Manganese activates NLRP3 inflammasome signaling and propagates exosomal release of ASC in microglial cells

Neuropathological links between T2DM and LOAD: systematic review and meta-analysis

Recent decades have described parallel neuropathological mechanisms increasing the risk for developing late-onset Alzheimer's dementia (LOAD) in type 2 diabetes mellitus (T2DM); however, still little is known of the role of diabetic encephalopathy and brain atrophy in LOAD. The aim of this systematic review is to provide a comprehensive view on diabetic encephalopathy/cerebral atrophy, taking into account neuroimaging data, neuropathology, metabolic and endocrine mechanisms, amyloid formation, brain perfusion impairments, neuroimmunology, and inflammasome activation. Key switches were identified, to further meta-analyze genomic candidate loci and epigenetic modifications. For the qualitative meta-analysis of genomic bases extracted, human linkage studies were examined; for epigenetic mechanisms, data from both human and animal studies are described. For the systematic review of pathophysiological mechanisms, 1,259 publications were evaluated and 93 gene loci extracted for candidate risk linkages. Sixty-six publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight the insulin signaling system, vascular markers, inflammation and inflammasome pathways, amylin interactions, and glycosylation mechanisms. The protocol was registered with PROSPERO (ID: CRD42023440535).

Role of manganese in brain health and disease: Focus on oxidative stress

Manganese (Mn) is an essential trace element crucial for various physiological processes, but excessive exposure can lead to significant health concerns, particularly neurotoxicity. This review synthesizes current knowledge on Mn-induced oxidative stress and its role in cellular dysfunction and disease. We discuss how Mn promotes toxicity through multiple mechanisms, primarily through reactive oxygen species (ROS) generation, which leads to oxidative stress and disruption of cellular processes. The review examines key pathways affected by Mn toxicity, including mitochondrial dysfunction, endoplasmic reticulum stress, inflammasome activation, and epigenetic modifications. Recent studies have identified promising therapeutic compounds, including both synthetic and natural substances such as probucol, metformin, curcumin, resveratrol, and daidzein, which demonstrate protective effects through various mechanisms, including antioxidant enhancement, mitochondrial function preservation, and epigenetic pathway modulation. Understanding these mechanisms provides new insights into potential therapeutic strategies for Mn-induced disorders. This review also highlights future research directions, emphasizing the need for developing targeted therapies and investigating combination approaches to address multiple aspects of Mn toxicity simultaneously.

Pathological α-synuclein dysregulates epitranscriptomic writer METTL3 to drive neuroinflammation in microglia

Recent reports suggest dysregulation of the N6-methyladenosine (m6A) RNA modification may contribute to the pathology of neurodegenerative diseases. Herein, we show the m6A methyltransferase complex including METTL3-the catalytic component of the nuclear-localized complex-is robustly upregulated in human microglia and astrocytes exposed to αSynf and Mn. Subcellular localization studies reveal METTL3 was predominantly cytoplasmic following Mn insult but remained nuclear following αSynf stimulation in activated microglia. Functional analysis revealed METTL3 and downstream m6A readers, including YTHDF2 and IGF2BP1-3, may regulate the proinflammatory secretome of activated microglia. Notably, methyltransferase activity and m6A abundance were significantly increased following Mn and αSynf treatment. METTL3 in Mn and αSynfin vivo models of neuroinflammation, along with human postmortem tissues from Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy bodies (DLB) patients, was significantly upregulated. This was further confirmed by single-cell RNA sequencing (scRNA-seq) analysis. Overall, we demonstrate the m6A writer METTL3 may function as a major regulator of chronic neuroinflammation in synucleinopathies.

Mitophagy in perioperative neurocognitive disorder: mechanisms and therapeutic strategies

Perioperative neurocognitive disorder (PND) is a common neurological complication after surgery/anesthesia in elderly patients that affect postoperative outcome and long-term quality of life, which increases the cost of family and social resources. The pathological mechanism of PND is complex and not fully understood, and the methods of prevention and treatment of PND are very limited, so it is particularly important to analyze the mechanism of PND. Research indicates that mitochondrial dysfunction is pivotal in the initiation and progression of PND, although the precise mechanisms remain elusive and could involve disrupted mitophagy. We reviewed recent studies on the link between mitophagy and PND, highlighting the role of key proteins in abnormal mitophagy and discussing therapeutic strategies aimed at mitophagy regulation. This provides insights into the mechanisms underlying PND and potential therapeutic targets.

Microglia-derived sEV: Friend or foe in the pathogenesis of cognitive impairment

As immune cells, microglia serve a dual role in cognition. Microglia-derived sEV actively contribute to the development of cognitive impairment by selectively targeting specific cells through various substances such as proteins, RNA, DNA, lipids, and metabolic waste. In recent years, there has been an increasing focus on understanding the pathogenesis and therapeutic potential of sEV. This comprehensive review summarizes the detrimental effects of M1 microglial sEV on pathogenic protein transport, neuroinflammation, disruption of the blood-brain barrier (BBB), neuronal death and synaptic dysfunction in relation to cognitive damage. Additionally, it highlights the beneficial effects of M2 microglia on alleviating cognitive impairment based on evidence from cellular experiments and animal studies. Furthermore, since microglial-secreted sEV can be found in cerebrospinal fluid or cross the BBB into plasma circulation, they play a crucial role in diagnosing cognitive impairment. However, using sEV as biomarkers is still at an experimental stage and requires further clinical validation. Future research should aim to explore the mechanisms underlying microglial involvement in various nervous system disorders to identify novel targets for clinical interventions.

KCa3.1 Contributes to Neuroinflammation and Nigral Dopaminergic Neurodegeneration in Experimental models of Parkinson's Disease

Chronic neuroinflammation and misfolded α-synuclein (αSyn) have been identified as key pathological correlates driving Parkinson's disease (PD) pathogenesis; however, the contribution of ion channels to microglia activation in the context of α-synucleinopathy remains elusive. Herein, we show that KCa3.1, a calcium-activated potassium channel, is robustly upregulated within microglia in multiple preclinical models of PD and, most importantly, in human PD and dementia with Lewy bodies (DLB) brains. Pharmacological inhibition of KCa3.1 via senicapoc or TRAM-34 inhibits KCa3.1 channel activity and the associated reactive microglial phenotype in response to aggregated αSyn, as well as ameliorates of PD like pathology in diverse PD mouse models. Additionally, proteomic and transcriptomic profiling of microglia revealed that senicapoc ameliorates aggregated αSyn-induced, inflammation-associated pathways and dysregulated metabolism in primary microglial cells. Mechanistically, FYN kinase in a STAT1 dependent manner regulates KCa3.1 mediated the microglial reactive activation phenotype after α-synucleinopathy. Moreover, reduced neuroinflammation and subsequent PD-like neuropathology were observed in SYN AAV inoculated KCa3.1 knockout mice. Together, these findings suggest that KCa3.1 inhibition represents a novel therapeutic strategy for treating patients with PD and related α-synucleinopathies.

Endoplasmic Reticulum-Targeted Polymer-Manganese Nanocomplexes for Tumor Immunotherapy

Manganese ions (Mn2+) are an immune activator that enhances the activation of both cGAS and STING proteins. The STING signaling activation and subsequential immune responses are predominantly associated with endoplasmic reticulum (ER). Therefore, ER targeting of Mn2+ in the subcellular compartments would promote the activation of STING signaling pathways. Herein, we report the design of ER-targeted manganese-based nanocomplexes (NCs) by complexation of Mn2+ with a zwitterionic polymer, poly[2-(N-oxide-N,N-dimethylamino) ethyl methacrylate] (OPDMA). The Mn/OPDMA nanocomplexes (Mn/OPDMA NCs) keep a long blood circulation for tumor accumulation and trigger adsorption-mediated transcytosis for extravasation and deep tumor penetration. Notably, in the tumor-associated macrophages, the Mn/OPDMA NCs can preferentially translocate to their ERs, significantly enhancing cGAS-STING pathway activation for tumor-associated macrophage polarization and IFN-β secretion. In mouse colon and hepatocellular cancer models, the intravenously administrated Mn/OPDMA NCs efficiently remodel tumor immune microenvironment, greatly retard tumor growths by 2.4- to 5-fold, and prolong the mouse survivals compared to free Mn2+-treated mice. This study provides the ER-targeted delivery of Mn2+ that achieves robust STING activation and, thus, potent systemic tumor inhibition without the toxicity of free Mn2+.

