Serum Protein-Based Profiles as Novel Biomarkers for the Diagnosis of Alzheimer's Disease.

As a multi-stage disorder, Alzheimer's disease (AD) is quickly becoming one of the most prevalent neurodegenerative diseases worldwide. Thus, a non-invasive, serum-based diagnostic platform is eagerly awaited. The goal of this study was to identify a serum-based biomarker panel using a predictive protein-based algorithm that is able to confidently distinguish AD patients from control subjects. One hundred and fifty-six patients with AD and the same number of gender- and age-matched control participants with standardized clinical assessments and neuroimaging measures were evaluated. Serum proteins of interest were quantified using a magnetic bead-based immunofluorescent assay, and a total of 33 analytes were examined. All of the subjects were then randomized into a training set containing 70% of the total samples and a validation set containing 30%, with each containing an equal number of AD and normal samples. Logistic regression and random forest analyses were then applied to develop a desirable algorithm for AD detection. The random forest method was found to generate a more robust predictive model than the logistic regression analysis. Furthermore, an eight-protein-based algorithm was found to be the most robust with a sensitivity of 97.7%, specificity of 88.6%, and AUC of 99%. Our study developed a novel eight-protein biomarker panel that can be used to distinguish AD and control multi-source candidates regardless of age. It is hoped that these results provide further insight into the applicability of serum-based screening methods and contribute to the development of lower-cost, less invasive methods for diagnosing AD and monitoring progression.

Plasma Amyloid-Beta Levels in Patients with Different Types of Cancer.

Several epidemiological investigations indicate that cancer survivors have a lower risk for Alzheimer's disease (AD) and vice versa. However, the associations between plasma amyloid-beta (Aß) levels with cancer remain largely unknown. In this case-control study, 110 cancer patients, 70 AD patients, and 70 age- and gender-matched normal controls were recruited. The cancer types include esophagus cancer, colorectal cancer, hepatic cancer, and lung cancer, all of which were reported to be associated with a lower risk for AD. Plasma levels of Aß40, Aß42, common pro-inflammatory cytokines, IL-1ß, IL-6, TNF-α, IFN-γ, anti-inflammatory IL-4, chemokines, and cytokines MCP-1 were measured with enzyme-linked immunosorbent assay (ELISA) kits. Plasma levels of Aß40 and Aß42 in all cancer patients were higher than that in normal controls. More specifically, hepatic cancer patients exhibited significantly higher plasma Aß levels. No significant difference in plasma Aß levels was found between chemotherapy and no chemotherapy subgroups. Plasma Aß levels were not significantly correlated with pro-inflammatory cytokines, anti-inflammatory, chemokines, and cytokines. Peripheral Aß levels increased in cancer patients, especially in patients with hepatic cancer, independent of chemotherapy and inflammation. Further verification is required for the association between plasma Aß and cancer.

Intramuscular delivery of p75NTR ectodomain by an AAV vector attenuates cognitive deficits and Alzheimer's disease-like pathologies in APP/PS1 transgenic mice.

The neurotrophin receptor p75 (p75NTR) is a receptor for amyloid-beta (Aß) and mediates Aß-induced neurodegenerative signals. The ectodomain of p75NTR (p75ECD) is a physiological protective factor against Aß in Alzheimer's disease (AD). We have previously demonstrated that the shedding of p75ECD from the cell surface is down-regulated in AD brains and restoration of the p75ECD level in the brain, through intracranial administration of p75ECD by adeno-associated virus vectors, attenuates AD-like pathologies in an AD mouse model. In this study, we further investigated the feasibility and efficacy of peripheral administration of AAV-p75ECD on brain amyloid burden and associated pathogenesis. We found that intramuscular delivery of AAV-p75ECD increased the level of p75ECD in the blood, significantly improved the behavioral phenotype of amyloid precursor protein/PS1 transgenic mice, and reduced brain amyloid burden, attenuated Tau hyperphosphorylation, and neuroinflammation. Furthermore, intramuscular delivery of AAV-p75ECD was well tolerated. Our results indicate that peripheral delivery of p75ECD represents a safe and effective therapeutic strategy for AD. The ectodomain of p75NTR (p75ECD) is a physiological protective factor against amyloid-beta (Aß) in Alzheimer's disease (AD). Intramuscular delivery of AAV-p75ECD increased the p75ECD levels in the blood, reduced brain amyloid burden through a 'peripheral sink' mechanism and alleviates AD-type pathologies. Peripheral delivery of p75ECD represents a promising therapeutic strategy for AD.

proBDNF Attenuates Hippocampal Neurogenesis and Induces Learning and Memory Deficits in Aged Mice.

