TIMP1 protects against blood-brain barrier disruption after subarachnoid haemorrhage by inhibiting ubiquitination of astrocytic ß1-integrin.

BACKGROUND: Astrocytes regulate blood-brain barrier (BBB) integrity, whereas subarachnoid haemorrhage (SAH) results in astrocyte dysregulation and BBB disruption. Here, we explored the involvement of tissue inhibitor of matrix metalloprotease-1 (TIMP1) in astrocyte-mediated BBB protection during SAH, along with its underlying mechanisms. METHODS: C57BL/6J mice were used to establish a model of SAH. The effects of TIMP1 on SAH outcomes were analysed by intraperitoneal injection of recombinant mouse TIMP1 protein (rm-TIMP1; 250 µg/kg). The roles of TIMP1 and its effector ß1-integrin on astrocytes were observed by in vivo transduction with astrocyte-targeted adeno-associated virus carrying TIMP1 overexpression plasmid or ß1-integrin RNAi. The molecular mechanisms underlying TIMP1 and ß1-integrin interactions were explored in primary cultured astrocytes stimulated with red blood cells (RBCs). RESULTS: TIMP1 was upregulated after SAH. Administration of rm-TIMP1 mitigated SAH-induced early brain injury (EBI) in male and female mice. TIMP1 was primarily expressed in astrocytes; its overexpression in astrocytes led to increased ß1-integrin expression in astrocytes, along with the preservation of astrocytic endfoot attachment to the endothelium and subsequent recovery of endothelial tight junctions. All of these effects were reversed by the knockdown of ß1-integrin in astrocytes. Molecular analysis showed that TIMP1 overexpression decreased the RBC-induced ubiquitination of ß1-integrin; this effect was partially achieved by inhibiting the interaction between ß1-integrin and the E3 ubiquitin ligase Trim21. CONCLUSION: TIMP1 inhibits the interaction between ß1-integrin and Trim21 in astrocytes, thereby rescuing the ubiquitination of astrocytic ß1-integrin. It subsequently restores interactions between astrocytic endfeet and the endothelium, as well as BBB integrity, eventually mitigating SAH-induced EBI.

Neutrophil-like pH-responsive pro-efferocytic nanoparticles improve neurological recovery by promoting erythrophagocytosis after intracerebral hemorrhage.

Rationale: Intracerebral hemorrhage (ICH) is a devastating cerebrovascular disease resulting from blood extravasating into the brain parenchyma. Escalation of erythrophagocytosis (a form of efferocytosis), avoiding the consequent release of the detrimental erythrocyte lysates, may be a promising target of ICH management. The ADAM17 inhibitor and liver X receptor (LXR) agonist could promote efficient efferocytosis and injury repair. Nevertheless, the poor bioavailability and restriction of the blood-brain barrier (BBB) hinder their application. Therefore, it is needed that biocompatible and smart nanoplatforms were designed and synthesized to realize effective therapy targeting erythrophagocytosis. Methods: We first assessed the synergistic effect of therapeutic GW280264X (an ADAM17 inhibitor) and desmosterol (an LXR agonist) on erythrophagocytosis in vitro. Then a pH-responsive neutrophil membrane-based nanoplatform (NPEOz) served as a carrier to accurately deliver therapeutic GW280264X and desmosterol to the damaged brain was prepared via co-extrusion. Afterwards, their pH-responsive performance was valued in vitro and targeting ability was assessed through fluorescence image in vivo. Finally, the pro-erythrophagocytic and anti-neuroinflammatory ability of the nanomedicine and related mechanisms were investigated. Results: After the synergistical effect of the above two drugs on erythrophagocytosis was confirmed, we successfully developed neutrophil-disguised pH-responsive nanoparticles to efficiently co-deliver them. The nanoparticles could responsively release therapeutic agents under acidic environments, and elicit favorable biocompatibility and ability of targeting injury sites. D&G@NPEOz nanoparticles enhanced erythrophagocytosis through inhibiting shedding of the efferocytotic receptors MERTK/AXL mediated by ADAM17 and accelerating ABCA-1/ABCG-1-mediated cholesterol efflux regulated by LXR respectively. In addition, the nano-formulation was able to modulate the inflammatory microenvironment by transforming efferocytes towards a therapeutic phenotype with reducing the release of proinflammatory cytokines while increasing the secretion of anti-inflammatory factors, and improve neurological function. Conclusions: This biomimetic nanomedicine is envisaged to offer an encouraging strategy to effectively promote hematoma and inflammation resolution, consequently alleviate ICH progression.

