Dexmedetomidine preconditioning plays a neuroprotective role and suppresses TLR4/NF-κB pathways model of cerebral ischemia reperfusion

Dexmedetomidine alleviates cognitive impairment by promoting hippocampal neurogenesis via BDNF/TrkB/CREB signaling pathway in hypoxic-ischemic neonatal rats

AIMS

Dexmedetomidine (DEX) has been reported to alleviate hypoxic-ischemic brain damage (HIBD) in neonates. This study aimed to investigate whether DEX improves cognitive impairment by promoting hippocampal neurogenesis via the BDNF/TrkB/CREB signaling pathway in neonatal rats with HIBD.

METHODS

HIBD was induced in postnatal day 7 rats using the Rice-Vannucci method, and DEX (25 μg/kg) was administered intraperitoneally immediately after the HIBD induction. The BDNF/TrkB/CREB pathway was regulated by administering the TrkB receptor antagonist ANA-12 through intraperitoneal injection or by delivering adeno-associated virus (AAV)-shRNA-BDNF via intrahippocampal injection. Western blot was performed to measure the levels of BDNF, TrkB, and CREB. Immunofluorescence staining was utilized to identify the polarization of astrocytes and evaluate the levels of neurogenesis in the dentate gyrus of the hippocampus. Nissl and TTC staining were performed to evaluate the extent of neuronal damage. The MWM test was conducted to evaluate spatial learning and memory ability.

RESULTS

The levels of BDNF and neurogenesis exhibited a notable decrease in the hippocampus of neonatal rats after HIBD, as determined by RNA-sequencing technology. Our results demonstrated that treatment with DEX effectively increased the protein expression of BDNF and the phosphorylation of TrkB and CREB, promoting neurogenesis in the dentate gyrus of the hippocampus in neonatal rats with HIBD. Specifically, DEX treatment significantly augmented the expression of BDNF in hippocampal astrocytes, while decreasing the proportion of detrimental A1 astrocytes and increasing the proportion of beneficial A2 astrocytes in neonatal rats with HIBD. Furthermore, inhibiting the BDNF/TrkB/CREB pathway using either ANA-12 or AAV-shRNA-BDNF significantly counteracted the advantageous outcomes of DEX on hippocampal neurogenesis, neuronal survival, and cognitive improvement.

CONCLUSIONS

DEX promoted neurogenesis in the hippocampus by activating the BDNF/TrkB/CREB pathway through the induction of polarization of A1 astrocytes toward A2 astrocytes, subsequently mitigating neuronal damage and cognitive impairment in neonates with HIBD.

Dexmedetomidine Alleviates Brain Ischemia/Reperfusion Injury by Regulating Metastasis-associated Lung Adenocarcinoma Transcript 1/MicroRNA-140-5p/ Nuclear Factor Erythroid-derived 2-like 2 Axis

BACKGROUND

Dexmedetomidine (Dex) is widely used in perioperative anesthesia, and recent studies have reported that it protects organs from ischemia/reperfusion (I/R) injury.

OBJECTIVES

This study was performed to investigate the role of Dex in alleviating cerebral I/R injury and its regulatory effects on metastasis-associated lung adenocarcinoma transcript 1 (MALAT1)/microRNA-140-5p (miR-140-5p)/nuclear factor erythroid-derived 2-like 2 (Nrf2) axis.

METHODS

In vivo rat middle cerebral artery occlusion (MCAO) model and in vitro oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced neuronal injury model were constructed. Dex was injected into the animals or used to culture HT22 cells to observe the pharmacological effects. The neurological defect, brain water content, infarct volume of the rats, and neuron viability were evaluated. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were detected. Besides, the regulatory effects of Dex on MALAT1, miR-140-5p, and Nrf2 expression levels and regulatory relationships among them were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and dual- luciferase reporter assay.

RESULTS

Dex significantly alleviated the neurological injury of rats with MCAO and promoted the viability of neurons. Dex treatment suppressed miR-140-5p expression, but elevated MALAT1 and Nrf2 expressions. MALAT1 knockdown down-regulated Nrf2 expression and promoted oxidative stress in neurons. Additionally, miR-140-5p directly targeted Nrf2, and it also functioned as a downstream target miRNA of MALAT1.

CONCLUSION

Dex, via regulating MALAT1/miR-140-5p/Nrf2 axis, plays a neuroprotective role against I/R-induced brain injury.

MicroRNA-323-5p Involved in Dexmedetomidine Preconditioning Impart Neuroprotection

Background and Objectives: Cerebral ischemia is one of the major preoperative complications. Dexmedetomidine is a well-known sedative-hypnotic agent that has potential organ-protective effects. We examine the miRNAs associated with preconditioning effects of dexmedetomidine in cerebral ischemia. Materials and Methods: Transient infarcts were induced in mice via reperfusion after temporary occlusion of one side of the middle cerebral artery. A subset of these mice was exposed to dexmedetomidine prior to cerebral infarction and miRNA profiling of the whole brain was performed. We administered dexmedetomidine and miRNA-323-5p mimic/inhibitor to oxygen-glucose deprivation/reoxygenation astrocytes. Additionally, we administered miR-323-5p mimic and inhibitor to mice via intracerebroventricular injection 2 h prior to induction of middle cerebral artery occlusion. Results: The infarct volume was significantly lower in the dexmedetomidine-preconditioned mice. Analysis of brain samples revealed an increased expression of five miRNAs and decreased expression of three miRNAs in the dexmedetomidine-pretreated group. The viability of cells significantly increased and expression of miR-323-5p was attenuated in the dexmedetomidine-treated oxygen-glucose deprivation/reoxygenation groups. Transfection with anti-miR-323-5p contributed to increased astrocyte viability. When miRNA-323-5p was injected intraventricularly, infarct volume was significantly reduced when preconditioned with the miR-323-5p inhibitor compared with mimic and negative control. Conclusions: Dexmedetomidine has a protective effect against transient neuronal ischemia-reperfusion injury and eight specific miRNAs were profiled. Also, miRNA-323-5p downregulation has a cell protective effect under ischemic conditions both in vivo and in vitro. Our findings suggest the potential of the miR-323-5p inhibitor as a therapeutic agent against cerebral infarction.

Dexmedetomidine, an α2 agonist, increases the morphine analgesic effect and decreases morphine tolerance development by suppressing oxidative stress and TNF/IL-1 signalling pathway in rats

BACKGROUND

The aim of the present study is to examine the possible effect de dexmedetomidine on the development of morphine tolerance in rats including nociception, morphine analgesia, apoptosis, oxidative stress, and tumour necrosis factor (TNF)/ interleukin-1 (IL-1) pathways.

MATERIALS AND METHODS

In this study, 36 Wistar Albino (225-245 g) rats were used. Animals were divided into 6 groups: saline (S), 20 mcg/kg dexmedetomidine (D), 5 mg/kg morphine (M), M + D, morphine tolerance (MT), and MT + D. The analgesic effect was measured with hot plate and tail-flick analgesia tests. After the analgesia tests, the dorsal root ganglia (DRG) tissues were excised. Oxidative stress parameters [total antioxidant status (TAS), total oxidant status (TOS)], TNF, IL-1 and apoptosis enzymes (Caspase-3, Caspase-9), were measured in DRG tissues.

RESULTS

Dexmedetomidine showed an antinociceptive effect when given alone (p < 0.05 to p < 0.001). In addition, dexmedetomidine increased the analgesic effect of morphine (p < 0.001), and also decreased the tolerance to morphine at a significant level (p < 0.01 to p < 0.001). Moreover, it decreased oxidative stress (p < 0.001) and TNF/IL-1 levels when given as an additional drug of single-dose morphine and morphine tolerance group (p < 0.001). Furthermore, dexmedetomidine decreased Caspase-3 and Caspase-9 levels after tolerance development (p < 0.001).

CONCLUSION

Dexmedetomidine has antinociceptive properties, and it increases the analgesic effect of morphine and also prevents tolerance development. These effects probably occur by the modulation of oxidative stress, inflammation and apoptosis.

Appraisal of the Neuroprotective Effect of Dexmedetomidine: A Meta-Analysis

Dexmedetomidine is an adrenergic receptor agonist that has been regarded as neuroprotective in several studies without an objective measure to it. Thus, the aim of this meta-analysis was to analyze and quantify the current evidence for the neuroprotective effects of dexmedetomidine in animals. The search was performed by querying the National Library of Medicine. Studies were included based on their language, significancy of their results, and complete availability of data on animal characteristics and interventions. Risk of bias was assessed using SYRCLE's risk of bias tool and certainty was assessed using the ARRIVE Guidelines 2.0. Synthesis was performed by calculating pooled standardized mean difference and presented in forest plots and tables. The number of eligible records included per outcome is the following: 22 for IL-1β, 13 for IL-6, 19 for apoptosis, 7 for oxidative stress, 7 for Escape Latency, and 4 for Platform Crossings. At the cellular level, dexmedetomidine was found protective against production of IL-1β (standardized mean difference (SMD) =  - 4.3 [- 4.8; - 3.7]) and IL-6 (SMD =  - 5.6 [- 6.7; - 4.6]), apoptosis (measured through TUNEL, SMD =  - 6.0 [- 6.8; - 4.6]), and oxidative stress (measured as MDA production, SMD =  - 2.0 [- 2.4; - 1.4]) exclusively in the central nervous system. At the organism level, dexmedetomidine improved behavioral outcomes measuring escape latency (SMD = - 2.4 [- 3.3; - 1.6]) and number of platform crossings (SMD = 9.1 [- 6.8; - 11.5]). No eligible study had high risk of bias and certainty was satisfactory for reproducibility in all cases. This meta-analysis highlights the complexity of adrenergic stimulation and sheds light into the mechanisms potentiated by dexmedetomidine, which could be exploited for improving current neuroprotective formulations.

Dexmedetomidine inhibits abnormal muscle hypertrophy of myofascial trigger points via TNF-α/ NF-κB signaling pathway in rats

Myofascial pain syndrome (MPS) is a chronic pain disorder with inflammation-related primarily characterized by the presence of myofascial trigger points (MTrPs). Myocyte enhancer factor 2C (MEF2C) is involved in the occurrence of a variety of skeletal muscle diseases. However, it is not yet clear if MEF2C is involved in MTrPs. The purpose of this study was to investigate whether MEF2C was involved in the inflammatory pathogenesis of MTrPs. In the present study, we used RNA sequencing (RNA-seq) to compare the differential expression of myocyte enhancer factor 2C (MEF2C) in healthy participants and MTrPs participants. The widely used rat MTrPs model was established to research the upstream and downstream regulatory mechanism of MEF2C and found that MEF2C was significantly increased in patients with MTrPs. Dexmedetomidine (Dex) was injected intramuscularly in the MTrPs animal to assess its effects on MEF2C. The expression of MEF2C protein and mRNA in skeletal muscle of rats in the MTrPs group were up-regulated. In addition, the expression of TNF- α, p-P65, MLCK, and Myocilin (MyoC) was up-regulated and the mechanical pain threshold was decreased. Peripheral TNF- α injection significantly decreased the mechanical pain threshold and increased the expression of p-P65, MLCK, MEF2C, and MyoC in healthy rats. Maslinic acid increased the mechanical pain threshold and inhibited the expression of p-P65, MLCK, MEF2C, and MyoC. In addition, peripheral injection of DEX in MTrPs rats also inhibited the expression of TNF- α, p-P65, MLCK, MEF2C, and MyoC. These results suggest that MEF2C is involved in the inflammatory pathogenesis of MTrPs and DEX serves as a potential therapeutic strategy for the treatment of MPS.

