Innate immune system and inflammation in Alzheimer's disease: from pathogenesis to treatment

Alterations in Immune Responses Are Associated with Dysfunctional Intracellular Signaling in Peripheral Blood Mononuclear Cells of Men and Women with Mild Cognitive Impairment and Alzheimer's disease

Deficits in the neuroendocrine-immune network in the periphery associated with the onset and progression of mild cognitive impairment (MCI) and Alzheimer's disease (AD) have not been extensively studied. The present study correlatively examines the association between cell-mediated immune responses, stress hormones, amyloid precursor protein (APP) expression, peripheral blood mononuclear cells (PBMC), and intracellular signaling molecules in the pathophysiology of MCI and AD compared to adults. Serum APP, lymphocyte proliferation, total cholinesterase (TChE), butyrylcholinesterase (BChE) activities, cytokines (IL-2, IFN-γ, IL-6, and TNF-α), and intracellular signaling molecules (p-ERK, p-CREB, and p-Akt) were measured in the PBMCs of adult, old, MCI, and AD men and women initially and after 3 years in the same population. An age- and disease-associated decline in mini-mental state examination (MMSE) scores and lymphocyte proliferation of MCI and AD men and women were observed. An age- and disease-related increase in serum APP, cortisol levels, and TChE activity were observed in men and women. Enhanced production of Th1 cytokine, IL-2, pro-inflammatory cytokines, and suppressed intracellular transcription factors may promote the inflammatory environment in MCI and AD patients. The expression of CREB and Akt was lower in MCI and AD men, while the expression of p-ERK was higher, and p-CREB was lower in MCI and AD women after 3 years. These results suggest that changes in specific intracellular signaling pathways may influence alterations in cell-mediated immunity to promote disease progression in MCI and AD patients.

A glance through the effects of CD4+ T cells, CD8+ T cells, and cytokines on Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. Unfortunately, despite numerous studies, an effective treatment for AD has not yet been established. There is remarkable evidence indicating that the innate immune mechanism and adaptive immune response play significant roles in the pathogenesis of AD. Several studies have reported changes in CD8+ and CD4+ T cells in AD patients. This mini-review article discusses the potential contribution of CD4+ and CD8+ T cells reactivity to amyloid β (Aβ) protein in individuals with AD. Moreover, this mini-review examines the potential associations between T cells, heme oxygenase (HO), and impaired mitochondria in the context of AD. While current mathematical models of AD have not extensively addressed the inclusion of CD4+ and CD8+ T cells, there exist models that can be extended to consider AD as an autoimmune disease involving these T cell types. Additionally, the mini-review covers recent research that has investigated the utilization of machine learning models, considering the impact of CD4+ and CD8+ T cells.

Cross-phenotype associations between Alzheimer's Disease and its comorbidities may provide clues to progression

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease worldwide, with one in nine people over the age of 65 living with the disease in 2023. In this study, we used a phenome wide association study (PheWAS) approach to identify cross-phenotype associations between previously identified genetic AD and for electronic health record (EHR) diagnoses from the UK Biobank (UKBB) (n=361,194 of European ancestry) and the eMERGE Network (n=105,108 of diverse ancestry). Based on 497 previously identified AD-associated variants from the Alzheimer's Disease Variant Portal (ADVP), we found significant associations primarily in immune and cardiac related diseases in our PheWAS. Replicating variants have widespread impacts on immune genes in diverse tissue types. This study demonstrates the potential of using the PheWAS strategy to improve our understanding of AD progression as well as identify potential drug repurposing opportunities for new treatment and disease prevention strategies.

Extract of Aster koraiensis Nakai Leaf Ameliorates Memory Dysfunction via Anti-inflammatory Action

Aster koraiensis Nakai (AK) leaf reportedly ameliorates health problems, such as diabetes. However, the effects of AK on cognitive dysfunction or memory impairment remain unclear. This study investigated whether AK leaf extract could attenuate cognitive impairment. We found that AK extract reduced the production of nitric oxide (NO), tumour necrosis factor (TNF)-α, phosphorylated-tau (p-tau), and the expression of inflammatory proteins in lipopolysaccharide- or amyloid-β-treated cells. AK extract exhibited inhibitory activity of control specific binding on N-methyl-D-aspartate (NMDA) receptors. Scopolamine-induced AD models were used chronically in rats and acutely in mice. Relative to negative controls (NC), hippocampal choline acetyltransferase (ChAT) and B-cell lymphoma 2 (Bcl2) activity was increased in rats chronically treated with scopolamine and fed an AK extract-containing diet. In the Y-maze test, spontaneous alterations were increased in the AK extract-fed groups compared to NC. Rats administered AK extract showed increased escape latency in the passive avoidance test. In the hippocampus of rats fed a high-AK extract diet (AKH), the expression of neuroactive ligand–receptor interaction-related genes, including Npy2r, Htr2c, and Rxfp1, was significantly altered. In the Morris water maze assay of mice acutely treated with scopolamine, the swimming times in the target quadrant of AK extract-treated groups increased significantly to the levels of the Donepezil and normal groups. We used Tg6799 Aβ-overexpressing 5XFAD transgenic mice to investigate Aβ accumulation in animals. In the AD model using 5XFAD, the administration of AK extract decreased amyloid-β (Aβ) accumulation and increased the number of NeuN antibody-reactive cells in the subiculum relative to the control group. In conclusion, AK extract ameliorated memory dysfunction by modulating ChAT activity and Bcl2-related anti-apoptotic pathways, affecting the expression of neuroactive ligand–receptor interaction-related genes and inhibiting Aβ accumulation. Therefore, AK extract could be a functional material improving cognition and memory.

The Contribution of the Locus Coeruleus-Noradrenaline System Degeneration during the Progression of Alzheimer's Disease

Alzheimer's disease (AD), which is characterized by extracellular accumulation of amyloid-beta peptide and intracellular aggregation of hyperphosphorylated tau, is the most common form of dementia. Memory loss, cognitive decline and disorientation are the ultimate consequences of neuronal death, synapse loss and neuroinflammation in AD. In general, there are many brain regions affected but neuronal loss in the locus coeruleus (LC) is one of the earliest indicators of neurodegeneration in AD. Since the LC is the main source of noradrenaline (NA) in the brain, degeneration of the LC in AD leads to decreased NA levels, causing increased neuroinflammation, enhanced amyloid and tau burden, decreased phagocytosis and impairment in cognition and long-term synaptic plasticity. In this review, we summarized current findings on the locus coeruleus-noradrenaline system and consequences of its dysfunction which is now recognized as an important contributor to AD progression.

Plasma MCP-1 and changes on cognitive function in community-dwelling older adults

Background

Monocyte Chemoattractant Protein-1 (MCP-1), a glial-derived chemokine, mediates neuroinflammation and may regulate memory outcomes among older adults. We aimed to explore the associations of plasma MCP-1 levels (alone and in combination with β-amyloid deposition—Aβ_42/40) with overall and domain-specific cognitive evolution among older adults.

Methods

Secondary analyses including 1097 subjects (mean age = 75.3 years ± 4.4; 63.8% women) from the Multidomain Alzheimer Preventive Trial (MAPT). MCP-1 (higher is worse) and Aβ_42/40 (lower is worse) were measured in plasma collected at year 1. MCP-1 in continuous and as a dichotomy (values in the highest quartile (MCP-1⁺)) were used, as well as a dichotomy of Aβ_42/40. Outcomes were measured annually over 4 years and included the following: cognitive composite z-score (CCS), the Mini-Mental State Examination (MMSE), and Clinical Dementia Rating (CDR) sum of boxes (overall cognitive function); composite executive function z-score, composite attention z-score, Free and Cued Selective Reminding Test (FCSRT - memory).

