The role of immune inflammation in aneurysmal subarachnoid hemorrhage

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.

All Three Supersystems-Nervous, Vascular, and Immune-Contribute to the Cortical Infarcts After Subarachnoid Hemorrhage

The recently published DISCHARGE-1 trial supports the observations of earlier autopsy and neuroimaging studies that almost 70% of all focal brain damage after aneurysmal subarachnoid hemorrhage are anemic infarcts of the cortex, often also affecting the white matter immediately below. The infarcts are not limited by the usual vascular territories. About two-fifths of the ischemic damage occurs within ~ 48 h; the remaining three-fifths are delayed (within ~ 3 weeks). Using neuromonitoring technology in combination with longitudinal neuroimaging, the entire sequence of both early and delayed cortical infarct development after subarachnoid hemorrhage has recently been recorded in patients. Characteristically, cortical infarcts are caused by acute severe vasospastic events, so-called spreading ischemia, triggered by spontaneously occurring spreading depolarization. In locations where a spreading depolarization passes through, cerebral blood flow can drastically drop within a few seconds and remain suppressed for minutes or even hours, often followed by high-amplitude, sustained hyperemia. In spreading depolarization, neurons lead the event, and the other cells of the neurovascular unit (endothelium, vascular smooth muscle, pericytes, astrocytes, microglia, oligodendrocytes) follow. However, dysregulation in cells of all three supersystems-nervous, vascular, and immune-is very likely involved in the dysfunction of the neurovascular unit underlying spreading ischemia. It is assumed that subarachnoid blood, which lies directly on the cortex and enters the parenchyma via glymphatic channels, triggers these dysregulations. This review discusses the neuroglial, neurovascular, and neuroimmunological dysregulations in the context of spreading depolarization and spreading ischemia as critical elements in the pathogenesis of cortical infarcts after subarachnoid hemorrhage.

Taurine ameliorates sensorimotor function by inhibiting apoptosis and activating A2 astrocytes in mice after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a form of severe acute stroke with very high mortality and disability rates. Early brain injury (EBI) and delayed cerebral ischemia (DCI) contribute to the poor prognosis of patients with SAH. Currently, some researchers have started to focus on changes in amino acid metabolism that occur in brain tissues after SAH. Taurine is a sulfur-containing amino acid that is semi-essential in animals, and it plays important roles in various processes, such as neurodevelopment, osmotic pressure regulation, and membrane stabilization. In acute stroke, such as cerebral hemorrhage, taurine plays a neuroprotective role. However, the role of taurine after subarachnoid hemorrhage has rarely been reported. In the present study, we established a mouse model of SAH. We found that taurine administration effectively improved the sensorimotor function of these mice. In addition, taurine treatment alleviated sensorimotor neuron damage and reduced the proportion of apoptotic cells. Furthermore, taurine treatment enhanced the polarization of astrocytes toward the neuroprotective phenotype while inhibiting their polarization toward the neurotoxic phenotype. This study is the first to reveal the relationship between taurine and astrocyte polarization and may provide a new strategy for SAH research and clinical treatment.

Clinical value of serum complement component 1q levels in the prognostic analysis of aneurysmal subarachnoid hemorrhage: a prospective cohort study

Objective

To analyze the relationship between serum complement component 1q (C1q) levels and functional prognosis in patients with aneurysmal subarachnoid hemorrhage (aSAH), and to reveal its clinical value.

Methods

In this prospective cohort study, we collected clinical data of aSAH patients admitted to the Department of Neurosurgery, Hangzhou First People's Hospital from January 2020 to October 2022. Parameters such as serum C1q levels, Hunt-Hess grade, modified Fisher grade, and the modified Rankin scale (mRS) at 3 months were included for evaluation. Patients were grouped based on the occurrence of delayed cerebral ischemia (DCI). Spearman rank correlation test and Kruskal-Wallis rank sum test were used to analyze the correlation between serum C1q levels, disease severity, and prognosis. Potential risk factors affecting prognosis and the occurrence of DCI were screened through Independent sample t-test or Mann-Whitney U test. Variables with significant differences (p < 0.05) were incorporated into a logistic regression model to identify independent risk factors affecting prognosis and DCI occurrence. Serum C1q levels were plotted as a ROC curve for predicting prognosis and DCI, and the area under the curve was calculated.

Results

A total of 107 aSAH patients were analyzed. Serum C1q levels positively correlated with Hunt-Hess grade, modified Fisher grade and mRS (all p < 0.001). Significant differences were observed in C1q levels among different Hunt-Hess grade, mFisher grade and mRS (all p < 0.001). Notably, higher serum C1q levels were seen in the poor prognosis group and DCI group, and correlated with worse prognosis (OR = 36.927, 95%CI 2.003-680.711, p = 0.015), and an increased risk for DCI (OR = 17.334, 95%CI 1.161-258.859, p = 0.039). ROC analysis revealed the significant discriminative power of serum C1q levels for poor prognosis (AUC 0.781; 95%CI 0.673-0.888; p < 0.001) and DCI occurrence (AUC 0.763; 95%CI 0.637-0.888; p < 0.001). Higher C1q levels independently predicted a poor prognosis and DCI with equivalent predictive abilities to Hunt-Hess grade and modified Fisher grade (both p < 0.05).

Conclusion

High levels of C1q in the blood is an independent risk factor for poor prognosis and the development of DCI in patients with aSAH. This can more objectively and accurately predict functional outcomes and the incidence of DCI. C1q may have a significant role in the mechanism behind DCI after aSAH.

Schizandrin A attenuates early brain injury following subarachnoid hemorrhage through suppressing neuroinflammation

BACKGROUND

Early brain injury (EBI) is the vital factor in determining the outcome of subarachnoid hemorrhage (SAH). Schizandrin A (Sch A), the bioactive ingredient extracted from Schisandra chinensis, has been proved to exert beneficial effects in multiple human diseases. However, the effect of Sch A on SAH remains unknown. The current study was designed to explored role and mechanism of Sch A in the pathophysiological process of EBI following SAH.

METHOD

A total of 74 male C57BL/6 J mice were subjected to endovascular perforation to establish the SAH model. Different dosages of Sch A were administrated post-modeling. The post-modeling assessments included neurological test, brain water content, RT-PCR, immunofluorescence, Nissl staining. Oxygenated hemoglobin was introduced into microglia to establish a SAH model in vitro.

RESULT

Sch A significantly alleviated SAH-induced brain edema and neurological impairment. Moreover, application of Sch A remarkably inhibited SAH-induced neuroinflammation, evidenced by the decreased microglial activation and downregulated TNF-α, IL-1β and IL-6 and expression. Additionally, Sch A, both in vivo and in vitro, protected neurons against SAH-induced inflammatory injury. Mechanismly, administration of Sch A inhibited miR-155/NF-κB axis and attenuated neuroinflammation, as well as alleviating neuronal injury.

CONCLUSION

Our data suggested that Sch A could attenuated EBI following SAH via modulating neuroinflammation. The anti-inflammatory effect was exerted, at least partly through the miR-155/NF-κB axis, which may shed light on a possible therapeutic target for SAH.

Safety and pharmacodynamic efficacy of eculizumab in aneurysmal subarachnoid hemorrhage (CLASH): A phase 2a randomized clinical trial

INTRODUCTION

Complement C5 antibodies reduce brain injury after experimental subarachnoid hemorrhage.

