Alzheimer disease

Prevalence of Constipation in Elderly and Its Association With Dementia and Mild Cognitive Impairment: A Cross-Sectional Study

Background

Constipation and dementia have similar epidemiological characteristics. Changes in intestinal flora and characteristics of the brain-gut axis play roles in the pathogeneses of the two diseases, suggesting that there may be a close connection between the two. Most of the studies on constipation in dementia patients have focused on the population with α-synucleinopathies [Parkinson’s disease dementia (PDD), dementia with Lewy bodies (DLB)]. Few studies have reported the prevalence of constipation in all-cause dementia and mild cognitive impairment (MCI) populations.

Objective

To assess the prevalence of constipation in patients with all-cause dementia and MCI subtypes and to explore the association between constipation with dementia and MCI subtypes.

Methods

From May 2019 to December 2019, we conducted a population-based cross-sectional survey. A total of 11,743 participants aged 65 or older from nine cities in China were surveyed. Participants underwent a series of clinical examinations and neuropsychological measurements. Constipation, dementia, MCI and MCI subtype were diagnosed according to established criteria through standard diagnostic procedures.

Results

The overall age- and sex-adjusted prevalence of constipation in individuals aged 65 years and older was 14.8% (95% CI, 14.6–15.0). The prevalence rates of constipation were19.2% (95% CI, 17.3–21.0), 19.1% (95% CI, 16.8–21.5), 14.4% (95% CI, 12.8–15.9), and 13.8% (95% CI, 13.0–14.6) in the dementia, non-amnestic (na)-MCI, amnestic (a)-MCI and normal cognition populations, respectively. Multivariate logistic regression analysis showed that higher prevalence of constipation was associated with dementia (p = 0.0.032, OR = 1.18, 95% CI: 1.02–1.38) and na-MCI (p = 0.003, OR = 1.30, 95% CI: 1.09–1.54).

Conclusion

The present study found a high prevalence of constipation in elderly individuals in China, and higher in patients with dementia and na-MCI.

Beta-Amyloid Instigates Dysfunction of Mitochondria in Cardiac Cells

Alzheimer's disease (AD) includes the formation of extracellular deposits comprising aggregated β-amyloid (Aβ) fibers associated with oxidative stress, inflammation, mitochondrial abnormalities, and neuronal loss. There is an associative link between AD and cardiac diseases; however, the mechanisms underlying the potential role of AD, particularly Aβ in cardiac cells, remain unknown. Here, we investigated the role of mitochondria in mediating the effects of Aβ1-40 and Aβ1-42 in cultured cardiomyocytes and primary coronary endothelial cells. Our results demonstrated that Aβ1-40 and Aβ1-42 are differently accumulated in cardiomyocytes and coronary endothelial cells. Aβ1-42 had more adverse effects than Aβ1-40 on cell viability and mitochondrial function in both types of cells. Mitochondrial and cellular ROS were significantly increased, whereas mitochondrial membrane potential and calcium retention capacity decreased in both types of cells in response to Aβ1-42. Mitochondrial dysfunction induced by Aβ was associated with apoptosis of the cells. The effects of Aβ1-42 on mitochondria and cell death were more evident in coronary endothelial cells. In addition, Aβ1-40 and Aβ1-42 significantly increased Ca2+ -induced swelling in mitochondria isolated from the intact rat hearts. In conclusion, this study demonstrates the toxic effects of Aβ on cell survival and mitochondria function in cardiac cells.

Deciphering the role of PGC-1α in neurological disorders: from mitochondrial dysfunction to synaptic failure

The onset and mechanisms underlying neurodegenerative diseases remain uncertain. The main features of neurodegenerative diseases have been related with cellular and molecular events like neuronal loss, mitochondrial dysfunction and aberrant accumulation of misfolded proteins or peptides in specific areas of the brain. The most prevalent neurodegenerative diseases belonging to age-related pathologies are Alzheimer's disease, Huntington's disease, Parkinson's disease and amyotrophic lateral sclerosis. Interestingly, mitochondrial dysfunction has been observed to occur during the early onset of several neuropathological events associated to neurodegenerative diseases. The master regulator of mitochondrial quality control and energetic metabolism is the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Additionally, it has been observed that PGC-1α appears to be a key factor in maintaining neuronal survival and synaptic transmission. In fact, PGC-1α downregulation in different brain areas (hippocampus, substantia nigra, cortex, striatum and spinal cord) that occurs in function of neurological damage including oxidative stress, neuronal loss, and motor disorders has been seen in several animal and cellular models of neurodegenerative diseases. Current evidence indicates that PGC-1α upregulation may serve as a potent therapeutic approach against development and progression of neuronal damage. Remarkably, increasing evidence shows that PGC-1α deficient mice have neurodegenerative diseases-like features, as well as neurological abnormalities. Finally, we discuss recent studies showing novel specific PGC-1α isoforms in the central nervous system that appear to exert a key role in the age of onset of neurodegenerative diseases and have a neuroprotective function in the central nervous system, thus opening a new molecular strategy for treatment of neurodegenerative diseases. The purpose of this review is to provide an up-to-date overview of the PGC-1α role in the physiopathology of neurodegenerative diseases, as well as establish the importance of PGC-1α function in synaptic transmission and neuronal survival.

Recent Advances in Molecular Pathways and Therapeutic Implications Targeting Mitochondrial Dysfunction for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder which leads to mental deterioration due to aberrant accretion of misfolded proteins in the brain. According to mitochondrial cascade hypothesis, mitochondrial dysfunction is majorly involved in the pathogenesis of AD. Many drugs targeting mitochondria to treat and prevent AD are in different phases of clinical trials for the evaluation of safety and efficacy as mitochondria are involved in various cellular and neuronal functions. Mitochondrial dynamics is regulated by fission and fusion processes mediated by dynamin-related protein (Drp1). Inner membrane fusion takes place by OPA1 and outer membrane fusion is facilitated by mitofusin1 and mitofusin2 (Mfn1/2). Excessive calcium release also impairs mitochondrial functions; to overcome this, calcium channel blockers like nilvadipine are used. Another process acting as a regulator of mitochondrial function is mitophagy which is involved in the removal of damaged and non-functional mitochondria however this process is also altered in AD due to mutations in Presenilin1 (PS1) and Amyloid Precursor Protein (APP) gene. Mitochondrial dynamics is altered in AD which led to the discovery of various fission protein (like Drp1) inhibitors and drugs that promote fusion. Modulations in AMPK, SIRT1 and Akt pathways can also come out to be better therapeutic strategies as these pathways regulate functions of mitochondria. Oxidative phosphorylation is major generator of Reactive Oxygen Species (ROS) leading to mitochondrial damage; therefore reduction in production of ROS by using antioxidants like MitoQ, Curcumin and Vitamin Eis quiteeffective.

Impaired Cognitive Function is Associated with Motor Function and Activities of Daily Living in Mild to Moderate Alzheimer's Dementia

BACKGROUND

The deterioration of cognitive and motor functions and activities of daily living is common in Alzheimer's dementia.

OBJECTIVES

The purpose of this study was to investigate the correlation and the strength of the relationship between cognitive function and motor function and activities of daily living after a diagnosis of Alzheimer's disease dementia.

