A quantitative and immunohistochemical study on apolipoprotein E in brain tissue in Alzheimer's disease

Apoliprotein E (ApoE) has been implicated in the pathogenesis of Alzheimer's disease (AD). Antibodies to ApoE label senile plaques (SP), and an interaction between ApoE and beta-amyloid has been found in in vitro studies. Further, an increased frequency of the ApoE epsilon4 allele in AD has been reported in numerous papers. However, the pathogenetic mechanism of ApoE in AD is not known. We studied ApoE in brain tissue (hippocampus, cerebellum, frontal and temporal cortex) from patients with AD and age-matched control subjects, using both quantitative Western blotting and immunohistochemistry. In AD, a reduction of ApoE was found in the hippocampus (50% of the control value) and in the frontal cortex (52% of the control value), while no significant changes in ApoE levels were found in the temporal cortex or in the cerebellum. Also by immunohistochemistry, ApoE staining was generally decreased in AD brains, both in the neuropil and in the neuronal cellular compartments. Within the AD group, there was no significant correlation between the ApoE level and SP or neurofibrillary tangle (NFT) counts, either in the hippocampus (r = -0.14 and r = 0.55, respectively), or in the frontal cortex (r = -0.03 and r = 0.01, respectively). There were no significant differences in duration, severity of dementia, SP or NFT counts, or ApoE levels between AD patients with different numbers of ApoE epsilon4 alleles. After experimental brain damage in animals, marked increases in ApoE are found, probably as part of lipid recycling in neuronal and synaptic remodelling and regeneration. One may speculate whether the decrease in ApoE may suggest a disturbance in the ApoE system in AD that is unrelated to ApoE isoforms, beta-amyloid deposition and NFT formation. Copyrightz1999S.KargerAG,Basel     

Synaptic pathology in Alzheimer's disease: Relation to severity of dementia,but not to senile plaques,neurofibrillary tangles,or the ApoE4 allele

Summary Alzheimer's disease (AD) is characterised by an increased number of senile plaques (SP) and neuroflbrillary tangles (NFT) as compared with that found in non-demented individuals of the same age, and a marked degeneration and loss of synapses. One of the main risk-factors for the disorder is inheritance of the apolipoprotein E4 (ApoE4) allele. To further study the relation between these pathogenetic substrates for AD, we quantified the synaptic vesicle membrane protein rab3a in brain tissue from 19 patients with AD and 9 age-matched control subjects. Rab3a levels were reduced in AD, both in the hippocampus (60% of control level, p < 0.0001), and in the frontal cortex (68% of control level, p < 0.01), but not in the cerebellum (92% of control level). Within the AD group, lower rab3a levels were found both with increasing duration and severity of dementia. These findings further support that synaptic pathology is closely correlated to the clinical dementia in AD. In contrast, no significant correlations were found between SP counts and duration or severity of dementia, while higher NFT counts in the frontal cortex were found with increasing severity of dementia (r=0.54, p < 0.05). There were no significant correlations between the rab3a level and SP or NFT counts, and by immunohistochemistry, reduced rab3a immunostaining was found throughout the neuropil in AD brain, without relation to SP or NFT. These findings suggest that the synaptic pathology in AD is not closely related to the presence of SP and NFT. No significant differences in rab3a levels were found in any brain region between AD patients possessing different numbers of the ApoE4 allele, suggesting that, although ApoE4 is a risk factor for earlier development of AD, the degree of synaptic pathology does not differ between patients with or without the ApoE4 allele.     

Normal levels of clusterin in cerebrospinal fluid in Alzheimer's disease,and no change after acute ischemic stroke

The protein clusterin has been suggested to be involved in the pathogenesis of Alzheimer's disease (AD). Its expression is increased in brain regions affected by AD pathology, and to elucidate if there is a concomitant increase of clusterin also in the cerebrospinal fluid (CSF) in different neurological disorders, CSF samples from patients with AD, vascular dementia (VAD), Parkinson's disease (PD), and controls were analysed. Also longitudinal (five occasions) samples from patients with acute stroke were analysed, to follow any degenerative/regenerative phase after acute brain damage. However, there were no changes in CSF-clusterin levels from patients in AD, VAD, PD or acute stroke, as compared to controls. The increase of clusterin in brain tissue is suggested to reflect a regenerative response process, which here is shown not to be followed by a concomitant increase in the CSF. Thus, CSF-clusterin can not be used as an indicator or a diagnostic marker for AD.     

