Anti-oxidative aspect of inhaled anesthetic gases against acute brain injury

Sevoflurane: an opportunity for stroke treatment

In developed countries, stroke is the leading cause of death and disability that affects long-term quality of life and its incidence is increasing. The incidence of ischemic stroke is much higher than that of hemorrhagic stroke. Ischemic stroke often leads to very serious neurological sequelae, which severely reduces the patients' quality of life and becomes a social burden. Therefore, ischemic stroke has received increasing attention. As a new type of anesthetic, sevoflurane has a lower solubility, works faster in the human body, and has less impact on the cardiovascular system than isoflurane. At the same time, studies have shown that preconditioning and postconditioning with sevoflurane have a beneficial effect on stroke. We believe that the role of sevoflurane in stroke may be a key area for future research. Therefore, this review mainly summarizes the relevant mechanisms of sevoflurane preconditioning and postconditioning in stroke in the past 20 years, revealing the bright prospects of sevoflurane in stroke treatment.

Xenon inhalation attenuates neuronal injury and prevents epilepsy in febrile seizure Sprague-Dawley pups

Background

Febrile seizures (FS) usually occur in childhood and may cause irreversible neuronal damage, cognitive functional defects, and an increase in the risk of epilepsy later in life. Anti-epileptic drugs (AEDs), currently used to treat FS in children, can relieve seizures. However, their effects in preventing the risk of developing epilepsy in later life are unsatisfactory. Moreover, AEDs may damage child brain development. Here, we evaluated the efficiency of xenon in treating prolonged FS (PFS) and preventing epilepsy in Sprague-Dawley pups.

Methods

Prolonged FS was induced by hyperthermic treatment. After 90 min of PFS, the pups in the xenon treatment group were immediately treated with 70% xenon/21% oxygen/9% nitrogen for 60 min. The levels of glutamate, mitochondrial oxidative stress, mitophagy, and neuronal injury, seizures, learning, and memory functions were measured at specific time points.

Results

Neonatal period PFS led to spontaneous seizure, learning and memory dysfunction, accompanied by increased levels of glutamate, mitochondrial oxidative stress, mitophagy, and neuronal injury. Xenon treatment alleviated the changes caused by PFS and reduced the risk of PFS developing into epilepsy later.

Conclusion

Our results suggest that xenon inhalation could be a potential therapeutic strategy to attenuate neuronal injury and prevent epilepsy in patients with FS.

Pharmacological properties and mechanisms of Notoginsenoside R1 in ischemia-reperfusion injury

Panax notoginseng is an ancient Chinese medicinal plant that has great clinical value in regulating cardiovascular disease in China. As a single component of panax notoginosides, notoginsenoside R1 (NGR1) belongs to the panaxatriol group. Many reports have demonstrated that NGR1 exerts multiple pharmacological effects in ischemic stroke, myocardial infarction, acute renal injury, and intestinal injury. Here, we outline the available reports on the pharmacological effects of NGR1 in ischemia-reperfusion (I/R) injury. We also discuss the chemistry, composition and molecular mechanism underlying the anti-I/R injury effects of NGR1. NGR1 had significant effects on reducing cerebral infarct size and neurological deficits in cerebral I/R injury, ameliorating the impaired mitochondrial morphology in myocardial I/R injury, decreasing kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin in renal I/R injury and attenuating jejunal mucosal epithelium injury in intestinal I/R injury. The various organ anti-I/R injury effects of NGR1 are mainly through the suppression of oxidative stress, apoptosis, inflammation, endoplasmic reticulum stress and promotion of angiogenesis and neurogenesis. These findings provide a reference basis for future research of NGR1 on I/R injury.

Attenuated iron stress and oxidative stress may participate in anti-seizure and neuroprotective roles of xenon in pentylenetetrazole-induced epileptogenesis

The previous studies have demonstrated the excellent neuroprotective effects of xenon. In this study, we verified the anti-seizure and neuroprotective roles of xenon in epileptogenesis and evaluated the involvement of oxidative stress and iron accumulation in the protective roles of xenon. Epileptogenesis was induced by pentylenetetrazole (PTZ) treatment in Sprague-Dawley rats. During epileptogenesis, we found increased levels of iron and oxidative stress accompanied by elevated levels of divalent metal transporter protein 1 and iron regulatory protein 1, which are closely associated with iron accumulation. Meanwhile, the levels of autophagy and mitophagy increased, alongside significant neuronal damage and cognitive deficits. Xenon treatment reversed these effects: oxidative stress and iron stress were reduced, neuronal injury and seizure severity were attenuated, and learning and memory deficits were improved. Thus, our results confirmed the neuroprotective and anti-seizure effects of xenon treatment in PTZ-induced epileptogenesis. The reduction in oxidative and iron stress may be the main mechanisms underlying xenon treatment. Thus, this study provides a potential intervention strategy for epileptogenesis.

