Nonsteroidal anti-inflammatory drugs for the prevention of Alzheimer's disease: a systematic review

Anisomycin alleviates cognitive impairments and pathological features in 3xTg-AD mice

Neuroinflammation plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). Anisomycin is a pyrrolidine antibiotic isolated from Streptomyces griseolus, which is an efficient anti-inflammatory agent that functions both in vivo and in vitro. However, it is not clear whether anisomycin can exert neuroprotective effect in AD. In the present study, anisomycin was intragastrically administrated to female triple-transgenic AD (3xTg-AD) model mice, then Morris water maze test was used to observe the long-term spatial memory of mice, the in vivo hippocampal field potential recording was performed to evaluate the synaptic plasticity, the Western blot and immunofluorescence were employed to detect pathological changes, and the bioinformatics analysis was used to predict the potential target of anisomycin exerting effects in AD. The results showed that anisomycin ameliorated the long-term spatial memory deficits, improved LTP depression and increased the expression of PSD-95, reduced the Aβ and tau pathologies, and alleviated the activation of microglia and astrocytes in the brains of 3xTg-AD mice. In addition, the results from bioinformatics analysis showed that the potential target of anisomycin focused on inflammatory pathway. These results indicated that anisomycin exerts neuroprotective effects in 3xTg-AD mice by alleviating neuroinflammation, but the potential mechanism of anisomycin exerting neuroprotective effects needs to be further investigated.

Inflammation in Metal-Induced Neurological Disorders and Neurodegenerative Diseases

Essential metals play critical roles in maintaining human health as they participate in various physiological activities. Nonetheless, both excessive accumulation and deficiency of these metals may result in neurotoxicity secondary to neuroinflammation and the activation of microglia and astrocytes. Activation of these cells can promote the release of pro-inflammatory cytokines. It is well known that neuroinflammation plays a critical role in metal-induced neurotoxicity as well as the development of neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Initially seen as a defense mechanism, persistent inflammatory responses are now considered harmful. Astrocytes and microglia are key regulators of neuroinflammation in the central nervous system, and their excessive activation may induce sustained neuroinflammation. Therefore, in this review, we aim to emphasize the important role and molecular mechanisms underlying metal-induced neurotoxicity. Our objective is to raise the awareness on metal-induced neuroinflammation in neurological disorders. However, it is not only just neuroinflammation that different metals could induce; they can also cause harm to the nervous system through oxidative stress, apoptosis, and autophagy, to name a few. The primary pathophysiological mechanism by which these metals induce neurological disorders remains to be determined. In addition, given the various pathways through which individuals are exposed to metals, it is necessary to also consider the effects of co-exposure to multiple metals on neurological disorders.

Alzheimer's disease and its treatment-yesterday, today, and tomorrow

Alois Alzheimer described the first patient with Alzheimer's disease (AD) in 1907 and today AD is the most frequently diagnosed of dementias. AD is a multi-factorial neurodegenerative disorder with familial, life style and comorbidity influences impacting a global population of more than 47 million with a projected escalation by 2050 to exceed 130 million. In the USA the AD demographic encompasses approximately six million individuals, expected to increase to surpass 13 million by 2050, and the antecedent phase of AD, recognized as mild cognitive impairment (MCI), involves nearly 12 million individuals. The economic outlay for the management of AD and AD-related cognitive decline is estimated at approximately 355 billion USD. In addition, the intensifying prevalence of AD cases in countries with modest to intermediate income countries further enhances the urgency for more therapeutically and cost-effective treatments and for improving the quality of life for patients and their families. This narrative review evaluates the pathophysiological basis of AD with an initial focus on the therapeutic efficacy and limitations of the existing drugs that provide symptomatic relief: acetylcholinesterase inhibitors (AChEI) donepezil, galantamine, rivastigmine, and the N-methyl-D-aspartate receptor (NMDA) receptor allosteric modulator, memantine. The hypothesis that amyloid-β (Aβ) and tau are appropriate targets for drugs and have the potential to halt the progress of AD is critically analyzed with a particular focus on clinical trial data with anti-Aβ monoclonal antibodies (MABs), namely, aducanumab, lecanemab and donanemab. This review challenges the dogma that targeting Aβ will benefit the majority of subjects with AD that the anti-Aβ MABs are unlikely to be the "magic bullet". A comparison of the benefits and disadvantages of the different classes of drugs forms the basis for determining new directions for research and alternative drug targets that are undergoing pre-clinical and clinical assessments. In addition, we discuss and stress the importance of the treatment of the co-morbidities, including hypertension, diabetes, obesity and depression that are known to increase the risk of developing AD.

The Contribution of Type 2 Diabetes to Parkinson's Disease Aetiology

Type 2 diabetes (T2D) and Parkinson's disease (PD) are chronic disorders that have a significant health impact on a global scale. Epidemiological, preclinical, and clinical research underpins the assumption that insulin resistance and chronic inflammation contribute to the overlapping aetiologies of T2D and PD. This narrative review summarises the recent evidence on the contribution of T2D to the initiation and progression of PD brain pathology. It also briefly discusses the rationale and potential of alternative pharmacological interventions for PD treatment.

FABP7 drives an inflammatory response in human astrocytes and is upregulated in Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia in the elderly, is characterized by the accumulation of intracellular neurofibrillary tangles, extracellular amyloid plaques, and neuroinflammation. In partnership with microglial cells, astrocytes are key players in the regulation of neuroinflammation. Fatty acid binding protein 7 (FABP7) belongs to a family of conserved proteins that regulate lipid metabolism, energy homeostasis, and inflammation. FABP7 expression is largely restricted to astrocytes and radial glia-like cells in the adult central nervous system. We observed that treatment of primary hippocampal astrocyte cultures with amyloid β fragment 25-35 (Aβ25-35) induces FABP7 upregulation. In addition, FABP7 expression is upregulated in the brain of APP/PS1 mice, a widely used AD mouse model. Co-immunostaining with specific astrocyte markers revealed increased FABP7 expression in astrocytes. Moreover, astrocytes surrounding amyloid plaques displayed increased FABP7 staining when compared to non-plaque-associated astrocytes. A similar result was obtained in the brain of AD patients. Whole transcriptome RNA sequencing analysis of human astrocytes differentiated from induced pluripotent stem cells (i-astrocytes) overexpressing FABP7 identified 500 transcripts with at least a 2-fold change in expression. Gene Ontology enrichment analysis identified (i) positive regulation of cytokine production and (ii) inflammatory response as the top two statistically significant overrepresented biological processes. We confirmed that wild-type FABP7 overexpression induces an NF-κB-driven inflammatory response in human i-astrocytes. On the other hand, the expression of a ligand-binding impaired mutant FABP7 did not induce NF-κB activation. Together, our results suggest that the upregulation of FABP7 in astrocytes could contribute to the neuroinflammation observed in AD.

Recent Aspects of Periodontitis and Alzheimer's Disease-A Narrative Review

Periodontitis is an inflammatory condition affecting the supporting structures of the teeth. Periodontal conditions may increase the susceptibility of individuals to various systemic illnesses, including Alzheimer's disease. Alzheimer's disease is a neurodegenerative condition characterized by a gradual onset and progressive deterioration, making it the primary cause of dementia, although the exact cause of the disease remains elusive. Both Alzheimer's disease and periodontitis share risk factors and clinical studies comparing the associations and occurrence of periodontitis among individuals with Alzheimer's disease have suggested a potential correlation between these conditions. Brains of individuals with Alzheimer's disease have substantiated the existence of microorganisms related to periodontitis, especially Porphyromonas gingivalis, which produces neurotoxic gingipains and may present the capability to breach the blood-brain barrier. Treponema denticola may induce tau hyperphosphorylation and lead to neuronal apoptosis. Lipopolysaccharides-components of bacterial cell membranes and mediators of inflammation-also have an impact on brain function. Further research could unveil therapeutic approaches targeting periodontal pathogens to potentially alleviate AD progression.

Cognitive Status is Better in Older Adults under Colchicine Treatment: A Case-Control Study

PURPOSE

We aimed to investigate the effects of colchicine, an important anti-inflammatory agent, on cognitive functions in a geriatric population diagnosed with gout or osteoarthritis by comparing it to non-colchicine users.

METHODS

138 geriatric patients (67 colchicine users and 71 non-users) were enrolled. Within comprehensive geriatric assessment (CGA), cognitive status assessment via Mini-Mental State Examination test (MMSE), Quick Mild Cognitive Impairment Screening test (Qmci), clock drowning test (CDT), and digit span tests were performed.