Clusterin mRNA and protein in Alzheimer's disease

Clusterin, a multifunctional lipoprotein is expressed in a number of tissues but expression is particularly high in the brain, where it binds to amyloid-β (Aβ), possibly facilitating Aβ transport into the bloodstream. Its concentration in peripheral blood was identified as a potential biomarker for Alzheimer's disease (AD) and predicted retention of (11)C-Pittsburgh Compound B in the temporal lobe. Single-nucleotide polymorphisms in the clusterin gene, CLU, are associated with the risk of developing AD. We measured clusterin mRNA levels in control and AD brains and investigated the relationship of the clusterin protein to soluble, insoluble, and plaque-associated Aβ. Clusterin mRNA levels were unchanged when normalized to GAPDH but modestly increased in the frontal and temporal cortex in AD in relation to NSE and MAP-2. Levels of NSE and MAP-2 mRNA were reduced in the AD frontal cortex. Clusterin protein concentration was unchanged and did not correlate with the amount of Aβ present. In the frontal cortex, clusterin concentration was higher in APOE ε4-negative brains but no effect of APOE was detected in the temporal cortex or thalamus. Overall clusterin mRNA and protein levels are unaltered in the neocortex in AD and clusterin concentration does not reflect Aβ content. The increase in clusterin noted in peripheral blood in AD may reflect increased passage of this chaperone protein across the blood-brain barrier but further work is needed to determine how CLU variants influence the development of AD.     

tau protein in cerebrospinal fluid

Cerebrospinal fluid (CSF) biochemical markers for Alzheimer disease (AD) would be of great value to improve the clinical diagnostic accuracy of the disorder. As abnormally phosphorylated forms of the microtubule-associated protein tau have been consistently found in the brains of AD patients, and since tau can be detected in CSF, two assays based on several well-defined monoclonal tau antibodies were used to study these proteins in CSF. One assay detects most normal and abnormal forms of tau (CSF-tau), while the other is highly specific for phosphorylated tau (CSF-PHFtau). A marked increase in CSF-PHFtau was found in AD (2230±930 pg/mL), as compared with controls (640±230 pg/mL;p<0.0001), vascular dementia, VAD (1610±840 pg/mL;p<0.05), frontal lobe dementia, FLD (1530±1000 pg/mL;p<0.05), Parkinson disease, PD (720±590 pg/mL;p<0.0001), and patients with major depression (230±130 pg/mL;p<0.0001). Parallel results were obtained for CSF-tau. No less than 35/40 (88%) of AD patients had a CSF-PHFtau value higher than the cutoff level of 1140 pg/mL in controls. The present study demonstrates that elevated tau/PHFtau levels are consistently found in CSF of AD patients. However, a considerable overlap is still present with other forms of dementia, both VAD and FLD. CSF-tau and CSF-PHFtau may therefore be useful as a positive biochemical marker, to discriminate AD from normal aging, PD, and depressive pseudodementia. Further studies are needed to clarify the sensitivity and specificity of these assays, including follow-up studies with neuropathological examinations.     

Neuropsychiatric profiles in dementia

We compared patterns of neuropsychiatric symptoms across 4 dementia types [Alzheimer disease (AD), vascular dementia (VAD), dementia with Lewy bodies (DLB), and Parkinson disease dementia], and 2 mixed groups (AD/VAD and AD/DLB) in sample of 2,963 individuals from the National Alzheimer's Coordinating Center Uniform Data Set between September 2005 and June 2008. We used confirmatory factor analysis to compare neuropsychiatric symptom severity ratings made by collateral sources on the Neuropsychiatric Inventory Questionnaire for people with Clinical Dementia Rating scores of 1 or higher. A 3-factor model of psychiatric symptoms (mood, psychotic, and frontal) was shared across all dementia types. Between-group comparisons revealed unique neuropsychiatric profiles by dementia type. The AD group had moderate levels of mood, psychotic, and frontal symptoms whereas VAD exhibited the highest levels and Parkinson disease dementia had the lowest levels. DLB and the mixed dementias had more complex symptom profiles. Depressed mood was the dominant symptom in people with mild diagnoses. Differing psychiatric symptom profiles provide useful information regarding the noncognitive symptoms of dementia.     

