The role of neuroinflammation in dementias

Investigating the Spatial Associations Between Amyloid-β Deposition, Grey Matter Volume, and Neuroinflammation in Alzheimer's Disease

Background:

It has been proposed that amyloid-β (Aβ) plays a causal role in Alzheimer’s disease (AD) by triggering a series of pathologic events—possibly including neuroinflammation—which culminate in progressive brain atrophy. However, the interplay between the two pathological molecular events and how both are associated with neurodegeneration is still unclear.

Objective:

We aimed to estimate the spatial inter-relationship between neurodegeneration, neuroinflammation and Aβ deposition in a cohort of 20 mild AD patients and 17 healthy controls (HC).

Methods:

We resorted to magnetic resonance imaging to measure cortical atrophy, using the radiotracer ¹¹C-PK11195 PET to measure neuroinflammation levels and ¹¹C-PiB PET to assess Aβ levels. Between-group comparisons were computed to explore AD-related changes in the three types of markers. To examine the effects of each one of the molecular pathologic mechanisms on neurodegeneration we computed: 1) ANCOVAs with the anatomic data, controlling for radiotracer uptake differences between groups and 2) voxel-based multiple regression analysis between-modalities. In addition, associations in anatomically defined regions of interests were also investigated.

Results:

We found significant differences between AD and controls in the levels of atrophy, neuroinflammation, and Aβ deposition. Associations between Aβ aggregation and brain atrophy were detected in AD in a widely distributed pattern, whereas associations between microglia activation and structural measures of neurodegeneration were restricted to few anatomically regions.

Conclusion:

In summary, Aβ deposition, as opposed to neuroinflammation, was more associated with cortical atrophy, suggesting a prominent role of Aβ in neurodegeneration at a mild stage of the AD.

Anti-inflammatory activity of Jatropha curcas L. in brain glial cells primary cultures

ETHNOPHARMACOLOGICAL RELEVANCE

Jatropha curcas L. (Euphorbiaceae), a medicinal plant known in Brazil as "Pinhão Manso", is highly adaptable, being cultivated in different tropical and subtropical regions of the world. Antimicrobial, antioxidant and antiinflammatory activities have been attributed to different parts of the plant. In the central nervous sytem (CNS), neuroinflammation is mediated by glial cells, mainly by astrocytes and microglia, a process that plays an important role in neurodegenerative diseases and other CNS disorders. In this study, we investigated the anti-inflammatory activity of the methanolic extract obtained from the leaves of J. curcas L. (MEJc) in primary cultures of glial cells submited to inflammatory stimulus.

MATERIALS AND METHODS

Primary cultures of glial cells obtained from the cerebral cortex of neonate Wistar rats were treated with MEJc (0.1-50,000 μg mL^-1) and its fractions (F_nJc) (0.1 μg mL^-1) with or without lipopolysaccharide of Escherichia coli (LPS) (1 μg mL^-1). Cell viability was determined with MTT test. Modifications in glial cell morphology were investigated by means of phase contrast microscopy and May-Grünwald staining. The reactivity of astrocytes and microglia were investigated with immunocytochemistry for GFAP, Iba1 and transcription factor NF-kB, as well as with Greiss reaction to determine the nitric oxide (NO) production.

RESULTS

MEJc at 0.1-1000 μg mL^-1 was non-toxic to glial cells and the DE₅₀ was 10.794 μg mL^-1. The treatment with LPS induced the activation of astrocytes and microglia marked by morphological modifications and changes in the expression of GFAP and Iba1, as well as the increase in NF-kB expression and NO production. Treatment with MEJc inhibited the morphological modifications, changes in GFAP and Iba1 expression, and the increase in NF-kB and NO production induced by LPS.

CONCLUSION

This study demonstrates that the MEJc and its fractions modulate inflammatory response of astrocytes and microglia to LPS and may be considered as a potential therapeutic strategy for neuroinflammation-related diseases.

Coniferyl Aldehyde Inhibits the Inflammatory Effects of Leptomeningeal Cells by Suppressing the JAK2 Signaling

Background

The brain is in many ways an immunologically and pharmacologically privileged site because of the blood-brain barrier (BBB). But for chronic peripheral inflammation, inflammatory signals can be transmitted from the peripheral system into the central nervous system (CNS) through multiple channels and result in neuroinflammation. Leptomeningeal cells that form the BBB can trigger one signaling pathway by releasing cytokines to transmit inflammatory signals. Besides, the Janus kinase (JAK) family may have a certain function in the activation of leptomeninges. In the present study, we try to use coniferyl aldehyde (CA), a natural anti-inflammatory phenolic compound, to inhibit this inflammatory process and elucidate the underlying molecular mechanisms.

Results

Secretion of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) significantly increased after incubation with P. gingivalis. Moreover, TNF-α, IL-1β, and IL-6 levels were upregulated, and the JAK2 signaling was enhanced in leptomeningeal cells in a conditioned medium from activated macrophages, which leads to the immune response in microglia. However, this inflammatory effect of leptomeningeal cells was reversed by CA administration, accompanied by the decreased immune response in microglia. The western blot assay revealed that JAK2 phosphorylation was suppressed in leptomeningeal cells treated with CA.

Conclusions

This study demonstrates that activated macrophages by P. gingivalis markedly induce the release of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) from leptomeningeal cells, thereby activating the JAK2 signaling pathway and subsequently enhancing immune responses in microglia in the CNS. CA effectively inhibits the inflammatory effect of leptomeningeal cells via suppressing the JAK2 signaling pathway.

The Retinal Inner Plexiform Synaptic Layer Mirrors Grey Matter Thickness of Primary Visual Cortex with Increased Amyloid β Load in Early Alzheimer's Disease

The retina may serve as putative window into neuropathology of synaptic loss in Alzheimer's disease (AD). Here, we investigated synapse-rich layers versus layers composed by nuclei/cell bodies in an early stage of AD. In addition, we examined the associations between retinal changes and molecular and structural markers of cortical damage. We recruited 20 AD patients and 17 healthy controls (HC). Combining optical coherence tomography (OCT), magnetic resonance (MR), and positron emission tomography (PET) imaging, we measured retinal and primary visual cortex (V1) thicknesses, along with V1 amyloid β (Aβ) retention ([11C]-PiB PET tracer) and neuroinflammation ([11C]-PK11195 PET tracer). We found that V1 showed increased amyloid-binding potential, in the absence of neuroinflammation. Although thickness changes were still absent, we identified a positive association between the synapse-rich inner plexiform layer (IPL) and V1 in AD. This retinocortical interplay might reflect changes in synaptic function resulting from Aβ deposition, contributing to early visual loss.

