Alzheimer's disease: evidence for the expression of interleukin-33 and its receptor ST2 in the brain

The role of IL-1 family of cytokines in the pathogenesis and therapy of Alzheimer's disease

Alzheimer's disease (AD) is a progressive and irreversible neurological condition that occurs with age and poses a significant global public health concern, is distinguished by the degeneration of neurons and synapses in various regions of the brain. While the exact processes behind the neurodegeneration in AD are not completely known, it is now acknowledged that inflammation may have a significant impact on the beginning and advancement of AD neurodegeneration. The severity of many neurological illnesses can be influenced by the equilibrium between pro-inflammatory and anti-inflammatory mediators. The IL-1 family of cytokines is linked to innate immune responses, which are present in both acute inflammation and chronic inflammatory diseases. Research on the role of the IL-1 family in chronic neurological disease has been concentrated on AD. In this context, there is indirect evidence suggesting its involvement in the development of the disease. This review aims to provide a summary of the contribution of every IL-1 family member in AD pathogenesis, current immunotherapies in AD disease, and present treatment possibilities for either targeting or boosting these cytokines.

Interleukin-33 ameliorates perioperative neurocognitive disorders by modulating microglial state

Perioperative neurocognitive disorders (PND) are cognitive dysfunctions that usually occur in elderly patients after anesthesia and surgery. Microglial overactivation is a key underlying mechanism. Interleukin-33 (IL-33) is a member of the IL-1 family that orchestrates microglial function. In the present study, we explored how IL-33, which regulates microglia, contributes to cognitive improvement in a male mouse model of PND. An exploratory laparotomy was performed to establish a PND model. The expression levels of IL-33 and its receptor ST2 were evaluated using Western blot. IL-33/ST2 secretion, microglial density, morphology, phagocytosis of synapse, and proliferation, and dystrophic microglia were assessed using immunofluorescence. Synaptic plasticity was measured using Golgi staining and long-term potentiation. The Morris water maze and open field test were used to evaluate cognitive function and anxiety. Hippocampal expression of IL-33 and ST2 were elevated on postoperative day 3. We confirmed that IL-33 was secreted by astrocytes and neurons, whereas ST2 mainly colocalized with microglia. IL-33 treatment induced microgliosis after anesthesia and surgery. These microglia had larger soma sizes and shorter and fragmented branches. Compared to the Surgery group, IL-33 treatment reduced the synaptic phagocytosis of microglia and increased microglial proliferation and dystrophic microglia. IL-33 treatment also reversed the impaired synaptic plasticity and cognitive function caused by anesthesia and surgery. In conclusion, these results indicate that IL-33 plays a key role in regulating microglial state and synaptic phagocytosis in a PND mouse model. IL-33 treatment has a therapeutic potential for improving cognitive dysfunction in PND.

Roles of Cytokines in Alzheimer's Disease

The neuroimmune system is a collection of immune cells, cytokines, and the glymphatic system that plays a pivotal role in the pathogenesis and progression of Alzheimer's disease (AD). Of particular focus are cytokines, a group of immune signaling molecules that facilitate communication among immune cells and contribute to inflammation in AD. Extensive research has shown that the dysregulated secretion of certain cytokines (IL-1β, IL-17, IL-12, IL-23, IL-6, and TNF-α) promotes neuroinflammation and exacerbates neuronal damage in AD. However, anti-inflammatory cytokines (IL-2, IL-3, IL-33, and IL-35) are also secreted during AD onset and progression, thereby preventing neuroinflammation. This review summarizes the involvement of pro- and anti-inflammatory cytokines in AD pathology and discusses their therapeutic potential.

Impact of Helicobacter pylori and metabolic syndrome on mast cell activation-related pathophysiology and neurodegeneration

Both Helicobacter pylori (H. pylori) infection and metabolic syndrome (MetS) are highly prevalent worldwide. The emergence of relevant research suggesting a pathogenic linkage between H. pylori infection and MetS-related cardio-cerebrovascular diseases and neurodegenerative disorders, particularly through mechanisms involving brain pericyte deficiency, hyperhomocysteinemia, hyperfibrinogenemia, elevated lipoprotein-a, galectin-3 overexpression, atrial fibrillation, and gut dysbiosis, has raised stimulating questions regarding their pathophysiology and its translational implications for clinicians. An additional stimulating aspect refers to H. pylori and MetS-related activation of innate immune cells, mast cells (MC), which is an important, often early, event in systemic inflammatory pathologies and related brain disorders. Synoptically, MC degranulation may play a role in the pathogenesis of H. pylori and MetS-related obesity, adipokine effects, dyslipidemia, diabetes mellitus, insulin resistance, arterial hypertension, vascular dysfunction and arterial stiffness, an early indicator of atherosclerosis associated with cardio-cerebrovascular and neurodegenerative disorders. Meningeal MC can be activated by triggers including stress and toxins resulting in vascular changes and neurodegeneration. Likewise, H.pylori and MetS-related MC activation is linked with: (a) vasculitis and thromboembolic events that increase the risk of cardio-cerebrovascular and neurodegenerative disorders, and (b) gut dysbiosis-associated neurodegeneration, whereas modulation of gut microbiota and MC activation may promote neuroprotection. This narrative review investigates the intricate relationship between H. pylori infection, MetS, MC activation, and their collective impact on pathophysiological processes linked to neurodegeneration. Through a comprehensive search of current literature, we elucidate the mechanisms through which H. pylori and MetS contribute to MC activation, subsequently triggering cascades of inflammatory responses. This highlights the role of MC as key mediators in the pathogenesis of cardio-cerebrovascular and neurodegenerative disorders, emphasizing their involvement in neuroinflammation, vascular dysfunction and, ultimately, neuronal damage. Although further research is warranted, we provide a novel perspective on the pathophysiology and management of brain disorders by exploring potential therapeutic strategies targeting H. pylori eradication, MetS management, and modulation of MC to mitigate neurodegeneration risk while promoting neuroprotection.

ST2 levels and neurodegenerative diseases: is this a significant relation?

Interleukin-33 (IL-33), belonging to the interleukin-1 cytokine family, has a decoy receptor soluble ST2 (sST2). IL-33 is found in oligodendrocytes and astrocytes and is involved in central nervous system healing and repair, whereas ST2 is found in microglia and astrocytes. Some studies have found a link between changes in the IL-33/ST2 pathway and neurodegenerative disorders. This review article investigates the relationship between the interleukin-33 (IL-33)/ST2 pathway and neurodegenerative disorders. It was discovered that soluble st2 levels were increased. Furthermore, IL-33 levels were found to be lower in many neurodegenerative diseases such as Alzheimer's and amyotrophic lateral sclerosis (ALS). The association with other disorders, such as ankylosing spondylitis, multiple sclerosis, and systemic lupus erythematosus (SLE), was also observed. Various studies suggest that ST2/IL-33 signalling may be pivotal in the disease modulation of neurodegenerative disorders. The serum sST2 level test can be useful in determining the inflammatory status and severity of illness in many neurodegenerative disorders. In this review, we will discuss recent findings concerning the interleukin-33 (IL-33)/ST2 pathway and its role in the diagnosis and treatment of diseases with neurodegeneration.

IL-33/ST2 Axis: A Potential Therapeutic Target in Neurodegenerative Diseases

Interleukin 33 (IL-33) belongs to the IL-1 family and is localized in the nucleus. IL-33 is primarily composed of three distinct domains, namely the N-terminal domain responsible for nuclear localization, the intermediate sense protease domain, and the C-terminal cytokine domain. Its specific receptor is the suppression of tumorigenicity 2 (ST2), which is detected in serum-stimulated fibroblasts and oncogenes. While most other cytokines are actively produced in cells, IL-33 is passively produced in response to tissue damage or cell necrosis, thereby suggesting its role as an alarm following cell infection, stress, or trauma. IL-33 plays a crucial role in congenital and acquired immunity, which assists in the response to environmental stress and maintains tissue homeostasis. IL-33/ST2 interaction further produces many pro-inflammatory cytokines. Moreover, IL-33 is crucial for central nervous system (CNS) homeostasis and the pathogenic mechanisms underlying CNS degenerative disorders. The present work summarizes the structure of IL-33, its fundamental activities, and its role in immunoregulation and neurodegenerative diseases. Therefore, this work proposes that IL-33 may play a role in the pathogenic mechanism of diseases and can be used in the development of treatment strategies.

