The role of ERp29/FOS/EMT pathway in excessive apoptosis of placental trophoblast cells in intrahepatic cholestasis of pregnancy

BACKGROUND

Abnormal bile acid metabolism leading to changes in placental function during pregnancy. To determine whether endoplasmic reticulum protein 29 (ERp29) can mediate the pregnancy effects of cholestasis by altering the level of trophoblast cell apoptosis.

METHODS

ERp29 in serum of 66 intrahepatic cholestasis of pregnancy (ICP) pregnant women and 74 healthy were detected by ELISA. Subcutaneous injection of ethinyl estradiol (E2) was used to induce ICP in pregnant rats. Taurocholic acid (TCA) was used to simulate the ICP environment, and TGF-β1 was added to induce the epithelial mesenchymal transformation (EMT) process. The scratch, migration, and invasion test were used to detect the EMT process. ERp29 overexpression/knockdown vector were constructed and transfected to verify the role of ERp29 in the EMT process. Downstream gene was obtained through RNA-seq.

RESULTS

Compared with the healthy pregnant women, the expression levels of ERp29 in serum of ICP pregnancy women were significantly increased (P < 0.001). ERp29 in the placenta tissue of the ICP pregnant rats increased significantly, and the level of apoptosis increased. The placental tissues of the ICP had high expression of E-cadherin and low expression of N-cadherin, snail1, vimentin. After HTR-8/SVneo cells were induced by TCA, EMT was inhibited, while the ERp29 increased. Cell and animal experiments showed that, knockdown of ERp29 reduced the inhibition of EMT, the ICP progress was alleviated. Overexpression of FOS salvaged the inhibitory effects of ERp29 on cell EMT.

DISCUSSION

The high level of ERp29 in placental trophoblast cells reduced FOS mRNA levels, inhibited the EMT process and aggravated the occurrence and development of ICP.

Influence of dietary sodium taurocholate on the growth performance and liver health of Nile tilapia (Oreochromis niloticus)

Bile acids (BAs) are a class of cholesterol-derived amphipathic molecules approved as new animal feed additives. However, the functional researches mainly focused on BAs mixture, and the influence of the individual BA on fishes was still limited. In the present study, Nile tilapia were fed basal diet with three levels of sodium taurocholate at 0 mg/kg (CON), 300 mg/kg (TCAL), and 600 mg/kg (TCAH) for 8 weeks. The results indicated that addition of sodium taurocholate did not significantly influence the growth performance. Instead, TCAH group had higher cholesterol accumulation with liver fibrosis. In TCAH group, the level of nuclear factor E2-related factor 2 (nrf2) signaling-associated oxidative stress factors significantly increased in the liver. Additionally, fish in TCAH group had the highest expression level of genes encoding endoplasmic reticulum (ER) stress and inflammatory cytokines in the liver. In conclusion, 300 mg/kg of sodium taurocholate did not significantly influence the growth performance of fish, while 600 mg/kg of sodium taurocholate markedly induced cholesterol accumulation and liver injury, suggesting that the application of taurocholic acid in aquafeed should be re-evaluated.

Taurocholate uptake by Caco-2 cells is inhibited by pro-inflammatory cytokines and butyrate

Inflammatory bowel disease (IBD) is a group of chronic and life-threating inflammatory diseases of the gastrointestinal tract. The active intestinal absorption of bile salts is reduced in IBD, resulting in higher luminal concentrations of these agents that contribute to the pathophysiology of IBD-associated diarrhea. Butyrate (BT) is a short-chain fatty acid produced by colonic bacterial fermentation of dietary fibers. BT utilization is impaired in the intestinal inflamed mucosa of IBD patients. Our aim was to investigate the link between IBD and bile acid absorption, by testing the effect of the pro-inflammatory cytokines TNF-α and IFN-γ and of BT upon 3H-TC uptake by Caco-2 cells. The proinflammatory cytokines TNF-α and IFN-γ inhibit Na+-independent, non-ASBT (sodium-dependent bile acid transporter)-mediated 3H-TC uptake by Caco-2 cells. The inhibitory effect of these cytokines on Na+-independent 3H-TC uptake is PI3K- and JAK/STAT1-mediated. These two compounds upregulate ASBT expression levels, but no corresponding increase in Na+-dependent component of 3H-TC is observed. Moreover, BT was also found to inhibit 3H-TC uptake and showed an additive effect with IFN-γ in reducing 3H-TC uptake. We conclude that an interaction between BT and bile acids appears to exist in IBD, which may participate in the link between diet, microbiota and IBD.

Mechanism of germination inhibition of Clostridioides difficile spores by an aniline substituted cholate derivative (CaPA)

Clostridioides difficile infection (CDI) is the major identifiable cause of antibiotic-associated diarrhea and has been declared an urgent threat by the CDC. C. difficile forms dormant and resistant spores that serve as infectious vehicles for CDI. To cause disease, C. difficile spores recognize taurocholate and glycine to trigger the germination process. In contrast to other sporulating bacteria, C. difficile spores are postulated to use a protease complex, CspABC, to recognize its germinants. Since spore germination is required for infection, we have developed anti-germination approaches for CDI prophylaxis. Previously, the bile salt analog CaPA (an aniline-substituted cholic acid) was shown to block spore germination and protect rodents from CDI caused by multiple C. difficile strains and isolates. In this study, we found that CaPA is an alternative substrate inhibitor of C. difficile spore germination. By competing with taurocholate for binding, CaPA delays C. difficile spore germination and reduces spore viability, thus diminishing the number of outgrowing vegetative bacteria. We hypothesize that the reduction of toxin-producing bacterial burden explains CaPA's protective activity against murine CDI. Previous data combined with our results suggests that CaPA binds tightly to C. difficile spores in a CspC-dependent manner and irreversibly traps spores in an alternative, time-delayed, and low yield germination pathway. Our results are also consistent with kinetic data suggesting the existence of at least two distinct bile salt binding sites in C. difficile spores.

Bile components affect the functions and transcriptome of the rainbow trout intestinal epithelial cell line RTgutGC

The concomitant increase in cultivation of fish and decrease in supply of marine ingredients, have greatly increased the demand for new nutrient sources. This also regards so-called functional ingredients which may benefit health and welfare of the fish. In vitro cell line-based intestinal epithelial barrier models may serve as tools for narrowing down the broad range of ingredient options, to identify the most promising candidates before in vivo feeding trials are run. In vivo, differentiation of the various epithelial cells in the fish intestine, from the multipotent stem cells, takes place in the presence of a variety of substances from dietary and endogenous origin. Among these, bile salts have recently received attention as regulators of epithelial function in health and disease but have not, until now, been included in the medium when culturing fish gut epithelial cells in vitro. As bile salts are present at high levels in the chyme of the fish intestine, in particular in salmon and rainbow trout, mostly as taurocholate (>90%), their role for effects of diet ingredients on the in vitro gut cell model should be understood. With this study, we wanted to investigate whether inclusion of bile from rainbow trout or pure taurocholate in the culture media would modulate functions of the RTgutGC epithelial cells. Here, we demonstrated that the rainbow trout intestinal epithelial cell line RTgutGC responded significantly to the presence of bile components. Treatment with rainbow trout bile taken from the gall bladder (RTbile) or pure taurocholate (TC) at taurocholate concentrations of ≤0.5 mg/mL retained normal cell morphology, cell viability as in cell oxidation-reduction metabolic activity and membrane integrity, and barrier features, while high concentrations of bile salts (≥1 mg/mL) were cytotoxic to the cells. After long-term (4 days) bile treatment, transcriptome responses showed how bile salts play important roles in intestinal epithelial cell metabolism. qPCR data demonstrated that barrier function genes, brush border enzyme genes and immune genes were significantly affected. Although similar trends were seen, treatment with bile salt as a component of rainbow trout bile or pure taurocholate, induced somewhat different effects. In conclusion, this study clearly indicates that bile salts should be included in the cell medium when running in vitro studies of gut cell functions, not at least immune functions, preferably at the level of ∼0.5 mg/mL supplemented as pure taurocholate to ensure reproducibility.

A High Hepatic Uptake of Conjugated Bile Acids Promotes Colorectal Cancer-Associated Liver Metastasis

The liver is the most common site for colorectal cancer (CRC)-associated metastasis. There remain unsatisfactory medications in liver metastasis given the incomplete understanding of pathogenic mechanisms. Herein, with an orthotopic implantation model fed either regular or high-fat diets (HFD), more liver metastases were associated with an expansion of conjugated bile acids (BAs), particularly taurocholic acid (TCA) in the liver, and an increased gene expression of Na⁺-taurocholate cotransporting polypeptide (NTCP). Such hepatic BA change was more apparently shown in the HFD group. In the same model, TCA was proven to promote liver metastases and induce a tumor-favorable microenvironment in the liver, characterizing a high level of fibroblast activation and increased proportions of myeloid-derived immune cells. Hepatic stellate cells, a liver-residing source of fibroblasts, were dose-dependently activated by TCA, and their conditioned medium significantly enhanced the migration capability of CRC cells. Blocking hepatic BA uptake with NTCP neutralized antibody can effectively repress TCA-triggered liver metastases, with an evident suppression of tumor microenvironment niche formation. This study points to a new BA-driven mechanism of CRC-associated liver metastases, suggesting that a reduction of TCA overexposure by limiting liver uptake is a potential therapeutic option for CRC-associated liver metastasis.

