Homocysteine alterations in experimental cholestasis and its subsequent cirrhosis

Urine metabolic profile in rats with arterial hypertension of different genesis

The diversity of pathogenetic mechanisms underlying arterial hypertension leads to the necessity to devise a personalized approach to the diagnosis and treatment of the disease. Metabolomics is one of the promising methods for personalized medicine, as it provides a comprehensive understanding of the physiological processes occurring in the body. The metabolome is a set of low-molecular substances available for detection in a sample and representing intermediate and final products of cell metabolism. Changes in the content and ratio of metabolites in the sample mark the corresponding pathogenetic mechanisms by highlighting them, which is especially important for such a multifactorial disease as arterial hypertension. To identify metabolomic markers for hypertensive conditions of different origins, three forms of arterial hypertension (AH) were studied: rats with hereditary AH (ISIAH rat strain); rats with AH induced by L-NAME administration (a model of endothelial dysfunction with impaired NO production); rats with AH caused by the administration of deoxycorticosterone in combination with salt loading (hormone-dependent form - DOCA-salt AH). WAG rats were used as normotensive controls. 24-hour urine samples were collected from all animals and analyzed by quantitative NMR spectroscopy for metabolic profiling. Then, potential metabolomic markers for the studied forms of hypertensive conditions were identified using multivariate statistics. Analysis of the data obtained showed that hereditary stress-induced arterial hypertension in ISIAH rats was characterized by a decrease in the following urine metabolites: nicotinamide and 1-methylnicotinamide (markers of inflammatory processes), N- acetylglutamate (nitric oxide cycle), isobutyrate and methyl acetoacetate (gut microbiota). Pharmacologically induced forms of hypertension (the L-NAME and DOCA+NaCl groups) do not share metabolomic markers with hereditary AH. They are differentiated by N,N-dimethylglycine (both groups), choline (the L-NAME group) and 1-methylnicotinamide (the group of rats with DOCA-salt hypertension).

Evaluation of the effect of heat shock protein 70 targeted drugs on cirrhotic cardiomyopathy in biliary cirrhotic rats

AIMS

Liver cirrhosis leads to cirrhotic cardiomyopathy (CCM) and chronotropic incompetence (CI). Heat shock protein 70 (Hsp70) regulates cellular apoptosis and autophagy in stress. Teprenone modulates the Hsp70 and protects against cellular injury. Thus, we aimed to evaluate the effect of teprenone on CI in biliary cirrhotic rats.

MAIN METHODS

Liver cirrhosis was induced in male Wistar rats through bile duct ligation (BDL). The chronotropic responses and QT interval were studied through electrocardiography (ECG) in sham, cirrhotic, and cirrhotic/teprenone (100 mg/kg) pre-treated groups. Brain natriuretic peptide (BNP), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and monocyte chemo-attractant protein-1 (MCP-1), and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were investigated in serum. The Hsp70, B-cell lymphoma 2 (Bcl-2), and B-cell lymphoma 2-associated X protein (Bax) expressions were quantified through real-time polymerase chain reaction (Real-time PCR).

KEY FINDINGS

The chronotropic responses were decreased significantly in cirrhotic and cirrhotic/teprenone groups. The QT interval and serum BNP, TNF-α, IL-6, ALT, AST, and MCP-1 levels were increased significantly in the cirrhotic and decreased significantly, except BNP, in the cirrhotic/teprenone group. The Hsp70 and Bax expressions increased significantly in cirrhotic and decreased significantly in the cirrhotic/teprenone group while the Bcl-2 decreased significantly in cirrhotic and increased significantly in the cirrhotic/teprenone group.

SIGNIFICANCE

Teprenone does not relieve the CI and BNP changes in CCM while other indices are treated. Given that CCM is a multifactorial disease and needs to target other genes and proteins concurrent with Hsp70 to relieve CCM.

