Genetic elimination of eNOS reduces secondary complications of experimental subarachnoid hemorrhage

Modulating the blood-brain barrier in CNS disorders: A review of the therapeutic implications of secreted protein acidic and rich in cysteine (SPARC)

Secreted protein acidic and rich in cysteine (SPARC), an essential stromal cell protein, plays a crucial role in angiogenesis and maintaining endothelial barrier function. This protein is expressed by diverse cell types, including endothelial cells, fibroblasts, and macrophages, with increased expression found in regions of tissues undergoing active remodeling, repair, and proliferation. The role of SPARC in non-neural tissues is of significant interest. In the central nervous system (CNS), SPARC is highly expressed in blood vessels during early development. It becomes down-regulated as the brain matures, a pattern consistent with its role in angiogenesis and blood-brain barrier (BBB) establishment. In this review, we explore the multifaceted roles of SPARC in regulating CNS disorders, particularly its action in angiogenesis, inflammatory responses, neural system development and repair, barrier establishment, maintenance of BBB function, and the pathogenesis of CNS disorders triggered by BBB dysfunction.

Huperzine A ameliorates neurological deficits after spontaneous subarachnoid hemorrhage through endothelial cell pyroptosis inhibition

Spontaneous subarachnoid hemorrhage (SAH) is a kind of hemorrhagic stroke which causes neurological deficits in survivors. Huperzine A has a neuroprotective effect, but its role in SAH is unclear. Therefore, we explore the effect of Huperzine A on neurological deficits induced by SAH and the related mechanism. In this study, Evans blue assay, TUNEL staining, immunofluorescence, western blot analysis, and ELISA are conducted. We find that Huperzine A can improve neurological deficits and inhibit the apoptosis of nerve cells in SAH rats. Huperzine A treatment can improve the upregulation of brain water content, damage of blood-brain barrier, fibrinogen and matrix metalloprotein 9 expressions and the downregulation of ZO-1 and occludin expressions induced by SAH. Huperzine A inhibit the expressions of proteins involved in pyroptosis in endothelial cells in SAH rats. The increase in MDA content and decrease in SOD activity in SAH rats can be partly reversed by Huperzine A. The ROS inducer H 2O 2 can induce pyroptosis and inhibit the expressions of ZO-1 and occludin in endothelial cells, which can be blocked by Huperzine A. In addition, the increase in the entry of p65 into the nucleus in endothelial cells can be partly reversed by Huperzine A. Huperzine A may delay the damage of blood-brain barrier in SAH rats by inhibiting oxidative stress-mediated pyroptosis and tight junction protein expression downregulation through the NF-κB pathway. Overall, Huperzine A may have clinical value for treating SAH.

Subarachnoid hemorrhage-associated brain injury and neurobehavioral deficits are reversed with synthetic adropin treatment through sustained Ser1179 phosphorylation of endothelial nitric oxide synthase

Background

Subarachnoid hemorrhage (SAH) is a life-threatening vascular condition without satisfactory treatment options. The secreted peptide adropin is highly expressed in the human brain and has neuroprotective effects in brain injury models, including actions involving the cerebrovasculature. Here, we report an endothelial nitric oxide synthase (eNOS)-dependent effect of synthetic adropin treatment that reverses the deleterious effects of SAH.

Methods

We tested the molecular, cellular, and physiological responses of cultured brain microvascular endothelial cells and two mouse models of SAH to treatment using synthetic adropin peptide or vehicle.

Results

SAH decreases adropin expression in cultured brain microvascular endothelial cells and in murine brain tissue. In two validated mouse SAH models, synthetic adropin reduced cerebral edema, preserved tight junction protein expression, and abolished microthrombosis at 1 day post-SAH. Adropin treatment also prevented delayed cerebral vasospasm, decreased neuronal apoptosis, and reduced sensorimotor deficits at seven days post-SAH. Delaying initial treatment of adropin until 24 h post-SAH preserved the beneficial effect of adropin in preventing vasospasm and sensorimotor deficits. Mechanistically, adropin treatment increased eNOS phosphorylation (Ser1179) at 1 & 7 days post-SAH. Treating eNOS-/- mice with adropin failed to prevent vasospasm or behavioral deficits, indicating a requirement of eNOS signaling.

Conclusions

Adropin is an effective treatment for SAH, reducing cerebrovascular injury in both the acute (1 day) and delayed (7 days) phases. These findings establish the potential of adropin or adropin mimetics to improve outcomes following subarachnoid hemorrhage.

Lower Serum Iron Level Predicts Postoperative Global Cerebral Edema Following Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Iron plays an important role in neuronal injury and edema formation after intracranial hemorrhage. However, the role of serum iron in aneurysmal subarachnoid hemorrhage (aSAH) is yet to be well-established. This study aims to identify whether serum iron could predict postoperative global cerebral edema (GCE) and poor outcome in aSAH.

METHODS

847 patients' aSAH clinical data were retrospectively collected at the First Affiliated Hospital of Fujian Medical University. Data on demographics, clinical characteristics, and laboratory values were collected and analyzed through univariate and multivariate analyses. Propensity score matching (PSM) analysis was performed to balance the baseline differences between the groups.

RESULTS

The incidence of high-grade global cerebral edema (H-GCE) following aSAH was 12.99% (110/847). Serum iron levels [odds ratio (OR) = 1.143; 95% confidence interval (CI), (1.097-1.191); p < 0.001] were associated with the occurrence of H-GCE following aSAH in the univariate analysis. This association remained statistically significant even after adjusting for other variables in the multivariate model, with serum iron having an OR of 1.091 (95% CI, 1.043-1.141; p < 0.001) for GCE. After 1:1 PSM, serum iron levels ≤ 10.7 µmol/L remained a significant independent predictor of GCE (p = 0.002). The receiver operating characteristic (ROC) curve analysis determined that a serum iron cut-off value of ≤ 10.7 µmol/L was optimal for predicting H-GCE [Areas under the ROC curves (AUC) = 0.701, 95% CI, (0.669-0.732), p < 0.001; sensitivity, 67.27%; specificity, 63.77%] in patients with aSAH. Additionally, a trend was observed in which higher Hunt-Hess grades (HH grade) were associated with lower serum iron levels, and higher modified Fisher grades (mFisher grade) were associated with lower serum iron levels. In addition, the serum iron level was also associated with a 3-month functional neurological outcome (p < 0.001).

CONCLUSIONS

The results of this study indicate that a decreased serum iron level serves as a clinically significant biomarker for the prediction of postoperative GCE and a poor outcome at 3-months in patients with aSAH.