Hydrogen gas alleviates lipopolysaccharide-induced acute lung injury and inflammatory response in mice

Background

Chronic inflammation and oxidant/antioxidant imbalance are two main pathological features associated with lipopolysaccharide (LPS)-induced acute lung injury (ALI). The following study investigated the protective role of hydrogen (H₂), a gaseous molecule without known toxicity, in LPS-induced lung injury in mice and explored its potential molecular mechanisms.

Methods

Mice were randomly divided into three groups: H₂ control group, LPS group, and LPS + H₂ group. The mice were euthanized at the indicated time points, and the specimens were collected. The 72 h survival rates, cytokines contents, pathological changes, expression of Toll-like receptor 4 (TLR4), and oxidative stress indicators were analyzed. Moreover, under different culture conditions, RAW 264.7 mouse macrophages were used to investigate the potential molecular mechanisms of H₂ in vitro. Cells were divided into the following groups: PBS group, LPS group, and LPS + H₂ group. The cell viability, intracellular ROS, cytokines, and expression of TLR4 and nuclear factor kappa-B (NF-κB) were observed.

Results

Hydrogen inhalation increased the survival rate to 80%, reduced LPS-induced lung damage, and decreased inflammatory cytokine release in LPS mice. Besides, H₂ showed remarked anti-oxidative activity to reduce the MDA and NO contents in the lung. In vitro data further indicated that H₂ down-regulates the levels of ROS, NO, TNF-α, IL-6, and IL-1β in LPS-stimulated macrophages and inhibits the expression of TLR4 and the activation of nuclear factor kappa-B (NF-κB).

Conclusion

Hydrogen gas alleviates lipopolysaccharide-induced acute lung injury and inflammatory response most probably through the TLR4-NF-κB pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12950-022-00314-x.

Dexmedetomidine Inhibits NF-κB-Transcriptional Activity in Neurons Undergoing Ischemia-Reperfusion by Regulating O-GlcNAcylation of SNW1

Dexmedetomidine (Dex) is neuroprotective in ischemia-reperfusion (I/R) by suppressing inflammation but the underlying molecular mechanisms are not known. SNW domain-containing protein 1 (SNW1) is a coactivator of the pro-inflammatory transcription factor NF-κB p65. Because SNW1 is regulated by O-GlcNAcylation, we aimed to determine whether this modification influences NF-κB transcriptional activity in neurons undergoing I/R and how Dex may affect the O-GlcNAcylation of SNW1. SH-SY5Y and PC12 cells under hypoxia/reoxygenation (H/R) conditions were treated with Dex and with inhibitors of O-GlcNAc transferase (OGT). O-GlcNAc levels in SNW1 and effects of SNW1 on NF-κB p65 were determined by immunoprecipitation. H/R increased SNW1 protein levels but inhibited O-GlcNAcylation of SNW1. A Luciferase reporter assay demonstrated that increased SNW1 levels led to increased NF-κB p65 activity and increased secretion of neuron-derived inflammatory factors demonstrated by ELISA. Dex reversed the H/R-induced increase of SNW1 protein by upregulating OGT and enhancing O-GlcNAcylation of SNW1. Dex suppression of the SNW1/NF-κB complex resulted in neuroprotection in vitro and in a middle cerebral artery occlusion model in vivo. PKA and ERK1/2 inhibitors abolished the effect of Dex on OGT protein. Taken together, these data indicate that Dex inhibits NF-κB-transcriptional activity in neurons undergoing I/R by regulating O-GlcNAcylation of SNW1.

Impact of Dexamethasone Preconditioning on Prevention of Development of Cognitive Impairment following Acute Inflammation

To assess the preventive role of dexamethasone (Dex) in the development of neuroinflammation and concomitant neurocognitive disorders following acute inflammation. C57BL6 mice were fallen into the sham group, ischemia-reperfusion (I/R) group, and I/R + Dex group randomly. In the end, behavioral alterations were assessed with the Morris water maze (MWM) test, passive avoidance test (PAT), and open field test (OFT). The serum levels of IL-1β and TNF-α were detected by ELISA. Immunofluorescence was adopted to observe the NF-kB expression in the hippocampus. In addition, TLR4, NF-kB, CD68, and CD206 were examined by Western blot. The cognitive ability of mice can be impaired by tourniquet-induced acute inflammation, and these changes were prevented by Dex. Compared to the I/R group, Dex pretreatment could decrease levels of IL-1β and TNF-α proteins in serum. Besides, Dex preconditioning significantly decreased the utterance of NF-kB immunoreactive cells and TLR4, NF-kB, and CD68 overexpression in the hippocampus. Dex partly through inhibiting microglia transformation to the M1 polarization state and inactivating the TLR4/NF-kB pathway attenuates the cognitive disorders in mice.

NUCB2/Nesfatin-1 Reduces Obesogenic Diet Induced Inflammation in Mice Subcutaneous White Adipose Tissue

Background: Excess adipose tissue accumulation and obesity are characterised by chronic, low-grade, systemic inflammation. Nestfatin-1 is a neuropeptide derived from the precursor protein nucleobindin-2 (NUCB2), which was initially reported to exert anorexigenic effects. The present study aimed to investigate the effects of an obesogenic diet (OD; high-fat, high-sugar) in NUCB2 knockout (KO) mice and of nesfatin-1 treatment in LPS-stimulated 3T3-L1 preadipocytes. Methods: Subcutaneous white adipose tissue (Sc-WAT) samples from wild type (WT) and NUCB2 KO mice that were fed a normal diet (ND), or the OD for 12 weeks were used for RNA and protein extraction, as well as immunohistochemistry. 3T3-L1 cells were treated with 100 nM nesfatin-1 during differentiation and stimulated with 1 µg/mL LPS for measuring the expression and secretion of pro-inflammatory mediators by qPCR, western blotting, immunofluorescence, Bioplex, and ELISA. Results: Following the OD, the mRNA, protein and cellular expression of pro-inflammatory mediators (Tnfα, Il-6, Il-1β, Adgre1, Mcp1, TLR4, Hmbgb1 and NF-kB) significantly increased in the ScWAT of NUCB2 KO mice compared to ND controls. Adiponectin and Nrf2 expression significantly decreased in the ScWAT of OD-fed NUCB2 KO, without changes in the OD-fed WT mice. Furthermore, nesfatin-1 treatment in LPS-stimulated 3T3-L1 cells significantly reduced the expression and secretion of pro-inflammatory cytokines (Tnfα, Il-6, Il-1β, Mcp1) and hmgb1. Conclusion: An obesogenic diet can induce significant inflammation in the ScWAT of NUCB2 KO mice, involving the HMGB1, NRF2 and NF-kB pathways, while nesfatin-1 reduces the pro-inflammatory response in LPS-stimulated 3T3-L1 cells. These findings provide a novel insight into the metabolic regulation of inflammation in WAT.

Sevoflurane protects mice from cerebral ischemic injury by regulating microRNA-203-3p/HDAC4/Bcl-2 axis

Sevoflurane (Sevo) is neuroprotective in ischemic injury, but its specific mechanism in the disease from microRNA-203-3p/histone deacetylases 4/B-cell lymphoma 2 (miR-203-3p/HDAC4/Bcl-2) axis asks for a comprehensive explanation. A middle cerebral artery occlusion (MCAO) mouse model was established by nylon suture method. miR-203-3p and HDAC4 expression was measured in mouse brain tissues. The MCAO mice were exposed to Sevo or injected with miR-203-3p- or HDAC4-related plasmids. In response to Sevo treatment or plasmid interference, neurological function, brain pathology, neuronal apoptosis and inflammation were determined. The interactions of miR-203-3p and HDAC4, and HDAC4 and Bcl-2 were verified. MCAO mice presented down-regulated miR-203-3p and up-regulated HDAC4. Sevo improved neurological function, brain pathological damage and reduced neuronal apoptosis and inflammation in MCAO mice, while overexpressing miR-203-3p further enhanced those effects. HDAC4 overexpression antagonized the impacts of miR-203-3p up-regulation on MCAO mice. The targeting relation existed between miR-203-3p and HDAC4, as well as between HDAC4 and Bcl-2. It is clearly elucidated that miR-203-3p enhances the protective effects of Sevo on MCAO mice through elevating Bcl-2 and down-regulating HDAC4, potentially and clinically offering an effective treatment method with Sevo for cerebral ischemic injury.

Bone marrow mesenchymal stem cells-derived exosomal microRNA-124-3p attenuates hypoxic-ischemic brain damage through depressing tumor necrosis factor receptor associated factor 6 in newborn rats

Mesenchymal stem cells (MSCs)-derived exosomes (Exo) are beneficial in the use of brain damages. Restrictively, the mechanism of Exo expressing miR-124-3p in hypoxic-ischemic brain damage (HIBD) is not completely comprehended. Thereupon, this work was put forward to reveal the action of bone marrow MSCs-derived Exo (BMSCs-Exo) expressing miR-124-3p in the illness. BMSCs were isolated and transfected with miR-124-3p agomir. Then, BMSCs-Exo were extracted and identified. The newborn HIBD rats were injected with miR-124-3p-modified BMSCs-Exo or tumor necrosis factor receptor associated factor 6 (TRAF6)-related vectors. Next, neurological functions, neuron pathological and structural damages, oxidative stress and neuronal apoptosis were observed. miR-124-3p and TRAF6 expression was tested, along with their targeting relationship. miR-124-3p was down-regulated, and TRAF6 was up-regulated in newborn HIBD rats. miR-124-3p targeted TRAF6. BMSCs-Exo improved neurological functions, alleviated neuron pathological and structural damages, suppressed oxidative stress and reduced neuronal apoptosis in newborn HIBD rats, whereas BMSCs-Exo-mediated effects were enhanced by restoring miR-124-3p. Silencing TRAF6 attenuated HIBD in newborn rats, but overexpression of TRAF6 reversed the protective role of miR-124-3p-overexpressing BMSCs-Exo. This work makes it comprehensive that up-regulated exosomal miR-124-3p ameliorates HIBD in newborn rats by targeting TRAF6, which replenishes the potential agents for curing HIBD.

