Cortical blood flow and cerebral perfusion pressure in a new noncraniotomy model of subarachnoid hemorrhage in the rat

PARP-1 dependent cell death pathway (Parthanatos) mediates early brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a neurological condition with high mortality and poor prognosis, and there are currently no effective therapeutic drugs available. Poly (ADP-ribose) polymerase 1 (PARP-1) dependent cell death pathway-parthanatos is closely associated with stroke. We investigated improvements in neurological function, oxidative stress, blood-brain barrier and parthanatos-related protein expression in rats with SAH after intraperitoneal administration of PARP-1 inhibitor (AG14361). Our study found that the expression of parthanatos-related proteins was significantly increased after SAH. Immunofluorescence staining showed increased expression of apoptosis-inducing factor (AIF) in the nucleus after SAH. Administration of PARP-1 inhibitor significantly reduced malondialdehyde (MDA) level and the expression of parthanatos-related proteins. Immunofluorescence staining showed that PARP-1 inhibitor reduced the expression of 8-hydroxy-2' -deoxyguanosine (8-OHdG) and thus reduced oxidative stress. Moreover, PARP-1 inhibitor could inhibit inflammation-associated proteins level and neuronal apoptosis, protect the blood-brain barrier and significantly improve neurological function after SAH. These results suggest that PARP-1 inhibitor can significantly improve SAH, and the underlying mechanism may be through inhibiting parthanatos pathway.

Diffuse microglial responses and persistent EEG changes correlate with poor neurological outcome in a model of subarachnoid hemorrhage

The mechanism by which subarachnoid hemorrhage (SAH) leads to chronic neurologic deficits is unclear. One possibility is that blood activates microglia to drive inflammation that leads to synaptic loss and impaired brain function. Using the endovascular perforation model of SAH in rats, we investigated short-term effects on microglia together with long-term effects on EEG and neurologic function for up to 3 months. Within the first week, microglia were increased both at the site of injury and diffusely across the cortex (2.5-fold increase in SAH compared to controls, p = 0.012). Concomitantly, EEGs from SAH animals showed focal increases in slow wave activity and diffuse reduction in fast activity. When expressed as a fast-slow spectral ratio, there were significant interactions between group and time (p < 0.001) with less ipsilateral recovery over time. EEG changes were most pronounced during the first week and correlated with neurobehavioral impairment. In vitro, the blood product hemin was sufficient to increase microglia phagocytosis nearly six-fold (p = 0.032). Immunomodulatory treatment with fingolimod after SAH reduced microglia, improved neurological function, and increased survival. These findings, which parallel many of the EEG changes seen in patients, suggest that targeting neuroinflammation could reduce long-term neurologic dysfunction following SAH.

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.

Role of microglia after subarachnoid hemorrhage

Subarachnoid hemorrhage is a devastating sequela of aneurysm rupture. Because it disproportionately affects younger patients, the population impact of hemorrhagic stroke from subarachnoid hemorrhage is substantial. Secondary brain injury is a significant contributor to morbidity after subarachnoid hemorrhage. Initial hemorrhage causes intracranial pressure elevations, disrupted cerebral perfusion pressure, global ischemia, and systemic dysfunction. These initial events are followed by two characterized timespans of secondary brain injury: the early brain injury period and the delayed cerebral ischemia period. The identification of varying microglial phenotypes across phases of secondary brain injury paired with the functions of microglia during each phase provides a basis for microglia serving a critical role in both promoting and attenuating subarachnoid hemorrhage-induced morbidity. The duality of microglial effects on outcomes following SAH is highlighted by the pleiotropic features of these cells. Here, we provide an overview of the key role of microglia in subarachnoid hemorrhage-induced secondary brain injury as both cytotoxic and restorative effectors. We first describe the ontogeny of microglial populations that respond to subarachnoid hemorrhage. We then correlate the phenotypic development of secondary brain injury after subarachnoid hemorrhage to microglial functions, synthesizing experimental data in this area.

Effects of vitamin C on the pharmacokinetics and pharmacodynamics of nimodipine in rats

In recent years, researchers have shown a growing interest in the interactions between different pharmaceutical agents. An intriguing instance lies in the possible interaction between nimodipine and vitamin C. To investigate the pharmacokinetic and pharmacodynamic effects of vitamin C on nimodipine in rats, rats were randomly divided into a nimodipine only group and a combination group (nimodipine + vitamin C). The two groups were given intragastric administration and nimodipine blood concentrations were determined using high-performance liquid chromatography-tandem mass spectrum at different time points. Blood pressure and heart rate were measured via carotid artery cannulation. Pharmacokinetic differences were observed between the nimodipine only group and the combination group at the same dose. Compared with the nimodipine only group, the combination group's main pharmacokinetic parameters of peak concentration and area under the curve increased significantly, and the difference was statistically significant (p < 0.05); furthermore, the combination group exhibited a significant reduction in average blood pressure, while no significant effects on heart rate were observed. Vitamin C did not affect the activity of CYP450 in rat liver. The pharmacokinetic characteristics and pharmacodynamics of nimodipine were changed by vitamin C administration in rats.

MiR-221-5p regulates blood-brain barrier dysfunction through the angiopoietin-1/-2/Tie-2 signaling axis after subarachnoid hemorrhage

AIM

To explore the potential role of microRNA miR-221-5p on the angiopoietin-1 (Ang-1)/Ang-2/Tie-2 signaling axis after subarachnoid hemorrhage (SAH) in a rat model.

METHODS

Aspects of the rat's behavior were measured using the Kaoutzanis scoring system to test neurological responses. This included feeding behavior, body contraction, motor, and eye-opening responses. Brain sections were studied using transmission electron microscopy and Evans blue extravasation. Levels of Ang-1, Ang-2, and Tie-2 were determined by Western blot, while miR-221-5p was quantified using stem-loop real-time quantitative PCR (RT-qPCR).

RESULTS

The SAH group responded worse to the neurological response test than the sham-operated group. The intercellular space was widened in the SAH group, but not in the sham-operated group. Evans blue dye leaked significantly more into brain tissue cells of the SAH group. Stem-loop qRT-PCR showed elevated miR-221-5p levels. Additionally, Ang-1 and Tie-2 were reduced but Ang-2 expression was increased after SAH. This led to a significant reduction of the Ang-1/Ang-2 ratio in the brain tissue, which was associated with the destruction of the blood-brain barrier.

CONCLUSION

The data indicate that miR-221-5p might regulate blood-brain barrier dysfunction through the Ang-1/Ang-2/Tie-2 signaling axis, suggesting that it should be further investigated as a potential novel biomarker.

Meta-review on Perforation Model of Subarachnoid Hemorrhage in Mice: Filament Material as a Possible Moderator of Mortality

Robust preclinical models are inevitable for researchers to unravel pathomechanisms of subarachnoidal hemorrhage (SAH). For the mouse perforation model of SAH, the goal of this meta-review was the determination of variances in mortality, SAH severity grade, and vasospasm, and their experimental moderators, as many researchers are facing with incomparable results. We searched on the databases PubMed, Embase, and Web of Science for articles describing in vivo experiments using the SAH perforation mouse model and measuring mortality, SAH grade, and/or vasospasm. After screening, 42 articles (total of 1964 mice) were included into systematic review and meta-analysis. Certain model characteristics were insufficiently reported, e.g., perforation location (not reported in six articles), filament (material (n = 15) and tip texture (n = 25)), mouse age (n = 14), and weight (n = 10). Used injective anesthetics and location of perforation showed large variation. In a random-effects meta-analysis, the overall animal mortality following SAH was 21.3% [95% CI: 17.5%, 25.7%] and increased with longer observational periods. Filament material significantly correlated with animal mortality (p = 0.024) after exclusion of hyperacute studies (time after SAH induction < 24 h). Reported mean SAH grade was 10.7 [9.6, 11.7] on the scale of Sugawara (J Neurosci Methods 167:327-34, 2008). Furthermore, mean diameter of large cerebral arteries after SAH was reduced by 27.6% compared to sham-operated non-SAH mice. Uniforming standards of experimental procedures and their reporting are indispensable to increase overall comparability.