Early Brain Injury and Neuroprotective Treatment after Aneurysmal Subarachnoid Hemorrhage: A Literature Review

Early brain injury (EBI) subsequent to subarachnoid hemorrhage (SAH) is strongly associated with delayed cerebral ischemia and poor patient prognosis. Based on investigations into the molecular mechanisms underlying EBI, neurovascular dysfunction resulting from SAH can be attributed to a range of pathological processes, such as microvascular alterations in brain tissue, ionic imbalances, blood-brain barrier disruption, immune-inflammatory responses, oxidative stress, and activation of cell death pathways. Research progress presents a variety of promising therapeutic approaches for the preservation of neurological function following SAH, including calcium channel antagonists, endothelin-1 receptor blockers, antiplatelet agents, anti-inflammatory agents, and anti-oxidative stress agents. EBI can be mitigated following SAH through neuroprotective measures. To enhance our comprehension of the relevant molecular pathways involved in brain injury, including brain ischemia-hypoxic injury, neuroimmune inflammation activation, and the activation of various cell-signaling pathways, following SAH, it is essential to investigate the evolution of these multifaceted pathophysiological processes. Facilitating neural repair following a brain injury is critical for improving patient survival rates and quality of life.

A Review of Genetic Polymorphisms and Susceptibilities to Complications after Aneurysmal Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) and vasospasm are two complications of subarachnoid hemorrhages (SAHs) which entail high risks of morbidity and mortality. However, it is unknown why only some patients who suffer SAHs will experience DCI and vasospasm. The purpose of this review is to describe the main genetic single nucleotide polymorphisms (SNPs) that have demonstrated a relationship with these complications. The SNP of the nitric oxide endothelial synthase (eNOS) has been related to the size and rupture of an aneurysm, as well as to DCI, vasospasm, and poor neurological outcome. The SNPs responsible for the asymmetric dimetilarginine and the high-mobility group box 1 have also been associated with DCI. An association between vasospasm and the SNPs of the eNOS, the haptoglobin, and the endothelin-1 receptor has been found. The SNPs of the angiotensin-converting enzyme have been related to DCI and poor neurological outcome. Studies on the SNPs of the Ryanodine Receptor yielded varying results regarding their association with vasospasm.

Admission Serum Iron as an Independent Risk Factor for Postoperative Delayed Cerebral Ischemia Following Aneurysmal Subarachnoid Hemorrhage: A Propensity-Matched Analysis

This study aimed to investigate the association between serum iron (SI) and postoperative delayed cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH). We retrospectively analyzed 985 consecutive adult patients diagnosed with aSAH. Demographic, clinical, and laboratory data were recorded. Univariate and multivariate analyses were employed to assess the association between SI and DCI. Propensity-score matching (PSM) analysis was implemented to reduce confounding. Postoperative DCI developed in 14.38% of patients. Lower SI upon admission was detected in aSAH patients with severe clinical conditions and severe aSAH. SI was negatively correlated with WFNS grade (r = −0.3744, p < 0.001) and modified Fisher (mFisher) grade (r = −0.2520, p < 0.001). Multivariable analysis revealed lower SI was independently associated with DCI [odds ratios (OR) 0.281, 95% confidence interval (CI) 0.177−0.448, p < 0.001], while WFNS grade and mFisher grade were not. The receiver-operating characteristics (ROC) curve analysis of SI for DCI gave an area under the curve (AUC) of 0.7 and an optimal cut-off of 7.5 μmol/L (95% CI 0.665 to 0.733, p < 0.0001). PSM demonstrated the DCI group had a significantly lower SI than the non-DCI group (10.91 ± 6.86 vs. 20.34 ± 8.01 μmol/L, p < 0.001). Lower SI remained a significant independent predictor for DCI and an independent poor prognostic factor of aSAH in multivariate analysis (OR 0.363, 95% CI 0.209−0.630, p < 0.001). The predictive performance of SI for poor outcome had a corresponding AUC of 0.718 after PSM. Lower SI upon admission is significantly associated with WFNS grade, mFisher grade, and predicts postoperative DCI and poor outcome at 90 days following aSAH.

SPARC Aggravates Blood-Brain Barrier Disruption via Integrin αVβ3/MAPKs/MMP-9 Signaling Pathway after Subarachnoid Hemorrhage

Blood-brain barrier (BBB) disruption is a common and critical pathology following subarachnoid hemorrhage (SAH). We investigated the BBB disruption property of secreted protein acidic and rich in cysteine (SPARC) after SAH. A total of 197 rats underwent endovascular perforation to induce SAH or sham operation. Small interfering ribonucleic acid (siRNA) for SPARC or scrambled siRNA was administered intracerebroventricularly to rats 48 h before SAH. Anti-SPARC monoclonal antibody (mAb) 236 for functional blocking or normal mouse immunoglobulin G (IgG) was administered intracerebroventricularly 1 h after SAH. Selective integrin αVβ3 inhibitor cyclo(-RGDfK) or phosphate-buffered saline was administered intranasally 1 h before SAH, along with recombinant SPARC treatment. Neurobehavior, SAH severity, brain edema, immunohistochemical staining, and Western blot were evaluated. The expression of SPARC and integrin αVβ3 was upregulated after SAH in the endothelial cells. SPARC siRNA and anti-SPARC mAb 236 prevented neuroimpairments and brain edema through protection of BBB as measured by IgG extravasation 24 and 72 h after SAH. Recombinant SPARC aggravated neuroimpairments and cyclo(-RGDfK) suppressed the harmful neurological effects via inhibition of activated c-Jun N-terminal kinase, p38, and matrix metalloproteinase-9 followed by retention of endothelial junction proteins. SPARC may induce post-SAH BBB disruption via integrin αVβ3 signaling pathway.

Pathophysiology of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: A Review

Delayed cerebral ischemia is a major predictor of poor outcomes in patients who suffer subarachnoid hemorrhage. Treatment options are limited and often ineffective despite many years of investigation and clinical trials. Modern advances in basic science have produced a much more complex, multifactorial framework in which delayed cerebral ischemia is better understood and novel treatments can be developed. Leveraging this knowledge to improve outcomes, however, depends on a holistic understanding of the disease process. We conducted a review of the literature to analyze the current state of investigation into delayed cerebral ischemia with emphasis on the major themes that have emerged over the past decades. Specifically, we discuss microcirculatory dysfunction, glymphatic impairment, inflammation, and neuroelectric disruption as pathological factors in addition to the canonical focus on cerebral vasospasm. This review intends to give clinicians and researchers a summary of the foundations of delayed cerebral ischemia pathophysiology while also underscoring the interactions and interdependencies between pathological factors. Through this overview, we also highlight the advances in translational studies and potential future therapeutic opportunities.

