The inflammatory response in Alzheimer's disease

Microglial polarization in Alzheimer's disease: Mechanisms, implications, and therapeutic opportunities

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid-β plaques, neurofibrillary tangles, and chronic neuroinflammation. Microglial cells, the resident immune cells in the central nervous system, play a crucial role in the pathogenesis of AD. Microglia can undergo polarization, shifting between pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes in response to different stimuli. Dysregulation of microglial polarization towards the pro-inflammatory phenotype leads to the release of inflammatory cytokines, oxidative stress, and synaptic dysfunction. These processes contribute to neuronal damage and cognitive decline in AD. However, several challenges remain in this field. The complex molecular mechanisms governing microglial polarization in AD need to be further elucidated. In this review, we discuss the mechanisms underlying microglial polarization in AD and its implications in disease progression.

Multimodal active subspace analysis for computing assessment oriented subspaces from neuroimaging data

BACKGROUND

For successful biomarker discovery, it is essential to develop computational frameworks that summarize high-dimensional neuroimaging data in terms of involved sub-systems of the brain, while also revealing underlying heterogeneous functional and structural changes covarying with specific cognitive and biological traits. However, unsupervised decompositions do not inculcate clinical assessment information, while supervised approaches extract only individual feature importance, thereby impeding qualitative interpretation at the level of subspaces.

NEW METHOD

We present a novel framework to extract robust multimodal brain subspaces associated with changes in a given cognitive or biological trait. Our approach involves active subspace learning on the gradients of a trained machine learning model followed by clustering to extract and summarize the most salient and consistent subspaces associated with the target variable.

RESULTS

Through a rigorous cross-validation procedure on an Alzheimer's disease (AD) dataset, our framework successfully extracts multimodal subspaces specific to a given clinical assessment (e.g., memory and other cognitive skills), and also retains predictive performance in standard machine learning algorithms. We also show that the salient active subspace directions occur consistently across randomly sub-sampled repetitions of the analysis.

COMPARISON WITH EXISTING METHOD(S)

Compared to existing unsupervised decompositions based on principle component analysis, the subspace components in our framework retain higher predictive information.

CONCLUSIONS

As an important step towards biomarker discovery, our framework not only uncovers AD-related brain regions in the associated brain subspaces, but also enables automated identification of multiple underlying structural and functional sub-systems of the brain that collectively characterize changes in memory and proficiency in cognitive skills related to brain disorders like AD.

Tooth loss and dementia amongst older adults residing in long-term care facilities in Vancouver: A case-control study

OBJECTIVE

The purpose of this case-control study was to determine the association between dementia and the number of missing teeth, functional occlusal units and denture use in older adults residing in Long-Term Care (LTC) facilities.

BACKGROUND

Many studies have shown an association between dementia and tooth loss. However, few studies with a large sample size have been reported describing the relationship between dementia and the number of missing teeth, remaining teeth and functional occlusal units.

METHODS

An oral health assessment database of 2160 older adults admitted to LTC facilities in Vancouver, Canada, between 2015-2019 was utilised. Participants with a diagnosis of dementia in their medical records (N = 1174) were compared to those without dementia (N = 986). Multiple logistic regression analysis was used to explore a potential association between the number of missing teeth, functional occlusal units and the use of dentures and dementia.

RESULTS

The number of remaining teeth (OR = 1.0, 95% Confidence Interval = 1.0-1.0; P = .054) and number of functional occlusal units (OR = 1.0, 95% CI = 1.0-1.0; P = .059) were not associated with dementia after adjusting for age, sex, oral self-care and systemic conditions. Denture use (OR = 1.1, 95% CI = 0.5-2.4; P = .790) was not associated with dementia in edentulous patients.

CONCLUSION

There was no association between dementia and the number of remaining teeth, functional occlusal units or wearing dentures.

Poor Oral Health as a Risk Factor for Dementia in a Swedish Population: A Cohort Study with 40 Years of Follow-Up

BACKGROUND

Whether poor oral health is associated with dementia risk remains unclear.

OBJECTIVE

We conducted a cohort study of 14,439 participants who were followed up for up to 40 years in Uppsala County, central Sweden, aiming to explore the association between poor oral health, namely the number of tooth loss, dental plaque status, and oral mucosal lesions, and the risk of dementia.

METHODS

We used Cox proportional hazards regression model to derive cause-specific hazard ratios (HR) and corresponding 95% confidence intervals (CI), while adjusting for baseline potential confounders as well as a time-varying covariate, Charlson's Comorbidity Index score.

RESULTS

Dementia risk was substantially higher among those with a higher number of tooth loss; compared to the group with tooth loss 0-10, the HRs were 1.21 (95% CI: 1.02, 1.42), 1.17 (95% CI: 0.97, 1.40), and 1.30 (95% CI: 1.09, 1.54) respectively for groups with increasing number of tooth loss. There was some evidence of dose-risk association in this study, with a HR of 1.10 (1.04, 1.18) comparing adjacent groups (ptrend = 0.001). In a stratified analysis by attained age, tooth loss was more pronouncedly associated with the risk of dementia onset before age 80 (those with 21-32 versus 0-10 lost teeth, HR = 1.82, (95% CI: 1.32, 2.51); HR = 1.22 (95% CI: 1.10, 1.35) comparing adjacent groups, ptrend < 0.001).

CONCLUSION

In summary, there are some indications that poor oral health, as indicated by more tooth loss, is positively associated with an increased risk of dementia, especially for dementia onset before age 80.

Interdisciplinary Approaches to Deal with Alzheimer's Disease-From Bench to Bedside: What Feasible Options Do Already Exist Today?

Alzheimer's disease is one of the most common neurodegenerative diseases in the western population. The incidence of this disease increases with age. Rising life expectancy and the resulting increase in the ratio of elderly in the population are likely to exacerbate socioeconomic problems. Alzheimer's disease is a multifactorial disease. In addition to amyloidogenic processing leading to plaques, and tau pathology, but also other molecular causes such as oxidative stress or inflammation play a crucial role. We summarize the molecular mechanisms leading to Alzheimer's disease and which potential interventions are known to interfere with these mechanisms, focusing on nutritional approaches and physical activity but also the beneficial effects of cognition-oriented treatments with a focus on language and communication. Interestingly, recent findings also suggest a causal link between oral conditions, such as periodontitis or edentulism, and Alzheimer's disease, raising the question of whether dental intervention in Alzheimer's patients can be beneficial as well. Unfortunately, all previous single-domain interventions have been shown to have limited benefit to patients. However, the latest studies indicate that combining these efforts into multidomain approaches may have increased preventive or therapeutic potential. Therefore, as another emphasis in this review, we provide an overview of current literature dealing with studies combining the above-mentioned approaches and discuss potential advantages compared to monotherapies. Considering current literature and intervention options, we also propose a multidomain interdisciplinary approach for the treatment of Alzheimer's disease patients that synergistically links the individual approaches. In conclusion, this review highlights the need to combine different approaches in an interdisciplinary manner, to address the future challenges of Alzheimer's disease.