METHODS

Sixty-three patients with mild to moderate Alzheimer's disease dementia in a community setting of South Korea were examined for cognitive and motor functions, and functional levels. The test or measures used for cognitive function were the Mini-Mental State Examination (MMSE), Global Deterioration Scale (GDS), and Clinical Dementia Rating (CDR). The 10-meter walking test (10MWT), Berg Balance Scale (BBS), and Timed Up and Go Test (TUG) were used to examine motor function, while the Modified Barthel Index (MBI) and Katz Index (KI) were used to examining activities of daily living.

RESULTS

The MMSE had a positive correlation with that from the BBS (r=.338, p<.05), MBI (r=.363, p<.05), and KI (r=.276, p<.05). The GDS was negatively correlated with BBS (r=.319, p<.05). Multivariate regression analysis showed that MMSE was a major explanatory variable for BBS (R2 =.115, β=.338, p<.05) MBI (R2 =.131, β=.363, p<.05), and KI (R2 =.076, β=.276, p<.05).

CONCLUSION

The results of the present study show that cognitive function by MMSE is correlated with balance by BBS and activities of daily living by MBI and KI, and MMSE, which are tests or measures for cognitive function, can be explanatory variable to explain variations in the BBS, MBI, and KI in the persons with mild to moderate Alzheimer's dementia. It may mean that a decrease in cognitive function was found to affect motor function and activities of daily living. Based on this study, appropriate intervention approaches including physical exercise, should be considered for caring for persons with mild to moderate Alzheimer's dementia in a community setting.

Microvascular degeneration occurs before plaque onset and progresses with age in 3xTg AD mice

Heart disease and vascular disease positively correlate with the incidence of Alzheimer's disease (AD). Although there is ostensible involvement of dysfunctional cerebrovasculature in AD pathophysiology, the characterization of the specific changes and development of vascular injury during AD remains unclear. In the present study, we established a time-course for the structural changes and degeneration of the angioarchitecture in AD. We used cerebrovascular corrosion cast and µCT imaging to evaluate the geometry, topology, and complexity of the angioarchitecture in the brain of wild type and 3xTg AD mice. We hypothesized that changes to the microvasculature occur early during the disease, and these early identifiable aberrations would be more prominent in the brain subregions implicated in the cognitive decline of AD. Whole-brain analysis of the angioarchitecture indicated early morphological abnormalities and degeneration of microvascular networks in 3xTg AD mice. Our analysis of the hippocampus and cortical subregions revealed microvascular degeneration with onset and progression that was subregion dependent.

Activated microglia mitigate Aβ-associated tau seeding and spreading

In Alzheimer's disease (AD) models, AD risk variants in the microglial-expressed TREM2 gene decrease Aβ plaque-associated microgliosis and increase neuritic dystrophy as well as plaque-associated seeding and spreading of tau aggregates. Whether this Aβ-enhanced tau seeding/spreading is due to loss of microglial function or a toxic gain of function in TREM2-deficient microglia is unclear. Depletion of microglia in mice with established brain amyloid has no effect on amyloid but results in less spine and neuronal loss. Microglial repopulation in aged mice improved cognitive and neuronal deficits. In the context of AD pathology, we asked whether microglial removal and repopulation decreased Aβ-driven tau seeding and spreading. We show that both TREM2KO and microglial ablation dramatically enhance tau seeding and spreading around plaques. Interestingly, although repopulated microglia clustered around plaques, they had a reduction in disease-associated microglia (DAM) gene expression and elevated tau seeding/spreading. Together, these data suggest that TREM2-dependent activation of the DAM phenotype is essential in delaying Aβ-induced pathological tau propagation.

Hyperactivation of monocytes and macrophages in MCI patients contributes to the progression of Alzheimer's disease

Background

Alzheimer’s disease (AD) is the most common neurodegenerative disease ultimately manifesting as clinical dementia. Despite considerable effort and ample experimental data, the role of neuroinflammation related to systemic inflammation is still unsettled. While the implication of microglia is well recognized, the exact contribution of peripheral monocytes/macrophages is still largely unknown, especially concerning their role in the various stages of AD.

Objectives

AD develops over decades and its clinical manifestation is preceded by subjective memory complaints (SMC) and mild cognitive impairment (MCI); thus, the question arises how the peripheral innate immune response changes with the progression of the disease. Therefore, to further investigate the roles of monocytes/macrophages in the progression of AD we assessed their phenotypes and functions in patients at SMC, MCI and AD stages and compared them with cognitively healthy controls. We also conceptualised an idealised mathematical model to explain the functionality of monocytes/macrophages along the progression of the disease.

Results

We show that there are distinct phenotypic and functional changes in monocyte and macrophage populations as the disease progresses. Higher free radical production upon stimulation could already be observed for the monocytes of SMC patients. The most striking results show that activation of peripheral monocytes (hyperactivation) is the strongest in the MCI group, at the prodromal stage of the disease. Monocytes exhibit significantly increased chemotaxis, free radical production, and cytokine production in response to TLR2 and TLR4 stimulation.

Conclusion

Our data suggest that the peripheral innate immune system is activated during the progression from SMC through MCI to AD, with the highest levels of activation being in MCI subjects and the lowest in AD patients. Some of these parameters may be used as biomarkers, but more holistic immune studies are needed to find the best period of the disease for clinical intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-021-00236-x.

Cellular Senescence: Pathogenic Mechanisms in Lung Fibrosis

Pulmonary fibrosis is a chronic and fatal lung disease that significantly impacts the aging population globally. To date, anti-fibrotic, immunosuppressive, and other adjunct therapy demonstrate limited efficacies. Advancing our understanding of the pathogenic mechanisms of lung fibrosis will provide a future path for the cure. Cellular senescence has gained substantial interest in recent decades due to the increased incidence of fibroproliferative lung diseases in the older age group. Furthermore, the pathologic state of cellular senescence that includes maladaptive tissue repair, decreased regeneration, and chronic inflammation resembles key features of progressive lung fibrosis. This review describes regulatory pathways of cellular senescence and discusses the current knowledge on the senescence of critical cellular players of lung fibrosis, including epithelial cells (alveolar type 2 cells, basal cells, etc.), fibroblasts, and immune cells, their phenotypic changes, and the cellular and molecular mechanisms by which these cells contribute to the pathogenesis of pulmonary fibrosis. A few challenges in the field include establishing appropriate in vivo experimental models and identifying senescence-targeted signaling molecules and specific therapies to target senescent cells, known collectively as "senolytic" or "senotherapeutic" agents.

