Neuropathology of Alzheimer's disease

The correlation between neuropathology levels and cognitive performance in centenarians

INTRODUCTION

Neuropathological substrates associated with neurodegeneration occur in brains of the oldest old. How does this affect cognitive performance?

METHODS

The 100-plus Study is an ongoing longitudinal cohort study of centenarians who self-report to be cognitively healthy; post mortem brain donation is optional. In 85 centenarian brains, we explored the correlations between the levels of 11 neuropathological substrates with ante mortem performance on 12 neuropsychological tests.

RESULTS

Levels of neuropathological substrates varied: we observed levels up to Thal-amyloid beta phase 5, Braak-neurofibrillary tangle (NFT) stage V, Consortium to Establish a Registry for Alzheimer's Disease (CERAD)-neuritic plaque score 3, Thal-cerebral amyloid angiopathy stage 3, Tar-DNA binding protein 43 (TDP-43) stage 3, hippocampal sclerosis stage 1, Braak-Lewy bodies stage 6, atherosclerosis stage 3, cerebral infarcts stage 1, and cerebral atrophy stage 2. Granulovacuolar degeneration occurred in all centenarians. Some high performers had the highest neuropathology scores.

DISCUSSION

Only Braak-NFT stage and limbic-predominant age-related TDP-43 encephalopathy (LATE) pathology associated significantly with performance across multiple cognitive domains. Of all cognitive tests, the clock-drawing test was particularly sensitive to levels of multiple neuropathologies.

Amyloid β-based therapy for Alzheimer's disease: challenges, successes and future

Amyloid β protein (Aβ) is the main component of neuritic plaques in Alzheimer's disease (AD), and its accumulation has been considered as the molecular driver of Alzheimer's pathogenesis and progression. Aβ has been the prime target for the development of AD therapy. However, the repeated failures of Aβ-targeted clinical trials have cast considerable doubt on the amyloid cascade hypothesis and whether the development of Alzheimer's drug has followed the correct course. However, the recent successes of Aβ targeted trials have assuaged those doubts. In this review, we discussed the evolution of the amyloid cascade hypothesis over the last 30 years and summarized its application in Alzheimer's diagnosis and modification. In particular, we extensively discussed the pitfalls, promises and important unanswered questions regarding the current anti-Aβ therapy, as well as strategies for further study and development of more feasible Aβ-targeted approaches in the optimization of AD prevention and treatment.

Effects of Sideritis scardica Extract on Scopolamine-Induced Learning and Memory Impairment in Mice

BACKGROUND

The neurodegenerative process in Alzheimer's disease, one of the most common types of dementia worldwide, mostly affects the cholinergic neurotransmitter system and, to a lesser extent, the monoaminergic one. The antioxidant acetylcholinesterase (AChE) and triple monoamine reuptake inhibitory activity of Sideritis scardica (S. scardica) and other Sideritis species has already been reported.

OBJECTIVE

To investigate the effects of S. scardica water extracts on the learning and memory processes, anxiety-like behavior, and locomotor activities in scopolamine (Sco)-induced dementia in mice.

METHODS

Male Albino IRC mice were used. The plant extract was administered for 11 consecutive days in the presence or absence of Sco (1 mg/kg, i.p). The behavioural performance of the animals was evaluated by passive avoidance, T-maze, and hole-board tests. The effects of extract on AChE activity, brain noradrenalin (NA), and serotonin (Sero) content, and antioxidant status were also monitored.

RESULTS

Our experimental data revealed that the S. scardica water extract caused a reduction in degree of memory impairment and anxiety-like behaviour in mice with scopolamine-induced dementia. The extract did not affect changed by the Sco AChE activity but impact reduced brain NA and Sero levels and demonstrated moderate antioxidant activity. In healthy mice we did not confirm the presence of anxiolytic-like and AChE inhibitory effects of the S. scardica water extract. The extract did not change the control Sero brain levels and reduce those of NA.

CONCLUSION

S. scardica water extract demonstrated memory preserving effect in mice with scopolamine-induced dementia and deserve further attention.

Resilience and resistance to the accumulation of amyloid plaques and neurofibrillary tangles in centenarians: An age-continuous perspective

INTRODUCTION

With increasing age, neuropathological substrates associated with Alzheimer's disease (AD) accumulate in brains of cognitively healthy individuals-are they resilient, or resistant to AD-associated neuropathologies?

METHODS

In 85 centenarian brains, we correlated NIA (amyloid) stages, Braak (neurofibrillary tangle) stages, and CERAD (neuritic plaque) scores with cognitive performance close to death as determined by Mini-Mental State Examination (MMSE) scores. We assessed centenarian brains against 2131 brains from AD patients, non-AD demented, and non-demented individuals in an age continuum ranging from 16 to 100+ years.

RESULTS

With age, brains from non-demented individuals reached the NIA and Braak stages observed in AD patients, while CERAD scores remained lower. In centenarians, NIA stages varied (22.4% were the highest stage 3), Braak stages rarely exceeded stage IV (5.9% were V), and CERAD scores rarely exceeded 2 (4.7% were 3); within these distributions, we observed no correlation with the MMSE (NIA: P = 0.60; Braak: P = 0.08; CERAD: P = 0.16).

DISCUSSION

Cognitive health can be maintained despite the accumulation of high levels of AD-related neuropathological substrates.

HIGHLIGHTS

Cognitively healthy elderly have AD neuropathology levels similar to AD patients. AD neuropathology loads do not correlate with cognitive performance in centenarians. Some centenarians are resilient to the highest levels of AD neuropathology.

Prediction of amyloid PET positivity via machine learning algorithms trained with EDTA-based blood amyloid-β oligomerization data

Background

The tendency of amyloid-β to form oligomers in the blood as measured with Multimer Detection System-Oligomeric Amyloid-β (MDS-OAβ) is a valuable biomarker for Alzheimer’s disease and has been verified with heparin-based plasma. The objective of this study was to evaluate the performance of ethylenediaminetetraacetic acid (EDTA)-based MDS-OAβ and to develop machine learning algorithms to predict amyloid positron emission tomography (PET) positivity.

Methods

The performance of EDTA-based MDS-OAβ in predicting PET positivity was evaluated in 312 individuals with various machine learning models. The models with various combinations of features (i.e., MDS-OAβ level, age, apolipoprotein E4 alleles, and Mini-Mental Status Examination [MMSE] score) were tested 50 times on each dataset.

Results

The random forest model best-predicted amyloid PET positivity based on MDS-OAβ combined with other features with an accuracy of 77.14 ± 4.21% and an F1 of 85.44 ± 3.10%. The order of significance of predictive features was MDS-OAβ, MMSE, Age, and APOE. The Support Vector Machine using the MDS-OAβ value only showed an accuracy of 71.09 ± 3.27% and F−1 value of 80.18 ± 2.70%.

Conclusions

The Random Forest model using EDTA-based MDS-OAβ combined with the MMSE and apolipoprotein E status can be used to prescreen for amyloid PET positivity.

Extracranial carotid atherosclerosis is associated with increased neurofibrillary tangle accumulation

OBJECTIVE

We sought to determine whether extracranial carotid atherosclerotic disease (ECAD) is associated with increased key neurodegenerative pathology such as neurofibrillary tangle (NFT), beta-amyloid plaque, or cerebral amyloid angiopathy (CAA) accumulation, findings associated with Alzheimer's disease (AD) and other dementias.

