Amyloid plaques and tau tangles are common pathological hallmarks for Alzheimer’s disease (AD), however reducing Aβ production failed to relieve the symptoms of AD patients. Here we report a high GABA (γ-aminobutyric acid) content in reactive astrocytes in the dentate gyrus (DG) of a mouse model for AD (5xFAD) that results in increased tonic inhibition and memory deficit. We also confirm in human AD patient brains that dentate astrocytes have a high GABA content, suggesting that high astrocytic GABA level may be a novel biomarker and a potential diagnostic tool for AD. The excessive GABA in 5xFAD astrocytes is released through an astrocyte-specific GABA transporter GAT3/4, and significantly enhanced tonic GABA inhibition in dentate granule cells. Importantly, reducing tonic inhibition in 5xFAD mice rescues the impairment of long-term potentiation (LTP) and memory deficit. Thus, reducing tonic GABA inhibition in the DG may lead to a novel therapy for Alzheimer’s disease.
Alzheimer’s disease; astrocyte; GABA transporter; GAT3; GAT4; GABAA receptor; α5 subunit; tonic inhibition; dentate gyrus; long-term potentiation; memory deficit; drug target; biomarker
Abnormal cytoplasmic accumulation of Fused in Sarcoma (FUS) in neurons defines subtypes of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). FUS is a member of the FET protein family that includes Ewing's sarcoma (EWS) and TATA-binding protein-associated factor 2N (TAF15). FET proteins are predominantly localized to the nucleus, where they bind RNA and DNA to modulate transcription, mRNA splicing, and DNA repair. In ALS cases with FUS inclusions (ALS-FUS), mutations in the FUS gene cause disease, whereas FTLD cases with FUS inclusions (FTLD-FUS) do not harbor FUS mutations. Notably, in FTLD-FUS, all FET proteins accumulate with their nuclear import receptor Transportin 1 (TRN1), in contrast ALS-FUS inclusions are exclusively positive for FUS. In the present study, we show that induction of DNA damage replicates several pathologic hallmarks of FTLD-FUS in immortalized human cells and primary human neurons and astrocytes. Treatment with the antibiotic calicheamicin γ1, which causes DNA double-strand breaks, leads to the cytoplasmic accumulation of FUS, TAF15, EWS, and TRN1. Moreover, cytoplasmic translocation of FUS is mediated by phosphorylation of its N terminus by the DNA-dependent protein kinase. Finally, we observed elevated levels of phospho-H2AX in FTLD-FUS brains, indicating that DNA damage occurs in patients. Together, our data reveal a novel regulatory mechanism for FUS localization in cells and suggest that DNA damage may contribute to the accumulation of FET proteins observed in human FTLD-FUS cases, but not in ALS-FUS.
amyotrophic lateral sclerosis (ALS); cytoplasmic translocation; DNA damage; frontotemporal lobar degeneration (FTLD); Fused in Sarcoma (FUS); phosphorylation
Many neurodegenerative disorders involve the abnormal accumulation of proteins. In addition to the well-known findings of neurofibrillary tangles and β-amyloid plaques in Alzheimer’s disease, here we show that abnormal accumulations of gephyrin, an inhibitory receptor anchoring protein, are highly correlated with the neuropathologic diagnosis of AD (odds ratio of 72.7; p = 6.844 × 10−6 by Fisher’s exact test, n = 17 AD and n = 14 control cases). Furthermore, the gephyrin accumulations are specific for AD and not seen in other neurodegenerative diseases. Gephyrin accumulations overlap with β-amyloid plaques and, more rarely, neurofibrillary tangles. Follow-up biochemical and proteomic studies suggest alterations in the gephyrin solubility and reveal elevated levels of gephyrin lower-molecular-weight species in the AD insoluble fraction. Since gephyrin is involved in synaptic organization and synaptic dysfunction is an early event in AD, these findings point to a possible role for gephyrin in AD pathogenesis.
gephyrin; Alzheimer’s disease; β-amyloid; presenilin; synapse; GABA
The first US Food and Drug Administration–approved clinical trial to treat amyotrophic lateral sclerosis (ALS) with neural stem cell–based therapy is in progress. The goal of the current study was to identify and assess the survival of human spinal cord–derived neural stem cells (HSSCs) transplanted into the spinal cord in patients with ALS.
