Stimulation Of Nicotinic Receptors Research Articles

Administration of Nicotine Can Inhibit Myopic Growth in Animal Models.

While previously investigating the mechanism by which atropine inhibits ocular growth, we observed that stimulation of nicotinic receptors can inhibit experimental myopia. This study expands on that preliminary finding and investigates the safety and efficacy of nicotinic stimulation in the inhibition of ocular growth. Nicotine's ability to inhibit form-deprivation myopia (FDM), following intravitreal injection (9 chicks per group) or topical application (6 chicks per group), was investigated over three doses. The ability of nicotine to inhibit lens-induced myopia (LIM) was also tested (in 12 chicks). For ocular safety, following 4weeks of topical treatment with nicotine (n = 10), pupillary reflex, intraocular pressure, corneal curvature/thickness, lens thickness, retinal health (retinal thickness/cell apoptosis), as well as retinal function (electroretinogram recordings) were assessed. We also examined the effects of nicotine on non-ocular autonomic functions in both chicks (n = 5) and mice (n = 5). Nicotine was observed to significantly inhibit the development of FDM in chicks when administered as an intravitreal injection (P<0.05) or topical eye drops (P<0.05), albeit not in a dose-dependent manner. Nicotine also inhibited LIM (P<0.05) to a similar degree to that seen for FDM. Although ocular health was (for the most part) unaffected by nicotine, the highest topical dose induced a temporary reduction in cardiorespiratory output (P<0.05). Nicotine, administered as an intravitreal injection or topical eye drop, significantly inhibits the development of experimental myopia. Although the anti-myopic effects observed presently are interesting, the well-reported side effects (expanded on presently) and addictive properties of nicotine would preclude its clinical use.

Dynamin-2 mutations linked to neonatal-onset centronuclear myopathy impair exocytosis and endocytosis in adrenal chromaffin cells.

Dynamins are large GTPases whose primary function is not only to catalyze membrane scission during endocytosis but also to modulate other cellular processes, such as actin polymerization and vesicle trafficking. Recently, we reported that centronuclear myopathy associated dynamin-2 mutations, p.A618T, and p.S619L, impair Ca2+-induced exocytosis of the glucose transporter GLUT4 containing vesicles in immortalized human myoblasts. As exocytosis and endocytosis occur within rapid timescales, here we applied high-temporal resolution techniques, such as patch-clamp capacitance measurements and carbon-fiber amperometry to assess the effects of these mutations on these two cellular processes, using bovine chromaffin cells as a study model. We found that the expression of any of these dynamin-2 mutants inhibits a dynamin and F-actin-dependent form of fast endocytosis triggered by single action potential stimulus, as well as inhibits a slow compensatory endocytosis induced by 500 ms square depolarization. Both dynamin-2 mutants further reduced the exocytosis induced by 500 ms depolarizations, and the frequency of release events and the recruitment of neuropeptide Y (NPY)-labeled vesicles to the cell cortex after stimulation of nicotinic acetylcholine receptors with 1,1-dimethyl-4-phenyl piperazine iodide (DMPP). They also provoked a significant decrease in the Ca2+-induced formation of new actin filaments in permeabilized chromaffin cells. In summary, our results indicate that the centronuclear myopathy (CNM)-linked p.A618T and p.S619L mutations in dynamin-2 affect exocytosis and endocytosis, being the disruption of F-actin dynamics a possible explanation for these results. These impaired cellular processes might underlie the pathogenic mechanisms associated with these mutations.

Comment on 'Accumbens cholinergic interneurons dynamically promote dopamine release and enable motivation'.

Acetylcholine is widely believed to modulate the release of dopamine in the striatum of mammals. Experiments in brain slices clearly show that synchronous activation of striatal cholinergic interneurons is sufficient to drive dopamine release via axo-axonal stimulation of nicotinic acetylcholine receptors. However, evidence for this mechanism in vivo has been less forthcoming. Mohebi, Collins and Berke recently reported that, in awake behaving rats, optogenetic activation of striatal cholinergic interneurons with blue light readily evokes dopamine release measured with the red fluorescent sensor RdLight1 (Mohebi et al., 2023). Here, we show that blue light alone alters the fluorescent properties of RdLight1 in a manner that may be misconstrued as phasic dopamine release, and that this artefactual photoactivation can account for the effects attributed to cholinergic interneurons. Our findings indicate that measurements of dopamine using the red-shifted fluorescent sensor RdLight1 should be interpreted with caution when combined with optogenetics. In light of this and other publications that did not observe large acetylcholine-evoked dopamine transients in vivo, the conditions under which such release occurs in behaving animals remain unknown.

