The human alpha7 nicotinic acetylcholine receptor is a host target for the rabies virus glycoprotein.

The rabies virus enters the nervous system by interacting with several molecular targets on host cells to modify behavior and trigger receptor-mediated endocytosis of the virion by poorly understood mechanisms. The rabies virus glycoprotein (RVG) interacts with the muscle acetylcholine receptor and the neuronal α4ß2 subtype of the nicotinic acetylcholine receptor (nAChR) family by the putative neurotoxin-like motif. Given that the neurotoxin-like motif is highly homologous to the α7 nAChR subtype selective snake toxin α-bungarotoxin (αBTX), other nAChR subtypes are likely involved. The purpose of this study is to determine the activity of the RVG neurotoxin-like motif on nAChR subtypes that are expressed in brain regions involved in rabid animal behavior. nAChRs were expressed in Xenopus laevis oocytes, and two-electrode voltage clamp electrophysiology was used to collect concentration-response data to measure the functional effects. The RVG peptide preferentially and completely inhibits α7 nAChR ACh-induced currents by a competitive antagonist mechanism. Tested heteromeric nAChRs are also inhibited, but to a lesser extent than the α7 subtype. Residues of the RVG peptide with high sequence homology to αBTX and other neurotoxins were substituted with alanine. Altered RVG neurotoxin-like peptides showed that residues phenylalanine 192, arginine 196, and arginine 199 are important determinants of RVG peptide apparent potency on α7 nAChRs, while serine 195 is not. The evaluation of the rabies ectodomain reaffirmed the observations made with the RVG peptide, illustrating a significant inhibitory impact on α7 nAChR with potency in the nanomolar range. In a mammalian cell culture model of neurons, we confirm that the RVG peptide binds preferentially to cells expressing the α7 nAChR. Defining the activity of the RVG peptide on nAChRs expands our understanding of basic mechanisms in host-pathogen interactions that result in neurological disorders.

Nicotine aggravates liver fibrosis via α7 nicotinic acetylcholine receptor expressed on activated hepatic stellate cells in mice.

BACKGROUND: Smoking is a risk factor for liver cirrhosis; however, the underlying mechanisms remain largely unexplored. The α7 nicotinic acetylcholine receptor (α7nAChR) has recently been detected in nonimmune cells possessing immunoregulatory functions. We aimed to verify whether nicotine promotes liver fibrosis via α7nAChR. METHODS: We used osmotic pumps to administer nicotine and carbon tetrachloride to induce liver fibrosis in wild-type and α7nAChR-deficient mice. The severity of fibrosis was evaluated using Masson trichrome staining, hydroxyproline assays, and real-time PCR for profibrotic genes. Furthermore, we evaluated the cell proliferative capacity and COL1A1 mRNA expression in human HSCs line LX-2 and primary rat HSCs treated with nicotine and an α7nAChR antagonist, methyllycaconitine citrate. RESULTS: Nicotine exacerbated carbon tetrachloride-induced liver fibrosis in mice (+42.4% in hydroxyproline assay). This effect of nicotine was abolished in α7nAChR-deficient mice, indicating nicotine promotes liver fibrosis via α7nAChR. To confirm the direct involvement of α7nAChRs in liver fibrosis, we investigated the effects of genetic suppression of α7nAChR expression on carbon tetrachloride-induced liver fibrosis without nicotine treatment. Profibrotic gene expression at 1.5 weeks was significantly suppressed in α7nAChR-deficient mice (-83.8% in Acta2, -80.6% in Col1a1, -66.8% in Tgfb1), and collagen content was decreased at 4 weeks (-22.3% in hydroxyproline assay). The in vitro analysis showed α7nAChR expression in activated but not in quiescent HSCs. Treatment of LX-2 cells with nicotine increased COL1A1 expression (+116%) and cell proliferation (+10.9%). These effects were attenuated by methyllycaconitine citrate, indicating the profibrotic effects of nicotine via α7nAChR. CONCLUSIONS: Nicotine aggravates liver fibrosis induced by other factors by activating α7nAChR on HSCs, thereby increasing their collagen-producing capacity. We suggest the profibrotic effect of nicotine is mediated through α7nAChRs.

