The pathophysiology of human obstructive cholestasis is mimicked in cholestatic Gold Syrian hamsters

Yinchenhao decoction alleviates obstructive jaundice liver injury by modulating epidermal growth factor receptor and constitutive androstane receptor signaling

BACKGROUND

Yinchenhao decoction (YCHD) is a traditional Chinese medicine widely used to treat liver damage caused by obstructive jaundice (OJ). Although YCHD has demonstrated protective effects against liver damage, reduced apoptosis, and mitigated oxidative stress in OJ, the precise molecular mechanisms involved remain poorly understood.

AIM

To investigate the beneficial effects of YCHD on OJ and elucidate the underlying mechanisms.

METHODS

The active constituents of YCHD were identified using liquid chromatography-tandem mass spectrometry, and their potential targets for OJ treatment were predicted through network pharmacology. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed. An OJ rat model was established by common bile duct ligation. Rats were divided into three groups: Sham surgery (S Group), model (O Group), and YCHD (Y Group). YCHD was administered to Group Y for one week. Bilirubin levels, liver function parameters, and bile acid concentrations in blood and urine were measured by enzyme-linked immunosorbent assay. The bile acid renal clearance rate (Clr) was calculated. Histopathological evaluation of liver and kidney tissues was performed using hematoxylin-eosin staining. Western blotting was utilized to assess the expression of key bile acid metabolism and transport proteins in both liver and kidney tissues. The expression of the constitutive androstane receptor (CAR) and its nuclear localization were evaluated by immunohistochemistry. Molecular docking studies identified the epidermal growth factor receptor (EGFR) as a potential target of YCHD's active components. An OJ cell model was created using human liver (L02) and renal tubular epithelial (HK-2) cells, which were treated with YCHD-containing serum. Western blotting and immunofluorescence assays were employed to evaluate CAR expression and its nuclear localization in relation to EGFR activation.

RESULTS

Network analysis identified the EGFR signaling pathway as a key mechanism through which YCHD exerts its effects on OJ. In vivo experiments showed that YCHD improved liver function, reduced OJ-induced pathology in liver and kidney tissues, and decreased serum bile acid content by enhancing bile acid Clr and urine output. YCHD also increased CAR expression and nuclear heterotopy, upregulating proteins involved in bile acid metabolism and transport, including CYP3A4, UGT1A1, MRP3, and MRP4 in the liver, and MRP2 and MRP4 in the kidneys. In vitro, YCHD increased CAR expression and nuclear heterotopy in L02 and HK-2 cells, an effect that was reversed by EGFR agonists.

CONCLUSION

YCHD enhances bile acid metabolism in the liver and promotes bile acid excretion in the kidneys, ameliorating liver damage caused by OJ. These effects are likely mediated by the upregulation of CAR and its nuclear translocation.

Comparing animal well-being between bile duct ligation models

A prevailing animal model currently used to study severe human diseases like obstructive cholestasis, primary biliary or sclerosing cholangitis, biliary atresia, and acute liver injury is the common bile duct ligation (cBDL). Modifications of this model include ligation of the left hepatic bile duct (pBDL) or ligation of the left bile duct with the corresponding left hepatic artery (pBDL+pAL). Both modifications induce cholestasis only in the left liver lobe. After induction of total or partial cholestasis in mice, the well-being of these animals was evaluated by assessing burrowing behavior, body weight, and a distress score. To compare the pathological features of these animal models, plasma levels of liver enzymes, bile acids, bilirubin, and within the liver tissue, necrosis, fibrosis, inflammation, as well as expression of genes involved in the synthesis or transport of bile acids were assessed. The survival rate of the animals and their well-being was comparable between pBDL+pAL and pBDL. However, surgical intervention by pBDL+pAL caused confluent necrosis and collagen depositions at the edge of necrotic tissue, whereas pBDL caused focal necrosis and fibrosis in between portal areas. Interestingly, pBDL animals had a higher survival rate and their well-being was significantly improved compared to cBDL animals. On day 14 after cBDL liver aspartate, as well as alanine aminotransferase, alkaline phosphatase, glutamate dehydrogenase, bile acids, and bilirubin were significantly elevated, but only glutamate dehydrogenase activity was increased after pBDL. Thus, pBDL may be primarily used to evaluate local features such as inflammation and fibrosis or regulation of genes involved in bile acid synthesis or transport but does not allow to study all systemic features of cholestasis. The pBDL model also has the advantage that fewer mice are needed, because of its high survival rate, and that the well-being of the animals is improved compared to the cBDL animal model.

