Presenilin-1 Mutations in Alzheimer’s Disease: An Update on Genotype-Phenotype Relationships
Abstract: Presenilin 1 (PSEN1) gene mutations deterministic for Alzheimer’s disease (AD) are associated with marked heterogeneity in clinical phenotype, with behavioral and psychiatric features, parkinsonism, myoclonus, epileptic seizures, spastic paraparesis, frontal behavioral changes features suggestive of the phenotype of frontotemporal dementia, aphasia, and cerebellar ataxia being described as well as cognitive decline. This article reviews publications on the clinical neurological phenotype of PSEN1 mutations published between October 2008 and April 2013 and integrates this information with previous reviews to produce tabular summaries of phenotype and genotype. With the possible exception of “variant AD” (familial AD with spastic paraparesis), no clinical genotype-phenotype correlations are obvious. The mechanisms underpinning the clinical heterogeneity associated with PSEN1 mutations remain unclear. The “presenilin hypothesis” posits a loss of essential presenilin protein functions as a consequence of gene mutation, which might be one factor influencing disease phenotype.
Renã A. S. Robinson, Zhiyun Cao, Christopher Williams (Handling Associate Editor: D. Allan Butterfield)
Oxidative Stress in CD90+ T-cells of AβPP/PS-1 Transgenic Mice
Abstract: Oxidative stress plays a role in Alzheimer’s disease (AD) with elevated levels being present in tissues such as brain, plasma, and cerebrospinal fluid. The role of oxidative stress in the immune system of AD is less established. Therefore, we measured protein markers of oxidative stress—protein carbonyls (PCO) and 3-nitrotyrosine (3NT)—in CD90+ T-cells of a double-transgenic AD mouse model. Higher levels of PCO and 3NT were detected in amyloid-β protein precursor/presenilin-1 (AβPP/PS-1) mice and increased with disease progression. These studies provide evidence that oxidative stress in the immune system may be useful for understanding disease pathogenesis.
Mara Taverna, Tobias Straub, Harald Hampel, Dan Rujescu, Stefan F. Lichtenthaler (Handling Associate Editor: Hilkka Soininen)
A New Sandwich Immunoassay for Detection of the α-Secretase Cleaved, Soluble Amyloid-β Protein Precursor in Cerebrospinal Fluid and Serum
Abstract: Alzheimer’s disease (AD) is the most common neurodegenerative disorder. Frequently used diagnostic biomarkers are amyloid-β42 (Aβ42), tau, and phospho-tau, which are measured in cerebrospinal fluid (CSF), and allow a reasonable, but not full, separation of AD patients and controls. Besides Aβ42, additional proteolytic cleavage products of the amyloid-β protein precursor (AβPP) have been investigated as potential biomarkers. This includes the α-secretase cleaved soluble AβPP ectodomain (sAβPPα). However, some studies found a reduction of sAβPPα, whereas other studies reported an increase of sAβPPα in the CSF of AD patients. The divergent findings may result from the detection of sAβPPα with antibodies, such as 6E10, which do not exclusively detect sAβPPα, but also the alternative β-secretase cleavage product sAβPPβ’. Here, we used the sAβPPα-specific antibody 14D6 and developed an ELISA-like sandwich immunoassay. The assay specifically detected sAβPPα in cell culture supernatants, in human CSF and even in serum, which is more readily accessible than CSF. The assay was used to analyze sAβPPα levels in CSF and serum of AD patients and controls. The assay detected a mild, but significant increase in sAβPPα in the CSF of AD patients compared to non-demented controls, while a mild reduction was observed in serum. The 14D6 assay in CSF allowed a better separation of AD patients from controls compared to the 6E10 antibody. Taken together, the new assay is widely applicable for specific sAβPPα measurement in culture media, CSF, and serum.