Results

Plasma MCP-1 as a continuous variable was associated with the worsening of episodic memory over 4 years of follow-up, specifically in measures of free and cued delayed recall. MCP-1⁺ was associated with worse evolution in the CCS (4-year between-group difference: β = −0.14, 95%CI = −0.26, −0.02) and the CDR sum of boxes (2-year: β = 0.19, 95%CI = 0.06, 0.32). In domain-specific analyses, MCP-1⁺ was associated with declines in the FCSRT delayed recall sub-domains. In the presence of low Aβ_42/40, MCP-1⁺ was not associated with greater declines in cognitive functions. The interaction with continuous biomarker values Aβ_42/40× MCP-1 × time was significant in models with CDR sum of boxes and FCSRT DTR as dependent variables.

Conclusions

Baseline plasma MCP-1 levels were associated with longitudinal declines in overall cognitive and episodic memory performance in older adults over a 4-year follow-up. How plasma MCP-1 interacts with Aβ_42/40 to determine cognitive decline at different stages of cognitive decline/dementia should be clarified by further research. The MCP-1 association on cognitive decline was strongest in those with amyloid plaques, as measured by blood plasma Aβ_42/40.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00940-2.

The role of the adaptive immune system and T cell dysfunction in neurodegenerative diseases

The adaptive immune system and associated inflammation are vital in surveillance and host protection against internal and external threats, but can secondarily damage host tissues. The central nervous system is immune-privileged and largely protected from the circulating inflammatory pathways. However, T cell involvement and the disruption of the blood-brain barriers have been linked to several neurodegenerative diseases including Parkinson's disease, Alzheimer's disease, and multiple sclerosis. Under normal physiological conditions, regulatory T cells (Treg cells) dampen the inflammatory response of effector T cells. In the pathological states of many neurodegenerative disorders, the ability of Treg cells to mitigate inflammation is reduced, and a pro-inflammatory environment persists. This perspective review provides current knowledge on the roles of T cell subsets (e.g., effector T cells, Treg cells) in neurodegenerative and ocular diseases, including uveitis, diabetic retinopathy, age-related macular degeneration, and glaucoma. Many neurodegenerative and ocular diseases have been linked to immune dysregulation, but the cellular events and molecular mechanisms involved in such processes remain largely unknown. Moreover, the role of T cells in ocular pathologies remains poorly defined and limited literature is available in this area of research. Adoptive transfer of Treg cells appears to be a vital immunological approach to control ocular pathologies. Similarities in T cell dysfunction seen among non-ocular neurodegenerative diseases suggest that this area of research has a great potential to develop better therapeutic agents for ocular diseases and warrants further studies. Overall, this perspective review article provides significant information on the roles of T cells in numerous ocular and non-ocular neurodegenerative diseases.

Peripheral Inflammatory Biomarkers of Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative disease of unknown pathological origin. The clinical diagnosis of AD is time-consuming and needs to a combination of clinical evaluation, psychological testing, and imaging assessments. Biomarkers may be good indicators for the clinical diagnosis of AD; hence, it is important to identify suitable biomarkers for the diagnosis and treatment of AD. Peripheral inflammatory biomarkers have been the focus of research in recent years. This review summarizes the role of inflammatory biomarkers in the disease course of AD.

Dysregulated miRNAs as Biomarkers and Therapeutical Targets in Neurodegenerative Diseases

Alzheimer’s disease (AD), Parkinson’s disease (PD), and Amyotrophic Lateral Sclerosis (ALS) are representative neurodegenerative diseases (NDs) characterized by degeneration of selective neurons, as well as the lack of effective biomarkers and therapeutic treatments. In the last decade, microRNAs (miRNAs) have gained considerable interest in diagnostics and therapy of NDs, owing to their aberrant expression and their ability to target multiple molecules and pathways. Here, we provide an overview of dysregulated miRNAs in fluids (blood or cerebrospinal fluid) and nervous tissue of AD, PD, and ALS patients. By emphasizing those that are commonly dysregulated in these NDs, we highlight their potential role as biomarkers or therapeutical targets and describe the use of antisense oligonucleotides as miRNA therapies.

Kai-Xin-San Inhibits Tau Pathology and Neuronal Apoptosis in Aged SAMP8 Mice

Alzheimer’s disease (AD) is an age-related neurological disorder. Currently, there is no effective cure for AD due to its complexity in pathogenesis. In light of the complex pathogenesis of AD, the traditional Chinese medicine (TCM) formula Kai-Xin-San (KXS), which was used for amnesia treatment, has been proved to improve cognitive function in AD animal models. However, the active ingredients and the mechanism of KXS have not yet been clearly elucidated. In this study, network pharmacology analysis predicts that KXS yields 168 candidate compounds acting on 863 potential targets, 30 of which are associated with AD. Enrichment analysis revealed that the therapeutic mechanisms of KXS for AD are associated with the inhibition of Tau protein hyperphosphorylation, inflammation, and apoptosis. Therefore, we chose 7-month-old senescence-accelerated mouse prone 8 (SAMP8) mice as AD mouse model, which harbors the behavioral and pathological hallmarks of AD. Subsequently, the potential underlying action mechanisms of KXS on AD predicted by the network pharmacology analyses were experimentally validated in SAMP8 mice after intragastric administration of KXS for 3 months. We observed that KXS upregulated AKT phosphorylation, suppressed GSK3β and CDK5 activation, and inhibited the TLR4/MyD88/NF-κB signaling pathway to attenuate Tau hyperphosphorylation and neuroinflammation, thus suppressing neuronal apoptosis and improving the cognitive impairment of aged SAMP8 mice. Taken together, our findings reveal a multi-component and multi-target therapeutic mechanism of KXS for attenuating the progression of AD, contributing to the future development of TCM modernization, including KXS, and broader clinical application.

Discovery of novel 6-hydroxybenzothiazole urea derivatives as dual Dyrk1A/α-synuclein aggregation inhibitors with neuroprotective effects

A role of Dyrk1A in the progression of Down syndrome-related Alzheimer's disease (AD) is well supported. However, the involvement of Dyrk1A in the pathogenesis of Parkinson's disease (PD) was much less studied, and it is not clear whether it would be promising to test Dyrk1A inhibitors in relevant PD models. Herein, we modified our previously published 1-(6-hydroxybenzo[d]thiazol-2-yl)-3-phenylurea scaffold of Dyrk1A inhibitors to obtain a new series of analogues with higher selectivity for Dyrk1A on the one hand, but also with a novel, additional activity as inhibitors of α-synuclein (α-syn) aggregation, a major pathogenic hallmark of PD. The phenyl acetamide derivative b27 displayed the highest potency against Dyrk1A with an IC50 of 20 nM and high selectivity over closely related kinases. Furthermore, b27 was shown to successfully target intracellular Dyrk1A and to inhibit SF3B1 phosphorylation in HeLa cells with an IC50 of 690 nM. In addition, two compounds among the Dyrk1A inhibitors, b1 and b20, also suppressed the aggregation of α-synuclein (α-syn) oligomers (with IC50 values of 10.5 μM and 7.8 μM, respectively). Both compounds but not the Dyrk1A reference inhibitor harmine protected SH-SY5Y neuroblastoma cells against α-syn-induced cytotoxicity, with b20 exhibiting a higher neuroprotective effect. Compound b1 and harmine were more efficient in protecting SH-SY5Y cells against 6-hydroxydopamine-induced cell death, an effect that was previously correlated to Dyrk1A inactivation in cells but not yet verified using chemical inhibitors. The presented dual inhibitors exhibited a novel activity profile encouraging for further testing in neurodegenerative disease models.

