Memory Impairment In Alzheimer's Disease Research Articles

HDAC9-mediated calmodulin deacetylation induces memory impairment in Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive dysfunction and memory impairment. AD pathology involves protein acetylation. Previous studies have mainly focused on histone acetylation in AD, however, the roles of nonhistone acetylation in AD are less explored. The protein acetylation and expression levels were detected by western blotting and co-immunoprecipitation. The stoichiometry of acetylation was measured by home-made and site-specific antibodies against acetylated-CaM (Ac-CaM) at K22, K95, and K116. Hippocampus-dependent learning and memory were evaluated by using the Morris water maze, novel object recognition, and contextual fear conditioning tests. We showed that calmodulin (CaM) acetylation is reduced in plasma of AD patients and mice. CaM acetylation and its target Ca2+ /CaM-dependent kinase II α (CaMKIIα) activity were severely impaired in AD mouse brain. The stoichiometry showed that Ac-K22, K95-CaM acetylation were decreased in AD patients and mice. Moreover, we screened and identified that lysine deacetylase 9 (HDAC9) was the main deacetylase for CaM. In addition, HDAC9 inhibition increased CaM acetylation and CaMKIIα activity, and hippocampus-dependent memory in AD mice. HDAC9-mediated CaM deacetylation induces memory impairment in AD, HDAC9, or CaM acetylation may become potential therapeutic targets for AD.

Immunohistochemical Analysis of Mitochondrial Dynamics in Different Zones of the Hippocampus during Experimental Modeling of Alzheimer's Disease.

We performed a comparative assessment of the immunohistochemical distribution of markers of mitochondrial fission (Drp-1), mitochondrial fusion (Mfn-2), and mitochondrial biogenesis (PGC-1α) in pyramidal neurons of different zones of the hippocampus in mice with intrahippocampal administration of β-amyloid peptide 25-35. The most pronounced changes in the dynamics associated with a decrease in the amount of the fission marker and an increase in the amount of the fusion marker were observed in the CA3 field on day 38 after peptide administration. In the CA1 field, a significant decrease in the marker of mitochondrial biogenesis PGC-1α was found on day 38, which can indicate a decrease in the intensity of mitochondrial biogenesis. Early mitochondrial changes can play an important role in the pathogenesis of all types of memory impairment in Alzheimer's disease.

Not all regions are created equal: identifying regions and cell types associated with cognitive resilience in the AD‐BXD model population

AbstractBackgroundThe relationship between regional cell composition, brain pathology, and memory impairment in Alzheimer’s disease (AD) remains incompletely understood. The specific brain regions and tracts (and their interactions) that explain the heterogeneity of cognitive decline with AD are not clear. By integrating brain‐wide immunohistochemistry and cognitive outcomes we can achieve unbiased detection of regions of interest (ROIs) and identify cellular correlates of cognitive resilience for causal testing.MethodImmunohistochemistry(IHC) was completed to evaluate neurodegeneration (NeuN), gliosis (Iba1&GFAP), amyloid beta(Aβ) pathology(AB1‐42), and cell bodies(Thionine) in adult (6 months(m)) and middle‐aged (14m) mice of the AD‐BXD genetic reference panel (n = 227). Using the QUINT workflow, hemibrain slices were systematically segmented and registered to the Allen Brain Atlas to gain a global perspective of percent cell and pathology coverage. IHC traits were correlated with contextual fear conditioning outcomes to identify regions whose stain composition is associated with memory performance.ResultsContrary to our prior work using ELISA‐based Aβ measurement, we find that Aβ quantified via IHC at the presymptomatic time point (6m) is strongly correlated with differences in short‐ and long‐term memory in 14m female 5XFAD carriers. Furthermore, the degree of astrogliosis at 6m in cortical, striatal, and thalamic regions acts as a predictor of cognitive outcomes at 14m. While age‐related decreases in NeuN load were not observed, wide variation in neurodegeneration levels could be attributed to strain differences and 14m NeuN load was positively correlated with 14m long‐term memory among this female 5XFAD population. Highlighting the importance of genetic background on AD progression, we were able to categorize strains as resilient or susceptible to pathological and cognitive decline and evaluate the overlap of these traits. Strains that exhibit the unique identity of being pathologically susceptible but cognitively resilient offer a novel opportunity to investigate the underlying mechanisms of protection from cognitive decline with AD.ConclusionIntegrating brain‐wide IHC and behavioral data, we were able to identify regional and cellular correlates that may predict downstream cognitive outcomes. Detection of these biomarkers may prove a valuable resource to disseminate the insidious prodromal stages of AD in which biochemical changes precede apparent clinical symptoms.

