In Vivo Evaluation of Brain [18F]F-FDG Uptake Pattern Under Different Anaesthesia Protocols.

BACKGROUND/AIM: Since the use of anaesthetics has the drawback of altering radiotracer distribution, preclinical positron emission tomography (PET) imaging findings of anaesthetised animals must be carefully handled. This study aimed at assessing the cerebral [18F]F-FDG uptake pattern in healthy Wistar rats under four different anaesthesia protocols using microPET/magnetic resonance imaging (MRI) examinations. MATERIALS AND METHODS: Post-injection of 15±1.2 MBq of [18F]F-FDG, either while awake or during the isoflurane-induced incubation phase was applied. Prior to microPET/MRI imaging, one group of the rats was subjected to forane-only anaesthesia while the other group was anaesthetised with the co-administration of forane and dexmedetomidine/Dexdor® Results: While as for the whole brain it was the addition of dexmedetomidine/Dexdor® to the anaesthesia protocol that generated the differences between the radiotracer concentrations of the investigated groups, regarding the cortex, the [18F]F-FDG accumulation was rather affected by the way of incubation. To ensure the most consistent and highest uptake, forane-induced anaesthesia coupled with an awake uptake condition seemed to be most suitable method of anaesthetisation for cerebral metabolic assessment. Diminished whole brain and cortical tracer accumulation detected upon dexmedetomidine/Dexdor® administration highlights the significance of the mechanism of action of different anaesthetics on radiotracer pharmacokinetics. CONCLUSION: Overall, the standardization of PET protocols is of utmost importance to avoid the confounding factors derived from anaesthesia.

Dexmedetomidine Stereotaxic Injection Alleviates Neuronal Loss Following Bilateral Common Carotid Artery Occlusion via Up-Regulation of BDNF Expression.

BACKGROUND/AIM: Neurogenesis is an important process in the recovery from neurological damage caused by ischemic lesions. Endogenous neurogenesis is insufficient to restore neuronal damage following cerebral ischemia. Dexmedetomidine (DEX) exerts neuroprotective effects against cerebral ischemia and ischemia/reperfusion injury. DEX promotes neurogenesis, including neuronal proliferation and maturation in the hippocampus. In a previous study, we showed that early neurogenesis increased 3 days after bilateral common carotid artery occlusion (BCCAO). In this study, we investigated the effect of DEX on neurogenesis 3 days after BCCAO. MATERIALS AND METHODS: Male Sprague-Dawley (SD) rats (7-8 weeks old) were used as a BCCAO model. Right and left common carotid arteries of the rats were occluded using 4-0 silk sutures. Two hours after surgery, an intracranial DEX injection was administered to rats that underwent surgery using a stereotaxic injector. Brains were obtained from control and BCCAO rats 3 days after surgery. Immunohistochemistry was performed on the cortex and dentate gyrus of the hippocampus using a NeuN antibody. Western blot was performed with HIF1α and brain-derived neurotrophic factor (BDNF) antibodies. RESULTS: The number of mature neurons decreased 3 days after BCCAO, but DEX treatment alleviated neural loss in the parietal cortex and hippocampus. Up-regulation of BDNF was also observed after dexmedetomidine treatment. CONCLUSION: Stereotaxic injection of dexmedetomidine alleviates neural loss following BCCAO by up-regulating BDNF expression.

Dexmedetomidine mitigates neuroinflammation and improves early postoperative neurocognitive dysfunction in rats by enhancing autophagy.

