Comparison of experimental rat models of early brain injury after subarachnoid hemorrhage

Progressive histological and behavioral deterioration of a novel mouse model of secondary hydrocephalus after subarachnoid hemorrhage

Hydrocephalus commonly occurs after subarachnoid hemorrhage (SAH) and is associated with increased morbidity and disability in patients with SAH. Choroid plexus cerebrospinal fluid (CSF) hypersecretion, obliterative arachnoiditis occluding the arachnoid villi, lymphatic obstruction, subarachnoid fibrosis, and glymphatic system injury are considered the main pathological mechanisms of hydrocephalus after SAH. Although the mechanisms of hydrocephalus after SAH are increasingly being revealed, the clinical prognosis of SAH still has not improved significantly. Further research on SAH is needed to reveal the underlying mechanisms of hydrocephalus and develop translatable therapies. A model that can stably mimic the histopathological and neuroethological features of hydrocephalus is critical for animal experiments. There have been fewer animal studies on hydrocephalus after SAH than on other stroke subtypes. The development of a reproducible and effective model of hydrocephalus after SAH is essential. In this study, we establish a mouse model of SAH that stably mimics brain injury and hydrocephalus after SAH through injections of autologous blood into the cisterna magna via different methods and characterize the model in terms of neurological behavior, histology, imaging, neuronal damage, and white matter damage.

The Role of Serum Monocytes and Tissue Macrophages in Driving Left Ventricular Systolic Dysfunction and Cardiac Inflammation Following Subarachnoid Hemorrhage

BACKGROUND

Neurocardiogenic injury is common after aneurysmal subarachnoid hemorrhage (aSAH) despite low prevalence of preexisting cardiac disease. Potential mechanisms include autonomic dysregulation due to excess catecholamines as well as systemic inflammation. Understanding how inflammation contributes to cardiac dysfunction may aid in identifying novel therapeutic strategies. Here, we investigated serum leukocytes as predictors of left ventricular systolic dysfunction in patients with aSAH. We also investigated increased cardiac macrophages in an animal model of SAH and whether immunomodulatory treatment could attenuate this inflammatory response.

METHODS

We retrospectively analyzed 256 patients with aSAH admitted to University of Illinois Hospital between 2013 and 2019. Our inclusion criteria included patients with aSAH receiving an echocardiogram within 72 h of admission. Our primary outcome was echocardiographic evidence of systolic dysfunction. We performed multinomial regression and receiver operating curve analysis. We also used the endovascular perforation model of SAH in male Sprague-Dawley rats to assess for myocardial inflammation. Two days after surgery, hearts were collected and stained for the macrophage marker Iba-1. We compared the presence and morphology of macrophages in cardiac tissue isolated from SAH animals and sham controls treated with and without the immunomodulatory agent fingolimod.

RESULTS

Of 256 patients with aSAH, 233 (91.0%) underwent echocardiography within 72 h of admission. Of 233, 81 (34.7%) had systolic dysfunction. Patients had baseline differences in the presence of hypertension, alcohol use, and admission Glasgow Coma Scale and Hunt-Hess score. On multivariable analysis, total leukocytes (odds ratio 1.312, p < 0.001), neutrophils (odds ratio 1.242, p = 0.012), and monocytes (odds ratio 6.112, p = 0.008) were independent predictors of reduced systolic function, whereas only monocytes (odds ratio 28.014, p = 0.030) predicted hyperdynamic function. Within the rodent heart, there were increased macrophages after SAH relative to controls, and this was attenuated by fingolimod treatment (p < 0.0001).

CONCLUSIONS

Increased serum leukocytes are associated with abnormal left ventricular systolic function following aSAH. The strongest independent predictor of both reduced and hyperdynamic systolic function was increased monocytes. Increased cardiac macrophages after experimental SAH can also be targeted by using immunomodulatory drugs.

Animal Welfare Aspects in Planning and Conducting Experiments on Rodent Models of Subarachnoid Hemorrhage

Subarachnoid hemorrhage is an acute life-threatening cerebrovascular disease with high socio-economic impact. The most frequent cause, the rupture of an intracerebral aneurysm, is accompanied by abrupt changes in intracerebral pressure, cerebral perfusion pressure and, consequently, cerebral blood flow. As aneurysms rupture spontaneously, monitoring of these parameters in patients is only possible with a time delay, upon hospitalization. To study alterations in cerebral perfusion immediately upon ictus, animal models are mandatory. This article addresses the points necessarily to be included in an animal project proposal according to EU directive 2010/63/EU for the protection of animals used for scientific purposes and herewith offers an insight into animal welfare aspects of using rodent models for the investigation of cerebral perfusion after subarachnoid hemorrhage. It compares surgeries, model characteristics, advantages, and drawbacks of the most-frequently used rodent models-the endovascular perforation model and the prechiasmatic and single or double cisterna magna injection model. The topics of discussing anesthesia, advice on peri- and postanesthetic handling of animals, assessing the severity of suffering the animals undergo during the procedure according to EU directive 2010/63/EU and weighing the use of these in vivo models for experimental research ethically are also presented. In conclusion, rodent models of subarachnoid hemorrhage display pathophysiological characteristics, including changes of cerebral perfusion similar to the clinical situation, rendering the models suited to study the sequelae of the bleeding. A current problem is low standardization of the models, wherefore reporting according to the ARRIVE guidelines is highly recommended. Animal welfare aspects of rodent models of subarachnoid hemorrhage. Rodent models for investigation of cerebral perfusion after subarachnoid hemorrhage are compared regarding surgeries and model characteristics, and 3R measures are suggested. Anesthesia is discussed, and advice given on peri- and postanesthetic handling. Severity of suffering according to 2010/63/EU is assessed and use of these in vivo models weighed ethically.

Nonpharmacological modulation of cortical spreading depolarization

AIMS

Cortical spreading depolarization (CSD) is a wave of pathologic neuronal dysfunction that spreads through cerebral gray matter, causing neurologic disturbance in migraine and promoting lesion development in acute brain injury. Pharmacologic interventions have been found to be effective in migraine with aura, but their efficacy in acutely injured brains may be limited. This necessitates the assessment of possible adjunctive treatments, such as nonpharmacologic methods. This review aims to summarize currently available nonpharmacological techniques for modulating CSDs, present their mechanisms of action, and provide insight and future directions for CSD treatment.

MAIN METHODS

A systematic literature review was performed, generating 22 articles across 3 decades. Relevant data is broken down according to method of treatment.

KEY FINDINGS

Both pharmacologic and nonpharmacologic interventions can mitigate the pathological impact of CSDs via shared molecular mechanisms, including modulating K⁺/Ca²⁺/Na⁺/Cl^- ion channels and NMDA, GABA_A, serotonin, and CGRP ligand-based receptors and decreasing microglial activation. Preclinical evidence suggests that nonpharmacologic interventions, including neuromodulation, physical exercise, therapeutic hypothermia, and lifestyle changes can also target unique mechanisms, such as increasing adrenergic tone and myelination and modulating membrane fluidity, which may lend broader modulatory effects. Collectively, these mechanisms increase the electrical initiation threshold, increase CSD latency, slow CSD velocity, and decrease CSD amplitude and duration.

SIGNIFICANCE

Given the harmful consequences of CSDs, limitations of current pharmacological interventions to inhibit CSDs in acutely injured brains, and translational potentials of nonpharmacologic interventions to modulate CSDs, further assessment of nonpharmacologic modalities and their mechanisms to mitigate CSD-related neurologic dysfunction is warranted.

Mild hypothermia alleviates early brain injury after subarachnoid hemorrhage via suppressing pyroptosis through AMPK/NLRP3 inflammasome pathway in rats

As a subtype of stroke, subarachnoid hemorrhage (SAH) has a notoriously high rate of disability and mortality owing to the lack of effective intervention. Early brain injury (EBI) is the main factor responsible for the dismal prognosis of SAH patients. The current study intends to explore the molecular mechanism underlying the effect of MH on EBI after SAH from a novel perspective of pyroptosis, a highly specific inflammatory programmed cell death, in the SAH rat model. Sprague-Dawley (SD) rats were divided into different groups in accordance with various treatments. In the treatment group, the rats underwent mild hypothermia for 4 h after modeling; in the inhibitor group, Compound C (an inhibitor of AMPK) was administered intravenous injections (i.v.) 30 min before modeling. Neurological score, neuronal death, brain water content, inflammatory reaction, and expression levels of pyroptosis-related proteins were evaluated in the rats. Our results indicate that the MH therapy significantly increased the neurological score and assuaged brain edema, neuronal injury, and inflammatory reaction induced by SAH. Meanwhile, MH therapy upregulated the level of AMPK phosphorylation whereas downregulated the protein expressions of NLRP3, ASC, cleaved caspase-1, GSDMD, IL-1β, and IL-18. The reversed effect of MH therapy by Compound C concretely indicated that MH therapy inhibited pyroptosis through an AMPK-dependent pathway. Our study also found that MH therapy potently curbed the increasing trend of brain temperature (BT), rectal temperature (RT), and ICP after SAH. Taken together, our data indicate that the neuroprotective effects of MH therapy were manifested by inhibiting pyroptosis via the AMPK/NLRP3 inflammasome pathway, which may serve as a promising therapy for the intervention of 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.