Memory impairment in Alzheimer’s disease is associated with Dentate Gyrus atrophy: A pilot study using the Uniform Data Set Neuropsychological Battery and 7 Tesla MRI

AbstractBackgroundThe neuropsychological battery of the Uniform Data Set (UDSNB3.0) (Weintraub et al., 2009) assesses cognition. The neuroanatomical correlates of the UDSNB3.0 have not yet been investigated. 7T MRI was used to investigate correlations between hippocampal subfield volumes and the UDSNB3.0 for Alzheimer’s disease (AD) and age‐matched healthy control (HC).Method28 (15 AD, 13 HC) participants (61% female; aged 42‐79) were recruited. A Phillips Achieva 7T scanner used a Nova Medical (Wilmington MA, USA) single‐channel transmit, 32 channel receive (1Tx32Rx) head‐coil. PSIR images (TE/TR = 119/59001ms, FA = 90o, 0.38×0.39×1.50 mm3 resolution) were segmented into Cornu Ammonis (CA = CA1+CA2+CA3), Subiculum (SUB), Dentate Gyrus (DG), and Entorhinal Cortex (ERC) (Figure 1). The UDSNB3.0, administered by trained Assistant Psychologists, included the MoCA and a variety of cognitive tests assessing memory (immediate/delayed recall, un‐cued/cued recall, and recognition), attention, language and visuospatial abilities.ResultIn the whole analysed sample (n = 28), there were strong positive correlations between UDS3.0 memory test scores and hippocampal subfield volumes (Figure 2). There were significant reductions in the volume of each hippocampal subfield in AD, compared with controls (p<0.05). No significant decrease in the whole brain volume was noted between the two groups (p>0.05), indicating that hippocampal volume loss was not part of whole brain atrophy. One‐way ANOVA’s demonstrated significant differences between HC and AD test scores (p<0.05), thus HC and AD participants were analysed separately. In AD participants, whole hippocampal volume correlated with MoCA memory category cue scores (R2 = 0.54, p<0.05) but only significantly in the DG of the hippocampal subfields (R2 = 0.52, p<0.05) (Figure 3), supporting Novellino et al.’s (2018) previous finding of associations between the DG volume and cued recall. No such significant correlations were observed in HC participants.ConclusionThe results of this study confirm that hippocampal atrophy in AD is associated with cognitive decline. Additionally, our results suggest that 7T MRI may be able to detect subtle in vivo DG atrophy in AD that is related to cued memory. The 7T scans appear to reveal DG changes in AD that to date have been confirmed in neuropathological studies only.Funding: The Medical Research Council, UK has funded AAH (MR/T005580/1).

Conceptual saliency: Core and peripheral semantic knowledge in Alzheimer’s disease

