Elevated cerebrospinal fluid sphingomyelin levels in prodromal Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder, but still without known disease mechanism, proper treatment and efficient diagnostic tools for an early stage diagnosis. There is increasing evidence that lipids, especially cholesterol and sphingolipids, may play a role in pathological processes that occur in the AD brain even in very early stages of the disease. However, lipid changes in cerebrospinal fluid (CSF) of individuals with AD have not been well studied. In previous work, we developed a reproducible and sensitive nano-HPLC-MS method for CSF phospholipids screening and conducted a pilot study to find potential phospholipid changes in CSF from individuals with AD dementia. We observed a slight increase (24%) of sphingomyelin (SM) in CSF samples from patients with probable AD compared to non-demented controls. The goal of this work was to validate our findings and to analyze how SM CSF levels change in different stages of AD from prodromal to mild and moderate AD. We found significantly increased SM levels (50.4±11.2%, p=0.003) in the CSF from individuals with prodromal AD compared to cognitively normal controls, but no change in CSF SM levels between mild and moderate AD groups and cognitively normal controls. These results suggest that alterations in the SM metabolism may contribute to early pathological processes leading to AD.     

Hourly variability of cerebrospinal fluid biomarkers in Alzheimer's disease subjects and healthy older volunteers

Large hour-to-hour variability has previously been demonstrated in the cerebrospinal fluid (CSF) concentrations of Alzheimer's disease (AD) biomarkers amyloid β(42) (Aβ(42)) and Aβ(40) in healthy younger subjects. We investigated the within-subject variability over 36 hours in CSF Aβ and tau proteins, in older subjects and AD patients. Six patients with mild stage AD (59-85 years, Mini Mental State Examination (MMSE) 16-26) and 6 healthy older volunteers (64-77 years) received an intrathecal catheter from which, during 36 hours, each hour 6 mL of CSF was drawn. Concentrations of Aβ(42), Aβ(40), total tau, and phosphorylated tau were determined and the variability was analyzed. Within-subject variability within 3-hour periods was assessed as the coefficient of variation, which was comparable for these 4 biomarkers in controls (4.2%-4.6%) and AD (3.1%-5.8%). Variability over 12 hour periods was 5.3% to 9.5%. These findings suggest that CSF biomarker variability is relatively low in healthy older controls and AD patients. Furthermore, continuous sampling of CSF proved to be a useful and robust method, which may also be used to investigate AD pathogenesis and to evaluate pharmacotherapeutic interventions.     

An Alzheimer's disease-specific β-amyloid fragment signature in cerebrospinal fluid

Pathogenic events in Alzheimer's disease (AD) involve an imbalance between the production and clearance of the neurotoxic β-amyloid peptide (Aβ), especially the 42 amino acid peptide Aβ1–42. While much is known about the production of Aβ1–42, many questions remain about how the peptide is degraded. To investigate the degradation pattern, we developed a method based on immunoprecipitation combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry that determines the Aβ degradation fragment pattern in cerebrospinal fluid (CSF). We found in total 18 C-terminally and 2 N-terminally truncated Aβ peptides and preliminary data indicated that there were differences in the detected Aβ relative abundance pattern between AD and healthy controls. Here, we provide direct evidence that an Aβ fragment signature consisting of Aβ1–16, Aβ1–33, Aβ1–39, and Aβ1–42 in CSF distinguishes sporadic AD patients from non-demented controls with an overall accuracy of 86%.     

ADAM10 expression and promoter haplotype in Alzheimer's disease

Alzheimer's disease is confirmed at autopsy according to the accumulation of brain neuritic plaques and neurofibrillary tangles in the brain. Neuritic plaques contain amyloid-β (Aβ) and lower levels of Aβ correspond to an increase in ADAM10 α-secretase activity. ADAM10 α-secretase activity produces a soluble amyloid precursor protein (APP) alpha (sAPPα) product and negates the pathological production of Aβ. In this investigation, it was hypothesized that genetic variation with the ADAM10 promoter is associated with ADAM10 expression levels as well as cerebrospinal fluid sAPPα levels. Results from this investigation suggest that the ADAM10 rs514049-rs653765 C-A promoter haplotype is associated with: (1) higher CSF sAPPα levels in cognitively normal controls compared with Alzheimer's disease (AD) patients, (2) higher postmortem brain hippocampus, but not cerebellum, ADAM10 protein levels in subjects with low plaque scores compared with those with high plaque scores, and (3) higher promoter activity for promoter-only reporter constructs compared with promoter 3' untranslated region (3'UTR) constructs in the human neuroblastoma SHSY5Y cell line, but not in HepG2 or U118 cell lines. Taken together, these findings suggest that ADAM10 expression is modulated according to a promoter haplotype that is influenced in a brain region- and cell type-specific manner.     