Ferroptosis as a Therapeutic Target in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a cerebrovascular disorder with significant mortality and morbidity. Neural injury in SAH is mediated through a variety of pathophysiological processes. Currently available treatments are either nonspecific in targeting the basic pathophysiological mechanisms that result in neural damage in SAH, or merely focus on vasospasm. Ferroptosis is a type of programmed iron dependent cell death, which has received attention due to its possible role in neural injury in SAH. Herein, we review how intracellular iron overload mediates the production of reactive free radicals and lipid peroxidation through a variety of biochemical pathways in SAH. This in turn results in induction of ferroptosis, as well as exacerbation of vasospasm. We also discuss several therapeutic agents that have been shown to inhibit ferroptosis through targeting different steps of the process. Such agents have proven effective in ameliorating vasospasm, neural damage, and neurobehavioral outcomes in animal models of SAH. Human studies to test the safety and efficacy of intrathecal or parenteral administration of the inhibitors of ferroptosis in improving outcomes of SAH patients are warranted. There are currently a few ongoing clinical trials pursuing this therapeutic concept, the results of which will be critical to determine the value of ferroptosis as a novel therapeutic target in SAH.

Power suppression in EEG after the onset of SAH is a significant marker of early brain injury in rat models

We analyzed the correlation between the duration of electroencephalogram (EEG) recovery and histological outcome in rats in the acute stage of subarachnoid hemorrhage (SAH) to find a new predictor of the subsequent outcome. SAH was induced in eight rats by cisternal blood injection, and the duration of cortical depolarization was measured. EEG power spectrums were given by time frequency analysis, and histology was evaluated. The appropriate frequency band and recovery percentage of EEG (defined as EEG recovery time) to predict the neuronal damage were determined from 25 patterns (5 bands × 5 recovery rates) of receiver operating characteristic (ROC) curves. Probit regression curves were depicted to evaluate the relationships between neuronal injury and duration of depolarization and EEG recovery. The optimal values of the EEG band and the EEG recovery time to predict neuronal damage were 10-15 Hz and 40%, respectively (area under the curve [AUC]: 0.97). There was a close relationship between the percentage of damaged neurons and the duration of depolarization or EEG recovery time. These results suggest that EEG recovery time, under the above frequency band and recovery rate, may be a novel marker to predict the outcome after SAH.

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.

Effect of isolated intracranial hypertension on cerebral perfusion within the phase of primary disturbances after subarachnoid hemorrhage in rats

Introduction

Elevated intracranial pressure (ICP) and blood components are the main trigger factors starting the complex pathophysiological cascade following subarachnoid hemorrhage (SAH). It is not clear whether they independently contribute to tissue damage or whether their impact cannot be differentiated from each other. We here aimed to establish a rat intracranial hypertension model that allows distinguishing the effects of these two factors and investigating the relationship between elevated ICP and hypoperfusion very early after SAH.

Methods

Blood or four different types of fluids [gelofusine, silicone oil, artificial cerebrospinal fluid (aCSF), aCSF plus xanthan (CX)] were injected into the cisterna magna in anesthetized rats, respectively. Arterial blood pressure, ICP and cerebral blood flow (CBF) were continuously measured up to 6 h after injection. Enzyme-linked immunosorbent assays were performed to measure the pro-inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) in brain cortex and peripheral blood.

Results

Silicone oil injection caused deaths of almost all animals. Compared to blood, gelofusine resulted in lower peak ICP and lower plateau phase. Artificial CSF reached a comparable ICP peak value but failed to reach the ICP plateau of blood injection. Injection of CX with comparable viscosity as blood reproduced the ICP course of the blood injection group. Compared with the CBF course after blood injection, CX induced a comparable early global ischemia within the first minutes which was followed by a prompt return to baseline level with no further hypoperfusion despite an equal ICP course. The inflammatory response within the tissue did not differ between blood or blood-substitute injection. The systemic inflammation was significantly more pronounced in the CX injection group compared with the other fluids including blood.

Discussion

By cisterna magna injection of blood substitution fluids, we established a subarachnoid space occupying rat model that exactly mimicked the course of ICP in the first 6 h following blood injection. Fluids lacking blood components did not induce the typical prolonged hypoperfusion occurring after blood-injection in this very early phase. Our study strongly suggests that blood components rather than elevated ICP play an important role for early hypoperfusion events in SAH.

Early Brain Injury After Subarachnoid Hemorrhage: Incidence and Mechanisms

Aneurysmal subarachnoid hemorrhage is a devastating condition causing significant morbidity and mortality. While outcomes from subarachnoid hemorrhage have improved in recent years, there continues to be significant interest in identifying therapeutic targets for this disease. In particular, there has been a shift in emphasis toward secondary brain injury that develops in the first 72 hours after subarachnoid hemorrhage. This time period of interest is referred to as the early brain injury period and comprises processes including microcirculatory dysfunction, blood-brain-barrier breakdown, neuroinflammation, cerebral edema, oxidative cascades, and neuronal death. Advances in our understanding of the mechanisms defining the early brain injury period have been accompanied by improved imaging and nonimaging biomarkers for identifying early brain injury, leading to the recognition of an elevated clinical incidence of early brain injury compared with prior estimates. With the frequency, impact, and mechanisms of early brain injury better defined, there is a need to review the literature in this area to guide preclinical and clinical study.

Increased NOX2 expression in astrocytes leads to eNOS uncoupling through dihydrofolate reductase in endothelial cells after subarachnoid hemorrhage

Introduction

Endothelial nitric oxide synthase (eNOS) uncoupling plays a significant role in acute vasoconstriction during early brain injury (EBI) after subarachnoid hemorrhage (SAH). Astrocytes in the neurovascular unit extend their foot processes around endothelia. In our study, we tested the hypothesis that increased nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression in astrocytes after SAH leads to eNOS uncoupling.

Methods

We utilized laser speckle contrast imaging for monitoring cortical blood flow changes in mice, nitric oxide (NO) kits to measure the level of NO, and a co-culture system to study the effect of astrocytes on endothelial cells. Moreover, the protein levels were assessed by Western blot and immunofluorescence staining. We used CCK-8 to measure the viability of astrocytes and endothelial cells, and we used the H2O2 kit to measure the H2O2 released from astrocytes. We used GSK2795039 as an inhibitor of NOX2, whereas lentivirus and adeno-associated virus were used for dihydrofolate reductase (DHFR) knockdown in vivo and in vitro.

Results

The expression of NOX2 and the release of H2O2 in astrocytes are increased, which was accompanied by a decrease in endothelial DHFR 12 h after SAH. Moreover, the eNOS monomer/dimer ratio increased, leading to a decrease in NO and acute cerebral ischemia. All of the above were significantly alleviated after the administration of GSK2795039. However, after knocking down DHFR both in vivo and in vitro, the protective effect of GSK2795039 was greatly reversed.

Discussion

The increased level of NOX2 in astrocytes contributes to decreased DHFR in endothelial cells, thus aggravating eNOS uncoupling, which is an essential mechanism underlying acute vasoconstriction after SAH.

Analysis of cerebral glucose metabolism following experimental subarachnoid hemorrhage over 7 days

Little is known about changes in brain metabolism following SAH, possibly leading towards secondary brain damage. Despite sustained progress in the last decade, analysis of in vivo acquired data still remains challenging. The present interdisciplinary study uses a semi-automated data analysis tool analyzing imaging data independently from the administrated radiotracer. The uptake of 2-[¹⁸F]Fluoro-2-deoxy-glucose ([¹⁸F]FDG) was evaluated in different brain regions in 14 male Sprague-Dawley rats, randomized into two groups: (1) SAH induced by the endovascular filament model and (2) sham operated controls. Serial [¹⁸F]FDG-PET measurements were carried out. Quantitative image analysis was performed by uptake ratio using a self-developed MRI-template based data analysis tool. SAH animals showed significantly higher [¹⁸F]FDG accumulation in gray matter, neocortex and olfactory system as compared to animals of the sham group, while white matter and basal forebrain region showed significant reduced tracer accumulation in SAH animals. All significant metabolic changes were visualized from 3 h, over 24 h (day 1), day 4 and day 7 following SAH/sham operation. This [¹⁸F]FDG-PET study provides important insights into glucose metabolism alterations following SAH-for the first time in different brain regions and up to day 7 during course of disease.

