Ursodeoxycholic acid in cholestasis: potential mechanisms of action and therapeutic applications

Tauroursodeoxycholic acid mobilizes alpha-PKC after uptake in human HepG2 hepatoma cells

BACKGROUND

Tauroursodeoxycholic acid (TUDCA) may exert anticholestatic effects via Ca(++)- and alpha-protein kinase C (alpha-PKC)-dependent apical vesicular insertion of canalicular transporters in cholestatic hepatocytes (Hepatology 2001; 33: 1206-16). Tauroursodeoxycholic acid is mainly taken up into liver cells by Na(+)-taurocholate cotransporting polypeptide (Ntcp). Tauroursodeoxycholic acid selectively translocates alpha-PKC, a key mediator of regulated exocytosis, to hepatocellular membranes. It is unclear whether TUDCA exerts its effects on alpha-PKC after carrier-mediated uptake into liver cells or by interaction with extracellular/membraneous structures.

MATERIALS AND METHODS

Human hepatoblastoma HepG2 cells lacking Ntcp were stably transfected with pcDNA3.1/Ntcp or sham-transfected with pcDNA3.1 [+]. Distribution of alpha-PKC was studied using a Western blotting technique. Uptake of [(3)H]taurocholic acid (TCA) was determined radiochemically.

RESULTS

[(3)H]taurocholic acid uptake was approximately 180-fold higher in Ntcp-transfected than in sham-transfected cells. Phorbol 12-myristate 13-acetate (1 micromol L(-1); positive control) increased membrane binding of alpha-PKC by 34% in Ntcp-transfected and by 37% in sham-transfected cells. Tauroursodeoxycholic acid (10 micromol L(-1)) increased membrane-associated alpha-PKC by 19% in Ntcp-transfected, but not in sham-transfected cells (-13%). Taurocholic acid (10 micromol L(-1)) did not affect the distribution of alpha-PKC.

CONCLUSION

Carrier-mediated uptake is a prerequisite for TUDCA-induced translocation of alpha-PKC to hepatocellular membranes.

Corticosteroids modulate the secretory processes of the rat intrahepatic biliary epithelium

BACKGROUND & AIMS

We investigated the expression of glucocorticoid receptors (GcRs) in the intrahepatic biliary epithelium and the role of corticosteroids in the regulation of cholangiocyte secretion.

METHODS

GcR was studied by immunohistochemistry, reverse-transcription polymerase chain reaction, and Western blots. The effects of dexamethasone and budesonide on biliary bicarbonate excretion and H+/HCO3- transport processes were investigated in bile fistula rats, isolated intrahepatic bile duct units (IBDUs), and purified cholangiocytes.

RESULTS

GcRs were expressed by rat cholangiocytes. Although acute administration of corticosteroids showed no effect, treatment for 2 days with dexamethasone or budesonide increased (P < 0.05) biliary bicarbonate concentration and secretion, which were blocked by the specific GcR antagonist, RU-486. IBDUs isolated from rats treated with dexamethasone or budesonide showed an increased (P < 0.05) activity of the Na+/H+ exchanger (NHE1 isoform) and Cl-/HCO3- exchanger (AE2 member), which was blocked by RU-486. Protein expression of NHE1 and AE2 and messenger RNA for NH1 but not AE2 were increased (P < 0.05) in isolated cholangiocytes by dexamethasone treatment.

CONCLUSIONS

The intrahepatic biliary epithelium expresses GcR and responds to corticosteroids by increasing bicarbonate excretion in bile. This is caused by corticosteroid-induced enhanced activities and protein expression of transport processes driving bicarbonate excretion in the biliary epithelium.

Neuroprotection by a bile acid in an acute stroke model in the rat

Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, is a strong modulator of apoptosis in both hepatic and nonhepatic cells, and appears to function by inhibiting mitochondrial membrane perturbation. Excitotoxicity, metabolic compromise, and oxidative stress are major determinants of cell death after brain ischemia-reperfusion injury. However, some neurons undergo delayed cell death that is characteristic of apoptosis. Therefore, the authors examined whether TUDCA could reduce the injury associated with acute stroke in a well-characterized model of transient focal cerebral ischemia. Their model of middle cerebral artery occlusion resulted in marked cell death with prominent terminal deoxynucleotidyl transferase-mediated 2;-deoxyuridine 5;-triphosphate-biotin nick end labeling (TUNEL) within the ischemic penumbra, mitochondrial swelling, and caspase activation. Tauroursodeoxycholic acid administered 1 hour after ischemia resulted in significantly increased bile acid levels in the brain, improved neurologic function, and an approximately 50% reduction in infarct size 2 and 7 days after reperfusion. In addition, TUDCA significantly reduced the number of TUNEL-positive brain cells, mitochondrial swelling, and partially inhibited caspase-3 processing and substrate cleavage. These findings suggest that the mechanism for in vivo neuroprotection by TUDCA is, in part, mediated by inhibition of mitochondrial perturbation and subsequent caspase activation leading to apoptotic cell death. Thus, TUDCA, a clinically safe molecule, may be useful in the treatment of stroke and possibly other apoptosis-associated acute and chronic injuries to the brain.

