Current understanding of autophagy in intrahepatic cholestasis of pregnancy.

Intrahepatic cholestasis of pregnancy (ICP) is the most common liver disease during pregnancy. Manifested with pruritus and elevation in bile acids, the etiology of ICP is still poorly understood. Although ICP is considered relatively benign for the mother, increased rates of adverse fetal outcomes including sudden fetal demise are possible devastating outcomes associated with ICP. Limited understanding of the underlying mechanisms restricted treatment options and managements of ICP. In recent decades, evolving evidence indicated the significance of autophagy in pregnancy and pregnancy complications. Autophagy is an ancient self-defense mechanism which is essential for cell survival, differentiation and development. Autophagy has pivotal roles in embryogenesis, implantation, and maintenance of pregnancy, and is involved in the orchestration of diverse physiological and pathological cellular responses in patients with pregnancy complications. Recent advances in these research fields provide tantalizing targets on autophagy to improve the care of pregnant women. This review summarizes recent advances in understanding autophagy in ICP and its possible roles in the causation and prevention of ICP.

[Bile acids in arrhythmia].

With the research advances on bile acid, it has gradually been discovered and confirmed that high levels of bile acids can cause various types of arrhythmias, such as sinus bradycardia, atrial fibrillation (AF), atrioventricular block and even occurrence of cardiac arrest in severe cases. In addition, it has also been found that fetuses are more susceptible to bile acid-induced arrhythmias than adults. It has been recognized that bile acids can cause arrhythmias through a variety of mechanisms, such as the effect of bile acids on ions and ion channels, receptor-mediated, vagal-mediated, and other pathways. Ursodeoxycholic acid (UDCA) is currently found to have protective effect on the heart and has an antiarrhythmic effect. This article mainly reviews the function and mechanism of bile acid in arrhythmia.

Ursodeoxycholic Acid (UDCA) Mitigates the Host Inflammatory Response during Clostridioides difficile Infection by Altering Gut Bile Acids.

Clostridioides difficile infection (CDI) is associated with increasing morbidity and mortality posing an urgent threat to public health. Recurrence of CDI after successful treatment with antibiotics is high, thus necessitating discovery of novel therapeutics against this enteric pathogen. Administration of the secondary bile acid ursodeoxycholic acid (UDCA; ursodiol) inhibits the life cycles of various strains of C. difficilein vitro, suggesting that the FDA-approved formulation of UDCA, known as ursodiol, may be able to restore colonization resistance against C. difficilein vivo However, the mechanism(s) by which ursodiol is able to restore colonization resistance against C. difficile remains unknown. Here, we confirmed that ursodiol inhibits C. difficile R20291 spore germination and outgrowth, growth, and toxin activity in a dose-dependent manner in vitro In a murine model of CDI, exogenous administration of ursodiol resulted in significant alterations in the bile acid metabolome with little to no changes in gut microbial community structure. Ursodiol pretreatment resulted in attenuation of CDI pathogenesis early in the course of disease, which coincided with alterations in the cecal and colonic inflammatory transcriptome, bile acid-activated receptors nuclear farnesoid X receptor (FXR) and transmembrane G-protein-coupled membrane receptor 5 (TGR5), which are able to modulate the innate immune response through signaling pathways such as NF-κB. Although ursodiol pretreatment did not result in a consistent decrease in the C. difficile life cycle in vivo, it was able to attenuate an overly robust inflammatory response that is detrimental to the host during CDI. Ursodiol remains a viable nonantibiotic treatment and/or prevention strategy against CDI. Likewise, modulation of the host innate immune response via bile acid-activated receptors FXR and TGR5 represents a new potential treatment strategy for patients with CDI.

Effects of ursodeoxycholic acid in esophageal motility and the role of the mucosa. An experimental study.

