Intercellular adhesion molecule-1 (ICAM-1) expression in the liver of patients with extrahepatic cholestasis

Are Selected Cytokines and Epstein-Barr Virus DNA Load Predictors of Hepatological Complications of Epstein-Barr Virus Infection in Children?

The aim of the study was to evaluate tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), soluble intracellular adhesion molecules 1 (s-ICAM-1) and Epstein-Barr virus (EBV) DNA load levels as predictors of hepatological complications of EBV infection in children. The study group consisted of 54 children aged one to eighteen years, who were hospitalised from 1 December 2018 to 31 December 2020 in the Department of Paediatrics, Infectious Diseases and Hepatology and who had hepatological complications in the course of serologically and molecularly confirmed EBV infection. It was shown that IL-6, TNF-α, and s-ICAM-1 concentrations were the highest in patients with hepatitis and biliary pole damage. Higher EBV DNA viremia positively correlated with increased C-reactive protein (CRP) and TNF-α levels and increased leukocyte, lymphocyte, and monocyte counts. Increases in lymphocyte counts and TNF-α concentrations were observed along with increases in gamma-glutamyl transpeptidase (GGTP) activity. Increased concentrations of IL-6, TNF-α, and s-ICAM-1 may indicate the risk of hepatitis with concomitant biliary pole damage during EBV infection.

Cutting Edge: Optimal Formation of Hepatic Tissue-Resident Memory CD4 T Cells Requires T-bet Regulation of CD18

CD4 tissue-resident memory T cells (TRMs) allow robust protection of barrier surfaces against pathogens. We investigated the role of T-bet in the formation of liver CD4 TRMs using mouse models. T-bet-deficient CD4 T cells did not efficiently form liver TRMs when compared with wild-type (WT). In addition, ectopic expression of T-bet enhanced the formation of liver CD4 TRMs, but only when in competition with WT CD4 T cells. Liver TRMs also expressed higher levels of CD18, which was T-bet dependent. The WT competitive advantage was blocked by Ab neutralization of CD18. Taken together, our data show that activated CD4 T cells compete for entry to liver niches via T-bet-induced expression of CD18, allowing TRM precursors to access subsequent hepatic maturation signals. These findings uncover an essential role for T-bet in liver TRM CD4 formation and suggest targeted enhancement of this pathway could increase the efficacy of vaccines that require hepatic TRMs.

Antipsychotic Drug Aripiprazole Protects Liver Cells from Oxidative Stress

Antipsychotics used to treat schizophrenia can cause drug-induced liver injury (DILI), according to the Roussel Uclaf Causality Assessment Method. The role of oxidative stress in triggering injury in these DILI cases is unknown. We repeatedly administrated two second-generation antipsychotics, aripiprazole and olanzapine, at laboratory alert levels to study underlying mechanisms in stress prevention upon acute oxidative stress. The drugs were administered continuously for up to 8 weeks. For this, hepatoma Fao cells, which are suitable for metabolic studies, were used, as the primary hepatocytes survive in the culture only for about 1 week. Four stress responses—the oxidative stress response, the DNA damage response and the unfolded protein responses in the endoplasmic reticulum and mitochondria—were examined in H₂O₂-treated cells by antioxidant enzyme activity measurements, gene expression and protein quantification. Oxidant conditions increased the activity of antioxidant enzymes and upregulated genes and proteins associated with oxidative stress response in aripiprazole-treated cells. While the genes associated with DNA damage response, Gadd45 and p21, were upregulated in both aripiprazole- and olanzapine-treated cells, only aripiprazole treatment was associated with upregulation in response to even more H₂O₂, which also coincided with better survival. Endoplasmic reticulum stress-induced Chop was also upregulated; however, neither endoplasmic reticulum nor mitochondrial unfolded protein response was activated. We conclude that only aripiprazole, but not olanzapine, protects liver cells against oxidative stress. This finding could be relevant for schizophrenia patients with high-oxidative-stress-risk lifestyles and needs to be validated in vivo.

