Restoration of Norepinephrine-Modulated Contextual Memory in a Mouse Model of Down Syndrome
by Ahmad Salehi, Mehrdad Faizi, Damien Colas, Janice S. Valletta, Jessania Laguna, Ryoko Takimoto-Kimura, Alexander Kleschevnikov, Steve L. Wagner, Paul Aisen, Mehrdad Shamloo, and William C. Mobley
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Neuroprotection of Host Cells by Human Central Nervous System Stem Cells in a Mouse Model of Infantile Neuronal Ceroid Lipofuscinosis
by Stanley J. Tamaki, Yakop Jacobs, Monika Dohse, Alexandra Capela, Jonathan D. Cooper, Michael Reitsma, Dongping He, Robert Tushinski, Pavel V. Belichenko, Ahmad Salehi, William Mobley, Fred H. Gage, Stephen Huhn, Ann S. Tsukamoto, Irving L. Weissman, and Nobuko Uchida
On the cover Neurodegeneration of purkinje cells. In a mouse model of neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disorder, accumulation of lipofuscin granules is followed by progressive neuronal cell death. Purkinje neurons in the cerebellum are severely affected as illustrated by loss of cell bodies and dendritic arbors. Massive lipofuscin deposits remain in the purkinje cell layer in the degenerating brain. The work by Tamaki et al. (pages 310 – 319) demonstrates that transplantation of human neural stem cells leads to neuroprotection of host cells in the NCL mouse brain. The cover image shows a section of cerebellum from a mouse with disease symptoms. Cover design by Monika Dohse.
The "Down syndrome critical region" is sufficient in the mouse model to confer behavioral, neurophysiological, and synaptic phenotypes characteristic of Down syndrome
by Nadia P. Belichenko, Pavel V. Belichenko, Alexander M. Kleschevnikov, Ahmad Salehi, Roger H. Reeves, and William C. Mobley
Abstract Down syndrome (DS) can be modeled in mice segmentally trisomic for mouse chromosome 16. Ts65Dn and Ts1Cje mouse models have been used to study DS neurobiological phenotypes including changes in cognitive ability, induction of long-term potentiation (LTP) in the fascia dentata (FD), the density and size of dendritic spines, and the structure of synapses. To explore the genetic basis for these phenotypes, we examined Ts1Rhr mice that are trisomic for a small subset of the genes triplicated in Ts65Dn and Ts1Cje mice. The 33 trisomic genes in Ts1Rhr represent a "DS critical region" that was once predicted to be sufficient to produce most DS phenotypes. We discovered significant alterations in an open field test, a novel object recognition test and in a T-maze task. As in Ts65Dn and Ts1Cje mice, LTP in FD of Ts1Rhr could be induced only after blocking GABA(A)-dependent inhibitory neurotransmission. In addition, widespread enlargement of dendritic spines and decreased density of spines in FD were preserved in Ts1Rhr. Twenty of 48 phenotypes showed significant differences between Ts1Rhr and 2N controls. We conclude that important neurobiological phenotypes characteristic of DS are conserved in Ts1Rhr mice. The data support the view that biologically significant trisomic phenotypes occur because of dosage effects of genes in the Ts1Rhr trisomic segment and that increased dosage is sufficient to produce these changes. The stage is now set for studies to decipher the gene(s) that play a conspicuous role in creating these phenotypes.
