Histone deacetylase inhibitors (HDACIs) alter gene expression epigenetically by interfering with the normal functions of HDAC. Given their ability to decrease Aβ levels, HDACIs area potential treatment for Alzheimer's disease (AD). However, it is unclear how HDACIs alter Aβ levels. We developed two novel HDAC inhibitors with improved pharmacological properties, such as a longer half-life and greater penetration of the blood-brain barrier: mercaptoacetamide-based class II HDACI (coded as W2) and hydroxamide-based class I and IIHDACI (coded as I2) and investigated how they affect Aβ levels and cognition. HDACI W2 decreased Aβ40 and Aβ42 in vitro. HDACI I2 also decreased Aβ40, but not Aβ42. We systematically examined the molecular mechanisms by which HDACIs W2 and I2 can decrease Aβ levels. HDACI W2 decreased gene expression of γ-secretase components and increased the Aβ degradation enzyme Mmp2. Similarly, HDACI I2 decreased expression of β- and γ-secretase components and increased mRNA levels of Aβ degradation enzymes. HDACI W2 also significantly decreased Aβ levels and rescued learning and memory deficits in aged hAPP 3x Tg AD mice. Furthermore, we found that the novel HDACI W2 decreased tau phosphorylation at Thr181, an effect previously unknown for HDACIs. Collectively, these data suggest that class II HDACls may serve as a novel therapeutic strategy for AD.

The tetra(ethylene glycol) derivative of benzothiazole aniline, BTA-EG 4 , is a novel amyloid-binding small molecule that can penetrate the blood-brain barrier and protect cells from A␤-induced toxicity. However, the effects of A␤-targeting molecules on other cellular processes, including those that modulate synaptic plasticity, remain unknown. We report here that BTA-EG 4 decreases A␤ levels, alters cell surface expression of amyloid precursor protein (APP), and improves memory in wild-type mice. Interestingly, the BTA-EG 4 -mediated behavioral improvement is not correlated with LTP, but with increased spinogenesis. The higher dendritic spine density reflects an increase in the number of functional synapses as determined by increased miniature EPSC (mEPSC) frequency without changes in presynaptic parameters or postsynaptic mEPSC amplitude. Additionally, BTA-EG 4 requires APP to regulate dendritic spine density through a Ras signaling-dependent mechanism. Thus, BTA-EG 4 may provide broad therapeutic benefits for improving neuronal and cognitive function, and may have implications in neurodegenerative disease therapy.

Apolipoprotein E (APOE) genotype affects outcomes of Alzheimer’s Disease and other conditions of brain damage. Using APOE knock-in mice, we have previously shown that APOE- ε4 Targeted Replacement (TR) mice have fewer dendritic spines and reduced branching in cortical neurons. Since dendritic spines are postsynaptic sites of excitatory neurotransmission, we used APOE TR mice to examine whether APOE genotype affected the various elements of the glutamate-glutamine cycle. We found that levels of glutamine synthetase and glutamate uptake transporters were unchanged among the APOE genotypes. However, compared to APOE- ε3 TR mice, APOE-ε4 TR mice had decreased glutaminase levels (18%, p<0.05), suggesting decreased conversion of glutamine to glutamate. APOE-ε4 TR mice also had increased levels of the vesicular glutamate transporter VGLUT1 (20%, p<0.05), suggesting that APOE genotype affects presynaptic terminal composition. To address whether these changes affected normal neurotransmission, we examined the production and metabolism of glutamate and glutamine at 4–5 months and 1 year. Using high frequency 13C/1H nuclear magnetic resonance (NMR) spectroscopy, we found that APOE-ε4 TR mice have decreased production of glutamate and increased levels of glutamine. These factors may contribute to the increased risk of neurodegeneration associated with APOE-ε4, and also act as surrogate markers for AD risk.

We recently reported that the tetra(ethylene glycol) derivative of benzothiazole aniline, BTA-EG4, acts as an amyloid-binding small molecule that promotes dendritic spine density and cognitive function in wild-type mice. This raised the possibility that BTA-EG4 may benefit the functional decline seen in Alzheimer’s disease (AD). In the present study, we directly tested whether BTA-EG4 improves dendritic spine density and cognitive function in a well-established mouse model of ADcarrying mutations in APP, PS1 and tau (APPswe;PS1M146V;tauP301L, 3xTg AD mice). We found that daily injections of BTA-EG4 for 2 weeks improved dendritic spine density and cognitive function of 3xTg AD mice in an age-dependent manner. Specifically, BTA-EG4 promoted both dendritic spine density and morphology alterations in cortical layers II/III and in the hippocampus at 6–10 months of age compared to vehicle-injected mice. However, at 13–16 months of age, only cortical spine density was improved without changes in spine morphology. The changes in dendritic spine density correlated with Ras activity, such that 6–10 month old BTA-EG4 injected 3xTg AD mice had increased Ras activity in the cortex and hippocampus, while 13–16 month old mice only trended toward an increase in Ras activity in the cortex. Finally, BTA-EG4 injected 3xTg AD mice at 6–10 months of age showed improved learning and memory; however, only minimal improvement was observed at 13–16 months of age. This behavioral improvement corresponds to a decrease in Aβ levels. Taken together, these findings suggest that BTA-EG4 may be beneficial in ameliorating the synaptic loss seen in early AD.

Background Over 70 million Americans inherit the strongest genetic risk factor for Alzheimer’s disease (AD), apolipoprotein E4 (APOE4), but have no course for reducing their risk. The association of non-steroidal anti-inflammatory drug (NSAID) use with reduced risk of AD for APOE4-carriers suggests that NSAIDs may be useful in AD prevention. Methods We identified phenotypes associated with APOE4 in APOE knock-in mice in order to define modifiable measures that correlate with risk of AD. Results APOE4 mouse brains showed altered post-translational modifications and biochemical distribution of APOE compared to APOE3 mice; these differences were also observed in brains of human APOE4 carriers. Two-month treatment with ibuprofen significantly altered the expression pattern of APOE in APOE4 mice to that of APOE3 mice; PPAR-γ agonist pioglitazone also had a significant effect. APOE4 mice also show deficits in dendritic spine density, and ibuprofen and pioglitazone significantly increased dendritic spine density. Conclusions We report new phenotypes associated with APOE4 in control human and APOE knock-in mice and their mitigation with NSAID treatment, through COX-2 inhibition and PPAR-γ activation.