METHODS

Our prospective, longitudinal, clinicopathologic study, the AZSAND (Arizona study of aging and neurodegenerative disorders) and Brain and Body Donation Program, recorded the presence or absence of clinically diagnosed ECAD and performed semiquantitative density estimates of NFT, beta-amyloid plaque, and CAA at death. After adjusting for potential confounding factors determined by logistic regression analysis, histopathology density scores were evaluated in individuals with ECAD (n = 66) and those without ECAD (n = 125).

RESULTS

We found that the presence of ECAD was associated with a 21% greater NFT burden at death compared with no ECAD (P = .02). Anatomically, an increased NFT burden was seen throughout the brain regions evaluated but was significant in the temporal lobe (P < .05) and entorhinal cortex (P = .02). In addition, we found that subjects who had undergone carotid endarterectomy (CEA), the surgical treatment of ECAD (n = 32), had decreased NFT densities compared with those with ECAD who had not undergone CEA (n = 66; P = .04). In contrast to NFT, ECAD was not associated with beta-amyloid plaques or CAA density.

CONCLUSIONS

These findings indicate that ECAD is associated with the NFT burden in the temporal lobe and entorhinal cortex, which has clinical significance for AD and non-AD dementias and cognitive dysfunction. Further understanding of whether ECAD increases the risk of neurodegenerative brain changes is highly relevant because ECAD is a treatable disease that has not, otherwise, been evaluated for nor specifically treated as a dementia risk factor.

Microdissected Pyramidal Cell Proteomics of Alzheimer Brain Reveals Alterations in Creatine Kinase B-Type, 14-3-3-γ, and Heat Shock Cognate 71

Novel insights on proteins involved in Alzheimer’s disease (AD) are needed. Since multiple cell types and matrix components are altered in AD, bulk analysis of brain tissue maybe difficult to interpret. In the current study, we isolated pyramidal cells from the cornu ammonis 1 (CA1) region of the hippocampus from five AD and five neurologically healthy donors using laser capture microdissection (LCM). The samples were analyzed by proteomics using ¹⁸O-labeled internal standard and nano-high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) for relative quantification. Fold change between AD and control was calculated for the proteins that were identified in at least two individual proteomes from each group. From the 10 cases analyzed, 62 proteins were identified in at least two AD cases and two control cases. Creatine kinase B-type (CKB), 14-3-3-γ, and heat shock cognate 71 (Hsc71), which have not been extensively studied in the context of the human AD brain previously, were selected for further studies by immunohistochemistry (IHC). In hippocampus, semi-quantitative measures of IHC staining of the three proteins confirmed the findings from our proteomic analysis. Studies of the same proteins in the frontal cortex revealed that the alterations remained for CKB and 14-3-3-γ but not for Hsc71. Protein upregulation in CA1 neurons of final stage AD is either a result of detrimental, pathological effects, or from cell-specific protective response mechanisms in surviving neurons. Based on previous findings from experimental studies, CKB and Hsc71 likely exhibit protective effects, whereas 14-3-3-γ may represent a detrimental pathway. These new players could reflect pathways of importance for the development of new therapeutic strategies.

Fluorescence detection of amyloid deposits in human tissues using histochemical dyes

Recently, fluorescence microscopy becomes more available, presenting new opportunities to face several challenges of experimental biology and medicine. The study was aimed to assess the effectiveness of fluorescence microscopy for the identification of amyloid deposits in human tissues. Post-mortem samples of the myocardium (n = 12) and cerebral cortex (n = 8) obtained from subjects of both sexes aged 60–98 with verified amyloidosis were used as a material for the study. The specimens were stained using 11 different histochemical dyes and subsequently analyzed by light and fluorescence microscopy. Qualitative and quantitative analysis has shown that Thioflavin T is the most effective stain for fluorescence detection of β- and transthyretin amyloid in human tissues. Congo red staining is highly effective for the detection of transthyretin amyloidosis, however, it is ill-suited for the identification of β-amyloid plaques. It has been found that the ability of Congo red to exhibit fluorescence when binding to amyloid fibrils can be used for verification of amyloid deposits instead of the traditional polarized light microscopy. As has been first noted, methyl violet can selectively bind to β-amyloid with fluorescent complex formation. In addition, methyl violet treatment effectively reduces the autofluorescent background in the nervous tissue. This makes methyl violet staining a promising diagnostic tool for Alzheimer's-type pathology.

Age-Specific Retinal and Cerebral Immunodetection of Amyloid-β Plaques and Oligomers in a Rodent Model of Alzheimer's Disease

BACKGROUND

Amyloid-β soluble oligomers (Aβo) are believed to be the cause of the pathophysiology underlying Alzheimer's disease (AD) and are normally detected some two decades before clinical onset of the disease. Retinal pathology associated with AD pathogenesis has previously been reported, including ganglion cell loss, accumulation of Aβ deposits in the retina, and reduction of nerve fiber layer thickness as well as abnormalities of the microvasculature.

OBJECTIVE

This study's aim is to better understand the relationship between brain and retinal Aβo deposition and in particular to quantify levels of the toxic Aβo as a function of age in the retina of a rodent model of AD.

METHODS

Retinas and brain tissue from 5×FAD mice were stained with Congo red, Thioflavin-T (Th-T), and Aβ plaque-specific and Aβo-specific antibodies.

RESULTS

We show that retinas displayed an age-dependent increase of Th-T-specific amyloid fibrils. Staining with anti-Aβ antibody confirmed the presence of the Aβ plaques in all 5×FAD retinas tested. In contrast, staining with anti-Aβo antibody showed an age-dependent decrease of retinal Aβo. Of note, Aβo was observed mainly in the retinal nuclear layers. Finally, we confirmed the localization of Aβo to neurons, typically accumulating in late endosomes, indicating possible impairment of the endocytic pathway.

CONCLUSION

Our results demonstrate the presence of intraneuronal Aβo in the retina and its accumulation inversely correlated with retinal Aβ plaque deposition, indicating an age-related conversion in this animal model. These results support the development of an early AD diagnostic test targeting Aβo in the eye.

Co-Prevalence of Alzheimer's Disease and Age-Related Macular Degeneration Established by Histopathologic Diagnosis

BACKGROUND

Previous epidemiologic studies have suggested an association between AMD and AD, and several therapeutic agents are being developed based on this principle. However, prior studies have provided conflicting results due in part to their reliance on clinical diagnoses that are not based on gold-standard histopathology.

OBJECTIVE

To use histopathologic standards for diagnosis in order to determine the co-prevalence of AD among patients with and without AMD.

METHODS

This is a cross-sectional study of 157 autopsy ocular specimens from patients with and without AMD that were greater than 75 years of age at death. Sarks staging was used to document the severity of AMD, and Braak and Braak staging was used to assess the severity of AD in corresponding brain specimens. The prevalence of AD within different severities of AMD was determined using univariable and multivariable logistic regression.

RESULTS

58% of autopsy eyes had AMD. The prevalence of AD was lower in AMD subjects (63%) compared to non-AMD subjects (73%), even when grouped by severity (all p > 0.15). The likelihood of AD was significantly less in AMD subjects, even after adjusting for age and sex in multivariable analysis (OR 0.47, p = 0.049).

