Mechanism Of Dexmedetomidine Research Articles

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 regulator1 (SIRT1), C/EBP homologousprotein (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.

Dexmedetomidine alleviates myocardial ischemia/reperfusion-induced injury and Ca2+ overload via the microRNA-346-3p/CaMKIId axis

Myocardial ischemia/reperfusion (MI/R) may impair cardiac functions. Dexmedetomidine (DEX) is protective in various clinical cases. Therefore, this study investigated the role and mechanism of DEX in MI/R. The myocardial infarct size, apoptosis, and levels of myocardial enzymes, SOD, ROS, Ca2+, and inflammatory factors in DEX-treated MI/R rats were measured. Differentially expressed microRNAs (miRs) in DEX-treated MI/R rats were detected. miR-346-3p was intervened to assess the effects of DEX on MI/R rats. The targeted binding relationship between miR-346-3p and CaMKIId was predicted and verified. DEX effect on hypoxia/reoxygenation (H/R)-induced cell model was evaluated. The role of CaMKIId in DEX protection was assessed after CaMKIId overexpression in H/R cells. NF-κB pathway and NLRP3 inflammasome-related protein levels were detected. DEX alleviated the myocardial injury and Ca2+ overload in MI/R rats, as evidenced by reduced infarct size, apoptosis and levels of myocardial enzymes, ROS, Ca2+, and inflammatory factors. DEX promoted miR-346-3p expression in MI/R rats, and miR-346-3p knockdown reversed DEX protection on MI/R rats. miR-346-3p targeted CaMKIId. DEX improved H/R-induced cell injury and Ca2+ overload and inhibited NF-κB/NLRP3 inflammasome-related protein levels, which were all reversed by CaMKIId overexpression. DEX alleviated injury and Ca2+ overload in MI/R via regulating the miR-346-3p/CaMKIId axis and inhibiting the NF-κB/NLRP3 inflammasome pathway.

右美托咪定肺保护作用及其机制的研究进展

右美托咪定肺保护作用及其机制的研究进展

Effects of Dexmedetomidine on Inflammatory Factors and Mitogen Activated Protein Kinase-Related Signaling Pathways of Alveolar Lavage Fluid in Mice with Lipopolysaccharide-Induced Acute Lung Injury

To investigate the effects and mechanisms of Dexmedetomidine on inflammatory factors and mitogenactivated protein kinase related signaling pathways in alveolar lavage fluid of mice with acute lung injury induced by lipopolysaccharide. 36 clean-grade male Kunming mice were randomly divided into blank control group (normal control group), lipopolysaccharide-induced acute lung injury model group, and lipopolysaccharide+dexmedetomidine group, with 12 mice in each group. The lipopolysaccharide group mice were intraperitoneally injected with 0.1 ml 5 mg kg-1 Lipopolysaccharide, lipopolysaccharide+Dexmedetomidine mice were injected with 25 μg kg-1. Dexmedetomidine intraperitoneally with 0.1 ml and 1 h later with 5 mg kg-1. Lipopolysaccharide injected with 0.1 ml intraperitoneally and the blank control group mice were intraperitoneally injected with normal saline of the same volume as the lipopolysaccharide group. All mice in each group were sacrificed after intraperitoneal injection for 6 h, and their lung tissues were separated by thoracotomy and their bronchoalveolar lavage fluid was recovered for subsequent detection. Analysis groups of mice lung tissue pathology, compare groups of mice lung tissue pathology score, lung wet weight/dry weight (W)/(D), mitogen-activated protein kinase pathways (p38 lightning, extracellular signal regulating kinase, c-jun amino terminal kinase) and bronchoalveolar lavage fluid protein expression level of tumor necrosis factor alpha beta, interleukin-1β, myeloperoxidase, protein concentration. In the blank control group, lung tissue structure was basically normal and alveolar structure was intact. lipopolysaccharide group mice had obvious lung tissue damage, and inflammatory cells appeared in the alveoli, with significantly increased exudation of red blood cells and proteins. Lipopolysaccharide+Dexmedetomidine group mice lung tissue damage significantly improved, inflammatory cell infiltration decreased, and red blood cell, protein exudation significantly decreased. Lung histopathological scores and bronchoalveolar lavage fluid levels of tumor necrosis factor alpha, interleukin- 1β and myeloperoxidase in lipopolysaccharide group were significantly higher than those in blank control group (p<0.05). The lung histopathological scores and the levels of tumor necrosis factor alpha, interleukin- 1β and myeloperoxidase in bronchoalveolar lavage fluid of lipopolysaccharide+Dexmedetomidine group were significantly lower than those of lipopolysaccharide group (p<0.05). The protein concentration in W/D and bronchoalveolar lavage fluid in lipopolysaccharide group was significantly higher than that in blank control group (p<0.05). Protein concentration in W/D and bronchoalveolar lavage fluid of lipopolysaccharide+Dexmedetomidine group was significantly lower than that of lipopolysaccharide group (p<0.05). The protein expression levels of extracellular signal regulating kinase, c-jun amino terminal kinase and P-P38 in THE lipopolysaccharide group were significantly higher than those in the blank control group (p<0.05). The protein expression levels of extracellular signal regulating kinase, c-jun amino terminal kinase and P-P38 in the lipopolysaccharide+Dexmedetomidine group were significantly lower than those in the lipopolysaccharide group (p<0.05). There was no significant difference in extracellular signal regulating kinase, c-jun amino terminal kinase and p38 protein expression levels in each group (p>0.05). Dexmedetomidine can significantly alleviate acute lung injury induced by lipopolysaccharide in mice, and its mechanism may be realized by blocking the activation of mitogen-activated protein kinaserelated signaling pathway and thereby reducing inflammatory response, providing a new target for the treatment of sepsis induced acute lung injury in the futurey.

