Beta-carotene prevents bile acid-induced cytotoxicity in the rat hepatocyte: Evidence for an antioxidant and anti-apoptotic role of beta-carotene in vitro

Melatonin and metformin co-loaded nanoliposomes efficiently attenuate liver damage induced by bile duct ligation in rats

In the current study, the therapeutic effectiveness of the metformin (Met) and melatonin (Mel) co-loaded liposomes was investigated on cholestasis induced by bile duct ligation (BDL) in male rats. Histopathological analysis, biochemical analysis, and oxidative stress markers were assayed to determine the therapeutic effect of Met and Mel co-loaded liposomes on cholestasis. Histopathological analysis revealed that the simultaneous administration of Met and Mel, whether in the free (C-Mel-Met) or liposomal (C-Lipo-Mel-Met) forms, reduced inflammation as well as proliferation of bile ducts; however, results were more prominent in the liposomal form of Mel and Met. Additionaly, serum levels of aspartate aminotransferase (AST) were significantly (p < 0.001) higher in (C-Mel-Met) treated rats compared with (BDL) rats; however, (C-Lipo-Mel-Met) treated rats exhibited significant (p < 0.05) lower AST rates in comparison to (BDL) rats. Moreover, a significant (p < 0.0001) drop in bilirubin levels was detected in (C-Lipo-Mel-Met) treated rats in comparison to (BDL) rats; it is noteworthy mentioning that bilirubin levels in (C-Lipo-Mel-Met) treated rats were insignificant in comparison to sham-control (SC) rats. Furthermore, rats concomitantly administered Met and Mel, exhibited significant downregulation in the expression levels of inflammatory cytokine genes such as TNF-α and IL-1 gene expression, where the downregulation was more prominent in the liposomal from. Our findings demonestrate that the concomitant administration of metformin and melatonin in the liposomal form had more therapeutic effect on liver injury than their free forms through improving histological changes, reducing biochemical markers and favoring oxidant- antioxidant balance.

Carotenoids: Role in Neurodegenerative Diseases Remediation

Numerous factors can contribute to the development of neurodegenerative disorders (NDs), such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis. Oxidative stress (OS), a fairly common ND symptom, can be caused by more reactive oxygen species being made. In addition, the pathological state of NDs, which includes a high number of protein aggregates, could make chronic inflammation worse by activating microglia. Carotenoids, often known as "CTs", are pigments that exist naturally and play a vital role in the prevention of several brain illnesses. CTs are organic pigments with major significance in ND prevention. More than 600 CTs have been discovered in nature, and they may be found in a wide variety of creatures. Different forms of CTs are responsible for the red, yellow, and orange pigments seen in many animals and plants. Because of their unique structure, CTs exhibit a wide range of bioactive effects, such as anti-inflammatory and antioxidant effects. The preventive effects of CTs have led researchers to find a strong correlation between CT levels in the body and the avoidance and treatment of several ailments, including NDs. To further understand the connection between OS, neuroinflammation, and NDs, a literature review has been compiled. In addition, we have focused on the anti-inflammatory and antioxidant properties of CTs for the treatment and management of NDs.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Case Report: Extended Clinical Spectrum of the Neonatal Diabetes With Congenital Hypothyroidism Syndrome

BACKGROUND

Neonatal diabetes with congenital hypothyroidism (NDH) syndrome is a rare condition caused by homozygous or compound heterozygous mutations in the GLI-similar 3 coding gene GLIS3. Almost 20 patients have been reported to date, with significant phenotypic variability.

CASE PRESENTATION

We describe a boy with a homozygous deletion (exons 5-9) in the GLIS3 gene, who presents novel clinical aspects not reported previously. In addition to neonatal diabetes, congenital hypothyroidism and other known multi-organ manifestations such as cholestasis and renal cysts, he suffered from hyporegenerative anemia during the first four months of life and presents megalocornea in the absence of elevated intraocular pressure. Compensation of partial exocrine pancreatic insufficiency and deficiencies in antioxidative vitamins seemed to have exerted marked beneficial impact on several disease symptoms including cholestasis and TSH resistance, although a causal relation is difficult to prove. Considering reports on persistent fetal hemoglobin detected in a few children with GLIS3 mutations, the transient anemia seen in our patient may represent a further symptom associated with either the GLIS3 defect itself or, secondarily, micronutrient deficiency related to exocrine pancreatic deficiency or cholestasis.

