Interleukin-6 gene alleles affect the risk of Alzheimer's disease and levels of the cytokine in blood and brain

Study of the multitarget mechanism of Astragalus (HUANGQI) in the treatment of Alzheimer's disease based on network pharmacology and molecular docking technology

CONTEXT

In China, HUANGQI is widely used for the treatment of Alzheimer's disease (AD). However, a comprehensive understanding of its mechanism of anti-AD effects is lacking.

OBJECTIVE

To explore the active ingredients of HUANGQI and its potential targets and mechanisms of action in AD.

MATERIALS AND METHODS

The active ingredients and targets of HUANGQI were screened from databases (TCSMP, ETCM, and BATMan), and AD-related genes were obtained from DrugBank and GeneCards. The same target genes were screened, and a drug-target disease network was constructed. The PPI network was constructed and GO and KEGG pathway enrichment analyses of the targets. The Cell Counting Kit-8 (CCK-8) assay was used to determine suitable HUANGQI treatment concentrations for HT-22 cells between 0-480 μg/mL. CCK-8, FITC-phalloidin and propidium iodide (PI) assays were used to examine the protective effect of (0, 60, 120, 240 μg/mL) of HUANGQI on 20 μM Aβ1-42-induced HT-22 cell cytotoxicity.

RESULTS

Twelve active ingredients of HUANGQI were selected, with 679 common targets associated with AD. GO and KEGG analysis revealed that the therapeutic mechanisms of HUANGQI involve TNF, AGE, the NF-κB pathway, and nuclear receptor activity-related processes. The CCK-8 assay indicated that HUANGQI was not cytotoxic to HT-22 cells at concentrations less than 240 μg/mL and was able to attenuate Aβ1-42-induced cellular damage (EC50 = 83.46 μg/mL). FITC-phalloidin and PI assays suggested that HUANGQI could alleviate 20 μM Aβ1-42-induced neuronal cell cytotoxicity in a dose-dependent manner.

CONCLUSION

HUANGQI has a protective effect on Aβ1-42-induced nerve cell injury; further mechanism research was needed.

Genetic Variability in Oxidative Stress, Inflammatory, and Neurodevelopmental Pathways: Impact on the Susceptibility and Course of Spinal Muscular Atrophy

The spinal muscular atrophy (SMA) phenotype strongly correlates with the SMN2 gene copy number. However, the severity and progression of the disease vary widely even among affected individuals with identical copy numbers. This study aimed to investigate the impact of genetic variability in oxidative stress, inflammatory, and neurodevelopmental pathways on SMA susceptibility and clinical progression. Genotyping for 31 genetic variants across 20 genes was conducted in 54 SMA patients and 163 healthy controls. Our results revealed associations between specific polymorphisms and SMA susceptibility, disease type, age at symptom onset, and motor and respiratory function. Notably, the TNF rs1800629 and BDNF rs6265 polymorphisms demonstrated a protective effect against SMA susceptibility, whereas the IL6 rs1800795 was associated with an increased risk. The polymorphisms CARD8 rs2043211 and BDNF rs6265 were associated with SMA type, while SOD2 rs4880, CAT rs1001179, and MIR146A rs2910164 were associated with age at onset of symptoms after adjustment for clinical parameters. In addition, GPX1 rs1050450 and HMOX1 rs2071747 were associated with motor function scores and lung function scores, while MIR146A rs2910164, NOTCH rs367398 SNPs, and GSTM1 deletion were associated with motor and upper limb function scores, and BDNF rs6265 was associated with lung function scores after adjustment. These findings emphasize the potential of genetic variability in oxidative stress, inflammatory processes, and neurodevelopmental pathways to elucidate the complex course of SMA. Further exploration of these pathways offers a promising avenue for developing personalized therapeutic strategies for SMA patients.

Periodontal disease as a model to study chronic inflammation in aging

Periodontal disease is a chronic inflammatory condition that results in the destruction of the teeth supporting tissues, eventually leading to the loss of teeth and reduced quality of life. In severe cases, periodontal disease can limit proper nutritional intake, cause acute pain and infection, and cause a withdrawal from social situations due to esthetic and phonetic concerns. Similar to other chronic inflammatory conditions, periodontal disease increases in prevalence with age. Research into what drives periodontal disease pathogenesis in older adults is contributing to our general understanding of age-related chronic inflammation. This review will present periodontal disease as an age-related chronic inflammatory disease and as an effective geroscience model to study mechanisms of age-related inflammatory dysregulation. The current understanding of the cellular and molecular mechanisms that drive inflammatory dysregulation as a function of age will be discussed with a focus on the major pathogenic immune cells in periodontal disease, which include neutrophils, macrophages, and T cells. Research in the aging biology field has shown that the age-related changes in these immune cells result in the cells becoming less effective in the clearance of microbial pathogens, expansion of pathogenic subpopulations, or an increase in pro-inflammatory cytokine secretions. Such changes can be pathogenic and contribute to inflammatory dysregulation that is associated with a myriad of age-related disease including periodontal disease. An improved understanding is needed to develop better interventions that target the molecules or pathways that are perturbed with age in order to improve treatment of chronic inflammatory conditions, including periodontal disease, in older adult populations.

The Role of IL-6 in Neurodegenerative Disorders

"Neurodegenerative disorder" is an umbrella term for a group of fatal progressive neurological illnesses characterized by neuronal loss and inflammation. Interleukin-6 (IL-6), a pleiotropic cytokine, significantly affects the activities of nerve cells and plays a pivotal role in neuroinflammation. Furthermore, as high levels of IL-6 have been frequently observed in association with several neurodegenerative disorders, it may potentially be used as a biomarker for the progression and prognosis of these diseases. This review summarizes the production and function of IL-6 as well as its downstream signaling pathways. Moreover, we make a comprehensive review on the roles of IL-6 in neurodegenerative disorders and its potential clinical application.

Systemic Inflammation Causes Microglial Dysfunction With a Vascular AD phenotype

Background

Studies in rodents and humans have indicated that inflammation outside CNS (systemic inflammation) affects brain homeostasis contributing to neurodevelopmental disorders. Itis becoming increasingly evident that such early insults may also belinked to neurodegenerative diseases like late-onset Alzheimer's disease (AD). Importantly, lifestyle and stress, such as viral or bacterial infection causing chronic inflammation, may contribute to neurodegenerative dementia. Systemic inflammatory response triggers a cascade of neuroinflammatory responses, altering brain transcriptome, cell death characteristic of AD, and vascular dementia. Our study aimed to assess the temporal evolution of the pathological impact of systemic inflammation evoked by prenatal and early postnatal peripheral exposure of viral mimetic Polyinosinic:polycytidylic acid (PolyI:C) and compare the hippocampal transcriptomic changes with the profiles of human post-mortem AD and vascular dementia brain specimens.

Methods

We have engineered the PolyI:C sterile infection model in wildtype C57BL6 mice to achieve chronic low-grade systemic inflammation. We have conducted a cross-sectional analysis of aging PolyI:C and Saline control mice (3 months, 6 months, 9 months, and 16 months), taking the hippocampus as a reference brain region, and compared the brain aging phenotype to AD progression in humans with mild AD, severe AD, and Controls (CTL), in parallel to Vascular dementia (VaD) patients' specimens.