Protective effect of dexmedetomidine on perioperative myocardial injury in patients with Stanford type-A aortic dissection.

To investigate the protective effect and mechanism of dexmedetomidine (Dex) on perioperative myocardial injury in patients with Stanford type-A aortic dissection (AD). Eighty-six patients with Stanford type-A AD were randomly divided into Dex and control groups, with 43 cases in each group. During the surgery, the control group received the routine anesthesia, and the Dex group received Dex treatment based on routine anesthesia. The heart rate (HR) and mean arterial pressure (MAP) were recorded before Dex loading (t0), 10 min after Dex loading (t1), at the skin incision (t2), sternum sawing (t3), before cardiopulmonary bypass (t4), at the extubation (t5), and at end of surgery (t6). The blood indexes were determined before anesthesia induction (T0) and postoperatively after 12h (T1), 24h (T2), 48h (T3), and 72h (T4). At t2 and t3, the HR and MAP in the Dex group were lower than in the control group (P < 0.05). Compared with the control group, in the Dex group at T1, T2, and T3, the serum creatine kinase-MB, cardiac troponin-I, C-reactive protein, and tumor necrosis factor-α levels were decreased, and the interleukin-10 level, the serum total superoxide dismutase, and total anti-oxidant capability increased, while the myeloperoxidase and malondialdehyde levels decreased (all P < 0.05). Dex treatment may alleviate perioperative myocardial injury in patients with Stanford type-A AD by resisting inflammatory response and oxidative stress.

Therapeutic efficacy of dexmedetomidine on chronic obstructive pulmonary disease via downregulating lncRNA PACER.

The aim of the study was to clarify the therapeutic mechanism of Dexmedetomidine (DEX) on the chronic obstructive pulmonary disease (COPD) and its regulatory effect on long non-coding RNA (lncRNA) PACER. Serum level of PACER in COPD patients was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The diagnostic potential of PACER in COPD was assessed by plotting ROC curves. The in vivo COPD model was generated in rats by cigarette smoking exposure. Primary rat alveolar epithelial cells were isolated, purified and cultured. After overexpression of PACER in primary rat alveolar epithelial cells, proliferative and migratory abilities were assessed by cell counting kit-8 (CCK-8) and transwell assay, respectively. Subsequently, we detected changes in PACER expression, viability and migratory potentials in primary rat alveolar epithelial cells harvested from control rats, and those harvested from COPD rats and induced with either DEX or not. Rescue experiments were conducted to uncover the involvement of PP2A in PACER-regulated cell phenotypes. PACER was upregulated in serum of COPD patients, which was a potential biomarker for diagnosing COPD. Overexpression of PACER in primary rat alveolar epithelial cells enhanced proliferative and migratory abilities. Compared with primary rat alveolar epithelial cells harvested from control rats, proliferative and migratory abilities were stronger in those harvested from COPD rats and induced with either DEX or not. Notably, DEX induction decreased PACER expression, and proliferative and migratory abilities in primary rat alveolar epithelial cells harvested from COPD rats. Overexpression of PP2A could partially abolish the promotive effects of PACER on proliferative and migratory abilities in DEX-induced primary rat alveolar epithelial cells harvested from COPD rats. PACER drives the proliferative and migratory abilities of alveolar epithelial cells through activating PP2A. Dexmedetomidine is conducive to COPD treatment by downregulating PACER.

