Dexmedetomidine preconditioning for myocardial protection in ischaemia-reperfusion injury in rats by downregulation of the high mobility group box 1-toll-like receptor 4-nuclear factor κB signalling pathway

Insight into Cardioprotective Effects and Mechanisms of Dexmedetomidine

PURPOSE

Cardiovascular disease remains the leading cause of death worldwide. Dexmedetomidine is a highly selective α2 adrenergic receptor agonist with sedative, analgesic, anxiolytic, and sympatholytic properties, and several studies have shown its possible protective effects in cardiac injury. The aim of this review is to further elucidate the underlying cardioprotective mechanisms of dexmedetomidine, thus suggesting its potential in the clinical management of cardiac injury.

RESULTS AND CONCLUSION

Our review summarizes the findings related to the involvement of dexmedetomidine in cardiac injury and discusses the results in the light of different mechanisms. We found that numerous mechanisms may contribute to the cardioprotective effects of dexmedetomidine, including the regulation of programmed cell death, autophagy and fibrosis, alleviation of inflammatory response, endothelial dysfunction and microcirculatory derangements, improvement of mitochondrial dysregulation, hemodynamics, and arrhythmias. Dexmedetomidine may play a promising and beneficial role in the treatment of cardiovascular disease.

Ketofol versus Dexmedetomidine for preventing postoperative delirium in elderly patients undergoing intestinal obstruction surgeries: a randomized controlled study

PURPOSE

Postoperative delirium (POD) is considered the most common postoperative neurological complication in elderly patients. The aim of this study was to evaluate the efficacy of the administration of ketofol versus dexmedetomidine (DEX) for minimizing POD in elderly patients undergoing urgent exploration for intestinal obstruction.

METHODS

This prospective double-blinded randomized clinical trial was conducted on 120 elderly patients undergoing urgent exploration for intestinal obstruction. Patients were randomly allocated to one of the three groups: Group C (control group) patients received normal saline 0.9%, group D received dexmedetomidine, and group K received ketofol (ketamine: propofol was 1:4). The primary outcome was the incidence of POD. Secondary outcomes were incidence of emergence agitation, postoperative pain, consumption of rescue opioids, hemodynamics, and any side effects.

RESULTS

The incidence of POD was statistically significantly lower in ketofol and DEX groups than in the control group at all postoperative time recordings. Additionally, VAS scores were statistically significantly decreased in the ketofol and DEX groups compared to the control group at all time recordings except at 48 and 72 h postoperatively, where the values of the three studied groups were comparable. The occurrence of emergence agitation and high-dose opioid consumption postoperatively were found to be significant predictors for the occurrence of POD at 2 h and on the evening of the 1st postoperative day.

CONCLUSION

The administration of ketofol provides a promising alternative option that is as effective as DEX in reducing the incidence of POD in elderly patients undergoing urgent exploration for intestinal obstruction.

TRIAL REGISTRATION

This clinical trial was approved by the Institutional Review Board (IRB) at Zagazig University (ZU-IRB# 6704// 3/03/2021) and ClinicalTrials.gov (NCT04816162, registration date 22/03/ 2021). The first research participant was enrolled on 25/03/2021).

Dexmedetomidine as a cardioprotective drug: a narrative review

Dexmedetomidine (DEX), a highly selective alpha2-adrenoceptors agonist, is not only a sedative drug used during mechanical ventilation in the intensive care unit but also a cardio-protective drug against ischemia-reperfusion injury (IRI). Numerous preclinical in vivo and ex vivo studies, mostly evaluating the effect of DEX pretreatment in healthy rodents, have shown the efficacy of DEX in protecting the hearts from IRI. However, whether DEX can maintain its cardio-protective effect in hearts with comorbidities such as diabetes has not been fully elucidated. Multiple clinical trials have reported promising results, showing that pretreatment with DEX can attenuate cardiac damage in patients undergoing cardiac surgery. However, evidence of the post-treatment effects of DEX in clinical practice remains limited. In this narrative review, we summarize the previously reported evidence of DEX-induced cardio-protection against IRI and clarify the condition of the hearts and the timing of DEX administration that has not been tested. With further investigations evaluating these knowledge gaps, the use of DEX as a cardio-protective drug could be further facilitated in the management of patients undergoing cardiac surgery and might be considered in a broader area of clinical settings beyond cardiac surgery, including patients with acute myocardial infarction.

Dexmedetomidine Preconditioning Attenuates Myocardial Ischemia/Reperfusion Injury in Rats by Suppressing Mitophagy Via Activating Α2-Adrenergic Receptor

BACKGROUND

Dexmedetomidine (DEX), a specific α2-adrenergic receptor agonist, is protective against myocardial ischemia/reperfusion injury (MIRI). However, the association between DEX preconditioning-induced cardioprotection and mitophagy suppression remains unclear.

OBJECTIVE

Hence, we aimed to investigate whether DEX preconditioning alleviates MIRI by suppressing mitophagy via α2-adrenergic receptor activation.

METHOD

Sixty isolated rat hearts were treated with or without DEX before inducing ischemia and reperfusion; an α2-adrenergic receptor antagonist, yohimbine (YOH), was also administered before ischemia, alone or with DEX. The heart rate (HR), left ventricular diastolic pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximal and minimal rate of left ventricular pressure development (±dp/dtmax), and myocardial infarction size were measured. The mitochondrial ultrastructure and autophagosomes were assessed using transmission electron microscopy. Mitochondrial membrane potential and reactive oxygen species (ROS) levels were measured using JC-1 and dichloride hydrofluorescein diacetate assays, respectively. The expression levels of the mitophagy-associated proteins Beclin1, LC3II/I ratio, p62, PINK1, and Parkin were detected by western blotting.

RESULTS

Compared with the control group, in the ischemia/reperfusion group, the HR, LVDP, and ±dp/dtmax were remarkably decreased (p< 0.05), whereas LVEDP and infarct sizes were significantly increased (p< 0.05). DEX preconditioning significantly improved cardiac dysfunction reduced myocardial infarction size, maintained mitochondrial structural integrity, increased mitochondrial membrane potential, inhibited autophagosomes formation, and decreased ROS production and Beclin1, LC3II/I ratio, PINK1, Parkin, and p62 expression(p< 0.05). When DEX and YOH were combined, YOH canceled the effect of DEX, whereas the use of YOH alone had no effect.