Vagus Nerve Stimulation Provides Neuroprotection Against Doxorubicin‐induced Chemobrain Via Activations of Both Muscarinic and Nicotinic Acetylcholine Receptors

AbstractBackgroundChemotherapy, particularly treatment with doxorubicin (Dox), is known to cause neurotoxicity in the brain known as chemobrain. Dox administration causes neuroinflammation, mitochondrial dysfunction, and subsequent cognitive decline (1). Additionally, cancer survivors who received Dox were found to have an increased risk of developing dementia (2). Interestingly, the activation of the parasympathetic nervous system by vagus nerve stimulation (VNS) exerted neuroprotective effects on Alzheimer’s disease (3). However, the neuroprotective effects of VNS against Dox‐induced chemobrain have never been investigated. Moreover, whether the therapeutic effects of VNS are achieved via stimulation of nicotinic acetylcholine receptors (AChRs) or muscarinic acetylcholine receptors (mAChRs) needs further investigation.MethodTwenty male Wistar rats were divided into sham‐operated and VNS device‐implanted groups. After 2 weeks of recovery, all sham‐operated rats were divided and received either 0.9% NSS (Control; n = 4) or 3 mg/kg Dox for 6 doses (Sham; n = 4) via intraperitoneal injection. In addition, all VNS device‐implanted rats were treated with 3 mg/kg Dox for 6 doses and then randomly divided into 3 groups to receive either 0.9% NSS (VNS; n = 4), a mAChR antagonist (atropine; 1 mg/kg/day, VNS+Atro; n = 4), or a nAChR antagonist (mecamylamine; 7.5 mg/kg/day, VNS+Mec; n = 4). At the end of treatment protocol, cognitive function was assessed using the novel object location (NOL) task. The brains were obtained for further molecular studies.ResultDox treatment impaired cognitive performance in rats, as demonstrated by a decrease in the preference index in the NOL task (Figure A). Microglia in the CA1 region of Dox‐treated rats exhibited decreased process complexity and increased microglial volume, indicating reactivation of microglia (Figure B and C). Notably, Dox administration caused mitochondrial dysfunction in the brain, as evidenced by increased levels of mitochondrial reactive oxygen species (ROS) and mitochondrial membrane depolarization (Figure D and E). Importantly, the intervention with VNS rescued long‐term cognitive function in Dox‐treated rats by ameliorating all chemobrain pathologies (Figure A‐E). In contrast, the therapeutic effects of VNS were completely abolished by blocking either mAChRs or nAChRs using their antagonists (Figure A‐E).ConclusionThe findings suggested that VNS protected against Dox‐induced chemobrain through activations of both nAChRs and mAChRs.

Activation of α7nAChR in AT2 promotes alveolar regeneration through WNT7B signaling in acute lung injury.

Reducing inflammatory damage and improving alveolar epithelium regeneration are two key approaches to promoting lung repair in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Stimulation of cholinergic-α7nAChR (α7 nicotinic acetylcholine receptor, coded by Chrna7) signaling could dampen lung inflammatory injury. However, whether activation of α7nAChR in alveolar type II (AT2) cells promotes alveolar epithelial injury repair and underlying mechanisms are elusive. Here, we found that α7nAChR was expressed on AT2 cells and was upregulated in response to LPS-induced ALI. Meanwhile, deletion of Chrna7 in AT2 cells impeded lung repair process and worsened lung inflammation in ALI. Using in vivo AT2 lineage-labeled mice and ex vivo AT2-derived alveolar organoids, we demonstrated that activation of α7nAChR expressed on AT2 cells improved alveolar regeneration by promoting AT2 cells to proliferate and subsequently differentiate toward alveolar type I (AT1) cells. Then we screened out the WNT7B signaling pathway by the RNA sequencing analysis of in vivo AT2 lineage-labeled cells, and further confirmed its indispensability for α7nAChR activation-mediated alveolar epithelial proliferation and differentiation. Thus, we have identified an unrecognized pathway that cholinergic-α7nAChR signaling determines alveolar regeneration and repair, which might provide us a novel therapeutic target for combating ALI.

Phospholipase C-ε defines a PACAP-stimulated pathway for secretion in the chromaffin cell.

