The immunology of neurodegeneration

Multi-cohort cerebrospinal fluid proteomics identifies robust molecular signatures across the Alzheimer disease continuum

Changes in β-amyloid (Aβ) and hyperphosphorylated tau (T) in brain and cerebrospinal fluid (CSF) precede Alzheimer's disease (AD) symptoms, making the CSF proteome a potential avenue to understand disease pathophysiology and facilitate reliable diagnostics and therapies. Using the AT framework and a three-stage study design (discovery, replication, and meta-analysis), we identified 2,173 analytes (2,029 unique proteins) dysregulated in AD. Of these, 865 (43%) were previously reported, and 1,164 (57%) are novel. The identified proteins cluster in four different pseudo-trajectories groups spanning the AD continuum and were enriched in pathways including neuronal death, apoptosis, and tau phosphorylation (early stages), microglia dysregulation and endolysosomal dysfunction (mid stages), brain plasticity and longevity (mid stages), and microglia-neuron crosstalk (late stages). Using machine learning, we created and validated highly accurate and replicable (area under the curve [AUC] > 0.90) models that predict AD biomarker positivity and clinical status. These models can also identify people that will convert to AD.

The neutrophil extracellular traps in neurological diseases: an update

Neutrophil extracellular traps (NETs) released by neutrophils are web-like DNA structures adhered to granulin proteins with bactericidal activity and can be an important mechanism for preventing pathogen dissemination or eliminating microorganisms. However, they also play important roles in diseases of other systems, such as the central nervous system. We tracked the latest advances and performed a review based on published original and review articles related to NETs and neurological diseases. Generally, neutrophils barely penetrate the blood-brain barrier into the brain parenchyma, but when pathological changes such as infection, trauma, or neurodegeneration occur, neutrophils rapidly infiltrate the central nervous system to exert their defensive effects. However, neutrophils may adversely affect the host when they uncontrollably release NETs upon persistent neuroinflammation. This review focused on recent advances in understanding the mechanisms and effects of NETs release in neurological diseases, and we also discuss the role of molecules that regulate NETs release in anticipation of clinical applications in neurological diseases.

Challenges and Future Perspectives in Modeling Neurodegenerative Diseases Using Organ-on-a-Chip Technology

Neurodegenerative diseases (NDDs) affect more than 50 million people worldwide, posing a significant global health challenge as well as a high socioeconomic burden. With aging constituting one of the main risk factors for some NDDs such as Alzheimer's disease (AD) and Parkinson's disease (PD), this societal toll is expected to rise considering the predicted increase in the aging population as well as the limited progress in the development of effective therapeutics. To address the high failure rates in clinical trials, legislative changes permitting the use of alternatives to traditional pre-clinical in vivo models are implemented. In this regard, microphysiological systems (MPS) such as organ-on-a-chip (OoC) platforms constitute a promising tool, due to their ability to mimic complex and human-specific tissue niches in vitro. This review summarizes the current progress in modeling NDDs using OoC technology and discusses five critical aspects still insufficiently addressed in OoC models to date. Taking these aspects into consideration in the future MPS will advance the modeling of NDDs in vitro and increase their translational value in the clinical setting.

Modelling the innate immune system in microphysiological systems

This critical review aims to highlight how modeling of the immune response has adapted over time to utilize microphysiological systems. Topics covered here will discuss the integral components of the immune system in various human body systems, and how these interactions are modeled using these systems. Through the use of microphysiological systems, we have not only expanded on foundations of basic immune cell information, but have also gleaned insight on how immune cells work both independently and collaboratively within an entire human body system.

Assessment of neurovascular uncoupling: APOE status is a key driver of early metabolic and vascular dysfunction

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia worldwide, with apolipoprotein Eε4 (APOEε4) being the strongest genetic risk factor. Current clinical diagnostic imaging focuses on amyloid and tau; however, new methods are needed for earlier detection.

METHODS

PET imaging was used to assess metabolism-perfusion in both sexes of aging C57BL/6J, and hAPOE mice, and were verified by transcriptomics, and immunopathology.

RESULTS

All hAPOE strains showed AD phenotype progression by 8 months, with females exhibiting the regional changes, which correlated with GO-term enrichments for glucose metabolism, perfusion, and immunity. Uncoupling analysis revealed APOEε4/ε4 exhibited significant Type-1 uncoupling (↓ glucose uptake, ↑ perfusion) at 8 and 12 months, while APOEε3/ε4 demonstrated Type-2 uncoupling (↑ glucose uptake, ↓ perfusion), while immunopathology confirmed cell specific contributions.

DISCUSSION

This work highlights APOEε4 status in AD progression manifests as neurovascular uncoupling driven by immunological activation, and may serve as an early diagnostic biomarker.

HIGHLIGHTS

We developed a novel analytical method to analyze PET imaging of 18F-FDG and 64Cu-PTSM data in both sexes of aging C57BL/6J, and hAPOEε3/ε3, hAPOEε4/ε4, and hAPOEε3/ε4 mice to assess metabolism-perfusion profiles termed neurovascular uncoupling. This analysis revealed APOEε4/ε4 exhibited significant Type-1 uncoupling (decreased glucose uptake, increased perfusion) at 8 and 12 months, while APOEε3/ε4 demonstrated significant Type-2 uncoupling (increased glucose uptake, decreased perfusion) by 8 months which aligns with immunopathology and transcriptomic signatures. This work highlights that there may be different mechanisms underlying age related changes in APOEε4/ε4 compared with APOEε3/ε4. We predict that these changes may be driven by immunological activation and response, and may serve as an early diagnostic biomarker.

Neuroglia targeting nano-therapeutic approaches to rescue aging and neurodegenerating brain

Despite intense efforts at the bench, the development of successful brain-targeting therapeutics to relieve malicious neural diseases remains primitive. The brain, being a beautifully intricate organ, consists of heterogeneous arrays of neuronal and glial cells. Primarily acting as the support system for neuronal functioning and maturation, glial cells have been observed to be engaged more apparently in the progression and worsening of various neural pathologies. The diseased state is often related to metabolic alterations in glial cells, thereby modulating their physiological homeostasis in conjunction with neuronal dysfunction. A plethora of data indicates the effect of oxidative stress, protein aggregation, and DNA damage in neuroglia impairments. Still, a deeper insight is needed to gain a conflict-free understanding in this arena. As a consequence, glial cells hold the potential to be identified as promising targets for novel therapeutic approaches aimed at brain protection. In this review, we describe the recent strides taken in the direction of understanding the impact of oxidative stress, protein aggregation, and DNA damage on neuroglia impairment and neuroglia-directed nanotherapeutic approaches to mitigate the burden of various neural disorders.

Assessment of Neurovascular Uncoupling: APOE Status is a Key Driver of Early Metabolic and Vascular Dysfunction

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia worldwide, with apolipoprotein ε4 (APOEε4) being the strongest genetic risk factor. Current clinical diagnostic imaging focuses on amyloid and tau; however, new methods are needed for earlier detection.

METHODS

PET imaging was used to assess metabolism-perfusion in both sexes of aging C57BL/6J, and hAPOE mice, and were verified by transcriptomics, and immunopathology.

RESULTS

All hAPOE strains showed AD phenotype progression by 8 mo, with females exhibiting the regional changes, which correlated with GO-term enrichments for glucose metabolism, perfusion, and immunity. Uncoupling analysis revealed APOEε4/ε4 exhibited significant Type-1 uncoupling (↓ glucose uptake, ↑ perfusion) at 8 and 12 mo, while APOEε3/ε4 demonstrated Type-2 uncoupling (↑ glucose uptake, ↓ perfusion), while immunopathology confirmed cell specific contributions.

DISCUSSION

This work highlights APOEε4 status in AD progression manifest as neurovascular uncoupling driven by immunological activation, and may serve as an early diagnostic biomarker.

Understanding immune microenvironment alterations in the brain to improve the diagnosis and treatment of diverse brain diseases

Abnormal inflammatory states in the brain are associated with a variety of brain diseases. The dynamic changes in the number and function of immune cells in cerebrospinal fluid (CSF) are advantageous for the early prediction and diagnosis of immune diseases affecting the brain. The aggregated factors and cells in inflamed CSF may represent candidate targets for therapy. The physiological barriers in the brain, such as the blood‒brain barrier (BBB), establish a stable environment for the distribution of resident immune cells. However, the underlying mechanism by which peripheral immune cells migrate into the brain and their role in maintaining immune homeostasis in CSF are still unclear. To advance our understanding of the causal link between brain diseases and immune cell status, we investigated the characteristics of immune cell changes in CSF and the molecular mechanisms involved in common brain diseases. Furthermore, we summarized the diagnostic and treatment methods for brain diseases in which immune cells and related cytokines in CSF are used as targets. Further investigations of the new immune cell subtypes and their contributions to the development of brain diseases are needed to improve diagnostic specificity and therapy.

