Isobavachalcone and bavachinin from Psoraleae Fructus modulate Aß42 aggregation process through different mechanisms in vitro.

Spontaneous aggregation of Aß is a key factor in the development of Alzheimer's disease. In searching for Aß aggregation inhibitors from traditional Chinese herbal medicines, we identified two active compounds from Psoraleae Fructus, namely isobavachalcone and bavachinin. We further demonstrated that the two compounds modulate Aß42 aggregation process through different mechanisms. Isobavachalcone significantly inhibits both oligomerization and fibrillization of Aß42, whereas bavachinin inhibits fibrillization and leads to off-pathway aggregation. Both of the compounds attenuated Aß42-induced toxicity in a SH-SY5Y cell model. These findings may provide valuable information for new drug development and Alzheimer's therapy in the future.

Valproic acid enhances microglial phagocytosis of amyloid-beta(1-42).

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder manifested by memory loss, confusion and changes in mood. A principal pathology of this debilitating disorder is extracellular deposits of amyloid-beta (Abeta) protein. The "amyloid hypothesis" postulates that a build-up of Abeta protein is responsible for neuronal loss and the ensuing symptoms of AD. One possible mechanism of Abeta clearance, and hence AD therapy, is phagocytosis of Abeta protein by microglial cells. Microglia are the brain's resident immune cells and phagocytosis is one of their innate functions. We are interested in identifying molecules that augment microglial-mediated phagocytosis of Abeta protein. We used the rodent BV-2 microglial cell line which readily phagocytose fluorescent latex beads and synthetic Abeta(1-42) peptide. BV-2 cells treated with the neuroactive drug valproic acid (VPA) showed greatly enhanced phagocytic activity for both latex beads and Abeta. VPA also reduced microglial viability by inducing apoptosis, as previously reported. The relevance of these in vitro results to the treatment of AD is unclear but further investigation into the effects of VPA on the clearance of Abeta through enhanced microglial phagocytosis is warranted.

A synthetic amyloid lawn system for high-throughput analysis of amyloid toxicity and drug screening.

Amyloid-beta (Abeta) is the major constituent of senile plaques in the brains of Alzheimer's disease patients. In order to develop an efficient in vitro system for studying the interaction of cells with Abeta aggregates, we have prepared a synthetic amyloid lawn by immobilizing Abeta peptides over a functionalized glass surface and subsequently incubating the template in a fresh Abeta solution. On the top of different types of amyloid lawns (e.g. monomeric, oligomeric, and fibrillar), we cultivated PC12 cells, creating physical contacts between the cells and the lawns. Results indicated that cell viability was differentially affected when grown atop different Abeta lawns while cells were well adhered onto the surface of these Abeta lawns. The mode of cell death by Abeta lawn was confirmed to be apoptotic rather than necrotic, showing that cells undergo suicide by just contact with Abeta lawn. While conventional 'solution-based' methods for testing amyloid toxicity suffer from problems such as lot-to-lot variations, continued fibrillation, and heterogeneous population of aggregates, our 'surface-based' lawn system is suitable for high-throughput analysis of amyloid toxicity, which may enable high-throughput screening of potential drug candidates for treating amyloid diseases with the goal of reducing the cell death on the lawn.

Memory impairment and neuronal dysfunction induced by beta-amyloid protein in rats.

Alzheimer's disease (AD) is characterized by the presence of senile plaques. The core of the plaque consists of beta-amyloid protein. In AD patients, learning and memory are impaired with a concomitant loss of the cholinergic marker enzyme, choline acetyltransferase (ChAT). However, direct evidence that beta-amyloid protein is related to the impairment of learning and memory has not been demonstrated. In this study, we investigated whether memory impairment and neuronal dysfunction were produced after 2 weeks continuous infusion of beta-amyloid protein (3, 30 and 300 pmol/day) into the cerebral ventricles in adult rats. To investigate the ability of learning and memory in beta-amyloid protein-treated rats, water maze and passive avoidance tasks were carried out. The performance of both tasks in beta-amyloid protein-treated rats was impaired. ChAT activity in the frontal cortex (3 and 30 pmol/day) and hippocampus (300 pmol/day) significantly decreased. These results suggest that beta-amyloid protein is related to the impairment of learning and memory, and neurodegeneration, and that beta-amyloid protein-treated rats could be used as an animal model for AD.