The clinical significance of acute brain injury in subarachnoid hemorrhage and opportunity for intervention

Mechanisms of Mitochondrial Oxidative Stress in Brain Injury: From Pathophysiology to Therapeutics

Mitochondrial oxidative stress has been implicated in various forms of brain injury, both traumatic and non-traumatic. Due to its oxidative demand, the brain is intimately dependent on its mitochondrial functioning. However, there remains appreciable heterogeneity in the development of these injuries regarding ROS and their effect on the sequelae. These include traumatic insults such as TBIs and intracranial hemorrhaging secondary to this. In a different vein, such injuries may be attributed to other etiologies such as infection, neoplasm, or spontaneous hemorrhage (strokes, aneurysms). Clinically, the manner of treatment may also be adjusted in relation to each injury and its unique progression in the context of ROS. In the current review, then, the authors highlight the role of mitochondrial ROS in various forms of brain injury, emphasizing both the collective and unique elements of each form. Lastly, these narratives are met with the current therapeutic landscape and the role of emerging therapies in treating reactive oxygen species in brain injuries.

Early prediction of clinical outcomes in patients with aneurysmal subarachnoid hemorrhage using computed tomography texture analysis

Radiological evaluation of subarachnoid hemorrhage (SAH) is often subject to interobserver variability. The aim of this study was to retrospectively detect computed tomography (CT) texture parameters in the early postictal state to predict cerebral vasospasm, delayed cerebral ischemia (DCI), and functional outcome in aneurysmal SAH using quantitative CT texture analysis (CTTA) via a commercially available software program and routine CT images. 40 patients with aneurysmal SAH surgically treated at the Keio University Hospital during a four-year period were analyzed. CT texture analyses were performed using a commercially available software program (Synapse Vincent). The following texture parameters of blood clots in the subarachnoid space and cerebral edema were assessed: mean CT value, entropy, skewness, and kurtosis. The mean CT value of blood clots in the subarachnoid space was significantly associated with cerebral vasospasm, DCI, and functional outcome. The mean CT value ≥ 49.64 Hounsfield units (HU) predicted cerebral vasospasm with a sensitivity and specificity of 85.7% and 61.5%, respectively (area under the curve [AUC] = 0.758). The mean CT value ≥ 49.95 HU predicted DCI with a sensitivity and specificity of 100% and 60.6%, respectively (AUC = 0.810). The mean CT value ≥ 53.00 HU predicted poor functional outcome with a sensitivity and specificity of 56.3% and 91.7%, respectively (AUC = 0.747). CTTA using a commercially available software program demonstrated that the mean CT value of clots in the subarachnoid space in the early postictal state could predict vasospasm, DCI, and clinical outcome with a high sensitivity and specificity.

Aloperine activates the Nrf2-ARE pathway when ameliorating early brain injury in a subarachnoid hemorrhage model

Aloperine (ALO) exhibits neuroprotective effects against oxidative stress in vitro; however, its protective effect in early brain injury (EBI) following experimental subarachnoid hemorrhage (SAH) remains to be elucidated. The aim of the current study was to evaluate the antioxidant activity of ALO in EBI, and its association with nuclear factor erythroid-related factor 2 and the antioxidant responsive element (Nrf2-ARE) survival pathway. In the present study, an experimental SAH model was induced in rats following a prechiasmatic cistern injection. All rats were randomly divided into five groups: Sham, SAH, SAH+ vehicle, and an SAH+ ALO group (including low and high doses). ALO was administrated intraperitoneally at 2 and 24 h following induction of the SAH model. Brain samples were collected from each group at 48 h after SAH induction. Subsequently, western blotting, immunohistochemistry and cell apoptosis assays were performed, along with assessments for brain edema, neurological deficit, and the activity of oxidant/antioxidant factors. It was observed that the expression of Nrf2-ARE pathway-associated agents, including Nrf2, and heme oxygenase-1, were markedly increased in the high concentration ALO group compared with that of the SAH group. In addition, the level of oxidative damage was reduced. Furthermore, early brain damage, including brain edema, neurological deficit and cellular apoptosis were significantly ameliorated. In conclusion, the results of the present study indicate that ALO can ameliorate oxidative damage against EBI following SAH, most likely via the Nrf2-ARE survival pathway.