CONCLUSIONS

Our report expands the phenotypic spectrum of patients with GLIS3 mutations and adds important information on the clinical course, highlighting the possible beneficial effects of pancreatic enzyme and antioxidative vitamin substitutions on characteristic NDH syndrome manifestations such as TSH resistance and cholestasis. We recommend to carefully screen infants with GLIS3 mutations for subtle biochemical signs of partial exocrine pancreatic deficiency or to discuss exploratory administration of pancreatic enzymes and antioxidative vitamins, even in case of good weight gain and fecal elastase concentrations in the low-to-normal range.

Nanodispersions of beta-carotene: effects on antioxidant enzymes and cytotoxic properties

Beta-carotene is a carotenoid precursor of vitamin A, known for its biological activities. Due to its high hydrophobicity, nanonization processes, i.e. the transformation into nanoparticles, can improve its water affinity, and therefore the activity in aqueous systems. The objective of this study was to produce beta-carotene nanoparticles by the solid dispersion method and to evaluate their effects on the activity of glutathione-S-transferase and acetylcholinesterase enzymes using Drosophila melanogaster (DM) homogenate, the superoxide dismutase- and catalase-like activities under in vitro conditions, and their cytotoxic properties against tumor and non-tumor cells. The formed nanometric beta-carotene particles resulted in stable colloids, readily dispersed in water, able to modulate acetylcholinesterase (AChE) activity, and presenting high potential to control the cholinergic system. Beta-carotene nanoparticles, at concentrations much lower than the pure pristine beta-carotene, presented in vitro mimetic activity to superoxide dismutase and altered glutathione-S-transferase activity in DM tissue. The content of hydrogen peroxide was neither affected by the nanoparticles (in aqueous solution) nor by pristine beta-carotene (in DMSO). In the cytotoxic assays, beta-carotene nanoparticles dispersed in water showed activity against four different tumor cell lines. Overall, beta-carotene nanoparticles presented significant bioactivity in aqueous medium surpassing their high hydrophobicity constraint.

Evaluating of β-carotene role in ameliorating of favism-induced disturbances in blood and testis

Background

Favism is an acute hemolytic anemia occurs in glucose 6-phosphate dehydrogenase (G6-PD) deficient individuals. β-Carotene occurs in vegetables such as carrots. This study aimed to establish the therapeutic effect of β-carotene to rebalance the testicular and blood proteins disturbances in favism.

Methods

Forty-eight male rats were divided into six equal groups; Groups 1, 2 and 3: normal rats were daily oral administrated with 1 ml saline, 1 ml corn oil and β-carotene (60 mg/kg dissolved in 1 ml corn oil), respectively, once a day over 15 days period. Group 4 (favism-induced group): normal rats injected intraperitoneal (ip) with diethyl maleate (5 μl/rat) and after 1 h injected ip with 1/3 LD50 of faba beans ethanolic extract for 15 day to induce favism. Groups 5 and 6: favism-induced rats were daily oral administered with 30 and 60 mg/kg β-carotene dissolved in 1 ml corn oil, respectively, once a day over 15 days.

Results

The results revealed that oral administration of corn oil or β-carotene into normal rats over 15 days period did not induce any change. In favism-induced groups, hematological parameters, liver function, serum glucose, G6-PD, luteinizing and follicle-stimulating hormones and sex-hormone binding globulin showed significant increase. Moreover, serum testosterone and dehydroepiandrosterone sulfate, testicular G6-PD, 3β-hydroxy steroid dehydrogenase, cholesterol and total protein were decreased. Treatment with both doses of β-carotene into favism groups restored all the abovementioned parameters to approach normal values. Favism inhibited blood proteins while β-carotene treatment into favism group stopped blood cells damage and blood proteins inhibition. These results were supported by histological studies.

Conclusions

In conclusion, taken β-carotene into favism group abolished testicular and blood proteins disturbances and this effect was dose dependent.

The antiapoptotic effects of different doses of β-carotene in chronic ethanol-fed rats

BACKGROUND

Ethanol consumption might induce hepatic apoptosis and cause liver damage. The study was to investigate the effects of different doses of β-carotene supplementation on the antioxidant capacity and hepatic apoptosis in chronic ethanol-fed rats.

METHODS

Rats were divided into 6 groups: C (control liquid diet), CLB [control liquid diet with β-carotene supplementation at 0.52 mg/kg body weight (BW)/day], CHB (control liquid diet with β-carotene supplementation at 2.6 mg/kg BW/day), E (ethanol liquid diet), ELB (ethanol liquid diet with β-carotene supplementation at 0.52 mg/kg BW/day), and EHB (ethanol liquid diet with β-carotene supplementation at 2.6 mg/kg BW/day). After 12 weeks, rats were sacrificed and blood and liver samples were collected for analysis.

