Pathogenesis Of Subarachnoid Hemorrhage Research Articles

Exosomes-mediated delivery of miR-486-3p alleviates neuroinflammation via SIRT2-mediated inhibition of mitophagy after subarachnoid hemorrhage

BackgroundNeuroinflammation participates in the pathogenesis of subarachnoid haemorrhage (SAH); however, no effective treatments exist. MicroRNAs regulate several aspects of neuronal dysfunction. In a previous study, we found that exosomal miR-486-3p...

The pivotal role of microglia in injury and the prognosis of subarachnoid hemorrhage.

Subarachnoid hemorrhage leads to a series of pathological changes, including vascular spasm, cellular apoptosis, blood-brain barrier damage, cerebral edema, and white matter injury. Microglia, which are the key immune cells in the central nervous system, maintain homeostasis in the neural environment, support neurons, mediate apoptosis, participate in immune regulation, and have neuroprotective effects. Increasing evidence has shown that microglia play a pivotal role in the pathogenesis of subarachnoid hemorrhage and affect the process of injury and the prognosis of subarachnoid hemorrhage. Moreover, microglia play certain neuroprotective roles in the recovery phase of subarachnoid hemorrhage. Several approaches aimed at modulating microglia function are believed to attenuate subarachnoid hemorrhage injury. This provides new targets and ideas for the treatment of subarachnoid hemorrhage. However, an in-depth and comprehensive summary of the role of microglia after subarachnoid hemorrhage is still lacking. This review describes the activation of microglia after subarachnoid hemorrhage and their roles in the pathological processes of vasospasm, neuroinflammation, neuronal apoptosis, blood-brain barrier disruption, cerebral edema, and cerebral white matter lesions. It also discusses the neuroprotective roles of microglia during recovery from subarachnoid hemorrhage and therapeutic advances aimed at modulating microglial function after subarachnoid hemorrhage. Currently, microglia in subarachnoid hemorrhage are targeted with TLR inhibitors, nuclear factor-κB and STAT3 pathway inhibitors, glycine/tyrosine kinases, NLRP3 signaling pathway inhibitors, Gasdermin D inhibitors, vincristine receptor α receptor agonists, ferroptosis inhibitors, genetic modification techniques, stem cell therapies, and traditional Chinese medicine. However, most of these are still being evaluated at the laboratory stage. More clinical studies and data on subarachnoid hemorrhage are required to improve the treatment of subarachnoid hemorrhage.

Iron Metabolism and Ferroptosis in Early Brain Injury after Subarachnoid Haemorrhage.

At present, it appears that the prognosis for subarachnoid haemorrhage (SAH), which has a high death and disability rate, cannot be greatly improved by medication or other treatment. Recent research suggests that different types of cell death are implicated in early brain injury (EBI) after SAH, and this has been recognised as a major factor impacting the prognosis of SAH. Ferroptosis, which is a recently identified imbalance of iron metabolism and programmed cell death triggered by phospholipid peroxidation, has been shown to be involved in EBI after SAH and is thought to have a significant impact on EBI. The decomposition of cleaved haemoglobin during SAH involves the release of enormous amounts of free iron, resulting in iron metabolism disorders. Potential therapeutic targets for the signalling pathways of iron metabolism disorders and ferroptosis after SAH are constantly being discovered. To serve as a guide for research into other possible therapeutic targets, this paper will briefly describe the mechanisms of dysregulated iron metabolism and ferroptosis in the pathogenesis of SAH and highlight how they are involved in the development and promotion of EBI in SAH.

Exploring the Role of Ferroptosis-Related Circular RNAs in Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular event associated with high mortality and significant morbidity. Recent studies have highlighted the emerging role of ferroptosis, a novel form of regulated cell death, in the pathogenesis of SAH. Circular RNAs (circRNAs), have been found to play essential roles in various cellular processes, including gene regulation and disease pathogenesis. The expression profile of circRNAs in neural tissues, particularly in the brain, suggests their critical role in synaptic function and neurogenesis. Moreover, the interplay between circRNAs and ferroptosis-related pathways, such as iron metabolism and lipid peroxidation, is explored in the context of SAH. Understanding the functional roles of specific circRNAs in the context of SAH may provide potential therapeutic targets to attenuate ferroptosis-associated brain injury. Furthermore, the potential of circRNAs as diagnostic biomarkers for SAH severity, prognosis, and treatment response is discussed. Overall, this review highlights the significance of studying the intricate interplay between circRNAs and ferroptosis in the context of SAH. Unraveling the mechanisms by which circRNAs modulate ferroptotic cell death may pave the way for the development of novel therapeutic strategies and diagnostic approaches for SAH management, ultimately improving patient outcomes and quality of life.

