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

Adjudin protects blood-brain barrier integrity and attenuates neuroinflammation following intracerebral hemorrhage in mice

Secondary brain injury exacerbates neurological dysfunction and neural cell death following intracerebral hemorrhage (ICH), targeting the pathophysiological mechanism of the secondary brain injury holds promise for improving ICH outcomes. Adjudin, a potential male contraceptive, exhibits neuroprotective effects in brain injury disease models, yet its impact in the ICH model remains unknown. In this study, we investigated the effects of adjudin on brain injury in a mouse ICH model and explored its underlying mechanisms. ICH was induced in male C57BL/6 mice by injecting collagenase into the right striatum. Mice received adjudin treatment (50 mg/kg/day) for 3 days before euthanization and the perihematomal tissues were collected for further analysis. Adjudin significantly reduced hematoma volume and improved neurological function compared with the vehicle group. Western blot showed that Adjudin markedly decreased the expression of MMP-9 and increased the expression of tight junctions (TJs) proteins, Occludin and ZO-1, and adherens junctions (AJs) protein VE-cadherin. Adjudin also decreased the blood-brain barrier (BBB) permeability, as indicated by the reduced albumin and Evans Blue leakage, along with a decrease in brain water content. Immunofluorescence staining revealed that adjudin noticeably reduced the infiltration of neutrophil, activation of microglia/macrophages, and reactive astrogliosis, accompanied by an increase in CD206 positive microglia/macrophages which exhibit phagocytic characteristics. Adjudin concurrently decreased the generation of proinflammatory cytokines, such as TNF-α and IL-1β. Additionally, adjudin increased the expression of aquaporin 4 (AQP4). Furthermore, adjudin reduced brain cell apoptosis, as evidenced by increased expression of anti-apoptotic protein Bcl-2, and decreased expression of apoptosis related proteins Bax, cleaved caspase-3 and fewer TUNEL positive cells. Our data suggest that adjudin protects against ICH-induced secondary brain injury and may serve as a potential neuroprotective agent for ICH treatment.

Validation of a Simplified Model for Subarachnoid Hemorrhage in Mice

BACKGROUND

Subarachnoid hemorrhage (SAH) represents a severe injury to the brain and is associated with a high mortality (40%). Several experimental SAH models are described in the literature requiring specialized equipment and a high degree of surgical expertise. Our goal was to validate a simplified, cost-effective model to permit future studies of SAH.

METHODS

SAH was induced by injection of homologous blood into the cisterna magna. Perfusion-fixation then perfusion of gelatinous India ink was performed. Brains and brainstems were collected and imaged for analysis of cerebral vasospasm. Triphenyl tetrazolium chloride (TTC) staining was used to analyze brain tissue cell death 24 hours following stroke. A composite neuroscore was utilized to assess SAH-related neurologic deficits.

RESULTS

Anterior cerebral artery and basilary artery diameters were significantly reduced at 24 hours post SAH induction. Middle cerebral artery diameter was also reduced; however, the results were not significant. TTC staining showed no infarcted tissue. Neuroscores were significantly lower in the SAH mice, indicating the presence of functional deficits.

CONCLUSIONS

This simplified model of SAH elicits pathological changes consistent with those described for more complex models in the literature. Therefore, it can be used in future preclinical studies examining the pathophysiology of SAH and novel treatment options.

Lateral fluid percussion injury: A rat model of experimental traumatic brain injury

Traumatic brain injury (TBI) represents one of the leading causes of disability and death worldwide. The annual economic impact of TBI-including direct and indirect costs-is high, particularly impacting low- and middle-income countries. Despite extensive research, a comprehensive understanding of the primary and secondary TBI pathophysiology, followed by the development of promising therapeutic approaches, remains limited. These fundamental caveats in knowledge have motivated the development of various experimental models to explore the molecular mechanisms underpinning the pathogenesis of TBI. In this context, the Lateral Fluid Percussion Injury (LFPI) model produces a brain injury that mimics most of the neurological and systemic aspects observed in human TBI. Moreover, its high reproducibility makes the LFPI model one of the most widely used rodent-based TBI models. In this chapter, we provide a detailed surgical protocol of the LFPI model used to induce TBI in adult Wistar rats. We further highlight the neuroscore test as a valuable tool for the evaluation of TBI-induced sensorimotor consequences and their severity in rats. Lastly, we briefly summarize the current knowledge on the pathological aspects and functional outcomes observed in the LFPI-induced TBI model in rodents.