RESULTS

Lipid peroxidation and hepatic cytochrome P450 2E1 (CYP2E1) expression had increased, and hepatic Fas ligand, caspase-8, cytochrome c, caspase-9, and -3 expressions had significantly increased in the E group. However, lipid peroxidation and CYP2E1, caspase-9, and -3 expressions were significantly lower and Bcl-xL expression was higher in the ELB group. The hepatic tumor necrosis factor (TNF)-α level, lipid peroxidation, and cytochrome c expression were significantly lower and Bcl-2 expression was significantly higher in the EHB group.

CONCLUSIONS

The results suggest that ethanol treatment causes oxidative stress and hepatic apoptosis leading to liver injury, and β-carotene supplementation (0.52 mg/kg BW/day) can prevent ethanol-induced liver damage by decreasing ethanol-induced oxidative stress and inhibiting apoptosis in the liver.

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.

Inhibition by zinc of deoxycholate-induced apoptosis in HCT-116 cells

The bile acid, deoxycholate, can induce apoptosis although the effect of trace elements on such cell death is unknown. The aim of this study was to determine if deoxycholate-induced apoptosis is influenced by zinc. HCT-116 colon epithelial cells were pre-treated with zinc and then exposed to deoxycholate. Membrane blebbing, formation of apoptotic bodies, and greater overall production of reactive oxygen species (ROS) occurred in cells exposed to deoxycholate, but zinc inhibited the occurrence of these three events caused by deoxycholate. Upon finer analysis, stimulation of mitochondrial superoxide production, mitochondrial dysfunction, and cytochrome c release were detected in cells exposed to deoxycholate, but zinc did not inhibit any of these three effects caused by deoxycholate. Additionally, caspase-3 activation, plasma membrane phospholipid translocation, and also chromatin condensation and fragmentation were observed in cells exposed to deoxycholate, but all of these effects of deoxycholate, including the greater overall ROS production, were all inhibited by zinc. Because zinc did not prevent the three mitochondrial effects caused by deoxycholate, the last set of findings suggested that zinc hampered activation of an initiator caspase upstream of effector caspase-3, in inhibiting deoxycholate-induced HCT-116 cell death. In examining this possibility, it was found that caspase-8 activation caused by deoxycholate was blocked by zinc. Collectively, the results suggest that zinc can inhibit deoxycholate-induced apoptotic cell death mediated by caspases.

beta-Carotene exhibits antioxidant and anti-apoptotic properties to prevent ethanol-induced cytotoxicity in isolated rat hepatocytes

The study was designed to evaluate the effects of 1 microM beta-carotene on antioxidant status in ethanol-treated rat hepatocytes and investigate possible anti-apoptotic mechanisms of beta-carotene in protecting ethanol-induced cytotoxicity. The isolated rat hepatocytes were incubated for 48 h in a medium with or without alcohol (100 mM) and mu-carotene (1 microM) using the following groups: the control (C), beta-carotene (CB), ethanol (E), and ethanol + beta-carotene (EB) groups. The cell viability, antioxidative status, cytochrome P450 2E1 (CYP2E1) and caspase expressions in hepatocytes were measured. The E group demonstrated lower cell viability, glutathione (GSH) levels, and lipid peroxide accumulation in rat hepatocytes; meanwhile, CYP2E1, caspase-3, and caspase-9 expressions increased. In contrast, cell viability, GSH levels, and glutathione reductase (GRD) activity significantly increased while lipid peroxides and expressions of CYP2E1, casapse-3, and caspase-9 decreased in the EB group. The results suggest that ethanol treatment decreases cell viability in rat hepatocytes via induced oxidative stress. 1 muM beta-carotene decreased oxidative stress and prevented ethanol-induced cell death by inhibiting caspase-9 and caspase-3 expression.