Interactions of combined bile acids on hepatocyte viability: cytoprotection or synergism

Cholestasis results from hepatocyte dysfunction due to the accumulation of bile acids in the cell, many of which are known to be cytotoxic. Recent evidence implicates competitive antagonism of key cytotoxic responses as the mechanism by which certain therapeutic bile acids might afford cytoprotection against cholestasis. In this work, we compare the relative cytotoxicity of bile acids in terms of dose- and time-dependence. To better elucidate the controversy related to the therapeutic use of ursodeoxycholate (UDCA) in cholestatic patients, we also evaluated the effects of bile acid combinations. Viability of Wistar rat hepatocytes in primary culture was measured by LDH leakage after 12 and 24 h exposure of cells to the various bile acids. All unconjugated bile acids caused a dose-dependent decrease in cell viability. The tauro- and glyco-conjugates of chenodeoxycholate (CDCA) and UDCA were all less toxic than the corresponding unconjugated form. Although relatively non-toxic, UDCA caused synergistic cell killing by lithocholate (LCA), CDCA, glyco-CDCA (GCDC) and tauro-CDCA (TCDC). Glycoursodeoxycholate decreased the toxicity of GCDC, but potentiated the toxicity of unconjugated CDCA and LCA. The tauro-conjugate of UDCA had no significant effect. These data suggest that at cholestatic concentrations, bile acid-induced cell death correlates with the degree of lipophilicity of individual bile acids. However, these results indicate that the reported improvement of biochemical parameters in cholestatic patients treated with UDCA is not due to a direct effect of UDCA on hepatocyte viability. Therefore, any therapeutic effect of UDCA must be secondary to some other process, such as altered membrane transport or nonparenchymal cell function.

Apoptosis in diseases of the liver

Apoptosis, or programmed cell death, and the elimination of apoptotic cells are crucial factors in the maintenance of liver health Apoptosis allows hepatocytes to die without provoking a potentially harmful inflammatory response In contrast to necrosis, apoptosis is tightly controlled and regulated via several mechanisms, including Fas/Fas ligand interactions, the effects of cytokines such as tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta), and the influence of pro- and antiapoptotic mitochondria-associated proteins of the B-cell lymphoma-2 (Bcl-2) family. Efficient elimination of apoptotic cells in the liver relies on Kupffer cells and endothelial cells and is thought to be regulated by the expression of certain cell surface receptors. Liver disease is often associated with enhanced hepatocyte apoptosis, which is the case in viral and autoimmune hepatitis, cholestatic diseases, and metabolic disorders. Disruption of apoptosis is responsible for other diseases, for example, hepatocellular carcinoma. Use and abuse of certain drugs, especially alcohol, chemotherapeutic agents, and acetaminophen, have been associated with increased apoptosis and liver damage. Apoptosis also plays a role in transplantation-associated liver damage, both in ischemia/reperfusion injury and graft rejection. The role of apoptosis in various liver diseases and the mechanisms by which apoptosis occurs in the liver may provide insight into these diseases and suggest possible treatments.

Stimulation of ATP secretion in the liver by therapeutic bile acids

ATP receptors are ubiquitously expressed and are potential targets for the therapy of a number of disorders. However, delivery of ATP or other nucleotides to specific tissues is problematic, and no pharmacological means to stimulate the release of endogenous ATP has been described. We examined the effects of the bile acid ursodeoxycholic acid (UDCA) on ATP release into bile, since this bile acid is the only agent known to be of therapeutic benefit in secretory disorders of the liver, and since its mechanism of action is not established. Both UDCA and its taurine conjugate stimulated secretion of ATP by isolated rat hepatocytes, and produced measurable increases in ATP in bile of isolated rat liver. Perfusion of ATP into microdissected bile-duct segments induced Ca(2+) signalling in bile-duct epithelia, while perfusion of bile acid did not. Thus UDCA may promote bile flow by inducing hepatocytes to release ATP into bile, which then stimulates fluid and electrolyte secretion by bile-duct epithelia downstream via changes in cytosolic Ca(2+). Moreover, these findings demonstrate the feasibility of using pharmacological means to induce secretion of endogenous ATP. Since the liver and other epithelial organs express luminal ATP receptors, these findings more generally suggest that a mechanism exists for pharmacological activation of this paracrine signalling pathway. This strategy may be useful for treatment of cystic fibrosis and other secretory disorders of the liver and other epithelial tissues.

The therapeutic effects of ursodeoxycholic acid as an anti-apoptotic agent

The dihydroxy bile acid, ursodeoxycholic acid (UDCA), has been in widespread clinical use in the Western world since the mid 1980s, when it was initially used for gallstone dissolution [1,2] and subsequently for the treatment of chronic cholestatic liver diseases [3,4]. Many clinical trials of UDCA in a variety of cholestatic disorders established biochemical and clinical improvements, and most importantly showed a significant prolongation of transplant-free survival after four years of treatment with UDCA in patients with primary biliary cirrhosis [5]. Despite its clinical efficacy, the precise mechanism(s) by which UDCA improves liver function during cholestasis is still a matter of debate [6]. It was initially considered that the choleretic effect of UDCA, coupled with its ability to cause a marked shift in the composition of the bile acid pool towards hydrophilicity, accounted for its mechanism of action. In recent years, however, it has become evident that UDCA and its conjugated derivatives are capable of exerting direct effects at the cellular, subcellular, and molecular levels by stabilising cell membranes, affecting signal transduction pathways, and regulating immune responses. In addition, we have shown that UDCA plays a unique role in modulating the apoptotic threshold in both hepatic and non-hepatic cells [7-10]. The purpose of this article is to examine the mechanism(s) by which UDCA prevents apoptotic cell death associated with cholestasis. In addition, we will also review a potentially novel and, heretofore, unrecognised role of UDCA as a therapeutic agent in the treatment of non-liver diseases associated with increased levels of apoptosis as a pathogenesis of the disorder.

