Nicotinic Acetylcholine Receptor Agonist Research Articles

The effects of intra-accumbal administration of the nicotinic acetylcholine receptor agonist cytisine on the operant oral self-administration of ethanol were prevented by the GABAB receptor agonist baclofen in rats

RationaleAlthough the mesocorticolimbic dopamine (DA) system is the main neurochemical substrate that regulates the addictive and reinforcing effects of ethanol (EtOH), other neurotransmitter systems, such as the acetylcholine (Ach) system, modulate DAergic function in the nucleus accumbens (nAcc). Previously, we reported that intra-nAcc administration of the nicotinic Ach receptor agonist cytisine increased oral EtOH self-administration. GABAB receptors in the nAcc are expressed in DAergic terminals, inhibit the regulation of DA release into the nAcc, and could modulate the effects of cytisine on oral EtOH self-administration. The present study assessed the effects of intra-nAcc administration of the GABAB receptor agonist baclofen (BCF) on the impacts of cytisine on oral EtOH self-administration. Methods: Male Wistar rats were deprived of water for 23.30 h and then trained to press a lever to receive EtOH on an FR3 schedule until a stable response rate of 80 % was achieved. After this training, the rats received an intra-nAcc injection of the nAch receptor agonist cytisine, BCF, and cytisine or 2-hydroxysaclofen, BCF, and cytisine before they were given access to EtOH on an FR3 schedule. Results: Intra-nAcc injections of cytisine increased oral EtOH self-administration; this effect was reduced by BCF, and 2-hydroxysaclofen blocked the effects of BCF. Conclusions: These findings suggest that the reinforcing effects of EtOH are modulated not only by the DA system but also by other neurotransmitter systems involved in regulating DA release from DAergic terminals.

Advances in attenuating opioid-induced respiratory depression: A narrative review.

Opioids exert analgesic effects by agonizing opioid receptors and activating signaling pathways coupled to receptors such as G-protein and/or β-arrestin. Concomitant respiratory depression (RD) is a common clinical problem, and improvement of RD is usually achieved with specific antagonists such as naloxone; however, naloxone antagonizes opioid analgesia and may produce more unknown adverse effects. In recent years, researchers have used various methods to isolate opioid receptor-mediated analgesia and RD, with the aim of preserving opioid analgesia while attenuating RD. At present, the focus is mainly on the development of new opioids with weak respiratory inhibition or the use of non-opioid drugs to stimulate breathing. This review reports recent advances in novel opioid agents, such as mixed opioid receptor agonists, peripheral selective opioid receptor agonists, opioid receptor splice variant agonists, biased opioid receptor agonists, and allosteric modulators of opioid receptors, as well as in non-opioid agents, such as AMPA receptor modulators, 5-hydroxytryptamine receptor agonists, phosphodiesterase-4 inhibitors, and nicotinic acetylcholine receptor agonists.

Activation of the Alpha 7 Nicotinic Acetylcholine Receptor by GTS-21 Mitigates Contrast Nephropathy in a Rat Model.

Contrast nephropathy (CN) is characterized by oxidative stress, vasoconstriction, tubular toxicity, and hypoxia of the renal medulla. We aimed to test the therapeutic effects of an α7 nicotinic acetylcholine receptor (nAChR) agonist, GTS-21, in an experimental CN model. Male Sprague-Dawley rats (n = 40) were divided into 4 groups: saline-treated control, GTS-21-treated control, contrast, and GTS-21-treated contrast groups. Starting on the 1st day, GTS-21 (4 mg/kg, intraperitoneally) or saline was administered twice a day for 3 days. CN was induced on the second day by intravenous injection of indomethacin (10 mg/kg), <sc>l</sc>-NAME (10 mg/kg), and a contrast agent with high osmolarity (6 mL/kg; Urografin 76%). At the 72nd hour, blood and kidney samples were obtained for the determination of biochemical, histological, and gene expression parameters. Compared to those in control rats, the elevated serum BUN level in the contrast group decreased with GTS-21 treatment, while H&amp;E staining and TUNEL assays showed that contrast-induced renal injury was improved by GTS-21. Moreover, GTS-21 treatment in the CN also increased the antioxidant glutathione level. In the contrast group, a significant increase in IL-6 expression and a decrease in TGF-β expression were observed; however, GTS-21 treatment decreased IL-6 expression and increased TGF-β expression. GTS-21 significantly alleviated renal injury parameters through antioxidant, anti-inflammatory, and antiapoptotic mechanisms in the CN model.

