Early brain injury, an evolving frontier in subarachnoid hemorrhage research

5-Lipoxygenase inhibition reduces inflammation and neuronal apoptosis via AKT signaling after subarachnoid hemorrhage in rats

Early brain injury (EBI) is a major contributor to the high mortality and morbidity after subarachnoid hemorrhage (SAH). Inflammatory responses and neuronal apoptosis are important causes of EBI. Because 5- lipoxygenase (5-LOX) is known to be involved various central nervous system diseases, we investigated the effects of 5-LOX inhibition during EBI after SAH. Zileuton and LY294002 were used to inhibit expression of 5-LOX and Akt, respectively. We found that 5-LOX expression was significantly increased in the cytoplasm of cortical neurons after SAH and was accompanied by upregulated expression of the inflammatory factors LTB4, TNF-α, IL-1β and IL-6; upregulation of the pro-apoptotic factor Bax; downregulation of the anti-apoptotic factor Bcl-2; and an increased apoptosis rate. Gastric Zileuton administration significantly suppressed all of those effects and improved neurological function. Zileuton also upregulated activated (phosphorylated) AKT levels, and these beneficial effects of Zileuton were abolished by intracerebroventricular infusion of the PI3K inhibitor LY294002. Taken together, these findings indicate that 5-LOX mediates pro-inflammatory and pro-apoptotic effects that contribute to EBI after SAH and that those effects are suppressed by activation of PI3K/Akt signaling. This suggests targeting 5-LOX may be an effective approach to treating EBI after SAH.

An overview of pharmacotherapy for cerebral vasospasm and delayed cerebral ischemia after subarachnoid hemorrhage

Introduction: Survival from aneurysmal subarachnoid hemorrhage has increased in the past few decades. However, functional outcome after subarachnoid hemorrhage is still suboptimal. Delayed cerebral ischemia (DCI) is one of the major causes of morbidity.Areas covered: Mechanisms underlying vasospasm and DCI after aneurysmal subarachnoid hemorrhage and pharmacological treatment are summarized in this review.Expert opinion: Oral nimodine, an L-type dihydropyridine calcium channel blocker, is the only FDA-approved drug for the prevention and treatment of neurological deficits after aneurysmal subarachnoid hemorrhage. Fasudil, a potent Rho-kinase inhibitor, has also been shown to improve the clinical outcome and has been approved in some countries for use in patients with aneurysmal subarachnoid hemorrhage. Although other drugs, including nicardipine, cilostazol, statins, clazosentan, magnesium and heparin, have been expected to have beneficial effects on DCI, there has been no convincing evidence supporting the routine use of those drugs in patients with aneurysmal subarachnoid hemorrhage in clinical practice. Further elucidation of the mechanisms underlying DCI and the development of effective therapeutic strategies for DCI, including combination therapy, are necessary to further improve the functional outcome and mortality after subarachnoid hemorrhage.

Monocyte-based inflammatory indices predict outcomes following aneurysmal subarachnoid hemorrhage

The contribution of specific immune cell populations to the post-hemorrhagic inflammatory response in aneurysmal subarachnoid hemorrhage (aSAH) and correlations with clinical outcomes, such as vasospasm and functional status, remains unclear. We aimed to compare the predictive value of leukocyte ratios that include monocytes as compared to the neutrophil-to-lymphocyte ratio (NLR) in aSAH. A prospectively accrued database of consecutive patients presenting to our institution with aSAH between January 2013 and December 2018 was used. Patients with signs and symptoms of infection (day 1-3) were excluded. Admission values of the NLR, monocyte-neutrophil-to-lymphocyte ratio (M-NLR), and lymphocyte-to-monocyte ratio (LMR) were calculated. Associations with functional status, the primary outcome, and vasospasm were evaluated using univariable and multivariable logistic regression analyses. In the cohort of 234 patients with aSAH, the M-NLR and LMR, but not the NLR, were significantly associated with poor functional status (modified Rankin scale > 2) at 12-18 months following discharge (p = 0.001, p = 0.023, p = 0.161, respectively). The area under the curve for predicting poor functional status was significantly lower for the NLR (0.543) compared with the M-NLR (0.603, p = 0.024) and LMR (0.608, p = 0.040). The M-NLR (OR = 1.01 [1.01-1.02]) and LMR (OR = 0.88 [0.78-0.99]) were independently associated with poor functional status while controlling for age, hypertension, Fisher grade, and baseline clinical status. The LMR was significantly associated with vasospasm (OR = 0.84 [0.70-0.99]) while adjusting for age, hypertension, Fisher grade, aneurysm size, and current smoking. Inflammatory indices that incorporate monocytes (e.g., M-NLR and LMR), but not those that include only neutrophils, predict outcomes after aSAH.

c-Abl Tyrosine Kinase-Mediated Neuronal Apoptosis in Subarachnoid Hemorrhage by Modulating the LRP-1-Dependent Akt/GSK3β Survival Pathway

Accumulating evidence suggests that neuronal apoptosis plays a critical role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and the inhibition of apoptosis can induce neuroprotective effects in SAH animal models. c-Abl has been reported to promote neuronal apoptosis in Alzheimer's disease and cerebral ischemia, but its role in SAH had not been illuminated until now. In the present study, the effect of c-Abl on neuronal apoptosis induced by SAH was investigated. c-Abl protein levels and neuronal apoptosis were markedly increased 24 h after SAH, and the inhibition of endogenous c-Abl reduced neuronal apoptosis and mortality and ameliorated neurological deficits. Furthermore, c-Abl inhibition decreased the expression of cleaved caspase-3 (CC-3) after SAH. These results demonstrate the proapoptotic effect of c-Abl in EBI after SAH. Additionally, c-Abl inhibition further enhanced the SAH-induced phosphorylation of Akt and glycogen synthase kinase (GSK)3β. LY294002 abrogated the beneficial effects of targeting c-Abl and exacerbated neuronal apoptosis after SAH. SAH decreased LRP-1 levels and downregulated LRP-1 by RAP, and LRP-1 small interfering RNA (siRNA) induced a dramatic decrease in Akt/GSK3β activation in the presence of c-Abl siRNA. This is the first report showing that the c-Abl tyrosine kinase may play a key role in SAH-induced neuronal apoptosis by regulating the LRP-1-dependent Akt/GSK3β survival pathway. Thus, c-Abl has the potential to be a novel target for EBI therapy after SAH.

The Role of Nanomaterials in Stroke Treatment: Targeting Oxidative Stress

Stroke has a high rate of morbidity and disability, which seriously endangers human health. In stroke, oxidative stress leads to further damage to the brain tissue. Therefore, treatment for oxidative stress is urgently needed. However, antioxidative drugs have demonstrated obvious protective effects in preclinical studies, but the clinical studies have not seen breakthroughs. Nanomaterials, with their characteristically small size, can be used to deliver drugs and have demonstrated excellent performance in treating various diseases. Additionally, some nanomaterials have shown potential in scavenging reactive oxygen species (ROS) in stroke according to the nature of nanomaterials. The drugs' delivery ability of nanomaterials has great significance for the clinical translation and application of antioxidants. It increases drug blood concentration and half-life and targets the ischemic brain to protect cells from oxidative stress-induced death. This review summarizes the characteristics and progress of nanomaterials in the application of antioxidant therapy in stroke, including ischemic stroke, hemorrhagic stroke, and neural regeneration. We also discuss the prospect of nanomaterials for the treatment of oxidative stress in stroke and the challenges in their application, such as the toxicity and the off-target effects of nanomaterials.

Ifenprodil Improves Long-Term Neurologic Deficits Through Antagonizing Glutamate-Induced Excitotoxicity After Experimental Subarachnoid Hemorrhage

Excessive glutamate leading to excitotoxicity worsens brain damage after SAH and contributes to long-term neurological deficits. The drug ifenprodil is a non-competitive antagonist of GluN1-GluN2B N-methyl-d-aspartate (NMDA) receptor, which mediates excitotoxic damage in vitro and in vivo. Here, we show that cerebrospinal fluid (CSF) glutamate level within 48 h was significantly elevated in aSAH patients who later developed poor outcome. In rat SAH model, ifenprodil can improve long-term sensorimotor and spatial learning deficits. Ifenprodil attenuates experimental SAH-induced neuronal death of basal cortex and hippocampal CA1 area, cellular and mitochondrial Ca²⁺ overload of basal cortex, blood-brain barrier (BBB) damage, and cerebral edema of early brain injury. Using in vitro models, ifenprodil declines the high-concentration glutamate-mediated intracellular Ca²⁺ increase and cell apoptosis in primary cortical neurons, reduces the high-concentration glutamate-elevated endothelial permeability in human brain microvascular endothelial cell (HBMEC). Altogether, our results suggest ifenprodil improves long-term neurologic deficits through antagonizing glutamate-induced excitotoxicity.

