Tumour immune rejection triggered by activation of α2-adrenergic receptors.

Immunotherapy based on immunecheckpoint blockade (ICB) using antibodies induces rejection of tumours and brings clinical benefit in patients with various cancer types1. However, tumours often resist immune rejection. Ongoing efforts trying to increase tumour response rates are based on combinations of ICB with compounds that aim to reduce immunosuppression in the tumour microenvironment but usually have little effect when used as monotherapies2,3. Here we show that agonists of α2-adrenergic receptors (α2-AR) have very strong anti-tumour activity when used as monotherapies in multiple immunocompetent tumour models, including ICB-resistant models, but not in immunodeficient models. We also observed marked effects in human tumour xenografts implanted in mice reconstituted with human lymphocytes. The anti-tumour effects of α2-AR agonists were reverted by α2-AR antagonists, and were absent in Adra2a-knockout (encoding α2a-AR) mice, demonstrating on-target action exerted on host cells, not tumour cells. Tumours from treated mice contained increased infiltrating T lymphocytes and reduced myeloid suppressor cells, which were more apoptotic. Single-cell RNA-sequencing analysis revealed upregulation of innate and adaptive immune response pathways in macrophages and T cells. To exert their anti-tumour effects, α2-AR agonists required CD4+ T lymphocytes, CD8+ T lymphocytes and macrophages. Reconstitution studies in Adra2a-knockout mice indicated that the agonists acted directly on macrophages, increasing their ability to stimulate T lymphocytes. Our results indicate that α2-AR agonists, some of which are available clinically, could substantially improve the clinical efficacy of cancer immunotherapy.

Resolving neuroinflammatory and social deficits in ASD model mice: Dexmedetomidine downregulates NF-κB/IL-6 pathway via α2AR.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that severely affects individuals' daily life and social development. Unfortunately, there are currently no effective treatments for ASD. Dexmedetomidine (DEX) is a selective agonist of α2 adrenergic receptor (α2AR) and is widely used as a first-line medication for sedation and hypnosis in clinical practice. In recent years, there have been reports suggesting its potential positive effects on improving emotional and cognitive functions. However, whether dexmedetomidine has therapeutic effects on the core symptoms of ASD, namely social deficits and repetitive behaviors, remains to be investigated. In the present study, we employed various behavioral tests to assess the phenotypes of animals, including the three-chamber, self-grooming, marble burying, open field, and elevated plus maze. Additionally, electrophysiological recordings, western blotting, qPCR were mainly used to investigate and validate the potential mechanisms underlying the role of dexmedetomidine. We found that intraperitoneal injection of dexmedetomidine in ASD model mice-BTBR T+ Itpr3tf/J (BTBR) mice could adaptively improve their social deficits. Further, we observed a significant reduction in c-Fos positive signals and interleukin-6 (IL-6) expression level in the prelimbic cortex (PrL) of the BTBR mice treated with dexmedetomidine. Enhancing or inhibiting the action of IL-6 directly affects the social behavior of BTBR mice. Mechanistically, we have found that NF-κB p65 is a key pathway regulating IL-6 expression in the PrL region. In addition, we have confirmed that the α2AR acts as a receptor switch mediating the beneficial effects of dexmedetomidine in improving social deficits. This study provides the first evidence of the beneficial effects of dexmedetomidine on core symptoms of ASD and offers a theoretical basis and potential therapeutic approach for the clinical treatment of ASD.

The effects of dexmedetomidine on intraoperative neurophysiologic monitoring modalities during corrective scoliosis surgery in pediatric patients: A systematic review.

