Molecular mechanisms of hepatoprotective effect of tectorigenin against ANIT-induced cholestatic liver injury: Role of FXR and Nrf2 pathways

Novel insights into bexarotene's role in preventing cholestasis: mechanisms and implications

Cholestasis is defined as an impairment in the flow of bile, resulting in the accumulation of its components. Despite ursodeoxycholic acid (UDCA) being the only FDA-approved drug for cholestasis, it has little value in treating or preventing cholestasis; hence, new medications are required to treat these illnesses. The farnesoid X receptor (FXR) maintains bile acid (BA) homeostasis. It exists as heterodimers with retinoid X receptor (RXR) and responds to ligands that bind to any one of the partners and are activated synergistically in the presence of both. The hepatoprotective effect of bexarotene (Bex) against cholestasis liver injury induced by α-naphthyl isothiocyanate (ANIT) was evaluated in male Wistar albino rats. Our study demonstrates that compared to the ANIT group, Bex improves liver function tests, liver histology, and considerably reduces inflammatory mediators. Additionally, antioxidant levels increased significantly. Besides that, Bex upregulates the gene expression of FXR, bile salt export pump, hepatocyte nuclear factor 1α, and small heterodimer partner. Moreover, it enhances antioxidative nuclear factor erythroid 2-related factor gene expression and the expression of the NAD(P)H quinone oxidoreductase 1, and heme-oxygenase 1 protein targets in the rats' livers, reinforcing its hepatoprotective potential. Furthermore, Bex increases protein expressions of FXR, The bile salt export pump, and sirtuin 1 levels in the rats' livers. This study demonstrates that Bex protects against ANIT-induced cholestasis. This protective strategy involves controlling BA metabolism, inhibiting inflammatory mediators, and reducing oxidative stress.

Glycyrrhiza uralensis Fisch. Attenuates Dioscorea bulbifera L.-induced liver injury by regulating the FXR/Nrf2-BAs-related proteins and intestinal microbiota

ETHNOPHARMACOLOGICAL RELEVANCE

Dioscorea bulbifera L. (DBL) was a traditional Chinese medicine commonly used to treat goitre and cancer. Nevertheless, its clinical application may lead to liver injury. Glycyrrhiza uralensis Fisch. (GRR) was primarily utilized in traditional Chinese medicine for its ability to harmonize various medicines and mitigate the toxic effects of poisonous herbs. However, the role of GRR in mitigating the liver toxicity of DBL has not been established after combination.

AIM OF THE STUDY

This study aimed to clarify the protective effect of GRR against DBL-induced liver injury in mice and investigate its mechanisms of action.

MATERIALS AND METHODS

75% ethanol was employed to extract DBL and GRR. The extracted components were characterized using LC-MS. Mice were orally gavaged with extracts from each group for 30 days. After the experiment, the pathological changes in the liver of mice were evaluated. Additionally, biochemical markers associated with liver injury were assessed. The primary mechanisms through which GRR mitigates DBL-induced liver injury and the modulation of the liver-intestinal axis by GRR were explored utilizing untargeted metabolomics, targeted BAs metabolomics and 16S rDNA analyses. Furthermore, Western blot and qPCR assessed the protein and mRNA transcription of the farnesoid X receptor (FXR) and nuclear factor-erythroid 2-related factor 2 (Nrf2) as well as BA-related transporters.

RESULTS

GRR dose-dependently attenuated DBL-induced liver injury in mice. It mitigated hepatic pathological changes and alleviated hepatic inflammation and oxidative stress. GRR improved metabolic disorders induced by DBL in mice at the metabolite level, focusing on the ABC transporter. Moreover, GRR may be attributed to its activation of FXR/Nrf2 expression, reduction of cholesterol 7-alpha hydroxylase (CYP7A1) expression, promotion of bile salt export pump (BSEP), multi-drug resistance protein 2 (MRP2), P-glycoprotein (P-gp) and sodium taurocholate cotransport polypeptide (NTCP) expression, reduction of bile acid (BA) synthesis, promotion of BA efflux and reabsorption, and improvement of BA metabolic disorders. In addition, GRR ameliorated DBL-induced intestinal barrier injury and improved the structural organization of the intestinal flora, restoring the overall composition of the intestinal microbiota.

