Identification of Bile Acids Responsible for Inhibiting the Bile Salt Export Pump, Leading to Bile Acid Accumulation and Cell Toxicity in Rat Hepatocytes

Altered bile acid and coproporphyrin-I disposition in patients with autosomal dominant polycystic kidney disease

AIMS

Serum, liver and urinary bile acids are increased, and hepatic transport protein levels are decreased in a non-clinical model of polycystic kidney disease. Similar changes in patients with autosomal dominant polycystic kidney disease (ADPKD) may predispose them to drug-induced liver injury (DILI) and hepatic drug-drug interactions (DDIs). Systemic coproporphyrin-I (CP-I), an endogenous biomarker for hepatic OATP1B function and MRP2 substrate, is used to evaluate OATP1B-mediated DDI risk in humans. In this clinical observational cohort-comparison study, bile acid profiles and CP-I concentrations in healthy volunteers and patients with ADPKD were compared.

METHODS

Serum and urine samples from healthy volunteers (n = 16) and patients with ADPKD (n = 8) were collected. Serum bile acids, and serum and urine CP-I concentrations, were quantified by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS).

RESULTS

Patients with ADPKD exhibited increased serum concentrations of total (1.3-fold) and taurine-conjugated (2.8-fold) bile acids compared to healthy volunteers. Specifically, serum concentrations of six bile acids known to be more hydrophobic/hepatotoxic (glycochenodeoxycholate, taurochenodeoxycholate, taurodeoxycholate, lithocholate, glycolithocholate and taurolithocholate) were increased (1.5-, 2.9-, 2.8-, 1.6-, 1.7- and 2.7-fold, respectively) in patients with ADPKD. Furthermore, serum CP-I concentrations were elevated and the renal clearance of CP-I was reduced in patients with ADPKD compared to healthy volunteers.

CONCLUSIONS

Increased exposure to bile acids may increase susceptibility to DILI in some patients with ADPKD. Furthermore, the observed increase in serum CP-I concentrations could be attributed, in part, to impaired OATP1B function in patients with ADPKD, which could increase the risk of DDIs involving OATP1B substrates compared to healthy volunteers.

FXR controls duodenogastric reflux-induced gastric inflammation through negatively regulating ER stress-associated TNXIP/NLPR3 inflammasome

Duodenogastric reflux (DGR) is closely associated with gastric inflammation and tumorigenesis; however, the precise mechanism is unclear. Hence, we aim to clarify this molecular mechanism and design an effective therapeutic strategy based on it. The present study found that DGR induced TXNIP/NLRP3 inflammasome activation and triggered pyroptosis in gastric mucosa in vitro and in vivo, in which endoplasmic reticulum (ER) stress via PERK/eIF2α/CHOP signaling was involved. Mechanistically, farnesoid X receptor (FXR) antagonized the DGR-induced PERK/eIF2α/CHOP pathway and reduced TXNIP and NLRP3 expression. Moreover, FXR suppressed NLRP3 inflammasome activation by physically interacting with NLRP3 and caspase-1. Administration of the FXR agonist OCA protected the gastric mucosa from DGR-induced barrier disruption and mucosal inflammation. In conclusion, our study demonstrates the involvement of TXNIP/NLRP3 inflammasome-mediated pyroptosis in DGR-induced gastric inflammation. FXR antagonizes gastric barrier disruption and mucosal inflammation induced by DGR. Restoration of FXR activity may be a therapeutic strategy for DGR-associated gastric tumorigenesis.

Culture methods focusing on bile canalicular formation using primary human hepatocytes in a short time

The development of models for predicting hepatotoxicity is warranted, as the hepatotoxicity risk of 38-51% of compounds is undetectable in nonclinical studies. Cholestatic drug-induced liver injury (DILI) is a condition in which bile acids are abnormally excreted into the capillary bile canaliculi and are accumulated in hepatocytes, caused by the inhibition of bile salt export pump (BSEP), a transporter that is mainly associated with excretion of bile acids. Although laboratory animals are used as models, the use of human-derived cells is required owing to species differences. Unfortunately, primary human hepatocytes (PHHs) show rapid loss of function in culture and difficulties in forming bile canaliculi. Therefore, we aimed to develop an in vitro culture method for the efficient formation of bile canaliculi and for assessing the function of BSEP in PHHs. Here, PHHs were cultured from 1 h after thawing to day 2 with Z-VAD-FMK, a total caspase inhibitor, and RevitaCell™ supplement, an irreversible Rho-associated coiled-coil forming kinase (ROCK) inhibitor, in combination with RM-101. The PHHs formed bile canaliculi and showed BSEP function on day 6 of culture. Our findings suggest that cultured PHHs may improve the prediction accuracy of the risks of cholestatic DILI-contained toxicity on bile canaliculi.

