The cardioprotective effect of dexmedetomidine on global ischaemia in isolated rat hearts

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.

Dexmedetomidine alleviates pulmonary fibrosis through the ADORA2B-Mediated MAPK signaling pathway

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronically progressive fibrotic pulmonary disease characterized by an uncertain etiology, a poor prognosis, and a paucity of efficacious treatment options. Dexmedetomidine (Dex), an anesthetic-sparing alpha-2 adrenoceptor (α2AR) agonist, plays a crucial role in organ injury and fibrosis. However, the underlying mechanisms of IPF remain unknown.

METHODS

In our study, the role of Dex in murine pulmonary fibrosis models was determined by Dex injection intraperitoneally in vivo. Fibroblast activation and myofibroblast differentiation were assessed after Dex treatment in vitro. The activation of MAPK pathway and the expression of Adenosine A2B receptor (ADORA2B) were examined in lung myofibroblasts. Moreover, the role of ADORA2B in Dex suppressing myofibroblast differentiation and pulmonary fibrosis was determined using the ADORA2B agonist BAY60-6583.

RESULTS

The results revealed that Dex could inhibit Bleo-induced pulmonary fibrosis in mice. In vitro studies revealed that Dex suppressed TGF-β-mediated MAPK pathway activation and myofibroblast differentiation. Furthermore, Dex inhibits myofibroblast differentiation and pulmonary fibrosis via downregulating ADORA2B expression.

CONCLUSIONS

Our findings suggest Dex as a potential therapeutic agent for pulmonary fibrosis. Dex may alleviate lung fibrosis and myofibroblast differentiation through the ADORA2B-mediated MAPK signaling pathway.

Multiple-Factors-Induced Rheumatoid Arthritis Synoviocyte Activation Is Attenuated by the α2-Adrenergic Receptor Agonist Dexmedetomidine

Dexmedetomidine (Dex) has analgesic and sedative properties and anti-inflammatory functions. Although the effects of Dex on arthritis have been revealed, the physiological mechanism underlying the interaction between Dex and rheumatoid arthritis (RA)-mediated inflammatory cytokines has not been fully studied. Inflamed and migrated fibroblast-like synoviocytes (FLSs) are involved in RA severity. Thus, we aimed to determine the effects of Dex on RA-FLSs treated with inflammatory cytokines and a growth factor as multiple stimulating inputs. TNF-α, IL-6, and EGF as multiple stimulating inputs increased the cAMP concentration of RA-FLSs, while Dex treatment reduced cAMP concentration. Dex reduced electroneutral sodium-bicarbonate cotransporter 1 (NBCn1) expression, NBC activity, and subsequent RA-FLS migration. The mRNA expression levels of RA-related factors, such as inflammatory cytokines and osteoclastogenesis factors, were enhanced by multiple-input treatment. Notably, Dex effectively reduced these expression levels in RA-FLSs. These results indicate that multiple inflammatory or stimulating inputs enhance RA-FLS migration, and treatment with Dex relieves activated RA-FLSs, suggesting that Dex is a potential therapeutic drug for RA.

Effect of Dexmedetomidine on Cardiac Surgery Patients

ABSTRACT

Dexmedetomidine, an alpha-2 adrenoreceptor agonist that is widely used as a sedative medication, is becoming more and more attractive in clinical application on cardiac surgery patients. In this review, we aim to summarize and discuss both retrospective studies and clinical trials regarding the effect of dexmedetomidine on patients who underwent cardiac surgery (including coronary artery bypass grafting, valve surgery, aortic surgery, percutaneous coronary intervention, and so on), which illustrates that the clinical effects of dexmedetomidine could effectively reduce mortality, major complications, and the intensive care unit and hospital length of stay without comprising safety. In addition, inconsistent results from both retrospective studies and clinical trials have also been demonstrated. Although the effectiveness and safety of dexmedetomidine on cardiac surgery patients is suggested, high-quality clinical trials are needed for further verification.

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.

Effects of dexmedetomidine on new oxidative stress markers on renal ischaemia-reperfusion injury in rats: thiol/disulphide homeostasis and the ischaemia-modified albumin

OBJECTIVES

This study investigated the effect of dexmedetomidine on the oxidant-antioxidant (thiol/disulphide) balance.

METHODS

A total of 24 rats were divided into four groups. The renal arteries in groups IR (ischaemia/reperfusion) and IR + D (ischaemia/reperfusion + dexmedetomidine) were clamped for 45 min and reperfused for 180 min. Groups D (Dexmedetomidine) and IR + D were administered 100 μg/kg dexmedetomidine. Oxidant-antioxidant (thiol/disulphide) levels were measured. Kidney tissue was examined histopathologically.

RESULTS

No statistically difference was found between the groups in terms of thiol-disulphide averages, while IMA, TOS and thiol-disulphide results showed a minimal decrease in Group IR + D compared to Group IR (p > 0.05). Tubular lesions and necrosis were found in 26-50% of tubules in Group IR. Tubular damage and necrosis in Group IR + D declined to 5-25% .

CONCLUSIONS

No statistically difference was found in the study where OSI index, thiol/disulphide balance and IMA were measured together as biochemical values.

Dexmedetomidine attenuates lipopolysaccharide-induced inflammation through macrophageal IL-10 expression following α7 nAchR activation

Dexmedetomidine, a highly selective α₂-adrenoceptor agonist, has been recently reported to alleviate systemic inflammatory response induced by lipopolysaccharide (LPS), in addition to its sedative, analgesic, bradycardic and hypotensive properties. This study aimed to illustrate the molecular mechanisms underlying dexmedetomidine-induced anti-inflammation. In the LPS-pretreated mice, subcutaneous injection of dexmedetomidine reduced the spleen weight as well as serum and spleen expression of proinflammatory cytokines, tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β, and increased serum and spleen expression of IL-10, a known anti-inflammatory cytokine. In addition, dexmedetomidine-attenuated proinflammatory cytokine reduction was entirely inhibited by selective α7 nicotinic acetylcholine receptor (nAChR) antagonist methyllycaconitine but not α₂-adrenoceptor antagonist yohimbine. Dexmedetomidine also increased macrophageal IL-10 expression in the presence and absence of LPS, which was also attenuated by methyllycaconitine but not yohimbine. Furthermore, the stimulatory effect of dexmedetomidine on the expression of IL-10 was also reduced by the α7 nAChR gene silencer siRNA/α7 nAChR. Lastly, pretreatment with the IL-10 neutralizing antibody reversed dexmedetomidine-supressed expression of proinflammatory cytokines. Our findings illustrate that dexmedetomidine-induced anti-inflammation is through macrophageal expression of IL-10 following activation of α7 nAchRs but not α₂-adrenoceptors.

