Amyloid imaging demonstrates the in vivo presence of amyloid-β (Aβ) deposits in the aging human brain but it is still unknown which structural forms and modifications of Aβ are detected. In Alzheimer's disease, most amyloid deposits are predominantly composed of Aβ ending at amino acid residues Val40 or Ala42. It has been reported that Aβ40 is largely restricted to neuritic plaques while Aβ42 may be deposited in amyloid plaques of all types, and is often the sole component of diffuse plaques. The distinction is important as it is mainly the neuritic plaques that correlate with cognitive impairment while diffuse plaques may be the initial type of Aβ deposited. Whether PET amyloid ligands such as florbetapir-18F (Amyvid) are partially or wholly selective for brain deposits of Aβ40 or Aβ42 is currently unknown. We compared antemortem florbetapir PET cortical/cerebellar signal intensity (SUVr) of 55 subjects with postmortem biochemical (ELISA) measurements employing specific antibodies against Aβ40 and Aβ42. Spearman's univariable correlations were significant for both Aβ40 and Aβ42, but were much stronger for Aβ42. Multiple linear regression showed significance only for Aβ42. These results suggest that florbetapir binds only weakly, if at all, to Aβ40. This may be in part due to the higher likelihood for Aβ42 to be present in a β-pleated sheet tertiary structure, or to differences between Aβ40 and Aβ42 in β-pleated sheet tertiary or quaternary structure.

The amyloid cascade hypothesis of Alzheimer's disease (AD) proposes amyloidb (Ab) is a chief pathological element of dementia. AD therapies have targeted monomeric and oligomeric Ab 1e40 and 1e42 peptides. However, alternative APP proteolytic processing produces a complex roster of Ab species. In addition, Ab peptides are subject to extensive posttranslational modification (PTM). We propose that amplified production of some APP/Ab species, perhaps exacerbated by differential gene expression and reduced peptide degradation, creates a diverse spectrum of modified species which disrupt brain homeostasis and accelerate AD neurodegeneration. We surveyed the literature to catalog Ab PTM including species with isoAsp at positions 7 and 23 which may phenocopy the Tottori and Iowa Ab mutations that result in early onset AD. We speculate that accumulation of these alterations induce changes in secondary and tertiary structure of Ab that favor increased toxicity, and seeding and propagation in sporadic AD. Additionally, amyloid-b peptides with a pyroglutamate modification at position 3 and oxidation of Met35 make up a substantial portion of sporadic AD amyloid deposits. The intrinsic physical properties of these species, including resistance to degradation, an enhanced aggregation rate, increased neurotoxicity, and associationwith behavioral deficits, suggest their emergence is linked to dementia. The generation of specific 3D-molecular conformations of Ab impart unique biophysical properties and a capacity to seed the prion-like global transmission of amyloid through the brain. The accumulation of rogue Ab ultimately contributes to the destruction of vascular walls, neurons and glial cells culminating in dementia. A systematic examination of Ab PTM and the analysis of the toxicity that they induced may help create essential biomarkers to more precisely stage AD pathology, design countermeasures and gauge the impacts of interventions. © 2017 Elsevier Ltd. All rights reserved.

The amyloid cascade hypothesis of Alzheimer's disease (AD) proposes amyloid- β (Aβ) is a chief pathological element of dementia. AD therapies have targeted monomeric and oligomeric Aβ 1–40 and 1–42 peptides. However, alternative APP proteolytic processing produces a complex roster of Aβ species. In addition, Aβ peptides are subject to extensive posttranslational modification (PTM). We propose that amplified production of some APP/Aβ species, perhaps exacerbated by differential gene expression and reduced peptide degradation, creates a diverse spectrum of modified species which disrupt brain homeostasis and accelerate AD neurodegeneration. We surveyed the literature to catalog Aβ PTM including species with isoAsp at positions 7 and 23 which may phenocopy the Tottori and Iowa Aβ mutations that result in early onset AD. We speculate that accumulation of these alterations induce changes in secondary and tertiary structure of Aβ that favor increased toxicity, and seeding and propagation in sporadic AD. Additionally, amyloid-β peptides with a pyroglutamate modification at position 3 and oxidation of Met35 make up a substantial portion of sporadic AD amyloid deposits. The intrinsic physical properties of these species, including resistance to degradation, an enhanced aggregation rate, increased neurotoxicity, and association with behavioral deficits, suggest their emergence is linked to dementia. The generation of specific 3D-molecular conformations of Aβ impart unique biophysical properties and a capacity to seed the prion-like global transmission of amyloid through the brain. The accumulation of rogue Aβ ultimately contributes to the destruction of vascular walls, neurons and glial cells culminating in dementia. A systematic examination of Aβ PTM and the analysis of the toxicity that they induced may help create essential biomarkers to more precisely stage AD pathology, design countermeasures and gauge the impacts of interventions.