Protective role of tauroursodeoxycholate during harvesting and cold storage of human liver: a pilot study in transplant recipients

BACKGROUND

Ischemia-reperfusion injury is a major cause of early graft dysfunction after liver transplantation. Tauroursodeoxycholic acid (TUDCA), a natural amidated hydrophilic bile salt, protects from cholestasis and hepatocellular damage in a variety of experimental models, as well as from ischemia-reperfusion injury. We investigated in the human liver transplantation setting the effect of the addition of TUDCA at time of liver harvesting and cold storage on the intra- and postoperative enzyme release and liver histopathology at the end of cold storage, at reperfusion, and 7 days after transplantation.

METHODS

Eighteen patients undergoing elective liver transplantation were studied, including 6 serving as controls. In six patients, TUDCA was added to the University of Wisconsin solution used during harvesting and cold storage, to reach final concentrations of 2 mM. In three of these patients, TUDCA (3 g) was infused in the portal vein of the donor before organ explantation; in the other three cases, TUDCA was given through both routes.

RESULTS

The use of TUDCA did not cause adverse events. The release of aspartate aminotransferase in the inferior vena cava blood during liver flushing was significantly lower (P=0.05) in TUDCA-treated than in control grafts, as were cytolytic enzyme levels in peripheral blood during the first postoperative week (P<0.02). At electron microscopy, an overt endothelial damage (cytoplasmic vacuolization, cell leakage, and destruction with exposure of hepatocytes to the sinusoidal lumen) was invariably found in control grafts, both at reperfusion and at day 7 after transplant. These features were significantly ameliorated by TUDCA (P<0.001). Several ultrastructural cytoplasmic abnormalities of hepatocytes were seen. Among these, damage to mitochondria matrix and crystae was significantly reduced in TUDCA-treated versus control grafts (P<0.01). Mild to severe damage of bile canaliculi was a constant feature in control biopsies, with dilatation of canalicular lumen and loss of microvilli. Both these abnormalities were markedly ameliorated (P<0.001 by TUDCA). The best preservation was observed when TUDCA was given through both routes.

CONCLUSIONS

The use of TUDCA during harvesting and cold storage of human liver is associated with significant protection from ischemia-reperfusion injury. The clinical significance of this findings must be studied.

MDR3 gene defect in adults with symptomatic intrahepatic and gallbladder cholesterol cholelithiasis

BACKGROUND & AIMS

Many studies indicate that gallstone susceptibility has genetic components. MDR3 is the phosphatidylcholine translocator across the hepatocyte canalicular membrane. Because phospholipids are a carrier and a solvent of cholesterol in hepatic bile, we hypothesized that a defect in the MDR3 gene could be the genetic basis for peculiar forms of cholesterol gallstone disease, in particular those associated with symptoms and cholestasis without evident common bile duct stone.

METHODS

We studied 6 adult patients with a peculiar form of cholelithiasis. MDR3 gene sequence was determined by reverse-transcription polymerase chain reaction amplification of mononuclear cell RNAs followed by direct sequencing. Hepatic bile was analyzed in 2 patients.

RESULTS

All patients shared the following features: at least 1 episode of biliary colic, pancreatitis, or cholangitis; biochemical evidence of chronic cholestasis; recurrence of symptoms after cholecystectomy; presence of echogenic material in the intrahepatic bile ducts; and prevention of recurrence by ursodeoxycholic acid therapy. Hepatic bile composition showed a high cholesterol/phospholipid ratio and cholesterol crystals. In all patients, we found MDR3 gene mutations involving a conserved amino acid region.

CONCLUSIONS

These preliminary observations suggest that MDR3 gene mutations represent a genetic factor involved in this peculiar form of cholesterol gallstone disease in adults. They require further studies to assess the prevalence of MDR3 gene defects in symptomatic and silent cholesterol gallstone disease.

High-dose ursodeoxycholic acid as a therapy for patients with primary sclerosing cholangitis

OBJECTIVES

To assess the tolerability and efficacy of high-dose (25-30 mg/kg per day) ursodeoxycholic acid (UDCA) in patients with primary sclerosing cholangitis (PSC).

METHODS

Thirty patients with PSC were enrolled in this pilot study and treated for 1 yr. Changes in the Mayo risk score at 1 yr of treatment and projected survival at 4 yr were compared with that observed in patients randomized to placebo (n = 52) or UDCA (n = 53) at a dose of 13-15 mg/kg per day.

