White Matter Injury in Early Brain Injury after Subarachnoid Hemorrhage

Advanced Diffusion Tensor Imaging in White Matter Injury After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is recognized as an especially severe stroke variant, notorious for its high mortality and long-term disability rates, in addition to a range of both immediate and enduring neurologic impacts. Over half of the SAH survivors experience varying degrees of neurologic disorders, with many enduring chronic neuropsychiatric conditions. Due to the limitations of traditional imaging techniques in depicting subtle changes within brain tissues posthemorrhage, the accurate detection and diagnosis of white matter (WM) injuries are complicated. Against this backdrop, diffusion tensor imaging (DTI) has emerged as a promising biomarker for structural imaging, renowned for its enhanced sensitivity in identifying axonal damage. This capability positions DTI as an invaluable tool for forming precise and expedient prognoses for SAH survivors. This study synthesizes an assessment of DTI for the diagnosis and prognosis of neurologic dysfunctions in patients with SAH, emphasizing the notable changes observed in DTI metrics and their association with potential pathophysiological processes. Despite challenges associated with scanning technology differences and data processing, DTI demonstrates significant clinical potential for early diagnosis of cognitive impairments following SAH and monitoring therapeutic effects. Future research requires the development of highly standardized imaging paradigms to enhance diagnostic accuracy and devise targeted therapeutic strategies for SAH patients. In sum, DTI technology not only augments our understanding of the impact of SAH but also may offer new avenues for improving patient prognoses.

Exosomal LncRNA TM7SF3-AU1 Aggravates White Matter Injury via MiR-702-3p/SARM1 Signaling After Subarachnoid Hemorrhage in Rats

Subarachnoid hemorrhage (SAH) is a devastating disease associated with a high mortality and morbidity. Exosomes have been considered as a potential therapeutic target for SAH. However, the effect of exosomes in SAH remains to be elucidated. In this study, we focused on investigating the effect of plasma exosomal lncRNA TM7SF3-AU1 in white matter injury after SAH. The SAH model was established by means of endovascular perforation. Exosomes were extracted from rat plasma samples. The expression of RNAs in the exosomes was detected by the transcriptomic microarray. Differentially expressed circRNA, lncRNA, and mRNA were obtained. The ceRNA network showed that the lncRNA TM7SF3-AU1 and miR-702-3p were closely associated with SARM1. Knocking down TM7SF3-AU1 promoted the expression of miR-702-3p and suppressed the expression of SARM1, and knocking down TM7SF3-AU1 also attenuated white matter injury after SAH. In addition, knocking down TM7SF3-AU1 improved the neurological deficits in locomotion, anxiety, learning, memory, and electrophysiological activity after SAH. Mechanistically, TM7SF3-AU1 was able to absorb miR-702-3p, which directly bind the SARM1 mRNA. Furthermore, the white matter injury attenuated by knockdown of TM7SF3-AU1 was partially reversed by the miR-702-3p antagomir in SAH rats. Taken together, this study showed that TM7SF3-AU1 acts as a sponge for miR-702-3p, reducing the inhibitory effect of miR-702-3p on SARM1, resulting in increased SARM1 expression and thus leading to white matter injury after SAH. Our study provides new insights into exosome-associated white matter injury. It also highlights TM7SF3-AU1 as a potential therapeutic target for white matter injury after SAH.

Single-Cell Transcriptomics Revealed White Matter Repair Following Subarachnoid Hemorrhage

Existing research indicates the potential for white matter injury repair during the subacute phase following subarachnoid hemorrhage (SAH). However, elucidating the role of brain cell subpopulations in the acute and subacute phases of SAH pathogenesis remains challenging due to the cellular heterogeneity of the central nervous system. In this study, single-cell RNA sequencing was conducted on SAH model mice to delineate distinct cell populations. Gene Set Enrichment Analysis was performed to identify involved pathways, and cellular interactions were explored using the CellChat package in R software. Validation of the findings involved a comprehensive approach, including magnetic resonance imaging, immunofluorescence double staining, and Western blot analyses. This study identified ten major brain clusters with cell type-specific gene expression patterns. Notably, we observed infiltration and clonal expansion of reparative microglia in white matter-enriched regions during the subacute stage after SAH. Additionally, microglia-associated pleiotrophin (PTN) was identified as having a role in mediating the regulation of oligodendrocyte precursor cells (OPCs) in SAH model mice, implicating the activation of the mTOR signaling pathway. These findings emphasize the vital role of microglia-OPC interactions might occur via the PTN pathway, potentially contributing to white matter repair during the subacute phase after SAH. Our analysis revealed precise transcriptional changes in the acute and subacute phases after SAH, offering insights into the mechanism of SAH and for the development of drugs that target-specific cell subtypes.

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.

