Zs. Nagy

Cell cycle markers in the hippocampus in Alzheimer’s disease

Abstract Using immunohistochemistry we have analysed the nuclear expression of cyclins A, B, D, and E in neurones in the hippocampi of control subjects and patients suffering from various neurodegenerative disorders including Alzheimer’s disease (AD). Cyclins A and D could not be detected but varying degrees of cyclin E expression were found in all patient groups including control subjects. Cyclin B expression was not detected in control subjects but it was expressed in the subiculum, dentate gyrus and CA1 region in patients with AD-type pathology and in the CA2 region and the dentate gyrus of cases of Pick’s disease. These reults suggest that some neurones may have re-entered the cell cycle. The expression of cyclin E without cyclin A expression may indicate an arrest in G1 with the possibility of re-differentiation and exit from G1 to G0. The expression pattern of cyclin E indicates that re-entry into the cell cycle is possible even in control patients, but it is accentuated in patients with AD-related pathology. However, cyclin B was only expressed in AD patients and occurred in areas that were severely affected by pathology. Neurones with cyclin B-reactive nuclei in AD were AT8 positive but did not contain fully developed tangles. In neurones, where cyclin B is expressed, it would appear that the G1/S checkpoint has been bypassed and that the cell cycle is arrested in G2. It is proposed that these neurones do not have the opportunity for subsequent re-differentiation. Since factors known to be present in G2 seem to be responsible for microtubule destabilisation and hyperphosphorylation of tau we hypothesise that cell cycle disturbances may be important in the pathogenesis of AD.

Relative Roles of Plaques and Tangles in the Dementia of Alzheimer's Disease: Correlations Using Three Sets of Neuropathological Criteria

We have performed a quantitative analysis of the amyloid load (plaques), neuritic plaques and neurofibrillary tangles (NFT) in the frontal, temporal and parietal association cortices of autopsied brains from 49 prospectively evaluated patients with Alzheimers disease (AD) diagnosed according to three sets of published pathological criteria. These patients had been assessed clinically with psychological testing of cognitive abilities within 6 months of death. Correlations were sought between severity of pathological change and cognitive status before death, duration of disease and age at death. Using Khachaturian and CERAD criteria highly positive correlations were obtained between the extent of cognitive deficit and the density of NFT in frontal and parietal lobes. The percentage area of cortex occupied by amyloid in the parietal lobe was correlated to the cognitive deficit only in the CERAD-diagnosed cases. The density of all amyloid plaques (AP) showed no correlation with the extent of cognitive deficit, but the densities of neuritic plaques did correlate with cognitive deficit. Both amyloid load and tangle densities were positively correlated with disease duration. All these correlations were reduced or absent in a subgroup of cases fulfilling the Tierney et al. A3 diagnostic criteria for AD. We found no pathological measure that correlated with the age of patients at death. Amyloid loads and NFT densities showed highly significant but selective positive correlations, the most striking being between temporal lobe NFT density and frontal and parietal lobe amyloid load and between temporal lobe NFT density and frontal and parietal lobe NFT densities. Correlations involving AP density as a measure of amyloid load were almost always less significant than those involving the percentage area of cortex occupied by amyloid, suggesting that the latter measures amyloid load more accurately. However, the highest correlations of NFT densities were with neuritic plaque densities. Overall this study highlights the relevance of neuritic changes (revealed by NFT and neuritic plaques) and the irrelevance of amyloid plaques to the dementia of AD.

Expression of cell division markers in the hippocampus in Alzheimer's disease and other neurodegenerative conditions

Abstract Recent studies, showing that cell cycle-related nuclear proteins p105 and Ki-67 are associated with Alzheimer’s disease (AD)-related cytoskeletal pathology, suggested that these proteins, in addition to their functions in regulating the cell cycle, may have more specialised functions in the adult nervous system. In order to test this hypothesis we studied the expression of the cell cycle-related proteins Ki-67, pCNA and p53 in the hippocampi of 33 subjects, including some with AD or other neurodegenerative disorders and some with no neurological disease. By immunohistochemistry we found nuclear expression of Ki-67 in all subregions of the hippocampus, with the highest levels in the dentate gyrus. Both neurons and glial cells expressed this protein. The proportion of cells positive for Ki-67 and the distribution pattern varied considerably depending on the pathological diagnosis. Neuronal nuclear expression of Ki-67 was increased in AD but was also elevated in young Down’s syndrome subjects and in those with Pick’s disease. Expression of this protein was therefore not AD-specific. We did not find nuclear pCNA or p53 expressed in our patient groups. Contrary to previous studies AD-type neurofibrillary tangles were not labelled with any of the cell cycle markers used. The presence of nuclear Ki-67 expression indicates that some hippocampal neurons are not in the quiescent G0 phase but have re-entered the cell cycle. The absence of nuclear pCNA or p53 suggests that the cycle is arrested in G1. The significance of our findings and their relationship to the production of neurodegenerative cell death via an apoptotic mechanism are discussed.

