New Pyridyl and Dihydroisoquinoline Alkaloids Isolated from the Chevron Nemertean Amphiporus angulatus.

Nemertean worms contain toxins that are used to paralyze their prey and to deter potential predators. Hoplonemerteans often contain pyridyl alkaloids like anabaseine that act through nicotinic acetylcholine receptors and crustacean chemoreceptors. The chemical reactivity of anabaseine, the first nemertean alkaloid to be identified, has been exploited to make drug candidates selective for alpha7 subtype nAChRs. GTS-21, a drug candidate based on the anabaseine scaffold, has pro-cognitive and anti-inflammatory actions in animal models. The circumpolar chevron hoplonemertean Amphiporus angulatus contains a multitude of pyridyl compounds with neurotoxic, anti-feeding, and anti-fouling activities. Here, we report the isolation and structural identification of five new compounds, doubling the number of pyridyl alkaloids known to occur in this species. One compound is an isomer of the tobacco alkaloid anatabine, another is a unique dihydroisoquinoline, and three are analogs of the tetrapyridyl nemertelline. The structural characteristics of these ten compounds suggest several possible pathways for their biosynthesis.

The Cloning and Characterization of a Three-Finger Toxin Homolog (NXH8) from the Coralsnake Micrurus corallinus That Interacts with Skeletal Muscle Nicotinic Acetylcholine Receptors.

Coralsnakes (Micrurus spp.) are the only elapids found throughout the Americas. They are recognized for their highly neurotoxic venom, which is comprised of a wide variety of toxins, including the stable, low-mass toxins known as three-finger toxins (3FTx). Due to difficulties in venom extraction and availability, research on coralsnake venoms is still very limited when compared to that of other Elapidae snakes like cobras, kraits, and mambas. In this study, two previously described 3FTx from the venom of M. corallinus, NXH1 (3SOC1_MICCO), and NXH8 (3NO48_MICCO) were characterized. Using in silico, in vitro, and ex vivo experiments, the biological activities of these toxins were predicted and evaluated. The results showed that only NXH8 was capable of binding to skeletal muscle cells and modulating the activity of nAChRs in nerve-diaphragm preparations. These effects were antagonized by anti-rNXH8 or antielapidic sera. Sequence analysis revealed that the NXH1 toxin possesses eight cysteine residues and four disulfide bonds, while the NXH8 toxin has a primary structure similar to that of non-conventional 3FTx, with an additional disulfide bond on the first loop. These findings add more information related to the structural diversity present within the 3FTx class, while expanding our understanding of the mechanisms of the toxicity of this coralsnake venom and opening new perspectives for developing more effective therapeutic interventions.

Molecular docking analysis of chlorpyrifos at the human α7-nAChR and its potential relationship with neurocytoxicity in SH-SY5Y cells.

The organophosphate insecticide chlorpyrifos (CPF), an acetylcholinesterase inhibitor, has raised serious concerns about human safety. Apart from inducing synaptic acetylcholine accumulation, CPF could also act at nicotinic acetylcholine receptors, like the α7-isoform (α7-nAChR), which could potentially be harmful to developing brains. Our aims were to use molecular docking to assess the binding interactions between CPF and α7-nAChR through, to test the neurocytotoxic and oxidative effects of very low concentrations of CPF on SH-SY5Y cells, and to hypothesize about the potential mediation of α7-nAChR. Docking analysis showed a significant binding affinity of CPH for the E fragment of the α7-nAChR (ΔGibbs: -5.63 to -6.85 Kcal/mol). According to the MTT- and Trypan Blue-based viability assays, commercial CPF showed concentration- and time-dependent neurotoxic effects at a concentration range (2.5-20 µM), ten-folds lower than those reported to have crucial effects for sheer CPF. A rise of the production of radical oxygen species (ROS) was seen at even lower concentrations (1-2.5 µM) of CPF after 24h. Notably, our docking analysis supports the antagonistic actions of CPF on α7-nAChR that were recently published. In conclusion, while α7-nAChR is responsible for neuronal survival and neurodevelopmental processes, its activity may also mediate the neurotoxicity of CPF.

Catharanthine Modulates Mesolimbic Dopamine Transmission and Nicotine Psychomotor Effects via Inhibition of α6-Nicotinic Receptors and Dopamine Transporters.