Lateralized response of skull bone marrow via osteopontin signaling in mice after ischemia reperfusion.

Skull bone marrow is thought to be an immune tissue closely associated with the central nervous system (CNS). Recent studies have focused on the role of skull bone marrow in central nervous system disorders. In this study, we performed single-cell RNA sequencing on ipsilateral and contralateral skull bone marrow cells after experimental stroke and then performed flow cytometry and analysis of cytokine expression. Skull marrow showed lateralization in response to stroke. Lateralization is demonstrated primarily by the proliferation and differentiation of myeloid and lymphoid lineage cells in the skull bone marrow adjacent to the ischemic region, with an increased proportion of neutrophils compared to monocytes. Analysis of chemokines in the skull revealed marked differences in chemotactic signals between the ipsilateral and contralateral skull, whereas sympathetic signals innervating the skull did not affect cranial bone marrow lateralization. Osteopontin (OPN) is involved in region-specific activation of the skull marrow that promotes inflammation in the meninges, and inhibition of OPN expression improves neurological function.

Ly6C-high monocytes alleviate brain injury in experimental subarachnoid hemorrhage in mice.

BACKGROUND: Subarachnoid hemorrhage (SAH) is an uncommon type of potentially fatal stroke. The pathophysiological mechanisms of brain injury remain unclear, which hinders the development of drugs for SAH. We aimed to investigate the pathophysiological mechanisms of SAH and to elucidate the cellular and molecular biological response to SAH-induced injury. METHODS: A cross-species (human and mouse) multiomics approach combining high-throughput data and bioinformatic analysis was used to explore the key pathophysiological processes and cells involved in SAH-induced brain injury. Patient data were collected from the hospital (n = 712). SAH was established in adult male mice via endovascular perforation, and flow cytometry, a bone marrow chimera model, qPCR, and microglial depletion experiments were conducted to explore the origin and chemotaxis mechanism of the immune cells. To investigate cell effects on SAH prognosis, murine neurological function was evaluated based on a modified Garcia score, pole test, and rotarod test. RESULTS: The bioinformatics analysis confirmed that inflammatory and immune responses were the key pathophysiological processes after SAH. Significant increases in the monocyte levels were observed in both the mouse brains and the peripheral blood of patients after SAH. Ly6C-high monocytes originated in the bone marrow, and the skull bone marrow contribute a higher proportion of these monocytes than neutrophils. The mRNA level of Ccl2 was significantly upregulated after SAH and was greater in CD11b-positive than CD11b-negative cells. Microglial depletion, microglial inhibition, and CCL2 blockade reduced the numbers of Ly6C-high monocytes after SAH. With CCR2 antagonization, the neurological function of the mice exhibited a slow recovery. Three days post-SAH, the monocyte-derived dendritic cell (moDC) population had a higher proportion of TNF-α-positive cells and a lower proportion of IL-10-positive cells than the macrophage population. The ratio of moDCs to macrophages was higher on day 3 than on day 5 post-SAH. CONCLUSIONS: Inflammatory and immune responses are significantly involved in SAH-induced brain injury. Ly6C-high monocytes derived from the bone marrow, including the skull bone marrow, infiltrated into mouse brains via CCL2 secreted from microglia. Moreover, Ly6C-high monocytes alleviated neurological dysfunction after SAH.