Comparison of effects of dexmedetomidine and amifostine against X-ray radiation-induced parotid damage

Radiotherapy can be employed as a therapeutic modality alone in the early stages of cancer and is used together with other treatments such as surgery and chemotherapy in more advanced stages. However, exposure to ionizing radiation in association with radiotherapy affects several organs in the head and neck and can give rise to early and late side effects. Exposure to ionizing radiation used in radiotherapy is known to cause cell damage by leading to oxygen stress through the production of free oxygen radicals (such as superoxide radicals, hydroxyl radical, hydrogen peroxide, and singlet oxygen), depending on the total radiation dosage, the fractionation rate, radiosensitivity, and linear energy transfer. The purpose of the present study was to determine the potential protective role of a powerful and highly selective α2-adrenoreceptor agonist with a broad pharmacological spectrum against salivary gland damage induced by ionizing radiation exposure. Forty Sprague-Dawley rats were divided into five groups-control, ionizing radiation, ionizing radiation + dexmedetomidine (100 µg/kg), ionizing radiation + dexmedetomidine (200 µg/kg), and ionizing radiation + amifostine (200 mg/kg). Following exposure to ionizing radiation, we observed necrosis, fibrosis, and vascular congestions in parotid gland epithelial cells. We also observed increases in malondialdehyde (MDA) and cleaved Caspase-3 levels and a decrease in glutathione (GSH). In groups receiving dexmedetomidine, we observed necrotic epithelial cells, fibrosis and vascular congestion in parotid gland tissue, a decrease in MDA levels, and an increase in GSH. Dexmedetomidine may be a promising antioxidant agent for the prevention of oxidative damage following radiation exposure.

Dexmedetomidine reduces enteric glial cell injury induced by intestinal ischaemia-reperfusion injury through mitochondrial localization of TERT

This study was performed to uncover the effects of dexmedetomidine on oxidative stress injury induced by mitochondrial localization of telomerase reverse transcriptase (TERT) in enteric glial cells (EGCs) following intestinal ischaemia-reperfusion injury (IRI) in rat models. Following establishment of intestinal IRI models by superior mesenteric artery occlusion in Wistar rats, the expression and distribution patterns of TERT were detected. The IRI rats were subsequently treated with low or high doses of dexmedetomidine, followed by detection of ROS, MDA and GSH levels. Calcein cobalt and rhodamine 123 staining were also carried out to detect mitochondrial permeability transition pore (MPTP) and the mitochondrial membrane potential (MMP), respectively. Moreover, oxidative injury of mtDNA was determined, in addition to analyses of EGC viability and apoptosis. Intestinal tissues and mitochondria of EGCs were badly damaged in the intestinal IRI group. In addition, there was a reduction in mitochondrial localization of TERT, oxidative stress, whilst apoptosis of EGCs was increased and proliferation was decreased. On the other hand, administration of dexmedetomidine was associated with promotion of mitochondrial localization of TERT, whilst oxidative stress, MPTP and mtDNA in EGCs, and EGC apoptosis were all inhibited, and the MMP and EGC viability were both increased. A positive correlation was observed between different doses of dexmedetomidine and protective effects. Collectively, our findings highlighted the antioxidative effects of dexmedetomidine on EGCs following intestinal IRI, as dexmedetomidine alleviated mitochondrial damage by enhancing the mitochondrial localization of TERT.

Dexmedetomidine suppresses serum syndecan-1 elevation and improves survival in a rat hemorrhagic shock model

Hemorrhagic shock causes vascular endothelial glycocalyx (EGCX) damage and systemic inflammation. Dexmedetomidine (DEX) has anti-inflammatory and EGCX-protective effects, but its effect on hemorrhagic shock has not been investigated. Therefore, we investigated whether DEX reduces inflammation and protects EGCX during hemorrhagic shock. Anesthetized Sprague-Dawley rats were randomly assigned to five groups (n=7 per group): no shock (SHAM), hemorrhagic shock (HS), hemorrhagic shock with DEX (HS+DEX), hemorrhagic shock with DEX and the α7 nicotinic type acetylcholine receptor antagonist methyllycaconitine citrate (HS+DEX/MLA), and hemorrhagic shock with MLA (HS+MLA). HS was induced by shedding blood to a mean blood pressure of 25–30 mmHg, which was maintained for 30 min, after which rats were resuscitated with Ringer’s lactate solution at three times the bleeding volume. The survival rate was assessed up to 3 h after the start of fluid resuscitation. Serum tumor necrosis factor-alpha (TNF-α) and syndecan-1 concentrations, and wet-to-dry ratio of the heart were measured 90 min after the start of fluid resuscitation. The survival rate after 3 h was significantly higher in the HS+DEX group than in the HS group. Serum TNF-α and syndecan-1 concentrations, and the wet-to-dry ratio of heart were elevated by HS, but significantly decreased by DEX. These effects were antagonized by MLA. DEX suppressed the inflammatory response and serum syndecan-1 elevation, and prolonged survival in rats with HS.

Coronary Spasm During Postoperative Sedation With Dexmedetomidine

This is a case report of an 81-year-old woman who underwent tracheostomy, bilateral cervical dissection, partial tongue resection, radial forearm free flap reconstruction, and split-thickness skin grafting under general anesthesia. After successful surgery, she was moderately sedated postoperatively with intravenous dexmedetomidine (DEX) and fentanyl. The fentanyl was discontinued 5 hours postoperatively. Eight hours after the operation, an atrioventricular junctional rhythm, a 2-mm elevation of the ST segment, and biphasic T waves were detected in lead II that lasted approximately 3 minutes. Hypotension and bradycardia were observed simultaneously with the abnormal electrocardiogram. The next day, a cardiologist examined the patient and suggested that coronary spasm had occurred based on those findings. The transient coronary spasm was likely caused by a combination of various factors including surgical stress and altered autonomic function. However, it is possible that stimulation of α-2 adrenergic receptors induced by DEX may also be linked to the coronary vasospasm that occurred.

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.

The Protective Effect of Dexmedetomidine Against Ischemia-Reperfusion Injury after Hepatectomy: A Meta-Analysis of Randomized Controlled Trials

Background: Hepatic inflow occlusion proceeded to reduce blood loss during hepatectomy induces ischemia-reperfusion (IR) injury in the remnant liver. Dexmedetomidine, a selective α₂-adrenoceptor agonist used as an anesthetic adjuvant, has been shown to attenuate IR injury in preclinical and clinical studies. However, a meta-analysis is needed to systematically evaluate the protective effect of perioperative dexmedetomidine use on IR injury induced by hepatectomy.

Methods: A prospectively registered meta-analysis following Cochrane and PRISMA guidelines concerning perioperative dexmedetomidine use on IR injury after hepatectomy was performed via searching Cochrane Library, PubMed, EMBASE, ClinicalTrials.gov, Web of Science, CNKI, WanFang, and Sinomed for eligible randomized controlled trials up to 2021.3.31. The main outcome is postoperative liver function. Risk of bias was assessed by the Cochrane Risk of Bias tool. Review Manager 5.3 and Stata12.0 were applied to perform data analyses.