LJ529 attenuates mast cell-related inflammation via A3R-PKCε-ALDH2 pathway after subarachnoid hemorrhage in rats

BACKGROUND AND PURPOSE

Mast cells (MCs) has been recognized as an effector of inflammation or a trigger of inflammatory factors during stroke. LJ529 was reported to attenuate inflammation through a Gi protein-coupled Adenosine A3 receptor (A₃R) after ischemia. Here, we aim to study the protective effect and its mechanism of LJ529 in subarachnoid hemorrhage (SAH) rat model for mast cell-related inflammation.

METHODS

155 Sprague-Dawley adult male rats were used in experiments. Endovascular perforation was used for SAH model. Intraperitoneal LJ529 was performed 1 h after SAH. Neurological scores were measured 24 h after SAH. Rotarod and morris water maze tests were evaluated for 21 days after SAH. Mast cell degranulation was assessed with Toluidine blue staining and Chymase/Typtase protein expressions. Mast cell-related inflammation was evaluated using IL-6, TNF-α and MCP-1 protein expressions. MRS1523, inhibitor of GPR18 and ε-V1-2, inhibitor of PKCε were respectively given intraperitoneally (i.p.) 1 h and 30 min before SAH for mechanism studies. Pathway related proteins were investigated with western blot and immunofluorescence staining.

RESULTS

Expression of A₃R, PKCε increased after SAH. LJ529 treatment attenuated mast cell degranulation and inflammation. Meanwhile, both short-term and long-term neurological functions were improved after LJ529 treatment. Administration of LJ529 resulted in increased expressions of A₃R, PKCε, ALDH2 proteins and decreased expressions of Chymase, Typtase, IL-6, TNF-α and MCP-1 proteins. MRS1523 abolished the treatment effects of LJ529 on neurobehavior and protein levels. ε-V1-2 also reversed the outcomes of LJ529 administration through reduction in protein expressions downstream of PKCε.

CONCLUSIONS

LJ529 attenuated mast cell-related inflammation through inhibiting degranulation via A3R-PKCε-ALDH2 pathway after SAH. LJ529 may serve as a potential treatment strategy to relieve post-SAH brain injury.

Age dependency and modification of the Subarachnoid Hemorrhage Early Brain Edema Score

OBJECTIVE

The Subarachnoid Hemorrhage Early Brain Edema Score (SEBES) system measures cerebral edema on CT and can be used to predict outcome after subarachnoid hemorrhage (SAH). The authors developed a modified SEBES (SEBES 6c) and assessed whether it could predict outcome after SAH better than the SEBES. Furthermore, they verified the age dependency of these scores.

METHODS

In this retrospective study, all patients with aneurysmal SAH in the period from January 2011 to February 2017 at a single institution were analyzed. The SEBES, which is based on the absence of visible sulci at two defined CT levels (0-4 points), and the SEBES 6c were determined from the initial CT. The SEBES 6c system includes the two levels from the original SEBES and one level located 2 cm below the vertex (0-6 points). The authors investigated whether the various SEBESs are age dependent and if they can predict delayed infarction (DI) and outcome.

RESULTS

Two hundred sixty-one patients met the study inclusion criteria. The SEBES was an independent predictor for DI (OR 1.6 per 1-point increase) and unfavorable outcome (OR 1.36 per 1-point increase), in accordance with findings in the first publication on SEBES. However, here the authors found that the SEBES was age dependent. In the age group younger than 60 years, the patients with high-grade SEBESs (3-4 points) had DIs and unfavorable outcomes significantly more often than the patients with low-grade scores (0-2 points). In the age groups 60-69 years and ≥ 70 years, no significant differences in DI and outcome were identified between high-grade and low-grade scores, although trends toward DI and unfavorable outcomes among the 60-69 age group were noted in patients with high-grade SEBESs.Receiver operating characteristic curve analysis showed that SEBES 6c had a higher prognostic value in predicting outcome than SEBES (p < 0.001). Furthermore, SEBES 6c predicted an unfavorable outcome (OR 1.31 per 1-point increase) and DI (OR 1.36 per 1-point increase) independent of vasospasms. SEBES 6c showed an age dependency similar to that of SEBES.

CONCLUSIONS

SEBES 6c is more suitable for predicting outcome after SAH than SEBES. Furthermore, it predicts outcome and DI independently of vasospasm, so it can be used to differentiate between early brain injury- and vasospasm-dependent infarctions and outcome. However, SEBES and SEBES 6c are both age dependent and can be used for patients aged < 60 years and may have limited suitability for patients aged 60-69 years and no suitability for patients aged ≥ 70 years.

Ultra-Early Cerebral Thrombosis Formation After Experimental Subarachnoid Hemorrhage Detected on T2* Magnetic Resonance Imaging

BACKGROUND AND PURPOSE

The mechanisms of brain damage during ultra-early subarachnoid hemorrhage (SAH) have not been well studied. The current study examined the SAH-induced hyperacute brain damage at 4 hours using magnetic resonance imaging and brain histology in a mouse model.

METHODS

SAH was induced by endovascular perforation in adult mice. First, adult male wild-type mice underwent magnetic resonance imaging T2 and T2* 4 hours after an endovascular perforation or a sham operation and were euthanized to assess brain histology. Second, male and female adult lipocalin-2 knockout mice had SAH. All animals underwent magnetic resonance imaging at 4 hours, and the brains were harvested for brain histology.

RESULTS

T2* hypointensity vessels were observed in the brain 4 hours after SAH in male wild-type mice. The numbers of T2*-positive vessels were significantly higher in SAH brains than in sham-operated mice. Brain histology showed thrombosis and erythrocyte plugs in the T2*-positive cerebral vessels which may be venules. The number of T2*-positive vessels correlated with SAH grade and the presence of T2 lesions. Brain thrombosis was also accompanied by albumin leakage and neuronal injury. LCN2 deficient male mice had lower numbers of T2*-positive vessels after SAH compared with wild-type male mice.

CONCLUSIONS

SAH causes ultra-early brain vessel thrombosis that can be detected by T2* gradient-echo sequence at 4 hours after SAH. LCN2 deficiency decreased the number of T2*-positive vessels.

Circulatory dipeptidyl peptidase 3 (cDPP3) is a potential biomarker for early detection of secondary brain injury after aneurysmal subarachnoid hemorrhage

INTRODUCTION

Delayed cerebral ischemia (DCI) is a common complication after aneurysmal subarachnoid hemorrhage (aSAH) that can culminate in secondary brain damage. Although it remains one of the main preventable causes of aSAH-related morbidity, there is still a lack of prognostic criteria for identification of patients at risk of developing DCI. Because elevated circulatory levels of the enzyme dipeptidyl peptidase 3 (cDPP3) were recently identified as a potential biomarker for outcome prediction in critically ill patients, we evaluated the time-course of changes in cDPP3 levels after aSAH.

MATERIALS AND METHODS

cDPP3 levels were quantified in serum obtained from 96 confirmed aSAH patients during the early (EP: d_1-4), critical (CP: d_5-8, d_9-12, d_13-15) and late (LP: d_16-21) phase after aSAH onset. Associations between cDPP3 levels and demographic or clinical parameters were evaluated. The relations between cDPP3 levels and DCI, DCI-related infarctions and long-term clinical outcomes were examined by receiver operating characteristics (ROC) curve analysis and multivariate logistic regression.

RESULTS

Significantly higher cDPP3 levels during CP (d_5-8, d_9-12, d_13-15) were observed in patients with poor clinical (p < 0.001 to p = 0.033) or radiological (p = 0.012 to p = 0.039) status on admission, DCI (p < 0.001 to p = 0.001), DCI-related infarctions (p = 0.002 to p = 0.007), and poorer long-term outcome (p = 0.007 to p = 0.019). ROC curve analysis indicated that higher cDPP3 levels on d_5-8 are predictive for a poor clinical outcome (area under the curve = 0.677, p = 0.007). In multivariate analysis, there was an independent association between cDPP3 levels on d_5-8 and development of DCI-related infarctions (p = 0.038).

CONCLUSION

Our results provide first evidence that cDPP3 could serve as a promising biomarker for early diagnosis of DCI-related infarctions in poor grade aSAH patients.

Microglia as target for anti-inflammatory approaches to prevent secondary brain injury after subarachnoid hemorrhage (SAH)

Background

Microglia-driven cerebral spreading inflammation is a key contributor to secondary brain injury after SAH. Genetic depletion or deactivation of microglia has been shown to ameliorate neuronal cell death. Therefore, clinically feasible anti-inflammatory approaches counteracting microglia accumulation or activation are interesting targets for SAH treatment. Here, we tested two different methods of interference with microglia-driven cerebral inflammation in a murine SAH model: (i) inflammatory preconditioning and (ii) pharmacological deactivation.

Methods

7T-MRI-controlled SAH was induced by endovascular perforation in four groups of C57Bl/6 mice: (i) Sham-operation, (ii) SAH naïve, (iii) SAH followed by inflammatory preconditioning (LPS intraperitoneally), and (iv) SAH followed by pharmacological microglia deactivation (colony-stimulating factor-1 receptor-antagonist PLX3397 intraperitoneally). Microglia accumulation and neuronal cell death (immuno-fluorescence), as well as activation status (RT-PCR for inflammation-associated molecules from isolated microglia) were recorded at day 4 and 14. Toll-like receptor4 (TLR4) status was analyzed using FACS.

