Postconditioning with isoflurane reduced ischemia-induced brain injury in rats

Isoflurane lowers the cerebral metabolic rate of oxygen and prevents hypoxia during cortical spreading depolarization in vitro: An integrative experimental and modeling study

Cortical spreading depolarization (SD) imposes a massive increase in energy demand and therefore evolves as a target for treatment following acute brain injuries. Anesthetics are empirically used to reduce energy metabolism in critical brain conditions, yet their effect on metabolism during SD remains largely unknown. We investigated oxidative metabolism during SD in brain slices from Wistar rats. Extracellular potassium ([K+]o), local field potential and partial tissue oxygen pressure (ptiO2) were measured simultaneously. The cerebral metabolic rate of oxygen (CMRO2) was calculated using a reaction-diffusion model. By that, we tested the effect of clinically relevant concentrations of isoflurane on CMRO2 during SD and modeled tissue oxygenation for different capillary pO2 values. During SD, CMRO2 increased 2.7-fold, resulting in transient hypoxia in the slice core. Isoflurane decreased CMRO2, reduced peak [K+]o, and prolonged [K+]o clearance, which indicates reduced synaptic transmission and sodium-potassium ATPase inhibition. Modeling tissue oxygenation during SD illustrates the need for increased capillary pO2 levels to prevent hypoxia. In the absence thereof, isoflurane could improve tissue oxygenation by lowering CMRO2. Therefore, isoflurane is a promising candidate for pre-clinical studies on neuronal survival in conditions involving SD.

Safety of local anesthesia in endovascular treatment of Aneurysms: A systematic review and Meta-Analysis

BACKGROUND

Endovascular treatment of intracranial aneurysms (EVTIAs) is increasingly popular due to its minimally invasive nature and high success rate. While general anesthesia (GA) has been the historical preference for EVTIAs, there's growing interest in local anesthesia (LA). However, concerns persist about LA safety for EVTIAs. Therefore, we conducted a systematic review and meta-analysis to assess LA safety for EVTIAs.

METHODS

Following PRISMA guidelines, we searched PubMed, Embase, and Web of Science databases. Pooled analysis with 95 % confidence intervals (CI) assessed effects, I2 statistics gauged heterogeneity, and a random-effects model was adopted. Conversion to GA, neurological or procedure-related complications, intraoperative intracranial hemorrhagic complications (IIHC), and mortality were assessed. Subanalyses for ruptured and unruptured cases were performed.

RESULTS

The analysis included eleven studies, 2,133 patients, and 2,369 EVTIAs under LA. Conversion to GA rate was 1 % (95 %CI: 0 to 2 %). Neurological or procedure-related complications rate was 13 % (95 % CI: 8 % to 17 %). IIHC analysis revealed a rate of 1 % (95 % CI: 1 % to 2 %). The mortality rate was 0 % (95 %CI: 0 % to 0 %). Subanalyses revealed similar rates in ruptured and unruptured subgroups, except for a slightly high rate of complications and IIHC in the ruptured subgroup.

CONCLUSION

Findings indicate that EVTIA under LA is safe, with low conversion and mortality rates, even for ruptured aneurysms. Complications rates, also in IIHC rates, are comparable to those reported for GA, emphasizing LA's comparable safety profile in EVTIAs. Considering these promising outcomes, the decision to opt for the LA approach emerges as meaningful and well-suited for the endovascular treatment of aneurysms. Beyond its safety, LA introduces inherent supplementary advantages, including shortened hospitalization periods, cost-effectiveness, and an expedited patient recovery process.

Influence of Remote Ischemic Conditioning and Nitrogen Monoxide on Angiogenesis and Microcirculation in a Mouse Ear Burn Model

INTRODUCTION

Remote ischemic conditioning (RIC) has been shown to improve tissue resilience against ischemia. The aim of this study was to investigate the influence of RIC and its key factor, nitrogen monoxide (NO), on angiogenesis in a burn wound.

MATERIALS AND METHODS

A unilateral burn injury on the ear of hairless mice (n = 48) was generated via a hot air jet in a contact-free manner. In four randomized groups, including the control (NoRIC group), RIC alone (RIConly group), RIC plus NO donor (ISDN group), and RIC plus NO synthase inhibitor (L-NAME group), the impact on angiogenesis, vessel diameter, blood flow, edema formation, and leukocyte-endothelial-cell interaction was evaluated over a 12-d period using intravital fluorescence microscopy.

RESULTS

Tissue perfusion was significantly improved by RIC (Day 3: ISDN group showed 182% and RIConly group showed 200% of baseline [BL], P < 0.001), while angiogenesis was not improved by RIC (nonperfused area on Day 12: mean 52% of BL in all groups, P >0.05). The application of ISDN did not further enhance the positive effect of RIC, whereas the application of L-NAME neutralized the effect of RIC. The most pronounced edema formation was observed in the RIConly group (mean 145% of BL, P ≤0.001), while the NoRIC group showed the least edema formation (Day 12: 117% of BL).

CONCLUSIONS

RIC led to increased tissue perfusion, which did not result in improved angiogenesis, which may have been due to increased edema formation after RIC performance. The results of the present study do not support the establishment of a causal therapy strategy for burn wounds, including RIC.

Desflurane Post-treatment Reduces Hypoxic-ischemic Brain Injury via Reducing Transient Receptor Potential Ankyrin 1 in Neonatal Rats

Perinatal hypoxic-ischemic (HI) brain injury leads to mortality and morbidity in neonates and children. There are no effective and practical methods to attenuate this brain injury. This study determined whether desflurane, a volatile anesthetic with limited effect on the cardiovascular system, protected against HI-induced brain damage and the role of transient receptor potential ankyrin 1 (TRPA1), a mediator for simulated ischemia-induced myelin damage, in this protection. Seven-day-old male and female Sprague-Dawley rats had brain HI. They were exposed to 4.8%, 7.6% or 11.4% desflurane immediately or 4.8% desflurane at 0.5, 1 or 2 h after the HI. Brain tissue loss was evaluated 7 days later. Neurological functions and brain structures of rats with HI and 4.8% desflurane post-treatment were evaluated 4 weeks after the HI. TRPA1 expression was determined by Western blotting. HC-030031, a TRPA1 inhibitor, was used to determine the role of TRPA1 in the HI-induced brain injury. HI induced brain tissue and neuronal loss, which was attenuated by all tested concentrations of desflurane. Desflurane post-treatment also improved motor function, learning and memory in rats with brain HI. Brain HI increased the expression of TRPA1 and this increase was inhibited by desflurane. TRPA1 inhibition reduced HI-induced brain tissue loss and impairment of learning and memory. However, the combination of TRPA1 inhibition and desflurane post-treatment did not preserve brain tissues, learning and memory better than TRPA1 inhibition or desflurane post-treatment alone. Our results suggest that desflurane post-treatment induces neuroprotection against neonatal HI. This effect may be mediated by inhibiting TRPA1.

Microglial IL-1RA ameliorates brain injury after ischemic stroke by inhibiting astrocytic CXCL1-mediated neutrophil recruitment and microvessel occlusion

Acute ischemic stroke (AIS), one of the leading causes of mortality worldwide, is characterized by a rapid inflammatory cascade resulting in exacerbation of ischemic brain injury. Microglia are the first immune responders. However, the role of postischemic microglial activity in ischemic brain injury remains far from being fully understood. Here, using the transgenic mouse line CX₃ CR1^creER :R26^iDTR to genetically ablate microglia, we showed that microglial deletion exaggerated ischemic brain injury. Associated with this worse outcome, there were increased neutrophil recruitment, microvessel blockade and blood flow stagnation in the acute phase, accompanied by transcriptional upregulation of chemokine (C-X-C motif) ligand 1 (CXCL1). Our study showed that microglial interleukin-1 receptor antagonist (IL-1RA) suppressed astrocytic CXCL1 expression induced by oxygen and glucose deprivation and inhibited neutrophil migration. Furthermore, neutralizing antibody therapy against CXCL1 or the administration of recombinant IL-1RA protein reduced brain infarct volume and improved motor coordination performance of mice after ischemic stroke. Our study suggests that microglia protect against acute ischemic brain injury by secreting IL-1RA to inhibit astrocytic CXCL1 expression, which reduces neutrophil recruitment and neutrophil-derived microvessel occlusion.

Brain DNA damaging effects of volatile anesthetics and 1 and 2 Gy gamma irradiation in vivo: Preliminary results

Although both can cause DNA damage, the combined impact of volatile anesthetics halothane/sevoflurane/isoflurane and radiotherapeutic exposure on sensitive brain cells in vivo has not been previously analyzed. Healthy Swiss albino male mice (240 in total, 48 groups) were exposed to either halothane/sevoflurane/isoflurane therapeutic doses alone (2 h); 1 or 2 gray of gamma radiation alone; or combined exposure. Frontal lobe brain samples from five animals were taken immediately and 2, 6, and 24 h after exposure. DNA damage and cellular repair index were analyzed using the alkaline comet assay and the tail intensity parameter. Elevated tail intensity levels for sevoflurane/halothane were the highest at 6 h and returned to baseline within 24 h for sevoflurane, but not for halothane, while isoflurane treatment caused lower tail intensity than control values. Combined exposure demonstrated a slightly halothane/sevoflurane protective and isoflurane protective effect, which was stronger for 2 than for 1 gray. Cellular repair indices and tail intensity histograms indicated different modes of action in DNA damage creation. Isoflurane/sevoflurane/halothane preconditioning demonstrated protective effects in sensitive brain cells in vivo. Owing to the constant increases in the combined use of radiotherapy and volatile anesthetics, further studies should explore the mechanisms behind these effects, including longer and multiple exposure treatments and in vivo brain tumor models.