SVR-based Multimodal Active Subspace Analysis for the Brain using Neuroimaging Data.. [DOI: 10.1101/2022.07.28.501879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Understanding the patterns of changes in brain function and structure due to various disorders and diseases is of utmost importance. There have been numerous efforts toward successful biomarker discovery for complex brain disorders by evaluating neuroimaging datasets with novel analytical frameworks. However, due to the multi-faceted nature of the disorders involving a wide and overlapping range of symptoms as well as complex changes in structural and functional brain networks, it is increasingly important to devise computational frameworks that can consider the underlying patterns of heterogeneous changes with specific target assessments, at the same time producing a summarizing output from the high-dimensional neuroimaging data. While various machine learning approaches focus on diagnostic prediction, many learning frameworks analyze important features at the level of brain regions involved in prediction using supervised methods. Unsupervised learning methods have also been utilized to break down the neuroimaging features into lower dimensional components. However, most learning frameworks either do not consider the target assessment information while extracting brain subspaces, or can extract only higher dimensional importance associations as an ordered list of involved features, making manual interpretation at the level of subspaces difficult. We present a novel multimodal active subspace learning framework to understand various subspaces within the brain that are associated with changes in particular biological and cognitive traits. For a given cognitive or biological trait, our framework performs a decomposition of the feature importances to extract robust multimodal subspaces that define the most significant change in the given trait. Through a rigorous cross-validation procedure on an Alzheimer’s disease (AD) dataset, we show that our framework can extract subspaces covering both functional and structural modalities, which are specific to a given clinical assessment (like memory and other cognitive skills) and also retain predictive performance in standard machine learning algorithms. We show that our framework not only uncovers AD-related brain regions (e.g., hippocampus, entorhinal cortex) in the associated brain subspaces, but also enables an automated identification of multiple underlying structural and functional sub-systems of the brain that collectively characterize changes in memory and cognitive skill proficiency related to brain disorders like AD.

Luteolin Suppresses Microglia Neuroinflammatory Responses and Relieves Inflammation-Induced Cognitive Impairments

Microglia-mediated neuroinflammation in response to injurious self and non-self-stimuli exerts detrimental effects on neurons, which may lead to cognitive impairment. Luteolin, a typical kind of natural flavonoid in honeysuckle, chrysanthemum, and Herba Schizonepetae, is widely recognized to be anti-inflammatory and antioxidant against peripheral inflammation. However, its protective effect against inflammation-induced cognitive impairment is currently unknown. In this paper, we investigated the relief potential of luteolin against lipopolysaccharide (LPS)-induced cognitive impairment and neuroinflammation and its possible anti-inflammatory mechanisms in lipopolysaccharide-stimulated BV2 microglia cells. In this study, luteolin ameliorated LPS-induced cognitive impairments, indicated by behavioral performance of neuroinflammatory model mice in Morris water maze tests. Protein analyses and histological examination also revealed protective effect of luteolin against neuronal damage, through inhibiting overproduction of inflammatory cytokines in both hippocampus and cortex of mice. We also observed luteolin in vitro significantly suppressed the levels of pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF-α) and interleukin-1 β (IL-1β), and inflammatory mediators like nitric oxide. Taken together, these results demonstrated luteolin was effective in alleviating cognitive impairment and limited neuronal damage via inhibiting the release of inflammatory mediators, suggesting luteolin is potential for further therapeutic research of neuroinflammation-related neurodegenerative diseases.

MOGONET integrates multi-omics data using graph convolutional networks allowing patient classification and biomarker identification

To fully utilize the advances in omics technologies and achieve a more comprehensive understanding of human diseases, novel computational methods are required for integrative analysis of multiple types of omics data. Here, we present a novel multi-omics integrative method named Multi-Omics Graph cOnvolutional NETworks (MOGONET) for biomedical classification. MOGONET jointly explores omics-specific learning and cross-omics correlation learning for effective multi-omics data classification. We demonstrate that MOGONET outperforms other state-of-the-art supervised multi-omics integrative analysis approaches from different biomedical classification applications using mRNA expression data, DNA methylation data, and microRNA expression data. Furthermore, MOGONET can identify important biomarkers from different omics data types related to the investigated biomedical problems.

ATP-sensitive potassium channel subunits in the neuroinflammation: novel drug targets in neurodegenerative disorders

Arachidonic acids and its metabolites modulate plenty of ligand-gated, voltage-dependent ion channels, and metabolically regulated potassium channels including ATP-sensitive potassium channels (KATP). KATP channels are hetero-multimeric complexes of sulfonylureas receptors (SUR1, SUR2A or SUR2B) and the pore-forming subunits (Kir6.1 and Kir6.2) likewise expressed in the pre-post synapsis of neurons and inflammatory cells, thereby affecting their proliferation and activity. KATP channels are involved in amyloid-β (Aβ)-induced pathology, therefore emerging as therapeutic targets against Alzheimer's and related diseases. The modulation of these channels can represent an innovative strategy for the treatment of neurodegenerative disorders; nevertheless, the currently available drugs are not selective for brain KATP channels and show contrasting effects. This phenomenon can be a consequence of the multiple physiological roles of the different varieties of KATP channels. Openings of cardiac and muscular KATP channel subunits, is protective against caspase-dependent atrophy in these tissues and some neurodegenerative disorders, whereas in some neuroinflammatory diseases benefits can be obtained through the inhibition of neuronal KATP channel subunits. For example, glibenclamide exerts an anti-inflammatory effect in respiratory, digestive, urological, and central nervous system (CNS) diseases, as well as in ischemia-reperfusion injury associated with abnormal SUR1-Trpm4/TNF-α or SUR1-Trpm4/ Nos2/ROS signaling. Despite this strategy is promising, glibenclamide may have limited clinical efficacy due to its unselective blocking action of SUR2A/B subunits also expressed in cardiovascular apparatus with pro-arrhythmic effects and SUR1 expressed in pancreatic beta cells with hypoglycemic risk. Alternatively, neuronal selective dual modulators showing agonist/antagonist actions on KATP channels can be an option.

Kv1.3 inhibition as a potential microglia-targeted therapy for Alzheimer's disease: preclinical proof of concept

Microglia significantly contribute to the pathophysiology of Alzheimer's disease but an effective microglia-targeted therapeutic approach is not yet available clinically. The potassium channels Kv1.3 and Kir2.1 play important roles in regulating immune cell functions and have been implicated by in vitro studies in the 'M1-like pro-inflammatory' or 'M2-like anti-inflammatory' state of microglia, respectively. We here found that amyloid-β oligomer-induced expression of Kv1.3 and Kir2.1 in cultured primary microglia. Likewise, ex vivo microglia acutely isolated from the Alzheimer's model 5xFAD mice co-expressed Kv1.3 and Kir2.1 as well as markers traditionally associated with M1 and M2 activation suggesting that amyloid-β oligomer induces a microglial activation state that is more complex than previously thought. Using the orally available, brain penetrant small molecule Kv1.3 blocker PAP-1 as a tool, we showed that pro-inflammatory and neurotoxic microglial responses induced by amyloid-β oligomer required Kv1.3 activity in vitro and in hippocampal slices. Since we further observed that Kv1.3 was highly expressed in microglia of transgenic Alzheimer's mouse models and human Alzheimer's disease brains, we hypothesized that pharmacological Kv1.3 inhibition could mitigate the pathology induced by amyloid-β aggregates. Indeed, treating APP/PS1 transgenic mice with a 5-month oral regimen of PAP-1, starting at 9 months of age, when the animals already manifest cognitive deficits and amyloid pathology, reduced neuroinflammation, decreased cerebral amyloid load, enhanced hippocampal neuronal plasticity, and improved behavioural deficits. The observed decrease in cerebral amyloid deposition was consistent with the in vitro finding that PAP-1 enhanced amyloid-β uptake by microglia. Collectively, these results provide proof-of-concept data to advance Kv1.3 blockers to Alzheimer's disease clinical trials.

