α7nAChR Agonist Research Articles

Mechanism of Pyroptosis in Postoperative Cognitive Dysfunction Rats and α7-nicotinic Receptor Agonist Regulating NLRP3 Inflammasome Activation

Background: This study investigates the efficacy of α7-nicotinic acetylcholine receptor (α7nAChR) agonists in mitigating postoperative cognitive dysfunction (POCD) in a rat model. This investigation aimed to elucidate the therapeutic potential of α7nAChR agonists in modulating neuroinflammatory pathways to improve cognitive outcomes post-surgery. Objective: Serum levels of pro-inflammatory cytokines IL-1β and IL-18 were measured as markers of systemic inflammation, while the expression levels of NLRP3 mRNA were quantified to evaluate pyroptosis and NLRP3 inflammasome activation. Methods: Adult male Sprague-Dawley rats were divided into control (no surgery), POCD (surgeryinduced), and POCD treated with an α7nAChR agonist. Cognitive function was assessed using the Morris Water Maze (MWM) and Novel Object Recognition (NOR) tests. Results: The results showed a notable cognitive impairment in the group with POCD, as shown by increased escape latency noted in the MWM test and decreased discrimination index in the NOR test, while controls had no change. However, treatment with the α7nAChR agonist led to a significant improvement in cognitive performance among the POCD rats such that it closely matched those of the controls. Furthermore, the POCD group exhibited elevated serum levels of IL-1β and IL-18 and increased expression of pyroptosis-related markers, indicating enhanced neuroinflammation and inflammasome activation. Conclusion: These findings highlighted the therapeutic efficacy of α7nAChR agonists in mitigating neuroinflammation and improving cognitive outcomes post-surgery. Our study supports the potential of targeting the cholinergic anti-inflammatory pathway, emphasizing clinical evaluation of α7nAChR agonists in postoperative patients.

Modulation of Ca2+ oscillation following ischemia and nicotinic acetylcholine receptors in primary cortical neurons by high-throughput analysis

Calcium oscillations in primary neuronal cultures and iPSCs have been employed to investigate arrhythmogenicity and epileptogenicity in drug development. Previous studies have demonstrated that Ca2+ influx via NMDA and nicotinic acetylcholine receptors (nAChRs) modulates Ca2+ oscillations. Nevertheless, there has been no comprehensive investigation into the impact of ischemia or nAChR-positive allosteric modulators (PAM) drugs on Ca2+ oscillations at a level that would facilitate high-throughput screening. We investigated the effects of ischemia and nAChR subtypes or nAChR PAM agonists on Ca2+ oscillations in high-density 2D and 3D-sphere primary neuronal cultures using 384-well plates with FDSS-7000. Ischemia for 1 and 2 h resulted in an increase in the frequency of Ca2+ oscillations and a decrease in their amplitude in a time-dependent manner. The NMDA and AMPA receptor inhibition significantly suppressed Ca2+ oscillation. Inhibition of NR2A or NR2B had the opposite effect on Ca oscillations. The potentiation of ischemia-induced Ca2+ oscillations was significantly inhibited by the NMDA receptor antagonist, MK-801, and the frequency of these oscillations was suppressed by the NR2B inhibitor, Ro-256981. In the 3D-neurosphere, the application of an α7nAChR agonist increased the frequency of Ca2+ oscillations, whereas the activation of α4β2 had no effect. The combination of nicotine and PNU-120596 (type II PAM) affected the frequency and amplitude of Ca2+ oscillations in a manner distinct from that of type I PAM. These systems may be useful not only for detecting epileptogenicity but also in the search for neuroprotective agents against cerebral ischemia.

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

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

Activation of α7 Nicotinic Acetylcholine Receptors Inhibits Hepatic Necroptosis and Ameliorates Acute Liver Injury in Mice.