Ganoderic Acid A To Alleviate Neuroinflammation of Alzheimer's Disease in Mice by Regulating the Imbalance of the Th17/Tregs Axis

Ganoderic acid A (GAA) is a kind of lanostane-type triterpenoid isolated from Ganoderma lucidum. Imbalance of the Th17/Tregs axis exists in the progress of neuroinflammation of Alzheimer's disease (AD). In this study, the alleviating neuroinflammatory effect of GAA on d-galactose mice was studied from the aspect of regulating the imbalance of the Th17/Tregs axis. The Morris water maze test was used to evaluate the cognitive ability of AD mice. Flow cytometry was used to detect the percentages of IL-17A, IL-17F, IL-21, IL-22, and CD4⁺CD25⁺Foxp3⁺ in peripheral blood. Transmission electron microscopy was used to assess the cerebral mitochondrial ultrastructure. Metabolomic analysis based on gas chromatography-mass spectrometry was used to evaluate the mitochondrial dysfunction metabolism. Western blot analysis was used to detect the protein expressions of cytokines secreted by Th17 cells and Treg cells in the brain. As the results show, GAA has an alleviating neuroinflammatory effect on AD mice via regulating the imbalance of the Th17/Tregs axis. The potential mechanism was related to inhibition of the JAK/STAT signaling pathway induced by Th17 cells and enhancement of the mitochondrial oxidative phosphorylation by regulating Treg cells, thereby improving mitochondrial dysfunction of AD mice.

Alzheimer's disease: a step closer to understanding type 3 diabetes in African Americans

Alzheimer's disease (AD) is the fourth leading cause of death in the United States and the most common cause of adult-onset dementia. Recent results suggest an increased prevalence and severity in African Americans compared to Caucasians. Our understanding of the potential mechanism(s) underlying this ethnicity difference is limited. We previously described ethnicity-related differences in levels of neurodegenerative proteins and cytokines/chemokines in the BA21 region of African Americans and Caucasians with AD. Here, similar multiplex assays were used to examine those endpoints in patient postmortem cerebrospinal fluid (CSF). Additionally, we measured levels of C-peptide, ghrelin, gastric inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1), glucagon, insulin, leptin, PAI-1, resistin, and visfatin using a human diabetes 10-plex assay. The cytokine and chemokine assays revealed that levels of 26 chemokines or cytokines differed significantly with ethnicity, and three of those were significantly associated with gender. The neurodegenerative disease panel indicated that levels of soluble RAGE were significantly elevated in African Americans compared to Caucasians. All measures in the diabetes disease panel assay were significantly elevated in African Americans: ghrelin, GIP, GLP-1, glucagon, insulin, and visfatin. Through peripheral sample analysis, these results provide further evidence that ethnicity is critically involved in the manifestation of AD.

Effects of Supplementation with Folic Acid and Its Combinations with Other Nutrients on Cognitive Impairment and Alzheimer's Disease: A Narrative Review

Cognitive impairment and Alzheimer's Disease, among other cognitive dysfunctions, has been recognized as a major public health problem. Folic acid is a well-known essential nutrient whose deficiency has been linked to neurocognitive dysfunctions, owing to hyperhomocysteinemia, an independent risk factor for cardio- and cerebrovascular diseases, including cognitive impairment, Alzheimer's Disease, and vascular dementia. However, to date, there is certain controversy about the efficacy of vitamin supplementation in patients with these pathologies. Therefore, we have reviewed the available dietary intervention studies based on folic acid, either alone or in combination with different vitamins or nutrients into the progression of Alzheimer's Disease and Cognitive impairment, highlighting the cognition and biochemical markers employed for the evaluation of the disease progression. Undeniably, the compiled information supports the potential benefits of vitamin supplementation in these pathologies, especially relevant to the aging process and quality of life, although more research is urgently needed to confirm these positive findings.

Effect of ganglioside combined with Chip Jiaji electro-acupuncture on Nogo-NgR signal pathway in SCI rats

At present, the effect of ganglioside combined with Jiaji electroacupuncture (Jiaji EA) on SCI still remains unclear. This study explores the effect of ganglioside combined with electroacupuncture on Nogo/NgR signal pathway in spinal cord tissue of spinal cord injury (SCI) rats. Basso Beattie Bresnahan (BBB) score was used to evaluate spinal cord function after modeling and 14 days post ganglioside and electroacupuncture treatment. RT-qPCR and western blot were performed to evaluate the expression levels of targets in spinal cord tissue. After 14 days of treatment, the BBB scores of Jiaji EA group, ganglioside group and combination group were all improved. The expression levels of IL-1β, IL-6 and TNF-α in Jiaji EA group, ganglioside group and combination group were significantly lower than those in model group. Both of mRNA and protein expression levels of Nogo-A, NgR and LINGO-1 in the model group were significantly higher than those in the Jiaji EA group, ganglioside group and combination group. Ganglioside combined with Jiaji EA has a stronger effect on promoting the recovery of nerve function. Its mechanism of action may be related to its inhibition of the expression of proinflammatory cytokines such as IL-1β, IL-6 and TNF-α and Nogo-NgR signal pathway to promote neuronal growth. Our results will provide fundamental information for further SCI studies.

All-trans retinoic acid reduces mammalian target of rapamycin via a Sirtuin1-dependent mechanism in neurons

Neuroinflammation has emerged as a key contributor in the pathogenesis of Alzheimer's disease (AD). Mammalian target of rapamycin (mTOR) is a key regulator of metabolism, cell growth and protein synthesis. And an elevated mTOR activity has been detected in AD-affected brain areas. Previous studies have suggested that all-trans retinoic acid (atRA) and rapamycin (RAPA), an mTOR inhibitor, protect lipopolysaccharide (LPS)-induced neuronal inflammation through inhibiting nuclear import of NFκB. The aim of this study was to test the effects of atRA on mTOR expression. Here we discovered that mTOR and p-mTOR expression are elevated in LPS-treated mice or primary rat neurons, while atRA blocks the mTOR gene upregulation via a SIRT1-dependent mechanism. The results of this study demonstrated that atRA may protect LPS-induced neuronal inflammation through suppressing mTOR signaling.

Preclinical Marmoset Model for Targeting Chronic Inflammation as a Strategy to Prevent Alzheimer's Disease

Due to the aging population, modern society is facing an increasing prevalence of neurological diseases such as Alzheimer’s disease (AD). AD is an age-related chronic neurodegenerative disorder for which no satisfying therapy exists. Understanding the mechanisms underlying the onset of AD is necessary to find targets for protective treatment. There is growing awareness of the essential role of the immune system in the early AD pathology. Amyloidopathy, the main feature of early-stage AD, has a deregulating effect on the immune function. This is reciprocal as the immune system also affects amyloidopathy. It seems that the inflammatory reaction shows a heterogeneous pattern depending on the stage of the disease and the variation between individuals, making not only the target but also the timing of treatment important. The lack of relevant translational animal models that faithfully reproduce clinical and pathogenic features of AD is a major cause of the delay in developing new disease-modifying therapies and their optimal timing of administration. This review describes the communication between amyloidopathy and inflammation and the possibility of using nonhuman primates as a relevant animal model for preclinical AD research.

Physical Exercise and Alzheimer's Disease: Effects on Pathophysiological Molecular Pathways of the Disease

Alzheimer’s disease (AD), the most common form of neurodegenerative dementia in adults worldwide, is a multifactorial and heterogeneous disorder characterized by the interaction of genetic and epigenetic factors and the dysregulation of numerous intracellular signaling and cellular/molecular pathways. The introduction of the systems biology framework is revolutionizing the study of complex diseases by allowing the identification and integration of cellular/molecular pathways and networks of interaction. Here, we reviewed the relationship between physical activity and the next pathophysiological processes involved in the risk of developing AD, based on some crucial molecular pathways and biological process dysregulated in AD: (1) Immune system and inflammation; (2) Endothelial function and cerebrovascular insufficiency; (3) Apoptosis and cell death; (4) Intercellular communication; (5) Metabolism, oxidative stress and neurotoxicity; (6) DNA damage and repair; (7) Cytoskeleton and membrane proteins; (8) Synaptic plasticity. Moreover, we highlighted the increasingly relevant role played by advanced neuroimaging technologies, including structural/functional magnetic resonance imaging, diffusion tensor imaging, and arterial spin labelling, in exploring the link between AD and physical exercise. Regular physical exercise seems to have a protective effect against AD by inhibiting different pathophysiological molecular pathways implicated in AD.