Fluorescent α-Conotoxin [Q1G, ΔR14]LvIB Identifies the Distribution of α7 Nicotinic Acetylcholine Receptor in the Rat Brain.

α7 nicotinic acetylcholine receptors (nAChRs) are mainly distributed in the central nervous system (CNS), including the hippocampus, striatum, and cortex of the brain. The α7 nAChR has high Ca2+ permeability and can be quickly activated and desensitized, and is closely related to Alzheimer's disease (AD), epilepsy, schizophrenia, lung cancer, Parkinson's disease (PD), inflammation, and other diseases. α-conotoxins from marine cone snail venom are typically short, disulfide-rich neuropeptides targeting nAChRs and can distinguish various subtypes, providing vital pharmacological tools for the functional research of nAChRs. [Q1G, ΔR14]LvΙB is a rat α7 nAChRs selective antagonist, modified from α-conotoxin LvΙB. In this study, we utilized three types of fluorescein after N-Hydroxy succinimide (NHS) activation treatment: 6-TAMRA-SE, Cy3 NHS, and BODIPY-FL NHS, labeling the N-Terminal of [Q1G, ΔR14]LvΙB under weak alkaline conditions, obtaining three fluorescent analogs: LvIB-R, LvIB-C, and LvIB-B, respectively. The potency of [Q1G, ΔR14]LvΙB fluorescent analogs was evaluated at rat α7 nAChRs expressed in Xenopus laevis oocytes. Using a two-electrode voltage clamp (TEVC), the half-maximal inhibitory concentration (IC50) values of LvIB-R, LvIB-C, and LvIB-B were 643.3 nM, 298.0 nM, and 186.9 nM, respectively. The stability of cerebrospinal fluid analysis showed that after incubation for 12 h, the retention rates of the three fluorescent analogs were 52.2%, 22.1%, and 0%, respectively. [Q1G, ΔR14]LvΙB fluorescent analogs were applied to explore the distribution of α7 nAChRs in the hippocampus and striatum of rat brain tissue and it was found that Cy3- and BODIPY FL-labeled [Q1G, ΔR14]LvΙB exhibited better imaging characteristics than 6-TAMARA-. It was also found that α7 nAChRs are widely distributed in the cerebral cortex and cerebellar lobules. Taking into account potency, imaging, and stability, [Q1G, ΔR14]LvΙB -BODIPY FL is an ideal pharmacological tool to investigate the tissue distribution and function of α7 nAChRs. Our findings not only provide a foundation for the development of conotoxins as visual pharmacological probes, but also demonstrate the distribution of α7 nAChRs in the rat brain.

Unconventional PDZ Recognition Revealed in α7 nAChR-PICK1 Complexes.

PDZ domains are modular domains that conventionally bind to C terminal or internal motifs of target proteins to control cellular functions through the regulation of protein complex assemblies. Almost all reported structures of PDZ-target protein complexes rely on fragments or peptides as target proteins. No intact target protein complexed with PDZ was structurally characterized. In this study, we used NMR spectroscopy and other biochemistry and biophysics tools to uncover insights into structural coupling between the PDZ domain of protein interacting with C-kinase 1 (PICK1) and α7 nicotinic acetylcholine receptors (α7 nAChR). Notably, the intracellular domains of both α7 nAChR and PICK1 PDZ exhibit a high degree of plasticity in their coupling. Specifically, the MA helix of α7 nAChR interacts with residues lining the canonical binding site of the PICK1 PDZ, while flexible loops also engage in protein-protein interactions. Both hydrophobic and electrostatic interactions mediate the coupling. Overall, the resulting structure of the α7 nAChR-PICK1 complex reveals an unconventional PDZ binding mode, significantly expanding the repertoire of functionally important PDZ interactions.

Reversal of lipopolysaccharide-induced cardiomyocyte apoptosis via α7nAChR by dexmedetomidine.