Risk of Death from Alzheimer's Disease Associated with Brain Tumor, Glioma, and Glioblastoma.

BACKGROUND: No study has compared the risk of Alzheimer's disease (AD) in patients with brain tumors, gliomas, or glioblastomas with the risk in patients with other tumors. OBJECTIVE: To determine whether, compared with other tumors, brain tumors, gliomas, and glioblastomas increase the risk of AD. METHODS: This study identified a case group of 24,441 patients from the Surveillance, Epidemiology, and End Results (SEER) database who were diagnosed with only one primary tumor at age > 20 years in 1975-2019 and died from AD at age > 65 years as case group. The control group comprised 122,205 subjects from the SEER database who died from causes other than AD but otherwise had the same conditions as those in the case group. RESULTS: There was a significantly lower prevalence of glioma (0.074% versus 0.14%, p = 0.007) and glioblastoma (0.0082% versus 0.074%, p = 0.001) in patients who died from AD than in those who died from other causes, while brain tumors were not significantly associated with AD death (p = 0.227). When adjusted for factors including age at death, sex, race, tumor behavior, radiation therapy and tumor-directed surgery, glioblastoma was related to a significantly lower AD risk than other tumors (odds ratio: 0.19, 95% CI: 0.05-0.77). Additionally, patients who were older, female, American Indian/Alaska Native, had a benign tumor, radiation therapy and tumor-directed surgery had a significantly higher risk of dying from AD. CONCLUSION: Gliomas and glioblastomas were associated with a significantly lower risk of death from AD than other tumors.

Current knowledge of thrombocytopenia in sepsis and COVID-19.

Thrombocytopenia, characterized by a decrease in platelet count, is commonly observed in sepsis and COVID-19. In sepsis, thrombocytopenia can result from various mechanisms, including impaired platelet production in the bone marrow, accelerated platelet destruction due to increased inflammation, sequestration of platelets in the spleen, immune-mediated platelet destruction, or dysregulated host responses. Similarly, thrombocytopenia has been reported in COVID-19 patients, but the immune-related mechanisms underlying this association remain unclear. Notably, interventions targeting thrombocytopenia have shown potential for improving outcomes in both sepsis and COVID-19 patients. Understanding these mechanisms is crucial for developing effective treatments.

Multiscale imaging of peroxynitrite in gliomas with a blood-brain barrier permeable probe reveals its potential as a biomarker and target for glioma treatment.

Cancer development is driven by diverse processes, and metabolic alterations are among the primary characteristics. Multiscale imaging of aberrant metabolites in cancer is critical to understand the pathology and identify new targets for treatment. While peroxynitrite (ONOO-) is reported being enriched in some tumors and plays important tumorigenic roles, whether it is upregulated in gliomas remains unexplored. To determine the levels and roles of ONOO- in gliomas, efficient tools especially those with desirable blood-brain barrier (BBB) permeability and can realize the in situ imaging of ONOO- in multiscale glioma-related samples are indispensable. Herein, we proposed a strategy of physicochemical property-guided probe design, which resulted in the development of a fluorogenic probe NOSTracker for smartly tracking ONOO-. The probe showed sufficient BBB permeability. ONOO- triggered oxidation of its arylboronate group was automatically followed by a self-immolative cleavage of a fluorescence-masking group, liberating its fluorescence signal. The probe was not only highly sensitive and selective towards ONOO-, but its fluorescence favored desirable stability in various complex biological milieus. Guaranteed by these properties, multiscale imaging of ONOO- was realized in vitro in patient-derived primary glioma cells, ex vivo in clinical glioma slices, and in vivo in the glioma of live mice. The results showed the upregulation of ONOO- in gliomas. Furthermore, a specific ONOO- scavenger uric acid (UA) was pharmaceutically used to downregulate ONOO- in glioma cell lines, and an anti-proliferative effect was observed. These results taken together imply the potential of ONOO- as a biomarker and target for glioma treatment, and propose NOSTracker as a reliable tool to further explore the role of ONOO- in glioma development.