Postoperative neurocognitive dysfunction (PND) is a common postoperative complication. Autophagy is correlated with the pathogenesis of PND. This study investigated the potential role of autophagy in the neuroprotection of dexmedetomidine (Dex) pretreatment in PND. The PND rat model was established by abdominal surgery. The cognitive function of rats was evaluated by Y-maze 3 days after surgery. Nissl staining assessed postoperative hippocampal damage. Immunofluorescence detected the expression of microglial activation (Iba-1) and autophagy-related protein (LC3B) in hippocampal tissues. Western blot detected the autophagy-related protein expression (Beclin 1, LC3B, and p62), proinflammatory cytokines, and the protein activation of the autophagy-related LKB1/AMPK/ULK-1 signaling pathway. RT-PCR quantified the expression of IL-1ß, TNF-α, and IL6. In this study, we found that Dex pretreatment improved spatial memory function impairment and reduced abdominal surgery-induced hippocampal tissue damage. Dex pretreatment significantly increased the expression of Beclin 1 and LC3 II/I and decreased the expression of p62 in the hippocampus after surgery. Furthermore, Dex effectively inhibited microglial activation and proinflammatory cytokines by enhancing autophagy in the hippocampus. Pretreatment with 3-MA, an autophagy inhibitor, significantly weakened the inhibitory effect of Dex on postoperative neuroinflammation. We further demonstrated that Dex suppressed surgery-induced neuroinflammation by activating the LKB1/AMPK/ULK-1 signaling pathway. In conclusion, our study indicated that Dex inhibited hippocampal neuroinflammation and ameliorated PND by enhancing autophagy after surgery in rats, which was related to the LKB1/AMPK/ULK-1 signaling pathway. These findings provide a potential therapeutic prospect for PND.NEW & NOTEWORTHY Dex inhibits hippocampal neuroinflammation and attenuates early cognitive impairment by enhancing autophagy following surgery in rats. Dex may protect postoperative cognitive function by activating the LKB1/AMPK/ULK-1 signaling pathway.

Combination of ion-pair strategy and chemical enhancers for design of dexmedetomidine long-acting patches: Dual action mechanism induced longer controlled release and better delivery efficiency.

The purpose of this study was to prepare a dexmedetomidine (Dex) 72 h long-acting patch by the combined use of ion-pair strategy and chemical enhancers (CEs), and to investigate molecular mechanisms of drug-loading enhancement and controlled release. The formulation of patch was optimized by single-factor investigation and Box-Behnken design. The pharmacokinetics, analgesic pharmacodynamics and irritation of the formulation were evaluated, respectively. Moreover, the effects of ion-pairs and CEs on the patch were characterized by DSC, rheology study, FTIR, and molecular docking, and the effects on the skin were evaluated by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman study, and molecular dynamics, respectively. The optimized formulation was 17.00 % (w/w) Dex-NA (Naphthoic acid), 7.20 % Polyglyceryl-3 dioleate (POCC), 25-AAOH as pressure sensitive adhesives (PSA) and 66.50 µm in thickness. Compared with the control group (Cmax = 62.02 ± 16.55 ng/mL, MRT0-t = 26.74 ± 1.27 h), the pharmacokinetics behavior of the optimization group was more stable and durable (Cmax = 31.22 ± 13.26 ng/mL, MRT0-t = 33.62 ± 1.62 h). Besides, it also showed good analgesic effect and no obvious irritation. The results indicated that Dex-NA both increased the drug-PSA interactions and inhibited the penetration of the drug into the skin. POCC increased the molecular mobility of the PSA and disrupted skin lipids thereby improving the drug penetration rate. In summary, the Dex long-acting patch was developed, which provided a reference for the combined application of ion-pair strategy and CEs in other long-acting transdermal delivery.

Dexmedetomidine Alters the Inflammatory Profile of Rat Microglia In Vitro.

BACKGROUND: Microglia are a primary mediator of the neuroinflammatory response to neurologic injury, such as that in traumatic brain injury. Their response includes changes to their cytokine expression, metabolic profile, and immunophenotype. Dexmedetomidine (DEX) is an α2 adrenergic agonist used as a sedative in critically ill patients, such as those with traumatic brain injury. Given its pharmacologic properties, DEX may alter the phenotype of inflammatory microglia. METHODS: Primary microglia were isolated from Sprague-Dawley rats and cultured. Microglia were activated using multiple mediators: lipopolysaccharide (LPS), polyinosinic-polycytidylic acid (Poly I:C), and traumatic brain injury damage-associated molecular patterns (DAMP) from a rat that sustained a prior controlled cortical impact injury. After activation, cultures were treated with DEX. At the 24-h interval, the cell supernatant and cells were collected for the following studies: cytokine expression (tumor necrosis factor-α [TNFα], interleukin-10 [IL-10]) via enzyme-linked immunosorbent assay, 6-phosphofructokinase enzyme activity assay, and immunophenotype profiling with flow cytometry. Cytokine expression and metabolic enzyme activity data were analyzed using two-way analysis of variance. Cell surface marker expression was analyzed using FlowJo software. RESULTS: In LPS-treated cultures, DEX treatment decreased the expression of TNFα from microglia (mean difference = 121.5 ± 15.96 pg/mL; p < 0.0001). Overall, DEX-treated cultures had a lower expression of IL-10 than nontreated cultures (mean difference = 39.33 ± 14.50 pg/mL, p < 0.0001). DEX decreased IL-10 expression in LPS-stimulated microglia (mean difference = 74.93 ± 12.50 pg/mL, p = 0.0039) and Poly I:C-stimulated microglia (mean difference = 23.27 ± 6.405 pg/mL, p = 0.0221). In DAMP-stimulated microglia, DEX decreased the activity of 6-phosphofructokinase (mean difference = 18.79 ± 6.508 units/mL; p = 0.0421). The microglial immunophenotype was altered to varying degrees with different inflammatory stimuli and DEX treatment. CONCLUSIONS: DEX may alter the neuroinflammatory response of microglia. By altering the microglial profile, DEX may affect the progression of neurologic injury.