Isoflurane reduces septic neuron injury by HO‑1‑mediated abatement of inflammation and apoptosis

Sepsis-associated encephalopathy (SAE) frequently occurs in critically ill patients with severe systemic infections. Subanesthetic isoflurane (0.7% ISO) possesses anti-inflammatory, antioxidant and anti-apoptotic properties against a number of human diseases, including brain injury. The activation of heme oxygenase-1 (HO-1) impedes inflammation, oxidation and apoptosis, thus alleviating sepsis-induced brain damage. However, whether 0.7% ISO affords protection against septic neuronal injury involving HO-1 activation is unclear. The present study aimed to investigate the neuroprotective effects of 0.7% ISO and its potential underlying mechanisms in SAE using a mouse model established by cecal ligation and puncture (CLP). The results indicated that the expression and activity of HO-1 in the mouse hippocampus were increased by CLP, and further enhanced by ISO. ISO reduced the death rate, brain water content and blood-brain barrier disruption, but improved the learning and memory functions of CLP-treated mice. ISO significantly decreased the production of pro-inflammatory cytokines and the levels of oxidative indictors in the serum and hippocampus, as well as the number of apoptotic neurons and the expression of pro-apoptotic proteins in the hippocampus. Inversely, anti-inflammatory factors, antioxidative enzymes and anti-apoptotic proteins were markedly increased by ISO administration. However, the neuroprotective effects of ISO were abolished by a HO-1 inhibitor. Overall, these findings suggested that 0.7% ISO alleviated SAE via its anti-inflammatory, antioxidative and anti-apoptotic properties, which involved the activated form of HO-1.

Attenuation of the mutual elevation of iron accumulation and oxidative stress may contribute to the neuroprotective and anti-seizure effects of xenon in neonatal hypoxia-induced seizures

Previous studies have suggested that xenon inhalation has neuroprotective and antiepileptic effects; however, the underlying mechanisms involved remain unclear. This study aimed to investigate the possible xenon inhalation mechanisms involved in the neuroprotection and antiepileptic effects. A neonatal hypoxic C57BL/6J mouse model was used for the experiments. Immediately after hypoxia treatment, the treatment group inhaled a xenon mixture (70% xenon/21% oxygen/9% nitrogen) for 60 min, while the hypoxia group inhaled a non-xenon mixture (21% oxygen/79% nitrogen) for 60 min. Seizure activity was recorded at designated time points using electroencephalography. Oxidative stress levels, iron levels, neuronal injury, and learning and memory functions were also studied. The results showed that hypoxia increased the levels of iron, oxidative stress, mitophagy, and neurodegeneration, which were accompanied by seizures and learning and memory disorders. In addition, our results confirmed that xenon treatment significantly attenuated the hypoxia-induced seizures and cognitive defects in neonatal C57 mice. Moreover, the increased levels of iron, oxidative stress, mitophagy, and neuronal injury were reduced in xenon-treated mice. This study confirms the significant protective effects of a xenon mixture on hypoxia-induced damage in neonatal mice. Furthermore, our results suggest that reducing oxidative stress levels and iron accumulation may be the underlying mechanisms of xenon activity. Studying the protective mechanisms of xenon will advance its applications in potential therapeutic strategies.

Nrf2 transcriptional activity in the mouse affects the physiological response to tribromoethanol

