Α7 Nicotinic Acetylcholine Receptor Antagonist Research Articles

Nicotine plays a protective role in rats with induced viral pneumonia with polyinosinic-polycytidylic acid through α7nAChR

ObjectiveTo study the effect of nicotine in rat model of pneumonia induced by polyinosinic-polycytidylic acid [Poly (I:C)] and explore the underlying mechanism. MethodsTwenty-four healthy adult male Sprague-Dawley (SD) rats (200–250 g) were randomly divided into normal saline control group (NS group); Poly (I:C) group; nicotine group (NIC group); and α7 nicotinic acetylcholine receptor (α7nAChR) antagonist group (α-BGT group) (n = 6 each). Rats in the Poly (I: C), NIC, and α-BGT groups were administered 1.5 mg/mL 100 μL Poly (I:C) intranasally to establish pneumonia model. In α-BGT group, 1 μg/kg α-bungarotoxin (α-BGT) was intraperitoneally injected 45 min before intranasal Poly (I:C), and 400 μg/kg nicotine was intraperitoneally injected 15 min after α-BGT injection. The NIC group received an equal volume of NS in place of α-BGT while the other treatments were same. The Poly (I:C) group received equal volume of NS in place of nicotine while the other treatments were same as in NIC group. In the NS group, only NS was administered at all three time points. PaCO2, PaO2, and PaO2/FiO2 levels were determined 24 h after administration of Poly (I:C). After euthanization, rat lung tissues were extracted for pathological examination, and wet weight/dry weight (W/D ratio) was determined. Expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-1β, and interferon (IFN)-γ in lung tissue was determined by ELISA. q-PCR was used to detect nuclear factor kappa-B P65 (NF-κBP65). ResultsCompared with NS group, Poly (I:C) and α-BGT groups showed significantly increased W/D ratio, PaCO2, TNF-α, IL-6, IL-1β, and IFN-γ content, NF-κB P65 expression, and reduced PaO2 and PaO2/FiO2 (p < 0.05), along with obvious signs of pathological injury. Nicotine pre-treatment reduced W/D ratio, PaCO2, proinflammatory cytokines, NF-κBP65 expression, and increased PaO2 and PaO2/FiO2 levels. The above effects were negated in α-BGT group. ConclusionPre-administration of nicotine improved Poly (I:C)-induced pneumonia by activating the cholinergic anti-inflammatory pathway.

Diagnoses and new therapeutic strategy focused on physiological alteration of tryptophan metabolism

The monoamine hypothesis has been common hypotheses for the pathophysiology of major depressive disorder (MDD). Since mainstream antidepressants are selective serotonin (5-HT) reuptake inhibitors, hypo-serotonergic function has been implicated in the MDD. However, one-third of patients are refractory to the treatment with antidepressants. Tryptophan (TRP) is metabolized via the kynurenine (KYN) and 5-HT pathways. Indoleamine 2,3-dioxygenase 1 (IDO1) is the first metabolizing enzyme in the TRP-KYN pathway which is inducible by pro-inflammatory cytokines, involved depression-like behavior via 5-HT depletion due to decreased level of TRP in the 5-HT pathway. Kynurenine 3-monooxygenase (KMO) is the enzyme in the metabolism of KYN to 3-hydroxykynurenine. KMO deficiency increases level of kynurenic acid (KA), a KYN metabolite by kynurenine aminotransferases (KATs) and induces depression-like behavior. Interestingly, Chronic unpredictable mild stress (CUMS) is associated with a disruption of the hypothalamus-pituitary-adrenocortical (HPA) system and increases KA level with decreased KMO expression in the prefrontal cortex. The decrease of KMO may be related to the reduction in expression of microglia, since KMO is mainly found in microglia in the nervous system. CUMS increases KA level via alternation of enzymes from KMO to KAT. KA is α7 nicotinic acetylcholine receptor (α7nAChR) antagonist. Activation of α7nAChR by nicotine or galantamine attenuates CUMS-induced depression-like behaviors. Taken together, depletion of 5-HT by induction of IDO1 and α7nAChR antagonism by KA via decreased KMO expression cause depression-like behavior, suggesting that metabolic alterations in TRP-KYN pathway are highly involved in the pathophysiology of MDD. Therefore, TRP-KYN pathway is expected to be an attractive target for the development of novel diagnosis of MDD and antidepressants.

