CX3CL1/CX3CR1 axis attenuates early brain injury via promoting the delivery of exosomal microRNA-124 from neuron to microglia after subarachnoid hemorrhage

Exosomal LncRNA TM7SF3-AU1 Aggravates White Matter Injury via MiR-702-3p/SARM1 Signaling After Subarachnoid Hemorrhage in Rats

Subarachnoid hemorrhage (SAH) is a devastating disease associated with a high mortality and morbidity. Exosomes have been considered as a potential therapeutic target for SAH. However, the effect of exosomes in SAH remains to be elucidated. In this study, we focused on investigating the effect of plasma exosomal lncRNA TM7SF3-AU1 in white matter injury after SAH. The SAH model was established by means of endovascular perforation. Exosomes were extracted from rat plasma samples. The expression of RNAs in the exosomes was detected by the transcriptomic microarray. Differentially expressed circRNA, lncRNA, and mRNA were obtained. The ceRNA network showed that the lncRNA TM7SF3-AU1 and miR-702-3p were closely associated with SARM1. Knocking down TM7SF3-AU1 promoted the expression of miR-702-3p and suppressed the expression of SARM1, and knocking down TM7SF3-AU1 also attenuated white matter injury after SAH. In addition, knocking down TM7SF3-AU1 improved the neurological deficits in locomotion, anxiety, learning, memory, and electrophysiological activity after SAH. Mechanistically, TM7SF3-AU1 was able to absorb miR-702-3p, which directly bind the SARM1 mRNA. Furthermore, the white matter injury attenuated by knockdown of TM7SF3-AU1 was partially reversed by the miR-702-3p antagomir in SAH rats. Taken together, this study showed that TM7SF3-AU1 acts as a sponge for miR-702-3p, reducing the inhibitory effect of miR-702-3p on SARM1, resulting in increased SARM1 expression and thus leading to white matter injury after SAH. Our study provides new insights into exosome-associated white matter injury. It also highlights TM7SF3-AU1 as a potential therapeutic target for white matter injury after SAH.

Treadmill Exercise Enhances Post-Stroke Functional Recovery in Mice via the CX3CL1/CX3CR1 Signaling Pathway

To validate that treadmill exercise promotes neurofunctional recovery post ischemic stroke and to specifically explore the role of the CX3CL1/CX3CR1 signaling pathway in this treadmill-mediated recovery process. C57BL/6 J mice were used to establish a middle cerebral artery occlusion (MCAO) model. From days 5 to 28 post-stroke, the experimental group did 10-min treadmill sessions twice daily at 12 r/min; the control group remained inactive. On day 6 post-stroke, mice received three intraperitoneal injections of Bromodeoxyuridine (BrdU) or PBS. On days 1, 3, and 5 post-stroke, mice received intracerebroventricular injections of exogenous recombinant CX3CL1, CX3CL1 antagonist, or PBS. The modified neurological severity score (mNSS) and the corner test were used to assess sensorimotor function, and the morris water maze (MWM) test was employed to evaluate cognitive function. Western blot detected CX3CL1 and CX3CR1 protein expression, while immunofluorescence observed these proteins, neurogenesis in the subventricular zone (SVZ), rostral migratory stream (RMS), and dentate gyrus (DG), along with Iba1 and CD68 co-expression. ELISA quantified IL-1β, IL-4, and IL-10 levels. Treadmill exercise significantly improved neurofunctional recovery in MCAO mice, enhanced neurogenesis in the RMS and SVZ, and increased the expression of CX3CL1 and CX3CR1. The CX3CL1/CX3CR1 axis enhanced the impact of treadmill exercise on neurofunctional recovery, promoting neurogenesis in the RMS and SVZ, and reducing inflammation. Additionally, this axis also enhanced neurogenesis and suppressed microglial activation in the DG induced by treadmill exercise. This study demonstrates the CX3CL1/CX3CR1 pathway as critical for treadmill-induced post-stroke recovery, indicating its potential target for exercise mimetics in rehabilitation.

Role of microglia after subarachnoid hemorrhage

Subarachnoid hemorrhage is a devastating sequela of aneurysm rupture. Because it disproportionately affects younger patients, the population impact of hemorrhagic stroke from subarachnoid hemorrhage is substantial. Secondary brain injury is a significant contributor to morbidity after subarachnoid hemorrhage. Initial hemorrhage causes intracranial pressure elevations, disrupted cerebral perfusion pressure, global ischemia, and systemic dysfunction. These initial events are followed by two characterized timespans of secondary brain injury: the early brain injury period and the delayed cerebral ischemia period. The identification of varying microglial phenotypes across phases of secondary brain injury paired with the functions of microglia during each phase provides a basis for microglia serving a critical role in both promoting and attenuating subarachnoid hemorrhage-induced morbidity. The duality of microglial effects on outcomes following SAH is highlighted by the pleiotropic features of these cells. Here, we provide an overview of the key role of microglia in subarachnoid hemorrhage-induced secondary brain injury as both cytotoxic and restorative effectors. We first describe the ontogeny of microglial populations that respond to subarachnoid hemorrhage. We then correlate the phenotypic development of secondary brain injury after subarachnoid hemorrhage to microglial functions, synthesizing experimental data in this area.

Machine learning and deep learning to identifying subarachnoid haemorrhage macrophage-associated biomarkers by bulk and single-cell sequencing

We investigated subarachnoid haemorrhage (SAH) macrophage subpopulations and identified relevant key genes for improving diagnostic and therapeutic strategies. SAH rat models were established, and brain tissue samples underwent single-cell transcriptome sequencing and bulk RNA-seq. Using single-cell data, distinct macrophage subpopulations, including a unique SAH subset, were identified. The hdWGCNA method revealed 160 key macrophage-related genes. Univariate analysis and lasso regression selected 10 genes for constructing a diagnostic model. Machine learning algorithms facilitated model development. Cellular infiltration was assessed using the MCPcounter algorithm, and a heatmap integrated cell abundance and gene expression. A 3 × 3 convolutional neural network created an additional diagnostic model, while molecular docking identified potential drugs. The diagnostic model based on the 10 selected genes achieved excellent performance, with an AUC of 1 in both training and validation datasets. The heatmap, combining cell abundance and gene expression, provided insights into SAH cellular composition. The convolutional neural network model exhibited a sensitivity and specificity of 1 in both datasets. Additionally, CD14, GPNMB, SPP1 and PRDX5 were specifically expressed in SAH-associated macrophages, highlighting its potential as a therapeutic target. Network pharmacology analysis identified some targeting drugs for SAH treatment. Our study characterised SAH macrophage subpopulations and identified key associated genes. We developed a robust diagnostic model and recognised CD14, GPNMB, SPP1 and PRDX5 as potential therapeutic targets. Further experiments and clinical investigations are needed to validate these findings and explore the clinical implications of targets in SAH treatment.

Exosomes as a therapeutic tool to promote neurorestoration and cognitive function in neurological conditions: Achieve two ends with a single effort

Exosomes possess a significant role in intercellular communications. In the nervous system, various neural cells release exosomes that not only own a role in intercellular communications but also eliminate the waste of cells, maintain the myelin sheath, facilitate neurogenesis, and specifically assist in normal cognitive function. In neurological conditions including Parkinson's disease (PD), Alzheimer's disease (AD), traumatic brain injury (TBI), and stroke, exosomal cargo like miRNAs take part in the sequela of conditions and serve as a diagnostic tool of neurological disorders, too. Exosomes are not only a diagnostic tool but also their inhibition or administration from various sources like mesenchymal stem cells and serum, which have shown a worthy potential to treat multiple neurological disorders. In addition to neurodegenerative manifestations, cognitive deficiencies are an integral part of neurological diseases, and applying exosomes in improving both aspects of these diseases has been promising. This review discusses the status of exosome therapy in improving neurorestorative and cognitive function following neurological disease.

Single-cell transcriptomics reveal distinct immune-infiltrating phenotypes and macrophage-tumor interaction axes among different lineages of pituitary neuroendocrine tumors

BACKGROUND

Pituitary neuroendocrine tumors (PitNETs) are common gland neoplasms demonstrating distinctive transcription factors. Although the role of immune cells in PitNETs has been widely recognized, the precise immunological environment and its control over tumor cells are poorly understood.

METHODS

The heterogeneity, spatial distribution, and clinical significance of macrophages in PitNETs were analyzed using single-cell RNA sequencing (scRNA-seq), bulk RNA-seq, spatial transcriptomics, immunohistochemistry, and multiplexed quantitative immunofluorescence (QIF). Cell viability, cell apoptosis assays, and in vivo subcutaneous xenograft experiments have confirmed that INHBA-ACVR1B influences the process of tumor cell apoptosis.