Human CALHM5: Insight in large pore lipid gating ATP channel and associated neurological pathologies

Recently calcium homeostasis modulators (CALHMs) are identified as ATP release channels play crucial role in functioning of neurons including gustatory signaling and neuronal excitability. Pathologies of Alzheimer's disease and depression have been associated with the dysfunction of CALHMs. Recently, CALHMs has been emerged as an important therapeutic research particularly in neurobiological studies. CALHM1 is most extensively studied among CALHMs and is an ATP and ion channel that is activated by membrane depolarization or removal of extracellular Ca²⁺. Despite the emerged role of CALHM5 shown by an recently assembled data; however, the neuronal function remains obscure until the first Cryo-EM structure of CALHM5 was recently solved by various research group which acts as a template to study the hidden functional properties of the CALHM5 protein based on structure function mechanism. It provides insight in some of the different pathophysiological roles. CALHM5 structure showed an abnormally large pore channel structure assembled as an undecamer with four transmembrane helices (TM1-TM4), an N-terminal helix (NTH), an extracellular loop region and an intracellular C-terminal domain (CTD) that consists of three α-helices CH1-3. The TM1 and NTH were always poorly defined among all CALHMs; however, these regions were well defined in CALHM5 channel structure. In this context, this review will provide insight in structure, function and mechanism to understand its significant role in pathological diseases particularly in Alzheimer's disease. Moreover, it focuses on CALHM5 structure and recent associated properties based on Cryo-EM research.

Biogenic metallic elements in the human brain?

The chemistry of copper and iron plays a critical role in normal brain function. A variety of enzymes and proteins containing positively charged Cu+, Cu2+, Fe2+, and Fe3+ control key processes, catalyzing oxidative metabolism and neurotransmitter and neuropeptide production. Here, we report the discovery of elemental (zero-oxidation state) metallic Cu0 accompanying ferromagnetic elemental Fe0 in the human brain. These nanoscale biometal deposits were identified within amyloid plaque cores isolated from Alzheimer's disease subjects, using synchrotron x-ray spectromicroscopy. The surfaces of nanodeposits of metallic copper and iron are highly reactive, with distinctly different chemical and magnetic properties from their predominant oxide counterparts. The discovery of metals in their elemental form in the brain raises new questions regarding their generation and their role in neurochemistry, neurobiology, and the etiology of neurodegenerative disease.

Multi-target Natural and Nature-Inspired Compounds against Neurodegeneration: A Focus on Dual Cholinesterase and Phosphodiesterase Inhibitors

Alzheimer’s disease is a memory-related neurodegenerative condition leading to cognitive impairment. Cholinergic deficit, together with other underlying mechanisms, leads the to onset and progression of the disease. Consequently, acetylcholinesterase inhibitors are used for the symptomatic treatment of dementia, even if limited efficacy is observed. More recently, some specific phosphodiesterase isoforms emerged as promising, alternative targets for developing inhibitors to contrast neurodegeneration. Phosphodiesterase isoforms 4, 5 and 9 were found to be expressed in brain regions that are relevant for cognition. Given the complex nature of Alzheimer’s disease and the combination of involved biochemical mechanisms, the development of polypharmacological agents acting on more than one pathway is desirable. This review provides an overview of recent reports focused on natural and Nature-inspired small molecules, or plant extracts, acting as dual cholinesterase and phosphodiesterase inhibitors. In the context of the multi-target directed ligand approach, such molecules would pave the way for the development of novel agents against neurodegeneration. More precisely, according to the literature data, xanthines, other alkaloids, flavonoids, coumarins and polyphenolic acids represent promising scaffolds for future optimization.

Assessing the Possible Influence of Residues of Ractopamine, a Livestock Feed Additive, in Meat on Alzheimer Disease

The feed additive ractopamine, a β-adrenergic agonist, has been approved for use in livestock for nearly 2 decades. Studies of its possible adverse effects in humans have concentrated exclusively on cardiovascular disease and cardiovascular functional disorders in the past. In this article, whether and how ractopamine may affect neurodegeneration, either to promote or to reduce the incidence of Alz­heimer disease, will be discussed based on the recent controversial findings that β-adrenoreceptor activation not only can stimulate Alzheimer-pathogenic amyloid-β accumulation but also are able to enhance hippocampal neurogenesis and ameliorate mouse memory deficits in independent laboratory studies. Furthermore, environmental enrichment has been found to prevent impairment of memory-related hippocampal long-term potentiation and microglia-mediated neuroinflammation induced by amyloid-β. These beneficial effects are achieved mainly through enhanced β-adrenergic signaling and can be imitated by β agonist isoprotenerol. Finally, it has been demonstrated that the β-adrenergic agonist salbutamol could bind directly to tau protein and interfere with the tau filament formation seen in the prodromal phase of Alzheimer disease. These complex but interesting issues lead to contradictory speculations of possible effects of ractopamine residue in meat on Alzheimer disease. Hypotheses derived from this review surely deserve carefully designed laboratory investigations and clinical studies in the future.

Development of a Robust High-Throughput Screening Platform for Inhibitors of the Striatal-Enriched Tyrosine Phosphatase (STEP)

Many human diseases are the result of abnormal expression or activation of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Not surprisingly, more than 30 tyrosine kinase inhibitors (TKIs) are currently in clinical use and provide unique treatment options for many patients. PTPs on the other hand have long been regarded as “undruggable” and only recently have gained increased attention in drug discovery. Striatal-enriched tyrosine phosphatase (STEP) is a neuron-specific PTP that is overactive in Alzheimer’s disease (AD) and other neurodegenerative and neuropsychiatric disorders, including Parkinson’s disease, schizophrenia, and fragile X syndrome. An emergent model suggests that the increase in STEP activity interferes with synaptic function and contributes to the characteristic cognitive and behavioral deficits present in these diseases. Prior efforts to generate STEP inhibitors with properties that warrant clinical development have largely failed. To identify novel STEP inhibitor scaffolds, we developed a biophysical, label-free high-throughput screening (HTS) platform based on the protein thermal shift (PTS) technology. In contrast to conventional HTS using STEP enzymatic assays, we found the PTS platform highly robust and capable of identifying true hits with confirmed STEP inhibitory activity and selectivity. This new platform promises to greatly advance STEP drug discovery and should be applicable to other PTP targets.

A Comprehensive Review of Cholinesterase Modeling and Simulation

The present article reviews published efforts to study acetylcholinesterase and butyrylcholinesterase structure and function using computer-based modeling and simulation techniques. Structures and models of both enzymes from various organisms, including rays, mice, and humans, are discussed to highlight key structural similarities in the active site gorges of the two enzymes, such as flexibility, binding site location, and function, as well as differences, such as gorge volume and binding site residue composition. Catalytic studies are also described, with an emphasis on the mechanism of acetylcholine hydrolysis by each enzyme and novel mutants that increase catalytic efficiency. The inhibitory activities of myriad compounds have been computationally assessed, primarily through Monte Carlo-based docking calculations and molecular dynamics simulations. Pharmaceutical compounds examined herein include FDA-approved therapeutics and their derivatives, as well as several other prescription drug derivatives. Cholinesterase interactions with both narcotics and organophosphate compounds are discussed, with the latter focusing primarily on molecular recognition studies of potential therapeutic value and on improving our understanding of the reactivation of cholinesterases that are bound to toxins. This review also explores the inhibitory properties of several other organic and biological moieties, as well as advancements in virtual screening methodologies with respect to these enzymes.