Adrenomedullary chromaffin cells respond to splanchnic (sympathetic) nerve stimulation by releasing stress hormones into the circulation. The signal for hormone secretion is encoded in the neurotransmitters - especially acetylcholine (ACh) and pituitary adenylate cyclase activating polypeptide (PACAP) - that are released into the splanchnic-chromaffin cell synapse. However, functional differences in the effects of ACh and PACAP on the chromaffin cell secretory response are not well defined. Here, selective agonists of PACAP receptors or nicotinic and muscarinic acetylcholine receptors were applied to chromaffin cells. The major differences in the effects of these agents were not on exocytosis, per se, but rather on the steps upstream of exocytosis. In almost every respect, the properties of individual fusion events triggered by PACAP and cholinergic agonists were similar. On the other hand, the properties of the Ca2+ transients evoked by PACAP differed in several ways from those evoked by muscarinic and nicotinic receptor stimulation. A defining feature of the PACAP-stimulated secretory pathway was its dependence on signaling through exchange protein directly activated by cAMP (Epac) and PLCε. However, the absence of PLCε did not disrupt Ca2+ transients evoked by cholinergic agonists. Accordingly, inhibition of Epac activity did not disrupt secretion triggered by acetylcholine or specific agonists of muscarinic and nicotinic receptors. Thus, PACAP and acetylcholine stimulate chromaffin cell secretion via separate and independent pathways. This feature of stimulus-secretion coupling may be important for sustaining hormone release from the adrenal medulla under conditions associated with the sympathetic stress response.

You Don't Know Nicotine: Novel Applications of Nicotinic Therapeutics in Aging

Overall AbstractNicotine binds to nicotinic cholinergic receptors in the brain and the periphery. These receptors are ligand-gated ion channels that modulate other neurotransmitter systems and have important roles in cognitive and emotional functioning. Recent advances have expanded the understanding of how stimulation or blockade of nicotinic receptors affects brain activity, cortical networks, and behavior. While nicotine has been mostly thought of as a substance of abuse connected to tobacco smoking, the potential exists for utilizing nicotine and/or nicotinic stimulation as a therapeutic agent for the treatment of a variety of brain disorders. This symposium will present recent advances in the understanding of how nicotine and nicotinic drugs affect the brain and explore the possible utilization of nicotine for age-related brain disorders. While nicotinic therapeutics has a history dating back to the 1920s, work began in earnest in the 1980s with examining nicotine in Alzheimer's disease. This continued with the development of receptor-selective nicotinic agonists targeted towards Alzheimer’ disease, ADHD, and schizophrenia. These efforts failed, in part because of limited understanding of the appropriate brain system neural targets as well as lack of clarity as to whether the drugs engaged these targets in a meaningful way.Recent research has significantly expanded our understanding of the neural circuitry affected by nicotine and nicotinic stimulation and better human and animal models have offered new insights into the potential for nicotine therapeutics in areas as disparate as hearing loss and stress response mechanisms. Nicotine is now being investigated for its potential in age-related disorders including memory impairment, late life depression, cognitive impairment following cancer treatment and COVID, and age-related hearing loss. The symposium will examine how the effects of nicotine on cognitive functioning differ between older versus younger individuals to explore how nicotinic stimulation benefits may be age specific. We will also present the background and progress of the MIND study, a multi-center nicotine treatment study for mild cognitive impairment, the largest and longest nicotine study of non-smokers ever conducted. New clinical and neural evidence for nicotine as an augmentation treatment for late life depression and the cognitive deficits that accompany this condition will be discussed. Finally, the use of translational animal-human models for discerning the potential beneficial effects of nicotine and the potential for combination therapies to enhance the beneficial effects of nicotine will be presented. These studies of nicotine have broad clinical and scientific significance. If the hypotheses are validated, this will support a novel, broadly available, and inexpensive repurposed intervention for age-related brain disorders and would encourage early treatment to improve symptoms, retard progression of cognitive impairment or improve mood, and lead to combined trials with other agents for brain disorders of aging.

A single high-intensity nanosecond electric pulse stimulates NALCN and TRPC4/5 channels leading to Na+ accumulation in adrenal chromaffin cells as detected by live cell Na+ fluorescence imaging.