CONCLUSION

Histopathologic diagnoses fail to support an increase in prevalence of AD among subjects with AMD, even when disease severity is considered.

The complexity of Alzheimer's disease: an evolving puzzle

The history of Alzheimer's disease (AD) started in 1907, but we needed to wait until the end of the century to identify the components of pathological hallmarks and genetic subtypes and to formulate the first pathogenic hypothesis. Thanks to biomarkers and new technologies, the concept of AD then rapidly changed from a static view of an amnestic dementia of the presenium to a biological entity that could be clinically manifested as normal cognition or dementia of different types. What is clearly emerging from studies is that AD is heterogeneous in each aspect, such as amyloid composition, tau distribution, relation between amyloid and tau, clinical symptoms, and genetic background, and thus it is probably impossible to explain AD with a single pathological process. The scientific approach to AD suffers from chronological mismatches between clinical, pathological, and technological data, causing difficulty in conceiving diagnostic gold standards and in creating models for drug discovery and screening. A recent mathematical computer-based approach offers the opportunity to study AD in real life and to provide a new point of view and the final missing pieces of the AD puzzle.

Comorbidity of age-related macular degeneration with Alzheimer's disease: A histopathologic case-control study

Introduction

Previous studies evaluating the association between clinically diagnosed Alzheimer’s disease (AD) and age-related macular degeneration (AMD) have generated conflicting results. This study is the first to assess whether AMD prevalence is higher in AD patients than non-AD controls by using histopathology to definitively diagnose AD.

Methods

This was a retrospective case-control study utilizing diagnostic information extracted from autopsy reports of patients age 75 and above, including 115 with a neuropathological diagnosis of AD and 57 age-matched normal controls.

Results

The rate of AMD was not significantly higher in AD cases (53.0%) than in controls (59.6%) (z = 0.820, p = 0.794). AMD severity as determined by Sarks score was similar between AD patients and controls (χ² = 2.96, p = 0.706). There was also no significant association between Braak stage of AD severity and AMD (χ² = 4.55, p = 0.602).

Discussion

No significant effect of AD diagnosis or pathologic severity on AMD comorbidity was found, suggesting that any shared mechanisms between AMD and AD may be nondeterministic.

Investigating the Association Between Verbal Forgetting and Pathological Markers of Alzheimer's and Lewy Body Diseases

BACKGROUND

The percentage of verbal forgetting (VF%) measure of the Rey Auditory Verbal Learning Test (RAVLT) has been proposed to differentiate patients diagnosed clinically with Alzheimer's disease (AD) and dementia with Lewy bodies (DLB).

OBJECTIVE

To determine if VF% aligns with gold-standard biomarker and autopsy evidence of AD and DLB neuropathology.

METHODS

Clinical, cognitive, sociodemographic, and biomarker data were collected from 315 patients with baseline cognitive impairment and 485 normal controls from the Alzheimer's Disease Neuroimaging Initiative (ADNI). AD markers included reduced cerebrospinal fluid (CSF) amyloid-β, elevated total-tau and phosphorylated-tau, hippocampal atrophy, and the presence of amyloid plaques and neurofibrillary tangles at autopsy. DLB markers included reduced CSF α-synuclein, preserved hippocampus, atrophied putamen, occipital glucose metabolism, and the presence of Lewy bodies at autopsy. Cognitively impaired participants were classified as ADVF% (n = 190) or DLBVF% (n = 125) based on their RAVLT VF% scores using a 75% cut-off (≥75%  = ADVF%, <75%  = DLBVF%). Postmortem data were available for 13 ADVF% participants, 13 DLBVF% patients, and six healthy controls.

RESULTS

ADVF% and DLBVF% participants did not differ on CSF or neuroimaging biomarkers, with the exception of total tau levels which were higher in ADVF%. In the subset of participants with autopsy data, comorbid AD and DLB pathology was most frequent in ADVF% participants, and pure DLB pathology was most frequent in DLBVF% participants, however, these differences were not statistically significant.

CONCLUSION

The RAVLT VF% measure does not reliably align with AD and DLB neuropathology in ADNI participants.

Microglial response to increasing amyloid load saturates with aging: a longitudinal dual tracer in vivo μPET-study

BACKGROUND

Causal associations between microglia activation and β-amyloid (Aβ) accumulation during the progression of Alzheimer's disease (AD) remain a matter of controversy. Therefore, we used longitudinal dual tracer in vivo small animal positron emission tomography (μPET) imaging to resolve the progression of the association between Aβ deposition and microglial responses during aging of an Aβ mouse model.

METHODS

APP-SL70 mice (N = 17; baseline age 3.2-8.5 months) and age-matched C57Bl/6 controls (wildtype (wt)) were investigated longitudinally for 6 months using Aβ (18F-florbetaben) and 18 kDa translocator protein (TSPO) μPET (18F-GE180). Changes in cortical binding were transformed to Z-scores relative to wt mice, and microglial activation relative to amyloidosis was defined as the Z-score difference (TSPO-Aβ). Using 3D immunohistochemistry for activated microglia (Iba-1) and histology for fibrillary Aβ (methoxy-X04), we measure microglial brain fraction relative to plaque size and the distance from plaque margins.

RESULTS

Aβ-PET binding increased exponentially as a function of age in APP-SL70 mice, whereas TSPO binding had an inverse U-shape growth function. Longitudinal Z-score differences declined with aging, suggesting that microglial response declined relative to increasing amyloidosis in aging APP-SL70 mice. Microglial brain volume fraction was inversely related to adjacent plaque size, while the proximity to Aβ plaques increased with age.

CONCLUSIONS

Microglial activity decreases relative to ongoing amyloidosis with aging in APP-SL70 mice. The plaque-associated microglial brain fraction saturated and correlated negatively with increasing plaque size with aging.

Exercise Improves Recognition Memory and Acetylcholinesterase Activity in the Beta Amyloid-Induced Rat Model of Alzheimer's Disease

Objective

A correlation between physical exercise and cognitive improvement has been found in Alzheimer's disease (AD). This study aimed to investigate the effects of aerobic and resistance exercise on the recognition memory and acetylcholinesterase (AChE) activity in beta amyloid (Aβ) model of AD in rat.

Materials and Methods

Fifty male 8-week-old Wistar rats (250-280 g) were divided into 5 groups (n = 10 each) of control, sham surgery, Aβ-received sedentary, Aβ-received with aerobic exercise and Aβ-received with resistance exercise. AD was induced by intracerebroventricular injection of Aβ_25-35 peptide. The sham surgery group received normal saline using the same route and condition. Two groups of Aβ-received animals were trained by treadmill for aerobic exercise and by ladder for strength exercise for 8 weeks (4 days/week). Novel object recognition (NOR) task was used to assess recognitional memory in groups. AChE activity in the brain tissue was assessed using the Spectrophotometry method.

Results

There was no significant difference in memory index and AChE activity between the sham surgery and control groups (p > 0.05). Also, impairment of NOR indices was seen in the Aβ-injected sedentary rats (p < 0.05). However, both aerobic and strength training improved the exploration index in this test (p < 0.05). Further, AChE activity increased in the Aβ-injected sedentary group but declined in the aerobic and resistance exercise groups (p < 0.01).