Acetylcholine potentiates glutamate transmission from the habenula to the interpeduncular nucleus in losers of social conflict

Switching behaviors from aggression to submission in losers at the end of conspecific social fighting is essential to avoid serious injury or death. We have previously shown that the experience of defeat induces a loser-specific potentiation in the habenula (Hb)-interpeduncular nucleus (IPN) and show here that this is induced by acetylcholine. Calcium imaging and electrophysiological recording using acute brain slices from winners and losers of fighting behavior in zebrafish revealed that the ventral IPN (vIPN) dominates over the dorsal IPN in the neural response to Hb stimulation in losers. We also show that GluA1 α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits on the postsynaptic membrane increased in the vIPN of losers. Furthermore, these loser-specific neural properties disappeared in the presence of an α7 nicotinic acetylcholine receptor (nAChR) antagonist and, conversely, were induced in brain slices of winners treated with α7 nAChR agonists. These data suggest that acetylcholine released from Hb terminals in the vIPN induces activation of α7 nAChR followed by an increase in postsynaptic membrane GluA1. This results in an increase in active synapses on postsynaptic neurons, resulting in the potentiation of neurotransmissions to the vIPN. This acetylcholine-induced neuromodulation could be the neural foundation for behavioral switching in losers. Our results could increase our understanding of the mechanisms of various mood disorders such as social anxiety disorder and social withdrawal.

Dexmedetomidine attenuates lipopolysaccharide-induced inflammation through macrophageal IL-10 expression following α7 nAchR activation

Dexmedetomidine, a highly selective α2-adrenoceptor agonist, has been recently reported to alleviate systemic inflammatory response induced by lipopolysaccharide (LPS), in addition to its sedative, analgesic, bradycardic and hypotensive properties. This study aimed to illustrate the molecular mechanisms underlying dexmedetomidine-induced anti-inflammation. In the LPS-pretreated mice, subcutaneous injection of dexmedetomidine reduced the spleen weight as well as serum and spleen expression of proinflammatory cytokines, tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β, and increased serum and spleen expression of IL-10, a known anti-inflammatory cytokine. In addition, dexmedetomidine-attenuated proinflammatory cytokine reduction was entirely inhibited by selective α7 nicotinic acetylcholine receptor (nAChR) antagonist methyllycaconitine but not α2-adrenoceptor antagonist yohimbine. Dexmedetomidine also increased macrophageal IL-10 expression in the presence and absence of LPS, which was also attenuated by methyllycaconitine but not yohimbine. Furthermore, the stimulatory effect of dexmedetomidine on the expression of IL-10 was also reduced by the α7 nAChR gene silencer siRNA/α7 nAChR. Lastly, pretreatment with the IL-10 neutralizing antibody reversed dexmedetomidine-supressed expression of proinflammatory cytokines. Our findings illustrate that dexmedetomidine-induced anti-inflammation is through macrophageal expression of IL-10 following activation of α7 nAchRs but not α2-adrenoceptors.

Synthesis and characterization of αM-conotoxin SIIID, a reversible human α7 nicotinic acetylcholine receptor antagonist

α-Conotoxins, a group of small marine peptide toxins that target nAChRs with high potency and selectivity, are valuable pharmacological tools and potential drug leads. In this study, we reported the synthesis and physiological functions of a novel αM-superfamily conotoxin SIIID (CCGEGSSCPKYFKNNFICGCC) from a fish-hunting Conus striatus. Three SIIID isomers with different cystine connectivities were synthesized by solid-phase polypeptide synthesis and confirmed by mass spectrometry. Patch clamp experiments on HEK293 cells expressing nAChR subtypes showed that 1 μM SIIID (1–4, 2–5, 3–6) inhibited PNU-120596 and acetylcholine induced human α7 nAChR currents by 48.45%, which was higher than 5.08% of SIIID (1–5, 2–4, 3–6) and 9.57% of SIIID (1–6, 2–4, 3–5). Further study on the most active SIIID isomer showed that 10 μM SIIID inhibited PNU-120596 and acetylcholine induced human α7 nAChR currents by 76.33% but had no obvious effect on acetylcholine induced human α3β4 nAChR currents. In addition, SIIID inhibited PNU-120596 and acetylcholine induced human α7 nAChR currents with an IC50 value of 880.71 ± 271.91 nM, and this inhibition was reversible. Patch clamp experiments on rat DRG neurons showed that 10 μM SIIID had <15% inhibitory effects on sodium, potassium and calcium currents. Our results suggested that SIIID would be a promising neuropharmacology tool for the study of human α7 nAChR and its related diseases.