Dexmedetomidine Alleviates Lipopolysaccharide-Induced Acute Kidney Injury by Inhibiting p75NTR-Mediated Oxidative Stress and Apoptosis.

Oxidative stress and apoptosis play a key role in the pathogenesis of sepsis-associated acute kidney injury (AKI). Dexmedetomidine (DEX) may present renal protective effects in sepsis. Therefore, we studied antioxidant effects and the mechanism of DEX in an inflammatory proximal tubular epithelial cell model and lipopolysaccharide- (LPS-) induced AKI in mice. Methods. We assessed renal function (creatinine, urea nitrogen), histopathology, oxidative stress (malondialdehyde (MDA) and superoxide dismutase (SOD)), and apoptosis (TUNEL staining and Cleaved caspase-3) in mice. In vitro experiments including Cleaved caspase-3 and p75NTR/p38MAPK/JNK signaling pathways were evaluated using western blot. Reactive oxidative species (ROS) production and apoptosis were determined using flow cytometry. Results. DEX significantly improved renal function and kidney injury and also revert the substantially increased level of MDA concentrations as well as the reduction of the SOD enzyme activity found in LPS-induced AKI mice. In parallel, DEX treatment also reduced the apoptosis and Cleaved caspase-3 expression evoked by LPS. The expression of p75NTR was increased in kidney tissues of mice with AKI but decreased after treatment with DEX. In cultured human renal tubular epithelial cell line (HK-2 cells), DEX inhibited LPS-induced apoptosis and generation of ROS, but this was reversed by overexpression of p75NTR. Furthermore, pretreatment with DEX significantly downregulated phosphorylation of JNK and p38MAPK in LPS-stimulated HK-2 cells, and this effect was abolished by overexpression of p75NTR. Conclusion. DEX ameliorated AKI in mice with sepsis by partially reducing oxidative stress and apoptosis through regulation of p75NTR/p38MAPK/JNK signaling pathways.

Dexmedetomidine inhibits apoptosis of astrocytes induced by oxygen-glucose deprivation via targeting JAK/STAT3 signal pathway

ObjectiveThere is an increasing interest concerning the contribution of astrocytes to the intrinsic bioremediation of ischemic brain injury. The aim of this work was to disclose the effects and mechanism of dexmedetomidine (DEX) on the apoptosis of astrocytes under oxygen glucose deprivation (OGD) condition. MethodsPrimary cultured astrocytes separated from Sprague-Dawley (SD) rats were subjected to OGD treatment. Astrocytes were transfected with si-JMJD3 or pcDNA3.1-JMJD3 and then treated with DEX or JAK/STAT inhibitor (WP1066) before cell apoptosis was detected by TUNEL apoptosis kit. Western blot was applied to assess the level of apoptosis-related proteins Caspase-3, Bax and Bcl-2. Astrocyte cell viability was assessed by measuring the lactate dehydrogenase (LDH) level using a LDH assay kit. ResultsAstrocytes received OGD treatment had increased LDH and elevated apoptotic rate (P < 0.05). DEX could suppress OGD induced cytotoxic effect on astrocytes, as evidenced by decreased LDH release and suppressed cell apoptosis rate (P < 0.05). Meanwhile, DEX and WP1066 treatment were also found to inhibit the phosphorylation level of STAT1 and STAT3 (P < 0.05), indicating the DEX could suppress the activation of JAK/STAT signal pathway. JMJD3 overexpression in astrocytes could suppress the anti-apoptotic function of WP1066 in OGD treated astrocytes and hamper the protective effect of DEX in cell apoptosis (P < 0.05), suggesting that DEX and JAK/STAT signal pathway inhibits OGD induced apoptosis in astrocytes by down-regulating JMJD3. ConclusionDEX protects astrocytes against apoptosis via inhibiting JAK2/STAT3 signal pathway and downregulating JMJD3 expression in vitro.