Quantifying mRNA in postmortem human brain: influence of gender, age at death, postmortem interval, brain pH, agonal state and inter-lobe mRNA variance

The quantification of mRNA in postmortem human brain is often made complicated by confounding factors. To assess the importance of potential confounders TaqMan real-time RT-PCR was used to measure seven mRNAs (beta-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cyclophilin, microtubule-associated protein (MAP) 2, neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP), amyloid precursor protein (APP) isoform 770) in cortical samples taken from 90 Alzheimer's disease (AD) and 81 control brains. Demographic data for the brain samples were assessed for interaction between factors and amounts of mRNA. Gender was found to play a role in that females had lower levels of mRNA relative to males; this was consistent in both the AD and control brains. Age at death had inconsistent but significant correlations to amounts of mRNA; male and female controls both had negative correlations, female AD a positive correlation and male AD no correlation. Positive correlations were found between brain pH and amount of mRNA in all genes except glial fibrillary acidic protein (GFAP); correlations were consistent across all groupings of pathology and gender. Mean brain pH was significantly lower in AD (6.4) than in control subjects (6.5, ANOVA, p<0.01), though there was no difference between male and females of either group. No correlation was found between brain pH and age at death. Postmortem interval was correlated with brain pH in Alzheimer's disease brains but not controls. Agonal state was generally a poor predictor of mRNA levels whilst inter-lobe variance of mRNA was found to be non-significant in control brains. Given that gender, age at death and brain pH all have significant effects upon mRNA levels it is recommended that these factors be taken into account when quantifying gene expression in postmortem human brain.     

Insulin-like growth factor-I and its receptor in the frontal cortex, hippocampus, and cerebellum of normal human and alzheimer disease brains

Assimilated evidence indicates that the neurotoxic potential of amyloid beta (Abeta) peptide and an alteration in the level of growth factor(s) may possibly be involved in the loss of neurons observed in the brain of patients suffering from Alzheimer disease (AD), the prevalent cause of dementia in the elderly. In the present study, using receptor binding assays and immunocytochemistry, we evaluated the pharmacological profile of insulin-like growth factor-I (IGF-I) receptors and the distribution of IGF-I immunoreactivity in the frontal cortex, hippocampus, and cerebellum of AD and age-matched control brains. In control brains, [(125)I]IGF-I binding was inhibited more potently by IGF-I than by Des(1-3)IGF-I, IGF-II or insulin. The IC(50) values for IGF-I in the frontal cortex, hippocampus, and cerebellum of the normal brain did not differ significantly from the corresponding regions of the AD brain. Additionally, neither K(D) nor B(max) values were found to differ in the hippocampus of AD brains from the controls. At the regional levels, [(125)I]IGF-I binding sites in the AD brain also remained unaltered compared to the controls. As for the peptide itself, IGF-I immunoreactivity, in normal control brains, was evident primarily in a subpopulation of astrocytes in the frontal cortex and hippocampus, and in certain Purkinje cells of the cerebellum. In AD brains, a subset of Abeta-containing neuritic plaques, apart from astrocytes, exhibit IGF-I immunoreactivity. These results, taken together, suggest a role for IGF-I in compensatory plasticity and/or survival of the susceptible neurons in AD brains.     

