Gastroenterology

Gastroenterology

Volume 138, Issue 1, January 2010, Pages 347-359
Gastroenterology

Basic—Liver, Pancreas, and Biliary Tract
Modulation of Hepatic Fibrosis by c-Jun-N-Terminal Kinase Inhibition

https://doi.org/10.1053/j.gastro.2009.09.015Get rights and content

Background & Aims

c-Jun N-terminal kinase (JNK) is activated by multiple profibrogenic mediators; JNK activation occurs during toxic, metabolic, and autoimmune liver injury. However, its role in hepatic fibrogenesis is unknown.

Methods

JNK phosphorylation was detected by immunoblot analysis and confocal immunofluorescent microscopy in fibrotic livers from mice after bile duct ligation (BDL) or CCl4 administration and in liver samples from patients with chronic hepatitis C and non-alcoholic steatohepatitis. Fibrogenesis was investigated in mice given the JNK inhibitor SP600125 and in JNK1- and JNK2-deficient mice following BDL or CCl4 administration. Hepatic stellate cell (HSC) activation was determined in primary mouse HSCs incubated with pan-JNK inhibitors SP600125 and VIII.

Results

JNK phosphorylation was strongly increased in livers of mice following BDL or CCl4 administration as well as in human fibrotic livers, occurring predominantly in myofibroblasts. In vitro, pan-JNK inhibitors prevented transforming growth factor (TGF) β-, platelet-derived growth factor-, and angiotensin II-induced murine HSC activation and decreased platelet-derived growth factor and TGF-β signaling in human HSCs. In vivo, pan-JNK inhibition did not affect liver injury but significantly reduced fibrosis after BDL or CCl4. JNK1-deficient mice had decreased fibrosis after BDL or CCl4, whereas JNK2-deficient mice displayed increased fibrosis after BDL but fibrosis was not changed after CCl4. Moreover, patients with chronic hepatitis C who displayed decreased fibrosis in response to the angiotensin receptor type 1 blocker losartan showed decreased JNK phosphorylation.

Conclusions

JNK is involved in HSC activation and fibrogenesis and represents a potential target for antifibrotic treatment approaches.

Section snippets

Mice and Fibrosis Induction

Balb/c mice, JNK1-deficient mice (backcrossed 5 times to C57Bl/6 [http://jaxmice.jax.org/strain/004319.html]) and JNK2-deficient mice (in pure C57Bl/6 background [http://jaxmice.jax.org/strain/004321.html]), and C57Bl/6 mice were obtained from Jackson Laboratories (Bar Harbor, ME). JNK1-deficient mice were crossed with C57Bl/6 mice, and the resulting heterozygous mice were used to establish JNK1-deficient and wild-type JNK1 control strains. Mice were kept in a specific pathogen-free environment

JNK Is Activated in Hepatic Myofibroblasts During Hepatic Fibrogenesis

JNK plays a key role in liver injury after concanavalin A, TNF-α, high-fat diet, acetaminophen intoxication, carcinogen exposure, or ischemia reperfusion injury.9, 11, 12, 13, 14, 15, 16 To test the role of JNK in hepatic wound healing responses to chronic injury, we first analyzed the phosphorylation status of JNK and its target c-Jun in mice following BDL or CCl4 treatment. We observed a strong activation of the JNK pathway as demonstrated by elevated phosphorylated JNK (p-JNK),

Discussion

The activation of JNK occurs in response to a wide array of cellular stress including injury and wound healing responses.31, 32, 33 Moreover, JNK plays an important role in fibroblasts31, 34 and HSCs19, 20 and has been implicated in the regulation of injury in toxic, metabolic, autoimmune, and neoplastic liver disease.9, 11, 13, 14, 15, 16 Data from our study demonstrate for the first time a significant decrease in fibrosis by JNK inhibition in models of toxic and biliary liver fibrosis.

Acknowledgments

The authors thank Dr David Brenner (La Jolla, CA) for providing α-SMA-red fluorescent protein and Coll-GFP mice, Dr Javier Chaves (Valencia, Spain) for information on JNK1 SNPs, and Christina Millan (Barcelona, Spain) for excellent technical support.

S.de M.'s present address is Department of Gastroenterology, Università Politecnica delle Marche, Ancona, Italy.

C.H.O.'s present address is University of California at San Diego, La Jolla, California.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by grants U54CA126513 (PI of Project 2; to R.F.S.); DK076920 (to R.F.S.); and the 2008 Charles Trey, MD, Memorial Postdoctoral Research Fellowship from the American Liver Foundation (to J.K.).

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