Dexmedetomidine post-treatment induces neuroprotection via activation of extracellular signal-regulated kinase in rats with subarachnoid haemorrhage

Dexmedetomidine Protects Cortical Neurons from Propofol-Induced Apoptosis via Activation of Akt-IKK-NF-κB Signaling Pathway by α2A-adrenoceptor

CONTEXT

Propofol can induce neuroapoptosis. It has been reported that dexmedetomidine (DEX) has a protective effect on propofol-induced neuroapoptosis, but the specific mechanism needs to be further explored to provide a theoretical basis for their combined use.

OBJECTIVE

We aimed to explore the neuroprotective effect of DEX on primary cortical neurons treated by propofol and to elucidate the underlying mechanistic pathways.

METHODS

Cortical neurons were isolated from fetal rats and treated with propofol. MTT assays were performed to detect cell viability, α-tubulin immunofluorescent assays were conducted to observe cell abnormalities, and c-caspase3 immunofluorescent assays and flow cytometry were performed to examine cell apoptosis. Further, neurons were cotreated with propofol and DEX to study DEX's neuroprotective effects on propofol-caused neuronal injuries. Finally, the α2A-adrenoceptor was knocked out and/or the Akt activator (SC-79) was added to cells co-treated with propofol and DEX. The expression levels of Akt-IKK-NF-κB pathway-related proteins were detected by western blot.

RESULTS

Propofol decreased cell viability in a dose-dependent manner, triggered apoptosis, caused morphological abnormalities and down-regulated the phosphorylation levels of Akt, IKK, NF-κB and IκB in cortical neurons. DEX ameliorated the decrease of cell viability, alleviated neuronal apoptosis and promoted the downregulated expression levels of p-Akt, IKK, NF-κB, and IκB proteins which had been induced by propofol treatment. Western blot findings following the transfection of α2A-siRNA and the addition of SC-79 suggested that DEX's neuroprotective functions arose from the stimulation of α2A-adrenoceptors to activate the Akt-IKK-NF-κB signal pathway.

CONCLUSION

DEX protected neurons against propofol-induced apoptosis via activation of the Akt-IKK-NF-κB signal pathway through α2A-adrenoceptors.

Efficacy of dexmedetomidine combined with ropivacaine on postoperative analgesia and delirium in elderly patients with total knee arthroplasty

This study aimed to investigate the impact of dexmedetomidine combined with ropivacaine on continuous femoral nerve block (CFNB) in postoperative analgesia and delirium in elderly patients with total knee arthroplasty (TKA). A total of 120 patients who undergone TKA were randomly assigned into group D + R (dexmedetomidine combined with ropivacaine) and group R (only ropivacaine), with 60 cases in each group. The pain scores at rest and exercise at 6 h, 12 h, 24 h, and 48 h postoperatively. The occurrence of delirium on Day 1, Day 2, and Day 3 postoperatively were measured, and the sleep quality was evaluated before surgery, the night of surgery, and 24 h postoperatively to observe the occurrence of postoperative complications. The Visual analogu scale (VAS) of group D + R at 12 h, 24 h, and 48 h postoperatively were lower than those of group R in both rest and exercise states. The incidence of postoperative delirium in group D + R was lower than that in group R on Day 1 and Day 2. Pittsburgh sleep quality index (PSQI) scores in group D + R were lower than those in group R. There was no significant difference in postoperative adverse reactions between the two groups. Dexmedetomidine combined with ropivacaine improves postoperative analgesia and sleep quality, and alleviates the occurrence of postoperative delirium in elderly patients with TKA.

Long non-coding RNA HOXA11-AS regulates ischemic neuronal death by targeting miR-337-3p/YBX1 signaling pathway: protective effect of dexmedetomidine

Cerebral ischemia/reperfusion (I/R) is a common neurological disease. Homeobox A11 antisense RNA (HOXA11-AS), a long non-coding RNA (lncRNA), has been demonstrated as an important regulator in diverse human cancers. However, its function and regulatory mechanism in ischemic stroke remains largely unknown. Dexmedetomidine (Dex) have received wide attraction because of its neuroprotective effects. This study aimed to explore the possible link between Dex and HOXA11-AS in protecting neuronal cells from by ischemia/reperfusion-induced apoptosis. We used oxygen-glucose deprivation and reoxygenation (OGD/R) in mouse neuroblastoma Neuro-2a cells and middle cerebral artery occlusion (MACO) mouse model to test the link. We found that Dex significantly alleviated OGD/R-induced DNA fragmentation, cell viability and apoptosis, and rescued the decreased HOXA11-AS expression after ischemic damage in Neuro-2a cells. Gain-/loss-of-function studies revealed that HOXA11-AS promoted proliferation, inhibited apoptosis in Neuro-2a cells exposed to OGD/R. Knockdown of HOXA11-AS decreased the protective effect of Dex on OGD/R cells. HOXA11-AS was found to transcriptionally regulate microRNA-337-3p (miR-337-3p) expression as evidenced by luciferase reporter assay, while miR-337-3p expression was upregulated following ischemia in vitro and in vivo. Besides, knockdown of miR-337-3p protected OGD/R-induced apoptotic death of Neuro-2a cells. Furthermore, HOXA11-AS functioned as a competing endogenous RNA (ceRNA) and competed with Y box protein 1 (Ybx1) mRNA for directly binding to miR-337-3p, which protected ischemic neuronal death. Dex treatment protected against ischemic damage and improved overall neurological functions in vivo. Our data suggest a novel mechanism of Dex neuroprotection for ischemic stroke through regulating lncRNA HOXA11-AS by targeting the miR-337-3p/Ybx1 signaling pathway, which might help develop new strategies for the therapeutic interventions in cerebral ischemic stroke.

Dexmedetomidine for the prevention of delirium in adults admitted to the intensive care unit or post-operative care unit: A systematic review of randomised clinical trials with meta-analysis and Trial Sequential Analysis

OBJECTIVES

To assess any benefit or harm, we conducted a systematic review of randomised clinical trials (RCTs) allocating adults to dexmedetomidine versus placebo/no intervention for the prevention of delirium in intensive care or post-operative care units.

DATA SOURCES

We searched Medline, Embase, CENTRAL and other databases. The last search was 9 April 2022.

DATA EXTRACTION

Literature screening, data extraction and risk of bias volume 2 assessments were performed independently and in duplicate. Primary outcomes were occurrences of serious adverse events (SAEs), delirium and all-cause mortality. We used meta-analysis, Trial Sequential Analysis, and GRADE (Grading Recommendations Assessment, Development and Evaluation).

DATA SYNTHESIS

Eighty-one RCTs (15,745 patients) provided data for our primary outcomes. Results from trials at low risk of bias showed that dexmedetomidine may reduce the occurrence of the most frequently reported SAEs (relative risk [RR] 0.69; 95% CI 0.43-1.09), cumulated SAEs (RR 0.70; 95% CI 0.52-0.95) and the occurrence of delirium (RR 0.62; 95% CI 0.43-0.89). The certainty of evidence was very low for delirium. Mortality was very low in trials at low risk of bias (0.4% in the dexmedetomidine groups and 1.0% in the control groups) and meta-analysis did not provide conclusive evidence that dexmedetomidine may result in lower or higher all-cause mortality (RR 0.47; 95% CI 0.18-1.21). There was a lack of information from trial results at low risk of bias for all primary outcomes.

CONCLUSIONS

Trial results at low risk of bias showed that dexmedetomidine might reduce occurrences of SAEs and delirium, while no conclusive evidence was found for effects on all-cause mortality. The certainty of evidence ranged from very low for occurrence of delirium to low for the remaining outcomes.

