Apoptosis of hepatic stellate cells in carbon tetrachloride induced acute liver injury of the rat: analysis of isolated hepatic stellate cells

Apolipoprotein A4 regulates the immune response in carbon tetrachloride-induced chronic liver injury in mice

This article explores the role of ApoA4 in a CCl4-induced chronic liver injury (CLI) mouse model. C57BL/6J mice (WT) and ApoA4 knock-out (KO) mice were divided into CCl4 CLI (WT-CCl4 and KO-CCl4) and olive oil solvent control groups (WT-Veh and KO-Veh). Some of the KO-CCl4 mice were additionally treated with recombinant mouse ApoA4 and primary mouse T lymphocyte injections. After 6 weeks, histological analyses, biochemical and superoxide dismutase (SOD) and malondialdehyde (MDA) assays, flow cytometry of immune cells and qRT-PCR analyses were performed. KO mice after treatment with CCl4 showed reduced hepatic SOD and enhanced serum MDA activities leading to worsening liver injury and fibrosis compared with WT-CCl4, accompanied by enhanced hepatic alpha smooth muscle actin (α-SMA), tissue inhibitor of metalloproteinases-1 (TIMP-1) and collagen type I alpha 1 chain (COL1A1) transcriptions, elevated macrophage M1 levels, enhanced tumor necrosis factor-alpha (TNF-α), Interleukin 6 (IL-6) and C-C Motif Chemokine Ligand 5 (CCL5), but reduced Interleukin 10 (IL-10), monocyte chemotactic protein 1 (MCP-1), C-C Motif Chemokine Receptor 2 (CCR2), C-X3-C Motif Chemokine Receptor 1 (CX3CR1) and C-X-C Motif Chemokine Ligand 9 (CXCL9) transcription, as well as reduced CD3+, CD4+ and CD8+ T cell percentages in hepatic tissue, blood cells and spleen. In addition, CD11b+CD115+, CD11b+/Ly6Chigh, CD11b+/LyC6- and CD11b+/Ly6Cint cells were enhanced, which partly reversed by ApoA4 protein and T cell injections. In conclusion, we propose that ApoA4 might be involved in liver protection via inhibiting fibrotic mediators and inflammatory cytokines, suppression of pro-inflammatory hepatic M1 cell invasion and regulation of CD8+ T and CD4+ T lymphocytes.

Investigation of benfotiamine’s protective effects on liver tissue in experimental carbon tetrachloride induced liver injury

Purpose: In this study, we aimed to investigate the protective effects of benfotiamine on experimental liver injury caused by carbon tetrachloride (CCl4).Materials and Methods: In this study, 30 male Wistar albino rats were used. Rats were equally divided into 5 groups. No application was made to control group. The CCl4 group was injected i.p with1ml/kg CCl4:olive oil (1:2) mixture on the 1st and 8th days, and the CCl4+benfotiamine group was treated i.p with 1 ml/kg CCl4: olive oil (1:2) mixture twice on the 1st and 8th days and orally with 70 mg/kg/day benfotiamine. To the benfotiamine group, 70 mg/kg/day benfotiamine was given orally for 14 days. To the olive oil group, 2 ml/kg olive oil was given i.p. on 1st and 8th days. Finally, rats were decapitated. Liver tissues were removed and paraffin blocks were prepared. Tissues were stored at –80 oC for malonaldeyhde (MDA) assay.Results: There were no significant differences between the control, benfotiamine and olive oil groups. Compared with the control group, there was a significant increase in MDA, apoptosis and bax immunoreactivity in CCl4 group. Compared with the CCl4 group, there was a significant decrease in MDA, apoptosis and bax immunoreactivity in the CCl4+benfotiamine group.Conclusion: CCl4 increases MDA, apoptosis and bax immunoreactivity, and benfotiamine, given as treatment, reduces these parameters. 

High-content analysis of in vitro hepatocyte injury induced by various hepatotoxicants

In vitro prediction of hepatotoxicity can enhance the performance of non-clinical animal testing for identifying chemical hazards. In this study, we assessed high-content analysis (HCA) using multi-parameter cell-based assays as an in vitro hepatotoxicity testing model using various hepatotoxicants and human hepatocytes such as HepG2 cells and human primary hepatocytes (hPHs). Both hepatocyte types were exposed separately to multiple doses of ten hepatotoxicants associated with liver injury whose mechanisms of action have been described. HCA data were obtained using fluorescence probes for nuclear size (Hoechst), mitochondrial membrane potential (TMRM), cytosolic free calcium (Fluo-4AM), and lipid peroxidation (BODIPY). Cellular alterations were observed in response to all hepatotoxicants tested. The most sensitive parameter was TMRM, with high sensitivity at a low dose, next was BODIPY, followed by Fluo-4AM. HCA data from HepG2 cells and hPHs were generally concordant, although some inconsistencies were noted. Both hepatocyte types showed mild or severe mitochondrial impairment and lipid peroxidation in response to several hepatotoxicants. The results demonstrate that the application of HCA to in vitro hepatotoxicity testing enables more efficient hazard identification, and further, they suggest that certain parameters could serve as sensitive endpoints for predicting the hepatotoxic potential of chemical compounds.

Characterization of the properties of a selective, orally bioavailable autotaxin inhibitor in preclinical models of advanced stages of liver fibrosis

BACKGROUND AND PURPOSE

Autotaxin (ATX) is a secreted phospholipase which hydrolyses lysophosphatidylcholine to generate lysophosphatidic acid (LPA). The extracellular signalling molecule LPA exerts its biological actions through activation of six GPCRs expressed in various cell types including fibroblasts. Multiple preclinical studies using knockout animals, LPA receptor antagonists or ATX inhibitors have provided evidence for a potential role of the ATX/LPA axis in tissue fibrosis. Despite growing evidence for a correlation between ATX levels and the degree of fibrosis in chronic liver diseases, including viral hepatitis and hepatocellular carcinoma, the role of ATX in non-alcoholic steatohepatitis (NASH) remains unclear.