Surgery Trauma Severity but not Anesthesia Length Contributes to Postoperative Cognitive Dysfunction in Mice

BACKGROUND

Perioperative, modifiable factors contributing to perioperative neurocognitive disorders (PND) have not been clearly defined.

OBJECTIVE

To determine the contribution of anesthesia lengths and the degrees of surgical trauma to PND and neuroinflammation, a critical process for PND.

METHODS

Three-month-old C57BL/6J mice were subjected to 2 h or 6 h isoflurane anesthesia plus a 5 min or 15 min left common carotid artery exposure (surgery) in a factorial design (two factors: anesthesia with two levels and surgery with three levels). Their learning and memory were tested by Barnes maze and novel object recognition paradigms. Blood, spleen, and hippocampus were harvested for measuring interleukin (IL)-6 and IL-1β. Eighteen-month-old C57BL/6J mice (old mice) were subjected to 6 h isoflurane anesthesia or 2 h isoflurane anesthesia plus 15 min surgery and then had learning and memory tested.

RESULTS

Three-month-old mice with 15 min surgery (long surgery) under 2 h or 6 h anesthesia performed poorly in the learning and memory tests compared with controls. Anesthesia alone or anesthesia plus 5 min surgery did not affect mouse performance in these tests. Similarly, only mice with long surgery but not mice with other experimental conditions had increased IL-6 and IL-1β in the blood, spleen, and hippocampus and decreased spleen weights. Splenocytes were found in the hippocampus after surgery. Similarly, old mice with long surgery but not the mice with isoflurane anesthesia alone had poor performance in the Barnes maze and novel object recognition tests.

CONCLUSION

Surgical trauma, but not anesthesia, contributes to the development of PND and neuroinflammation. Splenocytes may modulate these processes.

Shogaol potentiates sevoflurane mediated neuroprotection against ischemia/reperfusion-induced brain injury via regulating apoptotic proteins and PI3K/Akt/mTOR/s6K signalling and HIF-1α/HO-1 expression

The current research was intended to evaluate the impact of 6-shogaol in rodent model of ischemic-reperfusion induced- brain injury and also assessed 6-shogaol enhanced sevoflurane's neuroprotective effects. Ischemic-Reperfusion (I/R) injury was induced by middle cerebral artery occlusion (MCAO) method in Sprague-Dawley rats. A separate group of animal was exposed to sevoflurane (2.5%) post-conditioning for 1 h immediately after reperfusion. The 6-shogaol (25 mg or 50 mg/kg body weight) was orally administered to treatment group rats for 14 days and then subjected to I/R. The 6-shogaol treatment along with/without sevoflurane post-conditioning reduced the number of apoptotic cell counts, brain edema and cerebral infarct volume. The western blotting analysis revealed a significant stimulation of the PI3K/Akt/mTOR signal pathway. RT-PCR and western blotting studies revealed improved expressions of HIF-1α and HO-1 at both gene level and protein levels. I/R induced neurological deficits were also alleviated on sevoflurane post-conditioning with/without 6-shogaol treatment. The present findings revealed that pre-treatment with 6-shogoal enhanced the neuroprotective properties of sevoflurane post-conditioning, illustrated the efficacy of the compound against I/R injury.

Dexmedetomidine and Phosphocreatine Post-treatment Provides Protection against Focal Cerebral Ischemia-reperfusion Injury in Rats

In this study we investigated the neuroprotective efficacy of dexmedetomidine (Dex) and phosphocreatine (PCr) alone or in combination in a rat model of focal cerebral ischemia-reperfusion injury (I/R). I/R was induced by intraluminal middle cerebral artery occlusion (MCAO) and reperfusion. Male Sprague-Dawley rats were randomly allocated to the Sham group and I/R group, and the I/R group was further divided into three subgroups: Dex (9 μg.kg⁻¹ Dex), PCr (180 mg.kg⁻¹ PCr) and Dex + PCr (9 μg.kg⁻¹ Dex + 180 mg.kg⁻¹ PCr). All treatments were given intravenously at the onset of reperfusion. After 24 hr of reperfusion, the neurological deficit score (NDS) was determined and a magnetic resonance imaging (MRI) scan was performed. Serum concentrations of malonaldehyde (MDA) and 4-hydroxynonenal (4-HNE) were measured and cerebral infarct volume was estimated by triphenyl tetrazolium chloride (TTC) staining. Blood brain barrier, neuronal and mitochondrial damage was assessed by optical and electron microscopy. Neuronal injury was further assessed using double cleaved caspase-3 and NeuN immunofluorescent staining. Compared with group I/R, Dex and PCr significantly reduced the neurological deficit score (P < 0.01), infarct volume (P < 0.01), and brain blood barrier, neuronal and mitochondrial damage. The level of oxidative stress (P < 0.001) and neuronal injury (P < 0.001) also decreased and surviving neurons increased (P < 0.001). Compared with Dex or PCr alone, the combination treatment had overall greater effects (P < 0.05). These results indicate that posttreatment with Dex or PCr decreases focal cerebral I/R injury and that these agents in combination have greater protective effects than each alone.

Systematic Study of Immune Cell Diversity in ischemic postconditioning Using High-Dimensional Single-Cell Analysis with Mass Cytometry

Ischemic postconditioning (IPostC) is a concept of ischemic stroke treatment, in which several cycles of brief reocclusion after reperfusion are repeated. It is essential to have an accurate understanding of the immune response in IPostC. By using high parametric single-cell mass cytometry, immune cell subsets and characterize their unique functions from ischemic brain and peripheral blood were identified after IPostC. This study enabled us to better understand the immune cell phenotypical and functional characteristics in ischemic brain and peripheral blood at the single-cell and protein levels. Since some cell surface markers can serve as functional markers, reflecting the degree of inflammation, the cell surface marker intensity among different groups was analyzed. The results showed that downregulation of 4E-BP1 and p38 of Microglia and MoDM in the ischemic brain was involved in IPostC-induced protection. In the peripheral blood, downregulation of P38 of CD4 T cell and Treg has also participated in IPostC-induced protection.

Intravenous versus Volatile Anesthetic Effects on Postoperative Cognition in Elderly Patients Undergoing Laparoscopic Abdominal Surgery

BACKGROUND

Delayed neurocognitive recovery after surgery is associated with poor outcome. Most surgeries require general anesthesia, of which sevoflurane and propofol are the most commonly used inhalational and intravenous anesthetics. The authors tested the primary hypothesis that patients with laparoscopic abdominal surgery under propofol-based anesthesia have a lower incidence of delayed neurocognitive recovery than patients under sevoflurane-based anesthesia. A second hypothesis is that there were blood biomarkers for predicting delayed neurocognitive recovery to occur.

METHODS

A randomized, double-blind, parallel, controlled study was performed at four hospitals in China. Elderly patients (60 yr and older) undergoing laparoscopic abdominal surgery that was likely longer than 2 h were randomized to a propofol- or sevoflurane-based regimen to maintain general anesthesia. A minimum of 221 patients was planned for each group to detect a one-third decrease in delayed neurocognitive recovery incidence in propofol group compared with sevoflurane group. The primary outcome was delayed neurocognitive recovery incidence 5 to 7 days after surgery.

RESULTS

A total of 544 patients were enrolled, with 272 patients in each group. Of these patients, 226 in the propofol group and 221 in the sevoflurane group completed the needed neuropsychological tests for diagnosing delayed neurocognitive recovery, and 46 (20.8%) in the sevoflurane group and 38 (16.8%) in the propofol group met the criteria for delayed neurocognitive recovery (odds ratio, 0.77; 95% CI, 0.48 to 1.24; P = 0.279). A high blood interleukin-6 concentration at 1 h after skin incision was associated with an increased likelihood of delayed neurocognitive recovery (odds ratio, 1.04; 95% CI, 1.01 to 1.07; P = 0.007). Adverse event incidences were similar in both groups.

CONCLUSIONS

Anesthetic choice between propofol and sevoflurane did not appear to affect the incidence of delayed neurocognitive recovery 5 to 7 days after laparoscopic abdominal surgery. A high blood interleukin-6 concentration after surgical incision may be an independent risk factor for delayed neurocognitive recovery.

EDITOR’S PERSPECTIVE

[D-Ala2, D-Leu5] Enkephalin Inhibits TLR4/NF-κB Signaling Pathway and Protects Rat Brains against Focal Ischemia-Reperfusion Injury

Background

Cerebral ischemia-reperfusion (I/R) injury is the main cause of acute brain injury, which is a life-threatening disease due to the lack of effective treatments. [D-Ala², D-Leu⁵] enkephalin (DADLE) is a synthetic delta-opioid receptor agonist that is reported to confer neuroprotective effect; however, the underlying mechanism is still being explored. The purpose of the present study is to determine whether DADLE administrated intracerebroventricularly could attenuate the cerebral I/R injury, to determine if this is through inhibiting the toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway and therefore inhibiting neuroinflammation in an ischemic stroke model.

