Sevoflurane Postconditioning Attenuates Spinal Cord Reperfusion Injury Through Free Radicals-Mediated Up-Regulation of Antioxidant Enzymes in Rabbits

Comparison of serum dynamic thiol/disulphide homeostasis and nitric oxide levels of total intravenous vs inhaled anaesthesia in endoscopic transsphenoidal pituitary surgery

BACKGROUND

Transsphenoidal pituitary surgery (TPS) is traditionally performed under general anaesthesia. This study aimed to compare the effects of total intravenous anaesthesia (TIVA) or sevoflurane, an inhalation anaesthetic, on thiol-disulphide homeostasis in patients undergoing endoscopic endonasal TPS.

METHODS

In this study, 84 patients scheduled for TPS were randomly categorised into two groups: propofol (n = 42, the TIVA group) or sevoflurane (n = 42, the SEVO group). Blood samples were taken before induction of general anaesthesia and at the 30 minutes of postoperation. Serum native thiol and total thiol levels were detected, and the number of dynamic disulphide bonds and related ratios were calculated from these values. Serum nitric oxide (NO) levels were measured using a chemiluminescence method.

RESULTS

Although native thiol levels in TIVA postoperation group were markedly increased (P < .05), total thiol levels in SEVO postoperation group were significantly decreased (P < .01). Disulphide levels were declined in both groups (P < .05 for TIVA and P = .001 for SEVO groups). Disulphide/native thiol (P < .05 for both groups) and disulphide/total thiol ratios (P < .05 for TIVA and P < .01 for SEVO groups) were depressed in postoperation groups. We found a marked elevation in native thiol/total thiol ratio in both groups (P < .05 for TIVA and P < .01 for SEVO groups). There was significant augmentation in serum NO levels in the SEVO postoperation group (P < .05).

CONCLUSION

These results are the first to show that both TIVA and sevoflurane showed similar antioxidant effect with reduced disulphide levels, but sevoflurane may offer more robust oxidative stress protection and augmented NO production than TIVA during TPS. However, the clinical effect is needed to further investigate.

Induction of ischemic tolerance by remote perconditioning or postconditioning as neuroprotective strategy for spinal cord motor neurons

AIMS

The study is focused on the investigation of the mechanisms leading to ischemic tolerance acquisition in the spinal cord neurons via application of non-invasive method of remote conditioning.

MATERIAL AND METHODS

We have verified the possibility of neuroprotection of spinal cord in rabbit by using remote perconditioning (PerC) applied during last 12 min of spinal cord ischemia (SC-ischemia) or postconditioning (PostC) applied after 1st (early) or 3rd (late) h of reperfusion. Spinal cord ischemia was induced by occlusion of the aorta below the left renal artery for 20 min. Reperfusion period was 24 or 72 h. Remote conditioning was induced by compression of left forelimb with a tourniquet in 3 cycles of 2 min of ischemia, each followed by 2 min of reperfusion. Damaged neurons were detected by Fluoro Jade B method and the modified Tarlov score was used for functional assessment.

KEY FINDINGS

The remote conditioning significantly attenuated degeneration of motor neurons in all remote conditioned groups versus both SC-ischemia groups. We detected significant changes in number of Hsp70 positive motor neurons. At 72time point, in the group with remote late PostC we observed significant increase (p < 0.001) of Hsp70 positive motor neurons versus SC- ischemia group and sham control. There was a trend towards improvement of hindlimbs movement.

SIGNIFICANCE

This study showed the effectiveness of remote conditioning as a neuroprotective strategy, evidenced by induction of ischemic tolerance leading to decrease of motor neuron degeneration.

Sevoflurane pretreatment regulates abnormal expression of MicroRNAs associated with spinal cord ischemia/reperfusion injury in rats

Background

Spinal cord ischemia/reperfusion injury (SCII) is one of the most serious spinal cord complications that stem from varied spine injuries or thoracoabdominal aortic surgery. Nevertheless, the molecular mechanisms underlying the SCII remain unclear.

