Blockage of transforming growth factor β receptors prevents progression of pig serum-induced rat liver fibrosis

Immunomodulatory effect of Linalool (Lin) against CCl4 -induced hepatotoxicity and oxidative damage in rats

The current study explored the hepatoprotective and immunomodulatory effects of Linalool (Lin) against carbon tetrachloride (CCl₄ )-induced toxicity in mice. Four study groups (n = 8 each) were used: (1) a negative control group and (2) a toxicity control group (single dose of CCl₄ administered on day 14 as 1 mL/kg of CCL₄ in 1% olive oil). Intraperitoneally (i.p.)), and two experimental groups where mice were treated with either (3) Lin (25 mg/kg b.w., orally, daily for 15 days) or (4) pretreated with Lin (25 mg/kg b.w., orally, daily for 14 days) and intoxicated with CCl₄ (1 mL/kg of CCL₄ in 1% olive oil. i.p.) on day 14. The levels of the anti-inflammatory cytokine interleukin 10 (IL-10), the proinflammatory cytokines TNF-α, IL-6, and TGF-1β, and the histopathology of the liver were assessed. According to our findings, IL-10 concentrations were significantly increased in Lin-treated groups, while other cytokine levels were marked by a considerable decrease in the toxicity model group (CCl₄ -treated group). Histopathological examinations of liver tissues showed that the Lin-treated groups had an almost normal structure. The current findings showed that Lin could inhibit CCl₄ -induced liver injury in mice, which warrants further investigation of Lin as a potential protective and therapeutic agent against hepatotoxicity.

Antioxidant and hepatoprotective effects of novel heteropolysaccharide isolated from Lobularia maritima on CCl4-induced liver injury in rats

The aim of the present study was to investigate the extraction and the characterization of a novel heteropolysaccharide from Tunisian halophyte Lobularia maritima (LmPS). We were also interested in its antioxidant, anti-inflammatory, and hepatoprotective effects on carbon tetrachloride (CCl4)-induced liver injury in rats. LmPS physicochemical properties were evaluated by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and UV absorption. According to TLC and HPLC results, LmPS was a heteropolysaccharide composed of glucose, galactose, and xylose. Its molecular weight was 130.62 kDa. This heteropolysaccharide was characterized by a significant antioxidant potential and was efficient against oxidative stress and CCL4-induced hepatotoxicity in rat Wistar models (n = 8) treated with a single dose of LmPS 250 mg/kg of body weight. This was evidenced by a significant increase in serum marker enzymes specially aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). The cytokines released after stimulation of rats with LmPS showed high anti-inflammatory profiles with an increased rate of interleukine-10 (IL-10) with 0.03 pg/mL compared to animals treated only with CCl4. On the contrary, we noticed a decrease of the other cytokines (tumor necrosis factor α: TNF-α, interleukine-6: IL-6, transforming growth factor beta 1: TGF-β1) with average concentration values of <0.2, 0.1, and 0.04 pg/mL, respectively. Besides, histopathological examinations revealed that CCl4 causes acute liver damage, characterized by extensive hepatocellular necrosis, vacuolization, and inflammatory cell infiltration, as well as DNA fragmentation. LmPS administration at a dose of 250 mg/kg resulted in a significant hepatoprotection, evidenced by a reduction of CCl4-induced oxidative damage for all tested markers. These findings eagerly confirmed that LmPS was effective in the protection against CCl4-induced hepatotoxicity and genotoxicity. It, therefore, suggested a potential therapeutic use of this polysaccharide as an alternative medicine for patients with acute liver diseases.

Immunomodulatory effect of curcumin on hepatic cirrhosis in experimental rats

Cirrhosis is a chronic liver disease. The present work aimed to evaluate the regulatory immune effect of curcumin in hepatic cirrhosis induced by carbon tetrachloride (CCl4) injections in experimental rats' model. Chronic liver fibrosis was induced in experiment animals by recurrent injections of CCl4 for more than 5 weeks. They were divided into five groups: first group was injected with normal saline, second group with CCl4, third, fourth, and fifth groups were injected with CCl4 (intraperitoneal injection) at dose 3 ml/kg, two times weekly for 6 weeks supplemented with the administration of curcumin with concentrations 250, 200, and 150 mg/kg. Immune response was analyzed to different treatments. Interleukin 10 (IL-10), pro-inflammatory cytokines TNF-α, TGF-1β, and liver histopathological examinations were conducted. The results showed that estimations of IL-10 concentrations were significantly increased in curcumin groups compared with CCl4 group, whereas TNF-α and TGF-1β levels were significantly decreased comparing with CCl4 group. The histopathological examinations for liver tissues showed that curcumin treated groups have almost retained the normal structure of liver tissues. In conclusion, curcumin inhibited hepatic fibrosis and liver fibrogenesis with regulation of the immune system mechanism against invader chemical toxicity. PRACTICAL APPLICATIONS: Curcumin is well documented for its medicinal properties, commonly used as a spice. Our work has thus demonstrated its effectiveness as an immunomodulatory agent. Practically, clinical studies have suggested that curcumin displays a diverse and powerful array of pharmacological effects in nearly all of the human body's major organ systems. These are: antidiabetes, anti-inflammatory, anticancer, antiaging, antioxidant, antibacterial infection, hepatoprotective, neurodegenerative, and cardiovascular effects.