Systematic review and meta-analyses of cytisine to support tobacco cessation.

Cytisine (also known as cytisinicline) is a low-cost partial agonist of nicotinic acetylcholine receptors used to assist tobacco cessation. We aimed to review the effectiveness of cytisine for tobacco cessation and the effects of dose and co-use of behavioural or other pharmacological interventions on cessation outcomes. We searched seven databases, Google Scholar, and reference lists of included publications for randomised controlled trials investigating use of cytisine as a tobacco cessation aid. Studies were eligible if participants were ≥15 years old and used tobacco upon study enrolment. We conducted four random effects meta-analyses and sensitivity analyses with fixed effects models. We used the Cochrane risk-of-bias tool for randomised trials version 2 to assess risk of bias in included studies, with adjustments recommended by the Cochrane Tobacco Addiction Group. Participants using cytisine were significantly more likely to quit tobacco than participants who received placebo/no intervention/usual care (risk ratio [RR] = 2.65, 95% confidence interval [CI] = 1.50-4.67, 6 trials, 5194 participants) or nicotine replacement therapy (RR = 1.36, 95% CI = 1.06-1.73, p = 0.0152, 2 trials, 1511 participants). The difference in cessation rates among participants receiving cytisine versus varenicline was not statistically significant (RR = 0.96, 95% CI 0.63-1.45, P = 0.8464, 3 trials, 2508 participants). Two trials examined longer versus shorter treatment duration, finding higher abstinence rates with longer treatment (RR = 1.29, 95% CI = 1.02-1.63, 2 trials, 1009 participants). The differences in the number of adverse events reported by participants who received cytisine versus placebo (RR = 1.19, 95% CI = 0.99-1.41, P = 0.0624; 6 trials; 4578 participants) or cytisine versus varenicline (RR = 1.37, 95% CI = 0.57-3.33, P = 0.4835; 2 trials; 1345 participants) were not statistically significant. Most adverse events were mild (e.g. abnormal dreams, nausea, headaches). Cytisine is an effective aid for tobacco cessation and appears to be more effective for tobacco cessation than placebo, no intervention, usual care and nicotine replacement therapy.

Chronic inhibition of angiotensin converting enzyme lowers blood pressure in spontaneously hypertensive rats by attenuation of sympathetic tone: The role of enhanced baroreflex sensitivity

Spontaneously hypertensive rats (SHR) are characterized by sympathetic hyperactivity and insufficient parasympathetic activity, and their high blood pressure (BP) can be lowered by long-term inhibition of the renin-angiotensin system. The aim of our study was to determine the influence of chronic inhibition of angiotensin converting enzyme (ACE) by captopril on cardiovascular regulation by the sympathetic and parasympathetic nervous system. Implanted radiotelemetric probes or arterial cannulas were used to measure mean arterial pressure (MAP), heart rate (HR), and arterial baroreflex in adult SHR and Wistar-Kyoto (WKY) rats under basal or stress conditions. MAP and the low-frequency component of systolic blood pressure variability (LF-SBPV, marker of sympathetic activity) were greater in SHR than in WKY rats. Under basal conditions chronic captopril treatment reduced both parameters more effectively in SHR, and the same was true during acute restraint stress. HR was similar in control rats of both strains, but WKY rats showed greater heart rate variability (HRV), indicating higher parasympathetic activity. Captopril administration increased HR in both strains, whereas HRV was decreased only in WKY. Chronic captopril treatment improved the impaired baroreflex-HR control in SHR by increasing the sensitivity but not the capacity of vagal arm of arterial baroreflex. Captopril treatment attenuated BP changes elicited by dimethylphenylpiperazinium (DMPP, agonist of nicotinic acetylcholine receptors), especially in SHR, indicating that sympathetic nerve transmission is facilitated by angiotensin II more in hypertensive than in normotensive animals. Thus, chronic ACE inhibition improves baroreflex sensitivity and lowers BP through both central and peripheral attenuation of sympathetic tone.

