Dexmedetomidine attenuates cerebral ischemia/reperfusion injury in neonatal rats by inhibiting TLR4 signaling

Lignans as multi-targeted natural products in neurodegenerative diseases and depression: Recent perspectives

As the global population ages, the treatment of neurodegenerative diseases is becoming more and more important. There is an urgent need to discover novel drugs that are effective in treating neurological diseases. In recent years, natural products and their biological activities have gained widespread attention. Lignans are a class of metabolites extensively present in Chinese herbal medicine and possess good pharmacological effects. Latest studies have demonstrated their neuroprotective pharmacological activity in preventing acute/chronic neurodegenerative diseases and depression. In this review, the pharmacological effects of these disorders, the pharmacokinetics, safety, and clinical trials of lignans were summarized according to the scientific literature. These results proved that lignans mainly exert antioxidant and anti-inflammatory activities. Anti-apoptosis, regulation of nervous system functions, and modulation of synaptic signals are also potential effects. Despite the substantial evidence of the neuroprotective potential of lignans, it is not sufficient to support their use in the clinical management. Our study suggests that lignans can be used as prospective agents for the treatment of neurodegenerative diseases and depression, with a view to informing their further development and utilization.

Locus Coeruleus and Noradrenergic Pharmacology in Neurodegenerative Disease

Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α₁-AR, α₂-AR, and β-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.

Differential effects of dexmedetomidine on Gram-positive and Gram-negative bacterial killing and phagocytosis

Dexmedetomidine is a commonly used sedative in perioperative and intensive care settings with purported immunomodulatory properties. Since its effects on immune functions against infections have not been extensively studied, we tested the effects of dexmedetomidine on Gram-positive [Staphylococcus aureus and Enterococcus faecalis] and Gram-negative bacteria [Escherichia coli], and on effector functions of human monocytes THP-1 cells against them. We evaluated phagocytosis, reactive oxygen species (ROS) formation, and CD11b activation, and performed RNA sequencing analyses. Our study revealed that dexmedetomidine improved Gram-positive but mitigated Gram-negative bacterial phagocytosis and killing in THP-1 cells. The attenuation of Toll-like receptor 4 (TLR4) signaling by dexmedetomidine was previously reported. Thus, we tested TLR4 inhibitor TAK242. Similar to dexmedetomidine, TAK242 reduced E. coli phagocytosis but enhanced CD11b activation. The reduced TLR4 response potentially increases CD11b activation and ROS generation and subsequently enhances Gram-positive bacterial killing. Conversely, dexmedetomidine may inhibit the TLR4-signaling pathway and mitigate the alternative phagocytosis pathway induced by TLR4 activation through LPS-mediated Gram-negative bacteria, resulting in worsened bacterial loads. We also examined another α2 adrenergic agonist, xylazine. Because xylazine did not affect bacterial clearance, we proposed that dexmedetomidine may have an off-target effect on bacterial killing process, potentially involving crosstalk between CD11b and TLR4. Despite its potential to attenuate inflammation, we provide a novel insight into potential risks of dexmedetomidine use during Gram-negative infections, highlighting the differential effect of dexmedetomidine on Gram-positive and Gram-negative bacteria.

Cerebral Protection of Intraoperative Infusion of Dexmedetomidine in Patients with Chronic Cerebrovascular Stenosis Undergoing Endovascular Interventional Therapies: A Prospective Randomized Controlled Trial

BACKGROUND

To investigate the cerebral protective effect of intraoperative dexmedetomidine infusion on patients with chronic cerebral vascular stenosis receiving endovascular interventional therapy.

METHODS

Sixty patients with carotid artery or cerebral artery stenosis or occlusion stenting under elective general anesthesia were divided into dexmedetomidine group (group D) and normal saline group (group N). Group D was given dexmedetomidine loading dose 1.0 μg/kg after peripheral vein opening for 10 min, and then adjusted infusion rate to 0.5 μg/kg/h until stopped 30 min before end.

RESULTS

At 7 days after operation, the contents of S100β, neuron-specific enolase (NSE) and interleukin-6 (IL-6) in group D were apparently lower than those in group N (P < 0.05), while the contents of IL-1β and tumor necrosis factor-α in 2 groups showed no statistical significance (P > 0.05). Additionally, at 4 days and 7 days after operation, the scores of Mini-Mental State Scale (MMSE) and Wechsler Memory Scale (WMS) in group D were significantly higher than those in group N (P < 0.05). Thirty days after surgery, the cerebral hemodynamic indexes (relative mean transit time, relative time to peak) in group D were significantly improved, and obviously better than those in group N (P < 0.05).

CONCLUSIONS

The S-100β, NSE, and inflammatory mediator IL-6 in group D were significantly decreased compared with group N, the MMSE and WMS cognitive function scores, and the cerebral blood perfusion were apparently improved in group D, clarifying dexmedetomidine has protective effect on nerve tissue injury by inhibiting inflammation.

Reperfusion injury in acute ischemic stroke: Tackling the irony of revascularization

Reperfusion injury is an unfortunate consequence of restoring blood flow to tissue after a period of ischemia. This phenomenon can occur in any organ, although it has been best studied in cardiac cells. Based on cardiovascular studies, neuroprotective strategies have been developed. The molecular biology of reperfusion injury remains to be fully elucidated involving several mechanisms, however these mechanisms all converge on a similar final common pathway: blood brain barrier disruption. This results in an inflammatory cascade that ultimately leads to a loss of cerebral autoregulation and clinical worsening. In this article, the authors present an overview of these mechanisms and the current strategies being employed to minimize injury after restoration of blood flow to compromised cerebral territories.

