Involvement of calcium ions in amyloid-ß-induced lamin fragmentation.

Amyloid-ß (Aß) peptide, the main pathogenic peptide in Alzheimer's disease, has been shown to induce an increase in cytoplasmic calcium concentration (CCC). In the current study, we explored the cytotoxic signal transduction pathway in 42-amino-acid Aß (Aß42)-treated HeLa cells in relation to the increase in CCC. The increase in CCC was prominent in cells treated twice with oligomeric Aß42. We previously showed that double treatment also promoted Aß-induced lamin fragmentation (AILF), which appears to be mediated by cathepsin L. Apoptotic caspase activation was a downstream event of AILF. The Ca2+ chelator BAPTA-AM suppressed cell death, cathepsin L activation, AILF, and caspase activation in Aß-treated cells. These results indicate that Aß42 induces an increase in CCC, which is an event upstream of the cytotoxic processes. The products of AILF are different from those produced by other cell death-inducing agents, such as staurosporine, which induces caspase-6-mediated lamin fragmentation (CMLF). CMLF was unaffected by BAPTA-AM and was not detected in cells treated with Aß42, indicating that Aß42 peptide induced a specific cytotoxic pathway involving AILF via increased CCC. We confirmed that the same processes (except caspase activation) operated in Aß42-treated neuroblastoma SH-SY5Y cells.

Avenanthramide-C Restores Impaired Plasticity and Cognition in Alzheimer's Disease Model Mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by cognitive decline and dementia with no effective treatment. Here, we investigated a novel compound from oats named avenanthramide-C (Avn-C), on AD-related memory impairment and behavioral deficits in transgenic mouse models. Acute hippocampal slices of wild-type or AD transgenic mice were treated with Avn-C in the presence or absence of oligomeric Aß42. LTP analyses and immunoblotting were performed to assess the effect of Avn-C on Aß-induced memory impairment. To further investigate the effect of Avn-C on impaired memory and Aß pathology, two different AD transgenic mice (Tg2576 and 5XFAD) models were orally treated with either Avn-C or vehicle for 2 weeks. They were then assessed for the effect of the treatment on neuropathologies and behavioral impairments. Avn-C reversed impaired LTP in both ex vivo- and in vivo-treated AD mice hippocampus. Oral administration (6 mg/kg per day) for 2 weeks in AD mice leads to improved recognition and spatial memory, reduced caspase-3 cleavage, reversed neuroinflammation, and to accelerated glycogen synthase kinase-3ß (pS9GSK-3ß) and interleukin (IL-10) levels. Avn-C exerts its beneficial effects by binding to α1A adrenergic receptors to stimulate adenosine monophosphate-activated kinase (AMPK). All of the beneficial effects of Avn-C on LTP retrieval could be blocked by prazosin hydrochloride, a specific inhibitor of α1A adrenergic receptors. Our findings provide evidence, for the first time, that oats' Avn-C reverses the AD-related memory and behavioral impairments, and establish it as a potential candidate for Alzheimer's disease drug development.

The inhibitory effects of Escherichia coli maltose binding protein on ß-amyloid aggregation and cytotoxicity.

The aggregation of ß-amyloid (Aß) peptide from its monomeric to its fibrillar form importantly contributes to the development of Alzheimer's disease. Here, we investigated the effects of Escherichia coli maltose binding protein (MBP), which has been previously used as a fusion protein, on Aß42 fibrillization, in order to improve understanding of the self-assembly process and the cytotoxic mechanism of Aß42. MBP, at a sub-stoichiometric ratio with respect to Aß42, was found to have chaperone-like inhibitory effects on ß-sheet fibril formation, due to the accumulation of Aß42 aggregates by sequestration of active Aß42 species as Aß42-MBP complexes. Furthermore, MBP increased the lag time of Aß42 polymerization, decreased the growth rate of fibril extension, and suppressed Aß42 mediated toxicity in human neuroblastoma SH-SY5Y cells. It appears that MBP decreases the active concentration of Aß42 by sequestering it as Aß42-MBP complex, and that this sequestration suppresses ongoing nucleation and retards the growth rate of Aß42 species required for fibril formation. We speculate that inhibition of the growth rate of potent Aß42 species by MBP suppresses Aß42-mediated toxicity in SH-SY5Y cells.

Keampferol-3-O-rhamnoside abrogates amyloid beta toxicity by modulating monomers and remodeling oligomers and fibrils to non-toxic aggregates.

BACKGROUND: Aggregation of soluble, monomeric ß- amyloid (Aß) to oligomeric and then insoluble fibrillar Aß is a key pathogenic feature in development of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Aß oligomers, rather than to insoluble fibrils. The use of naturally occurring small molecules for inhibition of Aß aggregation has recently attracted significant interest for development of effective therapeutic strategies against the disease. A natural polyphenolic flavone, Kaempferol-3-O-rhamnoside (K-3-rh), was utilized to investigate its effects on aggregation and cytotoxic effects of Aß42 peptide. Several biochemical techniques were used to determine the conformational changes and cytotoxic effect of the peptide in the presence and absence of K-3-rh. RESULTS: K-3-rh showed a dose-dependent effect against Aß42 mediated cytotoxicity. Anti-amyloidogenic properties of K-3-rh were found to be efficient in inhibiting fibrilogenesis and secondary structural transformation of the peptide. The consequence of these inhibitions was the accumulation of oligomeric structural species. The accumulated aggregates were smaller, soluble, non-ß-sheet and non-toxic aggregates, compared to preformed toxic Aß oligomers. K-3-rh was also found to have the remodeling properties of preformed soluble oligomers and fibrils. Both of these conformers were found to remodel into non-toxic aggregates. The results showed that K-3-rh interacts with different Aß conformers, which affects fibril formation, oligomeric maturation and fibrillar stabilization. CONCLUSION: K-3-rh is an efficient molecule to hinder the self assembly and to abrogate the cytotoxic effects of Aß42 peptide. Hence, K-3-rh and small molecules with similar structure might be considered for therapeutic development against AD.