Current Alzheimer Research - Volume 10, Issue 2, 2013

Alzheimer disease (AD) is one of the most common and serious neurodegenerative disorders in humans. For this reason, the search for new anti-AD treatments is a very active area. Only few biological receptors associated with AD have been well studied. The efficacy of the current drugs is limited by the fact that they inhibit only one target like protein. Thus, the rational design of new drug candidates as versatile inhibitors for different proteins associated with AD, constitutes a major goal. With the aim to overcome this problem, we developed here the first fragment-based approach by exploring quantitative-structure-activity relationships (QSAR). The principal purpose was the in silico design of multitarget (mt) inhibitors against five proteins associated with AD. Our approach was focused on the construction of an mt- QSAR discriminant model using a large and heterogeneous database of compounds and substructural descriptors, which permitted the simultaneous classification and prediction of inhibitors against five proteins associated with AD. The model correctly classified more than 90% of active and inactive compounds in both, training and prediction series. As principal advantage, this mt-QSAR discriminant model was used for the automatic and fast extraction of fragments responsible for the inhibitory activity against the five proteins under study, and new molecular entities were suggested as possible versatile inhibitors for these proteins.

The availability of an accurate genetic test to identify Huntington's Disease (HD) in the pre-symptomatic stage makes HD an important model to develop biomarkers for other neurodegenerative diseases, such as pre-clinical Alzheimer's Disease. We reasoned that functional changes, measured by functional MRI (fMRI), would precede gray matter changes and that performing a task specifically affected by the disease would carry the clearest signature. Separate cohorts of HD gene mutations carriers and controls performed four different fMRI tasks, probing functions either primarly affected by the disease (i.e. motor control), higher cognitive functions (i.e. working memory and irritability), or basic sensory functions (i.e. auditory system). With the aim to compare fMRI and structural MRI biomarkers, all subjects underwent an additional high-resolution T1-weighted MRI. Best classification performance was achived from fMRI-based activations with motor sequence tapping and task-induced irritation. Classification performance based on gray matter probability maps was also significantly above chance and similar to that of fMRI. Both were sufficiently informative to separate gene mutation carriers that were on average 17 years before predicted disease onset from controls with up to 80% accuracy. Further analyses showed that classification accuracy was best in regions of interest with low within-group heterogeneity in relation to disease specific changes. Our study indicates that structural and some functional markers can accurately detect pre-clinical neurodegeneration. However, the lower variability and easier processing of the strucutral MRI data make latter the more useful tool for disease detection in a clinical setting.

Inhibition of the β-secretase, BACE1, which cleaves amyloid precursor protein (APP) to produce β-amyloid protein (Aβ), is thought to be a feasible therapeutic strategy for Alzheimer's disease. Reticulon (RTN) proteins such as RTN3 have been identified as membrane proteins that interact with BACE1 and inhibit its Aβ-generating activity. In this study, we investigated whether RTN3 can regulate Aβ production in vivo, using transgenic (Tg) mice expressing APP with Swedish and London mutations (APP Tg mice) and those expressing RTN3; the latter mice showed ˜1.4-fold higher expression levels of RTN3 protein in the cerebral cortex than non-Tg controls. We analyzed the brains of single APP Tg and double APP/RTN3 Tg mice at the age of approximately 15 months. The levels of secreted APP-β, a direct BACE1 cleavage product of APP, in Tris-soluble fraction were considerably reduced in the hippocampus and cerebral cortex of APP/RTN3 Tg mice relative to those in APP Tg mice. Immunohistochemical analyses demonstrated that Aβ burden and plaques were significantly (by approximately 50%) decreased in both the hippocampus and cerebral cortex of double Tg mice compared to APP Tg mice. Furthermore, the levels of guanidine-soluble Aβ40 and Aβ42 in these brain regions of APP/RTN3 Tg mice were relatively lower than those in APP Tg mice. These findings indicate that even a small increase in RTN3 expression exerts suppressive effects on amyloidogenic processing of APP and Aβ accumulation through modulation of BACE1 activity in vivo, and suggest that induction of RTN3 might be an effective therapeutic strategy against Alzheimer's disease.