Early Predictors of Fever in Patients with Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Fever is commonly observed in patients who have had aneurysmal subarachnoid hemorrhage (SAH), and it has been associated with the occurrence of delayed cerebral ischemia and worse outcomes in previous studies. Frequently, fever is not the result of bacterial infections, and distinction between infection-related fever and fever secondary to brain injury (also referred as central fever) can be challenging.

OBJECTIVES

The current study aimed to identify risk factors on admission for the development of central fever in patients with SAH.

METHODS

Databank analysis was performed using information from demographic data (age, gender), imaging (transcranial Doppler ultrasound, computed tomography, and cerebral angiogram), laboratory (white blood cell count, hemoglobin, renal function, and electrolytes), and clinical assessment (Hunt-Hess and modified Fisher scales on admission, occurrence of fever). A multivariate logistic regression model was created.

RESULTS

Of 55 patients, 32 developed fever during the first 7 days of hospital stay (58%). None of the patients had identifiable bacterial infections during their first week in the neurocritical care unit. Hunt-Hess scale >2 and leukocytosis on admission were associated to the development of central fever, even after correction in a logistic regression model.

CONCLUSION

Leukocytosis and a poor neurologic examination on admission might help predict which subset of patients with SAH are at higher risk of developing central fever early in their hospital stay.

Mild exercise reduces cerebral vasospasm after aneurysm subarachnoid hemorrhage: a retrospective clinical study and correlation with laboratory investigation

BACKGROUND

Aneurysmal subarachnoid hemorrhage (SAH) is a leading cause of death and disability and is often complicated by cerebral vasospasm (CV). Conventional management to prevent CV includes bedrest; however, inactivity places the patient at risk for nonneurological complications. We investigated the effect of mild exercise after SAH in clinical and laboratory settings.

METHODS

Clinical: Data from 80 patients with SAH were analyzed retrospectively. After aneurysms were secured, physical therapy was initiated as tolerated. CV and complications were compared by the timing of active physical therapy. Laboratory: 18 Rodents were divided into three groups: (1) control, (2) SAH without exercise, and (3) SAH plus mild exercise. On day 5, brainstems were removed and analyzed for the injury marker inducible nitric oxide synthase (iNOS).

RESULTS

Clinical: Mild exercise before day 4 significantly lowered the incidence of symptomatic CV compared with the nonexercised group. There was no difference in the incidence of additional complications based upon exercise. Laboratory: Staining for iNOS was significantly higher in the SAH group than the control group, but there was no difference between exercised and nonexercised SAH groups, confirming that exercise did not promote neuronal injury.

CONCLUSION

Early mobilization significantly reduced clinical CV. The relationship should be studied further in a prospective trial with defined exercise regimens.

Time-dependent changes in cerebrospinal fluid metal ions following aneurysm subarachnoid hemorrhage and their association with cerebral vasospasm

Aneurysm subarachnoid hemorrhage affects 10 in 100,000 people annually, 40 % of whom will develop neurological deficits from ischemic stroke caused by cerebral vasospasm. Currently, the underlying mechanisms are uncertain. Metal ions are important modulators of neuronal electrophysiological conduction and smooth muscle cell activity, thereby potentially contributing to vasospasm. We hypothesized that metal ion concentrations in the cerebrospinal fluid (CSF) after aneurysm rupture would change over time and be associated with vasospasm. To test this hypothesis, for 21 days, we collected CSF from patients with aneurysmal rupture and subjected it to spectrometry to detect metals. A repeated measures analysis was performed to analyze concentration changes over time. Six of the seven patients with aneurysmal rupture experienced vasospasm, all resolving by day 14. Changes in Fe²⁺ and Zn²⁺ concentrations in the CSF paralleled the incidence of vasospasm in this study population. Na²⁺, Ca²⁺, Mg²⁺, and Cu²⁺ concentrations exhibited no statistically significant changes over time. In conclusion, Fe²⁺ concentration in the CSF was significantly elevated during days 7-10, whereas Zn²⁺ concentrations spiked shortly thereafter, during days 11-14. This suggests that Fe²⁺ may be related to the induction of vasospasm and Zn²⁺ may be a marker of early brain injury secondary to ischemic injury and inflammation.