Donepezil and Rivastigmine: Pharmacokinetic Profile and Brain-targeting After Intramuscular Administration in Rats

Current palliative pharmacotherapy of Alzheimer's disease based on the cholinergic hypothesis led to the development of four cholinesterase inhibitors. These compounds can bring prolongation of the symptom-free period in some patients. This is the first report directly comparing donepezil and rivastigmine plasma and brain levels in in-vivo study. Donepezil and rivastigmine were applied i.m. to rats; the dose was calculated from clinical recommendations. The samples were analysed on an Agilent 1260 Series LC with UV/VIS detector. An analytical column (Waters Spherisorb S5 W (250 mm × 4.6 i.d.; 5 μm particle size)) with guard column (Waters Spherisorb S5 W (30 mm × 4.6 mm i.d.)) was used. The mobile phase contained acetonitrile and 50 mM sodium dihydrogen phosphate (17:83; v/v); pH 3.1. The LLOQ in rat plasma was 0.5 ng/mL for donepezil and 0.8 ng/mL for rivastigmine, and the LLOQ in rat brain was 1.0 ng/mL for donepezil and 1.1 ng/mL for rivastigmine. Both compounds showed ability to target the central nervous system, with brain concentrations exceeding those in plasma. Maximum brain concentration after i.m. administration was reached in the 36 (8.34 ± 0.34 ng/mL) and 17 minute (6.18 ± 0.40 ng/mL), respectively for donepezil and rivastigmine. The differences in brain profile can be most easily expressed by plasma/brain AUC_total ratios: donepezil ratio in the brain was nine-times higher than in plasma and rivastigmine ratio was less than two-times higher than in plasma.

A Review of Automated Techniques for Assisting the Early Detection of Alzheimer's Disease with a Focus on EEG

In this paper, we review state-of-the-art approaches that apply signal processing (SP) and machine learning (ML) to automate the detection of Alzheimer's disease (AD) and its prodromal stages. In the first part of the document, we describe the economic and social implications of the disease, traditional diagnosis techniques, and the fundaments of automated AD detection. Then, we present electroencephalography (EEG) as an appropriate alternative for the early detection of AD, owing to its reduced cost, portability, and non-invasiveness. We also describe the main time and frequency domain EEG features that are employed in AD detection. Subsequently, we examine some of the main studies of the last decade that aim to provide an automatic detection of AD and its previous stages by means of SP and ML. In these studies, brain data was acquired using multiple medical techniques such as magnetic resonance imaging, positron emission tomography, and EEG. The main aspects of each approach, namely feature extraction, classification model, validation approach, and performance metrics, are compiled and discussed. Lastly, a set of conclusions and recommendations for future research on AD automatic detection are drawn in the final section of the paper.

Crosstalk between Different DNA Repair Pathways Contributes to Neurodegenerative Diseases

Simple Summary

Constant exposure to endogenous and environmental factors induces oxidative stress and DNA damage. Rare brain disorders caused by defects in DNA repair and DNA damage response (DDR) signaling establish that failure to process DNA damage may lead to neurodegeneration. In this review, we present mechanisms that link DDR with neurodegeneration in these disorders and discuss their relevance for common age-related neurodegenerative diseases (NDDs). Moreover, we highlight recent insight into the crosstalk between the DDR and other cellular processes known to be disturbed during NDDs.

Abstract

Genomic integrity is maintained by DNA repair and the DNA damage response (DDR). Defects in certain DNA repair genes give rise to many rare progressive neurodegenerative diseases (NDDs), such as ocular motor ataxia, Huntington disease (HD), and spinocerebellar ataxias (SCA). Dysregulation or dysfunction of DDR is also proposed to contribute to more common NDDs, such as Parkinson’s disease (PD), Alzheimer’s disease (AD), and Amyotrophic Lateral Sclerosis (ALS). Here, we present mechanisms that link DDR with neurodegeneration in rare NDDs caused by defects in the DDR and discuss the relevance for more common age-related neurodegenerative diseases. Moreover, we highlight recent insight into the crosstalk between the DDR and other cellular processes known to be disturbed during NDDs. We compare the strengths and limitations of established model systems to model human NDDs, ranging from C. elegans and mouse models towards advanced stem cell-based 3D models.

The most prevalent rare coding variants of TREM2 conferring risk of Alzheimer's disease: A systematic review and meta-analysis

Rare variants in the coding sequence of triggering receptor expressed on myeloid cells 2 (TREM2) have been identified in Alzheimer's disease (AD). They have been reported to be causative or confer risk of AD in several populations. However, the results are not conclusive. Therefore, a meta-analysis was performed to investigate the association between rare variants of TREM2 and the susceptibility to AD. Case-control studies meeting the inclusion criteria were identified by searching the PubMed, Embase and Web of Science databases. The association between four commonly analyzed variants of TREM2, p.Arg47His (R47H), p.Arg62His (R62H), p.Asp87Asn (D87N) and p.His157Tyr (H157Y), and the risk of AD were evaluated by meta-analyses with the fixed-effects model. Finally, a total of 26 datasets comprising 28,007 cases and 45,121 controls were included. There was no or low between-study heterogeneity in all comparisons. A significantly increased risk of AD was observed in carriers of R47H compared with non-carriers [odds ratio (OR)=3.88, 95% CI: 3.17-4.76, P<0.001], R62H (OR=1.37, 95% CI: 1.11-1.70, P=0.004) and H157Y (OR=4.22, 95% CI: 1.93-9.21, P<0.001). However, R62H only conferred a mild risk compared to R47H and H157Y (OR=1.37 vs. 3.88 and 4.22, respectively). D87N was not associated with AD susceptibility. Sensitivity analysis indicated that the association identified for R62H was not significant (P=0.192) when excluding a large-sample study. Subgroup analysis according to ethnicity revealed significant associations (R47H and H157Y) in Caucasians but not in Asians. In conclusion, rare coding variants of TREM2 were associated with an elevated risk of AD, particularly in Caucasians.

Cerebrospinal Fluid Biomarkers of Alzheimer's Disease: Current Evidence and Future Perspectives

Alzheimer's disease is a progressive, clinically heterogeneous, and particularly complex neurodegenerative disease characterized by a decline in cognition. Over the last two decades, there has been significant growth in the investigation of cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease. This review presents current evidence from many clinical neurochemical studies, with findings that attest to the efficacy of existing core CSF biomarkers such as total tau, phosphorylated tau, and amyloid-β (Aβ42), which diagnose Alzheimer's disease in the early and dementia stages of the disorder. The heterogeneity of the pathophysiology of the late-onset disease warrants the growth of the Alzheimer's disease CSF biomarker toolbox; more biomarkers showing other aspects of the disease mechanism are needed. This review focuses on new biomarkers that track Alzheimer's disease pathology, such as those that assess neuronal injury (VILIP-1 and neurofilament light), neuroinflammation (sTREM2, YKL-40, osteopontin, GFAP, progranulin, and MCP-1), synaptic dysfunction (SNAP-25 and GAP-43), vascular dysregulation (hFABP), as well as CSF α-synuclein levels and TDP-43 pathology. Some of these biomarkers are promising candidates as they are specific and predict future rates of cognitive decline. Findings from the combinations of subclasses of new Alzheimer's disease biomarkers that improve their diagnostic efficacy in detecting associated pathological changes are also presented.