Several lines of evidence suggest that the initial events of amyloid-β peptide (Aβ) oligomerization and deposition in Alzheimer's disease (AD) involve the interaction of soluble oligomers with neuronal membranes. In this study, we show that Aβ42 oligomers are recruited to lipid rafts, which are ordered membrane microdomains rich in cholesterol and gangliosides, resulting in lipid peroxidation, Ca2+ dyshomeostasis and membrane permeabilization in primary fibroblasts from familial AD patients (FAD) bearing APPVal717Ile, PS-1Leu392Val or PS-1Met146Leu gene mutations. Moreover, the presence of significantly higher levels of lipid peroxidation correlated with greater structural modification in detergent resistant domains (DRMs) isolated from APP and PS-1 fibroblasts, compared to WT fibroblasts from healthy subjects. Modulation of raft GM1, including modest depletion of GM1 content and interference with GM1 exposure or negative charge, precluded the interaction of amyloid aggregates with the plasma membrane and the resulting cell damage in FAD fibroblasts and rat brains cortical neurons. These findings suggest a specific role for raft domains as primary mediators of amyloid toxicity in AD neurons.

It was suggested that the gene encoding for sorLa, (SORL1) may affect Alzheimer's disease (LOAD) through a female-specific mechanism. The aims of this study were to confirm the role of gender in modulating the association between SORL1 and LOAD and to ascertain the influence of SORL1 on cognitive impairment, neuropsychiatric symptoms (BPSD) and secretion of pro-inflammatory cytokines. Ninety six outpatients with LOAD and 120 unrelated controls were genotyped for APOE and three SNPs at the 5' end of SORL1(intron 6): SNP 8 (rs668387); SNP 9 (rs68902); SNP 10 (rs641120). Clinical evaluation was made with the MMSE, Neuropsychiatric Inventory (NPI) and Cornell Scale for Depression in Dementia (CDDS). ELISPOT assays were used to measure pro-inflammatory cytokine (TNF-alpha; IL-6; IL-1beta; IFN-gamma) production in peripheral blood mononuclear cell (PBMC) supernatant from AD patients. SORL1 SNPs were not associated with LOAD in overall sample. Instead the G-alleles at SNPs 9 (p=0.015) and 10 (p=0.015) and the CGG haplotype (p=0.02) were associated with LOAD in the women subgroup. The TAA haplotype was marginally protective in AD patients being associated with lower BPSD scores (p=0.01). The same haplotype was also associated with higher IL-1beta (p=0.01) production. These genetic effects were not modified by APOE4 allele and controlled for illness duration and treatment. In conclusion, SORL1 does not appear to be a major risk factor for LOAD. Its contribution could be underestimated in our small sample. Sex-specific factors could modulate the association between SORL1 and AD. The influence of SORL1 variants on production of inflammatory cytokines warrants further investigation.

Multifunctional mitochondrial enzyme 17β-hydroxysteroid dehydrogenase type 10 plays a role in the development of Alzheimer's disease. However, changes in its expression in the brain or cerebrospinal fluid are not fully specific for this type of dementia. Our previous study revealed that complexes of the enzyme and amyloid β in cerebrospinal fluid could serve as a more specific biomarker of Alzheimer's disease than either the enzyme or amyloid β individually when compared to autoimmune multiple sclerosis. In this study, enzyme-linked immunosorbent assay and the surface plasmon resonance biosensor method were used to analyse cerebrospinal fluid of patients with various neuroinflammatory diseases. Significant differences in the levels of the total enzyme, complexes, amyloid β 1-42 and total τ/phospho-τ were found in Alzheimer's disease patients while differences in complexes, total amyloid β and amyloid β 1- 42 were observed in patients with neuroinflammatory diseases (except for multiple sclerosis) when compared to nonneuroinflammatory controls. The interactions of the enzyme with amyloid β appeared to depend strongly on neuroinflammation-sensitive amyloid β. Our data demonstrated that oligomerisation/aggregation of intracellular amyloid β peptides was important in Alzheimer's disease while extracellular amyloid β could play a role in neuroinflammatory diseases. Phospho-τ is currently the best biomarker of Alzheimer's disease.