Protective effect of beta carotene pretreatment on renal ischemia/reperfusion injury in rat

Renal ischemia/reperfusion injury is a major cause of acute renal failure. The production of free radicals and reactive oxygen species are important factors contributing to ischemia/reperfusion injury. Thus, scavenging of the excess free radicals can be an important therapeutic approach. The present study examined the protective effect of beta carotene against renal ischemia/reperfusion injury in rat. Male adult Wistar rats (250-300 g) were exposed to 45 min of renal ischemia followed by 4 h of reperfusion. Beta carotene (10, 30 and 100 mg kg(-1)) or vehicle was administered for 5 days prior to ischemia. Renal function was assessed by plasma and urinary analysis. Present results showed that ischemia/reperfusion injury increased (p < 0.05-p < 0.001) serum urea and creatinine levels, as well as urinary excretion of protein and calcium and fractional excretion of sodium, while decreased glomerular filtration rate and potassium excretion. However, alterations in these biochemical indices due to ischemia/reperfusion injury were attenuated by beta carotene pretreatment (p < 0.05-p < 0.001), although not by all doses. Since, beta carotene administration improved renal function, it seems that beta carotene protects renal tissue against ischemia/reperfusion-induced oxidative damage.

Synergic effects of α-tocopherol and β-carotene on tert-butylhydroperoxide-induced HepG2 cell injury

Oxidative stress produced by the dietary or chemical substrates is one of the major causes of liver cell injury. In this study, we compared the effects of two dietary antioxidants, α-tocopherol (α-T) and β-carotene (β-C) against tert-butyl hydroperxide (tBHP)-induced oxidative stress in human hepatoma HepG2 cells. Cell proliferation, lipid peroxidation (LPO), cellular lactate dehydrogenase (LDH), [3H]-aflatoxin B1(AFB1)-DNA adduct formation, and cytochrome P450 2E1 (CYP2E1) expression were determined after antioxidants were added to the tBHP-stressed cells. When compared to an ethanol-based control, all biomarkers for the cell damage were significantly increased by treatments. Treatments of β-C or the combination of two antioxidants at 50 ppm for 48 h enhanced cell proliferation ( P < 0.05) compared to tBHP control. The antioxidative and cytoprotective actions of α-T and β-C, alone or in combination, were associated with modulation of microsomal CYP2E1 expression, corresponding to the regulation of LPO production ( P < 0.0001). Our results indicate that α-T and β-C may contribute differently to protection of cellular membrane disruption in CYP2E1-expressing HepG2 cells. Moreover, the combination of α-T and β-C appears to impel the greater protection of pathogenic processes of oxidative stress in liver.

Bile acids as endogenous etiologic agents in gastrointestinal cancer

Bile acids are implicated as etiologic agents in cancer of the gastrointestinal (GI) tract, including cancer of the esophagus, stomach, small intestine, liver, biliary tract, pancreas and colon/rectum. Deleterious effects of bile acid exposure, likely related to carcinogenesis, include: induction of reactive oxygen and reactive nitrogen species; induction of DNA damage; stimulation of mutation; induction of apoptosis in the short term, and selection for apoptosis resistance in the long term. These deleterious effects have, so far, been reported most consistently in relation to esophageal and colorectal cancer, but also to some extent in relation to cancer of other organs. In addition, evidence is reviewed for an association of increased bile acid exposure with cancer risk in human populations, in specific human genetic conditions, and in animal experiments. A model for the role of bile acids in GI carcinogenesis is presented from a Darwinian perspective that offers an explanation for how the observed effects of bile acids on cells contribute to cancer development.

Immune-mediated liver diseases: programmed cell death ligands and circulating apoptotic markers

Primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis are the three major immune-mediated liver diseases. The etiologies of primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis are largely unknown, but seem to be influenced by genetic and environmental factors. Autoantibodies can be found in nearly all patients with primary sclerosing cholangitis and autoimmune hepatitis, and in the vast majority of patients with primary sclerosing cholangitis. In addition, autoimmune hepatitis is associated with high concentrations of serum globulins. Enhanced liver cell death by apoptosis has been described in all of these liver diseases, although the precise mechanisms remain unclear. In general, apoptosis can be initiated via an extrinsic pathway that is triggered by engagement of death receptors on the cell surface, or via an intrinsic pathway that is induced by mitochondrial injury and is influenced by members of the Bcl-2 family. In both pathways, effector caspases are finally activated that cleave and degrade cell structures, resulting in the release of apoptotic products into the circulation. New diagnostic tests can detect these apoptotic markers and programmed cell death ligands such as Fas and Fas-ligands, nucleosomes, caspases, cytokeratin fragments, macrophage migration inhibitory factor, soluble intracellular adhesion molecule, natural killer cells group 2D and programmed death ligands. Several of these markers have been found to be altered in tissue and/or blood of immune-mediated liver diseases, some also in nonimmune-mediated liver diseases. Beyond their potential usefulness as additional diagnostic markers, they may be valuable for the estimation of disease severity and therapy monitoring. This review summarizes current knowledge on apoptotic mechanisms, death receptor ligands and circulating apoptotic markers in immune-mediated liver diseases.

