Vascular neural network in subarachnoid hemorrhage

Dual-energy X-ray absorptiometry for detecting neurogenic pulmonary edema in a mouse model of subarachnoid hemorrhage

Murine subarachnoid hemorrhage (SAH) induced using the filament perforation method is a useful in vivo experimental model to investigate the pathophysiological mechanisms in the brain underlying SAH. However, identifying mice with comorbid acute neurogenic pulmonary edema (NPE), a life-threatening systemic consequence often induced by SAH, in this model is difficult without histopathological investigations. Herein, we present an imaging procedure involving dual-energy X-ray absorptiometry (DXA) to identify NPE in a murine model of SAH. We quantified the lung lean mass (LM) and compared the relationship between micro-computed tomography (CT) evidence of Hounsfield unit (HU) values and histopathological findings of PE. Of the 85 mice with successful induction of SAH by filament perforation, 16 (19%) had NPE, as verified by postmortem histology. The DXA-LM values correlate well with CT-HU levels (r = 0.63, p < 0.0001). Regarding the relationship between LM and HU in mice with post-SAH NPE, the LM was positively associated with HU values (r2 = 0.43; p = 0.0056). A receiver operating characteristics curve of LM revealed a sensitivity of 87% and specificity of 57% for detecting PE, with a similar area under the curve as the HU (0.79 ± 0.06 vs. 0.84 ± 0.07; p = 0.21). These data suggest that confirming acute NPE using DXA-LM is a valuable method for selecting a clinically relevant murine NPE model that could be used in future experimental SAH studies.

Subarachnoid Hemorrhage Depletes Calcitonin Gene-Related Peptide Levels of Trigeminal Neurons in Rat Dura Mater

Subarachnoid hemorrhage (SAH) remains a major cause of cerebrovascular morbidity, eliciting severe headaches and vasospasms that have been shown to inversely correlate with vasodilator calcitonin gene-related peptide (CGRP) levels. Although dura mater trigeminal afferents are an important source of intracranial CGRP, little is known about the effects of SAH on these neurons in preclinical models. The present study evaluated changes in CGRP levels and expression in trigeminal primary afferents innervating the dura mater 72 h after experimentally induced SAH in adult rats. SAH, eliciting marked damage revealed by neurological examination, significantly reduced the density of CGRP-immunoreactive nerve fibers both in the dura mater and the trigeminal caudal nucleus in the medulla but did not affect the total dural nerve fiber density. SAH attenuated ex vivo dural CGRP release by ~40% and in the trigeminal ganglion, reduced both CGRP mRNA levels and the number of highly CGRP-immunoreactive cell bodies. In summary, we provide novel complementary evidence that SAH negatively affects the integrity of the CGRP-expressing rat trigeminal neurons. Reduced CGRP levels suggest likely impaired meningeal neurovascular functions contributing to SAH complications. Further studies are to be performed to reveal the importance of impaired CGRP synthesis and its consequences in central sensory processing.

Simple procedure for assessing diffuse subarachnoid hemorrhage successfully created using filament perforation method in mice

The murine model of subarachnoid hemorrhage (SAH) is a valuable experimental tool for investigating molecular and cellular mechanisms, and the endovascular filament perforation technique can be used to simulate prominent pathophysiological features observed after human SAH; however, current validation methods for assessing an appropriate SAH model are limited. Here, we introduce a simple procedure for selecting a mouse model of diffuse SAH. SAH was induced in 24 mice using a standard filament perforation method. After confirming survival at 24 h, SAH was scored 0-1 based on T2*-weighted images on whole-brain magnetic resonance imaging (MRI) and visual surveillance of the cisterna magna (CM) through the dura mater. The CM-based SAH grading correlated well with a reference parameter defined by extracted brain (r2 = 0.53, p < 0.0001). The receiver operating characteristic curve revealed a sensitivity of 85% and a specificity of 91% for detecting diffuse SAH, with a similar area under the curve (0.89 ± 0.06 [standard error of the mean]) as the MRI-based grading (0.72 ± 0.10, p = 0.12). Our data suggest that confirming an SAH clot in the CM is a valuable way to select a clinically relevant diffuse SAH model that can be used in future experimental studies.

Pathophysiology, Management, and Therapeutics in Subarachnoid Hemorrhage and Delayed Cerebral Ischemia: An Overview

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke resulting from the rupture of an arterial vessel within the brain. Unlike other stroke types, SAH affects both young adults (mid-40s) and the geriatric population. Patients with SAH often experience significant neurological deficits, leading to a substantial societal burden in terms of lost potential years of life. This review provides a comprehensive overview of SAH, examining its development across different stages (early, intermediate, and late) and highlighting the pathophysiological and pathohistological processes specific to each phase. The clinical management of SAH is also explored, focusing on tailored treatments and interventions to address the unique pathological changes that occur during each stage. Additionally, the paper reviews current treatment modalities and pharmacological interventions based on the evolving guidelines provided by the American Heart Association (AHA). Recent advances in our understanding of SAH will facilitate clinicians' improved management of SAH to reduce the incidence of delayed cerebral ischemia in patients.

