Impact of pan-caspase inhibition in animal models of established steatosis and non-alcoholic steatohepatitis.

ABSTRACT

BACKGROUND & AIMS: Non-alcoholic fatty liver disease is a progressive condition comprising steatosis, steatohepatitis, and cirrhosis. Caspase activation mediates apoptosis and the inflammatory response. Studies demonstrate increased apoptotic activity in NASH although its pathophysiological importance is uncertain. We sought to determine the effects of irreversible pan-caspase inhibition in murine models of established steatosis (high fat diet, HFD) and steatohepatitis (methionine-choline deficient diet, MCD). METHODS: In one study arm, male C3H/HeN mice were fed HFD; in the other, Db/Db mice were fed MCD. Once disease was established, animals were randomised to receive caspase inhibitor (VX-166), TPGS/PEG vehicle or no additional therapy until the end of the study. Biochemical and histological indices were examined to determine NASH activity and tissue oxidative stress. Apoptotic activity and cell turnover were assessed immunohistochemically by staining for caspase-cleaved CK-18 and PCNA. RESULTS: MCD and HFD significantly increased apoptosis, which was reduced by VX-166 treatment. VX-166 did not reduce steatosis but reduced histological inflammation, serum ALT levels, and oxidative stress, particularly in the MCD model. TPGS/PEG vehicle also exhibited some anti-inflammatory activity. CONCLUSIONS: In both models, VX-166 inhibited apoptosis and reduced histological inflammatory infiltrate although there was a more modest impact on other indices of liver injury. In addition, TPGS/PEG vehicle also exhibited some anti-inflammatory activity, likely through the antioxidant effects of vitamin E and changes in gut flora/mucosal interactions. These data suggest that caspase inhibition may represent a valid therapeutic approach; however, further studies to assess the long-term value of more selective caspase inhibition are merited.