The rodent endovascular puncture model of subarachnoid hemorrhage: mechanisms of brain damage and therapeutic strategies

Subarachnoid hemorrhage (SAH) represents a considerable health problem. To date, limited therapeutic options are available. In order to develop effective therapeutic strategies for SAH, the mechanisms involved in SAH brain damage should be fully explored. Here we review the mechanisms of SAH brain damage induced by the experimental endovascular puncture model. We have included a description of similarities and distinctions between experimental SAH in animals and human SAH pathology. Moreover, several novel treatment options to diminish SAH brain damage are discussed.SAH is accompanied by cerebral inflammation as demonstrated by an influx of inflammatory cells into the cerebral parenchyma, upregulation of inflammatory transcriptional pathways and increased expression of cytokines and chemokines. Additionally, various cell death pathways including cerebral apoptosis, necrosis, necroptosis and autophagy are involved in neuronal damage caused by SAH.Treatment strategies aiming at inhibition of inflammatory or cell death pathways demonstrate the importance of these mechanisms for survival after experimental SAH. Moreover, neuroregenerative therapies using stem cells are discussed as a possible strategy to repair the brain after SAH since this therapy may extend the window of treatment considerably. We propose the endovascular puncture model as a suitable animal model which resembles the human pathology of SAH and which could be applied to investigate novel therapeutic therapies to combat this debilitating insult.

Early brain injury and subarachnoid hemorrhage: Where are we at present?

The current era has adopted many new innovations in nearly every aspect of management of subarachnoid hemorrhage (SAH); however, the neurological outcome has still not changed significantly. These major therapeutic advances mainly addressed the two most important sequels of the SAH-vasospasm and re-bleed. Thus, there is a possibility of some different pathophysiological mechanism that would be responsible for causing poor outcome in these patients. In this article, we have tried to compile the current role of this different yet potentially treatable pathophysiological mechanism in post-SAH patients. The main pathophysiological mechanism for the development of early brain injury (EBI) is the apoptotic pathways. The macro-mechanism includes increased intracranial pressure, disruption of the blood-brain barrier, and finally global ischemia. Most of the treatment strategies are still in the experimental phase. Although the role of EBI following SAH is now well established, the treatment modalities for human patients are yet to be testified.

Fatal hemorrhagic stroke in a Caucasian girl with moyamoya disease

INTRODUCTION

Moyamoya disease (MMD) is an extremely rare neurovascular disorder in Caucasian children. To the best of our knowledge, the aggressive variant including hemorrhagic malignant stroke and consecutive global ischemia has not been reported for this population before.

CASE REPORT

We present the case of an 11-year-old girl with sudden neurological deterioration due to intracerebral hemorrhage with early irruption into the ventricular system. MMD with extensive neovascularization was diagnosed by means of computed tomography and magnetic resonance imaging. Despite immediate ventricular drainage, intracranial pressure increased above the mean arterial pressure resulting in malignant bi-hemispheric ischemia. The girl died within 53 h after admission to hospital.

DISCUSSION

Intracerebral hemorrhage in young patients is often attributed to vascular malformation. This case shows that MMD may constitute a potential diagnosis in the case of sudden neurological deterioration and loss of consciousness, even in previously healthy children.

Evidence for direct impairment of neuronal function by subarachnoid metabolites following SAH

Dysfunction of neuronal signal processing and transmission occurs after subarachnoid hemorrhage (SAH) and contributes to the high morbidity and mortality of this pathology. The underlying mechanisms include early brain injury due to elevation of the intracranial pressure, disruption of the blood-brain barrier, brain edema, reduction of cerebral blood flow, and neuronal cell death. Direct influence of subarachnoid blood metabolites on neuronal signaling should be considered. After SAH, some metabolites were shown to directly induce disruption of neuronal integrity and neuronal signaling, whereas the effects of other metabolites on neurotoxicity and neuronal signaling have not yet been investigated. Therefore, this mini-review will discuss recent evidence for a direct influence of subarachnoid blood and its metabolites on neuronal function.