Activation of the RARα Attenuated CSF Hypersecretion to Inhibit Hydrocephalus Development via Regulating the MAFB/MSR1 Pathway.

Hydrocephalus has been observed in rats with spontaneous hypertension (SHRs). It has been demonstrated that activation of the oxidative stress related protein retinoic acid receptor alpha (RARα) has neuroprotective impacts. Our investigation aims to determine the potential role and mechanism of RARα in hydrocephalus. The RARα-specific agonist (Am80) and RARα inhibitor (AGN196996) were used to investigate the role of RARα in cerebrospinal fluid (CSF) secretion in the choroid plexus of SHRs. Evaluations of CSF secretion, ventricular volume, Western blotting, and immunofluorescent staining were performed. Hydrocephalus and CSF hypersecretion were identified in SHRs but not in Wistar-Kyoto rats, occurring at the age of 7 weeks. The RARα/MAFB/MSR1 pathway was also activated in SHRs. Therapy with Am80 beginning in week 5 decreased CSF hypersecretion, hydrocephalus development, and pathological changes in choroid plexus alterations by week 7. AGN196996 abolished the effect of Am80. In conclusion, activation of the RARα attenuated CSF hypersecretion to inhibit hydrocephalus development via regulating the MAFB/MSR1 pathway. RARα may act as a possible therapeutic target for hydrocephalus.

BST2 induced macrophage M2 polarization to promote the progression of colorectal cancer.

Background: Tumor-associated macrophages (TAMs) are one of the most prominent tumor-infiltrating immune cells in the tumor microenvironment (TME) of CRC and play a vital role in the progression of CRC. BST2 was predicted to be associated with the infiltration of TAMs. However, its potential function by which CRC cells and TAMs interact with each other still needs further investigation. Methods: The target genes in CRC were selected by bioinformatics screening. The level of bone marrow stromal cell antigen 2 (BST2) in CRC cells and tissues was determined by qRT‒PCR, Western blotting, and immunohistochemistry staining. In vitro and in vivo assays were applied to clarify the function of BST2. Results: In this study, according to bioinformatics analysis, a nomogram based on the risk score (constructed by BST2 and CAV1 (caveolin-1)) and clinical features was built and displayed satisfactory prognostic value. Upregulated BST2 was significantly related to Braf mutation, dMMR/MSI-H, CMS1 subtype, and immune response and was a potential biomarker for predicting immune checkpoint blockade therapy. Silencing BST2 in CRC obviously restrained CRC progression and M2 TAM polarization. The infiltration of TAMs was positively correlated with the high expression of BST2, and depletion of TAMs alleviated the protumoural effect of BST2 in CRC in vivo. In vitro experiments revealed that a reduction in BST2 in CRC inhibited CRC proliferation and migration and also M2 polarization. Conclusion: These findings indicated that BST2 played a vital role in CRC progression and might be a predictable marker for immunotherapy.

Role of complement C1q/C3-CR3 signaling in brain injury after experimental intracerebral hemorrhage and the effect of minocycline treatment.