Results

We found that PolyI:C mice display both peripheral and central inflammation with a peak at 6 months, associated with memory deficits. The hippocampus is characterized by a pronounced and progressive tauopathy. In PolyI:C brains, microglia undergo aging-dependent morphological shifts progressively adopting a phagocytic phenotype. Transcriptomic analysis reveals a profound change in gene expression throughout aging, with a peak in differential expression at 9 months. We show that the proinflammatory marker Lcn2 is one of the genes with the strongest upregulation in PolyI:C mice upon aging. Validation in brains from patients with increasing severity of AD and VaD shows the reproducibility of some gene targets in vascular dementia specimens as compared to AD ones.

Conclusions

The PolyI:C model of sterile infection demonstrates that peripheral chronic inflammation causes progressive tau hyperphosphorylation, changes in microglia morphology, astrogliosis and gene reprogramming reflecting increased neuroinflammation, vascular remodeling, and the loss of neuronal functionality seen to some extent in human AD and Vascular dementia suggesting early immune insults could be crucial in neurodegenerative diseases.

The emerging neuroprotective roles of exerkines in Alzheimer’s disease

Despite the extensive knowledge of the beneficial effects of physical exercise, a sedentary lifestyle is still a predominant harm in our society. Sedentarism is one of the major modifiable risk factors for metabolic diseases such as diabetes mellitus, obesity and neurological disorders, including Alzheimer’s disease (AD)–characterized by synaptic failure, amyloid protein deposition and memory loss. Physical exercise promotes neuroprotective effects through molecules released in circulation and mediates the physiological crosstalk between the periphery and the brain. This literature review summarizes the current understanding of the roles of exerkines, molecules released during physical exercise, as systemic and central factors that mediate the beneficial effects of physical exercise on cognition. We highlight the neuroprotective role of irisin—a myokine released from the proteolytic cleavage of fibronectin type III domain-containing protein 5 (FNDC5) transmembrane protein. Lastly, we review evidence pointing to physical exercise as a potential preventative and interventional strategy against cognitive decline in AD.

Modeling the early stages of Alzheimer's disease by administering intracerebroventricular injections of human native Aβ oligomers to rats

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease characterized by the accumulation of aggregated amyloid beta (Aβ) and hyperphosphorylated tau along with a slow decline in cognitive functions. Unlike advanced AD, the initial steps of AD pathophysiology have been poorly investigated, partially due to limited availability of animal models focused on the early, plaque-free stages of the disease. The aim of this study was to evaluate the early behavioral, anatomical and molecular alterations in wild-type rats following intracerebroventricular injections of human Aβ oligomers (AβOs). Bioactive human AD and nondemented control brain tissue extracts were characterized using ELISA and proteomics approaches. Following a bilateral infusion, rats underwent behavioral testing, including the elevated plus maze, social recognition test, Morris water maze and Y-maze within 6 weeks postinjection. An analysis of brain structure was performed with manganese-enhanced MRI. Collected brain tissues were analyzed using stereology, immunohistochemistry, ELISA and qPCR. No sensorimotor deficits affecting motor performance on different maze tasks were observed, nor was spatial memory disturbed in AD rats. In contrast, a significant impairment of social memory became evident at 21 days postinjection. This deficit was associated with a significantly decreased volume of the lateral entorhinal cortex and a tendency toward a decrease in the total brain volume. Significant increase of cleaved caspase-3-positive cells, microglial activation and proinflammatory responses accompanied by altered expression of synaptic markers were observed in the hippocampus of AD rats with immunohistochemical and qPCR approaches at 6 weeks postinjection. Our data suggest that the social memory impairment observed in AβO-injected rats might be determined by neuroinflammatory responses and synaptopathy. An infusion of native oligomeric Aβ in the rat brain represents a feasible tool to model early plaque-free events associated with AD.

The Muscle-Brain Axis and Neurodegenerative Diseases: The Key Role of Mitochondria in Exercise-Induced Neuroprotection

Regular exercise is associated with pronounced health benefits. The molecular processes involved in physiological adaptations to exercise are best understood in skeletal muscle. Enhanced mitochondrial functions in muscle are central to exercise-induced adaptations. However, regular exercise also benefits the brain and is a major protective factor against neurodegenerative diseases, such as the most common age-related form of dementia, Alzheimer's disease, or the most common neurodegenerative motor disorder, Parkinson's disease. While there is evidence that exercise induces signalling from skeletal muscle to the brain, the mechanistic understanding of the crosstalk along the muscle-brain axis is incompletely understood. Mitochondria in both organs, however, seem to be central players. Here, we provide an overview on the central role of mitochondria in exercise-induced communication routes from muscle to the brain. These routes include circulating factors, such as myokines, the release of which often depends on mitochondria, and possibly direct mitochondrial transfer. On this basis, we examine the reported effects of different modes of exercise on mitochondrial features and highlight their expected benefits with regard to neurodegeneration prevention or mitigation. In addition, knowledge gaps in our current understanding related to the muscle-brain axis in neurodegenerative diseases are outlined.

IL-1β, IL-6, IL-10, and TNFα Single Nucleotide Polymorphisms in Human Influence the Susceptibility to Alzheimer's Disease Pathology

BACKGROUND

Neuroinflammation plays an important role in Alzheimer's disease (AD). During this process, activated microglia release pro-inflammatory cytokines such as interleukin (IL)-1α, IL-1β, IL-6, and tumor necrosis factor α (TNFα) that participate in neuron damage, but also anti-inflammatory cytokines (such as IL-10), which maintain homeostasis of immune response. Previous studies showed the association of IL-1α -889C/T (rs1800587), IL-1β-1473G/C (rs1143623), IL-6 -174C/G (rs1800795), IL-10 -1082G/A (rs1800896), and TNFα -308A/G (rs1800629) polymorphisms with AD.

OBJECTIVE

We aimed to investigate whether people with certain IL-1α, IL-1β, IL-6, IL-10, and TNFα genotypes in these polymorphisms are more prone to develop AD-related pathology, reflected by pathological levels of cerebrospinal fluid (CSF) AD biomarkers including amyloid-β1-42, total tau (t-tau), tau phosphorylated at Thr 181 (p-tau181), Ser 199 (p-tau199), and Thr 231 (p-tau231), and visinin-like protein 1 (VILIP-1).

METHODS

The study included 115 AD patients, 53 patients with mild cognitive impairment, and 11 healthy controls. The polymorphisms were determined using real-time polymerase chain reaction. Levels of CSF biomarkers were determined by enzyme-linked immunosorbent assay.

RESULTS

A significant increase in p-tau CSF levels was found in patients with the AA IL-10 -1082G/A and GG TNFα -308A/G genotypes, and in carriers of a G allele in IL-1β -1473C/G and IL-6 -174C/G polymorphisms. t-tau levels were increased in carriers of a G allele in IL-1β -1473C/G polymorphism. An increase in VILIP-1 levels was observed in patients with CG and GG IL-1β -1473C/G, GC IL-6 -174C/G, and GG TNFα -308A/G genotype.

CONCLUSION

These results suggest that persons carrying certain genotypes in IL10 (-1082G/A), IL1β (1473C/G), IL6 (-174C/G), and TNFIα (-308A/G) could be more vulnerable to development of neuroinflammation, and consequently of AD.

Searching the Dark Genome for Alzheimer's Disease Risk Variants

Sporadic Alzheimer's disease (AD) is a complex genetic disease, and the leading cause of dementia worldwide. Over the past 3 decades, extensive pioneering research has discovered more than 70 common and rare genetic risk variants. These discoveries have contributed massively to our understanding of the pathogenesis of AD but approximately half of the heritability for AD remains unaccounted for. There are regions of the genome that are not assayed by mainstream genotype and sequencing technology. These regions, known as the Dark Genome, often harbour large structural DNA variants that are likely relevant to disease risk. Here, we describe the dark genome and review current technological and bioinformatics advances that will enable researchers to shed light on these hidden regions of the genome. We highlight the potential importance of the hidden genome in complex disease and how these strategies will assist in identifying the missing heritability of AD. Identification of novel protein-coding structural variation that increases risk of AD will open new avenues for translational research and new drug targets that have the potential for clinical benefit to delay or even prevent clinical symptoms of disease.

