Dual alpha(2)-adrenergic agonist and alpha(1)-adrenergic antagonist actions of dexmedetomidine on human isolated endothelium-denuded gastroepiploic arteries

Effects of intravenous lidocaine, dexmedetomidine, and their combination on IL-1, IL-6 and TNF-α in patients undergoing laparoscopic hysterectomy: a prospective, randomized controlled trial

BACKGROUND

Surgical-related inflammatory responses have negative effects on postoperative recovery. Intravenous (IV) lidocaine and dexmedetomidine inhibits the inflammatory response. We investigated whether the co-administration of lidocaine and dexmedetomidine could further alleviate inflammatory responses compared with lidocaine or dexmedetomidine alone during laparoscopic hysterectomy.

METHODS

A total of 160 patients were randomly allocated into four groups following laparoscopic hysterectomy: the control group (group C) received normal saline, the lidocaine group (group L) received lidocaine (bolus infusion of 1.5 mg/kg over 10 min, 1.5 mg/kg/h continuous infusion), the dexmedetomidine group (group D) received dexmedetomidine (bolus infusion of 0.5 μg/kg over 10 min, 0.4 μg/kg/h continuous infusion), and the lidocaine plus dexmedetomidine group (group LD) received a combination of lidocaine (bolus infusion of 1.5 mg/kg over 10 min, 1.5 mg/kg/h continuous infusion) and dexmedetomidine (bolus infusion of 0.5 μg/kg over 10 min, 0.4 μg/kg/h continuous infusion). The levels of plasma interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) at different time points were the primary outcomes. Secondary outcomes included hemodynamic variables, postoperative visual analogue scale (VAS) scores, time to first flatus, and incidence of nausea and vomiting after surgery.

RESULTS

The levels of plasma IL-1, IL-6, and TNF-α were lower in groups D and LD than in group C and were lowest in group LD at the end of the procedure and 2 h after the operation (P < 0.05). The VAS scores were decreased in groups D and LD compared with group C (P < 0.05). The heart rate (HR) was decreased at the end of the procedure and 2 h after the operation in groups D and LD compared to groups C and L (P < 0.001). The mean blood pressure (MBP) was lower at 2 h after the operation in groups L, D, and LD than in group C (P < 0.001). There was a lower incidence of postoperative nausea and vomiting (PONV) in group LD than in group C (P < 0.05).

CONCLUSIONS

The combination of lidocaine and dexmedetomidine significantly alleviated the inflammatory responses, decreased postoperative pain, and led to fewer PONV in patients undergoing laparoscopic hysterectomy.

TRIAL REGISTRATION

ClinicalTrials.gov ( NCT03276533 ), registered on August 23, 2017.

Effects of dexmedetomidine on porcine pulmonary artery vascular smooth muscle

Background

The α₂-receptor agonist dexmedetomidine (Dex) has been shown to produce sedative and analgesic effects not only with systemic administration but also when administered in the extradural space and around peripheral nerves. The effects and mechanism of action of Dex on pulmonary arteries, however, have not been determined. This study therefore aimed to investigate the effect of Dex on pulmonary arterial vascular smooth muscle by evaluating changes in isometric contraction tension. We then attempted to determine the effects of Dex on depolarization stimulation and receptor stimulation.

Methods

Endothelium-denuded porcine pulmonary arteries were sliced into 2- to 3-mm rings. We then exposed them to certain substances at various concentrations under different conditions of baseline stimulation (with KCl, adrenaline, caffeine, or histamine) and to α₂-receptor stimulants or antagonists, or α₁-receptor antagonists (imidazoline, yohimbine, rauwolscine, prazosin), and different conditions of Ca²⁺ depletion of the intracellular reservoir or extracellular stores. We measured the changes in isometric contraction tension with each addition or change in conditions.

