A novel role for ursodeoxycholic acid in inhibiting apoptosis by modulating mitochondrial membrane perturbation

Efficacy of ursodesoxycholic acid in treatment of nonalcoholic fatty liver disease: A meta-analysis

AIM: To evaluate the efficacy and safety of ursodesoxycholic acid in the treatment of nonalcoholic fatty liver disease (NAFLD).

METHODS: Randomized controlled clinical trials comparing the efficacy of ursodesoxycholic acid alone or in combination with other drugs versus other drugs or placebo alone in the treatment of NAFLD were retrieved by searching PubMed, Embase, OVID, Cochrane Library , CNKI, and Wanfang database. Review Manager 5.0 was used for meta-analysis.

RESULTS: Compared to the ursodesoxycholic acid monotherapy group, the drug combination group had significantly improved total effective rate (RR = 1.23, 95%CI: 1.07-1.41, P = 0.004) and decreased serum levels of TC (WMD = -1.69, 95%CI: -2.77--0.62, P = 0.002), TG (WMD = -1.01, 95%CI: -1.59--0.43, P = 0.0006), ALT (WMD = -22.65, 95%CI: -35.27--10.04, P = 0.0004), and AST (WMD =- 21.93, 95%CI: -23.74--20.12, P < 0.00001). The decrease in GGT was significant in both the ursodesoxycholic acid monotherapy group and drug combination group (WMD = -21.96, 95%CI: -35.73--8.18, P = 0.002; WMD = -28.80, 95%CI: -51.85--5.76, P = 0.01). There was no statistically significant difference in the incidence of adverse reactions (RR = 2.26, 95%CI: 0.88-5.83, P = 0.09).

CONCLUSION: Ursodesoxycholic acid is effective and safe in the management of NAFLD, and better efficacy can be achieved when it is combined with other positive agents.

The immunophysiology and apoptosis of biliary epithelial cells: primary biliary cirrhosis and primary sclerosing cholangitis

Biliary epithelial cells (BECs) provide the first line of defense against lumenal microbes in the biliary system. BECs express a variety of pathogen recognition receptors and can activate several intracellular signaling cascades to initiate antimicrobial defenses, including production of several anti-microbial peptides, cytokines, chemokines, and adhesion molecules. BECs also secrete immunoglobulin A and interact with other cells through expression and release of adhesion molecules and immune mediators. Recently, several reports suggest a correlation between apoptosis and autoimmunity through ineffective clearance of self-antigens. Primary biliary cirrhosis (PBC) is a slowly progressive, autoimmune cholestatic liver disease characterized by highly specific antimitochondrial antibodies (AMAs) and the specific immune-mediated destruction of BECs. We have demonstrated that the AMA self-antigen, namely the E2 subunit of the pyruvate dehydrogenase complex, is detectable in its antigenically reactive form within apoptotic blebs from human intrahepatic biliary epithelial cells and activates innate immune responses. Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by inflammation and the presence of concentric fibrosis of intrahepatic and/or extrahepatic bile ducts, eventually leading to cirrhosis. However, apoptosis does not appear to play a central role in PSC. Despite both diseases involving immune-mediated injury to bile ducts, apoptosis occurs more commonly overall in PBC where it likely plays a unique role.

Interventions for treating cholestasis in pregnancy

BACKGROUND

Obstetric cholestasis has been linked to adverse maternal and fetal/neonatal outcomes. As the pathophysiology is poorly understood, therapies have been empiric. The first version of this review, published in 2001, and including nine randomised controlled trials involving 227 women, concluded that there was insufficient evidence to recommend any of the interventions alone or in combination. This is the first update.

OBJECTIVES

To evaluate the effectiveness and safety of therapeutic and delivery interventions in women with cholestasis of pregnancy.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (20 February 2013) and reference lists of identified studies.

SELECTION CRITERIA

Randomised controlled trials that compared two intervention strategies for women with a clinical diagnosis of obstetric cholestasis.

DATA COLLECTION AND ANALYSIS

The review authors independently assessed trials for eligibility and risk of bias. We independently extracted data and checked these for accuracy.

MAIN RESULTS

We included 21 trials with a total of 1197 women. They were mostly at moderate to high risk of bias. They assessed 11 different interventions resulting in 15 different comparisons.Compared with placebo, ursodeoxycholic acid (UDCA) showed improvement in pruritus in five (228 women) out of seven trials. There were no significant differences in instances of fetal distress in the UDCA groups compared with placebo (average risk ratio (RR) 0.67; 95% confidence interval (CI) 0.22 to 2.02; five trials, 304 women; random-effects analysis: T² = 0.74; I² = 48%). There were significantly fewer total preterm births with UDCA (RR 0.46; 95% CI 0.28 to 0.73; two trials, 179 women). The difference for spontaneous preterm births was not significant (RR 0.99; 95% CI 0.41 to 2.36, two trials, 109 women).Two trials (48 women) reported lower (better) pruritus scores for S-adenosylmethionine (SAMe) compared with placebo, while two other trials of 34 women reported no significant differences between groups.UDCA was more effective in improving pruritus than either SAMe (four trials; 133 women) or cholestyramine (one trial; 84 women), as was combined UDCA+SAMe when compared with placebo (one trial; 16 women) and SAMe alone (two trials; 68 women). However, combined UDCA+SAMe was no more effective than UDCA alone in regard to pruritus improvement (one trial; 53 women) and two trials (80 women) reported data were insufficient to draw any conclusions from. In one trial comparing UDCA and dexamethasone (83 women), a significant improvement with UDCA was seen only in a subgroup of women with severe obstetric cholestasis (23 women).Danxiaoling significantly improved pruritus in comparison to Yiganling. No significant differences were seen in pruritus improvement with other interventions.Eight trials reported fetal or neonatal deaths, with two deaths reported overall (both in the placebo groups).Women receiving UDCA and cholestyramine experienced nausea, vomiting and diarrhoea. Guar gum caused mild abdominal distress, diarrhoea and flatulence during the first days of treatment. Women found charcoal suspension unpleasant to swallow. Dexamethasone caused nausea, dizziness and stomach pain in one woman.One trial (62 women) looked at the timing of delivery intervention. There were no stillbirths or neonatal deaths in 'early delivery' or the 'await spontaneous labour' group. There were no significant differences in the rates of caesarean section, meconium passage or admission to neonatal intensive care unit between the two groups.

AUTHORS' CONCLUSIONS

Different approaches to assessing and reporting pruritus precluded pooling of trials comparing the effects of UDCA versus placebo on pruritus, but examination of individual trials suggests that UDCA significantly improves pruritus, albeit by a small amount. Fewer instances of fetal distress/asphyxial events were seen in the UDCA groups when compared with placebo but the difference was not statistically significant. Large trials of UDCA to determine fetal benefits or risks are needed.A single trial was too small to rule in or out a clinically important effect of early term delivery on caesarean section.There is insufficient evidence to indicate that SAMe, guar gum, activated charcoal, dexamethasone, cholestyramine, Salvia, Yinchenghao decoction (YCHD), Danxioling and Yiganling, or Yiganling alone or in combination are effective in treating women with cholestasis of pregnancy.

Non-alcoholic steatohepatitis in morbidly obese patients

The hepatic complications of morbid obesity range from steatosis to steatohepatitis (Non-alcoholic steatohepatitis [NASH]), fibrosis, cirrhosis and finally hepatocellular carcinoma. The pathophysiological mechanisms of the progression of a normal liver to a liver showing steatosis and then steatohepatitis are complex, including, per se, insulin-resistance, iron accumulation, oxidative stress and hepatocyte death. An imbalance in anti- and pro-inflammatory factors may be the trigger. These factors can originate from intra- or extrahepatic sites, particularly the adipose tissue and the gut. This review will provide insight into the current diagnosis and understanding of hepatic inflammation including non-invasive markers of NASH (markers of hepatocyte death), intrahepatic mechanisms (regulation of the immune and inflammatory response, hepatocellular iron deposition, hepatocyte death) and extrahepatic factors (from adipose tissue and gut) in morbidly obese patients.

miR-34a/SIRT1/p53 is suppressed by ursodeoxycholic acid in the rat liver and activated by disease severity in human non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) comprises a spectrum of stages from simple steatosis to non-alcoholic steatohepatitis (NASH). However, disease pathogenesis remains largely unknown. microRNA (miRNA or miR) expression has recently been reported to be altered in human NASH, and modulated by ursodeoxycholic acid (UDCA) in the rat liver. Here, we aimed at evaluating the miR-34a/Sirtuin 1(SIRT1)/p53 pro-apoptotic pathway in human NAFLD, and to elucidate its function and modulation by UDCA in the rat liver and primary rat hepatocytes.