Results: Eight RCTs enrolling 468 participants were included. Compared with 0.9% sodium chloride, dexmedetomidine decreased serum concentration of ALT (WMD = −66.54, 95% CI: −92.10–−40.98), AST (WMD= −82.96, 95% CI: −106.74–−59.17), TBIL (WMD = −4.51, 95% CI: −7.32–−1.71), MDA (WMD = −3.09, 95% CI: −5.17–−1.01), TNF-α (WMD = −36.54, 95% CI: −61.33–−11.95) and IL-6 (WMD = −165.05, 95% CI: −225.76–−104.34), increased SOD activity (WMD = 24.70, 95% CI: 18.09–31.30) within postoperative one day. There was no significant difference in intraoperative or postoperative recovery parameters between groups.

Conclusions: Perioperative administration of dexmedetomidine can exert a protective effect on liver IR injury after hepatectomy. Additional studies are needed to further evaluate postoperative recovery outcomes of dexmedetomidine with different dosing regimens.

Effect of Dexmedetomidine on Perioperative Hemodynamics and Myocardial Protection in Thoracoscopic-Assisted Thoracic Surgery

BACKGROUND This study aimed to clarify the protective role of dexmedetomidine in thoracoscopic-assisted thoracic surgery (TATS), including control of the intraoperative heart rate, blood pressure, and myocardial injury markers. MATERIAL AND METHODS The patients who underwent TATS were divided into 2 equal groups: the dexmedetomidine group (dexmedetomidine pumped at 0.5 µg/kg for >10 min before the administration of anesthesia and at 0.5 µg/kg in the maintenance period) and the control group (pumped normal saline for >10 min before the administration of anesthesia). The data recorded for each patient were heart rate (preoperative, maximum intraoperative, and minimum intraoperative), systolic and diastolic blood pressure, intraoperative hemodynamic data, and intraoperative cardiovascular drugs administered. An enzyme-linked immunosorbent assay was performed to assess the postoperative levels of cardiac troponin I (cTnI), creatine kinase isoenzyme, myoglobin, and N-terminal pro-B-type natriuretic peptide (NT-proBNP). RESULTS There were no significant differences in the age, sex, body height, body weight, American Society of Anesthesiologists classification grade, resection mode, operation time, ejection fraction, basal heart rate, and systolic and diastolic blood pressure of the 2 groups. In the dexmedetomidine group, the patients' maximum intraoperative heart rate and diastolic pressure decreased, and the postoperative hospital stay period was shorter. The postoperative peripheral blood test for the dexmedetomidine group showed higher NT-proBNP levels and lower cTnI levels. CONCLUSIONS Preoperative administration of dexmedetomidine can benefit hemodynamic stability, protect the cardiovascular system in the intraoperative and postoperative periods, and shorten postoperative hospitalization.

Dexmedetomidine attenuates H2O2-induced apoptosis of rat cardiomyocytes independently of antioxidant enzyme expression

INTRODUCTION AND OBJECTIVES

Dexmedetomidine is a highly selective alpha-2 adrenoceptor agonist that has sedative and analgesic properties and myocardial protective effects. However, the mechanism underlying the protective effect of dexmedetomidine on cardiomyocytes remains unknown. This study mainly aimed to investigate the effects of dexmedetomidine on the generation of reactive oxygen species (ROS) in cardiomyocytes and whether it inhibits the apoptosis of cardiomyocytes by affecting antioxidant enzyme expression.

METHODS

Neonatal rat cardiomyocytes were pretreated with dexmedetomidine (100 nM) for 24 h. The cardiomyocytes were then incubated with 200 μM hydrogen peroxide solution (H₂O₂) for 4 h. PCR assay was used to determine the mRNA expression of antioxidant enzymes. Western blot assay was used to determine the protein expression of antioxidant enzymes. Fluorescence microscopy with the MitoSOX probe was used to detect the formation of ROS in cardiomyocytes, and fluorescence-activated cell sorting with annexin V/PI was used to determine the number of apoptotic cardiomyocytes.

RESULTS

Dexmedetomidine reduced ROS generation and antioxidant enzymes levels in cardiomyocytes before H₂O₂ stimulation (p<0.05). However, ROS generation and apoptosis in cardiomyocytes were significantly increased after H₂O₂ treatment, and dexmedetomidine pretreatment markedly inhibited the changes (p<0.05).

CONCLUSION

For the first time, to the best of our knowledge, our study shows that dexmedetomidine has a protective effect on cardiomyocytes through inhibition of ROS-induced apoptosis, and more importantly, this effect is independent of antioxidant enzyme mRNA and protein expression.

The Effects of Dexmedetomidine Post-Conditioning on Cardiac and Neurological Outcomes After Cardiac Arrest and Resuscitation in Swine

INTRODUCTION

One of the main contents of post-resuscitation care is to alleviate cardiac and neurological damage in cardiac arrest (CA) victims. Recently, dexmedetomidine pre- and post-conditioning have been shown to both effectively protect the heart and brain against regional ischemia reperfusion injury. In this study, we investigated the effects of dexmedetomidine post-conditioning on cardiac and neurological outcomes after CA and resuscitation in swine.

METHODS

A total of 28 male domestic swine were randomized into four groups: sham, cardiopulmonary resuscitation (CPR), low-dose dexmedetomidine post-conditioning (LDP), and high-dose dexmedetomidine post-conditioning (HDP). Sham animals underwent the surgical preparation only. The animal model was established by 8 min of CA and then 5 min of CPR. After the animal was successfully resuscitated, a loading dose of 0.25 μg/kg of dexmedetomidine was intravenously injected followed by continuous infusion of 0.25 μg/kg/h for 6 h in the LDP group, and meanwhile a double dose of dexmedetomidine was similarly administered in the HDP group. The same amount of saline was given in the other two groups. All the resuscitated animals were monitored for 6 h and then returned to their cages for an additional 18 h of observation.

RESULTS

After resuscitation, significantly greater cardiac, neurological dysfunction, and injuries were observed in all animals experiencing CA and resuscitation when compared with the sham group. However, the severity of cardiac and neurological damage was significantly milder in the two dexmedetomidine-treated groups than in the CPR group. Dexmedetomidine post-conditioning also significantly decreased post-resuscitation tissue inflammation, oxidative stress, and cell apoptosis and necroptosis in the heart and brain when compared with the CPR group. In addition, these protective effects produced by dexmedetomidine post-conditioning were significantly greater in the HDP group than in the LDP group.

CONCLUSIONS

Dexmedetomidine post-conditioning dose-dependently improved post-resuscitation cardiac and neurological outcomes through the inhibition of tissue inflammation, oxidative stress, and cell apoptosis and necroptosis.

Antioxidant effects of dexmedetomidine against hydrogen peroxide-induced DNA damage in vitro by alkaline Comet assay

Background/aim

Dexmedetomidine (DEX) is an alpha-2 adrenergic agonist that is commonly used as a sedative and anesthetic. The protective effects of DEX against oxidative damage under both in vitro and in vivo conditions have been demonstrated. It was aimed to evaluate and compare the protective effects of DEX and vitamin C (Vit C) on DNA against H₂O₂-induced DNA damage in human lymphocyte cell cultures in vitro by alkaline Comet assay.