IL-33/ST2 signaling pathway and Alzheimer's disease: A systematic review and meta-analysis

The IL-33/ST2 signaling pathway has potential relevance for clinical identification and treatment of Alzheimer's disease (AD). Here, eight databases (including CNKI, Wanfang, SinoMed, VIP, PubMed, Cochrane library, Embase and Web of Science) were employed to search for studies on IL-33/ST2 signaling pathway and its association with AD. Totally, 15 articles were included, of which 5 studies investigated the connection between IL-33 gene polymorphisms and AD, 4 studies explored the serum IL-33 and sST2 levels in patients with AD and Mild cognitive impairment (MCI), and the exact mechanisms underlying IL-33/ST2 signaling pathway in AD were explored in 6 studies. Then, the RevMan 5.4 software was used for meta-analysis, and the related studies were systematically reviewed. The results of the meta-analysis showed that serum IL-33 levels were higher in patients with AD and MCI than in healthy controls (HC), with serum IL-33 levels in AD patients significantly higher than in MCI patients (SMD = 0.26, 95 % CI: 0.02, 0.51; P = 0.04). Compared with HC, the sST2 level was significantly higher in AD patients (SMD = 1.23, 95 % CI: 0.93, 1.53; P < 0.00001) and tended to elevate in patients with MCI. The systematic review indicated that there is a significant relationship between IL-33 gene polymorphisms and susceptibility to AD; The IL-33/ST2 signaling pathway may be one of the future treatment targets for AD. Our study provides evidence to prove that serum IL-33 and sST2 have potential clinical application value as biomarkers for identifying AD.

Cause or consequence? The role of IL-1 family cytokines and receptors in neuroinflammatory and neurodegenerative diseases

Cytokines and receptors of the IL-1 family are key mediators in innate immune and inflammatory reactions in physiological defensive conditions, but are also significantly involved in immune-mediated inflammatory diseases. Here, we will address the role of cytokines of the IL-1 superfamily and their receptors in neuroinflammatory and neurodegenerative diseases, in particular Multiple Sclerosis and Alzheimer's disease. Notably, several members of the IL-1 family are present in the brain as tissue-specific splice variants. Attention will be devoted to understanding whether these molecules are involved in the disease onset or are effectors of the downstream degenerative events. We will focus on the balance between the inflammatory cytokines IL-1β and IL-18 and inhibitory cytokines and receptors, in view of future therapeutic approaches.

Increased Risk of Dementia in Patients with Atopic Dermatitis: A Nationwide Population-Based Cohort Study

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with bimodal incidence peaks in early childhood and middle-aged and older adults. Few studies have focused on the risk of dementia in AD. The aims of this study were to analyse the incidence, and risk factors for dementia in patients with AD. This nationwide population-based retrospective cohort study enrolled 38,391 adults ≥ 40 years of age with AD and 2,643,602 controls without AD from the Korean National Health Insurance System (NHIS) database from 2009 to 2016. The cumulative incidence probability of all-cause dementia, Alzheimer's disease, or vascular dementia at 8 years was 50, 39, and 7 per 1,000 person-years in patients with AD, respectively. The adjusted risks of all-cause dementia (hazard ratio (HR), 1.072; 95% confidence interval (95% CI) 1.026-1.120), and Alzheimer's disease (HR 1.051; 95% CI 1.000-1.104) were increased in patients with AD. The effect of AD on the development of all-cause dementia and Alzheimer's dementia varied according to age and diabetes mellitus (all p for interaction, < 0.05). The risks of all-cause dementia and Alzheimer's disease were increased in patients with AD. Management of modifiable risk factors is important for preventing dementia in patients with AD.

Plasma Soluble ST2 Levels Are Higher in Neurodegenerative Disorders and Associated with Poorer Cognition

BACKGROUND

Suppressor of tumorgenicity 2 (ST2) is highly expressed in brain tissue and is a receptor for interleukin 33 (IL-33). ST2 exists in two forms, a transmembrane receptor (ST2L) and a soluble decoy receptor (sST2). IL-33 binds to ST2L, triggering downstream signaling pathways involved in amyloid plaque clearance. Conversely, sST2 binds competitively to IL-33, attenuating its neuroprotective effects. High sST2 levels have been reported in mild cognitive impairment (MCI) and Alzheimer's disease (AD), suggesting that the IL-33/ST2 signaling pathway may be implicated in neurodegenerative diseases.

OBJECTIVE

To investigate plasma sST2 levels in controls and patients with MCI, AD, frontotemporal dementia (FTD), and Parkinson's disease (PD).

METHODS

Plasma sST2 levels were measured using ELISA in 397 subjects (91 HC, 46 MCI, 38 AD, 28 FTD, and 194 PD). Cerebrospinal fluid (CSF) levels of sST2 were measured in 22 subjects. Relationship between sST2 and clinical outcomes were analyzed.

RESULTS

Plasma sST2 levels were increased across all disease groups compared to controls, with highest levels seen in FTD followed by AD and PD. Dementia patients with higher sST2 had lower cross-sectional cognitive scores in Frontal Assessment Battery and Digit Span Backward. At baseline, PD-MCI patients had higher sST2, associated with worse attention. In the longitudinal PD cohort, higher sST2 significantly associated with decline in global cognition and visuospatial domains. Plasma sST2 levels correlated with CSF sST2 levels.

CONCLUSION

Plasma sST2 is raised across neurodegenerative diseases and is associated with poorer cognition. Higher baseline sST2 is a potential biomarker of disease severity in neurodegeneration.

The IL-33/ST2 Pathway in Cerebral Malaria

Interleukin-33 (IL-33) is an immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. IL-33 is abundant within the brain and spinal cord tissues where it acts as a key cytokine to coordinate the exchange between the immune and central nervous system (CNS). In this review, we report the recent advances to our knowledge regarding the role of IL-33 and of its receptor ST2 in cerebral malaria, and in particular, we highlight the pivotal role that IL-33/ST2 signaling pathway could play in brain and cerebrospinal barriers permeability. IL-33 serum levels are significantly higher in children with severe Plasmodium falciparum malaria than children without complications or noninfected children. IL-33 levels are correlated with parasite load and strongly decrease with parasite clearance. We postulate that sequestration of infected erythrocytes or merozoites liberation from schizonts could amplify IL-33 production in endothelial cells, contributing either to malaria pathogenesis or recovery.

Mast Cell Cytokines in Acute and Chronic Gingival Tissue Inflammation: Role of IL-33 and IL-37

Much evidence suggests autoimmunity in the etiopathogenesis of periodontal disease. In fact, in periodontitis, there is antibody production against collagen, DNA, and IgG, as well as increased IgA expression, T cell dysfunction, high expression of class II MHC molecules on the surface of gingival epithelial cells in inflamed tissues, activation of NK cells, and the generation of antibodies against the azurophil granules of polymorphonuclear leukocytes. In general, direct activation of autoreactive immune cells and production of TNF can activate neutrophils to release pro-inflammatory enzymes with tissue damage in the gingiva. Gingival inflammation and, in the most serious cases, periodontitis, are mainly due to the dysbiosis of the commensal oral microbiota that triggers the immune system. This inflammatory pathological state can affect the periodontal ligament, bone, and the entire gingival tissue. Oral tolerance can be abrogated by some cytokines produced by epithelial cells and activated immune cells, including mast cells (MCs). Periodontal cells and inflammatory-immune cells, including mast cells (MCs), produce cytokines and chemokines, mediating local inflammation of the gingival, along with destruction of the periodontal ligament and alveolar bone. Immune-cell activation and recruitment can be induced by inflammatory cytokines, such as IL-1, TNF, IL-33, and bacterial products, including lipopolysaccharide (LPS). IL-1 and IL-33 are pleiotropic cytokines from members of the IL-1 family, which mediate inflammation of MCs and contribute to many key features of periodontitis and other inflammatory disorders. IL-33 activates several immune cells, including lymphocytes, Th2 cells, and MCs in both innate and acquired immunological diseases. The classic therapies for periodontitis include non-surgical periodontal treatment, surgery, antibiotics, anti-inflammatory drugs, and surgery, which have been only partially effective. Recently, a natural cytokine, IL-37, a member of the IL-1 family and a suppressor of IL-1b, has received considerable attention for the treatment of inflammatory diseases. In this article, we report that IL-37 may be an important and effective therapeutic cytokine that may inhibit periodontal inflammation. The purpose of this paper is to study the relationship between MCs, IL-1, IL-33, and IL-37 inhibition in acute and chronic inflamed gingival tissue.