PPARα: A potential therapeutic target of cholestasis

The accumulation of bile acids in the liver leads to the development of cholestasis and hepatocyte injury. Nuclear receptors control the synthesis and transport of bile acids in the liver. Among them, the farnesoid X receptor (FXR) is the most common receptor studied in treating cholestasis. The activation of this receptor can reduce the amount of bile acid synthesis and decrease the bile acid content in the liver, alleviating cholestasis. Ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) have a FXR excitatory effect, but the unresponsiveness of some patients and the side effect of pruritus seriously affect the results of UDCA or OCA treatment. The activator of peroxisome proliferator-activated receptor alpha (PPARα) has emerged as a new target for controlling the synthesis and transport of bile acids during cholestasis. Moreover, the anti-inflammatory effect of PPARα can effectively reduce cholestatic liver injury, thereby improving patients’ physiological status. Here, we will focus on the function of PPARα and its involvement in the regulation of bile acid transport and metabolism. In addition, the anti-inflammatory effects of PPARα will be discussed in some detail. Finally, we will discuss the application of PPARα agonists for cholestatic liver disorders.

The Hepatotoxicity of Alantolactone and Germacrone: Their Influence on Cholesterol and Lipid Metabolism in Differentiated HepaRG Cells

The sesquiterpenes alantolactone (ATL) and germacrone (GER) are potential anticancer agents of natural origin. Their toxicity and biological activity have been evaluated using the differentiated HepaRG (dHepaRG) cells, a hepatocyte-like model. The half-maximal inhibitory concentrations of cell viability after 24-h treatment of dHepaRG cells are approximately 60 µM for ATL and 250 µM for GER. However, both sesquiterpenes induce reactive oxygen species (ROS) formation in non-toxic concentrations and significantly dysregulate the mRNA expression of several functional markers of mature hepatocytes. They similarly decrease the protein level of signal transducer and activator of transcription 3 (STAT3), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and their transcription target, intercellular adhesion molecule 1 (ICAM-1). Based on the results of a BATMAN-TCM analysis, the effects of sesquiterpenes on cholesterol and lipid metabolism were studied. Sesquiterpene-mediated dysregulation of both cholesterol and lipid metabolism was observed, during which these compounds influenced the protein expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and sterol regulatory element-binding protein 2 (SREBP-2), as well as the mRNA expression of HMGCR, CYP19A1, PLIN2, FASN, SCD, ACACB, and GPAM genes. In conclusion, the two sesquiterpenes caused ROS induction at non-toxic concentrations and alterations in cholesterol and lipid metabolism at slightly toxic and toxic concentrations, suggesting a risk of liver damage if administered to humans.

Yinchenzhufu decoction protects against alpha-naphthylisothiocyanate-induced acute cholestatic liver injury in mice by ameliorating disordered bile acid homeostasis and inhibiting inflammatory responses

ETHNOPHARMACOLOGICAL RELEVANCE

Intrahepatic cholestasis is a common condition of many liver diseases with few therapies. Yinchenzhufu decoction (YCZFD) is a representative traditional Chinese herbal formula used for treating jaundice and liver disease.

AIM OF THE STUDY

To investigate the hepatoprotective effect of YCZFD against cholestatic liver injury and reveal its potential mechanism.

MATERIALS AND METHODS

Mice with alpha-naphthyl isothiocyanate (ANIT)-induced intrahepatic cholestasis were orally administered YCZFD at doses of 3, 6, and 12g crude drug/kg for 2 weeks followed by subsequent analyses. A serum metabolomics study was then performed to explore the different metabolites influenced by YCZFD using ultra-high-performance liquid chromatography coupled with linear ion trap-Orbitrap hybrid mass spectrometry (UPLC-LTQ-Orbitrap-MS/MS).The levels of individual bile acids in the serum, liver, and bile were determined by UPLC-MS/MS. The expression of metabolic enzymes, transporters, inflammatory factors, and cytokeratin-19 (CK-19) was determined by real-time PCR, western blotting, and immunohistochemistry.

RESULTS

YCZFD administration decreased the serum biochemical indexes and ameliorated pathological damage, such as hepatic necrosis and inflammatory cell infiltration. Serum metabolomics revealed that the metabolites influenced by YCZFD were mainly associated with bile acid metabolism and inflammation. YCZFD administration effectively ameliorated the disordered bile acid homeostasis. The bile acid transporter, multidrug-resistance associated protein 2 (Mrp2), and the metabolic enzyme, cytochrome P450 2b10 (Cyp2b10), were upregulated in the YCZFD intervention group compared to those in the ANIT-induced group. YCZFD administration also significantly inhibited nuclear factor-κB (NF-κB) and its phosphorylation and decreased the expression of proinflammatory cytokines including tumor necrosis factor-α, interleukin-1β, and intercellular adhesion molecule-1 in ANIT-induced cholestatic mice. Additionally, the level of CK-19 was lower in the YCZFD intervention group than in the ANIT-induced cholestatic mice.

