Ascorbate inhibits apoptosis of Kupffer cells during warm ischemia/reperfusion injury

This study sought to determine whether ascorbate (Asc), a scavenger of reactive oxygen species, inhibits apoptosis of hepatic cells consisting of hepatocytes, Kupffer cells, and sinusoidal endothelial cells (SECs) in the rat liver after warm ischemia/reperfusion (I/R) injury.

Hepatic warm ischemia (69% of the total liver) was induced for 30 min, followed by reperfusion for 60 min. In some animals, ascorbate (at 1 or 10 mg/kg) was infused intravenously immediately before the onset of reperfusion. Hepatic cell apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). Mitochondrial release of cytochrome c into the cytoplasm was assessed by Western blot analysis, and the activation of caspase-3 in liver tissue was determined by colorimetric assays.

Assays of cytochrome c release and caspase-3 showed increased levels of these apoptotic related proteins and enzyme activity. While few apoptotic hepatocytes or SECs were detected in the ischemic group by TUNEL staining, the number of TUNEL-positive Kupffer cells was approximately 4.5-fold greater than that seen in the sham-treatment group. Ascorbate treatment reduced this increase in apoptotic Kupffer cells.

The hepatic cells most vulnerable to oxidative stress in the first hour of reperfusion were Kupffer cells. These may play a key role in hepatic warm I/R injury.