METHODS

Liver biopsies were obtained from NAFLD morbid obese patients undergoing bariatric surgery. Rat livers were collected from animals fed a 0.4% UDCA diets. Primary rat hepatocytes were incubated with bile acids or free fatty acids (FFAs) and transfected with a specific miRNA-34a precursor and/or with a p53 overexpression plasmid. p53 transcriptional activity was assessed by ELISA and target reporter constructs.

RESULTS

miR-34a, apoptosis and acetylated p53 increased with disease severity, while SIRT1 diminished in the NAFLD liver. UDCA inhibited the miR-34a/SIRT1/p53 pathway in the rat liver in vivo and in primary rat hepatocytes. miR-34a overexpression confirmed its targeting by UDCA, which prevented miR-34a-dependent repression of SIRT1, p53 acetylation, and apoptosis. Augmented apoptosis by FFAs in miR-34a overexpressing cells was also inhibited by UDCA. Finally, p53 overexpression activated miR-34a/SIRT1/p53, which in turn was inhibited by UDCA, via decreased p53 transcriptional activity.

CONCLUSIONS

Our results support a link between liver cell apoptosis and miR-34a/SIRT1/p53 signaling, specifically modulated by UDCA, and NAFLD severity. Potential endogenous modulators of NAFLD pathogenesis may ultimately provide new tools for therapeutic intervention.

Prevention of acute kidney injury by tauroursodeoxycholic acid in rat and cell culture models

BACKGROUND

Acute kidney injury (AKI) has grave short- and long-term consequences. Often the onset of AKI is predictable, such as following surgery that compromises blood flow to the kidney. Even in such situations, present therapies cannot prevent AKI. As apoptosis is a major form of cell death following AKI, we determined the efficacy and mechanisms of action of tauroursodeoxycholic acid (TUDCA), a molecule with potent anti-apoptotic and pro-survival properties, in prevention of AKI in rat and cell culture models. TUDCA is particularly attractive from a translational standpoint, as it has a proven safety record in animals and humans.

METHODOLOGY/PRINCIPAL FINDINGS

We chose an ischemia-reperfusion model in rats to simulate AKI in native kidneys, and a human kidney cell culture model to simulate AKI associated with cryopreservation in transplanted kidneys. TUDCA significantly ameliorated AKI in the test models due to inhibition of the mitochondrial pathway of apoptosis and upregulation of survival pathways.

CONCLUSIONS

This study sets the stage for testing TUDCA in future clinical trials for prevention of AKI, an area that needs urgent attention due to lack of effective therapies.

Novel insight into mechanisms of cholestatic liver injury

Cholestasis results in a buildup of bile acids in serum and in hepatocytes. Early studies into the mechanisms of cholestatic liver injury strongly implicated bile acid-induced apoptosis as the major cause of hepatocellular injury. Recent work has focused both on the role of bile acids in cell signaling as well as the role of sterile inflammation in the pathophysiology. Advances in modern analytical methodology have allowed for more accurate measuring of bile acid concentrations in serum, liver, and bile to very low levels of detection. Interestingly, toxic bile acid levels are seemingly far lower than previously hypothesized. The initial hypothesis has been based largely upon the exposure of μmol/L concentrations of toxic bile acids and bile salts to primary hepatocytes in cell culture, the possibility that in vivo bile acid concentrations may be far lower than the observed in vitro toxicity has far reaching implications in the mechanism of injury. This review will focus on both how different bile acids and different bile acid concentrations can affect hepatocytes during cholestasis, and additionally provide insight into how these data support recent hypotheses that cholestatic liver injury may not occur through direct bile acid-induced apoptosis, but may involve largely inflammatory cell-mediated liver cell necrosis.

Tauroursodeoxycholic acid (TUDCA) supplementation prevents cognitive impairment and amyloid deposition in APP/PS1 mice

Alzheimer's disease (AD) is a neurodegenerative disease hallmarked by extracellular Aβ(1-42) containing plaques, and intracellular neurofibrillary tangles (NFT) containing hyperphosphorylated tau protein. Progressively, memory deficits and cognitive disabilities start to occur as these hallmarks affect hippocampus and frontal cortex, regions highly involved in memory. Connective tissue growth factor (CTGF) expression, which is high in the vicinity of Aβ plaques and NFTs, was found to influence γ-secretase activity, the molecular crux in Aβ(1-42) production. Tauroursodeoxycholic acid (TUDCA) is an endogenous bile acid that downregulates CTGF expression in hepatocytes and has been shown to possess therapeutic efficacy in neurodegenerative models. To investigate the possible in vivo therapeutic effects of TUDCA, we provided 0.4% TUDCA-supplemented food to APP/PS1 mice, a well-established AD mouse model. Six months of TUDCA supplementation prevented the spatial, recognition and contextual memory defects observed in APP/PS1 mice at 8 months of age. Furthermore, TUDCA-supplemented APP/PS1 mice displayed reduced hippocampal and prefrontal amyloid deposition. These effects of TUDCA supplementation suggest a novel mechanistic route for Alzheimer therapeutics.

Treatment of NASH with ursodeoxycholic acid: pro

Ursodeoxycholic acid (UDCA) is one of hepatologists'oldest friends, always ready to help, throughout the years, in numerous and various liver and biliary tract diseases. On paper, it has had an impeccable track record of cytoprotection in vitro and in vivo due to its pleiotropic effects on many pathways leading to cell injury. Most of its hepatoprotective effects demonstrated under experimental conditions proved able to counteract pathogenic mechanisms involved in the transition from steatosis to steatohepatitis, and early clinical studies suggested a potentially beneficial effect in non-alcoholic steatohepatitis (NASH) as well. Yet, only scant data on the efficacy of UDCA specifically in experimental models of steatosis/NASH are available, and the few available randomized controlled clinical studies have substantial methodological issues and are discussed in this review. Thus, at this point, there is not enough evidence to either confirm or reject the efficacy of UDCA in NASH, although many NASH patients clearly experience biochemical improvements with prolonged UDCA treatment. Also, a few new UDCA derivatives have shown promising activity in preclinical models and may be worth testing in clinical trials.

Primary biliary cirrhosis and bile acids

The dihydroxylated bile acid ursodeoxycholic acid (UDCA) has now been regarded for 20 years as the standard treatment for primary biliary cirrhosis (PBC), a chronic cholestatic immune-mediated condition marked by progressive destruction of small intrahepatic bile ducts, impaired biliary secretion, hepatocellular retention of toxic endogenous bile acids and, ultimately, the development of fibrosis leading to cirrhosis that commonly requires liver transplantation. At first sight, it seems intriguing that a bile acid could be considered for use as a therapeutic agent in a bile-acid secretion disorder. Yet, in addition to its inherently greater hydrophilic nature and competitive effect on endogenous bileacid recycling, UDCA has indeed been demonstrated to be a potent post-transcriptional secretagogue as well as a potential anti-inflammatory and anti-apoptotic agent. While the combined glucocorticoid receptor/pregnane X receptor (PXR) agonist budesonide, in combinaison with UDCA, has been shown to exert additional beneficial effects in PBC, significant progress in understanding the regulatory mechanisms involved in bile-acid homeostasis has led to the identification of nuclear [farnesoid X receptor (FXR), PXR, peroxisome proliferator-activated receptor alpha (PPARα)] and membrane (the membrane G protein-coupled bile acid receptor TGR5) receptors as critical pharmacological targets for future therapeutic approaches. Encouraging data from recent experimental and phase-II studies tend to confirm that the FXR agonist obeticholic acid and the PPARα agonists bezafibrate and fenofibrate may be used as add-on therapies in PBC patients with inadequate responses to UDCA or even as alternative first-line agents. These results could mark the beginning of a new therapeutic era for PBC.

