Long-term trans-inhibition of the hepatitis B and D virus receptor NTCP by taurolithocholic acid.

Human hepatic bile acid transporter Na+/taurocholate cotransporting polypeptide (NTCP) represents the liver-specific entry receptor for the hepatitis B and D viruses (HBV/HDV). Chronic hepatitis B and D affect several million people worldwide, but treatment options are limited. Recently, HBV/HDV entry inhibitors targeting NTCP have emerged as promising novel drug candidates. Nevertheless, the exact molecular mechanism that NTCP uses to mediate virus binding and entry into hepatocytes is still not completely understood. It is already known that human NTCP mRNA expression is downregulated under cholestasis. Furthermore, incubation of rat hepatocytes with the secondary bile acid taurolithocholic acid (TLC) triggers internalization of the rat Ntcp protein from the plasma membrane. In the present study, the long-term inhibitory effect of TLC on transport function, HBV/HDV receptor function, and membrane expression of human NTCP were analyzed in HepG2 and human embryonic kidney (HEK293) cells stably overexpressing NTCP. Even after short-pulse preincubation, TLC had a significant long-lasting inhibitory effect on the transport function of NTCP, but the NTCP protein was still present at the plasma membrane. Furthermore, binding of the HBV/HDV myr-preS1 peptide and susceptibility for in vitro HDV infection were significantly reduced by TLC preincubation. We hypothesize that TLC rapidly accumulates in hepatocytes and mediates long-lasting trans-inhibition of the transport and receptor function of NTCP via a particular TLC-binding site at an intracellularly accessible domain of NTCP. Physiologically, this trans-inhibition might protect hepatocytes from toxic overload of bile acids. Pharmacologically, it provides an interesting novel NTCP target site for potential long-acting HBV/HDV entry inhibitors.NEW & NOTEWORTHY The hepatic bile acid transporter NTCP is a high-affinity receptor for hepatitis B and D viruses. This study shows that TLC rapidly accumulates in NTCP-expressing hepatoma cells and mediates long-lasting trans-inhibition of NTCP's transporter and receptor function via an intracellularly accessible domain, without substantially affecting its membrane expression. This domain is a promising novel NTCP target site for pharmacological long-acting HBV/HDV entry inhibitors.

Salidroside alleviates taurolithocholic acid 3-sulfate-induced AR42J cell injury.

OBJECTIVES: To investigate the protective effects of Salidroside (Sal) on AP cell model induced by taurolithocholic acid 3-sulfate (TLC-S) as well as its underlying mechanism. METHODS: AR42J cells were divided into normal group (N group), AP cell model group (Mod group), Sal treated alone group (S+N group) and Sal treated AP cell model group (S+Mod group). The cell viability was examined by CCK-8 assay. Secretion of lipase and trypsin by AR42J cells, quantified using commercial assay kits, was used as the markers of TLC-S-induced pancreatitis. The levels of TNF-α, IL-1ß, IL-8, IL-6 and IL-10 in the cell supernatant were measured by ELISA. The effect of Sal on molecules in the NF-κB signaling pathway and autophagy was investigated by qRT-PCR and western blot. RESULTS: The decreased cell viability in Mod group was increased by Sal (P < 0.01). The upheaved activities of lipase and trypsin in AP cell model were declined by Sal (P < 0.01). The levels of TNF-α, IL-1ß, IL-8 and IL-6 in the cell supernatant, Beclin-1 and LC3-Ⅱ mRNA and protein, p-p65/p65 protein, which were increased in AP cell model, were decreased by Sal; and IL-10 in the cell supernatant, LAMP2 mRNA and protein, p-IκBα/IκBα protein which was declined in AP cell model, was increased by Sal (P < 0.05 or 0.01). There were no significant differences in all indexes between the N and S+N groups (P > 0.05). CONCLUSIONS: Sal alleviated AR42J cells injury induced by TLC-S, inhibited the inflammatory responses and modulated the autophagy, mainly through inhibiting the NF-κB signaling pathway.