Emerging Microglial Therapies and Targets in Clinical Trial

Modulation of microglia function for treatment of neurodegenerative and neuropsychiatric disorders is an emerging field of neuroscience drug development. This is largely attributed to human genetic association studies combined with biological evidence indicating that the innate immune system acts as a causal contributor superimposed on the reactive component of neuronal loss in neurological dysfunction. The identification of disease risk gene variants that encode immune-modulatory proteins in microglia provides tools to evaluate how microglia cellular function or dysfunction affect neuronal health. The development of clinical stage therapeutic compounds that modify myeloid cell function enables us to investigate how modulating microglia function could become a transformational approach to mitigate neurological disorders. Improving our ability to boost microglia-promoting homeostatic and reparative functions hopefully will translate into achieving a better outcome for patients affected by neurological diseases. In this chapter, we aim to provide an overview of the microglial emerging therapies and targets being studied in current clinical trials.

Attenuation of Chronic Stress-Induced Depressive-like Symptoms by Fish Oil via Alleviating Neuroinflammation and Impaired Tryptophan Metabolism in Aging Rats

The prevalence of depression is increasing, and geriatric depression, in particular, is difficult to recognize and treat. Depression in older adults is often accompanied by neuroinflammation in the central nervous system (CNS). Neuroinflammation affects the brain's physiological and immune functions through several pathways and induces depressive symptoms. This study investigated the relationship among depression, neuroinflammation, and fish oil supplementation. Thirty-six male Sprague-Dawley rats were used in an aging-related depression animal model to simulate geriatric depression. Cognitive function, depressive-like symptoms, peripheral nervous system and CNS inflammation status, and the tryptophan-related metabolic pathway were analyzed. The geriatric depression animal model was associated with depressive-like behaviors and cognitive impairment. The integrity of the blood-brain barrier was compromised, resulting in increased expression of ionized calcium-binding adapter molecule 1 and the glial fibrillary acidic protein in the brain, indicating increased neuroinflammation. Tryptophan metabolism was also negatively affected. The geriatric-depressive-like rats had high levels of neurotoxic 5-hydroxyindoleacetic acid and kynurenine in their hippocampus. Fish oil intake improved depressive-like symptoms and cognitive impairment, reduced proinflammatory cytokine expression, activated the brain's glial cells, and increased the interleukin-10 level in the prefrontal cortex. Thus, fish oil intervention could ameliorate abnormal neurobehaviors and neuroinflammation and elevate the serotonin level in the hippocampus.

Oxytocin as neuro-hormone and neuro-regulator exert neuroprotective properties: A mechanistic graphical review

BACKGROUND

Neurodegeneration is progressive cell loss in specific neuronal populations, often resulting in clinical consequences with significant medical, societal, and economic implications. Because of its antioxidant, anti-inflammatory, and anti-apoptotic properties, oxytocin has been proposed as a potential neuroprotective and neurobehavioral therapeutic agent, including modulating mood disturbances and cognitive enchantment.

METHODS

Literature searches were conducted using the following databases Web of Science, PubMed, Elsevier Science Direct, Google Scholar, the Core Collection, and Cochrane from January 2000 to February 2023 for articles dealing with oxytocin neuroprotective properties in preventing or treating neurodegenerative disorders and diseases with a focus on oxidative stress, inflammation, and apoptosis/cell death.

RESULTS

The neuroprotective effects of oxytocin appears to be mediated by its anti-inflammatory properties, inhibition of neuro inflammation, activation of several antioxidant enzymes, inhibition of oxidative stress and free radical formation, activation of free radical scavengers, prevent of mitochondrial dysfunction, and inhibition of apoptosis.

CONCLUSION

Oxytocin acts as a neuroprotective agent by preventing neuro-apoptosis, neuro-inflammation, and neuronal oxidative stress, and by restoring mitochondrial function.

Neuroprotective potential of trimetazidine against tramadol-induced neurotoxicity: role of PI3K/Akt/mTOR signaling pathways

Tramadol (TRA) causes neurotoxicity whereas trimetazidine (TMZ) is neuroprotective. The potential involvement of the PI3K/Akt/mTOR signaling pathway in the neuroprotection of TMZ against TRA-induced neurotoxicity was evaluated. Seventy male Wistar rats were divided into groups. Groups 1 and 2 received saline or TRA (50 mg/kg). Groups 3, 4, and 5 received TRA (50 mg/kg) and TMZ (40, 80, or 160 mg/kg) for 14 days. Group 6 received TMZ (160 mg/kg). Hippocampal neurodegenerative, mitochondrial quadruple complex enzymes, phosphatidylinositol-3-kinases (PI3Ks)/protein kinase B levels, oxidative stress, inflammatory, apoptosis, autophagy, and histopathology were evaluated. TMZ decreased anxiety and depressive-like behavior induced by TRA. TMZ in tramadol-treated animals inhibited lipid peroxidation, GSSG, TNF-α, and IL-1β while increasing GSH, SOD, GPx, GR, and mitochondrial quadruple complex enzymes in the hippocampus. TRA inhibited Glial fibrillary acidic protein expression and increased pyruvate dehydrogenase levels. TMZ reduced these changes. TRA decreased the level of JNK and increased Beclin-1 and Bax. TMZ decreased phosphorylated Bcl-2 while increasing the unphosphorylated form in tramadol-treated rats. TMZ activated phosphorylated PI3Ks, Akt, and mTOR proteins. TMZ inhibited tramadol-induced neurotoxicity by modulating the PI3K/Akt/mTOR signaling pathways and its downstream inflammatory, apoptosis, and autophagy-related cascades.

Reelin through the years: From brain development to inflammation

Reelin was originally identified as a regulator of neuronal migration and synaptic function, but its non-neuronal functions have received far less attention. Reelin participates in organ development and physiological functions in various tissues, but it is also dysregulated in some diseases. In the cardiovascular system, Reelin is abundant in the blood, where it contributes to platelet adhesion and coagulation, as well as vascular adhesion and permeability of leukocytes. It is a pro-inflammatory and pro-thrombotic factor with important implications for autoinflammatory and autoimmune diseases such as multiple sclerosis, Alzheimer's disease, arthritis, atherosclerosis, or cancer. Mechanistically, Reelin is a large secreted glycoprotein that binds to several membrane receptors, including ApoER2, VLDLR, integrins, and ephrins. Reelin signaling depends on the cell type but mostly involves phosphorylation of NF-κB, PI3K, AKT, or JAK/STAT. This review focuses on non-neuronal functions and the therapeutic potential of Reelin, while highlighting secretion, signaling, and functional similarities between cell types.

Therapeutic Potential of Microbiota Modulation in Alzheimer's Disease: A Review of Preclinical Studies

Alzheimer's disease (AD) is the most common neurodegenerative disease, yet it currently lacks effective treatment due to its complex etiology. The pathological changes in AD have been linked to the neurotoxic immune responses following aggregation of Aβ and phosphorylated tau. The gut microbiota (GM) is increasingly studied for modulating neuroinflammation in neurodegenerative diseases and in vivo studies emerge for AD. This critical review selected 7 empirical preclinical studies from 2019 onwards assessing therapy approaches targeting GM modulating microglia neuroinflammation in AD mouse models. Results from probiotics, fecal microbiota transplantation, and drugs were compared and contrasted, including for cognition, neuroinflammation, and toxic aggregation of proteins. Studies consistently reported significant amelioration or prevention of cognitive deficits, decrease in microglial activation, and lower levels of pro-inflammatory cytokines, compared to AD mouse models. However, there were differences across papers for the brain regions affected, and changes in astrocytes were inconsistent. Aβ plaques deposition significantly decreased in all papers, apart from Byur dMar Nyer lNga Ril Bu (BdNlRB) treatment. Tau phosphorylation significantly declined in 5 studies. Effects in microbial diversity following treatment varied across studies. Findings are encouraging regarding the efficacy of study but information on the effect size is limited. Potentially, GM reverses GM derived abnormalities, decreasing neuroinflammation, which reduces AD toxic aggregations of proteins in the brain, resulting in cognitive improvements. Results support the hypothesis of AD being a multifactorial disease and the potential synergies through multi-target approaches. The use of AD mice models limits conclusions around effectiveness, as human translation is challenging.