Results

Following SAH, significant cerebral spreading inflammation occurred. Microglia accumulation and pro-inflammatory gene expression were accompanied by neuronal cell death with a maximum on day 14 after SAH. Inflammatory preconditioning as well as PLX3397-treatment resulted in significantly reduced microglia accumulation and activation as well as neuronal cell death. TLR4 surface expression in preconditioned animals was diminished as a sign for receptor activation and internalization.

Conclusions

Microglia-driven cerebral spreading inflammation following SAH contributes to secondary brain injury. Two microglia-focused treatment strategies, (i) inflammatory preconditioning with LPS and (ii) pharmacological deactivation with PLX3397, led to significant reduction of neuronal cell death. Increased internalization of inflammation-driving TLR4 after preconditioning leaves less receptor molecules on the cell surface, providing a probable explanation for significantly reduced microglia activation. Our findings support microglia-focused treatment strategies to overcome secondary brain injury after SAH. Delayed inflammation onset provides a valuable clinical window of opportunity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02085-3.

Selective Ferroptosis Inhibitor Liproxstatin-1 Attenuates Neurological Deficits and Neuroinflammation After Subarachnoid Hemorrhage

Ferroptosis is a form of iron-dependent regulated cell death. Evidence of its existence and the effects of its inhibitors on subarachnoid hemorrhage (SAH) is still lacking. In the present study, we found that liproxstatin-1 protected HT22 cells against hemin-induced injury by protecting mitochondrial functions and ameliorating lipid peroxidation. In in vivo experiments, we demonstrated the presence of characteristic shrunken mitochondria in ipsilateral cortical neurons after SAH. Moreover, liproxstatin-1 attenuated the neurological deficits and brain edema, reduced neuronal cell death, and restored the redox equilibrium after SAH. The inhibition of ferroptosis by liproxstatin-1 was associated with the preservation of glutathione peroxidase 4 and the downregulation of acyl-CoA synthetase long-chain family member 4 as well as cyclooxygenase 2. In addition, liproxstatin-1 decreased the activation of microglia and the release of IL-6, IL-1β, and TNF-α. These data enhance our understanding of cell death after SAH and shed light on future preclinical studies.

Resolvin D1 Attenuates Innate Immune Reactions in Experimental Subarachnoid Hemorrhage Rat Model

Excessive inflammation is a major cause contributing to early brain injury (EBI) and is associated with negative or catastrophic outcomes of subarachnoid hemorrhage (SAH). Resolvin D1 (RvD1) exerts strong anti-inflammatory and pro-resolving effects on either acute or chronic inflammation of various origin. Henceforth, we hypothesized that RvD1 potentially attenuates excessive inflammation in EBI following SAH. Therefore, we generated a filament perforation SAH model and administered 3 different doses (0.3, 0.6, and 1.2 nmol) of RvD1 after experimental SAH. Neurological scores, brain edema, and blood-brain barrier integrity were evaluated; besides, neutrophil infiltration, neuronal deaths, and microglial pro-inflammatory polarization were observed using histopathology or immunofluorescence staining, western blots, and qPCR. After confirming the effectiveness of RvD1 in SAH, we administered the FPR2-specific antagonist Trp-Arg-Trp-Trp-Trp-Trp-NH2 (WRW4) 30 min before SAH establishment to observe whether this compound could abolish the anti-inflammatory effect of RvD1. Altogether, our results showed that RvD1 exerted a strong anti-inflammatory effect and markedly reduced neutrophil infiltration and microglial pro-inflammatory activation, leading to remarkable improvements in neurological function and brain tissue restoration. After addition of WRW4, the anti-inflammatory effects of RvD1 were abolished. These results indicated that RvD1 could exert a good anti-inflammatory effect and alleviate EBI, which suggested that RvD1 might be a novel therapeutic alternative for SAH-induced injury.

TRAF3 mediates neuronal apoptosis in early brain injury following subarachnoid hemorrhage via targeting TAK1-dependent MAPKs and NF-κB pathways

Neuronal apoptosis has an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). TRAF3 was reported as a promising therapeutic target for stroke management, which covered several neuronal apoptosis signaling cascades. Hence, the present study is aimed to determine whether downregulation of TRAF3 could be neuroprotective in SAH-induced EBI. An in vivo SAH model in mice was established by endovascular perforation. Meanwhile, primary cultured cortical neurons of mice treated with oxygen hemoglobin were applied to mimic SAH in vitro. Our results demonstrated that TRAF3 protein expression increased and expressed in neurons both in vivo and in vitro SAH models. TRAF3 siRNA reversed neuronal loss and improved neurological deficits in SAH mice, and reduced cell death in SAH primary neurons. Mechanistically, we found that TRAF3 directly binds to TAK1 and potentiates phosphorylation and activation of TAK1, which further enhances the activation of NF-κB and MAPKs pathways to induce neuronal apoptosis. Importantly, TRAF3 expression was elevated following SAH in human brain tissue and was mainly expressed in neurons. Taken together, our study demonstrates that TRAF3 is an upstream regulator of MAPKs and NF-κB pathways in SAH-induced EBI via its interaction with and activation of TAK1. Furthermore, the TRAF3 may serve as a novel therapeutic target in SAH-induced EBI.

INT-777 attenuates NLRP3-ASC inflammasome-mediated neuroinflammation via TGR5/cAMP/PKA signaling pathway after subarachnoid hemorrhage in rats

BACKGROUND

Inflammasome-mediated neuroinflammation plays an important role in the pathogenesis of early brain injury (EBI) following subarachnoid hemorrhage (SAH). The activation of the TGR5 receptor has been shown to be neuroprotective in a variety of neurological diseases. This study aimed to investigate the effects of the specific synthetic TGR5 agonist, INT-777, in attenuating NLRP3-ASC inflammasome activation and reducing neuroinflammation after SAH.

METHODS

One hundred and eighty-four male Sprague Dawley rats were used. SAH was induced by the endovascular perforation. INT-777 was administered intranasally at 1 h after SAH induction. To elucidate the signaling pathway involved in the effect of INT-777 on inflammasome activation during EBI, TGR5 knockout CRISPR and PKA inhibitor H89 were administered intracerebroventricularly and intraperitoneally at 48 h and 1 h before SAH. The SAH grade, short- and long-term neurobehavioral assessments, brain water content, western blot, immunofluorescence staining, and Nissl staining were performed.

RESULTS

The expressions of endogenous TGR5, p-PKA, and NLRP3-ASC inflammasome were increased after SAH. INT-777 administration significantly decreased NLRP3-ASC inflammasome activation in microglia, reduced brain edema and neuroinflammation, leading to improved short-term neurobehavioral functions at 24 h after SAH. The administration of TGR5 CRISPR or PKA inhibitor (H89) abolished the anti-inflammation effects of INT-777, on NLRP3-ASC inflammasome, pro-inflammatory cytokines (IL-6, IL-1β, and TNF-a), and neutrophil infiltration at 24 h after SAH. Moreover, early administration of INT-777 attenuated neuronal degeneration in hippocampus on 28 d after SAH.

CONCLUSIONS

INT-777 attenuated NLRP3-ASC inflammasome-dependent neuroinflammation in the EBI after SAH, partially via TGR5/cAMP/PKA signaling pathway. Early administration of INT-777 may serve as a potential therapeutic strategy for EBI management in the setting of SAH.

Neurovascular disease, diagnosis, and therapy: Subarachnoid hemorrhage and cerebral vasospasm

The worldwide incidence of spontaneous subarachnoid hemorrhage is about 6.1 per 100,000 cases per year (Etminan et al., 2019). Eighty-five percent of cases are due to intracranial aneurysms. The mean age of those affected is 55 years, and two-thirds of the patients are female. The prognosis is related mainly to the neurologic condition after the subarachnoid hemorrhage and the age of the patient. Overall, 15% of patients die before reaching the hospital, another 20% die within 30 days, and overall 75% are dead or remain disabled. Case fatality has declined by 17% over the last 3 decades. Despite the improvement in outcome probably due to improved diagnosis, early aneurysm repair, administration of nimodipine, and advanced intensive care support, the outcome is not very good. Even among survivors, 75% have permanent cognitive deficits, mood disorders, fatigue, inability to return to work, and executive dysfunction and are often unable to return to their premorbid level of functioning. The key diagnostic test is computed tomography, and the treatments that are most strongly supported by scientific evidence are to undertake aneurysm repair in a timely fashion by endovascular coiling rather than neurosurgical clipping when feasible and to administer enteral nimodipine. The most common complications are aneurysm rebleeding, hydrocephalus, delayed cerebral ischemia, and medical complications (fever, anemia, and hyperglycemia). Management also probably is optimized by neurologic intensive care units and multidisciplinary teams.