Iboga alkaloids, also known as coronaridine congeners, have shown promise in the treatment of alcohol and opioid use disorders. The objective of this study was to evaluate the effects of catharanthine and 18-methoxycoronaridine (18-MC) on dopamine (DA) transmission and cholinergic interneurons in the mesolimbic DA system, nicotine-induced locomotor activity, and nicotine-taking behavior. Utilizing ex vivo fast-scan cyclic voltammetry (FSCV) in the nucleus accumbens core of male mice, we found that catharanthine or 18-MC differentially inhibited evoked DA release. Catharanthine inhibition of evoked DA release was significantly reduced by both α4 and α6 nicotinic acetylcholine receptors (nAChRs) antagonists. Additionally, catharanthine substantially increased DA release more than vehicle during high-frequency stimulation, although less potently than an α4 nAChR antagonist, which confirms previous work with nAChR antagonists. Interestingly, while catharanthine slowed DA reuptake measured via FSCV ex vivo, it also increased extracellular DA in striatal dialysate from anesthetized mice in vivo in a dose-dependent manner. Superfusion of catharanthine or 18-MC inhibited the firing rate of striatal cholinergic interneurons in a concentration dependent manner, which are known to potently modulate presynaptic DA release. Catharanthine or 18-MC suppressed acetylcholine currents in oocytes expressing recombinant rat α6/α3ß2ß3 or α6/α3ß4 nAChRs. In behavioral experiments using male Sprague-Dawley rats, systemic administration of catharanthine or 18-MC blocked nicotine enhancement of locomotor activity. Importantly, catharanthine attenuated nicotine self-administration in a dose-dependent manner while having no effect on food reinforcement. Lastly, administration of catharanthine and nicotine together greatly increased head twitch responses, indicating a potential synergistic hallucinogenic effect. These findings demonstrate that catharanthine and 18-MC have similar, but not identical effects on striatal DA dynamics, striatal cholinergic interneuron activity and nicotine psychomotor effects.

Nicotinic Acetylcholine Receptors in Glial Cells as Molecular Target for Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by resting tremor, bradykinesia, rigidity, and postural instability that also includes non-motor symptoms such as mood dysregulation. Dopamine (DA) is the primary neurotransmitter involved in this disease, but cholinergic imbalance has also been implicated. Current intervention in PD is focused on replenishing central DA, which provides remarkable temporary symptomatic relief but does not address neuronal loss and the progression of the disease. It has been well established that neuronal nicotinic cholinergic receptors (nAChRs) can regulate DA release and that nicotine itself may have neuroprotective effects. Recent studies identified nAChRs in nonneuronal cell types, including glial cells, where they may regulate inflammatory responses. Given the crucial role of neuroinflammation in dopaminergic degeneration and the involvement of microglia and astrocytes in this response, glial nAChRs may provide a novel therapeutic target in the prevention and/or treatment of PD. In this review, following a brief discussion of PD, we focus on the role of glial cells and, specifically, their nAChRs in PD pathology and/or treatment.

Influence of age on nicotinic cholinergic regulation of blood flow in rat's olfactory bulb and neocortex.

The olfactory bulb receives cholinergic basal forebrain inputs as does the neocortex. With a focus on nicotinic acetylcholine receptors (nAChRs), this review article provides an overview and discussion of the following findings: (1) the nAChRs-mediated regulation of regional blood flow in the neocortex and olfactory bulb, (2) the nAChR subtypes that mediate their responses, and (3) their activity in old rats. The activation of the α4ß2-like subtype of nAChRs produces vasodilation in the neocortex, and potentiates olfactory bulb vasodilation induced by olfactory stimulation. The nAChR activity producing neocortical vasodilation was similarly maintained in 2-year-old rats as in adult rats, but was clearly reduced in 3-year-old rats. In contrast, nAChR activity in the olfactory bulb was reduced already in 2-year-old rats. Thus, age-related impairment of α4ß2-like nAChR function may occur earlier in the olfactory bulb than in the neocortex. Given the findings, the vasodilation induced by α4ß2-like nAChR activation may be beneficial for neuroprotection in the neocortex and the olfactory bulb.

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.

Agonists or positive allosteric modulators of α7 nicotinic acetylcholine receptor prevent interaction of SARS-Cov-2 receptor-binding domain with astrocytoma cells.