Impact of TREM2R47H variant on tau pathology-induced gliosis and neurodegeneration

Alzheimer's disease (AD) is characterized by plaques containing amyloid-β (Aβ) and neurofibrillary tangles composed of aggregated, hyperphosphorylated tau. Beyond tau and Aβ, evidence suggests that microglia play an important role in AD pathogenesis. Rare variants in the microglia-expressed triggering receptor expressed on myeloid cells 2 (TREM2) gene increase AD risk 2- to 4-fold. It is likely that these TREM2 variants increase AD risk by decreasing the response of microglia to Aβ and its local toxicity. However, neocortical Aβ pathology occurs many years before neocortical tau pathology in AD. Thus, it will be important to understand the role of TREM2 in the context of tauopathy. We investigated the impact of the AD-associated TREM2 variant (R47H) on tau-mediated neuropathology in the PS19 mouse model of tauopathy. We assessed PS19 mice expressing human TREM2CV (common variant) or human TREM2R47H. PS19-TREM2R47H mice had significantly attenuated brain atrophy and synapse loss versus PS19-TREM2CV mice. Gene expression analyses and CD68 immunostaining revealed attenuated microglial reactivity in PS19-TREM2R47H versus PS19-TREM2CV mice. There was also a decrease in phagocytosis of postsynaptic elements by microglia expressing TREM2R47H in the PS19 mice and in human AD brains. These findings suggest that impaired TREM2 signaling reduces microglia-mediated neurodegeneration in the setting of tauopathy.

The Correlations Between Plasma Fibrinogen With Amyloid-Beta and Tau Levels in Patients With Alzheimer's Disease

Recent studies show that fibrinogen plays a role in the pathogenesis of Alzheimer's disease (AD), which may be crucial to neurovascular damage and cognitive impairment. However, there are few clinical studies on the relationship between fibrinogen and AD. 59 ¹¹C-PiB-PET diagnosed AD patients and 76 age- and gender-matched cognitively normal controls were included to analyze the correlation between plasma β-amyloid (Aβ) and tau levels with fibrinogen levels. 35 AD patients and 76 controls with cerebrospinal fluid (CSF) samples were included to further analyze the correlation between CSF Aβ and tau levels with fibrinogen levels. In AD patients, plasma fibrinogen levels were positively correlated with plasma Aβ40 and Aβ42 levels, and negatively correlated with CSF Aβ42 levels. Besides, fibrinogen levels were positively correlated with CSF total tau (t-tau), and phosphorylated tau-181 (p-tau) levels and positively correlated with the indicators of Aβ deposition in the brain, such as t-tau/Aβ42, p-tau/Aβ42 levels. In normal people, fibrinogen levels lack correlation with Aβ and tau levels in plasma and CSF. This study suggests that plasma fibrinogen levels are positively correlated with Aβ levels in the plasma and brain in AD patients. Fibrinogen may be involved in the pathogenesis of AD.

Effects of Phenylethanoid Glycosides Extracted from Herba Cistanches on the Learning and Memory of the APP/PSI Transgenic Mice with Alzheimer's Disease

Background

To investigate the effects of phenylethanoid glycosides (PhGs) extracted from Herba Cistanches on the behavioral and cognition capacity of the APP/PSI transgenic mice with Alzheimer's disease (AD).

Methods

AD mice were randomly divided into the control group, model group, donepezil group, PhG groups, and verbascose group, respectively. Three weeks later, the animals were subject to behavioral and cognition evaluation by the nesting test, Morris water maze test, and step-down test.

Results

The cognition capacity in these groups showed a significant increase compared with that in the model group. The step-down test indicated that the errors induced by the memory decrease in the PhG groups and verbascose group showed a significant decrease compared with those in the model group (P < 0.05).

Conclusions

PhGs attenuated the cognitive dysfunction features of the APP/PSI transgenic gene. Besides, PhGs were the active components for the anti-AD activity of H. Cistanches.

TREM2 alters the phagocytic, apoptotic and inflammatory response to Aβ42 in HMC3 cells

Alzheimer's disease (AD) is characterized by the accumulation in the brain of extracellular amyloid β (Aβ) plaques as well as intraneuronal inclusions (neurofibrillary tangles) consisting of total tau and phosphorylated tau. Also present are dystrophic neurites, loss of synapses, neuronal death, and gliosis. AD genetic studies have highlighted the importance of inflammation in this disease by identifying several risk associated immune response genes, including TREM2. TREM2 has been strongly implicated in basic microglia function including, phagocytosis, apoptosis, and the inflammatory response to Aβ in mouse brain and primary cells. These studies show that microglia are key players in the response to Aβ and in the accumulation of AD pathology. However, details are still missing about which apoptotic or inflammatory factors rely on TREM2 in their response to Aβ, especially in human cell lines. Given these previous findings our hypothesis is that TREM2 influences the response to Aβ toxicity by enhancing phagocytosis and inhibiting both the BCL-2 family of apoptotic proteins and pro-inflammatory cytokines. Aβ₄₂ treatment of the human microglial cell line, HMC3 cells, was performed and TREM2 was overexpressed or silenced and the phagocytosis, apoptosis and inflammatory response were evaluated. Results indicate that a robust phagocytic response to Aβ after 24 h requires TREM2 in HMC3 cells. Also, TREM2 inhibits Aβ induced apoptosis by activating the Mcl-1/Bim complex. TREM2 is involved in activation of IP-10, MIP-1a, and IL-8, while it inhibits FGF-2, VEGF and GRO. Taken together, TREM2 plays a role in enhancing the microglial functional response to Aβ toxicity in HMC3 cells. This novel information suggests that therapeutic strategies that seek to activate TREM2 may not only enhance phagocytosis and inhibit apoptosis, but may also inhibit beneficial inflammatory factors, emphasizing the need to define TREM2-related inflammatory activity in not only mouse models of AD, but also in human AD.

Prolonged Systemic Inflammation Alters Muscarinic Long-Term Potentiation (mLTP) in the Hippocampus

The cholinergic system plays a fundamental role in learning and memory. Pharmacological activation of the muscarinic receptor M1R potentiates NMDA receptor activity and induces short-term potentiation at the synapses called muscarinic LTP, mLTP. Dysfunction of cholinergic transmission has been detected in the settings of cognitive impairment and dementia. Systemic inflammation as well as neuroinflammation has been shown to profoundly alter synaptic transmission and LTP. Indeed, intervention which is aimed at reducing neuroinflammatory changes in the brain has been associated with an improvement in cognitive functions. While cognitive impairment caused either by cholinergic dysfunction and/or by systemic inflammation suggests a possible connection between the two, so far whether systemic inflammation affects mLTP has not been extensively studied. In the present work, we explored whether an acute versus persistent systemic inflammation induced by LPS injections would differently affect the ability of hippocampal synapses to undergo mLTP. Interestingly, while a short exposure to LPS resulted in a transient deficit in mLTP expression, a longer exposure persistently impaired mLTP. We believe that these findings may be involved in cognitive dysfunctions following sepsis and possibly neuroinflammatory processes.