Acute liver injury is a disease characterized by severe liver dysfunction, caused by significant infiltration of immune cells and extensive cell death with a high mortality. Previous studies demonstrated that the α7 nicotinic acetylcholine receptor (α7nAChR) played a crucial role in various liver diseases. The hypothesis of this study was that activating α7nAChR could alleviate acute liver injury and investigate its possible mechanisms. Acute liver injury was induced by intraperitoneal injection of lipopolysaccharide (LPS)/D-galactosamine (D-Gal) in wild type, α7nAChR knockout (α7nAChR-/-) and stimulator of interferon gene (STING) mutation (Stinggt/gt) mice in the presence or absence of a pharmacologic selective α7nAChR agonist (PNU-282987). The effects of α7nAChR on hepatic injury, inflammatory response, mitochondrial damage, necroptosis, and infiltration of immune cells during acute liver injury were assessed. The expression of α7nAChR in liver tissue was increased in LPS/D-Gal-induced acute liver injury mice. Compared to the age-matched wild-type mice, α7nAChR deficiency decreased the survival rate, exacerbated the hepatic injury accompanied with enhanced inflammatory response and oxidative stress, and aggravated hepatic mitochondrial damage and necroptosis. Conversely, pharmacologic activation of α7nAChR by PNU-282987 displayed the opposite trends. Furthermore, PNU-282987 significantly reduced the proportion of infiltrating monocyte-derived macrophages (CD45+CD11bhiF4/80int), M1 macrophages (CD45+CD11b+F4/80+CD86hiCD163low), and Ly6Chi monocytes (CD45+CD11b+MHC [major histocompatibility complex] ⅡlowLy6Chi), but increased the resident Kupffer cells (CD45+CD11bintF4/80hiTIM4hi) in the damaged hepatic tissues caused by LPS/D-Gal. Interestingly, α7nAChR deficiency promoted the STING signaling pathway under LPS/D-Gal stimulation, while PNU-282987 treatment significantly prevented its activation. Finally, it was found that Sting mutation abolished the protective effects against hepatic injury by activating α7nAChR. The authors' study revealed that activating α7nAChR could protect against LPS/D-Gal-induced acute liver injury by inhibiting hepatic inflammation and necroptosis possibly via regulating immune cells infiltration and inhibiting STING signaling pathway.

Activation of α7 nicotinic receptors attenuated hyperalgesia and anxiety induced by palatable obesogenic diet withdrawal

Consumption of palatable food (PF) can alleviate anxiety, and pain in humans. Contrary, spontaneous withdrawal of long-term PF intake produces anxiogenic-like behavior and abnormal pain sensation, causing challenges to weight-loss diet and anti-obesity agents. Thus, we examined α7-nicotinic acetylcholine receptors (α7nAChR) involvement since it plays essential role in nociception and psychological behaviors. MethodsAdult male C57BL/6 mice were placed on a Standard Chow (SC) alone or with PF on intermittent or continuous regimen for 6 weeks. Then, mice were replaced with normal SC (spontaneous withdrawal). Body weight, food intake, and calories intake with and without the obesogenic diet were measured throughout the study. During PF withdrawal, anxiety-like behaviors and pain sensitivity were measured with PNU-282987 (α7nAChR agonist) administration. ResultsSix weeks of SC + PF-intermittent and continuous paradigms produced a significant weight gain. PF withdrawal displayed hyperalgesia and anxiety-like behaviors. During withdrawal, PNU-282987 significantly attenuated hyperalgesia and anxiety-like behaviors. ConclusionThe present study shows that a PF can increase food intake and body weight. Also, enhanced pain sensitivity and anxiety-like behavior were observed during PF withdrawal. α7nAChR activation attenuated anxiolytic-like behavior and hyperalgesia in PF abstinent mice. These data suggest potential therapeutic effects of targeting α7 nAChRs for obesity-withdrawal symptoms in obese subjects.

The potential effect of α7 nicotinic receptors modulation on palatable food-induced dependence-like behaviors