Serum short chain fatty acids mediate hippocampal BDNF and correlate with decreasing neuroinflammation following high pectin fiber diet in mice

Introduction

Dietary components, such as prebiotic fiber, are known to impact brain chemistry via the gut-brain axis. In particular, short chain fatty acids (SCFAs) generated from excessive soluble fiber consumption are thought to impact neuroimmune signaling and brain function through increased production of neurotropic factors. Given reports that high dietary fiber intake is associated with increased mental health and improved quality of life scores, we set out to identify whether changes in SCFA levels as a result of a high soluble fiber diet mediate hippocampal neuroinflammation and brain derived neurotrophic factor (BDNF) in mice.

Methods

Adult male and female C57BL/6 mice were fed a 1-month high pectin fiber or cellulose-based control diet. Following 1 month of excessive pectin consumption, serum SCFAs were measured using gas chromatography-mass spectrometry (GC-MS) and hippocampal cytokines and BDNF were assessed via multiplex magnetic bead immunoassay.

Results

Pectin-based fiber diet increased circulating acetic acid in both sexes, with no effect on propionic or butyric acid. In the hippocampus, a high fiber diet decreased TNFa, IL-1ß, IL-6, and IFNγ and increased BDNF levels. Furthermore, increased SCFA levels were inversely correlated with neuroinflammation in the hippocampus, with acetic acid revealed as a strong mediator of increased BDNF production.

Conclusion

Collectively, these findings highlight the beneficial effects of fiber-induced molecular changes in a brain region known to influence mood- and cognition-related behaviors. Dietary composition should be considered when developing mental health management plans for men and women with an emphasis on increasing soluble fiber intake.

Extracellular vesicles and Alzheimer's disease in the novel era of Precision Medicine: implications for disease progression, diagnosis and treatment

Extracellular vesicles (EVs), secreted membranous nano-sized particles, are critical intercellular messengers participating in nervous system homeostasis, while recent evidence implicates EVs in Alzheimer's disease (AD) pathogenesis. Specifically, small EVs have been shown to spread toxic proteins, induce neuronal loss, and contribute to neuroinflammation and AD progression. On the other hand, EVs can reduce amyloid-beta deposition and transfer neuroprotective substances between cells, mitigating disease mechanisms. In addition to their roles in AD pathogenesis, EVs also exhibit great potential for the diagnosis and treatment of other brain disorders, representing an advantageous tool for Precision Medicine. Herein, we summarize the contribution of small EVs to AD-related mechanisms and disease progression, as well as their potential as diagnostic and therapeutic agents for AD.

Inflammation and immune dysfunction in Parkinson disease

Parkinson disease (PD) is a progressive neurodegenerative disease that affects peripheral organs as well as the central nervous system and involves a fundamental role of neuroinflammation in its pathophysiology. Neurohistological and neuroimaging studies support the presence of ongoing and end-stage neuroinflammatory processes in PD. Moreover, numerous studies of peripheral blood and cerebrospinal fluid from patients with PD suggest alterations in markers of inflammation and immune cell populations that could initiate or exacerbate neuroinflammation and perpetuate the neurodegenerative process. A number of disease genes and risk factors have been identified as modulators of immune function in PD and evidence is mounting for a role of viral or bacterial exposure, pesticides and alterations in gut microbiota in disease pathogenesis. This has led to the hypothesis that complex gene-by-environment interactions combine with an ageing immune system to create the 'perfect storm' that enables the development and progression of PD. We discuss the evidence for this hypothesis and opportunities to harness the emerging immunological knowledge from patients with PD to create better preclinical models with the long-term goal of enabling earlier identification of at-risk individuals to prevent, delay and more effectively treat the disease.

Age-linked suppression of lipoxin A4 associates with cognitive deficits in mice and humans

Age increases the risk for cognitive impairment and is the single major risk factor for Alzheimer's disease (AD), the most prevalent form of dementia in the elderly. The pathophysiological processes triggered by aging that render the brain vulnerable to dementia involve, at least in part, changes in inflammatory mediators. Here we show that lipoxin A4 (LXA4), a lipid mediator of inflammation resolution known to stimulate endocannabinoid signaling in the brain, is reduced in the aging central nervous system. We demonstrate that genetic suppression of 5-lipoxygenase (5-LOX), the enzyme mediating LXA4 synthesis, promotes learning impairment in mice. Conversely, administration of exogenous LXA4 attenuated cytokine production and memory loss induced by inflammation in mice. We further show that cerebrospinal fluid LXA4 is reduced in patients with dementia and positively associated with cognitive performance, brain-derived neurotrophic factor (BDNF), and AD-linked amyloid-β. Our findings suggest that reduced LXA4 levels may lead to vulnerability to age-related cognitive disorders and that promoting LXA4 signaling may comprise an effective strategy to prevent early cognitive decline in AD.

Alzheimer's disease: insights from a network medicine perspective

Alzheimer’s disease (AD) is the most common neurodegenerative disease that currently lacks available effective therapy. Thus, identifying novel molecular biomarkers for diagnosis and treatment of AD is urgently demanded. In this study, we exploited tools and concepts of the emerging research area of Network Medicine to unveil a novel putative disease gene signature associated with AD. We proposed a new pipeline, which combines the strengths of two consolidated algorithms of the Network Medicine: DIseAse MOdule Detection (DIAMOnD), designed to predict new disease-associated genes within the human interactome network; and SWItch Miner (SWIM), designed to predict important (switch) genes within the co-expression network. Our integrated computational analysis allowed us to enlarge the set of the known disease genes associated to AD with additional 14 genes that may be proposed as new potential diagnostic biomarkers and therapeutic targets for AD phenotype.

Neurodegeneration: Microglia: Nf-Kappab Signaling Pathways

Microglia is cells of mesodermal/mesenchymal origin that migrate into the central nervous system (CNS) to form resident macrophages inside the special brain microenvironment. Intact with both neuronal and non-neuronal cells, microglia is highly active cells. Continuous process extension and retraction allows microglia to scan the brain parenchyma for threats. They are also able to change their morphology from ramified to amoeboid, which is a sign of cell activity. In response to pleiotropic stimuli such as neurotransmitters, cytokines, and plasma proteins, microglia express a diverse range of receptors. As controllers of synaptic activities and phagocytosis of developing neurons, they serve a critical role in the healthy brain and have significant effects on synaptic plasticity and adult neurogenesis. A frequent cause of hypoparathyroidism is a mutation in the gene glial cells missing-2 (GCM2). Neonatal hypoparathyroidism has an amorphic recessive GCM2 mutation, while autosomal dominant hypoparathyroidism has a dominant-negative GCM2 mutation. Curiously, familial isolated hyperparathyroidism has been associated with activating GCM2 mutation. In addition to seizures, neurocognitive impairment, carpopedal spasm, tingling and numbness are common clinical manifestations of hypoparathyroidism. Biogenic amines are a group of four neurotransmitters that belong to that category and these include serotonin, dopamine, norepinephrine, and epinephrine. Numerous antidepressants prevent the reuptake from occurring the brain-gut axis is hardwired through the CNS, enteric nervous system (ENS), neuroendocrine linkages and highly innervated nerve plexuses.

The potential use of tetracyclines in neurodegenerative diseases and the role of nano-based drug delivery systems

Neurodegenerative diseases are still a challenge for effective treatments. The high cost of approved drugs, severity of side effects, injection site pain, and restrictions on drug delivery to the Central Nervous System (CNS) can overshadow the management of these diseases. Due to the chronic and progressive evolution of neurodegenerative disorders and since there is still no cure for them, new therapeutic strategies such as the combination of several drugs or the use of existing drugs with new therapeutic applications are valuable strategies. Tetracyclines are traditionally classified as antibiotics. However, in this class of drugs, doxycycline and minocycline exhibit also anti-inflammatory effects by inhibiting microglia/macrophages. Hence, they have been studied as potential agents for the treatment of neurodegenerative diseases. The results of in vitro and in vivo studies confirm the effective role of these two drugs as anti-inflammatory agents in experimentally induced models of neurodegenerative diseases. In clinical studies, satisfactory results have been obtained in Multiple sclerosis (MS) but not yet in other disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), or Amyotrophic lateral sclerosis (ALS). In recent years, researchers have developed and evaluated nanoparticulate drug delivery systems to improve the clinical efficacy of these two tetracyclines for their potential application in neurodegenerative diseases. This study reviews the neuroprotective roles of minocycline and doxycycline in four of the main neurodegenerative disorders: AD, PD, ALS and MS. Moreover, the potential applications of nanoparticulate delivery systems developed for both tetracyclines are also reviewed.