The Association between Tooth Loss and Alzheimer's Disease: a Systematic Review with Meta-Analysis of Case Control Studies

Alzheimer's disease is classified as a neurodegenerative condition, a heterogeneous group of illnesses characterized by the slow and progressive loss of one or more functions of the nervous system. Its incidence tends to increase gradually from 65 years of age, up to a prevalence of 4% at age 75. The loss of dental elements is more prevalent in this population and might negatively affect the masticatory capacity, quality of life, and pathogenesis of Alzheimer's disease. This study investigated problems related to oral health and the loss of dental elements in elderly patients suffering from Alzheimer's and considered whether local inflammatory processes could affect the etiopathogenesis of Alzheimer's disease. The purpose of this systematic review is to identify a link between the causes leading to tooth loss and the onset/progression of Alzheimer's disease. We also studied whether there is a higher incidence of tooth loss (primary outcome) and edentulism (secondary outcome) among Alzheimer's patients. We searched records in electronic databases such as PubMed, EBSCO, and Web of Science using the following keywords: Alzheimer's Disease AND periodontal, Alzheimer's Disease AND periodontitis, dementia AND (periodontitis OR periodontal) "Alzheimer's Disease" AND "tooth" OR "dental loss," "dementia" AND "edentulous," "Alzheimer's Disease" AND "edentulous," "dementia" AND "tooth" OR "dental loss." The records were screened, and after applying the eligibility and inclusion criteria, nine articles were left, six of which were analyzed for the primary outcome (loss of dental elements) and six for the secondary outcome (tooth loss). Results from this meta-analysis revealed that Alzheimer's disease patients have an increased risk of dental loss (hazard ratio (HR) 1.52, 95% confidence interval (CI) 1.00-2.30, p = 0.05) and edentulous condition (HR 2.26, 95% CI 1.70-3.01, p < 0.001). A quantitative analysis of the included studies indicated that patients suffering from Alzheimer's disease are characterized by a greater number of lost dental elements and general edentulism compared to the control groups.

Tooth loss as a risk factor for dementia: systematic review and meta-analysis of 21 observational studies

BACKGROUND

Tooth loss is suggested to be associated with an increased risk of dementia in many studies. But the relationship between tooth loss and dementia is not yet fully understood. This systematic review and meta-analysis aimed to determine the relative effect of tooth loss on dementia risk.

METHODS

An electronic search of PubMed, Scopus, Embase, and Web of Knowledge was conducted in March 2018 to identify relevant observational studies with the English language restriction. Studies were included if they assessed the relationship between tooth loss and risk of dementia. Study quality was detected by the modified Downs and Black scale. Odds risks (ORs) were pooled using a random-effects model in the crude model.

RESULTS

The literature search initially yielded 1574 articles, and 21 observational studies published between 1994 and 2017 were finally included for the analyses. The crude results with random-effects model showed that patients with multiple tooth loss had higher incidence of dementia (OR 2.62, 95% CI 1.90-3.61, P < 0.001, I² = 90.40%). The association remained noted when only adjusted results were pooled from 18 studies (OR 1.55, 95% CI 1.41-1.70, P = 0.13, I² = 28.00%). Meta-regression analysis showed that study design explained about 16.52% of heterogeneity in the crude model. The overall quality rating scores of studies ranged from 11 to 16.

CONCLUSIONS

Findings from this review evidenced that tooth loss is positively associated with an increased risk of dementia in adults. Future well-designed longitudinal researches examining the direct and indirect relationship between tooth loss and dementia risk are encouraged.

Oral Infections and Cytokine Levels in Patients with Alzheimer's Disease and Mild Cognitive Impairment Compared with Controls

BACKGROUND

Oral infections are prevalent in the adult population. Their impact includes the implication as a risk factor for Alzheimer's disease (AD), altering its progression. One of the potential mechanisms involves immune mediators such as circulating cytokines.

OBJECTIVE

The goal of the present study was to investigate the prevalence of oral infections and blood levels of IL-1β, TNF-α, and IL-6 in patients with AD, mild cognitive impairment (MCI), and controls.

METHODS

Sixty-five elderly were evaluated (25 AD, 19 MCI, and 21 controls) by the following methods: Mini Mental State Exam, Questionnaire of Functional Activities, periodontal and oral evaluation, and blood concentrations of IL-1β, TNF-α and IL-6.

RESULTS

Patients with AD had high serum IL-6 levels (p = 0.029), and patients with periodontitis had high serum TNF-α levels (p = 0.005). There was an association between IL-6 and TNF-α in patients with AD/MCI and periodontitis (p = 0.023).

CONCLUSION

The increased levels of TNF-α and IL-6 in this study suggests their implication in the overlapping mechanisms between oral infections and AD. Longitudinal studies are necessary for further investigation.

Periodontitis and Alzheimer's Disease: A Possible Comorbidity between Oral Chronic Inflammatory Condition and Neuroinflammation

Periodontitis is an oral chronic infection/inflammatory condition, identified as a source of mediators of inflammation into the blood circulation, which may contribute to exacerbate several diseases. There is increasing evidence that inflammation plays a key role in the pathophysiology of Alzheimer’s disease (AD). Although inflammation is present in both diseases, the exact mechanisms and crosslinks between periodontitis and AD are poorly understood. Therefore, this article aims to review possible comorbidity between periodontitis and AD. Here, the authors discuss the inflammatory aspects of periodontitis, how this oral condition produces a systemic inflammation and, finally, the contribution of this systemic inflammation for worsening neuroinflammation in the progression of AD.

Inhibitory effect of donepezil on bradykinin-induced increase in the intracellular calcium concentration in cultured cortical astrocytes

Donepezil is a potent and selective acetylcholinesterase inhibitor developed for the treatment of Alzheimer's disease. In the present study, we investigated the responses of astrocytes to bradykinin, an inflammatory mediator, and the effect of donepezil on these responses using cultured cortical astrocytes. Bradykinin induced a transient increase of intracellular calcium concentration ([Ca²⁺]_i) in cultured astrocytes. Bradykinin-induced [Ca²⁺]_i increase was inhibited by the exposure to thapsigargin, which depletes Ca²⁺ stores on endoplasmic reticulum, but not by the exclusion of extracellular Ca²⁺. Twenty four hours pretreatment of donepezil reduced the bradykinin-induced [Ca²⁺]_i increase. This reduction was inhibited not only by mecamylamine, a nAChR antagonist, but also by PI3K and Akt inhibitors. In addition, donepezil inhibited bradykinin-induced increase of the intracellular reactive oxygen species level in astrocytes. These results suggest that donepezil inhibits the inflammatory response induced by bradykinin via nAChR and PI3K-Akt pathway in astrocytes.

Expression of neprilysin in periodontitis-affected gingival tissues

OBJECTIVE

Although the pathogeneses of Alzheimer's disease (AD) and periodontal diseases have overlapping features, including ageing and chronic inflammation, the association between AD and periodontitis remains unclear. To explore the pathogenesis of periodontitis, a comprehensive gene expression/transcriptome analysis in periodontitis-affected gingival tissues found that the AD pathway was significantly up-regulated in periodontitis-affected gingival tissues. AD-related genes, amyloid beta precursor protein (APP), interleukin-1 beta and compliment 1QA, were significantly elevated in periodontitis. In the present study, balance between mRNA expression of APP and a potent amyloid degradation enzyme, neprilysin (NEP), as well as protein localisation of APP and NEP were analysed.

DESIGN

Eighteen periodontitis-affected and 18 clinically healthy control gingival tissues were taken from patients with severe chronic periodontitis or undergoing tooth extraction. Total RNA was purified and used for quantitative reverse transcription real-time polymerase chain reaction (qRT-PCR). The localisation of APP and NEP was analysed by immunohistochemistry (IHC).

RESULTS

Both APP and NEP genes were up-regulated in periodontitis-affected gingival tissues. APP-expressing macrophages and NEP-expressing neutrophils and fibroblasts, reflecting inflammatory stages, were detected in inflamed gingival tissues by IHC.

CONCLUSION

The up-regulation of APP and NEP mRNA levels in periodontitis-affected gingival tissues compared with healthy controls was confirmed by qRT-PCR analyses. Since NEP is one of the primary enzymes that degrades amyloid beta, increased NEP mRNA levels in periodontitis may act as an inhibitor of amyloid beta accumulation in gingival tissues, balancing increased APP mRNA expression. However, NEP has several effects including degradation of vasoactive substances; therefore, further sresearch is needed.