Abstract 16: Integrin α9β1 and VCAM-1 Interaction Promotes Neutrophil Hyperactivation and Cognitive Decline Following Subarachnoid Hemorrhage

Background: Integrin α9β1 is a transmembrane glycoprotein that is highly expressed on neutrophils and mediates transendothelial migration via vascular cell adhesion molecule-1 (VCAM-1). Neutrophils are major contributors to cerebral thrombosis and oxidative stress following subarachnoid hemorrhage (SAH); however, the mechanism by which neutrophil integrin α9 contributes to SAH pathogenesis is unclear. Here, we evaluated the mechanistic role of neutrophil integrin α9 in the post-SAH sensorimotor and cognitive recovery. Methods: SAH was induced by filament perforation in neutrophil-specific α9 -/- (α9 fl/fl Mrp8Cre +/- ) mice and littermate controls. Cognitive recovery (Y-maze, Barnes maze, and novel object recognition test) and sensorimotor recovery (modified neurological severity score, corner, and cylinder test) were performed for up to 4-weeks. Unbiased RNA sequencing (RNA-seq) was used to evaluate the potential mechanisms by which neutrophil integrin α9-VCAM-1 interactions promote SAH. Computational modeling, docking, virtual screening, and cell-free assays were used to identify small-molecule inhibitors of the integrin α9-VCAM-1 interactions. Results: Experimental SAH resulted in increased levels of neutrophil integrin α9 which was concomitant with neutrophil hyperactivation. Post-SAH neutrophil-specific α9 -/- mice exhibited improved sensorimotor and cognitive recovery, along with reduced plasma elastase and MPO levels and brain neutrophil infiltration. Mechanistically, integrin α9/VCAM-1 interactions promote neutrophil hyperactivation, extracellular signal-regulated kinase (ERK) phosphorylation, and endothelial cell apoptosis. RNA-seq data revealed that α9/VCAM-1 interactions promotes gene expression related to neutrophil inflammation, exocytosis, NF-κB signaling, and chemotaxis. Virtual screening and cell-free assay identified macitentan as a potent inhibitor of integrin α9-VCAM-1 interactions. In vitro, macitentan treatment decreased neutrophil adhesion to VCAM-1 and macitentan treatment at a dose of 5 mg/kg resulted in improved SAH outcomes. Conclusion: The results of this study describe a previously unrecognized pathway involving integrin α9 and VCAM-1 in the pathogenesis of SAH.

Multimodal imaging of the role of hyperglycemia following experimental subarachnoid hemorrhage

Hyperglycemia has been linked to worsening outcomes after subarachnoid hemorrhage (SAH). Nevertheless, the mechanisms involved in the pathogenesis of SAH have been scarcely evaluated so far. The role of hyperglycemia was assessed in an experimental model of SAH by T2 weighted, dynamic contrast-enhanced magnetic resonance imaging (T2W and DCE-MRI), [18F]BR-351 PET imaging and immunohistochemistry. Measures included the volume of bleeding, the extent of cerebral infarction and brain edema, blood brain barrier disruption (BBBd), neutrophil infiltration and matrix metalloprotease (MMP) activation. The neurofunctional outcome, neurodegeneration and myelinization were also investigated. The induction of hyperglycemia increased mortality, the size of the ischemic lesion, brain edema, neurodegeneration and worsened neurological outcome during the first 3 days after SAH in rats. In addition, these results show for the first time the exacerbating effect of hyperglycemia on in vivo MMP activation, Intercellular Adhesion Molecule 1 (ICAM-1) expression and neutrophil infiltration together with increased BBBd, bleeding volume and fibrinogen accumulation at days 1 and 3 after SAH. Notably, these data provide valuable insight into the detrimental effect of hyperglycemia on early BBB damage mediated by neutrophil infiltration and MMP activation that could explain the worse prognosis in SAH.