Neutrophils and Neutrophil Extracellular Traps Cause Vascular Occlusion and Delayed Cerebral Ischemia After Subarachnoid Hemorrhage in Mice

BACKGROUND

After subarachnoid hemorrhage (SAH), neutrophils are deleterious and contribute to poor outcomes. Neutrophils can produce neutrophil extracellular traps (NETs) after ischemic stroke. Our hypothesis was that, after SAH, neutrophils contribute to delayed cerebral ischemia (DCI) and worse outcomes via cerebrovascular occlusion by NETs.

METHODS

SAH was induced via endovascular perforation, and SAH mice were given either a neutrophil-depleting antibody, a PAD4 (peptidylarginine deiminase 4) inhibitor (to prevent NETosis), DNAse-I (to degrade NETs), or a vehicle control. Mice underwent daily neurological assessment until day 7 and then euthanized for quantification of intravascular brain NETs (iNETs). Subsets of mice were used to quantify neutrophil infiltration, NETosis potential, iNETs, cerebral perfusion, and infarction. In addition, NET markers were assessed in the blood of aneurysmal SAH patients.

RESULTS

In mice, SAH led to brain neutrophil infiltration within 24 hours, induced a pro-NETosis phenotype selectively in skull neutrophils, and caused a significant increase in iNETs by day 1, which persisted until at least day 7. Neutrophil depletion significantly reduced iNETs, improving cerebral perfusion, leading to less neurological deficits and less incidence of DCI (16% versus 51.9%). Similarly, PAD4 inhibition reduced iNETs, improved neurological outcome, and reduced incidence of DCI (5% versus 30%), whereas degrading NETs marginally improved outcomes. Patients with aneurysmal SAH who developed DCI had elevated markers of NETs compared with non-DCI patients.

CONCLUSIONS

After SAH, skull-derived neutrophils are primed for NETosis, and there are persistent brain iNETs, which correlated with delayed deficits. The findings from this study suggest that, after SAH, neutrophils and NETosis are therapeutic targets, which can prevent vascular occlusion by NETs in the brain, thereby lessening the risk of DCI. Finally, NET markers may be biomarkers, which can predict which patients with aneurysmal SAH are at risk for developing DCI.

Knockdown of LCN2 Attenuates Brain Injury After Intracerebral Hemorrhage via Suppressing Pyroptosis

Objective

The aims of this study are to screen novel differentially expressed genes (DEGs) for intracerebral hemorrhage (ICH) and reveal the role of Lipocalin-2 (LCN2) in ICH.

Methods

We constructed the ICH model by injection of autologous whole blood into the right basal ganglia in rats. RNA-sequencing and bioinformatics analyses were performed to identify the DEGs between ICH and sham rats, and some important ones were confirmed using quantitative real-time PCR (qRT-PCR). LCN shRNA was used to knockdown of LCN2 in ICH rats. Pathological examination was carried out using 2,3,5-triphenyltetrazolium chloride (TTC) staining and Hematoxylin-eosin (HE) staining. Immunohistochemistry detected Caspase-3, and co-staining of Terminal dUTP nick end labeling (TUNEL) and NEUN staining were performed for neuron apoptosis assessment. Western blot analysis was performed to quantify pyroptosis-related proteins. Enzyme-linked immunosorbent assay (ELISA) was used to measure inflammatory cytokine levels.

Results

ICH rats exhibited significant hematomas, higher brain water content, obvious interstitial edema, and inflammatory infiltration, as well as more apoptotic cells in brain tissues. RNA-seq analysis identified 103 upregulated and 81 downregulated DEGs. The expression of LCN2, HSPB1, CXCL10, and MEF2B were upregulated in ICH rats. ICH triggered the release of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-18, and promoted the expression of pyroptosis-related proteins Caspase-1, GSDMD, NLRP3, and ASC. LCN2 knockdown attenuated the pathological characteristics of ICH, and also reduced pyroptosis in brain tissues.

Conclusion

Inhibition of LCN2 attenuates brain injury after ICH via suppressing pyroptosis, which provide guidance for ICH management.

Hydrophobic Polystyrene-Modified Gelatin Enhances Fast Hemostasis and Tissue Regeneration in Traumatic Brain Injury

