Microglial immunophenotype in dementia with Alzheimer's pathology.

BACKGROUND: Genetic risk factors for Alzheimer's disease imply that inflammation plays a causal role in development of the disease. Experimental studies suggest that microglia, as the brain macrophages, have diverse functions, with their main role in health being to survey the brain parenchyma through highly motile processes. METHODS: Using the Medical Research Council Cognitive Function and Ageing Studies resources, we have immunophenotyped microglia to investigate their role in dementia with Alzheimer's pathology. Cerebral cortex obtained at post-mortem from 299 participants was analysed by immunohistochemistry for cluster of differentiation (CD)68 (phagocytosis), human leukocyte antigen (HLA)-DR (antigen-presenting function), ionized calcium-binding adaptor molecule (Iba1) (microglial motility), macrophage scavenger receptor (MSR)-A (plaque-related phagocytosis) and CD64 (immunoglobulin Fcγ receptor I). RESULTS: The presence of dementia was associated positively with CD68 (P < 0.001), MSR-A (P = 0.010) and CD64 (P = 0.007) and negatively with Iba1 (P < 0.001). Among participants without dementia, the cognitive function according to the Mini-Mental State Examination was associated positively with Iba1 (P < 0.001) and negatively with CD68 (P = 0.033), and in participants with dementia and Alzheimer's pathology, positively with all microglial markers except Iba1. Overall, in participants without dementia, the relationship with Alzheimer's pathology was negative or not significant, and positive in participants with dementia and Alzheimer's pathology. Apolipoprotein E (APOE) ε2 allele was associated with expression of Iba1 (P = 0.001) and MSR-A (P < 0.001) and APOE ε4 with CD68, HLA-DR and CD64 (P < 0.001). CONCLUSIONS: Our findings raise the possibility that in dementia with Alzheimer's pathology, microglia lose motility (Iba-1) necessary to support neurons. Conversely, other microglial proteins (CD68, MSR-A), the role of which is clearance of damaged cellular material, are positively associated with Alzheimer's pathology and impaired cognitive function. In addition, our data imply that microglia may respond differently to Aβ and tau in participants with and without dementia so that the microglial activity could potentially influence the likelihood of developing dementia, as supported by genetic studies, highlighting the complexity and diversity of microglial responses

Deconvolving the contributions of cell-type heterogeneity on cortical gene expression

Complexity of cell-type composition has created much skepticism surrounding the interpretation of bulk tissue transcriptomic studies. Recent studies have shown that deconvolution algorithms can be applied to computationally estimate cell-type proportions from gene expression data of bulk blood samples, but their performance when applied to brain tissue is unclear. Here, we have generated an immunohistochemistry (IHC) dataset for five major cell-types from brain tissue of 70 individuals, who also have bulk cortical gene expression data. With the IHC data as the benchmark, this resource enables quantitative assessment of deconvolution algorithms for brain tissue. We apply existing deconvolution algorithms to brain tissue by using marker sets derived from human brain single cell and cell-sorted RNA-seq data. We show that these algorithms can indeed produce informative estimates of constituent cell-type proportions. In fact, neuronal subpopulations can also be estimated from bulk brain tissue samples. Further, we show that including the cell-type proportion estimates as confounding factors is important for reducing false associations between Alzheimer\u27s disease phenotypes and gene expression. Lastly, we demonstrate that using more accurate marker sets can substantially improve statistical power in detecting cell-type specific expression quantitative trait loci (eQTLs)

EVI1 triggers metabolic reprogramming associated with leukemogenesis and increases sensitivity to L-asparaginase

Metabolic reprogramming of leukemia cells is important for survival, proliferation, and drug resistance under conditions of metabolic stress in the bone marrow. Deregulation of cellular metabolism, leading to development of leukemia, occurs through abnormally high expression of transcription factors such as MYC and Ecotropic Virus Integration site 1 protein homolog (EVI1). Overexpression of EVI1 in adults and children with mixed lineage leukemia-rearrangement acute myeloid leukemia (MLL-r AML) has a very poor prognosis. To identify a metabolic inhibitor for EVI1-induced metabolic reprogramming in MLL-r AML, we used an XFp extracellular flux analyzer to examine metabolic changes during leukemia development in mouse models of AML expressing MLL-AF9 and Evi1 (Evi1/MF9). Oxidative phosphorylation (OXPHOS) in Evi1/MF9 AML cells accelerated prior to activation of glycolysis, with a higher dependency on glutamine as an energy source. Furthermore, EVI1 played a role in glycolysis as well as driving production of metabolites in the tricarboxylic acid cycle. L-asparaginase (L-asp) exacerbated growth inhibition induced by glutamine starvation and suppressed OXPHOS and proliferation of Evi1/MF9 both in vitro and in vivo; high sensitivity to L-asp was caused by low expression of asparagine synthetase (ASNS) and L-asp-induced suppression of glutamine metabolism. In addition, samples from patients with EVI1+MF9 showed low ASNS expression, suggesting that it is a sensitive marker of L-asp treatment. Clarification of metabolic reprogramming in EVI1+ leukemia cells may aid development of treatments for EVI1+MF9 refractory leukemia