Spinal cords transplanted with HSSCs were examined from six autopsy cases. Homogenized tissues were interrogated for the presence of donor versus recipient DNA using real-time PCR methods (qPCR). Fluorescence in situ hybridization (FISH) was performed using DNA probes for XY chromosomes to identify male donor HSSCs in one female case, and immunohistochemistry (IHC) was used to characterize the identified donor cells.
Genomic DNA from donor HSSCs was identified in all cases, comprising 0.67–5.4% of total tissue DNA in patients surviving 196 to 921 days after transplantation. In the one female patient a “nest” of cells identified on H&E staining were XY-positive by FISH, confirming donor origin. A subset of XY-positive cells labeled for the neuronal marker NeuN and stem cell marker SOX2.
This is the first study to identify human neural stem cells transplanted into a human spinal cord. Transplanted HSSCs survived up to 2.5 years posttransplant. Some cells differentiated into neurons, while others maintained their stem cell phenotype. This work is a proof of concept of the survival and differentiation of human stems cell transplanted into the spinal cord of ALS patients.
The causes of late-onset Alzheimer disease (AD) are not yet understood but likely include a combination of genetic, environmental, and lifestyle factors. Limited epidemiological studies suggest that occupational pesticide exposures are associated with AD. Previously, we reported that serum levels of dichlorodiphenyldichloroethylene (DDE), the metabolite of the pesticide dichlorodiphenyltrichloroethane (DDT), were elevated in a small number of patients with AD (n=20).
To evaluate the association between serum levels of DDE and AD and whether the apolipoprotein E (APOE) genotype modifies the association.
DESIGN, SETTING, AND PARTICIPANTS
A case-control study consisting of existing samples from patients with AD and control participants from the Emory University Alzheimer’s Disease Research Center and the University of Texas Southwestern Medical School’s Alzheimer’s Disease Center. Serum levels of DDE were measured in 79 control and 86 AD cases.
MAIN OUTCOMES AND MEASURES
Serum DDE levels, AD diagnosis, severity of AD measured by the Mini-Mental State Examination score, and interaction with APOE4 status.
Levels of DDE were 3.8-fold higher in the serum of those with AD (mean [SEM], 2.64 [0.35] ng/mg cholesterol) when compared with control participants (mean [SEM], 0.69 [0.1] ng/mg cholesterol; P < .001). The highest tertile of DDE levels was associated with an odds ratio of 4.18 for increased risk for AD (95% CI, 2.54–5.82; P < .001) and lower Mini-Mental State Examination scores (−1.605; range, −3.095 to −0.114; P < .0001). The Mini-Mental State Examination scores in the highest tertile of DDE were −1.753 points lower in the subpopulation carrying an APOE ε4 allele compared with those carrying an APOE ε3 allele (P interaction = .04). Serum levels of DDE were highly correlated with brain levels of DDE (ρ = 0.95). Exposure of human neuroblastoma cells to DDT or DDE increased levels of amyloid precursor protein.
CONCLUSIONS AND RELEVANCE
Elevated serum DDE levels are associated with an increased risk for AD and carriers of an APOE4 ε4 allele may be more susceptible to the effects of DDE. Both DDT and DDE increase amyloid precursor protein levels, providing mechanistic plausibility for the association of DDE exposure with AD. Identifying people who have elevated levels of DDE and carry an APOE ε4 allele may lead to early identification of some cases of AD.
Osteopontin is a cytokine found in many tissues and plays a role in tissue injury and repair. This study had two goals: to characterize osteopontin expression after status epilepticus (SE), and to test the hypotheses that osteopontin affects the susceptibility to seizures or alters cell death and inflammation after SE.
Pilocarpine was used to induce SE in OPN−/− and OPN+/+ mice to compare seizure susceptibility, neuropathological markers including real time PCR for inflammatory genes, and osteopontin immunohistochemistry. The effect of added osteopontin on excitotoxicity by N-methyl-d-aspartate in neuronal cultures of ONP−/− mice was determined.