EXPERIMENTAL APPROACH

The relevance of ATX in the pathogenesis of liver fibrosis was investigated by oral administration of Ex_31, a selective ATX inhibitor, in a 10 week model of carbon tetrachloride-induced liver injury and in a 14 week model of choline-deficient amino acid-defined diet-induced liver injury in rats.

KEY RESULTS

Oral administration of Ex_31, a selective ATX inhibitor, at 15 mg·kg^-1 twice daily in therapeutic intervention mode resulted in efficient ATX inhibition and more than 95% reduction in plasma LPA levels in both studies. Treatment with Ex_31 had no effect on biomarkers of liver function, inflammation, or fibrosis and did not result in histological improvements in diseased animals.

CONCLUSIONS AND IMPLICATIONS

Our findings question the role of ATX in the pathogenesis of hepatic fibrosis and the potential of small molecule ATX inhibitors for the treatment of patients with NASH and advanced stages of liver fibrosis.

Role of growth factor receptor-bound 2 in CCl4-induced hepatic fibrosis

BACKGROUND

Growth Factor Receptor-bound 2 (GRB2) plays a crucial role in regulation of cellular function including proliferation and differentiation, and we previously identified GRB2 as promoting HSCs (HSCs) proliferation. However, the underlying mechanisms that are involving in the regulation of GRB2 in hepatic fibrogenesis remain unknown.

METHODS

In the present study, we tested the function of GRB2 in hepatic fibrosis. Hepatic fibrosis was induced by subcutaneous CCl₄ administration at a dose of 3mL/kg in rats. The rat HSC cell line HSC-T6 were cultured for proliferation investigation by CCK-8 and BrdU incorporation method. The levels of GRB2, HMGB1, PI3K/AKT, COL1A1 and α-SMA were analyzed by western blot or real-time PCR.

RESULTS

showed that the expression of GRB2 and HMGB1 was obviously increased in liver tissues of hepatic fibrosis rats accompanied by up-regulation of COL1A1 and α-SMA. In cultured HSCs, application of exogenous HMGB1 induced cell proliferation and cell proliferation rate concomitantly with up-regulation of GRB2 expression and PI3K/AKT phosphorylation. The effects of HMGB1-induced proliferation of HSCs and up-regulation of COL1A1 and α-SMA were abolished by GRB2 siRNA. HMGB1-induced proliferation of HSCs and up-regulation of COL1A1 and α-SMA was reversed in the presence of LY294002, an inhibitor of PI3K inhibitor.

CONCLUSIONS

These findings suggest that GRB2 plays an important role in CCl₄-induced hepatic fibrosis by regulating HSCs' function, and up-regulation of GRB2 induced by HMGB1 is mediated via the PI3K/AKT pathway.

Effects of Acute Toluene Toxicity on Different Regions of Rabbit Brain

The acute phase effects of toluene on the brain have been investigated in this study using rabbit brain via histopathological, immunohistochemical, and biochemical methods. A total of 20 male rabbits were used as control and experimental groups. Moreover, nerve growth factor (NGF), tumor necrosis factor-alpha (TNF-alpha), dopamine (DA), and glial fibrillary acidic protein (GFAP) tests were performed in order to designate the severity of the biochemical damage. In the biochemical evaluation of the prefrontal cortex, hippocampus, hypothalamus, substantia nigra, and entorhinal cortex, the TNF-alpha levels in the brain were found to be significantly higher than in the control group. Levels of dopamine, secreted from the substantia nigra, nerve growth factor (NGF) developed from the hippocampal neurons, and GFAP, secreted from astrocyte cells, were detected to be significantly lower in the toluene-administration group than in the control group (p < 0.05). In addition, areas of focal vacuolar degeneration (abscess formation), gliosis, and perivascular demyelination, many pyknotic cells and necrosis were observed. In the toluene-administration group compared to the control group, distinct excessive expansions of the blood vessels and severe degeneration in the structure of cells and also dispersed cell borders were observed. Furthermore, abnormal malformations of the nuclei structure of the oligodendrocyte cells were seen. Bodies of the sequential neurons of the hippocampus in the toluene-administration group were distinctly structurally damaged compared to the control group. In addition, cytoplasm of the cortex cell showed serious immune reactivity in the experimental group.

Corona-directed nucleic acid delivery into hepatic stellate cells for liver fibrosis therapy

Strategies to modify nanoparticles with biological ligands for targeted drug delivery in vivo have been widely studied but met with limited clinical success. A possible reason is that, in the blood circulation, serum proteins could rapidly form a layer of protein "corona" on the vehicle surface, which might block the modified ligands and hamper their targeting functions. We speculate that strategies for drug delivery can be designed based upon elegant control of the corona formation on the vehicle surfaces. In this study, we demonstrate a retinol-conjugated polyetherimine (RcP) nanoparticle system that selectively recruited the retinol binding protein 4 (RBP) in its corona components. RBP was found to bind retinol, and direct the antisense oligonucleotide (ASO)-laden RcP carrier to hepatic stellate cells (HSC), which play essential roles in the progression of hepatic fibrosis. In both mouse fibrosis models, induced by carbon tetrachloride (CCl4) and bile duct ligation (BDL), respectively, the ASO-laden RcP particles effectively suppressed the expression of type I collagen (collagen I), and consequently ameliorated hepatic fibrosis. Such findings suggest that this delivery system, designed to exploit the power of corona proteins, can serve as a promising tool for targeted delivery of therapeutic agents for the treatment of hepatic fibrosis.

