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

Early brain injury, an evolving frontier in subarachnoid hemorrhage research

Subarachnoid hemorrhage (SAH), predominantly caused by a ruptured aneurysm, is a devastating neurological disease that has a morbidity and mortality rate higher than 50%. Most of the traditional in vivo research has focused on the pathophysiological or morphological changes of large-arteries after intracisternal blood injection. This was due to a widely held assumption that delayed vasospasm following SAH was the major cause of delayed cerebral ischemia and poor outcome. However, the results of the CONSCIOUS-1 trial implicated some other pathophysiological factors, independent of angiographic vasospasm, in contributing to the poor clinical outcome. The term early brain injury (EBI) has been coined and describes the immediate injury to the brain after SAH, before onset of delayed vasospasm. During the EBI period, a ruptured aneurysm brings on many physiological derangements such as increasing intracranial pressure (ICP), decreased cerebral blood flow (CBF), and global cerebral ischemia. These events initiate secondary injuries such as blood-brain barrier disruption, inflammation, and oxidative cascades that all ultimately lead to cell death. Given the fact that the reversal of vasospasm does not appear to improve patient outcome, it could be argued that the treatment of EBI may successfully attenuate some of the devastating secondary injuries and improve the outcome of patients with SAH. In this review, we provide an overview of the major advances in EBI after SAH research.

Cannabinoid receptor type 2 agonist attenuates apoptosis by activation of phosphorylated CREB-Bcl-2 pathway after subarachnoid hemorrhage in rats

Early brain injury (EBI) which comprises of vasogenic edema and apoptotic cell death is an important component of subarachnoid hemorrhage (SAH) pathophysiology. This study evaluated whether cannabinoid receptor type 2 (CB2R) agonist, JWH133, attenuates EBI after SAH and whether CB2R stimulation reduces pro-apoptotic caspase-3 via up-regulation of cAMP response element-binding protein (CREB)-Bcl-2 signaling pathway. Male Sprague-Dawley rats (n=123) were subjected to SAH by endovascular perforation. Rats received vehicle or JWH133 at 1h after SAH. Neurological deficits and brain water content were evaluated at 24h after SAH. Western blot was performed to quantify phosphorylated CREB (pCREB), Bcl-2, and cleaved caspase-3 levels. Neuronal cell death was evaluated with terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Additionally, CREB siRNA was administered to manipulate the proposed pathway. JWH133 (1.0mg/kg) improved neurological deficits and reduced brain water content in left hemisphere 24h after SAH. JWH133 significantly increased activated CREB (pCREB) and Bcl-2 levels and significantly decreased cleaved caspase-3 levels in left hemisphere 24h after SAH. CREB siRNA reversed the effects of treatment. TUNEL positive neurons in the cortex were reduced with JWH133 treatment. Thus, CB2R stimulation attenuated EBI after SAH possibly through activation of pCREB-Bcl-2 pathway.

The role of microclot formation in an acute subarachnoid hemorrhage model in the rabbit

Background. Microvascular dysfunction and microthrombi formation are believed to contribute to development of early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (SAH). Objective. This study aimed to determine (i) extent of microthrombus formation and neuronal apoptosis in the brain parenchyma using a blood shunt SAH model in rabbits; (ii) correlation of structural changes in microvessels with EBI characteristics. Methods. Acute SAH was induced using a rabbit shunt cisterna magna model. Extent of microthrombosis was detected 24 h post-SAH (n = 8) by fibrinogen immunostaining, compared to controls (n = 4). We assessed apoptosis by terminal deoxynucleotidyl transferase nick end labeling (TUNEL) in cortex and hippocampus. Results. Our results showed significantly more TUNEL-positive cells (SAH: 115 ± 13; controls: 58 ± 10; P = 0.016) and fibrinogen-positive microthromboemboli (SAH: 9 ± 2; controls: 2 ± 1; P = 0.03) in the hippocampus after aneurysmal SAH. Conclusions. We found clear evidence of early microclot formation in a rabbit model of acute SAH. The extent of microthrombosis did not correlate with early apoptosis or CPP depletion after SAH; however, the total number of TUNEL positive cells in the cortex and the hippocampus significantly correlated with mean CPP reduction during the phase of maximum depletion after SAH induction. Both microthrombosis and neuronal apoptosis may contribute to EBI and subsequent DCI.

Memantine alleviates brain injury and neurobehavioral deficits after experimental subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) causes brain injury via glutamate excitotoxicity, which leads to an excessive Ca(2+) influx and this starts an apoptotic cascade. Memantine has been proven to reduce brain injury in several types of brain insults. This study investigated the neuro-protective potential of memantine after SAH and explored the underlying mechanisms. An endovascular perforation rat model of SAH was used and Sprague-Dawley rats were randomized into sham surgery, SAH + vehicle, and SAH + memantine groups. The effects of memantine on SAH were evaluated by assessing the neuro-behavioral functions, blood-brain barrier (BBB) permeability and neuronal cell preservation. The mechanisms of action of memantine, with its N-methyl-D-aspartate (NMDA) antagonistic characteristics on nitric oxide synthase (NOS) expression and peroxynitrite formation, were also investigated. The apoptotic cascade after SAH was suppressed by memantine. Neuronal NOS (nNOS) expression, peroxynitrite formation, and subsequent oxidative/nitrosative stress were also reduced. Memantine effectively preserved BBB integrity, rescued neuronal injury, and improved neurological outcome in experimental SAH. Memantine has neuro-protective potential in experimental SAH and may help combat SAH-induced brain damage in the future.

Voltage-dependent anion channels (VDACs) promote mitophagy to protect neuron from death in an early brain injury following a subarachnoid hemorrhage in rats

The term mitophagy is coined to describe the selective removal of mitochondria by autophagy but the process itself is still contentious, especially in the early period following subarachnoid hemorrhage (SAH). In the present study, we investigated the role of mitophagy following 48h after SAH injury in rats. Specifically evaluating whether mitophagy, through voltage dependant anion channels (VDACs) interacting with microtubule-associated protein 1 light chain 3, could orchestrate the induction of apoptotic and necrotic cell death in neurons, a VDAC1siRNA and an activitor Rapamycian (RAPA), were engaged. One hundred and twelve male Sprague-Dawley rats were randomly divided into 4 groups: Sham, SAH, SAH+VDAC1siRNA, and SAH+RAPA. Outcomes measured included mortality rate, brain edema, BBB disruption, and neurobehavioral testing. We also used western blotting techniques to analyze the expressions of key mitophagic/autophagic proteins and pro-apoptotic protein such as ROS, VDAC1, LC-3II and Caspase-3. Rapamycin treatment significantly improved the mortality rate, cerebral edema, and neurobehavioral deficits; apoptotic and necrotic cell death in neurons were reduced by Rapamycin following SAH injury. However, VDAC1siRNA worsened the brain injury following SAH. Immunohistochemical staining and western blot analysis demonstrated a decreased expression of VDAC1, LC3II, and an increase of ROS and Caspase-3 followed by VDAC1siRNA administration. In conclusion, mitophagy induced by VDAC1 following SAH injury may in fact play a significant role in neuroprotection, the mechanism which may be through the attenuation of the apoptosic and necrosic molecular pathways. This translates a preservation of functional integrity and an improvement in mortality.