Influence of the apolipoprotein E genotype on amyloid deposition and neurofibrillary tangle formation in Alzheimer's disease

The effect of the apolipoprotein E genotype on the development of late onset Alzheimers disease is still debated. Neuropathological studies of Alzheimers disease have found a great extent of amyloid deposition in cortex and blood vessel walls in association with the apolipoprotein E epsilon 4 genotype [Rebeck G. W. et al. (1993) Neuron 11, 575-580; Schmechel et al. (1993) Proc. natn. Acad. Sci. U.S.A. 90, 9649-9653]. In contrast, the relationship of apolipoprotein E genotype to neurofibrillary pathology in Alzheimers disease has been less clear. In this study we present evidence on the influence of the apolipoprotein E genotype on Alzheimers disease related pathology in a series of 76 autopsy cases that had pathology that fulfilled the CERAD criteria for Alzheimers disease. We found that the presence of the apolipoprotein E epsilon 4 allele is correlated with increased amounts of both amyloid and neuritic pathology in the neocortex as determined using an image analysis system. Comparison of plaque and tangle densities with the allele doses of epsilon 2 and epsilon 4 revealed a striking parallelism, suggesting that the alleles exert their effects very early in the pathological process before deposition of plaques and tangles. Although the apolipoprotein E epsilon 2 allele had a protective effect against both amyloid deposition and neurofibrillary tangle formation, in the presence of the epsilon 4 allele this protective effect against neuritic pathology was less marked than against amyloid deposition. This differential effect on amyloid deposition and the accumulation of neuritic pathology suggests that different molecular mechanisms are involved in the effect of apolipoprotein E on amyloid deposition and on tau phosphorylation.

Cell cycle-related protein expression in vascular dementia and Alzheimer's disease.

Recent findings from our and other laboratories indicate that cell cycle-related phenomena may play a key role in the formation of Alzheimer-type pathology and neuronal cell death in both Alzheimers and cerebro-vascular diseases. In this study we examine the expression patterns of cyclins A, B1, D1 and E in neuronal nuclei in the hippocampus in autopsied healthy elderly individuals, Alzheimers disease patients and subjects suffering from cerebrovascular disease with and without co-existing Alzheimers disease. Nuclear cyclin B1 and cyclin E expression was detected in hippocampal neurones in each subject category. However, cyclin B1 expression was significantly elevated in the CA1 of patients suffering from cerebro-vascular disease alone, while cyclin E expression was significantly higher in the CA4 subfield in patients suffering from mixed Alzheimers and cerebro-vascular diseases compared to subjects in other categories. We hypothesize that cell cycle re-entry may occur in healthy elderly people leading to age-related cell death and mild Alzheimer-type pathology in the hippocampus. However, in pathological conditions, the cell cycle arrest may lead either to the development of severe Alzheimer-related pathology or to excess apoptotic cell death as in vascular dementia.

Accuracy of Clinical Operational Diagnostic Criteria for Alzheimer’s Disease in Relation to Different Pathological Diagnostic Protocols

In this study we analysed the accuracy of two sets of clinical diagnostic criteria, the NINCDS/ADRDA and DSM-III-R, in relation to the currently used pathological diagnostic criteria for Alzheimer’s disease (AD), the Khachaturian criteria, the Tierney A3 criteria and the CERAD protocol. The sensitivity of the individual clinical diagnostic criteria, NINCDS/ADRDA and DSM-III-R, is poor (34–58%) irrespective of the pathological diagnostic criteria applied for the definite diagnosis of AD. The combination of the NINCDS/ADRDA ‘possible’ and ‘probable dementia of the Alzheimer type’ (DAT) categories has a high sensitivity (91–98%). However the combination resulted in very poor specificity (40–61%). Thus, none of the clinical diagnostic criteria is satisfactory. We found similar results when we analysed the predictive value of these clinical diagnostic criteria. The positive predictive value of NINCDS ‘probable DAT’ category and that of the DAT diagnosis by DSM-III-R is very high (89–100%). This makes the use of these categories suitable for research purposes. However, the negative predictive value of both diagnoses is poor (33–63%), making these criteria unsuitable for diagnostic purposes in clinical practice.