RESULTS

Median age was 68 (65-72), and there were 82 female (59.4%) patients. The scores of CDT, Backward Digit Span Test, MMSE-Total, MMSE-Attention, MMSE-Motor Function, Qmci-Total Score, Qmci-Clock drawing, and Qmci-Logical Memory were significantly higher in the colchicine user group (p < .005), showing better cognitive function. Adjusted model analysis showed that colchicine usage is independently correlated with higher Qmci-Total Score and Qmci-Logical Memory Score (For Qmci total score β = 7.87 95%CI = 5.48-10.27, p = <0.0001, and for Qmci Logical memory score β = 3.52, 95%CI = 2.12-4.91, p = <0.0001).

CONCLUSION

To the best of our knowledge, this is the first study revealing that colchicine usage is associated with better cognitive performance in older adults. Further investigations with a prospective, larger-sampled and randomized design are needed to show the causal relationship between colchicine and cognition.

The effect of AQP4 on tau protein aggregation in neurodegeneration and persistent neuroinflammation after cerebral microinfarcts

This study aimed to investigate the effect of aquaporin-4 (AQP4) on tau protein aggregation in neurodegeneration and persistent neuroinflammation after cerebral microinfarcts. A model of diffuse ischemic brain injury was established, and adenovirus was injected stereotactically through the lateral ventricle of mice. The water content of the brain tissue was measured. The co-expression of glial fibrillary acidic protein (GFAP) and AQP4 and the aggregation of p-tau and neuronal marker were detected through immunofluorescence double staining. The expression of phosphorylated microtubule-associated protein tau (p-tau, Ser202/Thr205, Thr205, Ser396, Ser404), interleukin(IL)-6, IL-1β, tumor necrosis factor (TNF)-a, growth associated protein43 (GAP43), GFAP, and ionized calcium-binding adapter molecule 1 (Iba1) was detected through Western blot. It was found that the brain water content in the model group was increased and decreased after the AQP4 interference. Compared with the sham group, the expression of GFAP, p-tau, IL-1β, TNF-a, Iba1, and p-tau was increased in the model group (p < 0.05). Compared with the model group, the expression of p-tau, IL-6, IL-1β, TNF-a, GFAP, and Iba1 was decreased after AQP4 interference (p < 0.05). It is indicated that AQP4 positively regulates neurodegeneration and persistent neuroinflammation caused by tau protein aggregation after cerebral microinfarcts.

Bacteroides Fragilis in the gut microbiomes of Alzheimer's disease activates microglia and triggers pathogenesis in neuronal C/EBPβ transgenic mice

Gut dysbiosis contributes to Alzheimer's disease (AD) pathogenesis, and Bacteroides strains are selectively elevated in AD gut microbiota. However, it remains unknown which Bacteroides species and how their metabolites trigger AD pathologies. Here we show that Bacteroides fragilis and their metabolites 12-hydroxy-heptadecatrienoic acid (12-HHTrE) and Prostaglandin E2 (PGE2) activate microglia and induce AD pathogenesis in neuronal C/EBPβ transgenic mice. Recolonization of antibiotics cocktail-pretreated Thy1-C/EBPβ transgenic mice with AD patient fecal samples elicits AD pathologies, associated with C/EBPβ/Asparaginyl endopeptidase (AEP) pathway upregulation, microglia activation, and cognitive disorders compared to mice receiving healthy donors' fecal microbiota transplantation (FMT). Microbial 16S rRNA sequencing analysis shows higher abundance of proinflammatory Bacteroides fragilis in AD-FMT mice. Active components characterization from the sera and brains of the transplanted mice revealed that both 12-HHTrE and PGE2 activate primary microglia, fitting with poly-unsaturated fatty acid (PUFA) metabolites enrichment identified by metabolomics. Strikingly, recolonization with live but not dead Bacteroides fragilis elicited AD pathologies in Thy1-C/EBPβ transgenic mice, so did 12-HHTrE or PGE2 treatment alone. Collectively, our findings support a causal role for Bacteroides fragilis and the PUFA metabolites in activating microglia and inducing AD pathologies in Thy1- C/EBPβ transgenic mice.

Carprofen alleviates Alzheimer-like phenotypes of 5XFAD transgenic mice by targeting the pathological hallmarks induced by amyloid-β aggregation

Alzheimer's disease (AD) is characterized by misfolding, oligomerization, and accumulation of amyloid-β (Aβ) peptides in the brain. Aβ monomers transform into Aβ oligomers, which are toxic species, inducing tau hyperphosphorylation and the downstream effects on microglia and astrocytes, triggering synaptic and cognitive dysfunctions. The oligomers then deposit into Aβ plaques, primarily composed of β-stranded fibrils, required for definitive AD diagnosis. As amyloid burden plays the pivotal role in AD pathogenesis, many efforts are devoted in preventing amyloidosis as a therapeutic approach to impede the disease progression. Here, we discovered carprofen, a non-steroidal anti-inflammatory drug, accelerates Aβ aggregating into fibrils and increases Aβ plaques when intraperitoneally injected to 5XFAD transgenic mouse model. However, the drug seems to alleviate the key Alzheimer-like phenotypes induced by Aβ aggregation as we found attenuated neuroinflammation, improved post-synaptic density expression, associated with synaptic plasticity, and decreased phosphorylated tau levels. Carprofen also rescued impaired working memory as we discovered improved spontaneous alternation performance through Y-maze test assessed with Aβ(1-42)-infused mouse model. Collectively, while carprofen accelerates the conversion of Aβ monomers into fibrils in vitro, the drug ameliorates the major pathological hallmarks of AD in vivo.

Cognitive resilience and severe Alzheimer's disease neuropathology

Cognitive resilience in Alzheimer's disease (AD) can be defined as retention of high cognition despite presence of considerable cerebral AD lesions. We sought to identify factors associated with this phenomenon. Data were obtained from National Alzheimer's Coordinating Centre (NACC) dataset. Subjects with severe AD neuropathology, based on National Institute on Aging-Reagan (NIA-Reagan) criteria, no other primary neuropathology, and a ≤ 2-year interval between last follow-up and death were included. Mini-mental status examination score ≥ 24 was used as a proxy for normal cognition. In total, 654 cases were included; 59 (9%) were cognitively resilient. Multivariable logistic regression model showed that resilient participants were more educated, had a lower body mass index (BMI), were more likely to be lifetime/recent smoker or use an anticoagulant/antiplatelet agent, compared with cognitively impaired subjects. In addition to expected protective factors such as higher education and lower BMI, our results showed that smoking (especially recent smoking) and anticoagulant/antiplatelet consumption are associated with resilience to clinical cognitive expression of severe AD pathology. Pharmacological approaches using this information might be explored for clinical AD amelioration.

Aspirin reverts lipopolysaccharide-induced learning and memory impairment: first evidence from an invertebrate model system

By employing a reductionistic (but not simplistic) approach using an established invertebrate model system, the pond snail Lymnaea stagnalis, we investigated whether (1) lipopolysaccharide (LPS)-induced inflammation would cause a sickness state and impair cognitive function, and-if so-(2) would aspirin (acetylsalicylic acid-ASA) restore the impaired cognition. To test our hypotheses, we first determined if the injection of 25 mg (6.25 μg/mL) of Escherichia coli-derived LPS serotype O127:B8 altered homeostatic behavior, aerial respiration, and then determined if LPS altered memory formation when this behavior was operantly conditioned. Next, we determined if ASA altered the LPS-induced changes in both aerial respiration and cognitive functions. LPS induced a sickness state that increased aerial respiration and altered the ability of snails to form or recall long-term memory. ASA reverted the LPS-induced sickness state and thus allowed long-term memory both to be formed and recalled. We confirmed our hypotheses and provided the first evidence in an invertebrate model system that an injection of LPS results in a sickness state that obstructs learning and memory, and this impairment can be prevented by a non-steroidal anti-inflammatory.

Baicalin Mitigates the Neuroinflammation through the TLR4/MyD88/NF-κB and MAPK Pathways in LPS-Stimulated BV-2 Microglia

Baicalin (BA) is a major flavone from Scutellaria baicalensis Georgi and has showed significant curative effects in Parkinson's and Alzheimer's diseases. In the present study, we investigated the effects of BA on antineuroinflammation and related signaling cascade in lipopolysaccharide- (LPS-) induced BV-2 microglial model. The results showed that BA significantly attenuated inflammatory mediators (NO, iNOS, IL-1β, COX-2, and PGE2) and suppressed the expression of miR-155. More crucially, BA could regulate the expression of related proteins in Toll-like receptor 4 (TLR4)/myeloid differentiation protein 88 (MyD88)/nuclear factor κB (NF-κB) pathway and suppress the phosphorylation of mitogen-activated protein kinase (MAPK) family. In addition, molecular docking analysis indicated that BA binds to the amino acids Lie 63 and Tyr 65 of TLR4 by π-σ and π-π T-shaped interaction. Thus, BA suppressed the LPS-stimulated neuroinflammation in BV-2 microglia by blocking the TLR4-mediated signal transduction through TLR4/MyD88/NF-κB and MAPK pathways and inhibiting the miR-155 expression. Our findings demonstrated that BA could be a valuable therapeutic for the treatment of neuroinflammation and neurodegenerative diseases.