BACKGROUND: During scoliosis surgery, motor evoked potentials (MEP), and somatosensory evoked potentials (SSEP) have been reported to be affected by the use of higher doses of anesthetic agents. Dexmedetomidine, a sympatholytic agent, an alpha-2 receptor agonist, has been used as an adjunctive agent to lower anesthetic dose. However, there is conflicting evidence regarding the effects of dexmedetomidine on the intraoperative neurophysiological monitoring of MEP and SSEP during surgery, particularly among pediatric patients. OBJECTIVES: This systematic review aimed to determine whether, during spinal fusion surgery in pediatric patients with scoliosis, dexmedetomidine alters MEP amplitude or SSEP latency and amplitude and, if so, whether different doses of dexmedetomidine display different effects (PROSPERO registration number CRD42022300562). METHODS: We searched PubMed, Scopus, and Cochrane Library on January 1, 2022 and included randomized controlled trials, observational cohort and case-control studies and case series investigating dexmedetomidine in the population of interest and comparing against a standardized anesthesia regimen without dexmedetomidine or comparing multiple doses of dexmedetomidine. Animal and in vitro studies and conference abstracts were excluded. RESULTS: We found substantial heterogeneity in the risk of bias (per Cochrane-preferred tools) of the included articles (n = 5); results are summarized without meta-analysis. Articles with the lowest risk of bias indicated that dexmedetomidine was associated with MEP loss and that higher doses of dexmedetomidine increased risk. In contrast, articles reporting no association between dexmedetomidine and MEP loss suffered from higher risk of bias, including suspected or confirmed problems with confounding, outcome measurement, participant selection, results reporting, and lack of statistical transparency and power. CONCLUSION: Given the limitations of the studies available in the literature, it would be advisable to conduct rigorous randomized controlled trials with larger sample sizes to assess the effects of dexmedetomidine use of in scoliosis surgery in pediatric patients.

A Comparative Study of the Antiemetic Effects of α2-Adrenergic Receptor Agonists Clonidine and Dexmedetomidine against Diverse Emetogens in the Least Shrew (Cryptotis parva) Model of Emesis.

In contrast to cats and dogs, here we report that the α2-adrenergic receptor antagonist yohimbine is emetic and corresponding agonists clonidine and dexmedetomidine behave as antiemetics in the least shrew model of vomiting. Yohimbine (0, 0.5, 0.75, 1, 1.5, 2, and 3 mg/kg, i.p.) caused vomiting in shrews in a bell-shaped and dose-dependent manner, with a maximum frequency (0.85 ± 0.22) at 1 mg/kg, which was accompanied by a key central contribution as indicated by increased expression of c-fos, serotonin and substance P release in the shrew brainstem emetic nuclei. Our comparative study in shrews demonstrates that clonidine (0, 0.1, 1, 5, and 10 mg/kg, i.p.) and dexmedetomidine (0, 0.01, 0.05, and 0.1 mg/kg, i.p.) not only suppress yohimbine (1 mg/kg, i.p.)-evoked vomiting in a dose-dependent manner, but also display broad-spectrum antiemetic effects against diverse well-known emetogens, including 2-Methyl-5-HT, GR73632, McN-A-343, quinpirole, FPL64176, SR141716A, thapsigargin, rolipram, and ZD7288. The antiemetic inhibitory ID50 values of dexmedetomidine against the evoked emetogens are much lower than those of clonidine. At its antiemetic doses, clonidine decreased shrews' locomotor activity parameters (distance moved and rearing), whereas dexmedetomidine did not do so. The results suggest that dexmedetomidine represents a better candidate for antiemetic potential with advantages over clonidine.

Effect of constant rate infusion of detomidine with and without vatinoxan on blood glucose and insulin concentrations in horses.