Acyl-CoA synthetase long chain family member 4 plays detrimental role in early brain injury after subarachnoid hemorrhage in rats by inducing ferroptosis

Aims

Acyl‐CoA synthetase long chain family member 4 (ACSL4) is closely related to tumor genesis and development in certain tissues. However, the function of ACSL4 in early brain injury (EBI) caused by subarachnoid hemorrhage (SAH) is unclear. In this study, we investigated the expression patterns and role of ACSL4 in SAH and post‐SAH EBI using a rat model of SAH.

Methods

The rat model of SAH was induced by autologous blood injection into the prechiasmatic cistern of rats. We also used two specific inhibitors of ferroptosis (Ferrostatin‐1 and Liproxstatin‐1) to investigate the role of ferroptosis in EBI.

Results

We found that ACSL4 levels in brain tissue increased significantly in post‐SAH EBI. Inhibiting the expression of ACSL4 using small interfering RNAs alleviated inflammation, blood‐brain barrier (BBB) impairment, oxidative stress, brain edema, and behavioral and cognitive deficits, and increased the number of surviving neurons, after SAH. Similar effects were obtained by suppressing ferroptosis.

Conclusions

ACSL4 exacerbated SAH‐induced EBI by mediating ferroptosis. These findings may provide a theoretical basis for potential therapy aimed at alleviating post‐SAH EBI.

The role of immune inflammation in aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating disease, which mainly caused by the rupture of an intracranial aneurysm. Clinical trials have demonstrated that cerebral vasospasm (CVS) is not the sole contributor to delayed cerebral ischemia (DCI) and poor outcomes in patients with aSAH. Currently, accumulating evidence suggests that early brain injury (EBI), which occurs within 72 h after the onset of aSAH, lays the foundation for subsequent pathophysiological changes and poor outcomes of patients. The pathological mechanisms of EBI mainly include increased intracranial pressure, oxidative stress, neuroinflammation, blood-brain barrier (BBB) disruption, cerebral edema and cell death. Among them, the brain immune inflammatory responses involve a variety of immune cells and active substances, which play an important role in EBI after aSAH and may be related to DCI and long-term outcomes. Thus, attention should be paid to strategies targeting cerebral immune inflammatory responses. In this review, we discuss the role of immune inflammatory responses in the occurrence and development of aSAH, as well as some inflammatory biomarkers related to CVS, DCI, and aSAH outcomes. In addition, we also summarize the potential therapeutic drugs that target cerebral immune inflammatory responses for patients with aSAH in current research.

Ginkgo biloba extract protects early brain injury after subarachnoid hemorrhage via inhibiting thioredoxin interacting protein/NLRP3 signaling pathway

Objective(s):

To investigate the effect of Ginkgo biloba extract EGb761 in early brain injury (EBI) after subarachnoid hemorrhage (SAH) and its mechanism.

Materials and Methods:

The SAH rat model was constructed and pre-treated with EGb761.The neurological function, severity of SAH, water content of brain tissue, damage degree of the blood-brain barrier, related indexes of oxidative stress, and the level of inflammatory cytokines were compared among the groups. The expression of TXNIP/NLRP3 signaling pathway-related proteins in brain tissues was detected by Western blot.

Results:

After SAH modeling, the neurological function score was significantly reduced, the degree of brain injury, levels of oxidative stress, inflammatory factors, expression of NLRP3 and TXNIP were all increased. Compared with the SAH rats, the neurological function score of rats pre-treated by EGb761 was higher, the degree of brain injury, levels of oxidative stress and inflammatory factors, expression of NLRP3 and TXNIP were all lower.

Conclusion:

EGb761 could protect neurological injury after SAH and its mechanism may be that EGb761 could inhibit the activation of the TXNIP/NLRP3 signaling pathway and inflammatory reaction after oxidative stress.

Inhibition of EZH2 (Enhancer of Zeste Homolog 2) Attenuates Neuroinflammation via H3k27me3/SOCS3/TRAF6/NF-κB (Trimethylation of Histone 3 Lysine 27/Suppressor of Cytokine Signaling 3/Tumor Necrosis Factor Receptor Family 6/Nuclear Factor-κB) in a Rat Model of Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

Neuroinflammation has been proven to play an important role in the pathogenesis of early brain injury after subarachnoid hemorrhage (SAH). EZH2 (enhancer of zeste homolog 2)-mediated H3K27Me3 (trimethylation of histone 3 lysine 27) has been recognized to play a critical role in multiple inflammatory diseases. However, there is still a lack of evidence to address the effect of EZH2 on the immune response of SAH. Therefore, the aim of this study was to determine the role of EZH2 in SAH-induced neuroinflammation and explore the effect of EZH2 inhibition with its specific inhibitor EPZ6438.

METHODS

The endovascular perforation method was performed on rats to induce subarachnoid hemorrhage. EPZ6438, a specific EZH2 inhibitor, was administered intraperitoneally at 1 hour after SAH. SOCS3 (Suppressor of cytokine signaling 3) siRNA and H3K27me3 CRISPR were administered intracerebroventricularly at 48 hours before SAH to explore potential mechanisms. The SAH grade, short-term and long-term neurobehavioral tests, immunofluorescence staining, and western blots were performed after SAH.

RESULTS

The expression of EZH2 and H3K27me3 peaked at 24 hours after SAH. In addition, inhibition of EZH2 with EPZ6438 significantly improved neurological deficits both in short-term and long-term outcome studies. Moreover, EPZ6438 treatment significantly decreased the levels of EZH2, H3K27Me3, pathway-related proteins TRAF6 (TNF [tumor necrosis factor] receptor family 6), NF-κB (nuclear factor-κB) p65, proinflammatory cytokines TNF-α, IL (interleukin)-6, IL-1β, but increased the expression levels of SOCS3 and anti-inflammatory cytokine IL-10. Furthermore, administration of SOCS3 siRNA and H3k27me3-activating CRISPR partly abolished the neuroprotective effect of EPZ6438, which indicated that the neuroprotective effect of EPZ6438 acted, at least partly, through activation of SOCS3.

CONCLUSIONS

In summary, the inhibition of EZH2 by EPZ6438 attenuated neuroinflammation via H3K27me3/SOCS3/TRAF6/NF-κB signaling pathway after SAH in rats. By targeting EZH2, this study may provide an innovative method to ameliorate early brain injury after SAH.

Serum Lactate Could Predict Mortality in Patients With Spontaneous Subarachnoid Hemorrhage in the Emergency Department

Background: Serum lactate is a useful biomarker for prediction of mortality in critically ill patients. The purpose of this study was to identify if serum lactate could be used as a biomarker for predicting mortality in patients with subarachnoid hemorrhage (SAH) in the emergency department.

Methods: This retrospective study enrolled 189 patients. Baseline demographic data and clinical characteristics of patients were obtained from medical record review. Multiple logistic regression analysis was performed to determine predictor variables significantly associated with mortality. Receiver operating characteristic (ROC) curve analysis was used to evaluate the performance of variables for mortality prediction in SAH.

Results: Using multivariate logistic regression analysis, age [OR 1.05; 95% confidence interval (CI) 1.00–1.10; p = 0.037], Hunt and Hess scale score (OR 3.29; 95% CI 1.62–6.70; p = 0.001), serum lactate level (OR 1.33; 95% CI 1.03–1.74; p = 0.032), and serum glucose level (OR 1.01; 95% CI 1.00–1.02; p = 0.049) predicted overall mortality in SAH. The area under the ROC curve (AUC) value for the use of serum lactate level to predict mortality in SAH was 0.815 (95% CI 0.753–0.868) (p < 0.001).

Conclusion: Serum lactate may be a useful biomarker for the early prediction of mortality in SAH patients in the emergency department.

Cerebrovascular pathophysiology of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) remains a serious cerebrovascular disease. Even if SAH patients survive the initial insults, delayed cerebral ischemia (DCI) may occur at 4 days or later post-SAH. DCI is characteristics of SAH, and is considered to develop by blood breakdown products and inflammatory reactions, or secondary to early brain injury, acute pathophysiological events that occur in the brain within the first 72 hours of aneurysmal SAH. The pathology underlying DCI may involve large artery vasospasm and/or microcirculatory disturbances by microvasospasm, microthrombosis, dysfunction of venous outflow and compression of microvasculature by vasogenic or cytotoxic tissue edema. Recent clinical evidence has shown that large artery vasospasm is not the only cause of DCI, and that both large artery vasospasm-dependent and -independent cerebral infarction causes poor outcome. Animal studies suggest that mechanisms of vasospasm may differ between large artery and arterioles or capillaries, and that many kinds of cells in the vascular wall and brain parenchyma may be involved in the pathogenesis of microcirculatory disturbances. The impairment of the paravascular and glymphatic systems also may play important roles in the development of DCI. As pathological mediators for DCI, glutamate and several matricellular proteins have been investigated in addition to inflammatory molecules. Glutamate is involved in excitotoxicity contributing to cortical spreading ischemia and epileptic activity-related events. Microvascular dysfunction is an attractive mechanism to explain the cause of poor outcomes independently of large cerebral artery vasospasm, but needs more studies to clarify the pathophysiologies or mechanisms and to develop a novel therapeutic strategy.