RESULTS

A marked improvement in serum alkaline phosphatase activity (1265+/-172 vs 693+/-110 U/L, p < 0.001), AST (161+/-037 vs 77+/-13 U/L, p = 0.001), albumin (4.0+/-0.1 vs 4.2+/-0.1 g/dl, p = 0.03), and total bilirubin (1.6+/-0.3 vs 1.3+/-0.2 mg/dl, p = 0.1) occurred at 1 yr of therapy with high-dose UDCA. Changes in the Mayo risk score after 1 yr of treatment were significantly different among the three groups (p < 0.001), and these changes would be translated into a significantly different expected survival at 4 yr (p = 0.05). This expected survival at 4 yr was significantly different between placebo and the dose of 25-30 mg/kg per day (p = 0.04), but not between placebo and the dose of 13-15 mg/kg per day (p = 0.4). High-dose UDCA was well tolerated.

CONCLUSIONS

UDCA at a dose of 25-30 mg/kg per day may be of benefit for patients with PSC, and this regimen deserves further evaluation in a long-term, randomized, placebo-controlled trial.

Cellular distribution of thrombomodulin as an early marker for warm ischemic liver injury in porcine liver transplantation: protective effect of prostaglandin I2 analogue and tauroursodeoxycholic acid

BACKGROUND

Warm ischemia of the graft from non-heart-beating donors is considered a risk factor for posttransplant graft dysfunction. The early administration of cytoprotective agents may help improve graft dysfunction.

METHODS

Four groups of 10 pigs each underwent orthotopic liver transplantation. Prostaglandin I2 analogue, OP-41483, was administered intraportally 30 min before warm ischemic insult in donors and after reperfusion in recipients in one group. In the other study group, additional intravenous tauroursodeoxycholic acid (TUDC) was given before the warm ischemic insult in donors and after reperfusion, then maintained continuously until postoperative day (POD) 7.

RESULTS

Exposure of liver grafts to warm ischemia resulted in severe congestion with the disappearance of thrombomodulin (Tm) from the sinusoidal endothelial cells (SECs) and smooth muscle cells (SMCs) around biliary epithelial cells (BEpCs) 2 hr after reperfusion, followed by positive immunoreactivity of Tm in BEpCs with hyperbilirubinemia, which was related to high mortality. Combined administration of OP-41483 and TUDC had a protective effect, demonstrated by sustained immunoreactivity of Tm from SECs and SMCs until POD 7, without that reactivity in BEpCs. This was associated with reduced congestion and hyperbilirubinemia, similar to the control group not subjected to warm ischemia.

CONCLUSIONS

These findings suggest that negative immunoreactivity of Tm in SECs and SMCs surrounding BEpCs and positive in BEpCs may be an early marker for ischemic liver injury, and that OP-41483 and TUDC may protect against the microcirculatory and biliary derangement.

An NO derivative of ursodeoxycholic acid protects against Fas-mediated liver injury by inhibiting caspase activity

Caspases are key mediators in liver inflammation and apoptosis. In the present study we provide evidence that a nitric oxide (NO) derivative of ursodeoxycholic acid (UDCA), NCX-1000 ([2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester]), protects against liver damage in murine models of autoimmune hepatitis induced by i.v. injection of Con A or a Fas agonistic antibody, Jo2. Con A administration causes CD4(+) T lymphocytes to accumulate in the liver and up-regulates FasL expression, resulting in FasL-mediated cytotoxicity. Cotreating mice with NCX-1000, but not with UDCA, protected against liver damage induced by Con A and Jo2, inhibited IL-1beta, IL-18, and IFN-gamma release and caspase 3, 8, and 9 activation. Studies on HepG2 cells demonstrated that NCX-1000, but not UDCA, directly prevented multiple caspase activation induced by Jo2. Incubating HepG2 cells with NCX-1000 resulted in intracellular NO formation and a DTT-reversible inhibition of proapoptotic caspases, suggesting that cysteine S-nitrosylation was the main mechanism responsible for caspase inhibition. Collectively, these data suggest that NCX-1000 protects against T helper 1-mediated liver injury by inhibiting both the proapoptotic and the proinflammatory branches of the caspase superfamily.

Effect of tauroursodeoxycholate and S-adenosyl-L-methionine on 17beta-estradiol glucuronide-induced cholestasis

BACKGROUND/AIMS

S-adenosyl-L-methionine (SAMe) and tauroursodeoxycholate (TUDC) exert an additive ameliorating effect on taurolithocholate (TLC)-induced cholestasis. The aims were to investigate the protective effect of SAMe on 17beta-estradiol-glucuronide (17betaEG) cholestasis and to find out whether SAMe and TUDC may exert an additive, ameliorating effect.

METHODS

Hepatocyte couplet function was assessed by canalicular vacuolar accumulation (cVA) of cholyllysylfluorescein (CLF). Cells were co-treated with 17betaEG and SAMe, TUDC, or both (protection study), or treated with 17betaEG and then with SAMe, TUDC or both (reversion study) before CLF uptake. Couplets were also co-treated with SAMe and dehydroepiandrosterone (DHEA), a competitive substrate for the sulfotransferase involved in 17betaEG detoxification. The effects of 17betaEG, SAMe and TUDC were also examined on intracellular distribution of F-actin.

RESULTS

Both SAMe and TUDC significantly protected against, and reversed, 17betaEG-induced cholestasis, but their effects were not additive. DHEA abolished the protective effect of SAMe. 17BetaEG did not affect the uptake of CLF into hepatocytes at the concentrations used, and also, it did not affect the intracellular distribution of F-actin.