We recently reported that a single 5 ns high intensity electric pulse (NEP) elicits an inwardly rectifying current carried mainly by Na+ in bovine adrenal chromaffin cells, with ∼75% of the current being carried by both TRPC4/5 channels and the Na+ leak channel (NALCN) (Yang et al. Arch Biochem Biophys 723: 109252, 2022). In this study we used Na+ fluorescence imaging to further investigate the involvement of these channels in mediating Na+ influx triggered by NEPs. Chromaffin cells were loaded with the Na+ fluorescent indicator ING-2/AM (2 μM; Ex/Em: 525/545 nm; Kd = 20 mM). Similar to patch clamp experiments, a single NEP (5 MV/m) consistently evoked Na+ accumulation in all cells, which was characterized by a gradual rise in fluorescence that reached a plateau by ∼4 min. Also consistent with the inward current monitored by patch clamp, a combination of the TRPC4/5 channel inhibitor M084 (40 µM) and the NALCN blocker CP-96345 (50 µM) blocked the increase in fluorescence by ∼69%. Surprisingly, Na+ influx was significantly reduced in the absence of extracellular Ca2+ or by blocking L-type voltage-gated Ca2+ channels with nitrendipine, nifedipine or verapamil. The NEP-evoked Na+ influx pathway did not involve nicotinic agonist receptor stimulation nor voltage-gated Na+ channels. Overall, these results suggest that a 5-ns pulse triggers a Na+ conductance through NALCN and TRPC4/5 channels, serving as a novel way to modify neural cell excitability. Future experiments will identify the mechanism by which the NEP activates Na+ influx through these channels and whether these channels can also be activated by conventional electric stimulation (i.e., milli- and micro-second electric pulses).

The nonopioid cholinergic agonist GTS-21 mitigates morphine-induced aggravation of burn injury pain together with inhibition of spinal microglia activation in young rats

BackgroundRepetitive opioid use does not always alleviate basal pain, procedural pain, or both after burn injury. Mitigation of burn injury-site pain can be achieved by GTS-21 stimulation of α7-acetylcholine nicotinic receptors (α7AChRs) and reduced microglia activation in rat. We tested the hypothesis that morphine exaggerates burn injury-site pain and GTS-21 alleviates both morphine-induced aggravated burn injury pain and microglia activation. MethodsYoung rats with dorsal paw burn injury or sham-burn received intraperitoneal saline, morphine, GTS-21, or a combination twice daily for 14 days. Ipsilateral plantar pain thresholds were tested every other day before morning drugs from days 0–20. Spinal microglia activation, evidenced as pain-transducer (tumour necrosis factor-α [TNF-α], interleukin [IL]-6, IL-1β, nuclear factor kappa B [NF-κB], Toll-like receptor 4 [TLR4]) expression, was examined using immunohistochemistry and immunoblot. In cultured microglia, morphine-induced cytokine expression was measured (quantitative polymerase chain reaction/enzyme-linked immunosorbent assay [qPCR/ELISA]). ResultsMorphine aggravated allodynia at day 5 in sham-burn (P=0.039, n=8–11) but significantly aggravated burn injury site allodynia by day 3 (P=0.010, n=8–11). Microgliosis paralleled nociceptive behaviour changes where burn injury with morphine had highest microgliosis compared with burn injury, morphine alone, or controls (number of cells per field [SD]: 33.8 [2.4], 18.0 [4.1], 8.2 [1.9], and 4.8 [2.0], respectively; P<0.001, n=4–5]. GTS-21 reversed the morphine-induced pain component in sham-burn and burn injury rats together with reduced microgliosis and spinal pain-transducer expression (TNF-α, IL-6, IL-1β, NF-κB, and TLR4). Morphine-exposed microglial cells showed increased cytokine expression, which was mitigated by GTS-21. ConclusionsMorphine or burn injury alone increases pain together with microgliosis and pain-transducer expression. Morphine administration augments burn injury-site nociception sooner and aggravated spinal microgliosis and inflammatory pain-transducer expression. GTS-21 has the potential to treat morphine-induced pain in burn injury.

Simultaneous whole-cell patch-clamp and calcium imaging on myenteric neurons.