Therapies designed to disrupt amyloid plaque deposits or prevent their formation have yielded disappointing results against cognitive failure, suggesting that both our mechanistic models of dementia and interventions must become more nuanced.These treatments targeted Aβ40/42, but the amyloid accumulated in Alzheimer's disease patients is modified extensively and far more structurally diverse.Despite intensive work, the structure and physical state of the most toxic amyloid species remains mysterious.In addition, multiple lines of evidence suggest the genesis and progression of dementia is more complicated than the accumulation of senile plaques beyond a tolerable threshold.If amyloid plays key, but non-exclusive, roles in dementia pathogenesis this hypothesis must be addressed through investigations that are more holistic in scope.New imaging methods provide investigators unprecedented capabilities to detect and classify neuropathology in living subjects.Interpreting future clinical trial outcomes will hinge on correlating effects against dementia in subject cohorts that are precisely differentiated with respect to neuropathology and neurochemistry.Improving understanding of the comorbidities and the environmental/lifestyle factors foreshadowing cognitive failure will aid in the interpretation of clinical trials.Most important, as we seek an elusive cure for AD, these findings may be rapidly translatable into concrete and achievable public health improvements.

Much of Alzheimer disease (AD) research has been traditionally based on the use of animals, which have been extensively applied in an effort to both improve our understanding of the pathophysiological mechanisms of the disease and to test novel therapeutic approaches. However, decades of such research have not effectively translated into substantial therapeutic success for human patients. Here we critically discuss these issues in order to determine how existing human-based methods can be applied to study AD pathology and develop novel therapeutics. These methods, which include patient-derived cells, computational analysis and models, together with large-scale epidemiological studies represent novel and exciting tools to enhance and forward AD research. In particular, these methods are helping advance AD research by contributing multifactorial and multidimensional perspectives, especially considering the crucial role played by lifestyle risk factors in the determination of AD risk. In addition to research techniques, we also consider related pitfalls and flaws in the current research funding system. Conversely, we identify encouraging new trends in research and government policy. In light of these new research directions, we provide recommendations regarding prioritization of research funding. The goal of this document is to stimulate scientific and public discussion on the need to explore new avenues in AD research, considering outcome and ethics as core principles to reliably judge traditional research efforts and eventually undertake new research strategies.

Studies of presenilin (PSEN) gene mutations producing early onset Alzheimer's disease (AD) have helped elucidate the pathogenic mechanisms of dementia and guided clinical trials of potential therapeutic interventions. Although familial and sporadic forms of AD share features, it is unclear if the two are precisely equivalent. In addition, PSEN mutations do not all produce a single phenotype, but exhibit substantial variability in clinical manifestations, which are related to the position and chemical nature of their amino acid substitutions as well as ratios of critical molecules such as Aβ40 and Aβ42. These differences complicate the interpretation of critical clinical trial results and their desired extrapolation to sporadic AD treatment. In this perspective, we examine differences between familial AD and sporadic AD as well as attributes shared by these uniquely arising disturbances in brain biochemical homeostasis that culminate in dementia.