A 90-Day Prognostic Model Based on the Early Brain Injury Indicators after Aneurysmal Subarachnoid Hemorrhage: the TAPS Score

This study aimed to establish a new scoring model based on the early brain injury (EBI) indicators to predict the 90-day functional outcomes in patients with aneurysmal subarachnoid hemorrhage (aSAH). We retrospectively enrolled 825 patients and prospectively enrolled 108 patients with aSAH who underwent surgical clipping or endovascular coiling (derivation cohort = 640; validation cohort = 185; prospective cohort = 108) in our institute. We established a logistic regression model based on independent risk factors associated with 90-day unfavorable outcomes. The discrimination of the prognostic model was assessed by the area under the curve in a receiver operating characteristic curve analysis. The Hosmer-Lemeshow goodness-of-fit test and a calibration plot were used to evaluate the calibration of the prediction model. The developed scoring model named "TAPS" (total score, 0-7 points) included the following admission variables: age > 55 years old, WFNS grade of 4-5, mFS grade of 3-4, Graeb score of 5-12, white blood cell count > 11.28 × 109/L, and surgical clipping. The model showed good discrimination with the area under the curve in the derivation, validation, and prospective cohorts which were 0.816 (p < 0.001, 95%CI = 0.77-0.86), 0.810 (p < 0.001, 95%CI = 0.73-0.90), and 0.803 (p < 0.001, 95%CI = 0.70-0.91), respectively. The model also demonstrated good calibration (Hosmer-Lemeshow goodness-of-fit test: X2 = 1.75, df = 8, p = 0.988). Compared with other predictive models, TAPS is an easy handle tool for predicting the 90-day unfavorable outcomes of aSAH patients, which can help clinicians better understand the concept of EBI and quickly identify those patients at risk of poor prognosis, providing more positive treatment strategies. Trial registration: NCT04785976. Registered 5 March 2021-retrospectively registered, http://www.clinicaltrials.gov .

Microscopic observation of morphological changes in cerebral arteries and veins in hyperacute phase after experimental subarachnoid hemorrhage: an in-vivo analysis

This observational study examined morphological changes in superficial cerebral arteries and veins, which were correlated with increased intracranial pressure (ICP)-dependent and -independent hypoperfusion in hyperacute phase after subarachnoid hemorrhage (SAH). The prechiasmatic injection model was used, and 32 male Sprague-Dawley rats were divided into the sham-operated, saline-injected (V group, ICP increase), and arterial blood-injected (SAH group, subarachnoid blood and plus increase) groups. Morphological changes in cortical arteries and veins were observed through the cranial window with a microscope before and up to 10 min after the injection. At 24 h, the stenotic and obstructive cortical arteries and veins were counted. After 6 min, 60% of rats in the V group showed vasodilatation, whereas all rats in the SAH group demonstrated vasodilation and vasoconstriction (arterial instability) within 10 min. Similar acute venous congestive changes were observed within 10 min in the V and SAH groups. At 24 h, stenotic and obstructive arteries and veins were observed in the SAH group. Neurological deteriorations were observed at 1 h in the V and SAH groups, and at 23 h in the SAH group. The sham-operated group showed no evident vascular changes and neurological deterioration. The same phenomena, including arterial changes after 6 min and immediate venous changes in the V and SAH groups, may have resulted from ICP increase, whereas subarachnoid blood-related factors produced arterial instability within 5 min after blood injection. Subarachnoid blood plays a significant role in hyperacute SAH pathophysiology in addition to ICP increase.

Intracranial Venous Alteration in Patients With Aneurysmal Subarachnoid Hemorrhage: Protocol for the Prospective and Observational SAH Multicenter Study (SMS)

Background

Arterial vasospasm has been ascribed as the responsible etiology of delayed cerebral infarction in patients with aneurysmal subarachnoid hemorrhage (aSAH), but other neurovascular structures may be involved. We present the protocol for a multicenter, prospective, observational study focused on analyzing morphological changes in cerebral veins of patients with aSAH.

Methods and Analysis

In a retrospective arm, we will collect head arterial and venous CT angiograms (CTA) of 50 patients with aSAH and 50 matching healthy controls at days 0–2 and 7–10, comparing morphological venous changes. A multicenter prospective observational study will follow. Patients aged ≥18 years of any gender with aSAH will be enrolled at 9 participating centers based on the predetermined eligibility criteria. A sample size of 52 aSAH patients is expected, and 52 healthy controls matched per age, gender, and comorbidities will be identified. For each patient, sequential CTA will be conducted upon admission (day 0–2), at 7–10 days, and at 14–21 days after aSAH, evaluating volumes and morphology of the cerebral deep veins and main cortical veins. One specialized image collecting center will analyze all anonymized CTA scans, performing volumetric calculation of targeted veins. Morphological venous changes over time will be evaluated using the Dice coefficient and the Jaccard index and scored using the Boeckh–Behrens system. Morphological venous changes will be correlated to clinical outcomes and compared between patients with aSAH and healthy-controls, and among groups based on surgical/endovascular treatments for aSAH.

