Dexmedetomidine mitigates sevoflurane-induced cell cycle arrest in hippocampus

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Dexmedetomidine alleviates hippocampal neuronal loss and cognitive decline in rats undergoing open surgery under sevoflurane anaesthesia by suppressing CCAAT/enhancer-binding protein beta

Dexmedetomidine (Dex) may exert neuroprotective effects by attenuating inflammatory responses. However, whether Dex specifically improves postoperative cognitive dysfunction (POCD) by inhibiting microglial inflammation through what pathway remains unclear. In this study, the POCD model was constructed by performing open surgery after 3 h of continuous inhalation of 3% sevoflurane to rats, which were intraperitoneally injected with 25 μg/kg Dex .5 h before anaesthesia. The results displayed that Dex intervention decreased rat escape latency, maintained swimming speed and increased the number of times rats crossed the platform and the time spent in the target quadrant. Furthermore, the rat neuronal injury was restored, alleviated POCD modelling-induced rat hippocampal microglial activation and inhibited microglial M1 type polarization. Besides, we administered Dex injection and/or CCAAT/enhancer-binding protein beta (CEBPB) knockdown on the basis of sevoflurane exposure and open surgery and found that CEBPB was knocked down, resulting in the inability of Dex to function, which confirmed CEBPB as a target for Dex treatment. To sum up, Dex improved POCD by considering CEBPB as a drug target to activate the c-Jun N-terminal kinase (JNK)/p-38 signaling pathway, inhibiting microglial M1 polarization-mediated inflammation in the central nervous system.

Sevoflurane Exposure in Neonates Perturbs the Expression Patterns of Specific Genes That May Underly the Observed Learning and Memory Deficits

Exposure to commonly used anesthetics leads to neurotoxic effects in animal models-ranging from cell death to learning and memory deficits. These neurotoxic effects invoke a variety of molecular pathways, exerting either immediate or long-term effects at the cellular and behavioural levels. However, little is known about the gene expression changes following early neonatal exposure to these anesthetic agents. We report here on the effects of sevoflurane, a commonly used inhalational anesthetic, on learning and memory and identify a key set of genes that may likely be involved in the observed behavioural deficits. Specifically, we demonstrate that sevoflurane exposure in postnatal day 7 (P7) rat pups results in subtle, but distinct, memory deficits in the adult animals that have not been reported previously. Interestingly, when given intraperitoneally, pre-treatment with dexmedetomidine (DEX) could only prevent sevoflurane-induced anxiety in open field testing. To identify genes that may have been altered in the neonatal rats after sevoflurane and DEX exposure, specifically those impacting cellular viability, learning, and memory, we conducted an extensive Nanostring study examining over 770 genes. We found differential changes in the gene expression levels after exposure to both agents. A number of the perturbed genes found in this study have previously been implicated in synaptic transmission, plasticity, neurogenesis, apoptosis, myelination, and learning and memory. Our data thus demonstrate that subtle, albeit long-term, changes observed in an adult animal's learning and memory after neonatal anesthetic exposure may likely involve perturbation of specific gene expression patterns.

Bicuculline and Bumetanide Attenuate Sevoflurane-Induced Impairment of Myelination and Cognition in Young Mice

Sevoflurane (Sevo) is one of the most commonly used general anesthetics for infants and young children. We investigated whether Sevo impairs neurological functions, myelination, and cognition via the γ-aminobutyric acid A receptor (GABA_AR) and Na⁺-K⁺-2Cl^- cotransporter (NKCC1) in neonatal mice. On postnatal days 5-7, mice were exposed to 3% Sevo for 2 h. On postnatal day 14, mouse brains were dissected, and oligodendrocyte precursor cell line level lentivirus knockdown of GABRB3, immunofluorescence, and transwell migration assays were performed. Finally, behavioral tests were conducted. Multiple Sevo exposure groups exhibited increased neuronal apoptosis levels and decreased neurofilament protein levels in the mouse cortex compared with the control group. Sevo exposure inhibited the proliferation, differentiation, and migration of the oligodendrocyte precursor cells, thereby affecting their maturation process. Electron microscopy revealed that Sevo exposure reduced myelin sheath thickness. The behavioral tests showed that multiple Sevo exposures induced cognitive impairment. GABA_AR and NKCC1 inhibition provided protection against Sevo-induced neurotoxicity and cognitive dysfunction. Thus, bicuculline and bumetanide can protect against Sevo-induced neuronal injury, myelination impairment, and cognitive dysfunction in neonatal mice. Furthermore, GABA_AR and NKCC1 may be mediators of Sevo-induced myelination impairment and cognitive dysfunction.

