Glycochenodeoxycholate Research Articles

Air-ventilated normothermic mechanical perfusion improves susceptibility to donation after circulatory death and cold preservation-induced cholestatic liver injury through PPAR-γ/UGT1A1 axis.

End-ischemic normothermic mechanical perfusion (NMP) could provide a curative treatment to reduce cholestatic liver injury from donation after circulatory death (DCD) in donors. However, the underlying mechanism remains elusive. Our previous study demonstrated that air-ventilated NMP could improve functional recovery of DCD in a preclinical NMP rat model. Here, metabolomics analysis revealed that air-ventilated NMP alleviated DCD- and cold preservation-induced cholestatic liver injury, as shown by the elevated release of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, and γ-glutamyl transferase (GGT) in the perfusate (p < .05) and the reduction in the levels of bile acid metabolites, including ω-muricholic acid, glycohyodeoxycholic acid, glycocholic acid, and glycochenodeoxycholate (GCDC) in the perfused livers (p < .05). In addition, the expression of the key bile acid metabolism enzyme UDP-glucuronosyltransferase 1A1 (UGT1A1), which is predominantly expressed in hepatocytes, was substantially elevated in the DCD rat liver, followed by air-ventilated NMP (p < .05), and invitro, this increase was induced by decreased GCDC and hypoxia-reoxygenation in the hepatic cells HepG2 and L02 (p < .05). Knockdown of UGT1A1 in hepatic cells by siRNA aggravated hepatic injury caused by GCDC and hypoxia-reoxygenation, as indicated by the ALT and AST levels in the supernatant. Mechanistically, UGT1A1 is transcriptionally regulated by peroxisome proliferator-activator receptor-γ (PPAR-γ) under hypoxia-physoxia. Taken together, our data revealed that air-ventilated NMP could alleviate DCD- and cold preservation-induced cholestatic liver injury through PPAR-γ/UGT1A1 axis. Based on the results from this study, air-ventilated NMP confers a promising approach for predicting and alleviating cholestatic liver injury through PPAR-γ/UGT1A1 axis.

Metabolomics analysis of patients with Schistosoma japonicum infection based on UPLC-MS method

BackgroundSchistosomiasis is still one of the most serious parasitic diseases. Evidence showed that the metabolite profile in serum can potentially act as a marker for parasitic disease diagnosis and evaluate disease progression and prognosis. However, the serum metabolome in patients with Schistosoma japonicum infection is not well defined. In this study, we investigated the metabolite profiles of patients with chronic and with advanced S. japonicum infection.MethodsThe sera of 33 chronic S. japonicum patients, 15 patients with advanced schistosomiasis and 17 healthy volunteers were collected. Samples were extracted for metabolites and analyzed with ultra-performance liquid chromatography-mass spectrometry (UPLC-MS).ResultsWe observed significant differences in metabolite profiles in positive and negative ion modes between patients with advanced and chronic S. japonicum infection. In patients with chronic S. japonicum infection, 199 metabolites were significantly upregulated while 207 metabolites were downregulated in advanced infection. These differential metabolites were mainly concentrated in steroid hormone biosynthesis, cholesterol metabolism and bile secretion pathways. We also found that certain bile acid levels were significantly upregulated in the progression from chronic to advanced S. japonicum infection. In receiver operator characteristic (ROC) analysis, we identified three metabolites with area under the curve (AUC) > 0.8, including glycocholic (GCA), glycochenodeoxycholate (GCDCA) and taurochenodeoxycholic acid (TCDCA) concentrated in cholesterol metabolism, biliary secretion and primary bile acid biosynthesis.ConclusionsThis study provides evidence that GCA, GCDCA and TCDCA can potentially act as novel metabolite biomarkers to distinguish patients in different stages of S. japonicum infection. This study will contribute to the understanding of the metabolite mechanisms of the transition from chronic to advanced S. japonicum infection, although more studies are needed to validate this potential role and explore the underlying mechanisms.Graphical

Multiple Timescale Dynamic Analysis of Functionally-Impairing Mutations in Human Ileal Bile Acid-Binding Protein.