Hemostatic sealant is required to deal with blood loss, especially in the scenario of traumatic brain injury (TBI), which presents high rates of morbidity and disability. Hemostasis in surgery with traditional gelatin-based sealants often leads to blood loss and other issues in brain because of the hydrophilic gelatin swelling. Herein, hydrophobic effects on the hemostasis in TBI surgery are studied by tuning the chain length of polystyrene (PS) onto methylacrylated gelatin (Gel-MA). The hydrophobicity and hemostatic efficiency can be tuned by controlling the length of PS groups. The platelet activation of modified sealants Gel-MA-2P, Gel-MA-P, and Gel-MA-0.5P is as much as 17.5, 9.1, and 2.1 times higher than Gel-MA in vitro. The hemostatic time of Gel-MA-2P, Gel-MA-P, and Gel-MA-0.5P groups is 2.0-, 1.6-, and 1.1-folds faster than that in Gel-MA group in TBI mice. Increased formation of fibrins and platelet aggregation can also be observed in vitro by scanning electron microscopy. Animal's mortality is lowered by 46%, neurologic deficiency is reduced by 1.5 times, and brain edema is attenuated by 10%. Protein expression is further investigated to exhibit toxic iron-related processes caused by delayed hemostasis and activation of platelets via PI3K/PKC-α signaling. The hydrophobic Gel-MA has the potential in hemostatic TBI and promotes nervous system recovery in brain with the potentials in clinics.

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.

A short review on behavioural assessment methods in rodents

The rodent behavioural examination techniques are used to assess various psychological, neurological models and neurotoxicity studies. Therefore, it is of interest to document the various behavioural assessment methods used in rodent model to study the motor, sensory, cognitive functions and emotional behaviour.

Protective effects of alpha-mangostin encapsulated in cyclodextrin-nanoparticle on cerebral ischemia

The production of reactive oxygen species (ROS) during and after the onset of an ischemic stroke induces neuronal cell death and severely damages brain function. Therefore, reducing ROS by administrating antioxidant compounds is a promising approach to improving ischemic symptoms. Alpha-mangostin (α-M) is an antioxidant compound extracted from the pericarp of the mangosteen fruit. Reportedly, α-M decreases neuronal toxicity in primary rat cerebral cortical neurons. In this study, we investigated the neuroprotective activity of α-M in both in vitro and in vivo assays. Pretreatment with α-M inhibited excessive cellular ROS production after oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro using an SH-SY5Y (human neuroblastoma) cell line. In addition, α-M maintained mitochondrial membrane potential and suppressed mitochondrial-specific ROS production induced by OGD/R. Meanwhile, the low bioavailability of α-M due to its poor water solubility has been an insuperable obstruction impeding extensive investigations of the biological functions of α-M and its medical applications. To overcome this problem, we synthesized a cyclodextrin-based nanoparticle (CDNP) that is known to increase the loading efficiency and binding constant of α-M, compared with cyclodextrins themselves. This nano-formulated α-M (α-M/CDNP) was optimized for an in vivo ischemic stroke model. Our results indicated that α-M/CDNP (25 mg/kg/injection) reduced infarct volume and improved neurological behavior (p = 0.036 and p = 0.046, respectively). These in vivo results suggest that α-M appears to cross the blood-brain barrier (BBB) with the help of a nano-formulation with CDNP. Combining an in vitro BBB model and a physicochemical binding assay between α-M and albumin, it is speculated that α-M released from CDNP would interact with albumin during its prolonged circulation in the blood, and the resultant α-M/albumin complex may cross the BBB through the absorptive-mediated transcytosis pathway. These findings suggest the potential clinical application of α-M in ischemic stroke treatment.

TRPM2 mediates CaMKⅡ-Beclin-1 signaling in early cortical injury after induced subarachnoid hemorrhage in mice

BACKGROUND

Though early brain injury (EBI) is the primary cause of poor outcomes among patients with subarachnoid hemorrhage (SAH), its exact molecular mechanisms remain unclear. Improved the understanding of how transient receptor potential melastatin-related 2 (TRPM2) is involved in SAH-induced EBI will help develop novel interventions.

METHODS

Wild type (WT) male C57BL/6J mice were subjected to SAH for 12 h, 24 h or 48 h, after which neurological scores and pathological changes in the hippocampus (CA3, DG, and CA1) and temporal base cortex were observed. Expressions of TRPM2, Ca²⁺/calmodulin (CaM)-dependent protein kinase Ⅱ (CaMKⅡ), and Beclin-1 in hippocampus (CA3, DG, and CA1) and temporal base cortex were compared across post-SAH timepoints. TRPM2-deficient (TRPM2^-/-) male C57BL/6 J mice and a CaMKⅡ inhibitor (KN-93) were used to analyze the effects oTRPM2 on the CaMKⅡ-Beclin-1 signaling post SAH.

RESULTS

Neurological and temporal base cortex deterioration were more severe with increased time post-SAH induction, whereas hippocampal damage was not observed. Post-SAH, TRPM2-CaMKⅡ-Beclin-1 cascade was activated in the temporal base cortex, but not the hippocampus. Using TRPM2^-/- mice and KN-93 administration, SAH-induced EBI was improved, and CaMKⅡ and Beclin-1 expressions in the temporal base cortex were significantly decreased compared with WT mice. TRPM2^-/- mice also showed better neurological improvement compared with KN-93 treated mice.

