Intracerebral GM-CSF contributes to transendothelial monocyte migration in APP/PS1 Alzheimer's disease mice

Overactivation of XBP1 in plasma cells implies worse survival through innate immunity in esophageal squamous cell carcinoma

To maintain protein homeostasis, X-box binding protein 1 (XBP1) undergoes splicing following the activation of the unfolded protein response (UPR) in response to endoplasmic reticulum (ER) stress. Although targeting ER stress represents a promising therapeutic strategy, a comprehensive understanding of XBP1 at the cellular level and the link between XBP1 and the innate nervous system is lacking. Here, TCGA pancancer datasets from 33 cancer types, scRNA pancancer datasets from 454 patients and bulk RNA-seq datasets from 155 paired esophageal squamous cell carcinoma (ESCC) patients were analyzed. To cope with ER stress, plasma cells tend to activate XBP1 after undergoing bacterial infection and inflammatory signaling from the innate immune system. Patients with high XBP1 expression in their plasma cells have a higher tumor grade and worse survival. However, activation of the innate immune system with increased XBP1 expression in plasma cells correlates with an increased lymphocyte ratio, indicative of a more robust immune response. Moreover, XBP1 activation appears to initiate leukocyte migration at the transcriptional level. Our study revealed that the XBP1-induced UPR could mediate the crosstalk between optimal acquired humoral immune responses and innate immunity in ESCC.

QKL injection ameliorates Alzheimer's disease-like pathology by regulating expression of RAGE

The onset of Alzheimer's disease is related to neuron damage caused by massive deposition of Aβ in the brain. Recent studies suggest that excessive Aβ in the brain mainly comes from peripheral blood, and BBB is the key to regulate Aβ in and out of the brain. In this study, we explored the pathogenesis of AD from the perspective of Aβ transport through the BBB and the effect of QKL injection in AD mice. The results showed that QKL could improve the cognitive dysfunction of AD mice, decrease the level of Aβ and Aβ transporter-RAGE, which was supported by the results of network pharmacology, molecular docking and molecular dynamics simulation. In conclusion, RAGE is a potential target for QKL's therapeutic effect on AD.

Central and Peripheral Inflammation in Mild Cognitive Impairment in the Context of Alzheimer's Disease

Mild cognitive impairment (MCI) is characterized by an abnormal decline in mental and cognitive function compared with normal cognitive aging. It is an underlying condition of Alzheimer's disease (AD), an irreversible neurodegenerative disease. In recent years, neuroinflammation has been investigated as a new leading target that contributes to MCI progression into AD. Understanding the mechanism underlying inflammatory processes involved in the early onset of the disease could help find a safe and effective way to diagnose and treat patients. In this article, we assessed over twenty different blood and cerebrospinal fluid (CSF) inflammatory biomarker concentrations with immunoassay methods in patients with MCI (mild cognitive impairment), non-impaired control (NIC), and serum healthy control (HC). We performed group comparisons and analyzed in-group correlations between the biomarkers. We included 107 participants (mean age: 64.7 ± 7.8, women: 58.9%). CSF osteopontin and YKL-40 were significantly increased in the MCI group, whereas serum C-reactive protein and interleukin-6 were significantly higher (p < 0.001) in the NIC group compared with the MCI and HC groups. Stronger correlations between interleukin-1β and inflammasome markers were observed in the serum of the MCI group. We confirmed specific inflammatory activation in the central nervous system and interleukin-1β pathway upregulation in the serum of the MCI cohort.

TSPO Modulates Oligomeric Amyloid-β-Induced Monocyte Chemotaxis: Relevance for Neuroinflammation in Alzheimer's Disease

BACKGROUND

Neuroinflammation is one of the cardinal mechanisms of Alzheimer's disease (AD). with amyloid-β (Aβ) playing a critical role by activating microglia to produce soluble inflammatory mediators, including several chemokines. Peripheral monocytes are, therefore, attracted into the central nervous system (CNS), where they change into blood-born microglia and participate in the attempt of removing toxic Aβ species. The translocator protein-18 kDa (TSPO) is a transmembrane protein overexpressed in response to neuroinflammation and known to regulate human monocyte chemotaxis.

OBJECTIVE

We aimed to evaluate the role of the oligomeric Aβ1-42 isoform at inducing peripheral monocyte chemotaxis, and the possible involvement of TSPO in this process.

METHODS

In vitro cell lines, and ex vivo monocytes from consecutive AD patients (n = 60), and comparable cognitively intact controls (n = 30) were used. Chemotaxis analyses were carried out through both μ-slide chambers and Boyden assays, using 125 pM oligomeric Aβ1-42 as chemoattractant. TSPO agonists and antagonists were tested (Ro5-4864, Emapunil, PK11195).

RESULTS

Oligomeric Aβ directly promoted chemotaxis in all our models. Interestingly, AD monocytes displayed a stronger response (about twofold) with respect to controls. Aβ-induced chemotaxis was prevented by the TSPO antagonist PK11195; the expression of the TSPO and of the C-C chemokine receptor type 2 (CCR2) was unchanged by drug exposure.

CONCLUSION

Oligomeric Aβ1-42 is able to recruit peripheral monocytes, and we provide initial evidence sustaining a role for TSPO in modulating this process. This data may be of value for future therapeutic interventions aimed at modulating monocytes motility toward the CNS.