Perioperative Management of Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage is an acute neurologic emergency. Prompt definitive treatment of the aneurysm by craniotomy and clipping or endovascular intervention with coils and/or stents is needed to prevent rebleeding. Extracranial manifestations of aneurysmal subarachnoid hemorrhage include cardiac dysfunction, neurogenic pulmonary edema, fluid and electrolyte imbalances, and hyperglycemia. Data on the impact of anesthesia on long-term neurologic outcomes of aneurysmal subarachnoid hemorrhage do not exist. Perioperative management should therefore focus on optimizing systemic physiology, facilitating timely definitive treatment, and selecting an anesthetic technique based on patient characteristics, severity of aneurysmal subarachnoid hemorrhage, and the planned intervention and monitoring. Anesthesiologists should be familiar with evoked potential monitoring, electroencephalographic burst suppression, temporary clipping, management of external ventricular drains, adenosine-induced cardiac standstill, and rapid ventricular pacing to effectively care for these patients.

GLP-1R Agonist Liraglutide Attenuates Inflammatory Reaction and Neuronal Apoptosis and Reduces Early Brain Injury After Subarachnoid Hemorrhage in Rats

Liraglutide, one of the glucagon-like peptide 1 receptor (GLP-1R) agonists, has been demonstrated to protect brain damage produced by ischemic stroke. However, it remains unknown whether liraglutide attenuates early brain injury after subarachnoid hemorrhage. The present study was performed to explore the effect of liraglutide on early brain injury after subarachnoid hemorrhage in rats, and further investigate the potential mechanisms. Sprague-Dawley rats underwent subarachnoid hemorrhage (SAH) by endovascular perforation, then received subcutaneous injection with liraglutide (50 or 100 μg/kg) or vehicle after 2 and 12 h of SAH. SAH grading, neurological scores, brain water content, and Evans Blue extravasation were measured 24 h after SAH. Immunofluorescent staining was performed to detect the extent of microglial activation in rat brain 24 h after SAH. TUNEL staining was performed to evaluate neuronal apoptosis in rat brain of SAH. Expression of GLP-1R, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), Bcl-2, Bax, and cleaved caspase-3 in rat brain were determined by western blot. Expression of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in rat brain was assessed by ELISA. Neurological dysfunction, brain water content, Evans Blue extravasation, microglial activation, and neuronal apoptosis were significantly reduced by GLP-1R agonist liraglutide. Expression of GLP-1R in rat brain was decreased after SAH, which is significantly elevated by liraglutide. Expression of inflammatory mediates like COX-2, iNOS, TNF-α, and IL-1β was increased after SAH, which were significantly inhibited by liraglutide. Furthermore, SAH caused the elevated expression of pro-apoptotic factors Bax and cleaved caspase-3 in rat brain, both of which were inhibited by liraglutide. In addition, liraglutide reversed the expression of anti-apoptotic protein Bcl-2. Our results demonstrated that liraglutide reduces early brain injury and attenuates inflammatory reaction and neuronal apoptosis in rats of SAH. Liraglutide provides neuroprotection against SAH, which might be associated with the inhibition of inflammation and apoptosis.

Negative Allosteric Modulator of mGluR1 Improves Long-Term Neurologic Deficits after Experimental Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) causes permanent neurological sequelae, but the underlying mechanism needs to be further clarified. Here, we show that inhibition of metabotropic glutamate receptor 1 (mGluR1) with negative allosteric modulator JNJ16259685 improves long-term neurobehavioral outcomes in an endovascular perforation model of SAH. JNJ16259685 improves cerebrovascular dysfunction through attenuation of cerebral blood flow (CBF) reduction, cerebral vasoconstrictio, and microthrombosis formation in a rat SAH model. Moreover, JNJ16259685 reduces experimental SAH-induced long-term neuronal damage through alleviation of neuronal death and degeneration. Mechanically, JNJ16259685 maintains phosphorylation of endothelial NO synthase (eNOS) and vasodilator-stimulated phosphoprotein (VASP) and decreases apoptosis-related factors Bax, active caspase-9, and active caspase-3 following experimental SAH. Altogether, our results suggest JNJ16259685 improves long-term functional impairment through neurovascular protection.

Role of brain tissue oxygenation (PbtO2) in the management of subarachnoid haemorrhage: a scoping review protocol

INTRODUCTION

In patients with subarachnoid haemorrhage (SAH), the initial brain oedema and increased blood volume can cause an increase in intracranial pressure (ICP) leading to impaired cerebral perfusion and tissue hypoxia. However, ICP monitoring may not be enough to detect tissue hypoxia, which can also occur in the absence of elevated ICP. Moreover, some patients will experience tissue hypoxia in a later phase after admission due to the occurrence of delayed cerebral ischaemia. Therefore, the measurement of brain oxygenation using invasive techniques has become of great interest. This scoping review seeks to examine the role of brain tissue oxygenation in the management of patients with SAH, mapping the existing literature to identify areas for future research.

METHODS AND ANALYSIS

This scoping review has been planned following the Joanna Briggs Institute recommendations and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The literature search will be performed using several databases: Medline, EMBASE, the Cochrane Central Register of Controlled Trials and Grey literature. The database searches are planned from the inception to May 2020. Two reviewers will independently screen titles and abstracts, followed by full-text screening of potentially relevant articles with a standardised data extraction. Articles eligible for the inclusion will be discussed with a third reviewer.

ETHICS AND DISSEMINATION

This paper does not require ethics approval. The results of our evaluation will be disseminated on author's web sites. Additional dissemination will occur through presentations at conferences, such as courses and science education conferences, regionally and nationally, and through articles published in peer-reviewed journals.

SCOPING REVIEW REGISTRATION

Open Science Framework Registration: https://doi.org/10.17605/OSF.IO/ZYJ7R.Trial registration numberClinicalTrials.gov Identifier: NCT03754114.

Comparison of radiological versus clinical cerebral vasospasm after aneurysmal subarachnoid hemorrhage: is vasospasm always present?

OBJECTIVES

Radiological and clinical cerebral vasospasm (CV) is defined either as a delayed narrowing of cerebral arteries after aneurysmal subarachnoid hemorrhage (aSAH) or/and occurrence of new neurological deficit/worsening of Modified Glasgow coma score for 2 or more points. The objective of this study is to determine the presence and correlation between clinical and radiological presence of vasospasm in patients with aSAH.

METHODS

This study was designed as a clinical, prospective single center study at the Clinic of Neurosurgery, Clinical Center of Vojvodina, Novi Sad, Serbia. A total of 50 patients was included in the study after having radiologically confirmed aSAH. Intensity and region of CV was determined by CT and CTA performed both on admission and on day 9 of hospitalization, except for cases where clinical protocol required earlier imaging due to occurrence of clinical signs and symptoms of CV. In all patients, values of arterial blood pressure (PABP), headache (HA), body temperature (PBT), nonspecific behaviors (NSB), deterioration of consciousness (DC), new neurological deficit (NND), deterioration of two points or more per modified Glasgow Coma Scale (DmGCS ≥ 2) were monitored.

RESULTS

CTA showed angiographic vasospasm detected in 100% patients with aSAH. Statistically significant positive correlation was found between the intensity of radiological CV and appearance of NND and DmGCS ≥ 2.

CONCLUSIONS

This study confirms that CV always follows aSAH. Future research into pathophysiology of CV is needed in order to determine exact treatment strategies and targets so treatment towards zero mortality can be achieved.

The Role of Losartan as a Potential Neuroregenerative Pharmacological Agent after Aneurysmal Subarachnoid Haemorrhage

Background: Cerebral vasospasm (CVS) remains a major cause of delayed cerebral ischaemia following aneurysmal subarachnoid haemorrhage (SAH), making it a life-threatening type of stroke with high morbidity and mortality. Endothelin-1 is known as key player mediating a strong vasocontractile effect. Interestingly, losartan restores the impaired vasorelaxative ET(B₁) receptor function in a non-competitive direct fashion. With this study, we aimed to investigate a potential losartan-dependent vasodilatory effect vice versa by inhibiting NO release through L-NAME, thus pushing forward concepts to alleviate vasospasm and possibly prevent ischaemia and neurodegeneration. Methods: Cerebral vasospasm was induced by the use of an established double-injection rat model. Sprague-Dawley rats were culled on Day 3 after the ictus, and the vasospastic basilar artery was harvested for isometric investigations of the vessel tone. Ring segments were preincubated with and without L-NAME and/or losartan. Results: Preincubation with L-NAME induced dose-dependent vasoconstriction via endothelin-1 in the non-SAH cohort, which was dose-dependently reduced by losartan. After SAH and dose-dependent endothelin-1 administration, maximal contraction was achieved in the control group without losartan. Furthermore, this maximal contraction was significantly decreased in the losartan group and was reversed by L-NAME. Conclusions: After SAH, losartan was shown to positively influence the ET(B₁) receptor pathway in a non-competitive direct agonistic and indirect fashion. Losartan alleviated the maximum contraction triggered by endothelin-1. This effect was resolved due to NO inhibition by L-NAME. Considering this spasmolytic effect of losartan besides its already well-known effects (attenuating cerebral inflammation, restoring cerebral autoregulation and reducing epileptogenic activity) and alleviating early brain injury, losartan seems to have potential as a promising pharmacological agent after SAH.

