An edited transcript of Neurology Grand Rounds held at the University of California, Los Angeles, Medical Center on January 27, 1988. John Mazziotta, MD, PhD, Professor of Neurology and Radiology, is the coordinator of these conferences. This conference was edited by Harry V. Vinters, MD.
Background and Purpose
Endovascular thrombectomy is an increasingly used treatment for arterial occlusion in acute stroke. Various devices (including most extensively the Mechanical Embolus Removal in Cerebral Ischemia/MERCI Retriever device) have been utilized for this.
We review the neuropathologic findings in 5 patients (age range 59–87 years) who died acutely or as late as 38 days after procedures using the Merci (4 patients) and Penumbra (1 patient) devices were carried out to remove thrombo-emboli from the middle cerebral artery (MCA). Partial recanalization was achieved by thrombectomy in all 5 patients.
All patients showed extensive cerebral infarcts, 3/5 with clinical hemorrhagic transformations of the infarct or frank intraparenchymal hemorrhage after thrombectomy— in one case this was judged to be at least partly on the basis of concomitant hypertensive microvascular disease. With one exception basal arteries examined in detail by immunohistochemistry, showed prominent, though usually non-occlusive (and generally non-ulcerated) atheromata, often with significant luminal stenosis. One patient showed a subintimal dissection with resultant occlusion of the MCA.
In this highly selected group of patients, the vascular pathologic abnormalities affecting basal arteries were variable, but complicated atherosclerosis was a common finding. Extensive irreversible brain necrosis prior to therapeutic procedures may have contributed to deaths.
Thrombectomy; stroke recovery; MERCI device; cerebral infarct; intracerebral hemorrhage
Aquaporins have recently been identified as protein channels involved in water transport. These channels may play a role in the edema formation and alterations in microvascular function observed in Alzheimer disease (AD) and cerebral amyloid angiopathy (CAA). We investigated the expression of aquaporin 1 (AQP1) and aquaporin 4 (AQP 4) in 24 human autopsy brains consisting of 18 with AD and varying degrees of CAA, and 6 with no pathologic abnormalities using immunohistochemistry. In cases of AD and CAA there was enhanced AQP 4 expression compared to age- and gender-matched controls. Aquaporin 4 immunoreactivity was prominent at CSF and brain interfaces, including subpial, subependymal, pericapillary and periarteriolar spaces. Aquaporin 1 expression in AD and CAA cases was not different from that in age- and gender-matched controls. Double-labeling studies demonstrated that both AQP1 and 4 were localized to astrocytes. Both enhanced AQP4 expression and its unique staining pattern suggest that these proteins may be important in the impaired water transport observed in AD and CAA.
Aquaporin; Alzheimer disease; Brain aging; Cerebral amyloid angiopathy
Among epilepsy-associated non-neoplastic lesions, mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE-HS) and malformation of cortical development (MCD) including focal cortical dysplasia (FCD), are the two most frequent causes of drug-resistant focal epilepsies constituting about 50% of all surgical pathology of epilepsy. Several distinct histological patterns have been historically recognized in both HS and FCD, and several studies have tried to perform clinicopathological correlation; results, however, have been controversial, particularly in terms of postsurgical seizure outcome. Recently, the International League Against Epilepsy constituted a Task Forces of Neuropathology and FCD within the Commission on Diagnostic Methods, to establish an international consensus of histological classification of HS and FCD, respectively, based on agreement with the recognition of the importance of defining a histopathological classification system that reliably has some clinicopathological correlation. Such consensus classifications are likely to facilitate future clinicopathological study. Meanwhile, we reviewed neuropathology of 41 surgical cases of mTLE, and confirmed three type/patterns of HS along with no HS, based on the qualitative evaluation of the distribution and severity of neuronal loss and gliosis within hippocampal formation; i.e., HS type 1 (61%) equivalent to ‘classical’ Ammon’s horn sclerosis, HS type 2 (2%) representing CA1 sclerosis, HS type 3 (17%) equivalent to end folium sclerosis, and no HS (19%). Furthermore we performed a neuropathological comparative study on mTLE-HS and dementia associated HS (d-HS) in elderly, and confirmed that neuropathological features differ between mTLE-HS and d-HS in the distribution of hippocampal neuronal loss and gliosis, morphology of reactive astrocytes and their protein expression, and presence of concomitant neurodegenerative changes particularly Alzheimer type and TDP-43 pathologies. These differences may account, at least in part, for the difference in pathogenesis and epileptogenicity of HS in mTLE and senile dementia. However, the etiology and pathogenesis of most epileptogenic lesions are yet to be elucidated.