Increased concentrations of pro-inflammatory blood cytokines and plasma homocysteine (Hcy) are frequently reported in Alzheimer's disease (AD). Hcy appears to have immunomodulating and pro-inflammatory activities. Further, emerging evidence from animal and non-AD human studies implicates Hcy in potentiating the activities of proinflammatory cytokines; Hcy toxicity may also, in part, be mediated by these cytokines. As little is known about the potential relationship between these inflammatory markers specific to AD, the aim of this study was to assess potential impact of Hcy on the widely reported increases in cytokine concentrations in AD. Blood concentrations of two proinflammatory cytokines, IL-1β and TNF-α, along with Hcy were assessed in 40 AD patients and 30 cognitively intact controls. Mean blood concentrations of IL-1β and TNF-α differed significantly between the AD and control groups (p=0.001 and p<0.001 resp). This difference survived adjustment for age and gender on logistic regression. Hcy was significantly correlated with age only in the patient (rs=0.38, p=0.02) but not the control group. There was no significant correlation between IL-1β and Hcy, and between TNF-α, and Hcy in either the AD or the control group. Hence, our AD data did not replicate results obtained from animal and non-AD human studies which have linked pro-inflammatory cytokines concentrations to Hcy. A different inflammatory focus may exist in AD which may be influenced at least in a significant part by non-vascular pathogenesis. However, these results indirectly support the notion that the observed mild hyperhocysteinemia in AD may be due to non-inflammatory factors.

Mild cognitive impairment (MCI) is considered a nosological entity or a translational state between normal aging and sporadic Alzheimer's disease (AD). From brain tissue to peripheral blood samples, it is evident that the early markers of metabolic dysfunction observed in AD have also been found in MCI subjects. These observations obtained from MCI and AD subjects leave open the possibility that mitochondrial dysfunction-induced oxidative damage happening a priori of symptom onset, may trigger other pathological hallmarks, namely Aβ oligomerization. In this study, we used a citoplasmic hybrid (cybrid) model created by the repopulation of human teratocarcinoma (NT2) cells depleted of endogenous mitochondrial DNA (mtDNA) with platelets from age-matched controls, MCI and AD subjects. We found mitochondrial deficits in MCI and AD cybrids as compared with controls, such as a decrease in cytochrome c oxidase (COX) activity, a decrease in mitochondrial membrane potential and in mitochondrial cytochrome c content. Consequently, we analyzed parameters of oxidative damage and found that AD and MCI cybrids exhibit an increase in lipid peroxides, higher production of superoxide radicals, and higher content in protein carbonyls. Since our data clearly show alterations in mitochondrial-mediated oxidative damage in MCI cybrids we propose that mitochondrial dysfunction is an early event in idiopathic AD. Moreover, we found that mitochondrial Aβ oligomeric content increases in AD, which may exacerbate initial mitochondrial damage. Altogether, our data strongly supports a key role for mitochondria/ mtDNA in aged-driven AD pathology.