The role of brain inflammation and abnormal brain oxygen homeostasis in the development of hepatic encephalopathy

Hepatic encephalopathy (HE) is a frequent complication of chronic liver disease (CLD) and has a complex pathogenesis. Several preclinical and clinical studies have reported the presence of both peripheral and brain inflammation in CLD and their potential impact in the development of HE. Altered brain vascular density and tone, as well as compromised cerebral and systemic blood flow contributing to the development of brain hypoxia, have also been reported in animal models of HE, while a decrease in cerebral metabolic rate of oxygen and cerebral blood flow has consistently been observed in patients with HE. Whilst significant strides in our understanding have been made over the years, evaluating all these mechanistic elements in vivo and showing causal association with development of HE, have been limited through the practical constraints of experimentation. Nonetheless, improvements in non-invasive assessments of different neurophysiological parameters, coupled with techniques to assess changes in inflammatory and metabolic pathways, will help provide more granular insights on these mechanisms. In this special issue we discuss some of the emerging evidence supporting the hypothesis that brain inflammation and abnormal oxygen homeostasis occur interdependently during CLD and comprise important contributors to the development of HE. This review aims at furnishing evidence for further research in brain inflammation and oxygen homeostasis as additional therapeutic targets and potentially diagnostic markers for HE.

The link between cutaneous inflammation and cognitive impairment

Cognitive impairment is a symptom of neurological disorders, including dementia and Alzheimer's disease; and mild cognitive impairment can be a precursor of both disorders. Aged humans and animal models with other systemic disorders, such as cardiovascular diseases and diabetes, display a higher incidence of cognitive decline. Epidemiological studies have shown that the incidence of cognitive impairment also is higher in subjects with certain inflammatory skin disorders, including psoriasis and chronic eczematous dermatitis. Chronologically aged individuals exhibit increased cutaneous inflammation and elevated circulating cytokine levels, linked to alterations in epidermal function, which itself can induce cutaneous inflammation. Conversely, strategies that improve epidermal function can lower cytokine levels in both the skin and circulation. Thus, it seems likely that epidermal dysfunction could contribute, at least in part, to the development of chronic low-grade inflammation, also termed 'inflammaging', in the elderly. The evidence of cognitive impairment in patients with inflammatory dermatoses suggests a link between cutaneous inflammation and cognitive impairment. Because of the pathogenic role of epidermal dysfunction in ageing-associated cutaneous inflammation, improvements in epidermal function could be an alternative approach for mitigation of the ageing-associated decline in cognitive function.

A Pathophysiological Intersection of Diabetes and Alzheimer's Disease

Diabetes is among the most prevalent diseases of the modern world and is strongly linked to an increased risk of numerous neurodegenerative disorders, although the exact pathophysiological mechanisms are not clear yet. Insulin resistance is a serious pathological condition, connecting type 2 diabetes, metabolic syndrome, and obesity. Recently, insulin resistance has been proven to be connected also to cognitive decline and dementias, including the most prevalent form, Alzheimer's disease. The relationship between diabetes and Alzheimer's disease regarding pathophysiology is so significant that it has been proposed that some presentations of the condition could be termed type 3 diabetes.

Pathophysiological mechanisms explaining the association between low skeletal muscle mass and cognitive function

Low skeletal muscle mass is associated with cognitive impairment and dementia in older adults. This review describes the possible underlying pathophysiological mechanisms: systemic inflammation, insulin metabolism, protein metabolism, and mitochondrial function. We hypothesize that the central tenet in this pathophysiology is the dysfunctional myokine secretion consequent to minimal physical activity. Myokines, such as fibronectin type III domain containing 5/irisin and cathepsin B, are released by physically active muscle and cross the blood–brain barrier. These myokines upregulate local neurotrophin expression such as brain-derived neurotrophic factor (BDNF) in the brain microenvironment. BDNF exerts anti-inflammatory effects that may be responsible for neuroprotection. Altered myokine secretion due to physical inactivity exacerbates inflammation and impairs muscle glucose metabolism, potentially affecting the transport of insulin across the blood–brain barrier. Our working model also suggests other underlying mechanisms. A negative systemic protein balance, commonly observed in older adults, contributes to low skeletal muscle mass and may also reflect deficient protein metabolism in brain tissues. As a result of age-related loss in skeletal muscle mass, decrease in the abundance of mitochondria and detriments in their function lead to a decrease in tissue oxidative capacity. Dysfunctional mitochondria in skeletal muscle and brain result in the excessive production of reactive oxygen species, which drives tissue oxidative stress and further perpetuates the dysfunction in mitochondria. Both oxidative stress and accumulation of mitochondrial DNA mutations due to aging drive cellular senescence. A targeted approach in the pathophysiology of low muscle mass and cognition could be to restore myokine balance by physical activity.

Glutamate and GABA in Microglia-Neuron Cross-Talk in Alzheimer's Disease

The physiological balance between excitation and inhibition in the brain is significantly affected in Alzheimer’s disease (AD). Several neuroactive compounds and their signaling pathways through various types of receptors are crucial in brain homeostasis, among them glutamate and γ-aminobutyric acid (GABA). Activation of microglial receptors regulates the immunological response of these cells, which in AD could be neuroprotective or neurotoxic. The novel research approaches revealed the complexity of microglial function, including the interplay with other cells during neuroinflammation and in the AD brain. The purpose of this review is to describe the role of several proteins and multiple receptors on microglia and neurons, and their involvement in a communication network between cells that could lead to different metabolic loops and cell death/survival. Our review is focused on the role of glutamatergic, GABAergic signaling in microglia–neuronal cross-talk in AD and neuroinflammation. Moreover, the significance of AD-related neurotoxic proteins in glutamate/GABA-mediated dialogue between microglia and neurons was analyzed in search of novel targets in neuroprotection, and advanced pharmacological approaches.

The inhibitory effects of Orengedokuto on inducible PGE2 production in BV-2 microglial cells

Background and aim

Reactive microglia has been associated with neuroinflammation caused by the production of proinflammatory molecules such as cytokines, nitric oxide, and prostaglandins. The overexpression of these molecules may provoke neuronal damage that can cause neurodegenerative diseases. A traditional herbal medicine, Orengedokuto (OGT), has been widely used for treating inflammation-related diseases. However, how it influences neuroinflammation remains poorly understood.

Experimental procedure

This study investigated the effects of OGT on inflammatory molecule induction in BV-2 microglial cells using real-time RT-PCR and ELISA. An in vivo confirmation of these effects was then performed in mice.

Results and conclusion

OGT showed dose-dependent inhibition of prostaglandin E2 (PGE2) production in BV-2 cells stimulated with lipopolysaccharide (LPS). To elucidate the mechanism of PGE2 inhibition, we examined cyclooxygenases (COXs) and found that OGT did not suppress COX-1 expression or inhibit LPS-induced COX-2 upregulation at either the transcriptional or translational levels. In addition, OGT did not inhibit COX enzyme activities within the concentration that inhibited PGE2 production, suggesting that the effect of OGT is COX-independent. The inhibitory effects of OGT on PGE2 production in BV-2 cells were experimentally replicated in primary cultured astrocytes and mice brains. OGT can be useful in the treatment of neuroinflammatory diseases by modulating PGE2 expression.

A Novel Inhibitor Targeting NLRP3 Inflammasome Reduces Neuropathology and Improves Cognitive Function in Alzheimer's Disease Transgenic Mice

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, and the most common type of dementia. A growing body of evidence has implicated neuroinflammation as an essential player in the etiology of AD. Inflammasomes are intracellular multiprotein complexes and essential components of innate immunity in response to pathogen- and danger-associated molecular patterns. Among the known inflammasomes, the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome plays a critical role in the pathogenesis of AD.

OBJECTIVE

We recently developed a novel class of small molecule inhibitors that selectively target the NLRP3 inflammasome. One of the lead compounds, JC124, has shown therapeutic efficacy in a transgenic animal model of AD. In this study we tested the preventative efficacy of JC124 in another strain of transgenic AD mice.

METHODS

In this study, 5-month-old female APP/PS1 and matched wild type mice were treated orally with JC124 for 3 months. After completion of treatment, cognitive functions and AD pathologies, as well as protein expression levels of synaptic proteins, were assessed.

RESULTS

We found that inhibition of NLRP3 inflammasome with JC124 significantly decreased multiple AD pathologies in APP/PS1 mice, including amyloid-β (Aβ) load, neuroinflammation, and neuronal cell cycle re-entry, accompanied by preserved synaptic plasticity with higher expression of pre- and post-synaptic proteins, increased hippocampal neurogenesis, and improved cognitive functions.