Conclusion

Aerobic and resistance exercise could improve recognition memory and decrease AChE activity in Aβ-induced AD in rats. The decrease in AChE activity may be one of the mechanisms by which exercise improves cognition and memory in AD.

Multi-targeted directed ligands for Alzheimer's disease: design of novel lead coumarin conjugates

Alzheimer's Disease (AD) is a neurodegenerative disease characterized by central nervous system insults with progressive cognitive (memory, attention) and non-cognitive (anxiety, depression) impairments. Pathophysiological events affect predominantly cholinergic neuronal loss and dysfunctions of the dopaminergic system. The aim of the current study was to design multi-targeted directed lead structures based on the coumarin scaffold with inhibitory properties at two key enzymes in disease relevant systems, i.e. acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B). Conventional and microwave synthetic methods were utilized to synthesize coumarin scaffold-based novel morpholino, piperidino, thiophene and erucic acid conjugates. Biological assays indicated that the coumarin-morpholine ether conjugate BPR 10 was the most potent hMAO-B inhibitor. The coumarin-piperidine conjugates BPR 13 and BPR 12 were the most potent inhibitors of eeAChE at 100 μM and 1 μM, respectively. Molecular modelling studies were conducted with Accelrys^® Discovery Studio^® V3.1.1 utilising the published hMAO-B (2V61) and hAChE (4EY7) crystal structures. Compound BPR 10 occupies both the entrance and substrate cavities of the active site of MAO-B. BPR 13 resides in both the peripheral anionic site (PAS) and the catalytic anionic site (CAS) of hAChE. This study demonstrated that the coumarin scaffold serves as a promising pharmacophore for MTDLs design.

Sleep and Alzheimer's disease: A pivotal role for the suprachiasmatic nucleus

Alzheimer's disease (AD), which accounts for most of the dementia cases, is, aside from cognitive deterioration, often characterized by the presence of non-cognitive symptoms. Society is desperately in need for interventions that alleviate the economic and social burden related to AD. Circadian dysrhythmia, one of these symptoms in particular, immensely decreases the self-care ability of AD patients and is one of the main reasons of caregiver exhaustion. Studies suggest that these circadian disturbances form the root of sleep-wake problems, diagnosed in more than half of AD patients. Sleep abnormalities have generally been considered merely a consequence of AD pathology. Recent evidence suggests that a bidirectional relationship exists between sleep and AD, and that poor sleep might negatively impact amyloid burden, as well as cognition. The suprachiasmatic nucleus (SCN), the main circadian pacemaker, is subjected to several alterations during the course of the disease. Its functional deterioration might fulfill a crucial role in the relation between AD pathophysiology and the development of sleep abnormalities. This review aims to give a concise overview of the anatomy and physiology of the SCN, address how AD pathology precisely impacts the SCN and to what degree these alterations can contribute to the progression of the disease.

Multimodality Review of Amyloid-related Diseases of the Central Nervous System

Amyloid-β (Aβ) is ubiquitous in the central nervous system (CNS), but pathologic accumulation of Aβ results in four distinct neurologic disorders that affect middle-aged and elderly adults, with diverse clinical presentations ranging from chronic debilitating dementia to acute life-threatening intracranial hemorrhage. The characteristic imaging patterns of Aβ-related CNS diseases reflect the pathophysiology of Aβ deposition in the CNS. Aβ is recognized as a key component in the neuronal damage that characterizes the pathophysiology of Alzheimer disease, the most common form of dementia. Targeted molecular imaging shows pathologic accumulation of Aβ and tau protein, and fluorine 18 fluorodeoxyglucose positron emission tomography and anatomic imaging allow differentiation of typical patterns of neuronal dysfunction and loss in patients with Alzheimer disease from those seen in patients with other types of dementia. Cerebral amyloid angiopathy (CAA) is an important cause of cognitive impairment and spontaneous intracerebral hemorrhage in the elderly. Hemorrhage and white matter injury seen at imaging reflect vascular damage caused by the accumulation of Aβ in vessel walls. The rare forms of inflammatory angiopathy attributed to Aβ, Aβ-related angiitis and CAA-related inflammation, cause debilitating neurologic symptoms that improve with corticosteroid therapy. Imaging shows marked subcortical and cortical inflammation due to perivascular inflammation, which is incited by vascular Aβ accumulation. In the rarest of the four disorders, cerebral amyloidoma, the macroscopic accumulation of Aβ mimics the imaging appearance of tumors. Knowledge of the imaging patterns and pathophysiology is essential for accurate diagnosis of Aβ-related diseases of the CNS. (©)RSNA, 2016.

Fingolimod modulates multiple neuroinflammatory markers in a mouse model of Alzheimer's disease

Sphingosine 1-phosphate (SP1) receptors may be attractive targets for modulation of inflammatory processes in neurodegenerative diseases. Recently fingolimod, a functional S1P1 receptor antagonist, was introduced for treatment of multiple sclerosis. We postulated that anti-inflammatory mechanisms of fingolimod might also be protective in Alzheimer’s disease (AD). Therefore, we treated a mouse model of AD, the 5xFAD model, with two doses of fingolimod (1 and 5 mg/kg/day) and measured the response of numerous markers of Aβ pathology as well as inflammatory markers and neurochemistry using biochemical, immunohistochemistry and high resolution magic angle spinning magnetic resonance spectroscopy (MRS). In mice at 3 months of age, we found that fingolimod decreased plaque density as well as soluble plus insoluble Aβ measured by ELISA. Fingolimod also decreased GFAP staining and the number of activated microglia. Taurine has been demonstrated to play a role as an endogenous anti-inflammatory molecule. Taurine levels, measured using MRS, showed a very strong inverse correlation with GFAP levels and ELISA measurements of Aβ, but not with plaque density or activated microglia levels. MRS also showed an effect of fingolimod on glutamate levels. Fingolimod at 1 mg/kg/day provided better neuroprotection than 5 mg/kg/day. Together, these data suggest a potential therapeutic role for fingolimod in AD.

[Clinically validated molecular biomarkers of neurodegenerative dementia]

As cerebrospinal fluid-based neurochemical dementia diagnostics (CSF-NDD) has now been validated at the S3 evidence level, the German Association for Psychiatry, Psychotherapy and Psychosomatics (DGPPN) and the German Society for Neurology (DGN) recommend CSF-NDD in the recent joint dementia guidelines for improved early and differential diagnostics of multigenic (sporadic) Alzheimer's dementia (AD). The CSF-NDD also provides a predictive diagnosis of incipient AD for high-risk patients when they are still in the prodromal stage of mild cognitive impairment (MCI) but as no (secondary) preventive therapy of AD is currently available, the use of CSF-NDD for the predictive molecular diagnosis of AD is not recommended in the neuropsychiatry guidelines (http://www.DGPPN.de). However, molecular diagnostics of preclinical AD by CSF-NDD and/or [18F]-amyloid positron emission tomography (PET) has meanwhile gained high clinical relevance for therapeutic clinical research, as this novel clinical model allows systematic screening for promising (secondary) preventive therapy options. Moreover, it has now become apparent that blood-based neurochemical diagnostics of preclinical and early AD will be possible by means of various formats of multiplex assays. However, so far promising blood assays have not been consistently validated by independent research groups and in contrast to CSF-NDD a blood-based diagnosis of AD is not yet available.

