SFRP1 modulates astrocyte-to-microglia crosstalk in acute and chronic neuroinflammation

Exploring biomarkers in trigeminal neuralgia patients operated with microvascular decompression: A comparison with multiple sclerosis patients and non-neurological controls

BACKGROUND

Trigeminal neuralgia (TN) is a severe facial pain condition often associated with a neurovascular conflict. However, neuroinflammation has also been implicated in TN, as it frequently co-occurs with multiple sclerosis (MS).

METHODS

We analysed protein expression levels of TN patients compared to MS patients and controls. Proximity Extension Assay technology was used to analyse the levels of 92 proteins with the Multiplex Neuro-Exploratory panel provided by SciLifeLab, Uppsala, Sweden. Serum and CSF samples were collected from TN patients before (n = 33 and n = 27, respectively) and after (n = 28 and n = 8, respectively) microvascular decompression surgery. Additionally, we included samples from MS patients (n = 20) and controls (n = 20) for comparison.

RESULTS

In both serum and CSF, several proteins were found increased in TN patients compared to either MS patients, controls, or both, including EIF4B, PTPN1, EREG, TBCB, PMVK, FKBP5, CD63, CRADD, BST2, CD302, CRIP2, CCL27, PPP3R1, WWP2, KLB, PLA2G10, TDGF1, SMOC1, RBKS, LTBP3, CLSTN1, NXPH1, SFRP1, HMOX2, and GGT5. The overall expression of the 92 proteins in postoperative TN samples seems to shift towards the levels of MS patients and controls in both serum and CSF, as compared to preoperative samples. Interestingly, there was no difference in protein levels between MS patients and controls.

CONCLUSIONS

We conclude that TN patients showed increased serum and CSF levels of specific proteins and that successful surgery normalizes these protein levels, highlighting its potential as an effective treatment. However, the similarity between MS and controls challenges the idea of shared pathophysiology with TN, suggesting distinct underlying mechanisms in these conditions.

SIGNIFICANCE

This study advances our understanding of trigeminal neuralgia (TN) and its association with multiple sclerosis (MS). By analysing 92 protein biomarkers, we identified distinctive molecular profiles in TN patients, shedding light on potential pathophysiological mechanisms. The observation that successful surgery normalizes many protein levels suggests a promising avenue for TN treatment. Furthermore, the contrasting protein patterns between TN and MS challenge prevailing assumptions of similarity between the two conditions and point to distinct pathophysiological mechanisms.

A 3D Bioprinted Human Neurovascular Unit Model of Glioblastoma Tumor Growth

A 3D bioprinted neurovascular unit (NVU) model is developed to study glioblastoma (GBM) tumor growth in a brain-like microenvironment. The NVU model includes human primary astrocytes, pericytes and brain microvascular endothelial cells, and patient-derived glioblastoma cells (JHH-520) are used for this study. Fluorescence reporters are used with confocal high content imaging to quantitate real-time microvascular network formation and tumor growth. Extensive validation of the NVU-GBM model includes immunostaining for brain relevant cellular markers and extracellular matrix components; single cell RNA sequencing (scRNAseq) to establish physiologically relevant transcriptomics changes; and secretion of NVU and GBM-relevant cytokines. The scRNAseq reveals changes in gene expression and cytokines secretion associated with wound healing/angiogenesis, including the appearance of an endothelial mesenchymal transition cell population. The NVU-GBM model is used to test 18 chemotherapeutics and anti-cancer drugs to assess the pharmacological relevance of the model and robustness for high throughput screening.

Mild Hypoxia Accelerates Cerebral Cavernous Malformation Disease Through CX3CR1-CX3CL1 Signaling

BACKGROUND

Heterogeneity in the severity of cerebral cavernous malformations (CCMs) disease, including brain bleedings and thrombosis that cause neurological disabilities in patients, suggests that environmental, genetic, or biological factors act as disease modifiers. Still, the underlying mechanisms are not entirely understood. Here, we report that mild hypoxia accelerates CCM disease by promoting angiogenesis, neuroinflammation, and vascular thrombosis in the brains of CCM mouse models.

METHODS

We used genetic studies, RNA sequencing, spatial transcriptome, micro-computed tomography, fluorescence-activated cell sorting, multiplex immunofluorescence, coculture studies, and imaging techniques to reveal that sustained mild hypoxia via the CX3CR1-CX3CL1 (CX3C motif chemokine receptor 1/chemokine [CX3C motif] ligand 1) signaling pathway influences cell-specific neuroinflammatory interactions, contributing to heterogeneity in CCM severity.