Inflammation and immune cell abnormalities in intracranial aneurysm subarachnoid hemorrhage (SAH): Relevant signaling pathways and therapeutic strategies

Intracranial aneurysm subarachnoid hemorrhage (SAH) is a cerebrovascular disorder associated with high overall mortality. Currently, the underlying mechanisms of pathological reaction after aneurysm rupture are still unclear, especially in the immune microenvironment, inflammation, and relevant signaling pathways. SAH-induced immune cell population alteration, immune inflammatory signaling pathway activation, and active substance generation are associated with pro-inflammatory cytokines, immunosuppression, and brain injury. Crosstalk between immune disorders and hyperactivation of inflammatory signals aggravated the devastating consequences of brain injury and cerebral vasospasm and increased the risk of infection. In this review, we discussed the role of inflammation and immune cell responses in the occurrence and development of aneurysm SAH, as well as the most relevant immune inflammatory signaling pathways [PI3K/Akt, extracellular signal-regulated kinase (ERK), hypoxia-inducible factor-1α (HIF-1α), STAT, SIRT, mammalian target of rapamycin (mTOR), NLRP3, TLR4/nuclear factor-κB (NF-κB), and Keap1/nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/ARE cascades] and biomarkers in aneurysm SAH. In addition, we also summarized potential therapeutic drugs targeting the aneurysm SAH immune inflammatory responses, such as nimodipine, dexmedetomidine (DEX), fingolimod, and genomic variation-related aneurysm prophylactic agent sunitinib. The intervention of immune inflammatory responses and immune microenvironment significantly reduces the secondary brain injury, thereby improving the prognosis of patients admitted to SAH. Future studies should focus on exploring potential immune inflammatory mechanisms and developing additional therapeutic strategies for precise aneurysm SAH immune inflammatory regulation and genomic variants associated with aneurysm formation.

Dexmedetomidine Attenuates Apoptosis and Neurological Deficits by Modulating Neuronal NADPH Oxidase 2-Derived Oxidative Stress in Neonates Following Hypoxic Brain Injury

Hypoxic-ischemic brain injury is an important cause of neonatal neurological deficits. Our previous study demonstrated that dexmedetomidine (Dex) provided neuroprotection against neonatal hypoxic brain injury; however, the underlying mechanisms remain incompletely elucidated. Overactivation of NADPH oxidase 2 (NOX2) can cause neuronal apoptosis and neurological deficits. Hence, we aimed to investigate the role of neuronal NOX2 in Dex-mediated neuroprotection and to explore its potential mechanisms. Hypoxic injury was modeled in neonatal rodents in vivo and in cultured hippocampal neurons in vitro. Our results showed that pre- or post-treatment with Dex improved the neurological deficits and alleviated the hippocampal neuronal damage and apoptosis caused by neonatal hypoxia. In addition, Dex treatment significantly suppressed hypoxia-induced neuronal NOX2 activation; it also reduced oxidative stress, as evidenced by decreases in intracellular reactive oxygen species (ROS) production, malondialdehyde, and 8-hydroxy-2-deoxyguanosine, as well as increases in the antioxidant enzymatic activity of superoxide dismutase and glutathione peroxidase in neonatal rat hippocampi and in hippocampal neurons. Lastly, the posthypoxicneuroprotective action of Dex was almost completely abolished in NOX2-deficient neonatal mice and NOX2-knockdown neurons. In conclusion, our data demonstrated that neuronal NOX2-mediated oxidative stress is involved in the neuroprotection that Dex provides against apoptosis and neurological deficits in neonates following hypoxia.

Dexmedetomidine alleviates inflammatory response and oxidative stress injury of vascular smooth muscle cell via α2AR/GSK-3β/MKP-1/NRF2 axis in intracranial aneurysm

Vascular smooth muscle cell (VSMC) phenotypic modulation regulates the initiation and progression of intracranial aneurysm (IA). Dexmedetomidine (DEX) is suggested to play neuroprotective roles in patients with craniocerebral injury. Therefore, we investigated the biological functions of DEX and its mechanisms against IA formation and progression in the current study. The rat primary VSMCs were isolated from Sprague-Dawley rats. IA and superficial temporal artery (STA) tissue samples were obtained from patients with IA. Flow cytometry was conducted to identify the characteristics of isolated VSMCs. Hydrogen peroxide (H₂O₂) was used to mimic IA-like conditions in vitro. Cell viability was detected using CCK-8 assays. Wound healing and Transwell assays were performed to detect cell motility. ROS production was determined by immunofluorescence using DCFH-DA probes. Western blotting and RT-qPCR were carried out to measure gene expression levels. Inflammation responses were determined by measuring inflammatory cytokines. Immunohistochemistry staining was conducted to measure α₂-adrenergic receptor levels in tissue samples. DEX alleviated the H₂O₂-induced cytotoxicity, attenuated the promoting effects of H₂O₂ on cell malignancy, and protected VSMCs against H₂O₂-induced oxidative damage and inflammation response. DEX regulated the GSK-3β/MKP-1/NRF2 pathway via the α2AR. DEX alleviates the inflammatory responses and oxidative damage of VSMCs by regulating the GSK-3β/MKP-1/NRF2 pathway via the α2AR in IA.

Dexmedetomidine post-conditioning protects blood-brain barrier integrity by modulating microglia/macrophage polarization via inhibiting NF-κB signaling pathway in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is one of the most devastating forms of stroke. Dexmedetomidine (DEX) has shown certain neuroprotective roles in ICH. Nevertheless, the details concerning the underlying molecular mechanism of DEX’s protective effects still need further elucidation. Herein, a model of ICH was established. The rats were randomly divided into the sham group, the ICH group, and the ICH + DEX group. Neurological outcomes, neuronal injury, and apoptosis were evaluated. Brain water content, Evans blue extravasation, and the expression of tight junction-associated proteins were also detected to assess the blood-brain barrier (BBB) integrity. Subsequently, the microglia/macrophage polarization state and inflammatory cytokine levels were observed. To further explore the underlying mechanism, NF-κB signaling pathway-associated proteins were detected. The results showed that DEX exerted neuroprotective effects against ICH-induced neurological deficits. DEX significantly increased the numbers of the surviving neurons and ameliorated neuronal cell loss and apoptosis in ICH. The rats that received the DEX displayed a lower level of brain water content and EB extravasation, moreover, ZO-1, occludin, and claudin-5 were markedly increased by DEX. Additionally, DEX facilitated M2 microglia/macrophage polarization, the M1-associated markers were reduced by DEX, while the M2-associated identification significantly increased. We found that DEX dramatically diminished pro-inflammatory cytokines expression, simultaneously promoting anti-inflammatory cytokines expression. DEX inhibited nuclear translocation of NF-κB in ICH rats. Our data suggest that DEX post-conditioning protects BBB integrity by modulating microglia/macrophage polarization via inhibiting the NF-κB signaling pathway in ICH.

Ferroptosis as a mechanism of neurodegeneration in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia, with complex pathophysiology that is not fully understood. While β-amyloid plaque and neurofibrillary tangles define the pathology of the disease, the mechanism of neurodegeneration is uncertain. Ferroptosis is an iron-mediated programmed cell death mechanism characterised by phospholipid peroxidation that has been observed in clinical AD samples. This review will outline the growing molecular and clinical evidence implicating ferroptosis in the pathogenesis of AD, with implications for disease-modifying therapies.