The Role of Small Extracellular Vesicles Derived from Glial Cells in the Central Nervous System under both Normal and Pathological Conditions

In recent decades, researchers and clinicians have increasingly focused on glial cell function. One of the primary mechanisms influencing these functions is through extracellular vesicles (EVs), membrane-bound particles released by cells that are essential for intercellular communication. EVs can be broadly categorized into four main types based on their size, origin, and biogenesis: large EVs, small EVs (sEVs), autophagic EVs, and apoptotic bodies. Small EVs (sEVs) are involved in various physiological and pathological processes such as immune responses, angiogenesis, and cellular communication, primarily by transferring proteins, lipids, and nucleic acids to recipient cells. Interactions among glial cells mediated by small EVs can significantly modulate cell polarization and influence glial behavior through miRNA transfer. This communication, facilitated by small EVs in glial cells, is crucial for neuroinflammation, immune responses, and disease progression. This comprehensive review focuses on driven by glial small EVs, highlighting their roles in transporting biomolecules and modulating the functions of recipient cells. Furthermore, we provide an in-depth overview of the specific contributions of small EVs derived from three principal types of glial cells: oligodendrocytes, astrocytes, and microglia.

Biotin mitigates the development of manganese-induced, Parkinson's disease-related neurotoxicity in Drosophila and human neurons

Chronic exposure to manganese (Mn) induces manganism and has been widely implicated as a contributing environmental factor to Parkinson's disease (PD), featuring notable overlaps between the two in motor symptoms and clinical hallmarks. Here, we developed an adult Drosophila model of Mn toxicity that recapitulated key parkinsonian features, spanning behavioral deficits, neuronal loss, and dysfunctions in lysosomes and mitochondria. Metabolomics analysis of the brain and body tissues of these flies at an early stage of toxicity identified systemic changes in the metabolism of biotin (also known as vitamin B7) in Mn-treated groups. Biotinidase-deficient flies showed exacerbated Mn-induced neurotoxicity, parkinsonism, and mitochondrial dysfunction. Supplementing the diet of wild-type flies with biotin ameliorated the pathological phenotypes of concurrent exposure to Mn. Biotin supplementation also ameliorated the pathological phenotypes of three standard fly models of PD. Furthermore, supplementing the culture media of human induced stem cells (iPSCs) differentiated midbrain dopaminergic neurons with biotin protected against Mn-induced mitochondrial dysregulation, cytotoxicity, and neuronal loss. Last, analysis of the expression of genes encoding biotin-related proteins in patients with PD revealed increased amounts of biotin transporters in the substantia nigra compared with healthy controls, suggesting a potential role of altered biotin metabolism in PD. Together, our findings identified changes in biotin metabolism as underlying Mn neurotoxicity and parkinsonian pathology in flies, for which dietary biotin supplementation was preventative.

The gut-brain axis: Unveiling the impact of xenobiotics on neurological health and disorders

The Gut-Brain Axis (GBA) is a crucial link between the gut microbiota and the central nervous system. Xenobiotics, originating from diverse sources, play a significant role in shaping this interaction. This review examines how these compounds influence neurotransmitter dynamics within the GBA. Environmental pollutants can disrupt microbial populations, impacting neurotransmitter synthesis-especially serotonin, gamma-aminobutyric acid (GABA), and dopamine pathways. Such disruptions affect mood regulation, cognition, and overall neurological function. Xenobiotics also contribute to the pathophysiology of neurological disorders, with changes in serotonin levels linked to mood disorders and imbalances in GABA and dopamine associated with anxiety, stress, and reward pathway disorders. These alterations extend beyond the GBA, leading to complications in neurological health, including increased risk of neurodegenerative diseases due to neuroinflammation triggered by neurotransmitter imbalances. This review provides a comprehensive overview of how xenobiotics influence the GBA and their implications for neurological well-being.

Zinc homeostasis regulates caspase activity and inflammasome activation

Inflammasome activation drives pyroptotic cell death and the release of inflammatory cytokines, and many diseases involve its overactivation. Zinc is essential for all organisms as a trace element, but its functions in innate immunity remain undefined. Here, we reported that Zn2+ inhibits caspase-1 to hinder inflammasome activation. We first identified the zinc exporter solute carrier family 30 member 1 (SLC30A1) as an inflammasome regulator, using a genome-wide CRISPR-Cas9-mediated screen. SLC30A1 deficiency suppressed multiple inflammasomes by increasing intracellular levels of Zn2+, which bound and inhibited caspase-1 at its active site residues H237, C244 and C285. Mutation of these residues almost completely blocked zinc binding. Similarly, Zn2+ also inhibited caspase-4/5/11-mediated noncanonical inflammasome activation. Importantly, zinc supplementation significantly relieved cecal ligation and puncture (CLP)-induced sepsis, Imiquimod (IMQ)-induced psoriasis and Alzheimer's disease. Thus, zinc might be used to treat inflammasome-related diseases as a broad-spectrum inflammasome inhibitor.

NLRP1 inflammasome in neurodegenerative disorders: From pathology to therapies

Neuroinflammation is a critical component in neurodegenerative disorders. The inflammasome, facilitates the cleavage of caspase-1, leading to the maturation and subsequent secretion of inflammatory factors interleukin (IL)-1β and IL-18. Consequently, pyroptosis mediated by gasdermin D, exacerbates neuroinflammation. Among the inflammasomes, NLRP1/3 are predominant in the central nervous system (CNS), Although NLRP1 was the earliest discovered inflammasome, the specific involvement of NLRP1 in neurodegenerative diseases remains to be fully elucidated. Recently, the discovery of an endogenous inhibitor of NLRP1, dipeptidyl peptidase 9, suggests the feasibility of producing of small-molecule drugs targeting NLRP1. This review describes the latest findings on the role of the NLRP1 inflammasome in the pathology of neurodegenerative disorders, including Alzheimer's disease, and summarises the regulatory mechanisms of NLRP1 inflammasome activation in the CNS. Furthermore, we highlight the recent progress in developing small-molecule and biological inhibitors that modulate the NLRP1 infammasome for the treatment of neurodegenerative disorders, some of which are advancing to preclinical testing. SIGNIFICANCE STATEMENT: The objective of this review is to synthesise the research on the structure, activation, and regulatory mechanisms of the NLRP1 inflammasome, along with its potential impact on both acute and chronic neurodegenerative conditions. The discovery of endogenous inhibitors, such as dipeptidyl peptidase 9 and thioredoxin, and their interaction with NLRP1 suggest the possibility of developing NLRP1-targeted small-molecule drugs for the treatment of neurodegenerative disorders. This review also discusses the use of both direct and indirect NLRP1 inhibitors as prospective therapeutic strategies for these conditions.

Manganese Exposure Enhances the Release of Misfolded α-Synuclein via Exosomes by Impairing Endosomal Trafficking and Protein Degradation Mechanisms

Excessive exposure to manganese (Mn) increases the risk of chronic neurological diseases, including Parkinson's disease (PD) and other related Parkinsonisms. Aggregated α-synuclein (αSyn), a hallmark of PD, can spread to neighboring cells by exosomal release from neurons. We previously discovered that Mn enhances its spread, triggering neuroinflammatory and neurodegenerative processes. To better understand the Mn-induced release of exosomal αSyn, we examined the effect of Mn on endosomal trafficking and misfolded protein degradation. Exposing MN9D dopaminergic neuronal cells stably expressing human wild-type (WT) αSyn to 300 μM Mn for 24 h significantly suppressed protein and mRNA expression of Rab11a, thereby downregulating endosomal recycling, forcing late endosomes to mature into multivesicular bodies (MVBs). Ectopic expression of WT Rab11a significantly mitigated exosome release, whereas ectopic mutant Rab11a (S25N) increased it. Our in vitro and in vivo studies reveal that Mn exposure upregulated (1) mRNA and protein levels of endosomal Rab27a, which mediates the fusion of MVBs with the plasma membrane; and (2) expression of the autophagosomal markers Beclin-1 and p62, but downregulated the lysosomal marker LAMP2, thereby impairing autophagolysosome formation as confirmed by LysoTracker, cathepsin, and acridine orange assays. Our novel findings demonstrate that Mn promotes the exosomal release of misfolded αSyn by impairing endosomal trafficking and protein degradation.

