Standardized Herbal Formula PM012 Decreases Cognitive Impairment and Promotes Neurogenesis in the 3xTg AD Mouse Model of Alzheimer's Disease

Mechanism, prevention and treatment of cognitive impairment caused by high altitude exposure

Hypobaric hypoxia (HH) characteristics induce impaired cognitive function, reduced concentration, and memory. In recent years, an increasing number of people have migrated to high-altitude areas for work and study. Headache, sleep disturbance, and cognitive impairment from HH, severely challenges the physical and mental health and affects their quality of life and work efficiency. This review summarizes the manifestations, mechanisms, and preventive and therapeutic methods of HH environment affecting cognitive function and provides theoretical references for exploring and treating high altitude-induced cognitive impairment.

Herbal formula PM012 induces neuroprotection in stroke brain

Stroke is a major cause of long-term disability world-wide. Limited pharmacological therapy has been used in stroke patients. Previous studies indicated that herb formula PM012 is neuroprotective against neurotoxin trimethyltin in rat brain, and improved learning and memory in animal models of Alzheimer's disease. Its action in stroke has not been reported. This study aims to determine PM012-mediated neural protection in cellular and animal models of stroke. Glutamate-mediated neuronal loss and apoptosis were examined in rat primary cortical neuronal cultures. Cultured cells were overexpressed with a Ca++ probe (gCaMP5) by AAV1 and were used to examine Ca++ influx (Ca++i). Adult rats received PM012 before transient middle cerebral artery occlusion (MCAo). Brain tissues were collected for infarction and qRTPCR analysis. In rat primary cortical neuronal cultures, PM012 significantly antagonized glutamate-mediated TUNEL and neuronal loss, as well as NMDA-mediated Ca++i. PM012 significantly reduced brain infarction and improved locomotor activity in stroke rats. PM012 attenuated the expression of IBA1, IL6, and CD86, while upregulated CD206 in the infarcted cortex. ATF6, Bip, CHOP, IRE1, and PERK were significantly down-regulated by PM012. Using HPLC, two potential bioactive molecules, paeoniflorin and 5-hydroxymethylfurfural, were identified in the PM012 extract. Taken together, our data suggest that PM012 is neuroprotective against stroke. The mechanisms of action involve inhibition of Ca++i, inflammation, and apoptosis.

What can traditional Chinese medicine do for adult neurogenesis?

Adult neurogenesis plays a crucial role in cognitive function and mood regulation, while aberrant adult neurogenesis contributes to various neurological and psychiatric diseases. With a better understanding of the significance of adult neurogenesis, the demand for improving adult neurogenesis is increasing. More and more research has shown that traditional Chinese medicine (TCM), including TCM prescriptions (TCMPs), Chinese herbal medicine, and bioactive components, has unique advantages in treating neurological and psychiatric diseases by regulating adult neurogenesis at various stages, including proliferation, differentiation, and maturation. In this review, we summarize the progress of TCM in improving adult neurogenesis and the key possible mechanisms by which TCM may benefit it. Finally, we suggest the possible strategies of TCM to improve adult neurogenesis in the treatment of neuropsychiatric disorders.

Combined effects of Aerobic exercise and 40Hz light flicker exposure on early cognitive impairments in Alzheimer's disease of 3xTg mice

Alzheimer's disease (AD) is a progressive degenerative brain disease and the primary cause of dementia. At an early stage, AD is generally characterized by short-term memory impairment, owing to dysfunctions of the cortex and hippocampus. We previously reported that a combination of exercise and 40 Hz light flickering can protect against AD-related neuroinflammation, gamma oscillations, reduction in Aβ, and cognitive decline. Therefore, we sought to extend our previous findings to the 5-month-old 3xTg-AD mouse model to examine whether the same favorable effects occur in earlier stages of cognitive dysfunction. We investigated the effects of 12 weeks of exercise combined with 40-Hz light flickering on cognitive function by analyzing neuroinflammation, mitochondrial function, and neuroplasticity in the hippocampus in a 3xTg-AD mouse model. 5-month-old 3xTg-AD mice performed 12 weeks of exercise with 40-Hz light flickering administered independently and in combination. Spatial learning and memory, long-term memory, hippocampal Aβ, tau, neuroinflammation, pro-inflammatory cytokine expression, mitochondrial function, and neuroplasticity, were analyzed. Aβ and tau proteins levels were significantly reduced in the early stage of AD, resulting in protection against cognitive decline by reducing neuroinflammation and pro-inflammatory cytokines. Furthermore, mitochondrial function improved, apoptosis was reduced, and synapse-related protein expression increased. Overall, exercise with 40-Hz light flickering was significantly more effective than exercise or 40-Hz light flickering alone, and the improvement was comparable to the levels in the non-transgenic aged-match control group. Our results indicate a synergistic effect of exercise and 40-Hz light flickering on pathological improvements in the hippocampus during early AD associated cognitive impairment.