The Other Side of Alzheimer's Disease: Influence of Metabolic Disorder Features for Novel Diagnostic Biomarkers

Nowadays, the amyloid cascade hypothesis is the dominant model to explain Alzheimer's disease (AD) pathogenesis. By this hypothesis, the inherited genetic form of AD is discriminated from the sporadic form of AD (SAD) that accounts for 85-90% of total patients. The cause of SAD is still unclear, but several studies have shed light on the involvement of environmental factors and multiple susceptibility genes, such as Apolipoprotein E and other genetic risk factors, which are key mediators in different metabolic pathways (e.g., glucose metabolism, lipid metabolism, energetic metabolism, and inflammation). Furthermore, growing clinical evidence in AD patients highlighted the presence of affected systemic organs and blood similarly to the brain. Collectively, these findings revise the canonical understating of AD pathogenesis and suggest that AD has metabolic disorder features. This review will focus on AD as a metabolic disorder and highlight the contribution of this novel understanding on the identification of new biomarkers for improving an early AD diagnosis.

Role of Neuroinflammation in Autism Spectrum Disorder and the Emergence of Brain Histaminergic System. Lessons Also for BPSD?

Many behavioral and psychological symptoms of dementia (BPSD) share similarities in executive functioning and communication deficits with those described in several neuropsychiatric disorders, including Alzheimer's disease (AD), epilepsy, schizophrenia (SCH), and autism spectrum disorder (ASD). Numerous studies over the last four decades have documented altered neuroinflammation among individuals diagnosed with ASD. The purpose of this review is to examine the hypothesis that central histamine (HA) plays a significant role in the regulation of neuroinflammatory processes of microglia functions in numerous neuropsychiatric diseases, i.e., ASD, AD, SCH, and BPSD. In addition, this review summarizes the latest preclinical and clinical results that support the relevance of histamine H1-, H2-, and H3-receptor antagonists for the potential clinical use in ASD, SCH, AD, epilepsy, and BPSD, based on the substantial symptomatic overlap between these disorders with regards to cognitive dysfunction. The review focuses on the histaminergic neurotransmission as relevant in these brain disorders, as well as the effects of a variety of H3R antagonists in animal models and in clinical studies.

Microglial activation and tau burden predict cognitive decline in Alzheimer's disease

Tau pathology, neuroinflammation, and neurodegeneration are key aspects of Alzheimer's disease. Understanding whether these features predict cognitive decline, alone or in combination, is crucial to develop new prognostic measures and enhanced stratification for clinical trials. Here, we studied how baseline assessments of in vivo tau pathology (measured by 18F-AV-1451 PET), neuroinflammation (measured by 11C-PK11195 PET) and brain atrophy (derived from structural MRI) predicted longitudinal cognitive changes in patients with Alzheimer's disease pathology. Twenty-six patients (n = 12 with clinically probable Alzheimer's dementia and n = 14 with amyloid-positive mild cognitive impairment) and 29 healthy control subjects underwent baseline assessment with 18F-AV-1451 PET, 11C-PK11195 PET, and structural MRI. Cognition was examined annually over the subsequent 3 years using the revised Addenbrooke's Cognitive Examination. Regional grey matter volumes, and regional binding of 18F-AV-1451 and 11C-PK11195 were derived from 15 temporo-parietal regions characteristically affected by Alzheimer's disease pathology. A principal component analysis was used on each imaging modality separately, to identify the main spatial distributions of pathology. A latent growth curve model was applied across the whole sample on longitudinal cognitive scores to estimate the rate of annual decline in each participant. We regressed the individuals' estimated rate of cognitive decline on the neuroimaging components and examined univariable predictive models with single-modality predictors, and a multi-modality predictive model, to identify the independent and combined prognostic value of the different neuroimaging markers. Principal component analysis identified a single component for the grey matter atrophy, while two components were found for each PET ligand: one weighted to the anterior temporal lobe, and another weighted to posterior temporo-parietal regions. Across the whole-sample, the single-modality models indicated significant correlations between the rate of cognitive decline and the first component of each imaging modality. In patients, both stepwise backward elimination and Bayesian model selection revealed an optimal predictive model that included both components of 18F-AV-1451 and the first (i.e. anterior temporal) component for 11C-PK11195. However, the MRI-derived atrophy component and demographic variables were excluded from the optimal predictive model of cognitive decline. We conclude that temporo-parietal tau pathology and anterior temporal neuroinflammation predict cognitive decline in patients with symptomatic Alzheimer's disease pathology. This indicates the added value of PET biomarkers in predicting cognitive decline in Alzheimer's disease, over and above MRI measures of brain atrophy and demographic data. Our findings also support the strategy for targeting tau and neuroinflammation in disease-modifying therapy against Alzheimer's disease.

Neuroinflammation and protein aggregation co-localize across the frontotemporal dementia spectrum

The clinical syndromes of frontotemporal dementia are clinically and neuropathologically heterogeneous, but processes such as neuroinflammation may be common across the disease spectrum. We investigated how neuroinflammation relates to the localization of tau and TDP-43 pathology, and to the heterogeneity of clinical disease. We used PET in vivo with (i) 11C-PK-11195, a marker of activated microglia and a proxy index of neuroinflammation; and (ii) 18F-AV-1451, a radioligand with increased binding to pathologically affected regions in tauopathies and TDP-43-related disease, and which is used as a surrogate marker of non-amyloid-β protein aggregation. We assessed 31 patients with frontotemporal dementia (10 with behavioural variant, 11 with the semantic variant and 10 with the non-fluent variant), 28 of whom underwent both 18F-AV-1451 and 11C-PK-11195 PET, and matched control subjects (14 for 18F-AV-1451 and 15 for 11C-PK-11195). We used a univariate region of interest analysis, a paired correlation analysis of the regional relationship between binding distributions of the two ligands, a principal component analysis of the spatial distributions of binding, and a multivariate analysis of the distribution of binding that explicitly controls for individual differences in ligand affinity for TDP-43 and different tau isoforms. We found significant group-wise differences in 11C-PK-11195 binding between each patient group and controls in frontotemporal regions, in both a regions-of-interest analysis and in the comparison of principal spatial components of binding. 18F-AV-1451 binding was increased in semantic variant primary progressive aphasia compared to controls in the temporal regions, and both semantic variant primary progressive aphasia and behavioural variant frontotemporal dementia differed from controls in the expression of principal spatial components of binding, across temporal and frontotemporal cortex, respectively. There was a strong positive correlation between 11C-PK-11195 and 18F-AV-1451 uptake in all disease groups, across widespread cortical regions. We confirmed this association with post-mortem quantification in 12 brains, demonstrating strong associations between the regional densities of microglia and neuropathology in FTLD-TDP (A), FTLD-TDP (C), and FTLD-Pick's. This was driven by amoeboid (activated) microglia, with no change in the density of ramified (sessile) microglia. The multivariate distribution of 11C-PK-11195 binding related better to clinical heterogeneity than did 18F-AV-1451: distinct spatial modes of neuroinflammation were associated with different frontotemporal dementia syndromes and supported accurate classification of participants. These in vivo findings indicate a close association between neuroinflammation and protein aggregation in frontotemporal dementia. The inflammatory component may be important in shaping the clinical and neuropathological patterns of the diverse clinical syndromes of frontotemporal dementia.