Dexmedetomidine reduces the apoptosis of rat hippocampal neurons via mediating ERK1/2 signal pathway by targeting miR-155

Rat hippocampal neurons were isolated and divided into Normal, oxygen glucose deprivation/reoxygenation (OGD/R), OGD/R + DEX, OGD/R + NC mimic, OGD/R + miR-155 mimic and OGD/R + DEX + miR-155 mimic groups. In OGD/R group, LDH, ROS and MDA levels and apoptosis rate was increased, with up-regulations of miR-155, Cyt c and Bax/Bcl-2 ratio, but decreases of SOD, GSH-Px and MMP levels, as well as down-regulations of p-ERK1/2/ERK1/2. As compared to the OGD/R group, parameters above in the OGD/R + DEX group were ameliorated evidently, while OGD/R + miR-155 mimic group manifested the opposite changes. Besides, miR-155 mimic could abolish the protective effect of DEX on the hippocampal neurons under OGD/R. DEX, via down-regulating the expression of miR-155, could activate the ERK1/2 pathway, thereby mitigating the apoptosis and oxidative stress injury and increasing the MMP, thereby protecting hippocampal cells from OGD/R injury.

Role of Anesthetics and Their Adjuvants in Neurovascular Protection in Secondary Brain Injury after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal rupture accounts for the majority of subarachnoid hemorrhage and is responsible for most cerebrovascular deaths with high mortality and morbidity. Initial hemorrhage severity and secondary brain injury due to early brain injury and delayed cerebral ischemia are the major determinants of outcomes after aneurysmal subarachnoid hemorrhage. Several therapies have been explored to prevent these secondary brain injury processes after aneurysmal subarachnoid hemorrhage with limited clinical success. Experimental and clinical studies have shown a neuroprotective role of certain anesthetics in cerebrovascular disorders including aneurysmal subarachnoid hemorrhage. The vast majority of aneurysmal subarachnoid hemorrhage patients require general anesthesia for surgical or endovascular repair of their aneurysm. Given the potential impact certain anesthetics have on secondary brain injury after SAH, appropriate selection of anesthetics may prove impactful on overall outcome of these patients. This narrative review focuses on the available evidence of anesthetics and their adjuvants in neurovascular protection in aneurysmal subarachnoid hemorrhage and discusses current impact on clinical care and future investigative directions.

Dexmedetomidine as an Analgesic Agent with Neuroprotective Properties: Experimental and Clinical Aspects

Dexmedetomidine (Dexdor or Precedex®) is considered as a sedative agent which is widely used as an adjuvant in general anesthesia and critical care practice. There is extensive evidence indicating its neuroprotective properties especially in various ischemic and hemorrhagic brain injury models of animals. Clinical trials have shown that dexmedetomidine (DEX) can improve the outcome of intensive care unit (ICU) patients. Also, DEX is appropriate as a non-opioid analgesic therapy whenever minimizing opioid-related side effects is necessary. The present article reviews the recent advances in the use of DEX as a neuroprotective agent in both animal and human studies including newest findings about the mechanism of the drug as well as analgesic efficacy of this drug at all perioperative stages. In spite of the beneficial effects of the drug on the nervous system, there are potential adverse effects, such as hypotension and bradycardia, which can be treated pharmacologically and must be taken into consideration by clinicians.

Dexmedetomidine Reverses Postoperative Spatial Memory Deficit by Targeting Surf1 and Cytochrome c

Anesthesia and surgery are associated with perioperative neurocognitive disorders (PND). Dexmedetomidine is known to improve PND in rats; however, little is known about the mechanisms. Male Sprague-Dawley rats were subjected to resection of the hepatic apex under propofol anesthesia to clinically mimic human abdominal surgery. The rats were divided into four groups: control group (C), anesthesia group (A), model group (M), and model + dex group (D). Cognitive function was evaluated with the Morris water maze (MWM). Neuronal morphology was observed with H&E staining, Nissl's staining and immunohistochemistry. Transcriptome analysis and quantitative real-time PCR were performed to investigate functional mitochondrial mRNA changes in the hippocampus. Protein levels were measured by Western blotting at 1, 3, and 7 days after surgery. Surgery-induced cognitive decline lasted for three days, but not seven days after surgery in the M group; however, rats in the D group were significantly improved by dexmedetomidine. No significant differences in the number of neurons were observed between the groups after surgery. Rats from the M group showed significantly greater expression levels of Iba-1 and GFAP compared with the C group and the D group. Rats in the M group demonstrated increased Surf1 and Cytochrome c expression on days 1 and 3, but not day 7; similar changes were not induced in rats in the D group. Dexmedetomidine appears to reverse surgery-induced behavior, mitigate the higher density of Iba-1 and GFAP, and downregulate the expression of Surf1 and Cytochrome c protein in the hippocampus of rats in a PND model.

Factors affecting successful use of intranasal dexmedetomidine: a cohort study from a national paediatrics tertiary centre

BACKGROUND

Use of intranasal (IN) dexmedetomidine for procedural sedation has been reported in recent years. Good patient selection is important to ensure high success rates. We aimed to identify factors that influence the successful use of IN dexmedetomidine in non-invasive investigations.

METHODS

All paediatric patients who received IN dexmedetomidine for investigations between 01 July 2019 to 01 July 2020 were included. Baseline demographics, time to reach adequate sedation level, duration of sedation, dose, indications for sedation and need for rescue sedatives were recorded. Procedures were classified into "long" or "short" according to completion time. Successful sedation was defined by completion of investigations by IN dexmedetomidine alone.

RESULTS

Of 105 patients included, median age was 20.0 months, and median weight 11.0 kg. Magnetic resonance imaging (56, 53.3%) was the most common indication. Sixty (57.1%) were successfully sedated using IN dexmedetomidine alone. Automated auditory brainstem response, computerised tomography and mercaptoacetyltriglycine-3 renogram scans had the highest success rate (83.3%, 83.3%, and 100% respectively). On multivariate analysis, short procedures had an adjusted odds ratio of 5.30 (95% CI: 1.69-16.61; P=0.004) compared to long procedures.

CONCLUSIONS

IN dexmedetomidine is effective for procedural sedation for paediatric patients. The most important predictor for sedation success was indication of sedation and duration of procedures.

Effects of dexmedetomidine on the function of distal organs and oxidative stress after lower limb ischaemia-reperfusion in elderly patients undergoing unilateral knee arthroplasty

Aims

This study aims to evaluate the effects of dexmedetomidine on organ function, inflammation response, and oxidative stress in elderly patients following iatrogenic lower limb ischaemia–reperfusion (IR) during unilateral total knee arthroplasty.

Methods

Following unilateral total knee arthroplasty, 54 elderly patients were randomized to receive either intraoperative intravenous injection of dexmedetomidine (n = 27) or equivalent volume of 0.9% saline (n = 27). Blood samples were harvested at 5 minutes before lower limb tourniquet release (baseline); and 1, 6 and 24 hours after tourniquet release. Surrogate markers of cardiac, pulmonary, hepatic and renal function, oxidative stress, inflammatory response, along with parasympathetic and sympathetic activity were recorded and analysed.

Results

The levels of blood xanthine oxidase, creatine kinase, lactic acid and respiratory index increased in patients following tourniquet‐induced lower limb IR injury. Dexmedetomidine administration decreased the respiratory index (P = .014, P = .01, and P = .043) and the norepinephrine level (P < .001) at 1, 6 and 24 hours; and decreased the xanthine oxidase level (P = .049, P < .001) at 6 and 24 hours after tourniquet release compared with the Control group. Other measurements, including creatine kinase isoenzyme, lactate dehydrogenase, creatinine, urea nitrogen, glutamic–oxalacetic transaminase, glutamic–pyruvic transaminase, malondialdehyde, interleukin‐1, interleukin‐6 and tumour necrosis factor‐α, were not statistically significantly different between the 2 groups.