The Role of miRNAs in Dexmedetomidine's Neuroprotective Effects against Brain Disorders

There are limited neuroprotective strategies for various central nervous system conditions in which fast and sustained management is essential. Neuroprotection-based therapeutics have become an intensively researched topic in the neuroscience field, with multiple novel promising agents, from natural products to mesenchymal stem cells, homing peptides, and nanoparticles-mediated agents, all aiming to significantly provide neuroprotection in experimental and clinical studies. Dexmedetomidine (DEX), an α2 agonist commonly used as an anesthetic adjuvant for sedation and as an opioid-sparing medication, stands out in this context due to its well-established neuroprotective effects. Emerging evidence from preclinical and clinical studies suggested that DEX could be used to protect against cerebral ischemia, traumatic brain injury (TBI), spinal cord injury, neurodegenerative diseases, and postoperative cognitive disorders. MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level, inhibiting the translation of mRNA into functional proteins. In vivo and in vitro studies deciphered brain-related miRNAs and dysregulated miRNA profiles after several brain disorders, including TBI, ischemic stroke, Alzheimer’s disease, and multiple sclerosis, providing emerging new perspectives in neuroprotective therapy by modulating these miRNAs. Experimental studies revealed that some of the neuroprotective effects of DEX are mediated by various miRNAs, counteracting multiple mechanisms in several disease models, such as lipopolysaccharides induced neuroinflammation, β-amyloid induced dysfunction, brain ischemic-reperfusion injury, and anesthesia-induced neurotoxicity models. This review aims to outline the neuroprotective mechanisms of DEX in brain disorders by modulating miRNAs. We address the neuroprotective effects of DEX by targeting miRNAs in modulating ischemic brain injury, ameliorating the neurotoxicity of anesthetics, reducing postoperative cognitive dysfunction, and improving the effects of neurodegenerative diseases.

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.

Protective Effects of Dexmedetomidine on Hippocampal Neurons in Rats Anesthetized with Sevoflurane

To explore effects of dexmedetomidine (Dex) on cognitive function and hippocampal neuronal apoptosis in rats anesthetized with sevoflurane (Sevo), and regulation of brain-derived neurotrophic factor (BDNF) and its downstream signaling. 30 Sprague-Dawley (SD) rats were randomly divided into control group inhaled 29% concentration oxygen), Sevo group (2 L/min oxygen flow +1.5% Sevo), Dex+Sevo group (after injection of 20 μg/kg Dex, treated with 2L/min oxygen flow+1.5% Sevo). Haematoxylin and eosin (HE) staining and Nissl’s staining were adopted to detect morphological and functional changes in hippocampus of rats. Apoptosis was detected by immunofluorescence, BDNF expression was detected by immunohistochemistry. Reverse transcription PCR (RT-PCR) was conducted to detect mRNA expression of key proteins in downstream signaling of BDNF. The results showed that Sevo induced apoptosis of hippocampus neurons, while Dex improved Sevo induced apoptosis. In contrast to the control, the positive expression of BDNF in hippocampus of Sevo group was notably decreased (P < 0.05), and that of Dex+Sevo group was notably higher in contrast to Sevo group (P < 0.05). Signaling pathways of MAPK, PI3K-Akt, and Ras were predicted by String software as the downstream pathways of BDNF. RT-PCR results showed that these 3 signaling pathways were involved in Dex improving Sevo-induced cognitive impairment and hippocampal neuron apoptosis. In conclusion, Dex could improve cognitive dysfunction and hippocampal neuron apoptosis in rats induced by Sevo, and the mechanism was related to upregulation of BDNF expression and activation of pathways of MAPK, PI3K-Akt, and Ras.

The Protective Mechanism of Dexmedetomidine in Regulating Atg14L-Beclin1-Vps34 Complex Against Myocardial Ischemia-Reperfusion Injury

The blood flow restoration of ischemic tissues causes myocardial injury. Dexmedetomidine (Dex) protects multi-organs against ischemia/reperfusion (I/R) injury. This study investigated the protective mechanism of Dex post-treatment in myocardial I/R injury. The rat model of myocardial I/R was established. The effects of Dex post-treatment on cardiac function and autophagy flow were observed. Dex attenuated myocardial I/R injury and reduced I/R-induced autophagy in rats. Dex weakened the interactions between Beclin1 and Vps34 and Beclin1 and Atg14L, thus downregulating Vps34 kinase activity. In vitro, the cardiomyocytes subjected to oxygen glucose deprivation/reoxygenation were treated with Dex and PI3K inhibitor LY294002. LY294002 attenuated the myocardial protective effect of DEX, indicating that Dex protected against cardiac I/R by activating the PI3K/Akt pathway. In conclusion, Dex upregulated the phosphorylation of Beclin1 at S295 site by activating the PI3K/Akt pathway and reduced the interactions of Atg14L-Beclin1-Vps34 complex, thus inhibiting autophagy and protecting against myocardial I/R injury.