CONCLUSION

Therefore, DEX preconditioning was cardioprotective against MIRI in rats by suppressing mitophagy via α2-adrenergic receptor activation.

HMGB family proteins: Potential biomarkers and mechanistic factors in cardiovascular diseases

Cardiovascular disease (CVD) is the most fatal disease that causes sudden death, and inflammation contributes substantially to its occurrence and progression. The prevalence of CVD increases as the population ages, and the pathophysiology is complex. Anti-inflammatory and immunological modulation are the potential methods for CVD prevention and treatment. High-Mobility Group (HMG) chromosomal proteins are one of the most abundant nuclear nonhistone proteins which act as inflammatory mediators in DNA replication, transcription, and repair by producing cytokines and serving as damage-associated molecular patterns in inflammatory responses. The most common and well-studied HMG proteins are those with an HMGB domain, which participate in a variety of biological processes. HMGB1 and HMGB2 were the first members of the HMGB family to be identified and are present in all investigated eukaryotes. Our review is primarily concerned with the involvement of HMGB1 and HMGB2 in CVD. The purpose of this review is to provide a theoretical framework for diagnosing and treating CVD by discussing the structure and function of HMGB1 and HMGB2.

In a secondary analysis from a randomised, double-blind placebo-controlled trial Dexmedetomidine blocks cholinergic dysregulation in delirium pathogenesis in patients with major surgery

Dexmedetomidine is an alpha-2 adrenoreceptor agonist with anti-inflammatory and anti-delirogenic properties. Pathogenesis of postoperative delirium (POD) includes cholinergic dysfunction and deregulated inflammatory response to surgical trauma. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are discussed as biomarkers for both POD and severity in acute inflammation. To show whether there is a link between blood cholinesterase activities and dexmedetomidine, we performed a secondary analysis of a randomised, double-blind, placebo-controlled trial that recently showed a lower incidence of POD in the dexmedetomidine group. Abdominal or cardiac surgical patients aged ≥ 60 years were randomised to receive dexmedetomidine or placebo intra- and postoperatively in addition to standard general anaesthesia. We analysed the course of perioperative cholinesterase activities of 56 patients, measured preoperatively and twice postoperatively. Dexmedetomidine resulted in no change in AChE activity and caused a rapid recovery of BChE activity after an initial decrease, while placebo showed a significant decrease in both cholinesterase activities. There were no significant between-group differences at any point in time. From these data it can be assumed that dexmedetomidine could alleviate POD via altering the cholinergic anti-inflammatory pathway (CAIP). We advocate for further investigations to show the direct connection between dexmedetomidine and cholinesterase activity.

Dexmedetomidine protects cells from Angiotensin II-induced smooth muscle cell phenotype switch and endothelial cell dysfunction

Abdominal aortic aneurysm (AAA) is a vascular disorder greatly threatening life of the elderly population. Dexmedetomidine (DEX), an α2-adrenergic receptor agonist, has been shown to suppress AAA development. Nevertheless, the signaling pathways that might be mediated by DEX in AAA has not been clarified. Vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) were treated with Angiotensin II (Ang II) to mimic AAA in vitro. BrdU, wound healing, and Transwell assays were utilized for measuring VSMC proliferation and migration. Western blotting was used for evaluating protein levels of contractile VSMC markers, collagens and matrix metalloproteinases (MMPs) in VSMCs as well as apoptosis- and HMGB1/TLR4/NF-κB signaling-related markers in ECs. Cell adhesion molecule expression and monocyte-endothelial adhesion were assessed by immunofluorescence staining and adhesion assays. Flow cytometry was implemented for analyzing EC apoptosis. Hematoxylin-eosin staining and ELISA were used to detect the effect of DEX in vivo. In this study, DEX inhibited Ang II-evoked VSMC phenotype switch and extracellular matrix degradation. DEX suppressed the inflammatory response and apoptosis of ECs induced by Ang II. DEX inhibited HMGB1/TLR4/NF-κB signaling pathway in Ang II-treated ECs. DEX attenuated Ang II-induced AAA and inflammation in mice. Overall, DEX ameliorates Ang II-induced VSMC phenotype switch, and inactivates HMGB1/TLR4/NF-κB signaling pathway to alleviate Ang II-induced EC dysfunction.

Amelioration of myocardial ischemia/reperfusion injury in diabetes: A narrative review of the mechanisms and clinical applications of dexmedetomidine

Mechanisms contributing to the pathogenesis of myocardial ischemia-reperfusion (I/R) injury are complex and multifactorial. Many strategies have been developed to ameliorate myocardial I/R injuries based on these mechanisms. However, the cardioprotective effects of these strategies appear to diminish in diabetic states. Diabetes weakens myocardial responses to therapies by disrupting intracellular signaling pathways which may be responsible for enhancing cellular resistance to damage. Intriguingly, it was found that Dexmedetomidine (DEX), a potent and selective α2-adrenergic agonist, appears to have the property to reverse diabetes-related inhibition of most intervention-mediated myocardial protection and exert a protective effect. Several mechanisms were revealed to be involved in DEX’s protection in diabetic rodent myocardial I/R models, including PI3K/Akt and associated GSK-3β pathway stimulation, endoplasmic reticulum stress (ERS) alleviation, and apoptosis inhibition. In addition, DEX could attenuate diabetic myocardial I/R injury by up-regulating autophagy, reducing ROS production, and inhibiting the inflammatory response through HMGB1 pathways. The regulation of autonomic nervous function also appeared to be involved in the protective mechanisms of DEX. In the present review, the evidence and underlying mechanisms of DEX in ameliorating myocardial I/R injury in diabetes are summarized, and the potential of DEX for the treatment/prevention of myocardial I/R injury in diabetic patients is discussed.