CONCLUSION

TRPM2 mediates CaMKⅡ-Beclin-1 signaling that aggravates SAH-induced EBI in the temporal base cortex. TRPM2 may be an alternative therapy target in EBI after SAH.

DATA AVAILABILITY

The datasets generated and/or analysed during the current study are available from the corresponding author.

Inhibition of Mer exacerbates early brain injury by regulating microglia/macrophage phenotype after subarachnoid hemorrhage in mice

BACKGROUND

Polarization of microglia/macrophages toward the pro-inflammatory phenotype is a crucial contributor to neuroinflammation after subarachnoid hemorrhage (SAH). Mer belongs to the TAM receptor tyrosine kinases family, which is known to play a significant role in the resolution of inflammation. However, the effect and mechanism of Mer after SAH remain unclear. In this study, we explored the effect of Mer on modulating the microglia/macrophage phenotype and neuroinflammation and possible potential mechanism after SAH.

METHOD

Endovascular perforation model of SAH was performed. There are 3 parts in this study. Firstly, the time course of Mer expression was determined within 72 hours after SAH. Secondly, the effect of Mer downregulation on brain water content, neurological function, and microglial polarization was evaluated at 24 h after SAH. Thirdly, the neuroprotective effects of pharmacological Mer agonist were assessed.

RESULT

The expression of Mer increased after SAH, and was prominently localized in microglia/macrophages. Treatment with Mer siRNA increased pro-inflammatory phenotype and decreased anti-inflammatory phenotype of microglia/macrophage, thus resulted in exacerbation of neurological deficits and brain edema after SAH. Mechanistically, the downregulation of Mer inhibited the downstream anti-inflammatory signals, SOCS1/SOCS3, by decreasing phosphorylated STATs.

CONCLUSION

Mer is involved in the microglia/macrophage polarization and inflammation resolution after SAH, and that mechanism, at least in part, may contribute to the involvement of the STATs/SOCSs pathway.

High Expression of PDK4 Could Play a Potentially Protective Role by Attenuating Oxidative Stress after Subarachnoid Hemorrhage

Pyruvate dehydrogenase (PDH), a key enzyme on the mitochondrial outer membrane, has been found to decrease activity notably in early brain injury (EBI) after subarachnoid hemorrhage (SAH). It has been demonstrated that PDH is associated with the production of reactive oxygen species (ROS) and apoptosis. Hence, in this study, we aimed to determine the cause of the decreased PDH activity and explore the potential role of PDH in EBI. We investigated the expression changes of PDH and pyruvate dehydrogenase kinase (PDK) in vivo and in vitro. Then, we explored the possible effects of PDH and ROS after SAH. The results showed that early overexpression of PDK4 promoted the phosphorylation of PDH, inhibited PDH activity, and may play a protective role after SAH in vivo and in vitro. Finally, we investigated the levels of PDK4 and pyruvate, which accumulated due to decreased PDH activity, in the cerebrospinal fluid (CSF) of 34 patients with SAH. Statistical analysis revealed that PDK4 and pyruvate expression was elevated in the CSF of SAH patients compared with that of controls, and this high expression correlated with the degree of neurological impairment and long-term outcome. Taken together, the results show that PDK4 has the potential to serve as a new therapeutic target and biomarker for assisting in the diagnosis of SAH severity and prediction of recovery.

Dynamic Evolution of the Glymphatic System at the Early Stages of Subarachnoid Hemorrhage

The early stages of subarachnoid hemorrhage (SAH) are extremely important for the progression and prognosis of this disease. The glymphatic system (GS) has positive implications for the nervous system due to its ability to clearance tau and amyloid-β (Aβ) protein. Previous studies have shown that GS dysfunction will appear after SAH. However, there is no systematic evaluation of the degree of damage and development process of GS function in the early stage after SAH. In this study, we evaluated the GS function and neurobehavioral in the sham, 6 h, 1, 3, and 7 days after SAH, respectively. Our results showed that the function of GS was severely attenuated in mice after SAH with a decreased polarity of Aquaporin-4 (AQP4), increased expression of AQP4, a linear correlation with the dystrophin-associated complex (DAC), the proliferation of reactive astrocytes, increased tau protein accumulation, and decreased neurological function. Collectively, these findings provide a comprehensive understanding of the functional changes of GS after SAH, provide references for subsequent scholars studying SAH, and suggest some potential mechanistic insight that affects AQP4 polarity and GS function.