Interrelationship and Sequencing of Interleukins4, 13, 31, and 33 - An Integrated Systematic Review: Dermatological and Multidisciplinary Perspectives

The interrelations and sequencing of interleukins are complex (inter)actions where each interleukin can stimulate the secretion of its preceding interleukin. In this paper, we attempt to summarize the currently known roles of IL-4, IL-13, IL-31, and IL-33 from a multi-disciplinary perspective. In order to conduct a comprehensive review of the current literature, a search was conducted using PubMed, Google Scholar, Medscape, UpToDate, and Key Elsevier for keywords. The results were compiled from case reports, case series, letters, and literature review papers, and analyzed by a panel of multi-disciplinary specialist physicians for relevance. Based on 173 results, we compiled the following review of interleukin signaling and its clinical significance across a multitude of medical specialties. Interleukins are at the bed rock of a multitude of pathologies across different organ systems and understanding their role will likely lead to novel treatments and better outcomes for our patients. New interleukins are being described, and the role of this inflammatory cascade is still coming to light. We hope this multi-discipline review on the role interleukins play in current pathology assists in this scope.

Dual roles of interleukin-33 in cognitive function by regulating central nervous system inflammation

With the advent of an aging society, the incidence of dementia is increasing, resulting in a vast burden on society. It is increasingly acknowledged that neuroinflammation is implicated in various neurological diseases with cognitive dysfunction such as Alzheimer’s disease, multiple sclerosis, ischemic stroke, traumatic brain injury, and central nervous system infections. As an important neuroinflammatory factor, interleukin-33 (IL-33) is highly expressed in various tissues and cells in the mammalian brain, where it plays a role in the pathogenesis of a number of central nervous system conditions. Reams of previous studies have shown that IL-33 has both pro- and anti-inflammatory effects, playing dual roles in the progression of diseases linked to cognitive impairment by regulating the activation and polarization of immune cells, apoptosis, and synaptic plasticity. This article will summarize the current findings on the effects IL-33 exerts on cognitive function by regulating neuroinflammation, and attempt to explore possible therapeutic strategies for cognitive disorders based on the adverse and protective mechanisms of IL-33.

Signaling and functions of interleukin-33 in immune regulation and diseases

Interleukin-33 (IL-33) which belongs to the interleukin-1 (IL-1) family is an alarmin cytokine with critical roles in tissue homeostasis, pathogenic infection, inflammation, allergy and type 2 immunity. IL-33 transmits signals through its receptor IL-33R (also called ST2) which is expressed on the surface of T helper 2 (Th2) cells and group 2 innate lymphoid cells (ILC2s), thus inducing transcription of Th2-associated cytokine genes and host defense against pathogens. Moreover, the IL-33/IL-33R axis is also involved in development of multiple types of immune-related diseases. In this review, we focus on current progress on IL-33-trigggered signaling events, the important functions of IL-33/IL-33R axis in health and diseases as well as the promising therapeutic implications of these findings.

Discovery of small molecular inhibitors for interleukin-33/ST2 protein-protein interaction: a virtual screening, molecular dynamics simulations and binding free energy calculations

The interleukin-1 receptor like ST2 has emerged as a potential drug discovery target since it was identified as the receptor of the novel cytokine IL-33, which is involved in many inflammatory and autoimmune diseases. For the treatment of such IL-33-related disorders, efforts have been made to discover molecules that can inhibit the protein–protein interactions (PPIs) between IL-33 and ST2, but to date no drug has been approved. Although several anti-ST2 antibodies have entered clinical trials, the exploration of small molecular inhibitors is highly sought-after because of its advantages in terms of oral bioavailability and manufacturing cost. The aim of this study was to discover ST2 receptor inhibitors based on its PPIs with IL-33 in crystal structure (PDB ID: 4KC3) using virtual screening tools with pharmacophore modeling and molecular docking. From an enormous chemical space ZINC, a potential series of compounds has been discovered with stronger binding affinities than the control compound from a previous study. Among them, four compounds strongly interacted with the key residues of the receptor and had a binding free energy <  − 20 kcal/mol. By intensive calculations using data from molecular dynamics simulations, ZINC59514725 was identified as the most potential candidate for ST2 receptor inhibitor in this study.

Role of IL-33/ST2 Axis in Chronic Inflammatory Neurological Disorderss

Interleukin-33 (IL-33) is a member of IL-1 family of cytokines, produced constitutively by fibroblasts, endothelial cells, and epithelial cells. IL-33 can be released passively from cells during tissue damage and cell necrosis, suggesting that it may act as an alarmin. Function of IL-33 is mediated by its interaction with ST2 molecule that is expressed on many immune cells: Th2 lymphocytes, NK, NKT and mast cells, monocytes, dendritic cells and granulocytes. IL-33/ST2 pathway plays, often dual, roles in different physiological and inflammatory processes, mediating both, pathological immune responses and tissue repair. Expression of IL-33 in the central nervous system (CNS) is significantly enhanced during various pathological processes, indicating its important role in the pathogenesis of neurological inflammatory and degenerative diseases. In this review the biological features, expression of IL-33 and its ligand ST2 in CNS, and the role of IL- 33/ST2 pathway in development of Alzheimer’s disease and multiple sclerosis are discussed.

Alzheimer's disease: a step closer to understanding type 3 diabetes in African Americans

Alzheimer's disease (AD) is the fourth leading cause of death in the United States and the most common cause of adult-onset dementia. Recent results suggest an increased prevalence and severity in African Americans compared to Caucasians. Our understanding of the potential mechanism(s) underlying this ethnicity difference is limited. We previously described ethnicity-related differences in levels of neurodegenerative proteins and cytokines/chemokines in the BA21 region of African Americans and Caucasians with AD. Here, similar multiplex assays were used to examine those endpoints in patient postmortem cerebrospinal fluid (CSF). Additionally, we measured levels of C-peptide, ghrelin, gastric inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1), glucagon, insulin, leptin, PAI-1, resistin, and visfatin using a human diabetes 10-plex assay. The cytokine and chemokine assays revealed that levels of 26 chemokines or cytokines differed significantly with ethnicity, and three of those were significantly associated with gender. The neurodegenerative disease panel indicated that levels of soluble RAGE were significantly elevated in African Americans compared to Caucasians. All measures in the diabetes disease panel assay were significantly elevated in African Americans: ghrelin, GIP, GLP-1, glucagon, insulin, and visfatin. Through peripheral sample analysis, these results provide further evidence that ethnicity is critically involved in the manifestation of AD.

The role of meningeal populations of type II innate lymphoid cells in modulating neuroinflammation in neurodegenerative diseases

Recent research into meningeal lymphatics has revealed a never-before appreciated role of type II innate lymphoid cells (ILC2s) in modulating neuroinflammation in the central nervous system (CNS). To date, the role of ILC2-mediated inflammation in the periphery has been well studied. However, the exact distribution of ILC2s in the CNS and therefore their putative role in modulating neuroinflammation in neurodegenerative diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), Parkinson's disease (PD), and major depressive disorder (MDD) remain highly elusive. Here, we review the current evidence of ILC2-mediated modulation of neuroinflammatory cues (i.e., IL-33, IL-25, IL-5, IL-13, IL-10, TNFα, and CXCL16-CXCR6) within the CNS, highlight the distribution of ILC2s in both the periphery and CNS, and discuss some challenges associated with cell type-specific targeting that are important for therapeutics. A comprehensive understanding of the roles of ILC2s in mediating and responding to inflammatory cues may provide valuable insight into potential therapeutic strategies for many dementia-related disorders.

Systematic review of human post-mortem immunohistochemical studies and bioinformatics analyses unveil the complexity of astrocyte reaction in Alzheimer's disease

AIMS

Reactive astrocytes in Alzheimer's disease (AD) have traditionally been demonstrated by increased glial fibrillary acidic protein (GFAP) immunoreactivity; however, astrocyte reaction is a complex and heterogeneous phenomenon involving multiple astrocyte functions beyond cytoskeletal remodelling. To better understand astrocyte reaction in AD, we conducted a systematic review of astrocyte immunohistochemical studies in post-mortem AD brains followed by bioinformatics analyses on the extracted reactive astrocyte markers.

METHODS

NCBI PubMed, APA PsycInfo and WoS-SCIE databases were interrogated for original English research articles with the search terms 'Alzheimer's disease' AND 'astrocytes.' Bioinformatics analyses included protein-protein interaction network analysis, pathway enrichment, and transcription factor enrichment, as well as comparison with public human -omics datasets.