Rasd1 is involved in white matter injury through neuron-oligodendrocyte communication after subarachnoid hemorrhage

AIMS

Rasd1 has been reported to be correlated with neurotoxicity, metabolism, and rhythm, but its effect in case of subarachnoid hemorrhage (SAH) remained unclear. White matter injury (WMI) and ferroptosis participate in the early brain injury (EBI) after SAH. In this work, we have investigated whether Rasd1 can cause ferroptosis and contribute to SAH-induced WMI.

METHODS

Lentivirus for Rasd1 knockdown/overexpression was administrated by intracerebroventricular (i.c.v) injection at 7 days before SAH induction. SAH grade, brain water content, short- and long-term neurobehavior, Western blot, real-time PCR, ELISA, biochemical estimation, immunofluorescence, diffusion tensor imaging (DTI), and transmission electron microscopy (TEM) were systematically performed. Additionally, genipin, a selective uncoupling protein 2(UCP2) inhibitor, was used in primary neuron and oligodendrocyte co-cultures for further in vitro mechanistic studies.

RESULTS

Rasd1 knockdown has improved the neurobehavior, glia polarization, oxidative stress, neuroinflammation, ferroptosis, and demyelination. Conversely, Rasd1 overexpression aggravated these changes by elevating the levels of reactive oxygen species (ROS), inflammatory cytokines, MDA, free iron, and NCOA4, as well as contributing to the decrease of the levels of UCP2, GPX4, ferritin, and GSH mechanistically. According to the in vitro study, Rasd1 can induce oligodendrocyte ferroptosis through inhibiting UCP2, increasing reactive oxygen species (ROS), and activating NCOA4-mediated ferritinophagy.

CONCLUSIONS

It can be concluded that Rasd1 exerts a modulated role in oligodendrocytes ferroptosis in WMI following SAH.

Pterostilbene as a Therapeutic Alternative for Central Nervous System Disorders: A Review of the Current Status and Perspectives

Neurological disorders are diverse, have complex causes, and often result in disability; yet, effective treatments remain scarce. The resveratrol derivative pterostilbene possesses numerous physiological activities that hold promise as a novel therapy for the central nervous system (CNS) disorders. This review aimed to summarize the protective mechanisms of pterostilbene in in vitro and in vivo models of CNS disorders and the pharmacokinetics and safety to assess its possible effects on CNS disorders. Available evidence supports the protective effects of pterostilbene in CNS disorders involving mechanisms such as antioxidant and anti-inflammatory activity, regulation of lipid metabolism and vascular smooth muscle cell proliferation, improvement of synaptic function and neurogenesis, induction of glioma cell cycle arrest, and inhibition of glioma cell migration and invasion. Studies have identified possible molecular targets and pathways for the protective actions of pterostilbene in CNS disorders including the AMPK/STAT3, Akt, NF-κB, MAPK, and ERK signaling pathways. The possible pharmacological effects and molecular pathways of pterostilbene in CNS disorders are critically discussed in this review. Future studies should aim to increase our understanding of pterostilbene in animal models and humans to further evaluate its role in CNS disorders and the detailed mechanisms.

MCC950 ameliorates cognitive function by reducing white matter microstructure damage in rats after SAH

Neuroinflammation and white matter microstructure damage are important causes of cognitive impairment after subarachnoid hemorrhage (SAH). Nod-like receptor protein 3 (NLRP3) plays an important role in neuroinflammation after SAH and may be a potential therapeutic target for treatment of white matter microstructure injury. In this study, we observed whether MCC950, a specific inhibitor of the NLRP3 inflammasome, exerted a therapeutic effect after SAH. The SAH model was induced by endovascular perforation in SpragueDawley rats. MCC950 was injected intraperitoneally 1 h after SAH at a dose of 10 mg/kg. The results showed that MCC950 significantly attenuated white matter microstructure damage in some brain regions, and behavioral experiments confirmed that MCC950 ameliorated cognitive function in rats after SAH, which may provide a new method for the treatment of cognitive dysfunction in SAH patients.

Apolipoprotein E Polymorphism Impacts White Matter Injury Through Microglial Phagocytosis After Experimental Subarachnoid Hemorrhage

Apolipoprotein E (apoE, protein; APOE, gene), divided into three alleles of E2, E3 and E4 in humans, is associated with the progression of white matter lesion load. However, mechanism evidence has not been reported regarding the APOE genotype in early white matter injury (WMI) under subarachnoid hemorrhage (SAH) conditions. In the present study, we investigated the effects of APOE gene polymorphisms, by constructing microglial APOE3 and APOE4-specific overexpression, on WMI and underlying mechanisms of microglia phagocytosis in a mice model of SAH. A total of 167 male C57BL/6J mice (weight 22-26 g) were used. SAH and bleeding environment were induced by endovascular perforation in vivo and oxyHb in vitro, respectively. Multi-technology approaches, including immunohistochemistry, high throughput sequencing, gene editing for adeno-associated viruses, and several molecular biotechnologies were used to validate the effects of APOE polymorphisms on microglial phagocytosis and WMI after SAH. Our results revealed that APOE4 significantly aggravated the WMI and decreased neurobehavioral function by impairing microglial phagocytosis after SAH. Indicators negatively associated with microglial phagocytosis increased like CD16, CD86 and the ratio of CD16/CD206, while the indicators positively associated with microglial phagocytosis decreased like Arg-1 and CD206. The increased ROS and aggravating mitochondrial damage demonstrated that the damaging effects of APOE4 in SAH may be associated with microglial oxidative stress-dependent mitochondrial damage. Inhibiting mitochondrial oxidative stress by Mitoquinone (mitoQ) can enhance the phagocytic function of microglia. In conclusion, anti-oxidative stress and phagocytosis protection may serve as promising treatments in the management of 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.