PATIENTS AND METHODS

In this randomized, controlled, open-label, phase 2a clinical trial with blinded-outcome assessment, we included adult aneurysmal subarachnoid hemorrhage (aSAH) patients admitted to a tertiary referral center ⩽11 h after ictus. Patients were randomized (1:1) to eculizumab plus care as usual or to care as usual. Eculizumab (1200 mg) was administered <12 h, and on days 3 and 7 after ictus. In the intervention group, all patients received prophylactic antibiotics and, after a protocol amendment, fluconazole if indicated. Primary outcome was C5a concentration in cerebrospinal fluid (CSF) on day 3 after ictus. Safety was monitored during 4 weeks. In each group, 13 patients with CSF assessments were needed to detect a 55% reduction in CSF C5a concentration.

RESULTS

From October 2018 to May 2021, we enrolled 31 patients of whom 26 with CSF samples, 13 per group. Median C5a concentration in CSF on day 3 was 251 pg/ml [IQR: 103-402] in the intervention group and 371 pg/ml [IQR: 131-534] in the control group (p = 0.29). Infections occurred in two patients in the intervention group and four patients in the control group. One patient in the intervention group developed a C. albicans meningitis prior to the protocol amendment.

DISCUSSION AND CONCLUSION

One dose of eculizumab did not result in a ⩾ 55% decrease in C5a concentration in CSF on day 3 after aSAH. The study did not reveal new safety concerns, except for a C. albicans drain-related infection prior to antifungal monitoring and treatment.

TRIAL REGISTRATION

EudraCT 2017-004307-51, https://www.clinicaltrialsregister.eu/.

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.

Predicting the Outcome of Patients with Aneurysmal Subarachnoid Hemorrhage: A Machine-Learning-Guided Scorecard

Aneurysmal subarachnoid hemorrhage (aSAH) frequently causes long-term disability, but predicting outcomes remains challenging. Routine parameters such as demographics, admission status, CT findings, and blood tests can be used to predict aSAH outcomes. The aim of this study was to compare the performance of traditional logistic regression with several machine learning algorithms using readily available indicators and to generate a practical prognostic scorecard based on machine learning. Eighteen routinely available indicators were collected as outcome predictors for individuals with aSAH. Logistic regression (LR), random forest (RF), support vector machines (SVMs), and fully connected neural networks (FCNNs) were compared. A scorecard system was established based on predictor weights. The results show that machine learning models and a scorecard achieved 0.75~0.8 area under the curve (AUC) predicting aSAH outcomes (LR 0.739, RF 0.749, SVM 0.762~0.793, scorecard 0.794). FCNNs performed best (~0.95) but lacked interpretability. The scorecard model used only five factors, generating a clinically useful tool with a total cutoff score of ≥5, indicating poor prognosis. We developed and validated machine learning models proven to predict outcomes more accurately in individuals with aSAH. The parameters found to be the most strongly predictive of outcomes were NLR, lymphocyte count, monocyte count, hypertension status, and SEBES. The scorecard system provides a simplified means of applying predictive analytics at the bedside using a few key indicators.

A dynamic online nomogram for predicting death in hospital after aneurysmal subarachnoid hemorrhage

BACKGROUND

This study aimed to validate the efficacy the multiplication of neutrophils and monocytes (MNM) and a novel dynamic nomogram for predicting in-hospital death in patients with aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

Retrospective study was done on 986 patients with endovascular coiling for aSAH. Independent risk factors associated with in-hospital death were identified using both univariate and multivariate logistic regression analysis. In the development cohort, a dynamic nomogram of in-hospital deaths was introduced and made available online as a straightforward calculator. To predict the in-hospital death from the external validation cohort by nomogram, calibration analysis, decision curve analysis, and receiver operating characteristic analysis were carried out.

RESULTS

72/687 patients (10.5%) in the development cohort and 31/299 patients (10.4%) in the validation cohort died. MNM was linked to in-hospital death in univariate and multivariate regression studies. In the development cohort, a unique nomogram demonstrated a high prediction ability for in-hospital death. According to the calibration curves, the nomogram has a reliable degree of consistency and calibration. With threshold probabilities between 10% and 90%, the nomogram's net benefit was superior to the basic model. The MNM and nomogram also exhibited good predictive values for in-hospital death in the validation cohort.

CONCLUSIONS

MNM is a novel predictor of in-hospital mortality in patients with aSAH. For aSAH patients, a dynamic nomogram is a useful technique for predicting in-hospital death.

Inflammatory Burden Index: Association Between Novel Systemic Inflammatory Biomarkers and Prognosis as Well as in-Hospital Complications of Patients with Aneurysmal Subarachnoid Hemorrhage

Purpose

Systemic inflammation plays an important role in the pathophysiology and progression of aneurysmal subarachnoid hemorrhage (aSAH). In this study, we aimed to investigate the association between a new biomarker, the inflammatory burden index (IBI) and the prognosis as well as in-hospital complications of aSAH patients.

Patients and Methods

We analyzed data from patients with aSAH between January 2019 and September 2022 who were included in the LongTEAM (Long-term Prognosis of Emergency Aneurysmal Subarachnoid Hemorrhage) registry study. The IBI was formulated as C-reactive protein × neutrophils/lymphocytes. The unfavorable functional prognosis was assessed by the modified Rankin Scale (mRS). Receiver operating characteristic (ROC) curve analysis was conducted to determine the optimal cut-off values for IBI to distinguish the unfavorable functional prognosis. Multivariate logistic regression was applied to investigate the association between IBI and in-hospital complications. Propensity score matching was adjusted for imbalances in baseline characteristics to assess the effect of IBI on prognosis.

Results

A total of 408 consecutive patients with aSAH enrolled in the study, of which 235 (57.6%) were female patients and the mean age was 55.28 years old. An IBI equal to 138.03 was identified as the best cut-off threshold to distinguish the unfavorable prognosis at 3 months (area under the curve [AUC] [95% CI] 0.637 [0.568-0.706]). ln IBI was independently associated with 3-month functional prognosis (OR [95% CI] 1.362 [1.148-1.615]; P<0.001), pneumonia (OR [95% CI] 1.427 [1.227-1.659]; P<0.001) and deep venous thrombosis (DVT). (OR [95% CI] 1.326 [1.124-1.564]; P=0.001). After propensity score matching (57:57), an increased proportion of patients with IBI ≥138.03 had a poor functional prognosis at 3 months and in-hospital complications including developed pneumonia and DVT.

Conclusion

In patients with aSAH, high IBI level at admission was associated with unfavorable functional prognosis as well as pneumonia and deep vein thrombosis.

Controlling nutritional status score during hospitalization as a predictor of clinical outcome in patients with aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a serious condition with high mortality and a high permanent disability rate. In this study, we examined the association of clinical outcome with the Controlling Nutritional Status (CONUT) score during hospitalization in aSAH patients. A single-center, retrospective observational study was conducted at Gifu University Hospital. Patients transported to the emergency room for aSAH and diagnosed with World Federation of Neurosurgical Societies (WFNS) grade III and IV aSAH between April 2004 and March 2021 were enrolled. A logistic regression model was constructed to evaluate the association of the CONUT score with a modified Rankin scale (mRS) ≥ 3 and delayed cerebral ischemia (DCI). 127 patients diagnosed with WFNS grade III and IV aSAH were analyzed. CONUT score was significantly associated with mRS ≥ 3 during hospitalization. The score obtained by subtracting the CONUT score at admission from the maximum CONUT score was significantly associated with mRS ≥ 3 at discharge. Moreover, the score obtained by subtracting the CONUT score at admission from the maximum CONUT score during the first 14 days was significantly associated with DCI within 14 days from admission. These findings indicate that CONUT score during hospitalization may be a useful daily marker for predicting poor outcomes in aSAH patients.

