Cholestasis is a pathological common component of numerous
liver diseases that results in hepatotoxicity,
inflammation, and
cirrhosis when untreated. While the predominant hypothesis in cholestatic liver injury remains hepatocyte apoptosis due to direct toxicity of hydrophobic
bile acid exposure, recent work suggests that the injury occurs through inflammatory
necrosis. In order to resolve this controversy, we used novel plasma
biomarkers to assess the mechanisms of cell death during early cholestatic liver injury. C57Bl/6 mice underwent bile duct
ligation (BDL) for 6-72 h, or
sham operation. Another group of mice were given d-
galactosamine and
endotoxin as a positive control for apoptosis and inflammatory
necrosis. Plasma levels of full length
cytokeratin-18 (FL-K18), microRNA-122 (miR-122) and high mobility group box-1
protein (
HMGB1) increased progressively after BDL with peak levels observed after 48 h. These results indicate extensive cell
necrosis after BDL, which is supported by the time course of plasma
alanine aminotransferase activities and histology. In contrast, plasma
caspase-3 activity, cleaved
caspase-3 protein and
caspase-cleaved
cytokeratin-18 fragments (cK18) were not elevated at any time during BDL suggesting the absence of apoptosis. In contrast, all plasma
biomarkers of
necrosis and apoptosis were elevated 6 h after Gal/End treatment. In addition, acetylated
HMGB1, a marker for macrophage and monocyte activation, was increased as early as 12 h but mainly at 48-72 h. However, progressive neutrophil accumulation in the area of
necrosis started at 6h after BDL. In conclusion, these data indicate that early cholestatic liver injury in mice is an inflammatory event, and occurs through
necrosis with little evidence for apoptosis.