Dexmedetomidine suppresses serum syndecan-1 elevation and improves survival in a rat hemorrhagic shock model.

Hemorrhagic shock causes vascular endothelial glycocalyx (EGCX) damage and systemic inflammation. Dexmedetomidine (DEX) has anti-inflammatory and EGCX-protective effects, but its effect on hemorrhagic shock has not been investigated. Therefore, we investigated whether DEX reduces inflammation and protects EGCX during hemorrhagic shock. Anesthetized Sprague-Dawley rats were randomly assigned to five groups (n=7 per group): no shock (SHAM), hemorrhagic shock (HS), hemorrhagic shock with DEX (HS+DEX), hemorrhagic shock with DEX and the α7 nicotinic type acetylcholine receptor antagonist methyllycaconitine citrate (HS+DEX/MLA), and hemorrhagic shock with MLA (HS+MLA). HS was induced by shedding blood to a mean blood pressure of 25–30 mmHg, which was maintained for 30 min, after which rats were resuscitated with Ringer’s lactate solution at three times the bleeding volume. The survival rate was assessed up to 3 h after the start of fluid resuscitation. Serum tumor necrosis factor-alpha (TNF-α) and syndecan-1 concentrations, and wet-to-dry ratio of the heart were measured 90 min after the start of fluid resuscitation. The survival rate after 3 h was significantly higher in the HS+DEX group than in the HS group. Serum TNF-α and syndecan-1 concentrations, and the wet-to-dry ratio of heart were elevated by HS, but significantly decreased by DEX. These effects were antagonized by MLA. DEX suppressed the inflammatory response and serum syndecan-1 elevation, and prolonged survival in rats with HS.

N1H- and N1-Substituted Phenylguanidines as α7 Nicotinic Acetylcholine (nACh) Receptor Antagonists: Structure-Activity Relationship Studies.

We previously reported that N-(3-chlorophenyl)guanidine (1) represents a novel α7 nicotinic ACh (nACh) receptor antagonist chemotype. In the present study, a small series of compounds was synthesized with the intent to investigate the structure-activity relationship (SAR). Preliminary data suggested that the N-methyl analog of 1, 2, was several times more potent. Therefore, the chloro group at the aryl 3-position of 1 and its N1-methyl counterpart 2 were replaced with a number of substituents considering the electronic, lipophilic, and steric nature of the substituents. The potencies of the compounds to inhibit acetylcholine (ACh)-induced responses were obtained in Xenopus laevis oocytes expressing human α7 nicotinic ACh receptors (nAChRs) using a two-electrode voltage-clamp assay. We found that the nature of the 3-position substituents had relatively little (i.e., <10-fold) effect on potency, and the presence of an N1-isopropyl substituent was tolerated. Here, we report the first SAR investigation of this novel α7 nAChR antagonist chemotype.

Computational analysis of non-competitive antagonist arylguanidine-α7 nAChR complexes

meta-Chlorophenylguanidine (1) is a non-competitive α7 nicotinic acetylcholine receptor (nAChR) antagonist. Here we examined the hydrogen bond donor role of the anilinic N1–H on the inhibitory effect of 1 by preparing its N1–CH3 counterpart 2. Analog 2 was found to be at least as potent as 1 as a non-competitive α7 nAChR antagonist in a patch-clamp assay.To establish a structural basis for the mode of interaction of guanidines 1 and 2, we generated 100 homology models of the hα7 nAChR. This was followed by Connolly surface (SYBYL-X2.1) and blind docking (AutoDock 4.1) studies to identify eight possible binding pockets, two of which were supported by empirical data and employed in our docking studies. The optimized model-ligand complexes were analyzed using a Hydropathic INTeractions (HINT) analysis in order to compare and contrast different binding pockets and modes. We identified a potential allosteric binding site and distinct rotameric binding modes for 1 and 2 at α7 nAChRs. These differences in the binding orientations minimized the importance of an anilinic NH function for the antagonist activity at nACh receptors.

Contrasting effects of the α7 nicotinic receptor antagonist methyllycaconitine in different rat models of heroin reinstatement.