Analysis of the levels of inflammatory parameters in persons over the age of 90

Chronic inflammatory conditions resulting from elevated levels of circulating proinflammatory mediators are common in the elderly. The aim of the paper was to analyze the balance between proinflammatory and anti-inflammatory markers in longevous individuals. The study was conducted in persons aged >90 years old, residents of Poland living either at home or staying at residential care facilities. The study included 90 persons (69 women and 21 men) aged between 90 and 103 years. Persons with abnormal CRP presented with a statistical tendency toward higher fibrinogen and lower IL10 and IL-1α levels compared to patients in whom CRP level was within the normal range. IL-6 concentration predicted abnormality within CRP. Inflammation in persons above the age of 90 years old might be linked to abnormal fibrinogen and IL-6 levels.

Genetic variants and cognitive functions in patients with brain tumors

BACKGROUND

Patients with brain tumors treated with radiotherapy (RT) and chemotherapy (CT) often experience cognitive dysfunction. We reported that single nucleotide polymorphisms (SNPs) in the APOE, COMT, and BDNF genes may influence cognition in brain tumor patients. In this study, we assessed whether genes associated with late-onset Alzheimer's disease (LOAD), inflammation, cholesterol transport, dopamine and myelin regulation, and DNA repair may influence cognitive outcome in this population.

METHODS

One hundred and fifty brain tumor patients treated with RT ± CT or CT alone completed a neurocognitive assessment and provided a blood sample for genotyping. We genotyped genes/SNPs in these pathways: (i) LOAD risk/inflammation/cholesterol transport, (ii) dopamine regulation, (iii) myelin regulation, (iv) DNA repair, (v) blood-brain barrier disruption, (vi) cell cycle regulation, and (vii) response to oxidative stress. White matter (WM) abnormalities were rated on brain MRIs.

RESULTS

Multivariable linear regression analysis with Bayesian shrinkage estimation of SNP effects, adjusting for relevant demographic, disease, and treatment variables, indicated strong associations (posterior association summary [PAS] ≥ 0.95) among tests of attention, executive functions, and memory and 33 SNPs in genes involved in: LOAD/inflammation/cholesterol transport (eg, PDE7A, IL-6), dopamine regulation (eg, DRD1, COMT), myelin repair (eg, TCF4), DNA repair (eg, RAD51), cell cycle regulation (eg, SESN1), and response to oxidative stress (eg, GSTP1). The SNPs were not significantly associated with WM abnormalities.

CONCLUSION

This novel study suggests that polymorphisms in genes involved in aging and inflammation, dopamine, myelin and cell cycle regulation, and DNA repair and response to oxidative stress may be associated with cognitive outcome in patients with brain tumors.

Role of mtDNA disturbances in the pathogenesis of Alzheimer's and Parkinson's disease

Neurodegenerative diseases (e.g. Alzheimer's and Parkinson's disease) are becoming increasingly problematic to healthcare systems. Therefore, their underlying mechanisms are trending topics of study in medicinal research. Numerous studies have evidenced a strong association between mitochondrial DNA disturbances (e.g. oxidative damage, mutations, and methylation shifts) and the initiation and progression of neurodegenerative diseases. Therefore, this review discusses the risk and development of neurodegenerative diseases in terms of disturbances in mitochondrial DNA and as a part of a complex ecosystem that includes other important mechanisms (e.g. neuroinflammation and the misfolding and aggregation of amyloid-β peptides, α-synuclein, and tau proteins). In addition, the influence of individual mitochondrial DNA haplogroups on the risk and development of neurodegenerative diseases is also described and discussed.

Regulation of interleukin 6 by a polymorphic CpG within the frontal cortex in Alzheimer's disease

The cytokine interleukin 6 (IL-6) has been linked to the pathogenesis of Alzheimer's disease (AD). This is the first study to investigate the genetic and epigenetic interactions in the control of IL-6 in human brain and its relation to AD neuropathology in prefrontal cortex tissues from AD and controls genotyped for the SNP -174 C/G rs1800795, a polymorphic CpG in which the G allele creates a CpG site. Within CC homozygotes there were significantly higher brain levels of IL-6 protein compared to G allele carriers. The C allele that resulted in an absence of methylation at a CpG was also associated with significant changes in methylation at neighboring CpGs. Furthermore, there were significant differences in methylation between CC and CG/GG at CpG sites in the AD and control groups. That DNA methylation was altered in the brains by the presence of rs1800795, which further correlated with protein levels suggests the presence of a polymorphic CpG and genetic-epigenetic interactions in the regulation of IL-6 in the prefrontal cortex within AD brains.

Haplotype analysis on association between variants of interleukin 6 (IL-6) and late-onset Alzheimer's disease in a Chinese Han population

OBJECTIVE

The aim of this study was to evaluate the influence of single nucleotide polymorphisms (SNPs) in interleukin-6 (IL-6) gene and the haplotype on late-onset Alzheimer's disease (LOAD).

METHODS

A total of 896 participants were enrolled, including 446 LOAD patients and 450 controls. Total genomic DNA was extracted from the blood of participants and genotyping was then performed. Hardy-Weinberg equilibrium test was conducted in controls. Multivariate analysis was performed to determine the association between 4 SNPs (rs1800796, rs7802308, rs1800795 and rs13447446) in IL-6 gene and LOAD. Pairwise LD analysis was employed to identify the association between haplotype and LOAD.

RESULTS

Multivariate logistic analysis showed that T allele of rs7802308 and G allele of rs1800796 were correlated with decreased risk of LOAD, adjusted ORs were 0.68 (95% CI: 0.50-0.91) and 0.71 (95% CI: 0.51-0.92), respectively. However, rs1800795 and rs13447446 were not associated with LOAD. Pairwise LD analysis among the 4 SNPs showed that only rs1800796 and rs1800795 in IL-6 gene was in heavy LD, the D' value was >0.75 (0.825). In all samples, the haplotype C-G was observed most frequently in two groups, with 55.79% and 49.46% in the LOAD patients and controls, respectively. The results also indicated that haplotype G-C was significantly associated with decreased LOAG risk.

CONCLUSIONS

T allele of rs7802308 and G allele of rs1800796 were correlated with decreased risk of LOAD. The haplotype G-C were also correlated with decreased risk of LOAD.

Friend, Foe or Both? Immune Activity in Alzheimer's Disease

Alzheimer's disease (AD) is marked by the presence of amyloid beta (Aβ) plaques, neurofibrillary tangles (NFT), neuronal death and synaptic loss, and inflammation in the brain. AD research has, in large part, been dedicated to the understanding of Aβ and NFT deposition as well as to the pharmacological reduction of these hallmarks. However, recent GWAS data indicates neuroinflammation plays a critical role in AD development, thereby redirecting research efforts toward unveiling the complexities of AD-associated neuroinflammation. It is clear that the innate immune system is intimately associated with AD progression, however, the specific roles of glia and neuroinflammation in AD pathology remain to be described. Moreover, inflammatory processes have largely been painted as detrimental to AD pathology, when in fact, many immune mechanisms such as phagocytosis aid in the reduction of AD pathologies. In this review, we aim to outline the delicate balance between the beneficial and detrimental aspects of immune activation in AD as a more thorough understanding of these processes is critical to development of effective therapeutics for AD.