High neuron-specific enolase level of cerebrospinal fluid in the early stage of Creutzfeldt-Jakob disease

Summary The measurement of neuron-specific enolase level in serum and cerebrospinal fluid was conducted time-sequentially in an autopsy confirmed patient with Creutzfeld-Jakob disease. The level was markedly high in the early stage of the disease at which time the brain CT showed no or minimal abnormalities, while falling into the normal range in the advanced stage. This is the first report of the elevated level of neuron-specific enolase in Creutzfeldt-Jakob disease.Abbreviations CT Computed tomography - CSF Cerebrospinal fluid - CJD Creutzfeldt-Jakob disease - NSE Neuronspecific enolase - CEA Carcinoembryonic antigen - PSD Periodic synchronous discharge - PET Positron emission tomography     

Differential increase in cerebrospinal fluid-acetylcholinesterase after treatment with acetylcholinesterase inhibitors in patients with Alzheimer's disease

The clinical significance and the effects of pharmacological treatment of patients with Alzheimer's disease (AD) were evaluated by measurement of acetylcholinesterase (AChE) in the cerebrospinal fluid (CSF). CSF–AChE of AD patients was lower, not significantly, compared with controls. However, CSF–AChE was significantly increased after treatment of AD patients with AChE inhibitors (donepezil and galantamine). The increase was higher in patients treated with donezepil than in those treated with galantamine, which might be related to different mechanisms for the substances. The increase was also dose-dependent, and was especially marked in patients showing a clinical response. These data suggest that CSF biomarkers are capable not only of identifying a biochemical effect of drugs, but also of differentiating between different compounds in a dose-dependent manner.     

Elevated levels of phosphorylated neurofilament proteins in cerebrospinal fluid of Alzheimer disease patients

Neurofilament (NF) subunits NF-H, NF-M and NF-L are hyperphosphorylated and elevated in Alzheimer disease (AD) brain. We investigated the level and phosphorylation states of NF subunits in lumbar cerebrospinal fluid (CSF) from living patients by bienzyme substrate-recycle enzyme-linked immunosorbent assay. We found: (i), that the levels of phosphorylated NF-H/M (pNF-H/M), non-phosphorylated NF-H/M (npNF-H/M) and NF-L were significantly higher (pNF-H/M, 12–24-fold; npNF-H/M, 3–4-fold) in neurologically healthy aged people than young control individuals; (ii), that in AD, the levels of npNF-H/M, and NF-L were similar to vascular dementia (VaD), and higher than in age-matched controls; and (iii), that the levels of pNF-H/M were significantly higher than in aged controls, non-AD neurological disorders and VaD. Based on these findings, it is suggested that the increased level of total NF proteins in CSF could be used as a marker for brain aging and neurodegenerative disorders in general, and the levels of pNF-H/M as a marker to discriminate AD from normal brain aging and as well as neurological conditions including VaD.     

Relationship of cognitive reserve and cerebrospinal fluid biomarkers to the emergence of clinical symptoms in preclinical Alzheimer's disease

The levels of β-amyloid (Aβ) and phosphorylated tau (p-tau), as measured in cerebrospinal fluid, have been associated with the risk of progressing from normal cognition to onset of clinical symptoms during preclinical Alzheimer's disease. We examined whether cognitive reserve (CR) modifies this association. Cerebrospinal fluid was obtained at baseline from 239 participants (mean age, 57.2 years) who had been followed for up to 17 years with clinical and cognitive assessments (mean follow-up, 8 years). A composite score based on the National Adult Reading Test, vocabulary, and years of education at baseline was used as an index of CR. Cox regression models showed that the increased risk of progressing from normal cognition to symptom onset was associated with lower CR, lower baseline Aβ, and higher baseline p-tau. There was no interaction between CR and Aβ, suggesting that the protective effects of higher CR are equivalent across the observed range of amyloid levels. In contrast, both tau and p-tau interacted with CR, indicating that CR was more protective at lower levels of tau and p-tau.     