Pharmacogenetic and Association Studies on the Influence of HLA Alleles and Rivastigmine on the Iranian Patients with Late-Onset Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting cognitive function. A number of allelic genes from HLA complex have shown variable associations with AD in different populations. In this study, we investigated the association of DQB1*06:00/x, DRB1*04:00/x, DRB1*15:00/x, and B*07:00/x genotypes with AD and their relevance to the efficacy of rivastigmine treatment in the Iranian population. Our findings suggest that DQB1*06:00/x genotype offers strong protection against AD (P = 0.0074), while B*07:00/x genotype imposes a significant susceptibility for sporadic Alzheimer's disease (SAD) (P = 0.009). Interestingly, B*07:00/x genotype does not show any apparent associations with familial Alzheimer's disease (FAD). Our studies also suggest a pharmacogenetic relationship between drug treatment and presence of a particular genotype in the Iranian LOAD patient population. The Clinical Dementia Rating analysis showed that LOAD patients carrying DRB1*04:00/x genotype tend to display a downward trend in the disease severity and symptoms after 2-year follow-up with rivastigmine treatment. Moreover, in our total patient population, the carriers of DQB1*06:00/x and B*07:00/x alleles have better and worse responses to rivastigmine respectively. We also measured the clinical relevance of the testing for these genotypes employing prevalence-corrected positive predictive value (PcPPV) formula. The PcPPV of testing for DQB1*06:00/x in the Iranian LOAD patients was 1.17% which means that people carrying this genotype have half of the probability of the absolute risk for developing LOAD, whereas the PcPPV of testing for B*07:00/x was 4.45% for SAD, which can be interpreted as a doubling chance for developing LOAD among the Iranian population carrying this genotype. These results also suggest that DQβ1 peptide containing positively charged AAs histidine³⁰ and arginine⁵⁵ and HLA class I β chain containing negatively charges aspartic acid¹¹⁴ and glutamic acid^45,152 in their binding groove plays important roles in protection against and susceptibility for LOAD respectively.

Age-related cognitive decline is associated with microbiota-gut-brain axis disorders and neuroinflammation in mice

Age-related cognitive decline is associated with chronic low grade neuroinflammation that may result from a complex interplay among many factors, such as bidirectional communication between the central nervous system (CNS) and gut microbiota. The present study used 2-month-old (young group) and 15-month-old (aged group) male C57BL/6 mice to explore the potential association between age-related cognitive decline and the microbiota-gut-brain axis disorder. We observed that aged mice exhibited significant deficits in learning and memory, neuronal and synaptic function compared with young mice. Aged mice also exhibited significant dysbiosis of the gut microbiota. Disruptions of the intestinal barrier and blood-brain barrier were also observed, including increases in intestinal, low-grade systemic and cerebral inflammation. Furthermore, plasma and brain levels of lipopolysaccharide (LPS) were significantly higher in aged mice compared with young mice, with increasing expression of Toll-like receptor 4 (TLR4) and myeloid differential protein-88 (MyD88) and the nuclear translocation of nuclear factor κB (NF-κB) in intestinal and brain tissues. These findings showed that microbiota-gut-brain axis dysfunction that occurs through LPS-induced activation of the TLR4/NF-κB signaling pathway is implicated in age-related neuroinflammation and cognitive decline.

Peripheral Leukocytosis Predicts Cognitive Decline but Not Behavioral Disturbances: A Nationwide Study of Alzheimer's and Parkinson's Disease Patients

INTRODUCTION

Peripheral and central nervous system inflammation have been linked to the classic symptoms of Parkinson's disease (PD) and Alzheimer's disease (AD). However, it remains unclear whether the analysis of routine systemic inflammatory markers could represent a useful prediction tool to identify clinical subtypes in patients with Parkinson's and Alzheimer's at higher risk of dementia-associated symptoms, such as behavioral and psychological symptoms of dementia (BPSD).

METHODS

We performed a multivariate logistic regression using the 2016 and 2017 National Inpatient Sample with International Classification of Diseases 10th edition codes to assess if pro-inflammatory white blood cells (WBCs) anomalies correlate with dementia and BPSD in patients with these disorders.

RESULTS

We found that leukocytosis was the most common WBC inflammatory marker identified in 3.9% of Alzheimer's and 3.3% Parkinson's patients. Leukocytosis was also found to be an independent risk factor for Parkinson's dementia. Multivariate analysis of both cohorts showed that leukocytosis is significantly decreased in patients with BPSD compared to patients without BPSD.

CONCLUSIONS

These results suggest a link between leukocytosis and the pathophysiology of cognitive dysfunction in both PD and AD. A better understanding of the role of systemic neuroinflammation on these devastating neurodegenerative disorders may facilitate the development of cost-effective blood biomarkers for patient's early diagnosis and more accurate prognosis.

Genetic Association of FERMT2, HLA-DRB1, CD2AP, and PTK2B Polymorphisms With Alzheimer's Disease Risk in the Southern Chinese Population

Objectives

This study aimed to explore the relationship between 18 single nucleotide polymorphisms (SNPs) and Alzheimer’s disease (AD) within the southern Chinese population.

Methods

A total of 420 participants, consisting of 215 AD patients and 205 sex- and age-matched controls, were recruited. The SNaPshot technique and polymer chain reaction (PCR) were used to detect the 18 SNPs. Combined with the apolipoprotein E (APOE) ε4 allele and age at onset, we performed an association analysis between these SNPs and AD susceptibility. Furthermore, we analyzed SNP-associated gene expression using the expression quantitative trait loci analysis.

Results

Our study found that rs17125924 of FERMT2 was associated with the risk of developing AD in the dominant (P = 0.022, odds ratio [OR] = 1.57, 95% confidence interval [CI]: 1.07–2.32) and overdominant (P = 0.005, OR = 1.76, 95% CI: 1.18–2.61) models. Moreover, compared with APOE ε4 non-carriers, the frequency of the G-allele at rs17125924 was significantly higher among AD patients in APOE ε4 allele carriers (P = 0.029). The rs9271058 of HLA-DRB1 (dominant, overdominant, and additive models), rs9473117 of CD2AP (dominant and additive models), and rs73223431 of PTK2B (dominant, overdominant, and additive models) were associated with early onset AD (EOAD). Using the genotype-tissue expression (GTEx) and Braineac database, we found a significant association between rs9271058 genotypes and HLA-DRB1 expression levels, while the CC genotype at rs9473117 and the TT genotype of rs73223431 increased CD2AP and PTK2B gene expression, respectively.

Conclusion

Our study identifies the G-allele at rs17125924 as a risk factor for developing AD, especially in APOE ε4 carriers. In addition, we found that rs9271058 of HLA-DRB1, rs9473117 of CD2AP, and rs73223431 of PTK2B were associated with EOAD. Further studies with larger sample sizes are needed to confirm our results.

Increased inflammation in BA21 brain tissue from African Americans with Alzheimer's disease

Chronic neuroinflammation is strongly associated with AD and altered peripheral and central levels of chemokines and cytokines have been frequently described in those with AD. Given the increasing evidence of ethnicity-related differences in AD, it was of interest to determine if those altered chemokine and cytokine levels are ethnicity-related. Because African Americans exhibit a higher incidence of AD and increased symptom severity, we explored chemokine and cytokine concentrations in post-mortem brain tissue from the BA21 region of African Americans and Caucasians with AD using multiplex assays. IL-1β, MIG, TRAIL, and FADD levels were significantly increased in African Americans while levels of IL-3 and IL-8 were significantly decreased. Those effects did not interact with gender; however, overall levels of CCL25, CCL26 and CX3CL1 were significantly decreased in women. The NLRP3 inflammasome is thought to be critically involved in AD. Increased activation of this inflammasome in African Americans is consistent with the current results.