Materials and methods

Lymphocyte cell cultures were divided into 5 groups, as the negative control, solvent control, positive control, hydrogen peroxide (H₂O₂; 150 μM) + DEX (1 μM; 2.5 μM; 5 μM), and H₂O₂ (150 μM) + Vit C (1 μM; 2.5 μM; 5 μM), and incubated at 37 °C for 1 h. Cell viability was measured using the Trypan blue test. DNA damage was measured using the Alkali Comet Technique and the % percent tail intensity was evaluated. Statistical analysis was performed using 1-way ANOVA and the Tukey multiple comparison test.

Results

It was observed that H₂O₂ significantly induced DNA damage in the lymphocytes and this damage was decreased significantly with Vit C and DEX. It was observed that Vit C at doses of 1 μM and 2.5 μM had a significantly stronger antioxidant effect, but there was no significant difference between the antioxidant effects of Vit C and DEX with a dose of 5 μM. The dose of 5 μM DEX was found to be the most effective in reducing oxidative DNA damage.

Conclusion

There is limited data on the protective effects of DEX against oxidative DNA damage. The primary effect might be cytoprotection. The results herein showed that DEX was protective against H₂O₂-induced in vitro oxidative DNA damage in lymphocyte cell cultures in a dose-dependent manner. DEX might have a potential therapeutic value in the prevention of oxidative DNA damage in patients.

Ischaemic preconditioning and pharmacological preconditioning with dexmedetomidine in an equine model of small intestinal ischaemia-reperfusion

Small intestinal strangulation associated with ischaemia-reperfusion injury (IRI) is common in horses. In laboratory animals IRI can be ameliorated by ischaemic preconditioning (IPC) and pharmacological preconditioning (PPC) with dexmedetomidine. The aim of this study was to determine the effect of PPC with dexmedetomidine or IPC in an equine model of small intestinal ischaemia-reperfusion (IR). In a randomized controlled experimental trial, 15 horses were assigned to three groups: control (C), IPC, and PPC with dexmedetomidine (DEX). All horses were placed under general anaesthesia and 90% jejunal ischaemia was induced for 90 minutes, followed 30 minutes of reperfusion. In group IPC, three short bouts of ischaemia and reperfusion were implemented, and group DEX received a continuous rate infusion of dexmedetomidine prior to the main ischaemia. Jejunal biopsies were collected before ischaemia (P), and at the end of ischaemia (I) and reperfusion (R). Mucosal injury was assessed by the Chiu-Score, inflammatory cells were stained by cytosolic calprotectin. The degree of apoptosis and cell necrosis was assessed by cleaved-caspase-3 and TUNEL. Parametric data were analyzed by two-way ANOVA for repeated measurements followed by Dunnetts t-test. Non parametric data were compared between groups at the different time points by a Kruskal-Wallis-Test and a Wilcoxon-2-Sample-test. The mucosal injury score increased during I in all groups. After reperfusion, IRI further progressed in group C, but not in IPC and DEX. In all groups the number of cleaved caspase-3 and TUNEL positive cells increased from P to I. The number of TUNEL positive cells were lower in group DEX compared to group C after I and R. Infiltration with calprotectin positive cells was less pronounced in group DEX compared to group C, whereas in group IPC more calprotectin positive cells were seen. In conclusion, IPC and DEX exert protective effects in experimental small intestinal ischaemia in horses.

Dexmedetomidine alleviates H2O2-induced oxidative stress and cell necroptosis through activating of α2-adrenoceptor in H9C2 cells

Oxidative stress induced necroptosis is important in myocardial ischemia/reperfusion injury. Dexmedetomidine (Dex), an α2-adrenoceptor (α2-AR) agonist, has protective effect on oxidative stress induced cell apoptosis, but effects of Dex and Dex-mediated α2-AR activation on oxidant induced necroptosis was unclear. H9C2 cardiomyocytes were pre-treated with or without Dex and α2-AR antagonist yohimbine hydrochloride (YOH) before being exposed to H₂O₂ to induce oxidative cellular damage. Cell viability and lactate dehydrogenase (LDH) were detected by ELISA kits, protein expressions of Heme Oxygenase 1(HO-1), receptor interacting protein kinase 1 (RIPK1) and receptor interacting protein kinase 3 (RIPK3) were observed by WB, and TUNEL was used to detected cell apoptosis. H₂O₂ significantly decreased cell viability and increased LDH release and necroptotic and apoptotic cell deaths (all p < 0.05, H₂O₂ vs. Control). Dex preconditioning alleviated these injuries induced by H₂O₂. Dex preconditioning significantly increased expression of protein HO-1 and decreased expressions of proteins RIPK1 and RIPK3 induced by H₂O₂, while all these protective effects of Dex were reversed by YOH (all p < 0.05, Dex + H₂O₂ vs. H₂O₂; and YOH + Dex + H₂O₂ vs. Dex + H₂O₂). However, YOH did not prevent this protective effect of Dex against H₂O₂ induced apoptosis (YOH + Dex + H₂O₂ vs. Dex + H₂O₂, p > 0.05). These findings indicated that Dex attenuates H₂O₂ induced cardiomyocyte necroptotic and apoptotic cell death respectively dependently and independently of α2-AR activation.

Characteristics of Dexmedetomidine Postconditioning in the Field of Myocardial Ischemia-Reperfusion Injury

BACKGROUND

Timing and onset of myocardial ischemia are mostly unpredictable. Therefore, postconditioning could be an effective cardioprotective intervention. Because ischemic postconditioning is an invasive and not practicable treatment, pharmacological postconditioning would be a more suitable alternative cardioprotective measure. For the α2-adrenoreceptor agonist, dexmedetomidine postconditioning has been shown. However, data on a concentration-dependent effect of dexmedetomidine are lacking. Furthermore, it is unclear whether the time point and/or duration of dexmedetomidine administration in the reperfusion period is of relevance. We set out to determine whether infarct size reduction by dexmedetomidine is concentration dependent and whether time point and/or duration of dexmedetomidine application has an impact on the effect size of cardio protection.

METHODS

Hearts of male Wistar rats were randomized and placed on a Langendorff system perfused with Krebs-Henseleit buffer at a constant pressure of 80 mm Hg. All hearts were subjected to 33 minutes of global ischemia and 60 minutes of reperfusion. In part I of the study, a concentration-response effect was determined by perfusing hearts with various concentrations of dexmedetomidine (0.3-100 nM) at the onset of reperfusion. Based on these results, part II of the study was conducted with 3 nM dexmedetomidine. Application of dexmedetomidine started directly at the onset of reperfusion (Dex60) and 15 minutes (Dex15), 30 minutes (Dex30), or 45 minutes (Dex45) after the start of reperfusion and lasted always until the end of the reperfusion period. Infarct size was determined by triphenyltetrazolium chloride staining.