Entry of spores into intestinal epithelial cells contributes to recurrence of Clostridioides difficile infection

Clostridioides difficile spores produced during infection are important for the recurrence of the disease. Here, we show that C. difficile spores gain entry into the intestinal mucosa via pathways dependent on host fibronectin-α5β1 and vitronectin-αvβ1. The exosporium protein BclA3, on the spore surface, is required for both entry pathways. Deletion of the bclA3 gene in C. difficile, or pharmacological inhibition of endocytosis using nystatin, leads to reduced entry into the intestinal mucosa and reduced recurrence of the disease in a mouse model. Our findings indicate that C. difficile spore entry into the intestinal barrier can contribute to spore persistence and infection recurrence, and suggest potential avenues for new therapies.

Taurocholic acid inhibits the response to interferon-α therapy in patients with HBeAg-positive chronic hepatitis B by impairing CD8+ T and NK cell function

Pegylated interferon-alpha (PegIFNα) therapy has limited effectiveness in hepatitis B e-antigen (HBeAg)-positive chronic hepatitis B (CHB) patients. However, the mechanism underlying this failure is poorly understood. We aimed to investigate the influence of bile acids (BAs), especially taurocholic acid (TCA), on the response to PegIFNα therapy in CHB patients. Here, we used mass spectrometry to determine serum BA profiles in 110 patients with chronic HBV infection and 20 healthy controls (HCs). We found that serum BAs, especially TCA, were significantly elevated in HBeAg-positive CHB patients compared with those in HCs and patients in other phases of chronic HBV infection. Moreover, serum BAs, particularly TCA, inhibited the response to PegIFNα therapy in HBeAg-positive CHB patients. Mechanistically, the expression levels of IFN-γ, TNF-α, granzyme B, and perforin were measured using flow cytometry to assess the effector functions of immune cells in patients with low or high BA levels. We found that BAs reduced the number and proportion and impaired the effector functions of CD3+CD8+ T cells and natural killer (NK) cells in HBeAg-positive CHB patients. TCA in particular reduced the frequency and impaired the effector functions of CD3+CD8+ T and NK cells in vitro and in vivo and inhibited the immunoregulatory activity of IFN-α in vitro. Thus, our results show that BAs, especially TCA, inhibit the response to PegIFNα therapy by impairing the effector functions of CD3+CD8+ T and NK cells in HBeAg-positive CHB patients. Our findings suggest that targeting TCA could be a promising approach for restoring IFN-α responsiveness during CHB treatment.

Long-term intervention of taurocholic acid over-expressing in cholestatic liver disease inhibits the growth of hepatoma cells

Bile acids usually build up in patients with cholestatic liver disease. It was found that the concentration of taurocholic acid (TCA), one of the taurine conjugates of primary bile acids in serum, was elevated the most. While the role played by TCA in the disease is unclear, there is concern whether TCA contributes to the development of hepatocarcinoma from cholestasis. In the present study, the cell viability, flow cytometry, real-time polymerase chain reaction, intracellular ROS measurement, and intracellular Ca2+ measurement were used to investigate the effects of TCA on THLE-2 and HepG2 cells. The results showed that TCA is capable of inhibiting HepG2 cell growth whereas it has relatively little or no impact on that of THLE-2 cells until later stages of 16-day treatment. The growth inhibition is a result of cell apoptosis induced by the increase of Ca2+ and ROS level, and also associated with the increased expression of c-Myc, CEBPα, TNF-α, ICAM-1, VCAM-1, CXCL-2, Egr-1. HepG2 growth inhibition could contribute to the research on the treatment methods of patients already with hepatocarcinoma.

Systemic bile acids induce insulin resistance in a TGR5-independent manner

Bile acids are involved in the emulsification and absorption of dietary fats, as well as acting as signaling molecules. Recently, bile acid signaling through farnesoid X receptor and G protein-coupled bile acid receptor (TGR5) has been reported to elicit changes in not only bile acid synthesis but also metabolic processes, including the alteration of gluconeogenic gene expression and energy expenditure. A role for bile acids in glucose metabolism is also supported by a correlation between changes in the metabolic state of patients (i.e., obesity or postbariatric surgery) and altered serum bile acid levels. However, despite evidence for a role for bile acids during metabolically challenging settings, the direct effect of elevated bile acids on insulin action in the absence of metabolic disease has yet to be investigated. The present study examines the impact of acutely elevated plasma bile acid levels on insulin sensitivity using hyperinsulinemic-euglycemic clamps. In wild-type mice, elevated bile acids impair hepatic insulin sensitivity by blunting the insulin suppression of hepatic glucose production. The impaired hepatic insulin sensitivity could not be attributed to TGR5 signaling, as TGR5 knockout mice exhibited a similar inhibition of insulin suppression of hepatic glucose production. Canonical insulin signaling pathways, such as hepatic PKB (or Akt) activation, were not perturbed in these animals. Interestingly, bile acid infusion directly into the portal vein did not result in an impairment in hepatic insulin sensitivity. Overall, the data indicate that acute increases in circulating bile acids in lean mice impair hepatic insulin sensitivity via an indirect mechanism.

Conjugated Bile Acids Promote Invasive Growth of Esophageal Adenocarcinoma Cells and Cancer Stem Cell Expansion via Sphingosine 1-Phosphate Receptor 2-Mediated Yes-Associated Protein Activation

Esophageal adenocarcinoma (EAC) is the sixth leading cause of cancer deaths worldwide and has been dramatically increasing in incidence over the past decade. Gastroesophageal reflux and Barrett esophagus are well-established risk factors for disease progression. Conjugated bile acids (CBAs), including taurocholate (TCA), represent the major bile acids in the gastroesophageal refluxate of advanced Barrett esophagus and EAC patients. Our previous studies suggested that CBA-induced activation of sphingosine 1-phosphate receptor 2 (S1PR2) plays a critical role in promoting cholangiocarcinoma cell invasive growth. However, the role of CBAs in EAC development and underlying mechanisms remains elusive. In the current study, we identified that the expression level of S1PR2 is correlated to invasiveness of EAC cells. TCA significantly promoted cell proliferation, migration, invasion, transformation, and cancer stem cell expansion in highly invasive EAC cells (OE-33 cells), but had less effect on the lower invasive EAC cells (OE-19 cells). Pharmacologic inhibition of S1PR2 with specific antagonist JTE-013 or knockdown of S1PR2 expression significantly reduced TCA-induced invasive growth of OE-33 cells, whereas overexpression of S1PR2 sensitized OE-19 cells to TCA-induced invasive growth. Furthermore, TCA-induced activation of S1PR2 was closely associated with YAP and β-catenin signaling pathways. In conclusion, CBA-induced activation of the S1PR2 signaling pathway is critically involved in invasive growth of EAC cells and represents a novel therapeutic target for EAC.

Oral siRNA Delivery to Treat Colorectal Liver Metastases

Convenient multiple dosing makes oral administration an ideal route for delivery of therapeutic siRNA. However, hostile GI environments and nonspecific biological trafficking prevent achieving appropriate bioavailability of siRNA. Here, an orally administered AuNP-siRNA-glycol chitosan-taurocholic acid nanoparticle (AR-GT NPs) was developed to selectively deliver Akt2 siRNA and treat colorectal liver metastases (CLM). AR-GT NPs are dual padlocked nonviral vectors in which the initially formed AuNP-siRNA (AR) conjugates are further encompassed by bifunctional glycol chitosan-taurocholic acid (GT) conjugates. Covering the surface of AR with GT protected the Akt2 siRNA from GI degradation, facilitated active transport through enterocytes, and enhanced selective accumulation in CLM. Our studies in CLM animal models resulted in the reduction in Akt2 production, followed by initiation of apoptosis in cancer cells after oral administration of Akt2 siRNA-loaded AR-GT. This therapeutic siRNA delivery system may be a promising approach in treating liver-associated diseases.

Ursodeoxycholic acid prevents ventricular conduction slowing and arrhythmia by restoring T-type calcium current in fetuses during cholestasis

Background

Increased maternal serum bile acid concentrations in intrahepatic cholestasis of pregnancy (ICP) are associated with fetal cardiac arrhythmias. Ursodeoxycholic acid (UDCA) has been shown to demonstrate anti-arrhythmic properties via preventing ICP-associated cardiac conduction slowing and development of reentrant arrhythmias, although the cellular mechanism is still being elucidated.