White Matter Injury: An Emerging Potential Target for Treatment after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) refers to vascular brain injury mainly from a ruptured aneurysm, which has a high lifetime risk and imposes a substantial burden on patients, families, and society. Previous studies on SAH mainly focused on neurons in gray matter (GM). However, according to literature reports in recent years, in-depth research on the mechanism of white matter (WM) is of great significance to injury and recovery after SAH. In terms of functional recovery after SAH, all kinds of cells in the central nervous system (CNS) should be protected. In other words, it is necessary to protect not only GM but also WM, not only neurons but also glial cells and axons, and not only for the lesion itself but also for the prevention and treatment of remote damage. Clarifying the mechanism of white matter injury (WMI) and repair after SAH is of great importance. Therefore, this present review systematically summarizes the current research on WMI after SAH, which might provide therapeutic targets for treatment after SAH.

MicroRNA-140-5p shuttled by microglia-derived extracellular vesicles attenuates subarachnoid hemorrhage-induced microglia activation and inflammatory response via MMD downregulation

BACKGROUND

It is documented that microglia-secreted extracellular vesicles (microglia-EVs) exert neuroprotection which is important following subarachnoid hemorrhage (SAH). Herein, we focused on the mechanism of microglia-EVs harboring microRNA-140-5p (miR-140-5p) in SAH development.

METHODS

After the successful establishment of SAH rats, neurological function was evaluated, and behaviors were observed. Serum inflammatory factors (IL-1β and TNF-α) were quantified by ELISA, followed by the detection of microglial polarization by immunofluorescence. The relationship between miR-140-5p and monocyte to macrophage differentiation-associated (MMD) was evaluated using luciferase assay. Following the extraction of microglia and microglia-EVs, the transferring of miR-140-5p by microglia-EVs was assessed by co-culture experiments. SAH rats were treated with the EVs sourced from microglia overexpressing miR-140-5p (microglia-EVs-miR-140-5p) or EVs sourced from miR-140-5p-deficient microglia (microglia-EVs-miR-140-5p inhibitor) for in vivo effect assessment.

RESULTS

Microglia-EVs inhibited microglia activation and secretion of TNF-α and IL-1β by delivering miR-140-5p. Microglia-EVs could transmit miR-140-5p into microglia. Furthermore, microglia-EVs-miR-140-5p reduced the expression of its target MMD, resulting in blocked inflammatory response and activation of microglia in SAH rats by disrupting the PI3K/AKT and Erk1/2 signaling.

CONCLUSION

In summary, microglia-EVs transmitted miR-140-5p into microglia to downregulate MMD and finally contributed to neuroprotection in SAH rats.

Deletion of Bak1 alleviates microglial necroptosis and neuroinflammation after experimental subarachnoid hemorrhage

Microglial necroptosis exacerbates neurodegenerative diseases, central nervous system (CNS) injury, and demonstrates a proinflammatory process, but its contribution to subarachnoid hemorrhage (SAH) is poorly characterized. BCL-2 homologous antagonist-killer protein (Bak1), a critical regulatory molecule of endogenous apoptosis, can be involved in the pathologic process of necroptosis by regulating mitochondrial permeability. In this study, we revealed microglia undergo necroptosis after SAH in vivo and vitro. Western blot revealed that Bak1 was elevated at 24 h after SAH. Knocked down of Bak1 by adeno-associated virus attenuates microglial necroptosis, alleviates neuroinflammation, and improves neurologic function after SAH in mice. Furthermore, oxyhemoglobin (10 μM) induced necroptosis in BV2 microglia, increasing Bak1 expression and mediating proinflammatory phenotype transformation, exacerbating oxidative stress and neuroinflammation. Abrogating BV2 Bak1 could reduce necroptosis by down-regulating the expression of phosphorylated pseudokinase mixed lineage kinase domain-like protein (p-MLKL), then down-regulating proinflammatory phenotype gene expression. RNA-Seq showed that disrupting BV2 Bak1 down-regulates multiple immune and inflammatory pathways and ameliorates cell injury by elevating thrombospondin 1 (THBS1) expression. In summary, we identified a critical regulatory role for Bak1 in microglial necroptosis and neuroinflammation after SAH. Bak1 is expected to be a potential target for the treatment strategy of SAH.