Methods

Male Sprague-Dawley (SD) rats were randomly divided into 5 groups of sham, SCII 24 h, SCII 72 h, sevoflurane preconditioning SCII 24 h (SCII 24 h+sevo), and sevoflurane preconditioning SCII 72 h (SCII 72 h+sevo) group. We then analyzed the expression of differentially expressed micro RNAs (DEmiRNAs) in these groups and their target genes. Functional enrichment analysis of their target genes was further performed using Metascape software. The microRNA-messenger RNA-pathway (miRNA-mRNA-pathway) network and the sevoflurane-miRNA-mRNA-pathway integrative network were further constructed to explore the molecular mechanisms underlying SCII and neuroprotective effects of sevoflurane against SCII. Molecular docking was also performed to evaluate the interactions between hub targets and sevoflurane. Finally, the expression levels of miR-21-5p and its target genes [mitogen-activated protein kinase kinase 3 and protein phosphatase 1 regulatory subunit 3B (MAP2K3 and PPP1R3B)] were measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot analyses.

Results

We found that sevoflurane alters several miRNA expression following SCII at 24 and 72 h after reperfusion. It was shown that miR-221-3p, miR-181a-1-3p, and miR-21-5p were upregulated both at 24 and 72 h in the sevoflurane pre-treatment reperfusion groups. Functional enrichment analysis revealed that target genes for the above co-DEmiRNAs at 24 and 72 h in the SCII group with sevoflurane pretreatment participated in the mitogen-activated protein kinase (MAPK), ErbB, apoptosis, and transforming growth factor-beta (TGF-beta) signaling pathways. Both MAP2K3 and PPP1R3B were found to be common targets for sevoflurane and miRNA-mRNA-pathway (rno-miR-21-5p). It was shown that MAP2K3 regulates the MAPK signaling and the T cell receptor signaling pathways, whereas PPP1R3B regulates the ErbB signaling pathway. Molecular docking further revealed that sevoflurane strongly binds the MAP2K3 and PPP1R3B proteins. Compared to the sham group, SCII induced significant under-expression of miR-21-5p but upregulated PPP1R3B and MAP2K3 proteins; sevoflurane pretreatment increased the expression of miR-21-5p but decreased those of PPP1R3B and MAP2K3 proteins.

Conclusions

In general, sevoflurane regulates the expression of several miRNAs following SCII. In particular, sevoflurane might protect against SCII via regulating the expression of miR-21-5p, its target genes (MAP2K3 and PPP1R3B), and related signaling pathways.

Ubiquitin and endogenous antioxidant enzymes participate in neuroprotection of the rabbit spinal cord after ischemia and bradykinin postconditioning

The aim of this study was to investigate neuroprotective effect of bradykinin postconditioning on the rabbit spinal cord after 20 min of ischemia and 3 days of reperfusion. Bradykinin was administered by single i.p. application at 1, 6, 12 or 24 h after ischemia. Assessment of neurological function of hind limbs (Tarlov score) was estimated. Quantitative analysis was evaluated by Fluoro Jade B method, NeuN and ubiquitin immunohistochemistry in anterior horn neurons of the spinal cord. Histomorphologically distribution of ubiquitin and endogenous antioxidant enzymes (SOD1, SOD2, catalase) immunoreaction was described. Bradykinin postconditioning showed decreased number of degenerated neurons, increased number of surviving neurons and increase in number of ubiquitin positive neurons in all bradykinin postconditioned groups versus ischemia/reperfusion group. According to our results bradykinin postconditioning applied 24 h after ischemia significantly decreased (p < 0.001) number of degenerated neurons versus ischemia/reperfusion group. The least effective time window for bradykinin postconditioning was at 12 h after ischemia. Tarlov score was significantly improved (p < 0.05) in groups with bradykinin postconditioning applied 1, 6 or 24 h after ischemia versus ischemia/reperfusion group. Tarlov score in group with bradykinin application 12 h after ischemia was significantly decreased (p < 0.05) versus sham control group. Neuronal immunoreaction of ubiquitin, SOD1, SOD2 and catalase influenced by bradykinin postconditioning was dependent on neuronal survival or degeneration. In conclusion, bradykinin postconditioning showed protective effect on neurons in anterior horns of the rabbit spinal cord and improved motor function of hind limbs.