Human ileal bile acid-binding protein (hI-BABP) has a key role in the enterohepatic circulation of bile salts. Its two internal binding sites exhibit positive cooperativity accompanied by a site-selectivity of glycocholate (GCA) and glycochenodeoxycholate (GCDA), the two most abundant bile salts in humans. To improve our understanding of the role of dynamics in ligand binding, we introduced functionally impairing single-residue mutations at two key regions of the protein and subjected the mutants to NMR relaxation analysis and MD simulations. According to our results, mutation in both the vicinity of the C/D (Q51A) and the G/H (Q99A) turns results in a redistribution of motional freedom in apo hI-BABP. Mutation Q51A, deteriorating the site-selectivity of GCA and GCDA, results in the channeling of ms fluctuations into faster motions in the binding pocket hampering the realization of key side chain interactions. Mutation Q99A, abolishing positive binding cooperativity for GCDA, leaves ms motions in the C-terminal half unchanged but by decoupling βD from a dynamic cluster of the N-terminal half displays an increased flexibility in the vicinity of site 1. MD simulations of the variants indicate structural differences in the portal region and mutation-induced changes in dynamics, which depend on the protonation state of histidines. A dynamic coupling between the EFGH portal, the C/D-region, and the helical cap is evidenced highlighting the interplay of structural and dynamic effects in bile salt recognition in hI-BABP.

Glycochenodeoxycholate Affects Iron Homeostasis via Up-Regulating Hepcidin Expression.

Increasing hepcidin expression is a vital factor in iron homeostasis imbalance among patients with chronic kidney disease (CKD). Recent studies have elucidated that abnormal serum steroid levels might cause the elevation of hepcidin. Glycochenodeoxycholate (GCDCA), a steroid, is significantly elevated in patients with CKD. However, the correlation between GCDCA and hepcidin has not been elucidated. Decreased serum iron levels and increased hepcidin levels were both detected in patients with CKD in this study. Additionally, the concentrations of GCDCA in nephropathy patients were found to be higher than those in healthy subjects. HepG2 cells were used to investigate the effect of GCDCA on hepcidin in vitro. The results showed that hepcidin expression increased by nearly two-fold against control under 200 μM GCDCA treatment. The phosphorylation of SMAD1/5/8 increased remarkably, while STAT3 and CREBH remained unchanged. GCDCA triggered the expression of farnesoid X receptor (FXR), followed with the transcription and expression of both BMP6 and ALK3 (upward regulators of SMAD1/5/8). Thus, GCDCA is a potential regulator for hepcidin, which possibly acts by triggering FXR and the BMP6/ALK3-SMAD signaling pathway. Furthermore, 40 C57/BL6 mice were treated with 100 mg/kg/d, 200 mg/kg/d, and 300 mg/kg/d GCDCA to investigate its effect on hepcidin in vivo. The serum level of hepcidin increased in mice treated with 200 mg/kg/d and 300 mg/kg/d GCDCA, while hemoglobin and serum iron levels decreased. Similarly, the FXR-mediated SMAD signaling pathway was also responsible for activating hepcidin in liver. Overall, it was concluded that GCDCA could induce the expression of hepcidin and reduce serum iron level, in which FXR activation-related SMAD signaling was the main target for GCDCA. Thus, abnormal GCDCA level indicates a potential risk of iron homeostasis imbalance.

Imidazole Propionate is Increased in Diabetes and Associated with Stool Consistency.

BackgroundImidazole Propionate (ImP) is a new marker of Type 2 diabetes mellitus (T2DM), which can induce impaired glucose metabolism and weaken the efficacy of metformin. An extensive exploration into literature suggests that ImP may be associated with stool consistency.PurposeThrough an in-depth study of the relationship between stool consistency, bile acids, fecal microbiota and ImP, we intend to explore the mechanism driving the ImP content difference in T2DM.Patients Under Study and MethodsThis is a single-center, prospective, cross-sectional study. Plasma ImP and stool consistency were analyzed among 96 diabetic subjects and 45 healthy subjects. All subjects were divided into the stool consistency normal (N) group and the stool consistency abnormal group, of which the abnormal group was sub-divided into the hard stool (H) group and the soft stool (S) group. After identifying the correlation between ImP and stool consistency, we analyzed the influence of bile acids and fecal microbiota on ImP in diabetic subjects.ResultsFor T2DM patients, the ImP level of the abnormal stool consistency group was significantly higher than that of the normal stool consistency group (P < 0.001). Results were verified in 45 healthy subjects (P = 0.002). ImP was significantly associated with taurocholic acid (TCA) (P = 0.003) in feces, taurodeoxycholate (TDCA) (P = 0.003), glycochenodeoxycholate (GCDCA) (P = 0.021), and glycocholic acid (GCA) (P = 0.031) in plasma. The Shannon index of Group N was significantly higher than that of Group H (P = 0.041) and Group S (P = 0.003).ConclusionImP was higher in diabetic patients with abnormal stool consistency than in those with normal stool consistency, which was related to the proportion of bile acids and fecal microbial structure. These findings may improve our understanding of ImP and contribute to the treatment of T2DM by improving stool consistency.