Polymorphisms of Proinflammatory Cytokines in Relation to APOE Epsilon 4 and Risk of Alzheimer's Disease in the Lithuanian Population

Background and objective: Neuroinflammation is one of the pathological pathways of Alzheimer's disease (AD), mediating the progression of neurodegeneration. Polymorphisms of proinflammatory cytokines have been linked to increased AD risk. Identification of certain combinations of polymorphisms could help predict disease in its preclinical stage. The aim of the study was to evaluate differences in the prevalence of TNFα -850T (rs1799724), IL1A -889T (rs1800587), and IL6 -174C (rs1800795, Intron type) polymorphisms between AD patients and healthy controls (HC) and determine the impact of these SNPs in combination with the APOEε4 allele on AD risk. Materials and Methods: The study population is comprised of 107 patients with sporadic AD (AD group) and age- and gender-matched 110 persons without impaired cognitive functions (control group). TNFα -850C > T polymorphism was revealed by a PCR and restriction fragment length polymorphism (RFLP) method. Real time PCR was used for IL1A and IL6 SNP genotyping. APOEε genotyping was done via hybridization method. Results: The frequencies of TNFα -850T, IL1A -889T, IL6 -174C allele and genotype did not differ between the AD and HC groups (p > 0.05). IL6 -174C was not in HWE, and it was not analysed further. APOEε4 allele (p = 0.001) and 3/4 and 4/4 genotypes (p = 0.005) were more prevalent in AD patients. APOEε4 carriage increased the risk of AD (OR 2.65, p = 0.001), while TNFα -850T and IL1A -889T polymorphisms were not found as significant independent risk factors for AD. The presence of at least one IL1A -889T allele in combination with APOEε4+ was associated with a lower risk of AD (OR 2.24, p = 0.047) than the carriage of APOEε4+ alone (OR 2.70, p = 0.015). Conclusions: No significant differences of TNFα -850, IL1A -889, and IL6 -174 polymorphisms frequencies were found between AD and control groups. In APOEε4 carriers IL1A -889T polymorphism was found to reduce the AD risk determined by APOEε4 alone.

Neuroimmune nexus of depression and dementia: Shared mechanisms and therapeutic targets

Dysfunctional immune activity is a physiological component of both Alzheimer's disease (AD) and major depressive disorder (MDD). The extent to which altered immune activity influences the development of their respective cognitive symptoms and neuropathologies remains under investigation. It is evident, however, that immune activity affects neuronal function and circuit integrity. In both disorders, alterations are present in similar immune networks and neuroendocrine signalling pathways, immune responses persist in overlapping neuroanatomical locations, and morphological and structural irregularities are noted in similar domains. Epidemiological studies have also linked the two disorders, and their genetic and environmental risk factors intersect along immune-activating pathways and can be synonymous with one another. While each of these disorders individually contains a large degree of heterogeneity, their shared immunological components may link distinct phenotypes within each disorder. This review will therefore highlight the shared immune pathways of AD and MDD, their overlapping neuroanatomical features, and previously applied, as well as novel, approaches to pharmacologically manipulate immune pathways, in each neurological condition. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

The exploration of novel Alzheimer's therapeutic agents from the pool of FDA approved medicines using drug repositioning, enzyme inhibition and kinetic mechanism approaches

Novel drug development is onerous, time consuming and overpriced process with particularly low success and relatively high enfeebling rates. To overcome this burden, drug repositioning approach is being used to predict the possible therapeutic effects of FDA approved drugs in different diseases. Herein, we designed a computational and enzyme inhibitory mechanistic approach to fetch the promising drugs from the pool of FDA approved drugs against AD. The binding interaction patterns and conformations of screened drugs within active region of AChE were confirmed through molecular docking profiles. The possible associations of selected drugs with AD genes were predicted by pharmacogenomics analysis and confirmed through data mining. The stability behaviour of docked complexes (Drugs-AChE) were checked by MD simulations. The possible therapeutic potential of repositioned drugs against AChE were checked by in vitro analysis. Taken together, Cinitapride displayed a comparable results with standard and can be used as possible therapeutic agent in the treatment of AD.

Molecular Bases of Alzheimer's Disease and Neurodegeneration: The Role of Neuroglia

Neuroglia is an umbrella term indicating different cellular types that play a pivotal role in the brain, being involved in its development and functional homeostasis. Glial cells are becoming the focus of recent researches pertaining the pathogenesis of neurodegenerative disorders, Alzheimer's Disease (AD) in particular. In fact, activated microglia is the main determinant of neuroinflammation, contributing to neurodegeneration. In addition, the oxidative insult occurring during pathological brain aging can activate glial cells that, in turn, can favor the production of free radicals. Moreover, the recent Glycogen Synthase Kinase 3 (GSK-3) hypothesis of AD suggests that GSK3, involved in the regulation of glial cells functioning, could exert a role in amyloid deposition and tau hyper-phosphorylation. In this review, we briefly describe the main physiological functions of the glial cells and discuss the link between neuroglia and the most studied molecular bases of AD. In addition, we dedicate a section to the glial changes occurring in AD, with particular attention to their role in terms of neurodegeneration. In the light of the literature data, neuroglia could play a fundamental role in AD pathogenesis and progression. Further studies are needed to shed light on this topic.

Systemic infection modifies the neuroinflammatory response in late stage Alzheimer's disease

Clinical studies indicate that systemic infections accelerate cognitive decline in Alzheimer’s disease. Animal models suggest that this may be due to enhanced pro-inflammatory changes in the brain. We have performed a post-mortem human study to determine whether systemic infection modifies the neuropathology and in particular, neuroinflammation, in the late-stage of the disease.

Sections of cerebral cortex and underlying white matter from controls and Alzheimer's patients who died with or without a terminal systemic infection were immunolabelled and quantified for: (i) Αβ and phosphorylated-tau; (ii) the inflammation-related proteins Iba1, CD68, HLA-DR, FcγRs (CD64, CD32a, CD32b, CD16), CHIL3L1, IL4R and CCR2; and (iii) T-cell marker CD3. In Alzheimer's disease, the synaptic proteins synaptophysin and PSD-95 were quantified by ELISA, and the inflammatory proteins and mRNAs by MesoScale Discovery Multiplex Assays and qPCR, respectively.

Systemic infection in Alzheimer's disease was associated with decreased CD16 (p = 0.027, grey matter) and CD68 (p = 0.015, white matter); increased CD64 (p = 0.017, white matter) as well as increased protein expression of IL6 (p = 0.047) and decreased IL5 (p = 0.007), IL7 (p = 0.002), IL12/IL23p40 (p = 0.001), IL15 (p = 0.008), IL16 (p < 0.001) and IL17A (p < 0.001). Increased expression of anti-inflammatory genes CHI3L1 (p = 0.012) and IL4R (p = 0.004) were detected in this group. T-cell recruitment to the brain was reduced when systemic infection was present. However, exposure to systemic infection did not modify the pathology. In Alzheimer's disease, CD68 (p = 0.026), CD64 (p = 0.002), CHI3L1 (p = 0.016), IL4R (p = 0.005) and CCR2 (p = 0.010) were increased independently of systemic infection.

Our findings suggest that systemic infections modify neuroinflammatory processes in Alzheimer's disease. However, rather than promoting pro-inflammatory changes, as observed in experimental models, they seem to promote an anti-inflammatory, potentially immunosuppressive, environment in the human brain.