BackgroundThe recent global increase in obesity rates, coupled with excessive palatable food (PF) consumption, has become a serious societal concern. Literature indicates that rewarding PF, especially upon cessation, can lead to overeating, binge eating, and compulsive eating, potentially resulting in obesity. Challenges in dietary paradigms, alongside limitations in approved treatments for eating disorders and anti-obesity medications, underscore the need to explore novel targets. In this context, α7nAChR (alpha-7 nicotinic acetylcholine receptor) may serve as a promising therapeutic target in combating food dependence and obesity. The present study aims to assess the role of α7nAChR in palatable food-induced dependence-like behaviors. MethodThe study involved male C57BL/6J mice exposed to three different feeding paradigms over 6 weeks to induce obesity and food addiction. On day 43, palatable food was replaced with standard chow, and the mice received treatments (vehicle, PNU-282987 [α7nAChR agonist], or methyllycaconitine citrate [MLA; α7nAChR antagonist]). Addiction-like behaviors, including craving for palatable food, motivation-effort interaction tests, and compulsive eating-like behavior, were measured during abstinence with and without treatment. ResultsThe present study shows that chronic intermittent and continuous exposure to palatable food induces craving, motivation, and effort interaction behaviors as well as compulsive eating-like behaviors in palatable food-abstinent mice. Administration of the α7nAChR agonist, PNU-282987, significantly attenuated the craving behavior only in mice continuously fed palatable food (reduced calorie intake from 63.19 % to 48.21 %; p = 0.0053). Also, PNU-282987 suppressed the effort behaviors in either intermittently or continuously fed mice (significant reduction in the Δ number of active events per minute; p-values = 0.038 and 0.0098, respectively). However, it attenuated the compulsive-like eating behavior exclusively in the continuously fed group (p = 0.0433). Active and total interaction efforts were reversed by the MLA. These findings indicate the involvement of α7nAChR in dependence-like behaviors toward palatable food in mice. ConclusionOur findings demonstrate that dependence-like behaviors toward palatable food can emerge after prolonged exposure. Mice fed on palatable food continuously exhibited more dependence-like behaviors toward palatable food, and activation of α7nAChR signaling attenuated the vulnerability to develop such behaviors.

Activation of the α7nAChR by GTS-21 mitigates septic tubular cell injury and modulates macrophage infiltration

The most common and serious complication among hospitalized and critically ill patients is sepsis-associated acute kidney damage (S-AKI), which raises the risk of comorbidities and is linked to a high mortality rate. Cholinergic anti-inflammatory pathway (CAP), an anti-inflammatory pathway mediated by the vagus nerve, acetylcholine, and α7 nicotinic acetylcholine receptors (α7nAChRs), offers new perspectives for the treatment of S-AKI. In this study, we investigated the role of CAP and α7nAChR in kidney injury by employing an LPS-induced septic kidney injury mouse model and GTS-21 intervention. C57BL/6 mice were injected with LPS, with or without GTS-21, in different subgroups. Kidney function was assessed by plasma creatinine, histology, and markers of kidney injury 24 h after intervention. The results demonstrated that GTS-21 could inhibit the systemic inflammatory response and directly protect the tubular cell injury from LPS. To explore the novel gene involved in this response, RNA sequencing of the renal proximal tubular epithelial cell (HK-2), pretreated with LPS and GTS-21, was conducted. The results indicate that GTS-21 administration reduces LPS-induced cytokines and chemokines secretion by HK-2, including CCL20, a potent chemokine attracting monocytes/macrophages. Furthermore, a macrophage transmigration assay revealed that GTS-21 inhibits macrophage transmigration by downregulating the expression of CCL20 in HK-2 cells. In conclusion, GTS-21, as an α7nAChR agonist, emerges as a noteworthy and versatile treatment for S-AKI. Its dual function of directly protecting renal tubular cells and regulating inflammatory responses represents a major advancement in the treatment of sepsis-induced AKI. This finding might pave the way for novel approaches to improving patient outcomes and reducing death rates in sepsis-related complications.

α7 nicotinic receptor activation mitigates herpes simplex virus type 1 infection in microglia cells

Herpes simplex virus type 1 (HSV-1), a neurotropic DNA virus, establishes latency in neural tissues, with reactivation causing severe consequences like encephalitis. Emerging evidence links HSV-1 infection to chronic neuroinflammation and neurodegenerative diseases. Microglia, the central nervous system's (CNS) immune sentinels, express diverse receptors, including α7 nicotinic acetylcholine receptors (α7 nAChRs), critical for immune regulation. Recent studies suggest α7 nAChR activation protects against viral infections. Here, we show that α7 nAChR agonists, choline and PNU-282987, significantly inhibit HSV-1 replication in microglial BV2 cells. Notably, this inhibition is independent of the traditional ionotropic nAChR signaling pathway. mRNA profiling revealed that choline stimulates the expression of antiviral factors, IL-1β and Nos2, and down-regulates the apoptosis genes and type A Lamins in BV2 cells. These findings suggest a novel mechanism by which microglial α7 nAChRs restrict viral infections by regulating innate immune responses.

Evaluation of the effect of intraoperative tropisetron on postoperative rebound pain after brachial plexus block: a randomized controlled trial.

