Search Results (352)

Many vertebrates have evolved resistance to snake venom as a result of coevolutionary chemical arms races. In Australian skinks (family Scincidae), who often encounter venomous elapid snakes, the frequency, diversity, and molecular basis of venom resistance have been unexplored. This study investigated the evolution of neurotoxin resistance in Australian skinks, focusing on mutations in the muscle nicotinic acetylcholine receptor (nAChR) α1 subunit’s orthosteric site that prevent pathophysiological binding by α-neurotoxins. We sampled a broad taxonomic range of Australian skinks and sequenced the nAChR α1 subunit gene. Key resistance-conferring mutations at the toxin-binding site (N-glycosylation motifs, proline substitutions, arginine insertions, changes in the electrochemical state of the receptor, and novel cysteines) were identified and mapped onto the skink organismal phylogeny. Comparisons with other venom-resistant taxa (amphibians, mammals, and reptiles) were performed, and structural modelling and binding assays were used to evaluate the impact of these mutations. Multiple independent origins of α-neurotoxin resistance were found across diverse skink lineages. Thirteen lineages evolved at least one resistance motif and twelve additional motifs evolved within these lineages, for a total of twenty-five times of α-neurotoxic venoms resistance. These changes sterically or electrostatically inhibit neurotoxin binding. Convergent mutations at the orthosteric site include the introduction of N-linked glycosylation sites previously known from animals as diverse as cobras and mongooses. However, an arginine (R) substitution at position 187 was also shown to have evolved on multiple occasions in Australian skinks, a modification previously shown to be responsible for the Honey Badger’s iconic resistance to cobra venom. Functional testing confirmed this mode of resistance in skinks. Our findings reveal that venom resistance has evolved extensively and convergently in Australian skinks through repeated molecular adaptations of the nAChR in response to the enormous selection pressure exerted by elapid snakes subsequent to their arrival and continent-wide dispersal in Australia. These toxicological findings highlight a remarkable example of convergent evolution across vertebrates and provide insight into the adaptive significance of toxin resistance in snake–lizard ecological interactions. Full article

Three-finger toxins (3FTxs) are the largest group of nonenzymatic toxins found in snake venoms. Among them, neurotoxins that target nicotinic acetylcholine receptors are the most well-studied ligands. In addition to the classical neurotoxins, several other new classes have been characterized for their structure, receptor subtype, and species selectivity. Here, we systematically analyzed over 700 amino acid sequences of three-finger neurotoxins that interact with nicotinic acetylcholine receptors. Based on the amino acid residue substitutions in the functional sites and structural features of various classes of neurotoxins, we have classified them into over 150 distinct subgroups. Currently, only a small number of typical examples representing these subgroups have been studied for their structure, function, and subtype selectivity. The functional site residues responsible for their interaction with specific receptor subtypes of several toxins are yet to be identified. The molecular details of each subgroup representative toxin with its target receptor will contribute towards the understanding of subtype- and/or interface-selectivity. Thus, this review will provide new impetus in the toxin research and pave the way for the design of potent, selective ligands for nicotinic acetylcholine receptors. Full article

Background/Objectives: Myasthenia Gravis (MG) and myasthenic syndrome (MSyn) are neurological disorders induced by different types of autoantibodies, characterized by generalized muscle weakness, sometimes involving the respiratory muscles and necessitating ventilatory support. One therapeutic option for severe Myasthenia Gravis (MG) is total plasma exchange (TPE). This procedure reduces the concentration of autoantibodies by extracting the patient’s plasma and replacing it with donor plasma. The TPE efficacy varies among different types of MG, and patient response to TPE is evaluated solely through clinical markers, such as muscle strength. So far, no laboratory method is available for monitoring TPE treatment progress. Objective: In this study, we aimed to determine whether differential scanning calorimetry (DSC) of blood plasma from myasthenic patients is an appropriate tool to monitor and evaluate their condition and the TPE effect. Methods: We performed DSC prior to and after TPE course on blood plasma from three patients with different types of MG: Case 1. Patient with Acetylcholine Receptor Myasthenia Gravis (AChR MG); Case 2. Patient with Muscle-specific tyrosine kinase Myasthenia Gravis (MuSK MG); Case 3. Patient with Myasthenic syndrome (MSyn). Results: DSC thermogram examination revealed increased plasma protein fractions, primarily immunoglobulins (IG), as well as to some extent fibrinogen, relative to a suppressed serum albumin fraction. Successive TPE procedures resulted in IG fraction decline in AChR MG (Case 1) and MSyn (Case 3), and upsurge of the IG fraction in MuSK MG (Case 2). These findings aligned with the clinical presentation of all three cases. Conclusions: DSC revealed distinct, very significant differences in the heat capacity profiles of blood plasma from MG patients relative to healthy controls, as well as strong TPE influence on the plasma thermal behavior. DSC showed promise as a reliable and informative technique for the monitoring of myasthenia and TPE effects across diverse myasthenic patient populations. Further research is needed to confirm and expand on these findings. Full article