RESULTS

Histological and expression profiles of CCM neurovascular lesions (Slco1c1-iCreERT2;Pdcd10fl/fl; Pdcd10BECKO) in male and female mice found that sustained mild hypoxia (12% O2, 7 days) accelerates CCM disease. Our findings indicate that a small reduction in oxygen levels can significantly increase angiogenesis, neuroinflammation, and thrombosis in CCM disease by enhancing the interactions between endothelium, astrocytes, and immune cells. Our study indicates that the interactions between CX3CR1 and CX3CL1 are crucial in the maturation of CCM lesions and propensity to CCM immunothrombosis. In particular, this pathway regulates the recruitment and activation of microglia and other immune cells in CCM lesions, which leads to lesion growth and thrombosis. We found that human CX3CR1 variants are linked to lower lesion burden in familial CCMs, proving it is a genetic modifier in human disease and a potential marker for aggressiveness. Moreover, monoclonal blocking antibody against CX3CL1 or reducing 1 copy of the Cx3cr1 gene significantly reduces hypoxia-induced CCM immunothrombosis.

CONCLUSIONS

Our study reveals that interactions between CX3CR1 and CX3CL1 can modify CCM neuropathology when lesions are accelerated by environmental hypoxia. Moreover, a hypoxic environment or hypoxia signaling caused by CCM disease influences the balance between neuroinflammation and neuroprotection mediated by CX3CR1-CX3CL1 signaling. These results establish CX3CR1 as a genetic marker for patient stratification and a potential predictor of CCM aggressiveness.

A New Strategy for the Regulation of Neuroinflammation: Exosomes Derived from Mesenchymal Stem Cells

Neuroinflammation is an important pathogenesis of neurological diseases and causes a series of physiopathological changes, such as abnormal activation of glial cells, neuronal degeneration and death, and disruption of the blood‒brain barrier. Therefore, modulating inflammation may be an important therapeutic tool for treating neurological diseases. Mesenchymal stem cells (MSCs), as pluripotent stem cells, have great therapeutic potential for neurological diseases due to their regenerative ability, immunity, and ability to regulate inflammation. However, recent studies have shown that MSC-derived exosomes (MSC-Exos) play a major role in this process and play a key role in neuroprotection by regulating neuroglia. This review summarizes the recent progress made in regulating neuroinflammation by focusing on the mechanisms by which MSC-Exos are involved in the regulation of glial cells through signaling pathways such as the TLR, NF-κB, MAPK, STAT, and NLRP3 pathways to provide some references for subsequent research and therapy.

Application of LRG mechanism in normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) is a prevalent type of hydrocephalus, including secondary normal pressure hydrocephalus (SNPH) and idiopathic normal pressure hydrocephalus (INPH). However, its clinical diagnosis and pathological mechanism are still unclear. Leucine-rich α-2 glycoprotein (LRG) is involved in various human diseases, including cancer, diabetes, cardiovascular disease, and nervous system diseases. Now the physiological mechanism of LRG is still being explored. According to the current research results on LRG, we found that the agency of LRG has much to do with the known pathological process of NPH. This review focuses on analyzing the LRG signaling pathways and the pathological mechanism of NPH. According to the collected literature evidence, we speculated that LRG probably be involved in the pathological process of NPH. Finally, based on the mechanism of LRG and NPH, we also summarized the evidence of molecular targeted therapies for future research and clinical application.

Comprehensive analysis of the clinical and prognostic significance of SFRP1 and PRKCB expression in non-small cell lung cancer: a retrospective analysis

OBJECTIVES

Secreted frizzled-related protein 1 (SFRP1) and protein kinase C-B (PRKCB) contribute to cancer progression and angiogenesis. This study intended to detect SFRP1 and PRKCB expression in non-small-cell lung cancer (NSCLC) patients and analyze its association with clinicopathological features.

METHODS

A total of 108 NSCLC patients who underwent surgical resection in our hospital between 2012 and 2017 were retrospectively analyzed. SFRP1 and PRKCB expression was detected using immunohistochemical staining. The relationships between SFRP1 and PRKCB expression and clinicopathological data were analyzed using the chi-square method. Kaplan-Meier analysis was used to investigate survival probability over time. The potential risk of NSCLC morbidity associated with SFRP1 and PRKCB levels was analyzed using univariate and multivariate Cox proportional risk models.

RESULTS

SFRP1 and PRKCB expression was negative in 114 and 109 of the 180 NSCLC specimens, respectively. SFRP1 expression was significantly associated with TNM stage ( P  < 0.001) and tumor diameter ( P  < 0.001). PRKCB expression was significantly associated with the TNM stage ( P  < 0.001). The correlation between SFRP1 and PRKCB expression was evident ( P  = 0.023). SFRP1(-) or PRKCB(-) patients shows lower survival rates than SFRP1(+) or PRKCB(+) patients ( P < 0.001). SFRP1(-)/PRKCB(-) patients had the worst prognosis ( P < 0.001). Furthermore, the mortality of SFRP1(-) or PRKCB(-) patients was significantly higher than that of SFRP1(+) or PRKCB(+).

