Ursodeoxycholate protects oxidative mitochondrial metabolism from bile acid toxicity: dose-response study in isolated rat liver mitochondria

Gut microbial metabolites in MASLD: Implications of mitochondrial dysfunction in the pathogenesis and treatment

With an increasing prevalence, metabolic dysfunction-associated steatotic liver disease (MASLD) has become a major global health problem. MASLD is well-known as a multifactorial disease. Mitochondrial dysfunction and alterations in the gut bacteria are 2 vital events in MASLD. Recent studies have highlighted the cross-talk between microbiota and mitochondria, and mitochondria are recognized as pivotal targets of the gut microbiota to modulate the host's physiological state. Mitochondrial dysfunction plays a vital role in MASLD and is associated with multiple pathological changes, including hepatocyte steatosis, oxidative stress, inflammation, and fibrosis. Metabolites are crucial mediators of the gut microbiota that influence extraintestinal organs. Additionally, regulation of the composition of gut bacteria may serve as a promising therapeutic strategy for MASLD. This study reviewed the potential roles of several common metabolites in MASLD, emphasizing their impact on mitochondrial function. Finally, we discuss the current treatments for MASLD, including probiotics, prebiotics, antibiotics, and fecal microbiota transplantation. These methods concentrate on restoring the gut microbiota to promote host health.

Mitochondrial metabolic dysfunction and non-alcoholic fatty liver disease: new insights from pathogenic mechanisms to clinically targeted therapy

Metabolic dysfunction-associated fatty liver disease (MAFLD) is among the most widespread metabolic disease globally, and its associated complications including insulin resistance and diabetes have become threatening conditions for human health. Previous studies on non-alcoholic fatty liver disease (NAFLD) were focused on the liver's lipid metabolism. However, growing evidence suggests that mitochondrial metabolism is involved in the pathogenesis of NAFLD to varying degrees in several ways, for instance in cellular division, oxidative stress, autophagy, and mitochondrial quality control. Ultimately, liver function gradually declines as a result of mitochondrial dysfunction. The liver is unable to transfer the excess lipid droplets outside the liver. Therefore, how to regulate hepatic mitochondrial function to treat NAFLD has become the focus of current research. This review provides details about the intrinsic link of NAFLD with mitochondrial metabolism and the mechanisms by which mitochondrial dysfunctions contribute to NAFLD progression. Given the crucial role of mitochondrial metabolism in NAFLD progression, the application potential of multiple mitochondrial function improvement modalities (including physical exercise, diabetic medications, small molecule agonists targeting Sirt3, and mitochondria-specific antioxidants) in the treatment of NAFLD was evaluated hoping to provide new insights into NAFLD treatment.

Redox-Dependent Effects in the Physiopathological Role of Bile Acids

Bile acids (BA) are recognized by their role in nutrient absorption. However, there is growing evidence that BA also have endocrine and metabolic functions. Besides, the steroidal-derived structure gives BA a toxic potential over the biological membrane. Thus, cholestatic disorders, characterized by elevated BA on the liver and serum, are a significant cause of liver transplant and extrahepatic complications, such as skeletal muscle, central nervous system (CNS), heart, and placenta. Further, the BA have an essential role in cellular damage, mediating processes such as membrane disruption, mitochondrial dysfunction, and the generation of reactive oxygen species (ROS) and oxidative stress. The purpose of this review is to describe the BA and their role on hepatic and extrahepatic complications in cholestatic diseases, focusing on the association between BA and the generation of oxidative stress that mediates tissue damage.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

Protocols for Mitochondria as the Target of Pharmacological Therapy in the Context of Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent metabolic chronic liver diseases in developed countries and puts the populations at risk of progression to liver necro-inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Mitochondrial dysfunction is involved in the onset of NAFLD and contributes to the progression from NAFLD to nonalcoholic steatohepatitis (NASH). Thus, liver mitochondria could become the target for treatments for improving liver function in NAFLD patients. This chapter describes the most important steps used for potential therapeutic interventions in NAFLD patients, discusses current options gathered from both experimental and clinical evidence, and presents some novel options for potentially improving mitochondrial function in NAFLD.

Altered bile acid profile in mild cognitive impairment and Alzheimer's disease: Relationship to neuroimaging and CSF biomarkers

INTRODUCTION

Bile acids (BAs) are the end products of cholesterol metabolism produced by human and gut microbiome co-metabolism. Recent evidence suggests gut microbiota influence pathological features of Alzheimer's disease (AD) including neuroinflammation and amyloid-β deposition.

METHOD

Serum levels of 20 primary and secondary BA metabolites from the AD Neuroimaging Initiative (n = 1562) were measured using targeted metabolomic profiling. We assessed the association of BAs with the "A/T/N" (amyloid, tau, and neurodegeneration) biomarkers for AD: cerebrospinal fluid (CSF) biomarkers, atrophy (magnetic resonance imaging), and brain glucose metabolism ([18F]FDG PET).

RESULTS

Of 23 BAs and relevant calculated ratios after quality control procedures, three BA signatures were associated with CSF Aβ1-42 ("A") and three with CSF p-tau181 ("T") (corrected P < .05). Furthermore, three, twelve, and fourteen BA signatures were associated with CSF t-tau, glucose metabolism, and atrophy ("N"), respectively (corrected P < .05).

DISCUSSION

This is the first study to show serum-based BA metabolites are associated with "A/T/N" AD biomarkers, providing further support for a role of BA pathways in AD pathophysiology. Prospective clinical observations and validation in model systems are needed to assess causality and specific mechanisms underlying this association.

The Characteristics of Antioxidant Activity after Liver Transplantation in Biliary Atresia Patients

Purpose. Cholestatic liver injury is associated with a high production of free radicals. The pathogenesis of liver injury in biliary atresia (BA) patients is largely undefined. The goal of the present study was to clarify the oxidative damage and the changes in antioxidant enzyme activities that occur during the development of BA and after liver transplantation (LT). Methods. We enrolled BA patients and control subjects and collected their clinical information. The activities of antioxidant enzymes in BA patients before LT (BA group) and after LT (LT group) were analyzed. Results. The number of mitochondrial DNA copies had increased in the LT group compared with the BA group. Similarly, the activity of glutathione peroxidase had increased in the LT group compared with the BA group. The level of glutathione was higher in the LT group than in the BA group. Malondialdehyde levels were decreased in the LT group compared with the BA group. Conclusions. These data indicate that LT is associated with increased antioxidant enzyme activities and decreased malondialdehyde levels in BA patients. The manipulation of mitochondria-associated antioxidative activity might be an important future management strategy for BA.