Methods

High-resolution fluorescent optical mapping of electrical activity and electrocardiogram measurements were used to characterize effects of UDCA on one-day-old neonatal and adult female Langendorff-perfused rat hearts. ICP was modelled by perfusion of taurocholic acid (TC, 400μM). Whole-cell calcium currents were recorded from neonatal rat and human fetal cardiomyocytes.

Results

TC significantly prolonged the PR interval by 11.0±3.5% (P<0.05) and slowed ventricular conduction velocity (CV) by 38.9±5.1% (P<0.05) exclusively in neonatal and not in maternal hearts. A similar CV decline was observed with the selective T-type calcium current (I_Ca,T) blocker mibefradil 1μM (23.0±6.2%, P<0.05), but not with the L-type calcium current (I_Ca,L) blocker nifedipine 1μM (6.9±6.6%, NS). The sodium channel blocker lidocaine (30μM) reduced CV by 60.4±4.5% (P<0.05). UDCA co-treatment was protective against CV slowing induced by TC and mibefradil, but not against lidocaine. UDCA prevented the TC-induced reduction in the I_Ca,T density in both isolated human fetal (−10.2±1.5 versus −5.5±0.9 pA/pF, P<0.05) and neonatal rat ventricular myocytes (−22.3±1.1 versus −9.6±0.8 pA/pF, P<0.0001), whereas UDCA had limited efficacy on the I_Ca,L.

Conclusion

Our findings demonstrate that I_Ca,T plays a significant role in ICP-associated fetal cardiac conduction slowing and arrhythmogenesis, and is an important component of the fetus-specific anti-arrhythmic activity of UDCA.

Investigation of Glycochenodeoxycholate Sulfate and Chenodeoxycholate Glucuronide as Surrogate Endogenous Probes for Drug Interaction Studies of OATP1B1 and OATP1B3 in Healthy Japanese Volunteers

PURPOSE

To assess the use of glycochenodeoxycholate-3-sulfate (GCDCA-S) and chenodeoxycholate 3- or 24-glucuronide (CDCA-3G or -24G) as surrogate endogenous substrates in the investigation of drug interactions involving OATP1B1 and OATP1B3.

METHODS

Uptake of GCDCA-S and CDCA-24G was examined in HEK293 cells transfected with cDNA for OATP1B1, OATP1B3, and NTCP and in cryopreserved human hepatocytes. Plasma concentrations of bile acids and their metabolites (GCDCA-S, CDCA-3G, and CDCA-24G) were determined by LC-MS/MS in eight healthy volunteers with or without administration of rifampicin (600 mg, po).

RESULTS

GCDCA-S and CDCA-24G were substrates for OATP1B1, OATP1B3, and NTCP. The uptake of [³H]atorvastatin, GCDCA-S, and CDCA-24G by human hepatocytes was significantly inhibited by both rifampicin and pioglitazone, whereas that of taurocholate was inhibited only by pioglitazone. Rifampicin elevated plasma concentrations of GCDCA-S more than those of other bile acids. The area under the plasma concentration-time curve for GCDCA-S was 20.3 times higher in rifampicin-treated samples. CDCA-24G could be detected only in plasma from the rifampicin-treatment phase, and CDCA-3G was undetectable in both phases.

CONCLUSIONS

We identified GCDCA-S and CDCA-24G as substrates of NTCP, OATP1B1, and OATP1B3. GCDCA-S is a surrogate endogenous probe for the assessment of drug interactions involving hepatic OATP1B1 and OATP1B3.

Bile-Induced Laryngitis: Is There a Basis in Evidence?

Most agree that bile reflux occurs with regularity in an otherwise healthy population and that biliary and acid reflux may play a synergistic role in damaging esophageal mucosa. But to what extent is laryngeal mucosa at risk? We constructed a saline-controlled rat model (n = 40) in which active component solutions of bile — taurocholic acid and chenodeoxycholic acid — were applied to intact laryngeal mucosa at various pH levels. Histologic sampling of the laryngeal mucosa allowed inflammation scores to be generated by a pathologist blinded to the solutions used. Both taurocholic acid at acid pH and chenodeoxycholic acid at basic pH preferentially induced statistically greater inflammation scores than did the saline control, approaching or exceeding inflammation scores attributed to hydrochloric acid at pH 1.2. These observations may clarify reasons for failure to uniformly control laryngeal injury by adequate suppression of gastric acid alone and may further justify alternative methods of laryngeal protection in patients refractory to adequate acid control.

Phage Transduction

Bacteriophages mediate horizontal gene transfer through a mechanism known as transduction. Phage transduction carried out in the laboratory involves a bacterial donor and a recipient, both of which are susceptible to infection by the phage of interest. Phage is propagated in the donor, concentrated, and exposed transiently to recipient at different multiplicity of infection ratios. Transductants are selected for the desired phenotype by culture on selective medium. Here we describe transduction of ermB conferring resistance to erythromycin by the C. difficile phage ϕC2.

Enhancement of sodium taurocholate to the absorption of cefquinome

The objective of the research was to detect the enhancement effect of sodium taurocholate on the absorption of cefquinome both in Caco-2 cells and rats. The absorption efficiency of cefquinome was determined by high performance liquid chromatography and calculated with apparent permeability coefficients (Papp) after Caco-2 cell monolayers treated odium taurocholate(2 mmol/L) and cefquinome. The results showed that the absorption of cefquinome in Caco-2 cell monolayers was significantly increased with the sodium taurocholate (2mmol/L). Similar results were also detected in the rats orally administrated with 1 mL PBS of cefquinome (20mg/mL) containing different concentration of sodium taurocholate (5 mmol/L, 10mmol/L and 20mmol/L) respectively. Compared with control group, sodium taurocholate at 10 and 20 mmol/L increased the absorption of cefquinome in rats from 0.26±0.04μg/mL to 0.57±0.03μg/mL, 0.78 ±0.07μg/mL respectively. These results indicated that sodium taurocholate could increase the intestinal permeability in a concentration-dependent mode, which will be useful for clinical treatment.

Regulation of human hepatic drug transporter activity and expression by diesel exhaust particle extract

Diesel exhaust particles (DEPs) are common environmental air pollutants primarily affecting the lung. DEPs or chemicals adsorbed on DEPs also exert extra-pulmonary effects, including alteration of hepatic drug detoxifying enzyme expression. The present study was designed to determine whether organic DEP extract (DEPe) may target hepatic drug transporters that contribute in a major way to drug detoxification. Using primary human hepatocytes and transporter-overexpressing cells, DEPe was first shown to strongly inhibit activities of the sinusoidal solute carrier (SLC) uptake transporters organic anion-transporting polypeptides (OATP) 1B1, 1B3 and 2B1 and of the canalicular ATP-binding cassette (ABC) efflux pump multidrug resistance-associated protein 2, with IC50 values ranging from approximately 1 to 20 μg/mL and relevant to environmental exposure situations. By contrast, 25 μg/mL DEPe failed to alter activities of the SLC transporter organic cation transporter (OCT) 1 and of the ABC efflux pumps P-glycoprotein and bile salt export pump (BSEP), whereas it only moderately inhibited those of sodium taurocholate co-transporting polypeptide and of breast cancer resistance protein (BCRP). Treatment by 25 μg/mL DEPe was next demonstrated to induce expression of BCRP at both mRNA and protein level in cultured human hepatic cells, whereas it concomitantly repressed mRNA expression of various transporters, including OATP1B3, OATP2B1, OCT1 and BSEP. Such changes in transporter expression were found to be highly correlated to those caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a reference activator of the aryl hydrocarbon receptor (AhR) pathway. This suggests that DEPe, which is enriched in known ligands of AhR like polycyclic aromatic hydrocarbons, alters drug transporter expression via activation of the AhR cascade. Taken together, these data established human hepatic transporters as targets of organic chemicals containing in DEPs, which may contribute to their systemic effects through impairing hepatic transport of endogenous compound or drug substrates of these transporters.

Simultaneous bile duct and portal vein ligation induces faster atrophy/hypertrophy complex than portal vein ligation: role of bile acids

Portal vein ligation (PVL) induces atrophy/hypertrophy complex (AHC). We hypothesised that simultaneous bile duct and portal vein ligation (BPL) might induce proper bile acid (BA) retention to enhance AHC by activating BA-mediated FXR signalling in the intact liver and promoting apoptosis in the ligated liver. We established rat models of 90% BPL and 90% PVL and found that BPL was well-tolerated and significantly accelerated AHC. The enhanced BA retention in the intact liver promoted hepatocyte proliferation by promoting the activation of FXR signalling, while that in the ligated liver intensified caspase3-mediated apoptosis. Decreasing the BA pools in the rats that underwent BPL could compromise these effects, whereas increasing the bile acid pools of rats that underwent PVL could induce similar effects. Second-stage resection of posterior-caudate-lobe-spearing hepatectomy was performed 5 days after BPL (B-Hx), PVL (V-Hx) or sham (S-SHx), as well as whole-caudate-lobe-spearing hepatectomy 5 days after sham (S-Hx). The B-Hx group had the most favourable survival rate (93.3%, the S-SHx group 0%, the S-Hx group 26.7%, the V-Hx group 56.7%, P < 0.01) and the most sustained regeneration. We conclude that BPL is a safe and effective method, and the acceleration of AHC was bile acid-dependent.

