Developing strategies for liver fibrosis treatment

Collagenase loaded chitosan nanoparticles for digestion of the collagenous scar in liver fibrosis: The effect of chitosan intrinsic collagen binding on the success of targeting

A variety of hepatic insults result in the accumulation of collagen-rich new extracellular matrix in the liver, ultimately culminating in liver fibrosis and cirrhosis. For such reasons, approaches looking into digestion of the collagen-rich extracellular matrix present an interesting therapeutic approach for cases of chronic liver disease, where the fibrotic scar is well established. Portal collagenase administration has recently led to the successful reversion of cirrhosis in an experimental rabbit model. Notwithstanding, the question of how such a sensitive therapeutic macromolecule could be administered in a less invasive manner, and in a way that preserves its functionality and avoids digestion of other non-hepatic vital collagen presents itself. Chitosan is a biodegradable polymer that has been reported to interact and bind to collagen. Chitosan nanoparticles (CS NPs) have also been reported to encapsulate therapeutic proteins, maintaining their functional form and protecting them from in-vivo degradation. For such reasons, CS NPs were loaded with collagenase and evaluated in-vitro and in-vivo for their ability to target and digest collagen. CS NPs were able to encapsulate collagenase (≈ 60% encapsulation efficiency) and release its content in active form. To determine whether chitosan's collagen interaction would enable NP collagen binding or whether the modification with collagen binding peptides (CBPs) is necessary, CS NPs were modified with the CBP; CCQDSETRTFY. Since the density of targeting ligand and the length of tether play a significant role in the success of active targeting, the surface of NPs was modified with different densities of the CBP either directly or using a polyethylene glycol (PEG) spacer. PEGylated NPs showed higher levels of CBP tagging; high, intermediate and low density of CBPs corresponded to 585.8 ± 33, 252.9 ± 25.3 and 56.5 ± 8.8 µg/mL for PEGylated NPs and 425.56 ± 12.67, 107.91 ± 10.3 and 49.86 ± 3.2 µg/mL for unPEGylated NPs, respectively. In-vitro collagen binding experiments showed that unmodified CS NPs were able to bind collagen and that modification with CBPs either directly or via PEG did not enhance collagen binding. In-vivo experiments demonstrated that unmodified CS NPs were able to reverse fibrosis with a survival rate of 100% at the end of the study, indicating the ability of CS NPs to deliver functional collagenase to the fibrotic liver and making the use of CBPs unnecessary.

Natural Sulfur-Containing Compounds: An Alternative Therapeutic Strategy against Liver Fibrosis

Liver fibrosis is a pathophysiologic process involving the accumulation of extracellular matrix proteins as collagen deposition. Advanced liver fibrosis can evolve in cirrhosis, portal hypertension and often requires liver transplantation. At the cellular level, hepatic fibrosis involves the activation of hepatic stellate cells and their transdifferentiation into myofibroblasts. Numerous pro-fibrogenic mediators including the transforming growth factor-β1, the platelet-derived growth factor, endothelin-1, toll-like receptor 4, and reactive oxygen species are key players in this process. Knowledge of the cellular and molecular mechanisms underlying hepatic fibrosis development need to be extended to find novel therapeutic strategies. Antifibrotic therapies aim to inhibit the accumulation of fibrogenic cells and/or prevent the deposition of extracellular matrix proteins. Natural products from terrestrial and marine sources, including sulfur-containing compounds, exhibit promising activities for the treatment of fibrotic pathology. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans are largely unknown. This review aims to provide a reference collection on experimentally tested natural anti-fibrotic compounds, with particular attention on sulfur-containing molecules. Their chemical structure, sources, mode of action, molecular targets, and pharmacological activity in the treatment of liver disease will be discussed.