Nicotine Exposure Causes Nitrosative and Oxidative Stress in Glomerular Podocytes, Resulting in Renal Damage

Introduction: Nicotine consumption is the leading cause of preventable disease and death. Patients with hypertension or kidney disease are more likely to exhibit renal pathologies associated with nicotine, such as glomerulopathy. In endothelial cells, nicotine was linked to mitochondrial oxidative stress and nitric oxide synthase (NOS) remodeling. However, there is a gap in knowledge regarding the effects of nicotine in glomerular epithelial cells, podocytes. We hypothesized that nicotine promotes nitrosative stress in the podocytes by producing peroxynitrite (ONOO-) and mitochondrial damage, thereby reducing glomerular function. Methods: We performed confocal imaging on human cultured podocytes to detect ONOO− (HPF), Ca2+ (Fluo-8) and nitric oxide NO (DAF-FM) in response to nicotine. Seahorse assay (Agilent XFe24) was used to test mitochondrial respiration. Then, nicotine was chronically infused in Dahl SS rats (0.2 mg/kg/day s.c., 0.4% NaCl, 21 days), and blood pressure was recorded with telemetry. Glomerular damage was evaluated, and electron microscopy was employed to assess mitochondrial ultrastructure. Electron paramagnetic resonance (EPR) spectroscopy was used to access the NO levels in cultured podocytes and in vivo. OriginPro was used for statistical analysis. Results: Acute application of nicotine promoted intracellular Ca2+ and ONOO− transients in podocytes. The ONOO− response was blocked in the presence of SOD, indicating that ONOO− production requires superoxide. The application of specific α7 or α4β2, α2β4, α4β4, and α3β4 nicotinic acetylcholine receptor (nAChR) agonists elicited Ca2+ transients but did not produce ONOO−, suggesting that nitrosative stress occurs independently from Ca2+ influx or nAChR activation. Incubation with nicotine (12 hrs) resulted in a decrease in podocytes’ mitochondrial respiration (two-sample t-test, p&lt;0.05). In vivo, nicotine infusion did not affect blood pressure but promoted mitochondrial damage in podocytes, which exhibited swelling, loss of cristae, and mitophagy (t-test, p&lt;0.05). Histopathological assessment showed higher glomerular damage in nicotine-exposed rats (t-test, p&lt;0.05). Both EPR and confocal approaches demonstrated nicotine-mediated changes in NO bioavailability and an increase in NOS2 activity (t-test, p&lt;0.05) Conclusion: Nicotine elicits superoxide-mediated nitrosative stress and peroxynitrite formation in podocytes, promoting mitochondrial damage and glomerular dysfunction. Revealing the mechanisms of nicotine-mediated damage in the podocytes impacts our progress towards new treatments for smoking and vaping-associated renal pathologies. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Nicotinic and Muscarinic Acetylcholine Receptor Agonists Counteract Cognitive Impairment in a Rat Model of Doxorubicin-Induced Chemobrain via Attenuation of Multiple Programmed Cell Death Pathways.

Chemotherapy causes undesirable long-term neurological sequelae, chemotherapy-induced cognitive impairment (CICI), or chemobrain in cancer survivors. Activation of programmed cell death (PCD) has been proposed to implicate in the development and progression of chemobrain. Neuronal apoptosis has been extensively recognized in experimental models of chemobrain, but little is known about alternative forms of PCD in response to chemotherapy. Activation of acetylcholine receptors (AChRs) is emerging as a promising target in attenuating a wide variety of the neuronal death associated with neurodegeneration. Thus, this study aimed to investigate the therapeutic capacity of AChR agonists on cognitive function and molecular hallmarks of multiple PCD against chemotherapy neurotoxicity. To establish the chemobrain model, male Wistar rats were assigned to receive six doses of doxorubicin (DOX: 3mg/kg) via intraperitoneal injection. The DOX-treated rats received either an a7nAChR agonist (PNU-282987: 3mg/kg/day), mAChR agonists (bethanechol: 12mg/kg/day), or the two as a combined treatment. DOX administration led to impaired cognitive function via neuroinflammation, glial activation, reduced synaptic/blood-brain barrier integrity, defective mitochondrial ROS-detoxifying capacity, and dynamic imbalance. DOX insult also mediated hyperphosphorylation of Tau and simultaneously induced various PCD, including apoptosis, necroptosis, and pyroptosis in the hippocampus. Concomitant treatment with either PNU-282987, bethanechol, or a combination of the two potently attenuated neuroinflammation, mitochondrial dyshomeostasis, and Tau hyperphosphorylation, thereby suppressing excessive apoptosis, necroptosis, and pyroptosis and improving cognitive function in DOX-treated rats. Our findings suggest that activation of AChRs using their agonists effectively protected against DOX-induced neuronal death and chemobrain.