Altered Vessel Signalling Molecules in Subjects with Down's Syndrome

Down's syndrome (DS) is the most frequent human chromosomal abnormality and is associated with mental retardation. Some evidence indicates that certain inflammatory molecules may be increased in DS. Proinflammatory and vasoactive molecules in the blood of non demented subjects with DS were measured in the present investigation. Plasma levels of interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1) and C reactive protein (CRP) were measured in child (2–14 years), adult (20–50 yrs) and elderly (> 60 yrs) DS subjects. Increased plasma levels of IL-6 and MCP-1 were present in DS. Plasma levels of VEGF were increased only in DS adults. Positive linear correlation between IL-6 and MCP-1 levels was present. However, no subclinical inflammation was apparent in DS, since neopterin and CRP levels were within the normal range. An altered regulation of these molecules might interfere with some processes involved in cognitive performances of DS subjects.

Aging, inflammation, immunity and periodontal disease

The increased prevalence and severity of periodontal disease have long been associated with aging, such that this oral condition affects the majority of the adult population over 50 years of age. Although the immune system is a critical component for maintaining health, aging can be characterized by quantitative and qualitative modifications of the immune system. This process, termed 'immunosenescence', is a progressive modification of the immune system that leads to greater susceptibility to infections, neoplasia and autoimmunity, presumably reflecting the prolonged antigenic stimulation and/or stress responses that occur across the lifespan. Interestingly, the global reduction in the host capability to respond effectively to these challenges is coupled with a progressive increase in the general proinflammatory status, termed 'inflammaging'. Consistent with the definition of immunosenescence, it has been suggested that the cumulative effect of prolonged exposure of the periodontium to microbial challenge is, at least in part, a contributor to the effects of aging on these tissues. Thus, it has also been hypothesized that alterations in the function of resident immune and nonimmune cells of the periodontium contribute to the expression of inflammaging in periodontal disease. Although the majority of aging research has focused on the adaptive immune response, it is becoming increasingly clear that the innate immune compartment is also highly affected by aging. Thus, the phenomenon of immunosenescence and inflammaging, expressed as age-associated changes within the periodontium, needs to be more fully understood in this era of precision and personalized medicine and dentistry.

The role of astrocytes in amyloid production and Alzheimer's disease

Alzheimer's disease (AD) is marked by the presence of extracellular amyloid beta (Aβ) plaques, intracellular neurofibrillary tangles (NFTs) and gliosis, activated glial cells, in the brain. It is thought that Aβ plaques trigger NFT formation, neuronal cell death, neuroinflammation and gliosis and, ultimately, cognitive impairment. There are increased numbers of reactive astrocytes in AD, which surround amyloid plaques and secrete proinflammatory factors and can phagocytize and break down Aβ. It was thought that neuronal cells were the major source of Aβ. However, mounting evidence suggests that astrocytes may play an additional role in AD by secreting significant quantities of Aβ and contributing to overall amyloid burden in the brain. Astrocytes are the most numerous cell type in the brain, and therefore even minor quantities of amyloid secretion from individual astrocytes could prove to be substantial when taken across the whole brain. Reactive astrocytes have increased levels of the three necessary components for Aβ production: amyloid precursor protein, β-secretase (BACE1) and γ-secretase. The identification of environmental factors, such as neuroinflammation, that promote astrocytic Aβ production, could redefine how we think about developing therapeutics for AD.

Cellular immune activation in Sardinian middle-aged, older adults and centenarians

In addition to viral infections, malignant disorders, autoimmune diseases, and allograft rejection episodes, neopterin increases in older people where it is found to be predictive of overall mortality. Thus, the serum concentrations of this biomarker of systemic immune and inflammation activation, were measured in a small cohort of Sardinian middle-aged, older adults and centenarians. There was a significant positive correlation between neopterin concentrations and age with the subjects in the 95-year-old group with the highest values. Notably, the group of centenarians had neopterin values comparable to those of 80- and 90-year-old groups, and significantly lower than that of 95-year-old group. This suggests a decreased monocyte/macrophage-mediated immune activation and an apparently preserved immune status in centenarians.

Bioactive Nutrients and Nutrigenomics in Age-Related Diseases

The increased life expectancy and the expansion of the elderly population are stimulating research into aging. Aging may be viewed as a multifactorial process that results from the interaction of genetic and environmental factors, which include lifestyle. Human molecular processes are influenced by physiological pathways as well as exogenous factors, which include the diet. Dietary components have substantive effects on metabolic health; for instance, bioactive molecules capable of selectively modulating specific metabolic pathways affect the development/progression of cardiovascular and neoplastic disease. As bioactive nutrients are increasingly identified, their clinical and molecular chemopreventive effects are being characterized and systematic analyses encompassing the "omics" technologies (transcriptomics, proteomics and metabolomics) are being conducted to explore their action. The evolving field of molecular pathological epidemiology has unique strength to investigate the effects of dietary and lifestyle exposure on clinical outcomes. The mounting body of knowledge regarding diet-related health status and disease risk is expected to lead in the near future to the development of improved diagnostic procedures and therapeutic strategies targeting processes relevant to nutrition. The state of the art of aging and nutrigenomics research and the molecular mechanisms underlying the beneficial effects of bioactive nutrients on the main aging-related disorders are reviewed herein.

Familial late-onset Alzheimer's disease: description of an Italian family with four affected siblings and one case of early-onset dementia in the preceding generation

We describe a family composed of six siblings, four of which affected by late-onset Alzheimer's disease (LOAD). We constructed the family pedigree, evaluated mutations usually associated with early-onset Alzheimer's disease (APP, PSEN1, PSEN2), and assessed polymorphisms in the apolipoprotein E (APOE) gene and in cytokine genes that we had previously found to be associated with a higher risk of LOAD (IL-10, IL-6, TNF-α). Results showed that all subjects carried one ε4 allele of the APOE gene and those with the earliest age of onset exhibited the AA (-1082) IL-10 and the CC (-174) IL-6 genotypes. The only male had a genetic profile which also included the A (-308) TNF-α allele. These data confirm the role of the APOE gene as genetic risk factor in LOAD, and suggest that the risk of developing AD may be governed by a "susceptibility profile" involving polymorphisms in inflammatory genes.

Inflammatory Cytokines and Alzheimer's Disease: A Review from the Perspective of Genetic Polymorphisms

Neuroinflammatory processes are a central feature of Alzheimer's disease (AD) in which microglia are over-activated, resulting in the increased production of pro-inflammatory cytokines. Moreover, deficiencies in the anti-inflammatory system may also contribute to neuroinflammation. Recently, advanced methods for the analysis of genetic polymorphisms have further supported the relationship between neuroinflammatory factors and AD risk because a series of polymorphisms in inflammation-related genes have been shown to be associated with AD. In this review, we summarize the polymorphisms of both pro- and anti-inflammatory cytokines related to AD, primarily interleukin-1 (IL-1), IL-6, tumor necrosis factor alpha, IL-4, IL-10, and transforming growth factor beta, as well as their functional activity in AD pathology. Exploration of the relationship between inflammatory cytokine polymorphisms and AD risk may facilitate our understanding of AD pathogenesis and contribute to improved treatment strategies.

Peripheral cytokines, C-X-C motif ligand10 and interleukin-13, are associated with Malaysian Alzheimer's disease

AIM

Cytokines released from chronically-activated microglia could result in neuroinflammation. An accurate profile of the relationship between cytokines and Alzheimer's disease (AD) pathogenesis, as well as the patterns of these inflammatory mediators in AD patients could lead to the identification of peripheral markers for the disease. The present study was undertaken to identify pro- and anti-inflammatory cytokines associated with AD in the Malaysian population.