BIN1 protein isoforms are differentially expressed in astrocytes, neurons, and microglia: neuronal and astrocyte BIN1 are implicated in tau pathology

Background Identified as an Alzheimer’s disease (AD) susceptibility gene by genome wide-association studies, BIN1 has 10 isoforms that are expressed in the Central Nervous System (CNS). The distribution of these isoforms in different cell types, as well as their role in AD pathology still remains unclear. Methods Utilizing antibodies targeting specific BIN1 epitopes in human post-mortem tissue and analyzing mRNA expression data from purified microglia, we identified three isoforms expressed in neurons and astrocytes (isoforms 1, 2 and 3) and four isoforms expressed in microglia (isoforms 6, 9, 10 and 12). The abundance of selected peptides, which correspond to groups of BIN1 protein isoforms, was measured in dorsolateral prefrontal cortex, and their relation to neuropathological features of AD was assessed. Results Peptides contained in exon 7 of BIN1’s N-BAR domain were found to be significantly associated with AD-related traits and, particularly, tau tangles. Decreased expression of BIN1 isoforms containing exon 7 is associated with greater accumulation of tangles and subsequent cognitive decline, with astrocytic rather than neuronal BIN1 being the more likely culprit. These effects are independent of the BIN1 AD risk variant. Conclusions Exploring the molecular mechanisms of specific BIN1 isoforms expressed by astrocytes may open new avenues for modulating the accumulation of Tau pathology in AD

Brain "Metaflammasome" and risk factors associated with Alzheimer's disease

A number of environmental and genetic risk factors have been identified for Alzheimer’s disease (AD) in addition to the well-known factors of ageing and APOE gene polymorphism. These include mainly lipid metabolism (e.g.diabetes) and inflammation. Recent evidence in models of the metabolic disorders obesity and type 2 diabetes suggest the involvement of a metabolic inflammasome (“metaflammasome”) in mediating chronic inflammation. The central component of the metaflammasome is the double-stranded RNA-dependent protein kinase (PKR), which also accumulates in AD brains. Other components of the metaflammasome include the proteins JNK, IKK?and IRS1. Chronic neuroinflammation is a key feature of AD. Therefore my hypothesis is that metabolic risk factors for AD activate a cerebral metaflammasome which, in turn, results in inflammation. To test my hypothesis, I investigated the expression of cerebral metaflammasome components in animals and humans. The effect of the absence of PKR on other metaflammasome components was studied using PKR-/- mice. In an acute model of systemic inflammation, using western blots and immunohistochemistry (IHC) methods, my study showed the absence of the expression of a cerebral metaflammasome in Wild-Type (WT) (n=8) and PKR-/- mice (n=3) at day 1. Similar results were obtained at day 3 (n=3 for both strains) by IHC. However, the results of our chronic high fat diet model (HFD), to reproduce obesity, showed in the WT obese mice (n=14), which developed type 2 diabetes and dyslipidaemia, increased expression of cerebral metaflammasome proteins compared to WT control mice (n=12). Interestingly, no significant difference in the expression of the metaflammasome was observed in PKR-/- HFD mice (n=5) compared to controls (n=4), supporting a key role for PKR in the metaflammasome. Furthermore, no development of type 2 diabetes and dyslipidaemia was found in PKR-/- HFD mice unlike in WT HFD mice. The inhibition of PKR and metaflammasome components could protect against metabolic disorders, which are known risk factors for AD.In the human study, analysis obtained by IHC on brain tissue from 298 participants in the Cognitive Function and Ageing Studies (CFAS) showed that high levels of PKR, JNK and IRS1 were significantly associated with poor cognitive function while a high level of IKK? was associated with good cognitive function (p&lt;0.05). Among participants without dementia, an increase in metaflammasome proteins was related to a lower neuropathological burden such as plaques and tangles. In contrast, among those with AD, higher levels of metaflammasome proteins were mainly associated with more severe AD pathology (p&lt;0.05). Metaflammasome proteins were positively related to hypertension in non-demented participants, but negatively in those with AD (p&lt;0.05). Regarding diabetes, metaflammasome proteins were negatively associated in both groups, except for JNK (p&lt;0.05). Interestingly, in the presence of dementia, a novel relationship was observed between JNK and IKK?. APOE genotype did not affect metaflammasome proteins. In these studies, we have demonstrated for the first time the presence of a cerebral metaflammasome in the context of metabolic disorders in animals and humans. The animal data suggest an association of the cerebral metaflammasome with metabolic disorders and support the central function of PKR in the expression of metaflammasome components. The human data show an association between the metaflammasome and metabolic disorders, cognitive function and AD pathology, and highlight the modification of relationship between JNK and IKK? during dementia.<br/

PKR modulates abnormal brain signaling in experimental obesity

data for <br><h3>PKR modulates abnormal brain signaling in experimental obesity</h3

Peripheral inflammation increases PKR activation, Tau phosphorylation and amyloid β production in wild-type mice

