Current Alzheimer Research - Volume 6, Issue 3, 2009

Human memory can be split into familiarity and recollection processes which contribute to different aspects of memory function. These separate processes result in different experiential states. In this review, we examine how this dominant theoretical framework can explain the subjective experience of people with Alzheimer's disease, the profile of their memory impairments and their inability to reflect on their performance metacognitively. We conclude with a brief overview of the brain regions supporting conscious experience of memory, and propose that the memory and awareness deficits seen in Alzheimer's disease could be conceived of as a deficit in autonoetic consciousness. A future priority for research is to take these robust constructs into research programmes examining rehabilitation and pharmacological intervention.

Cancer and Alzheimer's disease (AD) are two common disorders for which the final pathophysiological mechanism is not yet clearly defined. In a prospective longitudinal study we have previously shown an inverse association between AD and cancer, such that the rate of developing cancer in general with time was significantly slower in participants with AD, while participants with a history of cancer had a slower rate of developing AD. In cancer, cell regulation mechanisms are disrupted with augmentation of cell survival and/or proliferation, whereas conversely, AD is associated with increased neuronal death, either caused by, or concomitant with, beta amyloid (Aβ) and tau deposition. The possibility that perturbations of mechanisms involved in cell survival/death regulation could be involved in both disorders is discussed. Genetic polymorphisms, DNA methylation or other mechanisms that induce changes in activity of molecules with key roles in determining the decision to “repair and live”- or “die” could be involved in the pathogenesis of the two disorders. As examples, the role of p53, Pin1 and the Wnt signaling pathway are discussed as potential candidates that, speculatively, may explain inverse associations between AD and cancer.

Alzheimer's disease (AD) is an irreversible, progressive brain disease that slowly destroys memory and thinking skills. With over 26 million patients in 2006, AD is the most prevalent neurodegenerative disease worldwide. Different hypotheses have been suggested to explain the pathogenesis of AD, like those involving inflammation, mitochondrial dysfunction or oxidative stress. Many of these studies have addressed amyloid plaque formation, tau hyperphosphorylation and apoptotic neuronal loss, the three main histopathological hallmarks of this disease. Increasing evidences, however, suggest another feature that can also be considered a neuropathological marker for AD: ectopic cell cycle re-entry. Cell cycle events have been frequently registered in the brains of AD patients. Although the exact starting point of cell cycle re-entry remains unclear, a number of subsequent cascades, which include events such as kinase upregulation, DNA replication and cytoskeletal alterations, have already been described. There are also increasing reports suggesting that cell cycle reactivation in mature neurons occurs as part of the apoptotic process. Upon a brief overview of the different theories and models addressing cell cycle reactivation in AD, we will describe possible mechanisms that trigger cell cycle re-entry, with special attention to links between this feature and the main neuropathological markers of AD. Finally, we will also analyze possible similarities between cell cycle dysregulation in AD and in other pathologies, such as Prion-Related Encephalopathies.

In different clinical studies, an association of type 2 diabetes and Alzheimer's disease (AD) has been described. However, the underlying mechanisms are still unclear. One explanation could be that vascular complications of diabetes result in neurodegeneration. Alternatively, the mechanism might be directly related to insulin and insulin-like growth factor( IGF)-1 signaling, leading to the proposal that AD is a “brain-type diabetes”. Furthermore, postmortem analyses of brains from patients with AD revealed a markedly downregulated expression of insulin receptor (IR), IGF-1 receptor (IGF-1R), insulin receptor substrate (IRS)-1 and IRS-2, and these changes progress with severity of neurodegeneration. These findings raise the question, whether this phenomenon is cause or consequence of neurodegeneration. Recently, Cohen and coworkers have show that knocking down DAF-2 in C. elegans, the homolog of the mammalian IR/IGF-1R, reduces β-amyloid(Aβ)1-42 toxicity. Cell based experiments suggest a specific role for the IGF-1/IRS-2 signaling pathway in regulating α-/β-secretase activity. Moreover circulating IGF-1 might influence Aβ clearance from the brain by promoting Aβ transport over the blood brain barrier. Interestingly, brain specific deletion of IRS-2 increases life span, suggesting that long term neuronal IGF-1R signaling might be harmful. Taken together, the data from humans and different model organisms indicate a role of IR/IGF-1R signaling in Aβ metabolism, and clearance as well as longevity. Since more studies are needed to elucidate the impact of insulin and/or IGF-1 treatment in AD, the time to propose these hormones as a potential treatment option for AD has not come yet.