CONCLUSION

Our study demonstrates the importance of the NLRP3 inflammasome in AD pathological development, and pharmacological inhibition of NLRP3 inflammasome with small molecule inhibitors represents a potential therapy for AD.

Indomethacin Disrupts the Formation of β-Amyloid Plaques via an α2-Macroglobulin-Activating lrp1-Dependent Mechanism

Epidemiological studies have implied that the nonsteroidal anti-inflammatory drug (NSAID) indomethacin slows the development and progression of Alzheimer’s disease (AD). However, the underlying mechanisms are notably understudied. Using a chimeric mouse/human amyloid precursor protein (Mo/HuAPP695swe) and a mutant human presenilin 1 (PS1-dE9) (APP/PS1) expressing transgenic (Tg) mice and neuroblastoma (N) 2a cells as in vivo and in vitro models, we revealed the mechanisms of indomethacin in ameliorating the cognitive decline of AD. By screening AD-associated genes, we observed that a marked increase in the expression of α₂-macroglobulin (A2M) was markedly induced after treatment with indomethacin. Mechanistically, upregulation of A2M was caused by the inhibition of cyclooxygenase-2 (COX-2) and lipocalin-type prostaglandin D synthase (L-PGDS), which are responsible for the synthesis of prostaglandin (PG)H₂ and PGD₂, respectively. The reduction in PGD₂ levels induced by indomethacin alleviated the suppression of A2M expression through a PGD₂ receptor 2 (CRTH2)-dependent mechanism. Highly activated A2M not only disrupted the production and aggregation of β-amyloid protein (Aβ) but also induced Aβ efflux from the brain. More interestingly, indomethacin decreased the degradation of the A2M receptor, low-density lipoprotein receptor-related protein 1 (LRP1), which facilitated the brain efflux of Aβ. Through the aforementioned mechanisms, indomethacin ameliorated cognitive decline in APP/PS1 Tg mice by decreasing Aβ production and clearing Aβ from the brains of AD mice.

The structural simplification of lysergic acid as a natural lead for synthesizing novel anti-Alzheimer agents

Alzheimer's disease (AD) is a neurodegenerative disorder, projected to be the second leading cause of mortality by 2040. AD is characterized by a progressive impairment of memory leading to dementia and loss of ability to carry out daily functions. In addition to the deficiency of acetylcholine release in synapse, there are other mechanisms explaining the etiology of the disease. The most disputing ones are associated with the accumulation of damaged proteins β-amyloid (Aβ) and hyperphosphorylated tau outside and inside neurons, respectively. Lysergic acid derivatives have been shown to possess promising anti-Alzheimer effect. Moreover, lysergic acid structure encompasses the general structural requirements for acetylcholinesterase inhibition. In this study, sixteen analogues, derived from lysergic acid structure, were synthesized. Heck and Mannich reactions were carried out to 4-bromo indole nucleus to generate potentially active analogues. Some of them were subsequently cyclized by nitromethane and zinc reduction procedures. Some of these compounds showed neuroprotective and anti-inflammatory effects stronger than the currently used anti-Alzheimer drug; donepezil. Some of the synthesized com-pounds showed a noticeable acetylcholinesterase inhibition. Twelve molecular targets attributed with AD etiology were tested versus the synthesized compounds by in silico modeling. Docking scores of modeling were plotted against in vitro activity of the compounds. The one afforded the strongest positive correlation was ULK-1 which has a significant role in autophagy.

Inflammation: A Major Target for Compounds to Control Alzheimer's Disease

Several hypotheses have been postulated to explain how Alzheimer's disease is triggered, but none of them provide a unified view of its pathogenesis. The dominant hypothesis based on build-ups of the amyloid-β peptide has been around for longer than three decades; however, up to today, numerous clinical trials based on the amyloid postulates have been attempted, but all of them have failed. Clearly, the revisited tau hypothesis provides a better explanation of the clinical observations of patients, but it needs to integrate the cumulative observations on the onset of this disease. In this context, the neuroimmuno modulation theory, based on the involvement of inflammatory events in the central nervous system, accounts for all these observations. In this review we intend to emphasize the idea that neuroinflammation is a main target for the search of new therapeutic strategies to control Alzheimer's disease. Beyond mono-targeting approaches using synthetic drugs that control only specific pathophysiological events, emerging therapeutics views based on multi targeting compounds appear to provide a new pathway for Alzheimer's disease treatment.

Neuropsychiatric symptoms and comorbidity: Associations with dementia progression rate in a memory clinic cohort

OBJECTIVES

Neuropsychiatric symptoms (NPS) are associated with dementia severity and progression rate. NPS clusters have different neurobiological underpinnings; therefore, their effect on dementia progression may differ. Furthermore, little is known about whether individual comorbidities affect progression rate. We investigated the effect of NPS clusters and individual comorbidities on dementia progression.

METHODS

A memory clinic cohort with all-cause dementia (N = 442) was followed for up to 3 years from diagnosis. Previously, we found trajectory groups of dementia progression in this cohort: one with slow progression and two with rapid progression. In the present study, using principal component analysis, three symptom clusters of NPS were identified on the Neuropsychiatric Inventory Questionnaire (NPI-Q): agitation, affective and psychosis symptom clusters. Data regarding comorbidity were collected by linkage to the Norwegian Patient Registry. Multinomial logistic regression was applied to explore the association between NPS clusters and comorbidity with trajectory-group membership.

RESULTS

Adjusted for demographics, dementia aetiology, comorbidity and cognition, we found that, at the time of dementia diagnosis, for every point within the psychosis symptom cluster of the NPI-Q, the risk of rapid progression increased by 53%; for every point within the affective symptom cluster, the risk of rapid progression increased by 29%. A previous diagnosis of mental and behavioural disorders (excluding dementia) decreased the risk of rapid dementia progression by 65%.

CONCLUSIONS

Psychosis and affective symptom clusters at the time of diagnosis were associated with rapid progression of dementia. Previous diagnoses of mental and behavioural disorders (excluding dementia) were associated with slow progression.

Current and Future Directions for Targeting Lipoxin A4 in Alzheimer's Disease

Neuroinflammation has been implicated in Alzheimer's disease onset and progression. Chronic neuroinflammation is initiated by amyloid-β-activated microglial cells that secrete immuno-modulatory molecules within the brain and into the vasculature. Inflammation is normally self-limiting and actively resolves by "switching off" the generation of pro-inflammatory mediators and by non-phlogistic clearance of spent cells and their debris to restore tissue homeostasis. Deficits in these anti-inflammatory/pro-resolution pathways may predispose to the development of chronic inflammation. The synthesis of endogenous lipid mediators from arachidonic acid, lipoxins via cyclooxygenase 2 and lipoxygenases, and conversion of exogenous polyunsaturated fatty acids, namely docosahexaenoic acid and eicosapentaenoic acid, to resolvins contributes to effective, timely resolution of acute inflammation. Work by Xiuzhe et al., 2020 in the Journal of Alzheimer's Disease reported that plasma level of LXA4 is related to cognitive status in ischemic stroke patients suggesting that decreased LXA4 may be a potential risk factor for post post-stroke cognitive impairment. As evident by recent clinical trials and development of drug analogues, there is recent drive to search for lipoxin analogues as therapeutics for inflammatory diseases. Understanding how bioactive lipid signaling is involved in resolution will increase our understanding of controlling inflammation and may facilitate the discovery of new classes of therapeutic pro-resolution agents for evaluation in AD prevention studies.

Inflammation Spreading: Negative Spiral Linking Systemic Inflammatory Disorders and Alzheimer's Disease

As a physiological response to injury in the internal body organs, inflammation is responsible for removing dangerous stimuli and initiating healing. However, persistent and exaggerative chronic inflammation causes undesirable negative effects in the organs. Inflammation occurring in the brain and spinal cord is known as neuroinflammation, with microglia acting as the central cellular player. There is increasing evidence suggesting that chronic neuroinflammation is the most relevant pathological feature of Alzheimer’s disease (AD), regulating other pathological features, such as the accumulation of amyloid-β (Aβ) and hyperphosphorylation of Tau. Systemic inflammatory signals caused by systemic disorders are known to strongly influence neuroinflammation as a consequence of microglial activation, inflammatory mediator production, and the recruitment of peripheral immune cells to the brain, resulting in neuronal dysfunction. However, the neuroinflammation-accelerated neuronal dysfunction in AD also influences the functions of peripheral organs. In the present review, we highlight the link between systemic inflammatory disorders and AD, with inflammation serving as the common explosion. We discuss the molecular mechanisms that govern the crosstalk between systemic inflammation and neuroinflammation. In our view, inflammation spreading indicates a negative spiral between systemic diseases and AD. Therefore, “dampening inflammation” through the inhibition of cathepsin (Cat)B or CatS may be a novel therapeutic approach for delaying the onset of and enacting early intervention for AD.