This study aims to analyze the reversal of lipopolysaccharide (LPS)-induced cardiomyocyte apoptosis via α7nAChR by dexmedetomidine (Dex), so as to provide references for clinical treatment of myocardial disorders in the future. First, the research team divided cardiomyocytes (H9C2) were divided into a control group (normal culture), an LPS group (LPS-induced injury model), and an experimental group (pretreated with Dex before LPS induction). Subsequently, lactate dehydrogenase (LDH) and cell activity were detected, and the research team found that the LDH content of the control, experimental and LPS groups were in ascending order (P<0.05). The cell viability decreased and apoptosis increased in the LPS group, with cells mainly concentrating in the G2-M phase; the viability increased and apoptosis decreased in the experimental group, with blocked G1-G0 phase (P<0.05). This demonstrates that Dex can reverse LPS-induced apoptosis in cardiomyocytes. Subsequently, the research group also detected the expression of α7nAChR and NF-κB/AKT pathway, and it was seen that the expression of α7nAChR in the LPS group was higher than that in the control group, with activated NF-κB/AKT pathway; the α7nAChR expression in the experimental group was further elevated, but the NF-κB/AKT pathway was inhibited (P<0.05). The effects of Dex on cardiomyocytes were seen to be related to the α7nAChR and NF-κB/AKT pathways.

Sevoflurane-induced cognitive effect on α7-nicotine receptor and M1 acetylcholine receptor expression in the hippocampus of aged rats.

BACKGROUND: Sevoflurane treatment increases the incidence of postoperative cognitive dysfunction (POCD), and patients with POCD show a decline in cognitive abilities compared to preoperative levels. OBJECTIVES: This study aimed to investigate whether the activation of α7 nicotinic acetylcholine receptor (α7nAChR) and the expression of M1 acetylcholine receptor (mAChR M1) in the hippocampus affects the cognitive function of aged rats. METHODS: Forty-eight Sprague-Dawley (SD) rats of 1-week- and 12-months-old were divided into eight groups: four groups for α7nAChR and four groups for mAChR M1, respectively. All SD rats received 1.0-02% sevoflurane for α7nAChR and 1.0-02% sevoflurane for mAChR M1 for 2-6 h, respectively. The Y-maze test was used to assess the ability to learn and memory after receiving sevoflurane for 7 days at the same moment portion. RT-PCR was used to determine the expression of α7nAChR and mAChR M1 in the hippocampus of rats. RESULTS: The α7nAChR mitigated the formation of sevoflurane-induced memory impairment by modulating the translocation of NR2B from the intracellular reservoir to the cell surface reservoir within the hippocampus. Next, sevoflurane-induced decline of cognitive function and significantly decreased mAChR M1 expression at mRNA levels. CONCLUSION: α7nAChR regulates the trafficking of NR2B in the hippocampus of rats via the Src-family tyrosine kinase (SFK) pathway. This regulation is associated with cognitive deficits induced by sevoflurane in hippocampal development. Sevoflurane affects the cognitive function of rats by suppressing the mAChR M1 expression at mRNA levels in the hippocampus.

α7nAChR attenuates sevoflurane-induced memory deficits by regulating NR2B.α7nAChR controls NR2B via the SFK in the hippocampus of rats that contribute to sevoflurane-induced cognitive deficits.Sevoflurane may affect cognitive function in rats by suppressing the mAChR M1 expression at the mRNA levels in the hippocampus.Dysregulation of the α7nAChR and mAChR M1 receptors may contribute to cognitive deficits and neurodegenerative disorders.

Tabernanthalog and ibogainalog inhibit the α7 and α9α10 nicotinic acetylcholine receptors via different mechanisms and with higher potency than the GABAA receptor and CaV2.2 channel.

In this study, we have investigated the pharmacological activity and structural interaction of two novel psychoplastogens, tabernanthalog (TBG) and ibogainalog (IBG) at heterologously-expressed rat (r) and human (h) nicotinic acetylcholine receptors (nAChRs), the rα1ß2γ2L γ-aminobutyric acid type A receptor (GABAAR), and the human voltage-gated N-type calcium channel (CaV2.2 channel). Both compounds inhibited the nAChRs with the following receptor selectivity: α9α10 > α7 > α3ß2 â‰… α3ß4, indicating that ß2/ß4 subunits are relatively less important for their activity. The potencies of TBG and IBG were comparable at hα7 and hα9α10 subtypes, and comparable to their rat counterparts. TBG- and IBG-induced inhibition of rα7 was ACh concentration-independent and voltage-dependent, whereas rα9α10 inhibition was ACh concentration-dependent and voltage-independent, suggesting that they interact with the α7 ion channel pore and α9α10 orthosteric ligand binding site, respectively. These results were supported by molecular docking studies showing that at the α7 model TBG forms stable interactions with luminal rings at 9', 13', and 16', whereas IBG mostly interacts with the extracellular-transmembrane junction. In the α9α10 model, however, these compounds interacted with several residues from the principal (+) and complementary (-) sides in the transmitter binding site. Ibogaminalog (DM506) also interacted with a non-luminal site at α7, and one α9α10 orthosteric site. TBG and IBG inhibited the GABAAR and CaV2.2 channels with 10 to 30-fold lower potencies. In sum, we show that TBG and IBG inhibit the α7 and α9α10 nAChRs by noncompetitive and competitive mechanisms, respectively, and with higher potency than the GABAAR and CaV2.2 channel.