Role of endothelial nitric oxide synthase for early brain injury after subarachnoid hemorrhage in mice

The first few hours and days after subarachnoid hemorrhage (SAH) are characterized by cerebral ischemia, spasms of pial arterioles, and a significant reduction of cerebral microperfusion, however, the mechanisms of this early microcirculatory dysfunction are still unknown. Endothelial nitric oxide production is reduced after SAH and exogenous application of NO reduces post-hemorrhagic microvasospasm. Therefore, we hypothesize that the endothelial NO-synthase (eNOS) may be involved in the formation of microvasospasms, microcirculatory dysfunction, and unfavorable outcome after SAH. SAH was induced in male eNOS deficient (eNOS^-/-) mice by endovascular MCA perforation. Three hours later, the cerebral microcirculation was visualized using in vivo 2-photon-microscopy. eNOS^-/- mice had more severe SAHs, more severe ischemia, three time more rebleedings, and a massively increased mortality (50 vs. 0%) as compared to wild type (WT) littermate controls. Three hours after SAH eNOS^-/- mice had fewer perfused microvessels and 40% more microvasospasms than WT mice. The current study indicates that a proper function of eNOS plays a key role for a favorable outcome after SAH and helps to explain why patients suffering from hypertension or other conditions associated with impaired eNOS function, have a higher risk of unfavorable outcome after SAH.

Mechanisms of neuroinflammation and inflammatory mediators involved in brain injury following subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disorder. Neuroinflammation is a critical cause of brain injury following SAH in both acute and chronic phases. While accumulating evidence has shown that therapies targeting neuroinflammation exerted beneficial effects in experimental SAH, there is little clinical evidence. One of the factors making neuroinflammation complicated is that inflammatory signaling pathways and mediators act as protective or detrimental responses at different phases. In addition, biomarkers to detect neuroinflammation are little known in clinical settings. In this review, first, we discuss how the inflammatory signaling pathways contribute to brain injury and other secondary pathophysiological changes in SAH. Damage-associated molecular patterns arising from mechanical stress, transient global cerebral ischemia, red blood cell breakdown and delayed cerebral ischemia following SAH trigger to activate pattern recognition receptors (PRRs) such as Toll-like receptors, nucleotide-binding oligomerization domain-like receptors, and receptors for advanced glycation end products. Most of PRRs activate common downstream signaling transcriptional factor nuclear factor-κΒ and mitogen-activated protein kinases, releasing pro-inflammatory mediators and cytokines. Next, we focus on how pro-inflammatory substances play a role during the course of SAH. Finally, we highlight an important inducer of neuroinflammation, matricellular protein (MCP). MCPs are a component of extracellular matrix and exert beneficial and harmful effects through binding to receptors, other matrix proteins, growth factors, and cytokines. Treatment targeting MCPs is being proved efficacious in pre-clinical models for preventing brain injury including neuroinflammation in SAH. In addition, MCPs may be a candidate of biomarkers predicting brain injury following SAH in clinical settings.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental-Clinical Disconnect and the Unmet Need

BACKGROUND

Delayed cerebral ischemia (DCI) is among the most dreaded complications following aneurysmal subarachnoid hemorrhage (SAH). Despite advances in neurocritical care, DCI remains a significant cause of morbidity and mortality, prolonged intensive care unit and hospital stay, and high healthcare costs. Large artery vasospasm has classically been thought to lead to DCI. However, recent failure of clinical trials targeting vasospasm to improve outcomes has underscored the disconnect between large artery vasospasm and DCI. Therefore, interest has shifted onto other potential mechanisms such as microvascular dysfunction and spreading depolarizations. Animal models can be instrumental in dissecting pathophysiology, but clinical relevance can be difficult to establish.

METHODS

Here, we performed a systematic review of the literature on animal models of SAH, focusing specifically on DCI and neurological deficits.

RESULTS

We find that dog, rabbit and rodent models do not consistently lead to DCI, although some degree of delayed vascular dysfunction is common. Primate models reliably recapitulate delayed neurological deficits and ischemic brain injury; however, ethical issues and cost limit their translational utility.

CONCLUSIONS

To facilitate translation, clinically relevant animal models that reproduce the pathophysiology and cardinal features of DCI after SAH are urgently needed.

Complement C5 Contributes to Brain Injury After Subarachnoid Hemorrhage

Previous studies showed that complement activation is associated with poor functional outcome after aneurysmal subarachnoid hemorrhage (SAH). We investigated whether complement activation is underlying brain injury after aneurysmal SAH (n = 7) and if it is an appropriate treatment target. We investigated complement expression in brain tissue of aneurysmal SAH patients (n = 930) and studied the role of common genetic variants in C3 and C5 genes in outcome. We analyzed plasma levels (n = 229) to identify the functionality of a single nucleotide polymorphism (SNP) associated with outcome. The time course of C5a levels was measured in plasma (n = 31) and CSF (n = 10). In an SAH mouse model, we studied the extent of microglia activation and cell death in wild-type mice, mice lacking the C5a receptor, and in mice treated with C5-specific antibodies (n = 15 per group). Brain sections from aneurysmal SAH patients showed increased presence of complement components C1q and C3/C3b/iC3B compared to controls. The complement component 5 (C5) SNP correlated with C5a plasma levels and poor disease outcome. Serial measurements in CSF revealed that C5a was > 1400-fold increased 1 day after aneurysmal SAH and then gradually decreased. C5a in plasma was 2-fold increased at days 3–10 after aneurysmal SAH. In the SAH mouse model, we observed a ≈ 40% reduction in both microglia activation and cell death in mice lacking the C5a receptor, and in mice treated with C5-specific antibodies. These data show that C5 contributes to brain injury after experimental SAH, and support further study of C5-specific antibodies as novel treatment option to reduce brain injury and improve prognosis after aneurysmal SAH.

Blood-Related Toxicity after Traumatic Brain Injury: Potential Targets for Neuroprotection

Emergency visits, hospitalizations, and deaths due to traumatic brain injury (TBI) have increased significantly over the past few decades. While the primary early brain trauma is highly deleterious to the brain, the secondary injury post-TBI is postulated to significantly impact mortality. The presence of blood, particularly hemoglobin, and its breakdown products and key binding proteins and receptors modulating their clearance may contribute significantly to toxicity. Heme, hemin, and iron, for example, cause membrane lipid peroxidation, generate reactive oxygen species, and sensitize cells to noxious stimuli resulting in edema, cell death, and increased morbidity and mortality. A wide range of other mechanisms such as the immune system play pivotal roles in mediating secondary injury. Effective scavenging of all of these pro-oxidant and pro-inflammatory metabolites as well as controlling maladaptive immune responses is essential for limiting toxicity and secondary injury. Hemoglobin metabolism is mediated by key molecules such as haptoglobin, heme oxygenase, hemopexin, and ferritin. Genetic variability and dysfunction affecting these pathways (e.g., haptoglobin and heme oxygenase expression) have been implicated in the difference in susceptibility of individual patients to toxicity and may be target pathways for potential therapeutic interventions in TBI. Ongoing collaborative efforts are required to decipher the complexities of blood-related toxicity in TBI with an overarching goal of providing effective treatment options to all patients with TBI.