Methods

Rats were subjected to 120 minutes of ischemia by transient middle cerebral artery occlusion (MCAO). At 45 minutes after ischemia, DADLE or control vehicle (artificial cerebrospinal fluid, ACSF) was given to the rats intracerebroventricularly. Neurological deficit, cerebral infarct volume, and histopathological changes were assessed at 24 hours after reperfusion. Brain inflammation was assessed by measuring tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the ischemic penumbra by ELISA. The expression of TLR4 was determined by immunohistochemistry staining and western blotting. The expression of NF-κB was investigated by western blotting.

Results

Compared with the vehicle-treatment (ACSF), DADEL improved neurological deficit (9.6 ± 2.1 versus 13.8 ± 1.9), reduced cerebral infarct volume (18.74 ± 3.30% versus 10.57 ± 2.50%), and increased the number of normal neurons (29.72 ± 8.53% versus 51.37 ± 9.18%) after cerebral I/R injury in rats (all P < 0.05). Expressions of inflammatory molecules including TNF-α and IL-6 were highly expressed in the vehicle-treated rats, whereas treatment with DADLE downregulated these expressions (P < 0.05). Additionally, cerebral I/R injury significantly increased the TLR4 and NF-κB expression in vehicle-control group, which was markedly inhibited by DADLE (P < 0.05).

Conclusions

DADLE, administrated intracerebroventricularly at 45 minutes after cerebral ischemia, significantly ameliorated I/R-induced brain damage in rats. This kind of neuroprotective effect appears to be related to the downregulation of TLR4-mediated inflammatory responses.

Anesthetic management of unruptured intracranial aneurysms: a qualitative systematic review

Intracranial aneurysms (IA) occur in 3-5% of the general population and may require surgical or endovascular obliteration if the patient is symptomatic or has an increased risk of rupture. These procedures carry an inherent risk of neurological complications, and the outcome can be influenced by the physiological and pharmacological effects of the administered anesthetics. Despite the critical role of anesthetic agents, however, there are no current studies to systematically assess the intraoperative anesthetic risks, benefits, and outcome effects in this population. In this systematic review of the literature, we carefully examine the existing evidence on the risks and benefits of common anesthetic agents during IA obliteration, their physiological and clinical characteristics, and effects on neurological outcome. The initial search strategy captured a total of 287 published studies. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 28 studies were included in the final report. Our data showed that both volatile and intravenous anesthetics are commonly employed, without evidence that either is superior. Although no specific anesthetic regimens are promoted, their unique neurological, cardiovascular, and physiological properties may be critical to the outcome in vulnerable patients. In particular, patients at risk for perioperative ischemia may benefit from timely administration of anesthetic agents with neuroprotective properties and optimization of their physiological parameters. Further studies are warranted to examine if these anesthetic regimens can reduce the risk of neurological injury and improve the overall outcome in these patients.

Subanesthetic isoflurane abates ROS-activated MAPK/NF-κB signaling to repress ischemia-induced microglia inflammation and brain injury

Isoflurane (ISO) elicits protective effects on ischemia-induced brain injury. We investigated whether sub-anesthetic (0.7%) ISO post-conditioning attenuates the inflammation and apoptosis in oxygen-glucose deprivation (OGD)-insulted co-cultures (microglia and neurons) in vitro and the brain injury of the middle cerebral arterial occlusion (MCAO) rat. We demonstrated that ISO augmented the viability of OGD-treated microglia and neurons. ISO reduced the expression and activation of COX2 and iNOS in OGD-challenged microglia. ISO repressed the production of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8, and monocyte chemoattractant protein-1 in OGD-exposed microglia. ISO also decreased nucleosomal fragmentation and caspase-3 activity but increased mitochondrial membrane potential in OGD-stimulated microglia and neurons. Mechanistically, ISO suppressed OGD-induced microglial inflammation by blocking ROS-regulated p38 MAPK/NF-κB signaling pathway and hampered OGD-triggered microglial apoptosis in a ROS- or NO-dependent fashion. In vivo results with MCAO rats were partly consistent with the in vitro observation. These findings indicate that sub-anesthetic ISO post-conditioning abates the inflammation and apoptosis in OGD-stimulated rat microglia and the apoptosis of OGD-exposed neurons and the brain injuries of MCAO rats, suggesting it as a potentially effective therapeutic approach for ischemic brain damages.

Isoflurane post-conditioning attenuates cerebral ischemia/reperfusion injury by reducing apoptotic through activating the BMP7/SMAD signaling pathway in rats

The expressions of different temporal patterns of bone morphogenetic proteins (BMPs) have changed after ischemic strokes, and ischemic preconditioning-induced neuroprotection was attenuated when BMP7 was inhibited. In the previous study, the neuroprotection of isoflurane postconditioning (ISPOC) against cerebral ischemia-reperfusion (I/R) injury has been addressed, with particular relevance to the role of BMP7. Consequently, in the present study, we continued to explore the mechanisms involved in the BMP7 signal mediated the neuroprotection of ISPOC. A rat model of the middle cerebral artery occlusion was used in this study. Rats were administered 1.5 % isoflurane, 60 min after 90 min of ischemia, followed by a 24 h reperfusion period. The 1.5 % ISPOC significantly ameliorated the cerebral infarct volumes, neurologic deficit scores, damaged neurons, and apoptotic neurons. Moreover, ISPOC unregulated the expressions of BMP7, p-Smad1/5/9, and p-p38. Whereas, the neuroprotective effect was weakened by LDN-193189 and SB203580, respectively, a BMP7/Smad1/5/9 and p38MAPK signaling pathway inhibitor. Furthermore, LDN-193189 downregulated the expression of p-p38. The present results of this study indicated that the neuroprotection of 1.5 % isoflurane postconditioning to cerebral ischemia-reperfusion injury is related to the activating of BMP7/Smad1/5/9 and p38MAPK signal pathway.

Perioperative Dexmedetomidine attenuates brain ischemia reperfusion injury possibly via up-regulation of astrocyte Connexin 43

BACKGROUND

Astrocyte Connexin 43 (Cx43) is essential for the trophic and protective support of neurons during brain ischemia reperfusion (I/R) injury. It is believed that dexmedetomidine participates in Cx43-mediated effects. However, its mechanisms remained unclear. This study aims to address the relationship and regulation among them.

METHODS

Adult male Sprague-Dawley rats were allocated to the 90-min right middle cerebral arterial occlusion with or without dexmedetomidine pretreatment (5 μg/kg). Neurological functions were evaluated and brain lesions, as well as inflammatory factors (IL-1β, IL-6, TNF-α), were assessed. Ischemic penumbral cortex was harvested to determine the expression of astrocyte Cx43. Primary astrocytes were cultured to evaluate the effect of dexmedetomidine on Cx43 after oxygen-glucose deprivation.

RESULTS

Dexmedetomidine pretreatment attenuated neurological injury, brain lesions and expression of inflammatory factors (IL-1β, IL-6, TNF-α) after brain ischemia (P < 0.05). Astrocyte Cx43 was down-regulated by brain I/R injury, both in vivo and in vitro, which were reversed by dexmedetomidine (P < 0.05). This effect was mediated by the phosphorylation of Akt and GSK-3β. Further studies with LY294002 (PI3K inhibitor) or SB216763 (GSK-3β inhibitor) confirmed the effect of dexmedetomidine on astrocyte Cx43.

CONCLUSIONS

Perioperative dexmedetomidine administration attenuates neurological injury after brain I/R injury, possibly through up-regulation of astrocyte Cx43. Activation of PI3K-Akt-GSK-3β pathway might contribute to this protective effect.

Ischemic Postconditioning Reduces NMDA Receptor Currents Through the Opening of the Mitochondrial Permeability Transition Pore and KATP Channel in Mouse Neurons

Ischemic postconditioning (PostC) is known to reduce cerebral ischemia/reperfusion (I/R) injury; however, whether the opening of mitochondrial ATP-dependent potassium (mito-K_ATP) channels and mitochondrial permeability transition pore (mPTP) cause the depolarization of the mitochondrial membrane that remains unknown. We examined the involvement of the mito-K_ATP channel and the mPTP in the PostC mechanism. Ischemic PostC consisted of three cycles of 15 s reperfusion and 15 s re-ischemia, and was started 30 s after the 7.5 min ischemic load. We recorded N-methyl-D-aspartate receptors (NMDAR)-mediated currents and measured cytosolic Ca²⁺ concentrations, and mitochondrial membrane potentials in mouse hippocampal pyramidal neurons. Both ischemic PostC and the application of a mito-K_ATP channel opener, diazoxide, reduced NMDAR-mediated currents, and suppressed cytosolic Ca²⁺ elevations during the early reperfusion period. An mPTP blocker, cyclosporine A, abolished the reducing effect of PostC on NMDAR currents. Furthermore, both ischemic PostC and the application of diazoxide potentiated the depolarization of the mitochondrial membrane potential. These results indicate that ischemic PostC suppresses Ca²⁺ influx into the cytoplasm by reducing NMDAR-mediated currents through mPTP opening. The present study suggests that depolarization of the mitochondrial membrane potential by opening of the mito-K_ATP channel is essential to the mechanism of PostC in neuroprotection against anoxic injury.