Neuroprotective Effect of Bcl-2 on Lipopolysaccharide-Induced Neuroinflammation in Cortical Neural Stem Cells

Neuroinflammation is involved in the pathogenesis of neurodegenerative diseases due to increased levels of pro-inflammatory cytokines in the central nervous system (CNS). Chronic neuroinflammation induced by neurotoxic molecules accelerates neuronal damage. B-cell lymphoma 2 (Bcl-2) is generally accepted to be an important anti-apoptotic factor. However, the role of Bcl-2 in neuroprotection against neuroinflammation remains to be determined. The purpose of this study was to investigate the neuroprotective effect of Bcl-2 on lipopolysaccharide (LPS)-induced neuroinflammation in cortical neural stem cells (NSCs). LPS decreased mRNA and protein levels of Tuj-1, a neuron marker, and also suppressed neurite outgrowth, indicating that LPS results in inhibition of neuronal differentiation of NSCs. Furthermore, LPS treatment inhibited Bcl-2 expression during neuronal differentiation; inhibition of neuronal differentiation by LPS was rescued by Bcl-2 overexpression. LPS-induced pro-inflammatory cytokines, including interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α), were decreased by Bcl-2 overexpression. Conversely, Bcl-2 siRNA increased the LPS-induced levels of IL-6 and TNF-α, and decreased neuronal differentiation of NSCs, raising the possibility that Bcl-2 mediates neuronal differentiation by inhibiting the LPS-induced inflammatory response in NSC. These results suggest that Bcl-2 has a neuroprotective effect by inhibiting the LPS-induced inflammatory response in NSCs.

Expression of toll like receptor 8 (TLR8) in specific groups of mouse hippocampal interneurons

Toll-like receptors (TLR) are one of the main constituents of the innate immune system in mammals. They can detect conserved microbial structures (pathogen-associated molecular patterns) and host-derived ligands that are produced during cellular stress and damage (danger-associated molecular patterns) and may then initiate an intracellular signaling cascade leading to the expression of pro-inflammatory cytokines and immediate immune responses. Some TLR (TLR1, 2, 4, 5, and 6) are expressed on the cell surface while others (TLR3, 7, 8 and 9) are present on the surface of endosomes and their ligands require internalization before recognition is possible. Several TLR have also been detected in neurons where they may serve functions that are not related to immune responses. TLR2, 3, and 4 have been described in cortical neurons and, for TLR4, a seizure-promoting role in epilepsies associated with inflammation has been shown. TLR3, 7, and 8 expressed in neurons seem to influence the growth or withdrawal of neurites and robust activation of TLR8 in neurons may even induce neuronal death. The goal of the current study was to investigate the expression of TLR8 in the hippocampus of mice during postnatal development and in adulthood. We focused on three functionally distinct groups of GABAergic interneurons characterized by the expression of the molecular markers parvalbumin, somatostatin, or calretinin, and we applied double fluorescence immunohistochemistry and cell counts to quantify co-expression of TLR8 in the three groups of GABA-interneurons across hippocampal subregions. We found subregion-specific differences in the expression of TLR8 in these interneurons. During postnatal development, TLR8 was detected only in mice older than P5. While only a small fraction of hippocampal calretinin-positive interneurons expressed TLR8, most parvalbumin-positive interneurons in all hippocampal subregions co-expressed TLR8. Somatostatin-positive interneurons co-expressing TLR8 were mainly present in hippocampal sector CA3 but rare in the dentate gyrus and CA1. High expression of TLR8 in parvalbumin-interneurons may contribute to their high vulnerability in human temporal lobe epilepsy.

Selectin-Mediated Signaling-Shedding Light on the Regulation of Integrin Activity in Neutrophils

As a consequence of tissue injury or infection, neutrophils are recruited in a stepwise recruitment process from the bloodstream into the surrounding tissue. Selectins are a family of adhesion molecules comprised of L-, E-, and P-selectin. Differences in expression patterns, protein structure, and ligand binding characteristics mediate distinct functions of each selectin. Interactions of selectins and their counter-receptors mediate the first contact of neutrophils with the endothelium, as well as subsequent neutrophil rolling along the endothelial surface. For efficient neutrophil recruitment, activation of β₂-integrins on the cell surface is essential. Integrin activation can be elicited via selectin- as well as chemokine-mediated inside-out signaling resulting in integrin conformational changes and clustering. Dysregulation of selectin-induced integrin activation on neutrophils is involved in the development of severe pathological disease conditions including leukocyte adhesion deficiency (LAD) syndromes in humans. Here, we review molecular mechanisms involved in selectin-mediated signaling pathways in neutrophils and their impact on integrin activation, neutrophil recruitment, and inflammatory diseases.

Inhibition of the CEBPβ-NFκB interaction by nanocarrier-packaged Carnosic acid ameliorates glia-mediated neuroinflammation and improves cognitive function in an Alzheimer's disease model

Neuroinflammation occurs early in Alzheimer’s disease (AD). The initial stage of AD is related to glial dysfunction, which contributes to impairment of Aβ clearance and disruption of synaptic connection. CEBPβ, a member of the CCAAT-enhancer-binding protein (CEBP) family, modulates the expression of inflammation-associated genes, and its expression is elevated in brains undergoing degeneration and injured brains. However, the mechanism underlying CEBPβ-mediated chronic inflammation in AD is unclear. In this study, we observed that increases in the levels of nuclear CEBPβ facilitated the interaction of CEBPβ with the NFκB p65 subunit, increasing the transcription of proinflammatory cytokines in the APP/PS1 mouse brain. Oral administration of nanocarrier-packaged carnosic acid (CA) reduced the aberrant activation of microglia and astrocytes and diminished mature IL-1β, TNFα and IL-6 production in the APP/PS1 mouse brain. CA administration reduced β-amyloid (Aβ) deposition and ameliorated cognitive impairment in APP/PS1 mice. We observed that CA blocked the interaction of CEBPβ with NFκB p65, and chromatin immunoprecipitation revealed that CA reduced the transcription of the NFκB target genes TNFα and IL-6. We confirmed that CA alleviated inflammatory mediator-induced neuronal degeneration and reduced Aβ secretion by inhibiting the CEBPβ-NFκB signalling pathway in vitro. Sulfobutyl ether-beta-cyclodextrin (SBEβCD) was used as the encapsulation agent for the CA-loaded nanocarrier to overcome the poor water solubility and enhance the brain bioavailability of CA. The CA nanoparticles (NPs) had no obvious toxicity. We demonstrated a feasible SBEβCD-based nanodelivery system targeting the brain. Our data provide experimental evidence that CA-loaded NPs are potential therapeutic agents for AD treatment.

Lysophosphatidic Acid Receptor 5 (LPA5) Knockout Ameliorates the Neuroinflammatory Response In Vivo and Modifies the Inflammatory and Metabolic Landscape of Primary Microglia In Vitro

Systemic inflammation induces alterations in the finely tuned micromilieu of the brain that is continuously monitored by microglia. In the CNS, these changes include increased synthesis of the bioactive lipid lysophosphatidic acid (LPA), a ligand for the six members of the LPA receptor family (LPA_1-6). In mouse and human microglia, LPA₅ belongs to a set of receptors that cooperatively detect danger signals in the brain. Engagement of LPA₅ by LPA polarizes microglia toward a pro-inflammatory phenotype. Therefore, we studied the consequences of global LPA₅ knockout (^-/-) on neuroinflammatory parameters in a mouse endotoxemia model and in primary microglia exposed to LPA in vitro. A single endotoxin injection (5 mg/kg body weight) resulted in lower circulating concentrations of TNFα and IL-1β and significantly reduced gene expression of IL-6 and CXCL2 in the brain of LPS-injected LPA₅^-/- mice. LPA₅ deficiency improved sickness behavior and energy deficits produced by low-dose (1.4 mg LPS/kg body weight) chronic LPS treatment. LPA₅^-/- microglia secreted lower concentrations of pro-inflammatory cyto-/chemokines in response to LPA and showed higher maximal mitochondrial respiration under basal and LPA-activated conditions, further accompanied by lower lactate release, decreased NADPH and GSH synthesis, and inhibited NO production. Collectively, our data suggest that LPA₅ promotes neuroinflammation by transmiting pro-inflammatory signals during endotoxemia through microglial activation induced by LPA.