Targeting Impaired Antimicrobial Immunity in the Brain for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and aging is the most common risk factor for developing the disease. The etiology of AD is not known but AD may be considered as a clinical syndrome with multiple causal pathways contributing to it. The amyloid cascade hypothesis, claiming that excess production or reduced clearance of amyloid-beta (Aβ) and its aggregation into amyloid plaques, was accepted for a long time as the main cause of AD. However, many studies showed that Aβ is a frequent consequence of many challenges/pathologic processes occurring in the brain for decades. A key factor, sustained by experimental data, is that low-grade infection leading to production and deposition of Aβ, which has antimicrobial activity, precedes the development of clinically apparent AD. This infection is chronic, low grade, largely clinically silent for decades because of a nearly efficient antimicrobial immune response in the brain. A chronic inflammatory state is induced that results in neurodegeneration. Interventions that appear to prevent, retard or mitigate the development of AD also appear to modify the disease. In this review, we conceptualize further that the changes in the brain antimicrobial immune response during aging and especially in AD sufferers serve as a foundation that could lead to improved treatment strategies for preventing or decreasing the progression of AD in a disease-modifying treatment.

Nanoscale chemical speciation of β-amyloid/iron aggregates using soft X-ray spectromicroscopy

Nanoscale resolution X-ray spectromicroscopy shows the co-incubation of β-amyloid (Aβ) and iron(iii) to result in aggregate structures displaying nanoscale heterogeneity in Aβ and iron chemistry, including the formation of potentially cytotoxic Fe⁰.

Polygala tenuifolia: a source for anti-Alzheimer's disease drugs

Context: Alzheimer's disease (AD) is a chronic neurodegenerative disease that originates from central nervous system lesions or recessions. Current estimates suggest that this disease affects over 35 million people worldwide. However, lacking effective drugs is the biggest handicap in treating AD. In traditional Chinese medicine (TCM), Polygala tenuifolia Willd. (Polygalaceae) is generally used to treat insomnia, memory dysfunction and neurasthenia.Objective: This review article explores the role of P. tenuifolia and its active components in anti-Alzheimer's disease.Methods: Literature for the last ten years was obtained through a search on PubMed, SciFinder, CNKI, Google Scholar, Web of Science, Science Direct and China Knowledge Resource Integrated with the following keywords: Polygala tenuifolia, polygalasaponin XXXII (PGS 32), tenuifolin, polygalacic acid, senegenin, tenuigenin, Alzheimer's disease.Results: Polygala tenuifolia and its active components have multiplex neuroprotective potential associated with AD, such as anti-Aβ aggregation, anti-Tau protein, anti-inflammation, antioxidant, anti-neuronal apoptosis, enhancing central cholinergic system and promote neuronal proliferation.Conclusions: Polygala tenuifolia and its active components exhibit multiple neuroprotective effects. Hence, P. tenuifolia is a potential drug against Alzheimer's disease, especially in terms of prevention.

Mitochondrial Protein Import Dysfunction in Pathogenesis of Neurodegenerative Diseases

Mitochondria play an essential role in maintaining energy homeostasis and cellular survival. In the brain, higher ATP production is required by mature neurons for communication. Most of the mitochondrial proteins transcribe in the nucleus and import in mitochondria through different pathways of the mitochondrial protein import machinery. This machinery plays a crucial role in determining mitochondrial morphology and functions through mitochondrial biogenesis. Failure of this machinery and any alterations during mitochondrial biogenesis underlies neurodegeneration resulting in Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD) etc. Current knowledge has revealed the different pathways of mitochondrial protein import machinery such as translocase of the outer mitochondrial membrane complex, the presequence pathway, carrier pathway, β-barrel pathway, and mitochondrial import and assembly machinery etc. In this review, we have discussed the recent studies regarding protein import machinery, beyond the well-known effects of increased oxidative stress and bioenergetics dysfunctions. We have elucidated in detail how these types of machinery help to import and locate the precursor proteins to their specific location inside the mitochondria and play a major role in mitochondrial biogenesis. We further discuss their involvement in mitochondrial dysfunctioning and the induction of toxic aggregates in neurodegenerative diseases like AD and PD. The review supports the importance of import machinery in neuronal functions and its association with toxic aggregated proteins in mitochondrial impairment, suggesting a critical role in fostering and maintaining neurodegeneration and therapeutic response.

Drug Development for Central Nervous System Diseases Using In vitro Blood-brain Barrier Models and Drug Repositioning

An important goal of biomedical research is to translate basic research findings into practical clinical implementation. Despite the advances in the technology used in drug discovery, the development of drugs for central nervous system diseases remains challenging. The failure rate for new drugs targeting important central nervous system diseases is high compared to most other areas of drug discovery. The main reason for the failure is the poor penetration efficacy across the blood-brain barrier. The blood-brain barrier represents the bottleneck in central nervous system drug development and is the most important factor limiting the future growth of neurotherapeutics. Meanwhile, drug repositioning has been becoming increasingly popular and it seems a promising field in central nervous system drug development. In vitro blood-brain barrier models with high predictability are expected for drug development and drug repositioning. In this review, the recent progress of in vitro BBB models and the drug repositioning for central nervous system diseases will be discussed.

Scopolamine-Induced Memory Impairment in Mice: Neuroprotective Effects of Carissa edulis (Forssk.) Valh (Apocynaceae) Aqueous Extract

Alzheimer's disease is first characterised by memory loss related to the central cholinergic system alteration. Available drugs provide symptomatic treatment with known side effects. The present study is aimed to evaluate the properties of Carissa edulis aqueous extract on a Scopolamine mouse model as an attempt to search for new compounds against Alzheimer's disease-related memory impairment. Memory impairment was induced by administration of 1 mg/kg (i.p.) of Scopolamine for 7 days, and mice were treated with Carissa edulis aqueous extract. Behavioural studies were performed using T-maze and novel object recognition task for assessing learning and memory and open field test for locomotion. Brain acetylcholinesterase enzyme (AChE) activity was measured to evaluate the central cholinergic system. The level of MDA, glutathione, and catalase activity were measured to evaluate the oxidative stress level. Administration of Scopolamine shows a decrease in learning and memory enhancement during behavioural studies. A significant decrease in the time spent in the preferred arm of T-maze, in the time spent in the exploration of the novel object, and in the discrimination index of the familiar object was also observed. The significant impairment of the central cholinergic system was characterised in mice by an increase of AChE activity to 2.55 ± 0.10 mol/min/g with an increase in oxidative stress. Treatment with the different doses of Carissa edulis (62.8, 157, 314, and 628 mg/kg orally administrated) significantly increased the memory of mice in T-maze and novel object recognition tests and also ameliorated locomotion of mice in the open field. Carissa edulis aqueous extract treatment also decreases the AChE activity and brain oxidative stress. It is concluded that administration of Carissa edulis aqueous extract enhances memory of mice by reducing AChE activity and demonstrating antioxidant properties. This could be developed into a novel therapy against memory impairment related to Alzheimer's disease.