Motor behavior improvement in ischemic gerbils by cholinergic receptor activation and treadmill training

Introduction: Treadmill exercise training is one of the most investigated non-pharmacological treatment options for experimental brain ischemia. However, the cholinergic system is essential for improving motor behavior responses. Objective: To analyze the effects of a nicotinic acetylcholine receptor (nAChR) agonist (1, 2, and 4 mg/kg) on the motor behavior of ischemic gerbils subjected to forced treadmill training.Methods: In this experimental study, 72 gerbils, weighing 65–80 g, were divided into eight groups: Sal, Ni1, Ni2, Ni4, I, INi1, INi2, and INi4. Behavioral assessment was initiated 24 hours after the last motor stimulation on the treadmill. Rotarod test (RR) was employed to analyze animal behavior. The data were analyzed using one-way analysis of variance (ANOVA), and the Newman-Keuls post hoc test evidenced differences detected between groups. Results: Data regarding the RR test revealed decreased time spent on the RR apparatus for the Ni1, Ni4, and I groups compared to the Sal and Ni2 groups. However, the INi1 and INi2 groups showed increased time spent compared with the ischemia and INi4 groups (F7,64=4.63; p&lt;0.05).Conclusions: The present study indicates that treadmill training with a concomitant 1 and 2 mg/kg of nAChR agonist effectively improves the behavior of ischemic gerbils.

Activation of α7 nAChR improves white fat homeostasis and promotes beige adipogenesis and thermogenesis in obese mice

To investigate the effects of α7 nicotinic acetylcholine receptor (nAChR) agonist on β3-adrenoceptor agonist-induced impairment of white fat homeostasis and beige adipose formation and heat production in obese mice. Forty obese C57BL/6J mice were randomized into high-fat feeding group, β3-adrenoceptor agonist-treated model group, α7 nAChR agonist group, and α7 nAChR inhibitor group (n=10), with another 10 mice with normal feeding as the blank control group. White adipose tissue from the epididymis of the mice were sampled for HE staining of the adipocytes. The expression levels of TNF-α, IL-1β, IL-10 and TGF-β in the white adipose tissue were determined by ELISA, and the mRNA levels of iNOS, Arg1, UCP-1, PRDM-16 and PGC-1α were detected using RT-qPCR. Western blotting was performed to detect the expression levels of NF-κB P65, p-JAK2, p-STAT3 in the white adipose tissue. Compared with those in the blank control group, the mice with high-fat feeding showed significantly increased body weight, more fat vacuoles in the white adipose tissue, increased volume of lipid droplets in the adipocytes, upregulated iNOS mRNA expression and protein expression of TNF-α and IL-1β, and lowered expression of Arg-1 mRNA and IL-10 and TGF-β proteins (P < 0.01). Treatment with α7 nAChR significantly reduced mRNA levels of PRDM-16, PGC-1α and UCP-1, lowered TNF-α and IL-1β expressions, increased IL-10 and TGF-β expressions, and reduced M1/M2 macrophage ratio in the white adipose tissues (P < 0.05 or 0.01). Activation of α7 nAchR improves white adipose tissue homeostasis impairment induced by β3 agonist, promotes transformation of M1 to M2 macrophages, reduces inflammatory response in white adipose tissue, and promote beige adipogenesis and thermogenesis in obese mice.

Activation of alpha-7 nicotinic acetylcholine receptor by tropisetron mitigates 3-nitropropionic acid-induced Huntington's disease in rats: Role of PI3K/Akt and JAK2/NF-κB signaling pathways

