Brain Amyloid-β Plays an Initiating Role in the Pathophysiological Process of the PS1 V97L -Tg Mouse Model of Alzheimer’s Disease

Abstract

Amyloid-β (Aβ) aggregation, tau hyperphosphorylation, oxidative stress, and neuroinflammation are major pathophysiological events in Alzheimer’s disease (AD). However, the relationships among these processes and which first exerts an effect are unknown. In the present study, we investigated age-dependent behavioral changes and the sequential pathological progression from the brain to the periphery in AD transgenic (PS1_V97L-Tg) mice and their wild-type littermates. We discovered that the brain Aβ significantly increased at 6 months old, the increased brain Aβ caused memory dysfunction, and the ability of Aβ to induce tau hyperphosphorylation might be due to oxidative stress and neuroinflammatory reactions. The levels of Aβ₄₂, total tau (t-tau), oxidative stress parameters, and proinflammatory cytokines in plasma can be used to differentiate between PS1_V97L-Tg mice and their wild-type littermates at different time points. Collectively, our findings support the hypothesis that Aβ is a trigger among these pathophysiological processions and show that plasma biomarkers can reflect the condition of the AD brain.

Keywords

Alzheimer’s disease amyloid-β oxidative stress proinflammatory cytokines tau

INTRODUCTION

Alzheimer’s disease (AD) is the most common type of dementia in the elderly population. Aggregated amyloid-β (Aβ) and hyperphosphorylated tau are very important constituents of the neuropathological hallmarks of AD [1]. A comprehensive understanding of the link between Aβ aggregation and tau hyperphosphorylation in the etiology of AD is a necessary prerequisite in developing effective intervention strategies [2]. In addition to Aβ and tau, multiple pathological events, such as oxidative stress and neuroinflammation, are involved in AD pathogenesis and synergistically drive disease progression [3, 4]. However, the causal relationships amongst Aβ aggregation, tau hyperphosphorylation, neuroinflammation, and oxidative stress are unknown.

Animal models are used extensively to study AD pathogenesis since brain samples can be obtained from presymptomatic to symptomatic stages of AD, which allows analyses of pathophysiological changes at different disease stages. Transgenic mouse models of amyloidosis expressing mutant forms of human amyloid-β protein precursor (AβPP) and/or presenilin-1 (PS1) are the most widely used models to study various aspects of AD pathology and therapy. We first reported a single missense mutation Val97Leu (V97L) of PS1 in a Chinese pedigree suffering from early onset AD [5] and subsequently generated a transgenic mouse line bearing the PS1 V97L mutation (PS1_V97L-Tg mouse). In a previous study, we detected abnormal behavioral changes in PS1_V97L-Tg mice that correlated with abnormal Aβ species and tau hyperphosphorylation in the brain parenchyma [6, 7], demonstrating that the PS1_V97L-Tg mouse model is a useful tool for studying AD pathogenesis. In the present study, we investigated the age-dependent behavioral changes and sequential pathological progression from the brain to the periphery in PS1_V97L-Tg mice and wild-type littermates in order to evaluate the causal relationships among Aβ aggregation, tau hyperphosphorylation, neuroinflammation, and oxidative stress.

MATERIALS AND METHODS

Ethics statement

The study protocol was approved by the Ethics Committee of Capital Medical University, and every effort was made to minimize the number and suffering of animals.

Animals

Male and female PS1_V97L-Tg mice aged 3 to 18 months and sex- and age-matched wild-type littermates (3 male and 3 female in each group) were housed in a room at constant temperature (25 ± 1°C) and humidity (40% –60%) that was kept on a 12-h light/dark cycle (lights on at 8:00 AM). They had free access to food and water. The PS1_V97L-Tg mice expressing the human PS1 gene with the V97L mutation were generated as previously described [7]. PS1_V97L-Tg mice lines were maintained by crossing heterozygous transgenic mice with wild-type C57BL/6J animals. Mice were screened by polymerase chain reaction (PCR) to determine their genotypes, as previously described [7].

Behavioral tests

The mice were tested for spatial learning and memory in the Morris water maze (MWM) to assess age-dependent cognitive impairments at 6 and 9 months of age. Mice were kept under a 12 h:12 h light-dark cycle to ensure that the tests were carried out during the animals’ active period. For 5 consecutive days, all mice were trained to find a platform hidden below the water surface in a 100-cm diameter pool. MWM protocols were carried out by coworkers who were blinded to the genotypes. Training consisted of four trials per day, with a 30-s intertrial interval. On the sixth day, trained spatial memory was assessed using a probe trial in which mice performed a 60-s free search of the pool with the platform removed. The frequency of crossing the “platform position” and the time in the target quadrant where the platform had been located was recorded with a DNS-2 type MWM testing set equipped with an online video tracking system (camera, TOTA-450III, Japan).