Natural Products in Therapeutic Management of Multineurodegenerative Disorders by Targeting Autophagy

Autophagy is an essential cellular process that involves the transport of cytoplasmic content in double-membraned vesicles to lysosomes for degradation. Neurons do not undergo cytokinesis, and thus, the cell division process cannot reduce levels of unnecessary proteins. The primary cause of neurodegenerative disorders (NDs) is the abnormal deposition of proteins inside neuronal cells, and this could be averted by autophagic degradation. Thus, autophagy is an important consideration when considering means of developing treatments for NDs. Various pharmacological studies have reported that the active components in herbal medicines exhibit therapeutic benefits in NDs, for example, by inhibiting cholinesterase activity and modulating amyloid beta levels, and α-synuclein metabolism. A variety of bioactive constituents from medicinal plants are viewed as promising autophagy controllers and are revealed to recover the NDs by targeting the autophagic pathway. In the present review, we discuss the role of autophagy in the therapeutic management of several NDs. The molecular process responsible for autophagy and its importance in various NDs and the beneficial effects of medicinal plants in NDs by targeting autophagy are also discussed.

Exacerbated Age-Related Hippocampal Alterations of Microglia Morphology, β-Amyloid and Lipofuscin Deposition and Presenilin Overexpression in Per1-/--Mice

In humans, alterations of circadian rhythms and autophagy are linked to metabolic, cardiovascular and neurological dysfunction. Autophagy constitutes a specific form of cell recycling in many eukaryotic cells. Aging is the principal risk factor for the development of neurodegenerative diseases. Thus, we assume that both the circadian clock and autophagy are indispensable to counteract aging. We have previously shown that the hippocampus of Per1^−/−-mice exhibits a reduced autophagy and higher neuronal susceptibility to ischemic insults compared to wild type (WT). Therefore, we chose to study the link between aging and loss of clock gene Per1^−/−-mice. Young and aged C3H- and Per1^−/−-mice were used as models to analyze the hippocampal distribution of Aβ42, lipofuscin, presenilin, microglia, synaptophysin and doublecortin. We detected several changes in the hippocampus of aged Per1^−/−-mice compared to their wild type littermates. Our results show significant alterations of microglia morphology, an increase in Aβ42 deposition, overexpression of presenilin, decrease in synaptophysin levels and massive accumulation of lipofuscin in the hippocampus of 24-month-old Per1^−/−-mice, without alteration of adult neurogenesis. We suggest that the marked lipofuscin accumulation, Aβ42 deposition, and overexpression of presenilin-2 observed in our experiments may be some of the consequences of the slowed autophagy in the hippocampus of aged Per1^−/−-mice. This may lead during aging to excessive accumulation of misfolded proteins which may, consequently, result in higher neuronal vulnerability.

Targeting the TLR4/NF-κB pathway in β-amyloid-stimulated microglial cells: A possible mechanism that oxysophoridine exerts anti-oxidative and anti-inflammatory effects in an in vitro model of Alzheimer's disease

β-amyloid (Aβ) accumulation is a major neuropathological characteristic of Alzheimer's disease (AD) and serves as an inflammatory stimulus for microglial cells. Oxysophoridine has multiple pharmacological effects, including anti-inflammatory and anti-oxidative activities. In view of this, the current study aimed to investigate the effects of oxysophoridine on Aβ-induced activation of microglial BV-2 cells. Cell Counting Kit-8 assay showed that oxysophoridine concentration-dependently attenuated Aβ-induced viability reduction of BV-2 cells. Aβ stimulation reduced the activities of glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) and elevated malondialdehyde (MDA) content in BV-2 cells, but these effects were attenuated by oxysophoridine. Oxysophoridine abolished Aβ-induced increase of mRNA expression, secretion, and protein expression of tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β) in BV-2 cells. Additionally, western blot suggested that oxysophoridine inhibited Aβ-induced activation of the toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB) pathways in BV-2 cells. Inhibition of the TLR4/NF-κB pathway by TAK-242 enhanced the effects of oxysophoridine on Aβ-induced viability reduction, oxidative stress, and inflammation in BV-2 cells. Taken together, oxysophoridine suppressed Aβ-induced oxidative stress and inflammation in BV-2 cells by inhibition of the TLR4/NF-κB pathway.

Epileptic Mechanisms Shared by Alzheimer's Disease: Viewed via the Unique Lens of Genetic Epilepsy

Our recent work on genetic epilepsy (GE) has identified common mechanisms between GE and neurodegenerative diseases including Alzheimer's disease (AD). Although both disorders are seemingly unrelated and occur at opposite ends of the age spectrum, it is likely there are shared mechanisms and studies on GE could provide unique insights into AD pathogenesis. Neurodegenerative diseases are typically late-onset disorders, but the underlying pathology may have already occurred long before the clinical symptoms emerge. Pathophysiology in the early phase of these diseases is understudied but critical for developing mechanism-based treatment. In AD, increased seizure susceptibility and silent epileptiform activity due to disrupted excitatory/inhibitory (E/I) balance has been identified much earlier than cognition deficit. Increased epileptiform activity is likely a main pathology in the early phase that directly contributes to impaired cognition. It is an enormous challenge to model the early phase of pathology with conventional AD mouse models due to the chronic disease course, let alone the complex interplay between subclinical nonconvulsive epileptiform activity, AD pathology, and cognition deficit. We have extensively studied GE, especially with gene mutations that affect the GABA pathway such as mutations in GABA_A receptors and GABA transporter 1. We believe that some mouse models developed for studying GE and insights gained from GE could provide unique opportunity to understand AD. These include the pathology in early phase of AD, endoplasmic reticulum (ER) stress, and E/I imbalance as well as the contribution to cognitive deficit. In this review, we will focus on the overlapping mechanisms between GE and AD, the insights from mutations affecting GABA_A receptors, and GABA transporter 1. We will detail mechanisms of E/I imbalance and the toxic epileptiform generation in AD, and the complex interplay between ER stress, impaired membrane protein trafficking, and synaptic physiology in both GE and AD.

Key role of the CCR2-CCL2 axis in disease modification in a mouse model of tauopathy

BACKGROUND

For decades, dementia has been characterized by accumulation of waste in the brain and low-grade inflammation. Over the years, emerging studies highlighted the involvement of the immune system in neurodegenerative disease emergence and severity. Numerous studies in animal models of amyloidosis demonstrated the beneficial role of monocyte-derived macrophages in mitigating the disease, though less is known regarding tauopathy. Boosting the immune system in animal models of both amyloidosis and tauopathy, resulted in improved cognitive performance and in a reduction of pathological manifestations. However, a full understanding of the chain of events that is involved, starting from the activation of the immune system, and leading to disease mitigation, remained elusive. Here, we hypothesized that the brain-immune communication pathway that is needed to be activated to combat tauopathy involves monocyte mobilization via the C-C chemokine receptor 2 (CCR2)/CCL2 axis, and additional immune cells, such as CD4⁺ T cells, including FOXP3⁺ regulatory CD4⁺ T cells.

METHODS

We used DM-hTAU transgenic mice, a mouse model of tauopathy, and applied an approach that boosts the immune system, via blocking the inhibitory Programmed cell death protein-1 (PD-1)/PD-L1 pathway, a manipulation previously shown to alleviate disease symptoms and pathology. An anti-CCR2 monoclonal antibody (αCCR2), was used to block the CCR2 axis in a protocol that partially eliminates monocytes from the circulation at the time of anti-PD-L1 antibody (αPD-L1) injection, and for the critical period of their recruitment into the brain following treatment.

RESULTS

Performance of DM-hTAU mice in short-term and working memory tasks, revealed that the beneficial effect of αPD-L1, assessed 1 month after a single injection, was abrogated following blockade of CCR2. This was accompanied by the loss of the beneficial effect on disease pathology, assessed by measurement of cortical aggregated human tau load using Homogeneous Time Resolved Fluorescence-based immunoassay, and by evaluation of hippocampal neuronal survival. Using both multiparametric flow cytometry, and Cytometry by Time Of Flight, we further demonstrated the accumulation of FOXP3⁺ regulatory CD4⁺ T cells in the brain, 12 days following the treatment, which was absent subsequent to CCR2 blockade. In addition, measurement of hippocampal levels of the T-cell chemoattractant, C-X-C motif chemokine ligand 12 (Cxcl12), and of inflammatory cytokines, revealed that αPD-L1 treatment reduced their expression, while blocking CCR2 reversed this effect.

