Effect of anesthesia and cerebral blood flow on neuronal injury in a rat middle cerebral artery occlusion (MCAO) model

Commonly used anesthetics modify alcohol and (-)-trans-delta9-tetrahydrocannabinol in vivo effects on rat cerebral arterioles

BACKGROUND

Ethyl alcohol and cannabis are widely used recreational substances with distinct effects on the brain. These drugs increase accidental injuries requiring treatment under anesthesia. Moreover, alcohol and cannabis are often used in anesthetized rodents for biomedical research. Here, we compared the influence of commonly used forms of anesthesia, injectable ketamine/xylazine (KX) versus inhalant isoflurane, on alcohol- and (-)-trans-delta9-tetrahydrocannabinol (THC) effects on cerebral arteriole diameter evaluated in vivo.

METHODS

Studies were performed on male and female Sprague-Dawley rats subjected to intracarotid catheter placement for drug infusion, and cranial window surgery for monitoring pial arteriole diameter. Depth of anesthesia was monitored every 10-15 min by toe-pinch. Under KX, the number of toe-pinch responders was maximal after the first dose of anesthesia and diminished over time in both males and females. In contrast, the number of toe-pinch responders under isoflurane slowly raised over time, leading to increase in isoflurane percentage until deep anesthesia was re-established. Rectal temperature under KX remained stable in males while dropping in females. As expected for gaseous anesthesia, both males and females exhibited rectal temperature drops under isoflurane.

RESULTS

Infusion of 50 mM alcohol (ethanol, EtOH) into the cerebral circulation rendered robust constriction in males under KX anesthesia, this alcohol action being significantly smaller, but still present under isoflurane anesthesia. In females, EtOH did not cause measurable changes in pial arteriole diameter regardless of the anesthetic. These findings indicate a strong sex bias with regards to EtOH induced vasoconstriction. Infusion of 42 nM THC in males and females under isoflurane tended to constrict cerebral arterioles in both males and females when compared to isovolumic infusion of THC vehicle (dimethyl sulfoxide in saline). Moreover, THC-driven changes in arteriole diameter significantly differed in magnitude depending on the anesthetic used. Simultaneous administration of 50 mM alcohol and 42 nM THC to males constricted cerebral arterioles regardless of the anesthetic used. In females, constriction by the combined drugs was also observed, with limited influence by anesthetic presence.

CONCLUSIONS

We demonstrate that two commonly used anesthetic formulations differentially influence the level of vasoconstriction caused by alcohol and THC actions in cerebral arterioles.

Impoverished Conceptions of Gene Causation and Therapy in Developmental Neurology

We offer a primer to the modifiability of genetic neurological disease, particularly during development. One goal is to harness several unexpected observations made in the course of experimental gene modification or therapy into an explanatory conceptual context based on biological first principles. To this end, we anchor growing, disparate reports of unusual or untoward effects to a plausible framework wherein genes exhibit different degrees of modifiability and may result, when mutated or therapeutically modified, in unsuspected consequences. We propose that genetic pathogenic variant effects and modifiability depend on the number and complexity of associated protein-protein or higher-order interactions. Thus, gene malleability may range from that characteristic of the favorably modifiable primarily structural genes that subserve relatively invariant or circumscribed phenomena such as cell shape to that typical of some transcription factors, which are less functionally predictable when altered. The latter may be expressed developmentally, in compartmentalized manner, or only intermittently and yet exert vastly ramified influences sometimes circumscribed only to select species. We also argue that genetic diseases may steer the organism toward often poorly understood biological end points and co-opt multiple processes into hardly modifiable biology. Addition or modification of genes to approximate a normal state not previously experienced by the organism may lead to further aberration due to extraneous interference with the native biology of the disease state. Therefore, an understanding as perspicuous as possible of gene function, regulation, modifiability, and biological directionality down to seemingly minute but disease-relevant consequences is a prerequisite to intervention. Although we provide some groundwork steps to such an understanding, this may occasionally prove unattainable.

Effects of isoflurane and xylazine on inducing cerebral ischemia by the model of middle cerebral artery occlusion in mice

Preclinical ischemic stroke studies extensively utilize the intraluminal suture method of middle cerebral artery occlusion (MCAo). General anesthesia administration is an essential step for MCAo, but anesthetic agents can lead to adverse effects causing death and making a considerable impact on inducing cerebral ischemia. The purpose of this study was to comparatively assess the effect of isoflurane and xylazine on transient cerebral ischemia in a mouse model of MCAo. Twenty animals were randomly divided into four groups: sham group (no MCAo), control group (MCAo under isoflurane, no agent till reperfusion), isoflurane group (MCAo under isoflurane continued till reperfusion), xylazine group (MCAo under isoflurane, and administration of xylazine till reperfusion). The survival rate, brain infarct volume, and neurologic deficits were studied to assess the effect of isoflurane and xylazine on the stroke model. Our results showed that the body weight showed statistically significant change before and 24 h after surgery in the control and Isoflurane groups, but no difference in the Xylazine group. Also, the survival rate, brain infarct volume, and neurologic deficits were slightly reduced in the isoflurane group at 24 h after reperfusion injury. However, the xylazine and control groups showed similar BIV and neurologic deficits. Interestingly, a high survival rate was observed in the xylazine group. Our results indicate that the modified method of inhalation anesthetics combined with xylazine can reduce the risk of mortality and develop a reproducible MCAo model with predictable brain ischemia. In addition, extended isoflurane anesthesia after MCAo is associated with the risk of mortality.

The impact of anesthetic drugs on hemodynamic parameters and neurological outcomes following temporal middle cerebral artery occlusion in rats

The induction of ischemic stroke in the experimental model requires general anesthesia. One of the factors that can be effective in the size of ischemic brain lesions and neurological outcomes is the type of anesthesia. So, the current study was designed to compare the impacts of the most important and widely used anesthetics including halothane, isoflurane, and chloral hydrate on the transient middle cerebral artery occlusion (MCAO) outcomes. Adult Male Sprague-Dawley rats were randomly divided into three groups as follows: (1) MCAO + halothane group, (2) MCAO + isoflurane group, and (3) MCAO + chloral hydrate group. After 24 h, the mortality rate, infarct size, tissue swelling, neurological function, hemodynamic, and arterial blood gas parameters were assessed. Our finding showed that 60 min MCAO rats anesthetized with chloral hydrate significantly increased mortality rate, infarct size, tissue swelling, and neurological deficits compared with halothane and isoflurane anesthetics after 24 h of MCAO. Also, chloral hydrate caused a significant decrease in mean arterial pressure and arterial pO2 compared to halothane and isoflurane anesthetics. On the basis of the current data, we concluded that chloral hydrate increased cerebral infarct volume and neurological outcomes and reduced hemodynamic and metabolic parameters compared with halothane and isoflurane-anesthetized rats temporal MCAO.