Background:α7 Nicotinic acetylcholine receptors are implicated in the reinstatement of drug-seeking, an important component of relapse. We showed previously that the α7 nicotinic acetylcholine receptor antagonist, methyllycaconitine, specifically attenuated morphine-primed reinstatement of conditioned place preference in rodents and this effect was mediated in the ventral hippocampus.Aims:The purpose of this study was to evaluate α7 nicotinic acetylcholine receptor antagonism in reinstatement of the conditioned place preference for the more widely abused opioid, heroin, and to compare the effect of α7 nicotinic acetylcholine receptor blockade on reinstatement of heroin-seeking and heroin self-administration in an intravenous self-administration model of addictive behaviour.Methods:Rats were trained to acquire heroin conditioned place preference or heroin self-administration; both followed by extinction of responding. Methyllycaconitine or saline was given prior to reinstatement of drug-primed conditioned place preference, or drug-prime plus cue-induced reinstatement of intravenous self-administration, using two protocols: without delivery of heroin in response to lever pressing to model heroin-seeking, or with heroin self-administration, using fixed and progressive ratio reward schedules, to model relapse.Results:Methyllycaconitine had no effect on acquisition of heroin conditioned place preference or lever-pressing for food rewards. Methyllycaconitine blocked reinstatement of heroin-primed conditioned place preference. Methyllycaconitine did not prevent drug-prime plus cue-induced reinstatement of heroin-seeking, reinstatement of heroin self-administration, or diminish the reinforcing effect of heroin.Conclusions:The α7 nicotinic acetylcholine receptor antagonist, methyllycaconitine, prevented reinstatement of the opioid conditioned place preference, consistent with a role for α7 nicotinic acetylcholine receptors in the retrieval of associative memories of drug liking. The lack of effect of methyllycaconitine in heroin-dependent rats in two intravenous self-administration models suggests that α7 nicotinic acetylcholine receptors do not play a role in later stages of heroin abuse.

Effect of Tobacco-specific Nitrosamines on MUC5AC Expression in Human Airway Epithelial Cells

Background and Objectives: Nicotine is oxidized into tobacco-specific nitrosamines (TSNAs; NAB, NAT, NNN, NNAL, NNK) at high temperature and high pressure. TSNAs are associated with airway diseases characterized by mucus hypersecretion as a major pathophysiologic phenomenon. The aim of study is to investigate the effect of TSNAs on mucin overexpression and its molecular mechanism in human airway epithelial cells.Materials and Method: The cytotoxicity of TSNAs was evaluated using EX-Cytox and inverted microscopy. The mRNA and protein levels of MUC5AC and MUC5B were measured using real-time PCR and ELISA.Results: NAB, NNN, NNAL, and NNK did not affect cell viability. NAT did not affect cell viability up to a concentration of 100 μM in human airway epithelial cells. NAT, NNN, NNAL, and NNK significantly induced MUC5AC expression, but not MUC5B expression. NAB did not affect the expression of MUC5AC and MUC5B. Propranolol (a β-adrenergic receptor antagonist) inhibited NAT, NNN, NNAL, and NNK-induced MUC5AC expression, whereas α-bungarotoxin (an α7-nicotinic acetylcholine receptor antagonist) only inhibited NNN- and NNK-induced MUC5AC expression.Conclusion: These results suggested that NAT, NNN, NNAL, and NNK induce MUC5AC expression through β-adrenergic receptor and/or α7-nicotinic acetylcholine receptor in human airway epithelial cells, which may be involved in mucus hypersecretion in inflammatory airway diseases.

Shati/Nat8l deficiency disrupts adult neurogenesis and causes attentional impairment through dopaminergic neuronal dysfunction in the dentate gyrus.

Successful completion of daily activities relies on the ability to select the relevant features of the environment for memory and recall. Disruption to these processes can lead to various disorders, such as attention-deficit hyperactivity disorder (ADHD). Dopamine is a neurotransmitter implicated in the regulation of several processes, including attention. In addition to the higher-order brain function, dopamine is implicated in the regulation of adult neurogenesis. Previously, we generated mice lacking Shati, an N-acetyltransferase-8-like protein on a C57BL/6J genetic background (Shati/Nat8l-/- ). These mice showed a series of changes in the dopamine system and ADHD-like behavioral phenotypes. Therefore, we hypothesized that deficiency of Shati/Nat8l would affect neurogenesis and attentional behavior in mice. We found aberrant morphology of neurons and impaired neurogenesis in the dentate gyrus of Shati/Nat8l-/- mice. Additionally, research has suggested that impaired neurogenesis might be because of the reduction of dopamine in the hippocampus. Galantamine (GAL) attenuated the attentional impairment observed in the object-based attention test via increasing the dopamine release in the hippocampus of Shati/Nat8l-/- mice. The α7 nicotinic acetylcholine receptor antagonist, methyllycaconitine, and dopamine D1 receptor antagonist, SCH23390, blocked the ameliorating effect of GAL on attentional impairment in Shati/Nat8l-/- mice. These results suggest that the ameliorating effect of GAL on Shati/Nat8l-/- attentional impairment is associated with activation of D1 receptors following increased dopamine release in the hippocampus via α7 nicotinic acetylcholine receptor. In summary, Shati/Nat8l is important in both morphogenesis and neurogenesis in the dentate gyrus and attention, possible via modulation of dopaminergic transmission. Cover Image for this issue: https://doi.org/10.1111/jnc.15061.

