Aβ1-42 In Mice Research Articles

Hippocampal GPR35 Participates in the Pathogenesis of Cognitive Deficits and Emotional Alterations Induced by Aβ1-42 in Mice.

The amyloid-beta (Aβ) aggregation in Alzheimer's disease (AD) triggers neuroinflammation, and neurodegeneration, which lead to cognitive deficits along with other neuropsychiatric symptoms, including depression and anxiety. G protein-coupled receptor 35 (GPR35) is expressed in the brain and is involved in metabolic stresses. However, the role of GPR35 in AD pathogenesis remains unknown. Herein, pharmacological blockade, shRNA-mediated knockdown or knockout of GPR35 was performed to investigate the role and mechanisms of GPR35 in Aβ1-42-induced cognitive impairment and emotional alterations in mice. A series of behavioral, histopathological, and biochemical tests were performed in mice. Our results showed that hippocampal GPR35 expression was significantly increased in Aβ1-42-induced and APP/PS1 AD mouse models. Pharmacological blockade or knockdown of GPR35 ameliorated cognitive impairment and emotional alterations induced by Aβ1-42 in mice. We also found that blockade or knockdown of GPR35 decreased the accumulation of Aβ, and improved neuroinflammation, cholinergic system deficiency, and neuronal apoptosis via the RhoA/ROCK2 pathway in Aβ1-42-treaed mice. However, activation of GPR35 aggravates Aβ1-42-induced cognitive deficits and emotional alterations in mice. In addition, genetic deletion of GPR35 protects against the Aβ1-42-induced cognitive deficits and emotional alterations in mice. Moreover, GPR35 could bind to TLR4. These results indicate that GPR35 participates in the pathogenesis of cognitive deficits and emotional alterations induced by Aβ1-42 in mice, suggesting that GPR35 could be a potential therapeutic target for AD.

Sex differences in luteinizing hormone aggravates Aβ deposition in APP/PS1 and Aβ1-42-induced mouse models of Alzheimer's disease

Alzheimer's disease (AD) exhibits a higher incidence rate among older women, and dysregulation of the hypothalamic-pituitary-gonadal (HPG) axis during aging is associated with cognitive impairments and the development of dementia. luteinizing hormone (LH) has an important role in CNS function, such as mediating neuronal pregnenolone production, and modulating neuronal plasticity and cognition. The sex differences in LH and its impact on Aβ deposition in AD individuals remain unclear, with no reported specific mechanisms. Here, we show through data mining that LH-related pathways are significantly enriched in female AD patients. Additionally, LH levels are elevated in female AD patients and exhibit a negative correlation with cognitive levels but a positive correlation with AD pathology levels, and females exhibit a greater extent of AD pathology, such as Aβ deposition. In vivo, we observed that the exogenous injection of LH exacerbated behavioral impairments induced by Aβ1-42 in mice. LH injection resulted in worsened neuronal damage and increased Aβ deposition. In SH-SY5Y cells, co-administration of LH with Aβ further exacerbated Aβ-induced neuronal damage. Furthermore, LH can dose-dependently decrease the levels of NEP and LHR proteins while increasing the expression of GFAP and IBA1 in vivo and in vitro. Taken together, these results indicate that LH can exacerbate cognitive impairment and neuronal damage in mice by increasing Aβ deposition. The potential mechanism may involve the reduction of NEP and LHR expression, along with the exacerbation of Aβ-induced inflammation.

Pinoresinol diglucoside attenuates neuroinflammation, apoptosis and oxidative stress in a mice model with Alzheimer's disease.

For Alzheimer's disease (AD), there is still no effective treatment strategy. Pinoresinol diglucoside (PDG) is one of the major lignans isolated from Eucommia ulmoides. It is endowed with multiple pharmacological activities, including anti-inflammatory, antioxidant and anticancer activities. In this study, we investigated the potential neuroprotective functions of PDG in AD. Mice model with AD was established adopting stereotactic hippocampal injection of Aβ1-42 (410 pmol/mouse), and 3 days later, mice were administrated with 5 and 10 mg/kg PDG by intragastric administration every day for 3 weeks. Morris water maze and Y-maze tests demonstrated that PDG treatment could markedly reverse Aβ1-42-induced memory impairment in mice. It is found that PDG restrained the release of proinflammatory cytokines (tumor necrosis factor α and interleukin 1β), reactive oxygen species and malondialdehyde, and promoted the activity of the antioxidant enzyme (superoxide dismutase and catalase) by quantitative real-time-PCR, colorimetric method and ELISA assay. Western blot assay results have shown that PDG could also upregulate the ratio of Bcl-2/Bax and downregulate cytochrome c and cleaved caspase-3 expressions, thereby inhibiting neuronal apoptosis. Furthermore, PDG also significantly reduced the expression of Toll-like receptor 4 (TLR4) and the activation of nuclear factor-κB (NF-κB) p65, and promoted nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expressions. In conclusion, PDG can attenuate neuroinflammation, neuronal apoptosis and oxidative stress through the TLR4/NF-κB and Nrf2/HO-1 pathways, and ameliorate memory dysfunction induced by Aβ1-42 in mice.