Aim: The complement cascade is activated and may play an important pathophysiologic role in brain injury after experimental intracerebral hemorrhage (ICH). However, the exact mechanism of specific complement components has not been well studied. This study determined the role of complement C1q/C3-CR3 signaling in brain injury after ICH in mice. The effect of minocycline on C1q/C3-CR3 signaling-induced brain damage was also examined. Methods: There were three parts to the study. First, the natural time course of C1q and CR3 expression was determined within 7 days after ICH. Second, mice had an ICH with CR3 agonists, LA-1 or vehicle. Behavioral score, neuronal cell death, hematoma volume, and oxidative stress response were assessed at 7 days after ICH. Third, the effect of minocycline on C1q/C3-CR3 signaling and brain damage was examined. Results: There were increased numbers of C1q-positive and CR3-positive cells after ICH. Almost all perihematomal C1q-positive and CR3-positive cells were microglia/macrophages. CR3 agonist LA-1 aggravated neurological dysfunction, neuronal cell death, and oxidative stress response on day 7 after ICH, as well as enhancing the expression of the CD163/HO-1 pathway and accelerating hematoma resolution. Minocycline treatment exerted neuroprotective effects on brain injury following ICH, partly due to the inhibition of C1q/C3-CR3 signaling, and that could be reversed by LA-1. Conclusions: The complement C1q/C3-CR3 signaling is upregulated after ICH. The activation of C1q/C3-CR3 signaling by LA-1 aggravates brain injury following ICH. The neuroprotection of minocycline, at least partly, is involved with the repression of the C1q/C3-CR3 signaling pathway.

Multi-Band High-Efficiency Multi-Functional Polarization Controller Based on Terahertz Metasurface.

Electromagnetic metasurfaces with excellent electromagnetic wave regulation properties are promising for designing high-performance polarization control devices, while the application prospect of electromagnetic metasurfaces is limited because of the current development situations of the complex structure, low conversion efficiency, and narrow working bandwidth. In this work, we design a type of reflective terahertz metasurface made of a simple structure that can achieve multiple polarization modulation with high efficiency. It is shown that the presented metasurface can realize ultra-broadband, cross-polarization conversion with the relative working bandwidth reaching 94% and a conversion efficiency of over 90%. In addition, the proposed metasurface can also efficiently accomplish different polarization conversion functions, such as linear-to-linear, linear-to-circular, or circular-to-linear polarization conversion in multiple frequency bands. Due to the excellent properties, the designed metasurface can be used as a high-efficiency multi-functional polarization modulation device, and it has important application value in terahertz imaging, communication, biological detection, and other fields.

Neutrophil to lymphocyte ratio predicting poor outcome after aneurysmal subarachnoid hemorrhage: A retrospective study and updated meta-analysis.

Background: The relationship between neutrophil to lymphocyte ratio (NLR) and poor outcome of aneurysmal subarachnoid hemorrhage (aSAH) is controversial. We aim to evaluate the relationship between NLR on admission and the poor outcome after aSAH. Method: Part I: Retrospective analysis of aSAH patients in our center. Baseline characteristics of patients were collected and compared. Multivariate analysis was used to evaluate parameters independently related to poor outcome. Receiver operating characteristic (ROC) curve analysis was used to determine the best cut-off value of NLR. Part II: Systematic review and meta-analysis of relevant literature. Related literature was selected through the database. The pooled odds ratio (OR) and corresponding 95% confidence interval (CI) were calculated to evaluate the correlation between NLR and outcome measures. Results: Part I: A total of 240 patients with aSAH were enrolled, and 52 patients had a poor outcome. Patients with poor outcome at 3 months had a higher admission NLR, Hunt & Hess score, Barrow Neurological Institute (BNI) scale score, Subarachnoid Hemorrhage Early Brain Edema Score (SEBES), and proportion of hypertension history. After adjustment, NLR at admission remained an independent predictor of poor outcome in aSAH patients (OR 0.76, 95% CI 0.69-0.83; P < 0.001). The best cut-off value of NLR in ROC analysis is 12.03 (area under the curve 0.805, 95% CI 0.735 - 0.875; P < 0.001). Part II: A total of 16 literature were included. Pooled results showed that elevated NLR was significantly associated with poor outcome (OR 1.31, 95% CI 1.14-1.49; P < 0.0001) and delayed cerebral ischemia (DCI) occurrence (OR 1.32, 95% CI 1.11-1.56; P = 0.002). The results are more reliable in large sample sizes, low NLR cut-off value, multicenter, or prospective studies. Conclusion: Elevated NLR is an independent predictor of poor outcome and DCI occurrence in aSAH.