Periodontitis as a Modifiable Risk Factor for Dementia: A Nationwide Population-Based Cohort Study

OBJECTIVES

To determine whether periodontitis is a modifiable risk factor for dementia.

DESIGN

Prospective cohort study.

SETTING

National Health Insurance Research Database in Taiwan.

PARTICIPANTS

Individuals aged 65 and older with periodontitis (n = 3,028) and an age- and sex-matched control group (n = 3,028).

MEASUREMENTS

Individuals with periodontitis were compared age- and sex-matched controls with for incidence density and hazard ratio (HR) of new-onset dementia. Periodontitis was defined according to International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes 523.3-5 diagnosed by dentists. To ensure diagnostic validity, only those who had concurrently received antibiotic therapies, periodontal treatment other than scaling, or scaling more than twice per year performed by certified dentists were included. Dementia was defined according to ICD-9-CM codes 290.0-290.4, 294.1, 331.0-331.2.

RESULTS

After adjustment for confounding factors, the risk of developing dementia was calculated to be higher for participants with periodontitis (HR = 1.16, 95% confidence interval = 1.01-1.32, P = .03) than for those without.

CONCLUSION

Periodontitis is associated with greater risk of developing dementia. Periodontal infection is treatable, so it might be a modifiable risk factor for dementia. Clinicians must devote greater attention to this potential association in an effort to develop new preventive and therapeutic strategies for dementia.

Metformin, besides exhibiting strong in vivo anti-inflammatory properties, increases mptp-induced damage to the nigrostriatal dopaminergic system

Metformin is a widely used oral antidiabetic drug with known anti-inflammatory properties due to its action on AMPK protein. This drug has shown a protective effect on various tissues, including cortical neurons. The aim of this study was to determine the effect of metformin on the dopaminergic neurons of the substantia nigra of mice using the animal model of Parkinson's disease based on the injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, an inhibitor of the mitochondrial complex I. In vivo and in vitro experiments were used to study the activation of microglia and the damage of the dopaminergic neurons. Our results show that metformin reduced microglial activation measured both at cellular and molecular levels. Rather than protecting, metformin exacerbated dopaminergic damage in response to MPTP. Our data suggest that, contrary to other brain structures, metformin treatment could be deleterious for the dopaminergic system. Hence, metformin treatment may be considered as a risk factor for the development of Parkinson's disease.

Patients undergoing elective coronary artery bypass grafting exhibit poor pre-operative intakes of fruit, vegetables, dietary fibre, fish and vitamin D

CHD may ensue from chronic systemic low-grade inflammation. Diet is a modifiable risk factor for both, and its optimisation may reduce post-operative mortality, atrial fibrillation and cognitive decline. In the present study, we investigated the usual dietary intakes of patients undergoing elective coronary artery bypass grafting (CABG), emphasising on food groups and nutrients with putative roles in the inflammatory/anti-inflammatory balance. From November 2012 to April 2013, we approached ninety-three consecutive patients (80% men) undergoing elective CABG. Of these, fifty-five were finally included (84% men, median age 69 years; range 46-84 years). The median BMI was 27 (range 18-36) kg/m(2). The dietary intake items were fruits (median 181 g/d; range 0-433 g/d), vegetables (median 115 g/d; range 0-303 g/d), dietary fibre (median 22 g/d; range 9-45 g/d), EPA+DHA (median 0.14 g/d; range 0.01-1.06 g/d), vitamin D (median 4.9 μg/d; range 1.9-11.2 μg/d), saturated fat (median 13.1% of energy (E%); range 9-23 E%) and linoleic acid (LA; median 6.3 E%; range 1.9-11.3 E%). The percentages of patients with dietary intakes below recommendations were 62% (fruits; recommendation 200 g/d), 87 % (vegetables; recommendation 150-200 g/d), 73% (dietary fibre; recommendation 30-45 g/d), 91% (EPA+DHA; recommendation 0.45 g/d), 98% (vitamin D; recommendation 10-20 μg/d) and 13% (LA; recommendation 5-10 E%). The percentages of patients with dietary intakes above recommendations were 95% (saturated fat; recommendation < 10 E%) and 7% (LA). The dietary intakes of patients proved comparable with the average nutritional intake of the age- and sex-matched healthy Dutch population. These unbalanced pre-operative diets may put them at risk of unfavourable surgical outcomes, since they promote a pro-inflammatory state. We conclude that there is an urgent need for intervention trials aiming at rapid improvement of their diets to reduce peri-operative risks.

The role of the immune system in triplet repeat expansion diseases

Trinucleotide repeat expansion disorders (TREDs) are a group of dominantly inherited neurological diseases caused by the expansion of unstable repeats in specific regions of the associated genes. Expansion of CAG repeat tracts in translated regions of the respective genes results in polyglutamine- (polyQ-) rich proteins that form intracellular aggregates that affect numerous cellular activities. Recent evidence suggests the involvement of an RNA toxicity component in polyQ expansion disorders, thus increasing the complexity of the pathogenic processes. Neurodegeneration, accompanied by reactive gliosis and astrocytosis is the common feature of most TREDs, which may suggest involvement of inflammation in pathogenesis. Indeed, a number of immune response markers have been observed in the blood and CNS of patients and mouse models, and the activation of these markers was even observed in the premanifest stage of the disease. Although inflammation is not an initiating factor of TREDs, growing evidence indicates that inflammatory responses involving astrocytes, microglia, and the peripheral immune system may contribute to disease progression. Herein, we review the involvement of the immune system in the pathogenesis of triplet repeat expansion diseases, with particular emphasis on polyglutamine disorders. We also present various therapeutic approaches targeting the dysregulated inflammation pathways in these diseases.

Overexpression of mutant amyloid-β protein precursor and presenilin 1 modulates enteric nervous system

Alzheimer's disease (AD) is a neurodegenerative disorder histologically characterized by amyloid-β (Aβ) protein accumulation and activation of associated microglia. Although these features are well described in the central nervous system, the process and consequences of Aβ accumulation in the enteric nervous system have not been extensively studied. We hypothesized that Aβ also may accumulate in the enteric nervous system and lead to immune cell activation and neuronal dysfunction in the digestive tract not unlike that observed in diseased brain. To test this hypothesis, ileums of the small intestine of thirteen month old AβPP/PS1 and C57BL/6 (wild type) mice were collected and analyzed using immunohistochemistry, western blot analysis, cytokine arrays, and ELISA. AβPP/PS1 mice demonstrated no differences in intestinal motility or water absorption but elevated luminal IgA levels compared to wild type mice. They also had increased protein levels of AβPP and the proteolytic enzyme, BACE, corresponding to an increase in Aβ1-40 in the intestinal lysate as well as an increase in both Aβ1-40 and Aβ1-42 in the stool. This correlated with increased protein markers of proinflammatory and immune cell activation. Histologic analysis localized AβPP within enteric neurons but also intestinal epithelial cells with elevated Aβ immunoreactivity in the AβPP/PS1 mice. The presence of AβPP, Aβ, and CD68 immunoreactivity in the intestines of some patients with neuropathologically-confirmed AD are consistent with the findings in this mouse model. These data support the hypothesis that in AD the intestine, much like the brain, may develop proinflammatory and immune changes related to AβPP and Aβ.

Alzheimer's disease and chronic periodontitis: is there an association?