The autoregulatory feedback loop of microRNA-21/programmed cell death protein 4/activation protein-1 (MiR-21/PDCD4/AP-1) as a driving force for hepatic fibrosis development

Sustained activation of hepatic stellate cells (HSCs) leads to hepatic fibrosis, which is characterized by excessive collagen production, and for which there is no available drug clinically. Despite tremendous progress, the cellular activities underlying HSC activation, especially the driving force in the perpetuation stage, are only partially understood. Recently, microRNA-21 (miR-21) has been found to be prevalently up-regulated during fibrogenesis in different tissues, although its detailed role needs to be further elucidated. In the present study, miR-21 expression was examined in human cirrhotic liver samples and in murine fibrotic livers induced by thioacetamide or carbon tetrachloride. A dramatic miR-21 increase was noted in activated HSCs. We further found that miR-21 maintained itself at constant high levels by using a microRNA-21/programmed cell death protein 4/activation protein-1 (miR-21/PDCD4/AP-1) feedback loop. Disrupting this loop with miR-21 antagomir or AP-1 inhibitors significantly suppressed fibrogenic activities in HSCs and ameliorated liver fibrosis. In contrast, reinforcing this loop with small interfering RNA (siRNA) against PDCD4 promoted fibrogenesis in HSCs. Further analysis indicated that the up-regulated miR-21 promoted the central transforming growth factor-β (TGF-β) signaling pathway underlying HSC activation. In summary, we suggest that the miR-21/PDCD4/AP-1 autoregulatory loop is one of the main driving forces for hepatic fibrosis progression. Targeting this aberrantly activated feedback loop may provide a new therapeutic strategy and facilitate drug discovery against hepatic fibrosis.

Apoptosis and angiogenesis: an evolving mechanism for fibrosis

Fibrosis, seen in the liver, lung, heart, kidney, and skin, is a significant global disease burden. Currently, therapeutic treatment is limited, and the number of cases continues to grow. Apoptosis has been identified as a potential initiator and propagator of fibrosis. This review specifically examines the correlation between the presence of apoptotic cells and their effect on fibroblast phenotype and collagen metabolism in several different experimental models of fibrosis. Fibrosis in these models is generally preceded by robust angiogenesis and vascular regression, suggesting that the vascular apoptotic burden may be important to fibrotic outcomes. This review considers the emerging evidence that angiogenesis or vascular regression contributes to fibrosis and identifies initial vascular outgrowth or vascular apoptotic cell presence as possible regulators of fibrosis. A further understanding of the cellular mechanisms of fibrosis may suggest novel methods for the reduction of the fibrotic response and promotion of regeneration.

Absence of Nogo-B (reticulon 4B) facilitates hepatic stellate cell apoptosis and diminishes hepatic fibrosis in mice

Nogo-B (reticulon 4B) accentuates hepatic fibrosis and cirrhosis, but the mechanism remains unclear. The aim of this study was to identify the role of Nogo-B in hepatic stellate cell (HSC) apoptosis in cirrhotic livers. Cirrhosis was generated by carbon tetrachloride inhalation in wild-type (WT) and Nogo-A/B knockout (Nogo-B KO) mice. HSCs were isolated from WT and Nogo-B KO mice and cultured for activation and transformation to myofibroblasts (MF-HSCs). Human hepatic stellate cells (LX2 cells) were used to assess apoptotic responses of activated HSCs after silencing or overexpressing Nogo-B. Livers from cirrhotic Nogo-B KO mice showed significantly reduced fibrosis (P < 0.05) compared with WT mice. Apoptotic cells were more prominent in fibrotic areas of cirrhotic Nogo-B KO livers. Nogo-B KO MF-HSCs showed significantly increased levels of apoptotic markers, cleaved poly (ADP-ribose) polymerase, and caspase-3 and -8 (P < 0.05) compared with WT MF-HSCs in response to staurosporine. Treatment with tunicamycin, an endoplasmic reticulum stress inducer, increased cleaved caspase-3 and -8 levels in Nogo-B KO MF-HSCs compared with WT MF-HSCs (P < 0.01). In LX2 cells, Nogo-B knockdown enhanced apoptosis in response to staurosporine, whereas Nogo-B overexpression inhibited apoptosis. The absence of Nogo-B enhances apoptosis of HSCs in experimental cirrhosis. Selective blockade of Nogo-B in HSCs may represent a potential therapeutic strategy to mitigate liver fibrosis.

Silymarin suppresses hepatic stellate cell activation in a dietary rat model of non-alcoholic steatohepatitis: analysis of isolated hepatic stellate cells

Non-alcoholic steatohepatitis (NASH) is characterized by hepatocellular injury and initial fibrosis severity has been suggested as an important prognostic factor of NASH. Silymarin was reported to improve carbon tetrachloride-induced liver fibrosis and reduce the activation of hepatic stellate cells (HSC). We investigated whether silymarin could suppress the activation of HSCs in NASH induced by methionine- and choline-deficient (MCD) diet fed to insulin-resistant rats. NASH was induced by feeding MCD diet to obese diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Non-diabetic Long-Evans Tokushima Otsuka (LETO) rats were fed with standard chow and served as the control. OLETF rats were fed on either standard laboratory chow, or MCD diet or MCD diet mixed with silymarin. Histological analysis of the liver showed improved non-alcoholic fatty liver disease (NAFLD) activity score in silymarin-fed MCD-induced NASH. Silymarin reduced the activation of HSCs, evaluated by counting α-smooth muscle actin (SMA)-positive cells and measuring α-SMA mRNA expression in the liver lysates as well as in HSCs isolated from the experimental animals. Although silymarin decreased α₁-procollagen mRNA expression in isolated HSCs, the anti-fibrogenic effect of silymarin was not prominent so as to show significant difference under histological analysis. Silymarin increased the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and decreased tumor necrosis factor (TNF)-α mRNA expression in the liver. Our study suggested that the possible protective effect of silymarin in diet induced NASH by suppressing the activation of HSCs and disturbing the role of the inflammatory cytokine TNF-α.