OBJECTIVE: To assess the effects of an α2-adrenoceptor agonist (detomidine) constant rate infusion (CRI) with and without an α2-adrenoceptor antagonist (vatinoxan) CRI on blood insulin and glucose concentrations, heart rate, intestinal borborygmi, and sedation during and after infusion in horses. STUDY DESIGN: Randomized, blinded, crossover, experimental study. ANIMALS: A total of nine healthy, adult Finnhorse mares. METHODS: Horses were treated with an intravenous (IV) detomidine loading dose (0.01 mg kg-1), followed by CRI (0.015 mg kg-1 hour-1), and the same doses of detomidine combined with an IV vatinoxan loading dose (0.15 mg kg-1), followed by CRI (detomidine and vatinoxan; 0.05 mg kg-1 hour-1) with an 18 day washout period. Infusion time was 60 minutes and horses were monitored for 240 minutes after the infusion. Heart rate, borborygmi score and sedation were assessed, and blood glucose, insulin and triglyceride concentrations were measured. Data were analyzed using repeated measures ancova and Wilcoxon signed-rank tests. Values of p < 0.05 were considered statistically significant. RESULTS: Insulin concentration decreased during (median nadir 1.7, range 0.0-2.9 µIU mL-1 at 60 minutes, p < 0.0001) and increased after detomidine CRI (median 36.6, range 11.7-78.4 µIU mL-1 at 180 minutes, p = 0.0001) significantly compared with detomidine and vatinoxan CRI. A significant elevation of blood glucose (peak 11.5 ± 1.6 mmol L-1 at 60 minutes, p < 0.0001) was detected during detomidine CRI. Vatinoxan alleviated the insulin changes and abolished the significant increase in blood glucose. Vatinoxan alleviated the decrease in heart rate (p = 0.0001) during detomidine infusion. No significant differences were detected in sedation scores between treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Vatinoxan attenuated the negative adverse effects of detomidine CRI and thus is potentially beneficial when used in combination with an α2-adrenoceptor agonist CRI in horses.

Dexmedetomidine alleviates acute postoperative anxiety in rats by suppressing the NF-ĸB pathway.

Evidence suggests that surgical procedures can effect the central nervous system and lead to changes in mood and behavior, rarely understood about the role of acute inflammation in promoting acute anxiety postoperatively. This study was designed to explore the possible mechanism of dexmedetomidine (DEX, a2-adrenergic receptor agonist) for reducing acute postoperative anxiety, which may be related to the activation of nuclear factor kappa B (NF-κB) and downstream signal pathway in the hippocampus. Experiments were conducted with rat, the elevated plus-maze and open field test were performed to evaluate anxiety-like behavior. Inhibit DEX with Atipamezole (AT, α2-adrenergic receptor antagonist) and inhibit NF-κB with Pyrrolidinedithiocarbamate (PDTC, inhibit phosphorylation of IκB, prevent the activation of NF-κB), the level of interleukin-6 (IL-6), IL-1ß, IL-10 and Tumor necrosis factor-α (TNF-α); the nuclear translocation of NF-κB in the hippocampus and anxiety-like behavior were measured. Rats exhibited anxiety-like behavior at 6h and 12h after surgery. Preoperative administration of DEX significantly alleviated postoperative anxiety-like behavior. DEX premedication inhibited the nuclear translocation of NF-κB alleviate acute postoperative anxiety. These findings are the first to show that acute postoperative anxiety may be related to NF-κB nuclear translocation in the hippocampus in rats, which can be alleviated by DEX premedication.

Dexmedetomidine in Psychiatry: Repurposing of its Fast-Acting Anxiolytic, Analgesic and Sleep Modulating Properties.

Drug repurposing is a strategy to identify new indications for already approved drugs. A recent successful example in psychiatry is ketamine, an anesthetic drug developed in the 1960s, now approved and clinically used as a fast-acting antidepressant. Here, we describe the potential of dexmedetomidine as a psychopharmacological repurposing candidate. This α2-adrenoceptor agonist is approved in the US and Europe for procedural sedation in intensive care. It has shown fast-acting inhibitory effects on perioperative stress-related pathologies, including psychomotor agitation, hyperalgesia, and neuroinflammatory overdrive, proving potentially useful in clinical psychiatry. We offer an overview of the pharmacological profile and effects of dexmedetomidine with potential utility for the treatment of neuropsychiatric symptoms. Dexmedetomidine exerts fast-acting and robust sedation, anxiolytic, analgesic, sleep-modulating, and anti-inflammatory effects. Moreover, the drug prevents postoperative agitation and delirium, possibly via neuroprotective mechanisms. While evidence in animals and humans supports these properties, larger controlled trials in clinical samples are generally scarce, and systematic studies with psychiatric patients do not exist. In conclusion, dexmedetomidine is a promising candidate for an experimental treatment targeting stress-related pathologies common in neuropsychiatric disorders such as depression, anxiety disorders, and posttraumatic stress disorder. First small proof-of-concept studies and then larger controlled clinical trials are warranted in psychiatric populations to test the feasibility and efficacy of dexmedetomidine in these conditions.