Dexmedetomidine Mitigates Myocardial Ischemia/Reperfusion-Induced Mitochondrial Apoptosis through Targeting lncRNA HCP5

Our study aimed to explore the function and mechanism of Dexmedetomidine (Dex) in regulating myocardial ischemia/reperfusion (I/R)-induced mitochondrial apoptosis through lncRNA HCP5. We demonstrated Dex suppressed I/R-induced myocardial infarction and mitochondrial apoptosis in vivo. Dex induced the expression of lncRNA HCP5 and MCL1, inhibited miR-29a expression and activated the JAK2/STAT3 signaling. Dex attenuated hypoxia/reoxygenation (H/R)-induced mitochondrial apoptosis by upregulating lncRNA HCP5 in cardiomyocytes. Overexpression of lncRNA HCP5 sponged miR-29a to suppress H/R-induced mitochondrial apoptosis. Knockdown of miR-29a also alleviated cardiomyocyte apoptosis by upregulating MCL1. Overexpression of lncRNA HCP5 activated the JAK2/STAT3 signaling through sponging miR-29a and enhancing MCL1 expression in cardiomyocytes. Dex mitigated myocardial I/R-induced mitochondrial apoptosis through the lncRNA HCP5/miR-29a/MCL1 axis and activation of the JAK2/STAT3 signaling.

Short-term pretreatment of naringin isolated from Citrus wilsonii Tanaka attenuates rat myocardial ischemia/reperfusion injury

Pretreatment or treatment with anti-apoptotic, anti-inflammatory, or anti-oxidative approaches could be critical for attenuated the severity of myocardial ischemia/reperfusion (I/R) injury. Naringin, a natural flavonoid, plays important roles in inflammation-related diseases. Immature dry fruits of Citrus wilsonii Tanaka (Xiang Yuan) are rich in naringin that can be used as traditional Chinese medicine to treat inflammation-related symptoms. However, its roles in cardioprotective role remain unclear. This study aimed to isolate naringin from Citrus wilsonii Tanaka fruit and tested their cardioprotective effect. The dry fruits of Citrus wilsonii Tanaka were extracted with boiling water and then supernatants were freeze-dried to yield aqueous extract (ZQAE). The extract was chemoprofiled using UPLC-MS/MS to stand for major constituents, and then subjected to different chromatographic separation steps, and naringin was isolated in a high yield. The cardioprotective effects of the aqueous extract of ZQAE and naringin were investigated in a myocardial I/R rat model and to elucidate the mechanism underlying its cardioprotective effect. Our results indicated that 5-day ZQAE and naringin pretreatments both promoted histopathological changes and reduced myocardial enzymes (cTnl, CK-MB, CK and LDH) induced by I/R. Moreover, the 50 mg/kg and 100 mg/kg ZQAE dose pretreatments presented a significantly decreased infarct size as well as myocardial enzyme levels but also inhibited myocardial apoptosis (cleaved-caspase3 protein expression), the inflammatory response (IL-23, IL-6, and TNF-α) and oxidative stress (MDA and SOD). The cardioprotective effect of 5 mg/kg dose of naringin pretreatment is comparable with that of 5 mg/kg drug ditiazem pretreatment. Additionally, naringin pretreatment exhibited striking decreases in the apoptosis index and downregulation of the protein expression levels of cleaved-Caspase3, Bcl2 and Bax. Meanwhile, naringin downregulated HMGB1 expression and upregulated SIRT1 expression in the myocardium. These findings suggest that short-term pretreatments with ZQAE and naringin both protect against myocardial I/R injury by suppressing myocardial apoptosis, the inflammatory response, and oxidative stress. The cardioprotective effect of naringin involves SIRT1 activation and may interact with HMGB1 and inhibit the release of HMGB1.

Dexmedetomidine Preconditioning Reduces Myocardial Ischemia-Reperfusion Injury in Rats by Inhibiting the PERK Pathway

BACKGROUND

Ischemic heart disease has attracted much attention due to its high mortality rates, treatment costs and the increasing morbidity in the young population. Strategies for reperfusion have reduced mortality. However, reperfusion can lead to cardiomyocyte death and subsequent irreversible myocardial damage. At present, the timely and targeted treatment of ischemia-reperfusion (I/R) injury is often lacking.

OBJECTIVES

To evaluate if dexmedetomidine (DEX) has a protective effect in myocardiual I/R and explore the possible mechanism behind it.

METHODS

Rat hearts were perfused with a Langendorff perfusion system, and randomly assigned to five groups: control group, perfused with Krebs-Henseleit (K-H) solution for 205 minutes without ischemia; and four test groups that underwent 40 minutes of global ischemia and 120 min of reperfusion. The DEX group, the yohimbine (YOH) group and the DEX + YOH group were perfused with DEX (10 nM), YOH (1 μM) or the combination of DEX and YOH prior to reperfusion, respectively. Cardiac hemodynamics, myocardial infarct size, and myocardial histology were evaluated. The expression of glucose-related protein 78 (GRP78), protein kinase R-like ER kinase (PERK), phosphorylated PERK, eukaryotic initiation factor 2α (eIF2α), phosphorylated eIF2α, activating transcription factor 4 (ATF4), and CCAAT/enhancer-binding protein homologous protein (CHOP) were assessed. P<0.05 was considered to indicate a statistically significant difference.

RESULTS

DEX preconditioning improved the cardiac function of I/R hearts, reduced myocardial infarction, myocardial apoptosis, and the expression of GRP78, p-PERK, eIF2α, p-eIF2α, ATF4 and CHOP.

CONCLUSIONS

DEX pretreatment reduced myocardial I/R injury by suppressing apoptosis, which was induced by the PERK pathway.

Dexmedetomidine Attenuates Hypoxia/Reoxygenation Injury of H9C2 Myocardial Cells by Upregulating miR-146a Expression via the MAPK Signal Pathway

INTRODUCTION AND OBJECTIVE

Dexmedetomidine (Dex) and a number of miRNAs contribute to ischemia/reperfusion injury. We aimed to explore the role of Dex and miR-146a on myocardial cells injured by hypoxia/reoxygenation (H/R).

METHOD

H9C2 cells were injured by H/R. Cell viability was tested using the cell counting kit-8. Lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) levels were determined using commercial kits. Flow cytometry was performed to determine apoptosis rate and reactive oxygen species (ROS) level. Protein and mRNA levels were assessed using Western blot and qPCR.