Identifying an Optimal Neuroinflammation Treatment Using a Nanoligomer Discovery Engine

Acute activation of innate immune response in the brain, or neuroinflammation, protects this vital organ from a range of external pathogens and promotes healing after traumatic brain injury. However, chronic neuroinflammation leading to the activation of immune cells like microglia and astrocytes causes damage to the nervous tissue, and it is causally linked to a range of neurodegenerative diseases such as Alzheimer's diseases (AD), Multiple Sclerosis (MS), Parkinson's disease (PD), and many others. While neuroinflammation is a key target for a range of neuropathological diseases, there is a lack of effective countermeasures to tackle it, and existing experimental therapies require fairly invasive intracerebral and intrathecal delivery due to difficulty associated with the therapeutic crossover between the blood-brain barrier, making such treatments impractical to treat neuroinflammation long-term. Here, we present the development of an optimal neurotherapeutic using our Nanoligomer Discovery Engine, by screening downregulation of several proinflammatory cytokines (e.g., Interleukin-1β or IL-1β, tumor necrosis factor-alpha or TNF-α, TNF receptor 1 or TNFR1, Interleukin 6 or IL-6), inflammasomes (e.g., NLRP1), key transcription factors (e.g., nuclear factor kappa-B or NF-κβ) and their combinations, as upstream regulators and canonical pathway targets, to identify and validate the best-in-class treatment. Using our high-throughput drug discovery, target validation, and lead molecule identification via a bioinformatics and artificial intelligence-based ranking method to design sequence-specific peptide molecules to up- or downregulate gene expression of the targeted gene at will, we used our discovery engine to perturb and identify most effective upstream regulators and canonical pathways for therapeutic intervention to reverse neuroinflammation. The lead neurotherapeutic was a combination of Nanoligomers targeted to NF-κβ (SB.201.17D.8_NF-κβ1) and TNFR1 (SB.201.18D.6_TNFR1), which were identified using in vitro cell-based screening in donor-derived human astrocytes and further validated in vivo using a mouse model of lipopolysaccharide (LPS)-induced neuroinflammation. The combination treatment SB_NI_111 was delivered without any special formulation using a simple intraperitoneal injection of low dose (5 mg/kg) and was found to significantly suppress the expression of LPS-induced neuroinflammation in mouse hippocampus. These results point to the broader applicability of this approach towards the development of therapies for chronic neuroinflammation-linked neurodegenerative diseases, sleep countermeasures, and others, and the potential for further investigation of the lead neurotherapeutic molecule as reversible gene therapy.

Impaired spatial navigation and age-dependent hippocampal synaptic dysfunction are associated with chronic inflammatory response in db/db mice

Type 2 diabetes mellitus (T2DM) increases the risk of developing Alzheimer's disease (AD), which has been proposed to be driven by an abnormal neuroinflammatory response affecting cognitive function. However, the impact of T2DM on hippocampal function and synaptic integrity during aging has not been investigated. Here, we investigated the effects of aging in T2DM on AD-like pathology using the leptin receptor-deficient db/db mouse model of T2DM. Our results indicate that adult T2DM mice exhibited impaired spatial acquisition in the Morris water maze (MWM). Morphological analysis showed an age-dependent neuronal loss in the dentate gyrus. We found that astrocyte density was significantly decreased in all regions of the hippocampus in T2DM mice. Our analysis showed that microglial activation was increased in the CA3 and the dentate gyrus of the hippocampus in an age-dependent manner in T2DM mice. However, the expression of presynaptic marker protein (synaptophysin) and the postsynaptic marker protein [postsynaptic density protein 95 (PSD95)] was unchanged in the hippocampus of adult T2DM mice. Interestingly, synaptophysin and PSD95 expression significantly decreased in the hippocampus of aged T2DM mice, suggesting an impaired hippocampal synaptic integrity. Cytokine profiling analysis displayed a robust pro-inflammatory cytokine profile in the hippocampus of aged T2DM mice compared with the younger cohort, outlining the role of aging in exacerbating the neuroinflammatory profile in the diabetic state. Our results suggest that T2DM impairs cognitive function by promoting neuronal loss in the dentate gyrus and triggering an age-dependent deterioration in hippocampal synaptic integrity, associated with an aberrant neuroinflammatory response.

Neuroinflammation: Extinguishing a blaze of T cells

Inflammation is a biological process that dynamically alters the surrounding microenvironment, including participating immune cells. As a well-protected organ surrounded by specialized barriers and with immune privilege properties, the central nervous system (CNS) tightly regulates immune responses. Yet in neuroinflammatory conditions, pathogenic immunity can disrupt CNS structure and function. T cells in particular play a key role in promoting and restricting neuroinflammatory responses, while the inflamed CNS microenvironment can influence and reshape T cell function and identity. Still, the contraction of aberrant T cell responses within the CNS is not well understood. Using autoimmunity as a model, here we address the contribution of CD4 T helper (Th) cell subsets in promoting neuropathology and disease. To address the mechanisms antagonizing neuroinflammation, we focus on the control of the immune response by regulatory T cells (Tregs) and describe the counteracting processes that preserve their identity under inflammatory challenges. Finally, given the influence of the local microenvironment on immune regulation, we address how CNS-intrinsic signals reshape T cell function to mitigate abnormal immune T cell responses.

Blood-brain barrier leakage in Alzheimer's disease: From discovery to clinical relevance

Alzheimer's disease (AD) is the most common form of dementia. AD brain pathology starts decades before the onset of clinical symptoms. One early pathological hallmark is blood-brain barrier dysfunction characterized by barrier leakage and associated with cognitive decline. In this review, we summarize the existing literature on the extent and clinical relevance of barrier leakage in AD. First, we focus on AD animal models and their susceptibility to barrier leakage based on age and genetic background. Second, we re-examine barrier dysfunction in clinical and postmortem studies, summarize changes that lead to barrier leakage in patients and highlight the clinical relevance of barrier leakage in AD. Third, we summarize signaling mechanisms that link barrier leakage to neurodegeneration and cognitive decline in AD. Finally, we discuss clinical relevance and potential therapeutic strategies and provide future perspectives on investigating barrier leakage in AD. Identifying mechanistic steps underlying barrier leakage has the potential to unravel new targets that can be used to develop novel therapeutic strategies to repair barrier leakage and slow cognitive decline in AD and AD-related dementias.

A novel approach to type 3 diabetes mechanism: The interplay between noncoding RNAs and insulin signaling pathway in Alzheimer's disease

Today, growing evidence indicates that patients with type 2 diabetes (T2D) are at a higher risk of developing Alzheimer's disease (AD). Indeed, AD as one of the main causes of dementia in people aged more than 65 years can be aggravated by insulin resistance (IR) and other metabolic risk factors related to T2D which are also linked to the function of the brain. Remarkably, a new term called "type 3 diabetes" has been suggested for those people who are diagnosed with AD while also showing the symptoms of IR and T2D. In this regard, the role of genetic and epigenetic changes associated with AD has been confirmed by many studies. On the other hand, it should be noted that the insulin signaling pathway is highly regulated by various mechanisms, including epigenetic factors. Among these, the role of noncoding RNAs (ncRNAs), including microRNAs and long noncoding RNAs has been comprehensively studied with respect to the pathology of AD and the most well-known underlying mechanisms. Nevertheless, the number of studies exploring the association between ncRNAs and the downstream targets of the insulin signaling pathway in the development of AD has notably increased in recent years. With this in view, the present study aimed to review the interplay between different ncRNAs and the insulin signaling pathway targets in the pathogenesis of AD to find a new approach in the field of combining biomarkers or therapeutic targets for this disease.