CONCLUSIONS

The CCR2/CCL2 axis is required to modify pathology using PD-L1 blockade in a mouse model of tauopathy. This modification involves, in addition to monocytes, the accumulation of FOXP3⁺ regulatory CD4⁺ T cells in the brain, and the T-cell chemoattractant, Cxcl12.

Neutrophil Extracellular Traps: A Perspective of Neuroinflammation and Complement Activation in Alzheimer's Disease

Complement system (CS) components are associated with Alzheimer's disease (AD), the commonest cause of dementia in the world. Neutrophils can be attracted to amyloid-β plaques by several pro-inflammatory factors, including the complement anaphylatoxin C5a. They may release neutrophil extracellular traps (NETs), which are chromatin nets associated with myeloperoxidase, elastase, and other enzymes. Some CS molecules, such as C5a, C1q, and CR1, are associated with increased neutrophil recruitment and NETs release. However, the relationship between CS molecules and NETs in AD is poorly understood. In this work, we detected higher NET concentrations in plasma and serum of Brazilian AD patients, than in elderly controls (medians = 2.78 [2.07-6.19] vs. 2.23 [0.33-4.14] ng/mL, p = 0.0005). We discussed these results within the context of our former findings on complement and AD and the context of the literature on complement and NET release, suggesting both as possible therapeutic targets to prevent the progress of the disease.

Early intervention attenuates synaptic plasticity impairment and neuroinflammation in 5xFAD mice

BACKGROUND

As an increasing population of Alzheimer's disease (AD) patients year by year, which is a serious threat to human health, an effective approach to prevent and treat AD is required. Biomarker changes relevant to β-amyloid (Aβ) 20 years or more in advance of cognitive impairment, so early intervention is a feasible idea for AD therapy. Repetitive transcranial magnetic stimulation (rTMS) as a non-invasive technique offers the possibility of early intervention.

OBJECTIVE

To explore the effect of high-frequency rTMS on the pathological symptoms of AD transgenic mice and its mechanisms, a figure-of-eight coil was placed 2 mm above the head of mouse to apply 20 Hz high-intensity rTMS for 14 consecutive days.

METHODS

In vivo electrophysiological recording, behavioral test, Western blots assay and immunofluorescence were used to measure the pathological symptoms of AD.

RESULTS

Our data showed that early intervention effectively reduced Aβ levels and the activation of microglia on the one hand, and decreased levels of pro-inflammatory cytokines including IL-6 and TNF-α as well as regulated PI3K/Akt/NF-κB signaling pathway on the other hand, which created a favorable brain environment. Thus, it increased the expression of synapse-associated proteins and improved neuronal synaptic plasticity in brain of early-stage of 5xFAD transgenic mice.

CONCLUSIONS

This study is the first to suggest that early intervention of 20 Hz rTMS ameliorates neuroinflammation to improve synaptic plasticity of early-stage of 5xFAD mice through PI3K/Akt/NF-κB signaling pathway.

Loss of TAX1BP1-Directed Autophagy Results in Protein Aggregate Accumulation in the Brain

Protein aggregates disrupt cellular homeostasis, causing toxicity linked to neurodegeneration. Selective autophagic elimination of aggregates is critical to protein quality control, but how aggregates are selectively targeted for degradation is unclear. We compared the requirements for autophagy receptor proteins: OPTN, NBR1, p62, NDP52, and TAX1BP1 in clearance of proteotoxic aggregates. Endogenous TAX1BP1 is recruited to and required for the clearance of stress-induced aggregates, whereas ectopic expression of TAX1BP1 increases clearance through autophagy, promoting viability of human induced pluripotent stem cell-derived neurons. In contrast, TAX1BP1 depletion sensitizes cells to several forms of aggregate-induced proteotoxicity. Furthermore, TAX1BP1 is more specifically expressed in the brain compared to other autophagy receptor proteins. In vivo, loss of TAX1BP1 results in accumulation of high molecular weight ubiquitin conjugates and premature lipofuscin accumulation in brains of young TAX1BP1 knockout mice. TAX1BP1 mediates clearance of a broad range of cytotoxic proteins indicating therapeutic potential in neurodegenerative diseases.

Both Amyloid-β Peptide and Tau Protein Are Affected by an Anti-Amyloid-β Antibody Fragment in Elderly 3xTg-AD Mice

Alzheimer's disease (AD) is the most common dementia worldwide. According to the amyloid hypothesis, the early accumulation of the Aβ-peptide triggers tau phosphorylation, synaptic dysfunction, and eventually neuronal death leading to cognitive impairment, as well as behavioral and psychological symptoms of dementia. ScFv-h3D6 is a single-chain variable fragment that has already shown its ability to diminish the amyloid burden in 5-month-old 3xTg-AD mice. However, tau pathology is not evident at this early stage of the disease in this mouse model. In this study, the effects of scFv-h3D6 on Aβ and tau pathologies have been assessed in 22-month-old 3xTg-AD mice. Briefly, 3xTg-AD female mice were treated for 2 weeks with scFv-h3D6 and compared with 3xTg-AD and non-transgenic (NTg) mice treated with PBS. The treatment with scFv-h3D6 was unequivocally effective in reducing the area of Aβ staining. Furthermore, a tendency for a reduction in tau levels was also observed after treatment that points to the interplay between Aβ and tau pathologies. The pro-inflammatory state observed in the 3xTg-AD mice did not progress after scFv-h3D6 treatment. In addition, the treatment did not alter the levels of apolipoprotein E or apolipoprotein J. Thus, a 2-week treatment with scFv-h3D6 was able to reduce AD-like pathology in elderly 3xTg-AD female mice.

Current Evidence on the Effect of Dietary Polyphenols Intake on Brain Health

Background:

In recent years, the possibility of favorably influencing the cognitive capacity through the promotion of lifestyle modifications has been increasingly investigated. In particular, the relationship between nutritional habits and brain health has attracted special attention. Polyphenols are secondary metabolites of plants. These phytochemicals are present in vegetables, fruits, legumes, olive oil, nuts. They include several antioxidant compounds and are generally considered to be involved in defense against chronic human diseases. In recent years, there has been a growing scientific interest in their potential health benefits to the brain.

Objective:

In this mini-review, we focus on the current evidence defining the position of polyphenols dietary intake in the prevention/slowdown of human neurodegenerative diseases.

Methods:

A literature research was performed using the keywords “polyphenols”, “brain”, “nutrition”, individually or all together, focusing on human trials.

Results:

The available clinical studies on the effect of polyphenols on cognitive functions are quite convincing. Regular dietary intake of polyphenols would seem to reduce the risk of neurodegenerative diseases. Moreover, beyond their beneficial power on the central nervous system, these phytochemicals seem also to be able to work on numerous cellular targets. They show different biological actions, that however, have to be confirmed in long-term randomized clinical trials. Currently, most data propose that a combination of phytonutrients instead of any single polyphenol is responsible for health benefits.

Conclusions:

Evolving indications suggest that dietary polyphenols may exercise beneficial actions on the central nervous system, thus representing a possible tool to preserve cognitive performance. Key questions to improve the coherence and reproducibility in the development of polyphenols as a possible future therapeutic drug require a better understanding of the sources of polyphenols, their treatment and more standardized tests including bioavailability of bioactive metabolites and studies of permeability of the brain.

Association between anti-inflammatory interleukin-10 and executive function in African American women at risk for Alzheimer's disease

INTRODUCTION

African-Americans (AAs) are 64% more likely to be diagnosed with AD than non-Hispanic Whites. AAs with elevated AD biomarkers exhibit greater neurodegeneration in AD signature regions compared to non-Hispanic Whites with elevated AD biomarkers. This pilot trial examined whether normal or elevated plasma levels of interleukin (IL)-10 are associated with changes in executive function and short-term memory in AA women at risk for developing AD due to parental history.

METHOD

Observational study comparing groups with elevated and normal plasma IL-10 levels. Study included 31 AA women (age=58.9±8 years) with parental history of AD. Measures included inflammatory blood biomarkers, executive function and visuospatial short-term memory tests. Multivariate linear regression with adjustment for comorbidities, and Bonferroni corrections for multiple comparisons were used to compare groups. Effect sizes (Cohen's d) were generated. Using endpoints with moderate-large effects between groups, Pearson correlations determined associations between biomarker levels and cognitive performance.

RESULTS

The elevated IL-10 group performed worse on the Trail-Making Test proportional score ((B-A)/A) (effect size (d =-0.87 (-1.6, -.1)). Moderate effects with large confident intervals were noted in inhibition, set-switching, and body position spatial memory. Significant differences between groups in levels of other inflammatory markers were noted, including IL-7 (p=0.002) and interferon γ (p=0.02). IL-7 remained significant after Bonferroni correction. Correlation matrices revealed moderate-large, significant correlations (yet with wide confidence intervals) between levels of IL-10 and IL-9 with BPST total correct trials, and between interferon γ and delayed recall.