Salvia miltiorrhiza: A source for anti-Alzheimer's disease drugs

CONTEXT

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that affects millions of elderly people worldwide. However, no efficient therapeutic method for AD has yet been developed. Recently, Salvia miltiorrhiza Bunge (Lamiaceae), a well-known traditional Chinese medicine which is widely used for treating cardio-cerebrovascular, exerts multiple neuroprotective effects and is attracting increased attention for the treatment of AD.

OBJECTIVE

The objective of this study is to discuss the neuroprotective effects and neurogenesis-inducing activities of S. miltiorrhiza components.

METHODS

A detailed search using major electronic search engines (such as Pubmed, ScienceDirect, and Google Scholar) was undertaken with the search terms: Salvia miltiorrhiza, the components of S. miltiorrhiza such as salvianolic acid B, salvianolic acid A, danshensu, tanshinone I, tanshinone IIA, cryptotanshinone, dihydrotanshinone, and neuroprotection.

RESULTS

Salvia miltiorrhiza components exert multiple neuroprotective potentials relevant to AD, such as anti-amyloid-β, antioxidant, anti-apoptosis, acetylcholinesterase inhibition, and anti-inflammation. Moreover, S. miltiorrhiza promotes neurogenesis of neural progenitor cells/stem cells in vitro and in vivo.

CONCLUSIONS

The properties of S. miltiorrhiza indicate their therapeutic potential in AD via multiple mechanisms. In addition, S. miltiorrhiza provides lead compounds for developing new drugs against AD.

The role of microglia in human disease: therapeutic tool or target?

Microglia have long been the focus of much attention due to their strong proliferative response (microgliosis) to essentially any kind of damage to the CNS. More recently, we reached the realization that these cells play specific roles in determining progression and outcomes of essentially all CNS disease. Thus, microglia has ceased to be viewed as an accessory to underlying pathologies and has now taken center stage as a therapeutic target. Here, we review how our understanding of microglia's involvement in promoting or limiting the pathogenesis of diseases such as amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, multiple sclerosis, X-linked adrenoleukodystrophy (X-ALD) and lysosomal storage diseases (LSD) has changed over time. While strategies to suppress the deleterious and promote the virtuous functions of microglia will undoubtedly be forthcoming, replacement of these cells has already proven its usefulness in a clinical setting. Over the past few years, we have reached the realization that microglia have a developmental origin that is distinct from that of bone marrow-derived myelomonocytic cells. Nevertheless, microglia can be replaced, in specific situations, by the progeny of hematopoietic stem cells (HSCs), pointing to a strategy to engineer the CNS environment through the transplantation of modified HSCs. Thus, microglia replacement has been successfully exploited to deliver therapeutics to the CNS in human diseases such as X-ALD and LSD. With this outlook in mind, we will discuss the evidence existing so far for microglial involvement in the pathogenesis and the therapy of specific CNS disease.

Neuroimaging and the search for a cure for Alzheimer disease

As radiologists, our role in the workup of the dementia patient has long been limited by the sensitivity of our imaging tools and lack of effective treatment options. Over the past 30 years, we have made tremendous strides in understanding the genetic, molecular, and cellular basis of Alzheimer disease (AD). We now know that the pathologic features of AD are present 1 to 2 decades prior to development of symptoms, though currently approved symptomatic therapies are administered much later in the disease course. The search for true disease-modifying therapy continues and many clinical trials are underway. Current outcome measures, based on cognitive tests, are relatively insensitive to pathologic disease progression, requiring long, expensive trials with large numbers of participants. Biomarkers, including neuroimaging, have great potential to increase the power of trials by matching imaging methodology with therapeutic mechanism. One of the most important advances over the past decade has been the development of in vivo imaging probes targeted to amyloid beta protein, and one agent is already available for clinical use. Additional advances include automated volumetric imaging methods to quantitate cerebral volume loss. Use of such techniques in small, early phase trials are expected to significantly increase the number and quality of candidate drugs for testing in larger trials. In addition to a critical role in trials, structural, molecular, and functional imaging techniques can give us a window on the etiology of AD and other neurodegenerative diseases. This combination of developments has potential to bring diagnostic radiology to the forefront in AD research, therapeutic trials, and patient care.

Model Hirano bodies protect against tau-independent and tau-dependent cell death initiated by the amyloid precursor protein intracellular domain

The main pathological hallmarks of Alzheimer's disease are amyloid-beta plaques and neurofibrillary tangles, which are primarily composed of amyloid precursor protein (APP) and tau, respectively. These proteins and their role in the mechanism of neurodegeneration have been extensively studied. Hirano bodies are a frequently occurring pathology in Alzheimer's disease as well as other neurodegenerative diseases. However, the physiological role of Hirano bodies in neurodegenerative diseases has yet to be determined. We have established cell culture models to study the role of Hirano bodies in amyloid precursor protein and tau-induced cell death mechanisms. Exogenous expression of APP and either of its c-terminal fragments c31 or Amyloid Precursor Protein Intracellular Domain c58 (AICDc58) enhance cell death. The presence of tau is not required for this enhanced cell death. However, the addition of a hyperphosphorylated tau mimic 352PHPtau significantly increases cell death in the presence of both APP and c31 or AICDc58 alone. The mechanism of cell death induced by APP and its c-terminal fragments and tau was investigated. Fe65, Tip60, p53, and caspases play a role in tau-independent and tau-dependent cell death. In addition, apoptosis was determined to contribute to cell death. The presence of model Hirano bodies protected against cell death, indicating Hirano bodies may play a protective role in neurodegeneration.

Cotinine: a potential new therapeutic agent against Alzheimer's disease

Tobacco smoking has been correlated with a lower incidence of Alzheimer's disease (AD). This negative correlation has been attributed to nicotine's properties. However, the undesired side-effects of nicotine and the absence of clear evidence of positive effects of this drug on the cognitive abilities of AD patients have decreased the enthusiasm for its therapeutic use. In this review, we discuss evidence showing that cotinine, the main metabolite of nicotine, has many of the beneficial effects but none of the negative side-effects of its precursor. Cotinine has been shown to be neuroprotective, to improve memory in primates as well as to prevent memory loss, and to lower amyloid-beta (Aβ)) burden in AD mice. In AD, cotinine's positive effect on memory is associated with the inhibition of Aβ aggregation, the stimulation of pro-survival factors such as Akt, and the inhibition of pro-apoptotic factors such as glycogen synthase kinase 3 beta (GSK3β). Because stimulation of the α7 nicotinic acetylcholine receptors (α7nAChRs) positively modulates these factors and memory, the involvement of these receptors in cotinine's effects are discussed. Because of its beneficial effects on brain function, good safety profile, and nonaddictive properties, cotinine may represent a new therapeutic agent against AD.

Subjective cognition and amyloid deposition imaging: a Pittsburgh Compound B positron emission tomography study in normal elderly individuals

OBJECTIVE

To study the relationship between subjective cognition and the neuropathological hallmark of Alzheimer disease (AD), amyloid-β (Aβ) deposition, using carbon 11-labeled Pittsburgh Compound B (PiB) positron emission tomography in normal elderly individuals.