Neurons undergoing degeneration showed osteopontin immunoreactivity 2–3 days after SE. After 10 to 31 days degenerating axons in the thalamus were osteopontin-positive. The susceptibility to seizures of OPN−/− and OPN+/+ mice in the pilocarpine, fluorothyl, and maximal electroshock models was similar. There were no significant differences in the extent of neuronal damage after pilocarpine-induced SE, the expression of several neuropathological markers or the RNA levels of selected inflammatory genes. Recombinant and natural bovine osteopontin did not affect the extent of NMDA-induced cell death in OPN−/− mouse neuronal cultures.
We demonstrated that osteopontin is up-regulated in response to SE in distinct temporal sequences in the hippocampus, specifically in degenerating neurons and axons. However, osteopontin did not appear to regulate neurodegeneration or inflammation within the first 3 days after SE.
Seizure; Pilocarpine; Inflammation; Axonal degeneration; Neuronal degeneration
The brain consists of diverse cell types including neurons, astrocytes, oligodendrocytes and microglia. The isolation of nuclei from these distinct cell populations provides an opportunity to identify cell-type specific nuclear proteins, histone modifications and regulation networks that are altered with normal brain aging or neurodegenerative disease. In this study, we used a method by which intact neuronal and non-neuronal nuclei were purified from human post-mortem brain employing a modification of fluorescence activated cell sorting (FACS) we term fluorescence activated nuclei sorting (FANS). An antibody against NeuN, a neuron specific splicing factor, was used to isolate neuronal nuclei. Utilizing mass spectrometry (MS) based label-free quantitative proteomics we identified 1,755 proteins from sorted NeuN positive and negative nuclear extracts. Approximately 20 percent of these proteins were significantly enriched or depleted in neuronal versus non-neuronal populations. Immunoblots of primary cultured rat neuron, astrocyte and oligodendrocyte extracts confirmed that distinct members of the major nucleocytoplasmic structural linkage complex (LINC), nesprin-1 and nesprin-3, were differentially enriched in neurons and astrocytes, respectively. These comparative proteomic data sets also reveal a number of transcription and splicing factors that are selectively enriched in a cell-type specific manner in human brain.
Cell type; astrocyte; neuron; oligodendrocyte; microglia; liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS); transcription; splicing; nucleus; neuroproteomics; epigenetic
RING finger protein 11 (RNF11), a negative regulator of NF-κB signaling pathway, colocalizes with α-synuclein and is sequestered in Lewy bodies in Parkinson’s disease (PD). Since persistent NF-κB activation is reported in PD, in this report we investigated if RNF11 expression level is correlated to activated NF-κB in PD. We examined RNF11 expression levels in correlation to phospho-p65, a marker for activated NF-κB, in control and PD brain tissue from cerebral cortex. In addition we performed double immunofluorescence labeling experiments to confirm this correlation. Our investigations demonstrated that the neuronal RNF11 expression was down-regulated in PD and was usually associated with increased expression of phospho-p65. Double labeling confirmed that loss of neuronal RNF11 was linked to increased phospho-p65 expression, suggesting that persistent presence of NF-κB activation could be due to decreased levels of its negative regulator. Our data exemplifies the relevance of RNF11 and persistent NF-κB activation in PD.
phospho-p65; immunofluorescence; cingulate cortex; substantia nigra
Hirano bodies are actin-rich paracrystalline inclusions found in brains of patients with Alzheimer’s disease (AD), frontotemporal dementia (FTD), and in normal aged individuals. Although studies of post-mortem brain tissue provide clues of etiology, the physiological function of Hirano bodies remains unknown. A cell culture model was utilized to study the interactions of mutant tau proteins, model Hirano bodies, and GSK3β in human astrocytoma cells.
Most tau variants showed co-localization with model Hirano bodies. Cosedimentation assays revealed this interaction may be direct, as recombinant purified forms of tau are all capable of binding F-actin. Model Hirano bodies had no effect or enhanced cell death induced by tau in the absence of amyloid precursor protein intracellular domain (AICD). In the presence of AICD and tau, synergistic cell death was observed in most cases, and model Hirano bodies decreased this synergistic cell death, except for forms of tau that caused significant cell death in the presence of Hirano bodies only. A role for the kinase GSK3β is suggested by the finding that a dominant negative form of GSK3β reduces this synergistic cell death. A subset of Hirano bodies in brain tissue of both Alzheimer’s disease and normal aged individuals was found to contain tau, with some Hirano bodies in Alzheimer’s disease brains containing hyperphosphorylated tau.