Biological Hallmarks of Cancer in Alzheimer's Disease

Although Alzheimer's disease (AD) is an international health research priority for our aging population, little therapeutic progress has been made. This lack of progress may be partially attributable to disease heterogeneity. Previous studies have identified an inverse association of cancer and AD, suggesting that cancer history may be one source of AD heterogeneity. These findings are particularly interesting in light of the number of common risk factors and two-hit models hypothesized to commonly drive both diseases. We reviewed the ten hallmark biological alterations of cancer cells to investigate overlap with the AD literature and identified overlap of all ten hallmarks in AD, including (1) potentially common underlying risk factors, such as increased inflammation, deregulated cellular energetics, and genome instability; (2) inversely regulated mechanisms, including cell death and evading growth suppressors; and (3) functions with more complex, pleiotropic mechanisms, some of which may be stage-dependent in AD, such as cell adhesion/contact inhibition and angiogenesis. Additionally, we discuss the recent observation of a biological link between cancer and AD neuropathology. Finally, we address the therapeutic implications of this topic. The significant overlap of functional pathways and molecules between these diseases, some similarly and some oppositely regulated or functioning in each disease, supports the need for more research to elucidate cancer-related AD genetic and functional heterogeneity, with the aims of better understanding AD risk mediators, as well as further exploring the potential for some types of drug repurposing towards AD therapeutic development.

Integration of Machine Learning Methods to Dissect Genetically Imputed Transcriptomic Profiles in Alzheimer's Disease

The genetic component of many common traits is associated with the gene expression and several variants act as expression quantitative loci, regulating the gene expression in a tissue specific manner. In this work, we applied tissue-specific cis-eQTL gene expression prediction models on the genotype of 808 samples including controls, subjects with mild cognitive impairment, and patients with Alzheimer's Disease. We then dissected the imputed transcriptomic profiles by means of different unsupervised and supervised machine learning approaches to identify potential biological associations. Our analysis suggests that unsupervised and supervised methods can provide complementary information, which can be integrated for a better characterization of the underlying biological system. In particular, a variational autoencoder representation of the transcriptomic profiles, followed by a support vector machine classification, has been used for tissue-specific gene prioritizations. Interestingly, the achieved gene prioritizations can be efficiently integrated as a feature selection step for improving the accuracy of deep learning classifier networks. The identified gene-tissue information suggests a potential role for inflammatory and regulatory processes in gut-brain axis related tissues. In line with the expected low heritability that can be apportioned to eQTL variants, we were able to achieve only relatively low prediction capability with deep learning classification models. However, our analysis revealed that the classification power strongly depends on the network structure, with recurrent neural networks being the best performing network class. Interestingly, cross-tissue analysis suggests a potentially greater role of models trained in brain tissues also by considering dementia-related endophenotypes. Overall, the present analysis suggests that the combination of supervised and unsupervised machine learning techniques can be used for the evaluation of high dimensional omics data.

Classic Prescription, Kai-Xin-San, Ameliorates Alzheimer's Disease as an Effective Multitarget Treatment: From Neurotransmitter to Protein Signaling Pathway

Alzheimer's disease (AD) is a widespread neurodegenerative disease caused by complicated disease-causing factors. Unsatisfactorily, curative effects of approved anti-AD drugs were not good enough due to their actions on single-target, which led to desperate requirements for more effective drug therapies involved in multiple pathomechanisms of AD. The anti-AD effect with multiple action targets of Kai-Xin-San (KXS), a classic prescription initially recorded in Bei Ji Qian Jin Yao Fang and applied in the treatment of dementia for thousands of years, was deciphered with modern biological methods in our study. Aβ_25-35 and D-gal-induced AD rats and Aβ_25-35-induced PC12 cells were applied to establish AD models. KXS could significantly improve cognition impairment by decreasing neurotransmitter loss and enhancing the expression of PI3K/Akt. For the first time, KXS was confirmed to improve the expression of PI3K/Akt by neurotransmitter 5-HT. Thereinto, PI3K/Akt could further inhibit Tau hyperphosphorylation as well as the apoptosis induced by oxidative stress and neuroinflammation. Moreover, all above-mentioned effects were verified and blocked by PI3K inhibitor, LY294002, in Aβ_25-35-induced PC12 cells, suggesting the precise regulative role of KXS in the PI3K/Akt pathway. The utilization and mechanism elaboration of KXS have been proposed and dissected in the combination of animal, molecular, and protein strategies. Our results demonstrated that KXS could ameliorate AD by regulating neurotransmitter and PI3K/Akt signal pathway as an effective multitarget treatment so that the potential value of this classic prescription could be explored from a novel perspective.

Combined Plasma Elevation of CRP, Intestinal-Type Fatty Acid-Binding Protein (I-FABP), and sCD14 Identify Older Patients at High Risk for Health Care-Associated Infections

Background

We hypothesized that low-grade inflammation was driven by microbial translocation and associated with an increased risk of health care-associated infections (HAIs).

Methods

We included 121 patients aged 75 years or over in this prospective cohort study. High-sensitivity C-reactive protein (hs-CRP), I-FABP, and sCD14-as markers for low-grade inflammation, intestinal epithelial barrier integrity, and monocyte activation, respectively-were measured at admission.

Results

HAIs occurred during hospitalization in 62 (51%) patients. Elevated hs-CRP (≥6.02 mg/L, ie, the median) was associated with a significantly higher HAI risk when I-FABP was in the highest quartile (odds ratio [OR], 4; 95% confidence interval [95% CI], 1.39-11.49; p = .010). In patients with hs-CRP elevation and highest-quartile I-FABP, sCD14 elevation (≥0.65 µg/mL, ie, the median) was associated with an 11-fold higher HAI risk (OR, 10.8; 95% CI, 2.28-51.1; p = .003). Multivariate analyses adjusted for invasive procedures and comorbidities did not change the associations linking the three markers to the HAI risk.

Conclusion

Increased levels of hs-CRP, I-FABP, and sCD14 may reflect loss of intestinal epithelial barrier integrity with microbial translocation leading to monocyte activation and low-grade inflammation. In our cohort, these markers identified patients at high risk for HAIs.

Inhibition of DYRK1A proteolysis modifies its kinase specificity and rescues Alzheimer phenotype in APP/PS1 mice

Recent evidences suggest the involvement of DYRK1A (dual specificity tyrosine phosphorylation-regulated kinase 1 A) in Alzheimer's disease (AD). Here we showed that DYRK1A undergoes a proteolytic processing in AD patients hippocampus without consequences on its kinase activity. Resulting truncated forms accumulate in astrocytes and exhibit increased affinity towards STAT3ɑ, a regulator of inflammatory process. These findings were confirmed in APP/PS1 mice, an amyloid model of AD, suggesting that this DYRK1A cleavage is a consequence of the amyloid pathology. We identified in vitro the Leucettine L41 as a compound able to prevent DYRK1A proteolysis in both human and mouse protein extracts. We then showed that intraperitoneal injections of L41 in aged APP/PS1 mice inhibit STAT3ɑ phosphorylation and reduce pro-inflammatory cytokines levels (IL1- β, TNF-ɑ and IL-12) associated to an increased microglial recruitment around amyloid plaques and decreased amyloid-β plaque burden. Importantly, L41 treatment improved synaptic plasticity and rescued memory functions in APP/PS1 mice. Collectively, our results suggest that DYRK1A may contribute to AD pathology through its proteolytic process, reducing its kinase specificity. Further evaluation of inhibitors of DYRK1A truncation promises a new therapeutic approach for AD.