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

ObjectiveTo investigate the role of dexmedetomidine (DEX) in the inhibition of diabetic peripheral neuropathy (DPN) and the protection in the nerve damage.MethodsEighty male Sprague-Dawley (SD) rats were randomly allocated to four groups: the control group (C group), DPN model group (DPN group), DEX-treated group (DEX group), and the yohimbine treated group (YOH group). DPN was induced by intraperitoneal administration of streptozocin (STZ) (35 mg/kg). The body weights, blood glucose level, mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), the motor, and sensory nerve conduction velocities (MNCV and SNCV) of sciatic nerve were measured. Then the sciatic nerve was isolated for H&E staining and immunohistochemical staining. The oxidative stress makers such as malondialdehyde (MDA), superoxide-dismutase (SOD), and glutathione peroxidase (GSH-Px) and apoptosis related cytokines such as Bax, Bcl-2, and caspase-3 were estimated.ResultsThere was no significant difference of the blood glucose and body weight among the DPN group, DEX group, and YOH group. H&E staining showed that DEX treatment can ameliorate the damage of sciatic nerve cells. In the DPN group, MWT, TWL, MNCV, and SNCV were significantly reduced compared with the C group (P < 0.05). In DEX group rats, MWT, TWL, MNCV, and SNCV were increased significantly (P < 0.05) compared with the DPN group and YOH group rats. Lower SOD and GSH-Px, and higher MDA were found in the DPN group compared with the C group (P < 0.01), and DEX treatment restored SOD, GSH-px, and MDA activity significantly (P < 0.01). The expression levels of Bax and caspase-3 were increased, while that of Bcl-2 was decreased significantly in the DPN group compared with the C group (P < 0.05). In the DEX group, the expression levels of Bax and caspase-3 were decreased significantly (P < 0.05), while that of Bcl-2 was increased significantly (P < 0.05) compared with the DPN group and the YOH group.ConclusionThe results of this study demonstrated that DEX has the inhibitory and protective effects on DPN of rats. This may be associated with its antioxidative and anti-apoptosis responses.

Dexmedetomidine alleviated neuropathic pain in dorsal root ganglion neurons by inhibition of anaerobic glycolysis activity and enhancement of ROS tolerance.

Neuropathic pain is a kind of chronic pain that is triggered or caused primarily by damage to the nervous system and neurological dysfunction. It’s known that dexmedetomidine is a new type of highly selective alpha2-adrenoceptor agonist with sedation, anti-anxiety, analgesic and other effects. However, the function and mechanism of dexmedetomidine on neuropathic pain are not clear. Rat DRG neurons were isolated and identified using immunofluorescence assay. Following treatment with H2O2, dexmedetomidine or ROS inhibitor (NAC), the apoptosis and ROS levels were examined by flow cytometery; apoptosis- and anaerobic glycolysis-related proteins were determined by Western blot assay; glucose consumption, pyruvic acid, lactic acid and ATP/ADP ratios were also measured. The results revealed that dexmedetomidine inhibited H2O2-induced apoptosis and reactive oxygen species (ROS) in rat DRG neurons and in addition, dexmedetomidine down-regulated the expression levels of anaerobic glycolysis-related proteins, significantly reduced glucose, pyruvic acid and lactic acid levels. It also increased the ATP/ADP ratio in H2O2-treated rat dorsal root ganglion (DRG) neurons. Moreover, we also demonstrated that ROS inhibitor (NAC) also inhibited H2O2-induced apoptosis and anaerobic glycolysis in rat DRG neurons. In conclusion, dexmedetomidine suppressed H2O2-induced apoptosis and anaerobic glycolysis activity by inhibiting ROS, in rat DRG neurons. Therefore, dexmedetomidine might play a pivotal role in neuropathic pain by the inhibition of ROS.

Mechanisms of Dexmedetomidine in Neuropathic Pain.

Dexmedetomidin is a new-generation, highly selective α2 adrenergic receptor agonist with a large number of advantages, including its sedative and analgesic properties, its ability to inhibit sympathetic nerves, its reduced anesthetic dosage, its hemodynamic stability, its mild respiratory depression abilities, and its ability to improve postoperative recognition. Its safety and effectiveness, as well as its ability to provide a certain degree of comfort to patients, make it a useful anesthetic adjuvant for a wide range of clinical applications. For example, dexmedetomidine is commonly used in patients undergoing general anesthesia, and it also exerts sedative effects during tracheal intubation or mechanical ventilation in intensive care unit patients. In recent years, with the deepening of clinical research on dexmedetomidine, the drug is still applied in the treatment of spastic pain, myofascial pain, neuropathic pain, complex pain syndrome, and chronic headache, as well as for multimodal analgesia. However, we must note that the appropriateness of patient and dose selection should be given attention when using this drug; furthermore, patients should be observed for adverse reactions such as hypotension and bradycardia. Therefore, the safety and effectiveness of this drug for long-term use remain to be studied. In addition, basic experimental studies have also found that dexmedetomidine can protect important organs, such as the brain, heart, kidney, liver, and lung, through various mechanisms, such as antisympathetic effects, the inhibition of apoptosis and oxidative stress, and a reduction in the inflammatory response. Moreover, the neuroprotective properties of dexmedetomidine have received the most attention from scholars. Hence, in this review, we mainly focus on the characteristics and clinical applications of dexmedetomidine, especially the role of dexmedetomidine in the nervous system and the use of dexmedetomidine in the relief of neuropathic pain.