Effects of dexmedetomidine on oxygenation and inflammatory factors in patients undergoing uvulopalatopharyngoplasty: a prospective, randomized, placebo-controlled trial.

PURPOSE: Uvulopalatopharyngoplasty (UPPP) can aggravate lung inflammatory reactions in patients with obstructive sleep apnoea syndrome (OSAS). Dexmedetomidine (Dex) is a selective α-2 adrenoreceptor agonist that can alleviate lung injury. This study was designed to investigate the effects of Dex on oxygenation and inflammatory factors in patients undergoing UPPP in the early perioperative period. METHODS: Patients with OSAS undergoing UPPP were randomly allocated to the Dex Group or Control Group. Arterial blood gas analyses were performed, and the respiratory index (RI) and oxygenation index (OI) were calculated upon entering the operating room (T0) and immediately after surgery (T3). The inflammatory factors tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) were measured at T0 and T3. RESULTS: A total of 44 patients with OSAS were randomized. There was no significant difference in basic patient characteristics between the two groups. The preoperative RI and OI were not significantly different between the two groups, but they were altered immediately after surgery relative to the corresponding preoperative value (p < 0.05). Compared with the Control Group, the RI was significantly lower at T3 in the Dex Group (p < 0.001). However, there was no significant difference in the OI between the two groups (p = 0.128). The inflammatory factors TNF-α (p < 0.001) and IL-6 (p = 0.018) were lower, while IL-10 was higher in the Dex Group than in the Control Group (p < 0.001). CONCLUSION: Dexmedetomidine can improve the oxygenation and inhibit the inflammatory response in patients undergoing UPPP in the early perioperative period. TRIAL REGISTRATION: The present clinical study has been registered at Clinical Trials under number NCT03612440.

Rapid emergence from dexmedetomidine sedation in Sprague Dawley rats by repurposing an α2-adrenergic receptor competitive antagonist in combination with caffeine.

BACKGROUND: The α2 adrenergic receptor agonist dexmedetomidine is an important intravenous sedative with analgesic properties. Currently available dexmedetomidine reversal agents, like the α2-receptor antagonist atipamezole, cause serious adverse effects at the large dosages required for effective reversal; they are not used clinically. Without reversal agents, emergence times from dexmedetomidine sedation are slow. In this study we tested the ability of low-dose atipamezole, in combination with caffeine, to reverse dexmedetomidine sedation. The low dose of atipamezole employed should not be associated with unwanted effects. METHODS: Two different sedation protocols were employed. In the first protocol, a bolus of dexmedetomidine was rapidly applied and the drug was allowed to equilibrate for 10 min before rats received either saline (as control) or low-dose atipamezole with caffeine. Following this procedure, rats were placed on their backs. Emergence from sedation was the time for rats to recover their righting reflex and stand with 4 paws on the floor. A second sedation protocol simulated a pediatric magnetic resonance imaging (MRI) scan. Adult rats were sedated with dexmedetomidine for one hour followed by 30 min with both dexmedetomidine and propofol. At the end of 90 min, rats received either saline (control) or a combination of low-dose atipamezole, and caffeine. Recovery of the righting reflex was used as a proxy for emergence from sedation. RESULTS: Emergence from sedation, the time for rats to recover their righting reflex, decreased by ~ 90% when using an atipamezole dose ~ 20 fold lower than manufacturer's recommendation, supplemented with caffeine. Using an atipamezole dose ~ tenfold lower than recommended, with caffeine, emergence times decreased by ~ 97%. A different stimulant, forskolin, when tested, was as effective as caffeine. For the MRI simulation, emergence times were decreased by ~ 93% by low-dose atipamezole with caffeine. CONCLUSIONS: Low dose atipamezole with caffeine was effective at reversing dexmedetomidine sedation. Emergence was rapid and the rats regained not only their righting reflex but also their balance and their ability to carry out complex behaviors. These findings suggest that the combination of low dose atipamezole with caffeine may permit rapid clinical reversal of dexmedetomidine without unwanted effects.