Abstract TP225: Cell-type-based Pathway Analysis In Experimental Subarachnoid Hemorrhage

Introduction: Recently, increasing evidence points to a pivotal role of neuroinflammation in the pathogenesis of Subarachnoid hemorrhage (SAH). However, the pattern of cell interaction after SAH is not clear. Methods: Endovascular perforation (EVP) murine SAH model was established to reproduce experimental SAH. Post-SAH CD11b+ single-cell suspension was harvested at day 3 and sequenced using 10X single-cell RNA-sequencing platform. Then, the detailed single-cell information of post-SAH cells was analyzed with bioinformatics. The same pathways and related ligand-receptors in microglia and other cells were compared. Results: More than 51 pathways were found in the crosstalk of brain cells after SAH, these cells including: microglia (microglia worked in 25 pathways), CNS-associated macrophage, astrocyte, neuron, monocyte and macrophage and Oligodendrocyte. In the microglia subsets’ interaction, 15 pathways upregulated, of which four pathways were specific to microglia subsets, including amyloid-β precursor protein (APP), Tumor necrosis factor (TNF), growth differentiation factor (GDF) and oncostatin M (OSM) signaling pathways. We precisely distinguished the ligand-receptor pattern in which microglia differ with other cells in 7 pathways, including chemokine ligands (CCL), colony-stimulating factor (CSF), GALECTIN, growth arrest-specific (GAS), intercellular adhesion molecule (ICAM), junction adhesion molecule (JAM) and secreted phosphoprotein 1 (SPP1) signaling pathways. Gene ontology (GO) results showed that compared with non-microglia cells, post-SAH microglia with upregulated function like leukocyte, glia cell activation and migration, while have downregulated functions of protein-lipid complex remodeling. Conclusions: Collectively, we first systematically report the interaction patterns of seven brain cells after SAH. Further the cell type based ligand-receptor analysis of microglia and other cells in the same pathway was comparatively conducted. These results revealed the cellular mechanisms for neuroinflammation after SAH, and the ligand-receptor results provided a theoretical basis and opportunities for accurate monitoring and modulation of SAH in the future.

Trimethylamine N-oxide (TMAO) in patients with subarachnoid hemorrhage: a prospective observational study

BackgroundIt is suspected that microbiome-derived trimethylamine N-oxide (TMAO) may enhance platelet responsiveness and accordingly be thrombophilic. The purpose of this prospective observational study is to evaluate TMAO in patients with subarachnoid hemorrhage (SAH) and compare it with a control group. A secondary aim was to investigate TMAO in the cerebrospinal fluid (CSF) from SAH patients. This should provide a better understanding of the role of TMAO in the pathogenesis of SAH and its thrombotic complications.MethodsThe study included patients with diagnosed spontaneous SAH recruited after initial treatment on admission and patients with nerve, nerve root, or plexus disorders serving as controls. Blood samples were gathered from all patients at recruitment. Additionally, sampling of SAH patients in the intensive care unit continued daily for 14 days. The CSF was collected out of existing external ventricular drains whenever possible.ResultsThirty-four patients diagnosed with SAH, and 108 control patients participated in this study. Plasma TMAO levels at baseline were significantly lower in the SAH group (1.7 μmol/L) compared to the control group (2.9 μmol/L). TMAO was detectable in the CSF (0.4 μmol/L) and significantly lower than in plasma samples of the SAH group at baseline. Plasma and CSF TMAO levels correlated positively. The TMAO levels did not differ significantly during the observation period of 15 days.ConclusionsAlthough we assumed that patients with higher TMAO levels were at higher risk for SAH a priori, plasma TMAO levels were lower in patients with SAH compared with control subjects with nerve, nerve root, or plexus disorders on admission to the hospital. A characteristic pattern of plasma TMAO levels in patients with SAH was not found.

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-1β, 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.

Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) remains an important cause of mortality and long-term morbidity. This article uses a case-based approach to guide readers through the fundamental epidemiology and pathogenesis of SAH, the approach to diagnosis and management, the results of clinical trials and evidence to date, prognostic considerations, controversies, recent developments, and future directions in SAH. Historically, management of SAH focused on prevention and treatment of subsequent cerebral vasospasm, which was thought to be the primary cause of delayed cerebral ischemia. Clinical and translational studies over the past decade, including several therapeutic phase 3 randomized clinical trials, suggest that the pathophysiology of SAH-associated brain injury is multiphasic and multifactorial beyond large vessel cerebral vasospasm. The quest to reduce SAH-associated brain injury and improve outcomes is shifting away from large vessel cerebral vasospasm to a new paradigm targeting multiple brain injury mechanisms, including early brain injury, delayed cerebral ischemia, microcirculatory dysfunction, spreading cortical depolarization, inflammation, and the brain-body interaction in vascular brain injury with critical illness.Despite multiple negative randomized clinical trials in search of potential therapeutic agents ameliorating the downstream effects after SAH, the overall outcome of SAH has improved over recent decades, likely related to improvements in interventional options for ruptured cerebral aneurysms and in critical care management. Emerging clinical evidence also suggests potential harmful impact of historic empiric treatments for SAH-associated vasospasm, such as prophylactic induction of hypertension, hypervolemia, and hemodilution (triple H therapy).With decreasing mortality, long-term SAH survivorship and efforts to reduce chronic morbidity and to improve quality of life and patient-centered outcome are growing areas of unmet need. Despite existing guidelines, significant variabilities in local and regional practices and in scientific terminologies have historically limited advancement in SAH care and therapeutic development. Large global collaborative efforts developed harmonized SAH common data elements in 2019, and studies are under way to examine how existing variabilities in SAH care impact long-term SAH outcomes. Although the overall incidence and mortality of SAH is decreasing with advances in preventive and acute care, SAH remains a major cause of long-term morbidity in survivors. Significant variabilities in care settings and empiric treatment protocols and inconsistent scientific terminologies have limited advancement in patient care and therapeutic clinical studies. Large consensus efforts are under way to introduce clinical guidelines and common data elements to advance therapeutic approaches and improve patient outcome.

Identification of upregulated NF-\u03baB inhibitor alpha and IRAK3 targeting lncRNA following intracranial aneurysm rupture-induced subarachnoid hemorrhage

BackgroundThis study was performed to identify genes and lncRNAs involved in the pathogenesis of subarachnoid hemorrhage (SAH) from ruptured intracranial aneurysm (RIA).MethodsMicroarray GSE36791 was downloaded from Gene Expression Omnibus (GEO) database followed by the identification of significantly different expressed RNAs (DERs, including lncRNA and mRNA) between patients with SAH and healthy individuals. Then, the functional analyses of DEmRNAs were conducted and weighted gene co-expression network analysis (WGCNA) was also performed to extract the modules associated with SAH. Following, the lncRNA-mRNA co-expression network was constructed and the gene set enrichment analysis (GSEA) was performed to screen key RNA biomarkers involved in the pathogenesis of SAH from RIA. We also verified the results in a bigger dataset GSE7337.ResultsTotally, 561 DERs, including 25 DElncRNAs and 536 DEmRNAs, were identified. Functional analysis revealed that the DEmRNAs were mainly associated with immune response-associated GO-BP terms and KEGG pathways. Moreover, there were 6 modules significantly positive-correlated with SAH. The lncRNA-mRNA co-expression network contained 2 lncRNAs (LINC00265 and LINC00937) and 169 mRNAs. The GSEA analysis showed that these two lncRNAs were associated with three pathways (cytokine-cytokine receptor interaction, neurotrophin signaling pathway, and apoptosis). Additionally, IRAK3 and NFKBIA involved in the neurotrophin signaling pathway and apoptosis while IL1R2, IL18RAP and IL18R1 was associated with cytokine-cytokine receptor interaction pathway. The expression levels of these genes have the same trend in GSE36791 and GSE7337.ConclusionLINC00265 and LINC00937 may be implicated with the pathogenesis of SAH from RIA. They were involved in three important regulatory pathways. 5 mRNAs played important roles in the three pathways.