Downregulation of miR-26b attenuates early brain injury induced by subarachnoid hemorrhage via mediating the KLF4/STAT3/HMGB1 axis

BACKGROUND

Early brain injury (EBI) refers to early-onset secondary complications that occur after subarachnoid hemorrhage (SAH), and associated with high rate of disability and mortality. Recent investigations have indicated microRNA-26b (miR-26b) as a biomarker in the progression of SAH. Accordingly, the present study was designed to elucidate the role of miR-26b in influencing EBI following SAH and the downstream mechanisms.

METHODS

Firstly, SAH rat models and neuron injury models were developed to assess the effect of miR-26b on EBI-like symptoms and subsequent inflammation. Dual-luciferase reporter gene assay was further implemented to evaluate the binding of miR-26b to its putative target gene STAT3. Loss-of-function and rescue experiments were performed to assess the functionality of miR-26b-mediated STAT3 in both models.

RESULTS

miR-26b was found to target KLF4 and negative-modulate its expression, whereby aggravating EBI and inflammatory response in SAH rat models and stimulating hemoglobin-induced apoptosis in astrocytes. On the other hand, silencing of miR-26b reversed these changes in SAH rat models and hemoglobin (Hb)-induced astrocytes. miR-26b could further activate STAT3 via down-regulation of KLF4. Furthermore, KLF4 knockdown up-regulated HMGB1 to aggravate EBI following SAH.

CONCLUSIONS

Collectively, our findings highlighted the ameliorative effect of miR-26b inhibition on EBI in SAH and the possible mechanism associated with the KLF4/STAT3/HMGB1 axis.

Influence of neurovascular anatomy on perforation site in different mouse strains using the filament perforation model for induction of subarachnoid hemorrhage

BACKGROUND

Filament perforation is a widely-used method to induce subarachnoid hemorrhage (SAH) in mice. Whereas the perforation site has been assumed to be in the branching of middle cerebral artery (MCA) and anterior cerebral artery (ACA), we recently observed more proximal perforations.

METHODS

Filament perforation was performed in CD1- (n = 10) and C57Bl/6N-mice (n = 9) ex vivo. The filament was left in place and the perforation site was microscopically assessed. Digital subtraction angiography (DSA) was performed in CD1- (n = 9) and C57Bl/6J-mice (n = 29) and anatomical differences of the internal carotid artery (ICA) were determined.

RESULTS

Whereas in C57Bl/6N-mice perforation occurred in the proximal intracranial ICA in 89% (n = 8), in CD1-mice the perforation site was in the proximal ICA in 50% (n = 5), in the branching between MCA and ACA in 40% (n = 4), and in the proximal ACA in 10% (n = 1). DSA revealed a stronger angulation (p<0.001) of the ICA in CD1-mice (163.5±2.81°) compared to C57Bl/6J-mice (124.5±5.49°). Body weight and ICA-angle showed no significant correlation in C57Bl/6J- (r = -0.06, pweight/angle = 0.757) and CD1-mice (r = -0.468, pweight/angle = 0.242).

CONCLUSION

Filament perforation in mice occurs not only at the hitherto presumed branching between MCA and ACA, but seems to depend on mouse strain and anatomy as the proximal intracranial ICA may also be perforated frequently.

Assessment of cardiac function in rat endovascular perforation model of subarachnoid hemorrhage; A model of subarachnoid hemorrhage-induced cardiac dysfunction

Although the association between cardiac dysfunction and subarachnoid hemorrhage (SAH) has been recognized, its precise underlying mechanism remains unknown. Furthermore, no suitable animal models are available to study this association. Here, we established an appropriate animal model of SAH-induced cardiac dysfunction and elucidated its mechanism. In this rat model, contrast-enhanced computed tomography of the brain confirmed successful induction of SAH. Electrocardiography detected abnormalities in 55% of the experimental animals, while echocardiography indicated cardiac dysfunction in 30% of them. Further evaluation of left ventriculography confirmed cardiac dysfunction, which was transient and recovered over time. Additionally, in this SAH model, the expression of the acute phase reaction protein, proto-oncogene c-Fos increased in the paraventricular hypothalamic nucleus (PVN), the sympathetic nerve center of the brain. Polymerase chain reaction analysis revealed that the SAH model with cardiac dysfunction had higher levels of the macrophage-associated chemokine (C-X-C motif) ligand 1 (CXCL-1) and chemokine (C-C motif) ligand 2 (CCL-2) than the SAH model without cardiac dysfunction. Our results suggested that SAH caused inflammation and macrophage activation in the PVN, leading to sympathetic hyperexcitability that might cause cardiac dysfunction directly and indirectly. This animal model may represent a powerful tool to investigate the mechanisms of the brain-heart pathway.

A Review on Preclinical Models of Ischemic Stroke: Insights Into the Pathomechanisms and New Treatment Strategies

BACKGROUND

Stroke is a serious neurovascular problem and the leading cause of disability and death worldwide. The disrupted demand to supply ratio of blood and glucose during cerebral ischemia develops hypoxic shock, and subsequently necrotic neuronal death in the affected regions. Multiple causal factors like age, sex, race, genetics, diet, and lifestyle play an important role in the occurrence as well as progression of post-stroke deleterious events. These biological and environmental factors may be contributed to vasculature variable architecture and abnormal neuronal activity. Since recombinant tissue plasminogen activator is the only clinically effective clot bursting drug, there is a huge unmet medical need for newer therapies for the treatment of stroke. Innumerous therapeutic interventions have shown promise in the experimental models of stroke but failed to translate it into clinical counterparts.

METHODS

Original publications regarding pathophysiology, preclinical experimental models, new targets and therapies targeting ischemic stroke have been reviewed since the 1970s.

RESULTS

We highlighted the critical underlying pathophysiological mechanisms of cerebral stroke and preclinical stroke models. We discuss the strengths and caveats of widely used ischemic stroke models, and commented on the potential translational problems. We also describe the new emerging treatment strategies, including stem cell therapy, neurotrophic factors and gut microbiome-based therapy for the management of post-stroke consequences.

CONCLUSION

There are still many inter-linked pathophysiological alterations with regards to stroke, animal models need not necessarily mimic the same conditions of stroke pathology and newer targets and therapies are the need of the hour in stroke research.