Dexmedetomidine modulates neuronal activity of horizontal limbs of diagonal band via α2 adrenergic receptor in mice.

BACKGROUND AND OBJECTIVES: Dexmedetomidine (DEX) is widely used in clinical sedation which has little effect on cardiopulmonary inhibition, however the mechanism remains to be elucidated. The basal forebrain (BF) is a key nucleus that controls sleep-wake cycle. The horizontal limbs of diagonal bundle (HDB) is one subregions of the BF. The purpose of this study was to examine whether the possible mechanism of DEX is through the α2 adrenergic receptor of BF (HDB). METHODS: In this study, we investigated the effects of DEX on the BF (HDB) by using whole cell patch clamp recordings. The threshold stimulus intensity, the inter-spike-intervals (ISIs) and the frequency of action potential firing in the BF (HDB) neurons were recorded by application of DEX (2 µM) and co-application of a α2 adrenergic receptor antagonist phentolamine (PHEN) (10 µM). RESULTS: DEX (2 µM) increased the threshold stimulus intensity, inhibited the frequency of action potential firing and enlarged the inter-spike-interval (ISI) in the BF (HDB) neurons. These effects were reversed by co-application of PHEN (10 µM). CONCLUSION: Taken together, our findings revealed DEX decreased the discharge activity of BF (HDB) neuron via α2 adrenergic receptors.

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.

Features of α2-Adrenergic Regulation of Isolated Rat Heart after Hypokinesia.

We studied the effect of the α2-adrenergic receptor agonist clonidine hydrochloride (10-9-10-6 M) on the isolated heart of adult rats after 30-day restriction of motor activity. In hypokinetic rats, in comparison with control animals, clonidine caused a positive inotropic effect; the dynamics of coronary flow was changed after stimulation of α2-adrenergic receptors by clonidine in the minimum and maximum concentrations. Moreover, clonidine in concentrations of 10-8 and 10-7 M reduced coronary flow both in the control group and against the background of hypokinesia. Clonidine (10-8-10-6 M) had a negative chronotropic effect in control and hypokinetic animals, while the dynamics of HR was multidirectional, i.e. either an increase or decrease in the effects was observed depending of the agonist concentration. Overall, the data obtained indicate the participation of α2-adrenergic receptors in adaptive processes after motor activity limitation.

Predictive Feedback, Early Sensory Representations, and Fast Responses to Predicted Stimuli Depend on NMDA Receptors.

Learned associations between stimuli allow us to model the world and make predictions, crucial for efficient behavior (e.g., hearing a siren, we expect to see an ambulance and quickly make way). While there are theoretical and computational frameworks for prediction, the circuit and receptor-level mechanisms are unclear. Using high-density EEG, Bayesian modeling, and machine learning, we show that inferred "causal" relationships between stimuli and frontal alpha activity account for reaction times (a proxy for predictions) on a trial-by-trial basis in an audiovisual delayed match-to-sample task which elicited predictions. Predictive ß feedback activated sensory representations in advance of predicted stimuli. Low-dose ketamine, an NMDAR blocker, but not the control drug dexmedetomidine, perturbed behavioral indices of predictions, their representation in higher-order cortex, feedback to posterior cortex, and pre-activation of sensory templates in higher-order sensory cortex. This study suggests that predictions depend on alpha activity in higher-order cortex, ß feedback, and NMDARs, and ketamine blocks access to learned predictive information.SIGNIFICANCE STATEMENT We learn the statistical regularities around us, creating associations between sensory stimuli. These associations can be exploited by generating predictions, which enable fast and efficient behavior. When predictions are perturbed, it can negatively influence perception and even contribute to psychiatric disorders, such as schizophrenia. Here we show that the frontal lobe generates predictions and sends them to posterior brain areas, to activate representations of predicted sensory stimuli before their appearance. Oscillations in neural activity (α and ß waves) are vital for these predictive mechanisms. The drug ketamine blocks predictions and the underlying mechanisms. This suggests that the generation of predictions in the frontal lobe, and the feedback pre-activating sensory representations in advance of stimuli, depend on NMDARs.