Cell Cycle Deficits in Neurodegenerative Disorders: Uncovering Molecular Mechanisms to Drive Innovative Therapeutic Development

Cell cycle dysregulation has been implicated in the pathogenesis of neurodegenerative disorders. Specialised function obligates neuronal cells to subsist in a quiescent state of cell cycle once differentiated and therefore the circumstances and mechanisms underlying aberrant cell cycle activation in post-mitotic neurons in physiological and disease conditions remains an intriguing area of research. There is a strict requirement of concurrence to cell cycle regulation for neurons to ensure intracellular biochemical conformity as well as interrelationship with other cells within neural tissues. This review deliberates on various mechanisms underlying cell cycle regulation in neuronal cells and underscores potential implications of their non-compliance in neural pathology. Recent research suggests that successful duplication of genetic material without subsequent induction of mitosis induces inherent molecular flaws that eventually assert as apoptotic changes. The consequences of anomalous cell cycle activation and subsequent apoptosis are demonstrated by the increased presence of molecular stress response and apoptotic markers. This review delineates cell cycle events under normal physiological conditions and deficits amalgamated by alterations in protein levels and signalling pathways associated with cell-division are analysed. Cell cycle regulators essentially, cyclins, CDKs, cip/kip family of inhibitors, caspases, bax and p53 have been identified to be involved in impaired cell cycle regulation and associated with neural pathology. The pharmacological modulators of cell cycle that are shown to impart protection in various animal models of neurological deficits are summarised. Greater understanding of the molecular mechanisms that are indispensable to cell cycle regulation in neurons in health and disease conditions will facilitate targeted drug development for neuroprotection.

Aster ageratoides Turcz. extract attenuates Alzheimer's disease-associated cognitive deficits and vascular dementia-associated neuronal death

Dementia is the common neurodegenerative disorder affecting the elderly, with a progressive cognitive decline and memory loss. Since Alzheimer’s disease (AD) and vascular dementia (VD) share key pathologies including oxidative damage, oral supplement of phytochemical medicines, which are well-known for their antioxidant properties, can be a viable therapy for both types of dementia. In this study, the therapeutic potential of the Aster ageratoides extract (AAE), an oriental drug with multiple medicinal properties, was tested on experimental rat models of AD and VD. After confirming the in vitro attenuation of neuronal excitotoxicity by AAE, rats were orally administered with AAE for 7 days and subsequently tested under 2 different experimental paradigms: efficacy screening against #1 AD and #2 VD. For paradigm #1, the rats received intraperitoneal scopolamine and subsequently underwent 3 different behavior tests i.e., the Y-maze, novel object recognition, and passive avoidance tests. For paradigm #2, the rats were operated with the 2-vessel occlusion and hypovolemia (2VO/H) technique, and at postoperative day 7, their hippocampal neuronal viability and the neuroinflammatory changes were quantified. The results showed that the scopolamine-induced impairment of memory performance was significantly improved by AAE intake. Furthermore, while the 2VO/H operation induced marked hippocampal neuronal death and microglial activation, both these effects were significantly attenuated by AAE supplements. Some of the aforementioned effects of AAE intake were dose-dependent. These results provided evidence that AAE supplements can exert anti-AD and -VD efficacies and suggested that AAE might be used as an edible phytotherapeutic for the 2 major types of dementia.

Exploring the Role of PSEN Mutations in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia. Mutations of presenilin (PSEN) genes that encode presenilin proteins have been found as the vital causal factors for early-onset familial AD (FAD). AD pathological features such as memory loss, synaptic dysfunction, and formation of plaques have been successfully mimicked in the transgenic mouse models that coexpress FAD-related presenilin and amyloid precursor protein (APP) variants. γ-Secretase (GS) is an enzyme that plays roles in catalyzing intramembranous APP proteolysis to release pathogenic amyloid beta (Aβ). It has been found that presenilins can play a role as the GS's catalytic subunit. FAD-related mutations in presenilins can modify the site of GS cleavage in a way that can elevate the production of longer and highly fibrillogenic Aβ. Presenilins can interact with β-catenin to generate presenilin complexes. Aforesaid interactions have also been studied to observe the mutational and physiological activities in the catenin signal transduction pathway. Along with APP, GS can catalyze intramembrane proteolysis of various substrates that play a vital role in synaptic function. PSEN mutations can cause FAD with autosomal dominant inheritance and early onset of the disease. In this article, we have reviewed the current progress in the analysis of PSENs and the correlation of PSEN mutations and AD pathogenesis.

Dynamic changes of autophagic flux induced by Abeta in the brain of postmortem Alzheimer's disease patients, animal models and cell models

Autophagy has been reported to play a dual "double-edged sword" role in the occurrence and development of Alzheimer’s disease (AD). To assess the relationship between AD and autophagy, the dynamic changes of autophagic flux in the brain of postmortem AD patients, animal models and cell models were studied. The results showed that autophagosomes (APs) accumulation and expression of lysosomal markers were decreased in the brains of AD patients. In the brain of APP/PS1 double transgenic mice, APs did not accumulate before the formation of SPs but accumulated along with the deposition of SPs, as well as the level of lysosomal markers cathepsin B and Lamp1 protein decreased significantly. In the brains of APP/PS1/LC3 triple - transgenic mice, the number of APs increased with age, but the number of ALs did not increase accordingly. The activation of autophagy is mainly due to the increase in Aβ rather than the overexpression of mutated APP gene. However, both the treatment with exogenous Aβ_25-35 and the mutation of the endogenous APP gene blocked the fusion of APs with lysosomes and decreased lysosomal functioning in AD model cells, which may be the main mechanism of autophagy dysregulation in AD.

Harnessing regulatory T cell neuroprotective activities for treatment of neurodegenerative disorders

Emerging evidence demonstrates that adaptive immunity influences the pathobiology of neurodegenerative disorders. Misfolded aggregated self-proteins can break immune tolerance leading to the induction of autoreactive effector T cells (Teffs) with associated decreases in anti-inflammatory neuroprotective regulatory T cells (Tregs). An imbalance between Teffs and Tregs leads to microglial activation, inflammation and neuronal injury. The cascade of such a disordered immunity includes the drainage of the aggregated protein antigens into cervical lymph nodes serving to amplify effector immune responses. Both preclinical and clinical studies demonstrate transformation of this altered immunity for therapeutic gain. We posit that the signs and symptoms of common neurodegenerative disorders such as Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke can be attenuated by boosting Treg activities.

Changes in PGC-1α/SIRT1 Signaling Impact on Mitochondrial Homeostasis in Amyloid-Beta Peptide Toxicity Model

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive impairment that increasingly afflicts the elderly population. Soluble oligomers (AβOs) has been implicated in AD pathogenesis: however, the molecular events underlying a role for Aβ are not well understood. We studied the effects of AβOs on mitochondrial function and on key proteins that regulate mitochondrial dynamics and biogenesis in hippocampal neurons and PC-12 cells. We find that AβOs treatment caused a reduction in total Mfn1 after a 2 h exposure (42 ± 11%); while DRP1 increased at 1 and 2 h (205 ± 22% and 198 ± 27%, respectively), correlating to changes in mitochondrial morphology. We also observed that SIRT1 levels were reduced after acute and chronic AβOs treatment (68 ± 7% and 77 ± 6%, respectively); while PGC-1α levels were reduced with the same time treatments (68 ± 8% and 67 ± 7%, respectively). Interestingly, we found that chronic treatment with AβOs increased the levels of pSIRT1 (24 h: 157 ± 18%), and we observed changes in the PGC-1α and p-SIRT1 nucleus/cytosol ratio and SIRT1-PGC-1α interaction pattern after chronic exposure to AβOs. Our data suggest that AβOs induce important changes in the level and localization of mitochondrial proteins related with the loss of mitochondrial function that are mediated by a fast and sustained SIRT1/PGC-1α complex disruption promoting a “non-return point” to an irreversible synaptic failure and neuronal network disconnection.