Regulation of Th17/Treg Balance by 27-Hydroxycholesterol and 24S-Hydroxycholesterol Correlates with Learning and Memory Ability in Mice

Dysregulation of cholesterol metabolism and its oxidative products-oxysterols-in the brain is known to be associated with neurodegenerative diseases. It is well-known that 27-hydroxycholesterol (27-OHC) and 24S-hydroxycholesterol (24S-OHC) are the main oxysterols contributing to the pathogenesis of Alzheimer's disease (AD). However, the molecular mechanism of how 27-OHC and 24S-OHC cause cognitive decline remains unclear. To verify whether 27-OHC and 24S-OHC affect learning and memory by regulating immune responses, C57BL/6J mice were subcutaneously injected with saline, 27-OHC, 24S-OHC, 27-OHC+24S-OHC for 21 days. The oxysterols level and expression level of related metabolic enzymes, as well as the immunomodulatory factors were measured. Our results indicated that 27-OHC-treated mice showed worse learning and memory ability and higher immune responses, but lower expression level of interleukin-10 (IL-10) and interferon (IFN-λ2) compared with saline-treated mice, while 24S-OHC mice performed better in the Morris water maze test than control mice. No obvious morphological lesion was observed in these 24S-OHC-treated mice. Moreover, the expression level of interleukin-17A (IL-17A), granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage inflammatory protein 3α (MIP-3α) were significantly decreased after 24S-OHC treatment. Notably, compared with 27-OHC group, mice treated with 27-OHC+24S-OHC showed higher brain 24S-OHC level, accompanied by increased CYP46A1 expression level while decreased CYP7B1, retinoic acid-related orphan receptor gamma t (RORγt) and IL-17A expression level. In conclusion, our study indicated that 27-OHC is involved in regulating the expression of RORγt, disturbing Th17/Treg balance-related immune responses which may be associated with the learning and memory impairment in mice. In contrast, 24S-OHC is neuroprotective and attenuates the neurotoxicity of 27-OHC.

Interconnections between Inflammageing and Immunosenescence during Ageing

Acute inflammation is a physiological response to injury or infection, with a cascade of steps that ultimately lead to the recruitment of immune cells to clear invading pathogens and heal wounds. However, chronic inflammation arising from the continued presence of the initial trigger, or the dysfunction of signalling and/or effector pathways, is harmful to health. While successful ageing in older adults, including centenarians, is associated with low levels of inflammation, elevated inflammation increases the risk of poor health and death. Hence inflammation has been described as one of seven pillars of ageing. Age-associated sterile, chronic, and low-grade inflammation is commonly termed inflammageing-it is not simply a consequence of increasing chronological age, but is also a marker of biological ageing, multimorbidity, and mortality risk. While inflammageing was initially thought to be caused by "continuous antigenic load and stress", reports from the last two decades describe a much more complex phenomenon also involving cellular senescence and the ageing of the immune system. In this review, we explore some of the main sources and consequences of inflammageing in the context of immunosenescence and highlight potential interventions. In particular, we assess the contribution of cellular senescence to age-associated inflammation, identify patterns of pro- and anti-inflammatory markers characteristic of inflammageing, describe alterations in the ageing immune system that lead to elevated inflammation, and finally assess the ways that diet, exercise, and pharmacological interventions can reduce inflammageing and thus, improve later life health.

Colony stimulating factors in the nervous system

Although traditionally seen as regulators of hematopoiesis, colony-stimulating factors (CSFs) have emerged as important players in the nervous system, both in health and disease. This review summarizes the cellular sources, patterns of expression and physiological roles of the macrophage (CSF-1, IL-34), granulocyte-macrophage (GM-CSF) and granulocyte (G-CSF) colony stimulating factors within the nervous system, with a particular focus on their actions on microglia. CSF-1 and IL-34, via the CSF-1R, are required for the development, proliferation and maintenance of essentially all CNS microglia in a temporal and regional specific manner. In contrast, in steady state, GM-CSF and G-CSF are mainly involved in regulation of microglial function. The alterations in expression of these growth factors and their receptors, that have been reported in several neurological diseases, are described and the outcomes of their therapeutic targeting in mouse models and humans are discussed.

Improved Spatial Memory And Neuroinflammatory Profile Changes in Aged Rats Submitted to Photobiomodulation Therapy

Recent evidences have shown the therapeutic potential of transcranial photobiomodulation on traumatic brain injury and Alzheimer's disease. Despite the promising benefits in the brain, little is known about the laser's effects in the absence of pathological conditions. We submitted young (4 months old) and aged (20 months old) rats to transcranial low-level laser and evaluated their exploratory activity and habituation in open field, anxiety in elevated plus maze, spatial memory in Barnes maze, and aversive memory in a step-down inhibitory avoidance task. Additionally, the levels of a panel of inflammatory cytokines and chemokines were quantified in two different brain regions: the cerebral cortex and the hippocampus. Young and aged rats submitted to transcranial laser exhibited better cognitive performance in Barnes maze than did control rats. Transcranial laser therapy decreased cortical levels of GM-CSF, IL-10, MCP-1, LIX, and TNFα in young rats and IL-5 in aged rats. High levels of IL-6, IL-10, and TNF-alpha were found in the cerebral cortex of aged rats submitted to transcranial laser. In the hippocampus, a decrease in IP-10 and fractalkine levels was observed in the aged rats from the laser group when compared to the aged rats from the control group. Our data indicate that transcranial photobiomodulation improves spatial learning and memory and alters the neuroinflammatory profile of young and aged rats' brains.