Treatment of NASH with ursodeoxycholic acid: cons

Non-alcoholic steatohepatitis (NASH) has a prevalence of 1% in Western countries. Its causes as well as its medical treatment are, to date, still debated. Recently, studies of agents suggested to have antiapoptotic, insulin-sensitizing or anti-inflammatory effects in patients with NASH have been conducted, one of which is ursodeoxycholic acid (UDCA), a tertiary bile acid. Between 1994 and 2008, four prospective randomized, double-blind, placebo-controlled studies of the treatment of NASH with UDCA were conducted. The first study, by Lindor et al., compared the impact of 13-15 mg/kg/day of UDCA to a placebo. The second study by Dufour et al. had an additional third arm that administered combination therapy with UDCA and vitamin E. The third and fourth studies by Leuschner et al. and by Ratziu et al. evaluated high doses of UDCA at 25-35 mg/kg/day, and used liver biopsies and serum liver enzyme levels to evaluate the impact of UDCA. With the exception of Ratziu et al.'s study, which was lacking a second liver biopsy, none of these studies showed any significant differences in the treatment of NASH with UDCA compared with a placebo. However, Dufour et al. did observe a significant improvement of NASH with the combination (UDCA/VitE) vs placebo therapy, whereas UDCA monotherapy was not effective in the treatment of NASH. Nevertheless, the effects of other bile acids and combination therapies need to be explored.

Molecular mechanisms of ursodeoxycholic acid toxicity & side effects: ursodeoxycholic acid freezes regeneration & induces hibernation mode

Ursodeoxycholic acid (UDCA) is a steroid bile acid approved for primary biliary cirrhosis (PBC). UDCA is reported to have “hepato-protective properties”. Yet, UDCA has “unanticipated” toxicity, pronounced by more than double number of deaths, and eligibility for liver transplantation compared to the control group in 28 mg/kg/day in primary sclerosing cholangitis, necessitating trial halt in North America. UDCA is associated with increase in hepatocellular carcinoma in PBC especially when it fails to achieve biochemical response (10 and 15 years incidence of 9% and 20% respectively). “Unanticipated” UDCA toxicity includes hepatitis, pruritus, cholangitis, ascites, vanishing bile duct syndrome, liver cell failure, death, severe watery diarrhea, pneumonia, dysuria, immune-suppression, mutagenic effects and withdrawal syndrome upon sudden halt. UDCA inhibits DNA repair, co-enzyme A, cyclic AMP, p53, phagocytosis, and inhibits induction of nitric oxide synthatase. It is genotoxic, exerts aneugenic activity, and arrests apoptosis even after cellular phosphatidylserine externalization. UDCA toxicity is related to its interference with drug detoxification, being hydrophilic and anti-apoptotic, has a long half-life, has transcriptional mutational abilities, down-regulates cellular functions, has a very narrow difference between the recommended (13 mg/kg/day) and toxic dose (28 mg/kg/day), and it typically transforms into lithocholic acid that induces DNA strand breakage, it is uniquely co-mutagenic, and promotes cell transformation. UDCA beyond PBC is unjustified.

Bile acids: from digestion to cancers

Bile acids (BAs) are cholesterol metabolites that have been extensively studied these last decades. BAs have been classified in two groups. Primary BAs are synthesized in liver, when secondary BAs are produced by intestinal bacteria. Recently, next to their ancestral roles in digestion and fat solubilization, BAs have been described as signaling molecules involved in many physiological functions, such as glucose and energy metabolisms. These signaling pathways involve the activation of the nuclear receptor FXRα or of the G-protein-coupled receptor TGR5. These two receptors have selective affinity to different types of BAs and show different expression patterns, leading to different described roles of BAs. It has been suggested for long that BAs could be molecules linked to tumor processes. Indeed, as many other molecules, regarding analyzed tissues, BAs could have either protective or pro-carcinogen activities. However, the molecular mechanisms responsible for these effects have not been characterized yet. It involves either chemical properties or their capacities to activate their specific receptors FXRα or TGR5. This review highlights and discusses the potential links between BAs and cancer diseases and the perspectives of using BAs as potential therapeutic targets in several pathologies.

Tauroursodeoxycholic acid suppresses amyloid β-induced synaptic toxicity in vitro and in APP/PS1 mice

Synapses are considered the earliest site of Alzheimer's disease (AD) pathology, where synapse density is reduced, and synaptic loss is highly correlated with cognitive impairment. Tauroursodeoxycholic acid (TUDCA) has been shown to be neuroprotective in several models of AD, including neuronal exposure to amyloid β (Aβ) and amyloid precursor protein (APP)/presenilin 1 (PS1) double-transgenic mice. Here, we show that TUDCA modulates synaptic deficits induced by Aβ in vitro. Specifically, TUDCA reduced the downregulation of the postsynaptic marker postsynaptic density-95 (PSD-95) and the decrease in spontaneous miniature excitatory postsynaptic currents (mEPSCs) frequency, while increasing the number of dendritic spines. This contributed to the induction of more robust and synaptically efficient neurons, reflected in inhibition of neuronal death. In vivo, TUDCA treatment of APP/PS1 mice abrogated the decrease in PSD-95 reactivity in the hippocampus. Taken together, these results expand the neuroprotective role of TUDCA to a synaptic level, further supporting the use of this molecule as a potential therapeutic strategy for the prevention and treatment of AD.

Damage to mtDNA in liver injury of patients with extrahepatic cholestasis: the protective effects of mitochondrial transcription factor A

Oxidative stress and mitochondrial dysfunction are involved in the pathogenesis of chronic liver cholestasis. Mitochondrial DNA (mtDNA) is highly susceptible to oxidative stress and mtDNA damage leads to mitochondrial dysfunction. This study aimed to investigate the mtDNA alterations that occurred during liver injury in patients with extrahepatic cholestasis. Along with an increase in malondialdehyde (MDA) levels and a decrease in ATP levels, extrahepatic cholestatic patients presented a significant increase in mitochondrial 8-hydroxydeoxyguanosine (8-OHdG) levels and decreases in mtDNA copy number, mtDNA transcript levels, and mtDNA nucleoid structure. In L02 cells, glycochenodeoxycholic acid (GCDCA) induced similar damage to the mtDNA and mitochondria. In line with the mtDNA alterations, the mRNA and protein levels of mitochondrial transcription factor A (TFAM) were significantly decreased both in cholestatic patients and in GCDCA-treated L02 cells. Moreover, overexpression of TFAM could efficiently attenuate the mtDNA damage induced by GCDCA in L02 cells. However, without its C-tail, ΔC-TFAM appeared less effective against the hepatotoxicity of GCDCA than the wild-type TFAM. Overall, our study demonstrates that mtDNA damage is involved in liver damage in extrahepatic cholestatic patients. The mtDNA damage is attributable to the loss of TFAM. TFAM has mtDNA-protective effects against the hepatotoxicity of bile acid during cholestasis.

Ursodeoxycholic acid protects colon cancer HCT116 cells from deoxycholic acid-induced apoptosis by inhibiting apoptosome formation

We previously demonstrated that ursodeoxycholic acid (UDC) requires prolonged (≥5 h) preincubation to exhibit effective protection of colon cancer HCT116 cells from deoxycholic acid (DC)-induced apoptosis. Although UDC diminished DC-mediated caspase-9 activation, cytochrome c release from the mitochondria was not inhibited, indicating that UDC acts on the steps of caspase-9 activation. In the present study, therefore, we investigated the effects of UDC on the factors involved in caspase-9 activation. We found that UDC had no significant effect on the expression of antiapoptotic XIAP. Furthermore, UDC did not affect the expression or release of proapoptotic Smac/DIABLO, or the association of XIAP and Smac/DIABLO. In contrast, association of Apaf-1 and caspase-9 stimulated by 500 μM DC was inhibited by UDC pretreatment. Although UDC caused remarkable activation of Akt/PKB, phosphatidylinositol-3-kinase (PI3K) inhibitor did not significantly reduce UDC-mediated cytoprotection. Furthermore, phosphorylation of threonine residues on caspase-9 after UDC pretreatment could not be detected. UDC-mediated cytoprotection was independent of the MAPK pathway, and cyclic AMP (cAMP) analogue did not inhibit DC-induced apoptosis. Our results indicate that UDC protects colon cancer cells from apoptosis induced by hydrophobic bile acids, by inhibiting apoptosome formation independently of the survival signals mediated by the PI3K, MAPK, or cAMP pathways.