Huntington's disease (HD) is an inheritable autosomal-dominant disorder that targets mainly the striatum. 3-Nitropropionic acid (3-NP) induces obvious deleterious behavioral, neurochemical, and histological effects similar to the symptoms of HD. Our study aimed to examine the neuroprotective activity of tropisetron, an alpha-7 neuronal nicotinic acetylcholine receptor (α-7nAChR) agonist, against neurotoxic events associated with 3-NP-induced HD in rats. Forty-eight rats were randomly allocated into four groups. Group I received normal saline, while Groups II, III and IV received 3-NP for 2 weeks. In addition, Group III and IV were treated with tropisetron 1 h after 3-NP administration. Meanwhile, Group IV received methyllycaconitine (MLA), an α-7nAChR antagonist, 30 min before tropisetron administration. Treatment with tropisetron improved motor deficits as confirmed by the behavioral tests and restored normal histopathological features of the striatum. Moreover, tropisetron showed an anti-oxidant activity via increasing the activities of SDH and HO-1 as well as Nrf2 expression along with reducing MDA level. Tropisetron also markedly upregulated the protein expression of p-PI3K and p-Akt which in turn hampered JAK2/NF-κB inflammatory cascade. In addition, tropisetron showed an anti-apoptotic activity through boosting the expression of Bcl-2 and reducing Bax expression and caspase-3 level. Interestingly, all the aforementioned effects of tropisetron were blocked by pre-administration of MLA, which confirms that such neuroprotective effects are mediated via activating of α-7nAChR. In conclusion, tropisetron showed a neuroprotective activity against 3-NP-induced HD via activating PI3K/Akt signaling and suppressing JAK2/NF-κB inflammatory axis. Thus, repositioning of tropisetron could represent a promising therapeutic strategy in management of HD.

Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling

Western diet (WD) consumption during early life developmental periods is associated with impaired memory function, particularly for hippocampus (HPC)-dependent processes. We developed an early life WD rodent model associated with long-lasting HPC dysfunction to investigate the neurobiological mechanisms mediating these effects. Rats received either a cafeteria-style WD (ad libitum access to various high-fat/high-sugar foods; CAF) or standard healthy chow (CTL) during the juvenile and adolescent stages (postnatal days 26–56). Behavioral and metabolic assessments were performed both before and after a healthy diet intervention period beginning at early adulthood. Results revealed HPC-dependent contextual episodic memory impairments in CAF rats that persisted despite the healthy diet intervention. Given that dysregulated HPC acetylcholine (ACh) signaling is associated with memory impairments in humans and animal models, we examined protein markers of ACh tone in the dorsal HPC (HPCd) in CAF and CTL rats. Results revealed significantly lower protein levels of vesicular ACh transporter in the HPCd of CAF vs. CTL rats, indicating chronically reduced ACh tone. Using intensity-based ACh sensing fluorescent reporter (iAChSnFr) in vivo fiber photometry targeting the HPCd, we next revealed that ACh release during object-contextual novelty recognition was highly predictive of memory performance and was disrupted in CAF vs. CTL rats. Neuropharmacological results showed that alpha 7 nicotinic ACh receptor agonist infusion in the HPCd during training rescued memory deficits in CAF rats. Overall, these findings reveal a functional connection linking early life WD intake with long-lasting dysregulation of HPC ACh signaling, thereby identifying an underlying mechanism for WD-associated memory impairments.

Effects of Cholinergic Receptor Activation and Magnetic Fields on Motor Behavior in Ischemic Gerbils

Introduction: Ischemic stroke stands as a leading global cause of death and disability, prompting the need for animal model experiments in stroke research and the protection of motor function. Recently, magnetic fields have gained significant interest in various biological contexts, showing promise in preserving neurons and reversing behavioral and morphological changes in stroke models. This study explores the potential synergy between static magnetic field and nAChR agonist administration in safeguarding motor behavior in ischemic gerbils. Objective: To determine whether the combined use of a static magnetic field and an agonist for nicotinic acetylcholine receptors (nAChR) can preserve motor behavior in ischemic gerbils.Methods: In this experimental study, 72 Mongolian gerbils were randomly allocated into nine groups (n=8): S, SISM, SINSM, ISM, INP, ISP, INSM, INNP, INSP, distributed according to surgical procedure and treatment. The animals were trained and evaluated on the Rotarod (RR) to assess motor performance.Results: The main finding was the preservation of motor behavior in the Sham Ischemia and Nicotine and Sham Magnetic Stimulation (SINSM) and Ischemia and Nicotine and South Pole Magnetic Field (INSP) groups, as evidenced by the results of the RR test.Conclusions: The findings are consistent with previous literature and provide insight into the mechanism of potentiation, as results showed that adding a nAChR agonist to the magnetic field preserved motor performance in the RR test of ischemic animals.