RESULTS

miR-146a expression and cell viability of H9C2 cells were downregulated under the circumstance of H/R injury. The tendency could be reversed by Dex, which could also upregulate SOD activity and decrease apoptosis, LDH activity, MDA, 78-kDa glucose-regulated protein (GRP78), and C/EBP homologous protein (CHOP) levels of H9C2 cells. GRP78, CHOP levels, and cell viability were negatively modulated by miR-146a. Dex elevated cell viability, catalase, MnSOD, and NAD(P)H dehydrogenase (NQO1) levels but suppressed apoptosis rate, GRP78, and CHOP levels by increasing miR-146a expression and downregulating ROS, phosphorylation of p38, and extracellular signal-regulated kinases 1/2 levels. By using SB203580 (SB), the p38 mitogen-activated protein kinase (MAPK) inhibitor, Dex or the inhibition of miR-146 upregulated cell viability but downregulated GRP78 and CHOP levels.

CONCLUSION

Dex might regulate miR-146a expression, which could further modulate the endoplasmic reticulum stress and oxidative stress and eventually affect the cell viability and apoptosis of myocardial cells injured by H/R via the MAPK signal pathway.

Dexmedetomidine attenuates haemorrhage-induced thalamic pain by inhibiting the TLR4/NF-κB/ERK1/2 pathway in mice

BACKGROUND

Thalamic pain, a neuropathic pain syndrome, frequently occurs after stroke. This research aimed to investigate the effect of dexmedetomidine (DEX) on thalamic pain.

METHODS

The cellular localization of the TLR4 protein was determined by immunostaining. The expression of Iba1, GFAP and protein associated with the TLR4/NF-κB/ERK1/2 pathway was measured by Western blotting. Continuous pain hypersensitivity was evaluated by behavioural tests. The results were analysed by one-way ANOVA, two-way ANOVA and Tukey's post hoc test.

RESULTS

The results demonstrated that DEX obviously alleviated thalamic pain induced by haemorrhage on the ipsilateral side and delayed the development of pain hypersensitivity. Furthermore, the expression levels of Iba1, GFAP and proteins associated with the TLR4/NF-κB/ERK1/2 signalling pathway were greatly increased in mice with thalamic pain, but these effects were reversed by DEX.

CONCLUSION

Our findings suggest that DEX alleviates the inflammatory response during thalamic pain through the TLR4/NF-κB/ERK1/2 signalling pathway and might be a potential therapeutic agent for thalamic pain.

Protective effects of dexmedetomidine on cerebral ischemia/reperfusion injury via the microRNA-214/ROCK1/NF-κB axis

BACKGROUND

Cerebral ischemia/reperfusion injury (CIRI) is a complication of surgical procedure associated with high mortality. The protective effect of dexmedetomidine (DEX) on CIRI has been explored in previous works, yet the underlying molecular mechanism remains unclear. Our study explored the protective effect of DEX and its regulatory mechanism on CIRI.

METHODS

A CIRI rat model was established using middle cerebral artery occlusion (MCAO). Neurological deficit scores for rats received MCAO modeling or DEX treatment were measured. Cerebral infarction area of rats was detected by TTC staining, while damage of neurons in hippocampal regions of rats was determined by hematoxylin-eosin (HE) staining. Apoptosis rate of neurons in hippocampal regions was examined by TUNEL staining. The dual-luciferase assay was performed to detect the binding of microRNA-214 (miR-214) to Rho-associated kinase 1 (ROCK1).

RESULTS

DEX treatment significantly reduced infarction area of MCAO rats and elevated miR-214 expression. Injection of miR-214 inhibitor attenuated the effect of DEX in MCAO rats by increasing the area of cerebral infarction in rats and apoptosis rate of hippocampal neurons. ROCK1 was targeted and negatively regulated by miR-214. The overexpression of ROCK1 led to activation of NF-κB to aggravate CIRI.

CONCLUSION

Therapeutic effects of DEX on CIRI was elicited by overexpressing miR-214 and impairing ROCK1 expression and NF-κB activation. Our finding might provide novel insights into the molecular mechanism of DEX in rats with CIRI.

Dexmedetomidine preconditioning mitigates myocardial ischemia/reperfusion injury via inhibition of mast cell degranulation

The degranulation of cardiac mast cells is associated with occurrence and development of myocardial ischemia/reperfusion (I/R) injury. Dexmedetomidine has a cardioprotective effect from I/R injury. The purpose of this study was to investigate whether dexmedetomidine preconditioning induced cardioprotection is related to suppression of degranulation of cardiac mast cell. Both in vivo and in vitro experimental results revealed that hemodynamic disorder, arrhythmia, infarct size, histopathological score, and mast cell degranulation were dramatically increased in I/R injury groups compared with non-I/R groups, and mastocyte secretagogue compound 48/80 aggravated these damages, but it can be improved by dexmedetomidine preconditioning. Similarly, compound 48/80 increased levels of cardiac troponin I (cTnI) and tryptase, cardiomyocytes apoptosis, and expression of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), and nuclear factor-kappa B p65 (NF-κB p65) in cardiac tissues induced by I/R injury, but it can be partially decreased by dexmedetomidine pretreatment. Compound 48/80 inhibited proliferation of H9C2(2-1) and RBL-2H3, exacerbated apoptosis of H9C2(2-1), and elevated levels of cTnI and tryptase, while both of which were abolished by dexmedetomidine pretreatment. Our data suggest that dexmedetomidine preconditioning alleviates the degranulation of mast cells and the apoptosis of cardiomyocytes caused by I/R injury, and inhibits the activation of inflammatory related factors HMGB1, TLR4, and NF-κB p65.

Perioperative dexmedetomidine and 5-year survival in patients undergoing cardiac surgery

BACKGROUND

Dexmedetomidine sedation has been associated with favourable outcomes after surgery. We aimed to assess whether perioperative dexmedetomidine use is associated with improved survival after cardiac surgery.

METHODS

This retrospective cohort study included 2068 patients undergoing on-pump coronary artery bypass grafting and/or valve surgery. Among them, 1029 patients received dexmedetomidine, and 1039 patients did not. Intravenous dexmedetomidine infusion of 0.007 μg kg^-1 min^-1 was initiated before or immediately after cardiopulmonary bypass and lasted for < 24 h. The primary outcome was 5-year survival after cardiac surgery. The propensity scores matching (PSM), inverse probability of treatment weighting (IPTW), and overlap weighting approaches were used to minimise bias. Survival analyses were performed with Cox proportional-hazard models.