Excitatory-inhibitory relationship in the fascia dentata in the Ts65Dn mouse model of Down syndrome
by Pavel V. Belichenko, Alexander M. Kleschevnikov, E. Masliah, Chengbioa Wu, Ryoko Takimoto-Kimura, Ahmad Salehi, and Willam C. Mobley
Abstract Down syndrome (DS) is a neurological disorder causing impaired learning and memory. Partial trisomy 16 mice (Ts65Dn) are a genetic model for DS. Previously, we demonstrated widespread alterations of pre- and postsynaptic elements and physiological abnormalities in Ts65Dn mice. The average diameter of presynaptic boutons and spines in the neocortex and hippocampus was enlarged. Failed induction of long-term potentiation (LTP) due to excessive inhibition was observed. In this paper we investigate the morphological substrate for excessive inhibition in Ts65Dn. We used electron microscopy (EM) to characterize synapses, confocal microscopy to analyze colocalization of the general marker for synaptic vesicle protein with specific protein markers for inhibitory and excitatory synapses, and densitometry to characterize the distribution of the receptor and several proteins essential for synaptic clustering of neurotransmitter receptors. EM analysis of synapses in the Ts65Dn vs. 2N showed that synaptic opposition lengths were significantly greater for symmetric synapses (approximately 18%), but not for asymmetric ones. Overall, a significant increase in colocalization coefficients of glutamic acid decarboxylase (GAD)65/p38 immunoreactivity (IR) (approximately 27%) and vesicular GABA transporter (VGAT)/p38 IR (approximately 41%) was found, but not in vesicular glutamate transporter 1 (VGLUT1)/p38 IR. A significant overall decrease of IR in the hippocampus of Ts65Dn mice compared with 2N mice for glutamate receptor 2 (GluR2; approximately 13%) and anti-gamma-aminobutyric acid (GABA)(A) receptor beta2/3 subunit (approximately 20%) was also found. The study of proteins essential for synaptic clustering of receptors revealed a significant increase in puncta size for neuroligin 2 (approximately 13%) and GABA(A) receptor-associated protein (GABARAP; approximately 13%), but not for neuroligin 1 and gephyrin. The results demonstrate a significant alteration of inhibitory synapses in the fascia dentata of Ts65Dn mice. 2008 Wiley-Liss, Inc.
Mental Retardation and Developmental Disabilities Research Reviews
Using mouse models to explore genotype-phenotype relationship in Down syndrome
by Ahmad Salehi, Mehrdad Faizi, Pavel V. Belichenko, and William C. Mobley
Abstract Down Syndrome (DS) caused by trisomy 21 is characterized by a variety of phenotypes and involves multiple organs. Sequencing of human chromosome 21 (HSA21) and subsequently of its orthologues on mouse chromosome 16 have created an unprecedented opportunity to explore the complex relationship between various DS phenotypes and the extra copy of approximately 300 genes on HSA21. Advances in genetics together with the ability to generate genetically well-defined mouse models have been instrumental in understanding the relationships between genotype and phenotype in DS. Indeed, elucidation of these relationships will play an important role in understanding the pathophysiological basis of this disorder and helping to develop therapeutic interventions. A successful example of using such a strategy is our recent studies exploring the relationship between failed nerve growth factor (NGF) transport and amyloid precursor protein (App) overexpression. We found that increased dosage of the gene for App is linked to failed NGF signaling and cholinergic neurodegeneration in a mouse model of DS. Herein, we discuss several mouse models of DS and explore the emergence of exciting new insights into genotype-phenotype relationships, particularly those related to nervous system abnormalities. An important conclusion is that uncovering these relationships is enhanced by working from carefully defined phenotypes to the genes responsible. 2007 Wiley-Liss, Inc.
Increased App expression in a mouse model of Down's syndrome disrupts NGF transport and causes cholinergic neuron degeneration
by Ahmad Salehi, Jean-Dominique Delcroix, Pavel V. Belichenko, Ke Zhan, Chengbioa Wu, Janice S. Valletta, Ryoko Takimoto-Kimura, Alexander M. Kleschevnikov, Kumar Sambamurti, Peter P. Chung, Weiming Xia, Angela Villar, William A. Campbell, Laura S. Kulnane, Randy A. Nixon, Bruce T. Lamb, Charles J. Epstein, Gorazd B. Stokin, Larry S. Goldstein, and William C. Mobley
by Ahmad Salehi, Jean-Dominique Delcroix, and Dick F. Swaab
Abstract Age-related degeneration of basal forebrain cholinergic neurons (BFCNs) occurs early and contributes significantly to cognitive decline in Alzheimer's disease (AD). Proper function and morphology of BFCNs depends on the supply of nerve growth factor (NGF) from the cortex and the hippocampus. A large number of experiments have shown that decreased supply of NGF at the level of BFCN cell bodies leads to loss of neuronal markers and shrinkage, mimicking what is observed in AD. The delivery of sufficient amounts of NGF signal to BFCN cell bodies depends on the effective participation of several factors including sufficient synthesis and release of NGF, adequate synthesis and expression of NGF receptors by BFCNs, normal signaling and retrograde transport of NGF-receptor complex, and finally effective induction of gene expression by NGF. In the past few years it has become clear that decreased amounts of NGF at the level of BFCN cell bodies is largely due to failed retrograde transport rather than decreased synthesis, binding or expression of NGF receptors in the BFCN terminals. We will discuss in vivo evidence supporting decreased retrograde transport of NGF in a mouse model with BFCN degeneration, and will attempt to match these findings with our studies in postmortem human AD brain. We will speculate about the possible mechanisms of failed NGF retrograde transport and its relationship to AD pathology.