Embracing Heterogeneity in The Multicenter Stroke Preclinical Assessment Network (SPAN) Trial

The Stroke Preclinical Assessment Network (SPAN) is a multicenter preclinical trial platform using rodent models of transient focal cerebral ischemia to address translational failure in experimental stroke. In addition to centralized randomization and blinding and large samples, SPAN aimed to introduce heterogeneity to simulate the heterogeneity embodied in clinical trials for robust conclusions. Here, we report the heterogeneity introduced by allowing the 6 SPAN laboratories to vary most of the biological and experimental model variables and the impact of this heterogeneity on middle cerebral artery occlusion (MCAo) performance. We included the modified intention-to-treat population of the control mouse cohort of the first SPAN trial (n=421) and examined the biological and procedural independent variables and their covariance. We then determined their impact on the dependent variables cerebral blood flow drop during MCAo, time to achieve MCAo, and total anesthesia duration using multivariable analyses. We found heterogeneity in biological and procedural independent variables introduced mainly by the site. Consequently, all dependent variables also showed heterogeneity among the sites. Multivariable analyses with the site as a random effect variable revealed filament choice as an independent predictor of cerebral blood flow drop after MCAo. Comorbidity, sex, use of laser Doppler flow to monitor cerebral blood flow, days after trial onset, and maintaining anesthesia throughout the MCAo emerged as independent predictors of time to MCAo. Total anesthesia duration was predicted by most independent variables. We present with high granularity the heterogeneity introduced by the biological and model selections by the testing sites in the first trial of cerebroprotection in rodent transient filament MCAo by SPAN. Rather than trying to homogenize all variables across all sites, we embraced the heterogeneity to better approximate clinical trials. Awareness of the heterogeneity, its sources, and how it impacts the study performance may further improve the study design and statistical modeling for future multicenter preclinical trials.

Near infrared spectroscopy detection of hemispheric cerebral ischemia following middle cerebral artery occlusion in rats

Timely and sensitive in vivo estimation of ischemic stroke-induced brain infarction are necessary to guide diagnosis and evaluation of treatments' efficacy. The gold standard for estimation of the cerebral infarction volume is magnetic resonance imaging (MRI), which is expensive and not readily accessible. Measuring regional cerebral blood flow (rCBF) with Laser Doppler flowmetry (LDF) is the status quo for confirming reduced blood flow in experimental ischemic stroke models. However, rCBF reduction following cerebral artery occlusion often does not correlate with subsequent infarct volume. In the present study, we employed the continuous-wave near infrared spectroscopy (NIRS) technique to monitor cerebral oxygenation during 90 min of the intraluminal middle cerebral artery occlusion (MCAO) in Sprague-Dawley rats (n = 8, male). The NIRS device consisted of a controller module and an optical sensor with two LED light sources and two photodiodes making up two parallel channels for monitoring left and right cerebral hemispheres. Optical intensity measurements were converted to deoxyhemoglobin (Hb) and oxyhemoglobin (HbO2) changes relative to a 2-min window prior to MCAO. Area under the curve (auc) for Hb and HbO2 was calculated for the 90-min occlusion period for each hemisphere (ipsilateral and contralateral). To obtain a measure of total ischemia, auc of the contralateral side was subtracted from the ipsilateral side resulting in ΔHb and ΔHbO2 parameters. Infarct volume (IV) was calculated by triphenyl tetrazolium chloride (TTC) staining at 24h reperfusion. Results showed a significant negative correlation (r = -0.81, p = 0.03) between ΔHb and infarct volume. In conclusion, our results show feasibility of using a noninvasive optical imaging instrument, namely NIRS, in monitoring cerebral ischemia in a rodent stroke model. This cost-effective, non-invasive technique may improve the rigor of experimental models of ischemic stroke by enabling in vivo longitudinal assessment of cerebral oxygenation and ischemic injury.

Chlorogenic acid modulates the ubiquitin-proteasome system in stroke animal model

BACKGROUND

Chlorogenic acid, a phenolic compound, has potent antioxidant and neuroprotective properties. The ubiquitin-proteasome system is an important regulators of neurodevelopment and modulators of neuronal function. This system is associated with neurodevelopment and neurotransmission through degradation and removal of damaged proteins. Activation of the ubiquitin-proteasome system is a critical factor in preventing cell death. We have previously reported a decrease in the activity of the ubiquitin-proteasome system during cerebral ischemia. This study investigated whether chlorogenic acid regulates the ubiquitin-proteasome system in an animal stroke model. In adult rats, middle cerebral artery occlusion (MCAO) surgery was performed to induce focal cerebral ischemia. Chlorogenic acid (30 mg/kg) or normal saline was injected into the abdominal cavity 2 h after MCAO surgery, and cerebral cortex tissues were collected 24 h after MCAO damage.

RESULTS

Chlorogenic acid attenuated neurobehavioral disorders and histopathological changes caused by MCAO damage. We identified the decreases in ubiquitin C-terminal hydrolase L1, ubiquitin thioesterase OTUB1, proteasome subunit α type 1, proteasome subunit α type 3, and proteasome subunit β type 4 expression using a proteomics approach in MCAO animals. The decrease in these proteins was alleviated by chlorogenic acid. In addition, the results of reverse transcription-polymerase chain reaction confirmed these changes. The identified proteins were markedly reduced in MCAO damage, while chlorogenic acid prevented these reductions induced by MCAO. The decrease of ubiquitin-proteasome system proteins in ischemic damage was associated with neuronal apoptosis.

CONCLUSIONS

Our results showed that chlorogenic acid regulates ubiquitin-proteasome system proteins and protects cortical neurons from neuronal damage. These results provide evidence that chlorogenic acid has neuroprotective effects and maintains the ubiquitin-proteasome system in ischemic brain injury.

Optimizing intraluminal monofilament model of ischemic stroke in middle-aged Sprague-Dawley rats

Intraluminal monofilament model of middle cerebral artery occlusion (MCAO) is widely adopted for ischemic stroke; and Sprague-Dawley (SD) rats are commonly used rodents for preclinical research. Due to the paucity of information on the appropriate monofilament size for inducing MCAO in SD rats and the importance of including middle-aged models in ischemic stroke studies, we aimed to: (i). determine an appropriate Doccol^® monofilament size for middle-aged male SD rats which weighed > 500 g following 24-h transient MCAO survival as well as (ii). demonstrate the optimal Doccol^® filament size for middle-aged males (≤ 500 g) and females (273-300 g) while using young adult male SD rats (372-472 g) as control for severity of infarct volume following 7-days post-MCAO. All rats were subjected to 90-min transient MCAO. We show that 0.43 mm Doccol^® monofilament size is more appropriate to induce large infarct lesion and optimal functional deficit when compared to 0.45 mm and 0.47 mm at 24 h post-MCAO. Our data on infarct volumes at 7 days post-MCAO as well as the observed weight loss and functional deficits at post-MCAO days 1, 3 and 7 demonstrate that 0.41 mm, 0.37 mm and 0.39 mm are optimal Doccol^® filament sizes for middle-aged male (477.3 ± 39.61 g) and female (302.6 ± 26.28 g) as well as young-adult male (362.2 ± 28.38 g) SD rats, respectively.