Continued P2X7 activation leads to mitochondrial fission and compromising microglial phagocytosis after subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) has a high rate of disability and mortality. Extremely damaging molecules, including adenosine triphosphate (ATP), are released from extravasated red blood cells and nerve cells, which activate microglia and induce sterile tissue injury and organ dysfunction. P2X purinoceptor 7 (P2X7) is one of the most important purine receptors on the microglial surface and is involved in the proinflammatory activation of microglia. While P2X7 can also affect microglial phagocytosis, the mechanism is not clear. Here, we demonstrated that microglial phagocytosis is progressively impaired under continued BzATP exposure and P2X7 activation. Furthermore, we found that P2X7 activation leads to increased intracellular Ca²⁺ levels and activates Calcineurin, which dephosphorylates dynamin-related protein 1 (DRP1) S637. The dephosphorylation of DRP1 at S637 leads to increased mitochondrial fission and decreased mitochondrial function, which may be responsible for the decreased microglial phagocytosis. Finally, we pharmacologically inhibited P2X7 activation in mice, which resulted in rescue of mitochondrial function and decreased microglial proliferation, but improved phagocytosis after SAH. Our study confirmed that P2X7 activation after SAH leads to the impairment of microglial phagocytosis through mitochondrial fission and verified that P2X7 inhibition restores microglial phagocytosis both in vitro and in vivo.

GPR18 Agonist Resolvin D2 Reduces Early Brain Injury in a Rat Model of Subarachnoid Hemorrhage by Multiple Protective Mechanisms

Early brain injury (EBI) is the early phase of secondary complications arising from subarachnoid hemorrhage (SAH). G protein-coupled receptor 18 (GPR18) can exert neuroprotective effects during ischemia. In this study, we investigated the roles of GPR18 in different brain regions during EBI using a GPR18 agonist, resolvin D2 (RvD2). Location and dynamics of GPR18 expression were assessed by immunohistochemistry and western blotting in a rat model of SAH based on endovascular perforation. RvD2 was given intranasally at 1 h after SAH, and SAH grade, brain water content and behavior were assayed before sacrifice. TUNEL and dihydroethidium staining of the cortex were performed at 24 h after SAH. Selected brain regions were also examined for pathway related proteins using immunofluorescence and Western blotting. We found that GPR18 was expressed in meninges, hypothalamus, cortex and white matter before EBI. After SAH, GPR18 expression was increased in meninges and hypothalamus but decreased in cortex and white matter. RvD2 improved neurological scores and brain edema after SAH. RvD2 attenuated mast cell degranulation and reduced expression of chymase and tryptase expression in the meninges. In the hypothalamus, RvD2 attenuated inflammation, increased expression of proopiomelanocortin and interleukin-10, as well as decreased expression of nerve peptide Y and tumor necrosis factor-α. In cortex, RvD2 alleviated oxidative stress and apoptosis, and protected the blood-brain barrier. RvD2 also ameliorated white matter injury by elevating myelin basic protein and suppressing amyloid precursor protein. Our results suggest that GPR18 may help protect multiple brain regions during EBI, particularly in the cortex and hypothalamus. Upregulating GPR18 by RvD2 may improve neurological functions in different brain regions via multiple mechanisms.

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.

S100A8 regulates autophagy-dependent ferroptosis in microglia after experimental subarachnoid hemorrhage

Targeting microglial activation has been shown to ameliorate early brain injury (EBI) after subarachnoid hemorrhage (SAH). Ferroptosis is a new form of programmed cell death after SAH, but these molecular features were not recognized as evidence of microglial function so far. In this study, we constructed microglial S100A8-specific knockdown and established the SAH model in vivo and in vitro. Multi-technology strategies, including high throughput sequencing, adeno-associated virus gene gene-editing and several molecular biotechnologies to validate the effects of S100A8 on microglial autophagy and ferroptosis after SAH. Our results revealed that the expression of S100A8 was significantly increased in brain tissue after SAH. Targeted microglial S100A8 inhibition improved neural function and neuronal apoptosis in mice after SAH. Further mechanism exploration found that favourable effects of S100A8 depletion in EBI may be through the inhibition of microglia autophagy-dependent ferroptosis. In conclusion, S100A8 may be a potential intervention target for microglial ferroptosis in EBI after SAH.

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.

Serum Gas6 contributes to clinical outcome after aneurysmal subarachnoid hemorrhage: A prospective cohort study

BACKGROUND

Growth-arrest-specific protein 6 (Gas6) exerts nervous protective effects on acute brain injury. We endeavored to ascertain whether serum Gas6 concentrations are associated with severity, delayed cerebral ischemia (DCI) and prognosis following aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

We measured serum Gas6 concentrations of 124 aSAH patients. The Hunt-Hess scale and modified Fisher grading scale were used to evaluate illness severity. Multivariate analysis was utilized to determine relationships between serum Gas6 concentrations and severity, DCI plus 90-day unfavorable outcome (Glasgow outcome scale score of 1-3).

