Pulmonary, Gastrointestinal and Urogenital Pharmacology
Comparison of early treatment with low doses of nilotinib, imatinib and a clinically relevant dose of silymarin in thioacetamide-induced liver fibrosis

https://doi.org/10.1016/j.ejphar.2011.08.041Get rights and content

Abstract

Our previous study has already confirmed a promising anti-fibrotic activity especially for nilotinib; when given at a daily dose of 10 mg/kg during the last 4 weeks of thioacetamide (TAA)-induced liver fibrosis for 12 weeks in rats. Therefore, this study was carried out to compare the prophylactic potential of low dose of nilotinib to that of its predecessor, imatinib, and a clinically relevant dose of the standard hepatoprotective treatment, silymarin, in TAA-intoxication. Male Wistar rats received intraperitoneal injections of TAA (150 mg/kg, twice weekly) for 8 weeks, as well as oral treatments with imatinib (5 mg/kg/day), nilotinib (5 mg/kg/day) and silymarin (50 mg/kg/day) from the first day of TAA-intoxication. At the end of the study, chronic hepatic injury was evaluated by analysis of liver function tests in serum. Hepatic oxidative stress was assessed by measuring malondialdehyde, 4-hydroxynonenal, total nitrate/nitrite and reduced glutathione contents, as well as myeloperoxidase and superoxide dismutase activities. Hepatic fibrosis was evaluated by histopathology and collagen content. Our results suggest that the prophylactic potential of nilotinib (5 mg/kg/day), imatinib (5 mg/kg/day) and silymarin (50 mg/kg/day) in TAA-intoxication for 8 weeks is lower than the late treatments of nilotinib (10 mg/kg/day), imatinib (10 mg/kg/day) and silymarin (100 mg/kg/day) during the last 4 weeks of TAA-intoxication for 12 weeks in rats. Taken together, this study suggests that nilotinib may have higher anti-fibrotic activity when administered at a significant stage of fibrosis as a result of impairment of its metabolism in the fibrotic livers.

Introduction

Liver fibrosis represents the wound healing response of the liver to repeated injury that engages a range of cell types and mediators (Kisseleva and Brenner, 2006). After a chronic liver injury of any etiology, the damaged hepatocytes, their membrane components, metabolites of toxic agents, and infiltrating inflammatory cells activate Kupffer cells, which release a number of soluble agents, including cytokines and reactive oxygen species (Gabele et al., 2003). As a result, hepatic stellate cells are transdifferentiated into proliferative, fibrogenic and contractile myofibroblasts. Myofibroblasts are capable of secreting large amounts of extracellular matrix proteins, which represent the matrix of the fibrotic liver (Gressner et al., 2007). Only removal of the liver injury-causing factors, such as viral agents (hepatitis C and B), alcohol and toxins, has been shown to prevent the progression of liver fibrosis and lead to its regression (Friedman and Bansal, 2006). In situations in which treating the caustive agent is not possible, specific anti-fibrotic therapy is desirable.

Imatinib, the first tyrosine kinase inhibitor to be approved, revolutionized the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors (Cohen et al., 2002, Demetri et al., 2002). Nilotinib, a novel imatinib derivative, is a second generation tyrosine kinase inhibitor that has been introduced to treat imatinib-resistant chronic myeloid leukemia (Weisberg et al., 2006). Similar to imatinib, nilotinib inhibits the receptor tyrosine kinases, such as platelet-derived growth factor (PDGF) receptors and stem cell factor receptor (c-Kit), and the nonreceptor tyrosine kinases, such as breakpoint cluster region-abelson kinase (Bcr-Abl), in addition to more selectivity towards abelson kinase (c-Abl) (Manley et al., 2010). Recent advances have implicated the activation of tyrosine kinases, including PDGF receptors, c-Abl and Bcr-Abl in the pathogenesis of liver fibrosis (Liu et al., 2011, Wang et al., 2010). Besides, c-Abl has been shown to be a downstream signal involved in transforming growth factor beta1 (TGF-β1) induced-collagen expression (Liu et al., 2011). Moreover, a therapeutic potential for imatinib and nilotinib has been proposed in fibrotic disorders (Akhmetshina et al., 2008, Day et al., 2008, Distler and Distler, 2008). Silymarin, the standardized extract of the milk thistle (Silybum marianum), is a popular herbal product marketed to treat liver disorders. Silymarin has been reported to have anti-fibrotic, antioxidant, anti-inflammatory and immunomodulating properties (Hussain et al., 2009, Johnson et al., 2003, Tsai et al., 2008).