AbstractBackgroundSemantic memory impairment in Alzheimer’s disease (AD) is indicative of an actual degradation of semantic knowledge – the conceptual and factual knowledge necessary to engage with others and the physical world – rather than merely to a retrieval deficit. Historically, studies in semantic knowledge in AD have relied on predetermined sets of stimuli to probe knowledge. The analysis presented here compares the contents, sequences and organization of lists of salient concepts generated by 19 patients at the mild to moderates stages AD and by 15 age‐matched cognitively normal control individuals by means of a free‐listing task, for two semantic categories, living kinds and man‐made objects. The free elicitation by participants prevents the imposition of a priori ideas by the experimenter, which might not correspond to the native knowledge of the specific cultural group studied.MethodData collection starts with the ‘demarcation’ of a domain of knowledge X by a sample of participants who are being asked to write the names of as many items as they can conjure up, which they think belong to that domain X. Terms that appear earlier, or with higher frequency, on free‐lists indicate high consensus among respondents (i.e., the concept is an important component of the category); those items are considered as more salient in the domain under investigation.ResultEvidence of knowledge devolution is detected in the lists of participants with AD for both semantic categories. However, the core conceptual information and central aspects of the structuration of those knowledge domains are preserved to an extent. The peripheral conceptual knowledge is showing the greatest disease impact.ConclusionThe study starts the investigation of the aspects of living kinds and artefactual categorial knowledge especially resilient as neurodegeneration sets. Semantic knowledge holds the information about what one knows. Its integrity is critical in daily functioning, and interactions with others and the world at large. Because semantic memory supports various aspects of daily life, it is a prime candidate for therapeutic targets that can lead to meaningful outcomes for both patients and their care partners.

N6-methyladenosine-modified circRIMS2 mediates synaptic and memory impairments by activating GluN2B ubiquitination in Alzheimer's disease

BackgroundSynaptic degeneration occurs in the early stage of Alzheimer's disease (AD) before devastating symptoms, strongly correlated with cognitive decline. Circular RNAs (circRNAs) are abundantly enriched in neural tissues, and aberrant expression of circRNAs precedes AD symptoms, significantly correlated with clinical dementia severity. However, the direct relationship between circRNA dysregulation and synaptic impairment in the early stage of AD remains poorly understood.MethodsHippocampal whole-transcriptome sequencing was performed to identify dysregulated circRNAs and miRNAs in 4-month-old wild-type and APP/PS1 mice. RNA antisense purification and mass spectrometry were utilized to unveil interactions between circRIMS2 and methyltransferase 3, N6-adenosine-methyltransferase complex catalytic subunit (METTL3). The roles of circRIMS2/miR-3968 in synaptic targeting of UBE2K-mediated ubiquitination of GluN2B subunit of NMDA receptor were evaluated via numerous lentiviruses followed by morphological staining, co-immunoprecipitation and behavioral testing. Further, a membrane-permeable peptide was used to block the ubiquitination of K1082 on GluN2B in AD mice.ResultscircRIMS2 was significantly upregulated in 4-month-old APP/PS1 mice, which was mediated by METTL3-dependent N6-methyladenosine (m6A) modification. Overexpression of circRIMS2 led to synaptic and memory impairments in 4-month-old C57BL/6 mice. MiR-3968/UBE2K was validated as the downstream of circRIMS2. Elevated UBE2K induced synaptic dysfunction of AD through ubiquitinating K1082 on GluN2B. Silencing METTL3 or blocking the ubiquitination of K1082 on GluN2B with a short membrane-permeable peptide remarkably rescued synaptic dysfunction in AD mice.ConclusionsIn conclusion, our study demonstrated that m6A-modified circRIMS2 mediates the synaptic and memory impairments in AD by activating the UBE2K-dependent ubiquitination and degradation of GluN2B via sponging miR-3968, providing novel therapeutic strategies for AD.

Rbm8a regulates neurogenesis and reduces Alzheimer's disease-associated pathology in the dentate gyrus of 5×FAD mice.

Alzheimer's disease is a prevalent and debilitating neurodegenerative condition that profoundly affects a patient's daily functioning with progressive cognitive decline, which can be partly attributed to impaired hippocampal neurogenesis. Neurogenesis in the hippocampal dentate gyrus is likely to persist throughout life but declines with aging, especially in Alzheimer's disease. Recent evidence indicated that RNA-binding protein 8A (Rbm8a) promotes the proliferation of neural progenitor cells, with lower expression levels observed in Alzheimer's disease patients compared with healthy people. This study investigated the hypothesis that Rbm8a overexpression may enhance neurogenesis by promoting the proliferation of neural progenitor cells to improve memory impairment in Alzheimer's disease. Therefore, Rbm8a overexpression was induced in the dentate gyrus of 5×FAD mice to validate this hypothesis. Elevated Rbm8a levels in the dentate gyrus triggered neurogenesis and abated pathological phenotypes (such as plaque formation, gliosis reaction, and dystrophic neurites), leading to ameliorated memory performance in 5×FAD mice. RNA sequencing data further substantiated these findings, showing the enrichment of differentially expressed genes involved in biological processes including neurogenesis, cell proliferation, and amyloid protein formation. In conclusion, overexpressing Rbm8a in the dentate gyrus of 5×FAD mouse brains improved cognitive function by ameliorating amyloid-beta-associated pathological phenotypes and enhancing neurogenesis.