Role of homocysteine and folic acid on the altered calcium homeostasis of platelets from rats with biliary cirrhosis

Previously, we have found that intracellular calcium homeostasis is altered in platelets from an experimental model of liver cirrhosis, the bile-duct ligated (BDL) rat; these alterations are compatible with the existence of a hypercoagulable state. Different studies indicate that cholestatic diseases are associated with hyperhomocysteinemia; thus, we hypothetized that it could contribute to those platelet alterations. In the present study, we have investigated the role of homocysteine (HCY) in platelet aggregation and calcium signaling in the BDL model. The effect of chronic folic acid treatment was also analyzed. Acute treatment with HCY increased the aggregation response to ADP and calcium responses to thrombin in platelets of control and BDL rats. Capacitative calcium entry was not altered by HCY. Chronic treatment with folic acid decreased platelet aggregation in control and BDL rats, but this decrease was greater in BDL rats. In folic acid-treated rats, thrombin-induced calcium entry and release were decreased in platelet of control rats but unaltered in BDL rats; however, capacitative calcium entry was decreased in platelets of control and BDL rats treated with folic acid. Reactive oxygen species were produced at higher levels by BDL platelets after stimulation with HCY or thrombin and folic acid normalized these responses. HCY plays a role in the enhanced platelet aggregation response of BDL rats, probably through an enhanced formation of ROS. Folic acid pretreatment normalizes many of the platelet alterations shown by BDL rats.

Deregulated methionine adenosyltransferase α1, c-Myc, and Maf proteins together promote cholangiocarcinoma growth in mice and humans(‡)

c-Myc induction drives cholestatic liver injury and cholangiocarcinoma (CCA) in mice, and induction of Maf proteins (MafG and c-Maf) contributes to cholestatic liver injury, whereas S-adenosylmethionine (SAMe) administration is protective. Here, we determined whether there is interplay between c-Myc, Maf proteins, and methionine adenosyltransferase α1 (MATα1), which is responsible for SAMe biosynthesis in the liver. We used bile duct ligation (BDL) and lithocholic acid (LCA) treatment in mice as chronic cholestasis models, a murine CCA model, human CCA cell lines KMCH and Huh-28, human liver cancer HepG2, and human CCA specimens to study gene and protein expression, protein-protein interactions, molecular mechanisms, and functional outcomes. We found that c-Myc, MATα1 (encoded by MAT1A), MafG, and c-Maf interact with one another directly. MAT1A expression fell in hepatocytes and bile duct epithelial cells during chronic cholestasis and in murine and human CCA. The opposite occurred with c-Myc, MafG, and c-Maf expression. MATα1 interacts mainly with Mnt in normal liver, but this switches to c-Maf, MafG, and c-Myc in cholestatic livers and CCA. Promoter regions of these genes have E-boxes that are bound by MATα1 and Mnt in normal liver and benign bile duct epithelial cells that switched to c-Myc, c-Maf, and MafG in cholestasis and CCA cells. E-box positively regulates c-Myc, MafG, and c-Maf, but it negatively regulates MAT1A. MATα1 represses, whereas c-Myc, MafG, and c-Maf enhance, E-box-driven promoter activity. Knocking down MAT1A or overexpressing MafG or c-Maf enhanced CCA growth and invasion in vivo.

CONCLUSION

There is a novel interplay between MATα1, c-Myc, and Maf proteins, and their deregulation during chronic cholestasis may facilitate CCA oncogenesis. (Hepatology 2016;64:439-455).

Gadolinium chloride, a Kupffer cell inhibitor, attenuates hepatic injury in a rat model of chronic cholestasis

The aim of the current study was to elucidate the effect of Kupffer cells inhibition on hepatic injury induced by chronic cholestasis. Sprague-Dawley rats underwent bile duct ligation (BDL) or sham operation and were treated with either saline solution or gadolinium chloride (GdCl(3), a specific Kupffer cell inhibitor, 20 mg/kg i.p. daily). Serum and liver samples were collected after 28 days. Direct and total bilirubin concentrations and serum enzyme activities of alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and γ-glutamyl transpeptidase (GGT) increased following BDL (p < 0.01). On the contrary to bilirubin concentrations and AST activity, GdCl(3) partially prevented the elevation in ALP, ALT and GGT enzyme activities (p < 0.05). GdCl(3) alleviated lipid peroxidation (reflected by malondialdehyde [MDA] concentration) and increased the activities of antioxidant enzymes (i.e. catalase and glutathione peroxidase) in liver samples after BDL (p < 0.05). Fibrosis, ductular proliferation and portal inflammation were also scored in liver samples. Among morphological changes appeared following BDL (i.e. marked fibrosis, portal inflammation and ductular proliferation); only ductular proliferation was not alleviated by GdCl(3). Therefore, Kupffer cells inhibition has beneficial effects against the development of hepatic injury induced by chronic cholestasis.