METHODS

Further to informed consent from 39 healthy subjects and 39 probable AD patients, 8.5 mL of peripheral blood was collected and serum was extracted. The differential levels of 12 serum cytokines extracted from peripheral blood samples were measured using Procarta Multiplex Cytokine and enzyme-linked immunoassay kits. Concentrations of cytokines were measured at 615 nm using a fluorometer.

RESULTS

Except for tumor necrosis factor-α, all classical pro-inflammatory cytokines (interleukin [IL]-1β, IL-6, IL-12 and interferon-γ) were found to be significantly upregulated (P < 0.001) in AD patients. Three of the five non-classical pro-inflammatory cytokines (C-X-C motif ligand 10 [CXCL-10], monocyte chemoattractant protein-1 and macrophage inflammatory protein-1α) showed similar patterns. Both classical IL-10 and non-classical IL-13 anti-inflammatory cytokines were significantly downregulated (P < 0.001) in AD patients when compared with non-AD controls. Receiver operating characteristic curve analyses for both CXCL-10 (IP-10) and IL-13 showed a high level of diagnostic accuracy (area under curve = 1 [95% confidence interval]). Both CXCL-10 and IL-13 also showed sensitivity of 100% and specificity of 100% for diagnosis of AD (cut-off values >53.65 ρg/mL and <9.315 ρg/mL, respectively).

CONCLUSIONS

Both the non-classical pro-inflammatory CXCL-10 and anti-inflammatory IL-13 cytokines showed promising potential as blood-based cytokine biomarkers for AD. This is the first study of non-classical cytokine profiles of Malaysian AD patients. Geriatr Gerontol Int 2017; 17: 839-846.

Genetic polymorphisms of interleukin genes and the risk of Alzheimer's disease: An update meta-analysis

Objectives

Recently, several meta-analyses have reported an association between interleukin (IL) gene polymorphisms and the risk of Alzheimer's disease (AD). Several further papers discussing the relationship with the risk of AD have recently been published. The aim of this meta-analysis was to re-evaluate and update the associations between IL gene polymorphisms and the risk of AD.

Methods

The search sources were PubMed, Science Direct, Scopus, and Google Scholar up to July 2015, and the following search terms were used: “interleukin 1 or interleukin 6 or interleukin 10” and “variant or polymorphism or SNP” in combination with “Alzheimer's disease”. A meta-analysis using the pooled odds ratios and 95% confidence intervals was carried out to assess the associations between four polymorphisms of IL genes (− 889C > T in IL-1α, − 511C > T in IL-1β, − 174G > C in IL-6 and − 1082G > A in IL-10) and the risk of AD under the heterozygous, homozygous, dominant, and recessive models with fixed- or random-effects models.

Results

A total of 21,864 cases and 40,321 controls from 93 individual studies were included in this meta-analysis. Our results indicated that the − 889C > T polymorphism was strongly associated with the increased risk of AD. However, three polymorphisms were not associated with the risk of AD.

Conclusions

Similar to previous meta-analyses, our updated meta-analysis suggested that the − 889C > T polymorphism may be a factor in AD. However, the results of our meta-analysis of the − 174G > C polymorphism differed from those of previous meta-analyses. Consequently, we suggest that the − 174G > C polymorphism may not be a risk factor for AD.

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889 C > T polymorphism of IL-1α was significantly associated with increased risk of Alzheimer's disease

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Three polymorphisms (− 511C > T in IL − 1β, − 174G > C in IL-6 and − 1082G > A in IL-10) were no associated with risk of Alzheimer's disease

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The results of our meta-analyses for three polymorphisms (− 889C > T, − 511C > T and − 1082G > A) were similar to those previous meta-analyses. However, the results of the − 174G > C polymorphism were different.

A potential endophenotype for Alzheimer's disease: cerebrospinal fluid clusterin

Genome-wide association studies have associated clusterin (CLU) variants with Alzheimer's disease (AD). However, the role of CLU on AD pathogenesis is not totally understood. We used cerebrospinal fluid (CSF) and plasma CLU levels as endophenotypes for genetic studies to understand the role of CLU in AD. CSF, but not plasma, CLU levels were significantly associated with AD status and CSF tau/amyloid-beta ratio, and highly correlated with CSF apolipoprotein E (APOE) levels. Several loci showed almost genome-wide significant associations including LINC00917 (p = 3.98 × 10(-7)) and interleukin 6 (IL6, p = 9.94 × 10(-6), in the entire data set and in the APOE ε4- individuals p = 7.40 × 10(-8)). Gene ontology analyses suggest that CSF CLU levels may be associated with wound healing and immune response which supports previous functional studies that demonstrated an association between CLU and IL6. CLU may play a role in AD by influencing immune system changes that have been observed in AD or by disrupting healing after neurodegeneration.

Amino- and Carboxyl-Terminal CCR5 Mutations in Brazilian HIV-1-Infected Women and Homology Model of p.L55Q CCR5 Mutant

Genetic factors from an HIV-1 host can affect the rate of progression to AIDS and HIV infection. To investigate the frequency of mutations in the CCR5 gene, HIV-1 samples from infected women and uninfected individuals were selected for sequencing of the CCR5 gene regions encoding the N- and C-terminal protein domains. Physicochemical CCR5 modeling and potential protein domain analysis were performed in order to evaluate the impact of the mutations found in the properties and structure of CCR5. The p.L55Q mutation in the N-terminal protein domain was observed only in uninfected individuals, with an allelic frequency of 1.8%. Physicochemical analysis revealed that the p.L55Q mutation magnified the flexibility and accessibility profiles and the modeling of CCR5 structures showed resulting in a small deviation to the right, as well as a hydrophobic to hydrophilic property alteration. The p.L55Q mutation also resulted in a slight modification of the electrostatic load of this region. Additionally, three novel silent mutations were found at the C-terminal coding region among HIV-1-infected women. The results suggest that the p.L55Q mutation might alter CCR5 conformation. Further studies should be conducted to verify the role of this mutation in HIV-1 susceptibility.

Proteins induced by telomere dysfunction are associated with human IgA nephropathy

Aging is one of the contributing risk factors for kidney diseases. Accumulating evidence prompts the view that telomere length in kidney tissue cells is an indicator for organismal aging. Previously identified aging markers (cathelin-related antimicrobial peptide (CRAMP), stathmin, elongation factor-1α (EF-1α), and chitinase) were associated not only with telomere driven aging in mice but also with human aging and chronic diseases. This study focuses on the relationship between these biomarkers and IgA nephropathy (IgAN) progression in the Chinese population. For 260 individuals, the four markers are determined in blind datasets using direct enzyme-linked immunosorbent assay (ELISA) and immunofluorescence staining. The expression levels of CRAMP and chitinase increased in blood plasma, urine, and kidney tissues during human IgAN progression. And for the other nephropathy, such as systemic lupus erythematosus (SLE), diabetic nephropathy (DN), and focal segmental glomerulosclerosis (FSGS), there is no protein upregulation with telomere shortening. Moreover, a combination of CRAMP and chitinase can distinguish patients with IgAN from healthy individuals with 88.2%/92.5% (plasma) and 74.3%/84.2% (urine) sensitivity/specificity. These data provide the experimental evidence that telomere shortening and related inflammatory proteins are associated with human IgAN, and it could be a new direction for the disease progression study.

