Activation Of α7nAChR Research Articles

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.

α7 Nicotinic Acetylcholine Receptor Agonists Regulate Inflammation and Growth Hormone Resistance in Sepsis.

During sepsis the normal induction of circulating insulin-like growth factor-I (IGF-I) by growth hormone (GH) action on liver is attenuated, a phenomenon called hepatic GH resistance. Hepatic GH resistance can be caused by cytokine-mediated activation of the NF-κB pathway which interferes with normal GH-signaling. The afferent and efferent fibers of the vagus nerve are integral to the cholinergic anti-inflammatory pathway (CAP) which attenuates hepatic TNFα production by activating the α7 nicotinic acetylcholine receptor (α7nAChR). We examined the effects of selective afferent vagotomy (SAV) and α7nAChR activation on sepsis-induced mortality, hepatic and systemic inflammation, the GH/IGF system and hepatic GH resistance using Sprague Dawley (SD) rats, C57BL/6 wild type (WT) mice, and α7nAChR knockout (KO) mice. Capsaicin was used to perform SAV and GTS-21 (α7nAChR agonist) was used to activate the α7nAChR. Sepsis-induced mortality, hepatic NF-κB activation, and plasma cytokine levels were increased in SAV rats and reduced in GTS-21-treated mice. The effects of sepsis on the GH/IGF-I system plasma IGF-I, IGF binding protein-1 (IGFBP-1), hepatic IGF-I, IGFBP-1, and GH receptor (GHR) mRNA and rhGH-responsiveness in mice were improved by GTS-21. Collectively these results confirm the protective effects of the anti-inflammatory CAP and α7nAChR activation in sepsis. They also provide evidence the CAP and α7nAChR activation could be used to attenuate hepatic GH resistance and anabolic failure in sepsis.

Nicotinic Acetylcholine Receptor α7 Subunit Is an Essential Regulator of Seizure Susceptibility.

A large body of data has confirmed that α7 nicotinic acetylcholine receptors (nAChRs) play a pivotal role in cognition, memory, and other neuropsychiatric diseases, but their effect on seizure susceptibility in C57BL/6 wild-type mice is not fully understood. Here, we showed that decreased activity of α7 nAChRs could increase the excitability of CA1 pyramidal neurons and shorten the onset time of epilepsy in pilocarpine-induced mouse models. However, compared with the control group, there was no apparent effect of increasing the activity of α7 nAChRs. Moreover, the expression of α7 nAChRs is downregulated in human epileptogenic tissues. Taken together, our findings indicate that α7 nAChR is an essential regulator of seizure susceptibility.

Central Activation of Alpha7 Nicotinic Signaling Attenuates LPS-Induced Neuroinflammation and Sickness Behavior in Adult but Not in Aged Animals.

We previously reported that lipopolysaccharide (LPS) challenge caused microglial-mediated neuroinflammation and sickness behavior that was amplified in aged mice. As α7 nAChRs are implicated in the “Cholinergic anti-inflammatory pathway”, we aimed to determine how α7 nAChR stimulation modulates microglial phenotype in an LPS-induced neuroinflammation model in adult and aged mice. For this, BALB/c mice were injected intraperitoneally with LPS (0.33 mg/kg) and treated with the α7 nAChR agonist PNU282987, using different administration protocols. LPS challenge reduced body weight and induced lethargy and social withdrawal in adult mice. Peripheral (intraperitoneal) co-administration of the α7 nAChR agonist PNU282987 with LPS, attenuated body weight loss and sickness behavior associated with LPS challenge in adult mice, and reduced microglial activation with suppression of IL-1β and TNFα mRNA levels. Furthermore, central (intracerebroventricular) administration of the α7 nAChR agonist, even 2 h after LPS injection, attenuated the decrease in social exploratory behavior and microglial activation induced by peripheral administration of LPS, although this recovery was not achieved if activation of α7 nAChRs was performed peripherally. Finally, we observed that the positive results of central activation of α7 nAChRs were lost in aged mice. In conclusion, we provide evidence that stimulation of α7 nAChR signaling reduces microglial activation in an in vivo LPS-based model, but this cholinergic-dependent regulation seems to be dysfunctional in microglia of aged mice.