Molecular Pathways Governing the Termination of Liver Regeneration

The liver has the unique capacity to regenerate, and up to 70% of the liver can be removed without detrimental consequences to the organism. Liver regeneration is a complex process involving multiple signaling networks and organs. Liver regeneration proceeds through three phases: the initiation phase, the growth phase, and the termination phase. Termination of liver regeneration occurs when the liver reaches a liver-to-body weight that is required for homeostasis, the so-called "hepatostat." The initiation and growth phases have been the subject of many studies. The molecular pathways that govern the termination phase, however, remain to be fully elucidated. This review summarizes the pathways and molecules that signal the cessation of liver regrowth after partial hepatectomy and answers the question, "What factors drive the hepatostat?" SIGNIFICANCE STATEMENT: Unraveling the pathways underlying the cessation of liver regeneration enables the identification of druggable targets that will allow us to gain pharmacological control over liver regeneration. For these purposes, it would be useful to understand why the regenerative capacity of the liver is hampered under certain pathological circumstances so as to artificially modulate the regenerative processes (e.g., by blocking the cessation pathways) to improve clinical outcomes and safeguard the patient's life.

Recent progress on the application of compound formulas of traditional Chinese medicine in clinical trials and basic research in vivo for chronic liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic liver diseases mainly include chronic viral liver disease, metabolic liver disease, cholestatic liver disease (CLD), autoimmune liver disease, and liver fibrosis or cirrhosis. Notably, the compound formulas of traditional Chinese medicine (TCM) is effective for chronic liver diseases in clinical trials and basic research in vivo, which provide evidence of chronic liver disease treatment with integrated TCM and traditional Western medicine.

AIM OF THE REVIEW

This paper aims to provide a comprehensive review of the compound formulas of TCM for treating different chronic liver diseases to elucidate the composition, main curative effects, and mechanisms of these formulas and research methods.

MATERIALS AND METHODS

Different keywords related to chronic liver diseases and keywords related to the compound formulas of TCM were used to search the literature. PubMed, Scopus, Web of Science, and CNKI were searched to screen out original articles about the compound formulas of TCM related to the treatment of chronic liver diseases, mainly including clinical trials and basic in vivo research related to Chinese patent drugs, classic prescriptions, proven prescriptions, and hospital preparations. We excluded review articles, meta-analysis articles, in vitro experiments, articles about TCM monomers, articles about single-medicine extracts, and articles with incomplete or uncertain description of prescription composition. Plant names were checked with MPNS (http://mpns.kew.org).

RESULTS

In this review, the clinical efficacy and mechanism of compound formulas of TCM were summarized for the treatment of chronic viral hepatitis, nonalcoholic fatty liver disease, CLD, and liver fibrosis or cirrhosis developed from these diseases and other chronic liver diseases. For each clinical trial and basic research in vivo, this review provides a detailed record of the specific composition of the compound formulas of TCM, type of clinical research, modeling method of animal experiments, grouping methods, medication administration, main efficacy, and mechanisms.

CONCLUSION

The general development process of chronic liver disease can be summarized as chronic hepatitis, liver fibrosis or cirrhosis, and hepatocellular carcinoma. The compound formulas of TCM have some applications in these stages of chronic liver diseases. Owing to the continuous progress of medical technology, the benefits of the compound formulas of TCM in the treatment of chronic liver diseases are constantly changing and developing.

Exploring the Potential Mechanisms of Action of Gentiana Veitchiorum Hemsl. Extract in the Treatment of Cholestasis using UPLC-MS/MS, Systematic Network Pharmacology, and Molecular Docking

INTRODUCTION

Gentiana veitchiorum Hemsl. (GV) has a long history in Tibetan medicine for treating hepatobiliary disease cholestasis. However, the mechanisms mediating its efficacy in treating cholestasis have yet to be determined.

AIM

To elucidate the mechanisms of action of GV in the treatment of cholestasis, an integrated approach combining ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis with network pharmacology was established.