Sample harvesting

Cerebrospinal fluid (CSF) sampling was performed as described previously [8]. Anesthetized mice were placed prone, and their cisterna magna were surgically exposed. The exposed meninges were penetrated with a laboratory produced capillary tube that had a tapered tip, and CSF was removed. CSF samples were then centrifuged at 13,000 × g for 30 s and visually assessed for blood contamination. Typically, a total of 5 to 10 μl of CSF was collected. Blood-contaminated samples were discarded. Collected CSF samples were frozen immediately on liquid nitrogen and then stored in a –80°C freezer.

After CSF collection, blood collected from the retro-orbital plexus was transferred to a heparinized tube and shaken gently. All blood samples were kept on ice and centrifuged (2000 × g, 10 min) at 4°C within 15 min after collection. The plasma layer was then collected in 200 μl polypropylene tubes. The samples were then allowed to freeze immediately on liquid nitrogen and kept at –80°C until analysis.

Thereafter, mice were immediately decapitated, and the brain was rapidly dissected. The cerebellum was discarded, and the remainder of the brain was hemisected. The left brain hemisection was used for Aβ and tau analysis, and the right brain hemisection was used to assess oxidative stress parameters and proinflammatory cytokine concentrations. The brain tissue was frozen in liquid nitrogen for 30 min and stored at –80°C until analysis.

Biochemical analysis of brain tissue

In this study, the frozen brains were sequentially extracted according to a three-step extraction procedure. The left hemibrains from PS1_V97L-Tg mice and wild-type littermates were homogenized (sonicated for 35 s at 4°C) at 10% (w/v) in Tris-buffered saline (TBS) containing a complete miniprotease inhibitor cocktail tablet (Roche, Switzerland) and a phosphatase inhibitor cocktail tablet (Roche, Switzerland). The homogenates were centrifuged at 100,000 × g for 1 h at 4°C, and the supernatants were harvested. The homogenized brain tissue was aliquoted and stored at –80°C until use. For Aβ measurements, the pellets were suspended in 2% sodium dodecyl sulfate (SDS) to the original volume, sonicated for 35 s and centrifuged at 25,000 × g at 4°C for 1 h, then the supernatants were collected (SDS-soluble Aβ fraction). Afterward, the remaining SDS-insoluble pellets were suspended in 70% formic acid (FA) (Sigma, USA) to the original volume, sonicated for 35 s and centrifuged at 25,000 × g at 4°C for 1 h. The supernatant was collected as the “FA-soluble fraction” and equilibrated (1:20) in neutralization buffer (1 M Tris base, 0.5 M Na₂HPO₄, 0.05% NaN₃).

Electrochemical luminescence-linked immunoassay for Aβ and tau

Aβ and tau concentrations in brain, CSF, and plasma were determined with an electrochemical luminescence (ECL)-immunoassay using the MSD 96-Well V-PLEX Aβ Peptide Panel 1 (4G8) Kit (K15199E-1, Meso Scale Discovery, USA) and the MSD 96-Well Mouse Phospho (Thr231)/Total tau Kit (K15121D-1, Meso Scale Discovery, USA). Detection was carried out according to the manufacturer’s instructions. Briefly, 96-well plates prespotted with capture antibodies were blocked for 1 h with 1% blocking solution (1% bovine serum albumin (BSA) in Tris buffer) and washed three times with 1 × Tris buffer. In the second step, plasma were not diluted, CSF samples (5 μl) were diluted 1:10, and brain extracts were diluted up to 1:20 (depending on Aβ and tau load, to stay within the linear range of the assay) in blocking solution and co-incubated with the antibody conjugated with SULFO-TAG reagent solution on the plate for 2 h. After washing, Meso Scale Discovery Read Buffer T was added, and the plate was read immediately on a Sector Imager 6000. Data analysis using MSD DISCOVERY WORK-BENCH software 2.0. Each sample was tested in duplicate, and those with a coefficient of variance (CV) >20% were excluded from the analysis. Internal reference samples were used as a control in every plate, and the results were adjusted for interplatevariability.