INTRODUCTION:Based on the amyloid cascade hypothesis of Alzheimer's disease (AD) pathogenesis, a series of clinical trials involving immunotherapies have been undertaken including infusion with the IgG1 monoclonal anti-Aβ antibody solanezumab directed against the middle of the soluble Aβ peptide. In this report, we give an account of the clinical history, psychometric testing, gross and microscopic neuropathology as well as immunochemical quantitation of soluble and insoluble Aβ peptides and other proteins of interest related to AD pathophysiology in a patient treated with solanezumab. MATERIALS AND METHODS:The solanezumab-treated AD case (SOLA-AD) was compared to non-demented control (NDC, n = 5) and non-immunized AD (NI-AD, n = 5) subjects. Brain sections were stained with H&E, Thioflavine-S, Campbell-Switzer and Gallyas methods. ELISA and Western blots were used for quantification of proteins of interest. RESULTS:The SOLA-AD subject's neuropathology and biochemistry differed sharply from the NDC and NI-AD groups. The SOLA-AD case had copious numbers of amyloid laden blood vessels in all areas of the cerebral cortex, from leptomeningeal perforating arteries to arteriolar deposits which attained the cerebral amyloid angiopathy (CAA) maximum score of 12. In contrast, the maximum CAA for the NI-AD cases averaged a total of 3.6, while the NDC cases only reached 0.75. The SOLA-AD subject had 4.4-fold more soluble Aβ40 and 5.6-fold more insoluble Aβ40 in the frontal lobe compared to NI-AD cases. In the temporal lobe of the SOLA-AD case, the soluble Aβ40 was 80-fold increased, and the insoluble Aβ40 was 13-fold more abundant compared to the non-immunized AD cases. Both soluble and insoluble Aβ42 levels were not dramatically different between the SOLA-AD and NI-AD cohort. DISCUSSION:Solanezumab immunotherapy provided no apparent relief in the clinical evolution of dementia in this particular AD patient, since there was a continuous cognitive deterioration and full expression of amyloid deposition and neuropathology.

Based on the amyloid cascade hypothesis of Alzheimer's disease (AD) pathogenesis, a series of clinical trials involving immunotherapies have been undertaken including infusion with the IgG1 monoclonal anti-Aβ antibody solanezumab directed against the middle of the soluble Aβ peptide. In this report, we give an account of the clinical history, psychometric testing, gross and microscopic neuropathology as well as immunochemical quantitation of soluble and insoluble Aβ peptides and other proteins of interest related to AD pathophysiology in a patient treated with solanezumab.The solanezumab-treated AD case (SOLA-AD) was compared to non-demented control (NDC, n = 5) and non-immunized AD (NI-AD, n = 5) subjects. Brain sections were stained with H&E, Thioflavine-S, Campbell-Switzer and Gallyas methods. ELISA and Western blots were used for quantification of proteins of interest.The SOLA-AD subject's neuropathology and biochemistry differed sharply from the NDC and NI-AD groups. The SOLA-AD case had copious numbers of amyloid laden blood vessels in all areas of the cerebral cortex, from leptomeningeal perforating arteries to arteriolar deposits which attained the cerebral amyloid angiopathy (CAA) maximum score of 12. In contrast, the maximum CAA for the NI-AD cases averaged a total of 3.6, while the NDC cases only reached 0.75. The SOLA-AD subject had 4.4-fold more soluble Aβ40 and 5.6-fold more insoluble Aβ40 in the frontal lobe compared to NI-AD cases. In the temporal lobe of the SOLA-AD case, the soluble Aβ40 was 80-fold increased, and the insoluble Aβ40 was 13-fold more abundant compared to the non-immunized AD cases. Both soluble and insoluble Aβ42 levels were not dramatically different between the SOLA-AD and NI-AD cohort.Solanezumab immunotherapy provided no apparent relief in the clinical evolution of dementia in this particular AD patient, since there was a continuous cognitive deterioration and full expression of amyloid deposition and neuropathology.

Tau becomes excessively phosphorylated in Alzheimer's disease (AD) and is widely studied within the brain. Further examination of the extent and types of tau present in peripheral tissues and their relation to AD is warranted given recent publications on pathologic spreading. Cases were selected based on the presence of pathological tau spinal cord deposits (n = 18). Tissue samples from sigmoid colon, scalp, abdominal skin, liver, and submandibular gland were analyzed by western blot and enzyme-linked immunosorbent assays (ELISAs) for certain tau species; frontal cortex gray matter was used for comparison. ELISAs revealed brain to have the highest total tau levels, followed by submandibular gland, sigmoid colon, liver, scalp, and abdominal skin. Western blots with antibodies recognizing tau phosphorylated at threonine 231(pT231), serine 396 and 404 (PHF-1), and an unmodified total human tau between residues 159 and 163 (HT7) revealed multiple banding patterns, some of which predominated in peripheral tissues. As submandibular gland had the highest levels of peripheral tau, a second set of submandibular gland samples were analyzed (n = 36; 19 AD, 17 non-demented controls). ELISAs revealed significantly lower levels of pS396 (p = 0.009) and pT231 (p = 0.005) in AD cases but not total tau (p = 0.18). Furthermore, pT231 levels in submandibular gland inversely correlated with Braak neurofibrillary tangle stage (p = 0.04), after adjusting for age at death, gender, and postmortem interval. These results provide evidence that certain tau species are present in peripheral tissues. Of potential importance, submandibular gland pT231 is progressively less abundant with increasing Braak neurofibrillary tangle stage.