Salvianolic acid B ameliorates neuroinflammation and neuronal injury via blocking NLRP3 inflammasome and promoting SIRT1 in experimental subarachnoid hemorrhage

The nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated immuno-inflammatory response plays a critical role in exacerbating early brain injury (EBI) after subarachnoid hemorrhage (SAH). Salvianolic acid B (SalB) has previously been shown to suppress neuroinflammatory responses in many disorders. Meanwhile, a previous study has demonstrated that SalB mitigated oxidative damage and neuronal degeneration in a prechiasmatic injection model of SAH. However, the therapeutic potential of SalB on immuno-inflammatory responses after SAH remains unclear. In the present study, we explored the therapeutic effects of SalB on neuroinflammatory responses in an endovascular perforation SAH model. We observed that SalB ameliorated SAH-induced functional deficits. Additionally, SalB significantly mitigated microglial activation, pro-inflammatory cytokines release, and neuronal injury. Mechanistically, SalB inhibited NLRP3 inflammasome activation and increased sirtuin 1 (SIRT1) expression after SAH. Administration of EX527, an inhibitor of SIRT1, abrogated the anti-inflammatory effects of SalB against SAH and further induced NLRP3 inflammasome activation. In contrast, MCC950, a potent and selective NLRP3 inflammasome inhibitor, reversed the detrimental effects of SIRT1 inhibition by EX527 on EBI. These results indicated that SalB effectively repressed neuroinflammatory responses and neuronal damage after SAH. The action of SalB appeared to be mediated by blocking NLRP3 inflammasome and promoting SIRT1 signaling.

The Critical Role of Sirt1 in Subarachnoid Hemorrhages: Mechanism and Therapeutic Considerations

The subarachnoid hemorrhage (SAH) is an important cause of death and long-term disability worldwide. As a nicotinamide adenine dinucleotide-dependent deacetylase, silent information regulator 1 (Sirt1) is a multipotent molecule involved in many pathophysiological processes. A growing number of studies have demonstrated that Sirt1 activation may exert positive effects on SAHs by regulating inflammation, oxidative stress, apoptosis, autophagy, and ferroptosis. Thus, Sirt1 agonists may serve as potential therapeutic drugs for SAHs. In this review, we summarized the current state of our knowledge on the relationship between Sirt1 and SAHs and provided an updated overview of the downstream molecules of Sirt1 in SAHs.

Identification of immune-related molecular markers in intracranial aneurysm (IA) based on machine learning and cytoscape-cytohubba plug-in

BACKGROUND

Intracranial aneurysm (IA) is a common cerebrovascular disease. The immune mechanism of IA is more complicated, and it is unclear so far. Therefore, it is necessary to continue to explore the immune related molecular mechanism of IA.

METHODS

All data were downloaded from the public database. Limma package and ssGSEA algorithm was used to identify differentially expressed mRNAs (DEmRNAs) and analyze immune cell infiltration, respectively. Machine learning and cytoscape-cytohubba plug-in was used to identify key immune types and multicentric DEmRNAs of IA, respectively. Multicentric DEmRNAs related to key immune cells were screened out as key DEmRNAs by Spearman correlation analysis. Diagnostic models, competing endogenous RNA (ceRNA) regulatory network and transcription factor regulatory network were constructed based on key DEmRNAs. Meanwhile, drugs related to key DEmRNAs were screened out based on DGIdb database. The expression of key DEmRNAs was also verified by real time-PCR.

RESULTS

In this study, 7 key DEmRNAs (NRXN1, GRIA2, SLC1A2, SLC17A7, IL6, VEGFA and SYP) associated with key differential immune cell infiltration (CD56bright natural killer cell, Immature B cell and Type 1 T helper cell) were identified. Functional enrichment analysis showed that VEGFA and IL6 may be involved in the regulation of the PI3K-Akt signaling pathway. Moreover, IL6 was also found to be enriched in cytokine-cytokine receptor interaction signaling pathway. In the ceRNA regulatory network, a large number of miRNAs and lncRNAs were found. In the transcription factor regulatory network, the transcription factor SP1 was correlated with VEGFA, SYP and IL6. It is also predicted that drugs related to key DEmRNAs such as CARBOPLATIN, FENTANYL and CILOSTAZOL may contribute to the treatment of IA. In addition, it was also found that SVM and RF models based on key DEmRNAs may be potential markers for diagnosing IA and unruptured intracranial aneurysm (UIA), respectively. The expression trend of key DEmRNAs verified by real-time PCR was consistent with the bioinformatics analysis results.

CONCLUSION

The identification of molecules and pathways in this study provides a theoretical basis for understanding the immune related molecular mechanism of IA. Meanwhile, the drug prediction and diagnosis model construction may also be helpful for clinical diagnosis and management.

Construction and Verification of a Risk Prediction Model for the Occurrence of Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage Requiring Mechanical Ventilation

Objectives

Delayed cerebral ischemia (DCI) contributes to poor aneurysm prognosis. Subarachnoid hemorrhage and DCI have irreversible and severe consequences once they occur; therefore, early prediction and prevention are important. We investigated the risk factors for postoperative complications of DCI in patients with aneurysmal subarachnoid hemorrhage (aSAH) requiring mechanical ventilation in intensive care and validated a prediction model.

Methods

We retrospectively analyzed patients with aSAH who were treated in a French university hospital neuro-ICU between January 2010 and December 2015. The patients were randomized into a training group (144) and verification groups (60). Nomograms were validated in the training and verification groups, where receiver operating characteristic curve analysis was used to verify model discrimination; calibration curve and Hosmer-Lemeshow test were used to determine model calibration; and decision curve analysis (DCA) was used to verify clinical validity of the model.

Results

External ventricular drain (EVD), duration of mechanical ventilation, and treatment were significantly associated in the univariate analysis; EVD and rebleeding were significantly associated with the occurrence of DCI after aSAH. Binary logistic regression was used to select five clinicopathological characteristics to predict the occurrence of DCI in patients with aSAH requiring mechanical ventilation nomograms of the risk of DCI. Area under the curve values for the training and verification groups were 0.768 and 0.246, with Brier scores of 0.166 and 0.163, respectively. Hosmer-Lemeshow calibration test values for the training and verification groups were x ² = 3.824 (P = 0.923) and x ² = 10.868 (P = 0.285), respectively. Calibration curves showed good agreement. DCA indicated that the training and verification groups showed large positive returns in the broad risk range of 0-77% and 0-63%, respectively.

Conclusions

The predictive model of concurrent DCI in aSAH has theoretical and practical values and can provide individualized treatment options for patients with aSAH who require mechanical ventilation.

Inhibition of CCR2 attenuates neuroinflammation and neuronal apoptosis after subarachnoid hemorrhage through the PI3K/Akt pathway

BACKGROUND

Neuroinflammation and neuronal apoptosis are closely associated with a poor prognosis in patients with subarachnoid hemorrhage (SAH). We investigated the role of C-C motif chemokine receptor 2 (CCR2) in SAH.

METHODS

Pre-processed RNA-seq transcriptome datasets GSE167110 and GSE79416 from the Gene Expression Omnibus (GEO) database were screened for genes differentially expressed between mice with SAH and control mice, using bioinformatics analysis. The endovascular perforation model was performed to establish SAH. RS504393 (a CCR2 antagonist) and LY294002 (PI3K inhibitor) were administered to explore the mechanism of neuroinflammation after SAH. SAH grading, neurological scoring, brain water content and blood-brain barrier (BBB) permeability determination, enzyme-linked immunosorbent assay (ELISA), western blotting, and immunofluorescence were performed. An in vitro model of SAH was induced in H22 cells by hemin treatment. The protective mechanism of CCR2 inhibition was studied by adding RS504393 and LY294002. Clinical cerebrospinal fluid (CST) samples were detected by ELISA.