The use of marine-derived bioactive compounds as potential hepatoprotective agents

The marine environment may be explored as a rich source for novel drugs. A number of marine-derived compounds have been isolated and identified, and their therapeutic effects and pharmacological profiles are characterized. In the present review, we highlight the recent studies using marine compounds as potential hepatoprotective agents for the treatment of liver fibrotic diseases and discuss the proposed mechanisms of their activities. In addition, we discuss the significance of similar studies in Oman, where the rich marine life provides a potential for the isolation of novel natural, bioactive products that display therapeutic effects on liver diseases.

Effect of N-acetyl cysteine (NAC), an organosulfur compound from Allium plants, on experimentally induced hepatic prefibrogenic events in Wistar rat

Aim of present study was to investigate the effect of NAC on experimental chronic hepatotoxicity models induced by carbon tetrachloride (CCl₄) and thioacetamide (TAA). CCl₄ toxicity was induced by administering 200 μl CCl₄ (diluted 2:3 in coconut oil)/100 g body weight, p.o., twice weekly for 8 weeks. TAA toxicity was induced by administering 150 mg/kg b. wt. of TAA i.p., twice weekly for 8 weeks. NAC treatment was started along with toxicants (CCl₄ and TAA) for 8 weeks and continued for further 4 weeks. Self reversal group was kept without any treatment for 4 weeks after completion of toxicant treatments. Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), Alkaline phosphatase (ALP), Bilirubin were measured in serum. Hydroxyproline (HP), lipid peroxidation (LPO), catalase (CAT), Glutathione peroxidase (GPx) and Glutathione (GSH) were determined in liver samples by colorimetric methods. Cytochrome P450 2E1 (CYP 450 2E1), activity was determined as hydroxylation of aniline in liver microsomes. General examination and histological analysis were also performed. Serum markers of liver damage (AST, ALT, ALP and Bilirubin) were increased by CCl₄ and TAA intoxication (p<0.001), whereas co-treatment with NAC reversed such changes (p<0.001). HP was enhanced in toxicant groups (p<0.001 in CCl₄ and TAA), but inhibited by NAC (p<0.001). LPO was increased while as GSH, CAT and GPx decreased by the administration of CCl₄ and TAA (p<0.001); co-administration of NAC restored these liver markers to normal levels (p<0.001). Biochemical determinations were corroborated by general and histological findings. Keeping in view the biochemical and histopathological studies, it was concluded that CCl₄ and TAA are strong hepatotoxic agents that produce liver fibrosis with close proximity to human etiology (micronodular cirrhosis) and NAC has a significant protective activity against CCl₄ and TAA. NAC has also been validated as a model against oxidative burden in chronic liver pathology.

Stellate cell contraction: role, regulation, and potential therapeutic target

The contraction of hepatic stellate cells has been proposed to mediate fibrosis by regulating sinusoidal blood flow and extracellular matrix remodeling. Abundant data from diverse, yet complementary, experimental methods support a robust model for the regulation of contractile force generation by stellate cells. In this model, soluble factors associated with liver injury, including endothelin 1 and nitric oxide, are transduced primarily through Rho signaling pathways that promote the myosin II-powered generation of contractile force by stellate cells. The enhanced knowledge of the role and differential regulation of stellate cell contraction may facilitate the discovery of new and targeted strategies for the prevention and treatment of hepatic fibrosis.