Introduction: Epidemiologic data show strong link between cardiovascular risk factors and dementia-related illnesses (DRI) such as Alzheimer’s disease (AD) with evidence that the earliest changes in AD involve vascular dysfunction. The mechanisms behind vascular impairment in DRI remain poorly understood, and lack of a human model to study them impedes progress towards a cure. Aim: The aim of the study is to determine the effects of acute exposure to palmitic acid (PA), a saturated fatty acid implicated in atherosclerosis, on endothelium-dependent and smooth muscle dependent function in human leptomeningeal arterioles (LMA) and peripheral adipose tissue arterioles (AA). Methods: LMA from cadavers of brain donors (post-mortem interval 3.3±0.4 hours; 2 with mild cognitive impairment, 1 Parkinson's disease, 1 Lewy body dementia) and abdominal subcutaneous AA from living subjects with no vascular disease undergoing routine surgery were isolated, cannulated and pressurized. Following preconstriction with endothelin-1, baseline (control) dilation response to acetylcholine and papaverine was measured. Arterioles were then exposed to 1 hour of PA (150 μM) and a second dilation response was measured. Results: (see Figure) PA decreased dilator response to acetylcholine in both LMA and AA (PA-induced change in dilator response to acetylcholine 10-4M: -28.1±6.8 % for LMA and -33.8±7.4% for AA, both p<0.05 versus baseline control). There was no significant reduction in dilator response to papaverine. The changes in dilator response with PA versus control were not different between LMA and AA. Conclusions: Acute exposure to PA induced endothelial dysfunction in human leptomeningeal arterioles suggesting a potential mechanism for vascular dysfunction that could contribute to AD. Similarity in response to saturated fatty acid between LMA and AA suggests that AA, which is easier to obtain, may be a novel surrogate human model to study brain microvascular function.

Importance β-Amyloid peptide (Aβ) plaques are a cardinal neuropathologic feature of Alzheimer disease (AD), yet more than one-third of apolipoprotein E ε4 (APOE4) noncarriers with the clinical diagnosis of mild to moderate Alzheimer dementia may not meet positron emission tomographic criteria for significant cerebral amyloidosis. Objectives To clarify the percentage ofAPOE4carriers and noncarriers with the primary clinical diagnosis of mild to moderate Alzheimer dementia near the end of life and minimal Aβ plaques noted at autopsy and the extent to which these cases are associated with appreciable neurofibrillary degeneration or a primary neuropathologic diagnosis other than AD. Design, Setting, and Participants Data on participants included in this study were obtained from the National Alzheimer Coordinating Center's Uniform Data Set, which comprises longitudinal clinical assessments performed at the AD centers funded by the National Institute on Aging. Neuropathology data are available for the subset of participants who died. A total of 100APOE4noncarriers and 100APOE4carriers had the primary clinical diagnosis of mild to moderate Alzheimer dementia at their last visit, knownAPOE4genotype, died within the ensuing 24 months, and underwent neuropathologic evaluation on autopsy. The study was conducted from September 1, 2005, to September 1, 2012; analysis was performed from October 9, 2012, to March 20, 2015. Main Outcomes and Measures Standardized histopathologic assessments of AD neuropathologic changes were the primary measures of interest in this study, specifically Consortium to Establish a Registry for Alzheimer's Disease neuritic plaque density score, diffuse plaque density score, and Braak stage for neurofibrillary degeneration. The distributions of scores for these measures were the primary outcomes. Results Of the 37APOE4noncarriers with minimal neuritic plaques, 16 individuals (43.2%) had Braak stages III to VI ratings, and 15 of the others (75.0%) met neuropathologic criteria for other dementia-related diseases. Of the 13APOE4carriers with minimal neuritic plaques, 6 individuals (46.2%) had Braak stages III to VI ratings and met neuropathologic criteria for other dementia-related diseases. Similarly, of the 7APOE4carriers with minimal neuritic plaques and Braak stages 0 to II, 4 participants (57.1%) were thought to have pathologic changes and alterations resulting from non-AD neuropathologic features. Conclusions and Relevance In this study, more than one-third ofAPOE4noncarriers with the primary clinical diagnosis of mild to moderate Alzheimer dementia had minimal Aβ plaque accumulation in the cerebral cortex and, thus, may show limited or no benefit from otherwise effective anti-Aβ treatment. Almost half of the participants with a primary clinical diagnosis of mild to moderate Alzheimer dementia and minimal Aβ plaque accumulation had an extensive topographic distribution of neurofibrillary degeneration. Additional studies are needed to better understand and provide treatment for patients with this unexpectedly common cliniconeuropathologic condition.