CONCLUSION

SFRP1 and PRKCB expression can be used to predict prognosis in patients with NSCLC.

Macrophage polarization in spinal cord injury repair and the possible role of microRNAs: A review

The prevention, treatment, and rehabilitation of spinal cord injury (SCI) have always posed significant medical challenges. After mechanical injury, disturbances in microcirculation, edema formation, and the generation of free radicals lead to additional damage, impeding effective repair processes and potentially exacerbating further dysfunction. In this context, inflammatory responses, especially the activation of macrophages, play a pivotal role. Different phenotypes of macrophages have distinct effects on inflammation. Activation of classical macrophage cells (M1) promotes inflammation, while activation of alternative macrophage cells (M2) inhibits inflammation. The polarization of macrophages is crucial for disease healing. A non-coding RNA, known as microRNA (miRNA), governs the polarization of macrophages, thereby reducing inflammation following SCI and facilitating functional recovery. This study elucidates the inflammatory response to SCI, focusing on the infiltration of immune cells, specifically macrophages. It examines their phenotype and provides an explanation of their polarization mechanisms. Finally, this paper introduces several well-known miRNAs that contribute to macrophage polarization following SCI, including miR-155, miR-130a, and miR-27 for M1 polarization, as well as miR-22, miR-146a, miR-21, miR-124, miR-223, miR-93, miR-132, and miR-34a for M2 polarization. The emphasis is placed on their potential therapeutic role in SCI by modulating macrophage polarization, as well as the present developments and obstacles of miRNA clinical therapy.

The role of astrocytes response triggered by hyperglycaemia during spinal cord injury

Objective: This manuscript aimed to provide a comprehensive overview of the physiological, molecular, and cellular mechanisms triggered by reactive astrocytes (RA) in the context of spinal cord injury (SCI), with a particular focus on cases involving hyperglycaemia.Methods: The compilation of articles related to astrocyte responses in neuropathological conditions, with a specific emphasis on those related to SCI and hyperglycaemia, was conducted by searching through databases including Science Direct, Web of Science, and PubMed.Results and Conclusions: This article explores the dual role of astrocytes in both neurophysiological and neurodegenerative conditions within the central nervous system (CNS). In the aftermath of SCI and hyperglycaemia, astrocytes undergo a transformation into RA, adopting a distinct phenotype. While there are currently no approved therapies for SCI, various therapeutic strategies have been proposed to alleviate the detrimental effects of RAs following SCI and hyperglycemia. These strategies show promising potential in the treatment of SCI and its likely comorbidities.

Lysosomal acidification dysfunction in microglia: an emerging pathogenic mechanism of neuroinflammation and neurodegeneration

Microglia are the resident innate immune cells in the brain with a major role in orchestrating immune responses. They also provide a frontline of host defense in the central nervous system (CNS) through their active phagocytic capability. Being a professional phagocyte, microglia participate in phagocytic and autophagic clearance of cellular waste and debris as well as toxic protein aggregates, which relies on optimal lysosomal acidification and function. Defective microglial lysosomal acidification leads to impaired phagocytic and autophagic functions which result in the perpetuation of neuroinflammation and progression of neurodegeneration. Reacidification of impaired lysosomes in microglia has been shown to reverse neurodegenerative pathology in Alzheimer's disease. In this review, we summarize key factors and mechanisms contributing to lysosomal acidification impairment and the associated phagocytic and autophagic dysfunction in microglia, and how these defects contribute to neuroinflammation and neurodegeneration. We further discuss techniques to monitor lysosomal pH and therapeutic agents that can reacidify impaired lysosomes in microglia under disease conditions. Finally, we propose future directions to investigate the role of microglial lysosomal acidification in lysosome-mitochondria crosstalk and in neuron-glia interaction for more comprehensive understanding of its broader CNS physiological and pathological implications.

Microglia-Astrocyte Interaction in Neural Development and Neural Pathogenesis

The interaction between microglia and astrocytes exhibits a relatively balanced state in order to maintain homeostasis in the healthy central nervous system (CNS). Disease stimuli alter microglia-astrocyte interaction patterns and elicit cell-type-specific responses, resulting in their contribution to various pathological processes. Here, we review the similarities and differences in the activation modes between microglia and astrocytes in various scenarios, encompassing different stages of neural development and a wide range of neural disorders. The aim is to provide a comprehensive understanding of their roles in neural development and regeneration and guiding new strategies for restoring CNS homeostasis.

Role of astrocytes in sleep deprivation: accomplices, resisters, or bystanders?

