Toxic Bile Acids Research Articles

Three measurable and modifiable enteric microbial biotransformations relevant to cancer prevention and treatment.

Interdisciplinary scientific evaluation of the human microbiota has identified three enteric microbial biotransformations of particular relevance for human health and well-being, especially cancer. Two biotransformations are counterproductive; one is productive. First, selective bacteria can reverse beneficial hepatic hydroxylation to produce toxic secondary bile acids, especially deoxycholic acid. Second, numerous bacterial species can reverse hepatic detoxification—in a sense, retoxify hormones and xeonobiotics—by deglucuronidation. Third, numerous enteric bacteria can effect a very positive biotransformation through the production of butyrate, a small chain fatty acid with anti-cancer activity. Each biotransformation is addressed in sequence for its relevance in representative gastrointestinal and extra-intestinal cancers. This is not a complete review of their connection with every type of cancer. The intent is to introduce the reader to clinically relevant microbial biochemistry plus the emerging evidence that links these to both carcinogenesis and treatment. Included is the evidence base to guide counseling for potentially helpful dietary adjustments.

Role of NADPH Oxidases in Liver Fibrosis

Hepatic fibrosis is the common pathophysiologic process resulting from chronic liver injury, characterized by the accumulation of an excessive extracellular matrix. Multiple lines of evidence indicate that oxidative stress plays a pivotal role in the pathogenesis of liver fibrosis. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) is a multicomponent enzyme complex that generates reactive oxygen species (ROS) in response to a wide range of stimuli. In addition to phagocytic NOX2, there are six nonphagocytic NOX proteins. In the liver, NOX is functionally expressed both in the phagocytic form and in the nonphagocytic form. NOX-derived ROS contributes to various kinds of liver disease caused by alcohol, hepatitis C virus, and toxic bile acids. Recent evidence indicates that both phagocytic NOX2 and nonphagocytic NOX isoforms, including NOX1 and NOX4, mediate distinct profibrogenic actions in hepatic stellate cells, the main fibrogenic cell type in the liver. The critical role of NOX in hepatic fibrogenesis provides a rationale to assess pharmacological NOX inhibitors that treat hepatic fibrosis in patients with chronic liver disease. Although there is compelling evidence indicating a crucial role for NOX-mediated ROS generation in hepatic fibrogenesis, little is known about the expression, subcellular localization, regulation, and redox signaling of NOX isoforms in specific cell types in the liver. Moreover, the exact mechanism of NOX-mediated fibrogenic signaling is still largely unknown. A better understanding through further research about NOX-mediated fibrogenic signaling may enable the development of novel anti-fibrotic therapy using NOX inhibition strategy. Antio

Correction: Role of Glucuronidation for Hepatic Detoxification and Urinary Elimination of Toxic Bile Acids during Biliary Obstruction

Correction: Role of Glucuronidation for Hepatic Detoxification and Urinary Elimination of Toxic Bile Acids during Biliary Obstruction

Molecular mechanisms of hepatic apoptosis

Apoptosis is a prominent feature of liver diseases. Causative factors such as alcohol, viruses, toxic bile acids, fatty acids, drugs, and immune response, can induce apoptotic cell death via membrane receptors and intracellular stress. Apoptotic signaling network, including membrane death receptor-mediated cascade, reactive oxygen species (ROS) generation, endoplasmic reticulum (ER) stress, lysosomal permeabilization, and mitochondrial dysfunction, is intermixed each other, but one mechanism may dominate at a particular stage. Mechanisms of hepatic apoptosis are complicated by multiple signaling pathways. The progression of liver disease is affected by the balance between apoptotic and antiapoptotic capabilities. Therapeutic options of liver injury are impacted by the clear understanding toward mechanisms of hepatic apoptosis.

