Emulsified Isoflurane Protects Against Transient Focal Cerebral Ischemia Injury in Rats via the PI3K/Akt Signaling Pathway

Neuro-Inflammation Modulation and Post-Traumatic Brain Injury Lesions: From Bench to Bed-Side

Head trauma is the most common cause of disability in young adults. Known as a silent epidemic, it can cause a mosaic of symptoms, whether neurological (sensory-motor deficits), psychiatric (depressive and anxiety symptoms), or somatic (vertigo, tinnitus, phosphenes). Furthermore, cranial trauma (CT) in children presents several particularities in terms of epidemiology, mechanism, and physiopathology-notably linked to the attack of an immature organ. As in adults, head trauma in children can have lifelong repercussions and can cause social and family isolation, difficulties at school, and, later, socio-professional adversity. Improving management of the pre-hospital and rehabilitation course of these patients reduces secondary morbidity and mortality, but often not without long-term disability. One hypothesized contributor to this process is chronic neuroinflammation, which could accompany primary lesions and facilitate their development into tertiary lesions. Neuroinflammation is a complex process involving different actors such as glial cells (astrocytes, microglia, oligodendrocytes), the permeability of the blood-brain barrier, excitotoxicity, production of oxygen derivatives, cytokine release, tissue damage, and neuronal death. Several studies have investigated the effect of various treatments on the neuroinflammatory response in traumatic brain injury in vitro and in animal and human models. The aim of this review is to examine the various anti-inflammatory therapies that have been implemented.

Isoflurane Attenuates Cerebral Ischaemia-Reperfusion Injury via the TLR4-NLRP3 Signalling Pathway in Diabetic Mice

Ischaemic stroke is a severe disease worldwide. Restoration of blood flow after ischaemic stroke leads to cerebral ischaemia-reperfusion injury (CIRI). Various operations, such as cardiac surgery with deep hypothermic circulatory arrest, predictably cause cerebral ischaemia. Diabetes is related to the occurrence of perioperative stroke and exacerbates neurological impairment after stroke. Therefore, the choice of anaesthetic drugs has certain clinical significance for patients with diabetes. Isoflurane (ISO) exerts neuroprotective and anti-neuroinflammatory effects in patients without diabetes. However, the role of ISO in cerebral ischaemia in the context of diabetes is still unknown. Toll-like receptor 4 (TLR4) and NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation play important roles in microglia-mediated neuroinflammatory injury. In this study, we treated a diabetic middle cerebral artery occlusion mouse model with ISO. We found that diabetes exacerbated cerebral ischaemia damage and that ISO exerted neuroprotective effects in diabetic mice. Then, we found that ISO decreased TLR4-NLRP3 inflammasome activation in microglia and the excessive autophagy induced by CIRI in diabetic mice. The TLR4-specific agonist CRX-527 reversed the neuroprotective effects of ISO. In summary, our study indicated that ISO exerts neuroprotective effects against the neuroinflammation and autophagy observed during diabetic stroke via the TLR4-NLRP3 signalling pathway.

Cerebral-Cardiac Syndrome and Diabetes: Cardiac Damage After Ischemic Stroke in Diabetic State

Cerebral-cardiac syndrome (CCS) refers to cardiac dysfunction following varying brain injuries. Ischemic stroke is strongly evidenced to induce CCS characterizing as arrhythmia, myocardial damage, and heart failure. CCS is attributed to be the second leading cause of death in the post-stroke stage; however, the responsible mechanisms are obscure. Studies indicated the possible mechanisms including insular cortex injury, autonomic imbalance, catecholamine surge, immune response, and systemic inflammation. Of note, the characteristics of the stroke population reveal a common comorbidity with diabetes. The close and causative correlation of diabetes and stroke directs the involvement of diabetes in CCS. Nevertheless, the role of diabetes and its corresponding molecular mechanisms in CCS have not been clarified. Here we conclude the features of CCS and the potential role of diabetes in CCS. Diabetes drives establish a “primed” inflammatory microenvironment and further induces severe systemic inflammation after stroke. The boosted inflammation is suspected to provoke cardiac pathological changes and hence exacerbate CCS. Importantly, as the key element of inflammation, NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome is indicated to play an important role in diabetes, stroke, and the sequential CCS. Overall, we characterize the corresponding role of diabetes in CCS and speculate a link of NLRP3 inflammasome between them.