NGF and Related Molecules in Health and Disease, Progress in Brain Research
Volume 146 [Book]
Trafficking the NGF signal: implications for normal and degenerating neurons
by Jean-Dominique Delcroix, Janice S. Valletta, Chengbioa Wu, Charles L. Howe, Chun-Fai Lai, John D. Cooper, Pavel V. Velichenko, Ahmad Salehi, and William C. Mobley
Traffic at the intersection of neurotrophic factor signaling and neurodegeneration
by Ahmad Salehi , Jean-Dominique Delcroix, and William C. Mobley
Abstract Advances in understanding the biology of neurotrophic factors and their signaling pathways have provided important insights into the normal growth, differentiation and maintenance of neurons. Stimulated by neuropathological observations and genetic discoveries, studies in cell and animal models of neurodegenerative disorders have begun to clarify pathogenetic mechanisms. We examine the intersection of these research themes and identify several potential mechanisms for linking failed neurotrophic factor signaling to neurodegeneration. Studies of nerve growth factor signaling in a mouse model of Down syndrome encourage the views that neuronal dysfunction and atrophy might be linked to failed neurotrophic support and that additional studies focused on this possibility would enhance our understanding of the mechanisms of neurodegenerative disorders and their treatment.
The Proceedings of the National Academy of Sciences (U.S.A.)
Failed retrograde transport of NGF in a mouse model of Down's syndrome: reversal of cholinergic neurodegenerative phenotypes following NGF infusion
by John D. Cooper, Ahmad Salehi, Jean-Dominique Delcroix, Charles L. Howe, Pavel V. Belichenko, Jane Chua-Couzens, Joshua F. Kilbridge, Elaine J. Carlson, Charles J. Epstein, and William C. Mobley
Abstract Age-related degeneration of basal forebrain cholinergic neurons (BFCNs) contributes to cognitive decline in Alzheimer's disease and Down's syndrome. With aging, the partial trisomy 16 (Ts65Dn) mouse model of Down's syndrome exhibited reductions in BFCN size and number and regressive changes in the hippocampal terminal fields of these neurons with respect to diploid controls. The changes were associated with significantly impaired retrograde transport of nerve growth factor (NGF) from the hippocampus to the basal forebrain. Intracerebroventricular NGF infusion reversed well established abnormalities in BFCN size and number and restored the deficit in cholinergic innervation. The findings are evidence that even BFCNs chronically deprived of endogenous NGF respond to an intervention that compensates for defective retrograde transport. We suggest that age-related cholinergic neurodegeneration may be a treatable disorder of failed retrograde NGF signaling.
Molecular misreading: a new type of transcript mutation expressed during aging
by Fred W. van Leeuwen, David F. Fischer, Darlene Kamel, Jacqueline A. Sluijs, Marc A. Sonnemans, Rob Benne, Dick F. Swaab, Ahmad Salehi, and Elly M. Hol
Abstract Dinucleotide deletions (e.g. DeltaGA, DeltaGU) are created by molecular misreading in or adjacent to GAGAG motifs of neuronal mRNAs. As a result, the reading frame shifts to the +1 frame, and so-called "+1 proteins" are subsequently synthesized. +1 Proteins have a wild-type N-terminus, but an aberrant C-terminus downstream from the site of the dinucleotide deletion. Molecular misreading was discovered in the rat vasopressin gene associated with diabetes insipidus and subsequently in human genes linked to Alzheimer's disease (AD), e.g. beta amyloid precursor protein (betaAPP) and ubiquitin-B (UBB). Furthermore, betaAPP(+1) and UBB(+1) proteins accumulate in the neuropathological hallmarks (i.e. in the tangles, neuritic plaques, and neuropil threads) of AD. As these +1 proteins were also found in elderly nondemented controls, but not in younger ones (<51 years), molecular misreading in nondividing cells might act as a factor that only becomes manifest at an advanced age. Frameshift mutations (UBB(+1)) and pretangle staining (Alz-50 and MC1) seem to occur independently of each other during early stages of AD. We recently detected +1 proteins, not only in proliferating cells present in non-neuronal tissues such as the liver and epididymis, but also in neuroblastoma cell lines. These observations suggest that molecular misreading is a general source of transcript errors that are involved in cellular derangements in various age-related pathologies.