RESULTS

Expression of CCR2 was upregulated in both datasets and was identified as a hub gene. CCR2 expression was significantly upregulated in the cytoplasm of neurons after SAH, both in vitro and in vivo. RS significantly reduced the brain water content and blood-brain barrier permeability, alleviated neuroinflammation, and reduced neuronal apoptosis after SAH. Additionally, the protective effects of CCR2 inhibition were abolished by LY treatment. Finally, the levels of CCR2, inflammatory factors, and apoptotic factors were elevated in the CSF of patients with SAH. CCR2 levels were associated with patient outcomes at the 6-month follow-up.

CONCLUSION

CCR2 expression was upregulated in both in vitro and in vivo SAH models. Additionally, inhibition of CCR2, at least partly through the PI3K/AKT pathway, alleviated neuroinflammation and neuronal apoptosis in vivo and in vitro. CCR2 levels in the CSF have a moderate diagnostic value for 6-month outcome prediction in patients with SAH.

Subarachnoid hemorrhage triggers neuroinflammation of the entire cerebral cortex, leading to neuronal cell death

BACKGROUND

Subarachnoid hemorrhage (SAH) is a fatal disease, with early brain injury (EBI) occurring within 72 h of SAH injury contributes to its poor prognosis. EBI is a complicated phenomenon involving multiple mechanisms. Although neuroinflammation has been shown to be important prognosis factor of EBI, whether neuroinflammation spreads throughout the cerebrum and the extent of its depth in the cerebral cortex remain unknown. Knowing how inflammation spreads throughout the cerebrum is also important to determine if anti-inflammatory agents are a future therapeutic strategy for EBI.

METHODS

In this study, we induced SAH in mice by injecting hematoma into prechiasmatic cistern and created models of mild to severe SAH. In sections of the mouse cerebrum, we investigated neuroinflammation and neuronal cell death in the cortex distal to the hematoma injection site, from anterior to posterior region 24 h after SAH injury.

RESULTS

Neuroinflammation caused by SAH spread to all layers of the cerebral cortex from the anterior to the posterior part of the cerebrum via the invasion of activated microglia, and neuronal cell death increased in correlation with neuroinflammation. This trend increased with the severity of the disease.

CONCLUSIONS

Neuroinflammation caused by SAH had spread throughout the cerebrum, causing neuronal cell death. Considering that the cerebral cortex is responsible for long-term memory and movement, suppressing neuroinflammation in all layers of the cerebral cortex may improve the prognosis of patients with SAH.

Comprehensive analysis of immune cell infiltration and role of MSR1 expression in aneurysmal subarachnoid haemorrhage

Aneurysmal subarachnoid haemorrhage (aSAH), resulting from the rupture of intracranial aneurysms, can yield high mortality and disability. This study aimed to explore the immune infiltration of aneurysmal tissues and investigate a novel mechanism underlying aSAH. We downloaded datasets containing expression profiles of aneurysmal and normal arterial tissues from the online database. Then a comprehensive bioinformatic strategy was conducted to select the biomarkers of aneurysmal tissues. Two calculation algorithms were performed to identify the unique immune characteristics between aneurysmal tissues and normal arteries. Double immunofluorescence staining was used to investigate the role of pathway-related proteins in the inflammatory process after aSAH. Six microarray datasets were integrated, and another RNA-sequencing dataset was used as the validation dataset. Functional enrichment analysis of the differentially expressed genes indicated that immune-related processes were closely related to the progression of aSAH. We then performed immune microenvironment infiltration analysis, and the results suggested macrophages were abnormally enriched in aneurysmal tissues. Core gene MSR1 was filtered through a comprehensive bioinformatic strategy. Our analysis suggested that MSR1 might be associated with macrophage activation and migration. Our study elucidated the impact of macrophage and MSR1 on aSAH progression. These findings were helpful in gaining insight into the immune heterogeneity of aneurysmal tissues and normal arteries, and in identifying patients who might benefit from immunotherapy.

Progress in Research on TLR4-Mediated Inflammatory Response Mechanisms in Brain Injury after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is one of the common clinical neurological emergencies. Its incidence accounts for about 5-9% of cerebral stroke patients. Even surviving patients often suffer from severe adverse prognoses such as hemiplegia, aphasia, cognitive dysfunction and even death. Inflammatory response plays an important role during early nerve injury in SAH. Toll-like receptors (TLRs), pattern recognition receptors, are important components of the body's innate immune system, and they are usually activated by damage-associated molecular pattern molecules. Studies have shown that with TLR 4 as an essential member of the TLRs family, the inflammatory transduction pathway mediated by it plays a vital role in brain injury after SAH. After SAH occurrence, large amounts of blood enter the subarachnoid space. This can produce massive damage-associated molecular pattern molecules that bind to TLR4, which activates inflammatory response and causes early brain injury, thus resulting in serious adverse prognoses. In this paper, the process in research on TLR4-mediated inflammatory response mechanism in brain injury after SAH was reviewed to provide a new thought for clinical treatment.

Inflammation and immune cell abnormalities in intracranial aneurysm subarachnoid hemorrhage (SAH): Relevant signaling pathways and therapeutic strategies

Intracranial aneurysm subarachnoid hemorrhage (SAH) is a cerebrovascular disorder associated with high overall mortality. Currently, the underlying mechanisms of pathological reaction after aneurysm rupture are still unclear, especially in the immune microenvironment, inflammation, and relevant signaling pathways. SAH-induced immune cell population alteration, immune inflammatory signaling pathway activation, and active substance generation are associated with pro-inflammatory cytokines, immunosuppression, and brain injury. Crosstalk between immune disorders and hyperactivation of inflammatory signals aggravated the devastating consequences of brain injury and cerebral vasospasm and increased the risk of infection. In this review, we discussed the role of inflammation and immune cell responses in the occurrence and development of aneurysm SAH, as well as the most relevant immune inflammatory signaling pathways [PI3K/Akt, extracellular signal-regulated kinase (ERK), hypoxia-inducible factor-1α (HIF-1α), STAT, SIRT, mammalian target of rapamycin (mTOR), NLRP3, TLR4/nuclear factor-κB (NF-κB), and Keap1/nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/ARE cascades] and biomarkers in aneurysm SAH. In addition, we also summarized potential therapeutic drugs targeting the aneurysm SAH immune inflammatory responses, such as nimodipine, dexmedetomidine (DEX), fingolimod, and genomic variation-related aneurysm prophylactic agent sunitinib. The intervention of immune inflammatory responses and immune microenvironment significantly reduces the secondary brain injury, thereby improving the prognosis of patients admitted to SAH. Future studies should focus on exploring potential immune inflammatory mechanisms and developing additional therapeutic strategies for precise aneurysm SAH immune inflammatory regulation and genomic variants associated with aneurysm formation.