Conclusions

Intraoperative dexmedetomidine administration in elderly patients dampens the deterioration in respiratory function and suppresses the oxidative stress response in elderly patients following iatrogenic lower limb IR injury.

Dexmedetomidine Alleviates Hypoxia-Induced Synaptic Loss and Cognitive Impairment via Inhibition of Microglial NOX2 Activation in the Hippocampus of Neonatal Rats

BACKGROUND

Perinatal hypoxia is a universal cause of death and neurological deficits in neonates worldwide. Activation of microglial NADPH oxidase 2 (NOX2) leads to oxidative stress and neuroinflammation, which may contribute to hypoxic damage in the developing brain. Dexmedetomidine has been reported to exert potent neuroprotection in several neurological diseases, but the mechanism remains unclear. We investigated whether dexmedetomidine acts through microglial NOX2 to reduce neonatal hypoxic brain damage.

METHODS

The potential role of microglial NOX2 in dexmedetomidine-mediated alleviation of hypoxic damage was evaluated in cultured BV2 microglia and neonatal rats subjected to hypoxia. In vivo, neonatal rats received dexmedetomidine (25 μg/kg, i.p.) 30 min before or immediately after hypoxia (5% O2, 2 h). Apocynin-mediated NOX inhibition and lentivirus-mediated NOX2 overexpression were applied to further assess the involvement of microglial NOX2 activation.

RESULTS

Pre- or posttreatment with dexmedetomidine alleviated hypoxia-induced cognitive impairment, restored damaged synapses, and increased postsynaptic density-95 and synaptophysin protein expression following neonatal hypoxia. Importantly, dexmedetomidine treatment suppressed hypoxia-induced microglial NOX2 activation and subsequent oxidative stress and the neuroinflammatory response, as reflected by reduced 4-hydroxynonenal and ROS accumulation, and decreased nuclear NF-κB p65 and proinflammatory cytokine levels in cultured BV2 microglia and the developing hippocampus. In addition, treating primary hippocampal neurons with conditioned medium (CM) from hypoxia-activated BV2 microglia resulted in neuronal damage, which was alleviated by CM from dexmedetomidine-treated microglia. Moreover, the neuroprotective effect of dexmedetomidine was reversed in NOX2-overexpressing BV2 microglia and diminished in apocynin-pretreated neonatal rats.

CONCLUSION

Dexmedetomidine targets microglial NOX2 to reduce oxidative stress and neuroinflammation and subsequently protects against hippocampal synaptic loss following neonatal hypoxia.

Changes in Plasma Glial Fibrillary Acidic Protein in Children Receiving Sevoflurane Anesthesia: A Preliminary Randomized Trial

We investigated changes in plasma glial fibrillary acidic protein concentration during sevoflurane anesthesia induction in children < 3 years old and determined the effect of co-administering dexmedetomidine. This preliminary randomized trial included 60 pediatric patients who received sevoflurane anesthesia for >3 h. Patients were assigned to dexmedetomidine or control groups at a 1:1 ratio. The primary outcome was changes in plasma glial fibrillary acidic protein concentration of dexmedetomidine and control groups over time. Fifty-five patients were included in the final analysis. The median (interquartile range (IQR)) of the plasma glial fibrillary acidic protein level was 387.7 (298.9-510.8) pg·mL-1 immediately after anesthetic induction, 302.6 (250.9-412.5) pg·mL-1 at 30 min, and 321.9 (233.8-576.2) pg·mL-1 at 180 min after the first sample. These values did not change over time (p = 0.759). However, plasma glial fibrillary acidic protein increased after 180 min of infusion of dexmedetomidine compared with values at 30 min infusion (p = 0.04, mean difference and 95% confidence interval of 221.6 and 2.2 to 441.0 pg·mL-1). In conclusion, three hours of sevoflurane anesthesia in pediatric patients < 3 years old did not provoke neuronal injury assessed by the plasma biomarker. Further studies regarding the effect of prolonged dexmedetomidine infusion on anesthetic neuronal injury are required.

Dexmedetomidine inhibits the PSD95-NMDA receptor interaction to promote functional recovery following traumatic brain injury

The present study examined the effects of dexmedetomidine (Dex) on cognitive and motor recovery in mice following traumatic brain injury (TBI). TBI induces synaptic damage, which leads to motor dysfunction and cognitive decline. Although Dex is known to induce neuroprotection, its role following TBI remains unknown. In the present study, male C57BL/6 mice (8 weeks old; n=72) were subjected to cortical impact injury to generate a TBI mice model. Mice were divided into four groups: TBI, sham, TBI + vehicle, and TBI + Dex. Mice in the TBI + vehicle and TBI + Dex groups received intraperitoneal injections of saline (n=18) and 100 µg/kg Dex (n=18), respectively, at 1 and 12 h following surgery. At 24 h post-injury, 10 animals from each group were sacrificed, and brain tissue was isolated for Fluoro-Jade B staining and RNA and protein extraction. At 72 h post-TBI, motor function was evaluated. Furthermore, cognitive impairment was assessed between day 14 and 19 using the Morris water maze. The results demonstrated that the mRNA and protein expression of post-synaptic density 95 (PSD95) was reduced post-TBI. In addition, neuronal degeneration was evaluated using FJB staining, where PSD95 formed a complex with the N-methyl-D-aspartic acid (NMDA) receptor subunit (NR2B) and neuronal nitric oxide synthase (nNOS) inducing neuronal death post-TBI. Treatment with Dex efficiently decreased the PSD95-NR2B-nNOS interaction, which reduced the TBI-induced neuronal death. Furthermore, Dex treatment contributed to the enhanced cognitive and motor recovery following TBI. The results from the present study reported a potential mechanistic action of Dex treatment post-TBI, which may be associated with the inhibition of PSD95-NMDA interaction.

Dexmedetomidine: What's New for Pediatrics? A Narrative Review

Over the past few years, despite the lack of approved pediatric labelling, dexmedetomidine’s (DEX) use has become more prevalent in pediatric clinical practice as well as in research trials. Its respiratory-sparing effects and bioavailability by various routes are only some of the valued features of DEX. In recent years the potential organ-protective effects of DEX, with the possibility for preserving neurocognitive function, has put it in the forefront of clinical and bench research. This comprehensive review focused on the pediatric literature but presents relevant, supporting adult and animal studies in order to detail the recent growing body of literature around the pharmacology, end-organ effects, organ-protective effects, alternative routes of administration, synergetic effects, and clinical applications, with considerations for the future.

The clinical effect of dexmedetomidine combined with parecoxib sodium on sedation, antianxiety and prevention of intubation stress in patients undergoing functional endoscopic sinus surgery: a randomised controlled trial

Background

To investigate the effect of intravenous injection of dexmedetomidine combined with parecoxib sodium on sedation and anxiety and stress response of tracheal intubation in patients undergoing functional endoscopic sinus surgery.