Modulation of the cannabinoid receptors by andrographolide attenuates hepatic apoptosis following bile duct ligation in rats with fibrosis

Bile acid-induced apoptosis plays an important role in the pathogenesis of cholestatic liver disease, and its prevention is of therapeutic interest. The aim of this study was to test whether the andrographolide limits the evolution of apoptosis in a murine model of bile duct ligation (BDL)-induced hepatic fibrosis. Male Sprague-Dawley rats were divided into four groups and hepatic apoptosis was induced by BDL for 2 weeks. The BDL animals were also treated with andrographolide (50, 100, and 200 mg/kg, i.p.) during the same time period. BDL-induced liver injury was associated with apoptosis and fibrosis, and the latter was significantly reduced in animals receiving andrographolide. The increase in serum alanine aminotransferase, asparate aminotransferase, tumor necrosis factor-alpha and IL-1beta levels caused by BDL were also significantly reduced by treatment with andrographolide. Andrographolide decreased the intrahepatic protein levels of cannabinoid receptor 1 (CB1), Bax, and cytochrome c, along with of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta (TGF-beta), two markers of fibrogenesis. This effect was mediated by the inactivation of the c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK1/2) phosphorylation cascade, but it did not affect the p38 mitogen-activated protein kinase pathway. Additionally, andrographolide reduced the generation of hepatic lipid peroxidation and enhance senescence marker protein-30 levels to resist the hepatic oxidative stress in the presence of BDL. In conclusion, this study has identified AP as a potent protector against cholestasis-induced apoptosis in vivo. Its anti-apoptotic action largely relies on the inhibition of the oxidative stress pathway.

Inhibition of nitric oxide synthesis during induced cholestasis ameliorates hepatocellular injury by facilitating S-nitrosothiol homeostasis

Cholestatic liver injury following extra- or intrahepatic bile duct obstruction causes nonparenchymal cell proliferation and matrix deposition leading to end-stage liver disease and cirrhosis. In cholestatic conditions, nitric oxide (NO) is mainly produced by a hepatocyte-inducible NO synthase (iNOS) as a result of enhanced inflow of endotoxins to the liver and also by accumulation of bile salts in hepatocytes and subsequent hepatocellular injury. This study was aimed to investigate the role of NO and S-nitrosothiol (SNO) homeostasis in the development of hepatocellular injury during cholestasis induced by bile duct ligation (BDL) in rats. Male Wistar rats (200-250 g) were divided into four groups (n=10 each), including sham-operated (SO), bile duct-ligated (BDL), tauroursodeoxycholic acid (TUDCA, 50 mg/kg) and S-methylisothiourea (SMT, 25 mg/kg) treated. After 7 days, BDL rats showed elevated serum levels of gamma-glutamiltranspeptidase, aspartate aminotransferase, alanine aminotransferase, LDH, and bilirubin, bile duct proliferation and fibrosis, compared with the SO group. TUDCA treatment did not significantly alter these parameters, but the iNOS inhibitor SMT ameliorated hepatocellular injury, as shown by lower levels of circulating hepatic enzymes and bilirubin, and a decreased grade of bile duct proliferation and fibrosis. Both TUDCA and SMT treatments reversed Mrp2 canalicular pump expression to control levels. However, only SMT treatment significantly lowered the increased levels of plasma NO and S-nitrosation (S-nitrosylation) of liver proteins in BDL rats. Moreover, BDL resulted in a reduction of the S-nitrosoglutathione reductase (GSNOR/Adh5) enzymatic activity and a downregulation of the GSNOR/Adh5 mRNA expression that was reverted by SMT, but not TUDCA, treatment. A total of 25 liver proteins, including S-adenosyl methionine synthetase, betaine-homocysteine S-methyltransferase, Hsp90 and protein disulfide isomerase, were found to be S-nitrosated in BDL rats. In conclusion, the inhibition of NO production during induced cholestasis ameliorates hepatocellular injury. This effect is in part mediated by the improvement of cell proficiency in maintaining SNO homeostasis.