epilepsy; hippocampal sclerosis; focal cortical dysplasia; histological classification; surgical pathology
Cholinesterase inhibitors (ChEIs) are widely used for the symptomatic treatment of Alzheimer’s disease (AD). In vitro and in animal studies, ChEIs have been shown to influence the processing of Aβ and the phosphorylation of tau, proteins that are the principal constituents of the plaques and neurofibrillary tangles, respectively, in AD brain. However, little is known about the effects of these drugs on Aβ and tau pathology in AD. Using avidin-biotin immunohistochemistry and computer-assisted image analysis, we compared Aβ and tau loads in the frontal and temporal cortices of 72 brains from matched cohorts of AD patients who had or had not received ChEIs. Patients treated with ChEIs had accumulated significantly more phospho-tau in their cerebral cortex than had untreated patients (P = 0.004). Aβ accumulation was reduced but not significantly. These data raise the possibility that increased tau phosphorylation may influence long-term clinical responsiveness to ChEIs.
Alzheimer’s disease; Cholinesterase inhibitors; Amyloid; Tau; Neuropathology
Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA) are two common pathologies associated with β-amyloid (Aβ) accumulation and inflammation in the brain; neither is well understood. The objective of this study was to evaluate human post mortem brains from AD subjects with purely parenchymal pathology, and those with concomitant CAA (and age-matched controls) for differential expression of microglia-associated Aβ ligands thought to mediate Aβ clearance and the association of these receptors with complement activation. Homogenates of brain parenchyma and enriched microvessel fractions from occipital cortex were probed for levels of C3b, membrane attack complex (MAC), CD11b and α-2-macroglobulin and immunoprecipitation was used to immunoprecipitate (IP) CD11b complexed with C3b and Aβ. Both C3b and MAC were significantly increased in CAA compared to AD-only and controls and IP showed significantly increased CD11b/C3b complexes with Aβ in AD/CAA subjects. Confocal microscopy was used to visualize these interactions. MAC was remarkably associated with CAA affected blood vessels compared to AD-only and control vessels. These findings are consistent with an Aβ clearance mechanism via microglial CD11b that delivers Aβ and C3b to blood vessels in AD/CAA, which leads to Aβ deposition and propagation of complement to the cytolytic MAC, possibly leading to vascular fragility.
Frozen tissue, a gold standard biospecimen, can yield well preserved nucleic acids and proteins after over a decade but is vulnerable to thawing and has substantial fiscal, spatial, and environmental costs. A long-term room temperature biospecimen storage alternative that preserves broad analytical utility can potentially empower tissue-based research. As there is scant data on the analytical utility of lyophilized brain tumor biospecimens, we evaluated lyophilized (freeze-dried) samples stored for 1 year at room temperature. Lyophilized tumor tissue processed into paraffin sections produced good histology. Yields of extracted DNA, RNA, and protein approximated those of frozen tissue. After 1 year, lyophilized samples yielded high molecular weight DNA that permitted copy number variation analysis, IDH 1 mutation detection, and MGMT promoter methylation PCR. A 27 % decrease in RIN scores over the 1 year suggests that RNA degradation was inhibited though incompletely. Nevertheless, RT-PCR studies on lyophilized tissue performed similarly to frozen tissue. In contrast to FFPE tissues where protein bands were absent or shifted to a lower molecular weight, lyophilized samples showed similar protein bands as frozen tissue on SDS-PAGE analysis. Lyophilized tissue performed similarly to frozen tissue for Western blots and enzyme activity assays. Immunohistochemistry of lyophilized tissue that were processed into FFPE blocks often required longer incubation times for staining than standard FFPE samples but generally provided robust antigen detection. This preliminary study suggests that lyophilization has promise for long-term room temperature storage while permitting varied tests; however, further work is required to better stabilize nucleic acids particularly RNA.