Gene of the month: Interleukin 6 (IL-6)

The Interleukin 6 (IL-6) gene encodes the classic proinflammatory cytokine IL-6. It is also known as interferon-β2 (IFN-β2), B cell stimulatory factor-2 and hybridoma/plasmacytoma growth factor. IL-6 is a multifunctional cytokine with a central role in many physiological inflammatory and immunological processes. Due to its major role in initiation as well as resolving inflammation, deregulation of IL-6 is a mainstay of chronic inflammatory and autoimmune diseases. Additionally, IL-6 has been shown to be implicated in pathogenesis of many human malignancies. Thus, a better understanding of IL-6 and its role in various pathological conditions could enable the development of strategies to use it as a therapeutic target. This short review focuses on the structure, regulation and biological activities of IL-6. In addition we discuss the role of IL-6 in diseases with inflammatory background and cancer and also the therapeutic applications of anti-IL-6 agents.

Circulating mitochondrial DNA increases with age and is a familiar trait: Implications for "inflamm-aging"

Mitochondrial components, including mitochondrial DNA (mtDNA), when released extracellularly, can act as "damage-associated molecular pattern" (DAMP) agents and cause inflammation. As many elderly people are characterized by a low-grade, chronic inflammatory status defined "inflamm-aging," we evaluated if circulating mtDNA can contribute to this phenomenon. Eight hundred and thirty-one Caucasian subjects were enrolled in the study, including 429 siblings aged 90-104 (90+ siblings). mtDNA plasma levels increased gradually after the fifth decade of life. In 90+ subjects, mtDNA values of two members of the same sibling relationship were directly correlated, suggesting a role for familiar/genetic background in controlling the levels of circulating mtDNA. The subjects with the highest mtDNA plasma levels had the highest amounts of TNF-α, IL-6, RANTES, and IL-1ra; the subjects with the lowest mtDNA levels had the lowest levels of the same cytokines. In vitro stimulation of monocytes with mtDNA concentrations similar to the highest levels observed in vivo resulted in an increased production of TNF-α, suggesting that mtDNA can modulate the production of proinflammatory cytokines. Our findings therefore show that circulating mtDNA increases with age, and can significantly contribute to the maintenance of the low-grade, chronic inflammation observed in elderly people.

Impaired regulation of immune responses in cognitive decline and Alzheimer’s disease: lessons from genetic association studies

Altered levels of cytokines and acute-phase proteins have been described in the blood and brain of patients with Alzheimer's disease. Microglia are resident cells of the brain and metabolic upregulation of these cells may play a crucial role in the development of the neurodegeneration associated with Alzheimer's disease. Studies focusing on gene polymorphisms of molecules with immune regulatory function have demonstrated an association with increased risk of the disease and confirmed the pivotal role of immune responses in Alzheimer's disease pathogenesis. Several gene variants may also influence the rate of the cognitive decline associated with the disease. A definite immune-related gene polymorphism profile may be a feature of a limited group of patients with early onset of the disease and fast clinical deterioration. Only this group of patients may benefit from anti-inflammatory treatment.

Zinc and the aging brain

Alterations in trace element homeostasis could be involved in the pathology of dementia, and in particular of Alzheimer's disease (AD). Zinc is a structural or functional component of many proteins, being involved in numerous and relevant physiological functions. Zinc homeostasis is affected in the elderly, and current evidence points to alterations in the cellular and systemic distribution of zinc in AD. Although the association of zinc and other metals with AD pathology remains unclear, therapeutic approaches designed to restore trace element homeostasis are being tested in clinical trials. Not only could zinc supplementation potentially benefit individuals with AD, but zinc supplementation also improves glycemic control in the elderly suffering from diabetes mellitus. However, the findings that select genetic polymorphisms may alter an individual's zinc intake requirements should be taken into consideration when planning zinc supplementation. This review will focus on current knowledge regarding pathological and protective mechanisms involving brain zinc in AD to highlight areas where future research may enable development of new and improved therapies.

Interleukin-6 gene polymorphism (-174 G/C) is associated with toxoplasmic retinochoroiditis

PURPOSE

Experimental data have demonstrated a relevant role for IL-6 in the modulation of acute ocular toxoplasmosis. Therefore, we aim to investigate the possible association between the IL-6 gene polymorphism at position -174 and toxoplasmic retinochoroiditis (TR) in humans.

METHODS

Ninety-seven patients with diagnosed TR were recruited from the Uveitis Section, Federal University of Minas Gerais. For comparison, 83 healthy blood donors with positive serology for toxoplasmosis and without retinal signs of previous TR were included in the study. Genomic DNA was obtained from oral swabs of individuals and amplified using polymerase chain reaction (PCR) with specific primers flanking the locus -174 of IL-6 (-174G/C). PCR products were submitted to restriction endonuclease digestion and analysed by polyacrylamide gel electrophoresis to distinguish allele G and C of the IL-6 gene, allowing the detection of the polymorphism and determination of genotypes.

RESULTS

There was a significant difference in the genotype (χ(2) = 12.9, p = 0.001) and allele (χ(2) = 6.62, p = 0.01) distribution between TR patients and control subjects. In a subgroup analysis, there was no significant difference in genotypes and allele frequencies regarding TR recurrence.

CONCLUSIONS

This study suggests that the genotypes related with a lower production of IL-6 may be associated with the occurrence of TR.

Association between interleukin-6 -174G/C polymorphism and the risk of Alzheimer's disease: a meta-analysis

BACKGROUND

The -174G/C polymorphism in interleukin 6 (IL-6) gene has been extensively investigated for association to Alzheimer's disease (AD); however, results of different studies have been inconsistent. The objective of this study is to assess the relationship of IL-6 -174G/C polymorphism and Alzheimer's disease (AD) risk by using meta-analysis.

METHODS

All eligible case-control studies were searched in PubMed and EMBASE. Odds ratios (ORs) with the 95% confidence intervals (CIs) were used to assess the association.

RESULTS

A total of 5316 cases and 10 757 controls in 21 case-control studies were included. Obvious heterogeneity among studies was detected, and no significant association was observed between the IL-6 -174G/C polymorphism and AD risk. After exclusion of three studies, the heterogeneity disappeared and significant association was observed between the polymorphism and AD risk in Asians (CC vs. CG+GG: OR = 0.5; 95%CI, 0.33-0.75) but not in Caucasians.

CONCLUSION

This meta-analysis suggested that the -174G/C polymorphism of IL-6 gene would be a protective risk factor for AD in Asians. To further evaluate gene-to-gene and gene-to-environmental interactions between polymorphisms of IL-10 gene and AD risk, more studies with large groups of patients are required.

Establishment of an optimized PCR method using sequence-specific primers for screening multiple gene polymorphisms simultaneously

The present study aimed to explore the factors that affect polymerase chain reaction using sequence-specific primers (PCR-SSP) and to establish an optimized PCR-SSP method for detecting multiple gene polymorphisms simultaneously. The amplification system parameters, including the concentrations of Mg2+, dNTPs, pfu Taq, primers and control primers, were optimized using the designed PCR-SSP reactions. The resulting optimized reaction system was used to determine the melting temperature of the genomic DNA and the cycling parameters. The optimized PCR-SSP method was used to analyze the polymorphisms of the following genes: mutations -308A/G and -238G/A in TNF-α, -174G/C in IL-6 and C/T mutation at exon 188 of CYP2D6 *10B. The PCR-SSP amplification system was optimized; in a 20 µl reaction system, the quantities of Mg2+, dNTPs, pfu Taq, primers, control primers and genomic DNA were 3.25 µM, 0.5 mM, 2.5 units, 0.5 µM, 0.2 µM and 0.15 µg, respectively. The cycling system comprised 5 start cycles and took 15 min to melt a genomic DNA sample using a touchdown protocol. The optimized PCR-SSP is suitable for polymorphism analysis of polygenic SNPs in large genomic DNA samples and a number of different genes.

