Dexmedetomidine preconditioning activates pro-survival kinases and attenuates regional ischemia/reperfusion injury in rat heart

Protective mechanical ventilation in critically ill patients after surgery

PURPOSE OF REVIEW

This review aims to provide an updated overview of lung protective strategies in critically ill patients after surgery, focusing on the utility of postoperative open-lung ventilation during the transition from the operating room to the intensive care unit.

RECENT FINDINGS

Mechanically ventilated patients after surgery represent a challenge in the intensive care unit. Different protective strategies have been proposed to minimize the risk of ventilator-induced lung injury (VILI) and facilitate adequate weaning from mechanical ventilation. Fast-track extubation protocols, increasingly standard in the care of critically ill patients postsurgery, have demonstrated improvements in recovery and reductions in acute lung injury, primarily based on retrospective studies. Open-lung ventilation strategies, such as individualization of positive-end expiratory pressure based on driving pressure and postoperative noninvasive ventilation support with high-flow nasal cannula, are becoming standard of care in high-risk surgical patients after major abdominal or thoracic surgeries.

SUMMARY

Mechanical ventilation in surgical patients should adhere to lung protective strategies (i.e., individualizing positive end expiratory pressure and prioritize alveolar recruitment) during the transition from the operating room to the intensive care unit.

New insights in cardiovascular anesthesia: a dual focus on clinical practice and research

Accumulation of the results of basic and clinical research has advanced the safety and quality of management in cardiovascular anesthesia. To address recent developments in this field, a symposium was held during the 71th Japanese Society of Anesthesiologists annual meetings in 2024, focusing on new advancements in both clinical and basic research in cardiovascular anesthesia. During this symposium, four experts reviewed recent findings in their respective areas of study, covering the following topics: clinical reliability and concerns regarding volatile anesthetics during cardiopulmonary bypass; novel basic and clinical findings regarding the cardioprotective effects of dexmedetomidine; advancements in optimizing blood and hemostasis management during cardiovascular surgery; and innovative strategies for managing postoperative cognitive disorders following cardiovascular and thoracic surgery. Each expert summarized recent novel findings, clinical reliability and concerns, as well as future directions in their respective topics. We believe that this special article provides valuable insights into both clinical practice and basic research in cardiovascular anesthesia while also inspiring anesthesiologists to pursue further research in this field.

Dexmedetomidine administration is associated with improved outcomes in critically ill patients with acute myocardial infarction partly through its anti-inflammatory activity

Background

Dexmedetomidine (DEX) is a commonly used sedative in the intensive care unit and has demonstrated cardioprotective properties against ischemia-reperfusion injury in preclinical studies. However, the protective effects of early treatment of DEX in patients with acute myocardial infarction (AMI) and its underlying mechanism are still not fully understood. This study aims to investigate the association between early DEX treatment and in-hospital mortality in patients with AMI, and to explore the potential mediating role of white blood cell (WBC) reduction in this relationship.

Methods

A retrospective cohort analysis was conducted using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Patients with AMI were divided into the DEX and non-DEX group, based on whether they received DEX treatment in the early stage of hospitalization. The primary outcome measured was in-hospital mortality. The study evaluated the association between DEX use and in-hospital mortality using the Kaplan-Meier (KM) method and Cox proportional hazards model. Additionally, 1:1 propensity score matching (PSM) was conducted to validate the results. Furthermore, causal mediation analysis (CMA) was utilized to explore potential causal pathways mediated by WBC reduction between early DEX use and the primary outcome.

Results

This study analyzed data from 2,781 patients, with 355 in the DEX group and 2,426 in the non-DEX group. KM survival analysis revealed a significantly lower in-hospital mortality rate in the DEX group compared to the non-DEX group. After adjusting for multiple confounding factors, the Cox regression model demonstrated a significant positive impact of DEX on the risk of in-hospital mortality in patients with AMI, with hazard ratios (HR) of 0.50 (95% confidence interval (CI): 0.35-0.71, p < 0.0001). PSM analysis confirmed these results, showing HR of 0.49 (95% CI: 0.31-0.77, p = 0.0022). Additionally, CMA indicated that 13.7% (95% CI: 1.8%-46.9%, p = 0.022) of the beneficial effect of DEX on reducing in-hospital mortality in patients with AMI was mediated by the reduction in WBC.

Conclusion

The treatment of DEX was associated with a lower risk of in-hospital mortality in patients with AMI, potentially due to its anti-inflammatory properties.

Research progress on the protective effect of hormones and hormone drugs in myocardial ischemia-reperfusion injury

Ischemic heart disease (IHD) is a condition where the heart muscle does not receive enough blood flow, leading to cardiac dysfunction. Restoring blood flow to the coronary artery is an effective clinical therapy for myocardial ischemia. This strategy helps lower the size of the myocardial infarction and improves the prognosis of patients. Nevertheless, if the disrupted blood flow to the heart muscle is restored within a specific timeframe, it leads to more severe harm to the previously deprived heart tissue. This condition is referred to as myocardial ischemia/reperfusion injury (MIRI). Until now, there is a dearth of efficacious strategies to prevent and manage MIRI. Hormones are specialized substances that are produced directly into the circulation by endocrine organs or tissues in humans and animals, and they have particular effects on the body. Hormonal medications utilize human or animal hormones as their active components, encompassing sex hormones, adrenaline medications, thyroid hormone medications, and others. While several studies have examined the preventive properties of different endocrine hormones, such as estrogen and hormone analogs, on myocardial injury caused by ischemia-reperfusion, there are other hormone analogs whose mechanisms of action remain unexplained and whose safety cannot be assured. The current study is on hormones and hormone medications, elucidating the mechanism of hormone pharmaceuticals and emphasizing the cardioprotective effects of different endocrine hormones. It aims to provide guidance for the therapeutic use of drugs and offer direction for the examination of MIRI in clinical therapy.

Dexmedetomidine improves pulmonary outcomes in thoracic surgery under one-lung ventilation: A meta-analysis

INTRODUCTION

Dexmedetomidine improves intrapulmonary shunt in thoracic surgery and minimizes inflammatory response during one-lung ventilation (OLV). However, it is unclear whether such benefits translate into less postoperative pulmonary complications (PPCs). Our objective was to determine the impact of dexmedetomidine on the incidence of PPCs after thoracic surgery.