RESULTS

In part I, infarct size in control (Con) hearts was 62% ± 4%. Three-nanometer dexmedetomidine was the lowest most effective cardioprotective concentration and reduced infarct size to 24% ± 7% (P < .0001 versus Con). Higher concentrations did not confer stronger protection. Infarct size in control hearts from part II was 66% ± 6%. Different starting times and/or durations of application resulted in similar infarct size reduction (all P < .0001 versus Con).

CONCLUSIONS

Postconditioning by dexmedetomidine is concentration dependent in ranges between 0.3 and 3 nM. Increased concentrations above 3 nM do not further enhance this cardioprotective effect. This cardioprotective effect is independent of time point and length of application in the reperfusion period.

Dexmedetomidine Improves Cardiovascular and Ventilatory Outcomes in Critically Ill Patients: Basic and Clinical Approaches

Dexmedetomidine (DEX) is a highly selective α2-adrenergic agonist with sedative and analgesic properties, with minimal respiratory effects. It is used as a sedative in the intensive care unit and the operating room. The opioid-sparing effect and the absence of respiratory effects make dexmedetomidine an attractive adjuvant drug for anesthesia in obese patients who are at an increased risk for postoperative respiratory complications. The pharmacodynamic effects on the cardiovascular system are known; however the mechanisms that induce cardioprotection are still under study. Regarding the pharmacokinetics properties, this drug is extensively metabolized in the liver by the uridine diphosphate glucuronosyltransferases. It has a relatively high hepatic extraction ratio, and therefore, its metabolism is dependent on liver blood flow. This review shows, from a basic clinical approach, the evidence supporting the use of dexmedetomidine in different settings, from its use in animal models of ischemia-reperfusion, and cardioprotective signaling pathways. In addition, pharmacokinetics and pharmacodynamics studies in obese subjects and the management of patients subjected to mechanical ventilation are described. Moreover, the clinical efficacy of delirium incidence in patients with indication of non-invasive ventilation is shown. Finally, the available evidence from DEX is described by a group of Chilean pharmacologists and clinicians who have worked for more than 10 years on DEX.

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 Monocyte-Endothelial Adherence via Inhibiting Connexin43 on Vascular Endothelial Cells

Current studies have identified the multifaceted protective functions of dexmedetomidine on multiple organs. For the first time, we clarify effects of dexmedetomidine on monocyte-endothelial adherence and whether its underlying mechanism is relative to connexin43 (Cx43), a key factor regulating monocyte-endothelial adherence. U937 monocytes and human umbilical vein endothelial cells (HUVECs) were used to explore monocyte-endothelial adherence. Two special siRNAs were designed to knock down Cx43 expression on HUVECs. U937-HUVEC adhesion, adhesion-related molecules, and the activation of the MAPK (p-ERK1/2, p-p38, and p-JNK1/2) signaling pathway were detected. Dexmedetomidine, at its clinically relevant concentrations (0.1 nM and 1 nM), was given as pretreatments to HUVECs. Its effects on Cx43 and U937-HUVEC adhesion were also investigated. The results show that inhibiting Cx43 on HUVECs could attenuate the contents of MCP-1, soluble ICAM-1 (sICAM-1), soluble VCAM-1 (sVCAM-1), and the nonprocessed variants of the adhesion molecules ICAM-1 and VCAM-1 and ultimately result in U937-HUVEC adhesion decrease. Meanwhile, the activation of MAPKs was also inhibited. U0126 (inhibiting p-ERK1/2) and SB202190 (inhibiting p38) decreased the contents of MCP-1, sICAM-1, and sVCAM-1, but SP600125 (inhibiting p-JNK1/2) had none of these effects. ICAM-1 and VCAM-1 could be regulated in a similar way. Dexmedetomidine pretreatment inhibited Cx43 on HUVECs, the activation of MAPKs, and U937-HUVEC adhesion. Therefore, we conclude that dexmedetomidine attenuates U937-HUVEC adhesion via inhibiting Cx43 on HUVECs modulating the activation of MAPK signaling pathways.

Dexmedetomidine enhances tolerance to bupivacaine cardiotoxicity in the isolated rat hearts: alpha 2 adrenoceptors were not involved

Background

Dexmedetomidine was proved to mitigate bupivacaine-induced cardiotoxicity but mechanism of this ability is still unclear. This study was designed to investigate the direct effects of dexmedetomidine on cardiotoxicity induced by bupivacaine on Langendorff rat heart preparation and the role of alpha 2 adrenoceptors in this process was explored.

Methods

Hearts of rat were isolated, mounted on a Langendorff system. Five experimental groups were assessed after 10 min Krebs-Henseleit buffer (KHB) infusions as follow: (1) Group Con, only KHB was perfused; (2) Group Dex, KHB was perfused for 5 min, then dexmedetomidine (10 nmol/L) was added; (3) Group Bupi, KHB was perfused for 25 min, then bupivacaine (50 μmol/L) was added; (4) Group Bupi + Dex, KHB was perfused for 5 min, then the dexmedetomidine (10 nmol/L) was added for 20 min, at last a mixture of KHB + dexmedetomidine + bupivacaine were perfused; (5) Group Bupi + Dex + Yoh, a combination of KHB + yohimbine (alpha 2 adrenoceptor antagonists, 1 μmol/L) was perfusion for 5 min, then dexmedetomidine (10 nmol/L) was added for 20 min, at last a mixture of KHB + yohimbine + dexmedetomidine + bupivacaine was perfused. The experimental perfusion was maintained for 35 min in group Con and group Dex, and the experimental perfusion was sustained until asystole in the other three groups.

Results

Compared with group Bupi, dexmedetomidine significantly increased the time to first arrhythmia (P <  0.001) and time to asystole (P <  0.001) in group Bupi + Dex. In addition, dexmedetomidine also significantly increased the time to 25, 50 and 75% reductions in heart rate (P <  0.001) and the time to 25, 50 and 75% reductions in rate-pressure product (P <  0.001) in group Bupi + Dex. Dexmedetomidine increased the cardiac tissue bupivacaine content when asystole (Bupi + Dex vs. Bupi, 58.5 ± 6.3 vs. 46.8 ± 5.6 nmol/g, P = 0.003). The benefit of dexmedetomidine on bupivacaine-induced cardiotoxicity were not eliminated by yohimbine.

Conclusions

Dexmedetomidine could delay the occurrence of bupivacaine-induced arrhythmia and asystole in the isolated rat hearts, but the alpha 2 adrenoceptors were not involved in this process.

