Low Neural Exosomal Levels of Cellular Survival Factors in Alzheimer\u27s Disease

Transcription factors that mediate neuronal defenses against diverse stresses were quantified in plasma neural-derived exosomes of Alzheimer\u27s disease or frontotemporal dementia patients and matched controls. Exosomal levels of low-density lipoprotein receptor-related protein 6, heat-shock factor-1, and repressor element 1-silencing transcription factor all were significantly lower in Alzheimer\u27s disease patients than controls (P \u3c 0.0001). In frontotemporal dementia, the only significant difference was higher levels of repressor element 1-silencing transcription factor than in controls. Exosomal transcription factors were diminished 2-10 years before clinical diagnosis of Alzheimer\u27s disease. Low exosomal levels of survival proteins may explain decreased neuronal resistance to Alzheimer\u27s disease neurotoxic proteins

Extracellular Vesicle-Associated Aβ Mediates Trans-Neuronal Bioenergetic and Ca\u3csup\u3e2+\u3c/sup\u3e-Handling Deficits in Alzheimer\u27s Disease Models

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder in which aggregation-prone neurotoxic amyloid β-peptide (Aβ) accumulates in the brain. Extracellular vesicles (EVs), including exosomes, are small 50–150 nm membrane vesicles that have recently been implicated in the prion-like spread of self-aggregating proteins. Here we report that EVs isolated from AD patient cerebrospinal fluid and plasma, from the plasma of two AD mouse models, and from the medium of neural cells expressing familial AD presenilin 1 mutations, destabilize neuronal Ca2+ homeostasis, impair mitochondrial function, and sensitize neurons to excitotoxicity. EVs contain a relatively low amount of Aβ but have an increased Aβ42/ Aβ40 ratio; the majority of Aβ is located on the surface of the EVs. Impairment of lysosome function results in increased generation of EVs with elevated Aβ42 levels. EVs may mediate transcellular spread of pathogenic Aβ species that impair neuronal Ca2+ handling and mitochondrial function, and may thereby render neurons vulnerable to excitotoxicity

Detection of Aggregation-Competent Tau in Neuron-Derived Extracellular Vesicles

Progressive cerebral accumulation of tau aggregates is a defining feature of Alzheimer’s disease (AD). A popular theory that seeks to explain the apparent spread of neurofibrillary tangle pathology proposes that aggregated tau is passed from neuron to neuron. Such a templated seeding process requires that the transferred tau contains the microtubule binding repeat domains that are necessary for aggregation. While it is not clear how a protein such as tau can move from cell to cell, previous reports have suggested that this may involve extracellular vesicles (EVs). Thus, measurement of tau in EVs may both provide insights on the molecular pathology of AD and facilitate biomarker development. Here, we report the use of sensitive immunoassays specific for full-length (FL) tau and mid-region tau, which we applied to analyze EVs from human induced pluripotent stem cell (iPSC)-derived neuron (iN) conditioned media, cerebrospinal fluid (CSF), and plasma. In each case, most tau was free-floating with a small component inside EVs. The majority of free-floating tau detected by the mid-region assay was not detected by our FL assays, indicating that most free-floating tau is truncated. Inside EVs, the mid-region assay also detected more tau than the FL assay, but the ratio of FL-positive to mid-region-positive tau was higher inside exosomes than in free solution. These studies demonstrate the presence of minute amounts of free-floating and exosome-contained FL tau in human biofluids. Given the potential for FL tau to aggregate, we conclude that further investigation of these pools of extracellular tau and how they change during disease is merited