Aquaporin 4 Depolarization-Enhanced Transferrin Infiltration Leads to Neuronal Ferroptosis after Subarachnoid Hemorrhage in Mice

The infiltration of blood components into the brain parenchyma through the lymphoid system is an important cause of subarachnoid hemorrhage injury. AQP4, a water channel protein located at the astrocyte foot, has been reported to regulate blood-brain barrier integrity, and its polarization is disrupted after SAH. Neuronal ferroptosis is involved in subarachnoid hemorrhage- (SAH-) induced brain injury, but the inducing factors are not completely clear. Transferrin is one of the inducing factors of ferroptosis. This study is aimed at researching the role and mechanism of AQP4 in brain injury after subarachnoid hemorrhage in mice. An experimental mouse SAH model was established by endovascular perforation. An AAV vector encoding AQP4 with a GFAP-specific promoter was administered to mice to achieve specific overexpression of AQP4 in astrocytes. PI staining, Fer-1 intervention, and transmission electron microscopy were used to detect neuronal ferroptosis, and dextran (40 kD) leakage was used to detect BBB integrity. Western blot analysis of perfused brain tissue protein samples was used to detect transferrin infiltration. First, neuronal ferroptosis 24 h after SAH was observed by PI staining and Fer-1 intervention. Second, a significant increase in transferrin infiltration was found in the brain parenchyma 24 h after SAH modeling, while transferrin content was positively correlated with neuronal ferroptosis. Then, we observed that AQP4 overexpression effectively improved AQP depolarization and BBB injury induced by SAH and significantly reduced transferrin infiltration and neuronal ferroptosis after SAH. Finally, we found that AQP4 overexpression could effectively improve the neurobehavioral ability of SAH mice, and the neurobehavioral ability was negatively correlated with transferrin brain content. Taken together, these data indicate that overexpression of AQP4 in the mouse brain can effectively improve post-SAH neuronal ferroptosis and brain injury, at least partly by inhibiting transferrin infiltration into the brain parenchyma in the glymphatic system.

PDK4 Decrease Neuronal Apoptosis via Inhibiting ROS-ASK1/P38 Pathway in Early Brain Injury After Subarachnoid Hemorrhage

Aims: Metabolic disorders may play key roles in oxidative stress and neuronal apoptosis in response to early brain injury (EBI) after subarachnoid hemorrhage (SAH). Pyruvate dehydrogenase (PDH) is related to oxidative stress in EBI, and its activity obviously decreases after SAH. We discovered that only pyruvate dehydrogenase kinase 4 (PDK4) expression was obviously increased among the four PDK isozymes after SAH in preliminary experiments. Therefore, we attempted to investigate the effects and corresponding mechanisms of PDK4 on oxidative stress after SAH. Results: First, we confirmed that PDK4 overexpression promoted PDH phosphorylation, inhibited PDH activity, and changed cell metabolism after SAH. A small interfering RNA (siRNA) targeting PDK4, a lentiviral PDK4 overexpression vector, and dichloroacetic acid (DCA) were used to regulate the expression and activity of PDK4. The siRNA decreased PDH phosphorylation, promoted reactive oxygen species (ROS) production, activated the apoptosis signal-regulating kinase 1 (ASK1)/P38 pathway, and induced neuronal apoptosis. The lentivirus further attenuated PDH activity, oxidative stress, and neuronal apoptosis. DCA inhibited the activity of PDK4, but increased the expression of PDK4 due to a feedback mechanism. Inactivated PDK4 did not effectively suppress PDH activity, which increased ROS production, activated the ASK1/P38 pathway, and led to neuronal apoptosis. Innovation: This study provides new insights into the potential antioxidant and antiapoptotic effects of the PDK4-PDH axis on EBI after SAH. Conclusions: The early overexpression of PDK4 after SAH may attenuate neuronal apoptosis by reducing oxidative stress via the ROS/ASK1/P38 pathway. PDK4 may be a new potential therapeutic target to ameliorate EBI after SAH. Antioxid. Redox Signal. 36, 505-524.

MFGE8 decreased neuronal apoptosis and neuroinflammation to ameliorate early brain injury induced by subarachnoid hemorrhage through the inhibition of HMGB1

AIM

Both MFGE8 and HMGB1 were vital players for aneurysmal subarachnoid hemorrhage. However, whether HMGB1 was served as the downstream target of MFGE8 was unknown. To test this new mechanism, we performed the SAH model in rats.

METHOD

All treatments were injected intraventricularly into the right lateral ventricles. SAH grade, brain water content, and neurological function scores were evaluated. HMGB1 expression was studied by double immunofluorescence staining. HE and Nissl's staining were performed to observe the pathological change. Inflammatory factors were measured by ELISA method.