Review Cerebral Ischemic Tolerance and Preconditioning: Methods, Mechanisms, Clinical Applications, and Challenges

Stroke is one of the leading causes of morbidity and mortality worldwide, and it is increasing in prevalence. The limited therapeutic window and potential severe side effects prevent the widespread clinical application of the venous injection of thrombolytic tissue plasminogen activator and thrombectomy, which are regarded as the only approved treatments for acute ischemic stroke. Triggered by various types of mild stressors or stimuli, ischemic preconditioning (IPreC) induces adaptive endogenous tolerance to ischemia/reperfusion (I/R) injury by activating a multitude cascade of biomolecules, for example, proteins, enzymes, receptors, transcription factors, and others, which eventually lead to transcriptional regulation and epigenetic and genomic reprogramming. During the past 30 years, IPreC has been widely studied to confirm its neuroprotection against subsequent I/R injury, mainly including local ischemic preconditioning (LIPreC), remote ischemic preconditioning (RIPreC), and cross preconditioning. Although LIPreC has a strong neuroprotective effect, the clinical application of IPreC for subsequent cerebral ischemia is difficult. There are two main reasons for the above result: Cerebral ischemia is unpredictable, and LIPreC is also capable of inducing unexpected injury with only minor differences to durations or intensity. RIPreC and pharmacological preconditioning, an easy-to-use and non-invasive therapy, can be performed in a variety of clinical settings and appear to be more suitable for the clinical management of ischemic stroke. Hoping to advance our understanding of IPreC, this review mainly focuses on recent advances in IPreC in stroke management, its challenges, and the potential study directions.

Prazosin blocks apoptosis of endothelial progenitor cells through downregulating the Akt/NF-κB signaling pathway in a rat cerebral infarction model

Endothelial progenitor cells (EPCs) can enhance the recanalization of thrombosis during the progression of cerebral infarction. Prazosin plays a therapeutic role in expanding the peripheral vasculature and regulating infarction cardiosclerosis by inhibiting phosphoinositide signaling. However, the possible mechanisms underlying the therapeutic effects of prazosin have not been fully explored. The purpose of the present study was to analyze the anti-apoptotic effects of prazosin on EPCs in a rat cerebral infarction model. The results showed that prazosin treatment decreased apoptosis of EPCs. Prazosin treatment decreased the serum expression levels of the inflammatory factors, interleukin-1β and tumor necrosis factor-α in rats with cerebral infarctions as well as in EPCs in vitro. In addition, prazosin reduced the expression levels of Akt, NF-κB, phosphorylated (p)-Akt and p-NF-κB in EPCs and the middle cerebral artery of rats with cerebral infarction. These findings demonstrated that prazosin inhibited EPC apoptosis in the cerebral infarction rats through targeting the Akt/NF-κB signaling pathway. In conclusion, these results indicated that prazosin has a preventive effect on cerebral infarction by inhibiting EPC apoptosis and by inhibiting the inflammatory response in vitro and in vivo through regulating the Akt/NF-κB signaling pathway.

Pharmacological postconditioning: a molecular aspect in ischemic injury

OBJECTIVE

Ischaemia/reperfusion (I/R) injury is defined as the damage to the tissue which is caused when blood supply returns to tissue after ischaemia. To protect the ischaemic tissue from irreversible injury, various protective agents have been studied but the benefits have not been clinically applicable due to monotargeting, low potency, late delivery or poor tolerability.

KEY FINDINGS

Strategies involving preconditioning or postconditioning can address the issues related to the failure of protective therapies. In principle, postconditioning (PoCo) is clinically more applicable in the conditions in which there is unannounced ischaemic event. Moreover, PoCo is an attractive beneficial strategy as it can be induced rapidly at the onset of reperfusion via series of brief I/R cycles following a major ischaemic event or it can be induced in a delayed manner. Various pharmacological postconditioning (pPoCo) mechanisms have been investigated systematically. Using different animal models, most of the studies on pPoCo have been carried out preclinically.

SUMMARY

However, there is a need for the optimization of the clinical protocols to quicken pPoCo clinical translation for future studies. This review summarizes the involvement of various receptors and signalling pathways in the protective mechanisms of pPoCo.

Isoflurane versus sevoflurane for early brain injury and expression of sphingosine kinase 1 after experimental subarachnoid hemorrhage

The first step to treat aneurysmal subarachnoid hemorrhage (SAH) is aneurysmal obliteration under general anesthesia but not treat the SAH itself and the secondary effects. However, the identification of anesthetics with properties that help to attenuate post-SAH brain injury can be useful for improving outcomes of SAH patients. We examined whether 2% isoflurane and 3% sevoflurane posttreatment are protective against early brain injury (EBI) after SAH. This study used 87 8-week-old male CD-1 mice. We induced SAH by endovascular perforation in mice. Animals were randomly divided into 4 groups: sham-operated (n = 16), SAH + vehicle-medical air (n = 26), SAH + 2% isoflurane (n = 22), and SAH + 3% sevoflurane (n = 23). Neurobehavioral function, brain water content and Western blotting were evaluated at 24 h. The expression of sphingosine kinase (SphK), cleaved caspase-3 and cyclooxygenase-2 (COX2) was determined by Western blotting. Cell death was examined by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Both 2% isoflurane and 3% sevoflurane significantly improved neurobehavioral function, and brain edema at 24 h after SAH and attenuated cell death, associated with an increase in SphK1, a decrease in cleaved caspase-3 and COX2. The neuroprotective effects were similar between 2% isoflurane and 3% sevoflurane. These findings suggest that both 2% isoflurane and 3% sevoflurane significantly inhibited EBI by suppressing post-SAH apoptosis and brain inflammation possibly via the SphK1-related pathway.

Distinctive effect of anesthetics on the effect of limb remote ischemic postconditioning following ischemic stroke

Limb remote ischemic postconditioning (LRIP) has been reported as an effective method to reduce the induced experimental stroke damage after ischemic reperfusion (IR) injury. Studies suggest that anesthetics used during induction of ischemic stroke can reduce IR injury, which could affect the actual mechanisms of neuroprotection by LRIP. This study focuses on the comparative effects of anesthetics such as isoflurane and ketamine-xylazine on ischemic injury when used during LRIP. Adult C57BL/6 mice were anesthetized by isoflurane or halothane, and transient middle cerebral artery occlusion (MCAO) was induced through insertion of the filament. Under isoflurane or ketamine-xylazine anesthesia, LRIP was performed after 90 min of reperfusion by carrying out three cycles of 5 min ischemia/5 min reperfusion of the bilateral hind limbs for one session per day for a total of 3 days. Results showed that the use of different anesthetics—isoflurane or ketamine-xylazine—during LRIP had no effects on body weight. However, LRIP was able to improve neurological function as observed by the neurological deficit score in ischemic mice. Interestingly, the neurological deficit in the group where ketamine-xylazine was used was better than the group where isoflurane was used during LRIP. Furthermore, the LRIP was able to prolong the period of the ischemic mice on the rotarod and this effect was more significant in the groups where ketamine-xylazine was used during LRIP. Moreover, LRIP significantly attenuated the infarction volume; however, this effect was independent of the anesthetic used during LRIP. From these results, we conclude that ischemic mice that were subjected to LRIP under ketamine-xylazine anesthesia had better neurological deficit outcomes after stroke.

Role of reactive oxygen species at reperfusion stage in isoflurane preconditioning-induced neuroprotection

In this in vivo and in vitro study, we aimed to investigate whether isoflurane preconditioning-induced neuronal protection is mediated by reactive oxygen species (ROS) signaling at the reperfusion stage. In the in vivo study, Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) and in the in vitro study, rat pheochromocytoma (PC12) cells were subjected to oxygen glucose deprivation (OGD). Isoflurane preconditioning was carried out prior to MCAO or OGD and the ROS scavenger, N-2-mercaptopropiopylglycine (2-MPG), was administered at the start of reperfusion. Infarct volume, neurological severity score, and TUNEL staining were analyzed in the in vivo study and cell viability, Bcl-2/Bax ratio, cleaved caspase 3/caspase 3 ratio, and ROS fluorescence intensity were measured in the in vitro study. In the in vivo study, infarct volume, neurological severity score, and TUNEL-positive cell count were significantly decreased with preconditioning but were abrogated by administration of 2-MPG. In the in vitro study, cell viability and Bcl-2/Bax ratio were significantly increased with preconditioning, and cleaved caspase-3/caspase-3 ratio and ROS fluorescence intensity were significantly decreased. Administration of 2-MPG for 10 min abrogated this preconditioning effect, but it did not abolish the protection when administered for 60 min of reperfusion. Isoflurane preconditioning-induced protection was abolished by ROS scavengers at the start of reperfusion, indicating that ROS signaling can mediate the isoflurane preconditioning effect, which suggests that the time window can be important.