Dexmedetomidine alleviates hepatic ischaemia-reperfusion injury via the PI3K/AKT/Nrf2-NLRP3 pathway

Hepatic ischaemia-reperfusion (I/R) injury constitutes a tough difficulty in liver surgery. Dexmedetomidine (Dex) plays a protective role in I/R injury. This study investigated protective mechanism of Dex in hepatic I/R injury. The human hepatocyte line L02 received hypoxia/reoxygenation (H/R) treatment to stimulate cell model of hepatic I/R. The levels of pyroptosis proteins and inflammatory factors were detected. Functional rescue experiments were performed to confirm the effects of miR-494 and JUND on hepatic I/R injury. The levels of JUND, PI3K/p-PI3K, AKT/p-AKT, Nrf2, and NLRP3 activation were detected. The rat model of hepatic I/R injury was established to confirm the effect of Dex in vivo. Dex reduced pyroptosis and inflammation in H/R cells. Dex increased miR-494 expression, and miR-494 targeted JUND. miR-494 inhibition or JUND upregulation reversed the protective effect of Dex. Dex repressed NLRP3 inflammasome by activating the PI3K/AKT/Nrf2 pathway. In vivo experiments confirmed the protective effect of Dex on hepatic I/R injury. Overall, Dex repressed NLRP3 inflammasome and alleviated hepatic I/R injury via the miR-494/JUND/PI3K/AKT/Nrf2 axis.

Dexmedetomidine inhibits endoplasmic reticulum stress to suppress pyroptosis of hypoxia/reoxygenation-induced intestinal epithelial cells via activating the SIRT1 expression

Dexmedetomidine (Dex) can protect the intestine against ischemia/reperfusion (I/R)-induced injury. Sirtuin 1 (SIRT1) pathway, which could be activated by Dex, was reported to inhibit I/R injury. Pyroptosis plays an important role in intestinal diseases. We aimed to investigate whether Dex could attenuate pyroptosis of hypoxia/reoxygenation (H/R)-induced intestinal epithelial cells via activating SIRT1. The intestinal epithelial cell line IEC-6 with or without SIRT1 knockdown after H/R treatment was exposed to Dex, then cell viability, endoplasmic reticulum stress (ERS), apoptosis, pyroptosis, inflammatory cytokines production and SIRT1 expression were detected. Results showed that Dex treatment had no significant effect on IEC-6 cell viability but rescued the H/R-reduced cell viability. The expression of proteins involved in ERS including Grp78, Gadd153 and caspase 12 was enhanced upon H/R stimulation, but was reversely reduced by Dex. The cell apoptosis increased by H/R was also decreased by Dex. Additionally, Dex inhibited pyroptosis and inflammation, which were markedly promoted upon H/R stimulation. The expression of SIRT1, which was reduced after H/R treatment was also partially rescued by Dex. Finally, the above effects of Dex were all blocked by SIRT1 knockdown. In conclusion, Dex could inhibit H/R-induced intestinal epithelial cells ERS, apoptosis and pyroptosis via activating SIRT1 expression.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

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

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

Syringin protects against cerebral ischemia/reperfusion injury via inhibiting neuroinflammation and TLR4 signaling

INTRODUCTION

Cerebral ischemia/reperfusion injury (CI/R) is associated with high mortality and remains a large challenge in the clinic. Syringin is a bioactive compound with anti-inflammation, antioxidant, as well as neuroprotective effects. Nevertheless, whether syringin could protect against CI/R injury and its potential mechanism was still unclear.

METHODS

Rats were randomly divided into five groups: sham group, syringin group, CI/R group, CI/R + syringin group, and CI/R + syringin + LPS (TLR4 agonist) group. The CI/R injury rat model was established by the middle cerebral artery occlusion (MCAO). The learning and memory ability of rats was estimated by the Morris water maze test. Modified neurological severity score test (mNSS) and infarct volume were detected to assess the neuroprotective effect of syringin. ELISA and RT-qPCR were used to analyze the concentration of proinflammation cytokines and the expression of TLR4.

RESULTS

CI/R injury induced increased mNSS scores and decreased learning and memory ability of rats. Syringin could significantly protect against CI/R injury as it decreased the cerebral damage and improved the cognitive ability of CI/R rats. Moreover, syringin also reduced neuroinflammation of CI/R injury rats. Additionally, TLR4 was significantly upregulated in CI/R injury rats, which was suppressed by syringin. The activation of TLR4 reversed the neuroprotective effect of syringin in CI/R rats.

CONCLUSION

Syringin decreased the inflammation reaction and cerebral damage in CI/R injury rats. The neuroprotective effect of syringin may be correlated with the inhibition of TLR4.

Abnormal Rat Cortical Development Induced by Ventricular Injection of rHMGB1 Mimics the Pathophysiology of Human Cortical Dysplasia