Abstract 048: Changes In Bile Acid Metabolism, Circulating MicroRNA-34a, And Improvements In Lipid Profiles In Response To Weight-loss Diets: The Pounds Lost Trial

Background: Bile acids are synthesized from cholesterol in the liver and play pivotal roles in nutrient absorption and metabolic regulation. Altered bile acid metabolism is related to dyslipidemia, and microRNA-34a (miR-34a) may play a pivotal role in the treatment of lipid homeostasis by regulating the bile acid biosynthesis. Hypothesis: We investigated whether weight-loss diet-induced changes in primary and secondary bile acids were associated with the improvements in lipid profiles. We also tested the role of circulating miR-34a in the altered bile acid metabolism in adults with overweight and obesity. Methods: A total of 520 participants of a weight-loss dietary intervention (the POUNDS Lost trial) with data on bile acids and miR-34a were included in the present analysis. Circulating levels of miR-34a and bile acid subtypes (primary and secondary unconjugated bile acids and their taurine-/glycine-conjugates) were measured at baseline and 6 months after the intervention. Outcome measurements were improvements in lipids (triglycerides and cholesterol) in response to the interventions. Results: At baseline, higher levels of primary bile acids (chenodeoxycholate (CDCA), glycocholate (GCA), taurocholate (TCA), and glycochenodeoxycholate (GCDCA) were associated with elevated levels of triglycerides ( P FDR &lt;0.05). Greater decreases in the primary bile acid subtypes (CDCA, GCA, TCA, GCDCA, and taurochenodeoxycholate [TCDCA]) in response to the interventions were significantly associated with larger reductions of triglycerides at 6 months ( P FDR &lt;0.05 for all). Decreases in secondary bile acids (deoxycholate and its conjugated forms) also showed significant associations with decreases in triglycerides. Similarly, reductions of total cholesterol at 6 months were associated with decreases in the primary (such as GCA, GCDCA, TCDCA) and secondary bile acid subtypes. We found that greater levels of miR-34a at baseline were related to higher levels of triglycerides at baseline (p=0.038) and higher levels of primary bile acids (such as CA, CDCA, GCA, and TCA [PFDR &lt;0.05 for all]) but not with the secondary bile acids at baseline. Further, weight-loss diet-induced changes in miR-34a were positively correlated with changes in the primary bile acid subtypes (CDCA, GCA, and GCDCA). Conclusions: Changes in the specific primary and secondary bile acid subtypes were related to the improvements in lipid profiles in response to weight-loss diet interventions. Circulating miR-34a might in part contribute to the alterations in the primary bile acid subtypes in obese adults.

Targeted Metabolomics Analysis of Bile Acids in Patients with Idiosyncratic Drug-Induced Liver Injury.