Complement Molecule C3a Exacerbates Early Brain Injury After Subarachnoid Hemorrhage by Inducing Neuroinflammation Through the C3aR-ERK-P2X7-NLRP3 Inflammasome Signaling Axis

An important aspect of the pathophysiology of early brain damage (EBI) after subarachnoid hemorrhage (SAH) is inflammasome-mediated neuroinflammation. It has been demonstrated that C3aR activation exacerbates neuronal damage in a number of neurological disorders. This study aims to explore the role of C3a in activating the NLRP3 inflammasome and exacerbating neuroinflammation after SAH. Preprocessing of RNA-seq transcriptome datasets using bioinformatics analysis, and screening of differentially expressed genes between SAH patients and healthy individuals from the GEO database. Internal carotid artery puncture was performed to establish SAH models in rats and mice. SAH grading, neurological scoring, brain water content, behavioral analysis, and assessments using ELISA, Western blot, immunofluorescence, and immunohistochemistry were conducted. An in vitro model of SAH was induced in BV-2 cells treated with heme (200 μM). The mechanism of C3a in post-SAH neuroinflammation was studied by interfering with and inhibiting C3aR. Results showed that the expression of C3aR was upregulated in the GEO dataset (serum of SAH patients) and identified as a key differential gene in SAH. Further, elevated levels of C3a were found in the cerebrospinal fluid of clinically collected SAH patients. In the cerebral cortex and/or serum of SAH rats, expression of C3a, IL-1β, IL-6, TNF-α, CD11b, and Ki67 were significantly increased, while IL-10 was significantly decreased. Correlation analysis revealed that C3a showed negative correlation with IL-10 and positive correlation with IL-1β, IL-6, TNF-α, CD11b, and Ki67. After stimulation with heme, protein levels of C3a increased in BV-2 cells. Interfering with C3aR significantly reduced LDH release, IL-1β secretion, Caspase1 activation, levels of NLRP3 expression and ASC oligomerization, and ATP release after heme stimulation in BV-2. Subsequently, the addition of inhibitors of ERK1/2 phosphorylation demonstrated that C3a promotes ATP efflux by activating ERK1/2 phosphorylation, thereby activating P2X7. Further addition of JNJ-55308942 (a P2X7R antagonist) revealed that C3a activated the NLRP3 inflammasome via P2X7. Finally, administering SB290157 (a C3aR inhibitor) in vivo effectively alleviated brain edema, reduced mortality, improved Garcia score, ameliorated motor dysfunction, and suppressed inflammation and NLRP3 inflammasome activation in mice after SAH. Overall, C3a exacerbates EBI-associated NLRP3 inflammasome and neuroinflammation via the C3aR-ERK-P2X7 pathway after SAH. Inhibiting C3aR may serve as a one possible treatment approach to alleviate SAH after EBI.

The Yin and Yang of Microglia-Derived Extracellular Vesicles in CNS Injury and Diseases

Microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in maintaining neural homeostasis but can also contribute to disease and injury when this state is disrupted or conversely play a pivotal role in neurorepair. One way that microglia exert their effects is through the secretion of small vesicles, microglia-derived exosomes (MGEVs). Exosomes facilitate intercellular communication through transported cargoes of proteins, lipids, RNA, and other bioactive molecules that can alter the behavior of the cells that internalize them. Under normal physiological conditions, MGEVs are essential to homeostasis, whereas the dysregulation of their production and/or alterations in their cargoes have been implicated in the pathogenesis of numerous neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), spinal cord injury (SCI), and traumatic brain injury (TBI). In contrast, MGEVs may also offer therapeutic potential by reversing inflammation or being amenable to engineering for the delivery of beneficial biologics or drugs. The effects of MGEVs are determined by the phenotypic state of the parent microglia. Exosomes from anti-inflammatory or pro-regenerative microglia support neurorepair and cell survival by delivering neurotrophic factors, anti-inflammatory mediators, and molecular chaperones. Further, MGEVs can also deliver components like mitochondrial DNA (mtDNA) and proteins to damaged neurons to enhance cellular metabolism and resilience. MGEVs derived from pro-inflammatory microglia can have detrimental effects on neural health. Their cargo often contains pro-inflammatory cytokines, molecules involved in oxidative stress, and neurotoxic proteins, which can exacerbate neuroinflammation, contribute to neuronal damage, and impair synaptic function, hindering neurorepair processes. The role of MGEVs in neurodegeneration and injury-whether beneficial or harmful-largely depends on how they modulate inflammation through the pro- and anti-inflammatory factors in their cargo, including cytokines and microRNAs. In addition, through the propagation of pathological proteins, such as amyloid-beta and alpha-synuclein, MGEVs can also contribute to disease progression in disorders such as AD and PD, or by the transfer of apoptotic or necrotic factors, they can induce neuron toxicity or trigger glial scarring during neurological injury. In this review, we have provided a comprehensive and up-to-date understanding of the molecular mechanisms underlying the multifaceted role of MGEVs in neurological injury and disease. In particular, the role that specific exosome cargoes play in various pathological conditions, either in disease progression or recovery, will be discussed. The therapeutic potential of MGEVs has been highlighted including potential engineering methodologies that have been employed to alter their cargoes or cell-selective targeting. Understanding the factors that influence the balance between beneficial and detrimental exosome signaling in the CNS is crucial for developing new therapeutic strategies for neurodegenerative diseases and neurotrauma.

Manganese inhibits HBV transcription and promotes HBsAg degradation at non-toxic levels

Chronic hepatitis B virus (HBV) infection continues to pose a significant global health challenge. However, therapeutic measures for a cure are lacking in clinical practice. Manganese, an essential trace element, has garnered attention due to its potential to activate innate immune pathways and its significant role in antiviral and antitumor immunity. Yet, the specific impact of manganese on chronic hepatitis B has been largely unexplored. Our research reveals that manganese substantially inhibits HBV replication in hepatocellular carcinoma cells at non-toxic levels. This suppression occurs independently of well-known anti-HBV innate immune pathways, such as the cGAS-STING pathway. Mechanistically, manganese decreases HBV transcription by diminishing the levels of liver-specific transcription factors. Furthermore, it activates the mTOR pathway, enhancing HBsAg ubiquitination through the upregulation of the ubiquitin ligase β-TrCP and increasing proteasome activity via the augmentation of its subunits, leading to a ubiquitin-dependent degradation of HBsAg. Significantly, our study also uncovers a notable clinical correlation between manganese levels and chronic hepatitis B infection. These findings position manganese as a critical element in diminishing HBV replication, offering a new direction in the management of chronic hepatitis B.

Brain incoming call from glia during neuroinflammation: Roles of extracellular vesicles

The functionality of the central nervous system (CNS) relies on the connection, integration, and the exchange of information among neural cells. The crosstalk among glial cells and neurons is pivotal for a series of neural functions, such as development of the nervous system, electric conduction, synaptic transmission, neural circuit establishment, and brain homeostasis. Glial cells are crucial players in the maintenance of brain functionality in physiological and disease conditions. Neuroinflammation is a common pathological process in various brain disorders, such as neurodegenerative diseases, and infections. Glial cells, including astrocytes, microglia, and oligodendrocytes, are the main mediators of neuroinflammation, as they can sense and respond to brain insults by releasing pro-inflammatory or anti-inflammatory factors. Recent evidence indicates that extracellular vesicles (EVs) are pivotal players in the intercellular communication that underlies physiological and pathological processes. In particular, glia-derived EVs play relevant roles in modulating neuroinflammation, either by promoting or inhibiting the activation of glial cells and neurons, or by facilitating the clearance or propagation of pathogenic proteins. The involvement of EVs in neurodegenerative diseases such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Huntington's Disease (HD), and Multiple Sclerosis (MS)- which share hallmarks such as neuroinflammation and oxidative stress to DNA damage, alterations in neurotrophin levels, mitochondrial impairment, and altered protein dynamics- will be dissected, showing how EVs act as pivotal cell-cell mediators of toxic stimuli, thereby propagating degeneration and cell death signaling. Thus, this review focuses on the EVs secreted by microglia, astrocytes, oligodendrocytes and in neuroinflammatory conditions, emphasizing on their effects on neurons and on central nervous system functions, considering both their beneficial and detrimental effects.

Epitranscriptomic reader YTHDF2 regulates SEK1(MAP2K4)-JNK-cJUN inflammatory signaling in astrocytes during neurotoxic stress

As the most abundant glial cells in the central nervous system (CNS), astrocytes dynamically respond to neurotoxic stress, however, the key molecular regulators controlling the inflammatory status of these sentinels during neurotoxic stress are many and complex. Herein, we demonstrate that the m6A epitranscriptomic mRNA modification tightly regulates the pro-inflammatory functions of astrocytes. Specifically, the astrocytic neurotoxic stressor, manganese (Mn), downregulated the m6A reader YTHDF2 in human and mouse astrocyte cultures and in the mouse brain. Functionally, YTHDF2 knockdown augmented, while its overexpression dampened, the neurotoxic stress-induced proinflammatory response, suggesting YTHDF2 serves as a key upstream regulator of inflammatory responses in astrocytes. Mechanistically, YTHDF2 RIP-sequencing identified MAP2K4 (MKK4; SEK1) mRNA as a YTHDF2 target influencing inflammatory signaling. Our target validation revealed that Mn-exposed astrocytes mediate proinflammatory responses by activating the phosphorylation of SEK1, JNK, and cJUN signaling. Collectively, YTHDF2 serves as a key upstream 'molecular switch' controlling SEK1(MAP2K4)-JNK-cJUN proinflammatory signaling in astrocytes.