The results demonstrate a complex interaction between tau and AICD involving activation of GSK3β in promoting cell death, and the ability of Hirano bodies to modulate this process.
Hirano bodies; Actin; Tau; Amyloid precursor protein; Neurodegeneration; Alzheimer’s disease; Frontotemporal dementia
Chronic activation of the NF-κB pathway is associated with progressive neurodegeneration in Parkinson’s disease (PD). Given the role of neuronal RING finger protein 11 (RNF11) as a negative regulator of the NF-κB pathway, in this report we investigated the function of RNF11 in dopaminergic cells in PD-associated neurodegeneration. We found that RNF11 knock-down in an in vitro model of PD mediated protection against 6-OHDA-induced toxicity. In converse, over-expression of RNF11 enhanced 6-OHDA-induced dopaminergic cell death. Furthermore, by directly manipulating NF-κB signaling, we showed that the observed RNF11-enhanced 6-OHDA toxicity is mediated through inhibition of NF-κB-dependent transcription of TNF-α, antioxidants GSS and SOD1, and anti-apoptotic factor BCL2. Experiments in an in vivo 6-OHDA rat model of PD recapitulated the in vitro results. In vivo targeted RNF11 over-expression in nigral neurons enhanced 6-OHDA toxicity, as evident by increased amphetamine-induced rotations and loss of nigral dopaminergic neurons as compared to controls. This enhanced toxicity was coupled with down-regulation of NF-κB transcribed GSS, SOD1, BCL2, and neurotrophic factor BDNF mRNA levels, in addition to decreased TNF-α mRNA levels in ventral mesenchephalon samples. In converse, knockdown of RNF11 was associated with protective phenotypes and increased expression of above-mentioned NF-κB transcribed genes. Collectively, our in vitro and in vivo data suggest that RNF11-mediated inhibition of NF-κB in dopaminergic cells exaggerates 6-OHDA toxicity by inhibiting neuroprotective responses while loss of RNF11 inhibition on NF-κB activity promotes neuronal survival. The decreased expression of RNF11 in surviving cortical and nigral tissue detected in PD patients, thus implies a compensatory response in the diseased brain to PD-associated insults. In summary, our findings demonstrate that RNF11 in neurons can modulate susceptibility to 6-OHDA toxicity through NF-κB mediated responses. This neuron-specific role of RNF11 in the brain has important implications for targeted therapeutics aimed at preventing neurodegeneration.
Parkinson’s disease; NF-κB; E3 ligase; 6-hydroxydopamine; 6-OHDA; neurodegeneration; human tissue; AAV; antioxidants
We recently identified U1 small nuclear ribonucleoprotein (snRNP) tangle-like aggregates and RNA splicing abnormalities in sporadic Alzheimer’s disease (AD). However little is known about snRNP biology in early onset AD due to autosomal dominant genetic mutations or trisomy 21 in Down syndrome. Therefore we investigated snRNP biochemical and pathologic features in these disorders.
We performed quantitative proteomics and immunohistochemistry in postmortem brain from genetic AD cases. Electron microscopy was used to characterize ultrastructural features of pathologic aggregates. U1-70k and other snRNPs were biochemically enriched in the insoluble fraction of human brain from subjects with presenilin 1 (PS1) mutations. Aggregates of U1 snRNP-immunoreactivity formed cytoplasmic tangle-like structures in cortex of AD subjects with PS1 and amyloid precursor protein (APP) mutations as well as trisomy 21. Ultrastructural analysis with electron microscopy in an APP mutation case demonstrated snRNP immunogold labeling of paired helical filaments (PHF).
These studies identify U1 snRNP pathologic changes in brain of early onset genetic forms of AD. Since dominant genetic mutations and trisomy 21 result in dysfunctional amyloid processing, the findings suggest that aberrant β-amyloid processing may influence U1 snRNP aggregate formation.