RESULTS

The present study evaluated scRNA-seq data from 23 PitNET samples categorized into 3 primary lineages. The objective was to explore the diversity of tumors and the composition of immune cells across these lineages. Analyzed data from scRNA-seq and 365 bulk RNA sequencing samples conducted in-house revealed the presence of three unique subtypes of tumor immune microenvironment (TIME) in PitNETs. These subtypes were characterized by varying levels of immune infiltration, ranging from low to intermediate to high. In addition, the NR5A1 lineage is primarily associated with the subtype characterized by limited infiltration of immune cells. Tumor-associated macrophages (TAMs) expressing CX3CR1+, C1Q+, and GPNMB+ showed enhanced contact with tumor cells expressing NR5A1 + , TBX19+, and POU1F1+, respectively. This emphasizes the distinct interaction axes between TAMs and tumor cells based on their lineage. Moreover, the connection between CX3CR1+ macrophages and tumor cells via INHBA-ACVR1B regulates tumor cell apoptosis.

CONCLUSIONS

In summary, the different subtypes of TIME and the interaction between TAM and tumor cells offer valuable insights into the control of TIME that affects the development of PitNET. These findings can be utilized as prospective targets for therapeutic interventions.

Exosomes in Vascular/Neurological Disorders and the Road Ahead

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), stroke, and aneurysms, are characterized by the abnormal accumulation and aggregation of disease-causing proteins in the brain and spinal cord. Recent research suggests that proteins linked to these conditions can be secreted and transferred among cells using exosomes. The transmission of abnormal protein buildup and the gradual degeneration in the brains of impacted individuals might be supported by these exosomes. Furthermore, it has been reported that neuroprotective functions can also be attributed to exosomes in neurodegenerative diseases. The potential neuroprotective functions may play a role in preventing the formation of aggregates and abnormal accumulation of proteins associated with the disease. The present review summarizes the roles of exosomes in neurodegenerative diseases as well as elucidating their therapeutic potential in AD, PD, ALS, HD, stroke, and aneurysms. By elucidating these two aspects of exosomes, valuable insights into potential therapeutic targets for treating neurodegenerative diseases may be provided.

Rasd1 is involved in white matter injury through neuron-oligodendrocyte communication after subarachnoid hemorrhage

AIMS

Rasd1 has been reported to be correlated with neurotoxicity, metabolism, and rhythm, but its effect in case of subarachnoid hemorrhage (SAH) remained unclear. White matter injury (WMI) and ferroptosis participate in the early brain injury (EBI) after SAH. In this work, we have investigated whether Rasd1 can cause ferroptosis and contribute to SAH-induced WMI.

METHODS

Lentivirus for Rasd1 knockdown/overexpression was administrated by intracerebroventricular (i.c.v) injection at 7 days before SAH induction. SAH grade, brain water content, short- and long-term neurobehavior, Western blot, real-time PCR, ELISA, biochemical estimation, immunofluorescence, diffusion tensor imaging (DTI), and transmission electron microscopy (TEM) were systematically performed. Additionally, genipin, a selective uncoupling protein 2(UCP2) inhibitor, was used in primary neuron and oligodendrocyte co-cultures for further in vitro mechanistic studies.

RESULTS

Rasd1 knockdown has improved the neurobehavior, glia polarization, oxidative stress, neuroinflammation, ferroptosis, and demyelination. Conversely, Rasd1 overexpression aggravated these changes by elevating the levels of reactive oxygen species (ROS), inflammatory cytokines, MDA, free iron, and NCOA4, as well as contributing to the decrease of the levels of UCP2, GPX4, ferritin, and GSH mechanistically. According to the in vitro study, Rasd1 can induce oligodendrocyte ferroptosis through inhibiting UCP2, increasing reactive oxygen species (ROS), and activating NCOA4-mediated ferritinophagy.

CONCLUSIONS

It can be concluded that Rasd1 exerts a modulated role in oligodendrocytes ferroptosis in WMI following SAH.

Exosomes: A Cellular Communication Medium That Has Multiple Effects On Brain Diseases

Exosomes, as membranous vesicles generated by multiple cell types and secreted to extracellular space, play a crucial role in a range of brain injury-related brain disorders by transporting diverse proteins, RNA, DNA fragments, and other functional substances. The nervous system's pathogenic mechanisms are complicated, involving pathological processes like as inflammation, apoptosis, oxidative stress, and autophagy, all of which result in blood-brain barrier damage, cognitive impairment, and even loss of normal motor function. Exosomes have been linked to the incidence and progression of brain disorders in recent research. As a result, a thorough knowledge of the interaction between exosomes and brain diseases may lead to the development of more effective therapeutic techniques that may be implemented in the clinic. The potential role of exosomes in brain diseases and the crosstalk between exosomes and other pathogenic processes were discussed in this paper. Simultaneously, we noted the delicate events in which exosomes as a media allow the brain to communicate with other tissues and organs in physiology and disease, and compiled a list of natural compounds that modulate exosomes, in order to further improve our understanding of exosomes and propose new ideas for treating brain disorders.

Impaired cortical neuronal homeostasis and cognition after diffuse traumatic brain injury are dependent on microglia and type I interferon responses

Neuropsychiatric complications including depression and cognitive decline develop in the years after traumatic brain injury (TBI), negatively affecting quality of life. Microglial and type 1 interferon (IFN-I) responses are associated with the transition from acute to chronic neuroinflammation after diffuse TBI in mice. Thus, the purpose of this study was to determine if impaired neuronal homeostasis and increased IFN-I responses intersected after TBI to cause cognitive impairment. Here, the RNA profile of neurons and microglia after TBI (single nucleus RNA-sequencing) with or without microglia depletion (CSF1R antagonist) was assessed 7 dpi. There was a TBI-dependent suppression of cortical neuronal homeostasis with reductions in CREB signaling, synaptogenesis, and synaptic migration and increases in RhoGDI and PTEN signaling (Ingenuity Pathway Analysis). Microglial depletion reversed 50% of TBI-induced gene changes in cortical neurons depending on subtype. Moreover, the microglial RNA signature 7 dpi was associated with increased stimulator of interferon genes (STING) activation and IFN-I responses. Therefore, we sought to reduce IFN-I signaling after TBI using STING knockout mice and a STING antagonist, chloroquine (CQ). TBI-associated cognitive deficits in novel object location and recognition (NOL/NOR) tasks at 7 and 30 dpi were STING dependent. In addition, TBI-induced STING expression, microglial morphological restructuring, inflammatory (Tnf, Cd68, Ccl2) and IFN-related (Irf3, Irf7, Ifi27) gene expression in the cortex were attenuated in STINGKO mice. CQ also reversed TBI-induced cognitive deficits and reduced TBI-induced inflammatory (Tnf, Cd68, Ccl2) and IFN (Irf7, Sting) cortical gene expression. Collectively, reducing IFN-I signaling after TBI with STING-dependent interventions attenuated the prolonged microglial activation and cognitive impairment.

Transfer of cGAMP from neuron to microglia activates microglial type I interferon responses after subarachnoid hemorrhage

Primary subarachnoid hemorrhage (SAH) is a type of acute stroke, accounting for approximately 10% of cases, with high disability and mortality rate. Early brain injury (EBI) is a critical factor in determining SAH mortality; however, there are no effective treatment interventions for EBI. Based on our results, the transmission of cyclic GMP-AMP (cGAMP) from neurons to microglia is a key molecular event that triggers type I interferon response, amplifies neuroinflammation, and leads to neuronal apoptosis. Abnormal intracytoplasmic mitochondrial DNA (mtDNA) is the initiating factor of the cGAS-cGAMP-STING signaling axis. Overall, the cGAS-cGAMP-STING signaling axis is closely associated with neuroinflammation after subarachnoid hemorrhage. Targeting cGAS triggered by cytoplasmic mtDNA may be useful for comprehensive clinical treatment of patients after SAH. Further studies targeting cGAS-specific antagonists for treating SAH are warranted. Video Abstract.

Exosomal microRNAs: implications in the pathogenesis and clinical applications of subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a severe acute neurological disorder with a high fatality rate. Early brain injury (EBI) and cerebral vasospasm are two critical complications of SAH that significantly contribute to poor prognosis. Currently, surgical intervention and interventional therapy are the main treatment options for SAH, but their effectiveness is limited. Exosomes, which are a type of extracellular vesicles, play a crucial role in intercellular communication and have been extensively studied in the past decade due to their potential influence on disease progression, diagnosis, and treatment. As one of the most important components of exosomes, miRNA plays both direct and indirect roles in affecting disease progression. Previous research has found that exosomal miRNA is involved in the development of various diseases, such as tumors, chronic hepatitis, atherosclerosis, diabetes, and SAH. This review focuses on exploring the impact of exosomal miRNA on SAH, including its influence on neuronal apoptosis, inflammatory response, and immune activation following SAH. Furthermore, this review highlights the potential clinical applications of exosomal miRNA in the treatment of SAH. Although current research on this topic is limited and the clinical application of exosomal miRNA has inherent limitations, we aim to provide a concise summary of existing research progress and offer new insights for future research directions and trends in this field.