Systemic exosomal miR-193b-3p delivery attenuates neuroinflammation in early brain injury after subarachnoid hemorrhage in mice

BackgroundInflammation is a potential crucial factor in the pathogenesis of subarachnoid hemorrhage (SAH). Circulating microRNAs (miRNAs) are involved in the regulation of diverse aspects of neuronal dysfunction. The therapeutic potential of miRNAs has been demonstrated in several CNS disorders and is thought to involve modulation of neuroinflammation. Here, we found that peripherally injected modified exosomes (Exos) delivered miRNAs to the brains of mice with SAH and that the potential mechanism was regulated by regulation of neuroinflammation.MethodsNext-generation sequencing (NGS) and qRT-PCR were used to define the global miRNA profile of plasma exosomes in aSAH patients and healthy controls. We peripherally injected RVG/Exos/miR-193b-3p to achieve delivery of miR-193b-3p to the brain of mice with SAH. The effects of miR-193b-3p on SAH were assayed using a neurological score, brain water content, blood-brain barrier (BBB) injury, and Fluoro-Jade C (FJC) staining. Western blotting analysis, enzyme-linked immunosorbent assay (ELISA), and qRT-PCR were used to measure various proteins and mRNA levels.ResultsNGS and qRT-PCR revealed that four circulating exosomal miRNAs were differentially expressed. RVG/Exos exhibited improved targeting to the brains of SAH mice. MiR-193b-3p suppressed the expression and activity of HDAC3, upregulating the acetylation of NF-κB p65. Finally, miR-193b-3p treatment mitigated the neurological behavioral impairment, brain edema, BBB injury, and neurodegeneration induced by SAH, and reduced inflammatory cytokine expression in the brains of mice after SAH.ConclusionsExos/miR-193b-3p treatment attenuated the inflammatory response by acetylation of the NF-κB p65 via suppressed expression and activity of HDAC3. These effects alleviated neurobehavioral impairments and neuroinflammation following SAH.

Gene expression profiles and related immune-inflammatory factors in the cerebral arteries in mouse models of subarachnoid haemorrhage

The study aimed to identify key genes involved in cerebral vasospasm (CVS) after subarachnoid haemorrhage (SAH). GSE46696 of basilar arteries of SAH mice and normal controls were downloaded from the Gene Expression Omnibus (GEO). Integrated microarray analysis was performed to identify differentially expressed genes (DEGs). GO and KEGG pathway enrichment analyses of DEGs were performed with ClueGO. The protein–protein interaction (PPI) networks were constructed using Cytoscape software. A total of 4103 DEGs were identified; among them, 254 DEGs (63 up-regulated genes and 191 down-regulated genes) showed significant differences at p < 0.05. GO analysis showed that the identified DEGs were over-represented in 16 GO terms. KEGG pathway analysis showed that pathways in immune inflammation were significantly enriched pathways for DEGs. DEGs with relatively frequent interactions after CVS secondary to SAH included MIKI, Cmpk2, TIr3, Psmb9, Ddx58, Lgals9, Ifi44, Stat2, Rsad2, Oas2, Usp18, H28, Irf7 and als3bp. Multiple genes were involved in the regulation of the immune response in the pathogenesis of SAH, including Ripk3, Ifih1, IL10, Reg3g, SIc11a1, NF-κB, Tlr7, Parp9, Rab7b, Dhx58, Gpx2, Zbp1, Aim2, Rsad2, Lgals9, TLR4, Adar, Zc3hav1, KIrk1, Irf7, IL-1β, Trafd1, Ddx58 and Trim5. Our findings revealed the gene expression profiles of the cerebral arteries in SAH mouse models, and speculated that DHx58 gene plays an important role in the immune response through regulating inflammatory cytokines expression, which may be a potential target in the treatment of CVS after SAH. Our finding provided new clues for understanding the mechanism of SAH.

The Dynamics of Microglial Polarization Reveal the Resident Neuroinflammatory Responses After Subarachnoid Hemorrhage.