Cholic acid induces a Cftr dependent biliary secretion and liver growth response in mice

The cause of Cystic fibrosis liver disease (CFLD), is unknown. It is well recognized that hepatic exposure to hydrophobic bile salts is associated with the development of liver disease. For this reason, we hypothesize that, CFTR dependent variations, in the hepatic handling of hydrophobic bile salts, are related to the development CFLD. To test our hypothesis we studied, in Cftr^-/- and control mice, bile production, bile composition and liver pathology, in normal feeding condition and during cholate exposure, either acute (intravenous) or chronic (three weeks via the diet). In Cftr^-/- and control mice the basal bile production was comparable. Intravenous taurocholate increased bile production to the same extent in Cftr^-/- and control mice. However, chronic cholate exposure increased the bile flow significantly less in Cftr^-/- mice than in controls, together with significantly higher biliary bile salt concentration in Cftr^-/- mice. Prolonged cholate exposure, however, did not induce CFLD like pathology in Cftr^-/- mice. Chronic cholate exposure did induce a significant increase in liver mass in controls that was absent in Cftr^-/- mice. Chronic cholate administration induces a cystic fibrosis-specific hepatobiliary phenotype, including changes in bile composition. These changes could not be associated with CFLD like pathological changes in CF mouse livers. However, chronic cholate administration induces liver growth in controls that is absent in Cftr^-/- mice. Our findings point to an impaired adaptive homeotrophic liver response to prolonged hydrophobic bile salt exposure in CF conditions.

Contaminant-specific targeting of olfactory sensory neuron classes: connecting neuron class impairment with behavioural deficits

The olfactory system of fish comprises several classes of olfactory sensory neurons (OSNs). The odourants L-alanine and taurocholic acid (TCA) specifically activate microvillous or ciliated OSNs, respectively, in fish. We recorded electro-olfactograms (EOG) in fathead minnows (Pimephales promelas; a laboratory-reared model species) and wild yellow perch (Perca flavescens) whose olfactory chambers were perfused with either L-alanine or TCA to determine if OSN classes were differentially vulnerable to contaminants, in this case copper or nickel. Results were consistent in both species and demonstrated that nickel targeted and impaired microvillous OSN function, while copper targeted and impaired ciliated OSN function. This result suggests that contaminant-specific effects observed in model laboratory species extrapolate to wild fish populations. Moreover, fathead minnows exposed to copper failed to perceive a conspecific alarm cue in a choice maze, whereas those exposed to nickel could respond to the same conspecific cue. These results demonstrate that fathead minnows perceive conspecific, damage-released alarm cue by ciliated, but not microvillous, OSNs. Fish living in copper-contaminated environments may be more vulnerable to predation than those in clean lakes owing to targeted effects on ciliated OSNs.

Molecular regulation of organic anion transporting polypeptide 1A2 (OATP1A2)by taurocholic acid in Bewo Cells

To characterize the mechanisms of action of taurocholic acid(TCA) and farnesoid X receptor(FXR) on organic anion transporting polypeptide 1A2(OATP1A2) expression in placental Bewo cell line. Quantitative real-time PCR and Western blots were used to detect OATP1A2 in Bewo cells cultured with TCA and pcDNA3.1(+)-hFXR transfected Bewo cells after incubation with 2 mM TCA for 48 hours. TCA(0.02 mM) induced the mRNA and protein expression of OATP1A2 by 3 and 1.6 fold (p<0.05), respectively, while 0.2 and 2 mM TCA induced mRNA and protein expression by 1.5 and 1.3 fold, respectively. The concentration of TCA was negatively correlated with OATP1A2 gene expression (P<0.05). In pcDNA3.1(+)-hFXR transfected Bewo cells with 2 mM TCA demonstrated a 2-3 fold increase in OATP1A2 over controls (P<0.05). TCA is one of the regulation factors for OATP1A2 in the Bewo cell line. A low dose of TCA can induce fetal membrane expression of OATP1A2. This may present a physiological or compensatory mechanism of the placenta, while the high dose of TCA may produce a pathological or pathogenic mechanism. Farnesoid X receptor may act in synergy with TCA to increase the expression of OATP1A2. This may be a treatment strategy for fetal cholestasis.

Taurocholic Acid Does Not Induce Apoptosis in HCT116 Cells Regardless of Its Intracellular Concentration

Hydrophobic bile acids but not hydrophilic bile acids induce apoptosis in HCT116 cells. We expressed sodium-dependent bile acid transporters in HCT116 cells, and the intracellular concentration of hydrophilic bile acids increased to that of the hydrophobic bile acids. But no sign of apoptosis was observed, which suggests a hydrophobic-bile acid-specific mechanism for the induction of apoptosis in HCT116 cells.

LKB1/AMPK and PKA control ABCB11 trafficking and polarization in hepatocytes

Polarization of hepatocytes is manifested by bile canalicular network formation and activation of LKB1 and AMPK, which control cellular energy metabolism. The bile acid, taurocholate, also regulates development of the canalicular network through activation of AMPK. In the present study, we used collagen sandwich hepatocyte cultures from control and liver-specific LKB1 knockout mice to examine the role of LKB1 in trafficking of ABCB11, the canalicular bile acid transporter. In polarized hepatocytes, ABCB11 traffics from Golgi to the apical plasma membrane and endogenously cycles through the rab 11a-myosin Vb recycling endosomal system. LKB1 knockout mice were jaundiced, lost weight and manifested impaired bile canalicular formation and intracellular trafficking of ABCB11, and died within three weeks. Using live cell imaging, fluorescence recovery after photobleaching (FRAP), particle tracking, and biochemistry, we found that LKB1 activity is required for microtubule-dependent trafficking of ABCB11 to the canalicular membrane. In control hepatocytes, ABCB11 trafficking was accelerated by taurocholate and cAMP; however, in LKB1 knockout hepatocytes, ABCB11 trafficking to the apical membrane was greatly reduced and restored only by cAMP, but not taurocholate. cAMP acted through a PKA-mediated pathway which did not activate AMPK. Our studies establish a regulatory role for LKB1 in ABCB11 trafficking to the canalicular membrane, hepatocyte polarization, and canalicular network formation.

[Enhancers on the transmembrane transport of chlorogenic acid]

To investigate the influence of the difference enhancers on the transport mechanism of chlorogenic acid (CGA) across Caco-2 cells model, a RP-HPLC method was adopted to detect the concentrations of CGA. At the concentrations of 20 to 80 microg x mL(-1), the difference of absorption rate constants (K(a)) was not statistically significant. At the concentrations of 40 and 20 microg x mL(-1), the ratios of apparent permeability coefficients (P(app)) of the apical to basolateral and the basolateral to apical were 1.14 and 1.18, respectively. With the effect of enhancers K(a) and P(app) increased, the absorption half-life (T1/2) decreased. CGA passed through the Caco-2 cell membrane mainly by passive transport. It showed that monocarboxylic acid transporter (MCT) could be involved in the across membrane transport process of CGA. Borneol had no effect on the cell membrane transport processes. The order of increasing absorption of CGA caused by the enhancers was sodium lauryl sulphate > sodium taurocholate > carbomer.

Evaluation of the endothelin receptor antagonists ambrisentan, bosentan, macitentan, and sitaxsentan as hepatobiliary transporter inhibitors and substrates in sandwich-cultured human hepatocytes

Background

Inhibition of the transporter-mediated hepatobiliary elimination of bile salts is a putative mechanism for liver toxicity observed with some endothelin receptor antagonists (ERAs).

Methods

Sandwich-cultured human hepatocytes were used to study the hepatobiliary distribution and accumulation of exogenous taurocholate, ERAs and endogenous bile acids. The molecular mechanisms for findings in hepatocytes or clinical observations were further explored using either vesicular assays (efflux transporters) or transfected cell-lines (uptake transporters). Inhibition constants (IC₅₀) were measured for the human hepatobiliary transporters bile salt export pump (BSEP), sodium taurocholate cotransporting polypeptide (NTCP), multidrug resistance protein 2 (MRP2), P-glycoprotein (Pgp), breast cancer resistance protein (BCRP), organic anion-transporting polypeptide 1B1 (OATP1B1) and OATP1B3.