DESIGN

Cross-sectional analysis.

SUBJECTS

Forty-eight cognitively normal elderly subjects (11 with high PiB uptake and 28 with low PiB uptake) were included. All underwent clinical and neuropsychological evaluations, magnetic resonance imaging, and positron emission tomography.

SETTING

Berkeley Aging Cohort Study.

MAIN OUTCOME MEASURE

Relationship between PiB uptake and subjective cognition measures.

RESULTS

Subjects with high PiB uptake showed significantly lower performance than those with low PiB uptake on an episodic memory measure and were less confident about their general memory abilities when required to evaluate themselves relative to other people of the same age. High and low PiB uptake groups did not differ on the accuracy of their cognitive self-reports compared with objective cognitive performance. General memory self-reports from the whole group were significantly correlated with regional PiB uptake in the right medial prefrontal cortex and anterior cingulate cortex and in the right precuneus and posterior cingulate cortex. Reduced confidence about memory abilities was associated with greater PiB uptake in these brain regions. All results were independent of demographic variables and depressive affects.

CONCLUSIONS

A decrease of self-confidence about memory abilities in cognitively normal elderly subjects may be related to the neuropathological hallmark of AD measured with PiB-positron emission tomography. Subjective cognitive impairment may represent a very early clinical manifestation of AD.

Formulation development and systematic optimization of solid lipid nanoparticles of quercetin for improved brain delivery

Objective

This study aims at formulating solid lipid nanoparticles (SLNs) of quercetin, a natural flavonoid with established antioxidant activity, for intravenous administration in order to improve its permeation across the blood–brain barrier into the CNS, and eventually to improve the therapeutic efficacy of this molecule in Alzheimer's disease.

Methods

The SLNs of quercetin were formulated using Compritol as the lipid and Tween 80 as the surfactant through a microemulsification technique, and optimized employing a 32 central composite design (CCD). Selection of the optimized SLN formulation, using brute-force methodology and overlay plots, was based on its efficiency of entrapping quercetin inside the lipophilic core, particle size, surface charge potential and ability of the SLNs to release the entrapped drug completely. The optimized formulation was subjected to various in-vivo behavioral and biochemical studies in Wistar rats.

Key findings

The optimized formulation exhibited a particle size of less than 200 nm, 85.73% drug entrapment efficiency and a zeta potential of 21.05 mV. In all the in-vivo behavioral and biochemical experiments, the rats treated with SLN-encapsulated quercetin showed markedly better memory-retention vis-à-vis test and pure quercetin-treated rats.

Conclusions

The studies demonstrated successful targeting of the potent natural antioxidant, quercetin, to brain as a novel strategy having significant therapeutic potential to treat Alzheimer's disease.

Characterization of the 3xTg-AD mouse model of Alzheimer's disease: part 1. Circadian changes

Circadian disturbances, including a fragmented sleep-wake pattern and sundowning, are commonly reported early in the progression of Alzheimer's disease (AD). These changes are distinctly different from those observed in non-pathological aging. Transgenic models of AD are a promising tool in understanding the underlying mechanisms and cause of disease. A novel triple-transgenic model of AD, 3xTg-AD, is the only model to exhibit both Abeta and tau pathology, and mimic human AD. The present study characterized changes pertaining to circadian rhythmicity that occur prior to and post-AD pathology. Both male and female 3xTg-AD mice demonstrated alterations to their circadian pacemaker with decreased nocturnal behavior when compared to controls. Specifically, males showed greater locomotor activity during the day and shorter freerunning periods prior to the onset of AD-pathology, and females had a decrease in activity levels during their typical active phase. Both sexes did not differ in terms of their freerunning periods or photic phase shifting ability. A decrease in vasoactive intestinal polypeptide-containing and vasopressin-containing cells was observed in the suprachiasmatic nucleus of 3xTg-AD mice relative to controls. This study demonstrates that abnormalities in circadian rhythmicity in 3xTg-AD mice precede expected AD pathology. This suggests that human studies may wish to determine if similar circadian dysfunction is predictive of early-onset AD.

Multiphoton in vivo imaging of amyloid in animal models of Alzheimer's disease

Amyloid-beta (Abeta) deposition is a defining feature of Alzheimer's disease (AD). The toxicity of Abeta aggregation is thought to contribute to clinical deficits including progressive memory loss and cognitive dysfunction. Therefore, Abeta peptide has become the focus of many therapeutic approaches for the treatment of AD due to its central role in the development of neuropathology of AD. In the past decade, taking the advantage of multiphoton microscopy and molecular probes for amyloid peptide labeling, the dynamic progression of Abeta aggregation in amyloid plaques and cerebral amyloid angiopathy has been monitored in real time in transgenic mouse models of AD. Moreover, amyloid plaque-associated alterations in the brain including dendritic and synaptic abnormalities, changes of neuronal and astrocytic calcium homeostasis, microglial activation and recruitment in the plaque location have been extensively studied. These studies provide remarkable insight to understand the pathogenesis and pathogenicity of amyloid plaques in the context of AD. The ability to longitudinally image plaques and related structures facilitates the evaluation of therapeutic approaches targeting toward the clearance of plaques.

Cardiovascular dementia - a different perspective

The number of dementia patients has been growing in recent years and dementia represents a significant threat to aging people all over the world. Recent research has shown that the number of people affected by Alzheimer's disease (AD) and dementia is growing at an epidemic pace. The rapidly increasing financial and personal costs will affect the world's economies, health care systems, and many families. Researchers are now exploring a possible connection among AD, vascular dementia (VD), diabetes mellitus (type 2, T2DM) and cardiovascular diseases (CD). This correlation may be due to a strong association of cardiovascular risk factors with AD and VD, suggesting that these diseases share some biologic pathways. Since heart failure is associated with an increased risk of AD and VD, keeping the heart healthy may prove to keep the brain healthy as well. The risk for dementia is especially high when diabetes mellitus is comorbid with severe systolic hypertension or heart disease. In addition, the degree of coronary artery disease (CAD) is independently associated with cardinal neuropathological lesions of AD. Thus, the contribution of T2DM and CD to AD and VD implies that cardiovascular therapies may prove useful in preventing AD and dementia.

Immunohistochemical analysis of human brain suggests pathological synergism of Alzheimer's disease and diabetes mellitus

It has been extensively reported that diabetes mellitus (DM) patients have a higher risk of developing Alzheimer's disease (AD), but a mechanistic connection between both pathologies has not been provided so far. Carbohydrate-derived advanced glycation endproducts (AGEs) have been implicated in the chronic complications of DM and have been reported to play an important role in the pathogenesis of AD. The earliest histopathological manifestation of AD is the apparition of extracellular aggregates of the amyloid beta peptide (Abeta). To investigate possible correlations between AGEs and Abeta aggregates with both pathologies, we have performed an immuhistochemical study in human post-mortem samples of AD, AD with diabetes (ADD), diabetic and nondemented controls. ADD brains showed increased number of Abeta dense plaques and receptor for AGEs (RAGE)-positive and Tau-positive cells, higher AGEs levels and major microglial activation, compared to AD brain. Our results indicate that ADD patients present a significant increase of cell damage through a RAGE-dependent mechanism, suggesting that AGEs may promote the generation of an oxidative stress vicious cycle, which can explain the severe progression of patients with both pathologies.