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

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

Carbon monoxide attenuates vasospasm and improves neurobehavioral function after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating form of hemorrhagic stroke and is a serious medical condition caused by bleeding usually due to a ruptured aneurysm. Oxidative stress and inflammation from hemoglobin and heme released from lysed red blood cells are some postulated causes of vasospasm during SAH, which could lead to delayed cerebral ischemia. At low amounts, carbon monoxide (CO) gas may be neuroprotective through anti-inflammation, anti-cell death, and restoration of normal blood flow. Hence, this study focuses on a noninvasive strategy to treat SAH by using CO as a therapeutic medical gas. Mice were treated with 250 ppm CO or air for 1h started at 2h after SAH. Various anatomical and functional outcomes were monitored at 1 and 7d after SAH. CO decreased neurological deficit score (47.4 ± 10.5%) and increased activity (30.0 ± 9.1%) and stereotypic counts (261.5 ± 62.1%) at 7d. There was a significant increase in lumen area/wall thickness ratio in the middle cerebral artery (173.5 ± 19.3%), which tended to increase in the anterior cerebral artery (25.5 ± 4.3%) at 7d. This is the first report to demonstrate that CO minimizes delayed SAH-induced neurobehavioral deficits, which suggests that post-treatment with CO gas or CO-donors can be further tested as a potential therapy against SAH.

The dual-functional memantine nitrate MN-08 alleviates cerebral vasospasm and brain injury in experimental subarachnoid haemorrhage models

BACKGROUND AND PURPOSE

Cerebral vasospasm and neuronal apoptosis after subarachnoid haemorrhage (SAH) is the major cause of morbidity and mortality in SAH patients. So far, single-target agents have not prevented its occurrence. Memantine, a non-competitive NMDA re3ceptor antagonist, is known to alleviate brain injury and vasospasm in experimental models of SAH. Impairment of NO availability also contributes to vasospasm. Recently, we designed and synthesized a memantine nitrate MN-08, which has potent dual functions: neuroprotection and vasodilation. Here, we have tested the therapeutic effects of MN-08 in animal models of SAH.

EXPERIMENTAL APPROACH

Binding to NMDA receptors (expressed in HEK293 cells), NO release and vasodilator effects of MN-08 were assessed in vitro. Therapeutic effects of MN-08 were investigated in vivo, using rat and rabbit SAH models.

KEY RESULTS

MN-08 bound to the NMDA receptor, slowly releasing NO in vitro and in vivo. Consequently, MN-08 relaxed the pre-contracted middle cerebral artery ex vivo and increased blood flow velocity in small vessels of the mouse cerebral cortex. It did not, however, lower systemic blood pressure. In an endovascular perforation rat model of SAH, MN-08 improved the neurological scores and ameliorated cerebral vasospasm. Moreover, MN-08 also alleviated cerebral vasospasm in a cisterna magna single-injection model in rabbits. MN-08 attenuated neural cell apoptosis in both rat and rabbit models of SAH. Importantly, the therapeutic benefit of MN-08 was greater than that of memantine.

CONCLUSION AND IMPLICATIONS

MN-08 has neuroprotective potential and can ameliorate vasospasm in experimental SAH models.

The Role of Oxidative Stress in Microvascular Disturbances after Experimental Subarachnoid Hemorrhage

Oxidative stress was shown to play a crucial role in the diverse pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Microcirculatory dysfunction is thought to be an important and fundamental pathological change in EBI. However, other than blood-brain barrier (BBB) disruption, the influence of oxidative stress on microvessels remains to be elucidated. The aim of this study was to investigate the role of oxidative stress on microcirculatory integrity in EBI. SAH was induced in male Sprague-Dawley rats using an endovascular perforation technique. A free radical scavenger, edaravone, was administered prophylactically by intraperitoneal injection. SAH grade, neurological score, brain water content, and BBB permeability were measured at 24 h after SAH induction. In addition, cortical samples taken at 24 h after SAH were analyzed to explore oxidative stress, microvascular mural cell apoptosis, microspasm, and microthrombosis. Edaravone treatment significantly ameliorated neurological deficits, brain edema, and BBB disruption. In addition, oxidative stress-induced modifications and subsequent apoptosis of microvascular endothelial cells and pericytes increased after SAH induction, while the administration of edaravone suppressed this. Consistent with apoptotic cell inhibition, microthromboses were also inhibited by edaravone administration. Oxidative stress plays a pivotal role in the induction of multiple pathological changes in microvessels in EBI. Antioxidants are potential candidates for the treatment of microvascular disturbances after SAH.

Prospective Multicenter Study of Changes in MTT after Aneurysmal SAH and Relationship to Delayed Cerebral Ischemia in Patients with Good- and Poor-Grade Admission Status

BACKGROUND AND PURPOSE

Patients with aneurysmal SAH and good clinical status at admission are considered at a lower risk for delayed cerebral ischemia. Prolonged MTT may be associated with an increased risk. It is unclear whether this is dependent on clinical status. Our purpose was to determine whether increased MTT within 3 days of aneurysmal SAH compared with baseline is associated with a higher risk of delayed cerebral ischemia in patients with good (World Federation of Neurosurgical Societies I-III) versus poor (World Federation of Neurosurgical Societies IV-V) admission status.

MATERIALS AND METHODS

This prolonged MTT was a multicenter, prospective cohort investigation of 87 patients with aneurysmal SAH. MTT was measured at admission before aneurysm treatment (MTT1) and following repair (MTT2) within 3 days of admission; MTT_diff was calculated as the difference between MTT2 and MTT1. Changes in MTT across time were assessed with repeated measures analyses. Risk of delayed cerebral ischemia or death was determined with multivariate logistic regression analysis.

RESULTS

In patients with a good grade (n = 49), MTT was prolonged in patients who developed delayed cerebral ischemia, with MTT_diff significantly greater (0.82 ± 1.5) compared with those who did not develop delayed cerebral ischemia (-0.14 ± 0.98) (P = .03). Prolonged MTT was associated with a significantly higher risk of delayed cerebral ischemia or death (OR = 3.1; 95% CI, 1.3-7.4; P = .014) on multivariate analysis. In patients with poor grades (n = 38), MTT_diff was not greater in patients who developed delayed cerebral ischemia; MTT1 was significantly prolonged compared with patients with a good grade.