Ethics and Dissemination

This protocol has been approved by the ethics committee and institutional review board of Ethikkommission, SALK, Salzburg, Austria, and will be approved at all participating sites. The study will comply with the Declaration of Helsinki. Written informed consent will be obtained from all enrolled patients or their legal tutors. We will present our findings at academic conferences and peer-reviewed journals.

Approved Protocol Version and Registration

Version 2, 09 June 2021.

Central sympathetic nerve activation in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a life-threatening condition, and although its two main complications-cerebral vasospasm (CVS)/delayed cerebral ischemia (DCI) and early brain injury (EBI)-have been widely studied, prognosis has not improved over time. The sympathetic nerve (SN) system is important for the regulation of cardiovascular function and is closely associated with cerebral vessels and the regulation of cerebral blood flow and cerebrovascular function; thus, excessive SN activation leads to a rapid breakdown of homeostasis in the brain. In the hyperacute phase, patients with SAH can experience possibly lethal conditions that are thought to be associated with SN activation (catecholamine surge)-related arrhythmia, neurogenic pulmonary edema, and irreversible injury to the hypothalamus and brainstem. Although the role of the SN system in SAH has long been investigated and considerable evidence has been collected, the exact pathophysiology remains undetermined, mainly because the relationships between the SN system and SAH are complicated, and many SN-modulating factors are involved. Thus, research concerning these relationships needs to explore novel findings that correlate with the relevant concepts based on past reliable evidence. Here, we explore the role of the central SN (CSN) system in SAH pathophysiology and provide a comprehensive review of the functional CSN network; brain injury in hyperacute phase involving the CSN system; pathophysiological overlap between the CSN system and the two major SAH complications, CVS/DCI and EBI; CSN-modulating factors; and SAH-related extracerebral organ injury. Further studies are warranted to determine the specific roles of the CSN system in the brain injuries associated with SAH.

Post-Event Application of Neurotropin Protects against Ischemic Insult toward Better Outcomes in a Murine Model of Subarachnoid Hemorrhage

Early brain injury (EBI) is closely linked to the development of delayed cerebral ischemia and poor outcomes after aneurysmal subarachnoid hemorrhage (SAH). This study aimed to evaluate the neuroprotective effect of neurotropin on EBI in a murine model of SAH. Twenty-four C57BL/6N mice were treated with intraperitoneal injections of either saline or 2.4 units of neurotropin at 1 h after SAH induction and for 3 days consecutively. SAH was created by an endovascular perforation method. In addition to the assessment of cerebral infarction and survival rate, motor and neurocognitive functions were also measured after SAH. Compared to the saline control group, the neurotropin group showed better recovery from locomotive and neurological declines after SAH. The neurotropin group also showed lower rates of post-SAH acute cerebral infarction and better memory and route-learning scores (p < 0.05). Meanwhile, there was no significant between-group differences in the overall mortality, hemodynamic parameters, or body weights. In conclusion, post-event treatment with neurotropin could be protective against EBI, lowering the incidence of ischemia and improving some motor and neurocognitive functions after SAH.

Non-invasive three-dimensional power Doppler imaging for the assessment of acute cerebral blood flow alteration in a mouse model of subarachnoid haemorrhage

We aimed to evaluate the feasibility of a non-invasive method of cerebral blood flow (CBF) measurement using high-frequency power Doppler ultrasound imaging in a mouse model of subarachnoid haemorrhage (SAH). The 3-dimensionally (3D) reconstructed blood flow signals (%vascularity) within the brain volume of the middle cerebral artery territory correlated well with reference parameters, baseline carotid artery blood flow (r²  = 0.52, P < 0.0001) and normalized CBF changes (r²  = 0.74 P < 0.0001). These data suggest that the 3D power Doppler analysis may have the potential for reflecting real-time CBF changes during the acute phase of experimental SAH, which may be applicable to preclinical studies on early brain injury.

Cerebral venous circulation changes caused by aneurysmal subarachnoid hemorrhage

BACKGROUND

The aneurysmal subarachnoid hemorrhage (aSAH) is an acute severe hemorrhagic stroke with high morbidity and mortality with poor prognosis.

OBJECTIVE

This study aims to analyze the changes of cerebral venous circulation in patients with aneurysmal subarachnoid hemorrhage by digital subtraction angiography (DSA).

MATERIALS AND METHODS

Totally, 57 patients with aSAH, 48 patients with unruptured aneurysms, and 45 patients without aneurysms (control group) were enrolled. The microvascular cerebral circulation time (mCCT), venous cerebral circulation time (vCCT), cerebral arterioles and cortical veins were analyzed by DSA.