Recording of pig neuronal activity in the comparative context of the awake human brain

Gyriform mammals display neurophysiological and neural network activity that other species exhibit only in rudimentary or dissimilar form. However, neural recordings from large mammals such as the pig can be anatomically hindered and pharmacologically suppressed by anesthetics. This curtails comparative inferences. To mitigate these limitations, we set out to modify electrocorticography, intracerebral depth and intracortical recording methods to study the anesthetized pig. In the process, we found that common forms of infused anesthesia such as pentobarbital or midazolam can be neurophysiologic suppressants acting in dose-independent fashion relative to anesthetic dose or brain concentration. Further, we corroborated that standard laboratory conditions may impose electrical interference with specific neural signals. We thus aimed to safeguard neural network integrity and recording fidelity by developing surgical, anesthesia and noise reduction methods and by working inside a newly designed Faraday cage, and evaluated this from the point of view of neurophysiological power spectral density and coherence analyses. We also utilized novel silicon carbide electrodes to minimize mechanical disruption of single-neuron activity. These methods allowed for the preservation of native neurophysiological activity for several hours. Pig electrocorticography recordings were essentially indistinguishable from awake human recordings except for the small segment of electrical activity associated with vision in conscious persons. In addition, single-neuron and paired-pulse stimulation recordings were feasible simultaneously with electrocorticography and depth electrode recordings. The spontaneous and stimulus-elicited neuronal activities thus surveyed can be recorded with a degree of precision similar to that achievable in rodent or any other animal studies and prove as informative as unperturbed human electrocorticography.

SCO-spondin-derived peptide NX210 rescues neurons from cerebral ischemia/reperfusion injury through modulating the Integrin-β1 mediated PI3K/Akt pathway

Ischemic stroke is a common condition with high morbidity and mortality, causing irreversible neuronal damage and seriously affecting neurological function. There has been no ideal effective treatment so far. The NX210 peptide is derived from the thrombospondin type 1 repeat (TSR) sequence of SCO-spondin, and has been reported to exert various neurogenic properties. This study investigated whether NX210 had therapeutic effects and possible underlying mechanisms against cerebral ischemia/reperfusion (I/R). Therefore, primary embryonic rat cortical neurons and Sprague-Dawley (SD) rats that were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) and middle cerebral artery occlusion/reperfusion (MCAO/R) injuries, respectively, were treated with or without NX210. We found that NX210 reduced OGD/R-induced cell viability loss and cytotoxicity. NX210 decreased cerebral infarct volume and brain edema, ameliorated neurological dysfunction, attenuated oxidative stress damage, and diminished neuronal apoptosis in MCAO/R rats. Furthermore, western blot analysis shown that treatment with NX210 up-regulated the expression of Integrin-β1, phosphorylated-PI3K (p-PI3K) and phosphorylated-Akt (p-Akt). The Integrin-β1 specific inhibitor, ATN-161, was used to identify pathways involved. The anti-oxidation activities and anti-apoptosis of NX210 was reversed by treatment with ATN-161. Overall, our results indicated that NX210 prevents oxidative stress and neuronal apoptosis in cerebral I/R via upregulation of the Integrin-β1/PI3K/Akt signaling pathway. These results indicated that NX210 may be a promising therapeutic candidate for ischemic stroke.

Procedural and Methodological Quality in Preclinical Stroke Research-A Cohort Analysis of the Rat MCAO Model Comparing Periods Before and After the Publication of STAIR/ARRIVE

The translation of preclinical stroke research into successful human clinical trials remains a challenging task. The first Stroke Therapy Academic Industry Roundtable (STAIR) recommendations for preclinical research and several other guidelines were published to address these challenges. Most guidelines recommend the use of physiological monitoring to detect the occurrence of undesired pathologies such as subarachnoid hemorrhage and to limit the variability of the infarct volume and–therefore-homogenize the experimental result for complete reporting particularly with respect to transparency and methodological rigor. From the years 2009 and 2019, 100 published articles each using a rat stroke model were analyzed to quantify parameters related to anesthesia, physiological monitoring, stroke model type, ischemia verification, and overall study quality over time. No significant difference in the frequency of cerebral blood flow (CBF) measurements over time (28/34% for 2009/2019) was found. Notably, significantly fewer studies reported temperature, blood pressure, and blood gas monitoring data in 2019 compared to 2009. On the other hand, an increase in general study quality parameters (e.g., randomization, reporting of approval) was seen. In conclusion, the frequency of periinterventional monitoring has decreased over time. Some general methodological quality aspects, however, partially have increased. CBF measurement–the gold standard for ischemia verification-was applied rarely. Despite the growing recognition of current guidelines such as STAIR and ARRIVE (both widely approved in 2019) reporting, methods and procedures mostly do not follow these guidelines. These deficits may contribute to the translational failure of preclinical stroke research in search for neuroprotective therapies.

Retinoic acid regulates the ubiquitin-proteasome system in a middle cerebral artery occlusion animal model

Background

Retinoic acid is a major metabolite of vitamin A and exerts beneficial effects including anti-oxidant and anti-inflammatory activities in neurons. The ubiquitin–proteasome system is an important biological system that regulates cell survival. Ubiquitination regulates protein degradation and plays an important role in oxidative stress. Deubiquitinating enzymes cleave ubiquitin from proteins and control ubiquitination-induced degradation. We detected decreases in ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in cerebral ischemic damage. In this study, we investigated whether retinoic acid regulates the expression of deubiquitinating enzymes ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in cerebral ischemic injury. Right middle cerebral artery occlusion (MCAO) was performed to induce cerebral ischemic damage in male rats. Retinoic acid (5 mg/kg) or vehicle was intraperitoneally injected every day from 4 days before surgery. Neurological behavioral tests were performed 24 h after MCAO, and right cerebral cortical tissues were collected.

Results

MCAO damage caused neurological behavioral dysfunction, and retinoic acid alleviated these deficits. The identified proteins decreased in MCAO animals with vehicle, while retinoic acid treatment attenuated these decreases. The results of proteomic study were confirmed by a reverse transcription-PCR technique. Expressions of ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 were decreased in MCAO animals treated with vehicle. Retinoic acid treatment alleviated these MCAO-induced reductions. The ubiquitin–proteasome system plays an essential role in maintaining cell function and preserving cell shape against ischemic damage.

Conclusions

These findings suggest that retinoic acid regulates ubiquitin- and proteasome-related proteins including ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in a brain ischemia model. Changes in these proteins are involved in the neuroprotective effects of retinoic acid.

Effects of Volatile Anesthetics on Postoperative Ischemic Stroke Incidence

Background

Preclinical studies suggest that volatile anesthetics decrease infarct volume and improve the outcome of ischemic stroke. This study aims to determine their effect during noncardiac surgery on postoperative ischemic stroke incidence.

Methods and Results

This was a retrospective cohort study of surgical patients undergoing general anesthesia at 2 tertiary care centers in Boston, MA, between October 2005 and September 2017. Exclusion criteria comprised brain death, age <18 years, cardiac surgery, and missing covariate data. The exposure was defined as median age‐adjusted minimum alveolar concentration of all intraoperative measurements of desflurane, sevoflurane, and isoflurane. The primary outcome was postoperative ischemic stroke within 30 days. Among 314 932 patients, 1957 (0.6%) experienced the primary outcome. Higher doses of volatile anesthetics had a protective effect on postoperative ischemic stroke incidence (adjusted odds ratio per 1 minimum alveolar concentration increase 0.49, 95% CI, 0.40–0.59, P<0.001). In Cox proportional hazards regression, the effect was observed for 17 postoperative days (postoperative day 1: hazard ratio (HR), 0.56; 95% CI, 0.48–0.65; versus day 17: HR, 0.85; 95% CI, 0.74–0.99). Volatile anesthetics were also associated with lower stroke severity: Every 1‐unit increase in minimum alveolar concentration was associated with a 0.006‐unit decrease in the National Institutes of Health Stroke Scale (95% CI, −0.01 to −0.002, P=0.002). The effects were robust throughout various sensitivity analyses including adjustment for anesthesia providers as random effect.