Glucocorticoid receptor-dependent immunomodulatory effect of ursodeoxycholic acid on liver lymphocytes in mice

Although ursodeoxycholic acid (UDCA) has long been used for patients with chronic cholestatic liver diseases, particularly primary biliary cirrhosis, it may modulate the host immune response. This study investigated the effect of UDCA feeding on experimental hepatitis, endotoxin shock, and bacterial infection in mice. C57BL/6 mice were fed a diet supplemented with or without 0.3% (wt/vol) UDCA for 4 wk. UDCA improved hepatocyte injury and survival in concanavalin-A (Con-A)-induced hepatitis by suppressing IFN-γ production by liver mononuclear cells (MNC), especially NK and NKT cells. UDCA also increased survival after lipopolysaccharide (LPS)-challenge; however, it increased mortality of mice following Escherichia coli infection due to the worsening of infection. UDCA-fed mice showed suppressed serum IL-18 levels and production of IL-18 from liver Kupffer cells, which together with IL-12 potently induce IFN-γ production. However, unlike normal mice, exogenous IL-18 pretreatment did not increase the serum IFN-γ levels after E. coli, LPS, or Con-A challenge in the UDCA-fed mice. Interestingly, however, glucocorticoid receptor (GR) expression was significantly upregulated in the liver MNC of the UDCA-fed mice but not in their whole liver tissue homogenates. Silencing GR in the liver MNC abrogated the suppressive effect of UDCA on LPS- or Con-A-induced IFN-γ production. Furthermore, RU486, a GR antagonist, restored the serum IFN-γ level in UDCA-fed mice after E. coli, LPS, or Con-A challenge. Taken together, these results suggest that IFN-γ-reducing immunomodulatory property of UDCA is mediated by elevated GR in the liver lymphocytes in an IL-12/18-independent manner.

Plasma metabolomics identifies lipid abnormalities linked to markers of inflammation, microbial translocation, and hepatic function in HIV patients receiving protease inhibitors

Background

Metabolic abnormalities are common in HIV-infected individuals on antiretroviral therapy (ART), but the biochemical details and underlying mechanisms of these disorders have not been defined.

Methods

Untargeted metabolomic profiling of plasma was performed for 32 HIV patients with low nadir CD4 counts (<300 cells/ul) on protease inhibitor (PI)-based ART and 20 healthy controls using liquid or gas chromatography and mass spectrometry. Effects of Hepatitis C (HCV) co-infection and relationships between altered lipid metabolites and markers of inflammation, microbial translocation, and hepatic function were examined. Unsupervised hierarchical clustering, principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), Random forest, pathway mapping, and metabolite set enrichment analysis (MSEA) were performed using dChip, Metaboanalyst, and MSEA software.

Results

A 35-metabolite signature mapping to lipid, amino acid, and nucleotide metabolism distinguished HIV patients with advanced disease on PI-based ART from controls regardless of HCV serostatus (p<0.05, false discovery rate (FDR)<0.1). Many altered lipids, including bile acids, sulfated steroids, polyunsaturated fatty acids, and eicosanoids, were ligands of nuclear receptors that regulate metabolism and inflammation. Distinct clusters of altered lipids correlated with markers of inflammation (interferon-α and interleukin-6), microbial translocation (lipopolysaccharide (LPS) and LPS-binding protein), and hepatic function (bilirubin) (p<0.05). Lipid alterations showed substantial overlap with those reported in non-alcoholic fatty liver disease (NALFD). Increased bile acids were associated with noninvasive markers of hepatic fibrosis (FIB-4, APRI, and YKL-40) and correlated with acylcarnitines, a marker of mitochondrial dysfunction.

Conclusions

Lipid alterations in HIV patients receiving PI-based ART are linked to markers of inflammation, microbial translocation, and hepatic function, suggesting that therapeutic strategies attenuating dysregulated innate immune activation and hepatic dysfunction may be beneficial for prevention and treatment of metabolic disorders in HIV patients.

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.

Sodium deoxycholate inhibits chick duodenal calcium absorption through oxidative stress and apoptosis

High concentrations of sodium deoxycholate (NaDOC) produce toxic effects. This study explores the effect of a single high concentration of NaDOC on the intestinal Ca(2+) absorption and the underlying mechanisms. Chicks were divided into two groups: 1) controls and 2) treated with different concentrations of NaDOC in the duodenal loop for variable times. Intestinal Ca(2+) absorption was measured as well as the gene and protein expressions of molecules involved in the Ca(2+) transcellular pathway. NaDOC inhibited the intestinal Ca(2+) absorption, which was concentration dependent. Ca(2+)-ATPase mRNA decreased by the bile salt and the same occurred with the protein expression of Ca(2+)-ATPase, calbindin D(28k) and Na(+)/Ca(2+) exchanger. NaDOC produced oxidative stress as judged by ROS generation, mitochondrial swelling and glutathione depletion. Furthermore, the antioxidant quercetin blocked the inhibitory effect of NaDOC on the intestinal Ca(2+) absorption. Apoptosis was also triggered by the bile salt, as indicated by the TUNEL staining and the cytochrome c release from the mitochondria. As a compensatory mechanism, enzyme activities of the antioxidant system were all increased. In conclusion, a single high concentration of NaDOC inhibits intestinal Ca(2+) absorption through downregulation of proteins involved in the transcellular pathway, as a consequence of oxidative stress and mitochondria mediated apoptosis.

Metabolomic profiling of 17 bile acids in serum from patients with primary biliary cirrhosis and primary sclerosing cholangitis: a pilot study

BACKGROUND

Primary biliary cirrhosis and primary sclerosing cholangitis are two cholestatic diseases characterised by hepatic accumulation of bile acids.

AIMS

This study compares serum bile acid levels in patients with primary biliary cirrhosis and primary sclerosing cholangitis and from age and sex-matched non cholestatic donors.

METHODS

Seventeen bile acids were quantified using liquid chromatography coupled to tandem mass spectrometry. Serum samples from cholestatic patients were compared with those of non-cholestatic donors.

RESULTS

The concentration of total bile acids, taurine and glycine conjugates of primary bile acids was elevated in both patients with primary biliary cirrhosis and primary sclerosing cholangitis when compared to non-cholestatic donors. Samples from primary sclerosing cholangitis patients displayed reduced levels of secondary acids, when compared to non cholestatic and primary biliary cirrhosis sera. The ratio of total glycine versus total taurine conjugates was reduced in patients with primary biliary cirrhosis, but not in primary sclerosing cholangitis.

CONCLUSION

The present study suggests that circulating bile acids are altered differentially in primary biliary cirrhosis and primary sclerosing cholangitis patients.