Sleep plays an essential role in all studied animals with a nervous system. However, sleep deprivation leads to various pathological changes and neurobehavioral problems. Astrocytes are the most abundant cells in the brain and are involved in various important functions, including neurotransmitter and ion homeostasis, synaptic and neuronal modulation, and blood-brain barrier maintenance; furthermore, they are associated with numerous neurodegenerative diseases, pain, and mood disorders. Moreover, astrocytes are increasingly being recognized as vital contributors to the regulation of sleep-wake cycles, both locally and in specific neural circuits. In this review, we begin by describing the role of astrocytes in regulating sleep and circadian rhythms, focusing on: (i) neuronal activity; (ii) metabolism; (iii) the glymphatic system; (iv) neuroinflammation; and (v) astrocyte-microglia cross-talk. Moreover, we review the role of astrocytes in sleep deprivation comorbidities and sleep deprivation-related brain disorders. Finally, we discuss potential interventions targeting astrocytes to prevent or treat sleep deprivation-related brain disorders. Pursuing these questions would pave the way for a deeper understanding of the cellular and neural mechanisms underlying sleep deprivation-comorbid brain disorders.

Neurodegeneration and inflammation crosstalk: Therapeutic targets and perspectives

Glia, which was formerly considered to exist just to connect neurons, now plays a key function in a wide range of physiological events, including formation of memory, learning, neuroplasticity, synaptic plasticity, energy consumption, and homeostasis of ions. Glial cells regulate the brain's immune responses and confers nutritional and structural aid to neurons, making them an important player in a broad range of neurological disorders. Alzheimer's, ALS, Parkinson's, frontotemporal dementia (FTD), and epilepsy are a few of the neurodegenerative diseases that have been linked to microglia and astroglia cells, in particular. Synapse growth is aided by glial cell activity, and this activity has an effect on neuronal signalling. Each glial malfunction in diverse neurodegenerative diseases is distinct, and we will discuss its significance in the progression of the illness, as well as its potential for future treatment.

Aging alters mechanisms underlying voluntary movements in spinal motor neurons of mice, primates, and humans

Spinal motor neurons have been implicated in the loss of motor function that occurs with advancing age. However, the cellular and molecular mechanisms that impair the function of these neurons during aging remain unknown. Here, we show that motor neurons do not die in old female and male mice, rhesus monkeys, and humans. Instead, these neurons selectively and progressively shed excitatory synaptic inputs throughout the soma and dendritic arbor during aging. Thus, aged motor neurons contain a motor circuitry with a reduced ratio of excitatory to inhibitory synapses that may be responsible for the diminished ability to activate motor neurons to commence movements. An examination of the motor neuron translatome (ribosomal transcripts) in male and female mice reveals genes and molecular pathways with roles in glia-mediated synaptic pruning, inflammation, axonal regeneration, and oxidative stress that are upregulated in aged motor neurons. Some of these genes and pathways are also found altered in motor neurons affected with amyotrophic lateral sclerosis (ALS) and responding to axotomy, demonstrating that aged motor neurons are under significant stress. Our findings show mechanisms altered in aged motor neurons that could serve as therapeutic targets to preserve motor function during aging.

Want of Wnt in Parkinson's disease: Could sFRP disrupt interplay between Nurr1 and Wnt signaling?

Nuclear receptor related 1 (Nurr1) is a transcription factor known to regulate the development and maintenance of midbrain dopaminergic (mDA) neurons. Reports have confirmed that defect or obliteration of Nurr1 results in neurodegeneration and motor function impairment leading to Parkinson's disease (PD). Studies have also indicated that Nurr1 regulates the expression of alpha-synuclein (α-SYN) and mutations in Nurr1 cause α-SYN overexpression, thereby increasing the risk of PD. Nurr1 is modulated via various pathways including Wnt signaling pathway which is known to play an important role in neurogenesis and deregulation of it contributes to PD pathogenesis. Both Wnt/β-catenin dependent and independent pathways are implicated in the activation of Nurr1 and subsequent downregulation of α-SYN. This review highlights the interaction between Nurr1 and Wnt signaling pathways in mDA neuronal development. We further hypothesize how modulation of Wnt signaling pathway by its antagonist, secreted frizzled related proteins (sFRPs) could be a potential route to treat PD.

GABAB receptor activation alters astrocyte phenotype changes induced by trimethyltin via ERK signaling in the dentate gyrus of mice

AIMS

We examined the effect of γ-aminobutyric acid (GABA)_B receptor activation on astrocyte phenotype changes induced by trimethyltin (TMT) in the dentate gyrus of mice.