Live calcium imaging is often used as a proxy for electrophysiological measurements and has been a valuable tool that allows simultaneous analysis of neuronal activity in multiple cells at the population level. In the enteric nervous system, there are two main electrophysiological classes of neurons, after-hyperpolarizing (AH)- and synaptic (S)-neurons, which have been shown to have different calcium handling mechanisms. However, they are rarely considered separately in calcium imaging experiments. A handful of studies have shown that in guinea pig, a calcium transient will accompany a single action potential in AH-neurons, but multiple action potentials are required to generate a calcium transient in S-neurons. How this translates to different modes of cellular depolarization and whether this is consistent across species is unknown. In this study, we used simultaneous whole-cell patch-clamp electrophysiology together with calcium imaging to investigate how enteric neurons respond to different modes of depolarization. Using both traditional (4 Hz) and also high-speed (1,000 Hz) imaging techniques, we found that single action potentials elicit calcium transients in both AH-neurons and S-neurons. Subthreshold membrane depolarizations were also able to elicit calcium transients, although calcium responses were generally amplified if an action potential was present. Furthermore, we identified that responses to nicotinic acetylcholine receptor stimulation can be used to distinguish between AH- and S-neurons in calcium imaging.NEW & NOTEWORTHY Live calcium imaging is an important tool for investigating enteric nervous system (ENS) function. Previous studies have shown that multiple action potentials are needed to generate a calcium response in S-neurons, which has important implications for the interpretation of calcium imaging data. Here, we show that in mouse myenteric neurons, calcium transients are elicited by single action potentials in both AH- and S-neurons. In addition, nicotinic acetylcholine receptor stimulation can be used to distinguish between these two classes.

α7 nicotinic acetylcholine receptor agonist GTS-21 attenuates DSS-induced intestinal colitis by improving intestinal mucosal barrier function

Background and aimsCholinergic output, which could modulate innate immune responses through stimulation of α7 nicotinic acetylcholine receptor (α7nAChR), might be a target to minimize tissue damage in autoimmune disease. GTS-21, a selective α7nAChR agonist, has previously demonstrated to inhibit synovium inflammation in rheumatoid arthritis. In this study, we investigated the effect of GTS-21 on dextran sulfate sodium (DSS)-induced colitis model and its potential mechanism.MethodsMale BABL/c mice (n = 32) were randomly divided into four groups: normal control group, DSS-induced colitis group, GTS-21 treatment with or without α7nAChR antagonist α-BGT treatment group. Disease activity index (DAI), histological activity index (HAI) and colonic macroscopic damage were evaluated. Fluorescein isothiocyanate (FITC)–dextran assay was applied to measure intestinal permeability. The expressions of tight junction (TJ) proteins and NF-κB associated proteins were detected by Western blot.ResultsGTS-21 could decrease DAI scores, HAI scores, intestinal permeability and reduce the intestinal bacterial translocation in DSS-induced colitis group, whereas α7nAChR antagonist α-BGT could impair this protective influence. The expressions of TJ proteins were increased with administration of GTS-21 both in vivo and in vitro. Furthermore, GTS-21 also inhibited the NF-қB activation in intestinal epithelial cells and colitis model, while α-BGT reversed the inhibitory effect.ConclusionThe α7nAChR agonist GTS-21 attenuated DSS-induced colitis through increasing expressions of TJ proteins in colon tissues and improved intestinal barrier function, which might be due to modulating NF-қB activation in intestinal epithelial cells.

Nicotine Rather Than Non-Nicotine Substances in 3R4F WCSC Increases Behavioral Sensitization and Drug-Taking Behavior in Rats.

Nicotine increases reinforcing effects of cigarette smoking by upregulating glutamate and dopamine releases via stimulation of nicotinic acetylcholine receptors (nAChRs) in the dorsal striatum (CPu). The present study was conducted to evaluate whether non-nicotine substances in cigarette smoke potentiate nicotine-induced behaviors by increasing glutamate and dopamine concentrations in the CPu. Changes in the levels of glutamate and dopamine in the CPu were analyzed using a glutamate colorimetric assay and dopamine enzyme-linked immunosorbent assay, respectively, after repeated administration of nicotine or whole cigarette smoke condensate (WCSC) in male Sprague-Dawley rats. Changes in locomotion and drug-taking behavior were analyzed using the measurements of locomotor activity and self-administration under a fixed ratio 1 schedule in response to repeated administration of nicotine or WCSC. Repeated subcutaneous (s.c.) injections of nicotine (0.25mg/kg/day) for 7 consecutive days significantly increased the levels of glutamate and dopamine in the CPu. Similar results were obtained from repeated injections of WCSC (0.25mg/kg nicotine/day, s.c.) extracted from 3R4F Kentucky reference cigarettes. Parallel with the increases in the neurotransmitter levels in the CPu, both nicotine and WCSC increased locomotor activity and self-administration (0.03mg/kg nicotine/infusion). However, repeated injections of WCSC did not change the nicotine-induced increases in neurotransmitter levels, locomotor activity, and self-administration. Nicotine rather than non-nicotine substances in WCSC play a major role in potentiating behavioral sensitization and drug-taking behavior via elevation of glutamate and dopamine concentrations in the CPu of rats. WCSC does not augment the nicotine-induced increases in behavioral sensitization, drug-taking behavior, and glutamate and dopamine concentrations, suggesting that non-nicotine substances do not potentiate the nicotine-induced behaviors by increasing the concentrations of the neurotransmitters in the CPu. These findings imply that nicotine, but not non-nicotine substances in WCSC, may be a major contributor that induces tobacco dependence in rats.