Local and systemic GM-CSF increase in Alzheimer's disease and vascular dementia

A growing body of evidence points out the potential role of inflammatory mechanisms in the pathophysiology of brain damage in dementia. The aim of the present study was to investigate patterns of local and systemic cytokine release in patients with Alzheimer's disease (AD) and vascular dementia (VAD). The intrathecal levels of cytokines were related to neuronal damage and cerebral apoptosis. Twenty patients with early AD and 26 patients with VAD were analyzed with respect to cerebrospinal fluid (CSF) and serum levels of pro- and anti-inflammatory cytokines. In addition, CSF levels of Fas/APO-1 and bcl-2, a measure for apoptosis, and Tau protein, a marker for neuronal degradation, were studied. Significantly increased CSF levels of GM-CSF but not of other cytokines were observed in both dementia groups. These patients displayed a significant correlation between the GM-CSF levels and the levels of Fas/APO-1 and Tau protein in CSF. Our study demonstrates an intrathecal production of GM-CSF, a cytokine stimulating microglial cell growth and exerting inflammatogenic properties. It is suggested that GM-CSF once secreted induces programmed cell death in the brain tissue of patients with dementia.     

Fibrous astrocytes in Alzheimer's disease and senile dementia of Alzheimer's type

In four patients with Alzheimer's disease (AD), on patient with senile dementia of Alzheimer's type (SDAT) and five age-matched controls, occipital cortex, frontal cortex, and hippocampus were evaluated for the distribution of fibrous astrocytes (FA), using peroxidase-anti-peroxidase for glial fibrillary acidic protein (GFAP). FA, neuronal cells, neurofibrillary tangles (NFT), and senile plaques (SP) have been quantified in the occipital cortex. In AD and SDAT there was a significant increase in the number of FA in the molecular layer as well as in the other layers of the cortex. No correlation was found between the increase in FA and the number of neurons, NFT or SP.The GFAP positivity was most pronounced around small blood vessels. Electron-microscopic studies of four cortical biopsies of AD revealed dense perivascular gliosis in 48.8% of the capillaries examined as opposed to 17.8% of capillaries in three controls without dementia. The significance of increased perivascular gliosis in AD and SDAT is unknown. It may be related to a defect in the blood-brain barrier.     

High-affinity choline uptake carrier in Alzheimer''s disease: implications for the cholinergic hypothesis of dementia

We examined the density and the state of affinity of [3H]hemicholinium-3 ([3H]HC-3) binding sites, a marker of the presynaptic high-affinity choline uptake (HACU) carrier, in 4 representative regions of 13 postmortem Alzheimer's disease (AD) brains, as well as in 12 matched control brains. Significant reductions in the densities of [3H]HC-3 binding sites were found both in frontal cortex (-44.7%) and hippocampus (-36.5%) of AD brains in comparison to controls. On the other hand the densities of [3H]HC-3 binding sites in AD brains in caudate-putamen and cerebellar cortex showed no significant differences when compared to controls. No significant change in the state of affinity of these sites could be observed in the saturation assays carried out in hippocampus and frontal cortex. Our findings concur with the reported data by using other presynaptic cholinergic markers in AD and confirm that some degree of cholinergic degeneration, highly specific for the basal forebrain neurons, occurs in AD. However, these results, obtained in a group of AD brains belonging to severely demented patients, do not show a dramatic loss of the HACU in many AD brains. Although this fact could be due to the existence of a compensatory mechanism, our results probably suggest that dementia in AD cannot be explained only by the loss of neocortical cholinergic presynaptic terminals arising from the basal forebrain and also may clarify as to why the acetylcholine precursors or the muscarinic agonists are not effective in AD dementia.     

NADPH-diaphorase-containing neurons in cortex, subcortical white matter and neostriatum are selectively spared in Alzheimer's disease

To investigate the involvement of NADPH-diaphorase (NADPH-d)-containing neurons in Alzheimer's disease (AD), NADPH-d enzyme histochemistry in vibratome sections was applied to the superior frontal and superior temporal cortex and the neostriatum in 5 AD and 6 aged control brains. Overall there was a neuronal loss and atrophy in the cortex of AD. Despite slight morphological neuronal changes in the cortex of AD, we found no significant difference in the number of NADPH-d-positive neurons in both cortex and neostriatum between control and AD cases. These results provide further evidence for a selective preservation of NADPH-d neurons in AD. In order to check whether nNOS-immunoreactive neurons are identical to NADPH-d-positive neurons in the human brain, we examined the frontal and temporal cortex and neostriatum of normal human brains in serial cryostat sections. We found that nNOS-containing neurons paralleled NADPH-d-positive neurons in these brain regions. Copyrightz1999S.KargerAG,Basel     