Drug-induced liver injury (DILI) is rare but clinically important due to a high rate of mortality. However, specific biomarkers for diagnosing and predicting the severity and prognosis of DILI are lacking. Here, we used targeted metabolomics to identify and quantify specific types of bile acids that can predict the severity of DILI. A total of 161 DILI patients were enrolled in this prospective cohort study, as well as 31 health controls. A targeted metabolomics method was used to identify 24 types of bile acids. DILI patients were divided into mild, moderate, and severe groups according to disease severity. A multivariate analysis was performed to identify characteristic bile acids. Then the patients were divided into severe and non-severe groups, and logistic regression was used to identify bile acids that could predict DILI severity. Among the enrolled DILI patients, 32 were in the mild group, 90 were in the moderate group, and 39 were in the severe group. Orthogonal partial least squares-discriminant analysis (OPLS-DA) modeling clearly discriminated among the different groups. Among the four groups, glycochenodeoxycholate (GCDCA), taurochenodeoxycholate (TCDCA), deoxycholic acid (DCA), Nor Cholic acid (NorCA), glycocholic acid (GCA), and taurocholic acid (TCA) showed significant differences in concentration between at least two groups. NorCA, GCDCA, and TCDCA were all independent risk factors that differentiated severe DILI patients from the other groups. The area under the receiver operating characteristic curve (AUROC) of GCDCA, TCDCA, and NorCA was 0.856, 0.792, and 0.753, respectively. Together, these three bile acids had an AUROC of 0.895 for predicting severe DILI patients. DILI patients with different disease severities have specific bile acid metabolomics. NorCA, GCDTA, and TCDCA were independent risk factors for differentiating severe DILI patients from less-severe patients and have the potential to predict DILI severity.

Vitexin ameliorates glycochenodeoxycholate-induced hepatocyte injury through SIRT6 and JAK2/STAT3 pathways.

Objective(s):Vitexin, a natural flavonoid, is commonly found in many foods and traditional herbal medicines and has clear health benefits. However, the role of vitexin in cholestasis is presently unclear. This study investigated whether vitexin mitigated glycochenodeoxycholate (GCDC)-induced hepatocyte injury and further elucidated the underlying mechanisms.Materials and Methods:A cell counting kit-8 (CCK-8) assay was conducted to evaluate cell viability. The mitochondrial membrane potential (MMP, Δψm), reactive oxygen species (ROS) levels, and apoptosis rate of hepatocytes exposed to GCDC were detected by flow cytometry (FCM). We then measured the cytoprotective effects of vitexin against oxidative stress. The molecular signaling pathway was further investigated by using Western blotting and signaling pathway inhibitors.Results:Here, we showed that vitexin increased cell viability and reduced cell apoptosis, necroptosis, and oxidative stress in a dose-dependent manner in GCDC-treated hepatocytes. In addition, by using selective inhibitors, we further confirmed that inhibition of the JAK2/STAT3 pathway by vitexin was mediated by prolonged activation of Sirtuin 6 (SIRT6).Conclusion: Vitexin attenuated GCDC-induced hepatocyte injury via SIRT6 and the JAK2/STAT3 pathways.

Suppressing ERK Pathway Impairs Glycochenodeoxycholate-Mediated Survival and Drug-Resistance in Hepatocellular Carcinoma Cells

Glycochenodeoxycholate (GCDA), a toxic component in bile salts, is involved in carcinogenesis of gastrointestinal tumors. The objective of this research was to study the function of ERK1/2 in the GCDA-mediated survival and drug-resistance in hepatocellular carcinoma cells (HCCs). Firstly, extracellular signal-regulated kinase 1/2 (ERK1/2) was detected extensively expressed in liver cancer cells, and silencing ERK1/2 by RNA interference could suppress GCDA-stimulated survival and promote apoptosis. Furthermore, phosphorylation of endogenous ERK1/2 could be potently stimulated by GCDA in combination with enhanced chemoresistance in QGY-7703 hepatocellular carcinoma cells. The GCDA-mediated proliferation and chemoresistance could be impaired by PD98059, which acted as an inhibitor to block the phosphorylation of ERK1/2. Mechanistically, PD98059 was able to potently suppress GCDA-stimulated nuclear aggregation of ERK1/2 and p-ERK1/2, upregulate pro-survival protein Mcl-1 and downregulate pro-apoptotic protein Bim. The results of this study indicated that disruption of ERK1/2 by blocking phosphorylation or nuclear translocation may put forward new methods for solving the problem of GCDA-related proliferation and drug-resistance in liver cancer treatment.