Multiple nicotinic acetylcholine receptor subtypes regulate social or cognitive behaviors in mice repeatedly administered phencyclidine

Habitual smoking in patients with schizophrenia (SCZ) is considered to improve their own psychoses or to develop a vulnerability to psychological dependence on (-)-nicotine ([-]-NIC) by stimulating nicotinic acetylcholine receptors (nAChRs) in the central nervous system. In the present study, we investigated whether habitual smoking is due to get therapeutic effect or to psychological dependence and which nAChR subunits are associated with them using mice that were repeatedly administered phencyclidine (PCP: 10 mg/kg/day, s.c. for 14 days) as SCZ-like model mice. Mice that were repeatedly administered PCP showed impairments in social or cognitive behaviors; decreased expression of α7 and/or α4 nAChR subunits in the prefrontal cortex (PFC); and increased expression of α7, α4, and β2 nAChR subunits in the nucleus accumbens (NAc). These changes were attenuated by repeated administration of (-)-NIC. The attenuating effects on behavioral impairments were prevented by a selective α7 nAChR antagonist and a selective α4β2 nAChR antagonist. At non- or weak effective dose by themselves, co-administration of (-)-NIC (0.03 mg/kg) and risperidone (0.03 mg/kg) showed synergistic effects on behavioral impairments in PCP-administered mice. Repeated (-)-NIC administration did not affect the performance of conditioned place preference, while it showed behavioral sensitization to (-)-NIC in the PCP-administered mice. Repeated (-)-NIC administration did not affect the performance of conditioned place preference, while it showed behavioral sensitization to (-)-NIC and attenuating effect on haloperidol-induced catalepsy in the PCP-administered mice. Our findings suggest that habitual smoking in SCZ might be attributed to get therapeutic and reduce side effects mediated by α7 and α4β2 nAChR activation by (-)-NIC.

α7-nAChRs-mediated therapeutic angiogenesis accounts for the advantageous effect of low nicotine doses against myocardial infarction in rats

Angiogenesis accelerates tissue regeneration in a variety of ischemic conditions including myocardial infarction (MI). Here we tested the hypothesis that angiogenesis induced by α7-nicotinic acetylcholine receptors (α7-nAChRs) mitigates histopathological, electrocardiographic, and molecular consequences of MI in rats. These profiles were evaluated in the isoprenaline (85 mg/kg/day i. p. For 2 days) MI rat model treated with or without nicotine or PHA-543613 (PHA, selective α7-nAChR agonist). Isoprenaline-insulted rats showed (i) ECG signs of MI such as significant ST-segment elevations and prolonged QT-intervals, (ii) deteriorated left ventricular histopathological scoring and elevated inflammatory cell infiltration, (iii) reduced immunohistochemical expression of cardiac CD34, a surrogate marker of capillary density, (iv) decreased cardiac expression of iNOS and α7-nAChRs, and (v) adaptive increases in cardiac HO-1 expression and plasma angiogenic markers such as vascular endothelial growth factor (VEGF) and nitric oxide (NO). These effects of isoprenaline, except cardiac iNOS and α7-nAChRs downregulation, were ameliorated in rats treated with a low dose (20 μg/kg/day s. c. For 16 days) of nicotine or PHA. We also show that concurrent α7-nAChR blockade by methyllycaconitine (MLA, 40 μg/kg/day, for 16 days) reversed the ECG, histopathological, and capillary density effects of nicotine, thereby reinforcing the advantageous cardioprotective and anti-ischemic roles of α7-nAChRs in this setting. The observed results showed promising effects on isoprenaline induced myocardial damage. In conclusion, the activation of α7-nAChRs by doses of nicotine or PHA in the microgram scale promotes neovascularization and offers a promising therapeutic strategy for MI. CategoryCardiovascular Pharmacology.

Cellular responses and functions of α7 nicotinic acetylcholine receptor activation in the brain: a narrative review.