International audienceSystemic inflammation is correlated with dementia progression. Pro-inflammatory molecules can communicate from the periphery to the central nervous system to induce neuroinflammation and neurodegeneration. Our protein of interest is the pro-apoptotic kinase PKR (the double strand-RNA dependent protein kinase). Increased activated PKR levels were found in AD patients brain and cerebrospinal fluid. PKR activation can be triggered by inflammatory stresses and induces neurotoxicity in vitro. Is in vivo PKR-mediated inflammation involved in AD neurodegenerative process

A niche-mimicking polymer hydrogel-based approach to identify molecular targets for tackling human pancreatic cancer stem cells

Abstract Background Pancreatic adenocarcinoma (PAAD) is one of the most fatal human cancers, but effective therapies remain to be established. Cancer stem cells (CSCs) are highly resistant to anti-cancer drugs and a deeper understanding of their microenvironmental niche has been considered important to provide understanding and solutions to cancer eradication. However, as the CSC niche is composed of a wide variety of biological and physicochemical factors, the development of multidisciplinary tools that recapitulate their complex features is indispensable. Synthetic polymers have been studied as attractive biomaterials due to their tunable biofunctionalities, while hydrogelation technique further renders upon them a diversity of physical properties, making them an attractive tool for analysis of the CSC niche. Methods To develop innovative materials that recapitulate the CSC niche in pancreatic cancers, we performed polymer microarray analysis to identify niche-mimicking scaffolds that preferentially supported the growth of CSCs. The niche-mimicking activity of the identified polymers was further optimized by polyethylene glycol (PEG)-based hydrogelation. To reveal the biological mechanisms behind the activity of the optimized hydrogels towards CSCs, proteins binding onto the hydrogel were analyzed by liquid chromatography with tandem mass spectrometry (LC–MS/MS), and the potential therapeutic targets were validated by looking at gene expression and patients’ outcome in the TCGA database. Results PA531, a heteropolymer composed of 2-methoxyethyl methacrylate (MEMA) and 2-(diethylamino)ethyl methacrylate (DEAEMA) (5.5:4.5) that specifically supports the growth and maintenance of CSCs was identified by polymer microarray screening using the human PAAD cell line KLM1. The polymer PA531 was converted into five hydrogels (PA531-HG1 to HG5) and developed to give an optimized scaffold with the highest CSC niche-mimicking activities. From this polymer that recapitulated CSC binding and control, the proteins fetuin-B and angiotensinogen were identified as candidate target molecules with clinical significance due to the correlation between gene expression levels and prognosis in PAAD patients and the proteins associated with the niche-mimicking polymer. Conclusion This study screened for biofunctional polymers suitable for recapitulation of the pancreatic CSC niche and one hydrogel with high niche-mimicking abilities was successfully fabricated. Two soluble factors with clinical significance were identified as potential candidates for biomarkers and therapeutic targets in pancreatic cancers. Such a biomaterial-based approach could be a new platform in drug discovery and therapy development against CSCs, via targeting of their niche

Metaflammasome components in the human brain: a role in dementia with Alzheimer’s pathology?

Epidemiological and genetic studies have identified metabolic disorders and inflammation as risk factors for Alzheimer’s disease (AD). Evidence in obesity and type-2 diabetes suggests a role for a metabolic inflammasome (“metaflammasome”) in mediating chronic inflammation in peripheral organs implicating IKK? (inhibitor of nuclear factor kappa-B kinase subunit beta), IRS1 (insulin receptor substrate 1), JNK (c-jun N-terminal kinase), and PKR (double-stranded RNA protein kinase). We hypothesized that these proteins are expressed in the brain in response to metabolic risk factors in AD. Neocortex from 299 participants from the MRC Cognitive Function and Ageing Studies was analysed by immunohistochemistry for the expression of the phosphorylated (active) form of IKK? [pSer176/180], IRS1 [pS312], JNK [pThr183/Tyr185] and PKR [pT451]. The data were analysed to investigate whether the proteins were expressed together and in relation with metabolic disorders, dementia, Alzheimer’s pathology and APOE genotype. We observed a change from a positive to a negative association between the proteins and hypertension according to the dementia status. Type-2 diabetes was negatively related with the proteins among participants without dementia; whereas participants with dementia and AD pathology showed a positive association with JNK. A significant association between IKK? and JNK in participants with dementia and AD pathology was observed, but not in those without dementia. Otherwise, weak to moderate associations were observed among the protein loads. The presence of dementia was significantly associated with JNK and negatively associated with IKK? and IRS1. Cognitive scores showed a significant positive relationship with IKK? and a negative with IRS1, JNK and PKR. The proteins were significantly associated with pathology in Alzheimer’s participants with the relationship being inverse or not significant in participants without dementia. Expression of the proteins was not related to APOE genotype. These findings highlight a role for these proteins in AD pathophysiology but not necessarily as a complex

Additional file 4 of A niche-mimicking polymer hydrogel-based approach to identify molecular targets for tackling human pancreatic cancer stem cells

Additional file 4. PA531-HG5 binding factors