Dexmedetomidine attenuates P2X4 and NLRP3 expression in the spine of rats with diabetic neuropathic pain

Abstract Purpose: To evaluate the effects of Dexmedetomidine (Dex) on spinal pathology and inflammatory factor in a rat model of Diabetic neuropathic pain (DNP). Methods: The rats were divided into 3 groups (eight in each group): normal group (N group), diabetic neuropathic pain model group (DNP group), and DNP model with dexmedetomidine (Dex group). The rat model of diabetes was established with intraperitoneal streptozotocin (STZ) injections. Nerve cell ultrastructure was evaluated with transmission electron microscopy (TEM). The mechanical withdrawal threshold (MWT) and motor nerve conduction velocity (MNCV) tests documented that DNP rat model was characterized by a decreased pain threshold and nerve conduction velocity. Results: Dex restored the phenotype of neurocytes, reduced the extent of demyelination and improved MWT and MNCV of DNP-treated rats (P=0.01, P=0.038, respectively). The expression of three pain-and inflammation-associated factors (P2X4, NLRP3, and IL-IP) was significantly upregulated at the protein level in DNP rats, and this change was reversed by Dex administration (P=0.0022, P=0.0092, P=0.0028, respectively). Conclusion: The P2X4/NLRP3 signaling pathway is implicated in the development and presence of DNP in vivo, and Dex protects from this disorder.

Protective effect of dexmedetomidine against myocardial ischemia-reperfusion injury in rabbits

Abstract Purpose: To investigate the influence of dexmedetomidine on myocardial ischemia-reperfusion injury (IRI) in rabbits. Methods: Twenty-four New Zealand white rabbits were randomly divided into two equal-sized groups: IRI group (group IR) and dexmedetomidine group (group D). Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), left ventricular diastolic pressure (LVDP), +dp/dtmax, -dp/dtmax, and t-dp/dtmax were recorded and calculated at the following time points: before (T0) and after (T1) dexmedetomidine infusion, after 30-min ischemia (T2), and after 120-min reperfusion (T3). The levels of plasma endothelin 1 (ET-1), thromboxane A2 (TXA2), and platelet activating factor (PAF); area of myocardial infarction (MI); and no-reflow area were evaluated. Results: SBP, DBP, LVSP, LVEDP, LVDP, and +dp/dtmax at T3 were higher in group D than in group IR (P<0.05). The average no-reflow area in group IR was significantly smaller than that in group D (14±3% vs. 38±5%, P=0.0116). The ET-1, TXA2, and PAF levels at T2 and T3 were higher than those at T0 in both groups (P<0.05). Conclusion: Dexmedetomidine could reduce the magnitude of ischemic myocardial no-reflow area and protect the myocardium with ischemia-reperfusion injury.

The protective effect of dexmedetomidine in a rat ex vivo lung model of ischemia-reperfusion injury

Abstract Purpose: To investigate the effect of dexmedetomidine (Dex) in a rat ex vivo lung model of ischemia-reperfusion injury. Methods: An IL-2 ex vivo lung perfusion system was used to establish a rat ex vivo lung model of ischemia-reperfusion injury. Drugs were added to the perfusion solution for reperfusion. Lung injury was assessed by histopathological changes, airway pressure (Res), lung compliance (Compl), perfusion flow (Flow), pulmonary venous oxygen partial pressure (PaO2), and lung wet/dry (W/D) weight ratio. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), 78 kDa glucose-regulated protein (GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) were measured, respectively. Results: The introduction of Dex attenuated the post-ischemia-reperfusion lung damage and MDA level, improved lung histology, W/D ratio, lung injury scores and SOD activity. Decreased mRNA and protein levels of GRP78 and CHOP compared with the IR group were observed after Dex treatment. The effect of Dex was dosage-dependence and a high dose of Dex (10 nM) was shown to confer the strongest protective effect against lung damage (P<0.05). Yohimbine, an α2 receptor antagonist, significantly reversed the protective effect of Dex in lung tissues (P<0.05). Conclusion: Dex reduced ischemia-reperfusion injury in rat ex vivo lungs.