Overexpression of ORX or MCH Protects Neurological Function Against Ischemic Stroke

In recent years, orexin (ORX) and melanin-concentrating hormone (MCH) have been demonstrated to exert neuroprotective roles in cerebral ischemia. Hence, this study investigated the regulatory function of ORX and MCH in neurological function following ischemic stroke and explored the molecular mechanism underlying these functions. A rat model of ischemic stroke was developed by middle cerebral artery occlusion (MCAO), and Longa scoring was employed to evaluate the degree of neurological function deficit. The expression patterns of ORX and MCH were examined by real-time polymerase chain reaction in the brain tissues of rats with ischemic stroke induced by middle cerebral artery occlusion (MCAO). Moreover, electroencephalography (EEG) analysis and high-performance liquid chromatography (HPLC) were respectively performed to detect rapid-eye movement (REM) sleep, the glutamate (Glu) uptake, and the expression of γ-aminobutyric acid B receptor (GABA_B). Immunoblotting was performed to test the levels of autophagic markers LC3, BECLIN-1, and p62. Immunohistochemistry (IHC) staining and TUNEL assays were respectively used to assess the autophagy and neuronal apoptosis. Results demonstrated that ORX and MCH were lowly expressed in brain of rats with ischemic stroke. ORX or MCH overexpression decreased neuronal apoptosis and autophagy, and improved the sleep architecture of post-stroke rats, while rescuing Glu uptake and GABA expression. ORX or MCH upregulation exerted protective effects on neurological function. Taken together, ORX and/or MCH protect against ischemic stroke in a rat model, highlighting their value as targets for the clinical treatment of ischemic stroke.

The role of the vagus nerve on dexmedetomidine promoting survival and lung protection in a sepsis model in rats

BACKGROUND

Sepsis often results in acute lung injury (ALI). Dexmedetomidine (Dex) was reported to protect cells and organs due to its direct cellular effects. This study aims to investigate the role of vagus nerves on Dex induced lung protection in lipopolysaccharide (LPS)-induced ALI rats.

METHODS

The bilateral cervical vagus nerve of male Sprague-Dawley rats was sectioned or just exposed as sham surgery. After LPS administration, Dex antagonist yohimbine (YOH) and/or Dex was injected intraperitoneally to rats with or without vagotomy. The severity of ALI was determined with survival curve analysis and lung pathological scores. The plasma concentrations of interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), catecholamine and acetylcholine were measured with enzyme-linked immunosorbent assay.

RESULTS

The median survival time of LPS-induced ALI rats was prolonged by Dex (22 h, 95% CI, [24.46, 92.20]) vs. 14 h, 95% CI, [14.60, 89.57] of the LPS control group, P < 0.05), and the ALI score was reduced by Dex (6.5, 95% CI, [5.23, 8.10] vs. 11.5, 95% CI, [10.23, 13.10] in the LPS group, P < 0.01). However, these protective effects were significantly decreased by either YOH administration or vagotomy. Dex decreased LPS-induced IL-1β, TNF-α, and catecholamine but increased acetylcholine in blood serum; these effects of Dex was partially abolished by vagotomy.

CONCLUSIONS

Our data suggested that Dex increased vagal nerve tone that partially contributed to its anti-inflammatory and lung-protective effects. The indirect anti-inflammation and direct cytoprotection of Dex are likely through high vagal nerve tone and α₂-adrenoceptor activation, respectively.

Exosomal microRNA-150-5p from bone marrow mesenchymal stromal cells mitigates cerebral ischemia/reperfusion injury via targeting toll-like receptor 5

MicroRNA (miR)-150-5p has been investigated in many studies, while the role of exosomal miR-150-5p from bone arrow mesenchymal stromal cells (BMSCs) on cerebral ischemia/reperfusion (I/R) injury is not fully explored. This research aims to probe the effects of exosomal miR-150-5p from BMSCs on cerebral I/R injury via regulating B-cell translocation gene 2 (TLR5). Bone marrow mesenchymal stem cell-derived exosomes (BMSCs-Exo) were isolated and identified. The middle cerebral artery occlusion (MCAO) rat model was established and treated by BMSCs-Exo. Then, functional assays were conducted to explore neurological function, pathological changes, neuron apoptosis and inflammatory factors in MCAO rats. miR-150-5p and TLR5 expression in rat brain tissues were detected. Then, gain and loss-function assays were conducted to determine the impact of exosomes, miR-150-5p and TLR5 on neurological function, pathological changes, neuron apoptosis and inflammatory factors of MCAO rats. The binding relation between miR-150-5p and TLR5 was validated. It was found that miR-150-5p expression was decreased while TLR5 level was augmented in MCAO rats. BMSCs-Exo could improve neurological function, pathological changes, decelerate neuron apoptosis and reduce inflammatory factors in MCAO rats. Enriched miR-150-5pcould enhance the protective effects of BMSCs-Exo on cerebral I/R injury. The elevated TLR5 reversed the impacts of elevated exosomal miR-150-5p on cerebral I/R injury. TLR5 was targeted by miR-150-5p. This research manifested that exosomal miR-150-5p from BMSCs exerts protective effects on cerebral I/R injury via repressing TLR5. This study provided novel therapeutic targets for the treatment of cerebral I/R injury.

Sleep‐based therapy: A new treatment for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a worldwide problem with no effective treatment. Patients usually die of respiratory failure. The basic pathological process of ALS is the degeneration and necrosis of motor neurons. Neuroglial cell dysfunction is considered closely related to the development of ALS. Sleep plays an important role in repairing the nervous system, and sleep disorders can worsen ALS. Herein, we review the pathogenesis of ALS and the neuroprotective mechanism of sleep‐based therapy. Sleep‐based therapy could be a potential strategy to treat ALS.

Effects of Dexmedetomidine and Oxycodone on Neurocognitive and Inflammatory Response After Tourniquet-Induced Ischemia-Reperfusion Injury

To evaluate the effects of dexmedetomidine (Dex) and oxycodone (Oxy) on neurocognitive and inflammatory response after tourniquet-induced ischemia-reperfusion (I/R) injury. C57/BL6 mice were used to construct the mouse model of tourniquet-induced I/R injury. Mice (n = 48) were randomly divided into sham, I/R, Dex or Oxy group. Morris water maze test was performed to assess the spatial learning and memory function. The expression of NF-κB, TLR4, NR2B, M1 (CD68 and TNF-α) and M2 (CD206 and IL-10) polarization markers in mice hippocampus were detected by western blot or immunofluorescent staining. Spontaneous excitatory post-synaptic currents (sEPSCs) were recorded by electrophysiology. Dex treatment alleviated I/R-induced declines in learning and memory (p < 0.05), while Oxy had no significant effect on it. Compared with I/R group, Dex and Oxy treatment down-regulated the expression of NF-κB, TLR4, TNF-α and CD68 (all p < 0.05), while no significantly different was found in CD206 and IL-10. In addition, Dex treatment down-regulated the expression of NR2B and reduced the frequency and amplitude of sEPSCs in I/R model mice (all p < 0.05), while Oxy had no significant effect on them. Tourniquet-induced I/R could impair the neurocognitive function of mice. Dex treatment could alleviate I/R-induced neurocognitive disorder by inhibiting abnormal synaptic transmission in hippocampal neurons. Both Dex and Oxy could alleviate the inflammatory response likely by inhibiting the polarization of microglia toward M1 phenotype via TLR4/NF-κB pathway. Future studies are needed to further examine the effects of Dex on neurocognitive disorder after tourniquet-induced I/R injury and investigate the exact mechanism.

Dexmedetomidine preconditioning ameliorates lung injury induced by pulmonary ischemia/reperfusion by upregulating promoter histone H3K4me3 modification of KGF-2

Keratinocyte growth factor (KGF)-2 has been highlighted to play a significant role in maintaining the endothelial barrier integrity in lung injury induced by ischemia-reperfusion (I/R). However, the underlying mechanism remains largely unknown. The aims of this study were to determine whether dexmedetomidine preconditioning (DexP) modulates pulmonary I/R-induced lung injury through the alteration in KGF-2 expression. In our I/R-modeled mice, DexP significantly inhibited pathological injury, inflammatory response, and inflammatory cell infiltration, while promoted endothelial barrier integrity and KGF-2 promoter activity in lung tissues. Bioinformatics prediction and ChIP-seq revealed that I/R significantly diminished the level of H3K4me3 modification in the KGF-2 promoter, which was significantly reversed by DexP. Moreover, DexP inhibited the expression of histone demethylase JMJD3, which in turn promoted the expression of KGF-2. In addition, overexpression of JMJD3 weakened the protective effect of DexP on lung injury in mice with I/R. Collectively, the present results demonstrated that DexP ameliorates endothelial barrier dysfunction via the JMJD3/KGF-2 axis.

Dexmedetomidine Ameliorates Postoperative Cognitive Dysfunction via the MicroRNA-381-Mediated EGR1/p53 Axis

Postoperative cognitive dysfunction (POCD; cognitive change associated with anesthesia and surgery) is one of the most serious long-term postoperative complications that occur in elderly patients. Dexmedetomidine (DEX) has been shown to be beneficial for improving outcomes of postoperative cognitive function. However, the exact mechanism underlying this role requires is yet to be found. The present study aims to determine the pathways involved in the protective effects of DEX against POCD in C57BL/6 J aged mice. DEX was administered after POCD modeling in C57BL/6 J aged mice. The cognitive function was evaluated after DEX treatment using novel object recognition, open field, and Y-maze tests. We also assessed its effects on neuron apoptosis and production of TNF-α and IL-1β in mouse brain tissues as well as expression levels of DNA damage-related proteins p53, p21, and γH2AX. Interactions between early growth response 1 (EGR1) and p53, microRNA (miR)-381, and EGR1 were identified by ChIP and luciferase reporter assays, and gain- and loss-of-function experiments were performed to confirm the involvement of their interaction in POCD. DEX administration attenuated hippocampal neuron apoptosis, neuroinflammation, DNA damage, and cognitive impairment in aged mice. miR-381 targeted EGR1 and disrupted its interaction with p53, leading to a decline in hippocampal neuron apoptosis, DNA damage, neuroinflammation, and cognitive impairment. Furthermore, DEX administration resulted in the enhancement of miR-381 expression and the subsequent inhibition of EGR1/p53 to protect against cognitive impairment in aged mice. Overall, these results indicate that DEX may have a potential neuroprotective effect against POCD via the miR-381/EGR1/p53 signaling, shedding light on the mechanisms involved in neuroprotection in POCD.

