Showing papers in "Current Alzheimer Research in 2009"

Baseline MRI predictors of conversion from MCI to probable AD in the ADNI cohort.

Abstract: The Alzheimer’s Disease Neuroimaging Initiative (ADNI) is a multi-center study assessing neuroimaging in diagnosis and longitudinal monitoring. Amnestic Mild Cognitive Impairment (MCI) often represents a prodromal form of dementia, conferring a 10-15% annual risk of converting to probable AD. We analyzed baseline 1.5T MRI scans in 693 participants from the ADNI cohort divided into four groups by baseline diagnosis and one year MCI to probable AD conversion status to identify neuroimaging phenotypes associated with MCI and AD and potential predictive markers of imminent conversion. MP-RAGE scans were analyzed using publicly available voxel-based morphometry (VBM) and automated parcellation methods. Measures included global and hippocampal grey matter (GM) density, hippocampal and amygdalar volumes, and cortical thickness values from entorhinal cortex and other temporal and parietal lobe regions. The overall pattern of structural MRI changes in MCI (n=339) and AD (n=148) compared to healthy controls (HC, n=206) was similar to prior findings in smaller samples. MCI-Converters (n=62) demonstrated a very similar pattern of atrophic changes to the AD group up to a year before meeting clinical criteria for AD. Finally, a comparison of effect sizes for contrasts between the MCI-Converters and MCI-Stable (n=277) groups on MRI metrics indicated that degree of neurodegeneration of medial temporal structures was the best antecedent MRI marker of imminent conversion, with decreased hippocampal volume (left > right) being the most robust. Validation of imaging biomarkers is important as they can help enrich clinical trials of disease modifying agents by identifying individuals at highest risk for progression to AD.

Long-term follow-up of patients immunized with AN1792: reduced functional decline in antibody responders.

Abstract: Background: Immunization of patients with Alzheimers disease (AD) with synthetic amyloid-β peptide (Aβ42) (AN1792) was previously studied in a randomized, double-blind, placebo-controlled phase 2a clinical trial, Study AN1792(QS-21)-201. Treatment was discontinued following reports of encephalitis. One year follow-up revealed that AN1792 antibody responders showed improvements in cognitive measures as assessed by the neuropsychological test battery (NTB) and a decrease in brain volume compared with placebo. Methods: A follow-up study, Study AN1792(QS-21)-251, was conducted to assess the long-term functional, psychometric, neuroimaging, and safety outcomes of patients from the phase 2a study 4.6 years after immunization with AN1792. The results were analyzed by comparing patients originally identified as antibody responders in the AN1792 phase 2a study with placebo-treated patients. Results: One hundred and fifty-nine patients/caregivers (30 placebo; 129 AN1792) participated in this follow-up study. Of the 129 AN1792-treated patients, 25 were classified in the phase 2a study as antibody responders (anti-AN1792 titers 1:2,200 at any time after the first injection). Low but detectable, sustained anti- AN1792 titers were found in 17 of 19 samples obtained from patients classified as antibody responders in the phase 2a study. No detectable anti-AN1792 antibodies were found in patients not classified as antibody responders in the phase 2a study. Significantly less decline was observed on the Disability Assessment for Dementia scale among antibody responders than placebo-treated patients (p=0.015) after 4.6 years. Significant differences in favor of responders were also observed on the Dependence Scale (p=0.033). Of the small number of patients who underwent a follow-up MRI, antibody responders showed similar brain volume loss during the follow-up period subsequent to the AN1792 phase 2a study compared with placebo-treated patients. Conclusions: Approximately 4.6 years after immunization with AN1792, patients defined as responders in the phase 2a study maintained low but detectable, sustained anti-AN1792 antibody titers and demonstrated significantly reduced functional decline compared with placebo-treated patients. Brain volume loss in antibody responders was not significantly different from placebo-treated patients approximately 3.6 years from the end of the original study. No further cases of encephalitis were noted. These data support the hypothesis that Aβ immunotherapy may have long-term functional benefits.

Early diagnosis of Alzheimer's disease: is MCI too late?