Impact of HMGB1, RAGE, and TLR4 in Alzheimer's Disease (AD): From Risk Factors to Therapeutic Targeting

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder and a leading cause of dementia, with accumulation of amyloid-beta (Aβ) and neurofibrillary tangles (NFTs) as defining pathological features. AD presents a serious global health concern with no cure to date, reflecting the complexity of its pathogenesis. Recent evidence indicates that neuroinflammation serves as the link between amyloid deposition, Tau pathology, and neurodegeneration. The high mobility group box 1 (HMGB1) protein, an initiator and activator of neuroinflammatory responses, has been involved in the pathogenesis of neurodegenerative diseases, including AD. HMGB1 is a typical damage-associated molecular pattern (DAMP) protein that exerts its biological activity mainly through binding to the receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4). RAGE and TLR4 are key components of the innate immune system that both bind to HMGB1. Targeting of HMGB1, RAGE, and TLR4 in experimental AD models has demonstrated beneficial effects in halting AD progression by suppressing neuroinflammation, reducing Aβ load and production, improving spatial learning, and inhibiting microglial stimulation. Herein, we discuss the contribution of HMGB1 and its receptor signaling in neuroinflammation and AD pathogenesis, providing evidence of its beneficial effects upon therapeutic targeting.

Xanthones, A Promising Anti-Inflammatory Scaffold: Structure, Activity, and Drug Likeness Analysis

Inflammation is the body's self-protective response to multiple stimulus, from external harmful substances to internal danger signals released after trauma or cell dysfunction. Many diseases are considered to be related to inflammation, such as cancer, metabolic disorders, aging, and neurodegenerative diseases. Current therapeutic approaches include mainly non-steroidal anti-inflammatory drugs and glucocorticoids, which are generally of limited effectiveness and severe side-effects. Thus, it is urgent to develop novel effective anti-inflammatory therapeutic agents. Xanthones, a unique scaffold with a 9H-Xanthen-9-one core structure, widely exist in natural sources. Till now, over 250 xanthones were isolated and identified in plants from the families Gentianaceae and Hypericaceae. Many xanthones have been disclosed with anti-inflammatory properties on different models, either in vitro or in vivo. Herein, we provide a comprehensive and up-to-date review of xanthones with anti-inflammatory properties, and analyzed their drug likeness, which might be potential therapeutic agents to fight against inflammation-related diseases.

P2Y6 and P2X7 Receptor Antagonism Exerts Neuroprotective/ Neuroregenerative Effects in an Animal Model of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by decreased dopamine bioavailability in the substantia nigra and the striatum. Taking into account that adenosine-5’-triphosphate (ATP) and its metabolites are intensely released in the 6-hydroxydopamine (6-OHDA) animal model of PD, screening of purinergic receptor gene expression was performed. Effects of pharmacological P2Y6 or P2X7 receptor antagonism were studied in preventing or reversing hemiparkinsonian behavior and dopaminergic deficits in this animal model. P2X7 receptor antagonism with Brilliant Blue G (BBG) at a dose of 75 mg/kg re-established the dopaminergic nigrostriatal pathway in rats injured with 6-OHDA. Selective P2Y6 receptor antagonism by MRS2578 prevented dopaminergic neuron death in SH-SY5Y cells in vitro and in vivo in the substantia nigra of rats injured with 6-OHDA. Moreover, in vivo analysis showed that both treatments were accompanied by a reduction of microglial activation in the substantia nigra. Altogether, these data provide evidence that antagonism of P2X7 or P2Y6 receptors results in neuroregenerative or neuroprotective effects, respectively, possibly through modulation of neuroinflammatory responses.

Neuroglial patterns are shared by cerebella from prion and prion-like disorder affected patients

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, are considered prion-like disorders because they are all proteinopathies in which aberrant proteins spread throughout the brain during disease progression. The overall aim of this study is to determine how glial cells are commonly involved in the neurodegeneration progress observed in all these pathologies. The suggestion that they are cell types in which prion and prion-like disorders have common behaviour is the hypothesis on which this study is based. Morphological and distribution differences in astroglial and microglial cells in the cerebellum from prion and prion-like disease-affected patients were assessed here by histopathological and immunochemical tools. To our knowledge, this is the first study to focus on the comparative assessment of glial profiles in these human brains. Activated microglial population was demonstrated in both, prion and prion-like disorders, although in higher extent in the first. In astroglial activation, specific patterns of alterations suggesting both degenerative and potentially neuroprotective or restorative stem cell response, were shown to be alternatively shared by cerebella from all disorders studied. Neuro-protective strategies for these disabling disorders are particularly desirable.

Cellular and regional vulnerability in frontotemporal tauopathies

The frontotemporal tauopathies all deposit abnormal tau protein aggregates, but often of only certain isoforms and in distinguishing pathologies of five main types (neuronal Pick bodies, neurofibrillary tangles, astrocytic plaques, tufted astrocytes, globular glial inclusions and argyrophilic grains). In those with isoform specific tau aggregates glial pathologies are substantial, even though there is limited evidence that these cells normally produce tau protein. This review will assess the differentiating features and clinicopathological correlations of the frontotemporal tauopathies, the genetic predisposition for these different pathologies, their neuroanatomical selectivity, current observations on how they spread through the brain, and any potential contributing cellular and molecular changes. The findings show that diverse clinical phenotypes relate most to the brain region degenerating rather than the type of pathology involved, that different regions on the MAPT gene and novel risk genes are associated with specific tau pathologies, that the 4-repeat glial tauopathies do not follow individual patterns of spreading as identified for neuronal pathologies, and that genetic and pathological data indicate that neuroinflammatory mechanisms are involved. Each pathological frontotemporal tauopathy subtype with their distinct pathological features differ substantially in the cell type affected, morphology, biochemical and anatomical distribution of inclusions, a fundamental concept central to future success in understanding the disease mechanisms required for developing therapeutic interventions. Tau directed therapies targeting genetic mechanisms, tau aggregation and pathological spread are being trialled, although biomarkers that differentiate these diseases are required. Suggested areas of future research to address the regional and cellular vulnerabilities in frontotemporal tauopathies are discussed.

Neuroinflammation in frontotemporal dementia

Frontotemporal dementia (FTD) refers to a group of progressive neurodegenerative disorders with different pathological signatures, genetic variability and complex disease mechanisms, for which no effective treatments exist. Despite advances in understanding the underlying pathology of FTD, sensitive and specific fluid biomarkers for this disease are lacking. As in other types of dementia, mounting evidence suggests that neuroinflammation is involved in the progression of FTD, including cortical inflammation, microglial activation, astrogliosis and differential expression of inflammation-related proteins in the periphery. Furthermore, an overlap between FTD and autoimmune disease has been identified. The most substantial evidence, however, comes from genetic studies, and several FTD-related genes are also implicated in neuroinflammation. This Review discusses specific evidence of neuroinflammatory mechanisms in FTD and describes how advances in our understanding of these mechanisms, in FTD as well as in other neurodegenerative diseases, might facilitate the development and implementation of diagnostic tools and disease-modifying treatments for FTD.