Activity of vasopressinergic neurons of the human supraoptic nucleus is age- and sex-dependent
by Tatjana A. Ishunina, Ahmad Salehi, Michel A. Hofman, and Dick F. Swaab
Abstract In the human hypothalamus, arginine-vasopressin (AVP) is produced for a major part by the neurones of the supraoptic nucleus (SON). Since plasma AVP levels in men were reported to be higher than those of women and we did not find a sex difference in the neurone number, a higher vasopressinergic neurone activity was supposed to be present in the SON of men. Therefore we studied the size of the Golgi-apparatus (GA), which has been demonstrated previously to be a sensitive parameter for protein synthetic ability of neurones, in 15 men and 17 women ranging in age from 29 to 94 years. A polyclonal antibody against immunoaffinity purified MG-160, a sialoglycoprotein of the medial cisternae of the GA was applied on paraffin-embedded sections containing the dorsolateral SON (dl-SON) from which 90-95% of neurones are vasopressinergic. SON areas that contain oxytocin (OT) cells were excluded on the basis of adjacent sections stained with a monoclonal antibody against OT. By means of an image analysis system the size of the GA and the cellular profile area were determined in dl-SON neurones with a nucleolus. Our results showed indeed an age-dependent sex difference in the size of the GA that appeared to be twice as large in young men (< or = 50 years old) than in young women of the same age. The size of the GA increased with age in women but not in men. In addition, the mean cell profile area, another measure for neuronal activity, was significantly larger in young men than in young women and was in old women larger than in young women. In conclusion, these data show the presence of a sex-dependent age-difference in the activity of vasopressinergic neurones in dl-SON which may relate to differences in AVP and sex hormone levels and kidney AVP receptors.
Diminished neuronal metabolic activity in Alzheimer's disease
by Ahmad Salehi and Dick F. Swaab
Abstract An increasing number of studies have appeared in the literature suggesting that Alzheimer's disease (AD) is a hypometabolic brain disorder. Decreased metabolism in AD has been revealed by a variety of in vivo and postmortem methods and techniques including positron emission tomography and glucose metabolism. We used the size of the Golgi apparatus (GA) and cell profile area as indicators of neuronal activity in postmortem material. Using an antibody against MG-160, a sialoglycoprotein of the medial cisternae of the GA, we were able to visualize and quantify the GA area. In a series of experiments, we tried to relate neuronal metabolism to different hallmarks of AD, i.e. plaques and tangles, and also to genetic risk factors for AD like age and (apolipoprotein E) ApoE polymorphism. Our results showed that in AD there is indeed a clear reduction in brain metabolism in several severely affected brain regions including the nucleus basalis of Meynert (NBM), the CA1 area of the hippocampus and the hypothalamic tuberomamillary nucleus. However, the reduction in neuronal activity did not seem to be caused by the presence of neuropathological hallmarks of AD, i.e. plaques and tangles. There was, however, a clear relationship between the presence of ApoE epsilon4 alleles and a decrease in GA size. Our data suggest that decreased neuronal activity and neuropathological hallmarks of AD, such as plaques and tangles, are basically independent phenomena. Moreover, ApoE epsilon4 may participate in the pathogenesis of AD by decreasing neuronal metabolism. The main implication of these findings is that therapeutic strategies in AD should be focussed on reactivation of neuronal metabolism.