Current concepts in Alzheimer's disease: a multidisciplinary review

This comprehensive, pedagogically-oriented review is aimed at a heterogeneous audience representative of the allied disciplines involved in research and patient care. After a foreword on epidemiology, genetics, and risk factors, the amyloid cascade model is introduced and the main neuropathological hallmarks are discussed. The progression of memory, language, visual processing, executive, attentional, and praxis deficits, and of behavioral symptoms is presented. After a summary on neuropsychological assessment, emerging biomarkers from cerebrospinal fluid assays, magnetic resonance imaging, nuclear medicine, and electrophysiology are discussed. Existing treatments are briefly reviewed, followed by an introduction to emerging disease-modifying therapies such as secretase modulators, inhibitors of Abeta aggregation, immunotherapy, inhibitors of tau protein phosphorylation, and delivery of nerve growth factor.

Mechanisms of microglia accumulation in Alzheimer's disease: therapeutic implications

In Alzheimer's disease (AD), and other conditions affecting integrity of the blood-brain barrier, microglia can originate in the bone marrow, migrate into the blood and enter the brain in a chemokine-dependent manner. CCR2, a chemokine receptor that controls mononuclear phagocyte infiltration into the brain in multiple sclerosis, bacterial meningitis and neuropathic pain, also regulates microglia accumulation in mouse models of AD. CCR2 deficiency leads to lower microglia accumulation and higher brain beta-amyloid (Abeta) levels, indicating that early microglial accumulation promotes Abeta clearance. In support of this protective role, enhancing microglia accumulation delays progression of AD. AD mice that constitutively express interleukin-1 in the brain, or that are deficient in peripheral mononuclear phagocyte transforming growth factor-beta signaling, have increased microglia accumulation around beta-amyloid plaques and reduced AD-like pathology. Regulating microglia recruitment into the brain is a novel therapeutic strategy to delay or stop progression of AD. Here, we review the role of microglia in AD and the mechanisms of their accumulation and discuss implications for AD therapy.

Microglial dysfunction and defective beta-amyloid clearance pathways in aging Alzheimer's disease mice

Early microglial accumulation in Alzheimer's disease (AD) delays disease progression by promoting clearance of beta-amyloid (Abeta) before formation of senile plaques. However, persistent Abeta accumulation despite increasing microglial numbers suggests that the ability of microglia to clear Abeta may decrease with age and progression of AD pathology. To determine the effects of aging and Abeta deposition on microglial ability to clear Abeta, we used quantitative PCR to analyze gene expression in freshly isolated adult microglia from 1.5-, 3-, 8-, and 14-month-old transgenic PS1-APP mice, an established mouse model of AD, and from their nontransgenic littermates. We found that microglia from old PS1-APP mice, but not from younger mice, have a twofold to fivefold decrease in expression of the Abeta-binding scavenger receptors scavenger receptor A (SRA), CD36, and RAGE (receptor for advanced-glycosylation endproducts), and the Abeta-degrading enzymes insulysin, neprilysin, and MMP9, compared with their littermate controls. In contrast, PS1-APP microglia had a 2.5-fold increase in the proinflammatory cytokines IL-1beta (interleukin-1beta) and tumor necrosis factor alpha (TNFalpha), suggesting that there is an inverse correlation between cytokine production and Abeta clearance. In support of this possibility, we found that incubation of cultured N9 mouse microglia with TNFalpha decreased the expression of SRA and CD36 and reduced Abeta uptake. Our data indicate that, although early microglial recruitment promotes Abeta clearance and is neuroprotective in AD, as disease progresses, proinflammatory cytokines produced in response to Abeta deposition downregulate genes involved in Abeta clearance and promote Abeta accumulation, therefore contributing to neurodegeneration. Antiinflammatory therapy for AD should take this dichotomous microglial role into consideration.

Emerging amyloid beta (Ab) peptide modulators for the treatment of Alzheimer's disease (AD)

BACKGROUND

According to the 'amyloid cascade hypothesis' of Alzheimer's disease (AD), abnormal processing of beta-amyloid precursor protein (betaAPP) into toxic amyloid beta (Abeta)-peptides is central to the etiopathology of this uniquely human brain disorder.

OBJECTIVE

To review current AD drugs, pharmacological approaches and strategies aimed at modulating Abeta-peptide generation and/or aggregation in the treatment of AD.

METHODS

Data searches at various websites: Alzheimer Research Forum; individual drug company databases; Medline; Pharmaprojects database; unpublished research; inter-University research communications.

RESULTS/CONCLUSION

Considerable research effort has focused on secretase-mediated mechanisms of betaAPP processing, and the latest pharmacological strategies have used selective Abeta-peptide-lowering agents (SALA) to provide therapeutic benefit against Abeta-initiated neurodegenerative pathology. Currently, dedicated anticholinesterase, glutamatergic agonist and Abeta-peptide immunization have had little impact in the clinical treatment of AD. One unexpected benefit of statins (HMG-CoA inhibitors), besides their cholesterol lowering abilities, has been their ancillary effects in potentiating the enzymatic mechanisms that generate Abeta-peptides. The long-term benefits or complications of statin-based therapies for use in the clinical management of AD are not known.

Development of photocrosslinked sialic acid containing polymers for use in Abeta toxicity attenuation

beta-Amyloid peptide (Abeta), the primary protein component in senile plaques associated with Alzheimer's disease (AD), has been implicated in neurotoxicity associated with AD. Previous studies have shown that the Abeta-neuronal membrane interaction plays a crucial role in Abeta toxicity. More specifically, it is thought that Abeta interacts with ganglioside rich and sialic acid rich regions of cell surfaces. In light of such evidence, we have hypothesized that the Abeta-membrane sialic acid interaction could be inhibited through use of a biomimic multivalent sialic acid compound that would compete with the cell surface for Abeta binding. To explore this hypothesis, we synthesized a series of photocrosslinked sialic acid containing oligosaccharides and tested their ability to bind Abeta and attenuate Abeta toxicity in cell culture assays. We show that a polymer prepared via the photocrosslinking of disialyllacto-N-tetraose (DSLNT) was able to attenuate Abeta toxicity at low micromolar concentrations without adversely affecting the cell viability. Polymers prepared from mono-sialyl-oligosaccharides were less effective at Abeta toxicity attenuation. These results demonstrate the feasibility of using photocrosslinked sialyl-oligosaccharides for prevention of Abeta toxicity in vitro and may provide insight into the design of new materials for use in attenuation of Abeta toxicity associated with AD.

Immunophenotypes in the circulation of patients with mild cognitive impairment

Alterations in the peripheral immune system are associated with dementia and the neuropathology of Alzheimer's disease, but have yet to be studied early in the disease process. To test the hypothesis that the balance of immune cell phenotypes is disrupted in the early progression of memory deterioration, patients with mild cognitive impairment (MCI) and healthy elderly controls were examined for the distribution of subpopulations of leukocytes (lymphocytes, granulocytes, and monocytes) and lymphocyte subtypes (helper/inducer and suppressor/cytotoxic T lymphocytes and B lymphocytes) in blood. MCI subjects had a significantly higher percentage of total lymphocytes and a lower percentage of granulocytes compared to elderly controls. Furthermore, the expression of cell surface amyloid precursor protein (APP) and intracellular amyloid-beta peptide (Abeta) in lymphocytes and monocytes were determined. We found lymphocyte APP expression to be significantly increased in MCI subjects compared to controls. Our data indicate that changes in immunological parameters may be detected early in MCI, and an alteration of the immune response may precede clinical AD.