Dexmedetomidine-mediated protection against septic liver injury depends on TLR4/MyD88/NF-κB signaling downregulation partly via cholinergic anti-inflammatory mechanisms

BackgroundUncontrolled inflammatory responses exacerbate the pathogenesis of septic acute liver injury (ALI), posing a lethal threat to the host. Dexmedetomidine (DEX) has been reported to possess protective properties in inflammatory conditions. This study aimed to investigate whether DEX pretreatment exhibits hepatoprotection against ALI induced by lipopolysaccharide (LPS) in rats and determine its possible molecular mechanism. MethodsSeptic ALI was induced by intravenous injection of LPS. The rats received DEX intraperitoneally 30 min before LPS administration. α-Bungarotoxin (α-BGT), a specific α7 nicotinic acetylcholine receptor (α7nAChR) antagonist, was administered intraperitoneally 1 h before LPS exposure. The role of the vagus nerve was verified by performing unilateral cervical vagotomy or sham surgery before sepsis. ResultsThe expression of α7nAChR, toll-like receptor 4 (TLR4), high mobility group box 1 (HMGB1), and cleaved caspase-3 increased, peaking 24 h during sepsis. DEX enhanced α7nAChR activation and reduced TLR4 expression upon challenge with LPS. DEX significantly prevented LPS-induced ALI, which was associated with increased survival, the mitigation of pathological changes, the attenuation of inflammatory cytokine expression and apoptosis, and the downregulation of TLR4/MyD88/NF-κB pathway. Moreover, the hepatoprotective effect of DEX was abolished by α-BGT. Further investigation established that vagotomy, compared to sham surgery, triggered more severe pathogenic manifestations and higher proinflammatory cytokine levels. The inhibitory effects of DEX were shown in sham-operated rats but not in vagotomized rats. ConclusionsOur data highlight the pivotal function of α7nAChR and intact vagus nerves in protecting against LPS-induced ALI through inhibiting the TLR4/MyD88/NF-κB signaling pathway upon pretreatment with DEX.

Neuroprotective mechanism involved in spinal cord stimulation postconditioning

ObjectivesDelayed paraplegia developed postoperatively after thoracoabdominal aneurysm surgery is primarily associated with spinal cord ischemia/reperfusion injury. Our previous study suggested that spinal cord stimulation postconditioning protected the spinal cord from ischemia/reperfusion injury through microglia inhibition. In this study, we further investigated whether α7 nicotinic acetylcholine receptors were involved in the neuroprotective mechanism of spinal cord stimulation. MethodsRabbits were randomly assigned to sham, control, 2 Hz, α-bungarotoxin, and 2 Hz-α-bungarotoxin groups (n = 24/group). Transient spinal cord ischemia was performed on all rabbits except rabbits in the sham group. Rabbits in the control group received no further intervention, rabbits in the 2 Hz group were given 2 Hz spinal cord stimulation, rabbits in the α-bungarotoxin group received prescribed intrathecal α-bungarotoxin (α-bungarotoxin, a specific α7 nicotinic acetylcholine receptor antagonist) injections, and rabbits in the 2 Hz-α-bungarotoxin group received both α-bungarotoxin injections and 2 Hz spinal cord stimulation. Hind-limb neurologic function was assessed, and spinal cord histologic examination, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining, and microglia staining were performed at 8 hours, 1 day, 3 days, and 7 days of reperfusion. ResultsRabbits in the 2 Hz group had significantly better neurologic functions, more α-motor neurons, and lower terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling–positive neuron rates and microglia area/anterior horn area ratios (microglia area ratios) than the control group. The neurologic functions of the α-bungarotoxin group were significantly worse than those of the control group, whereas other results were not significantly different from the control group. The results of the 2 Hz-α-bungarotoxin group were insignificant to the control group except for the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling–positive neuron rates, which were significantly lower than in the control group. ConclusionsThe neuroprotective effects of spinal cord stimulation postconditioning against spinal cord ischemia/reperfusion injury were partially mediated by activating α7 nicotinic acetylcholine receptors.