Cholinergic projections from the basal forebrain to the cortex and hippocampus play a critical role in cognitive functions, many of which rely on signaling through the alpha7 nicotinic acetylcholine receptor (α7nAChR). The Alzheimer’s disease (AD) brain is characterized by the profound impairment of the basal forebrain cholinergic system, including alterations in the levels of α7nAChR in various brain areas. In addition, α7nAChR binds with high affinity to beta amyloid (Aβ), suggesting α7nAChR might mediate some of Aβ’s effects in the brain. Under normal physiological conditions, the interaction between Aβ and α7nAChR appears to be beneficial, supporting normal neurotransmission, synaptic plasticity, and memory functions. However, when levels of Aβ are pathologically elevated, their interaction leads to deleterious effects, implicating α7nAChR in the pathophysiology of AD. In addition to expression in neurons, α7nAChR is expressed in astrocytes and microglia, where it serves as a key component of a cholinergic pathway that regulates neuroinflammation. This review article will cover the role of α7nAChR in neurons, astrocytes and microglia under normal conditions, summarize changes in the expression or function of α7nAChR in neurons and glia in the AD brain, and discuss cell-type specific contributions of α7nAChR to AD pathology with an emphasis on interactions of α7nAChR with Aβ. Full article

Breast cancer is a major global health burden with the highest incidence in women, and triple-negative breast cancer (TNBC) stands out as the most malignant subtype. Effective therapeutic targets are urgently needed to develop new therapies for TNBC. Nicotinic acetylcholine receptor is a ligand-gated ion channel receptor that is associated with the advancement of multiple cancers. Notably, α9 nicotinic acetylcholine receptor (α9 nAChR) is less investigated towards its role in cancer. This study sought to clarify the significance of α9 nAChR in TNBC. Firstly, our results uncovered that the expression of CHRNA9 was notably elevated in TNBC tissues and was associated with poor prognosis of TNBC patients. Further, our data indicated that overexpression of α9 nAChR facilitated the growth of TNBC cells, via mechanisms of simultaneously activating AKT-, ERK- and STAT3-mediated proliferation and negatively regulating ferroptosis through promoting SLC7A11/GSH/GPX4 and Keap1/Nrf2/HO1 signaling. Conversely, CHRNA9 knockdown would completely reverse all this signaling, ultimately inhibiting TNBC tumor growth both in vitro and in vivo. Finally, we reported a specific polypeptide antagonist of α9 nAChR, GeXIVA[1,2] and exerted good anti-tumor effects in tumor-bearing mice of TNBC, which indicated a great potential of GeXIVA[1,2] to be further studied as a novel targeted therapy for TNBC. This study provides a scientific basis for establishing α9 nAChR as a novel therapeutic target for TNBC, which is worthy of further development in the future. Full article

It has long been recognised that airway smooth muscle cells (ASMCs) possess an abundance of M2 muscarinic receptors (M2Rs). However, the contribution of postjunctional M2Rs to contractions of airway smooth muscle (ASM) induced by the release of acetylcholine (ACh) from parasympathetic nerves was thought to be minimal. Instead, it was believed that these responses were exclusively mediated by activation of M3Rs. However, evidence is emerging that postjunctional M2Rs may have a greater role than previously realised. In this review, we discuss ACh signalling in airways, highlighting the well-established autoinhibitory role of prejunctional M2Rs and the putative roles of postjunctional M2Rs to cholinergic contractions of ASM. The cellular mechanisms that underpin M2R-dependent contractions of ASM are reviewed, with a particular emphasis on the role of ion channels in these responses. The regulation of M2R signalling pathways by β-adrenoceptor activation is also considered, along with the potential involvement of postjunctional M2Rs in airway diseases such as asthma and chronic obstructive pulmonary disease (COPD). Full article