The Novel Nrf2 Activator Omaveloxolone Regulates Microglia Phenotype and Ameliorates Secondary Brain Injury after Intracerebral Hemorrhage in Mice.

The polarization of microglia is recognized as a crucial factor in reducing neuroinflammation and promoting hematoma clearance after intracerebral hemorrhage (ICH). Previous studies have revealed that redox components participate in the regulation of microglial polarization. Recently, the novel Nrf2 activator omaveloxolone (Omav) has been validated to improve neurological function in patients with neurodegenerative disorders by regulating antioxidant responses. In this study, we examined the efficacy of Omav in ICH. Omav significantly promoted Nrf2 nuclear accumulation and the expression of HO-1 and NQO1 in BV2 cells. In addition, both in vitro and in vivo experiments showed that Omav treatment inhibited M1-like activation and promoted the activation of the M2-like microglial phenotype. Omav inhibited OxyHb-induced ROS generation and preserved the function of mitochondria in BV2 cells. Intraperitoneal administration of Omav improved sensorimotor function in the ICH mouse model. Importantly, these effects were blocked by pretreatment with ML385, a selective inhibitor of Nrf2. Collectively, Omav modulated microglial polarization by activating Nrf2 and inhibiting ROS generation in ICH models, suggesting that it might be a promising drug candidate for the treatment of ICH.

CD47 Blockade Accelerates Blood Clearance and Alleviates Early Brain Injury After Experimental Subarachnoid Hemorrhage.

Aims: Subarachnoid hemorrhage (SAH) is a devastating stroke subtype. Following SAH, erythrocyte lysis contributes to cell death and brain injuries. Blockage of the anti-phagocytic receptor Cluster of Differentiation 47 (CD47) enhances phagocyte clearance of erythrocytes, though it has not been well-studied post-SAH. The current study aims to determine whether anti-CD47 treatment can enhance blood clearance after experimental SAH. Methods: The prechiasmatic blood injection model of SAH was used in mice. Mice were either treated with the CD47-blocking antibody or IgG as control. The effect of the anti-CD47 antibody on blood clearance and neurological function following SAH was determined. Neuroinflammation and neuronal injury were compared between the treatment and control samples on day 1 and day 7 after SAH using flow cytometry, immunofluorescence, Fluoro-Jade C, and Nissl staining, RT-PCR, and Western blot analysis. Results: CD47-blocking antibody sped-up blood clearance after SAH, and resulted in less neuronal injury and neurological deficits than control samples. Microglia played a role in the anti-CD47 blockade. Following SAH Following SAH, CD47 antibody-treated mice had less neuroinflammation and lower levels of apoptosis compared to controls and both one and 7 days. Conclusions: CD47 antibody treatment has a neuroprotective effect following SAH, by increasing blood clearance rate and reducing brain injury. These findings suggest CD47 antibody treatment may improve SAH patient outcomes.

The antagonistic interactions between a polyvalent phage SaP7 and ß-lactam antibiotics on combined therapies.

Phage therapy is a promising alternative antibiotic strategy to combat multidrug-resistant bacteria infections. Most studies focus on the synergistic effects, while the antagonistic interactions between phage and antibiotics is rarely studied. Here, we isolated and identified a novel polyvalent phage SaP7, which is capable of infecting multidrug-resistant Salmonella S7 and several E. coli strains. Morphology via electron microscopy showed that SaP7 belonged to the Myoviridae family. Genomic analysis revealed that the genome of SaP7 lacked any genes associated with antibiotic resistance, toxins, lysogeny, and virulence factors. We discovered the antagonism efficacy of SaP7 combined amoxicillin/potassium clavulanate (AMC) in counteracting Salmonella S7 in piglet-models by bacterial loads in feces and tissues. The consistent result as above between SaP7 and amoxicillin (AMX) was further verified in BALB/c mice-models. Furthermore, in vitro, plaque assay and minimum inhibitory concentration (MIC) determinations showed that AMX or AMC or cefepime (FEP) inhibited SaP7 plaque formation respectively and SaP7 decreased bacterial susceptibility of Salmonella S7 to AMX, AMC and FEP. And the negative interference of SaP7 with the bacteriostasis to Salmonella S7 of these three ß-lactam antibiotics was observed in planktonic cultures via microtiter plates, but could not prevent the bacteriostasis of high titer of phage or high concentration of antibiotics. Finally, our research suggested that a polyvalent phage SaP7 existed antagonism with several ß-lactam antibiotics. It is therefore crucial to fully and cautiously evaluate phage/antibiotic interactions and probable outcomes to avoid antagonistic impacts and failure of antibiotic and phage combination therapy.