Relaxin receptors in hepatic stellate cells and cirrhotic liver

The polypeptide hormone relaxin has antifibrotic effects on a number of tissues, including the liver. Central to the progression of hepatic fibrosis is the transdifferentiation of hepatic stellate cells (HSC) from a quiescent state to an activated, myofibroblastic phenotype that secretes fibrillar collagen. Relaxin inhibits markers of HSC activation, but relaxin receptor expression in the liver is unclear. The purpose of this study was to determine the expression of the relaxin receptors LGR7 and LGR8 in activated HSC. Production of cAMP was induced by treatment of HSC with relaxin, or the relaxin-related peptides InsL3 or relaxin-3, selective activators of LGR8 and LGR7, respectively. Quiescent HSC expressed low levels of LGR7 but not LGR8. During progression to the activated phenotype, expression of both receptors increased markedly. Immunocytochemistry confirmed the presence of both receptors in activated HSC. In normal rat liver, LGR7, but not LGR8, was expressed at low levels. In cirrhotic liver, expression of both receptors significantly increased. Neither receptor was detectable in normal liver by immunohistochemistry, but both LGR7 and LGR8 were readily detectable in cirrhosis. These results were confirmed in human cirrhotic tissue, with the additional finding of occasional perisinusoidal LGR7 immunoreactivity in non-cirrhotic tissue. In conclusion, the expression of LGR7 and LGR8 is increased with activation of HSC in culture. Cirrhosis also caused increased expression of both receptors. Therefore, agents that stimulate LGR8 and LGR7 may be therapeutically useful to limit the activation of hepatic stellate cells in liver injury.

Morphological and serum hyaluronic acid, laminin and type IV collagen changes in dimethylnitrosamine-induced hepatic fibrosis of rats

AIM

To study the morphological and serum hyaluronic acid (HA), laminin (LN), and type IV collagen changes in hepatic fibrosis of rats induced by dimethylnitrosamine (DMN).

METHODS

The rat model of liver fibrosis was induced by DMN. Serum HA, type IV collagen, and LN were measured by ELISA. The liver/weight index and morphological changes were examined under electron microscope on d 7, 14, 21, and 28 by immunohistochemical alpha smooth muscle actin alpha-SMA staining as well as Sirius-red and HE staining.

RESULTS

The levels of serum HA, type IV collagen and LN significantly increased from d 7 to d 28 (P = 0.043). The liver/weight index increased on d 7 and decreased on d 28. In the model group, the rat liver stained with HE and Sirius-red showed evident hemorrhage and necrosis in the central vein of hepatic 10 lobules on d 7. Thin fibrotic septa were formed joining central areas of the liver on d 14. The number of alpha-SMA positive cells was markedly increased in the model group. Transitional hepatic stellate cells were observed under electron microscope. All rats in the model group showed micronodular fibrosis in the hepatic parenchyma and a network of alpha-SMA positive cells. Typical myofibroblasts were embedded in the core of a fibrous septum. Compared to the control group, the area-density percentage of collagen fibrosis and pathologic grading were significantly different in the model group (P<0.05) on different d (7, 14, and 28). The area-density percentage of collagen fibrosis in hepatic tissue had a positive correlation with the levels of serum HA, LN, and type IV collagen.

CONCLUSION

The morphological and serum HA, type IV collagen, and LN are changed in DMN-induced liver fibrosis in rats.

Apoptosis and necrosis in the liver: a tale of two deaths?

Death of hepatocytes and other hepatic cell types is a characteristic feature of liver diseases as diverse as cholestasis, viral hepatitis, ischemia/reperfusion, liver preservation for transplantation and drug/toxicant-induced injury. Cell death typically follows one of two patterns: oncotic necrosis and apoptosis. Necrosis is typically the consequence of acute metabolic perturbation with ATP depletion as occurs in ischemia/reperfusion and acute drug-induced hepatotoxicity. Apoptosis, in contrast, represents the execution of an ATP-dependent death program often initiated by death ligand/death receptor interactions, such as Fas ligand with Fas, which leads to a caspase activation cascade. A common event leading to both apoptosis and necrosis is mitochondrial permeabilization and dysfunction, although the mechanistic basis of mitochondrial injury may vary in different settings. Prevention of these modes of cell death is an important target of therapy, but controversies still exist regarding which mode of cell death predominates in various forms of liver disease and injury. Resolution of these controversies may come with the recognition that apoptosis and necrosis frequently represent alternate outcomes of the same cellular pathways to cell death, especially for cell death mediated by mitochondrial permeabilization. An understanding of processes leading to liver cell death will be important for development of effective interventions to prevent hepatocellular death leading to liver failure and to promote cancer and stellate cell death in malignancy and fibrotic disease.

