Isoflurane posttreatment reduces neonatal hypoxic-ischemic brain injury in rats by the sphingosine-1-phosphate/phosphatidylinositol-3-kinase/Akt pathway

Neuroprotective Effect of Sodium Butyrate against Cerebral Ischemia/Reperfusion Injury in Mice

Sodium butyrate (NaB) is a dietary microbial fermentation product of fiber and serves as an important neuromodulator in the central nervous system. In this study, we further investigated that NaB attenuated cerebral ischemia/reperfusion (I/R) injury in vivo and its possible mechanisms. NaB (5, 10 mg/kg) was administered intragastrically 3 h after the onset of reperfusion in bilateral common carotid artery occlusion (BCCAO) mice. After 24 h of reperfusion, neurological deficits scores were estimated. Morphological examination was performed by electron microscopy and hematoxylin-eosin (H&E) staining. The levels of oxidative stress and inflammatory cytokines were assessed. Apoptotic neurons were measured by TUNEL; apoptosis-related protein caspase-3, Bcl-2, Bax, the phosphorylation Akt (p-Akt), and BDNF were assayed by western blot and immunohistochemistry. The results showed that 10 mg/kg NaB treatment significantly ameliorated neurological deficit and histopathology changes in cerebral I/R injury. Moreover, 10 mg/kg NaB treatment markedly restored the levels of MDA, SOD, IL-1β, TNF-α, and IL-8. 10 mg/kg NaB treatment also remarkably inhibited the apoptosis, decreasing the levels of caspase-3 and Bax and increasing the levels of Bcl-2, p-Akt, and BDNF. This study suggested that NaB exerts neuroprotective effects on cerebral I/R injury by antioxidant, anti-inflammatory, and antiapoptotic properties and BDNF-PI3K/Akt pathway is involved in antiapoptotic effect.

Isoflurane anesthesia initiated at the onset of reperfusion attenuates oxidative and hypoxic-ischemic brain injury

This study demonstrates that in mice subjected to hypoxia-ischemia (HI) brain injury isoflurane anesthesia initiated upon reperfusion limits a release of mitochondrial oxidative radicals by inhibiting a recovery of complex-I dependent mitochondrial respiration. This significantly attenuates an oxidative stress and reduces the extent of HI brain injury. Neonatal mice were subjected to HI, and at the initiation of reperfusion were exposed to isoflurane with or without mechanical ventilation. At the end of HI and isoflurane exposure cerebral mitochondrial respiration, H2O2 emission rates were measured followed by an assessment of cerebral oxidative damage and infarct volumes. At 8 weeks after HI navigational memory and brain atrophy were assessed. In vitro, direct effect of isoflurane on mitochondrial H2O2 emission was compared to that of complex-I inhibitor, rotenone. Compared to controls, 15 minutes of isoflurane anesthesia inhibited recovery of the compex I-dependent mitochondrial respiration and decreased H2O2 production in mitochondria supported with succinate. This was associated with reduced oxidative brain injury, superior navigational memory and decreased cerebral atrophy compared to the vehicle-treated HI-mice. Extended isoflurane anesthesia was associated with sluggish recovery of cerebral blood flow (CBF) and the neuroprotection was lost. However, when isoflurane anesthesia was supported with mechanical ventilation the CBF recovery improved, the event associated with further reduction of infarct volume compared to HI-mice exposed to isoflurane without respiratory support. Thus, in neonatal mice brief isoflurane anesthesia initiated at the onset of reperfusion limits mitochondrial release of oxidative radicals and attenuates an oxidative stress. This novel mechanism contributes to neuroprotective action of isoflurane. The use of mechanical ventilation during isoflurane anesthesia counterbalances negative effect of isoflurane anesthesia on recovery of cerebral circulation which potentiates protection against reperfusion injury.

HIF-1α Mediates Isoflurane-Induced Vascular Protection in Subarachnoid Hemorrhage

Objective

Outcome after aneurysmal subarachnoid hemorrhage (SAH) depends critically on delayed cerebral ischemia (DCI) – a process driven primarily by vascular events including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction. This study sought to determine the impact of postconditioning – the phenomenon whereby endogenous protection against severe injury is enhanced by subsequent exposure to a mild stressor – on SAH-induced DCI.

Methods

Adult male C57BL/6 mice were subjected to sham, SAH, or SAH plus isoflurane postconditioning. Neurological outcome was assessed daily via sensorimotor scoring. Contributors to DCI including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction were measured 3 days later. Isoflurane-induced changes in hypoxia-inducible factor 1alpha (HIF-1α)-dependent genes were assessed via quantitative polymerase chain reaction. HIF-1α was inhibited pharmacologically via 2-methoxyestradiol (2ME2) or genetically via endothelial cell HIF-1α-null mice (EC-HIF-1α-null). All experiments were performed in a randomized and blinded fashion.

Results

Isoflurane postconditioning initiated at clinically relevant time points after SAH significantly reduced cerebral vasospasm, microvessel thrombosis, microvascular dysfunction, and neurological deficits in wild-type (WT) mice. Isoflurane modulated HIF-1α-dependent genes – changes that were abolished in 2ME2-treated WT mice and EC-HIF-1α-null mice. Isoflurane-induced DCI protection was attenuated in 2ME2-treated WT mice and EC-HIF-1α-null mice.

Interpretation

Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome. These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection. They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.

Anesthetic preconditioning inhibits isoflurane-mediated apoptosis in the developing rat brain

BACKGROUND

We hypothesized that preconditioning (PC) with a short exposure to isoflurane (ISO) would reduce neurodegeneration induced by prolonged exposure to ISO in neonatal rats, as previously shown in neuronal cell culture.

METHODS

We randomly divided 7-day-old Sprague-Dawley rats into 3 groups: control, 1.5% ISO, and PC + 1.5% ISO. The control group was exposed to carrier gas (30% oxygen balanced in nitrogen) for 30 minutes and then to carrier gas again for 6 hours the following day. The 1.5% ISO group was exposed to carrier gas for 30 minutes and then to 1.5% ISO for 6 hours the following day. The PC + 1.5% ISO group was preconditioned with a 30-minute 1.5% ISO exposure and then exposed to 1.5% ISO for 6 hours the following day. Blood and brain samples were collected 2 hours after the exposures for determination of neurodegenerative biomarkers, including caspase-3, S100β, caspase-12, and an autophagy biomarker Beclin-1.

RESULTS

Prolonged exposure to ISO significantly increased cleaved caspase-3 expression in the cerebral cortex of 7-day-old rats compared with the group preconditioned with ISO and the controls using Western blot assays. However, significant differences were not detected for other markers of neuronal injury.

CONCLUSIONS

The ISO-mediated increase in cleaved caspase-3 in the postnatal day 7 rat brain is ameliorated by PC with a brief anesthetic exposure, and differences were not detected in other markers of neuronal injury.

