GBA mutations in Parkinson disease: earlier death but similar neuropathological features.

BACKGROUND AND PURPOSE: Mutations in the glucocerebrosidase (GBA) gene are known to be a risk factor for Parkinson's disease (PD). Data on clinicopathological correlation are limited. The purpose of this study was to determine the clinicopathological findings that might distinguish PD cases with and without mutations in the GBA gene. METHODS: Data from the Arizona Study of Aging and Neurodegenerative Disorders were used to identify autopsied PD cases that did or did not have a GBA gene mutation. Clinical and neuropathological data were compared. RESULTS: Twelve PD cases had a GBA mutation and 102 did not. The GBA mutation cases died younger (76 vs. 81 years of age) but there was no difference in disease duration or clinical examination findings. No neuropathological differences were found in total or regional semi-quantitative scores for Lewy-type synucleinopathy, senile plaques, neurofibrillary tangles, white matter rarefaction or cerebral amyloid angiopathy scores. CONCLUSIONS: In longitudinally assessed, autopsied PD cases, those with GBA mutations had a younger age at death but there was no evidence for clinical or neuropathological differences compared to cases without GBA mutations. Due to the small GBA group size, small differences cannot be excluded.

Differential spectral quantitative electroencephalography patterns between control and Parkinson's disease cohorts.

BACKGROUND AND PURPOSE: It is believed that progressive Lewy-type synucleinopathy (LTS) is primarily responsible for the worsening of motor and non-motor Parkinson's disease (PD) signs and symptoms. Characterization of quantitative electroencephalography (QEEG) abnormalities across the spectrum of LTS to PD dementia (PD-D) may provide insight into the pathophysiology of PD cortical dysfunction. Here our enlarged EEG database was leveraged to characterize spectral QEEG abnormalities in asymptomatic autopsy-defined groups of control participants and incidental Lewy body disease (ILBD) and three clinically defined groups of participants with PD (cognitively normal PD, mild cognitive impairment PD, and PD-D). METHODS: The PD cohort was studied as part of the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). AZSAND utilizes its Brain and Body Donation Program to perform prospective, standardized, regular longitudinal pre-mortem assessments until death. Resting EEG from subjects was analyzed for spectral domain QEEG measures of background rhythm frequency and global relative power in delta, theta, alpha and beta bands. RESULTS: The various spectral QEEG measures showed differential changes specific to the groups compared. Important findings were background rhythm frequency showing the most pairwise differences across the groups, and this also was the only significant difference between control and ILBD. An increase in delta bandpower was characteristic of worsening cognitive deficits. CONCLUSIONS: Different patterns of change amongst QEEG measures across LTS and PD cognitive states suggest that they correlate with heterogeneous pathophysiologies of cortical dysfunction within the PD clinical spectrum. In addition, the biomarker application of a specific spectral QEEG measure needs to be selectively suited to its study purpose.

Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder.

OBJECTIVE: To determine the pathologic substrates in patients with rapid eye movement (REM) sleep behavior disorder (RBD) with or without a coexisting neurologic disorder. METHODS: The clinical and neuropathologic findings were analyzed on all autopsied cases from one of the collaborating sites in North America and Europe, were evaluated from January 1990 to March 2012, and were diagnosed with polysomnogram (PSG)-proven or probable RBD with or without a coexisting neurologic disorder. The clinical and neuropathologic diagnoses were based on published criteria. RESULTS: 172 cases were identified, of whom 143 (83%) were men. The mean±SD age of onset in years for the core features were as follows - RBD, 62±14 (range, 20-93), cognitive impairment (n=147); 69±10 (range, 22-90), parkinsonism (n=151); 68±9 (range, 20-92), and autonomic dysfunction (n=42); 62±12 (range, 23-81). Death age was 75±9 years (range, 24-96). Eighty-two (48%) had RBD confirmed by PSG, 64 (37%) had a classic history of recurrent dream enactment behavior, and 26 (15%) screened positive for RBD by questionnaire. RBD preceded the onset of cognitive impairment, parkinsonism, or autonomic dysfunction in 87 (51%) patients by 10±12 (range, 1-61) years. The primary clinical diagnoses among those with a coexisting neurologic disorder were dementia with Lewy bodies (n=97), Parkinson's disease with or without mild cognitive impairment or dementia (n=32), multiple system atrophy (MSA) (n=19), Alzheimer's disease (AD)(n=9) and other various disorders including secondary narcolepsy (n=2) and neurodegeneration with brain iron accumulation-type 1 (NBAI-1) (n=1). The neuropathologic diagnoses were Lewy body disease (LBD)(n=77, including 1 case with a duplication in the gene encoding α-synuclein), combined LBD and AD (n=59), MSA (n=19), AD (n=6), progressive supranulear palsy (PSP) (n=2), other mixed neurodegenerative pathologies (n=6), NBIA-1/LBD/tauopathy (n=1), and hypothalamic structural lesions (n=2). Among the neurodegenerative disorders associated with RBD (n=170), 160 (94%) were synucleinopathies. The RBD-synucleinopathy association was particularly high when RBD preceded the onset of other neurodegenerative syndrome features. CONCLUSIONS: In this large series of PSG-confirmed and probable RBD cases that underwent autopsy, the strong association of RBD with the synucleinopathies was further substantiated and a wider spectrum of disorders which can underlie RBD now are more apparent.