Methods

One hundred twenty patients undergoing endoscopic sinus surgery were randomly divided into four groups: group DP, group D, group P and group N. The blood pressure (BP), heart rate (HR), blood oxygen saturation (SPO2), EEG, bispectral index (BIS), Ramsay sedation score and state anxiety questionnaire (SAI) were recorded before administration (T0), 10 min (T1), 20 min (T2) and 30 min (T3) after administration. After 30 min, endotracheal intubation was performed after anesthesia induction. The BP, HR, SPO2 were recorded 1 min before intubation (T4), intubation (T5), 3 min (T6) after intubation, 5 min (T7) after intubation, and blood samples were collected from patients before administration and after intubation 2 min to detect serum cortisol (Cor), adrenalin (E) norepinephrine (NE) and blood glucose (BS).

Results

There was no significant difference in Ramsay sedation score before anesthesia, but the Ramsay sedation score in group D、DP was significantly higher than that in group P and group N, the BIS, BP, HR and anxiety scores were significantly lower than those in the group P and group N (p < 0.05). There was no significant difference in Ramsay sedation score, BIS value, anxiety score and BP, HR between group D and group DP (p > 0.05). Compared with T4, there was no significant difference in BIS and BP, HR in group D, group DP and group P (p > 0.05), but the BIS, BP and HR in group N were significantly higher than T4, (p < 0.05). Three minutes after intubation there was no statistical difference in the changes of Cor, E, NE and BS values compared with before intubation in group P and group DP (p > 0.05), but the changes of Cor, E, NE and BS values were significantly lower than that in group N (p < 0.05). Compared with T0, the values of NE, E, Cor, BS decreased in group D, DP and P at T4, group DP decreased more significantly than group D (p < 0.05). while the NE, E, Cor, BS of T6 are at the same level as the base value. In group N, the NE, E, Cor, BS of T4 were at the same level of T0, but significantly higher at T6.And at T6, NE and E in group D, P and N were significantly different from those in group DP (p < 0.05).

Conclusion

Preoperative intravenous infusion of dexmedetomidine combined with parecoxib sodium by functional nasal endoscopy can not only calm and resist anxiety, but also better prevent stress response of endotracheal intubation, which is a safe and effective way of preoperative medication.

Trial registration

ChiCTR-OPN-17010444. Prospectively registered on 16 January 2017.

Dexmedetomidine Inhibits Neuroinflammation by Altering Microglial M1/M2 Polarization Through MAPK/ERK Pathway

Neuroinflammation is critical in the pathogenesis of neurological diseases. Microglial pro-inflammatory (M1) and anti-inflammatory (M2) status determines the outcome of neuroinflammation. Dexmedetomidine exerts anti-inflammatory effects in many neurological conditions. Whether dexmedetomidine functions via modulation of microglia M1/M2 polarization remains to be fully elucidated. In the present study, we investigated the anti-inflammatory effects of dexmedetomidine on the neuroinflammatory cell model and explored the potential mechanism. BV2 cells were stimulated with LPS to establish a neuroinflammatory model. The cell viability was determined with MTT assay. NO levels were assessed using a NO detection kit. The protein levels of IL-10, TNF-α, iNOS, CD206, ERK1/2, and pERK1/2 were quantified using Western blotting. LPS significantly increased pro-inflammatory factors TNF-α and NO, and M1 phenotypic marker iNOS, and decreased anti-inflammatory factor IL-10 and M2 phenotypic marker CD206 in BV2 cells. Furthermore, exposure of BV2 cells to LPS significantly raised pERK1/2 expression. Pretreatment with dexmedetomidine attenuated LPS-elicited changes in p-ERK, iNOS, TNF-α, NO, CD206 and IL-10 levels in BV2 cells. However, co-treatment with dexmedetomidine and LM22B-10, an agonist of ERK, reversed dexmedetomidine-elicited changes in p-ERK, iNOS, TNF-α, NO, CD206 and IL-10 levels in LPS-exposed BV2 cells. We, for the first time, showed that dexmedetomidine increases microglial M2 polarization by inhibiting phosphorylation of ERK1/2, by which it exerts anti-inflammatory effects in BV2 cells.

Calcitriol alleviates global cerebral ischemia-induced cognitive impairment by reducing apoptosis regulated by VDR/ERK signaling pathway in rat hippocampus

BACKGROUND

Vitamin D (VD) has important neuroprotective functions in the central nervous system. However, further exploration is still needed in the neuroprotective effects of VD monomer therapy on global cerebral ischemia (GCI) and its potential molecular mechanism.

OBJECTIVE

To investigate whether calcitriol, a biologically active metabolite of VD, could alleviate cognitive impairment induced by GCI via reducing cell apoptosis and activating the extracellular signal-regulated kinase (ERK) signaling pathway.

METHODS

A total of 145 adult male Sprague Dawley rats were randomly divided into five groups: Sham group (n = 45), GCI group (n = 45), calcitriol treatment group (GCI + calcitriol, n = 45), PD98059 treatment group (n = 5) and vehicle group (n = 5). Morris water maze test was used for evaluating spatial learning and memory functions. Neurological Severity Score and wet-dry weight method were applied to detect neurological deficits and brain water content, respectively. Hematoxylin and eosin staining, transmission electron microscopy, and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end-labeling staining were performed for evaluating the changes of hippocampal CA1 neurons. Immunocytochemistry, immunofluorescence chemistry, and western blot analysis were performed for evaluating the changes of related proteins.

RESULTS

Calcitriol significantly ameliorated the spatial learning and memory impairments, improved neurological function, attenuated brain edema, and improved the morphological defects in the CA1 area of the hippocampus. Besides, calcitriol reduced GCI-induced cell apoptosis and reversed the up-regulation of pro-apoptotic proteins (Caspase-3 and Bax) and the down-regulation of anti-apoptotic protein (Bcl-2). Furthermore, calcitriol also increased the expression of VD receptors (VDR) and activated the ERK signaling pathway. Moreover, the p-ERK1/2 inhibitor PD98059 reversed the effect of calcitriol on the expression of apoptosis-related proteins.

CONCLUSIONS

Calcitriol may have a protective effect against GCI-induced cognitive impairments via inhibition of apoptotic cascade by activating the VDR/ERK signaling pathway.

Effect of intraoperative infusion of dexmedetomidine on postoperative recovery in patients undergoing endovascular interventional therapies: A prospective, randomized, controlled trial

BACKGROUND

Rapid emergence from general anesthesia during endovascular interventional therapies (EITs) is important. However, the solution that improved quality of both analepsia and postoperative recovery after EITs has not been specifically addressed. We conducted this prospective, randomized, controlled trial to evaluate the intraoperative infusion of dexmedetomidine on quality of analepsia and postoperative recovery in patients undergoing EITs.

METHODS

Eighty-six patients undergoing EITs were divided into three groups: RD1 (dexmedetomidine at an initial dose of 0.5 μg/kg for 10 min adjusted to 0.2 μg kg^-1  hr^-1 throughout EIT), RD2 (dexmedetomidine at an initial dose of 0.5 μg/kg for 10 min adjusted to 0.4 μg kg^-1  hr^-1 throughout EIT), and RD3 (dexmedetomidine at an initial dose of 0.5 μg/kg for 10 min adjusted to 0.6 μg kg^-1  hr^-1 throughout EIT). An analgesia system delivered sufentanil only. The primary outcome measure was the total consumption of nimodipine during the first 48 hr after surgery. The secondary outcome measures were sufentanil consumption, pain intensity, hemodynamics, functional activity score (FAS), neurologic examination, level of sedation (LOS), and Bruggrmann comfort scale (BCS). We also recorded the intraoperative hemodynamic data, requirement of narcotic and vasoactive drugs, prevalence of complications and symptomatic cerebral vasospasm, duration of postanesthesia care unit (PACU) stay, Glasgow Outcome Score (GOS) at 3 months, and prevalence of cerebral infarction 30 days after surgery.