Neuroimaging of Mouse Models of Alzheimer’s Disease

Magnetic resonance imaging (MRI) and positron emission tomography (PET) have made great strides in the diagnosis and our understanding of Alzheimer’s Disease (AD). Despite the knowledge gained from human studies, mouse models have and continue to play an important role in deciphering the cellular and molecular evolution of AD. MRI and PET are now being increasingly used to investigate neuroimaging features in mouse models and provide the basis for rapid translation to the clinical setting. Here, we provide an overview of the human MRI and PET imaging landscape as a prelude to an in-depth review of preclinical imaging in mice. A broad range of mouse models recapitulate certain aspects of the human AD, but no single model simulates the human disease spectrum. We focused on the two of the most popular mouse models, the 3xTg-AD and the 5xFAD models, and we summarized all known published MRI and PET imaging data, including contrasting findings. The goal of this review is to provide the reader with broad framework to guide future studies in existing and future mouse models of AD. We also highlight aspects of MRI and PET imaging that could be improved to increase rigor and reproducibility in future imaging studies.

Recent Updates in the Alzheimer's Disease Etiopathology and Possible Treatment Approaches: A Narrative Review of Current Clinical Trials

BACKGROUND

Alzheimer's disease (AD) is the most frequent subtype of incurable neurodegenerative dementias and its etiopathology is still not clearly elucidated.

OBJECTIVE

Outline the ongoing clinical trials (CTs) in the field of AD, in order to find novel master regulators.

METHODS

We strictly reviewed all scientific reports from Clinicaltrials.gov and PubMed databases from January 2010 to January 2019. The search terms were "Alzheimer's disease" or "dementia" and "medicine" or "drug" or "treatment" and "clinical trials" and "interventions". Manuscripts that met the objective of this study were included for further evaluations.

RESULTS

Drug candidates have been categorized into two main groups including antibodies, peptides or hormones (such as Ponezumab, Interferon β-1a, Solanezumab, Filgrastim, Levemir, Apidra, and Estrogen), and naturally-derived ingredients or small molecules (such as Paracetamol, Ginkgo, Escitalopram, Simvastatin, Cilostazo, and Ritalin-SR). The majority of natural candidates acted as anti-inflammatory or/and anti-oxidant and antibodies exert their actions via increasing amyloid-beta (Aβ) clearance or decreasing Tau aggregation. Among small molecules, most of them that are present in the last phases act as specific antagonists (Suvorexant, Idalopirdine, Intepirdine, Trazodone, Carvedilol, and Risperidone) or agonists (Dextromethorphan, Resveratrol, Brexpiprazole) and frequently ameliorate cognitive dysfunctions.

CONCLUSION

The presences of a small number of candidates in the last phase suggest that a large number of candidates have had an undesirable side effect or were unable to pass essential eligibility for future phases. Among successful treatment approaches, clearance of Aβ, recovery of cognitive deficits, and control of acute neuroinflammation are widely chosen. It is predicted that some FDA-approved drugs, such as Paracetamol, Risperidone, Escitalopram, Simvastatin, Cilostazoand, and Ritalin-SR, could also be used in off-label ways for AD. This review improves our ability to recognize novel treatments for AD and suggests approaches for the clinical trial design for this devastating disease in the near future.