Assessment of tissue permeability by early CT perfusion as a surrogate parameter for early brain injury after subarachnoid hemorrhage

OBJECTIVE

The severity of early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (aSAH) correlates with delayed cerebral ischemia (DCI) and outcome. A disruption of the blood-brain barrier is part of EBI pathophysiology. The aim of this study was to assess tissue permeability (PMB) by CT perfusion (CTP) in the acute phase after aSAH and its impact on DCI and outcome.

METHODS

CTP was performed on day 3 after aSAH. Qualitative and quantitative analyses of all CTP parameters, including PMB, were performed. The areas with increased PMB were documented. The value of an early PMB increase as a predictor of DCI and outcome according to the modified Rankin Scale (mRS) grade 3 to 24 months after aSAH was assessed. Possible associations of increased PMB with the Subarachnoid Hemorrhage Early Brain Edema Score (SEBES) and with early perfusion deficits, as radiographic EBI markers, were evaluated.

RESULTS

A total of 69 patients were enrolled in the study. An increased PMB on early CTP was detected in 10.1% (7/69) of all patients. A favorable outcome (mRS grade ≤ 2) occurred in 40.6% (28/69) of all patients. DCI was detected in 25% (17/69) of all patients. An increased PMB was a predictor of DCI (logistic regression, p = 0.03) but not of outcome (logistic regression, p = 0.40). The detection of increased PMB predicted DCI with a sensitivity of 25%, a specificity of 94%, a positive predictive value of 57%, and a negative predictive value of 79% (chi-square test p = 0.03). Early perfusion deficits were seen in 68.1% (47/69) of the patients, a finding that correlated with DCI (p = 0.005) but not with the outcome. No correlation was found between the SEBES and increased PMB.

CONCLUSIONS

Changes in PMB can be detected by early CTP after aSAH, which correlates with DCI. Future studies are needed to evaluate the time course of PMB changes and their interaction with therapeutic measures.

Neuroprotective Effects of Early Brain Injury after Subarachnoid Hemorrhage in Rats by Calcium Channel Mediating Hydrogen Sulfide

The present study explored the modulating apoptosis effect of hydrogen sulfide (H₂S) in subarachnoid hemorrhage (SAH) rats and its exact mechanism. A rat SAH model established by intravascular puncturing was used for the present study. After giving NaHS (donor of H₂S), an L-type calcium channel opener (Bay K8644), or a calcium channel agonist (nifedipine), the neurological function of the rats, associated pathological changes, and expression of apoptosis-related proteins (Bcl-2, Bax, and caspase-3) and microtubule-associated protein (MAP-2) were examined. The concentration of H₂S and expression of cystathionine beta synthase in the hippocampus changed upon early brain injury (EBI) after SAH. Compared with the SAH group, the neurological function of the rats and microstructure observed by electron microscopy were better in the SAH + NaHS group and SAH + Bay K8644 group. It was observed that apoptosis was more obvious in the SAH group than in the control group and was alleviated in the SAH + NaHS group. Furthermore, the alleviating effect of NaHS was partially weakened by nifedipine, indicating that the effect of anti-apoptosis in H₂S might be correlated with the calcium channel. The expression of Bax and caspase-3 was elevated, while the expression of Bcl-2 decreased in the SAH group but improved in the SAH + NaHS and SAH + Bay K8644 group. Compared with the SAH + NaHS group, the expression of pro-apoptotic proteins was higher in the SAH + NaHS + nifedipine group. Therefore, upon EBI following SAH, the H₂S system plays an important neurological protective effect by modulating the function of the L-type calcium channel and inhibiting apoptosis.

Functions of resolvin D1-ALX/FPR2 receptor interaction in the hemoglobin-induced microglial inflammatory response and neuronal injury

Background

Early brain injury (EBI) has been thought to be a key factor affecting the prognosis of subarachnoid hemorrhage (SAH). Many pathologies are involved in EBI, with inflammation and neuronal death being crucial to this process. Resolvin D1 (RvD1) has shown superior anti-inflammatory properties by interacting with lipoxin A4 receptor/formyl peptide receptor 2 (ALX/FPR2) in various diseases. However, it remains not well described about its role in the central nervous system (CNS). Thus, the goal of the present study was to elucidate the potential functions of the RvD1-ALX/FPR2 interaction in the brain after SAH.

Methods

We used an in vivo model of endovascular perforation and an in vitro model of hemoglobin (Hb) exposure as SAH models in the current study. RvD1 was used at a concentration of 25 nM in our experiments. Western blotting, quantitative polymerase chain reaction (qPCR), immunofluorescence, and other chemical-based assays were performed to assess the cellular localizations and time course fluctuations in ALX/FPR2 expression, evaluate the effects of RvD1 on Hb-induced primary microglial activation and neuronal damage, and confirm the role of ALX/FPR2 in the function of RvD1.

Results

ALX/FPR2 was expressed on both microglia and neurons, but not astrocytes. RvD1 exerted a good inhibitory effect in the microglial pro-inflammatory response induced by Hb, possibly by regulating the IRAK1/TRAF6/NF-κB or MAPK signaling pathways. RvD1 could also potentially attenuate Hb-induced neuronal oxidative damage and apoptosis. Finally, the mRNA expression of IRAK1/TRAF6 in microglia and GPx1/bcl-xL in neurons was reversed by the ALX/FPR2-specific antagonist Trp-Arg-Trp-Trp-Trp-Trp-NH2 (WRW4), indicating that ALX/FPR2 could mediate the neuroprotective effects of RvD1.

Conclusions

The results of the present study indicated that the RvD1-ALX/FPR2 interaction could potentially play dual roles in the CNS, as inhibiting Hb promoted microglial pro-inflammatory polarization and ameliorating Hb induced neuronal oxidant damage and death. These results shed light on a good therapeutic target (ALX/FPR2) and a potential effective drug (RvD1) for the treatment of SAH and other inflammation-associated brain diseases.

Calcium sensing receptor contribute to early brain injury through the CaMKII/NLRP3 pathway after subarachnoid hemorrhage in mice

The subversive role of Calcium sensing receptor (CaSR) in cerebral ischemia and traumatic brain injury has been recently reported. Nevertheless, the role of CaSR in early brain injury (EBI) after subarachnoid hemorrhage (SAH) remains unexplored. Using the endovascular perforation model in mice, this study was aimed at investigating the role and potential mechanism of CaSR in EBI after SAH. Gadolinium trichloride (GdCI3), an agonist of CaSR, and NPS-2143, an inhibitor of CaSR, were administered intraperitoneally. The CaMKII inhibitor KN-93 was injected to intracerebroventricular. We found that CaSR expression was increased and widely expressed in neurons, astrocytes, and microglia after SAH. GdCI3 further deteriorated neurological function, brain edema, neurodegeneration, which were alleviated by NPS-2143. Also, GdCI3 increased the level of CaMKII phosphorylation, and upregulated expression of NLRP3, cleaved caspase-1, and IL-1β, which were attenuated by NPS-2143. Besides, CaMKII inhibitor KN-93 down-regulated the upregulated expression of NLRP3, cleaved caspase-1, and IL-1β induced by GdCI3. In conclusion, CaSR activation promotes early brain injury, which may be related to the CaMKII/NLRP3 signaling pathway.

Early High Cerebrospinal Fluid Glutamate: A Potential Predictor for Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) is an important complication after aneurysmal subarachnoid hemorrhage (aSAH). Early identification of cerebrospinal fluid (CSF) markers is helpful for warning of impending DCI. This study assessed whether early high CSF glutamate levels can be observed in aSAH patients who later developed DCI. In this prospective clinical study, patients with normal pressure hydrocephalus or aSAH were enrolled. We found that the early CSF levels of glutamate were significantly elevated in aSAH patients compared to patients with normal pressure hydrocephalus. There was a significant difference in early CSF levels of glutamate between aSAH patients without DCI and with DCI. The early CSF levels of glutamate are significantly related to the Hunt and Hess grade, the World Federation of Neurological Surgeons (WFNS) grade, and the modified Fisher score on admission and occurrence of DCI in aSAH patients. Preliminary evidence of this study suggests that early high CSF glutamate levels are correlated with DCI in aSAH patients.