Oligomer β-amyloid Induces Hyperactivation of Ras to Impede NMDA Receptor-Dependent Long-Term Potentiation in Hippocampal CA1 of Mice.

The activity of Ras, a small GTPase protein, is increased in brains with Alzheimer’s disease. The objective of this study was to determine the influence of oligomeric Aβ1-42 on the activation of Ras, and the involvement of the Ras hyperactivity in Aβ1-42-induced deficits in spatial cognition and hippocampal synaptic plasticity. Herein, we show that intracerebroventricular injection of Aβ1-42 in mice (Aβ-mice) enhanced hippocampal Ras activation and expression, while 60 min incubation of hippocampal slices in Aβ1-42 (Aβ-slices) only elevated Ras activity. Aβ-mice showed deficits in spatial cognition and NMDA receptor (NMDAR)-dependent long-term potentiation (LTP) in hippocampal CA1, but basal synaptic transmission was enhanced. The above effects of Aβ1-42 were corrected by the Ras inhibitor farnesylthiosalicylic acid (FTS). ERK2 phosphorylation increased, and Src phosphorylation decreased in Aβ-mice and Aβ1-42-slices. Both were corrected by FTS. In CA1 pyramidal cells of Aβ1-42-slices, the response of AMPA receptor and phosphorylation of GluR1 were enhanced with dependence on Ras activation rather than ERK signaling. In contrast, NMDA receptor (NMDAR) function and GluN2A/2B phosphorylation were downregulated in Aβ1-42-slices, which was recovered by application of FTS or the Src activator ouabain, and mimicked in control slices treated with the Src inhibitor PP2. The administration of PP2 impaired the spatial cognition and LTP induction in control mice and FTS-treated Aβ-mice. The treatment of Aβ-mice with ouabain rescued Aβ-impaired spatial cognition and LTP. Overall, the results indicate that the oligomeric Aβ1-42 hyperactivates Ras and thereby causes the downregulation of Src which impedes NMDAR-dependent LTP induction resulting in cognitive deficits.

The Interplay Between Beta-Amyloid 1-42 (Aβ1-42)-Induced Hippocampal Inflammatory Response, p-tau, Vascular Pathology, and Their Synergistic Contributions to Neuronal Death and Behavioral Deficits.

Alzheimer’s disease (AD), the most common chronic neurodegenerative disorder, has complex neuropathology. The principal neuropathological hallmarks of the disease are the deposition of extracellular β-amyloid (Aβ) plaques and neurofibrillary tangles (NFTs) comprised of hyperphosphorylated tau (p-tau) protein. These changes occur with neuroinflammation, a compromised blood-brain barrier (BBB) integrity, and neuronal synaptic dysfunction, all of which ultimately lead to neuronal cell loss and cognitive deficits in AD. Aβ1–42 was stereotaxically administered bilaterally into the CA1 region of the hippocampi of 18-month-old male C57BL/6 mice. This study aimed to characterize, utilizing immunohistochemistry and behavioral testing, the spatial and temporal effects of Aβ1–42 on a broad set of parameters characteristic of AD: p-tau, neuroinflammation, vascular pathology, pyramidal cell survival, and behavior. Three days after Aβ1–42 injection and before significant neuronal cell loss was detected, acute neuroinflammatory and vascular responses were observed. These responses included the up-regulation of glial fibrillary acidic protein (GFAP), cell adhesion molecule-1 (PECAM-1, also known as CD31), fibrinogen labeling, and an increased number of activated astrocytes and microglia in the CA1 region of the hippocampus. From day 7, there was significant pyramidal cell loss in the CA1 region of the hippocampus, and by 30 days, significant localized up-regulation of p-tau, GFAP, Iba-1, CD31, and alpha-smooth muscle actin (α-SMA) in the Aβ1–42-injected mice compared with controls. These molecular changes in Aβ1–42-injected mice were accompanied by cognitive deterioration, as demonstrated by long-term spatial memory impairment. This study is reporting a comprehensive examination of a complex set of parameters associated with intrahippocampal administration of Aβ1–42 in mice, their spatiotemporal interactions and combined contribution to the disease progression. We show that a single Aβ injection can reproduce aspects of the inflammatory, vascular, and p-tau induced pathology occurring in the AD human brain that lead to cognitive deficits.