RESULTS

There were changes of cerebral microvessels and cortical veins in patients with aSAH. The mCCT (6.15±1.37 s) and vCCT (2.79±0.34 s) of aSAH patients significantly increased compared with control patients (3.74±0.50 s; 2.64±0.32 s) (P < 0.05). However, the mCCT increased more compared with vCCT in aSAH patients (P < 0.001), while the vCCT increased more compared with mCCT in severe aSAH cases (P < 0.01). There was no significant difference in mCCT and vCCT between patients with unruptured aneurysms and controls (P = 0.131; P = 0.621).

CONCLUSIONS

The mCCT increases in acute aSAH patients within 72 hours and vCCT increases in severe aSAH cases.

Hematoma Expansion Following Intracerebral Hemorrhage: Mechanisms Targeting the Coagulation Cascade and Platelet Activation

Hematoma expansion (HE), defined as a greater than 33% increase in intracerebral hemorrhage (ICH) volume within the first 24 hours, results in significant neurological deficits, and enhancement of ICH-induced primary and secondary brain injury. An escalation in the use of oral anticoagulants has led to a surge in the incidences of oral anticoagulation-associated ICH (OAT-ICH), which has been associated with a greater risk for HE and worse functional outcomes following ICH. The oral anticoagulants in use include vitamin K antagonists, and direct thrombin and factor Xa inhibitors. Fibrinolytic agents are also frequently administered. These all act via differing mechanisms and thus have varying degrees of impact on HE and ICH outcome. Additionally, antiplatelet medications have also been increasingly prescribed, and result in increased bleeding risks and worse outcomes after ICH. Aspirin, thienopyridines, and GPIIb/IIIa receptor blockers are some of the most common agents in use clinically, and also have different effects on ICH and hemorrhage growth, based on their mechanisms of action. Recent studies have found that reduced platelet activity may be more effective in predicting ICH risk, hemorrhage expansion, and outcomes, than antiplatelet agents, and activating platelets may thus be a novel target for ICH therapy. This review explores how dysfunctions or alterations in the coagulation and platelet cascades can lead to, and/or exacerbate, hematoma expansion following intracerebral hemorrhage, and describe the mechanisms behind these effects and the drugs that induce them. We also discuss potential future therapy aimed at increasing platelet activity after ICH.

Permeability imaging as a predictor of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Blood-brain barrier (BBB) dysfunction has been implicated in ischemic risk following aneurysmal subarachnoid hemorrhage (aSAH), but never directly imaged. We prospectively examined whether post-bleed day 4 dynamic contrast-enhanced magnetic resonance (DCE-MR) BBB permeability imaging could predict development of delayed cerebral ischemia (DCI). Global MR-derived BBB permeability ( K_trans) was significantly higher in aSAH patients who subsequently developed DCI (five patients; 2.28 ± 0.09 × 10^-3 min^-1) compared to those who experienced radiographic vasospasm only (three patients; 1.85 ± 0.12 × 10^-3 min^-1; p < 0.05), or no vasospasm/ischemia (eight patients; 1.74 ± 0.07 × 10^-3 min^-1; p < 0.01). K_trans > 2 × 10^-3 min^-1 predicted development of DCI (AUC = 0.98, 95% CI: 0.93-1). Global BBB dysfunction following aSAH is detectable with DCE-MR and predictive of ischemic risk.

Acute-Phase Plasma Osteopontin as an Independent Predictor for Poor Outcome After Aneurysmal Subarachnoid Hemorrhage

Experimental studies reported that osteopontin (OPN), a matricellular protein, is induced in brain after subarachnoid hemorrhage (SAH). The aim of this study was to investigate the relationships between plasma OPN levels and outcome after aneurysmal SAH in a clinical setting. This is a prospective study consisting of 109 aneurysmal SAH patients who underwent aneurysmal obliteration within 48 h of SAH. Plasma OPN concentrations were serially determined at days 1-3, 4-6, 7-9, and 10-12 after onset. Various clinical factors as well as OPN values were compared between patients with 90-day good and poor outcomes. Plasma OPN levels were significantly higher in SAH patients compared with control patients and peaked at days 4-6. Poor-outcome patients had significantly higher plasma OPN levels through all sampling points. Receiver-operating characteristic curves demonstrated that OPN levels at days 10-12 were the most useful predictor of poor outcome at cutoff values of 915.9 pmol/L (sensitivity, 0.694; specificity, 0.845). Multivariate analyses using the significant variables identified by day 3 showed that plasma OPN ≥ 955.1 pmol/L at days 1-3 (odds ratio, 10.336; 95% confidence interval, 2.563-56.077; p < 0.001) was an independent predictor of poor outcome, in addition to increasing age, preoperative World Federation of Neurological Surgeons grades IV-V, and modified Fisher grade 4. Post hoc analyses revealed no correlation between OPN levels and serum levels of C-reactive protein, a non-specific inflammatory parameter, at days 1-3. Acute-phase plasma OPN could be used as a useful prognostic biomarker in SAH.