Microglial activation correlates in vivo with both tau and amyloid in Alzheimer's disease

Alzheimer's disease is characterized by the histopathological presence of amyloid-β plaques and tau-containing neurofibrillary tangles. Microglial activation is also a recognized pathological component. The relationship between microglial activation and protein aggregation is still debated. We investigated the relationship between amyloid plaques, tau tangles and activated microglia using PET imaging. Fifty-one subjects (19 healthy controls, 16 mild cognitive impairment and 16 Alzheimer's disease subjects) participated in the study. All subjects had neuropsychometric testing, MRI, amyloid (18F-flutemetamol), and microglial (11C-PBR28) PET. All subjects with mild cognitive impairment and Alzheimer's disease and eight of the controls had tau (18F-AV1451) PET. 11C-PBR28 PET was analysed using Logan graphical analysis with an arterial plasma input function, while 18F-flutemetamol and 18F-AV1451 PET were analysed as target:cerebellar ratios to create parametric standardized uptake value ratio maps. Biological parametric mapping in the Statistical Parametric Mapping platform was used to examine correlations between uptake of tracers at a voxel-level. There were significant widespread clusters of positive correlation between levels of microglial activation and tau aggregation in both the mild cognitive impairment (amyloid-positive and amyloid-negative) and Alzheimer's disease subjects. The correlations were stronger in Alzheimer's disease than in mild cognitive impairment, suggesting that these pathologies increase together as disease progresses. Levels of microglial activation and amyloid deposition were also correlated, although in a different spatial distribution; correlations were stronger in mild cognitive impairment than Alzheimer's subjects, in line with a plateauing of amyloid load with disease progression. Clusters of positive correlations between microglial activation and protein aggregation often targeted similar areas of association cortex, indicating that all three processes are present in specific vulnerable brain areas. For the first time using PET imaging, we show that microglial activation can correlate with both tau aggregation and amyloid deposition. This confirms the complex relationship between these processes. These results suggest that preventative treatment for Alzheimer's disease should target all three processes.

Early Secure Attachment as a Protective Factor Against Later Cognitive Decline and Dementia

The etiology of neurodegenerative disorders such as dementia is complex and incompletely understood. Interest in a developmental perspective to these pathologies is gaining momentum. An early supportive social environment seems to have important implications for social, affective and cognitive abilities across the lifespan. Attachment theory may help to explain the link between these early experiences and later outcomes. This theory considers early interactions between an infant and its caregiver to be crucial to shaping social behavior and emotion regulation strategies throughout adult life. Furthermore, research has demonstrated that such early attachment experiences can, potentially through epigenetic mechanisms, have profound neurobiological and cognitive consequences. Here we discuss how early attachment might influence the development of affective, cognitive, and neurobiological resources that could protect against cognitive decline and dementia. We argue that social relations, both early and late in life, are vital to ensuring cognitive and neurobiological health. The concepts of brain and cognitive reserve are crucial to understanding how environmental factors may impact cognitive decline. We examine the role that attachment might play in fostering brain and cognitive reserve in old age. Finally, we put forward the concept of affective reserve, to more directly frame the socio-affective consequences of early attachment as protectors against cognitive decline. We thereby aim to highlight that, in the study of aging, cognitive decline and dementia, it is crucial to consider the role of affective and social factors such as attachment.

Recent Developments in TSPO PET Imaging as A Biomarker of Neuroinflammation in Neurodegenerative Disorders

Neuroinflammation is an inflammatory response in the brain and spinal cord, which can involve the activation of microglia and astrocytes. It is a common feature of many central nervous system disorders, including a range of neurodegenerative disorders. An overlap between activated microglia, pro-inflammatory cytokines and translocator protein (TSPO) ligand binding was shown in early animal studies of neurodegeneration. These findings have been translated in clinical studies, where increases in TSPO positron emission tomography (PET) signal occur in disease-relevant areas across a broad spectrum of neurodegenerative diseases. While this supports the use of TSPO PET as a biomarker to monitor response in clinical trials of novel neurodegenerative therapeutics, the clinical utility of current TSPO PET radioligands has been hampered by the lack of high affinity binding to a prevalent form of polymorphic TSPO (A147T) compared to wild type TSPO. This review details recent developments in exploration of ligand-sensitivity to A147T TSPO that have yielded ligands with improved clinical utility. In addition to developing a non-discriminating TSPO ligand, the final frontier of TSPO biomarker research requires developing an understanding of the cellular and functional interpretation of the TSPO PET signal. Recent insights resulting from single cell analysis of microglial phenotypes are reviewed.

Neuroprotective effects of EpoL against oxidative stress induced by soluble oligomers of Aβ peptide

Erythropoietin is a glycoproteic hormone that regulates hematopoiesis by acting on its specific receptor (EpoR). The expression of EpoR in the central nervous system (CNS) suggests a role for this hormone in the brain. Recently, we developed a new Epo variant without hematopoietic activity called EpoL, which showed marked neuroprotective effects against oxidative stress in brain ischemia related models. In this study, we have evaluated the neuroprotective effects of EpoL against oxidative stress induced by chronic treatment with Aβ. Our results show that EpoL was neuroprotective against Aβ-induced toxicity by a mechanism that implicates EpoR, reduction in reactive oxygen species, and reduction in astrogliosis. Furthermore, EpoL treatment improved calcium handling and SV2 levels. Interestingly, the neuroprotective effect of EpoL against oxidative stress induced by chronic Aβ treatment was achieved at a concentration 10 times lower than that of Epo. In conclusion, EpoL, a new variant of Epo without hematopoietic activity, is of potential interest for the treatment of diseases related to oxidative stress in the CNS such as Alzheimer disease.

Inflammatory cytokines in highly myopic eyes

Currently, myopic retinopathy is the most common irreversible blinding disease but its pathophysiology is not completely clear. A cross-sectional, observational study was conducted in a single center to analyze aqueous samples from highly myopic eyes (axial length >25 mm, n = 92) and ametropic or mild myopic eyes (n = 88) for inflammatory cytokines. Vascular endothelial growth factor (VEGF), Interleukin 6 (IL-6), and matrix metalloproteinase-2 (MMP-2) were measured using an enzyme-linked immunosorbent assay. IL-6 and MMP-2 were significantly higher in the highly myopic eyes than in the non-high myopic eyes (IL-6: 11.90 vs. 4.38 pg/mL, p < 0.0001; MMP-2: 13.10 vs. 8.82 ng/mL, p = 0.0003) while adjusting for age, gender, and intraocular pressure. There was a significant positive association between levels of IL-6 and MMP-2 in aqueous humor and the axial lengths of the eye globes (IL-6, β = 0.065, p < 0.0001, n = 134; MMP-2, β = 0.097, p < 0.0001, n = 131). Conversely, VEGF in aqueous humor was significantly lower in the highly myopic eyes than in the non-high myopic eyes (45.56 vs. 96.90 pg/mL, p < 0.0001, n = 153) while age, gender, and intraocular pressure were adjusted. The results suggest that low-grade intraocular inflammation may play an important role in the development and progression of high myopia and myopic retinopathy.

