Dana J. Gant

β-Amyloid Oligomers Induce Phosphorylation of Tau and Inactivation of Insulin Receptor Substrate via c-Jun N-Terminal Kinase Signaling: Suppression by Omega-3 Fatty Acids and Curcumin

Both insulin resistance (type II diabetes) and β-amyloid (Aβ) oligomers are implicated in Alzheimers disease (AD). Here, we investigate the role of Aβ oligomer-induced c-Jun N-terminal kinase (JNK) activation leading to phosphorylation and degradation of the adaptor protein insulin receptor substrate-1 (IRS-1). IRS-1 couples insulin and other trophic factor receptors to downstream kinases and neuroprotective signaling. Increased phospho-IRS-1 is found in AD brain and insulin-resistant tissues from diabetics. Here, we report Aβ oligomers significantly increased active JNK and phosphorylation of IRS-1 (Ser616) and tau (Ser422) in cultured hippocampal neurons, whereas JNK inhibition blocked these responses. The omega-3 fatty acid docosahexaenoic acid (DHA) similarly inhibited JNK and the phosphorylation of IRS-1 and tau in cultured hippocampal neurons. Feeding 3xTg-AD transgenic mice a diet high in saturated and omega-6 fat increased active JNK and phosphorylated IRS-1 and tau. Treatment of the 3xTg-AD mice on high-fat diet with fish oil or curcumin or a combination of both for 4 months reduced phosphorylated JNK, IRS-1, and tau and prevented the degradation of total IRS-1. This was accompanied by improvement in Y-maze performance. Mice fed with fish oil and curcumin for 1 month had more significant effects on Y-maze, and the combination showed more significant inhibition of JNK, IRS-1, and tau phosphorylation. These data indicate JNK mediates Aβ oligomer inactivation of IRS-1 and phospho-tau pathology and that dietary treatment with fish oil/DHA, curcumin, or a combination of both has the potential to improve insulin/trophic signaling and cognitive deficits in AD.

Curcumin Suppresses Soluble Tau Dimers and Corrects Molecular Chaperone, Synaptic, and Behavioral Deficits in Aged Human Tau Transgenic Mice

Background: Various types of Tau aggregates in AD brains may differentially impact neurodegeneration. Results: Curcumin selectively suppresses soluble Tau dimers and corrects molecular chaperone, synaptic, and behavioral deficits. Conclusion: A drug increasing HSPs involved in Tau clearance reduced Tau dimers and improved cognition. Significance: Curcumin that reduced Tau dimers and increased molecular chaperones was efficacious without altering insoluble Tau. The mechanisms underlying Tau-related synaptic and cognitive deficits and the interrelationships between Tau species, their clearance pathways, and synaptic impairments remain poorly understood. To gain insight into these mechanisms, we examined these interrelationships in aged non-mutant genomic human Tau mice, with established Tau pathology and neuron loss. We also examined how these interrelationships changed with an intervention by feeding mice either a control diet or one containing the brain permeable beta-amyloid and Tau aggregate binding molecule curcumin. Transgene-dependent elevations in soluble and insoluble phospho-Tau monomer and soluble Tau dimers accompanied deficits in behavior, hippocampal excitatory synaptic markers, and molecular chaperones (heat shock proteins (HSPs)) involved in Tau degradation and microtubule stability. In human Tau mice but not control mice, HSP70, HSP70/HSP72, and HSP90 were reduced in membrane-enriched fractions but not in cytosolic fractions. The synaptic proteins PSD95 and NR2B were reduced in dendritic fields and redistributed into perikarya, corresponding to changes observed by immunoblot. Curcumin selectively suppressed levels of soluble Tau dimers, but not of insoluble and monomeric phospho-Tau, while correcting behavioral, synaptic, and HSP deficits. Treatment increased PSD95 co-immunoprecipitating with NR2B and, independent of transgene, increased HSPs implicated in Tau clearance. It elevated HSP90 and HSC70 without increasing HSP mRNAs; that is, without induction of the heat shock response. Instead curcumin differentially impacted HSP90 client kinases, reducing Fyn without reducing Akt. In summary, curcumin reduced soluble Tau and elevated HSPs involved in Tau clearance, showing that even after tangles have formed, Tau-dependent behavioral and synaptic deficits can be corrected.