Alzheimer's disease (AD) is a late-onset progressive neurodegenerative disorder which results in the irreversible loss of cortical neurons, particularly in the associative neocortex and hippocampus. AD is the most common form of dementia in the elderly. Apart from the neuronal loss, the pathological hallmarks are extracellular senile plaques, containing the peptide beta-amyloid (Aβ), and neurofibrillary tangles. The Aβ cascade hypothesis remains the main pathogenetic model, as suggested by familiar AD, mainly associated to mutation in amyloid precursor protein and presenilin genes. The remaining 95% of AD patients are mostly sporadic late-onset cases, with a complex aetiology due to interactions between environmental conditions and genetic features of the individual. A relationship between genetic and acquired vascular factors and AD has been hypothesized. Many vascular risk factors for AD, such as atherosclerosis, stroke and cardiac disease in the aging individual, could result in cerebrovascular dysfunction and trigger AD pathology. A major vascular susceptibility factor gene is the apolipoprotein E gene, found to be associated with sporadic late-onset AD cases. Another interesting vascular susceptibility gene is angiotensin converting enzyme. Other possible genes include VLDL-R, LRP, NOS3, CST3, OLR1, MTHFR, PON1 and VEGF, but many of the related studies have shown conflicting results. In this paper, we review the role of molecular vascular abnormalities and of the “vascular risk” genes supposed to be involved in the pathogenesis of AD, in an attempt to provide a comprehensive picture of what is known about the mechanisms underlying the role of vascular factors in late-onset sporadic AD.

The central role of peroxisomes in ROS and lipid metabolism and their importance in brain functioning are well established. The aim of this work was to study the modulation of peroxisomal and peroxisome-related proteins in cortical neurons in vitro challenged with chronic or acute Aβ treatment, in order to investigate whether peroxisomes represent one of the cellular target of Aβ in these cells. The expression of peroxisomal (PMP70, catalase, acyl-CoA oxidase and thiolase), peroxisome-related (PPARα, insulin-degrading enzyme) and anti-oxidant (SOD1, SOD2, GSTP1) proteins was studied. The results obtained, demonstrating an early upregulation of the peroxisomal proteins during the chronic challenge, followed by their dramatic impairment after acute challenge, suggest that peroxisomes represent one of the first line of defence against Aβ-mediated oxidative injury. Our results support the notion that substances able to activate PPARα and/or to induce peroxisomal proliferation may constitute a novel preventive and/or therapeutic tool against neurodegenerative diseases.

To better model the characteristics of crowded intracellular environments, we examined the effect of several factors known to induce partial folding and accelerated fibrillation of α-synuclein in dilute solutions, on the fibrillation of this protein in a crowded milieu. We found that low pH, certain metals and pesticides, polyanions, polycations and low concentrations of organic solvents cause a significant acceleration of α-synuclein fibrillation in the presence of high concentrations of polyethylene glycol. This suggests that the fibril-promoting effects of factors inducing partial folding of α- synuclein and the fibril-stimulating effects of macromolecular crowding are relatively independent and thus might act additively or even synergistically.