Abstract: The field of aging and dementia research is advancing rapidly toward the stage of earlier identification of clinical symptoms. Ultimately, clinicians would like to be able to identify individuals who are asymptomatic but at risk for developing dementia. In the interim, the construct of mild cognitive impairment (MCI) has come to represent an intermediate clinical state between the cognitive changes of aging and the very earliest features of Alzheimer's disease. A great deal of research has been generated in the past several years on MCI, and epidemiologic studies are characterizing its frequency in the general population. There are predictors of a more rapid progression from MCI to Alzheimer's disease, and these studies are suggesting techniques for altering future clinical trials. The neuropathology of MCI is intermediate between the neuropathologic changes of aging and fully developed Alzheimer's disease. The breadth of research in MCI is expanding and will be reviewed.

Cholinesterase Inhibitors and Beyond

Abstract: Cholinesterase inhibitors (ChEIs) were introduced in the therapy of Alzheimer Disease (AD) in the nineteen nineties with great expectations. The hopes and large interest raised by these drugs are well demonstrated by 12,000 references listed by PubMed under 'ChEI' for 1995-2007. The list is reduced to 2500 if we confine ourselves to 'ChEIs and dementia'. Of them, about 500 were published in the last two years. Whereas an increase in brain acetylcholine and an improvement of cognitive deficits have been consistently demonstrated in animal models of AD, from aging rats to transgenic mice, the clinical effectiveness of ChEIs has been and is still a matter of contrasting opinions. These range from the negative conclusions of the AD2000 trial on donepezil, claiming that it is not cost effective, with benefits below a minimally relevant threshold, to the NICE appraisal of 2007 declaring that donepezil, rivastigmine, galantamine are efficacious for mild to moderate AD, irrespective of their different selectivity for acetyl- (AChE) and butyrylcholinesterase (BuChE). The possibility that ChEIs may exert their effects through mechanisms beyond cholinesterase inhibition has been envisaged. However, according to the information presented in this review, the "classical" ChEIs, donepezil, rivastigmine and galantamine, show no pharmacological actions beyond cholinesterase inhibition which may play an important role in their therapeutic efficacy. The diverging opinions on clinical efficacy do not discourage from developing new ChEIs, and particularly the so called multifunctional ChEIs. They represent the future of the cholinergic therapy for AD but other indications for these drugs may be considered, including vascular dementia, mild cognitive impairment, and the ethically sensitive improvement of memory and learning in healthy subjects.

A common biological mechanism in cancer and Alzheimer's disease?

Abstract: 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 (Abeta) 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.

Amyloid deposition and inflammation in APPswe/PS1dE9 mouse model of Alzheimer's disease.

Abstract: Alzheimers disease (AD) is characterized by amyloid plaques and neurofibrillary tangles associated with chronic inflammation. APPswe/PS1dE9 is an AD mouse model bearing mutant transgenes of amyloid precursor protein and presenilin-1. Amyloid deposition is present in this mouse model at early stage of life. However, the progression of inflammation and its relationship with amyloid deposition have not been characterized. Here we showed that amyloid plaques were present at 4 months of age and increased with age. CD11b-positive microglia clusters appeared in hippocampus and neocortex at 4 months of age and increased with age. Clustered glial fibrillary acidic protein (GFAP)-positive astrocytes were observed in hippocampus and cortex after 6 months of age and increased with age. Double staining with CD11b/GFAP antibody and thioflavin S showed clustered microglia and astrocytes were in close association with amyloid plaques. Expression of TNF-α was detected at 8 months of age, while IL-1β, IL-6 and MCP-1 at 10 months. These cytokines increased with age. Double immunostaining of cell specific marker and cytokine indicated TNF-α, IL-1β, IL-6 and MCP-1 were expressed by activated microglia and a small part of activated astrocytes. MCP-1 was also expressed by neurons, which support recent finding that MCP-1 expression was increased in neurons of AD patient. These results demonstrate amyloid plaques and its associated inflammatory response developed at early stage of life and progressively increased with age, both activated glia and neurons are involved in chronic inflammation in AD. APPswe/PS1dE9 model provides a mean for studying the mechanisms and novel therapeutics for AD.

Alzheimer's disease and retinal neurodegeneration.