Isoflurane exposure in infant rats acutely increases aquaporin 4 and does not cause neurocognitive impairment

Isoflurane is commonly used in pediatric population, but its mechanism of action in cognition is unclear. Aquaporin 4 (AQP4) regulates water content in blood, brain, and cerebrospinal fluid. Various studies have provided evidence for the role of AQP4 in synaptic plasticity and neurocognition. In this study, we aimed to determine whether a prolonged exposure to isoflurane in infant rats is associated with cognition and what effect this exposure has on AQP4 expression. Ten-day-old [postnatal day (P) 10] Wistar albino rats were randomly allocated to isoflurane group (n = 32; 1.5% isoflurane in 50% oxygen for 6 hours) or control group (n = 32; only 50% oxygen for 6 hours). Acute (P11) and long-term (P33) effects of 6-hour anesthetic isoflurane exposure on AQP4 expression were analyzed in whole brains of P11 and P33 rats by RT-qPCR and Western blot. Spatial learning and memory were assessed on P28 to P33 days by Morris Water Maze (MWM) test. The analysis revealed that isoflurane increased acutely both mRNA (~4.5 fold) and protein (~90%) levels of AQP4 in P11 rats compared with control group. The increasing levels of AQP4 in P11 were not observed in P33 rats. Also, no statistically significant change between isoflurane and control groups was observed in the latency to find the platform during MWM training and probe trial. Our results indicate that a single exposure to isoflurane anesthesia does not influence cognition in infant rats. In this case, acutely increased AQP4 after isoflurane anesthesia may have a protective role in neurocognition.

Isoflurane exposure in infant rats acutely increases aquaporin 4 and does not cause neurocognitive impairment

Isoflurane is commonly used in pediatric population, but its mechanism of action in cognition is unclear. Aquaporin 4 (AQP4) regulates water content in blood, brain, and cerebrospinal fluid. Various studies have provided evidence for the role of AQP4 in synaptic plasticity and neurocognition. In this study, we aimed to determine whether a prolonged exposure to isoflurane in infant rats is associated with cognition and what effect this exposure has on AQP4 expression. Ten-day-old [postnatal day (P) 10] Wistar albino rats were randomly allocated to isoflurane group (n = 32; 1.5% isoflurane in 50% oxygen for 6 hours) or control group (n = 32; only 50% oxygen for 6 hours). Acute (P11) and long-term (P33) effects of 6-hour anesthetic isoflurane exposure on AQP4 expression were analyzed in whole brains of P11 and P33 rats by RT-qPCR and Western blot. Spatial learning and memory were assessed on P28 to P33 days by Morris Water Maze (MWM) test. The analysis revealed that isoflurane increased acutely both mRNA (~4.5 fold) and protein (~90%) levels of AQP4 in P11 rats compared with control group. The increasing levels of AQP4 in P11 were not observed in P33 rats. Also, no statistically significant change between isoflurane and control groups was observed in the latency to find the platform during MWM training and probe trial. Our results indicate that a single exposure to isoflurane anesthesia does not influence cognition in infant rats. In this case, acutely increased AQP4 after isoflurane anesthesia may have a protective role in neurocognition.

Ischemic Postconditioning Recovers Cortex Ascorbic Acid during Ischemia/Reperfusion Monitored with an Online Electrochemical System

As a promising therapeutic treatment, ischemic postconditioning has recently received considerable attention. Although the neuroprotection effect of postconditioning has been observed, a reliable approach that can evaluate the neuroprotective efficiency of postconditioning treatment during the acute period after ischemia remains to be developed. This study investigates the dynamics of cortex ascorbic acid during the acute period of cerebral ischemia before and after ischemic postconditioning with an online electrochemical system (OECS). The cerebral ischemia/reperfusion injury and the neuronal functional outcome are evaluated with triphenyltetrazolium chloride staining, immunohistochemistry, and electrophysiological recording techniques. Electrochemical recording results show that cortex ascorbic acid sharply increases 10 min after middle cerebral artery occlusion and then reaches a plateau. After direct reperfusion following ischemia (i.e., without ischemic postconditioning), the cortex ascorbic acid further increases and then starts to decrease slowly at a time point of about 40 min after reperfusion. In striking contrast, the cortex ascorbic acid drops and recovers to its basal level after ischemic postconditioning followed by reperfusion. With the recovery of cortex ascorbic acid, ischemic postconditioning concomitantly promotes the recovery of neural function and reduces the oxidative damage. These results demonstrate that our OECS for monitoring cortex ascorbic acid can be used as a platform for evaluating the neuroprotective efficiency of ischemic postconditioning in the acute phase of cerebral ischemia, which is of great importance for screening proper postconditioning parameters for preventing ischemic damages.

Outcomes of general anesthesia versus conscious sedation for Stroke undergoing endovascular treatment: a meta-analysis

Background

The impact of anesthesia strategy on the outcomes of acute ischemic stroke (AIS) patients undergoing endovascular treatment is currently controversy. Thus, we performed this meta-analysis to compare the differences of clinical and angiographic outcomes between general anesthesia (GA) and conscious sedation (CS).

Methods

A literature search in PubMed, Embase, and Web of Knowledge databases through February 2019 was conducted for related records on GA and CS of AIS undergoing endovascular treatment. The results of the studies were pooled and meta-analyzed with fixed- or random-effect model based on heterogeneity test in total and subgroup analyses.

Results

Twenty-three studies including 6703 patients were analyzed in this meta-analysis. We found that patients in the GA group have lower odds of favorable functional outcome (mRS scores ≤2) compared with the CS group (odds ratio [OR] = 0.62, 95% confidence interval [CI]: 0.49–0.77), and higher risk of mortality (OR = 1.68, 95% CI: 1.49–1.90), pneumonia (OR = 1.78, 95% CI: 1.40–2.26), symptomatic intracranial hemorrhage (OR = 1.64, 95% CI: 1.13–2.37). However, no significant differences were seen between the groups in the rate of recanalization (OR = 1.07, 95% CI: 0.89–1.28), vessel dissection or perforation (OR = 1.00, 95% CI: 0.98–1.03) and asymptomatic intracranial hemorrhage (OR = 1.19, 95% CI: 0.96–1.47). While in the RCT subgroup analysis, we found patients in the GA group does not show lower rate of favorable functional outcome compared with the CS group (OR = 1.84, 95% CI: 1.17–2.89). And there was no significant difference in the rate of mortality between GA and CS groups during RCT subgroup analysis (OR = 0.74, 95% CI: 0.43–1.27).

Conclusions

AIS patients performed endovascular treatment under GA compared with CS was associated with worse functional outcome and increased rate of mortality, but differences in worsened outcomes do not exist when one looks into the GA vs. CS RCTs. Moreover, these findings are mainly based on the retrospective studies and additional multi-center randomized controlled trials to definitively address these issues is warranted.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0741-7) contains supplementary material, which is available to authorized users.

Attenuating oxygen-glucose deprivation-caused autophagosome accumulation may be involved in sevoflurane postconditioning-induced protection in human neuron-like cells

Application of the commonly used volatile anesthetic sevoflurane after brain ischemia (sevoflurane postconditioning) attenuates ischemic brain injury. It is not known whether autophagy plays a role in this sevoflurane postconditioning-induced neuroprotection. Human SH-SY5Y cells were induced to become neuron-like cells. These cells were subjected to 1 h oxygen-glucose deprivation (OGD) and then exposed to sevoflurane for 1 h. Chloroquine, an inhibitor of autolysosomes, rapamycin, an autophagy inducer, or 3-methyladenine (3-MA), an autophagy inhibitor, were incubated with cells during OGD and sevoflurane exposure. OGD and the subsequent simulated reperfusion increased lactate dehydrogenase (LDH) release from the cells. This increase was dose-dependent inhibited by sevoflurane postconditioning. OGD increased the ratio of microtubule-associated protein 1 light chain 3 (LC3) II to LC3I and the expression of beclin-1 and p62. These increases were attenuated by sevoflurane. Sevoflurane alone did not have any effects on the expression of p62, beclin-1 and the ratio of LC3II to LC3I. Sevoflurane also enhanced the co-location of autophagosomes and lysosomes. Chloroquine increased the ratio of LC3II to LC3I, p62 and LDH release in cells subjected to OGD. Sevoflurane postconditioning attenuated OGD-induced inactivation of Akt and mechanistic target of rapamycin (mTOR). Inducing autophagosome generation by rapamycin attenuated sevoflurane postconditioning-reduced LDH release. Inhibition of autophagosome generation by 3-MA decreased OGD-induced LDH release. These results suggest that OGD increase autophagosome accumulation via increased formation of autophagosomes and reduced autophagosome clearance and that attenuation of OGD-induced autophagosome accumulation may contribute to sevoflurane postconditioning-induced cell protection.