Time Course of Metabolomic Alterations in Cerebrospinal Fluid After Aneurysmal Subarachnoid Hemorrhage

Object: The aim of this study was to investigate metabolite levels in cerebrospinal fluid (CSF) in their time-dependent course after aneurysmal subarachnoid hemorrhage (aSAH) comparing them to patients harboring unruptured intracranial aneurysms. Methods: Eighty CSF samples of 16 patients were analyzed. The study population included patients undergoing endovascular/microsurgical treatment of ruptured intracranial aneurysms (n = 8), which were assessed for 9 days after aSAH. Control samples were collected from the basal cisterns in elective aneurysm surgery (n = 8). The CSF samples were consecutively collected with extraventricular drain (EVD) placement/intraoperatively, 6 h later, and daily thereafter (day 1-9). The endogenous metabolites were analyzed with a targeted quantitative and quality controlled metabolomics approach using the AbsoluteIDQ®p180Kit. Differences inbetween timepoints and compared to the control group were evaluated. Results: Numerous alterations of amino acid (AA) levels were detected within the first hours after bleeding. The highest mean concentrations occurred 1 week after aSAH. AA levels were continuously increasing over time starting 6 h after aSAH. Taurine concentration was highest briefly after aSAH starting to decrease already after 6 h (vs. day 1-9, p = 0.02). The levels of sphingomyelins/ phosphatidylcholines/ lysophosphatidylcholines/mono-unsaturated fatty acid chain were highly elevated on day 0 (compared to other timepoints or controls, p < 0.01) and decreased over the next several days to concentrations comparable to the control group. Carnitine concentrations were decreased after SAH (vs. day 7, p < 0.01), while they recovered within the next day. The Fischer ratio of branched-chain AA to aromatic AA was lowest immediately after SAH and increased in 7 days (p < 0.001). Conclusion: AA levels in CSF increased overtime and often differ from patients without SAH. There was a peak concentration of structural AA within the first 6 h after aneurysm treatment. Time-dependent alterations of CSF metabolites and compounds may elucidate pathophysiological processes after aSAH, providing potential predictors assessed non-invasively by routine lab testing.

HLY78 Attenuates Neuronal Apoptosis via the LRP6/GSK3β/β-Catenin Signaling Pathway After Subarachnoid Hemorrhage in Rats

Neuronal apoptosis is one of the essential mechanisms of early brain injury after subarachnoid hemorrhage (SAH). Recently, HLY78 has been shown to inhibit apoptosis in tumor cells and embryonic cells caused by carbon ion radiation through activation of the Wnt/β-catenin pathway. This study was designed to explore the anti-apoptotic role of HLY78 in experimental SAH. The results demonstrated that HLY78 attenuated neuronal apoptosis and the neurological deficits after SAH through the activation of low-density lipoprotein receptor-related protein 6 (LRP6), which subsequently increased the level of phosphorylated glycogen synthesis kinase 3 beta (p-GSK3β) (Ser9), β-catenin, and Bcl-2, accompanied by a decrease of p-β-catenin, Bax, and cleaved caspase 3. An LRP6 small-interfering ribonucleic acid reversed the effects of HLY78. In conclusion, HLY78 attenuates neuronal apoptosis and improves neurological deficits through the LRP6/GSK3β/β-catenin signaling pathway after SAH in rats. HLY78 is a promising therapeutic agent to attenuate early brain injury after SAH.

Isoflurane versus sevoflurane for early brain injury and expression of sphingosine kinase 1 after experimental subarachnoid hemorrhage

The first step to treat aneurysmal subarachnoid hemorrhage (SAH) is aneurysmal obliteration under general anesthesia but not treat the SAH itself and the secondary effects. However, the identification of anesthetics with properties that help to attenuate post-SAH brain injury can be useful for improving outcomes of SAH patients. We examined whether 2% isoflurane and 3% sevoflurane posttreatment are protective against early brain injury (EBI) after SAH. This study used 87 8-week-old male CD-1 mice. We induced SAH by endovascular perforation in mice. Animals were randomly divided into 4 groups: sham-operated (n = 16), SAH + vehicle-medical air (n = 26), SAH + 2% isoflurane (n = 22), and SAH + 3% sevoflurane (n = 23). Neurobehavioral function, brain water content and Western blotting were evaluated at 24 h. The expression of sphingosine kinase (SphK), cleaved caspase-3 and cyclooxygenase-2 (COX2) was determined by Western blotting. Cell death was examined by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Both 2% isoflurane and 3% sevoflurane significantly improved neurobehavioral function, and brain edema at 24 h after SAH and attenuated cell death, associated with an increase in SphK1, a decrease in cleaved caspase-3 and COX2. The neuroprotective effects were similar between 2% isoflurane and 3% sevoflurane. These findings suggest that both 2% isoflurane and 3% sevoflurane significantly inhibited EBI by suppressing post-SAH apoptosis and brain inflammation possibly via the SphK1-related pathway.

Intranasal Insulin Treatment Attenuates Metabolic Distress and Early Brain Injury After Subarachnoid Hemorrhage in Mice

BACKGROUND

Intranasal administration of insulin to the brain bypasses the blood brain barrier (BBB) and can increase cerebral glucose uptake and prevent energy failure. Intranasal insulin treatment has shown neuroprotective effects in multiple central nervous system (CNS) lesions, but the effects of intranasal insulin on the metabolic and pathological process of subarachnoid hemorrhage (SAH) are not clear. This study is designed to explore the effects of intranasal insulin treatment on metabolic distress and early brain injury (EBI) after experimental SAH.

METHODS

SAH model was built by endovascular filament perforation method in adult male C57BL/6J mice, and then, insulin was administrated via intranasal route at 0, 24, and 48 h post-SAH. EBI was assessed according to the neurological performance, BBB damage, brain edema, neuroinflammatory reaction, and neuronal apoptosis at each time point. To evaluate metabolic conditions, microdialysis was used to continuously monitor the real-time levels of glucose, pyruvate, and lactate in interstitial fluid (ISF) in living animals. The mRNA and protein expression of glucose transporter-1 and 3 (GLUT-1 and -3) were also tested by RT-PCR and Western blot in brain after SAH.

RESULTS

Compared to vehicle, intranasal insulin treatment promoted the relative mRNA and protein levels of GLUT-1 in SAH brain (0.98 ± 0.020 vs 0.33 ± 0.016 at 24 h, 0.91 ± 0.25 vs 0.21 ± 0.013 at 48 h and 0.94 ± 0.025 vs 0.28 ± 0.015 at 72 h in mRNA/0.96 ± 0.023 vs 0.36 ± 0.015 at 24 h, 0.91 ± 0.022 vs 0.22 ± 0.011 at 48 h and 0.95 ± 0.024 vs 0.27 ± 0.014 at 72 h in protein, n = 8/Group, p < 0.001). Similar results were also observed in GLUT-3. Intranasal insulin reduced the lactate/pyruvate ratio (LPR) and increased ISF glucose level. It also improved neurological dysfunction, BBB damage, and brain edema and attenuated the levels of pro-inflammatory cytokines as well as neuronal apoptosis after SAH.

CONCLUSIONS

The intranasal insulin treatment protects brain from EBI possibly via improving metabolic distress after SAH.

β-Caryophyllene Liposomes Attenuate Neurovascular Unit Damage After Subarachnoid Hemorrhage in Rats

This study was conducted to prepare β-caryophyllene loaded liposomes (BCP-LP) and investigated their effects on neurovascular unit (NVU) damage after subarachnoid hemorrhage (SAH) in rats. A blood injection into the pre-chiasmatic cistern was used to achieve SAH. BCP-LP were prepared, characterized and administrated to rats with SAH. The prepared BCP-LP were spherical with a size distribution of approximately 189.3 nm and Zeta potential of - 13.9 mV. Neurological scoring, the balance beam test, cerebral blood flow monitoring, brain edema and biochemical analyses were applied to evaluate the effects of BCP-LP on rat NVU damage after SAH. The results demonstrated that BCP-LP treatment improved neurological function disorder, balance ability and cerebral blood perfusion in rats. Brain edema detection and blood-brain barrier permeability detection revealed that BCP-LP could reduce brain edema and promote repairment of blood-brain barrier after SAH. Using the western blot experiments, we demonstrated that BCP-LP attenuated the loss of tight junction proteins Occludin and Zonula occludens-1, inhibit the high expression of VEGFR-2 and GFAP, and promote the repair of laminin. These results demonstrate the protective effect BCP-LP exert in the NVU after SAH in rats, and supports the use of BCP-LP for future study and therapy of SAH.

Hydrogen gas therapy improves survival rate and neurological deficits in subarachnoid hemorrhage rats: a pilot study

The high morbidity, high mortality, and significant shortage of effective therapies for subarachnoid hemorrhage (SAH) have created an urgency to discover novel therapies. Human studies in Asia have established the safety of hydrogen gas in the treatment of hepatic, renal, pulmonary, and cardiac diseases. Mechanistically, hydrogen gas has been shown to affect oxidative stress, inflammation, and apoptosis. We hypothesized that hydrogen therapy would improve neurological function and increase survival rate in SAH. High dose hydrogen gas (66% at 3 L/min) was administered for 2 hours at 0.5, 8, and 18 hours after SAH. This treatment increased 72-hour survival rate and provided 24-hour neuroprotection after SAH in rats. To our knowledge, this is the first report demonstrating that high dose hydrogen gas therapy reduces mortality and improves outcome after SAH. Our results correlate well with the proposed mechanisms of hydrogen gas therapy within the literature. We outline four pathways and downstream targets of hydrogen gas potentially responsible for our results. A potentially complex network of pathways responsible for the efficacy of hydrogen gas therapy, along with a limited mechanistic understanding of these pathways, justifies further investigation to provide a basis for clinical trials and the advancement of hydrogen gas therapy in humans. This study was approved by the Institutional Animal Care and Use Committee of Loma Linda University, USA (Approval No. 8160016) in May 2016.