Conclusions

Among patients undergoing noncardiac surgery, volatile anesthetics showed a dose‐dependent protective effect on the incidence and severity of early postoperative ischemic stroke.

The role of spreading depolarizations and electrographic seizures in early injury progression of the rat photothrombosis stroke model

Spreading depolarization (SD) and seizures are pathophysiological events associated with cerebral ischemia. Here, we investigated their role for injury progression in the cerebral cortex. Cerebral ischemia was induced in anesthetized male Wistar rats using the photothrombosis (PT) stroke model. SD and spontaneous neuronal activity were recorded in the presence of either urethane or ketamine/xylazine anesthesia. Blood-brain barrier (BBB) permeability, cerebral perfusion, and cellular damage were assessed through a cranial window and repeated intravenous injection of fluorescein sodium salt and propidium iodide until 4 h after PT. Neuronal injury and early lesion volume were quantified by stereological cell counting and manual and automated assessment of ex vivo T2-weighted magnetic resonance imaging. Onset SDs originated at the thrombotic core and invaded neighboring cortex, whereas delayed SDs often showed opposite propagation patterns. Seizure induction by 4-aminopyridine caused no increase in lesion volume or neuronal injury in urethane-anesthetized animals. Ketamine/xylazine anesthesia was associated with a lower number of onset SDs, reduced lesion volume, and neuronal injury despite a longer duration of seizures. BBB permeability increase inversely correlated with the number of SDs at 3 and 4 h after PT. Our results provide further evidence that ketamine may counteract the early progression of ischemic injury.

Salidroside regulates imbalance of Th17/Treg and promotes ischemic tolerance by targeting STAT-3 in cerebral ischemia-reperfusion injury

INTRODUCTION

The balance between Th17 and Treg cells controls the immune response and is an important regulator of helper T cells acting on autoimmune diseases. Focal cerebral ischemia-reperfusion injury can induce imbalance of Th17/Treg cells in the brain and the peripheral immune system of rats. The aim of this study was to investigate the effect of salidroside (Sal) on the ratio of Th17 and Treg cells in an adult rat model of middle cerebral artery occlusion (MCAO).

MATERIAL AND METHODS

Forty rats were divided into 4 groups: normal group, sham group, surgery group, and Sal group. After treatment, the neurological deficits in rats were evaluated. Peripheral blood mononuclear cells were isolated and the count of Th17 and Treg cells was detected by flow cytometry. The infarct size and expression of RORγt and Foxp3 were detected in rat brain tissue. Rat spleen cells were isolated, CD4⁺ T cells were purified by immunomagnetic beads. Treg cells were induced by adding cytokine TGF-β. Th17 cells were induced by adding cytokine IL-6. The expression of STAT-3 was inhibited by SiRNA, and the effect of Sal on the differentiation of Th17/Treg cells was analyzed. The expression levels of IL-6, TNF-α, MCP-1, STAT-3 and NF-κ-B2 proteins were examined.

RESULTS

The results show that MCAO can induce an imbalance of Th17 and Treg cells in peripheral blood of rats. Sal treatment can significantly reduce the neurological deficit and infarct size of MCAO rats, reverse the oxidative stress of rat brain tissue, and inhibit the apoptosis of brain cells in MCAO rats. In the brain tissue of MCAO rats, Sal could significantly inhibit the expression of IL-6, TNF-α, MCP-1, STAT-3 and NF-κ-B2. Down-regulation of STAT-3 significantly reversed the therapeutic effects of Sal treatment.

CONCLUSIONS

Our results indicate that Sal can increase the tolerance of rat brain tissue to ischemia, inhibit cell apoptosis and reduce oxidative stress by targeting STAT-3.

Predicting experimental success: a retrospective case-control study using the rat intraluminal thread model of stroke

The poor translational success rate of preclinical stroke research may partly be due to inaccurate modelling of the disease. We provide data on transient middle cerebral artery occlusion (tMCAO) experiments, including detailed intraoperative monitoring to elaborate predictors indicating experimental success (ischemia without occurrence of confounding pathologies). The tMCAO monitoring data (bilateral cerebral blood flow, CBF; heart rate, HR; and mean arterial pressure, MAP) of 16 animals with an 'ideal' outcome (MCA-ischemia), and 48 animals with additional or other pathologies (subdural haematoma or subarachnoid haemorrhage), were checked for their prognostic performance (receiver operating characteristic curve and area under the curve, AUC). Animals showing a decrease in the contralateral CBF at the time of MCA occlusion suffered from unintended pathologies. Implementation of baseline MAP, in addition to baseline HR (AUC, 0.83, 95% c.i. 0.68 to 0.97), increased prognostic relevance (AUC, 0.89, 95% c.i. 0.79 to 0.98). Prediction performance improved when two additional predictors referring to differences in left and right CBF were considered (AUC, 1.00, 95% c.i. 1.0 to 1.0). Our data underline the importance of peri-interventional monitoring to verify a successful experimental performance in order to ensure a disease model as homogeneous as possible.

Mesenchymal stem cells-derived mitochondria transplantation mitigates I/R-induced injury, abolishes I/R-induced apoptosis, and restores motor function in acute ischemia stroke rat model

Acute ischemia stroke (AIS) is one of the leading causes of mortality and disability worldwide, and its neurological impacts are devastating and permanent. There is no efficient and real treatment for acute ischemia stroke so far. Therefore, development of efficient therapeutic strategies is under focus of investigations by basic and clinical scientists. Brain is one of the organs with high energy consumption and metabolism. Hence, its functionality is highly dependent on mitochondrial activity and integrity. Therefore, mitochondria play a vital homeostatic role in neurons physiology and mitochondrial dysfunction implications have been reported in a variety of nervous system diseases including acute ischemia stroke. In an attempt to investigate and introduce a novel potential therapeutic strategy for AIS, we isolated healthy mitochondria from human umbilical cord derived mesenchymal stem cells (hUC-MSCs) followed by their intracerebroventricular transplantation in a rat model of ischemia, i.e. middle cerebral artery occlusion (MCAO). Here we report that the mitochondrial transplantation ameliorated the reperfusion/ischemia-induced damages as reflected by declined blood creatine phosphokinase level, abolished apoptosis, decreased astroglyosis and microglia activation, reduced infarct size, and improved motor function. Although further preclinical and clinical studies are required, our findings strongly suggest that transplantation of MSCs-derived mitochondria is a suitable, potential and efficient therapeutic option for acute ischemia stroke.

Laser-Induced Brain Injury in the Motor Cortex of Rats

A common technique for inducing stroke in experimental rodent models involves the transient (often denoted as MCAO-t) or permanent (designated as MCAO-p) occlusion of the middle cerebral artery (MCA) using a catheter. This generally accepted technique, however, has some limitations, thereby limiting its extensive use. Stroke induction by this method is often characterized by high variability in the localization and size of the ischemic area, periodical occurrences of hemorrhage, and high death rates. Also, the successful completion of any of the transient or permanent procedures requires expertise and often lasts for about 30 minutes. In this protocol, a laser irradiation technique is presented that can serve as an alternative method for inducing and studying brain injury in rodent models. When compared to rats in the control and MCAO groups, the brain injury by laser induction showed reduced variability in body temperature, infarct volume, brain edema, intracranial hemorrhage, and mortality. Furthermore, the use of a laser-induced injury caused damage to the brain tissues only in the motor cortex unlike in the MCAO experiments where destruction of both the motor cortex and striatal tissues is observed. Findings from this investigation suggest that laser irradiation could serve as an alternative and effective technique for inducing brain injury in the motor cortex. The method also shortens the time for completing the procedure and does not require expert handlers.