High-fat diet reduces neuroprotection of isoflurane post-treatment: Role of carboxyl-terminal modulator protein-Akt signaling

OBJECTIVE

High-fat diet (HFD) contributes to the increased prevalence of obesity and hyperlipidemia in young adults, a possible cause for their recent increase in stroke. Isoflurane post-treatment provides neuroprotection. Isoflurane post-treatment induced neuroprotection in HFD-fed mice was determined.

METHODS

Six-week old CD-1 male mice were fed HFD or regular diet (RD) for 5 or 10 weeks. Their hippocampal slices (400 µm) were subjected to oxygen-glucose deprivation (OGD). Some slices were exposed to isoflurane for 30 min immediately after OGD. Some mice had a 90-min middle cerebral arterial occlusion and were post-treated with 2% isoflurane for 30 min.

RESULTS

OGD time-dependently induced cell injury. This injury was dose-dependently reduced by isoflurane. The effect was apparent at 1% or 2% isoflurane in RD-fed mice but required 3% isoflurane in HFD-fed mice. HFD influenced the isoflurane effects in DG. OGD increased carboxyl-terminal modulator protein (CTMP), an Akt inhibitor, and decreased Akt signaling. Isoflurane reduced these effects. LY294002, an Akt activation inhibitor, attenuated the isoflurane effects. HFD increased CTMP and reduced Akt signaling. Isoflurane improved neurological outcome in the RD-fed mice but not in the HFD-fed mice.

CONCLUSIONS

HFD attenuated isoflurane post-treatment-induced neuroprotection possibly because of decreased prosurvival Akt signaling.

L-3-n-butylphthalide protects against vascular dementia via activation of the Akt kinase pathway

As a neuroprotective drug for the treatment of ischemic stroke, 3-n-butylphthalide, a celery seed extract, has been approved by the State Food and Drug Administration of China as a clinical therapeutic drug for ischemic stroke patients. L-3-n-butylphthalide possesses significant efficacy in the treatment of acute ischemic stroke. The activated Akt kinase pathway can prevent the death of nerve cells and exhibit neuroprotective effects in the brain after stroke. This study provides the hypothesis that l-3-n-butylphthalide has a certain therapeutic effect on vascular dementia, and its mechanism depends on the activation of the Akt kinase pathway. A vascular dementia mouse model was established by cerebral repetitive ischemia/reperfusion, and intragastrically administered l-3-n-butylphthalide daily for 28 consecutive days after ischemia/reperfusion, or 7 consecutive days before ischemia/reperfusion. The Morris water maze test showed significant impairment of spatial learning and memory at 4 weeks after operation, but intragastric administration of l-3-n-butylphthalide, especially pretreatment with l-3-n-butylphthalide, significantly reversed these changes. Thionine staining and western blot analylsis showed that preventive and therapeutic application of l-3-n-butylphthalide can reduce loss of pyramidal neurons in the hippocampal CA1 region and alleviate nerve damage in mice with vascular dementia. In addition, phosphorylated Akt expression in hippocampal tissue increased significantly after l-3-n- butylphthalide treatment. Experimental findings demonstrate that l-3-n-butylphthalide has preventive and therapeutic effects on vascular dementia, and its mechanism may be mediated by upregulation of phosphorylated Akt in the hippocampus.

Isoflurane preconditioning ameliorates renal ischemia-reperfusion injury through antiinflammatory and antiapoptotic actions in rats

Renal ischemia-reperfusion (I/R) injury is a major cause of acute kidney injury via inflammation and cell apoptosis. Volatile anesthetics have been shown to exert organ-protective effects against kidney damage in vivo and in vitro. In the present study, we investigated the effects of isoflurane, a commonly used volatile anesthetic, on renal I/R injury and the underlying mechanisms. Rats subjected to renal I/R displayed higher serum creatinine and blood urea nitrogen levels than sham rats as well as severe histopathological damage. Renal I/R also resulted in a nuclear factor-κB (NF-κB)-mediated inflammatory response and dysfunction of the p53-Bax-caspase-3 apoptotic pathway. Rats preconditioned with 1.5% isoflurane for 2 h had better renal function and less tubular apoptosis 24 h after I/R injury than control rats. Pretreatment with isoflurane suppressed renal NF-κB activation, leading to a reduction in proinflammatory molecules (high-mobility group box 1, interleukin-1β, and tumor necrosis factor-α) both in the kidneys and circulation. In addition, rats subjected to isoflurane preconditioning had a higher Bcl-2/Bax ratio and less cleaved caspase-3. Our findings suggest that preconditioning with a clinically relevant concentration of isoflurane attenuates renal I/R injury, based at least in part on its ability to modulate renal inflammation and apoptosis.

Role of the sphingosine metabolism pathway on neurons against experimental cerebral ischemia in rats

Although there is evidence that sphingosine-1-phosphate receptor-1 (S1P1) activation occurs following experimental brain injury, there is little information about its metabolic pathway in cerebral ischemia. The purpose of this study was to evaluate the role of the sphingosine metabolic pathway including S1P1, sphingosine kinases 1 (SphK1), and 2 (SphK2) in transient middle cerebral artery occlusion (MCAO). Fifty-eight male Sprague-Dawley rats were used to asses temporal profiles of S1P1, SphK1 and 2 on neurons in infarct and periinfarct cortices at pre-infarct state, 6, and 24 hours after MCAO. The animals were then treated with vehicle and 0.25 mg/kg FTY720, which is an agonist of S1P receptors, and evaluated regarding neurological function, infarct volume, and S1P1 expression on neurons at 24 hours after MCAO. The expressions of S1P1, SphK1, and SphK2 were significantly decreased after MCAO. Labeling of all markers were reduced in the infarct cortex but remained present in the periinfarct cortex, and some were found to be on neurons. Significant improvements of neurological function and brain injury were observed in the FTY720 group compared with the vehicle and untreated groups, although S1P1 expression on neurons was reduced in the FTY720 group compared with the vehicle group. We demonstrated that S1P1, SphK1, and SphK2 were downregulated in the infarct cortex, whereas they were preserved in the periinfarct cortex where FTY720 reduced neuronal injury possibly via S1P1 activation. Our findings suggest that activation of the sphingosine metabolic pathway may be neuroprotective in cerebral ischemia.

Proteomic analysis of immature rat pups brain in response to hypoxia and ischemia challenge

Hypoxia and ischemia significantly affects perinatal brain development, even worse in preterm infants. However, the details of the mechanism leading to permanent brain damage after hypoxia-ischemia attack have not been fully elucidated. Proteomics could provide insight into the potential mechanism and help to promote the clinical treatment. In this study, quantitative analysis was performed 24 hours after hypoxia-ischemia using liquid-chromatography mass spectrometry coupled to label-free analysis. Compared to control, 193 proteins were present only in hypoxic-ischemic group. In addition, 34 proteins were more than 2 folds up-regulated and 14 proteins were more than 2 folds down-regulated in hypoxia-ischemia group. Gene Ontology database showed that the majority of differentially expressed proteins comprised mitochondrial proteins et al. Molecular function analysis revealed that the majority of proteins were involved in ion binding et al. Biological process analysis showed that the majority of proteins were involved in response to organic substance et al. STRING 9.0 software analysis were used to explore the complex interactions existed among the proteins. Western blot were used to verify the fold changes of some proteins-microtubule-associated protein 2 and microtubule-associated protein tau. This novel study performed a full-scale screening of the proteomics research in hypoxic-ischemic brain damage of immature rat.

