Current Alzheimer Research - Volume 12, Issue 9, 2015

A potential strategy to alleviate the aggregation of intrinsically disordered proteins (IDPs) is to maintain the native functional state of the protein by small molecule binding. However, the targeting of the native state of IDPs by small molecules has been challenging due to their heterogeneous conformational ensembles. To tackle this challenge, we applied a high-throughput chemical microarray surface plasmon resonance imaging screen to detect the binding between small molecules and monomeric full-length Tau, a protein linked with the onset of a range of Tauopathies. The screen identified a novel set of drug-like fragment and lead-like compounds that bound to Tau. We verified that the majority of these hit compounds reduced the aggregation of different Tau constructs in vitro and in N2a cells. These results demonstrate that Tau is a viable receptor of drug-like small molecules. The drug discovery approach that we present can be applied to other IDPs linked to other misfolding diseases such as Alzheimer’s and Parkinson’s diseases.

Differential diagnosis of AD is still a challenge due to overlapping features with other types of dementia. Biomarkers for the differential diagnosis of AD can improve the diagnostic value of the disease and ensure an appropriate treatment of patients. The aim of this study was to evaluate the potential of two neo-epitope fragments of Tau as serum biomarkers for differential diagnosis of AD. The neo-epitope fragments of Tau were assessed in a cross-sectional cohort of subjects with AD, MCI, other dementias or subjects with non-dementia related memory complaints. The two Tau neo-epitope fragments were an ADAM10-generated fragment (Tau-A) and a caspase-3-generated fragment (Tau-C). The serum levels of the fragments were measured by two competitive ELISAs detecting Tau-A and Tau-C, respectively. Tau-A and Tau-C were able to separate subjects with AD and MCI from those with other dementias (p < 0.0042 and p < 0.05), and Tau-A could also discriminate between AD and MCI patients and subjects with non-dementia related memory complaints (p < 0.05). Tau-A showed a significantly greater discrimination between AD and MCI subjects and patients with other dementias when compared to CSF biomarkers t-Tau and p-Tau. The ability of Tau-A to differentiate between AD and MCI from other dementias was comparable with CSF Aβ1-42, t-Tau/Aβ1-42 and p-Tau/Aβ1-42. The separation between the diagnostic groups was significantly improved when the CSF biomarkers as well as age and BMI were used in combination with Tau-A (AUC = 0.87, 95% CI: 0.75-0.94) (p < 0.0001). In conclusion, this study shows that a neoepitope fragment of Tau detected in serum can provide guidance on the differential diagnosis of AD.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the fourth leading cause of death in the United States and most common cause of adult-onset dementia. The major hallmarks of AD are the formation of senile amyloid plaques made of beta amyloid and neurofibrillary tangles (NFT) which are primarily composed of phosphorylated tau protein. Although numerous agents have been considered as providing protection against AD, identification of potential agents with neuroprotective ability is limited. Thioflavin T has been used in the past to stain amyloid beta plaques in brain. In this study, Thioflavin T (ThT) and vehicle (infant formula) were administered orally by gavage to transgenic (B6C3 APP PS1; AD-Tg) mice beginning at 4 months age and continuing until sacrifice at 9 months of age at 40mg/kg dose. The number of amyloid plaques was reduced dramatically by ThT treatment in both male and female transgenic mice compared to those in control mice. Additionally, GFAP and Amylo-Glo labeling suggest that astrocytic hypertrophy is minimized in ThT-treated animals. Similarly, CD68 labeling, which detects activated microglia, along with Amylo-Glo labeling, suggests that microglial activation is significantly less in ThT-treated mice. Both Aβ-40 and Aβ-42 concentrations in blood rose significantly in the ThT-treated animals suggesting that ThT may inhibit the deposition, degradation, and/or clearance of Aβ plaques in brain.