Hepatic fibrogenesis and transforming growth factor/Smad signaling activation in rats chronically exposed to low doses of lead

Lead is an important heavy metal pollutant in the environment. The nervous system, kidney and liver are the most susceptible organs to lead deposition, showing that this pollutant has no single target system. To examine the cellular and molecular mechanisms involved in their pathobiology of chronic lead at low-dose exposure in the liver, male Wistar rats were exposed to 0.06% lead acetate in drinking water every day for 4 months. At the end of the study, hepatic metal accumulation, morphology and function were examined. Immunochemical staining and Western blot analysis were performed to detect extracellular matrix proteins, α-smooth muscle actin and transforming growth factor (TGF)β1/Smad pathway expression. Results showed increased laminin, collagen IV and fibronectin, located at the perisinusoidal space. Phenotypic transformation of hepatic stellate cells into myofibroblast-like cells was evidenced at the ultrastructural level and a significant expression of α-smooth muscle actin in Disse’s space was observed. These findings were associated with a marked increase in TGFβ1/Smad2/3 signaling. Our data suggest that, chronically, exposure to low levels of lead could trigger the onset of a hepatic fibrogenic process through upregulated TGFβ1/Smad signaling.

3,3'-Diindolylmethane ameliorates experimental hepatic fibrosis via inhibiting miR-21 expression

BACKGROUND AND PURPOSE

Hepatic fibrosis is a type of liver disease characterized by excessive collagen deposition produced by activated hepatic stellate cells (HSCs), and no appropriate drug treatment is available clinically. The microRNA, miR-21 exhibits an important role in the pathogenesis and progression of hepatic fibrosis. 3,3'-Diindolylmethane (DIM) is a natural autolytic product in plants and can down-regulate miR-21 expression. Here we have assessed the therapeutic effects of DIM against hepatic fibrosis and investigated the underlying mechanisms.

EXPERIMENTAL APPROACH

The effects of DIM on HSC activation were measured by analysing the expression of α-smooth muscle actin and collagen I in both HSC-T6 cell line and primary HSCs. Expression of miR-21 was also measured after DIM treatment and the therapeutic effect of DIM was further studied in vivo, using the model of hepatic fibrosis induced by thioacetamide in mice. The antagonist oligonucleotide, antagomir-21, was also used to suppress the effects of miR-21.

KEY RESULTS

DIM suppressed the central TGF-β signalling pathway underlying HSC activation by down-regulating the expression of miR-21. The decreased miR-21 expression was achieved by inhibiting the activity of the transcription factor, AP-1. Moreover, DIM blunted the activation phenotype of primary HSCs. Administration of DIM in vivo attenuated liver fibrosis induced by thioacetamide, as assessed by collagen deposition and profiles of profibrogenic markers.

CONCLUSIONS AND IMPLICATIONS

DIM shows potential as a therapeutic agent for the treatment of hepatic fibrosis.

Advances in understanding the role of transforming growth factor-β1 in the pathogenesis of liver fibrosis

Transforming growth factor-β1 (TGF-β1) is one of the most important cytokines leading to liver fibrosis and is most closely to the development and progression of liver fibrosis and extracellular matrix (ECM) metabolism. Numerous studies have demonstrated that TGF-β1 plays a significant role in the occurrence, development and progression of live fibrosis. Many therapeutic approaches targeting TGF-β1, especially gene therapy and immunotherapy, have been proposed to treat hepatic fibrosis in recent years. Here, we will review the recent advances in understanding the role of TGF-β1 in the pathogenesis of liver fibrosis.

Effects of S-adenosylmethionine on liver methionine metabolism and steatosis with ethanol-induced liver injury in rats

Background

Hyperhomocysteinemia is implicated in the pathogenesis of various liver diseases. In this study, the effects of S-adenosylmethionine (SAM) on hyperhomocysteinemia and steatosis with ethanol-induced liver injury in rats were examined and their mechanisms were explored.