Cortical dysplasia (CD) is a common cause of drug-resistant epilepsy. Increasing studies have implicated innate immunity in CD with epilepsy. However, it is unclear whether innate immune factors induce epileptogenic CD. Here, we injected recombinant human high mobility group box 1 (rHMGB1) into embryonic rat ventricles to determine whether rHMGB1 can induce epileptogenic CD with pathophysiological characteristics similar to those of human CD. Compared with controls and 0.1 μg rHMGB1-treated rats, the cortical organization was severely disrupted in the 0.2 μg rHMGB1-treated rats, and microgyria and heterotopia also emerged; additionally, disoriented and deformed neurons were observed in the cortical lesions and heterotopias. Subcortical heterotopia appeared in the white matter and the gray–white junction of the 0.2 μg rHMGB1-treated rats. Moreover, there was decreased number of neurons in layer V–VI and an increased number of astrocytes in layer I and V of the cortical lesions. And the HMGB1 antagonist dexmedetomidine alleviated the changes induced by rHMGB1. Further, we found that TLR4 and NF-κB were increased after rHMGB1 administration. In addition, the excitatory receptors, N-methyl-D-aspartate receptor 1 (NR1), 2A (NR2A), and 2B (NR2B) immunoreactivity were increased, and immunoreactivity of excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2) were reduced in 0.2 μg rHMGB1-treated rats compared with controls. While there were no differences in the glutamic acid decarboxylase 65/67 (GAD65/67) immunoreactivity between the two groups. These results indicate that the excitation of cortical lesions was significantly increased. Furthermore, electroencephalogram (EEG) showed a shorter latency of seizure onset and a higher incidence of status epilepticus in the 0.2 μg rHMGB1-treated rats; the frequency and amplitude of EEG were higher in the treated rats than controls. Intriguingly, spontaneous electrographic seizure discharges were detected in the 0.2 μg rHMGB1-treated rats after 5 months of age, and spike-wave discharges of approximately 8 Hz were the most significantly increased synchronous propagated waves throughout the general brain cortex. Taken together, these findings indicate that rHMGB1 exposure during pregnancy could contribute to the development of epileptogenic CD, which mimicked some pathophysiological characteristics of human CD.

LncRNA MEG3 regulates microglial polarization through KLF4 to affect cerebral ischemia-reperfusion injury

This study aimed to explore whether long noncoding RNA (lncRNA) maternally expressed gene 3 (MEG3) affects the polarization of microglia in cerebral ischemia-reperfusion (I/R) injury through regulating Krüppel-like factor 4 (KLF4). A middle cerebral artery occlusion/reperfusion-induced (MCAO/R-induced) mouse model was established as an in vivo model. Oxygen and glucose confinement/reoxygenation-induced (OGD/R-induced) microglia (BV2 cells) were used as an in vitro model. RNA pull-down and RNA immunoprecipitation were used to detect the binding between MEG3 and KLF4. The MEG3 expression was signally elevated in the MCAO/R-induced mice or OGD/R-induced BV2 cells. The inhibition of MEG3 reversed the effects of OGD/R injury on the polarization and inflammation of BV2 cells. Moreover, MEG3 bound to KLF4 and inhibited its protein expression. Furthermore, the overexpression of MEG3 promoted M1 polarization and inflammation but inhibited M2 polarization by inhibiting KLF4 in BV2 cells. The transfection of small interfering RNAs against MEG3 inhibited M1 polarization and inflammation and promoted M2 polarization in vitro and in vivo. Inhibition of MEG3 can alleviate cerebral I/R injury via regulating the polarization of microglia through KLF4.NEW & NOTEWORTHY To study the role of long noncoding RNA (lncRNA) maternally expressed gene 3 (MEG3) in cerebral ischemia-reperfusion (I/R) injury, we clarified the mechanism by which lncRNA MEG3 regulates the secretion of inflammatory cytokines in microglia through in vitro and in vivo experiments. We discovered that inhibition of MEG3 could alleviate cerebral I/R injury via inhibiting M1 polarization and promoting M2 polarization through Krüppel-like factor 4 (KLF4), indicating an effective theoretical basis for potential therapeutic targets of cerebral I/R injury.

Procyanidins exhibits neuroprotective activities against cerebral ischemia reperfusion injury by inhibiting TLR4-NLRP3 inflammasome signal pathway

BACKGROUND

Ischemic stroke is a serious cardiovascular disease with high morbidity and mortality rates that affects millions of people worldwide.Currently, the only therapy with proven efficacy for acute ischemic stroke is alteplase, however, it still has many shortcomings and limitations. Therefore,we screen new compounds from traditional Chinese medicine to explore their efficacy against ischemic reperfusion injury. Procyanidins, a natural productextracted from grapes seed, which have been shown can ameliorate cerebral ischemic injury. However, the underlying mechanism is still not very clear. Theaim of this study was to investigate the effect of procyanidins on middle cerebral artery occlusion/reperfusion (MCAO/R)-mediated cerebral ischemic injuryand its underlying possible mechanisms.

METHODS

SD rats were used to evaluate the effect of procyanidins on MCAO/R induced cerebral ischemic injury in vivo. Histological analysis was used toassess neuronal apoptosis. Cell signaling was assayed by Western blot.

RESULTS

In this study, we found that procyanidins can significantly ameliorate the middle cerebral artery occlusion/reperfusion (MCAO/R)-mediatedneurological deficits, and relieved brain edema, cerebral infarction volume, histopathological damage and apoptosis in rats. In addition, procyanidins canalso markedly inhibit MCAO/R and oxygen-glucose deprivation/reoxygenation (OGD/R)-mediated activation of TLR4-p38-NF-κB-NLRP3 signalingpathway in vitro and in vivo. Moreover, procyanidins can inhibit MCAO/R and OGD/R-induced the production of inflammatory cytokines such asinterleukin-1β (IL-1β) in vitro and in vivo. Besides, treatment with TLR4 inhibitor (Cli-095) in BV2 cell also shows the same effect.

CONCLUSION

Altogether, these data suggested that procyanidins exerted a potential neuroprotective effect may by inhibit the TLR4-p38-NF-κB-NLRP3signaling pathway in the brain in MCAO/R rats.