Depletion of cholinergic neurons in the nucleus of the medial septum and the vertical limb of the diagonal band in dementia with Lewy bodies

The cholinergic basal forebrain is divided into four subregions (Ch1–4), and cholinergic neuronal loss in the nucleus basalis of Meynert (Ch4) has been correlated with cognitive impairments in both Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB). However, the Ch1–2 regions, which provide the major cholinergic innervation to the hippocampus, have not been investigated in DLB. The purpose of this study was to reveal the cholinergic neuronal changes in the medial septum (Ch1) and the nucleus of the vertical limb of the diagonal band (Ch2) of DLB brains. Using choline acetyltransferase (ChAT) immunohistochemistry, we showed that the number of ChAT-immunoreactive neurons in DLB brains was significantly lower than the numbers in AD and non-demented (control) brains. No significant difference in the number of ChAT-immunoreactive neurons was found between the AD and control brains. Moreover, the size of the ChAT-immunoreactive neurons was significantly smaller in the AD and DLB brains than in the control brains. These results show that cholinergic neurons of the Ch1-2 regions are more severely affected in DLB than in AD. Our DLB cases did not fulfill the neuropathologic criteria for definite AD. Furthermore, some Lewy bodies were observed in the Ch1-2 regions. Thus, cholinergic neuronal loss in the Ch1-2 regions might be specific to the pathology of DLB. Taking the distribution of cholinergic fibers in the hippocampus into consideration, this study suggests a possibility that hippocampal cholinergic projection is involved in Lewy-related neurites in the CA2–3 regions, the origin of which remains unclear.     

The possible role of capillary cerebral amyloid angiopathy in Alzheimer lesion development: a regional comparison

Recent studies have observed β-amyloid-positive capillaries in lesion-prone regions of Alzheimer’s disease (AD) brains. It is possible that there is a pathogenic link between neurofibrillary tangles (NFTs) and/or senile plaques (SPs) and altered capillary structure/function. In this study, we examined and compared brain tissue from a frequently observed NFT abundant area, the superior temporal cortex (ST), and a comparatively much NFT sparser area, the calcarine cortex (COC), in ten AD and ten normal adult control brain samples. We recorded the densities of NFTs, and β-amyloid_8–17,40,42 peptide forms in SPs, capillaries and large vessels [cerebral amyloid angiopathy (CAA)] in these areas. Our results demonstrated that there was a significant difference between the means of NFT and SP β_8–17,40 lesions when comparing the ST and COC cortical regions in both AD and control brains. In AD brains, we observed a positive correlation between NFTs and SPs in both regions, and between NFTs and β-amyloid-positive capillaries and CAA vessels, particularly in the calcarine cortex. In addition, significant correlations were observed between some SP β-amyloid peptide forms and CAA β₄₂, in particular, in both regions. These new observations support the view that there are regional (focal) differences in the presence of each AD lesion, and that there may be a pathogenic relationship between the development of AD lesions and β-amyloid-positive vessels. The data are also consistent with the concept that a focally dysfunctional blood–brain barrier (BBB) that is unable to regulate the influx/efflux of neurotoxic amyloid peptides may participate in the pathogenesis of AD lesions.     