Alzheimer's disease, an affliction of old age, is one of the leading causes for dementia worldwide. Various risk factors including family history, genetics and infections have been implicated in its pathogenesis. The cognitive decline in this condition is mainly a result of the formation of amyloid deposits that provoke neuroinflammation, ultimately resulting in cell death. Recently, an association between peripheral inflammation and Alzheimer's disease was hypothesized. It was suggested that chronic systemic inflammation worsened the inflammatory processes in the brain. This was mainly attributed to increased levels of pro-inflammatory mediators, such as interleukin-1, interleukin -6 and tumor necrosis factor-α in the plasma. As chronic periodontitis is a widespread peripheral immunoinflammatory condition, it has been proposed to play a significant role in the aggravation of Alzheimer's disease. With this background, the current review focuses on the relationship between Alzheimer's disease and chronic periodontitis, and its therapeutic implications.

A-kinase anchoring proteins: cAMP compartmentalization in neurodegenerative and obstructive pulmonary diseases

The universal second messenger cAMP is generated upon stimulation of Gs protein-coupled receptors, such as the β2 -adreneoceptor, and leads to the activation of PKA, the major cAMP effector protein. PKA oscillates between an on and off state and thereby regulates a plethora of distinct biological responses. The broad activation pattern of PKA and its contribution to several distinct cellular functions lead to the introduction of the concept of compartmentalization of cAMP. A-kinase anchoring proteins (AKAPs) are of central importance due to their unique ability to directly and/or indirectly interact with proteins that either determine the cellular content of cAMP, such as β2 -adrenoceptors, ACs and PDEs, or are regulated by cAMP such as the exchange protein directly activated by cAMP. We report on lessons learned from neurons indicating that maintenance of cAMP compartmentalization by AKAP5 is linked to neurotransmission, learning and memory. Disturbance of cAMP compartments seem to be linked to neurodegenerative disease including Alzheimer's disease. We translate this knowledge to compartmentalized cAMP signalling in the lung. Next to AKAP5, we focus here on AKAP12 and Ezrin (AKAP78). These topics will be highlighted in the context of the development of novel pharmacological interventions to tackle AKAP-dependent compartmentalization.

Increase of angiotensin II type 1 receptor auto-antibodies in Huntington's disease

Background

In the recent years, a role of the immune system in Huntington’s disease (HD) is increasingly recognized. Here we investigate the presence of T cell activating auto-antibodies against angiotensin II type 1 receptors (AT1R) in all stages of the disease as compared to healthy controls and patients suffering from multiple sclerosis (MS) as a prototype neurologic autoimmune disease.

Results

As compared to controls, MS patients show higher titers of anti-AT1R antibodies, especially in individuals with active disease. In HD, anti-AT1R antibodies are more frequent than in healthy controls or even MS and occur in 37.9% of patients with relevant titers ≥ 20 U/ml. In a correlation analysis with clinical parameters, the presence of AT1R antibodies in the sera of HD individuals inversely correlated with the age of onset and positively with the disease burden score as well as with smoking and infection.

Conclusions

These data suggest a dysfunction of the adaptive immune system in HD which may be triggered by different stimuli including autoimmune responses, infection and possibly also smoking.

Schizophrenia and periodontal disease: An oro-neural connection? A cross-sectional epidemiological study

Background:

Schizophrenia is a psychosis characterized by delusions and hallucinations occurring in clear consciousness. Studies have shown that the cytokines may modulate dopaminergic metabolism and schizophrenic symptomatology in schizophrenia. Cytokine involvement in periodontal disease is also well documented. To date, however, there has been relatively little research assessing periodontal status of patients with schizophrenia. The present study was therefore mainly intended to understand the exact link, if any, between periodontal disease and schizophrenia.

Materials and Methods:

A total of 250 schizophrenic patients (140 males and 110 females), between 25 and 55 years of age, were selected from the out patient department of National Institute of Mental Health and Neural Sciences, Bangalore and their periodontal status was assessed as part of this cross-sectional epidemiological survey.

Results:

ANOVA showed that there was increased evidence of poor periodontal condition, as evidenced by gingival index and plaque index in patients who had been schizophrenic for a longer duration of time (P < 0.001). So also, higher probing pocket depths were found in schizophrenics suffering from a longer period of time than others (P < 0.001).

Conclusions:

Although oral neglect might be a cause of poor periodontal health in schizophrenics, the possible link between periodontal diseases giving rise to schizophrenia cannot be overlooked due to the presence of cytokine activity which is present both in schizophrenia and periodontal disease.

RIG-1 receptor expression in the pathology of Alzheimer's disease

BACKGROUND

Neuroinflammation plays a critical role in the pathogenesis of Alzheimer's disease (AD) and involves activation of the innate immune response via recognition of diverse stimuli by pattern recognition receptors (PRRs). The inflammatory inducers and precise innate signaling pathway contributing to AD pathology remain largely undefined.

RESULTS

In the present study we analyzed expression levels of innate immune proteins in temporal and occipital cortices from preclinical (no cognitive impairment, NCI, N = 22) to mild cognitive impairment (MCI, N = 20) associated with AD pathology (N = 20) and AD patients (N = 23). We found that retinoic acid-inducible gene-I (RIG-1) is significantly elevated in the temporal cortex and plasma in patients with MCI. In addition, primary human astrocytes stimulated with the RIG-1 ligand 5'ppp RNA showed increased expression of amyloid precursor protein (APP) and amyloid-β (Aβ), supporting the idea that RIG-1 is involved in the pathology of MCI associated with early progression to AD.

CONCLUSION

These findings suggest that RIG-1 may play a critical role in incipient AD.

Longitudinal study of differential protein expression in an Alzheimer's mouse model lacking inducible nitric oxide synthase

Alzheimer's disease (AD) is a complex neurodegenerative process that involves altered brain immune, neuronal and metabolic functions. Understanding the underlying mechanisms has relied on mouse models that mimic components of AD pathology. We used gel-free, label-free LC-MS/MS to quantify protein and phosphopeptide levels in brains of APPSwDI/NOS2-/- (CVN-AD) mice. CVN-AD mice show a full spectrum of AD-like pathology, including amyloid deposition, hyperphosphorylated and aggregated tau, and neuronal loss that worsens with age. Tryptic digests, with or without phosphopeptide enrichment on an automated titanium dioxide LC system, were separated by online two-dimensional LC and analyzed on a Waters Synapt G2 HDMS, yielding relative expression for >950 proteins and >1100 phosphopeptides. Among differentially expressed proteins were known markers found in humans with AD, including GFAP and C1Q. Phosphorylation of connexin 43, not previously described in AD, was increased at 42 weeks, consistent with dysregulation of gap junctions and activation of astrocytes. Additional alterations in phosphoproteins suggests dysregulation of mitochondria, synaptic transmission, vesicle trafficking, and innate immune pathways. These data validate the CVN-AD mouse model of AD, identify novel disease and age-related changes in the brain during disease progression, and demonstrate the utility of integrating unbiased and phosphoproteomics for understanding disease processes in AD.

The role of the immune system in Huntington's disease

Huntington's disease (HD) is characterized by a progressive course of disease until death 15-20 years after the first symptoms occur and is caused by a mutation with expanded CAG repeats in the huntingtin (htt) protein. Mutant htt (mhtt) in the striatum is assumed to be the main reason for neurodegeneration. Knowledge about pathophysiology has rapidly improved discussing influences of excitotoxicity, mitochondrial damage, free radicals, and inflammatory mechanisms. Both innate and adaptive immune systems may play an important role in HD. Activation of microglia with expression of proinflammatory cytokines, impaired migration of macrophages, and deposition of complement factors in the striatum indicate an activation of the innate immune system. As part of the adaptive immune system, dendritic cells (DCs) prime T-cell responses secreting inflammatory mediators. In HD, DCs may contain mhtt which brings the adaptive immune system into the focus of interest. These data underline an increasing interest in the peripheral immune system for pathomechanisms of HD. It is still unclear if neuroinflammation is a reactive process or if there is an active influence on disease progression. Further understanding the influence of inflammation in HD using mouse models may open various avenues for promising therapeutic approaches aiming at slowing disease progression or forestalling onset of disease.