RESULTS

The median age was 63 yr old and the male to female ratio was 71:29 in both groups. Baseline covariates were balanced between groups after adjustment using PSM, IPTW, or overlap weighting. Patients receiving dexmedetomidine in cardiac surgical procedures had higher survival during postoperative 5 yr in unadjusted analysis (hazard ratio [HR]=0.63; 95% confidence interval [CI], 0.51-0.78; P<0.001), and after adjustment with PSM (HR=0.63; 95% CI, 0.45-0.89; P=0.009), IPTW (HR=0.70; 95% CI, 0.51-0.95; P=0.023), or overlap weighting (HR=0.67; 95% CI, 0.51-0.89; P=0.006). The 5-yr mortality rate after cardiac surgery was 13% and 20% in the dexmedetomidine and non-dexmedetomidine groups, respectively (PSM adjusted odds ratio=0.61; 95% CI, 0.42-0.89; P=0.010).

CONCLUSION

Perioperative dexmedetomidine infusion was associated with improved 5-yr survival in patients undergoing cardiac surgery.

Dexmedetomidine at a dose of 1 µM attenuates H9c2 cardiomyocyte injury under 3 h of hypoxia exposure and 3 h of reoxygenation through the inhibition of endoplasmic reticulum stress

Myocardial ischemia-reperfusion injury (MIRI) has been confirmed to induce endoplasmic reticulum stress (ERS) during downstream cascade reactions after the sufficient deterioration of cardiomyocyte function. However, clinically outcomes have been inconsistent with experimental findings because the mechanism has not been entirely elucidated. Dexmedetomidine (DEX), an α² adrenergic receptor agonist with anti-inflammatory and organ-protective activity, has been shown to attenuate IRI in the heart. The present study aimed to determine whether DEX is able to protect injured cardiomyocytes under in vitro hypoxia/reoxygenation (H/R) conditions and evaluate the conditions under which ERS is efficiently ameliorated. The cytotoxicity of DEX in H9c2 cells was evaluated 24 h after treatment with several different concentrations of DEX. The most appropriate H/R model parameters were determined by the assessment of cell viability and injury with Cell Counting Kit-8 and lactate dehydrogenase (LDH) release assays after incubation under hypoxic conditions for 3 h and reoxygenation conditions for 3, 6, 12 and 24 h. Additionally, the aforementioned methods were used to assess cardiomyocytes cultured with various concentrations of DEX under H/R conditions. Furthermore, the degree of apoptosis and the mRNA and protein expression levels of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and caspase-12 were evaluated in all groups. The addition of 1, 5 and 10 µM DEX to the cell culture significantly increased the proliferation of H9c2 cells by >80% under normal culture conditions. In the H/R model assessment, following 3 h of anoxia exposure, H9c2 cell viability decreased to 62.67% with 3 h of reoxygenation and to 36% with 6 h of reoxygenation compared with the control. The viability of H9c2 cells subjected to hypoxia for 3 h and reoxygenation for 3 h increased by 61.3% when pretreated with 1 µM DEX, and the LDH concentration in the supernatant was effectively decreased by 13.7%. H/R significantly increased the percentage of apoptotic cells, as detected by flow cytometry, and increased the expression levels of GRP78, CHOP and caspase-12, while treatment with either DEX or 4-phenylbutyric acid (4-PBA) significantly attenuated these effects. Additionally, despite the protective effect of DEX against H/R injury, 4-PBA attenuated the changes induced by DEX and H/R. In conclusion, treatment with 1 µM DEX alleviated cell injury, apoptosis and the increases in GRP78, CHOP and caspase-12 expression levels in H9c2 cells induced by 3 h of hypoxia and 3 h of reoxygenation.

Role of HSP90 in suppressing TLR4-mediated inflammation in ischemic postconditioning

BACKGROUND

Myocardial inflammation mediated by toll-like receptor 4 (TLR4) plays an active role in myocardial ischemia/reperfusion (I/R) injury. Studies show that heat shock protein 90 (HSP90) is involved in ischemic postconditioning (IPostC) cardioprotection. This study investigates the roles of TLR4 and HSP90 in IPostC.

METHODS

Rats were subjected to 30 min ischemia, then 2 h reperfusion. IPostC was applied by three cycles of 30 s reperfusion, then 30 s reocclusion at reperfusion onset. Sixty rats were randomly divided into four groups: sham, I/R, IPostC, and geldanamycin (GA, HSP90 inhibitor, 1 mg/kg) plus IPostC (IPostC + GA).

RESULTS

IPostC significantly reduced I/R-induced infarct size (40.2±2.1% versus 28.4±2.4%; P < 0.05); the release of cardiac Troponin T, creatine kinase-MB, and lactate dehydrogenase (191.5±3.1 versus 140.6±3.3 pg/ml, 3394.6±132.7 versus 2880.7±125.5 pg/ml, 2686.2±98.6 versus 1848.8±90.1 pg/ml, respectively; P < 0.05); and cardiomyocyte apoptosis (40.3±2.2% versus 27.0±1.6%; P < 0.05). Further, local and circulating IL-1β, IL-6, TNF-α, and ICAM-1 levels decreased; TLR4 expression and nuclear factor-KB (NF-κB) signaling decreased; and cardiac HSP90 expression increased. Blocking HSP90 function with GA inhibited IPostC protection and anti-inflammation, suggesting that IPostC has a HSP90-dependent anti-inflammatory effect.

CONCLUSION

HSP90 may play a role in IPostC-mediated cardioprotection by inhibiting TLR4 activation, local and systemic inflammation, and NF-kB signaling.