The effect of ursodeoxycholic acid on oxidative stress level and DNase activity in rat liver after bile duct ligation

Accumulation of hydrophobic bile acids (BAs) during cholestasis plays an important role in apoptosis initiation as well as oxidative stress increase in liver cells. Ursodeoxycholic acid (UDCA) acts as a protector in BA-induced cell injury.The aim of the study was to evaluate the effect of UDCA on oxidative stress level and DNase I and II activity caused by liver injury in bile duct ligation (BDL) rats.Wistar rats were divided in four groups: group 1, control (sham-operated); group 2, sham-operated and injected with UDCA (30 mg/kg); group 3,animals with BDL; and group 4,UDCA-treatedcholestatic rats. Animals were sacrificed after 9 days. Malondialdehyde (MDA; lipid peroxidation end-product) level and protein-molecule oxidative modification (carbonyl group content) significantly increased in BDL rat liver. Catalase (CAT) activity in liver tissue was found to be decreased in BDL rats. In addition, xanthine oxidase (XO) activity, which is thought to be one of the key enzymes producing reactive oxygen species, was found to be increased in the cholestatic group. The apoptotic effect in cholestasis was probably triggered by the increased activation of DNase I and II. The protective effect of UDCA on liver tissue damage in BDL rats, in comparison to cholestatic liver, were 1) decrease of MDA levels, 2) increased CAT activity, 3) reduced XO activity, and 4) effect on terminal apoptotic reaction, shown as a decrease in DNase I and II activity.Therefore, UDCA may be useful in the preservation of liver function in cholestasis treatment.

Mitochondrial genome depletion dysregulates bile acid- and paracetamol-induced expression of the transporters Mdr1, Mrp1 and Mrp4 in liver cells

BACKGROUND AND PURPOSE

Mitochondria are involved in the toxicity of several compounds, retro-control of gene expression and apoptosis activation. The effect of mitochondrial genome (mtDNA) depletion on changes in ABC transporter protein expression in response to bile acids and paracetamol was investigated.

EXPERIMENTAL APPROACH

Hepa 1-6 mouse hepatoma cells with 70% decrease in 16S/18S rRNA ratio (Rho cells) were obtained by long-term treatment with ethidium bromide.

KEY RESULTS

Spontaneous apoptosis and reactive oxygen species (ROS) generation were decreased in Rho cells. Following glycochenodeoxycholic acid (GCDCA) or paracetamol, Rho cells generated less ROS and were more resistant to cell death. Apoptosis induced by GCDCA and Fas was also reduced. The basal expression of Mdr1 was significantly enhanced, but this was not further stimulated by GCDCA or paracetamol, as observed in wild-type (WT) cells. Basal expression of Mrp1 and Mrp4 was similar in WT and Rho cells, whereas they were up-regulated only in WT cells after GCDCA or paracetamol, along with the transcription factors Shp and Nrf2, but not Fxr or Pxr. Increased expression of Nrf2 was accompanied by its enhanced nuclear translocation. Glycoursodeoxycholic acid failed to cause any of the effects observed for GCDCA or paracetamol.

CONCLUSIONS AND IMPLICATIONS

The Nrf2-mediated pathway is partly independent of ROS production. Nuclear translocation of Nrf2 is insufficient to up-regulate Mdr1, Mrp1 and Mrp4, which requires the participation of other regulatory element(s) whose activation in response to GCDCA and paracetamol is impaired in Rho cells and hence probably sensitive to ROS.

Profiling circulating and urinary bile acids in patients with biliary obstruction before and after biliary stenting

Bile acids are considered as extremely toxic at the high concentrations reached during bile duct obstruction, but each acid displays variable cytotoxic properties. This study investigates how biliary obstruction and restoration of bile flow interferes with urinary and circulating levels of 17 common bile acids. Bile acids (conjugated and unconjugated) were quantified by liquid chromatography coupled with tandem mass spectrometry in serum and urine samples from 17 patients (8 men and 9 women) with biliary obstruction, before and after biliary stenting. Results were compared with serum concentrations measured in 40 age- and sex-paired control donors (20 men and 20 women). The total circulating bile acid concentration increases from 2.7 µM in control donors to 156.9 µM in untreated patients with biliary stenosis. Serum taurocholic and glycocholic acids exhibit 304- and 241-fold accumulations in patients with biliary obstruction compared to controls. The enrichment in chenodeoxycholic acid species reached a maximum of only 39-fold, while all secondary and 6α-hydroxylated species--except taurolithocholic acids--were either unchanged or significantly reduced. Stenting was efficient in restoring an almost normal circulating profile and in reducing urinary bile acids.

CONCLUSION

These results demonstrate that biliary obstruction affects differentially the circulating and/or urinary levels of the various bile acids. The observation that the most drastically affected acids correspond to the less toxic species supports the activation of self-protecting mechanisms aimed at limiting the inherent toxicity of bile acids in face of biliary obstruction.

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.

Bile acid toxicity structure-activity relationships: correlations between cell viability and lipophilicity in a panel of new and known bile acids using an oesophageal cell line (HET-1A)

The molecular mechanisms and interactions underlying bile acid cytotoxicity are important to understand for intestinal and hepatic disease treatment and prevention and the design of bile acid-based therapeutics. Bile acid lipophilicity is believed to be an important cytotoxicity determinant but the relationship is not well characterized. In this study we prepared new azido and other lipophilic BAs and altogether assembled a panel of 37 BAs with good dispersion in lipophilicity as reflected in RPTLC RMw. The MTT cell viability assay was used to assess cytotoxicity over 24 h in the HET-1A cell line (oesophageal). RMw values inversely correlated with cell viability for the whole set (r2=0.6) but this became more significant when non-acid compounds were excluded (r2=0.82, n=29). The association in more homologous subgroups was stronger still (r2>0.96). None of the polar compounds were cytotoxic at 500 microM, however, not all lipophilic BAs were cytotoxic. Notably, apart from the UDCA primary amide, lipophilic neutral derivatives of UDCA were not cytotoxic. Finally, CDCA, DCA and LagoDCA were prominent outliers being more toxic than predicted by RMw. In a hepatic carcinoma line, lipophilicity did not correlate with toxicity except for the common naturally occurring bile acids and their conjugates. There were other significant differences in toxicity between the two cell lines that suggest a possible basis for selective cytotoxicity. The study shows: (i) azido substitution in BAs imparts lipophilicity and toxicity depending on orientation and ionizability; (ii) there is an inverse correlation between RMw and toxicity that has good predictive value in homologous sets; (iii) lipophilicity is a necessary but apparently not sufficient characteristic for BA cytocidal activity to which it appears to be indirectly related.

Antioxidant enzyme activities in hepatic tissue from children with chronic cholestatic liver disease

BACKGROUND/AIM

To study the oxidative stress status in children with cholestatic chronic liver disease by determining activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) in liver tissue.

MATERIALS AND METHODS

A total of 34 children suffering from cholestatic chronic liver disease were studied. They were selected from the Hepatology Clinic, Cairo University, and compared with seven children who happened to have incidental normal liver biopsy. The patients were divided into three groups: extrahepatic biliary atresia (n=13), neonatal hepatitis (n=15) and paucity of intrahepatic bile ducts (n=6); GPx, SOD and CAT levels were measured in fresh liver tissue using ELISA.

RESULTS

In the cholestatic patients, a significant increase was found in mean levels of SOD, GPx and CAT in hepatic tissue compared to control children. The three enzymes significantly increased in the extrahepatic biliary atresia group, whereas in the groups of neonatal hepatitis and paucity of intrahepatic bile ducts, only GPx and CAT enzymes were significantly increased.