METHODS

Major databases were used to identify randomized trials that compared dexmedetomidine versus placebo during thoracic surgery in terms of PPCs. Our primary outcome was atelectasis within 7 days after surgery. Other specific PPCs included hypoxemia, pneumonia, and acute respiratory distress syndrome (ARDS). Secondary outcome included intraoperative respiratory mechanics (respiratory compliance [Cdyn]) and postoperative lung function (forced expiratory volume [FEV1]). Random effects models were used to estimate odds ratios (OR).

RESULTS

Twelve randomized trials, including 365 patients in the dexmedetomidine group and 359 in the placebo group, were analyzed in this meta-analysis. Patients in the dexmedetomidine group were less likely to develop postoperative atelectasis (2.3% vs 6.8%, OR 0.42, 95%CI 0.18-0.95, P = 0.04; low certainty) and hypoxemia (3.4% vs 11.7%, OR 0.26, 95%CI 0.10-0.68, P = 0.01; moderate certainty) compared to the placebo group. The incidence of postoperative pneumonia (3.2% vs 5.8%, OR 0.57, 95%CI 0.25-1.26, P = 0.17; moderate certainty) or ARDS (0.9% vs 3.5%, OR 0.39, 95%CI 0.07-2.08, P = 0.27; moderate certainty) was comparable between groups. Both intraoperative Cdyn and postoperative FEV1 were higher among patients that received dexmedetomidine with a mean difference of 4.42 mL/cmH2O (95%CI 3.13-5.72) and 0.27 L (95%CI 0.12-0.41), respectively.

CONCLUSION

Dexmedetomidine administration during thoracic surgery may potentially reduce the risk of postoperative atelectasis and hypoxemia. However, current evidence is insufficient to demonstrate an effect on pneumonia or ARDS.

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 postconditioning attenuates myocardial ischemia/reperfusion injury by activating the Nrf2/Sirt3/SOD2 signaling pathway in the rats

OBJECTIVES

To observe the protective effects of dexmedetomidine (Dex) postconditioning on myocardial ischemia/reperfusion injury (IRI) and to explore its potential molecular mechanisms.

METHODS

One-hundred forty-seven male Sprague-Dawley rats were randomly divided into five groups receiving the different treatments: Sham, ischemia/reperfusion (I/R), Dex, Brusatol, Dex + Brusatol. By the in vivo rat model of myocardial IRI, cardioprotective effects of Dex postconditioning were evaluated by assessing serum CK-MB and cTnI levels, myocardial HE and Tunel staining and infarct size. Furthermore, the oxidative stress-related markers including intracellular ROS level, myocardial tissue MDA level, SOD and GSH-PX activities were determined.

RESULTS

Dex postconditioning significantly alleviated myocardial IRI, decreased intracellular ROS and myocardial tissue MDA level, increased SOD and GSH-PX activities. Dex postconditioning significantly up-regulated myocardial expression of Bcl-2, down-regulated Bax and cleaved caspase-3 and decreased cardiomyocyte apoptosis rate. furthermores, Dex postconditioning promoted Nrf2 nuclear translocation, increased myocardial expression of Sirt3 and SOD2 and decreased Ac-SOD2. However, brusatol reversed cardioprotective benefits of Dex postconditioning, significantly decreased Dex-induced Nrf2 nuclear translocation and reduced myocardial expression of Sirt3 and SOD2.

CONCLUSIONS

Dex postconditioning can alleviate myocardial IRI by suppressing oxidative stress and apoptosis, and these beneficial effects are at least partly mediated by activating the Nrf2/Sirt3/SOD2 signaling pathway.

Protocol: dexmedetomidine on myocardial injury after noncardiac surgery-a multicenter, double-blind, controlled trial

AIMS

Myocardial injury after noncardiac surgery (MINS) is common in elderly patients and considered as an independent predictor of 30-day mortality after noncardiac surgery. Dexmedetomidine possesses cardiac-protective profile. Previous clinical studies have found that perioperative application of dexmedetomidine is associated with decreased 1-year mortality in patients undergoing cardiac surgery. The current study protocol aims to investigate the effects of dexmedetomidine on the incidence of MINS, complications, and 30-day mortality in elderly patients subjected to noncardiac surgery.

METHODS

A multicenter, randomized, controlled, double-blind, prospective trial is designed to explore cardiac protection of dexmedetomidine in the elderly patients undergoing noncardiac surgery. A total of 960 patients aged over 65 years will be recruited and randomly assigned to dexmedetomidine group (group Dex) and normal saline placebo group (group NS) in a ratio of 1:1. Patients in group Dex will receive a bolus dose of 0.5 μg/kg dexmedetomidine within 10 min before surgical incision, followed by a consistent infusion at the rate of 0.3-0.5 μg/kg/h throughout the operation. Group NS patients will receive the same volume of normal saline. The primary outcome is the incidence of MINS via detecting the hs-TnT level within 3 days after the operation. The secondary outcome includes myocardial ischemic symptoms, the incidence of major adverse cardiovascular events (MACE) in hospital, length of ICU and postoperative hospital stay, the incidence of inhospital complications, and 30-day all-cause mortality.

DISCUSSION

The results of the current study will illustrate the effect of dexmedetomidine on myocardial injury for elderly patients undergoing major noncardiac surgery.

TRIAL REGISTRATION

The trial was registered with Chinese Clinical Trial Registry (CHICTR) on Aug 24, 2021 (ChiCTR2100049946, http://www.chictr.org.cn/showproj.aspx?proj=131804 ).

Dexmedetomidine Pretreatment Protects Against Myocardial Ischemia/Reperfusion Injury by Activating STAT3 Signaling

BACKGROUND

Myocardial infarction is a common perioperative complication, and blood flow restoration causes ischemia/reperfusion injury (IRI). Dexmedetomidine (DEX) pretreatment can protect against cardiac IRI, but the mechanism is still insufficiently understood.

METHODS

In vivo, myocardial ischemia/reperfusion (30 minutes/120 minutes) was induced via ligation and then reperfusion of the left anterior descending coronary artery (LAD) in mice. Intravenous infusion of 10 μg/kg DEX was performed 20 minutes before ligation. Moreover, the α2-adrenoreceptor antagonist Yohimbine and STAT3 inhibitor Stattic were applied 30 minutes ahead of DEX infusion. In vitro, hypoxia/reoxygenation (H/R) with DEX pretreatment for 1 hour was performed in isolated neonatal rat cardiomyocytes. In addition, Stattic was applied before DEX pretreatment.