Stem cell transplantation in neurological diseases: improving effectiveness in animal models

Neurological diseases afflict a growing proportion of the human population. There are two reasons for this: first, the average age of the population (especially in the industrialized world) is increasing, and second, the diagnostic tools to detect these pathologies are now more sophisticated and can be used on a higher percentage of the population. In many cases, neurological disease has a pharmacological treatment which, as in the case of Alzheimer's disease, Parkinson's disease, Epilepsy, and Multiple Sclerosis can reduce the symptoms and slow down the course of the disease but cannot reverse its effects or heal the patient. In the last two decades the transplantation approach, by means of stem cells of different origin, has been suggested for the treatment of neurological diseases. The choice of slightly different animal models and the differences in methods of stem cell preparation make it difficult to compare the results of transplantation experiments. Moreover, the translation of these results into clinical trials with human subjects is difficult and has so far met with little success. This review seeks to discuss the reasons for these difficulties by considering the differences between human and animal cells (including isolation, handling and transplantation) and between the human disease model and the animal disease model.

Cannabinoid type 2 receptor stimulation attenuates brain edema by reducing cerebral leukocyte infiltration following subarachnoid hemorrhage in rats

Early brain injury (EBI), following subarachnoid hemorrhage (SAH), comprises blood-brain barrier (BBB) disruption and consequent edema formation. Peripheral leukocytes can infiltrate the injured brain, thereby aggravating BBB leakage and neuroinflammation. Thus, anti-inflammatory pharmacotherapies may ameliorate EBI and provide neuroprotection after SAH. Cannabinoid type 2 receptor (CB2R) agonism has been shown to reduce neuroinflammation; however, the precise protective mechanisms remain to be elucidated. This study aimed to evaluate whether the selective CB2R agonist, JWH133 can ameliorate EBI by reducing brain-infiltrated leukocytes after SAH. Adult male Sprague-Dawley rats were randomly assigned to the following groups: sham-operated, SAH with vehicle, SAH with JWH133 (1.0mg/kg), or SAH with a co-administration of JWH133 and selective CB2R antagonist SR144528 (3.0mg/kg). SAH was induced by endovascular perforation, and JWH133 was administered 1h after surgery. Neurological deficits, brain water content, Evans blue dye extravasation, and Western blot assays were evaluated at 24h after surgery. JWH133 improved neurological scores and reduced brain water content; however, SR144528 reversed these treatment effects. JWH133 reduced Evans blue dye extravasation after SAH. Furthermore, JWH133 treatment significantly increased TGF-β1 expression and prevented an SAH-induced increase in E-selectin and myeloperoxidase. Lastly, SAH resulted in a decreased expression of the tight junction protein zonula occludens-1 (ZO-1); however, JWH133 treatment increased the ZO-1 expression. We suggest that CB2R stimulation attenuates neurological outcome and brain edema, by suppressing leukocyte infiltration into the brain through TGF-β1 up-regulation and E-selectin reduction, resulting in protection of the BBB after SAH.

Amelioration of oxidative stress and protection against early brain injury by astaxanthin after experimental subarachnoid hemorrhage

OBJECT.: Aneurysmal subarachnoid hemorrhage (SAH) causes devastating rates of mortality and morbidity. Accumulating studies indicate that early brain injury (EBI) greatly contributes to poor outcomes after SAH and that oxidative stress plays an important role in the development of EBI following SAH. Astaxanthin (ATX), one of the most common carotenoids, has a powerful antioxidative property. However, the potential role of ATX in protecting against EBI after SAH remains obscure. The goal of this study was to assess whether ATX can attenuate SAH-induced brain edema, blood-brain barrier permeability, neural cell death, and neurological deficits, and to elucidate whether the mechanisms of ATX against EBI are related to its powerful antioxidant property.

METHODS

Two experimental SAH models were established, including a prechiasmatic cistern SAH model in rats and a one-hemorrhage SAH model in rabbits. Both intracerebroventricular injection and oral administration of ATX were evaluated in this experiment. Posttreatment assessments included neurological scores, body weight loss, brain edema, Evans blue extravasation, Western blot analysis, histopathological study, and biochemical estimation.

RESULTS

It was observed that an ATX intracerebroventricular injection 30 minutes post-SAH could significantly attenuate EBI (including brain edema, blood-brain barrier disruption, neural cell apoptosis, and neurological dysfunction) after SAH in rats. Meanwhile, delayed treatment with ATX 3 hours post-SAH by oral administration was also neuroprotective in both rats and rabbits. In addition, the authors found that ATX treatment could prevent oxidative damage and upregulate the endogenous antioxidant levels in the rat cerebral cortex following SAH.

CONCLUSIONS

These results suggest that ATX administration could alleviate EBI after SAH, potentially through its powerful antioxidant property. The authors conclude that ATX might be a promising therapeutic agent for EBI following 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.

Assessment of cerebral circulation in the acute phase of subarachnoid hemorrhage using perfusion computed tomography

BACKGROUND AND PURPOSE

Primary brain damage, caused by acute ischemic changes during initial hemorrhage, is an important cause of death and disability following subarachnoid hemorrhage (SAH). However, the mechanism underlying the reduction in cerebral circulation in patients in the acute stage of SAH remains unclear. The goal of this study was to clarify this mechanism with the aid of perfusion computed tomography (CT).

METHODS

We prospectively evaluated 21 patients who had been undergone perfusion CT within 3 hours of SAH onset. Mean transit time (MTT) was estimated. Forty circular regions of interest 5 mm in diameter were delineated in the cortical region of the bilateral hemispheres on perfusion CT images. Neurological condition was graded with the Hunt and Hess scale, and initial CT findings were graded with the Fisher scale. We defined a good outcome as a modified Rankin scale (mRs) score of ≤2 at 3 months after SAH onset.

RESULTS

Global MTT was an independent predictor of outcome. The global MTT of patients with poor outcomes was longer than that of patients with good outcome. Furthermore, global MTT correlated significantly with Hunt & Hess grades, and disturbances in higher cerebral function.

CONCLUSION

Hemodynamic disturbances frequently occur after SAH. These abnormalities probably reflect the primary brain damage caused by initial hemorrhage. Perfusion CT is valuable for detecting hemodynamic changes in the acute stages of SAH.