Fractalkine Enhances Hematoma Resolution and Improves Neurological Function via CX3CR1/AMPK/PPARγ Pathway After GMH

BACKGROUND

Hematoma clearance has been a proposed therapeutic strategy for hemorrhagic stroke. This study investigated the impact of CX3CR1 (CX3C chemokine receptor 1) activation mediated by r-FKN (recombinant fractalkine) on hematoma resolution, neuroinflammation, and the underlying mechanisms involving AMPK (AMP-activated protein kinase)/PPARγ (peroxisome proliferator-activated receptor gamma) pathway after experimental germinal matrix hemorrhage (GMH).

METHODS

A total of 313 postnatal day 7 Sprague Dawley rat pups were used. GMH was induced using bacterial collagenase by a stereotactically guided infusion. r-FKN was administered intranasally at 1, 25, and 49 hours after GMH for short-term neurological evaluation. Long-term neurobehavioral tests (water maze, rotarod, and foot-fault test) were performed 24 to 28 days after GMH with the treatment of r-FKN once daily for 7 days. To elucidate the underlying mechanism, CX3CR1 CRISPR, or selective CX3CR1 inhibitor AZD8797, was administered intracerebroventricularly 24 hours preinduction of GMH. Selective inhibition of AMPK/PPARγ signaling in microglia via intracerebroventricularly delivery of liposome-encapsulated specific AMPK (Lipo-Dorsomorphin), PPARγ (Lipo-GW9662) inhibitor. Western blot, Immunofluorescence staining, Nissl staining, Hemoglobin assay, and ELISA assay were performed.

RESULTS

The brain expression of FKN and CX3CR1 were elevated after GMH. FKN was expressed on both neurons and microglia, whereas CX3CR1 was mainly expressed on microglia after GMH. Intranasal administration of r-FKN improved the short- and long-term neurobehavioral deficits and promoted M2 microglia polarization, thereby attenuating neuroinflammation and enhancing hematoma clearance, which was accompanied by an increased ratio of p-AMPK (phosphorylation of AMPK)/AMPK, Nrf2 (nuclear factor erythroid 2-related factor 2), PPARγ, CD36 (cluster of differentiation 36), CD163 (hemoglobin scavenger receptor), CD206 (the mannose receptor), and IL (interleukin)-10 expression, and decreased CD68 (cluster of differentiation 68), IL-1β, and TNF (tumor necrosis factor) α expression. The administration of CX3CR1 CRISPR or CX3CR1 inhibitor (AZD8797) abolished the protective effect of FKN. Furthermore, selective inhibition of microglial AMPK/PPARγ signaling abrogated the anti-inflammation effects of r-FKN after GMH.

CONCLUSIONS

CX3CR1 activation by r-FKN promoted hematoma resolution, attenuated neuroinflammation, and neurological deficits partially through the AMPK/PPARγ signaling pathway, which promoted M1/M2 microglial polarization. Activating CX3CR1 by r-FKN may provide a promising therapeutic approach for treating patients with GMH.

P38-DAPK1 axis regulated LC3-associated phagocytosis (LAP) of microglia in an in vitro subarachnoid hemorrhage model

BACKGROUND

The phagocytosis and homeostasis of microglia play an important role in promoting blood clearance and improving prognosis after subarachnoid hemorrhage (SAH). LC3-assocaited phagocytosis (LAP) contributes to the microglial phagocytosis and homeostasis via autophagy-related components. With RNA-seq sequencing, we found potential signal pathways and genes which were important for the LAP of microglia.

METHODS

We used an in vitro model of oxyhemoglobin exposure as SAH model in the study. RNA-seq sequencing was performed to seek critical signal pathways and genes in regulating LAP. Bioparticles were used to access the phagocytic ability of microglia. Western blot (WB), immunoprecipitation, quantitative polymerase chain reaction (qPCR) and immunofluorescence were performed to detect the expression change of LAP-related components and investigate the potential mechanisms.

RESULTS

In vitro SAH model, there were increased inflammation and decreased phagocytosis in microglia. At the same time, we found that the LAP of microglia was inhibited in all stages. RNA-seq sequencing revealed the importance of P38 MAPK signal pathway and DAPK1 in regulating microglial LAP. P38 was found to regulate the expression of DAPK1, and P38-DAPK1 axis was identified to regulate the LAP and homeostasis of microglia after SAH. Finally, we found that P38-DAPK1 axis regulated expression of BECN1, which indicated the potential mechanism of P38-DAPK1 axis regulating microglial LAP.

CONCLUSION

P38-DAPK1 axis regulated the LAP of microglia via BECN1, affecting the phagocytosis and homeostasis of microglia in vitro SAH model. Video Abstract.

Attenuating Neuronal Autophagy Alleviates Inflammatory Injury in OGDDeprived Co-culture of HT22 with BV2

Neuronal CX3CL1 suppressed microglial inflammation by binding to its receptor CX3CR1 expressed on microglia. Neuronal autophagy was prominently activated by cerebral ischemia, whereas CX3CL1 expression in autophagic neurons was conversely down-regulated to exacerbate microglial inflammation. Accordingly, this study was meant to investigate whether ischemia-activated microglial inflammation could be repressed by promoting CX3CL1 expression via the attenuation of neuronal autophagy. Immunofluorescence showed that autophagy predominantly occurred in neurons but barely in microglia. Western blot and immunofluorescence demonstrated that attenuating HT22 autophagy significantly increased its CX3CL1 expression and subsequently mitigated the BV2-mediated inflammatory responses, as indicated by decreased inflammatory factors of NF-κB-p65, IL-6, IL-1β, TNF-α, and PGE2. Meanwhile, CCK-8, Nissl staining, and FJC staining showed that an OGD (Oxygen-glycogen deprivation)-created neuronal injury was greatly alleviated by CX3CL1-suppressed microglial inflammation. Contrarily, elevating HT22 autophagy markedly decreased its CX3CL1 expression, which consequently worsened microglial inflammation and the neuronal injury. Our data suggests that attenuating neuronal autophagy may be an effective method to alleviate a microglial inflammatory injury after an ischemic stroke.

MicroRNAs' Role in Diagnosis and Treatment of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is most commonly seen in patients over 55 years of age and often results in a loss of many productive years. SAH has a high mortality rate, and survivors often suffer from early and secondary brain injuries. Understanding the pathophysiology of the SAH is crucial in identifying potential therapeutic agents. One promising target for the diagnosis and prognosis of SAH is circulating microRNAs, which regulate gene expression and are involved in various physiological and pathological processes. In this review, we discuss the potential of microRNAs as a target for diagnosis, treatment, and prognosis in SAH.

Extracellular vesicles: a new communication paradigm of complement in neurological diseases

The complement system is crucial to the innate immune system. It has the function of destroying pathogens by activating the classical, alternative, and lectin pathways. The complement system is important in nervous system diseases such as cerebrovascular and neurodegenerative diseases. Activation of the complement system involves a series of intercellular signaling and cascade reactions. However, research on the source and transport mechanisms of the complement system in neurological diseases is still in its infancy. Studies have increasingly found that extracellular vesicles (EVs), a classic intercellular communication paradigm, may play a role in complement signaling disorders. Here, we systematically review the EV-mediated activation of complement pathways in different neurological diseases. We also discuss the prospect of EVs as future immunotherapy targets.

Activation of TRPV1 receptor facilitates myelin repair following demyelination via the regulation of microglial function

The transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel that is activated by capsaicin (CAP), the main component of chili pepper. Despite studies in several neurological diseases, the role of TRPV1 in demyelinating diseases remains unknown. Herein, we reported that TRPV1 expression was increased within the corpus callosum during demyelination in a cuprizone (CPZ)-induced demyelination mouse model. TRPV1 deficiency exacerbated motor coordinative dysfunction and demyelination in CPZ-treated mice, whereas the TRPV1 agonist CAP improved the behavioral performance and facilitated remyelination. TRPV1 was predominantly expressed in Iba1+ microglia/macrophages in human brain sections of multiple sclerosis patients and mouse corpus callosum under demyelinating conditions. TRPV1 deficiency decreased microglial recruitment to the corpus callosum, with an associated increase in the accumulation of myelin debris. Conversely, the activation of TRPV1 by CAP enhanced the recruitment of microglia to the corpus callosum and potentiated myelin debris clearance. Using real-time live imaging we confirmed an increased phagocytic function of microglia following CAP treatment. In addition, the expression of the scavenger receptor CD36 was increased, and that of the glycolysis regulators Hif1a and Hk2 was decreased. We conclude that TRPV1 is an important regulator of microglial function in the context of demyelination and may serve as a promising therapeutic target for demyelinating diseases such as multiple sclerosis.