Effect of (m)VD-hemopressin against Aβ1-42-induced oxidative stress and apoptosis in mouse hippocampal neurons

Alzheimer’s disease (AD) is a serious neurodegenerative disease. Senile plaques (SPs) composed of amyloid-β (Aβ) are typical features of AD. Aβ plays a key role in the disease and has the ability to induce other pathological characteristics of AD, including oxidative stress injury. (m)VD-hemopressin (VD), a peptide derived from mouse brain extracts, can bind cannabinoid 1 receptor (CB1R) as an agonist. Our previous report indicated that VD reverses memory impairment induced by Aβ1-42 in mice. This study aimed to clarify the mechanism by which VD protects hippocampal neurons against Aβ1-42-induced impairment. Our results showed that VD inhibited oxidative stress injury induced by Aβ1-42, as demonstrated by the VD-induced reversal of the upregulation of reactive oxygen species (ROS) and the intracellular lipid peroxidation product malondialdehyde (MDA) and the downregulation of the activities of the antioxidative enzymes catalase (CAT) and glutathione peroxidase (GSH-PX) in mouse hippocampal neurons. We also found that VD restored the decrease in cell growth and viability induced by Aβ1-42 and reversed Aβ1-42-induced apoptosis mediated by the apoptosis-associated proteins Bcl-2 and Bax. However, cotreatment with AM251 (an antagonist of CB1R) blocked the effects of VD. In brief, this study suggested that through CB1R, VD reversed the impairment of cell growth and viability, oxidative stress injury and apoptosis induced by Aβ1-42. Therefore, VD may be a promising agent for the treatment of diseases that involve oxidative stress injury and apoptosis induced by Aβ1-42, such as AD.

Ameliorative Effects of Dendropanax morbifera on Cognitive Impairment Via Enhancing Cholinergic Functions and Brain-Derived Neurotrophic Factor Expression in β-Amyloid-Induced Mice.

Alzheimer's disease accounts for the majority of dementia and shows hallmarks such as sequential cognitive dysfunction and abnormal behavior. Dendropanax morbifera (DM) has traditionally been used to treat a variety of diseases in East Asia. The aim of this study was to assess the therapeutic effects of DM on brain neuron damage and on cognitive deficit in neuronal cell induced by Aβ1-42 in mice. Treatment with DM reduced the levels of intracellular reactive oxygen species and protected against the death of neuronal cells induced by Aβ1-42 peptide. In addition, it was also found that pretreatment with DM decreased cognitive damage induced by Aβ peptide via enhancing the cholinergic system and antioxidant defense system in mice. Furthermore, the study verified that the change in the expression of both cyclic-adenosine monophosphate response element binding protein and of brain-derived neurotrophic factor in the hippocampus in Aβ peptide-treated mice was significantly ameliorated after treatment with DM. Accordingly, these results suggest that pretreatment with DM defends against oxidative stress and cognitive impairment caused by Aβ peptide.

Administration of Repetitive Transcranial Magnetic Stimulation Attenuates Aβ 1-42-Induced Alzheimer's Disease in Mice by Activating β-Catenin Signaling.

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive and painless technique that has been applied for the treatments of diverse neurodegenerative disorders. In the current study, its anti-Alzheimer's disease (AD) effect was assessed and the mechanism driving the effect was explored. The AD symptoms were induced via the intracranial injection of Aβ1-42 in mice and then treated with rTMS of 1 Hz or 10 Hz. The anti-AD effect of rTMS was assessed by Morris water maze (MWM), histological staining and western blotting. The results showed that rTMS administrations of both frequencies improved the cognitive function and suppressed neuron apoptosis in AD mice. Moreover, the treatment also increased the brain BDNF, NGF, and doublecortin levels, which represented the increased viability of neurons by rTMS. The injection of Aβ1-42 also increased the expressions of p-GSK-3β, p-Tau, and p-β-catenin and suppressed the level of total β-catenin. After the treatments of rTMS, the level of β-catenin was restored, indicating the activation of β-catenin signaling. In conclusion, the findings outlined in the current study demonstrated that the anti-AD effect of rTMS was associated with the activation of β-catenin, which would promote the survival of neurons.