Expression and cell distribution of neuroglobin in the brain tissue after experimental subarachnoid hemorrhage in rats: a pilot study

Neuroglobin (Ngb) is a member of the globin superfamily expressed mainly in the nervous system and retina of vertebrates. Accumulated evidence has clearly demonstrated that Ngb has a neuro-protective role enhancing cell viability under hypoxia and other types of oxidative stress. It was suggested that oxidant stress could play an important role in neuronal injury after subarachnoid hemorrhage (SAH). The present study aims to examine the expression of Ngb in the temporal cortex and its cellular localization after SAH. We used a prechiasmatic cistern model of SAH. Ngb expression was examined at 3, 6, 12, 24, 48, and 72 h after SAH by western blot analysis and real-time polymerase chain reaction (PCR). Immunohistochemistry and immunofluorescence were performed to detect the localization of Ngb. Real-time PCR demonstrated that Ngb mRNA levels increased from 3 h after SAH, peaked at 6 h. Western blot showed Ngb protein levels were significantly increased in SAH groups in the temporal cortex and reached the peak at 24 h after SAH. The immunohistochemical staining demonstrated that Ngb was weakly expressed in the cortex in the control group while the enhanced expression of Ngb could be detected in the SAH groups. In addition, immunofluorescence results revealed that the over-expressed Ngb was located in the neuronal and microglia cell cytoplasm. These findings indicated that Ngb might play an important neuro-protective effect after SAH.

Molecular alterations in the hippocampus after experimental subarachnoid hemorrhage

Patients with aneurysmal subarachnoid hemorrhage (SAH) frequently have deficits in learning and memory that may or may not be associated with detectable brain lesions. We examined mediators of long-term potentiation after SAH in rats to determine what processes might be involved. There was a reduction in synapses in the dendritic layer of the CA1 region on transmission electron microscopy as well as reduced colocalization of microtubule-associated protein 2 (MAP2) and synaptophysin. Immunohistochemistry showed reduced staining for GluR1 and calmodulin kinase 2 and increased staining for GluR2. Myelin basic protein staining was decreased as well. There was no detectable neuronal injury by Fluoro-Jade B, TUNEL, or activated caspase-3 staining. Vasospasm of the large arteries of the circle of Willis was mild to moderate in severity. Nitric oxide was increased and superoxide anion radical was decreased in hippocampal tissue. Cerebral blood flow, measured by magnetic resonance imaging, and cerebral glucose metabolism, measured by positron emission tomography, were no different in SAH compared with control groups. The results suggest that the etiology of loss of LTP after SAH is not cerebral ischemia but may be mediated by effects of subarachnoid blood such as oxidative stress and inflammation.

Astragaloside IV alleviates early brain injury following experimental subarachnoid hemorrhage in rats

Astragaloside IV, one of the main effective components isolated from Astragalus membranaceus, has multiple neuroprotective properties, while the effects of astragaloside IV on the attenuation of subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) and its possible mechanisms are unknown. In the present study, we aimed to determine whether astragaloside IV could inhibit oxidative stress, reduce neuronal apoptosis, and improve neurological deficits after experimental SAH in rats. Rats (n=68) were randomly divided into the following groups: Sham group, SAH group, SAH+vehicle group, and SAH+astragaloside IV group. Astragaloside IV or an equal volume of vehicle was administered at 1 h and 6 h after SAH, all the rats were subsequently sacrificed at 24 h after SAH. Mortality, neurological scores, and brain edema were assessed, biochemical tests and histological studies were also performed at that point. SAH induced an increase in the malondialdehyde (MDA) level, neuronal apoptosis, cleaved caspase 3, brain edema and decreased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Astragaloside IV treatment reversed these changes and improved neurobehavioral outcomes of SAH rats. Our findings suggested that astragaloside IV may alleviate EBI after SAH through antioxidative and anti-apoptotic effects.

Clinical application of perfusion computed tomography in neurosurgery

OBJECT

Currently, perfusion CT (PCT) is a valuable imaging technique that has been successfully applied to the clinical management of patients with ischemic stroke and aneurysmal subarachnoid hemorrhage (SAH). However, recent literature and the authors' experience have shown that PCT has many more important clinical applications in a variety of neurosurgical conditions. Therefore, the authors share their experiences of its application in various diseases of the cerebrovascular, neurotraumatology, and neurooncology fields and review the pertinent literature regarding expanding PCT applications for neurosurgical conditions, including pitfalls and future developments.

METHODS

A pertinent literature search was conducted of English-language articles describing original research, case series, and case reports from 1990 to 2011 involving PCT and with relevance and applicability to neurosurgical disorders.

RESULTS

In the cerebrovascular field, PCT is already in use as a diagnostic tool for patients suspected of having an ischemic stroke. Perfusion CT can be used to identify and define the extent of the infarct core and ischemic penumbra core, and thus aid patient selection for acute reperfusion therapy. For patients with aneurysmal SAH, PCT provides assessment of early brain injury, cerebral ischemia, and infarction, in addition to vasospasm. It may also be used to aid case selection for aggressive treatment of patients with poor SAH grade. In terms of oncological applications, PCT can be used as an imaging biomarker to assess angiogenesis and response to antiangiogenetic treatments, differentiate between glioma grades, and distinguish recurrent tumor from radiation necrosis. In the setting of traumatic brain injury, PCT can detect and delineate contusions at an early stage. In patients with mild head injury, PCT results have been shown to correlate with the severity and duration of postconcussion syndrome. In patients with moderate or severe head injury, PCT results have been shown to correlate with patients' functional outcome.

CONCLUSIONS

Perfusion CT provides quantitative and qualitative data that can add diagnostic and prognostic value in a number of neurosurgical disorders, and also help with clinical decision making. With emerging new technical developments in PCT, such as characterization of blood-brain barrier permeability and whole-brain PCT, this technique is expected to provide more and more insight into the pathophysiology of many neurosurgical conditions.

A murine model of subarachnoid hemorrhage

In this video publication a standardized mouse model of subarachnoid hemorrhage (SAH) is presented. Bleeding is induced by endovascular Circle of Willis perforation (CWp) and proven by intracranial pressure (ICP) monitoring. Thereby a homogenous blood distribution in subarachnoid spaces surrounding the arterial circulation and cerebellar fissures is achieved. Animal physiology is maintained by intubation, mechanical ventilation, and continuous on-line monitoring of various physiological and cardiovascular parameters: body temperature, systemic blood pressure, heart rate, and hemoglobin saturation. Thereby the cerebral perfusion pressure can be tightly monitored resulting in a less variable volume of extravasated blood. This allows a better standardization of endovascular filament perforation in mice and makes the whole model highly reproducible. Thus it is readily available for pharmacological and pathophysiological studies in wild type and genetically altered mice.