Linking physiology to toxicity using DILIsym®, a mechanistic mathematical model of drug‐induced liver injury

The drug development industry faces multiple challenges in the realization of safe effective drugs. Computational modeling approaches can be used to support these efforts. One approach, mechanistic modeling, is new to the realm of drug safety. It holds the promise of not only predicting toxicity for novel compounds, but also illuminating the mechanistic underpinnings of toxicity. To increase the scientific community's familiarity with mechanistic modeling in drug safety, this article seeks to provide perspective on the type of data used, how they are used and where they are lacking. Examples are derived from the development of DILIsym(®) software, a mechanistic model of drug-induced liver injury (DILI). DILIsym(®) simulates the mechanistic interactions and events from compound administration through the progression of liver injury and regeneration. Modeling mitochondrial toxicity illustrates the type and use of in vitro data to represent biological interactions, as well as insights on key differences between in vitro and in vivo conditions. Modeling bile acid toxicity illustrates a case in which the over-arching mechanism is well accepted, but many mechanistic details are lacking. Modeling was used to identify measurements predicted to strongly impact toxicity. Finally, modeling innate immune responses illustrates the importance of time-series data, particularly in the presence of positive and negative feedback loops, as well as the need for data from different animal species for better translation. These concepts are germane to most mechanistic models, although the details will vary. The use of mechanistic models is expected to improve the rational design of new drugs.

New highly toxic bile acids derived from deoxycholic acid, chenodeoxycholic acid and lithocholic acid

We have prepared a new panel of 23 BA derivatives of DCA, chenodeoxycholic acid (CDCA) and lithocholic acid (LCA) in order to study the effect of dual substitution with 3-azido and 24-amidation, features individually associated with cytotoxicity in our previous work. The effect of the compounds on cell viability of HT-1080 and Caco-2 was studied using the 3-[4,5-dimethylthizol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Compounds with high potency towards reduction of cell viability were further studied using flow cytometry in order to understand the mechanism of cell death. Several compounds were identified with low micromolar IC50 values for reducing cell viability in the Caco-2 and HT1080 cell lines, making them among the most potent BA apoptotic agents reported to date. There was no evidence of relationship between overall hydrophobicity and cytotoxicity supporting the idea that cell death induction by BAs may be structure–specific. Compounds derived from DCA caused cell death through apoptosis. There was some evidence of selectivity between the two cell lines studied which may be due to differing expression of CD95/FAS. The more toxic compounds increased ROS production in Caco-2 cells, and co-incubation with the antioxidant N-acetyl cysteine blunted pro-apoptotic effects. The properties these compounds suggest that there may be specific mechanism(s) mediating BA induced cell death. Compound 8 could be useful for investigating this phenomenon.

Role of Glucuronidation for Hepatic Detoxification and Urinary Elimination of Toxic Bile Acids during Biliary Obstruction

Biliary obstruction, a severe cholestatic condition, results in a huge accumulation of toxic bile acids (BA) in the liver. Glucuronidation, a conjugation reaction, is thought to protect the liver by both reducing hepatic BA toxicity and increasing their urinary elimination. The present study evaluates the contribution of each process in the overall BA detoxification by glucuronidation. Glucuronide (G), glycine, taurine conjugates, and unconjugated BAs were quantified in pre- and post-biliary stenting urine samples from 12 patients with biliary obstruction, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The same LC-MS/MS procedure was used to quantify intra- and extracellular BA-G in Hepatoma HepG2 cells. Bile acid-induced toxicity in HepG2 cells was evaluated using MTS reduction, caspase-3 and flow cytometry assays. When compared to post-treatment samples, pre-stenting urines were enriched in glucuronide-, taurine- and glycine-conjugated BAs. Biliary stenting increased the relative BA-G abundance in the urinary BA pool, and reduced the proportion of taurine- and glycine-conjugates. Lithocholic, deoxycholic and chenodeoxycholic acids were the most cytotoxic and pro-apoptotic/necrotic BAs for HepG2 cells. Other species, such as the cholic, hyocholic and hyodeoxycholic acids were nontoxic. All BA-G assayed were less toxic and displayed lower pro-apoptotic/necrotic effects than their unconjugated precursors, even if they were able to penetrate into HepG2 cells. Under severe cholestatic conditions, urinary excretion favors the elimination of amidated BAs, while glucuronidation allows the conversion of cytotoxic BAs into nontoxic derivatives.