Abstract: Alzheimer's disease (AD) is the major cause of dementia in the world. Although the entorhinal cortex and hippocampal complex are best known as the sites of early pathology in AD, increasing evidence shows that the eye, particularly the retina, is also affected. The AD-related changes in the retina are associated with degeneration and loss of neurons, reduction of the retinal nerve fibres, increase in optic disc cupping, retinal vascular tortusity and thinning, and visual functional impairment. Given the fact that evaluating pathologic changes in the brain during life has always been an indirect process, largely shielded from view by the barrier of the skull, the eye can be used as a window into diseases of the brain. Using modern techniques, the changes in the retina can be visualized in real-time. In addition to the changes in the eyes of AD patients, similar mechanisms of neurodegeneration in the brain have also been demonstrated in the eye. Targeting AD-liked changes in the retina has been recently shown to be effective in the reduction of retinal neuronal degeneration and loss in eye diseases. This review will cover recent findings on retinal degeneration in AD, pathological similarities between AD and eye diseases, and highlight the potential of modern technologies for the detection of prospective biomarkers in the eye in early AD.

Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI) patients are characterized by increased BDNF serum levels.

Abstract: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline with loss of memory. In the last years there has been a great interest on the early phases of AD, trying to identify the pathogenic mechanisms of AD and define early treatment modalities. In particular, Mild Cognitive Impairment (MCI) is attractive because it represents a transitional state between normal aging and dementia, although not all MCI patients automatically convert to AD. The neurotrophin brain-derived neurotrophic factor (BDNF) is critical for survival and function of neurons that degenerate in AD and represents a potential neuroprotective agent. However, opposite data on serum levels of BDNF have been reported in AD patients, probably reflecting differences in patient recruitment and stage of the disease. Thus, in this study we measured BDNF serum levels in AD patients (with different degree of severity), MCI patients and healthy subjects. We found that serum BNDF levels were significantly increased in MCI and AD patients when compared to healthy subjects and this increase in AD patients was neither dependent on illness severity, nor on treatment with Acetylcholinesterase inhibitors and/or antidepressant medications. Our findings indicate that BDNF serum levels increase in MCI and AD patients, supporting the hypothesis of an upregulation of BDNF in both preclinical phase of dementia (MCI) and clinical stages of AD. Other studies are necessary to establish a direct link between BDNF peripheral levels and AD longitudinal course, as well as the role of other factors, such as blood cell activation, in determining these events.

The role of IGF-1 receptor and insulin receptor signaling for the pathogenesis of Alzheimer's disease: from model organisms to human disease.

Abstract: 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 beta-amyloid(Abeta)(1-42) toxicity. Cell based experiments suggest a specific role for the IGF 1/IRS-2 signaling pathway in regulating alpha-/beta-secretase activity. Moreover circulating IGF-1 might influence Abeta clearance from the brain by promoting Abeta 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 Abeta 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.

Cholesterol in Alzheimer’s Disease: Unresolved Questions

Abstract: The role of cholesterol as a susceptibility factor or a protective agent in neurodegeneration and, more generally, in amyloid-induced cytotoxicity is still controversial. Epidemiological studies on the hypercholesterolemia-AD risk relation and some reports indicating a beneficial effect of statin therapy suggest cholesterol as a susceptibility factor in AD. The ApoE4 genotype as a prevalent genetic risk factor for AD and the function of ApoE as main cholesterol carrier in the brain also underlie a close cholesterol load-AD risk relation. Finally, cell biology evidences support a critical involvement of lipid raft cholesterol in the modulation of beta- and gamma-secretase cleavage of APP with altered Abeta production. However, little exchange does exist between circulating and brain cholesterol, the latter arising from endogenous synthesis. In addition, increasing evidence supports the idea that amyloid cytotoxicity in most cases is initiated by oligomer recruitment at the cell membrane with loss of membrane integrity, Ca(2+) ingress into the cell, oxidative stress and apoptosis. In such a scenario, increased membrane cholesterol seems to be protective by disfavouring aggregate binding to the membrane. Recent findings also indicate that a reduction of cellular cholesterol favours co-localization of BACE1 and APP in non-raft membrane domains and hinders generation of plasmin, an Abeta-degrading enzyme. Finally, recent researches on Seladin-1, involved in cholesterol biosynthesis, show that modulation of membrane cholesterol affects Abeta generation and cell resistance against Abeta oligomer toxicity. These data confirm previous findings indicating a reduction of the cholesterol/phospholipid ratio in aged and AD brains. The aim of this review is to critically discuss some of the main results reported in the recent years in this field supporting a role of cholesterol either as a susceptibility factor or as a protective agent in AD.