An Integrated Analysis of Network Pharmacology and Experimental Validation to Reveal the Mechanism of Chinese Medicine Formula Naotaifang in Treating Cerebral Ischemia-Reperfusion Injury

BACKGROUND

Cerebral ischemia-reperfusion injury (CIRI) is a crucial factor leading to a poor prognosis for ischemic stroke patients. As a novel Chinese medicine formula, Naotaifang (NTF) was proven to exhibit a neuroprotective effect against ischemic stroke, clinically, and to alleviate CIRI in animals. However, the mechanisms underlying the beneficial effect have not been fully elucidated.

METHODS

In this study, we combined a network pharmacology approach and an in vivo experiment to explore the specific effects and underlying mechanisms of NTF in the treatment of ischemia-reperfusion injury. A research strategy based on network pharmacology, combining target prediction, network construction, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and molecular docking was used to predict the targets of NTF in treating the ischemic stroke and CIRI. On the other hand, we used HPLC and HRMS to identify biologically active components of NTF. Middle cerebral artery occlusion models in rats were utilized to evaluate the effect and the underlying mechanisms of NTF against CIRI after ischemic stroke.

RESULTS

Network pharmacology analysis revealed 43 potential targets and 14 signaling pathways for the treatment of NTF against CIRI after ischemic stroke. Functional enrichment analysis showed that a STAT3/PI3K/AKT signaling pathway serves as the target for in vivo experimental study validation. The results of animal experiments showed that NTF significantly alleviated CIRI by decreasing neurological score, infarct volume, numbers of apoptotic neuronal cells, increasing density of dendritic spines and survival of neurons. Furthermore, NTF could increase the expression of p-STAT3, PI3K, p-AKT. In addition, the detection of apoptosis-related factors showed that the NTF could raise the expression of Bcl-2 and reduce the expression of Bax.

CONCLUSION

This network pharmacological and experimental study indicated that NTF, as a therapeutic candidate for the management of CIRI following ischemic stroke, may exert a protective effect through the STAT3/PI3K/AKT signaling pathway.

NLRP3 Inflammasome: A Potential Target in Isoflurane Pretreatment Alleviates Stroke-Induced Retinal Injury in Diabetes

Ischemic stroke remains a devastating disease which is the leading cause of death worldwide. Visual impairment after stroke is a common complication which may lead to vision loss, greatly impacting life quality of patients. While ischemic stroke is traditionally characterized by a blockage of blood flow to the brain, this may coincide with reduced blood flow to the eye, resulting in retinal ischemia and leading to visual impairment. Diabetes increases the risk of ischemic stroke and induces diabetic retinopathy; the latter may be more sensitive to the ischemic retinal injury. In diabetic status, the underlying mechanism in stroke-induced retinal injury has not been fully clarified. The NLR pyrin domain containing 3 (NLRP3) inflammasome is an important activator of inflammation, which may play a critical role in catalyzing and forming certain pro-inflammatory cytokines in both cerebral and retinal ischemia. Isoflurane has been demonstrated to inhibit the activation of the NLRP3 inflammasome and show neuroprotective effects. In this study, we established a diabetic mouse model and performed the middle cerebral artery occlusion procedure to induce ischemic stroke. Our results revealed that cerebral ischemia-induced retinal injury in the diabetic model. Isoflurane pretreatment alleviated the cerebral and retinal injury after ischemic stroke. Of note, isoflurane pretreatment inhibited the NLRP3 inflammasome activation in the retina, indicating that isoflurane pretreatment may provide substantial retinal protection in stroke-induced retinal injury in diabetes.

Inflammation-Mediated Angiogenesis in Ischemic Stroke

Stroke is the leading cause of disability and mortality in the world, but the pathogenesis of ischemic stroke (IS) is not completely clear and treatments are limited. Mounting evidence indicate that neovascularization is a critical defensive reaction to hypoxia that modulates the process of long-term neurologic recovery after IS. Angiogenesis is a complex process in which the original endothelial cells in blood vessels are differentiated, proliferated, migrated, and finally remolded into new blood vessels. Many immune cells and cytokines, as well as growth factors, are directly or indirectly involved in the regulation of angiogenesis. Inflammatory cells can affect endothelial cell proliferation, migration, and activation by secreting a variety of cytokines via various inflammation-relative signaling pathways and thus participate in the process of angiogenesis. However, the mechanism of inflammation-mediated angiogenesis has not been fully elucidated. Hence, this review aimed to discuss the mechanism of inflammation-mediated angiogenesis in IS and to provide new ideas for clinical treatment of IS.