Cholinergic Reinforcement Signaling Is Impaired by Amyloidosis Prior to Its Synaptic Loss.

Alzheimer's disease (AD) is associated with amyloidosis and dysfunction of the cholinergic system, which is crucial for learning and memory. However, the nature of acetylcholine signaling within regions of cholinergic-dependent plasticity and how it changes with experience is poorly understood, much less the impact of amyloidosis on this signaling. Therefore, we optically measure the release profile of acetylcholine to unexpected, predicted, and predictive events in visual cortex (VC)-a site of known cholinergic-dependent plasticity-in a preclinical mouse model of AD that develops amyloidosis. We find that acetylcholine exhibits reinforcement signaling qualities, reporting behaviorally relevant outcomes and displaying release profiles to predictive and predicted events that change as a consequence of experience. We identify three stages of amyloidosis occurring before the degeneration of cholinergic synapses within VC and observe that cholinergic responses in amyloid-bearing mice become impaired over these stages, diverging progressively from age- and sex-matched littermate controls. In particular, amyloidosis degrades the signaling of unexpected rewards and punishments, and attenuates the experience-dependent (1) increase of cholinergic responses to outcome predictive visual cues, and (2) decrease of cholinergic responses to predicted outcomes. Hyperactive spontaneous acetylcholine release occurring transiently at the onset of impaired cholinergic signaling is also observed, further implicating disrupted cholinergic activity as an early functional biomarker in AD. Our findings suggest that acetylcholine acts as a reinforcement signal that is impaired by amyloidosis before pathologic degeneration of the cholinergic system, providing a deeper understanding of the effects of amyloidosis on acetylcholine signaling and informing future interventions for AD.SIGNIFICANCE STATEMENT The cholinergic system is especially vulnerable to the neurotoxic effects of amyloidosis, a hallmark of Alzheimer's disease (AD). Though amyloid-induced cholinergic synaptic loss is thought in part to account for learning and memory impairments in AD, little is known regarding how amyloid impacts signaling of the cholinergic system before its anatomic degeneration. Optical measurement of acetylcholine (ACh) release in a mouse model of AD that develops amyloidosis reveals that ACh signals reinforcement and outcome prediction that is disrupted by amyloidosis before cholinergic degeneration. These observations have important scientific and clinical implications: they implicate ACh signaling as an early functional biomarker, provide a deeper understanding of the action of acetylcholine, and inform on when and how intervention may best ameliorate cognitive decline in AD.

Isoamericanin A improves lipopolysaccharide-induced memory impairment in mice through suppression of the nicotinamide adenine dinucleotide phosphateoxidase-dependent nuclear factor kappa B signaling pathway.

Alzheimer's disease (AD) is the most frequent cause of dementia in the elderly. Isoamericanin A (ISOA) is a natural lignan possessing great potential for AD treatment. This study investigated the efficacy of ISOA on memory impairments in the mice intrahippocampal injected with lipopolysaccharide (LPS) and the underlying mechanism. Y-maze and Morris Water Maze data suggested that ISOA (5 and 10 mg/kg) ameliorated short- and long-term memory impairments, and attenuated neuronal loss and lactate dehydrogenase activity. ISOA exerted anti-inflammatory effect demonstrating by the reduction of ionized calcium-binding adapter molecule 1 positive cells and suppression of marker protein and pro-inflammation cytokines expressions induced by LPS. ISOA suppressed the nuclear factor kappa B (NF-κB) signaling pathway by inhibiting IκBα phosphorylation and NF-κB p65 phosphorylation and nuclear translocation. ISOA inhibited superoxide and intracellular reactive oxygen species accumulation by reducing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation, demonstrating by suppressing NADP+ and NADPH contents, gp91phox expression, and p47phox expression and membrane translocation. These effects were enhanced in combination with NADPH oxidase inhibitor apocynin. The neuroprotective effect of ISOA was further proved in the in vitro models. Overall, our data revealed a novel pharmacological activity of ISOA: ameliorating memory impairment in AD via inhibiting neuroinflammation.