Aging is associated with chronic innate immune activation and dysregulation of monocyte phenotype and function

Chronic inflammation in older individuals is thought to contribute to inflammatory, age-related diseases. Human monocytes are comprised of three subsets (classical, intermediate and nonclassical subsets), and despite being critical regulators of inflammation, the effect of age on the functionality of monocyte subsets remains to be fully defined. In a cross-sectional study involving 91 healthy male (aged 20-84 years, median 52.4) and 55 female (aged 20-82 years, median 48.3) individuals, we found age was associated with an increased proportion of intermediate and nonclassical monocytes (P = 0.002 and 0.04, respectively) and altered phenotype of specific monocyte subsets (e.g. increased expression of CD11b and decreased expression of CD38, CD62L and CD115). Plasma levels of the innate immune activation markers CXCL10, neopterin (P < 0.001 for both) and sCD163 (P = 0.003) were significantly increased with age. Whilst similar age-related changes were observed in both sexes, monocytes from women were phenotypically different to men [e.g. lower proportion of nonclassical monocytes (P = 0.002) and higher CD115 and CD62L but lower CD38 expression] and women exhibited higher levels of CXCL10 (P = 0.012) and sCD163 (P < 0.001) but lower sCD14 levels (P < 0.001). Monocytes from older individuals exhibit impaired phagocytosis (P < 0.05) but contain shortened telomeres (P < 0.001) and significantly higher intracellular levels of TNF both at baseline and following TLR4 stimulation (P < 0.05 for both), suggesting a dysregulation of monocyte function in the aged. These data show that aging is associated with chronic innate immune activation and significant changes in monocyte function, which may have implications for the development of age-related diseases.

Interleukin-6 trans-signaling in the senescent mouse brain is involved in infection-related deficits in contextual fear conditioning

Excessive production of pro-inflammatory cytokines in the senescent brain in response to peripheral immune stimulation is thought to induce behavioral pathology, however, few studies have examined if the increase in pro-inflammatory cytokines is accompanied by an increase in cytokine signaling. Here, we focused on IL-6 as a prototypic pro-inflammatory cytokine and used phosphorylated STAT3 as a marker of IL-6 signaling. In an initial study, IL-6 mRNA and the magnitude and duration of STAT3 activation were increased in the hippocampus of senescent mice compared to adults after i.p. injection of LPS. The LPS-induced increase in STAT3 activity was ablated in aged IL-6(-/-) mice, suggesting IL-6 is a key driver of STAT3 activity in the aged brain. To determine if IL-6 activated the classical or trans-signaling pathway, before receiving LPS i.p., aged mice were injected ICV with sgp130, an antagonist of the trans-signaling pathway. Importantly, the LPS-induced increases in both IL-6 and STAT3 activity in the hippocampus were inhibited by sgp130. To assess hippocampal function, aged mice were injected ICV with sgp130 and i.p. with LPS immediately after the acquisition phase of contextual fear conditioning, and immobility was assessed in the retention phase 48h later. LPS reduced immobility in aged mice, indicating immune activation interfered with memory consolidation. However, sgp130 blocked the deficits in contextual fear conditioning caused by LPS. Taken together, the results suggest IL-6 trans-signaling is increased in the senescent brain following peripheral LPS challenge and that sgp130 may protect against infection-related neuroinflammation and cognitive dysfunction in the aged.

IL-6-174 G/C and -572 C/G polymorphisms and risk of Alzheimer's disease

Associations between interleukin 6 (IL-6) polymorphisms and Alzheimer's disease (AD) remain controversial and ambiguous. The aim of this meta-analysis is to explore more precise estimations for the relationship between IL-6-174 G/C and -572 C/G polymorphisms and risk for AD. Electronic searches for all publications in databases PubMed and EMBASE were conducted on the associations between IL-6 polymorphisms and risk for AD until January 2012. Odds ratio (OR) and 95% confidence intervals (CIs) were calculated using fixed and random effects models. Twenty-seven studies were included with a total of 19,135 individuals, involving 6,632 AD patients and 12,503 controls. For IL-6-174 G/C polymorphism, the combined results showed significant differences in recessive model (CC vs. CG+GG: OR = 0.65, 95%CI = 0.52-0.82). As regards IL-6-572 C/G polymorphism, significant associations were shown in dominant model (CG+GG vs. CC: OR= 0.73, 95% CI = 0.62-0.86) and in additive model (GG vs. CC, OR= 0.66, 95% CI = 0.46-0.96). In conclusion, genotype CC of IL-6-174 G/C and genotype GG plus GC of IL-6-572 C/G could decrease the risk of AD.

Human Cytokine Response to ex vivo Amyloid-β Stimulation is Mediated by Genetic Factors

Through its ability to induce the enhanced release and production of cytokines, amyloid-β is responsible for the chronic inflammatory response that contributes to Alzheimer's disease (AD). Determining whether the response of monocytes to amyloid-β stimulation is under genetic control may help understand the basis of why some people are more prone to develop neuronal degeneration than others. In the current study we investigated the heritability of the cytokine (IL-10, IL-6, IL-1β, IL-1ra, TNF-[.alpha]) production capacity upon ex vivo stimulation with amyloid-β in whole blood samples of 222 twins and 85 singleton siblings from 139 extended twin families. It was found that individual differences in amyloid-β-induced cytokine production capacity are to a large extent of genetic origin, with heritability estimates ranging from 55% (IL-1β) to 68% (IL-6). We conclude that genes influencing amyloid-β-induced cytokine response may provide clues to the progression of AD pathology.

Sequence variants of interleukin 6 (IL-6) are significantly associated with a decreased risk of late-onset Alzheimer's disease

BACKGROUND

Interleukin 6 (IL-6) has been related to beta-amyloid aggregation and the appearance of hyperphosphorylated tau in Alzheimer's disease (AD) brain. However, previous studies relating IL-6 genetic polymorphisms to AD included few and unrepresentative single nucleotide polymorphisms (SNPs) and the results were inconsistent.

METHODS

This is a case-control study. A total of 266 patients with AD, aged≧65, were recruited from three hospitals in Taiwan (2007-2010). Controls (n = 444) were recruited from routine health checkups and volunteers of the hospital during the same period of time. Three common IL-6 haplotype-tagging SNPs were selected to assess the association between IL-6 polymorphisms and the risk of late-onset AD (LOAD).

RESULTS

Variant carriers of IL-6 rs1800796 and rs1524107 were significantly associated with a reduced risk of LOAD [(GG + GC vs. CC): adjusted odds ratio (AOR) = 0.64 and (CC + CT vs. TT): AOR = 0.60, respectively]. Haplotype CAT was associated with a decreased risk of LOAD (0 and 1 copy vs. 2 copies: AOR = 0.65, 95% CI = 0.44-0.95). These associations remained significant in ApoE e4 non-carriers only. Hypertension significantly modified the association between rs2069837 polymorphisms and the risk of LOAD (pinteraction = 0.03).

CONCLUSIONS

IL-6 polymorphisms are associated with reduced risk of LOAD, especially in ApoE e4 non-carriers. This study identified genetic markers for predicting LOAD in ApoE e4 non-carriers.