RESULTS

High expression of MFGE8 could improve neurological function and reduce the brain edema and pro-inflammatory factors. Injection of rhMFGE8 inhibited HMGB1. To further verify the regulation of MFGE8 in HMGB1, we used rhHMGB1 and glycyrrhizin, and the results indicated MFGE8 produced excellent effect on SAH rats via inhibiting HMGB1.

CONCLUSION

In a word, MFGE8 improved EBI caused by SAH, depending on HMGB1 that was the potential mechanism.

Nimodipine Attenuates Early Brain Injury by Protecting the Glymphatic System After Subarachnoid Hemorrhage in Mice

The glymphatic system (GS) plays an important role in subarachnoid hemorrhage (SAH). Nimodipine treatment provides SAH patients with short-term neurological benefits. However, no trials have been conducted to quantify the relationship between nimodipine and GS. We hypothesized that nimodipine could attenuate early brain injury (EBI) after SAH by affecting the function of the GS. In this study, we assessed the effects of nimodipine, a dihydropyridine calcium channel antagonist, on mice 3 days after SAH. The functions of GS were assessed by immunofluorescence and western blot. The effects of nimodipine were assessed behaviorally. Concurrently, correlation analysis was performed for the functions of GS, immunofluorescence and behavioral function. Our results indicated that nimodipine improved GS function and attenuated neurological deficits and brain edema in mice with SAH. Activation of the cAMP/PKA pathway was involved in this process. GS function was closely associated with perivascular AQP4 polarization, cortical GFAP/AQP4 expression, brain edema and neurobehavioral function. In conclusion, this study shows for the first time that nimodipine plays a neuroprotective role in the period of EBI after SAH in mice through the GS.

Mast Cells Mediate Inflammatory Injury and Aggravate Neurological Impairment in Experimental Subarachnoid Hemorrhage Through Microglial PAR-2 Pathway

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease with high mortality and disability. Aberrant neuroinflammation has been identified as a critical factor accounting for the poor prognosis of SAH patients. Mast cells (MCs), the sentinel cells of the immune system, play a critical in the early immune reactions and participate in multiple pathophysiological process. However, the exact role of MCs on the pathophysiological process after SAH has not been fully understood. The current study was conducted to determine the role of MCs and MC stabilization in the context of SAH. Mouse SAH model was established by endovascular perforation process. Mice received saline or cromolyn (MC stabilizer) or compound 48/80 (MCs degranulator). Post-SAH evaluation included neurobehavioral test, western blot, immunofluorescence, and toluidine blue staining. We demonstrated that SAH induced MCs activation/degranulation. Administration of MC stabilizer cromolyn conferred a better neurologic outcome and decreased brain edema when compared with SAH+vehicle group. Furthermore, cromolyn significantly inhibited neuroinflammatory response and alleviated neuronal damage after SAH. However, pharmacological activation of MCs with compound 48/80 dramatically aggravated SAH-induced brain injury and exacerbated neurologic outcomes. Notably, pharmacological inhibition of microglial PAR-2 significantly reversed MCs-induced inflammatory response and neurological impairment. Additionally, the effect of MCs-derived tryptase in mediating neuroinflammation was also abolished by the microglial PAR-2 blockage in vitro. Taken together, MCs yielded inflammatory injury through activating microglia-related neuroinflammation after SAH. These data shed light on the notion that MCs might be a novel and promising therapeutic target for SAH.

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.

α7-Acetylcholine Receptor Signaling Reduces Neuroinflammation After Subarachnoid Hemorrhage in Mice

Aneurysmal subarachnoid hemorrhage (aSAH) causes a robust inflammatory response which leads worse brain injury and poor outcomes. We investigated if stimulation of nicotinic acetylcholine α7 receptors (α7-AChR) (receptors shown to have anti-inflammatory effects) would reduce inflammation and improve outcomes. To investigate the level of peripheral inflammation after aSAH, inflammatory markers were measured in plasma samples collected in a cohort of aSAH patients. To study the effect of α7-AChR stimulation, SAH was induced in adult mice which were then treated with a α7-AChR agonist, galantamine, or vehicle. A battery of motor and cognitive tests were performed 24 h after subarachnoid hemorrhage. Mice were euthanized and tissue collected for analysis of markers of inflammation or activation of α7-AChR-mediated transduction cascades. A separate cohort of mice was allowed to survive for 28 days to assess long-term neurological deficits and histological outcome. Microglia cell culture subjected to hemoglobin toxicity was used to assess the effects of α7-AChR agonism. Analysis of eighty-two patient plasma samples confirmed enhanced systemic inflammation after aSAH. α7-AChR agonism reduced neuroinflammation at 24 h after SAH in male and female mice, which was associated with improved outcomes. This coincided with JAK2/STAT3 and IRAK-M activity modulations and a robust improvement in neurological/cognitive status that was effectively reversed by interfering with various components of these signaling pathways. Pharmacologic inhibition partially reversed the α7-AChR agonist's benefits, supporting α7-AChR as a target of the agonist's therapeutic effect. The cell culture experiment showed that α7-AChR agonism is directly beneficial to microglia. Our results demonstrate that activation of α7-AChR represents an attractive target for treatment of SAH. Our findings suggest that α7-AChR agonists, and specifically galantamine, might provide therapeutic benefit to aSAH patients.