Protective Effects of Yiqi Xingnao Oral Liquid on Cerebral Ischemia-Reperfusion Injury in Rats and Its Related Mechanisms

Purpose

This study aimed to investigate the effects of different concentrations of Yiqi Xingnao (YQXN) oral liquid on cerebral ischemia/reperfusion (I/R) injury in rats and YQXN's related mechanisms.

Methods

Rats were pretreated with 3 mL/kg, 6 mL/kg, and 12 mL/kg YQXN and Naoxuekang capsule (NXK). Afterwards, cerebral I/R model rats were established by a middle cerebral artery occlusion surgery. Neurological deficits, histopathology, and cerebral infarction volume were used to evaluate the effects of YQXN. Evans blue and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining were utilized to determine the blood-brain barrier permeability and cell apoptosis, respectively. The expression of VEGF and Bcl-2 was analyzed by real-time quantification PCR (RT-qPCR) and western blot. The malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were measured using corresponding assay kits.

Results

The rats pretreated with YQXN had improved neurological deficits, reduced infarct volume and blood-brain barrier permeability, and ameliorated ischemia-induced morphology change in injured brain tissues. TUNEL staining results showed that different concentrations of YQXN inhibited cell apoptosis of neurocytes in I/R rats. Besides, RT-qPCR and western blot analyses indicated that the expression levels of VEGF and Bcl-2 were significantly upregulated by YQXN compared with the I/R group (P < 0.05). Additionally, rats in the I/R group had lower SOD activity and higher MDA content than those in the sham-operated group, while their levels were recovered by YQXN (P < 0.05).

Conclusion

YQXN could alleviate cerebral I/R injury by suppressing blood-brain barrier permeability, neuron apoptosis, and oxidative stress, promoting angiogenesis.

The Protective Effect and Mechanism of Dexmedetomidine on Diabetic Peripheral Neuropathy in Rats

Objective

To investigate the role of dexmedetomidine (DEX) in the inhibition of diabetic peripheral neuropathy (DPN) and the protection in the nerve damage.

Methods

Eighty male Sprague-Dawley (SD) rats were randomly allocated to four groups: the control group (C group), DPN model group (DPN group), DEX-treated group (DEX group), and the yohimbine treated group (YOH group). DPN was induced by intraperitoneal administration of streptozocin (STZ) (35 mg/kg). The body weights, blood glucose level, mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), the motor, and sensory nerve conduction velocities (MNCV and SNCV) of sciatic nerve were measured. Then the sciatic nerve was isolated for H&E staining and immunohistochemical staining. The oxidative stress makers such as malondialdehyde (MDA), superoxide-dismutase (SOD), and glutathione peroxidase (GSH-Px) and apoptosis related cytokines such as Bax, Bcl-2, and caspase-3 were estimated.

Results

There was no significant difference of the blood glucose and body weight among the DPN group, DEX group, and YOH group. H&E staining showed that DEX treatment can ameliorate the damage of sciatic nerve cells. In the DPN group, MWT, TWL, MNCV, and SNCV were significantly reduced compared with the C group (P < 0.05). In DEX group rats, MWT, TWL, MNCV, and SNCV were increased significantly (P < 0.05) compared with the DPN group and YOH group rats. Lower SOD and GSH-Px, and higher MDA were found in the DPN group compared with the C group (P < 0.01), and DEX treatment restored SOD, GSH-px, and MDA activity significantly (P < 0.01). The expression levels of Bax and caspase-3 were increased, while that of Bcl-2 was decreased significantly in the DPN group compared with the C group (P < 0.05). In the DEX group, the expression levels of Bax and caspase-3 were decreased significantly (P < 0.05), while that of Bcl-2 was increased significantly (P < 0.05) compared with the DPN group and the YOH group.

Conclusion

The results of this study demonstrated that DEX has the inhibitory and protective effects on DPN of rats. This may be associated with its antioxidative and anti-apoptosis responses.

Protective role of microRNA-27a upregulation and HSP90 silencing against cerebral ischemia-reperfusion injury in rats by activating PI3K/AKT/mTOR signaling pathway

OBJECTIVE

MicroRNAs (miRNAs) have been reported in cerebral ischemia-reperfusion injury, yet the function of miR-27a in it has seldom been mentioned. This study aims to assess the mechanisms of miR-27a in rats with cerebral ischemia-reperfusion injury.

METHODS

The cerebral ischemia-reperfusion models of rat pups were established by bilateral carotid artery occlusion. Rats were treated with miR-27a agomir, silenced HSP90 expression plasmids or PI3K/AKT/mTOR pathway agonist. Oxidative stress indices, inflammatory factors, brain tissue water content, cerebral infarct volume, neurological function score and neuronal apoptosis in rats with cerebral ischemia-reperfusion injury were measured. MiR-27a and HSP90 expression and PI3K/AKT/mTOR phosphorylation levels in the brain tissues of rats were also detected.

RESULTS

MiR-27a expression and PI3K/AKT/mTOR phosphorylation levels were downregulated while HSP90 expression was upregulated in cerebral ischemia-reperfusion injury rats. Elevated miR-27a or reduced HSP90 diminished water content, neuronal apoptosis and infarct volume, suppressed oxidative stress and inflammatory response, as well as improved neurological deficits and pathological damages. Moreover, elevated miR-27a or silenced HSP90 upregulated PI3K/AKT/mTOR phosphorylation levels in cerebral ischemia-reperfusion injury rats. HSP90 silencing or PI3K/AKT/mTOR pathway agonist reversed the unfavorable effects of low miR-27a expression on cerebral ischemia-reperfusion injury rats.