RESULTS

Patients with unfavorable outcome or DCI had significantly higher serum Gas6 concentrations than other remainders (median, 35.0 vs 23.3 ng/ml; 36.1 vs 25.3 ng/ml; both P < 0.001). Serum Gas6 concentrations displayed independent correlations with Hunt-Hess scores (t = 5.518, P < 0.001) and modified Fisher scores (t = 3.531, P = 0.001). Serum Gas6 concentrations were independently associated with unfavorable outcome (OR: 1.125; 95% CI, 1.063-1.190; P = 0.014) and DCI (OR: 1.104; 95% CI, 1.041-1.170; P = 0.010) as well as exhibited AUCs of 0.786 (95% CI, 0.703-0.854) and 0.753 (95% CI, 0.668-0.826) for predicting unfavorable outcome and DCI respectively. Its discriminatory ability for risk of unfavorable outcome or DCI was similar to those of Hunt-Hess scores and modified Fisher scores (all P > 0.05).

CONCLUSIONS

Serum Gas6 concentrations are independently associated with stroke severity and worse clinical outcome after aSAH, indicating serum Gas6 may be a potential prognostic biomarker for aSAH.

Roles of Rufy3 in experimental subarachnoid hemorrhage-induced early brain injury via accelerating neuronal axon repair and synaptic plasticity

RUN and FYVE domain-containing 3 (Rufy3) is a well-known adapter protein of a small GTPase protein family and is bound to the activated Ras family protein to maintain neuronal polarity. However, in experimental subarachnoid hemorrhage (SAH), the role of Rufy3 has not been investigated. Consequently, we aimed to investigate the potential role of Rufy3 in an in vivo model of SAH-induced early brain injury (EBI). In addition, we investigated the relevant brain-protective mechanisms. Oxyhemoglobin (OxyHb) stimulation of cultured primary neurons simulated vitro SAH condition. The SAH rat model was induced by infusing autologous blood into the optic chiasma pool and treating the rats with lentivirus-negative control 1 (LV-NC1), lentivirus-Rufy3 shRNA (LV-shRNA), lentivirus-negative control 2 (LV-NC2), lentivirus-Rufy3 (LV-Rufy3), or 8-pCPT-2′-O-Me-cAMP (8p-CPT) (Rap1 agonist). In experiment one, we found that the protein level of Rufy3 decreased and neuronal axon injury in the injured neurons but was rectified by LV-Rufy3 treatment. In experiment two, mRNA and protein levels of Rufy3 were downregulated in brain tissue and reached the lowest level at 24 h after SAH. In addition, the expression of Myelin Basic Protein was downregulated and that of anti-hypophosphorylated neurofilament H (N52) was upregulated after SAH. In experiments three and four, Rufy3 overexpression (LV-Rufy3) increased the interactions between Rufy3 and Rap1, the level of Rap1-GTP, and the ratio of Rap1-GTP/total GTP. In addition, LV-Rufy3 treatment inhibited axon injury and accelerated axon repair by activating the Rap1/Arap3/Rho/Fascin signaling pathway accompanied by upregulated protein expression levels of ARAP3, Rho, Fascin, and Facin. LV-Rufy3 also enhanced synaptic plasticity by activating the Rap1/MEK/ERK/synapsin I signaling pathway accompanied by upregulated protein expression levels of ERK1, p-ERK1, MEK1, p-MEK1, synaspin I, and p-synaspin I. Moreover, LV-Rufy3 also alleviated brain damage indicators, including cortical neuronal cell apoptosis and degeneration, brain edema, and cognitive impairment after SAH. However, the downregulation of Rufy3 had the opposite effect and aggravated EBI induced by SAH. Notably, the combined application of LV-Rufy3 and 8p-CPT showed a significant synergistic effect on the aforementioned parameters. Our findings suggest that enhanced Rufy3 expression may reduce EBI by inhibiting axon injury and promoting neuronal axon repair and synaptic plasticity after SAH.

Mesenchymal Stem Cell-Derived Extracellular Vesicles Alleviate M1 Microglial Activation in Brain Injury of Mice With Subarachnoid Hemorrhage via microRNA-140-5p Delivery

BACKGROUND

It is documented that mesenchymal stem cells (MSCs) secrete extracellular vesicles (EVs) to modulate subarachnoid hemorrhage (SAH) development. miR-140-5p expression has been detected in MSC-derived EVs, while the mechanism of MSC-derived EVs containing miR-140-5p in SAH remains unknown. We aim to fill this void by establishing SAH mouse models and extracting MSCs and MSC-EVs.