Activity of Hippocampal CA1 Neurons in Alzheimer's Disease is not Affected by the Presence of Adjacent Neuritic Plaques in Alzheimer's disease
by Ahmad Salehi, Chris W. Pool, Monique Mulder, Rifka Ravid, Nikolas K. Gonatas, and Dick F. Swaab
Abstract Alzheimer's disease (AD) is neuropathologically characterized by neuritic plaques (NPs) and neurofibrillary tangles and functionally by a decreased metabolic rate of neurons. Our previous studies showed that in brain areas which are extensively affected by plaques and tangles, i.e. the CA1 area of the hippocampus and the hypothalamic tuberomamillary nucleus, neuronal protein synthetic ability is significantly lower in AD patients than in controls. However, the presence of tangles as shown by Bodian staining appeared not to be directly related to decreased protein synthetic ability of neurons. In order to study to what extent the metabolic function of neurons might be affected by the other neuropathological hallmark of AD, i.e. NPs, which are presumed to contain neurotoxic compounds, we studied eight severely demented AD patients matched for the ApoE genotype (ApoE 3/3). Using an image analysis system, the size of the neuronal Golgi apparatus (GA) and of the cell profile area was measured as a parameter for protein synthetic activity in the CA1 area of these patients. NPs were stained by Bodian, and subsequently the distance of each neuron with an immunostained GA to the nearest NP was measured. Our results showed that neither NP density nor the distance between NPs and neurons correlated with the protein synthetic ability of neurons as judged by the size of the GA. Based on these results we suggest that in AD the presence of NPs and decreased neuronal protein synthetic ability are basically two independent phenomena.
A sex difference and no effect of ApoE type on the amount of cytoskeletal alterations in the nucleus basalis of Meynert in Alzheimer's disease age- and sex-dependent
by Ahmad Salehi, Victoria Gonzalez Martinez, and Dick F. Swaab
Abstract n the nucleus basalis of Meynert (NBM) we studied the presence of early cytoskeletal alterations as shown by the antibody Alz-50 in ApoE-typed patients. Using an image analysis system, the area covered by Alz-50 staining and the percentage of neurons stained by Alz-50 were determined. There were no significant differences in the area covered by Alz-50 or in the proportion of Alz-50-stained neurons in the nucleus basalis of Meynert of Alzheimer's disease (AD) patients with one or two ApoE epsilon4 alleles as compared with those without any ApoE e4 allele. However, there was a significant sex difference in Alz-50 staining: female Alzheimer's disease patients showed more severe early cytoskeletal alterations than males. We also found a significant relationship between the number of Alz-50-stained neurons and the severity of dementia.
The Proceedings of the National Academy of Sciences (U.S.A.)
Aggravated decrease in the activity of nucleus basalis neurons in Alzheimer's disease is apolipoprotein E-type dependent
by Ahmad Salehi, Elisabeth J. Dubelaar, Monique Mulder, and Dick F. Swaab
Abstract As reported before, the metabolic activity of nucleus basalis neurons is reduced significantly in Alzheimer patients. Because the apolipoprotein E (ApoE) epsilon4 genotype is a major risk factor for Alzheimer's disease (AD), we determined whether the decrease in metabolic activity in nucleus basalis neurons in AD is ApoE-type dependent. The size of the Golgi apparatus (GA) was determined as a measure of neuronal metabolic activity in 30 controls and 41 AD patients with a known ApoE genotype by using an image analysis system in the nucleus basalis of Meynert. A polyclonal antibody directed against MG-160, a sialoglycoprotein of the GA, was used to visualize this organelle. There was a very strong reduction in the size of the GA in the nucleus basalis of AD patients. Furthermore, a strong and significant extra reduction in the size of the GA was found in the nucleus basalis neurons of AD patients with either one or two ApoE epsilon4 alleles compared with Alzheimer patients without ApoE epsilon4 alleles. Our data show that the decreased activity of nucleus basalis neurons in AD is ApoE epsilon4 dependent and suggest that ApoE epsilon4 participates in the pathogenesis of AD by decreasing neuronal metabolism.
Limited effect of neuritic plaques on neuronal density in the hippocampal CA1 area of Alzheimer patients
by Ahmad Salehi, Jan M. Bakker, Monique Mulder, and Dick F. Swaab
Abstract Neurofibrillary tangles (NFTs) and neuritic plaques (NPs) are the classic neuropathological hallmarks of Alzheimer disease (AD). It is generally assumed that the pathogenic process of AD could start by local neurotoxicity induced by the beta-amyloid core of plaques, followed by the appearance of NFTs and eventually cell death. To determine whether or not local neurotoxicity around NPs is indeed a major pathogenetic mechanism, we used an image analysis system to measure the neuronal density around Bodian-stained NPs in the hippocampal CA1 area of eight AD patients. Neuronal density, as measured within two arbitrary concentric circles around NPs with a radius of 74 and 123.5 microm, respectively, was on average 19% and 16% lower than the density in similar control circles without NPs in the same section. Furthermore, neuronal density around NPs was inversely related to their size. To investigate the impact of such a local reduction in cell density around NPs on the entire CA1 area, we also determined the proportion of the CA1 covered by the NPs and the arbitrary concentric circles around them. This appeared to be 16.3% of the total CA1 area, which means that the negative effect of NPs on the cell density can only explain 2.6% of cell death in the entire CA area. In conclusion, this study suggests that although NPs have a local negative effect on neighboring neurons, their contribution to the strong decrease in CA1 cell numbers is limited.
