Heat-induced inhibition of superoxide dismutase and accumulation of reactive oxygen species leads to HT-22 neuronal cell death

Superoxide dismutase (SOD) is major cytosolic antioxidant enzyme responsible for dismutation of superoxide anion (O2−). Alterations in SOD expression and activity are associated with various neurological disorders. In the present study, we utilized neuronal HT-22 cells to investigate heat-stressed induced cytotoxicity. Heat stress at 43 °C for 30 min caused a decrease in SOD-1 mRNA levels, cytoplasmic SOD protein and enzyme activity and a corresponding decline in cell number during a 48 h recovery at 37°C. During the recovery phase, there was an increase in reactive oxygen species generation and an increase in NADPH oxidase activity with a corresponding increase in DNA fragmentation and release of cytochrome c from the mitochondria. The increase in ROS accumulation and cell death was abolished by pretreatment with the SOD mimetics EUK-134 and Mn(III)TBAP and the NADPH oxidase inhibitor apocynin. These data suggest that hyperthermia increases ROS generation by increasing NADPH activity and decreasing SOD activity leading to cytotoxicity in HT-22 cells.