Bakuchiol Attenuates Oxidative Stress and Neuron Damage by Regulating Trx1/TXNIP and the Phosphorylation of AMPK After Subarachnoid Hemorrhage in Mice

Subarachnoid hemorrhage (SAH) is a fatal cerebrovascular condition with complex pathophysiology that reduces brain perfusion and causes cerebral functional impairments. An increasing number of studies indicate that early brain injury (EBI), which occurs within the first 72 h of SAH, plays a crucial role in the poor prognosis of SAH. Bakuchiol (Bak) has been demonstrated to have multiorgan protective effects owing to its antioxidative and anti-inflammatory properties. The present study was designed to investigate the effects of Bak on EBI after SAH and its underlying mechanisms. In this study, 428 adult male C57BL/6J mice weighing 20 to 25 g were observed to investigate the effects of Bak administration in an SAH animal model. The neurological function and brain edema were assessed. Content of MDA/3-NT/8-OHdG/superoxide anion and the activity of SOD and GSH-Px were tested. The function of the blood-brain barrier (BBB) and the protein levels of claudin-5, occludin, zonula occludens-1, and matrix metalloproteinase-9 were observed. TUNEL staining and Fluoro-Jade C staining were conducted to evaluate the death of neurons. Ultrastructural changes of the neurons were observed under the transmission electron microscope. Finally, the roles of Trx, TXNIP, and AMPK in the protective effect of Bak were investigated. The data showed that Bak administration 1) increased the survival rate and alleviated neurological functional deficits; 2) alleviated BBB disruption and brain edema; 3) attenuated oxidative stress by reducing reactive oxygen species, MDA, 3-NT, 8-OHdG, gp91^phox, and 4-HNE; increased the activities of SOD and GSH-Px; and alleviated the damage to the ultrastructure of mitochondria; 4) inhibited cellular apoptosis by regulating the protein levels of Bcl-2, Bax, and cleaved caspase-3; and 5) upregulated the protein levels of Trx1 as well as the phosphorylation of AMPK and downregulated the protein levels of TXNIP. Moreover, the protective effects of Bak were partially reversed by PX-12 and compound C. To summarize, Bak attenuates EBI after SAH by alleviating BBB disruption, oxidative stress, and apoptosis via regulating Trx1/TXNIP expression and the phosphorylation of AMPK. Its powerful protective effects might make Bak a promising novel drug for the treatment of EBI after SAH.

Extracellular vesicle-mediated transfer of miR-21-5p from mesenchymal stromal cells to neurons alleviates early brain injury to improve cognitive function via the PTEN/Akt pathway after subarachnoid hemorrhage

Patients with subarachnoid hemorrhage (SAH) often suffer from cognitive function impairments even when they have received proper treatment, such as the clipping or coiling of aneurysms, and this causes problems with returning to work and burdens the family. Increasing attention has been paid to mesenchymal stem cell (MSC)-derived extracellular vesicle (MSC-EV) as promising therapeutic vesicles for stroke management. In this study, we explored the potential role of MSC-EV in a rat model of SAH. We observed that MSC-EV ameliorated early brain injury (EBI) after SAH by reducing the apoptosis of neurons and that SAH induced an increase in the expression level of miR-21 in the prefrontal cortex and hippocampus. In addition, using miRNA profiling and CSF sequencing data from the exRNA Atlas, we demonstrated that EV-derived miR-21 protected neurons from apoptosis and alleviated SAH-induced cognitive dysfunction. The neuroprotective role of MSC-EV was abrogated by miR-21 knockdown or the administration of MK2206, a PTEN/Akt inhibitor. Overall, our results suggest that MSC-EV promotes neuronal survival and alleviates EBI after SAH through transferring miR-21 to recipient neurons.

The effect of pentoxifylline on cerebral vasospasm following experimental subarachnoid hemorrhage

OBJECTS

Cerebral vasospasm is an important event that occurs following subarachnoid hemorage which has significant mortality and morbidity. The goal in this study was to investigate the effect of pentoxifylline on vasospasm in an experimental subarachnoid hemorrhage model.

METHODS

In this study, 20 male New Zeland White rabbits weighing 3000-3500 g were assigned randomly to four groups. Animals in group 1 served as controls. Animals in group two received only intravenous pentoxifylline injection 3 times in 12 h intervals. In group 3, SAH was induced and no injection was given. Animals in group 4 received intravenous pentoxifylline (6 mg/kg) injections 3 times at 12^th, 24^th and 36^th hours after subarachnoid hemorrhage induction. All animals were sacrificed and basilar arteries were removed at 48th hour. Basilar artery vessel diameters, wall thicknesses and luminal section areas were measured with Spot for Windows version 4.1. Statistical analysis was performed using ANOVA and Kruskall-Wallis tests.

RESULTS

Mean basilar artery luminal section areas and luminal diameters in group 4 were significantly higher compared to group 3 (p < 0.05). Basilar artery wall thicknesses and were found to be higher in group 3 than in other groups and this was also statistically significant (p < 0.05).

CONCLUSION

Our study demonstrated that intravenous administration of pentoxifylline significantly decreases vasospasm after subarachnoid hemorrhage.

Cerebral cavernous malformation 3 relieves subarachnoid hemorrhage-induced neuroinflammation in rats through inhibiting NF-kB signaling pathway

Subarachnoid hemorrhage (SAH) is a severe acute cerebrovascular disease with high rates of disability and death. In recent years, a large number of studies has shown that early brain injury (EBI) may be a crucial cause of the poor prognosis of SAH and that microglia-mediated neuroinflammation is an important pathological process in EBI. Previous studies have indicated that tumor necrosis factor receptor-associated factor 6 (TRAF6) is involved in microglia-mediated neuroinflammation after SAH. In addition, it has been reported that cerebral cavernous malformation 3/mammalian sterile20-like kinase 4 (CCM3/MST4) directly phosphorylates TRAF6 to inhibit its ubiquitination and to limit inflammatory responses. However, the association between CCM3/MST4 and SAH has not been reported. In our present study, we established a SAH model in adult male rats through injecting autologous arterial blood into the prechiasmatic cistern. Additionally, BV-2 cells, as well as primary microglial cultures from rats treated with oxygen hemoglobin (OxyHb) for 24 h, were used as in vitro models of SAH. Then, western blot, immunofluorescence, Fluoro-JadeC staining and Enzyme-linked immunosorbent assay (ELISA) and behavioral tests was applied in this study. We observed no significant change in the level of CCM3/MST4 in brain tissues, but a markedly decline of CCM3 in microglia of rats. We also found that the protein level of CCM3 was decreased in BV-2 cells after OxyHb treatment, reaching the lowest point at 6 h post-treatment. In contrast, there was no significant change in the protein level of MST4. Additionally, we recapitulated decreased expression of CCM3 and changes in subcellular localization of CCM3 in vitro model of SAH with primary microglial cultures treated with OxyHb. Overexpression of CCM3 decreased cellular degeneration, neurocognitive impairment, NF-κB p65 level in the nuclear, and inflammatory factors level (TNF-a and IL-1β). These results suggest that overexpression of CCM3 alleviated brain injury and neurological damage through the NF-κB signaling pathway.

MiR-146a Ameliorates Hemoglobin-Induced Microglial Inflammatory Response via TLR4/IRAK1/TRAF6 Associated Pathways

Microglial activation and sustained inflammation in the brain can lead to neuronal damage. Hence, limiting microglial activation and brain inflammation is a good therapeutic strategy for inflammatory-associated central nervous disease. MiR-146a is a promising therapeutic microRNA, since it can negatively regulate the inflammatory response. We thus investigated the expression changes of miR-146a after experimental induction of a subarachnoid hemorrhage (SAH) in vivo and in vitro, and we assessed the anti-inflammatory effects of miR-146a in microglial cells in vitro. Primary microglial cells were preincubated with miR-146a before hemoglobin (Hb) treatment. The results indicated that miR-146a decreased gene expression of Hb-induced pro-inflammatory cytokines (TNF-α and IL-1β) and phenotype-related genes (iNOS and CD86) through IRAK1/TRAF6/NF-κB or MAPK signaling pathways, suggesting its pro-resolution activity in microglia. However, contrary to the LPS-induced microglia or macrophage activation model, we did not observe an elevation in miR-146a after activation. Overall, our findings demonstrated that miR-146a was involved in the regulation of brain inflammation and could be considered a novel therapeutic agent for treating brain inflammation.