CONCLUSION

GRR exhibited significant alleviation of DBL-induced liver injury, potentially by modulating FXR/Nrf2-BA-related proteins, reducing hepatic BA accumulation, mitigating liver inflammation and oxidative stress, and regulating intestinal flora.

Exploration of the Combined Mechanism of Direct and Indirect Effects of Paeoniflorin in the Treatment of Cholestasis

Cholestasis is a multifactorial hepatobiliary disorder, characterized by obstruction of bile flow and accumulation of bile, which in turn causes damage to liver cells and other tissues. In severe cases, it can result in the development of life-threatening conditions, including cirrhosis and liver cancer. Paeoniflorin (PF) has been demonstrated to possess favourable therapeutic potential for the treatment of cholestasis. The objective of this research was to examine the molecular mechanism of PF in the treatment of ANIT-induced cholestasis and to propose novel avenues for further research on the pharmacological effects of PF. In vivo and in vitro models of cholestasis were developed. The histopathological changes in the bile ducts and liver were evaluated through the use of hematoxylin and eosin (HE) staining. The extent of apoptosis was evaluated through the use of immunofluorescence (IF), immunoblotting (WB), and electron microscopy. The JNK signalling pathway was identified as the direct mechanism of action of PF through the utilisation of HuProt™ 20 K chips and other technologies. The present study demonstrated that PF markedly alleviated liver injury in an ANIT-induced cholestasis model. Specifically, PF was observed to attenuate cholestasis-induced liver injury by reducing the abnormal elevation of liver function indices and suppressing the expression of inflammatory mediators. Furthermore, PF exhibited anti-apoptotic properties in both in vivo and in vitro experiments, thereby mitigating cholestasis-induced hepatocyte apoptosis. These protective effects are attributable to the fact that PF exerts its action through direct interaction with the JNK pathway. It has been demonstrated that PF is capable of binding directly to MAPK8 (JNK1) and MAPK9 (JNK2), thereby inhibiting JNK activation and reducing apoptosis. With regard to the protection of bile ducts, PF may indirectly inhibit hepatocyte apoptosis by maintaining the structural integrity and tight junctions of bile duct cells. PF improved cholestasis by inhibiting hepatocyte apoptosis directly by targeting the JNK signaling pathway and indirectly inhibited hepatocyte apoptosis by improving the tight junctions of bile duct cells to regulate the bile duct microenvironment.

Ameliorative Effect of Glycyrrhizic Acid on Diosbulbin B-Induced Liver Injury and Its Mechanism

This study aimed to clarify the protective effect of Glycyrrhizic acid (GL) against Diosbulbin B (DB) - induced liver injury in mice and investigate its mechanisms of action. A liver injury DB was established in mice through the oral administration of DB for 15 days. At the same time, GL was administered to the mice for treatment. After the experiment, the pharmacodynamics and mechanisms of GL in ameliorating DB-induced liver injury were explored using biochemical indexes, non-targeted metabolomics, targeted metabolomics, Western blotting analysis of protein expression, 16S rDNA sequencing, and Spearman correlation analysis. The results show reduced liver function indices and improved DB-induced hepatic pathological changes. It also attenuated DB-induced hepatic inflammation and oxidative stress. Hepatic metabolomics revealed that GL regulated ABC transporters and bile secretion. Targeted bile acid (BA) metabolomics and Western blotting demonstrated that GL improved DB-induced reduction in BA efflux by regulating FXR-mediated efflux transporters. Furthermore, analysis of 16S rDNA gene sequencing revealed that GL effectively restored the relative abundance of beneficial bacteria, reduced the relative abundance of harmful bacteria, and reinstated the structure of the intestinal flora. Additionally, correlation analyses between BA and intestinal flora indicated that Firmicutes, Bacteroidota, TDGA, DGA, UDGA, GDGA, THDGA, and HDGA could serve as major markers for DB-induced liver injury. In conclusion, GL significantly improved DB-induced liver injury by increasing the expression of Nrf2/FXR-BSEP/MRP2/P-gp/UGT1A1, promoting BA efflux, regulating intestinal flora, and alleviating inflammation and oxidative stress.

