<0.01), while the levels of CYP7a1 proteins and mRNA levels were evidently decreased in the A4.00G and A1.00G groups (both P<0.01). Compared with the negative transfection group, the proteins and mRNA levels of CYP7a1 and LRH-1 were dramatically restrained (all P<0.01), while there was no change in SHP in the ZR group; compared with the ZR group, the proteins and mRNA levels of SHP were significantly increased (all P<0.01), while LRH-1 and CYP7a1 were not changed in the ZR4.00G, ZR1.00G and ZR0.25G groups. Compared with the negative transfection group, the protein and mRNA levels of CYP7a1 and LRH-1 were significantly suppressed in the OE group (all P<0.01). Compared with the OE group, the protein and mRNA levels of SHP were evidently increased in the OE4G and OE1G groups (all P<0.01), while LRH-1 and CYP7a1 were not changed in the OE4G, OE1G and OE0.25G groups. Conclusion: The over-expression of LRH-1 in RPH can up-regulate the mRNA and protein levels of CYP7a1. GPA can improve the biochemical and liver pathology of ANIT-induced cholestasis rats, which may be related to the decrease of CYP7a1 by activating SHP through LRH-1 in RPH.