DNA Damage and Repair in Alzheimers Disease

Abstract: The vast majority of the studies performed so far and aimed at elucidating DNA repair mechanisms has been performed in mitotic cells, such as transformed or cancer cell lines. Therefore, our understanding of DNA repair mechanisms in post-mitotic cells, such as neurons, remains one of the most exciting areas for future investigations. Markers of DNA damage, particularly oxidative DNA damage, have been largely found in brain regions, peripheral tissues, and biological fluids of Alzheimer's disease (AD) patients. Moreover, recent studies from our and other groups in individuals affected by Mild Cognitive Impairment provided evidence that oxidative DNA damage is one of the earliest detectable events within the progression from a normal brain to dementia. Almost one decade ago a decrease in the DNA base excision repair (BER) activity was observed in post mortem brain regions of AD individuals, leading to the hypothesis that the brain in AD might be subjected to the double insult of increased DNA damage, as well as deficiencies of DNA repair pathways. Subsequent studies have provided accumulating evidence of impaired DNA repair in AD. Moreover, functional variants and polymorphisms of DNA repair genes have been the focus of several cancer association studies, but only in recent years some of them have been investigated as possible AD risk factors. The few studies performed so far suggest that some variants might play a role in AD pathogenesis and deserve further investigations. Here, we summarize the current knowledge of DNA damage and repair in AD pathogenesis.

Microglial activation in Alzheimer's disease.

Abstract: Alzheimer's disease (AD) is a devastating chronic neurodegenerative disease with currently no available disease modifying treatment. In recent years, the peptide amyloid-beta has been proposed as the major pathogenic force in the development and progression of AD. Microglia, the resident immune and phagocytic cells of the brain, are known to constantly scan brain tissue and to respond to various pathological stimuli. Thus, newly formed plaque composed of A beta seem to activate and recruit microglia in AD transgenic mice. However, the role of microglia is only poorly understood in AD. Microglia may act as a double-edged sword being either detrimental or protective depending on the context. In this mini-review, we discuss the importance of microglia and its receptors in neuroinflammation and plaque clearance. A possible disease modifying role of blood-borne monocytes, which are close relatives of bone-marrow derived microglia, will also be addressed.

A PPARdelta Agonist Reduces Amyloid Burden and Brain Inflammation in a Transgenic Mouse Model of Alzheimers Disease

Abstract: Agonists of the peroxisome proliferator activated receptor gamma (PPARgamma) have been shown to reduce inflammatory responses in several animal models of neurological diseases and conditions and to reduce amyloid burden in transgenic mice expressing mutant forms of human amyloid precursor protein. However, the effects of activating the related receptor PPARdelta (PPARdelta), which is expressed at higher levels in the brain than PPARgamma, on inflammation and amyloid burden have not been explored. In this study we tested the effects of the selective PPARdelta agonist GW742 in 5xFAD mice which harbor 3 mutations in amyloid precursor protein and 2 mutations in presenilin 1, develop plaques by 5-6 weeks of age, and show robust inflammation and neuronal damage. Oral delivery of GW742 significantly reduced amyloid plaque burden in the subiculum region of 3-month old male and female 5xFAD mice. GW742 also significantly reduced astrocyte activation, suggesting anti-inflammatory effects on glia cells. The changes in plaque burden were accompanied by increased expression of the amyloid degrading enzymes neprilysin and insulin degrading enzyme, while in transfected HEK293 cells, GW742 activated a neprilysin promoter driving luciferase expression. These results suggest that, as found for some PPARgamma agonists, PPARdelta agonists can also reduce amyloid burden likely to be mediated by effects on amyloid clearance.

High PIB Retention in Alzheimer's Disease is an Early Event with Complex Relationship with CSF Biomarkers and Functional Parameters

Abstract: Background: New in vivo amyloid PET imaging tracers, such as C-11-PIB, provide possibilities to deeper understand the underlying pathological processes in Alzheimer's disease (AD). In this study we ...

Effects of cholinesterase inhibitors on the activities and protein levels of cholinesterases in the cerebrospinal fluid of patients with Alzheimer's disease: a review of recent clinical studies.

