Nicotinic Agonist Research Articles

Disruption of exploratory behavior and olfactory memory in cockroaches exposed to sublethal doses of the neonicotinoid Thiamethoxam

Neonicotinoid insecticides (NNI) are agonists of insect nicotinic acetylcholine receptors (nAChR) that induce non-elucidate mechanisms of abnormal behavior in insects. In this work, we investigated the effects of sublethal doses of the neonicotinoid thiamethoxam (TMX) on neurochemical and physiological parameters in cockroaches. Sublethal doses of TMX (0.01–10 ng.g−1 body mass) caused significant alterations in most of the neurophysiological parameters evaluated. TMX reduced sustained locomotor activity by 19.9–25.8 %, depending on the dose. Leg grooming activity increased by 124.5 ± 3.4 %, 158.7 ± 3.5 %, 168.3 ± 3.4 %, and 160.4 ± 3.4 % (mean ± SEM) with TMX doses of 0.01, 0.1, 1, and 10 ng.g−1, respectively. Exploratory activity was significantly reduced only at the lowest TMX dose (0.01 ng.g−1) – the time spent immobile increased from 30 % to ~45 %, whereas none of the doses affected the walking speed. Treatment with TMX (0.01 ng.g−1) markedly reduced the olfactory sensitivity of the cockroaches and also reduced the mechanosensory action potential amplitude, rise time and decay time by 61.2 ± 19 %, 50 ± 4 %, and 76.8 ± 9.5 %, respectively. In semi-isolated heart preparations, TMX caused positive chronotropism (increases of 34.7 ± 15.9 %, 26.8 ± 7.8 %, 43.0 ± 16.5 %, and 19.0 ± 13.7 % for 0.01, 0.1, 1, and 10 ng of TMX, respectively). TMX attenuated the activity of glutathione-S-transferase by 35.1 ± 6.4 % at the highest dose tested (10 ng.g−1). TMX caused alterations in the metal ion content of cockroach brains that varied with the dose tested and the ion examined. These findings indicate that sublethal doses of TMX can interfere with normal neurological function in cockroaches and disrupt brain metal ion homeostasis.

The alpha 7 nicotinic acetylcholine receptor agonist PHA 568487 dampens inflammation in PBMCs from patients with newly discovered coronary artery disease.

The alpha 7 nicotinic acetylcholine receptor (α7nAChR) regulates inflammation in experimental models and is expressed in human peripheral blood mononuclear cells (PBMCs) and in human atherosclerotic plaques. However, its role in regulating inflammation in patients with cardiovascular disease is unknown. This study aims to investigate whether α7nAChR stimulation can reduce the inflammatory response in PBMCs from patients with newly diagnosed coronary artery disease (CAD). Human PBMCs, extracted from patients with verified CAD (n = 38) and control participants with healthy vessels (n = 38), were challenged in vitro with lipopolysaccharide (LPS) in combination with the α7nAChR agonist PHA 568487. Cytokine levels of the supernatants were analyzed using a multiplex immunoassay. Patients in the CAD group were reexamined after 6 mo. The immune response to LPS did not differ between PBMCs from control and CAD groups. α7nAChR stimulation decreased TNFα in both control and CAD groups. The most pronounced effect of α7nAChR stimulation was observed in patients with CAD at their first visit, where 15 of 17 cytokines were decreased [IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-10, IL-12 (p70), IL-17A, G-CSF, GM-CSF, IFN-γ, MCP-1, MIP-1β, and TNFα]. In conclusion, stimulation with α7nAChR agonist PHA 568487 dampens the inflammatory response in human PBMCs. This finding suggests that the anti-inflammatory properties of the α7nAChR may have a role in treating CAD.NEW & NOTEWORTHY The α7nAChR is an important regulator of inflammation; however, its anti-inflammatory function in patients with newly diagnosed coronary artery disease (CAD) remains unclear. We demonstrate that stimulation of α7nAChR with PHA 568487 attenuates the inflammatory response in immune cells extracted from healthy controls and patients with newly diagnosed CAD, with a more pronounced effect observed in patients with CAD. This suggests that the anti-inflammatory properties of α7nAChR may have a role in treating chronic inflammatory diseases.

Exploring the efficacy of cholinergic agents for the treatment of psychostimulant use disorder: a systematic review.