SARS-Cov-2, the virus causing COVID-19, penetrates host target cells via the receptor of angiotensin-converting enzyme 2 (ACE2). Disrupting the virus interaction with ACE2 affords a plausible mechanism for prevention of cell penetration and inhibiting dissemination of the virus. Our studies demonstrate that ACE2 interaction with the receptor binding domain of SARS-Cov-2 spike protein (RBD) can be impaired by modulating the α7 nicotinic acetylcholine receptor (α7 nAChR) contiguous with ACE2. U373 cells of human astrocytoma origin were shown to bind both ACE2-specific antibody and recombinant RBD in Cell-ELISA. ACE2 was found to interact with α7 nAChR in U373 cell lysates studied by Sandwich ELISA. Our studies demonstrate that inhibition of RBD binding to ACE2-expressing U373 cells were defined with α7 nAChR agonists choline and PNU282987, but not a competitive antagonist methyllicaconitine (MLA). Additionally, the type 2 positive allosteric modulator (PAM2) PNU120596 and hydroxyurea (HU) also inhibited the binding. Our studies demonstrate that activation of α7 AChRs has efficacy in inhibiting the SARS-Cov-2 interaction with the ACE2 receptor and in such a way can prevent virus target cell penetration. These studies also help to clarify the consistent efficacy and positive outcomes for utilizing HU in treating COVID-19.

De Novo Screening and Mirror Image Isomerization of Linear Peptides Targeting α7 Nicotinic Acetylcholine Receptor.

As ligand-gated ion channels, nicotinic acetylcholine receptors (nAChRs) are widely distributed in the central and peripheral nervous systems and are associated with the pathogenesis of various degenerative neurological diseases. Here, we report the results of phage display-based de novo screening of an 11-residue linear peptide (named LKP1794) that targets the α7 nAChR, which is among the most abundant nAChR subtypes in the brain. Moreover, two d-peptides were generated through mirror image and/or primary sequence inverso isomerization (termed DRKP1794 and DKP1794) and displayed improved inhibitory effects (IC50 = 0.86 and 0.35 µM, respectively) on α7 nAChR compared with the parent l-peptide LKP1794 (IC50 = 2.48 µM), which markedly enhanced serum stability. A peptide-based fluorescence probe was developed using proteolytically resistant DKP1794 to specifically image the α7 nAChR in living cells. This work provides a new peptide tool to achieve inhibitory modulation and specifically image the α7 nAChR.

Subtype-Selective Peptide and Protein Neurotoxic Inhibitors of Nicotinic Acetylcholine Receptors Enhance Proliferation of Patient-Derived Glioblastoma Cell Lines.

Glioblastoma multiforme (GBM) is the most aggressive type of brain cancer, with a poor prognosis. GBM cells, which develop in the environment of neural tissue, often exploit neurotransmitters and their receptors to promote their own growth and invasion. Nicotinic acetylcholine receptors (nAChRs), which play a crucial role in central nervous system signal transmission, are widely represented in the brain, and GBM cells express several subtypes of nAChRs that are suggested to transmit signals from neurons, promoting tumor invasion and growth. Analysis of published GBM transcriptomes revealed spatial heterogeneity in nAChR subtype expression, and functional nAChRs of α1*, α7, and α9 subtypes are demonstrated in our work on several patient-derived GBM microsphere cultures and on the U87MG GBM cell line using subtype-selective neurotoxins and fluorescent calcium mobilization assay. The U87MG cell line shows reactions to nicotinic agonists similar to those of GBM patient-derived culture. Selective α1*, α7, and α9 nAChR neurotoxins stimulated cell growth in the presence of nicotinic agonists. Several cultivating conditions with varying growth factor content have been proposed and tested. The use of selective neurotoxins confirmed that cell cultures obtained from patients are representative GBM models, but the use of media containing fetal bovine serum can lead to alterations in nAChR expression and functioning.

Cell signaling and epigenetic regulation of nicotine-induced carcinogenesis.

