Modulation of caspase-3 activity and fas ligand mRNA expression in rat liver cells in vivo by alcohol and lipopolysaccharide

The purpose of this study was to determine if exacerbation of apoptosis precedes liver injury during chronic exposure of rats to alcohol. After 7 weeks of feeding an alcohol- or dextrin-containing liquid diet, the animals were treated with Gram-negative bacterial lipopolysaccharide (1 mg . kg(-1) body weight, intravenously) or sterile saline and sacrificed 3 hr after the treatment. Alanine:2-oxoglutarate aminotransferase (ALT) and lactate:NAD oxidoreductase [lactate dehydrogenase (LDH)] were measured in plasma. The caudate robe of the liver was resected for histology, while the rest of the organ was perfused with collagenase to isolate hepatocytes, Kupffer cells (KCs), and sinusoidal endothelial cells (SECs) by centrifugal elutriation. Hepatocyte mitochondria were isolated by differential centrifugation of the cell homogenate. Reduced acid oxidized glutathione (GSH and GSSG) in isolated hepatocytes and hepatocyte mitochondria, and malondialdehyde in hepatocytes were assayed, Caspase-3 activity and Pas ligand mRNA expression were determined in hepatocytes, KCs, and SECs. Plasma ALT and LDH activity, liver histology, GSH, GSSG and their ratio, and malondiaidehyde content were not affected by alcohol treatment. Caspase-3 activity was significantly increased in alcohol-treated rats in all three cell types, with the lowest response observed in hepatocytes and the highest in KCs. Pas ligand mRNA expression, which had the highest level in SECs, followed by KCs and hepatocytes, was not affected by alcohol administration. Lipopolysaccharide had the following effects: an increase in ALT in both pair- and alcohol-fed rats, and LDH only in alcohol-fed rats, a decrease in GSH + GSSG levels in both mitochondria and hepatocytes, an elevation of malondialdehyde content in hepatocytes, a raise in caspase-3 activity in all groups and cell types, end an augmentation of Fas ligand expression in hepatocytes and KCs, but not in SECs. These data suggest that, during chronic alcohol consumption, an exacerbated apoptosis precedes alcohol-induced liver injury.