Effect of dexmedetomidine on acute lung injury in experimental ischemia-reperfusion model / Efeito de dexmedetomidina sobre lesão pulmonar aguda em modelo experimental de isquemia-reperfusão

Abstract Purpose: Ischemia-reperfusion injury is one of the consequences of tourniquet application for extremity surgery. The aim of the study was to establish the effect of dexmedetomidine on the acute lung injury following lower extremity experimental ischemia-reperfusion model in rats. Methods: Twenty-eight Wistar-Albino breed Rats were recruited after Ethics Committee approval and allocated into 4 groups, each with 7 subjects. Group 1 (SHAM) received only anesthesia. Group 2 (IR) had experienced 3 h of ischemia and 3 h of reperfusion using left lower extremity tourniquet after anesthesia application. Groups 3 (D-50) and 4 (D-100) had undergone the same procedures as in the Group 2, except for receiving 50 and 100 mg·kg-1, respectively, dexmedetomidine intraperitoneally 1 h before the tourniquet release. Blood samples were obtained for the analysis of tumor necrosing factor-α and interleukin-6. Pulmonary tissue samples were obtained for histological analysis. Results: No significant difference regarding blood tumor necrosing factor-α and interleukin-6 values was found among the groups, whereas pulmonary tissue injury scores revealed significant difference. Histological scores obtained from the Group 2 were significantly higher from those in the Groups 1, 3 and 4 with p-values 0.001 for each comparison. Moreover, Group 1 scores were found to be significantly lower than those in the Groups 3 and 4 with p-values 0.001 and 0.011, respectively. No significant difference was observed between the Groups 3 and 4. Conclusion: Dexmedetomidine is effective in reduction of the experimental ischemia-reperfusion induced pulmonary tissue injury in rats, formed by extremity tourniquet application.

Resumo Objetivo: A lesão de isquemia-reperfusão é uma das consequências da aplicação do torniquete em cirurgias de extremidades. O objetivo do estudo foi determinar o efeito de dexmedetomidina em lesão pulmonar aguda após modelo experimental de isquemia-reperfusão em extremidade inferior de ratos. Métodos: Vinte e oito ratos albinos Wistar foram recrutados após aprovação do Comitê de Ética e alocados em quatro grupos, cada um com sete indivíduos. O Grupo 1 (Sham) recebeu apenas anestesia. O Grupo 2 (IR) foi submetido a 3 horas de isquemia e 3 horas de reperfusão com o uso de torniquete em extremidade inferior após a aplicação da anestesia. Os grupos 3 (D-50) e 4 (D-100) foram submetidos aos mesmos procedimentos do Grupo 2, exceto por receberem 50 e 100 mg.kg-1 de dexmedetomidina, respectivamente, por via intraperitoneal uma hora antes da liberação do torniquete. Amostras de sangue foram coletadas para análise de TNF-α e Interleucina-6 (IL-6). Amostras de tecido pulmonar foram coletadas para análise histológica. Resultados: Não houve diferença significativa quanto aos valores sanguíneos de TNF-α e IL-6 entre os grupos, enquanto os escores de lesão em tecidos pulmonares revelaram diferença significativa. Os escores histológicos obtidos no Grupo 2 foram significativamente maiores do que os dos grupos 1, 3 e 4, com valores-p de 0,001 para cada comparação. Além disso, os escores do Grupo 1 foram significativamente menores do que os dos grupos 3 e 4, com valores-p de 0,001 e 0,011, respectivamente. Não houve diferença significativa entre os grupos 3 e 4. Conclusão: Dexmedetomidina mostrou eficácia na redução de lesão em tecido pulmonar induzida por isquemia-reperfusão experimental em ratos, ocasionada por aplicação de torniquete em extremidade.