Dexmedetomidine attenuates renal ischemia-reperfusion injury through activating PI3K/Akt-eNOS signaling via α2 adrenoreceptors in renal microvascular endothelial cells.

Renal microvascular endothelial cells (RMECs), which are closely related to regulation of vascular reactivity and modulation of inflammation, play a crucial role in the process of renal ischemia and reperfusion (I/R) injury. Previous studies have reported the protective effects of dexmedetomidine (DEX) against renal I/R injury, but little is known about the role of DEX on RMECs. This study aimed to investigate whether DEX alleviated renal I/R injury via acting on the RMECs. Mice underwent bilateral renal artery clamping for 45 min followed by reperfusion for 48 h, and the cultured neonatal mice RMECs were subjected to hypoxia for 1 h followed by reoxygenation (H/R) for 24 h. The results suggest that DEX alleviated renal I/R injury in vivo and improved cell viability of RMECs during H/R injury in vitro. Gene sequencing revealed that the PI3K/Akt was the top enriched signaling pathway and the endothelial cells were widely involved in renal I/R injury. DEX activated phosphorylation of PI3K and Akt, increased eNOS expression, and attenuated inflammatory responses. In addition, the results confirmed the distribution of α2 adrenoreceptor (α2 -AR) in RMECs. Furthermore, the protective effects of DEX against renal I/R injury were abolished by α2 -AR antagonist (atipamezole), which was partly reversed by the PI3K agonist (740 Y-P). These findings indicated that DEX protects against renal I/R injury by activating the PI3K/Akt-eNOS pathway and inhibiting inflammation responses via α2 -AR in RMECs.

Mechanism of Dexmedetomidine Intervention on Neurogenic Inflammation in Cognitive Impairment Rats after Partial Hepatectomy.

Objective: To study the effect of dexmedetomidine on cognitive function in rats with cognitive impairment after partial hepatectomy and its mechanism. Methods: 60 SD rats were randomly divided into 4 groups (n = 15): blank control group (CG group), sham operation group (Sham group), cognitive impairment model group (POCD group), and dexmedetomidine + cognitive impairment model group (DEX group). Rats in the POCD group underwent left lobe hepatectomy and intraperitoneal injection of the same amount of normal saline after resuscitation. Rats in the DEX group underwent left lobe hepatectomy and intraperitoneal injection of dexmedetomidine 50 µg/kg. Group CG was not operated on and the same amount of normal saline was injected intraperitoneally. In the Sham group, liver resection was not allowed after the abdominal incision, and normal saline was injected intraperitoneally. Rats were injected every 24 hours for 5 consecutive days. Morris water maze (MWM) were used to evaluate the effects of dexmedetomidine on learning and memory ability of POCD rats. TUNEL method was used to detect apoptotic neurons in the hippocampus. INOS, Arg-1, IL-6, and TNF-αexpression levels were detected. Western blot detects the expression level of TNF-α, Bcl-2, and NF-κB protein. Result: Compared with the CG group, the escape latency of the other three groups was prolonged on the 5th day after the operation, and the number of crossing the platform was reduced. Compared with the Sham group, the escape latency of the POCD group and DEX group was significantly prolonged, and the number of crossing the platform was significantly reduced on day 5 (P < 0.05). Compared with the POCD group, the DEX group shortened the escape latency and increased the number of crossing the platform on the 5th day (P < 0.05). It shows that the spatial learning and memory function of rats has been restored to a certain extent.The number of iNOS and Arg-1 positive cells in the POCD group and DEX group was higher than that in the control group, and the number of Arg-1 positive cells in the DEX group was higher than that in the POCD group (P < 0.05). Western blot results the expression of Bcl-2 and NF-κB protein in POCD group, and DEX group was higher than that of the sham group (P < 0.05). The expression of Bcl-2 and NF-κB protein was the most in POCD group. The expression of Bcl-2 and NF-κB protein in DEX group was lower than that in POCD group (P < 0.05). Conclusion: Behavioral results showed that the learning and cognitive ability of POCD model rats after hepatectomy was impaired, and inflammatory factors and activated microglia were found in the hippocampus of POCD rats. Dexmedetomidine may improve the brain function of POCD rats by inhibiting neuronal apoptosis,partly through NF-κB apoptosis pathway.