Tectorigenin Reduces Dabie bandavirus-Induced Cytokine Storm by Regulating Toll-Like Receptor 7/Extracellular Signal-Regulated Kinase Pathway

Severe fever with thrombocytopenia syndrome (SFTS) is a severe emerging infectious disease caused by Dabie bandavirus (DBV). Tectorigenin has been demonstrated to exert anti-inflammatory effect. Here, we aimed to investigate the effects of tectorigenin on DBV-induced cytokine storm. Effects of tectorigenin on cytokines in DBV-infected THP-1 cells and plasma samples of Type I interferon receptor (IFNAR)-/- mice infected with DBV were detected. The changes in body weight and survival time of mice were recorded. The liver, spleen, kidney, and lymph node tissues were collected for hematoxylin-eosin staining. We demonstrated that tectorigenin reduced the expression levels of inflammatory cytokines in both DBV-infected THP-1 cells and plasma samples of IFNAR-/- mice infected with DBV. Tectorigenin attenuated DBV-induced histopathological changes in mice. Mechanistically, tectorigenin attenuated DBV-induced phosphorylation of inhibitor of kappa-B kinase alpha/beta (IKKα/β) of the nuclear factor-κB (NF-κB) signaling pathway, extracellular signal-regulated kinase (ERK) of the mitogen-activated protein kinase (MAPK) signaling pathway and might function by downregulation of Toll-like receptor. The result of this study suggested that tectorigenin exerted anti-inflammatory effects in vivo and in vitro and could serve as a novel potential therapeutic strategy for SFTS.

Dual-function natural products: Farnesoid X receptor agonist/inflammation inhibitor for metabolic dysfunction-associated steatotic liver disease therapy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent chronic liver disease globally, with only one Food and Drug Administration (FDA)-approved drug for its treatment. Given MASLD's complex pathophysiology, therapies that simultaneously target multiple pathways are highly desirable. One promising approach is dual-modulation of the farnesoid X receptor (FXR), which regulates lipid and bile acid metabolism. However, FXR agonists alone are insufficient due to their limited anti-inflammatory effects. This study aimed to dto identify natural products capable of both FXR activation and inflammation inhibition to provide a comprehensive therapeutic approach for MASLD. Potential FXR ligands from the Natural Product Library were predicted via virtual screening using the Protein Preparation Wizard module in Schrodinger (2018) for molecular docking. Direct binding and regulation of candidate compounds on FXR were analyzed using surface plasmon resonance (SPR) binding assay, reporter gene analysis, and reverse transcription-polymerase chain reaction (RT-PCR). The anti-inflammatory properties of these compounds were evaluated in AML12 cells treated with tumor necrosis factor-alpha (TNF-α). Dual-function compounds with FXR agonism and inflammation inhibition were further identified in cells transfected with Fxr siRNA and treated with TNF-α. The effects of these dual-function compounds on lipid accumulation and inflammation were evaluated in cells treated with palmitic acid. Results revealed that 17 natural products were predicted via computational molecular docking as potential FXR agonists, with 15 exhibiting a strong affinity for FXR recombinant protein. Nine isoflavone compounds significantly enhanced FXR reporter luciferase activity and the mRNA expressions of Shp and Ostb. Structure-activity relationship analysis indicated that introducing isopropyl or methoxy groups at the C7 position or a methoxy group at the C6 position could enhance the agonistic efficacy of isoflavones. Three compounds (2, 6, and 8) were identified as dual-function natural products functioning as FXR agonists and inflammatory inhibitors, while one compound (12) acted as an FXR agonist to inhibit inflammation. These natural products protected hepatocytes against palmitic acid-induced lipid accumulation and inflammation. In conclusion, compounds 2, 6, and 8 (genistein, biochanin A, and 7-methoxyisoflavone, respectively) were identified as dual-function bioactive products that transactivate FXR and inhibit inflammation, serving as potential candidates or lead compounds for MASLD therapy.