Temporal Lobe Epilepsy, Stroke, and Traumatic Brain Injury: Mechanisms of Hyperpolarized, Depolarized, and Flow-Through Ion Channels Utilized as Tri-Coordinate Biomarkers of Electrophysiologic Dysfunction

The brain is an integrated network of multiple variables that when compromised create a diseased state. The neuropathology of temporal lobe epilepsy (TLE), stroke, and traumatic brain injury (TBI) demonstrate both similarity and complexity that reflects this integrated variability; TLE with its live human tissue resection provides opportunity for translational science to demonstrate scale equivalent experimentation between the macroscopic world of clinical disease and the microscopic world of basic science. The extended value of this research is that the neuroinflammatory abnormalities that occur throughout astrocytes with hippocampal sclerosis and damaged or even reversed signaling pathways (inhibition to excitation such as with gaba-aminobutyric acid) are similar to those seen in post-stroke and TBI models. In evaluation of the epilepsy population this interconnectedness of pathology warrants further evaluation with collaborative efforts. This review summarizes patterns that could shift experimentation closer to the macro level of humanity, but still represent the micro world of genetics, epigenetics, and neuro-injury across etiologies of physiologic dysfunction such as TLE, stroke, and TBI with evaluation of cell function using electrophysiology. In conclusion we demonstrate the plausibility of electrophysiologic voltage and current measurement of brain tissue by patch clamp analysis to specify actual electrophysiologic function for comparison to electroencephalography in order to aid neurologic evaluation. Finally, we discuss the opportunity with multiscale modeling to display integration of the hyperpolarization cyclic-nucleotide gated channel, the depolarized calcium channels, and sodium-potassium-chloride-one/potassium-chloride-two co-transporter channels as potential mechanisms utilized as tri-coordinate biomarkers with these three forms of neurologic disease at a molecular scale of electrophysiologic pathology.

Remote Diffusion-Weighted Imaging Lesions in Intracerebral Hemorrhage: Characteristics, Mechanisms, Outcomes, and Therapeutic Implications

Spontaneous intracerebral hemorrhage (ICH) is one of the most fatal form of stroke, with high mortality and disability rate. Small diffusion-weighed imaging lesions are not rare to see in regions remote from the hematoma after ICH and have been generally considered as related with poor outcome. In this review, we described the characteristics of remote ischemic lesions, discussed the possible mechanisms and clinical outcomes of these lesions, and evaluated the potential therapeutic implications.

Recanalization, reperfusion, and recirculation in stroke

Recirculation, from arterial inflow routes through venous outflow pathways, was conceptualized in stroke research 50 years ago. As new technologies were developed, blocked arteries could be reopened, capillaries could be reperfused, and the use of recanalization and reperfusion grew to dominate therapeutic strategies. These approaches overwhelmingly focused on restoration of arterial and capillary inflow, but not on veins even though venous disorders may initiate or exacerbate brain injury. In this commentary, we advance the term "recirculation" after "recanalization" and "reperfusion" as a primary concept of stroke pathophysiology that targets the restoration of both the arterial and venous cerebral circulations.

MRI Characterization in the Acute Phase of Experimental Subarachnoid Hemorrhage

A number of mechanisms have been proposed for the early brain injury after subarachnoid hemorrhage (SAH). In this study, we investigated the radiographic characteristics and influence of gender on early brain injury after experimental SAH. SAH was induced by endovascular perforation in male and female rats. Magnetic resonance imaging was performed in a 7.0-T Varian MR scanner at 24 h after SAH. The occurrence and size of T2 lesions, ventricular dilation, and white matter injury (WMI) were determined on T2-weighted images (T2WI). The effects of SAH on heme oxygenase-1 and fibrin/fibrinogen were examined by Western blotting and immunohistochemistry. SAH severity was assessed using a MRI grading system, and neurological function was evaluated according to a modified Garcia's scoring system. T2 hyperintensity areas and enlarged ventricles were observed in T2WI coronal sections 24 h after SAH. The overall incidence of T2 lesions, WMI, and hydrocephalus was 54, 20, and 63%, respectively. Female rats had a higher incidence of T2 hyperintensity lesions and hydrocephalus, as well as larger T2 lesion volumes and higher average ventricular volume. SAH rats graded at 3-4 (our previously validated MRI grading scale) had larger T2 lesion volumes, more hydrocephalus, and worse neurological function compared with those graded at 0-2. In conclusion, T2 lesion, WMI, and hydrocephalus were the most prevalent MRI characteristics 24 h after experimental SAH. The T2 lesion area matched with fibrinogen/fibrin positive staining in the acute phase of SAH. SAH induced more severe brain injury in females compared to males in the acute phase of SAH.