Effects of dexmedetomidine on the expression of inflammatory factors in children with congenital heart disease undergoing intraoperative cardiopulmonary bypass: a randomized controlled trial.

ImportanceDexmedetomidine inhibits the inflammatory response associated with cardiopulmonary bypass (CPB) and protects neural function. However, the mechanism of dexmedetomidine’s anti‐inflammatory pathway is unclear.ObjectiveTo investigate the effect of dexmedetomidine on the cognitive level and expression of inflammatory factors in children with congenital heart disease undergoing intraoperative CPB.MethodsNinety children with congenital heart disease were recruited and randomly divided into 3 groups of 30 children in each. In Group 1, a 1.0 µg·kg‐1·h‐1 intravenous bolus of dexmedetomidine was administered 10 minutes after induction of anesthesia, followed by a 0.2 µg·kg‐1·h‐1 infusion until the surgical incision. In Group 2, a 0.5 µg/kg intravenous bolus of dexmedetomidine was administered 10 minutes after induction of anesthesia, followed by a 0.1 µg·kg‐1·h‐1 infusion until the surgical incision. The control group was given physiological saline using the same method as in Groups 1 and 2. The serum levels of nuclear factor‐kappa B (NF‐κB), S‐100β protein, neuron‐specific enolase (NSE), tumor necrosis factor‐α (TNF‐α), and interleukin‐6 (IL‐6) were measured before the surgery (T1), at the end of CPB (T2), 2 hours after CPB (T3), 6 hours after CPB (T4), and 24 hours after CPB (T5). The Wechsler Intelligence Scale for children (WISC) was measured before the operation and at 3, 6, and 12 months after the operation to evaluate the neurodevelopmental state of the children.ResultsThe levels of the NF‐κB, S‐100β protein, NSE, TNF‐α, IL‐6 were significantly higher at T2, T3, or T4 than before the surgery (T1) in the control group or the dexmedetomidine groups. However, the increases of NF‐κB, TNF‐α, IL‐6, S‐100β and NSE levels were significantly smaller in the dexmedetomidine groups than those in the control group (P < 0.017). The WISC scores were similar among the three groups before or after the operation.InterpretationThe increases in NF‐κB, TNF‐α, and IL‐6 levels indicated aggravation of the inflammatory reaction and the increase S‐100β protein and NSE levels indicated that the nervous system was damaged. Administration of dexmedetomidine to children with congenital heart disease undergoing intraoperative CPB can inhibit the inflammatory response and may ameliorate the neurodevelopmental damage caused by CPB.

Nrf2 mediates the antinociceptive activity of dexmedetomidine in an acute inflammatory visceral pain rat model by activating the NF-κB sensor.

Dexmedetomidine (DEX) is a highly selective α2 adrenoceptor agonist. In this study, we evaluated the antalgic effect of DEX on acetic acid-induced acute inflammatory visceral pain (AIVP) in rats. Additionally, we evaluated the role of Nrf2 signalling in antinociception. We administered acetic acid to male Sprague Dawley rats that were treated with DEX or saline. Twenty rats were randomly classified into the following groups: normal, model, vehicle, or DEX group. Both q-RT PCR and enzyme-linked immunosorbent assay data suggested that interleukin 1β (IL-1β), tumour necrosis factor α, and IL-6 were upregulated in the spinal cord. Western blotting and q-RT PCR analyses were performed to detect the protein and mRNA expression levels of Nrf2, Keap1, and HO-1 in the spinal cord. The DEX group exhibited a significant downregulation in Nrf2/Keap1/HO-1 signal activation compared with the model group. Furthermore, we used the Nrf2-/- knockout AIVP rat model to determine the role of Nrf2 in the antinociceptive effect of DEX. We observed that the Nrf2 knockout blocked the Keap1/Nrf2/HO-1 signal transduction and partially abated the antinociceptive and the anti-inflammatory effects of DEX. Moreover, our data also indicated that DEX treatment decreased the activation and expression of nuclear factor (NF)-κB. However, Nrf2 silencing restored the expression of NF-κB and its phosphorylated form to physiological levels. In summary, our results suggested that Nrf2 signalling plays an important role in the antinociceptive effect of DEX in the AIVP rat model and that Nrf2 exerts its function by enhancing the activation of the NF-κB sensor. SIGNIFICANCE OF THE STUDY: Currently, using the behavioural parameters is not adequate for the diagnosis of AIVP, and there are no studies that have investigated the role and the mechanism of DEX in ameliorating visceral pain. In this study, we demonstrated that acetic acid stimulation in rats induces AIVP. Additionally, the administration of DEX inhibited the acute inflammation response and decreased the visceromotor reaction (behavioural) to algesia. Further, DEX inhibited the Keap1/Nrf2 pathway, which was activated by acetic acid treatment. We suggest that suppressing the inflammatory response could partially regulate the antinociceptive effect of DEX through Nrf2-mediated NF-κB activation associated with AIVP.