Dexmedetomidine inhibits inflammatory response and oxidative stress through regulating miR-205-5p by targeting HMGB1 in cerebral ischemic/reperfusion

OBJECTIVE

To investigate effects of dexmedetomidine (DEX) on miR-205-5p/HMGB1 axis in cerebral ischemic/reperfusion (I/R) injury.

METHODS

Both in vivo I/R rat model and in vitro hypoxia/reoxygenation (H/R) cell model using rat hippocampal neurons cells were established. miR-205-5p was overexpressed or inhibited by transfection of miR-205-5p mimics or inhibitor. HMGB1 was overexpressed by transfection overexpression plasmids (OE-HMGB1). TTC staining was used for measurement of infraction volume. Oxidative stress was evaluated by measurement of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD) and inflammation was evaluated by measurement of IL-1β, IL-6 and TNF-α. Dual luciferase reporter assay was performed to confirm binding between miR-205-5p and HMGB1. The expression levels of miR-205-5p, and HMGB1 were measured using RT-qPCR. Western blotting was used to test the protein expression levels of HMGB1, nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione peroxidase (GPx), glutathione reductase (GR), heme oxygenase 1 (HO-1) and catalase (CAT).

RESULTS

Treatment of DEX significantly reduced brain infraction volume, decreased Longa's neurological function score and inhibited oxidative stress and inflammation in brain tissues of I/R rats, which were all reversed by inhibition of miR-205-5p. Both treatment of DEX or overexpression of miR-205-5p restricted oxidative stress and inflammation in H/R rat hippocampal neurons cells. The inhibition of miR-205-5p reversed the effects of DEX, while the overexpression of HMGB1 reversed the effects of miR-205-5p overexpression in H/R rat hippocampal neurons cells. Dual luciferase reporter assay showed miR-205-5p directly targeted HMGB1.

CONCLUSION

DEX improved I/R injury by suppressing brain oxidative stress and inflammation DEX improved I/R injury by suppressing brain oxidative stress and inflammation through activating miR-205-5p/HMGB1 axis through activating miR-205-5p/HMGB1 axis.

Pterostilbene alleviates cerebral ischemia and reperfusion injury in rats by modulating microglial activation

Ischemic stroke is a severe neurological disease without known effective therapy. Microglia-mediated neuroinflammation plays an important role in ischemic stroke. Therefore, finding a safe and effective microglial activation inhibitor might lead to an effective therapeutic strategy against ischemic stroke. In this project, our goal was to explore both the mechanism and effect of pterostilbene in MCAO/R rats. The potential effect of pterostilbene on ischemic stroke was tested using MCAO/R rats and its effect on microglial activation was tested in LPS-stimulated BV-2 cells. In vivo, pterostilbene decreased the neurological scores, brain water content and infarct volume in MCAO/R rats. Pterostilbene increased the number of mature neurons, decreased the number of activated microglia, and reduced iNOS and IL-1β mRNA expression. Pterostilbene inhibited phosphorylated-IκBα expression, thus promoting IκBα expression and inhibiting ROS overexpression. In vitro, pterostilbene inhibited the expression of inflammatory cytokines and suppressed NAPDH activity as well as activation of both the NF-κB pathway and ROS production. To our knowledge, our study is the first to demonstrate that pterostilbene-mediated alleviation of cerebral ischemia and reperfusion injury in rats may be correlated with the inhibition of the ROS/NF-κB-mediated inflammatory pathway in microglia, indicating the potential for the use of pterostilbene as a candidate therapeutic compound for ischemic stroke.

Ameliorative effects of escin on neuropathic pain induced by chronic constriction injury of sciatic nerve

ETHNOPHARMACOLOGY RELEVANCE

Escin is a natural mixture of triterpene saponins extracted from the seeds of Aesculus wilsonii Rehd. And has been reported to possess the therapeutic effects against neuropathic pain (NP). However, the underlying mechanisms remain unclear.

AIM OF THE STUDY

The present study aimed to investigate the therapeutic effects and explore the underlying mechanisms of escin on rats of NP induced by chronic constriction injury (CCI) of sciatic nerve.

MATERIALS AND METHODS

Rats were treated with escin (7, 14, and 28 mg/kg, i. g.) daily from the third day after the surgery (day 0) for consecutive 14 days. Regular behavior and thermal threshold were measured on days 0, 3, 5, 7, 10 and 14. Investigations into mechanisms involved measurement of inflammatory factors and biochemical factors in dorsal root ganglion (DRG). Inflammatory pain responses and nerve injuries were induced by the CCI model. Tonic pain model and acute inflammatory model induced by formalin or carrageenan were established to evaluated the pharmacological effects of escin on acute inflammatory pain. Corresponding behaviors were monitored and relevant gene expression such as c-fos, mu opioid receptor (MOR) and KCNK1 were detected by qRT-PCR. Investigate the neuroprotective effects of escin on PC12 cell injury induced by lipopolysaccharide (LPS). Cell morphology was observed under inverted microscope and neuroprotective effect of escin on cell activity was assessed by MTT assay.

RESULTS

Escin could widen thermal threshold, downregulate the concentration of inflammatory factors like tumor necrosis factor (TNF)-α and interleukin (IL)-1β, suppress the gene expression of toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB), decrease the level of glial fibrillary acidic protein (GFAP) and nerve growth factor (NGF) remarkably. In addition, escin significantly lowered the duration of licking, numbers of flinches and increase in paw edema, showing great therapeutic effects on inflammatory pain responses. Moreover, the activity of injured PC12 cells was significantly improved after escin administrated.

CONCLUSION

Escin exerted the ameliorative effects on NP induced by CCI which may be related to downregulating the release of pro-inflammatory cytokines, suppressing TLR-4/NF-κB signal pathway, thereafter decreasing the level of GFAP and NGF.

Activation of Opioid Receptors Attenuates Ischemia/Reperfusion Injury in Skeletal Muscle Induced by Tourniquet Placement

Method

Mice were randomly assigned to the sham, I/R, Oxy, and I/R with Oxy groups. Oxy was injected intraperitoneally 30 min before tourniquet placement. Morphological changes of the gastrocnemius muscle in these mice were assessed by hematoxylin-eosin (HE) staining and electron microscopy. Expression levels of TLR4, NF-κB, SIRT1, and PGC-1α in the skeletal muscles were detected by western blot. Blood TNF-α levels, gastrocnemius muscle contractile force, and ATP concentration were examined.

Results

Compared with the I/R group, Oxy pretreatment attenuated skeletal muscle damage, decreased serum TNF-α levels, and inhibited the expression levels of TLR4/NF-κB in the gastrocnemius muscle. Furthermore, Oxy treatment significantly increased serum ATP levels and the contractility of the skeletal muscles. SIRT1 and PGC-1α levels were significantly reduced in gastrocnemius muscle after I/R. Oxy pretreatment recovered these protein expression levels.

Conclusion

Tourniquet-induced acute limb I/R results in morphological and functional impairment in skeletal muscle. Pretreatment with Oxy attenuates skeletal muscle from acute I/R injury through inhibition of TLR4/NF-κB-dependent inflammatory response and protects SIRT1/PGC-1α-dependent mitochondrial function.

Neuroprotective Effects Against Cerebral Ischemic Injury Exerted by Dexmedetomidine via the HDAC5/NPAS4/MDM2/PSD-95 Axis

Numerous evidences have highlighted the efficient role of dexmedetomidine (DEX) in multi-organ protection. In the present study, the neuroprotective role of DEX on cerebral ischemic injury and the underlining signaling mechanisms were explored. In order to simulate cerebral ischemic injury, we performed middle cerebral artery occlusion in mice and oxygen-glucose deprivation in neurons. Immunohistochemistry, Western blot analysis, and RT-qPCR were used to examine expression of HDAC5, NPAS4, MDM2, and PSD-95 in hippocampus tissues of MCAO mice and OGD-treated neurons. MCAO mice received treatment with DEX and sh-PSD-95, followed by neurological function evaluation, behavioral test, infarct volume detection by TTC staining, and apoptosis by TUNEL staining. Additionally, gain- and loss-of-function approaches were conducted in OGD-treated neuron after DEX treatment. Cell viability and apoptosis were assessed with the application of CCK-8 and flow cytometry. The interaction between MDM2 and PSD-95 was evaluated using Co-IP assay, followed by ubiquitination of PSD-95 detection. As per the results, HDAC5 and MDM2 were abundantly expressed, while NPAS4 and PSD-95 were poorly expressed in hippocampus tissues of MCAO mice and OGD-treated neurons. DEX elevated viability, and reduced LDH leakage rate and apoptosis rate of OGD-treated neurons, which was reversed following the overexpression of HDAC5. Moreover, HDAC5 augmented MDM2 expression via NPAS4 inhibition. MDM2 induced PSD-95 ubiquitination and degradation. In MCAO mice, DEX improved neurological function and behaviors and decreased infarct volume and apoptosis, which was negated as a result of PSD-95 silencing. DEX plays a neuroprotective role against cerebral ischemic injury by disrupting MDM2-induced PSD-95 ubiquitination and degradation via HDAC5 and NPAS4.

Effects of intravenous lidocaine, dexmedetomidine, and their combination on IL-1, IL-6 and TNF-α in patients undergoing laparoscopic hysterectomy: a prospective, randomized controlled trial

BACKGROUND

Surgical-related inflammatory responses have negative effects on postoperative recovery. Intravenous (IV) lidocaine and dexmedetomidine inhibits the inflammatory response. We investigated whether the co-administration of lidocaine and dexmedetomidine could further alleviate inflammatory responses compared with lidocaine or dexmedetomidine alone during laparoscopic hysterectomy.

METHODS

A total of 160 patients were randomly allocated into four groups following laparoscopic hysterectomy: the control group (group C) received normal saline, the lidocaine group (group L) received lidocaine (bolus infusion of 1.5 mg/kg over 10 min, 1.5 mg/kg/h continuous infusion), the dexmedetomidine group (group D) received dexmedetomidine (bolus infusion of 0.5 μg/kg over 10 min, 0.4 μg/kg/h continuous infusion), and the lidocaine plus dexmedetomidine group (group LD) received a combination of lidocaine (bolus infusion of 1.5 mg/kg over 10 min, 1.5 mg/kg/h continuous infusion) and dexmedetomidine (bolus infusion of 0.5 μg/kg over 10 min, 0.4 μg/kg/h continuous infusion). The levels of plasma interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) at different time points were the primary outcomes. Secondary outcomes included hemodynamic variables, postoperative visual analogue scale (VAS) scores, time to first flatus, and incidence of nausea and vomiting after surgery.