Maria Manczak, Tatiana Sheiko, William J. Craigen, P. Hemachandra Reddy
Reduced VDAC1 Protects Against Alzheimer’s Disease, Mitochondria, and Synaptic Deficiencies
Abstract: The objective of this study was to elucidate the effect of VDAC1 on Alzheimer’s disease (AD)-related genes, mitochondrial activity, and synaptic viability. Recent knockout studies of VDAC1 revealed that homozygote VDAC1 knockout (VDAC1-/-) mice exhibited disrupted learning and synaptic plasticity, and in contrast, VDAC1+/- mice appeared normal in terms of lifespan, fertility, and viability relative to wild-type mice. However, the effects of reduced VDAC1 on mitochondrial/synaptic genes and mitochondrial function in AD-affected neurons are not well understood. In the present study, we characterized mitochondrial/synaptic and AD-related genes and mitochondrial function in VDAC1+/- mice and VDAC1+/+ mice. We found reduced mRNA levels in the AD-related genes, including AβPP, Tau, PS1, PS2, and BACE1; increased levels of the mitochondrial fusion genes Mfn1, Mfn2; reduced levels of the fission genes Drp1 and Fis1; and reduced levels of the mitochondrial permeability transition pore genes VDAC1, ANT, and CypD in VDAC+/+ mice relative to VDAC1+/+ mice. Hexokinase 1 and 2 were significantly upregulated in the VDAC+/- mice. The synaptic genes synaptophysin, synapsin 1 and 2, synaptobrevin 1 and 2, neurogranin, and PSD95 were also upregulated in the VDAC1+/- mice. Free radical production and lipid peroxidation levels were reduced in the VDAC1+/- mice, and cytochrome oxidase activity and ATP levels were elevated, indicating enhanced mitochondrial function in the VDAC1+/- mice. These findings suggest that reduced VDAC1 expression, such as that we found in the VDAC1+/- mice, may be beneficial to synaptic activity, may improve function, and may protect against toxicities of AD-related genes.
Moeko Noguchi-Shinohara, Sohshi Yuki, Chiaki Dohmoto, Yoshihisa Ikeda, Miharu Samuraki, Kazuo Iwasa, Masami Yokogawa, Kimiko Asai, Kiyonobu Komai, Hiroyuki Nakamura, Masahito Yamada (Handling Associate Editor: Robert Friedland)
Differences in the Prevalence of Dementia and Mild Cognitive Impairment and Cognitive Functions between Early and Delayed Responders in a Community-Based Study of the Elderly
Abstract: Significant differences exist in demographic characteristics between responders and non-responders in population-based studies on mental health and cognitive status, but much less is known regarding differences in the prevalence of dementia and cognitive dysfunction between them. Here we compared the prevalence of dementia and mild cognitive impairment between early responders of a mass brain function examination and delayed responders (non-responders of the mass brain function examination) in a survey of elderly Japanese citizens (≥65 years) to evaluate non-responder bias. All residents in an area of Nakajima, Japan, were considered as potential candidates (n = 783). Participants of a mass brain function examination were considered as “early responders.” The cognitive functions of delayed responders were assessed by home visits. To assess the correlation between sociodemographic characteristics and cognitive functions, the early and delayed responders completed the same questionnaires and neuropsychological tests. Delayed responders (n = 320) were significantly older and less educated than the early responders (n = 307). The delayed responders also exhibited a higher frequency of dementia and mild cognitive impairment than the early responders, even when the groups were restricted to the age group 65-89 years. Our results suggest that population-based studies likely underestimate the prevalence of dementia and mild cognitive impairment, especially if the participation rate is low.
Nan Wu*, Xiaoping Rao*, Yunling Gao, Jie Wang, Fuqiang Xu (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
Amyloid-β Deposition and Olfactory Dysfunction in an Alzheimer’s Disease Model
Abstract: Olfactory dysfunction is closely related to Alzheimer’s disease (AD). Yet the mechanism behind this dysfunction remains largely unknown. To clarify the relationship between olfactory and memory deficits, we assessed behavioral and olfactory system pathology in AβPP/PS1 transgenic mice using the olfactory threshold test, the Morris water maze, western blotting, immunohistochemistry (IHC), and thioflavine-s staining. Western blotting revealed the following spatial-temporal deposition of amyloid-β (Aβ): appeared in the olfactory epithelium at 1-2 months old (mo); expanded to the olfactory bulb at 3-4 mo; expanded to the anterior olfactory nucleus, piriform cortex, entorhinal cortex, and hippocampus at 6-7 mo; and increased with age (9-10 mo) in the more central cortices. IHC staining showed similar results, but the appearance time points for the spotty signals in these brain regions were earlier due to the higher spatial resolution compared with western blotting. The spread of Aβ deposits from the olfactory epithelium to the olfactory bulb, the anterior olfactory nucleus, and piriform cotex (faint) at 3-4 mo correlated with the olfactory detection deficit found at the corresponding age; and the high level of depositions in the more central regions at 9-10 mo correlated with spatial memory deficit at the same age. We also found that a decline in the levels of olfactory marker protein, a marker of functioning olfactory sensory neuron, coincided with soluble Aβ aggregates from a very early age in the olfactory epithelium, indicating early olfactory sensory neuron degeneration in the AβPP/PS1 mouse as in AD patients. The current data suggest that the early deposition of soluble Aβ aggregates in the olfactory system and the early deficit in olfactory dysfunction have the potential to serve as molecular markers for the early diagnosis of AD.