Microglia in Neurological Diseases: A Road Map to Brain-Disease Dependent-Inflammatory Response

Microglia represent a specialized population of macrophages-like cells in the central nervous system (CNS) considered immune sentinels that are capable of orchestrating a potent inflammatory response. Microglia are also involved in synaptic organization, trophic neuronal support during development, phagocytosis of apoptotic cells in the developing brain, myelin turnover, control of neuronal excitability, phagocytic debris removal as well as brain protection and repair. Microglial response is pathology dependent and affects to immune, metabolic. In this review, we will shed light on microglial activation depending on the disease context and the influence of factors such as aging, environment or cell-to-cell interaction.

Rosuvastatin alleviates high-salt and cholesterol diet-induced cognitive impairment in rats via Nrf2-ARE pathway

OBJECTIVE

The objectives of our study were to investigate the possible effect of rosuvastatin in ameliorating high salt and cholesterol diet (HSCD)-induced cognitive impairment and to also investigate its possible action via the Nrf2-ARE pathway.

METHODS

In silico studies were performed to check the theoretical binding of rosuvastatin to the Nrf2 target. HSCD was used to induce cognitive impairment in rats and neurobehavioral studies were performed to evaluate the efficacy of rosuvastatin in enhancing cognition. Biochemical analyses were used to estimate changes in oxidative markers. Western blot and immunohistochemical analyses were done to check Nrf2 translocation. TUNEL and caspase 3 tests were performed to evaluate reversal of apoptosis by rosuvastatin.

RESULTS

Rosuvastatin showed good theoretical affinity to Nrf2, significantly reversed changes in oxidative biomarkers which were induced by HSCD, and also improved the performance of rats in the neurobehavioral test. A rise in nuclear translocation of Nrf2 was revealed through immunohistochemical analysis and western blot. TUNEL staining and caspase 3 activity showed attenuation of apoptosis.

DISCUSSION

We have investigated a novel mechanism of action for rosuvastatin (via the Nrf2-ARE pathway) and demonstrated that it has the potential to be used in the treatment of cognitive impairment.

IL-1β, IL-6, TNF- α and CRP in Elderly Patients with Depression or Alzheimer's disease: Systematic Review and Meta-Analysis

We carried out systematic review and meta-analysis to evaluate whether peripheral levels of pro-inflammatory markers including Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF- α) and C-Reactive Protein (CRP) are significantly higher in elderly with depression and Alzheimer's disease. We searched Pubmed, PsycINFO and Embase, and thirty-four relevant studies (2609 with Depression, 1645 with Alzheimer's disease and 14363 Controls) were included. Compared with controls, IL-1β (pooled standardized mean difference [SMD]: 0.642; 95% confidence interval [CI]: 0.078-1.206; significant heterogeneity: I2 = 86.28%) and IL-6 (pooled SMD: 0.377; 95% CI: 0.156-0.598; significant heterogeneity: I2 = 88.75%) were significantly elevated in depression. There was no difference in TNF-α (p = 0.351) and CRP (p = 0.05) between those with depression and controls. Compared with controls, IL-1β (pooled SMD: 1.37, 95% CI: 0.06-2.68, significant heterogeneity: I2 = 96.01%) was significantly elevated in Alzheimer's disease. There were no differences in IL-6 (p = 0.138), TNF-α (p = 0.451) and CRP (p = 0.07) between elderly with Alzheimer's disease and controls. After Bonferroni adjustment, only IL-6 remained significantly higher in depression. Elderly with depression have higher IL-6 than controls, while those with Alzheimer's disease did not have higher peripheral inflammatory markers.

Ethnopharmacological Approaches for Dementia Therapy and Significance of Natural Products and Herbal Drugs

Dementia is a clinical syndrome wherein gradual decline of mental and cognitive capabilities of an afflicted person takes place. Dementia is associated with various risk factors and conditions such as insufficient cerebral blood supply, toxin exposure, mitochondrial dysfunction, oxidative damage, and often coexisting with some neurodegenerative disorders such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD). Although there are well-established (semi-)synthetic drugs currently used for the management of AD and AD-associated dementia, most of them have several adverse effects. Thus, traditional medicine provides various plant-derived lead molecules that may be useful for further medical research. Herein we review the worldwide use of ethnomedicinal plants in dementia treatment. We have explored a number of recognized databases by using keywords and phrases such as “dementia”, “Alzheimer's,” “traditional medicine,” “ethnopharmacology,” “ethnobotany,” “herbs,” “medicinal plants” or other relevant terms, and summarized 90 medicinal plants that are traditionally used to treat dementia. Moreover, we highlight five medicinal plants or plant genera of prime importance and discuss the physiological effects, as well as the mechanism of action of their major bioactive compounds. Furthermore, the link between mitochondrial dysfunction and dementia is also discussed. We conclude that several drugs of plant origin may serve as promising therapeutics for the treatment of dementia, however, pivotal evidence for their therapeutic efficacy in advanced clinical studies is still lacking.

Autoimmune rheumatic diseases and the risk of Parkinson disease: a nationwide population-based cohort study in Taiwan

BACKGROUNDS

In autoimmune rheumatic diseases (ARDs), the levels of inflammatory mediators are increased and microglia may be activated, resulting in an inflammatory state and the degeneration of dopaminergic neurons. We investigated the association between ARDs and Parkinson disease (PD).

METHODS

We identified ARD patients through the Taiwan National Health Insurance Research Database from 2001 to 2012. From the general population, we randomly selected a comparison cohort that was frequency-matched by age (in 5-year increments), sex and index year. We analysed the risk of PD, stratified by sex, age and comorbidities, by using a Cox regression model.

RESULTS

The risk of PD was 1.37 times greater in ARD patients than in controls after adjustment for age, sex, and comorbidities. ARD subgroups, such as the rheumatoid arthritis and Sjogren syndrome (SS) cohorts, were associated with a significantly higher risk of PD (adjusted hazard ratio [HR], 1.14; 95% confidence interval [CI], 1.03-1.2 and adjusted HR, 1.56; 95% CI, 1.35-1.79, respectively). Furthermore, primary and secondary SS patients had significantly higher risks of PD (adjusted HR, 1.58; 95% CI, 1.32-1.88 and adjusted HR, 1.53, 95% CI, 1.23-1.90, respectively).

CONCLUSIONS

The risk of PD was significantly higher in the ARD patients. Prospective studies are needed to confirm whether ARDs indeed increase the risk of PD.

Traumatic exposures, posttraumatic stress disorder, and cognitive functioning in World Trade Center responders

INTRODUCTION

This study examined whether World Trade Center (WTC)-related exposures and posttraumatic stress disorder (PTSD) were associated with cognitive function and whether WTC responders' cognition differed from normative data.

METHODS

A computer-assisted neuropsychological battery was administered to a prospective cohort study of 1193 WTC responders with no history of stroke or WTC-related head injuries. Data were linked to information collected prospectively since 2002. Sample averages were compared to published norms.