Possible mechanisms underlying the biphasic regulatory effects of arachidonic acid on Ca2+ signaling in HEK293 cells

Arachidonic acid (AA), an endogenous lipid signal molecule released from membrane upon cell activation, modulates intracellular Ca(2+) ([Ca(2+)](i)) signaling positively and negatively. However, the mechanisms underlying the biphasic effects of AA are rather obscure. Using probes for measurements of [Ca(2+)](i) and fluidity of plasma membrane (PM)/endoplasmic reticulum (ER), immunostaining, immunoblotting and shRNA interference approaches, we found that AA at low concentration, 3 μM, reduced the PM fluidity by activating PKCα and PKCβII translocation to PM and also the ER fluidity directly. In accordance, 3 μM AA did not impact the basal [Ca(2+)](i) but significantly suppressed the thapsigargin-induced Ca(2+) release and Ca(2+) influx. Inhibition of PKC with Gö6983 or knockdown of PKCα or PKCβ using shRNA significantly attenuated the inhibitory effects of 3 μM AA on PM fluidity and agonist-induced Ca(2+) signal. However, AA at high concentration, 30 μM, caused robust release and entry of Ca(2+) accompanied by a facilitated PM fluidity but decreased ER fluidity and dramatic PKCβI and PKCβII redistribution in the ER. Compared with ursodeoxycholate acid, a membrane stabilizing agent that only inhibited the 30 μM AA-induced Ca(2+) influx by 45%, Gd(3+) at concentration of 10 μM could completely abolish both release and entry of Ca(2+) induced by AA, suggesting that the potentiated PM fluidity is not the only reason for AA eliciting Ca(2+) signal. Therefore, the study herein demonstrates that a lowered PM fluidity by PKC activation and a direct ER stabilization contribute significantly for AA downregulation of [Ca(2+)](i) response, while Gd(3+)-sensitive 'pores' in PM/ER play an important role in AA-induced Ca(2+) signal in HEK293 cells.

Comparison of different bile acid-phospholipid conjugates in acute hepatitis

INTRODUCTION

The bile acid-phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE) is a promising novel compound with profound hepatoprotective functions in vitro and in vivo. Because of high costs of LPE synthesis from hydrolysis of phosphatidylethanolamide (PE), costs for UDCA-LPE synthesis for in vivo and human use can become quite high. In this study, we evaluated whether ursodeoxycholyl phosphatidylethanolamide (udca-pe), which is more cost-effective, could replace udca-lpe in terms of protection from hepatocellular injury.

MATERIALS AND METHODS

Anti-apoptotic and anti-inflammatory properties of UDCA-PE and UDCA-LPE were compared in TNFα/cyclohexamide (CHX)-treated HepG2 cells as well as in a mouse model of d-galactosamine/lipopolysaccharide (Gal/LPS)-induced acute liver injury.

RESULTS

Ursodeoxycholyl lysophosphatidylethanolamide inhibited TNFα/CHX-induced apoptosis in HepG2 cells in a dose-dependent manner and markedly ameliorated Gal/LPS-mediated fulminant hepatitis in mice. In contrast, UDCA-PE showed weaker hepatoprotective functions at low concentrations, and protection was lost at higher dosage. Analysis of hepatic gene expression showed that both conjugates significantly reduced Gal/LPS-mediated expression of chemoattractants, such as monocyte chemotactic protein 1 (MCP1) and RANTES. These inhibitory effects by UDCA-PE were transient while those by UDCA-LPE were sustained in attenuating expression of inflammatory MCP1 and RANTES expression.

CONCLUSIONS

Our data underline the superiority of UDCA-LPE compared to UDCA-PE in ameliorating acute liver inflammation. This indicates the significance of the lyso-functional group of bile acid conjugate for optimal hepatoprotection and reduction in inflammation in vivo.

Neuronal loss in the rostral ventromedial medulla in a rat model of neuropathic pain

Cell death has been reported in the CNS in models of neuropathic pain (Sugimoto et al., 1990; Whiteside and Munglani, 2001; Scholz et al., 2005; Fuccio et al., 2009). In our present study, we examined the effects of spinal nerve ligation (SNL) on the number of neurons in the rostral ventromedial medulla (RVM), a brainstem region involved in modulation of nociception. In rats receiving SNL, we found that the number of RVM neurons decreased by 23% in the side ipsilateral to the surgery. The loss of RVM neurons was also associated with a bilateral increase in the number of glia as well as bilateral activation of both astrocytes and microglia. Administration of tauroursodeoxycholic acid (TUDCA), which reportedly inhibits apoptosis, significantly reduced the loss of neurons, the increase in glia, and the mechanical hypersensitivity induced by SNL. Among RVM neurons, we found that serotonergic (5-hydroxytryptamine, 5-HT) neurons decreased by 35% ipsilateral to SNL. Consistent with these findings, the density of 5-HT-immunoreactive varicosities in the superficial dorsal horn of the spinal cord was 15-30% lower, ipsilateral to SNL. To test the function of the remaining 5-HT neurons, we administered the 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT). Interestingly, after 5,7-DHT, mechanical withdrawal thresholds increased significantly. We conclude that nerve injury induces death of antinociceptive RVM neurons that can be reduced or abolished by TUDCA. We propose that the loss of RVM neurons shifts the balance of descending control from pain inhibition to pain facilitation.

High-dose ursodeoxycholic acid increases risk of adverse outcomes in patients with early stage primary sclerosing cholangitis

BACKGROUND

Ursodeoxycholic acid (UDCA) in a dose of 28-30 mg/kg/day increases the likelihood of clinical deterioration of primary sclerosing cholangitis (PSC) patients.

AIM

To compare the risk of adverse clinical endpoints in patients with varying disease status.

METHODS

We reviewed records from patients previously enrolled in a study evaluating the effects of high dose (28-30 mg/kg/day) UDCA in PSC. Patients were grouped according to treatment (UDCA vs. placebo) and baseline disease status (histological stage of PSC, total serum bilirubin). Development of clinical endpoints including death, liver transplantation, cirrhosis, oesophageal varices and cholangiocarcinoma was sought.

RESULTS

A total of 150 patients were included of whom 49 patients developed endpoints. There was an increased development of endpoints among patients using UDCA vs. placebo (14 vs. 4, P=0.0151) with early histological disease (stage 1-2, n=88) but not with late stage (stage 3-4, n=62) disease (17 vs. 14, P=0.2031). Occurrence of clinical endpoints was also higher in patients receiving UDCA vs. placebo (16 vs. 2, P=0.0008) with normal bilirubin levels (total bilirubin ≤1.0 mg/dL) but not in patients with elevated bilirubin levels (15 vs. 16, P=0.6018). Among patients not reaching endpoints 31.7% had normalisation of their alkaline phosphatase levels when compared to 14.3% in patients who reached endpoints (P=0.073).

CONCLUSION

The increased risk of adverse events with UDCA treatment when compared with placebo is only apparent in patients with early histological stage disease or normal total bilirubin.