During the last 100 years, unprecedented progress in the medical sciences, nutrition and hygiene has contributed to a 30-year increase in average life expectancy. Increased longevity has meant that other morbidities related to ageing have become more apparent. Such is the case for Alzheimer's disease (AD), the most common form of dementia, which is neuropathologically characterized by extracellular plaques and intraneuronal neurofibrillary tangles. The pathogenesis of this complex disorder remains unclear despite decades of intensive research. Sporadic AD is an emergent pathology that results from the dynamic interplay between multiple genetic, epigenetic, environmental, lifestyle and behavioural factors against a background of senescence-related diseases and functional/cognitive declines. From a functional viewpoint, it is irrefutable that the brain needs a continuous and efficient blood supply to maintain the necessary energy levels for its development and adequate performance. Therefore, investigation of how cardiovascular pathology, through subtle and continuous hypoxic/ischaemic mechanisms, affects cognition and leads to or promotes dementia is urgently required. Cerebral blood flow (CBF) fluctuates with neuronal activity which is the regional regulator of brain energy consumption. In AD, CBF is consistently decreased when compared to age-matched nondemented control subjects. The aetiology of brain hypoperfusion in elderly and demented subjects is multifactorial and associated with the individual's unique cardiovascular/cerebrovascular system pathology and haemodynamic deterioration. Brain hypoperfusion may result from one or several concurrent conditions, including hypertension, hypotension, arterial stiffness, atherosclerosis, myocardial infarction, valvulopathies, arrhythmias and cardiomyopathies, which may lead to heart and vascular failure 1. In addition, in elderly individuals, chronic low-level inflammation and diabetes also play an important role in the development of neurodegenerative disorders 2, 3. Longevity itself through unavoidable cellular and physiological function decay along with unbalanced diets and sedentary lifestyles may contribute significantly to the increasing incidence of cardiovascular disease and neurodegeneration. At present, the development of therapeutic interventions demonstrating decisive beneficial affects against dementia has yet to be promoted. This reveals a basic inadequacy in the current definitions of and delineation of the complex processes underlying AD pathology and dementia. New clinical trials are underway, but definitive results may not be available for many years. In the current issue of the Journal of Internal Medicine, Cermakova et al. 4 comprehensively review the fascinating topic of ‘heart failure and Alzheimer's disease’. It is very refreshing that, apart from the important pathogenic issues related to the amyloid cascade hypothesis, the authors offer a detailed, compelling and well-documented account of the role of chronic heart disease and vascular failure in the pathogenesis, pathophysiology and epidemiology of AD. Cardiovascular disease is one of the major causes of morbidity and mortality in developed countries. The prevalence of heart failure (HF) increases sharply after 65 years of age and is as high as 20% amongst individuals over 75 years old. Multiple pathological and haemodynamic changes converge in the development of HF which is ultimately expressed as decreased cardiac output to a level that is insufficient to meet metabolic demands. The central aim of the review by Cermakova and colleagues is an assessment of the multiple risk factors for cardiovascular disease, which are the same shared hazards for AD development. These two diseases together generate brain hypoperfusion, cognitive impairment and dementia for which the authors utilize the appropriate term of ‘cardiogenic dementia’ 4. The levels of energy production in the brain fall with advancing age, in parallel with cardiac output decay and increasing impairment in mitochondrial ATP synthesis. This is accompanied by an adaptive adjustment that gradually shifts the brain's fuelling pathways from glycolytic metabolism to a ketonolytic strategy 5. Several studies have demonstrated a direct correlation between cognitive deficiencies and congestive HF, cardiac ejection fraction, cardiac output and cardiac surgical procedures 4, 6-8, although cognitive function improved in some patients after cardiac transplantation 9. Brain atrophy, resulting from the continuous loss of the cerebral cortex and subcortical nuclei as well as from the sustained reduction in white matter due to hypoxia/ischaemia, inexorably leads to dementia. Patients diagnosed with mild cognitive impairment or mild/moderate AD already demonstrate a significant loss in CBF 10, 11. As ageing progresses, other disorders contribute strongly to brain hypoperfusion. Increased peripheral resistance, as a consequence of stiffening of the arteries and veins, results in loss of vascular compliance (windkessel dysfunction). Arteriosclerosis promotes hypertension that severely impairs the microcirculation and disrupts the blood–brain barrier, irreversibly damaging the neurovascular unit and ultimately decreasing brain perfusion. Transcranial Doppler ultrasound studies have demonstrated a significant reduction in CBF velocities and increased pulsatility indices in AD subjects that support the diagnosis of diffuse microvascular disease 12. Hypotensive bouts are clearly equally harmful. In this respect, it is noteworthy that hypotension in the elderly population is at times iatrogenically induced by overmedication to reduce high blood pressure. All these serious consequences have been well documented in numerous structural and functional studies in humans and animal models. Atherosclerosis of the coronary, aortic, carotid and major cerebral arteries as well as of the circle of Willis is common amongst the elderly. This pathology, which has strong genetic and environmental/lifestyle backgrounds, is manifested by a variable degree of arterial stenosis. Advanced atherosclerosis restricts brain circulation from the heart to cerebral microvessels and is one of the major causes of heart ischaemia and brain hypoperfusion, and a cause of macro- and micro-emboli and cerebral infarction 13. Atherosclerosis of the coronary arteries warrants special attention because of its role in coronary stenosis and myocardial infarction. Overt or silent infarctions are capable of damaging the myocardium with clear alterations in diastolic and systolic functions. In the ageing population, cardiovascular system functional assessments should be extended to cardiac torsion mechanics involving left ventricular twist and untwist magnitudes and rates, longitudinal and circumferential strains as well as blood mechanical and haemodynamic and mechanical efficiency 14, 15. Left ventricular diastolic relaxation and filling naturally decline with age due to myocardial structural remodelling which affects ventricular performance and diastolic early and late filling velocities. This reduces cardiac output and decreases brain perfusion which will ultimately damage cognitive performance 1, 16. Atrial fibrillation is the most prevalent form of cardiac arrhythmia and a risk factor for the development of dementia 17, 18. Atrial fibrillation generates irregular cardiac rhythm and tachycardia and is a major source of brain hypoperfusion and also a risk factor for stroke. Likewise, obstructive sleep apnoea is a very common ailment; there is a high prevalence of obstructive sleep apnoea in the adult American population with the majority of individuals remaining underdiagnosed and untreated 19, 20. The complications of obstructive sleep apnoea are irregular cardiac rate, tachycardia, hypertension, atrial fibrillation, embolism, cerebral ischaemia/hypoxia and, consequently, cognitive damage and dementia. An effective treatment for AD may still be a distant goal. However, the recognition of the important cardiovascular-related disorders that cause brain hypoperfusion and, therefore, can synergistically aggravate the course of AD may offer important ways to mitigate or prevent the development of dementia 21, 22. There is sufficient justification for the use of existing cardiovascular pharmacological and surgical interventions for the immediate clinical benefit of the at-risk population to prevent or delay the onset of AD. The discovery of reliable cardiovascular/cerebrovascular parameters that are altered during the process of ageing and are related to cognitive decline may complement existing panels of biomarker tests to increase their diagnostic power. The main significance of the article by Cermakova et al. is their persuasive invitation to adopt a more comprehensive vision of AD aetiology and progression. It is clear that in most patients, AD pathology and dementia result from the combined net outcome of the complex and additive effects of multiple comorbidities in which cardiovascular and respiratory failures as well as diabetes play important roles. Viewing AD in this more comprehensive context is a crucial and overlooked requirement. Adopting this wider perspective of AD will shift this disorder from a virtually inevitable epidemiological and public health emergency to a severe medical challenge potentially subject to mitigation through proactive application of eminently feasible preventative and therapeutic measures. No conflict of interest to declare.