The ATP-binding cassette transporter-2 (ABCA2) is a member of a family of multipass transmembrane proteins that use the energy of ATP hydrolysis to transport substrates across membrane bilayers. ABCA2 has also been genetically linked with Alzheimer’s disease but the molecular mechanisms are unknown. In this report, we hypothesized that ABCA2 modulation of sphingolipid metabolism activates a signaling pathway that regulates amyloid precursor protein transcription. We found that ABCA2 overexpression in N2a cells was associated with increased mass of the sphingolipid sphingosine, derived from the catabolism of ceramide. ABCA2 overexpression increased in vitro alkaline and acid ceramidase activity. Sphingosine is a physiological inhibitor of protein kinase C (PKC) activity. Pharmacological inhibition of ceramidase activity or activation PKC activity with 12-myristate 13-acetate (PMA) or diacylglycerol (DAG) decreased endogenous APP mRNA levels in ABCA2 overexpressing cells. Treatment with PMA also decreased the expression of a transfected human APP promoter reporter construct, while treatment with a general PKC inhibitor, GF109203x, increased APP promoter activity. In N2a cells, chromatin immunoprecipitation experiments revealed that a repressive complex forms at the AP-1 site in the human APP promoter, consisting of c-jun, c-jun dimerization protein 2 (JDP2) and HDAC3 and this complex was reduced in ABCA2 overexpressing cells. Activation of the human APP promoter in A2 cells was directed by the upstream stimulatory factors USF-1 and USF-2 that bound to an E-box element in vivo. These findings indicate that ABCA2 overexpression modulates sphingosine levels and regulates transcription of the endogenous APP gene.

We previously reported that activity of the large conductance calcium-activated potassium (big-K, BK) channel is suppressed by intracellular Aβ in cortical pyramidal cells, and that this suppression was reversed by expression of the scaffold protein Homer1a in 3xTg Alzheimer’s disease model mice. Homer1a is known to be expressed by physiological photic stimulation (PS) as well. The possibility thus arises that PS also reverses Aβ-induced suppression of BK channels, and thereby improves cognition in 3xTg mice. This possibility was tested here. Chronic application of 6-hour-long PS (frequency, 2 Hz; duty cycle, about 1/10; luminance, 300 lx) daily for 4 weeks improved contextual and tone-dependent fear memory in 3xTg mice and, to a lesser extent, Morris water maze performance as well. Hippocampal long-term potentiation was also enhanced after PS. BK channel activity in cingulate cortex pyramidal cells and lateral amygdalar principal cells, suppressed in 3xTg mice, were facilitated. In parallel, neuronal excitability, elevated in 3xTg mice, was recovered to the control level. Gene expression of BK channel, as well as that of the scaffold protein Homer1a, was found decreased in 3xTg mice and reversed by PS. It is known that Homer1a is an activity-dependently inducible immediate early gene product. Consistently, our previous findings showed that Homer1a induced by electrical stimulation facilitated BK channels. By using Homer1a knockouts, we showed that the present PS-induced BK channel facilitation is mediated by Homer1a expression. We thus propose that PS might be potentially useful as a non-invasive therapeutic measure against Alzheimer’s disease.

There are currently no approved effective therapies for Alzheimer’s disease (AD). AD is a classic, multifactorial, complex syndrome. Thus, a polypharmacological or multitargeted approach to AD might provide better therapeutic benefits than monotherapies. However, it remains elusive which biological processes and biomolecules involved in the pathophysiologic processes of AD would constitute good targets for multitargeted therapy. This study proposes that a co-module, consisting of biological processes, cellular pathways and nodes, in a molecular subnetwork perturbed by different therapeutic drugs may be the optimal therapeutic target for an AD multitarget-based intervention. Based on this hypothesis, genes regulated in the hippocampus and cortex of senescence-accelerated mouse prone-8 (SAMP8) mice by traditional Chinese medicine (TCM) prescriptions with different constituents and the same beneficial effects on AD, including the decoctions Liu-Wei-Di-Huang (LW), Ba-Wei-Di-Huang (BW), Danggui-Shaoyao-San (DSS), Huang-Lian-Jie-Du (HL) and Tiao-Xin-Fang (TXF), were investigated via cDNA microarray, and the perturbed subnetworks were constructed and interpreted. After comparing 15 perturbed subnetworks based on genes affected by LW, BW, HL, DSS and TXF, the results showed that the most important common nodes perturbed by these interventions in the brains of SAMP8 mice were RPS6KA1 and FHIT, and that other important common nodes included UBE2D2, STUB1 and AMFR. These five drugs simultaneously and significantly disturbed the regulation of apoptosis and protein ubiquitination among biological processes. These nodes and processes were key components of the co-module regulated by therapeutic drugs in a molecular subnetwork of AD. These results suggest that targeting candidate regulator of apoptosis and protein ubiquitination might be effective for AD treatment, and that RPS6KA1, FHIT, UBE2D2, STUB1 and AMFR might be optimal combinational targets of an AD multitarget-based therapy.