Effect of sympathetic sprouting on the excitability of dorsal root ganglion neurons and afferents in a rat model of neuropathic pain.

Increased sympathetic nerve excitability has been reported to aggravate a variety of chronic pain conditions, and an increase in the number of sympathetic nerve fibers in the dorsal root ganglion (DRG) has been found in neuropathic pain (NP) models. However, the mechanism of the neurotransmitter norepinephrine (NE) released by sympathetic nerve fiber endings on the excitability of DRG neurons is still controversial, and the adrenergic receptor subtypes involved in this biological process are also controversial. In our study, we have two objectives: (1) To determine the effect of the neurotransmitter NE on the excitability of different neurons in DRG; (2) To determine which adrenergic receptors are involved in the excitability of DRG neurons by NE released by sprouting sympathetic fibers. In this experiment, a unique field potential recording method of spinal cord dorsal horn was innovatively adopted, which can be used for electrophysiological study in vivo. The results showed that： Forty days after SNI, patch clamp and field potential recording methods confirmed that NE enhanced the excitability of ipsilateral DRG large neurons, and then our in vivo electrophysiological results showed that the α2 receptor blocker Yohimbine could block the excitatory effect of NE on A-fiber and the inhibitory effect on C-fiber, while the α2A-adrenergic receptor agonist guanfacine (100 µM) had the same biological effect as NE. Finally, we concluded that NE from sympathetic fiber endings is involved in the regulation of pain signaling by acting on α2A-adrenergic receptors in DRG.

Activation of the α2B adrenoceptor by the sedative sympatholytic dexmedetomidine.

The α2 adrenergic receptors (α2ARs) are G protein-coupled receptors (GPCRs) that respond to adrenaline and noradrenaline and couple to the Gi/o family of G proteins. α2ARs play important roles in regulating the sympathetic nervous system. Dexmedetomidine is a highly selective α2AR agonist used in post-operative patients as an anxiety-reducing, sedative medicine that decreases the requirement for opioids. As is typical for selective αAR agonists, dexmedetomidine consists of an imidazole ring and a substituted benzene moiety lacking polar groups, which is in contrast to ßAR-selective agonists, which share an ethanolamine group and an aromatic system with polar, hydrogen-bonding substituents. To better understand the structural basis for the selectivity and efficacy of adrenergic agonists, we determined the structure of the α2BAR in complex with dexmedetomidine and Go at a resolution of 2.9 Å by single-particle cryo-EM. The structure reveals the mechanism of α2AR-selective activation and provides insights into Gi/o coupling specificity.

The unfolded protein response in amyotrophic later sclerosis: results of a phase 2 trial.