Deoxyschizandrin attenuates Aβ1–42-induced cognitive impairments through up-regulation of AMPA receptors in mice

The present study was undertaken to investigate the possible effect of deoxyschizandrin (DSD) on improving cognitive impairment in mice induced by β-amyloid (Aβ). The Aβ1-42 was injected into the hippocampus of male mice and the mice were treated by DSD (0.01 or 0.1 mg/kg) or their vehicles into the lateral ventricle until the start of behavioral tests. The cognitive improvement effect was assessed by the Y-maze, shuttle box and the Morris water maze test. The changes in the levels of AMPA receptors (GluR1 and GluR2), amounts of β-secretase and acetyl cholinesterase (AChE) in the cortex and hippocampus were detected. Moreover, hippocampus neurons in the CA1 subfield were examined. The results showed that intracerebroventricular (i.c.v.) administration of DSD (0.1 mg/kg) significantly reversed cognitive impairments induced by Aβ1-42 in mice. Remarkably, DSD (0.1 mg/kg, i.c.v.) was found to decrease the levels of AChE and β-secretase in hippocampus and frontal cortex, respectively. in addition to increasing the expressions both in GluR1 and GluR2. These results demonstrated DSD could improve the behavioral disorders, inhibit β-secretase and restore AChE, glutamate, synaptic dysfunction and loss induced by Aβ1-42. Moreover, the histology assay in the hippocampus of mice indicated that the neurotrophic effects of DSD.

Dose-Dependent Neuroprotection and Neurotoxicity of Simvastatin through Reduction of Farnesyl Pyrophosphate in Mice Treated with Intracerebroventricular Injection of Aβ 1-42.

Simvastatin (SV) has been reported to improve dementia and slow progression of Alzheimer's disease (AD), however there are conflicting reports. Intracerebroventricular injection of aggregated Aβ1-42 in mice (Aβ1-42-mice) caused spatial cognitive deficits, long-term potentiation (LTP) impairment, and death of hippocampal pyramidal cells. The present study focused on exploring the dose-dependent effects of SV (10-80 mg/kg) on Aβ1-42-impaired spatial memory and the underlying mechanisms. The treatment of Aβ1-42-mice with SV for continuous 15 days could attenuate the spatial cognitive deficits and recover the LTP induction in a "U" type dose-dependent manner. The death of pyramidal cells in Aβ1-42-mice was significantly reduced by the SV-treatment at 20 mg/kg, but not at a dose of 10 or 40 mg/kg, even was aggravated at a dose of 80 mg/kg. Hippocampal NMDA receptor (NMDAr) NR2B phosphorylation (phospho-NR2B) was elevated in Aβ1-42-mice, which was further dose-dependently increased by SV-treatment. Replenishment of isoprenoid farnesyl pyrophosphate (FPP) by applying farnesol (FOH) could abolish the SV-increased phospho-NR2B in Aβ1-42-mice, but had no effect on the Aβ1-42-enhanced phospho-NR2B. NMDAr antagonist blocked the neurotoxicity of Aβ1-42 and SV (80 mg/kg) in Aβ1-42-mice, whereas FOH only inhibited SV (80 mg/kg)-neurotoxicity. The SV-treatment in Aβ1-42-mice corrected the decrease in hippocampal Akt phosphorylation. The PI3K inhibitor abolished the SV (20 mg/kg)-neuroprotection in Aβ1-42-mice. SV-treatment in Aβ1-42-mice exerts dose-dependent neuroprotection and neurotoxicity by reducing FPP to enhance the phosphorylation of NR2B and Akt.

In vivo Diffusion Tensor Imaging of Amyloid-β-Induced White Matter Damage in Mice

Diffusion tensor imaging (DTI) suggests the presence of white matter abnormality at the prodromal stage in human Alzheimer's disease (AD). To use a mouse model of AD to determine whether the white matter abnormality detected by in vivo DTI is associated with functional deficits and axon damage. Amyloid-β1-42 (Aβ1-42) was injected into the left lateral ventricle in mice. Two months after the injection, in vivo DTI and visual evoked potential (VEP) recordings were performed, followed by immunohistochemistry of phosphorylated neurofilament and myelin basic protein. DTI of Aβ1-42-treated mice showed a significant increase of radial diffusivity in white matter including the optic nerves and tracts. The abnormality was associated with decreased amplitude and increased latency of VEP. Immunohistochemistry confirmed a significant loss of axons and myelin integrity. White matter damage induced by Aβ1-42 in mice can be detected non-invasively by DTI.