Methods

Forty-eight female Sprague–Dawley rats were randomly divided into four groups as control, model, low-dose, and high-dose SAM groups. Except the control group, all rats were fed high-fat-containing diet plus ethanol and fish oil gavaged for 8 weeks. SAM was administered by intraperitoneal injection after the 4 weeks’ exposure of ethanol. Serum homocysteine (Hcy), alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), tumor necrosis factor α (TNF-α), and transforming growth factor β1 (TGF-β1) levels were determined. The contents of liver malondialdehyde (MDA) and glutathione (GSH) were assayed. Liver histology was also examined. The expressions of TNF-α and TGF-β1 mRNAs in the liver were detected by the reverse transcriptase-polymerase chain reaction assay.

Results

Compared with the control group, the model group rats developed marked liver damage, accompanied by an increase in Hcy, ALT, AST, TC, TG, TNF-α, TGF-β1, and MDA levels. However, the levels of GSH were decreased. These responses were associated with the increased expression of TNF-α and TGF-β1 mRNAs in the livers, as well as the existence of hepatocellular necrosis and neutrophil infiltration in the livers. In treatment groups, SAM provided significant protection from the liver injury induced by alcohol, resulting in a decrease in serum TNF-α, TGF-β1 levels, lipid peroxidation, and the expressions of TNF-α and TGF-β1 mRNAs in the livers, as well as an increase in GSH levels. However, no statistical difference was observed in these parameters between the two different dose treatment groups. In the study, SAM did not affect plasma total homocysteine (tHcy) levels significantly.

Conclusion

SAM prevents alcohol-induced liver injury in rats by reducing liver lipid peroxidation, anti-inflammation, and antihyperplasia. In addition, it does not affect the plasma tHcy levels.

Rosiglitazone prevents murine hepatic fibrosis induced by Schistosoma japonicum

AIM: To evaluate the effect of rosiglitazone in a murine model of liver fibrosis induced by Schistosoma japonicum infection.

METHODS: A total of 50 mice were randomly and averagely divided into groups A, B, C, D and E. The mice in group A served as normal controls, while those in the other four groups were infected with Schistosoma japonicum to induce the model of liver fibrosis. Besides, the mice in groups C, D and E were treated with praziquantel, rosiglitazone and praziquantel plus rosiglitazone, respectively. NF-κB binding activity and expression of PPARγ-mRNA were determined by Western blot assay and real-time quantitative PCR. Radioimmunoassay technique was used to detect the serum content changes of TNF-α and IL-6. Histological specimens were stained with HE. Expression of TGF-β1, a-smooth muscle actin and type I and type III collagen was detected by immunohistochemistry and multimedia color pathographic analysis system.

RESULTS: Inflammation and fibrosis in the rosiglitazone plus praziquantel treatment group (group E) were lightest among the mice infected with Schistosoma (P < 0.05). To further explore the mechanism of rosiglitazone action, we found that rosiglitazone can significantly increase the expression of PPARγ [E: -18.212 ± (-3.909) vs B: -27.315 ± (-6.348) and C: -25.647 ± (-5.694), P < 0.05], reduce the NF-κB binding activity (E: 88.89 ± 19.34 vs B: 141.11 ± 15.37, C: 112.89 ± 20.17 and D: 108.89 ± 20.47, P < 0.05), and lower the serum level of TNF-α (E: 1.613 ± 0.420 ng/mL vs B: 2.892 ± 0.587 ng/mL, C: 2.346 ± 0.371 ng/mL and D: 2.160 ± 0.395 ng/mL, P < 0.05) and IL-6 (E: 0.106 ± 0.021 ng/mL vs B: 0.140 ± 0.031 ng/mL and C: 0.137 ± 0.027 ng/mL, P < 0.05) in mice with liver fibrosis. Rosiglitazone can also substantially reduce the hepatic expression of TGF-β1, α-SMA type I and type III collagen in mice with liver fibrosis.

CONCLUSION: The activation of PPARγ by its ligand can retard liver fibrosis and suggest the use of rosiglitazone for the treatment of liver fibrosis due to Schistosoma japonicum infection.

Effects of Zhuanggan Zhuyu Decoction on expression of TβRⅠ/Ⅱ, Smad3, Smad4 and Smad7 in experimental liver cirrhosis in rats

AIM: To investigate the effects of Zhuanggan Zhuyu Decoction (ZZD) on the expression of TβRⅠ/Ⅱ, Smad3, Smad4 and Smad7 in experimental liver fibrosis of rats, and to explore its anti-fibrotic molecular mechanism.