CONCLUSIONS

Patients in good clinical condition following aneurysmal SAH but with increasing MTT in the first few days after aneurysmal SAH are at high risk of delayed cerebral ischemia and warrant close clinical monitoring.

Neuroprotective Effect of ZnT3 Knockout on Subarachnoid Hemorrhage

Background

The pathophysiology of early brain injury (EBI) after subarachnoid hemorrhage (SAH) is poorly understood. The present study evaluates the influence of zinc transporter 3 (ZnT3) knockout and the depletion of vesicular zinc on EBI.

Methodology

SAH was induced in ZnT3 KO mice by internal carotid artery perforation. The changes in behavior were recorded at 24 hours after SAH. Hematoxylin-eosin, Nissl and TUNEL staining were performed to evaluate neuronal apoptosis. Data from mice with a score of 8-12 in intracerebral bleeding (i.e. moderate SAH), were analyzed.

Results

The degree of SAH-induced neuronal injury was directly correlated to the amount of blood lost, which in turn was negatively reflected in their behavior. The Wild Type (WT)-SAH group behaved poorly when compared to the knockout (KO)-SAH mice and their poor neurological score was accompanied by an increase in the number of apoptotic neurons. Conversely, the improvement of behavior in the KO-SAH group was associated with a marked reduction in apoptotic neurons.

Conclusions

These results suggest that ZnT3 knockout may have played a vital role in the attenuation of neuronal injury after SAH and that ZnT3 may prove to be a potential therapeutic target for neuroprotection in EBI.

Unique Contribution of Haptoglobin and Haptoglobin Genotype in Aneurysmal Subarachnoid Hemorrhage

Survivors of cerebral aneurysm rupture are at risk for significant morbidity and neurological deficits. Much of this is related to the effects of blood in the subarachnoid space which induces an inflammatory cascade with numerous downstream consequences. Recent clinical trials have not been able to reduce the toxic effects of free hemoglobin or improve clinical outcome. One reason for this may be the inability to identify patients at high risk for neurologic decline. Recently, haptoglobin genotype has been identified as a pertinent factor in diabetes, sickle cell, and cardiovascular disease, with the Hp 2-2 genotype contributing to increased complications. Haptoglobin is a protein synthesized by the liver that binds free hemoglobin following red blood cell lysis, and in doing so, prevents hemoglobin induced toxicity and facilitates clearance. Clinical studies in patients with subarachnoid hemorrhage indicate that Hp 2-2 patients may be a high-risk group for hemorrhage related complications and poor outcome. We review the relevance of haptoglobin in subarachnoid hemorrhage and discuss the effects of genotype and expression levels on the known mechanisms of early brain injury (EBI) and cerebral ischemia after aneurysm rupture. A better understanding of haptoglobin and its role in preventing hemoglobin related toxicity should lead to novel therapeutic avenues.

Inflammatory Events Following Subarachnoid Hemorrhage (SAH)

Acute SAH from a ruptured intracranial aneurysm contributes for 30% of all hemorrhagic strokes. The bleeding itself occurs in the subarachnoid space. Nevertheless, injury to the brain parenchyma occurs as a consequence of the bleeding, directly, via several well-defined mechanisms and pathways, but also indirectly, or secondarily. This secondary brain injury following SAH has a variety of causes and possible mechanisms. Amongst others, inflammatory events have been shown to occur in parallel to, contribute to, or even to initiate programmed cell death (PCD) within the central nervous system (CNS) in human and animal studies alike. Mechanisms of secondary brain injury are of utmost interest not only to scientists, but also to clinicians, as they often provide possibilities for translational approaches as well as distinct time windows for tailored treatment options. In this article, we review secondary brain injury due to inflammatory changes, that occur on cellular, as well as on molecular level in the various different compartments of the CNS: the brain vessels, the subarachnoid space, and the brain parenchyma itself and hypothesize about possible signaling mechanisms between these compartments.

Resveratrol supplementation confers neuroprotection in cortical brain tissue of nonhuman primates fed a high-fat/sucrose diet

Previous studies have shown positive effects of long-term resveratrol (RSV) supplementation in preventing pancreatic beta cell dysfunction, arterial stiffening and metabolic decline induced by high-fat/high-sugar (HFS) diet in nonhuman primates. Here, the analysis was extended to examine whether RSV may reduce dietary stress toxicity in the cerebral cortex of the same cohort of treated animals. Middle-aged male rhesus monkeys were fed for 2 years with HFS alone or combined with RSV, after which whole-genome microarray analysis of cerebral cortex tissue was carried out along with ELISA, immunofluorescence, and biochemical analyses to examine markers of vascular health and inflammation in the cerebral cortices. A number of genes and pathways that were differentially modulated in these dietary interventions indicated an exacerbation of neuroinflammation (e.g., oxidative stress markers, apoptosis, NF-κB activation) in HFS-fed animals and protection by RSV treatment. The decreased expression of mitochondrial aldehyde dehydrogenase 2, dysregulation in endothelial nitric oxide synthase, and reduced capillary density induced by HFS stress were rescued by RSV supplementation. Our results suggest that long-term RSV treatment confers neuroprotection against cerebral vascular dysfunction during nutrient stress.

Interruption of perivascular sympathetic nerves of cerebral arteries offers neuroprotection against ischemia

Sympathetic nervous system activity is increased after cardiopulmonary arrest, resulting in vasoconstrictor release from the perivascular sympathetic nerves of cerebral arteries. However, the pathophysiological function of the perivascular sympathetic nerves in the ischemic brain remains unclear. A rat model of global cerebral ischemia (asphyxial cardiac arrest, ACA) was used to investigate perivascular sympathetic nerves of cerebral arteries via bilateral decentralization (preganglionic lesion) of the superior cervical ganglion (SCG). Decentralization of the SCG 5 days before ACA alleviated hypoperfusion and afforded hippocampal neuroprotection and improved functional outcomes. These studies can provide further insights into the functional mechanism(s) of the sympathetic nervous system during ischemia.

NEW & NOTEWORTHY

Interruption of the perivascular sympathetic nerves can alleviate CA-induced hypoperfusion and neuronal cell death in the CA1 region of the hippocampus to enhance functional learning and memory.

Feasibility of Magnetoencephalography after Endovascular Treatment of Ruptured Intracranial Aneurysms

Objective

Among good outcome survivors of aneurysmal subarachnoid hemorrhage (aSAH), only 23% have normal neurocognitive performance, despite imaging that is often normal. The aim of this work is to explore the use of magnetoencephalography (MEG) after endovascular treatment of ruptured aneurysms.

