RESUMEN
ß-Amyloid peptide (Aß) is the main component of senile plaques in patients with Alzheimer's disease, and is known to be a main pathogenic factor of the disease. Recent evidence indicates that activation of NADPH oxidase (NOX) in microglia or astrocytes may be a source of Aß-induced reactive oxygen species (ROS). We investigated the role of neuronal NOX in Aß-induced neuronal death in mouse mixed cortical cultures. Cell death was assessed by measuring lactate dehydrogenase efflux to bathing media 24 or 48 hr after exposure to Aß25-35, a fragment of Aß with an equivalent neurotoxic effect. Aß25-35 induced neuronal death in concentration- and time- dependent manners with apoptotic features. Neuronal death was significantly attenuated, not only by anti-apoptotic drugs, such as z-VAD-fmk and cycloheximide, but also by antioxidants, such as trolox, ascorbic acid, and epigallocatethin gallate. We also demonstrated that treatment with 20 µM Aß25-35 increased fluorescent signals in mixed cortical cultures, but produced only weak signals in pure astrocyte cultures in the presence of 2',7'-dichlorofluorescin diacetate (DCF-DA), an indicator for intracellular ROS. Increased DCF-DA fluorescence was markedly inhibited, not only by trolox, but also by selective NOX inhibitors, such as apocynin and AEBSF. Western blot analyses revealed that Aß25-35 increased the expression of gp91phox, a main subunit of NOX in cells. The above antioxidants, apocynin, and AEBSF significantly attenuated neuronal death induced by Aß25-35. Furthermore, the gp91phox-specific siRNA-based knockdown of NOX significantly inhibited neuronal death. These results suggest that activation of neuronal NOX is involved in Aß25-35-induced neuronal death.