Spliceosome; snRNP; Alzheimer’s disease; Down syndrome; U1-70k; SmD; Presenilin; Amyloid precursor protein
Tauopathies are a family of neurodegenerative diseases that have the pathological hallmark of intraneuronal accumulation of filaments composed of hyperphosphorylated tau proteins that tend to aggregate in an ultrastructure known as neurofibrillary tangles. The identification of mutations on the tau gene in familial cases of tauopathies underscores the pathological role of the tau protein. However, the molecular process that underlines tau-mediated neurodegeneration is not understood. Here, a proteomics approach was used to identify proteins that may be affected during the course of tau-mediated neurodegeneration in the tauopathy mouse model JNPL3. The JNPL3 mice express human tau proteins bearing a P301L mutation, which mimics the neurodegenerative process observed in humans with tauopathy. The results showed that the protein amphiphysin-1 (AMPH1) is significantly reduced in terminally ill JNPL3 mice. Specifically, the AMPH1 protein level is reduced in brain regions known to accumulate aggregates of hyperphosphorylated tau proteins. The AMPH1 protein reduction was validated in Alzheimer’s disease cases. Taken together, the results suggest that the reduction of the AMPH1 protein level is a molecular event associated with the progression of tau-mediated neurodegeneration.
Alzheimer’s disease; amphiphysin; calpain; neurodegeneration; tau; tauopathy
Polychlorinated biphenyls (PCBs) are synthetic chemicals primarily used as coolants and insulators in electrical equipment. Although banned for several decades, PCBs continue to exist in the environment because of their long half-life, continued presence in items produced before the ban, and poor disposal practices. Epidemiological and experimental studies have identified exposure to PCBs as a potential risk factor for Parkinson’s disease, perhaps more so in females. The objective of this work was to examine the association between PCB levels in post-mortem human brain tissue and the diagnosis of Parkinson’s disease, as well as the degree of nigral depigmentation. We also sought to determine if this association was more significant when patients were stratified by sex. Post-mortem brain samples from control patients and those diagnosed with Parkinson’s disease were obtained from the Emory University Brain Bank and from the Nun Study. Concentrations of eight prevalent PCB congeners were extracted from post-mortem brain tissue and analyzed using gas chromatography-mass spectrometry. PCB congeners 153 and 180 were significantly elevated in the brains of Parkinson’s disease patients. When stratified by sex, the female Parkinson’s disease group demonstrated significantly elevated concentrations of total PCBs and specifically congeners 138, 153, and 180 compared to controls, whereas PCB concentrations in males were not significantly different between control and Parkinson’s disease groups. In a separate population of women (Nun Study) who had no clinical signs or symptoms of PD, elevated concentrations total PCB and congeners 138, 153 and 180 were also observed in post-mortem brain tissue exhibiting moderate nigral depigmentation compared to subjects with mild or no depigmentation. These quantitative data demonstrate an association between brain PCB levels and Parkinson’s disease-related pathology. Furthermore, these data support epidemiological and laboratory studies reporting a link between PCB exposure and an increased risk for Parkinson’s disease, including greater susceptibility of females.
Parkinson’s disease; polychlorinated biphenyl; PCB; sex; exposure; neurodegenerative disease; mass spectrometry
TAR DNA-binding protein 43 (TDP-43) is a nuclear protein involved in RNA splicing and a major protein component in ubiquitin-positive, tau-negative inclusions of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Under disease conditions TDP-43 redistributes to the cytoplasm where it can be phosphorylated, ubiquitinated, and proteolytically cleaved. Enzymes responsible for TDP-43 proteolytic processing in brain remain largely unreported. Using a mass spectrometry approach, we identified two truncated TDP-43 peptides, terminating C-terminal to asparagines 291 (N291) and 306 (N306). The only documented mammalian enzyme capable of cleaving C-terminal to asparagine is asparaginyl endopeptidase (AEP). TDP-43-immunoreactive fragments (~35 and 32 kDa) predicted to be generated by AEP cleavage at N291 and N306 were observed by western blot analyses of post-mortem FTLD brain tissue and cultured human cells over-expressing TDP-43. Studies in vitro determined that AEP can directly cleave TDP-43 at seven sites, including N291 and N306. Western blots of brain homogenates isolated from AEP-null mice and wild-type littermate controls revealed that TDP-43 proteolytic fragments were substantially reduced in the absence of AEP in vivo. Taken together, we conclude that TDP-43 is cleaved by AEP in brain. Moreover, these data highlight the utility of combining proteomic strategies in vitro and in vivo to provide insight into TDP-43 biology that will fuel the design of more detailed models of disease pathogenesis.