Frameshift Mutants of ß Amyloid Precursor Protein and Ubiquitin-B in Alzheimer's and Down Patients
by Fred W. van Leeuwen, Dominique P. V. de Kleijn, Helma H. van den Hurk, Andrea Neubauer, Marc A. F. Sonnemans, Jacqueline A. Sluijs, Soner Köycü, Ravindra D. J. Ramdjielal, Ahmad Salehi, Gerard J. M. Martens, Frank G. Grosveld, John P. H. Burbach, and Elly M. Hol
On the cover Alzheimer's is characterized by short-term memory loss and plaques and tangles in the cerebral cortex. Aberrant ubiquitin protein, likely resulting from an RNA mutation, is detectable in plaques (vague spots) and tangles (flame shapes, ~40 µm long) in the hippocampus (a region involved in short-term memory) from an Alzheimer's patient. This mutation mechanism is likely a factor in nonfamilial Alzheimer's and other neurodegenerative pathologies.
Abstract The cerebral cortex of Alzheimer's and Down syndrome patients is characterized by the presence of protein deposits in neurofibrillary tangles, neuritic plaques, and neuropil threads. These structures were shown to contain forms of beta amyloid precursor protein and ubiquitin-B that are aberrant (+1 proteins) in the carboxyl terminus. The +1 proteins were not found in young control patients, whereas the presence of ubiquitin-B+1 in elderly control patients may indicate early stages of neurodegeneration. The two species of +1 proteins displayed cellular colocalization, suggesting a common origin, operating at the transcriptional level or by posttranscriptional editing of RNA. This type of transcript mutation is likely an important factor in the widely occurring nonfamilial early- and late-onset forms of Alzheimer's disease.
Neuropeptides vasopressin (AVP), oxytocin (OXT) and corticotropin-releasing hormone (CRH) in the human hypothalamus: activity changes in aging, Alzheimer's disease and depression
by Paul J. Lucassen, F. J. Tilders, Ahmad Salehi, and Dick F. Swaab
Co-localization of high-affinity neurotrophin receptors in nucleus basalis of Meynert neurons and their differential reduction in Alzheimer's disease
by Ahmad Salehi, Joost Verhaagen, Paul A. Dijkhuizen, and Dick F. Swaab
Abstract It has been suggested that degeneration of neurons in Alzheimer's disease is the result of diminished trophic support. However, so far no evidence has been forwarded that neuronal degeneration in Alzheimer's disease is causally related to insufficient production of neurotrophins. The present study deals with (i) the expression and co-localization of tyrosine kinase receptors (trks) in the human nucleus basalis of Meynert and (ii) alterations of these receptors in Alzheimer's disease in the nucleus basalis of Meynert, an area severely affected in Alzheimer's disease. The expression of trkA, trkB and trkC in the nucleus basalis of Meynert of control and Alzheimer's disease brains was studied using three polyclonal antibodies specifically recognizing the extracellular domain of trkA, trkB and trkC. Brain material of eight controls and seven Alzheimer's disease patients was obtained at autopsy, embedded in paraffin and stained immunocytochemically. Using an image analysis system, we determined the proportion of trk neurons expressing the different trk receptors in controls and Alzheimer's disease patients. In control brains, trkA, trkB and trkC were differentially expressed in numerous nucleus basalis of Meynert neurons. The highest proportion of neurons was found to express trkB (75%), followed by trkC (58%) and trkA (54%). Furthermore, using consecutive sections, a clear co-localization of trk receptors was observed in the same neurons. The highest degree of co-localization was observed between trkA and trkB. In Alzheimer's disease patients, the number of immunoreactive neurons and the staining intensity of individual neurons was reduced dramatically. Reduction in the proportion of neurons expressing trkA was 69%, in trkB 47% and in trkC 49%, which indicated a differential reduction in the amount of trk receptors in Alzheimer's disease. These observations indicate that nucleus basalis of Meynert neurons can be supported by more than one neurotrophin and that the degeneration of these neurons in Alzheimer's disease is associated with a decreased expression of trk receptors, suggesting a decreased neurotrophin responsiveness of nucleus basalis of Meynert neurons in Alzheimer's disease.