Molecular mechanisms of altered adult hippocampal neurogenesis in Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia globally. AD is a progressive neurodegenerative disorder, eventually manifesting as severe cognitive impairment. Adult hippocampal neurogenesis (AHN) occurs throughout adulthood and plays an important role in hippocampus-dependent learning and memory. The stages of AHN, predominantly comprising the proliferation, differentiation, survival, and maturation of newborn neurons, are affected to varying degrees in AD. However, the exact molecular mechanisms remain to be elucidated. Recent evidence suggests that the molecules involved in AD pathology contribute to the compromised AHN in AD. Notably, various interventions may have common signaling pathways that, once identified, could be harnessed to enhance adult neurogenesis. This in turn could putatively rescue cognitive deficits associated with impaired neurogenesis as observed in animal models of AD. In this manuscript, we review the current knowledge concerning AHN under normal physiological and AD pathological conditions and highlight the possible role of specific molecules in AHN alteration in AD. In addition, we summarize in vivo experiments with emphasis on the effect of the activation of certain key signalings on AHN in AD rodent models. We propose that these signaling targets and corresponding interventions should be considered when developing novel therapies for AD.

Conductive Hearing Loss Aggravates Memory Decline in Alzheimer Model Mice

The study of cognitive impairment associated with hearing loss has recently garnered considerable interest. Epidemiological data have demonstrated that hearing loss is a risk factor for cognitive decline as a result of aging. However, no previous study has examined the effect of hearing loss in patients with cognitive problems such as Alzheimer’s disease. Therefore, we investigated the effect of conductive hearing loss in an Alzheimer’s mouse model. Positron emission tomography (PET) and magnetic resonance imaging (MRI) were used to evaluate changes in glucose metabolism and gray matter concentrations in the 5xFAD Alzheimer’s Disease (AD) transgenic mouse model with and without conductive hearing loss (HL). Conductive hearing loss was induced using chronic perforation of the tympanic membrane. Behavioral data from the Y-maze and passive avoidance tests revealed greater memory deficits in the AD with HL (AD-HL) group than in the AD group. Following induction of hearing loss, lower cerebral glucose metabolism in the frontal association cortex was observed in the AD-HL group than in the AD group. Although lower glucose metabolism in the hippocampus and cerebellum was found in the AD-HL group than in the AD group at 3 months, the gray matter concentrations in these regions were not significantly different between the groups. Furthermore, the gray matter concentrations in the simple lobule, cingulate/retrosplenial cortex, substantia nigra, retrosigmoid nucleus, medial geniculate nucleus, and anterior pretectal nucleus at 7 months were significantly lower in the AD-HL group than in the AD group. Taken together, these results indicate that even partial hearing loss can aggravate memory impairment in Alzheimer’s disease.

Ganoderma lucidum aqueous extract prevents hypobaric hypoxia induced memory deficit by modulating neurotransmission, neuroplasticity and maintaining redox homeostasis

Oxidative stress due to hypobaric hypoxia at extreme altitudes causes severe neuronal damage and irreversible cognitive loss. Owing to contraindications of current drug therapies, the aim of the study was to investigate memory enhancing potential of aqueous extract of Ganoderma lucidum (GLAQ) and underlying neuroprotective mechanism using rat hypobaric hypoxia test model. Rats exposed to hypobaric hypoxia showed deranged spatial memory in morris water maze test with hippocampal damage and vasogenic cerebral edema. All these changes were prevented with GLAQ treatment. Blood and biochemical analysis revealed activation of hypoxic ventilatory response, red blood cells induction, reversal of electrolyte and redox imbalance, and restoration of cellular bioenergetic losses in GLAQ treated animals. Notably, GLAQ treatment ameliorated levels of neurotransmitters (catecholamines, serotonin, glutamate), prevented glucocorticoid and α-synuclein surge, improved neuroplasticity by upregulating CREB/p-CREB/BDNF expression via ERK1/ERK2 induction. Further, restoration of nuclear factor erythroid 2-related factor with stabilization of hypoxia inducible factors and inflammatory markers were evidenced in GLAQ treated rats which was additionally established in gene reporter array using an alternative HT22 cell test model. Conclusively, our studies provide novel insights into systemic to molecular level protective mechanism by GLAQ in combating hypobaric hypoxia induced oxidative stress and memory impairment.