RESULTS

A total of 306 articles meeting eligibility criteria rendered 196 proteins, most of which were reported to be upregulated in AD vs control brains. Besides cytoskeletal remodelling (e.g., GFAP), bioinformatics analyses revealed a wide range of functional alterations including neuroinflammation (e.g., IL6, MAPK1/3/8 and TNF), oxidative stress and antioxidant defence (e.g., MT1A/2A, NFE2L2, NOS1/2/3, PRDX6 and SOD1/2), lipid metabolism (e.g., APOE, CLU and LRP1), proteostasis (e.g., cathepsins, CRYAB and HSPB1/2/6/8), extracellular matrix organisation (e.g., CD44, MMP1/3 and SERPINA3), and neurotransmission (e.g., CHRNA7, GABA, GLUL, GRM5, MAOB and SLC1A2), among others. CTCF and ESR1 emerged as potential transcription factors driving these changes. Comparison with published -omics datasets validated our results, demonstrating a significant overlap with reported transcriptomic and proteomic changes in AD brains and/or CSF.

CONCLUSIONS

Our systematic review of the neuropathological literature reveals the complexity of AD reactive astrogliosis. We have shared these findings as an online resource available at www.astrocyteatlas.org.

Nanomedicine against Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's are the two most rampant neurodegenerative disorders worldwide. Existing treatments have a limited effect on the pathophysiology but are unable to fully arrest the progression of the disease. This is due to the inability of these therapeutic molecules to efficiently cross the blood-brain barrier. We discuss how nanotechnology has enabled researchers to develop novel and efficient nano-therapeutics against these diseases. The development of nanotized drug delivery systems has permitted an efficient, site-targeted, and controlled release of drugs in the brain, thereby presenting a revolutionary therapeutic approach. Nanoparticles are also being thoroughly studied and exploited for their role in the efficient and precise diagnosis of neurodegenerative conditions. We summarize the role of different nano-carriers and RNAi-conjugated nanoparticle-based therapeutics for their efficacy in pre-clinical studies. We also discuss the challenges underlying the use of nanomedicine with a focus on their route of administration, concentration, metabolism, and any toxic effects for successful therapeutics in these diseases.

Therapeutic Opportunities of Interleukin-33 in the Central Nervous System

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is involved in various diseases. IL-33 exerts its effects via its heterodimeric receptor complex, which comprises suppression of tumorigenicity 2 (ST2) and the IL-1 receptor accessory protein (IL-1RAP). Increasing evidence has demonstrated that IL-33/ST2 signaling plays diverse but crucial roles in the homeostasis of the central nervous system (CNS) and the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infection, trauma, and ischemic stroke. In the current review, we focus on the functional roles and cellular signaling mechanisms of IL-33 in the CNS and evaluate the potential for diagnostic and therapeutic applications.

Soluble ST2, a biomarker of fibrosis, is associated with multiple risk factors, chronic diseases and total mortality in the OPERA study

Several diseases have a deleterious fibrosis component. Biomarkers indicating potential clinical utility that reliably reflect the degree of fibrosis have been introduced, one of them being soluble suppression of tumorigenicity 2 (sST2). The aim of our study was to explore the association of cardiometabolic risk factors, different diseases and total mortality with biomarker sST2 and see, how fibrosis is portrayed in these conditions. In addition, we were interested to see if sST2 levels could predict fibrosis in the long-term (21 years). The Oulu Project Elucidating Risk of Atherosclerosis (OPERA) survey collected data on the same individuals in years 1991-1993 (baseline, n = 1045), 2013-2014 (follow-up, n = 600) and mortality data until year 2019. Smoking at baseline retained a significant association with sST2 levels reflecting fibrosis development 20 years later. In the multivariate model male gender, diabetes, quick-index, levels of alanine aminotransferase (ALAT), high-density lipoprotein (HDL) cholesterol and high-sensitivity C-reactive protein (hsCRP) were associated with elevated sST2 levels at the examination 2013-2014. sST2 levels were higher among subjects suffering from cardiovascular disease (p = .031), cancer (p = .021), mild cognitive decline (p = .046) and diabetes (p < .001). Total mortality was assessed by using the Cox proportional hazard survival model analysis. sST2 (log-transformed) was an independent predictor of total mortality (HR 9.4; 95% CI 2.8-31.4, p<.001) when age, gender, diabetes, smoking, quick-index, levels of ALAT, HDL-cholesterol and hsCRP were added as covariates. In addition, elevated levels indicated worse prognosis and predicted mortality.

Atopic dermatitis and dementia risk: A nationwide longitudinal study

BACKGROUND

Retrospective studies have suggested that patients with dementia have higher prevalence of atopic dermatitis (AD) than those without dementia. However, the temporal association of AD with subsequent dementia remains unknown.

OBJECTIVE

To assess the temporal association of AD with subsequent dementia.

METHODS

We included data of patients with AD aged 45 years and older (n = 1059) and 1:10 age, sex, residence, income, and dementia-related comorbidity-matched controls (n = 10,590) from the Taiwan National Health Insurance Research Database and reviewed their subsequent dementia development from the enrollment date to the end of 2013.

RESULTS

After adjustments for dementia-related comorbidities, patients with AD were found to be more likely to develop any dementia (hazard ratio [HR], 2.02; 95% confidence interval [CI], 1.24-3.29), particularly Alzheimer's disease (HR, 3.74; 95% CI, 1.17-11.97), during the follow-up period than those in the control group. Moderate-to-severe AD was associated with a high subsequent dementia risk (HR, 4.64; 95% CI, 2.58-8.33). Sensitivity analyses with the exclusion of the first 3 (HR, 2.20; 95% CI, 1.28-3.80) or 5 (HR, 2.05; 95% CI, 1.08-3.89) years of observation revealed consistent findings.

CONCLUSION

AD may be an independent risk factor for new-onset dementia. Clinicians may monitor the trajectory of neurocognitive function among elderly patients with AD. Additional studies elucidating the pathomechanisms between AD and subsequent dementia are warranted.

The Role of the IL-33/ST2 Immune Pathway in Autoimmunity: New Insights and Perspectives

Interleukin (IL)-33, a member of IL-1 cytokine family, is produced by various immune cells and acts as an alarm to alert the immune system after epithelial or endothelial cell damage during cell necrosis, infection, stress, and trauma. The biological functions of IL-33 largely depend on its ligation to the corresponding receptor, suppression of tumorigenicity 2 (ST2). The pathogenic roles of this cytokine have been implicated in several disorders, including allergic disease, cardiovascular disease, autoimmune disease, infectious disease, and cancers. However, alerted levels of IL-33 may result in either disease amelioration or progression. Genetic variations of IL33 gene may confer protective or susceptibility risk in the onset of autoimmune diseases. The purpose of this review is to discuss the involvement of IL-33 and ST2 in the pathogenesis of a variety of autoimmune disorders, such as autoimmune rheumatic, neurodegenerative, and endocrine diseases.

The protective effect of Indian Catechu methanolic extract against aluminum chloride-induced neurotoxicity, A rodent model of Alzheimer's disease

Alzheimer's disease (AD) is the commonest neurodegenerative disorder with a wide array of manifestations, courses, and contributing causes. Despite being clinically characterized a long time ago; no treatment has been developed that could improve the pathology or slow down the disease manifestation- so far. Indian Catechu methanolic extract (ICME) has proved to have multiple beneficial effects that support its use in several disorders- especially those with complex etiology. In the present study, we evaluated the neuroprotective effect of ICME in a rat model of AD using Aluminum Chloride (AlCl3). The results showed that ICME could have a positive impact on the course of AD through its anticholinesterase effect and significant antioxidant effect which was reflected on the animals both on behavioral tests as well as hallmark pathological findings.

Structure-based discovery of interleukin-33 inhibitors: a pharmacophore modelling, molecular docking, and molecular dynamics simulation approach

Interleukin (IL)-33 is a new cytokine of the IL-1 family that is related to several inflammatory and autoimmune diseases. IL-33 binds to its ST2 receptor and leads to biological responses thereof. Currently, no drugs have been approved for the treatment of IL-33 related diseases. The aim of this study was to search for small molecules that inhibit the protein-protein interaction between IL-33 and ST2. A virtual screening was first performed to identify potential molecules that can bind IL-33. By analysing the interactions between key residues in the complex of IL-33/ST2, two pharmacophore hypotheses were then generated based on the 'mimicry' and 'pair-rule' principles. From a database of 62,074 compounds, 60 molecules satisfying the pharmacophore models were identified and docked to IL-33. Among 35 compounds successfully docked into the protein, 9 potential ligands in complex with IL-33 were selected for further analysis by molecular dynamics simulations. Based on the stability of the complexes and the interactions of each ligand with the key residues of IL-33, two compounds DB00158 and DB00642 were identified as the most potential inhibitors that can be further investigated as promising novel IL-33 inhibitory drugs.