RESULTS

Dexmedetomidine application in the regimen RD3 reduced the consumption of the total dose of nimodipine and sufentanil 48 hr after surgery, prevalence of symptomatic cerebral vasospasm, consumption of narcotic drugs and nimodipine during surgery, pain intensity during the first 8 hr after surgery, and increased both BCS during the first 4 hr after surgery and hemodynamic stability. However, the LOS was increased at the 0.5 hr after surgery and surgeon satisfaction score was lower. There were no significant differences among the groups for consumption of vasoactive drugs except urapidil, Glasgow coma scale (GCS) and FAS during the first 48 hr after surgery, GOS at 3 months, and cerebral infarction after 30 days.

CONCLUSIONS

Dexmedetomidine (an initial dose of 0.5 μg/kg for 10 min adjusted to 0.6 μg kg^-1 hr^-1 throughout EIT) could reduce the total consumption of nimodipine and opioid during the first 48 hr after surgery, the concerning adverse effects, and improve pain scores. The optimal dosage of dexmedetomidine during EITs merits further investigation.

Dexmedetomidine: present and future directions

Dexmedetomidine is a potent, highly selective α-2 adrenoceptor agonist, with sedative, analgesic, anxiolytic, sympatholytic, and opioid-sparing properties. Dexmedetomidine induces a unique sedative response, which shows an easy transition from sleep to wakefulness, thus allowing a patient to be cooperative and communicative when stimulated. Dexmedetomidine may produce less delirium than other sedatives or even prevent delirium. The analgesic effect of dexmedetomidine is not strong; however, it can be administered as a useful analgesic adjuvant. As an anesthetic adjuvant, dexmedetomidine decreases the need for opioids, inhalational anesthetics, and intravenous anesthetics. The sympatholytic effect of dexmedetomidine may provide stable hemodynamics during the perioperative period. Dexmedetomidine-induced cooperative sedation with minimal respiratory depression provides safe and acceptable conditions during neurosurgical procedures in awake patients and awake fiberoptic intubation. Despite the lack of pediatric labelling, dexmedetomidine has been widely studied for pediatric use in various applications. Most adverse events associated with dexmedetomidine occur during or shortly after a loading infusion. There are some case reports of dexmedetomidine-related cardiac arrest following severe bradycardia. Some extended applications of dexmedetomidine discussed in this review are promising, but still limited, and further research is required. The pharmacological properties and possible adverse effects of dexmedetomidine should be well understood by the anesthesiologist prior to use. Moreover, it is necessary to select patients carefully and to determine the appropriate dosage of dexmedetomidine to ensure patient safety.

The safety and efficacy of dexmedetomidine versus propofol for patients undergoing endovascular therapy for acute stroke: A prospective randomized control trial

BACKGROUND

It is uncertain if dexmedetomidine has more favorable pharmacokinetic profile than the traditional sedative drug propofol in patients who undergo endovascular therapy for acute stroke. We conducted a prospective randomized control trial to compare the safety and efficacy of dexmedetomidine with propofol for patients undergoing endovascular therapy for acute stroke.

METHODS

A total of 80 patients who met study inclusion criteria were received either propofol (n = 45) or dexmedetomidine (n = 35) between January 2016 and August 2018. We recorded the favorable neurologic outcome (modified Rankin score <3) both at discharge and 3 months after stroke, National Institute of Health Stroke scale (NIHSS) at 48 hours post intervention, modified thrombolysis in myocardial infarction score on digital subtraction angiography, intraprocedural hemodynamics, recovery time, relevant time intervals, satisfaction score of the surgeon, mortality, and complications.

RESULTS

There were no significant differences between the 2 groups (P > .05) with respect to heart rate, respiratory rate, and SPO2 during the procedure. The mean arterial pressure (MAP) was significantly low in the propofol group until 15 minutes after anesthesia was induced. No difference was recorded between the groups at the incidence of fall in MAP >20%, MAP >40% and time spent with MAP fall >20% from baseline MAP. In the propofol group, the time spent with MAP fall >40% from baseline MAP was significantly long (P < .05). Midazolam and fentanyl were similar between the 2 groups (P > .05) that used vasoactive drugs. The time interval from stroke onset to CT room, from stroke onset to groin puncture, and from stroke onset to recanalization/end of the procedure, was not significantly different between the 2 groups (P > .05). The recovery time was longer in the dexmedetomidine group (P < .05). There was no difference between the groups with respect to complications, favorable neurological outcome, and mortality both at hospital discharge and 3 months later, successful recanalization and NIHSS score after 48 hours (P > .05). However, the satisfaction score of the surgeon was higher in the dexmedetomidine group (P < .05).

CONCLUSIONS

Dexmedetomidine was undesirable than propofol as a sedative agent during endovascular therapy in patients with acute stroke for a long-term functional outcome, though the satisfaction score of the surgeon was higher in the dexmedetomidine group.

Dibutyl phthalate-induced activation of ROS and ERK1/2 causes hepatic and renal damage in Kunming mice

Dibutyl phthalate (DBP), a ubiquitous environmental contaminant, has been reported to be involved in hepatic and renal tissue damage. However, the role of DBP in oxidative stress and in extracellular signal-regulated kinase (ERK1/2) pathways remains unclear. To investigate the underlying mechanism, Kunming (KM) mice received daily doses of combinations of 50 mg/kg DBP, 50 mg/kg vitamin E (VitE), and 1 mg/kg PD98059 for 28 consecutive days. Any changes in reactive oxygen species (ROS) and malondialdehyde (MDA) levels, as well as any histopathological alterations in tissues, were observed to assess oxidative stress. In addition, the levels of alanine aminotransferase, aspartate aminotransferase, and albumin in serum were used to evaluate liver function. The levels of creatinine and urea nitrogen in serum were measured to evaluate kidney function. We found that DBP significantly increased oxidative damage and the expression of phosphorylated ERK1/2. Furthermore, pretreatment with the ERK inhibitor PD98059 followed by the antioxidant VitE attenuated the levels of ROS, MDA, ERK1/2 phosphorylation, and DBP-mediated disorders, indicating that the oxidative stress and the ERK1/2 pathways are associated with DBP-induced hepatic and renal dysfunction in KM mice.

Dexmedetomidine for the prevention of delirium in critically ill patients - A protocol for a systematic review

BACKGROUND

Delirium is a common complication in critically ill patients and carries an increased risk of mortality and morbidity. Dexmedetomidine can potentially prevent delirium by diminishing predisposing factors. The evidence regarding the use of dexmedetomidine in preventing delirium is conflicting. This protocol aims to identify the beneficial and harmful effects of dexmedetomidine in the prevention of delirium.

METHODS

This protocol uses the recommendations of the Cochrane Collaboration, the Preferred Report Items of Systematic Reviews with Meta-Analysis Protocols, and the eight-step assessment procedure suggested by Jakobsen and colleagues. We wish to assess in critically ill patients, if dexmedetomidine versus placebo can reduce the incidence of delirium and improve clinical outcomes. We will include all randomised trials assessing the use of dexmedetomidine in the prevention of delirium. To identify trials, we will search the Cochrane Central Register of Controlled Trials, Medical Literature Analysis and Retrieval System Online, Excerpta Medica database, Latin American and Caribbean Health Sciences Literature, Science Citation Index Expanded on Web of Science, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, Chinese Science Journal Database, and BIOSIS. Two authors will screen the literature and extract data. We will use the Cochrane risk of bias tool to evaluate trials. Extracted data will be analysed using Review Manager 5 and Trial Sequential Analysis. We will create a "Summary of Findings"-table in which we will present our primary and secondary outcomes. We will assess the quality of evidence using GRADE.