Augmenter of Liver Regeneration (ALR) regulates bile acid synthesis and attenuates bile acid-induced apoptosis via glycogen synthase kinase-3β (GSK-3β) inhibition

Bile acid synthesis is restricted to hepatocytes and is rate-limited by CYP7A1 (cholesterol 7α hydroxylase). CYP7A1 expression undergoes tight regulation and is repressed after partial hepatectomy to prevent the accumulation of toxic bile acids. Augmenter of Liver Regeneration (ALR) is a hepatotrophic factor shown to support liver regeneration by augmenting cell proliferation and reducing apoptosis. Nevertheless, less is known about ALR's role in protecting hepatocytes from bile acid accumulation and bile acid-induced apoptosis. Therefore, HepG2 and Huh-7 cells were incubated with recombinant human ALR (rALR) and the expression of CYP7A1, bile acid-induced apoptosis as well as potential molecular mechanisms were analyzed. We found that rALR reduces CYP7A1 expression by increasing nuclear NFκB levels. Moreover, rALR reduced glycochenodeoxycholate (GCDC)-induced-apoptosis by decreased expression of pro-apoptotic Bax and enhanced expression of anti-apoptotic Mcl-1, which is regulated by phosphatidylinositol-3-kinase (PI3K)/Akt activation and glycogen synthase kinase-3β (GSK3β) phosphorylation. Inhibitors for PI3K/Akt (GSK690693) and GSK3β (SB415286) confirmed the specificity of rALR treatment for this pathway. In addition, rALR reduces pro-death signaling by decreasing GCDC-induced JNK phosphorylation. Taken all together, rALR might contribute to protecting hepatocytes from toxic concentrations of bile acids by down-regulating their denovo synthesis, attenuating apoptosis by activation of PI3K/Akt - GSK3β pathway and inhibition of JNK signaling. Thereby this suggests a new role of ALR in augmenting the process of liver regeneration.

Characterization of a recombinant bile salt hydrolase (BSH) from Bifidobacterium bifidum for its glycine-conjugated bile salts specificity

Deconjugation of bile salts in vivo not only promotes the cholesterol metabolism of the host, but also provides cellular carbon, nitrogen and sulphur for some probiotics. In this study, the gene of BSH from Bifidobacterium bifidum (ATCC 29521) was amplified and expressed using glutathione S-transferase (GST) Gene Fusion System. The enzyme was purified in a mild conditions without denaturation and renaturation, and the molecular mass was estimated to be 35 kDa. The optimum pH for the enzyme catalysis was 5.5. The BSH enzyme was stable from 37 to 57 °C. In addition, this enzyme was completely inhibited by Cu2+, while many other metal ions only gave moderate inhibition. Hydrolysis efficiency of BSH was quantified in two ways: ninhydrin colouration method and high-performance liquid chromatography coupled with evaporative light scattering detector (HPLC-ELSD). The hydrolysis process was clearly observed through real-time picture monitoring. The activity of BSH on glycine-conjugated bile salts was better than on taurine-conjugated bile salts. The proportion of hydrolysis for both sodium glycochenodeoxycholate (GCDCA) and sodium glycoursodeoxycholate (GUDCA) were more than 90% in 60 min. However, the proportion of hydrolysis for sodium taurochenodeoxycholate (TCDCA) and sodium tauroursodeoxycholate (TUDCA) were only 68% and 43% at the same condition. The study of this paper provides a better choice for hydrolysis of glycine-conjugated bile salts. Highlights The specificity of BSH was high for glycine-conjugated bile salts. Hydrolysis process of bile acid was obtained through real-time picture monitoring. Hydrolysis efficiency of BSH was quantified in two ways: ninhydrin colouration method and HPLC-ELSD.

Sirt6 opposes glycochenodeoxycholate-induced apoptosis of biliary epithelial cells through the AMPK/PGC-1\u03b1 pathway

BackgroundInduction of biliary epithelial cell apoptosis by toxic bile acids is involved in the development of cholestatic disease, but the underlying molecular mechanism is not clear. The purpose of this study was to investigate the molecular mechanisms involved in Sirt6 protection against the apoptosis of human intrahepatic biliary epithelial cells (HiBEC) induced by the bile acid glycochenodeoxycholate (GCDC).ResultsSirt6 was either overexpressed or knocked down in HiBEC, with or without GCDC pretreatment. The CCK-8 assay was used to assess cell viability and, Hoechst 33258 staining was used to determine apoptotic rate. Mitochondrial DNA (mtDNA) copy number, malondialdehyde (MDA) and reactive oxygen species (ROS) production were detected to evaluate the severity of the mitochondrial dysfunction and oxidative stress. The mRNA and protein levels of PGC-1α, Nrf1, and Nrf2 were analyzed using RT-qPCR and western blot assay. The results showed that Sirt6 opposed GCDC-induced apoptosis in HiBEC via up-regulating PGC-1α expression and stabilizing mtDNA. We used agonists and inhibitors of AMPK to demonstrate that Sirt6 increased PGC-1α expression through the AMPK pathway whereas GCDC had the opposite effect. Finally, western blot, luciferase assay, and co-immunoprecipitation were used to describe a direct interaction and acetylation modification of PGC-1α by Sirt6.ConclusionOur data illuminated that Sirt6 ameliorated GCDC-induced HiBEC apoptosis by upregulating PGC-1α expression through the AMPK pathway and its deacetylation effect.

