Abnormal phosphorylation of the microtubule-associated protein tau develops in selected brain regions in normal aging and becomes widespread throughout the brain in Alzheimer’s disease (AD). Braak and others have described the distribution of neurofibrillary tangles and deposition of abnormally phosphorylated tau (p-tau) and correlated this with the progressive cognitive dysfunction in AD. However, to date there have been no comprehensive studies examining abnormally phosphorylated tau deposition in the spinal cord as part of normal aging or AD. We investigated, using immunohistochemical methods, the presence of p-tau in the spinal cord of 46 cases with a clinicopathological diagnosis of AD as well as 37 non-demented (ND) individuals lacking any defined central nervous system-related clinicopathological diagnosis. We found the cervical cord segments to be the most frequently affected subdivision (96% AD vs. 43% ND), followed by thoracic (69% AD vs. 37% ND), lumbar (65% AD vs. 27% ND) and sacral (53% AD vs. 13% ND). The spinal cord was often affected at early-stage brain disease, with p-tau spinal cord immunoreactivity in 40% of subjects at Braak neurofibrillary stage I, however, there were no cases having spinal cord p-tau that did not have p-tau within the brain. As p-tau immunoreactivity is present within the spinal cords of ND as well as AD subjects, it is likely that the phosphorylation of spinal cord tau occurs in the preclinical stage of AD, prior to dementia. The presence of significant spinal cord p-tau-immunoreactive pathology has important implications for both the pathogenesis and clinical manifestations of AD.
pathology; autopsy; senile dementia; neurofibrillary tangle; aging; systemic disorder; peripheral nervous system
Parkinson’s disease (PD) is a neurodegenerative disease primarily characterized by cardinal motor symptoms and central nervous system pathology. As current drug therapies can often stabilize these cardinal motor symptoms attention has shifted to the other motor and non-motor symptoms of PD which are resistant to drug therapy. Dysphagia in PD is perhaps the most important drug resistant symptom as it leads to aspiration and pneumonia, the leading cause of death. Here, we present direct evidence for degeneration of the pharyngeal motor nerves in PD. In this study, we examined the cervical vagal (X) nerve, pharyngeal branch of the X nerve (Ph-X), and pharyngeal plexus innervating the pharyngeal muscles in 14 postmortem specimens, 10 subjects with PD and 4 age-matched control subjects. Synucleinopathy in the pharyngeal nerves was detected using an immunohistochemical method for phosphorylated α-synuclein. α-Synuclein aggregates were revealed in the X nerve and Ph-X and immunoreactive intramuscular nerve twigs and axon terminals within the neuromuscular junctions were identified in all the PD subjects and in none of the controls. These findings indicate that the motor nervous system of the pharynx is involved in the pathological process of PD. Notably, PD subjects with dysphagia had a higher density of α-synuclein aggregates in the pharyngeal nerves as compared with those without dysphagia. Motor involvement of the pharynx in PD appears to be one of the factors leading to oropharyngeal dysphagia commonly seen in PD patients.
α-Synuclein aggregates; Dysphagia; Immunohistochemistry; Intramuscular nerve twigs; Lewy bodies; Lewy neurites; Motor nerve; Nerve degeneration; Parkinson’s disease; Peripheral nervous system; Pharyngeal constrictor muscles; Pharyngeal plexus; Swallowing; Upper esophageal sphincter; Vagus nerve
The clinical diagnosis of Parkinson disease (PD) is incorrect in 30% or more of subjects, particularly at the time of symptom onset. Because Lewy-type α-synucleinopathy (LTS) is present in the submandibular glands of PD patients, we assessed the feasibility of submandibular gland biopsy for diagnosing PD. We performed immunohistochemical staining for LTS in sections of large segments (simulating open biopsy) and needle cores of submandibular gland from 128 autopsied and neuropathologically classified subjects, including 28 PD, 5 incidental Lewy body disease, 5 progressive supranuclear palsy ([PSP] 3 with concurrent PD), 3 corticobasal degeneration, 2 multiple system atrophy, 22 Alzheimer disease with Lewy bodies (ADLB), 16 Alzheimer disease without Lewy bodies and 50 normal elderly. Immunoreactive nerve fibers were present in large submandibular gland sections of all 28 PD subjects (including 3 that also had PSP); 3 ADLB subjects were also positive, but none of the other subjects were positive. Cores from frozen submandibular glands taken with 18 gauge needles (total length 15–38 mm, between 10 and 118 sections per subject examined) were positive for LTS in 17 of 19 PD patients. These results suggest that biopsy of the submandibular gland may be a feasible means of improving PD clinical diagnostic accuracy. This would be particularly advantageous for subject selection in early-stage clinical trials, for invasive therapies or for verifying other biomarker studies.
