Inhibition of hepatic stellate cell proliferation and activation by the semisynthetic analogue of fumagillin TNP-470 in rats

Liver extracellular matrix in health and disease

Liver fibrosis is the hallmark of every chronic liver disease. It is also the major factor of morbidity and mortality due to the development of cirrhosis and its complications including hepatocellular carcinoma. But even at the beginning of the process of liver fibrosis and due to the strategic position of the extracellular matrix at the interface between blood flow and epithelial compartment, any quantitative or qualitative modification of extracellular matrix will rapidly affect structure and function of the liver. The development of several animal models of liver fibrosis as well as isolation and cultivation of hepatic stellate cells, the major fibrogenic cell type in the liver, led to the gathering of recent knowledge on the mechanism of liver fibrosis. Activation of hepatic stellate cells is a key event in this process and many details on this finely tuned mechanism are now available. In addition to these experimental data, experience from chronic hepatitis C now allows the development of new concepts and perspectives such as liver fibrosis regression and antifibrotic therapies.

Apoptosis of T cells in the hepatic fibrotic tissue of the rat: a possible inducing role of hepatic myofibroblast-like cells

Apoptosis of T cells contributes to the immune homeostasis in inflamed organs. A prominent T-cell infiltration is usually seen in human chronic active hepatitis, being associated with liver fibrosis. In order to demonstrate T-cell apoptosis in the hepatic fibrotic tissue, we induced T-cell infiltration in the fibrotic liver of the rat by injecting concanavalin A (Con A), a T-cell mitogen. Lymphocytes increased in number with a peak at 1 day, preferentially distributing in the fibrotic tissue rather than the parenchyma. They consisted of CD4-positive and CD8-positive cells, and gave the feature of lymphoblasts. Double staining for CD3 and TUNEL demonstrated that T cells underwent apoptosis. Apoptotic cells were more frequent in the fibrotic livers than the normal livers, and were spatially associated with alpha-smooth muscle actin-positive myofibroblast-like cells that possibly derived from hepatic stellate cells (HSCs) and portal fibroblasts through activation. In vitro experiments demonstrated that lymphocyte apoptosis was more frequently induced in the co-culture of Con A-activated splenic T cells/activated HSCs compared to that induced in activated T cells/quiescent HSCs or resting T cells/activated HSCs. The present results indicate that T cells which have extravasated and infiltrated the hepatic fibrotic tissue undergo apoptosis probably through an interaction with myofibroblast-like cells, suggesting the regulatory role of the latter cells in T-cell accumulation in the fibrotic liver.

Approaches for treatment of liver fibrosis in chronic hepatitis C

In the past 20 years, the elucidation of the mechanisms responsible for liver fibrogenesis has provided many potential targets for antifibrotic treatments. Difficulty has arisen, however, from the fact that fibrogenesis is part of a general beneficial wound healing process. To be successful, an antifibrotic treatment of HCV might need to be delivered selectively to the hepatic site of fibrogenesis or targeted precisely at an HCV-specific regulatory mechanism. It is likely that in the future, besides viral eradication, another treatment goal in chronic HCV infection will be to reverse existing fibrosis, but considerable work is necessary before making this a reality.

Developing strategies for liver fibrosis treatment

Liver fibrosis represents a major worldwide healthcare burden. Current therapy is limited to removing the causal agent. This approach is successful in some diseases; particularly haemochromatosis and chronic viral hepatitis. However, for many patients treatment is not possible, while other patients present to medical attention at an advanced stage of fibrosis. There is therefore a great need for novel therapies for liver fibrosis. The hepatic stellate cell has been recognised to be responsible for most of the excess extracellular matrix observed in chronic liver fibrosis. The detailed understanding of hepatic stellate cell biology has allowed the rational design of novel antifibrotic therapies. This review describes for the general reader the novel emerging therapies for liver fibrosis.

Effects of the tyrosine protein kinase inhibitor genistein on the proliferation, activation of cultured rat hepatic stellate cells

AIM: Hepatic stellate cell (HSC) plays a pivotal role in liver fibrosis and is considered as the therapeutic target for the treatment of hepatic fibrosis. Tyrosine protein kinase plays an important role in the proliferation, activation of HSC. The purpose of the study is to investigate the effects of the tyrosine protein kinase inhibitor genistein on the proliferation and activation of cultured rat HSC.

METHODS: Rat HSC were isolated from Wistar rats by in situ perfusion of collagenase and pronase and single-step density Nycodenz gradient. Culture-activated HSC were serum-starved and incubated with 10^-9 to 10^-5 mol/L concentration of genistein for 24, 48 or 72 h. In PDGF-induced HSC proliferation, HSC were stimulated with 10 μg·L^-1 PDGF-BB for 15 min, and then treated with genistein for the same time. Cell proliferation was measured by MTT assay and based on flow cytometric analysis of cell cycle. The α-smooth muscle actin (α-SMA) expression in HSC was studied with confocal laser microscopy and flow cytometry. c-fos, c-jun and cyclin D1 expression in HSC was also detected by flow cytometry.

RESULTS: Genistein inhibited basal and PDGF-induced proliferation of HSC at the concentration of 10^-8 to 10^-5 mol/L, and treatment with 10^-7 mol/L concentration of genistein for 48 h inhibited the HSC proliferation significantly (the inhibition rate was 70.3%, P < 0.05). Immunofluorescence detected by confocal laser microscopy and flow cytometry showed that treatment with 10^-7 mol/L genistein for 48 h suppressed the expression of α-SMA significantly in HSC (the specific fluorescence intensity were 60.2 ± 21.5 vs 35.3 ± 11.6 and 12.8 ± 10.4 vs 9.54 ± 6.39, respectively, both P < 0.05). The intensity of c-fos, c-jun and cyclin D1 expression of HSCs treated with 10^-7 mol/L genistein for 48 h was also significantly decreased compared with the controls.

CONCLUSION: Genistein influences proliferation of HSC, suppresses the expression of α-SMA in HSC and t inhibits the intensity of c-fos, c-jun and cyclin D1 expression of HSCs. Genistein has therapeutic potential against liver fibrosis.