The alpha-7 nicotinic acetylcholine receptor agonist PHA-543613 reduces food intake in male rats

Obesity is a prevalent disease, but effective treatment options remain limited. Agonists of the alpha-7 nicotinic acetylcholine receptor (α7nAChR) promote negative energy balance in mice, but these effects are not well-studied in rats. We tested the hypothesis that central administration of the α7nAChR agonist PHA-543613 (PHA) would decrease food intake and body weight in adult male Sprague Dawley rats. Intracerebroventricular (ICV) PHA administration in chow-fed rats produced a suppression of energy intake and weight gain over 24 h. Next, to evaluate effects of ICV PHA on palatable food intake, rats were maintained on a choice diet of rodent chow and 45 % high fat diet (HFD); under these conditions, ICV PHA produced no significant changes in energy intake from either food, or body weight gain, in the 24 h post-injection. However, when given a choice of chow or a higher-fat 60 % HFD, ICV PHA reduced intake of 60 % HFD, but not chow; body weight gain was also suppressed. Further experiments evaluating conditioned taste avoidance (CTA) and pica in response to ICV PHA suggested that the suppressive food intake and body weight effects after ICV injection of PHA were not due to nausea/malaise. Finally, an operant conditioning study showed that responding on a progressive ratio schedule of reinforcement for high-fat food pellets decreased after ICV PHA. Collectively, these studies show that PHA reduces energy intake under some but not all dietary conditions. Importantly, central PHA decreases both food intake as well as motivation for highly palatable, energy dense foods in rats without inducing nausea/malaise, suggesting that the α7nAChR could be a viable target for developing treatments for obesity.

GTS-21 attenuates ACE/ACE2 ratio and glycocalyx shedding in lipopolysaccharide-induced acute lung injury by targeting macrophage polarization derived ADAM-17

Acute lung injury (ALI) has received considerable attention in intensive care owing to its high mortality rate. It has been demonstrated that the selective alpha7 nicotinic acetylcholine receptor agonist Gainesville Tokushima scientists (GTS)-21 is promising for treating ALI caused by lipopolysaccharides (LPS). However, the precise underlying mechanism remains unknown. This study aimed to investigate the potential efficacy of GTS-21 in the treatment of ALI. We developed mouse models of ALI and alveolar epithelial type II cells (AT2s) injury following treatment with LPS and different polarized macrophage supernatants, respectively. Pathological changes, pulmonary edema, and lung compliance were assessed. Inflammatory cells count, protein content, and pro-inflammatory cytokine levels were analysed in the bronchoalveolar lavage fluid. The expression of angiotensin-converting enzyme (ACE), ACE2, syndecan-1 (SDC-1), heparan sulphate (HS), heparanase (HPA), exostosin (EXT)-1, and NF-κB were tested in lung tissues and cells. GTS-21-induced changes in macrophage polarization were verified in vivo and in vitro. Polarized macrophage supernatants with or without recombination a disintegrin and metalloproteinase-17 (ADAM-17) and small interfering (si)RNA ADAM-17 were used to verify the role of ADAM-17 in AT2 injury. By reducing pathological alterations, lung permeability, inflammatory response, ACE/ACE2 ratio, and glycocalyx shedding, as well as by downregulating the HPA and NF-κB pathways and upregulating EXT1 expression in vivo, GTS-21 significantly diminished LPS-induced ALI compared to that of the LPS group. GTS-21 significantly attenuated macrophage M1 polarization and augmented M2 polarization in vitro and in vivo. The destructive effects of M1 polarization supernatant can be inhibited by GTS-21 and siRNA ADAM-17. GTS-21 exerted a protective effect against LPS-induced ALI, which was reversed by recombinant ADAM-17. Collectively, GTS-21 alleviates LPS-induced ALI by attenuating AT2s ACE/ACE2 ratio and glycocalyx shedding through the inhibition of macrophage M1 polarization derived ADAM-17.

Effects of α7 nicotinic acetylcholine receptor agonist against α-synuclein-induced neurotoxicity

The α7 neuronal nicotinic acetylcholine receptor (α7 nAChR) is a potential target for the development of Parkinson’s disease (PD) therapeutics. α-Synuclein (α-Syn), a principal component of Lewy bodies (cytoplasmic inclusions), is a major contributor to PD pathophysiology. Previous studies have demonstrated that activating α7 nAChR protects against nigrostriatal dopamine degeneration in acute and chronic PD animal models induced by 6-hydroxydopamine and rotenone, respectively. In the present study, we investigated the effects of PNU282987, a selective α7 nAChR agonist, against α-Syn-induced neurotoxicity in α-SynWT-, α-SynA30P-, and α-SynE46K-N2a cells. PNU282987 exhibited substantial neuroprotection against both wild-type and mutant-type α-Syn-induced toxicity. Furthermore, PNU282987 promoted transcription factor EB activity and reduced intracellular α-Syn protein levels through autophagy induction. These results highlight the therapeutic potential of α7 nAChR activation in diseases characterized by α-Syn aggregation, such as PD.