Targeted over-expression of endothelin-1 in astrocytes leads to more severe brain damage and vasospasm after subarachnoid hemorrhage

Background

Endothelin-1 (ET-1) is a potent vasoconstrictor, and astrocytic ET-1 is reported to play a role in the pathogenesis of cerebral ischemic injury and cytotoxic edema. However, it is still unknown whether astrocytic ET-1 also contributes to vasogenic edema and vasospasm during subarachnoid hemorrhage (SAH). In the present study, transgenic mice with astrocytic endothelin-1 over-expression (GET-1 mice) were used to investigate the pathophysiological role of ET-1 in SAH pathogenesis.

Results

The GET-1 mice experienced a higher mortality rate and significantly more severe neurological deficits, blood–brain barrier breakdown and vasogenic edema compared to the non-transgenic (Ntg) mice following SAH. Oral administration of vasopressin V_1a receptor antagonist, SR 49059, significantly reduced the cerebral water content in the GET-1 mice. Furthermore, the GET-1 mice showed significantly more pronounced middle cerebral arterial (MCA) constriction after SAH. Immunocytochemical analysis showed that the calcium-activated potassium channels and the phospho-eNOS were significantly downregulated, whereas PKC-α expression was significantly upregulated in the MCA of the GET-1 mice when compared to Ntg mice after SAH. Administration of ABT-627 (ET_A receptor antagonist) significantly down-regulated PKC-α expression in the MCA of the GET-1 mice following SAH.

Conclusions

The present study suggests that astrocytic ET-1 involves in SAH-induced cerebral injury, edema and vasospasm, through ET_A receptor and PKC-mediated potassium channel dysfunction. Administration of ABT-627 (ET_A receptor antagonist) and SR 49059 (vasopressin V_1a receptor antagonist) resulted in amelioration of edema and vasospasm in mice following SAH. These data provide a strong rationale to investigate SR 49059 and ABT-627 as therapeutic drugs for the treatment of SAH patients.

Nuclear factor-κB/Bcl-XL pathway is involved in the protective effect of hydrogen-rich saline on the brain following experimental subarachnoid hemorrhage in rabbits

Early brain injury (EBI), a significant contributor to poor outcome after subarachnoid hemorrhage (SAH), is intimately associated with neuronal apoptosis. Recently, the protective role of hydrogen (H2 ) in the brain has been widely studied, but the underlying mechanism remains elusive. Numerous studies have shown nuclear factor-κB (NF-κB) as a crucial survival pathway in neurons. Here we investigated the role of H2 in EBI following SAH, focusing on the NF-κB pathway. A double blood injection model was used to produce experimental SAH, and H2 -rich saline was injected intraperitoneally. NF-κB activity within the occipital cortex was measured. Immunofluorescence was performed to demonstrate the activation of NF-κB; Bcl-xL and cleaved caspase-3 were determined via Western blot. Gene expression of Bcl-xL was detected by real-time PCR, and TUNEL and Nissl staining were performed to illustrate brain injury in the occipital cortex. SAH induced a significant increase of cleaved caspase-3. Correspondingly, TUNEL staining demonstrated obvious neuronal apoptosis following SAH. In contrast, H2 treatment markedly increased NF-κB activity and the expression of Bcl-xL and decreased the level of cleaved caspase-3. Additionally, H2 treatment significantly reduced post-SAH neuronal apoptosis. The current study shows that H2 treatment alleviates EBI in the rabbits following SAH and that NF-κB/Bcl-xL pathway is involved in the protective role of H2 .

Chronic hydrocephalus after experimental subarachnoid hemorrhage

Chronic communicating hydrocephalus is a significant health problem affecting up to 20% of survivors of spontaneous subarachnoid hemorrhage (SAH). The development of new treatment strategies is hampered by the lack of well characterized disease models. This study investigated the incidence of chronic hydrocephalus by evaluating the temporal profile of intracranial pressure (ICP) elevation after SAH, induced by endovascular perforation in rats. Twenty-five adult male Sprague-Dawley rats (260-320 g) were subjected to either endovascular perforation or sham surgery. Five animals died after SAH induction. At 7, 14 and 21 days after surgery ICP was measured by stereotaxic puncture of the cisterna magna in SAH (n=10) and SHAM (n=10) animals. On day 21 T-maze test was performed and the number of alterations and latency to decision was recorded. On day 23, samples were processed for histological analyses. The relative ventricle area was evaluated in coronal Nissl stained sections. On day 7 after surgery all animals showed normal ICP. The absolute ICP values were significantly higher in SAH compared to SHAM animals on day 21 (8.26±4.53 mmHg versus 4.38±0.95 mmHg) but not on day 14. Observing an ICP of 10 mmHg as cut-off, 3 animals showed elevated ICP on day 14 and another animal on day 21. The overall incidence of ICP elevation was 40% in SAH animals. On day 21, results of T-maze testing were significantly correlated with ICP values, i.e. animals with elevated ICP showed a lower number of alterations and a delayed decision. Histology yielded a significantly higher (3.59 fold increased) relative ventricle area in SAH animals with ICP elevation compared to SAH animals without ICP elevation. In conclusion, the current study shows that experimental SAH leads to chronic hydrocephalus, which is associated with ICP elevation, behavioral alterations and ventricular dilation in about 40% of SAH animals.

Evidence that 20-HETE contributes to the development of acute and delayed cerebral vasospasm

Recent studies have indicated that arachidonic acid (AA) is metabolized by the cytochrome P450 4A (CYP4A) enzymes in cerebral arteries to produce 20-hydroxyeicosatetraenoic acid (20-HETE) and that this compound has effects on cerebral vascular tone that mimic those seen following subarachnoid hemorrhage (SAH). In this regard, 20-HETE is a potent constrictor of cerebral arteries that decreases the open state probability of Ca(2+)-activated K(+) channels through activation of protein kinase C (PKC). It increases the sensitivity of the contractile apparatus to Ca(2+) by activating PKC and rho kinase. The formation of 20-HETE is stimulated by angiotensin II (AII), endothelin, adenosine triphosphate (ATP) and serotonin, and inhibited by NO, CO and superoxide radicals. Inhibitors of the formation of 20-HETE block the myogenic response of cerebral arterioles to elevations in transmural pressure in vitro and autoregulation of cerebral blood flow (CBF) in vivo. 20-HETE also plays an important role in modulating the cerebral vascular responses to vasodilators (NO and CO) and vasoconstrictors (AII, endothelin, serotonin). Recent studies have indicated that the levels of 20-HETE in cerebrospinal fluid (CSF) increase in rats, dogs and human patients following SAH and that inhibitors of the synthesis of 20-HETE prevent the acute fall in CBF in rats and reverse delayed vasospasm in both dogs and rats. This review examines the evidence that an elevation in the production of 20-HETE contributes to the initial fall in CBF following SAH and the later development of delayed vasospasm.