Postoperative rebound pain after peripheral nerve block increases patient suffering and delays recovery after surgery. We tested whether the 5HT-3 receptor antagonist and α7nAChR agonist tropisetron could prevent postoperative rebound pain. A total of 115 patients were randomized to receive 5-mg/5-mL tropisetron or the same volume of normal saline. Pain intensity was measured with the numerical rating scale of pain (NRS). Rebound pain was defined as a change from mild pain (NRS ≤ 3) measured in the postanesthesia care unit to severe pain (NRS ≥ 7) within 24 hours after peripheral nerve blockade. Logistic regression was used to identify relevant factors associated with postoperative rebound pain. Tropisetron did not affect the NRS score or the incidence of rebound pain after peripheral nerve block. Logistic regression revealed that preoperative pain, bone surgery, and length of incision were risk factors for postoperative rebound pain, and patient-controlled analgesia was protective against postoperative rebound pain. Tropisetron does not affect the incidence of rebound pain after peripheral nerve block. Patients at high risk of postoperative rebound pain should be identified for appropriate management. Registration site: www.chictr.org.cn (ChiCTR2300069994).

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.

Apigenin Alleviates Autistic-like Stereotyped Repetitive Behaviors and Mitigates Brain Oxidative Stress in Mice.

Studying the involvement of nicotinic acetylcholine receptors (nAChRs), specifically α7-nAChRs, in neuropsychiatric brain disorders such as autism spectrum disorder (ASD) has gained a growing interest. The flavonoid apigenin (APG) has been confirmed in its pharmacological action as a positive allosteric modulator of α7-nAChRs. However, there is no research describing the pharmacological potential of APG in ASD. The aim of this study was to evaluate the effects of the subchronic systemic treatment of APG (10-30 mg/kg) on ASD-like repetitive and compulsive-like behaviors and oxidative stress status in the hippocampus and cerebellum in BTBR mice, utilizing the reference drug aripiprazole (ARP, 1 mg/kg, i.p.). BTBR mice pretreated with APG (20 mg/kg) or ARP (1 mg/g, i.p.) displayed significant improvements in the marble-burying test (MBT), cotton-shredding test (CST), and self-grooming test (SGT) (all p < 0.05). However, a lower dose of APG (10 mg/kg, i.p.) failed to modulate behaviors in the MBT or SGT, but significantly attenuated the increased shredding behaviors in the CST of tested mice. Moreover, APG (10-30 mg/kg, i.p.) and ARP (1 mg/kg) moderated the disturbed levels of oxidative stress by mitigating the levels of catalase (CAT) and superoxide dismutase (SOD) in the hippocampus and cerebellum of treated BTBR mice. In patch clamp studies in hippocampal slices, the potency of choline (a selective agonist of α7-nAChRs) in activating fast inward currents was significantly potentiated following incubation with APG. Moreover, APG markedly potentiated the choline-induced enhancement of spontaneous inhibitory postsynaptic currents. The observed results propose the potential therapeutic use of APG in the management of ASD. However, further preclinical investigations in additional models and different rodent species are still needed to confirm the potential relevance of the therapeutic use of APG in ASD.

Characterizing the binding of TC-5619 and encenicline on the alpha7 nicotinic acetylcholine receptor using PET imaging in the pig.

The alpha7 nicotinic acetylcholine receptor (α7-nAChR) has has long been considered a promising therapeutic target for addressing cognitive impairments associated with a spectrum of neurological and psychiatric disorders, including Alzheimer's disease and schizophrenia. However, despite this potential, clinical trials employing α7-nAChR (partial) agonists such as TC-5619 and encenicline (EVP-6124) have fallen short in demonstrating sufficient efficacy. We here investigate the target engagement of TC-5619 and encenicline in the pig brain by use of the α7-nAChR radioligand 11C-NS14492 to characterize binding both with in vitro autoradiography and in vivo occupancy using positron emission tomography (PET). In vitro autoradiography demonstrates significant concentration-dependent binding of 11C-NS14492, and both TC-5619 and encenicline can block this binding. Of particular significance, our in vivo investigations demonstrate that TC-5619 achieves substantial α7-nAChR occupancy, effectively blocking approximately 40% of α7-nAChR binding, whereas encenicline exhibits more limited α7-nAChR occupancy. This study underscores the importance of preclinical PET imaging and target engagement analysis in informing clinical trial strategies, including dosing decisions.