Strategies for the development of metalloimmunotherapies

Metal ions play crucial roles in the regulation of immune pathways. In fact, metallodrugs have a long record of accomplishment as effective treatments for a wide range of diseases. Here we argue that the modulation of interactions of metal ions with molecules and cells involved in the immune system forms the basis of a new class of immunotherapies. By examining how metal ions modulate the innate and adaptive immune systems, as well as host-microbiota interactions, we discuss strategies for the development of such metalloimmunotherapies for the treatment of cancer and other immune-related diseases.

Dopaminergic REST/NRSF is protective against manganese-induced neurotoxicity in mice

Chronic exposure to elevated levels of manganese (Mn) may cause a neurological disorder referred to as manganism. The transcription factor REST is dysregulated in several neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. REST upregulated tyrosine hydroxylase and induced protection against Mn toxicity in neuronal cultures. In the present study, we investigated if dopaminergic REST plays a critical role in protecting against Mn-induced toxicity in vivo using dopaminergic REST conditional knockout (REST-cKO) mice and REST loxP mice as wild-type (WT) controls. Restoration of REST in the substantia nigra (SN) with neuronal REST AAV vector infusion was performed to further support the role of REST in Mn toxicity. Mice were exposed to Mn (330 μg, intranasal, daily for 3 weeks), followed by behavioral tests and molecular biology experiments. Results showed that Mn decreased REST mRNA/protein levels in the SN-containing midbrain, as well as locomotor activity and motor coordination in WT mice, which were further decreased in REST-cKO mice. Mn-induced mitochondrial insults, such as impairment of fission/fusion and mitophagy, apoptosis, and oxidative stress, in the midbrain of WT mice were more pronounced in REST-cKO mice. However, REST restoration in the SN of REST-cKO mice attenuated Mn-induced neurotoxicity. REST's molecular target for its protection is unclear, but REST attenuated Mn-induced mitochondrial dysregulation, indicating that it is a primary intracellular target for both Mn and REST. These novel findings suggest that dopaminergic REST in the nigrostriatal pathway is critical in protecting against Mn toxicity, underscoring REST as a potential therapeutic target for treating manganism.

Signal Transduction Associated with Mn-induced Neurological Dysfunction

Manganese (Mn) is a heavy metal that occurs widely in nature and has a vital physiological role in growth and development. However, excessive exposure to Mn can cause neurological damage, especially cognitive dysfunction, such as learning disability and memory loss. Numerous studies on the mechanisms of Mn-induced nervous system damage found that this metal targets a variety of metabolic pathways, for example, endoplasmic reticulum stress, apoptosis, neuroinflammation, cellular signaling pathway changes, and neurotransmitter metabolism interference. This article reviews the latest research progress on multiple signaling pathways related to Mn-induced neurological dysfunction.

Lead exposure induces neurodysfunction through caspase-1-mediated neuronal pyroptosis

Chronic lead (Pb) exposure causes neurodysfunction and contributes to the development of neurodegenerative disease. However, the mechanism of Pb-induced neurological dysfunction have yet to be fully elucidated. This study determined the role pyroptosis plays in Pb-induced neurodysfunction in neurons. We used both in vitro and in vivo approaches to explore whether Pb exposure induces caspase-1-mediated pyroptosis in neurons and its relationship to Pb-induced neurological disorders. Our findings showed that caspase-1-mediated pyroptosis in Pb-exposed neurons activated glycogen synthase kinase 3 protease activity by disrupting Ca2+/calmodulin-dependent protein kinase II/cAMP-response element binding protein pathway, leading to neurological disorders. Moreover, the caspase-1 inhibition VX-765 or the non-steroidal anti-inflammatory drug sodium para-aminosalicylic acid (PAS-Na) attenuated the Pb-induced neurological disorders by alleviating caspase-1 mediated neuronal pyroptosis. Our novel studies suggest that caspase-1-mediated pyroptosis in neurons represents a potential mechanism for Pb-induced neurodysfunction, identifying a putative target for attenuating the neurodegenerative effects induced by this metal.

Manganese in autism spectrum disorder and attention deficit hyperactivity disorder: The state of the art

The objective of the present narrative review was to synthesize existing clinical and epidemiological findings linking manganese (Mn) exposure biomarkers to autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), and to discuss key pathophysiological mechanisms of neurodevelopmental disorders that may be affected by this metal. Existing epidemiological data demonstrated both direct and inverse association between Mn body burden and ASD, or lack of any relationship. In contrast, the majority of studies revealed significantly higher Mn levels in subjects with ADHD, as well as direct relationship between Mn body burden with hyperactivity and inattention scores in children, although several studies reported contradictory results. Existing laboratory studies demonstrated that impaired attention and hyperactivity in animals following Mn exposure was associated with dopaminergic dysfunction and neuroinflammation. Despite lack of direct evidence on Mn-induced neurobiological alterations in patients with ASD and ADHD, a plethora of studies demonstrated that neurotoxic effects of Mn overexposure may interfere with key mechanisms of pathogenesis inherent to these neurodevelopmental disorders. Specifically, Mn overload was shown to impair not only dopaminergic neurotransmission, but also affect metabolism of glutamine/glutamate, GABA, serotonin, noradrenaline, thus affecting neuronal signaling. In turn, neurotoxic effects of Mn may be associated with its ability to induce oxidative stress, apoptosis, and neuroinflammation, and/or impair neurogenesis. Nonetheless, additional detailed studies are required to evaluate the association between environmental Mn exposure and/or Mn body burden and neurodevelopmental disorders at a wide range of concentrations to estimate the potential dose-dependent effects, as well as environmental and genetic factors affecting this association.

Spatiotemporal proteomic profiling of cellular responses to NLRP3 agonists

Nucleotide-binding domain and leucine-rich repeat pyrin-domain containing protein 3 (NLRP3) is an innate immune sensor that forms an inflammasome in response to various cellular stressors. Gain-of-function mutations in NLRP3 cause autoinflammatory diseases and NLRP3 signalling itself exacerbates the pathogenesis of many other human diseases. Despite considerable therapeutic interest, the primary drivers of NLRP3 activation remain controversial due to the diverse array of signals that are integrated through NLRP3. Here, we mapped subcellular proteome changes to lysosomes, mitochondrion, EEA1-positive endosomes, and Golgi caused by the NLRP3 inflammasome agonists nigericin and CL097. We identified several common disruptions to retrograde trafficking pathways, including COPI and Shiga toxin-related transport, in line with recent studies. We further characterized mouse NLRP3 trafficking throughout its activation using temporal proximity proteomics, which supports a recent model of NLRP3 recruitment to endosomes during inflammasome activation. Collectively, these findings provide additional granularity to our understanding of the molecular events driving NLRP3 activation and serve as a valuable resource for cell biological research. We have made our proteomics data accessible through an open-access Shiny browser to facilitate future research within the community, available at: https://harperlab.connect.hms.harvard.edu/inflame/. We will display anonymous peer review for this manuscript on pubpub.org (https://harperlab.pubpub.org/pub/nlrp3/) rather than a traditional journal. Moreover, we invite community feedback on the pubpub version of this manuscript, and we will address criticisms accordingly.

Manganese@Albumin Nanocomplex and Its Assembled Nanowire Activate TLR4-Dependent Signaling Cascades of Macrophages

The immunomodulatory effect of divalent manganese cations (Mn2+ ), such as activation of the cGAS-STING pathway or NLRP3 inflammasomes, positions them as adjuvants for cancer immunotherapy. In this study, it is found that trace Mn2+ ions, bound to bovine serum albumin (BSA) to form Mn@BSA nanocomplexes, stimulate pro-inflammatory responses in human- or murine-derived macrophages through TLR4-mediated signaling cascades. Building on this, the assembly of Mn@BSA nanocomplexes to obtain nanowire structures enables stronger and longer-lasting immunostimulation of macrophages by regulating phagocytosis. Furthermore, Mn@BSA nanocomplexes and their nanowires efficiently activate peritoneal macrophages, reprogramme tumor-associated macrophages, and inhibit the growth of melanoma tumors in vivo. They also show better biosafety for potential clinical applications compared to typical TLR4 agonists such as lipopolysaccharides. Accordingly, the findings provide insights into the mechanism of metalloalbumin complexes as potential TLR agonists that activate macrophage polarization and highlight the importance of their nanostructures in regulating macrophage-mediated innate immunity.