Loss of MAP Function Leads to Hippocampal Synapse Loss and Deficits in the Morris Water Maze with Aging

Hyperphosphorylation and accumulation of tau aggregates are prominent features in tauopathies, including Alzheimers disease, but the impact of loss of tau function on synaptic and cognitive deficits remains poorly understood. We report that old (19–20 months; OKO) but not middle-aged (8–9 months; MKO) tau knock-out mice develop Morris Water Maze (MWM) deficits and loss of hippocampal acetylated α-tubulin and excitatory synaptic proteins. Mild motor deficits and reduction in tyrosine hydroxylase (TH) in the substantia nigra were present by middle age, but did not affect MWM performance, whereas OKO mice showed MWM deficits paralleling hippocampal deficits. Deletion of tau, a microtubule-associated protein (MAP), resulted in increased levels of MAP1A, MAP1B, and MAP2 in MKO, followed by loss of MAP2 and MAP1B in OKO. Hippocampal synaptic deficits in OKO mice were partially corrected with dietary supplementation with docosahexaenoic acid (DHA) and both MWM and synaptic deficits were fully corrected by combining DHA with α-lipoic acid (ALA), which also prevented TH loss. DHA or DHA/ALA restored phosphorylated and total GSK3β and attenuated hyperactivation of the tau C-Jun N-terminal kinases (JNKs) while increasing MAP1B, dephosphorylated (active) MAP2, and acetylated α-tubulin, suggesting improved microtubule stability and maintenance of active compensatory MAPs. Our results implicate the loss of MAP function in age-associated hippocampal deficits and identify a safe dietary intervention, rescuing both MAP function and TH in OKO mice. Therefore, in addition to microtubule-stabilizing therapeutic drugs, preserving or restoring compensatory MAP function may be a useful new prevention strategy.

Attributional and relational processing in pigeons

Six pigeons were trained using a matching-to-sample procedure where sample and rewarded comparisons matched on both attributional (color) and relational (horizontal or vertical orientation) dimensions. Probes then evaluated the pigeons’ preference to comparisons that varied in these dimensions. A strong preference was found for the attribute of color. The discrimination was not found to transfer to novel colors, however, suggesting that a general color rule had not been learned. Further, when color could not be used to guide responding, some influence of other attributional cues such as shape, but not relational cues, was found. We conclude that pigeons based their performance on attributional properties of but not on relational properties between elements in our matching-to-sample procedure. Future studies should look at examining other attributes to compare attributional versus relational processing.

Early intervention with docosahexanoic Acid (DHA) protects APOE4 acceleration of cognitive decline and plasma biomarkers in APOE4/5xFAD mice

healthy elderly (age > 65) in WHICAP, a community-based and ethnically diverse cohort in New York. The associations between plasma As40 and As42 levels and calorie-adjusted dietary intake of 10 nutrients [saturated fatty acid (SFA), mono-unsaturated fatty acid (MUFA), u-3 poly-unsaturated fatty acid (PUFA), u-6 PUFA, vitamin E, vitamin C, s-carotene, vitamin B12, folate, and vitamin D], selected due to their potential association with dementia risk, were examined using linear regression models, first unadjusted and then adjusted for age, gender, ethnicity, education, and s-amyloid assessment wave. Results: In an unadjusted model that simultaneously included all 10 nutrients, higher intake of u-3 PUFA was significantly associated with lower As40 (s 1⁄4 -25.9, p1⁄40.001) and lower As42 (s1⁄4 -11.9, p1⁄40.001) levels; higher intake of MUFAwas significantly associated with lower As40 (s 1⁄4 -1.6, p1⁄40.046) and As42 (s 1⁄4 -0.8, p1⁄40.023) levels. In an adjusted model, u-3 retained a strong association with lower plasma levels of As42 (s 1⁄4-13.6, p1⁄40.045) and As40 (s 1⁄4 -7.2, p1⁄40.021), while MUFAwas no longer associated with As. Other nutrients did not seem to be significantly associated with plasma levels of either As40 or As42. Conclusions: In cognitively healthy elders, higher dietary intake of u-3 PUFA is associated with lower plasma levels of both As40 and As42 (which are markers of slower cognitive decline and lower dementia risk inour cohort). Thus, plasma s-amyloid may be related to dietary habits.