Ursodeoxycholic acid treatment of hepatic steatosis: a (13)C NMR metabolic study

Ursodeoxycholic acid (UDCA) is commonly used for the treatment of hepatobiliary disorders. In this study, we tested whether a 4-week treatment with this bile acid (12-15 mg/kg/day) could improve hepatic fatty acid oxidation in obese Zucker rats - a model for nonalcoholic fatty liver disease and steatosis. After 24 h of fasting, livers were perfused with physiological concentrations of [U-(13) C]nonesterified fatty acids and [3-(13) C]lactate/[3-(13) C]pyruvate. Steatosis was associated with abundant intracellular glucose, lactate, alanine and methionine, and low concentrations of choline and betaine. Steatotic livers also showed the highest output of glucose and lactate. Glucose and glycolytic products were mostly unlabeled, indicating active glycogenolysis and glycolysis after 24 h of fasting. UDCA treatment resulted in a general amelioration of liver metabolic abnormalities with a decrease in intracellular glucose and lactate, as well as their output. Hepatic betaine and methionine were also normalized after UDCA treatment, suggesting the amelioration of anti-oxidative defenses. Choline levels were not affected by the bile acid, which may indicate a deficient synthesis of very-low-density lipoproteins. The percentage contribution of [U-(13) C]nonesterified fatty acids to acetyl-coenzyme A entering the tricarboxylic acid (TCA) cycle was significantly lower in livers from Zucker obese rats relative to control rats: 23.1 ± 4.9% versus 44.1 ± 2.7% (p < 0.01). UDCA treatment did not alter significantly fatty acid oxidation in control rats, but improved significantly oxidation in Zucker obese rats to 46.0 ± 6.1% (p > 0.05), comparable with control group values. The TCA cycle activity subsequent to fatty acid oxidation was reduced in steatotic livers and improved when UDCA was administered (0.24 ± 0.04 versus 0.37 ± 0.05, p = 0.05). We further suggest that the mechanism of action of UDCA is either related to the activity of the farnesoid receptor, or to the amelioration of the anti-oxidative defenses and cell nicotinamide adenine dinucleotide (NAD(+) /NADH) ratio, favoring TCA cycle activity and β-oxidation.

Ursodeoxycholic acid in cholestasis: linking action mechanisms to therapeutic applications

UDCA (ursodeoxycholic acid) is the therapeutic agent most widely used for the treatment of cholestatic hepatopathies. Its use has expanded to other kinds of hepatic diseases, and even to extrahepatic ones. Such versatility is the result of its multiple mechanisms of action. UDCA stabilizes plasma membranes against cytolysis by tensioactive bile acids accumulated in cholestasis. UDCA also halts apoptosis by preventing the formation of mitochondrial pores, membrane recruitment of death receptors and endoplasmic-reticulum stress. In addition, UDCA induces changes in the expression of metabolizing enzymes and transporters that reduce bile acid cytotoxicity and improve renal excretion. Its capability to positively modulate ductular bile flow helps to preserve the integrity of bile ducts. UDCA also prevents the endocytic internalization of canalicular transporters, a common feature in cholestasis. Finally, UDCA has immunomodulatory properties that limit the exacerbated immunological response occurring in autoimmune cholestatic diseases by counteracting the overexpression of MHC antigens and perhaps by limiting the production of cytokines by immunocompetent cells. Owing to this multi-functionality, it is difficult to envisage a substitute for UDCA that combines as many hepatoprotective effects with such efficacy. We predict a long-lasting use of UDCA as the therapeutic agent of choice in cholestasis.

Meta-analysis: ursodeoxycholic acid for primary sclerosing cholangitis

BACKGROUND

There is no satisfactory medical treatment for patients with primary sclerosing cholangitis. There are conflicting data regarding the clinical benefit of high doses of ursodeoxycholic acid (UDCA) in primary sclerosing cholangitis.

AIM

To evaluate using meta-analysis, if UDCA (standard or high-dose) is useful in primary sclerosing cholangitis.

METHODS

We searched MEDLINE using the textwords 'PSC', 'treatment', 'UDCA' and retrieved all abstracts from the major Gastroenterology and Liver meetings. We included randomised clinical trials comparing standard or high-dose of UDCA (>15 mg/kg body weight per day) vs. placebo or no intervention. End-points: mortality or liver transplantation, pruritus, fatigue, cholangiocarcinoma and histological progression.

RESULTS

We identified eight randomised clinical trials comprising 567 patients. Five used standard doses and three high doses of UDCA. There was no significant difference in mortality [OR, 0.6 (95% CI, 0.4-1.4)], in pruritus [OR, 1.5 (95% CI, 0.3-7.2)], in fatigue [OR, 0.0 (95% CI, 0.1-7.7)], in cholangiocarcinoma [OR, 1.7 (95% CI, 0.6-5.1)] and in histology stage progression [OR, 0.9 (95% CI, 0.34-2.44)]. No differences were found in the subgroup analyses.

CONCLUSION

Neither standard nor high-dose UDCA influence favourably the progression of primary sclerosing cholangitis.

Alternative therapeutic advantages of catfish bile on atopic dermatitis: protection of T cell-mediated skin disease via antioxidant activities

Objectives

In the present study, we aimed to examine the anti-atopic properties of bile from the cat fish, Silurus asotus, to determine its possible use as a pharmaceutical product.

Methods

The anti-atopic activities of cat fish bile were examined in a non-cell antioxidant, in-vitro assay (splenocytes and mast cells) and a 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis-like mouse model.

Results

The results of these experiments revealed that Silurus asotus bile (SAB) scavenges radicals and protects proteins from superoxide attacks, suggesting that SAB suppresses the T helper (Th) type 2-skewed immune response. Th1/Th2 mRNA cytokines (interleukin (IL)-2, interferon (IFN)-γ and IL-4) from mouse splenocytes were effectively inhibited, and the release of β-hexosaminidase in RBL-2H3 mast cells was significantly suppressed by SAB. These results were supported by screening the Th1/Th2 cytokine mRNAs (IL-2, IFN-γ and IL-4) from lymph nodes in DNCB-treated mice. More dramatic results were observed in the histological changes at higher SAB concentrations (5%) compared to the therapeutic control, visualized using hematoxylin–eosin (H&E) staining.

Conclusions

The results presented in this study suggest that SAB may provide functional advantages with regard to treating atopic dermatitis because of its antioxidant and immune-suppressive effects.

The role of the innate immune recognition system in the pathogenesis of primary biliary cirrhosis: a conceptual view

The aetiology of primary biliary cirrhosis (PBC) remains unknown. Infectious and non-infectious noxious insults in combination with tissue-specific factors may precipitate PBC. Activation of innate immune response because of impending danger signals seems to be a key event in early PBC, as evidenced by granuloma formation, eosinophilic reaction and IgM elevation. Aberrant mitophagy in 'stressed' biliary epithelia cells may initiate the immune response against mitochondrial antigens. Antimitochondrial autoantibodies recognize evolutionarily conserved molecules. The question arises, whether they are pathogenic or rather an expression of beneficial autoimmunity. The generally stable course of PBC suggests that stimulatory and inhibitory autoimmune reactions govern the inflammatory biliary process. Tissue repair and defense are the heart of innate immunity. But continuous exposure of exogenous stimuli may precipitate functional antireceptor autoantibodies that are no more protective but rather harmful. Mitophagy, apoptosis and bile duct proliferation define the inflammatory response within bile ducts. Autoantigens may be clustered in different blebs on the surface of apoptotic cells targeting a variety of membrane and non-membrane-associated antigens. Thus, the autoantibody response in PBC may target, for instance, the pro- and anti-apoptotic proteins of the Bcl-2 family or receptors of the adrenergic or cholinergic system, hereby interfering with the programme of apoptosis and the proliferation of biliary epithelial cells. Consideration of there being functional autoantibodies into the pathogenesis of PBC may help to improve our understanding of the aetiopathogenesis of PBC.

Nitric oxide mimics transcriptional and post-translational regulation during α-tocopherol cytoprotection against glycochenodeoxycholate-induced cell death in hepatocytes

BACKGROUND & AIMS

Reactive oxygen species (ROS) and nitric oxide (NO) exert a relevant role during bile acid-induced hepatotoxicity. Whether α-Tocopherol regulates oxidative and nitrosative stress, bile acid transporter expression and their NO-dependent post-translational modifications, and cell death were assessed in vitro and in vivo.

METHODS

α-Tocopherol and/or NO donors (DETA-NONOate or CSNO, and V-PYRRO/NO) were administered to glycochenodeoxycholic acid (GCDCA)-treated cultured human hepatocytes or to bile duct obstructed rats. Cell injury, superoxide anion (O⁻₂) production, as well as inducible nitric oxide synthase (NOS-2), cytochrome P4507A1 (CYP7A1), heme oxygenase-1, (HO-1) and bile acid transporter expression were determined. Cysteine S-nitrosylation and tyrosine nitration of Na(+)-taurocholate co-transporting polypeptide (NTCP), as well as taurocholic acid (TC) uptake were also evaluated.