MATERIALS AND METHODS

A comprehensive analysis of the chemical composition of GV was achieved by UPLC-MS/MS. Subsequently, a network pharmacology method that integrated target prediction, a protein-protein interaction (PPI) network, gene set enrichment analysis, and a component- target-pathway network was established, and finally, molecular docking and experiments in vitro were conducted to verify the predicted results.

RESULTS

Twenty compounds that were extracted from GV were identified by UPLC-MS/MS analysis. Core proteins such as AKT1, TNF, and IL6 were obtained through screening in the Network pharmacology PPI network. The Kyoto Encyclopedia of the Genome (KEGG) pathway predicted that GV could treat cholestasis by acting on signaling pathways such as TNF/IL-17 / PI3K-Akt. Network pharmacology suggested that GV might exert a therapeutic effect on cholestasis by regulating the expression levels of inflammatory mediators, and the results were further confirmed by the subsequent construction of an LPS-induced RAW 264.7 cell model.

CONCLUSIONS

In this study, UPLC-MS/MS analysis, network pharmacology, and experiment validation were used to explore potential mechanisms of action of GV in the treatment of cholestasis.

A physiologically based model of bile acid metabolism in mice

Bile acid (BA) metabolism is a complex system that includes a wide variety of primary and secondary, as well as conjugated and unconjugated BAs that undergo continuous enterohepatic circulation (EHC). Alterations in both composition and dynamics of BAs have been associated with various diseases. However, a mechanistic understanding of the relationship between altered BA metabolism and related diseases is lacking. Computational modeling may support functional analyses of the physiological processes involved in the EHC of BAs along the gut-liver axis. In this study, we developed a physiologically based model of murine BA metabolism describing synthesis, hepatic and microbial transformations, systemic distribution, excretion, and EHC of BAs at the whole-body level. For model development, BA metabolism of specific pathogen-free (SPF) mice was characterized in vivo by measuring BA levels and composition in various organs, expression of transporters along the gut, and cecal microbiota composition. We found significantly different BA levels between male and female mice that could only be explained by adjusted expression of the hepatic enzymes and transporters in the model. Of note, this finding was in agreement with experimental observations. The model for SPF mice could also describe equivalent experimental data in germ-free mice by specifically switching off microbial activity in the intestine. The here presented model can therefore facilitate and guide functional analyses of BA metabolism in mice, e.g., the effect of pathophysiological alterations on BA metabolism and translation of results from mouse studies to a clinically relevant context through cross-species extrapolation.

Targeted bile acid profiles reveal the liver injury amelioration of Da-Chai-Hu decoction against ANIT- and BDL-induced cholestasis

Multiple types of liver diseases, particularly cholestatic liver diseases (CSLDs) and biliary diseases, can disturb bile acid (BA) secretion; however, BA accumulation is currently seen as an important incentive of various types of liver diseases’ progression. Da-Chai-Hu decoction (DCHD) has long been used for treating cholestatic liver diseases; however, the exact mechanisms remain unclear. Currently, our study indicates that the liver damage and cholestasis status of the α-naphthylisothiocyanate (ANIT)-induced intrahepatic cholestasis and bile duct ligation (BDL)-induced extrahepatic cholestasis, following DCHD treatment, were improved; the changes of BA metabolism post-DCHD treatment were investigated by targeted metabolomics profiling by UPLC-MS/MS. DCHD treatment severely downregulated serum biochemical levels and relieved inflammation and the corresponding pathological changes including necrosis, inflammatory infiltration, ductular proliferation, and periductal fibrosis in liver tissue. The experimental results suggested that DCHD treatment altered the size, composition, and distribution of the BAs pool, led the BAs pool of the serum and liver to sharply shrink, especially TCA and TMCA, and enhanced BA secretion into the gallbladder and the excretion of BAs by the urinary and fecal pathway; the levels of BAs synthesized by the alternative pathway were increased in the liver, and the conjugation of BAs and the pathway of BA synthesis were actually affected. In conclusion, DCHD ameliorated ANIT- and BDL-induced cholestatic liver injury by reversing the disorder of BAs profile.