Lin Zheng, Javier Calvo-Garrido, Martin Hallbeck, Kjell Hultenby, Jan Marcusson, Angel Cedazo-Minguez, Alexei Terman
Intracellular Localization of Amyloid-β Peptide in SH-SY5Y Neuroblastoma Cells
Abstract: Amyloid-β peptide (Aβ), the main component of Alzheimer’s disease (AD) senile plaques, has been found to accumulate within the lysosomal compartment of AD neurons. We have previously shown that in differentiated SH-SY5Y neuroblastoma cells cultured under normal conditions, the majority of Aβ is localized extralysosomally, while oxidative stress significantly increases intalysosomal Aβ content through activation of macroautophagy. It is, however, not clear which cellular compartments contain extralysosomal Aβ in intact SH-SY5Y cells, and how oxidative stress influences the distribution of extralysosomal Aβ. Using confocal laser scanning microscopy and immunoelectron microscopy, we showed that in differentiated neuroblastoma cells cultured under normal conditions Aβ (Aβ40, Aβ42, and Aβ oligomers) is colocalized with both membrane-bound organelles (endoplasmic reticulum, Golgi complexes, multivesicular bodies/late endosomes, lysosomes, exocytotic vesicles and mitochondria) and non-membrane-bound cytosolic structures. Neuroblastoma cells stably transfected with AβPP Swedish KM670/671NL double mutation showed enlarged amount of Aβ colocalized with membrane compartments. Suppression of exocytosis by 5 nM tetanus toxin resulted in a significant increase of the amount of cytosolic Aβ as well as Aβ colocalized with exocytotic vesicles, endoplasmic reticulum, Golgi complexes, and lysosomes. Hyperoxia increased Aβ localization in the endoplasmic reticulum, Golgi apparatus, mitochondria, and lysosomes, but not in the secretory vesicles. These results indicate that in SH-SY5Y neuroblastoma cells intracellular Aβ is not preferentially localized to any particular organelle and, to a large extent, is secreted from the cells. Challenging cells to hyperoxia, exocytosis inhibition, or Aβ overproduction increased intracellular Aβ levels but did not dramatically changed its localization pattern.
Juan M. Zolezzi, Francisco J. Carvajal, Juvenal A. Ríos, Daniela Ordenes, C. Silva-Alvarez, Juan A. Godoy, Nibaldo C. Inestrosa
Tetrahydrohyperforin Induces Mitochondrial Dynamics and Prevents Mitochondrial Ca2+ Overload after Aβ and Aβ-AChE Complex Challenge in Rat Hippocampal Neurons
Abstract: St. John’s wort has been the subject of studies focused on its therapeutic properties against several diseases, including Alzheimer’s disease (AD). Amyloid β-peptide (Aβ), a critical peptide in AD, has been linked to the mitochondrial dysfunction often observed in this disease. Despite many efforts to prevent Aβ levels from increasing in AD, less has been done regarding the mitochondrial component. Therefore, we studied the effects of tetrahydrohyperforin (THH) on mitochondrial dysfunction of hippocampal neurons, challenged with Aβ oligomers (Aβo) and Aβo-AChE complexes. We show that THH prevents mitochondrial calcium overload and induces the modulation of fusion-fission events, arresting mitochondrial dysfunction. Moreover, our results suggest that the modulation of mitochondrial dynamics probably occurs through a peroxisome proliferator-activated receptor γ co-activator 1α-mediated mechanism, inducing mitochondrial fusion-fission protein expression. Our results offer further explanation for the effects observed for THH and the beneficial effects of this ethno-botanical drug in AD.