Neuropathology for the neuroradiologist: plaques and tangles

Histologically identified intracellular and extracellular inclusions and structures often provide a tissue diagnosis of a specific disease process. Moreover, these deposits may provide clues about the pathogenesis of the disease in which they are found. Two distinctive structures seen within the brains of patients clinically diagnosed with dementia of the Alzheimer type are extracellular plaques and intracellular neurofibrillary tangles. The purpose of this report is to review the significance of plaques and neurofibrillary tangles in the context of Alzheimer disease.

Reduction of sortilin-1 in Alzheimer hippocampus and in cytokine-stressed human brain cells

Sortilin 1 (SORL1) is a transmembrane sorting receptor that regulates the intracellular trafficking of beta-amyloid precursor protein (betaAPP). Interactions between SORL1 and betaAPP result in the decreased processing of betaAPP into toxic amyloid-beta42 (Abeta42) peptides that accumulate in Alzheimer's disease brain. Here, we report selectively decreased levels of SORL1 in limbic and occipital regions of Alzheimer brain that inversely correlate with amyloid plaque and neurofibrillary tangle density. Reduced SORL1, coupled to elevated beta-amyloid cleaving enzyme, presenilin-1 and increased Abeta42 peptide secretion, was observed after incubation of cultured human neural cells with the proinflammatory cytokine interleukin-1beta. The results suggest that SORL1 deficits may not only promote the pathogenic processing of betaAPP but may also contribute to Abeta42-mediated inflammatory signaling in stressed human brain cells.

Various dendritic abnormalities are associated with fibrillar amyloid deposits in Alzheimer's disease

Dystrophic neurites are associated with fibrillar amyloid deposition in Alzheimer's disease (AD), but the frequency and types of changes in synaptic structures near amyloid deposits have not been well characterized. Using high-resolution confocal microscopy to image lipophilic dye-labeled dendrites and thioflavin-S-labeled amyloid plaques, we systematically analyzed the structural changes of dendrites associated with amyloid deposition in both a transgenic mouse model of AD (PSAPP) and in human postmortem brain. We found that in PSAPP mice, dendritic branches passing through or within 40 mum from amyloid deposits displayed various dendritic abnormalities such as loss of dendritic spines, shaft atrophy, bending, abrupt branch endings, varicosity formation, and sprouting. Similar structural alterations of dendrites were seen in postmortem human AD tissue, with spine loss as the most common abnormality in both PSAPP mice and human AD brains. These results demonstrate that fibrillar amyloid deposits and their surrounding microenvironment are toxic to dendrites and likely contribute to significant disruption of neuronal circuits in AD.

The coming problem of HIV-associated Alzheimer's disease

BACKGROUND

Dementia associated with human immunodeficiency virus (HIV) is a subcortical neuropathology that does not resemble Alzheimer's disease. However, several lines of evidence suggest that in the future there may be significant numbers of long-term HIV survivors with true Alzheimer's disease. Age is itself a risk factor Alzheimer's disease, and an aging population and widespread use of highly active antiretroviral therapy (HAART) means more elderly HIV patients. Immune reconstitution inflammatory syndrome, lypodystrophic effects of HAART medications, HIV-induced amyloid deposition and excitotoxic effects of gp120 and TAT protein all could be risk factors for subsequent Alzheimer's disease. Finally, HIV patients will have greater vulnerability to common non-HIV pathogens that may contribute to development of Alzheimer's disease.

PRESENTATION OF THE HYPOTHESIS

It is predicted that in the future there will be seen measurable numbers of long-term HIV survivors on HAART who have Alzheimer's disease, with a cortical deficit profile on neuropsychological tests, pronounced cerebral atrophy seen on brain MRI, and neurofibrillary tangles, senile plaques and neuronal loss in post-mortem brain tissue. VALIDATING THE HYPOTHESIS: The hypothesis could be validated through case reports, longitudinal clinical studies, brain bank programs and animal models.

IMPLICATIONS OF THE HYPOTHESIS

Management of HIV may become more difficult, requiring greater provisions for long-term care of HIV patients with chronic dementia. However, it may be possible to reduce or prevent HIV-associated Alzheimer's disease through early use of cholinesterase inhibitors, glutamate-blocking drugs, insulin sensitizing agents, statins and anti-oxidants.

Therapeutic RNA interference for neurodegenerative diseases: From promise to progress

RNA interference (RNAi) has emerged as a powerful tool to manipulate gene expression in the laboratory. Due to its remarkable discriminating properties, individual genes, or even alleles can be targeted with exquisite specificity in cultured cells or living animals. Among its many potential biomedical applications, silencing of disease-linked genes stands out as a promising therapeutic strategy for many incurable disorders. Neurodegenerative diseases represent one of the more attractive targets for the development of therapeutic RNAi. In this group of diseases, the progressive loss of neurons leads to the gradual appearance of disabling neurological symptoms and premature death. Currently available therapies aim to improve the symptoms but not to halt the process of neurodegeneration. The increasing prevalence and economic burden of some of these diseases, such as Alzheimer's disease (AD) or Parkinson's disease (PD), has boosted the efforts invested in the development of interventions, such as RNAi, aimed at altering their natural course. This review will summarize where we stand in the therapeutic application of RNAi for neurodegenerative diseases. The basic principles of RNAi will be reviewed, focusing on features important for its therapeutic manipulation. Subsequently, a stepwise strategy for the development of therapeutic RNAi will be presented. Finally, the different preclinical trials of therapeutic RNAi completed in disease models will be summarized, stressing the experimental questions that need to be addressed before planning application in human disease.

The M694V variant of the familial Mediterranean fever gene is associated with sporadic early-onset Alzheimer's disease in an Italian population sample

BACKGROUND

Inflammation is deemed to play a crucial role in the pathogenesis of Alzheimer's disease (AD). We sought to determine whether the proinflammatory M694V mutation of pyrin, the gene responsible for familial Mediterranean fever, could lead to an increased risk for AD.

METHODS

We compared the M694V variant genotypes in 378 sporadic AD patients and 384 healthy control subjects of Italian descent.

RESULTS

After adjustment for potential confounders, the M694V mutation was found to be associated with an increased risk for AD in subjects with an age at onset of 65 years or younger (multivariate-adjusted odds ratio, OR: 3.01, 95% confidence interval, CI: 1.24-6.72, p = 0.021), but not in patients with an age at onset older than 65 years (multivariate-adjusted OR: 0.81, 95% CI: 0.34-1.99, p = 0.847). Kaplan-Meier analysis indicated that AD patients bearing the M694V mutation presented with disease onset 7 years earlier than carriers of the wild-type genotype (log rank = 41.61, p < 0.001).

CONCLUSION

Our data indicate that the M694V sequence variant in the pyrin gene might influence the age at onset of AD in the Italian population.