Dexmedetomidine Alleviates CCI-Induced Neuropathic Pain via Inhibiting HMGB1-Mediated Astrocyte Activation and the TLR4/NF-κB Signaling Pathway in Rats

To investigate the effects of dexmedetomidine on chronic constriction injury (CCI)-induced neuropathic pain and to further explore its mechanism. A CCI rat model was established and treatment with dexmedetomidine. The paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were monitored at different time points, and the effects of hematoxylin-eosin staining on the sciatic nerve morphology of rats were observed. Immunohistochemical and immunofluorescence analyses were used to detect the expression of high mobility group box-1 (HMGB1) protein and glial fibrillary acidic protein (GFAP), and protein fluorescence intensity of GFAP in spinal cord tissue, respectively. Moreover, the expression of HMGB1 and Toll-like receptor-4/nuclear factor kappa-B (TLR4/NF-κB) pathway-related proteins were detected by western blot assay. To verify whether dexmedetomidine alleviates CCI-induced neuropathic pain by inhibiting HMGB1-mediated astrocyte activation and the TLR4/NF-κB signaling pathway, the rats were further treated with an HMGB1 activator or antagonist. Dexmedetomidine was found to improve the pathological changes of the sciatic nerve and alleviate pain in the CCI rats. The expression of HMGB1, GFAP, TLR4, TRAF6, MyD88, and p-P65 were greatly downregulated in the spinal cord tissues of the CCI rats. In addition, a further study showed that an HMGB1 activator can reverse the inhibition of neuropathic pain behaviors of dexmedetomidine. Overexpression of HMGB1 downregulated the PWMT and PWTL and enhanced the astrocyte activity and the TLR4/NF-κB signaling pathway in CCI rats. These results indicated that dexmedetomidine can alleviate neuropathic pain in CCI rats by inhibiting HMGB1-mediated astrocyte activation and the TLR4/NF-κB signaling pathway.

Perioperative Dexmedetomidine Improves Outcomes of Kidney Transplant

Graft function is crucial for successful kidney transplantation. Many factors may affect graft function or cause delayed graft function (DGF), which decreases the prognosis for graft survival. This study was designed to evaluate whether the perioperative use of dexmedetomidine (Dex) could improve the incidence of function of graft kidney and complications after kidney transplantation. A total of 780 patients underwent kidney transplantations, 315 received intravenous Dex infusion during surgery, and 465 did not. Data were adjusted with propensity scores and multivariate logistic regression was used. The primary outcomes are major adverse complications, including DGF and acute rejection in the early post‐transplantation phase. The secondary outcomes included length of hospital stay (LOS), infection, overall complication, graft functional status, post‐transplantation serum creatinine values, and estimated glomerular filtration rate (eGFR). Dex use significantly decreased DGF (19.37% vs. 23.66%; adjusted odds ratio, 0.744; 95% confidence interval, 0.564–0.981; P = 0.036), risk of infection, risk of acute rejection in the early post‐transplantation phase, the risk of overall complications, and LOS. However, there were no statistical differences in 90‐day graft functional status or 7‐day, 30‐day, and 90‐day eGFR. Perioperative Dex use reduced incidence of DGF, risk of infection, risk of acute rejection, overall complications, and LOS in patients who underwent kidney transplantation.

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 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.

Dexmedetomidine post-treatment attenuates cardiac ischaemia/reperfusion injury by inhibiting apoptosis through HIF-1α signalling

Hypoxia‐inducible factor 1α (HIF‐1α) plays a critical role in the apoptotic process during cardiac ischaemia/reperfusion (I/R) injury. This study aimed to investigate whether post‐treatment with dexmedetomidine (DEX) could protect against I/R‐induced cardiac apoptosis in vivo and in vitro via regulating HIF‐1α signalling pathway. Rat myocardial I/R was induced by occluding the left anterior descending artery for 30 minutes followed by 6‐hours reperfusion, and cardiomyocyte hypoxia/reoxygenation (H/R) was induced by oxygen‐glucose deprivation for 6 hours followed by 3‐hours reoxygenation. Dexmedetomidine administration at the beginning of reperfusion or reoxygenation attenuated I/R‐induced myocardial injury or H/R‐induced cell death, alleviated mitochondrial dysfunction, reduced the number of apoptotic cardiomyocytes, inhibited the activation of HIF‐1α and modulated the expressions of apoptosis‐related proteins including BCL‐2, BAX, BNIP3, cleaved caspase‐3 and cleaved PARP. Conversely, the HIF‐1α prolyl hydroxylase‐2 inhibitor IOX2 partly blocked DEX‐mediated cardioprotection both in vivo and in vitro. Mechanistically, DEX down‐regulated HIF‐1α expression at the post‐transcriptional level and inhibited the transcriptional activation of the target gene BNIP3. Post‐treatment with DEX protects against cardiac I/R injury in vivo and H/R injury in vitro. These effects are, at least in part, mediated via the inhibition of cell apoptosis by targeting HIF‐1α signalling.

Dexmedetomidine for the prevention of postoperative delirium in elderly patients undergoing noncardiac surgery: A meta-analysis of randomized controlled trials

BACKGROUND

Postoperative delirium (POD) among the elderly population that undergoes noncardiac surgery is significantly associated with adverse clinical outcomes. We conducted this meta-analysis to evaluate the effectiveness and safety of dexmedetomidine for the prophylaxis of POD among the elderly population after noncardiac surgery.

METHODS

We searched Embase, PubMed, and the Cochrane Library from inception date to March 2019 for randomized controlled trials (RCTs) that compared dexmedetomidine and placebo for the prevention of POD and evaluated the major cardiovascular outcomes among elderly people after noncardiac surgery. Two authors independently screened the studies and extracted data from the published articles. The main outcome was the incidence of POD. The secondary outcomes included the occurrence of bradycardia, hypotension, hypertension, tachycardia, myocardial infarction, stroke, hypoxaemia, and all-cause mortality.

RESULTS

A total of 6 RCTs with 2102 participants were included. Compared with placebo, dexmedetomidine significantly reduced the prevalence of POD (RR = 0.61, 95% CI 0.34-0.76, P = 0.001, I2 = 66%), and the risk of tachycardia (RR = 0.48, 95% CI 0.30-0.76, P = 0.002, I2 = 0%), hypertension (RR = 0.59, 95% CI 0.44-0.79, P < 0.001, I2 = 20%), stroke (RR = 0.22, 95% CI 0.06-0.76, P = 0.02, I2 = 0%), and hypoxaemia (RR = 0.50, 95% CI 0.32-0.78, P = 0.002, I2 = 0%) in elderly patients who underwent noncardiac surgery. However, dexmedetomidine accelerated the occurrence of bradycardia (RR = 1.36, 95% CI 1.11-1.67, P = 0.003, I2 = 0%). Furthermore, no significant differences were observed in the incidence of hypotension, myocardial infarction, and all-cause mortality between the dexmedetomidine and placebo groups.