No drugs are currently validated to treat psychostimulant use disorder (PUD). Pathophysiological studies consistently highlight the contribution of cholinergic mechanisms in psychostimulant use, including the vulnerability to PUD, paving the way for potential therapeutic strategies. The aim of this systematic review is to describe and discuss the efficacy of cholinergic agents in drug trials for patients with PUD. A systematic review was conducted on April 4, 2024 in MedLine, Embase and Cochrane Library databases on controlled clinical drug trial of cholinergic agents in humans with PUD, psychostimulant abuse or dependence and psychostimulant use in recent year. Twenty-eight articles were included, twenty-one on cocaine and seven on amphetamines. Cholinergic agents used in these studies were biperiden (a muscarinic antagonist), mecamylamine (a nicotinic antagonist), nicotinic agonists, acetylcholinesterase inhibitors (AChEI), or citicoline. Two types of trials were identified. There were seventeen randomized controlled clinical trials evaluating cholinergic agents on psychostimulant use reduction in outpatients seeking treatment. Additionally, we retrieved eleven short-term «proof-of-concept» laboratory trials mainly with supervised psychostimulant administration and/or triggered craving challenges. Outpatient trials were heterogeneous and for most, inconclusive. Only two studies on galantamine (AChEI) and citicoline, reported a significant reduction of cocaine consumption. «Proof-of-concept» laboratory trials showed no evidence of efficacy on the selected outcomes, notably on craving. This review does not support the current prescription of cholinergic agents to treat PUD. Replication clinical trials notably on galantamine or other AChEI, and proof-of-concept trials on comedown symptoms will be necessary to identify a potential therapeutic indication for cholinergic agents in PUD.

Loss of the Na+/K+ cation pump CATP-1 suppresses nekl-associated molting defects.

The conserved Caenorhabditis elegans protein kinases NEKL-2 and NEKL-3 regulate membrane trafficking and are required for larval molting. Through a forward genetic screen we identified a mutation in catp-1 as a suppressor of molting defects in synthetically lethal nekl-2; nekl-3 double mutants. catp-1 encodes a membrane-associated P4-type ATPase involved in Na+-K+ exchange. A previous study found that wild-type worms exposed to the nicotinic agonist dimethylphenylpiperazinium (DMPP) exhibited larval arrest and molting-associated defects, which were suppressed by inhibition of catp-1. By testing a spectrum catp-1 alleles, we found that resistance to DMPP toxicity and the suppression of nekl defects did not strongly correlate, suggesting key differences in the mechanism of catp-1-mediated suppression. Through whole genome sequencing of additional nekl-2; nekl-3 suppressor strains, we identified two additional coding-altering mutations in catp-1. However, neither mutation, when introduced into nekl-2; nekl-3 mutants using CRISPR, was sufficient to elicit robust suppression of molting defects, suggesting the involvement of other loci. Endogenously tagged CATP-1 was primarily expressed in epidermal cells within punctate structures located near the apical plasma membrane, consistent with a role in regulating cellular processes within the epidermis. Based on previous studies, we tested the hypothesis that catp-1 inhibition induces entry into the pre-dauer L2d stage, potentially accounting for the ability of catp-1 mutants to suppress nekl molting defects. However, we found no evidence that loss of catp-1 leads to entry into L2d. As such, loss of catp-1 may suppress nekl-associated and DMPP-induced defects by altering electrochemical gradients within membrane-bound compartments.

Tropisetron, an Antiemetic Drug, Exerts an Anti-Epileptic Effect Through the Activation of α7nAChRs in a Rat Model of Temporal Lobe Epilepsy.

Temporal lobe epilepsy (TLE), a prevalent chronic neurological disorder, affects millions of individuals and is often resistant to anti-epileptic drugs. Increasing evidence has shown that acetylcholine (ACh) and cholinergic neurotransmission play a role in the pathophysiology of epilepsy. Tropisetron, an antiemetic drug used for chemotherapy in clinic, has displayed potential in the treatment of Alzheimer's disease, depression, and schizophrenia in animal models. However, as a partial agonist of α7 nicotinic acetylcholine receptors (α7nAChRs), whether tropisetron possesses the therapeutic potential for TLE has not yet been determined. In this study, tropisetron was intraperitoneally injected into pilocarpine-induced epileptic rats for 3 weeks. Alpha-bungarotoxin (α-bgt), a specific α7nAChR antagonist, was applied to investigate the mechanism of tropisetron. Rats were assessed for spontaneous recurrent seizures (SRS) and cognitive function using video surveillance and Morris's water maze testing. Hippocampal impairment and synaptic structure were evaluated by Nissl staining, immunohistochemistry, and Golgi staining. Additionally, the levels of glutamate, γ-aminobutyric acid (GABA), ACh, α7nAChRs, neuroinflammatory cytokines, glucocorticoids and their receptors, as well as synapse-associated protein (F-actin, cofilin-1) were quantified. The results showed that tropisetron significantly reduced SRS, improved cognitive function, alleviated hippocampal sclerosis, and concurrently suppressed synaptic remodeling and the m6A modification of cofilin-1 in TLE rats. Furthermore, tropisetron lowered glutamate levels without affecting GABA levels, reduced neuroinflammation, and increased ACh levels and α7nAChR expression in the hippocampi of TLE rats. The effects of tropisetron treatment were counteracted by α-bgt. In summary, these findings indicate that tropisetron exhibits an anti-epileptic effect and provides neuroprotection in TLE rats through the activation of α7nAChRs. The potential mechanism may involve the reduction of glutamate levels, enhancement of cholinergic transmission, and suppression of synaptic remodeling. Consequently, the present study not only highlights the potential of tropisetron as an anti-epileptic drug but also identifies α7nAChRs as a promising therapeutic target for the treatment of TLE.