Anesthetic Potency of Intravenous Infusion of 20% Emulsified Sevoflurane and Effect on the Blood-Gas Partition Coefficient in Dogs

BACKGROUND

Intravenous (IV) infusions of volatile anesthetics in lipid emulsion may increase blood lipid concentration, potentially altering the anesthetic agent's blood solubility and blood-gas partition coefficient (BGPC). We examined the influence of a low-lipid concentration 20% sevoflurane emulsion on BGPC, and the anesthetic potency of this emulsion using dogs.

METHODS

We compared BGPC and anesthetic characteristics in 6 dogs between the IV anesthesia of emulsion and the sevoflurane inhalation anesthesia in a randomized crossover substudy. Minimum alveolar concentrations (MACs) were determined by tail-clamp stimulation by using the up-and-down method. Blood sevoflurane concentration and partial pressure were measured by gas chromatography; end-tidal sevoflurane concentration was measured using a gas monitor. The primary outcome was BGPC at the end of IV anesthesia and inhalation anesthesia. Secondary outcomes were time to loss/recovery of palpebral reflex, finish intubation and awakening, MAC, blood concentration/partial pressure at MAC and awakening, correlation between blood partial pressure and gas monitor, and the safety of emulsions.

RESULTS

BGPC showed no difference between IV and inhaled anesthesia (0.859 [0.850-0.887] vs 0.813 [0.791-0.901]; P = .313). Induction and emergence from anesthesia were more rapid in IV anesthesia of emulsion than inhalation anesthesia. MAC of emulsion (1.33% [1.11-1.45]) was lower than that of inhalation (2.40% [2.33-2.48]; P = .031), although there was no significant difference in blood concentration. End-tidal sevoflurane concentration could be estimated using gas monitor during IV anesthesia of emulsion. No major complications were observed.

CONCLUSIONS

IV anesthesia with emulsion did not increase the BGCP significantly compared to inhalation anesthesia. It was suggested that the anesthetic potency of this emulsion may be equal to or more than that of inhalation.

[Isoflurane preconditioning inhibits caspase-11-related noncanonical pyroptosis pathway to alleviate hepatic ischemia-reperfusion injury in mice]

OBJECTIVE

To study the protective effect of isoflurane preconditioning on hepatic ischemia-reperfusion (I/R) injury mediated by the noncanonical pyroptosis pathway.

METHODS

Thirty C57BL/6 mice were randomly divided into sham-operated group, isoflurane group and I/R group, and in the latter two groups, hepatic I/R injury was induced by clamping the portal vein for 30 min. In isoflurane group, the mice were pretreated with 1.4% isoflurane 30 min before the surgery. The protective effect of isoflurane preconditioning against hepatic I/R injury was evaluated by assessing the pathological score of HE staining of the liver tissue and serum ALT and AST levels. Serum IL-1β and IL-18 levels and the protein expression of GSDMS were detected by ELISA and Western blotting to evaluate the inhibitory effect of isoflurane preconditioning on pyroptosis. Western blotting and immunofluroescence were used to detect the protein expression of caspase-11 in the liver tissues to evaluate the inhibitory effect of isoflurane preconditioning on noncanonical pyroptosis pathway.

RESULTS

The Suzuki's score of the liver tissue was significantly higher in I/R group than in the sham group (P < 0.05), while the score in the isoflurane group was significantly lower than that in the I/R group (P < 0.05). Serum ALT and AST levels significantly increased in the sham group (P < 0.05), and were significantly lower in isoflurane group than in I/R group (P < 0.05). The serum levels of IL-1β and IL-18 were significantly higher in I/R group than in sham group (P < 0.05), and were significantly lower in isoflurane group than in I/R group (P < 0.05). The expression of GSDMD in the I/R group was significantly higher than that in sham group, and was significantly lower in isoflurane group than in I/R group (P < 0.05). The hepatic expression of caspase-11 was significantly higher in I/R group than in sham group (P < 0.05), and was significantly lower in isoflurane group than in I/R group (P < 0.05).

CONCLUSIONS

Isoflurane preconditioning has protective effect against hepatic I/R injury, which is related to the inhibition of the noncanonical pyroptosis pathway.