Freeze-dry; Lyophilization; Brain tumor; Tissue; Nucleic acid; Protein; Biobank; Biorepository; Room temperature; Frozen tissue
Background and Purpose
Some studies have reported associations between intracranial atherosclerosis and Alzheimer disease (AD) pathology. We aimed to correlate severity of cerebral atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy (CAA) with neurofibrillary tangles, neuritic plaques, and cerebral infarcts.
This autopsy study (n = 163) was drawn from a longitudinal study of subcortical ischemic vascular disease, AD, and normal aging. Multivariable logistic regression models were used to test associations among the 3 forms of cerebrovascular disease and the presence of ischemic and neurodegenerative brain lesions. Apolipoprotein E genotype was included as a covariate in these multivariable models.
Cerebral atherosclerosis was positively associated with microinfarcts (odds ratio (OR) = 2.3; 95% confidence interval (CI) = 1.2–4.4) and cystic infarcts (OR = 2.0, 95%CI = 1.0–4.2), but not AD pathology. Arteriolosclerosis showed a positive correlation with lacunar infarcts (OR = 2.0, 95%CI = 1.0–4.2), but not AD pathology. CAA was inversely associated with lacunar infarcts (OR = 0.6, 95%CI = 0.41–1.1), but positively associated with Braak & Braak stage (OR = 1.5, 95%CI = 1.1–2.1) and CERAD plaque score (OR = 1.5, 95%CI = 1.1–2.2).
Microinfarcts, which have been correlated with severity of cognitive impairment, were most strongly associated with atherosclerosis. Possible pathogenetic mechanisms include artery-to-artery emboli, especially micro-emboli that may include atheroemboli or platelet-fibrin emboli. Arteriolosclerosis was positively, while CAA was negatively correlated with lacunar infarcts, which might prove helpful in clinical differentiation of arteriolosclerotic from CAA-related vascular brain injury.
Atherosclerosis; Alzheimer; Microinfarct; Infarct
Acquired resistance to tyrosine kinase inhibitors (TKI) represents a major challenge for personalized cancer therapy. Multiple genetic mechanisms of acquired TKI resistance have been identified in several types of human cancer. However, the possibility that cancer cells may also evade treatment by co-opting physiologically regulated receptors has not been addressed. Here we demonstrate the first example of this alternate mechanism in brain tumors by showing that EGFR-mutant glioblastomas (GBMs) evade EGFR TKIs by transcriptionally de-repressing PDGFRβ. Mechanistic studies demonstrate that EGFRvIII signaling actively suppresses PDGFRβ transcription in an mTORC1 and ERK-dependent manner. Genetic or pharmacologic inhibition of oncogenic EGFR renders GBMs dependent on the consequently de-repressed PDGFRβ signaling for growth and survival. Importantly, combined inhibition of EGFR and PDGFRβ signaling potently suppresses tumor growth in vivo. These data identify a novel, non-genetic TKI resistance mechanism in brain tumors and provide compelling rationale for combination therapy.
Receptor Tyrosine Kinase; EGFR; glioma; mTOR and PDGFRβ
The purpose of this study was to evaluate the changes of left stellate ganglionic nerve activity (SGNA) and left thoracic vagal nerve activity (VNA) after acute myocardial infarction (MI).
Whether MI results in remodeling of extracardiac nerve activity remains unclear.