Elevated Serum CCL23 Levels at Admission Predict Delayed Cerebral Ischemia and Functional Outcome after Aneurysmal Subarachnoid Hemorrhage

(1) Background: CC chemokine ligand 23 (CCL23) is a chemokine implicated in the inflammatory response following brain damage. The aim of this study is to identify the change in serum CCL23 levels within 24 h after aSAH and whether serum CCL23 levels are associated with initial clinical severity, delayed cerebral ischemia (DCI), and functional outcome in patients with aneurysmal subarachnoid hemorrhage (aSAH). (2) Methods: 102 patients with aSAH and 61 controls were included in this prospective observational study. All clinical data were collected prospectively, and their serum CCL23 levels were measured. Initial clinical severity was reflected by the Hunt-Hess score and mFisher score. Functional outcome was evaluated in terms of the Glasgow Outcome Scale (GOS) score at 6-month follow-up. (3) Results: Patients with aSAH had higher serum CCL23 levels than controls. The temporal profile of serum CCL23 levels and neutrophils count exhibited a sustained increase within 24 h after aSAH. Serum CCL23 levels were related to blood neutrophils count, blood CRP levels, and initial clinical severity. Serum CCL23 level was an independent predictor of DCI and 6-month poor outcome in aSAH patients. (4) Conclusions: Serum CCL23 levels emerged as an independent predictor for DCI and poor outcome in patients with aSAH.

Systemic Inflammatory Response in Spontaneous Subarachnoid Hemorrhage from Aneurysmal Rupture versus Subarachnoid Hemorrhage of Unknown Origin

OBJECTIVE

It is well known that spontaneous non-aneurysmal subarachnoid hemorrhage (SAH), also known as sine materia SAH (smSAH), has usually a better course and prognosis than its aneurysmal counterpart (aSAH). This might depend on different inflammatory mechanisms initiated by bleeding events of different origins. The aim of the present study was to explore the systemic inflammatory response in spontaneous SAH, comparing aSAH and smSAH.

METHODS

We performed a prospective observational study over a consecutive series of patients with SAH. For these patients, we collected all clinical data and, furthermore, performed venous blood sampling over six time points to analyze blood cells. We further performed the analysis of lymphocytes and monocytes by means of flow cytometry to quantify common subtypes. Statistical analysis included a t-student test, Chi-square test, multivariate logistic regression, and ROC analysis.

RESULTS

48 patients were included: six (12.5%) with a diagnosis of spontaneous smSAH, and forty-two patients (87.5%) with aSAH. Significant differences on Day 0 were found for neutrophils and a systemic neuro-inflammatory index, namely, systemic inflammatory response index (SIRI). At the ROC analysis, neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and SIRI exhibited satisfactory predictive power on day 0. At the multivariable logistic regression analysis, the combined index (NLR, LMR, SIRI at day 0) yielded an OR of 0.59 (95% CI 0.29-1.21]). LMR at day 0 yielded an OR of 1.25 ([95% CI 0.94-1.68]), NLR at day 0 exhibited an OR of 0.68 ([95% CI 0.42-1.09]), and SIRI at day 0 displayed an OR of 0.31 ([95% CI 0.06-1.49]).

CONCLUSION

This preliminary study indicated a possible role of some inflammatory indices that point out the importance of innate and adaptive immunity in the etiopathogenetic mechanisms. Drugs modulating these responses could eventually counteract or, at least, reduce secondary damage associated with SAH.

Effect of early stellate ganglion block in cerebral vasospasm after aneurysmal subarachnoid hemorrhage (BLOCK-CVS): study protocol for a randomized controlled trial

Introduction

Stellate ganglion block has been reported to expand cerebral vessels and alleviate vasospasm after aneurysmal subarachnoid hemorrhage. However, the causal relationship between early stellate ganglion block and cerebral vasospasm prevention has not yet been established. The purpose of this study was to explore the effectiveness and safety of early stellate ganglion block as a preventive treatment for cerebral vasospasm and delayed cerebral ischemia.

Methods/design

This is a single-center, prospective, randomized, controlled, blinded endpoint assessment superiority trial. A total of 228 patients will be randomized within 48 h of aneurysmal subarachnoid hemorrhage onset in a 1:1 ratio into two groups, one group receiving an additional e-SGB and the other group receiving only a camouflaging action before anesthesia induction in the operating room. The primary outcome is the incidence of symptomatic vasospasm within 14 days after aSAH. Further safety and efficacy parameters include the incidence of radiographic vasospasm, new cerebral infarction, postoperative delirium, and complications up to 90 days after surgery; postoperative cerebral hemodynamics; Mini-Mental State Examination score; modified Rankin scale score; and all-cause mortality up to 90 days after surgery.

Discussion

This is a randomized controlled trial to explore the effectiveness and safety of early stellate ganglion block as a preventive treatment to reduce cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage. If the results are positive, it may provide a new direction for the prevention and treatment of cerebral vasospasm and delayed cerebral ischemia.

Trial registration

The study was registered on Clincaltrials.gov on December 13, 2020 (NCT04691271).

Identification of the key immune-related genes in aneurysmal subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a major cause of death and morbidity worldwide, often due to rupture of intracranial aneurysms (IAs). Immune infiltration and inflammatory activation play key roles in the process of aneurysmal SAH (aSAH). This study aimed to elaborate the immune infiltration and identify related biomarkers both in blood and tissue samples from patients with aSAH. Expression data of aSAH and healthy control samples were obtained from gene expression omnibus (GEO) database. Overall, a blood sample dataset GSE36791 and a tissue sample dataset GSE122897 were included. Differentially expressed genes (DEGs) between aSAH and healthy samples were explored. We applied GO biological and Gene Set Enrichment Analyses (GSEA) processes to access the functional enrichment. Then feature elimination algorithms based on random forest were used to screen and verify the biomarkers of aSAH. We performed three computational algorithms including Cell type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT), Microenvironment Cell Populations-counter (MCPcounter), and xcell to evaluate the immune cell infiltration landscape to identify the unique infiltration characteristics associated with rupturing. We found 2,220 DEGs (856 upregulated and 1,364 downregulated) in the original dataset. Functional analysis revealed most of these genes are enriched in immunological process, especially related with neutrophil response. Similar signaling pathway enrichment patterns were observed in tissue sample dataset and ClueGo. Analysis of immune microenvironment infiltration suggested neutrophils were abnormally upregulated in aSAH compared with those in the control group. Key gene SRPK1 was then filtered based on feature elimination algorithms, and transcription factor (TF) ZNF281 is assumed to participate in immunomodulation by regulating expression of SRPK1. Several immunomodulators such as CXCR1 and CXCR2 also appear to be involved in the progression of aSAH. In the present study, we performed a comprehensive stratification and quantification of the immune infiltration status of aSAH. By exploring the potential mechanism for aSAH based on several computational algorithms, key genes including SRPK1 and ZNF281 were filtered. This study may be of benefit to patients who are at high risk of suffering aSAH which allows for early diagnosis and potential therapy.

A review for the pharmacological effects of paeoniflorin in the nervous system

Paeoniflorin, a terpenoid glycoside compound extracted from Paeonia lactiflora Pall, shows preventive and therapeutic effects in various types of nervous system disorders. However, to date, no comprehensive knowledge on the pharmacological effects of paeoniflorin on the nervous system is available online. Clarification of this issue may be useful for the development of paeoniflorin as a new drug for the treatment of nervous system disorders. To this end, the authors summarize the pharmacological aspects of paeoniflorin and its possible mechanisms, such as restoration of mitochondrial function; inhibition of neuroinflammation, oxidative stress, and cellular apoptosis; activation of adenosine A1 receptor, cAMP response element-binding protein (CREB) and extracellular signal-regulated kinase 1/2 (ERK1/2); or enhancement of brain-derived neurotrophic factor and serotonin function, in the prevention of disorders such as cerebral ischemia, subarachnoid hemorrhage, vascular dementia, Alzheimer's disease, Parkinson's disease, depression, post-traumatic syndrome disorder, and epilepsy, by reviewing the previously published literature.

