Glucose promotes caspase-dependent delayed cell death after a transient episode of oxygen and glucose deprivation in SH-SY5Y cells

Brain ischemia causes neuronal cell death by several mechanisms involving necrotic and apoptotic processes. The contributions of each process depend on conditions such as the severity and duration of ischemia, and the availability of ATP. We examined whether glucose affected the development of apoptosis after transient ischemia, and whether this was sensitive to caspase inhibition. Retinoic acid-differentiated SH-SY5Y human neuroblastoma cells were subjected to oxygen and glucose deprivation for 15 h followed by various periods of reoxygenation in either the presence or absence of glucose. Oxygen and glucose deprivation induced cell death in the hours following reoxygenation, as detected by propidium iodide staining. At the end of the period of oxygen and glucose deprivation, both cytochrome c and apoptosis-inducing factor translocated from mitochondria to cytosol. Reoxygenation in the presence of glucose accelerated cell death, and enhanced caspase-3 activity and apoptosis. The glucose-dependent increase in apoptosis was prevented by treatment with the caspase inhibitor zVAD-fmk, but not with calpeptin, a calpain inhibitor. Nevertheless, both zVAD-fmk and calpeptin decreased cell death in the glucose-treated group. ATP levels dropped dramatically after oxygen and glucose deprivation, but recovered steadily thereafter, and were significantly higher at 6 h of reoxygenation in the glucose-treated group. This indicates that energy recovery may promote the glucose-dependent cell death. We conclude that glucose favours the development of caspase-dependent apoptosis during reoxygenation following oxygen and glucose deprivation.