TMEM106B regulates progranulin levels and the penetrance of FTLD in GRN mutation carriers.

OBJECTIVES: To determine whether TMEM106B single nucleotide polymorphisms (SNPs) are associated with frontotemporal lobar degeneration (FTLD) in patients with and without mutations in progranulin (GRN) and to determine whether TMEM106B modulates GRN expression. METHODS: We performed a case-control study of 3 SNPs in TMEM106B in 482 patients with clinical and 80 patients with pathologic FTLD-TAR DNA-binding protein 43 without GRN mutations, 78 patients with FTLD with GRN mutations, and 822 controls. Association analysis of TMEM106B with GRN plasma levels was performed in 1,013 controls and TMEM106B and GRN mRNA expression levels were correlated in peripheral blood samples from 33 patients with FTLD and 150 controls. RESULTS: In our complete FTLD patient cohort, nominal significance was identified for 2 TMEM106B SNPs (top SNP rs1990622, p(allelic) = 0.036). However, the most significant association with risk of FTLD was observed in the subgroup of GRN mutation carriers compared to controls (corrected p(allelic) = 0.0009), where there was a highly significant decrease in the frequency of homozygote carriers of the minor alleles of all TMEM106B SNPs (top SNP rs1990622, CC genotype frequency 2.6% vs 19.1%, corrected p(recessive) = 0.009). We further identified a significant association of TMEM106B SNPs with plasma GRN levels in controls (top SNP rs1990622, corrected p = 0.002) and in peripheral blood samples a highly significant correlation was observed between TMEM106B and GRN mRNA expression in patients with FTLD (r = -0.63, p = 7.7 × 10(-5)) and controls (r = -0.49, p = 2.2 × 10(-10)). CONCLUSIONS: In our study, TMEM106B SNPs significantly reduced the disease penetrance in patients with GRN mutations, potentially by modulating GRN levels. These findings hold promise for the development of future protective therapies for FTLD.

Functional, global and cognitive decline correlates to accumulation of Alzheimer's pathology in MCI and AD.

BACKGROUND: Cognitive, global and functional instruments have been extensively investigated for correlations with neuropathological changes such as neurofibrillary tangles (NFTs), plaques, and synapse loss in the brain. OBJECTIVE: Our objective is to correlate the functional, global and cognitive decline assessed clinically with the neuropathological changes observed in a large prospectively characterized cohort of mild cognitive impairment (MCI) and Alzheimer's disease (AD). METHODS: We examined 150 subjects (16 MCI and 134 AD) that were prospectively assessed and longitudinally followed to autopsy. MCI subjects clinically met Petersen criteria for single or multi-domain amnestic MCI. AD subjects clinically met NINCDS-ADRDA criteria for probable or possible AD. All subjects received the Functional Assessment Staging (FAST), the Global Deterioration Scale (GDS), and the Mini Mental State Examination (MMSE) ante-mortem. Plaque and tangle counts were gathered for hippocampus, entorhinal cortex, frontal, temporal and parietal cortices. Braak staging was performed as well. RESULTS: The GDS, FAST and MMSE correlated with plaque counts in all regions. The GDS, FAST and MMSE correlated with tangle counts in in all regions. The three instruments also correlated with the Braak score. The MMSE and GDS correlate better than the FAST in most regions. CONCLUSIONS: Accumulation of neuropathology appears to correlate with functional, global, and cognitive decline as people progress from MCI through AD.