RESULTS

In the mouse cardiac ischemia/reperfusion model, DEX pretreatment lowered the serum creatine kinase-MB isoenzyme (CK-MB) levels (2.47 ± 0.165 vs 1.55 ± 0.183; P < .0001), downregulated the inflammatory response ( P ≤ .0303), decreased 4-hydroxynonenal (4-HNE) production and cell apoptosis ( P = .0074), and promoted the phosphorylation of STAT3 (4.94 ± 0.690 vs 6.68 ± 0.710, P = .0001), which could be blunted by Yohimbine and Stattic. The bioinformatic analysis of differentially expressed mRNAs further confirmed that STAT3 signaling might be involved in the cardioprotection of DEX. Upon H/R treatment in isolated neonatal rat cardiomyocytes, 5 μM DEX pretreatment improved cell viability ( P = .0005), inhibited reactive oxygen species (ROS) production and calcium overload (both P ≤ .0040), decreased cell apoptosis ( P = .0470), and promoted STAT3 phosphorylation at Tyr705 (0.102 ± 0.0224 vs 0.297 ± 0.0937; P < .0001) and Ser727 (0.586 ± 0.177 vs 0.886 ± 0.0546; P = .0157), which could be abolished by Stattic.

CONCLUSIONS

DEX pretreatment protects against myocardial IRI, presumably by promoting STAT3 phosphorylation via the α2-adrenoreceptor in vivo and in vitro.

Pharmaceutical Therapies for Necroptosis in Myocardial Ischemia-Reperfusion Injury

Cardiovascular disease morbidity/mortality are increasing due to an aging population and the rising prevalence of diabetes and obesity. Therefore, innovative cardioprotective measures are required to reduce cardiovascular disease morbidity/mortality. The role of necroptosis in myocardial ischemia-reperfusion injury (MI-RI) is beyond doubt, but the molecular mechanisms of necroptosis remain incompletely elucidated. Growing evidence suggests that MI-RI frequently results from the superposition of multiple pathways, with autophagy, ferroptosis, and CypD-mediated mitochondrial damage, and necroptosis all contributing to MI-RI. Receptor-interacting protein kinases (RIPK1 and RIPK3) as well as mixed lineage kinase domain-like pseudokinase (MLKL) activation is accompanied by the activation of other signaling pathways, such as Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), NF-κB, and JNK-Bnip3. These pathways participate in the pathological process of MI-RI. Recent studies have shown that inhibitors of necroptosis can reduce myocardial inflammation, infarct size, and restore cardiac function. In this review, we will summarize the molecular mechanisms of necroptosis, the links between necroptosis and other pathways, and current breakthroughs in pharmaceutical therapies for necroptosis.

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.

Antioxidant Cardioprotection against Reperfusion Injury: Potential Therapeutic Roles of Resveratrol and Quercetin

Ischemia-reperfusion myocardial damage is a paradoxical tissue injury occurring during percutaneous coronary intervention (PCI) in acute myocardial infarction (AMI) patients. Although this damage could account for up to 50% of the final infarct size, there has been no available pharmacological treatment until now. Oxidative stress contributes to the underlying production mechanism, exerting the most marked injury during the early onset of reperfusion. So far, antioxidants have been shown to protect the AMI patients undergoing PCI to mitigate these detrimental effects; however, no clinical trials to date have shown any significant infarct size reduction. Therefore, it is worthwhile to consider multitarget antioxidant therapies targeting multifactorial AMI. Indeed, this clinical setting involves injurious effects derived from oxygen deprivation, intracellular pH changes and increased concentration of cytosolic Ca²⁺ and reactive oxygen species, among others. Thus, we will review a brief overview of the pathological cascades involved in ischemia-reperfusion injury and the potential therapeutic effects based on preclinical studies involving a combination of antioxidants, with particular reference to resveratrol and quercetin, which could contribute to cardioprotection against ischemia-reperfusion injury in myocardial tissue. We will also highlight the upcoming perspectives of these antioxidants for designing future studies.

Dexmedetomidine attenuates hypoxia-induced cardiomyocyte injury by promoting telomere/telomerase activity: Possible involvement of ERK1/2-Nrf2 signaling pathway

Dexmedetomidine (Dex), an α2-adrenergic receptor (α2-AR) agonist, possesses cardioprotection against ischaemic/hypoxic injury, but the exact mechanism is not fully elucidated. Since telomere/telomerase dysfunction is involved in myocardial ischemic damage, the present study aimed to investigate whether Dex ameliorates cobalt chloride (CoCl_2; a hypoxia mimic agent in vitro)-induced the damage of H9c2 cardiomyocytes by improving telomere/telomerase dysfunction and further explored the underlying mechanism focusing on ERK1/2-Nrf2 signaling pathway. Result showed that Dex increased cell viability, decreased apoptosis, and reduced cardiomyocyte hypertrophy as illustrated by the decreases in cell surface area and the biomarker levels for cardiac hypertrophy including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and myosin heavy chain β (β-MHC) mRNA and protein in CoCl₂ -exposed H9c2 cells. Intriguingly, Dex increased the telomere length and telomerase activity as well as telomere reverse transcriptase (TERT) protein and mRNA levels in H9c2 cells exposed to CoCl₂ , indicating that Dex promotes telomere/telomerase function under hypoxia. In addition, Dex remarkably diminished the ROS generation, reduced MDA content, and increased antioxidative signaling as evidenced by the increases in SOD and GSH-Px activities. Furthermore, Dex increased the ratio of P-ERK1/2/T-ERK1/2 and P-Nrf2/T-Nrf2 and enhanced Nrf2 nuclear translocation in CoCl₂ -subjected H9c2 cells, suggesting that Dex promotes the activation of the ERK1/2-Nrf2 signaling pathway. These novel findings indicated that Dex attenuates myocardial ischemic damage and reduces myocardial hypertrophy by promoting telomere/telomerase function, which may be associated with the activation of the ERK1/2-Nrf2 signaling pathway in vitro. This article is protected by copyright. All rights reserved.