Effects of Dexmedetomidine on the RhoA /ROCK/ Nox4 Signaling Pathway in Renal Fibrosis of Diabetic Rats.

ObjectiveTo investigate the effects and mechanisms of dexmedetomidine (Dex) on model rats of diabetic nephropathy (DN).MethodsRats were divided into NC, model, Dex-L (1μg/ kg), Dex-M (5μg/kg) and Dex-H (10μg/kg) groups. Rats in all groups except in the NC group were injected with streptozotocin (STZ) combined with right nephrectomy. Rats in Dex (1, 5 and 10μg/kg) groups received gavage with Dex (1, 5 and 10μg/kg). After 4 weeks, rats were sacrificed and kidneys were collected. HE staining was performed for a renal injury. Masson staining was applied to detect the fibrotic accumulation in rat kidney. Radioimmunoassay was used to test the renal function. Immunohistochemical method was used to detect protein expressions of RhoA, p-MYPT and Nox4 in rat kidney.ResultsCompared with the NC group, the levels of urine microalbumin in protein, α1-MG and β2-MG, renal fibrotic accumulation, RhoA, p-MYPT, Nox4 and α-SMA in model group increased significantly (P＜0.001, respectively). Compared with the model group, Dex low, medium and high groups improved the deposition of renal fiber in rats, inhibited the expression levels of microalbumin, α1-MG and β2-MG in urine and decreased expression of RhoA, p-MYPT, Nox4 and α-SMA proteins (P＜0.05, P＜0.01).ConclusionDex is possible to inhibit the expression of α-SMA and renal fibrous substance deposition in rat kidney via RhoA/ROCK/Nox4 signaling pathway, thereby reducing early kidney damage in model rats.

Upregulation of GLT-1 via PI3K/Akt Pathway Contributes to Neuroprotection Induced by Dexmedetomidine.

Perioperative ischemic stroke usually leads to neurological dysfunction caused by neuron death. During the ischemic condition, excitotoxity due to extracellular glutamate accumulation is a main mechanism of neuron damage. The clearance of glutamate mainly depends on glutamate transporter-1 (GLT-1) which is expressed in astrocytes. Dexmedetomidine, an α2 adrenergic receptor agonist, is proved to induce neuroprotection. This study was set out to investigate the glutamate-related mechanism involved in the neuroprotective effect of dexmedetomidine. Middle cerebral artery occlusion (MCAO) was used as a model of ischemic stroke in our study. We determined Neurological deficit scores (NDS) and Magnetic resonance imaging (MRI) at three points (2, 6, and 24 h) after middle cerebral artery occlusion (MCAO) to evaluate the neuroprotective effect of dexmedetomidine. Besides, we performed western blot (6 and 24 h after MACO) and immunofluorescent staining (24 h after MCAO) to observe the expression of GLT-1. The effect and mechanism of dexmedetomidine on GLT-1 in primary cultured astrocytes were investigated using western blot and RT-PCR. Our results showed that pretreatment with dexmedetomidine improved NDS and reduced infarct volume as well as upregulating GLT-1 expression. Furthermore, using Atipamezole and LY294002, we found that dexmedetomidine significantly increased GLT-1 levels in astrocytes via activating α2 adrenergic receptor and PI3K/AKT pathway both in vitro and in vivo study. Overall, our present study indicated that dexmedetomidine had neuroprotective effects on ischemia stroke and upregulation of GLT-1 levels by PI3K/AKT dependent pathway might be the potential mechanism.