Ischemic postconditioning prevents surge of presynaptic glutamate release by activating mitochondrial ATP-dependent potassium channels in the mouse hippocampus

A mild ischemic load applied after a lethal ischemic insult reduces the subsequent ischemia–reperfusion injury, and is called ischemic postconditioning (PostC). We studied the effect of ischemic PostC on synaptic glutamate release using a whole-cell patch-clamp technique. We recorded spontaneous excitatory post-synaptic currents (sEPSCs) from CA1 pyramidal cells in mouse hippocampal slices. The ischemic load was perfusion of artificial cerebrospinal fluid (ACSF) equilibrated with mixed gas (95% N₂ and 5% CO₂). The ischemic load was applied for 7.5 min, followed by ischemic PostC 30 s later, consisting of three cycles of 15 s of reperfusion and 15 s of re-ischemia. We found that a surging increase in sEPSCs frequency occurred during the immediate-early reperfusion period after the ischemic insult. We found a significant positive correlation between cumulative sEPSCs and the number of dead CA1 neurons (r = 0.70; p = 0.02). Ischemic PostC significantly suppressed this surge of sEPSCs. The mitochondrial K_ATP (mito-K_ATP) channel opener, diazoxide, also suppressed the surge of sEPSCs when applied for 15 min immediately after the ischemic load. The mito-K_ATP channel blocker, 5-hydroxydecanoate (5-HD), significantly attenuated the suppressive effect of both ischemic PostC and diazoxide application on the surge of sEPSCs. These results suggest that the opening of mito-K_ATP channels is involved in the suppressive effect of ischemic PostC on synaptic glutamate release and protection against neuronal death. We hypothesize that activation of mito-K_ATP channels prevents mitochondrial malfunction and breaks mutual facilitatory coupling between glutamate release and Ca²⁺ entry at presynaptic sites.

Photoacoustic microscopy reveals the hemodynamic basis of sphingosine 1-phosphate-induced neuroprotection against ischemic stroke

Rationale: Emerging evidence has suggested that sphingosine 1-phosphate (S1P), a bioactive metabolite of sphingolipids, may play an important role in the pathophysiological processes of cerebral hypoxia and ischemia. However, the influence of S1P on cerebral hemodynamics and metabolism remains unclear. Material and Methods: Uniquely capable of high-resolution, label-free, and comprehensive imaging of hemodynamics and oxygen metabolism in the mouse brain without the influence of general anesthesia, our newly developed head-restrained multi-parametric photoacoustic microscopy (PAM) is well suited for this mechanistic study. Here, combining the cutting-edge PAM and a selective inhibitor of sphingosine kinase 2 (SphK2) that can increase the blood S1P level, we investigated the role of S1P in cerebral oxygen supply-demand and its neuroprotective effects on global brain hypoxia induced by nitrogen gas inhalation and focal brain ischemia induced by transient middle cerebral artery occlusion (tMCAO). Results: Inhibition of SphK2, which increased the blood S1P, resulted in the elevation of both arterial and venous sO2 in the hypoxic mouse brain, while the cerebral blood flow remained unchanged. As a result, it gradually and significantly reduced the metabolic rate of oxygen. Furthermore, pre-treatment of the mice subject to tMCAO with the SphK2 inhibitor led to decreased infarct volume, improved motor function, and reduced neurological deficit, compared to the control treatment with a less potent R-enantiomer. In contrast, post-treatment with the inhibitor showed no improvement in the stroke outcomes. The failure for the post-treatment to induce neuroprotection was likely due to the relatively slow hemodynamic responses to the SphK2 inhibitor-evoked S1P intervention, which did not take effect before the brain injury was induced. Conclusions: Our results reveal that elevated blood S1P significantly changes cerebral hemodynamics and oxygen metabolism under hypoxia but not normoxia. The improved blood oxygenation and reduced oxygen demand in the hypoxic brain may underlie the neuroprotective effect of S1P against ischemic stroke.

Investigating the efficacy of a new intravenous (IV) nanoemulsified sevoflurane/arginine formulation for maintenance of general anesthesia for embolization of cerebral aneurysm

The aim of this research investigation was to profound analysis the mitigating impact of sevoflurane/arginine post-molding on cerebral ischemia-reperfusion damage in rats. The authors fabricated emulsions fusing sevoflurane, perfluorooctyl bromide as a settling specialist, and mixes of arginine polymer. Cell suitability and gene expression of tubulin and NeuN were assessed. The stability, morphology and functional group were evaluated utilizing dynamic light scattering (DLS), Transmission Electron Microscope (TEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR). Cerebral aneurysms were prompted through hypertension and a solitary stereotactic infusion of elastase into the basal storage in rat. The capacity of the emulsions to decreased cerebral aneurysm was tried in vivo by regulating them IV delivery of Se/Arg samples to rats. Se/Arg pre-conditioning expanded cell feasibility in neuroblast (SK-N-DZ) cells. Se/Arg pre-conditioning diminished infarct volume and enhanced neurological result in rats subjected to cerebral hypoxia-ischemia. Se/Arg preconditioning expanded levels of tubulin and NeuN. The prepared sevoflurane/arginine material pre-conditioning-incited neuroprotective impacts in vitro as well as in vivo analyses. Sevoflurane/arginine post-molding decreased cerebral tissue misfortune detected 7 days after cerebrum hypoxia-ischemia. This impact was prompted by clinically significant focuses and canceled by Sevoflurane/arginine. These outcomes recommend that Sevoflurane/arginine post-conditioning ensures neonatal cerebrum against cerebrum hypoxia-ischemia.

A Comparative Study of Two Blast-Induced Traumatic Brain Injury Models: Changes in Monoamine and Galanin Systems Following Single and Repeated Exposure

Repeated mild blast-induced traumatic brain injury (rmbTBI), caused by recurrent exposure to low levels of explosive blast, is a significant concern for military health systems. However, the pathobiology of rmbTBI is currently poorly understood. Animal models are important tools to identify the molecular changes of rmbTBI, but comparisons across different models can present their own challenges. In this study, we compared two well-established rodent models of mbTBI, the "KI model" and the "USU/WRAIR model." These two models create different pulse forms, in terms of peak pressure and duration. Following single and double exposures to mild levels of blast, we used in situ hybridization (ISH) to assess changes in mRNA levels of tyrosine hydroxylase (TH), tryptophan hydroxylase (TPH2), and galanin in the locus coeruleus (LC) and dorsal raphe nucleus (DRN). These systems and their transmitters are known to mediate responses to stress and anxiety. We found increased mRNA levels of TH, TPH2 and galanin in the LC and DRN of single-exposed rats relative to sham rats in the KI but not the USU/WRAIR model. Sham mRNA values measured in the USU/WRAIR model were substantially higher than their KI counterparts. Double exposure caused similarly significant increases in mRNA values in the KI model but not the USU/WRAIR model, except TPH2 and galanin levels in the DRN. We detected no cumulative effect of injury in either model at the used inter-injury interval (30 min), and there were no detectable neuropathological changes in any experimental group at 1 day post-injury. The apparent lack of early response to injury as compared to sham in the USU/WRAIR model is likely caused by stressors (e.g., transportation and noise), associated with the experimental execution, that were absent in the KI model. This study is the first to directly compare two established rodent models of rmbTBI, and to highlight the challenges of comparing findings from different animal models. Additional studies are needed to understand the role of stress, dissect the effects of psychological and physical injuries and to identify the window of increased cerebral vulnerability, i.e., the inter-injury interval that results in a cumulative effect following repeated blast exposure.

Curative effects of GM1 in the treatment of severe ischemic brain injury and its effects on serum TNF-α and NDS

The curative effects of monosialotetrahexosyl ganglioside (GM1) in the treatment of severe ischemic brain injury and its effects on tumor necrosis factor-α (TNF-α) and neuropathy disability score (NDS). Sixty patients with severe ischemic brain injury admitted to The First People's Hospital of Jining (Jining, China) from June 2014 to March 2016 were selected. They were randomly divided into the control group (n=30) and the experimental group (n=30). The patients in the control group were treated with routine therapy while those in the experimental group were treated with GM1. The level of TNF-α in the serum was measured by the enzyme-linked immunosorbent assay. The NDS was used to grade the two groups; Pearson's correlation coefficient was applied to analyze the correlation between the content of TNF-α and NDS; the content of superoxide dismutase (SOD) was detected using xanthine oxidase assay, and the content of malondialdehyde (MDA) was detected by thiobarbituric acid method. The clinical recovery time of two groups of patients was recorded. At 14 days after GM1 treatment, the serum TNF-α content and the NDS in the experimental group were significantly lower than those in the control group (P<0.05). The content of TNF-α in the patients was positively correlated with the NDS. After treatment, the serum MDA content of patients in the experimental group was lower, while the SOD content was significantly higher than that in the control group (P<0.05). After GM1 treatment, hemodynamic parameters of patients in the experimental group were significantly improved compared with those in the control group. The total effective rate of GM1 treatment in the experimental group was higher than that in the control group (P<0.05). GM1 has a good clinical significance in the treatment of patients with severe ischemic brain injury and is worthy of clinical promotion and application.

Anaesthesia for neuroradiology: thrombectomy: 'one small step for man, one giant leap for anaesthesia'

PURPOSE OF REVIEW

Endovascular management of acute thrombotic strokes is a new management technique. Anaesthesia will play a key role in the management of these patients. To date there is no established method of managing these patients from an anaesthetic perspective.

RECENT FINDINGS

In 2015, five landmark studies popularized intra-arterial clot retrieval for ischaemic strokes. Since then there have been a number of small studies investigating the best anaesthetic technique, taking into account patient, technical, and clinical factors. This review summarizes these studies and discusses the different anaesthetic options, with their relative merits and pitfalls.

SUMMARY

There is a paucity of robust evidence for the best anaesthetic practice in this cohort of patients. Airway protection seems to be an issue in 2.5% of cases. Timing of the procedure is vital, and any delay may be detrimental to neurological outcome. In a survey of neurointerventionalists, the main concern they expressed was the potential delay to revascularization posed by anaesthesia. Patients complain of pain during mechanical clot retrieval if awake. The overall consensus seems to be favouring conscious sedation over general anaesthesia in the acute setting.