Strong evidence suggests that endoplasmic reticulum stress plays a critical role in the pathogenesis of amyotrophic lateral sclerosis (ALS) through altered regulation of proteostasis. Robust preclinical findings demonstrated that guanabenz selectively inhibits endoplasmic reticulum stress-induced eIF2α-phosphatase, allowing misfolded protein clearance, reduces neuronal death and prolongs survival in in vitro and in vivo models. However, its safety and efficacy in patients with ALS are unknown. To address these issues, we conducted a multicentre, randomized, double-blind trial with a futility design. Patients with ALS who had displayed an onset of symptoms within the previous 18 months were randomly assigned in a 1:1:1:1 ratio to receive 64 mg, 32 mg or 16 mg of guanabenz or placebo daily for 6 months as an add-on therapy to riluzole. The purpose of the placebo group blinding was to determine safety but not efficacy. The primary outcome was the proportion of patients progressing to higher stages of disease within 6 months as measured using the ALS Milano-Torino staging system, compared with a historical cohort of 200 patients with ALS. The secondary outcomes were the rate of decline in the total revised ALS functional rating scale score, slow vital capacity change, time to death, tracheotomy or permanent ventilation and serum light neurofilament level at 6 months. The primary assessment of efficacy was performed using intention-to-treat analysis. The treatment arms using 64 mg and 32 mg guanabenz, both alone and combined, reached the primary hypothesis of non-futility, with the proportions of patients who progressed to higher stages of disease at 6 months being significantly lower than that expected under the hypothesis of non-futility and a significantly lower difference in the median rate of change in the total revised ALS functional rating scale score. This effect was driven by patients with bulbar onset, none of whom (0/18) progressed to a higher stage of disease at 6 months compared with those on 16 mg guanabenz (4/8; 50%), the historical cohort alone (21/49; 43%; P = 0.001) or plus placebo (25/60; 42%; P = 0.001). The proportion of patients who experienced at least one adverse event was higher in any guanabenz arm than in the placebo arm, with higher dosing arms having a significantly higher proportion of drug-related side effects and the 64 mg arm a significantly higher drop-out rate. The number of serious adverse events did not significantly differ between the guanabenz arms and the placebo. Our findings indicate that a larger trial with a molecule targeting the unfolded protein response pathway without the alpha-2 adrenergic related side-effect profile of guanabenz is warranted.

Dexmedetomidine preconditioning ameliorates lung injury induced by pulmonary ischemia/reperfusion by upregulating promoter histone H3K4me3 modification of KGF-2.

Keratinocyte growth factor (KGF)-2 has been highlighted to play a significant role in maintaining the endothelial barrier integrity in lung injury induced by ischemia-reperfusion (I/R). However, the underlying mechanism remains largely unknown. The aims of this study were to determine whether dexmedetomidine preconditioning (DexP) modulates pulmonary I/R-induced lung injury through the alteration in KGF-2 expression. In our I/R-modeled mice, DexP significantly inhibited pathological injury, inflammatory response, and inflammatory cell infiltration, while promoted endothelial barrier integrity and KGF-2 promoter activity in lung tissues. Bioinformatics prediction and ChIP-seq revealed that I/R significantly diminished the level of H3K4me3 modification in the KGF-2 promoter, which was significantly reversed by DexP. Moreover, DexP inhibited the expression of histone demethylase JMJD3, which in turn promoted the expression of KGF-2. In addition, overexpression of JMJD3 weakened the protective effect of DexP on lung injury in mice with I/R. Collectively, the present results demonstrated that DexP ameliorates endothelial barrier dysfunction via the JMJD3/KGF-2 axis.

Dexmedetomidine improved one-lung ventilation-induced cognitive dysfunction in rats.

BACKGROUND: One-lung ventilation (OLV) is widely used in thoracic surgery. However, OLV may also increase CERO2 and aggravate delayed cognitive recovery. Here, we aimed to investigate the effect of dexmedetomidine (DEX) on cognitive function in rats undergoing OLV. METHODS: Sprague-Dawley rats were randomly divided into two-lung ventilation (TLV) group, OLV group and OLV treated with DEX group. Group DEX received 25 µg/kg DEX i.p. 30 min before induction. After mechanical ventilation (MV), Morris water maze (MWM) test was carried out to examine spatial memory function. Western blotting was used to detect pERK1/2, pCREB, Bcl-2 and BAX in hippocampal tissues. Transmission electron microscopy (TEM) was used to observe the hippocampal CA1 region. RESULTS: Post-MV, compared with group OLV, group DEX showed increases in percentage of target quadrant time (P < 0.05), platform crossings (P < 0.05), a reduction in CERO2 (P < 0.05), and pERK1/2, pCREB, and Bcl-2 significantly increased (P < 0.01 or P < 0.05), while BAX significantly decreased (P < 0.01), besides, a less damaged synaptic structure was observed in group DEX. CONCLUSIONS: DEX improved post-MV cognitive function in rats undergoing OLV, reduced cerebral oxygen consumption, protected synaptic structure and upregulated ERK1/2-CREB anti-apoptotic signaling pathway in hippocampal CA1 region.