A Systematic Review of Meta-Analyses that Evaluate Risk Factors for Dementia to Evaluate the Quantity, Quality, and Global Representativeness of Evidence

Background:

The translation of evidence on dementia risk factors into clinical advice requires careful evaluation of the methodology and scope of data from which risk estimates are obtained.

Objective:

To evaluate the quantity, quality, and representativeness of evidence, we conducted a review of reviews of risk factors for Alzheimer’s disease (AD), Vascular dementia (VaD), and Any Dementia.

Methods:

PubMed, Cochrane library, and the Global Index Medicus were searched to identify meta-analyses of observational studies of risk factors for AD, VaD, and Any Dementia. PROSPERO CRD42017053920.

Results:

Meta-analysis data were available for 34 risk factors for AD, 26 risk factors for Any Dementia and eight for VaD. Quality of evidence varied greatly in terms of the number of contributing studies, whether data on midlife exposure was available, and consistency of measures. The most evidence was available for cardiovascular risk factors. The most geographically representative evidence (five of six global regions) was available for alcohol, physical activity, diabetes, high midlife BMI, antihypertensives, and motor function. Evidence from Australia/Oceana or Africa was limited. With the exception of diabetes, meta-analysis data were unavailable from Latin America/Caribbean. Midlife specific data were only available for cholesterol and arthritis.

Conclusion:

There is a lack of midlife specific data, limited data on VaD, and a lack of geographical representation for many risk factors for dementia. The quality, quantity, and representativeness of evidence needs to be considered before recommendations are made about the relevance of risk factors in mid- or late-life or for dementia subtypes.

Short-term exposure to dietary cholesterol is associated with downregulation of interleukin-15, reduced thigmotaxis and memory impairment in mice

Alzheimer's disease (AD) is a neurodegenerative condition associated with loss of memory function, depression and anxiety. The etiology of AD is poorly understood, but both cholesterol dyshomeostasis and dysregulation of the immune system are contributing factors. Current evidence is consistent with a detrimental effect of excess cholesterol on neuroinflammation, both in mouse models of memory loss and in dementia in humans. However, whether the impact of cholesterol on neuroinflammation occurs early and contributes to pathogenesis of the disease or simply reflects a pleiotropic impact at advanced stages of disease is unclear. To explore this question, we measured, in 9-13 week-old mice, cognitive status and changes in brain inflammatory mediators in response to a short-term high-cholesterol diet. We hypothesized that short-term exposure to excess dietary cholesterol would alter the early inflammatory responses associated with cognitive and/or behavioral impairment. We report that short-term exposure to a high-cholesterol diet led to decreased thigmotaxis and short-term spatial memory impairment without affecting long-term recognition memory. Furthermore, cognitive and behavioral phenotypes in these mice were associated with a reduction in interleukin-15 levels in the absence of changes in other inflammatory mediators. Our findings indicate that interleukin-15 may play a role in early stages of cognitive impairment secondary to hypercholesterolemia. Consequently, optimization of interleukin-15 signaling may be a viable effective cognitive therapy in the population susceptible to developing dementia due to risk factors associated with cholesterol dysregulation.

Aspirin and other non-steroidal anti-inflammatory drugs for the prevention of dementia

BACKGROUND

Dementia is a worldwide concern. Its global prevalence is increasing. At present, there is no medication licensed to prevent or delay the onset of dementia. Inflammation has been suggested as a key factor in dementia pathogenesis. Therefore, medications with anti-inflammatory properties could be beneficial for dementia prevention.

OBJECTIVES

To evaluate the effectiveness and adverse effects of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) for the primary or secondary prevention of dementia.

SEARCH METHODS

We searched ALOIS, the specialised register of the Cochrane Dementia and Cognitive Improvement Group up to 9 January 2020. ALOIS contains records of clinical trials identified from monthly searches of several major healthcare databases, trial registries and grey literature sources. We ran additional searches across MEDLINE (OvidSP), Embase (OvidSP) and six other databases to ensure that the searches were as comprehensive and up-to-date as possible. We also reviewed citations of reference lists of included studies.

SELECTION CRITERIA

We searched for randomised controlled trials (RCTs) and controlled clinical trials (CCTs) comparing aspirin or other NSAIDs with placebo for the primary or secondary prevention of dementia. We included trials with cognitively healthy participants (primary prevention) or participants with mild cognitive impairment (MCI) or cognitive complaints (secondary prevention).

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures according to the Cochrane Handbook for Systematic Reviews of Interventions. We rated the strength of evidence for each outcome using the GRADE approach.

MAIN RESULTS

We included four RCTs with 23,187 participants. Because of the diversity of these trials, we did not combine data to give summary estimates, but presented a narrative description of the evidence. We identified one trial (19,114 participants) comparing low-dose aspirin (100 mg once daily) to placebo. Participants were aged 70 years or older with no history of dementia, cardiovascular disease or physical disability. Interim analysis indicated no significant treatment effect and the trial was terminated slightly early after a median of 4.7 years' follow-up. There was no evidence of a difference in incidence of dementia between aspirin and placebo groups (risk ratio (RR) 0.98, 95% CI 0.83 to 1.15; high-certainty evidence). Participants allocated aspirin had higher rates of major bleeding (RR 1.37, 95% CI 1.17 to 1.60, high-certainty evidence) and slightly higher mortality (RR 1.14, 95% CI 1.01 to 1.28; high-certainty evidence). There was no evidence of a difference in activities of daily living between groups (RR 0.84, 95% CI 0.70 to 1.02; high-certainty evidence). We identified three trials comparing non-aspirin NSAIDs to placebo. All three trials were terminated early due to adverse events associated with NSAIDs reported in other trials. One trial (2528 participants) investigated the cyclo-oxygenase-2 (COX-2) inhibitor celecoxib (200 mg twice daily) and the non-selective NSAID naproxen (220 mg twice daily) for preventing dementia in cognitively healthy older adults with a family history of Alzheimer's disease (AD). Median follow-up was 734 days. Combining both NSAID treatment arms, there was no evidence of a difference in the incidence of AD between participants allocated NSAIDs and those allocated placebo (RR 1.91, 95% CI 0.89 to 4.10; moderate-certainty evidence). There was also no evidence of a difference in rates of myocardial infarction (RR 1.21, 95% CI 0.61 to 2.40), stroke (RR 1.82, 95% CI 0.76 to 4.37) or mortality (RR 1.37, 95% CI 0.78 to 2.43) between treatment groups (all moderate-certainty evidence). One trial (88 participants) assessed the effectiveness of celecoxib (200 mg or 400 mg daily) in delaying cognitive decline in participants aged 40 to 81 years with mild age-related memory loss but normal memory performance scores. Mean duration of follow-up was 17.6 months in the celecoxib group and 18.1 months in the placebo group. There was no evidence of a difference between groups in test scores in any of six cognitive domains. Participants allocated celecoxib experienced more gastrointestinal adverse events than those allocated placebo (RR 2.66, 95% CI 1.05 to 6.75; low-certainty evidence). One trial (1457 participants) assessed the effectiveness of the COX-2 inhibitor rofecoxib (25 mg once daily) in delaying or preventing a diagnosis of AD in participants with MCI. Median duration of study participation was 115 weeks in the rofecoxib group and 130 weeks in the placebo group. There was a higher incidence of AD in the rofecoxib than the placebo group (RR 1.32, 95% CI 1.01 to 1.72; moderate-certainty evidence). There was no evidence of a difference between groups in cardiovascular adverse events (RR 1.07, 95% CI 0.68 to 1.66; moderate-certainty evidence) or mortality (RR 1.62, 95% CI 0.85 to 3.05; moderate-certainty evidence). Participants allocated rofecoxib had more upper gastrointestinal adverse events (RR 3.53, 95% CI 1.17 to 10.68; moderate-certainty evidence). Reported annual mean difference scores showed no evidence of a difference between groups in activities of daily living (year 1: no data available; year 2: 0.0, 95% CI -0.1 to 0.2; year 3: 0.1, 95% CI -0.1 to 0.3; year 4: 0.1, 95% CI -0.1 to 0.4; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

There is no evidence to support the use of low-dose aspirin or other NSAIDs of any class (celecoxib, rofecoxib or naproxen) for the prevention of dementia, but there was evidence of harm. Although there were limitations in the available evidence, it seems unlikely that there is any need for further trials of low-dose aspirin for dementia prevention. If future studies of NSAIDs for dementia prevention are planned, they will need to be cognisant of the safety concerns arising from the existing studies.