Results

The ERAs showed dose-dependent reductions in exogenous taurocholate cellular accumulation in human hepatocytes, with macitentan having the greatest effect. Consistent with their effects on bile acids, the ERAs inhibited bile transporters. IC₅₀ values for OATP1B1 and OATP1B3 ranged from 2 µM for macitentan to 47 µM for ambrisentan. Macitentan and bosentan also inhibited NTCP with IC₅₀ values of 10 and 36 µM, respectively. Similar to previously reported findings with sitaxsentan, BSEP inhibition was observed for bosentan and macitentan with IC₅₀ values of 42 and 12 µM, respectively. In contrast, ambrisentan showed little or no inhibition of these transporters. Other transporters tested were weakly inhibited by the ERAs. Accumulation in hepatocytes was also a factor in the effects on bile transport. Macitentan demonstrated the greatest accumulation in human hepatocytes (∼100x) followed by sitaxsentan (∼40x), bosentan (∼20x) and ambrisentan (∼2x).

Conclusions

Significant differences in the inhibition of hepatic transporters were observed between the evaluated ERAs in vitro. Macitentan had the highest level of cellular accumulation and caused the greatest effects on bile acid distribution in human hepatocytes followed by sitaxsentan and bosentan. Ambrisentan showed a low potential to affect bile acids.

Surveillance of intra-abdominal pressure and intestinal barrier function in a rat model of acute necrotizing pancreatitis and its potential early therapeutic window

OBJECTIVES

To monitor intra-abdominal pressure (IAP) and intestinal barrier function in a rat model of acute necrotizing pancreatitis (ANP) to elucidate a potential relevant therapeutic window.

METHODS

Sprague-Dawley rats were randomly divided into experimental or control groups. The ANP group (n = 40) was injected with 4.5% sodium taurocholate into the pancreatic duct to induce ANP. The controls received only abdominal opening surgery (sham-operated, SO; n = 40) or no treatment or surgery (baseline; 0 h, n = 20). The SO and ANP groups were then randomly subdivided into 3, 6, 12 and 24 h groups (n = 10 each). IAP was measured at each time point and the rats were sacrificed to measure the weight of accumulated ascites fluid and the amylase, endogenous creatinine (Cr), total bilirubin (TB), tumor necrosis factor- alpha (TNF-alpha), diamine oxidase (DAO), and D-lactate. Mortality and the development of pathological changes in the pancreas and intestines were also monitored.

RESULTS

IAP showed a continuous upward trend in the ANP group, with values 2 to 3 times higher than those in the SO group at the corresponding time points and the rising rate was peaking at 6 h. The levels of plasma amylase, TNF-alpha, Cr, TB, DAO, and D-lactate also gradually increased in the ANP group over time and were significantly higher than in the SO group at 3, 6, 12 and 24 h (all P<0.05). Moreover, the rising rate of TNF-alpha, DAO, and D-lactate also peaked at 6 h.

CONCLUSIONS

The ANP-induced changes in IAP, inflammatory factors and intestinal barrier that we observed in the rat model were especially obvious at 6 h post-induction, suggesting an early therapeutic window for the treatment of ANP in humans.

Bile salt inhibition of host cell damage by Clostridium difficile toxins

Virulent Clostridium difficile strains produce toxin A and/or toxin B that are the etiological agents of diarrhea and pseudomembranous colitis. Treatment of C. difficile infections (CDI) has been hampered by resistance to multiple antibiotics, sporulation, emergence of strains with increased virulence, recurrence of the infection, and the lack of drugs that preserve or restore the colonic bacterial flora. As a result, there is new interest in non-antibiotic CDI treatments. The human conjugated bile salt taurocholate was previously shown in our laboratory to inhibit C. difficile toxin A and B activities in an in vitro assay. Here we demonstrate for the first time in an ex vivo assay that taurocholate can protect Caco-2 colonic epithelial cells from the damaging effects of the C. difficile toxins. Using caspase-3 and lactate dehydrogenase assays, we have demonstrated that taurocholate reduced the extent of toxin B-induced apoptosis and cell membrane damage. Confluent Caco-2 cells cultured with toxin B induced elevated caspase-3 activity. Remarkably, addition of 5 mM taurocholate reduced caspase-3 activity in cells treated with 2, 4, 6, and 12 µg/ml of toxin B by 99%, 78%, 64%, and 60%, respectively. Furthermore, spent culture medium from Caco-2 cells incubated with both toxin B and taurocholate exhibited significantly decreased lactate dehydrogenase activity compared to spent culture medium from cells incubated with toxin B only. Our results suggest that the mechanism of taurocholate-mediated inhibition functions at the level of toxin activity since taurocholate did not affect C. difficile growth and toxin production. These findings open up a new avenue for the development of non-antibiotic therapeutics for CDI treatment.

Fate of ingested Clostridium difficile spores in mice

Clostridium difficile infection (CDI) is a leading cause of antibiotic-associated diarrhea, a major nosocomial complication. The infective form of C. difficile is the spore, a dormant and resistant structure that forms under stress. Although spore germination is the first committed step in CDI onset, the temporal and spatial distribution of ingested C. difficile spores is not clearly understood. We recently reported that CamSA, a synthetic bile salt analog, inhibits C. difficile spore germination in vitro and in vivo. In this study, we took advantage of the anti-germination activity of bile salts to determine the fate of ingested C. difficile spores. We tested four different bile salts for efficacy in preventing CDI. Since CamSA was the only anti-germinant tested able to prevent signs of CDI, we characterized CamSa’s in vitro stability, distribution, and cytotoxicity. We report that CamSA is stable to simulated gastrointestinal (GI) environments, but will be degraded by members of the natural microbiota found in a healthy gut. Our data suggest that CamSA will not be systemically available, but instead will be localized to the GI tract. Since in vitro pharmacological parameters were acceptable, CamSA was used to probe the mouse model of CDI. By varying the timing of CamSA dosage, we estimated that C. difficile spores germinated and established infection less than 10 hours after ingestion. We also showed that ingested C. difficile spores rapidly transited through the GI tract and accumulated in the colon and cecum of CamSA-treated mice. From there, C. difficile spores were slowly shed over a 96-hour period. To our knowledge, this is the first report of using molecular probes to obtain disease progression information for C. difficile infection.

Effects of rectal administration of taurocholic acid on glucagon-like peptide-1 and peptide YY secretion in healthy humans

Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), secreted by enteroendocrine L-cells located most densely in the colon and rectum, are of fundamental importance in blood glucose and appetite regulation. In animal models, colonic administration of bile acids can stimulate GLP-1 and PYY by TGR5 receptor activation. We evaluated the effects of taurocholic acid (TCA), administered as an enema, on plasma GLP-1 and PYY, as well as gastrointestinal sensations in 10 healthy male subjects, and observed that rectal administration of TCA promptly stimulated secretion of both GLP-1 and PYY, and increased fullness, in a dose-dependent manner. These observations confirm that topical application of bile acids to the distal gut may have potential for the management of type 2 diabetes and obesity.

Time-course proteomic analysis of taurocholate-induced necrotizing acute pancreatitis

Acute pancreatitis is an inflammatory disease of the pancreas, which varies greatly in course and severity. Severe forms are associated with serious local and/or systemic complications, and eventually death. The pathobiology of acute pancreatitis is complex. Animal models have been developed to investigate pathobiological processes and identify factors determining disease course. We performed a time-course proteomic analysis using a rat model of severe necrotizing acute pancreatitis induced by taurocholate perfusion in the pancreatic ducts. Results showed that levels of proteins associated to a given biological process changed in a coordinated fashion after disease onset. It was possible to follow the response of a particular pathobiological process to pancreatitis induction and to compare the course of protein pathways. Proteins involved in acinar cell secretion were found to follow a different kinetics than other cellular processes. After an initial decrease, secretory pathway-associated proteins raised again at 18 h post-induction. This phenomenon coincided with a burst in the expression of pancreatitis-associated protein (REG3A), an acute phase protein produced by the exocrine pancreas, and with the decrease of classical markers of pancreatic injury, suggesting that the expression of proteins associated to the secretory pathway may be a modulating factor of pancreas injury.

BIOLOGICAL SIGNIFICANCE

Acute pancreatitis (AP) is a complex inflammatory disease, the pathobiology of which is not yet fully understood. Various animal models, relying on different mechanisms of disease induction, have been developed in order to investigate pathobiological processes of AP. In this study, we performed a time-course proteomic analysis to investigate changes of the pancreas proteome occurring in an experimental model of AP induced by perfusion of taurocholate, a bile acid, into the pancreatic duct. This experimental model is characterized by a severe disease with pancreatic necrosis and systemic inflammation. The objectives of this study were to determine the kinetics of functionally related proteins in the early steps of the experimental disease in order to identify protein pathways playing key roles in AP pathobiology and to correlate these data with parameters classically used to assess disease severity. The present work provides for the first time an overview of protein expression in the pancreas during the course of taurocholate-induced necrotizing AP. We believe that correlation of these results with data obtained using proteomic or biochemical approaches in various experimental models of AP will help in highlighting new features, generating hypotheses and constitute therefore a strong and reliable basis for further targeted investigations.