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 protects against sepsis‑associated encephalopathy through Hsp90/AKT signaling

Sepsis‑associated encephalopathy (SAE) is characterized by neuronal apoptosis and changes in mental status. Accumulating evidence has. indicated that dexmedetomidine is capable of protecting the brain against external stimuli and improving cognitive dysfunctions. The aim of the present study was to investigate the possible neuroprotective effects of dexmedetomidine on SAE and the role of heat‑shock protein (Hsp)90/AKT signaling in an experimental model of sepsis. The SAE model was established by cecal ligation and perforation (CLP) in vivo and lipopolysaccharide (LPS) treated hippocampal neuronal cultures in vitro. It was found that dexmedetomidine inhibited caspase‑3, but increased the expression level ofBcl‑2 in CLP rats. CLP rats also exhibited a decreased level of phosphorylated AKT Thr 308 and Hsp90, and their expression could be reversed by treatment with dexmedetomidine. Additionally, application of dexmedetomidine increased cell survival and decreased neuronal apoptosis in vitro. Furthermore, the neuroprotective effects of dexmedetomidine could be reversed by 17‑AAG (a Hsp90 inhibitor), or wortmannin (a PI3K inhibitor). Analysis of TUNEL staining indicated that dexmedetomidine improved LPS‑induced neuronal apoptosis, which could be eradicated by AKT short hairpin RNA transfection, prazosin or yohimbine. Finally, dexmedetomidine ameliorated both the emotional and spatial cognitive disorders without alteration in locomotor activity. The present findings suggested that dexmedetomidine may protect the brain against SAE, and that the Hsp90/AKT pathway may be involved in this process.

The administration of dexmedetomidine changes microRNA expression profiling of rat hearts

BACKGROUND

Dexmedetomidine is widely used for perioperative and ICU patients. microRNAs (miRNAs) function as regulators of gene expression. The aim of the study was to assay expression profiling of microRNA in rat hearts following administration of dexmedetomidine.

METHODS

In this study 6 rats were randomly divided into two groups (n = 3): dexmedetomidine group and control group. The rats of dexmedetomidine group were intraperitoneally given dexmedetomidine in a dose of 100 μg/kg whereas the rats in control group were administered normal saline intraperitoneally. The hearts were excised 30 min after the administration of dexmedetomidine or normal saline under anesthesia. The samples were analyzed for differentially expressed microRNAs with Exiqon miRNA Array. The differentially expressed microRNAs were confirmed by using qRT-PCR. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to find the target genes and signaling pathways of the aberrantly expressed miRNAs.

RESULTS

Six microRNAs were identified to be significantly expressed, among of which, five microRNAs (miRNA-434-3p, miRNA-3596d, miRNA-496-5p, miRNA-7a-2-3p and miRNA-702-3p) were up-regulated and 1 microRNA (miRNA-208b-3p) down-regulated compared to those of control group. The aberrantly expressed microRNAs were further validated by Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). GO and KEGG analyses were used to identify target genes and the signaling pathways.

CONCLUSIONS

The use of dexmedetomidine is associated with differentially expressed microRNAs which may be involved in cardioprotection following administration of dexmedetomidine.

Hepatic Protective Effect of Dexmedetomidine after Partial Hepatectomy Surgery: A Prospective Controlled Study

Background:

Inflow occlusion of the portal triad is a common blood loss-reducing method during hepatectomy which may induce ischemic-reperfusion injury of the remaining parts of the liver. Dexmedetomidine is used for reducing ischemic-reperfusion injury in hepatectomy.

Aim:

The aim of this study was to assess the protective effect of dexmedetomidine on liver after partial hepatectomy using inflow occlusion.

Setting and Design:

This prospective controlled, double-blinded, randomized study included any patients of either sex with age between 20 and 70 years, those in physical status American Society of Anesthesiologists Classes I and II, and those who were planned for partial hepatectomy.

Patients and Methods:

Patients with elective hepatectomy were randomized into dexmedetomidine group, which received dexmedetomidine at 0.3 mg/kg/h, and control group, which received a placebo.

Statistical Analysis:

Statistical analysis was performed using IBM SPSS software version 18. Data were tested using Kolmogorov–Smirnov test, independent t-test or Mann–Whitney U-test, and Chi-square or Fisher's exact test. The statistical significance was considered at P < 0.05.

Results:

Serum albumin, aspartate aminotransferase, alanine aminotransferase, prothrombin time were higher in control group in comparison to dexmedetomidine group. Hypotension duration was lower in control group in comparison to dexmedetomidine group. Vasoconstrictor usage, amount of blood loss, and colloid, crystalloid, and blood given to patients were higher in control group in comparison to the study group.

Conclusions:

Dexmedetomidine can protect the liver during hepatic resection surgery with inflow occlusion with decreasing blood loss and need for blood transfusion.

Involvement of miR-665 in protection effect of dexmedetomidine against Oxidative Stress Injury in myocardial cells via CB2 and CK1

BACKGROUND

Dexmedetomidine (Dex) can confer cardioprotective effects against ischemia/reperfusion (I/R) injury. While there are no studies addressing cardioprotection of Dex via regulation of microRNAs. The purpose of this study was to examine the roles and mechanisms of microRNA in cardioprotection of dexmedetomidine.

METHODS

Rat heart Langendorff preparation was established. We assayed expression profiling of miRNAs in perfused rat hearts and predicted Target genes using MiRanda, MiRDB, and TargetScan. Oxide stress (H₂O₂) was employed to simulate I/R injury. miR-665 mimic, inhibitor, and siRNA of AK1 and Cnr2 were transfected to H9C2. The real-time quantitative polymerase chain reaction was used to quantify miR-665 and Ak1 and Cnr2 mRNA. The apoptosis of the cells was examined. The expression levels of cleaved caspase-3, Bcl-2, Bax, AK1, and Cnr2 were detected by Western blot. The combination between miR-665 and the 3'-untranslated region of AK1 and Cnr2 was validated by a luciferase reporter assay.

RESULTS

Dex precondition down-regulated miR-665 expression in hearts compared to I/R group. Dex reduced miR-665 expression and apoptosis increased by oxide stress. However, up-regulation of miR-665 exacerbated the changes caused by oxide stress and inhibited the effects of Dex. Down-regulation of miR-665 also reduced apoptosis, but inhibition of AK1 and Cnr2 aggravated apoptosis. The luciferase reporter assay indicated that miR-665 could down-regulate expression levels of AK1 and Cnr2.

CONCLUSIONS

Dex precondition confers hearts protective effect against I/R injury by down-regulating expression of miR-665 and up-regulating expression of AK1 and Cnr2.

Identification of Candidate Genes and Pathways in Dexmedetomidine-Induced Cardioprotection in the Rat Heart by Bioinformatics Analysis

Dexmedetomidine (DEX), a highly selective alpha2 adrenergic receptor agonist, directly protects hearts against ischemia/reperfusion (I/R) injury. However, the detailed mechanism has not been fully elucidated. We studied differentially expressed mRNAs and miRNAs after DEX administration in rat hearts by comprehensive analysis. Additionally, bioinformatics analysis was applied to explore candidate genes and pathways that might play important roles in DEX-induced cardioprotection. The results of microarray analysis showed that 165 mRNAs and 6 miRNAs were differentially expressed after DEX administration. Through bioinformatics analysis using differentially expressed mRNAs, gene ontology (GO) terms including MAP kinase tyrosine/serine/threonine phosphatase activity and pathways including the p53 pathway were significantly enriched in the down-regulated mRNAs. Dusp1 and Atm were associated with the GO term of MAP kinase tyrosine/serine/threonine phosphatase activity and the p53 pathway, respectively. On the other hand, no significant pathway was found in the target mRNAs of deregulated miRNAs. The results indicated some possible key genes and pathways that seem to be of significance in DEX-induced cardioprotection, although miRNAs seem to be unlikely to contribute to cardioprotection induced by DEX.