Implications of the non-neuronal cholinergic system for therapeutic interventions of inflammatory skin diseases.

The pivotal roles of acetylcholine (ACh) in physiological processes encompass both the nervous and non-neuronal cholinergic systems (NNCS). This review delineates the synthesis, release, receptor interactions, and degradation of ACh within the nervous system, and explores the NNCS in depth within skin cells including keratinocytes, endothelial cells, fibroblasts, macrophages, and other immune cells. We highlight the NNCS's essential functions in maintaining epidermal barrier integrity, promoting wound healing, regulating microcirculation, and modulating inflammatory responses. The potential of the NNCS as a therapeutic target for localized ACh regulation in the skin is discussed, though the translation of these findings into clinical practice remains uncertain due to the complexity of cholinergic signalling and the lack of comprehensive human studies. The review progresses to therapeutic modulation strategies of the NNCS, including AChE inhibitors, nicotinic and muscarinic receptor agonists and antagonists, choline uptake enhancers, and botulinum toxin, highlighting their relevance in dermatology. We highlight the impact of the NNCS on prevalent skin diseases such as psoriasis, atopic dermatitis, rosacea, acne, bullous diseases, hyperhidrosis and hypohidrosis, illustrating its significance in disease pathogenesis and therapy. This comprehensive overview aims to enhance understanding of the NNCS's role in skin health and disease, offering a foundation for future research and therapeutic innovation.

Sex-dependent differences in the ability of nicotine to modulate discrimination learning and cognitive flexibility in mice.

Nicotine, an addictive compound found in tobacco, functions as an agonist of nicotinic acetylcholine receptors (nAChRs) in the brain. Interestingly, nicotine has been reported to act as a cognitive enhancer in both human subjects and experimental animals. However, its effects in animal studies have not always been consistent, and sex differences have been identified in the effects of nicotine on several behaviors. Specifically, the role that sex plays in modulating the effects of nicotine on discrimination learning and cognitive flexibility in rodents is still unclear. Here, we evaluated sex-dependent differences in the effect of daily nicotine intraperitoneal (i.p.) administration at various doses (0.125, 0.25, and 0.5 mg/kg) on visual discrimination (VD) learning and reversal (VDR) learning in mice. In male mice, 0.5 mg/kg nicotine significantly improved performance in the VDR, but not the VD, task, while 0.5 mg/kg nicotine significantly worsened performance in the VD, but not VDR task in female mice. Furthermore, 0.25 mg/kg nicotine significantly worsened performance in the VD and VDR task only in female mice. Next, to investigate the cellular mechanisms that underlie the sex difference in the effects of nicotine on cognition, transcriptomic analyses were performed focusing on the medial prefrontal cortex tissue samples from male and female mice that had received continuous administration of nicotine for 3 or 18 days. As a result of pathway enrichment analysis and protein-protein interaction analysis using gene sets of differentially expressed genes, decreased expression of postsynaptic-related genes in males and increased expression of innate immunity-related genes in females were identified as possible molecular mechanisms related to sex differences in the effects of nicotine on cognition in discrimination learning and cognitive flexibility. Our result suggests that nicotine modulates cognitive function in a sex-dependent manner by alternating the expression of specific gene sets in the medial prefrontal cortex.