Impact of Novel Teflon-DCA Nanogel Matrix on Cellular Bioactivity

The biocompatibility and effects on cells' bioactivity of developed pharmaceuticals are crucial properties, required to permit their safe delivery. Nanogel matrices offer a promising role in emerging pharmaceutics; however, it is crucial that they and their excipients do not demonstrate detrimental effects on the cells to which they interact. This study investigated the use of Teflon and the secondary bile acid deoxycholic acid in the formation of novel nanogel matrices. Each has properties which may be of benefit for the nanogels created and their use in the pharmaceutical industry. Rheological parameters and scanning electron microscopy studies were conducted. In order to assess the developed nanogels' impacts on cellular bioactivity, studies using Seahorse assays were conducted on three cell types, hepatic, muscle and pancreatic beta cells. Results demonstrated the addition of Teflon did not alter the morphological characteristics of resulting nanogels or the metabolic profiles of the cell lines. Interestingly, pancreatic beta cells highlighted the potential of Teflon to exert a protective profile from mitochondrial damage. Overall, the developed nanogels showed potentially promising profiles in certain studies conducted which may lead to future research.

Paeoniflorin alleviates 17α-ethinylestradiol-induced cholestasis via the farnesoid X receptor-mediated bile acid homeostasis signaling pathway in rats

Cholestasis, characterized by disturbance of bile formation, is a common pathological condition that can induce several serious liver diseases. As a kind of trigger, estrogen-induced cholestasis belongs to drug-induced cholestasis. Paeoniflorin is the most abundant bioactive constituent in Paeonia lactiflora Pall., Paeonia suffruticosa Andr., or Paeonia veitchii Lynch, a widely used herbal medicine for treating hepatic disease over centuries in China. However, the pharmacologic effect and mechanism of paeoniflorin on estrogen-induced cholestasis remain unclear. In this experiment, the pharmacological effect of paeoniflorin on EE-induced cholestasis in rats was evaluated comprehensively for the first time. Ultra-high-performance liquid chromatography coupled with Q-Exactive orbitrap mass spectrometer was used to monitor the variation of bile acid levels and composition. It was demonstrated that paeoniflorin alleviated 17α-ethinylestradiol (EE)-induced cholestasis dose-dependently, characterized by a decrease of serum biochemical indexes, recovery of bile flow, amelioration of hepatic and ileal histopathology, and reduction of oxidative stress. In addition, paeoniflorin intervention restored EE-disrupted bile acid homeostasis in enterohepatic circulation. Further mechanism studies using western blot, quantitative Real-Time PCR, and immunohistochemical showed that paeoniflorin could upregulate hepatic efflux transporters expression but downregulate hepatic uptake transporter expression. Meanwhile, paeoniflorin reduced bile acids synthesis by repressing cholesterol 7α-hydroxylase in hepatocytes. Paeoniflorin affected the above transporters and enzyme via activation of a nuclear receptor, farnesoid X receptor (FXR), which was recognized as a vital regulator for maintaining bile acid homeostasis. In conclusion, paeoniflorin alleviated EE-induced cholestasis and maintained bile acid homeostasis via FXR-mediated regulation of bile acids transporters and synthesis enzyme. The findings indicated that paeoniflorin might exert a potential therapeutic medicine for estrogen-induced cholestasis.

Cyp2c-deficiency depletes muricholic acids and protects against high-fat diet-induced obesity in male mice but promotes liver damage

Objective

Murine-specific muricholic acids (MCAs) are reported to protect against obesity and associated metabolic disorders. However, the response of mice with genetic depletion of MCA to an obesogenic diet has not been evaluated. We used Cyp2c-deficient (Cyp2c^−/−) mice, which lack MCAs and thus have a human-like bile acid (BA) profile, to directly investigate the potential role of MCAs in diet-induced obesity.

Methods

Male and female Cyp2c^−/− mice and wild-type (WT) littermate controls were fed a standard chow diet or a high-fat diet (HFD) for 18 weeks. We measured BA composition from a pool of liver, gallbladder, and intestine, as well as weekly body weight, food intake, lean and fat mass, systemic glucose homeostasis, energy expenditure, intestinal lipid absorption, fecal lipid, and energy content.