Blood-brain barrier integrity is the primary target of alcohol abuse

The effects of long-term alcohol consumptions on cognitive function remain elusive with contradictory results. Whilst it is widely accepted that long-term intoxication can cause cognitive impairment, moderate drinking can improve cognitive function. In reality, many older people and those with chronic medical conditions are long-term alcohol consumers in Asian countries. Our previous studies have suggested that long-term alcohol consumption can damage blood-brain barrier (BBB) integrity and aggravate cognitive deficit in APPswe/PS1De9 mice, but little is known about the underlying mechanisms, especially whether this consumption can cause cognitive decline via aggravating BBB damage in people who are exposed to the risk factors for cognitive disorders such as aging or inflammation. These questions were addressed in this study. The mouse models of cognitive deficit induced by d-galactose or lipopolysaccharide, the important risk conditions in human on cognitive function, were used to evaluate the effects of long-term alcohol consumption on the BBB integrity. After alcohol administration for 30 days in these models the BBB integrity was significantly destroyed with remarkably increased permeability and down-regulated protein expression of zonula occludens-1, VE-cadherin, occludin, low-density lipoprotein receptor-related protein-1, receptor for advanced glycation end products, major facilitator superfamily domain-containing protein-2a and aquaporin-4, which is the most closely related with the structure and function of BBB integrity. Meanwhile, the level of oxidative stress in d-galactose mice or inflammatory factors in cortex and serum in lipopolysaccharide mice, which might be involved in the cognitive dysfunctions, was significantly amplified. Furthermore, the impaired memory and hippocampal neuron damage induced by d-galactose and lipopolysaccharide were concurrently aggravated. Collectively, our study provided novel and compelling evidence that the structural and functional proteins for BBB integrity may be the primary targets for the detrimental effects of alcohol abuse that lead to cognitive dysfunction and neurological deficits in high risk populations.

Integrative Identification of Hub Genes Associated With Immune Cells in Atrial Fibrillation Using Weighted Gene Correlation Network Analysis

Background: Atrial fibrillation (AF) is the most common tachyarrhythmia in the clinic, leading to high morbidity and mortality. Although many studies on AF have been conducted, the molecular mechanism of AF has not been fully elucidated. This study was designed to explore the molecular mechanism of AF using integrative bioinformatics analysis and provide new insights into the pathophysiology of AF. Methods: The GSE115574 dataset was downloaded, and Cibersort was applied to estimate the relative expression of 22 kinds of immune cells. Differentially expressed genes (DEGs) were identified through the limma package in R language. Weighted gene correlation network analysis (WGCNA) was performed to cluster DEGs into different modules and explore relationships between modules and immune cell types. Functional enrichment analysis was performed on DEGs in the significant module, and hub genes were identified based on the protein-protein interaction (PPI) network. Hub genes were then verified using quantitative real-time polymerase chain reaction (qRT-PCR). Results: A total of 2,350 DEGs were identified and clustered into eleven modules using WGCNA. The magenta module with 246 genes was identified as the key module associated with M1 macrophages with the highest correlation coefficient. Three hub genes (CTSS, CSF2RB, and NCF2) were identified. The results verified using three other datasets and qRT-PCR demonstrated that the expression levels of these three genes in patients with AF were significantly higher than those in patients with SR, which were consistent with the bioinformatic analysis. Conclusion: Three novel genes identified using comprehensive bioinformatics analysis may play crucial roles in the pathophysiological mechanism in AF, which provide potential therapeutic targets and new insights into the treatment and early detection of AF.

CXC chemokine ligand 5 (CXCL5) disrupted the permeability of human brain microvascular endothelial cells via regulating p38 signal

The ischemia-reperfusion-induced damage in human brain microvascular endothelial cells (BMECs) is associated with disruption of the blood-brain barrier. CXC chemokine ligand 5 (CXCL5) is reported to be up-regulated in ischemic stroke. However, the detailed function of CXCL5 in this pathological process remains largely unclear. To further analyze the function of CXCL5 in ischemic stroke, an oxygen-glucose deprivation model on human BMECs was constructed to mimic the ischemic stroke condition in vitro. Cell proliferation was analyzed using a cell counting kit-8 (CCK-8) assay. Quantitative real-time polymerase chain reaction and western blot were utilized to determine gene expression. The barrier function of BMECs was assessed using a fluorescently labeled dextran assay and a trans-epithelial/endothelial electrical resistance (TEER) technique. The results indicated that CXCL5 antibody (anti-CXCL5) promoted the proliferation of model cells, whereas it reduced the permeability. Moreover, the TEER value of model cells was enhanced in the presence of anti-CXCL5. Therefore, these findings demonstrated that CXCL5 silencing attenuated the ischemic/hypoxic-induced injury in human BMECs. Importantly, human recombinant protein CXCL5 (Re-CXCL5) deeply disrupted the function of BMECs in the normoxic condition. Furthermore, the p38 inhibitor SB203580 significantly abolished the function of CXCL5 in model cells. More importantly, similar results were also obtained in BMECs under normoxic conditions in the presence of Re-CXCL5. These results indicated that CXCL5 might regulate the function of BMECs by mediating the p38 pathway. This investigation not only enhanced the understanding of the biological effect of CXCL5 in human BMECs under ischemic/hypoxic conditions but also indicated its potential value as a therapeutic target for ischemic-induced brain disease.

Integrative genomics approach identifies conserved transcriptomic networks in Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurological disorder characterized by changes in cell-type proportions and consequently marked alterations of the transcriptome. Here we use a data-driven systems biology meta-analytical approach across three human AD cohorts, encompassing six cortical brain regions, and integrate with multi-scale datasets comprising of DNA methylation, histone acetylation, transcriptome- and genome-wide association studies and quantitative trait loci to further characterize the genetic architecture of AD. We perform co-expression network analysis across more than 1200 human brain samples, identifying robust AD-associated dysregulation of the transcriptome, unaltered in normal human aging. We assess the cell-type specificity of AD gene co-expression changes and estimate cell-type proportion changes in human AD by integrating co-expression modules with single-cell transcriptome data generated from 27 321 nuclei from human postmortem prefrontal cortical tissue. We also show that genetic variants of AD are enriched in a microglial AD-associated module and identify key transcription factors regulating co-expressed modules. Additionally, we validate our results in multiple published human AD gene expression datasets, which can be easily accessed using our online resource (https://swaruplab.bio.uci.edu/consensusAD).