Loss of Tau Function Causes Synaptic and Cognitive Deficits Resembling AD: Correction With Late Intervention Treatment

within 15 minutes of contact. Finally, these three biomarkers showed different adsorption ability and may cause difficulty to choose a unique tube with low adsorption for all biomarkers. Composition analysis of PP tubes revealed that only 3 tubes were pure PP, all others presenting copolymers with at least polyethylene. Surprisingly, pure PP tubes did not give the best results. This first comparative analysis of «PP» tubes strongly suggests the importance of tube types used in the observed between-center effects. Conclusions: Optimization of tube quality by surface pre-treatment or use of common tubes is needed for biomarker standardization, eventually leading to consensus medical decision points used in clinical routine or drug trials.

Protection of excitatory synapses by DHA through preserving function of NMDA-Tiam1-PAK signal pathway in Alzheimer models

Background: Epigenetic mechanisms such as post-translational histone modifications are increasingly recognized for their contribution to gene activation and silencing in the brain. Histone acetylation in particular has been shown to be important both in hippocampal long-term potentiation (LTP) and memory formation in mice. The involvement of the epigenetic modulation of memory formation has also been proposed in neuropathological models, although up to now no clear-cut connection has been demonstrated between histone modifications and Alzheimer’s disease (AD) etiology. Thus, we have undertaken preclinical studies in the APP/PS1 mouse model of AD to determine whether there are differences in histone acetylation levels during associative memory formation. Methods: Westen blot, LTP and contextual fear conditioning Results: After fear conditioning training, levels of hippocampal acetylated histone 4 (H4) in APP/PS1 mice were about 50% lower than in wild-type littermates. Interestingly, acute treatment with a histone deacetylase inhibitor, Trichostatin A (TSA), rescued the defect in CA3-CA1 LTP in slices from APP/PS1 mice. Moreover, TSA administration prior to training rescued both the defect in acetylated H4 levels and contextual freezing to wildtype values. This effect was likley due to amyloid-beta elevation as TSA rescued also the amyloid-beta induced defect in contextual fear memory. Conclusions: Based on this evidence, we propose the hypothesis that epigenetic mechanisms are involved in the altered synaptic function and memory associated with AD. In this respect, histone deacetylase inhibitors represent a new therapeutic target to effectively counteract disease progression.

Novel, small molecule inhibitors of protein aggregation for treatment of amyloid-related diseases

Ab plaque burden. Catalytically incompetent 2E6 treated with a protease inhibitor and a non-proteolytic control IgVL2 did not express these activities. The major 2E6-cleavage site in Ab was the His14-Gln15 peptide bond. Epitope mapping indicated competitive inhibition of 2E6-catalyzed I-Ab degradation by the remote Ab29-40 peptide, identifying this region as the noncovalent recognition epitope. 2E6-Ab immune complexes were undetectable by ELISA, consistent with rapid progress of the reaction to the catalysis step. 2E6 did not cleave His-Gln containing proteins, indicating that specificity for Ab derives from the noncovalent binding step. Conclusions: The Ab fragment targets monomer and aggregate forms of Ab and clears brain Ab plaques by initial noncovalent recognition of the amyloidogenic C terminal region followed by cleavage at remote peptide bonds. Catalysis is rapid and no immune complexes are detectable. This catalytic antibody fragment can be developed for more effective and safe AD immunotherapy.