Dexmedetomidine Pre-Treatment of Neonatal Rats Prevents Sevoflurane-Induced Deficits in Learning and Memory in the Adult Animals

Anesthetics have been shown to cause cytotoxicity, cell death, affect neuronal growth and connectivity in animal models; however, their effects on learning and memory remain to be fully defined. Here, we examined the effects of the inhalation anesthetic sevoflurane (SEV)-both in vivo by examining learning and memory in freely behaving animals, and in vitro using cultured neurons to assess its impact on viability, mitochondrial structure, and function. We demonstrate here that neonatal exposure to sub-clinically used concentrations of SEV results in significant, albeit subtle and previously unreported, learning and memory deficits in adult animals. These deficits involve neuronal cell death, as observed in cell culture, and are likely mediated through perturbed mitochondrial structure and function. Parenthetically, both behavioural deficits and cell death were prevented when the animals and cultured neurons were pre-treated with the anesthetic adjuvant Dexmedetomidine (DEX). Taken together, our data provide direct evidence for sevoflurane-induced cytotoxic effects at the neuronal level while perturbing learning and memory at the behavioural level. In addition, our data underscore the importance of adjuvant agents such as DEX that could potentially counter the harmful effects of commonly used anesthetic agents for better clinical outcomes.

Ultrasonic Image Restoration Algorithm for Prevention of Nervous Disorders during the Recovery Period of Patients Receiving Sevoflurane Anesthesia

In this article, dexmedetomidine (Dex) was used to prevent neurological disorders in patients anesthetized with sevoflurane and the effect was analyzed using ultrasound images based on the restoration algorithm of the linear system model. Children injected with Dex were in the experimental group, while children injected with normal saline were in the control group. The mean arterial pressure (MAP), arterial oxygen saturation (SpO2), heart rate (HR), Pediatric anesthesia agitation scale (PAED) score, Face, Legs, Activity, Cry, Consolability (FLACC) score, and adverse drug event (ADE) in the two groups were compared before the injection (T1), at 5 min (T2), 10 min (T3), and 20 min (T4) after the injection, and when the patient came to himself (T5). It was found that in contrast with the control group, the MAP in the experimental group at T2, T3, and T4 periods was lower, while it was higher at T5 period and its HR at T2, T3, T4, and T5 periods was higher (P < 0.05); the PAED and FLACC scores were lower (P < 0.05), and the incidence of ADE (10.53%) was lower than that in the control group (31.58%) (P < 0.05). However, SpO2 at different periods showed no obvious differences between the two groups (P > 0.05). In conclusion, the restoration algorithm-based ultrasound images had high quality, and they demonstrated good application value in evaluating the effect of Dex to prevent neurological disorders in patients anesthetized by sevoflurane.

Anesthetic management of unruptured intracranial aneurysms: a qualitative systematic review

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

Dexmedetomidine regulates sevoflurane-induced neurotoxicity through the miR-330-3p/ULK1 axis

Sevoflurane (Sev), a widely used volatile anesthetic, can cause long-term neurotoxicity and learning and memory impairment. Dexmedetomidine (Dex) has been reported to exhibit neuroprotective effects in numerous neurological disorders. Our work aimed to evaluate the molecular mechanisms of Dex in Sev-induced neurotoxicity. In this study, it was found that Dex mitigated Sev-induced neurotoxicity. Moreover, Sev treatment upregulated the miR-330-3p expression in hippocampus tissues, while this effect was reversed by the Dex treatment. Additionally, microRNA-330-3p (miR-330-3p) inhibition was verified to inhibit cell apoptosis and facilitate mitophagy. ULK1 was confirmed as a downstream target of miR-330-3p and miR-330-3p could negatively regulate ULK1 expression. Finally, the effects of miR-330-3p inhibition on Sev-induced neurotoxicity could be offset by ULK1 knockdown or further intensified by Dex treatment. In summary, our study demonstrated that Dex regulated cell apoptosis and mitophagy in Sev-induced neurotoxicity through the miR-330-3p/ULK1 axis. These findings might provide novel insights into the treatment of Sev-induced neurotoxicity.