Asparaginyl endopeptidase; degradomics; frontotemporal dementia; neurodegeneration; TAR DNA-binding protein 43
Brain donation and neuropathological examination of brain tissues is the only way to obtain definitive diagnostic information on research subjects enrolled in aging studies. We investigated predictors of brain donation in a population-based study of centenarians in Phase III of the Georgia Centenarian Study (GCS).
Sixty-six individuals (mean age = 100.6 years, 91% female, 20% African American) were successfully recruited from the core sample of 244 individuals residing in 44 counties of Northeast Georgia to provide brain donation.
Bivariate (t-tests, chi-square tests) and multivariate analyses (logistic regression) showed no significant differences between donors and non-donors across a wide range of demographic, religious, personality, cognitive and physical functioning characteristics.
We succeeded in recruiting a diverse, population-based sample of centenarians for brain donation. Our findings also suggest that barriers to brain donation reported in other studies may have less impact in these exceptional survivors.
Rare mutations in the gene encoding for tau (MAPT, microtubule-associated protein tau) cause frontotemporal dementia-spectrum (FTD-s) disorders, including FTD, progressive supranuclear palsy (PSP) and corticobasal syndrome, and a common extended haplotype spanning across the MAPT locus is associated with increased risk of PSP and Parkinson's disease. We identified a rare tau variant (p.A152T) in a patient with a clinical diagnosis of PSP and assessed its frequency in multiple independent series of patients with neurodegenerative conditions and controls, in a total of 15 369 subjects.
Tau p.A152T significantly increases the risk for both FTD-s (n = 2139, OR = 3.0, CI: 1.6–5.6, P = 0.0005) and Alzheimer's disease (AD) (n = 3345, OR = 2.3, CI: 1.3–4.2, P = 0.004) compared with 9047 controls. Functionally, p.A152T (i) decreases the binding of tau to microtubules and therefore promotes microtubule assembly less efficiently; and (ii) reduces the tendency to form abnormal fibers. However, there is a pronounced increase in the formation of tau oligomers. Importantly, these findings suggest that other regions of the tau protein may be crucial in regulating normal function, as the p.A152 residue is distal to the domains considered responsible for microtubule interactions or aggregation. These data provide both the first genetic evidence and functional studies supporting the role of MAPT p.A152T as a rare risk factor for both FTD-s and AD and the concept that rare variants can increase the risk for relatively common, complex neurodegenerative diseases, but since no clear significance threshold for rare genetic variation has been established, some caution is warranted until the findings are further replicated.
Activation of innate and adaptive immune responses is tightly regulated, as insufficient activation could result in defective clearance of pathogens, while excessive activation might lead to lethal systemic inflammation or autoimmunity. A20 functions as a negative regulator of innate and adaptive immunity by inhibiting NF-κB activation. A20 mediates its inhibitory function in a complex with other proteins including RNF11 and Itch, both E3 ubiquitin ligases and TAX1BP1, an adaptor protein. Since NF-κB has been strongly implicated in various neuronal functions, we predict that its inhibitor, the A20 complex, is also present in the nervous system. In efforts to better understand the role of A20 complex and NF-κB signaling pathway, we determined regional distribution of A20 mRNA as well as protein expression levels and distribution of RNF11, TAX1BP1 and Itch, in different brain regions. The distribution of TRAF6 was also investigated since TRAF6, also an E3 ligase, has an important role in NF-κB signaling pathway. Our investigations, for the first time, describe and demonstrate that the essential components of the A20 ubiquitin-editing complex are present and mainly expressed in neurons. The A20 complex components are also differentially expressed throughout the human brain. This study provides useful information about region specific expression of the A20 complex components that will be invaluable while determining the role of NF-κB signaling pathway in neuronal development and degeneration.