Abstract: Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by cognitive decline associated with a deficit in cholinergic function. Inhibitors of acetylcholinesterase (AChE) and/or butyrylcholinesterase (BuChE), such as donepezil, galantamine or rivastigmine, are widely prescribed as symptomatic treatments for AD. These agents exhibit a wide variation in their pharmacological properties. Here we review clinical data from 1998 to 2009 investigating the effect of different cholinesterase inhibitor treatments on the levels and activities of cholinesterases in the cerebrospinal fluid (CSF) of AD patients. These studies suggest that treatment with rapidly-reversible cholinesterase inhibitors (e.g. donepezil, galantamine, tacrine) are associated with marked and significant upregulation of AChE activities and protein levels in the CSF of AD patients. In contrast, pseudo-irreversible cholinesterase inhibition (e.g. rivastigmine) is associated with a significant decrease in both CSF AChE and BuChE activities, with no upregulation of CSF protein levels. Additionally, donepezil is associated with a decrease in the level of the AChE-R isoform relative to the synaptic AChE-S isoform, whereas rivastigmine seems to increase this ratio. These findings suggest that these agents exert different effects on CSF cholinesterases. The clinical effects of these pharmacological differences are yet to be fully established.

Serum Albumin Concentration and Cognitive Impairment

Abstract: Results from clinical samples suggest low serum albumin may be associated with cognitive impairment, though evidence from population-based studies is inconclusive. Participants were 1,752 adults (699 men and 1,053 women) aged 65 years and over from the Health Survey for England 2000, a nationally representative population-based study. Cognitive impairment was assessed using the Abbreviated Mental Test Score. The cross-sectional relation of serum albumin quartiles to cognitive impairment was modelled using logistic regression. Two hundred and twelve participants were cognitively impaired (68 men and 144 women). Odds ratios (95% confidence intervals) for cognitive impairment in the first (2.2–3.8 g/dl), second (3.9–4.0 g/dl), and third (4.1–4.3 g/dl) quartiles of serum albumin compared with the fourth (4.4–5.3 g/dl) were 2.5 (1.3–5.1), 1.7 (0.9–3.5), and 1.5 (0.7–2.9), after adjustment for age, sex, education and additional risk factors for cognitive impairment (p for linear trend = 0.002). A highly similar pattern of associations was observed for men and women. Our data provide new evidence to suggest that low serum albumin is independently associated with increased odds of cognitive impairment in the elderly population.

Natural non-trasgenic animal models for research in Alzheimer's disease.

Abstract: The most common animal models currently used for Alzheimer disease (AD) research are transgenic mice that express a mutant form of human Aβ precursor protein (APP) and/or some of the enzymes implicated in their metabolic processing. However, these transgenic mice carry their own APP and APP-processing enzymes, which may interfere in the production of different amyloid-beta (Aβ) peptides encoded by the human transgenes. Additionally, the genetic backgrounds of the different transgenic mice are a possible confounding factor with regard to crucial aspects of AD that they may (or may not) reproduce. Thus, although the usefulness of transgenic mice is undisputed, we hypothesized that additional relevant information on the physiopathology of AD could be obtained from other natural non-transgenic models. We have analyzed the chick embryo and the dog, which may be better experimental models because their enzymatic machinery for processing APP is almost identical to that of humans. The chick embryo is extremely easy to access and manipulate. It could be an advantageous natural model in which to study the cell biology and developmental function of APP and a potential assay system for drugs that regulate APP processing. The dog suffers from an age-related syndrome of cognitive dysfunction that naturally reproduces key aspects of AD including Aβ cortical pathology, neuronal degeneration and learning and memory disabilities. However, dense core neuritic plaques and neurofibrillary tangles have not been consistently demonstrated in the dog. Thus, these species may be natural models with which to study the biology of AD, and could also serve as assay systems for Aβ-targeted drugs or new therapeutic strategies against this devastating disease.

Towards disease-modifying treatment of Alzheimer's disease: drugs targeting beta-amyloid.