Nina Krako*, Maria Chiara Magnifico*, Marzia Arese, Giovanni Meli, Elena Forte, Agnese Lecci, Annalisa Manca, Alessandro Giuffrè, Daniela Mastronicola, Paolo Sarti, Antonino Cattaneo (Handling Associate Editor: ShiDu Yan) *These authors contributed equally to this work.
Characterization of Mitochondrial Dysfunction in the 7PA2 Cell Model of Alzheimer’s Disease
Abstract: The 7WD4 and 7PA2 cell lines, widely used as cellular models for Alzheimer’s disease (AD), have been used to investigate the effects of amyloid-β protein precursor overexpression and amyloid-β (Aβ) oligomer accumulation on mitochondrial function. Under standard culture conditions, both cell lines, compared to Chinese hamster ovary (CHO) control cells, displayed an approx. 5% decrease of O2 respiration as sustained by endogenous substrates. Functional impairment of the respiratory chain was found distributed among the protein complexes, though more evident at the level of complex I and complex IV. Measurements of ATP showed that its synthesis by oxidative phosphorylation is decreased in 7WD4 and 7PA2 cells by approx. 25%, this loss being partly compensated by glycolysis (Warburg effect). Compensation proved to be more efficient in 7WD4 than in 7PA2 cells, the latter cell line displaying the highest reactive oxygen species production. The strongest deficit was observed in mitochondrial membrane potential that is almost 40% and 60% lower in 7WD4 and 7PA2 cells, respectively, in comparison to CHO controls. All functional parameters point to a severe bioenergetic impairment of the AD cells, with the extent of mitochondrial dysfunction being correlated to the accumulation of Aβ peptides and oligomers.
Görsev G. Yener, Pinar Kurt, Derya D. Emek, Bahar Güntekin, Erol Başar
Reduced Visual Event-Related Delta Oscillatory Responses in Amnestic Mild Cognitive Impairment
Abstract: Mild cognitive impairment (MCI) is considered as a prodromal stage for Alzheimer’s disease (AD) in the majority of cases. Event-related oscillations might be used for detection of cognitive deficits. Our group’s earlier results showed diminished delta visual and auditory target oscillatory responses in AD, and we investigated whether this prevails for MCI. Eighteen MCI subjects and 18 age-matched healthy elderly controls were investigated. The maximum peak-to-peak amplitudes of oscillatory responses for each subject’s averaged oscillatory target responses in delta, theta, and alpha frequency bands upon application of visual oddball paradigm were measured. Repeated measures of ANOVA was used to analyze four locations (frontal, central, parietal, occipital), at three coronal (left, midline, right) sites. Independent t tests were applied for post-hoc analyses. The oddball target delta response (0.5-3.0 Hz) was 26–32% lower in MCI than healthy controls over fronto-central-parietal regions [F(1.34)=4.562, p=0.04]. Without a group effect, theta oscillatory responses (4-7 Hz) showed significant differences in coronal electrodes indicating highest values over mid-electrode sites, and a anteriorposterior x coronal effect, being maximum at mid-central. Alpha frequency band analyses indicated no statistical differences. Peak-to-peak amplitudes of visual target delta oscillatory responses were lower in fronto-central-parietal regions in MCI than in healthy controls. This supports our earlier findings in AD, showing hypoactive delta fronto-central-parietal regions during cognitive tasks. These results indicate that event-related oscillations may detect early changes of brain dynamics in MCI, and deserves to be investigated as a candidate biomarker in further studies using multimodal techniques.
Marie-Pierre Chaunu*, Vincent Deramecourt*, Valérie Buée-Scherrer, Isabelle Le Ber, Alexis Brice, Nathalie Ehrle, Khalid El Hachimi, Michel Pluot, Claude-Alain Maurage, Serge Bakchine, Luc Buée *These authors contributed equally to this article.