RESULTS

The levels of plasma IL-1, IL-6, and TNF-α were lower in groups D and LD than in group C and were lowest in group LD at the end of the procedure and 2 h after the operation (P < 0.05). The VAS scores were decreased in groups D and LD compared with group C (P < 0.05). The heart rate (HR) was decreased at the end of the procedure and 2 h after the operation in groups D and LD compared to groups C and L (P < 0.001). The mean blood pressure (MBP) was lower at 2 h after the operation in groups L, D, and LD than in group C (P < 0.001). There was a lower incidence of postoperative nausea and vomiting (PONV) in group LD than in group C (P < 0.05).

CONCLUSIONS

The combination of lidocaine and dexmedetomidine significantly alleviated the inflammatory responses, decreased postoperative pain, and led to fewer PONV in patients undergoing laparoscopic hysterectomy.

TRIAL REGISTRATION

ClinicalTrials.gov ( NCT03276533 ), registered on August 23, 2017.

Forkhead transcription factor FOXO1 is involved in hypoxia/reoxygenation-induced gonadotropin-releasing hormone decline

Previously, it has been demonstrated that aging is associated with nuclear factor-κB (NF-κB)-mediated hypothalamic gonadotropin-releasing hormone (GnRH) decrease. The hypothalamus is one of the brain regions that are vulnerable to ischemia-reperfusion injury. However, it is unclear whether ischemia-reperfusion has an influence on the hypothalamic GnRH release. In the current study, GT1-7 cells, which are a cell line of hypothalamic GnRH neurons, were subjected to hypoxia-reoxygenation to mimic ischemia-reperfusion. The effect of hypoxia-reoxygenation on the hypothalamic GnRH release was investigated. It was found that GnRH secretion from GT1-7 cells was decreased under the hypoxia-reoxygenation condition. Mechanistic studies revealed that hypoxia-reoxygenation activated nuclear factor-κB (NF-κB) via the protein kinase B (Akt)/forkhead box protein O1 (FOXO1) pathway, thereby inhibiting gnrh1 gene. The results of the current study suggested that hypoxia-reoxygenation injury may facilitate the hypothalamic programming of system aging through impairment of hypothalamic GnRH release.

Syringin exerts neuroprotective effects in a rat model of cerebral ischemia through the FOXO3a/NF-κB pathway

Inflammation plays an important role in the pathogenesis of cerebral ischemia. Syringin (SYR) is an active substance isolated from Acanthopanax senticosus plants, and possesses anti-inflammatory and neuroprotective properties. However, its effects on cerebral ischemic injury, as well as the underlying molecular events, are still unclear. The purpose of this study was to investigate the effect of SYR in a rat model of cerebral ischemia and address the related molecular mechanism. A middle cerebral artery occlusion/reperfusion model (MCAO) was used to simulate ischemic injury. SYR treatment clearly reduced the infarct volume, decreased cerebral water content, improved the neurological score, and attenuated neuronal death. Moreover, SYR decreased the expression of NF-κB, IL-1β, IL-6, TNF-α, and MPO, promoted FOXO3a phosphorylation and cytoplasmic retention, and inhibited the nuclear translocation of NF-κB. FOXO3a knockdown by RNA interference significantly prevented SYR-induced inhibition of NF-κB-mediated inflammation. Confocal microscopy revealed that SYR reduced NF-κB translocation to the nucleus, and FOXO3a silencing reversed this effect. Finally, immunofluorescence and CO-IP experiments showed that SYR promoted the interaction between FOXO3a and NF-κB. In conclusion, SYR exerted a protective effect against brain I/R injury by reducing the inflammation accompanying cerebral ischemia. This effect was mediated by the FOXO3a /NF-κB pathway.

Dexmedetomidine Reduces Atrial Fibrillation After Adult Cardiac Surgery: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Dexmedetomidine has been shown to have antiarrhythmic effects by exhibiting sympatholytic properties and activating the vagus nerve in preclinical studies. Results from clinical trials of dexmedetomidine on atrial fibrillation (AF) following adult cardiac surgery are controversial.

MATERIALS AND METHODS

We searched EMBASE, PubMed and Cochrane CENTRAL databases for randomized controlled trials (RCTs) comparing the antiarrhythmic effect of dexmedetomidine versus placebo or other anesthetic drugs in adult patients undergoing cardiac surgery. The primary outcome was the incidence of AF. The secondary outcomes were ventricular arrhythmias [ventricular fibrillation (VF), ventricular tachycardia (VT)], mechanical ventilation (MV) duration, intensive care unit (ICU) length of stay, and hospital length of stay, and all-cause mortality.

RESULTS

Thirteen trials with a total of 1684 study patients were selected. Compared with controls, dexmedetomidine significantly reduced the incidence of postoperative AF [odds ratio (OR) 0.75; 95% confidence interval (CI) 0.58-0.97; P = 0.03] and VT (OR 0.23; 95% CI 0.11-0.48; P < 0.0001). No significant difference for the incidence of VF existed (OR 0.80; 95% CI 0.21-3.03; P = 0.74). There was no significant difference between groups in MV duration [weighted mean difference (WMD) - 0.10; 95% CI - 0.42 to 0.21; P = 0.52], postoperative ICU stay (WMD - 0.49; 95% CI - 2.64 to 1.66; P = 0.65), hospital stay (WMD - 0.01; 95% CI - 0.16 to 0.13; P = 0.88) and mortality (OR 0.59; 95% CI 0.15-2.37; P = 0.46).

CONCLUSIONS

Perioperative administration of dexmedetomidine in adult patients undergoing cardiac surgery reduced the incidence of postoperative AF and VT. But there was no significant difference in incidence of VF, MV duration, ICU stay, hospital stay and mortality.

Dexmedetomidine protects PC12 cells from ropivacaine injury through miR-381/LRRC4 /SDF-1/CXCR4 signaling pathway

Introduction

Ropivacaine has been regularly used because of its good anesthetic and analgesic effects, but it may exert neurotoxic effects on neurocyte. Dexmedetomidine has presented special advantages in the fields of neuroprotection, and it also could improve peripheral nerve block combining with ropivacaine. However, if dexmedetomidine could repair neurocyte injury induced by ropivacaine, and the specific mechanism remain unclear.

Methods

Western blotting and qRT-PCR were applied for measuring expression of protein and mRNA, respectively. Flow cytometry was used for assessing apoptosis. Cell proliferation was detected using Cell Counting Kit-8 (CCK-8) and colony formation assays. Transwell assay was applied to measure the migration and invasion of cells. Dual luciferase reporter assay was applied for confirming the binding site between microRNA-381 (miR-381) and Leucine-rich repeat C4 protein (LRRC4).

Results

The viability of PC12 cells increased with raising the concentration of dexmedetomidine (0 μM, 10 μM, 50 μM, 100 μM). Dexmedetomidine reversed role of ropivacaine (0 mM, 0.1 mM, 0.5 mM, 1 mM) by upragulating the expression of miR-381 and suppressing the expression of LRRC4 in PC12 cells. miR-381 can directly interact with target gene LRRC4 and negatively regulate its expression. Dexmedetomidine promoted the proliferation, migration, and invasion and inhibited apoptosis of PC12 cells by suppressing LRRC4 via up-regulating the expressions of miR-381 and further activated SDF-1/CXCR4 signaling pathway.

Conclusions

Dexmedetomidine could protect PC12 cells from ropivacaine injury through miR-381/LRRC4/SDF-1/CXCR4 signaling pathway. This study may provide new therapeutic strategy targeting miR-381/LRRC4/SDF-1/CXCR4 signaling pathway about the prevention of ropivacaine induced neurocyte injury.

Mechanisms of Dexmedetomidine in Neuropathic Pain

Dexmedetomidin is a new-generation, highly selective α2 adrenergic receptor agonist with a large number of advantages, including its sedative and analgesic properties, its ability to inhibit sympathetic nerves, its reduced anesthetic dosage, its hemodynamic stability, its mild respiratory depression abilities, and its ability to improve postoperative recognition. Its safety and effectiveness, as well as its ability to provide a certain degree of comfort to patients, make it a useful anesthetic adjuvant for a wide range of clinical applications. For example, dexmedetomidine is commonly used in patients undergoing general anesthesia, and it also exerts sedative effects during tracheal intubation or mechanical ventilation in intensive care unit patients. In recent years, with the deepening of clinical research on dexmedetomidine, the drug is still applied in the treatment of spastic pain, myofascial pain, neuropathic pain, complex pain syndrome, and chronic headache, as well as for multimodal analgesia. However, we must note that the appropriateness of patient and dose selection should be given attention when using this drug; furthermore, patients should be observed for adverse reactions such as hypotension and bradycardia. Therefore, the safety and effectiveness of this drug for long-term use remain to be studied. In addition, basic experimental studies have also found that dexmedetomidine can protect important organs, such as the brain, heart, kidney, liver, and lung, through various mechanisms, such as antisympathetic effects, the inhibition of apoptosis and oxidative stress, and a reduction in the inflammatory response. Moreover, the neuroprotective properties of dexmedetomidine have received the most attention from scholars. Hence, in this review, we mainly focus on the characteristics and clinical applications of dexmedetomidine, especially the role of dexmedetomidine in the nervous system and the use of dexmedetomidine in the relief of neuropathic pain.

[Role of mitochondrial fusion and fission in protective effects of dexmedetomidine against cerebral ischemia/reperfusion injury in mice]

OBJECTIVE

To investigate the protective effects of dexmedetomidine (DEX) against cerebral ischemia/reperfusion (I/R) injury in mice and its relation with mitochondrial fusion and fission.

METHODS

Male ICR mice were randomly divided into sham-operated group, I/R group, I/R+DEX group and I/R+DEX+dorsomorphin group. Mouse models of cerebral I/R injury were established by modified thread occlusion of the middle cerebral artery. DEX (50 μg/kg) was injected intraperitoneally at 30 min before cerebral ischemia, which lasted for 1 h followed by reperfusion for 24 h. The neurobehavioral deficits of the mice were evaluated based on Longa's scores. The volume of cerebral infarction was detected by TTC staining. The changes in mitochondrial morphology of the brain cells were observed with transmission electron microscopy. Western blotting was performed to detect the expressions of phosphorylated AMP-activated protein kinase (p-AMPK), mitochondrial fusion protein (Mfn2) and mitochondrial fission protein (p-Drp1) in the brain tissues.

RESULTS

DEX pretreatment significantly reduced the neurobehavioral score and the percent volume of cerebral infarction in mice with cerebral I/R injury. Treatment with dorsomorphin (an AMPK inhibitor) in addition to DEX significantly increased the neurobehavioral score and the percent volume of cerebral infarction in the mouse models. Transmission electron microscopy showed that DEX obviously reduced mitochondrial damage caused by cerebral I/R injury and restored mitochondrial morphology of the brain cells, and such effects were abolished by dorsomorphin treatment. Western blotting showed that DEX pretreatment significantly increased the expressions of p-AMPK and Mfn2 protein and decreased the expression of p-Drp1 protein in the brain tissue of the mice, and these changes were also reversed by dorsomorphin treatment.