Effects of taurocholic acid on glycemic, glucagon-like peptide-1, and insulin responses to small intestinal glucose infusion in healthy humans

CONTEXT

In vitro and animal studies suggest that bile acids have the capacity to reduce blood glucose by stimulating glucagon-like peptide-1 (GLP-1) and, thereby, insulin.

OBJECTIVE

This study evaluated the effects of intrajejunal taurocholic acid (TCA) on blood glucose, GLP-1, and insulin responses to jejunal glucose infusion in healthy men.

PARTICIPANTS AND DESIGN

Ten healthy men were each studied on 2 days in a double-blind, randomized order. After the subjects fasted overnight, a jejunal catheter was positioned and a balloon inflated 30 cm beyond the pylorus with aspiration of endogenous bile. Two grams TCA in saline, or saline control, was infused beyond the balloon over 30 minutes, followed by 2 g TCA or control, together with 60 g glucose, over the next 120 minutes. Blood was sampled frequently for the measurements of blood glucose, total GLP-1, insulin, C-peptide, and glucagon.

RESULTS

Intrajejunal infusion of TCA alone (t = -30 to 0 minutes) had no effect on blood glucose, GLP-1, insulin, C-peptide, or glucagon concentrations. During intrajejunal glucose infusion (t = 0 to 120 minutes), blood glucose concentrations were lower (P < .001), and plasma GLP-1 (P < .001) and the C-peptide/glucose ratio (P = .008) were both greater, whereas plasma insulin, C-peptide, and glucagon levels were not significantly different after TCA than after control.

CONCLUSIONS

In healthy humans, small intestinal infusion of TCA potently reduces the glycemic response to small intestinal glucose, associated with an increase in GLP-1 and C-peptide/glucose ratio. These observations indicate the potential for bile acid-based therapy in type 2 diabetes.

An apoptosis-homing peptide-conjugated low molecular weight heparin-taurocholate conjugate with antitumor properties

Various angiogenesis inhibitors and apoptosis-targeting agents have been therapeutically applied in preclinical cancer models, some of which have been tested in clinical trials. In a previous study, we demonstrated that LHT7, a low molecular weight heparin (LMWH)-taurocholate conjugate, has strong antiangiogenic and tumor-suppressive activity and diminished anticoagulant properties. In this study, we developed LHT7-ApoPep-1, an apoptosis-homing peptide-conjugated variant of LHT7. LHT7-ApoPep-1 exhibited antiangiogenic activity in endothelial cell tube-formation assays and apoptotic cell-targeting ability in tumor cell binding assays; it also showed little toxicity toward healthy cells. Administration of LHT7-ApoPep-1 in mouse xenograft models of breast carcinoma delayed tumor growth compared to LHT7-only, and histological evaluations revealed decreased vessel formation and increased apoptotic area in tumor tissues. Moreover, an examination of LHT7-ApoPep-1-Cy7.5 localization within the body using in vivo live imaging showed accumulation at the tumor site of tumor-bearing mice, with a more prolonged circulation time and enhanced intensity compared to LHT7-Cy7.5. Inspection of the tumor microenvironment revealed that Cy5.5-labeled LHT7-ApoPep-1 was located on and near CD31-positive vessels in tumor tissue. We conclude that LHT7-ApoPep-1 has antiangiogenic and apoptosis-targeting properties and exerts antitumor effects by suppressing tumor vessel growth and homing to apoptotic cells within the tumor.

Cyclic RGDyk-conjugated LMWH-taurocholate derivative as a targeting angiogenesis inhibitor

LMWH-taurocholate derivative (LHT7) has been reported as a novel angiogenesis inhibitor, due to its ability to bind to several kinds of growth factors, which play critical roles in tumor angiogenesis. In this study, we have highlighted the enhanced antiangiogenic activity of LHT7, by using cyclic RGDyk (cRGD), a targeting moiety that was chemically conjugated to LHT7 via amide bond. The SPR study revealed that cRGD-LHT7 bound to α(v)β(3) integrin as strongly as cRGD, and it bound to VEGF as strongly as LHT7. Importantly, in vitro anti-angiogenesis studies revealed that cRGD-LHT7 had a significant inhibition effect on HUVEC tubular formation. Finally, cRGD-LHT7 showed a greater inhibitory efficiency on the tumor growth in the U87MG xenograft model than the original LHT7, which was owed to its ability to target the tumor cells. All of these findings demonstrated that cRGD-LHT7 targeted α(v)β(3) integrin-positive cancer cells and endothelial cells, resulting in a greater anti-angiogenesis effect on the solid tumors.

Rectal taurocholate increases L cell and insulin secretion, and decreases blood glucose and food intake in obese type 2 diabetic volunteers

AIMS/HYPOTHESIS

Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are secreted from enteroendocrine L cells in response to numerous stimuli, including bile salts. Both have multiple effects that are potentially useful in treating diabetes and obesity. L cell number and hormone content in the intestine are highest in the rectum in humans. We investigated the effects of intrarectal sodium taurocholate on plasma GLP-1, PYY, insulin and glucose concentrations, and on food intake of a subsequent meal.

METHODS

Ten obese type 2 diabetic volunteers were each studied on five separate occasions after an overnight fast and oral administration of 100 mg sitagliptin 10 h before the study. They then received an intrarectal infusion of either one of four doses of taurocholate (0.66, 2, 6.66 or 20 mmol, each in 20 ml of vehicle) or vehicle alone (1% carboxymethyl cellulose) single-blind over 1 min. Hormone and glucose measurements were made prior to, and for 1 h following, the infusion. The consumption of a previously selected favourite meal eaten to satiety was measured 75 min after the infusion.

RESULTS

Taurocholate dose-dependently increased GLP-1, PYY and insulin, with 20 mmol doses resulting in peak concentrations 7.2-, 4.2- and 2.6-fold higher, respectively, than those achieved with placebo (p < 0.0001 for each). Plasma glucose decreased by up to 3.8 mmol/l (p < 0.001). Energy intake was decreased dose-dependently by up to 47% (p < 0.0001). The ED(50) values for effects on integrated GLP-1, insulin, PYY, food intake and glucose-lowering responses were 8.1, 10.5, 18.5, 24.2 and 25.1 mmol, respectively.

CONCLUSIONS/INTERPRETATION

Therapies that increase bile salts (or their mimics) in the distal bowel may be valuable in the treatment of type 2 diabetes and obesity.

Differences in the inflammatory response induced by acute pancreatitis in different white adipose tissue sites in the rat

BACKGROUND

There is increasing evidence of the role of adipose tissue on the systemic effects of acute pancreatitis. Patients with higher body mass index have increased risk of local and systemic complications and patients with android fat distribution and higher waist circumference are at greater risk for developing the severe form of the disease. Here we evaluated the changes on different areas of adipose tissue and its involvement on the inflammatory response in an experimental model of acute pancreatitis.

METHODS

Pancreatitis was induced in male Wistar rats by intraductal administration of sodium taurocholate. Orlistat was administered to inhibit lipase activity. Activation of peritoneal macrophages was evaluated by measuring IL1β and TNFα expression. Inflammation was evaluated by measuring myeloperoxidase activity in mesenteric, epididymal and retroperitoneal areas of adipose tissue. Changes in the expression of inflammatory mediator in these areas of adipose tissue were also evaluated by RT-PCR.

RESULTS

Pancreatitis induces the activation of peritoneal macrophages and a strong inflammatory response in mesenteric and epididymal sites of adipose tissue. By contrast, no changes were found in retroperitoneal adipose tissue. Inhibition of lipase prevented the activation of macrophages and the local inflammation in adipose tissue.

CONCLUSIONS

Our results confirm the involvement of adipose tissue on the progression of systemic inflammatory response during acute pancreatitis. However, there is a considerable diversity in different adipose tissue sites. These differences need to be taken into account in order to understand the progression from local pancreatic damage to systemic inflammation during acute pancreatitis.

Dietary-fat-induced taurocholic acid promotes pathobiont expansion and colitis in Il10-/- mice

The composite human microbiome of Western populations has probably changed over the past century, brought on by new environmental triggers that often have a negative impact on human health. Here we show that consumption of a diet high in saturated (milk-derived) fat, but not polyunsaturated (safflower oil) fat, changes the conditions for microbial assemblage and promotes the expansion of a low-abundance, sulphite-reducing pathobiont, Bilophila wadsworthia. This was associated with a pro-inflammatory T helper type 1 (T(H)1) immune response and increased incidence of colitis in genetically susceptible Il10(−/−), but not wild-type mice. These effects are mediated by milk-derived-fat-promoted taurine conjugation of hepatic bile acids, which increases the availability of organic sulphur used by sulphite-reducing microorganisms like B. wadsworthia. When mice were fed a low-fat diet supplemented with taurocholic acid, but not with glycocholic acid, for example, a bloom of B. wadsworthia and development of colitis were observed in Il10(−/−) mice. Together these data show that dietary fats, by promoting changes in host bile acid composition, can markedly alter conditions for gut microbial assemblage, resulting in dysbiosis that can perturb immune homeostasis. The data provide a plausible mechanistic basis by which Western-type diets high in certain saturated fats might increase the prevalence of complex immune-mediated diseases like inflammatory bowel disease in genetically susceptible hosts.