Neurofilament light chain and S100B serum levels are associated with disease severity and outcome in patients with aneurysmal subarachnoid hemorrhage

Objectives

Serum neurofilament light chain (NfL) is a biomarker for neuroaxonal damage, and S100B is a blood marker for cerebral damage. In the present study, we investigated the relationship between serum NfL and S100B levels, severity, and outcomes in patients with aneurysmal subarachnoid hemorrhage (aSAH).

Methods

We prospectively recruited aSAH patients and healthy controls between January 2016 and January 2021. Clinical results included mortality and poor outcomes (modified Rankin scale score of 3-6) after 6 months. The ultrasensitive Simoa technique was used to evaluate NfL levels in the blood, and ELISA was used to detect S100B.

Results

A total of 91 patients and 25 healthy controls were included in the study, with a death rate of 15.4%. The group of aSAH patients had significantly higher serum levels of NfL and S100B (P &lt; 0.01). Furthermore, the levels of NfL and S100B increased when the Hunt-Hess, World Federation of Neurological Surgeons (WFNS), and Fisher grades increased (P &lt; 0.01). Serum NfL and S100B levels were linked to poor prognoses and low survival rates. The blood levels of NfL and S100B were found to be an independent predictor related to 6-month mortality in multivariable analysis. Additionally, the areas under the curves for NfL and S100B levels in serum were 0.959 and 0.912, respectively; the clinical diagnostic critical thresholds were 14.275 and 26.54 pg/ml, respectively; sensitivities were 0.947 and 0.921, and specificities were 0.849 and 0.811.

Conclusions

The NfL and S100B values for aSAH patients within 12 days of admission were considerably associated with Hunt-Hess grade, WFNS, and Fisher grade. The higher the grade, the higher the NfL and S100B value, and the poorer the prognosis. Serum NfL and S100B values could be feasible biomarkers to predict the clinical prognosis of patients with aSAH.

Role of hydrogen sulfide in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a common acute and severe disease worldwide, which imposes a heavy burden on families and society. However, the current therapeutic strategies for SAH are unsatisfactory. Hydrogen sulfide (H₂ S), as the third gas signaling molecule after carbon monoxide and nitric oxide, has been widely studied recently. There is growing evidence that H₂ S has a promising future in the treatment of central nervous system diseases. In this review, we focus on the effects of H₂ S in experimental SAH and elucidate the underlying mechanisms. We demonstrate that H₂ S has neuroprotective effects and significantly reduces secondary damage caused by SAH via antioxidant, antiinflammatory, and antiapoptosis mechanisms, and by alleviating cerebral edema and vasospasm. Based on these findings, we believe that H₂ S has great potential in the treatment of SAH and warrants further study to promote its early clinical application.

Transcriptome-Based Dissection of Intracranial Aneurysms Unveils an “Immuno-Thermal” Microenvironment and Defines a Pathological Feature-Derived Gene Signature for Risk Estimation

Immune inflammation plays an essential role in the formation and rupture of intracranial aneurysm (IA). However, the current limited knowledge of alterations in the immune microenvironment of IA has hampered the mastery of pathological mechanisms and technological advances, such as molecular diagnostic and coated stent-based molecular therapy. In this study, seven IA datasets were enrolled from the GEO database to decode the immune microenvironment and relevant biometric alterations. The ssGSEA algorithm was employed for immune infiltration assessment. IAs displayed abundant immune cell infiltration, activated immune-related pathways, and high expression of immune-related genes. Several immunosuppression cells and genes were also coordinately upregulated in IAs. Five immune-related hub genes, including CXCL10, IL6, IL10, STAT1, and VEGFA, were identified from the protein-protein interaction network and further detected at the protein level. CeRNA networks and latent drugs targeting the hub genes were predicted for targeted therapy reference. Two gene modules recognized via WCGNA were functionally associated with contractile smooth muscle loss and extracellular matrix metabolism, respectively. In blood datasets, a pathological feature-derived gene signature (PFDGS) for IA diagnosis and rupture risk prediction was established using machine learning. Patients with high PFDGS scores may possess adverse biological alterations and present with a high risk of morbidity or IA rupture, requiring more vigilance or prompt intervention. Overall, we systematically unveiled an “immuno-thermal” microenvironment characterized by co-enhanced immune activation and immunosuppression in IA, which provides a novel insight into molecular pathology. The PFDGS is a promising signature for optimizing risk surveillance and clinical decision-making in IA patients.

The Role of Caspase Family in Acute Brain Injury: The Potential Therapeutic Targets in the Future

The caspase family is commonly involved in the pathophysiology of acute brain injury (ABI) through complex apoptotic, pyroptotic, and inflammatory pathways. Current translational strategies for caspase modulation in ABI primarily focus on caspase inhibitors. Because there are no caspase-inhibiting drugs approved for clinical use on the market, the development of caspase inhibitors remains an attractive challenge for researchers and clinicians. Therefore, we conducted the present review with the aim of providing a comprehensive introduction of caspases in ABI. In this review, we summarized the available evidence and potential mechanisms regarding the biological function of caspases. We also reviewed the therapeutic effects of caspase inhibitors on ABI and its subsequent complications. However, various important issues remain unclear, prompting further verification of the efficacy and safety regarding clinical application of caspase inhibitors. We believe that our work will be helpful to further understand the critical role of the caspase family and will provide novel therapeutic potential for ABI treatment.

Monocyte Count on Admission Is Predictive of Shunt-Dependent Hydrocephalus After Aneurysmal Subarachnoid Hemorrhage

The authors sought to evaluate whether immunologic counts on admission were associated with shunt-dependent hydrocephalus following aneurysmal subarachnoid hemorrhage. A retrospective analysis of 143 consecutive patients with aneurysmal subarachnoid hemorrhage over a 9-year period was performed. A stepwise algorithm was followed for external ventricular drain weaning and determining the necessity of shunt placement. Data were compared between patients with and without shunt-dependent hydrocephalus. Overall, 11.19% of the cohort developed shunt-dependent hydrocephalus. On multivariate logistic regression analysis, acute hydrocephalus (OR: 61.027, 95% CI: 3.890–957.327; p = 0.003) and monocyte count on admission (OR: 3.362, 95% CI: 1.024–11.037; p = 0.046) were found to be independent predictors for shunt dependence. Receiver operating characteristic curve analysis for the prediction of shunt-dependent hydrocephalus confirmed that monocyte count exhibited an acceptable area under the curve (AUC = 0.737, 95% CI: 0.601–0.872; p < 0.001). The best predictive cutoff value to discriminate between successful external ventricular drain weaning and shunt-dependent hydrocephalus was identified as a monocyte count ≥0.80 × 10³/uL at initial presentation. These preliminary data demonstrate that a monocyte count ≥0.80 × 10³/uL at admission predicts shunt-dependent hydrocephalus in patients with aneurysmal subarachnoid hemorrhage; however, further large-scale prospective trials and validation are necessary to confirm these findings.

2-Methoxyestradiol Alleviates Neuroinflammation and Brain Edema in Early Brain Injury After Subarachnoid Hemorrhage in Rats

Objective

Numerous studies have shown that neuroinflammation and brain edema play an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH). 2-Methoxyestradiol (2-ME) has been shown to have anti-inflammatory and anti-angiogenic effects. This study aimed to investigate the effects of 2-ME on neuroinflammation and brain edema after SAH and its underlying mechanism of action.