CONCLUSION

Oxidative stress could play a role in the pathogenesis of cholestatic chronic liver diseases. These preliminary results are encouraging to conduct more extensive clinical studies using adjuvant antioxidant therapy.

Lithocholic acid as a biomarker of intrahepatic cholestasis of pregnancy during ursodeoxycholic acid treatment

BACKGROUND

The diagnosis and treatment of intrahepatic cholestasis of pregnancy (ICP) has important implications on fetal health. The biochemical parameter commonly used in the diagnosis of ICP is the determination of the concentration of total serum bile acids (TSBA). However, bile acid profile, especially lithocholic acid (LCA) analysis is a more sensitive and specific biomarker for differential diagnosis of this pathology and also could be an alternative to evaluate the efficiency of ursodeoxycholic acid (UDCA) for ICP treatment.

METHODS

Serum bile acid (SBA) profiles including LCA determination, were studied in 28 ICP patients using a capillary electrophoresis method. The effects of UDCA treatment on bile acid profile, were analysed in 23 out of 28 ICP patients and the two samples obtained before and 15 days after treatment were compared. Two samples taken as controls were also obtained from each of five patients without therapy.

RESULTS

A dramatic decrease in LCA concentrations and maintenance of TSBA concentrations were found in all patients after UDCA therapy, whereas SBA profiles together with LCA values did not change in patients without therapy.

CONCLUSION

We propose LCA as an alternative biomarker and a more sensitive parameter than TSBA to evaluate the effectiveness of UDCA treatment, at least in ICP patients from Argentina.

Altered expression and distribution of aquaporin-9 in the liver of rat with obstructive extrahepatic cholestasis

Rat hepatocytes express aquaporin-9 (AQP9), a basolateral channel permeable to water, glycerol, and other small neutral solutes. Although liver AQP9 is known for mediating the uptake of sinusoidal blood glycerol, its relevance in bile secretion physiology and pathophysiology remains elusive. Here, we evaluated whether defective expression of AQP9 is associated to secretory dysfunction of rat hepatocytes following bile duct ligation (BDL). By immunoblotting, 1-day BDL resulted in a slight decrease of AQP9 protein in basolateral membranes and a simultaneous increase of AQP9 in intracellular membranes. This pattern was steadily accentuated in the subsequent days of BDL since at 7 days BDL basolateral membrane AQP9 decreased by 85% whereas intracellular AQP9 increased by 115%. However, the AQP9 immunoreactivity of the total liver membranes from day 7 of BDL rats was reduced by 49% compared with the sham counterpart. Results were confirmed by immunofluorescence and immunogold electron microscopy and consistent with biophysical studies showing considerable decrease of the basolateral membrane water and glycerol permeabilities of cholestatic hepatocytes. The AQP9 mRNA was slightly reduced only at day 7 of BDL, indicating that the dysregulation was mainly occurring at a posttranslational level. The altered expression of liver AQP9 during BDL was not dependent on insulin, a hormone known to negatively regulate AQP9 at a transcriptional level, since insulinemia was unchanged in 7-day BDL rats. Overall, these results suggest that extrahepatic cholestasis leads to downregulation of AQP9 in the hepatocyte basolateral plasma membrane and dysregulated aquaporin channels contribute to bile flow dysfunction of cholestatic hepatocyte.

Role of mitochondria in drug-induced cholestatic injury

Mitochondria have multiple functions in eukaryotic cells and are organized into dynamic tubular networks that continuously undergo changes through coordinated fusion and fission and migration through the cytosol. Mitochondria integrate cell-signaling networks, especially those involving the intracellular messenger Ca(2+), into the regulation of metabolic pathways. Recently, it has become clear that mitochondria are central to the three main cell death pathways, namely necrosis, apoptosis, and autophagic cell death. This article discusses the role of mitochondria in drug-induced cholestatic injury to the liver. The role of mitochondria in the cellular adaptation against the toxic effects of bile acids is discussed also.

Activation of nuclear factor (erythroid-2 like) factor 2 by toxic bile acids provokes adaptive defense responses to enhance cell survival at the emergence of oxidative stress

Oxidative stress, causing necrotic and apoptotic cell death, is associated with bile acid toxicity. Using liver (HepG2, Hepa1c1c7, and primary human hepatocytes) and intestinal (C2bbe1, a Caco-2 subclone) cells, we demonstrated that toxic bile acids, such as lithocholic acid (LCA) and chenodeoxycholic acid, induced the nuclear factor (erythroid-2 like) factor 2 (Nrf2) target genes, especially the rate-limiting enzyme in glutathione (GSH) biosynthesis [glutamate cysteine ligase modulatory subunit (GCLM) and glutamate cysteine ligase catalytic subunit (GCLC)] and thioredoxin reductase 1. Nrf2 activation and induction of Nrf2 target genes were also evident in vivo in the liver of CD-1 mice treated 7 to 8 h or 4 days with LCA. Silencing of Nrf2 via small-interfering RNA suppressed basal and bile acid-induced mRNA levels of the above-mentioned genes. Consistent with this, overexpression of Nrf2 enhanced, but dominant-negative Nrf2 attenuated, Nrf2 target gene induction by bile acids. The activation of Nrf2-antioxidant responsive element (ARE) transcription machinery by bile acids was confirmed by increased nuclear accumulation of Nrf2, enhanced ARE-reporter activity, and increased Nrf2 binding to ARE. It is noteworthy that Nrf2 silencing increased cell susceptibility to LCA toxicity, as evidenced by reduced cell viability and increased necrosis and apoptosis. Concomitant with GCLC/GCLM induction, cellular GSH was significantly increased in bile acid-treated cells. Cotreatment with N-acetyl-l-cysteine, a GSH precursor, ameliorated LCA toxicity, whereas cotreatment with buthionine sulfoximine, a GSH synthesis blocker, exacerbated it. In summary, this study provides molecular evidence linking bile acid toxicity to oxidative stress. Nrf2 is centrally involved in counteracting such oxidative stress by enhancing adaptive antioxidative response, particularly GSH biosynthesis, and hence cell survival.

17 Beta-estradiol prevents cytotoxicity from hydrophobic bile acids in HepG2 and WRL-68 cell cultures

BACKGROUND

Epidemiological and clinical studies suggest the possibility that estrogens might have a cytoprotective effect on the liver. The aim of the present study was to test the hypothesis that 17beta-estradiol (E2) prevents hepatocellular damage induced by deoxycholic acid (DCA), a hydrophobic bile acid.

METHODS

HepG2 cells were exposed for 24 h to DCA (350 micromol/L). Cell viability, aspartate aminotransferase and lactate dehydrogenase activity and apoptosis were measured as indices of cell toxicity. The effect of DCA was compared to that observed using either a hydrophilic bile acid, ursodeoxycholic acid (UDCA; 100 micromol/L), or E2 at different concentrations (1 nmol/L, 10 nmol/L, 50 nmol/L and 50 micromol/L) or mixtures of E2/DCA or UDCA/DCA. The same experiments were performed using WRL-68 cells that, at variance with HepG2, express a higher level of nuclear estrogen receptor.