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

OBJECTIVE: To investigate the effects of α7 nicotinic acetylcholine receptor (nAChR) agonist on ß3-adrenoceptor agonist-induced impairment of white fat homeostasis and beige adipose formation and heat production in obese mice. METHODS: Forty obese C57BL/6J mice were randomized into high-fat feeding group, ß3-adrenoceptor agonist-treated model group, α7 nAChR agonist group, and α7 nAChR inhibitor group (n=10), with another 10 mice with normal feeding as the blank control group. White adipose tissue from the epididymis of the mice were sampled for HE staining of the adipocytes. The expression levels of TNF-α, IL-1ß, IL-10 and TGF-ß in the white adipose tissue were determined by ELISA, and the mRNA levels of iNOS, Arg1, UCP-1, PRDM-16 and PGC-1α were detected using RT-qPCR. Western blotting was performed to detect the expression levels of NF-κB P65, p-JAK2, p-STAT3 in the white adipose tissue. RESULTS: Compared with those in the blank control group, the mice with high-fat feeding showed significantly increased body weight, more fat vacuoles in the white adipose tissue, increased volume of lipid droplets in the adipocytes, upregulated iNOS mRNA expression and protein expression of TNF-α and IL-1ß, and lowered expression of Arg-1 mRNA and IL-10 and TGF-ß proteins (P < 0.01). Treatment with α7 nAChR significantly reduced mRNA levels of PRDM-16, PGC-1α and UCP-1, lowered TNF-α and IL-1ß expressions, increased IL-10 and TGF-ß expressions, and reduced M1/M2 macrophage ratio in the white adipose tissues (P < 0.05 or 0.01). CONCLUSION: Activation of α7 nAchR improves white adipose tissue homeostasis impairment induced by ß3 agonist, promotes transformation of M1 to M2 macrophages, reduces inflammatory response in white adipose tissue, and promote beige adipogenesis and thermogenesis in obese mice.

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.

Attenuation of Nicotine Effects on A549 Lung Cancer Cells by Synthetic α7 nAChR Antagonists APS7-2 and APS8-2.

Nicotine binds to nicotinic acetylcholine receptors (nAChRs) that are overexpressed in different cancer cells, promoting tumor growth and resistance to chemotherapy. In this study, we aimed to investigate the potential of APS7-2 and APS8-2, synthetic analogs of a marine sponge toxin, to inhibit nicotine-mediated effects on A549 human lung cancer cells. Our electrophysiological measurements confirmed that APS7-2 and APS8-2 act as α7 nAChR antagonists. APS8-2 showed no cytotoxicity in A549 cells, while APS7-2 showed concentration-dependent cytotoxicity in A549 cells. The different cytotoxic responses of APS7-2 and APS8-2 emphasize the importance of the chemical structure in determining their cytotoxicity on cancer cells. Nicotine-mediated effects include increased cell viability and proliferation, elevated intracellular calcium levels, and reduced cisplatin-induced cytotoxicity and reactive oxygen species production (ROS) in A549 cells. These effects of nicotine were effectively attenuated by APS8-2, whereas APS7-2 was less effective. Our results suggest that APS8-2 is a promising new therapeutic agent in the chemotherapy of lung cancer.

KYNA Ameliorates Glutamate Toxicity of HAND by Enhancing Glutamate Uptake in A2 Astrocytes.

