Mechanisms of death induced by cisplatin in proximal tubular epithelial cells: Apoptosis vs. necrosis

We have examined the mechanisms of cell death induced by cisplatin in primary cultures of mouse proximal tubular cells. High concentrations of cisplatin (800 mu M) led to necrotic cell death over a few hours. Much lower concentrations of cisplatin (8 mu M) led to apoptosis, which caused loss of the cell monolayer over several days. Necrosis was characterized by cytosolic swelling and early loss of plasma membrane integrity. In contrast, early features of cells undergoing apoptosis included cell shrinkage and loss of attachment to the monolayer. Nuclear chromatin became condensed and fragmented in apoptosing cells. These features were absent in necrotic cells. DNA electrophoresis of cells exposed to 800 mu M cisplatin yielded a ''smear'' pattern, due to random DNA degradation. In contrast, the DNA of apoptosing cells demonstrated a ''ladder'' pattern resulting from internucleosomal DNA cleavage. Antioxidants delayed cisplatin-induced apoptosis but not necrosis. Thus the mechanism of cell death induced by cisplatin is concentration dependent. Reactive oxygen species play a role in mediating apoptosis but not necrosis induced by cisplatin.