CONCLUSIONS

Preconditioning with DEX produces protective effects against cerebral I/R injury in mice possibly by activating AMPK signaling to regulate mitochondrial fusion and fission in the brain cells.

Dexmedetomidine had neuroprotective effects on hippocampal neuronal cells via targeting lncRNA SHNG16 mediated microRNA-10b-5p/BDNF axis

Dexmedetomidine (DEX), a highly selective alpha2 adrenergic receptor agonist, is a commonly used anesthetic drug in surgical procedures. Previous studies have indicated that DEX exerts neuroprotective effects while the detailed mechanism has not been fully elucidated. Here, we aim to study the role of lncRNA SHNG16 in DEX-induced brain protection and its underlying molecular mechanism. The rats underwent middle cerebral artery occlusion (MCAO) surgery and oxygen-glucose deprivation (OGD)-treated HT22 hippocampal neurons were treated with DEX, respectively. CCK8 was used to evaluate cell viability. sh-SHNG16 as well as miR-10b-5p mimics were transfected into hippocampal neurons to further explore the bio-function of SNHG16 and miR-10b-5p in vitro. Furthermore, the interactions between SHNG16 and miR-10b-5p, miR-10b-5p and BDNF gene were confirmed by dual-luciferase report assay. Our data revealed that DEX attenuated neurological damage of the MCAO rats and also increased the cell viability of the neurons significantly. Besides, expression of SHNG16 and BDNF were both downregulated while miR-10b-5p was upregulated in MCAO brain tissues or OGD treated neurons. DEX inhibited miR-10b-5p expression but increased SHNG16 and BDNF levels with a dosage effect. After transfection with sh-SHNG16 or miR-10b-5p mimics, the expression of BDNF protein was downregulated, accompanied with decreased neuron viability. Dual-luciferase assay showed that SHNG16 targeted on miR-10b-5p, which also could bind directly to the 3'-UTR sites of BDNF and negatively regulate its expression. In conclusion, DEX exerts neuroprotective in ischemic stroke via improving neuron damage, the underlying mechanism may be upregulating SHNG16 and BDNF via sponging miR-10b-5p.

microRNA-195 attenuates neuronal apoptosis in rats with ischemic stroke through inhibiting KLF5-mediated activation of the JNK signaling pathway

BACKGROUND

Accumulating evidence has implicated the regulation of microRNAs (miRs) in ischemia stroke. The current study aimed to elucidate the role of microRNA-195 (miR-195) in neuronal apoptosis and brain plasticity in rats with ischemic stroke via the JNK signaling pathway/KLF5 axis.

METHODS

Ischemic stroke rat models were established by middle cerebral artery occlusion (MCAO), and oxygen deprivation (OGD) models were constructed in rat neuronal cells, followed by gain- or loss-of-function of miR-195 and/or KLF5 in rats and cells. Infarct volume, neuronal loss and ultrastructure, the expression of GAP-43, SYP and KLF5 protein as well as cell apoptosis were determined in the rats. Caspase-3 activity as well as the expression of miR-195, KLF5, GAP-43, SYP, JNK, phosphorylated JNK, Bax and Bcl-2 was measured in the cells.

RESULTS

The infarct size, expression of GAP-43 and SYP protein and apoptotic cells were increased in the miR-195^-/- MCAO rats, while reductions were detected in the miR-195 mimic MCAO and KLF5^-/- MCAO rats. Bcl-2 expression was increased, Bax and Caspase-3 expression as well as the ratio of phosphorylated JNK/JNK was decreased in response to miR-195 overexpression or KLF5 knockdown. Interestingly, the silencing of KLF5 reversed the effects exerted by the miR-195 inhibitor on the expression of Bcl-2, phosphorylated JNK/JNK, Bax and Caspase-3.

CONCLUSIONS

Collectively, our study unraveled that miR-195 could down-regulate KLF5 and block the JNK signaling pathway, ultimately inhibiting neuronal apoptosis in rats with ischemic stroke.

Salvianolic Acid D Alleviates Cerebral Ischemia-Reperfusion Injury by Suppressing the Cytoplasmic Translocation and Release of HMGB1-Triggered NF-κB Activation to Inhibit Inflammatory Response

Inflammatory response participates in the overall pathophysiological process of stroke. It is a promising strategy to develop antistroke drugs targeting inflammation. This study is aimed at investigating the therapeutic effect and anti-inflammatory mechanism of salvianolic acid D (SalD) against cerebral ischemia/reperfusion (I/R) injury. A rat middle cerebral artery occlusion/reperfusion (MCAO/R) injury model was established, and an oxygen-glucose deprivation/reoxygenation (OGD/R) injury model was established in PC12 cells. Neurological deficit score, cerebral infarction, and edema were studied in vivo. Cell viability was achieved using the MTT method in vitro. The Bax, Bcl-2, cytochrome c, HMGB1, TLR4, TRAF6, NF-κB p65, p-NF-κB p65, and cleaved caspase-3 and -9 were tested via the Western blot method. Cytokines and cytokine mRNA, including TNF-α, IL-1β, and IL-6, were studied via ELISA and PCR methods. The translocation of HMGB1 and NF-κB were studied by immunofluorescence assay. The HMGB1/NeuN, HMGB1/GFAP, and HMGB1/Iba1 double staining was carried out to observe the localization of HMGB1 in different cells. Results showed that SalD alleviated neurological impairment, decreased cerebral infarction, and reduced edema in I/R rats. SalD improved OGD/R-downregulated PC12 cell viability. SalD also promoted Bcl-2 expression and suppressed Bax, cytochrome c, and cleaved caspase-3 and -9 expression. SalD decreased the intensity of TLR4, MyD88, and TRAF6 proteins both in vivo and in vitro, and significantly inhibited the NF-κB nuclear translocation induced by I/R and OGD/R. What's more, SalD inhibited HMGB1 cytoplasmic translocation in neurons, astrocytes, and microglia in both the cortex and hippocampus regions of I/R rats. In conclusion, SalD can alleviate I/R-induced cerebral injury in rats and increase the PC12 cell viability affected by OGD/R. The anti-inflammatory mechanism of SalD might result from the decreased nuclear-to-cytoplasmic translocation of HMGB1 and the inhibition on its downstream TLR4/MyD88/NF-κB signaling.

miR-137 alleviates focal cerebral ischemic injury in rats by regulating JAK1/STAT1 signaling pathway

The repairing effect and potential mechanism of miR-137 on cerebral ischemic injury in rats was investigated. The volume of cerebral infarction and calculated brain water content was detected by triphenyltetrazolium chloride staining. The expression of inflammatory factors was detected by enzyme-linked immunosorbent assay. The pathological damage of brain tissue was analyzed by hematoxylin and eosin and Nissl staining. The apoptosis in ischemic brain tissue was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. The levels of STAT1 and JAK1 proteins were analyzed by Western blot. The expression of miR-137 in primary hippocampal neurons was detected by reverse transcription polymerase chain reaction. miR-137 overexpression significantly improved brain damage in rats. miR-137 overexpression can reduce the expression of TNF-α, IL-1β, and IL-6. miR-137 overexpression can reduce the degree of brain tissue damage and inhibit the expression of JAK1 and STAT1 proteins. miR-137 overexpression can reduce oxygen-glucose deprivation (OGD)/R-induced cell damage, improve cell proliferation, and reduce apoptotic rate. JAK1 and STAT1 protein expression was inhibited in hippocampal neurons after OGD/R treatment after transfection with miR-137 mimic. After the addition of the Filgotinib inhibitor, the levels of JAK1 and STAT1 proteins were significantly reduced. The results suggested that miR-137 overexpression can effectively improve ischemic injury after focal cerebral ischemia and protect against by inhibiting JAK1/STAT1 pathway.

Dexmedetomidine Post-Conditioning Alleviates Cerebral Ischemia-Reperfusion Injury in Rats by Inhibiting High Mobility Group Protein B1 Group (HMGB1)/Toll-Like Receptor 4 (TLR4)/Nuclear Factor kappa B (NF-κB) Signaling Pathway

BACKGROUND Cerebral ischemia-reperfusion injury is a pivotal cause of deaths due to cerebrovascular accident. Increased research efforts are needed to reveal the mechanism underlying its aggravation or alleviation. In this study, the effects of dexmedetomidine post-conditioning on the HMGB1/TLR4/NF-kappaB signaling pathway in cerebral ischemia-reperfusion rats was explored. MATERIAL AND METHODS Ninety rats were randomly divided into 5 groups - a sham group (Sham), a model group (I/R), a dexmedetomidine post-conditioning group (Dex), a recombinant high mobility group protein B1 group (rHMGB1), and a recombinant HMGB1+dexmedetomidine post-conditioning group (rHMGB1+Dex) - with 18 rats in each group. Longa grading, wet-dry weighing, TTC staining, HE staining, and immunohistochemical staining were used to assess brain damage. ELISA, RT-PCR, and Western blot analyses were performed to assess expression of IL-1ß, TNF-alpha, IL-6, IL-8, HMGB1, TLR4, and NF-kappaB. RESULTS Compared with the I/R group, the neurological function score, brain water content, infarction area, and the number of COX-2- and IBA-1-positive cells in the Dex group were significantly lower, accompanied by downregulated expression of the HMGB1/TLR4/NF-kappaB pathway, alleviated inflammation, and oxidative stress injury in brain tissue. These trends were mostly reversed in the rHMGB1 group and rHMGB1+Dex group, but not in the Dex group. Furthermore, when compared to the Dex group, there were significant increases of H₂O₂, MDA, NO, IL-1ß, TNF-alpha, IL-6, IL-8, HMGB1, TLR4, and p-P65 in the rHMGB1 group and rHMGB1+Dex group, in which a significant decrease of T-AOC, SOD, and p-IkappaBalpha was also detected. CONCLUSIONS Dexmedetomidine post-conditioning can alleviate cerebral ischemia-reperfusion injury in rats by inhibiting the HMGB1/TLR4/NF-kappaB signaling pathway.