Neutrophil Extracellular Traps may be a Potential Target for Treating Early Brain Injury in Subarachnoid Hemorrhage.

Neuroinflammation is closely associated with poor prognosis in patients with subarachnoid hemorrhage (SAH). The purpose of this study was to investigate the role of neutrophil extracellular traps (NETs), which are important regulators of sterile inflammation, in SAH. In this study, markers of NET formation, quantified by the level of citrullinated histone H3 (CitH3), were significantly increased after SAH and correlated with SAH severity. CitH3 peaked at 12 h in peripheral blood and at 24 h in the brain. Administration of the peptidyl arginine deiminase 4 (PAD4) selective antagonist GSK484 substantially attenuated SAH-induced brain edema and neuronal injury. Moreover, the benefit of NET inhibition was also confirmed by DNAse I treatment and neutrophil depletion. Mechanistically, NETs markedly exacerbated microglial inflammation in vitro. NET formation aggravated neuroinflammation by promoting microglial activation and increased the levels of TNF-α, IL-1ß, and IL-6, while inhibiting NETs demonstrated anti-inflammatory effects by decreasing the levels of these proinflammatory factors. Moreover, neurogenic pulmonary edema (NPE), a severe nonneurological complication after SAH, is associated with a high level of NET formation. However, GSK484 effectively inhibited the formation of NETs in the lungs of NPE mice, thereby preventing the diffusion of neutrophilic infiltration and attenuating the swelling of the alveolar interstitium. In conclusion, NETs promoted neuroinflammation after SAH, while pharmacological inhibition of PAD4-NETs could reduce the inflammatory damage caused by SAH. These results supported the idea that NETs might be potential therapeutic targets for SAH.

TREM1 Regulates Neuroinflammatory Injury by Modulate Proinflammatory Subtype Transition of Microglia and Formation of Neutrophil Extracellular Traps via Interaction With SYK in Experimental Subarachnoid Hemorrhage.

Neuroinflammation is a key process in the pathogenesis of subarachnoid hemorrhage (SAH) and contributes to poor outcome in patients. The purpose of this study is to explore the effect of triggering receptor expressed on myeloid cells 1 (TREM1) in the SAH, as well as its potential mechanism. In our study, plasma levels of soluble TREM1 was increased significantly after SAH and correlated to SAH severity and serum C-reactiveprotein. TREM1 inhibitory peptide LP17 alleviated the neurological deficits, attenuated brain water content, and reduced neuronal damage after SAH. Meanwhile, TREM1 inhibitory peptide decreased neuroinflammation (evidenced by the decreased levels of markers including IL-6, IL-1ß, TNF-α) by attenuating proinflammatory subtype transition of microglia (evidenced by the decreased levels of markers including CD68, CD16, CD86) and decreasing the formation of neutrophil extracellular traps (evidenced by the decreased levels of markers including CitH3, MPO, and NE). Further mechanistic study identified that TREM1 can activate downstream proinflammatory pathways through interacting with spleen tyrosine kinase (SYK). In conclusion, inhibition of TREM1 alleviates neuroinflammation by attenuating proinflammatory subtype transition of microglia and decreasing the formation of neutrophil extracellular traps through interacting with SYK after SAH. TREM1 may be a a promising therapeutic target for SAH.