RESULTS

GCDCA-induced cell death was associated with increased (O⁻₂) production, NTCP and HO-1 expression, and with a reduction of CYP7A1 and NOS-2 expression. α-Tocopherol reduced cell death, (O⁻₂) production, CYP7A1, NTCP, and HO-1 expression, as well as increased NOS-2 expression and NO production in GCDCA-treated hepatocytes. α-Tocopherol and NO donors increased NTCP cysteine S-nitrosylation and tyrosine nitration, and reduced TC uptake in hepatocytes. α-Tocopherol and V-PYRRO/NO reduced liver injury and NTCP expression in obstructed rats.

CONCLUSIONS

The regulation of CYP7A1, NTCP, and HO-1 expression may be relevant for the cytoprotective properties of α-Tocopherol and NO against mitochondrial dysfunction, oxidative stress and cell death in GCDCA-treated hepatocytes. The regulation of NO-dependent post-translational modifications of NTCP by α-Tocopherol and NO donors reduces the uptake of toxic bile acids by hepatocytes.

A randomized controlled trial of high-dose ursodesoxycholic acid for nonalcoholic steatohepatitis

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH) is a prevalent liver disease associated with increased morbidity and mortality. Ursodeoxycholic acid (UDCA) may have antioxidant, anti-inflammatory, and antifibrotic properties and may reduce liver injury in NASH. To date, no studies have assessed the efficacy and safety of high-dose UDCA (HD-UDCA) in patients with NASH.

METHODS

We conducted a 12-month, randomized, double-blind, placebo-controlled multicenter trial to evaluate the efficacy and safety of HD-UDCA (28-35 mg/kg per day) in 126 patients with biopsy-proven NASH and elevated alanine aminotransferase (ALT) levels. The primary study end point was reduction in ALT levels from baseline in patients treated with HD-UDCA compared with placebo. Secondary study end points were the proportion of patients with ALT normalization, relative reduction in the scores of serum markers of fibrosis and hepatic inflammation, and safety and tolerability.

RESULTS

HD-UDCA significantly reduced mean ALT levels -28.3% from baseline after 12 months compared with -1.6% with placebo (p<0.001). At the end of the trial, ALT levels normalized (≤35 IU/L) in 24.5% of patients treated with HD-UDCA and in 4.8% of patients who received placebo (p=0.003). Both results were not accounted for by changes in weight during the trial. HD-UDCA significantly reduced the FibroTest® serum fibrosis marker (p<0.001) compared with placebo. HD-UDCA also significantly improved markers of glycemic control and insulin resistance. There were no safety issues in this population.

CONCLUSIONS

Treatment with HD-UDCA was safe, improved aminotransferase levels, serum fibrosis markers, and selected metabolic parameters. Studies with histologic end points are warranted.

The synthetic bile acid-phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide suppresses TNFα-induced liver injury

BACKGROUND & AIMS

Excessive apoptosis and leukocyte-dependent inflammation mediated by pro-inflammatory cytokines, such as TNFα, are cardinal features of acute liver injury. This study evaluated the ability of the newly designed bile acid-phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE) to protect from hepatocellular injury in comparison to the known hepatoprotectant ursodeoxycholic acid (UDCA) and phosphatidylcholine (PC).

METHODS

Anti-apoptotic and anti-inflammatory properties of UDCA-LPE were evaluated after TNFα treatment of embryonic human hepatocyte cell line CL48 as well as of primary human hepatocytes. Acute liver injury was induced in C57BL/6 mice with d-galactosamine/lipopolysaccharide (GalN/LPS) in order to determine in vivo efficacy of the conjugate.

RESULTS

UDCA-LPE inhibited TNFα-induced apoptosis and inflammation in hepatocytes in vitro and markedly ameliorated GalN/LPS-mediated fulminant hepatitis in mice, whereas UDCA or PC failed to show protection. The conjugate was able to decrease injury-induced elevation of phospholipase A(2) activity as well as its product lysophosphatidylcholine. Analysis of hepatic gene expression showed that UDCA-LPE treatment led to favourable inhibitory effects on expression profiles of key pro-inflammatory cytokines and chemokines, which are crucial for leukocyte recruitment and activation thereby inhibiting chemokine-mediated aggravation of parenchymal damage.

CONCLUSIONS

Thus, UDCA-LPE as a synthetic bile acid-phospholipid conjugate may represent a potent anti-inflammatory agent that is more effective than UDCA and PC for treatment of liver diseases.

Bile acids induce inflammatory genes in hepatocytes: a novel mechanism of inflammation during obstructive cholestasis

Inflammation contributes to liver injury during cholestasis. The mechanism by which cholestasis initiates an inflammatory response in the liver, however, is not known. Two hypotheses were investigated in the present studies. First, activation of Toll-like receptor 4 (TLR4), either by bacterial lipopolysaccharide or by damage-associated molecular pattern molecules released from dead hepatocytes, triggers an inflammatory response. Second, bile acids act as inflammagens, and directly activate signaling pathways in hepatocytes that stimulate production of proinflammatory mediators. Liver inflammation was not affected in lipopolysaccharide-resistant C3H/HeJ mice after bile duct ligation, indicating that Toll-like receptor 4 is not required for initiation of inflammation. Treatment of hepatocytes with bile acids did not directly cause cell toxicity but increased the expression of numerous proinflammatory mediators, including cytokines, chemokines, adhesion molecules, and other proteins that influence immune cell levels and function. Up-regulation of several of these genes in hepatocytes and in the liver after bile duct ligation required early growth response factor-1, but not farnesoid X receptor. In addition, early growth response factor-1 was up-regulated in the livers of patients with cholestasis and correlated with levels of inflammatory mediators. These data demonstrate that Toll-like receptor 4 is not required for the initiation of acute inflammation during cholestasis. In contrast, bile acids directly activate a signaling network in hepatocytes that promotes hepatic inflammation during cholestasis.

The correlation between NF-κB inhibition and disease activity by coadministration of silibinin and ursodeoxycholic acid in experimental colitis

NF-κB is one of the most important nuclear factors responsible for overexpression of proinflammatory cytokines. This is demonstrated by increased NF-κB activity and other dependent immune factors in inflammatory bowel disease (IBD). Anti-inflammatory effects of silibinin and ursodeoxycholic acid (UDCA) along with their NF-κB inhibitory property are thought to be beneficial in colitis. Trinitrobenzene sulfonic acid was used to induce colitis rat models. After instillation, 48 rats were treated with oral silibinin, UDCA alone or a combination of both. Intraperitoneal dexamethasone was used in the control group. After 12 days of treatment, colonic samples were tested for the severity of mucosal damage macroscopically and microscopically. The levels of activated NF-κB, IL-1β, TNF-α, myeloperoxidase, thiobarbituric acid reactive substances (TBARS), protein carbonyl, and the antioxidant power of the bowel homogenates were determined. The results indicated a significant reduction in NF-κB activity as well as the levels of IL-1β, TNF-α, TBARS, protein carbonyl, myeloperoxidase activity, and an improvement in antioxidant power of colitis in treated rats. Combination therapy resulted in a more prominent improvement in bowel antioxidant power and myeloperoxidase activity. In conclusion, combination of silibinin and UDCA by inhibition of NF-κB and other relevant inflammatory factors of colitis is a good candidate for management of Crohn's disease.

A role for protein kinase C in the regulation of membrane fluidity and Ca²(+) flux at the endoplasmic reticulum and plasma membranes of HEK293 and Jurkat cells

Protein kinase C (PKC) plays a prominent role in the regulation of a variety of cellular functions, including Ca²(+) signalling. In HEK293 and Jurkat cells, the Ca²(+) release and Ca²(+) uptake stimulated by several different activators were attenuated by activation of PKC with phorbol myristate acetate (PMA) or 1-oleoyl-2-acetyl-sn-glycerol (OAG) and potentiated by PKC inhibition with Gö6983 or knockdown of PKCα or PKCβ using shRNA. Immunostaining and Western blotting analyses revealed that PKCα and PKCβII accumulated at the plasma membrane (PM) and that these isoforms, along with PKCβI, also translocated to the endoplasmic reticulum (ER) upon activation with PMA. Measurements of membrane fluidity showed that, like the cell membrane stabilizers bovine serum albumin (BSA) and ursodeoxycholate (UDCA), PMA and OAG significantly reduced the fluidity of both the PM and ER membranes; these effects were blocked in PKC-knockdown cells. Interestingly, both BSA and UDCA inhibited the Ca²(+) responses to agonists to the same extent as PMA, whereas Tween 20, which increases membrane fluidity, raised the internal Ca²(+) concentration. Thus, activation of PKC induces both translocation of PKC to the PM and ER membranes and downregulation of membrane fluidity, thereby negatively modulating Ca²(+) flux.