The apoptotic effect of a high dose of toluene on liver tissue during the acute phase: an experimental study

The aim of this study is to investigate the acute toxic effects of high-dose toluene and its mechanisms on the liver tissue of toluene-treated rats. In this study, 16 adult male Wistar albino rats (200–220 g) were divided into two equal groups. Group I was used as a control group, while group II was exposed to high dose of toluene, 5200 mg/kg (6 ml/kg per gavage). After the 3-hour experimental period, blood samples and liver tissues were taken from the euthanized animals. Serum aspartate and alanine aminotransferase levels were assayed. Liver tissues were fixed in 10% neutral formalin, then embedded in paraffin and sectioned (5 μm thickness). Sections were stained with hematoxylin and eosin for histopathological examination. A terminal transferase dUTP nick end labeling assay was also done for the determination of apoptosis in liver tissues. For the determination of Bax and caspase-3 immunoreactivity, the sections were stained using avidin–biotin–peroxidase immunohistochemical method. The level of plasma transaminase was found to be increased in toluene administered rats. Additionally, slight degeneration of hepatocyte and mononuclear cell infiltration was observed in the liver tissue sections and a high (+++) immunoreactivity for Bax and caspase-3 protein was observed in the toluene group. This study showed that the high dose of toluene triggers apoptosis in the liver of rats via the mitochondrial pathway in acute period.

HSP70 immune reactivity and TUNEL positivity in the liver of toluene-inhaled and melatonin-treated rats

Toluene is a clear, colorless and volatile hydrocarbon that is metabolized in liver, produced free oxygen radicals and can mediate cellular damage. Melatonin which is a pineal gland hormone is a very potent antioxidant. It can make the cellular membrane more durable against oxidative attacks and protect nuclear DNA from oxidative damage. This study aimed to investigate heat shock protein (HSP)70 immune reactivity and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positivity (apoptotic activity) in the liver of toluene-inhaled and melatonin-treated rats. A total of 21 adult male Wistar albino rats were divided at random into 3 equal groups. Animals in group I were designated as control. The rats in group II were exposed to toluene (3000 ppm/1 h/day) for 30 days, while the rats in group III were treated with melatonin (10 mg/kg/day, intraperitoneally) plus toluene inhalation. At the end of the 30-day experimental period, all rats were killed by decapitation. Then the liver tissues of rats were removed and tissue specimens were embedded in paraffin blocks. The specimens were stained with periodic acid-schiff (PAS) following routine histological procedures. Sections obtained from paraffin blocks were used for immune detection of TUNEL and HSP70. In light microscopic observations of tissues from toluene-inhaled rats, massive hepatocyte degeneration, ballooning degeneration and decreased PAS positivity were observed. Increased TUNEL positivity and HSP70 immune reactivity were determined in toluene-inhaled group and melatonin treatment decreased all these adverse effects.

Hepatoprotective effects and mechanisms of dehydrocavidine in rats with carbon tetrachloride-induced hepatic fibrosis

AIM OF THE STUDY

The current study was designed to examine the effects and possible mechanisms of dehydrocavidine (DC) on carbon tetrachloride (CCl4)-induced hepatic fibrosis in male Sprague-Dawley (SD) rats.

MATERIALS AND METHODS

Hepatic fibrosis was induced in male rats with CCl4 administration for 12 weeks. Liver histopathological study was performed, and the liver function was examined by determining the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and total bilirubin (TBIL) for evaluating the effect of DC on hepatic fibrosis. The possible mechanisms were investigated by measuring hepatic collagen metabolism and oxidative stress level. Furthermore, oligo microarray analysis of 263 genes was performed, and quantitative real-time RT-PCR was used to verify 4 of the abnormally expressed genes (Bcl2, Cyp3a13, IL18 and Rad50).

RESULTS

DC treatment significantly inhibited the loss of body weight and the increase of liver weight induced by CCl4. DC also improved the liver function of rats as indicated by decreased serum enzymatic activities of ALT, AST, ALP and TBIL. Histopathological results indicated that DC alleviated liver damage and reduced the formation of fibrous septa. Moreover, DC significantly decreased liver hydroxyproline (Hyp) and increased urine Hyp. It also decreased liver malondialdehyde concentration, increased activities of liver superoxide dismutase, catalase and glutathione peroxidase. Microarray analysis revealed that DC altered the expression of genes related to apoptosis, cytokines and other proteins involved in tissue repair.

CONCLUSIONS

Our findings indicate that DC can protect rats from CCl4-induced hepatic fibrosis through reducing oxidative stress, promoting collagenolysis, and regulating fibrosis-related genes.