MiR-202-5p attenuates neurological deficits and neuronal injury in MCAO model rats and OGD-induced injury in Neuro-2a cells by targeting eIF4E-mediated induction of autophagy and inhibition of Akt/GSK-3β pathway

Ischemic stroke is a common cerebrovascular disease caused by insufficient blood supply to the brain. In recent years, studies have demonstrated that microRNAs (miRNAs) are involved in a variety of biological processes in the nervous system. However, the effects of miR-202-5p on cerebral ischemic stroke injury have not been completely elucidated. In our study, N2a cells were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) treatment, and middle cerebral artery occlusion (MCAO) rat models were constructed. Our results indicated that decreased miR-202-5p expression was connected to N2a cells after OGD/R-induced injury and rats after MCAO. In addition, high miR-202-5p expression increased proliferation and prevented apoptosis and autophagy of OGD/R-treated N2a cells, while also effectively decreasing the infarct volume in MCAO model rats. We validated the interplay between miR-202-5p and eukaryotic translation initiation factor 4E (eIF4E), and found that miR-202-5p downregulated eIF4E by targeted combination. Moreover, we demonstrated that miR-202-5p accelerated proliferation and suppressed autophagy of OGD/R-induced N2a cells by targeting eIF4E. Meanwhile, our other results suggest that upregulation of miR-202-5p may activate the Akt/GSK-3β pathway in ischemic brain injury. Our findings suggest that miR-202-5p may serve as a protective agent for ischemia-reperfusion injury in stroke via eIF4E.

miR‑335 promotes stress granule formation to inhibit apoptosis by targeting ROCK2 in acute ischemic stroke

Under harmful environmental conditions, stress granules (SGs), macromolecular aggregates that are associated with cell survival and death, are produced in the eukaryotic cytoplasm. However, whether and how microRNAs (miRNAs/miRs) modulate SG formation induced by acute ischemic stroke has not been investigated. In the present study, a rat model of middle cerebral artery occlusion (MCAO) was utilized and miRNA array profiling and reverse transcription‑quantitative polymerase chain reaction were performed. The results revealed that miR‑335 was downregulated during acute ischemic stroke, which was concomitant with reduced SG formation, enhanced apoptosis levels and increased Rho associated protein kinase 2 (ROCK2) expression. In the MCAO rat and serum‑free cell models, miR‑335 treatment upregulated SG formation, alleviated the ischemia‑induced infarction, and decreased ROCK2 protein expression and apoptosis levels. By contrast, when compared with miR‑335 treatment, the inhibition of miR‑335 resulted in reduced SG formation and higher ROCK2 expression and apoptosis levels. Target prediction analysis and luciferase 3'‑untranslated region reporter assay identified ROCK2 as the direct target of miR‑335. Furthermore, ROCK2 silencing enhanced SG formation and attenuated the level of apoptosis in the serum‑free cell model. In addition, ROCK2 silencing markedly inhibited the effect of miR‑335 on SG formation and apoptosis levels. Unexpectedly, the phosphorylation of T‑cell intracellular antigen‑1 was significantly inhibited by miR‑335 in the MCAO rat model, which provides a reasonable explanation for the promotional effect of miR‑335 on SG formation by specifically targeting ROCK2. In conclusion, these results demonstrate that miR‑335 promotes SG formation and inhibits apoptosis by reducing ROCK2 expression in acute ischemic stroke, which provides a possible therapeutic target for brain injury.

Effect of Mannitol Infusion on Optic Nerve Injury After Acute Traumatic Subarachnoid Hemorrhage and Brain Injury

The primary aim of this paper is to investigate the neuroprotective and antiinflammatory effects of mannitol on optic nerve injury after acute traumatic subarachnoid hemorrhage and brain injury in rat models. Traumatic brain injury (TBI) and traumatic subarachnoid hemorrhage (tSAH) were produced by a custom-made weight-drop impact acceleration device. Thirty male Wistar rats were divided into 3 groups. Group I (n = 10) was the sham group, group II (n = 10) received TBI, and group III (n = 10) received TBI + mannitol (1 mg/kg intravenously). Optic nerve tissue glutathione peroxidase (GPx) and interleukin 1 beta (IL-1β) levels were measured 4 hours after the trauma. The authors used Kruskal-Wallis variance analysis and Mann-Whitney U tests for statistical analysis. Optic nerve tissue GPx levels were significantly higher in group III than in groups I and II (P < 0.05). Optic nerve tissue IL-1β levels were significantly lower in group III than in group II (P < 0.05) and higher than in group I (P < 0.05).Mannitol increased the antioxidant GPx levels and decreased the IL-1β levels, which can protect the optic nerve from secondary injury after severe acute trauma. Mannitol plays an important role in the treatment of acute severe indirect optic nerve injury after TBI and tSAH.

MRI Guiding of the Middle Cerebral Artery Occlusion in Rats Aimed to Improve Stroke Modeling

The middle cerebral artery occlusion (MCAO) model in rats closely imitates ischemic stroke and is widely used. Existing instrumental methods provide a certain level of MCAO guidance, but monitoring of the MCA-occluding intraluminal filament position and possible complications can be improved. The goal of this study was to develop a MRI-based method of simultaneous control of the filament position, blood flow in the intracranial vessels, and hemorrhagic complications. Rats were subjected to either MRI-guided MCAO (group 1, n = 51) or MCAO without MRI control (group 2, n = 38). After operation, group 1 rats were transferred into a MRI scanner for the control of the filament position and possible complications. Ninety minutes after the onset of MCAO, the filament was removed in rats of both groups and MRI control of the infarct volume and hemorrhagic complications performed. High-resolution T1- and T2-weighted imaging performed immediately after filament insertion provided visualization of the filament position, blood flow in brain arteries, and complications related to inappropriate filament insertion. It permitted replacement of wrongly positioned filaments and exclusion of animals with complications from the experiment. MRI-based MCAO guiding provided real-time intra-operational monitoring of crucial parameters determining MCAO suitability for stroke modeling, including better assessment of the operation outcomes in individual animals and significant enhancement of the model success rate. The possibility of simultaneous visualization of the filament, blood flow in the arteries, brain tissue, and hemorrhagic complications is the principal advantage of the proposed method over other instrumental methods of MCAO quality control. Graphical Abstract MRI-guided middle cerebral artery occlusion technique permits intra-operational monitoring via direct non-invasive simultaneous visualization of the filament, blood flow in the arteries, brain tissue, and hemorrhagic complications. It provides better assessment of MCAO outcomes in individual animals and significant enhancement of MCAO success rate.

Propofol, but not ketamine or midazolam, exerts neuroprotection after ischaemic injury by inhibition of Toll-like receptor 4 and nuclear factor kappa-light-chain-enhancer of activated B-cell signalling: A combined in vitro and animal study

BACKGROUND

Propofol, midazolam and ketamine are widely used in today's anaesthesia practice. Both neuroprotective and neurotoxic effects have been attributed to all three agents.