RESULTS

High concentrations of E2 and UDCA prevented DCA-induced decrease in cell viability, increase in enzyme activity and apoptosis evaluated both by 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) and TdT-mediated dUTP nick-end labeling (TUNEL) assays. In addition, DCA-related apoptosis, assessed by caspase activity, was also prevented by E2 (P < 0.01) in physiological (1-10 nmol/L) doses. The cytoprotective effects of E2 and UDCA was also observed in the WRL-68 cell line.

CONCLUSIONS

17Beta-Estradiol prevents DCA-induced cell damage in HepG2 and WRL-68 cell lines to an extent comparable to UDCA. The hypothesis that the protective effect of E2 may be mediated by a mechanism that is nuclear estrogen receptor independent, deserves further verification.

Mitochondrially-mediated toxicity of bile acids

In the healthy hepatocyte, uptake of bile acids across the basolateral membrane and export via the canalicular export pump, are tightly coupled. Impairment of bile formation or excretion results in cholestasis, characterized by accumulation of bile acids in systemic blood and within the hepatocyte. When the concentration of bile acids exceeds the binding capacity of the binding protein located in the cytosol of the hepatocyte, bile acids induce apoptosis and necrosis, by damage to mitochondria. Mitochondria play a central role on the toxicity of bile acids. In this article, we review the published literature regarding bile acid effects on cell function, especially at the mitochondrial level. In patients with cholestatic liver disease, the extent of hepatocyte damage caused by intracellular accumulation of bile acids appears to be delayed by ingesting a hydrophilic bile acid. However, its effects on disease progression are not completely clarified. Therefore, identification of the mechanisms of cell injury will be of clinical utility, helping in the development of new therapeutic strategies. The goal of this review is to include a fresh consideration of all possible targets and integrating pathways that are involved in cholestasis, as well as in the benefits of bile acid therapy.

Cardiac Mitochondrial Calcium Loading Capacity is Severely Affected after Chronic Cholestasis in Wistar Rats

Background

Cardiovascular changes correlated with some forms of hepatic disease are being reported in the literature. Objectives: The aim of this work was to characterize cardiac mitochondrial bioenergetics and calcium buffering capacity in Wistar rats injected with six weekly doses of α-naphthylisothio-cyanate (ANIT), a compound known to induce cholestasis in animal models.

Methods

Isolated heart mitochondria were obtained from both injected and control animals and bioenergetic parameters were measured, as well as the capacity to buffer externally added calcium and the mitochondrial content of reduced protein thiol groups. Blood biochemistry analyses were obtained at the initial and end points of treatment. The in vitro ANIT effect on isolated heart mitochondria was also studied.

Results and Discussion

Our results showed that the respiratory control ratio was the only parameter affected in injected animals ( p < .05, n = 5). Nevertheless, heart mitochondria from injected animals showed an inability to accumulate added calcium owing to an increased susceptibility to the calcium-dependent mitochondrial permeability transition ( p < .0001, n = 5). The effects were still present 1 week after ending ANIT administration, when serum markers for liver injury and hyperbilirubinemia were already abated (although in the presence of bile duct proliferation). To our knowledge, this is the first time that cardiac mitochondrial calcium homeostasis and mitochondrial respiratory ratio are seen affected during ANIT-induced cholestasis, prevailing even in the absence of hepatic damage serum markers.

Diagnosis and management of hepatic copper accumulation in a Skye terrier

A one-year-old, neutered female Skye terrier presented with anorexia, vomiting, seizures and ascites. Portal venography demonstrated the presence of multiple acquired portosystemic shunts. Hepatic biopsy confirmed the presence of copper accumulation and fibrosis. Treatment included ursodeoxycholic acid therapy, colchicine and oral zinc. To the authors' knowledge, this is the first case report detailing successful management of Skye terrier hepatopathy.

Reduction in cardiac mitochondrial calcium loading capacity is observable during alpha-naphthylisothiocyanate-induced acute cholestasis: a clue for hepatic-derived cardiomyopathies?

Cardiovascular changes of still obscure origin are sometimes correlated with co-existing liver diseases, as cholestasis. The aim of this work was to examine and compare cardiac mitochondrial bioenergetics and calcium loading capacity from rats injected with a single dose of alpha-naphthylisothiocyanate (ANIT), a cholestasis-inducing compound. Forty-eight hours after ANIT administration, blood samples were collected and markers for hepatic disease were determined. Heart mitochondria from both control and ANIT-injected rats were isolated and subjected to biochemical characterization, including the susceptibility to the calcium-dependent permeability transition. The results showed that cardiac mitochondria from cholestatic animals did not have significant changes in respiratory parameters or in the basal levels of adenine nucleotide. The most impressive result from this work was that cardiac mitochondria from ANIT-injected animals had a lower calcium loading capacity. The prevention of this property by cyclosporin-A, a specific inhibitor of the mitochondrial permeability transition, showed that this phenomenon was reason for the reduced calcium loading capacity in ANIT-injected animals. The results suggest that, during the development of ANIT-induced cholestasis, heart mitochondria loose their default ability to buffer calcium. Our results may contribute to explain the occurrence of cardiomyopathies sometimes associated with cholestatic disease.

Mitochondrially mediated synergistic cell killing by bile acids

The accumulation of endogenous bile acids contributes to hepatocellular damage during cholestatic liver disease. To examine the controversy regarding the therapeutic use of ursodeoxycholate (UDCA) in cholestatic patients, we investigated the possible cytoprotection or synergistic effects of UDCA against chenodeoxycholate (CDCA)-induced injury to isolated rat hepatocytes. Our aim was to investigate the role of the mitochondrial permeability transition (MPT) in the mechanism of cytotoxicity caused by UDCA plus CDCA. Although not toxic by itself, UDCA potentiated the mitochondrial depolarization, ATP depletion and cell killing caused by CDCA. Fructose maintained ATP levels and prevented bile acid-induced cell killing. Cyclosporine A (CyA), a potent inhibitor of the MPT, substantially reduced mitochondrial depolarization, ATP depletion and cell killing caused by CDCA. Our results demonstrate that the synergistic cytotoxicity by UDCA plus CDCA is mediated by impairment of mitochondrial function, an event that is expressed via induction of the MPT.

Hepatic oxidative alterations in patients with extra-hepatic cholestasis. Effect of surgical drainage

BACKGROUND/AIMS

The mechanisms of liver injury in conditions of biliary obstruction are poorly understood. Hepatic oxidative injury has been observed in experimental models of cholestasis. Little is known in humans. This study aimed to gain more insights into the hepatic redox status in human cholestasis.

METHODS

Liver concentrations of total glutathione, protein sulfhydryls and malondialdehyde (end-product of lipid peroxidation) were measured in hepatic specimens of 12 patients with obstructive jaundice before and after the application of an external biliary drainage and in six control subjects.