Nicotine, a naturally occurring tobacco alkaloid responsible for tobacco addiction, has long been considered non-carcinogenic. However, emerging evidence suggests that nicotine may possess carcinogenic properties in mice and could be a potential carcinogen in humans. This review aims to summarize the potential molecular mechanisms underlying nicotine-induced carcinogenesis, with a specific focus on epigenetic regulation and the activation of nicotinic acetylcholine receptors (nAChRs) in addition to genotoxicity and excess reactive oxygen species (ROS). Additionally, we explore a novel hypothesis regarding nicotine's carcinogenicity involving the downregulation of stem-loop binding protein (SLBP), a critical regulator of canonical histone mRNA, and the polyadenylation of canonical histone mRNA. By shedding light on these mechanisms, this review underscores the need for further research to elucidate the carcinogenic potential of nicotine and its implications for human health.

Neuronal Excitability in the Medial Habenula and Ventral Tegmental Area Is Differentially Modulated by Nicotine Dosage and Menthol in a Sex-Specific Manner.

The medial habenula (MHb) has been identified as the limiting factor for nicotine intake and facilitating nicotine withdrawal. However, few studies have assessed MHb neuronal excitability in response to nicotine, and, currently, a gap in knowledge is present for finding behavioral correlates to neuronal excitability in the region. Moreover, no study to date has evaluated sex or nicotine dosage as factors of excitability in the MHb. Here, we utilized an e-vape self-administration (EVSA) model to determine differences between sexes with different nicotine dosages ± menthol. Following this paradigm, we employed patch-clamp electrophysiology to assess key metrics of MHb neuronal excitability in relation to behavioral endpoints. We observed female mice self-administered significantly more than males, regardless of dosage. We also observed a direct correlation between self-administration behavior and MHb excitability with low-dose nicotine + menthol in males. Conversely, a high dose of nicotine ± menthol yields an inverse correlation between excitability and self-administration behavior in males only. In addition, intrinsic excitability in the ventral tegmental area (VTA) does not track with the amount of nicotine self-administered. Rather, they correlate to the active/inactive discrimination of mice. Using fast-scan cyclic voltammetry, we also observed that dopamine release dynamics are linked to reinforcement-related behavior in males and motivation-related behaviors in females. These results point to a sex-specific difference in the activity of the MHb and VTA leading to distinct differences in self-administration behavior. His could lend evidence to clinical observations of smoking and nicotine-use behavior differing between males and females.

A review on the effect of COX-2-mediated mechanisms on development and progression of gastric cancer induced by nicotine.

Smoking is a documented risk factor for cancer, e.g., gastric cancer. Nicotine, the principal tobacco alkaloid, would exert its role of contribution to gastric cancer development and progression through nicotinic acetylcholine receptors (nAChRs) and ß-adrenergic receptors (ß-ARs), which then promote cancer cell proliferation, migration and invasion. As a key isoenzyme in conversion of arachidonic acid to prostaglandins, cyclooxygenase-2 (COX-2) has been demonstrated to have a wide range of effects in carcinogenesis and tumor development. At present, many studies have reported the effect of nicotine on gastric cancer by binding to nAChR, as well as indirectly stimulating ß-AR to mediate COX-2-related pathways. This review summarizes these studies, and also proposes more potential COX-2-mediated mechanisms. These events might contribute to the growth and progression of gastric cancer exposed to nicotine through tobacco smoke or cigarette substitutes. Also, this review article has therefore the potential not only to make a significant contribution to the treatment and prognosis of gastric cancer for smokers but also to the clinical application of COX-2 antagonists. In addition, this work also discusses the considerable challenges of this field with special reference to the future perspective of COX-2-mediated mechanisms in development and progression of gastric cancer induced by nicotine.

Nicotinic receptors in airway disease.

With continued smoking of tobacco products and expanded use of nicotine delivery devices worldwide, understanding the impact of smoking and vaping on respiratory health remains a major global unmet need. Although multiple studies have shown a strong association between smoking and asthma, there is a relative paucity of mechanistic understanding of how elements in cigarette smoke impact the airway. Recognizing that nicotine is a major component in both smoking and vaping products, it is critical to understand the mechanisms by which nicotine impacts airways and promotes lung diseases such as asthma. There is now increasing evidence that α7 nicotinic acetylcholine receptors (α7nAChRs) are critical players in nicotine effects on airways, but the mechanisms by which α7nAChR influences different airway cell types have not been widely explored. In this review, we highlight and integrate the current state of knowledge regarding nicotine and α7nAChR in the context of asthma and identify potential approaches to alleviate the impact of smoking and vaping on the lungs.