CONCLUSION

To conclude, our study demonstrates that elevated miR-27a or decreased HSP90 attenuates oxidative stress and inflammatory response, and improves neurological function in cerebral ischemia-reperfusion injury rats by activating PI3K/AKT/mTOR signaling pathway.

Effects of Pre-Cardiopulmonary Bypass Administration of Dexmedetomidine on Cardiac Injuries and the Inflammatory Response in Valve Replacement Surgery With a Sevoflurane Postconditioning Protocol: A Pilot Study

Supplemental Digital Content is Available in the Text.

Background:

Preventing myocardial ischemia–reperfusion injury in on-pump cardiac surgeries remains an enormous challenge. Sevoflurane postconditioning has been effective at overcoming this challenge by modulating inflammatory mediators and ameliorating antioxidative stress. Dexmedetomidine (DEX) is a commonly used medication for cardiac patients with organ-protective properties that lead to positive outcomes. Whether DEX also has cardiac-protective properties and the associated mechanism in sevoflurane postconditioning–based valve replacement surgeries are unknown.

Objective:

This study was conducted to observe the effect of DEX administration before cardiopulmonary bypass (CPB) on myocardial injury, oxidative stress, and inflammatory response indicators in the peripheral blood.

Methods:

Twenty-eight eligible cardiac patients who underwent valve replacement surgery with standard sevoflurane postconditioning were included in the study. The patients were randomly divided into a DEX group and a non-DEX group according to whether DEX (0.5-µg/kg overload dose for 10 minutes and a 0.5-μg/kg/h maintenance dose) or saline was administered from induction to the beginning of CPB. The primary outcome was the cardiac troponin I concentration (cTnI) in the blood 24 hours after CPB. The levels of malondialdehyde (MDA), superoxide dismutase, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) were also measured.

Results:

The mean cTnI at 24 hours after CPB was clearly decreased in the DEX group compared with that in the non-DEX group (4.16 ± 1.58 vs. 6.90 ± 3.73, P < 0.05). TNF-α levels were lower in the DEX group after CPB (T1–T5), with a significant difference found at 1–6 hours after CPB (1 hour, 19.03 vs. 28.09; 6 hours, 20.74 vs. 30.94, P < 0.05). The IL-6 and IL-8 concentrations in the DEX group were dramatically increased at 6 hours after CPB (P < 0.05). The MDA content and superoxide dismutase activity were comparable between the 2 groups. A lower proportion of anemia cases were noted after CPB in the DEX group than in the non-DEX group (non-DEX, 10% vs. DEX, 5%, P < 0.05).

Conclusions:

In valve replacement surgery with sevoflurane postconditioning, pre-CPB administration of DEX can reduce the cTnI level at 24 hours after CPB and brings synergic benefits of the inflammatory response.

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.

Exosomes-carried microRNA-26b-5p regulates microglia M1 polarization after cerebral ischemia/reperfusion

Exosome and microRNAs (miRs) are implicated in ischemia/reperfusion (I/R) process. In this study, I/R mouse model was established, and exosomes derived from human umbilical cord mesenchymal stem cells (hUCMSCs) were isolated, identified, and injected to I/R mice to observe nerve injury and microglia M1 polarization. The differentially expressed genes in I/R microglia from databases were analyzed, and miRs differentially expressed in exosomes-treated microglia were analyzed by microarray. miR-26b-5p expression in hUCMSCs was intervened. Besides, microglia was extracted and co-cultured with SH-SY5Y or PC12 cells in oxygen-glucose deprivation/reperfusion (OGD/R) models to simulate I/R in vivo. Additionally, Toll-like receptor (TLR) activator GS-9620 was added to microglia. Exosomes alleviated nerve injury and inhibited M1 polarization in microglia. After I/R modeling, CH25H expression in microglia was upregulated but decreased after exosome treatment. miR-26b-5p was upregulated in microglia after exosome treatment and could target CH25H. Reduction in exosomal miR-26b-5p reversed the effects of hUCMSCs-exos on microglia. TLR pathway was activated in microglia after I/R but exosomes prevented its activation. Exosomal miR-26b-5p could repress M1 polarization of microglia by targeting CH25H to inactivate the TLR pathway, so as to relieve nerve injury after cerebral I/R. This investigation may offer new approaches for I/R treatment.

Role of JNK Signaling Pathway in Dexmedetomidine Post-Conditioning-Induced Reduction of the Inflammatory Response and Autophagy Effect of Focal Cerebral Ischemia Reperfusion Injury in Rats