Results

Dex enhanced the contraction induced by high-concentration KCl stimulation. Dex-induced enhancement of contraction induced by high-concentration KCl was completely suppressed by yohimbine and rauwolscine, which are α₂-receptor antagonists, but not by prazosin. Dex, imidazoline, yohimbine, and rauwolscine reduced the increases in contraction tension induced by the receptor stimulant adrenaline. Dex suppressed the adrenaline-induced increases in contraction tension after depletion of the Ca²⁺ reservoir. In the absence of extracellular Ca²⁺, Dex suppressed the adrenaline- and histamine-induced increases in contraction tension but did not affect caffeine-induced increases.

Conclusions

Dex-enhanced, high-concentration KCl-induced contraction was mediated by α₂-receptors. Adrenaline-induced contraction was suppressed by the α₂-receptor stimulant Dex and α₂-receptor antagonists yohimbine and rauwolscine, suggesting that the effect of Dex on adrenaline-induced contraction is attributable to its α₂-receptor-blocking action. Dex inhibited receptor-activated Ca²⁺ channels and phosphatidylinositol-1,4,5-triphosphate-induced Ca²⁺ release but not Ca²⁺-induced Ca²⁺ release.

Injectable Anesthesia for Mice: Combined Effects of Dexmedetomidine, Tiletamine-Zolazepam, and Butorphanol

Anesthetic protocols for murine models are varied within the literature and medetomidine has been implicated in the development of urethral plugs in male mice. Our objective was to evaluate the combination of butorphanol, dexmedetomidine, and tiletamine-zolazepam. A secondary objective was to identify which class of agent was associated with urethral obstructions in male mice. BALB/c male (n = 13) and female (n = 23) mice were assigned to dexmedetomidine and tiletamine-zolazepam with or without butorphanol or to single agent dexmedetomidine or tiletamine-zolazepam. Anesthesia was achieved in 58% (14/24) of mice without butorphanol and in 100% (24/24) of mice with butorphanol. The combination of dexmedetomidine (0.2 mg/kg), tiletamine-zolazepam (40 mg/kg), and butorphanol (3 mg/kg) resulted in an induction and anesthetic duration of 12 and 143 minutes, respectively. Urethral obstructions occurred in 66% (25/38) of trials in male mice that received dexmedetomidine with a mortality rate of 38% (5/13). Tiletamine-zolazepam, when used alone, resulted in a 0% (0/21) incidence of urethral obstructions. Combination use of dexmedetomidine, tiletamine-zolazepam, and butorphanol results in a longer and more reliable duration of anesthesia than the use of dexmedetomidine and tiletamine-zolazepam alone. Dexmedetomidine is not recommended for use in nonterminal procedures in male mice due to the high incidence of urethral obstructions and resultant high mortality rate.

Dexmedetomidine Inhibits Phenylephrine-induced Contractions via Alpha-1 Adrenoceptor Blockade and Nitric Oxide Release in Isolated Rat Aortae

The goal of this in vitro study was to examine the effect of the alpha-2 adrenoceptor agonist dexmedetomidine on phenylephrine (alpha-1 adrenoceptor agonist)-induced contraction in isolated rat aortae and to elucidate the associated cellular mechanisms, with a particular focus on alpha-1 adrenoceptor antagonism. Dexmedetomidine dose-response curves were generated in isolated endothelium-intact and endothelium-denuded rat aortae precontracted with phenylephrine or 5-hydroxytryptamine. Endothelium-denuded aortic rings were pretreated with either dexmedetomidine or the reversible alpha-1 adrenoceptor antagonist phentolamine, followed by post-treatment with the irreversible alpha-1 adrenoceptor blocker phenoxybenzamine. Control rings were treated with phenoxybenzamine alone. All rings were repeatedly washed with Krebs solution to remove all pretreatment drugs, including phenoxybenzamine, phentolamine and dexmedetomidine. Phenylephrine dose-response curves were then generated. The effect of rauwolscine on the dexmedetomidine-mediated change in phenylephrine-induced endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells was examined using western blotting. The magnitude of the dexmedetomidine-mediated inhibition of phenylephrine-induced contraction was higher in endothelium-intact aortae than in endothelium-denuded aortae or endothelium-intact aortae treated with N^ω-nitro-L-arginine methyl ester. However, dexmedetomidine did not significantly alter 5-hydroxytryptamine-induced contraction. In further experiments, prazosin attenuated dexmedetomidine-induced contraction. Additionally, pretreatment with either dexmedetomidine plus phenoxybenzamine or phentolamine plus phenoxybenzamine produced greater phenylephrine-induced contraction than phenoxybenzamine alone, suggesting that dexmedetomidine protects aortae from the alpha-1 adrenoceptor blockade induced by phenoxybenzamine. Rauwolscine attenuated the dexmedetomidine-mediated enhancement of phenylephrine-induced eNOS phosphorylation. Taken together, these results suggest that dexmedetomidine attenuates phenylephrine-induced contractions via alpha-1 adrenoceptor blockade and endothelial nitric oxide release in the isolated rat aorta.

