Visualizing Microglia with a Fluorescence Turn‐On Ugt1a7c Substrate

Microglia, the brain‐resident macrophage, are involved in brain development and contribute to the progression of neural disorders. Despite the importance of microglia, imaging of live microglia at a cellular resolution has been limited to transgenic mice. Efforts have therefore been dedicated to developing new methods for microglia detection and imaging. Using a thorough structure–activity relationships study, we developed CDr20, a high‐performance fluorogenic chemical probe that enables the visualization of microglia both in vitro and in vivo. Using a genome‐scale CRISPR‐Cas9 knockout screen, the UDP‐glucuronosyltransferase Ugt1a7c was identified as the target of CDr20. The glucuronidation of CDr20 by Ugt1a7c in microglia produces fluorescence.     

Metabolic responses of BV-2 cells to puerarin on its polarization using ultra-performance liquid chromatography–mass spectrometry

Microglia are the primary immune cells in the central nervous system with functional plasticity. They can be activated into M1 and M2 phenotypes when neuroinflammation-related diseases occur. M1 phenotype cells produce pro-inflammatory mediators that cause neuroinflammation and the M2 phenotype can secrete anti-inflammatory cytokines that protect neurons from damage. Therefore, inhibiting the M1 phenotype while stimulating the M2 phenotype has been suggested as a potential therapeutic approach for treating neuroinflammation-related diseases. Puerarin has been demonstrated to exert anti-inflammatory and neuroprotective effects. However, the role of puerarin in regulating microglia polarization and its reaction mechanism has not been fully elucidated. In this paper, a metabolomics approach with ultra-performance liquid chromatography–mass spectrometry was performed to investigate the metabolic changes of BV-2 cells in different phenotypes and test the effects of puerarin on polarization. Thirty-nine metabolites were identified as the biomarkers related to the polarization of BV-2 cells and puerarin intervention reverted the content of most of the biomarkers. Our study demonstrated that puerarin could play a key role in M1/M2 polarization of BV-2 cells from a perspective of metabolomics, and it could regulate the balance between promotion and suppression of inflammation.     

Convergence of hormones and autoinducers at the host/pathogen interface

Most living organisms possess sophisticated cell-signaling networks in which lipid-based signals modulate biological effects such as cell differentiation, reproduction and immune responses. Acyl homoserine lactone (AHL) autoinducers are fatty acid-based signaling molecules synthesized by several Gram-negative bacteria that are used to coordinate gene expression in a process termed “quorum sensing” (QS). Recent evidence shows that autoinducers not only control gene expression in bacterial cells, but also alter gene expression in mammalian cells. These alterations include modulation of proinflammatory cytokines and induction of apoptosis. Some of these responses may have deleterious effects on the host’s immune response, thereby leading to increased bacterial pathogenesis. Prokaryotes and eukaryotes have cohabited for approximately two billion years, during which time they have been exposed to each others’ soluble signaling molecules. We postulate that organisms from the different kingdoms of nature have acquired mechanisms to sense and respond to each others signaling molecules, and we have named this process interkingdom signaling. We further propose that autoinducers, which exhibit structural and functional similarities to mammalian lipid-based hormones, are excellent candidates for mediating this interkingdom communication. Here we will compare and contrast bacterial QS systems with eukaryotic endocrine systems, and discuss the mechanisms by which autoinducers may exploit mammalian signal transduction pathways.     

Nicotinic Acetylcholine Receptors and Microglia as Therapeutic and Imaging Targets in Alzheimer’s Disease

Amyloid-β (Aβ) accumulation and tauopathy are considered the pathological hallmarks of Alzheimer’s disease (AD), but attenuation in choline signaling, including decreased nicotinic acetylcholine receptors (nAChRs), is evident in the early phase of AD. Currently, there are no drugs that can suppress the progression of AD due to a limited understanding of AD pathophysiology. For this, diagnostic methods that can assess disease progression non-invasively before the onset of AD symptoms are essential, and it would be valuable to incorporate the concept of neurotheranostics, which simultaneously enables diagnosis and treatment. The neuroprotective pathways activated by nAChRs are attractive targets as these receptors may regulate microglial-mediated neuroinflammation. Microglia exhibit both pro- and anti-inflammatory functions that could be modulated to mitigate AD pathogenesis. Currently, single-cell analysis is identifying microglial subpopulations that may have specific functions in different stages of AD pathologies. Thus, the ability to image nAChRs and microglia in AD according to the stage of the disease in the living brain may lead to the development of new diagnostic and therapeutic methods. In this review, we summarize and discuss the recent findings on the nAChRs and microglia, as well as their methods for live imaging in the context of diagnosis, prophylaxis, and therapy for AD.     

