Dexmedetomidine modulates neuroinflammation and improves outcome via alpha2-adrenergic receptor signaling after rat spinal cord injury

Transplantation of olfactory mucosa mesenchymal stromal cells repairs spinal cord injury by inducing microglial polarization

STUDY DESIGN

Animal studies OBJECTIVES: To evaluate the therapeutic effect of olfactory mucosa mesenchymal stem cell (OM-MSCs) transplantation in mice with spinal cord injury (SCI) and to explore the mechanism by which OM-MSCs inhibit neuroinflammation and improve SCI.

SETTING

Xiangya Hospital, Central South University; Affiliated Hospital of Guangdong Medical University.

METHODS

Mice (C57BL/6, female, 6-week-old) were randomly divided into sham, SCI, and SCI + OM-MSC groups. The SCI mouse model was generated using Allen's method. OM-MSCs were immediately delivered to the lateral ventricle after SCI using stereotaxic brain injections. One day prior to injury and on days 1, 5, 7, 14, 21, and 28 post-injury, the Basso Mouse Scale and Rivlin inclined plate tests were performed. Inflammation and microglial polarization were evaluated using histological staining, immunofluorescence, and qRT-PCR.

RESULTS

OM-MSCs originating from the neuroectoderm have great potential in the management of SCI owing to their immunomodulatory effects. OM-MSCs administration improved motor function, alleviated inflammation, promoted the transformation of the M1 phenotype of microglia into the M2 phenotype, facilitated axonal regeneration, and relieved spinal cord injury in SCI mice.

CONCLUSIONS

OM-MSCs reduced the level of inflammation in the spinal cord tissue, protected neurons, and repaired spinal cord injury by regulating the M1/M2 polarization of microglia.

Dexmedetomidine attenuates acute stress-impaired learning and memory in mice by maintaining the homeostasis of intestinal flora

Dexmedetomidine (Dex) has been used in surgery to improve patients' postoperative cognitive function. However, the role of Dex in stress-induced anxiety-like behaviors and cognitive impairment is still unclear. In this study, we tested the role of Dex in anxiety-like behavior and cognitive impairment induced by acute restrictive stress and analyzed the alterations of the intestinal flora to explore the possible mechanism. Behavioral and cognitive tests, including open field test, elevated plus-maze test, novel object recognition test, and Barnes maze test, were performed. Intestinal gut Microbe 16S rRNA sequencing was analyzed. We found that intraperitoneal injection of Dex significantly improved acute restrictive stress-induced anxiety-like behavior, recognition, and memory impairment. After habituation in the environment, mice (male, 8 weeks, 18-23 g) were randomly divided into a control group (control, N = 10), dexmedetomidine group (Dex, N = 10), AS with normal saline group (AS + NS, N = 10) and AS with dexmedetomidine group (AS + Dex, N = 10). By the analysis of intestinal flora, we found that acute stress caused intestinal flora disorder in mice. Dex intervention changed the composition of the intestinal flora of acute stress mice, stabilized the ecology of the intestinal flora, and significantly increased the levels of Blautia (A genus of anaerobic bacteria) and Coprobacillus. These findings suggest that Dex attenuates acute stress-impaired learning and memory in mice by maintaining the homeostasis of intestinal flora.

ATF3 is a neuron-specific biomarker for spinal cord injury and ischaemic stroke

BACKGROUND

Although many molecules have been investigated as biomarkers for spinal cord injury (SCI) or ischemic stroke, none of them are specifically induced in central nervous system (CNS) neurons following injuries with low baseline expression. However, neuronal injury constitutes a major pathology associated with SCI or stroke and strongly correlates with neurological outcomes. Biomarkers characterized by low baseline expression and specific induction in neurons post-injury are likely to better correlate with injury severity and recovery, demonstrating higher sensitivity and specificity for CNS injuries compared to non-neuronal markers or pan-neuronal markers with constitutive expressions.

METHODS

In animal studies, young adult wildtype and global Atf3 knockout mice underwent unilateral cervical 5 (C5) SCI or permanent distal middle cerebral artery occlusion (pMCAO). Gene expression was assessed using RNA-sequencing and qRT-PCR, while protein expression was detected through immunostaining. Serum ATF3 levels in animal models and clinical human samples were measured using commercially available enzyme-linked immune-sorbent assay (ELISA) kits.

RESULTS

Activating transcription factor 3 (ATF3), a molecular marker for injured dorsal root ganglion sensory neurons in the peripheral nervous system, was not expressed in spinal cord or cortex of naïve mice but was induced specifically in neurons of the spinal cord or cortex within 1 day after SCI or ischemic stroke, respectively. Additionally, ATF3 protein levels in mouse blood significantly increased 1 day after SCI or ischemic stroke. Importantly, ATF3 protein levels in human serum were elevated in clinical patients within 24 hours after SCI or ischemic stroke. Moreover, Atf3 knockout mice, compared to the wildtype mice, exhibited worse neurological outcomes and larger damage regions after SCI or ischemic stroke, indicating that ATF3 has a neuroprotective function.

CONCLUSIONS

ATF3 is an easily measurable, neuron-specific biomarker for clinical SCI and ischemic stroke, with neuroprotective properties.

HIGHLIGHTS

ATF3 was induced specifically in neurons of the spinal cord or cortex within 1 day after SCI or ischemic stroke, respectively. Serum ATF3 protein levels are elevated in clinical patients within 24 hours after SCI or ischemic stroke. ATF3 exhibits neuroprotective properties, as evidenced by the worse neurological outcomes and larger damage regions observed in Atf3 knockout mice compared to wildtype mice following SCI or ischemic stroke.

The effect of dexmedetomidine on postoperative wound healing in neurosurgical patients: A meta-analysis

This meta-analysis investigates the effect of dexmedetomidine on postoperative wound healing in neurosurgical patients. A thorough literature search resulted in the selection of seven studies from an initial pool of 1546 records. The analysis focused on wound healing outcomes, evaluated by the Redness, Oedema, Ecchymosis, Discharge, Approximation (REEDA) scale and the Manchester Scar Scale (MSS). Results indicated significant improvements in the dexmedetomidine group: the REEDA scale scores at day seven post-surgery showed a Standardized Mean Difference group (SMD = -16.18, 95% CI: [-22.30, -10.06], p < 0.01), and the MSS scores at 3 months post-operation demonstrated an (SMD = -8.95, 95% CI: [-14.27, -3.62], p < 0.01). These findings suggest that dexmedetomidine may enhance wound healing and reduce scar formation in neurosurgical patients. Bias assessment indicated a low risk of bias across the studies.

Activating astrocytic α2A adrenoceptors in hippocampus reduces glutamate toxicity to attenuate sepsis-associated encephalopathy in mice

BACKGROUND

Glutamate metabolism disorder is an important mechanism of sepsis-associated encephalopathy (SAE). Astrocytes regulate glutamate metabolism. In septic mice, α2A adrenoceptor (α2A-AR) activation in the central nervous system provides neuroprotection. α2A-ARs are expressed abundantly in hippocampal astrocytes. This study was performed to determine whether hippocampal astrocytic α2A-AR activation confers neuroprotection against SAE and whether this protective effect is astrocyte specific and achieved by the modulation of glutamate metabolism.

METHODS

Male C57BL/6 mice with and without α2A-AR knockdown were subjected to cecal ligation and puncture (CLP). They were treated with intrahippocampal guanfacine (an α2A-AR agonist) or intraperitoneal dexmedetomidine in the presence or absence of dihydrokainic acid [DHK; a glutamate transporter 1 (GLT-1) antagonist] and/or UCPH-101 [a glutamate/aspartate transporter (GLAST) antagonist]. Hippocampal tissue was collected for the measurement of astrocyte reactivity, GLT-1 and GLAST expression, and glutamate receptor subunit 2B (GluN2B) phosphorylation. In vivo real-time extracellular glutamate concentrations in the hippocampus were measured by ultra-performance liquid chromatography tandem mass spectrometry combined with microdialysis, and in vivo real-time hippocampal glutamatergic neuron excitability was assessed by calcium imaging. The mice were subjected to the Barnes maze and fear conditioning tests to assess their learning and memory. Golgi staining was performed to assess changes in the hippocampal synaptic structure. In vitro, primary astrocytes with and without α2A-AR knockdown were stimulated with lipopolysaccharide (LPS) and treated with guanfacine or dexmedetomidine in the presence or absence of 8-bromo- cyclic adenosine monophosphate (8-Br-cAMP, a cAMP analog). LPS-treated primary and BV2 microglia were also treated with guanfacine or dexmedetomidine. Astrocyte reactivity, PKA catalytic subunit, GLT-1 an GLAST expression were determined in primary astrocytes. Interleukin-1β, interleukin-6 and tumor necrosis factor-alpha in the medium of microglia culture were measured.