Indole-3-carbinol enhances the resolution of rat liver fibrosis and stimulates hepatic stellate cell apoptosis by blocking the inhibitor of κB kinase α/inhibitor of κB-α/nuclear factor-κB pathway

Hepatic stellate cells (HSC) play a pivotal role in liver fibrosis, and the clearance of activated HSC by apoptosis is associated with the resolution of liver fibrosis. The development of strategies that promote this process in a selective way is therefore important. We evaluated the effects of indole-3-carbinol (I3C), a nutritional component derived from vegetables from the Brassica family, on liver fibrosis and HSC apoptosis. The in vivo therapeutic effects of I3C were monitored in three rat models of liver fibrosis induced by porcine serum, bile duct ligation, or multiple hepatotoxic factors, and its proapoptotic effect and molecular mechanism were studied in vitro in HSC-T6, a rat HSC line. The results showed that I3C treatment significantly reduced the number of activated HSC in the livers of rats with liver fibrosis. In histopathology, I3C reduced hepatocyte degeneration and necrosis, accelerated collagen degradation, and promoted the reversal of liver fibrosis. I3C prescribed to HSC-T6 resulted in morphologic alterations typical of apoptosis and DNA cleavage to a nucleosomal ladder. Moreover, I3C significantly increased the HSC-T6 apoptosis rate and the expression ratio of Bax to Bcl-2. High-throughput protein array analysis indicated that the tumor necrosis factor-α/nuclear factor-κB (NF-κB) signal pathway participated in I3C-induced HSC-T6 apoptosis. Western blot and electrophoretic mobility-shift assay confirmed that I3C inhibited the phosphorylation of inhibitor of κB kinase α and inhibitor of κB-α and NF-κB DNA binding activity. In conclusion, I3C could promote the reverse process of liver fibrosis in vivo and induce apoptosis of activated HSC in vitro, which indicates the use of I3C as a potential therapeutic agent in liver fibrosis treatment.

Effect of antiviral therapy on the immunohistochemical expression of bcl-xL and bax protein in patients with HBeAg-negative chronic hepatitis B

The effect of antiviral treatment on apoptosis in chronic hepatitis B (CHB) has not been clarified. We evaluated the hepatic immunohistochemical expression of the pro-apoptotic bax and the antiapoptotic bcl-xL protein in HBeAg-negative CHB patients before and after treatment. In our study we included 72 paired biopsies from 36 HBeAg-negative CHB patients: 29 treated (interferon-alfa: 17, adefovir: 12) and 7 untreated. Changes in expression of apoptotic proteins (D-bax, D-bcl-xL), necroinflammation and fibrosis (D-grade/D-stage) (Ishak classification) were evaluated. We found that Bax-positive compared to bax-negative biopsies had worse necroinflammation (8.2 vs. 6.7, P = 0.05) and fibrosis score (3.9 vs. 3, P = 0.036). bcl-xL-positive compared to bcl-xL-negative biopsies had lower intralobular inflammation (1.6 vs. 2.2, P = 0.03). Decreased compared to stable/increased D-bax was associated with greater improvement in necroinflammation only in treated patients (D-grade: -4.6 vs. -1.6, P = 0.05) and greater fibrosis improvement in interferon treated patients (D-stage: -0.4 vs. 0.55, P = 0.05). Increased compared to stable/decreased total apoptotic trend [D-apoptosis: (D-bax)-(D-bcl-xL)], was associated with worsening fibrosis, particularly in adefovir treated patients (D-stage: 2.3 vs. 0, P = 0.004). In the 11 patients without significant changes from 1st to 2nd biopsy, increased apoptosis was more frequent in treated than untreated cases (P = 0.046). In multivariate analysis, bax change was independently associated with change of grade (P = 0.038) and antiviral therapy (P = 0.015). In conclusions, in HBeAg-negative CHB, histological improvement after treatment is associated with decreased hepatocyte apoptosis. In patients without substantial histological changes, treatment seems to increase the apoptosis of hepatocytes, thus having a possible protective effect on hepatocarcinogenesis.

Hepatotoxic activity of toluene inhalation and protective role of melatonin

This study was designed to investigate the harmful effects of toluene inhalation in the liver of rats and possible protective effects of melatonin on these detrimental effects. For this purpose, 21 adult male Wistar-albino rats were randomly divided into three equal groups. Animals in group I were used as control. The rats in group II were exposed to toluene (3000 ppm/1 hour/day) for 4 weeks, while the rats in group III were treated with melatonin (10 mg/kg/day, intraperitoneally [ip]) plus toluene inhalation. At the end of the experimental period, liver and blood samples were taken from the decapitated animals. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bilirubin and albumin levels were determined. Liver tissue sections were stained with routine histological methods and examined under the light microscope. In addition, the sections were immunohistochemically stained using avidin-biotin-peroxidase method for determination of apoptosis. The liver tissue activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA) levels were also measured. Toluene inhalation significantly increased serum ALT, AST and tissue MDA, and decreased serum albumin, but did not affect serum ALP, total bilirubin levels and tissue SOD, GSH-Px and CAT activity when compared with controls. The increases in tissue MDA and serum ALT and AST levels induced by toluene inhalation were significantly inhibited by melatonin treatment. In light microscopic observations of tissues from toluene-inhaled rats, massive hepatocyte degeneration, ballooning degeneration and mild pericentral fibrosis were observed. Bax immune reactivity was also increased significantly. Melatonin treatment decreased the balloon degeneration, fibrosis and Bax immune reactivity in the liver of toluene-inhaled rats. In view of the present findings, it is suggested that melatonin has hepatoprotective effects against toluene toxicity via primarily antioxidative properties.