Multiomics Analysis Reveals Leucine Deprivation Promotes Bile Acid Synthesis by Upregulating Hepatic CYP7A1 and Intestinal Turicibacter sanguinis in Mice

BACKGROUND

Leucine, a branched-chain amino acid, participates in the regulation of lipid metabolism and the composition of the intestinal microbiota. However, the related mechanism remains unclear.

OBJECTIVES

Here, we aimed to reveal the potential mechanisms by which hepatic CYP7A1 (a rate-limiting enzyme for bile acid [BA] synthesis) and gut microbiota coregulate BA synthesis under leucine deprivation.

METHODS

To this end, 8-wk-old C57BL/6J mice were fed with either regular diets or leucine-free diets for 1 wk. Then, we investigated whether secondary BAs were synthesized by Turicibacter sanguinis in 7-wk-old C57BL/6J germ-free mice gavaged with T. sanguinis for 2 wk by determining BA concentrations in the plasma, liver, and cecum contents using liquid chromatography-tandem mass spectrometry.

RESULTS

The results showed that leucine deprivation resulted in a significant increase in total BA concentration in the plasma and an increase in the liver, but no difference in total BA was observed in the cecum contents before and after leucine deprivation. Furthermore, leucine deprivation significantly altered BA profiles such as taurocholic acid and ω-muricholic acid in the plasma, liver, and cecum contents. CYP7A1 expression was significantly upregulated in the liver under leucine deprivation. Leucine deprivation also regulated the composition of the gut microbiota; specifically, it significantly upregulated the relative abundance of T. sanguinis, thus enhancing the conversion of primary BAs into secondary BAs by intestinal T. sanguinis in mice.

CONCLUSIONS

Overall, leucine deprivation regulated BA profiles in enterohepatic circulation by upregulating hepatic CYP7A1 expression and increasing intestinal T. sanguinis abundance. Our findings reveal the contribution of gut microbiota to BA metabolism under dietary leucine deprivation.

Mechanistic studies on the alleviation of ANIT-induced cholestatic liver injury by Polygala fallax Hemsl. polysaccharides

ETHNOPHARMACOLOGICAL RELEVANCE

Polygala fallax Hemsl. is a traditional folk medicine commonly used by ethnic minorities in the Guangxi Zhuang Autonomous Region, and has a traditional application in the treatment of liver disease. Polygala fallax Hemsl. polysaccharides (PFPs) are of interest for their potential health benefits.

AIM OF THIS STUDY

This study explored the impact of PFPs on a mouse model of cholestatic liver injury (CLI) induced by alpha-naphthyl isothiocyanate (ANIT), as well as the potential mechanisms.

MATERIALS AND METHODS

A mouse CLI model was constructed using ANIT (80 mg/kg) and intervened with different doses of PFPs or ursodeoxycholic acid. Their serum biochemical indices, hepatic oxidative stress indices, and hepatic pathological characteristics were investigated. Then RNA sequencing was performed on liver tissues to identify differentially expressed genes and signaling pathways and to elucidate the mechanism of liver protection by PFPs. Finally, Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were used to verify the differentially expressed genes.

RESULTS

Data analyses showed that PFPs reduced the levels of liver function-related biochemical indices, such as ALT, AST, AKP, TBA, DBIL, and TBIL. PFPs up-regulated the activities of SOD and GSH, down-regulated the contents of MDA, inhibited the release of IL-1β, IL-6, and TNF-α, or promoted IL-10. Pathologic characterization of the liver revealed that PFPs reduced hepatocyte apoptosis or necrosis. The RNA sequencing indicated that the genes with differential expression were primarily enriched for the biosynthesis of primary bile acids, secretion or transportation of bile, the reactive oxygen species in chemical carcinogenesis, and the NF-kappa B signaling pathway. In addition, the results of qRT-PCR and Western blotting analysis were consistent with those of RNA sequencing analysis.