Journal of Neuropathology & Experimental Neurology
Decreased activity of hippocampal neurons in Alzheimer's disease is not related to the presence of neurofibrillary tangles
by Ahmad Salehi, Rifka Ravid, Nikolas K. Gonatas, and Dick F. Swaab
Abstract Numerous studies have established the key role of the Golgi apparatus (GA) in post-translational processing, transport and targeting of proteins destined for secretion, lysosomes and plasma membranes. Moreover, several studies performed in our laboratories have shown that the size of the immunocytochemically detected neuronal GA is a reliable index of neuronal activity in aging, Alzheimer's disease (AD) and amyotrophic lateral sclerosis. It has been suggested that in AD there is decreased neuronal activity, e.g. in terms of glucose metabolism and protein synthetic capability. To further explore the hypothesis of decreased neuronal activity in AD, in this study the size of the GA was measured in pyramidal neurons of the CAI area of the hippocampus of non-demented controls and AD patients. The size of the GA was measured separately in neurons with and without neurofibrillary tangles (NFT). Moreover, in order to establish a correlation between the density of NFT and the size of the GA, the density of extraneuronal NFT was determined around each neuron and related to the size of its GA. The results, quantified by image analysis, indicate that there is a significant reduction in GA size in the neurons of the CAI area of the hippocampus of AD patients. However, there was no significant relationship between the size of the GA and the presence or absence of intracellular NFT. In addition, there was no correlation between the density of extracellular NFT and GA size of adjacent neurons. These findings are consistent with the conclusion that in AD there is evidence of decreased protein processing and secretion in the affected neurons of the CAI area of the hippocampus. However, we failed to detect a relationship between intracellular or extracellular NFT and neuronal protein synthetic ability. These results justify the hypothesis that in AD a primary lesion is hypoactivity of neurons that is not directly linked with the development of intracellular or extracellular NFT.
Decreased protein synthetic activity of the hypothalamic tuberomamillary nucleus in Alzheimer's disease as suggested by smaller Golgi apparatus.
by Ahmad Salehi, S. Heyn, Nikolas K. Gonatas, and Dick F. Swaab
Abstract The nucleus tuberalis lateralis (NTL) and tuberomamillary nucleus (TM), which are located close together in the tuberal region of the human hypothalamus, are differentially affected by Alzheimer's disease (AD), In the AD, the NTL shows only early cytoskeletal alterations, i.e. pre-tangle stages, while the TM is characterised by advanced Alzheimer's changes, e.g. neurofibrillary degeneration, senile plaques and amyloid deposition. Earlier we showed that the early cytoskeletal alterations in the NTL are not accompanied by changes in protein synthetic activity. The present study was carried out in order to measure the protein synthetic activity of the neighbouring area, the TM, which is severely affected by advanced Alzheimer changes. A polyclonal antibody against MG-160, a conserved membrane sialoglycoprotein of the Golgi apparatus, was used to stain this organelle and using an image analysis system, the size of the Golgi apparatus was measured as an index for synthetic and secretory activity in 15 Alzheimer patients and 21 controls. A significant decrease in the size of the Golgi apparatus was found in the TM neurons in AD, although the cell profile area remained unchanged. These data suggest that the protein synthetic and secretory activity of TM neurons is indeed decreased in AD.