RESULTS

CLP induced synaptic injury, impaired neurocognitive function, increased astrocyte reactivity and reduced GLT-1 and GLAST expression in the hippocampus of mice. The extracellular glutamate concentration, phosphorylation of GluN2B at Tyr-1472 and glutamatergic neuron excitability in the hippocampus were increased in the hippocampus of septic mice. Intraperitoneal dexmedetomidine or intrahippocampal guanfacine administration attenuated these effects. Hippocampal astrocytes expressed abundant α2A-ARs; expression was also detected in neurons but not microglia. Specific knockdown of α2A-ARs in hippocampal astrocytes and simultaneous intrahippocampal DHK and UCPH-101 administration blocked the neuroprotective effects of dexmedetomidine and guanfacine. Intrahippocampal administration of DHK or UCPH-101 alone had no such effect. In vitro, guanfacine or dexmedetomidine inhibited astrocyte reactivity, reduced PKA catalytic subunit expression, and increased GLT-1 and GLAST expression in primary astrocytes but not in primary astrocytes that received α2A-AR knockdown or were treated with 8-Br-cAMP. Guanfacine or dexmedetomidine inhibited microglial reactivity in BV2 but not primary microglia.

CONCLUSIONS

Our results suggest that neurocognitive protection against SAE after hippocampal α2A-AR activation is astrocyte specific. This protection may involve the inhibition of astrocyte reactivity and alleviation of glutamate neurotoxicity, thereby reducing synaptic injury. The cAMP/protein kinase A (PKA) signaling pathway is a potential cellular mechanism by which activating α2A-AR modulates astrocytic function.

Clinical study of the combined use of dexmedetomidine and remifentanil in patients with coronary heart disease undergoing 3D laparoscopic surgery with EEG bispectral index monitoring

OBJECTIVE

This study sought to investigate the safety and clinical outcomes associated with the combined administration of dexmedetomidine (Dex) and remifentanil (Rem) in patients with coronary heart disease undergoing three-dimensional (3D) laparoscopic surgery, with concurrent monitoring of the electroencephalography (EEG) bispectral index.

METHODS

This study is of a retrospective nature and involved a total of 60 patients with coronary heart disease who underwent 3D laparoscopic surgery at our hospital between June 2020 and September 2021. In a double-blind manner, these patients were randomly assigned to two groups: the control group (Group I), which consisted of 30 patients, and the treatment group (Group II) receiving a combination of Dex and Rem, also comprising 30 patients. The study's primary objective was to compare and assess the treatment outcomes in these two patient groups.

RESULTS

Patients in Group II who developed postoperative coronary heart disease experienced a significant reduction in blood pressure, heart rate, and electrocardiogram values (P<0.05). Additionally, Group II exhibited lower bispectral index (BIS) and visual analog scale (VAS) values (P<0.05).

CONCLUSION

In patients with coronary heart disease undergoing 3D laparoscopic surgery, the intraoperative use of Dex combined with Rem anesthesia offers several advantages. It helps stabilize hemodynamics, reducing the risk of myocardial ischemia, and significantly alleviates postoperative pain, all without increasing the likelihood of adverse postoperative reactions. Furthermore, this approach effectively dampens the intraoperative and postoperative stress response, facilitating enhanced recovery after surgery (ERAS). Overall, the clinical impact is positive, safe, and reliable.

Major Publications in the Critical Care Pharmacotherapy Literature: 2022

OBJECTIVES

A number of trials related to critical care pharmacotherapy were published in 2022. We aimed to summarize the most influential publications related to the pharmacotherapeutic care of critically ill patients in 2022.

DATA SOURCES

PubMed/Medical Literature Analysis and Retrieval System Online and the Clinical Pharmacy and Pharmacology Pharmacotherapy Literature Update.

STUDY SELECTION

Randomized controlled trials, prospective studies, or systematic review/meta-analyses of adult critically ill patients assessing a pharmacotherapeutic intervention and reporting clinical endpoints published between January 1, 2022, and December 31, 2022, were included in this article.

DATA EXTRACTION

Articles from a systematic search and the Clinical Pharmacy and Pharmacology Pharmacotherapy Literature Update were included and stratified into clinical domains based upon consistent themes. Consensus was obtained on the most influential publication within each clinical domain utilizing an a priori defined three-round modified Delphi process with the following considerations: 1) overall contribution to scientific knowledge and 2) novelty to the literature.

DATA SYNTHESIS

The systematic search and Clinical Pharmacy and Pharmacology Pharmacotherapy Literature Update yielded a total of 704 articles, of which 660 were excluded. The remaining 44 articles were stratified into the following clinical domains: emergency/neurology, cardiovascular, gastroenterology/fluids/nutrition, hematology, infectious diseases/immunomodulation, and endocrine/metabolic. The final article selected from each clinical domain was summarized following a three-round modified Delphi process and included three randomized controlled trials and three systematic review/meta-analyses. Article topics summarized included dexmedetomidine versus other sedatives during mechanical ventilation, beta-blocker treatment in the critically ill, restriction of IV fluids in septic shock, venous thromboembolism prophylaxis in critically ill adults, duration of antibiotic therapy for Pseudomonas aeruginosa ventilator-associated pneumonia, and low-dose methylprednisolone treatment in severe community-acquired pneumonia.

CONCLUSIONS

This concise review provides a perspective on articles published in 2022 that are relevant to the pharmacotherapeutic care of critically ill patients and their potential impact on clinical practice.

Dexmedetomidine attenuates sleep deprivation-induced inhibition of hippocampal neurogenesis via VEGF-VEGFR2 signaling and inhibits neuroinflammation

Long periods of sleep deprivation (SD) have serious effects on health. While the α2 adrenoceptor agonist dexmedetomidine (DEX) can improve sleep quality for patients who have insomnia, the effect of DEX on cognition and mechanisms after SD remains elusive. C57BL/6 mice were subjected to 20 h SD daily for seven days. DEX (100 μg/kg) was administered intravenously twice daily (at 1:00 p.m. and 3:00 p.m.) during seven days of SD. We found that systemic administration of DEX attenuated cognitive deficits by performing the Y maze and novel object recognition tests and increased DCX+, SOX2+, Ki67+, and BrdU+NeuN+/NeuN+ cell numbers in the dentate gyrus (DG) region of SD mice by using immunofluorescence, western blotting, and BrdU staining. DEX did not reverse the decrease in DCX+, SOX2+, or Ki67+ cell numbers in SD mice after administration of the α2A-adrenoceptor antagonist BRL-44408. Furthermore, the vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR2) expression was upregulated in SD+DEX mice compared with SD mice. Luminex analysis showed that the neurogenic effects of DEX were possibly related to the inhibition of neuroinflammation, including IL-1α, IL-2, CCL5, and CXCL1. Our results suggested that DEX alleviated the impaired learning and memory of SD mice potentially by inducing hippocampal neurogenesis via the VEGF-VEGFR2 signaling pathway and by suppressing neuroinflammation, and α2A adrenoceptors are required for the neurogenic effects of DEX after SD. This novel mechanism may add to our knowledge of DEX in the clinical treatment of impaired memory caused by SD.

Dexmedetomidine mediates the mechanism of action of ferroptosis in mice with Alzheimer's disease by regulating the mTOR-TFR1 pathway

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disorder, and there are currently no effective drugs to delay progression of the disease. Ferroptosis may play a vital part in AD, and is therefore receiving increasing attention by researchers.

AIM

To investigate the effects of dexmedetomidine (Dex) on ferroptosis in AD mouse hippocampus.

METHODS

Hippocampal neurons (HNs) HT22 were induced by amyloid β-protein (Aβ) and both in vitro and in vivo AD mouse models were prepared via injections. The cell-counting kit-8 assay and immunofluorescence technique were adopted to determine cell proliferation activity and intracellular Fe2+ levels, and the TBA method and microplate method were employed for malondialdehyde and glutathione measurements, respectively. Hippocampal tissue damage was determined using hematoxylin and eosin and Nissl staining. Mouse learning and memory ability in each group was assessed by the Morris water maze test, and the expression levels of mammalian target of rapamycin (mTOR) signal molecules and ferroptosis-related proteins transferrin receptor 1 (TFR1), SLC7A11 and glutathione peroxidase 4 were examined by western blotting.

RESULTS

Dex enhanced lipid peroxidation and iron influx in mouse HNs in both in vitro and in vivo experiments, while inhibition of the mTOR axis blocked this process. These findings demonstrate that Dex can inhibit ferroptosis-induced damage in mouse HNs by activating mTOR-TFR1 signaling to regulate ferroptosis-associated proteins, thus alleviating cognitive dysfunction in AD mice.

CONCLUSION

Dex can activate the mTOR-TFR1 axis to inhibit ferroptosis in mouse HNs, thereby improving the learning and memory ability of mice.