Most recently, we reported an anti-fibrotic activity for late treatment with nilotinib; when given at a daily dose of 10 mg/kg during the last 4 weeks of thioacetamide (TAA)-intoxication for 12 weeks in rats (Shaker et al., 2011a). Thereafter, the anti-fibrotic activity was further confirmed by our study related with administration of nilotinib (10 and 20 mg/kg) during the last 4 weeks of carbon tetrachloride (CCl4)-intoxication for 8 weeks in rats (Shaker et al., 2011b). As a consequence, we extended our studies to investigate and compare the prophylactic potential of low dose of nilotinib to that of its predecessor, imatinib, and a clinically relevant dose of the standard hepatoprotective treatment, silymarin, in TAA-intoxication for 8 weeks in rats.

Section snippets

Drugs and chemicals

Imatinib mesylate (formerly STI571; Gleevec®) and nilotinib hydrochloride monohydrate (formerly AMN107; Tasigna®) were generously supplied by Novartis (Basel, Switzerland). Silymarin (milk thistle powder containing 80% silymarin) was purchased from Bulk Nutrition (Northborough, MA, USA). 1-Methyl-2-phenylindole, 1,1,3,3-tetramethoxypropane, 5,5′-dithiobis(2-nitrobenzoic acid), vanadium III chloride (VCl3) and sirius red F3B were purchased from Sigma-Aldrich (St. Louis, MO, USA). TAA and

Effects of early treatments with imatinib (5 mg/kg), nilotinib (5 mg/kg) and silymarin (50 mg/kg) on serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) activities

The intoxication with TAA for 8 weeks produced mediocre liver damage characterized by significant increase in serum ALT (P < 0.05) and AST (P < 0.001) activities, compared with the control group (Fig. 1). A significant decrease in serum aminotransferases was observed by early treatments with nilotinib (5 mg/kg) and silymarin (50 mg/kg) at P < 0.01 and P < 0.001, respectively, compared with the group intoxicated with TAA for 8 weeks. The mediocre liver damage produced because of TAA-administration for 8 

Discussion

The pathogenic mechanisms behind chronic injury to hepatocytes play a crucial role in liver diseases, including liver fibrosis and its complications, cirrhosis, portal hypertension, liver failure and carcinoma (Friedman, 2008). Thus, therapeutics that block the signaling pathways implicated in hepatic injury may prove useful for the treatment of these complications. In the present study, early treatment with nilotinib (5 mg/kg) considerably attenuated TAA-induced chronic liver injury as

Conclusions

The prophylactic potential of low doses of nilotinib (5 mg/kg/day), imatinib (5 mg/kg/day) and silymarin (50 mg/kg/day) in TAA-intoxication for 8 weeks is lower than the late treatments of nilotinib (10 mg/kg/day), imatinib (10 mg/kg/day) and silymarin (100 mg/kg/day) during the last 4 weeks of TAA-intoxication for 12 weeks in rats. Taken together, this study suggests that nilotinib may have higher anti-fibrotic activity when administered at a significant stage of fibrosis as a result of impairment of

Conflict of interest

The authors have no conflict of interest to disclose.

Acknowledgments

This work was supported by a grant from the Science and Technology Development Fund (STDF no. 1739 to G.E. Shiha). The authors are grateful to Prof. Dr. Khaled Zalata (Department of Pathology, Faculty of Medicine, University of Mansoura, Mansoura, Egypt) for histopathological evaluation, Dr. Elisabeth Buchdunger (Novartis Pharma, Basel, Switzerland) for providing imatinib and Dr. Paul Manley (Novartis Pharma, Basel, Switzerland) for providing nilotinib.

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