Spores of Clostridium difficile clinical isolates display a diverse germination response to bile salts

Clostridium difficile spores play a pivotal role in the transmission of infectious diarrhoea, but in order to cause disease spores must complete germination and return to vegetative cell growth. While the mechanisms of spore germination are well understood in Bacillus, knowledge of C. difficile germination remains limited. Previous studies have shown that bile salts and amino acids play an important role in regulating the germination response of C. difficile spores. Taurocholate, in combination with glycine, can stimulate germination, whereas chenodeoxycholate has been shown to inhibit spore germination in a C. difficile clinical isolate. Our recent studies of C. difficile sporulation characteristics have since pointed to substantial diversity among different clinical isolates. Consequently, in this study we investigated how the germination characteristics of different C. difficile isolates vary in response to bile salts. By analysing 29 isolates, including 16 belonging to the BI/NAP1/027 type, we show that considerable diversity exists in both the rate and extent of C. difficile germination in response to rich medium containing both taurocholate and glycine. Strikingly, we also show that although a potent inhibitor of germination for some isolates, chenodeoxycholate does not inhibit the germination, or outgrowth, of all C. difficile strains. Finally, we provide evidence that components of rich media may induce the germination of C. difficile spores, even in the absence of taurocholate. Taken together, these data suggest that the mechanisms of C. difficile spore germination in response to bile salts are complex and require further study. Furthermore, we stress the importance of studying multiple isolates in the future when analysing the nutrients or chemicals that either stimulate or inhibit C. difficile spore germination.

Cryptosporidium parvum oocyst viability and behaviour of the residual body during the excystation process

This study was conducted as a comparative evaluation of time-dependent changes in the viability of purified Cryptosporidium parvum oocysts by means of different excystation methods. Oocyst samples were 2 weeks to 12 months old and were treated with bile or sodium taurocholate, partly after pretreatment with hypochlorite. Pretreatment markedly enhanced the excystation of younger oocyst samples but did not increase excystation rates of 9 or 12-month-old oocysts. A cell culture-PCR assay was used as a second indicator for oocyst viability and was most consistent with excystation trials including oocyst pretreatment. In experiments aiming at the determination of the behaviour of the oocyst residual body during excystation, it could be demonstrated that it might be involved in this process.

Partial characterization of pyloric-duodenal lipase of gilthead seabream (Sparus aurata)

In the present study, we report the isolation and characterization of seabream Sparus aurata pyloric caeca-duodenal lipase. Optimum activity was found at pH 8.5 and salinity of 50 mM NaCl. Lipase activity was sensitive to divalent ions, and extreme pH values (4, 5, and 12), being more stable at alkaline than acid pH. Optimum temperature was found at 50°C, but lipase was stable at temperatures below 40°C. Lipase has a bile salt sodium taurocholate requirement for increased activity. Gradient PAGE electrophoresis revealed the presence of four isoforms with apparent molecular masses of 34, 50, 68, and 84 KDa, respectively. Pyloric-duodenal lipase was able to hydrolyze emulsified alimentary oils. Results confirm the presence of true lipases in Sparus aurata digestive tract.

Participation of asparagine 370 and glutamine 235 in the catalysis by acid beta-glucosidase: the enzyme deficient in Gaucher disease

The hydrolysis of glucosylceramide by acid beta-glucosidase proceeds via a two-step, double displacement mechanism that includes cleavage of the O-beta-glucosidic bond, enzyme-glucosylation and, then, enzyme-deglucosylation. Two residues that may impact this cycle are N370 and E235. The N370S mutant enzyme is very common in Gaucher disease type 1 patients. Homology and crystal data predictions suggested that E235 is the acid/base catalyst in the hydrolytic reaction. Here, the roles of N370 and E235 in hydrolysis were explored using mutant proteins with selected amino acid substitutions. Heterologously expressed enzymes were characterized using inhibitors, activators, and alternative substrates to gain insight into the effects on the glucosylation (single turnover) and deglucosylation (transglucosylation) steps in catalysis. Specific substitutions at N370 selectively altered only the glucosylation step whereas N370S altered this and the deglucosylation steps. To provide functional data to support E235 as the acid/base catalyst, progress curves with poor substrates with more acidic leaving groups were used in the presence and absence of azide as an exogenous nucleophile. The restoration of E235G activity to nearly wild-type levels was achieved using azide with 2,4-dinitrophenyl-beta-glucoside as substrate. The loss of the acidic arm of the pH optimum activity curve of E235G provided additional functional support for E235 as the acid/base in catalysis. This study provides insight into the function of these residues in acid beta-glucosidase active site function.

Interaction by cholestyramine on the uptake of hydrocortisone in the gastrointestinal tract

An absolute reduction of the plasma cortisol levels and a delay of the peak concentrations were recorded in 10 healthy subjects, when a bile-sequestering anionic exchange resin, cholestyramine, was given prior to a single oral hydrocortisone dose, indicating that the resin interferes with the uptake of a neutral sterol in the human gastrointestinal tract. The possibility of a direct binding of drug to resin is supported by the affinity of hydrocortisone to cholestyramine in vitro, which was uninfluenced by the presence of sodium taurocholate. Cholestyramine significantly delayed the gastric emptying of a glucose solution, indicating that the resin not only decreases but also delays hydrocortisone absorption. Careful supervision is recommended when treatment with cholestyramine is given concomitant to neutral sterol drugs.

Taurocholate feeding to bile duct ligated rats prevents caffeic acid-induced bile duct damage by changes in cholangiocyte VEGF expression

Cholangiocytes are the target cells in cholestatic models of ductal hyperplasia including bile duct ligation (BDL). We have shown that: (i) cholangiocytes express VEGFR-2 and VEGFR-3; (ii) VEGF-A and VEGF-C stimulate cholangiocyte proliferation via an autocrine mechanism; and (iii) chronic administration of VEGF-A prevents cholangiocyte damage induced by hepatic artery ligation. Caffeic acid phenethyl ester (CAPE) induces growth inhibition in different cells. Taurocholic acid (TC) protects cholangiocytes against injury induced by parasympathetic or sympathetic denervation. The aims of this study were to determine if: (i) CAPE induces bile duct damage; and (ii) TC prevents CAPE-induced bile duct damage by increasing cholangiocyte VEGF expression.

METHODS

Normal and BDL rats (immediately after surgery) were fed 1% TC or control diet in the absence/presence of daily IP injections of CAPE (10 mg/Kg BW). One week later, we evaluated: (i) cholangiocyte apoptosis, proliferation and ductal mass in liver sections; (ii) functional activity by measuring secretin-stimulated bile and bicarbonate secretion; and (iii) VEGF-A/C and VEGFR-2/R-3 expression in liver sections. In vitro, BDL cholangiocytes were exposed to CAPE (40 microM) in the absence/presence of TC (40 microM) with and without pretreatment with VEGF receptor inhibitors before evaluating cholangiocyte apoptosis and proliferation.

RESULTS

Chronic CAPE administration to BDL rats increased cholangiocyte apoptosis and decreased ductal mass. This effect was associated with reduced expression of VEGF-A, VEGF-C, VEGFR-2 and VEGFR-3. In vivo, TC feeding partly prevented CAPE-induced changes in cholangiocyte apoptosis and growth and loss of ductal secretion. The protective effect of TC was associated with enhanced VEGF-A, VEGF-C, VEGFR-2 and VEGFR-3. In vitro, TC partially prevented CAPE-induced increases in apoptosis and decreases in cholangiocyte proliferation. These changes were reversed by pretreatment with VEGF-receptor inhibitors.

CONCLUSION

Manipulation of cholangiocyte VEGF expression by bile acids may be important in preventing the impairment of cholangiocyte proliferation by exogenous agents.

Transport evaluation of alendronate across Caco-2 cell monolayers

The transport of alendronate through Caco-2 monolayers in the absence and presence of absorption enhancers (sodium taurocholate-STC and dimethyl-beta-cyclodextrin-DM-beta-CD) was studied. The viability of Caco-2 cells was determined by MTT assay. The effects of the experiment period and serum existence in Dubelco's Modified Eagle's Medium (DMEM) on cell viability were examined. The least toxic concentrations of alendronate, STC and DM-beta-CD were found as 0.2% (w/v), 5 mM and 0.3% (w/v), respectively. Transport experiments were performed with these concentrations in DMEM supplemented with serum for an 8 h period. DM-beta-CD increased the transport of alendronate through Caco-2 monolayers significantly. No significance was observed with STC. Cell integrity was determined by measuring the electrical resistance values at the end of the transport experiments and found to be decreased to a greater extent with DM-beta-CD. These results indicate that DM-beta-CD is a promising agent for improving the transport of alendronate.