CONCLUSIONS

17BetaEG does not affect the uptake of CLF into hepatocytes. SAMe and TUDC protect and reverse 17betaEG-induced cholestasis, but without an additive effect. Protection by SAMe may involve facilitating the sulfation of 17betaEG.

Use of ursodeoxycholic acid in liver diseases

Ursodeoxycholic acid is currently the only established drug for the treatment of chronic cholestatic liver diseases. It has cytoprotective, anti-apoptotic, membrane stabilizing, anti-oxidative and immunomodulatory effects. Prolonged administration of ursodeoxycholic acid in patients with primary biliary cirrhosis (PBC) is associated with survival benefit and a delaying of liver transplantation. There is evidence that it might even prevent progression of the histologic stage of PBC. It also has a beneficial effect on primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy, liver disease associated with cystic fibrosis, chronic graft versus host disease, total parenteral nutrition associated cholestasis and various pediatric cholestatic liver diseases. In the present review the current knowledge about the mechanisms of the action and role of ursodeoxycholic acid in the treatment of various liver diseases has been discussed.

Treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a presumed autoimmune disease of the liver, which predominantly affects middle age women. Most patients are diagnosed when asymptomatic. The disease is characterised by chronic, granulomatous inflammation of the small bile ducts, which leads to progressive ductopenia, cholestasis, fibrosis, cirrhosis and eventual liver failure. All PBC patients with abnormal liver biochemistry should be considered for therapy. Ursodeoxycholic acid (URSO) treatment reduces intracellular hydrophobic bile acid levels and thereby may have a cytoprotective effect on cell membranes. URSO may also act as an immunomodulating agent. Multicenter randomised controlled trials proved that the treatment is associated with a marked improvement in serum biochemical markers of cholestasis, i.e. bilirubin, ALP, GGT, including fall in serum cholesterol levels. Treatment does not seem to benefit the symptoms of fatigue, pruritus, and osteoporosis. UDCA has been shown when given in a dose of 15 mg/kg daily for up to 4 years to prolong the time to liver transplantation or death. Immunosuppressive therapy: based on the immunological abnormalities, several immunosuppressive drugs have been tested. Neither azathioprine nor cyclosporine was found in large enough trials to show beneficial effect on survival. D-penicillamine, cholchicin, methotrexát, prednisolone were found without significant long-term benefit. Combination therapy with URSO and budenoside appears to add some benefit to URSO monotherapy, but further studies are needed. Liver transplantation. The most crucial question is the timing. Serum bilirubin, Mayo risk score and some other factors such as uncontrollable pruritus and severe osteoporosis influence the decision. Recurrence of PBC in allograft is rare, the progress is slow, and is no reason for not recommending transplantation. Symptomatic treatment of pruritus, sicca syndrome and preventive treatment of osteoporosis, neuropathy and fat soluble vitamin deficiency is also important.

Tauroursodeoxycholic acid partially prevents apoptosis induced by 3-nitropropionic acid: evidence for a mitochondrial pathway independent of the permeability transition

Ursodeoxycholic acid (UDCA) has been shown to be a strong modulator of the apoptotic threshold in both hepatic and nonhepatic cells. 3-Nitropropionic acid (3-NP), an irreversible inhibitor of succinate dehydrogenase, appears to cause apoptotic neuronal cell death in the striatum, reminiscent of the neurochemical and anatomical changes associated with Huntington's disease (HD). This study was undertaken (a) to characterize further the mechanism by which 3-NP induces apoptosis in rat neuronal RN33B cells and (b) to determine if and how the taurine-conjugated UDCA, tauroursodeoxycholic acid (TUDCA), inhibits apoptosis induced by 3-NP. Our results indicate that coincubation of cells with TUDCA and 3-NP was associated with an approximately 80% reduction in apoptosis (p < 0.001), whereas neither taurine nor cyclosporin A, a potent inhibitor of the mitochondrial permeability transition (MPT), inhibited cell death. Moreover, TUDCA, as well as UDCA and its glycine-conjugated form, glycoursodeoxycholic acid, prevented mitochondrial release of cytochrome c (p < 0.001), which probably accounts for the observed inhibition of DEVD-specific caspase activity and poly(ADP-ribose) polymerase cleavage. 3-NP decreased mitochondrial transmembrane potential (p < 0.001) and increased mitochondrial-associated Bax protein levels (p < 0.001). Coincubation with TUDCA was associated with significant inhibition of these mitochondrial membrane alterations (p < 0.01). The results suggest that TUDCA inhibits 3-NP-induced apoptosis via direct inhibition of mitochondrial depolarization and outer membrane disruption, together with modulation of Bax translocation from cytosol to mitochondria. In addition, cell death by 3-NP apparently occurs through pathways that are independent of the MPT.