Results

Cyp2c-deficiency depleted MCAs and caused other changes in BA composition, namely a decrease in the ratio of 12α-hydroxylated (12α-OH) BAs to non-12α-OH BAs, without altering the total BA levels. While WT male mice became obese after HFD feeding, Cyp2c^−/− male mice were protected from obesity and associated metabolic dysfunctions. Cyp2c^−/− male mice also showed reduced intestinal lipid absorption and increased lipid excretion, which was reversed by oral gavage with the 12α-OH BA and taurocholic acid (TCA). Cyp2c^−/− mice also showed increased liver damage, which appeared stronger in females.

Conclusions

MCA does not protect against diet-induced obesity but may protect against liver injury. Reduced lipid absorption in Cyp2c-deficient male mice is potentially due to a reduced ratio of 12α-OH/non-12α-OH BAs.

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Presence of MCA does not necessarily protect against diet-induced obesity.

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Cyp2c deficiency promotes resistance to diet-induced obesity in males.

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Cyp2c-knockout mice have decreased the ratio of 12α-OH/non-12α-OH BAs that promotes decreased intestinal lipid absorption.

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Cyp2c-knockout mice have improved glucose homeostasis.

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Cyp2c-deficiency promotes mild and severe liver injury in male and female mice, respectively.

The many facets of bile acids in the physiology and pathophysiology of the human liver

Bile acids perform vital functions in the human liver and are the essential component of bile. It is therefore not surprising that the biology of bile acids is extremely complex, regulated on different levels, and involves soluble and membrane receptors as well as transporters. Hereditary disorders of these proteins manifest in different pathophysiological processes that result in liver diseases of varying severity. In this review, we summarize our current knowledge of the physiology and pathophysiology of bile acids with an emphasis on recently established analytical approaches as well as the molecular mechanisms that underlie signaling and transport of bile acids. In this review, we will focus on ABC transporters of the canalicular membrane and their associated diseases. As the G protein-coupled receptor, TGR5, receives increasing attention, we have included aspects of this receptor and its interaction with bile acids.

Comparative study of the ditrophic interaction between Beauveria bassiana and Plutella xylostella

In the present investigation, hyperparasitic interaction between B. bassiana, TM (MH590235) and P. xylostella was studied through scanning electron microscopy and chromatographic techniques. Dose-mortality responses showed an increase in mortality of larva with an increase in spore concentration. The LC₅₀ value for B. bassiana isolate TM (MH590235) was 2.4 × 10⁷ spores mL^-1. The ditrophic interaction between B. bassiana and P. xylostella after 24 h revealed the adherence of conidia on stemmata, sensory setae, maxillary palpi and legs. After 48 h post-infection (hpi), germination of the conidia and appressorium formation was observed. Formation of hyphae and initiation of fungal networking was observed at 72 hpi. Complete ramification by mycelia and conidiogenesis of B. bassiana was observed over the mycosed cadaver after 168 hpi. Subsequently, typical sympodial conidiophores of B. bassiana bearing secondary spores were also observed. The metabolome profile of healthy larvae of P. xylostella revealed the presence of non-volatile organic compounds (NVOCs) like docosene, nonadecene, palmitic acid and heneicosane. However, the NVOC profile was different in the P. xylostella larvae hyperparasitized by B. bassiana. The metabolites present in the infected cadaver were phthalate esters, hydroxyquebrachamine and lactones.

Metabolomics analysis delineates the therapeutic effects of Huangqi decoction and astragalosides on α-naphthylisothiocyanate (ANIT) -induced cholestasis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestasis caused by bile secretion and excretion disorders is a serious manifestation of liver disease. With limited treatment methods, it affects millions of people worldwide. Huangqi decoction (HQD), an effective traditional Chinese medicine, is used to treat chronic cholestatic liver diseases. However, the action mechanisms of it were not fully elucidated.

AIM OF THE STUDY

We aim to investigate the therapeutic effect of HQD, and its active component, astragalosides, against α-naphthylisothiocyanate (ANIT)-induced cholestasis in rats based on targeted metabolomics analysis and revel the potential mechanism.

MATERIALS AND METHODS

The therapeutic effect of HQD and astragalosides on ANIT-induced cholestasis model rats were evaluated by serum biochemical analysis. Liver damage was identified by histopathology. The levels of bile acids (BAs) and free fatty acids (FFAs) in serum and liver tissues were measured by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-TQMS). qRT-PCR and Western blot analysis were used to measure the expression of nuclear hormone receptor, membrane receptor and BA transporter protein in cholestatic rats before and after HQD and astragalosides treatment.