Construction of prokaryotic expression system of TGF-β1 epitope gene and identification of recombinant fusion protein immunity

AIM: To insert the constructed TGF-β₁ epitope gene into the el loop of C-terminus of truncated hepatitis B core antigen to increase TGF-β₁ antigenicity in its prokaryotic expression system and to identify immunity of the expressed recombinant protein in order to exploit the possibility for obtaining anti- TGF-β₁ vaccine.

METHODS: The TGF-β₁ encoding epitope gene (the mature TGF-β₁ from 78-109 amino acid residues, TGF-β₁³²) was amplified by polymerase chain reaction from the recombinant pGEM-7z/ TGF-β₁³² vector. The HBcAg gene fragments (encoding HBcAg from 1-71 and 89-144 amino acid residues) were amplified from PYTA1-HBcAg vector. The recombinant vector pGEMEX-1 was used to insert HBcAg1-71, TGF-β₁³² and HBcAg89-144 into restrictive endonuclease enzyme and ligated with T₄ ligase. The fusion gene fragments HBcAg1-71-TGF-β₁³²- HBcAg89-144 were recloned to pET28a(+) and the DNA sequence was confirmed by the dideoxy chain termination method. The recombinant vector pET28a (+)/CTC was transformed and expressed in E. coli BL21 (DE3) under induction of IPTG. After purification with Ni⁺²-NTA agarose resins, the antigenicity of purified protein was detected by ELISA and Western blot and visualized under electron microscope.

RESULTS: Enzyme digestion analysis and sequencing showed that TGF-β₁ epitope gene was inserted into the el loop of C-terminus of truncated hepatitis B core antigen. SDS-PAGE analysis showed that relative molecular mass (Mr) of the expressed product by pET28a (+)/CTC was Mr 24 600.The output of the target recombinant protein was approximately 34.8% of the total bacterial protein, mainly presented in the form of inclusion body. Western blotting and ELISA demonstrated that the fusion protein could combine with anti-TGF-β₁ polyclonal IgG but not with anti-HBcAg. The purity of protein was about 90 % and the protein was in the form of self-assembling particles visualized under electron microscope. This fusion protein had good anti-TGF-β₁ antigenicity and could be used as anti-TGF-β₁ vaccine.

CONCLUSION: A recombinant prokaryotic expression system with high expression efficiency of the target TGF-β₁ epitope gene was successfully established. The fusion protein is in the form of self-assembling particles and HBcAg can increase the antigenicity of TGF-β₁. The expressed TGF-β₁ epitope gene shows good immunogenicity and antigenicity.

Relaxin receptor expression in hepatic stellate cells and in cirrhotic rat liver tissue

Relaxin has antifibrotic effects on the hepatic stellate cells (HSCs) responsible for collagen deposition in cirrhosis. The expression of relaxin receptors LGR7 and LGR8 in HSCs and liver disease was examined. Activated and quiescent HSCs expressed LGR7, whereas only activated HSCs expressed LGR8. Relaxin, relaxin-3, or InsL3 treatment increased cAMP, suggesting activation of both receptors. LGR8 and LGR7 were present in cirrhotic rat liver, but were undetectable in normal liver. In conclusion, both LGR7 and LGR8 are expressed in activated HSCs and cirrhotic liver, suggesting that relaxin, InsL3, or relaxin-3 may be useful in the treatment of hepatic fibrosis.

Effect of Astragalus complanatus flavonoid on anti-liver fibrosis in rats

AIM: To observe the anti-liver fibrosis effect of Astragalus complanatus flavonoids (ACF) in rats.