Mature brain-derived neurotrophic factor has shown promotive effect on neural cells in rodents, including neural proliferation, differentiation, survival, and synaptic formation. Conversely, the precursor of brain-derived neurotrophic factor (proBDNF) has been emerging as a differing protein against its mature form, for its critical role in aging process and neurodegenerative diseases. In the present study, we investigated the role of proBDNF in neurogenesis in the hippocampal dentate gyrus of aged mice and examined the changes in mice learning and memory functions. The results showed that the newborn cells in the hippocampus revealed a significant decline in proBDNF-treated group compared with bovine serum albumin group, but an elevated level in anti-proBDNF group. During the maturation period, no significant change was observed in the proportions of phenotype of the newborn cells among the three groups. In water maze, proBDNF-treated mice had poorer scores in place navigation test and probe test, compared with those from any other group. Thus, we conclude that proBDNF attenuates neurogenesis in the hippocampus and induces the deficits in learning and memory functions of aged mice.

Perspectives on the Tertiary Prevention Strategy for Alzheimer's Disease.

Amyloid-beta (Aß) plays a pivotal role in Alzheimer's disease (AD) pathogenesis, and is the most promising disease-modifying target for AD. A succession of failures in Aß-targeting clinical trials, however, has prompted questions on whether Aß is the true cause of AD and a valid therapeutic target. Therefore, current therapeutic targets and intervention strategies must be reconsidered. In addition to Aß, multiple pathological events such as tau hyperphosphorylation, oxidative stress and neuroinflammation are involved in the disease pathogenesis and cause cross-talk between these pathological pathways, which synergistically drive disease progression. Increasing evidence also reveals that the pathogenesis varies at different stages of the disease. Therefore, targeting Aß alone at all stages of the disease would not be sufficient to halt or reverse disease progression. In the light of the pathophysiologic similarities between the development of ischemic stroke and AD, we can formulate management strategies for AD from the successful practice of ischemic stroke management, namely the tertiary prevention strategy. These new perspectives of tertiary prevention target both Aß and different pathological pathways of AD pathogenesis at different stages of the disease, and may represent a promising avenue for the effective prevention and treatment of AD.

Diagnostic utility of VEGF and soluble CD40L levels in serum of Alzheimer's patients.

BACKGROUND: Non-invasive blood-based biomarkers are eagerly awaited for the diagnosis of Alzheimer's disease (AD). The present study aimed to evaluate the individual and combined diagnostic value of soluble CD40 ligand (sCD40L) and vascular endothelial growth factor (VEGF) for AD. METHODS: Fifty patients with AD and forty gender and age-matched control participants with standardized clinical assessments and neuroimaging measures were enrolled. VEGF and sCD40L were qualified in 90 subjects using immunomagnetic beads assay. RESULTS: To evaluate the individual and combined diagnostic value of sCD40L and VEGF for AD, receiver operating characteristic curves were generated and logistic regression analysis was conducted. The AUCs (area under ROCs) of sCD40L and VEGF and their corresponding 95% confidence interval (CI) were 0.824 (95% CI: 0.737-0.910) and 0.731 (95% CI: 0.622-0.839), respectively. Combined ROC analysis based on these 2 biomarkers revealed an elevated AUC of 0.858 (95% CI: 0.775-0.941), which indicates an additive effect in the diagnostic value of these two biomarkers. CONCLUSIONS: We identified the feasibility of a blood-based biomarker approach in AD diagnostics though the results warrant validation in large-scale studies. A combination of sCD40L and VEGF could be a useful diagnostic biomarker for future clinical trials with AD and may act as a suitable add-on biomarker to the panel of markers already existing for AD.