CONCLUSION

YCZFD administration ameliorated disordered bile acid homeostasis, inhibited NF-κB pathway-mediated inflammation, and protected the liver from bile duct injury. Therefore, YCZFD exerted a protective effect against cholestatic liver injury.

Mechanisms of bile acid mediated inflammation in the liver

Bile acids are synthesized in the liver and are the major component in bile. Impaired bile flow leads to cholestasis that is characterized by elevated levels of bile acid in the liver and serum, followed by hepatocyte and biliary injury. Although the causes of cholestasis have been extensively studied, the molecular mechanisms as to how bile acids initiate liver injury remain controversial. In this chapter, we summarize recent advances in the pathogenesis of bile acid induced liver injury. These include bile acid signaling pathways in hepatocytes as well as the response of cholangiocytes and innate immune cells in the liver in both patients with cholestasis and cholestatic animal models. We focus on how bile acids trigger the production of molecular mediators of neutrophil recruitment and the role of the inflammatory response in this pathological process. These advances point to a number of novel targets where drugs might be judged to be effective therapies for cholestatic liver injury.

Na(+) /H(+) exchanger regulatory factor 1 knockout mice have an attenuated hepatic inflammatory response and are protected from cholestatic liver injury

The intercellular adhesion molecule 1 (ICAM-1) is induced in mouse liver after bile duct ligation (BDL) and plays a key role in neutrophil-mediated liver injury in BDL mice. ICAM-1 has been shown to interact with cytoskeletal ezrin-radixin-moesin (ERM) proteins that also interact with the PDZ protein, Na(+) /H(+) exchanger regulatory factor 1 (NHERF-1/EBP50). In NHERF-1(-/-) mice, ERM proteins are significantly reduced in brush-border membranes from kidney and small intestine. ERM knockdown reduces ICAM-1 expression in response to tumor necrosis factor alpha. Here we show that NHERF-1 assembles ERM proteins, ICAM-1 and F-actin into a macromolecule complex that is increased in mouse liver after BDL. Compared to wild-type (WT) mice, both sham-operated and BDL NHERF-1(-/-) mice have lower levels of activated ERM and ICAM-1 protein in the liver accompanied by significantly reduced hepatic neutrophil accumulation, serum alanine aminotransferase, and attenuated liver injury after BDL. However, total bile acid concentrations in serum and liver of sham and BDL NHERF-1(-/-) mice were not significantly different from WT controls, although hepatic tetrahydroxylated bile acids and Cyp3a11 messenger RNA levels were higher in NHERF-1(-/-) BDL mice.

CONCLUSION

NHERF-1 participates in the inflammatory response that is associated with BDL-induced liver injury. Deletion of NHERF-1 in mice leads to disruption of the formation of ICAM-1/ERM/NHERF-1 complex and reduction of hepatic ERM proteins and ICAM-1, molecules that are up-regulated and are essential for neutrophil-mediated liver injury in cholestasis. Further study of the role of NHERF-1 in the inflammatory response in cholestasis and other forms of liver injury should lead to discovery of new therapeutic targets in hepatic inflammatory diseases.

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

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

Upregulation of early growth response factor-1 by bile acids requires mitogen-activated protein kinase signaling

Cholestasis results when excretion of bile acids from the liver is interrupted. Liver injury occurs during cholestasis, and recent studies showed that inflammation is required for injury. Our previous studies demonstrated that early growth response factor-1 (Egr-1) is required for development of inflammation in liver during cholestasis, and that bile acids upregulate Egr-1 in hepatocytes. What remains unclear is the mechanism by which bile acids upregulate Egr-1. Bile acids modulate gene expression in hepatocytes by activating the farnesoid X receptor (FXR) and through activation of mitogen-activated protein kinase (MAPK) signaling. Accordingly, the hypothesis was tested that bile acids upregulate Egr-1 in hepatocytes by FXR and/or MAPK-dependent mechanisms. Deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) stimulated upregulation of Egr-1 to the same extent in hepatocytes isolated from wild-type mice and FXR knockout mice. Similarly, upregulation of Egr-1 in the livers of bile duct-ligated (BDL) wild-type and FXR knockout mice was not different. Upregulation of Egr-1 in hepatocytes by DCA and CDCA was prevented by the MEK inhibitors U0126 and SL-327. Furthermore, pretreatment of mice with U0126 prevented upregulation of Egr-1 in the liver after BDL. Results from these studies demonstrate that activation of MAPK signaling is required for upregulation of Egr-1 by bile acids in hepatocytes and for upregulation of Egr-1 in the liver during cholestasis. These studies suggest that inhibition of MAPK signaling may be a novel therapy to prevent upregulation of Egr-1 in liver during cholestasis.