Higher Cerebrospinal Fluid pH may Contribute to the Development of Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage

Recent investigations have shown that many factors may cause delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH). To find new potential contributors to DCI, this retrospective study compared gas data in the cerebrospinal fluid (CSF) between patients with and without DCI. The subjects were 61 consecutive patients with SAH classified as Fisher group III on admission computed tomography scans, whose aneurysms were obliterated by clipping or coiling within 24 h post-SAH. Thirty-three patients were treated with CSF drainage. CSF samples were chronologically obtained from CSF drains or lumbar taps. Patients with DCI were more frequently treated with CSF drainage, especially cisternal drainage, and were associated with significantly higher pH and lower partial pressure of carbon dioxide (PCO₂) in the CSF compared with patients without DCI, although CSF concentrations of bicarbonate ion as well as arterial blood gas data were not different between the two groups. Total hemoglobin concentrations in the drained or tapped CSF were higher in patients with no DCI compared with patients with DCI at any sampling time, suggesting that CSF hemoglobin was not efficiently removed in patients with DCI. This study revealed higher CSF pH and lower CSF PCO₂ as new potential contributors to the development of DCI, which might result from inappropriate CSF drainage that failed to remove clot and acid metabolites in it efficiently. Both of the disturbed CSF gas and inappropriate CSF drainage may cause constriction of the arteries and arterioles, leading to DCI.

Delayed Docosahexaenoic Acid Treatment Combined with Dietary Supplementation of Omega-3 Fatty Acids Promotes Long-Term Neurovascular Restoration After Ischemic Stroke

Prophylactic dietary intake of omega-3 polyunsaturated fatty acids (n-3 PUFAs) has been shown to remarkably ameliorate ischemic brain injury. However, the therapeutic efficacy of n-3 PUFA administration post-stroke, especially its impact on neurovascular remodeling and long-term neurological recovery, has not been fully characterized thus far. In this study, we investigated the effect of n-3 PUFA supplementation, as well as in combination with docosahexaenoic acid (DHA) injections, on long-term stroke outcomes. Mice were subjected to transient middle cerebral artery occlusion (MCAO) before randomly assigned to four groups to receive the following: (1) low dose of n-3 PUFAs as the vehicle control, (2) intraperitoneal DHA injections, (3) n-3 PUFA dietary supplement, or (4) combined treatment of (2) and (3). Neurological deficits and brain atrophy, neurogenesis, angiogenesis, and glial scar formation were assessed up to 28 days after MCAO. Results revealed that groups 2 and 3 showed only marginal reduction in post-stroke tissue loss and attenuation of cognitive deficits. Interestingly, group 4 exhibited significantly reduced tissue atrophy and improved cognitive functions compared to groups 2 and 3 with just a single treatment. Mechanistically, the combined treatment promoted post-stroke neurogenesis and angiogenesis, as well as reduced glial scar formation, all of which significantly correlated with the improved spatial memory in the Morris water maze. These results demonstrate an effective therapeutic regimen to enhance neurovascular restoration and long-term cognitive recovery in the mouse model of MCAO. Combined post-stroke DHA treatment and n-3 PUFA dietary supplementation thus may be a potential clinically translatable therapy for stroke or related brain disorders.

Inhibition of mammalian target of rapamycin attenuates early brain injury through modulating microglial polarization after experimental subarachnoid hemorrhage in rats

Here, we aimed to study the role and underlying mechanism of mTOR in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Experiment 1, the time course of mTOR activation in the cortex following SAH. Experiment 2, the role of mTOR in SAH-induced EBI. Adult SD rats were divided into four groups: sham group (n=18), SAH+vehicle group (n=18), SAH+rapamycin group (n=18), SAH+AZD8055 group (n=18). Experiment 3, we incubated enriched microglia with OxyHb. Rapamycin and AZD8055 were also used to demonstrate the mTOR's role on microglial polarization in vitro. The phosphorylation levels of mTOR and its substrates were significantly increased and peaked at 24h after SAH. Rapamycin or AZD8055 markedly decreased the phosphorylation levels of mTOR and its substrates and the activation of microglia in vivo, and promoted the microglial polarization from M1 phenotype to M2 phenotype. In addition, administration of rapamycin and AZD8055 following SAH significantly ameliorated EBI, including neuronal apoptosis, neuronal necrosis, brain edema and blood-brain barrier permeability. Our findings suggested that the rapamycin and AZD8055 could attenuate the development of EBI in this SAH model, possibly through inhibiting the activation of microglia by mTOR pathway.

Critical Role of the Sphingolipid Pathway in Stroke: a Review of Current Utility and Potential Therapeutic Targets

Sphingolipids are a series of cell membrane-derived lipids which act as signaling molecules and play a critical role in cell death and survival, proliferation, recognition, and migration. Sphingosine-1-phosphate acts as a key signaling molecule and regulates lymphocyte trafficking, glial cell activation, vasoconstriction, endothelial barrier function, and neuronal death pathways which plays a critical role in numerous neurological conditions. Stroke is a second leading cause of death all over the world and effective therapies are still in great demand, including ischemic stroke and hemorrhagic stroke as well as poststroke repair. Significantly, sphingolipid activities change after stroke and correlate with stroke outcome, which has promoted efforts to testify whether the sphingolipid pathway could be a novel therapeutic target in stroke. The sphingolipid metabolic pathway, the connection between the pathway and stroke, as well as therapeutic interventions to manipulate the pathway to reduce stroke-induced brain injury are discussed in this review.