MAIN METHODS

Male C57BL/6N mice received TMT (2.6 mg/kg, i.p.), and the expression of GABA_B receptors was evaluated in the hippocampus. The GABA_B receptor agonist baclofen (2.5, 5, or 10 mg/kg, i.p. × 5 at 12-h intervals) was administered 3-5 days after TMT treatment, and the expression of Iba-1, GFAP, and astrocyte phenotype markers was evaluated 6 days after TMT. SL327 (30 mg/kg, i.p.), an extracellular signal-related kinase (ERK) inhibitor, was administered 1 h after each baclofen treatment.

KEY FINDINGS

TMT insult significantly induced the astroglial expression of GABA_B receptors in the dentate molecular layer. Baclofen significantly promoted the expression of S100A10, EMP1, and CD109, but not that of C3, GGTA1, and MX1 induced by TMT. In addition, baclofen significantly increased the TMT-induced expression of p-ERK in the dentate molecular layer. Interestingly, p-ERK was more colocalized with S100A10 than with C3 after TMT insult, and a significant positive correlation was found between the expression of p-ERK and S100A10. Consistently, SL327 reversed the effect of baclofen on astrocyte phenotype changes. Baclofen also enhanced the TMT-induced astroglial expression of glial cell-derived neurotrophic factor (GDNF), an anti-inflammatory astrocytes-to-microglia mediator, and consequently attenuated Iba-1 expression and delayed apoptotic neuronal death.

SIGNIFICANCE

Our results suggest that GABA_B receptor activation increases S100A10-positive anti-inflammatory astrocytes and astroglial GDNF expression via ERK signaling after TMT excitotoxicity in the dentate molecular layer of mice.

Glia Signaling and Brain Microenvironment in Migraine

Migraine is a complicated neurological disorder affecting 6% of men and 18% of women worldwide. Various mechanisms, including neuroinflammation, oxidative stress, altered mitochondrial function, neurotransmitter disturbances, cortical hyperexcitability, genetic factors, and endocrine system problems, are responsible for migraine. However, these mechanisms have not completely delineated the pathophysiology behind migraine, and they should be further studied. The brain microenvironment comprises neurons, glial cells, and vascular structures with complex interactions. Disruption of the brain microenvironment is the main culprit behind various neurological disorders. Neuron-glia crosstalk contributes to hyperalgesia in migraine. In the brain, microenvironment and related peripheral regulatory circuits, microglia, astrocytes, and satellite cells are necessary for proper function. These are the most important cells that could induce migraine headaches by disturbing the balance of the neurotransmitters in the nervous system. Neuroinflammation and oxidative stress are the prominent reactions glial cells drive during migraine. Understanding the role of cellular and molecular components of the brain microenvironment on the major neurotransmitters engaged in migraine pathophysiology facilitates the development of new therapeutic approaches with higher effectiveness for migraine headaches. Investigating the role of the brain microenvironment and neuroinflammation in migraine may help decipher its pathophysiology and provide an opportunity to develop novel therapeutic approaches for its management. This review aims to discuss the neuron-glia interactions in the brain microenvironment during migraine and their potential role as a therapeutic target for the treatment of migraine.

Interactions between non-coding RNAs and HIF-1α in the context of cancer

Hypoxia-inducible factor 1α (HIF-1α) is a subunit of the HIF-1 transcription factor which is encoded by the HIF1A gene. This transcription factor is the main modulator of the cell response to hypoxia. Hypoxia-induced up-regulation of HIF-1α is involved in the pathogenesis of cancer. Recently, the interactions of several long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) with HIF-1α have been reported. These ncRNAs regulate the expression of HIF-1α through different mechanisms. The regulatory roles of ncRNAs on HIF-1α are involved in the response of cancer cells to a wide range of anticancer drugs such as sorafenib, cisplatin, propofol, doxorubicin, and paclitaxel. Therefore, identification of the complex network between ncRNAs and HIF-1α not only facilitates the design of novel therapies but also promotes the efficacy of conventional anticancer treatments. This review aims to explain the interactions between these classes of ncRNAs and HIF-1α in the context of cancer.

Autophagy-mediated circHIPK2 promotes lipopolysaccharide-induced astrocytic inflammation via SIGMAR1

Circular RNAs (circRNAs) are a subclass of noncoding RNAs and widely involve in the occurrence of multiple human diseases. It is an urgent task to clarify circRNA upstream regulation mechanism and seek their biofunction. Our previous study has confirmed that circular RNA HIPK2 (circHIPK2) promotes astrocyte activation via SIGMAR1, sigma non-opioid intracellular receptor 1, in a mouse model of single high-dose lipopolysaccharide (LPS) injection. However, what mechanism circHIPK2 is regulated by and whether it is involved in the inflammatory response of astrocytes remain unclear. In this study, we reported that circHIPK2 and SIGMAR1 were significantly increased in mouse prefrontal cortex after multiple intraperitoneal injection of LPS, with the elevation of inflammatory mediators. Knockdown circHIPK2 in primary astrocytes suppressed the SIGMAR1 expression and inflammation. Pretreatment of autophagy inducer rapamycin on astrocytes suppressed the circHIPK2 expression and inactivated inflammatory response. These results implied that autophagy inducer rapamycin could suppress astrocytic inflammation by inactivating circHIPK2-SIGMAR1 axis. Autophagy may be a promising upstream administrator of circHIPK2 and therapeutic target for central nervous system inflammation.