Dexmedetomidine post-conditioning alleviates myocardial ischemia-reperfusion injury in rats by ferroptosis inhibition via SLC7A11/GPX4 axis activation

The SLC7A11/GPX4 axis plays an important role in ferroptosis during cardiac ischemia/reperfusion injury (IRI). The present study was designed to evaluate the impact of dexmedetomidine (DEX) post-conditioning on cardiac IRI and to explore whether the effect was achieved by SLC7A11/GPX4 signaling pathway regulation. Rat myocardial IRI was established by occluding the left anterior descending artery for 30 min followed by 2-h reperfusion. The infarct area was detected by diphenyltetrazolium chloride (TTC) staining; the cardiac function was evaluated by echocardiography. The levels of lipid peroxide biomarkers were measured to estimate the injury caused by lipid peroxide. HE staining and Sirius staining were utilized to assess myocardial damage and fibrosis. The mitochondrial morphology was observed by electron micrography. Western blot and quantitative real-time polymerase chain reaction were employed to measure the relative molecular characteristics. Our results showed that DEX administration at the beginning of reperfusion attenuated IRI-induced myocardial injury, alleviated mitochondrial dysfunction, decreased the level of reactive oxygen species (ROS), alleviated mitochondrial dysfunction, inhibited the activation of SLC7A11/GPX4, and modulated the expression of ferroptosis-related proteins, including SLC7A11, glutathione peroxidase 4 (GPX4), ferritin heavy chain (FTH), and cyclooxygenase-2 (COX-2). Conversely, the ferroptosis activator erastin partly suppressed the DEX-mediated cardio protection. Altogether, these results reveal that DEX inhibits ferroptosis by enhancing the expression of SLC7A11 and GPX4, thereby preventing cardiac I/R injury.

Subcellular distribution of α2-adrenoceptor subtypes in the rodent kidney

Renal α2-adrenoceptors have been reported to play a role in the regulation of urinary output, renin secretion, and water and sodium excretion in the kidneys. However, the distribution of α2-adrenoceptor subtypes in the kidneys remains unclear. In this study, we aimed to investigate the localization of α2-adrenoceptor subtypes in rat kidneys using 8-week-old Sprague-Dawley rats. Immunofluorescence imaging revealed that both α2A- and α2B-adrenoceptors were expressed in the basolateral, but not apical, membrane of the epithelial cells of the proximal tubules. We also found that α2A- and α2B-adrenoceptors were not expressed in the glomeruli, collecting ducts, or the descending limb of the loop of Henle and vasa recta. In contrast, α2C-adrenoceptors were found to be localized in the glomeruli and lumen of the cortical and medullary collecting ducts. These results suggest that noradrenaline may act on the basement membrane of the proximal tubules through α2A- and α2B-adrenoceptors. Moreover, noradrenaline may be involved in the regulation of glomerular filtration and proteinuria through the induction of morphological changes in mesangial cells and podocytes via α2C-adrenoceptors. In the collecting ducts, urinary noradrenaline may regulate morphological changes of the microvilli through α2C-adrenoceptors. Our findings provide an immunohistochemical basis for understanding the cellular targets of α2-adrenergic regulation in the kidneys. This may be used to devise therapeutic strategies targeting α2-adrenoceptors.

Dexmedetomidine protects the heart against ischemia reperfusion injury via regulation of the bradykinin receptors

BACKGROUND

Dexmedetomidine (DEX) has been reported to protect the heart against ischemia reperfusion (I/R) injury. However, the exact mechanisms are still not fully understood.

METHODS AND RESULTS

A rat cardiac I/R injury model was induced by ligation of the left anterior descending coronary artery for 1 h and subsequent reperfusion for 2 h, and DEX was administered intravenously 30 min before ischemia. We confirmed that DEX treatment mitigated cardiac I/R injury. Interestingly, we found that DEX regulated the expression of bradykinin (BK) receptors (B1R and B2R) in rat hearts during I/R injury and enhanced the protective action of BK administered during reperfusion. Moreover, in vitro hypoxia reoxygenation (H/R) injury was induced in neonatal rat cardiomyocytes (CMs), and DEX was administered 1 h before hypoxia. The in vitro findings were consistent with the in vivo experiments. We found that an α2-adrenoceptor (α2-AR) antagonist (yohimbine) completely aborted DEX-induced B1R and B2R regulation; an adenylyl cyclase (AC) agonist (forskolin) blocked B1R downregulation, while a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002) blocked B2R upregulation. The above findings indicated that DEX interacted with α2-AR in cardiomyocytes, inhibited B1R expression via suppression of AC, and stimulated B2R expression via activation of PI3K.

CONCLUSIONS

DEX regulates BK receptor expression and potentiates the protection of BK in cardiac I/R injury, which suggests that modulating endogenous cardioprotective factors may play an important role in DEX-induced cardioprotection.

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.

Clemastine Fumarate Attenuates Myocardial Ischemia Reperfusion Injury Through Inhibition of Mast Cell Degranulation

Mast cell (MC) activation is associated with myocardial ischemia reperfusion injury (MIRI). Suppression of MC degranulation might be a target of anti-MIRI. This study aimed to determine whether clemastine fumarate (CLE) could attenuate MIRI by inhibiting MC degranulation. A rat ischemia and reperfusion (I/R) model was established by ligating the left anterior descending coronary artery for 30 min followed by reperfusion for 120 min. Compound 48/80 (C48/80) was used to promote MC degranulation. The protective effect of CLE by inhibiting MC degranulation on I/R injury was detected by cardiac function, 2,3,5-triphenyl tetrazolium chloride (TTC) staining, hematoxylin-eosin (HE) staining, arrhythmia, and myocardial enzyme detection. Inflammatory factor mRNA levels, such as TNF-α, interleukin (IL)-1β, and IL-6, were detected. Cultured RBL-2H3 mast cells were pretreated with CLE and subjected to C48/80 treatment to determine whether CLE suppressed MC degranulation. Degranulation of MCs was visualized using tryptase release, Cell Counting Kit-8 (CCK-8), and cell toluidine blue (TB) staining. RBL cells were conditionally cultured with H9C2 cells to explore whether CLE could reverse the apoptosis of cardiomyocytes induced by MC degranulation. Apoptosis of H9C2 cells was detected by CCK-8, the LDH Cytotoxicity Assay Kit (LDH), TUNEL staining, and protein expression of BAX and Bcl-2. We found that CLE pretreatment further inhibited cardiac injury manifested by decreased infarct size, histopathological changes, arrhythmias, MC degranulation, and myocardial enzyme levels, improving cardiac function compared with that in the I/R group. C48/80 combined with I/R exacerbated these changes. However, pretreatment with CLE for C48/80 combined with I/R significantly reversed these injuries. In addition, CLE pretreatment improved the vitality of RBL cells and reduced tryptase release in vitro. Similarly, the supernatant of RBL cells pretreated with CLE decreased the cytotoxicity, TUNEL-positive cell rate, and BAX expression of conditioned H9C2 cells and increased the cell vitality and expression of Bcl-2. These results suggested that pretreatment with CLE confers protection against I/R injury by inhibiting MC degranulation.