RESULTS

The obtained data showed that the administration of ANIT caused obvious cholestasis with significantly increased intrahepatic retention of hydrophobic BAs and altered FFAs, which were consistent with the liver histopathological and serum biochemical findings. HQD and astragalosides treatment were able to attenuate ANIT-induced BAs and FFAs perturbation, ameliorate the impaired liver function, histopathological ductular reaction, and lipid peroxidation damage by ANIT. Elevated mRNA and protein expression of transporters related to BA metabolism and genes related to lipogenesis and lipid oxidation metabolism in cholestasis were attenuated or normalized by HQD and astragalosides treatment.

CONCLUSIONS

Intervention by ANIT can significantly change the homeostasis of BAs and FFAs. HQD and astragalosides exerted a hepatoprotective effect against cholestatic liver injury by restoring the altered BA and FFA metabolism through the improvement of BA transporter, nucleus hormone receptor, and membrane receptor.

Chronic Alcohol Consumption Increased Bile Acid Levels in Enterohepatic Circulation and Reduced Efficacy of Irinotecan

AIMS

To investigate the effect of ethanol intake on the whole enterohepatic circulation (EHC) of bile acids (BAs) and, more importantly, on pharmacokinetics of irinotecan.

METHODS

The present study utilized a mouse model administered by gavage with 0 (control), 240 mg/100 g (30%, v/v) and 390 mg/100 g (50%, v/v) ethanol for 6 weeks, followed by BA profiles in the whole EHC (including liver, gallbladder, intestine and plasma) and colon using ultra-high performance liquid chromatography with tandem mass spectrometry analysis. Pharmacokinetic parameters of irinotecan were measured after administration of irinotecan (i.v. 5 mg/kg) on alcohol-treated mice.

RESULTS

The results showed that compared with the control group, concentrations of most free-BAs, total amount of the three main forms of BAs (free-BA, taurine-BA and glycine-BA) and total BAs (TBAs) in 50% ethanol intake group were significantly increased, which are mostly attributed to the augmentation of free-BAs and taurine-BAs. Additionally, the TBAs in liver and gallbladder and the BA pool were markedly increased in the 30% ethanol intake group. Importantly, ethanol intake upregulated the expression of BA-related enzymes (Cyp7a1, Cyp27a1, Cyp8b1 and Baat) and transporters (Bsep, Mrp2, P-gp and Asbt) and downregulated the expression of transporter Ntcp and nuclear receptor Fxr in the liver and ileum, respectively. Additionally, 50% ethanol intake caused fairly distinct liver injury. Furthermore, the AUC0-24 h of irinotecan and SN38 were significantly reduced but their clearance was significantly increased in the disrupted EHC of BA by 50% ethanol intake.

CONCLUSIONS

The present study demonstrated that ethanol intake altered the expression of BA-related synthetases and transporters. The BA levels, especially the toxic BAs (chenodeoxycholic acid, deoxycholic acid and lithocholic acid), in the whole EHC were significantly increased by ethanol intake, which may provide a potential explanation to illuminate the pathogenesis of alcoholic liver injury. Most importantly, chronic ethanol consumption had a significant impact on the pharmacokinetics (AUC0-24 h and clearance) of irinotecan and SN38; hence colon cancer patients with chronic alcohol consumption treated with irinotecan deserve our close attention.

Bile Acid Toxicity and Protein Kinases

If the bile acids reach to pathological concentrations due to cholestasis, accumulation of hydrophobic bile acids within the hepatocyte may result in cell death. Thus, hydrophobic bile acids induce apoptosis in hepatocytes, while hydrophilic bile acids increase intracellular adenosine 3',5'-monophosphate (cAMP) levels and activate mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways to protect hepatocytes from apoptosis.Two apoptotic pathways have been described in bile acids-induced death. Both are controlled by multiple protein kinase signaling pathways. In mitochondria-controlled pathway, caspase-8 is activated with death domain-independent manner, whereas, Fas-dependent classical pathway involves ligand-independent oligomerization of Fas.Hydrophobic bile acids dose-dependently upregulate the inflammatory response by further stimulating production of inflammatory cytokines. Death receptor-mediated apoptosis is regulated at the cell surface by the receptor expression, at the death-inducing signaling complex (DISC) by expression of procaspase-8, the death receptors Fas-associated death domain (FADD), and cellular FADD-like interleukin 1-beta (IL-1β)-converting enzyme (FLICE) inhibitory protein (cFLIP). Bile acids prevent cFLIP recruitment to the DISC and thereby enhance initiator caspase activation and lead to cholestatic apoptosis. At mitochondria, the expression of B-cell leukemia/lymphoma-2 (Bcl-2) family proteins contribute to apoptosis by regulating mitochondrial cytochrome c release via Bcl-2, Bcl-2 homology 3 (BH3) interacting domain death agonist (Bid), or Bcl-2 associated protein x (Bax). Fas receptor CD95 activation by hydrophobic bile acids is initiated by reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) signaling. However, activation of necroptosis by ligands of death receptors requires the kinase activity of receptor interacting protein1 (RIP1), which mediates the activation of RIP3 and mixed lineage kinase domain-like protein (MLKL). In this chapter, mainly the effect of protein kinases signal transduction on the mechanisms of hydrophobic bile acids-induced inflammation, apoptosis, necroptosis and necrosis are discussed.