Microglia, major player in the brain inflammation: their roles in the pathogenesis of Parkinson's disease

Inflammation, a self-defensive reaction against various pathogenic stimuli, may become harmful self-damaging process. Increasing evidence has linked chronic inflammation to a number of neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis. In the central nervous system, microglia, the resident innate immune cells play major role in the inflammatory process. Although they form the first line of defense for the neural parenchyma, uncontrolled activation of microglia may directly toxic to neurons by releasing various substances such as inflammatory cytokines (IL-1beta, TNF-alpha, IL-6), NO, PGE(2), and superoxide. Moreover, our recent study demonstrated that activated microglia phagocytose not only damaged cell debris but also neighboring intact cells. It further supports their active participation in self-perpetuating neuronal damaging cycles. In the following review, we discuss microglial responses to damaging neurons, known activators released from injured neurons and how microglia cause neuronal degeneration. In the last part, microglial activation and their role in PD are discussed in depth.     

A synthetic photoactivated protein to generate local or global Ca(2+) signals

Ca(2+) signals regulate diverse physiological processes through tightly regulated fluxes varying in location, time, frequency, and amplitude. Here, we developed LOVS1K, a genetically encoded and photoactivated synthetic protein to generate local or global Ca(2+) signals. With 300?ms blue light exposure, LOVS1K translocated to Orai1, a plasma membrane Ca(2+) channel, within seconds, generating a local Ca(2+) signal on the plasma membrane, and returning to the cytoplasm after tens of seconds. With repeated photoactivation, global Ca(2+) signals in the cytoplasm were generated to modulate engineered Ca(2+)-inducible proteins. Although Orai1 is typically associated with global store-operated Ca(2+) entry, we demonstrate that Orai1 can also generate local Ca(2+) influx on the plasma membrane. Our photoactivation system can be used to generate spatially and temporally precise Ca(2+) signals and to engineer synthetic proteins that respond to specific Ca(2+) signals.     

A Calixarene Assembly Strategy of Combined Anti-Neuroinflammation and Drug Delivery Functions for Traumatic Brain Injury Therapy

Excessive inflammatory reaction aggravates brain injury and hinders the recovery of neural function in nervous system diseases. Microglia, as the major players of neuroinflammation, control the progress of the disease. There is an urgent need for effective non-invasive therapy to treat neuroinflammation mediated by microglia. However, the lack of specificity of anti-inflammatory agents and insufficient drug dose penetrating into the brain lesion area are the main problems. Here, we evaluated a series of calixarenes and found that among them the self-assembling architecture of amphiphilic sulfonatocalix[8]arene (SC8A12C) had the most potent ability to suppress neuroinflammation in vitro and in vivo. Moreover, SC8A12C assemblies were internalized into microglia through macropinocytosis. In addition, after applying the SC8A12C assemblies to the exposed brain tissue, we observed that SC8A12C assemblies penetrated into the brain parenchyma and eliminated the inflammatory factor storm, thereby restoring neurobiological functions in a mouse model of traumatic brain injury.     

Targeting Microglia in Alzheimer’s Disease: From Molecular Mechanisms to Potential Therapeutic Targets for Small Molecules

Alzheimer’s disease (AD) is a common, progressive, and devastating neurodegenerative disorder that mainly affects the elderly. Microglial dysregulation, amyloid-beta (Aβ) plaques, and intracellular neurofibrillary tangles play crucial roles in the pathogenesis of AD. In the brain, microglia play roles as immune cells to provide protection against virus injuries and diseases. They have significant contributions in the development of the brain, cognition, homeostasis of the brain, and plasticity. Multiple studies have confirmed that uncontrolled microglial function can result in impaired microglial mitophagy, induced Aβ accumulation and tau pathology, and a chronic neuroinflammatory environment. In the brain, most of the genes that are associated with AD risk are highly expressed by microglia. Although it was initially regarded that microglia reaction is incidental and induced by dystrophic neurites and Aβ plaques. Nonetheless, it has been reported by genome-wide association studies that most of the risk loci for AD are located in genes that are occasionally uniquely and highly expressed in microglia. This finding further suggests that microglia play significant roles in early AD stages and they be targeted for the development of novel therapeutics. In this review, we have summarized the molecular pathogenesis of AD, microglial activities in the adult brain, the role of microglia in the aging brain, and the role of microglia in AD. We have also particularly focused on the significance of targeting microglia for the treatment of AD.     