Methods

Rats were used to produce an endovascular puncture model of SAH. 2-ME or the control agent was injected intraperitoneally 1 h after SAH induction. At 24 h after surgery, the neurological score, SAH grading, brain water content, and blood–brain barrier (BBB) permeability were examined. The microglial activation level in the rat brain tissue was determined using immunofluorescence staining, whereas the cell apoptosis in the rat brain tissue was assessed using terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, the levels of Interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were measured by enzyme linked immunosorbent assay, and the expression levels of ZO-1, occludin, hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and matrix metallopeptidase (MMP)-9 in the rat brain tissue were determined using western blotting.

Results

Twenty-four hours after SAH, brain water content, BBB permeability, microglial activation, and cell apoptosis were significantly increased, whereas neurological function deteriorated significantly in rats. Treatment with 2-ME significantly decreased brain water content, BBB permeability, microglial cell activation, and cell apoptosis and improved neurological dysfunction in rats. Treatment with 2-ME reduced the expression levels of inflammatory factors (IL-1β, IL-6, and TNF-α), which were significantly elevated 24 h after SAH. Treatment with 2-ME alleviated the disruption of tight junction proteins (ZO-1 and occludin), which significantly decreased 24 h after SAH. To further determine the mechanism of this protective effect, we found that 2-ME inhibited the expression of HIF-1α, MMP-9, and VEGF, which was associated with the inflammatory response to EBI and BBB disruption after SAH.

Conclusion

2-ME alleviated neuroinflammation and brain edema as well as improved neurological deficits after SAH in rats. The neuroprotective effect of 2-ME on EBI after SAH in rats may be related to the inhibition of neuroinflammation and brain edema.

The Role of Soluble Urokinase Plasminogen Activator Receptor (suPAR) in the Context of Aneurysmal Subarachnoid Hemorrhage (aSAH)—A Prospective Observational Study

Objective

Outcome after aneurysmal subarachnoid hemorrhage (aSAH) is highly variable and largely determined by early brain injury and delayed cerebral ischemia (DCI). Soluble urokinase plasminogen activator receptor (suPAR) represents a promising inflammatory marker which has previously been associated with outcome in traumatic brain injury and stroke patients. However, its relevance in the context of inflammatory changes after aSAH is unclear. Here, we aimed to characterize the role of circulating suPAR in both serum and cerebrospinal fluid (CSF) as a novel biomarker for aSAH patients.

Methods

A total of 36 aSAH patients, 10 control patients with unruptured abdominal aneurysm and 32 healthy volunteers were included for analysis. suPAR was analyzed on the day of admission in all patients. In aSAH patients, suPAR was also determined on the day of DCI and the respective time frame in asymptomatic patients. One- and two-sample t-tests were used for simple difference comparisons within and between groups. Regression analysis was used to assess the influence of suPAR levels on outcome in terms of modified Rankin score.

Results

Significantly elevated suPAR serum levels (suPAR-SL) on admission were found for aSAH patients compared to healthy controls, but not compared to vascular control patients. Disease severity as documented according to Hunt and Hess grade and modified Fisher grade was associated with higher suPAR CSF levels (suPAR-CSFL). In aSAH patients, suPAR-SL increased daily by 4%, while suPAR-CSFL showed a significantly faster daily increase by an average of 22.5% per day. Each increase of the suPAR-SL by 1 ng/ml more than tripled the odds of developing DCI (OR = 3.06). While admission suPAR-CSFL was not predictive of DCI, we observed a significant correlation with modified Rankin's degree of disability at discharge.

Conclusion

Elevated suPAR serum level on admission as a biomarker for early inflammation after aSAH is associated with an increased risk of DCI. Elevated suPAR-CSFL levels correlate with a higher degree of disability at discharge. These distinct relations and the observation of a continuous increase over time affirm the role of inflammation in aSAH and require further study.

The mechanism of microglia-mediated immune inflammation in ischemic stroke and the role of natural botanical components in regulating microglia: A review

Ischemic stroke (IS) is one of the most fatal diseases. Neuroimmunity, inflammation, and oxidative stress play important roles in various complex mechanisms of IS. In particular, the early proinflammatory response resulting from the overactivation of resident microglia and the infiltration of circulating monocytes and macrophages in the brain after cerebral ischemia leads to secondary brain injury. Microglia are innate immune cells in the brain that constantly monitor the brain microenvironment under normal conditions. Once ischemia occurs, microglia are activated to produce dual effects of neurotoxicity and neuroprotection, and the balance of the two effects determines the fate of damaged neurons. The activation of microglia is defined as the classical activation (M1 type) or alternative activation (M2 type). M1 type microglia secrete pro-inflammatory cytokines and neurotoxic mediators to exacerbate neuronal damage, while M2 type microglia promote a repairing anti-inflammatory response. Fine regulation of M1/M2 microglial activation to minimize damage and maximize protection has important therapeutic value. This review focuses on the interaction between M1/M2 microglia and other immune cells involved in the regulation of IS phenotypic characteristics, and the mechanism of natural plant components regulating microglia after IS, providing novel candidate drugs for regulating microglial balance and IS drug development.

An Update on Antioxidative Stress Therapy Research for Early Brain Injury After Subarachnoid Hemorrhage

The main reasons for disability and death in aneurysmal subarachnoid hemorrhage (aSAH) may be early brain injury (EBI) and delayed cerebral ischemia (DCI). Despite studies reporting and progressing when DCI is well-treated clinically, the prognosis is not well-improved. According to the present situation, we regard EBI as the main target of future studies, and one of the key phenotype-oxidative stresses may be called for attention in EBI after laboratory subarachnoid hemorrhage (SAH). We summarized the research progress and updated the literature that has been published about the relationship between experimental and clinical SAH-induced EBI and oxidative stress (OS) in PubMed from January 2016 to June 2021. Many signaling pathways are related to the mechanism of OS in EBI after SAH. Several antioxidative stress drugs were studied and showed a protective response against EBI after SAH. The systematical study of antioxidative stress in EBI after laboratory and clinical SAH may supply us with new therapies about SAH.

The management of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a rare event affecting relatively young patients therefore leading to a high social impact. The management of SAH follows a biphasic course with early brain injuries in the first 72 hours followed by a phase at risk of secondary deterioration due to delayed cerebral ischemia (DCI) in 20 to 30% patients. Cerebral infarction from DCI is the most preventable cause of mortality and morbidity after SAH. DCI prevention, early detection and treatment is therefore advocated. Formerly limited to the occurrence of vasospasm, DCI is now associated with multiple pathophysiological processes involving for instance the macrocirculation, the microcirculation, neurovascular units, and inflammation. Therefore, the therapeutic targets and management strategies are also evolving and are not only focused on proximal vasospasm. In this review, we describe the current knowledge of DCI pathophysiology. We then discuss the diagnosis strategies that may guide physicians at the bedside with a multimodal approach in the unconscious patient. We will present the prevention strategies that have proven efficient as well as future targets and present the therapeutic approach that is currently being developed when a DCI occurs.

NBTI attenuates neuroinflammation and apoptosis partly by ENT1/NLRP3/Bcl2 pathway after subarachnoid hemorrhage in rats

OBJECTIVES

Neuroinflammation and apoptosis are two key factors contributing to early brain injury (EBI) after subarachnoid hemorrhage (SAH) and are strongly associated with a poor prognosis. Recently, equilibrative nucleoside transporter 1 (ENT1) was emerged to accelerate the severity of inflammation and cell apoptosis in several nervous system diseases, including cerebral ischemia, neurodegeneration and epilepsy. However, no study has yet elaborated the expression levels and effects of ENT1 in EBI after SAH.