Tau as a mediator of neurotoxicity associated to cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is typified by the cerebrovascular deposition of amyloid. Currently, there is no clear understanding of the mechanisms underlying the contribution of CAA to neurodegeneration. Despite the fact that CAA is highly associated with accumulation of Aβ, other types of amyloids have been shown to associate with the vasculature. Interestingly, in many cases, vascular amyloidosis is accompanied by significant tau pathology. However, the contribution of tau to neurodegeneration associated to CAA remains to be determined. We used a mouse model of Familial Danish Dementia (FDD), a neurodegenerative disease characterized by the accumulation of Danish amyloid (ADan) in the vasculature, to characterize the contribution of tau to neurodegeneration associated to CAA. We performed histological and biochemical assays to establish tau modifications associated with CAA in conjunction with cell-based and electrophysiological assays to determine the role of tau in the synaptic dysfunction associated with ADan. We demonstrated that ADan aggregates induced hyperphosphorylation and misfolding of tau. Moreover, in a mouse model for CAA, we observed tau oligomers closely associated to astrocytes in the vicinity of vascular amyloid deposits. We finally determined that the absence of tau prevents synaptic dysfunction induced by ADan oligomers. In addition to demonstrating the effect of ADan amyloid on tau misfolding, our results provide compelling evidence of the role of tau in neurodegeneration associated with ADan-CAA and suggest that decreasing tau levels could be a feasible approach for the treatment of CAA.

The Role of Biomarkers in Alzheimer's Disease Drug Development

Biomarkers have a key role in Alzheimer's disease (AD) drug development. Biomarkers can assist in diagnosis, demonstrate target engagement, support disease modification, and monitor for safety. The amyloid (A), tau (T), neurodegeneration (N) Research Framework emphasizes brain imaging and CSF measures relevant to disease diagnosis and staging and can be applied to drug development and clinical trials. Demonstration of target engagement in Phase 2 is critical before advancing a treatment candidate to Phase 3. Trials with biomarker outcomes are shorter and smaller than those required to show clinical benefit and are important to understanding the biological impact of an agent and inform go/no-go decisions. Companion diagnostics are required for safe and effective use of treatments and may emerge in AD drug development programs. Complementary biomarkers inform the use of therapies but are not mandatory for use. Biomarkers promise to de-risk AD drug development, attract sponsors to AD research, and accelerate getting new drugs to those with or at risk for AD.

In Vitro Macrophage Assay Predicts the In Vivo Anti-inflammatory Potential of Exosomes from Human Mesenchymal Stromal Cells

Extracellular vesicles (EVs) play key roles in cell biology and may provide new clinical diagnostics and therapies. However, it has proven difficult to develop protocols for their purification and characterization. One of the major barriers in the field has been a lack of convenient assays for their bioactivity. Developing assays has not been a trivial matter, because of the heterogeneity of EVs, the multiple activities they demonstrate, and the uncertainty about their modes of action. Therefore, it is likely that multiple assays for their activities are needed. One important assay will be for the anti-inflammatory activity observed in mice after administration of the small EVs commonly referred to as exosomes. We developed an assay for the anti-inflammatory activity of exosomes with a line of mouse macrophages. The assay makes it possible to rank different preparations of exosomes by their anti-inflammatory activity, and their ranking predicts their efficacy in suppressing LPS-stimulated inflammation in mice. The assay is convenient for comparing multiple samples and, therefore, should be useful in developing protocols for the purification and characterization of anti-inflammatory exosomes.

Emodin Rescued Hyperhomocysteinemia-Induced Dementia and Alzheimer's Disease-Like Features in Rats

BACKGROUND

Hyperhomocysteinemia is an independent risk factor for dementia, including Alzheimer's disease. Lowering homocysteine levels with folic acid treatment with or without vitamin B12 has shown few clinical benefits on cognition.

METHODS

To verify the effect of emodin, a naturally active compound from Rheum officinale, on hyperhomocysteinemia-induced dementia, rats were treated with homocysteine injection (HCY, 400 μg/kg/d, 2 weeks) via vena caudalis. Afterwards, HCY rats with cognitive deficits were administered intragastric emodin at different concentrations for 2 weeks: 0 (HCY-E0), 20 (HCY-E20), 40 (HCY-E40), and 80 mg/kg/d (HCY-E80).

RESULTS

β-Amyloid overproduction, tau hyperphosphorylation, and losses of neuron and synaptic proteins were detected in the hippocampi of HCY-E0 rats with cognitive deficits. HCY-E40 and HCY-E80 rats had better behavioral performance. Although it did not reduce the plasma homocysteine level, emodin (especially 80 mg/kg/d) reduced the levels of β-amyloid and tau phosphorylation, decreased the levels of β-site amyloid precursor protein-cleaving enzyme 1, and improved the activity of protein phosphatase 2A. In the hippocampi of HCY-E40 and HCY-E80 rats, the neuron numbers, levels of synaptic proteins, and phosphorylation of the cAMP responsive element-binding protein at Ser133 were increased. In addition, depressed microglial activation and reduced levels of 5-lipoxygenase, interleukin-6, and tumor necrosis factor α were also observed. Lastly, hyperhomocysteinemia-induced microangiopathic alterations, oxidative stress, and elevated DNA methyltransferases 1 and 3β were rescued by emodin.

CONCLUSIONS

Emodin represents a novel potential candidate agent for hyperhomocysteinemia-induced dementia and Alzheimer's disease-like features.

Effect of growth differentiation factor-15 secreted by human umbilical cord blood-derived mesenchymal stem cells on amyloid beta levels in in vitro and in vivo models of Alzheimer's disease

Alzheimer's disease (AD), which is the most common progressive neurodegenerative disease, causes learning and memory impairment. The pathological progress of AD can derive from imbalanced homeostasis of amyloid beta (Aβ) in the brain. In such cases, microglia play important roles in regulating the brain Aβ levels. In the present study, we found that human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) can increase, through paracrine action, the ability of microglial cells to clear Aβ. In order to identify the associated paracrine factors, a secretome of hUCB-MSCs co-cultured with Aβ-treated BV2 microglial cells was analyzed using a human cytokine protein array. As a result, growth differentiation factor-15 (GDF-15) was identified as a predominant candidate, and its association with Aβ clearance by microglial cells was investigated in vitro and in a 5XFAD mouse model. When Aβ-treated BV2 cells were treated with exogenous recombinant GDF-15, the Aβ levels in the culture medium decreased. Moreover, GDF-15 injection in the brain parenchyma of 5XFAD mice also led to decrease in Aβ plaques. In contrast, co-culture of BV2 cells and hUCB-MSCs treated with GDF-15-specific siRNA did not influence the Aβ levels in the culture medium. To elucidate how these phenomena are related, we confirmed that GDF-15 specifically increases insulin-degrading enzyme (IDE) expression in microglial cells through TGFβ receptor type II (TGFβRII), both in vitro and in vivo. These findings suggest that hUCB-MSCs promote the Aβ clearance ability of microglial cells through regulation of GDF-15 secretion, thus elucidating a therapeutic mechanism for AD.

Increased quinolinic acid in peripheral mononuclear cells in Alzheimer's dementia

The role of monocytes and macrophages in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD) is poorly understood. Recently, we have shown that the number of CD14+ monocytes remained constant during healthy aging and in AD patients. Although only little is known about the function of activated macrophages and microglia in AD, one important mechanism involves the expression of quinolinic acid (QUIN), an endogenous N-methyl-D-aspartate glutamate receptor (NMDA-R) agonist which mediates excitotoxicity especially in the hippocampus. We used immunofluorescence stainings of PBMCs to determine the expression of quinolinic acid (QUIN) and the MHC class II molecule HLA-DR in peripheral monocytic cells in 51 healthy volunteers aged 22-87 years and 43 patients with AD at diagnosis (0 weeks) and during the course of rivastigmine treatment at 0.25 year (12 weeks), 0.5 year (30 weeks), 1 year, and 1.5 years. The number of QUIN+ HLA-DR+ cells rises in healthy persons aged 30-40 years compared to persons aged 60-70 years, indicating that this cell population increases with aging. AD patients at diagnosis had an increased frequency of QUIN+, QUIN+ HLA-DR+, and QUIN+ HLA-DR+/HLA-DR+ cells compared to aged-matched controls. These cell populations remained increased in AD for up to one year after initiation of treatment with rivastigmine; no alterations were detected in aged healthy persons. We conclude that the expression of the neurotoxic agent QUIN is increased in peripheral monocytes from AD patients. These cells could enter the brain and contribute to excitotoxicity.