METHODS: Forty-four Wistar rats were used in this study, 8 of which were selected as normal controls (group A), and the rest were used to establish liver fibrosis model with carbon tetrachloride (CCl₄) and combined factors. At the 4th wk, four rats were executed to confirm the formation of liver fibrosis, and then the rest of rats were randomly divided into the pathological model group (B), ZZD-treated group (C), colchicine-treated group (D) and Dahuang Zhechong Pill-treated group (E). The rats in group B were treated (ig) with saline. At the end of the 6th wk, the formation of hepatic fibrosis was observed by HE staining and the expression of TβRⅠ/Ⅱ, Smad3, Smad4 and Smad7 were detected by SP immunohistochemistry.

RESULTS: Six weeks later, in comparison with that in group B, the structure of liver lobules almost restored to normal in groups C, D and E; the fibrous septum became thinner; the expression of TβRⅠ/Ⅱ, Smad3 and Smad4 were also significantly decreased (TβR-Ⅰ: 2.75 ± 0.10, 3.14 ± 0.07, 3.44 ± 0.06 vs 5.47 ± 0.13, P < 0.01; TβR-Ⅱ: 1.86 ± 0.12, 2.09 ± 0.10, 2.53 ± 0.12 vs 3.52 ± 0.15, P < 0.01; Smad3: 2.28 ± 0.59, 3.84 ± 1.11, 3.97 ± 0.90 vs 5.65 ± 1.28, P < 0.01; Smad4: 1.57 ± 0.53, 3.15 ± 0.79, 3.37 ± 0.78 vs 5.25 ± 1.60, P < 0.01), whereas the expression of Smad7 was significantly increased (3.45 ± 0.58, 2.09 ± 0.38, 1.75 ± 0.29 vs 0.73 ± 0.34, P < 0.01). The effect in group C was stronger than that in group D or E, and the differences were significant (both P < 0.01).

CONCLUSION: ZZD can reverse liver fibrosis induced by CCl₄ and combined factors and the mechanism may be associated with its effect on regulating and controlling the expression of TβRⅠ/Ⅱ, Smad3, Smad4 and Smad7.

Gene therapy for hepatic fibrosis

Hepatic fibrosis is a common pathological process of chronic liver diseases, characterized by increased synthesis and relatively low degradation of extracellular matrix (ECM) resulting from their dynamic imbalance. Recent progress in molecular biology techniques has made it possible to treat hepatic fibrosis with gene therapy. At present, the commonly used method is to induce the expression of exogenous genes by transducing enough therapeutic genes into injured liver to delay or cure liver fibrosis.

Gene modulation for treating liver fibrosis

Despite tremendous progress in our understanding of fibrogenesis, injury stimuli process, inflammation, and hepatic stellate cell (HSC) activation, there is still no standard treatment for liver fibrosis. Delivery of small molecular weight drugs, proteins, and nucleic acids to specific liver cell types remains a challenge due to the overexpression of extracellular matrix (ECM) and consequent closure of sinusoidal gaps. In addition, activation of HSCs and subsequent release of inflammatory cytokines and infiltration of immune cells are other major obstacles to the treatment of liver fibrosis. To overcome these barriers, different therapeutic approaches are being investigated. Among them, the modulation of certain aberrant protein production is quite promising for treating liver fibrosis. In this review, we describe the mechanism of antisense, antigene, and RNA interference (RNAi) therapies and discuss how the backbone modification of oligonucleotides affects their in vivo stability, biodistribution, and bioactivity. Strategies for delivering these nucleic acids to specific cell types are discussed. This review critically addresses various insights developed with each individual strategy and for multipronged approaches, which will be helpful in achieving more effective outcomes.

Cyclic Arg-Gly-Asp peptide-labeled liposomes for targeting drug therapy of hepatic fibrosis in rats

Targeting hepatic stellate cells (HSCs) has been challenging due to the lack of specific receptors or motifs on the cells. The aim of the present study was to develop a HSC-specific system for improving drug delivery to HSCs. The affinity of a cyclic peptide containing Arg-Gly-Asp (cRGD) to collagen type VI receptor on HSCs was examined in both in vitro and in vivo experiments. Sterically stable liposomes (SSLs) were modified with this peptide to yield a new carrier, cRGD-SSL. The targeting efficiency of this carrier in delivering interferon (IFN)-alpha1b was investigated in a rat model of liver fibrosis induced by bile duct ligation (BDL). When incubating HSCs or hepatocytes with cyclic RGD peptide, the peptide was bound preferentially to activated HSCs. Biodistribution study showed that the accumulation of cRGD peptide-labeled liposomes in HSCs isolated from BDL rats was 10-fold more than unlabeled SSLs. BDL rats receiving injections of IFN-alpha1b entrapped in cRGD-SSL exhibited significantly reduced extent of liver fibrosis compared with BDL control rats or BDL rats treated with IFN-alpha1b entrapped in SSLs. Thus, cRGD-SSL is an efficient drug carrier, which selectively targets activated HSCs and improves drug therapy for liver fibrosis to a significant extent. This liposomal formulation represents a new means of targeting drug carrier for the treatment of liver fibrosis, and it may have potential clinical applications.