Isoflurane provides neuroprotection in neonatal hypoxic ischemic brain injury

Isoflurane is a volatile anesthetic that is widely used clinically as an inhalational anesthetic. In recent years, several studies have indicated that isoflurane has neuroprotective properties. This has led to the beneficial effects of isoflurane being analyzed in both cell culture and animal models, including various models of brain injury. Neonatal hypoxia ischemia may be characterized as injury that occurs in the immature brain, resulting in delayed cell death via excitotoxicity and oxidative stress. These adverse events in the developing brain often lead to detrimental neurological defects in the future. Currently, there are no well-established effective therapies for neonatal hypoxia ischemia. In line with this, isoflurane, which displays neuroprotective properties in several paradigms and has been shown to improve neurological deficits caused by brain injuries, has the capability to be an extremely relevant clinical therapy for the resolution of deficits concomitant with neonatal hypoxic ischemic brain injuries. This review therefore seeks to explore and analyze the current information on isoflurane, looking at general isoflurane anesthetic properties, and the protection it confers in different animal models, focusing particularly on neuroprotection as shown in studies with neonatal hypoxic ischemic brain injury.

Hyperbaric oxygen therapy fails to reduce hydrocephalus formation following subarachnoid hemorrhage in rats

Background & purpose

Approximately 40% of hemorrhagic stroke survivors develop hydrocephalus. Hyperbaric oxygen (HBO) has been shown to be anti-inflammation following experimental stroke; however, its effect upon post-hemorrhagic hydrocephalus formation is not known. The objective of this study is to investigate whether HBO therapy can effectively reduce hydrocephalus formation and improve neurobehavioral functions in a rat model of subarachnoid hemorrhage (SAH).

Method

Thirty-eight male Sprague–Dawley rats (300-320 g) rats survived for 21 days from SAH by endovascular perforation or sham surgery were used. At 24 hours after SAH, HBO (3 atmospheres absolute) or normobaric oxygen (NBO) administrated for 1 hour once daily for a total of 7 days. Wire hanging and rotarod testing were conducted at 14 days after SAH, and cognitive functions were evaluated via the Morris water maze, between day 17 to day 21 after surgery. At day 21, rats were sacrificed and cerebroventricular volumes were measured histologically.

Results

Hydrocephalus exacerbated neurological deficits after SAH, and HBO multiple treatment tendentially improved the neurobehavioral functions. Spatial learning and memory deficits were noticed after SAH, and rats with hydrocephalus showed worse learning and memory abilities and HBO treatment showed a minor improvement. In the SAH group (room air) 4 rats showed an increased ventricular volume at day 21 after SAH-induction (n = 10). HBO or NBO therapy did not alter the occurrence of hydrocephalus after SAH, as 4 rats in each of these groups showed an increased ventricular volume (n = 10 per group).

Conclusion

Multiple HBO therapy does not ameliorate hydrocephalus formation in a rat model of SAH; however, HBO tendentially improved the neurological functions and spatial learning and memory abilities in rats with hydrocephalus.

Delayed hyperbaric oxygen therapy promotes neurogenesis through reactive oxygen species/hypoxia-inducible factor-1α/β-catenin pathway in middle cerebral artery occlusion rats

BACKGROUND AND PURPOSE

Hyperbaric oxygen (HBO) has been reported to be neuroprotective and to improve neurofunctional outcomes in acute stroke. However, it is not clear whether delayed HBO enhances endogenous neurogenesis and promotes neurofunctional recovery. The aim of this study is to evaluate the effects of delayed HBO therapy on neurogenesis and its potential mechanisms.

METHODS

One hundred eleven male Sprague-Dawley rats that survived for 7 days from 2 hours of middle cerebral artery occlusion and reperfusion were used. Delayed and multiple HBO were administrated beginning at 7 days after middle cerebral artery occlusion and lasting for 42 days with 3 HBO-free intervals (5 days each). Motor sensory deficits were measured by foot-fault test, and learning and memory abilities were evaluated by Morris water maze. Neurogenesis was examined by double immunostaining of bromodeoxyuridine and doublecortin, bromodeoxyuridine and neuronal nuclei at day 42. For mechanism studies, inhibitors for reactive oxygen species (ROS), hypoxia-inducible factor (HIF)-1α, and β-catenin were administrated, and the levels of ROS, HIF-1α, β-catenin, lymphoid enhancer-binding factor-1, T-cell factor-1, neurogenin-1, doublecortin, and synapsin-1 were assessed by ELISA or Western blot at day 14.

RESULTS

Delayed HBO treatment promoted neurogenesis and improved neurofunctional recovery at day 42, and the improvements were reversed by inhibition of ROS and HIF-1α. Delayed HBO significantly increased ROS and HIF-1α, and upregulated the expression of neurogenin-1, doublecortin, and synapsin-1. Inhibition of ROS and HIF-1α removed the effects of delayed HBO.

CONCLUSIONS

Delayed HBO enhanced endogenous neurogenesis and improved neurofunctional recovery in the late-chronic phase of stroke possibly mediated by ROS/HIF-1α/β-catenin pathway. Delayed HBO may serve as an alternative treatment to improve long-term recovery of stroke survivors.

A double-edged sword: volatile anesthetic effects on the neonatal brain

The use of volatile anesthetics, a group of general anesthetics, is an exceedingly common practice. These anesthetics may have neuroprotective effects. Over the last decade, anesthetic induced neurotoxicity in pediatric populations has gained a certain notoriety based on pre-clinical cell and animal studies demonstrating that general anesthetics may induce neurotoxicity, including neuroapoptosis, neurodegeneration, and long-term neurocognitive and behavioral deficits. With hundreds of millions of people having surgery under general anesthesia worldwide, and roughly six million children annually in the U.S. alone, the importance of clearly defining toxic or protective effects of general anesthetics cannot be overstated. Yet, with our expanding body of knowledge, we have come to learn that perhaps not all volatile anesthetics have the same pharmacological profiles; certain ones may have a more favorable neurotoxic profile and may actually exhibit neuroprotection in specific populations and situations. Thus far, very few clinical studies exist, and have not yet been convincing enough to alter our practice. This review will provide an update on current data regarding volatile anesthetic induced neurotoxicity and neuroprotection in neonatal and infant populations. In addition, this paper will discuss ongoing studies and the trajectory of further research over the coming years.

Sevoflurane postconditioning provides neuroprotection against brain hypoxia-ischemia in neonatal rats

Application of volatile anesthetics after brain ischemia provides neuroprotection in adult animals (anesthetic postconditioning). We tested whether postconditioning with sevoflurane, the most commonly used general anesthetic in pediatric anesthesia, reduced neonatal brain injury in rats. Seven-day-old Sprague-Dawley rats were subjected to brain hypoxia-ischemia (HI). They were postconditioned with sevoflurane in the presence or absence of 5-hydroxydecanoic acid, a mitochondrial KATP channel inhibitor. Sevoflurane postconditioning dose-dependently reduced brain tissue loss observed 7 days after brain HI. This effect was induced by clinically relevant concentrations and abolished by 5-hydroxydecanoic acid. These results suggest that sevoflurane postconditioning protects neonatal brain against brain HI via mitochondrial KATP channels.