Nicotine promotes development of bile duct ligation-induced liver fibrosis by increasing expression of nicotinic acetylcholine receptors in rats.

Liver fibrosis and cigarette smoking seem to be directly linked. Nicotine, as an agonist of nicotinic acetylcholine receptors (nAChRs), induces many downstream signaling pathways. The pathways through which nicotine affects the process of liver fibrosis have not been clarified. The present study aimed to investigate the nicotine-induced effects on fibrosis progression in cholestatic rats. First, the Wistar rats were subjected to sham or bile duct ligation (BDL) surgery. The rats were treated with low and high doses of nicotine (1 or 10 mg/kg) for three weeks. They were monitored for their body weights before and 21 days after BDL. Also, spleens were weighed to calculate the spleen/body weight ratio. Ductular proliferation and fibrosis were evaluated using hematoxylin and eosin (H&E) as well as Masson's trichrome staining. The mRNA expression of α4nAChR, α7nAChR, and fibrosis gene α-smooth muscle actin (α-SMA) was measured by real-time PCR. The findings showed that nicotine promotes the development of BDL-induced liver fibrosis. The ratio of spleen/body weight was significantly affected by nicotine exposure. H&E and Masson's trichrome staining showed that the level of liver fibrosis was higher in the cholestatic BDL groups, and this effect was significantly augmented in the nicotine-treated rats. Also, α4nAChR, α7nAChR, and α-SMA expression was observed in the BDL rats and increased following nicotine treatment. The activation of nAChR triggers biliary proliferation and liver fibrosis. Studying the intracellular mechanism of nicotine and alteration in the expression of nicotinic receptors following nicotine exposure can be useful both in diagnosing nicotine-related diseases and finding new treatment strategies.

Quantification of Proliferating and Mitotically Active Retinal Cells in Mice by Flow Cytometry.

Adult mammals lack the ability to regenerate retinal neurons after injury. However, in previous studies from this lab, topical application of the selective alpha7 nicotinic acetylcholine receptor (nAChR) agonist, PNU-282987, has been associated with an increase in the number of retinal neurons in adult murine models both in the presence and absence of injury to the retina. Additionally, studies assaying mitotic markers have shown a substantial increase in the amount of mitotically active and proliferating cells with the topical application of the alpha7 nAChR agonist. However, these previous studies were performed using fluorescent immunolabeling and subsequent confocal microscopy, thus limiting the number of antibodies that can be multiplexed. As a result, we have developed a flow cytometry method that allows for the multiplexing and analysis of multiple external and internal markers in dissociated retinal cells. In this paper, a step-by-step protocol is described for the labeling of multiple retinal cell types such as retinal ganglion cells, rod photoreceptors, and Müller glia, concurrently with Müller glia-derived progenitor cells that arise after treatment with PNU-282987. Key features • Neurogenesis in the adult mammalian retina. • Flow cytometry of retinal cells. • PNU-282987-induced mitotic activity in the retina. • Dissociation of the retina for flow cytometry analysis. Graphical overview Schematic demonstrating the protocol for preparation of retinal cells for flow cytometry analysis. (A) Adult mice (3-6 months) are subjected to topical PBS eyedrop treatment containing DMSO (control groups) or PNU-282987 (experimental groups). Both eyedrop treatments contain 1 mg/mL of BrdU to label proliferating cells. After treatment, mice are euthanized, and retinae are harvested for dissociation using papain. (B) Dissociated retina cells are fixed and permeabilized before aliquots are taken for cell counts on a hemocytometer. After determining the number of cells present, conjugated antibodies and unconjugated primary antibodies are added at the appropriate dilutions. Fluorescent secondary antibodies are added for markers that are unconjugated. Cells are then subjected to flow cytometric analysis using a BD LSRFortessa.

α7 nicotinic acetylcholine receptor agonist attenuates allergen-induced immediate nasal response in murine model of allergic rhinitis.