METHODS

After ALK5 was silenced in SAH mice, neurological function was evaluated, neuron apoptosis was detected by TdT-mediated dUTP-biotin nick end labeling with NeuN staining, and expression of serum inflammatory factors (interleukin-6, interleukin-1β, and tumor necrosis factor-α) was determined by enzyme-linked immunosorbent assay. The effect of ALK5 on NOX2 expression was assessed by western-blot analysis. Targeting the relationship between miR-140-5p and ALK5 was evaluated by dual luciferase assay. Following extraction of MSCs and MSC-EVs, EVs and miR-140-5p were labeled by PKH67 and Cy3, respectively, to identify the transferring of miR-140-5p by MSC-EVs. SAH mice were treated with EVs from miR-140-5p mimic/inhibitor-transfected MSCs to detect effects of MSC-EV-miR-140-5p on brain injury and microglial polarization.

RESULTS

ALK5 silencing increased the neurological score and reduced neuron apoptosis and neuroinflammation in SAH mice. ALK5 silencing inhibited M1 microglia activation by inactivating NOX2. ALK5 was a target gene of miR-140-5p. MSC-derived EVs contained miR-140-5p and transferred miR-140-5p into microglia. MSC-EV-delivered miR-140-3p reduced ALK5 expression to contribute to repression of brain injury and M1 microglia activation in SAH mice.

CONCLUSIONS

MSC-derived EVs transferred miR-140-5p into microglia to downregulate ALK5 and NOX2, thus inhibiting M1 microglia activation in SAH mice.

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

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

Loss of monocarboxylate transporter 1 aggravates white matter injury after experimental subarachnoid hemorrhage in rats

Monocarboxylic acid transporter 1 (MCT1) maintains axonal function by transferring lactic acid from oligodendrocytes to axons. Subarachnoid hemorrhage (SAH) induces white matter injury, but the involvement of MCT1 is unclear. In this study, the SAH model of adult male Sprague-Dawley rats was used to explore the role of MCT1 in white matter injury after SAH. At 48 h after SAH, oligodendrocyte MCT1 was significantly reduced, and the exogenous overexpression of MCT1 significantly improved white matter integrity and long-term cognitive function. Motor training after SAH significantly increased the number of ITPR2⁺SOX10⁺ oligodendrocytes and upregulated the level of MCT1, which was positively correlated with the behavioral ability of rats. In addition, miR-29b and miR-124 levels were significantly increased in SAH rats compared with non-SAH rats. Further intervention experiments showed that miR-29b and miR-124 could negatively regulate the level of MCT1. This study confirmed that the loss of MCT1 may be one of the mechanisms of white matter damage after SAH and may be caused by the negative regulation of miR-29b and miR-124. MCT1 may be involved in the neurological improvement of rehabilitation training after SAH.

White Matter Injury After Intracerebral Hemorrhage

Spontaneous intracerebral hemorrhage (ICH) accounts for 15% of all stroke cases. ICH is a devastating form of stroke associated with high morbidity, mortality, and disability. Preclinical studies have explored the mechanisms of neuronal death and gray matter damage after ICH. However, few studies have examined the development of white matter injury (WMI) following ICH. Research on WMI indicates that its pathophysiological presentation involves axonal damage, demyelination, and mature oligodendrocyte loss. However, the detailed relationship and mechanism between WMI and ICH remain unclear. Studies of other acute brain insults have indicated that WMI is strongly correlated with cognitive deficits, neurological deficits, and depression. The degree of WMI determines the short- and long-term prognosis of patients with ICH. This review demonstrates the structure and functions of the white matter in the healthy brain and discusses the pathophysiological mechanism of WMI following ICH. Our review reveals that the development of WMI after ICH is complex; therefore, comprehensive treatment is essential. Understanding the relationship between WMI and other brain cells may reveal therapeutic targets for the treatment of ICH.

The Role of NLRP3 Inflammasome in Cerebrovascular Diseases Pathology and Possible Therapeutic Targets

Cerebrovascular diseases are pathological conditions involving impaired blood flow in the brain, primarily including ischaemic stroke, intracranial haemorrhage, and subarachnoid haemorrhage. The nucleotide-binding and oligomerisation (NOD) domain-like receptor (NLR) family pyrin domain (PYD)-containing 3 (NLRP3) inflammasome is a protein complex and a vital component of the immune system. Emerging evidence has indicated that the NLRP3 inflammasome plays an important role in cerebrovascular diseases. The function of the NLRP3 inflammasome in the pathogenesis of cerebrovascular diseases remains an interesting field of research. In this review, we first summarised the pathological mechanism of cerebrovascular diseases and the pathological mechanism of the NLRP3 inflammasome in aggravating atherosclerosis and cerebrovascular diseases. Second, we outlined signalling pathways through which the NLRP3 inflammasome participates in aggravating or mitigating cerebrovascular diseases. Reactive oxygen species (ROS)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), ROS/thioredoxin-interacting protein (TXNIP) and purinergic receptor-7 (P2X7R) signalling pathways can activate the NLRP3 inflammasome; activation of the NLRP3 inflammasome can aggravate cerebrovascular diseases by mediating apoptosis and pyroptosis. Autophagy/mitochondrial autophagy, nuclear factor E2-related factor-2 (Nrf2), interferon (IFN)-β, sirtuin (SIRT), and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) reportedly alleviate cerebrovascular diseases by inhibiting NLRP3 inflammasome activation. Finally, we explored specific inhibitors of the NLRP3 inflammasome based on the two-step activation of the NLRP3 inflammasome, which can be developed as new drugs to treat cerebrovascular diseases.