The Novel Omega-6 Fatty Acid Docosapentaenoic Acid Positively Modulates Brain Innate Immune Response for Resolving Neuroinflammation at Early and Late Stages of Humanized APOE-Based Alzheimer's Disease Models

Neuroinflammation plays a crucial role in the development and progression of Alzheimer's disease (AD), in which activated microglia are found to be associated with neurodegeneration. However, there is limited evidence showing how neuroinflammation and activated microglia are directly linked to neurodegeneration in vivo. Besides, there are currently no effective anti-inflammatory drugs for AD. In this study, we report on an effective anti-inflammatory lipid, linoleic acid (LA) metabolite docosapentaenoic acid (DPAn-6) treatment of aged humanized EFAD mice with advanced AD pathology. We also report the associations of neuroinflammatory and/or activated microglial markers with neurodegeneration in vivo. First, we found that dietary LA reduced proinflammatory cytokines of IL1-β, IL-6, as well as mRNA expression of COX2 toward resolving neuroinflammation with an increase of IL-10 in adult AD models E3FAD and E4FAD mice. Brain fatty acid assays showed a five to six-fold increase in DPAn-6 by dietary LA, especially more in E4FAD mice, when compared to standard diet. Thus, we tested DPAn-6 in aged E4FAD mice. After DPAn-6 was administered to the E4FAD mice by oral gavage for three weeks, we found that DPAn-6 reduced microgliosis and mRNA expressions of inflammatory, microglial, and caspase markers. Further, DPAn-6 increased mRNA expressions of ADCYAP1, VGF, and neuronal pentraxin 2 in parallel, all of which were inversely correlated with inflammatory and microglial markers. Finally, both LA and DPAn-6 directly reduced mRNA expression of COX2 in amyloid-beta42 oligomer-challenged BV2 microglial cells. Together, these data indicated that DPAn-6 modulated neuroinflammatory responses toward resolution and improvement of neurodegeneration in the late stages of AD models.

Hippocampal interleukin-33 mediates neuroinflammation-induced cognitive impairments

Background

Interleukin (IL)-33 is expressed in a healthy brain and plays a pivotal role in several neuropathologies, as protective or contributing to the development of cerebral diseases associated with cognitive impairments. However, the role of IL-33 in the brain is poorly understood, raising the question of its involvement in immunoregulatory mechanisms.

Methods

We administered recombinant IL-33 (rmIL-33) by intra-hippocampal injection to C57BL/6 J (WT) and IL-1αβ deficient mice. Chronic minocycline administration was performed and cognitive functions were examined trough spatial habituation test. Hippocampal inflammatory responses were investigated by RT-qPCR. The microglia activation was assessed using immunohistological staining and fluorescence-activated cell sorting (FACS).

Results

We showed that IL-33 administration in mice led to a spatial memory performance defect associated with an increase of inflammatory markers in the hippocampus while minocycline administration limited the inflammatory response. Quantitative assessment of glial cell activation in situ demonstrated an increase of proximal intersections per radius in each part of the hippocampus. Moreover, rmIL-33 significantly promoted the outgrowth of microglial processes. Fluorescence-activated cell sorting analysis on isolated microglia, revealed overexpression of IL-1β, 48 h post-rmIL-33 administration. This microglial reactivity was closely related to the onset of cognitive disturbance. Finally, we demonstrated that IL-1αβ deficient mice were resistant to cognitive disorders after intra-hippocampal IL-33 injection.

Conclusion

Thus, hippocampal IL-33 induced an inflammatory state, including IL-1β overexpression by microglia cells, being causative of the cognitive impairment. These results highlight the pathological role for IL-33 in the central nervous system, independently of a specific neuropathological model.

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.

IL-33 and its decoy sST2 in patients with Alzheimer's disease and mild cognitive impairment

BACKGROUND

Interleukin-33 is a cytokine endowed with pro- and anti-inflammatory properties that plays a still poorly defined role in the pathogenesis of a number of central nervous system (CNS) conditions including Alzheimer's disease (AD). We analyzed this cytokine and its decoy receptor sST2 in Alzheimer's disease (AD) and mild cognitive impairment (MCI).

METHOD

IL-33 and sST2 were analyzed in serum and CSF of AD and MCI patients, comparing the results to those obtained in age-matched healthy controls (HC). Because of the ambiguous role of IL-33 in inflammation, the concentration of both inflammatory (IL-1β and IL-6) and anti-inflammatory (IL-10) cytokines was analyzed as well in serum and cerebrospinal fluid (CSF) of the same individuals. Finally, the effect of IL-33 on in vitro Aβ₄₂-stimulated monocytes of AD, MCI, and HC individuals was examined.

RESULTS

As compared to HC, (1) IL-33 was significantly decreased in serum and CSF of AD and MCI, (2) sST2 was increased in serum of AD and MCI but was undetectable in CSF, (3) serum and CSF IL-1β concentration was significantly increased and that of IL-10 was reduced in AD and MCI, whereas no differences were observed in IL-6. In vitro addition of IL-33 to LPS+Aβ ₄₂-stimulated monocytes downregulated IL-1β generation in MCI and HC, but not in AD, and stimulated IL-10 production in HC alone. IL-33 addition also resulted in a significant reduction of NF-kB nuclear translocation in LPS+Aβ₄₂-stimulated monocytes of HC alone.

CONCLUSIONS

These data support the hypothesis that IL-33 plays a complex anti-inflammatory role that is lost in AD- and MCI-associated neuroinflammation; results herein also suggest a possible use of IL-33 as a novel therapeutic approach in AD and MCI.

Mast cell-mediated neuroinflammation may have a role in attention deficit hyperactivity disorder (Review)

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental and behavioral disorder with a serious negative impact on the quality of life from childhood until adulthood, which may cause academic failure, family disharmony and even social unrest. The pathogenesis of ADHD has remained to be fully elucidated, leading to difficulties in the treatment of this disease. Genetic and environmental factors contribute to the risk of ADHD development. Certain studies indicated that ADHD has high comorbidity with allergic and autoimmune diseases, with various patients with ADHD having a high inflammatory status. Increasing evidence indicated that mast cells (MCs) are involved in the pathogenesis of brain inflammation and neuropsychiatric disorders. MCs may cause or aggravate neuroinflammation via the selective release of inflammatory factors, interaction with glial cells and neurons, activation of the hypothalamic-pituitary adrenal axis or disruption of the blood-brain barrier integrity. In the present review, the notion that MC activation may be involved in the occurrence and development of ADHD through a number of ways is discussed based on previously published studies. The association between MCs and ADHD appears to lack sufficient evidence at present and this hypothesis is considered to be worthy of further study, providing a novel perspective for the treatment of ADHD.

Increased inflammation in BA21 brain tissue from African Americans with Alzheimer's disease

Chronic neuroinflammation is strongly associated with AD and altered peripheral and central levels of chemokines and cytokines have been frequently described in those with AD. Given the increasing evidence of ethnicity-related differences in AD, it was of interest to determine if those altered chemokine and cytokine levels are ethnicity-related. Because African Americans exhibit a higher incidence of AD and increased symptom severity, we explored chemokine and cytokine concentrations in post-mortem brain tissue from the BA21 region of African Americans and Caucasians with AD using multiplex assays. IL-1β, MIG, TRAIL, and FADD levels were significantly increased in African Americans while levels of IL-3 and IL-8 were significantly decreased. Those effects did not interact with gender; however, overall levels of CCL25, CCL26 and CX3CL1 were significantly decreased in women. The NLRP3 inflammasome is thought to be critically involved in AD. Increased activation of this inflammasome in African Americans is consistent with the current results.

Glia Maturation Factor in the Pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative and neuroinflammatory disease characterized by the presence of extracellular amyloid plaques (APs) and intracellular neurofibrillary tangles (NFTs) in the brain. There is no disease modifying therapeutic options currently available for this disease. Hippocampus, entorhinal cortex (Broadmann area 28), perirhinal cortex (Broadmann area 35) and insular cortices are areas within the brain that are first ones to be severely affected in AD. Neuroinflammation is an important factor that induces neurodegeneration in AD. Glia maturation factor (GMF), a proinflammatory factor plays a crucial role in AD through activation of microglia and astrocytes to release proinflammatory mediators in the brain. Through immunohistochemical studies, we have previously shown that GMF is highly expressed in the vicinity of APs and NFTs in AD brains. Glial fibrillary acidic protein (GFAP), reactive astrocytes, ionized calcium binding adaptor molecule-1 (Iba-1) labelled activated microglia and GMF immunoreactive glial cells are increased in the entorhinal cortical layers especially at the sites of APs and Tau containing NFTs indicating a role for GMF. Overexpression of GMF in glial cells leads to neuroinflammation and neurodegeneration. Inhibition of GMF expression reduces neurodegeneration. Therefore, we suggest that GMF is a novel therapeutic target not only for AD but also for various other neurodegenerative diseases.