α-Synuclein; Biomarker; Clinical trial; Deep brain stimulation; Gene therapy; Lewy body; Parkinson disease; Surgery; Transplantation
Modifications of α-synuclein resulting in changes in its conformation are considered to be key pathological events for Lewy body diseases (LBD), which include Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). We have previously described a histopathological Unified Staging System for LBD that classifies the spread of α-synuclein phosphorylated at serine 129 (pS129-α-synuclein) from olfactory bulb to brainstem or limbic regions, and finally neocortex. Lewy bodies and Lewy neurites are highly enriched in pS129-α-synuclein. Increased formation of pS129-α-synuclein changes its solubility properties enhancing its tendency to aggregate and disrupt normal function. As in vitro and animal studies have shown that inhibiting formation of pS129-α-synuclein can prevent toxic consequences, this has become one of the therapeutic targets for LBD. However, detailed biochemical descriptions of the changes in pS129-α-synuclein properties in diseased human brains are needed to further our understanding of how these might contribute to molecular pathogenesis. In this study, we used 130 separate brain samples from cingulate cortex (limbic cortex) and 131 from temporal cortex (neocortex) that had been staged according to our Unified Staging System to examine progressive changes in properties of pS129-α-synuclein with the formation of progressively more severe histological Lewy-type pathology. The brain samples from these staged cases had been separated into cytosol-enriched, membrane-enriched (detergent soluble) and insoluble (ureas/SDS soluble) fractions. We also characterized the nature and appearance of higher molecular weight forms of pS129-α-synuclein. The major species was the 16 kD monomeric form; this accumulated with increasing stage with a large increase in Stage IV samples. By comparing two brain regions, we showed higher accumulation of insoluble pS129-α-synuclein in cingulate cortex, where histological deposits occur first, than in temporal cortex in samples with advanced (Stage IV) LB pathology.
Western blots; Parkinson’s disease; antibodies; fractionation; post-translational modification; postmortem brain tissue; dementia with Lewy bodies; incidental Lewy body disease; pathogenesis; aggregation
The white matter (WM) represents approximately half the cerebrum volume and is profoundly affected in Alzheimer’s disease (AD). However, both the WM responses to AD as well as potential influences of this compartment to dementia pathogenesis remain comparatively neglected. Neuroimaging studies have revealed WM alterations are commonly associated with AD and renewed interest in examining the pathologic basis and importance of these changes.
In AD subjects, immunohistochemistry and electron microscopy revealed changes in astrocyte morphology and myelin loss as well as up to 30% axonal loss in areas of WM rarefaction when measured against non-demented control (NDC) tissue. Comparative proteomic analyses were performed on pooled samples of periventricular WM (PVWM) obtained from AD (n = 4) and NDC (n = 5) subjects with both groups having a mean age of death of 86 years. All subjects had an apolipoprotein E ε3/3 genotype with the exception of one NDC subject who was ε2/3. Urea-detergent homogenates were analyzed using two different separation techniques: 2-dimensional isoelectric focusing/reverse-phase chromatography and 2-dimensional difference gel electrophoresis (2D-DIGE). Proteins with different expression levels between the 2 diagnostic groups were identified using MALDI-Tof/Tof mass spectrometry. In addition, Western blots were used to quantify proteins of interest in individual AD and NDC cases.
Our proteomic studies revealed that when WM protein pools were loaded at equal amounts of total protein for comparative analyses, there were quantitative differences between the 2 groups. Molecules related to cytoskeleton maintenance, calcium metabolism and cellular survival such as glial fibrillary acidic protein, vimentin, tropomyosin, collapsin response mediator protein-2, calmodulin, S100-P, annexin A1, α-internexin, α-and β-synuclein, α-B-crystalline, fascin-1, ubiquitin carboxyl-terminal esterase and thymosine were altered between AD and NDC pools.
Our experiments suggest that WM activities become globally impaired during the course of AD with significant morphological, biochemical and functional consequential implications for gray matter function and cognitive deficits. These observations may endorse the hypothesis that WM dysfunction is not only a consequence of AD pathology, but that it may precipitate and/or potentiate AD dementia.
Alzheimer’s disease; periventricular white matter; white matter rarefaction; proteomics; glial fibrillary acidic protein; axonal loss; myelin loss
This study compared individuals whose clinical diagnosis of Alzheimer’s disease (AD) matched or did not match neuropathologic results at autopsy on clinical and functional outcomes (cognitive impairment, functional status and neuropsychiatric symptoms). The study also assessed the extent of potentially inappropriate medication use (using potentially unnecessary medications or potentially inappropriate prescribing) among misdiagnosed patients.
Longitudinal data from the National Alzheimer’s Coordinating Center Uniform Data Set (NACC-UDS, 2005–2010) and corresponding NACC neuropathological data were utilized to compare 88 misdiagnosed and 438 accurately diagnosed patients.