Up to date, there is no information on the influence of 2,2,2-tribromoethanol (TBE; Avertin), a commonly used anaesthetic, on mice with impaired antioxidant capacity. We aimed to analyse the effect of a single dose of Avertin on anaesthesia duration time, inflammatory response, oxidative stress and collagen deposition in the large intestine of Nrf2 transcriptional knockout mice (tNrf2^-/-). The studies were performed on six-month-old female mice Nrf2^+/+ and tNrf2^-/- randomly assigned to Avertin (250 mg/kg b.w. single i.p. injection) or vehicle group. We observed a 2-fold increase in anaesthesia time and longer recovery time (p = 0.015) in tNrf2^-/- in comparison to Nrf2^+/+. However, no hepato- or nephrotoxicity was detected. Interestingly, we found severe changes in colon morphology of untreated tNrf2^-/- mice associated with colon shortening (p = 0.02) and thickening (p = 0.015). Avertin treatment caused colon damage manifested with epithelial layer damage and goblet depletion in Nrf2^+/+ mice but not in tNrf2^-/- individuals. Additionally, Avertin did not induce oxidative stress in colon tissue, but it increased leukocyte infiltration in Nrf2^+/+ mice (p = 0.02). Immunofluorescent staining also revealed enhanced deposition of collagen I and collagen III in the colon of untreated tNrf2^-/- mice. Avertin contributed to increased deposition of collagen I in Nrf2^+/+ mice but reduced deposition of collagen I and III in tNrf2^-/- individuals. In conclusion, tNrf2^-/- respond to Avertin with prolonged anaesthesia that is not associated with acute toxicity, inflammatory reaction or enhanced oxidative stress. Avertin does not impair intestine morphology in tNrf2^-/- mice but can normalise the enhanced fibrosis.

Ischemic preconditioning provides long-lasting neuroprotection against ischemic stroke: The role of Nrf2

BACKGROUND AND PURPOSE

A major gap in the field of ischemic preconditioning (IPC) is whether or not long-lasting neuroprotection can be achieved. Moreover, the specific mechanisms underlying IPC and how they can be translated into the clinic remain uncertain. To fill these gaps, we tested the hypothesis that IPC exerts long-lasting structural and functional neuroprotection against ischemic stroke through the master gatekeeper of antioxidant defenses, nuclear factor erythroid 2-related factor 2 (Nrf2). We also tested whether the brain could be pharmaceutically preconditioned with a potent and blood-brain barrier-permeable Nrf2 activator, 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-trifluoethyl amide (CDDO-TFEA).

METHODS

IPC was induced by transient middle cerebral artery occlusion (MCAO) for 12 min, and ischemic stroke was generated by MCAO for 60 min in wild-type (WT) or Nrf2 knockout (KO) mice. Sensorimotor function, learning/memory skills, and brain tissue loss were measured up to 35 days after stroke. Primary rodent cortical neurons from wildtype (WT) and Nrf2 KO mice were subjected to lethal oxygen-glucose deprivation (OGD) or a brief OGD episode as a preconditioning (PC) stimulus before OGD. Cell viability/death, lipid electrophile generation, and Nrf2 activation were measured. CDDO-TFEA or its vehicle was administered in vivo for three consecutive days before MCAO. Tissue loss and neurological tests were performed 35 days after stroke.

RESULTS

IPC significantly reduced sensorimotor deficits, post-stroke cognitive impairments, and brain tissue loss, 35 days after MCAO in WT mice. These enduring protective effects of IPC were inhibited in Nrf2 KO mice. In neuronal cultures, PC also endowed primary neurons with ischemic tolerance against OGD-induced cell death, an effect that was abolished by loss of Nrf2 expression in KO neurons. PC induced the generation of low levels of lipid electrophiles and led to activation of the Nrf2 pathway. The mechanism underlying IPC may be translatable, as exogenous administration of the Nrf2 activator CDDO-TFEA significantly reduced neurological dysfunction and ischemic brain damage after MCAO.

CONCLUSIONS

IPC provides long-lasting neuroprotection against ischemic brain injury and post-stroke cognitive dysfunction. Nrf2 activation plays a key role in this beneficial outcome and is a promising therapeutic target for the attenuation of ischemic brain injury.

Brain ischemic preconditioning protects against ischemic injury and preserves the blood-brain barrier via oxidative signaling and Nrf2 activation

Brain ischemic preconditioning (IPC) with mild ischemic episodes is well known to protect the brain against subsequent ischemic challenges. However, the underlying mechanisms are poorly understood. Here we demonstrate the critical role of the master redox transcription factor, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), in IPC-mediated neuroprotection and blood-brain barrier (BBB) preservation. We report that IPC causes generation of endogenous lipid electrophiles, including 4-hydroxy-2-nonenal (4-HNE), which release Nrf2 from inhibition by Keap1 (via Keap1-C288) and inhibition by glycogen synthase kinase 3β (via GSK3β-C199). Nrf2 then induces expression of its target genes, including a new target, cadherin 5, a key component of adherens junctions of the BBB. These effects culminate in mitigation of BBB leakage and of neurological deficits after stroke. Collectively, these studies are the first to demonstrate that IPC protects the BBB against ischemic injury by generation of endogenous electrophiles and activation of the Nrf2 pathway through inhibition of Keap1- and GSK3β-dependent Nrf2 degradation.