Role of α2-Adrenoceptor Subtypes in Suppression of L-Type Ca2+ Current in Mouse Cardiac Myocytes

Sarcolemmal α2 adrenoceptors (α2-AR), represented by α2A, α2B and α2C isoforms, can safeguard cardiac muscle under sympathoadrenergic surge by governing Ca²⁺ handling and contractility of cardiomyocytes. Cardiomyocyte-specific targeting of α2-AR would provide cardiac muscle-delimited stress control and enhance the efficacy of cardiac malfunction treatments. However, little is known about the specific contribution of the α2-AR subtypes in modulating cardiomyocyte functions. Herein, we analyzed the expression profile of α2A, α2B and α2C subtypes in mouse ventricle and conducted electrophysiological antagonist assay evaluating the contribution of these isoforms to the suppression of L-type Ca²⁺ current (I_CaL). Patch-clamp electro-pharmacological studies revealed that the α2-agonist-induced suppression of I_CaL involves mainly the α2C, to a lesser extent the α2B, and not the α2A isoforms. RT-qPCR evaluation revealed the presence of adra2b and adra2c (α2B and α2C isoform genes, respectively), but was unable to identify the expression of adra2a (α2A isoform gene) in the mouse left ventricle. Immunoblotting confirmed the presence only of the α2B and the α2C proteins in this tissue. The identified α2-AR isoform-linked regulation of I_CaL in the mouse ventricle provides an important molecular substrate for the cardioprotective targeting.

Mitochondria and Pharmacologic Cardiac Conditioning-At the Heart of Ischemic Injury

Pharmacologic cardiac conditioning increases the intrinsic resistance against ischemia and reperfusion (I/R) injury. The cardiac conditioning response is mediated via complex signaling networks. These networks have been an intriguing research field for decades, largely advancing our knowledge on cardiac signaling beyond the conditioning response. The centerpieces of this system are the mitochondria, a dynamic organelle, almost acting as a cell within the cell. Mitochondria comprise a plethora of functions at the crossroads of cell death or survival. These include the maintenance of aerobic ATP production and redox signaling, closely entwined with mitochondrial calcium handling and mitochondrial permeability transition. Moreover, mitochondria host pathways of programmed cell death impact the inflammatory response and contain their own mechanisms of fusion and fission (division). These act as quality control mechanisms in cellular ageing, release of pro-apoptotic factors and mitophagy. Furthermore, recently identified mechanisms of mitochondrial regeneration can increase the capacity for oxidative phosphorylation, decrease oxidative stress and might help to beneficially impact myocardial remodeling, as well as invigorate the heart against subsequent ischemic insults. The current review highlights different pathways and unresolved questions surrounding mitochondria in myocardial I/R injury and pharmacological cardiac conditioning.

Dexmedetomidine reversed hypoxia/reoxygenation injury-induced oxidative stress and endoplasmic reticulum stress-dependent apoptosis of cardiomyocytes via SIRT1/CHOP signaling pathway

We aimed to investigate the protective role and mechanism of dexmedetomidine (DEX) on H9c2 cardiomyocytes after hypoxia/reoxygenation (H/R) injury. Six experimental groups were designed as follows: normal control group (group C), H/R group, H/R + DEX group, H/R + gastrodin group, H/R + Ex527 (SIRT1 inhibitor) group, and H/R + DEX + Ex527 group. Lactate dehydrogenase (LDH) activity and the levels of oxidative stress-related enzymes such as malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) were measured using corresponding commercial kits. Cell counting kit (CCK)-8 assay was used to detect cell survival rate while flow cytometry and caspase 3/7 activity were used to determine cell apoptosis, respectively. Western blot was used to detect the expression of silent information regulator 1 (SIRT1), C/EBP homologous protein (CHOP), cleaved-caspase-12/3 and pro-caspase-12/3 in each group. From our findings, when compared with H/R, H/R + Ex527 and H/R + DEX + Ex527 groups, DEX pretreatment of cells in H/R + DEX group significantly increased cell survival rate, and simultaneously reduced LDH activity, oxidative stress and the apoptosis rate of H9c2 cells with H/R injury. Moreover, DEX up-regulated SIRT1 expression level and down-regulated the levels of endoplasmic reticulum (ER) stress-related markers such as CHOP, cleaved-caspase-12 and cleaved-caspase-3, respectively. Ex527 could completely block DEX-induced upregulated expression of SIRT1, and partially blocked the DEX-induced downregulated expression levels of CHOP, cleaved-caspase-12 and cleaved-caspase-3. These results proved that DEX reversed H/R injury-induced oxidative stress and ER stress-dependent apoptosis of cardiomyocytes via SIRT1/CHOP signaling pathway.

Targeting the Endothelium to Achieve Cardioprotection

Despite considerable improvements in the treatment of myocardial infarction, it is still a highly prevalent disease worldwide. Novel therapeutic strategies to limit infarct size are required to protect myocardial function and thus, avoid heart failure progression. Cardioprotection is a research topic with significant achievements in the context of basic science. However, translation of the beneficial effects of protective approaches from bench to bedside has proven difficult. Therefore, there is still an unmet need to study new avenues leading to protecting the myocardium against infarction. In line with this, the endothelium is an essential component of the cardiovascular system with multiple therapeutic targets with cardioprotective potential. Endothelial cells are the most abundant non-myocyte cell type in the heart and are key players in cardiovascular physiology and pathophysiology. These cells can regulate vascular tone, angiogenesis, hemostasis, and inflammation. Accordingly, endothelial dysfunction plays a fundamental role in cardiovascular diseases, which may ultimately lead to myocardial infarction. The endothelium is of paramount importance to protect the myocardium from ischemia/reperfusion injury via conditioning strategies or cardioprotective drugs. This review will provide updated information on the most promising therapeutic agents and protective approaches targeting endothelial cells in the context of myocardial infarction.

Cardiac Preconditioning Effect of Ketamine-Dexmedetomidine versus Fentanyl-Propofol during Arrested Heart Revascularization

Background

Myocardial damage due to ischemia and reperfusion is still unavoidable during coronary surgery. Anesthetic agents have myocardial preconditioning effect. Ketamine has sympathomimetic effect, while dexmedetomidine has a sympatholytic effect in addition to anesthetic, analgesic, and anti-inflammatory properties of both the drugs. This study was carried out to compare ketamine-dexmedetomidine (KD) combination with fentanyl-propofol (FP) combination on the release of cardiac troponin T (cTnT) and outcome after coronary artery bypass graft.