Geniposide attenuates Aβ25–35-induced neurotoxicity via the TLR4/NF-κB pathway in HT22 cells

Alzheimer's disease (AD), a neurodegenerative disorder, is marked by the accumulation of amyloid-β (Aβ) and neuroinflammation which promote the development of AD. Geniposide, the main ingredient isolated from Chinese herbal medicine Gardenia jasminoides Ellis, has a variety of pharmacological functions such as anti-apoptosis and anti-inflammatory activity. Hence, we estimated the inflammatory cytotoxicity caused by Aβ_25–35 and the neuroprotective effects of geniposide in HT22 cells. In this research, following incubation with Aβ_25–35 (40 μM, 24 h) in HT22 cells, the methylthiazolyl tetrazolium (MTT) and lactate dehydrogenase (LDH) release assays showed that the cell survival rate was significantly decreased. In contrast, the reactive oxygen species (ROS) assay indicated that Aβ_25–35 enhanced ROS accumulation and apoptosis showed in both hoechst 33342 staining and annexin V-FITC/PI double staining. And then, immunofluorescence test revealed that Aβ_25–35 promoted p65 to transfer into the nucleus indicating p65 was activated by Aβ_25–35. Moreover, western blot analysis proved that Aβ_25–35 increased the expression of nitric oxide species (iNOS), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and interleukin-1β (IL-1β). Simultaneously, Aβ_25–35 also promoted the expression of toll-like receptor 4 (TLR4), p-p65 and p-IκB-α accompanied with the increase in the level of beta-secretase 1 (BACE1) and caspase-3 which further supported Aβ_25–35 induced apoptosis and inflammation. Fortunately, this up-regulation was reversed by geniposide. In conclusion, our data suggest that geniposide can alleviate Aβ_25–35-induced inflammatory response to protect neurons, which is possibly involved with the inhibition of the TLR4/NF-κB pathway in HT22 cells. Geniposide may be the latent treatment for AD induced by neuroinflammation and apoptosis.

Alzheimer's disease (AD), a neurodegenerative disorder, is marked by the accumulation of amyloid-β (Aβ) and neuroinflammation which promote the development of AD.

Association of HLA-DRB1 polymorphism with Alzheimer's disease: a replication and meta-analysis

Genome-wide association studies (GWAS) have identified one single-nucleotide polymorphism (SNP) rs9271192 within HLA-DRB1 as a risk factor for Alzheimer's disease (AD) in Caucasians. The effect of rs9271192 on AD needed to be verified in other ethnic cohorts. In order to evaluate the association between HLA-DRB1 rs9271192 polymorphism and late-onset AD (LOAD) in the Northern Han Chinese population, we recruited 982 LOAD patients and 1344 sex- and age-matched healthy controls. The results showed that HLA-DRB1 rs9271192 was associated with LOAD (genotype P = 0.015, allele P = 0.04). The results of logistic regression revealed the C allele homozygosity strongly increased the risk of LOAD under a recessive model in the total sample (P = 0.004, OR =2.069, 95% CI = 1.262–3.434). When these data were stratified by apolipoprotein E (APOE) ε4 status, the observed association was confined to APOE ε4 non-carriers (additive model: P=0.048, OR =1.191, 95% CI =1.001–1.417; recessive model: P < 0.001, OR = 2.601, 95% CI =1.519–4.566). Furthermore, meta-analysis after sensitive analysis confirmed that rs9271192 within HLA-DRB1 increased the risk of LOAD (OR = 1.12, 95% CI = 1.08–1.15). To summarize, the C allele in HLA-DRB1 rs9271192 may be an independent risk factor for LOAD.

Type 2 diabetes mellitus in the pathophysiology of Alzheimer's disease

Both Alzheimer's disease (AD) and type 2 diabetes mellitus (DM) are two common forms of disease worldwide and many studies indicate that people with diabetes, especially DM, are at higher risk of developing AD. AD is characterized by progressive cognitive decline and accumulation of β-amyloid (Aβ) forming senile plaques. DM is a metabolic disorder characterized by hyperglycemia in the context of insulin resistance and relative lack of insulin. Both diseases also share common characteristics such as loss of cognitive function and inflammation. Inflammation resulting from Aβ further induces production of Aβ_1-42 peptides. Inflammation due to overnutrition induces insulin resistance and consequently DM. Memory deficit and a decrease in GLUT4 and hippocampal insulin signaling have been observed in animal models of insulin resistance. The objective of this review was to show the shared characteristics of AD and DM.

Interleukin-2 improves amyloid pathology, synaptic failure and memory in Alzheimer's disease mice

Interleukin-2 (IL-2)-deficient mice have cytoarchitectural hippocampal modifications and impaired learning and memory ability reminiscent of Alzheimer's disease. IL-2 stimulates regulatory T cells whose role is to control inflammation. As neuroinflammation contributes to neurodegeneration, we investigated IL-2 in Alzheimer's disease. Therefore, we investigated IL-2 levels in hippocampal biopsies of patients with Alzheimer's disease relative to age-matched control individuals. We then treated APP/PS1ΔE9 mice having established Alzheimer's disease with IL-2 for 5 months using single administration of an AAV-IL-2 vector. We first found decreased IL-2 levels in hippocampal biopsies of patients with Alzheimer's disease. In mice, IL-2-induced systemic and brain regulatory T cells expansion and activation. In the hippocampus, IL-2 induced astrocytic activation and recruitment of astrocytes around amyloid plaques, decreased amyloid-β42/40 ratio and amyloid plaque load, improved synaptic plasticity and significantly rescued spine density. Of note, this tissue remodelling was associated with recovery of memory deficits, as assessed in the Morris water maze task. Altogether, our data strongly suggest that IL-2 can alleviate Alzheimer's disease hallmarks in APP/PS1ΔE9 mice with established pathology. Therefore, this should prompt the investigation of low-dose IL-2 in Alzheimer's disease and other neuroinflammatory/neurodegenerative disorders.

Rapamycin suppresses Aβ25-35- or LPS-induced neuronal inflammation via modulation of NF-κB signaling

Rapamycin (RAPA), an inhibitor of mammalian target of rapamycin (mTOR), exhibits a high neuroprotective action against neurodegenerative diseases in mouse models. Since neuroinflammation has been shown to be involved in Alzheimer's disease (AD) development and progression, the aim of this study was to examine the anti-inflammatory role of RAPA in AD in vivo and in vitro, and investigate the underlying mechanisms. We found that amyloid-β (Aβ) induced neuronal inflammation and a remarkable increase in mTOR activity in in-vivo and in-vitro models of inflammation, suggesting the critical role of mTOR signaling in neuronal inflammation. In addition, administration of RAPA was found to down-regulate mTOR, p-mTOR, Nuclear factor kappa B (NF-κB) p65, p-p65, TNF-α, IL-1β and Bax protein expression in Aβ_25-35- or lipopolysaccharides (LPS)-treated mice and cultured Neuro-2a (N2a) cells. Moreover, RAPA disrupted Aβ_25-35-induced nuclear translocation of mTOR and NF-κB. Our findings indicate that RAPA inhibits Aβ_25-35- or LPS-induced neuronal inflammation through suppressing mTOR signaling and reducing nuclear import of NF-κB.