The α7 nicotinic acetylcholine receptor (α7nAChR) has been studied for many years since its discovery. Although many functions and characteristics of brain α7nAChR are widely understood, much remains to be elucidated. The α7nAChR is widely expressed in the central nervous system, not only in neurons but also in astrocytes, microglia, and endothelial cells. α7nAChR can be activated by endogenous agonist like acetylcholine or exogenous agonists like nicotine and PNU282987. Its agonists can be divided into selective agonists and non-selective agonists. The activation of α7nAChR results in a series of physiological processes which have both short-term and long-term effects on cells, for example, calcium influx, neurotransmitter release, synaptic plasticity, and excitatory transmission. It also induces other downstream events, such as inflammation, autophagy, necrosis, transcription, and apoptosis. The cellular responses to α7nAChR activation vary according to cell types and conditions. For example, α7nAChR activation in pyramidal neurons leads to long-term potentiation, while α7nAChR activation in GABAergic interneurons leads to long-term depression. Studies have also shown some contradictory phenomena, which requires further study for clarification. Herein, the cellular responses of α7nAChR activation are summarized, and the functions of α7nAChR in neurons and non-neuronal cells are discussed. We also summarized contradictory conclusions to show where we stand and where to go for future studies.

Activation of α7-nAChRs Promotes the Clearance of α-Synuclein and Protects Against Apoptotic Cell Death Induced by Exogenous α-Synuclein Fibrils.

Misfolding and abnormal aggregation of α-synuclein (αSyn) have been shown to increase the risk of developing Parkinson's disease (PD). Finding some way to reduce the aggregation of αSyn is particularly important for the treatment of PD. The main route in prion-like αSyn spreading is the cholinergic innervated vagus nervous system and central cholinergic neurons. Since the degenerative changes and death of cholinergic neurons also run through the pathological process of PD, we hypothesize an involvement of the cholinergic system in αSyn aggregation. The α7 nicotinic acetylcholine receptors (α7-nAChRs) are one of the most abundant nAChRs in the mammalian brain. Using nicotine and a selective α7-nAChRs agonist PNU-282987, we found a protective effect of α7-nAChRs on the cell damage induced by αSyn-PFF (preformed fibrils) through inhibiting apoptotic cell death. We further discovered an additive effect of α7-nAChRs on the clearance of αSyn in normal and αSyn stably transduced SH-SY5Y cells. Moreover, using α7-nAChRs knockout mice, we noticed that α7-nAChRs deficiency increased the deposition of αSyn and aggravated the loss of dopaminergic neurons in a chronic MPTP mouse model of PD. Our findings for the first time indicated that α7-nAChRs activation exhibited a neuroprotective effect on αSyn pathology and aggregation by promoting the clearance of αSyn.

Therapeutic efficacy of α7 ligands after acute ischaemic stroke is linked to conductive states of α7 nicotinic ACh receptors

Targeting α7 nicotinic ACh receptors (nAChRs) in neuroinflammatory disorders including acute ischaemic stroke holds significant therapeutic promise. However, therapeutically relevant signalling mechanisms remain unidentified. Activation of neuronal α7 nAChRs triggers ionotropic signalling, but there is limited evidence for it in immunoglial tissues. The α7 ligands which are effective in reducing acute ischaemic stroke damage promote α7 ionotropic activity, suggesting a link between their therapeutic effects for treating acute ischaemic stroke and activation of α7 conductive states. This hypothesis was tested using a transient middle cerebral artery occlusion (MCAO) model of acute ischaemic stroke, NS6740, a known selective non-ionotropic agonist of α7 nAChRs and 4OH-GTS-21, a partial α7 agonist. NS6740-like ligands exhibiting low efficacy/potency for ionotropic activity will be referred to as non-ionotropic agonists or "metagonists". 4OH-GTS-21, used as a positive control, significantly reduced neurological deficits and brain injury after MCAO as compared to vehicle and NS6740. By contrast, NS6740 was ineffective in identical assays and reversed the effects of 4OH-GTS-21 when these compounds were co-applied. Electrophysiological recordings from acute hippocampal slices obtained from NS6740-injected animals demonstrated its remarkable brain availability and protracted effects on α7 nAChRs as evidenced by sustained (>8 h) alterations in α7 ionotropic responsiveness. These results suggest that α7 ionotropic activity may be obligatory for therapeutic efficacy of α7 ligands after acute ischaemic stroke yet, highlight the potential for selective application of α7 ligands to disease states based on their mode of receptor activation.