The metal ion hypothesis of Alzheimer's disease and the anti-neuroinflammatory effect of metal chelators

Alzheimer's disease (AD), characterized by the β-amyloid protein (Aβ) deposition and tau hyperphosphorylation, is the most common dementia with uncertain etiology. The clinical trials of Aβ monoclonal antibody drugs have almost failed, giving rise to great attention on the other etiologic hypothesis regarding AD such as metal ions dysmetabolism and chronic neuroinflammation. Mounting evidence revealed that the metal ions (iron, copper, and zinc) were dysregulated in the susceptible brain regions of AD patients, which was highly associated with Aβ deposition, tau hyperphosphorylation, neuronal loss, as well as neuroinflammation. Further studies uncovered that iron, copper and zinc could not only enhance the production of Aβ but also directly bind to Aβ and tau to promote their aggregations. In addition, the accumulation of iron and copper could respectively promote ferroptosis and cuproptosis. Therefore, the metal ion chelators were recognized as promising agents for treating AD. This review comprehensively summarized the effects of metal ions on the Aβ dynamics and tau phosphorylation in the progression of AD. Furthermore, taking chronic neuroinflammation contributes to the progression of AD, we also provided a summary of the mechanisms concerning metal ions on neuroinflammation and highlighted the metal ion chelators may be potential agents to alleviate neuroinflammation under the condition of AD. Nevertheless, more investigations regarding metal ions on neuroinflammation should be taken into practice, and the effects of metal ion chelators on neuroinflammation should gain more attention. Running title: Metal chelators against neuroinflammation.

Bidirectional Communication Between Microglia and Astrocytes in Neuroinflammation

Neuroinflammation is a common feature of diverse nervous system pathologies. In many instances, it begins at an early stage of the disease, paving the way for further exacerbations. The main drivers of neuroinflammation are brain-resident glial cells, such as microglia and astrocytes. Microglia are the primary responders to any insult to the brain parenchyma, translating the signals into diverse molecules. These molecules derived from microglia can regulate the stimuli-dependent reactivity of astrocytes. Once activated, astrocytes in turn, can control microglia phenotypes. Recent evidence indicates that the crosstalk between these glial cells plays an important role in delaying or accelerating neuroinflammation and overall disease progression. To date, various molecules have been recognized as key mediators of the bidirectional communication between microglia and astrocytes. The current review aims to discuss the novel molecules identified recently, which play a critical role in interglial crosstalk, highlighting their therapeutic potential.

Activation of the STING pathway induces peripheral sensitization via neuroinflammation in a rat model of bone cancer pain

BACKGROUND

Neuroinflammation in the peripheral nervous system has been linked to cancer metastasis-induced bone pain. The stimulator of interferon genes (STING), an innate immune sensor for cytosolic DNA, plays an important role in inflammation and cancer metastasis and is reported to be a critical regulator of nociception. Here, we examined the role of STING in primary nociceptive neurons and chronic pain to determine if it could be a new target for treating bone cancer pain (BCP).

METHODS

Walker 256 cancer cells were injected intratibially to induce bone cancer pain in rats. STING and its downstream inflammatory factors in dorsal root ganglia (DRG) were detected using western blotting and immunofluorescent staining. Transmission electron microscopy and the BCL2-associated X (Bax) expression were used to detect the mitochondrial stress in DRG neurons. C-176, a specific inhibitor of STING, was used to block STING activation and to test the pain behavior.

RESULTS

Mechanical hyperalgesia and spontaneous pain were observed in BCP rats, accompanied by the upregulation of the STING expression in the ipsilateral L4-5 DRG neurons which showed significant mitochondrion stress. The STING/TANK-binding kinase 1 (TBK1)/nuclear factor-kappa B (NF-κB) pathway activation was observed in the DRGs of BCP rats as well as increased IL-1β, IL-6, and TNF-α expression. C-176 alleviated bone cancer pain and reduced the STING and its downstream inflammatory pathway.

CONCLUSION

We provide evidence that STING pathway activation leads to neuroinflammation and peripheral sensitization. Pharmacological blockade of STING may be a promising novel strategy for preventing BCP.