The link between biometals and Alzheimer's disease (AD) has been investigated with a focus on local metal accumulations. In this work, we have looked at systemic metal changes and computed a score (M-score) based on metal disarrangements to discriminate patients with AD from patients with vascular dementia (VaD) and from controls. We measured serum levels of iron, copper, ceruloplasmin, transferrin, and total antioxidant capacity (TAS), performed Apolipoprotein E (APOE) genotyping and calculated non-ceruloplasmin copper (‘free’ copper') levels, transferrin saturation, total iron binding capacity, and ceruloplasmin-transferrin ratio (Cp/Tf) in 93 patients with AD, 45 patients with VaD, and 48 controls. All subjects underwent biochemical, neuroimaging and cognitive evaluations. Significant differences were observed among the tested groups for the levels of copper, free copper, peroxides, and TAS and for the Cp/Tf with disparity in couple comparison. On this basis we created the M-score as linear combination of biometal variables and APOE genotype. Besides its ability to discriminate AD patients vs. controls (ROC AUC=90%), M-score was able to distinguish AD vs. VaD (ROC AUC=79%). Moreover, we calculated the sensitivity and the specificity for M-score and for the other significant variables: M-score reached the highest sensitivity without a relevant loss in terms of specificity. When we compared M-score with APOE genotype and Medial Temporal Atrophy score, it resulted statistically better than these diagnostic markers. In conclusion, we confirm the link between biometals and AD and suggest its potential as diagnostic tool. Further studies may elucidate its potential role as reliable diagnostic test.

Quetiapine, an atypical antipsychotic drug, is effective in treating the behavioral and psychological symptoms in Alzheimer's disease (AD). However, it is presently unclear whether quetiapine has beneficial effects on memory and whether the effects of quetiapine on psychological symptoms are associated with its effect on memory in AD. The present study was designed to examine the effect of chronic administration of quetiapine on the conditioned (generalized) anxiety that is related to learning experience of open arm exposure in the elevated T-maze (ETM) test in an amyloid precursor protein (APP)/presenilin 1 (PS1) double transgenic mouse model of AD. In a 2nd experiment, the effect of quetiapine on memory per se was investigated in a Y-maze test in AD mice. Non-transgenic and transgenic mice were treated with quetiapine in drinking water from the age of 2 months. After continuous treatment with quetiapine (5 mg/kg/day) for 10 months, mice were tested for conditioned anxiety on the ETM task. After ETM testing, the expression of brain-derived neurotrophic factor (BDNF), a neuroprotective protein, was examined by immunohistochemistry in the basolateral amygdala (BLA) and hippocampus. In the 2nd experiment, the effect of quetiapine (2.5 or 5 mg/kg/day) on the short-term memory in AD mice was tested in a Y-maze test. After 10 months of administration, quetiapine prevented the decrease of conditioned anxiety and cerebral BDNF in AD mice. In addition, quetiapine also prevented memory impairment in the Y-maze test in AD mice. These findings suggest that the therapeutic mechanism of quetiapine on anxiety in AD may be associated with its beneficial effect on memory and its neuroprotective effect on cerebral BDNF expression.

Background: The societal costs of Alzheimer's Disease (AD) are enormous and pose a great challenge for the health and social care in any society. It is of vital importance to develop and identify cost effective treatment. The aim of the study was to present a hypothetical economic model of Disease Modifying Treatment (DMT) in AD. Methods: A 20 year Markov cohort model of DMT was constructed, based on Swedish care conditions. States and progression were defined according to the Mini Mental State Examination (MMSE). Epidemiological studies of incidence of dementia, prevalence and costs of Mild Cognitive Impairment (MCI) and AD as well as conversion studies of MCI and demographic statistics were used as inputs in the model. Results: Total costs were 113,797 million SEK for patients treated with DMT vs 88,562 million SEK for untreated patients. The corresponding gained QALYs were 529,945 and 450,307 respectively, giving an incremental cost effectiveness ratio of 293,002 SEK/QALY in the base option. Survival in the model was 8.72 years with DMT and 7.77 years for untreated. With an assumed Willingness to pay (WTP) of 600,000 SEK (about 86,200 US$ and 62,000 €) per gained QALY, the model indicated cost effectiveness with DMT. The sensitivity analysis implied no cost savings with DMT, but most options indicated cost effectiveness vs. the chosen WTP. Conclusion: The main reasons for the higher costs with DMT were the costs of DMT itself and the prolonged survival with DMT. Even if costs increase with DMT, the model indicates cost effectiveness.