Sedative Properties of Dexmedetomidine Are Mediated Independently from Native Thalamic Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel Function at Clinically Relevant Concentrations.

Dexmedetomidine is a selective α2-adrenoceptor agonist and appears to disinhibit endogenous sleep-promoting pathways, as well as to attenuate noradrenergic excitation. Recent evidence suggests that dexmedetomidine might also directly inhibit hyperpolarization-activated cyclic-nucleotide gated (HCN) channels. We analyzed the effects of dexmedetomidine on native HCN channel function in thalamocortical relay neurons of the ventrobasal complex of the thalamus from mice, performing whole-cell patch-clamp recordings. Over a clinically relevant range of concentrations (1-10 µM), the effects of dexmedetomidine were modest. At a concentration of 10 µM, dexmedetomidine significantly reduced maximal Ih amplitude (relative reduction: 0.86 [0.78-0.91], n = 10, and p = 0.021), yet changes to the half-maximal activation potential V1/2 occurred exclusively in the presence of the very high concentration of 100 µM (-4,7 [-7.5--4.0] mV, n = 10, and p = 0.009). Coincidentally, only the very high concentration of 100 µM induced a significant deceleration of the fast component of the HCN activation time course (τfast: +135.1 [+64.7-+151.3] ms, n = 10, and p = 0.002). With the exception of significantly increasing the membrane input resistance (starting at 10 µM), dexmedetomidine did not affect biophysical membrane properties and HCN channel-mediated parameters of neuronal excitability. Hence, the sedative qualities of dexmedetomidine and its effect on the thalamocortical network are not decisively shaped by direct inhibition of HCN channel function.

Dexmedetomidine-Induced Aortic Contraction Involves Transactivation of the Epidermal Growth Factor Receptor in Rats.

In this study, we examined whether aortic contraction, induced by the alpha-2 adrenoceptor agonist dexmedetomidine, is involved in the transactivation of the epidermal growth factor receptor (EGFR) in isolated endothelium-denuded rat aortas. Additionally, we aimed to elucidate the associated underlying cellular mechanisms. The effects of the alpha-2 adrenoceptor inhibitor rauwolscine, EGFR tyrosine kinase inhibitor AG1478, Src kinase inhibitors PP1 and PP2, and matrix metalloproteinase inhibitor GM6001 on EGFR tyrosine phosphorylation and c-Jun NH2-terminal kinase (JNK) phosphorylation induced by dexmedetomidine in rat aortic smooth muscles were examined. In addition, the effects of these inhibitors on dexmedetomidine-induced contraction in isolated endothelium-denuded rat aorta were examined. Dexmedetomidine-induced contraction was inhibited by the alpha-1 adrenoceptor inhibitor prazosin, rauwolscine, AG1478, PP1, PP2, and GM6001 alone or by a combined treatment with prazosin and AG1478. AG1478 (3 × 10-6 M) inhibited dexmedetomidine-induced contraction in isolated endothelium-denuded rat aortas pretreated with rauwolscine. Dexmedetomidine-induced EGFR tyrosine and JNK phosphorylation were inhibited by rauwolscine, PP1, PP2, GM6001, and AG1478. Furthermore, dexmedetomidine-induced JNK phosphorylation reduced upon EGFR siRNA treatment. Therefore, these results suggested that the transactivation of EGFR associated with dexmedetomidine-induced contraction, mediated by the alpha-2 adrenoceptor, Src kinase, and matrix metalloproteinase, caused JNK phosphorylation and increased calcium levels.