Bombycis corpus extract prevents Amyloid-β-induced cytotoxicity and protects superoxide dismutase activity in cultured rat astrocytes

Bombycis corpus (BC) or Bombyx Batryticatus, a batryticated silkworm and white-stiff silkworm, is a drug consisting of the dried larva of silkworm, Mobyz mori L., dead and stiffened due to the infection of Beauveria (Bals.) Vuill. In the present study, we have examined the protective effect of the water extracts against Amyloid-β (Aβ) 25-35 peptide-induced cytotoxicity by microscopic observation and LDH assay, and its action on antioxidative enzymes using cultured astrocyte cells. Aβ 25-35-induced cell death was protected by the application of water extract of BC in a dose-dependent manner, and concentrations of 10^-6 to 10^-7 g ml^-1 showed a significant effect compared to exposure of Aβ 25-35 alone. When antioxidative enzyme activities such as catalase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione-S transferase (GST) were assayed after Aβ 25-35 treatment, most enzyme activities were decreased in a similar fashion. BC treatment of Aβ 25-35-treated astrocytes did not affect the enzyme activities of catalase, GSH-Px and GST. However, only SOD activity was enhanced by BC treatment and this may result from the potentiation of the antioxidative ability of BC. The protective effect of BC against cytotoxicity induced by Aβ 25-35 strongly indicates that BC could be a protective agent for free radical generating compounds, and that Aβ 25-35 is not only a potent lipid peroxide inducer, but can also cause changes in antioxidative enzymes. From the results, it was concluded that BC has a protective effect against Aβ-induced cytotoxicity in cultured astrocyte cells through the inhibition of lipid peroxidation and protection of antioxidative enzymes.