Glycochenodeoxycholate Promotes Liver Fibrosis in Mice with Hepatocellular Cholestasis.

Hydrophobic bile salts are considered to promote liver fibrosis in cholestasis. However, evidence for this widely accepted hypothesis remains scarce. In established animal models of cholestasis, e.g., by Mdr2 knockout, cholestasis and fibrosis are both secondary to biliary damage. Therefore, to test the specific contribution of accumulating bile salts to liver fibrosis in cholestatic disease, we applied the unique model of inducible hepatocellular cholestasis in cholate-fed Atp8b1G308V/G308V mice. Glycochenodeoxycholate (GCDCA) was supplemented to humanize the murine bile salt pool, as confirmed by HPLC. Biomarkers of cholestasis and liver fibrosis were quantified. Hepatic stellate cells (HSC) isolated from wild-type mice were stimulated with bile salts. Proliferation, cell accumulation, and collagen deposition of HSC were determined. In cholestatic Atp8b1G308V/G308V mice, increased hepatic expression of αSMA and collagen1a mRNA and excess hepatic collagen deposition indicated development of liver fibrosis only upon GCDCA supplementation. In vitro, numbers of myofibroblasts and deposition of collagen were increased after incubation with hydrophobic but not hydrophilic bile salts, and associated with EGFR and MEK1/2 activation. We concluded that chronic hepatocellular cholestasis alone, independently of biliary damage, induces liver fibrosis in mice in presence of the human bile salt GCDCA. Bile salts may have direct pro-fibrotic effects on HSC, putatively involving EGFR and MEK1/2 signaling.

Glycochenodeoxycholate induces cell survival and chemoresistance via phosphorylation of STAT3 at Ser727 site in HCC.

Glycochenodeoxycholate (GCDA) is closely associated with carcinogenesis and chemoresistance of hepatocellular carcinoma (HCC). Signal transducer and activator of transcription 3 (STAT3), a transcription factor, is involved in various human tumors. Whether GCDA induces chemoresistance through STAT3 and the mechanism of action remains elusive. In this study, we firstly found that the expression level of STAT3 has a positive correlation with chemoresistance of HCC cells. Moreover, GCDA can upregulate the expression of STAT3 protein. Hence, we suspect that GCDA may induce chemoresistance of HCC cells via STAT3. Mechanistically, GCDA stimulates phosphorylation of STAT3 at Ser727 site and mediates pSer727-STAT3 protein to translocate and aggregate in the nucleus, which is important for cell survival. When Ser727 of STAT3 mutated to Asp, the capacity of STAT3 to accumulate in the nucleus was attenuated, STAT3-induced cell survival was impaired and GCDA-induced chemoresistance was abolished. In addition, while activation of extracellular signal-regulated kinase 1/2 (ERK1/2) was inhibited by PD98059, phosphorylation of STAT3 at Ser727 induced by GCDA was suppressed. Taken together, these data demonstrate that GCDA-enhanced survival of liver cancer cells may occur through the activation of STAT3 by phosphorylation at Ser727 site via mitogen-activated protein kinase/ERK1/2 pathway, which may contribute to the progression of human liver cancer and chemoresistance.

Glycochenodeoxycholate promotes the metastasis of gallbladder cancer cells by inducing epithelial to mesenchymal transition via activation of SOCS3/JAK2/STAT3 signaling pathway.