Denervation injury of scalp hair due to trigeminal ganglion ischemia: the first experimental study

Aim: Scalp hairs are mainly innervated by sensitive fibers of trigeminal nerves. Ischemic neurodegeneration of trigeminal ganglion can cause denervation injury of scalp hairs. We investigated if there is a relationship between the degenerated neuron densities of trigeminal ganglion neuron densities and the numbers of degenerated hair follicles numbers following subarachnoid hemorrhage (SAH). Material and Method: Five normal (n=5), five SHAM (n=5), and ten (n=10) male rabbits were chosen from formerly experimental SAH created by cisternal homologous blood injection (0.75cc) group, which followed for three weeks. Degenerated neuron numbers of trigeminal ganglion and atrophic hair follicles numbers in the frontal areas of the scalp were examined by stereological methods. Degenerated neuron densities of trigeminal ganglions and atrophic hair follicles numbers were analyzed by the Mann-Whitney U test. Results: The mean degenerated neuron densities trigeminal ganglions (n/mm3) and atrophic hair follicles (n/mm2) were determined as 5±2/m3 and12±4/mm2 in control; 12±3/m3 and 41±8/mm2 in Sham and, 168±23/m3 and 79±14/mm2 in the study group (p>0.001). In the post-hoc analysis, all groups differed significantly from each other. A linear association was observed between the degenerated neuron densities of trigeminal ganglions and atrophic hair follicles (r: 0.343, p: 0.007). Conclusion: Trigeminal ganglion neurodegeneration may be an essential factor in hair follicles atrophy after SAH, which has not been mentioned in the literature so far.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Is There a Relevant Experimental Model? A Systematic Review of Preclinical Literature

Delayed cerebral ischemia (DCI) is one of the main prognosis factors for disability after aneurysmal subarachnoid hemorrhage (SAH). The lack of a consensual definition for DCI had limited investigation and care in human until 2010, when a multidisciplinary research expert group proposed to define DCI as the occurrence of cerebral infarction (identified on imaging or histology) associated with clinical deterioration. We performed a systematic review to assess whether preclinical models of SAH meet this definition, focusing on the combination of noninvasive imaging and neurological deficits. To this aim, we searched in PUBMED database and included all rodent SAH models that considered cerebral ischemia and/or neurological outcome and/or vasospasm. Seventy-eight publications were included. Eight different methods were performed to induce SAH, with blood injection in the cisterna magna being the most widely used (n = 39, 50%). Vasospasm was the most investigated SAH-related complication (n = 52, 67%) compared to cerebral ischemia (n = 30, 38%), which was never investigated with imaging. Neurological deficits were also explored (n = 19, 24%). This systematic review shows that no preclinical SAH model meets the 2010 clinical definition of DCI, highlighting the inconsistencies between preclinical and clinical standards. In order to enhance research and favor translation to humans, pertinent SAH animal models reproducing DCI are urgently needed.

Oleanolic acid reduces oxidative stress and neuronal apoptosis after experimental subarachnoid hemorrhage by regulating Nrf2/HO-1 pathway

Oxidative stress is an early major pathological feature after subarachnoid hemorrhage (SAH) and involves in the development of acute brain injury, neuronal apoptosis and cerebral vasospasm following SAH. Antioxidant stress is an effective way to improve the prognosis of SAH. Oleanolic acid is a widely used triterpenoid from plants, which has strong antioxidant activities, hepatoprotective, anti-inflammatory and anti-cancer activities. However, whether oleanolic acid exerts its anti-oxidant effect after SAH and the underlying mechanisms involved in it is unclear. In current study, the SAH model was established on Sprague Dawley rats using a standard intravascular puncture model. We found OA treatment significantly reduced malondialdehyde levels, and increased the levels of superoxide dismutase, catalase and GSH-Px after SAH, and reduced many EBI-related indicators, including brain edema, BBB disruption, SAH grades, and neurological score. In addition, the activation of Nrf2/HO-1 pathway after SAH was also detected. And by using Nrf2 siRNA intracerebroventricular injections, apoptosis related factors downstream of Nrf2/HO-1 pathway were detected. By TUNEL staining, OA treatment obviously reduced neuronal apoptosis. Therefore, we suggest that OA could alleviate oxidative stress and reduce neuronal apoptosis through activating Nrf 2/HO-1 pathway.

Characteristics of MRI Findings after Subarachnoid Hemorrhage and D-Dimer as a Predictive Value for Early Brain Injury

BACKGROUND

The pathological mechanisms of early brain injury (EBI) have remained obscure. Several studies have reported on the neuroradiological findings of EBI. However, to our knowledge, no study has attempted to explore the mechanism of EBI after subarachnoid hemorrhage (SAH). Therefore, this study evaluates whether the initial plasma D-dimer levels were associated with EBI, classifies magnetic resonance imaging (MRI) findings, and speculates about the mechanism of EBI.

METHODS

This study included 97 patients hospitalized within 24 h from the onset of nontraumatic SAH. The patients underwent MRI within 0-5 days from onset (before vasospasm) to detect EBI. EBI was radiologically defined as diffusion-weighted imaging (DWI)-positive lesions that appear dark on apparent diffusion coefficient maps, excluding procedure-related lesions. EBI, plasma D-dimer levels, and clinical features were retrospectively investigated.

RESULTS

Elevated D-dimer levels were associated with poor outcomes. Patients with EBI had significantly higher D-dimer levels than those without EBI. EBI was detected in 24 patients (27.3%) of all, and in 22 (45%) of 49 patients with World Federation of Neurosurgical Societies (WFNS) grade 4-5 SAH. EBI was frequently observed in the paramedian frontal lobe. There were several types of the pathology in EBI, including widespread symmetrical cerebral cortex lesions, focal cortex lesions, periventricular injury, and other lesions impossible to classify due to unknown mechanisms such as thrombotic complication and microcirculatory disturbance, ultra-early spasm, and spreading depolarization.

CONCLUSIONS

This study suggests that D-dimer levels predict poor outcomes in patients with SAH and that EBI was associated high D-dimer levels.

Involvement of Cerebral Blood Flow on Neurological and Behavioral Functions after Subarachnoid Hemorrhage in Mice

OBJECTIVE

Cerebral Blood Flow (CBF) change after Subarachnoid Hemorrhage (SAH) is strongly associated with brain injuries such as early brain injury and delayed cerebral ischemia. We evaluated the correlation between CBF using Laser Speckle Flow Imaging (LSFI) after SAH and neurological findings in the sub-acute phase.

METHOD

An SAH was induced by endovascular perforation in male mice. CBF was quantitatively measured by using LSFI at six time points, immediately to 14 days after SAH induction. Behavior tests and survival rate were evaluated. The mice were divided into recovery and hypo-perfusion groups according to their CBF at 1 day after the procedure.

RESULT

Forty mice were included in this study. Five mice (20%) were included in the hypo-perfusion group, and the remaining 20 (80%) mice were classified as the recovery group. The decrease of CBF in the recovery group was observed until 1 day after the procedure. However, the decrease of CBF in the hypo-perfusion group was prolonged until 7 days after the procedure. Neurological findings and survival rates in the hypo-perfusion group were significantly worse than those in the recovery group. The low alternation cases (≤ 50%) in the Y-maze test in the recovery group (n = 5) had significantly lower CBF at 1 day after the procedure.

CONCLUSION

Low blood flow at 1 day after SAH was associated with worse survival rate, neurological findings, and memory disturbance. Early improvement in CBF may be associated with an improved prognosis after SAH.

Neuroprotective Strategies in Aneurysmal Subarachnoid Hemorrhage (aSAH)

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

FGF-2 suppresses neuronal autophagy by regulating the PI3K/Akt pathway in subarachnoid hemorrhage

The degree of early brain injury (EBI) is a significant factor that affects the prognosis of patients with subarachnoid hemorrhage (SAH). Evidence has shown that fibroblast growth factor-2 (FGF-2) may alleviate the serious consequences of EBI after SAH. The objective of the current study was to investigate the underlying mechanism that mediates the neuroprotective effects of FGF-2 in the SAH rat model. Sprague-Dawley (SD) rats that underwent different treatments were divided into various groups. FGF-2 was administered intranasally to rats in the treatment group within 30 min after modeling. Rapamycin (an autophagy activator) or LY294002 (a PI3K/Akt pathway inhibitor) was administered intracerebroventricularly (i.c.v.) 30 min before modeling. Neurological scale and brain water content were measured in the brain tissue of the rats. TUNEL staining, Western blot, and immunofluorescence staining were performed to examine and compare the diverse effects of FGF-2 treatment, activated autophagy, and inhibited the PI3K/Akt pathway. We found that FGF-2 treatment effectively reduced the number of TUNEL-positive cells, decreased the brain water content, and improved the neurological function of rats after SAH. Additionally, the expression levels of autophagy-related proteins (LC3 and Beclin-1) were obviously decreased in the FGF-2 treatment group compared with the SAH + vehicle group. The therapeutic effects of FGF-2 in the SAH + FGF-2+rapamycin group were weakened compared with that in the SAH + FGF-2+DMSO group. In the event of the PI3K/Akt pathway inhibition, the expression levels of LC3 and Beclin-1 were enhanced, and the therapeutic effects of FGF-2 were compromised. In summary, our data collectively demonstrated that FGF-2 may suppress autophagy levels to play a neuroprotective role, at least partially by activating the PI3K/Akt pathway. These results highlight FGF-2 as a promising solution to the clinical intervention of SAH.