In vivo T1 mapping for quantifying glymphatic system transport and cervical lymph node drainage

Dynamic contrast-enhanced magnetic resonance imaging (MRI) for tracking glymphatic system transport with paramagnetic contrast such as gadoteric acid (Gd-DOTA) administration into cerebrospinal fluid (CSF) requires pre-contrast data for proper quantification. Here we introduce an alternative approach for glymphatic system quantification in the mouse brain via T1 mapping which also captures drainage of Gd-DOTA to the cervical lymph nodes. The Gd-DOTA injection into CSF was performed on the bench after which the mice underwent T1 mapping using a 3D spoiled gradient echo sequence on a 9.4 T MRI. In Ketamine/Xylazine (KX) anesthetized mice, glymphatic transport and drainage of Gd-DOTA to submandibular and deep cervical lymph nodes was demonstrated as 25–50% T1 reductions in comparison to control mice receiving CSF saline. To further validate the T1 mapping approach we also verified increased glymphatic transport of Gd-DOTA transport in mice anesthetized with KX in comparison with ISO. The novel T1 mapping method allows for quantification of glymphatic transport as well as drainage to the deep and superficial cervical lymph nodes. The ability to measure glymphatic transport and cervical lymph node drainage in the same animal longitudinally is advantageous and time efficient and the coupling between the two systems can be studied and translated to human studies.

Monocytes in the Peripheral Clearance of Amyloid-β and Alzheimer's Disease

Aging societies have high incidence rates of Alzheimer's disease (AD). AD is diagnosed at later disease stages and has a poor prognosis, and effective drugs and treatments for AD are lacking. The molecular mechanism of AD is not clear, and current research focuses primarily on amyloid-β (Aβ) deposition and tau protein hyperphosphorylation. Aβ deposition is the most frequently hypothesized initiating factor of AD, and Aβ clearance during the pathogenesis of AD may be an optional strategy to suppress AD development. Monocytes play important roles in the peripheral clearance of Aβ. Therefore, the present review summarizes our current knowledge of the potential roles of infiltrating macrophages, circulating monocytes, and Kupffer cells in the peripheral clearance of Aβ in AD.

Inter-Tumor Heterogeneity-Melanomas Respond Differently to GM-CSF-Mediated Activation

Granulocyte-monocyte colony stimulating factor (GM-CSF) is used as an adjuvant in various clinical and preclinical studies with contradictory results. These were attributed to opposing effects of GM-CSF on the immune or myeloid systems of the treated patients or to lack of optimal dosing regimens. The results of the present study point to inter-tumor heterogeneity as a possible mechanism accounting for the contrasting responses to GM-CSF incorporating therapies. Employing xenograft models of human melanomas in nude mice developed in our lab, we detected differential functional responses of melanomas from different patients to GM-CSF both in vitro as well as in vivo. Whereas cells of one melanoma acquired pro metastatic features following exposure to GM-CSF, cells from another melanoma either did not respond or became less malignant. We propose that inter-melanoma heterogeneity as manifested by differential responses of melanoma cells (and perhaps also of other tumor) to GM-CSF may be developed into a predictive marker providing a tool to segregate melanoma patients who will benefit from GM-CSF therapy from those who will not.

TRA2A-induced upregulation of LINC00662 regulates blood-brain barrier permeability by affecting ELK4 mRNA stability in Alzheimer's microenvironment

The blood-brain barrier (BBB) plays a pivotal role in the maintenance and regulation of the neural microenvironment. The BBB breakdown is a pathological change in early Alzheimer's disease (AD). RNA-binding proteins (RBPs) and long non-coding RNAs (lncRNAs) are involved in the regulation of BBB permeability. Our study demonstrates the role of TRA2A/LINC00662/ELK4 axis in regulating BBB permeability in AD microenvironment. In Aβ_1-42-incubated microvascular endothelial cells (ECs) of the BBB model in vitro, TRA2A and LINC00662 were enriched. TRA2A increased the stability of LINC00662 by binding with it. The knockdown of either TRA2A or LINC00662 decreased BBB permeability due to increased expression of tight junction-related proteins. ELK4 was less expressed in the BBB model in AD microenvironment in vitro. LINC00662 mediated the degradation of ELK4 mRNA by SMD pathway. Downregulation of ELK4 increased BBB permeability by increasing the tight junction-related protein expression.TRA2A/LINC00662/ELK4 axis plays a crucial role in the regulation of BBB permeability in AD microenvironment, which may provide a novel target for the therapy of AD.

Effects of RO27-3225 on neurogenesis, PDGFRβ+ cells and neuroinflammation after cerebral infarction

Cerebral infarction causes severe social and economic burdens to patients due to its high morbidity and mortality rates, and the available treatments are limited. RO27-3225 is a highly selective melanocortin receptor 4 agonist that alleviates damage in many nervous system diseases, such as cerebral hemorrhage, traumatic brain injury and chronic neurodegenerative diseases. However, the effect of RO27-3225 on cerebral infarction remains unclear. In this study, we used a mouse model of transient middle cerebral artery occlusion (tMCAO) and administered RO27-3225 or saline to the mice through intraperitoneal injection. RO27-3225 increased the number of Nestin⁺/BrdU⁺ cells and doublecortin (DCX)⁺/BrdU⁺ cells in the subventricular zone (SVZ) and the number of DCX⁺/BrdU⁺ cells in the peri-infarct area on day 7 after tMCAO. Furthermore, RO27-3225 decreased the number of activated microglia (Iba1⁺ cells with a specific morphology) and the expression levels of Iba1, TNFα, IL6, and iNOS proteins and increased the number of PDGFRβ⁺ cells in the peri-infarct region on day 3 after tMCAO. Finally, RO27-3225-treated mice exhibited significantly decreased infarct volumes, brain water contents, and neurological deficits after cerebral infarction. Thus, RO27-3225 can improve the outcomes following cerebral infarction, partially by regulating neurogenesis in the SVZ, PDGFRβ⁺ cell survival and neuroinflammation in the peri-infarct zone. Our research reveals that RO27-3225 is a potential new treatment for cerebral infarction.