Total antioxidant capacity of cerebrospinal fluid is decreased in patients with motor neuron disease

Oxidative stress has been associated with motor neuron disease (MND). The human body has several antioxidant defense systems to repair the damage caused by oxidative stress. The activity of these systems is thought to be reduced in neurodegenerative diseases, which may increase the level of oxidative damage and be a contributing factor to motor neuron death. In the present study, we compared the total antioxidant capacity (TAC) of human serum and cerebrospinal fluid (CSF) of MND patients with that of a control group including patients with migraine, tension headache and psychiatric disorders. Within-subject serum and CSF TAC were strongly correlated (r=0.639; p=0.000), and CSF TAC was significantly lower in MND patients as compared to controls after adjustment for known influencing factors (112.7 micromol Fe/L+/-11.7 versus 135.2 micromol Fe/L+/-19.7; p=0.012). No differences in serum or CSF TAC were observed among the clinical forms of MND considered in this work. In conclusion, the CSF TAC was strongly correlated with serum TAC, and a decrease in CSF TAC was demonstrated in MND patients compared to controls that was not independent from serum antioxidants, this translating in a systemic (but prevailing in the CNS) oxidative damage in this pathology.     

Alzheimer's disease and Alzheimer's dementia: distinct but overlapping entities

Much of the controversy about the “amyloid cascade hypothesis” may reflect unrecognized differences in the use of language, including the use of the word “cause.” This commentary proposes that the term Alzheimer disease refer to the neuropathological entity and the term Alzheimer dementia to clinical dementia in people who also have Alzheimer neuropathology. The ultimate causes of Alzheimer disease are proposed to be aging, environmental stresses, and genetic predispositions. The fundamental cause of Alzheimer dementia is proposed to be Alzheimer disease, i.e. the neurobiological abnormalities in Alzheimer brain. The neurobiology of Alzheimer disease includes changes that may initially be adaptive but can become excessive and thereby harmful; they include increased expression of APP with accumulation of potentially damaging peptides such as Aβ, inflammation, and increased ROS activity. The neurobiological abnormality that is the proximate cause of Alzheimer dementia appears to be decreases in cerebral metabolic rate. Decreased metabolism occurs not only in this but in essentially all dementias, and impairing brain metabolism induces neuropsychological deficits characteristic of dementias. The immediate cause of Alzheimer dementia is proposed to be deficiencies in signaling, both intracellular and intercellular (neurotransmission), that follow directly from the decrease in cerebrometabolic rate.     

Somatostatin-like immunoreactivity in lumbar cerebrospinal fluid from neurohistologically examined demented patients

The concentration of somatostatin-like immunoreactivity (SLI) in lumbar cerebrospinal fluid was measured in clinically suspected examples of either Alzheimer's disease (AD) or Pick's disease and controls. No significant correlation was found between the concentration of SLI and the age (22-73 years) of controls. Histological examination of brain material from the demented patients enabled the samples to be divided into AD and examples of clinically suspected AD or Pick's disease without specific histological change. The mean concentration of SLI was only slightly reduced in patients with AD in the presenium compared to control, and was unaltered from control in the examples of AD of senile age. The group of demented patients without specific histological change had a reduced concentration of SLI in lumbar CSF compared to control patients.     

Flow cytometric cerebrospinal fluid analysis in children

Flow cytometry (FC) is of increasing importance for the analysis of cerebrospinal fluid (CSF) lymphocytes because of its ability to detect a large spectrum of cellular characteristics (granularity, volume, surface antigen expression) even in small amounts of cells. Data on CSF FC in children are very limited. Here, we summarize our 3-year experience of CSF FC routinely performed in pediatric patients with assumed inflammatory central nervous system (CNS) disease. Among 109 samples sent for analysis, flow cytometric detection of major leukocyte subsets was possible in 78% (85 out of 109), which exceeds the 31% rate of our retrospective microscopic pediatric control group. Apart from physiologic lymphocytes (100%) or monocytes (48%), 11 out of these 85 samples showed granulocytes, two showed proliferated monocytes, and nine displayed proliferated lymphocytes. In most children, the proliferated lymphocytes consisted of a polyclonal population of CD4+ and CD8+ T cells. Compared with literature data, eight children showed abnormally composed lymphocyte subsets (surface antigen expression) within the main lymphocyte population. However, none of these changes was specific for distinct diseases or allowed a distinction between patients with and without primary inflammatory processes. These data suggest that CSF FC may be the most effective modality to differentiate major CSF leukocyte subsets. At present, further differentiation of distinct cell populations, such as proliferated lymphocytes, is of limited clinical impact. This may, however, gain increasing interest in the future.     

