β-Amyloid activates nitric oxide synthesis and causes neuronal death in hippocampal astrocytes

Digital fluorescence imaging was used to study the effects of the amyloid-beta peptide βA (full-length peptide, βA 1–42) and its neurotoxic fragment (βA 25–35) on nitric oxide (NO) synthesis and cell viability in mixed cultures of rat hippocampal neurons and astrocytes. It was found that both βA 1–42 and βA 25–35 stimulated NO synthesis in astrocytes, but not in neurons. L-NAME, an inhibitor of the inducible NO synthase, blocked the effect of βA on NO production almost completely, reduced βA-induced mitochondrial depolarization in astrocytes, and partly prevented neuronal death. The rate of NO synthesis was decreased in Ca2+-free medium, increased in the presence of antioxidants and the NADPH oxidase inhibitor, and decreased in the presence of the SH-reagent thimerosal.