RESULTS

Approximately 14.8% of sampled responders had cognitive dysfunction. WTC responders had worse cognitive function compared to normative data. PTSD symptom severity and working >5 weeks on-site was associated with lower cognition.

DISCUSSION

Results from this sample highlight the potential for WTC responders to be experiencing an increased burden of cognitive dysfunction and linked lowered cognitive functioning to physical exposures and to PTSD. Future research is warranted to understand the extent to which cognitive dysfunction is evident in neural dysfunction.

Spinal cord injury and Alzheimer's disease risk: a population-based, retrospective cohort study

STUDY DESIGN

Propensity score-matched, retrospective cohort study.

OBJECTIVES

To determine the risk of developing Alzheimer's disease (AD) in patients with spinal cord injury (SCI).

SETTING

The present study used Taiwan's National Health Insurance Research Database.

METHODS

A total of 9257 patients who had ⩾2 ambulatory visits with a diagnosis of SCI in 2001 were included in the SCI group. The non-SCI group consisted of 37,028 propensity score-matched patients without a diagnosis of SCI. The cumulative incidence of AD was estimated for each of the two patient groups using the Kaplan-Meier method. Stratified Cox proportional hazard regression was then employed to assess the influence of SCI on the risk of AD.

RESULTS

During the follow-up period, 25 subjects in the SCI group and 57 in the non-SCI group developed AD. The cumulative incidence of AD in the SCI group was higher than in the non-SCI group (P = 0.0168); and the hazard ratio of AD for the SCI group, as compared to the non-SCI group, was 1.71 (95% CI 1.06-2.76, P = 0.0273).

CONCLUSIONS

This study suggests that patients with SCI have an increased risk of developing AD.

Neuroprotective effects of erythropoietin on neurodegenerative and ischemic brain diseases: the role of erythropoietin receptor

Erythropoietin (Epo) is a fundamental hormone in the regulation of hematopoiesis, and other secondary roles mediated by the binding of the hormone to its specific receptor (EpoR), which leads to an activation of key signaling pathways that induce an increase in cell differentiation, apoptosis control and neuroprotection. It has been suggested that their function depends on final conformation of glycosylations, related with affinity to the receptor and its half-life. The presence of EpoR has been reported in different tissues including central nervous system, where it has been demonstrated to exert a neuroprotective function against oxidative stress conditions, such as ischemic injury and neurodegenerative diseases. There is also evidence of an increase in EpoR expression in brain cell lysates of Alzheimer's patients with respect to healthy patients. These results are related with extensive in vitro experimental data of neuroprotection obtained from cell lines, primary cell cultures and hippocampal slices. Additionally, this data is correlated with in vivo experiments (water maze test) in mouse models of Alzheimer's disease where Epo treatment improved cognitive function. These studies support the idea that receptor activation induces a neuroprotective effect in neurodegenerative disorders including dementias, and especially Alzheimer's disease. Taken together, available evidence suggests that Epo appears to be a central element for EpoR activation and neuroprotective properties in the central nervous system. In this review, we will describe the mechanisms associated with neuroprotection and its relation with the activation of EpoR in order with identify new targets to develop pharmacological strategies.

The Role of Microglia in Retinal Neurodegeneration: Alzheimer's Disease, Parkinson, and Glaucoma

Microglia, the immunocompetent cells of the central nervous system (CNS), act as neuropathology sensors and are neuroprotective under physiological conditions. Microglia react to injury and degeneration with immune-phenotypic and morphological changes, proliferation, migration, and inflammatory cytokine production. An uncontrolled microglial response secondary to sustained CNS damage can put neuronal survival at risk due to excessive inflammation. A neuroinflammatory response is considered among the etiological factors of the major aged-related neurodegenerative diseases of the CNS, and microglial cells are key players in these neurodegenerative lesions. The retina is an extension of the brain and therefore the inflammatory response in the brain can occur in the retina. The brain and retina are affected in several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and glaucoma. AD is an age-related neurodegeneration of the CNS characterized by neuronal and synaptic loss in the cerebral cortex, resulting in cognitive deficit and dementia. The extracellular deposits of beta-amyloid (Aβ) and intraneuronal accumulations of hyperphosphorylated tau protein (pTau) are the hallmarks of this disease. These deposits are also found in the retina and optic nerve. PD is a neurodegenerative locomotor disorder with the progressive loss of dopaminergic neurons in the substantia nigra. This is accompanied by Lewy body inclusion composed of α-synuclein (α-syn) aggregates. PD also involves retinal dopaminergic cell degeneration. Glaucoma is a multifactorial neurodegenerative disease of the optic nerve, characterized by retinal ganglion cell loss. In this pathology, deposition of Aβ, synuclein, and pTau has also been detected in retina. These neurodegenerative diseases share a common pathogenic mechanism, the neuroinflammation, in which microglia play an important role. Microglial activation has been reported in AD, PD, and glaucoma in relation to protein aggregates and degenerated neurons. The activated microglia can release pro-inflammatory cytokines which can aggravate and propagate neuroinflammation, thereby degenerating neurons and impairing brain as well as retinal function. The aim of the present review is to describe the contribution in retina to microglial-mediated neuroinflammation in AD, PD, and glaucomatous neurodegeneration.

Suspected non-Alzheimer's pathology - Is it non-Alzheimer's or non-amyloid?

Neurodegeneration, the progressive loss of neurons, is a major process involved in dementia and age-related cognitive impairment. It can be detected clinically using currently available biomarker tests. Suspected Non-Alzheimer Pathology (SNAP) is a biomarker-based concept that encompasses a group of individuals with neurodegeneration, but no evidence of amyloid deposition (thereby distinguishing it from Alzheimer's disease (AD)). These individuals may often have a clinical diagnosis of AD, but their clinical features, genetic susceptibility and progression can differ significantly, carrying crucial implications for precise diagnostics, clinical management, and efficacy of clinical drug trials. SNAP has caused wide interest in the dementia research community, because it is still unclear whether it represents distinct pathology separate from AD, or whether in some individuals, it could represent the earliest stage of AD. This debate has raised pertinent questions about the pathways to AD, the need for biomarkers, and the sensitivity of current biomarker tests. In this review, we discuss the biomarker and imaging trials that first recognized SNAP. We describe the pathological correlates of SNAP and comment on the different causes of neurodegeneration. Finally, we discuss the debate around the concept of SNAP, and further unanswered questions that are emerging.

Sodium thiosulphate attenuates brain inflammation induced by systemic lipopolysaccharide administration in C57BL/6J mice

It has been demonstrated that peripheral infections accompanied by neuroinflammation may modify brain development or affect normal brain aging and represent major risk factors for the development of neurological disorders. A wide range of synthetic and natural compounds with anti-inflammatory properties have been evaluated in animal models of neuroinflammation and neurodegeneration as an adjuvant therapeutic strategy. In the present study we have demonstrated for the first time that sodium thiosulphate (STS), a known antidote approved for treatment of certain medical conditions, is capable of reducing brain inflammation caused by systemic LPS administration. STS reduced brain levels of pro-inflammatory cytokine interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), ionized calcium binding adaptor molecule 1 (Iba-1) and 18 kDa translocator protein (TSPO) in an animal model of systemic LPS-induced neuroinflammation. In addition, we demonstrated for the first time elevated TSPO expression in retinal ganglion cells layer after peripheral LPS challenge and inhibition of ocular TSPO expression after treatment with STS. We think that STS may be used as an adjuvant anti-inflammatory therapy for many pathological conditions associated with inflammation in the brain.