Limb Remote Ischemic Conditioning: Mechanisms, Anesthetics, and the Potential for Expanding Therapeutic Options

Novel and innovative approaches are essential in developing new treatments and improving clinical outcomes in patients with ischemic stroke. Remote ischemic conditioning (RIC) is a series of mechanical interruptions in blood flow of a distal organ, following end organ reperfusion, shown to significantly reduce infarct size through inhibition of oxidation and inflammation. Ischemia/reperfusion (I/R) is what ultimately leads to the irreversible brain damage and clinical picture seen in stroke patients. There have been several reports and reviews about the potential of RIC in acute ischemic stroke; however, the focus here is a comprehensive look at the differences in the three types of RIC (remote pre-, per-, and postconditioning). There are some limited uses of preconditioning in acute ischemic stroke due to the unpredictability of the ischemic event; however, it does provide the identification of biomarkers for clinical studies. Remote limb per- and postconditioning offer a more promising treatment during patient care as they can be harnessed during or after the initial ischemic insult. Though further research is needed, it is imperative to discuss the importance of preclinical data in understanding the methods and mechanisms involved in RIC. This understanding will facilitate translation to a clinically feasible paradigm for use in the hospital setting.

Age-Related Upregulation of Carboxyl Terminal Modulator Protein Contributes to the Decreased Brain Ischemic Tolerance in Older Rats

Stroke remains one of the leading causes of death worldwide. The underlying neuropathology for stroke is ischemic brain injury. Carboxyl terminal modulator protein (CTMP), an endogenous inhibitor of the prosurvival Akt, may increase brain ischemic injury in young animals. Aging decreases brain ischemic tolerance. We hypothesize that CTMP is increased with aging and that this increase contributes to the decreased brain ischemic tolerance. To address these hypotheses, we determined the expression of CTMP and its downstream proteins in the brain of various ages of rats (Fischer 344 and Sprague-Dawley rats). The role of CTMP in ischemic brain injury was investigated by RNA interference. Here, we showed that CTMP in the brain was increased with aging in rats. The phosphorylated/activated Akt was decreased with aging. Six- and 20-month-old rats had poorer neurological outcome than did 2-month-old rats after brain ischemia. The neurological outcome of 2-month-old rats was worsened by LY294002, an Akt inhibitor. The poor neurological outcome in 6-month-old rats was improved by silencing CTMP. CTMP was increased in ischemic penumbral brain tissues. Silencing this increase activated Akt. These results suggest that CTMP increase with aging contributes to the aging-dependent decrease of brain ischemic tolerance.

Sevoflurane preconditioning ameliorates lipopolysaccharide-induced cognitive impairment in mice

Systemic inflammation induces brain neuronal inflammation, in turn causing acute cognitive disorders. Furthermore, neuronal inflammation is one cause of postoperative cognitive disorder (POCD) and delirium. However, no sufficiently established pharmacological treatment is available for neurocognitive inflammation. This study evaluated the possible neuroprotective effects of preconditioning with sevoflurane anesthesia on cognition and neuroinflammatory changes in an animal model of lipopolysaccharide (LPS)-induced systemic inflammation. Adult mice were randomly divided into (1) control, (2) 2% sevoflurane preconditioning for 1 h, (3) intraperitoneal 5 mg/kg LPS injection, and (4) 2% sevoflurane preconditioning for 1 h + LPS injection groups. At 24 h after 5 mg/kg LPS injection, microglial activation based on ionized calcium-binding adapter molecule 1 (Iba-1) expression in the hippocampus was determined using immunostaining and immunoblotting. IL-1β and IL-6 immunoblotting were used as inflammation markers, and β-site of amyloid precursor protein cleaving enzyme 1 (BACE1) immunoblotting was performed to evaluate amyloid β-protein (Aβ) accumulation. Long-term cognitive impairment was evaluated using fear conditioning tests. Intraperitoneal LPS increased levels of Iba-1 (150%), inflammation markers (160%), and Aβ accumulation (350%), and sevoflurane preconditioning suppressed these increases. Systemic LPS caused learning deficits. Sevoflurane also maintained long-term memory in mice receiving LPS injection. Sevoflurane preconditioning prevented long-term memory impairment in the mouse model administered systemic LPS by decreasing excessive microglial activation, inflammation, and Aβ accumulation. This study supports the hypothesis that sevoflurane preconditioning might also be beneficial for neuronal inflammation. Sevoflurane might be beneficial for reducing delirium and POCD.

Comparison of the cerebroprotective effect of inhalation anaesthesia and total intravenous anaesthesia in patients undergoing cardiac surgery with cardiopulmonary bypass: a systematic review and meta-analysis

OBJECTIVE

Neurological dysfunction remains a devastating postoperative complication in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB), and previous studies have shown that inhalation anaesthesia and total intravenous anaesthesia (TIVA) may produce different degrees of cerebral protection in these patients. Therefore, we conducted a systematic literature review and meta-analysis to compare the neuroprotective effects of inhalation anaesthesia and TIVA.

DESIGN

Searching in PubMed, EMBASE, Science Direct/Elsevier, China National Knowledge Infrastructure and Cochrane Library up to August 2016, we selected related randomised controlled trials for this meta-analysis.

RESULTS

A total of 1485 studies were identified. After eliminating duplicate articles and screening titles and abstracts, 445 studies were potentially eligible. After applying exclusion criteria (full texts reported as abstracts, review article, no control case, lack of outcome data and so on), 13 studies were selected for review. Our results demonstrated that the primary outcome related to S100B level in the inhalation anaesthesia group was significantly lower than in the TIVA group after CPB and 24 hours postoperatively (weighted mean difference (WMD); 95% CI (CI): -0.41(-0.81 to -0.01), -0.32 (-0.59 to -0.05), respectively). Among secondary outcome variables, mini-mental state examination scores of the inhalation anaesthesia group were significantly higher than those of the TIVA group 24 hours after operation (WMD (95% CI): 1.87 (0.82 to 2.92)), but no significant difference was found in arteriovenous oxygen content difference, cerebral oxygen extraction ratio and jugular bulb venous oxygen saturation, which were assessed at cooling and rewarming during CPB.

CONCLUSION

This study demonstrates that anaesthesia with volatile agents appears to provide better cerebral protection than TIVA for patients undergoing cardiac surgery with CPB, suggesting that inhalation anaesthesia may be more suitable for patients undergoing cardiac surgery.

Comparing anesthesia with isoflurane and fentanyl/fluanisone/midazolam in a rat model of cardiac arrest

Only one in ten patients survives cardiac arrest (CA), underscoring the need to improve CA management. Isoflurane has shown cardio- and neuroprotective effects in animal models of ischemia-reperfusion injury. Therefore, the beneficial effect of isoflurane should be tested in an experimental CA model. We hypothesize that isoflurane anesthesia improves short-term outcome following resuscitation from CA compared with a subcutaneous fentanyl/fluanisone/midazolam anesthesia. Male Sprague-Dawley rats were randomized to anesthesia with isoflurane ( n = 11) or fentanyl/fluanisone/midazolam ( n = 11). After 10 min of asphyxial CA, animals were resuscitated by mechanical chest compressions, ventilations, and epinephrine and observed for 30 min. Hemodynamics, including coronary perfusion pressure, systemic O2 consumption, and arterial blood gases, were recorded throughout the study. Plasma samples for endothelin-1 and cathecolamines were drawn before and after CA. Compared with fentanyl/fluanisone/midazolam anesthesia, isoflurane resulted in a shorter time to return of spontaneous circulation (ROSC), less use of epinephrine, increased coronary perfusion pressure during cardiopulmonary resusitation, higher mean arterial pressure post-ROSC, increased plasma levels of endothelin-1, and decreased levels of epinephrine. The choice of anesthesia did not affect ROSC rate or systemic O2 consumption. Isoflurane reduces time to ROSC, increases coronary perfusion pressure, and improves hemodynamic function, all of which are important parameters in CA models.

NEW & NOTEWORTHY The preconditioning effect of volatile anesthetics in studies of ischemia-reperfusion injury has been demonstrated in several studies. This study shows the importance of anesthesia in experimental cardiac arrest studies as isoflurane raised coronary perfusion pressure during resuscitation, reduced time to return of spontaneous circulation, and increased arterial blood pressure in the post-cardiac arrest period. These effects on key outcome measures in cardiac arrest research are important in the interpretation of results from animal studies.

BNIP3L/NIX-mediated mitophagy protects against ischemic brain injury independent of PARK2

Cerebral ischemia induces massive mitochondrial damage. These damaged mitochondria are cleared, thus attenuating brain injury, by mitophagy. Here, we identified the involvement of BNIP3L/NIX in cerebral ischemia-reperfusion (I-R)-induced mitophagy. Bnip3l knockout (bnip3l^-/-) impaired mitophagy and aggravated cerebral I-R injury in mice, which can be rescued by BNIP3L overexpression. The rescuing effects of BNIP3L overexpression can be observed in park2^-/- mice, which showed mitophagy deficiency after I-R. Interestingly, bnip3l and park2 double-knockout mice showed a synergistic mitophagy deficiency with I-R treatment, which further highlighted the roles of BNIP3L-mediated mitophagy as being independent from PARK2. Further experiments indicated that phosphorylation of BNIP3L serine 81 is critical for BNIP3L-mediated mitophagy. Nonphosphorylatable mutant BNIP3L^S81A failed to counteract both mitophagy impairment and neuroprotective effects in bnip3l^-/- mice. Our findings offer insights into mitochondrial quality control in ischemic stroke and bring forth the concept that BNIP3L could be a potential therapeutic target for ischemic stroke, beyond its accepted role in reticulocyte maturation.