Amyloid beta and diabetic pathology cooperatively stimulate cytokine expression in an Alzheimer's mouse model

BACKGROUND

Diabetes is a risk factor for developing Alzheimer's disease (AD); however, the mechanism by which diabetes can promote AD pathology remains unknown. Diabetes results in diverse molecular changes in the brain, including dysregulation of glucose metabolism and loss of cerebrovascular homeostasis. Although these changes have been associated with increased Aβ pathology and increased expression of glial activation markers in APPswe/PS1dE9 (APP/PS1) mice, there has been limited characterization, to date, of the neuroinflammatory changes associated with diabetic conditions.

METHODS

To more fully elucidate neuroinflammatory changes associated with diabetes that may drive AD pathology, we combined the APP/PS1 mouse model with either high-fat diet (HFD, a model of pre-diabetes), the genetic db/db model of type 2 diabetes, or the streptozotocin (STZ) model of type 1 diabetes. We then used a multiplexed immunoassay to quantify cortical changes in cytokine proteins.

RESULTS

Our analysis revealed that pathology associated with either db/db, HFD, or STZ models yielded upregulation of a broad profile of cytokines, including chemokines (e.g., MIP-1α, MIP-1β, and MCP-1) and pro-inflammatory cytokines, including IL-1α, IFN-γ, and IL-3. Moreover, multivariate partial least squares regression analysis showed that combined diabetic-APP/PS1 models yielded cooperatively enhanced expression of the cytokine profile associated with each diabetic model alone. Finally, in APP/PS1xdb/db mice, we found that circulating levels of Aβ1-40, Aβ1-42, glucose, and insulin all correlated with cytokine expression in the brain, suggesting a strong relationship between peripheral changes and brain pathology.

CONCLUSIONS

Altogether, our multiplexed analysis of cytokines shows that Alzheimer's and diabetic pathologies cooperate to enhance profiles of cytokines reported to be involved in both diseases. Moreover, since many of the identified cytokines promote neuronal injury, Aβ and tau pathology, and breakdown of the blood-brain barrier, our data suggest that neuroinflammation may mediate the effects of diabetes on AD pathogenesis. Therefore, strategies targeting neuroinflammatory signaling, as well as metabolic control, may provide a promising strategy for intervening in the development of diabetes-associated AD.

Nanotargeting of Drug(s) for Delaying Dementia: Relevance of Covid-19 Impact on Dementia

By incorporating appropriate drug(s) into lipid (biobased) nanocarriers, one obtains a combination therapeutic for dementia treatment that targets certain cell-surface scavenger receptors (mainly class B type I, or "SR-BI") and thereby crosses the blood-brain barrier. The cardiovascular risk factors for dementia trigger widespread inflammation -- which lead to neurodegeneration, gradual cognitive/memory decline, and eventually (late-onset) dementia. Accordingly, one useful strategy to delay dementia could be based upon nanotargeting drug(s), using lipid nanocarriers, toward a major receptor class responsible for inflammation-associated (cytokine-mediated) cell signaling events. At the same time, the immune response and excessive inflammation, commonly observed in the very recent human coronavirus (COVID-19) pandemic, may accelerate the progression of brain inflammatory neurodegeneration-which increases the probability of post-infection memory impairment and accelerating progression of Alzheimer's disease. Hence, the proposed multitasking combination therapeutic, using a (biobased) lipid nanocarrier, may also display greater effectiveness at different stages of dementia.

Alpha-hemolysin of uropathogenic Escherichia coli induces GM-CSF-mediated acute kidney injury

Uropathogenic Escherichia coli (UPEC) is the leading cause of urinary tract infections (UTIs), inducing acute pyelonephritis and may result in permanent renal scarring and failure. Alpha-hemolysin (HlyA), a key UPEC toxin, causes serious tissue damage; however, the mechanism through which HlyA induces kidney injury remains unclear. In the present study, granulocyte-macrophage colony-stimulating factor (GM-CSF) secreted by renal epithelial cells was upregulated by HlyA in vitro and in vivo, which induced M1 macrophage accumulation in kidney, and ADAM10 was found involved in HlyA-induced GM-CSF. Macrophage elimination or GM-CSF neutralization protected against acute kidney injury in mice, and increased GM-CSF was detected in urine of patients infected by hlyA-positive UPEC. In addition, HlyA was found to promote UPEC invasion into renal epithelial cells by interacting with Nectin-2 in vitro. However, HlyA did not affect bacterial titers during acute kidney infections, and HlyA-induced invasion did not contribute to GM-CSF upregulation in vitro, which indicate that HlyA-induced GM-CSF is independent of bacteria invasion. The role of GM-CSF in HlyA-mediated kidney injury may lead to novel strategies to treat acute pyelonephritis.

Astrocyte-Derived Paracrine Signals: Relevance for Neurogenic Niche Regulation and Blood-Brain Barrier Integrity

Astrocytes are essential for proper regulation of the central nervous system (CNS). Importantly, these cells are highly secretory in nature. Indeed they can release hundreds of molecules which play pivotal physiological roles in nervous tissues and whose abnormal regulation has been associated with several CNS disorders. In agreement with these findings, recent studies have provided exciting insights into the key contribution of astrocyte-derived signals in the pleiotropic functions of these cells in brain health and diseases. In the future, deeper analysis of the astrocyte secretome is likely to further increase our current knowledge on the full potential of these cells and their secreted molecules not only as active participants in pathophysiological events, but as pharmacological targets or even as therapeutics for neurological and psychiatric diseases. Herein we will highlight recent findings in our and other laboratories on selected molecules that are actively secreted by astrocytes and contribute in two distinct functions with pathophysiological relevance for the astroglial population: i) regulation of neural stem cells (NSCs) and their progeny within adult neurogenic niches; ii) modulation of the blood–brain barrier (BBB) integrity and function.

Role of Blood-Brain Barrier in Alzheimer's Disease

The blood-brain barrier (BBB) is involved in the pathogenesis of Alzheimer's disease (AD). BBB is a highly selective semipermeable structural and chemical barrier which ensures a stable internal environment of the brain and prevents foreign objects invading the brain tissue. BBB dysfunction induces the failure of Aβ transport from brain to the peripheral circulation across the BBB. Especially, decreased levels of LRP-1 (low density lipoprotein receptor-related protein 1) and increased levels of RAGE (receptor for advanced glycation endproducts) at the BBB can cause the failure of Aβ transport. The pathogenesis of AD is related to the BBB structural components, including pericytes, astrocytes, vascular endothelial cells, and tight junctions. BBB dysfunction will trigger neuroinflammation and oxidative stress, then enhance the activity of β-secretase and γ-secretase, and finally promote Aβ generation. A progressive accumulation of Aβ in brain and BBB dysfunction may become a feedback loop that gives rise to cognitive impairment and the onset of dementia. The correlation between BBB dysfunction and tau pathology has been well-reported. Therefore, regulating BBB function may be a new therapeutic target for treating AD.