Sex Dimorphism Profile of Alzheimer's Disease-Type Pathologies in an APP/PS1 Mouse Model.

Alzheimer's disease (AD) is the most common form of dementia among the elderly, characterized by parenchymal and vascular beta-amyloid (Aß) burden, tau pathology, neuroinflammation, and loss of neurons and synapses. There is a clear sex difference in the prevalence of AD. However, sex differences in AD-type pathologies have not been systematically documented. Applying 12-month-old female and male APP/PS1 mice as a model, we investigated the sex dimorphism in these major pathological indices. Compared with male APP/PS1 mice, the females exhibited higher parenchymal Aß burdens, with the sex difference in hippocampus being the most significant. Female APP/PS1 mice had more severe cerebral amyloid angiopathy and subsequent microhemorrhage. In addition, female APP/PS1 mice also showed higher levels of phosphorylated tau and proinflammatory cytokines, more severe astrocytosis and microgliosis, and greater neuronal and synaptic degenerations. The present study systematically described a sex dimorphism in AD-type pathologic indices, suggesting that gender should be taken into account in designing studies involving these pathological indices and when interpreting the relevant findings in those studies.

Physiological amyloid-beta clearance in the periphery and its therapeutic potential for Alzheimer's disease.

Amyloid-beta (Aß) plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). The physiological capacity of peripheral tissues and organs in clearing brain-derived Aß and its therapeutic potential for AD remains largely unknown. Here, we measured blood Aß levels in different locations of the circulation in humans and mice, and used a parabiosis model to investigate the effect of peripheral Aß catabolism on AD pathogenesis. We found that blood Aß levels in the inferior/posterior vena cava were lower than that in the superior vena cava in both humans and mice. In addition, injected (125)I labeled Aß40 was located mostly in the liver, kidney, gastrointestinal tract, and skin but very little in the brain; suggesting that Aß derived from the brain can be cleared in the periphery. Parabiosis before and after Aß deposition in the brain significantly reduced brain Aß burden without alterations in the expression of amyloid precursor protein, Aß generating and degrading enzymes, Aß transport receptors, and AD-type pathologies including hyperphosphorylated tau, neuroinflammation, as well as neuronal degeneration and loss in the brains of parabiotic AD mice. Our study revealed that the peripheral system is potent in clearing brain Aß and preventing AD pathogenesis. The present work suggests that peripheral Aß clearance is a valid therapeutic approach for AD, and implies that deficits in the Aß clearance in the periphery might also contribute to AD pathogenesis.

Serum amyloid-beta levels are increased in patients with obstructive sleep apnea syndrome.

A critical link between amyloid-beta (Aß) and hypoxia has been demonstrated in in vitro and animal studies but has not yet been proven in humans. Obstructive sleep apnea syndrome (OSAS) is a common disorder that is characterized by nocturnal intermittent hypoxaemia. This study sought to examine the association between the chronic intermittent hypoxia and Aß in OSAS patients. Forty-five cognitively normal OSAS patients and forty-nine age- and gender-matched subjects diagnosed with simple snoring and not OSAS were included in the present study. Serum Aß40, Aß42, total tau and phosphorylated tau 181 (P-tau 181) levels were measured using ELISA kits. All subjects were evaluated with nighttime polysomnography and cognitive tests. Compared with the controls, the OSAS patients exhibited significantly higher serum Aß40, Aß42 and total Aß levels, and each of these levels was positively correlated with the apnea-hypopnea index, the oxygen desaturation index, and the mean and lowest oxyhaemoglobin saturations in the OSAS patients. Moreover, the OSAS patients exhibited strikingly higher serum P-tau 181 levels, and these levels were positively correlated with serum Aß levels. This study suggests that there is an association between chronic intermittent hypoxia and increased Aß levels, implying that hypoxia may contribute to the pathogenesis of Alzheimer's disease.