CONCLUSIONS

Among elderly patients after noncardiac surgery, the prophylactic use of dexmedetomidine, compared with the use of placebo, was related to a decline in the incidence of POD.

Pre-cardiopulmonary bypass administration of dexmedetomidine decreases cardiac troponin I level following cardiac surgery with sevoflurane postconditioning

Objective

This study was performed to determine the effect of dexmedetomidine (DEX) administration on myocardial damage in cardiac surgery with sevoflurane postconditioning.

Methods

We retrospectively examined all cardiac valve replacement surgeries from 1 April 2016 to 30 April 2017. Eligible patients were divided into two groups based on whether DEX was infused. DEX infusion was permitted only between intubation and the beginning of cardiopulmonary bypass (CPB). Sevoflurane was inhaled via the standard postconditioning procedure starting at aortic declamping. The cardiac troponin I (cTnI) level was measured at different time points. The postoperative outcomes and complications were also analyzed.

Results

One hundred patients were included in the study (DEX group, n = 53; non-DEX group, n = 47). Increased cTnI levels were significantly correlated with the New York Heart Association classification, CPB time, and DEX use. DEX use and the CPB time were potential independent factors contributing to changes in the cTnI level. The cTnI level at 6, 12, and 24 hours postoperatively was remarkably lower in the DEX than non-DEX group by 1.14, 7.83, and 5.86 ng/mL, respectively.

Conclusions

DEX decreased the cTnI level after CPB when sevoflurane postconditioning was used, especially at 6, 12, and 24 hours postoperatively.

Tilianin-loaded Reactive Oxygen Species-Scavenging Nano-Micelles Protect H9c2 Cardiomyocyte Against Hypoxia/Reoxygenation-Induced Injury

Previous studies have shown that tilianin alleviates ischemia-reperfusion-induced cardiomyocyte injury. However, its clinical translation has been hampered because of its insolubility in water. Tilianin-based nano-micelles that may overcome this critical issue are presented. A polyethylene glycol compound was covalently attached to propylene sulfide-formed amphiphilic diblock polymers. In the aqueous solution, tilianin is encapsulated in a hydrophobic shell to form nano-micelles. The Ph-PPS-PEG self-assembled into nanoscale micelles with a size of approximately 70 nm, termed "tilianin-loaded micelles" (TLMs). TLMs are highly efficient hydrogen peroxide scavengers and the activity of caspase-3 inhibition, thereby protecting cells from H/R-induced cytotoxicity. In addition, TLMs decreased levels of MDA, IL-1 and tumor necrosis factor (TNF-α), inhibited apoptosis, TLR4 and nuclear transcription factor (NF-κB p65) protein expression in hypoxia-reoxygenation (H/R) model. Taken together, the study suggests that TLMs may be of clinical value for the protective effects of cardiomyocytes by inhibiting Inflammation and oxidative stress during myocardial ischemia-reperfusion injury.

Dexmedetomidine preconditioning attenuates ischemia/reperfusion injury in isolated rat hearts with endothelial dysfunction

BACKGROUND AND PURPOSES

Dexmedetomidine preconditioning (DP) can mimic pharmacological preconditioning and induce cardiac protection. There are controversies on the roles of coronary endothelia in cardioprotection of dexmedetomidine. Herein, we tested the hypothesis that protection of dexmedetomidine is not endothelial dependent in heart against myocardial ischemia/reperfusion (I/R) injury.

METHODS

Langendorff-perfused rat hearts were pretreated by 60 mM of potassium to produce endothelial dysfunction (ED), then medicated with dexmedetomidine, and subsequently subjected to 30 min of global ischemia followed by 60 min of reperfusion. To investigate the cardioprotective effect of dexmedetomidine in heart with ED, isolated rat hearts were randomly divided into the following six groups: sham, I/R, DP, ED, ED + I/R, and ED + DP + I/R. Heart rates, left ventricular function, and coronary perfusion pressure were assessed for each heart. Infarct size was evaluated by triphenyltetrazolium chloride staining. High-sensitivity cardiac troponin T (hs-cTNT) of coronary flow perfusion was determined.

RESULTS

After the isolated hearts with pretreatment of 60 mM of potassium chloride, diastolic function of coronary endothelia in performance of response to histamine was significantly decreased (P < 0.05). DP attenuated I/R-induced infarct size of the left ventricle (P < 0.05) and decreased hs-cTNT (P < 0.05). Additionally, left ventricular developed pressure, +dp/dt_max, and -dp/dt_max were elevated in rat hearts pretreated with dexmedetomidine. Furthermore, dexmedetomidine-mediated cardiac protection against I/R injury was still remained in isolated hearts with coronary ED.

CONCLUSION

Continuous perfusion of 60 mM of potassium for 10 min can produce coronary ED in isolated rat hearts. Dexmedetomidine maintains its protective function against I/R injury in heart with coronary ED. Myocardial protection of dexmedetomidine is non-endothelial function dependent in alleviating I/R injury.

Dexmedetomidine Preconditioning Ameliorates Inflammation and Blood-Spinal Cord Barrier Damage After Spinal Cord Ischemia-Reperfusion Injury by Down-Regulation High Mobility Group Box 1-Toll-Like Receptor 4-Nuclear Factor κB Signaling Pathway

STUDY DESIGN

To evaluate the effect of Dexmedetomidine (Dex) on the inflammatory response and the integrity of blood-spinal cord barrier (BSCB) after spinal cord ischemia-reperfusion injury (SCIRI).

OBJECTIVE

To investigate the role of Dex in spinal cord I/R, particularly in the high mobility group box 1-toll-like receptor 4-nuclear factor κB (HMGB1-TLR4-NF-κB) pathway and the integrity of BSCB.

SUMMARY OF BACKGROUND DATA

High mobility group box 1 (HMGB1) has been identified as a key mediator for the inflammatory response after spinal cord injury. Toll-like receptor 4-nuclear factor κB (TLR4-NF-κB) signaling pathway is the downstream of HMGB1. Dex preconditioning could protect the spinal cord from I/R injury by inhibiting HMGB1 and stabilizing the integrity of BSCB. But its underlying mechanism is not fully understood.