Beta-secretase protein and activity are increased in the neocortex in Alzheimer disease

CONTEXT: Amyloid plaques, a major pathological feature of Alzheimer disease (AD), are composed of an internal fragment of amyloid precursor protein (APP): the 4-kd amyloid-beta protein (Abeta). The metabolic processing of APP that results in Abeta formation requires 2 enzymatic cleavage events, a gamma-secretase cleavage dependent on presenilin, and a beta-secretase cleavage by the aspartyl protease beta-site APP-cleaving enzyme (BACE). OBJECTIVE: To test the hypothesis that BACE protein and activity are increased in regions of the brain that develop amyloid plaques in AD. METHODS: We developed an antibody capture system to measure BACE protein level and BACE-specific beta-secretase activity in frontal, temporal, and cerebellar brain homogenates from 61 brains with AD and 33 control brains. RESULTS: In the brains with AD, BACE activity and protein were significantly increased (P<.001). Enzymatic activity increased by 63% in the temporal neocortex (P =.007) and 13% in the frontal neocortex (P =.003) in brains with AD, but not in the cerebellar cortex. Activity in the temporal neocortex increased with the duration of AD (P =.008) but did not correlate with enzyme-linked immunosorbent assay measures of insoluble Abeta in brains with AD. Protein level was increased by 14% in the frontal cortex of brains with AD (P =.004), with a trend toward a 15% increase in BACE protein in the temporal cortex (P =.07) and no difference in the cerebellar cortex. Immunohistochemical analysis demonstrated that BACE immunoreactivity in the brain was predominantly neuronal and was found in tangle-bearing neurons in AD. CONCLUSIONS: The BACE protein and activity levels are increased in brain regions affected by amyloid deposition and remain increased despite significant neuronal and synaptic loss in AD.     

Evidence for association of anaemia with vascular dementia.

The present investigation aimed to examine associations of anaemia with dementia. Analysis of community-dwelling, elderly subjects characterized for different dementias failed to confirm a previously reported association of anaemia with Alzheimer's disease (AD) but revealed instead a significant association with vascular dementia (VAD). Nearly 45% of VAD subjects were anaemic, compared with 17% of controls. Close to one-third of all subjects with haemoglobin levels > 0.5 g/dl below reference anaemia levels had VAD. Co-existing VAD may explain previous links between AD and anaemia. The association was independent of age, dementia severity and a range of other factors including vitamin B 12 and folate levels. Anaemia can exacerbate focal cerebral ischaemia and could precipitate or amplify VAD symptoms in elderly subjects with vasculopathy.     

Neuropeptides in Alzheimer type dementia

Five neuropeptides (cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP), somatostatin (SRIF), neurotensin (NT) and substance P (SP)) were measured in 14 brain areas (4 cortical areas, hippocampus, amygdala, 3 striatal areas, 2 thalamic areas and 3 subcortical areas-- septum, substantia innominata and hypothalamus) in 12 brains with neuropathologically confirmed Alzheimer type change and in 13 control brains. Choline acetyltransferase (CAT) activity was assessed in 6 of these areas. Levels of SRIF, but not those of the other peptides, were reduced in several cortical areas in Alzheimer-type dementia (ATD). The distribution and magnitude of the reduction in SRIF were less than that of CAT activity and the temporal cortex was the only region in which there was a significant relationship between CAT and SRIF deficits. Peptide levels were unchanged in hippocampus, amygdala, thalamus, hypothalamus and striatum (except for an increase in SP in the putamen). SRIF levels were increased in substantia innominata in ATD. NT and SRIF were significantly, and VIP and SP non-significantly, reduced in the septum in ATD. Thus, apart from these alterations in the septum, SRIF was the only neuropeptide for which major changes were identified and these did not follow either the pattern of neuropathological change (e.g. in amygdala and hippocampus) or of CAT deficits (e.g. in substantia innominata).     

高同型半胱氨酸血症与Alzheimer病的关系

目的 探讨高同型半胱氨酸血症与Alzheimer病(AD)的关系。方法 对38例AD患者及30例对照组老年人进行血浆同型半胱氨酸(Hcy)测定，并分析Hcy与认知功能障碍、痴呆严重程度、痴呆病程及精神症状的关系。结果 AD组血浆Hcy显著高于对照组IHcy水平与认知功能障碍、痴呆严重度密切相关，与痴呆病程和精神症状无关。结论 高同型半胱氨酸血症可能参与AD发病机制。     

Decreased release of the angiogenic peptide vascular endothelial growth factor in Alzheimer's disease: recovering effect with insulin and DHEA sulfate