English

BACKGROUND Organophosphorus poisoning is possibly the most common acute poisoning in the developing countries and is a global health problem.1,2 Between 750,000 and 3,000,000 of OP poisoning occur globally every year.3 OP insecticides bind and irreversibly inhibit butyrylcholinesterase. These compounds cause excessive stimulation of muscarinic and nicotinic cholinergic receptors in the central and autonomic nervous systems and at skeletal neuromuscular junctions.4 Butyrylcholinesterase (BChE) is also known as pseudocholinesterase.5 Due to the limitations in accuracy and cost of plasma pseudocholinesterase level estimation, alternate biochemical marker options for OP poisoning have been studied for evaluation of patients with OP poisoning. Increased creatine phosphokinase (CPK) levels are seen in OP poisoning in early phase.6,7 This study was conducted to correlate initial serum CPK levels with the clinical severity at presentation and the final clinical outcome. METHODS This descriptive study was carried out after reviewing case records of patients &gt;/= 18 years with acute organophosphorus (OP) poisoning who were admitted under the Internal medicine department of Government Medical College Thiruvananthapuram between January 2019 and December 2019. The severity of poisoning was categorized based on Peradeniya organophosphorus poisoning (POP) scale. Serum CPK level, serum pseudocholinesterase, and total dose of atropine in milligrams until the outcome in the hospital were recorded. The student's t-test and Pearson's correlation coefficient were used for the assessment of statistical significance. RESULTS Clinical severity as per POP SCALE was mild (score 0–3) in 24 (27 %), moderate (score 4–7) in 50 (55.81 %) and severe (score 8–11) in 16 (18 %) patients. Serum CPK, serum pseudocholinesterase level, and total atropine dose strongly correlated with clinical severity of OP poisoning. Our study strongly recommends serum CPK as an alternative marker. CONCLUSIONS Serum CPK level can be an effective biomarker in acute OP poisoning because its level can predict the prognosis of OP poisoning. KEY WORDS Creatine Phosphokinase, Organophosphorus Poisoning, Severity.

Long-term stimulation of α7 nicotinic acetylcholine receptor selectively suppresses thrombin-polarized M1 microglia

Long-term stimulation of α7 nicotinic acetylcholine receptor selectively suppresses thrombin-polarized M1 microglia

Neuroprotective Activities of Curcumin in Parkinson's Disease: A Review of the Literature.

Parkinson’s disease (PD) is a slowly progressive multisystem disorder affecting dopaminergic neurons of the substantia nigra pars compacta (SNpc), which is characterized by a decrease of dopamine (DA) in their striatal terminals. Treatment of PD with levodopa or DA receptor agonists replaces the function of depleted DA in the striatum. Prolonged treatment with these agents often has variable therapeutic effects and leads to the development of undesirable dyskinesia. Consequently, a crucial unmet demand in the management of Parkinson’s disease is the discovery of new approaches that could slow down, stop, or reverse the process of neurodegeneration. Novel potential treatments involving natural substances with neuroprotective activities are being developed. Curcumin is a polyphenolic compound isolated from the rhizomes of Curcuma longa (turmeric). It has been demonstrated to have potent anti-inflammatory, antioxidant, free radical scavenging, mitochondrial protecting, and iron-chelating effects, and is considered a promising therapeutic and nutraceutical agent for the treatment of PD. However, molecular and cellular mechanisms that mediate the pharmacological actions of curcumin remain largely unknown. Stimulation of nicotinic receptors and, more precisely, selective α7 nicotinic acetylcholine receptors (α7-nAChR), have been found to play a major modulatory role in the immune system via the “cholinergic anti-inflammatory pathway”. Recently, α7-nAChR has been proposed to be a potential therapeutic approach in PD. In this review, the detailed mechanisms of the neuroprotective activities of curcumin as a potential therapeutic agent to help Parkinson’s patients are being discussed and elaborated on in detail.