Kynurenine 3-monooxygenase deficiency induces depression-like behavior via enhanced antagonism of α7 nicotinic acetylcholine receptors by kynurenic acid

Tryptophan (TRP) is metabolized via the kynurenine (KYN) pathway, which is related to the pathogenesis of major depressive disorder (MDD). Kynurenine 3-monooxygenase (KMO) is a pivotal enzyme in the metabolism of KYN to 3-hydroxykynurenine. In rodents, KMO deficiency induces a depression-like behavior and increases the levels of kynurenic acid (KA), a KYN metabolite formed by kynurenine aminotransferases (KATs). KA antagonizes α7 nicotinic acetylcholine receptor (α7nAChR). Here, we investigated the involvement of KA in depression-like behavior in KMO knockout (KO) mice. KYN, KA, and anthranilic acid but not TRP or 3-hydroxyanthranilic acid were elevated in the prefrontal cortex of KMO KO mice. The mRNA levels of KAT1 and α7nAChR but not KAT2−4, α4nAChR, or β2nAChR were elevated in the prefrontal cortex of KMO KO mice. Nicotine blocked increase in locomotor activity, decrease in social interaction time, and prolonged immobility in a forced swimming test, but it did not decrease sucrose preference in the KMO KO mice. Methyllycaconitine (an α7nAChR antagonist) antagonized the effect of nicotine on decreased social interaction time and prolonged immobility in the forced swimming test, but not increased locomotor activity. Galantamine (an α7nAChR allosteric agonist) blocked the increased locomotor activity and prolonged immobility in the forced swimming test, but not the decreased social interaction time in the KMO KO mice. In conclusion, elevation of KA levels contributes to depression-like behaviors in KMO KO mice by α7nAChR antagonism. The ameliorating effects of nicotine and galantamine on depression-like behaviors in KMO KO mice are associated with the activation of α7nAChR.

The Spinal α7-Nicotinic Acetylcholine Receptor Contributes to the Maintenance of Cancer-Induced Bone Pain.

IntroductionCancer-induced bone pain (CIBP) is acknowledged as a multifactorial chronic pain that tortures advanced cancer patients, but existing treatment strategies for CIBP have not been satisfactory yet. Investigators have demonstrated that the activation of α7-nAChRs exerts analgesic effects in some chronic pain models. However, the role of spinal α7-nAChRs in CIBP remains unknown. This study was designed to investigate the role of α7-nAChRs in a well-established CIBP model induced by Walker 256 rat mammary gland carcinoma cells.MethodsThe paw withdrawal threshold (PWT) of the ipsilateral hind paw was measured using von Frey filament. The expressions of spinal α7-nAChRs and NF-κB were measured with Western blotting analysis. Immunofluorescence was employed to detect the expression of α7-nAChRs and co-expressed of α7-nAChRs with NeuN or GFAP or Iba1.ResultsExperiment results showed that the expression of spinal α7-nAChRs was significantly downregulated over time in CIBP rats, and in both CIBP rats and sham rats, most of the α7-nAChRs located in neurons. Behavioral data suggested PNU-282,987, a selective α7-nAChRs agonist, dose-dependently produced analgesic effect and positive allosteric modulator could intensify its effects. Further, repeated administration of PNU-282,987 reversed the expression of α7-nAChRs, inhibited the nuclear factor kappa B (NF-κB) signaling pathway, and attenuates CIBP-induced mechanical allodynia state as well.ConclusionThese results suggest that the reduced expression of spinal α7-nAChRs contributes to the maintenance of CIBP by upregulating NF-κB expression, which implying a novel pharmacological therapeutic target for the treatment of CIBP.