Background: Acute respiratory distress syndrome (ARDS) is a high-mortality disease strongly associated with an imbalance in the inflammatory response. The ratio of helper T 17 (Th17) cells to regulatory T (Treg) cells is significantly correlated with prognosis and outcomes in ARDS. Vagus nerve stimulation (VNS) alleviates lung injury in ARDS model rats. The objective of this study was to further investigate whether VNS attenuates lipopolysaccharide-induced ARDS by regulating Th17/Treg homeostasis and to explore the underlying mechanisms. Methods: We assessed the degree of lung injury using hematoxylin and eosin staining, the lung wet-to-dry ratio, and total protein and pro-inflammatory cytokine levels in bronchoalveolar lavage fluid. The expression levels of Th17 and Treg cells were determined using flow cytometry, Western blotting, quantitative real-time PCR, and enzyme-linked immunosorbent assays. Results: We found that VNS reduced lung injury in ARDS model rats. Additionally, VNS regulated Th17/Treg homeostasis and reduced the levels of inflammatory factors in both the lungs and spleens. Notably, the effects of VNS were consistent when the afferent or efferent vagus nerve, or both, were stimulated. Further investigation revealed that VNS upregulated splenic α7 nicotinic acetylcholine receptors (α7nAChRs). The administration of an α7nAChR agonist enhanced VNS-mediated regulation of Th17/Treg homeostasis and attenuated lung injury, while these effects were blocked by α7nAChR antagonists. Conclusions: Our study demonstrated that VNS regulates the Th17/Treg balance through α7nAChR activation in the spleen, thereby mitigating lung injury in ARDS. These findings provide new theoretical support for the use of VNS in attenuating ARDS. Full article

Myasthenia gravis (MG) is an autoimmune di sease characterized by muscle weakness. Experimental autoimmune myasthenia gravis (EAMG) serves as an animal model for MG research. Despite advancements in EAMG modeling, limited drug absorption and variability in disease manifestation among animals resulted in a low success rate of model induction. This study aimed to optimize and standardize the modeling process by exploring different induction conditions to improve success rates. We employed female Lewis rats and C57BL/6 mice to compare their sensitivity to model induction and applied a controlled variable approach to acetylcholine receptor (AChR) and H37Ra dosage, mixing time, and injection sites. Results showed that Lewis rats were more suitable than C57BL/6 mice, and 75 µg AChR peptides were more effective than 50 µg. The immune-boosting effect of 1 mg H37Ra Mycobacterium tuberculosis was weaker than 2 mg. While drug mixing time had little impact, increasing injection sites on backs and including foot pads injection, significantly improved drug absorption. Full article

The neuronal progenitor NG108-15 neuroblastoma x glioma cell line proliferates indefinitely in vitro and is capable of directed differentiation into cholinergic neurons. The cell line is a robust model for investigating neuronal differentiation and function in vitro. The lineage-specific transcription factor-mediated differentiation of pluripotent stem cell lines (PSCs) leads to more rapid, efficient, and functional neurons. In this study, we tested the hypothesis that transcription factors could also drive the fate of an immortalised cell line. We first established a stable NG108-15 cell line, by piggyBac (pBac) transposition, that conditionally expresses neurogenin-2 (Ngn2), a common transcription factor for specifying neuronal fate. Following doxycycline-induction of Ngn2, we observed more rapid and efficient differentiation, and improved neurite outgrowth and viability compared with the WT cell line. Moreover, when co-cultured with C2C12 mouse myotubes, the modified NG108-15 cells resulted in significantly larger acetylcholine receptor (AChR) aggregates, suggesting enhanced neuromuscular junction (NMJ) formation. These findings describe a novel methodology for differentiating NG108-15 cells more efficiently, to enhance the usefulness of the cell line as a motor neuron model. Full article