Lignans from Schisandra chinensis rattan stems suppresses primary Aβ1-42-induced microglia activation via NF-κB/MAPK signaling pathway

Microglia cells play important roles in neurodegenerative diseases for clearing amyloid-β and reducing the occurrence of inflammation. In this study, the neuroinflammatory effect and the mechanism of lignans from Schisandra chinensis rattan stems (rsSCH-L) were evaluated by Aβ_1-42-induced primary microglia cell model. The results have shown that rsSCH-L could reduce the levels of pro-inflammatory cytokines, including IL-1β, TNF-α and NO. Moreover, rsSCH-L suppressed the phosphorylations of NF-κB and IκBα as well as p38, JNK and ERK proteins in Aβ_1-42-induced microglia cells. Taken together, rsSCH-L could attenuate microglia cells from neuroinflammation by activating the NF-κB/MAPK signaling pathway.     

Structures of the dimeric and monomeric chromanones, gonytolides A-C, isolated from the fungus Gonytrichum sp. and their promoting activities of innate immune responses

Innate immunity is the front line of self-defense against microbial infection. After searching for natural substances that regulate innate immunity using an ex vivo Drosophila culture system, we identified a novel dimeric chromanone, gonytolide A, as an innate immune promoter from the fungus Gonytrichum sp. along with gonytolides B and C. Gonytolide A also increased TNF-α-stimulated production of IL-8 in human umbilical vein endothelial cells.     

Mucosal dendritic cells shape mucosal immunity

Dendritic cells (DCs) are key modulators that shape the immune system. In mucosal tissues, DCs act as surveillance systems to sense infection and also function as professional antigen-presenting cells that stimulate the differentiation of naive T and B cells. On the basis of their molecular expression, DCs can be divided into several subsets with unique functions. In this review, we focus on intestinal DC subsets and their function in bridging the innate signaling and adaptive immune systems to maintain the homeostasis of the intestinal immune environment. We also review the current strategies for manipulating mucosal DCs for the development of efficient mucosal vaccines to protect against infectious diseases.     

Hypothalamic primary cilium: A hub for metabolic homeostasis

Obesity is a global health problem that is associated with adverse consequences such as the development of metabolic disorders, including cardiovascular disease, neurodegenerative disorders, and type 2 diabetes. A major cause of obesity is metabolic imbalance, which results from insufficient physical activity and excess energy intake. Understanding the pathogenesis of obesity, as well as other metabolic disorders, is important in the development of methods for prevention and therapy. The coordination of energy balance takes place in the hypothalamus, a major brain region that maintains body homeostasis. The primary cilium is an organelle that has recently received attention because of its role in controlling energy balance in the hypothalamus. Defects in proteins required for ciliary function and formation, both in humans and in mice, have been shown to cause various metabolic disorders. In this review, we provide an overview of the critical functions of primary cilia, particularly in hypothalamic areas, and briefly summarize the studies on the primary roles of cilia in specific neurons relating to metabolic homeostasis.Subject terms: Homeostasis, Hypothalamus     

Human and Limulus Blood: Opportunity for Development of A Medical Biotechnology Project in Taiwan