Dexmedetomidine protects SH-SY5Y cells against MPP+ -induced declining of mitochondrial membrane potential and cell cycle deficits

Dexmedetomidine (Dex), an adrenergic α2 receptor agonist, is commonly used in deep-brain stimulation surgery for Parkinson's disease (PD). However, there is evidence that the use of anaesthetics may accelerate the progression of neurodegenerative diseases. The effect of Dex on PD remains unclear. Here, we cultured the all-trans-retinoicacid (ATRA) differentiated SH-SY5Y cells in vitro and then treated with MPP+ (1.5mM) with or without Dex (10nM) or Dex combined with Atipamezole (Ati,100nM, adrenergic α2 receptor inhibitor). The ratio of apoptotic cells, mitochondrial membrane potential (Δψm), reactive oxygen species (ROS), cell cycle and apoptotic markers (Cleaved caspase-3, 9) were analysed by flow cytometry and immunofluorescence. We found that the levels of apoptotic ratio and cleaved caspase-3, 9 increased, ROS accumulated, and mitochondrial membrane potential decreased after MPP+treatment, while these changes were partially reversed by Dex. Dex also prevented MPP+ induced cell arrest by increasing G1 phase cells, decreasing S phase cells, and decreasing the expression of cyclinD1 and Cdk4. Moreover the effects of Dex were partially reversed by Ati. These findings reveal that Dex attenuated MPP+ -induced apoptosis of SH-SY5Y cells by preventing the loss of Δψm, reducing ROS, and regulating the cell cycle. Our findings indicated that Dex is more likely to be a potential drug for the treatment of PD.

Prenatal sevoflurane exposure: Effects of iron metabolic dysfunction on offspring cognition and potential mechanism

For decades, the neurotoxicity caused by anesthetics in mammalian brain development has gained increasing attention. Exposure to anesthetics leads to neurotoxicity and apoptosis of nerve cells, which in turn induces cognitive dysfunction. Although most of the data came from animal studies, general anesthetics have been shown to have adverse effects on cognitive function in infants and young children in recent years. This concern has led to a number of retrospective studies that observed an association between general anesthesia in pregnant women and neurobehavioral problems in fetuses or offspring. Every year, many pregnant women undergo non-obstetric anesthesia due to various reasons such as traffic accidents, fetal interventions, acute appendicitis, symptomatic cholelithiasis, and trauma. A matter of concern for these pregnant women is whether anesthesia has a detrimental effect on fetal brain development in the womb and whether the fetus has cognitive impairment after birth. In humans, the association of anesthetic exposure in infants with the long-term impairment of neurologic functions has been reported in several retrospective clinical studies. Recently, we have found that sevoflurane anesthesia during pregnancy in mice-induced cognitive impairment in the offspring by causing iron deficiency and inhibiting myelinogenesis. Sevoflurane is a commonly used general anesthetic in the hospitals, which can induce neurotoxicity and cause cognitive impairment in fetuses, infants, children, and adults. However, the exact mechanism of sevoflurane-induced damage to the central nervous system (CNS) is not fully understood. Based on our recent results, this paper reviewed the effects of sevoflurane on cognitive impairment and pathological changes such as neurogenesis, neuronal apoptosis, and iron metabolism dysfunction in the offspring.

TrkC Overexpression Protects Sevoflurane-Induced Neurotoxicity in Human Induced Pluripotent Stem Cell-Derived Neurons

BACKGROUND

Inhaled anesthetic sevoflurane (SEVO) may induce cortical neurotoxicity and memory dysfunction in both animals and humans. In this study, we investigated the toxic effects of SEVO on human induced pluripotent stem cell (iPS)-derived neurons.

METHODS

Human iPS-derived neurons were exposed to SEVO in vitro. SEVO-induced toxic effects were examined with the viability, live caspase 3/7, and neurite density assays, respectively. The effects of SEVO on the receptors of the tyrosine kinases TrkA, TrkB, and TrkC were assessed by qRT-PCR. TrkA, TrkB, and TrkC were ectopically overexpressed in human iPS-derived neurons. Their functional effects on SEVO-induced human iPS-derived neuron toxicity were further investigated.