Abstract P203: Nicotine Exposure: A Catalyst for Nitrosative and Oxidative Stress in Glomerular Podocytes and Renal Impairment

Introduction: Nicotine consumption through vaping, cigarettes, or nicotine replacement therapy poses major risks for renal health, especially in individuals with hypertension or kidney disease. Nicotine induces oxidative stress and nitric oxide synthase (NOS) remodeling in endothelial cells, but a gap in knowledge persists regarding its impact on glomerular epithelial cells, particularly podocytes. We hypothesize that nicotine promotes nitrosative stress in podocytes, generating peroxynitrite (ONOO - ), causing mitochondrial damage, and glomerular impairment. Methods: We performed confocal imaging on human cultured podocytes to detect ONOO - , Ca 2+ , and nitric oxide (NO) in response to nicotine. We used Seahorse assay (Agilent XFe24) to test mitochondrial respiration. Nicotine was then chronically infused in Dahl SS rats (0.2 mg/kg/day s.c., 0.4% NaCl diet) for 21 days, and recorded blood pressure 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 Ca 2+ 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, α4β2, α2β4, α4β4, and α3β4 nicotinic acetylcholine receptor (nAChR) agonists elicited Ca 2+ transients but did not produce ONOO - , suggesting that nitrosative stress occurs independently from nAChR activation. Incubation with nicotine (12 hrs) resulted in a decrease in podocytes’ mitochondrial respiration (two-sample t-test, p<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<0.05). Histopathological assessment showed higher glomerular damage in nicotine-exposed rats (t-test, p<0.05). Both EPR and confocal approaches demonstrated nicotine-mediated changes in NO bioavailability and an increase in NOS2 activity (t-test, p<0.05). Conclusion: Nicotine products promote NOS uncoupling in podocytes, leading to ONOO - formation, redox stress, mitochondrial impairment, and glomerular damage. Understanding nicotine's impact on podocytes is crucial for preventing or developing therapies against smoking and vaping-related pathologies.

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.

Metabolic Changes Following Smoking Cessation in Patients with Type 2 Diabetes Mellitus.

Smoking cessation is crucial for reducing complications of type 2 diabetes mellitus (T2DM), but associated weight gain can worsen glycemic control, discouraging quitting attempts. Varenicline, a partial agonist of α4β2 nicotinic receptors, aids smoking cessation. This study examines the effects of varenicline on body weight and metabolic parameters in patients with T2DM and prediabetes. Fifty-three patients were enrolled, of which 32 successfully quit smoking after a three-month course of varenicline and were examined after an additional month with no medication. Measurements taken at baseline, 2.5 months, and 4 months included body weight, blood pressure, resting metabolic rate (RMR), glycated hemoglobin (HbA1c), fasting glucose, blood lipids, C-reactive protein (CRP), appetite-related hormones, and physical activity. Post-treatment, there were no significant changes in body weight, blood pressure, RMR, or glycemic control. Total (CHOL) and low-density lipoprotein (LDL-C) cholesterol decreased significantly at 4 months of the study (from 168 to 156 mg/dL, p = 0.013, and from 96 to 83 mg/dL, p = 0.013, respectively). Leptin levels increased (from 11 to 13.8 ng/dL, p = 0.004), as did glucagon-like peptide-1 (GLP-1) levels (from 39.6 to 45.8 pM, p = 0.016) at 4 months of follow-up. The percentage of participants who reported moderate-intensity activity increased from 28% to 56%, while those reporting high-intensity activity increased from 19% to 22%, respectively (p = 0.039). Our study showed that smoking cessation with varenicline in smokers with T2DM and prediabetes led to significant improvements in lipid profile, significant increase in plasma leptin and GLP-1 levels, and increased physical activity, without significant weight gain. Thus, smoking cessation without weight gain or deteriorated glycemic control is feasible for these smokers, with added benefits to lipid profiles, GLP-1 regulation, and physical activity.

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.

Neonicotinoids differentially modulate nicotinic acetylcholine receptors in immature and antral follicles in the mouse ovary†.

Neonicotinoids are the most widely used insecticides in the world. They are synthetic nicotine derivatives that act as nicotinic acetylcholine receptor agonists. Although parent neonicotinoids have low affinity for the mammalian nicotinic acetylcholine receptor, they can be activated in the environment and the body to positively charged metabolites with high affinity for the mammalian nicotinic acetylcholine receptor. Imidacloprid, the most popular neonicotinoid, and its bioactive metabolite desnitro-imidacloprid differentially interfere with ovarian antral follicle physiology in vitro, but their effects on ovarian nicotinic acetylcholine receptor subunit expression are unknown. Furthermore, ovarian nicotinic acetylcholine receptor subtypes have yet to be characterized in the ovary. Thus, this work tested the hypothesis that ovarian follicles express nicotinic acetylcholine receptors and their expression is differentially modulated by imidacloprid and desnitro-imidacloprid in vitro. We used polymerase chain reaction, RNA in situ hybridization, and immunohistochemistry to identify and localize nicotinic acetylcholine receptor subunits (α2, 4, 5, 6, 7 and β1, 2, 4) expressed in neonatal ovaries (NO) and antral follicles. Chrnb1 was expressed equally in NO and antral follicles. Chrna2 and Chrnb2 expression was higher in antral follicles compared to NO and Chrna4, Chrna5, Chrna6, Chrna7, and Chrnb4 expression was higher in NO compared to antral follicles. The α subunits were detected throughout the ovary, especially in oocytes and granulosa cells. Imidacloprid and desnitro-imidacloprid dysregulated the expression of multiple nicotinic acetylcholine receptor subunits in NO, but only dysregulated one subunit in antral follicles. These data indicate that mammalian ovaries contain nicotinic acetylcholine receptors, and their susceptibility to imidacloprid and desnitro-imidacloprid exposure varies with the stage of follicle maturity.