DNase-1 Treatment Exerts Protective Effects in Neurogenic Pulmonary Edema via Regulating the Neutrophil Extracellular Traps after Subarachnoid Hemorrhage in Mice

It has been reported that neutrophil extracellular traps (NETs) involve inflammation, coagulation and cell death. Acute lung injury is also considered to be connected with NETs. Deoxyribonuclease I (DNase-1), a clinical medication for the respiratory system, has been reported to degrade cell-free DNA (cfDNA), which is the main component of NETs. Herein, we did research to clarify the therapeutic value of DNase-1 in NPE after SAH. In this model, we found that the treatment of DNase-1 remarkably decreased lung water, neutrophilic infiltration and inflammation. In addition, DNase-1 inhibited the NETs and proinflammatory subtype transition of the macrophages. Moreover, the depletion of neutrophil also verified the role of NETs in NPE. Our results suggest that DNase-1 has the potential to effectively relieve the NPE after SAH and to be a clinical drug for use after SAH.

SIRT1 mediates hypoxic postconditioning- and resveratrol-induced protection against functional connectivity deficits after subarachnoid hemorrhage

Functional connectivity (FC) is a sensitive metric that provides a readout of whole cortex coordinate neural activity in a mouse model. We examine the impact of experimental SAH modeled through endovascular perforation, and the effectiveness of subsequent treatment on FC, through three key questions: 1) Does the endovascular perforation model of SAH induce deficits in FC; 2) Does exposure to hypoxic conditioning provide protection against these FC deficits and, if so, is this neurovascular protection SIRT1-mediated; and 3) does treatment with the SIRT1 activator resveratrol alone provide protection against these FC deficits? Cranial windows were adhered on skull-intact mice that were then subjected to either sham or SAH surgery and either left untreated or treated with hypoxic post-conditioning (with or without EX527) or resveratrol for 3 days. Mice were imaged 3 days post-SAH/sham surgery, temporally aligned with the onset of major SAH sequela in mice. Here we show that the endovascular perforation model of SAH induces global and network-specific deficits in FC by day 3, corresponding with the time frame of DCI in mice. Hypoxic conditioning provides SIRT1-mediated protection against these network-specific FC deficits post-SAH, as does treatment with resveratrol. Conditioning-based strategies provide multifaceted neurovascular protection in experimental SAH.

Neuroprotective Effect of Chrysophanol as a PI3K/AKT/mTOR Signaling Inhibitor in an Experimental Model of Autologous Blood-induced Intracerebral Hemorrhage

OBJECTIVE

Intracerebral hemorrhage (ICH) refers to predominant, sporadic, and non-traumatic bleeding in the brain parenchyma. The PI3K/AKT/mTOR signaling pathway is an important signal transduction pathway regulated by enzyme-linked receptors and has many biological functions in mammals. It plays a key role in neuronal metabolism, gene expression regulation, and tissue homeostasis in the healthy and diseased brain.

METHODS

In the present study, the role of the PI3K/AKT/mTOR pathway inhibitor chrysophanol (CPH) (10 mg/kg and 20 mg/kg, orally) in the improvement of ICH-associated neurological defects in rats was investigated. Autologous blood (20 µL/5 min/unilateral/intracerebroventricular) mimics ICH-like defects involving cellular and molecular dysfunction and neurotransmitter imbalance. The current study also included various behavioral assessments to examine cognition, memory, and motor and neuromuscular coordination. The protein expression levels of PI3K, AKT, and mTOR as well as myelin basic protein and apoptotic markers, such as Bax, Bcl-2, and caspase-3, were examined using ELISA kits. Furthermore, the levels of various neuroinflammatory cytokines and oxidative stress markers were assessed. Additionally, the neurological severity score, brain water content, gross brain pathology, and hematoma size were used to indicate neurological function and brain edema.

RESULTS

CPH was found to be neuroprotective by restoring neurobehavioral alterations and significantly reducing the elevated PI3K, AKT, and mTOR protein levels, and modulating the apoptotic markers such as Bax, Bcl-2, and caspase-3 in rat brain homogenate. CPH substantially reduced the inflammatory cytokines like interleukin (IL)-1β, IL-6, and tumor necrosis factor-α. CPH administration restored the neurotransmitters GABA, glutamate, acetylcholine, dopamine, and various oxidative stress markers.

CONCLUSION

Our results show that CPH may be a promising therapeutic approach for overcoming neuronal damage caused by the overexpression of the PI3K/AKT/mTOR signaling pathway in ICH-induced neurological dysfunctions in rats.

Neuroprotective Effect of Chrysophanol as a PI3K/AKT/mTOR Signaling Inhibitor in an Experimental Model of Autologous Blood-induced Intracerebral Hemorrhage

OBJECTIVE

Intracerebral hemorrhage (ICH) refers to predominant, sporadic, and non-traumatic bleeding in the brain parenchyma. The PI3K/AKT/mTOR signaling pathway is an important signal transduction pathway regulated by enzyme-linked receptors and has many biological functions in mammals. It plays a key role in neuronal metabolism, gene expression regulation, and tissue homeostasis in the healthy and diseased brain.

METHODS

In the present study, the role of the PI3K/AKT/mTOR pathway inhibitor chrysophanol (CPH) (10 mg/kg and 20 mg/kg, orally) in the improvement of ICH-associated neurological defects in rats was investigated. Autologous blood (20 µL/5 min/unilateral/intracerebroventricular) mimics ICH-like defects involving cellular and molecular dysfunction and neurotransmitter imbalance. The current study also included various behavioral assessments to examine cognition, memory, and motor and neuromuscular coordination. The protein expression levels of PI3K, AKT, and mTOR as well as myelin basic protein and apoptotic markers, such as Bax, Bcl-2, and caspase-3, were examined using ELISA kits. Furthermore, the levels of various neuroinflammatory cytokines and oxidative stress markers were assessed. Additionally, the neurological severity score, brain water content, gross brain pathology, and hematoma size were used to indicate neurological function and brain edema.

RESULTS

CPH was found to be neuroprotective by restoring neurobehavioral alterations and significantly reducing the elevated PI3K, AKT, and mTOR protein levels, and modulating the apoptotic markers such as Bax, Bcl-2, and caspase-3 in rat brain homogenate. CPH substantially reduced the inflammatory cytokines like interleukin (IL)-1β, IL-6, and tumor necrosis factor-α. CPH administration restored the neurotransmitters GABA, glutamate, acetylcholine, dopamine, and various oxidative stress markers.

CONCLUSION

Our results show that CPH may be a promising therapeutic approach for overcoming neuronal damage caused by the overexpression of the PI3K/AKT/mTOR signaling pathway in ICH-induced neurological dysfunctions in rats.

Vascular Reactivity to Hypercapnia Is Impaired in the Cerebral and Retinal Vasculature in the Acute Phase After Experimental Subarachnoid Hemorrhage

Objective: Impaired cerebral blood flow (CBF) regulation, such as reduced reactivity to hypercapnia, contributes to the pathophysiology after aneurysmal subarachnoid hemorrhage (SAH), but temporal dynamics in the acute phase are unknown. Featuring comparable molecular regulation mechanisms, the retinal vessels participate in chronic and subacute stroke- and SAH-associated vessel alterations in patients and can be studied non-invasively. This study is aimed to characterize the temporal course of the cerebral and retinal vascular reactivity to hypercapnia in the acute phase after experimental SAH and compare the potential degree of impairment.

Methods: Subarachnoid hemorrhage was induced by injecting 0.5 ml of heparinized autologous blood into the cisterna magna of male Wistar rats using two anesthesia protocols [isoflurane/fentanyl n = 25 (Sham + SAH): Iso—Group, ketamine/xylazine n = 32 (Sham + SAH): K/X—Group]. CBF (laser speckle contrast analysis) and physiological parameters were measured continuously for 6 h. At six predefined time points, hypercapnia was induced by hypoventilation controlled via blood gas analysis, and retinal vessel diameter (RVD) was determined non-invasively.