Induction of ischemic stroke in awake freely moving mice reveals that isoflurane anesthesia can mask the benefits of a neuroprotection therapy

Anesthetics such as isoflurane are commonly used to sedate experimental animals during the induction of stroke. Since these agents are known to modulate synaptic excitability, inflammation and blood flow, they could hinder the development and discovery of new neuroprotection therapies. To address this issue, we developed a protocol for inducing photothrombotic occlusion of cerebral vessels in fully conscious mice and tested two potential neuroprotectant drugs (a GluN2B or α4β2 nicotinic receptor antagonist). Our data show in vehicle treated mice that just 20 min of exposure to isoflurane during stroke induction can significantly reduce ischemic cortical damage relative to mice that were awake during stroke. When comparing potential stroke therapies, none provided any level of neuroprotection if the stroke was induced with anesthesia. However, if mice were fully conscious during stroke, the α4β2 nicotinic receptor antagonist reduced ischemic damage by 23% relative to vehicle treated controls, whereas the GluN2B antagonist had no significant effect. These results suggest that isoflurane anesthesia can occlude the benefits of certain stroke treatments and warrant caution when using anesthetics for pre-clinical testing of neuroprotective agents.

Delayed remote ischemic postconditioning improves long term sensory motor deficits in a neonatal hypoxic ischemic rat model

Objective

Remote Ischemic Postconditioning (RIPC) is a promising therapeutic intervention wherein a sub-lethal ischemic insult induced in one organ (limb) improves ischemia in an organ distant to it (brain). The main objective of this study was to investigate the long-term functional effects of delayed RIPC in a neonatal hypoxia-ischemia (HI) rat model.

Method

10 day old rat pups were subjected to delayed RIPC treatment and randomized into four groups: 1) Sham, 2) HI induced, 3) HI +24 hr delayed RIPC, and 4) HI +24 hr delayed RIPC with three consecutive daily treatments. Neurobehavioral tests, brain weights, gross and microscopic brain tissue morphologies, and systemic organ weights were evaluated at five weeks post surgery.

Results

HI induced rats performed significantly worse than sham but both groups of delayed RIPC treatment showed improvement of sensory motor functions. Furthermore, compared to the HI induced group, the delayed RIPC treatment groups showed no further detrimental changes on brain tissue, both grossly and morphologically, and no changes on the systemic organ weights.

Conclusion

Delayed RIPC significantly improves long term sensory motor deficits in a neonatal HI rat model. A 24 hr delayed treatment does not significantly attenuate morphological brain injury but does attenuate sensory motor deficits. Sensory motor deficits improve with both a single treatment and with three consecutive daily treatments, and the consecutive treatments are possibly being more beneficial.

Fetal hypoxia increases vulnerability of hypoxic-ischemic brain injury in neonatal rats: role of glucocorticoid receptors

Gestational hypoxia is a common stress to the fetal development and increases the risk of neonatal morbidity. The present study tested the hypothesis that fetal hypoxia results in heightened brain vulnerability to hypoxic-ischemic (HI) injury in neonatal rats via down-regulation of glucocorticoid receptor (GR) in the developing brain. Time-dated pregnant rats were exposed to hypoxia (10.5% O2) from days 15 to 21 of gestation. Brain HI injury was determined in day 10 pups. Maternal hypoxia resulted in asymmetric intrauterine growth restriction in the fetus. The brain HI injury was significantly increased in maternal hypoxia-treated pups as compared with the normoxia control in both males and females. Activation of brain GR by dexamethasone injection into the right lateral ventricle produced a concentration-dependent reduction of HI-induced brain injury in control pups. Maternal hypoxia significantly decreased GR mRNA and protein abundance in the fetal brain and neonatal hippocampus and abolished the dexamethasone-mediated neuroprotective effect in pup brains. This decreased GR expression was resulted from increased DNA methylation, decreased binding of transcription factors Egr-1 and Sp1 to GR gene exon 17 and 111 promoters, and reduced expression of GR exon 17 and 111 mRNA variants. The results demonstrate that gestational hypoxia causes epigenetic repression of GR gene expression in the developing brain resulting in the heightened brain vulnerability to HI injury in neonatal rats.

Volatile anesthetics and AKI: risks, mechanisms, and a potential therapeutic window

AKI is a major clinical problem with extremely high mortality and morbidity. Kidney hypoxia or ischemia-reperfusion injury inevitably occurs during surgery involving renal or aortic vascular occlusion and is one of the leading causes of perioperative AKI. Despite the growing incidence and tremendous clinical and financial burden of AKI, there is currently no effective therapy for this condition. The pathophysiology of AKI is orchestrated by renal tubular and endothelial cell necrosis and apoptosis, leukocyte infiltration, and the production and release of proinflammatory cytokines and reactive oxygen species. Effective management strategies require multimodal inhibition of these injury processes. Despite the past theoretical concerns about the nephrotoxic effects of several clinically utilized volatile anesthetics, recent studies suggest that modern halogenated volatile anesthetics induce potent anti-inflammatory, antinecrotic, and antiapoptotic effects that protect against ischemic AKI. Therefore, the renal protective properties of volatile anesthetics may provide clinically useful therapeutic intervention to treat and/or prevent perioperative AKI. In this review, we outline the history of volatile anesthetics and their effect on kidney function, briefly review the studies on volatile anesthetic-induced renal protection, and summarize the basic cellular mechanisms of volatile anesthetic-mediated protection against ischemic AKI.

Prolonged exposure to isoflurane ameliorates infarction severity in the rat pup model of neonatal hypoxia-ischemia

The neonatal hypoxia-ischemia rat model referred to as the Rice-Vannucci model is extensively used to study perinatal hypoxia-ischemia and child brain injury. One of the major weaknesses of this model is its inconsistency of brain infarction among animals. We hypothesize that the inconsistency of infarction is caused by prolonged operation time and therefore isoflurane exposure. Neonatal hypoxia-ischemia was induced in postnatal days 7 and 10 rat pups by unilateral right common carotid ligation followed by 2.5 h of hypoxia (8% oxygen). The incision-to-ligation (ITL) was defined as the amount of time from initial incision (4 min after 2% isoflurane exposure) to completion of carotid ligation (at which point isoflurane exposure was also terminated). In the first part of the study, the ITL of each group was designated to be 5, 13, and 21 min. In the second part of the study, the ITL is designated to 4 min; however, continued isoflurane was used to make 5, 13, and 21 min isoflurane exposure for each group. Percentages of brain infarction were assessed at 48 h following surgery. Motor deficits were accessed by Rotarod test. Marked brain infarction was observed in the 5-min ITL group and a decrease of brain infarction observed in the 13-and 21-min groups (P<0.05). In the second part of the study, marked brain infarction was observed in the 5-min isoflurane exposure group, and a decrease of brain infarction was observed in each of the 13- and 21-min isoflurane exposure groups (P<0.05). Similar tendencies were observed in Rotarod tests than 5-min ITL and 5-min isoflurane groups showed more marked deficits (P<0.05). This study demonstrated that brain infarction inconsistency of the neonatal hypoxia-ischemia rat pup model is related to the operation time. The observed time-dependent decrease of brain infarction is correlated to the isoflurane exposure time. Shorter operation and isoflurane exposure improves this model consistency of brain infarction and motor deficits.