Pachymic acid protects against cerebral ischemia/reperfusion injury by the PI3K/Akt signaling pathway

Pachymic acid (PA) from medicinal fungus Poria cocos has a variety of pharmacological potentials. However, there are no reports of the effects of PA on cerebral ischemia/reperfusion (I/R) injury. The purpose of this study was to investigate the mechanisms of PA on cerebral I/R injury in rats. The effects of PA on cerebral infarction size, brain water content, neurological symptoms and cerebral blood flow were evaluated. Nissl staining was used to observe the damage of ischemic brain neurons after I/R in rats. Apoptosis of ischemic brain neurons after I/R was observed by TUNEL staining. The effect of PA on the expression of some components of PI3K/Akt was detected by Western blotting. PA significantly increased cerebral blood flow after I/R in rats, reduced infarct volume and brain water content, and downgrade neurological function scores, significantly reduced neuronal damage after I/R in rats, and significantly decreased neuronal apoptosis. The effect of PA on rat I/R can be eliminated by LY294002. In addition, PA significantly up-regulated the protein expression of p-PTEN (Ser380), p-PDK1 (Ser241), p-Akt (Ser473), pc-Raf (Ser259) and p-BAD (Ser136), and down-regulated Cleaved caspase protein expression. LY294002 can reverse the effect of PA on the expression of PI3K / Akt signaling pathway related protein in rats after I/R. PA had obviously neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to activation of PI3K / Akt signaling pathway.

Novel susceptibility genes were found in a targeted sequencing of stroke patients with or without depression in the Chinese Han population

BACKGROUND

Both stroke and depression are multi-factorial diseases, with both genetic and environmental factors likely to participate in their pathogenesis. Post stroke depression (PSD) is a common complication after stroke leading to poor functional outcome, increased physical disability and mortality. Although several genes have been associated with PSD, the genetic basis of PSD remains poorly understood.

METHOD

A 2-stage candidate gene study by targeted sequencing was conducted involving stroke patients with or without depression and health controls. In the discovery stage (121 PSD, 131 non-PSD and 639 HC), logistic regression was used to test associations respectively in PSD and non-PSD groups. In the replication stage (200 PSD, 218 non-PSD and 983 HC), 54 selected SNPs were again genotyped in an independent cohort. Fixed-effects inverse variance-weighted meta-analysis was used in the combined samples.

RESULTS

The study identified 2 novel genes associated with PSD [HTR3D (rs55674402, p = 0.002512, odds ratio (OR) = 0.7431); NEUROG3 (rs144643855, p = 0.00325, OR = 0.6523)] and 3 risk SNPs in one risk gene associated with non-PSD [PIK3C2B (rs17406271, p = 0.0006801, OR = 1.446; rs2271419, p = 0.0005836, OR = 1.497; rs2271420, p = 0.001031, OR = 1.431)] in the Chinese sample. NEUROG3 shows highest expression level in hippocampus. Functional enrichment analysis shows that susceptibility genes for PSD are mostly enriched in chemical synaptic transmission and regulation of lipid synthetic process.

LIMITATIONS

The sample size was not sufficient to reach a genome-wide p value level. To overcome this shortage, some unique strategies were applied during the selection of SNPs for replication. Secondly, the age, gender composition and depressive severity between two stages were not well-matched. Different sample sources should be blamed, and to minimizing the influence, gender was corrected as co-variant in logistic regression.

CONCLUSION

This study identified that HTR3D and NEUROG3 were linked with the susceptibility of PSD and PIK3C2B with stroke in the Chinese Han population. Further replication of these findings in a larger and better matched sample is warranted. Functional analysis suggests that the pathogenesis of PSD may be implicated in 5-HT synaptic transmission, neural plasticity and lipid metabolism, and therapeutic interventions targeting these pathways may be effective approaches for PSD treatment.

Magnesium sulfate ameliorates carbon monoxide‑induced cerebral injury in male rats

Carbon monoxide (CO) has been shown to induce several cardiovascular abnormalities, as well as necrosis, apoptosis and oxidative stress in the brain. Magnesium sulfate (MS) has been shown to have beneficial activities against hypoxia in the brain. In the present study, the possible protective effects of MS against CO‑induced cerebral ischemia were investigated. For this purpose, 25 male Wistar rats were exposed to 3,000 ppm CO for 1 h. The animals were divided into 5 groups (n=5 in each group) as follows: The negative control group (not exposed to CO), the positive control group (CO exposed and treated with normal saline), and 3 groups of CO‑exposed rats treated with MS (75, 150 and 300 mg/kg/day) administered intraperitoneally for 5 consecutive days. On the 5th day, the animals were sacrificed and the brains were harvested for the evaluation of necrosis, apoptosis and oxidative stress. Histopathological evaluation revealed that MS reduced the number and intensity of necrotic insults. The Bax/Bcl2 ratio and malondialdehyde (MDA) levels were significantly decreased in a dose‑dependent manner in the MS‑treated rats compared to the positive control group, while a significant dose‑dependent increase in Akt expression, a pro‑survival protein, was observed. In addition, MS administration reduced pro‑apoptotic indice levels, ameliorated histological insults, favorably modulated oxidative status and increased Akt expression levels, indicating a possible neuroprotective effect in the case of CO poisoning. On the whole, the findings of this study indicate that MS may prove to be useful in protecting against CO‑induced cerebral injury.