Reactive astrocytes are key players in HIV-associated neurocognitive disorders (HAND), and different types of reactive astrocytes play opposing roles in the neuropathologic progression of HAND. A recent study by our group found that gp120 mediates A1 astrocytes (neurotoxicity), which secrete proinflammatory factors and promote HAND disease progression. Here, by comparing the expression of A2 astrocyte (neuroprotective) markers in the brains of gp120 tgm mice and gp120+/α7nAChR-/- mice, we found that inhibition of alpha 7 nicotinic acetylcholine receptor (α7nAChR) promotes A2 astrocyte generation. Notably, kynurenine acid (KYNA) is an antagonist of α7nAChR, and is able to promote the formation of A2 astrocytes, the secretion of neurotrophic factors, and the enhancement of glutamate uptake through blocking the activation of α7nAChR/NF-κB signaling. In addition, learning, memory and mood disorders were significantly improved in gp120 tgm mice by intraperitoneal injection of kynurenine (KYN) and probenecid (PROB). Meanwhile, the number of A2 astrocytes in the mouse brain was significantly increased and glutamate toxicity was reduced. Taken together, KYNA was able to promote A2 astrocyte production and neurotrophic factor secretion, reduce glutamate toxicity, and ameliorate gp120-induced neuropathological deficits. These findings contribute to our understanding of the role that reactive astrocytes play in the development of HAND pathology and provide new evidence for the treatment of HAND via the tryptophan pathway.

Contributions of Non-Neuronal Cholinergic Systems to the Regulation of Immune Cell Function, Highlighting the Role of α7 Nicotinic Acetylcholine Receptors.

Loewi's discovery of acetylcholine (ACh) release from the frog vagus nerve and the discovery by Dale and Dudley of ACh in ox spleen led to the demonstration of chemical transmission of nerve impulses. ACh is now well-known to function as a neurotransmitter. However, advances in the techniques for ACh detection have led to its discovery in many lifeforms lacking a nervous system, including eubacteria, archaea, fungi, and plants. Notably, mRNAs encoding choline acetyltransferase and muscarinic and nicotinic ACh receptors (nAChRs) have been found in uninnervated mammalian cells, including immune cells, keratinocytes, vascular endothelial cells, cardiac myocytes, respiratory, and digestive epithelial cells. It thus appears that non-neuronal cholinergic systems are expressed in a variety of mammalian cells, and that ACh should now be recognized not only as a neurotransmitter, but also as a local regulator of non-neuronal cholinergic systems. Here, we discuss the role of non-neuronal cholinergic systems, with a focus on immune cells. A current focus of much research on non-neuronal cholinergic systems in immune cells is α7 nAChRs, as these receptors expressed on macrophages and T cells are involved in regulating inflammatory and immune responses. This makes α7 nAChRs an attractive potential therapeutic target.

CHRFAM7A diversifies human immune adaption through Ca2+ signalling and actin cytoskeleton reorganization.

BACKGROUND: Human restricted genes contribute to human specific traits in the immune system. CHRFAM7A, a uniquely human fusion gene, is a negative regulator of the α7 nicotinic acetylcholine receptor (α7 nAChR), the highest Ca2+ conductor of the ACh receptors implicated in innate immunity. Understanding the mechanism of how CHRFAM7A affects the immune system remains unexplored. METHODS: Two model systems are used, human induced pluripotent stem cells (iPSC) and human primary monocytes, to characterize α7 nAChR function, Ca2+ dynamics and decoders to elucidate the pathway from receptor to phenotype. FINDINGS: CHRFAM7A/α7 nAChR is identified as a hypomorphic receptor with mitigated Ca2+ influx and prolonged channel closed state. This shifts the Ca2+ reservoir from the extracellular space to the endoplasmic reticulum (ER) leading to Ca2+ dynamic changes. Ca2+ decoder small GTPase Rac1 is then activated, reorganizing the actin cytoskeleton. Observed actin mediated phenotypes include cellular adhesion, motility, phagocytosis and tissue mechanosensation. INTERPRETATION: CHRFAM7A introduces an additional, human specific, layer to Ca2+ regulation leading to an innate immune gain of function. Through the actin cytoskeleton it drives adaptation to the mechanical properties of the tissue environment leading to an ability to invade previously immune restricted niches. Human genetic diversity predicts profound translational significance as its understanding builds the foundation for successful treatments for infectious diseases, sepsis, and cancer metastasis. FUNDING: This work is supported in part by the Community Foundation for Greater Buffalo (Kinga Szigeti) and in part by NIH grant R01HL163168 (Yongho Bae).