Retrospective evaluation of COVID-19 incidence during smoking cessation treatment with varenicline

Background: Cholinergic anti-inflammatory pathway endogenously controls inflammatory processes through activation of the α7-nicotinic acetylcholine receptor (α7nAChR). Varenicline, used in smoking cessation therapy, is a full α7nAChR agonist with anti-inflammatory effects. In this study, the frequency of coronavirus disease (COVID-19) was evaluated in patients using varenicline as a smoking cessation treatment.&#x0D; Methods: In this retrospective cross-sectional study, records of the 111 patients admitted to Smoking Cessation Outpatient Clinic of Dokuz Eylul University Faculty of Medicine during the COVID-19 pandemic were evaluated. The development of COVID-19 disease according to the status of the patients being positive for SARS-COV-2 was evaluated comparatively in patients who received varenicline or not. Additionally, the disease symptoms were questioned. &#x0D; Results: SARS-CoV-2 PCR positivity was not detected in any of 38 patients who regularly used varenicline out of 68 patients evaluated. SARS-CoV-2 PCR positivity was detected in 13 (43.3%) of 30 patients who received other treatments or irregularly used varenicline (p

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.

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

To investigate the effects of α7 nicotinic acetylcholine receptor (nAChR) agonist on β3-adrenoceptor agonist-induced impairment of white fat homeostasis and beige adipose formation and heat production in obese mice. Forty obese C57BL/6J mice were randomized into high-fat feeding group, β3-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-1β, IL-10 and TGF-β 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. 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-1β, and lowered expression of Arg-1 mRNA and IL-10 and TGF-β 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-1β expressions, increased IL-10 and TGF-β expressions, and reduced M1/M2 macrophage ratio in the white adipose tissues (P < 0.05 or 0.01). Activation of α7 nAchR improves white adipose tissue homeostasis impairment induced by β3 agonist, promotes transformation of M1 to M2 macrophages, reduces inflammatory response in white adipose tissue, and promote beige adipogenesis and thermogenesis in obese mice.

Vagus nerve stimulation as a promising neuroprotection for ischemic stroke via α7nAchR-dependent inactivation of microglial NLRP3 inflammasome.

Ischemic stroke is a major cause of disability and death worldwide, and its management requires urgent attention. Previous studies have shown that vagus nerve stimulation (VNS) exerts neuroprotection in ischemic stroke by inhibiting neuroinflammation and apoptosis. In this study, we evaluated the timing for VNS intervention in ischemic stroke, and the underlying mechanisms ofVNS-induced neuroprotection. Mice were subjected to transient middle cerebral artery occlusion (tMCAO) for 60 min. The left vagus nerve at cervical level was exposed and attached to an electrode connected to a low-frequency electrical stimulator. Vagus nerve stimulation (VNS) was given for 60 min before, during and after tMCAO (Pre-VNS, Dur-VNS, Post-VNS). Neurological function was assessed 24 h after reperfusion. We found that all the three VNS significantly protected against the tMCAO-induced injury evidenced by improved neurological function and reduced infarct volume. Moreover, the Pre-VNS was the most effective against the ischemic injury. We found that tMCAO activated microglia in the ischemic core and penumbra regions of the brain, followed by the NLRP3 inflammasome activation-induced neuroinflammation, which finally triggered neuronal death. VNS treatment preserved α7nAChR expression in the penumbra regions, inhibited NLRP3 inflammasome activation and ensuing neuroinflammation, rescuing cerebral neurons. The role of α7nAChR in microglial NLRP3 inflammasome activation in ischemic stroke was further validated using genetic manipulations, including Chrna7 knockout mice and microglial Chrna7 overexpression mice, as well as pharmacological interventions using the α7nAChR inhibitor methyllycaconitine and agonist PNU-282987. Collectively, this study demonstrates the potential of VNS as a safe and effective strategy to treat ischemic stroke, and presents a new approach targeting microglial NLRP3 inflammasome, which might be therapeutic for other inflammation-related diseases.

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.