Novel treatment modalities for nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the most common cause of chronic liver disease in the Western world. It can lead to cirrhosis and hepatocellular cancer, and is independently associated with an increased risk of death due to cardiovascular and liver diseases. Over the past 5 years, numerous advances in understanding its pathogenesis have been made, providing a rationale for translation of this information into clinical trials. Although the optimum therapy is still awaited, there is strong evidence to support the use of vitamin E in selected subjects. Many other potential therapeutic options are now available. In this paper, we review the status of both current and emerging therapeutic strategies for patients with NASH.

Conjugation is essential for the anticholestatic effect of NorUrsodeoxycholic acid in taurolithocholic acid-induced cholestasis in rat liver

NorUDCA (24-norursodeoxycholic acid), the C₂₃-homolog of ursodeoxycholic acid (UDCA), showed remarkable therapeutic effects in cholestatic Mdr2 (Abcb4) (multidrug resistance protein 2/ATP-binding cassette b4) knockout mice with sclerosing/fibrosing cholangitis. In contrast to UDCA, norUDCA is inefficiently conjugated in human and rodent liver, and conjugation has been discussed as a key step for the anticholestatic action of UDCA in cholestasis. We compared the choleretic, anticholestatic, and antiapoptotic properties of unconjugated and taurine-conjugated UDCA (C₂₄) and norUDCA (C₂₃) in isolated perfused rat liver (IPRL) and in natrium/taurocholate cotransporting polypeptide (Ntcp)-transfected human hepatoma (HepG2) cells. Taurolithocholic acid (TLCA) was used to induce a predominantly hepatocellular cholestasis in IPRL. Bile flow was determined gravimetrically; bile acids determined by gas chromatography and liquid chromatography/tandem mass spectrometry; the Mrp2 model substrate, 2,4-dinitrophenyl-S-glutathione (GS-DNP) was determined spectrophotometrically; and apoptosis was determined immunocytochemically. The choleretic effect of C₂₃-bile acids was comparable to their C₂₄-homologs in IPRL. In contrast, TnorUDCA, but not norUDCA antagonized the cholestatic effect of TLCA. Bile flow (percent of controls) was 8% with TLCA-induced cholestasis, and unchanged by coinfusion of norUDCA (14%). However, it was increased by TnorUDCA (83%), UDCA (73%) and TUDCA (136%). Secretion of GS-DNP was markedly reduced by TLCA (5%), unimproved by norUDCA (4%) or UDCA (17%), but was improved modestly by TnorUDCA (26%) or TUDCA (58%). No apoptosis was observed in IPRL exposed to low micromolar TLCA, but equivalent antiapoptotic effects of TUDCA and TnorUDCA were observed in Ntcp-HepG2 cells exposed to TLCA.

CONCLUSION

Conjugation is essential for the anticholestatic effect of norUDCA in a model of hepatocellular cholestasis. Combined therapy with UDCA and norUDCA may be superior to UDCA or norUDCA monotherapy in biliary disorders in which hepatocyte as well as cholangiocyte dysfunction contribute to disease progression.

Anti-oxidants do not prevent bile acid-induced cell death in rat hepatocytes

BACKGROUND

Bile acids, reactive oxygen species (ROS) and inflammatory cytokines are crucial regulators of cell death in acute and chronic liver diseases. The contribution of each factor to hepatocyte death, either apoptosis or necrosis, has not been clarified as yet. It has been suggested that the generation of oxidative stress by bile acids contributes to hepatocyte death during cholestasis and bile acid toxicity, although the beneficial role of ROS prevention in bile acid-mediated cell death is not fully understood.

AIM

Study the effects of anti-oxidants in bile acid-induced cell death in vitro.

METHODS

Primary rat hepatocytes were exposed to the bile acids glycochenodeoxycholic acid (GCDCA) or taurolithocholic acid-3 sulphate in the absence or presence of ROS scavengers or anti-oxidants. Haeme oxygenase (HO)-1 mRNA levels were analysed by quantitative polymerase chain reaction. Apoptosis was quantified by acridine orange staining and caspase-3 activity assay. Necrosis was detected by Sytox green staining.

RESULTS

Anti-oxidants do not attenuate bile acid-induced cell death. Furthermore, bile acid exposure does not enhance the mRNA expression of the oxidative stress-responsive gene HO-1. The Src-kinase inhibitor, SU6656, does reduce GCDCA-induced apoptosis and necrosis.

CONCLUSIONS

In hepatocytes, bile acid-induced toxicity is not prevented by scavengers of oxidative stress. The beneficial effects observed in patients might be because of the contribution of ROS and cytokines rather than bile acid-mediated oxidative stress. However, the use of specific Src kinase inhibitors might be a useful tool to prevent bile acid-induced injury in liver diseases.

Tauroursodeoxycholate counteracts hepatocellular lysis induced by tensioactive bile salts by preventing plasma membrane-micelle transition

Ursodeoxycholic acid is widely used as a therapeutic agent for the treatment of cholestatic liver diseases. In these hepatopathies, the bile secretory failure produces accumulation of endogenous, tensioactive bile salts, leading to plasma membrane damage and, eventually, hepatocellular lysis. In the present study, we analyzed the capacity of the ursodeoxycholic acid endogenous metabolite, tauroursodeoxycholate (TUDC), to stabilize the hepatocellular plasma membrane against its transition to the micellar phase induced by the tensioactive bile salt taurochenodeoxycholate (TCDC), the main endogenous bile salt accumulated in cholestasis. The disruption of the plasma membrane was evaluated (i) in isolated hepatocytes, through the release of the enzyme lactate dehydrogenase to the incubation medium and (ii) in isolated plasma membranes, through the self-quenching assay of the membranotropic probe octadecylrhodamine B; this assay allows for detergent-induced transition from membrane bilayer to micelle to be monitored. Our results showed that isolated hepatocytes treated with TUDC are more resistant to TCDC-induced cell lysis. When this effect was evaluated in isolated plasma membranes, the TCDC concentration necessary to reach half of the transition from bilayer to micelle was increased by 22% (p<0.05). This difference remained even when TUDC was removed from the incubation medium before adding TCDC, thus indicating that TUDC exerted its effect directly on the plasma membrane. When the same experiments were carried out using the non-ionic detergent TX-100 or the cholesterol-complexing detergent digitonin, no protective effect was observed. In conclusion, TUDC prevents selectively the bilayer to micelle transition of the hepatocellular plasma membrane induced by hydrophobic bile salts that typically build up and accumulate in cholestatic processes. Our results suggest that formation of a complex between negatively charged TUDC and cholesterol in the membrane favours repulsion of negatively charged detergent bile salts, thus providing a basis for the understanding of the TUDC protective effects.

Hepatocyte death: a clear and present danger

The hepatocyte is especially vulnerable to injury due to its central role in xenobiotic metabolism including drugs and alcohol, participation in lipid and fatty acid metabolism, its unique role in the enterohepatic circulation of bile acids, the widespread prevalence of hepatotropic viruses, and its existence within a milieu of innate immune responding cells. Apoptosis and necrosis are the most widely recognized forms of hepatocyte cell death. The hepatocyte displays many unique features regarding cell death by apoptosis. It is quite susceptible to death receptor-mediated injury, and its death receptor signaling pathways involve the mitochondrial pathway for efficient cell killing. Also, death receptors can trigger lysosomal disruption in hepatocytes which further promote cell and tissue injury. Interestingly, hepatocytes are protected from cell death by only two anti-apoptotic proteins, Bcl-x(L) and Mcl-1, which have nonredundant functions. Endoplasmic reticulum stress or the unfolded protein response contributes to hepatocyte cell death during alterations of lipid and fatty acid metabolism. Finally, the current information implicating RIP kinases in necrosis provides an approach to more fully address this mode of cell death in hepatocyte injury. All of these processes contributing to hepatocyte injury are discussed in the context of potential therapeutic strategies.