Effects of specific bile acids on c-fos messenger RNA levels in human colon carcinoma Caco-2 cells

Bile acids may play a role in the pathogenesis of intestinal inflammation by activating the signalling pathways that control cell proliferation, among other cell systems. We investigated the action of different bile acids, particularly chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA), on steady-state and transcriptional regulation of the protooncogene c-fos, involved in the regulation of cell proliferation and differentiation, in colon carcinoma Caco-2 cells. Specific bile acids had a stimulatory effect of on the expression of c-fos mRNA. This proved to be concentration- and time-dependent and may be partly due to an increase in the rate of transcription of the corresponding gene rather than to any change in the stability of mRNA. In Caco-2 cells exposed to 250 microM CDCA for 1 h a maximal increase of c-fos mRNA ( approximately 2.5-fold induction over the control) was observed; deoxycholic acid (DCA; 250 microM) and lithocholic acid (LCA; 250 microM) were less effective (approximately 2-fold induction over the control). UDCA and cholic acid (CA) did not modify c-fos gene expression in this cell line. Finally, we investigated the role of protein kinase C (PKC) in transcriptional regulation of the c-fos gene by bile acids. Although induction of c-fos by 12-O-tetradecanoyl 13-acetate (10 nM), a potent PKC activator, was completely antagonised by bis-indolyl-maleimide I (1 microM); only about 40% of the bile acid-mediated rise in c-fos mRNA was blocked. Thus it appears that PKC, as well as other signalling pathways, is involved in CDCA-, DCA- and LCA-induced c-fos gene expression.

Cetirizine-induce cholestasis

Cetirizine, a human metabolite of hydroxyzine, is a selective H1-receptor antagonist currently approved for the treatment of seasonal allergic rhinitis, perennial allergic rhinitis, and chronic urticaria. In U.S. clinical trials, transient reversible hepatic transaminase elevations were observed in <2% of patients during cetirizine therapy. We report a case of cetirizine-induced cholestasis in a 28-year-old man with no previous hepatobiliary disease after a 2-year period of taking cetirizine on a daily basis. The treatment of this patient included the use of ursodeoxycholic acid, as well as hydroxyzine, for symptomatic relief of pruritus. In light of the patient's clinical and biochemical improvement while using hydroxyzine, it appears that the hepatic metabolism of hydroxyzine to metabolites, including cetirizine, is not involved in the pathogenesis of this particular case of drug-induced hepatotoxicity. Cetirizine should be considered as a potential cause of drug-induced cholestasis.

Treatment of primary biliary cirrhosis

Although primary biliary cirrhosis (PBC) is generally a progressive disease, the rate of progression varies greatly from one patient to another. The terminal phase is characterized by hyperbilirubinaemia (>100 micromol/l), a major decrease in the number of intrahepatic bile ducts, and extensive fibrosis or cirrhosis. It is now well established that orthotopic liver transplantation is the treatment of choice for patients entering the terminal phase of the disease.A variety of therapeutic agents have been proposed for treatment of patients with PBC. However, most have been found ineffective or too toxic to be widely used. In contrast, there is accumulating evidence from large therapeutic trials that long-term administration of ursodeoxycholic acid (UDCA) is safe and prolongs survival free of liver transplantation. Treatment with UDCA slows the histological progression and delays the onset of cirrhosis. In patients who have a sub-optimal response to UDCA therapy alone, the combination of colchicine or methotrexate with UDCA has minimal or no additional benefit, whereas that with corticosteroids is more promising but not yet demonstrated. Among causes of non-response to UDCA therapy, the most common is the PBC-autoimmune hepatitis overlap syndrome. The benefit from the combination of corticosteroids and UDCA in this setting is obvious.Further studies are needed to define the patients who are most likely to respond to UDCA therapy and to assess the benefit of combined medical treatments.

Hepatobiliary transport

The alterations of hepatobiliary transport that occur in cholestasis can be divided into primary defects, such as mutations of transporter genes or acquired dysfunctions of transport systems that cause defective canalicular or cholangiocellular secretion, and secondary defects, which result from biliary obstruction. The dysfunction of distinct biliary transport systems as a primary cause of cholestasis is exemplified by the genetic defects in progressive familial intrahepatic cholestasis or by the direct inhibition of transporter gene expression by cytokines. In both, the hepatocellular accumulation of toxic cholephilic compounds causes multiple alterations of hepatocellular transporter expression. In addition, lack of specific components of bile caused by a defective transporter, as in the case of mdr2/MDR3 deficiency, unmasks the toxic potential of other components. The production of bile is critically dependent upon the coordinated regulation and function of sinusoidal and canalicular transporters, for instance of Na+-taurocholate cotransporting polypeptide (NTCP) and bile salt export pump (BSEP). Whereas the downregulation of the unidirectional sinusoidal uptake system NTCP protects the hepatocyte from further intracellular accumulation of bile salts, the relative preservation of canalicular BSEP expression serves to uphold bile salt secretion, even in complete biliary obstruction. Conversely, the strong downregulation of canalicular MRP2 (MRP, multidrug resistance protein) in cholestasis forces the hepatocyte to upregulate basolateral efflux systems such as MRP3 and MRP1, indicating an inverse regulation of basolateral and apical transporters The regulation of hepatocellular transporters in cholestasis adheres to the law of parsimony, since many of the cellular mechanisms are pivotally governed by the effect of bile salts. The discovery that bile salts are the natural ligand of the farnesoid X receptor has shown us how the major bile component is able to regulate its own enterohepatic circulation by affecting transcription of the genes critically involved in transport and metabolism.