Serum interleukin-33 as a novel marker for long-term prognosis and recurrence in acute ischemic stroke patients

OBJECTIVES

Interleukin-33, a newly identified member of interleukin-1 family, had been confirmed to play a crucial role in regulating inflammatory responses in various disease. However, the exact role of interleukin-33 in the disease process of acute ischemic stroke still remains unclear. This study aims to demonstrate the relationship between interleukin-33 levels and long-term functional outcome as well as ischemic stroke recurrence.

METHODS

Three hundred and four first-ever acute ischemic stroke patients were recruited and basic information and history of all subjects taken within 72 hr on admission. The functional outcome was estimated by Barthel index. The multivariate logistic regression was used to analyze the prognosis, while the Cox proportional hazard model was applied to assess the recurrence risk.

RESULTS

Out of 304 subjects, 259 patients successfully completed scheduled two-year follow-up. We found that higher interleukin-33 levels correlated positively with better prognosis as compared with those with lower interleukin-33 levels who presented with poorer outcome (62.45 ± 20.50 ng/ml vs. 51.58 ± 19.16 ng/ml, p < .001). After adjustment of all confounders, interleukin-33 was associated with the one-year prognosis with an adjusted odds ratio of 0.956 (95% confidence interval, 0.937-0.976, p < .001). Furthermore, interleukin-33 levels were also closely related to recurrent ischemic stroke with an adjusted hazard ratio of 0.979 (95% confidence interval, 0.961-0.997, p = .025).

CONCLUSIONS

IL-33 can be used to predict the long-term outcomes and ischemic stroke recurrence in first-ever acute ischemic stroke patients.

IL-33 suppresses GSK-3β activation through an ST2-independent MyD88/TRAF6/RIP/PI3K/Akt pathway

Aims

The present study was conducted to explore the effect of interleukin-33 (IL-33) on glycogen synthase kinase-3β (GSK-3β) activation involving Tau phosphorylation, a critical causative factor for Alzheimer's disease (AD).

Main methods

Experiments were performed using PC-12 cells. Target proteins were knocked-down by transfecting with the siRNA for each protein. The kinase activities were assessed by monitoring phosphorylation of Thr308 and Ser473 for Akt and phosphorylation of Ser9 and Tyr216 for GSK-3β in the Western blotting.

Key findings

Exogenously applied IL-33 activated Akt and inactivated GSK-3β. IL-33-induced Akt activation and GSK-3β inactivation were significantly inhibited by knocking-down myeloid differentiation factor 88 (MyD88), tumor necrosis factor receptor associated factor 6 (TRAF6), receptor-interacting protein (RIP), or phosphatidylinositol 3 kinase (PI3K). IL-33 neutralized amyloid β_1-42 (Aβ_1-42)-induced Akt inactivation and GSK-3β activation.

Significance

The results of the present study show that IL-33 inactivates GSK-3β through an ST2-independent MyD88/TRAF6/RIP/PI3K/Akt pathway and inhibits Aβ_1-42-induced GSK-3β activation. This suggests that IL-33 could restrain GSK-3β-mediated Tau phosphorylation in AD.

Expression and Function of IL-33/ST2 Axis in the Central Nervous System Under Normal and Diseased Conditions

Interleukin-33 (IL-33) is a well-recognized immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. The abundant expression of IL-33 in brain and spinal cord prompted many scientists to explore its unique role in the central nervous system (CNS) under physiological and pathological conditions. Indeed emerging evidence from over a decade's research suggests that IL-33 acts as one of the key molecular signaling cues coordinating the network between the immune and CNS systems, particularly during the development of neurological diseases. Here, we highlight the recent advances in our knowledge regarding the distribution and cellular localization of IL-33 and its receptor ST2 in specific CNS regions, and more importantly the key roles IL-33/ST2 signaling pathway play in CNS function under normal and diseased conditions.

Differential effects of apoE and apoJ mimetic peptides on the action of an anti-Aβ scFv in 3xTg-AD mice

Anti-Aβ immunotherapy has emerged as a promising approach to treat Alzheimer's disease (AD). The single-chain variable fragment scFv-h3D6 is an anti-Aβ antibody fragment that lacks the Fc region, which is associated with the induction of microglial reactivity by the full-length monoclonal antibody bapineuzumab. ScFv-h3D6 was previously shown to restore the levels of apolipoprotein E (apoE) and apolipoprotein J (apoJ) in a triple-transgenic-AD (3xTg-AD) mouse model. Since apoE and apoJ play an important role in the development of AD, we aimed to study the in vivo effect of the combined therapy of scFv-h3D6 with apoE and apoJ mimetic peptides (MPs). Four-and-a-half-month-old 3xTg-AD mice were treated for six weeks with scFv-h3D6, apoE-MP, apoJ-MP, or a combination of scFv-h3D6 with each of the MPs, or a vehicle, and then the results were compared to non-transgenic mice. Magnetic Resonance Imaging showed a general tendency of the different treatments to protect against the reduction in brain volume. Aβ burden decreased after treatment with scFv-h3D6, apoE-MP, or apoJ-MP, but the effect was not as evident with the combined therapies. In terms of glial reactivity, apoE-MP showed a potent anti-inflammatory effect that was eased by the presence of scFv-h3D6, whereas the combination of apoJ-MP and scFv-h3D6 was not detrimental. ScFv-h3D6 alone did not induce microglial reactivity, as full-length antibodies do; rather, it reduced it. Endogenous apoE and apoJ levels were decreased by scFv-h3D6, but the MPs lead to a simultaneous increase of both apolipoproteins. While apoE-MP and apoJ-MP demonstrated different effects in the combined therapies with scFv-h3D6, they did not improve the overall protective effect of scFv-h3D6 in reducing the Aβ burden, apolipoproteins levels or microglial reactivity.

Mast Cell Proteases Activate Astrocytes and Glia-Neurons and Release Interleukin-33 by Activating p38 and ERK1/2 MAPKs and NF-κB

Inflammatory mediators released from activated microglia, astrocytes, neurons, and mast cells mediate neuroinflammation. Parkinson's disease (PD) is characterized by inflammation-dependent dopaminergic neurodegeneration in substantia nigra. 1-Methyl-4-phenylpyridinium (MPP⁺), a metabolite of parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), induces inflammatory mediators' release from brain cells and mast cells. Brain cells' interaction with mast cells is implicated in neuroinflammation. However, the exact mechanisms involved are not yet clearly understood. Mouse fetal brain-derived cultured primary astrocytes and glia-neurons were incubated with mouse mast cell protease-6 (MMCP-6) and MMCP-7, and mouse bone marrow-derived mast cells (BMMCs) were incubated with MPP⁺ and brain protein glia maturation factor (GMF). Interleukin-33 (IL-33) released from these cells was quantitated by enzyme-linked immunosorbent assay. Both MMCP-6 and MMCP-7 induced IL-33 release from astrocytes and glia-neurons. MPP⁺ and GMF were used as a positive control-induced IL-33 and reactive oxygen species expression in mast cells. Mast cell proteases and MPP⁺ activate p38 and extracellular signal-regulated kinases 1/2 (ERK1/2), mitogen-activated protein kinases (MAPKs), and transcription factor nuclear factor-kappa B (NF-κB) in astrocytes, glia-neurons, or mast cells. Addition of BMMCs from wt mice and transduction with adeno-GMF show higher chemokine (C-C motif) ligand 2 (CCL2) release. MPP⁺ activated glial cells and reduced microtubule-associated protein 2 (MAP-2) expression indicating neurodegeneration. IL-33 expression increased in the midbrain and striatum of PD brains as compared with age- and sex-matched control subjects. Glial cells and neurons interact with mast cells and accelerate neuroinflammation and these interactions can be explored as a new therapeutic target to treat PD.