Methods

Good outcome aSAH patients treated with coiling and matched controls were recruited. Clinical assessments and resting-state MEG and anatomical MRI images were obtained. Brain space was normalized to standard Montreal Neurological Institute (MNI) brain. Areas of interest were identified with Automated Anatomical Labeling (AAL) and “electrodes” reconstructed using vector beamformer. Spectral power density estimates for each location was averaged across the brain to derive mean signal power. Virtual-sensor data closest to the coil was assessed for signal quality.

Results

Thirteen aSAH patients and 13 matched controls were recruited. Mean age was 54.5 years (SD = 9.9) for controls and 56.8 years (SD = 11.8) for aSAH. The majority of aneurysms (62%) were in the midline. Mean time from aSAH to MEG was 18.8 months (2.4–67.5; SD = 19). Data quality was comparable in both groups, including the virtual-sensors close to the coil mass. Mean signal power showed no significant spectral alterations in the aSAH group.

Conclusion

MEG is feasible in aSAH patients after endovascular treatment. Our results suggest that the signal quality and strength is good, and the presence of coils does not interfere with testing. Considering the common neurocognitive complaints of aSAH survivors MEG could be developed to diagnose, quantify, and monitor neurocognitive problems after aSAH.

Akt Specific Activator SC79 Protects against Early Brain Injury following Subarachnoid Hemorrhage

A growing body of evidence demonstrates that Akt may serve as a therapeutic target for treatment of early brain injury following subarachnoid hemorrhage (SAH). The purpose of the current study was to evaluate the neuroprotective effect of Akt specific activator SC79 in an experimental rat model of SAH. SAH was induced by injecting 300 μL of blood into the prechiasmatic cistern. Intracerebroventricular (ICV) injection of SC79 (30 min post-SAH) induced the p-Akt (Ser473) expression in a dose-dependent manner. A single ICV dose treatment of SC79 (100 μg/rat) significantly increased the expression of Bcl-2 and p-GSK-3β (Ser9), decreased the protein levels of Bax, cytoplasm cytochrome c, and cleaved caspase-3, indicating the antiapoptotic effect of SC79. As a result, the number of apoptotic cells was reduced 24 h post SAH. Moreover, SC79 treatment alleviated SAH-induced oxidative stress, restored mitochondrial morphology, and improved neurological deficits. Strikingly, treatment of SC79 provided a beneficial outcome against neurologic deficit with a therapeutic window of at least 4 h post SAH by ICV injection and 30 min post SAH by intraperitoneal injection. Collectively, SC79 exerts its neuroprotective effect likely through the dual activities of antioxidation and antiapoptosis. These data provide a basic platform to consider SC79 as a novel therapeutic agent for treatment of SAH.

Hemoglobin induced NO/cGMP suppression Deteriorate Microcirculation via Pericyte Phenotype Transformation after Subarachnoid Hemorrhage in Rats

Subarachnoid hemorrhage (SAH) usually results from ruptured aneurysm, but how leaked hemoglobin regulates the microcirculation in the pathophysiology of early brain injury after SAH is still unclear. In the present study, we sought to investigate the role and possible mechanism of hemoglobin induced pericyte phenotype transformation in the regulation of microcirculation after SAH. Endovascular perforation SAH rat model, brain slices and cultured pericytes were used, and intervened with endothelial nitric oxide synthase (eNOS) antagonist L-NNA and its agonist scutellarin, hemoglobin, DETA/NO (nitric oxide(NO) donor), PITO (NO scavenger), 8-Br-cGMP (cGMP analog). We found modulating eNOS regulated pericyte α-SMA phenotype transformation, microcirculation, and neurological function in SAH rats. Modulating eNOS also affected eNOS expression, eNOS activity and NO availability after SAH. In addition, we showed hemoglobins penetrated into brain parenchyma after SAH. And hemoglobins significantly reduced the microvessel diameters at pericyte sites, due to the effects of hemoglobin inducing α-SMA expressions in cultured pericytes and brain slices via inhibiting NO/cGMP pathway. In conclusion, pericyte α-SMA phenotype mediates acute microvessel constriction after SAH possibly by hemoglobin suppressing NO/cGMP signaling pathway. Therefore, by targeting the eNOS and pericyte α-SMA phenotype, our present data may shed new light on the management of SAH patients.

Erythropoietin for the Treatment of Subarachnoid Hemorrhage: A Feasible Ingredient for a Successful Medical Recipe

Subarachnoid hemorrhage (SAH) following aneurysm bleeding accounts for 6% to 8% of all cerebrovascular accidents. Although an aneurysm can be effectively managed by surgery or endovascular therapy, delayed cerebral ischemia is diagnosed in a high percentage of patients resulting in significant morbidity and mortality. Cerebral vasospasm occurs in more than half of all patients after aneurysm rupture and is recognized as the leading cause of delayed cerebral ischemia after SAH. Hemodynamic strategies and endovascular procedures may be considered for the treatment of cerebral vasospasm. In recent years, the mechanisms contributing to the development of vasospasm, abnormal reactivity of cerebral arteries and cerebral ischemia following SAH, have been investigated intensively. A number of pathological processes have been identified in the pathogenesis of vasospasm, including endothelial injury, smooth muscle cell contraction from spasmogenic substances produced by the subarachnoid blood clots, changes in vascular responsiveness and inflammatory response of the vascular endothelium. To date, the current therapeutic interventions remain ineffective as they are limited to the manipulation of systemic blood pressure, variation of blood volume and viscosity and control of arterial carbon dioxide tension. In this scenario, the hormone erythropoietin (EPO) has been found to exert neuroprotective action during experimental SAH when its recombinant form (rHuEPO) is administered systemically. However, recent translation of experimental data into clinical trials has suggested an unclear role of recombinant human EPO in the setting of SAH. In this context, the aim of the current review is to present current evidence on the potential role of EPO in cerebrovascular dysfunction following aneurysmal subarachnoid hemorrhage.

Memantine Attenuates Delayed Vasospasm after Experimental Subarachnoid Hemorrhage via Modulating Endothelial Nitric Oxide Synthase

Delayed cerebral vasospasm is an important pathological feature of subarachnoid hemorrhage (SAH). The cause of vasospasm is multifactorial. Impairs nitric oxide availability and endothelial nitric oxide synthase (eNOS) dysfunction has been reported to underlie vasospasm. Memantine, a low-affinity uncompetitive N-methyl-d-aspartate (NMDA) blocker has been proven to reduce early brain injury after SAH. This study investigated the effect of memantine on attenuation of vasospasm and restoring eNOS functionality. Male Sprague-Dawley rats weighing 350–450 g were randomly divided into three weight-matched groups, sham surgery, SAH + vehicle, and SAH + memantine groups. The effects of memantine on SAH were evaluated by assessing the severity of vasospasm and the expression of eNOS. Memantine effectively ameliorated cerebral vasospasm by restoring eNOS functionality. Memantine can prevent vasospasm in experimental SAH. Treatment strategies may help combat SAH-induced vasospasm in the future.