Dexmedetomidine-Induced Contraction Involves CPI-17 Phosphorylation in Isolated Rat Aortas

Dexmedetomidine, a highly selective α-2 adrenoceptor agonist, produces vasoconstriction, which leads to transiently increased blood pressure. The goal of this study was to investigate specific protein kinases and the associated cellular signal pathways responsible for the increased calcium sensitization induced by dexmedetomidine in isolated rat aortas, with a particular focus on phosphorylation-dependent inhibitory protein of myosin phosphatase (CPI-17). The effect of Y-27632 and chelerythrine on the dexmedetomidine-induced intracellular calcium concentration ([Ca²⁺]_i) and tension were assessed using fura-2-loaded aortic strips. The effects of rauwolscine, Y-27632, chelerythrine, and ML-7 hydrochloride on the dexmedetomidine-induced phosphorylation of CPI-17 or of the 20-kDa regulatory light chain of myosin (MLC₂₀) were investigated in rat aortic vascular smooth muscle cells. The effects of rauwolscine, Y-27632, and chelerythrine on the membrane translocation of Rho-kinase and protein kinase C (PKC) phosphorylation induced by dexmedetomidine were assessed. Y-27632 and chelerythrine each reduced the slopes of the [Ca²⁺]_i-tension curves of dexmedetomidine-induced contraction, and Y-27632 more strongly reduced these slopes than did chelerythrine. Rauwolscine, Y-27632, chelerythrine, and ML-7 hydrochloride attenuated the dexmedetomidine-induced phosphorylation of CPI-17 and MLC₂₀. Taken together, these results suggest that dexmedetomidine-induced contraction involves calcium sensitization, which appears to be mediated by CPI-17 phosphorylation via Rho-kinase or PKC.

Dexmedetomidine inhibits vasoconstriction via activation of endothelial nitric oxide synthase

Despite the complex vascular effects of dexmedetomidine (DEX), its actions on human pulmonary resistance arteries remain unknown. The present study tested the hypothesis that DEX inhibits vascular tension in human pulmonary arteries through the endothelial nitric oxide synthase (eNOS) mediated production of nitric oxide (NO). Pulmonary artery segments were obtained from 62 patients who underwent lung resection. The direct effects of DEX on human pulmonary artery tension and changes in vascular tension were determined by isometric force measurements recorded on a myograph. Arterial contractions caused by increasing concentrations of serotonin with DEX in the presence or absence of L-NAME (endothelial nitric oxide synthase inhibitor), yohimbine (α₂-adrenoceptor antagonist) and indomethacin (cyclooxygenase inhibitor) as antagonists were also measured. DEX had no effect on endothelium-intact pulmonary arteries, whereas at concentrations of 10^–8~10^–6 mol/L, it elicited contractions in endothelium-denuded pulmonary arteries. DEX (0.3, 1, or 3×10^–9 mmol/L) inhibited serotonin-induced contraction in arteries with intact endothelium in a dose-dependent manner. L-NAME and yohimbine abolished DEX-induced inhibition, whereas indomethacin had no effect. No inhibitory effect was observed in endothelium-denuded pulmonary arteries. DEX-induced inhibition of vasoconstriction in human pulmonary arteries is mediated by NO production induced by the activation of endothelial α₂-adrenoceptor and nitric oxide synthase.