Alzheimer's disease brain-derived extracellular vesicles reveal altered synapse-related proteome and induce cognitive impairment in mice.

Extracellular vesicles (EVs) have been implicated in the spread of neuropathology in Alzheimer's disease (AD), but their involvement in behavioral outcomes linked to AD remains to be determined. EVs isolated from post mortem brain tissue from control, AD, or frontotemporal dementia (FTD) donors, as well as from APP/PS1 mice, were injected into the hippocampi of wild-type (WT) or a humanized Tau mouse model (hTau/mTauKO). Memory tests were carried out. Differentially expressed proteins in EVs were assessed by proteomics. Both AD-EVs and APP/PS1-EVs trigger memory impairment in WT mice. We further demonstrate that AD-EVs and FTD-EVs carry Tau protein, present altered protein composition associated with synapse regulation and transmission, and trigger memory impairment in hTau/mTauKO mice. Results demonstrate that AD-EVs and FTD-EVs have negative impacts on memory in mice and suggest that, in addition to spreading pathology, EVs may contribute to memory impairment in AD and FTD. Aβ was detected in EVs from post mortem AD brain tissue and APP/PS1 mice. Tau was enriched in EVs from post mortem AD, PSP and FTD brain tissue. AD-derived EVs and APP/PS1-EVs induce cognitive impairment in wild-type (WT) mice. AD- and FTD-derived EVs induce cognitive impairment in humanized Tau mice. Proteomics findings associate EVs with synapse dysregulation in tauopathies.

Acute stressors do not impair short-term memory or attention in an aged mouse model of amyloidosis.

Memory impairment in Alzheimer's disease patients is thought to be associated with the accumulation of amyloid-beta peptides and tau proteins. However, inconsistent reports of cognitive deficits in pre-clinical studies have raised questions about the link between amyloid-beta and cognitive decline. One possible explanation may be that studies reporting memory deficits often involve behavioral assessments that entail a high stress component. In contrast, in tasks without a high stress component transgenic mice do not consistently show declines in memory. The glucocorticoid cascade hypothesis of aging and the vicious cycle of stress framework suggest that stress exacerbates dementia progression by initiating a cycle of hypothalamic-pituitary-adrenal axis activation and subsequent brain deterioration. Using the APPswe/PS1dE9 mouse model of amyloidosis, we assessed whether stressor exposure prior to testing differentially impaired cognitive performance of aged male and female mice. As part of a larger study, mice performed a delayed match-to-position (DMTP) or a 3-choice serial-reaction time (3CSRT) task. Unexpectedly, these mice did not exhibit cognitive declines during aging. Therefore, at 73 and 74 weeks of age, we exposed mice to a predator odor or forced swim stressor prior to testing to determine if stress revealed cognitive deficits. We predicted stressor exposure would decrease performance accuracy more robustly in transgenic vs. non-transgenic mice. Acute stressor exposure increased accuracy in the DMTP task, but not in the 3CSRT task. Our data suggest that acute stressor exposure prior to testing does not impair cognitive performance in APPswe/PS1dE9 mice.

In Silico Interactions of Natural and Synthetic Compounds with Key Proteins Involved in Alzheimer's Disease: Prospects for Designing New Therapeutics Compound.