Statin-induced T-lymphocyte modulation and neuroprotection following experimental subarachnoid hemorrhage

INTRODUCTION

Statins influence immune system activities through mechanisms independent of their lipid-lowering properties. T cells can be subdivided based on cytokine secretion patterns into two subsets: T-helper cells type 1 (Th1) and type 2 (Th2). Independent laboratory studies have shown statins to be potent inducers of a Th2 switch in immune cell response and be neuroprotective in several models of central nervous system (CNS) disease. This study was the first to evaluate the immune modulating effects of statins in subarachnoid hemorrhage (SAH).

METHODS

Simvastatin was administered to rats intraperitoneally in two dosages (1 and 20 mg/kg) 30 min after the induction of SAH using endovascular perforation. Neurological scores were assessed 24 h later. Animals were then sacrificed, and samples of cortex and brain stem were tested for expression of the T-regulatory cell cytokine transforming growth factor (TGF) β1, as well as interleukin (IL) 1β, a proinflammatory cytokine associated with Th1 immune responses. The presence of TGF-β1 secreting T cells was evaluated with the use of brain slices.

RESULTS

SAH significantly impaired neurological function in all SAH groups (treated and untreated) versus sham. Animals treated with high-dose simvastatin had less neurological impairment than both untreated and low-dose groups. Cortical and brain-stem levels of TGF-β1 were significantly elevated following SAH in the high-dose group. IL-1β was significantly elevated following the induction of SAH but was inhibited by high-dose simvastatin. Double-labeled fluorescent immunohistochemical data demonstrated the presence of lymphocytes in the subarachnoid and perivascular spaces following SAH. Expression of TGF-β1 by lymphocytes was markedly increased following treatment with high-dose simvastatin.

CONCLUSION

The present study elucidated the potential role of a Th2 immune switch in statin provided neuroprotection following SAH.

Cardiac and central vascular functional alterations in the acute phase of aneurysmal subarachnoid hemorrhage

OBJECTIVES

To investigate aortic functional alterations in the acute phase of aneurysmal subarachnoid hemorrhage and to evaluate the relationship between potential cardiovascular alterations and delayed cerebral infarctions or poor Glasgow Outcome Scale score at discharge from critical care unit.

DESIGN

Prospective observational study.

SETTING

Critical Care Departments of two tertiary centers.

PATIENTS

Thirty-seven patients with aneurysmal subarachnoid hemorrhage.

INTERVENTIONS

Patients were evaluated at two time points: on admission (acute aneurysmal subarachnoid hemorrhage phase) and at least 21 days later (stable aneurysmal subarachnoid hemorrhage state). At baseline, the severity of aneurysmal subarachnoid hemorrhage was assessed clinically (Hunt and Hess scale) and radiologically (brain computed tomography Fisher grading). Aortic elasticity was evaluated by Doppler-derived pulse-wave velocity and left ventricular function by echocardiography. Serum B-type natriuretic peptide and troponin I were also assessed at the same time points.

MEASUREMENTS AND MAIN RESULTS

At the acute phase, 23 patients (62%) were found to present supranormal pulse-wave velocity and 14 patients (38%) presented left ventricular systolic dysfunction; there were significant associations between pulse-wave velocity values and left ventricular ejection fraction (p < .001). Left ventricular ejection fraction and pulse-wave velocity were both associated with Hunt and Hess (p ≤ .004) and Fisher grading (p ≤ .03). Left ventricular ejection fraction and pulse-wave velocity were improved between acute aneurysmal subarachnoid hemorrhage and stable state (p ≤ .005); changes (Δ%) were greater in patients who initially had regional wall motion abnormalities compared to patients who had not (28.7% ± 10.2% vs. 2.4% ± 1.8% [p = .002] and -17.9% ± 3.7% vs. -3.5% ± 4.7% [p = .045], respectively). Pulse-wave velocity/left ventricular ejection fraction ratio was the only independent predictor for delayed cerebral infarctions. Left ventricular ejection fraction, B-type natriuretic peptide, pulse-wave velocity, and pulse-wave velocity/left ventricular ejection fraction showed significant diagnostic performance for predicting delayed cerebral infarctions or poor Glasgow Outcome Scale score (1-3).