Abstract: Pathological, genetic, biochemical and pharmacological studies support the hypothesis that brain accumulation of oligomeric species of β-amyloid (Aβ) peptides may cause Alzheimers disease (AD). Drugs currently used for the treatment of AD produce limited clinical benefits and do not treat the underlying causes of the disease. In the last 10 years, new therapeutic approaches targeting Aβ have been discovered and developed with the hope of modifying the natural history of the disease. Several active and passive immunotherapy approaches are under investigation in clinical trials with the aim of accelerating Aβ clearance from the brain of the AD patients. The most advanced of these immunological approaches is bapineuzumab, composed of humanized anti-Aβ monoclonal antibodies, that is being tested in two large late-stage trials. Compounds that interfere with proteases regulating Aβ formation from amyloid precursor protein (APP) are also actively pursued. Unfortunately, the most biologically attractive of these proteases, β-secretase, that regulates the first step of the amyloidogenic APP metabolism, was found to be particularly problematic to block and only one compound (CTS21166) has reached clinical testing so far. Conversely, several inhibitors of β-secretase, the protease that regulates the last metabolic step generating Aβ, have been identified, the most advanced being LY-450139 (semagacestat), presently in Phase III clinical development. Compounds that stimulate β-secretase, the enzyme responsible for the nonamyloidogenic metabolism of APP, are also being developed one of them, EHT-0202, has recently started a Phase II study. Furthermore, brain penetrant inhibitors of Aβ aggregation have been identified and one of such compounds, PBT-2, has produced encouraging neuropsychological results in a recently completed Phase II study. With all these anti-Aβ approaches in clinical testing, we will know in few years if the Av hypothesis of AD is correct.

Anesthesia, Calcium Homeostasis and Alzheimer’s Disease

Abstract: While anesthetics are indispensable clinical tools generally safe and effective, in some situations there is grown concern about selective neurotoxicity of these agents; the clinical significance is unclear as of yet. The mechanisms for inhalational anesthetics mediated cell damage are still not clear, although a role for calcium dysregulation has been suggested. For example, the inhaled anesthetic isoflurane decreases endoplasmic reticulum (ER) calcium concentration and increases that in the cytosol and mitochondria. Inhibition of ER calcium release, via either IP(3) or ryanodine receptors, significantly inhibited isoflurane neurotoxicity. Neurons made vulnerable to calcium dysregulation by overexpression of mutated presenilin-1 (PS1) or huntingtin (Q-111) proteins showed enhanced apoptosis upon isoflurane exposure. Sevoflurane and desflurane were less potent than isoflurane in altering intracellular calcium, and produced less apoptosis. Short exposures to inhalational anesthetics may provide neuroprotection by preconditioning via a sublethal stress, while prolonged exposures to inhalational anesthetics may induce cell damage by apoptosis through direct cytotoxic effects.

Structural and functional MRI in mild cognitive impairment.

Abstract: Mild cognitive impairment (MCI), and the amnestic subtype of MCI in particular, is the most recent concept used to describe the intermediary state between healthy aging and Alzheimer's disease (AD). It is hoped that research focusing on MCI would yield markers for early identification of individuals with prodromal AD at such a pre-dementia stage when potential disease modifying therapies would be most efficacious. Magnetic resonance imaging (MRI) combined with various data analysis methods provides tools to investigate alterations in brain structure and function in vivo. Structurally, MCI is characterized by atrophy of the medial temporal lobe (MTL) structures such as the hippocampus and entorhinal cortex, and the amount of atrophy in MCI is intermediate between healthy aging and AD. Additionally, atrophy of the posteromedial cortices such as the posterior cingulum and precuneus as well as of the lateral temporal cortices has been reported. The pattern of atrophy appears to vary according to the subtype of MCI. Functional MRI studies in MCI, compared to healthy aging and AD, have demonstrated both increased and decreased MTL activity during encoding novel visually presented material. Differences in the MTL activation pattern in MCI subjects may relate to differences in the severity of cognitive decline. There is some evidence that increased MTL activity observed during encoding may be compensatory due to incipient atrophy in the MTL structures. The resting state (or, "default mode") network, and the posteromedial cortical regions in particular, appear to malfunction in MCI. It is suggested that both altered MTL and posteromedial cortical function may be indicative of future cognitive decline from MCI to clinical AD.

Thin, stubby or mushroom: spine pathology in Alzheimer's disease.

Abstract: 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 Alzheimers 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.