Clonidine-stimulated growth hormone concentrations (cut-off values) measured by immunochemiluminescent assay (ICMA) in children and adolescents with short stature

OBJECTIVES: To establish cut-off values for growth hormone concentrations using clonidine as a secretagogue and an immunochemiluminescent assay as the method of measurement and to analyze the response time as well as the influence of gender, nutritional status and pubertal stage. METHODS: A total of 225 tests were performed in 3 patient groups, categorized as group 1 (normal), group 2 (idiopathic short stature) and group 3 (growth hormone deficiency). Among the 199 disease-free individuals, 138 were prepubertal, and 61 were pubertal. Clonidine (0.1 mg/m2) was orally administered, and the growth hormone level was measured by immunochemiluminescent assay. The growth hormone peak and the difference between the growth hormone peak and the baseline level were then analyzed. Statistical analyses were performed using Student’s t-test or the Mann-Whitney test and Kruskal-Wallis test followed by Dunn’s post hoc test. Cut-off values were determined using a receiver operating characteristic curve. RESULTS: Group 1 and group 2 had no difference in growth hormone peak, gender, body mass index standard deviation score, or pubertal stage. Group 3 exhibited a significantly lower growth hormone peak than the other groups did. The receiver operating characteristic curve demonstrated that growth hormone concentrations ≥ 3.0 ng/mL defined responsiveness to clonidine. In total, 3.02% of individuals in group 1 and group 2 were considered false positive, i.e., these children lacked growth hormone deficiency and had a peak below 3.0 ng/mL. CONCLUSION: Clonidine-stimulated growth hormone concentrations ≥3 ng/mL, as measured by immunochemiluminescent assay, suggest responsiveness to the stimulus regardless of gender, body mass index standard deviation score or pubertal stage.

Dexmedetomidine decreases the inflammatory response to myocardial surgery under mini-cardiopulmonary bypass

Cardiopulmonary bypass (CPB) with extracorporeal circulation produces changes in the immune system accompanied by an increase in proinflammatory cytokines and a decrease in anti-inflammatory cytokines. We hypothesize that dexmedetomidine (DEX) as an anesthetic adjuvant modulates the inflammatory response after coronary artery bypass graft surgery with mini-CPB. In a prospective, randomized, blind study, 12 patients (4 females and 8 males, age range 42-72) were assigned to DEX group and compared with a conventional total intravenous anesthesia (TIVA) group of 11 patients (4 females and 7 males). The endpoints used to assess inflammatory and biochemical responses to mini-CPB were plasma interleukin (IL)-1, IL-6, IL-10, interferon (INF)-γ, tumor necrosis factor (TNF)-α, C-reactive protein, creatine phosphokinase, creatine phosphokinase-MB, cardiac troponin I, cortisol, and glucose levels. These variables were determined before anesthesia, 90 min after beginning CPB, 5 h after beginning CPB, and 24 h after the end of surgery. Endpoints of oxidative stress, including thiobarbituric acid reactive species and delta-aminolevulinate dehydratase activity in erythrocytes were also determined. DEX+TIVA use was associated with a significant reduction in IL-1, IL-6, TNF-α, and INF-γ (P<0.0001) levels compared with TIVA (two-way ANOVA). In contrast, the surgery-induced increase in thiobarbituric acid reactive species was higher in the DEX+TIVA group than in the TIVA group (P<0.01; two-way ANOVA). Delta-aminolevulinate dehydratase activity was decreased after CPB (P<0.001), but there was no difference between the two groups. DEX as an adjuvant in anesthesia reduced circulating IL-1, IL-6, TNF-α, and INF-γ levels after mini-CPB. These findings indicate an interesting anti-inflammatory effect of DEX, which should be studied in different types of surgical interventions.