Transcriptomics of cortical gray matter thickness decline during normal aging

INTRODUCTION

We performed a whole-transcriptome correlation analysis, followed by the pathway enrichment and testing of innate immune response pathway analyses to evaluate the hypothesis that transcriptional activity can predict cortical gray matter thickness (GMT) variability during normal cerebral aging.

METHODS

Transcriptome and GMT data were available for 379 individuals (age range=28-85) community-dwelling members of large extended Mexican American families. Collection of transcriptome data preceded that of neuroimaging data by 17 years. Genome-wide gene transcriptome data consisted of 20,413 heritable lymphocytes-based transcripts. GMT measurements were performed from high-resolution (isotropic 800 μm) T1-weighted MRI. Transcriptome-wide and pathway enrichment analysis was used to classify genes correlated with GMT. Transcripts for sixty genes from seven innate immune pathways were tested as specific predictors of GMT variability.

RESULTS

Transcripts for eight genes (IGFBP3, LRRN3, CRIP2, SCD, IDS, TCF4, GATA3, and HN1) passed the transcriptome-wide significance threshold. Four orthogonal factors extracted from this set predicted 31.9% of the variability in the whole-brain and between 23.4 and 35% of regional GMT measurements. Pathway enrichment analysis identified six functional categories including cellular proliferation, aggregation, differentiation, viral infection, and metabolism. The integrin signaling pathway was significantly (p<10(-6)) enriched with GMT. Finally, three innate immune pathways (complement signaling, toll-receptors and scavenger and immunoglobulins) were significantly associated with GMT.

CONCLUSION

Expression activity for the genes that regulate cellular proliferation, adhesion, differentiation and inflammation can explain a significant proportion of individual variability in cortical GMT. Our findings suggest that normal cerebral aging is the product of a progressive decline in regenerative capacity and increased neuroinflammation.

β-Defensin Genomic Copy Number Does Not Influence the Age of Onset in Huntington's Disease

BACKGROUND

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by the abnormal expansion of a CAG triplet repeat tract in the huntingtin gene. While the length of this CAG expansion is the major determinant of the age of onset (AO), other genetic factors have also been shown to play a modulatory role. Recent evidence suggests that neuroinflammation is a pivotal factor in the pathogenesis of HD, and that targeting this process may have important therapeutic ramifications. The human β-defensin 2 (hBD2) - encoded by DEFB4 - is an antimicrobial peptide that exhibits inducible expression in astrocytes during inflammation and is an important regulator of innate and adaptive immune response. Therefore, DEFB4 may contribute to the neuroinflammatory processes observed in HD.

OBJECTIVE

In this study we tested the hypothesis that copy number variation (CNV) of the β-defensin region, including DEFB4, modifies the AO in HD.

METHODS AND RESULTS

We genotyped β-defensin CNV in 490 HD individuals using the paralogue ratio test and found no association between β-defensin CNV and onset of HD.

CONCLUSIONS

We conclude that it is unlikely that DEFB4 plays a role in HD pathogenesis.

Hypercholesterolemia accelerates amyloid β-induced cognitive deficits

Hypercholesterolemia is a known risk factor for Alzheimer's disease (AD). In the present study, we investigated whether diet-induced hypercholesterolemia affects AD-like pathologies such as amyloid β-peptide (Aβ) deposition, tau pathology, inflammation and cognitive impairment, using an Aβ25-35-injected AD-like pathological mouse model. Hypercholesterolemia was induced by providing apolipoprotein E knock out (Apo E KO) mice with a high-fat diet for 4 weeks prior to Aβ25-35 injection and for 4 weeks following Aβ25-35 injection, for a total of 8 weeks of treatment. Our data showed that intracerebroventricular injection of C57BL/6J mice with Aβ25-35 resulted in increased immunoreactivity of Aβ and phosphorylated-tau (p-tau), which was accompanied by enhanced microglial CD11b-like immunoreactivity in the brain. Moreover, hypercholesterolemia slightly increased Aβ and p-tau levels and microglial activation in the vehicle group, while further increasing the Aβ and p-tau levels and microglial activation in Aβ25-35-injected mice. Consistent with the neuropathological analysis, hypercholesterolemia resulted in significant spatial learning and memory deficits in Aβ25-35-injected mice as revealed by water maze testing. Collectively, these findings demonstrated that hypercholesterolemia accelerated Aβ accumulation and tau pathology, which was accompanied by microglial activation and subsequent aggravation of memory impairment induced by Aβ25-35. Thus, we suggest that the modulation of cholesterol can be used to reduce the risk of developing AD.

Alzheimer's disease related markers, cellular toxicity and behavioral deficits induced six weeks after oligomeric amyloid-β peptide injection in rats

Alzheimer’s disease (AD) is a neurodegenerative pathology associated with aging characterized by the presence of senile plaques and neurofibrillary tangles that finally result in synaptic and neuronal loss. The major component of senile plaques is an amyloid-β protein (Aβ). Recently, we characterized the effects of a single intracerebroventricular (icv) injection of Aβ fragment (25–35) oligomers (oAβ_25–35) for up to 3 weeks in rats and established a clear parallel with numerous relevant signs of AD. To clarify the long-term effects of oAβ_25–35 and its potential role in the pathogenesis of AD, we determined its physiological, behavioral, biochemical and morphological impacts 6 weeks after injection in rats. oAβ_25–35 was still present in the brain after 6 weeks. oAβ_25–35 injection did not affect general activity and temperature rhythms after 6 weeks, but decreased body weight, induced short- and long-term memory impairments, increased corticosterone plasma levels, brain oxidative (lipid peroxidation), mitochondrial (caspase-9 levels) and reticulum stress (caspase-12 levels), astroglial and microglial activation. It provoked cholinergic neuron loss and decreased brain-derived neurotrophic factor levels. It induced cell loss in the hippocampic CA subdivisions and decreased hippocampic neurogenesis. Moreover, oAβ_25–35 injection resulted in increased APP expression, Aβ_1–42 generation, and increased Tau phosphorylation. In conclusion, this in vivo study evidenced that the soluble oligomeric forms of short fragments of Aβ, endogenously identified in AD patient brains, not only provoked long-lasting pathological alterations comparable to the human disease, but may also directly contribute to the progressive increase in amyloid load and Tau pathology, involved in the AD physiopathology.

Melatonin attenuated mediators of neuroinflammation and alpha-7 nicotinic acetylcholine receptor mRNA expression in lipopolysaccharide (LPS) stimulated rat astrocytoma cells, C6

Melatonin has been known to affect a variety of astrocytes functions in many neurological disorders but its mechanism of action on neuroinflammatory cascade and alpha-7 nicotinic acetylcholine receptor (α7-nAChR) expression are still not properly understood. Present study demonstrated that treatment of C6 cells with melatonin for 24 hours significantly decreased lipopolysaccharide (LPS) induced nitrative and oxidative stress, expressions of cyclooxigenase-2 (COX-2), inducible nitric-oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP). Melatonin also modulated LPS-induced mRNA expressions of α7-nAChR and inflammatory cytokine genes. Furthermore, melatonin reversed LPS-induced changes in C/EBP homologous protein 10 (CHOP), microsomal prostaglandin E synthase-1(mPGES-1) and phosphorylated p38 mitogen activated protein kinase (P-p38). Treatment with pyrrolidine dithiocarbamate (PDTC) inhibited α7-nAChR mRNA expression in LPS-induced C6 cells. Our findings explored anti-neuroinflammatory action of melatonin, which may suggests its beneficial roles in the neuroinflammation associated disorders.