Low‑frequency pulsed electromagnetic field promotes functional recovery, reduces inflammation and oxidative stress, and enhances HSP70 expression following spinal cord injury

Low-frequency pulsed electromagnetic fields (LPEMFs) have been reported to be protective for multiple diseases. However, whether the administration of LPEMFs inhibits inflammation and oxidative stress following spinal cord injury requires further investigation. In the current study, a contusion spinal cord injury model was used and LPEMFs administration was applied to investigate the molecular changes, including inflammation, oxidative stress and heat shock protein 70 (HSP70) levels. The results revealed that LPEMFs significantly promoted functional recovery following spinal cord injury, as demonstrated by an increased Basso, Beattie and Bresnahan score. The results demonstrated that LPEMFs decreased the expression of inflammatory factors, including tumor necrosis factor-α, interleukin-1β and nuclear factor-κB. Additionally, LPEMFs exposure reduced the levels of inducible nitric oxide synthase and reactive oxygen species, and upregulated the expression of catalase and superoxide dismutase. Furthermore, treatment with LPEMFs significantly enhanced the expression of HSP70 in spinal cord-injured rats. Overall, the present study revealed that LPEMFs promote functional recovery following spinal cord injury, potentially by modulating inflammation, oxidative stress and HSP70.

The effect of pre- and after-treatment of sevoflurane on central ischemia tolerance and the underlying mechanisms

In recent years, with continuous research efforts targeted at studying the effects of pre- and after-treatment of inhaled anesthetics, significant progress has been made regarding the common clinical use of low concentrations of inhaled sevoflurane and its effect on induced central ischemia tolerance by pre- and post-treatment. In this study, we collected, analyzed, classified, and summarized recent literature regarding the effect of sevoflurane on central ischemia tolerance and its related mechanisms. In addition, we provide a theoretical basis for the clinical application of sevoflurane to protect the central nervous system and other important organs against ischemic injury.

Ischemic Tolerance of the Brain and Spinal Cord: A Review

Ischemic tolerance is an endogenous neuroprotective phenomenon induced by sublethal ischemia. Ischemic preconditioning (IPC), the first discovered form of ischemic tolerance, is widely seen in many species and in various organs including the brain and the spinal cord. Ischemic tolerance of the spinal cord is less familiar among neurosurgeons, although it has been reported from the viewpoint of preventing ischemic spinal cord injury during aortic surgery. It is important for neurosurgeons to have opportunities to see patients with spinal cord ischemia, and to understand ischemic tolerance of the spinal cord as well as the brain. IPC has a strong neuroprotective effect in animal models of ischemia; however, clinical application of IPC for ischemic brain and spinal diseases is difficult because they cannot be predicted. In addition, one drawback of preconditioning stimuli is that they are also capable of producing injury with only minor changes to their intensity or duration. Numerous methods to induce ischemic tolerance have been discovered that vary in their timing and the site at which short-term ischemia occurs. These methods include ischemic postconditioning (IPoC), remote ischemic preconditioning (RIPC), remote ischemic perconditioning (RIPerC) and remote ischemic postconditioning (RIPoC), which has had a great impact on clinical approaches to treatment of ischemic brain and spinal cord injury. Especially RIPerC and RIPoC to induce spinal cord tolerance are considered clinically useful, however the evidence supporting these methods is currently insufficient; further experimental or clinical research in this area is thus necessary.