The alpha-7 nicotinic acetylcholine receptor agonist PHA-543613 reduces food intake in male rats

Obesity is a prevalent disease, but effective treatment options remain limited. Agonists of the alpha-7 nicotinic acetylcholine receptor (α7nAChR) promote negative energy balance in mice, but these effects are not well-studied in rats. We tested the hypothesis that central administration of the α7nAChR agonist PHA-543613 (PHA) would decrease food intake and body weight in adult male Sprague Dawley rats. Intracerebroventricular (ICV) PHA administration in chow-fed rats produced a suppression of energy intake and weight gain over 24 h. Next, to evaluate effects of ICV PHA on palatable food intake, rats were maintained on a choice diet of rodent chow and 45 % high fat diet (HFD); under these conditions, ICV PHA produced no significant changes in energy intake from either food, or body weight gain, in the 24 h post-injection. However, when given a choice of chow or a higher-fat 60 % HFD, ICV PHA reduced intake of 60 % HFD, but not chow; body weight gain was also suppressed. Further experiments evaluating conditioned taste avoidance (CTA) and pica in response to ICV PHA suggested that the suppressive food intake and body weight effects after ICV injection of PHA were not due to nausea/malaise. Finally, an operant conditioning study showed that responding on a progressive ratio schedule of reinforcement for high-fat food pellets decreased after ICV PHA. Collectively, these studies show that PHA reduces energy intake under some but not all dietary conditions. Importantly, central PHA decreases both food intake as well as motivation for highly palatable, energy dense foods in rats without inducing nausea/malaise, suggesting that the α7nAChR could be a viable target for developing treatments for obesity.

Effects of α7 nicotinic acetylcholine receptor agonist against α-synuclein-induced neurotoxicity

The α7 neuronal nicotinic acetylcholine receptor (α7 nAChR) is a potential target for the development of Parkinson’s disease (PD) therapeutics. α-Synuclein (α-Syn), a principal component of Lewy bodies (cytoplasmic inclusions), is a major contributor to PD pathophysiology. Previous studies have demonstrated that activating α7 nAChR protects against nigrostriatal dopamine degeneration in acute and chronic PD animal models induced by 6-hydroxydopamine and rotenone, respectively. In the present study, we investigated the effects of PNU282987, a selective α7 nAChR agonist, against α-Syn-induced neurotoxicity in α-SynWT-, α-SynA30P-, and α-SynE46K-N2a cells. PNU282987 exhibited substantial neuroprotection against both wild-type and mutant-type α-Syn-induced toxicity. Furthermore, PNU282987 promoted transcription factor EB activity and reduced intracellular α-Syn protein levels through autophagy induction. These results highlight the therapeutic potential of α7 nAChR activation in diseases characterized by α-Syn aggregation, such as PD.

Alpha-7 Nicotinic Receptor Agonist Protects Mice Against Pulmonary Emphysema Induced by Elastase.

Pulmonary emphysema is a primary component of chronic obstructive pulmonary disease (COPD), a life-threatening disorder characterized by lung inflammation and restricted airflow, primarily resulting from the destruction of small airways and alveolar walls. Cumulative evidence suggests that nicotinic receptors, especially the α7 subtype (α7nAChR), is required for anti-inflammatory cholinergic responses. We postulated that the stimulation of α7nAChR could offer therapeutic benefits in the context of pulmonary emphysema. To investigate this, we assessed the potential protective effects of PNU-282987, a selective α7nAChR agonist, using an experimental emphysema model. Male mice (C57BL/6) were submitted to a nasal instillation of porcine pancreatic elastase (PPE) (50µl, 0.667IU) to induce emphysema. Treatment with PNU-282987 (2.0mg/kg, ip) was performed pre and post-emphysema induction by measuring anti-inflammatory effects (inflammatory cells, cytokines) as well as anti-remodeling and anti-oxidant effects. Elastase-induced emphysema led to an increase in the number of α7nAChR-positive cells in the lungs. Notably, both groups treated with PNU-282987 (prior to and following emphysema induction) exhibited a significant decrease in the number of α7nAChR-positive cells. Furthermore, both groups treated with PNU-282987 demonstrated decreased levels of macrophages, IL-6, IL-1β, collagen, and elastic fiber deposition. Additionally, both groups exhibited reduced STAT3 phosphorylation and lower levels of SOCS3. Of particular note, in the post-treated group, PNU-282987 successfully attenuated alveolar enlargement, decreased IL-17 and TNF-α levels, and reduced the recruitment of polymorphonuclear cells to the lung parenchyma. Significantly, it is worth noting that MLA, an antagonist of α7nAChR, counteracted the protective effects of PNU-282987 in relation to certain crucial inflammatory parameters. In summary, these findings unequivocally demonstrate the protective abilities of α7nAChR against elastase-induced emphysema, strongly supporting α7nAChR as a pivotal therapeutic target for ameliorating pulmonary emphysema.