Exploration of Emodin to treat alpha-naphthylisothiocyanate-induced cholestatic hepatitis via anti-inflammatory pathway

Emodin, 1,3,8-trihydroxy-6-methyl-anthraquinone, is an anthraquinone derivative from the roots of Rheum officinale Baill that has been used to treat many diseases in digestive system for thousands of years. This study is to disclose the mechanism of Emodin to treat cholestatic hepatitis via anti-inflammatory pathway. Rats were divided into Emodin, ursodeoxycholic acid, Dexamethasone, model and blank control groups with treatment of respective agent after administration of alpha-naphthylisothiocyanate. At 24 h, 48 h and 72 h time points after administration, liver function, pathological changes of hepatic tissue, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, myeloperoxidase (MPO), malondialdehyde (MDA), superoxide dismutase (SOD), cytokine-induced neutrophil chemoattractant (CINC)-1, macrophage inflammatory protein (MIP)-2, intercellular adhesion molecule (ICAM)-1, nuclear factor (NF)-kappaB and early growth response (Egr)-1, nitric oxide (NO) and inducible nitric oxide synthase (iNOS) were detected. As a result, compared to the controls, Emodin had a notable effect on rat's living condition, pathological manifestation of hepatic tissue, total bilirubin, direct bilirubin, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (P<0.05), but had little effect on alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT) and total bile acid. With Emodin intervention, levels of TNF-alpha, IL-6, MPO, MDA, CINC-1, MIP-2, ICAM-1 and translocation of NF-kappaB were remarkably decreased, and levels of NO and iNOS were markedly increased (P<0.05). Emodin had no effect on Egr-1. In conclusion, Emodin has a protective effect on hepatocytes and a restoring activity on cholestatic hepatitis by anti-inflammation. The effects are mainly due to antagonizing pro-inflammatory cytokines and mediators, inhibiting oxidative damage, improving hepatic microcirculation, reducing impairment signals, and controlling neutrophil infiltration.

Fluvastatin reduced liver injury in rat model of extrahepatic cholestasis

Inhibitors of 3-hydroxy-3methylglutarly coenzyme A, reductase, namely statins, exert pleiotropic actions beyond lipid-lowering effects. In ex vivo and in vitro studies, statins have antioxidative and antiinflammatory effects. Herein, we sought to determine whether treatment with fluvastatin (FV) would be beneficial in a rat model of common bile duct ligation (BDL)-induced liver injury. Female rats were subjected to a sham (n=10) or BDL (n=20). Obstructive jaundice was induced in rats by the ligation and division of the common bile duct. Three days after operation, rats subjected to CBDL were randomized to receive treatment with either FV (10 mg/kg) or saline every day over a 10 days experimental period. High levels of alanine aminotransferase, aspartate aminotransferase, and gamma glutamyltransferase decreased significantly (P<0.05) in animals treated with FV with compared to saline-administrated BDL animals. Compared with sham-operated rats, CBDL rats showed significantly higher levels of total nitrite and nitrate, malondihaldehyde, tumor necrosis factor alpha, myeloperoxidase, and lower concentrations of glutathione, superoxide dismutase, and catalase in the liver tissue (P<0.001). All of these changes were significantly attenuated (P<0.05) by treatment with FV after CBDL. CBDL was associated with increased apoptosis and nuclear factor kappa beta expression in saline-treated rats. Treatment with FV also decreased these parameters. These data support the view that FV ameliorates hepatic inflammation, lipid peroxidation, and tissue injury in rats subjected to CDBL. FV warrants further evaluation as an adjunctive treatment to ameliorate liver injury from extrahepatic biliary obstruction.

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.