Could dexmedetomidine be repurposed as a glymphatic enhancer?

Cerebrospinal fluid (CSF) flows through the central nervous system (CNS) via the glymphatic pathway to clear the interstitium of metabolic waste. In preclinical studies, glymphatic fluid flow rate increases with low central noradrenergic tone and slow-wave activity during natural sleep and general anesthesia. By contrast, sleep deprivation reduces glymphatic clearance and leads to intracerebral accumulation of metabolic waste, suggesting an underlying mechanism linking sleep disturbances with neurodegenerative diseases. The selective α2-adrenergic agonist dexmedetomidine is a sedative drug that induces slow waves in the electroencephalogram, suppresses central noradrenergic tone, and preserves glymphatic outflow. As recently developed dexmedetomidine formulations enable self-administration, we suggest that dexmedetomidine could serve as a sedative-hypnotic drug to enhance clearance of harmful waste from the brain of those vulnerable to neurodegeneration.

Dexmedetomidine Attenuates Total Body Radiation-Induced Acute Liver Injury in Mice Through the Nrf2/HO-1 Pathway.

BACKGROUND: The purpose of this study was to investigate the protective effects of dexmedetomidine (DEX) on total body radiation-induced acute liver injury in mice and to explore the possible mechanisms. METHODS: A total of 40 mice were randomly divided into the Control group (Group C), Dexmedetomidine group (Group Dex), Radiation group (Group R), and Group R+Dex. Mice in Group Dex and Group R+Dex were intraperitoneally injected with 10 µg/mL Dex at 50 mg/kg. Both Group C and Group R received normal saline instead of Dex. Mice were treated via continuous administration for 10 days and injection once a day (pre-administration for 3 days and 7 days after radiation). One hour after administration on the third day, the mice in Group R and R+Dex received total body radiation with a total dose of 6 Gy at a rate of 2 Gy/min. Group C received sham radiation. Levels of aspartate aminotransferase (AST), serum alanine aminotransferase (ALT), and liver levels of tumor necrosis factor (TNF-α), interleukin-1ß (IL-1ß), reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA) were measured. HE staining was employed to evaluate the pathological changes in liver tissues, and the expressions of Nrf2 and HO-1 proteins in the liver were measured by western blot. RESULTS: Compared with group C, serum levels of AST and ALT, liver TNF-α, IL-1ß, MDA, and ROS levels increased, and SOD decreased in Group R. Group R mice had higher liver injury scores, and the protein expressions of Nrf2 and HO-1 proteins were lower (p ＜ 0.05). Compared with Group R, the levels of AST, ALT, TNF-α, IL-1ß, MDA, and ROS decreased, SOD increased, liver injury scores were lower, and the expressions of Nrf2 and HO-1 proteins were higher in the Group R+Dex group (all p ＜ 0.05). CONCLUSIONS: Dex exhibits a protective effect on reducing acute radiation-induced liver injury and oxidative stress, and the mechanism may be associated with the activation of Nrf2/HO-1 pathways.

Dexmedetomidine reduces IL-4 and IgE expression through downregulation of theTLR4/NF-κB signaling pathway to alleviate airway hyperresponsiveness in OVA mice.