Results: Cerebral reactivity and retinal reactivity in Sham groups were stable with only a slight attenuation after 2 h in RVD of the K/X—Group. In the SAH Iso—Group, cerebral and retinal CO2 reactivity compared to baseline was immediately impaired starting at 30 min after SAH (CBF p = 0.0090, RVD p = 0.0135) and lasting up to 4 h (p = 0.0136, resp. p = 0.0263). Similarly, in the K/X—Group, cerebral CO2 reactivity was disturbed early after SAH (30 min, p = 0.003) albeit showing a recovery to baseline after 2 h while retinal CO2 reactivity was impaired over the whole observation period (360 min, p = 0.0001) in the K/X—Group. After normalization to baseline, both vascular beds showed a parallel behavior regarding the temporal course and extent of impairment.

Conclusion: This study provides a detailed temporal analysis of impaired cerebral vascular CO2 reactivity starting immediately after SAH and lasting up to 6 h. Importantly, the retinal vessels participate in these acute changes underscoring the promising role of the retina as a potential non-invasive screening tool after SAH. Further studies will be required to determine the correlation with functional outcomes.

Hepcidin Promoted Ferroptosis through Iron Metabolism which Is Associated with DMT1 Signaling Activation in Early Brain Injury following Subarachnoid Hemorrhage

Iron metabolism disturbances play an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and hepcidin largely influences iron metabolism. Importantly, iron metabolism may be associated with ferroptosis, recently a nonapoptotic iron-dependent form of cell death that may have a great impact on brain injury after SAH. We investigated hepcidin on iron metabolism and ferroptosis involving divalent metal transporter 1 (DMT1), and ferroportin-1 (FPN1) in a rat model of SAH. Male Sprague-Dawley rats were subjected to the endovascular perforation to induce SAH, and treated with heparin (inhibitor of hepcidin), or oncostatin M (OSM, inducer of hepcidin), or ebselen (inhibitor of DMT1) by intracerebroventricular injections. Hepcidin, DMT1, FPN1 and glutathione peroxidase 4 (GPX4), were detected by western blot and immunofluorescence. Iron metabolism was detected through Perl's iron staining and iron content assay. Ferroptosis, the ROS production, lipid peroxidation (LPO) was evaluated by monitoring methane dicarboxylic aldehyde (MDA), glutathione (GSH), glutathione peroxidase 4 (GPX4) activity, and transmission electron microscopy. Neurological deficit scores, Evans blue staining and brain water content were also determined to detect EBI 72 h after SAH. Our results showed that inhibition of DMT1 by ebselen could suppress iron accumulation and lipid peroxidation, and thereby alleviate ferroptosis and EBI in SAH rats. Heparin downregulated the expression of hepcidin and DMT1, increased FPN1, and exerted protective effects that were equivalent to those of ebselen on ferroptosis and EBI. In addition, OSM increased the expression of hepcidin and DMT1, decreased FPN1, and aggravated ferroptosis and EBI, while the effect on ferroptosis was reversed by ebselen. Therefore, the study revealed that hepcidin could regulate iron metabolism and contribute to ferroptosis via DMT1 signaling activation in rats with EBI after SAH.

Role of cyclin‑dependent kinase 5 in early brain injury following experimental subarachnoid hemorrhage

Increasing evidence indicates that early brain injury (EBI) can contribute to poor outcomes following subarachnoid hemorrhage (SAH), and is associated with apoptosis. Cyclin-dependent kinase 5 (Cdk5) is a key mediator of neuronal viability. The role of Cdk5 in several neurological disorders has been elucidated; however, its role in EBI after SAH remains unclear. The present study aimed to explore the involvement of Cdk5 in EBI after SAH. The expression levels of Cdk5, Cdk5 phosphorylated at Tyr15 (Cdk5-pTyr15) and p25 (a Cdk5 activator) were assessed by western blotting, and the cell distribution of Cdk5 was demonstrated by double immunofluorescence. The expression levels of caspase-3 and cytochrome c were evaluated by western blotting to assess the severity of neuronal apoptosis. Nissl and TUNEL staining experiments were performed to observe the effects of roscovitine, a Cdk5 inhibitor, on EBI following SAH. The results indicated that the expression levels of Cdk5, p25 and Cdk5-pTyr15 significantly increased in the rat temporal cortex following SAH. Immunofluorescence staining indicated that Cdk5 was expressed in the neurons and astrocytes of the rat cortex after SAH and that Cdk5 underwent nuclear translocation in neurons. Roscovitine administration effectively inhibited Cdk5 activation. In conclusion, roscovitine treatment significantly mitigated EBI and alleviated cerebral edema following SAH. These findings suggest that Cdk5 is an important target in SAH therapy.

Intra-arterial Contrast-enhanced Micro-computed Tomography Can Evaluate Intracranial Status in the Ultra-early Phase of Experimental Subarachnoid Hemorrhage in Rats

The endovascular perforation (EP) model is a common technique for experimental subarachnoid hemorrhage (SAH) in rats, simulating the pathophysiological features observed in the acute phase of SAH. Due to the drawbacks of large variations in the amount of bleeding, the results obtained from this model require severity evaluation. However, no less-invasive procedure could confirm the precise intracranial conditions immediately after establishing the rat EP model. We created a novel method for evaluating SAH immediately after establishing the rat EP model using intra-arterial contrast-enhanced micro-computed tomography (CT). We administered contrast agents continuously via the carotid artery during surgery and performed CT examination immediately after SAH induction. First, bleeding severity was classified by establishing a scoring system based on the CT findings (cSAH scoring system). Subsequently, we determined the actual SAH distribution macroscopically and histologically and compared it with the cSAH scores. Second, we investigated the contrast agent’s neurotoxicity in rats. Finally, we confirmed the correlation between cSAH scores and SAH severity, including neurological status, cerebral vasospasm, and hematoma volume 24 hr after SAH. Intra-arterial contrast-enhanced micro-CT could visualize the distribution of SAH proportionally to the bleeding severity immediately after establishing the EP model. Moreover, the contrast agent administration was determined not to be neurotoxic to rats. The cSAH scoring revealed a significant correlation with the SAH severity in the rat EP model (P <0.01). Thus, our minimally invasive method provided precise information on intracranial status in the ultra-early phase of SAH in rats EP model.

Aneurysmal subarachnoid hemorrhage survivors show long-term deficits in spatial reference memory in a pilot study of a virtual water maze paradigm

BACKGROUND

Limited data exists on the long-term effects of aneurysmal subarachnoid hemorrhage (SAH) on spatial memory. Herein, we used a computerized virtual water maze to evaluate the feasibility of spatial memory testing in pilot cohort of ten patients who survived previous SAH.

METHODS

Ten SAH survivors (5.8 ± 5.1 years after initial hemorrhage) and 7 age-matched controls underwent testing in a virtual water maze computer program. Additional subgroup analyses were performed to evaluate spatial reference memory correlation for ventricular size on admission, placement of an external ventricular drain and placement of a shunt.

RESULTS

With respect to the spatial memory acquisition phase, there was no significant difference of pathway length traveled to reach the platform between SAH survivors and control subjects. During the probe trial, control subjects spent significantly longer time in target quadrants compared to SAH survivors (F_{(3, 24)} = 10.32, p = 0.0001; Target vs. Right: Mean percent difference 0.16 [0-0.32], p = 0.045; Target vs. Across: Mean percent difference 0.35 [0.19-0.51], p < 0.0001; Target vs. Left: Mean percent difference 0.21 [0.05-0.37], p = 0.0094). Furthermore, patients who initially presented with smaller ventricles performed worse that those patients who had ventriculomegaly and/or required surgical management of hydrocephalus.

CONCLUSIONS

Our data demonstrate that SAH survivors have persistent spatial reference memory deficits years after the hemorrhage. Hydrocephalus at presentation and external ventricular drainage were not found to be associated with poor spatial memory outcomes in this pilot cohort. Therefore, other causes such as global cerebral edema or magnitude of initial ICP spike, need to be considered to be examined as root cause as well in subsequent studies. The protocol described in this manuscript is able to demonstrate a spatial reference memory deficit and can be used to study risk factors for spatial memory impairment on a larger scale.