Background: Evidence point to vascular dysfunction and hypoperfusion as early abnormalities in Alzheimer's disease (AD); probing their mechanistic bases can lead to new therapeutic approaches. We tested the hypotheses that beta-amyloid peptide induces endothelial dysfunction and oxidative stress in human microvasculature and that response will be similar between peripheral adipose and brain leptomeningeal arterioles.New method: Abdominal subcutaneous arterioles from living human subjects (n = 17) and cadaver leptomeningeal arterioles (n = 6) from rapid autopsy were exposed to A beta-42 (A beta) for 1-h and dilation response to acetylcholine/papaverine were measured and compared to baseline response. Adipose arteriole reactive oxygen species (ROS) production and nitrotyrosine content were measured.Comparison with existing methods: Methods described allow direct investigation of human microvessel functional response that cannot be replicated by human noninvasive imaging or post-mortem histology.Results: Adipose arterioles exposed to 2 mu M A beta showed impaired dilation to acetylcholine that was reversed by antioxidant polyethylene glycol superoxide dismutase (PEG-SOD) (A beta-60.9 +/- 6%, control-93.2 +/- 1.8%, A beta+PEGSOD-84.7 +/- 3.9%, both p<0.05 vs. A beta). A beta caused reduced dilation to papaverine. Ap increased adipose arteriole ROS production and increased arteriole nitrotyrosine content. Leptomeningeal arterioles showed similar impaired response to acetylcholine when exposed to A beta (43.0 +/- 6.2% versus 81.1 +/- 5.7% control, p<0.05).Conclusion: A beta exposure induced adipose arteriole endothelial and non-endothelial dysfunction and oxidative stress that were reversed by antioxidant treatment. A beta-induced endothelial dysfunction was similar between peripheral adipose and leptomeningeal arterioles. Ex vivo living adipose and cadaver leptomeningeal arterioles are viable, novel and practical human tissue models to study Alzheimer's vascular pathophysiology. Published by Elsevier B.V.