Mesenchymal stem cell-derived extracellular vesicles/exosome: A promising therapeutic strategy for intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the second largest type of stroke with high mortality and morbidity. The vast majority of survivors suffer from serious neurological defects. Despite the well-established etiology and diagnose, there is still some controversy over the ideal treatment strategy. MSC-based therapy has become an attractive and promising strategy for the treatment of ICH through immune regulation and tissue regeneration. However, accumulating studies have revealed that MSC-based therapeutic effects are mainly attributed to the paracrine properties of MSC, especially small extracellular vesicles/exosome (EVs/exo) which are considered to be the key mediators of the protective efficacy from MSCs. Moreover, some papers reported that MSC-EVs/exo have better therapeutic effects than MSCs. Therefore, EVs/exo has become a new choice for the treatment of ICH stroke in recent years. In this review, we mainly concentrate on the current research progress on the use of MSC-EVs/exo in the treatment of ICH and the existing challenges in their transplation from lab to clinical practice.

The link between neuroinflammation and the neurovascular unit in synucleinopathies

The neurovascular unit (NVU) is composed of vascular cells, glial cells, and neurons. As a fundamental functional module in the central nervous system, the NVU maintains homeostasis in the microenvironment and the integrity of the blood-brain barrier. Disruption of the NVU and interactions among its components are involved in the pathophysiology of synucleinopathies, which are characterized by the pathological accumulation of α-synuclein. Neuroinflammation contributes to the pathophysiology of synucleinopathies, including Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies. This review aims to summarize the neuroinflammatory response of glial cells and vascular cells in the NVU. We also review neuroinflammation in the context of the cross-talk between glial cells and vascular cells, between glial cells and pericytes, and between microglia and astroglia. Last, we discuss how α-synuclein affects neuroinflammation and how neuroinflammation influences the aggregation and spread of α-synuclein and analyze different properties of α-synuclein in synucleinopathies.

Elevated levels of several chemokines in the cerebrospinal fluid of patients with subarachnoid hemorrhage are associated with worse clinical outcome

BACKGROUND

Chemokines are small cytokines that exert chemotactic actions on immune cells and are involved in many inflammatory processes. The present study aims to provide insight in the role of this relatively unexplored family of proteins in the inflammatory pathophysiology of subarachnoid hemorrhage (SAH).

MATERIALS AND METHODS

Cerebrospinal fluid of 29 patients (17 female; mean age 57 years) was collected at days 1, 4 and 10 after SAH, centrifuged and frozen at -70°C. Analysis of 92 inflammation-related proteins was performed using Target 96 Inflammation ® assay (Olink Proteomics, Uppsala, Sweden) based on Proximity Extension Assay technology. The panel included 20 chemokines (CCL2 (or MCP-1), CCL3, CCL4, CCL7 (or MCP-3), CCL8 (or MCP-2), CCL11 (or Eotaxin), CCL13 (or MCP-4), CCL19, CCL20, CCL23, CCL25, CCL28, CXCL1, CXCL5, CXCL6, CXCL8 (or IL-8), CXCL9, CXCL10, CXCL11 and CX3CL1 (or Fractalkine)) that were analyzed for their temporal patterns of expression and compared in dichotomized clinical groups based on World Federation of Neurosurgical Societies (WFNS) admission score and amount of blood on admission CT based on Fisher scale; presence of delayed cerebral ischemia(DCI)/delayed ischemic neurological deficit (DIND); and clinical outcome based on Glasgow Outcome Scale. Protein expression levels were provided in output unit Normalized Protein Expression (NPX). ANOVA models were used for statistical analyses.

RESULTS

Four temporal patterns of expression were observed (i.e., early, middle, late peak and no peak). Significantly higher day 10 mean NPX values were observed in patients with poor outcome (GOS 1-3) for chemokines CCL2, CCL4, CCL7, CCL11, CCL13, CCL19, CCL20, CXCL1, CXCL5, CXCL6 and CXCL8. In the WFNS 4-5 group, CCL11 showed significantly higher day 4 and day 10 mean NPX values and CCL25 significantly higher day 4 values. In patients with SAH Fisher 4, CCL11 showed significantly higher mean NPX values on days 1, 4 and 10. Finally, patients with DCI/DIND had significantly higher day 4 mean NPX values of CXCL5.

CONCLUSION

Higher levels of multiple chemokines at the late stage of SAH seemed to correlate with worse clinical outcome. A few chemokines correlated with WFNS score, Fisher score and occurrence of DCI/DIND. Chemokines may be useful as biomarkers for describing the pathophysiology and prognosis of SAH. Further studies are needed to better understand their exact mechanism of action in the inflammatory cascade.

Role of Circulating Exosomes in Cerebrovascular Diseases: A Comprehensive Review

Exosomes are lipid bilayer vesicles that contain multiple macromolecules secreted by the parent cells and play a vital role in intercellular communication. In recent years, the function of exosomes in cerebrovascular diseases (CVDs) has been intensively studied. Herein, we briefly review the current understanding of exosomes in CVDs. We discuss their role in the pathophysiology of the diseases and the value of the exosomes for clinical applications as biomarkers and potential therapies.

MicroRNA-140-5p shuttled by microglia-derived extracellular vesicles attenuates subarachnoid hemorrhage-induced microglia activation and inflammatory response via MMD downregulation

BACKGROUND

It is documented that microglia-secreted extracellular vesicles (microglia-EVs) exert neuroprotection which is important following subarachnoid hemorrhage (SAH). Herein, we focused on the mechanism of microglia-EVs harboring microRNA-140-5p (miR-140-5p) in SAH development.

METHODS

After the successful establishment of SAH rats, neurological function was evaluated, and behaviors were observed. Serum inflammatory factors (IL-1β and TNF-α) were quantified by ELISA, followed by the detection of microglial polarization by immunofluorescence. The relationship between miR-140-5p and monocyte to macrophage differentiation-associated (MMD) was evaluated using luciferase assay. Following the extraction of microglia and microglia-EVs, the transferring of miR-140-5p by microglia-EVs was assessed by co-culture experiments. SAH rats were treated with the EVs sourced from microglia overexpressing miR-140-5p (microglia-EVs-miR-140-5p) or EVs sourced from miR-140-5p-deficient microglia (microglia-EVs-miR-140-5p inhibitor) for in vivo effect assessment.

RESULTS

Microglia-EVs inhibited microglia activation and secretion of TNF-α and IL-1β by delivering miR-140-5p. Microglia-EVs could transmit miR-140-5p into microglia. Furthermore, microglia-EVs-miR-140-5p reduced the expression of its target MMD, resulting in blocked inflammatory response and activation of microglia in SAH rats by disrupting the PI3K/AKT and Erk1/2 signaling.

CONCLUSION

In summary, microglia-EVs transmitted miR-140-5p into microglia to downregulate MMD and finally contributed to neuroprotection in SAH rats.

Implications of fractalkine on glial function, ablation and glial proteins/receptors/markers—understanding its therapeutic usefulness in neurological settings: a narrative review

Background

Fractalkine (CX3CL1) is a chemokine predominantly released by neurons. As a signaling molecule, CX3CL1 facilitates talk between neurons and glia. CX3CL1 is considered as a potential target which could alleviate neuroinflammation. However, certain controversial results and ambiguous role of CX3CL1 make it inexorable to decipher the overall effects of CX3CL1 on the physiopathology of glial cells.

Main body of the abstract

Implications of cross-talk between CX3CL1 and different glial proteins/receptors/markers will give a bird eye view of the therapeutic significance of CX3CL1. Keeping with the need, this review identifies the effects of CX3CL1 on glial physiopathology, glial ablation, and gives a wide coverage on the effects of CX3CL1 on certain glial proteins/receptors/markers.

Short conclusion

Pinpoint prediction of the therapeutic effect of CX3CL1 on neuroinflammation needs further research. This is owing to certain obscure roles and implications of CX3CL1 on different glial proteins/receptors/markers, which are crucial under neurological settings. Further challenges are imposed due to the dichotomous roles played by CX3CL1. The age-old chemokine shows many newer scopes of research in near future. Thus, overall assessment of the effect of CX3CL1 becomes crucial prior to its administration in neuroinflammation.