Esophageal motor abnormalities are frequently found in patients with gastroesophageal reflux disease. The role of bile in reflux-induced dysmotility is still elusive. Furthermore, it is questionable weather mucosal or muscular stimulation leads to motor dysfunction. The aims of this study were to analyze (i) the effect of bile in the amplitude of esophageal contractions; and (ii) the effect of mucosal versus muscular stimulation. Eighteen guinea pig esophagi were isolated, and its contractility assessed with force transducers. Three groups were studied. In group A (n= 6), the entire esophagus was incubated in 100 µmL ursodeoxycholic acid for 1 hour; in group B (n= 6) the mucosal layer was removed and the muscular layer incubated in 100 µmL ursodeoxycholic acid for 1 hour; and in group C (n= 6) (control group) the entire esophagus was incubated in saline solution. In all groups, five sequential contractions induced by 40 mm KCl spaced by 5 minutes were measured before and after incubation. Contractions amplitudes before incubation were 1.319 g, 0.306 g, and 1.795 g, for groups A, B, and C, respectively. There were no differences between groups A and C (P= 0.633), but there were differences between groups A and B (P= 0.039), and B and C (P= 0.048). After incubation amplitude of contraction were 0.709 g, 0.278 g, and 1.353 g for groups A, B, and C, respectively. Only group A showed difference when pre and post-stimulation amplitudes were compared (P= 0.030). Our results show that (i) bile exposure decreases esophageal contraction amplitude; and (ii) the esophageal mucosa seems to play an important role in esophageal motility.

The role of lipophilic bile acids in the development of cirrhotic cardiomyopathy.

Marked hemodynamic changes occur in humans and experimental animals with cirrhotic liver disease. In the heart, basal contractility, responsiveness to beta-adrenoceptor activation, and excitation-contraction coupling (ECC) are negatively affected in models of cirrhosis and portal hypertension with portosystemic shunting (PVS), and comprise what has been called cirrhotic cardiomyopathy. These effects are accompanied by elevated circulating levels of bile acids. We investigated whether elevated bile acids act as a myocardial toxicant by exposing cardiac muscle in vitro to bile acids and compared these results with two models of cirrhotic cardiomyopathy with elevated bile acids: CCl4-induced cirrhosis and PVS. Cholic acid, a lipophilic bile acid, produced a decrease in basal cardiac contractility and responsiveness to beta-adrenoceptor activation, both of which appeared to result from altered ECC. beta-Adrenoceptor density and signaling were unaffected. Acutely, ursodeoxycholic acid, a more hydrophilic bile acid, had no effect. Cirrhosis produced a decrease in basal force, depressed beta-adrenoceptor responsiveness, and altered ECC similar to cholic acid. However, cirrhosis also altered beta-adrenoceptor signaling including decreases in cyclic AMP formation, expression of the stimulatory G protein, GS, and beta-adrenoceptor density. Displacement of lipophilic bile acids by chronic administration of ursodeoxycholic acid to rats during the development of cirrhotic cardiomyopathy produced by PVS produced attenuation of the effect on ECC. These results suggest a possible role for lipophilic bile acids in some, but not all of the myocardial consequences of chronic portal vein stenosis and CCl4-induced cirrhosis.

Bilirubin selectively inhibits cytochrome c oxidase activity and induces apoptosis in immature cortical neurons: assessment of the protective effects of glycoursodeoxycholic acid.

High levels of unconjugated bilirubin (UCB) may initiate encephalopathy in neonatal life, mainly in pre-mature infants. The molecular mechanisms of this bilirubin-induced neurologic dysfunction (BIND) are not yet clarified and no neuroprotective strategy is currently worldwide accepted. Here, we show that UCB, at conditions mimicking those of hyperbilirubinemic newborns (50 microM UCB in the presence of 100 muM human serum albumin), rapidly (within 1 h) inhibited cytochrome c oxidase activity and ascorbate-driven oxygen consumption in 3 days in vitro rat cortical neurons. This was accompanied by a bioenergetic and oxidative crisis, and apoptotic cell death, as judged by the collapse of the inner-mitochondrial membrane potential, increased glycolytic activity, superoxide anion radical production, and ATP release, as well as disruption of glutathione redox status. Furthermore, the antioxidant compound glycoursodeoxycholic acid (GUDCA) fully abrogated UCB-induced cytochrome c oxidase inhibition and significantly prevented oxidative stress, metabolic alterations, and cell demise. These results suggest that the neurotoxicity associated with neonatal bilirubin-induced encephalopathy occur through a dysregulation of energy metabolism, and supports the notion that GUDCA may be useful in the treatment of BIND.

p53 and the regulation of hepatocyte apoptosis: implications for disease pathogenesis.