Microglial KCa3.1 Channels as a Potential Therapeutic Target for Alzheimer's Disease

There exists an urgent need for new target discovery to treat Alzheimer's disease (AD); however, recent clinical trials based on anti-Aβ and anti-inflammatory strategies have yielded disappointing results. To expedite new drug discovery, we propose reposition targets which have been previously pursued by both industry and academia for indications other than AD. One such target is the calcium-activated potassium channel KCa3.1 (KCNN4), which in the brain is primarily expressed in microglia and is significantly upregulated when microglia are activated. We here review the existing evidence supporting that KCa3.1 inhibition could block microglial neurotoxicity without affecting their neuroprotective phagocytosis activity and without being broadly immunosuppressive. The anti-inflammatory and neuroprotective effects of KCa3.1 blockade would be suitable for treating AD as well as cerebrovascular and traumatic brain injuries, two well-known risk factors contributing to the dementia in AD patients presenting with mixed pathologies. Importantly, the pharmacokinetics and pharmacodynamics of several KCa3.1 blockers are well known, and a KCa3.1 blocker has been proven safe in clinical trials. It is therefore promising to reposition old or new KCa3.1 blockers for AD preclinical and clinical trials.

The changing phenotype of microglia from homeostasis to disease

It has been nearly a century since the early description of microglia by Rio-Hortega; since then many more biological and pathological features of microglia have been recognized. Today, microglia are generally considered to be beneficial to homeostasis at the resting state through their abilities to survey the environment and phagocytose debris. However, when activated microglia assume diverse phenotypes ranging from fully inflamed, which involves the release of many pro-inflammatory cytokines, to alternatively activated, releasing anti-inflammatory cytokines or neurotrophins, the consequences to neurons can range from detrimental to supportive. Due to the different experimental sets and conditions, contradictory results have been obtained regarding the controversial question of whether microglia are “good” or “bad.” While it is well understood that the dual roles of activated microglia depend on specific situations, the underlying mechanisms have remained largely unclear, and the interpretation of certain findings related to diverse microglial phenotypes continues to be problematic. In this review we discuss the functions of microglia in neuronal survival and neurogenesis, the crosstalk between microglia and surrounding cells, and the potential factors that could influence the eventual manifestation of microglia.

Genetics of late-onset Alzheimer's disease: update from the alzgene database and analysis of shared pathways

The genetics of late-onset Alzheimer's disease (LOAD) has taken impressive steps forwards in the last few years. To date, more than six-hundred genes have been linked to the disorder. However, only a minority of them are supported by a sufficient level of evidence. This review focused on such genes and analyzed shared biological pathways. Genetic markers were selected from a web-based collection (Alzgene). For each SNP in the database, it was possible to perform a meta-analysis. The quality of studies was assessed using criteria such as size of research samples, heterogeneity across studies, and protection from publication bias. This produced a list of 15 top-rated genes: APOE, CLU, PICALM, EXOC3L2, BIN1, CR1, SORL1, TNK1, IL8, LDLR, CST3, CHRNB2, SORCS1, TNF, and CCR2. A systematic analysis of gene ontology terms associated with each marker showed that most genes were implicated in cholesterol metabolism, intracellular transport of beta-amyloid precursor, and autophagy of damaged organelles. Moreover, the impact of these genes on complement cascade and cytokine production highlights the role of inflammatory response in AD pathogenesis. Gene-gene and gene-environment interactions are prominent issues in AD genetics, but they are not specifically featured in the Alzgene database.

MicroRNA: Implications for Alzheimer Disease and other Human CNS Disorders

Understanding complex diseases such as sporadic Alzheimer disease (AD) has been a major challenge. Unlike the familial forms of AD, the genetic and environmental risks factors identified for sporadic AD are extensive. MicroRNAs are one of the major noncoding RNAs that function as negative regulators to silence or suppress gene expression via translational inhibition or message degradation. Their discovery has evoked great excitement in biomedical research for their promise as potential disease biomarkers and therapeutic targets. Key microRNAs have been identified as essential for a variety of cellular events including cell lineage determination, proliferation, apoptosis, DNA repair, and cytoskeletal organization; most, if not all, acting to fine-tune gene expression at the post-transcriptional level in a host of cellular signaling networks. Dysfunctional microRNA-mediated regulation has been implicated in the pathogenesis of many disease states. Here, the current understanding of the role of miRNAs in the central nervous system is reviewed with emphasis on their impact on the etiopathogenesis of sporadic AD.

Astrocytoma cells upregulate expression of pro-inflammatory cytokines after co-culture with activated peripheral blood mononuclear cells

In this study, we investigated the effect of CD3/CD28-activated peripheral blood mononuclear cells (PBMCs) on two human astrocytoma cell lines (1321N1 and CCF-STTG1), with respect to the expression of cytokines and chemokines. We used an in vitro co-culture system in which the astrocytoma cells and PBMCs were separated by a membrane in a transwell system. Proliferation of T cells was quantified by a [(3) H]-thymidine incorporation assay. Differential gene expression of astrocytoma cells cultured alone or with PBMCs was identified using gene arrays. Protein expression of CCL3, CCL5, CXCL8, CXCL9, CXCL10, IL6, and IL1β was determined by Luminex. Co-culture of activated T cells and astrocytoma cells resulted in inhibition of T cell proliferation. Moreover, astrocytoma cells upregulated a number of pro-inflammatory genes including CCL3, CCL5, CXCL8, CXCL9, CXCL10, IL6, and IL1β upon co-culture with activated PBMCs. These results were confirmed on the protein level. Astrocytoma cells inhibited the proliferation of T cells, indicating that astrocytes may play an important role in controlling T cell mediated immune responses in the brain. Contrary to this, soluble factors derived from CD3/CD28-activated PBMCs affected the transcriptome of astrocytoma cells, which then upregulated several pro-inflammatory genes and proteins. This could be part of neuroinflammatory events and may play a role in neurodegenerative diseases.

Systemic and central immunity in Alzheimer's disease: therapeutic implications

Clinical pharmaceutical trials aimed at modulating the immune system in Alzheimer's Disease have largely focused on either dampening down central proinflammatory innate immunity or have manipulated adaptive immunity to facilitate the removal of centrally deposited beta amyloid. To date, these trials have had mixed clinical therapeutic effects. However, a number of clinical studies have demonstrated disturbances of both systemic and central innate immunity in Alzheimer's Disease and attention has been drawn to the close communication pathways between central and systemic immunity. This paper highlights the need to take into account the potential systemic effects of drugs aimed at modulating central immunity and the possibility of developing novel therapeutic approaches based on the manipulation of systemic immunity and its communication with the central nervous system.

NF-κB signaling inhibits ubiquitin carboxyl-terminal hydrolase L1 gene expression

Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is a deubiquitinating enzyme that plays a regulatory role in targeting proteins for proteasomal degradation. UCH-L1 is highly expressed in neurons and has been demonstrated to promote cell viability and maintain neuronal integrity. Reduced UCH-L1 levels have been observed in various neurodegenerative diseases, and expression of UCH-L1 can rescue synaptic dysfunction and memory deficits in Alzheimer's Disease model mice. However, the mechanisms regulating UCH-L1 expression have not been determined. In this study, we cloned a 1782 bp of the 5' flanking region of the human UCH-L1 gene and identified a 43 bp fragment containing the transcription start site as the minimal region necessary for promoter activity. Sequence analysis revealed several putative regulatory elements including NF-κB, NFAT, CREB, NRSF, YY1, AP1, and STAT in the UCH-L1 promoter. A functional NF-κB response element was identified in the UCH-L1 promoter region. Expression of NF-κB suppressed UCH-L1 gene transcription. In the RelA knockout system where NF-κB activity is ablated, UCH-L1 expression was significantly increased. Furthermore, activation of NF-κB signaling by the inflammatory stimulator lipopolysaccharide and TNFα resulted in a decrease of UCH-L1 gene expression by inhibiting its transcription. As NF-κB is an important signaling module in inflammatory response, our study suggests a possibility that inflammation might compromise neuronal functions via the interaction of NF-κB and UCH-L1. A better understanding of the NF-κB-regulated UCH-L1 transcription will provide insights to the role of inflammatory responses in Alzheimer's disease and Parkinson's disease.