The α7 nicotinic acetylcholine receptor (α7-nAChR) is a pivotal regulator of neurotransmission, neuroprotection, and immune modulation in the central nervous system. This review explores its structural and functional attributes, highlighting its therapeutic potential in neurodegenerative disorders, particularly Parkinson’s disease (PD). α7-nAChRs mediate synaptic plasticity, modulate inflammatory responses, and influence dopamine release, positioning them as a promising pharmacological target. Positive allosteric modulators (PAMs) enhance α7-nAChR activity mainly by reducing desensitization, offering a superior therapeutic approach compared with direct agonists. Emerging preclinical studies suggest that α7-nAChR activation mitigates dopaminergic neurodegeneration, improves L-dopa-induced dyskinesia, and reduces neuroinflammation. Despite promising findings, clinical trials have yielded mixed results, necessitating further research into optimizing α7-targeted therapies. This review underscores the significance of α7-nAChRs in PD pathophysiology and highlights future directions for their translational potential in neuroprotection and symptomatic relief. Full article

Background: Gut barrier integrity plays a crucial role in the pathogenesis of metabolic dysfunction-associated fatty liver disease (MAFLD). Electroacupuncture (EA) at ST-36 can ameliorate inflammatory responses via stimulating the α7 nicotinic acetylcholine receptor (α7nAChR), but whether EA is effective in preserving the intestinal barrier of MAFLD has not been exactly illustrated. This investigation explored potential protection mechanisms of EA at ST-36 targeting the dismantled gut barrier in MAFLD. Methods: C57BL/6 mice were randomly allocated into several subgroups: control (CON), high-fat diet (HFD), HFD with EA, HFD with EA and α7nAChR inhibitor α-BGT, and HFD with EA and intestinal HO-1 knockout (KO). Body weight, liver weight, visceral fat index, and histopathological examination of the liver and the intestine were determined. Serum biological indexes were evaluated through corresponding kits. Furthermore, the expressions of HO-1, α7nAChR, gut barrier-associated proteins, and the molecular mechanisms in intestinal tissues were assessed via Western blot, RT-qPCR, immunohistology, or immunofluorescence examination. Results: EA treatment decreased body weight, liver weight, and visceral fat index gain and mitigated liver function injury and abnormal lipid indexes, exhibiting less severity of hepatic steatosis, fibrosis, and inflammation responses of MAFLD. Lower gut permeability, less intestinal epithelial disruption, and upregulation of tight junction proteins after EA suggested the protective effects in attenuating intestinal epithelial barrier dysfunction. These protective effects were abolished by α-BGT or intestinal HO-1 deletion. Mechanistically, EA markedly enriched α7nAChR and HO-1 expression and mitigated phosphorylated p38 MAPK/NF-κB activation, which was lost in α-BGT or HO-1 KO treatment. Conclusions: The protective effects of EA at ST-36 in the pathogenesis of MAFLD may be attributed to the preserved intestinal barrier, thereby alleviating systemic inflammatory responses and preventing subsequent liver hits, where the α7nAChR-mediated HO-1/p38 MAPK/NF-κB pathway was crucial to maintain homeostasis. Full article

Background/Objectives: Alzheimer’s disease (AD) severely hinders cognitive function in the hippocampus (HP) and subiculum (SUB), impacting the expression of nicotinic acetylcholine receptors (nAChRs) such as the α7-subtype. To investigate α7 nAChRs as a potential PET imaging biomarker, we report the quantitative binding of [¹²⁵I]α-Bungarotoxin ([¹²⁵I]α-Bgtx) for binding to postmortem human AD (n = 29; 13 males, 16 females) HP compared to cognitively normal (CN) (n = 28; 13 male, 15 female) HP. Methods: For comparisons with common AD biomarkers, adjacent slices were anti-Aβ and anti-Tau immunostained for analysis using QuPath. Results: The [¹²⁵I]α-Bgtx average SUB/HP ratio was 0.5 among the CN subjects, suggesting higher [¹²⁵I]α-Bgtx binding in the HP gray matter regions. The AD subjects showed overall less binding than the CN subjects, with no statistical significance. A positive correlation was found in the [¹²⁵I]α-Bgtx binding in the AD subjects as the age increased. The Braak stage comparisons of [¹²⁵I]α-Bgtx were made with [¹⁸F]flotaza binding to Aβ plaques and [¹²⁵I]IPPI binding to Tau. A positive correlation was found between [¹²⁵I]α-Bgtx and [¹⁸F]flotaza and there was a negative correlation between [¹²⁵I]α-Bgtx and [¹²⁵I]IPPI, implicating intricate relationships between the different AD biomarkers. Conclusions: [¹²⁵I]α-Bgtx shows complimentary potential as a α7 nAChR imaging agent but needs more preclinical assessments to confirm effectiveness for translational PET studies using α7 nAChR radioligands. Full article

