Molecular mechanism of stellate cell activation and therapeutic strategy for liver fibrosis

Tyrosine kinase inhibitors: friends or foe in treatment of hepatic fibrosis?

Aberrant activity of tyrosine kinases has been proved to be associated with multiple diseases including fibrotic diseases. Tyrosine kinases inhibitors (TKIs) might be a novel approach to transform the anti-fibrotic treatment. However, both beneficial and adverse effects are observed by researchers when using these TKIs in either preclinical animal models or patients with hepatic fibrosis. Since hepatotoxicity of TKIs is the leading cause for drug withdrawals thus limits its application in anti-fibrosis, not only efficacy but also safety of TKIs should be paid great concerns. It has been observed in a few studies that TKIs could induce relatively high rate of hepatic biochemical markers elevations and even result in liver failure. Fortunately, several strategies have been adopt to handle with the hepatotoxicity. Accumulating evidences suggest that hepatic stellate cells (HSC) play a pivotal role in hepatic fibrogenesis, so it might be a good option to develop selective TKIs specifically targeting HSCs. The present review will briefly summarize the anti-fibrotic mechanism of TKIs, adverse effects of TKIs as well as the novel developed selective delivery of TKIs.

Proteomics in liver fibrosis is more than meets the eye

Liver fibrosis is a serious health issue for many liver patients and is currently diagnosed using liver biopsy. The erroneous nature of this technique urges the search for better, noninvasive alternatives. In this regard, proteomics has been described as a useful biomarker discovery tool and has become increasingly applied in the study of liver fibrosis. Experimental and clinical studies have already provided deeper insights in the molecular pathways of liver fibrosis and even confirmed previous findings. Recent advances in proteomic strategies and tools enable multiple fractionation, multiple protein identifications and parallel analyses of multiple samples. Despite its increasing popularity, proteomics still faces certain pitfalls concerning preanalytical variability, protein coverage and statistic reliability. Proteomics is still evolving, but will undoubtedly contribute to a better understanding of the basics of the pathology and certainly offer opportunities in liver fibrosis diagnostics and therapeutics.

Protective effects of Ginkgo biloba, Panax ginseng, and Schizandra chinensis extract on liver injury in rats

This study investigated the effects of the combined extracts of Ginkgo biloba, Panax ginseng, and Schizandra chinensis at different doses on hepatic antioxidant status and fibrosis in rats with carbon tetrachloride (CCl4)-induced liver injury. Male Sprague-Dawley rats (n = 8-12 per group) were divided into the control, CCl4, CCl4 + silymarin (0.35%), CCl4 + low-dose herbal extract (0.24% of Ginkgo biloba, Panax ginseng, and Schizandra chinensis extract at 1:1:1; LE), and CCl4 + high-dose herbal extract (1.20% of the same herbal extract; HE) groups. Silymarin or herbal extract was orally given to rats a week before chronic intraperitoneal injection with CCl4 for 6 weeks. The pathological results showed that herbal extract suppressed hepatic bile duct proliferation, and low-dose herbal extract inhibited liver fibrosis. Hepatic superoxide dismutase (SOD) activity was lower in the CCl4 group, but there was no difference in the silymarin or herbal extract treated groups compared to the control group. Hepatic catalase activity and the ratio of reduced to oxidized glutathione were significantly higher (p < 0.05) in the HE group than those in the CCl4 group. Silymarin and herbal extract reversed the impaired hepatic total antioxidant status (p < 0.05). Herbal extract partially reduced the elevated hepatic lipid peroxides. Hepatic transforming growth factor-beta1 (TGF-beta1) level decreased significantly (p < 0.05) in the LE group. Therefore, high-dose herbal extract improved hepatic antioxidant capacity through enhancing catalase activity and glutathione redox status, whereas low-dose herbal extract inhibited liver fibrosis through decreasing hepatic TGF-beta1 level in rats with CCl4-induced liver injury.

Effect of angiotensin-converting enzyme inhibition on experimental hepatic fibrogenesis

The renin-angiotensin system is suggested to be important in liver fibrogenesis. It induces hepatic stellate cell proliferation and up-regulates transforming growth factor beta-1 (TGF-beta1) expression. Matrix metalloproteinase-2 (MMP-2) is involved in extracellular matrix remodelling. Fibrosis, a consequence of most chronic liver diseases, may be the result of a disturbed balance between fibrogenesis and fibrolysis. The aim of this study was to investigate the effect of enalapril on liver fibrogenesis induced in rats by bile-duct ligation. Forty-seven rats were divided into two groups: bile-duct ligated (BDL) (n = 24) and BDL + enalapril (n = 23). Fibrosis was evaluated by the Knodell scoring system, and TGF-beta1 and MMP-2 were assessed with immunohistochemistry at the second, fourth and sixth weeks after bile-duct ligation. In the BDL group, TGF-beta1 increased by the second week and this increase continued through weeks 4 and 6. In the BDL + enalapril group, TGF-beta1 was significantly lower than the other group (P < 0.05). MMP-2 progressively decreased after week 2 in the BDL group. In the BDL + enalapril group, MMP-2 was significantly higher than the BDL group at the fourth and sixth weeks. These results suggest that enalapril reduces the liver tissue TGF-beta1 and has an ameliorating effect on the fibrosis markers TGF-beta1 and MMP-2.

New insights into functional aspects of liver morphology

The liver is structurally and functionally complex and has been considered second only to brain in its complexity. Many mysteries still exist in this heterogeneous tissue whose functional unit of the lobule has continued to stump morphologists for over 300 years. The primary lobule, proposed by Matsumoto in 1979, has been gaining acceptance as the functional unit of the liver over other conceptual views because it's based on vessel architecture and includes the classic lobule as a secondary feature. Although hepatocytes comprise almost 80% of the liver, there are at least another dozen cell types, many of which provide "cross-talk" and play important functional roles in the normal and diseased liver. The distribution and functional roles of all cells in the liver must be carefully considered in both the analysis and interpretation of research data, particularly data in the area of genomics and "phenotypic anchoring" of gene expression results. Discoveries regarding the functional heterogeneity of the various liver cell types, including hepatocytes, hepatic stellate cells, sinusoidal endothelia, and Kupffer cells, are providing new insights into our understanding of the development, prevention and treatment of liver disease. For example, functional differences along zonal patterns (centrilobular or periportal) have been demonstrated for sinusoidal endothelium, Kupffer cells, and hepatocytes and can explain the gradients and manifestations of disease observed within lobules. Intralobular gradients of bile uptake, glycogen depletion, glutamine synthetase, and carboxylesterase by hepatocytes; widened fenestrations in centrilobular sinusoidal lining cells; and differences in the components of centrilobular extracellular matrix or function of Kupffer cells have been demonstrated. Awareness of the complexities and heterogeneity of the liver will add to a greater understanding of liver function and disease processes that lead to toxicity, cancer, and other diseases.