Exosomal miR-532-5p induced by long-term exercise rescues blood-brain barrier function in 5XFAD mice via downregulation of EPHA4

The breakdown of the blood-brain barrier, which develops early in Alzheimer's disease (AD), contributes to cognitive impairment. Exercise not only reduces the risk factors for AD but also confers direct protection against cognitive decline. However, the exact molecular mechanisms remain elusive, particularly whether exercise can liberate the function of the blood-brain barrier. Here, we demonstrate that long-term exercise promotes the clearance of brain amyloid-β by improving the function of the blood-brain barrier in 5XFAD mice. Significantly, treating primary brain pericytes or endothelial cells with exosomes isolated from the brain of exercised 5XFAD mice improves cell proliferation and upregulates PDGFRβ, ZO-1, and claudin-5. Moreover, exosomes isolated from exercised mice exhibit significant changes in miR-532-5p. Administration or transfection of miR-532-5p to sedentary mice or primary brain pericytes and endothelial cells reproduces the improvement of blood-brain barrier function. Exosomal miR-532-5p targets EPHA4, and accordingly, expression of EphA4 is decreased in exercised mice and miR-532-5p overexpressed mice. A specific siRNA targeting EPHA4 recapitulates the effects on blood-brain barrier-associated cells observed in exercised 5XFAD mice. Overall, our findings suggest that exosomes released by the brain contain a specific miRNA that is altered by exercise and has an impact on blood-brain barrier function in AD.

ISGylation is induced in neurons by demyelination driving ISG15-dependent microglial activation

The causes of grey matter pathology and diffuse neuron injury in MS remain incompletely understood. Axonal stress signals arising from white matter lesions has been suggested to play a role in initiating this diffuse grey matter pathology. Therefore, to identify the most upstream transcriptional responses in neurons arising from demyelinated axons, we analyzed the transcriptome of actively translating neuronal transcripts in mouse models of demyelinating disease. Among the most upregulated genes, we identified transcripts associated with the ISGylation pathway. ISGylation refers to the covalent attachment of the ubiquitin-like molecule interferon stimulated gene (ISG) 15 to lysine residues on substrates targeted by E1 ISG15-activating enzyme, E2 ISG15-conjugating enzymes and E3 ISG15-protein ligases. We further confirmed that ISG15 expression is increased in MS cortical and deep gray matter. Upon investigating the functional impact of neuronal ISG15 upregulation, we noted that ISG15 expression was associated changes in neuronal extracellular vesicle protein and miRNA cargo. Specifically, extracellular vesicle-associated miRNAs were skewed toward increased frequency of proinflammatory and neurotoxic miRNAs and decreased frequency of anti-inflammatory and neuroprotective miRNAs. Furthermore, we found that ISG15 directly activated microglia in a CD11b-dependent manner and that microglial activation was potentiated by treatment with EVs from neurons expressing ISG15. Further study of the role of ISG15 and ISGylation in neurons in MS and neurodegenerative diseases is warranted.

Microglial exosomal miR-466i-5p induces brain injury via promoting hippocampal neuron apoptosis in heatstroke

Background

Brain injury is the main cause of poor prognosis in heatstroke (HS) patients due to heat-stress-induced neuronal apoptosis. However, as a new cross-talk way among cells, whether microglial exosomal-microRNAs (miRNAs) are involved in HS-induced neuron apoptosis has not been elucidated.

Methods

We established a heatstroke mouse model and a heat-stressed neuronal cellular model on HT22 cell line. Then, we detected neuron apoptosis by histopathology and flow cytometry. The microglial exosomes are isolated by standard differential ultracentrifugation and characterized. Recipient neurons are treated with the control and HS exosomes, whereas in vivo, the exosomes were injected into the mice tail vein. The internalization of HS microglial exosomes by neurons was tracked. Apoptosis of HT22 was evaluated by flow cytometry and Western blot in vitro, TUNEL assay, and immunohistochemistry in vivo. We screened miR-466i-5p as the mostly upregulated microRNAs in HS exosomes by high-throughput sequencing and further conducted gene ontology (GO) pathway analysis. The effect and mechanism of HS exosomal miR-466i-5p on the induction of neuron apoptosis are demonstrated by nasal delivery of miR-466i-5p antagomir in vivo and transfecting miR-466i-5p mimics to HT22 in vitro.

Results

HS induced an increase in neurons apoptosis. Microglial exosomes are identified and taken up by neurons, which induced HT22 apoptosis in vivo and vitro. HS significantly changed the miRNA profiles of microglial exosomes based on high-throughput sequencing. We selected miR-466i-5p as a target, and upregulated miR-466i-5p induced neurons apoptosis in vivo and vitro experiments. The effects are exerted by targeting Bcl-2, activating caspase-3 to induce neurons apoptosis.

Conclusions

We demonstrate the effect of microglial exosomal miR-466i-5p on neurons apoptosis and reveal potentially Bcl-2/caspase-3 pathway in heatstroke.

Exosome-Encapsulated microRNA-140-5p Alleviates Neuronal Injury Following Subarachnoid Hemorrhage by Regulating IGFBP5-Mediated PI3K/AKT Signaling Pathway

Recent literature has highlighted the therapeutic implication of exosomes (Exos) released by adipose tissue-originated stromal cells (ADSCs) in regenerative medicine. Herein, the current study sought to examine the potential protective effects of ADSC-Exos on neuronal injury following subarachnoid hemorrhage (SAH) by delivering miR-140-5p. Firstly, isolated primary neurons were co-cultured together with well-identified ADSC-Exos. TDP-43-treated neurons were subsequently treated with PKH67-ADSC-Exos and Cy3-miR-140-5p to assess whether ADSC-Exos could transmit miR-140-5p to the recipient neurons to affect their behaviors. Moreover, a luciferase assay was carried out to identify the presumable binding of miR-140-5p to IGFBP5. IGFBP5 rescue experimentation was also performed to testify whether IGFBP5 conferred the impact of miR-140-5p on neuronal damage. The role of PI3K/AKT signaling pathway was further analyzed with the application of its inhibitor miltefosine. Lastly, SAH rat models were developed for in vivo validation. It was found that ADSC-Exos conferred protection against TDP-43-caused neuronal injury by augmenting viability and suppressing cell apoptosis. In addition, miR-140-5p was transmitted from ADSC-Exos to neurons and post-transcriptionally downregulated the expression of IGFBP5. As a result, by means of suppressing IGFBP5 and activating the PI3K/AKT signaling pathway, miR-140-5p from ADSC-Exos induced a neuroprotective effect. Furthermore, in vivo findings substantiated the aforementioned protective role of ADSC-Exos-miR-140-5p, contributing to protection against SAH-caused neurological dysfunction. Collectively, our findings indicated that ADSC-Exos-miR-140-5p could inhibit TDP-43-induced neuronal injury and attenuate neurological dysfunction of SAH rats by inhibiting IGFBP5 and activating the PI3K/Akt signaling pathway.

Exosomes in subarachnoid hemorrhage: A scoping review

INTRODUCTION

Vasospasm is a common complication following subarachnoid hemorrhage (SAH), causing increased ischemia and tissue injury, and is implicated as a major risk factor for poor outcomes. The success of current treatments for vasospasm is limited, with limited efficacy and unclear clinical benefits. Exosomes, vesicles that carry small molecules such as miRNA, have been theorized as a potential vasospasm treatment. In this study, we aim to survey the current literature discussing the role of exosomes in the setting of SAH.

METHODS

Following PRISMA guidelines, we performed a scoping review evaluating the role of exosomes in the treatment of SAH. The search was conducted using PubMed and Scopus, and all original research papers studying exosomal profiles of SAH research subjects or SAH therapy were eligible for inclusion.

RESULTS

After screening and full text review, seven papers were selected for final inclusion. Of these, two studies analyzed the expression profile of endogenous exosomes after SAH. Four papers identified and characterized miRNA-based exosomal therapies to attenuate early brain injury (EBI) after SAH. One paper discussed the role of protein overexpression in exosome delivery of miRNA for EBI after SAH. Interestingly, all identified papers studying exosomal therapy demonstrated anti-apoptotic or anti-inflammatory effects of miRNA exosomes acting via the BDNF/TrkB/CREB or HDAC3/NF-κB pathways.

CONCLUSION

Identified studies demonstrate potential neuroprotective benefits of miRNA-based exosomal treatment of EBI and SAH. Findings warrant further research investigating the anti-inflammatory and anti-apoptotic role of exosomal miRNA delivery in SAH models, specifically targeting the common pathway identified by the authors.