Amyloid deposition has been implicated as the key determinant of Alzheimer's disease (AD) pathogenesis. Interventions to antagonize amyloid accumulation and mitigate dementia are now under active investigation. We conducted a combined clinical, biochemical and neuropathological assessment of a participant in a clinical trial of the γ-secretase inhibitor, semagacestat. This patient received a daily oral dose of 140 mg of semagacestat for approximately 76 weeks. Levels of brain amyloid-β (Aβ) peptides were quantified using enzyme-linked immunosorbent assays (ELISA). Western blot/scanning densitometry was performed to reveal BACE1, presenilin1, amyloid precursor protein (APP) and its proteolysis-produced C-terminal peptides APP-CT99 and APP-CT83 as well as several γ-secretase substrates. To serve as a frame of reference, the ELISA and Western analyses were performed in parallel on samples from neuropathologically confirmed non-demented control (NDC) and AD subjects who did not receive semagacestat. Neuropathology findings confirmed a diagnosis of AD with frequent amyloid deposits and neurofibrillary tangles in most areas of the cortex and subcortical nuclei as well as cerebellar amyloid plaques. Mean levels of Tris-soluble Aβ40 and glass-distilled formic acid (GDFA)/guanidine hydrochloride (GHCl)-extractable Aβ40 in the frontal lobe and GDFA/GHCl-soluble Aβ40 in the temporal lobe were increased 4.2, 9.5 and 7.7-fold, respectively, in the semagacestat-treated subject compared to those observed in the non-treated AD group. In addition, GDFA/GHCl-extracted Aβ42 was increased 2-fold in the temporal lobe relative to non-treated AD cases. No major changes in APP, β- and γ-secretase and CT99/CT83 were observed between the semagacestat-treated subject compared to either NDC or AD cases. Furthermore, the levels of γ-secretase substrates in the semagacestat-treated subject and the reference groups were also similar. Interestingly, there were significant alterations in the levels of several γ-secretase substrates between the NDC and non-treated AD subjects. This is the first reported case study of an individual enrolled in the semagacestat clinical trial. The subject of this study remained alive for ~7 months after treatment termination, therefore it is difficult to conclude whether the outcomes observed represent a consequence of semagacestat therapy. Additional evaluations of trial participants, including several who expired during the course of treatment, may provide vital clarification regarding the impacts and aftermath of γ-secretase inhibition.