Constitutive Vagus Nerve Activation Modulates Immune Suppression in Sepsis Survivors.

Patients surviving a septic episode exhibit persistent immune impairment and increased mortality due to enhanced vulnerability to infections. In the present study, using the cecal ligation and puncture (CLP) model of polymicrobial sepsis, we addressed the hypothesis that altered vagus nerve activity contributes to immune impairment in sepsis survivors. CLP-surviving mice exhibited less TNFα in serum following administration of LPS, a surrogate for an infectious challenge, than control-operated (control) mice. To evaluate the role of the vagus nerve in the diminished response to LPS, mice were subjected to bilateral subdiaphragmatic vagotomy at 2 weeks post-CLP. CLP-surviving vagotomized mice exhibited increased serum and tissue TNFα levels in response to LPS-challenge compared to CLP-surviving, non-vagotomized mice. Moreover, vagus nerve stimulation in control mice diminished the LPS-induced TNFα responses while having no effect in CLP mice, suggesting constitutive activation of vagus nerve signaling in CLP-survivors. The percentage of splenic CD4+ ChAT-EGFP+ T cells that relay vagus signals to macrophages was increased in CLP-survivors compared to control mice, and vagotomy in CLP-survivors resulted in a reduced percentage of ChAT-EGFP+ cells. Moreover, CD4 knockout CLP-surviving mice exhibited an enhanced LPS-induced TNFα response compared to wild-type mice, supporting a functional role for CD4+ ChAT+ T cells in mediating inhibition of LPS-induced TNFα responses in CLP-survivors. Blockade of the cholinergic anti-inflammatory pathway with methyllcaconitine, an α7 nicotinic acetylcholine receptor antagonist, restored LPS-induced TNFα responses in CLP-survivors. Our study demonstrates that the vagus nerve is constitutively active in CLP-survivors and contributes to the immune impairment.

Role of cholinergic anti-inflammatory pathway in dexmedetomidine pretreatment-induced reduction of acute lung injury in a rat model of intestinal ischemia-reperfusion

Objective To evaluate the role of cholinergic anti-inflammatory pathway in dexmedetomidine pretreatment-induced reduction of acute lung injury in a rat model of intestinal ischemia-reperfusion (I/R). Methods Twenty-four healthy male Sprague-Dawley rats, aged 2-3 months, weighing 200-250 g, were divided into 4 groups (n=6) using a random number table method: sham operation group (S group), intestinal I/R group (II/R group ), dexmetomidine group (DEX group) and α7 nicotinic acetylcholine receptor antagonist α-bungarotoxin (α-BGT) group (α-BGT group). Intestinal I/R was produced by occlusion of the superior mesenteric artery (SMA) for 60 min followed by 120 min of reperfusion in anesthetized rats.Dexmetomidine 5 μg·kg-1·h-1 was injected via the tail vein at 1 h before operation in DEX group and α-BGT group.α-BGT 1 μg/kg was intraperitoneally injected at 15 min before dexmetomidine injection in α-BGT group.Rats were sacrificed at 120 min of reperfusion, and lung tissues were obtained for microscopic examination of pathological changes (with a light microscope) and for determination of wet/dry weight ratio (W/D ratio), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) contents (using enzyme-linked immunosorbent assay), malondialdehyde (MDA) content (using thiobarbital acid method) and superoxide dismutase (SOD) activity (by xanthine oxidase method). Results Compared with group S, the W/D ratio and contents of MDA, TNF-α and IL-6 were significantly increased, and the SOD activity was decreased in II/R and α-BGT groups, and TNF-α and IL-6 contents were significantly increased in group DEX (P<0.05). Compared with group II/R, the W/D ratio and contents of MDA, TNF-α and IL-6 were significantly decreased, SOD activity was increased (P<0.05), and the pathological changes were significantly attenuated in group DEX.Compared with group DEX, the W/D ratio and contents of MDA, TNF-α and IL-6 were significantly increased, SOD activity was decreased (P<0.05), and the pathological changes were accentuated in group α-BGT. Conclusion Activation of cholinergic anti-inflammatory pathway is involved in the mechanism by which dexmedetomidine pretreatment reduces acute lung injury in a rat model of intestinal I/R. Key words: Acetylcholine; Dexmetomidine; Reperfusion injury; Intestines; Hespiratory distress syndrome, adult