Pathologic findings in prospectively ascertained essential tremor subjects.

OBJECTIVE: To assess pathologic changes in prospectively characterized subjects with essential tremor (ET). METHODS: Subjects enrolled in the Sun Health Research Institute Brain and Body Donation Program were examined annually by a movement disorders neurologist, and semiannually by a behavioral neurologist and neuropsychologist. Twenty-four subjects without a prior diagnosis of dementia or other major movement disorder met clinical criteria for ET and came to autopsy. Subjects with mild cognitive impairment (n = 3) were included. These subjects were compared with 21 controls. Brains were examined postmortem according to standardized protocols for assessment of age-related changes and specific pathologic conditions (e.g., Parkinson disease, Alzheimer disease). RESULTS: Subjects had a mean age of 86.2 years and a mean duration of tremor of 11.1 years. Seven subjects had evidence for cerebellar pathology (Purkinje cell loss, cerebellar cortical sclerosis, and proliferation of Bergmann glia). Pigmented neurons were qualitatively depleted in the locus ceruleus in eight subjects and in the substantia nigra in five subjects. Of these, three had Lewy bodies, one subject had brainstem predominant disease, and two had limbic stage. Three subjects had a nonspecific cerebral tauopathy and another met pathologic criteria for progressive supranuclear palsy. However, when compared with controls, only changes in the locus ceruleus and gliosis of the cerebellum remained significant findings. CONCLUSIONS: This study supports previous findings of heterogenous pathology in essential tremor (ET). There is an increased frequency of cerebellar gliosis and locus ceruleus depletion. We did not find an increased incidence of Lewy bodies in subjects with ET.

PIB is a non-specific imaging marker of amyloid-beta (Abeta) peptide-related cerebral amyloidosis.

The in vivo imaging probe [11C]-PIB (Pittsburgh Compound B, N-methyl[11C]2-(4'-methylaminophenyl-6-hydroxybenzathiazole) is under evaluation as a key imaging tool in Alzheimer's disease (AD) and to date has been assumed to bind with high affinity and specificity to the amyloid structures associated with classical plaques (CPs), one of the pathological hallmarks of the disease. However, no studies have systematically investigated PIB binding to human neuropathological brain specimens at the tracer concentrations achieved during in vivo imaging scans. Using a combination of autoradiography and histochemical techniques, we demonstrate that PIB, in addition to binding CPs clearly delineates diffuse plaques and cerebrovascular amyloid angiopathy (CAA). The interaction of PIB with CAA was not fully displaceable and this may be linked to the apolipoprotein E-epsilon4 allele. PIB was also found to label neurofibrillary tangles, although the overall intensity of this binding was markedly lower than that associated with the amyloid-beta (Abeta) pathology. The data provide a molecular explanation for PIB's limited specificity in diagnosing and monitoring disease progression in AD and instead indicate that the ligand is primarily a non-specific marker of Abeta-peptide related cerebral amyloidosis.

Inflammatory changes parallel the early stages of Alzheimer disease.

Alzheimer disease (AD) is the most prominent cause of dementia in the elderly. To determine changes in the AD brain that may mediate the transition into dementia, the gene expression of approximately 10,000 full-length genes was compared in mild/moderate dementia cases to non-demented controls that exhibited high AD pathology. Including this latter group distinguishes this work from previous studies in that it allows analysis of early cognitive loss. Compared to non-demented high-pathology controls, the hippocampus of AD cases with mild/moderate dementia had increased gene expression of the inflammatory molecule major histocompatibility complex (MHC) II, as assessed with microarray analysis. MHC II protein levels were also increased and inversely correlated with cognitive ability. Interestingly, the mild/moderate AD dementia cases also exhibited decreased number of T cells in the hippocampus and the cortex compared to controls. In conclusion, transition into AD dementia correlates with increased MHC II(+) microglia-mediated immunity and is paradoxically paralleled by a decrease in T cell number, suggesting immune dysfunction.