CONCLUSIONS

In summary, this study showed that PFPs improved intrahepatic cholestasis and alleviated liver damage through the modulation of primary bile acid production, Control of protein expression related to bile secretion or transportation, decrease in inflammatory reactions, and inhibition of oxidative pressure. As a result, PFPs might offer a hopeful ethnic dietary approach for managing intrahepatic cholestasis.

Artemisia capillaris Thunb. Polysaccharide alleviates cholestatic liver injury through gut microbiota modulation and Nrf2 signaling pathway activation in mice

ETHNOPHARMACOLOGICAL RELEVANCE

According to traditional Chinese medicine (TCM) theory, cholestasis belongs to category of jaundice. Artemisia capillaris Thunb. has been widely used for the treatment of jaundice in TCM. The polysaccharides are the one of main active components of the herb, but its effects on cholestasis remain unclear.

AIM OF THE STUDY

To investigate the protective effect and mechanism of Artemisia capillaris Thunb. polysaccharide (APS) on cholestasis and liver injury.

MATERIALS AND METHODS

The amelioration of APS on cholestasis was evaluated in an alpha-naphthyl isothiocyanate (ANIT)-induced mice model. Then nuclear Nrf2 knockout mice, mass spectrometry, 16s rDNA sequencing, metabolomics, and molecular biotechnology methods were used to elucidate the associated mechanisms of APS against cholestatic liver injury.

RESULTS

Treatment with low and high doses of APS markedly decreased cholestatic liver injury of mice. Mechanistically, APS promoted nuclear translocation of hepatic nuclear factor erythroid 2-related factor (Nrf2), upregulated downstream bile acid (BA) efflux transporters and detoxifying enzymes expression, improved BA homeostasis, and attenuated oxidative liver injury; however, these effects were annulled in Nrf2 knock-out mice. Furthermore, APS ameliorated the microbiota dysbiosis of cholestatic mice and selectively increased short-chain fatty acid (SCFA)-producing bacteria growth. Fecal microbiota transplantation of APS also promoted hepatic Nrf2 activation, increased BA efflux transporters and detoxifying enzymes expression, ameliorated intrahepatic BA accumulation and cholestatic liver injury. Non-targeted metabolomics and in vitro microbiota culture confirmed that APS significantly increased the production of a microbiota-derived SCFA (butyric acid), which is also able to upregulate Nrf2 expression.

CONCLUSIONS

These findings indicate that APS can ameliorate cholestasis by modulating gut microbiota and activating the Nrf2 pathway, representing a novel therapeutic approach for cholestatic liver disease.

Tectorigenin inhibits oxidative stress by activating the Keap1/Nrf2/HO-1 signaling pathway in Th2-mediated allergic asthmatic mice

Asthma is a chronic obstructive airway condition and one of the most common non-communicable illnesses worldwide. Tectorigenin (Tec) is an isoflavonoid found in plants that possesses significant antioxidative and anti-inflammatory abilities. Nevertheless, the antioxidative properties of Tec have not yet been documented in allergic asthma. In this study, we created an asthmatic BALB/c mouse model induced by ovalbumin (OVA) and used it to assess the efficacy of Tec as a possible therapy agent. Tec decreased the serum OVA-specific immunoglobulin (Ig) E and IgG1 secretion levels. The total number of cells and the distribution of inflammatory cells decreased significantly in bronchoalveolar lavage fluid (BALF), with weakened inflammatory reaction in pulmonary tissues. Additionally, Tec regulated the T helper 1(Th1)/Th2 balance by increasing the expression of Th1- related factors (interleukin (IL)-12 and T-bet) and decreasing the expression of Th2-related factors (IL-4, IL-5, IL-13, and GATA binding protein 3. In addition, the pro-inflammatory cytokines such as IL-6, tumor necrosis factor-alpha, and IL-1β were also inhibited by Tec. Tec also dramatically increased antioxidant (catalase and superoxide dismutase) concentrations while lowering the intensity of the indicators of oxidative stress such as reactive oxygen species and malondialdehyde in BALF. Finally, Tec effectively activated the Keap1/Nrf2/HO-1 signaling pathway and prevented the epithelial-mesenchymal transition. The results of the current study show that Tec may be useful in relieving the inflammatory and oxidative stress responses associated with asthma.

