Study on dynamic characteristics' change of hippocampal neuron reduced models caused by the Alzheimer's disease

Electroacupuncture Improves Learning and Memory Abilities via Activating AMPK/mTOR-Induced Autophagy in APP/PS1 Mice

Alzheimer's disease (AD) has become a global public health problem characterized by memory and cognitive impairments. Electroacupuncture (EA) has been indicated to exert promising therapeutic effects on AD. This study aimed to further investigate the underlying mechanism of EA in AD treatment. APP/PS1 transgenic mice and wide-type mice underwent with or without EA treatment at GV20 and BL23 acupoints. Morris water maze test was utilized for examining the learning and memory of mice. Hematoxylin-eosin, Congo red, immunofluorescence, and TUNEL staining were employed for detecting the pathological changes of mouse brain hippocampus. Western blotting was implemented for measuring protein levels of autophagy- and AMPK/mTOR pathway-associated markers. APP/PS1 mice exhibited significant impairments in the spatial learning and memory. EA treatment improved the cognitive impairments, reduced amyloid-beta (Aβ) deposition, and alleviated neuronal apoptosis in the hippocampal tissues of APP/PS1 mice. EA promoted autophagy and activated the AMPK/mTOR signaling pathway in the hippocampus of APP/PS1 mice. EA improves the cognitive deficits, enhances Aβ clearance, and attenuates neuronal apoptosis in APP/PS1 mice in part by activating AMPK/mTOR-mediated autophagy.

Complexity decline of hippocampal CA1 circuit model due to cholinergic deficiency associated with Alzheimer's disease

A hallmark of Alzheimer's disease (AD) is cholinergic system dysfunction, directly affecting the hippocampal neurons. Previous experiments have demonstrated that reduced complexity is one significant effect of AD on electroencephalography (EEG). Motivated by these, this study explores reduced EEG complexity of cholinergic deficiency in AD by neurocomputation. We first construct a new hippocampal CA1 circuit model with cholinergic action. M-current I M and calcium-activated potassium current I AHP are newly introduced in the model to describe cholinergic input from the medial septum. Then, by enhancing I M and I AHP to mimic cholinergic deficiency, how cholinergic deficiency influences the model complexity is investigated by sample entropy (SampEn) and approximate entropy (ApEn). Numerical results show a more severe cholinergic deficit with lower model complexity. Furthermore, we conclude that the decline of SampEn and ApEn is due to the greatly diminished excitability of model neurons. These suggest that decreased neuronal excitability due to cholinergic impairment may contribute to reduced EEG complexity in AD. Subsequently, statistical analysis between simulated AD patients and normal control (NC) groups demonstrates that SampEn and auto-mutual-information (AMI) decrease rates significantly differ. Compared to NC, AD patients have a lower SampEn and a less negative AMI decline rate. These imply a low rate of new-generation information in AD brains with cholinergic deficits. Interestingly, the statistical correlation between SampEn and AMI is analyzed, and they have a large negative Pearson correlation coefficient. Thus, AMI reduction rates may be a complementary tool for complex analysis. Our modeling and complex analysis are expected to provide a deeper understanding of the reduced EEG complexity resulting from cholinergic deficiency.

The important role of glial transmitters released by astrocytes in Alzheimer's disease: A perspective from dynamical modeling

This paper aims to establish a coupling model of neuronal populations and astrocytes and, on this basis, explore the possible mechanism of electroencephalography (EEG) slowing in Alzheimer's disease (AD) from the viewpoint of dynamical modeling. First and foremost, excitatory and inhibitory time constants are shown to induce the early symptoms of AD. The corresponding dynamic nature is mainly due to changes in the amplitude and frequency of the oscillatory behavior. However, there are also a few cases that can be attributed to the change of the oscillation mode caused by the limit cycle bifurcation and birhythmicity. Then, an improved neural mass model influenced by astrocytes is proposed, considering the important effects of glutamate and adenosine triphosphate (ATP) released by astrocytes on the synaptic transmission process reported in experiments. The results show that a dysfunctional astrocyte disrupts the physiological state, causing three typical EEG slowing phenomena reported clinically: the decreased dominant frequency, the decreased rhythmic activity in the α band, and the increased rhythmic activity in the δ+θ band. In addition, astrocytes may control AD when the effect of ATP on synaptic connections is greater than that of glutamate. The control rate depends on the ratio of the effect of glutamate on excitatory and inhibitory synaptic connections. These modeling results can not only reproduce some experimental and clinical results, but, more importantly, may offer a prediction of some underlying phenomena, helping to inspire the disease mechanisms and therapeutic methods of targeting astrocytes.

Electroacupuncture at ST 36 ameliorates cognitive impairment and beta-amyloid pathology by inhibiting NLRP3 inflammasome activation in an Alzheimer's disease animal model

Background

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder leading to cognitive impairment in the elderly, and no effective treatment exists. Increasing evidence has demonstrated that physical therapy and electroacupuncture (EA) effectively improve spatial learning and memory abilities. Nevertheless, the mechanism underlying the effects of EA on AD pathology is largely unexplored. Acupuncture at Zusanli (ST 36) has previously been shown to improve cognitive impairment in AD, but the mechanism is unclear. According to recent studies, EA drives the vagal-adrenal axis from the hindlimb ST 36 acupoint but not from the abdominal Tianshu (ST 25) to curb severe inflammation in mice. This study examined whether ST 36 acupuncture improves cognitive dysfunction in AD model mice by improving neuroinflammation and its underlying mechanism.