Biological networks in ischemic tolerance - rethinking the approach to clinical conditioning

The adaptive response (conditioning) to environmental stressors evokes evolutionarily conserved programs in uni- and multicellular organisms that result in increased fitness and resistance to stressor induced injury. Although the concept of conditioning has been around for a while, its translation into clinical therapies targeting neurovascular diseases has only recently begun. The slow pace of clinical adoption might be partially explained by our poor understanding of underpinning mechanisms and of the complex responses of the organism to the stressor. At the 2(nd) Translational Preconditioning Meeting participants engaged in an intense discussion addressing whether the time has come to more aggressively implement clinical conditioning protocols in the treatment of cerebrovascular diseases or whether it would be better to wait until preclinical data would help to minimize clinical empiricism. This review addresses the complex involvement of biological networks in establishing ischemic tolerance at the organism level using two clinically promising conditioning modalities, namely remote ischemic preconditioning, and per- or post-conditioning, as examples.

Neuroprotective effects of sevoflurane against electromagnetic pulse-induced brain injury through inhibition of neuronal oxidative stress and apoptosis

Electromagnetic pulse (EMP) causes central nervous system damage and neurobehavioral disorders, and sevoflurane protects the brain from ischemic injury. We investigated the effects of sevoflurane on EMP-induced brain injury. Rats were exposed to EMP and immediately treated with sevoflurane. The protective effects of sevoflurane were assessed by Nissl staining, Fluoro-Jade C staining and electron microscopy. The neurobehavioral effects were assessed using the open-field test and the Morris water maze. Finally, primary cerebral cortical neurons were exposed to EMP and incubated with different concentration of sevoflurane. The cellular viability, lactate dehydrogenase (LDH) release, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level were assayed. TUNEL staining was performed, and the expression of apoptotic markers was determined. The cerebral cortexes of EMP-exposed rats presented neuronal abnormalities. Sevoflurane alleviated these effects, as well as the learning and memory deficits caused by EMP exposure. In vitro, cell viability was reduced and LDH release was increased after EMP exposure; treatment with sevoflurane ameliorated these effects. Additionally, sevoflurane increased SOD activity, decreased MDA levels and alleviated neuronal apoptosis by regulating the expression of cleaved caspase-3, Bax and Bcl-2. These findings demonstrate that Sevoflurane conferred neuroprotective effects against EMP radiation-induced brain damage by inhibiting neuronal oxidative stress and apoptosis.

Timing of xenon-induced delayed postconditioning to protect against spinal cord ischaemia-reperfusion injury in rats

BACKGROUND

This study was designed to assess the neuroprotective effect of xenon-induced delayed postconditioning on spinal cord ischaemia-reperfusion injury (IRI) and to determine the time of administration for best neuroprotection in a rat model of spinal cord IRI.

METHODS

Fifty male rats were randomly divided equally into a sham group, control group, and three xenon postconditioning groups (n=10 per group). The control group underwent spinal cord IRI and immediately inhaled 50% nitrogen/50% oxygen for 3 h at the initiation of reperfusion. The three xenon postconditioning groups underwent the same surgical procedure and immediately inhaled 50% xenon/50% oxygen for 3 h at the initiation of reperfusion or 1 and 2 h after reperfusion. The sham operation group underwent the same surgical procedure without aortic occlusion, and inhaled 50% nitrogen/50% oxygen. Neurological function was assessed using the Basso, Beattie, and Bresnahan score at 4, 24, and 48 h of reperfusion. Histological examination was performed using Nissl staining and immunohistochemistry, and apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling staining.

RESULTS

Compared with the control group, the three xenon postconditioning groups showed improvements in neurological outcomes, and had more morphologically normal neurones at 48 h of reperfusion. Apoptotic cell death was reduced and the ratio of Bcl-2/Bax immunoreactivity increased in xenon-treated rats compared with controls.

CONCLUSIONS

Xenon postconditioning up to 2 h after reperfusion provided protection against spinal cord IRI in rats, but the greatest neuroprotection occurred with administration of xenon for 1 h at reperfusion.