Oxidative stress is involved in age-related cognitive decline. The dietary antioxidants, carotenoids, tocopherols, and vitamin A may play a role in the prevention or delay in cognitive decline. In this study, sera were obtained from 78 octogenarians and 220 centenarians from the Georgia Centenarian Study. Brain tissues were obtained from 47 centenarian decedents. Samples were analyzed for carotenoids, α-tocopherol, and retinol using HPLC. Analyte concentrations were compared with cognitive tests designed to evaluate global cognition, dementia, depression and cognitive domains (memory, processing speed, attention, and executive functioning). Serum lutein, zeaxanthin, and β-carotene concentrations were most consistently related to better cognition (P < 0.05) in the whole population and in the centenarians. Only serum lutein was significantly related to better cognition in the octogenarians. In brain, lutein and β-carotene were related to cognition with lutein being consistently associated with a range of measures. There were fewer significant relationships for α-tocopherol and a negative relationship between brain retinol concentrations and delayed recognition. These findings suggest that the status of certain carotenoids in the old may reflect their cognitive function. The protective effect may not be related to an antioxidant effect given that α-tocopherol was less related to cognition than these carotenoids.
Pancreatitis is a complex, progressively destructive inflammatory disorder. Alcohol was long thought to be the primary causative agent, but genetic contributions have been of interest since the discovery that rare PRSS1, CFTR, and SPINK1 variants were associated with pancreatitis risk. We now report two significant genome-wide associations identified and replicated at PRSS1-PRSS2 (1×10-12) and x-linked CLDN2 (p < 1×10-21) through a two-stage genome-wide study (Stage 1, 676 cases and 4507 controls; Stage 2, 910 cases and 4170 controls). The PRSS1 variant affects susceptibility by altering expression of the primary trypsinogen gene. The CLDN2 risk allele is associated with atypical localization of claudin-2 in pancreatic acinar cells. The homozygous (or hemizygous male) CLDN2 genotype confers the greatest risk, and its alleles interact with alcohol consumption to amplify risk. These results could partially explain the high frequency of alcohol-related pancreatitis in men – male hemizygous frequency is 0.26, female homozygote is 0.07.
A hallmark of neurodegeneration is the aggregation of disease related proteins that are resistant to detergent extraction. In the major pathological subtype of frontotemporal lobar degeneration (FTLD), modified TAR-DNA binding protein 43 (TDP-43), including phosphorylated, ubiquitinated and proteolytically cleaved forms, is enriched in detergent-insoluble fractions from post-mortem brain tissue. Additional proteins that accumulate in the detergent-insoluble FTLD brain proteome remain largely unknown. In this study, we used proteins from stable isotope-labeled (SILAC) human embryonic kidney 293 cells (HEK293) as internal standards for peptide quantitation across control and FTLD insoluble brain proteomes. Proteins were identified and quantified by liquid-chromatography coupled with tandem mass spectrometry (LC-MS/MS) and twenty-one proteins were determined to be enriched in FTLD using SILAC internal standards. In parallel, label free quantification of only the unlabeled brain derived peptides by spectral counts (SC) and G-test analysis identified additional brain-specific proteins significantly enriched in disease. Several proteins determined to be enriched in FTLD using SILAC internal standards were not considered significant by G-test due to their low total number of SC. However immunoblotting of FTLD and control samples confirmed enrichment of these proteins, highlighting the utility of SILAC internal standard to quantify low abundance proteins in brain. Of these, the RNA binding protein PTB-associated splicing factor (PSF) was further characterized because of structural and functional similarities to TDP-43. Full-length PSF and shorter molecular weight fragments, likely resulting from proteolytic cleavage, were enriched in FTLD cases. Immunohistochemical analysis of PSF revealed predominately nuclear localization in control and FTLD brain tissue and was not associated with phosphorylated pathologic TDP-43 neuronal inclusions. However, in a subset of FTLD cases, PSF was aberrantly localized to the cytoplasm of oligodendrocytes. These data raise the possibility that PSF directed RNA processes in oligodendrocytes are altered in neurodegenerative disease.
The goals of this article are to (a) establish the concurrent and clinical validity of the Global Deterioration scale in assessing cognitive functions and stages of dementia among centenarians, (b) identify the prevalence of all-cause dementia in representative samples of centenarians, and (c) demonstrate how variations in sample demographic characteristics could significantly affect estimates of dementia prevalence. A quarter of the 244 centenarians in a population-based sample had no objective evidence of memory deficits. Another quarter showed signs of transient confusion, and about half showed classical behavioral signs of dementia with about 15% in each of Global Deterioration scale stages 4–6 and about 5% in the most severe stage 7. Variations in age, gender, race, residence status, and education of the study sample as well as criteria used for dementia rating were found to affect prevalence.