Following adjustment of sociodemographic characteristics, the misdiagnosed were found to have less severe cognitive and functional impairment. However, after statistical adjustment for sociodemographics, dementia severity level, time since onset of cognitive decline and probable AD diagnosis at baseline, the groups significantly differed on only one outcome: the misdiagnosed were less likely to be depressed/dysphoric. Among the misdiagnosed, 18.18% were treated with potentially inappropriate medication. An additional analysis noted this rate could be as high as 67.10%.
Findings highlight the importance of making an accurate AD diagnosis to help reduce unnecessary treatment and increase appropriate therapy. Additional research is needed to demonstrate the link between potentially inappropriate treatment and adverse health outcomes in misdiagnosed AD patients.
Alzheimer disease; Diagnosis; Misdiagnosis; Autopsy; Neuropathology
The neuropathological examination is considered to provide the gold standard for Alzheimer disease (AD). To determine the accuracy of currently employed clinical diagnostic methods, clinical and neuropathological data from the National Alzheimer's Coordinating Center (NACC), which gathers information from the network of National Institute on Aging (NIA)-sponsored Alzheimer's Disease Centers (ADCs), were collected as part of the NACC Uniform Data Set (UDS) between 2005 and 2010. A database search initially included all 1198 subjects with at least one UDS clinical assessment and who had died and been autopsied; 279 were excluded as being not demented or because critical data fields were missing. The final subject number was 919. Sensitivity and specificity were determined based on “probable” and “possible” AD levels of clinical confidence and 4 levels of neuropathological confidence based on varying neuritic plaque densities and Braak neurofibrillary stages. Sensitivity ranged from 70.9% to 87.3%; specificity ranged from 44.3% to 70.8%. Sensitivity was generally increased with more permissive clinical criteria and specificity was increased with more restrictive criteria, whereas the opposite was true for neuropathological criteria. When a clinical diagnosis was not confirmed by minimum levels of AD histopathology, the most frequent primary neuropathological diagnoses were tangle-only dementia or argyrophilic grain disease, frontotemporal lobar degeneration, cerebrovascular disease, Lewy body disease and hippocampal sclerosis. When dementia was not clinically diagnosed as AD, 39% of these cases met or exceeded minimum threshold levels of AD histopathology. Neurologists of the NIA-ADCs had higher predictive accuracy when they diagnosed AD in demented subjects than when they diagnosed dementing diseases other than AD. The misdiagnosis rate should be considered when estimating subject numbers for AD studies, including clinical trials and epidemiological studies.
Alzheimer disease; Autopsy; Clinical trials; Diagnosis; Histopathology; Neuropathology; Non-Alzheimer dementia
Gastrointestinal dysfunction is a prominent non-motor feature of Parkinson’s disease (PD) that contributes directly to the morbidity of patients, complicates management of motor symptoms, and may herald incipient PD in patients without motor disability. Although PD has traditionally been considered a disease of dopaminergic neurons in the substantia nigra, analyses of gastrointestinal samples from PD patients have consistently revealed pathology in the enteric nervous system (ENS). The relationship of PD pathology to GI dysmotility is poorly understood, and this lack of understanding has led to limited success in developing treatments for PD-related GI symptoms. We have quantitatively compared myenteric neuron density and relative abundance of NO, VIP, and catecholamine neurons between patients with PD and control individuals along the length of the GI tract. In addition, we have examined the frequency of GI α-synuclein neuritic pathology and its co-localization with the same neuronal markers. We have included a comparison with a small population of patients with incidental Lewy bodies (ILB) found at autopsy. These data indicate there is no neuronal loss in the myenteric plexus in PD. Lewy body pathology parallels parasympathetic autonomic input from the DMV, not the distribution of extrinsic sympathetic input or intrinsic enteric neurons, and is only rarely co-localized with tyrosine hydroxylase. These data provide a critical background to which further analyses of the effect of PD on the GI tract may be compared and suggest that neuropathology in myenteric neurons is unlikely to be a causative factor in PD-related GI dysmotility.