Juvenile Frontotemporal Dementia with Parkinsonism associated with Tau Mutation G389R
Abstract: Frontotemporal lobe degeneration includes a large spectrum of neurodegenerative disorders. Patients with frontotemporal dementia with parkinsonism linked to chromosome 17 exhibit heterogeneity in both clinical and neuropathological features. Here, we report the case of a young patient with a G389R mutation. This teenager girl was 17 years old when she progressively developed severe behavioral disturbances. First, she was considered to be suffering from atypical depression. After 2 years, she was referred to the department of neurology. By this time, the patient exhibited typical frontotemporal dementia with mild extrapyramidal disorders. The main behavioral features included apathy and reduced speech output. MRI and SPECT showed a frontotemporal atrophy and hypofixation, respectively. She died 7 years after onset. Three relatives on her father side had also died after early onset dementia. Genetic testing revealed a heterozygous guanine to cytosine mutation at the first base of codon 389 (Exon 13) of MAPT, the tau gene, resulting in a glycine to arginine substitution, in the patient and her non-affected father. Postmortem neuropathological and biochemical data indicate a Pick-like tau pathology but with phosphoserine 262-positive immunoreactivity. This case is remarkable because of the extremely early onset of the disease.
Ann Van der Jeugd, Ben Vermaercke*, Maxime Derisbourg*, Adrian C. Lo*, Malika Hamdane, David Blum, Luc Buée, Rudi D’Hooge *These authors contributed equally to this work.
Progressive Age-Related Cognitive Decline in Tau Mice
Abstract: Age-related cognitive decline and neurodegenerative diseases are a growing challenge for society. Accumulation of tau pathology has been proposed to partially contribute to these impairments. This study provides a behavioral characterization during aging of transgenic mice bearing tau mutations. THY-Tau22 mice were evaluated at ages wherein tau neuropathology in this transgenic mouse model is low (3-4 months), moderate (6-7 months), or extensive (>9 months). Spatial memory was found to be impaired only after 9 months of age in THY-Tau22 mice, whereas non-spatial memory was affected as early as 6 months, appearing to offer an opportunity for assessing potential therapeutic agents in attenuating or preventing tauopathies through modulation of tau kinetics.
Ludivine Chamard, David Wallon, Alexa Pijoff, Eric Berger, Gabriel Viennet, Didier Hannequin, Eloi Magnin (Handling Associate Editor: Jeremie Pariente)
Amyloid-Related Imaging Abnormalities in AβPP Duplication Carriers
Abstract: Immune response to vascular amyloid-β deposits leads to cerebral amyloid angiopathy related-inflammation (CAA-ri). Amyloid-related imaging abnormalities (ARIA) were initially reported during anti-amyloid trials and are associated with the APOE 4/4 genotype. We report the evolution of an AβPP duplication carrier with an APOE 3/3 genotype presenting ARIA-Effusion and then ARIA-Hemosiderin deposit, without anti-amyloid therapy, suggestive of a possible spontaneously resolutive CAA-ri (not neuropathologically proven). It suggests common mechanisms between ARIA and CAA-ri and raises questions about mechanisms of this acute episode without APOE risk factor. The high vascular amyloid burden, induced by AβPP duplication, might increase amyloid epitope presentation and lead to inflammatory process.
Dong-Xiao Duan*, Gao-Shang Chai*, Zhong-Fei Ni, Yu Hu, Yu Luo, Xiang-Shu Cheng, Ning-Ning Chen, Jian-Zhi Wang, Gong-Ping Liu *These authors have contributed equally to this work.