Brimonidine tartrate effect on retinal spreading depression depends on Müller cells / O efeito do tartarato de brimonidina sobre a depressão alastrante retiniana depende das células de Müller

Objective: Demonstrate the Brimonidine effect over Retinal Spreading Depression (SD). Brimonidine is an alpha-2–adrenergic receptor agonist, used in the management of glaucoma. Alpha2-agonists have been shown to be neuroprotective in various experimental models, however the molecular and cellular targets leading to these actions are still poorly defined. The SD of neuronal electric activity is a wave of cellular massive sustained depolarization that damages the nervous tissue. Local trauma, pressure, ischemic injuries and other chemical agents as high extracellular potassium concentration or glutamate, can trigger SD, leading to exaggerated focal electrical followed by an electrical silence. Methods: Using chicken retina as model, we performed alpha2-receptor detection by Western Blotting and Immunohistochemistry. After that we obtained electrical signals of SD by microelectrodes on retina in the absence or presence of Brimonidine. For in vivo visualization we observed retina with optical coherence tomography on normal state, with SD passing, and with SD + Brimonidine. Results: Our data demonstrated that: (1) alpha2-adrenergic receptors are present in Müller cells, (2) the treatment with Brimonidine decreases the SD‘s velocity as well as the voltage of SD waves and (3) OCT revealed that SD creates a hyper reflectance at inner plexiform layer, but on retinal treatment with brimonidine, SD was not visualized. Conclusions: Our study about brimonidine possible pathways of neuroprotection we observed it reduces SD (a neuronal damage wave), identified a new cellular target – the Müller cells, as well as, firstly demonstrated SD on OCT, showing that the inner plexiform layer is the main optically affected layer on SD. .

Objetivo: Demonstrar o efeito do Tartarato de Brimonidina, um alfa2-agonista usado no manejo do glaucoma, sobre a depressão alastrante (DA) retiniana. Esses agonistas têm demonstrado ser neuroprotetores em vários modelos experimentais, contudo seus alvos celulares e moleculares continuam indefinidos. A DA da atividade elétrica neuronal é uma onda de despolarização celular massiva e sustentada que leva ao dano no tecido nervoso. Trauma local, pressão, isquemia e outros agentes químicos como o aumento do potássio extracelular e o glutamato podem disparar a DA, levando a uma atividade elétrica exagerada seguida de silêncio elétrico. Métodos: Usando a retina de pinto como modelo, realizamos a detecção do alfa2-receptor por Western Blotting e ensaio Imunohistoquímico. Após isso, obtivemos os sinais elétricos da DA através de microeletrodos inseridos na retina durante sua passagem na presença ou ausência de Brimonidina. Para visualização do tecido utilizamos o tomógrafo de coerência optica (OCT), analisando como é a retina no seu estado de repouso, durante a passagem da DA, e a DA + brimonidina. Resultados: Nossos dados demonstraram que: (1) os receptores alfa adrenérgicos presentes na retina são do subtipo-2A e estão localizados nas células de Müller; (2) o tratamento com Brimonidina diminui a velocidade e a voltagem da onda de DA; (3) A OCT demonstrou que a DA retiniana possui um sinal óptico de maior reflectância na camada plexiforme interna, fato não observado quando foi associada à Brimonidina. Conclusão: A Brimonidina foi capaz de reduzir a DA (uma onda de lesão neuronal) e identificamos um novo possível alvo celular – a célula de Müller e demonstramos pela primeira vez uma OCT da DA, visualizando a camada plexiforme interna como a mais afetada opticamente pelo fenômeno. .