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.

Ratlarda Oluşturulan Renal İskemi Reperfüzyon Hasarında Epibatidinin Etkileri

Objective: The attenuation of renal ischemia reperfusion (I/R) injury by stimulating cholinergic antiinflamatory pathway has been demonstrated in the literature. The purpose of this study is to investigate the protective effects of epibatidine, a non selective nicotinic acethycholine receptor agonist, administered before ischemia on renal ischemia-reperfusion injury. Methods: After Ethics Committee approval, 24 Wistar Albino rats were randomly allocated into 4 groups. Group S: Sham (n=6), Group I/R: Ischemia/reperfusion (n=6), Group I/R-E: Ischemia/ reperfusion-Epibatidine (n=6), Group E: Epibatidine (n=6). All groups underwent laparotomy and bilateral renal artery and vein dissection under anesthesia. No further action was taken in Group S. In Group I/R and Group I/R-E, renal ischemia was applied for 25 minutes and then reperfusion for 24 hours. A single dose of 5 μg kg-1 epibatidine was administered subcutaneously before the laparotomy in Group I/R-E and Group E. At the end of the reperfusion period, blood and urine samples were taken for plasma BUN, creatine, plasma and urinary neutrophil gelatinase associated lipocalin (NGAL) and cystatin C, plasma IL-6 and TNF-α assessment. Results: Plasma BUN, creatine, NGAL, cystatin C, IL-6 and TNF-α levels were significantly higher in Group I/R when compared to Group S (p&lt;0.05). All the levels of the above biomarkers were comparable in Group S and Group I/R-E. Conclusion: These results indicate that epibatidine administration before ischemia has a protective effect on kidney in renal I/R injury induced rats. Keywords: Renal ischemia-reperfusion injury, cholinergic antiinflammatory pathway, n7AchR, epibatidine, NGAL

Autocrine activation of P2X7 receptors mediates catecholamine secretion in chromaffin cells.

ATP is highly accumulated in secretory vesicles and secreted upon exocytosis from neurons and endocrine cells. In adrenal chromaffin granules, intraluminal ATP reaches concentrations over 100 mM. However, how these large amounts of ATP contribute to exocytosis has not been investigated. Exocytotic events in bovine and mouse adrenal chromaffin cells were measured with single cell amperometry. Cytosolic Ca2+ measurements were carried out in Fluo-4 loaded cells. Submembrane Ca2+ was examined in PC12 cells transfected with a membrane-tethered Ca2+ indicator Lck-GCaMP3. ATP release was measured using the luciferin/luciferase assay. Knockdown of P2X7 receptors was induced with short interfering RNA (siRNA). Direct Ca2+ influx through this receptor was measured using a P2X7 receptor-GCamp6 construct. ATP induced exocytosis in chromaffin cells, whereas the ectonucleotidase apyrase reduced the release events induced by the nicotinic agonist dimethylphenylpiperazinium (DMPP), high KCl, or ionomycin. The purinergic agonist BzATP also promoted a secretory response that was dependent on extracellular Ca2+. A740003, a P2X7 receptor antagonist, abolished secretory responses of these secretagogues. Exocytosis was also diminished in chromaffin cells when P2X7 receptors were silenced using siRNAs and in cells of P2X7 receptor knockout mice. In PC12 cells, DMPP induced ATP release, triggering Ca2+ influx through P2X7 receptors. Furthermore, BzATP, DMPP, and KCl allowed the formation of submembrane Ca2+ microdomains inhibited by A740003. Autocrine activation of P2X7 receptors constitutes a crucial feedback system that amplifies the secretion of catecholamines in chromaffin cells by favouring submembrane Ca2+ microdomains.

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.