Positive association between soil arsenic concentration and mortality from alzheimer's disease in mainland China

OBJECTIVES

The current study was designed to investigate the relationship between the soil arsenic (As) concentration and the mortality from Alzheimer's disease (AD) in mainland China.

STUDY DESIGN

Ecological study.

METHODS

Twenty-two provinces and 3 municipal districts in mainland China were included in this study. The As concentrations in soil in 1990 was obtained from the China State Environmental Protection Bureau; the data on annual mortality of AD from 1991 to 2000 were obtained from the National Death Cause Surveillance Database of China. Using these data, we calculated the spearman correlation coefficient between soil As concentration and AD mortality, and the relative risk (RR) between soil As levels and AD mortality by quartile-dividing study groups.

RESULTS

The spearman correlation coefficient between As concentration and AD mortality was 0.552 (p = 0.004), 0.616 (p = 0.001) and 0.622 (p = 0.001) in the A soil As (eluvial horizon), the C soil As (parent material horizon), and the Total soil As (A soil As + C soil As), respectively. When the A soil As concentration was over 9.05 mg/kg, 10.40 mg/kg and 13.10 mg/kg, the relative risk was 0.835 (95 % CI: 0.832, 0.838), 1.969 (95 %CI: 1.955, 1.982), and 2.939 (95 % CI: 2.920, 2.958), respectively; when the C soil As reached 9.45 mg/kg, 11.10 mg/kg and 13.55 mg/kg, the relative risk was 4.349 (95 % CI: 4.303, 4.396), 6.108 (95 % CI: 6.044, 6.172), and 9.125 (95 %CI: 9.033, 9.219), respectively. No correlation was found between lead, cadmium, and mercury concentration in the soil and AD mortality.

CONCLUSION

There was an apparent soil As concentration dependent increase in AD mortality. Results of this study may provide evidence for a possible causal linkage between arsenic exposure and the death risk from AD.

Neuroprotective Properties of Resveratrol and Its Derivatives-Influence on Potential Mechanisms Leading to the Development of Alzheimer's Disease

The lack of effective Alzheimer's disease treatment is becoming a challenge for researchers and prompts numerous attempts to search for and develop better therapeutic solutions. Compounds that affect several routes of the neurodegeneration cascade leading to the development of disease are of particular interest. An example of such substances is resveratrol and its synthetic and natural derivatives, which have gained popularity in recent years and show promise as a possible new therapeutic option in the approach to Alzheimer's disease treatment. In this article, the state of the art evidence on the role of resveratrol (RSV) in neuroprotection is presented; research results are summarized and the importance of resveratrol and its derivatives in the treatment of Alzheimer's disease are underlined. It also focuses on various modifications of the resveratrol molecule that should be taken into account in the design of future research on drugs against Alzheimer's disease.

Oligomerization and Conformational Change Turn Monomeric β-Amyloid and Tau Proteins Toxic: Their Role in Alzheimer's Pathogenesis

The structural polymorphism and the physiological and pathophysiological roles of two important proteins, β-amyloid (Aβ) and tau, that play a key role in Alzheimer's disease (AD) are reviewed. Recent results demonstrate that monomeric Aβ has important physiological functions. Toxic oligomeric Aβ assemblies (AβOs) may play a decisive role in AD pathogenesis. The polymorph fibrillar Aβ (fAβ) form has a very ordered cross-β structure and is assumed to be non-toxic. Tau monomers also have several important physiological actions; however, their oligomerization leads to toxic oligomers (TauOs). Further polymerization results in probably non-toxic fibrillar structures, among others neurofibrillary tangles (NFTs). Their structure was determined by cryo-electron microscopy at atomic level. Both AβOs and TauOs may initiate neurodegenerative processes, and their interactions and crosstalk determine the pathophysiological changes in AD. TauOs (perhaps also AβO) have prionoid character, and they may be responsible for cell-to-cell spreading of the disease. Both extra- and intracellular AβOs and TauOs (and not the previously hypothesized amyloid plaques and NFTs) may represent the novel targets of AD drug research.

Lipopolysaccharide exposure during late embryogenesis triggers and drives Alzheimer-like behavioral and neuropathological changes in CD-1 mice

INTRODUCTION

Infections could contribute to Alzheimer's disease (AD) neuropathology in human. However, experimental evidence for a causal relationship between infections during the prenatal phase and the onset of AD is lacking.

METHODS

CD-1 mothers were intraperitoneally received lipopolysaccharide (LPS) with two doses (25 and 50 μg/kg) or normal saline every day during gestational days 15-17. A battery of behavioral tasks was used to assess the species-typical behavior, sensorimotor capacity, anxiety, locomotor activity, recognition memory, and spatial learning and memory in 1-, 6-, 12-, 18-, and 22-month-old offspring mice. An immunohistochemical technology was performed to detect neuropathological indicators consisting of amyloid-β (Aβ), phosphorylated tau (p-tau), and glial fibrillary acidic protein (GFAP) in the hippocampus.

RESULTS

Compared to the same-aged controls, LPS-treated offspring had similar behavioral abilities and the levels of Aβ42, p-tau, and GFAP at 1 and 6 months old. From 12 months onward, LPS-treated offspring gradually showed decreased species-typical behavior, sensorimotor ability, locomotor activity, recognition memory, and spatial learning and memory, and increased anxieties and the levels of Aβ42, p-tau, and GFAP relative to the same-aged controls. Moreover, this damage effect (especially cognitive decline) persistently progressed onwards. The changes in these neuropathological indicators significantly correlated with impaired spatial learning and memory.

CONCLUSIONS

Prenatal exposure to low doses of LPS caused AD-related features including behavioral and neuropathological changes from midlife to senectitude.

Lipid-based nanoformulations in the treatment of neurological disorders

The neurological disorders affect millions of people worldwide, and are bracketed as the foremost basis of disability-adjusted life years (DALYs). The treatment options are symptomatic and often the movement of drugs is restricted by a specialized network of endothelial cell layers (adjoined by tight cell-to-cell junction proteins; occludin, claudins, and junctional adhesion molecules), pericytes and astroglial foot processes. In recent years, advances in nanomedicine have led to therapies that target central nervous system (CNS) pathobiology via altering signaling mechanisms such as activation of PI3K/Akt pathway in ischemic stroke arrests apoptosis, interruption of α-synuclein aggregation prevents neuronal degeneration in Parkinson's. Often such interactions are limited by insufficient concentrations of drugs reaching neuronal tissues and/or insufficient residence time of drug/s with the receptor. Hence, lipid nanoformulations, SLNs (solid lipid nanoparticles) and NLCs (nanostructured lipid carriers) emerged to overcome these challenges by utilizing physiological transport mechanisms across blood-brain barrier, such as drug-loaded SLN/NLCs adsorb apolipoproteins from the systemic circulation and are taken up by endothelial cells via low-density lipoprotein (LDL)-receptor mediated endocytosis and subsequently unload drugs at target site (neuronal tissue), which imparts selectivity, target ability, and reduction in toxicity. This paper reviews the utilization of SLN/NLCs as carriers for targeted delivery of novel CNS drugs to improve the clinical course of neurological disorders, placing some additional discussion on the metabolism of lipid-based formulations.