DISCUSSION

This systematic review can potentially aid clinicians in decision-making and benefit the many critically ill patients at risk of delirium.

Dexmedetomidine for the management of delirium in critically ill patients-A protocol for a systematic review

BACKGROUND

Delirium is a common complication in critically ill patients and carries an increased risk of mortality and morbidity. Dexmedetomidine can potentially treat delirium by diminishing predisposing factors. The evidence regarding the use of dexmedetomidine in the management of delirium is conflicting. This protocol aims to identify the beneficial and harmful effects of dexmedetomidine in the management of delirium.

METHODS

This protocol uses the recommendations of the Cochrane Collaboration, the Preferred Report Items of Systematic reviews with Meta-Analysis Protocols, and the eight-step assessment procedure suggested by Jakobsen and colleagues. We wish to assess in critically ill patients with delirium, if dexmedetomidine vs placebo is effective in managing delirium and improving clinical outcomes. We will include all relevant randomised clinical trials assessing the use of dexmedetomidine in treating delirium. To identify trials, we will search the Cochrane Central Register of Controlled Trials, Medical Literature Analysis and Retrieval System Online, Excerpta Medica database, Latin American and Caribbean Health Sciences Literature, Science Citation Index Expanded on Web of Science, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, Chinese Science Journal Database, and BIOSIS. Two authors will screen the literature and extract data. The Cochrane risk of bias tool will be used to evaluate included trials. Extracted data will be analysed using Review Manager 5 and Trial Sequential Analysis. We will create a 'Summary of Findings'-table in which we will present our primary and secondary outcomes. We will assess the quality of evidence using GRADE assessment.

DISCUSSION

This systematic review can potentially aid clinicians in decision making and benefit the many critically ill patients developing delirium.

Dexmedetomidine Protects Against Neurological Dysfunction in a Mouse Intracerebral Hemorrhage Model by Inhibiting Mitochondrial Dysfunction-Derived Oxidative Stress

BACKGROUND

Intracerebral hemorrhage (ICH) is a subtype of stroke with high disability and mortality. Dexmedetomidine (Dex) has been shown to provide neuroprotection in several neurological diseases. The aim of present study was to investigate the effects of Dex on ICH-induced neurological deficits and brain injury and the underlying mechanisms.

METHODS

ICH mouse model was established by intracerebral injection of autologous blood, followed by Dex or vehicle treatment. Neurological function, brain water content, neuronal activity, and oxidative parameters were determined. The protein expressions of peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α), uncoupling protein 2, and manganese-dependent superoxide dismutase were examined by western blotting.

RESULTS

Dex administration significantly inhibited ICH-induced the memory impairment, dyskinesia, brain edema, and neuron loss. In addition, ICH-induced the increase in brain oxidative stress level was markedly attenuated after Dex treatment, as evidenced by increased glutathione peroxidase and superoxide dismutase levels and reduced malondialdehyde and nitric oxide levels. Compared with vehicle-treated ICH mice, Dex-treated ICH mice showed significantly decreased intracellular reactive oxygen species (ROS) and mitochondrial ROS (mROS) production in brain, but had no effects on the increased nicotinamide-adenine dinucleotide phosphate oxidase activity. However, stimulation of mROS abrogated the inhibitory effects of Dex on neurological deficits and oxidative stress. The decrease in production of adenosine triphosphate and the expressions of PGC-1α, uncoupling protein 2, and manganese-dependent superoxide dismutase induced by ICH was restored by Dex treatment.

CONCLUSIONS

Our results reveal that Dex improves ICH-induced neurological deficits and brain injury by inhibiting PGC-1α pathway inactivation and mitochondrial dysfunction-derived oxidative stress.

Dexmedetomidine attenuates the neurotoxicity of propofol toward primary hippocampal neurons in vitro via Erk1/2/CREB/BDNF signaling pathways

BACKGROUND

Propofol is a commonly used general anesthetic for the induction and maintenance of anesthesia and critical care sedation in children, which may add risk to poor neurodevelopmental outcome. We aimed to evaluate the effect of propofol toward primary hippocampal neurons in vitro and the possibly neuroprotective effect of dexmedetomidine pretreatment, as well as the underlying mechanism.

MATERIALS AND PROCEDURES

Primary hippocampal neurons were cultured for 8 days in vitro and pretreated with or without dexmedetomidine or phosphorylation inhibitors prior to propofol exposure. Cell viability was measured using cell counting kit-8 assays. Cell apoptosis was evaluated using a transmission electron microscope and flow cytometry analyses. Levels of mRNAs encoding signaling pathway intermediates were assessed using qRT-PCR. The expression of signaling pathway intermediates and apoptosis-related proteins was determined by Western blotting.

RESULTS

Propofol significantly reduced cell viability, induced neuronal apoptosis, and downregulated the expression of the BDNF mRNA and the levels of the phospho-Erk1/2 (p-Erk1/2), phospho-CREB (p-CREB), and BDNF proteins. The dexmedetomidine pretreatment increased neuronal viability and alleviated propofol-induced neuronal apoptosis and rescued the propofol-induced downregulation of both the BDNF mRNA and the levels of the p-Erk1/2, p-CREB, and BDNF proteins. However, this neuroprotective effect was abolished by PD98059, H89, and KG501, further preventing the dexmedetomidine pretreatment from rescuing the propofol-induced downregulation of the BDNF mRNA and p-Erk1/2, p-CREB, and BDNF proteins.

CONCLUSION

Dexmedetomidine alleviates propofol-induced cytotoxicity toward primary hippocampal neurons in vitro, which correlated with the activation of Erk1/2/CREB/BDNF signaling pathways.

Neuroanesthesiology Update

This review provides a summary of the literature pertaining to the perioperative care of neurosurgical patients and patients with neurological diseases. General topics addressed in this review include general neurosurgical considerations, stroke, traumatic brain injury, neuromonitoring, neurotoxicity, and perioperative disorders of cognitive function.

Comparison of dexmedetomidine vs. remifentanil combined with sevoflurane during radiofrequency ablation of hepatocellular carcinoma: a randomized controlled trial

BACKGROUND

Remifentanil is widely used for ultrasound-guided percutaneous radiofrequency ablation (RFA) of small hepatocellular carcinoma (HCC). We determined whether dexmedetomidine could be an alternative to remifentanil for RFA of HCC under general anesthesia with sevoflurane.

METHODS

We prospectively randomized patients scheduled to undergo RFA for HCC to a dexmedetomidine (DEX) group or remifentanil (REMI) group (47 patients each). In the DEX group, a bolus infusion (0.4 μg kg^- 1) was started 15 min before anesthesia induction and continued at 0.2 μg kg^- 1 h^- 1 until 10 min before the end of surgery. In the REMI group, 3 μg kg^- 1 h^- 1 of remifentanil was administered from 15 min before anesthesia induction to the end of the surgery. The primary endpoint was postoperative pain intensity. Secondary endpoints included analgesic requirement, postoperative liver function, patient comfort, and hemodynamic changes. Group allocation was concealed from patients and data analysts but not from anesthesiologists.

RESULTS

Postoperative pain intensity, analgesic consumption, comfort, liver function, and time to emergence and extubation did not differ between the two groups. Heart rate, but not mean arterial pressure, was significantly lower in the DEX group than in the REMI group, at 1 min after intubation and from 30 min after the start of the surgery until anesthesia recovery. Sevoflurane concentration and dosage were significantly lower in the DEX group than in the REMI group.