CONCLUSIONS

Our findings suggest that significant cardiovascular alterations in left ventricular function and in aortic stiffness occur during the early phase of aneurysmal subarachnoid hemorrhage. These phenomena were associated with adverse outcomes in this study and their role in the pathogenesis of delayed neurologic complications warrants further investigation.

Association of APOE polymorphism with the change of brain function in the early stage of aneurysmal subarachnoid hemorrhage

Recent studies have indicated that early brain injury may be responsible for the detrimental effects seen in patients after subarachnoid hemorrhage (SAH). In this study, we investigated the relationship between apolipoprotein E gene (APOE) polymorphism and the change of brain function in the early stage of aneurysmal SAH. A total of 79 patients admitted within 5 days after aneurysmal SAH were recruited in the study. Patient characteristics, such as age, gender, Fisher and Hunt-Hess grade were collected when admitted. Electroencephalogram (EEG) was recorded on admission and at 3-5 days after onset to assess the change of brain function of the patients in acute stage of SAH. The result of the second EEG recording was defined as EEG deterioration if the decrease in alpha wave frequency, increase in slow wave or decline in amplitude were observed when compared with the first EEG recording. The APOE polymorphism was determined in all patients by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Ten of 17 patients with APOEε4 (58.8%) showed the deteriorated EEGs, which was significantly different from those without APOEε4 (18 of 62 patients, 29.0%, p=0.023). However, neither the presence of ε2 nor of ε3 was significantly different from those absent of it (p>0.05). Univariate logistic regression analyses showed that both high Fisher grade (p=0.028, OR=2.917, 95% CI=1.124-7.572) and APOEε4 (p=0.027, OR=3.492, 95% CI=1.150-10.604) were risk factors to EEG aggravation after aneurysmal SAH. The association of APOEε4 for deteriorated EEG was more significant after adjustment for age, gender, Hunt-Hess grade on admission, and Fisher grade (p=0.007, OR=5.741, 95% CI=1.625-20.280). Our findings suggest that APOEε4 allele is a risk factor to brain function aggravation in the early stage of aneurysmal SAH, and it may contribute to early brain injury after SAH.

The neuroprotective effects of cyclooxygenase-2 inhibition in a mouse model of aneurysmal subarachnoid hemorrhage

The CNS inflammatory reaction occurring after aneurysmal subarachnoid hemorrhage (SAH) involves the upregulation of numerous cytokines and prostaglandins. Cyclooxygenase (COX) inhibition is a well-established pharmacological anti-inflammatory agent. Previous studies have shown marked increases in COX-2 expression in neurons, astrocytes, microglia, and endothelial cells following brain injury. COX-2 inhibition has been shown to be beneficial following various types of brain injury. This experiment investigates the role of COX-2 activity in early brain injury following SAH. CD-1 mice were subjected to an endovascular perforation model of SAH or SHAM surgery. Following experimental SAH animals were treated with the specific COX-2 inhibitor, NS398, in dosages of either 10 or 30 mg/kg. Neurological performance and brain edema were evaluated 24 and 72 h after SAH. NS398 at 30 mg/kg significantly reduced SAH-induced neurological deterioration. NS 398 at 30 mg/kg resulted in a trend toward the reduction of SAH-induced cerebral edema. Treatment had no effect on mortality. This experiment provides preliminary evidence that COX-2 inhibition is an effective pharmacological intervention for the prevention of brain edema and the preservation of neurological function following SAH.