Neuroinflammation plays a critical role in the pathogenesis of subarachnoid hemorrhage (SAH). Microglia, as the resident immune cells, orchestrate neuroinflammation distinctly in neurological diseases with different polarization statuses. However, microglial polarizations in the neuroinflammatory responses after SAH are not fully understood. In this study, we investigated the dynamics of microglial reaction in an endovascular perforated SAH model. By using the Cx3cr1GFP/GFP Ccr2RFP/RFP transgenic mice, we found that the reactive immune cells were largely from resident microglia pool rather than infiltrating macrophages. Immunostaining and real-time PCR were employed to analyze the temporal microglial polarization and the resulting inflammatory responses. Our results showed that microglia accumulated immediately after SAH with a centrifugal spreading through the Cortex Adjacent to the Perforated Site (CAPS) to the remote motor cortex. Microglia polarized dynamically from M1 to M2 phenotype along with the morphological transformation from ramified to amoeboid shapes. The ramified microglia demonstrated the M1 property, which suggested the function-related microglial polarization occurred prior to morphological transformation after SAH. Bipolar-shaped microglia appeared as the intermediate and transitional status with the capacity of bidirectional polarization. The microglial polarization status is distinct in molecular inflammatory responses; M1-related pro-inflammation was predominant in the early phase and subsequently transited to the M2-related anti-inflammation. The systematic characterization of the dynamics of microglial polarization in this study contributes to the understanding of the origin of neuroinflammatory responses after SAH and provides key foundation for further investigations to develop target treatment.

Abstract TP336: Renal Denervation Reduces Cerebral Vasospasm After Subarachnoid Hemorrhage in Rats

Background and Purpose: Renal denervation (RD) was shown to have several organ protective effects via suppression of sympathetic nerve activation. As sympathetic nerve activation is involved in the pathogenesis of subarachnoid hemorrhage (SAH), RD can be a good candidate treatment to improve SAH prognosis. In this study, we hypothesized that RD reduced early brain injury and cerebral vasospasm (CVS) in SAH rats, both of which were major prognostic factors of SAH. Methods: Sprague-Dawley rats were divided into 3 groups: (1) Sham operation, (2) SAH+vehicle, and (3) SAH+RD. Bilateral RD were performed at 60 minutes after SAH induction. Twenty-four hours after SAH, we examined the effect of RD on the blood pressure (BP), neurologic score (NS), cerebral blood flow (CBF), brain water content (BWC),and diameter of basilar artery (BA). Then,the cytotoxic changesand sympathetic nerve activation were evaluatedby immunohistochemistry and western blot. Finally, serum angiotensin II which is one of the predictor of sympathetic nerve activation was measured by ELISA. Results: Although RD decreased elevated BP after SAH, the values of CBF were similar among the 3 groups. RD didn’t show significant improvement of NS and BWC, whereas it significantly prevented CVS. In BA, theexpression levels ofphosphorylated Extracellular Signal-regulated Kinase, Tumor Necrosis Factor-α, Matrix metalloproteinase-9, p22-phagocytic oxidase, and infiltration of macrophages were upregulated by SAH, but they were significantly reduced by RD. In the paraventricular nucleus (PVN) of hypothalamus which are one of the important nucleuses for sympathetic nerve activation, the increased expression of dopamine β-hydroxylase and reactive astrocytes by SAH were significantly suppressed by RD.Moreover,RD significantly decreased serum angiotensin II which were elevated after SAH. Conclusions: The present study demonstrated that RD reduced CVS after SAH and it may be came from suppression of sympathetic nerve activation.

Mesenchymal stem cells alleviate the early brain injury of subarachnoid hemorrhage partly by suppression of Notch1-dependent neuroinflammation: involvement of Botch

