Ca2+ and reactive oxygen species in staurosporine-induced neuronal apoptosis

Abstract

Staurosporine (0.03-0.5 μM) induced a dose-dependent, apoptotic degeneration in cultured rat hippocampal neurons that was sensitive to 24-h pretreatments with the protein synthesis inhibitor cycloheximide (1 μM) or the cell cycle inhibitor mimosine (100 μM). To investigate the role of Ca2+ and reactive oxygen species in staurosporine-induced neuronal apoptosis, we overexpressed calbindin D(28K), a Ca2+ binding protein, and Cu/Zn superoxide dismutase, an antioxidative enzyme, in the hippocampal neurons using adenovirus-mediated gene transfer. Infection of the cultures with the recombinant adenoviruses (100 multiplicity of infection) resulted in a stable expression of the respective proteins assessed 48 h later. Overexpression of both calbindin D(28K) and Cu/Zn superoxide dismutase significantly reduced staurosporine neurotoxicity compared with control cultures infected with a β-galactosidase overexpressing adenovirus. Staurosporine-induced neuronal apoptosis was also significantly reduced when the culture medium was supplemented with 10 or 30 mM K+, suggesting that Ca2+ influx via voltage-sensitive Ca2+ channels reduces this apoptotic cell death. In contrast, neither the glutamate receptor agonist NMDA (1-10 μM) nor the NMDA receptor antagonist dizocilpine (MK-801; 1 μM) was able to reduce staurosporine neurotoxicity. Cultures treated with the antioxidants U- 74500A (1-10 μM) and N-acetylcysteine (100 μM) also demonstrated reduced staurosporine neurotoxicity. These results suggest a fundamental role for both Ca2+ and reactive oxygen species in staurosporine-induced neuronal apoptosis.