Dexmedetomidine restores autophagy and cardiac dysfunction in rats with streptozotocin-induced diabetes mellitus

AIMS

Dexmedetomidine (DEX), a highly selective and potent α2-adrenergic receptor agonist, has anti-apoptotic, anti-inflammatory, and anti-oxidative stress effects in diabetes mellitus (DM) rats. The underlying molecular mechanisms and signaling pathways of diabetic cardiomyopathy remain poorly understood. This study aimed to elucidate the effect of DEX on cardiac function in DM rats.

METHODS

Eight-week-old male Sprague Dawley rats were divided into three groups: control (n = 5), diabetes (DM, n = 7), and diabetes + DEX (DM + DEX, n = 10). DM was induced via intraperitoneal injection of streptozotocin (70 mg/kg); at 3 days later, DEX (1 µg/kg/h) was administered for 4 weeks. Cardiac function was evaluated using pressure-volume loop analysis and echocardiography. Left ventricular (LV) histological sections were used to analyze the interstitial collagen fraction. Using the LV samples, we performed a western blot analysis to evaluate signaling pathways and autophagic markers.

RESULTS

The DM group had lower body weight and higher blood glucose level and heart weight/body weight ratio than the control group. However, metabolic changes did not differ between the DM and DM + DEX groups. Pressure-volume loop analysis and echocardiography showed impaired cardiac function, evidenced by a decrease in systolic and diastolic function, in both DM groups. DEX treatment in DM rats was associated with increased LV end-systolic pressure, LV contractility, cardiac output, and relaxed LV function compared with that in non-treated DM rats. LC3B and autophagy-related gene (ATG) proteins increased in the hearts of DM rats compared with the hearts of control rats. However, DEX reduced the expression of LC3B and ATG proteins in the hearts of DM rats. Increased p-ERK and decreased p-AKT were reduced in the hearts of DEX-treated DM rats.

CONCLUSIONS

DEX reduces cardiac dysfunction and impaired autophagy in DM rats. This study reinforces our understanding of the potential anti-autophagic effect of DEX in patients with diabetic cardiomyopathy.

Dexmedetomidine preserves the endothelial glycocalyx and improves survival in a rat heatstroke model

PURPOSE

Heatstroke causes systemic inflammation, followed by vascular endothelial damage. The normal vascular endothelium is coated by endothelial glycocalyx (EGCX). Dexmedetomidine (DEX) has an anti-inflammatory effect, but there has been little investigation on the influence of heatstroke on EGCX and the effect of DEX on this condition. Therefore, we examined whether EGCX was disrupted in heatstroke and if DEX improved survival and preserves EGCX.

METHODS

Anesthetized Wistar rats were randomly assigned to three groups: a DEX group treated with DEX (5 µg/kg/h) and 0.9% saline infused continuously at 10 ml/kg/h during heat exposure; a NSS group given 0.9% saline during heat exposure; and a SHAM group given 0.9% saline alone without heat exposure. Heatstroke was induced by exposure to an ambient temperature of 40 °C with relative humidity of 60%. The survival rate was assessed up to 2 h after the start of heat exposure. Plasma levels of syndecan-1 and the thickness of EGCX using electron microscopy were measured when the systolic blood pressure fell to less than 80 mmHg.

RESULTS

The survival rate after 2 h of heat exposure was significantly higher in the DEX group compared to the NSS group (89% vs. 22%, P = 0.004). Plasma levels of syndecan-1 were 0.6 ± 1.3, 9.7 ± 5.9, and 2.1 ± 3.4 ng/ml in the SHAM, NSS and DEX groups, respectively (P = 0.013). The thickness of EGCX was significantly higher in the DEX group compared with the NSS group (P = 0.001).

CONCLUSIONS

EGCX was disrupted in heatstroke, and DEX improved survival and preserved EGCX.

Dexmedetomidine for prevention of skeletal muscle ischaemia-reperfusion injury in patients with chronic limb ischaemia undergoing aortobifemoral bypass surgery: A prospective double-blind randomized controlled study

Background:

Dexmedetomidine is a selective α-2 agonist used for sedation. It has also been shown to have myocardial protective effect and prevent ischemia-reperfusion injury in off-pump coronary artery bypass patients. The aim of our study was to assess the effect of dexmedetomidine for prevention of skeletal muscle ischemia-reperfusion injury in patients undergoing aortobifemoral bypass surgery.

Methodology:

Sixty adult patients (Group dexmedetomidine n = 30, Group normal saline n = 30) undergoing aortobifemoral bypass surgery were recruited over 3 months. Randomization was done using a computer-generated random table. The attending anesthesiologist would be blinded to whether the drug/normal saline was being administered. He would consider each unlabeled syringe as containing dexmedetomidine and calculate the volume to be infused via a syringe pump accordingly. Dexmedetomidine infusion (1 mcg/kg) over 15 minutes was given as a loading dose, followed by maintenance infusion of 0.5 mcg/kg/h till 2 h postprocedure in Group dexmedetomidine (D) while the same volume of normal saline was given in the control Group C till 2 h postprocedure. Creatine phosphokinase (CPK) values were noted at baseline (T0), 6 h (T1), 12 h (T2), and 24 h (T3) after the procedure. Hemodynamic variables (heart rate [HR] and mean blood pressure [MAP]) were recorded at T0, T1, T2, and T3. Results were analyzed using unpaired Student's t-test, P < 0.05 was considered statistically significant.

Results:

MAP and HR significantly decreased in Group D as compared to control group (P < 0.05). However, the decrease was never <20% of the baseline. The CPK values at 6, 12, and 24 h were statistically significant between the two groups.

Conclusion:

Dexmedetomidine prevents skeletal muscle ischemia-reperfusion injury in patients undergoing aortobifemoral bypass surgery.

The cardioprotective effect of dexmedetomidine on regional ischemia/reperfusion injury in type 2 diabetic rat hearts

BACKGROUND

Dexmedetomidine (DEX) is an α₂-adrenergic receptor agonist commonly used during perioperative periods due to its sedation and analgesia effect. It is confirmed that DEX has cardioprotective effects against ischemia/reperfusion (I/R) injury. We investigated whether DEX administration is beneficial to type 2 diabetic rats subjected to I/R injury.

METHODS

The diabetes model was established by providing a high-fat diet for 2 weeks followed by injecting 35 mg/kg streptozotocin (STZ). The myocardial I/R model consisted of left anterior descending coronary artery occlusion for 30 min followed by reperfusion for two-hours. DEX was administered before ischemia; alternatively, yohimbine was administered with or without DEX before ischemia. At the end of reperfusion, the rats were sacrificed, and hearts were isolated for histology. The levels of glycogen synthase kinase-3β (GSK-3β) and phosphorylated GSK-3β (p-GSK-3β) were quantitatively analyzed. The infarct size was measured via Evans Blue and 2,3,5‑triphenyltetrazolium chloride (TTC) staining. Plasma samples were collected to measure the levels of cardiac Troponin T (cTnT). Arrhythmia scores were recorded during the first few minutes of reperfusion.

