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Interactions of Nereistoxin and Its Analogs with Vertebrate Nicotinic Acetylcholine Receptors and Molluscan ACh Binding Proteins. Mar Drugs 2022; 20:md20010049. [PMID: 35049904 PMCID: PMC8777805 DOI: 10.3390/md20010049] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/09/2021] [Accepted: 12/14/2021] [Indexed: 02/04/2023] Open
Abstract
Nereistoxin (NTX) is a marine toxin isolated from an annelid worm that lives along the coasts of Japan. Its insecticidal properties were discovered decades ago and this stimulated the development of a variety of insecticides such as Cartap that are readily transformed into NTX. One unusual feature of NTX is that it is a small cyclic molecule that contains a disulfide bond. In spite of its size, it acts as an antagonist at insect and mammalian nicotinic acetylcholine receptors (nAChRs). The functional importance of the disulfide bond was assessed by determining the effects of inserting a methylene group between the two sulfur atoms, creating dimethylaminodithiane (DMA-DT). We also assessed the effect of methylating the NTX and DMA-DT dimethylamino groups on binding to three vertebrate nAChRs. Radioligand receptor binding experiments were carried out using washed membranes from rat brain and fish (Torpedo) electric organ; [3H]-cytisine displacement was used to assess binding to the predominantly high affinity alpha4beta2 nAChRs and [125I]-alpha-bungarotoxin displacement was used to measure binding of NTX and analogs to the alpha7 and skeletal muscle type nAChRs. While the two quaternary nitrogen analogs, relative to their respective tertiary amines, displayed lower α4β2 nAChR binding affinities, both displayed much higher affinities for the Torpedo muscle nAChR and rat alpha7 brain receptors than their respective tertiary amine forms. The binding affinities of DMA-DT for the three nAChRs were lower than those of NTX and MeNTX. An AChBP mutant lacking the C loop disulfide bond that would potentially react with the NTX disulfide bond displayed an NTX affinity very similar to the parent AChBP. Inhibition of [3H]-epibatidine binding to the AChBPs was not affected by exposure to NTX or MeNTX for up to 24 hr prior to addition of the radioligand. Thus, the disulfide bond of NTX is not required to react with the vicinal disulfide in the AChBP C loop for inhibition of [3H]-epibatidine binding. However, a reversible disulfide interchange reaction of NTX with nAChRs might still occur, especially under reducing conditions. Labeled MeNTX, because it can be readily prepared with high specific radioactivity and possesses relatively high affinity for the nAChR-rich Torpedo nAChR, would be a useful probe to detect and identify any nereistoxin adducts.
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Lupacchini L, Maggi F, Tomino C, De Dominicis C, Mollinari C, Fini M, Bonassi S, Merlo D, Russo P. Nicotine Changes Airway Epithelial Phenotype and May Increase the SARS-COV-2 Infection Severity. Molecules 2020; 26:E101. [PMID: 33379366 PMCID: PMC7794754 DOI: 10.3390/molecules26010101] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/17/2020] [Accepted: 12/24/2020] [Indexed: 02/07/2023] Open
Abstract
(1) Background: Nicotine is implicated in the SARS-COV-2 infection through activation of the α7-nAChR and over-expression of ACE2. Our objective was to clarify the role of nicotine in SARS-CoV-2 infection exploring its molecular and cellular activity. (2) Methods: HBEpC or si-mRNA-α7-HBEpC were treated for 1 h, 48 h or continuously with 10-7 M nicotine, a concentration mimicking human exposure to a cigarette. Cell viability and proliferation were evaluated by trypan blue dye exclusion and cell counting, migration by cell migration assay, senescence by SA-β-Gal activity, and anchorage-independent growth by cloning in soft agar. Expression of Ki67, p53/phospho-p53, VEGF, EGFR/pEGFR, phospho-p38, intracellular Ca2+, ATP and EMT were evaluated by ELISA and/or Western blotting. (3) Results: nicotine induced through α7-nAChR (i) increase in cell viability, (ii) cell proliferation, (iii) Ki67 over-expression, (iv) phospho-p38 up-regulation, (v) EGFR/pEGFR over-expression, (vi) increase in basal Ca2+ concentration, (vii) reduction of ATP production, (viii) decreased level of p53/phospho-p53, (ix) delayed senescence, (x) VEGF increase, (xi) EMT and consequent (xii) enhanced migration, and (xiii) ability to grow independently of the substrate. (4) Conclusions: Based on our results and on evidence showing that nicotine potentiates viral infection, it is likely that nicotine is involved in SARS-CoV-2 infection and severity.
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Affiliation(s)
- Leonardo Lupacchini
- Molecular and Cellular Neurobiology, IRCSS San Raffaele Pisana, Via di Val Cannuta 247, I-00166 Rome, Italy; (L.L.); (C.D.D.)
| | - Fabrizio Maggi
- Department of Medicine and Surgery, University of Insubria, viale Luigi Borri 57, I-21100 Varese, Italy;
| | - Carlo Tomino
- Scientific Direction, IRCSS San Raffaele Pisana, Via di Val Cannuta 247, I-00166 Rome, Italy;
| | - Chiara De Dominicis
- Molecular and Cellular Neurobiology, IRCSS San Raffaele Pisana, Via di Val Cannuta 247, I-00166 Rome, Italy; (L.L.); (C.D.D.)
| | - Cristiana Mollinari
- Institute of Translational Pharmacology, National Research Council, Via Fosso del Cavaliere 100, 00133 Rome, Italy;
- Department of Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, I-00161 Rome, Italy;
| | - Massimo Fini
- Scientific Direction, IRCSS San Raffaele Pisana, Via di Val Cannuta 247, I-00166 Rome, Italy;
| | - Stefano Bonassi
- Clinical and Molecular Epidemiology, IRCSS San Raffaele Pisana, Via di Val Cannuta 247, I-00166 Rome, Italy;
- Department of Human Sciences and Quality of Life Promotion, San Raffaele University, Via di Val Cannuta 247, I-00166 Rome, Italy
| | - Daniela Merlo
- Department of Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, I-00161 Rome, Italy;
| | - Patrizia Russo
- Clinical and Molecular Epidemiology, IRCSS San Raffaele Pisana, Via di Val Cannuta 247, I-00166 Rome, Italy;
- Department of Human Sciences and Quality of Life Promotion, San Raffaele University, Via di Val Cannuta 247, I-00166 Rome, Italy
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