Advances in hepatic stellate cell-targeted treatment of hepatic fibrosis with bone marrow-derived mesenchymal stem cells

Hepatic fibrosis is one of the most serious diseases that pose a great threat to human health. Liver transplantation is currently the most effective treatment for these patients. However, the worldwide shortage of donor livers has greatly limited the use of this treatment. As a result, searching for alternative cell therapy has attracted great interest in preclinical studies. The transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) holds great promise for treating hepatic fibrosis because experimental and clinical studies have shown that it has beneficial effects on hepatic fibrosis. However, the precise cellular and molecular mechanisms behind such treatment remain to be elucidated. In this article, we will review the advances in treatment of hepatic fibrosis with BMSCs using hepatic stellate cells (HSCs) as a target.

Growth arrest-specific protein 6 deficiency impairs liver tissue repair after acute toxic hepatitis in mice

BACKGROUND/AIMS

Resident macrophages and myofibroblasts derived from hepatic stellate cells play a key role in liver wound healing. We previously reported that these sinusoidal cells secrete the growth arrest-specific protein 6 (Gas6) and express Axl, one of its receptors. Here we address the role of Gas6 in the healing process during acute liver injury.

METHODS

Toxic hepatitis was induced by a single carbon tetrachloride injection in Gas6 deficient (Gas6(-/-)) mice and liver recovery was compared with wild-type animals.

RESULTS

Gas6 deficiency did not cause any change in CCl(4)-induced liver damage. At 72 h, an efficient tissue repair was observed in wild-type animals whereas in Gas6(-/-) mice, we noticed a defective wound healing accounted by reduced Kupffer cell activation revealed by a decrease in the induction of CD14, TNF-alpha, IL6 and MCP-1. Gas6-deficiency, by limiting cytokine/chemokine release, prevents hepatocyte proliferation, recruitment of circulating monocytes and accumulation of myofibroblasts in healing areas. We also report a direct chemotactic effect of Gas6 on circulating monocytes which might explain defective macrophage infiltration in liver necrotic areas of Gas6(-/-) mice. Interestingly in Gas6(-/-) mice, we observed a high and constitutive expression of Axl and an induction of the suppressor of cytokine signaling SOCS1 after CCl(4) treatment.

CONCLUSIONS

The lower level of cytokines/chemokines in Gas6(-/-) mice after CCl(4) injury, is the consequence of an inhibitory signal arising from Axl receptor overexpression, leading to delayed liver repair in deficient mice.

miR-15b and miR-16 are implicated in activation of the rat hepatic stellate cell: An essential role for apoptosis

BACKGROUND/AIMS

To reveal the microRNA (miRNA) expression profile and related roles in rat HSCs during activation.

METHODS

miRNA expression profiling was analyzed in quiescent and in culture-activated HSCs by microarray. The differentially expressed miRNAs, as verified by RT-PCR, were subjected to gene ontology (GO) analysis. Furthermore, the effects of miR-16 and miR-15b on the apoptosis of activated HSCs were investigated by Hoechst 33258, TUNEL staining and annexin-V/PI labeling flow cytometry. The underlying mechanism related to Bcl-2 and caspases was assessed.

RESULTS

The upregulated and downregulated miRNAs in activated HSCs were 12 miRNAs and 9 miRNAs, respectively. The differential expression of miR-16, -15b, -122, -138, -143, and -140 was validated. High-enrichment GOs containing apoptosis-related targeted genes and miRNA-gene networks characterized by Bcl-2, which was targeted by the miR-15/16 family, uncovered the critical role of miR-16 and miR-15b in apoptosis. Restoring the intracellular miRNAs by miR-16 and miR-15b administration greatly reduced Bcl-2, and increased the expression of caspases 3, 8, and 9. Significantly elevated rates of apoptosis were then induced in activated HSCs.

CONCLUSIONS

The activation of HSCs relate to 21 miRNAs. Among these, mir-15b and miR-16 may be essential for apoptosis by targeting Bcl-2 and the caspase signaling pathway.

Lymphocyte-hepatic stellate cell proximity suggests a direct interaction

Recent functional research studies suggest an anti-fibrotic role for natural killer (NK) cells coupled with a profibrotic role for CD8 cells. However, the morphological cellular interplay between the different cell types is less clear. To investigate lymphocyte/hepatic stellate cell (HSC) interactions, hepatic fibrosis was induced by administering carbon tetrachloride (CCl4) intraperitoneally (i.p.) for 4 weeks in C57Bl/6 mice. Animals were killed at 0, 1, 2, 3 and 4 weeks. Liver sections were stained for Sirius red. Confocal microscopy was used to evaluate alpha smooth-muscle actin (alphaSMA) and lymphocyte subsets in liver sections. At weeks 0 and 4, liver protein extracts were assessed for alphaSMA by Western blotting and isolated liver lymphocytes as well as HSC were analysed by fluorescence activated cell sorter (FACS). Similar to the results obtained from classical Sirius red staining and alphaSMA blotting, analysis of liver sections by confocal microscopy revealed a marked and continuous accumulation of alphaSMA staining along sequential experimental check-points after administering CCl4. Although the number of all liver lymphocyte subsets increased following fibrosis induction, FACS analysis revealed an increase in the distribution of liver CD8 subsets and a decrease of CD4 T cells. Confocal microscopy showed a significant early appearance of CD8 and NK cells, and to a lesser extent CD4 T cells, appearing only from week 2. Lymphocytes were seen in proximity only to HSC, mainly in the periportal area and along fibrotic septa, suggesting a direct interaction. Notably, lymphocyte subsets were undetectable in naive liver sections. Freshly isolated HCS show high expression of major histocompatibility complex (MHC) class II and CD11c. In the animal model of hepatic fibrosis, lymphocytes infiltrate into the liver parenchyma and it is thought that they attach directly to activated HSC. Because HSCs express CD11c/class II molecules, interactions involving them might reflect that HSCs have an antigen-presenting capacity.