RESULTS

DEX preconditioning significantly reduced myocardial infarct size, arrhythmia scores and the plasma cTnT levels, and increased the p-GSK-3β levels. All of these protective effects of DEX were reversed by co-administration of yohimbine.

CONCLUSIONS

These results suggested that DEX preconditioning exerted a cardioprotective effect against regional I/R injury in diabetic rats.

Editor’s Choice- Sedation in the coronary intensive care unit: An adapted algorithm for critically ill cardiovascular patient

In the current era, cardiovascular intensive care units care for more complex patients who are far sicker than historical post-myocardial infarction patients, and sedation has become a common intervention in these units. Current sedation best practices derive mainly from non-cardiac units which limits their generalization to the critically ill cardiac patient. Thus, a great variability in sedation protocols, especially the selection of sedative agents, is commonly seen in daily practice across cardiac units. We present an updated review on sedation in cardiovascular critical care medicine with emphasis on the hemodynamic impact. The goal of this review is to generate a general sedation algorithm specific for the cardiac patient.

Comparison of the cardioprotective effects of dexmedetomidineand remifentanil in cardiac surgery

Background/aim: Myocardial protection is an important factor of open heart surgery and biological biomarkers (lactate, CKMB, cardiac troponin I, and pyruvate) are used to assess myocardial damage. This study compares the effects of dexmedetomidine and remifentanil on myocardial protection during coronary artery bypass grafting (CABG) surgery. Materials and methods: Patients scheduled for elective CABG surgery (n = 60) were included in this study. Anesthesia induction was introduced with propofol, fentanyl, and vecuronium bromide. Anesthesia was maintained with remifentanil infusion and sevoflurane in the remifentanil group (Group R) and with dexmedetomidine infusion and sevoflurane in the dexmedetomidine group (Group D). Blood samples for biochemical markers were taken from the coronary sinus catheter before cardiopulmonary bypass (T1), 20 min after aortic cross-clamping (T2), 20 min after removal of the aortic cross-clamping (T3), and 10 min after separation from cardiopulmonary bypass (T4).Results: Demographic data were similar between the groups. Lactate level at the T2 period and CKMB levels during the study period were lower in Group D than in Group R. In both groups, all values except pyruvate significantly increased over time. Conclusion: The dexmedetomidine-sevoflurane combination may improve the cardioprotective effect in comparison with remifentanil-sevoflurane in CABG surgery.

The alpha2-adrenoreceptor agonist dexmedetomidine protects against lipopolysaccharide-induced apoptosis via inhibition of gap junctions in lung fibroblasts

The α2-adrenoceptor inducer dexmedetomidine protects against acute lung injury (ALI), but the mechanism of this effect is largely unknown. The present study investigated the effect of dexmedetomidine on apoptosis induced by lipopolysaccharide (LPS) and the relationship between this effect and gap junction intercellular communication in human lung fibroblast cell line. Flow cytometry was used to detect apoptosis induced by LPS. Parachute dye coupling assay was used to measure gap junction function, and western blot analysis was used to determine the expression levels of connexin43 (Cx43). The results revealed that exposure of human lung fibroblast cell line to LPS for 24 h increased the apoptosis, and pretreatment of dexmedetomidine and 18α-GA significantly reduced LPS-induced apoptosis. Dexmedetomidine exposure for 1 h inhibited gap junction function mainly via a decrease in Cx43 protein levels in human lung fibroblast cell line. These results demonstrated that the inhibition of gap junction intercellular communication by dexmedetomidine affected the LPS-induced apoptosis through inhibition of gap junction function by reducing Cx43 protein levels. The present study provides evidence of a novel mechanism underlying the effects of analgesics in counteracting ALI.

The effects of dexmedetomidine preconditioning on aged rat heart of ischaemia reperfusion injury

To assess the effect of dexmedetomidine on myocardial ischemia reperfusion injury in vivo aged rat heart. 40 healthy male, 20month aged, 350-400g Sprague-Dawley rats. Rats were divided into four groups randomly(n=10): group of ischemic preconditioning(IP group), group of Sham(CS group), group of dexmedetomidine(DP group), Ischemia-reperfusion injury group(IR group). The date of HR and ±dp/dtmax were detected before and after the occur of ischemia reperfusion. Superoxide dismutase (SOD) and malondialdehyde (MDA) activity were recorded; myocardial infarct size was calculated at the end of reperfusion. HR in each group decreased after thoracotomy. Compared with CS group, the HR in IR group reduced significantly (P<0.05). After given dexmedetomidine, HR in the DP group began to decrease significantly. Left heart function in IR group compared with the CS group showed that a statistically reduce of left ventricular function happened in IR group. ±dp/dtmax of the IR groups compared with the CS group were increased. SOD activity reduced and MDA in myocardial tissue homogenates increased in IR group (P<0.05); SOD activity in DP group compared with IR group deduced, MDA increased (P<0.05). Dexmedetomidine preconditioning can effectively reduce ischemia reperfusion injury of the aged rat in vivo, have a protective effect on aged rat heart.

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

Pharmacological preconditioning reduces myocardial infarct size in ischaemia-reperfusion (I-R) injury. Dexmedetomidine, a selective α₂ -adrenoceptor agonist, has a proven cardioprotective effect when administered prior to I-R, although the underlying mechanisms for this effect are not fully understood. We evaluated whether dexmedetomidine preconditioning could induce a myocardio-protective effect against I-R injury by inhibiting associated inflammatory processes through downregulation of the high mobility group box 1 (HMGB1)-toll-like receptor 4 (TLR4)-nuclear factor κB (NF-κB) signalling pathway. Seventy rats were randomly assigned to seven groups: a control and six test groups, involving I-R for 30 and 120 minutes, respectively, in isolated rat hearts and different pretreatment protocols with dexmedetomidine (10 nmol/L) as well as yohimbine (1 μmol/L) and recombinant HMGB1 peptide (rHMGB1; 20 μg/L), alone or in combination with dexmedetomidine. Cardiac function was recorded; myocardial HMGB1, TLR4, and NF-κB activities and levels of tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured as were lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary outflow. Dexmedetomidine preconditioning significantly improved cardiac function (P<.05), downregulated the expression of HMGB1-TLR4-NF-κB, reduced levels of TNF-α and IL-6 in isolated ventricles during I-R injury, and significantly reduced CK and LDH levels in coronary outflow (P<.05). All of these effects were partially reversed by yohimbine (P<.05) or rHMGB1 (P<.05). Dexmedetomidine preconditioning alleviated myocardial I-R injury in rats through inhibition of inflammatory processes associated with downregulation of the HMGB1-TLR4-NF-κB signalling pathway via activation at α₂ -adrenergic receptors.