Uptake of nicotinic acetylcholine receptor imaging agent is reduced in the pro-inflammatory macrophage

IntroductionMacrophages play a vital role in the development of atherosclerotic cardiovascular disease. Macrophages are functionally and phenotypically heterogeneous immune cells and commonly exist in two distinct or polarized subsets: pro-inflammatory M1 and anti-inflammatory M2 phenotypes. Previous reports suggest that stimulation of α7 or α4β2 nicotinic acetylcholine receptors (nAChRs) in macrophages leads to an anti-inflammatory response. However, the biological link between nAChR expression on macrophages and the polarization state is unknown. Therefore, we evaluated the relationship between nAChRs and polarized macrophages in peritoneal macrophages and atherosclerotic plaques of apolipoprotein E knockout (ApoE−/−) mice. MethodsPeritoneal macrophages isolated from mice were polarized into M1 and M2 macrophages, and the uptake of the nAChR-imaging agents, (R)-2-[11C]methylamino-benzoic acid 1-aza-bicyclo[2.2.2]oct-3-yl ester ([11C]MeQAA) or 2-[18F]fluoro-3-(2(S)-azetidinylmethoxy) pyridine ([18F]2FA), and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) was assessed. We also evaluated the accumulation of imaging agents in atherosclerotic plaques of ApoE−/− mice by autoradiography. After an autoradiogram was obtained, the same aortic tissue was used for immunohistochemical staining of CD68, inducible nitric oxide synthase (iNOS), and arginine-1. ResultsIn an in vitro assay, the uptake of [11C]MeQAA or [18F]2FA was lower in M1 than in M0 and M2 macrophages. In comparison, the uptake of [18F]FDG was higher in M1 macrophages. Ex vivo autoradiography showed that [11C]MeQAA was localized to the extensive plaque area. By contrast, the accumulation of [18F]2FA and [18F]FDG was heterogeneous and found only in some plaques. Moreover, the expression of CD68 and iNOS was higher in [18F]2FA non-uptake than [18F]2FA uptake plaques. ConclusionMacrophage polarization was related to nAChR expression, and α4β2 nAChR expression was suppressed in the M1 macrophage. These findings suggest that nAChR imaging has the potential to identify the inflammatory status of atherosclerotic plaque.

α4β2* Nicotinic Cholinergic Receptor Target Engagement in Parkinson Disease Gait-Balance Disorders.

Attentional deficits following degeneration of brain cholinergic systems contribute to gait-balance deficits in Parkinson disease (PD). As a step toward assessing whether α4β2* nicotinic acetylcholine receptor (nAChR) stimulation improves gait-balance function, we assessed target engagement of the α4β2* nAChR partial agonist varenicline. Nondemented PD participants with cholinergic deficits were identified with [18 F]fluoroethoxybenzovesamicol positron emission tomography (PET). α4β2* nAChR occupancy after subacute oral varenicline treatment was measured with [18 F]flubatine PET. With a dose selected from the nAChR occupancy experiment, varenicline effects on gait, balance, and cognition were assessed in a double-masked placebo-controlled crossover study. Primary endpoints were normal pace gait speed and a measure of postural stability. Varenicline doses (0.25mg per day, 0.25mg twice daily [b.i.d.], 0.5mg b.i.d., and 1.0mg b.i.d.) produced 60 to 70% receptor occupancy. We selected 0.5mg orally b.i.d for the crossover study. Thirty-three participants completed the crossover study with excellent tolerability. Varenicline had no significant impact on the postural stability measure and caused slower normal pace gait speed. Varenicline narrowed the difference in normal pace gait speed between dual task and no dual task gait conditions, reduced dual task cost, and improved sustained attention test performance. We obtained identical conclusions in 28 participants with treatment compliance confirmed by plasma varenicline measurements. Varenicline occupied α4β2* nicotinic acetylcholine receptors, was tolerated well, enhanced attention, and altered gait performance. These results are consistent with target engagement. α4β2* agonists may be worth further evaluation for mitigation of gait and balance disorders in PD. ANN NEUROL 2021;90:130-142.

Cholinergic calcium responses in cultured antennal lobe neurons of the migratory locust

Locusts are advantageous organisms to elucidate mechanisms of olfactory coding at the systems level. Sensory input is provided by the olfactory receptor neurons of the antenna, which send their axons into the antennal lobe. So far, cellular properties of neurons isolated from the circuitry of the olfactory system, such as transmitter-induced calcium responses, have not been studied. Biochemical and immunocytochemical investigations have provided evidence for acetylcholine as classical transmitter of olfactory receptor neurons. Here, we characterize cell cultured projection and local interneurons of the antennal lobe by cytosolic calcium imaging to cholinergic stimulation. We bulk loaded the indicator dye Cal-520 AM in dissociated culture and recorded calcium transients after applying cholinergic agonists and antagonists. The majority of projection and local neurons respond with increases in calcium levels to activation of both nicotinic and muscarinic receptors. In local interneurons, we reveal interactions lasting over minutes between intracellular signaling pathways, mediated by muscarinic and nicotinic receptor stimulation. The present investigation is pioneer in showing that Cal-520 AM readily loads Locusta migratoria neurons, making it a valuable tool for future research in locust neurophysiology, neuropharmacology, and neurodevelopment.