Extracellular Vesicles in the Central Nervous System: A Novel Mechanism of Neuronal Cell Communication

Cell-to-cell communication is essential for the appropriate development and maintenance of homeostatic conditions in the central nervous system. Extracellular vesicles have recently come to the forefront of neuroscience as novel vehicles for the transfer of complex signals between neuronal cells. Extracellular vesicles are membrane-bound carriers packed with proteins, metabolites, and nucleic acids (including DNA, mRNA, and microRNAs) that contain the elements present in the cell they originate from. Since their discovery, extracellular vesicles have been studied extensively and have opened up new understanding of cell-cell communication; they may cross the blood-brain barrier in a bidirectional way from the bloodstream to the brain parenchyma and vice versa, and play a key role in brain-periphery communication in physiology as well as pathology. Neurons and glial cells in the central nervous system release extracellular vesicles to the interstitial fluid of the brain and spinal cord parenchyma. Extracellular vesicles contain proteins, nucleic acids, lipids, carbohydrates, and primary and secondary metabolites. that can be taken up by and modulate the behaviour of neighbouring recipient cells. The functions of extracellular vesicles have been extensively studied in the context of neurodegenerative diseases. The purpose of this review is to analyse the role extracellular vesicles extracellular vesicles in central nervous system cell communication, with particular emphasis on the contribution of extracellular vesicles from different central nervous system cell types in maintaining or altering central nervous system homeostasis.

Epitranscriptomic Reader YTHDF2 Regulates SEK1( MAP2K4 )-JNK-cJUN Inflammatory Signaling in Astrocytes during Neurotoxic Stress

As the most abundant glial cells in the CNS, astrocytes dynamically respond to neurotoxic stress, however, the key molecular regulators controlling the inflammatory status of these sentinels during neurotoxic stress have remained elusive. Herein, we demonstrate that the m6A epitranscriptomic mRNA modification tightly regulates the pro-inflammatory functions of astrocytes. Specifically, the astrocytic neurotoxic stresser, manganese (Mn), downregulated the m6A reader YTHDF2 in human and mouse astrocyte cultures and in the mouse brain. Functionally, YTHDF2 knockdown augmented, while its overexpression dampened, neurotoxic stress induced proinflammatory response, suggesting YTHDF2 serves as a key upstream regulator of inflammatory responses in astrocytes. Mechnistically, YTHDF2 RIP-sequencing identified MAP2K4 ( MKK4; SEK1) mRNA as a YTHDF2 target influencing inflammatory signaling. Our target validation revealed Mn-exposed astrocytes mediates proinflammatory response by activating the phosphorylation of SEK1, JNK, and cJUN signaling. Collectively, YTHDF2 serves a key upstream 'molecular switch' controlling SEK1( MAP2K4 )-JNK-cJUN proinflammatory signaling in astrocytes.

cGAS-STING, inflammasomes and pyroptosis: an overview of crosstalk mechanism of activation and regulation

BACKGROUND

Intracellular DNA-sensing pathway cGAS-STING, inflammasomes and pyroptosis act as critical natural immune signaling axes for microbial infection, chronic inflammation, cancer progression and organ degeneration, but the mechanism and regulation of the crosstalk network remain unclear. Cellular stress disrupts mitochondrial homeostasis, facilitates the opening of mitochondrial permeability transition pore and the leakage of mitochondrial DNA to cell membrane, triggers inflammatory responses by activating cGAS-STING signaling, and subsequently induces inflammasomes activation and the onset of pyroptosis. Meanwhile, the inflammasome-associated protein caspase-1, Gasdermin D, the CARD domain of ASC and the potassium channel are involved in regulating cGAS-STING pathway. Importantly, this crosstalk network has a cascade amplification effect that exacerbates the immuno-inflammatory response, worsening the pathological process of inflammatory and autoimmune diseases. Given the importance of this crosstalk network of cGAS-STING, inflammasomes and pyroptosis in the regulation of innate immunity, it is emerging as a new avenue to explore the mechanisms of multiple disease pathogenesis. Therefore, efforts to define strategies to selectively modulate cGAS-STING, inflammasomes and pyroptosis in different disease settings have been or are ongoing. In this review, we will describe how this mechanistic understanding is driving possible therapeutics targeting this crosstalk network, focusing on the interacting or regulatory proteins, pathways, and a regulatory mitochondrial hub between cGAS-STING, inflammasomes, and pyroptosis.

SHORT CONCLUSION

This review aims to provide insight into the critical roles and regulatory mechanisms of the crosstalk network of cGAS-STING, inflammasomes and pyroptosis, and to highlight some promising directions for future research and intervention.

Exosomes in neuron-glia communication: A review on neurodegeneration

Introduction

Exosomes, a subset of extracellular vesicles (EVs), are crucial for intercellular communication in various contexts. Despite their small size, they carry diverse cargo, including RNA, proteins, and lipids. Internalization by recipient cells raises concerns about potential disruptions to cellular functions. Notably, the ability of exosomes to traverse the blood-brain barrier (BBB) has significant implications.

Methods

To conduct a thorough investigation into the existing academic literature on exosomes within the framework of neuron-glia communication, a comprehensive search strategy was implemented across the PubMed, Google Scholar, and Science Direct databases. Multiple iterations of the keywords "exosome," "neuron-glia communication," and "neurological disorders" were employed to systematically identify relevant publications. Furthermore, an exploration of the Clinicaltrials.gov database was undertaken to identify clinical trials related to cellular signaling, utilizing analogous terminology.

Results

Although the immediate practical applications of exosomes are somewhat limited, their potential as carriers of pathogenic attributes offers promising opportunities for the development of precisely targeted therapeutic strategies for neurological disorders. This review presents a comprehensive overview of contemporary insights into the pivotal roles played by exosomes as agents mediating communication between neurons and glial cells within the central nervous system (CNS).

Conclusion

By delving into the intricate dynamics of exosomal communication in the CNS, this review contributes to a deeper understanding of the roles of exosomes in both physiological and pathological processes, thereby paving the way for potential therapeutic advancements in the field of neurological disorders.

Microglia-derived extracellular vesicles in homeostasis and demyelination/remyelination processes

Microglia (MG) play a crucial role as the predominant myeloid cells in the central nervous system and are commonly activated in multiple sclerosis. They perform essential functions under normal conditions, such as actively surveying the surrounding parenchyma, facilitating synaptic remodeling, engulfing dead cells and debris, and protecting the brain against infectious pathogens and harmful self-proteins. Extracellular vesicles (EVs) are diverse structures enclosed by a lipid bilayer that originate from intracellular endocytic trafficking or the plasma membrane. They are released by cells into the extracellular space and can be found in various bodily fluids. EVs have recently emerged as a communication mechanism between cells, enabling the transfer of functional proteins, lipids, different RNA species, and even fragments of DNA from donor cells. MG act as both source and recipient of EVs. Consequently, MG-derived EVs are involved in regulating synapse development and maintaining homeostasis. These EVs also directly influence astrocytes, significantly increasing the release of inflammatory cytokines like IL-1β, IL-6, and TNF-α, resulting in a robust inflammatory response. Furthermore, EVs derived from inflammatory MG have been found to inhibit remyelination, whereas Evs produced by pro-regenerative MG effectively promote myelin repair. This review aims to provide an overview of the current understanding of MG-derived Evs, their impact on neighboring cells, and the cellular microenvironment in normal conditions and pathological states, specifically focusing on demyelination and remyelination processes.

Signaling Pathways Involved in Manganese-Induced Neurotoxicity

Manganese (Mn) is an essential trace element, but insufficient or excessive bodily amounts can induce neurotoxicity. Mn can directly increase neuronal insulin and activate insulin-like growth factor (IGF) receptors. As an important cofactor, Mn regulates signaling pathways involved in various enzymes. The IGF signaling pathway plays a protective role in the neurotoxicity of Mn, reducing apoptosis in neurons and motor deficits by regulating its downstream protein kinase B (Akt), mitogen-activated protein kinase (MAPK), and mammalian target of rapamycin (mTOR). In recent years, some new mechanisms related to neuroinflammation have been shown to also play an important role in Mn-induced neurotoxicity. For example, DNA-sensing receptor cyclic GMP-AMP synthase (cCAS) and its downstream signal efficient interferon gene stimulator (STING), NOD-like receptor family pyrin domain containing 3(NLRP3)-pro-caspase1, cleaves to the active form capase1 (CASP1), nuclear factor κB (NF-κB), sirtuin (SIRT), and Janus kinase (JAK) and signal transducers and activators of the transcription (STAT) signaling pathway. Moreover, autophagy, as an important downstream protein degradation pathway, determines the fate of neurons and is regulated by these upstream signals. Interestingly, the role of autophagy in Mn-induced neurotoxicity is bidirectional. This review summarizes the molecular signaling pathways of Mn-induced neurotoxicity, providing insight for further understanding of the mechanisms of Mn.