Dexmedetomidine protects against lipopolysaccharide-induced sepsis-associated acute kidney injury via an α7 nAChR-dependent pathway

Acute kidney injury (AKI) is a clinical syndrome that results in severe tubular damage with high morbidity and mortality. However, there is a lack of effective therapy strategies. Therefore, it is critical to develop effective drugs for AKI. Dexmedetomidine (DEX), a highly selective α2-adrenoreceptor agonist, has neuroprotective, anti-inflammatory and sympatholytic properties. The present study aimed to investigate the effect DEX on attenuating the inflammatory reaction and apoptosis in the kidney tissues of septic mice and to explore its underlying mechanisms. Sepsis-induced AKI mice models were generated via intraperitoneal injection of lipopolysaccaride (LPS). DEX reduced LPS-induced local inflammation and tubular apoptosis, which was aggravated in the pathogenesis of renal dysfunction. Reverse transcription-quantitative polymerase chain reaction and western blot analysis results revealed that the expression of pro-apoptotic genes and inflammatory factors were markedly reduced by DEX pretreatment. Furthermore, the protective role of DEX was markedly inhibited by the α7 nicotinic acetylcholine receptor (nAChR) antagonist α-bungarotoxin. These findings provided novel evidence for the anti-apoptotic and anti-inflammatory effects of DEX in LPS-induced AKI mice through an α7 nAChR-dependent signaling pathway.

Varenicline is a smoking cessation drug that blocks alveolar expansion in mice intratracheally administrated porcine pancreatic elastase

Smoking cessation is the most effective treatment in patients with emphysema and lung inflammation. The aim of the present study was to examine the effect of varenicline, a smoking cessation drug, on emphysema in porcine pancreatic elastase (PPE)-inhaled mice. PPE-inhaled mice were treated with varenicline and an α7 nicotinic acetylcholine receptor (nAChR) antagonist, methyllycaconitine (MLA) for 5 and 21 days. Varenicline markedly ameliorated alveolar expansion and inflammatory response in bronchoalveolar lavage fluid in PPE-inhaled mice. These blocking effects were inhibited by MLA. Our findings demonstrate that varenicline likely has an anti-inflammatory property including reduced inflammatory cell recruitment in lung tissue to protect PPE-induced alveolar expansion via α7 nAChR.

Vagal tonic activity modulates immune suppression in sepsis survivors

Abstract Sepsis survivors exhibit persistent immune dysfunction and compromised quality of life with premature mortality due to increased vulnerability to infections. Previously we demonstrated in a cecal ligation and puncture (CLP) model, sepsis survivors had a reduced TNFα response to LPS-challenge in vivo. The vagus nerve is known to modulate TNFα production. To evaluate the role of the vagus nerve in the diminished TNFα production, sepsis-surviving mice were subjected to bilateral subdiaphragmatic vagotomy 2 weeks post-CLP. CLP-surviving vagotomized mice exhibit increased (p&amp;lt;0.05) TNFα levels in response to LPS-challenge 4 weeks post surgery compared to CLP. Moreover, vagus nerve stimulation in sham mice dampened (p&amp;lt;0.05) the LPS-induced TNFα response while it had no effect in CLP-surviving mice; suggesting that vagus nerve signaling is constitutively active in CLP-sepsis survivors. To identify whether there was an alteration in the number of acetylcholine-producing T cells that relay the vagus signal to splenic macrophages, we used ChAT-EGFP mice. Our findings show that the frequency of splenic ChAT-EGFP+ cells among memory CD4+CD44highCD62LlowT cells is increased (p&amp;lt;0.001) in CLP-surviving mice compared to sham, and vagotomy in these mice resulted in decreased (p&amp;lt;0.01) frequency of ChAT-EGFP+ cells, buttressing the conclusion that the vagus nerve is constitutively firing action potentials to activate more ChAT+ T cells. Methyllycaconitine, the α7 nicotinic acetylcholine receptor antagonist, increased (p&amp;lt;0.01) LPS-induced TNFα secretion in CLP-surviving mice compared to saline treated-CLP. In summary, our study demonstrates that altered vagus nerve activity contributes to the immune impairment in sepsis survivors.