An N-terminal antibody promotes the transformation of amyloid fibrils into oligomers and enhances the neurotoxicity of amyloid-beta: the dust-raising effect.

BACKGROUND: Senile plaques consisting of amyloid-beta (Aß) are the major pathological hallmark of Alzheimer's disease (AD) and have been the primary therapeutic target. Immunotherapies, which are designed to remove brain Aß deposits, increased levels of soluble Aß and accelerated brain atrophy in some clinical trials, suggesting that the solubilization of Aß deposition might facilitate the formation of more toxic Aß oligomers and enhance neurotoxicity. METHODS: The capacity of antibodies against different epitopes of Aß to disaggregate preformed Aß fibrils was investigated. The co-incubation of antibodies and Aß fibrils was then tested for neurotoxicity both in vitro and in vivo. RESULTS: After the incubation of preformed Aß fibrils with the N-terminal antibody 6E10, the fibrils were decreased, while the oligomers, mostly dimers and trimers, were significantly increased. However, no such effects were observed for antibodies targeting the middle domain (4G8) and C-terminus of Aß (8G7). The co-incubates of preformed Aß fibrils with 6E10 were more neurotoxic, both in vitro and in vivo, than the co-incubates with 4G8 and 8G7. CONCLUSIONS: Our results indicate that the antibody targeting the N-terminus of Aß promoted the transformation of Aß from fibrils into oligomers and increased neurotoxicity. Immunotherapies should take into consideration the enhanced neurotoxicity associated with the solubilization of Aß deposits by antibodies against the Nterminus of Aß.

Serum Amyloid-Beta Levels are Increased in Patients with Chronic Obstructive Pulmonary Disease.

Chronic obstructive pulmonary disease (COPD) is associated with cognitive decline, but the molecular link between COPD and dementia or Alzheimer's disease (AD) remains unclear. This study was aimed to investigate whether serum Aß levels are correlated with COPD. 77 cognitively normal COPD patients and 45 age- and gender-matched normal controls were admitted to the study. Serum Aß40 and Aß42 levels were measured using ELISA kits. Serum C-reactive protein (CRP), interleukin 6 (IL-6), and procalcitonin (PCT) measurements were done using standard laboratory methods. Pulmonary function tests were performed to assess the pulmonary function and determine the degree of lung damage. Significantly increased levels of serum Aß40, Aß42, and total Aß levels were found in patients with COPD in comparison with normal controls. In COPD patients, serum Aß levels were higher in subjects with serum CRP, IL-6, and PCT upper the limit of normal. Moreover, serum Aß levels were dramatically higher in COPD patients with worse pulmonary function. Our study suggests that cognitively normal COPD patients may undergo AD-related pathological changes, and COPD might facilitate AD-type pathogenesis.

The association between infectious burden and Parkinson's disease: A case-control study.

INTRODUCTION: The etiology of Parkinson's disease (PD) remains unclear. The aim of this study was to examine the association between common pathogenic infections and PD. METHODS: Antibody titers to common infectious pathogens including cytomegalovirus (CMV), Epstein Barr virus (EBV)，herpes simplex virus type-1 (HSV-1), Borrelia burgdorferi (B. burgdorferi), Chlamydophila pneumoniae (C. pneumoniae) and Helicobacter pylori (H. pylori) were measured by ELISA in serum of 131 PD patients and 141 normal controls. Infectious burden (IB) was defined as a composite serologic measure of exposure to these common pathogens. RESULTS: Seropositivities toward zero-two, three-four and five-six of these pathogens were found in 11%, 74% and 15% of normal controls while in 4%, 61% and 35% of PD patients, respectively. IB, bacterial burden and viral burden were independently associated with PD. Schwab and England (S&E) scores were negatively correlated with IB in patients with PD. Serum α-synuclein protein levels and inflammatory cytokines (interleukin-1ß and interleukin-6) in individuals with higher IB were also significantly higher. CONCLUSIONS: IB consisting of CMV, EBV, HSV-1, B. burgdorferi, C. pneumoniae and H. pylori is associated with PD. This study supports the role of infection in the etiology of PD.