Early cytoskeletal changes as shown by Alz-50 are not accompanied by decreased neuronal activity.
by Ahmad Salehi, J. A. Van de Nes, Michel A. Hofman, Nikolas K. Gonatas, and Dick F. Swaab
Abstract The nucleus tuberalis lateralis (NTL) is located in the basolateral part of the hypothalamus and is only present as a well-delineated nucleus in human and higher primates. In Alzheimer's disease (AD), NTL neurons show strong early cytoskeletal alterations, as revealed by the antibody Alz-50, but practically no senile plaques or neurofibrillary tangles. To study whether the activity of NTL neurons decreases when cytoskeletal changes appear, i.e., during aging and in AD, we applied a polyclonal antibody raised against the medial cisternae of the Golgi apparatus (GA). The size of the GA and the cell profile of NTL neurons, two established parameters for neuronal activity, were measured by an image analysis system. No significant change in the size of the profiles of the GA or of the neurons was observed in this nucleus during aging or AD. Earlier studies have shown that there is no decrease in cell number in the NTL in AD. We conclude that in the NTL an early hallmark of AD, i.e., cytoskeletal changes as stained by Alz-50, does not correlate with decreased neuronal activity, as reflected by the size of the GA, nor with a decrease in cell number. In addition, we found that the very early occurring and abundant presence of lipofuscin in NTL neurons does not go together with decreased neuronal activity.
Activation of vasopressin neurons in aging and Alzheimer's disease
by Paul J. Lucassen, Ahmad Salehi, Chris W. Pool, Nikolas K. Gonatas, Dick F. Swaab
Abstract The supraoptic (SON) and paraventricular nuclei (PVN) of the human hypothalamus are production sites of vasopressin (AVP) and oxytocin (OXT). Although the hypothalamus is affected in Alzheimer's disease (AD), previous work has not only shown that in these two nuclei no neurons are lost, neither during aging nor in AD, but that the number of AVP-expressing neurons and their nucleolar size had even increased with age. These observations indicated that the peptide synthesis of the AVP neurons was activated in the oldest age-groups. Recently published, qualitative observations, using the area of the Golgi Apparatus (GA) as a sensitive parameter for neurosecretory activity, confirmed the activation of SON and PVN neurons with age in human; however, in this report the neurons were not identified according to their neuropeptide content. In the present quantitative study we determined whether the AVP neurons were indeed activated as a result of the aging process in controls and AD patients. We applied a polyclonal antiserum directed against the medial cisternae of the GA on formalin-fixed, paraffin-embedded tissue sections taken from the dorsolateral SON (dl-SON) of 10 controls and 10 AD patients, and performed our measurements in this area that is known to be predominantly occupied (90–95%) by AVP neurons. In addition, the sparse OXT cells present in the area of study, were excluded from the measurements on the basis of alternative sections stained for OXT. In the dl-SON, the area occupied by the GA and the cellular profile area per patient were quantified by means of image analysis. The results show a significant increase in GA area with age in controls and in AD, demonstrating an activation of the AVP neurons in the dl-SON of the human hypothalamus in these two conditions. No changes were observed in the cellular profile areas with age, neither in the controls nor in AD, suggesting that the GA area is a much more sensitive parameter for monitoring activity changes in post-mortem material than neuronal size. It is proposed that this activation of AVP cells with age, which has been suggested to be a compensatory response to the age-related loss of AVP receptors in the kidney, might be the basis of the stability of these neurons in aging and AD.
Decreased neuronal activity in the nucleus basalis of Meynert in Alzheimer's disease as suggested by the size of the Golgi apparatus.
by Ahmad Salehi, Paul J. Lucassen, Chris W. Pool, Nikolas K. Gonatas, Rifka Ravid, and Dick F. Swaab
Abstract In order to study changes in neuronal activity in the nucleus basalis of Meynert in aging and Alzheimer's disease, we applied a polyclonal antibody directed against the Golgi apparatus on formalin-fixed, paraffin-embedded material. Subsequently, an image analysis system was used to measure the size of the Golgi apparatus in (i) all nucleus basalis neurons and also separately in (ii) the remaining large cells (perikaryonal diameter > 30 microns). A significant reduction of 49% in the size of the Golgi apparatus was found in the entire population of nucleus basalis neurons in Alzheimer's disease. Furthermore, although there was no significant decrease in the size of the persisting large neurons in the nucleus basalis of Meynert, a significantly decreased size of the Golgi apparatus was found in these neurons in Alzheimer's disease. These results suggest that the overall activity of nucleus basalis neurons is severely decreased in Alzheimer's disease. Furthermore, these data support the idea that atrophy and decreased activity are the main phenomena in the nucleus basalis in Alzheimer's disease; they also indicate that the size of the Golgi apparatus is a sensitive parameter to follow this process.