PI3K/Akt signal pathway involved in the cognitive impairment caused by chronic cerebral hypoperfusion in rats

Chronic cerebral hypoperfusion (CCH) is a common pathophysiological state that usually occurs in conditions such as vascular dementia and Alzheimer's disease, both of which are characterized by cognitive impairment. In previous studies we found that learning capacity and memory were gradually impaired with CCH, which altered the expression of synaptophysin, microtubule associated protein-2, growth associated protein-43, brain-derived neurotrophic factor, nerve growth factor, N-methyl-D-aspartate receptor subunit 1, cAMP response element-binding protein and tau hyperphosphorylation in the hippocampus. However, the molecular basis of cognitive impairment in CCH remains obscure. Here we explore the hypothesis that the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signal pathway is involved in this type of cognitive impairment. In order to determine if the expression of PI3K, Akt and phosphorylated Akt (p-Akt) proteins are altered at different stages of CCH with differing levels of cognitive impairment. we performed permanent, bilateral occlusion of the common carotid arteries (2-VO) to induce CCH. Adult male SD rats were randomly divided into sham-operated group, 2-VO 1 week group, 2-VO 4 weeks group and 2-VO 8 weeks group. Behavior tests were utilized to assess cognitive abilities, while western blots were utilized to evaluate protein expression. Rats in the 2-VO groups spent less time exploring novel objects than those in the sham-operated group, and the discrimination ratio of the 2-VO 8 weeks group and the sham-operated group were higher than chance (0.50). Escape latencies in the Morris water maze task in the 2-VO 1 week group were longer than those in the sham-operated group on day 4 and day 5, while escape latencies in the 2-VO 4 weeks group were longer than those in the sham-operated group from day 3 to day 5. Escape latencies in 2-VO 8 weeks group were longer than those in the sham-operated group from day 2 to day 5. NE (northeast) square swimming times in the 2-VO 1 week group, 2-VO 4 weeks group and 2-VO 8 weeks group were shorter than that in the sham-operated group. Western blotting showed that the PI3K expression in the 2-VO 1 week group was lower than that in sham-operated group, while p-Akt expression in the 2-VO 8 weeks group was higher than that in the sham-operated group. There was a linear relationship between the PI3K expression and the discrimination ratio, as well as a linear relationship between the PI3K and NE square swimming time. Thus, we propose that the PI3K/Akt signal pathway is an important cell pathway that is associated with the cognitive impairment following CCH.

Dual effects of neuroprotection and neurotoxicity by general anesthetics: role of intracellular calcium homeostasis

Although general anesthetics have long been considered neuroprotective, there are growing concerns about neurotoxicity. Preclinical studies clearly demonstrated that commonly used general anesthetics are both neuroprotective and neurotoxic, with unclear mechanisms. Recent studies suggest that differential activation of inositol 1,4,5-trisphosphate receptors, a calcium release channel located on the membrane of endoplasmic reticulum (ER), play important role on determining the fate of neuroprotection or neurotoxicity by general anesthetics. General anesthetics at low concentrations for short duration are sublethal stress factors which induce endogenous neuroprotective mechanisms and provide neuroprotection via adequate activation of InsP3R and moderate calcium release from ER. On the other hand, general anesthetics at high concentrations for prolonged duration are lethal stress factors which induce neuronal damage by over activation of InsP3R and excessive and abnormal Ca(2+) release from ER. This review emphasizes the dual effects of both neuroprotection and neurotoxicity via differential regulation of intracellular Ca(2+) homeostasis by commonly used general anesthetics and recommends strategy to maximize neuroprotective but minimize neurotoxic effects of general anesthetics.

Isoflurane post-treatment ameliorates GMH-induced brain injury in neonatal rats

BACKGROUND AND PURPOSE

This study investigated whether isoflurane ameliorates neurological sequelae after germinal matrix hemorrhage (GMH) through activation of the cytoprotective sphingosine kinase/sphingosine-1-phosphate receptor/Akt pathway.

METHODS

GMH was induced in P7 rat pups by intraparenchymal infusion of bacterial collagenase (0.3 U) into the right hemispheric germinal matrix. GMH animals received 2% isoflurane either once 1 hour after surgery or every 12 hours for 3 days. Isoflurane treatment was then combined with sphingosine-1-phosphate receptor-1/2 antagonist VPC23019 or sphingosine kinase 1/2 antagonist N,N-dimethylsphingosine.

RESULTS

Brain protein expression of sphingosine kinase-1 and phosphorylated Akt were significantly increased after isoflurane post-treatment, and cleaved caspase-3 was decreased at 24 hours after surgery, which was reversed by the antagonists. Isoflurane significantly reduced posthemorrhagic ventricular dilation and improved motor, but not cognitive, functions in GMH animals 3 weeks after surgery; no improvements were observed after VPC23019 administration.

CONCLUSIONS

Isoflurane post-treatment improved the neurological sequelae after GMH possibly by activation of the sphingosine kinase/Akt pathway.

Isoflurane provides neuroprotection in neonatal hypoxic ischemic brain injury

Isoflurane is a volatile anesthetic that is widely used clinically as an inhalational anesthetic. In recent years, several studies have indicated that isoflurane has neuroprotective properties. This has led to the beneficial effects of isoflurane being analyzed in both cell culture and animal models, including various models of brain injury. Neonatal hypoxia ischemia may be characterized as injury that occurs in the immature brain, resulting in delayed cell death via excitotoxicity and oxidative stress. These adverse events in the developing brain often lead to detrimental neurological defects in the future. Currently, there are no well-established effective therapies for neonatal hypoxia ischemia. In line with this, isoflurane, which displays neuroprotective properties in several paradigms and has been shown to improve neurological deficits caused by brain injuries, has the capability to be an extremely relevant clinical therapy for the resolution of deficits concomitant with neonatal hypoxic ischemic brain injuries. This review therefore seeks to explore and analyze the current information on isoflurane, looking at general isoflurane anesthetic properties, and the protection it confers in different animal models, focusing particularly on neuroprotection as shown in studies with neonatal hypoxic ischemic brain injury.

