Roles of PPARγ/NF-κB signaling pathway in the pathogenesis of intrahepatic cholestasis of pregnancy

Abstract

Background: Intrahepatic cholestasis of pregnancy (ICP) is the most prevalent pregnancy specific liver disease. However, the pathogenesis and etiology of ICP is poorly understood.

Aim: To assess the expression of peroxisome proliferator-activated receptorγ (PPARγ) and nuclear factor kappa B (NF-κB) in placenta and HTR-8/SVneo cell, and evaluate the serum levels of cytokines, bile acids, hepatic function and lipids in control and ICP patients and the fetal outcome, in order to explore the role of PPARγ/NF-κB signaling pathway in the possible mechanism of ICP.

Methods: Clinical data of the pregnant women were collected and serum levels of cytokines, bile acids, hepatic function and lipids were measured. Expressions of PPARγ and NF-κB in placenta and HTR-8/SVneo cell were determined. The new-born information was collected to demonstrate the relationship between PPARγ/NF-κB signaling pathway and ICP.

Results: The serum levels of bile acids, hepatic function, triglycerides (TG), total cholesterol (TC), IL-6, IL-12 and TNF-α in ICP group were significantly increased (P<0.01), and serum level of IL-4 was significantly decreased (P<0.01). PPARγ and NF-κB staining were found in the membrane and cytoplasm of placental trophoblast cell. The expression of PPARγ and NF-κB were significantly higher in ICP group and taurocholate acid (TCA) treated HTR-8/SVneo cell (P<0.01). The new-born information in severe ICP group were significantly different as compared to that in control group (P<0.05), and part of information in mild ICP group were also difference to that in control group (P<0.05).

Conclusions: The higher expressions of PPARγ and NF-κB in ICP placenta and TCA treated HTR-8/SVneo cell, together with the abnormal serum levels of cytokines, might induced by the imbalance of inflammatory and immune reaction, and then disturb placental bile acid and serum lipids transportation, finally result in fatal cholestasis which probably be one of the mechanism of ICP.

Figure 1. PPARγ and NF-κB staining were found in the membrane and cytoplasm of placental trophoblast cell.

×400 (A–C) PPARγ protein expressed in the placenta of control patients, mild ICP patients and severe ICP patients. (D–F) NF-κB protein expressed in the placenta of control patients mild ICP patients and severe ICP patients. PPARγ and NF-κB proteins expression were significantly different in control group and ICP groups.

Figure 2. Expression of PPARγ and NF-κB mRNA in placentas from control group and ICP groups.

(A) RT-PCR analysis of placental PPARγ and NF-κB mRNAexpression in control, mild ICP and sever ICP groups. (B) Graphical summary of data on the expression of PPARγ mRNA. (C) Graphical summary of data on the expression of NF-κB mRNA. The data are expressed as the mean ± S.D., **p<0.01 vs. control group.

Figure 3. Expression of PPARγ and NF-κB protein in placentas from control group and ICP groups.

(A) Western blotting analysis of placental PPARγ and NF-κB protein expression in control, mild ICP and sever ICP groups. (B) Graphical summary of data on the expression of PPARγ protein. (C) Graphical summary of data on the expression of NF-κB protein. The data are expressed as the mean ± S.D., **p<0.01 vs. control group.

Figure 4. Expression of PPARγ andNF-κB mRNA in cultured HTR-8/SVneo cell.

(A) RT-PCR analysis of placental PPARγ and NF-κB mRNA expression in control, mild ICP and sever ICP group. (B) Graphical summary of data on the expression of PPARγ mRNA. (C) Graphical summary of data on the expression of NF-κB mRNA. The data are expressed as the mean ± S.D., ^## p<0.01vs. control group, **p<0.01 vs. TCA 10 µM/L group.

Figure 5. Expression of PPARγ and NF-κB protein in cultured HTR-8/SVneo cell.

(A) Western blotting analysis of placental PPARγ and NF-κB protein expression in control, mild ICP and sever ICP group. (B) Graphical summary of data on the expression of PPARγ mRNA. (C) Graphical summary of data on the expression of NF-κB protein. The data are expressed as the mean ± S.D., ^## p<0.01vs. control group, **p<0.01 vs. TCA10 µM/L group.