Memory impairment is a result of multiple factors including amyloid-beta (Aβ) accumulation. Several receptors are mediated for Aβ transport and signaling. Moreover, blood lipids are involved in Aβ signaling pathway through these receptors. Mediated blood lipid level by statins aims to regulate Aβ signaling cascade. First, the structure of receptors was taken from the RCSB PDB database and prepared with MGLTools and AutoDock tool 4. Second, the ligand was prepared for docking through AutoDock Vina. The binding affinity was calculated, and the binding sites were determined through LigPlot+ software. Besides, pharmacokinetic properties were calculated through multiple software. Finally, a molecular dynamics (MD) simulation was conducted to evaluate ligands stability along with clustering analysis to evaluate proteins connection. Our molecular docking and dynamic analyses revealed silymarin as a potential inhibitor of acetylcholinesterase (AChE), P-glycoprotein, and angiotensin-converting enzyme 2 (ACE2) with 0.704, 0.85, and 0.83Å for RMSD along with -114.27, -107.44, and -122.51kcal/mol for free binding energy, respectively. Moreover, rosuvastatin and quercetin have more stability compared to silymarin and donepezil in complex with P-glycoprotein and ACE2, respectively. Eventually, based on clustering and pharmacokinetics analysis, silymarin, rosuvastatin, and quercetin are suggested to be involved in peripheral clearance of Aβ. The bioactivity effects of mentioned statins and antioxidants are predicted to be helpful in treating memory impairment in Alzheimer's disease (AD). Nevertheless, mentioned drug effect could be improved by nanoparticles to facilitate penetration of the blood-brain barrier (BBB).

Lateral mammillary body neurons in mouse brain are disproportionately vulnerable in Alzheimer's disease.

The neural circuits governing the induction and progression of neurodegeneration and memory impairment in Alzheimer's disease (AD) are incompletely understood. The mammillary body (MB), a subcortical node of the medial limbic circuit, is one of the first brain regions to exhibit amyloid deposition in the 5xFAD mouse model of AD. Amyloid burden in the MB correlates with pathological diagnosis of AD in human postmortem brain tissue. Whether and how MB neuronal circuitry contributes to neurodegeneration and memory deficits in AD are unknown. Using 5xFAD mice and postmortem MB samples from individuals with varying degrees of AD pathology, we identified two neuronal cell types in the MB harboring distinct electrophysiological properties and long-range projections: lateral neurons and medial neurons. lateral MB neurons harbored aberrant hyperactivity and exhibited early neurodegeneration in 5xFAD mice compared with lateral MB neurons in wild-type littermates. Inducing hyperactivity in lateral MB neurons in wild-type mice impaired performance on memory tasks, whereas attenuating aberrant hyperactivity in lateral MB neurons ameliorated memory deficits in 5xFAD mice. Our findings suggest that neurodegeneration may be a result of genetically distinct, projection-specific cellular dysfunction and that dysregulated lateral MB neurons may be causally linked to memory deficits in AD.

Neuroprotective Activity of Ethanolic Extract of Red Ginger Containing 6-Shogaol on Scopolamine-Induced Memory Impairment in Alzheimer's Mice

Red ginger contains 6-shogaol, which has a neuroprotective effect and is crucial in several brain diseases, including Alzheimer’s. This study investigated the neuroprotective effect of red ginger extract (RGE) containing 6-shogaol on scopolamine-induced memory loss in mice. Male Balb/C mice (n = 30; 6–7 weeks old) were divided into six groups: normal, Alzheimer, drug control (donepezil), and RGE (100, 200, and 400 mg/kg BW). In the acute experiment, the mice were treated 60 minutes before the test, followed by 1 mg/kg of scopolamine 30 minutes later. Thirty minutes later, the mice were placed individually in a Y-maze to observe spontaneous alteration activity (SAA). In the chronic experiment, the mice were treated once daily for seven days. On days 8–14, the mice were administered scopolamine and treatment. SAA was observed every 3–4 days. On day 15, malondialdehyde (MDA) and acetylcholinesterase (AChE) levels in the serum and brain were determined. RGE treatment 400 mg/kg BW, containing 1.664 µg of 6-shogaol per 100 mg of ethanol RGE, reduced memory loss better than the other two doses. RGE successfully decreased MDA and increased AChE in the serum and brain. RGE also showed effectively to improve memory in Alzheimer’s disease.

Aerial part of Houttuynia cordata reverses memory impairment by regulating amyloid beta accumulation and neuroinflammation in Alzheimer's disease model.

