The Caspase Inhibitor IDN-6556 Attenuates Hepatic Injury and Fibrosis in the Bile Duct Ligated Mouse

摘要

Liver injury is characterized by hepatocyte apoptosis and collagen-producing activated hepatic stellate cells (HSC).Hepatocyte apoptosis promotes liver injury and fibrosis,whereas activatec HSC apoptosis limits hepatic fibrosis.Pharmacological inhibitior of liver cell apoptosis may potentially attenuate liver injury anc fibrosis by blocking hepatocyte apoptosis or promote fibrosis by permitting accumulation of activated HSCs.To ascertain the ne effect of inhibiting liver cell apoptosis on liver injury,inflammation and hepatic fibrogenesis,we examined the effect of a pancaspase inhibition IDN-6556 on these parameters in the bile due ligated (BDL) mouse.Hepatocyte apoptosis was assessed by the terminal deoxynucleotidyl transferase dUTP nick-end labeling as-say and immunofluorescence for active caspases 3/7,and livei injury by histopathology and serum alanine aminotransferase (ALT) determinations.Real-time polymerase chain reaction was used to measure mRNA transcripts for markers of hepatic inflammation,HSC activation,and fibrosis.Immunohistochemistry for alpha-smooth muscle actin was performed to identify HSC activation.Collagen deposition was quantitated by Sirius red staining and digital imaging techniques.Hepatocyte apoptosis and liver injury (bile infarcts and serum ALT values) were reduced in IDN-6556-treated versus saline-treated 3-day BDL mice.Markers for liver inflammation [ chemokine (C-X-C) ligand 1 and macrophage in-flammatory protein-2 chemokine expression] and hepatic fibro-genesis (transforming growth factor-beta and collagen I expression) were also attenuated.Consistent with these data,HSC activation as assessed by alpha-smooth muscle actin mRNA expression and immunohistochemistry was markedly reduced in both 3-and 10-day BDL animals.Collectively,these data suggest hepatocyte apoptosis initiates cascades culminating in liver injury and fibrosis.The pan-caspase inhibitor IDN-6556 is a promising agent for cholestatic liver injury.