The effect of repetitive exposure to intravenous anesthetic agents on the immunity in mice

Introduction: This study was designed to assess the effect of repetitive exposure to intravenous anesthetic agents on the immunity in mice. Materials and Methods: The mice were divided into six groups: three intravenous anesthetic agents groups (dexmedetomidine, midazolam and propofol groups), and three corresponding control groups (C_D, C_M, and C_P groups). The intravenous injections were administered once per day for 5 days. The immunity of mice was checked after the last intravenous injection. Histopathology and immunochemistry of liver and kidneys were evaluated. Cytokine levels in the blood was also checked. vs. evaluated with cytokine levels in the blood. Results: Cluster of differentiation (CD)4⁺ T cells were significantly less expressed in dexmedetomidine and propofol groups, compared with the corresponding control groups [34.08 ± 5.63% in the dexmedetomidine group vs. 59.74 ± 8.64% in the C_D group, p < 0.05; 25.28 ± 7.28% in the propofol group vs. 61.12 ± 2.70% in the C_p group, p < 0.05]. Apoptosis of CD4⁺ T cells was increased significantly in dexmedetomidine and propofol groups, compared with the corresponding control groups. Histopathological findings of liver and kidneys did not show any specific differences of any of three intravenous anesthetic agents groups with their corresponding control groups, although immunohistochemical examination indicated significantly lower expression of Toll-like receptor-4 from liver and kidneys in dexmedetomidine and propofol groups. The cytokine levels were not different between the groups. Conclusion: Repetitive exposure to dexmedetomidine and propofol reduced the expression of CD4⁺ T cells but did not induce any significant liver or kidney injuries.

Protective Effects of Dexmedetomidine and Oxycodone in Patients Undergoing Limb Ischemia-Reperfusion

Background

Tourniquet-related complications are a common clinical problem. In the present study, we compared the effects of dexmedetomidine vs. oxycodone in patients undergoing limb ischemia-reperfusion.

Material/Methods

Fifty-four patients undergoing unilateral lower-extremity surgery under combined spinal and epidural anesthesia were randomly assigned to a control (ischemia-reperfusion, I/R) group, a dexmedetomidine (Dex) group, and an oxycodone (Oxy) group. Tourniquet-induced hemodynamic parameters changes among groups were compared. The serum concentration of malondialdehyde (MDA), superoxide dismutase (SOD), tumor necrosis factor-a (TNF-α), interleukin-6 (IL-6), fatty acid binding protein 3 (FABP3), endothelin-1 (ET-1), and brain-derived neurotrophic factor (BDNF) were measured using ELISA before anesthesia and at 30 min and at 6 h after tourniquet release.

Results

In the control group, tourniquet use caused significant increases in systolic arterial pressure (SAP), mean arterial pressure (MAP), diastolic arterial pressure (DAP), and rate-pressure product. Compared with Oxy, Dex significantly decreased heart rate (HR). Both Dex and Oxy lowered SAP compared with the control group. No significant difference was observed in DAP between Dex and Oxy. The levels of MDA, TNF-α, IL-6, FABP3, and ET-1 were significantly higher, while the SOD and BDNF were significantly lower compared to baseline in the I/R group, but the variation range of those agents was significantly smaller in the Dex and Oxy groups, and the measured values were comparable between the 2 groups.

Conclusions

Compared with Dex, Oxy was not inferior in mitigating tourniquet-induced hyperdynamic response, ameliorating the inflammatory reaction, and protecting remote multiple organs in lower-extremity surgery patients.

Microglial V-set and immunoglobulin domain-containing 4 protects against ischemic stroke in mice by suppressing TLR4-regulated inflammatory response

Ischemic stroke is a leading cause of death among human in the world, and a critical cause for long-term disability. Accumulating studies have indicated that inflammatory response regulated by microglia contributes a lot to neuronal death, but the molecular mechanism still remains unclear. V-set and immunoglobulin domain-containing 4 (Vsig4), a complement receptor of the immunoglobulin superfamily (CRIg) that specifically expresses in resting tissue-resident macrophages, plays a critical role in regulating various inflammatory diseases via multiple signaling pathways. However, the effects of Vsig4 on ischemic stroke have not been investigated. In this study, we identified that Vsig4 expression was decreased after cerebral ischemic injury induced by middle cerebral artery occlusion (MCAO). Immunofluorescence staining showed that Vsig4 was co-localized with Iba1 in microglial cells from the infarct region of MCAO-operated mice. After over-expressing Vsig4 in mice, MCAO-induced infarction area and neurological deficits score were markedly attenuated. In addition, neurological dysfunction due to MCAO surgery was improved by Vsig4 over-expression. Microglial M1 polarization was detected in mice with MCAO surgery, which was markedly inhibited by Vsig4 over-expression, as evidenced by the markedly reduced expression of CD16, CD11b, inducible nitric oxide synthase (iNOS) and interleukin 6 (IL-6); however, the expression of M2-like phenotype hallmarks such as arginase 1 (Arg1), CD206, IL-10 and Ym-1 was significantly up-regulated. Mechanistically, the anti-inflammatory role of Vsig4 was mainly through the blockage of toll-like receptor 4/nuclear factor kappa B (TLR4/NF-κB) signaling via the in vivo and in vitro experiments. Also, we found that microglial TLR4 expression in the cerebral infarct area of MCAO mice was highly suppressed by Vsig4 over-expression. In vitro, the neuron-glial mixed culture by fluorescent staining showed that oxygen glucose deprivation (OGD) treatment led to significant cell death, while being attenuated by Vsig4 over-expression in primary microglial cells. Finally, we showed that Vsig4 could interact with TLR4 and repress its expression, subsequently alleviating ischemic stroke. Collectively, our findings demonstrated that microglial Vsig4 protected against post-stroke neuro-inflammation mainly through interacting with TLR4.

Involvement of apoptosis in the protective effects of Dracocephalum moldavaica in cerebral ischemia reperfusion rat model

An extract of Dracocephalum moldevica (DML) was found to exert protective effects on cerebral ischemia-reperfusion injury (CIRI); however, the mechanisms underlying the observed actions of this plant-derived mixture remain to be determined. Thus, the aim of this study was to examine the influence of DML on CIRI rat model induced by middle cerebral artery occlusion (MCAO). The following parameters were measured: (1) viable neurons in the infarcted area using Nissl staining; and (2) immunohistochemistry and Western blot were employed to determine protein expression levels of p53, bcl-2 associated X protein (bax) and B-cell lymphoma-2 (bcl-2), three biomarkers of apoptosis. MCAO significantly decreased the number of viable cortical pyramidal neurons in the infarcted area, while treatment with DML extract significantly elevated the number of viable neurons. MCAO was found to significantly elevate in gene expression levels of p53 and protein expression levels bax accompanied by diminished protein expression levels of bcl-2. Prior administration of DML extract produced marked reduction in gene expression levels of p53 and protein expression levels bax but increased in protein expression levels of bcl-2. Data suggested apoptosis was initiated in MCAO and that DML was effective in treating CIRI via an anti-apoptotic action as evidenced by inhibition of gene expression levels of p53 and protein expression levels of bax with concomitant elevation in protein expression levels of bcl-2. Our findings suggest that extract of DML may prove beneficial in treatment of cerebrovascular disorders.

Dexmedetomidine inhibits neuronal apoptosis by inducing Sigma-1 receptor signaling in cerebral ischemia-reperfusion injury

Dexmedetomidine is known to alleviate cerebral ischemia-reperfusion injury (CIRI). We established a rat model of CIRI, which exhibited higher neurological deficit scores and a greater number of apoptotic cells in the cerebral ischemic penumbra than controls. Dexmedetomidine reversed the neuronal apoptosis and improved neurological function in this model. We then examined Sigma-1 receptor (Sig-1R) expression on the endoplasmic reticulum (ER) in brain tissues at different reperfusion time points. Sig-1R expression increased with CIRI and decreased with increasing reperfusion times. After 24 hours of reperfusion, dexmedetomidine upregulated Sig-1R expression, and ER stress proteins (GRP78, CHOP, JNK and Caspase-3) were detected in brain tissues with Western blotting. Moreover, GRP78 expression followed a pattern similar to Sig-1R. Dexmedetomidine induced GRP78 expression but inhibited CHOP, Caspase-3 and phosphorylated-JNK expression in brain tissues. A Sig-1R-specific inhibitor reduced GRP78 expression and partially inhibited the upregulation of GRP78 by dexmedetomidine. The inhibitor also increased CHOP and Caspase-3 expression and partially reversed the inhibitory effects of dexmedetomidine on these pro-apoptotic ER stress proteins. These results suggest that dexmedetomidine at least partially inhibits ER stress-induced apoptosis by activating Sig-1R, thereby attenuating brain damage after 24 hours of ischemia-reperfusion.

High mobility group box-1 mediates hippocampal inflammation and contributes to cognitive deficits in high-fat high-fructose diet-induced obese rats

High-fat high-sugar diet-induced obesity can lead to hippocampal inflammation and cognitive deficits, but the detailed underlying mechanism is still not clear. We aim to investigate the role of HMGB1 in hippocampal inflammatory responses and cognitive impairment in high-fat high-fructose diet (HFHFD)-induced obesity. Rats were fed with a normal control diet or an HFHFD diet for 14 weeks. In the last 6 weeks on the diets, the rats were treated with control, or an HMGB1 inhibitor glycyrrhizin, or an anti-HMGB1 neutralizing monoclonal antibody (mAb). Obesity was induced in the HFHFD-fed rats, which had higher body weight, epididymal white adipose tissue (EWAT) weight and caloric efficiency, and lower brain/body weight ratio, glucose tolerance and insulin sensitivity than the ones on normal diets. In the HFHFD-induced obese rats, the HMGB1 levels in plasma and hippocampus were increased, and the nucleus-to-cytoplasm translocation of HMGB1 was promoted. The hippocampal inflammatory responses were enhanced in the HFHFD-induced obesity, including the activation of TLR4 and NF-κB, the production of IL-1β, TNF-α and IL-6, as well as the activation of microglia and astrocytes. In addition, the hippocampal cell apoptosis and cognitive impairment were observed in the HFHFD-fed rats. The treatment with glycyrrhizin or HMGB1 mAb successfully decreased the HMGB1 levels in plasma and hippocampus, and prevented the HMGB1 translocation from the nucleus to cytoplasm. Inhibiting HMGB1 by glycyrrhizin or HMGB1 mAb suppressed the hippocampal inflammatory, alleviated the apoptosis and ameliorated the cognitive impairment in HFHFD-fed rats. These findings indicate that HMGB1 mediates the hippocampal inflammation and contributes to the cognitive deficits in HFHFD-induced obesity. Therefore, inhibition of HMGB1 may have beneficial effect in protecting against hippocampal inflammation and cognitive deficits in dietary obesity.