enteric; gastrointestinal; nitric oxide; vasoactive intestinal peptide; catecholamine; acetylcholine; constipation; gastroparesis; Lewy body; synuclein
Synucleinopathies are a broad class of neurodegenerative disorders characterized by the presence of intracellular protein aggregates containing α-synuclein protein. The aggregated α-synuclein protein is hyperphosphorylated on serine 129 (S129) compared to the unaggregated form of the protein. While the precise functional consequences of S129 hyperphosphorylation are still being clarified, numerous in vitro and in vivo studies suggest that S129 phosphorylation is an early event in α-synuclein dysfunction and aggregation. Identifying the kinases and phosphatases that regulate this critical phosphorylation event may ultimately prove beneficial by allowing pharmacological mitigation of synuclein dysfunction and toxicity in Parkinson’s disease and other synucleinopathies. We report here the development of a high-content, fluorescence-based assay to quantitate levels of total and S129 phosphorylated α-synuclein protein. We have applied this assay to conduct high-throughput loss-of-function screens with siRNA libraries targeting 711 known and predicted human kinases and 206 phosphatases. Specifically, knockdown of the phosphatidylinositol 3-kinase related kinase SMG1 resulted in significant increases in the expression of pS129 phosphorylated α-synuclein (p-syn). Moreover, SMG1 protein levels were significantly reduced in brain regions with high p-syn levels in both dementia with Lewy bodies (DLB) and Parkinson’s disease with dementia (PDD). These findings suggest that SMG1 may play an important role in increased α-synuclein pathology during the course of PDD, DLB, and possibly other synucleinopathies.
Alzheimer’s disease (AD) dementia impacts all facets of higher order cognitive function and is characterized by the presence of distinctive pathological lesions in the gray matter (GM). The profound alterations in GM structure and function have fostered the view that AD impacts are primarily a consequence of GM damage. However, the white matter (WM) represents about 50% of the cerebrum and this area of the brain is substantially atrophied and profoundly abnormal in both sporadic AD (SAD) and familial AD (FAD). We examined the WM biochemistry by ELISA and Western blot analyses of key proteins in 10 FAD cases harboring mutations in the presenilin genes PSEN1 and PSEN2 as well as in 4 non-demented control (NDC) individuals and 4 subjects with SAD. The molecules examined were direct substrates of PSEN1 such as Notch-1 and amyloid precursor protein (APP). In addition, apolipoproteins, axonal transport molecules, cytoskeletal and structural proteins, neurotrophic factors and synaptic proteins were examined. PSEN-FAD subjects had, on average, higher amounts of WM amyloid-beta (Aβ) peptides compared to SAD, which may play a role in the devastating dysfunction of the brain. However, the PSEN-FAD mutations we examined did not produce uniform increases in the relative proportions of Aβ42 and exhibited substantial variability in total Aβ levels. These observations suggest that neurodegeneration and dementia do not depend solely on enhanced Aβ42 levels. Our data revealed additional complexities in PSEN-FAD individuals. Some direct substrates of γ-secretase, such as Notch, N-cadherin, Erb-B4 and APP, deviated substantially from the NDC group baseline for some, but not all, mutation types. Proteins that were not direct γ-secretase substrates, but play key structural and functional roles in the WM, likewise exhibited varied concentrations in the distinct PSEN mutation backgrounds. Detailing the diverse biochemical pathology spectrum of PSEN mutations may offer valuable insights into dementia progression and the design of effective therapeutic interventions for both SAD and FAD.
Sporadic Alzheimer’s disease; familial Alzheimer’s disease; presenilin; γ-secretase; white matter; gray matter; amyloid precursor protein; amyloid-beta
Amyloid imaging may revolutionize Alzheimer’s disease (AD) research and clinical practice but is critically limited by an inadequate correlation between cerebral cortex amyloid plaques and dementia. Also, amyloid imaging does not indicate the extent of neurofibrillary tangle (NFT) spread throughout the brain. Currently, the presence of dementia as well as a minimal brain load of both plaques and NFTs is required for the diagnosis of AD. Autopsy studies suggest that striatal amyloid plaques may be mainly restricted to subjects in higher Braak NFT stages that meet clinicopathological diagnostic criteria for AD. Striatal plaques, which are readily identified by amyloid imaging, might therefore be used to predict the presence of a higher Braak NFT stage and clinicopathological AD in living subjects. This study determined the sensitivity and specificity of striatal plaques for predicting a higher Braak NFT stage and clinicopathological AD in a postmortem series of 211 elderly subjects. Subjects included 87 clinicopathologically classified as non-demented elderly controls and 124 with AD. A higher striatal plaque density score (moderate or frequent) had 95.8% sensitivity, 75.7% specificity for Braak NFT stage V or VI and 85.6% sensitivity, 86.2% specificity for the presence of dementia and clinicopathological AD (National Institute on Aging – Reagan Institute “intermediate” or “high”). Amyloid imaging of the striatum may be useful as a predictor, in living subjects, of Braak NFT stage and the presence or absence of dementia and clinicopathological AD. Validation of this hypothesis will require autopsy studies of subjects that had amyloid imaging during life.
Alzheimer’s disease; amyloid imaging; striatum; amyloid plaques; diagnosis; therapy; asymptomatic; preclinical; autopsy
Parkinson's disease (PD) afflicts approximately 1-2% of the population over 50 years of age. No cures or effective modifying treatments exist and clinical diagnosis is currently confounded by a lack of definitive biomarkers. We sought to discover potential biomarkers in the cerebrospinal fluid (CSF) of neuropathologically confirmed PD cases.