Mechanisms of acute brain injury after subarachnoid hemorrhage

Brain injury after subarachnoid hemorrhage (SAH) is a biphasic event with an acute ischemic insult at the time of the initial bleed and secondary events such as cerebral vasospasm 3 to 7 days later. Although much has been learned about the delayed effects of SAH, less is known about the mechanisms of acute SAH-induced injury. Distribution of blood in the subarachnoid space, elevation of intracranial pressure, reduced cerebral perfusion and cerebral blood flow (CBF) initiates the acute injury cascade. Together they lead to direct microvascular injury, plugging of vessels and release of vasoactive substances by platelet aggregates, alterations in the nitric oxide (NO)/nitric oxide synthase (NOS) pathways and lipid peroxidation. This review will summarize some of these mechanisms that contribute to acute cerebral injury after SAH.

Hypothermia as a neuroprotective strategy in subarachnoid hemorrhage: a pathophysiological review focusing on the acute phase

Aneurysmal subarachnoid hemorrhage (SAH) remains a very prevalent challenge in neurosurgery associated with a high morbidity and mortality due to the lack of specific treatment modalities. The prognosis of SAH patients depends primarily on three factors: (i) the severity of the initial bleed, (ii) the endovascular or neurosurgical procedure to occlude the aneurysm and (iii) the occurrence of late sequelae, namely delayed ischemic neurological deficits due to cerebral vasospasm. While neurosurgeons and interventionalists have put significant efforts in minimizing periprocedural complications and a multitude of investigators have been devoted to the research on chronic vasospasm, the acute phase of SAH has not been studied in comparable detail. In various experimental studies during the past decade, hypothermia has been shown to reduce neuronal damage after ischemia, traumatic brain injury and other cerebrovascular diseases. Clinically, only some of these encouraging results could be reproduced. This review analyses results of studies on the effects of hypothermia on SAH with special respect to the acute phase in an experimental setting. Based on the available data, some considerations for the application of mild to moderate hypothermia in patients with subarachnoid hemorrhage are given.

Vascular aspects of neuroprotection

It is being increasingly suggested that the microcirculation, which is known to be in a large part responsible for maintaining an adequate and constant microenvironment for function of the central nervous system, functions as part of a neurovascular unit. The neurovascular unit includes neurons, astrocytes and elements of capillaries. The cerebral circulation exhibits unique functional characteristics and critical elements for the pathogenesis of cerebrovascular disease. For example, the blood-brain barrier formed by epithelial-like high resistance tight junctions within the endothelium is a key feature of microvessels of the central nervous system. Alterations in the microcirculation after ischemia/reperfusion include disruption of the blood-brain barrier, edema and swelling of perivascular astrocyte foot processes, decrease in arteriole endothelium-dependent relaxation and reduced inwardly-rectifying potassium channel function, altered expression of proteases and matrix metalloproteinases, increased inflammatory mediators and inflammation. Experiments studying the microcirculation in ischemia are few compared with those examining neuroprotection, although the two overlap because protection of the microcirculation might achieve some degree of neuroprotection and both processes may be mediated by at least some mechanisms in common.

Inhibiting HIF-1α by 2ME2 ameliorates early brain injury after experimental subarachnoid hemorrhage in rats

Although hypoxia-inducible factor-1α (HIF-1α) has been extensively studied in brain injury following hypoxia-ischemia, the role of HIF-1α in early brain injury (EBI) after subarachnoid hemorrhage (SAH) remains unclear. The present study was under taken to investigate a potential role of HIF-1α in EBI after SAH. Rats (n=60) were randomly divided into sham+vehicle, SAH+2-methoxyestradiol (2ME2), and SAH+vehicle groups. The SAH model was induced by endovascular perforation and all the rats were subsequently sacrificed at 24h after SAH. We found that treatment with 2ME2 suppressed the expression of HIF-1α, BNIP3 and VEGF and reduced cell apoptosis, blood-brain barrier (BBB) permeability, brain edema, and neurologic scores. Double fluorescence labeling revealed that HIF-1α was expressed predominantly in the nuclei of neurons and TUNEL-positive cells. Our work demonstrated that HIF-1α may play a role in EBI after SAH, causing cell apoptosis, BBB disruption, and brain edema by up-regulating its downstream targets, BNIP3 and VEGF. These effects were blocked by the HIF-1α inhibitor, 2ME2.

Aneurysmal subarachnoid hemorrhage models: do they need a fix?

The discovery of tissue plasminogen activator to treat acute stroke is a success story of research on preventing brain injury following transient cerebral ischemia (TGI). That this discovery depended upon development of embolic animal model reiterates that proper stroke modeling is the key to develop new treatments. In contrast to TGI, despite extensive research, prevention or treatment of brain injury following aneurysmal subarachnoid hemorrhage (aSAH) has not been achieved. A lack of adequate aSAH disease model may have contributed to this failure. TGI is an important component of aSAH and shares mechanism of injury with it. We hypothesized that modifying aSAH model using experience acquired from TGI modeling may facilitate development of treatment for aSAH and its complications. This review focuses on similarities and dissimilarities between TGI and aSAH, discusses the existing TGI and aSAH animal models, and presents a modified aSAH model which effectively mimics the disease and has a potential of becoming a better resource for studying the brain injury mechanisms and developing a treatment.

Magnesium treatment for neuroprotection in ischemic diseases of the brain

This article reviews experimental and clinical data on the use of magnesium as a neuroprotective agent in various conditions of cerebral ischemia. Whereas magnesium has shown neuroprotective properties in animal models of global and focal cerebral ischemia, this effect could not be reproduced in a large human stroke trial. These conflicting results may be explained by the timing of treatment. While treatment can be started before or early after ischemia in experimental studies, there is an inevitable delay of treatment in human stroke. Magnesium administration to women at risk for preterm birth has been investigated in several randomized controlled trials and was found to reduce the risk of neurological deficits for the premature infant. Postnatal administration of magnesium to babies after perinatal asphyxia has been studied in a number of controlled clinical trials. The results are promising but the trials have, so far, been underpowered. In aneurysmal subarachnoid hemorrhage (SAH), cerebral ischemia arises with the onset of delayed cerebral vasospasm several days after aneurysm rupture. Similar to perinatal asphyxia in impending preterm delivery, treatment can be started prior to ischemia. The results of clinical trials are conflicting. Several clinical trials did not show an additive effect of magnesium with nimodipine, another calcium antagonist which is routinely administered to SAH patients in many centers. Other trials found a protective effect after magnesium therapy. Thus, it may still be a promising substance in the treatment of secondary cerebral ischemia after aneurysmal SAH. Future prospects of magnesium therapy are discussed.