Toxicity and intracellular accumulation of bile acids in sandwich-cultured rat hepatocytes: Role of glycine conjugates

Excessive intrahepatic accumulation of bile acids (BAs) is a key mechanism underlying cholestasis. The aim of this study was to quantitatively explore the relationship between cytotoxicity of BAs and their intracellular accumulation in sandwich-cultured rat hepatocytes (SCRH). Following exposure of SCRH (on day-1 after seeding) to various BAs for 24h, glycine-conjugated BAs were most potent in exerting toxicity. Moreover, unconjugated BAs showed significantly higher toxicity in day-1 compared to day-3 SCRH. When day-1/-3 SCRH were exposed (0.5–4h) to 5–100μM (C)DCA, intracellular levels of unconjugated (C)DCA were similar, while intracellular levels of glycine conjugates were up to 4-fold lower in day-3 compared to day-1 SCRH. Sinusoidal efflux was by far the predominant efflux pathway of conjugated BAs both in day-1 and day-3 SCRH, while canalicular BA efflux showed substantial interbatch variability. After 4h exposure to (C)DCA, intracellular glycine conjugate levels were at least 10-fold higher than taurine conjugate levels. Taken together, reduced BA conjugate formation in day-3 SCRH results in lower intracellular glycine conjugate concentrations, explaining decreased toxicity of (C)DCA in day-3 versus day-1 SCRH. Our data provide for the first time a direct link between BA toxicity and glycine conjugate exposure in SCRH.

Bile acids trigger cholemic nephropathy in common bile-duct-ligated mice

Tubular epithelial injury represents an underestimated but important cause of renal dysfunction in patients with cholestasis and advanced liver disease, but the underlying mechanisms are unclear. To address the hypothesis that accumulation and excessive alternative urinary elimination of potentially toxic bile acids (BAs) may contribute to kidney injury in cholestasis, we established a mouse model for detailed in vivo time course as well as treatment studies. Three-day common bile duct ligation (CBDL) induced renal tubular epithelial injury predominantly at the level of aquaporin 2-positive collecting ducts with tubular epithelial and basement membrane defects. This was followed by progressive interstitial nephritis and tubulointerstitial renal fibrosis in 3-, 6-, and 8-week CBDL mice. Farnesoid X receptor knockout mice (with a hydrophilic BA pool) were completely protected from CBDL-induced renal fibrosis. Prefeeding of hydrophilic norursodeoxycholic acid inhibited renal tubular epithelial injury in CBDL mice. In addition, we provide evidence for renal tubular injury in cholestatic patients with cholemic nephropathy. We characterized a novel in vivo model for cholemic nephropathy, which offers new perspectives to study the complex pathophysiology of this condition. Our findings suggest that urinary-excreted toxic BAs represent a pivotal trigger for renal tubular epithelial injury leading to cholemic nephropathy in CBDL mice.

<i>In vitro</i> evidence of possible influence of scutellarein towards bile acids’ metabolism

The glucuronidation process has been regarded as the key elimination process for toxic bile acids. UDP-glucuronosyltransferase (UGT) 1A3 is one important metabolizing enzyme involved in this process. To evaluate the inhibition of UGT1A3 by scutellarein which is an important herbal ingredient using in vitro method, trying to indicate the possibility of toxicity due to the accumulation of toxic bile acids. Due to the difficulty to gain the standards of biles acids' glucuronides, the recombinant UGT1A3-catalyzed 4-methylumbelliferone (4-MU) glucuronidation reaction was employed to profile the activity of UGT1A3. The results showed that scutellarein inhibited UGT1A3 in a concentration-dependent behaviour. Competitive inhibition was demonstrated using both Dixon plot and Lineweaver-Burk plot, and the inhibition kinetic parameter (Ki) was calculated to be 5.8uM. All these data reminded the necessary monitoring of the levels of bile acids in plasma when utilizing scutellarein and the herbs containing this compound.