Intervention and Mechanism of Dexmedetomidine on A549 Cells Injured by Hypoxia/Reoxygenation

Objective: To investigate the effect and mechanism of dexmedetomidine (DEX) on hypoxia /reoxygenation (H/R) injury of A549 cells.&#x0D; Methods: A549 cells were cultured and randomly divided into four groups (n=10): Normoxic group;DEX group; H/R injury group;H/R injury+DEX intervention group. Observe the morphological changes of cells; Cell viability was detected by cck-8 assay. TUNEL assay was used to detect apoptosis index (AI).Expressions of GRP78, CHOP, JNK, caspase-12, caspase-3 proteins and mRNA were detected by Western Blot and RT-PCR;Detect the activity of caspase-3.&#x0D; Results: Compared with the H group, the OD value and AI value in the HD group were significantly up-regulated, apoptotic cells were significantly decreased, the expressions of CHOP, caspase-12, p-JNK and caspase-3 proteins and mRNA were significantly decreased, the GRP78 protein and mRNA increased, and the caspase-3 activity was significantly decreased, the differences were statistically significant (P&lt;0.01).&#x0D; Conclusion: Dexmedetomidine has a protective effect on A549 cells after H/R injury, which may be related to its inhibition of apoptosis induced by excessive endoplasmic reticulm stress.&#x0D; Keywords: Dexmedetomidine; Hypoxia/Reoxygenationinjury;Apoptosis;Endoplasmicreticulm stress.

Dexmedetomidine relieves neuropathic pain by inhibiting hyperpolarization-activated cyclic nucleotide-gated currents in dorsal root ganglia neurons.

This study was designed to examine the effect and mechanism of dexmedetomidine (Dex) on neuropathic pain (NP). The NP model was established by performing chronic sciatic nerve constriction injury (CCI). Seven days after CCI surgery, the rats were injected intraperitoneally with Dex, ZD7288 (an HCN channel inhibitor), and saline, respectively. The paw withdrawal threshold to mechanical stimulation and the thermal withdrawal latency tests were performed. After administration, the L4, L5 dorsal root ganglia (DRG) neurons of rats were isolated. In addition, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels subtype plasmids were transfected into human embryonic kidney (HEK)293 cells. Whole-cell clamp recordings were used to examine the properties of HCN currents (Ih) expressed in HEK293 cells and DRG neurons. After surgery, the paw withdrawal threshold to mechanical stimulation and thermal withdrawal latency were reduced, the HCN currents (Ih) amplitude of DRG neurons was increased, and the semiactivated voltage (V1/2) value was decreased in CCI rats (P<0.05). CCI rats treated with Dex or ZD7288 had reduced mechanical and thermal hyperalgesia. The Ih amplitude was lower and the V1/2 value was increased in DRG neurons in CCI rats treated with Dex or ZD7288 (P<0.05). In addition, Dex inhibited HCN1 and HCN2 currents in HEK293 cells; caused a decrease in maximal currents, an increase in the inhibition rate of Ih, and a negative shift in V1/2 (P<0.05). Taken together, our finding suggested that Dex alleviates NP and the effect is likely because of the inhibition of HCN currents.

Effect and mechanism of dexmedetomidine on lungs in patients of sepsis complicated with acute respiratory distress syndrome