NASH-related increases in plasma bile acid levels depend on insulin resistance.

BACKGROUND & AIMS: Plasma bile acids (BAs) have been extensively studied as pathophysiological actors in non-alcoholic steatohepatitis (NASH). However, results from clinical studies are often complicated by the association of NASH with type 2 diabetes (T2D), obesity, and insulin resistance (IR). Here, we sought to dissect the relationship between NASH, T2D, and plasma BA levels in a large patient cohort. METHODS: Four groups of patients from the Biological Atlas of Severe Obesity (ABOS) cohort (Clinical Trials number NCT01129297) were included based on the presence or absence of histologically evaluated NASH with or without coincident T2D. Patients were matched for BMI, homeostatic model assessment 2 (HOMA2)-assessed IR, glycated haemoglobin, age, and gender. To study the effect of IR and BMI on the association of plasma BA and NASH, patients from the HEPADIP study were included. In both cohorts, fasting plasma BA concentrations were measured. RESULTS: Plasma BA concentrations were higher in NASH compared with No-NASH patients both in T2D and NoT2D patients from the ABOS cohort. As we previously reported that plasma BA levels were unaltered in NASH patients of the HEPADIP cohort, we assessed the impact of BMI and IR on the association of NASH and BA on the combined BA datasets. Our results revealed that NASH-associated increases in plasma total cholic acid (CA) concentrations depend on the degree of HOMA2-assessed systemic IR, but not on ß-cell function nor on BMI. CONCLUSIONS: Plasma BA concentrations are elevated only in those NASH patients exhibiting pronounced IR. LAY SUMMARY: Non-alcoholic steatohepatitis (NASH) is a progressive liver disease that frequently occurs in patients with obesity and type 2 diabetes. Reliable markers for the diagnosis of NASH are needed. Plasma bile acids have been proposed as NASH biomarkers. Herein, we found that plasma bile acids are only elevated in patients with NASH when significant insulin resistance is present, limiting their utility as NASH markers.

Potent suppression of hydrophobic bile acids by aldafermin, an FGF19 analogue, across metabolic and cholestatic liver diseases.

BACKGROUND & AIMS: Higher serum bile acid levels are associated with an increased risk of cirrhosis and liver-related morbidity and mortality. Herein, we report secondary analyses of aldafermin, an engineered analogue of the gut hormone fibroblast growth factor 19, on the circulating bile acid profile in prospective, phase II studies in patients with metabolic or cholestatic liver disease. METHODS: One hundred and seventy-six patients with biopsy-confirmed non-alcoholic steatohepatitis (NASH) and fibrosis and elevated liver fat content (≥8% by magnetic resonance imaging-proton density fat fraction) received 0.3 mg (n = 23), 1 mg (n = 49), 3 mg (n = 49), 6 mg (n = 28) aldafermin or placebo (n = 27) for 12 weeks. Sixty-two patients with primary sclerosing cholangitis (PSC) and elevated alkaline phosphatase (>1.5× upper limit of normal) received 1 mg (n = 21), 3 mg (n = 21) aldafermin or placebo (n = 20) for 12 weeks. Serum samples were collected on day 1 and week 12 for determination of bile acid profile and neoepitope-specific N-terminal pro-peptide of type III collagen (Pro-C3), a direct measure of fibrogenesis. RESULTS: Treatment with aldafermin resulted in significant dose-dependent reductions in serum bile acids. In particular, bile acids with higher hydrophobicity indices, such as deoxycholic acid, lithocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, and glycocholic acid, were markedly lowered by aldafermin in both NASH and PSC populations. Moreover, aldafermin predominantly suppressed the glycine-conjugated bile acids, rather than the taurine-conjugated bile acids. Changes in levels of bile acids correlated with changes in the novel fibrogenesis marker Pro-C3, which detects a neo-epitope of the type III collagen during its formation, in the pooled NASH and PSC populations. CONCLUSIONS: Aldafermin markedly reduced major hydrophobic bile acids that have greater detergent activity and cytotoxicity. Our data provide evidence that bile acids may contribute to sustaining a pro-fibrogenic microenvironment in the liver across metabolic and cholestatic liver diseases. LAY SUMMARY: Aldafermin is an analogue of a gut hormone, which is in development as a treatment for patients with chronic liver disease. Herein, we show that aldafermin can potently and robustly suppress the toxic, hydrophobic bile acids irrespective of disease aetiology. The therapeutic strategy utilising aldafermin may be broadly applicable to other chronic gastrointestinal and liver disorders. CLINICAL TRIALS REGISTRATION: The study is registered at Clinicaltrials.govNCT02443116 and NCT02704364.