Limb remote postconditioning alleviates cerebral reperfusion injury through reactive oxygen species-mediated inhibition of delta protein kinase C in rats

BACKGROUND

Remote ischemic postconditioning (RPostC) is an emerging concept for cerebral infarction protection, and its potential protective mechanisms have not been well established. We attempted to investigate the implications of reactive oxygen species (ROS) and δ protein kinase C (δPKC) in neuroprotection induced by RPostC in a rat model of focal cerebral ischemia, and also to explore a possible relationship between ROS and εPKC.

METHODS

Focal cerebral ischemia was induced by middle cerebral artery occlusion using the intraluminal filament technique in male rats. RPostC was generated by 3 10-minute cycles of femoral artery occlusion/reperfusion on the right limb at the onset of middle cerebral artery reperfusion. RPostC was performed alone or with pretreatment of N-acetylcysteine, a ROS scavenger. In separate group, TAT-δV1-1, a δPKC-selective peptide inhibitor, was administered at the onset of reperfusion. Brain ischemic injury was evaluated by neurologic scores, infarction volumes, and TUNEL staining. Moreover, the activation of δPKC in the ischemic penumbra was investigated by Western blot after reperfusion.

RESULTS

RPostC improved neurologic outcome, reduced infarct size, and inhibited neuronal apoptosis as well as suppressed the activation of δPKC after reperfusion. Moreover, systemic delivery of TAT-δV1-1 conferred neuroprotection against cerebral reperfusion injury at the onset of reperfusion. Pretreatment with N-acetylcysteine not only completely prevented all aspects of RPostC-induced neuroprotection, but also reversed RPostC-induced inhibition of δPKC activation after reperfusion.

CONCLUSION

These findings suggested that RPostC performed in one limb alleviated reperfusion injury after focal cerebral ischemia through ROS-mediated inhibition of endogenous δPKC activation signaling cascade in an in vivo rat model of focal cerebral ischemia.

Volatile anesthetic post-treatment induces protection via inhibition of glycogen synthase kinase 3β in human neuron-like cells

Application of the volatile anesthetic isoflurane during the early phase of reperfusion reduces ischemic heart and brain injury (anesthetic post-conditioning). We hypothesize that inhibition of glycogen synthase kinase 3β (GSK3β), a protein whose activation can lead to cell death, participates in anesthetic post-conditioning-induced neuroprotection. SH-SY5Y cells, a human neuroblastoma cell line, were induced by retinoic acid to differentiate into terminal neuron-like cells. The cells were then subjected to a 1-h oxygen-glucose deprivation (OGD), a condition to simulate ischemia in vitro, and a 20-h simulated reperfusion. Isoflurane, sevoflurane or desflurane, three commonly used volatile anesthetics, were applied for 1 h during the early phase of simulated reperfusion. Cell injury was quantified by lactate dehydrogenase (LDH) release. Phospho-GSK3β at Ser9 and total GSK3β were quantified at 1 or 3 h after the OGD. OGD increased LDH release, suggesting that OGD induced cell injury. Post-treatment with isoflurane, sevoflurane or desflurane reduced this cell injury. This protection was apparent when 2% isoflurane was applied within 1 h after the onset of reperfusion. Isoflurane post-treatment also significantly increased the phosphorylation of GSK3β at Ser9 at 1 h after the OGD. GSK3β inhibitors reduced OGD and simulated reperfusion-induced LDH release. The combination of GSK3β inhibitors and isoflurane post-conditioning did not cause a greater protection than isoflurane post-conditioning alone. These results suggest that volatile anesthetic post-conditioning reduces OGD and simulated reperfusion-induced cell injury. Since phospho-GSK3β at Ser9 decreases GSK3β activity, our results suggest that volatile anesthetic post-conditioning in human neuron-like cells may be mediated by GSK3β inhibition.