Activation of Akt by SC79 decreased cerebral infarct in early cerebral ischemia-reperfusion despite increased BBB disruption

Activation of Akt has been suggested to produce neuronal protection in cerebral ischemia. Decreasing blood-brain barrier (BBB) disruption has been associated with a better neuronal outcome in cerebral ischemia. We hypothesized that activation of Akt would decrease BBB disruption and contribute to decreasing the size of infarct in the early stage of cerebral ischemia-reperfusion within the therapeutic window. Transient middle cerebral artery occlusion (MCAO) was performed in rats under isoflurane anesthesia with controlled ventilation. Rats were treated with SC79 (a selective Akt activator which is cell and BBB permeable) 0.05 mg/kg × 3 i.p. or vehicle i.p. perioperatively. After one hour of MCAO and two hours of reperfusion, the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid (¹⁴C-AIB, molecular weight 104 Da) and the volume of ³H-dextran (molecular weight 70,000 Da) distribution were determined to measure the degree of BBB disruption. At the same time point, the size of infarction was determined using tetrazolium staining. In an additional group of rats, a higher dose of SC79 (0.5 mg/kg × 3) was administered to determine the size of infarct. Administration of SC79 increased the K_i in the ischemic-reperfused cortex (IR-C, +32%, p < 0.05) as well as in the contralateral cortex (CC, +35%, p < 0.05) when compared with the untreated animals with MCAO/reperfusion. The volume of dextran distribution was not significantly changed by SC79. SC79 treatment significantly produced a decrease in the percentage of cortical infarct out of total cortical area (12.7 ± 1.7% vs 6.9 ± 0.9%, p < 0.001). Increasing the dose of SC79 by ten times did not significantly affect the size of cortical infarct. Contrary to our hypothesis, our data demonstrated that SC79 decreased the size of the infarct in the ischemic-reperfused cortex despite an increase in BBB disruption. Our data suggest the importance of activation of Akt for neuronal survival in the early stage of cerebral ischemia-reperfusion within the therapeutic window and that the mechanism of neuroprotection may not be related to the BBB effects of SC79.

Inhibition of NLRP3 Inflammasome Ameliorates Cerebral Ischemia-Reperfusion Injury in Diabetic Mice

Sustained activation of NLRP3 inflammasome is closely related to diabetes and stroke. However, it is unknown whether NLRP3 inflammasome plays an essential role in stroke in diabetes. We aim to investigate the effect and the potential mechanism of NLRP3 inflammasome in diabetic mice with cerebral ischemia-reperfusion injury. A type 2 diabetic mouse model was induced by a high-fat diet and streptozotocin (STZ). Diabetic mice received MCC950 (the specific molecule NLRP3 inhibitor) or vehicle 60 minutes before the middle cerebral artery occlusion (MCAO) and reperfusion. MCC950 reduced the neurological deficit score of 24 h after cerebral ischemia reperfusion and improved the 28-day survival rate of cerebral ischemia-reperfusion injury in diabetic mice. Furthermore, we found that the mRNA transcription levels of NLRP3, IL-1β, and caspase-1 in the core ischemic area were remarkably amplified in diabetic mice with cerebral ischemia-reperfusion injury, whereas this phenomenon was obviously attenuated by MCC950 pretreatment. In conclusion, the NLRP3 inflammasome was involved in the complex diseases of diabetic stroke. MCC950, the NLRP3 specific inhibitor, ameliorated diabetic mice with cerebral ischemia-reperfusion injury and improved the 28-day survival rate during the recovery stage of ischemic stroke.