Since their first description by Ramon y Cajal at the end of the 19th century, dendritic spines have been proposed as important sites of neuronal contacts and it has been suggested that changes in the activity of neurons directly affect spine morphology. In fact, since then it has been shown that about 90% of excitatory synapses end on spines. Recent data indicate that spines are highly dynamic structures and that spine shape correlates with the strength of synaptic transmission. Furthermore, several mental disorders including Alzheimer's disease (AD) are associated with spine pathology suggesting that spine alterations play a central role in mental deficits. The aim of this review is to provide an overview about the current knowledge on spine morphology and function as well as about different experimental models to analyze spine changes and dynamics. The second part concentrates on disease-relevant factors that are associated with AD and which lead to spine alterations. In particular, data that provide evidence that Aβ oligomers or fibrillar Aβ deposits influence spine morphology and function will be presented and the contribution of tau pathology will be discussed. The review ends with the discussion of potential mechanisms how disease-relevant factors influence dendritic spines and whether and how spine changes could be therapeutically suppressed or reversed.

Collapsin response mediator protein-2 (CRMP2) was recently identified as a physiological substrate for GSK3 and Cdk5, two protein kinases suggested to exhibit greater activity in Alzheimer’s disease (AD). Indeed, phosphorylation of CRMP2, at the residues targeted by GSK3 and Cdk5, is relatively high in cortex isolated from human AD brain, as well as in the brains of animal models of AD, while phospho-CRMP2 is found in neurofibrillary tangles. In mouse models of AD, increased phosphorylation occurs prior to pathology. Although CRMP2 has no known enzymatic activity, a great deal of information is appearing on its importance in neuronal development and polarity, as well as in axon growth and guidance. In this mini-review, we examine what is known about CRMP2 function, how that is controlled by phosphorylation, what alterations in molecular mechanisms could lead to the abnormally high CRMP2 phosphorylation in AD, and whether this is likely to be specific to AD or occur in other forms of neurodegeneration. This will include discussion of the evidence for increased GSK3 or Cdk5 activity, for decreased phosphatase activity, or the upregulation of other CRMP2 protein kinases in AD. Importantly, we will compare the processes that may contribute to increased CRMP2 phosphorylation with those known to increase tau hyperphosphorylation in AD, and whether these are likely to be part of disease development or a useful early marker for AD.

The aim of the present study was to investigate the role of CSF cytochrome c levels and auditory event-related potentials (AERPs) on the progress of mild cognitive impairment (MCI) to Alzheimers disease (AD). Fifty one patients diagnosed with MCI and fourtneen healthy individuals underwent lumbar puncture at baseline and their CSF cytochrome c levels were determined. A follow-up examination of cytochrome c levels took place in 20 patients after 11 months and in this period five of the patients progressed to AD. ERP examinations were also performed in all patients both at baseline and follow-up. MCI patients had significantly higher cytochrome c levels compared to healthy controls (Mann-Whitney test, Z=-2.110, p=0.018). Compared to MCI patients who remained stable, the AD-converters, had a higher increase over time in cytochrome c levels (Mann-Whitney test, p=0.002; effect size r=0.63) and significantly prolonged N200 latency (Mann-Whitney test, p<0.001; effect size r=0.50). Amongst investigated ERP variables, only N200 amplitude was significantly correlated with CSF cytochrome c levels (rs=0.310, p=0.03). Both parameters were proved capable of discriminating AD converters from those MCI patients who remained stable, with sensitivity and specificity >75%. Our results suggest that conversion from MCI to AD is associated with a marked elevated N200 latency at baseline and a high increase in cytochrome c levels during a relatively short period of time, and that both parameters could be possibly considered as candidate markers for the discrimination between MCI patients who convert to AD and those who remain stable.