Molecular Regulation of Bile Acid Homeostasis

Bile acids have been known for decades to aid in the digestion and absorption of dietary fats and fat-soluble vitamins in the intestine. The development of gene knockout mice models and transgenic humanized mouse models have helped us understand other functions of bile acids, such as their role in modulating fat, glucose, and energy metabolism, and in the molecular regulation of the synthesis, transport, and homeostasis of bile acids. The G-protein coupled receptor TGR5 regulates the bile acid induced alterations of intermediary metabolism, whereas the nuclear receptor FXR regulates bile acid synthesis and homeostasis. However, this review indicates that unidentified factors in addition to FXR must exist to aid in the regulation of bile acid synthesis and homeostasis. SIGNIFICANCE STATEMENT: This review captures the present understanding of bile acid synthesis, the role of bile acid transporters in the enterohepatic circulation of bile acids, the role of the nuclear receptor FXR on the regulation of bile acid synthesis and bile acid transporters, and the importance of bile acids in activating GPCR signaling via TGR5 to modify intermediary metabolism. This information is useful for developing drugs for the treatment of various hepatic and intestinal diseases, as well as the metabolic syndrome.

Unaltered Liver Regeneration in Post-Cholestatic Rats Treated with the FXR Agonist Obeticholic Acid

In a previous study, obeticholic acid (OCA) increased liver growth before partial hepatectomy (PHx) in rats through the bile acid receptor farnesoid X-receptor (FXR). In that model, OCA was administered during obstructive cholestasis. However, patients normally undergo PHx several days after biliary drainage. The effects of OCA on liver regeneration were therefore studied in post-cholestatic Wistar rats. Rats underwent sham surgery or reversible bile duct ligation (rBDL), which was relieved after 7 days. PHx was performed one day after restoration of bile flow. Rats received 10 mg/kg OCA per day or were fed vehicle from restoration of bile flow until sacrifice 5 days after PHx. Liver regeneration was comparable between cholestatic and non-cholestatic livers in PHx-subjected rats, which paralleled liver regeneration a human validation cohort. OCA treatment induced ileal Fgf15 mRNA expression but did not enhance post-PHx hepatocyte proliferation through FXR/SHP signaling. OCA treatment neither increased mitosis rates nor recovery of liver weight after PHx but accelerated liver regrowth in rats that had not been subjected to rBDL. OCA did not increase biliary injury. Conclusively, OCA does not induce liver regeneration in post-cholestatic rats and does not exacerbate biliary damage that results from cholestasis. This study challenges the previously reported beneficial effects of OCA in liver regeneration in cholestatic rats.

Hepatic bile formation: bile acid transport and water flow into the canalicular conduit

Advances in molecular biology identifying the many carrier-mediated organic anion transporters and advances in microscopy that have provided a more detailed anatomy of the canalicular conduit make updating the concept of osmotically determined canalicular flow possible. For the most part water flow is not transmembrane but via specific pore proteins in both the hepatocyte and the tight junction. These pores independently regulate the rate at which water flows in response to an osmotic gradient and therefore are determinants of canalicular bile acid concentration. Review of the literature indicates that the initial effect on hepatic bile flow of cholestatic agents such as Thorazine and estradiol 17β-glucuronide are on water flow and not bile salt export pump-mediated bile acid transport and thus provides new approaches to the pathogenesis of drug-induced liver injury. Attaining a micellar concentration of bile acids in the canaliculus is essential to the formation of cholesterol-lecithin vesicles, which mostly occur in the periportal region of the canalicular conduit. The other regions, midcentral and pericentral, may transport lesser amounts of bile acid but augment water flow. Broadening the concept of how hepatic bile flow is initiated, provides new insights into the pathogenesis of canalicular cholestasis.

Animal models to study bile acid metabolism

The use of animal models, particularly genetically modified mice, continues to play a critical role in studying the relationship between bile acid metabolism and human liver disease. Over the past 20 years, these studies have been instrumental in elucidating the major pathways responsible for bile acid biosynthesis and enterohepatic cycling, and the molecular mechanisms regulating those pathways. This work also revealed bile acid differences between species, particularly in the composition, physicochemical properties, and signaling potential of the bile acid pool. These species differences may limit the ability to translate findings regarding bile acid-related disease processes from mice to humans. In this review, we focus primarily on mouse models and also briefly discuss dietary or surgical models commonly used to study the basic mechanisms underlying bile acid metabolism. Important phenotypic species differences in bile acid metabolism between mice and humans are highlighted.