To investigate the mechanisms of protective effects of dexmedetomidine on lungs in patients of sepsis complicated with acute respiratory distress syndrome (ARDS). The adult patients with sepsis complicated with ARDS, the oxygenation index (PaO2/FiO2) was 150-200 mmHg (1 mmHg = 0.133 kPa), acute physiology and chronic health evaluation II (APACHE II) score was 10-20, need mechanical ventilation (MV) treatment > 72 hours, and admitted to intensive care unit (ICU) of the First Affiliated Hospital of Guangxi Medical University from September 2013 to June 2017 were enrolled. According to the random number table method, the patients were divided into three groups (n = 80): no sedation group, propofol group (0.3-4.0 mg×kg-1×h-1) and dexmedetomidine group (0.2-0.7 μg×kg-1×h-1). The three groups were adequately analgesic treated with remifentanil. The sedation target was -1-0 of Richmond agitation-sedation score (RASS). The levels of interlenkin-6 (IL-6) and tumor necrosis factor-α (INF-α) were determined by enzyme linked immunosorbent assay (ELISA) before sedation, and 24, 48, 72 hours after sedation. The expressions of inflammatory signaling proteins in bronchoalveolar lavage fluid (BALF) were determined by Western Blot before sedation and 72 hours after sedation. There were no significant changes for inflammatory factors in serum, and inflammatory signaling proteins and anti-apoptotic signaling proteins in alveolar exfoliated cells in no sedation group. The levels of IL-6 and TNF-α in serum and the expressions of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and phosphorylated c-Jun N-terminal kinase (p-JNK) in alveolar cells in propofol group and dexmedetomidine group were all significantly reduced after sedation, moreover, it was more significantly in the dexmedetomidine group compared with propofol group [48 hours: TNF-α (ng/L) was 153.76±29.16 vs. 179.82±30.28; 72 hours: IL-6 (ng/L) was 272.18±42.76 vs. 304.49±44.93, TNF-α (ng/L) was 102.18±30.25 vs. 140.28±28.92, TLR4 (IA value) was 0.288±0.034 vs. 0.648±0.029, MyD88 (IA value): 0.356±0.030 vs. 0.752±0.044, p-JNK (IA value): 0.256±0.027 vs. 0.303±0.034, all P < 0.05]. The expression of p-Akt in alveolar cells in propofol group and dexmedetomidine group was all significant increased after sedation, moreover, it was more significantly in the dexmedetomidine group compared with propofol group (IA value: 1.032±0.030 vs. 0.743±0.028, P < 0.05). Dexmedetomidine exerts the protective effects on lungs in patients of sepsis complicated with ARDS through the TLR4-MyD88-JNK signaling pathway.

Dexmedetomidine reduces the neuronal apoptosis related to cardiopulmonary bypass by inhibiting activation of the JAK2-STAT3 pathway.

Cardiopulmonary bypass (CPB) constitutes one of the primary methodologies pertaining to cardiac surgery. However, this form of surgery can cause damage to the body. Many studies have reported that dexmedetomidine confers cerebral protection. In this study, we aimed to investigate the effect and mechanism of dexmedetomidine on neuronal apoptosis caused by CPB. Here, rats were treated with different doses of dexmedetomidine by intravenous infusion 2 hours after CPB. We observed that dexmedetomidine treatment to rats reduces the S100β, NSE levels in plasma, and neuronal apoptosis following CPB in a dose-dependent manner. Furthermore, we observed that the beneficial effect of dexmedetomidine treatment following CPB was associated with a reduction in IL6, an inflammatory cytokine in plasma and cortex. Our results suggest that dexmedetomidine provides neuroprotective effects by inhibiting inflammation and reducing neuronal apoptosis. There was a correlation between the protective effect on the brain and the dose of dexmedetomidine. In addition, dexmedetomidine administration inhibits phosphorylation of JAK2 and STAT3 proteins in the hippocampus of rats 2 hours after CPB. Therefore, we speculate that the JAK2–STAT3 pathway plays an important role in the neuroprotective effects of dexmedetomidine following brain injury induced by CPB.

Effects and mechanism of dexmedetomidine on neuronal cell injury induced by hypoxia-ischemia

BackgroundThe present study aims to investigate the protective effects of dexmedetomidine (DMED) on hypoxia ischemia injury induced by oxygen and glucose deprivation (OGD) in PC12 and primary neuronal cells.MethodsPC12 cells exposed to OGD was used to establish ischemia model. The OGD-induced cell injury was evaluated by alterations of cell viability, apoptosis and expressions of apoptosis-associated proteins. Oxidative stress and expressions of neurotrophic factors after OGD and DMED treatments were also explored. The activation of possible involved signaling pathways were studied after OGD and DMED treatments, along with the addition of inhibitors of these pathways. Finally, the effects of DMED on primary neuronal cells were verified according to the alterations of inflammatory cytokines release and oxidative stress.ResultsDMED obviously increased cell viability and reduced cell apoptosis as well as ratio of Bax/Bcl-2 in OGD-treated PC12 cells. Then, the OGD-induced changes of LDH, MDA, SOD and GSH-Px as well as decreases of neurotrophic factors were all ameliorated by DMED treatment. Key kinases in Notch/NF-κB signaling pathway were up-regulated by OGD, whereas the up-regulations were decreased by DMED. In addition, inhibitor of Notch or NF-κB could augment the effects of DMED on OGD-induced cell injury. Finally, the protective effects of DMED were verified in primary neuronal cells.ConclusionDMED had protective effect on OGD-induced PC12 cell injury, depending on its anti-apoptotic, anti-oxidative activity and the inhibition of Notch/NF-κB activation. Our findings suggested that DMED could be used as a potential therapeutic drug for cerebral ischemia.