Neuron-Derived Plasma Exosome Proteins after Remote Traumatic Brain Injury

To identify long-term effects of traumatic brain injury (TBI) on levels of plasma neuron-derived exosome (NDE) protein biomarkers of cognitive impairment (CI), plasmas were obtained from four groups of older veterans, who were matched for age and sex: no TBI or CI (n = 42), no TBI with CI (n = 19), TBI without CI (n = 21), and TBI with CI (n = 26). The TBI was sustained 12 to 74 years before the study in 75%. The NDEs were enriched by sequential precipitation and anti-L1CAM antibody immunoabsorption, and extracted protein biomarkers were quantified by enzyme-linked immunosorbent assays. Chronic NDE biomarkers known to increase for three to 12 months after TBI, including cellular prion protein (PrPc), synaptogyrin-3, P-T181-tau, P-S396-tau, Aβ42, and interleukin (IL)-6, were elevated significantly in subjects who had TBI and CI compared with controls with TBI but no CI. Chronic NDE biomarker levels in subjects without TBI showed significantly higher levels of PrPc, synaptogyrin-3, P-T181-tau, and Aβ42, but not P-S396-tau and IL-6, in those with CI compared with controls without CI. The acute NDE biomarkers claudin-5, annexin VII, and aquaporin-4 were not increased in either group with CI. The NDE biomarkers P-S396-tau and IL-6, which are increased distinctively with CI after TBI, may prove useful in evaluating CI in older patients. Aβ42 and P-tau species, as well as their respective putative receptors, PrPc and synaptogyrin-3, remain elevated for decades after TBI and may mediate TBI-associated CI and be useful targets for development of drugs

Novel Hominid-Specific IAPP Isoforms: Potential Biomarkers of Early Alzheimer’s Disease and Inhibitors of Amyloid Formation

(1) Background and aims: Amyloidosis due to aggregation of amyloid-β (Aβ42) is a key pathogenic event in Alzheimer’s disease (AD), whereas aggregation of mature islet amyloid polypeptide (IAPP37) in human islets leads to β-cell dysfunction. The aim of this study is to uncover potential biomarkers that might additionally point to therapy for early AD patients. (2) Methods: We used bioinformatic approach to uncover novel IAPP isoforms and developed a quantitative selective reaction monitoring (SRM) proteomic assay to measure their peptide levels in human plasma and CSF from individuals with early AD and controls, as well as postmortem cerebrum of clinical confirmed AD and controls. We used Thioflavin T amyloid reporter assay to measure the IAPP isoform fibrillation propensity and anti-amyloid potential against aggregation of Aβ42 and IAPP37. (3) Results: We uncovered hominid-specific IAPP isoforms: hIAPPβ, which encodes an elongated propeptide, and hIAPPγ, which is processed to mature IAPP25 instead of IAPP37. We found that hIAPPβ was significantly reduced in the plasma of AD patients with the accuracy of 89%. We uncovered that IAPP25 and a GDNF derived DNSP11 were nonaggregating peptides that inhibited the aggregation of IAPP37 and Aβ42. (4) Conclusions: The novel peptides derived from hIAPP isoforms have potential to serve as blood-derived biomarkers for early AD and be developed as peptide based anti-amyloid medicine

The lack of effect of ziprasidone on platelet serotonin concentration in schizophrenic patients

Rationale Ziprasidone is an atypical antipsychotic, with the unique multireceptor-binding profile. If affects multiple serotonergic (5-HT) receptors, inhibits 5-HT transporter (5-HTT) and inhibits synaptic 5-HT reuptake. These effects might be responsible for the antidepressant effect of ziprasidone. Objectives Since there is a lack of in vivo data on the effects of ziprasidone on 5-HT concentration in humans, the aim of the study was to investigate the effect of ziprasidone treatment on platelet 5-HT concentration in patients with schizophrenia or schizoaffective disorders. Methods In and open-label study, the effect of ziprasidone (average dose of 109 mg/day) on platelet 5-HT concentration (determined fluorimetrically) was evaluated at baseline and after 7 and 28 days of treatment in 21 male and female patients with schizophrenia or schizoaffective disorders. Results Ziprasidone treatment for 7 or 28 days did not significantly change baseline platelet 5-HT concentration in male and female schizophrenic patients. Platelet 5-HT concentration was not correlated with gender, age and smoking status of patients. Conclusions There was a lack of effect of ziprasidone treatment on platelet 5-HT concentration in male and female schizophrenic patients. Although the clinical effects of ziprasidone were evident after 28 days of treatment, and ziprasidone has the highest potency among atypical antipsychotics to block 5-HTT, our data did not confirm the hypothesis that ziprasidone treatment decreases platelet 5-HT concentration, at least not in the doses used in our study

The lack of association between catechol-O-methyl-transferase Val108/158Met polymorphism and smoking in schizophrenia and alcohol dependence