RESULTS

Compared to control subjects, biliary obstructed patients showed significantly (P < 0.001) lower concentrations of hepatic glutathione and protein sulfhydryls, and higher (P < 0.001) levels of malondialdehyde, in the presence of comparable protein concentrations. Two-weeks after the application of external biliary drainage, cholestatic indices were significantly improved and the observed changes in glutathione, protein sulfhydryls and malondialdehyde levels, significantly decreased.

CONCLUSIONS

This study shows that cholestasis is associated with a decreased protein and non-protein sulfhydryl content in the liver and with an increased lipid peroxidation. These alterations reversed almost completely after biliary drainage, indicating the cholestasis itself as the determining factor for the redox status impairment observed in the liver of patients with extra-hepatic biliary obstruction.

Zeaxanthin dipalmitate from Lycium chinense fruit reduces experimentally induced hepatic fibrosis in rats

We previously reported that zeaxanthin dipalmitate (ZD), a carotenoid from Lycium chinense fruit, reduces myofibroblast-like cell proliferation and collagen synthesis in vitro. To determine whether ZD might reduce the severity of hepatic fibrosis in an animal model, hepatic fibrosis was induced in rats by bile duct ligation/scission (BDL) for a period of 6 weeks. Treatment of BDL rats with ZD at a dose of 25 mg/kg body weight significantly reduced the activities of aspartate transaminase (p<0.05) and alkaline phosphatase (p<0.001) in serum. Furthermore, collagen deposition was significantly reduced as assessed by the Sirius Red binding assay in BDL rats administered ZD at the dose of 25 mg/kg body weight (p<0.01). In addition, the levels of thiobarbituric acid-reactive substances and 4-hydroxyproline were reduced when BDL rats received ZD at the dose of 25 mg/kg body weight. These results showed that ZD effectively inhibited hepatic fibrosis in BDL rats, at least in part via its antioxidative activity.

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.

Chromosomal organization of candidate genes involved in cholesterol gallstone formation: a murine gallstone map

Epidemiologic and family studies indicate that cholesterol gallstone formation is in part genetically determined. The major contribution to our current understanding of gallstone genes derives from animal studies, particularly cross-breeding experiments in inbred mouse strains that differ in genetic susceptibility to cholesterol gallstone formation (quantitative trait loci mapping). In this review we summarize how the combined use of genomic strategies and phenotypic studies in inbred mice has proven to be a powerful means of dissecting the complex pathophysiology of this common disease. We present a "gallstone map" for the mouse, consisting of all genetic loci that have been identified to confer gallstone susceptibility as well as putative candidate genes. Translation of the genetic loci and genes between mouse and human predicts chromosomal regions in the human genome that are likely to harbor gallstone genes. Both the number and the precise understanding of gallstone genes are expected to further increase with rapid progress of the genome projects, and multiple new targets for early diagnosis and prevention of gallstone disease should become possible.

The effect of bile salts and calcium on isolated rat liver mitochondria

Intact mitochondria were incubated with and without calcium in solutions of chenodeoxycholate, ursodeoxycholate, or their conjugates. Glutamate dehydrogenase, protein and phospholipid release were measured. Alterations in membrane and organelle structure were investigated by electron paramagnetic resonance spectroscopy. Chenodeoxycholate enhanced enzyme liberation, solubilized protein and phospholipid, and increased protein spin label mobility and the polarity of the hydrophobic membrane interior, whereas ursodeoxycholate and its conjugates did not damage mitochondria. Preincubation with ursodeoxycholate or its conjugate tauroursodeoxycholate for 20 min partially prevented damage by chenodeoxycholate. Extended preincubation even with 1 mM ursodeoxycholate could no longer prevent structural damage. Calcium (from 0.01 mM upward) augmented the damaging effect of chenodeoxycholate (0.15-0.5 mM). The combined action of 0.01 mM calcium and 0.15 mM chenodeoxycholate was reversed by ursodeoxycholate only, not by its conjugates tauroursodeoxycholate and glycoursodeoxycholate. In conclusion, ursodeoxycholate partially prevents chenodeoxycholate-induced glutamate dehydrogenase release from liver cell mitochondria by membrane stabilization. This holds for shorter times and at concentrations below 0.5 mM only, indicating that the different constitution of protein-rich mitochondrial membranes does not allow optimal stabilization such as has been seen in phospholipid- and cholesterol-rich hepatocyte cell membranes, investigated previously.

Mechanism of hepatoprotective action of bile salts in liver disease

Ursodeoxycholic acid (UDCA) improves liver enzymes and in many instances liver histology in cholestatic liver diseases such as primary biliary cirrhosis and primary sclerosing cholangitis. Besides classic cholestatic diseases, UDCA also improves liver biochemistry in alcoholic liver disease and in chronic viral hepatitis C. The main target of UDCA treatment, however, is cholestasis, and consequently the mechanisms responsible for the beneficial effects in these diseases are of interest, and are discussed in detail in this article.

Ursodeoxycholate protects against ethanol-induced liver mitochondrial injury

The purpose of this work was to examine whether ursodeoxycholate (UDC), a hydrophilic bile salt, could reduce mitochondrial liver injury from chronic ethanol consumption in rats. Animals were pair-fed liquid diets containing 36% of calories as ethanol or isocaloric carbohydrates. They were randomly assigned into 4 groups of 7 rats each and received a specific treatment for 5 weeks: control diet, ethanol diet, control diet + UDC, and ethanol diet + UDC. Respiratory rates of isolated liver mitochondria were measured using a Clark oxygen electrode with sodium succinate as substrate. Mitochondria from rats chronically fed ethanol demonstrated an impaired ability to produce energy. At the fatty liver stage, the ADP-stimulated respiration (V3) was depressed by 33%, the respiratory control ratio (RC) by 25% and the P/O ratio by 15%. In ethanol-fed rats supplemented with UDC, both the rate and efficiency of ATP synthesis via the oxidative phosphorylation were improved: V3 was increased by 35%, P/O by 8%. All the respiratory parameters were similar in control group and control + UDC group. On the other hand, the number and size of mitochondria were assessed by electron microscopy and computer-assisted quantitative analysis. The number of mitochondria from ethanol-treated rats was decreased by 29%, and they were enlarged by 74%. Both parameters were normalized to control values by UDC treatment. These studies demonstrate that UDC has a protective effect against ethanol-induced mitochondrial injury by improving ATP synthesis and preserving liver mitochondrial morphology. These UDC positive effects may contribute to the observed decrease in fat accumulation and may delay the progression of alcoholic injury to more advanced stages.