OBJECTIVE

To establish whether propofol, midazolam and ketamine in the same neuronal injury model exert neuroprotective effects on injured neurones in vitro and in vivo by modulation of the Toll-like receptor 4-nuclear factor kappa-light-chain-enhancer of activated B cells (TLR-4-NF-κB) pathway.

DESIGN AND SETTING

Cell-based laboratory (n = 6 repetitions per experiment) and animal (n = 6 per group) studies using a neuronal cell line (SH-SY5Y cells) and adult Sprague-Dawley rats.

INTERVENTIONS

Cells were exposed to oxygen-glucose deprivation before or after treatment using escalating, clinically relevant doses of propofol, midazolam and ketamine. In animals, retinal ischaemia (60 min) was induced followed by reperfusion and randomised treatment with saline or propofol.

MAIN OUTCOME MEASURES

Neuronal cell death was determined using flow-cytometry (mitochondrial membrane potential) and lactate dehydrogenase (LDH) release. Nuclear factor NF-κB and hypoxia-inducible factor 1 α-activity were analysed by DNA-binding ELISA, expression of NF-κB-dependent genes and TLR-4 by luciferase-assay and flow-cytometry, respectively. In animals, retinal ganglion cell density, caspase-3 activation and gene expression (TLR-4, NF-κB) were used to determine in vivo effects of propofol. Results were compared using ANOVA (Analysis of Variance) and t test. A P value less than 0.05 was considered statistically significant.

RESULTS

Post-treatment with clinically relevant concentrations of propofol (1 to 10 μg ml) preserved the mitochondrial membrane potential in oxygen-glucose deprivation-injured cells by 54% and reduced LDH release by 21%. Propofol diminished TLR-4 surface expression and preserved the DNA-binding activity of the protective hypoxia-inducible factor 1 α transcription factor. DNA-binding and transcriptional NF-κB-activity were inhibited by propofol. Neuronal protection and inhibition of TLR-4-NF-κB signalling were not consistently seen with midazolam or ketamine. In vivo, propofol treatment preserved rat retinal ganglion cell densities (cells mm, saline 1504 ± 251 vs propofol 2088 ± 144, P = 0.0001), which was accompanied by reduced neuronal caspase-3, TLR-4 and NF-κB expression.

CONCLUSION

Propofol, but neither midazolam nor ketamine, provides neuroprotection to injured neuronal cells via inhibition of TLR-4-NF-κB-dependent signalling.

Toxicity of inhaled agents after prolonged administration

Inhaled anesthetics have been utilized mostly for general anesthesia in the operating room and oftentimes for sedation and for treatment of refractory status epilepticus and status asthmaticus in the intensive care unit. These contexts in the ICU setting are related to potential for prolonged administration wherein potential organ toxicity is a concern. Over the last decade, several clinical and animal studies of neurotoxicity attributable to inhaled anesthetics have been emerging, particularly in extremes of age. This review overviews potential for and potential mechanisms of neurotoxicity and systemic toxicity of prolonged inhaled anesthesia and clinical scenarios where inhaled anesthesia has been used in order to assess safety of possible prolonged use for sedation. High dose inhaled agents are associated with postoperative cognitive dysfunction (POCD) and other situations. However, thus far no strong indication of problematic neuro or organ toxicity has been demonstrated after prolonged use of low dose volatile anesthesia.

Moderate hypothermia induces protein SUMOylation in bone marrow stromal cells and enhances their tolerance to hypoxia

Acute cerebral infarction can progress rapidly, and there are limited specific and effective treatments. Small ubiquitin‑like modifiers (SUMOs) provide an important post‑translational modification of proteins. Following cerebral infarction, multiple proteins can combine with SUMOs to protect nerve cells. Furthermore, moderate hypothermia (core body temperature, 33‑34˚C) can increase the level of SUMOylation on multiple proteins. In the present study, it was examined whether moderate hypothermia increases the survival rate of bone marrow stromal stem cells (BMSCs) implanted in the cerebral ischemic penumbra via SUMOylation of multiple proteins. Firstly, BMSCs were exposed to oxygen‑glucose deprivation (OGD) under moderate hypothermic (33˚C) conditions. Subsequently, adult rats with middle cerebral artery occlusion were treated with a combination of BMSCs and moderate hypothermia (32‑34˚C). The results demonstrated that hypothermia promoted the combination of multiple proteins with SUMOs in BMSCs, and induced transport of SUMOs from the cytoplasm to the nucleus. Moderate hypothermia additionally reduced damage to BMSCs following OGD and improved BMSC survival following transplantation into the penumbra. These data suggest that moderate hypothermia may protect against BMSC injury via rapid SUMOylation of intracellular proteins. Thus, BMSC transplantation combined with moderate hypothermia may be a potential therapeutic strategy to treat cerebral infarction.

RETRACTED: Activation of the PI3K-Akt pathway promotes neuroprotection of the δ-opioid receptor agonist against cerebral ischemia-reperfusion injury in rat models

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. The authors contacted the journal to request a retraction: "Recently, we found that some experimental animal samples from another research were mistakenly used in this paper, resulting in the results and conclusions unreliable". Concern was also raised about the reliability of the brain section images in Figure 1, which seem to appear in other publications, as detailed here: https://pubpeer.com/publications/8AF402957928F3F27A1F46B6D556AD; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. In addition, suspected image duplications were detected in Figures 2A, 3B and 4B. The journal requested the corresponding author comment on these concerns and provide the raw data. The author did not fulfil this request and the Editor-in-Chief decided to retract the article.

Duration of isoflurane-based surgical anesthesia determines severity of brain injury and neurological deficits after a transient focal ischemia in young adult rats

Tremendous efforts and funds invested in discovery of novel drug treatments for ischemic stroke have so far failed to deliver clinically efficacious therapies. The reasons for these failures are not fully understood. An indiscriminate use of isoflurane-based surgical anesthesia with or without nitrous oxide may act as an unconstrained, untraceable source of data variability, potentially causing false-positive or false-negative results. To test this hypothesis, a common transient suture middle cerebral artery occlusion (tMCAO) model of ischemic stroke in young adult male rats was used to determine the impact of a typical range of anesthesia durations required for this model on data variability (i.e., infarct volume and neurological deficits). The animals were maintained on spontaneous ventilation. The study results indicated that: (1) Variable duration of isoflurane anesthesia prior, during and after tMCAO is a significant source of data variability as evidenced by measurements of infarct volume and neurological deficits; and (2) Severity of brain injury and neurological deficits after tMCAO is inversely related to the duration of isoflurane anesthesia: e.g., in our study, a 90min isoflurane anesthesia nearly completely protected brain tissues from tMCAO-induced injury and thus, would be expected to obscure the effects of stroke treatments in pre-clinical trials. To elevate transparency, rigor and reproducibility of stroke research and minimize undesirable effects of isoflurane on the outcome of novel drug testing, we propose to monitor, minimize and standardize isoflurane anesthesia in experimental surgeries and make anesthesia duration a required reportable parameter in pre-clinical studies. Specifically, we propose to adopt 20-30min as an optimal anesthesia duration that both minimizes neuroprotective effects of isoflurane and permits a successful completion of surgical procedures in a suture tMCAO model of ischemic stroke in rodents. As the mechanisms and neuroprotective, metabolic and immune effects of general anesthesia are not fully understood, the results of this study cannot be blindly generalized to other anesthetics, animal species and experimental models.