To investigate the effect of dexmedetomidine post-conditioning on the inflammatory response and autophagy effect of focal cerebral ischemia reperfusion injury in rats, and further to study its potential mechanisms. Water maze was conducted to evaluate spatial learning and memory ability of middle cerebral artery occlusion (MCAO) rats. TTC staining was used to observe the area of cerebral infarction. The expressions of inflammatory factors in serum were detected by ELISA. TUNEL assay, HE staining, and transmission electron microscopy were used to detect the apoptosis of neurons, neuro-cytopathic changes, and the formation of auto-phagosome in hippocampus CA1 region, respectively. The mRNA and protein expression of Beclin-1, Caspase-3, and light chain 3 (LC3) were detected by qRT-PCR and Western blot. Moreover, the activity of C-Jun N-terminal kinase (JNK) pathway was detected by Western blot. The escape latency (EL); cerebral infarction area ratio; positive apoptosis; neuron pathological changes; auto-phagosome numbers; inflammatory factor contents; mRNA and protein expressions of Beclin-1, Caspase-3 and LC3II/I; and the phosphorylation level of JNK were decreased, while the times across platform and the times stayed in the quadrant of the original platform were increased after dexmedetomidine treatment. However, the protective effect of dexmedetomidine on brain injury in MCAO rats was reversed by JNK pathway activator. Dexmedetomidine post-conditioning could improve learning and memory dysfunction caused by MCAO in rats and reduce the inflammatory response and autophagy effect. The mechanism may be related to inhibition of JNK pathway activation.

Dexmedetomidine protects H9C2 against hypoxia/reoxygenation injury through miR-208b-3p/Med13/Wnt signaling pathway axis

Dexmedetomidine (Dex) has been reported to be cardioprotective. Differential expression of miR-208b-3p is associated with myocardial injury. But it is unknown that aberrant expression of miR-208b-3p is implicated in myocardial protection of Dex. Hypoxia/reoxygenation (HR) model was established in H9C2 cells. qRT-PCR was performed to detect expression levels of miR-208b-3p in H9C2 undergoing HR, Dex preconditioning, overexpression of miR-208b-3p or inhibition, and to assess expression of Med13 in H9C2 following knockdown of Med13 mRNA. CCK8 and, flow cytometry and Western blot were conducted respectively to examine viability, apoptosis rate and protein expressions of H9C2 subjected to a variety of treatments. Dex preconditioning reduced expression of miR-208b-3p and apoptosis of H9C2 cells caused by HR, while Dex preconditioning increased viability of H9C2. Dex preconditioning increased expression of Med13, which was reduced after knockdown of Med13 mRNA in H9C2. Overexpression of miR-208b-3p attenuated Dex exerted protective effects of myocardial cells, which was reversed by inhibition of miR-208b-3p. Increased expression of Med13 or/and decreased expression of miR-208b-3p decreased expression levels of Wnt/β-catenin signaling pathway-related proteins (Wnt3a, Wnt5a and β-catenin), while knockdown of Med13 mRNA or increased expression of miR-208b-3p increased the expression levels of those proteins. Dex protects H9C2 cells against HR injury through miR-208b-3p/Med13/Wnt/β-catenin signaling pathway axis.

Dexmedetomidine attenuates neuronal injury after spinal cord ischaemia-reperfusion injury by targeting the CNPY2-endoplasmic reticulum stress signalling

Dexmedetomidine (Dex) has been proven to exert protective effects on multiple organs in response to ischaemia-reperfusion injury, but the specific mechanism by which this occurs has not been fully elucidated. The purpose of this study was to investigate whether Dex attenuates spinal cord ischaemia-reperfusion injury (SCIRI) by inhibiting endoplasmic reticulum stress (ERS). Our team established a model of SCIRI and utilized the endoplasmic reticulum agonist thapsigargin. Dex (25 g/kg) was intraperitoneally injected 30 minutes before spinal cord ischaemia. After 45 minutes of ischaemia, the spinal cord was reperfused for 24 hours. To evaluate the neuroprotective effect of Dex on SCIRI, neurological function scores were assessed in rats and apoptosis of spinal cord cells was determined by TUNEL staining. To determine whether the endoplasmic reticulum apoptosis pathway CNPY2-PERK was involved in the neuroprotective mechanism of Dex, the expression levels of related proteins (CNPY2, GRP78, PERK, CHOP, caspase-12, caspase-9 and caspase-3) were detected by western blot analysis and RT-PCR. We observed that Dex significantly increased the neurological function scores after SCIRI and decreased apoptosis of spinal cord cells. The expression of ERS-related apoptosis proteins was significantly increased by SCIRI but was significantly decreased in response to Dex administration. Taken together, the results of this study indicate that Dex may attenuate SCIRI by inhibiting the CNPY2-ERS apoptotic pathway.

Dexmedetomidine Attenuates Neuroinflammatory-Induced Apoptosis after Traumatic Brain Injury via Nrf2 signaling pathway

Objective

Dexmedetomidine (DEX) exhibits neuroprotective effects as a multifunctional neuroprotective agent in numerous neurological disorders. However, in traumatic brain injury (TBI), the molecular mechanisms of these neuroprotective effects remain unclear. The present study investigated whether DEX, which has been reported to exert protective effects against TBI, could attenuate neuroinflammatory‐induced apoptosis and clarified the underlying mechanisms.

Methods

A weight‐drop model was established, and DEX was intraperitoneally injected 30 min after inducing TBI in rats. The water content in the brain tissue was measured. Terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling (TUNEL) assays were performed on histopathological tissue sections to evaluate neuronal apoptosis. Enzyme‐linked immunosorbent assay and PCR were applied to detect the levels of the inflammatory factors, TNF‐α, IL‐1β, IL‐6, and NF‐κB.