Agonism of the α7-acetylcholine receptor/PI3K/Akt pathway promotes neuronal survival after subarachnoid hemorrhage in mice

Subarachnoid hemorrhage (SAH) results in severe neuronal dysfunction and degeneration. Since the nicotinic acetylcholine α₇ receptors (α₇-AChR) are involved in neuronal function and survival, we investigated if stimulation of α₇-AChR would promote neuronal survival and improve behavioral outcome following SAH in mice. Male mice subjected to SAH were treated with either galantamine (α₇-AChR agonist) or vehicle. Neurobehavioral testing was performed 24 h after SAH, and mice were euthanized for analysis of neuronal cell death or a cell survival (PI3K/Akt) signaling pathway. Neuron cell cultures were subjected to hemoglobin toxicity to assess the direct effects of α₇-AChR agonism independent of other cells. Treatment with the α₇-AChR agonist promoted neuronal survival and improved functional outcomes 24 h post-SAH. The improved outcomes corresponded with increased PI3K/Akt activity. Antagonism of α₇-AChR or PI3K effectively reversed galantamine's beneficial effects. Tissue from α₇-AChR knockout mice confirmed α₇-AChR's role in neuronal survival after SAH. Data from the neuronal cell culture experiment supported a direct effect of α₇-AChR agonism in promoting cell survival. Our findings indicate that α₇-AChR is a therapeutic target following SAH which can promote neuronal survival, thereby improving neurobehavioral outcome. Thus, the clinically relevant α₇-AChR agonist, galantamine, might be a potential candidate for human use to improve outcome after SAH.

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.

Importance of CBF measurement to exclude concomitant cerebral infarction in the murine endovascular perforation SAH model

OBJECTIVE

Concomitant cerebral infarction (CI) is could be a potential concern in experimental subarachnoid hemorrhage (SAH) induced by endovascular perforation. We propose a noninvasive method for excluding CI in a murine SAH model by using Laser speckle flow imaging (LSFI).

METHODS

An SAH was induced with endovascular perforation (EVP) in male ddY mice. The cerebral blood flow (CBF) was quantitatively measured in the bilateral cerebral cortex was performed by using LSFI at five timepoints (preprocedure, immediately after, and 3 hours, 6 hours, and 24 hours after the procedure). The mice were then euthanized, and the SAH grade and volume of the CI were evaluated. The mice were divided into the SAH group and the SAH + CI group. Differences between the groups were assessed.

RESULTS

Forty-eight mice were used in this study. Six were the sham control group. Five SAH mice died within 24 hours after the procedure. A large CI on the ipsilateral side occurred in 15 (40.5%) mice (i.e., SAH + CI group). The remaining 22 (59.5%) mice were classified as the SAH group. The SAH grading score was not significantly different between the groups. The neurological score and CBF of the ipsilateral hemisphere were significantly higher in the SAH group than in the SAH + CI group (neurological score: 12.3 vs. 8, p < 0.01; CBF: 343.1 vs. 205.5; p < 0.01). The cut-off modified neurological score for excluding CI was 8 (area under the curve [AUC]: 0.77) and CBF at 24 hours after the procedure was 279.2 (AUC:0.856).

CONCLUSIONS

Using LSFI is less invasive and effectively excludes concomitant CI in experimental SAH. This methodological protocol may ad in improving the quality of the EVP-SAH 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.

Microthrombi Correlates With Infarction and Delayed Neurological Deficits After Subarachnoid Hemorrhage in Mice

BACKGROUND AND PURPOSE

Delayed neurological deficits are a devastating consequence of subarachnoid hemorrhage (SAH), which affects about 30% of surviving patients. Although a very serious concern, delayed deficits are understudied in experimental SAH models; it is not known whether rodents recapitulate the delayed clinical decline seen in SAH patients. We hypothesized that mice with SAH develop delayed functional deficits and that microthrombi and infarction correlate with delayed decline.