The interplay between p53 and apoptosis in diseases such as cancer, neurodegeneration, ischemia and atherosclerosis underscores the need to understand the complexity of p53 networks. Here, we highlight recent studies of p53-induced apoptosis in human diseases, with a focus on the modulation of liver cell apoptosis. In addition, recent work has provided new insights into mechanisms underlying the antiapoptotic functions of the endogenous bile acid ursodeoxycholic acid (UDCA), suggesting that the finely tuned, complex control of p53 by Mdm2 is a key step in the UDCA modulation of deregulated, p53-triggered apoptosis. The effect of targeting cell death signaling proteins has been established in preclinical models of human diseases. Finally, we review recent therapeutic strategies and clinical applications of targeted agents, with a particular emphasis on the potential use of UDCA.

Ursodeoxycholic acid in neonatal hepatitis and infantile paucity of intrahepatic bile ducts: review of a historical cohort.

We retrospectively reviewed the role of ursodeoxycholic acid in infants having nonsurgical cholestasis attending the Hepatology Clinic, New Children Hospital, Cairo University, Egypt, from 1985 until 2005. Files of 496 infants with neonatal hepatitis and 97 with intrahepatic bile duct paucity were included; of them 241 (48.6%) and 52 (46.4%) received 20-40 mg/kg/day ursodeoxycholic acid for 319.2 +/- 506.9 days and 480.3 +/- 583.3 days, respectively. The outcome of infants with neonatal hepatitis with intake of ursodeoxycholic acid and those without was: 108 (44.8%) and 179 (70.2%) successful (P = 0.000), 11 (4.6%) and 13 (5.1%) improved (P = 0. 474), 112 (46.5%) and 61 (23.9%) suffered failed outcome (P = 0.000), and 10 (4.1%) and 2 (0.78%) died (P = 0.014), respectively. Likelihood of successful outcome with ursodeoxycholic acid intake was 0.345 (P = 0.000), and that of deterioration was 2.76 (P = 0.000). For those having intrahepatic bile duct paucity likelihood of successful outcome with ursodeoxycholic acid intake was 0.418 (P = 0.040) and that of deterioration was 2.64 (P = 0.028). Ursodeoxycholic acid failed in management of this cohort of infants with nonsurgical cholestasis.

Lessons from the toxic bile concept for the pathogenesis and treatment of cholestatic liver diseases.

Alterations in bile secretion at the hepatocellular and cholangiocellular levels may cause cholestasis. Formation of 'toxic bile' may be the consequence of abnormal bile composition and can result in hepatocellular and/or bile duct injury. The canalicular phospholipid flippase (Mdr2/MDR3) normally mediates biliary excretion of phospholipids, which normally form mixed micelles with bile acids and cholesterol to protect the bile duct epithelium from the detergent properties of bile acids. Mdr2 knockout mice are not capable of excreting phospholipids into bile and spontaneously develop bile duct injury with macroscopic and microscopic features closely resembling human sclerosing cholangitis. MDR3 mutations have been linked to a broad spectrum of hepatobiliary disorders in humans ranging from progressive familial intrahepatic cholestasis in neonates to intrahepatic cholestasis of pregnancy, drug-induced cholestasis, intrahepatic cholelithiasis, sclerosing cholangitis and biliary cirrhosis in adults. Other examples for bile injury due to the formation of toxic bile include the cholangiopathy seen in cystic fibrosis, after lithocholate feeding (in mice) and vanishing bile duct syndromes induced by drugs and xenobiotics. Therapeutic strategies for cholangiopathies may target bile composition/toxicity and the affected bile duct epithelium itself, and ideally should also have anti-cholestatic, anti-fibrotic and anti-neoplastic properties. Ursodeoxycholic acid (UDCA) shows some of these properties, but is of limited efficacy in the treatment of human cholangiopathies. By contrast to UDCA, its side chain-shortened homologue norUDCA undergoes cholehepatic shunting leading to a bicarbonate-rich hypercholeresis. Moreover, norUDCA has anti-inflammatory, anti-fibrotic and anti-proliferative effects, and stimulates bile acid detoxification. Upcoming clinical trials will have to demonstrate whether norUDCA or other side chain-modified bile acids are also clinically effective in humans. Finally, drugs for the treatment of cholangiopathies may target bile toxicity via nuclear receptors (FXR, PPARalpha) regulating biliary phospholipid and bile acid excretion.