Protection of human colon epithelial cells against deoxycholate by rottlerin

The bile salt, deoxycholate (DOC), can harm cells and cause disease. Hence, there is interest in identifying compounds capable of protecting cells against DOC. In HCT-116 colon epithelial cells, DOC increased generation of reactive oxygen species and caused DNA damage and apoptosis. These effects of DOC were inhibited by rottlerin, which is a phenolic compound of plant origin. In elucidating its mechansim, rottlerin prevented the release of cytochrome c from mitochondria into cytosol, and also prevented the cleavage of caspase-3. Yet, rottlerin by itself markedly decreased mitochondrial membrane potential and increased mitochondrial superoxide production, but this did not result in cytochrome c release or in caspase-3 cleavage. At a higher test concentration, two other phenolic phytochemicals, namely, quercetin and resveratrol, were each able to largely prevent the occurrence of apoptosis in cells exposed to DOC. In contrast, epigallocatechin gallate, curcumin, and genistein were ineffective.

Paradoxical effect of diphenyleneiodonium in inducing DNA damage and apoptosis

Diphenyleneiodonium (DPI) is often used as a molecular tool in unravelling redox-sensitive cellular events involving NADPH oxidase. However, to better understand unexpected actions of DPI, it was ascertained if DPI affects cellular DNA. DPI induced single-strand breaks in DNA of HCT-116 cells, although this only slightly increased GADD153 expression. Nevertheless, after sustaining DNA damage, the DPI-treated cells subsequently had features characteristic of apoptosis, such as translocated membrane phospholipid and nuclei containing condensed chromatin. Paradoxically, DPI attenuated the DNA damage and overall ROS production caused by sodium deoxycholate (DOC), although DPI did not inhibit DOC-induced generation of mitochondrial [image omitted] . Furthermore, DPI prevented the occurrence of apoptosis caused by DOC. However, other known chemical inhibitors of NADPH oxidase did not produce the same results as DPI in negating the effects of DOC. Collectively, these disparate findings suggest that DPI can act not in accord with conventional wisdom depending on the experimental conditions.

Subcutaneous vitamin E ameliorates liver injury in an in vivo model of steatocholestasis

Several genetic metabolic liver diseases share the pathological features of combined steatosis and cholestasis, or steatocholestasis. The aims of this study were to develop and characterize an in vivo model for steatocholestasis and to evaluate the effects of an antioxidant treatment on liver injury, oxidative stress, and mitochondrial perturbations in this model. Obese and lean Zucker rats received intravenous (IV) injections of glycochenodeoxycholic acid (GCDC) and were killed 4 hours later. Liver enzymes were measured; the liver histology was assessed, and hepatic mitochondria were analyzed for mitochondrial lipid peroxidation. In separate experiments, rats received daily injections of subcutaneous (SQ) vitamin E before GCDC infusion. Bile acid-induced injury (serum AST and ALT and liver histology) was more severe in the obese rats than in the lean rats, characterized predominantly by extensive cell necrosis with minimal evidence of apoptosis. SQ vitamin E provided significant protection against IV GCDC-induced hepatic injury, in vitro GCDC-induced permeability transition, and cytochrome C and apoptosis-inducing factor release from isolated mitochondria.

CONCLUSION

Steatosis sensitizes the liver to bile acid-induced necrotic hepatocyte injury, which is responsive to vitamin E therapy.

Dietary antioxidant compounds and liver health

Chronic liver damage is a widespread pathology characterized by a progressive evolution from steatosis to chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. As the oxidative stress plays a central role in liver diseases pathogenesis and progression, the use of antioxidants have been proposed as therapeutic agents, as well as drug coadjuvants, to counteract liver damage. In this work in vitro and in vivo studies, with emphasis on humans and animals experiments, have been considered and reviewed according to antioxidant typologies. Great differences emerge as far as ingested doses, bioavailability and liver ability to accumulate the various compounds. Results available up to now suggest that lycopene-rich foods could be proposed in therapeutic treatment of some liver pathologies. On the other hand contradictory results have been obtained with alpha-tocopherol, beta-carotene and trans-resveratrol. Quercetin, silymarin, esculetin and thyme and rosemary among phenolic compounds need further studies.