Identification of circRNA expression profiles and the potential role of hsa_circ_0006916 in silicosis and pulmonary fibrosis

Circular RNAs (circRNAs) are emerging as novel regulators in the biological development of various diseases, but their expression profiles, functions and mechanisms in silicosis and pulmonary fibrosis remain largely unexplored. In this study, we constructed a mouse model of pulmonary fibrosis by intratracheal injection of silica particles and then performed transcriptome RNA sequencing of lung tissues. The results showed that 78 circRNAs, 39 miRNAs and 262 mRNAs were differentially expressed. Among them, five circRNAs, three miRNAs and four mRNAs were further selected, and their abnormal expression was verified in mouse fibrotic lung tissues by RT-qPCR assay. The circRNA-associated ceRNA network including 206 ceRNA triplets was constructed based on abnormally expressed circRNAs, miRNAs and mRNAs, and miR-199b-5p, miR-296-5p and miR-708-5p were identified as hub miRNAs connected to circRNAs and mRNAs. Subsequently, GO and KEGG pathway enrichment analyses were performed to detect the potential roles of differentially expressed mRNAs in pulmonary fibrosis, which were mainly involved in immune response, Th17 cell differentiation, NF-κB signaling pathway and PI3K-Akt signaling pathway. Furthermore, we identified that hsa_circ_0006916 was up-regulated in pulmonary fibrosis. To characterize the potential role of hsa_circ_0006916, we transfected siRNA targeting hsa_circ_0006916 into alveolar macrophages and found that knockdown of hsa_circ_0006916 significantly increased the expression levels of M1 molecules IL-1β and TNF-α and reduced the expression level of M2 molecule TGF-β1, indicating that hsa_circ_0006916 may play an important role in the activation of M1-M2 polarization effect in macrophages. Our results provided important evidence on the possible contribution of these abnormal circRNAs to the development of silicosis and pulmonary fibrosis.

Interleukin-3 is associated with sTREM2 and mediates the correlation between amyloid-β and tau pathology in Alzheimer's disease

BACKGROUND

Dysfunction of glial cell communication is involved in Alzheimer's disease (AD) pathogenesis, and the recent study reported that astrocytic secreted interleukin-3 (IL-3) participated in astrocyte-microglia crosstalk and restricted AD pathology in mice, but the effect of IL-3 on the pathological progression of AD in human is still unclear.

METHODS

A total of 311 participants with cerebrospinal fluid (CSF) IL-3, soluble triggering receptor expressed on myeloid cells 2 (sTREM2), and AD biomarkers were included from the Alzheimer's disease Neuroimaging Initiative (ADNI). We assessed the associations of IL-3 with sTREM2 and AD biomarkers at baseline, and with cognitive change in longitudinal study. The mediation models were used to explore the potential mechanism of how IL-3 affects AD pathology.

RESULTS

We found that CSF IL-3 was significantly associated with CSF sTREM2 and CSF AD core biomarkers (Aβ42, p-tau, and t-tau) at baseline, and was also markedly related to cognitive decline in longitudinal analysis. Moreover, mediation analysis revealed that CSF IL-3 modulated the level of CSF sTREM2 and contributed to tau pathology (as measured by CSF p-tau/t-tau) and subsequent cognitive decline. In addition, Aβ pathology (as measured by CSF Aβ42) affected the development of tau pathology partly by modifying the levels of CSF IL-3 and CSF sTREM2. Furthermore, the effect of Aβ pathology on cognitive decline was partially mediated by the pathway from CSF IL-3 and CSF sTREM2 to tau pathology.

CONCLUSIONS

Our findings provide evidence to suggest that IL-3 is linked to sTREM2 and mediates the correlation between Aβ pathology to tau pathology. It indicates that IL-3 may be a major factor in the spreading from Aβ pathology to tau pathology to cognitive impairment.

Roles of Resolvins in Chronic Inflammatory Response

An inflammatory response is beneficial to the organism, while an excessive uncontrolled inflammatory response can lead to the nonspecific killing of tissue cells. Therefore, promoting the resolution of inflammation is an important mechanism for protecting an organism suffering from chronic inflammatory diseases. Resolvins are a series of endogenous lipid mediums and have the functions of inhibiting a leukocyte infiltration, increasing macrophagocyte phagocytosis, regulating cytokines, and alleviating inflammatory pain. By promoting the inflammation resolution, resolvins play an irreplaceable role throughout the pathological process of some joint inflammation, neuroinflammation, vascular inflammation, and tissue inflammation. Although a large number of experiments have been conducted to study different subtypes of resolvins in different directions, the differences in the action targets between the different subtypes are rarely compared. Hence, this paper reviews the generation of resolvins, the characteristics of resolvins, and the actions of resolvins under a chronic inflammatory response and clinical translation of resolvins for the treatment of chronic inflammatory diseases.