Automated phenotyping of postoperative delirium-like behaviour in mice reveals the therapeutic efficacy of dexmedetomidine

Postoperative delirium (POD) is a complicated and harmful clinical syndrome. Traditional behaviour analysis mostly focuses on static parameters. However, animal behaviour is a bottom-up and hierarchical organizational structure composed of time-varying posture dynamics. Spontaneous and task-driven behaviours are used to conduct comprehensive profiling of behavioural data of various aspects of model animals. A machine-learning based method is used to assess the effect of dexmedetomidine. Fourteen statistically different spontaneous behaviours are used to distinguish the non-POD group from the POD group. In the task-driven behaviour, the non-POD group has greater deep versus shallow investigation preference, with no significant preference in the POD group. Hyperactive and hypoactive subtypes can be distinguished through pose evaluation. Dexmedetomidine at a dose of 25 μg kg-1 reduces the severity and incidence of POD. Here we propose a multi-scaled clustering analysis framework that includes pose, behaviour and action sequence evaluation. This may represent the hierarchical dynamics of delirium-like behaviours.

As an inhibitor of norepinephrine release, dexmedetomidine provides no improvement on stroke-associated pneumonia in mice

Background: Dexmedetomidine (DEX) is commonly employed as a sedative agent to attenuate sympathetic tone and reduce norepinephrine (NE) levels. In the context of stroke-associated pneumonia (SAP), which is believed to arise from heightened sympathetic nervous system activity and elevated NE release, the precise influence of DEX remains uncertain. Methods: In this study, we generated an SAP model using middle cerebral artery occlusion (MCAO) and examined NE levels, immunological statuses in the brain and periphery, pneumonia symptoms, and extent of infarction. We aimed to determine the effects of DEX on SAP and explore the underlying. Despite its potential to reduce NE levels, DEX did not alleviate SAP symptoms or decrease the infarct area. Interestingly, DEX led to an increase in spleen size and spleen index. Furthermore, we observed a decrease in the CD3+ T cell population in both the blood and brain, but an increase in the spleen following DEX administration. The precise mechanism linking decreased CD3+ T cells and DEX's role in SAP requires further investigation. Conclusion: The clinical use of DEX in stroke patients should be approached with caution, considering its inability to alleviate SAP symptoms and reduce the infarct area. Further research is necessary to fully understand the relationship between decreased CD3+ T cells and DEX's influence on SAP.

Dexmedetomidine suppresses hippocampal astrocyte pyroptosis in cerebral hypoxic-ischemic neonatal rats by upregulating microRNA-148a-3p to inactivate the STAT/JMJD3 axis

OBJECTIVE

Dexmedetomidine (DEX), a selective α2-adrenoceptor agonist, is an anesthetic and sedative agent and has been reported to confer neuroprotective effects after cerebral hypoxic ischemia (CHI). This study was undertaken to elucidate the mechanisms by which microRNA (miR)-148a-3p is involved in the neuroprotective effect of DEX on hypoxic-ischemic brain damage in neonatal rats.

METHODS

Neonatal rats were exposed to CHI conditions, a miR-148a-3p inhibitor, and DEX. Hippocampal astrocytes were isolated to construct an oxygen-glucose deprivation (OGD) model. qRT-PCR and western blot were utilized to inspect miR-148a-3p, STAT1, STAT3, JMJD3, cleaved-Caspase-1, ASC, NLRP3, GSDMD, and GSDMD-N expression in rats and astrocytes. TUNEL staining was employed to measure astrocyte apoptosis rate, immunofluorescence to inspect cleaved-Caspase-1 and ASC levels, and ELISA to determine IL-1β and IL-18 expression. The target genes of miR-148a-3p were predicted using online software and verified by a dual-luciferase reporter gene assay.

RESULTS

A prominent increase in astrocyte apoptosis rate and the expression of pyroptosis- and inflammation-related factors were found in rats with CHI and OGD-treated astrocytes. DEX suppressed astrocyte apoptosis rate and decreased expression of pyroptosis- and inflammation-related factors. Knockdown of miR-148a-3p facilitated astrocyte pyroptosis, indicating that DEX exerted its protective effect by upregulating miR-148a-3p. miR-148a-3p negatively mediated STAT to inactivate JMJD3. Overexpression of STAT1 and STAT3 facilitated pyroptosis in astrocytes, which was negated by the overexpression of miR-148a-3p.

CONCLUSION

DEX inhibited hippocampal astrocyte pyroptosis by upregulating miR-148a-3p to inactivate the STAT/JMJD3 axis, thereby alleviating cerebral damage in neonatal rats with CHI.

ERAS Protocol Options for Perioperative Pain Management of Substance Use Disorder in the Ambulatory Surgical Setting

Even prior to the COVID-19 pandemic, rates of ambulatory surgeries and ambulatory patients presenting with substance use disorder were increasing, and the end of lockdown has further catalyzed the increasing rates of ambulatory patients presenting for surgery with substance use disorder (SUD). Certain subspecialty groups of ambulatory procedures have already established protocols to optimize early recovery after surgery (ERAS), and these groups have subsequently enjoyed improved efficiency and reduced adverse outcomes as a result. In this present investigation, we review the literature as it relates to substance use disorder patients, with a particular focus on pharmacokinetic and pharmacodynamic profiles, and their resulting impact on the acute- or chronic user ambulatory patient. The systematic literature review findings are organized and summarized. We conclude by identifying areas of opportunity for further study, specifically with the aim of developing a dedicated ERAS protocol for substance use disorder patients in the ambulatory surgery setting. - Healthcare in the USA has seen an increase in rates of both substance use disorder patients and separately in ambulatory surgery cases. - Specific perioperative protocols to optimize outcomes for patients who suffer from substance use disorder have been described in recent years. - Agents of interest like opioids, cannabis, and amphetamines are the top three most abused substances in North America. - A protocol and recommend further work should be done to integrate with concrete clinical data, in which strategies should be employed to confer benefits to patient outcomes and hospital quality metrics like those enjoyed by ERAS protocol in other settings.

Dexmedetomidine alleviates host ADHD-like behaviors by reshaping the gut microbiota and reducing gut-brain inflammation

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent psychiatric disorders that affects children and even continues into adulthood. Dexmedetomidine (DEX), a short-term sedative, can selectively activate the α2-adrenoceptor. Treatment with α2-adrenergic agonists in patients with ADHD is becoming increasingly common. However, the therapeutic potential of DEX for the treatment of ADHD is unknown. Here, we evaluated the effect of DEX on ADHD-like behavior in spontaneously hypertensive rats (SHRs), a widely used animal model of ADHD. DEX treatment ameliorated hyperactivity and spatial working memory deficits and normalized θ electroencephalogram (EEG) rhythms in SHRs. We also found that DEX treatment altered the gut microbiota composition and promoted the enrichment of beneficial gut bacterial genera associated with anti-inflammatory effects in SHRs. The gut pathological scores and permeability and the level of inflammation observed in the gut and brain were remarkably improved after DEX administration. Moreover, transplantation of fecal microbiota from DEX-treated SHRs produced effects that mimicked the therapeutic effects of DEX administration. Therefore, DEX is a promising treatment for ADHD that functions by reshaping the composition of the gut microbiota and reducing inflammation in the gut and brain.

Adrenoceptors as potential target for add-on immunomodulatory therapy in multiple sclerosis

This review summarizes recent findings related to the role of the sympathetic nervous system (SNS) in pathogenesis of multiple sclerosis (MS) and its commonly used experimental model - experimental autoimmune encephalomyelitis (EAE). They indicate that noradrenaline, the key end-point mediator of the SNS, acting through β-adrenoceptor, has a contributory role in the early stages of MS/EAE development. This stage is characterized by the SNS hyperactivity (increased release of noradrenaline) reflecting the net effect of different factors, such as the disease-associated inflammation, stress, vitamin D hypovitaminosis, Epstein-Barr virus infection and dysbiosis. Thus, the administration of propranolol, a non-selective β-adrenoceptor blocker, readily crossing the blood-brain barrier, to experimental rats before the autoimmune challenge and in the early (preclinical/prodromal) phase of the disease mitigates EAE severity. This phenomenon has been ascribed to the alleviation of neuroinflammation (due to attenuation of primarily microglial activation/proinflammatory functions) and the diminution of the magnitude of the primary CD4+ T-cell autoimmune response (the effect associated with impaired autoantigen uptake by antigen presenting cells and their migration into draining lymph nodes). The former is partly related to breaking of the catecholamine-dependent self-amplifying microglial feed-forward loop and the positive feedback loop between microglia and the SNS, leading to down-regulation of the SNS hyperactivity and its enhancing influence on microglial activation/proinflammatory functions and the magnitude of autoimmune response. The effects of propranolol are shown to be more prominent in male EAE animals, the phenomenon important as males (like men) are likely to develop clinically more severe disease. Thus, these findings could serve as a firm scientific background for formulation of a new sex-specific immune-intervention strategy for the early phases of MS (characterized by the SNS hyperactivity) exploiting anti-(neuro)inflammatory and immunomodulatory properties of propranolol and other relatively cheap and safe adrenergic drugs with similar therapeutic profile.

