NRF2 and FXR dual signaling pathways cooperatively regulate the effects of oleanolic acid on cholestatic liver injury.

BACKGROUND: Previous studies have shown that the anti-cholestatic effect of oleanolic acid (OA) is associated with FXR and NRF2. However, how the two signaling pathways cooperate to regulate the anti-cholestatic effect of OA remains unclear. PURPOSE: This study aimed to further demonstrate the effect of OA on alpha-naphthyl isothiocyanate (ANIT)-induced cholestatic liver injury and the interaction mechanism between NRF2 and FXR signaling pathways in maintaining bile acid homeostasis. METHODS: Gene knockout animals and cell models, metabolomics analysis, and co-immunoprecipitation were used to investigate the mechanism of OA against cholestatic liver injury. RESULTS: The effect of OA against ANIT-induced liver injury in rats was dramatically reduced after Nrf2 gene knockdown. With the silencing of Fxr, the hepatoprotective effect of OA was weakened, but it still effectively alleviated cholestatic liver injury in rats. In L02 cells, OA can up-regulate the levels of NRF2, FXR, BSEP and UGT1A1, and reduce the expression of CYP7A1. Silencing of NRF2 or FXR significantly attenuated the protective effect of OA on ANIT-induced L02 cell injury and its regulation on downstream target genes, and the influence of NRF2 gene silencing on OA appeared to be greater. The NRF2 activator sulforaphane, and the FXR activator GW4064 both remarkably promoted NRF2 binding to P300 and FXR to RXRα, but reduced ß-catenin binding to P300 and ß-catenin binding to FXR. CONCLUSION: The effect of OA on cholestatic liver injury is closely related to the simultaneous activation of NRF2 and FXR dual signaling pathways, in which NRF2 signaling pathway plays a more important role. The dual signaling pathways of NRF2 and FXR cooperatively regulate bile acid metabolic homeostasis through the interaction mechanism with ß-catenin/P300.

Effect of Shuangyu Tiaozhi Decoction on SRB1/CYP7A1/FXR Signaling Pathway in Liver of Hypercholesterolemic Rats / 中国实验方剂学杂志

Objective:To observe the effect of Shuangyu Tiaozhi decoction on B-type scavenger receptor （SRB1）/cholesterol 7<italic>α</italic>-hydroxylase protein （CYP7A1）/farnesol X receptor （FXR） signaling pathway in liver of hypercholesterolemic rats， and its mechanism in reducing blood lipid. Method:Among 40 SD rats， 8 were randomly selected as normal group， and the remaining 32 were successfully established as hypercholesterolemic model， and randomly divided into 4 groups： model group， low and high-dose Shuangyu Tiaozhi decoction groups （7.8， 15.6 g·kg^-1）， and simvastatin group （4 mg·kg^-1）， with 8 rats in each group. The drugs were continuously given for 8 weeks. Serum total cholesterol （TC）， triglyceride （TG） and liver TC，free cholesterol （FC） and total bile acid （TBA） were measured. The pathomorphological changes in liver were observed by Hematoxylin and eosin （HE） Staining. The mRNA and protein expressions of SRB1， CYP7A1 and FXR were determined by Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot. The immunohistochemistry was used to detect CYP7A1 and FXR expressions in liver. Result:Compared with the normal group， TC， TG， FC levels in the model group were significantly increased， while the TBA level was markedly decreased， the morphology showed obvious liver steatosis， and significant declines in expressions of SRB1， CYP7A1， FXR were observed by Real-time PCR， Western blot and immunohistochemistry assays （<italic>P</italic><0.05， <italic>P</italic><0.01）. Compared with the model group， the levels of TC，TG，FC in each treatment group were reduced significantly， and the TBA level was increased markedly， the liver steatosis decreased significantly， the results of Real-time PCR， Western blot and immunohistochemistry assays showed significant increase in the expressions of SRB1， CYP7A1， FXR （<italic>P</italic><0.05， <italic>P</italic><0.01）. The therapeutic effect of high-dose Shuangyu Tiaozhi decoction group was more remarkable than that in low-dose Shuangyu Tiaozhi Decoction group （<italic>P</italic><0.05）， with no obvious difference compared with simvastatin group. Conclusion:Shuangyu Tiaozhi decoction can promote hepatic RCT and synthesize bile acid by up-regulating SRB1/CYP7A1/FXR signaling pathway， so as to reduce the blood lipid levels and improve hepatic lipid metabolism of hypercholesterolemic rats.

[Study on protective mechanism of Tibetan medicine Ershiwuwei Songshi Pills on cholestatic liver injury in rats based on FXR signaling pathway].

This paper aimed to investigate the protective effect and mechanism of the Tibetan medicine Ershiwuwei Songshi Pills on α-naphthalene isothiocyanate(ANIT)-induced cholestatic liver injury in rats based on the farnesol X receptor(FXR) signaling pathway. SD rats were randomly divided into blank group, model group, ursodeoxycholic acid(UDCA) group, Tibetan medicine Ershiwuwei Songshi Pills low, medium and high dose groups(0.09, 0.18, 0.36 g·kg~(-1)). A prophylactic dosing regimen was used in the experiment. From the 1 st to 4 th days, the UDCA group and the Tibetan medicine Ershiwuwei Songshi Pills suspension groups received prophylactic gavage administration; on the 5 th day, the blank control group was given an equal volume of olive oil blank reagent, and the remaining groups were given ANIT modeling reagent. Administration was continued on day 5 to 6 in each administration group. Forty-eight hours after modeling on the 7 th day, blood was collected from the femoral artery of rats. Serum alkaline phosphatase(ALP), alanine aminotransferase(ALT), aspartate aminotransferase(AST), direct bilirubin(DBIL), total bilirubin(TBIL), and total bile acid(TBA) levels were detected, and liver histopathological changes were observed. The relative expression changes of FXR, SHP, CYP7 A1, MRP2, MRP3, NTCP, BSEP mRNA in liver tissues were detected by Real-time fluorescence quantitative method, and the expression changes of FXR, SHP, UGT2 B4 protein in liver tissues were detected by Western blot. The results showed that the Tibetan medicine Ershiwuwei Songshi Pills significantly reduced the levels of ALT, ALP, DBIL, TBIL and TBA in the serum of the ANIT mo-del rats(P<0.01, P<0.05), significantly up-regulated the mRNA expressions of SHP and NTCP(P<0.01, P<0.05), significantly down-regulated the mRNA expression of CYP7 A1 and MRP3(P<0.01, P<0.05); and significantly up-regulated the protein expressions of FXR and SHP(P<0.01, P<0.05). The Tibetan medicine Ershiwuwei Songshi Pills have an obvious protective effect on ANIT-induced cholestatic liver injury in rats, and its mechanism may be related to the bile acid metabolism mediated by the FXR signaling pathway.

Role of farnesol X receptor in glycolipid metabolism regulation / 上海交通大学学报（医学版）

Farnesol X receptor (FXR), also known as bile acid nuclear receptor, is a ligand-dependent nuclear transcription factor distributed in multiple tissues and organs such as liver and intestinal tract. And bile acid is its endogenous natural ligand. Recent studies have shown that intestinal FXR plays an indispensable role in glycolipid metabolism regulation, and intestinal specific FXR agonists or antagonists can participate in glucose and lipid metabolism regulation in vivo. In this paper, the role of intestinal FXR in glycolipid metabolism reported in recent years is systematically reviewed.