We implanted radiotransmitters to record the SGNA, VNA, and electrocardiogram in 9 ambulatory dogs. After baseline monitoring, MI was created by 1-h balloon occlusion of the coronary arteries. The dogs were then continuously monitored for 2 months. Both stellate ganglia were stained for growth-associated protein 43 and synaptophysin. The stellate ganglia from 5 normal dogs were used as control.
MI increased 24-h integrated SGNA from 7.44 ± 7.19 Ln(Vs)/day at baseline to 8.09 ± 7.75 Ln(Vs)/day after the MI (p < 0.05). The 24-h integrated VNA before and after the MI was 5.29 ± 5.04 Ln(Vs)/day and 5.58 ± 5.15 Ln(Vs)/day, respectively (p < 0.05). A significant 24-h circadian variation was noted for the SGNA (p < 0.05) but not the VNA. The SGNA/VNA ratio also showed significant circadian variation. The nerve densities from the left SG were 63,218 ± 34,719 μm2/mm2 and 20,623 ± 4,926 μm2/mm2 for growth-associated protein 43 (p < 0.05) and were 32,116 ± 8,190 μm2/mm2 and 16,326 ± 4,679 μm2/mm2 for synaptophysin (p < 0.05) in MI and control groups, respectively. The right SG also showed increased nerve density after MI (p < 0.05).
MI results in persistent increase in the synaptic density of bilateral stellate ganglia and is associated with increased SGNA and VNA. There is a circadian variation of the SGNA/VNA ratio. These data indicate significant remodeling of the extracardiac autonomic nerve activity and structures after MI.
acute myocardial infarction; autonomic nervous system; nerve recordings
Cervical vagal nerve (CVN) stimulation may improve left ventricular ejection fraction in patients with heart failure.
To test the hypothesis that sympathetic structures are present in the CVN and to describe the location and quantitate these sympathetic components of the CVN.
We performed immunohistochemical studies of the CVN from 11 normal dogs and simultaneously recorded stellate ganglion nerve activity, left thoracic vagal nerve activity, and subcutaneous electrocardiogram in 2 additional dogs.
A total of 28 individual nerve bundles were present in the CVNs of the first 11 dogs, with an average of 1.87 ± 1.06 per dog. All CVNs contain tyrosine hydroxylase-positive (sympathetic) nerves, with a total cross-sectional area of 0.97 ± 0.38 mm2. The sympathetic nerves were nonmyelinated, typically located at the periphery of the nerve bundles and occupied 0.03%–2.80% of the CVN cross-sectional area. Cholineacetyltransferase-positive nerve fibers occupied 12.90%–42.86% of the CVN cross-sectional areas. Ten of 11 CVNs showed tyrosine hydroxylase and cholineacetyltransferase colocalization. In 2 dogs with nerve recordings, we documented heart rate acceleration during spontaneous vagal nerve activity in the absence of stellate ganglion nerve activity.
Sympathetic nerve fibers are invariably present in the CVNs of normal dogs and occupy in average up to 2.8% of the cross-sectional area. Because sympathetic nerve fibers are present in the periphery of the CVNs, they may be susceptible to activation by electrical stimulation. Spontaneous activation of the sympathetic component of the vagal nerve may accelerate the heart rate.
Cervical vagus nerves; Sympathetic nerves; Ganglion cells; Heart failure; Vagal nerve stimulation
To advance disease-modifying therapies, it is critical to understand the relationship between the neuropathological changes of Alzheimer’s Disease (AD) and the clinical measures used in therapeutic trials. We reviewed neuropathologically proven cases of AD from the National Alzheimer’s Coordinating Center (NACC) and examined correlations between neuropathological changes and clinical-trial related instruments collected as part of the Uniform Dataset (UDS). We explored the relationships between neurofibrillary tangles, neuritic plaques, and total pathology burden with immediate and delayed recall, Clinical Dementia Rating-Sum of Boxes, Functional Activity Questionnaire, Neuropsychiatric Inventory Questionnaire, and Mini-Mental State Examination scores. 169 patients in NACC database had appropriate neuropathological and clinical data. All instruments correlated highly with neuritic plaques, Braak staging, and total pathology. Correlation coefficients for the relationships were relatively modest, suggesting that the pathologic burden examined accounts for between 13 and 40% of the variance of each of the instruments assessed. We conclude that there is a strong correlation between clinical trial-related measures and neuropathology identified at autopsy in AD. The amount of variance explained by the pathology is limited and other factors, both disease- and measurement-related, contribute to the variability observed in clinical measurements.