Decreased Superoxide Dismutase Concentrations (SOD) in Plasma and CSF and Increased Circulating Total Antioxidant Capacity (TAC) Are Associated with Unfavorable Neurological Outcome after Aneurysmal Subarachnoid Hemorrhage

Background: Subarachnoid hemorrhage (SAH) is a devastating disease with high morbidity and mortality. Hypoxia-induced changes and hemoglobin accumulation within the subarachnoid space are thought to lead to oxidative stress, early brain injury, and delayed vasospasm. This study aimed to evaluate the antioxidant status and its impact on neurological outcome in patients with aneurysmal SAH. Methods: In this prospective observational study, 29 patients with aneurysmal SAH were included (mean age 54.7 ± 12.4). Blood and cerebrospinal fluid (CSF) samples were collected on days (d) 1, 3, and 7. In addition, 29 patients without intracranial hemorrhage served as controls. The antioxidant system was analyzed by glutathione peroxidase (GSH-Px; U/L) and total and free glutathione-sulfhydryl (GSH; mg/L) in the plasma. Superoxide dismutase (SOD, U/mL) and total antioxidant capacity (TAC, µmol/L) were measured in the serum and CSF. Clinical data were compiled on admission (Hunt and Hess grade, Fisher grade, and GCS). Neurological and cognitive outcome (modified Rankin scale (mRS), Glasgow Outcome Scale Extended (GOSE) and Montreal Cognitive Assessment (MoCA)) was assessed after 6 weeks (6 w) and 6 months (6 m). Results: Plasma levels of SOD increased from day 1 to 7 after SAH (d1: 1.22 ± 0.36 U/L; d3: 1.25 ± 0.33 U/L, p = 0.99; d7: 1.52 ± 0.4 U/L, p = 0.019) and were significantly higher compared to controls (1.11 ± 0.27 U/L) at day 7 (p < 0.001). Concordantly, CSF levels of SOD increased from day 1 to 7 after SAH (d1: 1.22 ± 0.41 U/L; d3: 1.77 ± 0.73 U/L, p = 0.10; d7: 2.37 ± 1.29 U/L, p < 0.0001) without becoming significantly different compared to controls (1.74 ± 0.8 U/L, p = 0.09). Mean plasma TAC at day 1 (d1: 77.87 ± 49.72 µmol/L) was not statistically different compared to controls (46.74 ± 32.42 µmol/L, p = 0.25). TAC remained unchanged from day 1 to 7 (d3: 92.64 ± 68.58 µmol/L, p = 0.86; d7: 74.07 ± 54.95 µmol/L, p = 0.8) in plasma. TAC in CSF steeply declined from day 1 to 7 in patients with SAH becoming significantly different from controls at days 3 and 7 (d3: 177.3 ± 108.7 µmol/L, p = 0.0046; d7: 85.35 ± 103.9 µmol/L, p < 0.0001). Decreased SOD levels in plasma and CSF are associated with a worse neurological outcome 6 weeks (mRS: CSF p = 0.0001; plasma p = 0.027/GOSE: CSF p = 0.001; plasma p = 0.001) and 6 months (mRS: CSF p = 0.001; plasma p = 0.09/GOSE: CSF p = 0.001; plasma p = 0.001) after SAH. Increased plasma TAC correlated with a worse neurological outcome 6 weeks (mRS: p = 0.001/GOSE p = 0.001) and 6 months (mRS p = 0.001/GOSE p = 0.001) after SAH. Conclusion: In our study, a reduction in the antioxidative enzyme SOD and elevated TAC were associated with a poorer neurological outcome reflected by mRS and GOSE at 6 weeks and 6 months after SAH. A lower initial SOD CSF concentration was associated with the late deterioration of cognitive ability. These findings support the mounting evidence of the role of oxidative stress in early brain injury formation and unfavorable outcome after SAH.