Ergosta-7,9(11),22-trien-3β-ol Alleviates Intracerebral Hemorrhage-Induced Brain Injury and BV-2 Microglial Activation

Intracerebral hemorrhage (ICH) is a devastating neurological disorder characterized by an exacerbation of neuroinflammation and neuronal injury, for which few effective therapies are available at present. Inhibition of excessive neuroglial activation has been reported to alleviate ICH-related brain injuries. In the present study, the anti-ICH activity and microglial mechanism of ergosta-7,9(11),22-trien-3β-ol (EK100), a bioactive ingredient from Asian medicinal herb Antrodia camphorate, were evaluated. Post-treatment of EK100 significantly attenuated neurobehavioral deficit and MRI-related brain lesion in the mice model of collagenase-induced ICH. Additionally, EK100 alleviated the inducible expression of cyclooxygenase (COX)-2 and the activity of matrix metalloproteinase (MMP)-9 in the ipsilateral brain regions. Consistently, it was shown that EK100 concentration-dependently inhibited the expression of COX-2 protein in Toll-like receptor (TLR)-4 activator lipopolysaccharide (LPS)-activated microglial BV-2 and primary microglial cells. Furthermore, the production of microglial prostaglandin E₂ and reactive oxygen species were attenuated by EK100. EK100 also attenuated the induction of astrocytic MMP-9 activation. Among several signaling pathways, EK100 significantly and concentration-dependently inhibited activation of c-Jun N-terminal kinase (JNK) MAPK in LPS-activated microglial BV-2 cells. Consistently, ipsilateral JNK activation was markedly inhibited by post-ICH-treated EK100 in vivo. In conclusion, EK100 exerted the inhibitory actions on microglial JNK activation, and attenuated brain COX-2 expression, MMP-9 activation, and brain injuries in the mice ICH model. Thus, EK100 may be proposed and employed as a potential therapeutic agent for ICH.

Neuroprotective role of glutathione peroxidase 4 in experimental subarachnoid hemorrhage models

BACKGROUND AND PURPOSE

Early brain injury is an essential pathological process after subarachnoid hemorrhage (SAH), with many cell death modalities. Ferroptosis is a newly discovered regulated cell death caused by the iron-dependent accumulation of lipid peroxidation, which can be prevented by glutathione peroxidase 4 (GPX4). Our study aimed to investigate the role of GPX4 in neuronal cell death after experimental SAH.

METHODS

In vivo experimental SAH was induced by injecting autologous arterial blood into the prechiasmatic cistern in male Sprague-Dawley rats. Meanwhile, the in vitro SAH model was performed with primary rat cortical neurons cultured in medium containing hemoglobin (Hb). Adenovirus was used to overexpress GPX4 before experimental SAH. GPX4 expression was detected by western blot and immunofluorescence experiments. Malondialdehyde (MDA) was measured to evaluate the level of lipid peroxidation. Nissl staining was employed to assess cell death in vivo, whereas lactate dehydrogenase (LDH) release was used to evaluate cell damage in vitro. The brain water content and neurological deficits were evaluated to determine brain injury.

RESULTS

Endogenous GPX4 was mainly expressed in neurons, and its expression decreased at 24 h after experimental SAH. Overexpression of GPX4 significantly reduced lipid peroxidation and cell death in the experimental SAH models both in vivo and in vitro. Moreover, overexpression of GPX4 ameliorated brain edema and neurological deficits at 24 h after SAH.

CONCLUSIONS

The decrease of GPX4 expression potentially plays an important role in ferroptosis during early brain injury after SAH. Overexpression of GPX4 has a neuroprotective effect 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.

Toll-like receptor-4 pathway as a possible molecular mechanism for brain injuries after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is known as an acute catastrophic neurological disease that continues to be a serious and significant health problem worldwide. The mechanisms contributing to brain injury after SAH remain unclear despite decades of study focusing on early brain injury (EBI) and delayed brain injury (DBI). Neuroinflammation is a well-recognized consequence of SAH and may be responsible for EBI, cerebral vasospasm, and DBI. Toll-like receptors (TLRs) play a crucial role in the inflammatory response by recognizing damage-associated molecular patterns derived from the SAH. TLR4 is the most studied Toll-like receptor and is widely expressed in the central nervous system (CNS). It can be activated by the extravasated blood components in myeloid differentiation primary response-88/Toll/interleukin-1 receptor-domain-containing adapter-inducing interferon-β (MyD88/TRIF)-dependent pathway after SAH. Transcription factors, such as nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK) and interferon regulatory factor (IRF), that regulate the expression of proinflammatory cytokine genes are initiated by the activation of TLR4, which cause the brain damage after SAH. TLR4 may therefore be a useful therapeutic target for overcoming EBI and DBI in post-SAH neuroinflammation, thereby improving SAH outcome. In the present review, we summarized recent findings from basic and clinical studies of SAH, with a primary focus on the biological characteristics and functions of TLR4 and discussed the mechanisms associated with TLR4 signaling pathway in EBI and DBI following SAH.

Edaravone combined with cinepazide maleate on neurocyte autophagy and neurological function in rats with subarachnoid hemorrhage

Effects of edaravone combined with cinepazide maleate on neurocyte autophagy and neurological function in rats with subarachnoid hemorrhage were investigated. Eighty SD rats were selected to establish subarachnoid hemorrhage (SAH) rat models, which were divided into sham operation group, SAH group, MCI group and combined group. Hippocampal tissue of each group was taken to observe the number of neurocytes. The expression levels of Beclin-1 and (light chain LC3)-II of rats in each group were detected by ELISA. Pearson's correlation factors were used to analyze the correlation between Beclin-1 and LC3-11, and neurological function tests were carried out on rats of each group 14 and 28 days after administration. The morphological and structural damage of nerve cells in the combined group was further alleviated, and the survival rate of neurons significantly increased at all time points (P<0.05). The expression levels of Beclin-1 and LC3-11 in combined group was significantly higher than those in SAH group and CMI group (P<0.05), and Beclin-1 was positively correlated with LC3-11 (r=0.9454). Longa score of the combined group was significantly lower than that of the other two groups, and muscle strength score was significantly higher than that of the other two groups (P<0.05). Edaravone combined with cinepazide maleate can effectively increase the survival rate of brain cells and promote the volatilization of neurological function in the treatment of hemorrhage in the subretinal space of the omentum, which is worthy of popularization and application.

Neuroinflammation and Microvascular Dysfunction After Experimental Subarachnoid Hemorrhage: Emerging Components of Early Brain Injury Related to Outcome

Aneurysmal subarachnoid hemorrhage has a high mortality rate and, for those who survive this devastating injury, can lead to lifelong impairment. Clinical trials have demonstrated that cerebral vasospasm of larger extraparenchymal vessels is not the sole contributor to neurological outcome. Recently, the focus of intense investigation has turned to mechanisms of early brain injury that may play a larger role in outcome, including neuroinflammation and microvascular dysfunction. Extravasated blood after aneurysm rupture results in a robust inflammatory response characterized by activation of microglia, upregulation of cellular adhesion molecules, recruitment of peripheral immune cells, as well as impaired neurovascular coupling, disruption of the blood-brain barrier, and imbalances in endogenous vasodilators and vasoconstrictors. Each of these phenomena is either directly or indirectly associated with neuronal death and brain injury. Here, we review recent studies investigating these various mechanisms in experimental models of subarachnoid hemorrhage with special emphasis on neuroinflammation and its effect on microvascular dysfunction. We discuss the various therapeutic targets that have risen from these mechanistic studies and suggest the utility of a multi-targeted approach to preventing delayed injury and improving outcome after subarachnoid hemorrhage.

The Acute Phase of Experimental Subarachnoid Hemorrhage: Intracranial Pressure Dynamics and Their Effect on Cerebral Blood Flow and Autoregulation

Clinical presentation and neurological outcome in subarachnoid hemorrhage (SAH) is highly variable. Aneurysmal SAH (aSAH) is hallmarked by sudden increase of intracranial pressure (ICP) and acute hypoperfusion contributing to early brain injury (EBI) and worse outcome, while milder or non-aneurysmal SAH with comparable amount of blood are associated with better neurological outcome, possibly due to less dramatic changes in ICP. Acute pressure dynamics may therefore be an important pathophysiological aspect determining neurological complications and outcome. We investigated the influence of ICP variability on acute changes after SAH by modulating injection velocity and composition in an experimental model of SAH. Five hundred microliters of arterial blood (AB) or normal saline (NS) were injected intracisternally over 1 (AB₁, NS₁), 10 (AB_10, NS₁₀), or 30 min (AB₃₀) with monitoring for 6 h (n = 68). Rapid blood injection resulted in highest ICP peaks (AB₁ median 142.7 mmHg [1.Q 116.7-3.Q 230.6], AB₃₀ 33.42 mmHg [18.8-38.3], p < 0.001) and most severe hypoperfusion (AB₁ 16.6% [11.3-30.6], AB₃₀ 44.2% [34.8-59.8]; p < 0.05). However, after 30 min, all blood groups showed comparable ICP elevation and prolonged hypoperfusion. Cerebral autoregulation was disrupted initially due to the immediate ICP increase in all groups except NS₁₀; only AB₁, however, resulted in sustained impairment of autoregulation, as well as early neuronal cell loss. Rapidity and composition of hemorrhage resulted in characteristic hyperacute hemodynamic changes, with comparable hypoperfusion despite different ICP ranges. Only rapid ICP increase was associated with pronounced and early, but sustained disruption of cerebral autoregulation, possibly contributing to EBI.