Mast Cells Mediate Inflammatory Injury and Aggravate Neurological Impairment in Experimental Subarachnoid Hemorrhage Through Microglial PAR-2 Pathway.

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease with high mortality and disability. Aberrant neuroinflammation has been identified as a critical factor accounting for the poor prognosis of SAH patients. Mast cells (MCs), the sentinel cells of the immune system, play a critical in the early immune reactions and participate in multiple pathophysiological process. However, the exact role of MCs on the pathophysiological process after SAH has not been fully understood. The current study was conducted to determine the role of MCs and MC stabilization in the context of SAH. Mouse SAH model was established by endovascular perforation process. Mice received saline or cromolyn (MC stabilizer) or compound 48/80 (MCs degranulator). Post-SAH evaluation included neurobehavioral test, western blot, immunofluorescence, and toluidine blue staining. We demonstrated that SAH induced MCs activation/degranulation. Administration of MC stabilizer cromolyn conferred a better neurologic outcome and decreased brain edema when compared with SAH+vehicle group. Furthermore, cromolyn significantly inhibited neuroinflammatory response and alleviated neuronal damage after SAH. However, pharmacological activation of MCs with compound 48/80 dramatically aggravated SAH-induced brain injury and exacerbated neurologic outcomes. Notably, pharmacological inhibition of microglial PAR-2 significantly reversed MCs-induced inflammatory response and neurological impairment. Additionally, the effect of MCs-derived tryptase in mediating neuroinflammation was also abolished by the microglial PAR-2 blockage in vitro. Taken together, MCs yielded inflammatory injury through activating microglia-related neuroinflammation after SAH. These data shed light on the notion that MCs might be a novel and promising therapeutic target for SAH.

Autophagy protein NRBF2 attenuates endoplasmic reticulum stress-associated neuroinflammation and oxidative stress via promoting autophagosome maturation by interacting with Rab7 after SAH.

BACKGROUND: Neuroinflammation and oxidative stress plays an important role in the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). This study is the first to show that activation of autophagy protein nuclear receptor binding factor 2 (NRBF2) could reduce endoplasmic reticulum stress (ERS)-associated inflammation and oxidative stress after SAH. METHODS: Male C57BL/6J mice were subjected to endovascular perforation to establish a model of SAH. NRBF2 overexpression adeno-associated virus (AAV), NRBF2 small interfering RNAs (siRNA), lysosomal inhibitor-chloroquine (CQ), and late endosome GTPase Rab7 receptor antagonist-CID1067700 (CID) were used to investigate the role of NRBF2 in EBI after SAH. Neurological tests, brain water content, western blotting and immunofluorescence staining were evaluated. RESULTS: Our study found that the level of NRBF2 was increased after SAH and peaked at 24 h after SAH. In addition, we found that the overexpression of NRBF2 significantly improved neurobehavioral scores and reduced ERS, oxidative stress, and neuroinflammation in SAH, whereas the inhibition of NRBF2 exacerbated these phenotypes. In terms of mechanism, NRBF2 overexpression significantly promoted autophagosome maturation, with the downregulation of CHOP, Romo-1, TXNIP, NLRP3, TNF-α, and IL-1ß expression through interaction with Rab7. The protective effect of NRBF2 on ERS-associated neuroinflammation and oxidative stress after SAH was eliminated by treatment with CQ. Meanwhile, it was also reversed by intraperitoneal injection of CID. Moreover, the MIT domain of NRBF2 was identified as a critical binding site that interacts with Rab7 and thereby promotes autophagosome maturation. CONCLUSION: Our data provide evidence that the autophagy protein NRBF2 has a protective effect on endoplasmic reticulum stress-associated neuroinflammation and oxidative stress by promoting autophagosome maturation through interactions with Rab7 after SAH.