Published online Aug 8, 2016. doi: 10.4254/wjh.v8.i22.933
Peer-review started: March 4, 2016
First decision: April 15, 2016
Revised: June 22, 2016
Accepted: July 11, 2016
Article in press: July 13, 2016
Published online: August 8, 2016
Processing time: 153 Days and 18.7 Hours
AIM: To examine the effects of the endothelin type A receptor antagonist ambrisentan on hepatic steatosis and fibrosis in a steatohepatitis mouse model.
METHODS: Fatty liver shionogi (FLS) FLS-ob/ob mice (male, 12 wk old) received ambrisentan (2.5 mg/kg orally per day; n = 8) or water as a control (n = 5) for 4 wk. Factors were compared between the two groups, including steatosis, fibrosis, inflammation, and endothelin-related gene expression in the liver.
RESULTS: In the ambrisentan group, hepatic hydroxyproline content was significantly lower than in the control group (18.0 μg/g ± 6.1 μg/g vs 33.9 μg/g ± 13.5 μg/g liver, respectively, P = 0.014). Hepatic fibrosis estimated by Sirius red staining and areas positive for α-smooth muscle actin, indicative of activated hepatic stellate cells, were also significantly lower in the ambrisentan group (0.46% ± 0.18% vs 1.11% ± 0.28%, respectively, P = 0.0003; and 0.12% ± 0.08% vs 0.25% ± 0.11%, respectively, P = 0.047). Moreover, hepatic RNA expression levels of procollagen-1 and tissue inhibitor of metalloproteinase-1 (TIMP-1) were significantly lower by 60% and 45%, respectively, in the ambrisentan group. Inflammation, steatosis, and endothelin-related mRNA expression in the liver were not significantly different between the groups.
CONCLUSION: Ambrisentan attenuated the progression of hepatic fibrosis by inhibiting hepatic stellate cell activation and reducing procollagen-1 and TIMP-1 gene expression. Ambrisentan did not affect inflammation or steatosis.
Core tip: Endothelin (ET) can activate hepatic stellate cells, leading to the progression of hepatic fibrosis. Furthermore, ET-1 may increase the inflow of free fatty acids from the fat tissue into the liver and exacerbate hepatic steatosis. Therefore, ET-1 antagonism may be a novel target for steatohepatitis. The present study showed that ambrisentan, an ET type A receptor antagonist, attenuated hepatic fibrosis by inhibiting hepatic stellate cell activation, without affecting hepatic steatosis, in a non-alcoholic steatohepatitis mouse model.