Association of Brain CD163 Expression and Brain Injury/Hydrocephalus Development in a Rat Model of Subarachnoid Hemorrhage

Hemoglobin contributes to brain cell damage and death following subarachnoid hemorrhage (SAH). While CD163, a hemoglobin scavenger receptor, can mediate the clearance of extracellular hemoglobin it has not been well-studied in SAH. In the current study, a filament perforation SAH model was performed in male rats. T2-weighted and T2*-weighted scans were carried out using a 7.0-Tesla MR scanner 24 h after perforation. T2 lesions and hydrocephalus were determined on T2-weighted images. A grading system based on MRI was used to assess SAH severity. The effects of SAH on CD163 were determined by immunohistochemistry staining and Western blots. SAH led to a marked increase in CD163 levels in cortex, white matter and periventricular regions from days 1 to 7. CD163 stained cells were co-localized with neurons, microglia/macrophages, oligodendrocytes and cleaved caspase-3-positive cells, but not astrocytes. Furthermore, CD163 protein levels were increased in rats with higher SAH grades, the presence of T2 lesions on MRI, or hydrocephalus. In conclusion, CD163 expression is markedly upregulated after SAH. It is associated with more severe hemorrhage, as well as MRI T2 lesion and hydrocephalus development.

A Comparison of Pathophysiology in Humans and Rodent Models of Subarachnoid Hemorrhage

Non-traumatic subarachnoid hemorrhage (SAH) affects an estimated 30,000 people each year in the United States, with an overall mortality of ~30%. Most cases of SAH result from a ruptured intracranial aneurysm, require long hospital stays, and result in significant disability and high fatality. Early brain injury (EBI) and delayed cerebral vasospasm (CV) have been implicated as leading causes of morbidity and mortality in these patients, necessitating intense focus on developing preclinical animal models that replicate clinical SAH complete with delayed CV. Despite the variety of animal models currently available, translation of findings from rodent models to clinical trials has proven especially difficult. While the explanation for this lack of translation is unclear, possibilities include the lack of standardized practices and poor replication of human pathophysiology, such as delayed cerebral vasospasm and ischemia, in rodent models of SAH. In this review, we summarize the different approaches to simulating SAH in rodents, in particular elucidating the key pathophysiology of the various methods and models. Ultimately, we suggest the development of standardized model of rodent SAH that better replicates human pathophysiology for moving forward with translational research.

Delivery of xenon-containing echogenic liposomes inhibits early brain injury following subarachnoid hemorrhage

Xenon (Xe), a noble gas, has promising neuroprotective properties with no proven adverse side-effects. We evaluated neuroprotective effects of Xe delivered by Xe-containing echogenic liposomes (Xe-ELIP) via ultrasound-controlled cerebral drug release on early brain injury following subarachnoid hemorrhage (SAH). The Xe-ELIP structure was evaluated by ultrasound imaging, electron microscopy and gas chromatography-mass spectroscopy. Animals were randomly divided into five groups: Sham, SAH, SAH treated with Xe-ELIP, empty ELIP, or Xe-saturated saline. Treatments were administrated intravenously in combination with ultrasound application over the common carotid artery to trigger Xe release from circulating Xe-ELIP. Hematoma development was graded by SAH scaling and quantitated by a colorimetric method. Neurological evaluation and motor behavioral tests were conducted for three days following SAH injury. Ultrasound imaging and electron microscopy demonstrated that Xe-ELIP have a unique two-compartment structure, which allows a two-stage Xe release profile. Xe-ELIP treatment effectively reduced bleeding, improved general neurological function, and alleviated motor function damage in association with reduced apoptotic neuronal death and decreased mortality. Xe-ELIP alleviated early SAH brain injury by inhibiting neuronal death and bleeding. This novel approach provides a noninvasive strategy of therapeutic gas delivery for SAH treatment.

CHOP induces apoptosis by affecting brain iron metabolism in rats with subarachnoid hemorrhage

The endoplasmic reticulum stress-related factor CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) aggravates early brain injury (EBI) in rats after subarachnoid hemorrhage (SAH). Our research aims to investigate the role of CHOP-mediated iron metabolism in EBI after SAH and the underlying mechanism. Male Sprague-Dawley rats were used to establish SAH models. Tunicamycin (Tm) was employed to excite CHOP expression, and two CHOP small interfering RNAs (siRNAs) were used to inhibit CHOP expression. Neurological scores, brain water content, and blood-brain barrier (BBB) permeability were evaluated at 24h after SAH. Western blotting and immunofluorescence were implemented for the quantification and localization of GRP78 (glucoseregulated protein78), CHOP, C/EBPα (CCAAT/enhancer binding proteinα) and hepcidin. Apoptotic cells were detected by TUNEL staining, and the brain iron content was measured via Perls' staining. The expression of CHOP and hepcidin increased and the expression of C/EBPα decreased after SAH. Knockdown of CHOP decreased the brain water content, reduced Evans blue extravasation, and improved neurological functions. CHOP significantly increased hepcidin levels and significantly decreased C/EBPα levels after SAH. Hepcidin is expressed in the nuclei of neurons and is widely co-localized with TUNEL-positive cells both in the hippocampus and cortex. Along with increased hepcidin expression, the iron content in brain tissue and the apoptosis rate were increased. Thus, CHOP promotes hepcidin expression by regulating C/EBPα activity, which increases the brain iron content, induces apoptosis and is involved in the development of EBI after SAH.

Xenon Reduces Neuronal Hippocampal Damage and Alters the Pattern of Microglial Activation after Experimental Subarachnoid Hemorrhage: A Randomized Controlled Animal Trial

Objective

The neuroprotective properties of the noble gas xenon have already been demonstrated using a variety of injury models. Here, we examine for the first time xenon’s possible effect in attenuating early brain injury (EBI) and its influence on posthemorrhagic microglial neuroinflammation in an in vivo rat model of subarachnoid hemorrhage (SAH).

Methods

Sprague-Dawley rats (n = 22) were randomly assigned to receive either Sham surgery (n = 9; divided into two groups) or SAH induction via endovascular perforation (n = 13, divided into two groups). Of those randomized for SAH, 7 animals were postoperatively ventilated with 50 vol% oxygen/50 vol% xenon for 1 h and 6 received 50 vol% oxygen/50 vol% nitrogen (control). The animals were sacrificed 24 h after SAH. Of each animal, a cerebral coronal section (−3.60 mm from bregma) was selected for assessment of histological damage 24 h after SAH. A 5-point neurohistopathological severity score was applied to assess neuronal cell damage in H&E and NeuN stained sections in a total of four predefined anatomical regions of interest. Microglial activation was evaluated by a software-assisted cell count of Iba-1 stained slices in three cortical regions of interest.

Results

A diffuse cellular damage was apparent in all regions of the ipsilateral hippocampus 24 h after SAH. Xenon-treated animals presented with a milder damage after SAH. This effect was found to be particularly pronounced in the medial regions of the hippocampus, CA3 (p = 0.040), and dentate gyrus (DG p = 0.040). However, for the CA1 and CA2 regions, there were no statistical differences in neuronal damage according to our histological scoring. A cell count of activated microglia was lower in the cortex of xenon-treated animals. This difference was especially apparent in the left piriform cortex (p = 0.017).

Conclusion

In animals treated with 50 vol% xenon (for 1 h) after SAH, a less pronounced neuronal damage was observed for the ipsilateral hippocampal regions CA3 and DG, when compared to the control group. In xenon-treated animals, a lower microglial cell count was observed suggesting an immunomodulatory effect generated by xenon. As for now, these results cannot be generalized as only some hippocampal regions are affected. Future studies should assess the time and localization dependency of xenon’s beneficial properties after SAH.

Curcumin mitigates cerebral vasospasm and early brain injury following subarachnoid hemorrhage via inhibiting cerebral inflammation

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH)-induced cerebral vasospasm and early brain injury is a fatal clinical syndrome. Cerebral vasospasm and early brain injury are associated with inflammatory response and oxidative stress. Whether curcumin, which plays important roles to regulate inflammatory cytokines and inhibit oxidative stress, inhibits SAH-induced inflammation and oxidative stress are largely unknown.