The Impact of Estradiol on Neurogenesis and Cognitive Functions in Alzheimer's Disease

Alzheimer's disease (AD) is described as cognitive and memory impairments with a sex-related epidemiological profile, affecting two times more women than men. There is emerging evidence that alternations in the hippocampal neurogenesis occur at the early stage of AD. Therapies that may effectively slow, stop, or regenerate the dying neurons in AD are being extensively investigated in the last few decades, but none has yet been found to be effective. The regulation of endogenous neurogenesis is one of the main therapeutic targets for AD. Mounting evidence indicates that the neurosteroid estradiol (17β-estradiol) plays a supporting role in neurogenesis, neuronal activity, and synaptic plasticity of AD. This effect may provide preventive and/or therapeutic approaches for AD. In this article, we discuss the molecular mechanism of potential estradiol modulatory action on endogenous neurogenesis, synaptic plasticity, and cognitive function in AD.

Volatile Oil from Acorus gramineus Ameliorates the Injury Neurons in the Hippocampus of Amyloid Beta 1-42 Injected Mice

In recent years, the extraction fraction of volatile oil from Acorus gramineus has significant effects on anti-dementia and improving the learning and memory of animals. To date, limited studies have determined whether volatile oil from A. gramineus has the protective effect on neuronal damage. The aim of this study was to investigate the protective effects of volatile oil from A. gramineus on Alzheimer's disease (AD) mice, by means of behavior test, immunohistochemistry and western blot methods. In this study, mice were injected with Aβ_1-42 in the bilateral hippocampus to establish the AD model. On the seventh day after modeling, the mice with cognitive dysfunction were selected by the novel object recognition task. Subsequently, the volatile oil treatment groups underwent intragastric administration for per 10 g body weight 2.5 or 5 μL volatile oil from A. gramineus for 3 weeks. The control group and the AD group were given the same amount of saline. Our results showed that after treatment of volatile oil from A. gramineus, the number of Doublecortin and Nestin positive cells increased significantly, suggesting that the volatile oil from A. gramineus may induce the regeneration of hippocampal neurons in mice, and promote the growth of hippocampal neurons by upregulation of brain-derived neurotrophic factor, tyrosine protein kinase B, and neurotrophin-3 expression. These results might provide more experimental evidences for underlying mechanism about the neuroprotective effects of volatile oil from A. gramineus against AD relevant symptoms. Anat Rec, 302:2261-2270, 2019. © 2019 American Association for Anatomy.

Early Intervention with a Multi-Ingredient Dietary Supplement Improves Mood and Spatial Memory in a Triple Transgenic Mouse Model of Alzheimer's Disease

The increasing global burden of Alzheimer's disease (AD) and failure of conventional treatments to stop neurodegeneration necessitates an alternative approach. Evidence of inflammation, mitochondrial dysfunction, and oxidative stress prior to the accumulation of amyloid-β in the prodromal stage of AD (mild cognitive impairment; MCI) suggests that early interventions which counteract these features, such as dietary supplements, may ameliorate the onset of MCI-like behavioral symptoms. We administered a polyphenol-containing multiple ingredient dietary supplement (MDS), or vehicle, to both sexes of triple transgenic (3xTg-AD) mice and wildtype mice for 2 months from 2-4 months of age. We hypothesized that the MDS would preserve spatial learning, which is known to be impaired in untreated 3xTg-AD mice by 4 months of age. Behavioral phenotyping of animals was done at 1-2 and 3-4 months of age using a comprehensive battery of tests. As previously reported in males, both sexes of 3xTg-AD mice exhibited increased anxiety-like behavior at 1-2 months of age, prior to deficits in learning and memory, which did not appear until 3-4 months of age. The MDS did not reduce this anxiety or prevent impairments in novel object recognition (both sexes) or on the water maze probe trial (females only). Strikingly, the MDS specifically prevented 3xTg-AD mice (both sexes) from developing impairments (exhibited by untreated 3xTg-AD controls) in working memory and spatial learning. The MDS also increased sucrose preference, an indicator of hedonic tone. These data show that the MDS can prevent some, but not all, psychopathology in an AD model.

