Stephen M. Gentleman

βA4 amyloid protein deposition in brain after head trauma

Abstract Previous reports have suggested that both repetitive head trauma and a single injury can be associated with the presence of diffuse βA4 amyloid protein plaques in long-term survivors. We have studied sixteen patients (aged 10-63 years) who sustained head injury and survived for only 6-18 days. Immunostaining with an antibody to βA4 amyloid showed extensive deposits of the protein in the cortex in six of the sixteen patients (38%). Thus, severe head injury can trigger βA4 deposition in the brain within days.

Microglial interleukin-lα expression in human head injury: Correlations with neuronal and neuritic β-amyloid precursor protein expression

Activated microglia containing IL-1 alpha-immunoreactive (IL-1 alpha +) product were increased 3-fold in number in the acute phase following head injury, a risk factor for later development of Alzheimers disease, and this increase was correlated with a 7-fold increase in the number of neurons with elevated beta-amyloid precursor protein (beta-APP) levels (R = 0.78; P < 0.05). Furthermore, clusters of beta-APP+ dystrophic neurites present in these patients were invariably associated with activated IL-1 alpha + microglia. These findings suggest that early overexpression of IL-1 alpha and beta-APP is a priming event for later neuropathological changes evident at end stages of Alzheimers disease.

Staging/typing of Lewy body related α-synuclein pathology: a study of the BrainNet Europe Consortium

When 22 members of the BrainNet Europe (BNE) consortium assessed 31 cases with α-synuclein (αS) immunoreactive (IR) pathology applying the consensus protocol described by McKeith and colleagues in 2005, the inter-observer agreement was 80%, being lowest in the limbic category (73%). When applying the staging protocol described by Braak and colleagues in 2003, agreement was only 65%, and in some cases as low as 36%. When modifications of these strategies, i.e., McKeith’s protocol by Leverenz and colleagues from 2009, Braak’s staging by Müller and colleagues from 2005 were applied then the agreement increased to 78 and 82%, respectively. In both of these modifications, a reduced number of anatomical regions/blocks are assessed and still in a substantial number of cases, the inter-observer agreement differed significantly. Over 80% agreement in both typing and staging of αS pathology could be achieved when applying a new protocol, jointly designed by the BNE consortium. The BNE-protocol assessing αS-IR lesions in nine blocks offered advantages over the previous modified protocols because the agreement between the 22 observers was over 80% in most cases. Furthermore, in the BNE-protocol, the αS pathology is assessed as being present or absent and thus the quality of staining and the assessment of the severity of αS-IR pathology do not alter the inter-observer agreement, contrary to other assessment strategies. To reach these high agreement rates an entity of amygdala-predominant category was incorporated. In conclusion, here we report a protocol for assessing αS pathology that can achieve a high inter-observer agreement for both the assignment to brainstem, limbic, neocortical and amygdala-predominant categories of synucleinopathy and the Braak stages.

Life-long overexpression of S100β in Down’s syndrome: implications for Alzheimer pathogenesis

Chronic overexpression of the neurite growth-promoting factor S100beta has been implicated in the pathogenesis of neuritic plaques in Alzheimers disease. Such plaques are virtually universal in middle-aged Downs syndrome, making Downs a natural model of Alzheimers disease. We determined numbers of astrocytes overexpressing S100beta, and of neurons overexpressing beta-amyloid precursor protein (beta-APP), and assayed for neurofibrillary tangles in neocortex of 20 Downs syndrome patients (17 weeks gestation to 68 years). Compared to controls, there were twice as many S100beta-immunoreactive (S100beta+) astrocytes in Downs patients at all ages: fetal, young, and adult (p = 0.01, or better, in each age group). These were activated (i.e., enlarged), and intensely immunoreactive, even in the fetal group. There were no neurofibrillary changes in fetal or young Downs patients. The numbers of S100beta+ astrocytes in young and adult Downs patients correlated with the numbers of neurons overexpressing beta-APP (p < 0.05). Our findings are consistent with the idea that conditions--including Downs syndrome--that promote chronic overexpression of S100beta may confer increased risk for later development of Alzheimers disease.

Striatal β-Amyloid Deposition in Parkinson Disease With Dementia

Dementia is common in Parkinson disease (PD), although its anatomic and pathologic substrates remain undefined. Recently, striatal abnormalities in Lewy body diseases have been described, but their clinical relevance is not clear. Thirty PD cases from the United Kingdom Parkinsons Disease Society Tissue Bank were grouped as demented (PDD; n = 16) and nondemented (PD; n = 14) based on a review of clinical records. The extent of &agr;-synuclein, tau, and amyloid &bgr; peptide (A&bgr;) deposition in the caudate nucleus, putamen, and nucleus accumbens was assessed. All cases showed severe dopaminergic striatal terminal denervation based on tyrosine hydroxylase immunohistochemistry. &agr;-synuclein and tau deposition in the striatum were rare in both groups, but the A&bgr; burden was significantly greater in the striatum of PD cases with dementia than present in the nondemented PD group. Striatal A&bgr; deposition was type-independent of Alzheimer disease changes in the cortex and was minimal in nondemented PD cases. We conclude that A&bgr; deposition in the striatum strongly correlates with dementia in PD.