A Path Toward Precision Medicine for Neuroinflammatory Mechanisms in Alzheimer's Disease

Neuroinflammation commences decades before Alzheimer's disease (AD) clinical onset and represents one of the earliest pathomechanistic alterations throughout the AD continuum. Large-scale genome-wide association studies point out several genetic variants—TREM2, CD33, PILRA, CR1, MS4A, CLU, ABCA7, EPHA1, and HLA-DRB5-HLA-DRB1—potentially linked to neuroinflammation. Most of these genes are involved in proinflammatory intracellular signaling, cytokines/interleukins/cell turnover, synaptic activity, lipid metabolism, and vesicle trafficking. Proteomic studies indicate that a plethora of interconnected aberrant molecular pathways, set off and perpetuated by TNF-α, TGF-β, IL-1β, and the receptor protein TREM2, are involved in neuroinflammation. Microglia and astrocytes are key cellular drivers and regulators of neuroinflammation. Under physiological conditions, they are important for neurotransmission and synaptic homeostasis. In AD, there is a turning point throughout its pathophysiological evolution where glial cells sustain an overexpressed inflammatory response that synergizes with amyloid-β and tau accumulation, and drives synaptotoxicity and neurodegeneration in a self-reinforcing manner. Despite a strong therapeutic rationale, previous clinical trials investigating compounds with anti-inflammatory properties, including non-steroidal anti-inflammatory drugs (NSAIDs), did not achieve primary efficacy endpoints. It is conceivable that study design issues, including the lack of diagnostic accuracy and biomarkers for target population identification and proof of mechanism, may partially explain the negative outcomes. However, a recent meta-analysis indicates a potential biological effect of NSAIDs. In this regard, candidate fluid biomarkers of neuroinflammation are under analytical/clinical validation, i.e., TREM2, IL-1β, MCP-1, IL-6, TNF-α receptor complexes, TGF-β, and YKL-40. PET radio-ligands are investigated to accomplish in vivo and longitudinal regional exploration of neuroinflammation. Biomarkers tracking different molecular pathways (body fluid matrixes) along with brain neuroinflammatory endophenotypes (neuroimaging markers), can untangle temporal–spatial dynamics between neuroinflammation and other AD pathophysiological mechanisms. Robust biomarker–drug codevelopment pipelines are expected to enrich large-scale clinical trials testing new-generation compounds active, directly or indirectly, on neuroinflammatory targets and displaying putative disease-modifying effects: novel NSAIDs, AL002 (anti-TREM2 antibody), anti-Aβ protofibrils (BAN2401), and AL003 (anti-CD33 antibody). As a next step, taking advantage of breakthrough and multimodal techniques coupled with a systems biology approach is the path to pursue for developing individualized therapeutic strategies targeting neuroinflammation under the framework of precision medicine.

Bee Venom Soluble Phospholipase A2 Exerts Neuroprotective Effects in a Lipopolysaccharide-Induced Mouse Model of Alzheimer's Disease via Inhibition of Nuclear Factor-Kappa B

Neuroinflammation is important in the pathogenesis and development of Alzheimer's disease (AD). In the AD brain, microglial activation and upregulation of pro-inflammatory mediators both induce amyloid beta (Aβ) accumulation. Regulatory T cells (Tregs) and nuclear factor-kappa B (NF-κB) signaling have been implicated in AD development through their effects on neuroinflammation and microglial activation. The bee venom soluble phospholipase A2 (bv-sPLA2) enzyme is known to exert anti-inflammatory and anti-immune effects. Here, we investigated the inhibitory effects of bv-sPLA2 on memory deficiency in a lipopolysaccharide (LPS)-induced mouse model of AD. We examined whether bv-sPLA2 (0.02, 0.2, and 2 mg/kg by i.p. injection three times for 1 week) could inhibit neuroinflammation and memory impairment in LPS-treated mice (250 μg/kg by i.p. injection daily for 1 week). We also assessed the effects of bv-sPLA2 administration (0.01, 0.1, and 1 μg/ml) on LPS (1 μg/ml)-treated microglial BV-2 cells. In the LPS-injected mouse brain, sPLA2 treatment rescued memory dysfunction and decreased Aβ levels, through the downregulation of amyloidogenic proteins, and decreased the expression of inflammatory proteins and pro-inflammatory cytokines. Moreover, the LPS-mediated increase in inflammatory protein expression was attenuated bv-sPLA2 treatment in BV-2 cells. Treatment with bv-sPLA2 also downregulated signaling by NF-κB, which is considered to be an important factor in the regulation of neuroinflammatory and amyloidogenic responses, both in vivo and in vitro. Additionally, co-treatment with NF-κB (5 μM) and bv-sPLA2 (0.1 μg/ml) exerted more marked anti-inflammatory effects, compared to bv-sPLA2 treatment alone. These results indicate that bv-sPLA2 inhibits LPS-induced neuroinflammation and amyloidogenesis via inhibition of NF-κB.

Berberine ameliorates non-steroidal anti-inflammatory drugs-induced intestinal injury by the repair of enteric nervous system

The study was to detect the role of GDNF, PGP9.5 (a neuronal marker), and GFAP (EGCs' marker) in the mechanism of non-steroidal anti-inflammatory drugs (NSAIDs) related to intestinal injury and to clarify the protective effect of berberine in the treatment of NSAID-induced small intestinal disease. Forty male SD rats were divided randomly into five groups (A-E): Group A: control group; Group B: model group received diclofenac sodium 7.5 mg/(kg*day) for 5 days; Group C-E: berberine low, medium and high dose groups were treated by 7.5 mg/(kg*day) diclofenac sodium for 5 days then received berberine 25 mg/(kg*day), 50 mg/(kg*day), and 75 mg/(kg*day), respectively, between the sixth and eighth day. Intestinal mucosa was taken on the ninth day to observe the general, histological injuries, and to measure the intestinal epithelial thickness. Then, immunohistochemistry was performed to detect the expression of PGP9.5 and GFAP, and Western blot was performed to detect GDNF expression. The histological score and the general score in the model group were, respectively, 5.75 ± 1.04 and 4.83 ± 0.92. Scores in berberine medium and high berberine group were lower compared with the model group (P < 0.05). The intestinal epithelial thickness in the model group was lower than in the control group and the berberine groups (P < 0.05). PGP9.5, GFAP, and GDNF content in the model group and the three berberine groups were significantly lower than in the control groups (P < 0.05). PGP9.5, GFAP, and GDNF content in the control group and the three berberine groups were higher compared with the model groups (P < 0.05). Berberine can protect the intestinal mucosa of NSAID users, and the mechanism is associated with the reparation of the enteric nervous system via upregulating the expression of PGP9.5, GFAP, and GDNF.

Cyclooxygenase-2 Induced the β-Amyloid Protein Deposition and Neuronal Apoptosis Via Upregulating the Synthesis of Prostaglandin E2 and 15-Deoxy-Δ12,14-prostaglandin J2

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) have been shown to be involved in the pathogenesis of Alzheimer's disease. Analysis of the underlying mechanisms elucidated a function of sequential PGE2 and PGD2 synthesis in regulating β-amyloid protein (Aβ) deposition by modulating tumor necrosis factor α (TNF-α)-dependent presenilin (PS)1/2 activity in COX-2 and APP/PS1 crossed mice. Specifically, COX-2 overexpression accelerates the expression of microsomal PGE synthase-1 (mPGES-1) and lipocalin-type prostaglandin D synthase (L-PGDS), leading to the synthesis of PGE2 and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) in 6-month-old APP/PS1 mice. Consequently, PGE2 has the ability to increase Aβ production by enhancing the expression of PS1/2 in a TNF-α-dependent manner, which accelerates the cognitive decline of COX-2/APP/PS1 mice. More interestingly, low concentrations of 15d-PGJ2 treatment facilitate the effects of PGE2 on the deposition of Aβ via TNF-α-dependent PS1/2 mechanisms. In contrast, high concentrations of 15d-PGJ2 treatment inhibit the deposition of Aβ via suppressing the expression of TNF-α-dependent PS1/2. In this regard, a high concentration of 15d-PGJ2 appears to be a therapeutic agent against Alzheimer's disease. However, the high 15d-PGJ2 concentration treatment induces neuronal apoptosis via increasing the protein levels of Bax, cleaved caspase-3, and DFF45, which further impairs the learning ability of APP/PS1 mice.

Impact of Flavonoids on Cellular and Molecular Mechanisms Underlying Age-Related Cognitive Decline and Neurodegeneration

Purpose of Review

This review summarises the most recent evidence regarding the effects of dietary flavonoids on age-related cognitive decline and neurodegenerative diseases.

Recent Findings

Recent evidence indicates that plant-derived flavonoids may exert powerful actions on mammalian cognition and protect against the development of age-related cognitive decline and pathological neurodegeneration. The neuroprotective effects of flavonoids have been suggested to be due to interactions with the cellular and molecular architecture of brain regions responsible for memory.