Advances in stroke pharmacology

Stroke occurs when a cerebral blood vessel is blocked or ruptured, and it is the major cause of death and adult disability worldwide. Various pharmacological agents have been developed for the treatment of stroke either through interrupting the molecular pathways leading to neuronal death or enhancing neuronal survival and regeneration. Except for rtPA, few of these agents have succeeded in clinical trials. Recently, with the understanding of the pathophysiological process of stroke, there is a resurrection of research on developing neuroprotective agents for stroke treatment, and novel molecular targets for neuroprotection and neurorestoration have been discovered to predict or offer clinical benefits. Here we review the latest major progress of pharmacological studies in stroke, especially in ischemic stroke; summarize emerging potential therapeutic mechanisms; and highlight recent clinical trials. The aim of this review is to provide a panorama of pharmacological interventions for stroke and bridge basic and translational research to guide the clinical management of stroke therapy.

The Modification and Performance of a Large Animal Anesthesia Machine (Tafonius®) in Order to Deliver Xenon to a Horse

Introduction

Xenon, due to its interesting anesthetic properties, could improve the quality of anesthesia protocols in horses despite its high price. This study aimed to modify and test an anesthesia machine capable of delivering xenon to a horse.

Materials and methods

An equine anesthesia machine (Tafonius, Vetronic Services Ltd., UK) was modified by including a T-connector in the valve block to introduce xenon, so that the xenon was pushed into the machine cylinder by the expired gases. A xenon analyzer was connected to the expiratory limb of the patient circuit. The operation of the machine was modeled and experimentally tested for denitrogenation, wash-in, and maintenance phases. The system was considered to consist of two compartments, one being the horse’s lungs, the other being the machine cylinder and circuit. A 15-year-old, 514-kg, healthy gelding horse was anesthetized for 70 min using acepromazine, romifidine, morphine, diazepam, and ketamine. Anesthesia was maintained with xenon and oxygen, co-administered with lidocaine. Ventilation was controlled. Cardiorespiratory variables, expired fraction of xenon (FeXe), blood gases were measured and xenon was detected in plasma. Recovery was unassisted and recorded.

Results

FeXe remained around 65%, using a xenon total volume of 250 L. Five additional boli of ketamine were required to maintain anesthesia. PaO₂ was 45 ± 1 mmHg. The recovery was calm. Xenon was detected in blood during the entire administration time.

Conclusion

This pilot study describes how to deliver xenon to a horse. Although many technical problems were encountered, their correction could guide future endeavors to study the use of xenon in horses.

Melatonin Alleviates Intracerebral Hemorrhage-Induced Secondary Brain Injury in Rats via Suppressing Apoptosis, Inflammation, Oxidative Stress, DNA Damage, and Mitochondria Injury

Intracerebral hemorrhage (ICH) is a cerebrovascular disease with high mortality and morbidity, and the effective treatment is still lacking. We designed this study to investigate the therapeutic effects and mechanisms of melatonin on the secondary brain injury (SBI) after ICH. An in vivo ICH model was induced via autologous whole blood injection into the right basal ganglia in Sprague-Dawley (SD) rats. Primary rat cortical neurons were treated with oxygen hemoglobin (OxyHb) as an in vitro ICH model. The results of the in vivo study showed that melatonin alleviated severe brain edema and behavior disorders induced by ICH. Indicators of blood-brain barrier (BBB) integrity, DNA damage, inflammation, oxidative stress, apoptosis, and mitochondria damage showed a significant increase after ICH, while melatonin reduced their levels. Meanwhile, melatonin promoted further increasing of expression levels of antioxidant indicators induced by ICH. Microscopically, TUNEL and Nissl staining showed that melatonin reduced the numbers of ICH-induced apoptotic cells. Inflammation and DNA damage indicators exhibited an identical pattern compared to those above. Additionally, the in vitro study demonstrated that melatonin reduced the apoptotic neurons induced by OxyHb and protected the mitochondrial membrane potential. Collectively, our investigation showed that melatonin ameliorated ICH-induced SBI by impacting apoptosis, inflammation, oxidative stress, DNA damage, brain edema, and BBB damage and reducing mitochondrial membrane permeability transition pore opening, and melatonin may be a potential therapeutic agent of ICH.