We compared postmortem ventricular CSF (V-CSF) from PD and normal control (NC) subjects using two-dimensional difference gel electrophoresis (2D-DIGE). Spots exhibiting a 1.5-fold or greater difference in volume between PD patients and controls were excised from the 2D gels, subjected to tryptic digestion and identification of peptides assigned using mass spectrometric/data bank correlation methods.
Employing this strategy six molecules: fibrinogen, transthyretin, apolipoprotein E, clusterin, apolipoprotein A-1 and glutathione-S-transferase-Pi were found to be different between PD and NC populations.
These molecules have been implicated in PD pathogenesis. Combining biomarker data from multiple laboratories may create a consensus panel of proteins that may serve as a diagnostic tool for this neurodegenerative disorder.
2D-DIGE; cerebrospinal fluid; Parkinson's disease; proteomics
Missense mutations in LRRK2 (leucine-rich repeat kinase 2) are a major cause of PD (Parkinson's disease). Several antibodies against LRRK2 have been developed, but results using these polyclonal antibodies have varied widely leading to conflicting conclusions. To address this challenge, the Michael J. Fox Foundation for Parkinson's Research generated a number of monoclonal antibodies targeting epitopes across the LRRK2 protein. In the present paper, we report optimized protocols and results for ten monoclonal antibodies for immunoblotting, immunohistochemistry, immunoprecipitation and kinase activity assays, in rat, mouse and human brain tissue. Several efficacious antibodies were identified, but results demonstrate that the mouse monoclonal N241A/34 is suitable for most applications, with the best overall rabbit monoclonal antibody being c41-2. These antibodies produced a dominant band of the expected size via immunoblotting and a lack of labelling in tissue derived from LRRK2-knockout animals under optimized conditions. A significant proportion of LRRK2 protein localizes to insoluble fractions and no evidence of truncated LRRK2 protein was detected in any fraction from rodent or human tissues. An assay was developed for the robust detection of LRRK2 kinase activity directly from frozen mouse and human brain tissue, but precipitous declines in activity were observed that corresponded to increasing post-mortem intervals and processing times. Finally, we demonstrate the highest levels of brain-localized LRRK2 in the striatum, but note differential expression patterns between rat and mouse in both striatum and cortex. Anti-LRRK2 monoclonal antibodies that are unlimited in availability together with the proposed standardized protocols should aid in the definition of LRRK2 function in both health and disease.
immunohistochemistry; kinase assay; leucine-rich repeat kinase 2 (LRRK2); Parkinson’s disease; DAB, 3,3′-diaminobenzidine; DMEM, Dulbecco’s modified Eagle’s medium; eGFP, enhanced green fluorescent protein; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HEK, human embryonic kidney; KO, knockout; LRRK2, leucine-rich repeat kinase 2; MEF, mouse embryonic fibroblast; MJFF, Michael J. Fox Foundation for Parkinson’s Research; PD, Parkinson’s disease; PEI, polyethyleneimine; PFA, paraformaldehyde; UTSW, University of Texas Southwestern; VDAC, voltage-dependent anion channel; WT, wild-type
Dysphagia (impaired swallowing) is common in Parkinson disease (PD) patients and is related to aspiration pneumonia, the primary cause of death in PD. Therapies that ameliorate the limb motor symptoms of PD are ineffective for dysphagia. This suggests that the pathophysiology of PD dysphagia may differ from that affecting limb muscles but little is known about potential neuromuscular abnormalities in the swallowing muscles in PD. This study examined the fiber histochemistry of pharyngeal constrictor (PC) and cricopharyngeal (CP) sphincter muscles in postmortem specimens from 8 PD and 4 age-matched control patients. Pharyngeal muscles in PD patients exhibited many atrophic fibers, fiber type grouping, and fast-to-slow myosin heavy chain transformation. These alterations indicate that the pharyngeal muscles experienced neural degeneration and regeneration over the course of PD. Notably, the PD patients with dysphagia had a higher percentage of atrophic myofibers vs. with those without dysphagia and controls. The fast-to-slow fiber type transition is consistent with abnormalities in swallowing, slow movement of food and increased tone in the CP sphincter in PD patients. The alterations in the pharyngeal muscles may play a pathogenic role in the development of dysphagia in PD patients.
Dysphagia; Fiber types; Immunohistochemistry; Muscle fiber atrophy; Myosin heavy chain isoforms; Parkinson disease; Pharyngeal constrictor muscles; Swallowing; Upper esophageal sphincter
To compare autonomic function of subjects with Parkinson’s disease (PD) and essential tremor (ET) relative to controls.
It has been reported that patients with PD have autonomic dysfunction while no literature exists regarding autonomic function in ET.
Subjects with PD, ET, and controls had autonomic function measured using the SCOPA-Autonomic questionnaire, with the total and domain scores transformed to a scale of 0–100 points.