Protective Effect of the α7 Nicotinic Receptor Agonist PNU-282987 on Dopaminergic Neurons Against 6-Hydroxydopamine, Regulating Anti-neuroinflammatory and the Immune Balance Pathways in Rat.

Neuroinflammation and inner immune dysfunction are increasingly accepted as important components of the etiopathogenesis of Parkinson’s disease (PD). According to emerging evidence, a7 nicotinic acetylcholine receptor (α7nAChR), a ligand-gated ion channel, plays an important role in inflammatory reactions and is also expressed on the surface of T cells. In particular, regulatory T cells (Tregs) are critical for the maintenance of immunological tolerance. In the present study, we investigated the roles of α7nAChR in inhibiting inflammation and maintaining the immune balance in rats with 6-hydroxydopamine (6-OHDA)-induced lesions and the possible mechanisms regulating the proportion of Tregs in vivo. Adult male Wistar rats (n = 90) were subjected to a unilateral injection of 6-OHDA into the left medial forebrain bundle, and PNU-282987, an α7nAChR agonist, was intraperitoneally injected 2 h prior to the induction of lesions by 6-OHDA and again at days 1, 7, and 13 postlesion. Behavioral tests and immunohistochemical staining to detect the expression of tyrosine hydroxylase (TH) in the bilateral substantial nigra (SN) were performed. Subsequently, CD4+ T lymphocytes and the expression of forkhead/winged helix transcription factor p3 (Foxp3, which is a marker of Treg cells) in the SN were also assessed using immunofluorescence staining. The expression of glial fibrillary acidic protein (GFAP) in the SN was determined by performing immunohistochemical staining. Additionally, the protein levels of α7nAChR, extracellular signal-regulated kinase (Erk) phosphorylated-Erk (p-Erk) and Foxp3 in the ventral midbrain were determined using Western blotting, and the relative expression of the TNF-α, IL-1β, and IL-10 mRNAs were detected using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). We found that PNU-282987 significantly improved the motor deficits induced by 6-OHDA, reduced the loss of TH in the SN, suppressed the overactivation of GFAP+ cells and expression of related inflammatory cytokines, and increased the number of Foxp3+ cells. In addition, we also showed that PNU-282987 significantly increased the protein expression of the a7nAchR, p-Erk, and Foxp3 in 6-OHDA-lesioned rats (p < 0.05). These results indicated that α7nAChR activation could exert an anti-inflammatory effect and participate in the process of modulating the immune balance during 6-OHDA-induced injury, potentially through the α7nAChR/p-Erk/Foxp3 signaling pathway.

Molecular mechanisms of α7-nAchR-mediated anti-inflammatory effects

The cholinergic anti-inflammatory pathway is described as an interaction between the nervous system and the immune system. This interaction is regulated by the α7 subtype of cholinergic nicotinic Ach receptors (α7-nAchR), which leads to a marked decrease in the inflammatory cytokines, such as interleukin (IL)-1β, IL-6 and tumour necrosis factor α. Several ligands that interact with α7-nAchR have been recently discovered. These ligands vary in their source, chemical structure, selectivity, potency and efficacy. Activation of α7-nAchR either selectively or non-selectively showed an anti-inflammatory effect that could be due to the inhibition of inflammatory signalling pathways such as Toll-like receptor 4/nuclear factor kappa B inflammasome and mammalian target of rapamycin-mediated autophagy pathways. In addition, it was proved that continuous activation of α7-nAchR could stimulate several anti-inflammatory signalling mechanisms, including Janus activated kinase-2/signal transducer and activator of transcription 3, nuclear factor erythroid 2-related factor 2/HO-1 and adenosine monophosphate-activated protein kinase signalling. In this review, we focused on the recent discoveries of α7-nAchR agonists and antagonists and their anti-inflammatory mechanisms.

Vagal-α7nAChR signaling is required for lung anti-inflammatory responses and arginase 1 expression during an influenza infection.