Effect of bile acids on lipid peroxidation: the role of iron

The toxic effect of hydrophobic bile acids is claimed to be in part mediated by lipid peroxidation. Conversely, antioxidant properties of tauroursodeoxycholic acid (TUDC), a hydrophilic bile acid, have been suggested as a possible mechanism by which TUDC confers its beneficial effect in a variety of diseases. We have investigated the effect of taurodeoxycholic acid (TDC), a hydrophobic bile acid and TUDC on lipid peroxidation using a pure lipid system both in the presence and absence of iron ions. Neither TDC nor TUDC showed any effect on spontaneous lipid peroxidation of phosphatidylcholine liposomes or sodium arachidonate solution. This lack of effect excludes the possibility of direct prooxidant or antioxidant properties for TDC and TUDC. Addition of ferrous ions (0.1 mM) to the lipid system brought about a linear increase in lipid peroxidation with time. The presence of TDC caused an increase in the rate and extent of iron-stimulated lipid peroxidation. The propensity of bile acids to increase iron-induced lipid peroxidation was related to hydrophobicity of the individual bile acids, with the highest effect observed with taurolithocholic acid, whereas TUDC did not have any influence. The TDC-induced increase in the iron-stimulated lipid peroxidation was concentration dependent. Addition of TUDC (10 mM) completely abolished the effect of TDC (2 mM) on iron-induced lipid peroxidation. This finding suggests that TUDC does not function as an antioxidant per se but may prevent lipid peroxidation caused by TDC. In conclusion, only in the presence of iron ions, hydrophobic bile acids may enhance lipid peroxidation. TUDC has no antioxidant activity per se but may counter the TDC-induced increase in iron-stimulated lipid peroxidation.

Efficacy of ursodeoxycholic acid in Japanese patients with type 1 autoimmune hepatitis

Ursodeoxycholic acid (UDCA) has been shown to have beneficial effects on patients with primary biliary cirrhosis, suggesting that UDCA has immunomodulating effects. We investigated the effect of UDCA in patients with autoimmune hepatitis (AIH) which is characterized by immunological abnormalities. Eight patients with type 1 AIH were treated with 600 mg of UDCA per day for 2 years. Based on the criteria of the International Autoimmune Hepatitis Group, five patients were diagnosed as definite and three as probable type 1 AIH. Liver function tests were performed every 4 weeks, before and during UDCA therapy and the serum levels of anti-nuclear antibodies (ANA), smooth muscle antibodies (SMA), immunoglobulin G and gamma globulin were determined every 3 months. The levels of serum aspartate aminotransferase and alanine aminotransferase significantly decreased from 154 +/- 24 IU/L and 170 +/- 17 IU/L before UDCA therapy to 31 +/- 3 IU/L and 25 +/- 5 IU/L (P < 0.001) after 1 year of treatment and 28 +/- 2 IU/L and 23 +/- 4 IU/L (P < 0.001) after 2 years of treatment. After 2 years of treatment, the levels of serum immunoglobulin G and gamma globulin significantly decreased (P < 0.05) and ANA titres (5/8 patients) were reduced and SMA (3/5 patients) became negative. Furthermore, hepatic histopathological changes of four patients were assessed after 1 year of treatment, and an improvement of intrahepatic inflammation, but not fibrosis, was observed. In conclusion, these results suggest that UDCA has a beneficial therapeutic effect in patients with type 1 autoimmune hepatitis.

Effect of tauroursodeoxycholic acid on bile-acid-induced apoptosis and cytolysis in rat hepatocytes

BACKGROUND/AIMS

In cholestatic liver disease, bile acids may initiate or aggravate hepatocellular damage. Cellular necrosis and cell death may be due to detergent effects of bile acids, but apoptosis may also play a role. In cholestasis, the conditions determining either apoptotic or cytolytic cell death are still unclear. Primary rat hepatocytes in culture represent a suitable model to study bile-acid-induced liver damage.

METHODS

Glycochenodeoxycholic acid, a hydrophobic bile acid, was used to induce cell damage. Tauroursodeoxycholic acid, a hydrophilic bile acid, served as substrate to study possible protective effects of such compounds. To study the time and concentration dependency of bile-acid-induced cytolysis and apoptosis, morphologic alterations, hepatocellular enzyme release and nucleosomal DNA fragmentation were evaluated.

RESULTS

Bile-acid-induced cytolysis, as indicated by hepatocellular enzyme release and by morphologic signs of membrane destruction, increased with concentration and time. Addition of tauroursodeoxycholic acid to the incubation medium reduced cytolysis significantly, indicating a direct hepatoprotective effect of this bile acid against the detergent action of hydrophobic bile acids. In contrast to cytolysis, apoptosis with DNA fragmentation was induced by low concentrations of glycochenodeoxycholic acid a few hours after incubation. Coincubation with tauroursodeoxycholic acid in equimolar concentrations significantly reduced apoptosis, indicating another direct hepatoprotective effect of tauroursodeoxycholic acid.

CONCLUSIONS

It seems likely that in severe cholestasis, bile-acid-induced injury of hepatocytes is due mainly to cytolysis, whereas in moderately severe cholestasis apoptosis represents the predominant mechanism of bile acid toxicity. Tauroursodeoxycholic acid may reduce both bile-acid-induced apoptosis and cytolysis.

Ethanol-induced changes of intracellular thiol compartmentation and protein redox status in the rat liver: effect of tauroursodeoxycholate

BACKGROUND/AIMS

Ethanol impairs cellular antioxidant defense and protein metabolism. Hydrophilic bile acids are protective against ethanol-induced cytotoxicity. This study investigated the compartmentation of intracellular thiol and protein redox status after acute ethanol intoxication in the liver and the effect of tauroursodeoxycholate pretreatment.

METHODS

The concentrations of total glutathione, glutathione bound to proteins, sulfhydryl proteins, carbonyl proteins and malondialdehyde were measured in hepatic cytosol, mitochondria and nuclei after oral administration of 25% ethanol (4 g/kg) or isocaloric carbohydrate solution to rats. The metabolisms of ethanol and acetaldehyde were investigated by giving 4-methylpyrazole (1 mmol/kg i.p.) or cyanamide (15 mg/kg i.p.) 1 h prior to ethanol ingestion. One group of rats received tauroursodeoxycholate (12 mg/kg p.os) 1 h before ethanol ingestion.

RESULTS

Ethanol significantly decreased the glutathione concentrations. Significant increases in glutathione bound to proteins, carbonyl protein and malondialdehyde concentrations were also noted, especially at the mitochondrial level. Enhanced carbonyl protein formation was also observed (p < 0.01). The inhibition of acetaldehyde metabolism, but not ethanol metabolism, exaggerated the alterations produced by ethanol. Pretreatment with tauroursodeoxycholate significantly reduced lipid and protein oxidation, particularly in mitochondria. By contrast, no changes were observed in glutathione content and compartmentation.

CONCLUSIONS

Ethanol intoxication differentially impairs thiol and protein redox status in the subcellular fractions of rat liver. These alterations seem dependent on acetaldehyde rather than ethanol. Tauroursodeoxycholate administration protects proteins and lipids from ethanol-induced oxidative damage without influencing the glutathione content and compartmentation.

Antioxidant enzyme status in biliary obstructed rats: effects of N-acetylcysteine

BACKGROUND/AIMS

N-acetylcysteine (NAC) is a modulator of thiol levels that protects against hepatotoxic agents. The aim of this study was to investigate whether NAC might improve hepatic antioxidant defenses in chronically biliary obstructed rats.