Ursodeoxycholic acid in primary biliary cirrhosis improves glutathione status but fails to reduce lipid peroxidation.

BACKGROUND: Ursodeoxycholic acid (UDCA) may slow progression in primary biliary cirrhosis (PBC), but its effect on survival is controversial. We have previously demonstrated that oxidant stress, with severely depressed plasma glutathione, is a feature of untreated PBC; this study examines the effect of UDCA on lipid peroxidation, antioxidant status and associated processes. PATIENTS AND METHODS: Markers of lipid peroxidation, antioxidant status, hepatic fibrogenesis, inflammation, cholestasis and synthetic function were measured at 0, 3, 6, 9 and 12 months in blood and urine from 35 PBC patients receiving UDCA. RESULTS: Plasma glutathione, reflecting intrahepatic levels, climbed steadily on UDCA; although still subnormal, the median value at 12 months was 2.4-fold higher than the untreated level. Liver enzyme markers and C-reactive protein also improved, whilst PIIINP improved steadily, but the change did not attain statistical significance. Serum bilirubin remained unchanged and total antioxidant capacity, albumin and vitamin E decreased after 12 months' UDCA treatment. 8-Isoprostane increased and malondialdehyde was unchanged. CONCLUSIONS: UDCA treatment partially corrected plasma glutathione status and some other biomarkers greatly improved, but lipid peroxidation was not reduced. UDCA may, therefore, require supplementation with glutathione precursors and/or antioxidant cocktails to reduce oxidant stress and thus delay disease progression to cirrhosis.

Mechanisms of action and therapeutic efficacy of ursodeoxycholic acid in cholestatic liver disease.

Ursodeoxycholic acid (UDCA) is widely used for the treatment of cholestatic liver diseases. Multiple mechanisms of action of UDCA have been described aiming at one or more of the pathogenetic processes of cholestatic liver diseases: (1) protection of injured cholangiocytes against toxic effects of bile acids, (2) stimulation of impaired biliary secretion, (3) stimulation of detoxification of hydrophobic bile acids, and (4) inhibition of apoptosis of hepatocytes. Through one or more of these mechanisms, UDCA slows the progression of primary biliary cirrhosis and improves a number of other cholestatic disorders.

Role of nuclear bile acid receptor, FXR, in adaptive ABC transporter regulation by cholic and ursodeoxycholic acid in mouse liver, kidney and intestine.

BACKGROUND/AIMS: Adaptive changes in transporter expression in liver and kidney provide alternative excretory pathways for biliary constituents during cholestasis and may thus attenuate liver injury. Whether adaptive changes in ATP-binding cassette (ABC) transporter expression are stimulated by bile acids and their nuclear receptor FXR is unknown. METHODS: Hepatic, renal and intestinal ABC transporter expression was compared in cholic acid (CA)- and ursodeoxycholic acid (UDCA)-fed wild-type (FXR(+/+)) and FXR knock-out mice (FXR(-/-)). Expression was assessed by reverse transcription-polymerase chain reaction, immunoblotting and immunofluorescence microscopy. RESULTS: CA feeding stimulated hepatic Mrp2, Mrp3, Bsep and renal Mrp2 as well as intestinal Mrp2 and Mrp3 expression. Lack of Bsep induction by CA in FXR(-/-) was associated with disseminated hepatocyte necrosis which was not prevented by compensatory induction of Mrp2 and Mrp3. With the exception of Bsep, UDCA stimulated expression of hepatic, renal and intestinal ABC transporters independent of FXR without inducing liver toxicity. CONCLUSIONS: Toxic CA and non-toxic UDCA induce adaptive ABC transporter expression, independent of FXR with the exception of Bsep. Stimulation of hepatic Mrp3 as well as intestinal and renal Mrp2 by UDCA may contribute to its therapeutic effects by inducing alternative excretory routes for bile acids and other cholephiles.