Measurement of oxidative stress parameters and proinflammatory cytokines

The right hemibrains of the mice were weighed and homogenized in 9 volumes of ice-cold phosphate-buffered saline (PBS) containing a Complete Mini Protease Inhibitor Cocktail Tablet (Roche) and centrifuged at 5,000 × g for 20 min at 4°C to obtain a supernatant. Brain tissue homogenates and plasma were diluted with the buffer solution appropriate to the particular assay. The glutathione (GSH) and malondialdehyde (MDA) contents were determined spectrophotometrically with commercially available assay kits (Nanjing Jiancheng Bioengineering Institute, China), used according to the manufacturer’s instructions. The protein concentrations of the brain tissue homogenate samples were determined using a Pierce bicinchoninic acid (BCA) protein assay kit (Thermo Scientific, USA).

The levels of tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) in brain tissue homogenate and plasma were determined using TNF-α and IL-1β ELISA kits (Nanjing Jiancheng Bioengineering Institute, China) according to the manufacturer’sprotocols.

To measure the phospho tau (p-tau) and total tau (t-tau) in brain tissue using western blot

The protein concentrations of the left hemibrains tissue homogenate samples were determined using a BCA protein assay kit (Thermo Scientific, USA). The sample was separated by SDS/PAGE, transferred on to PVDF membranes. Membranes were blocked with 5% skimmed milk 1 h at room temperature, and then were probed with polyclonal pT23l antibody (1:500, Invitrogen, USA) and monoclonal anti-tau antibody (1:1000, Invitrogen, USA) overnight at 4°C. After washing three times with TPBS, IRDye^® 800-conjugated second antibody (1:3000, Rockland Immunochemicals, USA) was incubated with membranes for 1 h at room temperature. The relative density of bands was analyzed on an Odyssey infrared scanner (LI-COR Bioscience). The densitometric values were normalized with respect to the values of anti-actin (1:3000, Santa Cruz Biotechnology, USA) for immunoreactivity to correct for any loading and transfer differences between samples.

Statistical analysis

All data are presented as group means ± SEM. For the MWM learning test, we used univariate repeated measures ANOVA to analyze the data. To examine whether Aβ, tau, oxidative stress parameters, and proinflammatory cytokines levels change with aging in PS1_V97L-Tg mice and wild-type littermates, an Age trend × Genotype interaction (ANCOVA) was calculated. For the ratio of Aβ₄₂/Aβ₄₀ in mice brains, CSF, and plasma, a trend test derived from an ANOVA analysis was calculated. Differences between the youngest PS1_V97L-Tg mice group and all other age groups were analyzed with Bonferroni’s post hoc test for multiple comparisons. SPSS version 18.0 was used for statistical analysis. In all cases, statistical significance was set at p < 0.05.

RESULTS

Increased brain Aβ was the earliest pathological change in PS1_V97L-Tg mice

We examined SDS-soluble Aβ fraction in brain tissue, and Aβ in CSF and plasma using ECL-immunoassays. We found that Aβ₄₂ in brain tissues was significantly increased in the PS1_V97L-Tg mice compared with their wild-type littermates at 6 months (p < 0.01), and this discrepancy increased in older animals (Fig. 1A). Conversely, measurement of Aβ42 concentrations in the CSF and plasma of the same mice revealed marked age-related declines. Aβ₄₂ in CSF and plasma started to decrease significantly from 9 months old in the PS1_V97L-Tg mice compared with their wild-type littermates (Fig. 1B, C; p < 0.01). Similar to Aβ₄₂, Aβ₄₀ in brain tissue also started to significantly increase at 6 months (Fig. 1D; p < 0.05), but marked decreases in CSF and plasma were not observed until the animals were 18 months old (Fig. 1E, F; p < 0.05). This unequal decrease in different Aβ isoforms resulted in an age-dependent decrease in the ratio of Aβ₄₂ to Aβ₄₀ in CSF and plasma (Fig. 1H, I).

The wild-type littermates exhibited no age-related changes in brain, CSF, or plasma Aβ levels with age. We also examined the insoluble (FA-soluble fraction) Aβ₄₀ and Aβ₄₂ concentrations in brain tissues and found that insoluble Aβ₄₀ and Aβ₄₂ always remained below the lower limit of detection of the assay.