Defining the biochemical alterations that occur in the brain during "normal" aging is an important part of understanding the pathophysiology of neurodegenerative diseases and of distinguishing pathological conditions from aging-associated changes. Three groups were selected based on age and on having no evidence of neurological or significant neurodegenerative disease: 1) young adult individuals, average age 26 years (n = 9); 2) middle-aged subjects, average age 59 years (n = 5); 3) oldest-old individuals, average age 93 years (n = 6). Using ELISA and Western blotting methods, we quantified and compared the levels of several key molecules associated with neurodegenerative disease in the precuneus and posterior cingulate gyrus, two brain regions known to exhibit early imaging alterations during the course of Alzheimer's disease. Our experiments revealed that the bioindicators of emerging brain pathology remained steady or decreased with advancing age. One exception was S100B, which significantly increased with age. Along the process of aging, neurofibrillary tangle deposition increased, even in the absence of amyloid deposition, suggesting the presence of amyloid plaques is not obligatory for their development and that limited tangle density is a part of normal aging. Our study complements a previous assessment of neuropathology in oldest-old subjects, and within the limitations of the small number of individuals involved in the present investigation, it adds valuable information to the molecular and structural heterogeneity observed along the course of aging and dementia. This work underscores the need to examine through direct observation how the processes of amyloid deposition unfold or change prior to the earliest phases of dementia emergence.

Dementia pugilistica (DP), a suite of neuropathological and cognitive function declines after chronic traumatic brain injury (TBI), is present in approximately 20% of retired boxers. Epidemiological studies indicate TBI is a risk factor for neurodegenerative disorders including Alzheimer disease (AD) and Parkinson disease (PD). Some biochemical alterations observed in AD and PD may be recapitulated in DP and other TBI persons. In this report, we investigate long-term biochemical changes in the brains of former boxers with neuropathologically confirmed DP. Our experiments revealed biochemical and cellular alterations in DP that are complementary to and extend information already provided by histological methods. ELISA and one-dimensional and two dimensional Western blot techniques revealed differential expression of select molecules between three patients with DP and three age-matched non-demented control (NDC) persons without a history of TBI. Structural changes such as disturbances in the expression and processing of glial fibrillary acidic protein, tau, and α-synuclein were evident. The levels of the Aβ-degrading enzyme neprilysin were reduced in the patients with DP. Amyloid-β levels were elevated in the DP participant with the concomitant diagnosis of AD. In addition, the levels of brain-derived neurotrophic factor and the axonal transport proteins kinesin and dynein were substantially decreased in DP relative to NDC participants. Traumatic brain injury is a risk factor for dementia development, and our findings are consistent with permanent structural and functional damage in the cerebral cortex and white matter of boxers. Understanding the precise threshold of damage needed for the induction of pathology in DP and TBI is vital.

Identifying biomarkers that distinguish Parkinson's disease (PD) from normal control (NC) individuals has the potential to increase diagnostic sensitivity for the detection of early-stage PD. A previous proteomic study identified potential biomarkers in postmortem ventricular cerebrospinal fluid (V-CSF) from neuropathologically diagnosed PD subjects lacking Alzheimer's disease (AD) neuropathology. In the present study, we assessed these biomarkers as well as p-tau181, Aβ42, and S100B by ELISA in PD (n = 43) and NC (n = 49) cases. The p-tau181/Aβ42 ratio and ApoA-1 showed statistically significant differences between groups. Multiple regression analysis demonstrated that p-tau181/Aβ42 had a significant odds ratio: OR = 1.42 (95% confidence interval [CI], 1.12–1.84), P = 0.006. Among the molecules investigated, intriguing correlations were observed that require further investigation. Our results suggest coexistent AD CSF biomarkers within the PD group notwithstanding that it was selected to minimize AD neuropathological lesions.