Addressing Alzheimers Disease Tangles: From NAP to AL-108

Abstract: AL-108 is the intranasal formulation of NAP (a peptide of eight amino acids, NAPVSIPQ). Phase IIa clinical results have recently shown that AL-108 has a positive impact on memory function in patients with amnestic mild cognitive impairment (aMCI), a precursor to Alzheimer's disease (AD). The clinical development of AL-108 has been based on extensive studies showing pre-clinical efficacy for NAP. NAP has demonstrated potent neuroprotective activity in vitro and in vivo. Its mechanism of action is thought to center on the modulation of microtubule stability in the face of outside damage. Such an effect on structures of such central importance in a broad range of cellular functions is thought to explain NAP's activity in wide ranging models of cellular damage and neurodegeneration. The following article reviews NAP's discovery and pharmacological characterization that has led to clinical development of a novel tangle-directed drug candidate.

Tau-focused immunotherapy for Alzheimer's disease and related tauopathies.

Abstract: Immunotherapies targeting the amyloid-beta (Abeta) peptide in Alzheimer's disease (AD) have consistently been effective in mouse studies and shown promise in clinical trials, although some setbacks have occurred. First, encephalitis was observed in a small subset of patients. More recent autopsy data from a few subjects suggests that clearance of Abeta plaques may not halt cognitive deterioration once impairments are evident, emphasizing the need for other more effective approaches at that stage of the disease. Another important target in AD is the neurofibrillary tangles and its precursors, composed primarily of hyperphosphorylated tau proteins, which correlate well with the degree of dementia. As Abeta and tau pathologies are likely synergistic, targeting both together may be more effective, and perhaps essential as early diagnosis prior to cognitive decline is currently unavailable. Also, Abeta immunotherapy results in a very limited indirect clearance of tau aggregates, showing the importance of developing a separate therapy that directly targets pathological tau. Our findings in two tangle mouse models indicate that active immunization targeting an AD phospho-tau epitope reduces aggregated tau in the brain and prevents/slows progression of the tangle-related behavioral phenotype, including cognitive impairment. These antibodies enter the brain and bind to pathological tau within neurons although the therapeutic effect may at least in part be due to clearance of extracellular tau that may have biological effects. We are currently clarifying the mechanism of these promising findings, determining its epitope specificity as well as assessing the feasibility of this approach for clinical trials.

Development of a non invasive NGF-based therapy for Alzheimer's disease.

Abstract: Nerve growth factor (NGF) deficits are linked to Alzheimer's Disease (AD), due to the role of NGF on basal forebrain cholinergic neurons (BFCN). We have further established that a disequilibrium in NGF signaling and/or processing from its precursor proNGF is also directly and causally related to the aberrant activation of an amyloidogenic route to neurodegeneration. The therapeutic potential of using human NGF to provide a long-lasting cholinergic trophic support, thereby preventing or slowing cognitive decline in AD patients, has therefore a strong rationale. However, a simple and practical means of delivering NGF to the brain in a safe and long-term manner, limiting the undesired adverse effects of NGF in activating nociceptive responses, has represented a significant challenge. For this reason, pilot clinical studies have been performed so far with invasive approaches requiring neurosurgery. We obtained a proof of principle, in neurodegeneration animal models, of an alternative, non-invasive delivery of NGF through an intranasal route, which facilitates access of NGF to the central nervous system (CNS), while minimizing the biodistribution of NGF to compartments where it activates undesired effects, such as pain. The ideal NGF product for a non invasive NGF-based therapy would be a recombinant NGF that, while exhibiting an identical biological activity to that of human NGF, can be traced, against the endogenous NGF, in order to optimize the therapeutical dose range and meet the required therapeutic window. We describe an engineered mutein of hNGF, hNGF-61, that is selectively recognized, against endogenous NGF, by a specific antibody. hNGF-61 mutein has an identical potency and bioactivity profile as hNGF, in vitro and in vivo. Moreover, hNGF-61 and hNGF are equally effective in rescuing the behavioral and neurodegenerative phenotype in adult and aged AD11 anti-NGF mice. Finally, we demonstrated that intranasally delivered hNGF-61 is significantly more effective than ocularly applied hNGF-61, to determine phenotypic rescue in AD11 mice. The development of hNGF-61 towards clinical applications in AD patients is under way.