Identification of hsa-miR-365b-5p's role in Alzheimer's disease: a combined analysis of miRNA and mRNA microarrays

BACKGROUND

Alzheimer's disease is a prevalent health problem with a heavy global burden. Definitely diagnosed by autopsy, the clear mechanism of Alzheimer's disease pathogenesis process needs to be illustrated. MicroRNAs are suggested to be involved in many diseases. We aimed to investigate the role of microRNA in Alzheimer's disease.

METHODS

We attempted to discover the role of microRNA in Alzheimer's disease by microarray bioinformatics analysis using autopsy sample data from the GEO database. Temporal cortex samples were included in this study. Bioinformatics analyses and visualization were processed based on R.

RESULTS

After filtering out significantly differential expressed microRNAs and genes, enrichment analyses of both microRNAs and genes were conducted, respectively. Then, we constructed a transcription factor- microRNA-mRNA network and a protein-protein interaction network. In parallel, we used the receiver operating characteristic curve to evaluate the diagnostic value of microRNA. Based on the evidence, we finally identified hsa-miR-365b-5p as a key target in Alzheimer's disease.

CONCLUSIONS

Hsa-miR-365b-5p act as a key target in Alzheimer's disease. It regulates Alzheimer's disease pathogenesis process via neuroinflammation, Wnt and oxidative stress pathway which provides a potential target for Alzheimer's disease treatment.

The Multifaceted Neurotoxicity of Astrocytes in Ageing and Age-Related Neurodegenerative Diseases: A Translational Perspective

In a healthy physiological context, astrocytes are multitasking cells contributing to central nervous system (CNS) homeostasis, defense, and immunity. In cell culture or rodent models of age-related neurodegenerative diseases (NDDs), such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), numerous studies have shown that astrocytes can adopt neurotoxic phenotypes that could enhance disease progression. Chronic inflammatory responses, oxidative stress, unbalanced phagocytosis, or alteration of their core physiological roles are the main manifestations of their detrimental states. However, if astrocytes are directly involved in brain deterioration by exerting neurotoxic functions in patients with NDDs is still controversial. The large spectrum of NDDs, with often overlapping pathologies, and the technical challenges associated with the study of human brain samples complexify the analysis of astrocyte involvement in specific neurodegenerative cascades. With this review, we aim to provide a translational overview about the multi-facets of astrocyte neurotoxicity ranging from in vitro findings over mouse and human cell-based studies to rodent NDDs research and finally evidence from patient-related research. We also discuss the role of ageing in astrocytes encompassing changes in physiology and response to pathologic stimuli and how this may prime detrimental responses in NDDs. To conclude, we discuss how potentially therapeutic strategies could be adopted to alleviate or reverse astrocytic toxicity and their potential to impact neurodegeneration and dementia progression in patients.

Platelets, Thromboinflammation and Neurovascular Disease

The brain and spinal cord are immune-privileged organs, but in the disease state protection mechanisms such as the blood brain barrier (BBB) are ineffective or overcome by pathological processes. In neuroinflammatory diseases, microglia cells and other resident immune cells contribute to local vascular inflammation and potentially a systemic inflammatory response taking place in parallel. Microglia cells interact with other cells impacting on the integrity of the BBB and propagate the inflammatory response through the release of inflammatory signals. Here, we discuss the activation and response mechanisms of innate and adaptive immune processes in response to neuroinflammation. Furthermore, the clinical importance of neuroinflammatory mediators and a potential translational relevance of involved mechanisms are addressed also with focus on non-classical immune cells including microglia cells or platelets. As illustrative examples, novel agents such as Anfibatide or Revacept, which result in reduced recruitment and activation of platelets, a subsequently blunted activation of the coagulation cascade and further inflammatory process, demonstrating that mechanisms of neuroinflammation and thrombosis are interconnected and should be further subject to in depth clinical and basic research.

SFRP1 modulates astrocyte-to-microglia crosstalk in acute and chronic neuroinflammation

Neuroinflammation is a common feature of many neurodegenerative diseases. It fosters a dysfunctional neuron-microglia-astrocyte crosstalk that, in turn, maintains microglial cells in a perniciously reactive state that often enhances neuronal damage. The molecular components that mediate this critical communication are not fully explored. Here, we show that secreted frizzled-related protein 1 (SFRP1), a multifunctional regulator of cell-to-cell communication, is part of the cellular crosstalk underlying neuroinflammation. In mouse models of acute and chronic neuroinflammation, SFRP1, largely astrocyte-derived, promotes and sustains microglial activation, and thus a chronic inflammatory state. SFRP1 promotes the upregulation of components of the hypoxia-induced factor-dependent inflammatory pathway and, to a lower extent, of those downstream of the nuclear factor-kappa B. We thus propose that SFRP1 acts as an astrocyte-to-microglia amplifier of neuroinflammation, representing a potential valuable therapeutic target for counteracting the harmful effect of chronic inflammation in several neurodegenerative diseases.