Results

TBI–challenged rats exhibited significant neuronal apoptosis, which was characterized via the wet‐to‐dry weight ratio, neurobehavioral functions, TUNEL assay results and the levels of cleaved caspase‐3, Bax upregulation and Bcl‐2, which were attenuated by DEX. Western blot, immunohistochemistry, and PCR results revealed that DEX promoted Nrf2 expression and upregulated expression of the Nrf2 downstream factors, HO‐1 and NQO‐1. Furthermore, DEX treatment markedly prevented the downregulation of inflammatory response factors, TNF‐α, IL‐1β and NF‐κB, and IL‐6.

Interpretation

Administering DEX attenuated inflammation‐induced brain injury in a TBI model, potentially via the Nrf2 signaling pathway.

Opioids Preconditioning Upon Renal Function and Ischemia-Reperfusion Injury: A Narrative Review

Kidneys have an important role in regulating water volume, blood pressure, secretion of hormones and acid-base and electrolyte balance. Kidney dysfunction derived from acute injury can, under certain conditions, progress to chronic kidney disease. In the late stages of kidney disease, treatment is limited to replacement therapy: Dialysis and transplantation. After renal transplant, grafts suffer from activation of immune cells and generation of oxidant molecules. Anesthetic preconditioning has emerged as a promising strategy to ameliorate ischemia reperfusion injury. This review compiles some significant aspects of renal physiology and discusses current understanding of the effects of anesthetic preconditioning upon renal function and ischemia reperfusion injury, focusing on opioids and its properties ameliorating renal injury. According to the available evidence, opioid preconditioning appears to reduce inflammation and reactive oxygen species generation after ischemia reperfusion. Therefore, opioid preconditioning represents a promising strategy to reduce renal ischemia reperfusion injury and, its application on current clinical practice could be beneficial in events such as acute renal injury and kidney transplantation.

miR‑27a suppresses TLR4‑induced renal ischemia‑reperfusion injury

Ischemia reperfusion injury (IRI) is one of the primary causes of acute renal injury and even acute renal failure. An increasing body of evidence has indicated that the aberrant expression of microRNAs (miRNA/miR) is closely associated with the progression of IRI. In the process of renal IRI, inflammatory reactions, cell adhesion and the death of renal tubular epithelial cells serve important roles. The present study investigated the expression of renal miRNAs following renal IRI in an attempt to identify the miRNAs that exert pivotal functions in renal IRI. The present study revealed that miR-27a, which was downregulated in IRI, and the 3′-untranslated region (UTR) of Toll-like receptor 4 (TLR4) have associated binding sites. The levels of TLR4, miR-27a and specific associated proteins in the renal tissues of gestational rats were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, immunohistochemistry and western blotting. The associations between miR-27a and TLR4 were analyzed, and the regulatory effect of miR-27a on TLR4 was detected via a luciferase reporter gene assay, western blotting and RT-qPCR in vivo and in vitro. In addition, the present study demonstrated that miR-27a suppressed the expression of TLR4 by binding to the 3′UTR of TLR4. The overexpression of miR-27a downregulated the expression of TLR4, which in turn inhibited the inflammation, cell adhesion and cell death in IRI. Therefore, miR-27a inhibited inflammation in IRI by decreasing the expression of TLR4.

Neuroprotective role of dexmedetomidine pretreatment in cerebral ischemia injury via ADRA2A-mediated phosphorylation of ERK1/2 in adult rats

Neuroprotective effects of dexmedetomidine (Dex) have been reported in various models of brain injury. However, to our knowledge, the neuroprotective mechanism of Dex pretreatment in rats remains unknown. The aim of the present study was to detect the expression of the α2A adrenergic receptor (ADRA2A) in focal ischemic brain tissues and to investigate the protective role and corresponding mechanism of Dex pretreatment in cerebral ischemia in rats. A hypoxia/reoxygenation (H/R) cell model in primary cultured astrocytes and a focal cerebral ischemia/reperfusion (I/R) model in adult rats were used. The expression of ADRA2A and extracellular signal-regulated kinases 1 and 2 (ERK1/2) in the primary cultured astrocytes and rat brain ischemic tissues was detected in the different conditions prior to and following Dex pretreatment using western blotting. The H/R model of primary cultured astrocytes and the focal cerebral I/R model in adult rats were successfully constructed. Under the normal oxygen conditions, 500 ng/ml Dex pretreatment increased the expression of ADRA2A and phosphorylated (p)-ERK1/2 in the astrocytes compared with in the control group. Hypoxic culture for 6 h and then reoxygenation for 24 h decreased the levels of p-ERK1/2 in the astrocytes compared with those in control group. This decrease was prevented by Dex pretreatment for 3 h. The hypoxic culture and then reoxygenation increased the expression of ADRA2A. Similarly, compared with those prior to Dex treatment, the levels of ADRA2A and p-ERK1/2 in the brain ischemic tissues following Dex treatment were increased. The levels of ADRA2A and p-ERK1/2 were 0.72±0.23 and 0.66±0.25 following Dex treatment, compared with 0.76±0.22 and 0.31±0.18, respectively, prior to Dex treatment. The effect of Dex pretreatment increasing p-ERK1/2 expression was attenuated by AG1478 pretreatment. In summary, Dex appeared to promote phosphorylation of ERK1/2 in astrocytes under H/R. As a specific agonist of ADRA2A, Dex may activate phosphorylation of ERK1/2 via ADRA2A in astrocytes. Thus, the neuroprotective role of Dex pretreatment against cerebral ischemic injury may function via ADRA2A-mediated phosphorylation of ERK1/2.