Extracellular Vesicles: Therapeutic Potential in Central Nervous System Trauma by Regulating Cell Death

CNS (central nervous system) trauma, which is classified as SCI (spinal cord injury) and TBI (traumatic brain injury), is gradually becoming a major cause of accidental death and disability worldwide. Many previous studies have verified that the pathophysiological mechanism underlying cell death and the subsequent neuroinflammation caused by cell death are pivotal factors in the progression of CNS trauma. Simultaneously, EVs (extracellular vesicles), membrane-enclosed particles produced by almost all cell types, have been proven to mediate cell-to-cell communication, and cell death involves complex interactions among molecules. EVs have also been proven to be effective carriers of loaded bioactive components to areas of CNS trauma. Therefore, EVs are promising therapeutic targets to cure CNS trauma. However, the link between EVs and various types of cell death in the context of CNS trauma remains unknown. Therefore, in this review, we summarize the mechanism underlying EV effects, the relationship between EVs and cell death and the pathophysiology underlying EV effects on the CNS trauma based on information in published papers. In addition, we discuss the prospects of applying EVs to the CNS as feasible therapeutic strategies for CNS trauma in the future.

Biotin rescues manganese-induced Parkinson's disease phenotypes and neurotoxicity

Occupational exposure to manganese (Mn) induces manganism and has been widely linked as a contributing environmental factor to Parkinson's disease (PD), featuring dramatic signature overlaps between the two in motor symptoms and clinical hallmarks. However, the molecular mechanism underlying such link remains elusive, and for combating PD, effective mechanism-based therapies are lacking. Here, we developed an adult Drosophila model of Mn toxicity to recapitulate key parkinsonian features, spanning behavioral deficits, neuronal loss, and dysfunctions in lysosome and mitochondria. We performed global metabolomics on flies at an early stage of toxicity and identified metabolism of the B vitamin, biotin (vitamin B 7 ), as a master pathway underpinning Mn toxicity with systemic, body-brain increases in Mn-treated groups compared to the controls. Using Btnd RNAi mutant flies, we show that biotin depletion exacerbates Mn-induced neurotoxicity, parkinsonism, and mitochondrial dysfunction; while in Mn-exposed wild-type flies, biotin feeding dramatically ameliorates these pathophenotypes. We further show in human induced stem cells (iPSCs)- differentiated midbrain dopaminergic neurons that the supplemented biotin protects against Mn-induced neuronal loss, cytotoxicity, and mitochondrial dysregulation. Finally, human data profiling biotin-related proteins show for PD cases elevated circulating levels of biotin transporters but not of metabolic enzymes compared to healthy controls, suggesting humoral biotin transport as a key event involved in PD. Taken together, our findings identified compensatory biotin pathway as a convergent, systemic driver of Mn toxicity and parkinsonian pathology, providing new basis for devising effective countermeasures against manganism and PD.

Significance Statement

Environmental exposure to manganese (Mn) may increase the risk for Parkinson's disease (PD); however, the mechanistic basis linking the two remains unclear. Our adult fruit fly ( Drosophila ) model of Mn toxicity recapitulated key Parkinson's hallmarks in vivo spanning behavioral deficits, neuronal loss, and mitochondrial dysfunction. Metabolomics identified the biotin (vitamin B 7 ) pathway as a key mediator, featuring systemic biotin increases in the flies. Rescue trials leveraging biotin-deficient flies, wild-type flies, and human iPSC-derived dopaminergic neurons determined biotin as a driver of manganism, with the parkinsonian phenotypes dramatically reversed through biotin supplementation. Our findings, in line with overexpressed circulating biotin transporters observed in PD patients, suggest compensatory biotin pathway as a key to untangle the Mn-PD link for combating neurodegenerative disease.

Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

Environmental pollution is changing with economic development. Most environmental pollutants are characterized by stable chemical properties, strong migration, potential toxicity, and multiple exposure routes. Harmful substances are discharged excessively, and large quantities of unknown new compounds are emerging, being transmitted and amplifying in the food chain. The increasingly severe problems of environmental pollution have forced people to re-examine the relationship between environmental pollution and health. Pyroptosis and activation of the NLRP3 inflammasome are critical in maintaining the immune balance and regulating the inflammatory process. Numerous diseases caused by environmental pollutants are closely related to NLRP3 inflammasome activation and pyroptosis. We intend to systematically explain the steps and important events that are common in life but easily overlooked by which environmental pollutants activate the NLRP3 inflammasome and pyroptosis pathways. This comprehensive review also discusses the interaction network between environmental pollutants, the NLRP3 inflammasome, pyroptosis, and diseases. Thus, research progress on the impact of decreasing oxidative stress levels to inhibit the NLRP3 inflammasome and pyroptosis, thereby repairing homeostasis and reshaping health, is systematically examined. This review aims to deepen the understanding of the impact of environmental pollutants on life and health and provide a theoretical basis and potential programs for the development of corresponding treatment strategies.

Therapeutic application of manganese-based nanosystems in cancer radiotherapy

Radiotherapy is an important therapeutic modality in the treatment of cancers. Nevertheless, the characteristics of the tumor microenvironment (TME), such as hypoxia and high glutathione (GSH), limit the efficacy of radiotherapy. Manganese-based (Mn-based) nanomaterials offer a promising prospect for sensitizing radiotherapy due to their good responsiveness to the TME. In this review, we focus on the mechanisms of radiosensitization of Mn-based nanosystems, including alleviating tumor hypoxia, increasing reactive oxygen species production, increasing GSH conversion, and promoting antitumor immunity. We further illustrate the applications of these mechanisms in cancer radiotherapy, including the development and delivery of radiosensitizers, as well as their combination with other therapeutic modalities. Finally, we summarize the application of Mn-based nanosystems as contrast agents in realizing precision therapy. Hopefully, the present review will provide new insights into the biological mechanisms of Mn-based nanosystems, as well as their applications in radiotherapy, in order to address the difficulties and challenges that remain in their clinical application in the future.

Network pharmacology and molecular docking approaches predict the mechanisms of Corididius chinensis in treating manganese-induced nervous system diseases: A review

Neurotoxicity could be induced by long exposure to manganese (Mn). The traditional Chinese medicine, Corididius chinensis (Cc) has been proven to have a certain curative effect on Mn poisoning. Therefore, network pharmacology was performed to explore potential therapeutic targets and pharmacological mechanisms of Cc. We found ingredients by building our own database through literature, (which is the first to screen traditional Chinese medicine without traditional Chinese medicine systems pharmacology database and analysis platform databases and it is applicable whenever a Chinese medicine is not found in the traditional Chinese medicine systems pharmacology database and analysis platform database) and potential targets of Mn-induced nervous system diseases from the OMIM, GeneCards, and DrugBank database were identified. A protein-protein interaction network was constructed using Cytoscape. Gene ontology and Kyoto encyclopedia of genes and genomes pathway enrichment analysis was performed for the treatment of Mn-induced nervous system disease, and molecular docking was carried out to verify the results of network pharmacology analysis. After screening disease-related genes, 12 intersecting genes overlapped between 284 target proteins of the active compound and 195 potential disease targets. The pathways of neurodegeneration_multiple diseases and Alzheimer disease pathway may be the most potential pathway of Cc treating Mn-induced nervous system diseases. CASP9 and PTGS2 in neurodegeneration_multiple diseases, NOS1, NOS2 in Alzheimer disease pathway were identified as core targets. Especially, molecule docking analysis unveil that aspongpyrazine A docking NOS2 is the most potential therapeutic drug and target, which primarily involved in the processes of oxidative stress and inflammation.

Consequences of Disturbing Manganese Homeostasis

Manganese (Mn) is an essential trace element with unique functions in the body; it acts as a cofactor for many enzymes involved in energy metabolism, the endogenous antioxidant enzyme systems, neurotransmitter production, and the regulation of reproductive hormones. However, overexposure to Mn is toxic, particularly to the central nervous system (CNS) due to it causing the progressive destruction of nerve cells. Exposure to manganese is widespread and occurs by inhalation, ingestion, or dermal contact. Associations have been observed between Mn accumulation and neurodegenerative diseases such as manganism, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. People with genetic diseases associated with a mutation in the gene associated with impaired Mn excretion, kidney disease, iron deficiency, or a vegetarian diet are at particular risk of excessive exposure to Mn. This review has collected data on the current knowledge of the source of Mn exposure, the experimental data supporting the dispersive accumulation of Mn in the brain, the controversies surrounding the reference values of biomarkers related to Mn status in different matrices, and the competitiveness of Mn with other metals, such as iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), calcium (Ca). The disturbed homeostasis of Mn in the body has been connected with susceptibility to neurodegenerative diseases, fertility, and infectious diseases. The current evidence on the involvement of Mn in metabolic diseases, such as type 2 diabetes mellitus/insulin resistance, osteoporosis, obesity, atherosclerosis, and non-alcoholic fatty liver disease, was collected and discussed.