Research of medical gases in Poland

Research of medical gases is well established in Poland and has been marked with the foundation of several professional societies. Numerous academic centers including those dealing with hyperbaric and diving medicine conduct studies of medical gases, in vast majority supported with intramural funds. In general, Polish research of medical gases is very much clinical in nature, covering new applications and safety of medical gases in medicine; on the other hand there are several academic centers pursuing preclinical studies, and elaborating basic theories of gas physiology and mathematical modeling of gas exchange. What dominates is research dealing with oxygen and ozone as well as studies of anesthetic gases and their applications. Finally, several research directions involving noble gas, hydrogen and hydrogen sulfide for cell protection, only begin to gain recognition of basic scientists and clinicians. However, further developments require more monetary spending on research and clinical testing as well as formation of new collective bodies for coordinating efforts in this matter.

Sphingolipids in cardiovascular and cerebrovascular systems: Pathological implications and potential therapeutic targets

The sphingolipid metabolites ceramide, sphingosine, and sphingosine-1-phosphate (S1P) and its enzyme sphingosine kinase (SphK) play an important role in the regulation of cell proliferation, survival, inflammation, and cell death. Ceramide and sphingosine usually inhibit proliferation and promote apoptosis, while its metabolite S1P phosphorylated by SphK stimulates growth and suppresses apoptosis. Because these metabolites are interconvertible, it has been proposed that it is not the absolute amounts of these metabolites but rather their relative levels that determine cell fate. The relevance of this “sphingolipid rheostat” and its role in regulating cell fate has been borne out by work in many labs using many different cell types and experimental manipulations. A central finding of these studies is that SphK is a critical regulator of the sphingolipid rheostat, as it not only produces the pro-growth, anti-apoptotic messenger S1P, but also decreases levels of pro-apoptotic ceramide and sphingosine. Activation of bioactive sphingolipid S1P signaling has emerged as a critical protective pathway in response to acute ischemic injury in both cardiac and cerebrovascular disease, and these observations have considerable relevance for future potential therapeutic targets.

Anesthetic isoflurane posttreatment attenuates experimental lung injury by inhibiting inflammation and apoptosis

We investigated the effect of 1.4% isoflurane (ISO) on the development of inflammation and apoptosis caused by zymosan (ZY) in mice. We found that ZY-challenged mice exhibited significant body weight loss, markedly high mortality, and significant lung injury characterized by the deterioration of histopathology, histologic scores, and wet-to-dry ratio after ISO treatment. ISO dramatically attenuated ZY-induced lung neutrophil recruitment and inflammation, as evidenced by the reduced levels of total cells, neutrophils, and proinflammatory cytokines (i.e., tumor necrosis factor- α , interleukin- (IL-) 1 β , IL-6, and macrophage inflammatory protein-2) in bronchoalveolar lavage fluid and of their mRNA expression in lung tissues. ISO also inhibited ZY-induced expression and activation of nuclear factor-kappaB p65 and inducible nitric oxide synthase in pulmonary tissue. ZY administration also resulted in the upregulation of heme oxygenase-1 expression and activity in the lung, which was further enhanced by ISO treatment. Moreover, ISO markedly prevented ZY-induced pulmonary cell apoptosis in mice, as reflected by the decrease in expression of procaspase-8, procaspase-3, cleaved caspase-8, and cleaved caspase-3, as well as in caspase-3 activity and Bcl-2-associated X/B-cell lymphoma 2 ratio. These results indicate that ISO is a potential therapeutic drug for treating ZY-induced lung injury, and further investigations are warranted.

Isoflurane postconditioning reduces ischemia-induced nuclear factor-κB activation and interleukin 1β production to provide neuroprotection in rats and mice

Application of isoflurane, a volatile anesthetic, after brain ischemia can reduce ischemic brain injury in rodents (isoflurane postconditioning). This study is designed to determine whether isoflurane postconditioning improves long-term neurological outcome after focal brain ischemia and whether this protection is mediated by attenuating neuroinflammation. Adult male Sprague-Dawley rats were subjected to a 90-min middle cerebral arterial occlusion (MCAO). Isoflurane postconditioning was performed by exposing rats to 2% isoflurane for 60min immediately after the MCAO. Isoflurane postconditioning reduced brain infarct volumes, apoptotic cells in the ischemic penumbral brain tissues and neurological deficits of rats at 4weeks after the MCAO. Isoflurane postconditioning reduced brain ischemia/reperfusion-induced nuclear transcription factor (NF)-κB (NF-κB) activation as well as interleukin 1β (IL-1β) and interleukin-6 production in the ischemic penumbral brain tissues at 24h after the MCAO. IL-1β deficient mice had smaller brain infarct volumes and better neurological functions than wild-type mice at 24h after a 90-min focal brain ischemia. Isoflurane posttreatment failed to induce neuroprotection in the IL-1β deficient mice. Our results suggest that isoflurane postconditioning improved long-term neurological outcome after transient focal brain ischemia. This protection may be mediated by inhibiting NF-κB activation and the production of the proinflammatory cytokine IL-1β.

Astrocyte activation and wound healing in intact-skull mouse after focal brain injury

Localised brain tissue damage activates surrounding astrocytes, which significantly influences subsequent long-term pathological processes. Most existing focal brain injury models in rodents employ craniotomy to localise mechanical insults. However, the craniotomy procedure itself induces gliosis. To investigate perilesional astrocyte activation under conditions in which the skull is intact, we created focal brain injuries using light exposure through a cranial window made by thinning the skull without inducing gliosis. The lesion size was maximal at ~ 12 h and showed substantial recovery over the subsequent 30 days. Two distinct types of perilesional reactive astrocyte, identified by GFAP upregulation and hypertrophy, were found. In proximal regions the reactive astrocytes proliferated and expressed nestin, whereas in regions distal to the injury core the astrocytes showed increased GFAP expression but did not proliferate, lacked nestin expression, and displayed different morphology. Simply making the window did not induce any of these changes. There were also significant numbers of neurons in the recovering cortical tissue. In the recovery region, reactive astrocytes radially extended processes which appeared to influence the shapes of neuronal nuclei. The proximal reactive astrocytes also formed a cell layer which appeared to serve as a protective barrier, blocking the spread of IgG deposition and migration of microglia from the lesion core to surrounding tissue. The recovery was preceded by perilesional accumulation of leukocytes expressing vascular endothelial growth factor. These results suggest that, under intact skull conditions, focal brain injury is followed by perilesional reactive astrocyte activities that foster cortical tissue protection and recovery.

Isoflurane delays the development of early brain injury after subarachnoid hemorrhage through sphingosine-related pathway activation in mice

OBJECTIVE

Isoflurane, a volatile anesthetic agent, has been recognized for its potential neuroprotective properties and has antiapoptotic effects. We examined whether isoflurane posttreatment is protective against early brain injury after subarachnoid hemorrhage and determined whether this effect needs sphingosine-related pathway activation.

DESIGN

Controlled in vivo laboratory study.

SETTING

Animal research laboratory.

SUBJECTS

One hundred seventy-nine 8-wk-old male CD-1 mice weighing 30-38 g.