Effects of Quercetin and Mannitol on Erythropoietin Levels in Rats Following Acute Severe Traumatic Brain Injury

Objective

The aim of this study to investigate the normal values of erythropoietin (EPO) and neuroprotective effects of quercetin and mannitol on EPO and hematocrit levels after acute severe traumatic brain injury (TBI) in rat model.

Methods

A weight-drop impact acceleration model of TBI was used on 40 male Wistar rats. The animals were divided into sham (group I), TBI (group II), TBI+quercetin (50 mg/kg intravenously) (group III), and TBI+mannitol (1 mg/kg intravenously) (group IV) groups. The malondialdehyde, glutathione peroxidase, catalase, EPO, and hematocrit levels were measured 1 and 4 hour after injury. Two-way repeated measures analysis of variance and Tukey’s test were used for statistical analysis.

Results

The malondialdehyde levels decreased significantly after administration of quercetin and mannitol compared with those in group II. Catalase and glutathione peroxidase levels increased significantly in groups III and IV. Serum EPO levels decreased significantly after mannitol but not after quercetin administration. Serum hematocrit levels did not change significantly after quercetin and mannitol administration 1 hour after trauma. However, mannitol administration decreased serum hematocrit levels significantly after 4 hour.

Conclusion

This study suggests that quercetin may be a good alternative treatment for TBI, as it did not decrease the EPO levels.

Impact of Stroke Therapy Academic Industry Roundtable (STAIR) Guidelines on Peri-Anesthesia Care for Rat Models of Stroke: A Meta-Analysis Comparing the Years 2005 and 2015

Numerous studies using rats in stroke models have failed to translate into successful clinical trials in humans. The Stroke Therapy Academic Industry Roundtable (STAIR) has produced guidelines on the rodent stroke model for preclinical trials in order to promote the successful translation of animal to human studies. These guidelines also underline the importance of anaesthetic and monitoring techniques. The aim of this literature review is to document whether anaesthesia protocols (i.e., choice of agents, mode of ventilation, physiological support and monitoring) have been amended since the publication of the STAIR guidelines in 2009. A number of articles describing the use of a stroke model in adult rats from the years 2005 and 2015 were randomly selected from the PubMed database and analysed for the following parameters: country where the study was performed, strain of rats used, technique of stroke induction, anaesthetic agent for induction and maintenance, mode of intubation and ventilation, monitoring techniques, control of body temperature, vascular accesses, and administration of intravenous fluids and analgesics. For each parameter (stroke, induction, maintenance, monitoring), exact chi-square tests were used to determine whether or not proportions were significantly different across year and p values were corrected for multiple comparisons. An exact p-test was used for each parameter to compare the frequency distribution of each value followed by a Bonferroni test. The level of significant set at < 0.05. Results show that there were very few differences in the anaesthetic and monitoring techniques used between 2005 and 2015. In 2015, significantly more studies were performed in China and significantly fewer studies used isoflurane and nitrous oxide. The most striking finding is that the vast majority of all the studies from both 2005 and 2015 did not report the use of ventilation; measurement of blood gases, end-tidal carbon dioxide concentration, or blood pressure; or administration of intravenous fluids or analgesics. The review of articles published in 2015 showed that the STAIR guidelines appear to have had no effect on the anaesthetic and monitoring techniques in rats undergoing experimental stroke induction, despite the publication of said guidelines in 2009.

Hemodynamic effects of intraoperative anesthetics administration in photothrombotic stroke model: a study using laser speckle imaging

Background

Previous neuroimaging studies have shown the hemodynamic effect of either preconditioning or postconditioning anesthesia in ischemic stroke model. However, the anesthetic effect in hemodynamics during and immediately after the stroke modeling surgery remains unknown due to the lack of appropriate anesthesia-free stroke model and intraoperative imaging technology. In the present study, we utilized our recently developed photothrombotic model of focal cerebral ischemia in conscious and freely moving rats, and investigated transient hemodynamic changes with or without isoflurane administration. Laser speckle imaging was applied to acquire real-time two-dimensional full-field cerebral blood flow (CBF) information throughout the surgical operations and early after.

Results

Significantly larger CBF reduction area was observed in conscious rats from 8 min immediately after the onset of stroke modeling, compared with anesthetized rats. Stroke rats without isoflurane administration also showed larger lesion volume identified by magnetic resonance imaging 3 h post occlusion (58.9%), higher neurological severity score 24 h post occlusion (28.3%), and larger infarct volume from 2,3,5-triphenyltetrazolium chloride staining 24 h post occlusion (46.9%).

Conclusions

Our results demonstrated that the hemodynamic features were affected by anesthetics at as early as during the stroke induction. Also, our findings about the neuroprotection of intraoperative anesthetics administration bring additional insights into understanding the translational difficulty in stroke research.

Hypothalamic, thalamic and hippocampal lesions in the mouse MCAO model: Potential involvement of deep cerebral arteries?

Intraluminal monofilament occlusion of the middle cerebral artery (MCAO) in mice is the most used rodent model to study the pathophysiology of stroke. However, this model often shows brain damage in regions not supplied by the MCA such as the hypothalamus, hippocampus and thalamus. Several studies have suggested some explanations on these localized infarcts. We aim to provide an alternative explanation which could allow each experimenter to better grasp the MCAO model. We propose that the MCA occlusion by the monofilament also occludes deep and small cerebral arteries arising directly from the internal carotid artery, proximally to the origin of MCA. Then, drawbacks and pitfalls of the MCAO model must be appreciated and the almost systematic risk of inducing lesions in some unwanted territories for neuroanatomical reasons, i.e. vascular connections between deep arteries and hypothalamic, thalamic and hippocampal areas in rodents has to be integrated.

Experimental subarachnoid hemorrhage in rats: comparison of two endovascular perforation techniques with respect to success rate, confounding pathologies and early hippocampal tissue lesion pattern

Recently aside from the “classic” endovascular monofilament perforation technique to induce experimental subarachnoid hemorrhage (SAH) a modification using a tungsten wire advanced through a guide tube has been described. We aim to assess both techniques for their success rate (induction of SAH without confounding pathologies) as primary endpoint. Further, the early tissue lesion pattern as evidence for early brain injury will be analyzed as secondary endpoint. Sprague Dawley rats (n=39) were randomly assigned to receive either Sham surgery (n=4), SAH using the “classic” technique (n=18) or using a modified technique (n=17). Course of intracranial pressure (ICP) and regional cerebral blood flow (rCBF) was analyzed; subsequent pathologies were documented either 6 or 24 h after SAH. Hippocampal tissue samples were analyzed via immunohistochemistry and western blotting. SAH-induction, regardless of confounding pathologies, was independent from type of technique (p=0.679). There was no significant difference concerning case fatality rate (classic: 40%; modified: 20%; p=0.213). Successful induction of SAH without collateral ICH or SDH was possible in 40% with the classic and in 86.7% with the modified technique (p=0.008). Peak ICP levels differed significantly between the two groups (classic: 94 +/- 23 mmHg; modified: 68 +/- 19 mmHg; p=0.003). Evidence of early cellular stress response and activation of apoptotic pathways 6 h after SAH was demonstrated. The extent of stress response is not dependent on type of technique. Both tested techniques successfully produce SAH including activation of an early stress response and apoptotic pathways in the hippocampal tissue. However, the induction of SAH with less confounding pathologies was more frequently achieved with the modified tungsten wire technique.