Manganese overexposure induces Parkinson-like symptoms, altered lipid signature and oxidative stress in C57BL/6 J mouse

Although adequate intake of manganese (Mn) is essential to humans, Mn in excess is neurotoxic. Exposure to extremely high doses of Mn results in "manganism", a condition that exhibits Parkinson-like symptoms. However, the mechanisms underlying its neurotoxic effects in Mn-induced parkinsonism pathogenesis are unclear. In this study, 8-week-old male C57BL/6 J mice were injected intraperitoneally with saline and 50 mg/kg MnCl2 respectively once daily for 14 days to produce an acute Mn neurotoxicity model. Accumulation of Mn in the midbrain, motor dysfunction and loss of dopaminergic neurons in the substantia nigra evidenced Mn neurotoxicity. Untargeted lipidomic analysis demonstrated that Mn overexposure altered lipidome profiles. A significant modulation of 12 lipid subclasses belonging to 5 different categories were found in the midbrain and among the most abundant lipids were sphingolipids, glycerophospholipids, and glycerides. The levels of sphingomyelin (SM) were significantly decreased after Mn treatment. The expression of SM biosynthesis genes was decreased dramatically while sphingomyelinase was up-regulated. In addition, we observed oxidative stress in both the midbrain of mice and MN9D cells, indicated by the increase of MDA level, the decrease of reduced GSH level and the inhibition of SOD and GPx enzyme activities. There was a correlation between these changes and motor dysfunctions. Overall, our study is the first to use lipidomics techniques to explore the pathogenesis of Mn-induced parkinsonism in C57BL/6 J mice. Mn induced molecular events in the midbrain, such as lipid metabolism disorders, oxidative stress and dopaminergic neurons injury, may mechanistically play important roles in the pathogenesis of Parkinson-like symptoms. Moreover, these findings emphasize the necessity for reducing the health risk of environmental neurotoxic pollutants in relation to parkinsonism.

Manganese-Induced Parkinsonism: Evidence from Epidemiological and Experimental Studies

Manganese (Mn) exposure has evolved from acute, high-level exposure causing manganism to low, chronic lifetime exposure. In this latter scenario, the target areas extend beyond the globus pallidus (as seen with manganism) to the entire basal ganglia, including the substantia nigra pars compacta. This change of exposure paradigm has prompted numerous epidemiological investigations of the occurrence of Parkinson's disease (PD), or parkinsonism, due to the long-term impact of Mn. In parallel, experimental research has focused on the underlying pathogenic mechanisms of Mn and its interactions with genetic susceptibility. In this review, we provide evidence from both types of studies, with the aim to link the epidemiological data with the potential mechanistic interpretation.

The Role of Oxidative Stress in Manganese Neurotoxicity: A Literature Review Focused on Contributions Made by Professor Michael Aschner

This literature review focuses on the evidence implicating oxidative stress in the pathogenesis of manganese neurotoxicity. This review is not intended to be a systematic review of the relevant toxicologic literature. Instead, in keeping with the spirit of this special journal issue, this review highlights contributions made by Professor Michael Aschner's laboratory in this field of study. Over the past two decades, his laboratory has made significant contributions to our scientific understanding of cellular responses that occur both in vitro and in vivo following manganese exposure. These studies have identified molecular targets of manganese toxicity and their respective roles in mitochondrial dysfunction, inflammation, and cytotoxicity. Other studies have focused on the critical role astrocytes play in manganese neurotoxicity. Recent studies from his laboratory have used C. elegans to discover new facets of manganese-induced neurotoxicity. Collectively, his body of work has dramatically advanced the field and presents broader implications beyond metal toxicology.

The role of microglial LRRK2 kinase in manganese-induced inflammatory neurotoxicity via NLRP3 inflammasome and RAB10-mediated autophagy dysfunction

Chronic manganese (Mn) exposure can lead to manganism, a neurological disorder sharing common symptoms with Parkinson's disease (PD). Studies have shown that Mn can increase the expression and activity of leucine-rich repeat kinase 2 (LRRK2), leading to inflammation and toxicity in microglia. LRRK2 G2019S mutation also elevates LRRK2 kinase activity. Thus, we tested if Mn-increased microglial LRRK2 kinase is responsible for Mn-induced toxicity, and exacerbated by G2019S mutation, using WT and LRRK2 G2019S knock-in mice and BV2 microglia. Mn (30 mg/kg, nostril instillation, daily for 3 weeks) caused motor deficits, cognitive impairments, and dopaminergic dysfunction in WT mice, which were exacerbated in G2019S mice. Mn induced proapoptotic Bax, NLRP3 inflammasome, IL-1β, and TNF-α in the striatum and midbrain of WT mice, and these effects were more pronounced in G2019S mice. BV2 microglia were transfected with human LRRK2 WT or G2019S, followed by Mn (250 μM) exposure to better characterize its mechanistic action. Mn increased TNF-α, IL-1β, and NLRP3 inflammasome activation in BV2 cells expressing WT LRRK2, which was elevated further in G2019S-expressing cells, while pharmacological inhibition of LRRK2 mitigated these effects in both genotypes. Moreover, the media from Mn-treated G2019S-expressing BV2 microglia caused greater toxicity to the cath.a-differentiated (CAD) neuronal cells compared to media from microglia expressing WT. Mn-LRRK2 activated RAB10 which was exacerbated in G2019S. RAB10 played a critical role in LRRK2-mediated Mn toxicity by dysregulating the autophagy-lysosome pathway and NLRP3 inflammasome in microglia. Our novel findings suggest that microglial LRRK2 via RAB10 plays a critical role in Mn-induced neuroinflammation.

P2X7 Receptor and Extracellular Vesicle Release

Extensive evidence indicates that the activation of the P2X₇ receptor (P2X₇R), an ATP-gated ion channel highly expressed in immune and brain cells, is strictly associated with the release of extracellular vesicles. Through this process, P2X₇R-expressing cells regulate non-classical protein secretion and transfer bioactive components to other cells, including misfolded proteins, participating in inflammatory and neurodegenerative diseases. In this review, we summarize and discuss the studies addressing the impact of P2X₇R activation on extracellular vesicle release and their activities.

SIRT1/FOXO3-mediated autophagy signaling involved in manganese-induced neuroinflammation in microglia

Manganese (Mn), as one of the environmental risk factors for Parkinson's disease (PD), has been widely studied. Though autophagy dysfunction and neuroinflammation mainly are responsible for the causative issue of Mn neurotoxicity, the molecular mechanism of parkinsonism caused by Mn has not been explored clearly. The results of in vivo and in vitro experiments showed that overexposure to Mn caused neuroinflammation impairment and autophagy dysfunction, accompanied by the increase of IL-1β, IL-6, and TNF-α mRNA expression, and nerve cell apoptosis, microglia cell activation, NF-κB activation, poor neurobehavior performance. This is due to Mn-induced the downregulation of SIRT1. Upregulation of SIRT1 in vivo and in vitro could alleviate Mn-induced autophagy dysfunction and neuroinflammation, yet these beneficial effects were abolished following 3-MA administration. Furthermore, we found that Mn interfered with the acetylation of FOXO3 by SIRT1 in BV2 cells, leading to a decrease in the nuclear translocation of FOXO3, and its binding of LC3B promoter and transcription activity. This could be antagonized by the upregulation of SIRT1. Finally, it is proved that SIRT1/FOXO3-LC3B autophagy signaling involves in Mn-induced neuroinflammation impairment.