METHODS

Forty-eight male Japanese white rabbits were randomly assigned to three groups (16 rabbits/group): sham, I/R, and Dex + I/R. The hind-limb motor function was assessed at 12 hours intervals for 48 hours after reperfusion using the modified Tarlov scale score. The expression of HMGB1, TLR4, NF-κB, and tumor necrosis factor α (TNF-α) was evaluated by real-time polymerase chain reaction (RT-PCR) and Western blot. The permeability of BSCB was examined via Evans blue (EB) extravasation.

RESULTS

Compared with sham group, spinal cord I/R increased the expression of HMGB1, TLR4, NF-κB, and TNF-α as well as the permeability of BSCB (P < 0.05). Spinal cord I/R induced the decline of the score of hind-limb motor function (P < 0.01). Preconditioning with Dex attenuated the up-regulation of the express of HMGB1, TLR4, NF-κB, TNF-α, and stabilized the permeability of BSCB (P < 0.05). Dex preconditioning also improved the hiatopathological outcome and the motor function (P < 0.01).

CONCLUSION

Dex preconditioning may inhibit the inflammatory response and stabilize the integrity of BSCB at least partially by inhibiting the HMGB1-TLR4-NF-κB signaling pathway to protect spinal cord from ischemia/reperfusion injury.

LEVEL OF EVIDENCE

2.

Dexmedetomidine Protects Mouse Brain from Ischemia-Reperfusion Injury via Inhibiting Neuronal Autophagy through Up-Regulating HIF-1α

Stroke is the leading cause of death in China and produces a heavy socio-economic burden in the past decades. Previous studies have shown that dexmedetomidine (DEX) is neuroprotective after cerebral ischemia. However, the role of autophagy during DEX-mediated neuroprotection after cerebral ischemia is still unknown. In this study, we found that post-conditioning with DEX and DEX+3-methyladenine (3-MA) (autophagy inhibitor) reduced brain infarct size and improved neurological deficits compared with DEX+RAPA (autophagy inducer) 24 h after transient middle cerebral artery artery occlusion (tMCAO) model in mice. DEX inhibited the neuronal autophagy in the peri-ischemic brain, and increased viability and decreased apoptosis of primary cultured neurons in oxygen-glucose deprivation (OGD) model. DEX induced expression of Bcl-1 and p62, while reduced the expression of microtubule-associated protein 1 light chain 3 (LC3) and Beclin 1 in primary cultured neurons through inhibition of apoptosis and autophagy. Meanwhile, DEX promoted the expression of hypoxia-inducible factor-1α (HIF-1α) both in vivo and in vitro, and 2-Methoxyestradiol (2ME2), an inhibitor of HIF-1α, could reverse DEX-induced autophagic inhibition. In conclusion, our study suggests that post-conditioning with DEX at the beginning of reperfusion protects mouse brain from ischemia-reperfusion injury via inhibition of neuronal autophagy by upregulation of HIF-1α, which provides a potential therapeutic treatment for acute ischemic injury.

Effects of prostaglandin E1 on reperfusion injury patients: A meta-analysis of randomized controlled trials

BACKGROUND

Prostaglandin E1 (PGE1) is widely used as a pretreatment for myocardial reperfusion injury in animal experiments. However, the cardioprotective effects of PGE1 in patients have not been established. We performed a meta-analysis to investigate whether PGE1 is cardioprotective, based on the reduction of correlative reperfusion injury events (CRIE), major adverse cardiac events (MACE), and biomarker release in patients with ischemia reperfusion injury.

METHODS

The Medline, EMBASE, and Cochrane databases were searched for randomized clinical trials confirming the effects of PGE1. Two investigators independently selected suitable trials, assessed trial quality, and extracted data.

RESULTS

Six studies in patients undergoing percutaneous coronary intervention (4 studies) and cardiac surgery (2 studies), comprising a total of 445 patients, were included in this review. The results showed that PGE1 reduced the incidence of CRIE (relative ratio 0.4 [95% confidence interval 0.43, 0.95]), the incidence of MACE (0.35 [0.17, 0.70]), and the level of troponin T (standardized mean difference 20.28 [20.47, 20.09]), creatine kinase-MB (-1.74 [-3.21, - 0.27]), interleukin-6 (-1.37 [-2.69, - 0.04]), and interleukin-8 (-2.05 [-2.75, - 1.34]).

CONCLUSION

PGE1 may have beneficial effects on myocardial reperfusion injury in the clinic.

Dexmedetomidine Protects Cardiomyocytes against Hypoxia/Reoxygenation Injury by Suppressing TLR4-MyD88-NF-κB Signaling

OBJECTIVE

We previously reported that dexmedetomidine (DEX) offers cardioprotection against ischemia/reperfusion injury in rats. Here, we evaluated the role of toll-like receptors 4- (TLR4-) myeloid differentiation primary response 88- (MyD88-) nuclear factor-kappa B (NF-κB) signaling in DEX-mediated protection of cardiomyocytes using in vitro models of hypoxia/reoxygenation (H/R).

METHODS

The experiments were carried out in H9C2 cells and in primary neonatal rat cardiomyocytes. Cells pretreated with vehicle or DEX were exposed to hypoxia for 1 h followed by reoxygenation for 12 h. We analyzed cell viability and lactate dehydrogenase (LDH) activity and measured tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β mRNA levels, TLR4, MyD88, and nuclear NF-κB p65 protein expression and NF-κB p65 nuclear localization. TLR4 knock-down by TLR4 siRNA transfection and overexpression by TLR4 DNA transfection were used to further confirm our findings.

RESULTS

DEX protected against H/R-induced cell damage and inflammation, as evidenced by increased cell survival rates, decreased LDH activity, and decreased TNF-α, IL-6, and IL-1β mRNA levels, as well as TLR4 and NF-κB protein expression. TLR4 knock-down partially prevented cell damage following H/R injury, while overexpression of TLR4 abolished the DEX-mediated protective effects.

CONCLUSIONS

DEX pretreatment protects rat cardiomyocytes against H/R injury. This effect is partly mediated by TLR4 suppression via TLR4-MyD88-NF-κB signaling.