METHODS

Adult male rats underwent autologous blood injection into prechiasmatic cistern to induce SAH. Curcumin (150 mg/kg) was administered at 0.5, 24 and 48 hr post-SAH. Mortality calculation and neurological outcomes as well as morphological vasospasm of anterior cerebral artery were studied. Superoxide dismutase, lipid peroxidation, and inflammatory cytokines (MCP-1 and TNF-α) expression in prefrontal region were quantified. Furthermore, p65 and phosphor-p65 were quantitatively analyzed.

RESULTS

Curcumin remarkedly reduced mortality and ameliorated neurological deficits after SAH induction (p < .05); morphological results showed that cerebral vasospasm in curcumin-treated group was mitigated (p < .05). SAH-induced MCP-1 and TNF-α overexpression were inhibited in curcumin-treated group (p < .05). Importantly, phosphor-p65 was significantly inhibited after curcumin treatment (p < .05).

CONCLUSIONS

Curcumin can inhibit SAH-induced inflammatory response via restricting NF-κB activation to alleviate cerebral vasospasm and early brain injury.

High-Throughput Sequencing and Co-Expression Network Analysis of lncRNAs and mRNAs in Early Brain Injury Following Experimental Subarachnoid Haemorrhage

Subarachnoid haemorrhage (SAH) is a fatal neurovascular disease following cerebral aneurysm rupture with high morbidity and mortality rates. Long non-coding RNAs (lncRNAs) are a type of mammalian genome transcript, are abundantly expressed in the brain and are involved in many nervous system diseases. However, little is currently known regarding the influence of lncRNAs in early brain injury (EBI) after SAH. This study analysed the expression profiles of lncRNAs and mRNAs in SAH brain tissues of mice using high-throughput sequencing. The results showed a remarkable difference in lncRNA and mRNA transcripts between SAH and control brains. Approximately 617 lncRNA transcripts and 441 mRNA transcripts were aberrantly expressed at 24 hours after SAH. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the differentially expressed mRNAs were mostly involved in inflammation. Based on the lncRNA/mRNA co-expression network, knockdown of fantom3_F730004F19 reduced the mRNA and protein levels of CD14 and toll-like receptor 4 (TLR4) and attenuated inflammation in BV-2 microglia cells. These results indicate that lncRNA fantom3_F730004F19 may be associated with microglia induced inflammation via the TLR signaling pathway in EBI following SAH. LncRNA represent a potential therapeutic target for the prognosis, diagnosis, and treatment of SAH.

Thioredoxin-Interacting Protein Mediates Apoptosis in Early Brain Injury after Subarachnoid Haemorrhage

Early brain injury (EBI) is considered to be the major factor associated with high morbidity and mortality after subarachnoid haemorrhage (SAH). Apoptosis is the major pathological mechanism of EBI, and its pathogenesis has not been fully clarified. Here, we report that thioredoxin-interacting protein (TXNIP), which is induced by protein kinase RNA-like endoplasmic reticulum (ER) kinase (PERK), participates in EBI by promoting apoptosis. By using adult male Sprague-Dawley rats to establish SAH models, as well as Terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) staining, immunofluorescence, and western blot, we found that TXNIP expression significantly increased after SAH in comparison to the sham group and peaked at 48 h (up to 3.2-fold). Meanwhile, TXNIP was widely expressed in neurons and colocalized with TUNEL-positive cells in the hippocampus and cortex of SAH rats. After administration of TXNIP inhibitor-resveratrol (60 mg/kg), TXNIP small interfering RNA (siRNA) and the PERK inhibitor GSK2656157, TXNIP expression was significantly reduced, accompanied by an attenuation of apoptosis and prognostic indicators, including SAH grade, neurological deficits, brain water content, and blood-brain barrier (BBB) permeability. Collectively, these results suggest that TXNIP may participate in EBI after SAH by mediating apoptosis. The blockage of TXNIP induced by PERK could be a potential therapeutic strategy for SAH treatment.

MR-angiography allows defining severity grades of cerebral vasospasm in an experimental double blood injection subarachnoid hemorrhage model in rats

Objective

Magnetic resonance (MR) imaging has been used for the detection of cerebral vasospasm (VSP) related infarction in experimental subarachnoid hemorrhage (eSAH) in rats. Conventional angiography is generally used to visualize VSP, which is an invasive technique with a possible increase in morbidity and mortality. In this study we evaluated the validity of MR-angiography (MRA) in detecting VSP and its feasibility to define VSP severity grades after eSAH in rats.

Methods

SAH was induced using the double-hemorrhage model in 12 rats. In two rats, saline solution was injected instead of blood (sham group). MR was performed on day 1, 2 and on day 5. T1-, T2-, T2*-weighted and time-of-flight MR sequences were applied, which were analyzed by two blinded neuroradiologists. Vessel narrowing of 25–50% was defined as mild, 50–75% as moderate and >75% as severe VSP.

Results

We performed a total of 34 MRAs in 14 rats. In 14 rats, MRA was performed on day 2 and day 5. In six rats MRA was additionally performed on day1 before the blood injection. A good visualization of cerebral vessels was possible in all cases. No VSP was seen in the sham group neither on day 2 nor on day 5. We found vasospasm on day 2 in 7 of the 14 rats (50%) whereas all 7 rats had mild and one rat had additionally moderate and severe vasospasm in one vessel, respectively. On day 5 we found vasospasm in 8 of the 14 rats (60%) whereas 4 rats had severe vasospasm, 1 rat had moderate vasospasm and 3 rats demonstrated mild vasospasm. In 4 of the 14 rats (30%) an ischemic lesion was detected on day 5. Three of these rats had severe vasospasm and one rat had mild vasospasm. Severe vasospasm on day 5 was statistically significant correlated with the occurrence of ischemic lesions (Fisher’s Exact test, OR 19.5, p = 0.03).

Conclusions

MRA is a noninvasive diagnostic tool, which allows a good visualization of the cerebral vasculature and provides reproducible results concerning the detection of VSP and the differentiation into three severity grades in rats. Future studies are needed to directly compare MRA with conventional angiography.

Valproate Reduces Delayed Brain Injury in a Rat Model of Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

Spreading depolarizations (SDs) may contribute to delayed cerebral ischemia after subarachnoid hemorrhage (SAH). We tested whether SD-inhibitor valproate reduces brain injury in an SAH rat model with and without experimental SD induction.

METHODS

Rats were randomized in a 2×2 design and pretreated with valproate (200 mg/kg) or vehicle for 4 weeks. SAH was induced by endovascular puncture of the right internal carotid bifurcation. One day post-SAH, brain tissue damage was measured with T₂-weighted magnetic resonance imaging, followed by cortical application of 1 mol/L KCl (to induce SDs) or NaCl (no SDs). Magnetic resonance imaging was repeated on day 3 followed by histology to confirm neuronal death. Neurological function was measured with an inclined slope test.

RESULTS

In the groups with KCl application, lesion growth between days 1 and 3 was 57±73 mm3 in the valproate-treated versus 237±232 mm3 in the vehicle-treated group. In the groups without SD induction, lesion growth in the valproate- and vehicle-treated groups was 8±20 mm3 versus 27±52 mm3. On fitting a 2-way analysis of variance model, we found a significant interaction effect between treatment and KCl/NaCl application of 161 mm3 (P=0.04). Number and duration of SDs, mortality, and neurological function were not statistically significantly different between groups. Lesion growth on magnetic resonance imaging correlated to histological infarct volume (Spearman's rho =0.83; P=0.0004), with areas of lesion growth exhibiting reduced neuronal death compared with primary lesions.

CONCLUSIONS

In our rat SAH model, valproate treatment significantly reduced brain lesion growth after KCl application. Future studies are needed to confirm that this protective effect is based on SD inhibition.

Angiopoietin-1 and Angiopoietin-2 Expression Imbalance Influence in Early Period After Subarachnoid Hemorrhage

Purpose

Microvascular endothelial integrity is important for maintaining the blood-brain barrier (BBB). However, subarachnoid hemorrhage (SAH) disrupts this integrity, making the BBB dysfunctional—an important pathophysiological change after SAH. Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) regulate microvascular permeability by balancing each other’s expression.

Methods

This study investigated the dynamics of Ang-1 and Ang-2 expression after SAH and the protective effect of Ang-1 on BBB functioning using an endovascular puncture model of rat SAH. The Ang-1 and Ang-2 expression in brain tissue was determined by immunohistochemistry. In addition, Western blotting was used to estimate Ang-1 and Ang-2 concentration and to compare them at 6–72 hours post-SAH cortex and hippocampus. Evans blue viability assay was used to evaluate BBB permeability, and neurological testing was implemented to evaluate neurological impairment during SAH.