Alpha 7 Nicotinic Acetylcholine Receptor Agonist PHA 568487 Reduces Acute Inflammation but Does Not Affect Cardiac Function or Myocardial Infarct Size in the Permanent Occlusion Model.

Stimulation of the alpha 7 nicotinic acetylcholine receptor (α7nAChR) has shown beneficial effects in several acute inflammatory disease models. This study aims to examine whether treatment with the selective α7nAChR agonist PHA 568487 can dampen inflammation and thereby improve cardiac function after myocardial infarction in mice. The possible anti-inflammatory properties of α7nAChR agonist PHA 568487 were tested in vivo using the air pouch model and in a permanent occlusion model of acute myocardial infarction in mice. Hematologic parameters and cytokine levels were determined. Infarct size and cardiac function were assessed via echocardiography 24 h and one week after the infarction. Treatment with α7nAChR agonist PHA 568487 decreased 12 (CCL27, CXCL5, IL6, CXCL10, CXCL11, CXCL1, CCL2, MIP1a, MIP2, CXCL16, CXCL12 and CCL25) out of 33 cytokines in the air pouch model of acute inflammation. However, α7nAChR agonist PHA 568487 did not alter infarct size, ejection fraction, cardiac output or stroke volume at 24 h or at 7 days after the myocardial infarction compared with control mice. In conclusion, despite promising immunomodulatory effects in the acute inflammatory air pouch model, α7nAChR agonist PHA 568487 did not affect infarct size or cardiac function after a permanent occlusion model of acute myocardial infarction in mice. Consequently, this study does not strengthen the hypothesis that stimulation of the α7nAChR is a future treatment strategy for acute myocardial infarction when reperfusion is lacking. However, whether other agonists of the α7nAChR can have different effects remains to be investigated.

Vagus nerve stimulation modulates distinct acetylcholine receptors on B cells and limits the germinal center response.

Acetylcholine is produced in the spleen in response to vagus nerve activation; however, the effects on antibody production have been largely unexplored. Here, we use a chronic vagus nerve stimulation (VNS) mouse model to study the effect of VNS on T-dependent B cell responses. We observed lower titers of high-affinity IgG and fewer antigen-specific germinal center (GC) B cells. GC B cells from chronic VNS mice exhibited altered mRNA and protein expression suggesting increased apoptosis and impaired plasma cell differentiation. Follicular dendritic cell (FDC) cluster dispersal and altered gene expression suggested poor function. The absence of acetylcholine-producing CD4+ T cells diminished these alterations. In vitro studies revealed that α7 and α9 nicotinic acetylcholine receptors (nAChRs) directly regulated B cell production of TNF, a cytokine crucial to FDC clustering. α4 nAChR inhibited coligation of CD19 to the B cell receptor, presumably decreasing B cell survival. Thus, VNS-induced GC impairment can be attributed to distinct effects of nAChRs on B cells.

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.

Remimazolam Attenuates LPS-Derived Cognitive Dysfunction via Subdiaphragmatic Vagus Nerve Target α7nAChR-Mediated Nrf2/HO-1 Signal Pathway.

Sepsis-induced neuroinflammation is significantly associated with sepsis-related brain dysfunction. Remimazolam is a novel ultra-short-acting benzodiazepine anesthetic with multiple organ protective effects. However, it is unknown whether remimazolam can ameliorate LPS-induced brain impairment. In this study, Lipopolysaccharide (5 mg/kg, LPS) severely impaired Sprague-Dawley rats spatial learning ability, memory, and cognitive function. However, remimazolam treatment showed a protective effect on LPS-induced cognitive dysfunction. Remimazolam partly reversed LPS-induced splenomegaly, decreased serum cytokine expression, suppressed hippocampal M1 microglial activation, and mitigated oxidative stress injury and neuroinflammation. Electroacupuncture (EA) or PNU282987 treatment improved LPS-induced cognitive dysfunction and also significantly inhibited neuroinflammation and systemic inflammation. However, MLA, ML385, or subdiaphragmatic vagus nerve (SDV) treatment abolished the protective effects of remimazolam. Further mechanistic studies showed that remimazolam induces protective effects by activating subdiaphragmatic vagus nerve target α7nAChR-mediated Nrf2/HO-1 signaling pathway. These results demonstrate that remimazolam can up-regulate α7nAChR, Cyto-Nrf2, HO-1, and cognitive-related (CREB, BDNF, PSD95) protein expressions, suppress M1 microglia, ameliorate neuroinflammation or systemic inflammation, and reverse cognitive dysfunction. Therefore, this study provides insight into a new therapeutic target for the treatment of sepsis-induced cerebral dysfunction.