Chapter 16 Molecular pathology of head trauma: altered βAPP metabolism and the aetiology of Alzheimer's disease

Publisher Summary Considerable progress has been made in determining the identity of the proteins and molecular events involved in the molecular pathology of Alzheimers disease (AD), the most widely known of which are the inevitability of Alzheimers disease in Downs syndrome patients with trisomy of chromosome 21 and the point mutations at codon 717 within exon 17 of the β -amyloid precursor protein gene on chromosome 21. However, these genetic causes of Alzheimers disease account for a vanishingly small proportion of patients who suffer from the disease. It is probable that the overwhelming majority of cases are caused by a variety of environmental factors, which may be either sufficient to trigger disease by themselves or sufficient when acting synergistically with the patients genotype. One of the best-documented environmental precipitants of Alzheimers disease is a previous history of head trauma. AD can be caused by a variety of factors. Approximately 20% of AD cases are thought to be familial with almost 5% exhibiting an autosomal dominant pattern of inheritanc. Screening of the amyloid precursor protein ( β APP) gene on chromosome 21, which gives rise to the β -amyloid protein found in plaques, has revealed a mutation in some AD families.

Inter-laboratory comparison of neuropathological assessments of beta-amyloid protein: a study of the BrainNet Europe consortium.

Amyloid-β-protein (Aβ) is generally assessed by neuropathologists in diagnostics. This BrainNet Europe (http://www.brainnet-europe.org/) (15 centres and 26 participants) study was carried out to investigate the reliability of such an assessment. In the first part of this trial, tissue microarray sections were stained with the antibody of each centre’s choice. Reflecting the reality, seven antibodies and a plethora of pretreatment strategies were used. Ninety-two percent of the stainings were of good/acceptable quality and the estimation of presence of Aβ aggregates yielded good results. However, a poor agreement was reached particularly regarding quantitative (density) and qualitative (diffuse/cored plaques) results. During a joint meeting, the clone 4G8 was determined to label best the fleecy/diffuse plaques, and thus, this clone and the formic acid pretreatment technique were selected for the second part of this study. Subsequently, all stained sections were of good/acceptable quality and again a high level of concordance of the dichotomized (presence/absence) assessment of plaques and CAA was achieved. However, even when only one antibody was used, the type of Aβ-aggregates (diffuse/cored), type of vessel and Vonsattel grade, were not reliably assigned. Furthermore, the quantification of lesions was far from reliable. In line with the first trial, the agreement while assessing density (some, moderate and many) was unimpressive. In conclusion, we can confirm the utility of immunohistochemical detection of Aβ-protein in diagnostics and research. It is noteworthy that to reach reproducible results a dichotomized assessment of Aβ-immunoreactivity rather than quantification and assignment of various types of lesions should be applied, particularly when comparing results obtained by different neuropathologists.

Assessment of alpha-synuclein pathology: A study of the BrainNet Europe consortium

To determine the reliability of assessment of &agr;-synuclein-immunoreactive (&agr;S-IR) structures by neuropathologists, 28 evaluators from 17 centers of BrainNet Europe examined current methods and reproducibility of &agr;S-IR evaluation using a tissue microarray (TMA) technique. Tissue microarray blocks were constructed of samples from the participating centers that contained &agr;S-IR structures. Slides from these blocks were stained in each center and assessed for neuronal perikaryal inclusions, neurites, and glial cytoplasmic inclusions. The study was performed in 2 phases. First, the TMA slides were stained with the antibody of the centers choice. In this phase, 59% of the sections were of good or acceptable quality, and 4 of 9 antibodies used performed consistently. Differences in interpretation and categorization of &agr;S-IR structures, however, led to differing results between the laboratories. Prior to the second phase, the neuropathologists participated in a training session on the evaluation of &agr;S-IR structures. Based on the results of the first phase, selected antibodies using designated antigen retrieval methods were then applied to TMA slides in the second phase. When the designated methods of both staining and evaluation were applied, all 26 subsequently stained TMA sections evaluated were of good/acceptable quality, and a high level of concordance in the assessment of the presence or absence of specific &agr;S-IR structures was achieved. A semiquantitative assessment of &agr;S-IR neuronal perikaryal inclusions yielded agreements ranging from 49% to 82%, with best concordance in cortical core samples. These results suggest that rigorous methodology and dichotomized assessment (i.e. determining the presence or absence of &agr;S-IR) should be applied, and that semiquantitative assessment can be recommended only for the cortical samples. Moreover, the study demonstrates that there are limitations in the scoring of &agr;S-IR structures.

Increased numbers of .BETA.APP-immunoreactive neurones in the entorhinal cortex after head injury.

IN a previous publication we hypothesized that Alzheimers disease (AD) can be induced by the age-related increase in expression of β-amyloid precursor protein (βAPP) in the medial temporal lobe. Head injury has also been identified as a risk factor for AD, and as such, similarities should exist between the pathology found after head injury, and the earliest stages of pathology in AD. In this study, we have quantified the number of βAPP-immunoreactive neurones in the medial temporal cortex (pre-α cells, layer II) of 13 head injured, and 17 control patients. Significantly more βAPP immunoreactive neurones were observed in head injury cases (mean 18.4 per cluster) compared with controls (mean 13.4 per cluster, p < 0.05). These data provide a mechanism to explain how an environmental event such as head injury can generate the same molecular pathology (increased neuronal βAPP) as is found in the earliest stages of AD.

Alzheimer's peptide kills cells of retina in vivo

Alzheimers disease, the commonest form of dementia, is a progressive, age-dependent disorder characterized by the presence of large numbers of senile plaques and neurofibrillary tangles. The neuritic plaques consist of an accumulation of amyloid-β peptide (Aβ); this substance, which derives from proteolysis of β-amyloid precursor protein (APP), seems to play a central role in the pathology of the disease. The toxicity of Aβ to neurons has already been demonstrated in vitro. Here we show that the peptide is also cytotoxic in vivo.