Biofilm Inhibitor Taurolithocholic Acid Alters Colony Morphology, Specialized Metabolism, and Virulence of Pseudomonas aeruginosa.

Biofilm inhibition by exogenous molecules has been an attractive strategy for the development of novel therapeutics. We investigated the biofilm inhibitor taurolithocholic acid (TLCA) and its effects on the specialized metabolism, virulence, and biofilm formation of the clinically relevant bacterium Pseudomonas aeruginosa strain PA14. Our study shows that TLCA alters the specialized metabolism, thereby affecting P. aeruginosa colony biofilm physiology. We observed an upregulation of metabolites correlated to virulence such as the siderophore pyochelin. A wax moth virulence assay confirmed that treatment with TLCA increases the virulence of P. aeruginosa. On the basis of our results, we believe that future endeavors to identify biofilm inhibitors must consider how a putative lead alters the specialized metabolism of a bacterial community to prevent pathogens from entering a highly virulent state.

[Bile acids regulate anorexigenic neuropeptide through p-STAT3-SOCS3 signaling in mouse hypothalamic cells].

OBJECTIVE: To explore the effects of taurolithocholic acid (tLCA) and chenodeoxycholic acid (CDCA) on the expression of aorexigenic neuropeptide in mouse hypothalamus GT1-7 cells. METHODS: Mouse hypothalamic GT1-7 cells were treated with culture medium containing 10% FBS (control group, n=3) or with 10 nmol/L, 100 nmol/L, 1 µmol/L and 10 µmol/L tLCA (tLCA group, n=3) or CDCA (CDCA group, n=3) for 12, 24 or 48 h. Real-time PCR was performed to determine the expression levels of proopiomelanocortin (POMC) mRNA in the cells, and the production levels of α-melanocyte-stimulating hormone (α-MSH) were assessed using an ELISA kit. Signal transduction and activator of transcription 3 phosphorylation (p-STAT3), threonine kinase phosphorylation (p-AKT), suppressor of cytokine signaling 3 (SOCS3), G protein-coupled bile acid receptor-1 (TGR5) and farnesoid X receptor (FXR) protein were detected by Western blotting. RESULTS: Western blotting results showed that mouse hypothalamic GT1-7 cells expressed two bile acid receptors, TGR5 and FXR, whose expressions were regulated by bile acids. Real-time PCR showed that the expression of POMC mRNA was significantly increased in the cells after treatment with 10 µmol/L tLCA or CDCA for 24 h. POMC-derived anorexigenic peptide α-MSH increased significantly in GT1-7 cells after treatment with 10 µmol/L tLCA or CDCA for 24 h. Treatment of the cells with tLCA or CDCA significantly increased the expressions of intracellular signaling proteins including p-STAT3, p-AKT and SOCS3. CONCLUSIONS: Mouse hypothalamic GT1-7 cells express bile acid receptors TGR5 and FXR. Bile acids tLCA or CDCA can promote the expression of POMC mRNA and increase the production of the anorexigenic peptide α-MSH. The intracellular signaling proteins p-AKT, p-STAT3 and SOCS3 are likely involved in bile acid-induced anorexigenic peptide production.