Phosphorylation of Tau by Death-Associated Protein Kinase 1
Abstract: The intracellular accumulation of hyperphosphorylated tau plays a crucial role in neurodegeneration of Alzheimer’s disease (AD), but the mechanism is not fully understood. From the observation that tau hyperphosphorylation renders cells more resistant to chemically-induced cell apoptosis, we have proposed that tau-involved apoptotic abortion may be the trigger of neurodegeneration. Here, we further studied whether this phenomenon is also applicable for the cell death induced by constitutively expressed factors, such as death-associated protein kinase 1 (DAPK1). We found that DAPK1 was upregulated and accumulated in the brain of human tau transgenic mice. Overexpression of DAPK1 in HEK293 and N2a cells decreased cell viability with activation of caspase-3, whereas simultaneous expression of tau antagonized DAPK1-induced apoptotic cell death. Expression of DAPK1 induced tau hyperphosphorylation at Thr231, Ser262, and Ser396 with no effects on protein phosphatase 2A, glycogen synthase kinase-3β, protein kinase A, calcium/calmodulin dependent protein kinase II, cell division cycle 2, or cyclin dependent protein kinase 5. The phosphorylation level of microtubule affinity-regulating kinase 2 (MARK2) was increased by expression of DAPK1, but simultaneous downregulation of MARK2 did not affect the DAPK1-induced tau hyperphosphorylation. DAPK1 was co-immunoprecipitated with tau proteins both in vivo and in vitro, and expression of the kinase domain-truncated DAPK1 did not induce tau hyperphosphorylation. These data suggest that tau hyperphosphorylation at Thr231, Ser262, and Ser396 by DAPK1 renders the cells more resistant to the kinase-induced apoptotic cell death, providing new insights into the tau-involved apoptotic abortion in the course of chronic neurodegeneration.
Molly Fox, Carlo Berzuini, Leslie A. Knapp
Maternal Breastfeeding History and Alzheimer’s Disease Risk
Abstract: The effect of early and midlife factors on later-life cognitive function has attracted scientific and public interest in recent years, especially with respect to hormonal risk factors for dementia. There is substantial evidence for reproductive history affecting Alzheimer’s disease (AD) etiology. Here, we demonstrate how breastfeeding history affects women’s risk of AD. Reproductive history data was collected, and AD diagnostic interviews were performed, for a cohort of elderly British women. Using Cox proportional-hazard models, we find that longer breastfeeding duration corresponded to reduced risk of AD (p<0.01, n=81). Women who breastfed had lower AD risk than women who did not breastfeed (p=0.017, n=81). Breastfeeding practices are an important modifier of cumulative endogenous hormone exposure for mothers. Ovarian hormone deprivation and/or insulin sensitivity benefits of breastfeeding may be responsible for the observed reduction in AD risk. Future studies concerning hormone effects on AD risk should consider how reproductive history leads to variation in endogenous hormone exposure and how this may influence the relationship between hormones and AD.
Xiaorui Cheng*, Yu Zhou*, Wei Gu, Jie Wu, Aihua Nie, Junping Cheng, Jinwu Zhou, Wenxia Zhou, Yongxiang Zhang *These authors contributed equally to this work.
The Selective BACE1 Inhibitor VIa Reduces Amyloid-β Production in Cell and Mouse Models of Alzheimer’s Disease
Abstract: β-site amyloid-β protein precursor cleaving enzyme 1 (BACE1) is the first protease and the rate limiting enzyme in the genesis of amyloid-β (Aβ). This protein remains an important potential disease-modifying target for the development of drugs to treat Alzheimer’s disease (AD). We are pursuing potent BACE1 inhibitors in an effort to identify suitable AD drug candidates. Our results have shown that the novel compound VIa exhibits potent inhibitory effects with IC50=5.9 nM and displays 30.8-fold, 7500-fold, and 17533-fold selectivity against the other aspartic proteases BACE2, cathepsin D, and renin, respectively. In cellular assays, VIa moderately reduces Aβ production: Aβ1-40 with an IC50 =143 nM and 1 nM VIa reduced Aβ1-42 by 40.17%. Concomitant with VIa inhibiting the β-cleavage of amyloid-β protein precursor (AβPP), VIa increases the production of sAβPPα with an approximate EC50 of 16.5 nM. In testing this compound’s efficacy in vivo, the oral administration of VIa resulted in a significant decrease in Aβ1-40 and Aβ1-42 in the blood of a mouse model of AD by 17.5~72.44% and 14.5~80.32%, respectively. This indicates that the novel compound VIa is a small, potent, selective, and non-peptidic BACE1 inhibitor.