Vagal circuit-α7 nicotinic acetylcholine receptor (α7nAChR, coded by Chrna7) signaling can modulate lung proinflammatory responses. Arginase 1 (ARG1) plays a crucial role in the resolution of lung inflammation. However, whether vagal-α7nAChR signaling can regulate lung inflammation and ARG1 expression during an influenza infection is elusive. Here, we found that lung and spleen IL-4+ cells and lung ARG1 expression were reduced; however, bronchoalveolar lavage (BAL) protein and leukocytes and lung inflammatory cytokines were increased in PR8 (A/Puerto Rico/8/1934, H1N1)-infected vagotomized mice when compared to the control. In PR8-infected α7nAChR-deficient mice, lung Arg1, Il10, and Socs3 expression and BAL Ly6C+CD206+ cells were reduced. PR8-infected Chrna7+/+ recipient mice reconstituted with Chrna7-/- bone marrow had a lower survival as compared to PR8-infected Chrna7+/+ recipient mice reconstituted with Chrna7+/+ bone marrow. Mechanistically, the activation of α7nAChR by its agonist GTS-21 could enhance IL-4-induced Arg1 expression, reduced Nos2, and TNF-α expression in PR8-infected bone marrow-derived macrophages (BMDM). Stimulation with IL-4 increased phosphorylation of STAT6 and activation of α7nAChR increased STAT6 binding with the ARG1 promoter and relieved IL-4-induced H3K27me3 methylation by increasing JMJD3 expression in PR8-infected BMDM. Inhibition of JMJD3 increased H3K27me3 methylation and abolished α7nAChR activation and IL-4 induced ARG1 expression. Activation of α7nAChR also reduced phosphorylation of AKT1 and contained FOXO1 in the nucleus. Knockdown of Foxo1a reduced α7nAChR activation and IL-4 induced Arg1 expression in PR8-infected BMDM. Therefore, vagal-α7nAChR signaling is a novel therapeutic target for treating lung inflammatory responses during an influenza infection.

Disruption of the cholinergic anti-inflammatory response by R5-tropic HIV-1 protein gp120JRFL

Despite current pharmacological intervention strategies, patients with HIV still suffer from chronic inflammation. The nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the nervous and immune systems. In macrophages, activation of alpha7-nAChR (α7-nAChR) controls inflammatory processes through the cholinergic anti-inflammatory response (CAR). Given that this innate immune response controls inflammation and α7-nAChR plays a critical role in the regulation of systemic inflammation, we investigated the effects of an R5-tropic HIV soluble component, gp120JRFL, on the CAR functioning. We previously demonstrated that X4-tropic HIV-1 gp120IIIB disrupts the CAR as well as inducing upregulation of the α7-nAChR in vitro in monocyte-derived macrophages (MDMs), which correlates with the upregulation observed in monocytes, T-lymphocytes, and MDMs recovered from HIV-infected people. We demonstrate here using imaging and molecular assays that the R5-tropic HIV-1 glycoprotein gp120JRFL upregulates the α7-nAChR in MDMs dependent on CD4 and/or CCR5 activation. This upregulation was also dependent on MEK1 since its inhibition attenuates the upregulation of α7-nAChR induced by gp120JRFL and was concomitant with an increase in basal calcium levels, which did not result in apoptosis. Moreover, the CAR was determined to be disrupted, since α7-nAChR activation in MDMs did not reduce the production of the proinflammatory cytokines IL-6, GRO-α, or I-309. Furthermore, a partial antagonist of α7-nAChR, bupropion, rescued IL-6 but not GRO-α or I-309 production. Together, these results demonstrate that gp120JRFL disrupts the CAR in MDMs. Other medications targeting the α7-nAChR need to be tested to reactivate the CAR to ameliorate inflammation in HIV-infected subjects.