Patients and Methods

Ninety adult patients who underwent coronary artery bypass grafting (CABG) were assigned to receive either KD base anesthesia (KD group) or FP anesthesia (FP group). Trends of high-sensitive cTnT, CK-MB, and serum cortisol were followed in the first postoperative 24 h. Other outcomes were vital signs, weaning from cardiopulmonary bypass, tracheal extubation time, and echocardiographic findings.

Results

There was a significant lower release of cTnT in KD group than FP group during its peak values at 6 h after aortic unclamping (92.01 ± 7.332 in KD versus 96.73 ± 12.532 ng.L^-1 P = 0.032). significant lower levels of serum cortisol levels were noted KD group than in FP group at 6 and 12 h after aortic unclamping P < 0.001. As regard tracheal extubation time, patients assigned to KD group extubated earlier than whom in FP group 202.22 ± 28.674 versus 304.67 ± 40.598 min respectively P < 0.001.

Conclusion

The use of KD during on-pump CABG confers better myocardial protective and anti-inflammatory effect than fentanyl propofol.

Protective effects of dexmedetomidine on small intestinal ischaemia-reperfusion injury in horses

BACKGROUND

Strangulating small intestinal lesions in the horse have increased morbidity and mortality compared to nonstrangulating obstructions due to mucosal barrier disruption and subsequent endotoxaemia.

OBJECTIVES

To investigate protective effects of dexmedetomidine on small intestinal ischaemia-reperfusion injury in the horse.

STUDY DESIGN

Randomised, controlled, experimental study.

METHODS

Eighteen systemically healthy horses were randomly assigned to three groups: control, preconditioning, and post-conditioning. During isoflurane anaesthesia, complete ischaemia was induced in a 1-m segment of jejunum for 90 minutes. Horses in the preconditioning and post-conditioning groups received dexmedetomidine (3.5 µg/kg followed by 7 µg/kg/h) before (preconditioning) or after beginning ischaemia (post-conditioning), and during reperfusion. Jejunal biopsies were collected before ischaemia (baseline-1), at the end of the ischaemic period (ischaemia), and 30 minutes after reperfusion (reperfusion-1). Additional biopsies were taken 24 hours after reperfusion from ischaemia-reperfusion-injured jejunum (reperfusion-2). Epithelial injury was scored histologically, and morphometric analyses were used to calculate villus surface area (VSA) denuded of epithelium. Data were analysed using analysis of variance, Kruskal-Wallis and Wilcoxon two-sample tests.

RESULTS

In the control group, epithelial injury scores and percentage of VSA denudation for ischaemia-reperfusion-injured jejunum were higher compared to baseline-1 at all time points. The ischaemia and both reperfusion samples from the pre- and post-conditioning groups had lower epithelial injury scores and percentage of VSA epithelial denudation compared to the control group, with no difference from baseline-1 at any time point for the preconditioning group.

MAIN LIMITATIONS

Preconditioning has limited application in the clinical setting with naturally occurring strangulating small intestinal lesions.

CONCLUSIONS

Dexmedetomidine was protective for small intestinal ischaemia-reperfusion injury in the horse when administered before or during ischaemia.

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.

Influence of Hyperglycemia on Dexmedetomidine-Induced Cardioprotection in the Isolated Perfused Rat Heart

Pharmacological preconditioning (PC) and postconditioning (PoC), for example, by treatment with the α2-adrenoreceptor agonist Dexmedetomidine (Dex), protects hearts from ischemia-reperfusion (I/R) injury in experimental studies, however, translation into the clinical setting has been challenging. Acute hyperglycemia adversely affects the outcome of patients with myocardial infarction. Additionally, it also blocks cardioprotection by multiple pharmacological agents. Therefore, we investigated the possible influence of acute hyperglycemia on Dexmedetomidine-induced pre- and postconditioning. Experiments were performed on the hearts of male Wistar rats, which were randomized into 7 groups, placed in an isolated Langendorff system and perfused with Krebs-Henseleit buffer. All hearts underwent 33 min of global ischemia, followed by 60 min of reperfusion. Control (Con) hearts received Krebs-Henseleit buffer (Con KHB), glucose (Con HG) or mannitol (Con NG) as vehicle only. Hearts exposed to hyperglycemia (HG) received KHB, containing 11 mmol/L glucose (an elevated, but commonly used glucose concentration for Langendorff perfused hearts) resulting in a total concentration of 22 mmol/L glucose throughout the whole experiment. To ensure comparable osmolarity with HG conditions, normoglycemic (NG) hearts received mannitol in addition to KHB. Hearts were treated with 3 nM Dexmedetomidine (Dex) before (DexPC) or after ischemia (DexPoC), under hyperglycemic or normoglycemic conditions. Infarct size was determined by triphenyltetrazoliumchloride staining. Acute hyperglycemia had no impact on infarct size compared to the control group with KHB (Con HG: 56 ± 9% ns vs. Con KHB: 56 ± 7%). DexPC reduced infarct size despite elevated glucose levels (DexPC HG: 35 ± 3%, p < 0.05 vs. Con HG). However, treatment with Dex during reperfusion showed no infarct size reduction under hyperglycemic conditions (DexPoC HG: 57 ± 9%, ns vs. Con HG). In contrast, hearts treated with mannitol demonstrated a significant decrease in infarct size compared to the control group (Con NG: 37 ± 3%, p < 0.05 vs. Con KHB). The combination of Dex and mannitol presents exactly opposite results to hearts treated with hyperglycemia. While DexPC completely abrogates infarct reduction through mannitol treatment (DexPC NG: 55 ± 7%, p < 0.05 vs. Con NG), DexPoC had no impact on mannitol-induced infarct size reduction (DexPoC NG: 38 ± 4%, ns vs. Con NG). Acute hyperglycemia inhibits DexPoC, while it has no impact on DexPC. Treatment with mannitol induces cardioprotection. Application of Dex during reperfusion does not influence mannitol-induced infarct size reduction, however, administering Dex before ischemia interferes with mannitol-induced cardioprotection.