Dexmedetomidine enhances hypoxia-induced cancer cell progression

Dexmedetomidine (DEX) is widely used in perioperative settings for analgesia and sedation; however, little is known about its effects on the hypoxia-induced progression of tumor cells. In the present study, the effects of DEX on hypoxia-induced growth and metastasis of lung cancer cells and colorectal cancer cells was examined. A549 cells and HCT116 cells were treated with normoxia, hypoxia, co-treatment of hypoxia and DEX, and atipamezole (an α₂ adrenoceptor antagonist) for 4 h. The proliferation rate of cells was determined by MTT assays. Cell metastatic potential was evaluated by Transwell assays. Survivin and hypoxia inducible factor (HIF)-1α were detected by western blotting. Matrix metalloproteinase (MMP)-2 and MMP-9 were measured using reverse transcription-quantitative PCR. It was demonstrated that hypoxia treatment promoted the proliferation and may promote the metastasis of the two cancer cell lines. DEX substantially contributed to the survival and aggressiveness of the two cancer cell lines following hypoxia. Furthermore, DEX upregulated the expression of survivin, MMP-2, MMP-9 and HIF-1α in the two cancer cell lines in response to hypoxia. Finally, the effects of DEX on the hypoxia-induced growth and metastatic potential of cancer cells were reversed by atipamezole. Collectively, DEX enhances the hypoxia-induced progression of lung cancer cells and colorectal cancer cells by regulating HIF-1α signaling, which may be associated with the α₂ adrenoceptor pathway.

Effects of dexmedetomidine on glioma cells in the presence or absence of cisplatin

With the extensive use of dexmedetomidine (Dex) in the surgical resection of tumours for its potent sedative and analgesic properties, its effects on various properties of tumours have received increased attention. The study described herein aimed to investigate the effects of Dex on glioma cells in the presence or absence of cisplatin (DDP). Glioma U251 and U87MG cells were treated with different doses (1-50 nM) of Dex for 12 hours, then recultured in a Dex-free medium. In addition, Dex was added to U251 and U87MG cells 12 hours before or simultaneously with a 12-hour DDP treatment. Treatment with Dex increased the viability of both cell lines; this effect continued for at least 24 hours after Dex was removed. A cell invasion assay indicated that Dex inhibited cell invasion at 50 nM, but not at 10 nM. Western blot analysis showed that Dex increased the expression of phosphorylated extracellular-signal-regulated kinase 1/2, phosphoitide 3-kinase and p-AKT, but decreased ROCK protein levels at a dose of 50 nM. Intracellular Ca ²⁺ concentration was decreased by Dex in a dose-dependent manner. DDP toxicity was attenuated by 10 nM Dex added either before or with DDP treatment. However, pretreatment with 50 nM Dex instead enhanced the toxicity of DDP. Single-dose treatment with Dex did not significantly change glioma volume in nude mice, but changed the expression of Ki67 and matrix metalloproteinase-3 in the tumour. In conclusion, this study provides evidence of the regulatory effects of Dex on proliferation, invasion and chemosensitivity of glioma cells, and outlines potential mechanisms for these effects.

Dexmedetomidine protects against lung injury induced by limb ischemia-reperfusion via the TLR4/MyD88/NF-κB pathway

Dexmedetomidine (DEX) can protect the lung from ischemia-reperfusion (I/R) injury, but the underlying mechanisms are not fully understood. The aims of this study were to determine whether DEX attenuates lung injury following lower extremity I/R and to investigate the related toll-like receptor 4 (TLR4) signaling pathway. Twenty-eight SD rats were divided into four groups (n = 7): Sham, I/R, I/R + DEX (25 μg/kg prior to ischemia), and I/R + DEX + Atip (250 μg/kg atipamezole before DEX treatment). Lower extremity I/R was induced by left femoral artery clamping for 3 hours and followed by 2 hours reperfusion. Quantitative alveolar damage and the wet/dry (W/D) ratio were calculated. Interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α in the bronchoalveolar lavage fluid (BALF) and serum and myeloperoxidase (MPO) in the lung were measured. The TLR4 and MyD88 mRNA expression levels were measured by RT-PCR, nuclear factor (NF)-κB, and phosphorylated NF-κB by western blot, respectively. Quantitative alveolar damage, W/D ratio, MPO, BALF and serum IL-1, IL-6, and TNF-α, and TLR4, MyD88, NF-κB, and p-NF-κB expression significantly increased in the I/R group relative to the Sham group. DEX preconditioning significantly reduced lung edema, and histological injury relative to the I/R group. Serum and BALF IL-1, IL-6, and TNF-α levels, MPO activity and TLR4, MyD88, NF-κB, and p-NF-κB expression were also significantly reduced in the I/R + DEX group compared with the I/R group. Atipamezole partially reversed all the aforementioned effects. DEX preconditioning protects the lungs against lower extremity I/R injury via α2-adrenoceptor-dependent and α2-adrenoceptor-independent mechanisms. It also suppresses the TLR4 pathway and reduces inflammation.

Effects of dexmedetomidine vs sufentanil during percutaneous tracheostomy for traumatic brain injury patients: A prospective randomized controlled trial

BACKGROUND

Percutaneous tracheostomy, almost associated with cough reflex and hemodynamic fluctuations, is a common procedure for traumatic brain injury (TBI) patients, especially those in neurosurgery intensive care units (NICUs). However, there are currently a lack of effective preventive measures to reduce the risk of secondary brain injury. The aim of this study was to compare the effect of dexmedetomidine (DEX) vs sufentanil during percutaneous tracheostomy in TBI patients.

METHODS

The 196 TBI patients who underwent percutaneous tracheostomy were randomized divided into 3 groups: group D1 (n = 62, DEX infusion at 0.5 μg·kg for 10 minutes, then adjusted to 0.2-0.7 μg·kg·hour), group D2 (n = 68, DEX infusion at 1 μg·kg for 10 minutes, then adjusted to 0.2-0.7 μg·kg·hour), and group S (n = 66, sufentanil infusion 0.3 μg·kg for 10 minutes, then adjusted to 0.2-0.4 μg·kg·hour). The bispectral index (BIS) of all patients was maintained at 50 to 70 during surgery. Anesthesia onset time, hemodynamic variables, total cumulative dose of DEX/sufentanil, total doses of rescue propofol and fentanyl, time to first dose of rescue propofol and fentanyl, number of intraoperative patient movements and cough reflexes, adverse events, and surgeon satisfaction score were recorded.

RESULTS

Anesthesia onset time was significantly lower in group D2 than in both other groups (14.35 ± 3.23 vs 12.42 ± 2.12 vs 13.88 ± 3.51 minutes in groups D1, D2, and S, respectively; P < .001). Both heart rate and mean arterial pressure during percutaneous tracheostomy were more stable in group D2. Total doses of rescue propofol and fentanyl were significantly lower in group D2 than in group D1 (P < .001). The time to first dose of rescue propofol and fentanyl were significantly longer in group D2 than in both other groups (P < .001). The number of patient movements and cough reflexes during percutaneous tracheostomy were lower in group D2 than in both other groups (P < .001). The overall incidences of tachycardia and hypertension (which required higher doses of esmolol and urapidil, respectively) were also lower in group D2 than in both other groups (P < .05). Three patients in group S had respiratory depression compared to X in the D1 group and X in the D2 group. The surgeon satisfaction score was significantly higher in group D2 than in both other groups (P < .05).

CONCLUSIONS

During percutaneous tracheostomy, compared with sufentanil, DEX (1 μg·kg for 10 minutes, then adjusted to 0.2-0.7 μg·kg·hour) can provide the desired attenuation of the hemodynamic response without increased adverse events. Consequently, DEX could be used safely and effectively during percutaneous tracheostomy in TBI patients.

Dexmedetomidine-induced cardioprotection is mediated by inhibition of high mobility group box-1 and the cholinergic anti-inflammatory pathway in myocardial ischemia-reperfusion injury

OBJECTIVES

Dexmedetomidine (DEX) is a selective α2-adrenoceptor agonist that has anti-inflammatory and cardioprotective effects in myocardial ischemia/reperfusion (I/R) injury. The present study aimed to investigate the underlying mechanism by which DEX protects against myocardial I/R.

METHODS

Sprague Dawley rats were subjected to either sham operation or myocardial I/R, which was induced by ligating the left anterior descending coronary artery for 30 min followed by reperfusion for 120 min. Rats were treated with either DEX or saline prior to surgery. We measured heart infarct size, serum cardiac Troponin I (cTnI), cardiac High mobility group box-1 (HMGB1) expression, myocardial apoptosis and cytokine production of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Besides, we evaluated the heart function at 4 weeks post-reperfusion by echocardiography. Unilateral vagotomy or inhibition of the α7 nicotinic acetylcholine receptor (α7nAChR) with methyllycaconitine (MLA) was applied to investigate whether DEX-induced cardioprotection is mediated via the cholinergic anti-inflammatory pathway. Cardiac-selective overexpression of HMGB1 was administered to further confirm if HMGB1 is a key anti-inflammatory target during DEX-induced cardioprotection.

RESULTS

DEX pretreatment significantly attenuated I/R-induced cardiac damage, as evidenced by decreases in short-term injury indicators including myocardial infarct size, cTnI release, myocardial apoptosis, cardiac HMGB1 expression, IL-6 and TNF-α production, as well as improvement on long-term cardiac function at 4 weeks post-reperfusion. These effects were partially reversed by either unilateral vagotomy or methyllycaconitine treatment. Besides, cardiac HMGB1-overexpression nearly abolished DEX-induced cardioprotection.

CONCLUSIONS

DEX pretreatment protects against myocardial I/R by inhibiting cardiac HMGB1 production and activating the cholinergic anti-inflammatory 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 ameliorates LPS induced acute lung injury via GSK-3β/STAT3-NF-κB signaling pathway in rats

Acute lung injury (ALI) is a serious complication of sepsis and an important cause of death in intensive care. Studies have shown that DEX can inhibit inflammation. However, the anti-inflammatory effect and protective mechanism of DEX in lipopolysaccharide (LPS) induced ALI are still unclear. ALI model was established by intraperitoneal injection of LPS (10 mg/kg) in Sprague-Dawley (SD) male rats. Firstly, at 4, 6, 8, 12 and 24 h after LPS treatment, lung injury including pathologic histology, lung edema, and inflammation were detected. The optimal time point for lung injury was determined to be 12 h, at which time DEX was added to further test. Furthermore, STAT3 inhibitor (NSC74859) and GSK-3β inhibitor (SB216763) were added to verify the role of STAT3, GSK-3β and NF-κB in ameliorated ALI. Our results show that DEX pretreatment significantly decreased lung Wet-to-Dry weight (W/D) ratio and MPO activity and ameliorated LPS induced lung histopathological alterations. In addition, we confirmed that DEX can increased the phosphorylation of STAT3 and GSK-3β, and inhibit the phosphorylation of nuclear factor-κB (NF-κB) p65 in the inflammatory response induced by LPS. What's more, NSC74859 inhibited the phosphorylation of STAT3 and reversed the protect effect of DEX on LPS. SB216763 inhibited the phosphorylation of NF-κB and reversed the damage effect of LPS and plays the same anti-inflammatory effect as DEX. In summary, our data demonstrated that DEX can ameliorate ALI induced by LPS through GSK-3β/STAT3-NF-κB pathway.