The human-specific duplicated α7 gene inhibits the ancestral α7, negatively regulating nicotinic acetylcholine receptor-mediated transmitter release

Gene duplication generates new functions and traits, enabling evolution. Human-specific duplicated genes in particular are primary sources of innovation during our evolution although they have very few known functions. Here we examine the brain function of one of these genes (CHRFAM7A) and its product (dupα7 subunit). This gene results from a partial duplication of the ancestral CHRNA7 gene encoding the α7 subunit that forms the homopentameric α7 nicotinic acetylcholine receptor (α7-nAChR). The functions of α7-nAChR in the brain are well defined, including the modulation of synaptic transmission and plasticity underlying normal attention, cognition, learning, and memory processes. However, the role of the dupα7 subunit remains unexplored at the neuronal level. Here, we characterize that role by combining immunoblotting, quantitative RT-PCR and FRET techniques with functional assays of α7-nAChR activity using human neuroblastoma SH-SY5Y cell variants with different dupα7 expression levels. Our findings reveal a physical interaction between dupα7 and α7 subunits in fluorescent protein-tagged dupα7/α7 transfected cells that negatively affects normal α7-nAChR activity. Specifically, in both single cells and cell populations, the [Ca2+]i signal and the exocytotic response induced by selective stimulation of α7-nAChR were either significantly inhibited by stable dupα7 overexpression or augmented after silencing dupα7 gene expression with specific siRNAs. These findings identify a new role for the dupα7 subunit as a negative regulator of α7-nAChR-mediated control of exocytotic neurotransmitter release. If this effect is excessive, it would result in an impaired synaptic transmission that could underlie the neurocognitive and neuropsychiatric disorders associated with α7-nAChR dysfunction.

Farnesyl Transferase Inhibitor Lonafarnib Enhances α7nAChR Expression Through Inhibiting DNA Methylation of CHRNA7 and Increases α7nAChR Membrane Trafficking.

Inhibition of Ras farnesylation in acute has been found to upregulate the α7 nicotinic acetylcholine receptor (α7nAChR) activity. This study was carried out to investigate the effect of chronic administration for 7 days of farnesyl transferase inhibitor lonafarnib (50 mg/kg, intraperitoneally injected) to male mice on the expression and activity of α7nAChR in hippocampal CA1 pyramidal cells. Herein, we show that lonafarnib dose dependently enhances the amplitude of ACh-evoked inward currents (I ACh), owning to the increased α7nAChR expression and membrane trafficking. Lonafarnib inhibited phosphorylation of c-Jun and JNK, which was related to DNA methylation. In addition, reduced DNA methyltransferase 1 (DNMT1) expression was observed in lonafarnib-treated mice, which was reversed by JNK activator. Lonafarnib-upregulated expression of α7nAChR was mimicked by DNMT inhibitor, and repressed by JNK activator. However, only inhibited DNA methylation did not affect I ACh, and the JNK activator partially decreased the lonafarnib-upregulated I ACh. On the other hand, lonafarnib also increased the membrane expression of α7nAChR, which was partially inhibited by JNK activator or CaMKII inhibitor, without changes in the α7nAChR phosphorylation. CaMKII inhibitor had no effect on the expression of α7nAChR. Lonafarnib-enhanced spatial memory of mice was also partially blocked by JNK activator or CaMKII inhibitor. These results suggest that Ras inhibition increases α7nAChR expression through depressed DNA methylation of CHRNA7 via Ras-c-Jun-JNK pathway, increases the membrane expression of α7nAChR resulting in part from the enhanced CaMKII pathway and total expression of this receptor, and consequently enhances the spatial memory.

Chronic Ethanol Exposure Potentiates Cholinergic Neurotransmission in the Basolateral Amygdala