The expression of nicotinic acetylcholine receptor (nAChR) subunits on various immune cells suggests their involvement in allergic rhinitis. However, how exactly they contribute to this pathogenesis is not yet confirmed. Our present study examined the therapeutic potential of GTS-21, an α7 nAChR agonist, for treating allergic rhinitis by employing its mouse models. GTS-21 treatment reduced allergen-induced immediate nasal response in ovalbumin (OVA)-sensitized model. However, nasal hyperresponsiveness or eosinophil infiltration elicited in either the OVA-sensitized or T helper 2 cell-transplanted model was not affected by GTS-21. GTS-21 did not alter allergen-induced passive cutaneous anaphylaxis response in anti-dinitrophenyl IgE-sensitized mice. This evidence implies GTS-21's potential to alleviate allergic rhinitis without perturbing T cells or mast cells.

Cognitive-Enhancing Effects of Acetylcholine Receptor Agonists in Group-Housed Cynomolgus Monkeys Who Drink Ethanol.

The cognitive impairments that are often observed in patients with alcohol use disorder (AUD) partially contribute to the extremely low rates of treatment initiation and adherence. Brain acetylcholine receptors (AChR) mediate and modulate cognitive and reward-related behavior, and their distribution can be altered by long-term heavy drinking. Therefore, AChRs are promising pharmacotherapeutic targets for treating the cognitive symptoms of AUD. In the present study, the procognitive efficacy of two AChR agonists, xanomeline and varenicline, were evaluated in group-housed monkeys who self-administered ethanol for more than 1 year. The muscarinic AChR antagonist scopolamine was used to disrupt performance of a serial stimulus discrimination and reversal (SDR) task designed to probe cognitive flexibility, defined as the ability to modify a previously learned behavior in response to a change in reinforcement contingencies. The ability of xanomeline and varenicline to remediate the disruptive effects of scopolamine was compared between socially dominant and subordinate monkeys, with lighter and heavier drinking histories, respectively. We hypothesized that subordinate monkeys would be more sensitive to all three drugs. Scopolamine dose-dependently impaired performance on the serial SDR task in all monkeys at doses lower than those that produced nonspecific impairments (e.g., sedation); its potency did not differ between dominant and subordinate monkeys. However, both AChR agonists were effective in remediating the scopolamine-induced deficit in subordinate monkeys but not in dominant monkeys. These findings suggest xanomeline and varenicline may be effective for enhancing cognitive flexibility in individuals with a history of heavy drinking. SIGNIFICANCE STATEMENT: Procognitive effects of two acetylcholine (ACh) receptor agonists were assessed in group-housed monkeys who had several years' experience drinking ethanol. The muscarinic ACh receptor agonist xanomeline and the nicotinic ACh receptor agonist varenicline reversed a cognitive deficit induced by the muscarinic ACh receptor antagonist scopolamine. However, this effect was observed only in lower-ranking (subordinate) monkeys and not higher-ranking (dominant monkeys). Results suggest that ACh agonists may effectively remediate alcohol-induced cognitive deficits in a subpopulation of those with alcohol use disorder.

Central cholinergic transmission affects the compulsive-like behavior of mice in marble-burying test

The presence of the cholinergic system in the brain areas implicated in the precipitation of obsessive–compulsive behavior (OCB) has been reported but the exact role of the central cholinergic system therein is still unexplored. Therefore, the current study assessed the effect of cholinergic analogs on central administration on the marble-burying behavior (MBB) of mice, a behavior correlated with OCB. The result reveals that the enhancement of central cholinergic transmission in mice achieved by intracerebroventricular (i.c.v.) injection of acetylcholine (0.01 µg) (Subeffective: 0.1 and 0.5 µg), cholinesterase inhibitor, neostigmine (0.1, 0.3, 0.5 µg/mouse) and neuronal nicotinic acetylcholine receptor agonist, nicotine (0.1, 2 µg/mouse) significantly attenuated the number of marbles buried by mice in MBB test without affecting basal locomotor activity. Similarly, central injection of mAChR antagonist, atropine (0.1, 0.5, 5 µg/mouse), nAChR antagonist, mecamylamine (0.1, 0.5, 3 µg/mouse) per se also reduced the MBB in mice, indicative of anti-OCB like effect of all the tested cholinergic mAChR or nAChR agonist and antagonist. Surprisingly, i.c.v. injection of acetylcholine (0.01 µg), and neostigmine (0.1 µg) failed to elicit an anti-OCB-like effect in mice pre-treated (i.c.v.) with atropine (0.1 µg), or mecamylamine (0.1 µg). Thus, the findings of the present investigationdelineate the role of central cholinergic transmission in the compulsive-like behavior of mice probably via mAChR or nAChR stimulation.