Pramipexole-Induced Hypothermia Reduces Early Brain Injury via PI3K/AKT/GSK3β pathway in Subarachnoid Hemorrhage rats

Previous studies have shown neuroprotective effects of hypothermia. However, its effects on subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) remain unclear. In this study, a SAH rat model was employed to study the effects and mechanisms of pramipexole-induced hypothermia on EBI after SAH. Dose-response experiments were performed to select the appropriate pramipexole concentration and frequency of administration for induction of mild hypothermia (33–36 °C). Western blot, neurobehavioral evaluation, Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and Fluoro-Jade B (FJB) staining were used to detect the effects of pramipexole-induced hypothermia on SAH-induced EBI, as well as to study whether controlled rewarming could attenuate these effects. Inhibitors targeting the PI3K/AKT/GSK3β pathway were administered to determine whether the neuroprotective effect of pramipexole-induced hypothermia was mediated by PI3K/AKT/GSK3β signaling pathway. The results showed that intraperitoneal injection of pramipexole at 0.25 mg/kg body weight once per 8 hours was found to successfully and safely maintain rats at mild hypothermia. Pramipexole-induced hypothermia ameliorated SAH-induced brain cell death, blood-brain barrier damage and neurobehavioral deficits in a PI3K/AKT/GSK3β signaling-dependent manner. Therefore, we may conclude that pramipexole-induced hypothermia could effectively inhibit EBI after SAH in rats via PI3K/AKT/GSK3β signaling pathway.

Recombinant Osteopontin Stabilizes Smooth Muscle Cell Phenotype via Integrin Receptor/Integrin-Linked Kinase/Rac-1 Pathway After Subarachnoid Hemorrhage in Rats

BACKGROUND AND PURPOSE

Recombinant osteopontin (rOPN) has been reported to be neuroprotective in stroke animal models. The purpose of this study is to investigate a potential role and mechanism of nasal administration of rOPN on preserving the vascular smooth muscle phenotype in early brain injury after subarachnoid hemorrhage (SAH).

METHODS

One hundred and ninety-two male adult Sprague-Dawley rats were used. The SAH model was induced by endovascular perforation. Integrin-linked kinase small interfering RNA was intracerebroventricularly injected 48 hours before SAH. The integrin receptor antagonist fibronectin-derived peptide Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), focal adhesion kinase inhibitor Fib-14, and Rac-1 inhibitor NSC23766 were administered 1 hour before SAH induction. rOPN was administered via the intracerebroventricular and nasal route after SAH. SAH grade, neurological scores, brain water content, brain swelling, hematoxylin and eosin staining, India ink angiography, Western blots, and immunofluorescence were used to study the mechanisms of rOPN on the vascular smooth muscle phenotypic transformation.

RESULTS

The marker proteins of vascular smooth muscle phenotypic transformation α-smooth muscle actin decreased and embryonic smooth muscle myosin heavy chain (SMemb) increased significantly at 24 and 72 hours in the cerebral arteries after SAH. rOPN prevented the changes of α-smooth muscle actin and SMemb and significantly alleviated neurobehavioral dysfunction, increased the cross-sectional area and the lumen diameter of the cerebral arteries, reduced the brain water content and brain swelling, and improved the wall thickness of cerebral arteries. These effects of rOPN were abolished by GRGDSP, integrin-linked kinase small interfering RNA, and NSC23766. Intranasal application of rOPN at 3 hours after SAH also reduced neurological deficits.

CONCLUSIONS

rOPN prevented the vascular smooth muscle phenotypic transformation and improved the neurological outcome, which was possibly mediated by the integrin receptor/integrin-linked kinase/Rac-1 pathway.

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

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

The Effect of Gender on Acute Hydrocephalus after Experimental Subarachnoid Hemorrhage

Acute hydrocephalus is a common complication of subarachnoid hemorrhage (SAH). We investigated the effect of gender on acute hydrocephalus development in a rat SAH model. SAH was induced in adult male and female Sprague-Dawley rats using endovascular perforation. Sham rats underwent the same procedure without perforation. Magnetic resonance imaging (MRI) was performed 24 h after SAH to determine ventricular volume. Hydrocephalus was defined as a ventricular volume that was more than 3 standard deviations from the mean value in sham-operated animals. After MRI, animals were euthanized and the extent of SAH was assessed using a modified grading system. No sham animals died. Mortality rates after SAH induction in male and female animals were 27 and 22 %, respectively. SAH induced significant ventricular enlargement compared with sham-operated rats (p < 0.01). The T2* hypointensity volume in the ventricle (used to assess intraventricular blood) was correlated with ventricular volume after SAH (r = 0.33, p < 0.05). The incidence of acute hydrocephalus 24 h after SAH was greater in female (75 %) than in male animals (47 %, p < 0.05) and the relative changes in ventricular volume were significantly larger in female than in male rats (292 ± 150 % vs 216 ± 127 % of sham-operated animals, respectively, p < 0.05). The increased hydrocephalus occurred even though SAH severity grade and ventricular T2* hypointensity volumes were not significantly different between male and female animals. Our data demonstrate that gender influences acute hydrocephalus development in a rat SAH model. Future studies should determine the role of estrogen in SAH-induced hydrocephalus.