Identification of the native Torpedo californica nicotinic acetylcholine receptor's glycan composition after a multi-step sequential purification method using MALDI-ToF MS.

The Cys-loop pentameric ligand-gated ion channels comprise a dynamic group of proteins that have been extensively studied for decades, yielding a wealth of findings at both the structural and functional levels. The nicotinic acetylcholine receptor (nAChR) is no exception, as it is part of this large protein family involved in proper organismal function. Our efforts have successfully produced a highly pure nAChR in detergent complex (nAChR-DC), enabling more robust studies to be conducted on it, including beginning to experiment with high-throughput crystallization. Our homogeneous product has been identified and extensively characterized with 100% identity using Nano Lc MS/MS and MALDI ToF/ToF for each nAChR subunit. Additionally, the N-linked glycans in the Torpedo californica-nAChR (Tc-nAChR) subunits have been identified. To study this, the Tc-nAChR subunits were digested with PNGase F and the released glycans were analyzed by MALDI-ToF. The MS results showed the presence of high-mannose N-glycan in all native Tc-nAChR subunits. Specifically, the oligommanose population Man8-9GlcNac2 with peaks at m/z 1742 and 1904 ([M + Na]+ ions) were observed.

Transcriptome analysis revealed the function of five tandemly duplicated nAChRs in the transplantation immunity in pearl oyster Pinctada fucata martensii.

nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that play an important role in the homeostatic regulation of physiological functions. Our previous studies showed that nAChRs in the genome of pearl oyster Pinctada fucata martensii (PmnAChRs) were expanded through tandem duplication. This study aimed to analyze the function of five tandemly duplicated PmnAChRs in the transplantation immunity in P. f. martensii. Transcriptome analysis reveals that the differentially expressed genes (DEGs) shared between PmnAChR-RNAi and the control group were functionally involved in Signal transduction, Immune system et al., and most of the related genes were down-regulated in the PmnAChR-RNAi group. The different copies of PmnAChR may regulate transplantation immunity through various pathways, such as Wnt, protein digestion and absorption, Hippo, and gap junction pathway. The inflammation factor interleukin-17 (IL-17) and tumor necrosis factor-alpha (TNF-α) were down-regulated in PmnAChR-1, 4, 5-RNAi group, and the serum from the pearl oysters in the PmnAChR-1-4-RNAi group could promote the proliferation of the Vibrio harveyi, indicating the immunosuppressive function after down-regulation of PmnAChRs. The different responses of antioxidant enzymes and diverse signal pathways after down-regulation of PmnAChRs suggested that the five tandemly duplicated PmnAChRs may cooperate with different α type PmnAChRs and constitute the functional ion channel in the membrane. Results of this study not only provide insight for the effective regulation of the transplantation immunity, but also provide a theoretical reference for the study of the adaptive evolutionary mechanism of repeating genes.

PLEK2 mediates metastasis and invasion via α5-nAChR activation in nicotine-induced lung adenocarcinoma.

Evidence has shown a strong relationship between smoking and epithelial mesenchymal transition (EMT). α5-nicotinic acetylcholine receptor (α5-nAChR) contributes to nicotine-induced lung cancer cell EMT. The cytoskeleton-associated protein PLEK2 is mainly involved in cytoskeletal protein recombination and cell stretch migration regulation, which is closely related to EMT. However, little is known about the link between nicotine/α5-nAChR and PLEK2 in lung adenocarcinoma (LUAD). Here, we identified a link between α5-nAChR and PLEK2 in LUAD. α5-nAChR expression was correlated with PLEK2 expression, smoking status and lower survival in vivo. α5-nAChR mediated nicotine-induced PLEK2 expression via STAT3. α5-nAChR/PLEK2 signaling is involved in LUAD cell migration, invasion and stemness. Moreover, PLEK2 was found to interact with CFL1 in nicotine-induced EMT in LUAD cells. Furthermore, the functional link among α5-nAChR, PLEK2 and CFL1 was confirmed in mouse xenograft tissues and human LUAD tissues. These findings reveal a novel α5-nAChR/PLEK2/CFL1 pathway involved in nicotine-induced LUAD progression.

Varenicline but not cotinine increased the value of a visual stimulus reinforcer in rats: No evidence for synergy of the two compounds.