Oxidative stress was enhanced in PS1_V97L-Tg mice after detection of increased brain Aβ

We assessed the dynamic changes in oxidative stress parameters (GSH and MDA) of PS1_V97L-Tg mice, in the brain homogenates and plasma. As shown in Fig. 2, in parallel with the onset of the marked increase of brain Aβ, MDA expression in brain tissues in PS1_V97L-Tg mice was significantly increased from 6 months old onward compared with their wild-type littermates (p < 0.05). Conversely, GSH content in brain tissues was significantly decreased from 9 months old in PS1_V97L-Tg mice compared with wild-type animals (p < 0.05). The discrepancy persisted and increased over time (Fig. 2A, B). Concomitant with the changes of GSH and MDA in brain tissue, we found similar age-related changes of GSH and MDA plasma levels in the same mice (Fig. 2C, D). GSH and MDA levels were not significantly altered in the brain and plasma of wild-type littermates over time.

Neuroinflammation was activated in PS1_V97L-Tg mice after detection of increased brain Aβ

We assessed the neuroinflammation biomarkers IL-1β and TNFα in the brain homogenates and plasma of PS1_V97L-Tg mice and their wild-type littermates. As shown in Fig. 3, levels of both IL-1β and TNFα in brain homogenates and plasma of PS1_V97L–Tg mice significantly increased from 9 months old compared with their wild-type littermates (p < 0.05). These increases continued over time. Conversely, IL-1β and TNFα brain and plasma levels did not change over the lifetimes of wild-type mice.

PS1_V97L-Tg mice exhibited spatial memory impairment after detection of increased brain Aβ

We assessed spatial learning and memory in PS1_V97L-Tg mice and wild-type littermates using the MWM. At 6 months, there was no significant difference in escape latency between the two groups (p > 0.05, Fig. 4A). However, the escape latency in 9-month-old PS1_V97L-Tg mice was significantly longer than in age-matched wild-type littermates after the third training day (p < 0.05, Fig. 4B).

Spatial memory was further evaluated in the probe trial performed by removing the platform after 5 training days. We found that the PS1_V97L-Tg mice crossed the platform location less often than their wild-type littermates at 9 months (p < 0.05), but at 6 months, the two groups were not significantly different (p > 0.05, Fig. 4C). In the probe trial, PS1_V97L-Tg mice spent significantly less time in the target quadrant than their wild-type littermates at 9 months (p < 0.05), but no difference was observed at 6 months (p > 0.05, Fig. 4D). In addition, we did not find any difference in swimming speed on the first training day at either age (p > 0.05), which excludes any potential influence of motor dysfunction on escape latency (data not shown).

Tau concentrations increased as Aβ pathology progressed in PS1_V97L-Tg mice

We examined t-tau and p-tau concentrations in the same brain, CSF, and plasma samples used to determine Aβ concentrations by ECL-immunoassays. At the same time, we examined t-tau and p-tau concentrations in the brain tissue homogenate of PS1_V97L-Tg mice using western blot. As shown in Figs. 5 and 6, brain p-tau began significantly increasing from 9 months old (p < 0.01, Figs. 5A, 6B). The CSF and plasma t-tau began increasing from 12 months old (p < 0.01, Fig. 5B, D). The brain t-tau did not significantly change with advancing age in either PS1_V97L-Tg mice (Fig. 6C) or wild-type littermates (Fig. 5C). CSF and plasma p-tau levels always remained below the lower limit of detection of the assay.

DISCUSSION

In the present study, we found that shortly after the marked increase of Aβ in the brain of PS1_V97L-Tg mice, plasma and CSF Aβ₄₂ concentrations started to decline, oxidative stress and neuroinflammation were enhanced, PS1_V97L-Tg mice exhibited spatial memory impairment, and, finally, brain p-tau and CSF and plasma t-tau significantly increased compared to age-matched wild-type littermates. Simultaneously, we found that plasma levels of Aβ₄₂ and t-tau, oxidative stress parameters, and proinflammatory cytokines were capable of differentiating between PS1_V97L-Tgmice and wild-type littermates at different time points.