BACKGROUND: Airway hyperresponsiveness (AHR) is a clinical manifestation of airflow limitation due to abnormal tracheal and bronchial sensitivity and is the main basis for the diagnosis of asthma. Patients with AHR are at high risk of perioperative tracheal and bronchospasm, which can lead to hypoxaemia and haemodynamic instability and, in severe cases, to a life-threatening 'silent lung'. It is therefore important to reduce the incidence or intensity of AHR episodes in the perioperative period. The inflammatory response is key to the development and progression of AHR. HYPOTHESIS/PURPOSE: Based on the modulatory role of dexmedetomidine (DEX) in the inflammatory response, we hypothesised that dexmedetomidine (DEX) attenuates inflammatory properties by inhibiting the toll-like receptor 4 (TLR4)/nuclear factor (NF-κB) signalling pathway and can reduce the respiratory parameters of mechanical ventilation in ovalbumin-induced allergic airway hyperresponsiveness. STUDY DESIGN: BABL/C mice were divided into control and OVA groups (ovalbumin-induced allergy. Ten mice in all OVA models were randomly selected for in vivo invasive lung function monitoring to analyse airway resistance parameters and demonstrate successful model establishment. The remaining OVA mice were treated with dexmedetomidine 25 µg/kg for 5 days (OVA + DEX group) or dexmedetomidine 25 µg/kg + yohimbine 1 mg/kg for 5 days (OVA + DEX + yohimbine). After treatment, bronchoalveolar lavage fluid (BAL) and peripheral blood (ELISA) and lung tissue (H&E and PAS) were collected for analysis of inflammatory factors, and lung tissue was verified by PCR for genes and proteins that do correlate with inflammatory mediators. RESULTS: All airway resistance parameters were increased in OVA mice by invasive lung function monitoring. Proximal airway resistance (parameter Rn) and total respiratory resistance (parameter Rrs) were attenuated after dexmedetomidine intervention treatment. Dexmedetomidine reduced total inflammatory cell count and inflammatory infiltration of lung tissue in BALF and down-regulated IL-4 and IgE levels in BALF and peripheral blood, as shown by Giemsa, H&E, PAS staining and ELISA; this mechanism of action was found to be related to the TLR4/NFκB pathway, but not to TLR4/NFκB, as measured by PCR. CONCLUSION: Dexmedetomidine reduces hyperresponsiveness and airway inflammatory responses. This mechanism of action may be related to the TLR4/NFκB signalling pathway. Overall conclusions are presented in.

Dexmedetomidine protects H9C2 rat cardiomyocytes against hypoxia/reoxygenation injury by regulating the long non-coding RNA colon cancer-associated transcript 1/microRNA-8063/Wnt/ß-catenin axis.

Dexmedetomidine (Dex) protects the heart from ischemia/reperfusion (I/R) injury. The differential expression of long non-coding RNAs (lncRNAs) is associated with myocardial injury, but whether the lncRNA colon cancer-associated transcript 1 (CCAT1) is associated with Dex-mediated myocardial protection remains unclear. In this study, a hypoxia/reoxygenation (H/R) H9C2 model was established to simulate the in vitro characteristics of I/R. CCAT1 and microRNA (miR)-8063 expression levels in H/R H9C2 cells pretreated with Dex were determined via quantitative reverse transcription-polymerase chain reaction. The survival and apoptotic rates of H9C2 cells were determined via cell counting kit-8 and flow cytometry assays. Wnt3a, Wnt5a, and ß-catenin protein levels were measured via western blotting. Luciferase and RNA immunoprecipitation assays were used to explore the binding relationship between miR-8063 and CCAT1. Dex pretreatment increased H/R H9C2 cell viability and CCAT1 expression, while decreasing the cell apoptosis and Wnt3a, Wnt5a, and ß-catenin protein levels. Knockdown of CCAT1 abolished the protective effects of Dex on H/R H9C2 cells, and the downregulation of miR-8063 expression eliminated the effect of CCAT1 knockdown. These results revealed that CCAT1, a sponge for miR-8063, is involved in Dex-mediated H9C2 cell H/R injury by negatively targeting miR-8063 and inactivating the Wnt/ß-catenin pathway. Dex protects H9C2 cells from H/R impairment by regulating the lncRNA CCAT1/miR-8063/Wnt/ß-catenin axis.

Dexmedetomidine Mitigates Microglial Activation Associated with Postoperative Cognitive Dysfunction by Modulating the MicroRNA-103a-3p/VAMP1 Axis.