IL-33/ST2L Signaling Provides Neuroprotection Through Inhibiting Autophagy, Endoplasmic Reticulum Stress, and Apoptosis in a Mouse Model of Traumatic Brain Injury

Interleukin-33 (IL-33) is a member of the interleukin-1 (IL-1) cytokine family and an extracellular ligand for the orphan IL-1 receptor ST2. Accumulated evidence shows that the IL-33/ST2 axis plays a crucial role in the pathogenesis of central nervous system (CNS) diseases and injury, including traumatic brain injury (TBI). However, the roles and molecular mechanisms of the IL-33/ST2 axis after TBI remain poorly understood. In this study, we investigated the role of IL-33/ST2 signaling in mouse TBI-induced brain edema and neurobehavioral deficits, and further exploited underlying mechanisms, using salubrinal (SAL), the endoplasmic reticulum (ER) stress inhibitor and anti-ST2L. The increase in IL-33 level and the decrease in ST2L level at injured cortex were first observed at 24 h post-TBI. By immunofluorescent double-labeled staining, IL-33 co-localized in GFAP-positive astrocytes, and Olig-2-positive oligodendrocytes, and predominantly presented in their nucleus. Additionally, TBI-induced brain water content, motor function outcome, and spatial learning and memory deficits were alleviated by IL-33 treatment. Moreover, IL-33 and SAL alone, or their combination prevented TBI-induced the increase of IL-1β and TNF-α levels, suppressed the up-regulation of ER stress, apoptosis and autophagy after TBI. However, anti-ST2L treatment could significantly invert the above effects of IL-33. Together, these data demonstrate that IL-33/ST2 signaling mitigates TBI-induced brain edema, motor function outcome, spatial learning and memory deficits, at least in part, by a mechanism involving suppressing autophagy, ER stress, apoptosis and neuroinflammation.

Stress-Induced Synaptic Dysfunction and Neurotransmitter Release in Alzheimer's Disease: Can Neurotransmitters and Neuromodulators be Potential Therapeutic Targets?

The communication between neurons at synaptic junctions is an intriguing process that monitors the transmission of various electro-chemical signals in the central nervous system. Albeit any aberration in the mechanisms associated with transmission of these signals leads to loss of synaptic contacts in both the neocortex and hippocampus thereby causing insidious cognitive decline and memory dysfunction. Compelling evidence suggests that soluble amyloid-β (Aβ) and hyperphosphorylated tau serve as toxins in the dysfunction of synaptic plasticity and aberrant neurotransmitter (NT) release at synapses consequently causing a cognitive decline in Alzheimer's disease (AD). Further, an imbalance between excitatory and inhibitory neurotransmission systems induced by impaired redox signaling and altered mitochondrial integrity is also amenable for such abnormalities. Defective NT release at the synaptic junction causes several detrimental effects associated with altered activity of synaptic proteins, transcription factors, Ca2+ homeostasis, and other molecules critical for neuronal plasticity. These detrimental effects further disrupt the normal homeostasis of neuronal cells and thereby causing synaptic loss. Moreover, the precise mechanistic role played by impaired NTs and neuromodulators (NMs) and altered redox signaling in synaptic dysfunction remains mysterious, and their possible interlink still needs to be investigated. Therefore, this review elucidates the intricate role played by both defective NTs/NMs and altered redox signaling in synaptopathy. Further, the involvement of numerous pharmacological approaches to compensate neurotransmission imbalance has also been discussed, which may be considered as a potential therapeutic approach in synaptopathy associated with AD.

Critical Roles of IL-33/ST2 Pathway in Neurological Disorders

Interleukin-33 (IL-33) is an IL-1 family member, which exhibits both pro- and anti-inflammatory properties solely based on the type of the disease itself. Generally, IL-33 is expressed by both endothelial and epithelial cells and mediates its function based on the interaction with various receptors, mainly with ST2 variants. IL-33 is a potent inducer for the Th2 immune response which includes defence mechanism in brain diseases. Thus, in this paper, we review the biological features of IL-33 and the critical roles of IL-33/ST2 pathway in selected neurological disorders including Alzheimer's disease, multiple sclerosis, and malaria infection to discuss the involvement of IL-33/ST2 pathway during these brain diseases and its potential as future immunotherapeutic agents or for intervention purposes.

Inflammasome Involvement in Alzheimer's Disease

Inflammasomes are responsible for the maturation of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-18, and IL-33 and activation of inflammatory cell death, pyroptosis. They assemble in response to cellular infection and stress or to tissue damage, promote inflammatory reactions, and are important in regulating innate immunity particularly by acting as platforms for activation of caspase proteases. They appear to be involved in several pathological processes activated by microbes including Alzheimer's disease (AD). Best characterized in microbial pathogenesis is the nucleotide-binding domain and leucine-rich repeat (NLR)-protein 3 (NLRP3) inflammasome. AD is a neurodegenerative condition in which the neuropathological hallmarks are the deposition of amyloid-β (Aβ) and hyperphosphorylated tau protein coated neurofibrillary tangles. For decades, the role of the innate immune system in the etiology of AD was considered less important, but the recently discovered inflammatory genes by genome-wide association studies driving inflammation in this disease has changed this view. Innate immune inflammatory activity in the AD brain can result from the pathological hallmark protein Aβ as well as from specific bacterial infections that tend to possess weak immunostimulatory responses for peripheral blood myeloid cell recruitment to the brain. The weak immunostimulatory activity is a consequence of their immune evasion strategies and survival. In this review we discuss the possibility that inflammasomes, particularly via the NLR family of proteins NLRP3 are involved in the pathogenesis of AD. In addition, we discuss the plausible contribution of specific bacteria playing a role in influencing the activity of the NLRP3 inflammasome to AD progression.

Ameliorative effects and possible molecular mechanisms of action of fibrauretine from Fibraurea recisa Pierre on d-galactose/AlCl3-mediated Alzheimer's disease

Fibrauretine is one of the main active ingredients from the rattan stems of Fibraurea recisa Pierre It exhibits a series of significant pharmacological effects. The present study aimed to evaluate the potential anti Alzheimer's disease (AD) effects of fibrauretine on a d-galactose/AlCl₃-induced mouse model, and the underlying mechanisms of action were further investigated for the first time. Our results showed that pretreatment with fibrauretine significantly improved the ability of spatial short-term working memory in the model mice during the Y-maze test, as well as the abilities of spatial learning and memory during the Morris water maze. The levels of brain tissue amyloid (Aβ), P-Tau, Tau and acetylcholinesterase (AchE) were evidently increased in d-galactose/AlCl₃-intoxicated mice, and these effects were reversed by fibrauretine. In contrast, a significant increase in the levels of the neurotransmitter acetylcholine (Ach) and choline acetyl transferase (ChAT) was observed in the fibrauretine-treated groups compared with the model group. Neuronal oxidative stress, evidenced by increased malondialdehyde (MDA) and nitric oxide (NO) levels and a decline in glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) activity, was significantly alleviated by fibrauretine pretreatment. The suppression of the neuroinflammatory response by fibrauretine was realized not only by the decrease in the levels of tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the brain tissues and by the enzyme-linked immunosorbent assay (ELISA) but also by the protein expression levels of nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS), which were measured by immunohistochemistry and western blotting. In addition, the protein expression levels of inflammatory factors interleukin-33 (IL-33) and ST2 in the brain tissues were detected by immunohistochemistry. Furthermore, the effects of western blotting demonstrated that the administration of fibrauretine significantly suppressed the protein expression levels of caspase-3, cleaved caspase-3, and Bax and increased the protein expression levels of Bcl-2, and the results of the H&E and TUNEL assay all suggested the inhibition of apoptosis in the neurons. The results clearly suggest that the underlying molecular mechanisms of action of the fibrauretine-mediated alleviation of d-galactose/AlCl₃-induced Alzheimer's disease may involve antioxidant, anti-inflammatory, and anti-apoptotic effects.

Fibrauretine from Fibraurea recisa Pierre exhibits ameliorative effects on d-galactose/AlCl₃-induced Alzheimer's disease. Its mechanism may involve its antioxidant, anti-inflammatory and anti-apoptotic effects.