Clinical therapeutic trials; Alzheimer’s disease (AD); neuropathological changes; clinical-trial related instruments; correlation
Low income, government insurance, and minority status are associated with delayed treatment for neurosurgery patients. Less is known about the influence of referral location and how socioeconomic factors and referral patterns evolve over time. For pediatric epilepsy surgery patients at the University of California, Los Angeles (UCLA), this study determined how referral location and sociodemographic features have evolved over 25 years.
Children undergoing epilepsy neurosurgery at UCLA (453 patients) were classified by location of residence and compared with clinical epilepsy and sociodemographic factors.
From 1986 to 2010, referrals from Southern California increased (+33%) and referrals from outside of California decreased (−19%). Over the same period, the number of patients with preferred provider organization (PPO) and health maintenance organization (HMO) insurance increased (+148% and +69%, respectively) and indemnity insurance decreased (−96%). Likewise, the number of Hispanics (+117%) and Asians (100%) increased and Caucasians/whites decreased (−24%). The number of insurance companies decreased from 52 carriers per 100 surgical patients in 1986–1990 to 19 per 100 in 2006–2010. Patients living in the Eastern US had a younger age at surgery (−46%), shorter intervals from seizure onset to referral for evaluation (−28%) and from presurgical evaluation to surgery (−61%) compared with patients from Southern California. The interval from seizure onset to evaluation was shorter (−33%) for patients from Los Angeles County compared with those living in non-California Western US states.
Referral locations evolved over 25 years at UCLA, with more cases coming from local regions; the percentage of minority patients also increased. The interval from seizures onset to surgery was shortest for patients living farthest from UCLA but still within the US. Geographic location and race/ethnicity was not associated with differences in becoming seizure free after epilepsy surgery in children.
socioeconomic disparity; seizure; craniotomy; health inequity; epilepsy
The apolipoprotein E (APOE) ε4 allele enhances cerebral accumulation of β-amyloid (Aβ) and is a major risk factor for sporadic Alzheimer’s disease (AD). We hypothesized that HIV-associated neurocognitive disorders (HAND) would be associated with the APOE ε4 genotype and cerebral Aβ deposition.
Clinico-pathological study of HIV-infected adults from four prospective cohorts in the U.S. National NeuroAIDS Tissue Consortium.
We used multivariable logistic regressions to model outcomes (Aβ plaques [immunohistochemistry] and HAND [standard criteria]) on predictors (APOE ε4 [allelic discrimination assay], older age [≥ 50 years], Aβ plaques, and their two-way interactions) and co-morbid factors.
Isocortical Aβ deposits generally occurred as diffuse plaques and mild to moderate amyloid angiopathy. Isocortical phospho-Tau-immunoreactive neurofibrillary lesions were sparse. The APOE ε4 and older age were independently associated with the presence of Aβ plaques (adjusted odds ratio [OR] 10.16 and 5.77 [95% confidence interval (CI) 2.89–35.76 and 1.91–17.48], P=0.0003 and 0.0019, respectively, n=96). The probability of HAND was increased in the presence of Aβ plaques among APOE ε4 carriers (adjusted OR 30.00 [95% CI 1.41–638.63], P=0.029, n=15), but not in non-ε4 carriers (n=57).
