Inhibitory effects of β-amyloid peptide neurotoxicity by the aqueous extracts from Verbena officinalis

Abstract

Verbena officinialis (Verbenaceae) is a perennial plant which has been used as herbal medicine or health supplement in both Western and Eastern countries for centuries. It has been used to treat acute dysentery, enteritis, amenorrhea and depression without much knowledge about biological mechanisms. In view of its wide array of biological effects, we hypothesized that V. officinalis can exert cytoprotective effects on cells of central nervous system. In vitro cell culture model of primary cortical neurons were used to examine the neuroprotective effects of V. officinalis against toxins/biological stresses. Pre-treatment of aqueous extracts of V. officinalis significantly attenuated the toxicity of beta-amyloid (Aβ) peptide and reducing agent dithiothreitol. Since Aβ peptide plays important roles in pathogenesis of Alzheimer’s disease (AD), we have further explored the neuroprotection of V. officinalis against Aβ. Treatment of V. officinalis attenuated Aβ-triggered DEVD-and VDVAD- cleavage activities in dose-dependent manner. Furthermore, V. officinialis attenuated the phosphorylation of both interferon-inducing protein kinase (PKR) and c-Jun N–terminal kinase (JNK) in Aβ-treated neurons. Taken together, we have proved our hypothesis by showing the novel neuroprotective effects of V. officinalis. As V. officinalis has long been used for many years to be a folk medicine, our study may provide a lead for its potential to be a neuroprotective agent against neuronal loss in AD. Supported by SWL and MSY are supported by postgraduate studentship from The University of Hong Kong. The study is partially supported by HKU Seed Funding for Basic Research (2004 & 2005) to RCCC.