Clostridium scindens: a human gut microbe with a high potential to convert glucocorticoids into androgens

Clostridium scindens American Type Culture Collection 35704 is capable of converting primary bile acids to toxic secondary bile acids, as well as converting glucocorticoids to androgens by side-chain cleavage. The molecular structure of the side-chain cleavage product of cortisol produced by C. scindens was determined to be 11β-hydroxyandrost-4-ene-3,17-dione (11β-OHA) by high-resolution mass spectrometry, 1H and 13C NMR spectroscopy, and X-ray crystallography. Using RNA-Seq technology, we identified a cortisol-inducible (∼1,000-fold) operon (desABCD) encoding at least one enzyme involved in anaerobic side-chain cleavage. The desC gene was cloned, overexpressed, purified, and found to encode a 20α-hydroxysteroid dehydrogenase (HSDH). This operon also encodes a putative “transketolase” (desAB) hypothesized to have steroid-17,20-desmolase/oxidase activity, and a possible corticosteroid transporter (desD). RNA-Seq data suggests that the two-carbon side chain of glucocorticords may feed into the pentose-phosphate pathway and are used as a carbon source. The 20α-HSDH is hypothesized to function as a metabolic “rheostat” controlling rates of side-chain cleavage. Phylogenetic analysis suggests this operon is rare in nature and the desC gene evolved from a gene encoding threonine dehydrogenase. The physiological effect of 11β-OHAD on the host or other gut microbes is currently unknown.

Down-regulation of LPCAT expression increases platelet-activating factor level in cirrhotic rat liver: Potential antiinflammatory effect of silybin

Cholestasis is one of the major causes of liver diseases. A chronic accumulation of toxic bile acids in the liver, which occurs in this condition, can induce fibrosis and cirrhosis. Inflammation is a fundamental component of acute and chronic cholestatic liver injury.Platelet-activating factor (PAF) is a proinflammatory lipid which may be generated by two independent pathways called the de novo and remodeling pathway being the last responsible for the synthesis of PAF during inflammation. In recent years a key role in PAF remodeling has been attributed to lysophosphatidylcholine acyltransferase (LPCAT) enzymes. Although the knowledge on their characteristic is growing, the exact mechanism of LPCAT in pathological conditions remains still unknown.Here, we reported that the level of lyso-PAF and PAF significantly increased in the liver of cirrhotic vs. control rats together with a significant decrease in both mRNA abundance and protein level of both LPCAT1 and LPCAT2. Acyltransferase activities of both LPCAT1 and LPCAT2 were parallel decreased in the liver of cirrhotic animals. Interestingly, treatment with silybin strongly decreased the level of both pro-inflammatory lipids and restored the activity and expression of both LPCAT1 and LPCAT2 of cirrhotic liver. Silybin effect was specific for LPCAT1 and LPCAT2 since it did not affect LPCAT3 mRNA abundance of cirrhotic liver.

Clinical grading of Intrahepatic Cholestasis Pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is the pregnancy induced liver disorder causing intense itching of palm, sole or even whole body especially in the evening at late second and third trimester. This disease is categorized into mild and severe ICP according to raised level of LFT including serum level of bile acid and cholic acid. ICP has less morbidity to mother but significant risk to fetus in uterus. The predisposing element to cause intense pruritus is because of high amount of bile acid in maternal serum. Toxic bile acids affect fetal cardiomyocytes retained in fetus body causing sudden intrauterine fetal death. ICP is commonly found in winter months and mostly itching of body occurs in the evening after sunset. Fetus in uterus is unsafe if mother's bile acid exceeds normal value. ICP is successfully treated with Ursodeoxycholic acid (UDCA), S-adenosyl methionine (SAME), Dexamethasone and vitamin K.