Inhibition of miR-103-3p Preserves Neurovascular Integrity Through Caveolin-1 in Experimental Subarachnoid Hemorrhage

Caveolin-1 (Cav-1) is a constitutive structural protein of caveolae in the plasma membrane. It plays an important role in maintaining blood brain barrier (BBB) integrity. In this study, we identified that miR-103-3p, a hypoxia-responsive miRNA, could interact with Cav-1. In endothelial cells, miR-103-3p mimic diminished the expression of Cav-1 and tight junction proteins, which were rescued by the inhibition of miR-103-3p. We found a substantial increase of miR-103-3p and decease of Cav-1 in the rat subarachnoid hemorrhage (SAH) model. Pre-SAH intracerebroventricularly injection of miR-103-3p antagomir relieved Cav-1 loss, sequentially reduced BBB permeability and improved neurological function. Finally, we demonstrated that the salutary effects of miR-103-3p antagomir were abolished in Cav-1 knock-out mice, suggesting that Cav-1 was required for the miR-103-3p inhibition-induced neurovascular protection. Taken together, our findings suggest that the inhibition of miR-103-3p could exert neuroprotective effects through preservation of Cav-1 and BBB integrity, making miR-103-3p a novel therapeutic target for SAH.

Destructive Effects of Acidic Blood on the Intestines: Experimental Study

Objective

This study aimed to investigate the destructive effects of acidic blood on the intestinal structures, which has been reported as the most hazardous biochemical result of vagosympathetic autonomic imbalances in intensive care unit patients with subarachnoid hemorrhage (SAH).

Materials and Methods

In total, 27 hybrid rabbits were used; 5 rabbits were used as a control group, 7 as the SHAM group into whom 1 cc saline was injected into the cisterna magna, and the remaining 15 were used as the study group. These animals received 1 cc of autologous arterial blood injection into the cisterna magna to create the SAH group. Blood pH values were recorded before, during, and after the experimental procedures. Computed tomography was performed to examine the intestinal morphology. Normal and degenerated epithelial cell densities of the intestine were estimated by stereological methods. The relationship between pH values and intestinal tissue changes was analyzed statistically using the Mann-Whitney U test.

Results

The mean blood pH values were 7.364±0.042 in the control group, 7.326±0.059 in the SHAM group, and 7.23±0.021 in the study group. Intestinal epithelial cell injury, desquamation of villus, and cell loss were observed. It is observed that the number of degenerated epithelial cells, fragmented villi numbers, and vacuoles significantly increased in the study group (p<0.05).

Conclusion

Acidotic intestinal injury secondary to blood pH changes following SAH may be considered as a generalized and dangerous complication with their multiorgan insuficiency effect.

The Involvement of Aquaporin-4 in the Interstitial Fluid Drainage Impairment Following Subarachnoid Hemorrhage

The mechanism of brain injury following subarachnoid hemorrhage (SAH) has not yet been clarified. The glymphatic system (GS), a glia-dependent waste clearance pathway, drains away soluble waste proteins and metabolic products, even some toxic factors from the brain. Aquaporin-4 (Aqp4) is highly expressed on the astrocyte foot processes and facilitates the interstitial fluid (ISF) transportation in the GS system. In this study, the role of Aqp4 in the GS injury after SAH was explored using Aqp4 gene knockout (Aqp4^−/−) Sprague Dawley rats. The results of MRI, fluorescent imaging, and transmission electron microscopy (TEM) indicated that, after SAH, the inflow of cerebrospinal fluid (CSF) into the brain and the clearance of ISF from the brain were both significantly decreased. Meanwhile, the expression level of Aqp4 around the artery was markedly higher than that around the vein following SAH. Aqp4 knockout exacerbated the GS damage after SAH. In summary, after SAH, there was an apparent GS impairment, and Aqp4 played key roles in modulating the function of GS in the brain.

Effects of stellate ganglion block on early brain injury in patients with subarachnoid hemorrhage: a randomised control trial

Background

Subarachnoid hemorrhage (SAH) is a common neurosurgical emergency, and early brain injury (EBI) plays an important role in acute brain injury of SAH. Our objective is to investigate the effect of stellate ganglion block (SGB) on the clinical prognosis of patients with SAH (registration number ChiCTR2000030910).

Methods

A randomized controlled trial was conducted with 102 participants. Patients with SAH were assigned to the SGB or nSGB group. Patients in the SGB group received SGB four times (once every other day starting on the day of the surgery). In contrast, patients in the nSGB group only received standard care. Data were collected on the day before surgery (T0) and on the 1^st (T1), 3^rd (T2) and 7^th day (T3) after surgery. The primary outcomes included EBI markers (including IL-1β, IL-6, TNF-α, ET-1, NPY, NSE and S100β), the mean cerebral blood flow velocity of the middle cerebral artery (Vm-MCA) and the basilar artery (Vm-BA). All cases were followed up for 6 months after surgery.

Results

The levels of the EBI markers in both groups were higher at T1–T3 than at T0 (P<0.05), and the Vm-MCA and Vm-BA were also increased at the same times. However, the levels of the EBI markers were lower in the SGB group than in the nSGB group (P<0.05), and the increases of Vm-MCA and Vm-BA were also lower (P<0.05). The prognosis score and neurological deficit were better in the SGB group than in the nSGB group (P<0.05).

Conclusions

SGB can improve the prognosis of SAH patients by inhibiting the inflammatory response during EBI and by reducing endothelial dysfunction and relieving CVS.

Trial registration

Clinical trial number: ChiCTR2000030910; Registry URL: Chinese Clinical Trial Registry; Principal investigator's name: Ying Nie; Date of Trial registration: March, 2020 (retrospectively registered).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-020-01215-3.

New endovascular perforation subarachnoid hemorrhage model for investigating the mechanisms of delayed brain injury

OBJECTIVE

Delayed brain injury (DBI) is considered one of the most important causes of mortality and morbidity after subarachnoid hemorrhage (SAH). However, no suitable experimental rat endovascular perforation (EVP) SAH model was available for investigating DBI. The authors added early cerebral hypoperfusion to a mild EVP SAH model by unilateral common carotid artery occlusion (UCCAO) 24 hours after induction of SAH to mimic the clinical course of early cerebral hypoperfusion after SAH.

METHODS

A total of 109 adult male Sprague-Dawley rats were randomly divided into 2 groups: no SAH and SAH. Next, no-SAH rats were randomly divided on day 1 into 2 groups: sham and UCCAO. SAH rats with a neurological score of 15 or greater were randomly divided into 2 groups: SAH - UCCAO and SAH + UCCAO group.

RESULTS

The mild SAH model had a lower mortality rate of 5.4% within the first 24 hours. No rat died in the SAH + UCCAO group until day 7. DBI as well as early brain injury (EBI), reactive astrogliosis, and cerebral vasospasm significantly worsened in the SAH + UCCAO group.

CONCLUSIONS

The present SAH + UCCAO model can simulate EBI with aggravation of reactive astrogliosis, cerebral vasospasm, and DBI but without high mortality.