Interference of apoptosis in the pathophysiology of subarachnoid hemorrhage

Programmed cell death is crucial for the correct development of the organism and the clearance of harmful cells like tumor cells or autoreactive immune cells. Apoptosis is initiated by the activation of cell death receptors and in most cases it is associated with the activation of the cysteine proteases, which lead to apoptotic cell death. Cells shrink, chromatin clumps and forms a large, sharply demarcated, crescent-shaped or round mass; the nucleus condenses, apoptotic bodies are formed and eventually dead cells are engulfed by a neighboring cell or cleared by phagocytosis. The authors have summarized the most important data concerning apoptosis in subarachnoid hemorrhage that have been issued in the medical literature in the last 20 years.

Role of SCH79797 in maintaining vascular integrity in rat model of subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Plasma thrombin concentration is increased after subarachnoid hemorrhage (SAH). However, the role of thrombin receptor (protease-activated receptor-1 [PAR-1]) in endothelial barrier disruption has not been studied. The aims of this study were to investigate the role of PAR-1 in orchestrating vascular permeability and to assess the potential therapeutics of a PAR-1 antagonist, SCH79797, through maintaining vascular integrity.

METHODS

SCH79797 was injected intraperitoneally into male Sprauge-Dawley rats undergoing SAH by endovascular perforation. Assessment was conducted at 24 hours after SAH for brain water content, Evans blue content, and neurobehavioral testing. To explore the role of PAR-1 activation and the specific mechanism of SCH79797's effect after SAH, Western blot, immunoprecipitation, and immunofluorescence of hippocampus tissue were performed. A p21-activated kinase-1 (PAK1) inhibitor, IPA-3, was used to explore the underlying protective mechanism of SCH79797.

RESULTS

At 24 hours after SAH, animals treated with SCH79797 demonstrated a reduction in brain water content, Evans blue content, and neurobehavioral deficits. SCH79797 also attenuated PAR-1 expression and maintained the level of vascular endothelial-cadherin, an important component of adherens junctions. Downstream to PAR-1, c-Src-dependent activation of p21-activated kinase-1 led to an increased serine/threonine phosphorylation of vascular endothelial-cadherin; immunoprecipitation results revealed an enhanced binding of phosphorylated vascular endothelial-cadherin with endocytosis orchestrator β-arrestin-2. These pathological states were suppressed after SCH79797 treatment.

CONCLUSIONS

PAR-1 activation after SAH increases microvascular permeability, at least, partly through a PAR-1-c-Src-p21-activated kinase-1-vascular endothelial-cadherin phosphorylation pathway. Through suppressing PAR-1 activity, SCH79797 plays a protective role in maintaining microvascular integrity after SAH.

Acute microvascular changes after subarachnoid hemorrhage and transient global cerebral ischemia

Subarachnoid hemorrhage and transient global cerebral ischemia result in similar pathophysiological changes in the cerebral microcirculation. These changes include microvascular constriction, increased leukocyte-endothelial interactions, blood brain barrier disruption, and microthrombus formation. This paper will look at various animal and preclinical studies that investigate these various microvascular changes, perhaps providing insight in how these microvessels can be a therapeutic target in both subarachnoid hemorrhage and transient global cerebral ischemia.

A low mortality rat model to assess delayed cerebral vasospasm after experimental subarachnoid hemorrhage

OBJECTIVE

To characterize and establish a reproducible model that demonstrates delayed cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) in rats, in order to identify the initiating events, pathophysiological changes and potential targets for treatment.

METHODS

Twenty-eight male Sprague-Dawley rats (250 - 300 g) were arbitrarily assigned to one of two groups - SAH or saline control. Rat subarachnoid hemorrhage in the SAH group (n=15) was induced by double injection of autologous blood, 48 hr apart, into the cisterna magna. Similarly, normal saline (n=13) was injected into the cisterna magna of the saline control group. Rats were sacrificed on day five after the second blood injection and the brains were preserved for histological analysis. The degree of vasospasm was measured using sections of the basilar artery, by measuring the internal luminal cross sectional area using NIH Image-J software. The significance was tested using Tukey/Kramer's statistical analysis.

RESULTS

After analysis of histological sections, basilar artery luminal cross sectional area were smaller in the SAH than in the saline group, consistent with cerebral vasospasm in the former group. In the SAH group, basilar artery internal area (.056 μm ± 3) were significantly smaller from vasospasm five days after the second blood injection (seven days after the initial blood injection), compared to the saline control group with internal area (.069 ± 3; p=0.004). There were no mortalities from cerebral vasospasm.

CONCLUSION

The rat double SAH model induces a mild, survivable, basilar artery vasospasm that can be used to study the pathophysiological mechanisms of cerebral vasospasm in a small animal model. A low and acceptable mortality rate is a significant criterion to be satisfied for an ideal SAH animal model so that the mechanisms of vasospasm can be elucidated. Further modifications of the model can be made to adjust for increased severity of vasospasm and neurological exams.

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.

Cerebral microvasculature is an early target of subarachnoid hemorrhage

Most subarachnoid hemorrhage (SAH) patients exhibit clinical signs of cerebral ischemia at admission but no angiographic vasospasm. Consequently, the source of early cerebral ischemia is not understood. Parenchymal microvessels may contribute to early cerebral ischemia, but the low resolution of current imaging has prevented their analysis in SAH patients. Animal studies demonstrated that early after SAH structure and function of parenchymal vessels are compromised to the level that may very well contribute to early ischemia. We review these studies.

Calcium and potassium channels in experimental subarachnoid hemorrhage and transient global ischemia

Healthy cerebrovascular myocytes express members of several different ion channel families which regulate resting membrane potential, vascular diameter, and vascular tone and are involved in cerebral autoregulation. In animal models, in response to subarachnoid blood, a dynamic transition of ion channel expression and function is initiated, with acute and long-term effects differing from each other. Initial hypoperfusion after exposure of cerebral vessels to oxyhemoglobin correlates with a suppression of voltage-gated potassium channel activity, whereas delayed cerebral vasospasm involves changes in other potassium channel and voltage-gated calcium channels expression and function. Furthermore, expression patterns and function of ion channels appear to differ between main and small peripheral vessels, which may be key in understanding mechanisms behind subarachnoid hemorrhage-induced vasospasm. Here, changes in calcium and potassium channel expression and function in animal models of subarachnoid hemorrhage and transient global ischemia are systematically reviewed and their clinical significance discussed.

Subarachnoid hemorrhage-induced hydrocephalus in rats

BACKGROUND AND PURPOSE

Hydrocephalus is an important complication of subarachnoid hemorrhage (SAH). We investigated the occurrence of acute hydrocephalus in a rat SAH model.

METHODS

SAH was induced by endovascular perforation in adult male Sprague-Dawley rats (n=36). Sham rats (n=8) underwent the same procedure without perforation. MRI was performed 24 hours after SAH and the volume of the ventricular system and extent of T2* hypointensity lesions were measured. We defined hydrocephalus as ventricular volume > +3 SDs above the mean in sham animals. SAH grade was determined and brains were used for histology, immunohistochemistry, Perls staining, and Western blot analysis. Ventricular wall damage was defined as percentage of ependymal surface disruption.