Edaravone alleviates Alzheimer's disease-type pathologies and cognitive deficits.

Alzheimer's disease (AD) is one of most devastating diseases affecting elderly people. Amyloid-ß (Aß) accumulation and the downstream pathological events such as oxidative stress play critical roles in pathogenesis of AD. Lessons from failures of current clinical trials suggest that targeting multiple key pathways of the AD pathogenesis is necessary to halt the disease progression. Here we show that Edaravone, a free radical scavenger that is marketed for acute ischemic stroke, has a potent capacity of inhibiting Aß aggregation and attenuating Aß-induced oxidation in vitro. When given before or after the onset of Aß deposition via i.p. injection, Edaravone substantially reduces Aß deposition, alleviates oxidative stress, attenuates the downstream pathologies including Tau hyperphosphorylation, glial activation, neuroinflammation, neuronal loss, synaptic dysfunction, and rescues the behavioral deficits of APPswe/PS1 mice. Oral administration of Edaravone also ameliorates the AD-like pathologies and memory deficits of the mice. These findings suggest that Edaravone holds a promise as a therapeutic agent for AD by targeting multiple key pathways of the disease pathogenesis.

Serum Aß is predictive for short-term neurological deficits after acute ischemic stroke.

Mounting evidence suggests that ischemic stroke (IS) is associated with Alzheimer's disease (AD). IS and vascular risk factors increase the risk for AD. However, whether AD pathologies exist in IS and the effects of these pathologies on stroke remain unknown. In the present study, we aimed to investigate the alterations of serum Aß after acute IS (AIS), and its correlations with the neurological deficits, infarction volume, and site after stroke. AIS patients (n = 35) were recruited within 24 h of symptom onset. Age- and gender-matched AD patients (n = 48) and cognitively normal controls (NC, n = 37) were also enrolled. Serum Aß40 and Aß42 and the National Institute of Health Stroke Scale Score (NIHSS) were measured on day 1, 3, and 7 after stroke onset. We found that serum Aß40 and Aß42 levels were increased at day 1 and reached peak levels at day 3, and decreased to pre-stroke levels at day 7. Serum Aß40 levels at day 1 were correlated with the NIHSS scores and infarction volume of AIS patients. Serum Aß42 levels at day 1 were significantly higher in IS patients with dominant gray matter infarction. Serum Aß40 levels at day 1 were predictive for NIHSS at day 7. Our results indicate that AIS can induce the generation of Aß in the brain, which may in turn be involved in the pathogenesis of neurological deficits after stroke. Serum Aß might be predictive for the short-term neurological deficits after AIS.

Association Between Serum Amyloid-Beta and Renal Functions: Implications for Roles of Kidney in Amyloid-Beta Clearance.

Amyloid-beta (Aß) plays a central role in the pathogenesis of Alzheimer's disease (AD), and it is a major therapeutic target for AD. It is proposed that removal of Aß in blood can facilitate Aß clearance from the brain, representing a promising therapeutic approach for AD. However, the efficacy and mechanisms for Aß clearance by peripheral organs and tissues remain largely unknown. In the present study, 47 chronic kidney disease (CKD) patients (16 newly diagnosed patients who had never been dialyzed and 31 patients who were receiving dialysis) and 43 normal controls (NC) were enrolled. We found that serum Aß levels were significantly higher in CKD patients than NC. CKD patients who were receiving dialysis had lower serum Aß levels than patients without receiving dialysis, being comparable to NC. Furthermore, serum Aß levels were correlated with renal functions reflected by estimated glomerular filtration rate (eGFR) and residual GFR (rGFR). Our study suggests that kidney is involved in peripheral clearance of Aß, and dialysis might be a potential therapeutic approach of Aß removal.

Associations Between ApoEε4 Carrier Status and Serum BDNF Levels--New Insights into the Molecular Mechanism of ApoEε4 Actions in Alzheimer's Disease.