Organ-Protective Effects and the Underlying Mechanism of Dexmedetomidine

Dexmedetomidine (DEX) is a highly selective α2 adrenergic receptor (α2AR) agonist currently used in clinical settings. Because DEX has dose-dependent advantages of sedation, analgesia, antianxiety, inhibition of sympathetic nervous system activity, cardiovascular stabilization, and significant reduction of postoperative delirium and agitation, but does not produce respiratory depression and agitation, it is widely used in clinical anesthesia and ICU departments. In recent years, much clinical study and basic research has confirmed that DEX has a protective effect on a variety of organs, including the nervous system, heart, lungs, kidneys, liver, and small intestine. It acts by reducing the inflammatory response in these organs, activating antiapoptotic signaling pathways which protect cells from damage. Therefore, based on wide clinical application and safety, DEX may become a promising clinical multiorgan protection drug in the future. In this article, we review the physiological effects related to organ protection in α2AR agonists along with the organ-protective effects and mechanisms of DEX to understand their combined application value.

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.

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

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

Dexmedetomidine 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 reduces the inflammation and apoptosis of doxorubicin-induced myocardial cells

As the number of elderly patients increases, some patients with heart problems may also need surgery. The purpose of this study was to investigate whether dexmedetomidine (DEX), a common used anesthetic, was beneficial to the patients with heart problems. Myocardial cells induced by doxorubicin (DOX) was to simulate the myocardium injury in vitro. H9c2 cells were treated with DOX, DEX/DOX, Compound C and Compound C/DEX/DOX, respectively. The expression of p-AMPK, AMPK, p-GSK3β, GSK3β, Bcl2, Bax, Cleaved caspase3, Caspase3, TXNIP, NLRP3, ASC, Cleaved caspase-1 and Caspase-1 were analyzed by Western blot. CCK-8 assay and flow cytometry analysis were used to detect the cell viability and cell apoptosis. The levels of TNF-α, IL-1β and IL-18 were detected by ELISA assay and the levels of NO, ROS, LDH, SOD, MDA and taurine were detected by corresponding assay kits. As a result, DEX promoted the cell viability and inhibited the inflammation, oxidative stress and apoptosis. In addition, DEX suppressed the expression of taurine, TXNIP, NLRP3, ASC and cleaved caspase-1 and activated the expression of p-AMPK and p-GSK3β. However, those above changes could be reversed by Compound C. In conclusion, this study indicated that DEX could reduce the inflammation and apoptosis of DOX-induced myocardial cells through activating the AMPK-GSK3β signaling pathway. Because of the above effects of DEX, it may be beneficial for surgical patients with heart problems.

Dexmedetomidine alleviates insulin resistance in hepatocytes by reducing endoplasmic reticulum stress

PURPOSE

Dexmedetomidine (DEX) stabilizes intraoperative blood glucose levels and reduces insulin resistance (IR), a common perioperative complication. However, the molecular mechanisms underlying these effects remain unclear. Since endoplasmic reticulum stress (ERS) is a mechanism of IR, this study sought to examine whether DEX can effectively alleviate IR by reducing ERS.

METHODS

HepG2 and LO2 cells were treated with different concentrations of insulin. The glucose content assay and Cell Counting Kit-8 (CCK-8) were then employed to determine the optimal insulin concentration capable of inducing IR without affecting cell viability. Insulin-resistant hepatocytes were cultured with different concentrations of DEX for 24 h, and the glucose concentration in the supernatant was measured. ERS was assessed by qPCR and western blotting. The latter was also used to quantify the expression of phosphorylated protein kinase B (p-AKT), phosphoenolpyruvate carboxykinase (PEPCK), and glucose 6 phosphatase (G6Pase), which are key proteins involved in the action of insulin.

RESULTS

After 48-h of culturing with 10 μg/mL insulin, glucose consumption in hepatocytes was found to be reduced. IR hepatocytes cultured with 10, 100, or 1000 ng/ml DEX for 24 h showed a concentration-dependent increase in glucose consumption. Elevated mRNA and protein levels of ERS markers binding immunoglobulin protein (BIP) and ER protein 29 (ERp29), were reversed by DEX treatment. Moreover, reduced p-AKT and increased PEPCK and G6Pase protein levels in IR hepatocytes were also restored following DEX treatment.

CONCLUSION

DEX may alleviate IR in hepatocytes by reducing ERS serving to restore insulin action via the IRS-1/PI3K/AKT pathway.

An α2-adrenoceptor agonist: Dexmedetomidine induces protective cardiomyocyte hypertrophy through mitochondrial-AMPK pathway

Aims: Dexmedetomidine (Dex) as a highly selective α₂-adrenoceptor agonist, was widely used anesthetic in perioperative settings, whether Dex induces cardiac hypertrophy during perioperative administration is unknown. Methods: The effects of Dex on cardiac hypertrophy were explored using the transverse aortic constriction model and neonatal rat cardiomyocytes. Results: We reported that Dex induces cardiomyocyte hypertrophy with activated ERK, AKT, PKC and inactivated AMPK in both wild-type mice and primary cultured rat cardiomyocytes. Additionally, pre-administration of Dex protects against transverse aortic constriction induced-heart failure in mice. We found that Dex up-regulates the activation of ERK, AKT, and PKC via suppression of AMPK activation in rat cardiomyocytes. However, suppression of mitochondrial coupling efficiency and membrane potential by FCCP blocks Dex induced AMPK inactivation as well as ERK, AKT, and PKC activation. All of these effects are blocked by the α₂-adrenoceptor antagonist atipamezole. Conclusion: The present study demonstrates Dex preconditioning induces cardiac hypertrophy that protects against heart failure through mitochondria-AMPK pathway in perioperative settings.

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

BACKGROUND

Spinal cord injury induces inflammatory responses that include the release of cytokines and the recruitment and activation of macrophages and microglia. Neuroinflammation at the lesion site contributes to secondary tissue injury and permanent locomotor dysfunction. Dexmedetomidine (DEX), a highly selective α2-adrenergic receptor agonist, is anti-inflammatory and neuroprotective in both preclinical and clinical trials. We investigated the effect of DEX on the microglial response, and histological and neurological outcomes in a rat model of cervical spinal cord injury.

METHODS

Anaesthetised rats underwent unilateral (right) C5 spinal cord contusion (75 kdyne) using an impactor device. The locomotor function, injury size, and inflammatory responses were assessed. The effect of DEX was also studied in a microglial cell culture model.