TGFβ-activated Kinase 1 (TAK1) Inhibition by 5Z-7-Oxozeaenol Attenuates Early Brain Injury after Experimental Subarachnoid Hemorrhage

Accumulating evidence suggests that activation of mitogen-activated protein kinases (MAPKs) and nuclear factor NF-κB exacerbates early brain injury (EBI) following subarachnoid hemorrhage (SAH) by provoking proapoptotic and proinflammatory cellular signaling. Here we evaluate the role of TGFβ-activated kinase 1 (TAK1), a critical regulator of the NF-κB and MAPK pathways, in early brain injury following SAH. Although the expression level of TAK1 did not present significant alternation in the basal temporal lobe after SAH, the expression of phosphorylated TAK1 (Thr-187, p-TAK1) showed a substantial increase 24 h post-SAH. Intracerebroventricular injection of a selective TAK1 inhibitor (10 min post-SAH), 5Z-7-oxozeaenol (OZ), significantly reduced the levels of TAK1 and p-TAK1 at 24 h post-SAH. Involvement of MAPKs and NF-κB signaling pathways was revealed that OZ inhibited SAH-induced phosphorylation of p38 and JNK, the nuclear translocation of NF-κB p65, and degradation of IκBα. Furthermore, OZ administration diminished the SAH-induced apoptosis and EBI. As a result, neurological deficits caused by SAH were reversed. Our findings suggest that TAK1 inhibition confers marked neuroprotection against EBI following SAH. Therefore, TAK1 might be a promising new molecular target for the treatment of SAH.

Nitric oxide synthases: three pieces to the puzzle?

Subarachnoid hemorrhage remains to be a devastating diagnosis in this day and age, with very few effective interventions. Rising evidence is now pointing towards the marked importance of secondary complications after the hemorrhage, and its active role in morbidity and mortality of this stroke. This review will focus on the role of Nitric Oxide Synthases (NOSes) the role they play in the pathogenesis of SAH.

HIF-1α Mediates Isoflurane-Induced Vascular Protection in Subarachnoid Hemorrhage

Objective

Outcome after aneurysmal subarachnoid hemorrhage (SAH) depends critically on delayed cerebral ischemia (DCI) – a process driven primarily by vascular events including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction. This study sought to determine the impact of postconditioning – the phenomenon whereby endogenous protection against severe injury is enhanced by subsequent exposure to a mild stressor – on SAH-induced DCI.

Methods

Adult male C57BL/6 mice were subjected to sham, SAH, or SAH plus isoflurane postconditioning. Neurological outcome was assessed daily via sensorimotor scoring. Contributors to DCI including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction were measured 3 days later. Isoflurane-induced changes in hypoxia-inducible factor 1alpha (HIF-1α)-dependent genes were assessed via quantitative polymerase chain reaction. HIF-1α was inhibited pharmacologically via 2-methoxyestradiol (2ME2) or genetically via endothelial cell HIF-1α-null mice (EC-HIF-1α-null). All experiments were performed in a randomized and blinded fashion.

Results

Isoflurane postconditioning initiated at clinically relevant time points after SAH significantly reduced cerebral vasospasm, microvessel thrombosis, microvascular dysfunction, and neurological deficits in wild-type (WT) mice. Isoflurane modulated HIF-1α-dependent genes – changes that were abolished in 2ME2-treated WT mice and EC-HIF-1α-null mice. Isoflurane-induced DCI protection was attenuated in 2ME2-treated WT mice and EC-HIF-1α-null mice.

Interpretation

Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome. These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection. They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.

The role of the nitric oxide pathway in brain injury and its treatment--from bench to bedside

Nitric oxide (NO) is a key signalling molecule in the regulation of cerebral blood flow. This review summarises current evidence regarding the role of NO in the regulation of cerebral blood flow at rest, under physiological conditions, and after brain injury, focusing on subarachnoid haemorrhage, traumatic brain injury, and ischaemic stroke and following cardiac arrest. We also review the role of NO in the response to hypoxic insult in the developing brain. NO depletion in ischaemic brain tissue plays a pivotal role in the development of subsequent morbidity and mortality through microcirculatory disturbance and disordered blood flow regulation. NO derived from endothelial nitric oxide synthase (eNOS) appears to have neuroprotective properties. However NO derived from inducible nitric oxide synthase (iNOS) may have neurotoxic effects. Cerebral NO donor agents, for example sodium nitrite, appear to replicate the effects of eNOS derived NO, and therefore have neuroprotective properties. This is true in both the adult and immature brain. We conclude that these agents should be further investigated as targeted pharmacotherapy to protect against secondary brain injury.

Protocol for the induction of subarachnoid hemorrhage in mice by perforation of the Circle of Willis with an endovascular filament

Genetically engineered mice are a valuable tool to investigate the molecular and cellular mechanisms leading to brain damage following subarachnoid hemorrhage (SAH). Therefore, several murine SAH models were developed during the last 15 years. Among those models, the perforation of the Circle of Willis by an endovascular filament or “filament model” turned out to become the most popular one, since it is believed to reproduce some of the most prominent pathophysiological features observed after human SAH. Despite the importance of the endovascular filament model for SAH research, relatively few studies were published using this technique during the past years and a number of laboratories reported problems establishing the technique. This triggered discussions about the standardization, reproducibility, and the reliability of the model. In order to improve this situation, the current paper aims to provide a comprehensive hands-on protocol of the murine endovascular filament model. The protocol proved to result in induction of SAH in mice with high intrapersonal and interpersonal reproducibility and is based on our experience with this technique for more than 10 years. By sharing our experience with this valuable model, we aim to initiate a constantly ongoing discussion process on the improvement of standards and techniques in the field of experimental SAH research.

The L-arginine pathway in acute ischemic stroke and severe carotid stenosis: temporal profiles and association with biomarkers and outcome

BACKGROUND

Endothelial dysfunction is associated with increased levels of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) resulting in a decreased production of nitric oxide, which regulates the vascular tone.

METHODS

Patients with acute ischemic stroke (AIS, n = 55) and asymptomatic significant carotid stenosis (AsCS, n = 44) were prospectively investigated. L-arginine, ADMA, SDMA, S100 B, and high-sensitivity C-reactive protein (hsCRP) were serially measured within 6 hours after the onset of stroke, at 24 and 72 poststroke hours. All markers were compared with healthy subjects (n = 45). The severity of AIS was daily assessed by National Institute of Health Stroke Scale scoring.