62 subjects with PD, 84 with ET, and 291 controls were included. Women were more prevalent in control (69%) compared to PD (44%) and ET (44%) groups, and mean age was significantly younger in PD (73 yrs) and older in ET (83) compared to controls (81). The mean SCOPA-Aut Total score in PD was significantly higher than controls, with no difference in ET. No autonomic dysfunction was found in any domain in ET but in PD there were significant abnormalities in gastrointestinal, cardiovascular, urinary, and thermoregulatory domains. Individual question data revealed a significantly higher percentage of subjects with dysfunction on 11/23 questions in the PD group but only 1 question (sialorrhea) in the ET group compared with controls.
Autonomic scores, particularly gastrointestinal, cardiovascular, urinary, and thermoregulatory were increased in patients with PD, as assessed by SCOPA-Aut. Patients with ET did not exhibit autonomic dysfunction, with the exception of sialorrhea.
Autonomic dysfunction; Parkinson’s disease; Essential tremor
Identifying biomarkers that distinguish Parkinson’s disease (PD) from normal control (NC) individuals has the potential to increase diagnostic sensitivity for the detection of early-stage PD. A previous proteomic study identified potential biomarkers in postmortem ventricular cerebrospinal fluid (V-CSF) from neuropathologically diagnosed PD subjects lacking Alzheimer’s disease (AD) neuropathology. In the present study, we assessed these biomarkers as well as p-tau181, Aβ42, and S100B by ELISA in PD (n = 43) and NC (n = 49) cases. The p-tau181/Aβ42 ratio and ApoA-1 showed statistically significant differences between groups. Multiple regression analysis demonstrated that p-tau181/Aβ42 had a significant odds ratio: OR = 1.42 (95% confidence interval [CI], 1.12–1.84), P = 0.006. Among the molecules investigated, intriguing correlations were observed that require further investigation. Our results suggest coexistent AD CSF biomarkers within the PD group notwithstanding that it was selected to minimize AD neuropathological lesions.
Parkinson’s disease; biomarkers; ventricular cerebrospinal fluid; apolipoprotein A-1; p-tau181/Aβ42 ratio
The pathology of essential tremor is increasingly being studied; however, there are limited studies of biochemical changes in this condition.
We studied several candidate biochemical/anatomical systems in the brainstem, striatum and cerebellum of 23 essential tremor subjects who came to autopsy, comparing them to a control population.
Striatal tyrosine hydroxylase, a marker of dopaminergic neurons, was 91.7 ±113.2 ng/mg versus 96.4±102.7 ng/mg (not significant) in cases and controls. Locus ceruleus dopamine beta-hydroxylase, a marker of noradrenergic neurons, was not significantly different between essential tremor and control groups. Parvalbumin, a marker of GABAergic neurons, was 199.3±42.0 versus 251.4±74.8 ng/mg (p=0.025) in the pons in the region of the locus ceruleus of essential tremor versus controls, while there was no difference in cerebellar parvalbumin.
These results are supportive of a possible role for reduced GABAergic function within the locus ceruleus in essential tremor. The hypothesis that essential tremor represents early Parkinson’s disease was not supported as striatal dopaminergic markers were not reduced compared to control subjects.
tremor; pathology; GABA; norepinephrine
The current consensus criteria for the neuropathologic diagnosis of Alzheimer’s disease (AD), known as the National Institute on Aging/Reagan Institute of the Alzheimer Association Consensus Recommendations for the Postmortem Diagnosis of AD or NIA-Reagan Criteria , were published in 1997 (hereafter referred to as “1997 Criteria”). Knowledge of AD and the tools used for clinical investigation of cognitive impairment and dementia have advanced substantially since then and have prompted this update on the neuropathologic assessment of AD.
We present a practical guide for the implementation of recently revised National Institute on Aging-Alzheimer’s Association guidelines for the neuropathologic assessment of Alzheimer’s disease (AD). Major revisions from previous consensus criteria are: (i) recognition that AD neuropathologic changes may occur in the apparent absence of cognitive impairment, (ii) an “ABC” score for AD neuropathologic change that incorporates histopathologic assessments of amyloid β deposits (A), staging of neurofibrillary tangles (B), and scoring of neuritic plaques (C), and (iii) more detailed approaches for assessing commonly co-morbid conditions such as Lewy body disease, vascular brain injury, hippocampal sclerosis, and TAR DNA binding protein (TDP)-43 immunoreactive inclusions. Recommendations also are made for the minimum sampling of brain, preferred staining methods with acceptable alternatives, reporting of results, and clinico-pathologic correlations.