Dexmedetomidine preconditioning ameliorates kidney ischemia-reperfusion injury

Kidney ischemia-reperfusion (I/R) injury is a common cause of acute kidney injury. We tested whether dexmedetomidine (Dex), an alpha2 adrenoceptor (α2-AR) agonist, protects against kidney I/R injury. Sprague-Dawley rats were divided into four groups: (1) Sham-operated group; (2) I/R group (40 min ischemia followed by 24 h reperfusion); (3) I/R group + Dex (1 μg/kg i.v. 60 min before the surgery), (4) I/R group + Dex (10 μg/kg). The effects of Dex postconditiong (Dex 1 or 10 μg/kg i.v. after reperfusion) as well as the effects of peripheral α2-AR agonism with fadolmidine were also examined. Hemodynamic effects were monitored, renal function measured, and acute tubular damage along with monocyte/macrophage infiltration scored. Kidney protein kinase B, toll like receptor 4, light chain 3B, p38 mitogen-activated protein kinase (p38 MAPK), sirtuin 1, adenosine monophosphate kinase (AMPK), and endothelial nitric oxide synthase (eNOS) expressions were measured, and kidney transciptome profiles analyzed. Dex preconditioning, but not postconditioning, attenuated I/R injury-induced renal dysfunction, acute tubular necrosis and inflammatory response. Neither pre- nor postconditioning with fadolmidine protected kidneys. Dex decreased blood pressure more than fadolmidine, ameliorated I/R-induced impairment of autophagy and increased renal p38 and eNOS expressions. Dex downregulated 245 and upregulated 61 genes representing 17 enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, in particular, integrin pathway and CD44. Ingenuity analysis revealed inhibition of Rac and nuclear factor (erythroid-derived 2)-like 2 pathways, whereas aryl hydrocarbon receptor (AHR) pathway was activated. Dex preconditioning ameliorates kidney I/R injury and inflammatory response, at least in part, through p38-CD44-pathway and possibly also through ischemic preconditioning.

Vasodilatory mechanisms of beta receptor blockade

Beta-blockers are widely prescribed for the treatment of a variety of cardiovascular pathologies. Compared to traditional beta-adrenergic antagonists, beta-blockers of the new generation exhibit ancillary properties such as vasodilation through different mechanisms. This translates into a more favorable hemodynamic profile. The relative affinities of beta-adrenoreceptor antagonists towards the three beta-adrenoreceptor isotypes matter for predicting their functional impact on vasomotor control. This review will focus on the mechanisms underlying beta-blocker-evoked vasorelaxation with a specific emphasis on agonist properties of beta(3)-adrenergic receptors.

Vascular reactivity in human arteries: from experimental study to clinical application

The principal function of VSM cells in mature animals is contraction. The endothelium is now recognized to elaborate various vasoactive factors and to play a critical part in regulation of vascular tone. Many circulating mediators and hormones have effects on vascular tone that are mediated via multiple receptors. Vasoactive agents also exert their effects on tissues by acting on one or more processes in the contraction–relaxation cycle in VSM. In humans,systemic, pulmonary, and various organ circulation(s) are maintained by an intricate and complex cardiovascular system. We expect future studies to clarify the sophisticated but complex mechanisms of VSM in humans.

Dexmedetomidine does not produce vasocontraction on human isolated gastroepiploic artery

Background

Recently, the addition of dexmedetomidine to sedation regimens after cardiac surgery had been reported and there is a possibility that dexmedetomidine can cause vasoconstriction. Vasopressin has been used as a prophylactic treatment for refractory vasodilatory shock during coronary artery bypass graft (CABG). Also, vasopressin may play an important role in initiating spasms at the graft artery. Here we evaluate the direct effect of dexmedetomidine on isolated human gastroepiploic arteries and the synergistic effect of dexmedetomidine and vasopressin.