Huey T. Nguyen, Darrell R. Sawmiller, Olga Markovb, Ming Chen
Elevated [Ca2+]i Levels Occur with Decreased Calpain Activity in Aged Fibroblasts and Reversal by Energy-Rich Compounds: Implications for Alzheimer’s Disease Prevention
Abstract: Elevated intracellular Ca2+ levels in the aging brain are thought to hyperactivate Ca2+ signaling and Ca2+-dependent enzymes, leading to neuronal death through an excitatory mechanism in Alzheimer’s disease (AD). This “Ca2+ overload” hypothesis has been questioned by our theoretical analyses. To better understand the relationship between the “level” and functionality of Ca2+, in this study we simultaneously measured Ca2+ transients and calpain activity in cultured human fibroblasts. We found that Ca2+ transitions elicited by bradykinin were indeed overstayed or elevated in levels in old cells but, remarkably, calpain activity was decreased compared to young cells. Also, treating young cells with energy inhibitor rotenone or H2O2 recapitulated the Ca2+ overstay and calpain inactivation found in old cells. Importantly, treating old cells with high-energy compounds such as phosphoenol pyruvate or phosphocreatine, which boosted cellular ATP content, reduced the Ca2+ overstay and re-activated calpain. Moreover, Ca2+ levels and calpain activity were dramatically raised in the dying cells killed by detergent. Finally, Ca2+ oscillations induced by low dose of bradykinin in old cells exhibited lower spike frequency, but higher overall levels. Collectively, these results suggest that (a) Ca2+ overload in old cells arises from an inefficient Ca2+ handling system compromised by age-related energy depletion and oxidative stress; and (b) despite elevated Ca2+ levels, the functionality of Ca2+ signaling has diminished in old cells. Thus, the study reinforces the possibility that tonic promotion of bioenergetics and Ca2+ signaling function is a reasonable paradigm to strengthen and protect the aging brain cells to prevent AD.
Inelia Morales, José M. Jiménez, Marcela Mancilla, Ricardo B. Maccioni
Tau Oligomers and Fibrils Induce Activation of Microglial Cells
Abstract: Neuroinflammation is a process related to the onset of several neurodegenerative disorders, including Alzheimer’s disease (AD). Increasing sets of evidence support the major role of deregulation of the interaction patterns between glial cells and neurons in the pathway toward neuronal degeneration, a process we are calling neuroimmunomodulation in AD. On the basis of the hypothesis that pathological tau aggregates induce microglial activation with the subsequent events of the neuroinflammatory cascade, we have studied the effects of tau oligomeric species and filamentous structures over microglial cells in vitro. Tau oligomers and fibrils were induced by arachidonic acid and then their actions assayed upon addition to microglial cells. We showed activation of the microglia, with significant morphological alterations as analyzed by immunofluorescence. The augmentation of nitrites and the proinflammatory cytokine IL-6 was evaluated in ELISA assays. Furthermore, conditioned media of stimulated microglia cells were exposed to hippocampal neurons generating altered patterns in these cells, including shortening of neuritic processes and cytoskeleton reorganization.
Jinho Kim, Yong Jeong (Handling Associate Editor: Kyoung-Min Lee)
Augmentation of Sensory-Evoked Hemodynamic Response in an Early Alzheimer’s Disease Mouse Model
Abstract: Based on enlarged blood oxygen level-dependent (BOLD) responses in cognitively normal subjects at risk for Alzheimer’s disease (AD), compensatory neuronal hyperactivation has been proposed as an early marker for diagnosis of AD. The BOLD response results from neurovascular coupling, i.e., hemodynamic response induced by neuronal activity. However, there has been no evidence of task-induced increases in hemodynamic response in animal models of AD. Here, we observed an augmented hemodynamic response pattern in a transgenic AβPPSWE/PS1ΔE9 mouse model of AD using three in vivo imaging methods: intrinsic optical signal imaging, multi-photon laser scanning microscopy, and laser Doppler flowmetry. Sensory stimulation resulted in augmented and prolonged hemodynamic responses in transgenic mice evidenced by changes in total, oxygenated, and deoxygenated hemoglobin concentration. This difference between transgenic and wild-type mice was significant at 7 months of age when amyloid plaques and cerebral amyloid angiopathy had developed but not at younger or older ages. Correspondingly, sensory stimulation-induced pial arteriole diameter was also augmented and prolonged in transgenic mice at 7 months of age. Cerebral blood flow response in transgenic mice was augmented but not prolonged. These results are consistent with the existence of BOLD signal hyperactivation in non-demented AD-risk human subjects, supporting its potential use as an early diagnostic marker of AD.