INTERVENTIONS

Subarachnoid hemorrhage was induced in mice by endovascular perforation. Animals were randomly assigned to sham-operated, subarachnoid hemorrhage-vehicle, and subarachnoid hemorrhage+2% isoflurane. Neurobehavioral function and brain edema were evaluated at 24 and 72 hrs. The expression of sphingosine kinase, phosphorylated Akt, and cleaved caspase-3 was determined by Western blotting and immunofluorescence. Neuronal cell death was examined by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Effects of a sphingosine kinase inhibitor N, N-dimethylsphingosine or a sphingosine 1 phosphate receptor inhibitor VPC23019 on isoflurane's protective action against postsubarachnoid hemorrhage early brain injury were also examined.

MEASUREMENTS AND MAIN RESULTS

Isoflurane significantly improved neurobehavioral function and brain edema at 24 hrs but not 72 hrs after subarachnoid hemorrhage. At 24 hrs, isoflurane attenuated neuronal cell death in the cortex, associated with an increase in sphingosine kinase 1 and phosphorylated Akt, and a decrease in cleaved caspase-3. The beneficial effects of isoflurane were abolished by N, N-dimethylsphingosine and VPC23019.

CONCLUSIONS

Isoflurane posttreatment delays the development of postsubarachnoid hemorrhage early brain injury through antiapoptotic mechanisms including sphingosine-related pathway activation, implying its use for anesthesia during acute aneurysm surgery or intervention.

Isoflurane induces endothelial apoptosis of the post-hypoxic blood-brain barrier in a transdifferentiated human umbilical vein endothelial cell model

Isoflurane is a popular volatile anesthetic agent used in humans as well as in experimental animal research. In previous animal studies of the blood-brain barrier (BBB), observations towards an increased permeability after exposure to isoflurane are reported. In this study we investigated the effect of a 2-hour isoflurane exposure on apoptosis of the cerebral endothelium following 24 hours of hypoxia in an in vitro BBB model using astrocyte-conditioned human umbilical vein endothelial cells (AC-HUVECs). Apoptosis of AC-HUVECs was investigated using light microscopy of the native culture for morphological changes, Western blot (WB) analysis of Bax and Bcl-2, and a TUNEL assay. Treatment of AC-HUVECs with isoflurane resulted in severe cellular morphological changes and a significant dose-dependent increase in DNA fragmentation, which was observed during the TUNEL assay analysis. WB analysis confirmed increases in pro-apoptotic Bax levels at 4 hours and 24 hours and decreases in anti-apoptotic Bcl-2 in a dose-dependent manner compared with the control group. These negative effects of isoflurane on the BBB after a hypoxic challenge need to be taken into account not only in experimental stroke research, but possibly also in clinical practice.

Ultrasound-induced release of GDNF from lipid coated microbubbles injected into striatum reduces hypoxic-ischemic injury in neonatal rats

Previous studies showed that inflammation and apoptosis were involved in the pathogenesis of hypoxic-ischemic brain injury. The immature brain is particularly vulnerable to damage. Intracerebral injection of glial cell line-derived neurotrophic factor (GDNF) has been shown to reduce the injury induced by hypoxia-ischemia (HI). In this study, the neuroprotective effect of intracerebral ultrasound-induced dissolution of lipid-coated GDNF microbubbles was investigated in a neonatal rat model of hypoxic-ischemic brain injury. Hypoxic-ischemic injury was induced in 7-day-old rats in the present study. The rats with hypoxia-ischemia received intracerebral injections of GDNF-containing microbubbles (0.5 mg/kg). They then received low frequency ultrasound stimulation (20 kHz, 2 h intervals for a total of 24 h and each time lasted for 1 min) to induce release of GDNF into the right striatum. We found that low frequency ultrasound stimulation can induce lipid-coated GDNF microbubbles to release GDNF. Ultrasound-induced dissolution of lipid-coated GDNF microbubbles treatment reduced infarction volume and improved neurological outcomes in neonatal rats. In the meanwhile, the microbubbles attenuated the production of inducible nitric oxide synthase, nitric oxide and tumor necrosis factor-alpha, as well as the activation of caspase-3 in insulted side of brain in neonatal rats. These data demonstrated that ultrasound-induced dissolution of lipid-coated GDNF microbubbles treatment can provide a neuroprotective effect against hypoxia-ischemia in neonatal rats.

Are volatile anesthetics neuroprotective or neurotoxic?

Volatile anesthetics are one class of the most commonly used drugs. However, the mechanisms for these drugs to induce anesthesia are not fully understood and have been under intensive investigation. Two other effects of these anesthetics on the central nervous system, volatile anesthetics-induced neuroprotection and neurotoxicity, currently are hot research fields. Although data from animal studies for these two effects are extensive and convincing, clinical data for volatile anesthetics-induced neuroprotection are relatively weak. There is essentially lack of evidence to suggest volatile anesthetics-induced neurotoxicity in humans. In this regard, the contribution of general anesthesia/anesthetics to postoperative cognitive decline, a clinical entity whose existence has been supported by substantial evidence, also has not been established. This paper will be focused on reviewing the evidence, especially the clinical evidence, for volatile anesthetics-induced neuroprotection and neurotoxicity. Efforts will be devoted to facilitating the understanding of the two seemingly contradictory effects of these important drugs on the brain.

Ras family small GTPase-mediated neuroprotective signaling in stroke

Selective neuronal cell death is one of the major causes of neuronal damage following stroke, and cerebral cells naturally mobilize diverse survival signaling pathways to protect against ischemia. Importantly, therapeutic strategies designed to improve endogenous anti-apoptotic signaling appear to hold great promise in stroke treatment. While a variety of complex mechanisms have been implicated in the pathogenesis of stroke, the overall mechanisms governing the balance between cell survival and death are not well-defined. Ras family small GTPases are activated following ischemic insults, and in turn, serve as intrinsic switches to regulate neuronal survival and regeneration. Their ability to integrate diverse intracellular signal transduction pathways makes them critical regulators and potential therapeutic targets for neuronal recovery after stroke. This article highlights the contribution of Ras family GTPases to neuroprotective signaling cascades, including mitogen-activated protein kinase (MAPK) family protein kinase- and AKT/PKB-dependent signaling pathways as well as the regulation of cAMP response element binding (CREB), Forkhead box O (FoxO) and hypoxiainducible factor 1(HIF1) transcription factors, in stroke.

Induction of inducible nitric oxide synthase by isoflurane post-conditioning via hypoxia inducible factor-1α during tolerance against ischemic neuronal injury

Recent studies have shown that isoflurane protects against ischemic injury via inducible nitric oxide synthase (iNOS). Hypoxia inducible factor (HIF)-1α is a transcriptional factor that activates after cerebral ischemia. However, whether iNOS gene containing the sequence of the hypoxia response element (HRE) is a HIF-1α target during tolerance against ischemic neuronal injury induced by isoflurane post-conditioning remains unknown. In this study, we report that HIF-1α and iNOS gene expression were augmented after cerebral ischemia in rats. Furthermore, isoflurane post-conditioning resulted in greater accumulation of HIF-1α and iNOS gene expression, following by HIF-1α transcriptional activity enhancement and co-localization of HIF-1α and iNOS. Accordingly, in the primary cortical neuron cultures, silencing of HIF-1α attenuated the accumulation of iNOS and the protective effects of isoflurane post-conditioning. Our results suggest the involvement of HIF-1α in the regulation of iNOS during tolerance against cerebral ischemia induced by isoflurane post-conditioning, which provide a mechanistic basis of novel therapeutic strategies for ischemic stroke.