Ursodeoxycholic acid therapy in hepatobiliary disease

Ursodeoxycholic acid is a hydrophilic bile acid that under normal circumstances represents a small fraction of the bile acid pool in humans. It is effective in dissolving cholesterol gallstones in appropriately selected patients. Ursodeoxycholic acid improves serum alkaline phosphatase and aminotransferase levels in primary biliary cirrhosis, but its effects on rates of liver transplantation and death are less certain. Ursodeoxycholic acid has had promising [corrected] effects in several other cholestatic liver diseases, such as cystic fibrosis and intrahepatic cholestasis of pregnancy, but data are too preliminary to make recommendations about its routine use in these conditions. Its effects are mediated by amelioration of damage to cell membranes caused by retained toxic bile acids. Ursodeoxycholic acid improves biliary secretion of bile acids, may improve bile flow, and it has immunomodulatory properties that may reduce immune-mediated liver damage. However, its use in the treatment of cholestatic liver disease remains uncertain pending additional randomized trials.

URSO-panacea or placebo?

BACKGROUND

Ursodeoxycholic acid (UDCA) is the only approved treatment for primary biliary cirrhosis, but its effect on disease progression is uncertain. The aim of this study was to clarify the efficacy of UDCA in primary biliary cirrhosis.

METHODS

A systematic review, including the use of meta-analysis, was done for the randomised and switch-over phases of trials comparing UDCA with placebo, obtained from Medline and Embase databases, and from manual searches derived from review articles and abstracts of major international meetings. All trials had more than a mean of 6 months' follow-up and only included patients with primary biliary cirrhosis (PBC) according to established diagnostic criteria.

FINDINGS

17 relevant articles were identified: 11 randomised controlled trials, including 1272 patients, and six reports of the switch-over phases. UCDA had a favourable effect on liver biochemistry in most of the studies but not on symptoms or the progression of histological stage; two studies did not assess survival, liver transplantation, or complications of liver disease. Meta-analysis showed no difference between UDCA and placebo in the incidence of death (odds ratio 1.21, 95% CI 0.71-2.04), liver related death (0.72, 0.22-2.32), liver transplantation (1.72, 0.78-2.07), death or transplantation (1.26, 0.87-1.82) and in the development of complications of liver disease (1.11, 0.64-1.92). With the primary end-point defined by the authors (a combined end-point in three studies, and death or liver transplantation in the others) an odds ratio of 1.53 (0.97-2.42) was obtained. Assessment of the switch-over phases, during which there was a longer follow-up, did not change the results of the meta-analysis.

INTERPRETATION

Published randomised controlled trials of UDCA do not show evidence of therapeutic benefit in PBC and its use as standard therapy needs to be re-examined.

Effect of cholestyramine on bile acid pattern and synthesis during administration of ursodeoxycholic acid in man

BACKGROUND

Cholestyramine is the first-line treatment for cholestasis-induced pruritus and is prescribed along with ursodeoxycholic acid (UDCA) in patients with cholestatic liver diseases. Impairment of the intestinal absorption of endogenous hydrophobic bile acids by cholestyramine is well known. It is unclear, however, whether cholestyramine also impairs the absorption of the hydrophilic bile acid, UDCA, in man.

AIMS

To study serum levels of UDCA and endogenous bile acids as well as endogenous bile acid synthesis during simultaneous or separate administration of UDCA and cholestyramine in vivo; and absorption of UDCA both in the presence and absence of its hydrophobic epimer, chenodeoxycholic acid (CDCA), by cholestyramine in vitro.

PATIENTS AND METHODS

Five healthy subjects received UDCA (12.5 +/- 0.5 mg kg-1 daily) as a single dose for periods of 14 days with or without cholestyramine (4 g daily). Fasting serum levels of bile acids and of 7alpha-hydroxy-4-cholesten-3-one (alpha-HC), a measure of endogenous bile acid synthesis, were determined by gas chromatography and high pressure liquid chromatography, respectively. In vitro, bile acid solutions were incubated for 24 h in the presence or absence of cholestyramine, and bile acid concentrations were determined in the supernatant.

RESULTS

Simultaneous administration of UDCA and cholestyramine in man led to a decrease of fasting serum levels of UDCA by 60% when compared to UDCA serum levels during administration of UDCA alone. In contrast, serum levels of endogenous bile acids were not affected and alpha-HC serum levels were found increased 2. 7-fold indicating stimulation of endogenous bile acid synthesis by cholestyramine. Administration of cholestyramine and UDCA at an interval of 5 h tended to diminish the effect of cholestyramine on UDCA serum levels. In vitro, conjugated and unconjugated UDCA were effectively bound by cholestyramine both in the presence and absence of hydrophobic bile acids.

CONCLUSIONS

The results strongly support the recommendation to administer UDCA and cholestyramine at different times of day.

The significance of apoptosis in the liver

Apoptosis is a form of cell death which occurs in normal as well as in pathological tissues. We provide a description of the morphological changes during apoptosis and an overview of the role of apoptosis dysregulation in the pathogenesis of non-neoplastic liver diseases.

Randomised controlled trials of ursodeoxycholic-acid therapy for primary biliary cirrhosis: a meta-analysis

BACKGROUND

Ursodeoxycholic acid (UDCA) is the only approved treatment for primary biliary cirrhosis, but its effect on disease progression and survival is uncertain. The aim of this study was to clarify the efficacy of UDCA in primary biliary cirrhosis.