Involvement of microglial receptor for advanced glycation endproducts (RAGE) in Alzheimer's disease: identification of a cellular activation mechanism.

Receptor-mediated interactions with amyloid beta-peptide (Abeta) could be important in the evolution of the inflammatory processes and cellular dysfunction that are prominent in Alzheimer's disease (AD) pathology. One candidate receptor is the receptor for advanced glycation endproducts (RAGE), which can bind Abeta and transduce signals leading to cellular activation. Data are presented showing a potential mechanism for Abeta activation of microglia that could be mediated by RAGE and macrophage colony-stimulating factor (M-CSF). Using brain tissue from AD and nondemented (ND) individuals, RAGE expression was shown to be present on microglia and neurons of the hippocampus, entorhinal cortex, and superior frontal gyrus. The presence of increased numbers of RAGE-immunoreactive microglia in AD led us to further analyze RAGE-related properties of these cells cultured from AD and ND brains. Direct addition of Abeta(1-42) to the microglia increased their expression of M-CSF. This effect was significantly greater in microglia derived from AD brains compared to those from ND brains. Increased M-CSF secretion was also demonstrated using a cell culture model of plaques whereby microglia were cultured in wells containing focal deposits of immobilized Abeta(1-42). In each case, the Abeta stimulation of M-CSF secretion was significantly blocked by treatment of cultures with anti-RAGE F(ab')2. Treatment of microglia with anti-RAGE F(ab')2 also inhibited the chemotactic response of microglia toward Abeta(1-42). Finally, incubation of microglia with M-CSF and Abeta increased expression of RAGE mRNA. These microglia also expressed M-CSF receptor mRNA. These data suggest a positive feedback loop in which Abeta-RAGE-mediated microglial activation enhances expression of M-CSF and RAGE, possibly initiating an ascending spiral of cellular activation.

Reduction of cortical amyloid beta levels in guinea pig brain after systemic administration of physostigmine.

Overproduction of the peptide amyloid beta (Abeta) is thought to be a critical pathogenetic event in Alzheimer's disease (AD). Decreasing A production may therefore slow or halt the progression of AD. In vitro work has indicated that cholinergic muscarinic receptor agonists may reduce cellular production of Abeta. Here we show that systemic administration of physostigmine, an acetylcholinesterase inhibitor, lowers Abeta levels in vivo. Guinea pigs treated for 10 days with s.c. physostigmine had levels of cortical AbetaN-40 and N-42 which were 57% and 72%, respectively, of those in control animals. Levels of cortical beta-amyloid precursor protein were not significantly affected by drug treatment. These results suggest that cholinergic therapy may affect the course of AD by limiting Abeta accumulation.

Reduction of cerebrospinal fluid amyloid beta after systemic administration of M1 muscarinic agonists.

Overproduction of the peptide amyloid beta (A beta) is a critical event in Alzheimer's disease (AD). Systemic administration of 3 M1-selective muscarinic agonists, AF102B, AF150S and AF267B, decreased cerebrospinal fluid (CSF) A beta concentrations; levels of CSF secreted beta-APP were not significantly altered. Rabbits treated for 5 days with s.c. injections of each drug (2 mg/kg/day) had levels of CSF A beta which were between 55 and 71% of control for A beta 1-40 and between 59 and 84% of control for A beta 1--42.

Correlation of the expression level of C1q mRNA and the number of C1q-positive plaques in the Alzheimer Disease temporal cortex. analysis of C1q mrna and its protein using adjacent or nearby sections.

We compared the expression level of C1q mRNA and the number of C1q-positive plaques in adjacent or nearby brain sections from Alzheimer disease (AD) and control cases. Small blocks of temporal cortex were fixed with 4% paraformaldehyde for 2 days at 4 degrees C. After cryoprotection with solutions containing 10-20% glycerol and 2% dimethylsulfoxide, 40-microm sections were cut from the tissue blocks. A section from each case was stained by immunohistochemistry using a C1q antibody, while RNA was purified from adjacent or nearby sections using a combination of proteinase K pretreatment followed by extraction using Trizol reagent. The expression of C1q B chain mRNA was analyzed in these samples by the reverse-transcription polymerase chain reaction (RT-PCR). The intensities of the PCR products were measured by an image analyzer. The expression of C1q B chain mRNA was significantly more abundant in AD than in control cases (p < 0.05). Immunohistochemical analysis showed that C1q protein was localized in senile plaques in the AD brain. The number of C1q-positive plaques correlated with the expression level of C1q gene (p < 0.05). The present results suggest that C1q protein in senile plaques originates is endogenously produced in the AD brain.