Study on the in vitro and in vivo activation of rat hepatic stellate cells by Raman spectroscopy

The feasibility of a novel and efficient diagnostic method for liver fibrosis using Raman spectroscopy is studied. Confocal Raman spectroscopy (CRS) is utilized to monitor the molecular changes of hepatic stellate cells (HSCs) in vitro as well as in vivo activation. In vitro activation was induced by growth in uncoated plastic plates, while the in vivo activation is induced by a single intraperitoneal injection of carbon tetrachloride (CCl(4)). The biochemical changes of HSCs during activation such as the loss of retinoid, the increase of alpha-helical protein, and the increased production of extracellular matrix proteins are observed by CRS. A user-friendly autoclassifying system is also developed to classify Raman spectra of liver injury tissues with a 90% accuracy rate. Raman spectroscopy combined with a fiber optical probe could be potentially accomplished for in vivo detection, which can lead to a novel and efficient diagnosis for liver fibrosis.

Anti-fibrotic activity of NK cells in experimental liver injury through killing of activated HSC

BACKGROUND/AIMS

We have investigated the role of natural killer (NK) cells in hepatic fibrogenesis. Mouse NK cells express both inhibitory/activating-killing-immunoglobulin-related-receptors (iKIR/aKIR) specific for Class-I-molecules.

METHODS

Hepatic fibrosis induced by carbon-tetrachloride (CCl4) was compared between wild-type (WT) male-BALBc; combined-immunodeficiency (SCID, lacking B/T-cells); and SCID-BEIGE-mice (lacking B/T/NK cells), and naive mice.

RESULTS

Hepatic fibrosis significantly increased in all CCl4-treated groups. SCID-BEIGE mice had more fibrosis than SCID-mice (P<0.0001) as assessed by morphometry of sirius-red stained tissue sections. Following fibrosis, hepatic NK cells significantly decreased, the aKIR:iKIR-ratio significantly increased while Class-I expression on HSC decreased (P<0.001). Both freshly isolated and in situ HSC displayed a significant increase in cellular apoptosis following fibrosis induction. Confocal microscopy demonstrated the direct adhesion of NK cells to HSC in mouse liver sections and in vitro human NK/HSC co-culture. In human HSC there was decreased Class-I expression and increased apoptosis as well, which was further increased following blocking of either HSC-related Class-I or NK-related killer inhibitory receptors. Apoptosis was inhibited by pre-incubation of NK cells with the granzyme inhibitor 3,4-dichloroisocoumarin.

CONCLUSIONS

During liver injury, NK cells have an anti-fibrotic activity at least in part through stimulation of HSC killing.

Induction of Gas6 protein in CCl4-induced rat liver injury and anti-apoptotic effect on hepatic stellate cells

The protein product of the growth arrest-specific gene 6 (Gas6) is a secreted ligand for tyrosine kinase receptors, among which Axl is the most widely distributed and displays the highest affinity for Gas6. The Gas6/Axl signaling pathway has been increasingly implicated in growth and survival processes occurring during development and tissue repair. In liver, after an acute or chronic injury, repair involves macrophages and hepatic stellate cells (HSC) activated into myofibroblastic cells (HSC/MFB), which produce cytokines and matrix proteins. We investigated the expression and the role of Gas6 and its receptor Axl in liver repair. Three days after CCl4-induced liver injury in the rat, we detected the expression of Gas6 in ED1-positive macrophages as well as in desmin-positive HSC, which accumulated in injured areas. Axl, the high-affinity receptor for Gas6, was detected in macrophages, HSC, and HSC/MFB. In vitro, expression of gamma-carboxylated Gas6 was strongly induced in HSC along with their transformation into myofibroblasts, and it exerted an anti-apoptotic effect on both HSC and HSC/MFB mediated by the Axl/PI3-kinase/Akt pathway. In conclusion, Gas6 is a survival factor for these cells and we suggest that Gas6, secreted by macrophages and HSC/MFB in vivo after liver injury, promotes HSC and HSC/MFB survival and might support transient HSC/MFB accumulation during liver healing.

Pregnenolone-16alpha-carbonitrile inhibits rodent liver fibrogenesis via PXR (pregnane X receptor)-dependent and PXR-independent mechanisms

The effect of liver growth stimulation [using the rodent PXR (pregnane X receptor) activator PCN (pregnenolone-16alpha-carbonitrile)] in rats chronically treated with carbon tetrachloride to cause repeated hepatocyte necrosis and liver fibrogenesis was examined. PCN did not inhibit the hepatotoxicity of carbon tetrachloride. However, transdifferentiation of hepatic stellate cells and the extent of fibrosis caused by carbon tetrachloride treatment was significantly inhibited by PCN in vivo. In vitro, PCN directly inhibited hepatic stellate cell transdifferentiation to a profibrogenic phenotype, although the cells did not express the PXR (in contrast with hepatocytes), suggesting that PCN acts independently of the PXR. Mice with a functionally disrupted PXR gene (PXR-/-) did not respond to the antifibrogenic effects of PCN, in contrast with wild-type (PXR+/+) mice, demonstrating an antifibrogenic role for the PXR in vivo. However, PCN inhibited the transdifferentiation of PXR-/--derived mouse hepatic stellate cells in vitro, confirming that there is also a PXR-independent antifibrogenic effect of PCN through a direct interaction with hepatic stellate cells. These data suggest that the PXR is antifibrogenic in rodents in vivo and that a PXR-independent target for PXR activators exists in hepatic stellate cells that also functions to inhibit fibrosis.