Bioactive terpenoids from Silybum marianum and their suppression on NO release in LPS-induced BV-2 cells and interaction with iNOS

Three new (1-3) and one known (4) bioactive terpenoids were isolated from the seeds of Silybum marianum based on the investigation to get new NO inhibitors. Their structures were determined by extensive NMR (1D and 2D NMR) and MS spectroscopic data, and the absolute configurations were identified by experimental and calculated ECD spectra. The NO inhibitory activities in murine microglial BV-2 cells and interactions with iNOS protein by molecular docking were evaluated for all compounds. The results showed that these compounds had potent NO inhibitory effects.

Molecular Imaging of Neuroinflammation in Neurodegenerative Dementias: The Role of In Vivo PET Imaging

Neurodegeneration elicits neuroinflammatory responses to kill pathogens, clear debris and support tissue repair. Neuroinflammation is a dynamic biological response characterized by the recruitment of innate and adaptive immune system cells in the site of tissue damage. Resident microglia and infiltrating immune cells partake in the restoration of central nervous system homeostasis. Nevertheless, their activation may shift to chronic and aggressive responses, which jeopardize neuron survival and may contribute to the disease process itself. Positron Emission Tomography (PET) molecular imaging represents a unique tool contributing to in vivo investigating of neuroinflammatory processes in patients. In the present review, we first provide an overview on the molecular basis of neuroinflammation in neurodegenerative diseases with emphasis on microglia activation, astrocytosis and the molecular targets for PET imaging. Then, we review the state-of-the-art of in vivo PET imaging for neuroinflammation in dementia conditions associated with different proteinopathies, such as Alzheimer’s disease, frontotemporal lobar degeneration and Parkinsonian spectrum.

Reduced cerebrospinal fluid concentration of interleukin-12/23 subunit p40 in patients with cognitive impairment

Background

The role of inflammation in Alzheimer’s disease (AD) and other cognitive disorders is unclear. In a well-defined mono-center population, we measured cytokines and chemokines in paired serum and cerebrospinal fluid (CSF) samples.

Methods

Consecutive patients with AD (n = 30), stable mild cognitive impairment (SMCI, n = 11), other dementias (n = 11), and healthy controls (n = 18) were included. None of the subjects was treated with glucocorticoids, cholinesterase inhibitors, or non-steroidal anti-inflammatory drugs. Serum and CSF concentrations of interleukin-6 (IL-6), IL-8, IL-12/23 p40, IL-15, IL-16, vascular endothelial growth factor-A (VEGF-A), and three chemokines were measured using a multiplex panel.

Results

After correction for multiple comparisons, only CSF IL-12/23 p40 concentration differed significantly between the total patient group (n = 52) and controls (n = 18; p = 0.002). Further analyses showed that CSF IL-12/23 p40 concentration was decreased in all patient subgroups (AD, other dementias, and SMCI) compared to healthy controls (p < 0.01, p < 0.05, and p < 0.05, respectively). In the total study population (n = 70), CSF IL-12/23 p40 concentrations correlated positively with CSF concentrations of β-amyloid_1-42 (Aβ_1–42) and phosphorylated tau protein (P-tau) whereas in AD patients (n = 30), CSF IL-12/23 p40 only correlated positively with CSF P-Tau (r = 0.46, p = 0.01).

Conclusions

Most cytokines and chemokines were similar in patients and controls, but CSF IL-12/23 subunit p40 concentration was decreased in patients with cognitive impairment, and correlated with markers of AD disease status. Further studies are needed to evaluate the role of CSF IL-12/23 p40 in other dementias and SMCI.

An In Vivo 11C-(R)-PK11195 PET and In Vitro Pathology Study of Microglia Activation in Creutzfeldt-Jakob Disease

Microgliosis is part of the immunobiology of Creutzfeldt-Jakob disease (CJD). This is the first report using ¹¹C-(R)-PK11195 PET imaging in vivo to measure 18 kDa translocator protein (TSPO) expression, indexing microglia activation, in symptomatic CJD patients, followed by a postmortem neuropathology comparison. One genetic CJD (gCJD) patient, two sporadic CJD (sCJD) patients, one variant CJD (vCJD) patient (mean ± SD age, 47.50 ± 15.95 years), and nine healthy controls (mean ± SD age, 44.00 ± 11.10 years) were included in the study. TSPO binding potentials were estimated using clustering and parametric analyses of reference regions. Statistical comparisons were run at the regional and at the voxel-wise levels. Postmortem evaluation measured scrapie prion protein (PrP^Sc) immunoreactivity, neuronal loss, spongiosis, astrogliosis, and microgliosis. ¹¹C-(R)-PK11195-PET showed a significant TSPO overexpression at the cortical level in the two sCJD patients, as well as thalamic and cerebellar involvement; very limited parieto-occipital activation in the gCJD case; and significant increases at the subcortical level in the thalamus, basal ganglia, and midbrain and in the cerebellum in the vCJD brain. Along with misfolded prion deposits, neuropathology in all patients revealed neuronal loss, spongiosis and astrogliosis, and a diffuse cerebral and cerebellar microgliosis which was particularly dense in thalamic and basal ganglia structures in the vCJD brain. These findings confirm significant microgliosis in CJD, which was variably modulated in vivo and more diffuse at postmortem evaluation. Thus, TSPO overexpression in microglia activation, topography, and extent can vary in CJD subtypes, as shown in vivo, possibly related to the response to fast apoptotic processes, but reaches a large amount at the final disease course.

TRIAD3/RNF216 mutations associated with Gordon Holmes syndrome lead to synaptic and cognitive impairments via Arc misregulation

Multiple loss-of-function mutations in TRIAD3 (a.k.a. RNF216) have recently been identified in patients suffering from Gordon Holmes syndrome (GHS), characterized by cognitive decline, dementia, and movement disorders. TRIAD3A is an E3 ubiquitin ligase that recognizes and facilitates the ubiquitination of its target for degradation by the ubiquitin-proteasome system (UPS). Here, we demonstrate that two of these missense substitutions in TRIAD3 (R660C and R694C) could not regulate the degradation of their neuronal target, activity-regulated cytoskeletal-associated protein (Arc/Arg 3.1), whose expression is critical for synaptic plasticity and memory. The synaptic deficits due to the loss of endogenous TRIAD3A could not be rescued by TRIAD3A harboring GHS-associated missense mutations. Moreover, we demonstrate that the loss of endogenous TRIAD3A in the mouse hippocampal CA1 region led to deficits in spatial learning and memory. Finally, we show that these missense mutations abolished the interaction of TRIAD3A with Arc, disrupting Arc ubiquitination, and consequently Arc degradation. Our current findings of Arc misregulation by TRIAD3A variants suggest that loss-of-function mutations in TRIAD3A may contribute to dementia observed in patients with GHS driven by dysfunctional UPS components, leading to cognitive impairments through the synaptic protein Arc.