Comparative analysis of amyloid-beta chemical structure and amyloid plaque morphology of transgenic mouse and Alzheimer's disease brains.

We have undertaken an integrated chemical and morphological comparison of the amyloid-beta (Abeta) molecules and the amyloid plaques present in the brains of APP23 transgenic (tg) mice and human Alzheimer's disease (AD) patients. Despite an apparent overall structural resemblance to AD pathology, our detailed chemical analyses revealed that although the amyloid plaques characteristic of AD contain cores that are highly resistant to chemical and physical disruption, the tg mice produced amyloid cores that were completely soluble in buffers containing SDS. Abeta chemical alterations account for the extreme stability of AD plaque core amyloid. The corresponding lack of post-translational modifications such as N-terminal degradation, isomerization, racemization, pyroglutamyl formation, oxidation, and covalently linked dimers in tg mouse Abeta provides an explanation for the differences in solubility between human AD and the APP23 tg mouse plaques. We hypothesize either that insufficient time is available for Abeta structural modifications or that the complex species-specific environment of the human disease is not precisely replicated in the tg mice. The appraisal of therapeutic agents or protocols in these animal models must be judged in the context of the lack of complete equivalence between the transgenic mouse plaques and the human AD lesions.

The evolution of A beta peptide burden in the APP23 transgenic mice: implications for A beta deposition in Alzheimer disease.

BACKGROUND: High levels of A beta in the cerebral cortex distinguish demented Alzheimer's disease (AD) from nondemented elderly individuals, suggesting that decreased amyloid-beta (A beta) peptide clearance from the brain is a key precipitating factor in AD. MATERIALS AND METHODS: The levels of A beta in brain and plasma as well as apolipoprotein E (ApoE) in brain were investigated by enzyme-linked immunosorbent assay (ELISA) and Western blotting at various times during the life span of the APP23 transgenic (Tg) and control mice. Histochemistry and immunocytochemistry were used to assess the morphologic characteristics of the brain parenchymal and cerebrovascular amyloid deposits and the intracellular amyloid precursor protein (APP) deposits in the APP23 Tg mice. RESULTS: No significant differences were found in the plasma levels of A beta between the APP23 Tg and control mice from 2-20 months of age. In contrast, soluble A beta levels in the brain were continually elevated, increasing 4-fold at 2 months and 33-fold in the APP23 Tg mice at 20 months of age when compared to the control mice. Soluble A beta42 was about 60% higher than A beta40. In the APP23 Tg mice, insoluble A beta40 remained at basal levels in the brain until 9 months and then rose to 680 microg/g cortex by 20 months. Insoluble A beta40 was negligible in non-Tg mice at all ages. Insoluble A beta42 in APP23 Tg mice rose to 60 microg/g cortex at 20 months, representing 24 times the control A beta42 levels. Elevated levels of ApoE in the brain were observed in the APP23 Tg mice at 2 months of age, becoming substantially higher by 20 months. ApoE colocalized with A beta in the plaques. Beta-amyloid precursor protein (betaAPP) deposits were detected within the neuronal cytoplasm from 4 months of age onward. Amyloid angiopathy in the APP23 Tg mice increased markedly with age, being by far more severe than in the Tg2576 mice. CONCLUSIONS: We suggest that the APP23 Tg mouse may develop an earlier blockage in A beta clearance than the Tg2576 mice, resulting in a more severe accumulation of A beta in the perivascular drainage pathways and in the brain. Both Tg mice reflect decreased A beta elimination and as models for the amyloid cascade they are useful to study AD pathophysiology and therapy.

Gene expression profiling of amyloid beta peptide-stimulated human post-mortem brain microglia.

