12, Number 3, November 2007
Simona Cicconi, Antonietta Gentile, Maria Teresa Ciotti, Tiziana Parasassi, Annalucia Serafino, Pietro Calissano
(Communicated by Antonino Cattaneo)
Apoptotic death induces Aβ production and fibril formation to a much larger extent than necrotic-like death in CGNs
Abstract: In this study we report that apoptotic death of primary cultures of cerebellar granule neurons is accompanied by release of thioflavin-binding proteins -indicative of the presence of β-sheet structures- and fibril formation in the culture medium. When the same neurons are subjected to an excytotoxic death caused by 100 µM glutamate exposure, the amount of thioflavin binding is markedly reduced. Western blot analysis shows that fibrils contain monomers, dimers and trimers of amyloid-β (Aβ) which, when observed at the electron microscope, have morphologies reminiscent of fibrils of senile plaques. These findings demonstrate that triggering an apoptotic pathway leads to β-sheet transition and fibril formation of a protein primarily involved in Alzheimer disease and may be of direct relevance to the possible link between apoptosis and this neuropathology.
Alex Augusto Vendramini, Roger Willian de Lábio, Lucas Trevisani Rasmussen, Thais Minett, Paulo Henrique Ferreira Bertolucci, Marília de Arruda Cardoso Smith, Spencer Luiz Marques Payão
Interleukin-8 gene polymorphism -251T>A and Alzheimer's disease
Elisabete Ferreiro, Ana Eufrásio, Cláudia Pereira, Catarina R. Oliveira, A. Cristina Rego
Bcl-2 overexpression protects against amyloid-beta and prion toxicity in GT1-7 neural cells
Abstract: In this study we analysed the effect of Bcl-2 on the cytotoxicity induced by the amyloid-β (Aβ25-35) and prion (PrP106-126) peptides by using GT1-7puro and GT1-7bcl-2 (overexpressing the anti-apoptotic protein Bcl-2) neural cells. Exposure to Aβ25-35 (1-5 μM) and PrP106-126 (25 μM) caused a decrease in cell viability, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. These data were correlated with Aβ25-35- and PrP106-126-induced activation of caspase-9, which is linked to the mitochondrial death pathway, and the activation of the effector caspase-3, suggesting cell death by apoptosis. Furthermore, Bcl-2 overexpression protected from loss of cell viability and caspase-9 and -3 activation induced by Aβ25-35 and PrP106-126, showing that Bcl-2 is neuroprotective against apoptotic cell death caused by amyloidogenic peptides.
Miguel A. López-Toledano, Michael L. Shelanski (Communicated by Justo Garcia de Yebenes)
Increased neurogenesis in young transgenic mice overexpressing human APPsw, ind
Abstract: APP overexpressing mice have been widely used in the study of Alzheimer’s disease (AD), focusing mainly at older ages, with higher accumulation of amyloid-β peptide (Aβ). A decrease in hippocampal adult neurogenesis has been described in these models and proposed to be a consequence of Aβ accumulation. Only one study demonstrates increased neurogenesis in the hippocampus of APP-overexpressing J20 mice, and suggests it is a compensatory effect due to a subtle Aβ-induced damage. We have previously reported that a specific aggregation of Aβ has neurogenic potential on neural stem cells (NSC) in vitro. In order to clarify the contradicting data reported in vivo, we investigated NSC proliferation and neuronal differentiation in the hippocampi of J20 mice at a broader range of ages. Using immunohistochemistry, we show increased proliferation and neuronal differentiation in the hippocampi of 3 month-old J20 mice that reverted when animals became older. The increase in neurogenesis correlated with detectable levels of oligomeric Aβ measured by ELISA and western blot. We suggest that oligomeric Aβ directly induces neurogenesis in vivo as has been dsteine thiolactone is converted to 3-mercaptopropionaldehyde. This product is shown to react with proteins causing their precipitation (probably by cross-linking). The two reactions are extremely facile and appear to be physiologically compatible suggesting a mechanism by which homocysteine may promote the deposition of proteins in nerve cells as amyloid plaques and fibrillary tangles.
John I .Toohey (Communicated by Martha Claire Morris)
Mercaptopropionaldehyde from Homocysteine: Implications for Alzheimer’s Disease
Abstract: There has been evidence for a causal relationship between homocysteine and Alzheimer's disease for several years but the mechanism is unclear. In vivo, some homocysteine is converted to the thiolactone. This report describes a novel reaction between homocysteine thiolactone and dehydroascorbic acid in which the homocysteine thiolactone is converted to 3-mercaptopropionaldehyde. This product is shown to react with proteins causing their precipitation (probably by cross-linking). The two reactions are extremely facile and appear to be physiologically compatible suggesting a mechanism by which homocysteine may promote the deposition of proteins in nerve cells as amyloid plaques and fibrillary tangles.