RESULTS

DEX significantly improved the ipsilateral upper-limb motor dysfunction (grooming and paw placement; P<0.0001 and P=0.0012), decreased the injury size (P<0.05), spared white matter (P<0.05), and reduced the number of activated macrophages (P<0.05) at the injury site 4 weeks post-SCI. In DEX-treated rats after injury, tissue RNA expression indicated a significant downregulation of pro-inflammatory markers (e.g. interleukin [IL]-1β, tumour necrosis factor-α, interleukin (IL)-6, and CD11b) and an upregulation of anti-inflammatory and pro-resolving M2 responses (e.g. IL-4, arginase-1, and CD206) (P<0.05). In lipopolysaccharide-stimulated cultured microglia, DEX produced a similar inflammation-modulatory effect as was seen in spinal cord injury. The benefits of DEX on these outcomes were mostly reversed by an α2-adrenergic receptor antagonist.

CONCLUSIONS

DEX significantly improves neurological outcomes and decreases tissue damage after spinal cord injury, which is associated with modulation of neuroinflammation and is partially mediated via α2-adrenergic receptor signaling.

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.

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.

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.

Protective effect of dexmedetomidine against organ dysfunction in a two-hit model of hemorrhage/resuscitation and endotoxemia in rats

Dexmedetomidine (DEX), a selective agonist of α₂-adrenergic receptors, has anti-inflammation properties and potential beneficial effects against trauma, shock, or infection. Therefore, this study aimed to investigate whether DEX might protect against multiple-organ dysfunction in a two-hit model of hemorrhage/resuscitation (HS) and subsequent endotoxemia. Eighty Wistar rats were randomized into four groups: NS (normal saline), HS/L (HS plus lipopolysaccharide), HS/L+D (HS/L plus dexmedetomidine), and HS/L+D+Y (HS/L+D plus yohimbine). Six hours after resuscitation, blood gas (PaO₂) and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urine nitrogen (BUN), creatinine (Cr), TNF-α, IL-β, IL-6, IL-8, IL-10, and nitric oxide (NO) were measured. The histopathology was assayed by staining. Malondialdehyde (MDA) and superoxide dismutase (SOD) levels and heme oxygenase-1 (HO-1) were assayed. The PaO₂ levels in HS/L rats were lower whereas the ALT, AST, BUN, Cr, TNF-α, IL-β, IL-6, IL-8, IL-10, and NO levels were higher compared to the control group. The HS/L+D increased PaO₂ and further increased IL-10 and decreased ALT, AST, BUN, Cr, TNF-α, IL-β, IL-6, IL-8, and NO levels of the HS/L groups. In addition, the MDA in the HS/L groups increased whereas SOD activity decreased compared to the control group. Moreover, the HO-1 expression levels were increased by DEX administration in lung, liver, and kidney tissues. Lungs, livers, and kidneys of the HS/L group displayed significant damage, but such damage was attenuated in the HS/L+D group. All of the above-mentioned effects of DEX were partly reversed by yohimbine. DEX reduced multiple organ injury caused by HS/L in rats, which may be mediated, at least in part, by α₂-adrenergic receptors.

Sarcolemmal α2-adrenoceptors in feedback control of myocardial response to sympathetic challenge

α2-adrenoceptor (α2-AR) isoforms, abundant in sympathetic synapses and noradrenergic neurons of the central nervous system, are integral in the presynaptic feed-back loop mechanism that moderates norepinephrine surges. We recently identified that postsynaptic α2-ARs, found in the myocellular sarcolemma, also contribute to a muscle-delimited feedback control capable of attenuating mobilization of intracellular Ca²⁺ and myocardial contractility. This previously unrecognized α2-AR-dependent rheostat is able to counteract competing adrenergic receptor actions in cardiac muscle. Specifically, in ventricular myocytes, nitric oxide (NO) and cGMP are the intracellular messengers of α2-AR signal transduction pathways that gauge the kinase-phosphatase balance and manage cellular Ca²⁺ handling preventing catecholamine-induced Ca²⁺ overload. Moreover, α2-AR signaling counterbalances phospholipase C - PKC-dependent mechanisms underscoring a broader cardioprotective potential under sympathoadrenergic and angiotensinergic challenge. Recruitment of such tissue-specific features of α2-AR under sustained sympathoadrenergic drive may, in principle, be harnessed to mitigate or prevent cardiac malfunction. However, cardiovascular disease may compromise peripheral α2-AR signaling limiting pharmacological targeting of these receptors. Prospective cardiac-specific gene or cell-based therapeutic approaches aimed at repairing or improving stress-protective α2-AR signaling may offer an alternative towards enhanced preservation of cardiac muscle structure and function.

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.

The effect of dexmedetomidine on the perioperative hemodynamics and postoperative cognitive function of elderly patients with hypertension: Study protocol for a randomized controlled trial

INTRODUCTION

Cognitive dysfunction after surgery, a common clinical manifestation of postoperative psychonosema. It usually occurs after heart surgery, hip replacement, mandibular fractures, and other major operations. Dexmedetomidine can exert sedative, analgesic, anxiolytic effect, inhibits the sympathetic activity, maintains hemodynamic balance, helps reduce the amount of anesthetic agents, and relatively slightly depresses respiration. Preoperative administration of dexmedetomidine for sedation has been reported to reduce the incidence of acute postoperative delirium. But currently there is no study on the effect of dexmedetomidine on the postoperative cognitive function of elderly patients with essential hypertension.

METHODS/DESIGN

This study is a prospective, single-center, double-blind controlled clinical trial. Elderly patients aged between 60 and 80 years old, diagnosed with primary hypertension for 1 year or longer will be included, and randomized into 2 groups. Patients in observational group will be given a loading dose of dexmedetomidine at 0.8 μg/kg, pumped for over 10 minutes. Although patients in control group will be pumped of the same volume of normal saline within 10 minutes, before the induction of anesthesia. Minimental state examination and levels of interleukin-6, tumor necrosis factor alpha, and C-reactive protein will be set as primary endpoints. Baseline characteristics of patients will be summarized by groups and compared using Chi-square or Fisher exact tests for categorical variables and 2-sample t tests or Wilcoxon rank sum test for the continuous variables. Repeated measurement analysis of covariance model will also be used for the comparison of endpoints between 2 groups.

CONCLUSION

The present study is designed to investigate the effect of the application of dexmedetomidine on postoperative myocardial injury and postoperative cognitive dysfunction, also to explore the association between inflammatory factors and postoperative cognitive function. With this study, we are expecting to find out an appropriate anesthesia method for elderly people with hypertension to alleviate the postoperative adverse effects caused by medical treatments.

TRIALS REGISTRATION

This study was registered on Chinese Clinical Trial Registry (http://www.chictr.org.cn/) with the ID ChiCTR-IPR-16009156.

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.