Surgery-induced microglial activation is critical in mediating postoperative cognitive dysfunction (POCD) in elderly patients, where the important protective effect of dexmedetomidine has been indicated. However, the mechanisms of action of dexmedetomidine during the neuroinflammatory response that underlies POCD remain largely unknown. We found that lipopolysaccharide (LPS) induced substantial inflammatory responses in primary and BV2 microglial cells. The screening of differentially expressed miRNAs revealed that miR-103a-3p was downregulated in these cell culture models. Overexpression of miR-103a-3p mimics and inhibitors suppressed and enhanced the release of inflammatory factors, respectively. VAMP1 expression was upregulated in LPS-treated primary and BV-2 microglial cells, and it was validated as a downstream target of miR-103-3p. VAMP1-knockdown significantly inhibited the LPS-induced inflammatory response. Dexmedetomidine treatment markedly inhibited LPS-induced inflammation and the expression of VAMP1, and miR-103a-3p expression reversed this inhibition. Moreover, dexmedetomidine mitigated microglial activation and the associated inflammatory response in a rat model of surgical trauma that mimicked POCD. In this model, dexmedetomidine reversed miR-103a-3p and VAMP1 expression; this effect was abolished by miR-103a-3p overexpression. Taken together, the data show that miR-103a-3p/VAMP1 is critical for surgery-induced microglial activation of POCD.

Dexmedetomidine attenuates hippocampal neuroinflammation in postoperative neurocognitive disorders by inhibiting microRNA-329-3p and activating the CREB1/IL1RA axis.

RATIONALE: Due to its anti-inflammatory effect, dexmedetomidine (DEX) can confer neuroprotection in postoperative neurocognitive disorders (NCD). Here, the mechanism responsible for this effect of DEX is rarely ascertained. OBJECTIVES: Our research was implemented to figure out mechanism governing the protection of DEX against hippocampal neuroinflammation in postoperative NCD. METHODS: Exploratory laparotomy was applied for generating a postoperative NCD mouse model before bilateral hippocampal injection with microRNA (miR)-329-3p-agomir and intraperitoneal injection with DEX. Cognitive function of mice was evaluated by water maze test and fear conditioning test. Immunofluorescence was performed to assess microglial activation in hippocampus. After cell transfection and DEX treatment, mouse microglial cells (BV-2) were stimulated by lipopolysaccharide (LPS). IL-1ß, IL-6, and TNF-α levels and the number of phagocytes were assessed by ELISA and flow cytometry. Dual-luciferase reporter assay was adopted to assess the relationship between miR-329-3p and CREB1. RESULTS: miR-329-3p expression was reduced in the postoperative NCD mice after DEX treatment. DEX treatment or miR-329-3p downregulation caused attenuated cognitive dysfunction and microglia activation as well as reduced IL-1ß, IL-6, and TNF-α levels in the hippocampus of the postoperative NCD mice. Mechanistically, miR-329-3p inversely targeted CREB1 that activated IL1RA in LPS-induced BV-2 cells. DEX treatment, miR-329-3p inhibition, or CREB1 or IL1RA upregulation curtailed the release of proinflammatory proteins and the number of phagocytes in LPS-induced BV-2 cells. CONCLUSIONS: Collectively, our data provided the novel insight of the neuroprotective mechanism of DEX in postoperative NCD pertaining to the miR-329-3p/CREB1/IL1RA axis.

Dexmedetomidine prevents cardiomyocytes from hypoxia/reoxygenation injury via modulating tetmethylcytosine dioxygenase 1-mediated DNA demethylation of Sirtuin1.

Myocardial hypoxia/reoxygenation (H/R) injury is a common pathological change in patients with acute myocardial infarction undergoing reperfusion therapy. Dexmedetomidine (DEX) has been found to substantially improve ischemia-mediated cell damage. Here, we focus on probing the role and mechanism of DEX in ameliorating myocardial H/R injury. Oxygen-glucose deprivation and reoxygenation (OGD/R) were applied to construct the H/R injury model in human myocardial cell lines. After different concentrations of DEX's treatment, cell counting kit-8 (CCK-8) assay and BrdU assay were employed to test cell viability. The profiles of apoptosis-related proteins Bcl2, Bax, Bad and Caspase3, 8, 9 were determined by Western blot (WB). The expression of inflammatory factors interleukin 1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) was checked by reverse transcription-polymerase chain reaction (RT-PCR). By conducting WB, we examined the expression of NF-κB, Sirt1, Tet methylcytosine dioxygenase 1 (TET1) and DNA methylation-related proteins (DNA methyltransferase 1, DNMT1; DNA methyltransferase 3 alpha, DNMT3A; and DNA methyltransferase 3 beta, DNMT3B). Our data showed that OGD/R stimulation distinctly hampered the viability and elevated apoptosis and inflammatory factor expression in cardiomyocytes. DEX treatment notably impeded myocardial apoptosis and inflammation and enhanced cardiomyocyte viability. OGD/R enhanced total DNA methylation levels in cardiomyocytes, while DEX curbed DNA methylation. In terms of mechanism, inhibiting TET1 or Sirtuin1 (Sirt1) curbed the DEX-mediated myocardial protection. TET1 strengthened demethylation of the Sirt1 promoter and up-regulated Sirt1. DEX up-regulates Sirt1 by accelerating TET1 and mediating demethylation of the Sirt1 promoter and improves H/R-mediated myocardial injury.