CONCLUSION

During RFA for HCC, low-dose dexmedetomidine reduced the heart rate and need for inhalational anesthetics, without exacerbating postoperative discomfort or liver dysfunction. Although it did not exhibit outstanding advantages over remifentanil in terms of pain management, dexmedetomidine could be a safe alternative adjuvant for RFA under sevoflurane anesthesia.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR-OPC-15006613 . Registered on 16 June 2015.

Dexmedetomidine attenuated early brain injury in rats with subarachnoid haemorrhage by suppressing the inflammatory response: The TLR4/NF-κB pathway and the NLRP3 inflammasome may be involved in the mechanism

Early brain injury (EBI) plays a pivotal role in the prognosis of patients with subarachnoid haemorrhage (SAH). Dexmedetomidine (DEX), a highly selective α₂ receptor agonist, is reported to exert multiple protective effects in many neurological diseases. This study was designed to investigate whether DEX had neuroprotective functions in EBI after SAH, and to explore the possible mechanisms. The SAH model was established by an endovascular perforation in adult male Sprague-Dawley (SD) rats. DEX (25 µg/kg) or vehicle was administered intraperitoneally 2 h after SAH. Neurological deficits, brain oedema, inflammation, BBB damage, and cell apoptosis at 24 h after SAH were evaluated. Additionally, the expression of components of the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) pathway, and the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome were also assessed. We demonstrated that DEX treatment improved neurological scores, alleviated brain oedema, reduced the permeability of the blood-brain barrier (BBB), and up-regulated the expression of tight junction proteins. DEX treatment could reduce the neutrophil infiltration, microglial activation, and pro-inflammatory factor release. In addition, DEX alleviated cell apoptosis at 24 h after SAH. Notably, DEX could also suppress the activation of the TLR4/NF-κB pathway and the NLRP3 inflammasome. These findings suggested that treatment with DEX after SAH attenuated SAH-induced EBI, partially through the suppression of the TLR4/NF-κB pathway and the NLRP3 inflammasome.

Comparative effects of dexmedetomidine, propofol, sevoflurane, and S-ketamine on regional cerebral glucose metabolism in humans: a positron emission tomography study

INTRODUCTION

The highly selective α₂-agonist dexmedetomidine has become a popular sedative for neurointensive care patients. However, earlier studies have raised concern that dexmedetomidine might reduce cerebral blood flow without a concomitant decrease in metabolism. Here, we compared the effects of dexmedetomidine on the regional cerebral metabolic rate of glucose (CMR_glu) with three commonly used anaesthetic drugs at equi-sedative doses.

METHODS

One hundred and sixty healthy male subjects were randomised to EC₅₀ for verbal command of dexmedetomidine (1.5 ng ml^-1; n=40), propofol (1.7 μg ml^-1; n=40), sevoflurane (0.9% end-tidal; n=40) or S-ketamine (0.75 μg ml^-1; n=20) or placebo (n=20). Anaesthetics were administered using target-controlled infusion or vapouriser with end-tidal monitoring. ¹⁸F-labelled fluorodeoxyglucose was administered 20 min after commencement of anaesthetic administration, and high-resolution positron emission tomography with arterial blood activity samples was used to quantify absolute CMR_glu for whole brain and 15 brain regions.

RESULTS

At the time of [F¹⁸]fluorodeoxyglucose injection, 55% of dexmedetomidine, 45% of propofol, 85% of sevoflurane, 45% of S-ketamine, and 0% of placebo subjects were unresponsive. Whole brain CMR_glu was 63%, 71%, 71%, and 96% of placebo in the dexmedetomidine, propofol, sevoflurane, and S-ketamine groups, respectively (P<0.001 between the groups). The lowest CMR_glu was observed in nearly all brain regions with dexmedetomidine (P<0.05 compared with all other groups). With S-ketamine, CMR_glu did not differ from placebo.

CONCLUSIONS

At equi-sedative doses in humans, potency in reducing CMR_glu was dexmedetomidine>propofol>ketamine=placebo. These findings alleviate concerns for dexmedetomidine-induced vasoconstriction and cerebral ischaemia.

CLINICAL TRIAL REGISTRATION

NCT02624401.

Synergistic Interaction Between Dexmedetomidine and Ulinastatin Against Vincristine-Induced Neuropathic Pain in Rats

Antimicrotubulin chemotherapeutic agents such as vincristine (VCR), often induce peripheral neuropathic pain. It is usually permanent and seriously harmful to cancer patients' quality of life and can result in the hampering of clinical treatments. Currently, there is no definitive therapy, and many of the drugs approved for the treatment of other neuropathic pain have shown little or no analgesic effect. It is therefore vital to find new and novel therapeutic strategies for patients suffering from chemotherapeutic agent-induced neuropathic pain to improve patients' quality of life. This study shows that intrathecal injections of dexmedetomidine (DEX), or intraperitoneally administered ulinastatin (UTI) significantly reduces Sprague Dawley rats' mechanical allodynia induced by VCR via upregulation of interleukin-10 expression and activating the α2-adrenergic receptor in dorsal root ganglion (DRG). Moreover, when combined there is a synergistic interaction between DEX and UTI, which acts against VCR-induced neuropathic pain. This synergistic interaction between DEX and UTI may be partly attributed to a common analgesic pathway in which the upregulation of interleukin -10 plays an important role via activating α2-adrenergic receptor in rat dorsal root ganglion. The combined use of DEX and UTI does not affect the rat's blood pressure, heart rate, sedation, motor score, spatial learning, or memory function. All of these show that the combined use of DEX and UTI is an effective method in relieving VCR-induced neuropathic pain in rats.

PERSPECTIVE

This article documents the synergistic interaction between 2 widely used drugs, DEX and UTI, against VCR-induced neuropathic pain. The results provide a potential target and novel drug administrated method for the clinical treatment of chemotherapy-induced peripheral neuropathic pain.

Neuroprotection and neurotoxicity in the developing brain: an update on the effects of dexmedetomidine and xenon

Growing and consistent preclinical evidence, combined with early clinical epidemiological observations, suggest potentially neurotoxic effects of commonly used anesthetic agents in the developing brain. This has prompted the FDA to issue a safety warning for all sedatives and anesthetics approved for use in children under three years of age. Recent studies have identified dexmedetomidine, the potent α2-adrenoceptor agonist, and xenon, the noble gas, as effective anesthetic adjuvants that are both less neurotoxic to the developing brain, and also possess neuroprotective properties in neonatal and other settings of acute ongoing neurologic injury. Dexmedetomidine and xenon are effective anesthetic adjuvants that appear to be less neurotoxic than other existing agents and have the potential to be neuroprotective in the neonatal and pediatric settings. Although results from recent clinical trials and case reports have indicated the neuroprotective potential of xenon and dexmedetomidine, additional randomized clinical trials corroborating these studies are necessary. By reviewing both the existing preclinical and clinical evidence on the neuroprotective effects of dexmedetomidine and xenon, we hope to provide insight into the potential clinical efficacy of these agents in the management of pediatric surgical patients.

Dexmedetomidine-induced neuroprotection: is it translational?

Dexmedetomidine is often used in anesthesia and critical care medicine practice to sedate patients. Its neuroprotective effects have been shown in various ischemic and hemorrhagic brain injury models of animals. Randomized clinical trials have indicated that dexmedetomidine can improve outcome of patients under intensive care. Clinical trials are needed to determine whether dexmedetomidine can provide neuroprotection against ischemic and hemorrhagic stroke.