The function of blood is to deliver nourishments to and remove wastes from all parts of the body. It is made up of different kinds of cells bathed in a fluid called plasma. The major cellular components of blood include (1) red blood cells for carrying oxygen to the various tissues, (2) white blood cells for providing defense against infectious agents and cancer, and (3) platelets for inducing a cascade of events leading to blood clot formation that stops bleeding. The plasma also contains numerous proteins for maintaining normal balance in our body, and include (1) clotting factors such as factor VIII, factor IX, fibrinogen, and thrombin, (2) protease inhibitors and anticoagulants that regulate the coagulation pathway, the complement system, or the fibrinolytic system, (3) immunoglobulin which are antibodies directed against different infectious agents, and (4) albumin which functions as a volume expander to maintain our blood volume and is essential when threatened with severe blood loss. The plasma of the invertebrate horseshoe crab, contains three major proteins: hemocyanin, C-reactive protein (CRP), and α₂-macroglobulin. Hemocyanin functions as an oxygen-carrying protein. CRP is a lectin that binds to phosphocholine of the pneumococcus C-polysaccharide, to the chromatins of damaged cells, and to the galactose moiety of desialylated glycoprotein as a membrane-associated protein on liver marcrophages. CRP exists, however, as a normal component of the invertebrate hemolymph. α₂-macroglobulin exhibits proteinase inhibitory activity with a broad specificity that can block the activities of protease secreted from invading microorganisms. The Limulus CRP, along with the C3 homologue α₂-macroglobulin, participates in a complement - like hemolytic activity in horseshoe crab hemolymph. Whereas the vertebrate evolved to use both the innate and the adaptive immunity, the invertebrate only uses the innate immunity. The innate immunity uses germ-line encoded receptors to recognize conserved molecular constituents of infectious microorganisms, is phylogenetically older, with some of its form presumably presents in all multicellular organisms. The adaptive immunity is mediated by highly specific antigen receptors that are distributed clonally on the two types of lymphocytes, the T-cells and the B-cells. Evidence has accumulated in recent years to suggest that the innate immune system provides signals that are essential for the adaptive immune response to generate information on the origin of the antigen and the type of response to be induced. This linkage invites renewed interest in the study of the innate immune system of the horseshoe crab.     

Leukocyte invasion of the brain after peripheral trauma in zebrafish (Danio rerio)

Despite well-known systemic immune reactions in peripheral trauma, little is known about their roles in posttraumatic neurological disorders, such as anxiety, sickness, and cognitive impairment. Leukocyte invasion of the brain, a common denominator of systemic inflammation, is involved in neurological disorders that occur in peripheral inflammatory diseases, whereas the influences of peripheral leukocytes on the brain after peripheral trauma remain largely unclear. In this study, we found that leukocytes, largely macrophages, transiently invaded the brain of zebrafish larvae after peripheral trauma through vasculature-independent migration, which was a part of the systemic inflammation and was mediated by interleukin-1b (il1b). Notably, myeloid cells in the brain that consist of microglia and invading macrophages were implicated in posttraumatic anxiety-like behaviors, such as hyperactivity (restlessness) and thigmotaxis (avoidance), while a reduction in systemic inflammation or myeloid cells can rescue these behaviors. In addition, invading leukocytes together with microglia were found to be responsible for the clearance of apoptotic cells in the brain; however, they also removed the nonapoptotic cells, which suggested that phagocytes have dual roles in the brain after peripheral trauma. More importantly, a category of conserved proteins between zebrafish and humans or rodents that has been featured in systemic inflammation and neurological disorders was determined in the zebrafish brain after peripheral trauma, which supported that zebrafish is a translational model of posttraumatic neurological disorders. These findings depicted leukocyte invasion of the brain during systemic inflammation after peripheral trauma and its influences on the brain through il1b-dependent mechanisms.Subject terms: Neuroimmunology, Acute inflammation     

Custom‐Made Ceria Nanoparticles Show a Neuroprotective Effect by Modulating Phenotypic Polarization of the Microglia

The neuroprotective effect of ceria nanoparticles in the context of brain disorders has been explained by their antioxidant effect. However, the in‐depth mechanism remains unknown. As resident immune cells in the brain, microglia exert a variety of functional reprogramming termed as polarization in response to stress stimuli. Herein, custom‐made ceria nanoparticles were developed and found to scavenge multiple reactive oxygen species with extremely high efficiency. These nanoparticles drove microglial polarization from a pro‐inflammatory phenotype to an anti‐inflammatory phenotype under pathological conditions. Pretreatment of these nanoparticles changed the microglial function from detrimental to protective for the neuronal cells by blocking the pro‐inflammatory signaling. This work not only helps to elucidate the mechanism of ceria‐nanoparticle‐mediated neuroprotection but also provides a new strategy to rebalance the immuno‐environment by switching the equilibrium of the phenotypic activation of microglia.     