Intranasal BMP9 Ameliorates Alzheimer Disease-Like Pathology and Cognitive Deficits in APP/PS1 Transgenic Mice

Alzheimer’s disease (AD) is the most common type of dementia and has no effective therapies. Previous studies showed that bone morphogenetic protein 9 (BMP9), an important factor in the differentiation and phenotype maintenance of cholinergic neurons, ameliorated the cholinergic defects resulting from amyloid deposition. These findings suggest that BMP9 has potential as a therapeutic agent for AD. However, the effects of BMP9 on cognitive function in AD and its underlying mechanisms remain elusive. In the present study, BMP9 was delivered intranasally to 7-month-old APP/PS1 mice for 4 weeks. Our data showed that intranasal BMP9 administration significantly improved the spatial and associative learning and memory of APP/PS1 mice. We also found that intranasal BMP9 administration significantly reduced the amyloid β (Aβ) plaques overall, inhibited tau hyperphosphorylation, and suppressed neuroinflammation in the transgenic mouse brain. Furthermore, intranasal BMP9 administration significantly promoted the expression of low-density lipoprotein receptor-related protein 1 (LRP1), an important membrane receptor involved in the clearance of amyloid β via the blood-brain barrier (BBB), and elevated the phosphorylation levels of glycogen synthase kinase-3β (Ser9), which is considered the main kinase involved in tau hyperphosphorylation. Our results suggest that BMP9 may be a promising candidate for treating AD by targeting multiple key pathways in the disease pathogenesis.

PARP inhibition in leukocytes diminishes inflammation via effects on integrins/cytoskeleton and protects the blood-brain barrier

Background

Blood-brain barrier (BBB) dysfunction/disruption followed by leukocyte infiltration into the brain causes neuroinflammation and contributes to morbidity in multiple sclerosis, encephalitis, traumatic brain injury, and stroke. The identification of pathways that decreases the inflammatory potential of leukocytes would prevent such injury. Poly(ADP-ribose) polymerase 1 (PARP) controls various genes via its interaction with myriad transcription factors. Selective PARP inhibitors have appeared lately as potent anti-inflammatory tools. Their effects are outside the recognized PARP functions in DNA repair and transcriptional regulation. In this study, we explored the idea that selective inhibition of PARP in leukocytes would diminish their engagement of the brain endothelium.

Methods

Cerebral vascular changes and leukocyte-endothelium interactions were surveyed by intravital videomicroscopy utilizing a novel in vivo model of localized aseptic meningitis when TNFα was introduced intracerebrally in wild-type (PARP^+/+) and PARP-deficient (PARP^−/−) mice. The effects of selective PARP inhibition on primary human monocytes ability to adhere to or migrate across the BBB were also tested in vitro, employing primary human brain microvascular endothelial cells (BMVEC) as an in vitro model of the BBB.

Results

PARP suppression in monocytes diminished their adhesion to and migration across BBB in vitro models and prevented barrier injury. In monocytes, PARP inactivation decreased conformational activation of integrins that plays a key role in their tissue infiltration. Such changes were mediated by suppression of activation of small Rho GTPases and cytoskeletal rearrangements in monocytes. In vitro observations were confirmed in vivo showing diminished leukocyte-endothelial interaction after selective PARP suppression in leukocytes accompanied by BBB protection. PARP knockout animals demonstrated a substantial diminution of inflammatory responses in brain microvasculature and a decrease in BBB permeability.

Conclusions

These results suggest PARP inhibition in leukocytes as a novel approach to BBB protection in the setting of endothelial dysfunction caused by inflammation-induced leukocyte engagement.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0729-x) contains supplementary material, which is available to authorized users.

Nitric Oxide Inhibitory Meroterpenoids from the Fungus Penicillium purpurogenum MHZ 111

Five new meroterpenoids, purpurogenolides A-E (1-5), and four known metabolites (6-9) were isolated from the solid substrate fermentation cultures of the fungus Penicillium purpurogenum MHz 111. The structures of the new meroterpenoids were elucidated by analysis of spectroscopic and spectrometric data (1D and 2D NMR, IR, and HRESIMS). The absolute configurations of 1 and 5 were determined by single-crystal X-ray crystallographic analysis, and those of 2-4 were elucidated on the basis of experimental and calculated electronic circular dichroism spectra. Compounds 2-4 and 6 showed inhibition of nitric oxide production in lipopolysaccharide-activated BV-2 microglial cells with IC50 values of 0.8-30.0 μM.

Mini Review: Circular RNAs as Potential Clinical Biomarkers for Disorders in the Central Nervous System

Circular RNAs (circRNAs) are a type of non-coding RNAs (ncRNAs), produced in eukaryotic cells during post-transcriptional processes. They are more stable than linear RNAs, and possess spatio-temporal properties. CircRNAs do not distribute equally in the neuronal compartments in the brain, but largely enriched in the synapses. These ncRNA species can be used as potential clinical biomarkers in complex disorders of the central nervous system (CNS), which is supported by recent findings. For example, ciRS-7 was found to be a natural microRNAs sponge for miRNA-7 and regulate Parkinson's disease/Alzheimer's disease-related genes; circPAIP2 is an intron-retaining circRNA which upregulates memory-related parental genes PAIP2 to affect memory development through PABP reactivation. The quantity of circRNAs carry important messages, either when they are inside the cells, or in circulation, or in exosomes released from synaptoneurosomes and endothelial. In addition, small molecules such as microRNAs and microvesicles can pass through the blood-brain barrier (BBB) and get into blood. For clinical applications, the study population needs to be phenotypically well-defined. CircRNAs may be combined with other biomarkers and imaging tools to improve the diagnostic power.

LPS-induced Murine Neuroinflammation Model: Main Features and Suitability for Pre-clinical Assessment of Nutraceuticals

Neuroinflammation is an important feature in the pathogenesis and progression of neurodegenerative diseases such as Alzheimer´s disease (AD), Parkinson´s disease (PD), frontotemporal dementia and amyotrophic lateral sclerosis. Based on current knowledge in the field, suggesting that targeting peripheral inflammation could be a promising additional treatment/prevention approach for neurodegenerative diseases, drugs and natural products with anti-inflammatory properties have been evaluated in animal models of neuroinflammation and neurodegeneration. In this review, we provide an extensive analysis of one of the most important and widely-used animal models of peripherally induced neuroinflammation and neurodegeneration - lipopolysaccharide (LPS)-treated mice, and address the data reproducibility in published research. We also summarize briefly basic features of various natural products, nutraceuticals, with known anti-inflammatory effects and present an overview of data on their therapeutic potential for reducing neuroinflammation in LPS-treated mice.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.