Neuroprotection provided by isoflurane pre-conditioning and post-conditioning

Isoflurane, a volatile and inhalational anesthetic, has been extensively used in perioperative period for several decades. A large amount of experimental studies have indicated that isoflurane exhibits neuroprotective properties when it is administrated before or after (pre-conditioning and post-conditioning) neurodegenerative diseases (e.g., hypoxic ischemia, stroke and trauma). Multiple mechanisms are involved in isoflurane induced neuroprotection, including activation of glycine and γ-aminobutyric acid receptors, antagonism of ionic channels and alteration of the function and activity of other cellular proteins. Although neuroprotection provided by isoflurane is observed in many animal studies, convincing evidence is lacking in human trials. Therefore, there is still a long way to go before translating its neuroprotective properties into clinical practice.

TASK channels contribute to neuroprotective action of inhalational anesthetics

Postconditioning with inhalational anesthetics can reduce ischemia-reperfusion brain injury, although the cellular mechanisms for this effect have not been determined. The current study was designed to test if TASK channels contribute to their neuroprotective actions. Whole cell recordings were used to examine effects of volatile anesthetic on TASK currents in cortical neurons and to verify loss of anesthetic-activated TASK currents from TASK^−/− mice. A transient middle cerebral artery occlusion (tMCAO) model was used to establish brain ischemia-reperfusion injury. Quantitative RT-PCR analysis revealed that TASK mRNA was reduced by >90% in cortex and hippocampus of TASK^−/− mice. The TASK^−/− mice showed a much larger region of infarction than C57BL/6 J mice after tMCAO challenge. Isoflurane or sevoflurane administered after the ischemic insult reduced brain infarct percentage and neurological deficit scores in C57BL/6 J mice, these effect were reduced in TASK^−/− mice. Whole cell recordings revealed that the isoflurane-activated background potassium current observed in cortical pyramidal neurons from wild type mice was conspicuously reduced in TASK^−/− mice. Our studies demonstrate that TASK channels can limit ischemia-reperfusion damage in the cortex, and postconditioning with volatile anesthetics provides neuroprotective actions that depend, in part, on activation of TASK currents in cortical neurons.

Paradigms and mechanisms of inhalational anesthetics mediated neuroprotection against cerebral ischemic stroke

Cerebral ischemic stroke is a leading cause of serious long-term disability and cognitive dysfunction. The high mortality and disability of cerebral ischemic stroke is urging the health providers, including anesthesiologists and other perioperative professioners, to seek effective protective strategies, which are extremely limited, especially for those perioperative patients. Intriguingly, several commonly used inhalational anesthetics are recently suggested to possess neuroprotective effects against cerebral ischemia. This review introduces multiple paradigms of inhalational anesthetic treatments that have been investigated in the setting of cerebral ischemia, such as preconditioning, proconditioning and postconditioning with a variety of inhalational anesthetics. The pleiotropic mechanisms underlying these inhalational anesthetics-afforded neuroprotection against stroke are also discussed in detail, including the common pathways shared by most of the inhalational anesthetic paradigms, such as anti-excitotoxicity, anti-apoptosis and anti-inflammation. There are also distinct mechanisms involved in specific paradigms, such as preserving blood brain barrier integrity, regulating cerebral blood flow and catecholamine release. The ready availability of these inhalational anesthetics bedside and renders them a potentially translatable stroke therapy attracting great efforts for understanding of the underlying mechanisms.

The Effect of Propofol on Mitochondrial Fission during Oxygen-Glucose Deprivation and Reperfusion Injury in Rat Hippocampal Neurons

The neuroprotective role of propofol in transient global and focal cerebral ischemia reperfusion (I/R) animal model has recently been highlighted. However, no studies have conducted to explore the relationship between mitochondrial fission/fusion and I/R injury under the intervention of propofol. Moreover, neuroprotective mechanism of propofol is yet unclear. Culturing primary hippocampal cells were subjected to oxygen-glucose deprivation and re-oxygenation (OGD/R) model, as a model of cerebral I/R in vitro. Methods CCK-8 assay was used to test the effect of propofol on cell viability. We examined the effect of propofol on mitochondrial ultrastructure and mitochondrial fission evoked by OGD/R with transmission electron microscopy and immunofluorescence assay. To investigate possible neuroprotective mechanisms, the authors then examined whether propofol could inhibit calcium-overload, calcineurin (CaN) activation and the phosphorylation of dynamin-related protein 1 (Drp1) during the period of OGD/R, as well as the combination of Drp1-ser 637 and fission 1 (Fis1) protein by immunofluorescence assay, ELISA and double-labeling immunofluorescence analysis. Finally, the expression of Drp1-ser 637 and Fis1, apoptosis inducing factor (AIF) and cytochrome C (Cyt C) were detected by western blot. When added in culture media during OGD period, propofol (0.1μM-50μM) could alleviate neurons injury and protect mitochondrial ultrastructure, meanwhile inhibit mitochondrial fission. Furthermore, the concentration of intracellular free Ca2+, CaN activition and the phosphorylation of Drp1-ser637 were suppressed, as well as the translocation and combination of Drp1-ser 637 and Fis1. The authors also found that the expression of Cyt C, AIF, Drp1-ser637 and Fis1 were down-regulated. Notably, high dose of propofol (100μM-200μM) were confirmed to decrease the survival of neurons based on results of cell viability. Propofol could inhibit mitochondrial fission and mitochondrial apoptotic pathway evoked by OGD/R in rat hippocampal neurons, which may be via depressing calcium-overload.

Effects of activin A and its downstream ERK1/2 in oxygen and glucose deprivation after isoflurane-induced postconditioning

BACKGROUND

Isoflurane postconditioning (ISPOC) plays a neuroprotection role in the brain. Previous studies confirmed that isoflurane postconditioning can provide better protection than preconditioning in acute hypoxic-ischemic brain damage, such as acute craniocerebral trauma and ischemic stroke. Numerous studies have reported that activin A can protect rat's brain from cell injury. However, whether activin A and its downstream ERK1/2 were involved in isoflurane postconditioning-induced neuroprotection is unknown.

METHODS

A total of 80 healthy Sprague-Dawley rats weighing 50-70g were randomly divided into 10 groups of 8: normal control, oxygen and glucose deprivation (OGD), 1.5% ISPOC, 3.0% ISPOC, 4.5% ISPOC, blocker of activin A (SB431542), blocker of ERK1/2 (U0126), 3.0% ISPOC+SB431542, 3.0% ISPOC+U0126, and vehicle (dimethyl sulfoxide(DMSO)) group. Blockers (SB431542 and U0126) were used in each concentration of isoflurane before OGD. Hematoxylin-eosin staining, 2,3,5-triphenyl tetrazolium chloride staining, and propidium iodide (PI) staining were conducted to assess the reliability in the brain slices. Immunofluorescence, Western blot, and quantitative real-time PCR(Q-PCR) were performed to validate the protein expression levels of activin A, Smad2/3, P-Smad2/3, ERK1/2, and phosphorylation ERK1/2 (P-ERK1/2).

RESULTS

The number of damaged neurons and mean fluorescence intensity(MFI) of PI staining increased, but formazan generation, expression levels of activin A and P-ERK1/2 protein, and mRNA synthesis level of activin A decreased in the OGD group compared with the normal control group (p<0.05). The number of damaged neurons and MFI of PI staining decreased, but formazan production, expression levels of activin A, P-Smad2/3, and P-ERK1/2, and mRNA synthesis level of activin A increased significantly in the 1.5% ISPOC and 3.0% ISPOC groups (p<0.05) compared with the OGD group. The result in the 4.5% ISPOC group, was completely opposite to the 1.5% ISPOC and 3.0% ISPOC groups. The number of damage neuron and MFI of PI staining increased, but formazan production, expression levels of activin A, P-Smad2/3, and P-ERK1/2, and mRNA synthesis level of activin A decreased in the 4.5% ISPOC group. However, the expression levels of activin A, P-Smad2/3, and P-ERK1/2, and mRNA synthesis level of activin A in the 4.5% ISPOC group were higher than the OGD group (p<0.05). The other results were compared between the SB431542 group/the U0126 group and 3.0% ISPOC group. The MFI of PI staining increased, but the expression levels of activin A, P-Smad2/3, and P-ERK1/2 decreased (p<0.05). The expression level of ERK1/2 protein in all groups exhibited no change (p>0.05).

CONCLUSION

Results of this study showed that 3.0% concentration of isoflurane postconditioning provided better neuroprotection than 1.5% and 4.5% concentrations of isoflurane. Activin A/Smad 2/3 and activin A/ERK1/2 signaling pathway may be involved in ISPOC-induced neuroprotection.