Summary

Mechanisms for the beneficial effects of flavonoids on age-related cognitive decline and dementia are discussed, including modulating signalling pathways critical in controlling synaptic plasticity, reducing neuroinflammation, promoting vascular effects capable of stimulating new nerve cell growth in the hippocampus, bidirectional interactions with gut microbiota and attenuating the extracellular accumulation of pathological proteins. These processes are known to be important in maintaining optimal neuronal function and preventing age-related cognitive decline and neurodegeneration.

Associations between Use of Specific Analgesics and Concentrations of Amyloid-β 42 or Phospho-Tau in Regions of Human Cerebral Cortex

Analgesics are commonly used by older adults, raising the question of whether their use might contribute to dementia risk and neuropathologic changes of Alzheimer's disease (AD). The Adult Changes in Thought (ACT) study is a population-based study of brain aging and incident dementia among people 65 years or older who are community dwelling and not demented at entry. Amyloid-β (Aβ)42 and phospho-tau were quantified using Histelide in regions of cerebral cortex from 420 brain autopsies. Total standard daily doses of prescription opioid and non-aspirin nonsteroidal anti-inflammatory drug (NSAID) exposure during a defined 10-year exposure window were identified using automated pharmacy dispensing data and used to classify people as having no/low, intermediate, or high exposure. People with high NSAID exposure had significantly greater Aβ42 concentration in middle frontal gyrus and superior and middle temporal gyri, but not inferior parietal lobule; no Aβ42 regional concentration was associated with prescription opioid usage. People with high opioid usage had significantly greater concentration of phospho-tau in middle frontal gyrus than people with little-to-no opioid usage. Consistent with our previous studies, findings suggest that high levels of NSAID use in older individuals may promote Aβ42 accumulation in cerebral cortex.

(5R)-5-hydroxytriptolide inhibits the inflammatory cascade reaction in astrocytes

Many studies have shown that (5R)-5-hydroxytriptolide is the optimal modified analogue of triptolide, possessing comparable immunosuppressive activity but much lower cytotoxicity than triptolide. Whether (5R)-5-hydroxytriptolide has preventive effects on neuroinflammation is unclear. This study was designed to pretreat primary astrocytes from the brains of neonatal Sprague-Dawley rats with 20, 100 and 500 nM (5R)-5-hydroxytriptolide for 1 hour before establishing an in vitro neuroinflammation model with 1.0 μg/mL lipopolysaccharide for 24 hours. The generation of nitric oxide was detected by Griess reagents. Astrocyte marker glial fibrillary acidic protein was measured by immunohistochemical staining. The levels of tumor necrosis factor-α and interleukin-1β in the culture supernatant were assayed by enzyme linked immunosorbent assay. Nuclear factor-κB/p65 expression was examined by immunofluorescence staining. The phosphorylation of inhibitor of nuclear factor IκB-α and the location of nuclear factor-κB/P65 were determined using western blot assay. Our data revealed that (5R)-5-hydroxytriptolide inhibited the generation of nitric oxide, tumor necrosis factor-α and interleukin-1β from primary astrocytes activated by lipopolysaccharide, decreased the positive reaction intensity of glial fibrillary acidic protein, reduced the expression of tumor necrosis factor alpha and interleukin-1β in culture supernatant, inhibited the phosphorylation of IκB-α and the translocation of nuclear factor-κB/P65 to the nucleus. These results have confirmed that (5R)-5-hydroxytriptolide inhibits lipopolysaccharide-induced glial inflammatory response and provides cytological experimental data for (5R)-5-hydroxytriptolide in the treatment of neurodegenerative diseases.

Potential Role of Fluoride in the Etiopathogenesis of Alzheimer's Disease

The etiopathogenesis of Alzheimer's disease has not been fully explained. Now, the disease is widely attributed both to genetic and environmental factors. It is believed that only a small percentage of new AD cases result solely from genetic mutations, with most cases attributed to environmental factors or to the interaction of environmental factors with preexistent genetic determinants. Fluoride is widespread in the environment and it easily crosses the blood⁻brain barrier. In the brain fluoride affects cellular energy metabolism, synthesis of inflammatory factors, neurotransmitter metabolism, microglial activation, and the expression of proteins involved in neuronal maturation. Finally, and of specific importance to its role in Alzheimer's disease, studies report fluoride-induced apoptosis and inflammation within the central nervous system. This review attempts to elucidate the potential relationship between the effects of fluoride exposure and the pathogenesis of Alzheimer's disease. We describe the impact of fluoride-induced oxidative stress and inflammation in the pathogenesis of AD and demonstrate a role for apoptosis in disease progression, as well as a mechanism for its initiation by fluoride. The influence of fluoride on processes of AD initiation and progression is complex and warrants further investigation, especially considering growing environmental fluoride pollution.

Phenylpropanoids and Alzheimer's disease: A potential therapeutic platform

Alzheimer's disease (AD) is a neurodegenerative disorder, characterized by progressive dementia, neuroinflammation and the accumulation of intracellular neurofibrillary tangles and extracellular plaques. The etiology of AD is unclear, but is generally attributed to four leading hypotheses: (i) abnormal folding and aggregation of amyloid-β (Aβ)/tau proteins (ii) activation of the innate immune system, (iii) mitochondrial dysfunction, and (iv) oxidative stress. To date, therapeutic strategies have largely focused on Aβ-centric targets; however, the repeated failure of clinical trials and the continued lack of a disease-modifying therapy demand novel, multifaceted approaches. Natural products are common molecular platforms in drug development; in AD, compounds from the plant phenylpropanoid metabolic pathway have yielded promising associations. Herein, we review developments in the pathogenesis of AD and the metabolism of phenylpropanoids in plants. We further discuss the role of these metabolites as relevant to the four leading mechanisms of AD pathogenesis, and observe multiple protective effects among phenylpropanoids against AD onset and progression.

Integrated communications between cyclooxygenase-2 and Alzheimer's disease

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) are involved in the pathogenesis of Alzheimer's disease (AD), which is characterized by the accumulation of β-amyloid protein (Aβ) and tau hyperphosphorylation. However, the gaps in our knowledge of the roles of COX-2 and PGs in AD have not been filled. Here, we summarized the literature showing that COX-2 dysregulation obviously influences abnormal cleavage of β-amyloid precursor protein, aggregation and deposition of Aβ in β-amyloid plaques and the inclusion of phosphorylated tau in neurofibrillary tangles. Neuroinflammation, oxidative stress, synaptic plasticity, neurotoxicity, autophagy, and apoptosis have been assessed to elucidate the mechanisms of COX-2 regulation of AD. Notably, an imbalance of these factors ultimately produces cognitive decline. The current review substantiates our understanding of the mechanisms of COX-2-induced AD and establishes foundations for the design of feasible therapeutic strategies to treat AD.-Guan, P.-P., Wang, P. Integrated communications between cyclooxygenase-2 and Alzheimer's disease.

Mechanisms of Risk Reduction in the Clinical Practice of Alzheimer's Disease Prevention

Alzheimer’s disease (AD) is a neurodegenerative dementia that affects nearly 50 million people worldwide and is a major source of morbidity, mortality, and healthcare expenditure. While there have been many attempts to develop disease-modifying therapies for late-onset AD, none have so far shown efficacy in humans. However, the long latency between the initial neuronal changes and onset of symptoms, the ability to identify patients at risk based on family history and genetic markers, and the emergence of AD biomarkers for preclinical disease suggests that early risk-reducing interventions may be able to decrease the incidence of, delay or prevent AD. In this review, we discuss six mechanisms—dysregulation of glucose metabolism, inflammation, oxidative stress, trophic factor release, amyloid burden, and calcium toxicity—involved in AD pathogenesis that offer promising targets for risk-reducing interventions. In addition, we offer a blueprint for a multi-modality AD risk reduction program that can be clinically implemented with the current state of knowledge. Focused risk reduction aimed at particular pathological factors may transform AD to a preventable disorder in select cases.

NSAID Exposure and Risk of Alzheimer's Disease: An Updated Meta-Analysis From Cohort Studies

Background: Initial observational studies and a systematic review published recently have suggested that non-steroidal anti-inflammatory drug (NSAID) use has the trend to be associated with reduced risk of Alzheimer's disease (AD), while results remain conflicting. Thus, we performed an updated meta-analysis to reevaluate the evidence on this association.

Methods: Data sources from PUBMED, Embase and Cochrane Library from inception through April 2017 were searched by two independent reviewers. Eligible cohort studies were selected according to predefined keywords. We did a meta-analysis of available study data using a random-effects model to calculate overall relative risks (RRs) for associations between NSAID exposure and AD risk.