The Progression of Alzheimer’s Disease from Limbic Regions to the Neocortex: Clinical, Radiological and Pathological Relationships

Alzheimer’s disease (AD) is characterised by the gradual accumulation of neurofibrillary pathology in selected regions of the brain. Earlier studies indicate that the accumulation of neurofibrillary tangles is associated both with decline in patient’s cognitive performance as well as with medial temporal lobe atrophy on CT scans. There are also indications that progression through the pathological stages of AD is associated with decline in cognitive functions. The results of this study indicate that progression of disease, especially beyond the boundaries of the limbic regions, is associated with marked decline in the cognitive performance of patients suffering from AD. However the clinical manifestations of early pathological stages are not so well defined. We also found that the atrophy of the medial temporal lobe on CT scans is related to the progression of pathology. Atrophy is most apparent when the disease reaches its isocortical stages and is not marked in the limbic stages of the disease. The additive effect of pathologies co-existing with AD is apparent in reduced cognitive scores, while the atrophy of limbic structures, as measured on CT scans, seems to be mainly attributable to AD-related pathology.

Proliferation, bcl-2 expression and angiogenesis in pituitary adenomas: relationship to tumour behaviour

The prediction of pituitary tumour behaviour, in terms of response to treatment from which can be derived optimal management strategies, is a challenge that has been approached using several different means. Angiogenesis in other tumour types has been shown to be correlated with poor response to treatment and tumour recurrence. The aim of this paper is to assess the role of measurements of cell proliferation and angiogenesis in predicting pituitary tumour behaviour. The proliferative capacity of the tumour was assessed using the Ki-67 labelling index (LI) while bcl-2 expression was used to assess anti-apoptotic pathways. The microvessel density (MVD) was assessed using antibodies to CD31 and factor VIII-related antigen, and with biotinylated ulex europaeus agglutinin I. There was no difference between Ki-67 LI and MVD of functionless tumours that recurred and those that did not, but bcl-2 expression was significantly lower in tumours that subsequently regrew. Macroprolactinomas had significantly higher LI than microprolactinomas and than all other tumours. Cell proliferation and angiogenesis were not related, showing that both processes are under different control mechanisms in pituitary tumours. In contrast there was a positive relationship between markers of angiogenesis and bcl-2 expression in prolactinomas, GH-secreting tumours and non-recurrent functionless tumours with higher levels of bcl-2 expression being found in the more vascular tumours. These findings may suggest that angiogenesis is related to the ability of tumour cells to survive rather than their proliferative activity.

Hippocampal Pathology Reflects Memory Deficit and Brain Imaging Measurements in Alzheimers Disease: Clinicopathologic Correlations Using Three Sets of Pathologic Diagnostic Criteria

Neurofibrillary tangles (NFT), neuritic plaques and amyloid load were quantified in sections of the hippocampus at the level of the lateral geniculate body in 41 consecutive cases fulfilling pathological criteria for diagnosis of Alzheimers disease (AD) and coming to autopsy after longitudinal study during life. A strong correlation was found between NFT density in the hippocampus and cognitive impairment scores obtained shortly before death, particularly with scores of memory impairment. Weaker and less consistent correlations were found for hippocampal neuritic plaques and amyloid load with cognitive/memory deficits. No significant correlations were found between hippocampal pathology and either age of onset or disease duration. All three measures of hippocampal pathology were inversely correlated with the minimum medial temporal lobe (MTL) width, a measure of the MTL atrophy made from temporal-lobe-oriented X-ray computed tomography scans performed during life; the strongest correlation being between atrophy of the MTL and NFT density in the hippocampus.

Mitochondrial enzyme expression in the hippocampus in relation to Alzheimer-type pathology

Abstract Recent reports have suggested that mitochondrial dysfunction may contribute to the progression of the pathology of Alzheimer’s disease (AD). However, both increases and decreases in the activity of cytochrome oxidase have been described in the hippocampi of AD patients. In this study we used immunohistochemistry and quantitative autoradiographic methods to study the expression pattern of two cytochrome oxidase subunit proteins (nuclear-encoded COX IV and mitochondrial-encoded COX I) in the hippocampus in relation to the development of AD-type pathology. We found heterogeneous expression of both COX subunits in AD with an increased expression of both subunit proteins in healthy, non-tangle-bearing, neurones but absence of both subunit proteins in tangle-bearing neurones. Levels of COX IV but not of COX I were related to the amount of hyperphosphorylated tau accumulated in the same hippocampal region but not to the amount of amyloid deposited in sporadic AD. In Down’s syndrome COX I and COX IV were similarly increased in the presence of AD pathology in non-tangle-bearing neurones. However, in these cases levels of enzyme expression were correlated to the amount of amyloid accumulation but not the amount of hyperphosphorylated tau in the hippocampus. We believe that heterogeneity of expression of mitochondrial enzyme proteins between neurones may contribute to the conflicting conclusions in previous reports regarding relative levels of cytochrome oxidase activity in the hippocampus in AD. We hypothesise that the increased mitochondrial enzyme expression in healthy-appearing neurones of AD brains may represent a physiological response to increased functional demand on surviving neurones as a consequence of AD-related neuronal pathology.