C-Jun NH2-Terminal Kinase Contributes to Dexmedetomidine-Induced Contraction in Isolated Rat Aortic Smooth Muscle

PURPOSE: Dexmedetomidine, a full agonist of alpha2B-adrenoceptors, is used for analgesia and sedation in the intensive care units. Dexmedetomidine produces an initial transient hypertension due to the activation of post-junctional alpha2B-adrenoceptors on vascular smooth muscle cells (SMCs). The aims of this in vitro study were to identify mitogen-activated protein kinase (MAPK) isoforms that are primarily involved in full, alpha2B-adrenoceptor agonist, dexmedetomidine-induced contraction of isolated rat aortic SMCs. MATERIALS AND METHODS: Rat thoracic aortic rings without endothelium were isolated and suspended for isometric tension recording. Cumulative dexmedetomidine (10(-9) to 10(-6) M) dose-response curves were generated in the presence or absence of extracellular signal-regulated kinase (ERK) inhibitor PD 98059, p38 MAPK inhibitor SB 203580, c-Jun NH2-terminal kinase (JNK) inhibitor SP 600125, L-type calcium channel blocker (verapamil and nifedipine), and alpha2-adrenoceptor inhibitor atipamezole. Dexmedetomidine-induced phosphorylation of ERK, JNK, and p38 MAPK in rat aortic SMCs was detected using Western blotting. RESULTS: SP 600125 (10(-6) to 10(-5) M) attenuated dexmedetomidine-evoked contraction in a concentration-dependent manner, whereas PD 98059 had no effect on dexmedetomidine-induced contraction. SB 203580 (10(-5) M) attenuated dexmedetomidine-induced contraction. Dexmedetomidine-evoked contractions were both abolished by atipamezole and attenuated by verapamil and nifedipine. Dexmedetomidine induced phosphorylation of JNK and p38 MAPK in rat aortic SMCs, but did not induce phosphorylation of ERK. CONCLUSION: Dexmedetomidine-induced contraction involves a JNK- and p38 MAPK-mediated pathway downstream of alpha2-adrenoceptor stimulation in rat aortic SMCs. In addition, dexmedetomidine-induced contractions are primarily dependent on calcium influx via L-type calcium channels.

Modulation of WIN55, 212-2 state-dependent memory by alpha2-adrenergic receptors of the dorsal hippocampus

An overlapping distribution of alpha2-adrenergic receptors with cannabinoid receptors has been reported in certain brain structures such as the dorsal hippocampus. Thus, functional interactions between cannabinoid and alpha2-adrenergic systems in cognitive control seem possible. In the present study, we examine the possible role of alpha2-adrenergic receptors of the dorsal hippocampus on WIN55.212-2 state-dependent learning. Adult male Wistar rats were bilaterally implanted with chronic cannulae in the CA1 regions of their dorsal hippocampi trained in a step-down type inhibitory avoidance task and tested 24 hr after training, to measure step-down latency. Post-training or pre-test intra-CA1 administration of the cannabinoid receptor agonist, WIN 55,212-2 [0.25 and 0.5microg/rat] induced amnesia. Amnesia produced by post-training WIN55,212-2 [0.5 microg/rat] was reversed by pre-test administration of WIN55,212-2, that was due to a state-dependent effect. Pre-test intra-CA1 microinjections of clonidine [0.25, 0.5 and 1 microg/rat] or yohimbine [0.5, 0.75, and 1 MQ/rat] did not affect memory retrieval per se. Pre-test intra-CA1 administration of clonidine [0.5 and 1 micro9/rat] or clonidine [0.25, 0.5, and 1 microg/rat] with an ineffective dose of WIN 55,212-2 [0.25 microg/rat] reversed post-training WIN55,212-2 [0.5 microg/rat,intra-CA1] induced memory impairment. Pre-test intra-CA1 microinjection of yohimbine [1 microg/rat] before administration of WIN55,212-2 [0.5 microg/rat, intra-CA1], however, dose-dependently inhibited WIN55.212-2 state-dependent memory. Modulation of a2-adrenergic receptors in the dorsal hippocampal CA1 regions can influence WIN55, 212-2 induced amnesia and WIN55,212-2 state-dependent learning of an inhibitory avoidance task by pre- or post-synaptic mechanism[s]