MicroRNA-451 Attenuates the Inflammatory Response of Activated Microglia by Downregulating Nucleotide Binding Oligomerization Domain-Like Receptor Protein 3

BACKGROUND

Spinal cord injury is the most common problem encountered during spinal surgery. After the initial trauma, the disruption of the blood-brain barrier and subsequent microglia activation result in extensive inflammatory responses. Inflammasomes are large protein complexes that are essential during inflammation. One of the most studied inflammasome components, nucleotide binding oligomerization domain-like receptor protein 3 (NLRP; nucleotide binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing 3), is widely expressed in the central nervous system. Previous research has shown that microRNA-451 (miR-451) might play a role in regulating inflammatory conditions.

METHODS

Using bioinformatics analysis, we found that NLRP3 is a direct target of miR-451. This in silico prediction was confirmed using dual-luciferase reporter gene assays. To further demonstrate that miR-451 influenced microglial NLRP3 production, we activated microglial cells with lipopolysaccharides.

RESULTS

Activating microglial cells with lipopolysaccharides resulted in the production of NLRP3 inflammasomes and the secretion of the proinflammatory cytokines interleukin-1β and interleukin-18. We were able to demonstrate that overexpression of miR-451 suppressed this NLRP3-induced proinflammatory cascade of events.

CONCLUSIONS

Our findings have highlighted the potential anti-inflammatory role of miR-451 in reducing the secondary neuronal damage after spinal cord injury.

Galectin-3 in Microglia-Mediated Neuroinflammation: Implications for Central Nervous System Diseases

Microglial activation is one of the common hallmarks shared by various central nervous system (CNS) diseases. Based on surrounding circumstances, activated microglia play either detrimental or neuroprotective effects. Galectin-3 (Gal-3), a group of β-galactoside-binding proteins, has been cumulatively revealed to be a crucial biomarker for microglial activation after injuries or diseases. In consideration of the important role of Gal-3 in the regulation of microglial activation, it might be a potential target for the treatment of CNS diseases. Recently, Gal-3 expression has been extensively investigated in numerous pathological processes as a mediator of neuroinflammation, as well as in cell proliferation. However, the underlying mechanisms of Gal-3 involved in microgliamediated neuroinflammation in various CNS diseases remain to be further investigated. Moreover, several clinical studies support that the levels of Gal-3 are increased in the serum or cerebrospinal fluid of patients with CNS diseases. Thus, we summarized the roles and underlying mechanisms of Gal-3 in activated microglia, thus providing a better insight into its complexity expression pattern, and contrasting functions in CNS diseases.

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.

Effect of Dexmedetomidine as an adjuvant in quadratus lumborum block in patient undergoing caesarean section - A randomised controlled study

STUDY OBJECTIVE

This study was conducted to evaluate the effect of Dexmedetomidine as an adjuvant in quadratus lumborum block (QLB) for postoperative pain relief at rest in patients undergoing caesarean section (CS). The primary objective was to compare the time to the first request of rescue analgesia. Secondary objectives were to compare the amount of rescue analgesia, patient satisfaction, Numeric rating scale (NRS), and Ramsay sedation score (RSS) during the first 24 h.

DESIGN

A randomised, double-blinded study.

SETTING

The study was conducted at AIIMS Bhubaneswar from December 2019 to February 2021in the Operating Theatre complex (for the immediate postoperative follow-up) and in the Obstetric Ward (for follow-up at the later time points).

PATIENTS

A total of 70 patients were enrolled with singleton term pregnancies scheduled for CS under spinal anaesthesia after written informed consent.

INTERVENTION

Bilateral QLB was given in the recovery area. Group A received 30 ml of 0.25% Bupivacaine and group B received 30 ml 0.25% bupivacaine with Dexmedetomidine 1 μg/kg. They received inj. Paracetamol 15 mg/kg intravenously TDS and Inj. Tramadol 1 mg/kg as rescue analgesia (if Numeric rating scale (NRS) Score ≥ 4). We also compared the rescue analgesia in the first 24 h, patient satisfaction scores, Ramsay sedation score (RSS), and NRS scores at 2, 4, 6, 8, 12, 18, and 24 h.

MAIN RESULTS

The time to request the first rescue analgesia was significantly prolonged in group B [Mean ± SD (95% CI)] 880 ± 351 (720-1040) min. vs group A 439 ± 208 (368-510) min., p < 0.001). There was a significant decrease in the amount of rescue analgesia [(Inj. Tramadol (1 mg/ kg)] used in the group with dexmedetomidine [group B Mean ± SD (95% CI) (57 ± 18 (49-65) mg. vs group A - 81 ± 25 (73-90)] mg., p < 0.001]. A significant difference was seen in patient satisfaction scores and pain scores between the groups up to 18 h. (p < 0.05) but not in RSS.

CONCLUSION

Dexmedetomidine can be considered an effective adjuvant for QLB in CS in the absence of intrathecal morphine.

Dexmedetomidine exerts an anti-inflammatory effect via α2 adrenoceptors to alleviate cognitive dysfunction in 5xFAD mice

Background: Inflammation promotes the progression of Alzheimer’s disease (AD). In this study, we explored the effect of dexmedetomidine on inflammation and cognitive function in a mouse model of AD.

Methods: 5xFAD mice were intragastrically administered saline, dexmedetomidine, or dexmedetomidine and yohimbine for 14 days. The effects of dexmedetomidine on the acquisition and retention of memory in the Morris water-maze test and Y maze were evaluated. The deposition of amyloid beta protein (Abeta) and cytokine levels in the hippocampus were assessed. The expression of Bace1 protein and NFκB-p65 protein was assessed by Western blotting.

Results: Compared with WT mice, 5xFAD mice exhibited cognitive impairment in the Morris water maze test and Y maze test. Cognitive decline was alleviated by dexmedetomidine and this was reversed by the α2 adrenoceptor antagonist yohimbine. Compared with saline treatment, dexmedetomidine led to a reduction in the Abeta deposition area (p < 0.05) and in the mean gray value (p < 0.01) in the hippocampus of 5xFAD mice. Compared with saline treatment, dexmedetomidine inhibited the activation of astrocytes and microglia in the hippocampal DG of 5xFAD mice and reduced the area of GFAP (p < 0.01) and IBA1 (p < 0.01). The level of IL-1β in the hippocampus decreased significantly after dexmedetomidine treatment compared with saline treatment in 5xFAD mice (p < 0.01). Yohimbine neutralized the effects of dexmedetomidine. Dexmedetomidine inhibited the expression of BACE1 and NF-κB p65 (p < 0.01), and these changes were reversed by yohimbine treatment.

Conclusion: Dexmedetomidine alleviates cognitive decline, inhibits neuroinflammation, and prevents the deposition of Abeta in 5xFAD mice. The effect is mediated by the α2 adrenoceptor-mediated anti-inflammatory pathway. Dexmedetomidine may be effective for the treatment of AD and a better choice for the sedation of AD.

Dexmedetomidine suppresses the isoflurane-induced neurological damage by upregulating Heme Oxygenase-1 via activation of the mitogen-activated protein kinase kinase 1/extracellular regulated protein kinases 1/nuclear factor erythroid 2-related factor 2 axis in aged rats

Dexmedetomidine (DEX) displays a neuroprotective role in aged rats with isoflurane (ISO)-induced cognitive impairment through antioxidant, and anti-inflammatory, and anti-apoptotic effects. Therefore, the present study was performed to define the molecular mechanism of DEX on ISO-induced neurological impairment in aged rats in relation to the MEK1/ERK1/Nrf2/HO-1 axis. The study enrolled elderly patients undergoing ISO anesthesia. Patient cognitive function following treatment with DEX was evaluated using mini-mental state examination (MMSE). The results revealed that DEX supplementation of anesthesia contributed to higher MMSE scores in patients one week post treatment. Rat model of neurological impairment was also induced in 18-month-age Wistar rats by ISO, followed by DEX treatment. Based on the results of Morris water maze experiment, ELISA, and TUNEL and hematoxylin-eosin staining, in vivo experiments confirmed that DEX could reduce the oxidative stress and neurological damage induced by ISO in rats. DEX activated the nuclear factor erythroid 2-related factor (Nrf2)/Heme Oxygenase 1 (HO-1) pathway. DEX upregulated the expression of Nrf2 and HO-1 by activating the MEK1/ERK1 pathway, whereby attenuating the ISO-caused oxidative stress and neurological damage in rats. Collectively, DEX suppresses the ISO-induced neurological impairment in the aged rats by promoting HO-1 through activation of the MEK1/ERK1/Nrf2 axis.

Dexmedetomidine improved respiratory dynamics and arterial blood gas indices in patients with esophageal cancer after induction of anesthesia

OBJECTIVE

To retrospectively analyze the effects of dexmedetomidine after induction of anesthesia on intraoperative indices in patients with esophageal cancer.