Human hepatic mitochondria generate reactive oxygen species and undergo the permeability transition in response to hydrophobic bile acids

OBJECTIVES

Hydrophobic bile acids accumulate in the liver during cholestasis and are believed to cause hepatocellular necrosis and apoptosis in part through induction of the mitochondrial permeability transition (MPT) and the mitochondrial generation of oxidative stress. The purpose of this study was to determine if human hepatic mitochondria respond to bile acids in this manner.

METHODS

The MPT was measured spectrophotometrically and morphologically in normal human liver mitochondria exposed to glycochenodeoxycholic acid (GCDC) with and without cyclosporin A, an inhibitor of the MPT, antioxidants, and tauroursodeoxycholic acid (TUDC). Hydroperoxide generation was measured by dichlorofluorescein fluorescence. Cytochrome c and apoptosis-inducing factor were assessed by immunoblotting.

RESULTS

GCDC induced the MPT in a dose-dependent manner, which was inhibited by cyclosporin A, alpha-tocopherol, beta-carotene, idebenone, and TUDC. GCDC stimulated reactive oxygen species generation and release of cytochrome c and apoptosis-inducing factor, which were significantly inhibited by the antioxidants, cyclosporin A, and TUDC.

CONCLUSIONS

Mitochondrial pathways of cell death are stimulated in human hepatic mitochondria exposed to GCDC consistent with the role of mitochondrial dysfunction in the pathogenesis of cholestatic liver injury. These results parallel those reported in rodents, supporting the extrapolation of mechanistic studies of bile acid toxicity from rodent to humans.

Toxic effect of pregnancy intrahepatic cholestasis on liver and placenta in pregnant rats

AIM: To investigate the toxic effect of intrahepatic cholestasis of pregnancy (ICP) on the liver and placenta in pregnant rats.

METHODS: The animal model of ICP was induced by 17-a-ethinylestradiol and progesterone. Pathohistological changes of the liver and placenta of the pregnant rats were observed under light and electronic microscope.

RESULTS: The levels of serum alanine transaminase (ALT), aspartate transaminase (AST), and total bile acid (TBA) were significantly higher in ICP rats than the control (AST: 3 784±155 vs 747±158; ALT: 7 076±220 vs 847±198; TBA: 78.5±4.5 vs 25.2±3.7; P<0.01 for all of the three). Granule- and vacuole-like cells were observed in liver of ICP rats under light microscope and Bile canaliculi were dilated and deposition of substances with high electronic density was found in bile canaliculi and hepatocytes of ICP rats by electronic microscopy. Granule- and vacuole-like changes were also found in some placenta syncytiotrophoblast of ICP rats by light microscopy.

CONCLUSION: ICP with hyperbileacidemia has marked toxicity to hepatocytes and placenta trophoblasts of pregnant rats.

Licorice compounds glycyrrhizin and 18beta-glycyrrhetinic acid are potent modulators of bile acid-induced cytotoxicity in rat hepatocytes

The accumulation of hydrophobic bile acids results in cholestatic liver injury by increasing oxidative stress, mitochondrial dysfunction, and activation of cell signaling pathways. Licorice root and its constituents have been utilized as antihepatotoxic agents. The purpose of this study was to evaluate the potential modulation by a primary component of licorice root, glycyrrhizin (GL), and its metabolite, 18beta-glycyrrhetinic acid (GA), in a hepatocyte model of cholestatic liver injury. Preincubation of fresh rat hepatocyte suspensions with GL or GA reduced glycochenodeoxycholic acid (GCDC)-dependent reactive oxygen species generation, with GA more potent than GL. Interestingly, GL and GA had opposing effects toward GCDC-induced cytotoxicity; GA prevented both necrosis and apoptosis, whereas GL enhanced apoptosis. GCDC promoted activation of caspase 10, caspase 3, and PARP; all were inhibited by GA but not GL. Induction of apoptosis by GCDC was also associated with activation of JNK, which was prevented by GA. Activation of caspase 9 and dissipation of mitochondrial membrane potential were prevented by GA but not GL. In liver mitochondrial studies, GL and GA were both potent inhibitors of the mitochondrial permeability transition, reactive oxygen species generation, and cytochrome c release at submicromolar concentrations. Results from this study suggest that GL exhibits pro-apoptotic properties, whereas GA is a potent inhibitor of bile acid-induced apoptosis and necrosis in a manner consistent with its antioxidative effect.