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.

Direct vagus nerve stimulation: A new tool to control allergic airway inflammation through α7 nicotinic acetylcholine receptor.

BACKGROUND AND PURPOSE: Asthma is characterized by airway inflammation, mucus hypersecretion, and airway hyperresponsiveness. The use of nicotinic agents to mimic the cholinergic anti-inflammatory pathway (CAP) controls experimental asthma. Yet, the effects of vagus nerve stimulation (VNS)-induced CAP on allergic inflammation remain unknown. EXPERIMENTAL APPROACH: BALB/c mice were sensitized and challenged with house dust mite (HDM) extract and treated with active VNS (5 Hz, 0.5 ms, 0.05-1 mA). Bronchoalveolar lavage (BAL) fluid was assessed for total and differential cell counts and cytokine levels. Lungs were examined by histopathology and electron microscopy. KEY RESULTS: In the HDM mouse asthma model, VNS at intensities equal to or above 0.1 mA (VNS 0.1) but not sham VNS reduced BAL fluid differential cell counts and alveolar macrophages expressing α7 nicotinic receptors (α7nAChR), goblet cell hyperplasia, and collagen deposition. Besides, VNS 0.1 also abated HDM-induced elevation of type 2 cytokines IL-4 and IL-5 and was found to block the phosphorylation of transcription factor STAT6 and expression level of IRF4 in total lung lysates. Finally, VNS 0.1 abrogated methacholine-induced hyperresponsiveness in asthma mice. Prior administration of α-bungarotoxin, a specific inhibitor of α7nAChR, but not propranolol, a specific inhibitor of ß2-adrenoceptors, abolished the therapeutic effects of VNS 0.1. CONCLUSION AND IMPLICATIONS: Our data revealed the protective effects of VNS on various clinical features in allergic airway inflammation model. VNS, a clinically approved therapy for depression and epilepsy, appears to be a promising new strategy for controlling allergic asthma.

Electroacupuncture alleviates intestinal inflammation via a distinct neuro-immune signal pathway in the treatment of postoperative ileus.

BACKGROUND: The induction of intestinal inflammation as a result of abdominal surgery is an essential factor in postoperative ileus (POI) development. Electroacupuncture (EA) at ST36 has been demonstrated to relieve intestinal inflammation and restore gastrointestinal dysmotility in POI. This study aims to elucidate the neuroimmune pathway involved in the anti-inflammatory properties of EA in POI. METHODS: After intestinal manipulation (IM) was performed to induce POI, intestinal inflammation and motility were assessed 24 h post-IM, by evaluating gastrointestinal transit (GIT), cytokines expression, and leukocyte infiltration. Experimental surgery, pharmacological intervention, and genetic knockout mice were used to elucidate the neuroimmune mechanisms of EA. RESULTS: EA at ST36 significantly improved GIT and reduced the expression of pro-inflammatory cytokines and leukocyte infiltration in the intestinal muscularis following IM in mice. The anti-inflammatory effectiveness of EA treatment was abolished by sub-diaphragmatic vagotomy, whereas splenectomy did not hinder the anti-inflammatory benefits of EA treatment. The hexamethonium chloride (HEX) administration contributes to a notable reduction in the EA capacity to suppress inflammation and enhance motility dysfunction, and EA is ineffective in α7 nicotinic acetylcholine receptor (α7nAChR) knockout mice. CONCLUSIONS: EA at ST36 prevents intestinal inflammation and dysmotility through a neural circuit that requires vagal innervation but is independent of the spleen. Further findings revealed that the process involves enteric neurons mediating the vagal signal and requires the presence of α7nAChR. These findings suggest that utilizing EA at ST36 may represent a possible therapeutic approach for POI and other immune-related gastrointestinal diseases.