METHODS

The clinical data of 93 patients with esophageal cancer that admitted to our hospital from January 2019 to December 2020 were retrospectively analyzed. The patients were divided into control group (n=31), case group A (n=31, continuous intravenous infusion of 0.3 μg/(kg∙h) dexmedetomidine hydrochloride) and case group B (n=31, continuous intravenous infusion of 0.5 μg/(kg∙h) dexmedetomidine hydrochloride) according to the application condition of dexmedetomidine hydrochloride. Heart rate, blood pressure, arterial blood gas indicators (all measured by blood gas analyzer), respiratory mechanics index (measured by mechanical ventilation), ephedrine and atropine utilization rate of the three groups were compared.

RESULTS

The plateau pressure, peak pressure and airway resistance at the end of one-lung ventilation and at chest closure in case groups A and B were lower than those in the control group, and the pulmonary compliance in case group B was higher than that in the control group (P < 0.05). PaO2, P_(A-a)O2, and RI before the start of OLV, at the end of OLV, and at chest closure in the three groups were significantly increased compared with those before induction of anesthesia (P < 0.05). Compared with the control group, PaO2 significantly increased, while P_(A-a)O2 and RI significantly decreased at the end of OLV and at chest closure in the case group B.

CONCLUSION

Dexmedetomidine can improve respiratory dynamics and arterial blood gas indices after anesthesia induction of esophageal cancer, showing high safety and clinical feasibility.

Dexmedetomidine attenuates perioperative neurocognitive disorders by suppressing hippocampal neuroinflammation and HMGB1/RAGE/NF-κB signaling pathway

Surgical trauma can induce an inflammatory response in the central nervous system. Neuroinflammation is a crucial pathological mechanism of perioperative neurocognitive disorders (PND). Dexmedetomidine (Dex) is an alpha (α)-2 adrenoceptor agonist that is widely used in the perioperative period. Previous studies have shown that Dex has neuroprotection in various nerve injury models, but its role in PND remains unclear. Our study aimed to observe the neuroprotective effect of Dex pretreatment on postoperative cognitive change and explore the effects of hippocampal neuroinflammation, microglial polarization and HMGB1/RAGE/NF-κB signaling pathway involved in Dex on PND in rats. Rats were pretreated with Dex alone or in combination with yohimbine (α-2 adrenoceptor antagonist) before surgery. Behavioral tests results showed that Dex ameliorated surgery-induced cognitive impairment in rats. Nissl, immunohistochemistry and TUNEL-NeuN staining results indicated that Dex reduced hippocampus damage and neuronal apoptosis caused by surgery. Dex preconditioning reduced the expression of the proinflammatory cytokines IL-1β, TNF-α and IL-6 in hippocampus. Immunohistochemical and immunofluorescence results showed that Dex preconditioning inhibited the activation of glial cells induced by surgery. Western blot analysis showed that Dex preconditioning downregulated the expression of M1 phenotype markers (CD86 and iNOS), HMGB1, RAGE and nuclear NF-κB and upregulated the expression of M2 phenotype markers (Arginase 1 and CD206) and cytoplasmic NF-κB. Yohimbine could inhibit the neuroprotective effect of Dex. These results indicated that Dex pretreatment could improve postoperative short-term cognitive impairment, and the neuroprotective mechanism may involve the suppression of hippocampal neuroinflammation, regulation of M1/M2 polarization, and inhibition of HMGB1/RAGE/NF-κB signal transduction.

Mechanism of dexmedetomidine preconditioning on spinal cord analgesia in rats with functional chronic visceral pain

Purpose:

To analyze the effect and mechanism of dexmedetomidine (DEX) analgesia pretreatment on functional chronic visceral pain in rats.

Methods:

Rats were divided into six groups: W1, W2, W3, W4, W5, and W6. The behavioral changes and electrophysiological indexes of rats in each group before and after DEX treatment were detected.

Results:

The levels of abdominal withdrawal reflex (AWR) in W5 and W6 groups were significantly lower than those in group W3, while the levels of thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were significantly higher than those in group W3 (p < 0.05). The electromyographic signals of W1, W5, and W6 groups showed little fluctuation, while those of groups W2, W3, and W4 showed obvious fluctuation. TLR4 mRNA expression, IRF3, P65, and phosphorylation levels in W4, W5, and W6 groups were significantly lower than those in group W2 (p < 0.05).

Conclusions:

Dexmedetomidine epidural anesthesia pretreatment could significantly inhibit visceral pain response in rats with functional chronic visceral pain, and its mechanism was related to the activation of TLR4 in spinal dorsal horn tissue of rats and the activation inhibition of IRF3 and P65 in the downstream key signals.

Vagus Nerve Stimulation Reduces Neuroinflammation Through Microglia Polarization Regulation to Improve Functional Recovery After Spinal Cord Injury

Background

Spinal cord injury (SCI) is a devastating disease that lacks effective treatment. Interestingly, recent studies indicated that vagus nerve stimulation (VNS), neuromodulation that is widely used in a variety of central nervous system (CNS) diseases, improved motor function recovery after SCI. But the exact underlying mechanism of how VNS ameliorates SCI is unclear. This study aimed to confirm the efficacy and further explore the potential therapeutic mechanism of VNS in SCI.

Method

A T10 spinal cord compression model was established in adult female Sprague-Dawley rats. Then the stimulation electrode was placed in the left cervical vagus nerve (forming Sham-VNS, VNS, and VNS-MLA groups). Basso-Beattie-Bresnahan (BBB) behavioral scores and Motor evoked potentials (MEPs) analysis were used to detect motor function. A combination of histological and molecular methods was used to clarify the relevant mechanism.

Results

Compared with the Sham-VNS group, the VNS group exhibited better functional recovery, reduced scar formation (both glial and fibrotic scars), tissue damage, and dark neurons, but these beneficial effects of VNS were diminished after alpha 7 nicotinic acetylcholine receptor (α7nAchR) blockade. Specifically, VNS inhibited the pro-inflammatory factors TNF-α, IL-1β, and IL-6 and increased the expression of the anti-inflammatory factors IL-10. Furthermore, we found that VNS promotes the shift of M1-polarized Iba-1+/CD86+ microglia to M2-polarized Iba-1+/CD206+ microglia via upregulating α7nAchR to alleviate neuroinflammation after SCI.

Conclusion

Our results demonstrated that VNS promotes microglial M2 polarization through upregulating α7nAChR to reduce neuroinflammation, thus improving motor function recovery after SCI. These findings indicate VNS might be a promising neuromodulation strategy for SCI.

Role of Descending Serotonergic Fibers in the Development of Pathophysiology after Spinal Cord Injury (SCI): Contribution to Chronic Pain, Spasticity, and Autonomic Dysreflexia

As the nervous system develops, nerve fibers from the brain form descending tracts that regulate the execution of motor behavior within the spinal cord, incoming sensory signals, and capacity to change (plasticity). How these fibers affect function depends upon the transmitter released, the receptor system engaged, and the pattern of neural innervation. The current review focuses upon the neurotransmitter serotonin (5-HT) and its capacity to dampen (inhibit) neural excitation. A brief review of key anatomical details, receptor types, and pharmacology is provided. The paper then considers how damage to descending serotonergic fibers contributes to pathophysiology after spinal cord injury (SCI). The loss of serotonergic fibers removes an inhibitory brake that enables plasticity and neural excitation. In this state, noxious stimulation can induce a form of over-excitation that sensitizes pain (nociceptive) circuits, a modification that can contribute to the development of chronic pain. Over time, the loss of serotonergic fibers allows prolonged motor drive (spasticity) to develop and removes a regulatory brake on autonomic function, which enables bouts of unregulated sympathetic activity (autonomic dysreflexia). Recent research has shown that the loss of descending serotonergic activity is accompanied by a shift in how the neurotransmitter GABA affects neural activity, reducing its inhibitory effect. Treatments that target the loss of inhibition could have therapeutic benefit.

Recent Advances in the Clinical Value and Potential of Dexmedetomidine

Dexmedetomidine, a highly selective α2-adrenoceptor agonist, has sedative, anxiolytic, analgesic, sympatholytic, and opioid-sparing properties and 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. Recent studies indicate several emerging clinical applications via different routes. We review recent data on dexmedetomidine studies, particularly exploring the varying routes of administration, experimental implications, clinical effects, and comparative advantages over other drugs. A search was conducted on the PubMed and Web of Science libraries for recent studies using different combinations of the words “dexmedetomidine”, “route of administration”, and pharmacological effect. The current routes, pharmacological effects, and application categories of dexmedetomidine are presented. It functions by stimulating pre- and post-synaptic α2-adrenoreceptors within the central nervous system, leading to hyperpolarization of noradrenergic neurons, induction of an inhibitory feedback loop, and reduction of norepinephrine secretion, causing a sympatholytic effect, in addition to its anti-inflammation, sleep induction, bowel recovery, and sore throat reduction effects. Compared with similar α2-adrenoceptor agonists, dexmedetomidine has both pharmacodynamics advantage of a significantly greater α2:α1-adrenoceptor affinity ratio and a pharmacokinetic advantage of having a significantly shorter elimination half-life. In its clinical application, dexmedetomidine has been reported to present a significant number of benefits including safe sedation for various surgical interventions, improvement of intraoperative and postoperative analgesia, sedation for compromised airways without respiratory depression, nephroprotection and stability of hypotensive hemodynamics, reduction of postoperative nausea and vomiting and postoperative shivering incidence, and decrease of intraoperative blood loss. Although the clinical application of dexmedetomidine is promising, it is still limited and further research is required to enhance understanding of its pharmacological properties, patient selection, dosage, and adverse effects.