Insufficient neurotrophic support increases the risk for developing Alzheimer's disease (AD). Mounting evidence has confirmed the association of brain-derived neurotrophic factor (BDNF) and apolipoprotein E (ApoE) with AD. As both BDNF and ApoE are suggested to be involved in modulating brain integrity, the present study is aiming to investigate the associations between these two factors. In this study, 110 AD patients and 120 cognitively normal controls (NC) were recruited for measurement of serum BDNF levels and ApoE genotyping. Serum BDNF levels in the AD group were significantly lower than that in the NC group, reflecting insufficient neurotrophic supply in AD patients. We further found that ApoE ε4+/- and ε4+/+ subjects had significantly lower serum BDNF levels than ε4-/- subjects in the whole cohort and the NC group, suggesting altered BDNF metabolism in ApoE ε4 carriers. Further analysis indicated possible interactions between ApoEε4 and BDNF in their co-effects on AD and mini-mental state examination (MMSE) scores. Our findings imply that the possible involvement of ApoE ε4 in BDNF metabolism might be another molecular mechanism underlying the contribution of ApoE ε4 to the development of AD.

Olfactory ensheathing cells enhance Schwann cell-mediated anatomical and functional repair after sciatic nerve injury in adult rats.

Sciatic nerve injury results in axon damage, muscle degeneration, and loss of function. We compared the potential of Schwann cell (SC), olfactory ensheathing cell (OEC), or mixed SC/OEC transplants for anatomical and functional restoration after adult rat sciatic nerve transection. The cells were seeded into a 20mm long macroporous poly(dl-lactide-co-glycolide) acid conduit and grafted between the sciatic nerve stumps. Some rats received a conduit without cells (controls) or an autologous nerve graft, the clinical standard of care. Compared with SC transplants, axon regeneration was 25% less with OEC transplants but 28% more with SC/OEC transplants. Gastrocnemius muscle restoration was similar with a SC or OEC transplant and 35% better with a SC/OEC transplant. With SC transplants, motor and sensory function recovery and electrophysiological outcomes were similar as with OEC transplants and 33% better with SC/OEC transplants. Compared with the mixed SC/OEC transplants, axon regeneration was 21% better and gastrocnemius muscle restoration was 18% better with autologous peripheral nerve transplants, but these improvements did not translate into increased function and electrophysiological outcomes. Our results revealed that OEC synergistically improve SC mediated sciatic nerve repair. The data emphasized the promise of SC/OEC transplants as artificial nerves for peripheral nerve repair. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

PLGA conduit seeded with olfactory ensheathing cells for bridging sciatic nerve defect of rats.

PLGA is thought to be a promising material for nerve scaffold. OECs have been shown to promote axon outgrowth and myelination following peripheral nerve transection. This study assessed the compatibility between PLGA and OECs in vitro, and evaluated the effect of PLGA conduit filled with OECs and extracellular matrix gel (ECM) (POE group) on 10 mm-defect sciatic nerve of rats. Silicon-OECs-EMC (SOE group), PLGA-ECM (PE group), and silicon-ECM (SE group)-were used as the controls. The survival and distribution of OECs in vivo, neurohistology and neurofunction of the bridged nerve, were quantitatively evaluated from 1 week to 12 weeks after surgery. PLGA possessed complete compatibility with OECs. After implantation, OECs migrated along the axis of the nerve and survived longer in the POE group than in the SOE group. Gross recovery of the animal, like ulcerious and autophagical rate as well as relative diameter recovery rate of the fiber, was more successful in the POE group than in other groups. The number of the fiber in the middle and distal segments of bridged sites and neurons in anterior horn of the spinal cord was increased in both OECs-contained groups, but the diameter and the myeline thickness of the fiber were increased only in the POE group. The nerve conduction velocity and the amplitude of compound muscle active potential were improved much successfully in the PLGA-guided group than in the silicon-guided group, but the best improvement was encountered in the POE group. Sciatic function index was not improved in all groups at 12 weeks after surgery due to the injury model. These results suggested that PLGA filled with OECs is a significant alternative to conventional autograft in repairing peripheral nerve defects, and OECs are potential seed cells for peripheral nerve tissue engineering.