AMP-activated protein kinase (AMPK) is a metabolic sensor involved in intracellular energy metabolism through the control of several homeostatic mechanisms, which include autophagy and protein degradation. Recently, we reported that AMPK activation by resveratrol promotes autophagy-dependent degradation of the amyloid-β (Aβ) peptides, the core components of the cerebral senile plaques in Alzheimer's disease. To identify more potent enhancers of Aβ degradation, we screened a library of synthetic small molecules selected for their structural similarities with resveratrol. Here, we report the identification of a series of structurally related molecules, the RSVA series, which inhibited Aβ accumulation in cell lines nearly 40 times more potently than did resveratrol. Two of these molecules, RSVA314 and RSVA405, were further characterized and were found to facilitate CaMKKβ-dependent activation of AMPK, to inhibit mTOR (mammalian target of rapamycin), and to promote autophagy to increase Aβ degradation by the lysosomal system (apparent EC(50) ∼ 1 μM). This work identifies the RSVA compounds as promising lead molecules for the development of a new class of AMPK activating drugs controlling mTOR signaling, autophagy, and Aβ clearance.
The use of antibodies to treat neurodegenerative diseases has undergone rapid development in the past decade. To date, immunotherapeutic approaches to Alzheimer’s disease have mostly targeted amyloid beta as it is a secreted protein that can be found in plasma and CSF and is consequently accessible to circulating antibodies. Few recent publications have suggested the utility of treatment of tau pathology with monoclonal antibodies to tau. Our laboratory has begun a systematic study of different classes of tau monoclonal antibodies using mutant P301L mice. Three or seven months old mutant tau mice were inoculated weekly with tau monoclonal antibodies at a dose of 10 mg/Kg, until seven or ten months of age were reached respectively. Our data strongly support the notion that in P301L animals treated with MC1, a conformational monoclonal antibody specific for PHF-tau, the rate of development of tau pathology is effectively reduced, while injecting DA31, a high affinity tau sequence antibody, does not exert such benefit. MC1 appears superior to DA31 in overall effects, suggesting that specificity is more important than affinity in therapeutic applications. Unfortunately the survival rate of the P301L treated mice was not improved when immunizing either with MC1 or PHF1, a high affinity phospho-tau antibody previously reported to be efficacious in reducing pathological tau. These data demonstrate that passive immunotherapy in mutant tau models may be efficacious in reducing the development of tau pathology, but a great deal of work remains to be done to carefully select the tau epitopes to target.
Transgenic mouse models have been an invaluable resource in elucidating the complex roles of Aβ and tau in Alzheimer’s disease. While many laboratories rely on qualitative or semi-quantitative techniques when investigating tau pathology, we have developed four Low-Tau Sandwich ELISAs that quantitatively assess different epitopes of tau relevant to Alzheimer’s disease: total tau, pSer-202, pThr-231, pSer-396/404. In this study, after comparing our assays to commercially available ELISAs, we demonstrate our assays high specificity and quantitative capabilities using brain homogenates from tau transgenic mice, htau, JNPL3, tau KO mice. All four ELISAs show excellent specificity for mouse and human tau, with no reactivity to tau KO animals. An age dependent increase of serum tau in both tau transgenic models was also seen. Taken together, these assays are valuable methods to quantify tau and phospho-tau levels in transgenic animals, by examining tau levels in brain and measuring tau as a potential serum biomarker.
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