RESULTS

SEVO induced dose-dependent cell death, caspase 3/7 elevation, neurite degeneration, and the downregulation of Trk receptors in human iPS-derived neurons. Adenovirus-mediated Trk receptor overexpression selectively upregulated endogenous TrkA, TrkB, or TrkC gene expressions in human iPS-derived neurons. Specifically, TrkC overexpression, but not TrkA or TrkB overexpression was found to overcome the neurotoxic effects of SEVO in human iPS-derived neurons.

CONCLUSIONS

SEVO may induce neurotoxicity in human iPS-derived neurons, and its neurotoxic damage could be protected by the overexpression of TrkC.

Dexmedetomidine alleviates sevoflurane-induced neurotoxicity via mitophagy signaling

Dexmedetomidine, a class of α2-adrenergic agonist, was reported to exert a neuroprotective effect on sevoflurane-induced neurotoxicity. However, the specific mechanisms have not been fully clarified yet. The aim of our study is to uncover the role of dexmedetomidine in sevoflurane-induced neurotoxicity. The rats pretreated with dexmedetomidine and/or Rapamycin 3-Methyladenine were housed in a box containing 30% O₂, 68% N₂ and 2% sevoflurane for 4 h for anesthesia. 24 h after drug injection, Morris water maze test was used to evaluate rats' learning and memory ability. Hematoxylin & eosin (H&E) staining was adopted to analyze the pathological changes of hippocampus. TUNEL assay was performed to measure cell apoptosis in hippocampus. Immunofluorescent assay was utilized to detect HSP60 level. The protein levels of LC3I, LC3II, Beclin-1, CypD, VDAC1 and Tom20 were examined by western blot. 5 weeks after drug injection, Morris water maze test was used to evaluate rats' learning and memory ability again. Dexmedetomidine alleviated sevoflurane-induced nerve injury and the impairment of learning and memory abilities. Additionally, dexmedetomidine inhibited sevoflurane-induced cell apoptosis in hippocampus. In mechanism, dexmedetomidine activated mitophagy to mitigate neurotoxicity by enhancing LC3II/LC3I ratio, HSP60, Beclin-1, CypD, VDAC1 and Tom20 protein levels in hippocampus. Dexmedetomidine alleviates sevoflurane-induced neurotoxicity via mitophagy signaling, offering a potential strategy for sevoflurane-induced neurotoxicity treatment.

Use of dexmedetomidine and opioids as the primary anesthetic in infants and young children: A retrospective cohort study

BACKGROUND

Anesthetic regimens using dexmedetomidine and short-acting opioids have been suggested as potential alternatives to sevoflurane-based anesthesia in children. The primary aim of this study is to compare demographics, intraoperative characteristics, and complications of general anesthetics in which dexmedetomidine and opioids were used without sevoflurane, or in combination with a low sevoflurane concentration, in children 36 months old and younger. The secondary aim is to evaluate intraoperative bispectral index (BIS) values when available in these patients.

METHODS

General anesthetics performed between January 1, 2017, and May 1, 2018, in children 2 years and younger who received dexmedetomidine and remifentanil, with or without sevoflurane, were identified. Additional anesthetics performed during this time in children 36 months and younger who received dexmedetomidine and opioids and had BIS monitoring were also identified. Charts were reviewed for demographic and intraoperative variables, including drug administration and hemodynamic data.

RESULTS

A total of 244 patients were identified. All but 22 patients received remifentanil. Ninety-two patients received sevoflurane with a mean end-tidal concentration of 0.84% (SD 0.43). Compared to the sevoflurane group, the nonsevoflurane group received more remifentanil (median dose 0.4 μg/kg/min vs 0.2 μg/kg/min, difference of 0.1 μg/kg/min, 95% CI 0.1-0.3, P < .001) and more dexmedetomidine (median dose 0.9 μg/kg/h vs 0.3 μg/kg/h, difference of 0.6 μg/kg/h, 95% CI 0.4-0.8, P < .001), and had a higher mean arterial pressure (median 53 mm Hg vs 42 mm Hg, difference of 11 mm Hg, 95% CI 8.1-14.8, P < .001). Complications between the two groups were comparable. The median percent intraoperative time with BIS reading <60 was 71.6% (95% CI: 63.3%-79.8%).

CONCLUSION

Dexmedetomidine and opioids can effectively be used in young children as an alternative total intravenous anesthesia technique with or without <1 minimum alveolar concentration of sevoflurane. Bispectral index monitoring reveals a likely sufficient depth of hypnosis.