Methods

Male 5xFAD mice (aged 3, 6, and 9 months) were used as the AD animal model and were randomly divided into three groups: the AD model group (AD group), the electroacupuncture at ST 36 acupoint group (EA-ST 36 group), and the electroacupuncture at ST 25 acupoint group (EA-ST 25 group). Age-matched wild-type mice were used as the normal control (WT) group. EA (10 Hz, 0.5 mA) was applied to the acupoints on both sides for 15 min, 5 times per week for 4 weeks. Motor ability and cognitive ability were assessed by the open field test, the novel object recognition task, and the Morris water maze test. Thioflavin S staining and immunofluorescence were used to mark Aβ plaques and microglia. The levels of NLRP3, caspase-1, ASC, interleukin (IL)-1β, and IL-18 in the hippocampus were assayed by Western blotting or qRT-PCR.

Results

EA at ST 36, but not ST 25, significantly improved motor function and cognitive ability and reduced both Aβ deposition and microglia and NLRP3 inflammasome activation in 5×FAD mice.

Conclusion

EA stimulation at ST 36 effectively improved memory impairment in 5×FAD mice by a mechanism that regulated microglia activation and alleviated neuroinflammation by inhibiting the NLRP3 inflammatory response in the hippocampus. This study shows that ST 36 may be a specific acupoint to improve the condition of AD patients.

How glutamatergic synapse loss affects the firing rhythm of DG-CA3 model related with Alzheimer's disease

As well known that synapse loss is a significant pathological feature of Alzheimer's disease (AD), meanwhile, the hippocampus is one of brain regions to be first affected in the early stage of AD. Thus, this work employs a comprehensive DG-CA3 network model of the hippocampus so as to explore the neuronal correlation between glutamatergic synapse loss and abnormal firing rhythm associated with AD from the perspective of neurocomputation. The neuropathological condition of glutamatergic synapse loss caused by the reduction of Shank3 protein in AD patients is imitated by decreasing glutamatergic excitatory synapse strength between different neurons. By means of power spectral analysis and dynamics technique, the numerical results reveal that excitability of pyramidal neuron as well as oriens lacunosum-moleculare (O-LM) cell in CA3 region is strongly degraded by the decrease of NMDA or AMPA-type glutamatergic excitatory synapse strength. Moreover, the relative power together with the peak of relative power density within alpha band is also diminished by decreasing glutamatergic synapse strength. These findings accord with the electrophysiological experiment of EEG that there is a decrease of alpha rhythm for AD patients, on the same time, they could highlight the significance of glutamatergic synapse loss in the pathogenesis of AD.

Dynamics analysis of the hippocampal neuronal model subjected to cholinergic action related with Alzheimer's disease

There are evidences that the region of hippocampus is affected in the early stage of Alzheimer's disease (AD). Moreover, the hippocampal pyramidal neurons receive cholinergic input from the medial septum. Thus, this study, based on the results of electrophysiological experiments, first constructs a modified hippocampal CA1 pyramidal neuronal model by introducing two new currents of M-current and calcium ion-activated potassium ion current to depict the cholinergic input receiving from the medial septum, and then explores how acetylcholine deficiency and beta-amyloid accumulation under the pathological condition of AD influence the neuronal dynamics in terms of theta band power and spiking frequency using computational approach. By simulating acetylcholine potentiated M-current and calcium ion-activated potassium ion current, numerical results reveal that the relative theta band power increases significantly and the firing rate decreases obviously when acetylcholine is deficient. Similarly, by simulating beta-amyloid enhanced delay rectification potassium ion current, we also detect that the relative theta band power increases as well as the firing rate decreases remarkably as beta-amyloid is accumulated. In addition, the mechanism underlying these dynamical changes in theta rhythm and firing behavior is investigated by nonlinear behavioral analysis, which demonstrates that both deficiency in acetylcholine and accumulation in beta-amyloid can promote the emergence of stable equilibrium state in this modified hippocampal neuronal model. Note that acetylcholine deficiency together with beta-amyloid deposition plays key role in the pathogenesis of AD. We expect these findings could have important implications on better understanding pathogenesis and expounding potential biomarkers for AD.

Electroacupuncture ameliorate learning and memory by improving N-acetylaspartate and glutamate metabolism in APP/PS1 mice

Objective

To explore the precise mechanism of electroacupuncture (EA) to delay cognitive impairment in Alzheimer disease.

Methods

N-Acetylaspartate (NAA), glutamate (Glu) and myoinositol (mI) metabolism were measured by magnetic resonance spectroscopy, learning and memory of APP/PS1 mouse was evaluated by the Morris water maze test and the step-down avoidance test, neuron survival number and neuronal structure in the hippocampus were observed by Nissl staining, and BDNF and phosphorylated TrkB detected by Western blot.

Results

EA at DU20 acupuncture significantly improve learning and memory in behavioral tests, up-regulate NAA, Glu and mI metabolism, increase the surviving neurons in hippocampus, and promote the expression of BDNF and TrkB in the APP/PS1 transgenic mice.

Conclusion

These findings suggested that EA is a potential therapeutic for ameliorate cognitive dysfunction, and it might be due to EA could improve NAA and Glu metabolism by upregulation of BDNF in APP/PS1 mice.