Functional importance of ICAM-1 in the mechanism of neutrophil-induced liver injury in bile duct-ligated mice

Cholestasis-induced liver injury during bile duct obstruction causes an acute inflammatory response. To further characterize the mechanisms underlying the neutrophil-induced cell damage in the bile duct ligation (BDL) model, we performed experiments using wild-type (WT) and ICAM-1-deficient mice. After BDL for 3 days, increased ICAM-1 expression was observed along sinusoids, along portal veins, and on hepatocytes in livers of WT animals. Neutrophils accumulated in sinusoids [358 +/- 44 neutrophils/20 high-power fields (HPF)] and >50% extravasated into the parenchymal tissue. Plasma alanine transaminase (ALT) levels increased by 23-fold, and severe liver cell necrosis (47 +/- 11% of total cells) was observed. Chlorotyrosine-protein adducts (a marker for neutrophil-derived hypochlorous acid) and 4-hydroxynonenal adducts (a lipid peroxidation product) were detected in these livers. Neutrophils also accumulated in the portal venules and extravasated into the portal tracts. However, no evidence for chlorotyrosine or 4-hydroxynonenal protein adducts was detected in portal tracts. ICAM-1-deficient mice showed 67% reduction in plasma ALT levels and 83% reduction in necrosis after BDL compared with WT animals. The total number of neutrophils in the liver was reduced (126 +/- 25/20 HPF), and 85% of these leukocytes remained in sinusoids. Moreover, these livers showed minimal staining for chlorotyrosine and 4-hydroxynonenal adducts, indicating a substantially reduced oxidant stress and a diminished cytokine response. Thus neutrophils relevant for the aggravation of acute cholestatic liver injury in BDL mice accumulate in hepatic sinusoids, extravasate into the tissue dependent on ICAM-1, and cause cell damage involving reactive oxygen formation.

Neutrophils aggravate acute liver injury during obstructive cholestasis in bile duct-ligated mice

Obstruction of the common bile duct in a variety of clinical settings leads to cholestatic liver injury. An important aspect of this injury is hepatic inflammation, with neutrophils as the prominent cell type involved. However, the pathophysiologic role of the infiltrating neutrophils during cholestatic liver injury remains unclear. Therefore, we tested the hypothesis that neutrophils contribute to the overall pathophysiology by using bile duct-ligated (BDL) wild-type animals and mice deficient in the beta(2) integrin CD18. In wild-type animals, neutrophils were activated systemically as indicated by the increased expression of Mac-1 (CD11b/CD18) and L-selectin shedding 3 days after BDL. Histologic evaluation (48 +/- 10% necrosis) and plasma transaminase levels showed severe liver injury. Compared with sham-operated controls (< 10 neutrophils per 20 high-power fields), large numbers of neutrophils were present in livers of BDL mice (425 +/- 64). About 60% of these neutrophils had extravasated into the parenchyma. In addition, a substantial number of extravasated neutrophils were found in the portal tract. In contrast, Mac-1 was not up-regulated and plasma transaminase activities and the area of necrosis (21 +/- 9%) were significantly reduced in CD18-deficient animals. These mice had overall 62% less neutrophils in the liver. In particular, extravasation from sinusoids and portal venules (PV) was reduced by 91% and 47%, respectively. Immunohistochemical staining for chlorotyrosine, a marker of neutrophil-derived oxidant stress, was observed in the parenchyma of BDL wild-type but not CD18-deficient mice. In conclusion, neutrophils aggravated acute cholestatic liver injury after BDL. This inflammatory injury involves CD18-dependent extravasation of neutrophils from sinusoids and reactive oxygen formation.

Melatonin exerts a therapeutic effect on cholestatic liver injury in rats with bile duct ligation