Results

It was found that following SAH, Ang-1 expression decreases and Ang-2 expression increases in the cortex, hippocampus, and microvessels. The Ang-1/Ang-2 ratio decreased as quickly as 6 hours after SAH and reached its lowest 1 day after SAH. Finally, it was found that exogenous Ang-1 reduces SAH-associated BBB leakage and improves neurological function in post-SAH rats.

Conclusions

Our findings suggest that the equilibrium between Ang-1 and Ang-2 is broken in a period shortly after SAH, and the treatment of exogenous Ang-1 injection alleviates neurological dysfunctions through decreasing BBB destruction.

Severity assessment and scoring for neurosurgical models in rodents

The most important acute neurological diseases seen at neurosurgery departments are traumatic brain injuries (TBI) and subarachnoid hemorrhages (SAH). In both diseases the pathophysiological sequela are complex and have not been fully understood up to now, and rodent models using rats and mice are most suitable for the investigation of the pathophysiological details. In both models, surgery is performed under anesthesia, followed by assessment of their functional outcome and behavioral testing before brain tissue analysis after euthanasia. Postoperative analgesia is mandatory, and supplementary care is highly recommended for refinement purposes. Pain and stress assessment is mainly based on clinical and behavioral signs, and further research is needed to improve the evaluation of severity in these models.

MRI Characterization in the Acute Phase of Experimental Subarachnoid Hemorrhage

A number of mechanisms have been proposed for the early brain injury after subarachnoid hemorrhage (SAH). In this study, we investigated the radiographic characteristics and influence of gender on early brain injury after experimental SAH. SAH was induced by endovascular perforation in male and female rats. Magnetic resonance imaging was performed in a 7.0-T Varian MR scanner at 24 h after SAH. The occurrence and size of T2 lesions, ventricular dilation, and white matter injury (WMI) were determined on T2-weighted images (T2WI). The effects of SAH on heme oxygenase-1 and fibrin/fibrinogen were examined by Western blotting and immunohistochemistry. SAH severity was assessed using a MRI grading system, and neurological function was evaluated according to a modified Garcia's scoring system. T2 hyperintensity areas and enlarged ventricles were observed in T2WI coronal sections 24 h after SAH. The overall incidence of T2 lesions, WMI, and hydrocephalus was 54, 20, and 63%, respectively. Female rats had a higher incidence of T2 hyperintensity lesions and hydrocephalus, as well as larger T2 lesion volumes and higher average ventricular volume. SAH rats graded at 3-4 (our previously validated MRI grading scale) had larger T2 lesion volumes, more hydrocephalus, and worse neurological function compared with those graded at 0-2. In conclusion, T2 lesion, WMI, and hydrocephalus were the most prevalent MRI characteristics 24 h after experimental SAH. The T2 lesion area matched with fibrinogen/fibrin positive staining in the acute phase of SAH. SAH induced more severe brain injury in females compared to males in the acute phase of SAH.

Cortical microcirculatory disturbance in the super acute phase of subarachnoid hemorrhage - In vivo analysis using two-photon laser scanning microscopy

OBJECTIVE

Subarachnoid hemorrhage (SAH) causes cerebral ischemia and drastically worsens the clinical status at onset. However, the arterial flow is surprisingly well maintained on the cerebral surface. We investigated cortical microcirculatory changes in the super acute phase of SAH using two-photon laser scanning microscopy (TPLSM).

METHODS

SAH was induced at the skull base in 10 mice using a prone endovascular perforation model. Before SAH, and 1, 2, 5, 10, 20, 30 and 60min after SAH, the cortical microcirculation was observed with TPLSM through a cranial window. Diameters of penetrating and precapillary arterioles were measured and red blood cell (RBC) velocities in precapillary arterioles were analyzed using a line-scan method after administration of Q-dot 655 nanocrystals.

RESULTS

One minute after SAH, RBC velocity and flow in precapillary arterioles drastically decreased to <20% of the pre-SAH values, while penetrating and precapillary arterioles dilated significantly. Subsequently, the arterioles either dilated or constricted inconsistently for 60min with continual decreases in RBC velocity and flow in the arterioles, suggesting neurovascular dysfunction.

CONCLUSION

SAH caused sudden worsening of the cortical arteriolar velocity and flow at onset. The neurovascular unit cannot function sufficiently to maintain cortical microcirculatory flow in the super acute phase of SAH.

Histopathological Findings in Brains of Patients Who Died in the Acute Stage of Poor-grade Subarachnoid Hemorrhage

Patients with poor-grade aneurysmal subarachnoid hemorrhage (SAH) are likely to die due to irreversible acute-stage primary brain damage. However, the mechanism(s) and pathology responsible for their high mortality rate remain unclear. We report our findings on the brains of individuals who died in the acute stage of SAH. An autopsy was performed on the brains of 11 SAH patients (World Federation of Neurosurgical Societies grade 5) who died within 3 days of admission and who did not receive respiratory assistance. All brains were free of intracranial hematoma and hydrocephalus; all harbored ruptured aneurysms. In all brains, multiple infarcts with perifocal edema were scattered throughout the cortex and subcortical white matter of the whole brain. Infarcts with a patchy – were more often seen than infarcts with a wedge-shaped pattern. Microscopic examination revealed multiple areas with cytotoxic edema and neuronal death indicative of acute ischemic changes. Edema and congestion were more obvious in areas where the subarachnoid clot tightly adhered to the pia mater. Pathologically, the brains of deceased patients with acute poor-grade SAH were characterized by edema and multifocal infarcts spread throughout the whole brain; they were thought to be attributable to venous ischemia. Diffuse disturbance in venous drainage attributable to an abrupt increase in the intracranial pressure and focal disturbances due to tight adhesion of the subarachnoid clot to the pia mater, may contribute strongly to irreversible brain damage in the acute stage of SAH.

Multimodal MRI characterization of experimental subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is associated with significant morbidity and mortality. We implemented an in-scanner rat model of mild SAH in which blood or vehicle was injected into the cistern magna, and applied multimodal MRI to study the brain prior to, immediately after (5min to 4h), and upto 7days after SAH. Vehicle injection did not change arterial lumen diameter, apparent diffusion coefficient (ADC), T2, venous signal, vascular reactivity to hypercapnia, or foot-fault scores, but mildly reduce cerebral blood flow (CBF) up to 4h, and open-field activity up to 7days post injection. By contrast, blood injection caused: (i) vasospasm 30min after SAH but not thereafter, (ii) venous abnormalities at 3h and 2days, delayed relative to vasospasm, (iii) reduced basal CBF and to hypercapnia 1-4h but not thereafter, (iv) reduced ADC immediately after SAH but no ADC and T2 changes on days 2 and 7, and (v) reduced open-field activities in both SAH and vehicle animals, but no significant differences in open-field activities and foot-fault tests between groups. Mild SAH exhibited transient and mild hemodynamic disturbances and diffusion changes, but did not show apparent ischemic brain injury nor functional deficits.

Human Albumin Improves Long-Term Behavioral Sequelae After Subarachnoid Hemorrhage Through Neurovascular Remodeling

OBJECTIVE

Subarachnoid hemorrhage results in significant long-lasting neurologic sequelae. Here, we investigated whether human albumin improves long-term outcomes in experimental subarachnoid hemorrhage and whether neurovascular remodeling is involved in the protection of albumin.

DESIGN

Laboratory investigation.

SETTING

Hospital research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Rats underwent subarachnoid hemorrhage by endovascular perforation. Albumin of either 0.63 or 1.25 g/kg was injected IV immediately after the surgery. Modified Garcia test, beam-walking test, novel object recognition, and Morris water maze were employed to determine the behavioral deficits. The effects of albumin on early neurovascular dysfunction and chronic synaptic plasticity were also studied.

MEASUREMENTS AND MAIN RESULTS

Both doses of albumin significantly improved the sensorimotor scores (F = 31.277; p = 0.001) and cognitive performance (F = 7.982; p = 0.001 in novel object recognition test; and F = 3.431; p = 0.026 in the latency analysis of Morris water maze test) for at least 40 days after subarachnoid hemorrhage. There were remarkable microvasculature hypoperfusion, intracranial pressure rise, early vasoconstriction, neural apoptosis, and degeneration in subarachnoid hemorrhage rats, with albumin significantly attenuating such neurovascular dysfunction. Furthermore, albumin markedly prevented blood-brain barrier disruption, as indicated by less blood-brain barrier leakage, preserved blood-brain barrier-related proteins, and dampened gelatinase activities. The expressions of key synaptic elements were up-regulated with albumin supplementation in both acute and chronic phases. Accordingly, a higher dendritic spine density was observed in the prefrontal and hippocampal areas of albumin-treated subarachnoid hemorrhage animals.