The APOE ε4 and older age increased the likelihood of cerebral Aβ plaque deposition in HIV-infected adults. Generally Aβ plaques in HIV brains were immunohistologically different from those in symptomatic AD brains. Nonetheless, Aβ plaques were associated with HAND among APOE ε4 carriers. The detection of APOE ε4 genotype and cerebral Aβ deposition biomarkers may be useful in identifying living HAND subjects who could benefit from Aβ-targeted therapies.
Apolipoprotein E; β-amyloid; HIV dementia; neurofibrillary pathology; phospho-Tau
Like amyloid beta (Aβ) oligomers, tau aggregates are increasingly recognized as potential key toxic intermediates in Alzheimer’s disease and as therapeutic targets. P-tau co-localizes with Aβ in cortical AD synapses and may contribute to synapse dysfunction and loss. Flow cytometry analysis of synaptosomes from AD compared to aged cognitively normal cortex demonstrates increased immunolabeling for three p-tau antibodies (AT8, PHF-1 and pS422), indicating phosphorylation at multiple tau epitopes. Sequential extraction experiments show increased soluble p-tau in AD synapses, but a sizable pool of p-tau requires detergent solubilization, suggesting endosomal/lysosomal localization. P-tau is co-localized with Aβ in individual synaptosomes in dual labeling experiments, and flow cytometry sorting of Aβ-positive synaptosomes from an AD case reveals a marked enrichment of p-tau aggregates. The p-tau enrichment, a 76-fold increase over the initial homogenate, is consistent with sequestration of p-tau in internal synaptic compartments. Western analysis of a series of AD and normal cases shows SDS-stable tau oligomers in the dimer/trimer size range in AD samples. These results indicate that widespread synaptic p-tau pathology accompanies Aβ accumulations in surviving synaptic terminals, particularly in late-stage AD.
tau; synaptosome; flow cytometry; Alzheimer’s Disease; pS422 antibody; amyloid beta
Pathological findings in neonatal brain injury associated with preterm birth include focal and/or diffuse white matter injury (WMI). Despite the heterogeneous nature of this condition, reactive astrogliosis and microgliosis are frequently observed. Thus, molecular mechanisms by which glia activation contribute to WMI were investigated.
Postmortem brains of neonatal brain injury were investigated in order to identify molecular features of reactive astrocytes. The contribution of astrogliosis to WMI was further tested in a mouse model in genetically-engineered mice.
Activated STAT3 signaling in reactive astrocytes was found to be a common feature in postmortem brains of neonatal brain injury. In a mouse model of neonatal WMI, conditional deletion of STAT3 in astrocytes resulted in exacerbated WMI, which was associated with delayed maturation of oligodendrocytes. Mechanistically, the delay occurred in association with over-expression of TGFβ-1 in microglia, which in healthy controls, decreased with myelin maturation in age-dependent manner. TGFβ-1 directly and dose-dependently inhibited the maturation of purified oligodendrocyte progenitors, and pharmacological inhibition of TGFβ-1 signaling in vivo reversed the delay in myelin development. Factors secreted from STAT3-deficient astrocytes promoted elevated TGFβ-1 production in cultured microglia compared to wild type astrocytes.
These results suggest that myelin development is regulated by a mechanism involving cross-talk between microglia and oligodendrocyte progenitors. Reactive astrocytes may modify this signaling in STAT3-dependent manner, preventing the pathological expression of TGFβ-1 in microglia and the impairment of oligodendrocyte maturation.