We examined whether melatonin exerts a therapeutic effect on cholestatic liver injury in rats treated with bile duct ligation (BDL). Cholestatic liver injury was induced in male Wistar rats aged 4 wk by ligating the bile duct. Cholestatic liver injury developed 5 days after BDL and continued to 13 days, judging from the levels of serum hepatobiliary injury markers. The serum concentration of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, and the hepatic level of TBARS and the activity of hepatic myeloperoxidase, an index of tissue neutrophil infiltration, increased 5 days after BDL, and these increases were enhanced at 13 days. A similar increase in the serum total cholesterol concentration occurred 5 and 13 days after BDL, while the hepatic cholesterol concentration tended to increase at 13 days. When melatonin [10 or 100 mg/kg body weight (BW)] was orally administered to BDL-treated rats everyday for 8 days, starting 5 days after BDL, the indoleamine attenuated cholestatic liver injury observed at 13 days after BDL was more effective at the higher dose than at the lower dose. The administered melatonin (10 or 100 mg/kg BW) reduced the increases in serum and hepatic TBARS concentrations and hepatic myeloperoxidase activity observed at 13 days after BDL and the higher dose of indoleamine was more effective than the lower dose. Neither dose of melatonin affected the increased serum total cholesterol concentration or the hepatic cholesterol concentration observed at 13 days after BDL. These results indicate that orally administered melatonin at pharmacological doses exerts a therapeutic effect on cholestatic liver injury in rats with BDL possibly through its antioxidant and anti-inflammatory actions.

HCV immunology--death and the maiden T cell

Cellular immune responses play an important role in the control of hepatitis C virus (HCV), although in the majority of cases they ultimately fail. We examine the mechanisms by which virus-specific T cells may interact with a cell that is infected with HCV and how this interaction may explain the success and failure of the immune response. As an infected cell presenting foreign antigen, the hepatocyte will interact with a large number of lymphocytes, both by direct cell to cell contact and by indirect means through the secretion of cytokines and chemokines. These interactions may lead on the one hand to the death of infected hepatocytes or suppression of viral replication and on the other hand to the death of T lymphocytes or down regulation of their function. We suggest that activation of lymphocytes in lymphoid organs leads to generation of effector T cells (positive loop), while at the same time presentation of antigen in the liver either on hepatocytes or other specialised antigen presenting cells depresses these responses (negative loop). This model helps to explain both the specific phenotype and low frequencies of HCV specific CTL in chronic infection, through early elimination of cells before expansion and maturation can occur. The outcome of HCV infection is likely to result from the early balance between these two simultaneous loops.

Therapeutic effect of melatonin on cholestatic liver injury in rats with bile duct ligation

We examined the therapeutic effect of melatonin (MT) on cholestatic liver injury in rats with bile duct ligation (BDL). Cholestatic liver injury occurred 5 days after BDL and proceeded at 13 days, judging from the levels of serum hepatobiliary injury markers. Increases in the hepatic levels of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, and reduced glutathione (GSH) and the hepatic activity of myeloperoxidase (MPO), an index of tissue neutrophil infiltration, were observed 5 and 13 days after BDL. When MT at a dose of 10 or 100 mg/kg body weight was orally administered to rats with BDL everyday for one week, starting 6 days after BDL, a high dose of the indoleamine significantly attenuated cholestatic liver injury at 13 days after BDL. The daily administration of a high dose of MT significantly attenuated the increases in hepatic TBARS and GSH levels and MPO activity observed 13 days after BDL. These results indicate that MT administered orally at pharmacological doses exerts a therapeutic effect on cholestatic liver injury in rats with BDL possibly through its antioxidant and anti-inflammatory actions.

Bile duct ligation in rats induces biliary expression of cytokine-induced neutrophil chemoattractant

BACKGROUND & AIMS

Bile duct obstruction causes neutrophilic inflammation of the liver and leads to hepatic fibrosis. In obstructive liver disease, the localization of neutrophils in portal tracts suggests that cells within this region produce neutrophil chemoattractants. In this study, we investigated whether bile duct obstruction in rats induces portal expression of cytokine-induced neutrophil chemoattractant (CINC).

METHODS

Rats underwent bile duct ligation for 3 hours to 8 days. CINC regulation was examined in vivo at various intervals by immunohistochemistry, ribonuclease protection, and in situ hybridization. CINC production was also investigated in cell culture, in response to putative stimuli from obstructed liver.

RESULTS

Bile duct ligation caused neutrophilic infiltration of the liver within 3 hours. CINC was also rapidly induced, with specific expression identified in biliary cells. Rat intrahepatic biliary cells produced CINC constitutively in culture; when exposed to cholestatic bile, they showed a 12-fold increase in CINC secretion. The effect of bile was not attributable to toxicity or to dissolved cytokines or endotoxin. Mechanical strain, designed to mimic the stretching of biliary cells during obstruction, did not induce CINC.

CONCLUSIONS

Biliary cells contribute to hepatic inflammation during cholestasis by producing neutrophil chemoattractants. A major stimulus to biliary chemoattractant production in vivo may be bile itself.