Aβ is produced from the larger AβPP by proteolytic cleavages executed by different secretase enzymes; this process is reported as closely related to the pathological process of AD [9, 10]. We used the MSD platform of high-sensitivity assay for Aβ in brain parenchyma, CSF, and plasma in PS1_V97L-Tg mice. The results revealed that following the brain Aβ increase, CSF and plasma Aβ₄₂ concentrations began to decrease. We previously reported that the PS1 V97L gene mutation could lead to intraneuronal accumulation of Aβ oligomers without Aβ plaques in the PS1_V97L-Tg mice, and these oligomers first appeared in the brains of 6-month-old animals [6]. In agreement with previous study findings, we found that Aβ concentrations in the brain homogenate began to increase at the same time. It has been hypothesized that the decreases in CSF and plasma Aβ₄₂ reflect the pathological alteration of intraneuronal Aβ oligomer accumulation. Similar to Aβ₄₂, Aβ₄₀ in brain tissue also started to increase significantly at 6 months, but CSF and plasma levels did not decrease until 18 months old. We presumed that the main component of intraneuronal Aβ oligomers was Aβ₄₂. A recent study demonstrated that insoluble Aβ correlated with amyloid load, and its biochemical detection reflected plaque formation [11]. We found that the brain insoluble (FA-soluble fraction) Aβ₄₀ and Aβ₄₂ levels always remained below the lower limit of detection of the assay at all time points assessed, which is consistent with previous reports of a lack of Aβ plaques in the brain of PS1_V97L-Tg mouse [6]. In this study, we found a very interesting phenomenon— that the brain Aβ₄₀ levels are contrary with those shown in our previous study [6]. A recent study has shown that most of the Aβ required SDS for solubilization and surprisingly little was extracted into TBS. In the present study, we measured the SDS-soluble Aβ fraction. But, in a previous study, we only measured the TBS-soluble Aβ fraction. Other studieshave reached similar conclusions using the same experimental approaches [12].

Increasing evidence suggests that oxidative stress plays significant roles in disease progression, particularly in cellular and tissue damage, and oxidative damage in the brain is closely related to neurodegenerative conditions, including AD [13, 14]. However, whether oxidative stress is involved in AD onset remains unclear. The brain is particularly susceptible to oxidative stress because of its high oxygen consumption rate, abundance of unsaturated lipids, and relatively low availability of antioxidant enzymes compared with other organs [15]. MDA is an end product of free radical generation, and GSH is an endogenous antioxidant that plays a vital role as a free radical scavenger to protect cells against oxidative damage. In the present study, simultaneously with or shortly after the brain Aβ increase, MDA levels were significantly increased (at 6 months old). Later, GSH levels were markedly decreased (at 9 months old) in the brain and plasma of PS1_V97L-Tg mice compared with their wild-type littermates. Thus, our findings suggest that an antioxidant/oxidant imbalance may be responsible for increased Aβ in the brain. In agreement with our findings, oxidative stress was reported to play a significant role in AD pathogenesis[16].

Chronic inflammatory response has been widely documented in the AD brain. One study described activated microglia and increased expression of many inflammatory markers, including TNFα and IL-1β [17]. TNFα can induce neuronal apoptosis, interfere with intracellular calcium homeostasis, and suppress long-term potentiation (LTP) [18]. IL-1β is an important proinflammatory cytokine that can promote Aβ production and plaque deposition [19]. In the present study, IL-1β and TNFα concentrations in the brain and plasma of PS1_V97L-Tg mice showed marked age-related increases after the onset of increased brain Aβ levels. This result suggests that a chronic inflammatory response was induced by the higher brain Aβ levels in PS1_V97L-Tg mice. At the same time, we found that the changes of IL-1β and TNFα plasma levels can reflect the condition of the brain. Peripheral immune alterations in AD patients might be triggered by brain immune activation, given the existence of inflammatory signaling pathways from the brain to the periphery involving sympathetic and neuroendocrine systems [20]. Intracerebroventricular injection of Aβ₄₂ in mice causes increases IL-6 levels in both the brain and plasma, demonstrating that centrally administered Aβ induces a systemic IL-6 response [21].

The MWM test is used for assessing learning and memory [22]. In the present study, we found that after a detectable increase in brain Aβ levels, memory dysfunction was measurable in 9-month-old PS1_V97L-Tg mice. It is reasonable to hypothesize that the cognitive deficits in PS1_V97L-Tg mice are due to Aβ pathology. Other studies have reached similar conclusions using different experimental approaches [23, 24].Aβ toxicity can activate oxidative stress and neuroinflammation, which may induce synaptic loss and the inhibition of LTP, leading to memory dysfunction [6, 23].