Results: From 121 potentially relevant studies, 16 cohort studies including 236,022 participants, published between 1995 and 2016, were included in this systematic review. Meta-analysis demonstrated that current or former NSAID use was significantly associated with reduced risk of AD (RR, 0.81, 95% CI0.70 to 0.94) compared with those who did not use NSAIDs. This association existed in studies including all NSAID types, but not in aspirin (RR, 0.89, 95% CI 0.70 to 1.13), acetaminophen (RR, 0.87, 95% CI 0.40 to 1.91) or non-aspirin NSAID (RR, 0.84, 95% CI 0.58 to 1.23).

Conclusions: Current evidence suggests that NSAID exposure might be significantly associated with reduced risk of AD. However, further large-scale prospective studies are needed to reevaluate this association, especially the associations in individual NSAID type.

Neuroinflammation, Gut Microbiome, and Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that develops insidiously and causes dementia finally. There are also clinical complications in advanced dementia, such as eating problems, infections, which will lead to the decline of patients' life quality, and the rising cost of care for AD to our society. AD will be important public health challenge. Early detection of AD may be a key issue to prevent, delay, and stop the disease. Gut microbiome and neuroinflammation are closely related with nervous system diseases, although the specific mechanism is not clear. This review introduces the relationship between neuroinflammation, gut microbiome, and AD.

Principles for central nervous system inflammation research: A call for a consortium approach

INTRODUCTION

Neuroinflammation is now considered to be of pathophysiologic significance in Alzheimer's disease and other neurodegenerative conditions. Nonetheless, there is no consensus as to what inflammatory mechanisms need to be combated (or facilitated), how therapies for them should be applied, or when they might be efficacious.

METHODS

This article seeks to put forward cornerstone facts about neuroinflammation, with suggestions for future directions.

RESULTS

Multiple scientific points about neuroinflammation still remain unaddressed. The main issue, however, is political. An expert body is needed that can sort through the myriad findings and provide consensus advice to agencies that fund basic and clinical research.

DISCUSSION

Consortium approaches have shown immense value in other Alzheimer's disease research areas and are badly needed in neuroinflammation research. Lacking a consensus, neuroinflammation is just a very large number of isolated articles clamoring for attention.

Solid lipid curcumin particles provide greater anti-amyloid, anti-inflammatory and neuroprotective effects than curcumin in the 5xFAD mouse model of Alzheimer's disease

BACKGROUND

Neuroinflammation and the presence of amyloid beta protein (Aβ) and neurofibrillary tangles are key pathologies in Alzheimer's disease (AD). As a potent anti-amyloid and anti-inflammatory natural polyphenol, curcumin (Cur) could be potential therapies for AD. Unfortunately, poor solubility, instability in physiological fluids, and low bioavailability limit its clinical utility. Recently, different lipid modifications in the formulae of Cur have been developed that would enhance its therapeutic potential. For example, we have reported greater permeability and neuroprotection with solid lipid curcumin particles (SLCP) than with natural Cur in an in vitro model of AD. In the present study, we compared the Aβ aggregation inhibition, anti-amyloid, anti-inflammatory responses of Cur and or SLCP in both in vitro and in vivo models of AD. One-year-old 5xFAD-and age-matched wild-type mice were given intraperitoneal injections of Cur or SLCP (50 mg/kg body weight) for 2- or 5-days. Levels of Aβ aggregation, including oligomers and fibril formation, were assessed by dot blot assay, while Aβ plaque load and neuronal morphology in the pre-frontal cortex (PFC) and hippocampus were assayed by immunolabeling with Aβ-specific antibody and cresyl violet staining, respectively. In addition, neuroinflammation was assessed the immunoreactivity (IR) of activated astrocytes (GFAP) and microglia (Iba-1) in different brain areas. Finally, comparisons of solubility and permeability of Cur and SLCP were made in cultured N2a cells and in primary hippocampal neurons derived from E16 pups of 5xFAD mice.

RESULTS

We observed that relative to Cur, SLCP was more permeable, labeled Aβ plaques more effectively, and produced a larger decrease in Aβ plaque loads in PFC and dentate gyrus (DG) of hippocampus. Similarly, relative to Cur, SLCP produced a larger decrease of pyknotic, or tangle-like, neurons in PFC, CA1, and CA3 areas of hippocampus after 5 days of treatment. Both Cur and or SLCP significantly reduced GFAP-IR and Iba-1-IR in PFC, in the striatum as well as CA1, CA3, DG, subicular complex of hippocampus, and the entorhinal cortex in the 5xFAD mice after 5 days of treatment.

CONCLUSIONS

The use of SLCP provides more anti-amyloid, anti-inflammatory, and neuroprotective outcomes than does Cur in the 5xFAD mouse model of AD.

Peptides as Potential Therapeutics for Alzheimer's Disease

Intracellular synthesis, folding, trafficking and degradation of proteins are controlled and integrated by proteostasis. The frequency of protein misfolding disorders in the human population, e.g., in Alzheimer's disease (AD), is increasing due to the aging population. AD treatment options are limited to symptomatic interventions that at best slow-down disease progression. The key biochemical change in AD is the excessive accumulation of per-se non-toxic and soluble amyloid peptides (Aβ(1-37/44), in the intracellular and extracellular space, that alters proteostasis and triggers Aβ modification (e.g., by reactive oxygen species (ROS)) into toxic intermediate, misfolded soluble Aβ peptides, Aβ dimers and Aβ oligomers. The toxic intermediate Aβ products aggregate into progressively less toxic and less soluble protofibrils, fibrils and senile plaques. This review focuses on peptides that inhibit toxic Aβ oligomerization, Aβ aggregation into fibrils, or stabilize Aβ peptides in non-toxic oligomers, and discusses their potential for AD treatment.

Xanthoceraside attenuates amyloid β peptide1-42-induced memory impairments by reducing neuroinflammatory responses in mice

Xanthoceraside, a novel triterpenoid saponin extracted from the husks of Xanthoceras sorbifolia Bunge, has neuroprotective effects in vivo and anti-inflammatory properties in vitro. However, the exact mechanism of xanthoceraside on anti-amyloid beta (Aβ)-induced neuroinflammatory responses has not been elucidated. Therefore, we used intracerebroventricular injection of amyloid _1-42 (Aβ_1-42) to establish a mouse model to test the effects of xanthoceraside on Aβ-induced cognitive impairments and the TLR2/NF-κB and MAPK pathways. The mice received xanthoceraside (0.02, 0.08 or 0.32mg/kg) or vehicle from the day of Aβ_1-42 injection. The Morris water maze test was performed 4 days after Aβ_1-42 injection. The levels of inflammatory cytokines (interleukin (IL)-6 and IL-4) were measured by enzyme-linked immunosorbent assay (ELISA). The expression levels of glial fibrillary acidic protein (GFAP) and cluster of differentiation 11b (CD11b) in the hippocampus were determined with an immunohistochemistry assay. Inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) were analysed by Western blotting; iNOS, COX-2 and Toll-like receptor 2 (TLR2) mRNA expression levels were measured by reverse transcription-polymerase chain reaction (RT-PCR). Here, we observed that xanthoceraside at doses of 0.08 and 0.32mg/kg significantly improved learning and memory impairments and significantly inhibited GFAP and CD11b overexpression induced by Aβ_1-42 in mice. ELISA results revealed that xanthoceraside suppressed IL-6 release and increased IL-4 levels. Western blotting results showed that xanthoceraside reduced iNOS and COX-2 protein levels in hippocampus; xanthoceraside also inhibited translocation of NF-κB p50 and p65 into the nucleus and phosphorylation of extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38. RT-PCR confirmed that xanthoceraside decreased iNOS, COX-2 and TLR2 mRNA levels. These results suggest that xanthoceraside inhibition of the TLR2 pathway and down-regulation of MAPK and NF-κB activities may be related to the improvement in learning and memory impairments.

Protective effect of antirheumatic drugs on dementia in rheumatoid arthritis patients

Introduction

Rheumatoid arthritis is a systemic inflammatory disease, and classical disease-modifying antirheumatic drugs (cDMARDs) have proven efficacy. It is unknown what impact cDMARDs might have on dementia as an outcome.

Methods

Incident diagnoses of rheumatoid arthritis in persons over 18 years from 1995 to 2011 were identified from the UK Clinical Practice Research Datalink. There were 3876 cDMARD users and were propensity score matched to 1938 nonusers, on a wide range of confounders. Impact on dementia was assessed using survival models.

Results

cDMARD users were at reduced risk of dementia (hazard ratio: 0.60; 95% confidence interval: 0.42–0.85). The effect was strongest in methotrexate users (hazard ratio: 0.52; 95% confidence interval; 0.34–0.82).

Discussion

The strong effect of cDMARD use on halving of dementia risk requires replication in a trial and may provide an important therapeutic pharmacological treatment.