Varenicline promotes endothelial cell migration by lowering vascular endothelial-cadherin levels via the activated α7 nicotinic acetylcholine receptor-mitogen activated protein kinase axis.

Varenicline is a widely used and effective drug for smoking cessation. Despite its efficacy, varenicline increases the risk of cardiovascular disease. We previously demonstrated that varenicline aggravates atherosclerotic plaque formation in apolipoprotein E knockout mice. However, little is known about its effects in vascular endothelial cells. Therefore, we examined whether varenicline promotes migration of human umbilical vein endothelial cells (HUVECs) using the Boyden chamber assay. Varenicline (100μM) markedly promoted migration of HUVECs and decreased expression of vascular endothelial (VE)-cadherin, an endothelial adhesion molecule. Extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) signaling were markedly activated by varenicline. Methyllycaconitine (MLA; 100nM), an α7 nicotinic acetylcholine receptor (nAChR) antagonist, but not dihydro-β-erythroidine hydrobromide (DHβE; 20μM) blocked varenicline-stimulated migration and varenicline-activated ERK, p38 and JNK signaling in HUVECs. MLA (100nM), PD98059 (an ERK inhibitor; 20μM), SB203580 (a p38 inhibitor; 20μM) and SP600125 (a JNK inhibitor; 20μM) also blocked cell migration and varenicline-induced downregulation of VE-cadherin expression in HUVECs. These findings suggest that varenicline promotes HUVEC migration by lowering VE-cadherin expression due to activated ERK/p38/JNK signaling through α7 nAChR. These processes probably contribute to varenicline-aggravated atherosclerotic plaque. Hence, an increased risk of cardiovascular events upon varenicline treatment might occur and must be considered in patients with cardiovascular diseases.

Effect of electro-acupuncture at Zusanli acupoint on blood coagulation during intestinal ischemia-reperfusion in rats

Objective To evaluate the effect of electro-acupuncture (EA) at Zusanli (ST36) acupoint on blood coagulation during intestinal ischemia-reperfusion (I/R) in rats. Methods Forty healthy male Sprague-Dawley rats, aged 6-8 months, weighing 250-300 g, were divided into 5 groups (n=8 each) using a random number table: sham operation group (group S), intestinal I/R group (group I/R), EA at Zusanli acupoint group (group EA), EA at non-acupoint group (group NE) and α7 nicotinic acetylcholine receptor antagonist α-bungarotoxin (α-BGT) group (group α-BGT). Intestinal I/R was induced by clamping the superior mesenteric artery for 45 min followed by 120 min of reperfusion.Bilateral Zusanli acupoints were stimulated with an electric stimulator (frequency 3 Hz, voltage 2-4 V, wave length 2 ms) for 30 min starting from the time point immediately after beginning of ischemia in group EA, while EA was performed at the points 5 mm lateral to the bilateral Zusanli instead in group NE.In group α-BGT, α-BGT 1 μg/kg was intraperitoneally injected at 45 min before ischemia, and the other treatments were similar to those previously described in group EA.Blood samples were collected from the abdominal aorta at 120 min of reperfusion for determination of the concentrations of tumor necrosis factor alpha (TNFα), tissue factor (TF), antithrombin (AT), tissue plasminogen activator (tPA), fiber plasminogen activator inhibitor-1 (PAI-1) and D-dimer in plasma (by enzyme-linked immunosorbent assay) and platelet count (PLT). The animals were sacrificed after blood sampling, the distal ileum specimens were removed for examination of the pathological changes with a light microscope, and the damage to the intestinal mucous membrane was assessed and scored according to Chiu. Results Compared with group S, the concentrations of plasma TNFα, TF, tPA, PAI-1 and D-dimer were significantly increased, and the plasma AT concentration and PLT were decreased in I/R, NE and α-BGT groups, the concentrations of plasma TNFα and TF were significantly increased, and the plasma AT concentration was decreased in group EA, and Chiu′s scores were significantly increased in I/R, EA, NE and α-BGT groups (P 0.05). Compared with group EA, the concentrations of plasma TNFα, TF, tPA, PAI-1 and D-dimer were significantly increased, the plasma AT concentration and PLT were decreased, and Chiu′s scores were increased in group NE (P<0.05). Conclusion EA at Zusanli acupoint can improve blood coagulation during intestinal I/R in rats, and the mechanism is related to activating the cholinergic anti-inflammatory pathway. Key words: Electroacupuncture; POINT ST36 (ZUSANLI); Reperfusion injury; Intestines; Blood coagulation