Sestrin-2 is involved in p53-dependent antioxidant defenses and in the maintenance of metabolic homeostasis. We hypothesize that sestrin-2 expression is altered in the brains of subjects diagnosed with human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) due to neuronal oxidative stress. We studied sestrin-2 immunoreactivity in 42 isocortex sections from HIV-1-infected subjects compared to 18 age-matched non-HIV controls and 19 advanced Alzheimer's disease (AD) cases. With HIV infection, the sestrin-2 immunoreactivity pattern shifted from neuropil predominance (N) to neuropil and neuronal-soma co-dominance (NS) and neuronalsoma predominance (S; P < 0.0001, Chi-square test for linear trend). Among HIV cases showing the NS or S pattern, HAND cases were preferentially associated with the S pattern (n = 10 of 20) compared to cognitively intact cases (n = 1 of 11; P = 0.047, Fisher's exact test). In AD brains, sestrin-2 immunoreactivity was mostly intense in the neuropil and co-localized with phospho-Tau immunoreactivity in a subset of neurofibrillary lesions. Phospho-Tau-immunoreactive neurofibrillary lesions were rare in HIV cases and their occurrence was not associated with HAND. Levels of isocortical 8-hydroxy-deoxyguanosine (marker of nucleic acid oxidation) immunoreactivity were not significantly altered in HAND cases compared to cognitively intact HIV cases. In conclusion, the sestrin-2 immunoreactivity redistribution to neuronal soma in HAND suggests unique involvement of sestrin-2 in the pathophysiology of HAND, which is different from the role of sestrin-2 in AD pathogenesis. Alternatively, the difference in sestrin-2 immunoreactivity distribution between HAND and AD may be related to different degrees of severity or stages of oxidative stress.
Alzheimer's disease; HIV dementia; Neurofibrillary pathology; Oxidative stress; SESN2
The rapidly rising prevalence and cost of Alzheimer’s disease (AD) in recent decades has made the imaging of amyloid-β (Aβ) deposits the focus of intense research. Several amyloid imaging probes with purported specificity for Aβ plaques are currently at various stages of FDA approval. However, a number of factors appear to preclude these probes from clinical utilization. As the available “amyloid specific” PET imaging probes have failed to demonstrate diagnostic value and have shown limited utility for monitoring therapeutic interventions in humans, a debate on their significance has emerged. The aim of this review is to identify and discuss critically the scientific issues contributing to the extensive inconsistencies reported in the literature on their purported in vivo amyloid specificity and potential utilization in patients.
amyloid imaging; amyloid ‘specific’ imaging probes; Amyvid; PIB; critical review; neuropathologic criteria; silent medial temporal lobe
Much evidence indicates that soluble amyloid beta (Aβ) oligomers are key mediators of early cognitive loss, but the localization and key peptide species remain unclear. We have used flow cytometry analysis to demonstrate that surviving Alzheimer's disease (AD) synapses accumulate both Aβ and p-tau. The present experiments use peptide-specific xMAP assays and Western blotting to identify the Aβ peptide species in synaptosome-enriched samples from normal human subjects, neurologic controls, and AD cases. Aβ40 peptide levels did not vary, but both Aβ42 and Aβ oligomers were increased in soluble AD extracts, with oligomer levels 20-fold higher in aqueous compared to detergent extracts. In Western blots, a ladder of SDS-stable oligomers was observed in AD cases, varying in size from monomer, the major peptide observed, to larger assemblies up to about 200 kD and larger. Multiple oligomers, including monomer, small oligomers, a 56 kD assembly, and APP were correlated with the Aβ level measured in flow cytomety-purified synaptosomes. These results suggest that multiple APP processing pathways are active in AD synapses and multiple soluble oligomeric assemblies may contribute to synaptic dysfunction.