Roles of GM-CSF in the Pathogenesis of Autoimmune Diseases: An Update

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was first described as a growth factor that induces the differentiation and proliferation of myeloid progenitors in the bone marrow. GM-CSF also has an important cytokine effect in chronic inflammatory diseases by stimulating the activation and migration of myeloid cells to inflammation sites, promoting survival of target cells and stimulating the renewal of effector granulocytes and macrophages. Because of these pro-cellular effects, an imbalance in GM-CSF production/signaling may lead to harmful inflammatory conditions. In this context, GM-CSF has a pathogenic role in autoimmune diseases that are dependent on cellular immune responses such as multiple sclerosis (MS) and rheumatoid arthritis (RA). Conversely, a protective role has also been described in other autoimmune diseases where humoral responses are detrimental such as myasthenia gravis (MG), Hashimoto's thyroiditis (HT), inflammatory bowel disease (IBD), and systemic lupus erythematosus (SLE). In this review, we aimed for a comprehensive analysis of literature data on the multiple roles of GM-CSF in autoimmue diseases and possible therapeutic strategies that target GM-CSF production.

The antidepressant effects of GM-CSF are mediated by the reduction of TLR4/NF-ĸB-induced IDO expression

BACKGROUND

Indoleamine 2, 3-dioxygenase 1 (IDO) is responsible for the progression of the kynurenine pathway. This pathway has been implicated in the pathophysiology of inflammation-induced depression in which conventional antidepressants are not effective. It has been reported that granulocyte-macrophage stimulating factor (GM-CSF) could interfere with the induction of IDO in septic patients. We hypothesized that GM-CSF could exert antidepressant effects through IDO downregulation in a model for acute inflammation-induced depression.

METHODS

To produce the model, lipopolysaccharide (LPS) (0.83 mg/kg) was administered intraperitoneally to mice. It has been well documented that LPS mediates IDO overexpression through TLR4/NF-ĸB signaling. In the treatment group, mice received GM-CSF (30 μg/kg, i.p.) thirty minutes prior to LPS injection. A validated selective serotonin reuptake inhibitor, fluoxetine (30 mg/kg i.p.), was also administered to an experimental group 30 min prior to LPS. Depressive-like behaviors were evaluated based on the duration of immobility in the forced swim test. To confirm that GM-CSF interferes with IDO induction in LPS treated mice, real-time PCR was used to quantify IDO mRNA expression. Furthermore, in order to study whether GM-CSF inhibits the TLR4/NF-ĸB signaling pathway, we measured levels ofpNF-ĸB and TLR4 by western blotting.

RESULTS

GM-CSF demonstrated significant antidepressant activity in the presence of LPS on immobility (p < .001) and latency (p = .010) times in the forced swim test. In contrast, fluoxetine did not show any antidepressant activity on either immobility (p = .918) or latency (p = .566) times. Furthermore, GM-CSF inhibited the increase in IDO mRNA (p = .032) and protein (p = .016) expression as a result of LPS administration. A similar trend was observed for TLR4 (p = .042) and pNF-ĸB (p = .026) expression as both proteins showed reduced expression levels in the GM-CSF-pretreated group compared to the untreated (LPS) group.

CONCLUSION

Our results propose a promising antidepressant effect for GM-CSF possibly through the downregulation of IDO expression. This remedying effect of GM-CSF could be attributed to decreased amounts of TLR4 and active NF-ĸB in the treated mice.

Resistin-Inhibited Neural Stem Cell-Derived Astrocyte Differentiation Contributes to Permeability Destruction of the Blood-Brain Barrier

Neuroinflammation is an important part of the development of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's and amyotrophic lateral sclerosis. Inflammatory factors destroy the balance of the microenvironment, which results in changes in neural stem cell differentiation and proliferation behaviour. However, the mechanism underlying inflammatory factor-induced NSC behavioural changes is not clear. Resistin is a proinflammatory and adipogenic factor and is involved in several human pathology processes. The neural stem cell microenvironment changes when the concentration of resistin in the brain during an inflammatory response disease increases. In the present study, we explored the effect and mechanism of resistin on the proliferation and differentiation of neural stem cells. We found that intracerebroventricular injection of resistin induced a decrease in GFAP-positive cells in mice by influencing NSC differentiation. Resistin significantly decreased TEER and increased permeability in an in vitro blood-brain barrier model, which is consistent with the results of an HBMEC-astrocyte coculture system. Resistin-inhibited astrocyte differentiation is mediated through TLR4 on neural stem cells. To our knowledge, this is the first study reporting the effect of resistin on neural stem cells. Our findings shed light on resistin-involved neural stem cell degeneration mechanisms.

Role of the β Common (βc) Family of Cytokines in Health and Disease

The β common ([βc]/CD131) family of cytokines comprises granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5, all of which use βc as their key signaling receptor subunit. This is a prototypic signaling subunit-sharing cytokine family that has unveiled many biological paradigms and structural principles applicable to the IL-2, IL-4, and IL-6 receptor families, all of which also share one or more signaling subunits. Originally identified for their functions in the hematopoietic system, the βc cytokines are now known to be truly pleiotropic, impacting on multiple cell types, organs, and biological systems, and thereby controlling the balance between health and disease. This review will focus on the emerging biological roles for the βc cytokines, our progress toward understanding the mechanisms of receptor assembly and signaling, and the application of this knowledge to develop exciting new therapeutic approaches against human disease.

