Neuroprotective effect of some plant extracts in cultured CT105-induced PC12 cells

Carboxyl-terminal fragments of APP (CT) have been found in plaques, microvessels and the neurofibrillary tangles in the brains of AD patients. These carboxyl-terminal fragments, which contain the complete Abeta sequence, appear to be toxic to neurons in culture cells. However, the possible role of other cleaved products of APP is less clear. We showed that a recombinant carboxy-terminal 105 amino acid fragment (CT105) of APP induced strong neurotoxicity in PC12 cells. We prepared alcoholic extract from Oriental herbal plants and screened their protective effects against CT105-induced cell death in PC12 cells after the treatment of these extracts. Of the 10 kinds of plant extracts, 12 kinds of extracts had considerable protective effects against CT105-induced cell death, especially, Uncariae Ramulus et Uncus (UREU), Gastrodia elata (GAE), Evodia officinalis (EO) and Panax ginseng (PAG) showed the most protective effect at the concentration of 50 microg/ml. BuOH extract of UREU and GAE possessed the strongest protective effects against neurotoxicity of CT105-induced PC12 cells and showed inhibitory effect with IC50 values of 4.8 and 8.3 microg/ml, respectively. These plants are promising candidates of neuroprotective effects and would be useful for the treatment of the neuronal degenerative diseases such as Alzheimer's diseases.