Methods

Discarded gastroepiploic arteries from elective subtotal gastrectomy (n = 10) were used in this study. We measured the level of contraction in isolated human gastroepiploic arteries induced by increasing concentrations of dexmedetomidine (10^-10 to 10^-6 M) with or without vasopressin (10^-10, 10^-9 M). Arterial contractions caused by increasing concentrations of vasopressin (10^-10 to 10^-7.5 M) with or without dexmedetomidine (10^-9, 10^-7 M) were also measured in the tissue samples.

Results

Supraclinical concentrations of dexmedetomidine elicited contractions at concentrations of 10^-7 M and 10^-6 M (P < 0.05 versus resting tension). The same concentrations of dexmedetomidine (10^-7, 10^-6 M) significantly enhanced vasopressin-induced contractions (P < 0.05 versus vasopressin-induced contraction). Vasopressin produced concentration-dependent contractions and vasopressin (10^-10, 10^-9.5, 10^-9 M) also increased the intensity of dexmedetomidine (10^-7 M) induced contractions.

Conclusions

There was a synergistic effect between supraclinical doses of dexmedetomidine and vasopressin on the degree of contraction in isolated human gastroepiploic arteries. However, a sedative dose of dexmedetomidine (clinical dose: 0.2-0.7 µg/kg/hr, plasma concentration: 0.36-1.25 ng/ml) did not enhance vasopressin induced-contraction in isolated human gastroepiploic arteries.

Independent regulation of α1 and α2 adrenergic receptor-mediated vasoconstriction in vivo

BACKGROUND

Vascular α1 and α2 adrenergic receptors mediate vasoconstriction and are major determinants of peripheral vascular tone. There is a wide variability in vasoconstrictor sensitivity to α1 and α2 adrenergic receptor agonists among individuals. In previous studies, this variability was not explained by identified α1 and α2 adrenergic receptor genetic variants. Thus, we hypothesized that adrenergic vasoconstrictor sensitivity is determined by shared constrictor mechanisms downstream of the individual receptors and that α1 and α2 adrenergic receptor-mediated vasoconstrictor sensitivity would therefore be correlated.

METHODS

Dorsal hand vein responses to increasing doses of the α1 adrenergic receptor agonist phenylephrine (12-12 000 ng/min) and the α2 adrenergic receptor agonist dexmedetomidine (0.01-100 ng/min) were measured in healthy individuals using a linear variable differential transformer. From individual dose-response curves, we calculated the dose of phenylephrine and dexmedetomidine that produced 50% (ED50) of maximum venoconstriction (Emax) for each patient. We examined the correlation between phenylephrine and dexmedetomidine ED50 and Emax before and after adjustment for covariates (age, sex, ethnicity, BMI, blood pressure, heart rate, and baseline plasma norepinephrine concentrations).

RESULTS

In 62 patients (36 men, 34 African-American, 28 whites), the median ED50 for dexmedetomidine was 1.32 ng/min [interquartile range (IQR) 0.45-5.37 ng/min] and for phenylephrine 177.8 ng/min (IQR 40.7-436.5 ng/min). The Emax for phenylephrine was 90.8% (82.2-99.6%) and for dexmedetomidine 80.0% (64.7-95.2%). There was no correlation between individual sensitivities (ED50) to phenylephrine and dexmedetomidine, before and after adjustment for covariates (P > 0.30).

CONCLUSION

Both phenylephrine and dexmedetomidine produce strong venoconstriction in the dorsal hand vein; however, there is no significant correlation between vascular sensitivity to an α1 and α2 adrenergic receptor agonist. These findings suggest the independent regulation of vascular α1 and α2 adrenergic receptor-mediated responses.

c-Jun NH₂-terminal kinase contributes to dexmedetomidine-induced contraction in isolated rat aortic smooth muscle

PURPOSE

Dexmedetomidine, a full agonist of α2B-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 α2B-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, α2B-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 α₂-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 α₂-adrenoceptor stimulation in rat aortic SMCs. In addition, dexmedetomidine-induced contractions are primarily dependent on calcium influx via L-type calcium channels.