CONCLUSIONS

Interleukins may incite inflammation, leading to impaired aspects of executive function and short-term memory in this sample of African American women at risk for developing AD. This research provides effect sizes that will be used to power future research that will further investigate the relationship between inflammation, AD biomarkers, and cognitive function in an understudied population.

Pain- and Fatigue-Related Functional and Structural Changes in Ankylosing Spondylitis: An fRMI Study

Background: Chronic pain and fatigue are two cardinal features of ankylosing spondylitis (AS) and how to effectively treat these conditions continues to be a challenge. The underlying mechanisms and the relationship between AS-related pain and fatigue remain poorly understood. The present study was conducted, therefore, to explore the brain functional and structural changes associated with pain and fatigue in AS.

Methods: A total of 65 AS patients (48 men and 17 women; 32.33 ± 8.6 years) and 53 age- and sex-matched controls were enrolled in the study. The patients underwent clinical assessment based on Total Back Pain scores, Fatigue Severity Scale, Bath Ankylosing Spondylitis Disease Activity Index, (BASDAI), high-sensitivity C-reactive Protein (hsCRP), erythrocyte sedimentation rate (ESR), and Beck Depression Inventory (BDI). Using 3T magnetic resonance imaging (3T-MRI), we analyzed the brain functional (connectivity and nodal properties) and structural (covariance and gray matter volumes) differences between AS patients and controls. Furthermore, we extracted the values of the significantly changed regions in the AS cohort and explored their association with pain and fatigue.

Results: In AS patients, there were functional and structural abnormalities distributed in the default mode network (DMN), salience network (SN), sensory/somatomotor network (SMN), dorsal attention network (DAN), task control network (TCN), and visual network, and some regions showed both types of changes. Among these, the functional connectivity (FC) between the left insula and medial prefrontal cortex, the betweenness centrality of the left medial prefrontal cortex and the gray matter volume of the right putamen tracked both pain and fatigue. In addition, pain was related to within-DMN FC disruption and nodal function / gray matter volumes changes in DMN, SN, and the visual network, while fatigue mainly involved the SMN, DAN, and TCN. Moreover, certain changes were also related to BASDAI and inflammation level.

Conclusion: This study offers new insights into understanding the neural mechanism of AS-related pain and fatigue, and could help to stratify patients based on the correlation features and ultimately move towards a personalized therapy.

Chronic Peripheral Inflammation Causes a Region-Specific Myeloid Response in the Central Nervous System

Systemic immune dysregulation contributes to the development of neuropsychiatric and neurodegenerative diseases. The precise effect of chronic peripheral immune stimulation on myeloid cells across anatomical brain regions is unclear. Here, we demonstrate brain-region-specific differences in myeloid responses induced by chronic peripheral inflammation. This shift in the myeloid compartment is associated with the appearance of an inflammatory myeloid subpopulation in the cortex, striatum, and thalamus accompanied by regional transcriptomic fingerprints that include induction of chemokines, complement factors, and endothelial adhesion molecules. In contrast, myeloid immune responses within the hippocampus and cerebellum are subtle or absent. Treatment with the anti-tumor necrosis factor α (anti-TNF-α) antibody infliximab ablates the region-specific inflammatory response. A region-specific myeloid cell response to chronic peripheral inflammation is observed in postmortem brains from individuals with rheumatoid arthritis. Our data suggest that chronic peripheral inflammation has heterogeneous effects on the brain, as evidenced by the spectrum of myeloid cell responses observed across brain regions.

Design, synthesis and bioactivity study of N-salicyloyl tryptamine derivatives as multifunctional agents for the treatment of neuroinflammation

Because of the complex etiology in neuroinflammatory process, the design of multifunctional agents is a potent strategy to cure neuroinflammatory diseases including AD and PD. Herein, based on the combination principles, 23 of N-salicyloyl tryptamine derivatives as multifunctional agents were designed and their new application for anti-neuroinflammation was disclosed. In cyclooxygenase assay, two compounds 3 and 16 displayed extremely preferable COX-2 inhibition than N-salicyloyl tryptamine. In LPS-induced C6 and BV2 cell models, some compounds decreased the production of proinflammatory mediators NO, PGE₂, TNF-α, iNOS, COX-2 and ROS, while increased the production of IL-10. Among them, compound 3 and 16 showed approximately six-fold better inhibition on nitric oxide production than N-salicyloyl tryptamine in C6. Besides, compounds 3, 13 and 16 attenuated the activation of BV2 and C6 cells. More importantly, in vivo, compounds 3 and 16 reduced GFAP and Iba-1 levels in the hippocampus, and displayed neuroprotection in Nissl staining. Besides, both compounds 3 and 16 had high safety (LD₅₀ > 1000 mg/kg). Longer plasma half-life of compounds 3 and 16 than melatonin supported combination strategy. All these results demonstrated that N-salicyloyl tryptamine derivatives are potential anti-neuroinflammation agents for the treatment of neurodegenerative disorder.

Molecular changes associated with spinal cord aging

Age-related muscle weakness and loss of muscle mass (sarcopenia) is a universal problem in the elderly. Our previous studies indicate that alpha motor neurons (α-MNs) play a critical role in this process. The goal of the current study is to uncover changes in the aging spinal cord that contribute to loss of innervation and the downstream degenerative processes that occur in skeletal muscle. The number of α-MNs is decreased in the spinal cord of wildtype mice during aging, beginning in middle age and reaching a 41% loss by 27 months of age. There is evidence for age-related loss of myelin and mild inflammation, including astrocyte and microglia activation and an increase in levels of sICAM-1. We identified changes in metabolites consistent with compromised neuronal viability, such as reduced levels of N-acetyl-aspartate. Cleaved caspase-3 is more abundant in spinal cord from old mice, suggesting that apoptosis contributes to neuronal loss. RNA-seq analysis revealed changes in the expression of a number of genes in spinal cord from old mice, in particular genes encoding extracellular matrix components (ECM) and a 172-fold increase in MMP-12 expression. Furthermore, blood-spinal cord barrier (BSCB) permeability is increased in old mice, which may contribute to alterations in spinal cord homeostasis and exacerbate neuronal distress. Together, these data show for the first time that the spinal cord undergoes significant changes during aging, including progressive α-MNs loss that is associated with low-grade inflammation, apoptosis, changes in ECM, myelination, and vascular permeability.

Neurochemical and neuroinflammatory perturbations in two Gulf War Illness models: Modulation by the immunotherapeutic LNFPIII

Gulf War Illness (GWI) manifests a multitude of symptoms, including neurological and immunological, and approximately a third of the 1990-1991 Gulf War (GW) veterans suffer from it. This study sought to characterize the acute neurochemical (monoamine) and neuroinflammatory profiles of two established GWI animal models and examine the potential modulatory effects of the novel immunotherapeutic Lacto-N-fucopentaose III (LNFPIII). In Model 1, male C57BL/6 J mice were treated for 10 days with pyridostigmine bromide (PB) and permethrin (PM). In Model 2, a separate cohort of mice were treated for 14 days with PB and N,N-Diethyl-methylbenzamide (DEET), plus corticosterone (CORT) via drinking water on days 8-14 and diisopropylfluorophosphate (DFP) on day 15. LNFPIII was administered concurrently with GWI chemicals treatments. Brain and spleen monoamines and hippocampal inflammatory marker expression were examined by, respectively, HPLC-ECD and qPCR, 6 h post treatment cessation. Serotonergic (5-HT) and dopaminergic (DA) dyshomeostasis caused by GWI chemicals was apparent in multiple brain regions, primarily in the nucleus accumbens (5-HT) and hippocampus (5-HT, DA) for both models. Splenic levels of 5-HT (both models) and norepinephrine (Model 2) were also disrupted by GWI chemicals. LNFPIII treatment prevented many of the GWI chemicals induced monoamine alterations. Hippocampal inflammatory cytokines were increased in both models, but the magnitude and spread of inflammation was greater in Model 2; LNFPIII was anti-inflammatory, more so in the apparently milder Model 1. Overall, in both models, GWI chemicals led to monoamine disbalance and neuroinflammation. LNFPIII co-treatment prevented many of these disruptions in both models, which is indicative of its promise as a potential GWI therapeutic.