Chronic intermittent ethanol (CIE) exposure dysregulates glutamatergic and GABAergic neurotransmission, facilitating basolateral amygdala (BLA) pyramidal neuron hyperexcitability and the expression of anxiety during withdrawal. It is unknown whether ethanol-induced alterations in nucleus basalis magnocellularis (NBM) cholinergic projections to the BLA mediate anxiety-related behaviors through direct modulation of GABA and glutamate afferents. Following 10 days of CIE exposure and 24 h of withdrawal, we recorded GABAergic and glutamatergic synaptic responses in BLA pyramidal neurons with electrophysiology, assessed total protein expression of cholinergic markers, and quantified acetylcholine and choline concentrations using a colorimetric assay. We measured α7 nicotinic acetylcholine receptor (nAChR) dependent modulation of presynaptic function at distinct inputs in AIR- and CIE-exposed BLA coronal slices as a functional read-out of cholinergic neurotransmission. CIE/withdrawal upregulates the endogenous activity of α7 nAChRs, facilitating release at both GABAergic’ local’ interneuron and glutamatergic synaptic responses to stria terminalis (ST) stimulation, with no effect at GABAergic lateral paracapsular cells (LPCs). CIE caused a three-fold increase in BLA acetylcholine concentration, with no changes in α7 nAChR or cholinergic marker expression. These data illustrate that α7 nAChR-dependent changes in presynaptic function serve as a proxy for CIE-dependent alterations in synaptic acetylcholine levels. Thus, cholinergic projections appear to mediate CIE-induced alterations at GABA/glutamate inputs.

Role of the α7 Nicotinic Acetylcholine Receptor in the Pathophysiology of Atherosclerosis.

Atherosclerosis constitutes a major risk factor for cardiovascular diseases, the leading cause of morbidity and mortality worldwide. This slowly progressing, chronic inflammatory disorder of large- and medium-sized arteries involves complex recruitment of immune cells, lipid accumulation, and vascular structural remodeling. The α7 nicotinic acetylcholine receptor (α7nAChR) is expressed in several cell types involved in the genesis and progression of atherosclerosis, including macrophages, dendritic cells, T and B cells, vascular endothelial and smooth muscle cells (VSMCs). Recently, the α7nAChR has been described as an essential regulator of inflammation as this receptor mediates the inhibition of cytokine synthesis through the cholinergic anti-inflammatory pathway, a mechanism involved in the attenuation of atherosclerotic disease. Aside from the neuronal cholinergic control of inflammation, the non-neuronal cholinergic system similarly regulates the immune function. Acetylcholine released from T cells acts in an autocrine/paracrine fashion at the α7nAChR of various immune cells to modulate immune function. This mechanism additionally has potential implications in reducing atherosclerotic plaque formation. In contrast, the activation of α7nAChR is linked to the induction of angiogenesis and VSMC proliferation, which may contribute to the progression of atherosclerosis. Therefore, both atheroprotective and pro-atherogenic roles are attributed to the stimulation of α7nAChRs, and their role in the genesis and progression of atheromatous plaque is still under debate. This minireview highlights the current knowledge on the involvement of the α7nAChR in the pathophysiology of atherosclerosis.

The neuroprotective effects of activated \u03b17 nicotinic acetylcholine receptor against mutant copper\u2013zinc superoxide dismutase 1-mediated toxicity

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the selective and progressive loss of motor neurons. Although many drugs have entered clinical trials, few have shown effectiveness in the treatment of ALS. Other studies have shown that the stimulation of α7 nicotinic acetylcholine receptor (nAChR) can have neuroprotective effects in some models of neurodegenerative disease, as well as prevent glutamate-induced motor neuronal death. However, the effect of α7 nAChR agonists on ALS-associated mutant copper–zinc superoxide dismutase 1 (SOD1) aggregates in motor neurons remains unclear. In the present study, we examined whether α7 nAChR activation had a neuroprotective effect against SOD1G85R-induced toxicity in a cellular model for ALS. We found that α7 nAChR activation by PNU282987, a selective agonist of α7 nAChR, exhibited significant neuroprotective effects against SOD1G85R-induced toxicity via the reduction of intracellular protein aggregates. This reduction also correlated with the activation of autophagy through the AMP-activated protein kinase (AMPK)–mammalian target of rapamycin (mTOR) signaling pathway. Furthermore, the activation of α7 nAChRs was found to increase the biogenesis of lysosomes by inducing translocation of the transcription factor EB (TFEB) into the nucleus. These results support the therapeutic potential of α7 nAChR activation in diseases that are characterized by SOD1G85R aggregates, such as ALS.