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by amyloid-β (Aβ) deposition, accompanied by neuroinflammation and memory dysfunction. Houttuyniae Herba (aerial parts of Houttuynia cordata, also known as fish mint; HH), an herbal medicine traditionally used to treat fever, urinary disorders, and pus, is revealed to protect neurons from Aβ toxicity and regulate cholinergic dysfunction in AD models. In this study, we aimed to investigate the effects of HH on excessive accumulation of Aβ followed by neuroinflammation, synaptic degeneration, and memory impairment. Two-month-old 5xFAD transgenic mice were administered HH at 100 mg/kg for 4months. We observed that HH treatment ameliorated memory impairment and reduced Aβ deposits in the brains of the mice. HH directly inhibited Aβ aggregation in vitro using the Thioflavin T assay and indirectly suppressed the amyloidogenic pathway by increasing alpha-secretase expression in the mice brain. In addition, HH exerted antineuroinflammatory effects by reducing of glial activation and p38 phosphorylation. Moreover, HH treatment increased the expression of synaptophysin, a presynaptic marker protein. Overall, HH alleviates memory impairment in AD by facilitating nonamyloidogenic pathway and inhibiting neuroinflammation. Therefore, we suggest that HH can be a promising herbal drug for patients with AD requiring multifaceted improvement.

Adult neurogenesis in Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of age-related dementia, characterized by progressive memory loss and cognitive disturbances. The hippocampus, where adult hippocampal neurogenesis (AHN), a relatively novel form of brain plasticity that refers to the birth of new neurons, occurs, is one of the first brain regions to be affected in AD patients. Recent studies showed that AHN persists throughout life in humans, but it drops sharply in AD patients. Next questions to consider would be whether AHN impairment is a contributing factor to learning and memory impairment in AD and whether restoring AHN could ameliorate or delay cognitive dysfunction. Here, we outline and discuss the current knowledge about the state of AHN in AD patients, AHN impairment as a potentially relevant mechanism underlying memory deficits in AD, therapeutic potential of activating AHN in AD, and the mechanisms of AHN impairment in AD.

Adult hippocampal neurogenesis in Alzheimer's disease: A roadmap to clinical relevance.

Adult hippocampal neurogenesis (AHN) drops sharply during early stages of Alzheimer's disease (AD), via unknown mechanisms, and correlates with cognitive status in AD patients. Understanding AHN regulation in AD could provide a framework for innovative pharmacological interventions. We here combine molecular, behavioral, and clinical data and critically discuss the multicellular complexity of the AHN niche in relation to AD pathophysiology. We further present a roadmap toward a better understanding of the role of AHN in AD by probing the promises and caveats of the latest technological advancements in the field and addressing the conceptual and methodological challenges ahead.

Effects of diverse Types of Toxoplasma gondii on the outcome of Alzheimer's disease in the rat model.

Toxoplasma gondii has lifelong persistence in the brain and its cysts can affect gene expression and change diverse biological functions of neurons. Many studies indicated T. gondii infection as a risk factor for the development of behavioral changes and neurodegenerative diseases such as Alzheimer's disease (AD), although the etiopathogenetic link between them has not been exactly elucidated. The current study aimed to examine the effects of chronic toxoplasmosis infection with Types I, II, and III strains (RH, PRU, and VEG) alone and in combination on cognitive impairments and neuronal death in the Aβ1-42-induced rat model of Alzheimer's disease. In the chronic toxoplasmosis phase, Alzheimer's induction was conducted by injecting Aβ1-42 oligomers into the rat brain hippocampus. Behavioral tests were conducted 10 days after the AD induction. Real-time PCR was performed to evaluate T. gondii parasite burden by amplification of the B1 gene. Cytokines IL-1β, TNF-α, and IL-10 were assayed in brain tissue supernatant using ELISA. Also, histopathological examinations were conducted to calculate inflammatory changes and neuronal death in the brain. Our findings showed that chronic toxoplasmosis infection with PRU reduces cognitive disorders, while the RH strain of T. gondii plays a destructive role and aggravates cognitive impairments in AD. Also, infection with a combination of PRU and VEG strains significantly improved spatial learning and memory impairments in Alzheimer's rat model. Histopathological findings also confirmed the results of behavioral tests, so that in AβPRU and AβPRU+VEG groups, neuronal death and infiltration of inflammatory cells were negligible and significantly less than in Alzheimer's and AβRH groups. Our findings indicate that chronic toxoplasmosis infection with PRU strain alone, also in combination with VEG strain can significantly improve cognitive disorders in AD rats, while RH strain plays a destructive role in AD pathogenesis.