Florbetapir F 18 (18F-AV-45) is a positron emission tomography (PET) imaging ligand for the detection of amyloid aggregation associated with Alzheimer’s disease. Earlier data showed that florbetapir F 18 binds with high affinity to β-amyloid plaques in human brain homogenates (Kd = 3.7 nM) and has favorable imaging pharmacokinetic properties, including rapid brain penetration and washout. The present study used human autopsy brain tissue to evaluate the correlation between in vitro florbetapir F 18 binding and β-amyloid density measured by established neuropathological methods.
The localization and density of florbetapir F 18 binding in frozen and formalin-fixed paraffin-embedded sections of postmortem brain tissue from 40 subjects with a varying degree of neurodegenerative pathology was assessed by standard florbetapir F 18 autoradiography and correlated with the localization and density of β-amyloid identified by silver staining, thioflavin S staining, and immunohistochemistry.
There were strong quantitative correlations between florbetapir F 18 tissue binding and both β-amyloid plaques identified by light microscopy (sliver staining and thioflavin S fluorescence) and by immunohistochemical measurements of β-amyloid using three antibodies recognizing different epitopes of the β-amyloid peptide (Aβ). Florbetapir F 18 did not bind to neurofibrillary tangles.
Florbetapir F 18 selectively binds β-amyloid in human brain tissue. The binding intensity was quantitatively correlated with the density of β-amyloid plaques identified by standard neuropathological techniques and correlated with the density of Aβ measured by immunohistochemistry. Since β-amyloid plaques are a defining neuropathological feature for Alzheimer’s disease, these results support the use of florbetapir F 18 as an amyloid PET ligand to identify the presence of AD pathology in patients with signs and symptoms of progressive late-life cognitive impairment.
PET imaging; Alzheimer’s disease; β-amyloid plaque; autoradiography; β-amyloid; amyloid PET imaging; florbetapir F 18; 18F-AV-45; postmortem
Dementia is a frequent complication of Parkinson’s disease (PD). About half of PD dementia (PDD) is hypothesized to be due to progression of the underlying Lewy body pathology into limbic regions and the cerebral cortex while the other half is thought to be due to coexistent Alzheimer’s disease. Clinically, however, these are indistinguishable. The spread of amyloid plaques to the striatum has been reported to be a sensitive and specific indicator of dementia due to Alzheimer’s disease (AD). The purpose of the present study was to determine if the presence of striatal plaques might also be a useful indicator of the presence of diagnostic levels of AD pathology within PD subjects. We analyzed neuropathologically-confirmed cases of PD without dementia (PDND, N = 31), PDD without AD (PDD, N = 31) and PD with dementia meeting clinicopathological criteria for AD (PDAD, N =40). The minimum diagnostic criterion for AD was defined as including a clinical history of dementia, moderate or frequent CERAD cortical neuritic plaque density and Braak neurofibrillary stage III–VI. Striatal amyloid plaque densities were determined using Campbell-Switzer and Thioflavine S stains. Striatal plaque densities were significantly higher in PDAD compared to PDD (p<0.001). The presence of striatal plaques was approximately 80% sensitive and 80% specific for predicting AD. In comparison, the presence of cerebral cortex plaques alone was highly sensitive (100%) but had poor specificity (48% to 55%). The results suggest that striatal amyloid imaging may be clinically useful for making the distinction between PDD and PDAD.
striatum; Lewy body; diagnosis; autopsy; neuropathology; biomarker
Evaluate electrophysiologic findings in incidental Lewy Body disease (ILBD).
ILBD, Control, and Parkinson's disease (PD) subjects had electrophysiological evaluation within two years prior to autopsy. Data analyzed included surface electromyography (EMG) of upper extremity muscles during rest and muscle activation, and electroencephalography (EEG) recording at rest. For EMG, gross tracings and spectral peaks were analyzed. EEG measures analyzed were background frequency and power in delta, theta, alpha, and beta bands.
Three of ten ILBD subjects (30%) showed unilateral rhythmic EMG discharges at rest without a visually apparent rest tremor. The ILBD resting EMG frequency was lower than in the Control group with no overlap (P=0.03) and close to that of the PD group. The ILBD group had significantly lower background rhythm frequency than the Control group (P=0.001) but was greater than the PD group (P=0.01).
The electrophysiologic changes in ILBD cases are between those of Control and PD, suggesting that these findings may reflect changes correlating with ILBD as a possible precursor to PD.
Electrophysiologic changes in ILBD may assist with the identification of a preclinical stage for Lewy body disorders and help the development of a therapeutic agent for modifying Lewy body disease progression.
Lewy body; Electromyography; Electroencephalography; Pathology; Parkinson's disease; Tremor
Amyloid-β (Aβ) peptides are intimately involved in the inflammatory pathology of atherosclerotic vascular disease (AVD) and Alzheimer's disease (AD). Although substantial amounts of these peptides are produced in the periphery, their role and significance to vascular disease outside the brain requires further investigation.