The promotion of liver regeneration in mice after a partial hepatectomy as a result of the modulation of macrophage activation by dexmedetomidine.

BACKGROUND: This study investigates the effect of dexmedetomidine (DEX), a highly selective agonist of alpha 2-adrenergic receptors (α2-ARs), on the regulation of hepatic macrophage activation in liver regeneration. METHODS: A two-thirds partial hepatectomy (PHx) mouse model was performed. DEX (25 µg/kg) or a vehicle control (saline) was injected i.p. at 30 min before and every 12 h after PHx. The expression of α2B-ARs in the liver was detected using immunofluorescence staining. The effects of DEX on liver regeneration were assessed by Ki67 staining. The gene expression of inflammatory cytokines in isolated hepatic macrophages was quantified 36 h after the PHx. RESULTS: α2B-ARs colocalized with hepatic macrophages after the PHx. The number of Ki67-positive hepatocytes in the mice treated with DEX was markedly increased (p < 0.05). The increases in Ki67-positive hepatocytes after treatment with DEX were inhibited in the macrophage-depleted mice. DEX treatment inhibited the expression of major pro-inflammatory cytokines interleukin (IL)-1ß, IL-6, and tumor necrosis factor and elevated the expression of anti-inflammatory cytokines IL-4, IL-10, and transforming growth factor-ß1 in hepatic macrophages 36 h after the PHx (p < 0.05). CONCLUSIONS: The α2B-AR subtype is expressed in hepatic macrophages after a PHx. DEX modulates hepatic macrophage activation toward an anti-inflammatory phenotype via α2B-AR, which promotes the process of liver regeneration.

Dexmedetomidine represses TGF-ß1-induced extracellular matrix production and proliferation of airway smooth muscle cells by inhibiting MAPK signaling pathway.

BACKGROUND: Airway remodeling is implicated in the pathogenesis of asthma, and abnormal proliferation of airway smooth muscle cells (ASMCs) contribute to airway remodeling. Inflammatory mediator, transforming growth factor-ß1 (TGF-ß1), stimulates the proliferation of ASMCs, and is associated with airway remodeling in asthma. Dexmedetomidine (DEX) has been widely used in the adjuvant therapy of acute asthma. OBJECTIVE: The potential effects of DEX on extracellular matrix (ECM) production and proliferation of ASMCs were investigated in this study. MATERIAL AND METHODS: Human ASMCs were incubated with TGF-ß1 for 48 hours, and then treated with different concentrations of DEX for another 24 hours. Cell proliferation was detected by MTT and BrdU (5'-bromo-2'-deoxyuridine) staining. Flow cytometry was used to assess cell apoptosis, and western blot was applied to identify the underlying mechanism. RESULTS: TGF-ß1 induced increase in cell viability and bromodeoxyuridine (BrdU) positive cells in ASMCs while repressed cell apoptosis. Second, TGF-ß1-induced ASMCs were then treated with different concentrations of DEX. Cell viability of TGF-ß1-induced ASMCs was decreased by incubation of DEX. The number of BrdU positive cells in TGF-ß1-induced ASMCs was reduced by incubation of DEX. Moreover, incubation of DEX promoted cell apoptosis of TGF-ß1-induced ASMCs. Third, incubation of DEX attenuated TGF-ß1-induced increase in fibronectin, collagen I, MMP9, and versican in ASMCs. Lastly, the up-regulation of phosphorylated extracellular receptor kinase (p-ERK), phosphorylated Jun N-terminal Kinase (p-JNK), and p-p38 in TGF-ß1-induced ASMCs was reversed by incubation of DEX. CONCLUSION: DEX suppressed TGF-ß1-induced ECM production and proliferation of ASMCs through inactivation of p38 mitogen-activated protein kinase (MAPK) pathway, providing a potential strategy for prevention of asthma.