A popular area of AD pathogenesis research is the link between Aβ and tau pathology. Much of the present evidence favors Aβ formation as the primary driving force behind AD pathogenesis, with tau pathology following as a consequential event [25]. However, Braak and Del Tredici [26] argued for a primary deposition of tau, which in turn drives the formation, release, and accumulation of Aβ in the form of extracellular plaques. We investigated the age-dependent sequential appearance of pathology in an attempt to determine whether there is a potential causal relationship between Aβ aggregation and tau hyperphosphorylation in PS1_V97L-Tg mice. The dynamic changes of tau in brain, CSF, and plasma were examined along the PS1_V97L-Tg mouse lifespan using the highly sensitive MSD platform. We found that shortly after the brain Aβ increase, brain p-tau significantly increased at 9 months old, and the CSF and plasma t-tau significantly increased at 12 months old. The discrepancies between transgenic and wild-type animals persisted and increased over time. The findings of western blot are consistent with the results of ECL-immunoassay. Thus, our findings suggest that increased brain Aβ may induce tau hyperphosphorylation. Tau is highly expressed in cortical axons, and the increase of CSF t-tau reflects its extracellular release after neuronal degeneration and neurofibrillary tangle formation [27]. In our study, we measured both t-tau and p-tau 231 proteins, but the latter could not be detected in CSF or plasma. This may be attributable to two reasons. First, p-tau has a much lower concentration in both CSF and plasma. Second, p-tau proteins have different isoforms (e.g., p-tau 181, 199, 231) [28], we only measured p-tau231 proteins. These findings are consistent with those of several other studies [27, 29].

Oxidative stress and neuroinflammation participate in AD pathogenesis by promoting Aβ accumulation and tau hyperphosphorylation [30, 31]. In the present study, we found that following the brain Aβ increase in PS1_V97L-Tg mice, oxidative stress and neuroinflammation were enhanced, which was followed by tau hyperphosphorylation. Aβ-induced tau hyperphosphorylation may be due to greater oxidative stress and neuroinflammation. A number of studies have identified multiple interactive mechanisms that lead to the development of AD pathology, including Aβ production, tau hyperphosphorylation, oxidative stress, and neuroinflammatory responses [32, 33]. Intracellular Aβ accumulation promotes significant oxidative stress and neuroinflammation that stimulates a vicious cycle, with each event facilitating the other [32, 34], finally resulting in tau hyperphosphorylation. However, we cannot exclude the involvement of other mechanisms, and this needs to be clarified in further investigations.

In conclusion, our results indicate that the increased brain Aβ plays an initiating role in the pathophysiological process of AD. Aβ toxicity induces tau hyperphosphorylation, possibly via oxidative stress and neuroinflammation reaction. Importantly, plasma biomarkers can reflect the pathophysiological processes of the AD brain.

Footnotes

ACKNOWLEDGMENTS

This study was supported by the Key Project of the National Natural Science Foundation of China (81530036), Beijing Postdoctoral Research Foundation (2015ZZ-60), CHINA-CANADA Joint Initiative on Alzheimer’s Disease and Related Disorders (81261120571), Key Medical Professional Development Plan of Beijing Municipal Administration of Hospitals (ZYLX201301), Mission Program of Beijing Municipal Administration of Hospitals (SML20150801), the National Key Technology R&D Program in the Eleventh Five-year Plan Period (2006BAI02B01).

Authors’ disclosures available online ().

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Brain Amyloid-β Plays an Initiating Role in the Pathophysiological Process of the PS1 V97L -Tg Mouse Model of Alzheimer’s Disease

Abstract

Keywords

INTRODUCTION

MATERIALS AND METHODS

Ethics statement

Animals

Behavioral tests

Sample harvesting

Biochemical analysis of brain tissue

Electrochemical luminescence-linked immunoassay for Aβ and tau

Measurement of oxidative stress parameters and proinflammatory cytokines

To measure the phospho tau (p-tau) and total tau (t-tau) in brain tissue using western blot

Statistical analysis

RESULTS

Increased brain Aβ was the earliest pathological change in PS1V97L-Tg mice

Oxidative stress was enhanced in PS1V97L-Tg mice after detection of increased brain Aβ

Neuroinflammation was activated in PS1V97L-Tg mice after detection of increased brain Aβ

PS1V97L-Tg mice exhibited spatial memory impairment after detection of increased brain Aβ

Tau concentrations increased as Aβ pathology progressed in PS1V97L-Tg mice

DISCUSSION

Footnotes

ACKNOWLEDGMENTS

References

Increased brain Aβ was the earliest pathological change in PS1_V97L-Tg mice

Oxidative stress was enhanced in PS1_V97L-Tg mice after detection of increased brain Aβ

Neuroinflammation was activated in PS1_V97L-Tg mice after detection of increased brain Aβ

PS1_V97L-Tg mice exhibited spatial memory impairment after detection of increased brain Aβ

Tau concentrations increased as Aβ pathology progressed in PS1_V97L-Tg mice