Profiling Serum Bile Acid Glucuronides in Humans: Gender Divergences, Genetic Determinants, and Response to Fenofibrate

Glucuronidation, catalyzed by UDP-glucuronosyltransferase (UGT) enzymes detoxifies cholestatic bile acids (BAs). We aimed at i) characterizing the circulating BA-glucuronide (-G) pool composition in humans, ii) evaluating how sex and UGT polymorphisms influence this composition, and iii) analyzing the effects of lipid-lowering drug fenofibrate on the circulating BA-G profile in 300 volunteers and 5 cholestatic patients. Eleven BA-Gs were determined in pre- and post-fenofibrate samples. Men exhibited higher BA-G concentrations, and various genotype/BA-G associations were discovered in relevant UGT genes. The chenodeoxycholic acid-3G concentration was associated with the UGT2B7 802C>T polymorphism. Glucuronidation assays confirmed the predominant role of UGT2B7 and UGT1A4 in CDCA-3G formation. Fenofibrate exposure increased the serum levels of 5 BA-G species, including CDCA-3G, and up-regulated expression of UGT1A4, but not UGT2B7, in hepatic cells. This study demonstrates that fenofibrate stimulates BA glucuronidation in humans, and thus reduces bile acid toxicity in the liver.

Mitofusin 2 Protects Hepatocyte Mitochondrial Function from Damage Induced by GCDCA

Mitochondrial impairment is hypothesized to contribute to the pathogenesis of chronic cholestatic liver diseases. Mitofusin 2 (Mfn2) regulates mitochondrial morphology and signaling and is involved in the development of numerous mitochondrial-related diseases; however, a functional role for Mfn2 in chronic liver cholestasis which is characterized by increased levels of toxic bile acids remain unknown. Therefore, the aims of this study were to evaluate the expression levels of Mfn2 in liver samples from patients with extrahepatic cholestasis and to investigate the role Mfn2 during bile acid induced injury in vitro. Endogenous Mfn2 expression decreased in patients with extrahepatic cholestasis. Glycochenodeoxycholic acid (GCDCA) is the main toxic component of bile acid in patients with extrahepatic cholestasis. In human normal hepatocyte cells (L02), Mfn2 plays an important role in GCDCA-induced mitochondrial damage and changes in mitochondrial morphology. In line with the mitochondrial dysfunction, the expression of Mfn2 decreased significantly under GCDCA treatment conditions. Moreover, the overexpression of Mfn2 effectively attenuated mitochondrial fragmentation and reversed the mitochondrial damage observed in GCDCA-treated L02 cells. Notably, a truncated Mfn2 mutant that lacked the normal C-terminal domain lost the capacity to induce mitochondrial fusion. Increasing the expression of truncated Mfn2 also had a protective effect against the hepatotoxicity of GCDCA. Taken together, these findings indicate that the loss of Mfn2 may play a crucial role the pathogenesis of the liver damage that is observed in patients with extrahepatic cholestasis. The findings also indicate that Mfn2 may directly regulate mitochondrial metabolism independently of its primary fusion function. Therapeutic approaches that target Mfn2 may have protective effects against hepatotoxic of bile acids during cholestasis.

Therapeutic Equivalence of Ursodeoxycholic Acid Tablets and Ursodeoxycholic Acid Capsules for the Treatment of Primary Biliary Cirrhosis.