Update: Microdialysis for Monitoring Cerebral Metabolic Dysfunction after Subarachnoid Hemorrhage

Cerebral metabolic dysfunction has been shown to extensively mediate the pathophysiology of brain injury after subarachnoid hemorrhage (SAH). The characterization of the alterations of metabolites in the brain can help elucidate pathophysiological changes occurring throughout SAH and the relationship between secondary brain injury and cerebral energy dysfunction after SAH. Cerebral microdialysis (CMD) is a tool that can measure concentrations of multiple bioenergetics metabolites in brain interstitial fluid. This review aims to provide an update on the implication of CMD on the measurement of metabolic dysfunction in the brain after SAH. A literature review was conducted through a general PubMed search with the terms “Subarachnoid Hemorrhage AND Microdialysis” as well as a more targeted search using MeSh with the search terms “Subarachnoid hemorrhage AND Microdialysis AND Metabolism.” Both experimental and clinical papers were reviewed. CMD is a suitable tool that has been used for monitoring cerebral metabolic changes in various types of brain injury. Clinically, CMD data have shown the dramatic changes in cerebral metabolism after SAH, including glucose depletion, enhanced glycolysis, and suppressed oxidative phosphorylation. Experimental studies using CMD have demonstrated a similar pattern of cerebral metabolic dysfunction after SAH. The combination of CMD and other monitoring tools has also shown value in further dissecting and distinguishing alterations in different metabolic pathways after brain injury. Despite the lack of a standard procedure as well as the presence of limitations regarding CMD application and data interpretation for both clinical and experimental studies, emerging investigations have suggested that CMD is an effective way to monitor the changes of cerebral metabolic dysfunction after SAH in real-time, and alternatively, the combination of CMD and other monitoring tools might be able to further understand the relationship between cerebral metabolic dysfunction and brain injury after SAH, determine the severity of brain injury and predict the pathological progression and outcomes after SAH. More translational preclinical investigations and clinical validation may help to optimize CMD as a powerful tool in critical care and personalized medicine for patients with SAH.

The Updated Role of the Blood Brain Barrier in Subarachnoid Hemorrhage: From Basic and Clinical Studies

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke associated with high mortality and morbidity. The blood-brain-barrier (BBB) is a structure consisting primarily of cerebral microvascular endothelial cells, end feet of astrocytes, extracellular matrix, and pericytes. Post-SAH pathophysiology included early brain injury and delayed cerebral ischemia. BBB disruption was a critical mechanism of early brain injury and was associated with other pathophysiological events. These pathophysiological events may propel the development of secondary brain injury, known as delayed cerebral ischemia. Imaging advancements to measure BBB after SAH primarily focused on exploring innovative methods to predict clinical outcome, delayed cerebral ischemia, and delayed infarction related to delayed cerebral ischemia in acute periods. These predictions are based on detecting abnormal changes in BBB permeability. The parameters of BBB permeability are described by changes in computed tomography (CT) perfusion and magnetic resonance imaging (MRI). K_ep seems to be a stable and sensitive indicator in CT perfusion, whereas K^trans is a reliable parameter for dynamic contrast-enhanced MRI. Future prediction models that utilize both the volume of BBB disruption and stable parameters of BBB may be a promising direction to develop practical clinical tools. These tools could provide greater accuracy in predicting clinical outcome and risk of deterioration. Therapeutic interventional exploration targeting BBB disruption is also promising, considering the extended duration of post-SAH BBB disruption.

Tim-3 deteriorates neuroinflammatory and neurocyte apoptosis after subarachnoid hemorrhage through the Nrf2/HMGB1 signaling pathway in rats

Inflammation is known to play an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH). T cell immunoglobulin and mucin domain-3 (Tim-3) has emerged as a critical regulator of adaptive and innate immune responses, and has been identified to play a vital role in certain inflammatory diseases; The present study explored the effect of Tim-3 on inflammatory responses and detailed mechanism in EBI following SAH. We investigated the effects of Tim-3 on SAH models established by endovascular puncture method in Sprague–Dawley rats. The present studies revealed that SAH induced a significant inflammatory response and significantly increased Tim-3 expression. Tim-3-AAV administration aggravated neurocyte apoptosis, brain edema, blood-brain barrier permeability, and neurological dysfunction; significantly inhibited Nrf2 expression; and increased HMGB1 expression and secretion of pro-inflammatory cytokines, such as tumor necrosis factor alpha, interleukin (IL)-1 beta, IL-17, and IL-18. However, Tim-3 siRNA or NK252 administration abolished the pro-inflammatory effects of Tim-3. Our results indicate a function for Tim-3 as a molecular player that links neuroinflammation and brain damage after SAH. We reveal that Tim-3 overexpression deteriorates neuroinflammatory and neurocyte apoptosis after subarachnoid hemorrhage through the Nrf2/HMGB1 signaling pathway in rats.

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.

Sudden death in epilepsy: There is room for intracranial pressure

INTRODUCTION

Sudden unexpected death in patients with epilepsy (SUDEP) remains a poorly understood entity, and it is unclear whether the same pathomechanisms underlie all sudden deaths occurring in patients with epilepsy. One aspect not included in current models of SUDEP is the role of increased intracranial pressure (ICP) which can be observed immediately upon seizure activity in neurosurgical practice.

METHODS

We conducted a systematic review of the occurrence of edema in patients with epilepsy reported to have died of sudden death who underwent brain autopsy or postmortem brain imaging and discuss how increased ICP may contribute to clinical features of SUDEP.

RESULTS

19 eligible studies comprising a total of 623 patients were identified. Edema-mostly mild or moderate-was reported in 17% of cases and 74% of studies. 1% (n = 6) of the overall cases were clearly identified as having Dravet syndrome or an SCN1A mutation. In these patients, edema was found in 4 (67%) of cases.

CONCLUSION

Edema is regularly found in patients with epilepsy classified to have died from SUDEP. We argue that seizures preceding SUDEP may in certain cases elicit acute edema which may represent an additional contributing factor in the cascade of events leading to sudden death of patients with epilepsy. Furthermore, we hypothesize that mild edema may especially progress to severe edema in patients with sodium channel mutations which may represent an important mechanism to investigate in the context of understanding the significantly elevated risk of SUDEP in patients with SCN1A mutations.

Behavioral tests in rodent models of stroke

Rodents are the most widely used experimental animals in stroke research due to their similar vascular anatomy, high reproductive rates, and availability of transgenic models. However, the difficulties in assessing higher brain functions, such as cognition and memory, in rodents decrease the translational potential of these studies. In this review, we summarize commonly used motor/sensorimotor and cognition tests in rodent models of stroke. Specifically, we first briefly introduce the objective and procedure of each behavioral test. Next, we summarize the application of each test in both ischemic stroke and hemorrhagic stroke. Last, the advantages and disadvantages of these tests in assessing stroke outcome are discussed. This review summarizes commonly used behavioral tests in stroke studies and compares their applications in different stroke types.

TREM-1 Exacerbates Neuroinflammatory Injury via NLRP3 Inflammasome-Mediated Pyroptosis in Experimental Subarachnoid Hemorrhage

Neuroinflammation contributes to the pathogenesis of early brain injury induced by subarachnoid hemorrhage (SAH). Previous reports have demonstrated that triggering receptor expressed on myeloid cells 1 (TREM-1) regulates inflammatory response caused by ischemic stroke or myocardial infarction. However, whether TREM-1 could modulate neuroinflammation after SAH remains largely unknown. Here, using a mouse model of SAH, we found that the expression of TREM-1 was mainly located in microglia cells and increased to peak at 24 h following SAH. Then, TREM-1 antagonist or mimic was intranasally administrated to investigate its effect on SAH. TREM-1 inhibition with LP17 improved neurological deficits, mitigated brain water content, and preserved brain-blood barrier integrity 24 h after SAH, whereas recombinant TREM-1, a mimic of TREM-1, deteriorated these outcomes. In addition, LP17 administration restored long-term sensorimotor coordination and cognitive deficits. Pharmacological blockade of TREM-1 reduced TUNEL-positive and FJC-positive neurons, and CD68-stained microglia in ipsilateral cerebral cortex. Neutrophil invasion was inhibited as protein level of myeloperoxidase (MPO), and MPO-positive cells were both decreased. Moreover, we found that LP17 treatment ameliorated microglial pyroptosis by diminishing levels of N-terminal fragment of GSDMD (GSDMD-N) and IL-1β production. Mechanistically, both in vivo and in vitro, we depicted that TREM-1 can trigger microglial pyroptosis via activating NLRP3 inflammasome. In conclusion, our results revealed the critical role of TREM-1 in neuroinflammation following SAH, suggesting that TREM-1 inhibition might be a potential therapeutic approach for SAH.