A novel partial agonist of GPBA reduces blood glucose level in a murine glucose tolerance test.

GPBA is a G protein-coupled receptor that is activated by bile acids. Because activation of GPBA leads to increased cAMP levels and secretion of incretins and insulin, GPBA has been proposed as a promising drug target for the treatment of metabolic syndrome. Previously, we have developed a ligand-screening system to identify novel agonists of GPBA by means of a fusion protein of GPBA with G protein stimulatory α subunit (Gsα) and by a [35S]GTPγS-binding assay. To express the GPBA-Gsα fusion protein, transgenic silkworms were employed in this study, and cell membrane fractions were prepared from their fat body or pupae. We applied them to the screening of a chemical library that contains 10,625 compounds from the RIKEN Natural Products Depository (NPDepo). Eventually, a unique partial agonist, GUM2, was successfully identified. Our results indicated that the GPCR-Gα fusion proteins were beneficial for ligand identification and that the transgenic silkworms were useful for large-scale production of GPCRs. In HEK293 cells transiently expressing GPBA, GUM2 showed 50% effective concentration (EC50) of 3.5 ± 2.4µM and induced GPBA internalization as effectively as did an endogenous agonist, TLC. We also confirmed that GUM2 stimulates insulin secretion in MIN6 cells. Moreover, a single 2mg/kg dose of GUM2 significantly reduced blood glucose levels in mice during an intraperitoneal glucose tolerance test even though GUM2 is only a partial agonist with a low intrinsic activity. We concluded that GUM2 is a good candidate for research on GPBA signaling under physiological conditions and for the development of GPBA-targeting therapeutic compounds.

Study on anti-inflammatory effect of taurolithocholic acid based on network pharmacology and its mechanism / 中国药理学通报

Aim To explore the anti-inflammatory effect of taurolithocholic acid (TLCA) through network pharmacology-based analyses, to verify with in vitro macrophage study and to reveal the possible mechanisms. Methods The potential targets of TLCA were acquired from public database, and then the protein-protein interaction (PPI) networks against inflammation were constructed and visualized by using Cytoscape. Gene ontology (GO) analyses and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were performed. The binding activity of TLCA and its target (TGR5) was evaluated through molecular docking analysis. Lastly, the results of the network analysis were confirmed by lipopolysaccharide and interferon-γ induced RAW264.7 cells. Results There were 87 anti-inflammatory potential targets were screened. GO analysis revealed gene functions were mainly involved in regulation of inflammatory response, membrane raft and protein tyrosine kinase. The results of KEGG pathway analysis suggested that PI3K-Akt signaling pathway, human cytomegalovirus infection might be the critical pathways of TLCA against inflammation. The results of in vitro experiments showed that TLCA decreased the LPS and IFN-γ induced inflammatory response in RAW 264.7 macrophages. Furthermore, the expression of TGR5 protein increased after TLCA treatment. Conclusions The potential therapeutic targets of TLCA against inflammation are revealed through network pharmacology analysis. Our results indicate that TLCA might regulate key inflammatory markers through the membrane receptor TGR5.

Bile acids regulate anorexigenic neuropeptide through p-STAT3-SOCS3 signaling in mouse hypothalamic cells / 南方医科大学学报