Ursodeoxycholic acid 'mechanisms of action and clinical use in hepatobiliary disorders'.

UDCA exerts its beneficial effect in liver diseases through a diverse, probably, complementary array of mechanisms. The clinical use and efficacy of UDCA in PBC have been evident. UDCA may also have a place in the management of PSC, ICP, cystic fibrosis, PFIC and GVHD involving the liver, although, more studies are needed to further determine its therapeutic potential in these diseases and in other hepatobiliary disorders such as liver allograft rejection, drug and TPN-induced cholestasis, NASH, and alcoholic liver disease.

The role of bile salt composition in liver pathology of mdr2 (-/-) mice: differences between males and females.

BACKGROUND/AIMS: The mouse mdr2 gene encodes a P-glycoprotein expressed in the canalicular membrane of the hepatocyte. Mice in which this gene has been inactivated (mdr2 -/-) show a defect in biliary phospholipid and cholesterol secretion and develop non-suppurative cholangitis. We hypothesized that secretion of bile salts without lipids initiates this liver disease. METHODS: To delineate the pathologic process, mdr2 (-/-) mice were fed different bile salt-supplemented diets for 22 weeks after weaning. Aspects of liver pathology including eosinophilic bodies, portal inflammation, ductular proliferation, mitotic activity and fibrosis were semi-quantitatively scored. RESULTS: It was observed that liver pathology was more severe in female than in male mice when fed a purified control diet. This correlated with a more hydrophobic bile salt composition of female vs. male bile. When increasing amounts of cholate were added to the diet (0.01% and 0.1%), the secretion of taurocholate increased and this was accompanied by a more severe liver pathology. At the high dose of cholate (0.1%), the bile salt compositions of male and female mice became similar, as did the severity of the histological score. Addition of cholate to the diet did not induce liver pathology in (+/+) mice. Addition of ursodeoxycholate to the diet (0.5%) led to a near complete replacement of biliary bile salts by tauroursodeoxycholate and this reduced pathology and dissipated the difference between males and females. CONCLUSIONS: These observations support our hypothesis that liver pathology in the mdr2 (-/-) mouse is caused by bile salts and depends on the hydrophobicity c.q. cytotoxicity of biliary bile salts.

Intestinal absorption of bile acids in the rabbit: different transport rates in jejunum and ileum.

BACKGROUND & AIMS: A direct comparison of jejunal and ileal absorption rates of bile acids has not been reported. The aim of this study was to compare the relative transport rates of different bile acids in the jejunum and ileum. METHODS: Jejunal and ileal rabbit intestinal segments were separately perfused with bile acid solutions, and dose-response curves were obtained for taurocholate, ursodeoxycholate, chenodeoxycholate, deoxycholate, and their glycoconjugates. Membrane fluidity and bile acid transport were assessed in brush border membrane vesicles. RESULTS: Taurocholate showed active transport in the ileum and no transport in the jejunum. Unconjugated bile acids showed passive diffusion in the two tracts, whereas glycoconjugated bile acids showed both components of transport in the ileum and passive diffusion in the jejunum (lower in the latter). A higher membrane fluidity and lower cholesterol-to-phospholipid ratio were found in the jejunum. Ursodeoxycholate reduced bile acid uptake into membrane vesicles from both ileum and jejunum. CONCLUSIONS: Active transport is limited to the ileum. Passive diffusion is higher through a less fluid membrane with a higher cholesterol-to-phospholipid ratio in the ileum than in the jejunum. Ursodeoxycholate inhibition may be at the level of a facilitated, sodium-independent diffusion in the jejunum.