Effect of Anesthetics on Efficiency of Remote Ischemic Preconditioning

Remote ischemic preconditioning of hind limbs (RIPC) is an effective method for preventing brain injury resulting from ischemia. However, in numerous studies RIPC has been used on the background of administered anesthetics, which also could exhibit neuroprotective properties. Therefore, investigation of the signaling pathways triggered by RIPC and the effect of anesthetics is important. In this study, we explored the effect of anesthetics (chloral hydrate and Zoletil) on the ability of RIPC to protect the brain from injury caused by ischemia and reperfusion. We found that RIPC without anesthesia resulted in statistically significant decrease in neurological deficit 24 h after ischemia, but did not affect the volume of brain injury. Administration of chloral hydrate or Zoletil one day prior to brain ischemia produced a preconditioning effect by their own, decreasing the degree of neurological deficit and lowering the volume of infarct with the use of Zoletil. The protective effects observed after RIPC with chloral hydrate or Zoletil were similar to those observed when only the respective anesthetic was used. RIPC was accompanied by significant increase in the level of brain proteins associated with the induction of ischemic tolerance such as pGSK-3β, BDNF, and HSP70. However, Zoletil did not affect the level of these proteins 24 h after injection, and chloral hydrate caused increase of only pGSK-3β. We conclude that RIPC, chloral hydrate, and Zoletil produce a significant neuroprotective effect, but the simultaneous use of anesthetics with RIPC does not enhance the degree of neuroprotection.

LY294002, a PI3K inhibitor, attenuates Tourette syndrome in rats

The present study was designed to investigate the effects of LY294002 on Tourette syndrome (TS) in rats. TS model was induced in rats by DOI (the selective 5-HT2A/2C agonist 1- (2, 5- dimethoxy -4 - iodophenyl) -2- aminopropane). Behavior was assessed by stereotypic score and autonomic activity. Inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in serum and striatum were detected. The protein levels of PI3K/Akt/NF-B in striatum were detected by Western Blot. LY294002 treatment significantly reduced IL-6, IL-1β and TNF-α in serum and striatum of TS rats, Also, highly expressed P-PI3K, P-Akt, P-NF-κBp65, P-IκBα in TS rats were restored respectively by LY294002 treatment as indicted in western blot analysis and immunohistochemistry analysis. Thus, it was supposed that the protective effect of LY294002 against TS in rat might be associated with the regulation of PI3K/Akt/NF-B pathway.

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.

New Hypnotic Drug Development and Pharmacologic Considerations for Clinical Anesthesia

Since the public demonstration of ether as a novel, viable anesthetic for surgery in 1846, the field of anesthesia has continually sought the ideal anesthetic-rapid onset, potent sedation-hypnosis with a high therapeutic ratio of toxic dose to minimally effective dose, predictable clearance to inactive metabolites, and minimal side effects. This article aims to review current progress of novel induction agent development and provide an update on the most promising drugs poised to enter clinical practice. In addition, the authors describe trends in novel agent development, implications for health care costs, and implications for perioperative care.

Blood -brain barrier disruption was less under isoflurane than pentobarbital anesthesia via a PI3K/Akt pathway in early cerebral ischemia

One of the important factors altering the degree of blood-brain barrier (BBB) disruption in cerebral ischemia is the anesthetic used. The phosphoinositide 3-kinase (PI3K)/Akt signaling pathway has been reported to be involved in modulating BBB permeability and in isoflurane induced neuroprotection. This study was performed to compare the degree of BBB disruption in focal cerebral ischemia under isoflurane vs pentobarbital anesthesia and to determine whether inhibition of PI3K/Akt would affect the disruption in the early stage of focal cerebral ischemia. Permanent middle cerebral artery (MCA) occlusion was performed in rats under 1.4% isoflurane or pentobarbital (50mg/kg i.p.) anesthesia with controlled ventilation. In half of each group LY294002, which is a PI3K/Akt inhibitor, was applied on the ischemic cortex immediately after MCA occlusion. After one hour of MCA occlusion, the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid (¹⁴C-AIB) was determined to quantify the degree of BBB disruption. MCA occlusion increased the K_i both in the isoflurane and pentobarbital anesthetized rats. However, the value of K_i was lower under isoflurane (11.5±6.0μL/g/min) than under pentobarbital (18.3±7.1μL/g/min) anesthesia. The K_i of the contralateral cortex of the pentobarbital group was higher (+74%) than that of the isoflurane group. Application of LY294002 on the ischemic cortex increased the K_i (+99%) only in the isoflurane group. The degree of BBB disruption by MCA occlusion was significantly lower under isoflurane than pentobarbital anesthesia in the early stage of cerebral ischemia. Our data demonstrated the importance of choice of anesthetics and suggest that PI3K/Akt signaling pathway plays a significant role in altering BBB disruption in cerebral ischemia during isoflurane but not during pentobarbital anesthesia.