Cold-induced apoptosis in isolated rat hepatocytes: protective role of glutathione

Liver conservation for transplantation is usually made at 2-4 degreesC. We studied the effect of rewarming to 37 degreesC for up to 3 h of rat hepatocytes kept at 4 degreesC for 20 h, modulating intracellular glutathione (GSH) concentration either with a GSH precursor (N-acetyl-L-cysteine, NAC), or with GSH depleting agents (diethylmaleate and buthionine sulfoximine, DEM/BSO). Untreated hepatocytes showed time-dependent production of reactive oxygen species (ROS), lipid peroxidation, chromatin condensation and membrane blebbing, decrease in GSH concentration, and protein sulfhydryl groups. Fluorochromatization with Propidium Iodide (PI) and Annexin V (AnxV) of cells rewarmed for I h caused an increase of AnxV-positive cells without PI staining and any observed lactate dehydrogenase leakage. TUNEL and DNA-laddering tests were negative for all times and treatments, indicating that apoptosis may occur without DNA fragmentation. Cold preservation and rewarming in the presence of NAC induced a significant improvement in the morphology, less oxidative stress and apoptosis. Conversely, DEM/BSO caused a marked deterioration of morphology, increase of oxidative stress and apoptosis. These results suggested that marked changes in GSH status might play a critical role in triggering apoptosis during cold preservation of isolated rat hepatocytes. NAC, added before rewarming, might represent a therapeutic approach for preventing the early events of apoptosis during cold storage.