Regulation of bile acid synthesis in humans: studies on cholesterol 7 alpha-hydroxylation in vivo.

Over the last few years important progress has been made on the quantitation of cholesterol 7 alpha-hydroxylation, the rate-limiting step of bile acid synthesis. The use of a technique based on the determination of body water tritium enrichment after i.v. administration of [7 alpha-3H] cholesterol has allowed in vivo investigation of this step in humans in different experimental conditions. The cholesterol 7 alpha-hydroxylation rate was not affected by the administration of the hydrophilic bile acid ursodeoxycholic acid (UDCA) whereas it was significantly reduced by the more hydrophobic chenodeoxycholic acid (CDCA) and even more so by the strongly hydrophobic deoxycholic acid (DCA). The administration of cholestyramine induced a significant dose-related increase of 7 alpha-hydroxylation along with a correspondent decrease in plasma cholesterol. The administration of simvastatin exerted no effect on cholesterol 7 alpha-hydroxylation despite a marked decrease in serum cholesterol. Treatment with fibrates reduced plasma lipid levels and 7 alpha-hydroxylation rates. Hydroxylation rates were unchanged in familial hypercholesterolaemia and increased in familial combined hyperlipidaemia. These data suggest that in humans bile acid synthesis can be affected by quantitative and qualitative alterations of the enterohepatic circulation of bile acids. Changes in cholesterol 7 alpha-hydroxylation rates may be associated with alterations in plasma lipid levels, but such a relationship is ill-defined and seems to vary with the different experimental models.

[Pathophysiology of cholestasis: correlation between bile acid metabolism and liver damage]. / Die Pathophysiologie der Cholestase: Zusammenhänge zwischen Gallensäurenstoffwechsel und Leberschädigung.

In patients with cholestasis the biliary excretion of bile acids is diminished. Hepatic sulfation, glucuronidation and hydroxylation of bile acids are increased and enhance their urinary excretion. These metabolic pathways however, are not sufficient to prevent hepatic damage by bile salts. Ursodeoxycholic acid, a very hydrophilic and therefore untoxic bile acid, in part prevents the hepatotoxicity of more hydrophobic bile acids.

Stimulatory and inhibitory effects of bile salts on rat pancreatic secretion.

The effects of various species of bile salts (chenodeoxycholate, deoxycholate, ursodeoxycholate and cholate, and their taurine and glycine conjugates) on pancreatic exocrine secretion were studied in conscious rats with external bile and pancreatic fistulae. For examination of the stimulatory effects of bile salts, bile and pancreatic juice were collected for a basal period of 90 minutes and returned to the intestine, and then solutions of bile salts (60 mmol/L) were infused intraduodenally at a rate of 1 mL/h for 2 hours. For examination of their inhibitory effects, pancreatic secretion was stimulated by exclusion of the bile and pancreatic juice; and then solutions of the bile salts were again infused intraduodenally. Chenodeoxycholate, glycochenodeoxycholate, ursodeoxycholate, deoxycholate, and its conjugates (glycodeoxycholate and taurodeoxycholate) significantly increased the fluid, bicarbonate and protein outputs, and bicarbonate concentration, with decrease in protein concentration. These increases were partially inhibited by infusion of either a cholecystokinin antagonist or secretin antibody. In contrast, cholate, taurocholate, tauroursodeoxycholate, glycoursodeoxycholate, and taurochenodeoxycholate inhibited pancreatic secretion and increase in the plasma cholecystokinin concentration produced by exclusion of bile and pancreatic juice. Thus, some bile salts, including taurocholate and taurochenodeoxycholate (major bile salts in rat bile) inhibited pancreatic secretion and cholecystokinin release, whereas some other bile salts increased pancreatic secretion via cholecystokinin release and secretin release.