The study elucidated the association between the COMT Val108/158Met polymorphism and smoking in patients with schizophrenia, patients with alcohol dependence and healthy control subjects. The stepwise logistic regression (odds ratio (OR)=1.56, 95% confidence interval (CI)=1.10–2.23, P=0.014) and the χ2 test (P=0.008) revealed that the COMT Val/Val genotype was significantly associated with smoking in healthy male subjects. Although the hypothesis of the study was that COMT Val108/158Met genotypes will be significantly associated with smoking in schizophrenia and alcohol dependence, our study showed for the first time the lack of significant association between smoking and COMT Val108/158Met polymorphism in schizophrenia, and confirmed no association between smoking and COMT Val108/158Met in alcoholism

The catecholamine biosynthetic enzyme dopamine β-hydroxylase (DBH): first genome-wide search positions trait-determining variants acting additively in the proximal promoter.

Dopamine beta-hydroxylase (DBH) is the biosynthetic enzyme catalyzing formation of norepinephrine. Changes in DBH expression or activity have been implicated in the pathogenesis of cardiovascular and neuropsychiatric disorders. Genetic determination of DBH enzymatic activity and its secretion are only incompletely understood. We began with a genome-wide association search for loci contributing to DBH activity in human plasma. Initially, in a population sample of European ancestry, we identified the proximal DBH promoter as a region harboring three common trait-determining variants (top hit rs1611115, P = 7.2 × 10(-51)). We confirmed their effects on transcription and showed that the three variants each acted additively on gene expression. Results were replicated in a population sample of Native American descent (top hit rs1611115, P = 4.1 × 10(-15)). Jointly, DBH variants accounted for 57% of DBH trait variation. We further identified a genome-wide significant SNP at the LOC338797 locus on chromosome 12 as trans-quantitative trait locus (QTL) (rs4255618, P = 4.62 × 10(-8)). Conditional analyses on DBH identified a third genomic region contributing to DBH variation: a likely cis-QTL adjacent to DBH in SARDH (rs7040170, P = 1.31 × 10(-14)) on chromosome 9q. We conclude that three common SNPs in the DBH promoter act additively to control phenotypic variation in DBH levels, and that two additional novel loci (SARDH and LOC338797) may also contribute to the expression of this catecholamine biosynthetic trait. Identification of DBH variants with strong effects makes it possible to take advantage of Mendelian randomization approaches to test causal effects of this intermediate trait on disease

The catecholamine biosynthetic enzyme dopamine β-hydroxylase (DBH): first genome-wide search positions trait-determining variants acting additively in the proximal promoter.

Dopamine beta-hydroxylase (DBH) is the biosynthetic enzyme catalyzing formation of norepinephrine. Changes in DBH expression or activity have been implicated in the pathogenesis of cardiovascular and neuropsychiatric disorders. Genetic determination of DBH enzymatic activity and its secretion are only incompletely understood. We began with a genome-wide association search for loci contributing to DBH activity in human plasma. Initially, in a population sample of European ancestry, we identified the proximal DBH promoter as a region harboring three common trait-determining variants (top hit rs1611115, P = 7.2 × 10(-51)). We confirmed their effects on transcription and showed that the three variants each acted additively on gene expression. Results were replicated in a population sample of Native American descent (top hit rs1611115, P = 4.1 × 10(-15)). Jointly, DBH variants accounted for 57% of DBH trait variation. We further identified a genome-wide significant SNP at the LOC338797 locus on chromosome 12 as trans-quantitative trait locus (QTL) (rs4255618, P = 4.62 × 10(-8)). Conditional analyses on DBH identified a third genomic region contributing to DBH variation: a likely cis-QTL adjacent to DBH in SARDH (rs7040170, P = 1.31 × 10(-14)) on chromosome 9q. We conclude that three common SNPs in the DBH promoter act additively to control phenotypic variation in DBH levels, and that two additional novel loci (SARDH and LOC338797) may also contribute to the expression of this catecholamine biosynthetic trait. Identification of DBH variants with strong effects makes it possible to take advantage of Mendelian randomization approaches to test causal effects of this intermediate trait on disease