Dementia prevalence; Centenarians; Validation
The present study is a discovery mode proteomics analysis of the membrane enriched fraction of post-mortem brain tissue from Alzheimer’s disease (AD) and control cases. This study aims to validate a method to identify new proteins that could be involved in the pathogenesis of AD and potentially serve as disease biomarkers.
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the membrane enriched fraction of human post-mortem brain tissue from five AD and five control cases of similar age. Biochemical validation of specific targets was performed by immunoblotting.
1709 proteins were identified from the membrane enriched fraction of frontal cortex. Label free quantification by spectral counting and G-test analysis identified 13 proteins that were significantly changed in disease. In addition to Tau (MAPT), two additional proteins found to be enriched in AD, Ubiquitin carboxy-terminal hydrolase 1 (UCHL1), and syntaxin binding protein 1 (Munc-18), were validated through immunoblotting.
Discussion and clinical relevance
Proteomic analysis of the membrane enriched fraction of post-mortem brain tissue identifies proteins biochemically altered in AD. Further analysis of this sub-proteome may help elucidate mechanisms behind AD pathogenesis and provide new sources of biomarkers.
Alzheimer’s disease; membrane enrichment; proteomics; neurodegeneration
Abnormal neuronal aggregates of α-internexin and the three neurofilament (NF) subunits, NF-L, NF-M, and NF-H have recently been identified as the pathological hallmarks of neuronal intermediate filament (IF) inclusion disease (NIFID), a novel neurological disease of early onset with a variable clinical phenotype including frontotemporal dementia, pyramidal and extrapyramidal signs. α-Internexin, a class IV IF protein, a major component of inclusions in NIFID, has not previously been identified as a component of the pathological protein aggregates of any other neurodegenerative disease. Therefore, to determine the specificity of this protein, α-internexin immunohistochemistry was undertaken on cases of NIFID, non-tau frontotemporal dementias, motor neuron disease, α-synucleinopathies, tauopathies, and normal aged control brains. Our results indicate that class IV IF proteins are present within the pleomorphic inclusions of all cases of NIFID. Small subsets of abnormal neuronal inclusions in Alzheimer's disease, Lewy body diseases, and motor neuron disease also contain epitopes of α-internexin. Thus, α-internexin is a major component of the neuronal inclusions in NIFID and a relatively minor component of inclusions in other neurodegenerative diseases. The discovery of α-internexin in neuronal cytoplasmic inclusions implicates novel mechanisms of pathogenesis in NIFID and other neurological diseases with pathological filamentous neuronal inclusions.
α-Internexin; Neurofilament; Intermediate filament; Neuronal intermediate filament inclusion disease; Frontotemporal dementia
Pesticide exposure has been implicated as an environmental risk factor for the development of Parkinson’s disease (PD). However, few studies have identified specific pesticides. Previously, we identified elevated serum levels of the organochlorine pesticide β-hexachlorocyclohexane (β-HCH) in PD patients from a small clinical sample. Here, we conducted a case-control study to confirm the association between β-HCH and PD in a larger sample size (n=283) with serum samples of PD patients and controls obtained from UT Southwestern Medical Center and Emory University. Samples were obtained from two discrete periods at both sites, 2001–2003 and 2006–2008, and were analyzed for β-HCH levels. Adjusted odds ratios (ORs) for PD were estimated using logistic regression and generalized estimating equations. The mean serum β-HCH level across all cohorts in this study was 22.3 ng/mg cholesterol (Range: 0 to 376.7), and the levels were significantly higher between samples collected in 2001–2003 vs. 2006–2008. After controlling for age and gender, the OR for increased risk of PD for every 1 ng/mg increase in serum β-HCH ranged from 1.02 – 1.12 across the four different cohorts, and 1.03 (95% CI: 1.00–1.07, p value = 0.031) in the pooled analysis. Furthermore, the OR for increased risk of PD of subjects having serum β-HCH levels above the inter-quartile range of 39.08 ng/mg cholesterol was 2.85 (95% CI: 1.8, 4.48; p value < 0.001). These data are consistent with environmental decreases in β-HCH levels between 2001 and 2008, but they indicate that elevated levels of serum β-HCH are still associated with heightened risk for PD.
organochlorine; pesticide; Parkinson’s disease; beta-hexachlorocyclohexane