CONCLUSIONS

Albumin at low-to-moderate doses markedly improves long-term neurobehavioral sequelae after subarachnoid hemorrhage, which may involve an integrated process of neurovascular remodeling.

Functional response of cerebral blood flow induced by somatosensory stimulation in rats with subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is often accompanied by cerebral vasospasm (CVS), which is the phenomenon of narrowing of large cerebral arteries, and then can produce delayed ischemic neurological deficit (DIND) such as lateralized sensory dysfunction. CVS was regarded as a major contributor to DIND in patients with SAH. However, therapy for preventing vasospasm after SAH to improve the outcomes may not work all the time. It is important to find answers to the relationship between CVS and DIND after SAH. How local cerebral blood flow (CBF) is regulated during functional activation after SAH still remains poorly understood, whereas, the regulation of CBF may play an important role in weakening the impact of CVS on cortex function. Therefore, it is worthwhile to evaluate the functional response of CBF in the activated cortex in an SAH animal model. Most evaluation of the effect of SAH is presently carried out by neurological behavioral scales. The functional imaging of cortical activation during sensory stimulation may help to reflect the function of the somatosensory cortex more locally than the behavioral scales do. We investigated the functional response of CBF in the somatosensory cortex induced by an electrical stimulation to contralateral forepaw via laser speckle imaging in a rat SAH model. Nineteen Sprague-Dawley rats from two groups (control group, n=10 and SAH group, n=9) were studied. SAH was induced in rats by double injection of autologous blood into the cisterna magna after CSF aspiration. The same surgical procedure was applied in the control group without CSF aspiration or blood injection. Significant CVS was found in the SAH group. Meanwhile, we observed a delayed peak of CBF response in rats with SAH compared with those in the control group, whereas no significant difference was found in magnitude, duration, and areas under curve of relative CBF changes between the two groups. The results suggest that the regulation function of local CBF during functional activation induced by somatosensory stimulation might not be seriously impaired in the somatosensory cortex of rats with SAH. Therefore, our findings might help to understand the clinical phenomenon that DIND might not occur even when CVS was found in SAH patients.

Cerebral vasospasm and corticospinal tract injury induced by a modified rat model of subarachnoid hemorrhage

OBJECTIVE

Double-hemorrhage rat models of subarachnoid hemorrhages (SAH) are most effective at simulating delayed cerebral vasospasms (CVS). The present study modified the models to minimize additional trauma and investigated injury of the corticospinal tract (CST) using diffusion tensor imaging (DTI).

METHODS

On the first day, 0.3ml of autologous arterial blood was collected by puncturing the caudal artery and injected into the cisterna magna via percutaneous puncture; and the operation was repeated on the third day. The diameters of the basilar artery (BA), middle cerebral artery (MCA), and anterior cerebral artery (ACA) were measured by magnetic resonance angiography on days 3, 5, 7, 9, and 11 post-SAH. Meanwhile, on days 3, 7, 11, 15 and 19, DTI was performed to evaluate the injury of the CST at cerebral peduncle (CP) and pyramidal tract (Py) by measuring fractional anisotropy (FA) value.

RESULTS

Blood was deposited mainly in the basal cistern. Diameters of BA, MCA, and ACA were significantly reduced. FA value of the CP was lower in the SAH group than in the control group; but FA value of Py wasn't different between the two groups.

CONCLUSION

This is a minimally-invasive and high performance rat model of SAH. Additionally, the occurrence of CVS is firm and the axons in CP are injured.

Role of hemoglobin and iron in hydrocephalus after neonatal intraventricular hemorrhage

BACKGROUND

Neonatal germinal matrix hemorrhage/intraventricular hemorrhage is common and often results in hydrocephalus. The pathogenesis of posthemorrhagic hydrocephalus is not fully understood.

OBJECTIVE

To explore the potential role of hemoglobin and iron released after hemorrhage.

METHODS

Artificial cerebrospinal fluid (aCSF), hemoglobin, or iron was injected into the right lateral ventricle of postnatal day-7 Sprague Dawley rats. Ventricle size, heme oxygenase-1 (HO-1) expression, and the presence of iron were evaluated 24 and 72 hours after injection. A subset of animals was treated with an iron chelator (deferoxamine) or vehicle for 24 hours after hemoglobin injection, and ventricle size and cell death were evaluated.

RESULTS

Intraventricular injection of hemoglobin and iron resulted in ventricular enlargement at 24 hours compared with the injection of aCSF. Protoporphyrin IX, the iron-deficient immediate heme precursor, did not result in ventricular enlargement after injection into the ventricle. HO-1, the enzyme that releases iron from heme, was increased in the hippocampus and cortex of hemoglobin-injected animals at 24 hours compared with aCSF-injected controls. Treatment with an iron chelator, deferoxamine, decreased hemoglobin-induced ventricular enlargement and cell death.

CONCLUSION

Intraventricular injection of hemoglobin and iron can induce hydrocephalus. Treatment with an iron chelator reduced hemoglobin-induced ventricular enlargement. This has implications for the pathogenesis and treatment of posthemorrhagic hydrocephalus.

ABBREVIATIONS

aCSF, artificial cerebrospinal fluidDAB, 3,3'-diaminobenzidine-4HClGMH-IVH, germinal matrix hemorrhage/intraventricular hemorrhageHO-1, heme oxygenase-1ICH, intracerebral hemorrhagePBS, phosphate-buffered salineSVZ, subventricular zoneTBST, tris-buffered saline with Tween 20.

Hydrogen-Rich Saline Attenuated Subarachnoid Hemorrhage-Induced Early Brain Injury in Rats by Suppressing Inflammatory Response: Possible Involvement of NF-κB Pathway and NLRP3 Inflammasome

Early brain injury (EBI), highlighted with inflammation and apoptosis, occurring within 72 h after subarachnoid hemorrhage (SAH), is associated with the prognosis of SAH. Recent studies have revealed that hydrogen-rich saline (HS) exerted multiple neuroprotective properties in many neurological diseases including SAH, involved to anti-oxidative and anti-apoptotic effect. We have previously reported that HS could attenuate neuronal apoptosis as well as vasospasm. However, the underlying mechanism of HS on inflammation in SAH-induced EBI remains unclear. In this study, we explored the influence of HS on nuclear factor-κB (NF-κB) pathway and nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome at early stage after SAH, by injecting HS intraperitoneally to SAH rats. One hundred and twenty-nine SD rats were randomly divided into four groups: sham group, SAH group, SAH+vehicle group, and SAH+HS group. SAH model was conducted using endovascular perforation method; all rats were sacrificed at 24 h after SAH. Protein level of pIκBα, cytosolic and nuclear p65, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, interleukin-1β (IL-1β), and cleaved caspase-3 were measured by western blot. mRNA level of IL-1β, interleukin-6 (IL-6), tumor necrosis factor-c (TNF-α) were evaluated by RT-PCR. Cellular injury and death was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and Nissl staining, respectively. Our results showed that pIκBα, nuclear p65, NLRP3, ASC, caspase-1, IL-1β, cleaved caspase-3 proteins, as well as the mRNA of IL-1β, IL-6, and TNF-ɑ increased at 24 h after SAH, while cytosolic p65 decreased. TUNEL and Nissl staining presented severe cellular injury at 24 h post-SAH. However, after HS administration, the changes mentioned above were reversed. In conclusion, HS may inhibit inflammation in EBI and improve neurobehavioral outcome after SAH, partially via inactivation of NF-κB pathway and NLRP3 inflammasome. Graphical Abstract Schematic representation of the mechanism of HS-mediated anti-inflammatory effect in EBI after SAH. The NF-κB inflammatory pathway and NLRP3 inflammasome are involved in the anti-neuroinflammatory effect of HS post-SAH. SAH-induced oxidative stress enhances the activation of NF-κB, thus promoting the translocation of p65 subunit into nucleus and increasing the mRNA level of its downstream proinflammatory cytokines (IL-1β, IN-6, TNF-α) and NLRP3. Elevated expression of NLRP3 mRNA increases the assembly of NLRP3 inflammasome. In addition, oxidative stress after SAH stimulates the activation of NLRP3 inflammasome, therefore, promoting caspase-1 activation and the cleavage of pro-IL-1β into mature IL-1β. Finally, activation of NF-κB pathway and NLRP3 inflammasome contribute to the inflammation response and cellular injury in EBI after SAH. HS treatment reversed the detrimental effect mentioned above via inactivation of NF-κB pathway and NLRP3 inflammasome. NF-κB nuclear factor-κB, IκB inhibitor of NF-κB, IKK Iκ kinase, NLRP3 nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3, ASC apoptosis-associated speck-like protein containing a caspase recruitment domain.