Changes of vascular endothelial growth factor (VEGF) secretion have recently been demonstrated in patients with Alzheimer's disease (AD). Since VEGF has been involved in brain angiogenesis, neuroprotection and cerebromicrovascular exchange of substrates and nutrients, the study of VEGF could have important relapses into the pathogenesis and treatment of AD. Within this context, 35 healthy subjects (16 of young and 19 of old age), 18 patients with dementia of the vascular type (VAD) and 22 with dementia of the Alzheimer's type (AD) were included in the study. VEGF levels were determined in the supernates of circulating natural killer (NK) immune cells isolated by immunomagnetic separation (pure CD16 + CD56 + NK cells at a final density of 7.75 x 10(6) cells/ml). VEGF was measured in spontaneous conditions (without modulation) and after exposure of NK cells with IL-2, lipopolysaccharide (LPS), dehydroepiandrosterone sulfate (DHEAS), LPS + insulin, amyloid-beta (Abeta) fragment 1-42, the inactive sequence Abeta(40-1) and Abeta(1-42) + insulin. A significant decrease in VEGF released by NK cells was demonstrated in AD subjects compared to the other groups. No differences of VEGF levels were found between healthy subjects of old age and the VAD group. The incubation with LPS and DHEAS significantly increased, in a dose-dependent manner, VEGF levels in AD as well as in healthy subjects of young and old age and in VAD patients. The incubation of NK cells with Abeta(1-42) completely suppressed VEGF generation in AD subjects, also reducing VEGF release in the other groups. The co-incubation of NK with LPS + insulin, at different molar concentrations, significantly restored (4- and 6-fold increase from LPS alone) VEGF in AD, also enhancing VEGF secretion in healthy subjects and the VAD group, while the co-incubation of NK with Abeta(1-42) + insulin promptly abolished the negative effects of Abeta(1-42) on VEGF release. These data might suggest that the decreased VEGF secretion by peripheral immune cells of AD subjects could have a negative role for brain angiogenesis, neuroprotection and for brain microvascular permeability to nutrients, increasing brain frailty towards hypoxic injuries. On the contrary, insulin and DHEAS could have beneficial effects in AD, as well as in VAD and in physiological aging, by increasing, in a dose-dependent fashion, VEGF availability by peripheral and resident immune and endothelial cells, so contributing to increase its circulating pool.     

Growth-associated protein GAP-43 in the frontal cortex and in the hippocampus in Alzheimer's disease: an immunohistochemical and quantitative study

Summary. We studied the growth-associated protein, GAP-43 (also called neuromodulin and B-50) in post-mortem brain tissue using immunohistochemistry and quantitative Western blotting, from patients with Alzheimer's disease (AD) and age-matched control subjects. By immunohistochemistry, we found a clear reduction of GAP-43 in the frontal cortex, while in the hippocampus, there was a marked reduction in some areas (dentate molecular layer, stratum moleculare and radiale of CA1 and CA4), while not in other areas (stratum lacunosum, pyramidale and oriens of CA1). Moreover, in the hippocampus, neuritic staining was prominent, and was often associated with senile plaques. Quantitative analysis showed that GAP-43 was significantly reduced in AD, both in the frontal cortex (70% of the control value, p < 0.01) and in the hippocampus (81% of the control value, p < 0.05). In the frontal cortex, there was a significant negative correlation between GAP-43 and duration of dementia (r = −0.58; p < 0.02) and a positive correlation between GAP-43 and the synaptic vesicle-specific protein rab3a (r = 0.62; p < 0.05), while no such correlation were found in the hippocampus. In contrast, a significant positive correlation was found between GAP-43 and the number of senile plaques in the hippocampus (r = 0.64; p < 0.05), but not in the frontal cortex. GAP-43 is known to be involved in maintenance of synapses and in neuritic regeneration. Our findings may suggest that in the frontal cortex, GAP-43 levels decline as a consequence of the synaptic degeneration, while in the hippocampus, sprouting processes, involving GAP-43, are active. Received March 29, 1999; accepted September 2, 1999