synaptosome; flow cytometry; Parkinson's disease; synaptophysin; PSD-95; A11 antibody; OC antibody
FK506 binding protein (FKBP)-51 and FKBP52 act as molecular chaperones to control glucocorticoid receptor (GR) sensitivity. Dysregulation of proteins involved in GR-mediated signaling can lead to maladaptive stress response and aging-related cognitive decline. As HIV infection is related to chronic stress, we hypothesized that altered cortical expression of these proteins was associated with HIV-associated neurocognitive disorders (HAND). We used quantitative immunohistochemistry to assess expression levels of these proteins in the mid-frontal gyrus of 55 HIV-infected subjects free of cerebral opportunistic diseases compared to 20 age-matched non-HIV controls. The immunoreactivity normalized to the neuroanatomic area measured (IRn) for FKBP51 was increased in HIV subjects both in the cortex and subcortical white matter (p<0.0001, U test), while no significant alterations were observed for GR or FKBP52. Notably, the cortical FKBP51 IRn was higher in HAND subjects than in cognitively normal HIV subjects (p=0.02, U test). There was also a trend for increasing cortical FKBP51 IRn with the increasing severity of HAND (p=0.08, Kruskal-Wallis test). No significant changes in FKBP51 IRn were found with respect to hepatitis C virus infection, lifetime methamphetamine use, or antiretroviral treatment in HIV subjects. In conclusion, the increased cortical expression of FKBP51 (an inhibitor for GR activity) might represent negative feedback in an attempt to reduce GR sensitivity in the setting of chronic stress-induced elevation of GR-mediated signaling inherent in HIV infection. The further increased FKBP51 expression might lead to maladaptive stress response and HAND.
FKBP4; FKBP5; HIV dementia; Immunophilin; NR3C1
This work is aimed at correlating pre mortem [F-18]FDDNP PET scan results in a patient with dementia with Lewy bodies (DLB), with cortical neuropathology distribution determined post mortem in three physical dimensions in whole brain coronal sections. Analysis of total Aβ distribution in frontal cortex and posterior cingulate gyrus confirmed its statistically significant correlation with cortical [F-18]FDDNP PET binding values (distribution volume ratios, DVR) (p<0.001, R=0.97, R2=0.94). Neurofibrillary tangle (NFT) distribution correlated significantly with cortical [F-18]FDDNP PET DVR in the temporal lobe (p<0.001, R=0.87, R2=0.76). Linear combination of Aβ and NFT densities was highly predictive of [F-18]FDDNP-PET DVR through all analyzed regions of interest (p<0.0001, R=0.92, R2=0.85), and both densities contributed significantly to the model. Lewy bodies (LB) were present at a much lower level than either Aβ or NFTs and did not significantly contribute to the in vivo signal. [F-18]FDG PET scan results in this patient were consistent with the distinctive DLB pattern of hypometabolism. This work offers a mapping brain model applicable to all imaging probes for verification of imaging results with Aβ and/or tau neuropathology brain distribution using immunohistochemistry, fluorescence microscopy and autoradiography.
[F-18]FDDNP; dementia with Lewy bodies; brain pathology mapping; amyloid and tau immunocytochemistry
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.
While most forms of Parkinson’s Disease (PD) are sporadic in nature, a small percentage of PD have genetic causes as first described for dominant, single base pair changes as well as duplication and triplication in the α-synuclein gene. The α-synuclein gene encodes a 140 amino acid residue protein that interacts with a variety of organelles including synaptic vesicles, lysosomes, endoplasmic reticulum/Golgi vesicles and, reported more recently, mitochondria. Here we examined the structural and functional interactions of human α-synuclein with brain mitochondria obtained from an early, pre-manifest mouse model for PD over-expressing human α-synuclein (ASOTg). The membrane potential in ASOTg brain mitochondria was decreased relative to wildtype (WT) mitochondria, while reactive oxygen species (ROS) were elevated in ASOTg brain mitochondria. No selective interaction of human α-synuclein with mitochondrial electron transport complexes cI-cV was detected. Monomeric human α-synuclein plus carboxyl terminally truncated forms were the predominant isoforms detected in ASOTg brain mitochondria by 2-dimensional PAGE (Native/SDS) and immunoblotting. Oligomers or fibrils were not detected with amyloid conformational antibodies. Mass spectrometry of human α-synuclein in both ASOTg brain mitochondria and homogenates from surgically resected human cortex demonstrated that the protein was full-length and postranslationally modified by N-terminal acetylation. Overall the study showed that accumulation of full-length, N-terminally acetylated human α-synuclein was sufficient to disrupt brain mitochondrial function in adult mice.