Primary biliary cirrhosis (PBC) is a chronic cholestatic, progressive inflammatory liver disease with a suspected autoimmunological pathogenesis. The disease is typically diagnosed in women at an age between 30 and 65 years and has a prevalence of up to 1 in 1000 women over the age of 40. The only approved medical therapy for PBC is ursodeoxycholic acid (UDCA) in a recommended dose of 13–15mg/kg/day. UDCA is a hydrophilic dihydroxy bile acid (3a,7bdihydroxy-5b-cholanoic acid). In humans, UDCA accounts for up to 4% of the bile acid pool. Following oral administration, approximately 30–60% of UDCA is absorbed in the gut. After intestinal absorption, UDCA enters the portal circulation and is then taken up by the hepatocytes via specific bile acid transporters. Within the hepatocyte, UDCA is conjugated to glycine or taurine and is subsequently transported into the bile ducts by the bile salt export pump (BSEP). In bile, UDCA concentration peaks 1 3 h following oral administration. In humans, the biological half-life of UDCA is 3.5–5.8 days and the predominant route of elimination is by feces. UDCA exerts its beneficial effects at the level of hepatocytes and cholangiocytes. It stimulates hepatocyte secretion by mostly post-transcriptional mechanisms, including insertion of transporters like BSEP and the anion exchanger AE2. In addition, UDCA exerts antiapoptotic effects in hepatocytes and protects cholangiocytes against endogenous toxic bile acids by modifying micelle formation. UDCA consistently improves the biochemical parameters of cholestasis, delays the histological progression and the time to liver transplantation in patients suffering from PBC. Both, UDCA 250mg capsules and UDCA 500mg tablets (“Ursofalk1”), are registered in Germany and other European countries for the treatment of PBC. UDCA 500mg tablets were developed to facilitate medication intake compared to the standard UDCA 250mg capsule preparations. Tablets are considerably smaller, but contain twice as much active pharmaceutical ingredient compared to the capsule preparation, which might improve the compliance of patients and thereby increase its therapeutic efficacy. Ursofalk tablets were registered in Germany on the basis of bioequivalence studies comparing tmax, Cmax, and AUC values of UDCA between capsules and tablets. Cmax values of UDCA in plasma are probably of only limited clinical relevance for the efficacy and safety of UDCA. Aim of this trial was to assess if the therapeutic efficacy of UDCA 500mg tablets is equivalent to that of UDCA 250mg capsules (both at 14 2mg/kg BW/day once daily) in patients with PBC. Therapeutic efficacy was measured by comparing the liver enzyme parameters alkaline phosphatase (AP), g-glutamyl transferase (gGT), and alanine aminotransferase (ALT) under both treatments. The secondary objectives were to assess the safety Clinical Pharmacology in Drug Development XX(XX) 1–6 © The Author(s) 2013 DOI: 10.1002/cpdd.24

Pregnane X Receptor (PXR) at the Crossroads of Human Metabolism and Disease

Pregnane X Receptor (PXR), a member of the nuclear receptor (NR) superfamily, is expressed in liver and intestine, as also in other tissues and cells. PXR is activated by a wide variety of endobiotics, dietary compounds and pharmaceuticals. This nuclear receptor serves as a master transcriptional regulator of CYP3A isozymes, and also regulates a large number of enzymes and transporters involved in the pharmacokinetics of both endobiotics and xenobiotics. PXR has an impact on energy homeostasis through glucose and lipid metabolism regulation. PXR activation is also hepatoprotective against toxic bile acids. New roles for PXR have been identified in bone homeostasis, inflammatory bowel disease, liver steatosis and fibrogenesis. PXR directly regulates the expression of multidrug resistance protein 1 (MDR1) and other important proteins involved in drug metabolism. Drug-drug interactions can affect patients with cardiovascular disease, tuberculosis, HIV and cancer. Especially cancer patients are at high risk of such interactions, as treated with multi-drug combinations. PXR activation can affect the efficacy of chemotherapeutics, thus targeting PXR may represent a novel strategy for the improvement of the pharmacokinetics of chemotherapeutic agents, thereby providing safer and more effective therapies for cancer patients.