Hydrogen gas inhalation improves delayed brain injury by alleviating early brain injury after experimental subarachnoid hemorrhage

Molecular hydrogen (H₂) protect neurons against reactive oxygen species and ameliorates early brain injury (EBI) after subarachnoid hemorrhage (SAH). This study investigated the effect of H₂ on delayed brain injury (DBI) using the rat SAH + unilateral common carotid artery occlusion (UCCAO) model with the endovascular perforation method. 1.3% H₂ gas (1.3% hydrogen premixed with 30% oxygen and balanced nitrogen) inhalation was performed on days 0 and 1, starting from anesthesia induction and continuing for 2 h on day 0, and starting from anesthesia induction and continuing for 30 min on day 1. EBI was assessed on the basis of brain edema, expression of S100 calcium-binding protein B (S100B), and phosphorylation of C-Jun N-terminal kinase on day 2, and neurological deficits on day 3. Reactive astrogliosis and severity of cerebral vasospasm (CV) were assessed on days 3 and 7. DBI was assessed on the basis of neurological deficits and neuronal cell death on day 7. EBI, reactive astrogliosis, and DBI were ameliorated in the H₂ group compared with the control group. CV showed no significant improvement between the control and H₂ groups. This study demonstrated that H₂ gas inhalation ameliorated DBI by reducing EBI without improving CV in the rat SAH + UCCAO model.

Neurobehavioral Deficits After Subarachnoid Hemorrhage in Mice: Sensitivity Analysis and Development of a New Composite Score

Background

Because of the failure of numerous clinical trials, various recommendations have been made to improve the usefulness of preclinical studies. Specifically, the STAIR (Stroke Therapy Academic Industry Roundtable) recommendations highlighted functional outcome as a critical measure. Recent reviews of experimental subarachnoid hemorrhage (SAH) studies have brought to light the numerous neurobehavioral scoring systems that are used in preclinical SAH studies. To gain insight into the utility of these scoring systems, as well as to identify a scoring system that best captures the deficits caused by SAH in mice, we designed the current study.

Methods and Results

Adult male C57BL/6J mice were used. One cohort of mice was randomly allocated to either sham or SAH and had functional testing performed on days 1 to 3 post‐SAH using the modified Bederson Score, Katz Score, Garcia Neuroscore, and Parra Neuroscore, as well as 21 individual subtests. A new composite neuroscore was developed using the 8 most diagnostically accurate subtests. To validate the use of the developed composite neuroscore, another cohort of mice was randomly assigned to either the sham or SAH group and neurobehavior was evaluated on days 1 to 3, 5, and 7 after injury. Receiver operating characteristic curves were used to analyze the diagnostic accuracy of each scoring system, as well as the subtests. Of the 4 published scoring systems, the Parra Neuroscore was diagnostically accurate for SAH injury in mice versus the modified Bederson and Katz Scores, but not the Garcia Neuroscore. However, the newly developed composite neuroscore was found to be statistically more diagnostically accurate than even the Parra Neuroscore.

Conclusions

The findings of this study promote use of the newly developed composite neuroscore for experimental SAH studies in mice.

Hydrogen Sulfide Reduces Cognitive Impairment in Rats After Subarachnoid Hemorrhage by Ameliorating Neuroinflammation Mediated by the TLR4/NF-κB Pathway in Microglia

Background and Aims: Cognitive impairment is one of the major complications of subarachnoid hemorrhage (SAH) and is closely associated with neuroinflammation. Hydrogen sulfide (H₂S) has been shown to have an anti-inflammatory effect and reduce cognitive impairment in neurodegenerative diseases, but its effects in SAH have been little studied. This study aimed to investigate the effects of H₂S on cognitive impairment after SAH and the possible underlying mechanisms.

Methods: Forty-eight male Sprague–Dawley (SD) rats were randomly divided into three groups: a sham group, a SAH group, and a SAH + NaHS (an H₂S donor) group. The endovascular perforation technique was used to establish the experimental SAH model. NaHS was administered intraperitoneally. An active avoidance test (AAT) was performed to investigate cognitive function. The expression of TNF-α, toll-like receptor 4 (TLR4), and NF-κB p65 in the hippocampus was measured by Western blot and immunohistochemistry. The types of cells expressing TNF-α were detected by double immunofluorescence staining.

Results: Compared to that in the sham group, the learning and memory ability of rats in the SAH group was damaged. Furthermore, the expression of TNF-α, TLR4, and NF-κB p65 in the hippocampus was elevated in the SAH group (p < 0.05). TNF-α was mainly expressed in activated microglia, which was consistent with the expression of TLR4. Treatment with NaHS significantly decreased the cognitive impairment of rats after SAH and simultaneously reduced the expression of TNF-α, TLR4, and NF-κB p65 and alleviated the nuclear translocation of NF-κB p65 (p < 0.05).

Conclusions: The neuroinflammation reaction in microglia contributes to cognitive impairment after SAH. H₂S reduced the cognitive impairment of rats after SAH by ameliorating neuroinflammation in microglia, potentially via the TLR4/NF-κB pathway.

Neuroprotective effects of quercetin on cerebral vasospasm following experimental subarachnoid haemorrhage in rats

Background/aim

We examined the protective effects of the natural flavonoid, quercetin, against cerebral vasospasm in an experimental rat subarachnoid haemorrhage (SAH) model.

Materials and methods

Thirty-eight albino Wistar rats were divided into five groups as follows: group 1 (G1, n=8), no experimental intervention; group 2 (G2, n=8), subarachnoid physiological saline; group 3 (G3, n=8), SAH; group 4 (G4, n=7) SAH and low-dose (10 mg/kg) quercetin treatment; group 5 (G5, n=7), SAH and high-dose (50 mg/kg) quercetin treatment. Subarachnoid haemorrhage was induced by injection of 0.15 cc of autologous blood taken from the tail artery into the cisterna magna from the craniocervical junction and basilar arteries and blood samples were taken for biochemical and histopathological analyses.

Results

Malondialdehyde (MDA) levels were significantly higher in G2 and G3 than in G1 (P < 0.05). Significant decreases in MDA were observed in G4 and G5 compared with G2 (P < 0.05, G4–G2; P < 0.05, G5–G2). There were no significant differences between G2 and G3 or among G1, G4, and G5. No statistically significant differences were found in total antioxidant capacity between the groups (P > 0.05). There were no significant differences in basilar artery (BA) wall thickness between G3 and G4 or between G3 and G5, but G4 and G5 showed greater luminal diameters than G3 (P < 0.05). There were no significant differences in BA thickness or luminal diameter between G4 and G5.

Conclusion

Our results suggested that quercetin may be beneficial in SAH therapy by preventing vasospasm.

Targeting CCL20 inhibits subarachnoid hemorrhage-related neuroinflammation in mice

Recent evidence suggests that CC chemokine ligand 20 (CCL20) is upregulated after subarachnoid hemorrhage (SAH). Here, we investigated the functions of CCL20 in SAH injury and its underlying mechanisms of action. We found that CCL20 is upregulated in an SAH mouse model and in cultured primary microglia and neurons. CCL20-neutralizing antibody alleviated SAH-induced neurological deficits, decreased brain water content and neuronal apoptosis, and repressed microglial activation. We observed increased levels of CCL20, CC chemokine receptor 6 (CCR6), interleukin 1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α), as well as of microglial activation in microglia treated with oxyhemoglobin (OxyHb). CCL20 or CCR6 knockdown reversed the effects of OxyHb on microglia. Conditioned medium from OxyHb-treated microglia induced neuronal apoptosis, while the percentage of apoptotic neurons in the conditioned medium from microglia transfected with CCL20 siRNA or CCR6 siRNA was decreased. We observed no decrease in OxyHb-induced apoptosis in CCL20-knockdown neurons. Conditioned medium from OxyHb-treated neurons led to microglial activation and induced CCR6, IL-1β and TNF-α expression, while CCL20 knockdown in neurons or CCR6 knockdown in microglia reversed those effects. Our results thus suggest CCL20 may be targeted to elicit therapeutic benefits after SAH injury.