BackgroundActivated microglia-mediated neuroinflammation has been regarded as an underlying key player in the pathogenesis of subarachnoid hemorrhage (SAH)-induced early brain injury (EBI). The therapeutic potential of bone marrow mesenchymal stem cells (BMSCs) transplantation has been demonstrated in several brain injury models and is thought to involve modulation of the inflammatory response. The present study investigated the salutary effects of BMSCs on EBI after SAH and the potential mechanism mediated by Notch1 signaling pathway inhibition.MethodsThe Sprague-Dawley rats SAH model was induced by endovascular perforation method. BMSCs (3 × 106 cells) were transplanted intravenously into rats, and N-[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT), a Notch1 activation inhibitor, and Notch1 small interfering RNA (siRNA) were injected intracerebroventricularly. The effects of BMSCs on EBI were assayed by neurological score, brain water content (BWC), blood-brain barrier (BBB) permeability, magnetic resonance imaging, hematoxylin and eosin staining, and Fluoro-Jade C staining. Immunofluorescence and immunohistochemistry staining, Western blotting, and quantitative real-time polymerase chain reaction were used to analyze various proteins and transcript levels. Pro-inflammatory cytokines were measured by enzyme-linked immunosorbent assay.ResultsBMSCs treatment mitigated the neurobehavioral dysfunction, BWC and BBB disruption associated with EBI after SAH, reduced ionized calcium binding adapter molecule 1 and cluster of differentiation 68 staining and interleukin (IL)-1 beta, IL-6 and tumor necrosis factor alpha expression in the left hemisphere but concurrently increased IL-10 expression. DAPT or Notch1 siRNA administration reduced Notch1 signaling pathway activation following SAH, ameliorated neurobehavioral impairments, and BBB disruption; increased BWC and neuronal degeneration; and inhibited activation of microglia and production of pro-inflammatory factors. The augmentation of Notch1 signal pathway agents and phosphorylation of nuclear factor-κB after SAH were suppressed by BMSCs but the levels of Botch were upregulated in the ipsilateral hemisphere. Botch knockdown in BMSCs abrogated the protective effects of BMSCs treatment on EBI and the suppressive effects of BMSCs on Notch1 expression.ConclusionsBMSCs treatment alleviated neurobehavioral impairments and the inflammatory response in EBI after SAH; these effects may be attributed to Botch upregulation in brain tissue, which subsequently inhibited the Notch1 signaling pathway.

Blood Pressure and Risk of Subarachnoid Hemorrhage in China.

Background and Purpose—Subarachnoid hemorrhage (SAH) has a high case fatality rate and young mean age at onset compared with other types of stroke, but the pathogenesis of SAH is not fully understood. We examined associations of systolic and diastolic blood pressure with incident nontraumatic SAH in a large prospective study in China.Methods—In 2004 to 2008, 512 891 adults (59% women) from the general population were recruited into the CKB study (China Kadoorie Biobank). Participants were interviewed, measured, and followed up for fatal and nonfatal events. After excluding those with prior vascular disease, Cox regression analysis was used to relate blood pressure to incident SAH events. Analyses were adjusted for major confounders and corrected for regression dilution to give associations with long-term average blood pressure.Results—At baseline, mean age was 51 (SD, 11) years, and mean systolic blood pressure/diastolic blood pressure was 130.6/77.6 (SD, 21.0/11.1) mm Hg. During 3.5 million person-years of follow-up, there were 553 incident SAH cases (mean age at event, 61 [SD, 11] years), yielding an overall annual incidence rate of 12.9 per 100 000. Higher average levels of blood pressure were linearly and positively associated with higher risks of incident SAH: a 10 mm Hg higher systolic blood pressure and a 5 mm Hg higher diastolic blood pressure were associated with hazard ratios for SAH of 1.21 (95% CI, 1.13–1.29) and 1.20 (95% CI, 1.12–1.28), respectively. There was no evidence that the hazard ratios varied by age or sex or by levels of other vascular risk factors. Elevated blood pressure (systolic blood pressure, >120 mm Hg) accounted for 23% of all SAH cases.Conclusions—The incidence of SAH in China was comparable with estimates from Western populations. Higher levels of blood pressure were positively associated with higher risks of SAH, and elevated blood pressure accounted for about a quarter of all SAH cases.

The Role of Autophagy in Subarachnoid Hemorrhage: An Update.

Background: Autophagy is an extensive self-degradation process for the disposition of cytosolic aggregated or misfolded proteins and defective organelles which executes the functions of pro-survival and pro-death to maintain cellular homeostasis. The pathway plays essential roles in several neurological disorders. Subarachnoid Hemorrhage (SAH) is a devastating subtype of hemorrhagic stroke with high risk of neurological deficit and high mortality. Early brain injury (EBI) plays a role in the poor clinical course and outcome after SAH. Recent studies have paid attention on the role of the autopha-gy pathway in the development of EBI after SAH. We aim to update the multifaceted roles of autophagy pathway in the pathogenesis of SAH, especially in the phase of EBI.Methods: We reviewed early researches related to autophagy and SAH. The following three aspects of contents will be mainly discussed: the process of the autophagy pathway, the role of the autophagy in SAH and the interaction between organelle dysfunction and autophagy pathway after SAH.Results: Accumulating evidence shows an increased autophagy reaction in response to early stages of SAH. However, oth-ers suggest inadequate or excessive autophagy activation can result in cell injury and death. In addition to autophagy, apopto-sis and necrosis can occur in neurons simultaneously after SAH, leading to mixed features of cell death morphologies. And it is also known that there is extensive crosstalk between autophagy and apoptosis pathway. Subcellular organelles of neural cells generally participate in the formation and functional parts of autophagy process.Conclusion: Autophagy plays an important role in the SAH-induced brain injury. A better understanding of the interrelationship among autophagy, apoptosis, and necrosis might provide us better therapeutic targets for the treatment of SAH