Irisin Contributes to Neuroprotection by Promoting Mitochondrial Biogenesis After Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating form of stroke, which poses a series of intractable challenges to clinical practice. Imbalance of mitochondrial homeostasis has been thought to be the crucial pathomechanism in early brain injury (EBI) cascade after SAH. Irisin, a protein related to metabolism and mitochondrial homeostasis, has been reported to play pivotal roles in post-stroke neuroprotection. However, whether this myokine can exert neuroprotection effects after SAH remains unknown. In the present study, we explored the protective effects of irisin and the underlying mechanisms related to mitochondrial biogenesis in a SAH animal model. Endovascular perforation was used to induce SAH, and recombinant irisin was administered intracerebroventricularly. Neurobehavioral assessments, TdT-UTP nick end labeling (TUNEL) staining, dihydroethidium (DHE) staining, immunofluorescence, western blot, and transmission electron microscopy (TEM) were performed for post-SAH assessments. We demonstrated that irisin treatment improved neurobehavioral scores, reduced neuronal apoptosis, and alleviated oxidative stress in EBI after SAH. More importantly, the administration of exogenous irisin conserved the mitochondrial morphology and promoted mitochondrial biogenesis. The protective effects of irisin were partially reversed by the mitochondrial uncoupling protein-2 (UCP-2) inhibitor. Taken together, irisin may have neuroprotective effects against SAH via improving the mitochondrial biogenesis, at least in part, through UCP-2 related targets.

The Role of Oxidative Stress in Early Brain Injury after Subarachnoid Hemorrhage

This review focuses on the problem of oxidative stress in early brain injury (EBI) after spontaneous subarachnoid hemorrhage (SAH). EBI involves complex pathophysiological mechanisms, including oxidative stress. In the first section, we describe the main sources of free radicals in EBI. There are several sources of excessive generation of free radicals from mitochondrial free radicals’ generation and endoplasmic reticulum stress, to hemoglobin and enzymatic free radicals’ generation. The second part focuses on the disruption of antioxidant mechanisms in EBI. The third section describes some newly found molecular mechanisms and pathway involved in oxidative stress after EBI. The last section is dedicated to the pathophysiological mechanisms through which free radicals mediate early brain injury.

Peroxisomal Dysfunction Contributes to White Matter Injury Following Subarachnoid Hemorrhage in Rats via Thioredoxin-Interacting Protein-Dependent Manner

Background and Purpose

White matter injury (WMI) exists in the early stage of subarachnoid hemorrhage (SAH) and has not been well addressed so far.

Methods

We utilized short hairpin RNA (shRNA) and clustered regularly interspaced short palindromic repeats (CRISPR) to verify the role of peroxisomes in WMI following SAH. We evaluated short- and long-term neurobehavior after SAH. Western blotting, immunofluorescence, and Golgi staining techniques were performed to assess the changes in protein levels.

Results

Catalase (CAT) CRISPR treatment significantly attenuated neurological deficits and reduced long-term spatial learning and memory impairments after SAH by increasing the level of myelin basic protein (MBP) while decreasing the levels of amyloid precursor protein (APP), interleukin 6 (IL-6), and tumor necrosis factor (TNF)-α. The use of thioredoxin-interacting protein (TXNIP) shRNA significantly offset the effects of CAT shRNA, and the use of glycerone phosphate acyl transferase (GNPAT) shRNA significantly reversed the effects of CAT CRISPR by decreasing the levels of plasmalogens and reactive oxidative species (ROS).

Conclusion

Peroxisomal dysfunction induced by SAH reversely exacerbated cerebral WMI following SAH, which was at least partly mediated by TXNIP and GNPAT pathways.

Comparison of Subtracted Computed Tomography from Computed Tomography Perfusion and Digital Subtraction Angiography in Residue Evaluation of Treated Intracranial Aneurysms

BACKGROUND

Assessing clipped intracranial aneurysms for residues or incomplete occlusions is critical. Digital subtraction angiography (DSA) has been the gold standard for this. Previously, we presented subtracted computed tomography angiography (sub-CTA) from computed tomography perfusion as a more effective noninvasive technique for clipped aneurysms. The aim of this study was to compare effectiveness of sub-CTA with DSA in residue evaluation.

METHODS

A retrospective study of 17 patients with aneurysmal subarachnoid hemorrhage operated on at our institution between November 1, 2016, and December 31, 2018, was performed. Residue aneurysms were evaluated with both sub-CTA and DSA. Positive predictive value and negative predictive value were calculated. Correlation between techniques was determined by the McNemar test and κ value.

RESULTS

Sensitivity of sub-CTA in residue evaluation was low in aneurysms ≤3 mm (positive predictive value = 60%). DSA detected residue aneurysm in 29% (5/17) of patients, whereas sub-CTA detected residue aneurysm in 11% (2/17). Only 40% of aneurysms (2/5) were demonstrated by sub-CTA, all >3 mm; 60% (3/5) were missed, all ≤3 mm.

CONCLUSIONS

This is the first study comparing the effectiveness of sub-CTA from computed tomography perfusion with DSA in residue aneurysm evaluation. Our results were suggestive, but not conclusive. DSA is still the gold standard in residue evaluation. Sub-CTA from computed tomography perfusion can be a reliable method in evaluation of residual aneurysm >3 mm.