OBJECTIVE@#To explore the effects of taurolithocholic acid (tLCA) and chenodeoxycholic acid (CDCA) on the expression of aorexigenic neuropeptide in mouse hypothalamus GT1-7 cells.@*METHODS@#Mouse hypothalamic GT1-7 cells were treated with culture medium containing 10% FBS (control group, =3) or with 10 nmol/L, 100 nmol/L, 1 μmol/L and 10 μmol/L tLCA (tLCA group, =3) or CDCA (CDCA group, =3) for 12, 24 or 48 h. Real-time PCR was performed to determine the expression levels of proopiomelanocortin (POMC) mRNA in the cells, and the production levels of α-melanocyte-stimulating hormone (α-MSH) were assessed using an ELISA kit. Signal transduction and activator of transcription 3 phosphorylation (p-STAT3), threonine kinase phosphorylation (p-AKT), suppressor of cytokine signaling 3 (SOCS3), G protein-coupled bile acid receptor-1 (TGR5) and farnesoid X receptor (FXR) protein were detected by Western blotting.@*RESULTS@#Western blotting results showed that mouse hypothalamic GT1-7 cells expressed two bile acid receptors, TGR5 and FXR, whose expressions were regulated by bile acids. Real-time PCR showed that the expression of POMC mRNA was significantly increased in the cells after treatment with 10 μmol/L tLCA or CDCA for 24 h. POMC-derived anorexigenic peptide α-MSH increased significantly in GT1-7 cells after treatment with 10 μmol/L tLCA or CDCA for 24 h. Treatment of the cells with tLCA or CDCA significantly increased the expressions of intracellular signaling proteins including p-STAT3, p-AKT and SOCS3.@*CONCLUSIONS@#Mouse hypothalamic GT1-7 cells express bile acid receptors TGR5 and FXR. Bile acids tLCA or CDCA can promote the expression of POMC mRNA and increase the production of the anorexigenic peptide α-MSH. The intracellular signaling proteins p-AKT, p-STAT3 and SOCS3 are likely involved in bile acid-induced anorexigenic peptide production.

Bile acid nuclear receptor FXR and digestive system diseases.

Bile acids (BAs) are not only digestive surfactants but also important cell signaling molecules, which stimulate several signaling pathways to regulate some important biological processes. The bile-acid-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating bile acid, lipid and glucose homeostasis as well as in regulating the inflammatory responses, barrier function and prevention of bacterial translocation in the intestinal tract. As expected, FXR is involved in the pathophysiology of a wide range of diseases of gastrointestinal tract, including inflammatory bowel disease, colorectal cancer and type 2 diabetes. In this review, we discuss current knowledge of the roles of FXR in physiology of the digestive system and the related diseases. Better understanding of the roles of FXR in digestive system will accelerate the development of FXR ligands/modulators for the treatment of digestive system diseases.

Effect of maternal cholestasis on TGR5 expression in human and rat placenta at term.

BACKGROUND & AIMS: TGR5 (Gpbar-1) is a plasma membrane-bound bile acid receptor expressed in several tissues, including liver, intestine and brain. High levels of TGR5 mRNA have been detected in human and rodent placenta, however, localization of the TGR5 protein has not been studied in this tissue. We aimed at characterizing TGR5 expression in placental tissue and investigated the effect of bile acids and progesterone metabolites, which accumulate during intrahepatic cholestasis of pregnancy (ICP), on receptor expression and localization. METHODS: TGR5 mRNA levels and cell-specific localization were determined by quantitative PCR and immunofluorescence, respectively. RESULTS: In human term placentas, TGR5 was mainly localized in fetal macrophages and to a lower extent in trophoblasts. In placentas from ICP patients and pregnant rats with obstructive cholestasis a marked down-regulation of TGR5 mRNA expression was observed. However, the cell-specific distribution of the TGR5 protein was unaffected. Besides bile acids, progesterone and its metabolites (5α-pregnan-3α-ol-20-one/5α-pregnan-3ß-ol-20-one), which increase in serum during ICP, were able to dose-dependently activate TGR5. In addition, progesterone metabolites but not their sulfated derivatives nor taurolithocholic acid, significantly down-regulated TGR5 mRNA and protein expression in isolated human macrophages and a macrophage-derived cell line. CONCLUSION: Since fetal macrophages and trophoblast cells are exposed to changes in the flux of compounds across the placental barrier, the expression of TGR5 in these cells together with its sensitivity to bile acids and progesterone metabolites regarding receptor activity and mRNA expression suggest that TGR5 may play a role in the effect of maternal cholestasis on the placenta.