Neuroinflammation and Scarring After Spinal Cord Injury: Therapeutic Roles of MSCs on Inflammation and Glial Scar

Transected axons are unable to regenerate after spinal cord injury (SCI). Glial scar is thought to be responsible for this failure. Regulating the formation of glial scar post-SCI may contribute to axonal regrow. Over the past few decades, studies have found that the interaction between immune cells at the damaged site results in a robust and persistent inflammatory response. Current therapy strategies focus primarily on the inhibition of subacute and chronic neuroinflammation after the acute inflammatory response was executed. Growing evidences have documented that mesenchymal stem cells (MSCs) engraftment can be served as a promising cell therapy for SCI. Numerous studies have shown that MSCs transplantation can inhibit the excessive glial scar formation as well as inflammatory response, thereby facilitating the anatomical and functional recovery. Here, we will review the effects of inflammatory response and glial scar formation in spinal cord injury and repair. The role of MSCs in regulating neuroinflammation and glial scar formation after SCI will be reviewed as well.

Dexmedetomidine Alleviates Microglia-Induced Spinal Inflammation and Hyperalgesia in Neonatal Rats by Systemic Lipopolysaccharide Exposure

Noxious stimulus and painful experience in early life can induce cognitive deficits and abnormal pain sensitivity. As a major component of the outer membrane of gram-negative bacteria, lipopolysaccharide (LPS) injection mimics clinical symptoms of bacterial infections. Spinal microglial activation and the production of pro-inflammatory cytokines have been implicated in the pathogenesis of LPS-induced hyperalgesia in neonatal rats. Dexmedetomidine (DEX) possesses potent anti-neuroinflammatory and neuroprotective properties through the inhibition of microglial activation and microglial polarization toward pro-inflammatory (M1) phenotype and has been widely used in pediatric clinical practice. However, little is known about the effects of DEX on LPS-induced spinal inflammation and hyperalgesia in neonates. Here, we investigated whether systemic LPS exposure has persistent effects on spinal inflammation and hyperalgesia in neonatal rats and explored the protective role of DEX in adverse effects caused by LPS injection. Systemic LPS injections induced acute mechanical hyperalgesia, increased levels of pro-inflammatory cytokines in serum, and short-term increased expressions of pro-inflammatory cytokines and M1 microglial markers in the spinal cord of neonatal rats. Pretreatment with DEX significantly decreased inflammation and alleviated mechanical hyperalgesia induced by LPS. The inhibition of M1 microglial polarization and microglial pro-inflammatory cytokines expression in the spinal cord may implicate its neuroprotective effect, which highlights a new therapeutic target in the treatment of infection-induced hyperalgesia in neonates and preterm infants.

Dexmedetomidine vs. lidocaine for postoperative analgesia in pediatric patients undergoing craniotomy: a protocol for a prospective, randomized, double-blinded, placebo-controlled trial

Background

Postoperative pain is a common problem that occurs in pediatric patients following neurosurgery which may lead to severe complications. Dexmedetomidine is a commonly used adjuvant medicine in craniotomy owing to its sedative, amnestic, analgesic, and neuroprotective properties. Besides, studies suggest that lidocaine has similar effects on sedation, analgesia, and neuroprotection. Both two adjuvants can reduce postoperative pain after neurosurgery in adults. However, it is still unknown whether dexmedetomidine or lidocaine can reduce postoperative pain in children undergoing craniotomy, and if yes, which is a better medicine choice. Therefore, we aimed to compare the effect of dexmedetomidine vs. lidocaine on postoperative pain in pediatric patients after craniotomy.

Methods/design

We will perform a randomized (1:1:1), double-blind, placebo-controlled, single-center trial. Children aged 1–12 years scheduled for craniotomy will be eligible for inclusion. The 255 recruited participants will be stratified by age in two strata (1–6 years and 7–12 years), and then each stratum will be equally randomized to three groups: group D (infusion of dexmedetomidine [intervention group]), group L (infusion of lidocaine [intervention group]), and group C (infusion of normal saline [control group]). Patients will be followed up at 1 h, 2 h, 4 h, 24 h, and 48 h after surgery. The primary outcome will be total sufentanil consumption within 24 h after surgery.

Discussion

In this clinical trial, we expect to clarify and compare the postoperative analgesic effect of dexmedetomidine vs. lidocaine infusion on pediatric patients undergoing craniotomy. We believe that the results of this trial will provide more choices for postoperative analgesia for the pediatric population.

Trial registration

Chinese ClinicalTrials.gov ChiCTR1800019411. Registered on 10 November 2018

Dexmedetomidine alleviates traumatic spinal cord injury in rats via inhibiting apoptosis induced by endoplasmic reticulum stress

OBJECTIVE

To investigate the protective effect of dexmedetomidine (Dex) on traumatic spinal cord injury (TSCI) and to evaluate the involvement of inhibition of endoplasmic reticulum (ER) stress response in the potential mechanism.

METHOD

Sprague-Dawley rats were randomly divided into five groups. The hind limb locomotor function of rats was evaluated at 1, 3 and 7 days after the operation. At 7 days after the operation, spinal cord specimens were obtained for hematoxylin and eosin (H&E), Nissl and TUNEL staining, as well as immunofluorescence and Western blot analyses to detect the level of apoptosis and the levels of proteins related to ER stress.

RESULTS

7 days after the operation, Dex treatment promoted the recovery and also inhibited apoptosis of neurons in the spinal cord. Additionally, Dexinhibited the expression of proteins related to ER stress response after spinal cord injury.

CONCLUSIONS

Dex improves the neurological function of rats with TSCI and reduces apoptosis of spinal cord neurons. The potential mechanism is related to the inhibition of the ER stress response.

Dexmedetomidine Ameliorates Postoperative Cognitive Dysfunction in Aged Mice

Neuroinflammation and oxidative stress coexist and interact in the progression of postoperative cognitive dysfunction (POCD) and other neurodegenerative disease. Mounting studies reveal that Dexmedetomidine (Dex) possesses anti-inflammatory and antioxidant properties. Nevertheless, whether Dex exerts neuroprotective effect on the cognitive sequelae of oxidative stress and inflammatory process remains unclear. A mouse model of abdominal exploratory laparotomy-induced cognitive dysfunction was employed to explore the underlying mechanism of neuroprotective effects exerted by Dex in POCD. Aged mice were treated with Dex (20 µg/kg) 20 min prior to surgery. Open field test (OFT) and Morris water maze (MWM) were employed to examine the cognitive function on postoperative day 3 (POD 3) or POD 7. In the present study, mice underwent surgery exhibited cognitive impairment without altering spontaneous locomotor activity, while the surgery-induced cognitive impairment could be alleviated by Dex pretreatment. Dex inhibited surgery-induced pro-inflammatory cytokines accumulation and microglial activation in the hippocampi of mice. Furthermore, Dex decreased MDA levels, enhanced SOD activity, modulated CDK5 activity and increased BDNF expression in the hippocampus. In addition, Dex remarkably reduced the surgery-induced increased ratio of Bax/Bcl-2 and apoptotic neurons in the hippocampi of aged mice. Collectively, our study provides evidence that Dex may exert neuroprotective effects against surgery-induced cognitive impairment through mechanisms involving its anti-inflammatory and antioxidant properties, as well as the suppression on the mitochondrial permeability transition pore and apoptosis-related pathway.

Dexmedetomidine Ameliorates Perioperative Neurocognitive Disorders by Suppressing Monocyte-Derived Macrophages in Mice With Preexisting Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) initiates immune responses involving infiltration of monocyte-derived macrophages (MDMs) in the injured brain tissue. These MDMs play a key role in perioperative neurocognitive disorders (PNDs). We tested the hypothesis that preanesthetic treatment with dexmedetomidine (DEX) could suppress infiltration of MDMs into the hippocampus of TBI model mice, ameliorating PND.

METHODS

We first performed bone marrow transplantation from green fluorescent protein-transgenic mice to C57BL/6 mice to identify MDMs. We used only male mice for homogeneity. Four weeks after transplantation, a controlled cortical impact model of TBI was created using recipient mice. Four weeks after TBI, mice received pretreatment with DEX before general anesthesia (GA). Mice performed the Barnes maze test (8-12 mice/group) 2 weeks after GA and were euthanized for immunohistochemistry (4-5 mice/group) or immunoblotting (7 mice/group) 4 weeks after GA.