Activation of microglia is a central part of the chronic inflammatory processes in Alzheimer's disease (AD). In the brains of AD patients, activated microglia are associated with amyloid beta (Abeta) peptide plaques. A number of previous studies have shown that aggregated synthetic Abeta peptide activates cultured microglia to produce a range inflammatory products. The full extent of the inflammatory response still remains to be determined. In this study, gene array technology was employed to investigate in a more extensive manner the consequences of microglial activation by Abeta peptide. RNA was prepared from pooled samples of cortical human microglia isolated from post-mortem cases and incubated with a low dose (2.5 microM) of Abeta1-42 (or peptide solvent) for 24 h. This material was used to prepare cDNA probes, which were used to detect the differential pattern of expressed genes on a 1,176 Clontech membrane gene array. Results obtained showed that 104 genes were either upregulated or downregulated by 1.67 fold or greater. The most highly induced genes belonged to the chemokine family with interleukin-8 (IL-8) expression being increased by 11.7 fold. Interestingly, many of the highly induced genes had been identified as being responsive to activation by the transcription factor NF-kappaB. A number of genes were downregulated. Thymosin beta, prothymosin alpha and parathymosin, all belonging to the same gene family, were downregulated. To validate these semi-quantitative results, the expression of intercellular adhesion molecule-1 (ICAM-1) and rhoB were measured by RT-PCR in samples of cDNA derived from Abeta and control stimulated human cortical microglia. These results confirm the usefulness of the gene array approach for studying Abeta-mediated inflammatory processes.

Cortical cholinergic denervation elicits vascular A beta deposition.

Selective destruction of the cholinergic nucleus basalis magnocellularis (nbm) in the rabbit by the p75 neurotrophin receptor (NTR) immunoglobulin G (IgG) complexed to the toxin saporin leads to the deposition of amyloid-beta (A beta) in and around cerebral blood vessels. In some instances, the perivascular A beta resemble the diffuse deposits observed in Alzheimer's disease (AD). We propose that cortical cholinergic deprivation results, among other perturbations, in the loss of vasodilation mediated by acetylcholine. In addition to a dysfunctional cerebral blood flow, alterations in vascular chemistry affecting endothelial and smooth muscle cells may result in cerebral hypoperfusion and a breached blood-brain barrier (BBB). The selective removal of the rabbit nbm and A beta accumulation may serve as an important nontransgenic, and more physiological, model for the testing of pharmacological and immunological agents designed to control the deposition and the deleterious effects of A beta in AD.

The cholinergic deficit coincides with Abeta deposition at the earliest histopathologic stages of Alzheimer disease.

Effective therapeutic intervention in Alzheimer disease (AD) will be most effective if it is directed at early events in the pathogenic sequence. The cholinergic deficit may be such an early event. In the present study, the brains of 26 subjects who had no history of cognitive loss and who were in early histopathologic stages of AD (average Braak stage less than II) were examined at autopsy to determine whether a cortical cholinergic decrement was associated with Abeta concentration or deposition. In the superior frontal and inferior temporal gyri, the choline acetyltransferase (ChAT) activity of plaque-containing cases was significantly decreased (p < 0.05, unpaired, two-tailed t-tests), measuring 70.9% and 79.5%, respectively, relative to plaque-free cases. In the inferior temporal gyrus, Spearman's rank correlation analysis showed that ChAT activity had a significant inverse correlation with Abeta concentration (p = 0.075; r = -0.3552). The results indicate that the cholinergic deficit is established at an early histopathologic stage of AD, before the onset of clinical symptoms.

Cholinergic deafferentation of the rabbit cortex: a new animal model of Abeta deposition.

Brain deposition of the amyloid beta-peptide (Abeta) is a critical step in the pathogenesis of Alzheimer's disease (AD) and human cerebral amyloid angiopathy (CAA). A small fraction of AD and CAA cases are caused by gene mutations leading to increased production and deposition of Abeta, but for the majority, there is no known direct genetic cause. We have hypothesized that Abeta deposition in these sporadic cases occurs as a result of cortical cholinergic deafferentation. Here we show that cortical cholinergic deafferentation, induced in rabbits by a selective immunotoxin, leads to Abeta deposition in cerebral blood vessels and perivascular neuropil. Biochemical measurements confirmed that lesioned animals had 2.5- and 8-fold elevations of cortical Abeta40 and Abeta42, respectively. Cholinergic deafferentation may be one factor that can contribute to Abeta deposition.