Opioid receptor blockade improves mesenteric responsiveness in biliary cirrhosis

Arterial vasodilation with concomitant hyperdynamic circulation is a common finding in cirrhotic subjects. Elevated levels of plasma endogenous opioid peptides have been reported in cholestasis and cirrhosis. Increased opioid peptides contribute to different manifestations of chronic liver disease such as pruritus, ascitis, and hepatic encephalopathy. In this study the potential role of opioid system in cirrhosis-induced vascular hyporesponsiveness was investigated. Bile duct ligated and sham operated animals received daily subcutaneous administration of naltrexone, an opioid receptor antagonist (20 mg/kg/day), or saline for 28 days. After 4 weeks the superior mesenteric artery was cannulated and was perfused according to McGregor method and then phenylephrine vasoconstrictor response of mesenteric vessels (10(-10) to 10(-6 )mol) was examined. In order to evaluate the effects of acute opioid receptor blockade, additional groups of animals were treated by acute single intraperitoneal naltrexone injection (20 mg/kg). Plasma level of nitrite/nitrate as an indicator for nitric oxide production was measured. Biliary cirrhosis was accompanied with a decrease in baseline perfusion pressure in mesenteric vascular bed (P < 0.01). Chronic opioid receptor blockade significantly increased this parameter (P < 0.01). The maximum pressure response to phenylephrine was decreased significantly in cirrhosis while chronic naltrexone treatment completely improved it (P < 0.01). Acute single injection of naltrexone could not influence the understudied homodynamic parameters. Chronic opioid receptor blockade did not modulate the increased nitrite/nitrate levels following cholestasis. This study provided evidence on the contribution of endogenous opioid system to vascular hyporesponsiveness in cirrhosis which is not directly correlated to high plasma NO levels.

Regulation of glutathione synthesis

Glutathione (GSH) is a ubiquitous intracellular peptide with diverse functions that include detoxification, antioxidant defense, maintenance of thiol status, and modulation of cell proliferation. GSH is synthesized in the cytosol of all mammalian cells in a tightly regulated manner. The major determinants of GSH synthesis are the availability of cysteine, the sulfur amino acid precursor, and the activity of the rate-limiting enzyme, glutamate cysteine ligase (GCL). GCL is composed for a catalytic (GCLC) and modifier (GCLM) subunit and they are regulated at multiple levels and at times differentially. The second enzyme of GSH synthesis, GSH synthase (GS) is also regulated in a coordinated manner as GCL subunits and its up-regulation can further enhance the capacity of the cell to synthesize GSH. Oxidative stress is well known to induce the expression of GSH synthetic enzymes. Key transcription factors identified thus far include Nrf2/Nrf1 via the antioxidant response element (ARE), activator protein-1 (AP-1) and nuclear factor kappa B (NFkappaB). Dysregulation of GSH synthesis is increasingly being recognized as contributing to the pathogenesis of many pathological conditions. These include diabetes mellitus, pulmonary fibrosis, cholestatic liver injury, endotoxemia and drug-resistant tumor cells. Manipulation of the GSH synthetic capacity is an important target in the treatment of many of these disorders.

Successively postadministered melatonin prevents disruption of hepatic antioxidant status in rats with bile duct ligation

We have reported that orally administered melatonin exerts a therapeutic effect on cholestatic liver injury in rats treated with bile duct ligation (BDL) possibly through its antioxidant and anti-inflammatory actions. Herein, we examined whether successively postadministered melatonin prevents the disruption of hepatic antioxidant status in BDL-treated rats. Wistar rats with BDL were killed 5 and 13 days after BDL. Melatonin (10 or 100 mg/kg body weight) was orally administered to rats with and without BDL everyday for 8 days, starting 5 days after BDL. The hepatic concentrations of thiobarbituric acid reactive substances, an index of lipid peroxidation, and reduced glutathione increased 5 days after BDL and further increased at 13 days. Hepatic vitamin E concentration and catalase and Se-glutathione peroxidase (Se-GSH-Px) activities were similarly reduced at 5 and 13 days after BDL. Hepatic ascorbic acid concentration and the hepatic activities of Cu,Zn- and Mn-superoxide dismutases, glutathione reductase, and glucose-6-phosphate dehydrogenase decreased 13 days after BDL. Melatonin postadministered to BDL-treated rats attenuated all these changes observed at 13 days after the treatment more effectively at the higher dose than at the lower dose. Melatonin administered to BDL-untreated rats increased the hepatic Se-GSH-Px activity at both doses and the hepatic activities of Cu,Zn- and Mn-superoxide dismutases at the higher dose. These results indicate that successively postadministered melatonin at pharmacological doses prevents the disruption of hepatic antioxidant status in rats with BDL through its direct and indirect antioxidant action, which may contribute to its therapeutic effect of BDL-induced cholestatic liver injury.