First definition of burned choroid plexus in acidic cerebrospinal fluid-filled brain ventricles during subarachnoid hemorrhage: Experimental study

Blood and cerebrospinal fluid (CSF) acidosis is the most troubling complication in subarachnoid hemorrhage (SAH) if carotid body (CB) networks are disrupted. However, histopathological examination of the choroid plexus (CP) in acidic CSF has not been evaluated so far. In this study, we aimed to investigate the CP in acidic CSF following SAH. Twenty-eight rabbits were used. Five rabbits were used to analyze CB network (control group; n = 5); seven rabbits were injected 1 mL of saline (Sham group; n = 7); and the rest 16 rabbits were given 1 mL of autologous arterial blood inject into the cisterna magna to create SAH (SAH group; n = 16). Blood and CSF pH values were recorded before/during/after the experimental procedures. Nuclear darkening, cellular shrinkage and pyknosis suggested the presence of apoptosis of epithelial cells of CP. The densities of normal and degenerated epithelial cells of CPs were estimated using stereological methods. The relationship between the pH values and degenerated epithelial cell densities of CPs were statistically compared by Mann-Whitney U-test. The pH values of blood were estimated as 7.359 ± 0.039 in the control group, 7.318 ± 0.062 in the Sham group, 7.23 ± 0.013 in the SAH group. CSF pH values were 7.313 ± 0.028 in the control group, 7.296 ± 0.045 in the Sham group, and 7.224 ± 0.012 in the SAH group. Degenerated epithelial cell density of CP was 25 ± 7 in the control group, 226 ± 64 in the Sham group, and 2115 ± 635 in the SAH group. There was a considerable link between CSF pH values and degenerated epithelial cells of CP (P < 0.0001). This study shows that CB insult causes acidosis of CSF as well as cellular degeneration of CP during SAH. This is the first description of this in the literature.

The ESAS-score: A histological severity grading system of subarachnoid hemorrhage using the modified double hemorrhage model in rats

Objective

The amount of extravasated blood is an established surrogate marker for subarachnoid hemorrhage (SAH) severity, which varies in different experimental SAH (eSAH) models. A comprehensive eSAH grading system would allow a more reliable correlation of outcome parameters with SAH severity. The aim of this study was to define a severity score for eSAH related to the Fisher-Score in humans.

Material and methods

SAH was induced in 135 male rats using the modified double hemorrhage model. A sham group included 8 rats, in which saline solution instead of blood was injected. Histological analysis with HE(hematoxylin-eosin)-staining for the visualization of blood was performed in all rats on day 5. The amount and distribution of blood within the subarachnoid space and ventricles (IVH) was analyzed.

Results

The mortality rate was 49.6% (71/143). In all except five SAH rats, blood was visible within the subarachnoid space. As expected, no blood was detected in the sham group. The following eSAH severity score was established (ESAS-score): grade I: no SAH visible; grade II: local or diffuse thin SAH, no IVH; grade III: diffuse / thick layers of blood, no IVH; grade IV: additional IVH. Grade I was seen in five rats (7.9%), grade II in 28.6% (18/63), grade III in 41.3% (26/63) and grade IV in 22.2% (14/63) of the rats with eSAH.

Conclusion

The double hemorrhage model allows the induction of a high grade SAH in more than 60% of the rats, making it suitable for the evaluation of outcome parameters in severe SAH.

Neuroprotective mechanism of L-cysteine after subarachnoid hemorrhage

Hydrogen sulfide, which can be generated in the central nervous system from the sulfhydryl-containing amino acid, L-cysteine, by cystathionine-β-synthase, may exert protective effects in experimental subarachnoid hemorrhage; however, the mechanism underlying this effect is unknown. This study explored the mechanism using a subarachnoid hemorrhage rat model induced by an endovascular perforation technique. Rats were treated with an intraperitoneal injection of 100 mM L-cysteine (30 μL) 30 minutes after subarachnoid hemorrhage. At 48 hours after subarachnoid hemorrhage, hematoxylin-eosin staining was used to detect changes in prefrontal cortex cells. L-cysteine significantly reduced cell edema. Neurological function was assessed using a modified Garcia score. Brain water content was measured by the wet-dry method. L-cysteine significantly reduced neurological deficits and cerebral edema after subarachnoid hemorrhage. Immunofluorescence was used to detect the number of activated microglia. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the levels of interleukin 1β and CD86 mRNA in the prefrontal cortex. L-cysteine inhibited microglial activation in the prefrontal cortex and reduced the mRNA levels of interleukin 1β and CD86. RT-PCR and western blot analysis of the complement system showed that L-cysteine reduced expression of the complement factors, C1q, C3α and its receptor C3aR1, and the deposition of C1q in the prefrontal cortex. Dihydroethidium staining was applied to detect changes in reactive oxygen species, and immunohistochemistry was used to detect the number of NRF2- and HO-1-positive cells. L-cysteine reduced the level of reactive oxygen species in the prefrontal cortex and the number of NRF2- and HO-1-positive cells. Western blot assays and immunohistochemistry were used to detect the protein levels of CHOP and GRP78 in the prefrontal cortex and the number of CHOP- and GRP78-positive cells. L-cysteine reduced CHOP and GRP78 levels and the number of CHOP- and GRP78-positive cells. The cystathionine-β-synthase inhibitor, aminooxyacetic acid, significantly reversed the above neuroprotective effects of L-cysteine. Taken together, L-cysteine can play a neuroprotective role by regulating neuroinflammation, complement deposition, oxidative stress and endoplasmic reticulum stress. The study was approved by the Animals Ethics Committee of Shandong University, China on February 22, 2016 (approval No. LL-201602022).

Innate immunity activation in the early brain injury period following subarachnoid hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (SAH) is a catastrophic disease with devastating consequences, including a high mortality rate and severe disabilities among survivors. Inflammation is induced following SAH, but the exact role and phenotype of innate immune cells remain poorly characterized. We investigated the inflammatory components of the early brain injury in an animal model and in SAH patients.

Method

SAH was induced through injection of blood in the subarachnoid space of C57Bl/6 J wild-type mice. Prospective blood collections were obtained at 12 h, days 1, 2, and 7 to evaluate the systemic inflammatory consequences of SAH by flow cytometry and enzyme-linked immunosorbent-assay (ELISA). Brains were collected, enzymatically digested, or fixed to characterize infiltrating inflammatory cells and neuronal death using flow cytometry and immunofluorescence. Phenotypic evaluation was performed at day 7 using the holding time and footprint tests. We then compared the identified inflammatory proteins to the profiles obtained from the plasma of 13 human SAH patients.

Results

Following SAH, systemic IL-6 levels increased rapidly, whereas IL-10 levels were reduced. Neutrophils were increased both in the brain and in the blood reflecting local and peripheral inflammation following SAH. More intracerebral pro-inflammatory monocytes were found at early time points. Astrocyte and microglia activation were also increased, and mice had severe motor deficits, which were associated with an increase in the percentage of caspase-3-positive apoptotic neurons. Similarly, we found that IL-6 levels in patients were rapidly increased following SAH. ICAM-1, bFGF, IL-7, IL-12p40, and MCP-4 variations over time were different between SAH patients with good versus bad outcomes. Moreover, high levels of Flt-1 and VEGF at admission were associated with worse outcomes.

Conclusion

SAH induces an early intracerebral infiltration and peripheral activation of innate immune cells. Furthermore, microglia and astrocytic activation are present at later time points. Our human and mouse data illustrate that SAH is a systemic inflammatory disease and that immune cells represent potential therapeutic targets to help this population of patients in need of new treatments.