The role and regulation of hepatic stellate cell apoptosis in reversal of liver fibrosis

Liver fibrosis and its end-stage disease cirrhosis are major world health problems arising from chronic injury of the liver by a variety of etiological factors including viruses, alcohol and drug abuse, the metabolic syndrome, autoimmune disease and hereditary disorders of metabolism. Fibrosis is a progressive pathological process in which wound-healing myofibroblasts of the liver respond to injury by promoting replacement of the normal hepatic tissue with a scar-like matrix composed of cross-linked collagen. Until recently it was believed that this process was irreversible. However emerging experimental and clinical evidence is starting to show that even cirrhosis is potentially reversible. Key to this is the discovery that reversion of fibrosis is accompanied by clearance of hepatic stellate cells (HSC) by apoptosis. Furthermore, proof-of-concept studies in rodents have demonstrated that experimental augmentation of HSC apoptosis will promote the resolution of fibrosis. Consequently there is now considerable interest in determining the molecular events that regulate HSC apoptosis and the discovery of drugs that will stimulate HSC apoptosis in a selective manner. This review will consider the regulatory role played by growth factors (e.g. NGF, IGF-1, TGFbeta), death receptor ligands (TRAIL, FAS), components and regulators of extracellular matrix (integrins, collagen, matrix metalloproteinases and their tissue inhibitors) and signal transduction proteins and transcription factors (Rho/Rho kinase, Jun N-terminal Kinase (JNK), IkappaKinase (IKK), NF-kappa B). The potential for known pharmacological agents such as gliotoxin, sulfasalazine, benzodiazepine ligands, curcumin and tanshinone I to induce HSC apoptosis and therefore to be used therapeutically will be explored.

Roles of protein kinase C and fructose in hepatic injury caused by obstructive jaundice

The regulating mechanism in hepatic injury caused by obstructive jaundice (OJ) was examined in this study. Rat hepatocytes were harvested by in situ collagenase perfusion and subjected to primary culture. The heptocytes were pre-treated with various concentrations of protein kinase C (PKC) agonist PMA and its inhibitor chelerythrine and cultured for 20 min. After the treatment, 50 micromol/L glycochenodeoxycholate (GCDC) was added and the cells were cultured for an additional 24 h. Cells were then detected by flow cytometry (FCM) and TUNEL. After hepatocytes were treated with different concentrations of fructose and 100 microM GCDC, the cells were examined by FCM and TUNEL. Experimental obstructive jaundice (BDL) was induced by double ligation of the bile duct. After BDL, the rats were fed with or without fructos and sacrificed 3, 7, 14 and 21 days after the ligation. The apoptotic status was observed in liver of all rats with TUNEL and PKC protein in liver of OJ was studied by immunohistochemical method. Our results showed that PMA increased GCDC-induced apoptosis and chelerythrine decreased GCDC-induced apoptosis in a concentration-dependent manner. After the treatment with fructose of different concentrations, 100 microM GCDC decreased the apoptotic rate and the apoptotic rate decreased with the increase of fructose concentration. The apoptotic rate of liver was related to the time of OJ. Without the treatment of fructose, PKC and apoptosis index (AI) were highest 14 days after the bile duct ligation. With the treatment of fructose, apoptosis index (AI) and PKC were decreased from the 14th day after the bile duct ligation. It is concluded that PKC is involved in the regulation of apoptosis in the liver cells with OJ and plays important roles in the development and progression of liver injury caused by OJ. Fructose can protect hepatocytes in the bile salt-induced apoptosis by regulating PKC.

Effects of dietary supplementation with vitamin E and selenium on rat hepatic stellate cell apoptosis

AIM: To evaluate the effects of dietary supplementation with vitamin E and selenium on proliferation and apoptosis of hepatic stellate cells (HSCs), in acute liver injury induced by CCl4, and to explore their role in the recovery from hepatic fibrosis phase.

METHODS: An acute liver damage model of rats was established by intraperitoneal injection of carbon tetrachloride (0.3 mL/100 g body weight) twice a week, then the rats were killed at 6, 24, 48, and 72 h after the first and third injection, respectively. A liver fibrosis model was established by the same injection for 8 wk. Then three rats were killed at 3, 7, 14, and 28 d after the last injection, respectively. The rats from the intervention group were fed with chow supplemented with vitamin E (250 mg/kg) and selenium (0.2 mg/kg), and the rats in the normal control group and pathological group were given standard chow. Livers were harvested and stained with hematoxylin and eosin, Sirius red. Activated HSCs were determined by α-smooth muscle actin immunohistochemistry staining. Apoptotic HSCs were determined by dual staining with the terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL) and α-smooth muscle actin immunohistochemistry. Serum alanine aminotransferase and aspartate aminotransferase were also analyzed.

RESULTS: In the acute liver damage model, the degree of liver injury was more serious in the pathological group than in the intervention group. At each time point, the number of activated HSCs was less in the intervention group than in the pathological group, while the number of apoptotic HSCs was more in the intervention group than in the pathological group. In the liver fibrosis model, the degree of liver fibrosis was more serious in the pathological group than in the intervention group. At each time point, the number of activated HSCs was less in the intervention group than in the pathological group, and the number of apoptotic HSCs was more in the intervention group than in the pathological group.

CONCLUSION: Vitamin E and selenium supplementation at the given level can inhibit CCl4-induced activation and proliferation of HSCs and promote the apoptosis of activated HSCs in acute damage phase. Vitamin E and selenium can also effectively decrease the degree of hepatic fibrosis and promote the recovery process.