RESULTS

Even within 6 hours after the onset of stroke, L-arginine, ADMA, and SDMA were significantly higher in patients with AIS compared with both AsCS and healthy subjects. S100 B reflecting infarct size, positively correlated with the level of SDMA at 72 poststroke hours; changes in concentration of S100 B positively correlated with changes in the concentration of ADMA by 72 hours. Change in concentration of both ADMA and SDMA correlated with the change in concentration of hsCRP. Concentrations of L-arginine and hsCRP at 72 poststroke hours, respectively, were independent predictors of poststroke infection. S100 B level measured within 6 hours after the onset of AIS and hsCRP at 72 poststroke hours were independent predictors of death.

CONCLUSIONS

Metabolites of the L-arginine pathway were elevated in the very acute phase of ischemic stroke indicating a more pronounced endothelial dysfunction compared with AsCS. An increased basal L-arginine level in patients with AIS might be an adaptive mechanism; such transient elevation of the L-arginine/ADMA ratio at 24 poststroke hours may suggest that a temporary increase of L-arginine along with decrease of ADMA might be related to the protective role of L-arginine. Changes in the L-arginine pathway are predictive of poststroke infections.

Inflammation, vasospasm, and brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) can lead to devastating neurological outcomes, and there are few pharmacologic treatments available for treating this condition. Both animal and human studies provide evidence of inflammation being a driving force behind the pathology of SAH, leading to both direct brain injury and vasospasm, which in turn leads to ischemic brain injury. Several inflammatory mediators that are elevated after SAH have been studied in detail. While there is promising data indicating that blocking these factors might benefit patients after SAH, there has been little success in clinical trials. One of the key factors that complicates clinical trials of SAH is the variability of the initial injury and subsequent inflammatory response. It is likely that both genetic and environmental factors contribute to the variability of patients' post-SAH inflammatory response and that this confounds trials of anti-inflammatory therapies. Additionally, systemic inflammation from other conditions that affect patients with SAH could contribute to brain injury and vasospasm after SAH. Continuing work on biomarkers of inflammation after SAH may lead to development of patient-specific anti-inflammatory therapies to improve outcome after SAH.

Effect of recombinant ADAMTS-13 on microthrombosis and brain injury after experimental subarachnoid hemorrhage

BACKGROUND

A common complication after aneurysmal subarachnoid hemorrhage (SAH) is delayed cerebral ischemia (DCI), which is associated with vasospasm and other mechanisms such as microthrombosis. ADAMTS-13 activity plays a role in the prevention of thrombus formation in the cerebral microvasculature. Previously, we observed that patients with DCI have lower levels of ADAMTS-13.

OBJECTIVES

To examine whether recombinant human ADAMTS-13 (rADAMTS-13) reduces cerebral microthrombus formation and brain injury in an experimental mouse model of SAH including wild-type and ADAMTS-13(-/-) mice.

METHODS

Experimental SAH was induced with the prechiasmatic blood injection model. The following experimental groups were investigated: (i) C57BL/6J mice (n = 10); (ii) C57BL/6J mice (n = 10) treated with rADAMTS-13 20 min after SAH; (iii) ADAMTS-13(-/-) mice (n = 10); and (iv) ADAMTS-13(-/-) mice (n = 10) treated with rADAMTS-13 20 min after SAH. Mice were killed at 48 h. Results are presented as means with standard errors of the mean.

RESULTS

Infusion with rADAMTS-13 reduced the extent of microthrombosis by ~ 50% in both wild-type mice (mean fibrinogen area: 0.28% ± 0.09% vs. 0.15% ± 0.04%; P = 0.20) and ADAMTS-13(-/-) mice (mean fibrinogen area: 0.32% ± 0.05% vs. 0.16% ± 0.03%; P = 0.016). In addition, rADAMTS-13 reduced brain injury by > 60% in both wild-type mice (mean microglia area: 0.65% ± 0.18% vs. 0.18% ± 0.04%; P = 0.013) and ADAMTS-13(-/-) mice (mean microglia area: 1.24% ± 0.36% vs. 0.42% ± 0.13%; P = 0.077).

CONCLUSIONS

Our results support the further study of rADAMTS-13 as a treatment option for the prevention of microthrombosis and brain injury after SAH.

Controversies and evolving new mechanisms in subarachnoid hemorrhage

Despite decades of study, subarachnoid hemorrhage (SAH) continues to be a serious and significant health problem in the United States and worldwide. The mechanisms contributing to brain injury after SAH remain unclear. Traditionally, most in vivo research has heavily emphasized the basic mechanisms of SAH over the pathophysiological or morphological changes of delayed cerebral vasospasm after SAH. Unfortunately, the results of clinical trials based on this premise have mostly been disappointing, implicating some other pathophysiological factors, independent of vasospasm, as contributors to poor clinical outcomes. Delayed cerebral vasospasm is no longer the only culprit. In this review, we summarize recent data from both experimental and clinical studies of SAH and discuss the vast array of physiological dysfunctions following SAH that ultimately lead to cell death. Based on the progress in neurobiological understanding of SAH, the terms "early brain injury" and "delayed brain injury" are used according to the temporal progression of SAH-induced brain injury. Additionally, a new concept of the vasculo-neuronal-glia triad model for SAH study is highlighted and presents the challenges and opportunities of this model for future SAH applications.

Genetic elimination of Nrf2 aggravates secondary complications except for vasospasm after experimental subarachnoid hemorrhage in mice

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key endogenous protective regulator in the body. This study aimed to explore the role of Nrf2 in subarachnoid hemorrhage (SAH)-induced secondary complications. Wild type (WT) and Nrf2 knockout (KO) mice were subjected to experimental SAH by injecting fresh autologous blood into pre-chiasmatic cistern. The absence of Nrf2 function in mice resulted in exacerbated brain injury with increased brain edema, blood-brain barrier (BBB) disruption, neural apoptosis, and severe neurological deficits at 24h after SAH. Moreover, cerebral vasospasm was severe at 24h after SAH, but not significantly different between WT and Nrf2 KO mice after SAH. Meanwhile, Molondialdehyde (MDA) was increased and GSH/GSSG ratio was decreased in Nrf2 KO mice after SAH. Furthermore, higher expression of TNF-α and IL-1β was also found after SAH in Nrf2 KO mice. In conclusion, our results revealed that Nrf2 plays an important role in attenuating SAH-induced secondary complications by regulating excessive oxidative stress and inflammatory response.