Increased expression of the Nogo receptor in the hippocampus and its relation to the neuropathology in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent cause of dementia in human beings. Its best-known pathologic feature is the presence of senile plaques and neurofibrillary tangles in the brain. Nogo-66 receptor (NgR) is believed to contribute to the inhibitory activities of axon regeneration after injury. This study investigated the expression of NgR in the hippocampus and its relation to the pathologic changes of AD using immunohistochemistry and double-labeling immunofluorescence methods. The results showed that NgR immunoreactivity was present in more than 50% of the pyramidal layer cells of the CA1 to CA4 subfields of the hippocampus. No significant difference was observed in the number of NgR immunopositive cells in the CA1 to CA4 subfields between patients with AD and control subjects, whereas the ratio of NgR immunopositive cells to the total number of pyramidal layer cells was revealed to be significantly higher in the CA1 and CA2 subfields of the hippocampus of patients with AD than that in the same region of the control subjects. Moreover, high numbers of AT-8 immunopositive cells were found to be double-labeled with NgR in the CA1 subfields of patients with AD, whereas only few NgR deposits were observed in the senile plaques of the hippocampus in these patients. These results suggest that NgR may be related to the formation of tangles in AD.     

Angiotensin I converting enzyme in cerebrospinal fluid of patients with neurological diseases

Summary The angiotensin I converting enzyme activity (kininase II, EC 3.4.15.1) was measured fluorimetrically in cerebrospinal fluid (CACE) of 154 patients with neurological disorders and 27 controls. The concentrations of total protein, albumin, and immunoglobulins G and A were also determined. There was no correlation between CACE and sex or age, but a slight positive relation between CACE and total protein and an inverse correlation between CACE and albumin were observed. Compared to controls, significantly elevated CACE was found in acute untreated CNS sarcoidosis (P<0.0001), followed by viral encephalitis, CNS syphilis, Huntington's disease, and multiple sclerosis (P<0.001). In treated CNS sarcoidosis, only a minor increase of CACE was observed (P<0.05). The determination of CACE can be used for the diagnosis of neurological disorders.Abbreviations ACE Angiotensin I converting enzyme - CACE Angiotensin I converting enzyme of cerebrospinal fluid - CSF Cerebrospinal fluid - CNS Central nervous system With financial support from the Deutsche Forschungs Gemeinschaft (Schw 309/2-1)     

Age-related changes in the cerebrospinal fluid outflow glycosaminoglycans

The glycosaminoglycan distribution patterns of the cerebrospinal fluid (CSF) outflow pathway, dura mater and cerebral cortex of young New Zealand red rabbits and 1-, 3- and 12-week-old C-57 mice were identified by analyses of the glycosaminoglycan moieties and by the use of zone electrophoresis. The glycosaminoglycans were identified by specific degradation procedures, i.e., hyaluronate lyase, chondroitin ABC lyase, endo-gb-D-galactosidase and nitrous acid treatment. The CSF outflow pathway and dura mater glycosaminoglycan components were primarily hyaluronic acid and chondroitin sulfatedermatan sulfate, whereas the cerebral cortex glycosaminoglycan components were hyaluronic acid, chondroitin sulfatedermatan sulfate, keratan sulfate and heparan sulfate. The glycosaminoglycan components of the dura mater and cerebral cortex decreased and those of the CSF outflow pathway increased as a function of age. These results demonstrate the feasibility of analyses of the CSF outflow pathway glycosaminoglycan components and suggest that topographical changes in the glycosaminoglycan distribution profiles may contribute to the pattern of cerebrospinal fluid outflow.     

The influence of cerebrospinal fluid turnover on age-related changes in cerebrospinal fluid protein concentrations

Studies have shown that ageing and several neurological diseases of the central nervous system are often accompanied with increase in concentrations of many cerebrospinal fluid (CSF) proteins. However, few studies have actually looked into the mechanisms behind the increase in CSF protein concentrations. In this study, CSF secretion rates and turnovers were measured using the in situ perfused choroid plexus (CP) technique in a group of sheep between 1 and 10 years of age. CSF protein concentrations were determined using quantitative proteomic techniques. CSF turnover in hours correlated significantly with age, changing from 10.5 ± 2.7 h in the young to 17.1 ± 2.4 h in the old. The amount of CSF replaced per hour decreased from 2.46 ± 0.42 mL in the young to 1.17 ± 0.16 mL in the old. The age-related reduction in CSF turnover was calculated to have a concentrating effect of approximately 1.32 times in middle-aged and 2.10 times in old CSF proteins. After CSF turnover normalization, CSF albumin (a plasma-derived protein) concentration still increased significantly with age; however, both brain-derived and partially brain-derived protein concentrations in the CSF decreased with age after normalization. Regression analysis between turnovers and albumin concentrations has shown that reduced CSF turnover was the cause of increased CSF albumin concentrations with age. Therefore, CSF protein concentrations should be normalized according to their age-specific turnovers first before their concentrations can be compared logically between different ages.     