Effects of innate immune receptor stimulation on extracellular α-synuclein uptake and degradation by brain resident cells

Synucleinopathies are age-related neurological disorders characterized by the progressive deposition of α-synuclein (α-syn) aggregates and include Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Although cell-to-cell α-syn transmission is thought to play a key role in the spread of α-syn pathology, the detailed mechanism is still unknown. Neuroinflammation is another key pathological feature of synucleinopathies. Previous studies have identified several immune receptors that mediate neuroinflammation in synucleinopathies, such as Toll-like receptor 2 (TLR2). However, the species of α-syn aggregates varies from study to study, and how different α-syn aggregate species interact with innate immune receptors has yet to be addressed. Therefore, we investigated whether innate immune receptors can facilitate the uptake of different species of α-syn aggregates. Here, we examined whether stimulation of TLRs could modulate the cellular uptake and degradation of α-syn fibrils despite a lack of direct interaction. We observed that stimulation of TLR2 in vitro accelerated α-syn fibril uptake in neurons and glia while delaying the degradation of α-syn in neurons and astrocytes. Internalized α-syn was rapidly degraded in microglia regardless of whether TLR2 was stimulated. However, cellular α-syn uptake and degradation kinetics were not altered by TLR4 stimulation. In addition, upregulation of TLR2 expression in a synucleinopathy mouse model increased the density of Lewy-body-like inclusions and induced morphological changes in microglia. Together, these results suggest that cell type-specific modulation of TLR2 may be a multifaceted and promising therapeutic strategy for synucleinopathies; inhibition of neuronal and astroglial TLR2 decreases pathogenic α-syn transmission, but activation of microglial TLR2 enhances microglial extracellular α-syn clearance.Subject terms: Parkinson''s disease, Neurodegeneration     

Nickel induces secretion of IFN-�� by splenic natural killer cells

Although nickel hypersensitivity is known as a delayed-type hypersensitivity mediated by nickel-specific T cells, it is greatly influenced by other immune cells. Here we show that splenic natural killer cells (NK cells) directly or indirectly respond to nickel by secretion of IFN-γ. Using enzyme-linked immunosorbent spot (ELISPOT) assays, we found that nickel-reactive cells readily secreted IFN-γ when splenocytes were cultured in the presence of varying concentrations of nickel sulfate (NiSO₄) for 24 h. However, nickel-reactive IL-2- or IL- 4-secreting cells were infrequent during the 24-h culture with NiSO₄. Immune responses to nickel were innate, not adaptive, in nature since the frequency of nickel-reactive IFN-γ-secreting cells did not increase upon previous exposure to NiSO₄ and recombination activating gene (RAG)-1-deficient mice contained nickel-reactive IFN-γ-secreting cells. The involvement of NK cells in the innate response to NiSO₄ was confirmed since we could observe a significant reduction of the frequency of nickel-reactive cells in NK cell-depleted mice. Furthermore, the number of IFN-γ secreting cells was significantly reduced in the ELISPOT assays when NKG2D was blocked by anti-NKG2D antibody. These results suggest that there is an early and rapid innate immune response to nickel, which is mediated by NK cells and the NKG2D receptor. The significance of the innate response to nickel is that it may contribute to development of the late T cell-mediated delayed type hypersensitivity against nickel.     

Alterations in the peptidergic regulation of energy balance in the course of aging

With advancing age most aspects of the peptidergic regulation of energy balance are altered. The alteration involves both the peripheral peptides derived from the adipose tissue or the gastrointestinal tract and the peptides of the central nervous system (brainstem and hypothalamus). In general, the expression of orexigenic peptides and their receptors decreases with age, while that of the anorexic ones rather increases, but not simultaneously and not in a linear fashion. Apart from such quantitative changes, the efficacy of the related peptides may also change with age. These changes are not necessarily linear, either: instead of continuous decline or increase of its effects, the effects of a peptide may become less pronounced in some phases of aging and much enhanced in other ones. Comparing the individual peptides, the phasic alterations in their anabolic or catabolic roles in the regulation of energy balance may exhibit dissimilar time-patterns. In addition, within the overall anabolic or catabolic effects, the feeding and metabolic actions of certain peptides may not change simultaneously. Altogether, as compared with young adults, in middle-aged animals or individuals the anabolic processes (increased food intake with decreased energy expenditure) seem to prevail, which processes may contribute to the explanation of age-related obesity, while in the old ones the catabolic processes (anorexia with enhanced metabolic rate) dominate, which possibly explain the aging anorexia, frailty and sarcopenia.     

Anti-Neuroinflammatory Effects of Vanillin Through the Regulation of Inflammatory Factors and NF-κB Signaling in LPS-Stimulated Microglia

Applied Biochemistry and Biotechnology - Microglia, resident macrophages of the central nervous system (CNS), is responsible for immune responses and homeostasis of the CNS. Microglia plays a...