Role of hydrogen sulfide in early blood-brain barrier disruption following transient focal cerebral ischemia

We determined the role of endogenous hydrogen sulfide (H₂S) in cerebral vasodilation/hyperemia and early BBB disruption following ischemic stroke. A cranial window was prepared over the left frontal, parietal and temporal cortex in mice. Transient focal cerebral Ischemia was induced by directly ligating the middle cerebral artery (MCA) for two hours. Regional vascular response and cerebral blood flow (CBF) during ischemia and reperfusion were measured in real time. Early BBB disruption was assessed by Evans Blue (EB) and sodium fluorescein (Na-F) extravasation at 3 hours of reperfusion. Topical treatment with DL-propargylglycine (PAG, an inhibitor for cystathionine γ-lyase (CSE)) and aspartate (ASP, inhibitor for cysteine aminotransferase/3-mercaptopyruvate sulfurtransferase (CAT/3-MST)), but not O-(Carboxymethyl)hydroxylamine hemihydrochloride (CHH, an inhibitor for cystathionine β-synthase (CBS)), abolished postischemic cerebral vasodilation/hyperemia and prevented EB and Na-F extravasation. CSE knockout (CSE^-/-) reduced postischemic cerebral vasodilation/hyperemia but only inhibited Na-F extravasation. An upregulated CBS was found in cerebral cortex of CSE^-/- mice. Topical treatment with CHH didn’t further alter postischemic cerebral vasodilation/hyperemia, but prevented EB extravasation in CSE^-/- mice. In addition, L-cysteine-induced hydrogen sulfide (H₂S) production similarly increased in ischemic side cerebral cortex of control and CSE^-/- mice. Our findings suggest that endogenous production of H₂S by CSE and CAT/3-MST during reperfusion may be involved in postischemic cerebral vasodilation/hyperemia and play an important role in early BBB disruption following transient focal cerebral ischemia.

The effect of ASK1 on vascular permeability and edema formation in cerebral ischemia

Apoptosis signal-regulating kinase-1 (ASK1) is the mitogen-activated protein kinase kinase kinase (MAPKKK) and participates in the various central nervous system (CNS) signaling pathways. In cerebral ischemia, vascular permeability in the brain is an important issue because regulation failure of it results in edema formation and blood-brain barrier (BBB) disruption. To determine the role of ASK1 on vascular permeability and edema formation following cerebral ischemia, we first investigated ASK1-related gene expression using microarray analyses of ischemic brain tissue. We then measured protein levels of ASK1 and vascular endothelial growth factor (VEGF) in brain endothelial cells after hypoxia injury. We also examined protein expression of ASK1 and VEGF, edema formation, and morphological alteration through cresyl violet staining in ischemic brain tissue using ASK1-small interference RNA (ASK1-siRNA). Finally, immunohistochemistry was performed to examine VEGF and aquaporin-1 (AQP-1) expression in ischemic brain injury. Based on our findings, we propose that ASK1 is a regulating factor of vascular permeability and edema formation in cerebral ischemia.

A reproducible and translatable model of focal ischemia in the visual cortex of infant and adult marmoset monkeys

Models of ischemic brain injury in the nonhuman primate (NHP) are advantageous for investigating mechanisms of central nervous system (CNS) injuries and testing of new therapeutic strategies. However, issues of reproducibility and survivability persist in NHP models of CNS injuries. Furthermore, there are currently no pediatric NHP models of ischemic brain injury. Therefore, we have developed a NHP model of cortical focal ischemia that is highly reproducible throughout life to enable better understanding of downstream consequences of injury. Posterior cerebral arterial occlusion was induced through intracortical injections of endothelin-1 in adult (n = 5) and neonatal (n = 3) marmosets, followed by magnetic resonance imaging (MRI), histology and immunohistochemistry. MRI revealed tissue hyperintensity at the lesion site at 1-7 days followed by isointensity at 14-21 days. Peripheral macrophage and serum albumin infiltration was detected at 1 day, persisting at 21 days. The proportional loss of total V1 as a result of infarction was consistent in adults and neonates. Minor hemorrhagic transformation was detected at 21 days at the lesion core, while neovascularization was detected in neonates, but not in adults. We have developed a highly reproducible and survivable model of focal ischemia in the adult and neonatal marmoset primary visual cortex, demonstrating similar downstream anatomical and cellular pathology to those observed in post-ischemic humans.

Comparison of infarct volume and behavioral deficit in Wistar Kyoto and spontaneously hypertensive rat after transient occlusion of the middle cerebral artery

Rodent models of focal cerebral ischemia are important tools in experimental stroke research. Such models have proven instrumental for the understanding of injury mechanisms in cerebral stroke and helped to identify potential new therapeutic options. A plethora of neuroprotective substances have been shown to be effective in preclinical stroke research but failed to prove effectiveness in subsequent clinical trials. Interestingly, preclinical studies have shown that neuroprotective agents are selectively effective in different rat strains. The underlying mechanisms for this discrepancy are so far unknown, but differences in initial stroke volume with concomitant neuroinflammatory processes in the expanding stroke area might be relevant.

In the current project, we compared the stroke volume and behavioral outcome between Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR), subjected to transient middle cerebral artery occlusion (tMCAO) for 1 h, followed by 23 h reperfusion. We further analyzed the expression of well-known pro-inflammatory mediators in the cortical peri-infarct area region using a TTC-based isolation approach.

Initial reduction of local cerebral blood flow was comparable between both strains. Mean infarct volume and the extent of tMCAO-provoked functional deficits did not differ between WKY and SHR rats. Furthermore, the induction of pro-inflammatory mediators, among CCL3 and CCL5, in the isolated ischemic peri-infarct area region was equal in both rat strains.

We were able to demonstrate that stroke outcome is comparable 23 h after transient MCAO in WKY and SHR rats. Future studies have to show whether this observation confirms in the long-term, and which factors contribute to differences observed with respect to therapeutic responsiveness.

Levosimendan limits reperfusion injury in a rat middle cerebral artery occlusion (MCAO) model

Background

Neuroprotective strategies in ischemic stroke are an important challenge in clinical and experimental research as an adjunct to reperfusion therapy that may reduce neurologic injury and improve outcome. The neuroprotective properties of levosimendan in traumatic brain injury in vitro, transient global brain ischemia and focal spinal cord ischemia suggest the potential for similar effects in transient brain ischemia.

Methods

Transient brain ischemia was induced for 60 min by intraluminal occlusion of the middle cerebral artery in 40 male Wistar rats under general anesthesia with s-ketamine and xylazine and with continuous monitoring of their blood pressure and cerebral perfusion. Five minutes before inducing reperfusion, a levosimendan bolus (24 μg kg ^-1) was administered over a 20 minute period. Infarct size, brain swelling, neurological function and the expression of inflammatory markers were quantified 24 hours after reperfusion.

Results

Although levosimendan limited the infarct size and brain swelling by 40% and 53%, respectively, no effect on neurological outcome or mortality could be demonstrated. Upregulation of tumor necrosis factor α and intercellular adhesion molecule 1 was significantly impeded. Cerebral blood flow during reperfusion was significantly reduced as a consequence of sustained autoregulation.

Conclusions

Levosimendan demonstrated significant neuroprotective properties in a rat model of transient brain ischemia by reducing reperfusion injury.