Nrf2 regulates antioxidative and liver regeneration promoting genes

The liver is frequently challenged by insults such as toxins and alcohol, viral infection or metabolic overload. In contrast to other organs, the liver has a unique capability to regenerate after injury. However, sustained presence of the damaging insult prolongs the regeneration response, resulting in liver fibrosis and cirrhosis or acute liver failure. Liver regeneration can be impaired by permanent oxidative stress mediated by the formation of reactive oxygen species (ROS). ROS are produced by metabolic intermediates of xenobiotics, mitochondrial leakage, induction of CYP2 family and activation of inflammatory cells. A crucial player in the defense against oxidative stress is the transcription factor NF-E2-related factor 2 (Nrf2). It has been shown that Nrf2 binds to the cis-acting enhancer element, antioxidant response element (ARE), controlling expression of many antioxidant proteins such as glutathione S-transferase and NADH quinone oxidoreductase 1. Furthermore it was demonstrated that Nrf2 plays a crucial liver regeneration after partial hepatectomy, ethanol or bile acid toxicity.

Mastabol induced acute cholestasis: A case report.

A 26-year-old male presented with three weeks of jaundice after the self-initiation of the injectable anabolic steroid, Mastabol [Dromastanolone Di-Propionate (17 beta-Hydroxy-2alpha-methyl-5alpha-androstan-3-one propionate)]. He reported dark urine, light stools, and pruritus. He denied abdominal pain, intravenous drug use, intranasal cocaine, blood transfusions, newly placed tattoos, or sexually transmitted diseases. He used alcohol sparingly. Physical exam revealed jaundice with deep scleral icterus. The liver was palpable 2 cm below the right costal margin with no ascites. The peak bilirubin was 23.6 mg/dL, alkaline phosphatase was 441 units/L, and aspartate aminotransferase/alanine aminotransferase were 70 units/L and 117 units/L respectively. A working diagnosis of acute intrahepatic cholestasis was made. Liver biopsy revealed a centrilobular insult with neutrophilic infiltrates and Ito cell hyperplasia consistent with acute drug induced cholestasis. The patient's clinical symptoms resolved and his liver enzymes, bilirubin, and alkaline phosphatase normalized. Anabolic steroids with 17 alpha carbon substitutions have been associated with a bland variety of cholestatic injury with little hepatocellular injury. Cholestasis, under these circumstances, may be secondary to the binding of drugs to canalicular membrane transporters, accumulation of toxic bile acids from canalicular pump failure, or genetic defects in canalicular transport proteins. Mastabol is an injectable, 17 beta hydroxyl compound with no alpha alkyl groups at the 17 carbon position. As such, it has been reported to have little potential toxic effects on the liver. This is the first known reported case of Mastabol-induced cholestatic liver injury. It highlights the need for physicians to consider such widely available substances when faced with hepatic injury of unclear etiology.

Bile acids content in brain of common duct ligated rats

Introduction. Cholestasis leads to liver cell death, fibrosis, cirrhosis, and eventually liver failure. Bile duct ligated rats constitute an interesting model to study the mechanism of cholestasis, and its action on several organs and tissues, including the brain.Aim. To analyze brain bile acids individually in ligated rats to evaluate if its profile is altered towards a more toxic condition in cholestasis.Material and methods. Male Wistar rats were used and separated in two groups: bile duct ligated rats and sham operated rats (n = 5 in each group). Bile acid profile was assessed in brain homogenates. Alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase determinations, bilirubin and ammonia plasma concentration were also measured in both groups.Results. Although the total amount of bile acids in control animal brains showed a higher concentration than in bile duct ligated rats, the bile acid profile in this group was found more toxic composition than in controls. Lithocholic acid was present in brain in higher concentration (87.4 % of total brain bile acids) in ligated rats and absent in controls. Alkaline phosphatase, bilirubin and ammonia were significantly higher in bile duct ligated rats than in control group.Conclusion. It was found a toxic brain bile acid profile during hepatic cholestasis which could be one of the explanations of hepatic encephalopathy observed in cholestatic diseases.