METHODS: The liver fibrosis model in rats was established by injecting interperitoneally 0.2 mL/100 g 0.5% dimethylnitrosamine, thrice a week. Meanwhile, the rats were administered ACF (30, 60, 120 mg/kg) or colchicine (0.1 mg/kg) once a day for 1 mo. Serum N-propeptide of type I procollagen (PINP) and type III procollagen (PIIINP) was measured using ELISA. Malondialdehyde (MDA) and superoxide dismutase (SOD) in hepatic tissue were evaluated. Matrix metal protease-1 (MMP-1) mRNA expression was assayed by RT-PCR and the protein expression of tissue inhibitor of metal protease-1 (TIMP-1) was analyzed by immunohistochemistry.

RESULTS: In the ACF groups, SOD activity increased and MDA content decreased in comparison to the liver fibrosis model group. The serum PINP and PIIINP contents in ACF-2 and -3 group decreased compared to those in model group. In ACF-2 and -3 group, the expression of MMP-1 mRNA increased significantly and the protein expression of TIMP-1 decreased compared to that in model group.

CONCLUSION: The antifibrotic mechanisms of ACF are associated with its influence on lipid peroxidation and collagen synthesis and degradation.

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PGE2 exerts its effect on the LPS-induced release of TNF-alpha, ET-1, IL-1alpha, IL-6 and IL-10 via the EP2 and EP4 receptor in rat liver macrophages

Lipopolysaccharide (LPS) induces a release of tumor necrosis factor (TNF)-alpha, endothelin (ET)-1, interleukin (IL)-1alpha, IL-6 and IL-10 in rat liver macrophages (Kupffer cells). Prostaglandin (PG)E2 inhibits the release of the fibrogenic mediators TNF-alpha, ET-1 and IL-1alpha, and enhances the release of the anti-fibrogenic mediators IL-6 and IL-10. This effect of PGE2 is mimicked by specific agonists for the PGE2 receptors EP2 and EP4; whereas, agonists for the PGE2 receptors EP1 and EP3 are inactive. Rat liver macrophages express mRNA encoding the PGE2 receptors EP2 and EP4 but not the PGE2 receptors EP1 and EP3. These data suggest that PGE2 exerts its anti-fibrogenic effect through the EP2 and EP4 receptor by inhibiting the release of the fibrogenic mediators TNF-alpha, ET-1 and IL-1alpha, and by enhancing the release of the anti-fibrogenic mediators IL-6 and IL-10 in liver macrophages.

Inhibitory effect of Huangqi Zhechong decoction on liver fibrosis in rat

AIM: To assess the inhibitory effect of Huangqi Zhechong decoction on hepatic fibrosis in rats induced by CCl₄ plus alcohol and high fat low protein diet.

METHODS: Male SD rats were randomly divided into hepatic fibrosis model group, control group and 3 treatment groups consisting of 12 rats in each group. Except for the normal control group, all the rats were subcutaneously injected with CCl₄ at a dosage of 3 mL/kg. In 3 treated groups, either high-dose group (9 mL/kg), or medium-dose group (6 mL/kg), or low-dose group (3 mL/kg) was daily gavaged with Huangqi Zhechong decoction, and saline vehicle was given to model and normal control rats. Enzyme-linked immunosorbent assay (ELISA) and biochemical examinations were used to determine the changes of alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), laminin (LN), type-III-procollagen-N- peptide (PIIIP), and type IV collagen content in serum, and hydroxyproline (Hyp) content in liver after sacrificing the rats. Pathologic changes, particularly fibrosis were examined by hematoxylin and eosin (HE) and Van Gieson staining.