Attenuation in Nicotinic Acetylcholine Receptor α9 and α10 Subunit Double Knock-Out Mice of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is attenuated in nicotinic acetylcholine receptor (nAChR) α9 subunit knock-out (α9 KO) mice. However, protection is incomplete, raising questions about roles for related, nAChR α10 subunits in ionotropic or recently-revealed metabotropic contributions to effects. Here, we demonstrate reduced EAE severity and delayed onset of disease signs in nAChR α9/α10 subunit double knock-out (DKO) animals relative to effects in wild-type (WT) control mice. These effects are indistinguishable from contemporaneously-observed effects in nicotine-treated WT or in α9 KO mice. Immune cell infiltration into the spinal cord and brain, reactive oxygen species levels in vivo, and demyelination, mostly in the spinal cord, are reduced in DKO mice. Disease severity is not altered relative to WT controls in mice harboring a gain-of-function mutation in α9 subunits. These findings minimize the likelihood that additional deletion of nAChR α10 subunits impacts disease differently than α9 KO alone, whether through ionotropic, metabotropic, or alternative mechanisms. Moreover, our results provide further evidence of disease-exacerbating roles for nAChR containing α9 subunits (α9*-nAChR) in EAE inflammatory and autoimmune responses. This supports our hypothesis that α9*-nAChR or their downstream mediators are attractive targets for attenuation of inflammation and autoimmunity.

The Brain Entangled: The Contribution of Neutrophil Extracellular Traps to the Diseases of the Central Nervous System

Under normal conditions, neutrophils are restricted from trafficking into the brain parenchyma and cerebrospinal fluid by the presence of the brain–blood barrier (BBB). Yet, infiltration of the central nervous system (CNS) by neutrophils is a well-known phenomenon in the course of different pathological conditions, e.g., infection, trauma or neurodegeneration. Different studies have shown that neutrophil products, i.e., free oxygen radicals and proteolytic enzymes, play an important role in the pathogenesis of BBB damage. It was recently observed that accumulating granulocytes may release neutrophil extracellular traps (NETs), which damage the BBB and directly injure surrounding neurons. In this review, we discuss the emerging role of NETs in various pathological conditions affecting the CNS.

Beyond defense: regulation of neuronal morphogenesis and brain functions via Toll-like receptors

Toll-like receptors (TLRs) are well known as critical pattern recognition receptors that trigger innate immune responses. In addition, TLRs are expressed in neurons and may act as the gears in the neuronal detection/alarm system for making good connections. As neuronal differentiation and circuit formation take place along with programmed cell death, neurons face the challenge of connecting with appropriate targets while avoiding dying or dead neurons. Activation of neuronal TLR3, TLR7 and TLR8 with nucleic acids negatively modulates neurite outgrowth and alters synapse formation in a cell-autonomous manner. It consequently influences neural connectivity and brain function and leads to deficits related to neuropsychiatric disorders. Importantly, neuronal TLR activation does not simply duplicate the downstream signal pathways and effectors of classical innate immune responses. The differences in spatial and temporal expression of TLRs and their ligands likely account for the diverse signaling pathways of neuronal TLRs. In conclusion, the accumulated evidence strengthens the idea that the innate immune system of neurons serves as an alarm system that responds to exogenous pathogens as well as intrinsic danger signals and fine-tune developmental processes of neurons.

Harnessing Immunoproteostasis to Treat Neurodegenerative Disorders

Immunoproteostasis is a term used to reflect interactions between the immune system and the proteinopathies that are presumptive "triggers" of many neurodegenerative disorders. The study of immunoproteostasis is bolstered by several observations. Mutations or rare variants in genes expressed in microglial cells, known to regulate immune functions, or both can cause, or alter risk for, various neurodegenerative disorders. Additionally, genetic association studies identify numerous loci harboring genes that encode proteins of known immune function that alter risk of developing Alzheimer's disease (AD) and other neurodegenerative proteinopathies. Further, preclinical studies reveal beneficial effects and liabilities of manipulating immune pathways in various neurodegenerative disease models. Although there are concerns that manipulation of the immune system may cause more harm than good, there is considerable interest in developing immune modulatory therapies for neurodegenerative disorders. Herein, I highlight the promise and challenges of harnessing immunoproteostasis to treat neurodegenerative proteinopathies.

GABAAR α2-activated neuroimmune signal controls binge drinking and impulsivity through regulation of the CCL2/CX3CL1 balance

BACKGROUND AND PURPOSE

Toll-like receptors (TLRs) are a family of innate immune system receptors that respond to pathogen-derived and tissue damage-related ligands and are increasingly recognized for their impact on homeostasis and its dysregulation in the nervous system. TLR signaling participates in brain injury and addiction, but its role in the alcohol-seeking behavior, which initiates alcohol drinking, is still poorly understood. In this review, we discuss our findings designed to elucidate the potential contribution of the activated TLR4 signal located in neurons, on impulsivity and the predisposition to initiate alcohol drinking (binge drinking).

RESULTS

Our findings indicate that the TLR4 signal is innately activated in neurons from alcohol-preferring subjects, identifying a genetic contribution to the regulation of impulsivity and the alcohol-seeking propensity. Signal activation is through the non-canonical, previously unknown, binding of TLR4 to the α2 subunit of the γ-aminobutyric 2 acid A receptor (GABAAR α2). Activation is sustained by the stress hormone corticotrophin-releasing factor (CRF) and additional still poorly recognized ligand/scaffold proteins. Focus is on the effect of TLR4 signal activation on the balance between pro- and anti-inflammatory chemokines [chemokine (C-C motif) ligand 2 (CCL2)/chemokine (C-X3-C motif) ligand 1 (CX3CL1)] and its effect on binge drinking.

CONCLUSION

The results are discussed within the context of current findings on the distinct activation and functions of TLR signals located in neurons, as opposed to immune cells. They indicate that the balance between pro- and anti-inflammatory TLR4 signaling plays a major role in binge drinking. These findings have major impact on future basic and translational research, including the development of potential therapeutic and preventative strategies.

Mimicry of Central-Peripheral Immunity in Alzheimer's Disease and Discovery of Neurodegenerative Roles in Neutrophil

Neuroinflammatory roles of central innate immunity in brain parenchyma are well-regarded in the progression of neurodegenerative disorders including Alzheimer's disease (AD), however, the roles of peripheral immunity in central nervous system (CNS) diseases are less clear. Here, we created a microfluidic environment of human AD brains: microglial neuroinflammation induced by soluble amyloid-beta (Abeta), a signature molecule in AD and employed the environment to investigate the roles of neutrophils through the central-peripheral innate immunity crosstalk. We observed that soluble Abeta-activated human microglial cells produced chemoattractants for neutrophils including IL6, IL8, CCL2, CCL3/4, CCL5 and consequently induced reliable recruitment of human neutrophils. Particularly, we validated the discernable chemo-attractive roles of IL6, IL8, and CCL2 for neutrophils by interrupting the recruitment with neutralizing antibodies. Upon recruitment, microglia-neutrophils interaction results in the production of inflammatory mediators such as MIF and IL2, which are known to up-regulate neuroinflammation in AD. We envision that targeting the crosstalk between central-peripheral immune community is a potential strategy to reduce immunological burdens in other neuroinflammatory CNS diseases.

Myeloperoxidase Deficiency Inhibits Cognitive Decline in the 5XFAD Mouse Model of Alzheimer's Disease

Myeloperoxidase (MPO) is an enzyme expressed mostly by neutrophils and is a primary mediator of neutrophils oxidative stress response. While a profound body of evidence associates neutrophil-derived MPO in the pathogenesis of Alzheimer’s disease (AD), this role has not been assessed in an animal model of AD. Here, we produced hematologic chimerism in the 5XFAD mouse model of AD, with MPO deficient mice, resulting in 5XFAD with hematologic MPO deficiency (5XFAD-MPO KO). Behavioral examinations of 5XFAD-MPO KO showed significant superior performance in spatial learning and memory, associative learning, and anxiety/risk assessment behavior, as compared to 5XFAD mice transplanted with WT cells (5XFAD-WT). Hippocampal immunohistochemical and mRNA expression analyses showed significantly reduced levels of inflammatory mediators in 5XFAD-MPO KO mice with no apparent differences in the numbers of amyloid-β plaques. In addition, immunoblotting and mRNA analyses showed significantly reduced levels of APOE in 5XFAD-MPO KO. Together, these results indicate a substantial involvement of neutrophil-derived MPO in the pathology of 5XFAD model of AD and suggest MPO as a potential therapeutic target in AD.