Obeticholic acid protects against lithocholic acid-induced exogenous cell apoptosis during cholestatic liver injury

AIMS

Lithocholic acid (LCA)-induced cholestasis was accompanied by the occurrence of apoptosis, which indicated that anti-apoptosis was a therapeutic strategy for primary biliary cholangitis (PBC). As an agonist of (Farnesoid X receptor) FXR, we supposed that the hepatoprotection of Obeticholic acid (OCA) against cholestatic liver injury is related to anti-apoptosis beside of the bile acids (BAs) regulation. Herein, we explored the non-metabolic regulating mechanism of OCA for resisting LCA-induced cholestatic liver injury via anti-apoptosis.

MAIN METHODS

LCA-induced cholestatic liver injury mice were pretreated with OCA to evaluate its hepatoprotective effect and mechanism. Biochemical and pathological indicators were used to detect the protective effect of OCA on LCA-induced cholestatic liver injury. The bile acids (BAs) profile in serum was detected by LC-MS/MS. Hepatocyte BAs metabolism, apoptosis and inflammation related genes and proteins alteration were investigated by biochemical determination.

KEY FINDINGS

OCA improved LCA-induced cholestasis and hepatic apoptosis in mice. The BA profile in serum was changed by OCA mainly manifested as a reduction of taurine-conjugated bile acids, which was due to the upregulation of FXR-related bile acid efflux transporters bile salt export pump (BSEP), multi-drug resistant associated protein 2 (MRP2), MRP3 and multi-drug resistance 3 (MDR3). Apoptosis related proteins cleaved caspase-3, cleaved caspase-8 and cleaved PARP were obviously reduced after OCA treatment.

SIGNIFICANCE

OCA improved LCA-induced cholestatic liver injury via FXR-induced exogenous cell apoptosis, which will provide new evidence for the application of OCA to ameliorate PBC in clinical.

Naringenin prevents non-alcoholic steatohepatitis by modulating the host metabolome and intestinal microbiome in MCD diet-fed mice

Non-alcoholic steatohepatitis (NASH) is a severe inflammatory phase of the non-alcoholic fatty liver disease (NAFLD) spectrum and can progress to advanced stages of NAFLD if left untreated. This study uses multi-omics data to elucidate the underlying mechanism of naringenin's reported benefit in alleviating (NASH). Male mice were fed a NASH-inducing (methionine-choline-deficient) MCD diet with or without naringenin supplementation for 6 weeks. Naringenin prevented NASH-induced histopathological liver damage and reversed the abnormal levels of hepatic triglyceride (TG)/total cholesterol (TC), serum TG/TC, serum alanine aminotransferase/aspartate transaminase, and hepatic malondialdehyde and glutathione. Importantly, naringenin intervention significantly modulated the relative abundance of gut microbiota and the host metabolomic profile. We detected more than 700 metabolites in the serum and found that the gut genus levels of Anaeroplasma and the [Eubacterium] nodatum group were closely associated with xanthine, 2-picoline, and securinine, respectively. Tuzzerella alterations showed the highest number of associations with host endogenous metabolites such as FAHFA (8:0/10:0), FFA (20:2), carnitine C8:1, tridecanedioic acid, securinine, acetylvaline, DL-O-tyrosine, and Phe-Asn. This study indicates that the interplay between host serum metabolites and gut microbiota may contribute to the therapeutic effect of naringenin against NASH.