Basal Ganglia Damage in Experimental Subarachnoid Hemorrhage

Research suggests that early brain injury following subarachnoid hemorrhage (SAH) is a primary therapeutic target, and early SAH-induced basal ganglia injury is not well studied. The present study examined basal ganglia injury in a rat model of SAH. Adult male Sprague-Dawley rats (n = 78) weighing 275-300 g underwent endovascular perforation to mimic aneurysmal SAH. Sham rats (n = 12) underwent the same procedure but without perforation. Magnetic resonance imaging (T2 MRI) was performed at 24 h after SAH to measure ventricle volumes and brain T2 lesion. Hydrocephalus in SAH rats was defined as a ventricular volume greater than three standard deviations above that in shams. Western blotting and immunochemistry were utilized to assess basal ganglia damage. Sixty rats survived the SAH and 40 % of those animals had T2 lesions in the basal ganglia. Twenty-six SAH rats had hydrocephalus. Rats with hydrocephalus had higher incidence of basal ganglia lesion (69 vs. 18 % in rats without hydrocephalus; p < 0.01). Basal ganglia neuronal injury was also determined by examining the levels of dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDa (DARPP-32). We found that rats with hydrocephalus had more severe basal ganglia injury with greater DARPP-32 depletion (DARPP-32/beta-actin: 0.38 ± 0.32 vs. 0.86 ± 0.45 in rats without hydrocephalus and 1.10 ± 0.28 in sham, p < 0.05). In conclusion, SAH resulted in severe basal ganglia damage, which is associated with hydrocephalus development.

Diffusion tensor imaging in hemorrhagic stroke

Diffusion tensor imaging (DTI) has evolved considerably over the last decade to now be knocking on the doors of wider clinical applications. There have been several efforts over the last decade to seek valuable and reliable application of DTI in different neurological disorders. The role of DTI in predicting outcomes in patients with brain tumors has been extensively studied and has become a fairly established clinical tool in this scenario. More recently DTI has been applied in mild traumatic brain injury to predict clinical outcomes based on DTI of the white matter tracts. The resolution of white matter fiber tractography based on DTI has improved over the years with increased magnet strength and better tractography post-processing. The role of DTI in hemorrhagic stroke has been studied preliminarily in the scientific literature. There is some evidence that DTI may be efficacious in predicting outcomes of motor function in animal models of intracranial hemorrhage. Only a handful of studies of DTI have been performed in subarachnoid hemorrhage or intraventricular hemorrhage scenarios. In this manuscript we will review the evolution of DTI, the existing evidence for its role in hemorrhagic stroke and discuss possible application of this non-invasive evaluation technique of human cerebral white matter tracts in the future.

MFGE8/Integrin β3 pathway alleviates apoptosis and inflammation in early brain injury after subarachnoid hemorrhage in rats

BACKGROUND

Milk fat globule-epidermal growth factor-factor 8(MFGE8)/Integrin β3 pathway was reported to be involved in reducing oxidative stress and early brain injury after subarachnoid hemorrhage (SAH). In the present study, the potential effects of MFGE8 and its receptor Integrin β3 in the inhibition of apoptosis and neuroinflammation in early brain injury after SAH were investigated.

METHODS

Ninety-five (95) male Sprague-Dawley rats were used. The SAH model was induced by endovascular perforation. Recombinant human MFGE8 (rhMFGE8), MFGE8 small interfering RNA (siRNA) and Integrin β3 siRNA were injected intracerebroventricularly. SAH grade, neurologic scores, Western blots and immunofluorescence were employed to study the mechanisms of MFGE8 and its receptor Integrin β3, as well as neurological outcome.

RESULTS

SAH induced significant neuronal apoptosis and inflammation and exhibited neurological dysfunction in rats. Knockdown endogenous MFGE8 with siRNA significantly increased the protein levels of cleaved caspase 3 and IL-1β, accompanied with more neurological deficits. rhMFGE8 significantly reduced neural cell death in cortex, decreased cleaved caspase 3 and IL-1β expressions, and improved neurological functions 24h after SAH. The anti-apoptosis and anti-inflammation effects of rhMFGE8 were abolished by Integrin β3 siRNA.

CONCLUSION

MFGE8 could alleviate neurologic damage in early brain injury after SAH via anti-inflammation and anti-apoptosis effects. MFGE8 may serve as a promising therapeutic target for future management of SAH patients.