Nicotinic acetylcholine receptor (α7-nAChR) plays a crucial role in cognitive functions like memory and attention. Positron emission tomography (PET) imaging of α7-nAChR is gaining attraction for understanding and monitoring central nervous system disorders, such as Alzheimer’s disease, Parkinson’s disease, and schizophrenia. We developed [¹¹C]KIn83, a novel α7-nAChR radioligand, and evaluated its biological properties. This study focused on two objectives: (1) to validate its Good Manufacturing Practice (GMP)-compliant production, and (2) to assess the dosimetry of [¹¹C]KIn83 using non-human primate (NHP) whole-body PET data. Radiolabeling and drug product delivery of [¹¹C]KIn83 were conducted using an automated synthesis module within a controlled GMP environment. The quality control tests performed adhered to the European Pharmacopoeia guidelines. The production of [¹¹C]KIn83 was validated according to GMP standards, encompassing automated synthesis and quality control measures. For the dosimetry assessment, two female cynomolgus monkeys underwent whole-body PET scans. The radioactivity values injected for [¹¹C]KIn83 were 150 MBq and 155 MBq, respectively, with an estimated radiation dose of 0.0047 mSv/MBq. Our findings pave the way for future clinical studies that investigate the potential of [¹¹C]KIn83 to measure α7-nAChR, aiding our understanding and possibly supporting diagnoses of different cognitive disorders. Full article

Conotoxins are a class of peptide toxins secreted by marine mollusks of the Conus genus, characterized by their unique mechanism of action and significant biological activity, making them highly valuable for drug development. However, traditional methods of acquiring conotoxins, such as in vivo extraction or chemical synthesis, face challenges of high costs, long cycles, and limited exploration of sequence diversity. To address these issues, we propose the ConoGPT model, a conotoxin sequence generation model that fine-tunes the ProtGPT2 model by incorporating disulfide bond information. Experimental results demonstrate that sequences generated by ConoGPT exhibit high consistency with authentic conotoxins in physicochemical properties and show considerable potential for generating novel conotoxins. Furthermore, compared to models without disulfide bond information, ConoGPT outperforms in terms of generating sequences with ordered structures. The majority of the filtered sequences were shown to possess significant binding affinities to nicotinic acetylcholine receptor (nAChR) targets based on molecular docking. Molecular dynamics simulations of the selected sequences further confirmed the dynamic stability of the generated sequences in complex with their respective targets. This study not only provides a new technological approach for conotoxin design but also offers a novel strategy for generating functional peptides. Full article

Aging and age-related neurodegenerative disorders are characterized by the dysfunction or loss of brain nicotinic acetylcholine receptors (nAChRs), and these changes may be related to other senescence markers, such as oxidative stress and DNA repair dysfunction. However, the mechanism of nAChR loss in the aging brain and the modification of this process by drugs (e.g., memantine, Mem) are not yet fully understood. To study whether the differences in nAChR expression in the rat brain occur due to aging or oxidative stress and are modulated by Mem, we analyzed nAChR subunits (at RNA and protein levels) and other biomarkers by real-time quantitative polymerase chain reaction (RQ-PCR) and Western blot validation. Twenty-one female Wistar rats were divided into four groups, depending on age, and the oldest group received injections of Mem or water with the use of intragastric catheters. We studied the cerebral grey matter (CGM), subcortical white matter (SCWM), and cerebellum (Ce). Results showed an age-related decrease of α7 nAChR mRNA level in SCWM. The α7 nAChR mRNA loss was accompanied by reduced expression of 8-oxoguanine DNA glycosylase 1 (OGG1) and an increased tumor necrosis factor alpha (TNFα) level. In the water group, we observed a higher level of α7 nAChR protein in the SCWM and Ce. Biomarker levels changed, but to a different extent depending on the brain area. Importantly, the dysfunction in antioxidative status was stopped and even regressed under Mem treatment. After two weeks of treatment, an increase in TP53 protein level and a decrease in 8-oxo-2′deoxyguanosine (8-oxo-2′dG) level were observed. We conclude that Mem administration may be protective against the senescence process by antioxidative mechanisms. Full article