MiR-340-5p alleviates neuroinflammation and neuronal injury via suppressing STING in subarachnoid hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) is a severe acute neurological disorder. SAH causes neuroinflammation and leads to early brain injury (EBI) and secondary injury. MicroRNAs are crucial regulators in a variety of neurological diseases. This study was performed to decipher how miR-340-5p functions in SAH.

METHODS

An experimental mouse model with SAH was established by the intravascular perforation, and the in vitro SAH model was constructed by exposing cocultured primary neurons and microglia to oxyhemoglobin. After overexpression of miR-340-5p in mice, the neurobehavioral disorders were evaluated by Garcia test; brain edema was evaluated by wet-dry method; blood-brain barrier (BBB) damage was detected with Evan's blue staining; levels of inflammatory cytokines were detected with enzyme-linked immunosorbent assay. After miR-340-5p was transfected in to microglia, Iba-1 expression was detected by Western blot, and neuronal apoptosis were detected with flow cytometry. The targeting relationship between miR-340-5p and STING was verified by dual-luciferase reporter gene assay and RNA immunoprecipitation assay.

RESULTS

MiR-340-5p was significantly inhibited in the brain tissues of mice with SAH and microglia of SAH model, and neurological impairment, brain edema, BBB injury, and neuroinflammation were significantly alleviated in mice after overexpressing miR-340-5p. STING was identified as a target of miR-340-5p, and STING overexpression could counteract the effects of miR-340-5p overexpression on neurons.

CONCLUSION

MiR-340-5p can attenuate EBI caused by SAH-induced neuroinflammation by inhibiting STING.

Biomarker Associations in Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage

The prognosis for patients with aneurysmal subarachnoid hemorrhage (aSAH) is heavily influenced by the development of delayed cerebral ischemia (DCI), but the adequate and effective therapy of DCI to this day has not been resolved. Multiplex serum biomarker studies may help to understand the pathophysiological processes underlying DCI. Samples were collected from patients with aSAH at two time points: (1) 24 h (Day 1) and (2) 5−7 days after ictus. Serum concentrations of eotaxin, FGF-2, FLT-3L, CX3CL1, Il-1b, IL-4, IP-10, MCP3, and MIP-1b were determined using a customized MILLIPLEX Human Cytokine/Chemokine/Growth Factor Panel A multiplex assay. The functional outcome was defined by the modified Rankin scale (favorable: 0−2, unfavorable: 3−6) measured on the 30th day after aSAH. One-hundred and twelve patients with aSAH were included in this study. The median level of CX3CL1 and MCP-3 measured on Days 5−7 were significantly higher in patients with DCI compared with those without DCI (CX3CL1: with DCI: 110.5 pg/mL, IQR: 82−201 vs. without DCI: 82.6, 58−119, p = 0.036; and MCP-3: with DCI: 22 pg/mL (0−32) vs. without DCI: 0 (0−11), p < 0.001). IP-10, MCP-3, and MIP-1b also showed significant associations with the functional outcome after aSAH. MCP-3 and CX3CL1 may play a role in the pathophysiology of DCI.

Temporal alteration of microglia to microinfarcts in rat brain induced by the vascular occlusion with fluorescent microspheres

Microglia, the resident immune cells in the central nervous system, can monitor the microenvironment and actively respond to ischemic stroke and other brain injuries. In this procedure, microglia and neurons can cross-talk via transmembrane chemokine, Fractalkine (CX3CL1), to impact one another. We used a rat model of multifocal microinfarcts induced by the injection of fluorescent microspheres into the right common carotid artery and examined the morphological alteration of blood vessels, microglia, astrocytes, and neurons at 6 h, 1, 7, and 14 days after modeling, along with neurobehavioral tests and the staining of CX3CL1 in this study. Our results demonstrated that in the infarcted regions, astrocytes and microglia activated in response to neuronal degeneration and upregulation of cleaved caspase-3, which occurred concurrently with vascular alteration and higher expression of CX3CL1. We provided sequential histological data to shed light on the morphological changes after modeling, which would help in the identification of new targets and the choice of the ideal time window for therapeutic intervention in ischemic stroke.

Ghrelin inhibits early brain injury due to subarachnoid hemorrhage via the Tim-3-mediated HMGB1/NF-κB pathway

OBJECTIVE

To explore the protective effect of Ghrelin on EBI caused by SAH through the HMGB1/NF-κB pathway mediated by Tim-3.

METHODS

Rats were divided into four groups (n = 6): Sham group (Sham), SAH+vehicle group (SAH), SAH + 0.02 μg/kg rhGhrelin group (rhGhrelin-L), SAH + 0.04 μg/kg rhGhrelin group (rhGhrelin-H). At 48 h after SAH, the behavioral impairment in rats was examined for using neurobehavioral scores. The pathological change in the temporal basal brain tissue was observed by HE, and the expression of GHSR-1α and Tim-3 in the temporal basal brain tissue was observed by Western blot. To further validate that rhGhrelin could inhibit SAH-induced EBI by the Tim-3-mediated HMGB1/NF-κB pathway, we treated rats with the AAV-Tim-3. The contents of the inflammatory factors IL-1β, TNF-α, IL-6 was determined by ELISA, apoptosis was detected by TUNEL, the neurons were visualized by Nissl staining, the expression of GHSR-1α，Tim-3, HMGB1, RAGE, NF-κB p65 was determined by Western blot.

RESULTS

Compared with the SAH group, rats treated with rhGhrelin had a significantly lower neurobehavioral score, significantly decreased inflammatory factors IL-1β, TNF-α, IL-6 expression, significantly decreased apoptosis index, and significantly decreased Tim-3, HMGB1, RAGE, NF-κB p65 expression(p < 0.01). The protective effect of rhGhrelin on the SAH-induced EBI was reversed by the AAV-Tim-3.

CONCLUSION

Ghrelin has beneficial effects against SAH-induced EBI by inhibiting the HMGB1/NF-κB pathway, which may be regulated by Tim-3.

Prophylactic Zinc Administration Combined with Swimming Exercise Prevents Cognitive-Emotional Disturbances and Tissue Injury following a Transient Hypoxic-Ischemic Insult in the Rat

Exercise performance and zinc administration individually yield a protective effect on various neurodegenerative models, including ischemic brain injury. Therefore, this work was aimed at evaluating the combined effect of subacute prophylactic zinc administration and swimming exercise in a transient cerebral ischemia model. The prophylactic zinc administration (2.5 mg/kg of body weight) was provided every 24 h for four days before a 30 min common carotid artery occlusion (CCAO), and 24 h after reperfusion, the rats were subjected to swimming exercise in the Morris Water Maze (MWM). Learning was evaluated daily for five days, and memory on day 12 postreperfusion; anxiety or depression-like behavior was measured by the elevated plus maze and the motor activity by open-field test. Nitrites, lipid peroxidation, and the activity of superoxide dismutase (SOD) and catalase (CAT) were assessed in the temporoparietal cortex and hippocampus. The three nitric oxide (NO) synthase isoforms, chemokines, and their receptor levels were measured by ELISA. Nissl staining evaluated hippocampus cytoarchitecture and Iba-1 immunohistochemistry activated the microglia. Swimming exercise alone could not prevent ischemic damage but, combined with prophylactic zinc administration, reversed the cognitive deficit, decreased NOS and chemokine levels, prevented tissue damage, and increased Iba-1 (+) cell number. These results suggest that the subacute prophylactic zinc administration combined with swimming exercise, but not the individual treatment, prevents the ischemic damage on day 12 postreperfusion in the transient ischemia model.

Suberoylanilide hydroxamic acid suppresses axonal damage and neurological dysfunction after subarachnoid hemorrhage via the HDAC1/HSP70/TDP-43 axis

Increased focus has been placed on the role of histone deacetylase inhibitors as crucial players in subarachnoid hemorrhage (SAH) progression. Therefore, this study was designed to expand the understanding of SAH by exploring the downstream mechanism of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in SAH. The expression of TDP-43 in patients with SAH and rat models of SAH was measured. Then, western blot analysis, immunofluorescence staining, and transmission electron microscope were used to investigate the in vitro effect of TDP-43 on a neuronal cell model of SAH established by oxyhemoglobin treatment. Immunofluorescence staining and coimmunoprecipitation assays were conducted to explore the relationship among histone deacetylase 1 (HDAC1), heat shock protein 70 (HSP70), and TDP-43. Furthermore, the in vivo effect of HDAC1 on SAH was investigated in rat models of SAH established by endovascular perforation. High expression of TDP-43 in the cerebrospinal fluid of patients with SAH and brain tissues of rat models of SAH was observed, and TDP-43 accumulation in the cytoplasm and the formation of inclusion bodies were responsible for axonal damage, abnormal nuclear membrane morphology, and apoptosis in neurons. TDP-43 degradation was promoted by the HDAC1 inhibitor SAHA via the acetylation of HSP70, alleviating SAH, and this effect was verified in vivo in rat models. In conclusion, SAHA relieved axonal damage and neurological dysfunction after SAH via the HSP70 acetylation-induced degradation of TDP-43, highlighting a novel therapeutic target for SAH.