Validating GWAS Variants from Microglial Genes Implicated in Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a multifactorial neurodegenerative disorder that corresponds to most Alzheimer's disease (AD) cases. Inflammation is frequently related to AD, whereas microglial cells are the major phagocytes in the brain and mediate the removal of Aβ peptides. Microglial cell dsyregulation might contribute to the formation of amyloid plaques, a hallmark of AD. Genome-wide association studies have reported genetic loci associated with the inflammatory pathway involved in AD. Among them, rs3865444 CD33, rs3764650 ABCA7, rs6656401 CR1, and rs610932 MS4A6A variants in microglial genes are associated with LOAD. These variants are proposed to participate in the clearance of Aβ peptides. However, their association with LOAD was not validated in all case-control studies. Thus, the present work aimed to assess the involvement of CD33 (rs3865444), ABCA7 (rs3764650), CR1 (rs6656401), and MS4A6A (rs610932) with LOAD in a sample from southeastern Brazil. The genotype frequencies were assessed in 79 AD patients and 145 healthy elders matched for sex and age. We found that rs3865444 CD33 acts as a protective factor against LOAD. These results support a role for the inflammatory pathway in LOAD.

RAGE-TLR Crosstalk Sustains Chronic Inflammation in Neurodegeneration

Chronic inflammatory reactions are consistenly present in neurodegeneration of Alzheimer type and are considered important factors that accelerate progression of the disease. Receptors of innate immunity participate in triggering and driving inflammatory reactions. For example, Toll-like receptors (TLRs) and receptor for advanced glycation end product (RAGE), major receptors of innate immunity, play a central role in perpetuation of inflammation. RAGE activation should be perceived as a primary mechanism which determines self-perpetuated chronic inflammation, and RAGE cooperation with TLRs amplifies inflammatory signaling. In this review, we highlight and discuss that RAGE-TLR crosstalk emerges as an important driving force of chronic inflammation in Alzheimer's disease.

Folic acid supplementation improves cognitive function by reducing the levels of peripheral inflammatory cytokines in elderly Chinese subjects with MCI

This study aimed to evaluate whether folic acid supplementation would improve cognitive performance by reducing serum inflammatory cytokine concentrations. This RCT was performed in Tianjin, China. Participants with mild cognitive impairment (MCI) were randomly assigned to the folic acid (400 μg/day) or conventional treatment groups. Neuropsychological tests were administered, and folate, homocysteine, vitamin B₁₂, IL-6, TNF-α, Aβ-42, and Aβ-40 were measured at baseline and at 6- and 12-month time points.152 participants (folic acid: 77, conventional: 75) completed the trial. Significant improvements in folate (ηp² = 0.703, P = 0.011), homocysteine (ηp² = 0.644, P = 0.009), Aβ-42 (ηp² = 0.687, P = 0.013), peripheral IL-6 (ηp² = 0.477, P = 0.025), TNF-α (ηp² = 0.709, P = 0.009) levels were observed in folic acid group compared with conventional group. Folic acid supplementation improved the Full Scale Intelligence Quotient (P = 0.028; effect size d = 0.153), Information (P = 0.031; d = 0.157) and Digit Span (P = 0.009; d = 0.172) scores at 12 months compared with conventional treatment. Based on these findings, daily oral administration of a 400-μg folic acid supplement to MCI subjects for 12 months can significantly improve cognitive performance and reduce peripheral inflammatory cytokine levels.

Neuroinflammatory challenges compromise neuronal function in the aging brain: Postoperative cognitive delirium and Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that targets memory and cognition, and is the most common form of dementia among the elderly. Although AD itself has been extensively studied, very little is known about early-stage preclinical events and/or mechanisms that may underlie AD pathogenesis. Since the majority of AD cases are sporadic in nature, advancing age remains the greatest known risk factor for AD. However, additional environmental and epigenetic factors are thought to accompany increasing age to play a significant role in the pathogenesis of AD. Postoperative cognitive delirium (POD) is a behavioral syndrome that primarily occurs in elderly patients following a surgical procedure or injury and is characterized by disruptions in cognition. Individuals that experience POD are at an increased risk for developing dementia and AD compared to normal aging individuals. One way in which cognitive function is affected in cases of POD is through activation of the inflammatory cascade following surgery or injury. There is compelling evidence that immune challenges (surgery and/or injury) associated with POD trigger the release of pro-inflammatory cytokines into both the periphery and central nervous system. Thus, it is possible that cognitive impairments following an inflammatory episode may lead to more severe forms of dementia and AD pathogenesis. Here we will discuss the inflammation associated with POD, and highlight the advantages of using POD as a model to study inflammation-evoked cognitive impairment. We will explore the possibility that advancing age and immune challenges may provide mechanistic evidence correlating early life POD with AD. We will review and propose neural mechanisms by which cognitive impairments occur in cases of POD, and discuss how POD may augment the onset of AD.

Individual Patient Research (IPR) Outcomes with Alzheimer's Disease: The Psycho-neuro-immune Viewpoint

Traditional research in the health sciences has involved control and experimental groups of patients, and descriptive and inferential statistical analyses performed on the measurements obtained from the samples in each group. As the novel model of translational healthcare, which integrates translational research and translational effectiveness, becomes increasingly established in modern contemporary medicine, healthcare continues to evolve into a model of care that is evidence-based, effectiveness-focused and patientcentered. Patient-centered care requires the timely and critical development and validation of a new research paradigm, which is referred to as "individual patient research (IPR)", as opposed as the customary group research approach. That is to say, research in geriatric disease conditions, such as Alzheimer's Disease (AD) must be performed from the viewpoint of individual patient research outcomes, and individual patient data analysis. Here, we discuss IPR in patients with AD in the context of the best available research evidence that indicates psychological symptoms, endocrine deregulation, and immune alterations in AD. We propose a clinical adaptive cluster randomized stepped wedge blinded controlled trial, with sequential with sequential roll-out of an evidence-based intervention in a crossover paradigm.

Immunotherapeutic effects of lymphocytes co-cultured with human cord blood-derived multipotent stem cells transplantation on APP/PS1 mice

Alzheimer's disease (AD) is an inexorable neurodegenerative disease that involves neuroinflammation in the brain, in addition to abnormal accumulation of amyloid-β (Aβ) and hyperphosphorylated tau. Evidence shows that human cord blood-derived multipotent stem cells (CB-SCs) can modulate autoimmune responses by altering regulatory T cells (Tregs). Our previous study found that CB-SCs could regulate the peripheral immune system of AD patients in vitro, mainly increasing the proportion of Tregs and anti-inflammatory cytokines. To further investigate the effects of lymphocytes co-cultured with CB-SCs on AD, the APP/PS1 mice received monthly transplants of lymphocytes co-cultured with CB-SCs for 4 months. Then, the ethological and biochemical experiments were conducted. We found that APP/PS1 mice injected with lymphocytes co-cultured with CB-SCs showed improved spatial learning, which significantly correlated with fewer Aβ plaques in brain. The present study also indicated that lymphocytes co-cultured with CB-SCs could promote the protective and reparative cytokines in the peripheral blood and brain to alleviate neuroinflammation in AD mice. These findings conclude that the systemic transplantation of lymphocytes co-cultured with CB-SCs can improve cognitive and pathological impairment of APP/PS1 mice via an immunomodulatory effect.

Expression of HLA-DR, CD80, and CD86 in Healthy Aging and Alzheimer's Disease

Although monocytes and macrophages could serve as new therapeutic targets for treatment of Alzheimer's disease (AD) and aging of the human innate immune system, its role in the pathogenesis of neurodegenerative disorders such as AD are only poorly understood. We have addressed this here by determining the number of CD14+ monocytes and the frequency of HLA-DR-, CD80-, and CD86-expression in peripheral blood from healthy volunteers aged 20-79 years, and in AD patients at diagnosis and after 12, 30, and 52 weeks of rivastigmine treatment. While the number of CD14+ monocytes remained constant, the expression of HLA-DR, CD80, and CD86 by monocytes increased with age. However, no differences were identified by comparing AD patients with age-matched healthy controls or following treatment of AD patients with rivastigmine. These results indicate that changes in the expression of HLA-DR, CD80, and CD86 are caused by immunosenescence rather than by AD pathology or treatment of AD patients with rivastigmine.