LPS-mediated production of pro/anti-inflammatory cytokines and eicosanoids in whole blood samples: biological effects of +896A/G TLR4 polymorphism in a Sicilian population of healthy subjects

Toll-like receptors (TLRs) are the principal mediators of rapid microbial recognition: the lipopolysaccharide (LPS) receptor TLR4 seems to have a paradigmatic role. Single nucleotide polymorphisms (SNPs) in the TLR4 gene, such as +896A/G, known to attenuate receptor signaling, have been described. The +896A/G SNP is significantly less frequent in patients with myocardial infarction, Alzheimer's disease or prostate cancer, whereas it is overrepresented in centenarians. To clarify and confirm the biological effects of +896A/G SNP and its role in the pathophysiology of age-related diseases and longevity, we assessed the levels of IL-6, TNF-α, IL-10 and eicosanoids (LTB4 and PGE2) in LPS-stimulated whole blood samples in vitro of 50 young healthy Sicilians, screened for the presence of this SNP. To evaluate the possible influence of SNPs in PTGS2 and 5-Lo genes on eicosanoid production, the enrolled individuals were also genotyped for -765G/C PTGS2 and -1708G/A 5-Lo SNPs. Both pro-inflammatory cytokines and eicosanoids were significantly lower in carriers bearing the TLR4 mutation, whereas the anti-inflammatory IL-10 values were higher. On the basis of data reported herein, some suggestions can be drawn. First, pathogen load, by interacting with the host genotype, determines the type and intensity of inflammatory responses, according to the pro-inflammatory status and tissue injury, implicated in the pathophysiology of major age-related diseases. Second, adequate control of inflammatory response might reduce the risk of these diseases, and, reciprocally, might increase the chance of extended survival in an environment with reduced antigen (that is, pathogen) load.

Relationship of tooth loss to mild memory impairment and cognitive impairment: findings from the Fujiwara-kyo study

Background

This cross-sectional study investigated the relationship between the number of remaining teeth to mild memory impairment (MMI), which is a preclinical stage of dementia, and to cognitive impairment.

Methods

The subjects were aged 65 years or older and were grouped according to their score for the Mini-Mental State Examination (MMSE), the three-word delayed recall test in the MMSE, and the Geriatric Depression Scale into the control group (n = 3,696), the MMI group (n = 121), and the low MMSE score (23 or lower) group (n = 214). We collected data on the number of remaining teeth, the length of the edentulous period, health-related lifestyle, medical history, blood pressure, height, and body weight. Fasting venous blood samples were also obtained.

Results

Multiple logistic regression analysis, adjusted for depressive symptoms, age, sex, length of education, and other explanatory variables, revealed that the odds ratios of 0-10 remaining teeth to 22-32 remaining teeth were 1.679 (95% CI 1.073-2.627) for MMI and 2.177 (95% CI 1.510-3.140) for a low MMSE score. A significant relationship was also found between the length of the edentulous period and the risk of a low MMSE score (odds ratio 3.102, 95% CI 1.432-6.720) (15 years or more/less than 15 years).

Conclusions

Our findings suggest that tooth loss is associated with cognitive function.

Neuroinflammation in Alzheimer's disease: mechanisms, pathologic consequences, and potential for therapeutic manipulation

The concept of neuroinflammation has evolved over the past two decades from an initially controversial viewpoint to its present status as a generally accepted idea whose mechanisms and consequences are still actively under research and debate, particularly with regard to Alzheimer's disease (AD). This review summarizes the current status of neuroinflammation research as it specifically relates to AD. Neuroinflammation is discussed mechanistically with emphasis on the role of redox signal transduction linked to the activation of central nervous system-relevant innate immune pathways. Redox signaling is presented both as a causal factor and a consequence of sustained neuroinflammation. Functional relationships are discussed that connect distinct neuroinflammatory components such as cytokines, eicosanoids, classic AD pathology (amyloid plaques and neurofibrillary tangles), and the recently emergent notion of "damage-associated molecular patterns". The interaction of these paracrine factors likely can produce positive as well as negative effects on the AD brain, ranging from plaque clearance by microglia in the short term to glial dysfunction and neuronal compromise if the neuroinflammation is chronically sustained and unmitigated. Recent disappointments in AD clinical trials of anti-inflammatory drugs are discussed with reference to possible explanations and potential avenues for future pharmacological approaches to the disease.

Fibrillar amyloid-beta-activated human astroglia kill primary human neurons via neutral sphingomyelinase: implications for Alzheimer's disease

Glial activation plays an important role in the pathogenesis of various neurodegenerative disorders including Alzheimer's disease. However, molecular mechanisms by which activated glia could kill neurons are poorly understood. The present study underlines the importance of neutral sphingomyelinase (N-SMase) in mediating the damaging effect of fibrillar amyloid-β 1-42 (Aβ1-42) peptide-activated astroglia on neurons. In transwell experiments, soluble products released from activated primary human astroglia induced the activation of neutral sphingomyelinase (N-SMase), production of ceramide, and cell death in primary human neurons. Protection of neurons from cytotoxic effects of activated astroglia by antisense knockdown of N-SMase, but not acidic sphingomyelinase (A-SMase), suggests that soluble products released from activated astroglia kill neurons via N-SMase but not A-SMase. Next we examined the role of N-SMase in the activation of human astroglia. Interestingly, knockdown of N-SMase, but not A-SMase, by either antisense oligonucleotides or chemical inhibitor, prevented the induction of proinflammatory molecules [tumor necrosis factor-α, inducible nitric oxide synthase, interleukin-1β (IL-1β), and IL-6] and the activation of nuclear factor-κB in Aβ1-42-activated astroglia. Subsequently, fibrillar Aβ peptides also induced the activation of N-SMase and ceramide in vivo in mouse cortex. Most importantly, antisense knockdown of N-SMase, but not A-SMase, decreased the activation of astroglia and protected neurons from fibrillar Aβ toxicity in vivo in the cortex. Together, it is apparent that both the activation of astroglia by Aβ and that the cytotoxicity of activated astroglia on neurons depend on N-SMase.

Hypercholesterolemia in rats impairs the cholinergic system and leads to memory deficits

Alzheimer's disease (AD) is a chronic brain disorder characterized by cognitive impairment, cholinergic dysfunction, inflammation, tau and beta-amyloid pathology and vascular damage. Recent studies have shown, that high cholesterol levels are linked to the pathology of AD. The aim of our present work was to study the effects of hypercholesterolemia in adult rats. Five months after 5% cholesterol-enriched diet plasma cholesterol levels and total weight were significantly enhanced compared to controls. Spatial memory was studied in an 8-arm radial maze and cholesterol-treated rats showed an impaired learning and long-term memory. Hypercholesterolemia significantly reduced the number of cholinergic neurons in the basal nucleus of Meynert and decreased acetylcholine levels in the cortex. Nerve growth factor was only slightly enhanced in the cortex of cholesterol-treated animals. Levels of amyloid precursor protein, beta-amyloid(1–42), as well as tau and phospho-tau 181 were significantly enhanced in the cortex of cholesterol-fed rats. Hypercholesterolemia markedly increased several cerebral inflammatory markers and enhanced microglial CD11b-like immunoreactivity. Vascular density, stained by RECA-1 was not changed. However, cholesterol induced cortical microbleedings illustrated by intensive anti-rat IgG-positive spots in the cortex. In conclusion, our data demonstrate that hypercholesterolemia in rats caused memory impairment, cholinergic dysfunction, inflammation, enhanced cortical beta-amyloid and tau and microbleedings, all indications, which resemble an AD-like pathology.