Akinori Ueki, Hideo Ueno, Noriko Sato, Hidetaka Shinjo, Yoshio Morita
Serotonin transporter gene polymorphism and BPSD in mild Alzheimer's disease
Abstract: The purpose of the present study was to confirm an association of functional polymorphism within the serotonin transporter (5-HTT) gene with Alzheimer's disease (AD) and behavioral and psychological symptoms of dementia (BPSD) in mild AD. Apolipoprotein E (ApoE) gene polymorphism and 2 types of functional polymorphism in the 5-HTT gene, 5-HTT-linked polymorphic region (5-HTTLPR) and a 5-HTT variable number of tandem repeats sequence (5-HTTVNTR) were analyzed longitudinally in outpatients with mild AD to find out whether there was a relation between any such polymorphisms and the occurrence of BPSD. No significant differences in genotype distribution or allele frequencies were identified for 5-HTTLPR or 5-HTTVNTR between AD patients and age- and sex-matched non-demented controls regardless of ApoE 4 allele. No significant differences were noted in 5-HTTLPR genotype or allele distributions between AD patients with or without BPSD. However, significant associations were observed between presence of 5-HTTVNTR allele 10 and BPSD or aggressiveness. This difference was independent of the presence of the ApoE ε4 allele. As a result, 5-HTT polymorphisms are unlikely to play any substantial role in susceptibility to AD. Conversely, 5-HTTVNTR influences the risk of developing BPSD or aggressiveness and genetic variations in the 5-HTT gene may be involved in the development of symptomatology for mild AD.
Henrik Zetterberg, Mona Pedersen, Karin Lind, Maria Svensson, Sindre Rolstad, Carl Eckerström, Steinar Syversen, Ulla-Britt Mattsson, Christina Ysander, Niklas Mattsson, Arto Nordlund, Hugo Vanderstichele, Eugeen Vanmechelen, Michael Jonsson, Åke Edman, Kaj Blennow, Anders Wallin (Communicated by Giulio Pasinetti)
Intra-individual stability of CSF biomarkers for Alzheimer's disease over two years
Abstract: This study examines the intra-individual stability of cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) over 2 years in 83 patients with mild cognitive impairment (MCI) and 17 cognitively healthy control individuals. All participants underwent clinical and neuropsychological evaluation and lumbar puncture at baseline and after 2 years at a university hospital memory clinic. CSF was analyzed for total tau (T-tau), phospho-tau181 (P-tau181) and amyloid-β1-42 (Aβ1-42). During the 2-year observational time, 12 MCI patients progressed to AD and 3 progressed to vascular dementia, while 68 remained stable. Baseline T-tau and P-tau181 levels were elevated in the MCI-AD group as compared to the stable MCI patients and the control group (p<0.01), while baseline Aβ1-42 levels were lower (p<0.001). Stable MCI patients were biochemically indistinguishable from controls. The biomarker levels at baseline and after 2 years showed Pearson R values between 0.81 and 0.91 (p<0.001) and coefficients of variation of 7.2 to 8.7%. In conclusion, intra-individual biomarker levels are remarkably stable over 2 years. Thus, even minor biochemical changes induced by treatment against AD should be detectable using these biomarkers, which bodes well for their usefulness as surrogate markers for drug efficacy in clinical trials.
Harish Chander, Abha Chauhan, Ved Chauhan
Binding of Proteases to Fibrillar Amyloid-Beta Protein and Its Inhibition by Congo Red
Abstract: Fibrillar amyloid-β protein (fAβ) is the principal component of amyloid plaques in the brains of patients with Alzheimer's disease (AD). We have recently reported that activity of trypsin is inhibited by fAβ and that trypsin can bind to fAβ. Neprilysin and insulysin are important proteases for the clearance of soluble Aβ. Here, we report that fAβ also binds to neprilysin and insulysin, which results in the inhibition of their proteolytic activities. These findings suggest that clearance of soluble Aβ may be defective in AD because of binding of proteases to amyloid plaques, leading to inactivation of proteases that are required for catabolism of Aβ. The identification of compounds that can inhibit binding of proteases to fAβ may, therefore, be of significance for therapeutic intervention in AD. Congo red and Thioflavin T are widely used for histopathological examination of amyloid plaques because of their strong affinity to fibrillar amyloid proteins. We examined the effect of Congo red and Thioflavin T (potent fAβ-binding compounds) on the binding of different proteases to fAβ. While Congo red inhibited the binding of trypsin, neprilysin and insulysin to fAβ, Thioflavin T did not have any effect. The effect of Congo red was concentration-dependent and the inhibitory effect was in the order of trypsin > insulysin > neprilysin. When the effect of prebound-Congo red to fAβ was examined, trypsin was unable to bind to this complex suggesting that Congo red may have better affinity than trypsin for binding to fAβ. Based on these results, we propose that the inhibition of binding of proteases to amyloid plaques may help in reducing the deposition of Aβ in AD.
HyeSook Youn, Inhae Ji, Hanlee P. Ji, William R. Markesbery, Tae H. Ji (Communicated by Mark Lovell)
Under-expression of Kalirin-7 Increases iNOS Activity in Cultured Cells and Correlates to Elevated iNOS Activity in Alzheimer's Disease Hippocampus
Abstract: Recently, it has been reported that Kalirin gene transcripts are under-expressed in AD hippocampal specimens compared to the controls. The Kalirin gene generates a dozen Kalirin isoforms. Kalirin-7 is the predominant protein expressed in the adult brain and plays crucial roles in growth and maintenance of neurons. Yet its role in human diseases is unknown. We report that Kalirin-7 is significantly diminished both at the mRNA and protein levels in the hippocampus specimens from 19 AD patients compared to the specimens from 15 controls. Kalirin-7 associates with INOS in the hippocampus, and therefore, Kalirin-7 is complexed with iNOS less in AD hippocampus extracts than in control hippocampus extracts. In cultured cells, Kalirin-7 associates with iNOS and down-regulates the enzyme activity. The down-regulation is attributed to the highly conserved 33 amino acid sequence, K617-H649, of the 1,663 amino acids long Kalirin-7. Remarkably, the iNOS activity is considerably higher in the hippocampus specimens from AD patients than the specimens from 15 controls. These observations suggest that the under-expression of Kalirin-7 in AD hippocampus correlates to the elevated iNOS activity.