METHODS

Adult C57BL/6J mice of both sexes were subjected to endovascular perforation to induce SAH. Mice were allowed to survive for up to 1 week post-ictus and behavioral performance was assessed daily. Postmortem microthrombi, large artery diameters (to assess vasospasm), and infarct volume were measured. These measures were analyzed for differences between SAH mice that developed delayed deficits and SAH mice that did not get delayed deficits. Correlation analyses were performed to identify which measures correlated with delayed neurological deficits, sex, and infarction.

RESULTS

Twenty-three percent of males and 47% of females developed delayed deficits 3 to 6 days post-SAH. Female mice subjected to SAH had a significantly higher incidence of delayed deficits than male mice with SAH. Mice that developed delayed deficits had significantly more microthrombi and larger infarct volumes than SAH mice that did not get delayed deficits. Microthrombi positively correlated with infarct volume, and both microthrombi and infarction correlated with delayed functional deficits. Vasospasm did not correlate with either infarction delayed functional deficits.

CONCLUSIONS

We discovered that delayed functional deficits occur in mice following SAH. Sex differences were seen in the prevalence of delayed deficits. The mechanism by which microthrombi cause delayed deficits may be via formation of infarcts.

Stimulator of IFN genes mediates neuroinflammatory injury by suppressing AMPK signal in experimental subarachnoid hemorrhage

BACKGROUND

Neuroinflammation is closely associated with the poor prognosis in subarachnoid hemorrhage (SAH) patients. This study was aimed to determine the role of stimulator of IFN genes (STING), an essential regulator to innate immunity, in the context of SAH.

METHODS

A total of 344 male C57BL/6 J mice were subjected to endovascular perforation to develop a model of SAH. Selective STING antagonist C-176 and STING agonist CMA were administered at 30 min or 1 h post-modeling separately. To investigate the underlying mechanism, the AMPK inhibitor compound C was administered intracerebroventricularly at 30 min before surgery. Post-SAH assessments included SAH grade, neurological test, brain water content, western blotting, RT-PCR, and immunofluorescence. Oxygenated hemoglobin was introduced into BV2 cells to establish a SAH model in vitro.

RESULTS

STING was mainly distributed in microglia, and microglial STING expression was significantly increased after SAH. Administration of C-176 substantially attenuated SAH-induced brain edema and neuronal injury. More importantly, C-176 significantly alleviated both short-term and persistent neurological dysfunction after SAH. Meanwhile, STING agonist CMA remarkably exacerbated neuronal injury and deteriorated neurological impairments. Mechanically, STING activation aggravated neuroinflammation via promoting microglial activation and polarizing into M1 phenotype, evidenced by microglial morphological changes, as well as the increased level of microglial M1 markers including IL-1β, iNOS, IL-6, TNF-α, MCP-1, and NLRP3 inflammasome, while C-176 conferred a robust anti-inflammatory effect. However, all the mentioned beneficial effects of C-176 including alleviated neuroinflammation, attenuated neuronal injury and the improved neurological function were reversed by AMPK inhibitor compound C. Meanwhile, the critical role of AMPK signal in C-176 mediated anti-inflammatory effect was also confirmed in vitro.

CONCLUSION

Microglial STING yielded neuroinflammation after SAH, while pharmacologic inhibition of STING could attenuate SAH-induced inflammatory injury at least partly by activating AMPK signal. These data supported the notion that STING might be a potential therapeutic target for SAH.

Proposed Definition of Experimental Secondary Ischemia for Mouse Subarachnoid Hemorrhage

Inconsistency in outcome parameters for delayed cerebral ischemia (DCI) makes it difficult to compare results between mouse studies, in the same way inconsistency in outcome parameters in human studies has for long obstructed adequate comparison. The absence of an established definition may in part be responsible for the failed translational results. The present article proposes a standardized definition for DCI in experimental mouse models, which can be used as outcome measure in future animal studies. We used a consensus-building approach to propose a definition for "experimental secondary ischemia" (ESI) in experimental mouse subarachnoid hemorrhage that can be used as an outcome measure in preclinical studies. We propose that the outcome measure should be as follows: occurrence of focal neurological impairment or a general neurological impairment compared with a control group and that neurological impairment should occur secondarily following subarachnoid hemorrhage (SAH) induction compared with an initial assessment following SAH induction. ESI should not be used if the condition can be explained by general anesthesia or if other means of assessments sufficiently explain function impairment. If neurological impairment cannot reliably be evaluated, due to scientific setup. Verification of a significant secondary impairment of the cerebral perfusion compared with a control group is mandatory. This requires longitudinal examination in the same animal. The primary aim is that ESI should be distinguished from intervention-related ischemia or neurological deficits, in order establish a uniform definition for experimental SAH in mice that is in alignment with outcome measures in human studies.