RESULTS: Compared with the model control group, serum ALT, AST, HA, LN, PIIIP and type IV collagen levels dropped markedly in Huangqi Zhechong decoction groups, especially in the medium-dose Huangqi Zhechong decoction group (1 954 ± 576 U/L vs 759 ± 380 U/L, 2 735 ± 786 U/L vs 1 259 ± 829 U/L, 42.74 ± 7.04 ng/mL vs 20.68 ± 5.85 ng/mL, 31.62 ± 5.84 ng/mL vs 14.87 ± 1.45 ng/mL, 3.26 ± 0.69 ng/mL vs 1.47 ± 0.46 ng/mL, 77.68 ± 20.23 ng/mL vs 25.64 ± 4.68 ng/mL, respectively) (P < 0.05). The Hyp content in liver tissue was also markedly decreased (26.47 ± 11.24 mg/mgprot vs 9.89 ± 3.74 mg/mgprot) (P < 0.01). Moreover, the stage of the rat liver fibrosis in Huangqi Zhechong decoction groups was lower than that in model group, and more dramatic drop was observed in medium-dose Huangqi Zhechong decoction group (P < 0.01).

CONCLUSION: Huangqi Zhechong decoction can inhibit hepatic fibrosis resulted from chronic liver injure, retard the development of cirrhosis, and notably ameliorate the liver function. It may be a safe and effective therapeutic drug for patients with fibrosis.

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

AIM: To test the hypothesis that introduction of antisense TβR I and TβR II eukaryotic expressing plasmids into a rat model of immunologically induced liver fibrosis might block the action of TGF-β₁ and halt the progression of liver fibrosis.

METHODS: RT-Nest-PCR and gene recombination techniques were used to construct rat antisense TβR I and TβR II recombinant plasmids which could be expressed in eukaryotic cells. The recombinant plasmids and empty vector (pcDNA3) were encapsulated by glycosyl-poly-L-lysine and then transducted into rats of pig serum-induced liver fibrosis model. Expression of exogenously transfected gene was assessed by Northern blot, and hepatic expressions of TβR I and TβR II were evaluated by RT-PCR and Western blot.We also performed ELISA for serum TGF-β₁, hydroxyproline of hepatic tissues, immunohistoche-mistry for collagen types I and III, and VG staining for pathological study of the liver tissues.

RESULTS: The exogenous antisense TβR I and TβR II plasmids could be well expressed in vivo, and block mRNA and protein expression of TβR I and TβR II in the fibrotic liver at the level of mRNA respectively. These exogenous plasmid expressions reduced the level of TGF-β₁ (antisense TβR I group 23.998 ± 3.045 ng/mL, antisense TβR II group 23.156 ± 3.131 ng/mL, disease control group 32.960 ± 3.789 ng/mL; F = 38.19, 36.73, P < 0.01). Compared with disease control group, the contents of hepatic hydroxyproline (antisense TβR I group 0.169 ± 0.015 mg/g liver, antisense TβR II group 0.167 ± 0.009 mg/g liver, disease control group 0.296 ± 0.026 mg/g liver; F = 14.39, 15.48, P < 0.01) and the deposition of collagen types I and III decreased in the two antisense treatment groups (antisense TβR I group, collagen type I 669.90 ± 50.67, collagen type III 657.29 ± 49.48; antisense TβR II group, collagen type I 650.26 ± 51.51, collagen type III 661.58 ± 55.28; disease control group, collagen type I 1209.44 ± 116.60, collagen type III 1175.14 ± 121.44; F = 15.48 to 74.89, P < 0.01). Their expression also improved the pathologic classification of liver fibrosis models (compared with disease control group, χ² = 17.14, 17.24, P < 0.01). No difference was found in the level of TGF-β₁, the contents of hepatic hydroxyproline and collagen types I and III and pathologic grade between pcDNA3 control group and disease control group or between the two antisense treatment groups (F = 0.11 to 1.06, χ² = 0.13 to 0.16, P > 0.05).

CONCLUSION: Antisense TβR I and TβR II recombinant plasmids have certain reverse effects on liver fibrosis and can be used as possible candidates for gene therapy.

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Cirrhosis: new research provides a basis for rational and targeted treatments

Liver transplantation and antiviral treatments for hepatitis have improved the outlook for many patients with liver disease. For patients with cirrhosis, new developments herald targeted treatments