Smoking is the leading cause of preventable death worldwide, with <7 % of smoking cessation attempts being met with success. Nicotine, the main addictive agent in cigarettes, enhances the reinforcing value of other environmental rewards. Under some circumstances, this reward enhancement maintains nicotine consumption. Varenicline (i.e., cessation aid Chantix™) also has reward-enhancement effects via nicotinic acetylcholine receptor agonism (nAChRs) - albeit less robust than nicotine. Cotinine is the major metabolite of nicotine. Recent studies suggest that cotinine is a positive allosteric modulator (PAM) and/or a weak agonist at nAChRs. Thus, cotinine may enhance the behavioral effects of nAChR compounds such as varenicline and/or exert some behavioral effects alone. We used 20 (10M, 10F) Sprague-Dawley rats to assess reward-enhancement within-subjects by examining responding maintained by a reinforcing visual stimulus on a Variable Ratio 2 schedule of reinforcement. To assess the reward-enhancing effects of cotinine, rats received one injection of cotinine (saline, 0.1, 0.3, 1.0, 3.0, 6.0 mg/kg) before each 1 h session. To assess cotinine and varenicline interactions, rats received an injection of cotinine (saline, 0.1, 1.0, or 6.0 mg/kg) and of varenicline (saline, 0.1, 0.3, 1.0, or 3.0 mg/kg) before the session. While we replicated prior work identifying reward-enhancement by 0.1, 0.3, and 1.0 mg/kg varenicline, cotinine alone did not produce reward-enhancement nor augment the reward-enhancing effects of varenicline. Future studies may consider examining the reward-enhancing effects of cotinine with other reinforcers or co-administered with other smoking cessation aids such as bupropion.

Target-Based Design, Synthesis, and Biological Evaluation of Novel 1,2,4-Triazolone Derivatives as Potential nAChR Modulators.

Novel agrochemicals have been successfully developed using target-based drug design (TBDD). To discover a novel, efficient, and highly selective nicotinic insecticide candidate, we developed a unified pharmacological model using TBDD by studying the binding modes of 11 nicotinic acetylcholine receptor (nAChR) modulators with acetylcholine binding protein (AChBP) targets for the first time. This model was used to design and develop a series of 1,2,4-triazolone derivatives. Bioassays demonstrated excellent insecticidal activities against Aphis glycines of compounds 4k (LC50 = 4.95 mg/L) and 4q (LC50 = 3.17 mg/L), and low toxicities to Apis mellifera. Additionally, compound 4q was stably bound to Aplysia californica AChBP, which was consistent with the pharmacological model obtained via molecular docking and molecular dynamics simulations. Therefore, compound 4q could be a potential lead candidate targeting nAChR. The explicit pharmacological model of nAChR modulators with Ac-AChBP in this study may facilitate the future rational design of eco-friendly nicotinic insecticides.

Evaluation of an Image-Derived Input Function for Kinetic Modeling of Nicotinic Acetylcholine Receptor-Binding PET Ligands in Mice.

Positron emission tomography (PET) radioligands that bind with high-affinity to α4ß2-type nicotinic receptors (α4ß2Rs) allow for in vivo investigations of the mechanisms underlying nicotine addiction and smoking cessation. Here, we investigate the use of an image-derived arterial input function and the cerebellum for kinetic analysis of radioligand binding in mice. Two radioligands were explored: 2-[18F]FA85380 (2-FA), displaying similar pKa and binding affinity to the smoking cessation drug varenicline (Chantix), and [18F]Nifene, displaying similar pKa and binding affinity to nicotine. Time-activity curves of the left ventricle of the heart displayed similar distribution across wild type mice, mice lacking the ß2-subunit for ligand binding, and acute nicotine-treated mice, whereas reference tissue binding displayed high variation between groups. Binding potential estimated from a two-tissue compartment model fit of the data with the image-derived input function were higher than estimates from reference tissue-based estimations. Rate constants of radioligand dissociation were very slow for 2-FA and very fast for Nifene. We conclude that using an image-derived input function for kinetic modeling of nicotinic PET ligands provides suitable results compared to reference tissue-based methods and that the chemical properties of 2-FA and Nifene are suitable to study receptor response to nicotine addiction and smoking cessation therapies.