Signal transduction and activation of hepatic stellate cells

Liver fibrosis, which leads to cirrhosis, occurs as a result of various injurious processes and it is the common pathologic basis of all the chronic hepatic diseases. At present, a good many researches demonstrate that the activation of hepatic stellate cells play a critical role in fibrogenesis. Prolonged liver injury results in hepatocyte damages and secretion of many fibrogenic cytokines such as transforming growth factor-beta 1, angiotensin, and leptin, which triggers the activation of hepatic stellate cells through different intracellular signal transduction pathways. In this article, we reviewed the research advancement in the signal transduction pathway of nuclear receptor and membrane receptor during the activation of hepatic stellate cells.

How variable are hydroxyproline determinations made in different samples of the same liver?

OBJECTIVES

The haphazard distribution of fibrous tissue can interfere with quantitative methods for evaluating hepatic fibrosis. Inter-sample variation may represent a crucial issue when hydroxyproline measurement is used to quantify fibrosis. A comparative study of the hydroxyproline levels in normal and fibrotic rats is herein reported.

MATERIAL AND METHODS

Twelve normal and 20 Capillaria hepatica-infected Wistar rats were used. Two fragments of the liver (A and B) of each rat were taken from separate areas and hydroxyproline measurements were made. Calculated differences in hydroxyproline measurements between samples from the same liver were analyzed by BOOTSTRAP.

RESULTS

Differences in normal rats varied from 0.026 to 1.85 micromol of HP/g, in ten rats, the difference was less than 0.50 micromol. In infected rats, it varied from 0.04 to 2.86 micromol HP/g. Differences higher than 0.69 micromol/g were significant for normal rats (p<0.05) and above 1.22 micromol/g (p<0.05) for fibrotic rats.

CONCLUSIONS

Hydroxyproline ratio in a normal liver kept a fair degree of reproducibility. In the presence of hepatic fibrosis, the levels of hydroxyproline may vary significantly between samples from a single liver and may have limited value in quantifying the extent of fibrosis.

Therapeutic strategies against TGF-beta signaling pathway in hepatic fibrosis

Hepatic fibrosis is the common wound-healing response to chronic liver injury. In this process, activation of hepatic stellate cells is characteristic of cell proliferation and migration, production of collagen and other extracellular matrix (ECM) molecules, and contraction after transforming into myofibroblasts. It has been shown that the fibrogenic process is prominently regulated by transforming growth factor-beta1 (TGF-beta1) and that the specific blockade of TGF-beta1/Smad3 signaling may therapeutically intervene the fibrosis of various tissues. In this review, we attempt to integrate recent advances in the understanding of the mechanisms underlying TGF-beta1/Smad3 pathway modulation of ECM gene expression in the context of liver fibrosis, discuss intervention strategies targeting the blockade of related signal pathways, and look into novel ways to the safe and efficacious prevention and treatment of hepatic fibrosis.

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cDNA cloning and expression of human CD95 ligand and its role in apoptosis of HepG2 cell lines

AIM: To investigate CD95 ligand and its physiological function in liver neoplasms.

METHODS: The levels of soluble Fas ligand (sFasL) were evaluated in a group of patients affected by hepatitis B virus (HBV)-induced chronic hepatitis, HBV-positive liver cirrhosis and hepatocellular carcinoma (HCC).To further study, we constructed recombinant eukaryotic expression vector pcDNA3.1 hisB-CD95L, which was then tranfected into human hepatoma cell line HepG2 by lipofection.After stained by annexin V and propidium iodine, HepG2 cells were detected by flow cytometer.

RESULTS: CD95L levels were significantly decreased in patients with HCC when compared to the patients with hepatitis or liver cirrhosis.The correct recombinant pcDNA3.1hisB-CD95L was selected by PCR and restriction endonuclease digestion and confirmed by DNA sequencing respectively.Subsequently a significant proportion of cells became apoptotic, as evidenced by positive annexin staining.

CONCLUSION: CD95-CD95 ligand system can induce apoptosis of hepatoma cells.