METHODS

Sprague-Dawley rats were subjected to SAH by endovascular perforation. Nitrobenzylthioinosine (NBTI) was intranasally administered at 0.5 h after SAH. The protein expression levels of ENT1, NLRP3, Bcl2, Bax, ACS, Caspase-1, IL-1 were detected by western blot. The modified Garcia score and beam balance score were employed to evaluate the neurologic function of rats following SAH. In addition, hematoxylin-eosin, fluoro-jade C and TdT-mediated dUTP nick-end labeling staining were then used to evaluate brain tissue damage and neuronal apoptosis.

RESULTS

Analysis indicated that endogenous levels of ENT1 were significantly upregulated at 24-hour post-SAH, accompanied by NLRP3 inflammasome activation and Bcl2 decline. The administration of NBTI, an inhibitor of ENT1, at a dose of 15 mg/kg, ameliorated neurologic deficits and morphologic lesions at both 24 and 72 h after SAH. Moreover, ENT1 inhibition efficiently mitigated neuronal degeneration and cell apoptosis. In addition, NBTI at 15 mg/kg observably increased Bcl2 content and decreased Bax level. Furthermore, suppression of ENT1 notably reduced the expression levels of NLRP3, apoptosis associated speck like protein containing CARD, caspase-1 and IL-1β.

CONCLUSIONS

NBTI relieved SAH-induced EBI partly through ENT1/NLRP3/Bcl2 pathway.

RNase A Inhibits Formation of Neutrophil Extracellular Traps in Subarachnoid Hemorrhage

Background: Subarachnoid hemorrhage (SAH) caused by rupture of an intracranial aneurysm, is a life-threatening emergency that is associated with substantial morbidity and mortality. Emerging evidence suggests involvement of the innate immune response in secondary brain injury, and a potential role of neutrophil extracellular traps (NETs) for SAH-associated neuroinflammation. In this study, we investigated the spatiotemporal patterns of NETs in SAH and the potential role of the RNase A (the bovine equivalent to human RNase 1) application on NET burden. Methods: A total number of n=81 male C57Bl/6 mice were operated utilizing a filament perforation model to induce SAH, and Sham operation was performed for the corresponding control groups. To confirm the bleeding and exclude stroke and intracerebral hemorrhage, the animals received MRI after 24h. Mice were treated with intravenous injection of RNase A (42μg/kg body weight) or saline solution for the control groups, respectively. Quadruple-immunofluorescence (IF) staining for cell nuclei (DAPI), F-actin (phalloidin), citrullinated H3, and neurons (NeuN) was analyzed by confocal imaging and used to quantify NET abundance in the subarachnoid space (SAS) and brain parenchyma. To quantify NETs in human SAH patients, cerebrospinal spinal fluid (CSF) and blood samples from day 1, 2, 7, and 14 after bleeding onset were analyzed for double-stranded DNA (dsDNA) via Sytox Green. Results: Neutrophil extracellular traps are released upon subarachnoid hemorrhage in the SAS on the ipsilateral bleeding site 24h after ictus. Over time, NETs showed progressive increase in the parenchyma on both ipsi- and contralateral site, peaking on day 14 in periventricular localization. In CSF and blood samples of patients with aneurysmal SAH, NETs also increased gradually over time with a peak on day 7. RNase application significantly reduced NET accumulation in basal, cortical, and periventricular areas. Conclusion: Neutrophil extracellular trap formation following SAH originates in the ipsilateral SAS of the bleeding site and spreads gradually over time to basal, cortical, and periventricular areas in the parenchyma within 14days. Intravenous RNase application abrogates NET burden significantly in the brain parenchyma, underpinning a potential role in modulation of the innate immune activation after SAH.

Neutrophil Count on Admission Predicts Acute Symptomatic Hydrocephalus After Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

To investigate the association between immunologic counts on admission and acute symptomatic hydrocephalus after aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

We conducted a retrospective analysis of 143 consecutive patients with aSAH. Patient demographics, clinical parameters, laboratory values, and radiographic imaging were obtained. Univariate and multivariate logistic regression analyses were performed to investigate parameters independently associated with acute symptomatic hydrocephalus. Receiver operating characteristic (ROC) curve analysis determined the best threshold value of neutrophil count to differentiate patients with and without hydrocephalus.

RESULTS

Overall, acute symptomatic hydrocephalus developed in 39.16% of patients. In an adjusted multivariate logistic regression model, Hunt and Hess grade 4-5 (odds ratio [OR]: 16.052, 95% confidence interval [CI]: 1.188-216.983; P = 0.037), modified Fisher score 3-4 (OR: 10.107, 95% CI: 1.715-59.572; P = 0.011), intraventricular hemorrhage (OR: 4.578, 95% CI: 1.417-14.788; P = 0.011), neutrophil count (OR: 1.183, 95% CI: 1.033-1.354; P = 0.015), and prior ischemic stroke (OR: 7.003, 95% CI: 1.293-37.929; P = 0.024) were significantly associated with hydrocephalus. ROC analysis for neutrophil count confirmed an acceptable area under the curve (AUC 0.780, 95% CI: 0.701-0.859; P < 0.001). The best threshold value of neutrophil count to predict hydrocephalus was ≥9.80 × 10³/mL. Overall, 81.25% of patients who developed shunt dependence had a neutrophil count ≥9.80 × 10³/mL on admission (P = 0.003).

CONCLUSIONS

Neutrophil count ≥9.80 × 10³/mL on admission predicts acute symptomatic hydrocephalus after aSAH in an adjusted multivariate logistic regression model. Moreover, shunt dependence was associated with higher neutrophil counts.

Neuroprotective Strategies in Aneurysmal Subarachnoid Hemorrhage (aSAH)

Aneurysmal subarachnoid hemorrhage (aSAH) remains a disease with high mortality and morbidity. Since treating vasospasm has not inevitably led to an improvement in outcome, the actual emphasis is on finding neuroprotective therapies in the early phase following aSAH to prevent secondary brain injury in the later phase of disease. Within the early phase, neuroinflammation, thromboinflammation, disturbances in brain metabolism and early neuroprotective therapies directed against delayed cerebral ischemia (DCI) came into focus. Herein, the role of neuroinflammation, thromboinflammation and metabolism in aSAH is depicted. Potential neuroprotective strategies regarding neuroinflammation target microglia activation, metalloproteases, autophagy and the pathway via Toll-like receptor 4 (TLR4), high mobility group box 1 (HMGB1), NF-κB and finally the release of cytokines like TNFα or IL-1. Following the link to thromboinflammation, potential neuroprotective therapies try to target microthrombus formation, platelets and platelet receptors as well as clot clearance and immune cell infiltration. Potential neuroprotective strategies regarding metabolism try to re-balance the mismatch of energy need and supply following aSAH, for example, in restoring fuel to the TCA cycle or bypassing distinct energy pathways. Overall, this review addresses current neuroprotective strategies in aSAH, hopefully leading to future translational therapy options to prevent secondary brain injury.

Pharmaceutical Management for Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage can have deleterious consequences. Vasospasm, delayed cerebral ischemia, and re-hemorrhage can all cause delayed sequelae. Furthermore, severe headaches are common and require careful modulation of pain medications. Limited treatment options currently exist and are becoming more complex with the rising use of oral anticoagulants needing reversal. In this review, we highlight the current treatment options currently employed and address avenues of future discovery based on emerging preclinical data. Furthermore, we dive into the best treatment approach for managing headaches following subarachnoid hemorrhage. The review is designed to serve as a catalyst for further prospective investigation into this important topic.