Elucidating novel mechanisms of brain injury following subarachnoid hemorrhage: an emerging role for neuroproteomics

Subarachnoid hemorrhage (SAH) is a devastating neurological injury associated with significant patient morbidity and death. Since the first demonstration of cerebral vasospasm nearly 60 years ago, the preponderance of research has focused on strategies to limit arterial narrowing and delayed cerebral ischemia following SAH. However, recent clinical and preclinical data indicate a functional dissociation between cerebral vasospasm and neurological outcome, signaling the need for a paradigm shift in the study of brain injury following SAH. Early brain injury may contribute to poor outcome and early death following SAH. However, elucidation of the complex cellular mechanisms underlying early brain injury remains a major challenge. The advent of modern neuroproteomics has rapidly advanced scientific discovery by allowing proteome-wide screening in an objective, nonbiased manner, providing novel mechanisms of brain physiology and injury. In the context of neurosurgery, proteomic analysis of patient-derived CSF will permit the identification of biomarkers and/or novel drug targets that may not be intuitively linked with any particular disease. In the present report, the authors discuss the utility of neuroproteomics with a focus on the roles for this technology in understanding SAH. The authors also provide data from our laboratory that identifies high-mobility group box protein-1 as a potential biomarker of neurological outcome following SAH in humans.

Role of gap junctions in early brain injury following subarachnoid hemorrhage

Gap junction inhibition has been demonstrated to reverse the vascular contraction that follows experimental subarachnoid hemorrhage. This study hypothesizes that the use of established gap junction inhibitors: octonal and carbenoxolone, to interrupt cell to cell communication will provide neuroprotection against early brain injury after SAH. The filament perforation model of SAH was performed in male Sprague-Dawley rats weighing between 300 and 380 g. Octanol (260.46 mg or 781.38 mg/kg), carbenoxolone (100 mg/kg), or vehicles were given via intraperitoneal injection 1 h after SAH. Neurologic deficits and cerebral apoptosis were assessed 24 and 72 h after SAH. In addition, Western blot analysis was performed to confirm the in vivo inhibition of CNS gap junctions. The administration of octanol and carbenoxolone both failed to attenuate the neurological deficits induced by SAH, and they did not reduce neuronal apoptosis. Additionally, carbenoloxone increased post SAH mortality and exacerbated SAH-induced apoptosis. Despite previous studies that show gap junction inhibitors reverse vasospasm following experimental SAH, they failed to improve clinical outcomes or provide neuroprotection in this study.

Correlation of F4-neuroprostanes levels in cerebrospinal fluid with outcome of aneurysmal subarachnoid hemorrhage in humans

Aneurysmal subarachnoid hemorrhage (aSAH) is one type of hemorrhagic stroke in humans. F(2)-isoprostanes (F(2)-IsoPs) and F(4)-neuroprostanes (F(4)-NPs), derived from arachidonic acid and docosahexaenoic acid (DHA), respectively, are specific markers of lipid peroxidation. We previously demonstrated that F(2)-IsoPs levels in cerebrospinal fluid (CSF) of aSAH patients positively correlated with poor clinical conditions. In this work, we refined F(4)-NPs analysis and investigated the role of potential oxidative damage to neurons in aSAH patients by detecting F(4)-NPs in CSF. [(2)H(4)]-15-F(2t)-IsoP, rather than [(18)O(2)]-17-F(4c)-NP or [(2)H(4)]-PGF(2 alpha), was used as the internal standard for F(4)-NPs analysis. One problem of the use of [(18)O(2)]-17-F(4c)-NP was the potential interference resulting from F(2)-dihomo-IsoPs in CSF. CSF specimens of 15 aSAH patients for up to 10 days and those of 12 non-aSAH controls were analyzed. First day, mean, and peak levels of F(4)-NPs were all significantly higher in aSAH patients than in controls and correlated with the Fisher Scale and 3-month Glasgow Outcome Scale, but only mean levels of F(4)-NPs correlated with Hunt and Hess Grade. The results first demonstrate oxidative damage to DHA in brain tissue following aSAH and suggest that F(4)-NPs in CSF could be a better predictor for outcome of aSAH than F(2)-IsoPs at early time points.