Identification of altered exosomal microRNAs and mRNAs in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by decreased memory and cognitive functions. Exosomes carry a variety of important information such as proteins, lipids, DNA and RNA of mother cells. It is reported that exosomes play critical roles in nervous system physiology and neurodegenerative diseases. However, the functions of exosomes in AD progression are not fully elucidated. In this study, we detected the expression pattern of mRNAs and miRNAs in exosomes derived from the AD and health mice. A total of 1320 mRNAs and 29 miRNAs were differentially expressed in exosomes between the two groups. Subsequently, the downregulation of Chi3l1 and upregulation of Rhog in AD mice were verified by qRT-PCR. Meanwhile, the downregulation of miR-148a-5p and upregulation of miR-27a-5p in AD group were also tested by qRT-PCR. The functions of differentially expressed mRNAs and potential target genes of miRNAs were determined by GO and KEGG analysis. According to the ceRNA hypothesis, we established an integrated ceRNA network of circRNA-lncRNA-miRNA-mRNA. In conclusion, exosomal lncRNAs, mRNAs, circRNAs and miRNAs were identified to participate in the progression of AD which might be possible biomarkers and therapeutic targets for AD.     

Tau in cerebrospinal fluid: a sensitive sandwich enzyme-linked immunosorbent assay using tyramide signal amplification

Tau in cerebrospinal fluid (CSF) has been proposed as a diagnostic marker for Alzheimer's disease (AD). This paper presents a new sensitive sandwich ELISA allowing quantitation of tau from 8 microl CSF/well. A human specific monoclonal tau antibody HT7 was used as a capture antibody and a mixture of polyclonal tau antibodies, 92e and R134d was used as reporter antibodies. Tyramide signal amplification (TSA) technology was used in the last step to increase the sensitivity. With this TSA-ELISA, the lowest detection limit for tau was 14.3 pg/ml. Tau levels in CSF were found to be increased in AD patients (807+/-304 pg/ml, p<0.001) compared with controls (252+/-94 pg/ml). Thirty-five of 38 AD cases (92% sensitivity) yielded signals greater than cutoff, while only 1 of 38 control cases (97% specificity) was greater. A highly significant correlation was found between this assay and a commonly used kit, INNOTEST hTAU Antigen.     

Posterior cingulate atrophy and metabolic decline in early stage Alzheimer's disease

To test the hypothesis that Alzheimer's disease (AD) patients with posterior cingulate/precuneus (PCP) atrophy would be a distinct disease form in view of metabolic decline. Eighty-one AD patients underwent (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and structural magnetic resonance imaging (MRI). Positron emission tomography and voxel-based morphometry (VBM) Z-score maps were generated for the individual patients using age-specific normal databases. The patients were classified into 3 groups based on atrophic patterns (no-Hipp-PCP, atrophy in neither hippocampus nor PCP; Hipp, hippocampal atrophy; PCP, PCP atrophy). There were 16 patients classified as no-Hipp-PCP, 55 as Hipp, and 10 as PCP. The Mini Mental State Examination (MMSE) score was similar among the groups. The greater FDG decline than atrophy was observed in all groups, including the no-Hipp-PCP. The PCP group was younger, and was associated with a greater degree of FDG decline in PCP than the others. There are diverse atrophic patterns in a spectrum of AD. In particular, a subset of patients show PCP atrophy, which is associated with greater metabolic burden.     

Electrolyte and acid-base parameters of rat cerebrospinal fluid

Summary Values for various electrolytes and acid-base parameters of rat CSF were determined in adult animals anesthetized with pentobarbital or ether. In addition, the distribution of 5,5-dimethyl-2,4-oxazolidinedione (DMO) between CSF and arterial and venous blood was measured in the same animals. It was found a) that CSF electrolyte and acid-base parameters are the same in ether-and pentobarbital-treated animals; b) that DMO distributions between CSF and blood are not determined solely by pH gradients; and c) that in rat CSF electrolyte concentrations (mEq/l) —Na=148.4; K=3.16, Cl=117.9 —and acid-base values —pH=7.38, H₂CO₃=1.30 mM/l; HCO₃=24.5 mM/l —are very similar to those measured in other species.This study was supported, in part, by Grant NB 04553 from the U.S. Public Health Service, National Institutes of Health.Receipient of U.S. Public Health Service Research Career Development Program Award 1-K3-NB 7779.Receipient of U.S. Public Health Service Research Career Program Award 5-K6-NB-18, 838.