Novel oral absorption system containing polyamines and bile salts enhances drug transport via both transcellular and paracellular pathways across Caco-2 cell monolayers

The combinatorial use of spermine (SPM), a typical polyamine, and sodium taurocholate (STC), a typical bile salt, was found to be a promising safe preparation for improving the oral absorption of poorly water-soluble and/or poorly absorbable drug in our previous studies utilizing rats and dogs. To clarify the mechanisms behind the synergistic enhancement effect of the polyamine and bile salt, the transport of rebamipide, which is classified into Biopharmaceutics Classification System Class IV, was investigated in Caco-2 cell monolayers. The synergistic enhancement of rebamipide transport by SPM and STC was certainly observed in Caco-2 cells as well, while the separate use of either SPM or STC did not significantly improve the transport of rebamipide. The combinatorial use of SPM and STC significantly decreased the transepithelial electrical resistance (TEER) in Caco-2 cell monolayers, suggesting that the opening of paracellular pathway. On the other hand, it was also confirmed that the decrease in TEER was transient and reversible after removal of SPM and STC and that cell viability was maintained. Voltage-clamp study clearly showed that their combinatorial use improved rebamipide transport via both paracellular and transcellular pathways, and that the contribution of transcellular route could be larger than paracellular route.

Development of simulated intestinal fluids containing nutrients as transport media in the Caco-2 cell culture model: Assessment of cell viability, monolayer integrity and transport of a poorly aqueous soluble drug and a substrate of efflux mechanisms

The purpose of this study was to identify simulated intestinal fluids (SIFs) containing nutrients compatible with the Caco-2 cell culture model and to examine the impact of the identified medium on the transport of a poorly aqueous soluble model compound, estradiol, and a substrate of efflux mechanisms, etoposide. Monolayer integrity was evaluated by transepithelial electrical resistance and cellular viability by release of lactate dehydrogenase to the apical compartment and cellular protein content. It was shown that the viability of Caco-2 cells was enhanced by use of the CO(2) independent nutritional medium, Leibovitz's L-15 compared to Hanks' balanced salt solution. SIF containing 5mM sodium taurocholate and 1.25 mM phosphatidylcholine or lysophosphatidylcholine in Leibovitz's L-15 induced less release of lactate dehydrogenase than the traditional transport medium, HBSS. Addition of lipolysis products, 0.5mM oleic acid and 0.25 mM monoolein, did only cause increase in lactate dehydrogenase in 3 of 12 comparisons. The presence of SIFs in the apical compartment was shown to decrease flux of estradiol due to incorporation of estradiol in micelles and hence a decreased fraction of free estradiol. Further, a concentration dependent increase in the apparent permeability of etoposide was observed from apical to basolateral compartment, which indicated that components in the SIFs affects efflux mechanisms.

Involvement of prostaglandin E receptor EP3 subtype and prostacyclin IP receptor in decreased acid response in damaged stomach

We investigated the roles of cyclooxygenase (COX) isozymes and prostaglandin E (PGE) receptor EP1 and EP3 subtypes or prostacyclin IP receptors in the decrease in acid secretion in the damaged mouse stomach. Male C57/BL6 mice, both wild type and animals lacking EP1, EP3, or IP receptors, were used after 18 h of fasting. Under urethane anesthesia, the stomach was mounted on an ex-vivo chamber and perfused with saline, and acid secretion as well as transmucosal potential difference (PD) was measured before and after exposure to 20 mM taurocholate Na (TC) for 20 min. Indomethacin, SC-560 or rofecoxib was given i.d. 30 min before TC. Mucosal exposure to TC in wild-type mice caused a reduction in PD, followed by decrease in acid secretion. Indomethacin attenuated the decrease in acid secretion after exposure to TC in wild-type mice, an effect mimicked by SC-560 but not rofecoxib, yet none of these drugs affected the decrease in PD. An altered acid response after exposure to TC was similarly observed in EP1 (-/-) mice but mitigated in mice lacking either EP3 or IP receptors, although a decrease in PD was observed in all groups. Furthermore, the decreased acid response was also attenuated by prior administration of the EP3- but not EP1- antagonist. Mucosal levels of PGE(2) and 6-keto PGF(1a) increased after exposure to TC in all groups of mice. In conclusion, the decrease in acid secretion in the damaged stomach is mediated by endogenous PGs derived from COX-1, through PGE(2)/EP3 receptors and prostacyclin/IP receptors.

Absorptive profile of chlorogenic acid in rats

The objective of this work was to systematically investigate the absorptive profile of chlorogenic acid (CGA) in rats and to increase its intestinal absorption using absorption enhancers. The rat in situ intestinal perfusion technique was used to examine absorptive rate and extent of CGA. In vitro enzymatic drug degradation study was carried out with rat intestinal washings. Various experimental conditions such as different concentrations, extraction purity, and different absorption enhancers such as sodium taurocholate (ST), sodium lauryl sulphate (SLS), carbomer, borneol were examined. Absorption rate constants were determined by the plot of log remaining amount of drug in perfusate vs. time. During the in vitro enzymatic degradation study, no measurable degradation was observed. It was found that CGA could be poorly absorbed by the gastrointestinal tract. The absorptive rate of CGA is independent of the drug concentration. Absorption processes fit first order processes. Extraction of high purity is benefit to the absorption of CGA. Drug absorption extent could be increased via absorption enhancers except SLS. ST appeared to be more effective for enhancing the intestinal absorption of CGA than the other absorption enhancers. In vivo studies were carried out to compare the pharmacokinetic parameters of solutions with and without ST. The order of increasing CGA absorption caused by the enhancers was ST > carbomer > borneol > SLS.

Taurocholic acid feeding prevents tumor necrosis factor-alpha-induced damage of cholangiocytes by a PI3K-mediated pathway

Cholangiopathies, such as primary biliary cirrhosis and primary sclerosis cholangitis, are characterized at the end stage by ductopenia due to increased cholangiocyte apoptosis and decreased cholangiocyte proliferation. Although cholangiocyte proliferation is associated with an increased number of intra-hepatic bile ducts and secretin-stimulated ductal secretion, ductopenia is coupled with decreased ductal mass and secretin-induced ductal secretory activity. We have shown that a single injection of actinomycin D + tumor necrosis factor-alpha (TNF-alpha ) to bile duct-ligated (BDL) rats induces cholangiocyte injury, which is characterized by loss of cholangiocyte proliferation, and secretory activity and by an increase in cholangiocyte apoptosis. We also have shown that taurocholic acid both in vivo and in vitro stimulates cholangiocyte proliferation. We hypothesize that taurocholic acid feeding protects cholangiocytes against TNF-alpha -induced apoptosis through a phosphatidylinositol-3-kinase (PI3K)-dependent pathway. Immediately after BDL, rats were fed taurocholic acid or control diet in the absence/presence of daily injections of wortmannin for 1 week. Seven days later, control-fed or taurocholic acid-fed rats were treated with a single intraperitoneal injection of actinomycin D + TNF-alpha . Twenty-four hours later we evaluated: (i) cholangiocyte apoptosis and proliferation in liver sections and (ii) basal and secretin-stimulated bile and bicarbonate secretion in bile fistula rats. Taurocholic acid feeding prevented TNF-alpha -induced increases in cholangiocyte apoptosis and decreases in growth and secretin-stimulated bile and bicarbonate secretion, changes that were blocked by PI3K inhibition. The PI3K survival pathway is important in bile acid protection against immune-mediated cholangiocyte injury in cholestatic liver diseases.

Cytoprotective effects of taurocholic acid feeding on the biliary tree after adrenergic denervation of the liver

BACKGROUND

Cholangiopathies impair the balance between proliferation and apoptosis of cholangiocytes leading to the disappearance of bile ducts and liver failure. Taurocholic acid (TC) is essential for cholangiocyte proliferative and functional response to cholestasis. Bile acids and neurotransmitters co-operatively regulate the biological response of the biliary epithelium to cholestasis. Adrenergic denervation of the liver during cholestasis results in the damage of bile ducts.

AIM

To verify whether TC feeding prevents the damage of the biliary tree induced by adrenergic denervation in the course of cholestasis.

METHODS

Rats subjected to bile duct ligation (BDL) and to adrenergic denervation were fed a TC-enriched diet, in the absence or presence of daily administration of the phosphatidyl-inositol-3-kinase (PI3K) inhibitor wortmannin for 1 week.

RESULTS

TC prevented the induction of cholangiocyte apoptosis induced by adrenergic denervation. TC also restored cholangiocyte proliferation and functional activity, reduced after adrenergic denervation. TC prevented AKT dephosphorylation induced by adrenergic denervation. The cytoprotective effects of TC were abolished by the simultaneous administration of wortmannin.

SUMMARY/CONCLUSIONS

TC administration prevents the damage of the biliary tree induced by the adrenergic denervation of the liver. These novel findings open novel perspectives in the understanding of the potential of bile acids especially in post-transplant liver disease.