RESULTS

All surviving rats (n=27) after SAH had ventricular enlargement (33.6 ± 4.7 versus 13.5 ± 1.4 mm(3) in sham animals, P<0.01). Ventricular volume correlated with SAH severity (r=0.48; P<0.05). Out of 27 SAH rats, 12 demonstrated hydrocephalus and all had intraventricular blood accumulation. Rats with hydrocephalus had more severe ventricular wall damage (7.4 ± 1.2%) than the sham animals (0.6 ± 0.2%; P<0.01) and rats without hydrocephalus (1.1 ± 0.2%; P<0.01). Periventricular iron deposition was observed and heme oxygenase-1 and Iba-1 expression were markedly increased in hydrocephalus rats.

CONCLUSIONS

SAH causes ventricular enlargement in a rat endovascular perforation model, with hydrocephalus occurring in 44% of animals at 24 hours. Rats with hydrocephalus had more severe SAH, intraventricular hemorrhage, and greater ventricular wall damage.

A modified double injection model of cisterna magna for the study of delayed cerebral vasospasm following subarachnoid hemorrhage in rats

Delayed cerebral vasospasm following subarachnoid hemorrhage (SAH) is a serious medical complication, characterized by constriction of cerebral arteries leading to varying degrees of cerebral ischemia. Numerous clinical and experimental studies have been performed in the last decades; however, the pathophysiologic mechanism of cerebral vasospasm after SAH still remains unclear. Among a variety of experimental SAH models, the double hemorrhage rat model involving direct injection of autologous arterial blood into the cisterna magna has been used most frequently for the study of delayed cerebral vasospasm following SAH in last years. Despite the simplicity of the technique, the second blood injection into the cisterna magna may result in brainstem injury leading to high mortality. Therefore, a modified double hemorrhage model of cisterna magna has been developed in rat recently. We describe here step by step the surgical technique to induce double SAH and compare the degree of vasospasm with other cisterna magna rat models using histological assessment of the diameter and cross-sectional area of the basilar artery.

Cushing's mechanism maintains cerebral perfusion pressure in experimental subarachnoid haemorrhage

Mortality following subarachnoid haemorrhage (SAH) is high, especially within the first 48 h. Poor outcome is predicted by high intracranial pressure which causes diminished cerebral perfusion pressure unless a compensatory increase in mean arterial blood pressure occurs. Therefore blood pressure elevation can be protective following subarachnoid haemorrhage despite the potential for rebleeding. This study investigated blood pressure responses to SAH and the impact on cerebral perfusion pressure and outcome, as demonstrated by two experimental models. Various blood pressure responses were demonstrated, both at the ictus and within the following 5h. Elevated MABP at the ictus and at 2h following experimental SAH was associated with maintenance of CPP in the presence of raised ICP. Poor outcome (arrest of the cerebral circulation) was predicted by failure of MABP to increase significantly above sham levels within 2h of SAH. Rat SAH provides relatively inexpensive models to investigate physiological mechanisms that maintain cerebral perfusion in the presence of intracranial hypertension.

Delayed cerebral ischaemia after subarachnoid haemorrhage: looking beyond vasospasm

Despite improvements in the clinical management of aneurysmal subarachnoid haemorrhage over the last decade, delayed cerebral ischaemia (DCI) remains the single most important cause of morbidity and mortality in those patients who survive the initial bleed. The pathological mechanisms underlying DCI are still unclear and the calcium channel blocker nimodipine remains the only therapeutic intervention proven to improve functional outcomes after SAH. The recent failure of the drug clazosentan to improve functional outcomes despite reducing vasoconstriction has moved the focus of research into DCI away from cerebral artery constriction towards a more multifactorial aetiology. Novel pathological mechanisms have been suggested, including damage to cerebral tissue in the first 72 h after aneurysm rupture ('early brain injury'), cortical spreading depression, and microthrombosis. A greater understanding of the significance of these pathophysiological mechanisms and potential genetic risk factors is required, if new approaches to the prophylaxis, diagnosis, and treatment of DCI are to be developed. Furthermore, objective and reliable biomarkers are needed for the diagnosis of DCI in poor grade SAH patients requiring sedation and to assess the efficacy of new therapeutic interventions. The purpose of this article is to appraise these recent advances in research into DCI, relate them to current clinical practice, and suggest potential novel avenues for future research.

Etiology of stroke and choice of models

Animal models of stroke contribute to the development of better stroke prevention and treatment through studies investigating the pathophysiology of different stroke subtypes and by testing promising treatments before trials in humans. There are two broad types of animal models: those in which stroke is induced through artificial means, modeling the consequences of a vascular insult but not the vascular pathology itself; and those in which strokes occur spontaneously. Most animal models of stroke are in rodents due to cost, ethical considerations, availability of standardized neurobehavioral assessments, and ease of physiological monitoring. While there are similarities in cerebrovascular anatomy and pathophysiology between rodents and humans, there are also important differences, including brain size, length and structure of perforating arteries, and gray to white matter ratio, which is substantially lower in humans. The wide range of rodent models of stroke includes models of global and focal ischemia, and of intracerebral and sub-arachnoid hemorrhage. The most widely studied model of spontaneous stroke is the spontaneously hypertensive stroke-prone rat, in which the predominant lesions are small subcortical infarcts resulting from a vascular pathology similar to human cerebral small vessel disease. Important limitations of animal models of stroke - they generally model only certain aspects of the disease and do not reflect the heterogeneity in severity, pathology and comorbidities of human stroke - and key methodological issues (especially the need for adequate sample size, randomization, and blinding in treatment trials) must be carefully considered for the successful translation of pathophysiological concepts and therapeutics from bench to bedside.

A new percutaneous model of Subarachnoid Haemorrhage in rats

OBJECTIVE

Describe the results obtained with a new percutaneous, intracisternal model of Subarachnoid Haemorrhage (SAH) in Wistar rats by a single injection of non-heparinised, autologous blood.

METHODS

Once anaesthetized the rat was fixed prone in a stereotaxic frame. After identifying the projection of the occipital bone, the needle of the stereotaxic frame aspirated towards the foramen magnum until it punctured through the atlanto-occipital membrane and obtained cerebrospinal fluid. Autologous blood (100 μl) was withdrawn from the tail and injected intracisternally. This procedure was repeated in the sham group, injecting 100 μl of isotonic saline. On the fifth day post-intervention, the rats were anaesthetized and the brain was exposed. After a lethal injection of ketamine the brain was explanted and fixed in paraformaldehyde. Gross and microscopic inspection of the slices revealed the existence or non-existence of pathological findings.