Phytochemistry, Pharmacology, and Clinical Applications of Centella Asiatica (L.) Urban

Centella asiatica, a traditional Chinese medicine belonging to the Umbelliferae family, was recorded in the Eastern Han Dynasty. Owing to its wide developmental prospects, many scholars have extensively explored C. asiatica and made significant progress in recent years. In this study, we summarize the phytochemistry, pharmacology, and clinical applications of C. asiatica (L.) Urban based on Google Scholar, PubMed, and CNKI databases. Triterpenes and their glycosides, flavonoids, terpenoids, and volatile oils occur in herbs. The pharmacological effects mainly comprise improving cognition and memory impairment in Alzheimer’s disease and anti-inflammation activity. Clinical applications include the treatment of chronic kidney diseases, malignant intestinal obstruction, radiation dermatitis, precancerous lesions, chronic prostatitis, Alzheimer’s disease, and other diseases. This review provides insights into the phytochemistry, pharmacology, and clinical applications of C. asiatica and summarizes the shortcomings of the research in recent years to provide a reference for future research.

Comprehensive metabolomics and lipidomics profiling uncovering neuroprotective effects of Ginkgo biloba L. leaf extract on Alzheimer's disease.

Introduction: Ginkgo biloba L. leaf extract (GBLE) has been reported to be effective for alleviating cognitive and memory impairment in Alzheimer's disease (AD). Nevertheless, the potential mechanism remains unclear. Herein, this study aimed to explore the neuroprotective effects of GBLE on AD and elaborate the underlying therapeutic mechanism. Methods: Donepezil, the most widely prescribed drug for AD, was used as a positive control. An integrated metabolomics and lipidomics approach was adopted to characterize plasma metabolic phenotype of APP/PS1 double transgenic mice and describe the metabolomic and lipidomic fingerprint changes after GBLE intervention. The Morris water maze test and immunohistochemistry were applied to evaluate the efficacy of GBLE. Results: As a result, administration of GBLE significantly improved the cognitive function and alleviated amyloid beta (Aβ) deposition in APP/PS1 mice, showing similar effects to donepezil. Significant alterations were observed in metabolic signatures of APP/PS1 mice compared with wild type (WT) mice by metabolomic analysis. A total of 60 markedly altered differential metabolites were identified, including 28 lipid and lipid-like molecules, 13 organic acids and derivatives, 11 organic nitrogen compounds, and 8 other compounds, indicative of significant changes in lipid metabolism of AD. Further lipidomic profiling showed that the differential expressed lipid metabolites between APP/PS1 and WT mice mainly consisted of phosphatidylcholines, lysophosphatidylcholines, triglycerides, and ceramides. Taking together all the data, the plasma metabolic signature of APP/PS1 mice was primarily characterized by disrupted sphingolipid metabolism, glycerophospholipid metabolism, glycerolipid metabolism, and amino acid metabolism. Most of the disordered metabolites were ameliorated after GBLE treatment, 19 metabolites and 24 lipids of which were significantly reversely regulated (adjusted-p<0.05), which were considered as potential therapeutic targets of GBLE on AD. The response of APP/PS1 mice to GBLE was similar to that of donepezil, which significantly reversed the levels of 23 disturbed metabolites and 30 lipids. Discussion: Our data suggested that lipid metabolism was dramatically perturbed in the plasma of APP/PS1 mice, and GBLE might exert its neuroprotective effects by restoring lipid metabolic balance. This work provided a basis for better understanding the potential pathogenesis of AD and shed new light on the therapeutic mechanism of GBLE in the treatment of AD.