Bile acid changes after high-dose ursodeoxycholic acid treatment in primary sclerosing cholangitis: Relation to disease progression

High-dose (28-30 mg/kg/day) ursodeoxycholic acid (UDCA) treatment improves serum liver tests in patients with primary sclerosing cholangitis (PSC) but does not improve survival and is associated with increased rates of serious adverse events. The mechanism for the latter undesired effect remains unclear. High-dose UDCA could result in the production of hepatotoxic bile acids, such as lithocholic acid (LCA), because of limited small bowel absorption of UDCA and conversion of UDCA by bacteria in the colon. We determined the serum bile acid composition in 56 patients with PSC previously enrolled in a randomized, double-blind controlled trial of high-dose UDCA versus placebo. Samples for analysis were obtained at the baseline and at the end of treatment. The mean changes in the UDCA level (16.86 versus 0.05 micromol/L) and total bile acid level (17.21 versus -0.55 micromol/L) were significantly higher in the UDCA group (n = 29) versus the placebo group (n = 27) when pretreatment levels were compared (P < 0.0001). LCA was also markedly increased (0.22 versus 0.01 micromol/L) in the UDCA group compared to the placebo group (P = 0.001). No significant changes were detected for cholic acid, deoxycholic acid, or chenodeoxycholic acid. Patients (n = 9) in the UDCA group who reached clinical endpoints of disease progression (the development of cirrhosis, varices, liver transplantation, or death) tended to have greater increases in their posttreatment total bile acid levels (34.99 versus 9.21 micromol/L, P < 0.08) in comparison with those who did not.

CONCLUSION

High-dose UDCA treatment in PSC patients results in marked UDCA enrichment and significant expansion of the total serum bile acid pool, including LCA.

No evidence of direct binding between ursodeoxycholic acid and the p53 DNA-binding domain

UDCA (ursodeoxycholic acid) is used increasingly for the treatment of cholestatic liver diseases. Among other cytoprotective effects, this endogenous bile acid is a potent inhibitor of apoptosis, interfering with both intrinsic and extrinsic apoptotic pathways. In previous studies, we have demonstrated that the transforming growth factor β1-induced E2F-1/Mdm2 (murine double minute 2)/p53 apoptotic pathway was an upstream molecular target of UDCA. In agreement with this, we have recently established p53 as a key molecular target in UDCA prevention of cell death. The tumour suppressor p53 is a well-described transcription factor that induces the expression of multiple different pro-apoptotic gene products. Its regulation involves a variety of signalling proteins and small molecules, and occurs at multiple levels, including transcription, translation and post-translation levels. In the present study, by using different biophysical techniques, we have investigated the possibility of a direct interaction between the p53 core domain, also referred to as the DNA-binding domain, and UDCA. Our in vitro analysis did not provide any evidence for direct binding between the bile acid UDCA and the p53 core domain.

Pharmacotherapy of cholestatic liver diseases

New insights into the molecular mechanisms of bile formation and cholestasis have provided new concepts for pharmacotherapy of cholestatic liver diseases. The major aim in all forms of cholestasis is the reduction of hepatocellular retention of bile acids and other potentially toxic constituents of bile. Reduction of hepatocellular retention may be achieved by drugs that stimulate hepatocellular secretion via the canalicular route into the bile or via the alternative route across the basolateral membrane into the blood, and by drugs that stimulate the hepatocellular metabolism of hydrophobic bile acids to hydrophilic, less toxic metabolites. In cholestatic liver diseases that start with an injury of the biliary epithelium (e.g., primary biliary cirrhosis; PBC), protection of the cholangiocytes against the toxic effects of hydrophobic bile acids is most important. When hepatocellular retention of bile acids has occurred, the inhibition of bile acid-induced apoptosis becomes another target of therapy. Ursodeoxycholic acid protects the biliary epithelium by reducing the toxicity of bile, stimulates hepatobiliary secretion by upregulating transporters and inhibits apoptosis. It is the mainstay of therapy in PBC but of benefit also in a number of other cholestatic liver diseases. New drugs such as 6-ethyl-chenodeoxycholic acid and 24-nor-ursodeoxycholic acid are being evaluated for the treatment of cholestatic liver diseases.

Bile salts and cholestasis

Bile salts have a crucial role in hepatobiliary and intestinal homeostasis and digestion. Primary bile salts are synthesized by the liver from cholesterol, and may be modified by the intestinal flora to form secondary and tertiary bile salts. Bile salts are efficiently reabsorbed from the intestinal lumen to undergo enterohepatic circulation. In addition to their function as a surfactant involved in the absorption of dietary lipids and fat-soluble vitamins bile salts are potent signaling molecules in both the liver and intestine. Under physiological conditions the bile salt pool is tightly regulated, but the adaptive capacity may fall short under cholestatic conditions. Elevated serum and tissue levels of potentially toxic hydrophobic bile salts during cholestasis may cause mitochondrial damage, apoptosis or necrosis in susceptible cell types. Therapeutic nontoxic bile salts may restore impaired hepatobiliary secretion in cholestatic disorders. The hydrophilic bile salt ursodeoxycholate is today regarded as the effective standard treatment of primary biliary cirrhosis and intrahepatic cholestasis of pregnancy, and is implicated for use in various other cholestatic conditions. Novel therapeutic bile salts that are currently under evaluation may also prove valuable in the treatment of these diseases.

Antithrombin-III Attenuates Hepatocyte Apoptosis in Bile Duct Ligated Rat: A Striking Cellular Change

Background and purpose: Retention and accumulation of toxic hydrophobic bile salts within hepatocyte may cause hepatocyte toxicity by inducing apoptosis. This study was designed with the purpose of evaluating the possible effect of antithrombin-III on hepatocyte apoptosis in bile duct ligated rat. Materials and methods: The rats were randomized to 3 groups: group 1 (control, C) underwent sham operation; group 2 (obstructive jaundice, OB) underwent common bile duct ligation; and group 3 (obstructive jaundice with antithrombin-III, OBAT-III) underwent common bile duct ligation and simultaneously were treated with antithrombin-III. Liver tissues were harvested on the fifth postoperative day. Results: Hepatocyte apoptosis was significantly increased in bile duct ligated group when compared with the sham operation group. The administration of antithrombin-III effectively attenuates such phenomenon in obstructive jaundice with antithrombin-III group. Conclusion: Bile duct ligation significantly increased hepatocyte apoptosis and the administration of antithrombin-III effectively attenuates such phenomenon.

Mitochondrial-driven ubiquinone enhances extracellular calcium-dependent nitric oxide production and reduces glycochenodeoxycholic acid-induced cell death in hepatocytes

Ca(2+) mobilization, nitric oxide (NO), and oxidative stress have been involved in cell death induced by hydrophobic bile acid in hepatocytes. The aim of the study was the elucidation of the effect of the antioxidant mitochondrial-driven ubiquinone (Mito Q) on the intracellular Ca(2+) concentration, NO production, and cell death in glycochenodeoxycholic acid (GCDCA)-treated HepG2 cells. The role of the regulation of the intracellular Ca(2+) concentration by Ca(2+) chelators (EGTA or BAPTA-AM), agonist of Ca(2+) entrance (A23187) or NO (L-NAME or NO donor), was assessed during Mito Q cytoprotection in GCDCA-treated HepG2 cells. Cell death, NO synthase (NOS)-1, -2, and -3 expression, Ca(2+) mobilization, and NO production were evaluated. GCDCA reduced the intracellular Ca(2+) concentration and NOS-3 expression and enhanced cell death in HepG2. NO donor prevented and L-NAME enhanced GCDCA-induced cell death. The reduction of Ca(2+) entry by EGTA, but not its release from intracellular stores by BAPTA-AM, reduced the expression of NOS-3 and enhanced cell death in control and GCDCA-treated cells. Mito Q prevented the reduction of intracellular Ca(2+) concentration, NOS-3 expression, NO production, and cell death in GCDCA-treated HepG2 cells. The conclusion is that the recovery of Ca(2+)-dependent NOS-3 expression by Mito Q may be considered an additional cytoprotective property of an antioxidant.