Synthesis and Antagonist Activity of Methyllycaconitine Analogues on Human α7 Nicotinic Acetylcholine Receptors

Intramolecular through-space NMR spectroscopic effect of steric compression on 1H NMR spectroscopy

The intramolecular through-space NMR spectroscopic effect of steric compression is related to intramolecular through-space van der Waals repulsion. The electron cloud of a proton can be pushed away by the electron cloud of a nearby proton or functional group. As the electron population of the sterically compressed proton is decreased (therefore deshielded), the chemical shift sharply moves downfield, which may result in ambiguity for the proton signal assignment. Also, the conformation of the local area of the sterically compressed proton can be altered by the steric repulsion, therefore, the coupling constant/coupling pattern of a sterically compressed proton could be influenced. This review summarizes and presents the impacts on the chemical shift and coupling constant by the 1H NMR spectroscopic effect of steric compression extracted from the reported examples from the 1950s to 2021.

Cholinergic Mechanisms in Gastrointestinal Neoplasia

Acetylcholine-activated receptors are divided broadly into two major structurally distinct classes: ligand-gated ion channel nicotinic and G-protein-coupled muscarinic receptors. Each class encompasses several structurally related receptor subtypes with distinct patterns of tissue expression and post-receptor signal transduction mechanisms. The activation of both nicotinic and muscarinic cholinergic receptors has been associated with the induction and progression of gastrointestinal neoplasia. Herein, after briefly reviewing the classification of acetylcholine-activated receptors and the role that nicotinic and muscarinic cholinergic signaling plays in normal digestive function, we consider the mechanics of acetylcholine synthesis and release by neuronal and non-neuronal cells in the gastrointestinal microenvironment, and current methodology and challenges in measuring serum and tissue acetylcholine levels accurately. Then, we critically evaluate the evidence that constitutive and ligand-induced activation of acetylcholine-activated receptors plays a role in promoting gastrointestinal neoplasia. We focus primarily on adenocarcinomas of the stomach, pancreas, and colon, because these cancers are particularly common worldwide and, when diagnosed at an advanced stage, are associated with very high rates of morbidity and mortality. Throughout this comprehensive review, we concentrate on identifying novel ways to leverage these observations for prognostic and therapeutic purposes.

Targeting Alpha7 Nicotinic Acetylcholine Receptors in Lung Cancer: Insights, Challenges, and Therapeutic Strategies

Alpha7 nicotinic acetylcholine receptor (α7 nAChR) is an ion-gated calcium channel that plays a significant role in various aspects of cancer pathogenesis, particularly in lung cancer. Preclinical studies have elucidated the molecular mechanism underlying α7 nAChR-associated lung cancer proliferation, chemotherapy resistance, and metastasis. Understanding and targeting this mechanism are crucial for developing therapeutic interventions aimed at disrupting α7 nAChR-mediated cancer progression and improving treatment outcomes. Drug research and discovery have determined natural compounds and synthesized chemical antagonists that specifically target α7 nAChR. However, approved α7 nAChR antagonists for clinical use are lacking, primarily due to challenges related to achieving the desired selectivity, efficacy, and safety profiles required for effective therapeutic intervention. This comprehensive review provided insights into the molecular mechanisms associated with α7 nAChR and its role in cancer progression, particularly in lung cancer. Furthermore, it presents an update on recent evidence about α7 nAChR antagonists and addresses the challenges encountered in drug research and discovery in this field.

Apoptosis in the neuroprotective effect of α7 nicotinic receptor in neurodegenerative models

The α7 subtype of nicotinic receptors (α7 nAChRs) is one of the most abundant nicotinic receptor subtypes in the central nervous system (CNS) and both neurons and nonneuronal cells express α7 nAChRs. When activated, α7 nAChRs become permeable to cations and promote cellular responses such as anti-apoptotic signaling by modulating the caspases and proteins of the Bcl-2 family. Neuroprotection is an important function of these receptors, promoting neuronal survival under pathological conditions, including situations of stress and neuronal degeneration. Studies have demonstrated the relationship between the activation of these receptors and the reduction of neuronal or glial cell injury, by controlling apoptotic processes in different models, including neurodegenerative diseases such as Alzheimer's disease. Therefore, one of the most important signaling pathways activated by α7 nAChRs is the PI3K/Akt signaling cascade, which promotes the stimulation of anti-apoptotic molecules of the Bcl-2 family, Bcl-2 and Bcl-xl, and reduces the expression of caspases and proapoptotic molecules, resulting in cell survival. In Alzheimer's models, the literature shows that α7 nAChR activation attenuates Aβ-induced neurotoxicity through modulation of different intrinsic apoptotic pathways via PI3K/Akt and mitogen-activated protein kinase (MAPK). In this review, we provide an up-to-date summary of the current evidence on the relationship between the activation of α7 nAChRs, a subtype of nicotinic acetylcholine receptor, and its role in neuroprotection by modulating apoptotic pathways.