Early diagnosis of Alzheimer`s disease (AD) is currently difficult and involves a complex approach including clinical assessment, neuroimaging, and measurement of amyloid-β (Aβ) and tau levels in cerebrospinal fluid (CSF). A better mechanistic understanding is needed to develop more accurate and even presymptomatic diagnostic tools. It has been shown that Aβ derived from amyloid-containing brain tissue has prion-like properties: it induces misfolding and aggregation of Aβ when injected into human amyloid precursor protein (APP) transgenic mice. In contrast, Aβ in the CSF has been less studied, and it is not clear whether it also exhibits prion-like characteristics, which might provide a sensitive diagnostic tool. Therefore, we collected CSF from APP transgenic mice carrying the Swedish mutation (APP23 mice), and injected it intracerebrally into young mice from the same transgenic line. We found that CSF derived Aβ did not induce increased β-amyloidosis, even after long incubation periods and additional concentration. This suggests that Aβ present in the CSF does not have the same prion-like properties as the Aβ species in the brain.

Oxidative stress and neuroinflammation are highly relevant to the pathological processes of various neurodegenerative diseases including Alzheimer’s disease (AD). (+)-2-(1-hydroxyl-4-oxocyclohexyl) ethyl caffeate (HOEC), a novel 5-lipoxygenase inhibitor, was isolated from the whole plant of Incarvillea mairei var granditlora (Wehrhahn) Grierson. In this study, we investigated the protective effect of HOEC on hydrogen peroxide (H2O2) and lipopolysaccharide (LPS) -induced cytotoxicity and neuroinflammation in vitro and in vivo. MTT assay, LDH release assay, morphological observation and Hoechst 33342/PI dual staining followed by EIA, immunofluorescence staining and Western Blotting analysis were performed to elucidate the neuroprotective effect of HOEC. Treatment with HOEC at various concentrations prior to H2O2 exposure significantly enhanced cell viability, decreased LDH release, prevented cell morphologic changes and apoptosis. Instead of PGE2 reduction, HOEC markedly inhibited the production of LTB4 and suppressed the macrophage-mediated neurotoxicity. Western blotting and immunofluorescence staining showed that HOEC inhibited H2O2-induced p38 phosphorylation and NF-ΚB activation. Neuroprotective effect of HOEC was abolished by a p38 inhibitor. Further in vivo studies of LPS-induced neuroinflammation confirmed the anti-inflammatory effects of HOEC. These findings that HOEC protects SH-SY5Y cells from H2O2 and LPS-induced injury via arachidonic acid network modulation followed by p38 MAPK and NF-ΚB signaling, might make HOEC be considered as a therapeutic candidate for prevention and treatment of neurodegenerative diseases involving oxidative stress or/and inflammation.

Social development, better living conditions and medical advances lead to the fact that more people have the opportunity to live longer than in the past. The aging population is a characteristic feature of demographic trends in developed countries. This trend is closely linked with the issue of increasing number of diseases in old age and increasing government expenditure on health and social care. The most frequently mentioned diseases in old age include dementia. The cause may lie in all kinds of diseases, the most common are Alzheimer's disease and cerebrovascular disease. Now the care of current 35 million patients with dementia costs over $ 600 billion per year, it is approximately one percent of global Gross Domestic Product. This review discusses the recent issues and questions in the area of social and economic aspects of Alzheimer's disease. It focuses in detail on the national strategies in the approach to Alzheimer's disease, the anticipated problems concerning the insufficient number of social workers and necessary expenses of state budgets in the future. The situation in the area of health insurance companies' expenditures is illustrated in the context of the analysis of long-term care systems, in the chosen countries within the European Union.