The incidence of gallbladder cancer (GBC) is relatively rare but a high degree of malignancy. The migration and invasion potential of GBC severely affects the prognosis of patients with GBC. Glycochenodeoxycholate (GCDC) is one of the most important components in GBC-associated microenvironment. However, the role of GCDC in the metastatic feature of GBC cells is not fully understood. First, the results of this study found that GCDC could effectively enhance the metastasis of GBC cells. Furthermore, GCDC could lead to the enhancement of epithelial to mesenchymal transition (EMT) phenotype in GBC cells, which is concerned to be an important mechanism of tumor metastasis. Further studies showed that GCDC treatment induced the upregulation of matrix metalloproteinase-3 (MMP3), MMP9, and SOCS3/JAK2/p-STAT3 signal pathway in GBC cells, which could regulate the level of EMT. Beside that, we also found the positiveexpression of farnesoid X receptor (FXR) in GBC cells and inhibition of FXR could significantly block the effect of GCDC on the metastasis of GBC cells. These results indicated that GCDC promoted GBC cells metastasis by enhancing the level of EMT and inhibition of FXR could significantly block the effect of GCDC. On one hand, FXR might be an indicator for predicting the metastasis of patient with GBC. On the other hand, FXR might serve as a potential antimetastasis target in GBC therapy.

High- performance liquid chromatography method applied to investigate mechanism, kinetics, isotherm, and thermodynamics of bile acid adsorption onto bile acid sequestrants

The purpose of the study was to develop and validate a high-performance liquid chromatography (HPLC) method which can be further applied to understand the mechanism, kinetics, isotherm, and thermodynamics of bile acid adsorption onto bile acid sequestrants. To investigate these properties a HPLC method was developed using peerless C-8 (150 x 4.6 mm, 5 µm) column with a detection wavelength of 200 nm and run time of about 12.5 min. Bile salts glycocholic (GC), glycochenodeoxycholic (GCDC), and taurodeoxycholic acid (TDC), were used and colesevelam hydrochloride was employed as the bile acid sequestrant. The calibration range was found linear from 10 to 6500 mgL−1 for GC and GCDC and 4to 2400 mg L−1 for TDC. The precision was less than 8.8% and accuracy was found well within the range of 85 to 115%. On treating the data with various established models, it was known that, the adsorption kinetics followed the pseudo second order equation indicating chemisorption mechanism. Equilibrium isotherms revealed that the linear form of Langmuir model was the best fit. The separation factor (RL) calculated revealed that the reaction is favorable and reversible. The positive value of heat of sorption (B) calculated from Temkin model indicated towards the exothermic nature of adsorption. The adsorption energy (E) calculated from Dubinin-Kaganer-Radushkevich model was found to be greater than 8 KJmol−1 conforming chemisorption mechanism. The Gibbs free energy calculated established the affinity of bile salts as TDC > GCDC > GC.

Tauroursodeoxycholate protects from glycochenodeoxycholate-induced gene expression changes in perfused rat liver.

Tauroursodeoxycholate (TUDC) is well known to protect against glycochenodeoxycholate (GCDC)-induced apoptosis in rat hepatocytes. In the present study, we analyzed whether TUDC also exerts protective effects by modulating GCDC-induced gene expression changes. For this, gene array-based transcriptome analysis and quantitative polymerase chain reaction (qPCR) were performed on RNA isolated from rat livers perfused with GCDC, TUDC or a combination of both (each 20 μm for 2 h). GCDC led to a significant increase of lactate dehydrogenase (LDH) into the effluent perfusate, which was prevented by TUDC. GCDC, TUDC and co-perfusion induced distinct gene expression changes. While GCDC upregulated the expression of several pro-inflammatory genes, co-perfusion with TUDC increased the expression of pro-proliferative and anti-apoptotic p53 target genes. In line with this, levels of serine20-phosphorylated p53 and of its target gene p21 were elevated by GCDC in a TUDC-sensitive way. GCDC upregulated the oxidative stress surrogate marker 8OH(d)G and the pro-apoptotic microRNAs miR-15b/16 and these effects were prevented by TUDC. The upregulation of miR-15b and miR-16 in GCDC-perfused livers was accompanied by a downregulation of several potential miR-15b and miR-16 target genes. The present study identified changes in the transcriptome of the rat liver which suggest, that TUDC is hepatoprotective by counteracting GCDC-induced gene expression changes.

Regulation of Plasma Membrane Localization of the Na⁺-Taurocholate Co-Transporting Polypeptide by Glycochenodeoxycholate and Tauroursodeoxycholate.