METHODS

A systematic review, including the use of meta-analysis, was done for the randomised and switch-over phases of trials comparing UDCA with placebo, obtained from Medline and Embase databases, and from manual searches derived from review articles and abstracts of major international meetings. All trials had more than a mean of 6 months' follow-up and only included patients with primary biliary cirrhosis (PBC) according to established diagnostic criteria.

FINDINGS

17 relevant articles were identified: 11 randomised controlled trials, including 1272 patients, and six reports of the switch-over phases. UCDA had a favourable effect on liver biochemistry in most of the studies but not on symptoms or the progression of histological stage; two studies did not assess survival, liver transplantation, or complications of liver disease. Meta-analysis showed no difference between UDCA and placebo in the incidence of death (odds ratio 1.21, 95% CI 0.71-2.04), liver related death (0.72, 0.22-2.32), liver transplantation (1.27, 0.78-2.07), death or liver transplantation (1.26, 0.87-1.82), and in the development of complications of liver disease (1.11, 0.64-1.92). With the primary end point defined by the authors (a combined end point in three studies, and death or liver transplantation in the others) an odds ratio of 1.53 (0.97-2.42) was obtained. Assessment of the switch-over phases, during which there was a longer follow-up, did not change the results of the meta-analysis.

INTERPRETATION

Published randomised controlled trials of UDCA do not show evidence of therapeutic benefit in PBC and its use as standard therapy needs to be re-examined.

Effect of ursodeoxycholic acid administration in patients with acute viral hepatitis: a pilot study

BACKGROUND

Ursodeoxycholic acid (UDCA) is able to improve biochemical markers of cholestasis, with a parallel decrease in transaminases, in various cholestatic liver diseases.

AIM

To evaluate the effects of UDCA administration on acute viral hepatitis-related cholestasis and the course of acute viral hepatitis.

METHODS

Seventy-nine consecutive patients with acute viral hepatitis (HBV: 43, HCV: 11, HAV: 15, HEV: 3, Non A-E: 7) were randomized to receive either UDCA for 3 weeks or no treatment. Liver biochemistry and serum bile acid determinations were run at weekly intervals.

RESULTS

No significant differences were observed in mean percentage decreases in transaminases between treated and untreated patients. By contrast, cholestatic indexes decreased significantly more quickly in patients treated with UDCA than in controls, and this effect was more evident in patients with increasing alanine transaminase levels at admission. After a peak at the end of the first week of therapy, serum levels of conjugated ursodeoxycholic acid (CUDCA) showed a gradual decrease. Conjugated cholic acid (CCA) and chenodeoxycholic acid (CCDCA) showed a progressive decrease with the resolution of viral hepatitis, but no influence of UDCA administration was observed.

CONCLUSIONS

Our study demonstrates that UDCA significantly improves cholestatic indices in patients with acute viral hepatitis, but this effect does not seem to affect the course of the illness.

Review article: mechanisms of action and therapeutic applications of ursodeoxycholic acid in chronic liver diseases

Ursodeoxycholic acid (ursodiol) is a non-toxic, hydrophilic bile acid used to treat predominantly cholestatic liver disorders. Better understanding of the cellular and molecular mechanisms of action of ursodeoxycholic acid has helped to elucidate its cytoprotective, anti-apoptotic, immunomodulatory and choleretic effects. Ursodeoxycholic acid prolongs survival in primary biliary cirrhosis and it improves biochemical parameters of cholestasis in various other cholestatic disorders including primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy, cystic fibrosis and total parenteral nutrition-induced cholestasis. However, a positive effect on survival remains to be established in these diseases. Ursodeoxycholic acid is of unproven efficacy in non-cholestatic disorders such as acute rejection after liver transplantation, non-alcoholic steatohepatitis, alcoholic liver disease and chronic viral hepatitis. This review outlines the present knowledge of the modes of action of ursodeoxycholic acid, and presents data from clinical trials on its use in chronic liver diseases.

Intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy is one of the primary disorders of the liver that adversely affects maternal well-being and fetal outcome. Early identification of this condition, careful interdisciplinary monitoring, and prompt delivery at fetal maturity can improve outcomes in the mother and child. Although the cause is unclear, IHCP probably arises from a genetic predisposition for increased sensitivity to estrogens and progestogens and altered membrane composition and expression of bile ducts, hepatocytes, and canalicular transport systems. As a result, the elevations in maternal levels of bile acids and their molar ratios seen in healthy pregnancy rise further in IHCP patients. Also, as the normal fetal-to-maternal transfer of bile acids across the trophoblast is impaired, the excess bile acids with abnormal profiles accumulate and are toxic to the fetus. The management of IHCP is dictated by the increased risks of fetal distress, spontaneous preterm delivery, and sudden death, as well as by alleviating pruritus in the mother. These risks to the fetus rise progressively to delivery, regardless of serum levels of bile acids and ALT. Close monitoring of these markers is essential but does not prevent sudden fetal distress and death. Provision should be made to induce labor as soon as fetal lung maturity has been established. Ursodeoxycholic acid is the only therapy that has proven effective, albeit in small studies, in alleviating pruritus and restoring towards normal the abnormal profiles of bile acids and sulfated steroids in serum and other body fluids. Ursodeoxycholic acid seems to have no obvious adverse effects on the fetus, but experience is insufficient to draw conclusions regarding teratogenicity and prevention of adverse outcomes.