Organ-Protective Effects and the Underlying Mechanism of Dexmedetomidine

Dexmedetomidine (DEX) is a highly selective α2 adrenergic receptor (α2AR) agonist currently used in clinical settings. Because DEX has dose-dependent advantages of sedation, analgesia, antianxiety, inhibition of sympathetic nervous system activity, cardiovascular stabilization, and significant reduction of postoperative delirium and agitation, but does not produce respiratory depression and agitation, it is widely used in clinical anesthesia and ICU departments. In recent years, much clinical study and basic research has confirmed that DEX has a protective effect on a variety of organs, including the nervous system, heart, lungs, kidneys, liver, and small intestine. It acts by reducing the inflammatory response in these organs, activating antiapoptotic signaling pathways which protect cells from damage. Therefore, based on wide clinical application and safety, DEX may become a promising clinical multiorgan protection drug in the future. In this article, we review the physiological effects related to organ protection in α2AR agonists along with the organ-protective effects and mechanisms of DEX to understand their combined application value.

Dexmedetomidine suppresses sevoflurane anesthesia-induced neuroinflammation through activation of the PI3K/Akt/mTOR pathway

Background

Sevoflurane, an inhalational general anesthetic, has become one of the most widely used inhalational anesthetics in surgery. However, previous studies have found that sevoflurane anesthesia can trigger an inflammatory response, resulting in secondary damage. Dexmedetomidine (DEX), a highly-selective α adrenergic receptor agonist, is widely used as an anesthetic adjuvant in the clinic. In this study we investigated whether DEX was able to suppress sevoflurane-induced neuroinflammation.

Methods

The aim was to determine the mechanism of action of the suppressive effect of DEX using a rat model. Rats were randomly divided into a control group (n = 10), low-dose sevoflurane group (L-Sev; n = 10), high-dose sevoflurane group (H-Sev; n = 10), vehicle group (n = 10), DEX group (n = 10) and DEX + LY294002 (a specific inhibitor of PI3K) group (n = 10). The rats in vehicle, DEX and DEX + LY294002 groups were in the presence of high-dose sevoflurane exposure. Western blotting was used to measure the expression of proinflammatory cytokines (IL-6, IL-8, TNF-α) and the activity level of the phosphatidylinositol 3-hydroxy kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway.

Results

We found that sevoflurane anesthesia induced an increase in the levels of pro-inflammatory cytokines, while decreasing activation of the PI3K/Akt/mTOR pathway in both the cortex and hippocampus of rats. Treatment with DEX reduced pro-inflammatory cytokine levels and prevented inactivation of the PI3K/Akt/mTOR pathway. Moreover, LY294002, an inhibitor of the PI3K/Akt/mTOR pathway, reduced the anti-inflammatory activity of DEX.

Conclusions

These data suggest that the PI3K/Akt/mTOR pathway contributes to sevoflurane-induced neuroinflammation and that activation of PI3K/Akt/mTOR signaling by DEX could help reduce the neuroinflammatory effects of sevoflurane.

Anesthetics: from modes of action to unconsciousness and neurotoxicity

Modern anesthetic compounds and advanced monitoring tools have revolutionized the field of medicine, allowing for complex surgical procedures to occur safely and effectively. Faster induction times and quicker recovery periods of current anesthetic agents have also helped reduce health care costs significantly. Moreover, extensive research has allowed for a better understanding of anesthetic modes of action, thus facilitating the development of more effective and safer compounds. Notwithstanding the realization that anesthetics are a prerequisite to all surgical procedures, evidence is emerging to support the notion that exposure of the developing brain to certain anesthetics may impact future brain development and function. Whereas the data in support of this postulate from human studies is equivocal, the vast majority of animal research strongly suggests that anesthetics are indeed cytotoxic at multiple brain structure and function levels. In this review, we first highlight various modes of anesthetic action and then debate the evidence of harm from both basic science and clinical studies perspectives. We present evidence from animal and human studies vis-à-vis the possible detrimental effects of anesthetic agents on both the young developing and the elderly aging brain while discussing potential ways to mitigate these effects. We hope that this review will, on the one hand, invoke debate vis-à-vis the evidence of anesthetic harm in young children and the elderly, and on the other hand, incentivize the search for better and less toxic anesthetic compounds.