A longitudinal multimodal in vivo molecular imaging study of the 3xTg-AD mouse model shows progressive early hippocampal and taurine loss

The understanding of the natural history of Alzheimer's disease (AD) and temporal trajectories of in vivo molecular mechanisms requires longitudinal approaches. A behavioral and multimodal imaging study was performed at 4/8/12 and 16 months of age in a triple transgenic mouse model of AD (3xTg-AD). Behavioral assessment included the open field and novel object recognition tests. Molecular characterization evaluated hippocampal levels of amyloid β (Aβ) and hyperphosphorylated tau. Magnetic resonance imaging (MRI) included assessment of hippocampal structural integrity, blood-brain barrier (BBB) permeability and neurospectroscopy to determine levels of the endogenous neuroprotector taurine. Longitudinal brain amyloid accumulation was assessed using 11C Pittsburgh compound B positron emission tomography (PET), and neuroinflammation/microglia activation was investigated using 11C-PK1195. We found altered locomotor activity at months 4/8 and 16 months and recognition memory impairment at all time points. Substantial early reduction of hippocampal volume started at month 4 and progressed over 8/12 and 16 months. Hippocampal taurine levels were significantly decreased in the hippocampus at months 4/8 and 16. No differences were found for amyloid and neuroinflammation with PET, and BBB was disrupted only at month 16. In summary, 3xTg-AD mice showed exploratory and recognition memory impairments, early hippocampal structural loss, increased Aβ and hyperphosphorylated tau and decreased levels of taurine. In sum, the 3xTg-AD animal model mimics pathological and neurobehavioral features of AD, with early-onset recognition memory loss and MRI-documented hippocampal damage. The early-onset profile suggests temporal windows and opportunities for therapeutic intervention, targeting endogenous neuroprotectors such as taurine.

The neuroprotective effect of deep brain stimulation at nucleus basalis of Meynert in transgenic mice with Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common type of dementia and mainly treated by drugs, while the therapeutic outcomes are very limited. This study aimed to determine the optimized parameters of deep brain stimulation (DBS) which was applied to the treatment of AD and propose the involved mechanisms.

METHODS

Amyloid-β precursor protein/Presenilin1 (APP/PS1) transgenic mice were used and received DBS at nucleus basalis of Meynert (NBM). The optimized parameters of DBS were determined by using different stimulation frequencies, durations and ages of mice under Morris water maze test. The involved mechanisms and the possible signal pathways were also investigated.

RESULTS

The optimized parameters for DBS were high frequency (100 Hz) for 21 days starting from early age (4 months old). Under the above parameters, the soluble Aβ40 and Aβ42 in the hippocampus and cortex were down-regulated significantly. DBS increased survival neurons and reduced apoptotic cells in the hippocampus and cortex. Meanwhile, the apoptosis-related proteins caspase-3, caspase-8 and Bid were down-regulated. Moreover, DBS caused a significant increase of superoxide dismutase, glutathione peroxidase and choline acetyltransferase activity as well as a decrease of methane dicarboxylic aldehyde content and acetylcholine esterase activity. Phosphorylation of Akt (p-Akt)/total Akt (t-Akt) was up-regulated while p-extracellular signal-regulated kinase 1/2 (ERK1/2)/t-ERK1/2 was down-regulated. The neuroprotective effect of DBS was attenuated by their inhibitors.

CONCLUSIONS

NBM-DBS starting from 4 months of age for 21 days at a high frequency (100 Hz) has therapeutic effects on AD through activating phosphatidylinositol 3'-kinase (PI3K)/Akt pathway and inhibiting ERK1/2 pathway.