RESULTS

In Barnes maze tests, TBI model mice showed longer primary latency (mean difference, 76.5 [95% confidence interval, 41.4-111.6], P < .0001 versus Naïve), primary path length (431.2 [98.5-763.9], P = .001 versus Naïve), and more primary errors (5.7 [0.62-10.7], P = .017 versus Naïve) than Naïve mice on experimental day 3. Expression of MDMs in the hippocampus was significantly increased in TBI mice compared to Naïve mice (2.1 [0.6-3.7], P = .003 versus Naïve). Expression of monocyte chemotactic protein-1 (MCP1)-positive areas in the hippocampus was significantly increased in TBI mice compared to Naïve mice (0.38 [0.09-0.68], P = .007 versus Naïve). Immunoblotting indicated significantly increased expression of interleukin-1β in the hippocampus in TBI mice compared to Naïve mice (1.59 [0.08-3.1], P = .035 versus Naïve). In contrast, TBI mice pretreated with DEX were rescued from these changes and showed no significant difference from Naïve mice. Yohimbine, an α2 receptor antagonist, mitigated the effects of DEX (primary latency: 68.3 [36.5-100.1], P < .0001 versus TBI-DEX; primary path length: 414.9 [120.0-709.9], P = .0002 versus DEX; primary errors: 6.6 [2.1-11.2], P = .0005 versus TBI-DEX; expression of MDMs: 2.9 [1.4-4.4], P = .0001 versus TBI-DEX; expression of MCP1: 0.4 [0.05-0.67], P = .017 versus TBI-DEX; expression of interleukin-1β: 1.8 [0.34-3.35], P = .01 versus TBI-DEX).

CONCLUSIONS

Preanesthetic treatment with DEX suppressed infiltration of MDMs in the hippocampus and ameliorated PND in TBI model mice. Preanesthetic treatment with DEX appears to suppress infiltration of MDMs in the hippocampus and may lead to new treatments for PND in patients with a history of TBI.

Microglia as therapeutic targets after neurological injury: strategy for cell therapy

INTRODUCTION

Microglia is the resident tissue macrophages of the central nervous system. Prolonged microglial activation often occurs after traumatic brain injury and is associated with deteriorating neurocognitive outcomes. Resolution of microglial activation is associated with limited tissue loss and improved neurocognitive outcomes. Limiting the prolonged pro-inflammatory response and the associated secondary tissue injury provides the rationale and scientific premise for considering microglia as a therapeutic target.

AREAS COVERED

In this review, we discuss markers of microglial activation, such as immunophenotype and microglial response to injury, including cytokine/chemokine release, free radical formation, morphology, phagocytosis, and metabolic shifts. We compare the origin and role in neuroinflammation of microglia and monocytes/macrophages. We review potential therapeutic targets to shift microglial polarization. Finally, we review the effect of cell therapy on microglia.

EXPERT OPINION

Dysregulated microglial activation after neurologic injury, such as traumatic brain injury, can worsen tissue damage and functional outcomes. There are potential targets in microglia to attenuate this activation, such as proteins and molecules that regulate microglia polarization. Cellular therapeutics that limit, but do not eliminate, the inflammatory response have improved outcomes in animal models by reducing pro-inflammatory microglial activation via secondary signaling. These findings have been replicated in early phase clinical trials.

Dexmedetomidine promotes inflammation resolving through TGF-β1 secreted by F4/80+Ly6G+ macrophage

Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist, which can regulate inflammatory responses. However, whether DEX interferes with the inflammation resolving remains unclear. Here, we reported the effects of DEX on zymosan-induced generalized inflammation in mice during resolution. Mice were administered intraperitoneally with DEX after the initiation of sepsis. The resolution interval (Ri), a vital resolution indice, decreased from twelve hours to eight hours after the administration of DEX. The induction of peritoneal pro-inflammatory interleukin [IL] - 1β and tumour necrosis factor-α (TNF-α) appeared to be inhibited. Of interest, the anti-inflammatory transforming growth factor-β1 (TGF-β1) but not IL-10 levels were up-regulated at twenty-four hours in the DEX group along with 1.0 mg/mice zymosan A (ZyA) treatment. The expression levels of multiple genes related to protective immune processes and clearance functions were detected and revealed the same trends. DEX markedly increased the F4/80+Ly6G+ macrophage population. Additionally, the adequate apoptotic neutrophil clearance from injury after DEX installation could be reverse by opsonization or co-instillation of TGF-β1 neutralizing antibody in vivo, promoting the inflammation-resolution programs. In conclusion, DEX post-treatment, via the increase of F4/80+Ly6G+ macrophages, provokes further secretion of TGF-β1, leading to the attenuated cytokine storm and accelerated inflammation resolving.

Dexmedetomidine Protects Human Cardiomyocytes Against Ischemia-Reperfusion Injury Through α2-Adrenergic Receptor/AMPK-Dependent Autophagy

Background: Ischemia-reperfusion injury (I/R) strongly affects the prognosis of children with complicated congenital heart diseases (CHDs) who undergo long-term cardiac surgical processes. Recently, the α2-adrenergic receptor agonist Dexmedetomidine (Dex) has been reported to protect cardiomyocytes (CMs) from I/R in cellular models and adult rodent models. However, whether and how Dex may protect human CMs in young children remains largely unknown. Methods and Results: Human ventricular tissue from tetralogy of Fallot (TOF) patients and CMs derived from human-induced pluripotent stem cells (iPSC-CMs) were used to assess whether and how Dex protects human CMs from I/R. The results showed that when pretreated with Dex, the apoptosis marker-TUNEL and cleaved caspase 3 in the ventricular tissue were significantly reduced. In addition, the autophagy marker LC3II was significantly increased compared with that of the control group. When exposed to the hypoxia/reoxygenation process, iPSC-CMs pretreated with Dex also showed reduced TUNEL and cleaved caspase 3 and increased LC3II. When the autophagy inhibitor (3-methyladenine, 3-MA) was applied to the iPSC-CMs, the protective effect of Dex on the CMs was largely blocked. In addition, when the fusion of autophagosomes with lysosomes was blocked by Bafilomycin A1, the degradation of p62 induced by Dex during the autophagy process was suspended. Moreover, when pretreated with Dex, both the human ventricle and the iPSC-CMs expressed more AMP-activated protein kinase (AMPK) and phospho AMPK (pAMPK) during the I/R process. After AMPK knockout or the use of an α2-adrenergic receptor antagonist-yohimbine, the protection of Dex and its enhancement of autophagy were inhibited. Conclusion: Dex protects young human CMs from I/R injury, and α2-adrenergic receptor/AMPK-dependent autophagy plays an important role during this process. Dex may have a therapeutic effect for children with CHD who undergo long-term cardiac surgical processes.

Bone marrow mesenchymal stem cells-derived exosomes reduce apoptosis and inflammatory response during spinal cord injury by inhibiting the TLR4/MyD88/NF-κB signaling pathway

Spinal cord injury (SCI) is one of the most common destructive injuries, which may lead to permanent neurological dysfunction. Currently, transplantation of bone marrow mesenchymal stem cells (BMSCs) in experimental models of SCI shows promise as effective therapies. BMSCs secrete various factors that can regulate the microenvironment, which is called paracrine effect. Among these paracrine substances, exosomes are considered to be the most valuable therapeutic factors. Our study found that BMSCs-derived exosomes therapy attenuated cell apoptosis and inflammation response in the injured spinal cord tissues. In in vitro studies, BMSCs-derived exosomes significantly inhibited lipopolysaccharide (LPS)-induced PC12 cell apoptosis, reduced the secretion of pro-inflammatory factors including tumor necrosis factor (TNF)-α and IL (interleukin)-1β and promoted the secretion of anti-inflammatory factors including IL-10 and IL-4. Moreover, we found that LPS-induced protein expression of toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear transcription factor-κB (NF-κB) was significantly downregulated after treatment with BMSCs-derived exosomes. In in vivo studies, we found that hindlimb motor function was significantly improved in SCI rats with systemic administration of BMSCs-derived exosomes. We also observed that the expression of pro-apoptotic proteins and pro-inflammatory factors was significantly decreased, while the expression of anti-apoptotic proteins and anti-inflammatory factors were upregulated in SCI rats after exosome treatment. In conclusion, BMSCs-derived exosomes can inhibit apoptosis and inflammation response induced by injury and promote motor function recovery by inhibiting the TLR4/MyD88/NF-κB signaling pathway, which suggests that BMSCs-derived exosomes are expected to become a new therapeutic strategy for SCI.