α7-Acetylcholine Receptor Signaling Reduces Neuroinflammation After Subarachnoid Hemorrhage in Mice.

Aneurysmal subarachnoid hemorrhage (aSAH) causes a robust inflammatory response which leads worse brain injury and poor outcomes. We investigated if stimulation of nicotinic acetylcholine α7 receptors (α7-AChR) (receptors shown to have anti-inflammatory effects) would reduce inflammation and improve outcomes. To investigate the level of peripheral inflammation after aSAH, inflammatory markers were measured in plasma samples collected in a cohort of aSAH patients. To study the effect of α7-AChR stimulation, SAH was induced in adult mice which were then treated with a α7-AChR agonist, galantamine, or vehicle. A battery of motor and cognitive tests were performed 24h after subarachnoid hemorrhage. Mice were euthanized and tissue collected for analysis of markers of inflammation or activation of α7-AChR-mediated transduction cascades. A separate cohort of mice was allowed to survive for 28days to assess long-term neurological deficits and histological outcome. Microglia cell culture subjected to hemoglobin toxicity was used to assess the effects of α7-AChR agonism. Analysis of eighty-two patient plasma samples confirmed enhanced systemic inflammation after aSAH. α7-AChR agonism reduced neuroinflammation at 24h after SAH in male and female mice, which was associated with improved outcomes. This coincided with JAK2/STAT3 and IRAK-M activity modulations and a robust improvement in neurological/cognitive status that was effectively reversed by interfering with various components of these signaling pathways. Pharmacologic inhibition partially reversed the α7-AChR agonist's benefits, supporting α7-AChR as a target of the agonist's therapeutic effect. The cell culture experiment showed that α7-AChR agonism is directly beneficial to microglia. Our results demonstrate that activation of α7-AChR represents an attractive target for treatment of SAH. Our findings suggest that α7-AChR agonists, and specifically galantamine, might provide therapeutic benefit to aSAH patients.

Stimulation of α7 Nicotinic Acetylcholine Receptor by Nicotine Suppresses Decidual M1 Macrophage Polarization Against Inflammation in Lipopolysaccharide-Induced Preeclampsia-Like Mouse Model.

Changes in decidual macrophage polarization affect local inflammatory microenvironment and lead to adverse pregnancy outcomes. However, the regulatory mechanism of macrophage polarization in preeclampsia (PE) remains unclear. In this study, we found that α7nAChR expression was significantly down-regulated in decidual macrophages in PE patients compared to normal pregnant women, accompanied by a reduced proportion of M2 phenotype and an increased proportion of M1 phenotype; these results suggested that the reduced α7nAChR activity might contribute to changes in the polarization of decidual macrophages. Then, we further investigated the regulatory role of α7nAChR activation by nicotine on decidual macrophage polarization and placental remodeling in the PE-like mouse model. The PE mice were obtained by i.p. injection of 10 µg/kg lipopolysaccharide (LPS) gestational day (GD) 13, and 40 µg/kg LPS daily until GD16. Subcutaneous injection of 1.0 mg/kg nicotine was administrated from GD14 to GD18. Nicotine treatment increased the decreased M2 phenotype and inhibited the increased M1 phenotype in decidua of pregnant mice induced by LPS. The levels of pro-inflammatory cytokines in decidua were higher but the levels of anti-inflammatory cytokines were lower in PE mice compared to the controls, nicotine reversed these changes. The level of choline acetyltransferase (CHAT) was reduced in the LPS-treated group, it was increased following nicotine treatment. Damage of spiral artery remodeling and down-regulation of markers related to trophoblast invasion in placentas were found in PE mice; nicotine improved these pathological structures of placentas. α-bungarotoxin (α-BGT) which is specific antagonist for α7nAChR could abolish the effects of nicotine on decidual macrophage polarization, trophoblast arrangement and vascular structure in placental tissue in PE mice. These results suggest that α7nAChR plays an important regulatory role in maternal-fetal inflammation and placental remodeling in preeclampsia and may provide a theoretical basis for the discovery of new strategies for preeclampsia.