Roles of Rufy3 in experimental subarachnoid hemorrhage-induced early brain injury via accelerating neuronal axon repair and synaptic plasticity

RUN and FYVE domain-containing 3 (Rufy3) is a well-known adapter protein of a small GTPase protein family and is bound to the activated Ras family protein to maintain neuronal polarity. However, in experimental subarachnoid hemorrhage (SAH), the role of Rufy3 has not been investigated. Consequently, we aimed to investigate the potential role of Rufy3 in an in vivo model of SAH-induced early brain injury (EBI). In addition, we investigated the relevant brain-protective mechanisms. Oxyhemoglobin (OxyHb) stimulation of cultured primary neurons simulated vitro SAH condition. The SAH rat model was induced by infusing autologous blood into the optic chiasma pool and treating the rats with lentivirus-negative control 1 (LV-NC1), lentivirus-Rufy3 shRNA (LV-shRNA), lentivirus-negative control 2 (LV-NC2), lentivirus-Rufy3 (LV-Rufy3), or 8-pCPT-2′-O-Me-cAMP (8p-CPT) (Rap1 agonist). In experiment one, we found that the protein level of Rufy3 decreased and neuronal axon injury in the injured neurons but was rectified by LV-Rufy3 treatment. In experiment two, mRNA and protein levels of Rufy3 were downregulated in brain tissue and reached the lowest level at 24 h after SAH. In addition, the expression of Myelin Basic Protein was downregulated and that of anti-hypophosphorylated neurofilament H (N52) was upregulated after SAH. In experiments three and four, Rufy3 overexpression (LV-Rufy3) increased the interactions between Rufy3 and Rap1, the level of Rap1-GTP, and the ratio of Rap1-GTP/total GTP. In addition, LV-Rufy3 treatment inhibited axon injury and accelerated axon repair by activating the Rap1/Arap3/Rho/Fascin signaling pathway accompanied by upregulated protein expression levels of ARAP3, Rho, Fascin, and Facin. LV-Rufy3 also enhanced synaptic plasticity by activating the Rap1/MEK/ERK/synapsin I signaling pathway accompanied by upregulated protein expression levels of ERK1, p-ERK1, MEK1, p-MEK1, synaspin I, and p-synaspin I. Moreover, LV-Rufy3 also alleviated brain damage indicators, including cortical neuronal cell apoptosis and degeneration, brain edema, and cognitive impairment after SAH. However, the downregulation of Rufy3 had the opposite effect and aggravated EBI induced by SAH. Notably, the combined application of LV-Rufy3 and 8p-CPT showed a significant synergistic effect on the aforementioned parameters. Our findings suggest that enhanced Rufy3 expression may reduce EBI by inhibiting axon injury and promoting neuronal axon repair and synaptic plasticity after SAH.

α-Lipoic Acid-Plus Ameliorates Endothelial Injury by Inhibiting the Apoptosis Pathway Mediated by Intralysosomal Cathepsins in an In Vivo and In Vitro Endothelial Injury Model

α-Lipoic acid-plus (LAP), an amine derivative of α-lipoic acid, has been reported to protect cells from oxidative stress damage by reacting with lysosomal iron and is more powerful than desferrioxamine (DFO). However, the role of LAP in experimental carotid artery intimal injury (CAII) has not yet been well investigated. Therefore, we sought to uncover the role and potential endovascular protective mechanisms of LAP in endothelial injury. In vitro, oxyhemoglobin (OxyHb) stimulation of cultured human umbilical vein endothelial cells (HUVECs) simulated intimal injury. In vivo, balloon compression injury of the carotid artery was used to establish a rat CAII model. We found that the protein levels of cathepsin B/D, ferritin, transferrin receptor (TfR), cleaved caspase-3, and Bax increased in the injured endothelium and HUVECs but were rectified by DFO and LAP treatments, as revealed by western blotting and immunofluorescence staining. Additionally, DFO and LAP decreased oxidative stress levels and endothelial cell necrosis of the damaged endothelium. Moreover, DFO and LAP significantly ameliorated the increased oxidative stress, iron level, and lactic dehydrogenase activity of HUVECs and improved the reduced HUVEC viability induced by OxyHb. More importantly, DFO and LAP significantly reduced mitochondrial damage and were beneficial for maintaining lysosomal integrity, as indicated by acridine orange (AO), Lyso-Tracker Red, JC-1, and ATPB staining in HUVECs. Finally, LAP might offer more significant endovascular protective effects than DFO. Our data suggested that LAP exerted endovascular protective effects by inhibiting the apoptosis signaling pathway mediated by intralysosomal cathepsins by reacting with excessive iron in endothelial lysosomes after intimal injury.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

Enhancing S-nitrosoglutathione reductase decreases S-nitrosylation of Drp1 and reduces neuronal apoptosis in experimental subarachnoid hemorrhage both in vivo and in vitro

Subarachnoid hemorrhage (SAH) is a hemorrhagic stroke with a high mortality and disability rate. Nitric oxide (NO) can promote blood supply through vasodilation, leading to protein S-nitrosylation. However, the function of S-nitrosylation in neurons after SAH remains unclear. Excessive NO in the pathological state is converted into S-nitrosoglutathione (GSNO) and stored in cells, which leads to high S-nitrosylation of intracellular proteins and causes nitrosative stress. S-nitrosoglutathione reductase (GSNOR) promotes GSNO degradation and protects cells from excessive S-nitrosylation. We conducted an in vivo rat carotid puncture model and an in vitro neuron hemoglobin intervention. The results showed that SAH induction increased NO, GSNO, neuron protein S-nitrosylation, and neuronal apoptosis, while decreasing the level and activity of GSNOR. GSNOR overexpression by lentivirus decreased GSNO but had little effect on NO. GSNOR overexpression also improved short- and long-term neurobehavioral outcomes in rats and alleviated nitrosative stress. Furthermore, GSNOR reduced neuronal apoptosis and played a neuroprotective role by alleviating Drp1 S-nitrosylation, reducing mitochondrial division. Thus, the regulation of GSNOR in early brain injury and neuronal denitrosylation may play an important role in neuroprotection.

Crosstalk between Microglia and Neurons in Neurotrauma: An Overview of the Underlying Mechanisms

Microglia are the resident immune cells of the brain and play a crucial role in housekeeping and maintaining homeostasis of the brain microenvironment. Upon injury or disease, microglial cells become activated, at least partly, via signals initiated by injured neurons. Activated microglia, thereby, contribute to both neuroprotection and neuroinflammation. However, sustained microglial activation initiates a chronic neuroinflammatory response which can disturb neuronal health and disrupt communications between neurons and microglia. Thus, microglia-neuron crosstalk is critical in a healthy brain as well as during states of injury or disease. As most studies focus on how neurons and microglia act in isolation during neurotrauma, there is a need to understand the interplay between these cells in brain pathophysiology. This review highlights how neurons and microglia reciprocally communicate under physiological conditions and during brain injury and disease. Furthermore, the modes of microglia-neuron communication are exposed, focusing on cell-contact dependent signaling and communication by the secretion of soluble factors like cytokines and growth factors. In addition, it has been discussed that how microglia-neuron interactions could exert either beneficial neurotrophic effects or pathologic proinflammatory responses. We further explore how aberrations in microglia-neuron crosstalk may be involved in central nervous system (CNS) anomalies, namely traumatic brain injury (TBI), neurodegeneration, and ischemic stroke. A clear understanding of how the microglia-neuron crosstalk contributes to the pathogenesis of brain pathologies may offer novel therapeutic avenues of brain trauma treatment.

Microglia activation, classification and microglia-mediated neuroinflammatory modulators in subarachnoid hemorrhage

Subarachnoid hemorrhage is a devastating disease with significant mortality and morbidity, despite advances in treating cerebral aneurysms. There has been recent progress in the intensive care management and monitoring of patients with subarachnoid hemorrhage, but the results remain unsatisfactory. Microglia, the resident immune cells of the brain, are increasingly recognized as playing a significant role in neurological diseases, including subarachnoid hemorrhage. In early brain injury following subarachnoid hemorrhage, microglial activation and neuroinflammation have been implicated in the development of disease complications and recovery. To understand the disease processes following subarachnoid hemorrhage, it is important to focus on the modulators of microglial activation and the pro-inflammatory/anti-inflammatory cytokines and chemokines. In this review, we summarize research on the modulators of microglia-mediated inflammation in subarachnoid hemorrhage, including transcriptome changes and the neuroinflammatory signaling pathways. We also describe the latest developments in single-cell transcriptomics for microglia and summarize advances that have been made in the transcriptome-based classification of microglia and the implications for microglial activation and neuroinflammation.