Human-Induced Pluripotent Stem Cell-Derived Hepatocytes and their Culturing Methods to Maintain Liver Functions for Pharmacokinetics and Safety Evaluation of Pharmaceuticals

Human hepatocytes are essential cell types for pharmacokinetics and the safety evaluation of pharmaceuticals. However, widely used primary hepatocytes with individual variations in liver function lose those functions rapidly in culture. Hepatic cell lines are convenient to use but have low liver functions. Human-Induced Pluripotent Stem (hiPS) cells can be expanded and potentially differentiated into any cell or tissue, including the liver. HiPS cell-derived Hepatocyte-Like Cells (hiPSHeps) are expected to be extensively used as consistent functional human hepatocytes. Many laboratories are investigating methods of using hiPS cells to differentiate hepatocytes, but the derived cells still have immature liver functions. In this paper, we describe the current uses and limitations of conventional hepatic cells, evaluating the suitability of hiPS-Heps to pharmacokinetics and the safety evaluation of pharmaceuticals, and discuss the potential future use of non-conventional non-monolayer culture methods to derive fully functional hiPS-Heps.

Role of mitochondria in the differential action of sodium deoxycholate and ursodeoxycholic acid on rat duodenum

Sodium deoxycholate (NaDOC) inhibits the intestinal Ca²⁺ absorption and ursodeoxycholic acid (UDCA) stimulates it. The aim of this study was to determine whether NaDOC and UDCA produce differential effects on the redox state of duodenal mitochondria altering the Krebs cycle and the electron transport chain (ETC) functioning, which could lead to perturbations in the mitochondrial dynamics and biogenesis. Rat intestinal mitochondria were isolated from untreated and treated animals with either NaDOC, UDCA, or both. Krebs cycle enzymes, ETC components, ATP synthase, and mitochondrial dynamics and biogenesis markers were determined. NaDOC decreased isocitrate dehydrogenase (ICDH) and malate dehydrogenase activities affecting the ETC and ATP synthesis. NaDOC also induced oxidative stress and increased the superoxide dismutase activity and impaired the mitochondrial biogenesis and functionality. UDCA increased the activities of ICDH and complex II of ETC. The combination of both bile acids conserved the functional activities of Krebs cycle enzymes, ETC components, oxidative phosphorylation, and mitochondrial biogenesis. In conclusion, the inhibitory effect of NaDOC on intestinal Ca²⁺ absorption is mediated by mitochondrial dysfunction, which is avoided by UDCA. The stimulatory effect of UDCA alone is associated with amelioration of mitochondrial functioning. This knowledge could improve treatment of diseases that affect the intestinal Ca²⁺ absorption.

Association between bile salt export pump polymorphisms and intrahepatic cholestasis of pregnancy susceptibility: a meta-analysis of case-control studies

The purpose of this meta-analysis was to investigate the relationship between bile salt export pump (BSEP) polymorphisms and intrahepatic cholestasis of pregnancy (ICP) susceptibility. Retrieved studies from Pubmed, EMBASE, Web of Science, Cochrane Library and CBM databases about BSEP polymorphisms and ICP susceptibility were included. Odds ratio (OR) and 95% confidence interval (CI) and publication bias were calculated. Ten related case-control studies on BSEP polymorphisms and ICP susceptibility were included. The pooled results showed a significant association between BSEP rs2287622 polymorphism and ICP risk in Asian population (OR >1, p < .01 for A vs. a and AA vs. Aa/aa) and general population (OR >1, p < .05 for A vs. a, Aa vs. aa, AA/Aa vs. aa), and a borderline statistical significance was found between BSEP rs473351 polymorphism and ICP susceptibility (OR = 1.66, p < .05), and no statistical significance was found in D482G or rs853782 polymorphisms and ICP risk (all p > .05). Additionally, no publication bias was found in these studies (all p > .05). Our current meta-analysis indicated that BSEP rs2287622 polymorphism could increase the susceptibility of ICP in Asians and in general populations, while rs473351, D482G, and rs853782 polymorphisms were not obviously associated with ICP risk, but it needs further larger study with ethnicity and various etiologies.