Today, the most reliable diagnosis for Alzheimer's disease (AD) is the post mortem identification of amyloid plaques, consisting of the Amyloid-β (Aβ) peptide, (and neurofibrillary tangles) in the brain of the patient. Great efforts are being made to identify reliable biomarkers for AD that are suitable for minimal invasive early diagnosis and prognosis of AD. During the past years, body fluids of AD patients were assayed for their content of total or soluble Aβ(1-40) or Aβ(1-42) concentrations using classical (ELISA) or non-classical (with additional signal amplification) read-out. Cerebrospinal fluid (CSF) concentrations of soluble Aβ(1-42) are reduced by 40 to 50 % in AD patients compared to agematched healthy controls as confirmed in more than 30 studies, with both sensitivity and specificity exceeding 80 % in most of the studies. Thus, it was suggested that low levels of CSF Aβ(1-42) might be useful for preclinical diagnosis. Because the current average sensitivity of AD biomarker detection in the CSF is approximately 85 %, these assays do not offer a considerable increase in predictive value over existing algorithms based on neuropsychological and imaging modalities. Regarding the amyloid cascade hypothesis, Aβ oligomers and aggregates are directly involved in the pathogenic process. Therefore, presence of Aβ aggregates seem to be the most direct disease biomarker for AD and increasing effort is being made into the development of methods suitable for the detection of different Aβ aggregates in body fluids like CSF and plasma. We therefore give an overview of the current state of Aβ aggregate specific detection.

Changes in cerebrospinal fluid (CSF) biomarkers are representative of biochemical changes in the brain. Collection of CSF by lumbar puncture (LP) is essential for biomarker analysis, which is important for research in neurodegenerative disorders. However, LP for research purposes has been controversial due to a reported high incidence of severe LP headache when using standard 18g or 20g Quincke needles with a beveled cutting tip. A procedural safety analysis was performed using the database of a multicenter, 13-week study of CSF cholinesterase activity. A 24g Sprotte atraumatic needle was used to collect CSF at baseline and at Week 13 from 63 older patients with mild to moderate Alzheimer's disease. There was a < 2% LP headache incidence, and a favorable safety profile was reported. In conclusion, LP performed with a 24g Sprotte atraumatic needle (blunt, “bullet” tip) was a well tolerated procedure, with good acceptability.

This contribution focuses on the definition of music therapy as a specific applicative context to be seen as distinct from the generic use of music in a variety of pathologies. Music therapy is presented as a discipline grounded both upon relationship and upon the theoretical-methodological principles peculiar to each applicative model. The therapeutic nature proper to music therapy is highlighted with specific reference to the domain of the dementias. Music therapy facilitates expression, communication and relationship in the non-verbal context. Such an opportunity allows persons with dementia to establish contact, to express, and even contrive an organisation/regulation of their emotions, through the sonorous- musical relationship with the music therapist. On the basis of a brief analysis of the relevant literature, attention is drawn to the importance of both evidence-based clinical practice and music therapy evaluations, aimed at proving the effectiveness of music therapy, while promoting its correct application.

Alzheimer's disease(AD) is associated with a variety of pathophysiological features, including amyloid plaques, inflammation, immunological changes, cell death and regeneration processes, altered neurotransmission, and agerelated changes. Retinoic acid receptors (RARs) and retinoids are relevant to all of these. Here we review the pathology, pharmacology, and biochemistry of AD in relation to RARs and retinoids, and we suggest that retinoids are candidate drugs for treatment of AD.

The neurodegenerative disorder Alzheimer's disease (AD) is the most common form of dementia. It is characterized by progressive impairment of cognitive functions and behavior. To distinguish clinically AD from other forms of dementia is an ongoing challenge. In addition, although mild cognitive impairment (MCI) is recognized as a risk factor for dementia, it remains a challenge to predict on an individual level who will convert to become demented. Amyloid β (Aβ) is one of the crucial pathological findings in AD. Recently, amyloid tracers for PET imaging have been developed successfully which may offer the unique possibility for measuring fibrillar Aβ load in the living brain. Therefore, in the near future positron emission tomography (PET) may become an important tool for in vivo amyloid imaging contributing to early (differential) diagnosis as well as evaluation of treatment response in AD. Moreover, Aβ may play a role in prediction the conversion of MCI to AD. In this paper we review the recent development of the molecular imaging technique PET and its different radiopharmaceuticals on the trail for imaging amyloid in AD and the conversion of MCI to AD.

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