The role of microglial LRRK2 in manganese-induced inflammatory neurotoxicity via NLRP3 inflammasome and RAB10-mediated autophagy dysfunction

Chronic exposure to manganese (Mn) can lead to manganism, a neurological disorder sharing common symptoms with Parkinson's disease (PD). Studies have shown that Mn can increase the expression and activity of leucine-rich repeat kinase 2 (LRRK2), leading to inflammation and toxicity in microglia. LRRK2 G2019S mutation also elevates LRRK2 kinase activity. Thus, we tested if Mn-increased microglial LRRK2 kinase is responsible for Mn-induced toxicity, and exacerbated by G2019S mutation, using WT and LRRK2 G2019S knock-in mice, and BV2 microglia. Mn (30 mg/kg, nostril instillation, daily for 3 weeks) caused motor deficits, cognitive impairments, and dopaminergic dysfunction in WT mice, which were exacerbated in G2019S mice. Mn induced proapoptotic Bax, NLRP3 inflammasome, IL-1β and TNF-α in the striatum and midbrain of WT mice, and these effects were exacerbated in G2019S mice. BV2 microglia were transfected with human LRRK2 WT or G2019S, followed by Mn (250 μM) exposure to better characterize its mechanistic action. Mn increased TNF-α, IL-1β, and NLRP3 inflammasome activation in BV2 cells expressing WT LRRK2, which was exacerbated in G2019S-expressing cells, while pharmacological inhibition of LRRK2 mitigated these effects in both genotypes. Moreover, the media from Mn-treated BV2 microglia expressing G2019S caused greater toxicity to cath.a-differentiated (CAD) neuronal cells compared to media from microglia expressing WT. Mn-LRRK2 activated RAB10, which was exacerbated in G2019S. RAB10 played a critical role in LRRK2-mediated Mn toxicity by dysregulating the autophagy-lysosome pathway, and NLRP3 inflammasome in microglia. Our novel findings suggest that microglial LRRK2 via RAB10 plays a critical role in Mn-induced neuroinflammation.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

Manganese potentiates lipopolysaccharide-induced innate immune responses and septic shock

Divalent metal ions such as magnesium (Mg²⁺), manganese (Mn²⁺), and zinc (Zn²⁺) play important roles in regulating innate immune responses. Lipopolysaccharide stimulation led to increased intracellular Mn and Zn in macrophages. However, the effect of those metal ions in regulating lipopolysaccharide-induced innate immune responses remains unclear. Here, we uncovered that both Mn²⁺ and Zn²⁺ have immunostimulatory effects, which could potentiate the lipopolysaccharide-induced expression of interferon-stimulated genes (ISGs), cytokines and pro-inflammatory genes in a dose-dependent manner. Enhancement of lipopolysaccharide-induced innate immune gene expression by Mn²⁺ varies between 10 % and 900 %. Conversely, the chelating of Mn²⁺ almost totally diminished Mn²⁺-enhanced lipopolysaccharide-induced gene expression. In addition, Mn²⁺ exerted its ability to potentiate LPS-induced innate immune gene expression regardless of slight pH changes. Importantly, we found that Mn²⁺ potentiates lipopolysaccharide-induced immune responses independent of TLR4 but partially relies on cGAS-STING pathway. Further in vivo study showed that colloidal Mn²⁺ salt (Mn jelly [MnJ]) pretreatment exacerbated lipopolysaccharide-induced septic shock and mice death. In conclusion, we demonstrated that Mn²⁺ plays an essential role in boosting lipopolysaccharide-induced innate immune responses. These findings greatly expand the current understanding of the immunomodulatory potential of divalent metal Mn²⁺ and may provide a potential therapeutic target to prevent excessive immune responses.

GPX4 utilization by selenium is required to alleviate cadmium-induced ferroptosis and pyroptosis in sheep kidney

Cadmium (Cd), a persistent and harmful heavy metal in the environment, can accumulate in the kidneys and cause nephrotoxicity. Selenium (Se) is a beneficial natural element that alleviates the toxicity of Cd. To ascertain the relationship between the protective mechanism of Se against Cd nephrotoxicity and ferroptosis and pyroptosis, we randomly divided 48 sheep into four groups and treated them with Cd chloride and/or sodium selenite for 50 days. The data confirmed that Cd apparently resulted in impaired kidney histology and function, depletion of GSH and nicotinamide adenine dinucleotide phosphate contents and CAT and SOD activities, elevation of MDA level, as well as the reduction in selenoprotein mRNA (GPX1, GPX4, TXNRD1, SELP) levels and GPX4 protein level and immunofluorescence intensity. Meanwhile, Cd induced ferroptosis by causing iron overload, up-regulating PTGS2, NCOA4, TFR1, and LC3B mRNA levels and PTGS2 and LC3B-II/LC3B-I protein levels, reducing SLC7A11 and FTH1 mRNA and protein levels, and enhancing the immunofluorescence co-localization of FTH1/LC3B. Moreover, it was also found that Cd triggered pyroptosis, which was evidenced by the increase of NLRP3 immunohistochemical positive signal, GSDMD-N immunofluorescence intensity, IL-1β and IL-18 release and the levels of pyroptosis-related mRNA (NLRP3, ASC, Caspase-1, GSDMD, IL-1β and IL-18) and proteins (NLRP3, Caspase-1p20, GSDMD-N, IL-1β and IL-18). Notably, Se increased the expression level of GPX4 and the transcription factors TFAP2c and SP1, and ameliorated Cd-induced changes in aforementioned factors. In conclusion, GPX4 utilization by Se might be required to alleviate Cd-induced ferroptosis and pyroptosis in sheep kidney.

Sesamol alleviates manganese-induced neuroinflammation and cognitive impairment via regulating the microglial cGAS-STING/NF-κB pathway

Toxic effects of excessive manganese (Mn) from occupational or environmental exposure cause harm to human health. Excessive Mn exposure is intimately associated with neurodegeneration and cognitive dysfunction. Inflammatory responses mediated by microglia are essential contributors to the pathogenesis of Mn-induced neurotoxicity. Inhibition of microglia-mediated inflammation has been shown to alleviate Mn-induced neurotoxicity. Sesamol, derived from sesame, has neuroprotective properties in various disease models, including neurological diseases. Whether sesamol protects against Mn-induced neurological injuries has not been determined. Here, both in vivo and in vitro Mn exposure models were established to address the beneficial effects of sesamol on Mn-induced neurotoxicity. We showed that administration of sesamol mitigated learning and memory deficits of mice treated by Mn. Furthermore, sesamol reduced Mn-induced microglial activation and the expression of proinflammatory mediators (TNF-α, iNOS, and Cxcl10), while exerting a marginal effect on anti-inflammation and microglial phagocytosis. Mn exposure activated the microglial cGAS-STING pathway and sesamol inhibited this pathway by reducing the phosphorylation of STING and NF-κB, concomitantly decreasing IFN-α and IFN-β synthesis. In summary, our novel results indicated that sesamol exerted its protective effects on Mn-induced neuroinflammation and cognitive impairment via the microglial cGAS-STING/NF-κB pathway, providing evidence that sesamol may serve as an effective therapeutic for preventing and treating Mn-induced neurotoxicity.

NLRP3 inflammasome activation in response to metals

Implant surgery is followed by a series of inflammatory reactions that directly affect its postoperative results. The inflammasome plays a vital role in the inflammatory response by inducing pyroptosis and producing interleukin-1β, which plays a critical role in inflammation and tissue damage. Therefore, it is essential to study the activation of the inflammasome in the bone healing process after implant surgery. As metals are the primary implant materials, metal-induced local inflammatory reactions have received significant attention, and there has been more and more research on the activation of the NLRP3 (NOD-like receptor protein-3) inflammasome caused by these metals. In this review, we consolidate the basic knowledge on the NLRP3 inflammasome structures, the present knowledge on the mechanisms of NLRP3 inflammasome activation, and the studies of metal-induced NLRP3 inflammasome activation.

Relevance of Biochemical Deep Phenotyping for a Personalised Approach to Parkinson's Disease

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder characterised by the progressive loss of dopaminergic neurons in the nigrostriatal tract. The identification of disease-modifying therapies is the Holy Grail of PD research, but to date no drug has been approved as such a therapy. A possible reason is the remarkable phenotypic heterogeneity of PD patients, which can generate confusion in the interpretation of results or even mask the efficacy of a therapeutic intervention. This heterogeneity should be taken into account in clinical trials, stratifying patients by their expected response to drugs designed to engage selected molecular targets. In this setting, stratification methods (clinical and genetic) should be supported by biochemical phenotyping of PD patients, in line with the deep phenotyping concept. Collection, from single patients, of a range of biological samples would streamline the generation of these profiles. Several studies have proposed biochemical characterisations of patient cohorts based on analysis of blood, cerebrospinal fluid, urine, stool, saliva and skin biopsy samples, with extracellular vesicles attracting increasing interest as a source of biomarkers. In this review we report and critically discuss major studies that used a biochemical approach to stratify their PD cohorts. The analyte most studied is α-synuclein, while other studies have focused on neurofilament light chain, lysosomal proteins, inflammasome-related proteins, LRRK2 and the urinary proteome. At present, stratification of PD patients, while promising, is still a nascent approach. Deep phenotyping of patients will allow clinical researchers to identify homogeneous subgroups for the investigation of tailored disease-modifying therapies, enhancing the chances of therapeutic success.