Hydrophobic bile salts, such as glycochenodeoxycholate (GCDC) can trigger hepatocyte apoptosis, which is prevented by tauroursodesoxycholate (TUDC), but the effects of GCDC and TUDC on sinusoidal bile salt uptake via the Na⁺-taurocholate transporting polypeptide (Ntcp) are unclear. The effects of GCDC and TUDC on the plasma membrane localization of Ntcp were studied in perfused rat liver by means of immunofluorescence analysis and super-resolution microscopy. The underlying signaling events were investigated by Western blotting and inhibitor studies. GCDC (20 µmol/l) induced within 60 min a retrieval of Ntcp from the basolateral membrane into the cytosol, which was accompanied by an activating phosphorylation of the Src kinases Fyn and Yes. Both, Fyn activation and the GCDC-induced Ntcp retrieval from the plasma membrane were sensitive to the NADPH oxidase inhibitor apocynin, the antioxidant N-acetylcysteine and the Src family kinase inhibitors SU6656 and PP-2, whereas PP-2 did not inhibit GCDC-induced Yes activation. Internalization of Ntcp by GCDC was also prevented by the protein kinase C (PKC) inhibitor Gö6850. TUDC (20 µmol/l) reversed the GCDC-induced retrieval of Ntcp from the plasma membrane and prevented the activation of Fyn and Yes in GCDC-perfused rat livers. Reinsertion of Ntcp into the basolateral membrane in GCDC-perfused livers by TUDC was sensitive to the protein kinase A (PKA) inhibitor H89 and the integrin-inhibitory peptide GRGDSP, whereas the control peptide GRADSP was ineffective. Ex posure of cultured rat hepatocytes to GCDC (50 µmol/l, 15min) increased the fluorescence intensity of the reactive oxygen fluorescent indicator DCF to about 1.6-fold of untreated controls in a TUDC (50 µmol/l)-sensitive way. GCDC caused a TUDC-sensitive canalicular dilatation without evidence for Bsep retrieval from the canalicular membrane. The present study suggests that GCDC triggers the retrieval of Ntcp from the basolateral membrane into the cytosol through an oxidative stress-dependent activation of Fyn. TUDC prevents the GCDC-induced Fyn activation and Ntcp retrieval through integrin-dependent activation of PKA.

Glycochenodeoxycholate promotes hepatocellular carcinoma invasion and migration by AMPK/mTOR dependent autophagy activation.

Metastasis and recurrence severely impact the treatment effect of hepatocellular carcinoma (HCC). HCC complicated with cholestasis is more prone to recurrence and metastasis. Previous studies have implicated pathogenesis of HCC by bile acid; however, the underlying mechanism is unknown yet. Glycochenodeoxycholate (GCDC) is one of most important component of bile acid (BA). In the present study, the role of GCDC in HCC cells invasion was detected by in vitro and in vivo assays. GCDC was found to significantly enhance the invasive potential of HCC cells; Further studies showed that GCDC could induce autophagy activation and higher invasive capability in HCC cells. Interestingly, inhibition of autophagy by chloroquine (CQ) reversed this phenomenon. Subsequently, the correlation between TBA expression level and clinicopathological characteristics was analyzed in HCC patients. Clinically, high TBA level in HCC tissue was found to be associated with more invasive and poor survival in HCC patients. Mechanistic study showed that bile acid induced autophagy by targeting the AMPK/mTOR pathway in HCC cells. Therefore, our results suggest that bile acid may promote HCC invasion via activation of autophagy and the level of bile acid may serve as a potential useful indicator for prognosis of HCC patients.

Mesenchymal stem cells enhance autophagy of human intrahepatic biliary epithelial cells in vitro.

The present findings constitute the first report that human umbilical cord-derived MSCs enhance autophagic flux in HiBECs through a STAT3-dependent way: MSCs enhance the autophagic flux by increasing the formation of autophagosome and autolysosome in GCDC-treated HiBECs. MSCs decrease the STAT3 activity and the expression of eIF2α in GCDC-treated HiBECs; in addition, MSCs increase the expression of PKR. With STAT3 silencing, MSCs enhance neither the levels of LC3II nor the expression of PKR in GCDC-treated HiBECs.