Isoflurane protects against human endothelial cell apoptosis by inducing sphingosine kinase-1 via ERK MAPK

Endothelial dysfunction is a major clinical problem affecting virtually every patient requiring critical care. Volatile anesthetics are frequently used during the perioperative period and protect the heart and kidney against ischemia and reperfusion injury. We aimed to determine whether isoflurane, the most commonly used volatile anesthetic in the USA, protects against endothelial apoptosis and necrosis and the mechanisms involved in this protection. Human endothelial EA.hy926 cells were pretreated with isoflurane or carrier gas (95% room air + 5% CO₂) then subjected to apoptosis with tumor necrosis factor-α or to necrosis with hydrogen peroxide. DNA laddering and in situ Terminal Deoxynucleotidyl Transferase Biotin-dUTP Nick-End Labeling (TUNEL) staining determined EA.hy926 cell apoptosis and percent LDH released determined necrosis. We also determined whether isoflurane modulates the expression and activity of sphingosine kinase-1 (SK1) and induces the phosphorylation of extracellular signal regulated kinase (ERK MAPK) as both enzymes are known to protect against cell death. Isoflurane pretreatment significantly decreased apoptosis in EA.hy926 cells as evidenced by reduced TUNEL staining and DNA laddering without affecting necrosis. Mechanistically, isoflurane induces the phosphorylation of ERK MAPK and increased SK1 expression and activity in EA.hy926 cells. Finally, selective blockade of SK1 (with SKI-II) or S1P₁ receptor (with W146) abolished the anti-apoptotic effects of isoflurane. Taken together, we demonstrate that isoflurane, in addition to its potent analgesic and anesthetic properties, protects against endothelial apoptosis most likely via SK1 and ERK MAPK activation. Our findings have significant clinical implication for protection of endothelial cells during the perioperative period and patients requiring critical care.

Isoflurane postconditioning induces neuroprotection via Akt activation and attenuation of increased mitochondrial membrane permeability

We have shown that isoflurane application at the onset of reperfusion (postconditioning) reduces brain ischemic injury in rats. This study was designed to determine whether this protection involved activation of prosurvival protein kinases and maintenance of normal mitochondrial membrane permeability. Two-month-old male rats were subjected to a 90-min middle cerebral arterial occlusion. They then were exposed or were not exposed to 2% isoflurane for 1 h. Ischemic penumbral cerebral cortex was harvested immediately and separated into the mitochondrial and cytosolic fractions. We showed that the mitochondrial nicotinamide adenine dinucleotide content in the ischemic penumbral cortex was significantly reduced, suggesting an increased mitochondrial membrane permeability. This increase was partly attenuated by isoflurane postconditioning. The mitochondrial adenosine diphosphate content in the penumbral cortex was reduced no matter whether the animals were postconditioned with isoflurane. The mitochondrial adenosine triphosphate concentration was not different among various experimental conditions. The phospho-Akt in the cytosolic and mitochondrial fractions of the ischemic penumbral cortex was higher than that in the control cortex. This increase trended to be higher in animals with isoflurane postconditioning. A similar change pattern was observed in the mitochondrial phospho-glycogen synthase kinase 3β, an Akt substrate that can regulate the mitochondrial membrane permeability. Isoflurane postconditioning reduced oxygen-glucose deprivation-induced injury of rat cortical neuronal cultures and increased phospho-Akt in these cells. The isoflurane postconditioning-induced protection in the neuronal cultures was decreased by the Akt inhibitor LY294002. These results suggest that isoflurane postconditioning effects may be mediated by Akt and involve reduced mitochondrial membrane permeability.

Minocycline improves functional outcomes, memory deficits, and histopathology after endovascular perforation-induced subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) results in significant long-lasting cognitive dysfunction. Therefore, evaluating acute and long-term outcomes after therapeutic intervention is important for clinical translation. The aim of this study was to use minocycline, a known neuroprotectant agent, to evaluate the long-term benefits in terms of neurobehavior and neuropathology after experimental SAH in rats, and to determine which neurobehavioral test would be effective for long-term evaluation. SAH was induced by endovascular perforation in adult male Sprague-Dawley rats (n=118). The animals were treated with intraperitoneal injection of minocycline (45 mg/kg or 135 mg/kg) or vehicle 1 h after SAH induction. In the short-term, animals were euthanized at 24 and 72 h for evaluation of neurobehavior, brain water content, and matrix metalloproteinase (MMP) activity. In the long-term, neurobehavior was evaluated at days 21-28 post-SAH, and histopathological analysis was done at day 28. High-dose but not low-dose minocycline reduced brain water content at 24 h, and therefore only the high-dose regimen was used for further evaluation, which reduced MMP-9 activity at 24 h. Further, high-dose minocycline improved spatial memory and attenuated neuronal loss in the hippocampus and cortex. The rotarod, T-maze, and water maze tests, but not the inclined plane test, detected neurobehavioral deficits in SAH rats at days 21-28. This study demonstrates that minocycline attenuates long-term functional and morphological outcomes after endovascular perforation-induced SAH. Long-term neurobehavioral assessments using the rotarod, T-maze, and water maze tests could be useful to evaluate the efficacy of therapeutic intervention after experimental SAH.

Baby STEPS: a giant leap for cell therapy in neonatal brain injury

We advance Baby STEPS or Stem cell Therapeutics as an Emerging Paradigm in Stroke as a guide in facilitating the critical evaluation in the laboratory of the safety and efficacy of cell therapy for neonatal encephalopathy. The need to carefully consider the clinical relevance of the animal models in mimicking human neonatal brain injury, selection of the optimal stem cell donor, and the application of functional outcome assays in small and large animal models serve as the foundation for preclinical work and beginning to understand the mechanism of this cellular therapy. The preclinical studies will aid our formulation of a rigorous human clinical trial that encompasses not only efficacy testing but also monitoring of safety indices and demonstration of mechanisms of action. This schema forms the basis of Baby STEPS. Our goal is to resonate the urgent call to enhance the successful translation of cell therapy from the laboratory to the clinic.

Translational aspects of sphingosine 1-phosphate biology

Sphingosine 1-phosphate (S1P) is a bioactive lipid that has both physiological and pathophysiological roles. It regulates cellular processes such as proliferation, migration, survival and differentiation and affects all organ systems. S1P not only activates S1P-specific receptors to initiate cellular signalling pathways but also directly regulates specific intracellular target proteins. The therapeutic opportunities surrounding S1P signalling are numerous and exemplified by the recent approval of FTY720 (a sphingosine analogue, Gilenya™) for the treatment of relapsing multiple sclerosis. A major focus of research is to develop small-molecule antagonists/agonists/inhibitors that are specific to the different S1P receptor subtypes and the enzymes that regulate S1P levels. This review describes fundamental aspects of S1P biology with an emphasis on the translational potential of intervention therapeutics.