Fluoxetine attenuates the impairment of spatial learning ability and prevents neuron loss in middle-aged APPswe/PSEN1dE9 double transgenic Alzheimer's disease mice

Selective serotonin reuptake inhibitors (SSRIs) have been reported to increase cognitive performance in some clinical studies of Alzheimer's disease (AD). However, there is a lack of evidence supporting the efficacy of SSRIs as cognition enhancers in AD, and the role of SSRIs as a treatment for AD remains largely unclear. Here, we characterized the impact of fluoxetine (FLX), a well-known SSRI, on neurons in the dentate gyrus (DG) and in CA1 and CA3 of the hippocampus of middle-aged (16 to 17 months old) APPswe/PSEN1dE9 (APP/PS1) transgenic AD model mice. We found that intraperitoneal (i.p.) injection of FLX (10 mg/kg/day) for 5 weeks effectively alleviated the impairment of spatial learning ability in middle-aged APP/PS1 mice as evaluated using the Morris water maze. More importantly, the number of neurons in the hippocampal DG was significantly increased by FLX. Additionally, FLX reduced the deposition of beta amyloid, inhibited GSK-3β activity and increased the level of β-catenin in middle-aged APP/PS1 mice. Collectively, the results of this study indicate that FLX delayed the progression of neuronal loss in the hippocampal DG in middle-aged AD mice, and this effect may underlie the FLX-induced improvement in learning ability. FLX may therefore serve as a promising therapeutic drug for AD.

Chronic deep brain stimulation in an Alzheimer's disease mouse model enhances memory and reduces pathological hallmarks

BACKGROUND

Alzheimer's disease (AD) is a progressive degenerative disorder that currently remains extremely disabling. Recent work has shown that deep brain stimulation (DBS) has promising effects in AD patients. In parallel to the clinical trials, we investigated the impact of chronic DBS in 3xTg mice, a well-established animal model of AD.

METHODS

AD mice were assigned to control (Cont), non-stimulation (NS) and stimulation (DBS) groups, along with age matched wild type controls (WT-Cont). Bilateral electrodes were implanted in the entorhinal cortex to deliver chronic high frequency stimulation for 25 days. Animals were tested in memory behavioral tasks, with post-mortem measurements of pathological markers.

RESULTS

We found that chronic DBS in AD mice normalized their impaired performance in the Morris water maze task to that of the WT group in the probe test. In the novel object and novel place preference tasks, AD-DBS mice spent more time at the novel object and novice location compared to AD-NS mice. These cognitive improvements in AD-DBS mice were associated with DBS induced increased neurogenesis in the dentate gyrus, a significant reduction in β-amyloid plaques, a reduction in CA-1 cellular β-amyloid-42 levels, decreased cortical total-tau and phosphorylated-tau, along with decreased hippocampal total-tau.

CONCLUSION

Overall, we show that chronic DBS of the entorhinal cortex in AD mice improves both memory and AD specific pathological markers. These results support further testing of DBS as a potential treatment in AD patients.

Essential oils from two Allium species exert effects on cell proliferation and neuroblast differentiation in the mouse dentate gyrus by modulating brain-derived neurotrophic factor and acetylcholinesterase

Background

In the present study, we investigated the effects of oil products from two Allium species: Allium sativum (garlic) and Allium hookeri (Chinese chives) on cell proliferation and neuroblast differentiation in the mouse dentate gyrus.

Methods

Using corn oil as a vehicle, the essential oil from garlic (10 ml/kg), or Chinese chives (10 ml/kg) was administered orally to 9-week-old mice once a day for 3 weeks. One hour following the last treatment, a novel object recognition test was conducted and the animals were killed 2 h after the test.

Results

In comparison to the vehicle-treated group, garlic essential oil (GO) treatment resulted in significantly increased exploration time and discrimination index during the novel object recognition test, while Chinese chives essential oil (CO) reduced the exploration time and discrimination index in the same test. In addition, the number of Ki67-immunoreactive proliferating cells and doublecortin-immunoreactive neuroblasts significantly increased in the dentate gyrus of GO-treated animals. However, administration of CO significantly decreased cell proliferation and neuroblast differentiation. Administration of GO significantly increased brain-derived neurotrophic factor (BDNF) levels and decreased acetylcholinesterase (AChE) activity in the hippocampal homogenates. In contrast, administration of CO decreased BDNF protein levels and had no significant effect on AChE activity, compared to that in the vehicle-treated group.

Conclusions

These results suggest that GO significantly improves novel object recognition as well as increases cell proliferation and neuroblast differentiation, by modulating hippocampal BDNF protein levels and AChE activity, while CO impairs novel object recognition and decreases cell proliferation and neuroblast differentiation, by reducing BDNF protein levels in the hippocampus.