RESULTS

A total of 26 rats were operated on (13 in the SAH group/13 in the sham group). The average time between obtaining the blood and the start of the intracisternal injection was 10 (±1.2)s. The mortality rate was 16.12%. Intra- and extraparenchymal ischemic-haemorrhagic lesions were found in three animals (23.07%)--all from the SAH group--with ischemic neuronal cell injury detected in two of the three.

CONCLUSIONS

The new murine model of SAH is easy to perform, with low mortality, minimally invasive, which makes it interesting for future studies on vasospasm-related delayed SAH complications.

Inhibition of c-Jun N-terminal kinase prevents blood-brain barrier disruption and normalizes the expression of tight junction proteins clautin-5 and ZO-1 in a rat model of subarachnoid hemorrhage

BACKGROUND

The c-Jun N-terminal kinase (JNK) proteins are encoded by three genes (JNK1, JNK2, and JNK3), giving rise to multiple isoforms via alternative splicing. JNK inhibition using a chemical inhibitor SP600125 confers neuroprotection in an animal model of subarachnoid hemorrhage (SAH). The aim of this study is to investigate whether the protective effects of SP600125 were associated with modulation of tight junction proteins including claudin-5 and ZO-1 and to define which JNK isoforms were involved in the early brain injury after SAH.

METHODS

Seventy-five male Sprague Dawley rats (weighing 300-350 g) were randomly assigned to five groups (n = 15): (1) sham, (2) SAH, (3) SAH + DMSO (dimethyl sulfoxide), (4) SAH + 10 mg/kg SP600125, and (5) SAH + 30 mg/kg SP600125. SP600125 or DMSO was injected intraperitoneally 1 h before and 6 h after the induction of SAH. Animals from all the groups were killed 24 h after SAH, and brain tissues were dissected and subjected to electron microscopic examination, Western blot analysis, and histological evaluation.

RESULTS

SP600125 pretreatment restored tight junctions and attenuated blood-brain barrier (BBB) disruption and cerebral edema after SAH, coupled with reduced apoptosis in the cerebral cortex. SP600125 exposure restored the reduced expression of both claudin-5 and ZO-1 following SAH and normalized the levels of JNK1 and JNK3.

CONCLUSION

Our data demonstrate that the JNK signaling plays an important role in the regulation of tight junction proteins and BBB integrity, and thus represents a promising target against brain injuries after SAH.

Brain edema formation correlates with perfusion deficit during the first six hours after experimental subarachnoid hemorrhage in rats

Background

Severe brain edema is observed in a number of patients suffering from subarachnoid hemorrhage (SAH). Little is known about its pathogenesis and time-course in the first hours after SAH. This study was performed to investigate the development of brain edema and its correlation with brain perfusion after experimental SAH.

Methods

Male Sprague–Dawley rats, randomly assigned to one of six groups (n = 8), were subjected to SAH using the endovascular filament model or underwent a sham operation. Animals were sacrificed 15, 30, 60, 180 or 360 minutes after SAH. Intracranial pressure (ICP), mean arterial blood pressure (MABP), cerebral perfusion pressure (CPP) and bilateral local cerebral blood flow (LCBF) were continuously measured. Brain water content (BWC) was determined by the wet/dry-weight method.

Results

After SAH, CPP and LCBF rapidly decreased. The decline of LCBF markedly exceeded the decline of CPP and persisted until the end of the observation period. BWC continuously increased. A significant correlation was observed between the BWC and the extent of the perfusion deficit in animals sacrificed after 180 and 360 minutes.

Conclusions

The significant correlation with the perfusion deficit after SAH suggests that the development of brain edema is related to the extent of ischemia and acute vasoconstriction in the first hours after SAH.

Screen-imaging guidance using a modified portable video macroscope for middle cerebral artery occlusion

The use of operating microscopes is limited by the focal length. Surgeons using these instruments cannot simultaneously view and access the surgical field and must choose one or the other. The longer focal length (more than 1 000 mm) of an operating telescope permits a position away from the operating field, above the surgeon and out of the field of view. This gives the telescope an advantage over an operating microscope. We developed a telescopic system using screen-imaging guidance and a modified portable video macroscope constructed from a Computar MLH-10 × macro lens, a DFK-21AU04 USB CCD Camera and a Dell laptop computer as monitor screen. This system was used to establish a middle cerebral artery occlusion model in rats. Results showed that magnification of the modified portable video macroscope was appropriate (5–20 ×) even though the Computar MLH-10 × macro lens was placed 800 mm away from the operating field rather than at the specified working distance of 152.4 mm with a zoom of 1–40 ×. The screen-imaging telescopic technique was clear, life-like, stereoscopic and matched the actual operation. Screen-imaging guidance led to an accurate, smooth, minimally invasive and comparatively easy surgical procedure. Success rate of the model establishment evaluated by neurological function using the modified neurological score system was 74.07%. There was no significant difference in model establishment time, sensorimotor deficit and infarct volume percentage. Our findings indicate that the telescopic lens is effective in the screen surgical operation mode referred to as “long distance observation and short distance operation” and that screen-imaging guidance using an modified portable video macroscope can be utilized for the establishment of a middle cerebral artery occlusion model and micro-neurosurgery.

p53-induced uncoupling expression of aquaporin-4 and inwardly rectifying K+ 4.1 channels in cytotoxic edema after subarachnoid hemorrhage

AIMS

To investigate the mechanism behind cytotoxic edema formation following subarachnoid hemorrhage (SAH).

METHODS

We explored the role of aquaporin-4 (AQP4), inwardly rectifying K(+) 4.1 (Kir4.1) channels and their upstream orchestrators p53 and p38MAPK in this process. A p53 inhibitor, pifithrin-α (PFT-α) was administered intraperitoneally to rats undergoing SAH by endovascular perforation. Totally, 98 male SD rats were categorized into sham, SAH, SAH+ dimethyl sulfoxide (DMSO), SAH+ 0.2 or 2.0 mg/kg PFT-α groups. At 24 h after SAH, MRI (diffusion-weighted imaging [DWI]), immunohistochemistry, and Western blot were used.

RESULTS

MRI (DWI) showed a significant cytotoxic edema in the brain following SAH with PFT-α therapy reducing it. Immunohistochemistry and Western blot showed an increased level of p53, phosphorylated-p38MAPK and AQP4 and a reduced level of Kir4.1; all of which could be reversed following PFT-α treatment. Treble labeling staining revealed colocalization of p53 with phosphorylated-p38MAPK and unmatched expression of AQP4 and Kir4.1 within astrocyte cells.

CONCLUSION

These results indicated p53 mediates the formation of cytotoxic edema in the brain following SAH; an uncoupling expression of AQP4 and Kir4.1 on astrocytic end feet orchestrated by p38MAPK was partly responsible.