Behavioral Changes in Mice Lacking Interleukin-33

Interleukin (IL)-33 is a member of the IL-1 family of cytokines. IL-33 is expressed in nuclei and secreted as alarmin upon cellular damage to deliver a danger signal to the surrounding cells. Previous studies showed that IL-33 is expressed in the brain and that it is involved in neuroinflammatory and neurodegenerative processes in both humans and rodents. Nevertheless, the role of IL-33 in physiological brain function and behavior remains unclear. Here, we have investigated the behaviors of mice lacking IL-33 (Il33^−/− mice). IL-33 is constitutively expressed throughout the adult mouse brain, mainly in oligodendrocyte-lineage cells and astrocytes. Notably, Il33^−/− mice exhibited reduced anxiety-like behaviors in the elevated plus maze (EPM) and the open field test (OFT), as well as deficits in social novelty recognition, despite their intact sociability, in the three-chamber social interaction test. The immunoreactivity of c-Fos proteins, an indicator of neuronal activity, was altered in several brain regions implicated in anxiety-related behaviors, such as the medial prefrontal cortex (mPFC), amygdala, and piriform cortex (PCX), in Il33^−/− mice after the EPM. Altered c-Fos immunoreactivity in Il33^−/− mice was not correlated with IL-33 expression in wild-type (WT) mice nor was IL-33 expression affected by the EPM in WT mice. Thus, our study has revealed that Il33^−/− mice exhibit multiple behavioral deficits, such as reduced anxiety and impaired social recognition. Our findings also indicate that IL-33 may regulate the development and/or maturation of neuronal circuits, rather than control neuronal activities in adult brains.

Mast Cell Activation in Brain Injury, Stress, and Post-traumatic Stress Disorder and Alzheimer's Disease Pathogenesis

Mast cells are localized throughout the body and mediate allergic, immune, and inflammatory reactions. They are heterogeneous, tissue-resident, long-lived, and granulated cells. Mast cells increase their numbers in specific site in the body by proliferation, increased recruitment, increased survival, and increased rate of maturation from its progenitors. Mast cells are implicated in brain injuries, neuropsychiatric disorders, stress, neuroinflammation, and neurodegeneration. Brain mast cells are the first responders before microglia in the brain injuries since mast cells can release prestored mediators. Mast cells also can detect amyloid plaque formation during Alzheimer's disease (AD) pathogenesis. Stress conditions activate mast cells to release prestored and newly synthesized inflammatory mediators and induce increased blood-brain barrier permeability, recruitment of immune and inflammatory cells into the brain and neuroinflammation. Stress induces the release of corticotropin-releasing hormone (CRH) from paraventricular nucleus of hypothalamus and mast cells. CRH activates glial cells and mast cells through CRH receptors and releases neuroinflammatory mediators. Stress also increases proinflammatory mediator release in the peripheral systems that can induce and augment neuroinflammation. Post-traumatic stress disorder (PTSD) is a traumatic-chronic stress related mental dysfunction. Currently there is no specific therapy to treat PTSD since its disease mechanisms are not yet clearly understood. Moreover, recent reports indicate that PTSD could induce and augment neuroinflammation and neurodegeneration in the pathogenesis of neurodegenerative diseases. Mast cells play a crucial role in the peripheral inflammation as well as in neuroinflammation due to brain injuries, stress, depression, and PTSD. Therefore, mast cells activation in brain injury, stress, and PTSD may accelerate the pathogenesis of neuroinflammatory and neurodegenerative diseases including AD. This review focusses on how mast cells in brain injuries, stress, and PTSD may promote the pathogenesis of AD. We suggest that inhibition of mast cells activation and brain cells associated inflammatory pathways in the brain injuries, stress, and PTSD can be explored as a new therapeutic target to delay or prevent the pathogenesis and severity of AD.

IL-33/ST2 Pathway as a Rational Therapeutic Target for CNS Diseases

Interleukin (IL)-33 is a member of the interleukin-1 cytokine family that is produced by many different types of tissues including the central nervous system (CNS). IL-33 mediates its effects via its heterodimeric receptor complex, comprised of ST2 and the IL-1 receptor accessory protein (IL-1RAcp). As a pleiotropic nuclear cytokine, IL-33 is a crucial factor in the development of cardiovascular diseases, allergic diseases, infectious diseases, and autoimmune diseases. Recently, accumulated evidence shows that the IL-33/ST2 axis plays a crucial and diverse role in the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infectious diseases, traumatic CNS injury, chronic pain, etc. In this review, we discuss the recent findings in the cellular signaling of IL-33 and advancement of the role of IL-33 in several CNS diseases, as well as its therapeutic potential for the treatment of those diseases.

IL-33 Acts to Express Schaffer Collateral/CA1 LTP and Regulate Learning and Memory by Targeting MyD88

Interleukin-33 (IL-33) is recognized to transmit a signal through a heterodimeric receptor complex ST2/interleukin-1 receptor accessory protein (IL-1RAcP) bearing activation of myeloid differentiation factor 88 (MyD88). High-frequency stimulation to the Schaffer collateral induced long-term potentiation (LTP) in the CA1 region of hippocampal slices from wild-type control mice. Schaffer collateral/CA1 LTP in IL-33-deficient mice was significantly suppressed, which was neutralized by application with IL-33. Similar suppression of the LTP was found with MyD88-deficient mice but not with ST2-deficient mice. In the water maze test, the acquisition latency in IL-33-deficient and MyD88-deficient mice was significantly prolonged as compared with that in wild-type control mice. Moreover, the retention latency in MyD88-deficient mice was markedly prolonged. In contrast, the acquisition and retention latencies in ST2-deficient mice were not affected. Taken together, these results show that IL-33 acts to express Schaffer collateral/CA1 LTP relevant to spatial learning and memory in a MyD88-dependent manner and that the LTP might be expressed through an IL-1R1/IL-1RAcP-MyD88 pathway in the absence of ST2.

A phase I clinical trial of dTCApFs, a derivative of a novel human hormone peptide, for the treatment of advanced/metastatic solid tumors

The aim of the present phase I first-in-human study was to investigate the safety/efficacy of dTCApFs (a novel hormone peptide that enters cells through the T1/ST2 receptor), in advanced/metastatic solid tumors. The primary objective of this open-label dose-escalation study was to determine the safety profile of dTCApFs. The study enrolled patients (aged ≥18 years) with pathologically confirmed locally advanced/metastatic solid malignancies, who experienced treatment failure or were unable to tolerate previous standard therapy. The study included 17 patients (64% male; median age, 65 years; 47% colorectal cancer, 29% pancreatic cancer). The patients received 1-3 cycles of escalating dTCApFs doses (6-96 mg/m²). The mean number ± standard deviation of treatment cycles/patient was 3.2±1.4; no dose-limiting toxicities were observed up to a dose of 96 mg/m², and the maximum tolerated dose was not reached. Half-life, maximal plasma concentration, and dTCApFs exposure were found to be linearly correlated with dose. Five patients were treated for ≥3 months (12, 24, 48 mg/m²) and experienced stable disease throughout the treatment period, and 1 experienced pathological complete response. Analysis of serum biomarkers revealed decreased levels of angiogenic factors at dTCApFs concentrations of 12-48 mg/m², increased levels of anticancer cytokines, and induction of the endoplasmic reticulum (ER) stress biomarker GRP78/BiP. Efficacy and biomarker data suggest that patients whose tumors were T1/ST2-positive exhibited a better response to dTCApFs. In conclusion, dTCApFs was found to be safe/well-tolerated, and potentially efficacious, with linear pharmacokinetics. Consistent with preclinical studies, the mechanism through which dTCApFs exerts anticancer effects appears to involve induction of ER stress, suppression of angiogenesis, and activation of the innate immune response. However, further studies are warranted.

Interleukin33 deficiency causes tau abnormality and neurodegeneration with Alzheimer-like symptoms in aged mice

Late-onset Alzheimer's disease (AD) remains a medical mystery. Recent studies have linked it to impaired repair of aged neurons. Potential involvement of interleukin33 (IL33) in AD has been reported. Here we show that IL33, which was expressed by up to 75% astrocytes in the aged brains, was critical for repair of aged neurons. Mice lacking Il33 gene (Il33^-/-) developed AD-like disease after 60-80 weeks, which was characterized by tau abnormality and a heavy loss of neurons/neurites in the cerebral cortex and hippocampus accompanied with cognition/memory impairment. We detected an abrupt aging surge in the cortical and hippocampal neurons at middle age (40 weeks). To counter the aging surge, wild-type mice rapidly upregulated repair of DNA double-strand breaks (DSBs) and autophagic clearance of cellular wastes in these neurons. Il33^-/- mice failed to do so, but instead went on to develop rapid accumulation of abnormal tau, massive DSBs and abnormal autophagic vacuoles in these neurons. Thus, uncontrolled neuronal aging surge at middle age due to lack of IL33 resulted in neurodegeneration and late-onset AD-like symptome in Il33^-/- mice. Our study also suggests that the aging surge is a time to search for biomarkers for early diagnosis of AD before massive neuron loss.