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 ischemic/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 (CoCl2; 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 extracellular signal-regulated kinase (ERK1/2)-NF-E2-related factor 2 (Nrf2) signaling pathway. The 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, brain natriuretic peptide, and myosin heavy chain ß messenger RNA (mRNA) and protein in CoCl2 -exposed H9c2 cells. Intriguingly, Dex increased the telomere length and telomerase activity as well as telomere reverse transcriptase 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 reactive oxygen species generation, reduced malondialdehyde content, and increased antioxidative signaling as evidenced by the increases in superoxide dismutase and plasma glutathione peroxidase 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.

Dexmedetomidine attenuates motor deficits via restoring the function of neurons in the nigrostriatal circuit in Parkinson's disease model mice.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a progressive degeneration in nigrostriatal dopamine pathway that is essential to control motor functions. Dexmedetomidine (DEX), a sedative and analgesic drug, is often used in patients with PD undergoing surgery. Although DEX seems to have promising future applications in neuroprotection, whether and how DEX alter the function of nigrostriatal circuit and its roles on motor deficits in PD remain unclear. Here we report that DEX attenuated motor deficits in a dose-dependent manner and protected the degeneration of dopaminergic neurons in MPTP-induced PD model mice. The DEX acted on the neurons in the nigrostriatal circuits, including activation of dopaminergic neurons and the reduction of the excitabilities of striatal neurons via dopamine D2 receptors. We further found that DEX prevented the increase in glutamatergic transmission of cholinergic interneurons (CINs) to alleviate motor dysfunction. It also decreased the intrinsic excitability and glutamatergic transmission of striatal D2 medium spiny neurons (D2-MSNs). Finally, D2 receptor antagonists prevented the restoration of DEX on motor deficits. These results demonstrate that DEX, a neuroprotective drug, restores the function of nigrostriatal neurons and improves the motor deficits, providing a potential neural mechanism of the effects of anesthetic drugs on PD progression.

Effect of dexmedetomidine on cardiorespiratory regulation in spontaneously breathing adult rats.

PURPOSE: We examined the cardiorespiratory effect of dexmedetomidine, an α2- adrenoceptor/imidazoline 1 (I1) receptor agonist, in spontaneously breathing adult rats. METHODS: Male rats (226-301 g, n = 49) under isoflurane anesthesia had their tail vein cannulated for drug administration and their tail artery cannulated for analysis of mean arterial pressure (MAP), pulse rate (PR), and arterial blood gases (PaO2, PaCO2, pH). After recovery, one set of rats received normal saline for control recording and was then divided into three experimental groups, two receiving dexmedetomidine (5 or 50 µg·kg-1) and one receiving normal saline (n = 7 per group). Another set of rats was divided into four groups receiving dexmedetomidine (50 µg·kg-1) followed 5 min later by 0.5 or 1 mg∙kg-1 atipamezole (selective α2-adrenoceptor antagonist) or efaroxan (α2-adrenoceptor/I1 receptor antagonist) (n = 6 or 8 per group). Recordings were performed 15 min after normal saline or dexmedetomidine administration. RESULTS: Compared with normal saline, dexmedetomidine (5 and 50 µg·kg-1) decreased respiratory frequency (fR, p = 0.04 and < 0.01, respectively), PR (both p < 0.01), and PaO2 (p = 0.04 and < 0.01), and increased tidal volume (both p = 0.049). Dexmedetomidine at 5 µg·kg-1 did not significantly change minute ventilation (V'E) (p = 0.87) or MAP (p = 0.24), whereas dexmedetomidine at 50 µg·kg-1 significantly decreased V'E (p = 0.03) and increased MAP (p < 0.01). Only dexmedetomidine at 50 µg·kg-1 increased PaCO2 (p < 0.01). Dexmedetomidine (5 and 50 µg·kg-1) significantly increased blood glucose (p < 0.01), and dexmedetomidine at 50 µg·kg-1 increased hemoglobin (p = 0.04). Supplemental atipamezole or efaroxan administration similarly prevented the 50 µg·kg-1 dexmedetomidine-related cardiorespiratory changes. PRINCIPAL CONCLUSION: These results suggest that dexmedetomidine-related hypoventilation and hypertension are observed simultaneously and occur predominantly through activation of α2-adrenoceptors, but not I1 receptors, in spontaneously breathing adult rats.