Ascorbate Inhibits Apoptosis of Kupffer Cells During Warm Ischemia/Reperfusion Injury

Background/Aims: 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. Methodology: Hepatic warm ischemia (69% of the total liver) was induced for 30min, followed by reperfusion for 60min. In some animals, ascorbate (at 1 or 10mg/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. Results: 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. Conclusion: 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.