Dexmedetomidine attenuates sepsis-associated inflammation and encephalopathy via central α2A adrenoceptor

Sepsis-associated encephalopathy (SAE) is a significant clinical issue that is associated with increased mortality and cost of health care. Dexmedetomidine, an α2 adrenoceptor agonist that is used to provide sedation, has been shown to induce neuroprotection under various conditions. This study was designed to determine whether dexmedetomidine protects against SAE and whether α2 adrenoceptor plays a role in this protection. Six- to eight-week old CD-1 male mice were subjected to cecal ligation and puncture (CLP). They were treated with intraperitoneal injection of dexmedetomidine in the presence or absence of α2 adrenoceptor antagonists, atipamezole or yohimbine, or an α2A adrenoceptor antagonist, BRL-44408. Hippocampus and blood were harvested for measuring cytokines. Mice were subjected to Barnes maze and fear conditioning 14 days after CLP to evaluate their learning and memory. CLP significantly increased the proinflammatory cytokines including tumor necrosis factor α, interleukin (IL)-6 and IL-1β in the blood and hippocampus. CLP also increased the permeability of blood-brain barrier (BBB) and impaired learning and memory. These CLP detrimental effects were attenuated by dexmedetomidine. Intracerebroventricular application of atipamezole, yohimbine or BRL-44408 blocked the protection of dexmedetomidine on the brain but not on the systemic inflammation. Astrocytes but not microglia expressed α2A adrenoceptors. Microglial depletion did not abolish the protective effects of dexmedetomidine. These results suggest that dexmedetomidine reduces systemic inflammation, neuroinflammation, injury of BBB and cognitive dysfunction in septic mice. The protective effects of dexmedetomidine on the brain may be mediated by α2A adrenoceptors in the astrocytes.

Noradrenergic Signaling and Neuroinflammation Crosstalk Regulate Toxoplasma gondii-Induced Behavioral Changes

Infections of the nervous system elicit neuroimmune responses and alter neurotransmission, affecting host neurological functions. Chronic infection with the apicomplexan parasite Toxoplasma correlates with certain neurological disorders in humans and alters behavior in rodents. Here, we propose that the crosstalk between neurotransmission and neuroinflammation may underlie some of these cognitive changes. We discuss how T. gondii infection suppresses noradrenergic signaling and how the restoration of this pathway improves behavioral aberrations, suggesting that altered neurotransmission and neuroimmune responses may act in concert to perturb behavior. This interaction might apply to other infectious agents, such as viruses, that elicit cognitive changes. We hypothesize that neurotransmitter signaling in immune cells can contribute to behavioral changes associated with brain infection, offering opportunities for potential therapeutic targeting.

Dexmedetomidine reduces ventilator-induced lung injury via ERK1/2 pathway activation

Mechanical ventilation (MV) can contribute to ventilator-induced lung injury (VILI); dexmedetomidine (Dex) treatment attenuates MV-related pulmonary inflammation, but the mechanisms remain unclear. Therefore, the present study aimed to explore the protective effect and the possible molecular mechanisms of Dex in a VILI rodent model. Adult male Sprague-Dawley rats were randomly assigned to one of seven groups (n=24 rats/group). Rats were euthanized after 4 h of continuous MV, and pathological changes, lung wet/dry (W/D) weight ratio, the levels of inflammatory cytokines (IL-1β, TNF-α and IL-6) in the bronchoalveolar lavage fluid (BALF), and the expression levels of Bcl-2 homologous antagonist/killer (Bak), Bcl-2, pro-caspase-3, cleaved caspase-3 and the phosphorylation of ERK1/2 in the lung tissues were measured. Propidium iodide uptake and TUNEL staining were used to detect epithelial cell death. The Dex pretreatment group exhibited fewer pathological changes, lower W/D ratios and lower expression levels of inflammatory cytokines in BALF compared with the VILI group. Dex significantly attenuated the ratio of Bak/Bcl-2, cleaved caspase-3 expression levels and epithelial cell death, and increased the expression of phosphorylated ERK1/2. The protective effects of Dex could be partially reversed by PD98059, which is a mitogen-activated protein kinase (upstream of ERK1/2) inhibitor. Overall, dexmedetomidine was found to reduce the inflammatory response and epithelial cell death caused by VILI, via the activation of the ERK1/2 signaling pathway.

Dexmedetomidine alleviates neurobehavioral impairments and myelination deficits following lipopolysaccharide exposure in early postnatal rats

AIMS

White matter injury (WMI) is the main form of brain injury in preterm neonate survivors, and perinatal inflammation is implicated in the pathogenesis of WMI. It has been demonstrated that dexmedetomidine, an anesthetic adjuvant, possesses neuroprotective effects in both preclinical and clinical trials. The present study was conducted to explore whether dexmedetomidine could protect against neurobehavioral impairments and myelination deficits caused by lipopolysaccharide (LPS) exposure in the early postnatal rat brain.

MAIN METHODS

LPS (2 mg/kg) was intraperitoneally (i.p.) injected in Sprague-Dawley rat pups on postnatal day 2 (P2). Dexmedetomidine (25 μg/kg) or vehicle was given i.p. immediately after LPS injection. STAT3 and p-STAT3 expression were detected by western blot in rat brain 24 h after drug administration. Immunostaining for GFAP to was performed to evaluate astrocytic response at 24 h post-LPS and P14. Neurobehavioral tests (the righting reflex, negative geotaxis, and wire hanging maneuver tests) were performed from P5 to P10. Histological analysis of myelin content was accessed by immunohistochemistry for CNPase and MBP at P14.

KEY FINDINGS

Our results showed that treatment with dexmedetomidine significantly ameliorated LPS-induced neurobehavioral abnormalities and myelin damage, which is accompanied by suppression of STAT3 activation and reactive astrogliosis.

SIGNIFICANCE

Dexmedetomidine can alleviate neurobehavioral impairments and myelination deficits after LPS exposure in early postnatal rats, probably by mitigating STAT3-mediated reactive astrogliosis. Our results suggest that dexmedetomidine might be a promising agent to treat brain injury in neonates.

Dexmedetomidine Provides Protection Against Hippocampal Neuron Apoptosis and Cognitive Impairment in Mice with Alzheimer's Disease by Mediating the miR-129/YAP1/JAG1 Axis

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease that leads to progressive cognitive, memory, and learning dysfunction that affects the aging population. Dexmedetomidine (Dex) might be beneficial for postoperative cognitive function in elderly patients. However, the exact mechanism underlying the protective role of Dex against cognitive impairment requires further elucidation. The present study aims to determine whether miR-129 is involved in the protective effect of Dex against Aβ_1-42-induced hippocampal neuron apoptosis and cognitive impairment in mice. In our study, Y-shaped maze and water maze tests were conducted to evaluate the cognitive function of AD mice, while neuronal apoptosis was measured by Terminal Deoxynucleotidyl Transferase-Mediated dUTP Nick-End Labeling (TUNEL) staining. The findings showed that Dex administration resulted in the enhancement of miR-129 expression with declined hippocampal neuron apoptosis and attenuated cognitive impairment in Aβ_1-42-injected mice. miR-129 targeted YAP1 and disrupted its interaction with JAG1, leading to a decline in hippocampal neuron apoptosis and attenuated cognitive impairment in Aβ_1-42-injected mice. In conclusion, the miR-129/YAP1/JAG1 axis could potentially be the mechanism by which Dex protects AD mice from cognitive impairment.

Involvement of descending pain control system regulated by orexin receptor signaling in the induction of central post-stroke pain in mice

Central post-stroke pain (CPSP) is a type of neuropathic pain for which the mechanism and relevant drug pathways remain unknown. Recently, it was reported that intracerebroventricular (ICV) administration of orexin-A suppresses pain and ischemia. In this study, we tested the role of orexin-A in CPSP induction in mice. Male ddY mice were subjected to 30 min of bilateral carotid artery occlusion (BCAO). CPSP was assessed by von Frey test. Colocalization of orexin 1 receptor (OX1R) with various neuron markers were determined by double-immunofluorescence. The hindpaw withdrawal responses to mechanical stimuli were significantly increased 3 days post-BCAO compared with those of sham groups. ICV injection of orexin-A dose-dependently suppressed BCAO-induced mechanical allodynia. These effects were inhibited by pre-treatment with SB334867 (an OX1R antagonist; ICV injection), yohimbine (a noradrenaline α₂ receptor antagonist; intrathecal (IT) injection), and WAY100635 (a serotonin 5-HT_1A receptor antagonist; IT injection), but not TCS OX2 29 (an OX2R antagonist; ICV injection). OX1R colocalized with TH (a noradrenergic neuron marker) and TPH (a serotonergic neuron marker) in the locus ceruleus (LC) and the rostral ventromedial medulla (RVM), respectively. The number of c-Fos positive cells in the LC and the RVM of BCAO mice was increased at 90 min after ICV injection of orexin-A compared to saline group. These results indicate that orexin-A/OX1R signaling plays an important role through activation of the descending pain control system in the induction of CPSP in mice.