[Interaction among peroxisome proliferators-activated receptor alpha, cytochrome P450 oxysterol 7α-hydroxylase and estrogen receptor and its association with intrahepatic cholestasis in pregnant rats].

OBJECTIVE: To investigate the relationship between interaction of peroxisome proliferators-activated receptor alpha (PPARα), cytochrome P450 oxysterol 7α-hydroxylase (CYP7B1) and estrogen receptor (ER) and intrahepatic cholestasis in pregnant rats. METHODS: Eighty clean SD pregnant rats were selected and divided into four groups randomly with 20 in each. Since the 13th day of pregnancy, rats in the control group was injected subcutaneously with refined vegetable oil 2.0 ml×kg(-1)×d(-1), those in the low-dose, moderate-dose and high-dose groups received 17-α-ethynylestradiol (EE) 1.0 mg×kg(-1)×d(-1), 1.25 mg×kg(-1)×d(-1) and 1.5 mg×kg(-1)×d(-1), respectively. All rats were sacrificed at the 21(st) day of pregnancy and maternal hepatic tissues were collected. The serum levels of alanine aminotransferase (ALT), aspartate transaminase (AST), total bile acid (TBA) and bilirubin (BIL) were determined by enzyme linked immunosorbent assay (ELISA). The mRNA expressions of PPARα, CYP7B1, ERα and ERß in maternal rat livers were examined by real-time PCR. RESULTS: (1) Biochemical indicators: the serum levels of ALT, AST, TBA and BIL were significantly lower in the control group than in the rest 3 groups, respectively [control group: (41.1 ± 2.8) U/L, (44.4 ± 3.6) U/L, (26.4 ± 5.6) µmol/L and (2.8 ± 0.2) U/L; low-dose group: (48.2 ± 3.4) U/L, (47.9 ± 3.7) U/L, (36.4 ± 4.2) µmol/L and (4.2 ± 0.2) U/L; moderate-dose group: (70.4 ± 5.3) U/L, (68.4 ± 5.6) U/L, (64.3 ± 3.8) µmol/L and (6.2 ± 1.2) U/L; high-dose group: (72.4 ± 7.6) U/L, (70.2 ± 3.8) U/L, (72.4 ± 7.8) µmol/L and (8.2 ± 2.2) U/L, P < 0.05], and those in the moderate or high-dose groups were higher than in the low-dose group (P < 0.05). (2) mRNA expression of ERα and ERß: the mRNA expression of ERα in pregnant rat livers increased in a dose-dependent manner, which were all significantly higher than that in the control group, respectively (low-dose group: 0.76 ± 0.02); moderate-dose group: (0.99 ± 0.04; high-dose group: 1.21 ± 0.01; control group: 0.65 ± 0.01, P < 0.05), but no difference was found among the 4 groups in the mRNA expression of ERß (P > 0.05). (3) mRNA expression of CYP7B1 and PPARα: the mRNA expression of CYP7B1 in pregnant rat livers increased from the low-dose group to the high-dose group, and were all higher than that of the control group (low-dose group: 0.93 ± 0.01; moderate-dose group: 0.99 ± 0.06; high-dose group: 1.22 ± 0.04; control group: 0.75 ± 0.02, P < 0.05). However, the mRNA expression of PPARα decreased from the low-dose group to the high-dose group, and were all lower than that of the control group (low-dose group: 0.83 ± 0.05; moderate-dose group: 0.71 ± 0.02; high-dose group: 0.64 ± 0.03; control group: 1.35 ± 0.05; P < 0.05). CONCLUSIONS: The down regulated mRNA expression of PPARα, caused by higher dose of estrogen, may increase the expression of CYP7B1 due to the ineffectiveness of the inhibition of PPARα on CYP7B1, which may further stimulate the ERα activity and then induce intrahepatic cholestasis. Abnormal expression of PPARα, CYP7B1 and ER may play a role in the pathogenesis of estrogen-induced intrahepatic cholestasis.

[Expression of FXR mRNA, PPAR alpha mRNA and bile acid metabolism related genes in intrahepatic cholestasis of pregnant rats].

OBJECTIVE: To study the expressions of FXR, PPARa and Bile acid metabolism related genes in intrahepatic cholestasis of pregnant rats. METHODS: 60 clean SD pregnant rats were selected and divided randomly into three groups. Since the 13th day of pregnancy rats in control group were injected subcutaneously with refined vegetable oil 2.0 mg/kg/d Rats in no-treated group were injected subcutaneously with the 17-a-ethynylestradiol (EE) 1.25 mg/kg/d until the 17th day. Those rat ih treated group were injected subcutaneously with the 17-a-ethynylestradiol (EE) 1.25 mg/kg/d until the 17th day and then were treated with fenofibrate for another four days until the 21th day. All rats were killed at the 21th day and livers were collected for study. The levels of serum TBA were examined by ELISA. The mRNA expressions of PPARa, FXR, CYP7A1, CYP27A1 and CYP8B1 were examined by real-time PCR. (1) RESULTS: The levels of TBA were significantly higher in no-treated group (68.7+/-4.2)mumol/L and treated group (69.5+/-3.8)mumol/L compared with that of control group (26.6+/-2.3)mumol/L at the 17th day (P value is less than 0.05) and no difference found between treated and no-treated groups (P value is more than 0.05). The levels of TBA were higher in no-treated group (69.4+/-3.7)mumol/L and treated group (48.5+/-4.8)mumol/L as compared to control group (27.1+/-3.2)mumol/L at the 21th day (P value is less than 0.05). The lever of TBA was significantly lower in Treated group compared with No-treated group (P value is less than 0.05). (2) The mRNA expressions of CYP7A1, FXR, CYP27A1 and CYP8B1 increased in No-treated group (1.55+/-0.03, 1.75+/-0.02, 2.45+/-0.01, 2.15+/-0.01, respectively) and were all higher as compared to control group (0.75+/-0.02, 1.25+/-0.03, 0.65+/-0.03, 1.50+/-0.02, respectively) (P value is less than 0.05). However, the mRNA expression of PPARa decreased in No-treated group (0.85+/-0.02) compared with control group (1.45+/-0.02) (P value is less than 0.05). The mRNA expressions of CYP27A1, PPARa and CYP8B1 increased in treated group (1.25+/-0.01, 1.65+/-0.05, 1.65+/-0.02, respectively) and were all higher than that of control group (P value is less than 0.05). CONCLUSION: Abnormal expressions of CYP7A1, FXR, CYP27A1, CYP8B1 and PPARa may play a role in pathogenesis of estrogen-induced intrahepatic cholestasis. Activator of PPARa may be used as therapeutical drug for ICP.