METHODS

Secondary biliary cirrhosis was induced by 28 days of bile-duct obstruction. Groups of control and cirrhotic animals received NAC (50 mumol .kg-1.d-1 i.m.) through the experimental period.

RESULTS

Bile-duct obstruction resulted in decreased liver glutathione concentrations. Dichlorofluorescein (DCF) and thiobarbituric acid reactive substances (TBARS) concentrations, measured as markers of production of reactive oxygen species and lipid peroxidation, respectively, were significantly increased. Microsomal and mitochondrial membrane fluidity and the activities of catalase, cytosolic and mitochondrial superoxide dismutase (SOD), glutathione S-transferase, and cytosolic and mitochondrial Se-dependent and Se-independent glutathione peroxidase (GPx) were significantly reduced. NAC corrected the reduction in glutathione concentration and partially prevented the increases in DCF and TBARS concentrations. In addition, NAC treatment resulted in significant preservation of membrane fluidity and of the activities of catalase, mitochondrial SOD and the different forms of GPx.

CONCLUSIONS

Our data indicate that NAC maintains antioxidant defenses in biliary obstructed rats. These effects of NAC suggest that it may be a useful agent to preserve liver function in patients with biliary obstruction.

The Nordic multicenter double-blind randomized controlled trial of prophylactic ursodeoxycholic acid in liver transplant patients

BACKGROUND

Prophylactic treatment with ursodeoxycholic acid (UDCA) has been reported to reduce the incidence of acute rejection after liver transplantation compared with historical controls. We investigated this in a prospective, randomized, placebo-controlled multicenter study.

METHODS

Fifty-four liver transplant patients were allocated to the UDCA treatment group (15 mg/kg/day), and 48 patients were allocated to the placebo group. Trial medicine was started on the first postoperative day and was given for 3 months. Follow-up was for 12 months. Treatment was stratified for adults with chronic liver disease (n=77), adults with acute liver failure (n=10), and children (n=15).

RESULTS

The frequency of patients with acute rejection was 65% in the UDCA treatment group and 68% in the placebo group. The frequency of steroid-resistant rejection was similar in both groups. The probability of acute rejection, analyzed according to the intention-to-treat policy with Kaplan-Meier analysis, was similar in both treatment groups. No significant differences were found in patient survival and graft survival probabilities. For the biochemical markers of cholestasis, only gamma-glutamyltransferase was significantly improved after 2 months of UDCA treatment.

CONCLUSIONS

The initial optimistic report of a beneficial effect of prophylactic treatment with UDCA on acute rejection after liver transplantation was not confirmed in this controlled study.

Use of ursodeoxycholic acids in a dog with chronic hepatitis: effects on serum hepatic tests and endogenous bile acid composition

A dog with severe cholestasis secondary to chronic hepatitis was treated with ursodeoxycholic acid (UDCA) PO. After 2 weeks of daily treatment, the dog was more active and had an improved appetite. Monthly serum biochemical determinations and analysis of individual bile acid profiles documented improvement in hepatobiliary tests and a marked reduction in the concentrations of potentially hepatotoxic endogenous bile acids. These effects were maintained for approximately 6 months. The findings in this dog are similar to those reported for human patients treated with UDCA and provide preliminary evidence in support of its continued evaluation in the treatment of cholestatic liver disease in the dog.

Effect of deoxycholic acid and ursodeoxycholic acid on lipid peroxidation in cultured macrophages

BACKGROUND

Kupffer cells are essential for normal hepatic homeostasis and when stimulated, they secrete reactive oxygen species, nitric oxide, eicosanoids, and cytokines. Some of these products are cytotoxic and attack nucleic acids, thiol proteins, or membrane lipids causing lipid peroxidation. Hydrophobic bile acids, such as deoxycholic acid (DCA), can damage hepatocytes by solubilising membranes and impairing mitochondrial function, as well as increasing the generation of reactive oxygen species.

OBJECTIVES

The hypothesis that hydrophobic bile acids could stimulate Kupffer cells to increase their capacity to generate reactive oxygen species by measuring cellular lipid peroxidation was tested. Because the hydrophilic bile acid, ursodeoxycholic acid (UDCA) can block hydrophobic bile acid induced cellular phenomena, it was also hypothesised that UDCA could antagonise macrophage activation by hydrophobic bile acids to blunt their capacity to generate reactive oxygen species.

METHODS

J-774A.1 murine macrophages were incubated for 24 hours with either 10(-5) M and 10(-4) M (final concentration) DCA alone, or 10(-4) M UDCA alone, or a mixture of 10(-4) M 1:1 molar ratio of DCA and UDCA. At the end of the incubation period, the culture medium was collected for determination of cellular lipid peroxidation by measuring the malondialdehyde (MDA) content in the medium with the thiobarbituric acid reactive substances assay.

RESULTS

10(-5) M and 10(-4) M DCA increased MDA generation by cultured macrophages. 10(-4) M UDCA alone did not increase MDA generation but blocked the peroxidative actions of DCA.

CONCLUSIONS

Hydrophobic bile acids, after their hepatic retention, can oxidatively activate Kupffer cells to generate reactive oxygen species. Because UDCA can block this action, the beneficial effect of UDCA is, in part, related to its ability to act as an antioxidant.

Reduced antioxidative capacity in liver mitochondria from bile duct ligated rats

Lipid peroxidation and antioxidative mechanisms were investigated in liver mitochondria from bile duct ligated rats (BDL rats) and correlated with the activity of enzyme complexes of the electron transport chain. In comparison to pair-fed control rats, BDL rats had increased concentrations of thiobarbituric acid reacting substances (TBARS) per gram of liver and per milligram of mitochondrial protein 3, 7, 14, and 28 days after surgery. The hepatic glutathione (GSH) content was decreased in BDL rats 28 days after surgery when expressed per gram of liver but equal between BDL and control rats when expressed per liver. The mitochondrial GSH content was decreased in BDL rats by 20% to 33% from day 7 after surgery. The concentrations of ubiquinone-9 and ubiquinone-10, substances involved in electron transport and efficient antioxidants, were both decreased in BDL rats 14 and 28 days after surgery per gram of liver and per milligram of mitochondrial protein. When expressed per liver, ubiquinone-9 was decreased in BDL rats from day 7 after surgery. In comparison with controls, the decrease in total mitochondrial ubiquinone content in BDL rats averaged 52% 14 days and 38% 28 days after surgery. The activity of the succinate:ferricytochrome c oxidoreductase (complexes II and III of the electron transport chain) was decreased in BDL rats at days 7, 14, and 28 after surgery, and the activity of the ferrocytochrome c:oxygen oxidoreductase (complex IV) was reduced at 14 and 28 days after surgery. The mitochondrial concentration of TBARS showed a negative and the concentrations of GSH and ubiquinone a positive correlation with the activity of the succinate:ferricytochrome c oxidoreductase.(ABSTRACT TRUNCATED AT 250 WORDS)