MicroRNA-124: A Key Player in Microglia-Mediated Inflammation in Neurological Diseases

Neurological disorders are mainly characterized by progressive neuron loss and neurological deterioration, which cause human disability and death. However, many types of neurological disorders have similar pathological mechanisms, including the neuroinflammatory response. Various microRNAs (miRs), such as miR-21, miR-124, miR-146a, and miR-132 were recently shown to affect a broad spectrum of biological functions in the central nervous system (CNS). Microglia are innate immune cells with important roles in the physiological and pathological activities of the CNS. Recently, abnormal expression of miR-124 was shown to be associated with the occurrence and development of various diseases in CNS via regulating microglia function. In addition, miR-124 is a promising biomarker and therapeutic target. Studies on the role of miR-124 in regulating microglia function involved in pathogenesis of neurological disorders at different stages will provide new ideas for the use of miR-124 as a therapeutic target for different CNS diseases.

Fraxinellone ameliorates intracerebral hemorrhage-induced secondary brain injury by regulating Krüppel-like transcription factor 2 expression in rats

Damage to the blood-brain barrier (BBB) is an important factor leading to intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI). Krüppel-like transcription factor 2 (KLF2) plays an important role in the maintenance of the BBB. This study aims to detect the changes of KLF2 after ICH and evaluate the potential effects of fraxinellone on ICH-induced SBI and its correlation with KLF2. An ICH model was established by injecting autologous blood into the right basal ganglia of Sprague-Dawley (SD) rats. First, after ICH induction, the protein levels of KLF2 were reduced. Then, we found that the decrease of KLF2 protein levels induced by ICH could be effectively reversed with the treatment of fraxinellone in vascular endothelial cells. Furthermore, fraxinellone treatment effectively alleviated brain edema, decreased the levels of TNF-α and IL-1β, and improved neuronal cell degeneration induced by ICH. Meanwhile, fraxinellone ameliorated neurobehavioral disorders, motor and sensory impairments, and neurobehavioral disorders and memory loss caused by ICH. Collectively, these findings reveal that KLF2 may be a potential target for fraxinellone to exert neuroprotective effects after ICH, and fraxinellone could be a potential therapeutic agent for SBI after ICH.

The regulatory roles of microRNAs toward pathogenesis and treatments in Huntington's disease

Huntington's disease (HD) is one of neurodegenerative diseases, and is defined as a monogenetic disease due to the mutation of Huntingtin gene. This disease affects several cellular functions in neurons, and further influences motor and cognitive ability, leading to the suffering of devastating symptoms in HD patients. MicroRNA (miRNA) is a non-coding RNA, and is responsible for gene regulation at post-transcriptional levels in cells. Since one miRNA targets to several downstream genes, it may regulate different pathways simultaneously. As a result, it raises a potential therapy for different diseases using miRNAs, especially for inherited diseases. In this review, we will not only introduce the update information of HD and miRNA, but also discuss the development of potential miRNA-based therapy in HD. With the understanding toward the progression of miRNA studies in HD, we anticipate it may provide an insight to treat this devastating disease, even applying to other genetic diseases.

Extracellular vesicles (exosomes and ectosomes) play key roles in the pathology of brain diseases

Last century, neurons and glial cells were mostly believed to play distinct functions, relevant for the brain. Progressively, however, it became clear that neurons, astrocytes and microglia co-operate intensely with each other by release/binding of signaling factors, direct surface binding and generation/release of extracellular vesicles, the exosomes and ectosomes, called together vesicles in this abstract. The present review is focused on these vesicles, fundamental in various brain diseases. Their properties are extraordinary. The specificity of their membrane governs their fusion with distinct target cells, variable depending on the state and specificity of their cells of origin and target. Result of vesicle fusion is the discharge of their cargos into the cytoplasm of target cells. Cargos are composed of critical molecules, from proteins (various nature and function) to nucleotides (especially miRNAs), playing critical roles in immune and neurodegenerative diseases. Among immune diseases is multiple sclerosis, affected by extensive dysregulation of co-trafficking neural and glial vesicles, with distinct miRNAs inducing severe or reducing effects. The vesicle-dependent differences between progressive and relapsing-remitting forms of the disease are relevant for clinical developments. In Alzheimer’s disease the vesicles can affect the brain by changing their generation and inducing co-release of effective proteins, such Aβ and tau, from neurons and astrocytes. Specific miRNAs can delay the long-term development of the disease. Upon their traffic through the blood-brainbarrier, vesicles of various origin reach fluids where they are essential for the identification of biomarkers, important for diagnostic and therapeutic innovations, critical for the future of many brain patients.

The Role of the Blood Neutrophil-to-Lymphocyte Ratio in Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is an important type of stroke with the highest rates of mortality and disability. Recent evidence indicates that neuroinflammation plays a critical role in both early brain injury and delayed neural deterioration after aSAH, contributing to unfavorable outcomes. The neutrophil-to-lymphocyte ratio (NLR) is a peripheral biomarker that conveys information about the inflammatory burden in terms of both innate and adaptive immunity. This review summarizes relevant studies that associate the NLR with aSAH to evaluate whether the NLR can predict outcomes and serve as an effective biomarker for clinical management. We found that increased NLR is valuable in predicting the clinical outcome of aSAH patients and is related to the risk of complications such as delayed cerebral ischemia (DCI) or rebleeding. Combined with other indicators, the NLR provides improved accuracy for predicting prognosis to stratify patients into different risk categories. The underlying pathophysiology is highlighted to identify new potential targets for neuroprotection and to develop novel therapeutic strategies.

Modulation of inflammatory responses by fractalkine signaling in microglia

Reactive microglia are suggested to be involved in neurological disorders, and the mechanisms underlying microglial activity may provide insights into therapeutic strategies for neurological diseases. Microglia produce immunological responses to various stimuli, which include fractalkine (FKN or CX3CL1). CX3CR1, a FKN receptor, is present in microglial cells, and when FKN is applied before lipopolysaccharide (LPS) administration, LPS-induced inflammatory responses are inhibited, suggesting that the activation of the FKN signal is beneficial. Considering the practical administration for treatment, we investigated the influence of FKN on immunoreactive microglia using murine primary microglia and BV-2, a microglial cell line. The administration of LPS leads to nitric oxide (NO) production. NO was reduced when FKN was administered 4 h after LPS administration without a change in inducible nitric oxide synthase expression. In contrast, morphological changes, migratory activity, and proliferation were not altered by delayed FKN treatment. LPS decreases the CX3CR1 mRNA concentration, and the overexpression of CX3CR1 restores the FKN-mediated decrease in NO. CX3CR1 overexpression decreased the NO production that is mediated by LPS even without the application of FKN. ATP and ethanol also reduced CX3CR1 mRNA concentrations. In conclusion, the delayed FKN administration modified the LPS-induced microglial activation. The FKN signals were attenuated by a reduction in CX3CR1 by some inflammatory stimuli, and this modulated the inflammatory response of microglial cells, at least partially.

MiR-706 alleviates white matter injury via downregulating PKCα/MST1/NF-κB pathway after subarachnoid hemorrhage in mice

Increasing numbers of patients with spontaneous subarachnoid hemorrhage(SAH) who recover from surgery and intensive care management still live with cognitive impairment after discharge, indicating the importance of white matter injury at the acute stage of SAH. In the present study, standard endovascular perforation was employed to establish an SAH mouse model, and a microRNA (miRNA) chip was used to analyze the changes in gene expression in white matter tissue after SAH. The data indicate that 17 miRNAs were downregulated, including miR-706, miR-669a-5p, miR-669p-5p, miR-7116-5p and miR-195a-3p, while 13 miRNAs were upregulated, including miR-6907-5p, miR-5135, miR-6982-5p, miR-668-5p, miR-8119. Strikingly, miR-706 was significantly downregulated with the highest fold change. Further experiments confirmed that miR-706 could alleviate white matter injury and improve neurological behavior, at least partially by inhibiting the PKCα/MST1/NF-κB pathway and the release of inflammatory cytokines. These results might provide a deeper understanding of the pathophysiological processes in white matter after SAH, as well as potential therapeutic strategies for the translational research.