Recombinant Netrin-1 binding UNC5B receptor attenuates neuroinflammation and brain injury via PPARγ/NFκB signaling pathway after subarachnoid hemorrhage in rats

Neuroinflammation is an essential mechanism involved in the pathogenesis of subarachnoid hemorrhage (SAH)-induced brain injury. Recently, Netrin-1 (NTN-1) is well established to exert anti-inflammatory property in non-nervous system diseases through inhibiting infiltration of neutrophil. The present study was designed to investigate the effects of NTN-1 on neuroinflammation, and the potential mechanism in a rat model of SAH. Two hundred and ninety-four male Sprague Dawley rats (weight 280–330 g) were subjected to the endovascular perforation model of SAH. Recombinant human NTN-1 (rh-NTN-1) was administered intravenously. Small interfering RNA (siRNA) of NTN-1 and UNC5B, and a selective PPARγ antagonist bisphenol A diglycidyl ether (BADGE) were applied. Post-SAH evaluations included neurobehavioral function, brain water content, Western blot analysis, and immunohistochemistry. Our results showed that endogenous NTN-1 and its receptor UNC5B level were increased after SAH. Administration of rh-NTN-1 reduced brain edema, ameliorated neurological impairments, and suppressed microglia activation after SAH, which were concomitant with PPARγ activation, inhibition of NFκB, and decrease in TNF-α, IL-6, and ICAM-1, as well as myeloperoxidase (MPO). Knockdown of endogenous NTN-1 increased expression of pro-inflammatory mediators and MPO, and aggravated neuroinflammation and brain edema. Moreover, knockdown of UNC5B using specific siRNA and inhibition of PPARγ with BADGE blocked the protective effects of rh-NTN-1. In conclusion, our findings indicated that exogenous rh-NTN-1 treatment attenuated neuroinflammation and neurological impairments through inhibiting microglia activation after SAH in rats, which is possibly mediated by UNC5B/PPARγ/NFκB signaling pathway. Exogenous NTN-1 may be a novel therapeutic agent to ameliorating early brain injury via its anti-inflammation effect.

Role of glucose-regulated protein 78 in early brain injury after experimental subarachnoid hemorrhage in rats.

Early brain injury (EBI) plays a key role in the pathogenesis of subarachnoid hemorrhage (SAH). This study investigated the role of glucose-regulated protein 78 (GRP78) in EBI after SAH. Male Sprague-Dawley rats (n=108) weighing 260±40 g were divided into control, sham-operated, and operated groups. Blood was injected into the prechiasmatic cistern of rats in the operated group. Neurological scores, ultrastructures of neurons, apoptosis, and GRP78 expression in the hippocampus were examined using Garcia scoring system, transmission electron microscopy, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling, and Western blotting at 1, 6, 12, 24, 48, and 72 h after SAH, respectively. The results showed that neurological scores were significantly decreased in the operated group as compared with those in control and sham-operated groups at 12, 24, 48, and 72 h. Metachromatin, chromatin pyknosis at the edge, endoplasmic reticulum swelling, and invagination of nuclear membrane were observed at 24 h in the operated group, indicating the early morphological changes of apoptosis. The number of apoptotic cells was significantly increased in the operated group as compared with that in control and sham-operated groups at 6, 12, 24, 48, and 72 h. The GRP78 protein expression levels in the operated group were significantly elevated at all time points and reached the peak at 12 h. GRP78 expression was positively associated with apoptosis cells and negatively with neurological scores. In conclusion, EBI was demonstrated to occur after SAH and GRP78 was involved in the development of EBI after SAH.