ZO-1 expression is suppressed by GM-CSF via miR-96/ERG in brain microvascular endothelial cells

The level of granulocyte-macrophage colony-stimulating factor (GM-CSF) increases in some disorders such as vascular dementia, Alzheimer's disease, and multiple sclerosis. We previously reported that in Alzheimer's disease patients, a high level of GM-CSF in the brain parenchyma downregulated expression of ZO-1, a blood-brain barrier tight junction protein, and facilitated the infiltration of peripheral monocytes across the blood-brain barrier. However, the molecular mechanism underlying regulation of ZO-1 expression by GM-CSF is unclear. Herein, we found that the erythroblast transformation-specific (ETS) transcription factor ERG cooperated with the proto-oncogene protein c-MYC in regulation of ZO-1 transcription in brain microvascular endothelial cells (BMECs). The ERG expression was suppressed by miR-96 which was increased by GM-CSF through the phosphoinositide-3 kinase (PI3K)/Akt pathway. Inhibition of miR-96 prevented ZO-1 down-regulation induced by GM-CSF both in vitro and in vivo. Our results revealed the mechanism of ZO-1 expression reduced by GM-CSF, and provided a potential target, miR-96, which could block ZO-1 down-regulation caused by GM-CSF in BMECs.

Targeting Early Dementia: Using Lipid Cubic Phase Nanocarriers to Cross the Blood⁻Brain Barrier

Over the past decades, a frequent co-morbidity of cerebrovascular pathology and Alzheimer's disease has been observed. Numerous published studies indicate that the preservation of a healthy cerebrovascular endothelium can be an important therapeutic target. By incorporating the appropriate drug(s) into biomimetic (lipid cubic phase) nanocarriers, one obtains a multitasking combination therapeutic, which targets certain cell surface scavenger receptors, mainly class B type I (i.e., SR-BI), and crosses the blood⁻brain barrier. This targeting allows for various cell types related to Alzheimer's to be simultaneously searched out for localized drug treatment in vivo.

Nanotherapy for Alzheimer's disease and vascular dementia: Targeting senile endothelium

Due to the complexity of Alzheimer's disease, multiple cellular types need to be targeted simultaneously in order for a given therapy to demonstrate any major effectiveness. Ultrasound-sensitive coated microbubbles (in a targeted lipid nanoemulsion) are available. Versatile small molecule drug(s) targeting multiple pathways of Alzheimer's disease pathogenesis are known. By incorporating such drug(s) into the targeted "lipid-coated microbubble" [LCM]/"nanoparticle-derived" [ND] (or LCM/ND) nanoemulsion type, one obtains a multitasking combination therapeutic for translational medicine. This multitasking therapeutic targets cell-surface scavenger receptors (mainly class B type I), or SR-BI, making possible for various Alzheimer's-related cell types to be simultaneously searched out for localized drug treatment in vivo. Besides targeting cell-surface SR-BI, the proposed LCM/ND-nanoemulsion combination therapeutic(s) include a characteristic lipid-coated microbubble [LCM] subpopulation (i.e., a stable LCM suspension); such film-stabilized microbubbles are well known to substantially reduce the acoustic power levels needed for accomplishing temporary noninvasive (transcranial) ultrasound treatment, or sonoporation, if additionally desired for the Alzheimer's patient.

Alzheimer’s Disease, Brain Injury, and C.N.S. Nanotherapy in Humans: Sonoporation Augmenting Drug Targeting

Owing to the complexity of neurodegenerative diseases, multiple cellular types need to be targeted simultaneously in order for a given therapy to demonstrate any major effectiveness. Ultrasound-sensitive coated microbubbles (in a targeted nanoemulsion) are available. Versatile small-molecule drug(s) targeting multiple pathways of Alzheimer’s disease pathogenesis are known. By incorporating such drug(s) into the targeted lipid-coated microbubble/nanoparticle-derived (LCM/ND) lipid nanoemulsion type, one obtains a multitasking combination therapeutic for translational medicine. This multitasking therapeutic targets cell-surface scavenger receptors (mainly scavenger receptor class B type I (SR-BI)), making it possible for various Alzheimer’s-related cell types to be simultaneously sought for localized drug treatment in vivo. Besides targeting cell-surface SR-BI, the proposed LCM/ND-nanoemulsion combination therapeutic(s) include a characteristic lipid-coated microbubble (LCM) subpopulation (i.e., a stable LCM suspension); such LCM substantially reduce the acoustic power levels needed for accomplishing temporary noninvasive (transcranial) ultrasound treatment, or sonoporation, if additionally desired for the Alzheimer’s patient.

Alpha-7 Nicotinic Receptor Signaling Pathway Participates in the Neurogenesis Induced by ChAT-Positive Neurons in the Subventricular Zone

Choline acetyltransferase-positive (ChAT+) neurons within the subventricular zone (SVZ) have been shown to promote neurogenesis after stroke in mice by secreting acetylcholine (ACh); however, the mechanisms remain unclear. Receptors known to bind ACh include the nicotinic ACh receptors (nAChRs), which are present in the SVZ and have been shown to be important for cell proliferation, differentiation, and survival. In this study, we investigated the neurogenic role of the alpha-7 nAChR (α7 nAChR) in a mouse model of middle cerebral artery occlusion (MCAO) by using α7 nAChR inhibitor methyllycaconitine. Mice subjected to MCAO exhibited elevated expression of cytomembrane and nuclear fibroblast growth factor receptor 1 (FGFR1), as well as increased expression of PI3K, pAkt, doublecortin (DCX), polysialylated - neuronal cell adhesion molecule (PSA-NCAM), and mammalian achaete-scute homolog 1 (Mash1). MCAO mice also had more glial fibrillary acidic protein (GFAP)/5-bromo-2'-deoxyuridine (BrdU)-positive cells and DCX-positive cells in the SVZ than did the sham-operated group. Methyllycaconitine treatment increased cytomembrane FGFR1 expression and GFAP/BrdU-positive cells, upregulated the levels of phosphoinositide 3-kinase (PI3K) and phospho-Akt (pAkt), decreased nuclear FGFR1 expression, decreased the number of DCX-positive cells, and reduced the levels of DCX, PSA-NCAM, and Mash1 in the SVZ of MCAO mice compared with levels in vehicle-treated MCAO mice. MCAO mice treated with α7 nAChR agonist PNU-282987 exhibited the opposite effects. Our data show that α7 nAChR may decrease the proliferation of neural stem cells and promote differentiation of existing neural stem cells after stroke. These results identify a new mechanism of SVZ ChAT+ neuron-induced neurogenesis.