Amyloid-β peptides present in the walls of human aorta atherosclerotic lesions as well as activated and non-activated human platelets were isolated using sequential size-exclusion columns and HPLC reverse-phase methods. The Aβ peptide isolates were quantified by ELISA and structurally analyzed using MALDI-TOF mass spectrometry procedures.
Our experiments revealed that both aorta and platelets contained Aβ peptides, predominately Aβ40. The source of the Aβ pool in aortic atherosclerosis lesions is probably the activated platelets and/or vascular wall cells expressing APP/PN2. Significant levels of Aβ42 are present in the plasma, suggesting that this reservoir makes a minor contribution to atherosclerotic plaques.
Our data reveal that although aortic atherosclerosis and AD cerebrovascular amyloidosis exhibit clearly divergent end-stage manifestations, both vascular diseases share some key pathophysiological promoting elements and pathways. Whether they happen to be deposited in vessels of the central nervous system or atherosclerotic plaques in the periphery, Aβ peptides may promote and perhaps synergize chronic inflammatory processes which culminate in the degeneration, malfunction and ultimate destruction of arterial walls.
atherosclerosis; platelets; amyloid-beta; vascular inflammation; Alzheimer's disease; coagulation cascade
Banked tissue is essential to the study of neurological disease but using postmortem tissue introduces a number of possible confounds. Foremost amongst these are factors relating to variation in postmortem interval (PMI). Currently there are conflicting reports on how PMI affects overall RNA integrity, and very few reports of how gene expression is affected by PMI. We analyzed total RNA extracted from frozen cerebellar cortex from 79 deceased human subjects enrolled in the Banner Sun Health Research Institute Brain and Body Donation Program. The PMI, which ranged from 1.5 to 45 hours, correlated with overall RNA quality measures including RNA Integrity Number (RIN) (r = − 0.34, p = 0.002) and RNA quantitative yield (r = − 0.25, p = 0.02). Additionally, we determined the expression of 89 genes using a PCR-based gene expression array (RT2 ProfilerTM PCR Array: Human Alzheimer’s Disease; SABiosciencesTM, Frederick, MD). A greater proportion of genes had decreased rather than increased expression with increasing PMI (65/89 vs 20/89; p < 0.0001). Of these, transcripts from the genes ADAM9, LPL, PRKCG, and SERPINA3 had significantly decreased expression with increasing PMI (p < 0.01). No individual gene transcripts had significantly increased expression with increasing PMI. In conclusion, it is apparent that RNA degrades progressively with increasing PMI and that measurement of gene expression in brain tissue with longer PMI may give artificially low values. For tissue derived from autopsy, a short PMI optimizes its utility for molecular research.
RIN; RNA; postmortem; brain; gene expression; Alzheimer’s disease; neurological disease; research; methods
Down syndrome appears to be associated with a virtually certain risk of fibrillar amyloid-β (Aβ) pathology by the age of 40 and a very high risk of dementia at older ages. The positron emission tomography (PET) ligand florbetapir F18 has been shown to characterize fibrillar Aβ in the living human brain and to provide a close correlation with subsequent Aβ neuropathology in individuals proximate to and after the end of life. The extent to which the most frequently used PET ligands can be used to detect fibrillar Aβ in patients with Down syndrome remains to be determined.
To characterize PET estimates of fibrillar Aβ burden in a Down syndrome patient very close to the end of life and to compare them with neuropathologic assessment made after his death.
With the family’s informed consent, florbetapir PET was used to study a 55-year-old Down syndrome patient with Alzheimer disease near the end of life; his brain was donated for neuropathologic assessment when he died 14 days later. Visual ratings of cerebral florbetapir uptake were performed by trained readers who were masked to the patient’s diagnosis as part of a larger study, and an automated algorithm was used to characterize regional-to-cerebellar standard uptake value ratios in 6 cerebral regions of interest. Neuropathologic assessments were performed masked to the patient’s diagnosis or PET measurements.
Visual ratings and automated analyses of the PET image revealed a heavy fibrillar Aβ burden in cortical, striatal, and thalamic regions, similar to that reported for patients with late-onset Alzheimer disease. This matched neuropathologic findings of frequent neuritic and diffuse plaques, as well as frequent amyloid angiopathy, except for neuropathologically demonstrated frequent cerebellar diffuse plaques and amyloid angiopathy that were not detected by the PET scan.
Florbetapir PET can be used to detect increased cerebral-to-cerebellar fibrillar Aβ burden in a Down syndrome patient with Alzheimer disease, even in the presence of frequent amyloid angiopathy and diffuse plaques in the cerebellum. Additional studies are needed to determine the extent to which PET could be used to detect and to track fibrillar Aβ and to evaluate investigational Aβ-modifying treatments in the presymptomatic and symptomatic stages of Alzheimer disease.