Impact of Alzheimers Disease on the Functional Connectivity of Spontaneous Brain Activity

Abstract: Alzheimer's disease (AD) prominently affects the structure and function of cerebral networks. Reflecting the complex network structure of the brain, spontaneous brain activity is organized by synchronized activity across distinct temporal and spatial scales. Temporal correlations of the functional MRI (fMRI) signal during rest have been used to characterize the impact of AD on the functional connectivity of spontaneous brain activity. Here we review studies using resting-state fMRI (rs-fMRI) to explore AD-induced changes of synchronized intrinsic activity at three levels of brain organization: the regional, inter-regional and large-scale level. Changes in posterior areas of the default network (DN) and the medial temporal lobes seem to be central to AD. These areas show remarkable disturbances in neuronal communication at all spatial levels and in very early stages of the disease. Finally, rs-fMRI seems to have the potential to produce connectivity-related biomarkers that distinguish AD and healthy aging.

Towards retinoid therapy for Alzheimer's disease.

Abstract: Alzheimers 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

Diet-Induced Hyperhomocysteinemia Increases Amyloid-β Formation and Deposition in a Mouse Model of Alzheimers Disease

Abstract: Hyperhomocysteinemia (HHcy) has been recognized as a risk factor for developing Alzheimers disease (AD). However, its underlying molecular mechanisms are still elusive. Here we show that HHcy induces an elevation of amyloid beta (Aβ) levels and deposition, as well as behavioral impairments, in a mouse model of AD-like amyloidosis, the Tg2576 mice. This elevation is not associated with significant change of the steady state levels of the Aβ precursor protein (APP), β- or α-secretase pathways, nor with the Aβ catabolic pathways. By contrast, HHcy significantly reduces glycogen synthase kinase 3 (GSK3) Ser21/9 phosphorylation, but not total GSK3 protein levels. Similar results are obtained in brains homogenates from a genetic mouse model of HHcy. In vitro studies show that homocysteine increases Aβ formation, reduces phosphorylated GSK3 levels, without changes in total APP and its metabolism, and these effects are prevented by selective GSK3 inhibition. Overall, these data support a potential link between GSK3 and the pro-amyloidotic effect of HHcy in vivo and in vitro.

Nicotinic acetylcholine receptor interaction with β-amyloid:molecular, cellular, and physiological consequences

Abstract: Elevated amyloid-β peptide (Aβ) and loss of nicotinic acetylcholine receptors (nAChRs) stand prominently in the etiology of Alzheimer's disease (AD). Since the discovery of an Aβ - nAChR interaction, much effort has been expended to characterize the consequences of high versus low concentrations of Aβ on nAChRs. This review will discuss current knowledge on the subject at the molecular, cellular, and physiological levels with particular emphasis on understanding how Aβ - nAChR interaction may contribute to normal physiological processes as well as the etiology of AD. ©2010 Bentham Science Publishers Ltd.

Different Cholinesterase Inhibitor Effects on CSF Cholinesterases in Alzheimer Patients

Abstract: Background: The current study aimed to compare the effects of different cholinesterase inhibitors on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities and protein levels, in the cerebrospinal fluid (CSF) of Alzheimer disease (AD) patients. Methods and Findings: AD patients aged 50 – 85 years were randomized to open-label treatment with oral rivastigmine, donepezil or galantamine for 13 weeks. AChE and BuChE activities were assayed by Ellmans colorimetric method. Protein levels were assessed by enzyme-linked immunosorbent assay (ELISA). Primary analyses were based on the Completer population (randomized patients who completed Week 13 assessments). 63 patients were randomized to treatment. Rivastigmine was associated with decreased AChE activity by 42.6% and decreased AChE protein levels by 9.3%, and decreased BuChE activity by 45.6% and decreased BuChE protein levels by 21.8%. Galantamine decreased AChE activity by 2.1% and BuChE activity by 0.5%, but increased AChE protein levels by 51.2% and BuChE protein levels by 10.5%. Donepezil increased AChE and BuChE activities by 11.8% and 2.8%, respectively. Donepezil caused a 215.2% increase in AChE and 0.4% increase in BuChE protein levels. Changes in mean AChE-Readthrough/Synaptic ratios, which might reflect underlying neurodegenerative processes, were 1.4, 0.6, and 0.4 for rivastigmine, donepezil and galantamine, respectively. Conclusion: The findings suggest pharmacologically-induced differences between rivastigmine, donepezil and galantamine. Rivastigmine provides sustained inhibition of AChE and BuChE, while donepezil and galantamine do not inhibit BuChE and are associated with increases in CSF AChE protein levels. The clinical implications require evaluation.

Safety of lumbar puncture procedures in patients with Alzheimer's disease.

Abstract: 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.