1
|
Park J, Proux C, Ehanno W, Réthoré L, Vessières E, Bourreau J, Favre J, Kauffenstein G, Mattei C, Tricoire-Leignel H, Henrion D, Legendre C, Legros C. Tetrodotoxin Decreases the Contractility of Mesenteric Arteries, Revealing the Contribution of Voltage-Gated Na + Channels in Vascular Tone Regulation. Mar Drugs 2023; 21:md21030196. [PMID: 36976245 PMCID: PMC10059581 DOI: 10.3390/md21030196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 03/11/2023] [Accepted: 03/20/2023] [Indexed: 03/29/2023] Open
Abstract
Tetrodotoxin (TTX) poisoning through the consumption of contaminated fish leads to lethal symptoms, including severe hypotension. This TTX-induced hypotension is likely due to the downfall of peripheral arterial resistance through direct or indirect effects on adrenergic signaling. TTX is a high-affinity blocker of voltage-gated Na+ (NaV) channels. In arteries, NaV channels are expressed in sympathetic nerve endings, both in the intima and media. In this present work, we aimed to decipher the role of NaV channels in vascular tone using TTX. We first characterized the expression of NaV channels in the aorta, a model of conduction arteries, and in mesenteric arteries (MA), a model of resistance arteries, in C57Bl/6J mice, by Western blot, immunochemistry, and absolute RT-qPCR. Our data showed that these channels are expressed in both endothelium and media of aorta and MA, in which scn2a and scn1b were the most abundant transcripts, suggesting that murine vascular NaV channels consist of NaV1.2 channel subtype with NaVβ1 auxiliary subunit. Using myography, we showed that TTX (1 µM) induced complete vasorelaxation in MA in the presence of veratridine and cocktails of antagonists (prazosin and atropine with or without suramin) that suppressed the effects of neurotransmitter release. In addition, TTX (1 µM) strongly potentiated the flow-mediated dilation response of isolated MA. Altogether, our data showed that TTX blocks NaV channels in resistance arteries and consecutively decreases vascular tone. This could explain the drop in total peripheral resistance observed during mammal tetrodotoxications.
Collapse
Affiliation(s)
- Joohee Park
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Coralyne Proux
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - William Ehanno
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Léa Réthoré
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Emilie Vessières
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Jennifer Bourreau
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Julie Favre
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
- UMR INSERM 1121, CRBS, Strasbourg University, 67000 Strasbourg, France
| | - Gilles Kauffenstein
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
- UMR INSERM 1260, CRBS, Strasbourg University, 67084 Strasbourg, France
| | - César Mattei
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | | | - Daniel Henrion
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Claire Legendre
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| | - Christian Legros
- INSERM, CNRS, MITOVASC, Equipe CarME, SFR ICAT, University Angers, 49000 Angers, France
| |
Collapse
|
2
|
Réthoré L, Park J, Montnach J, Nicolas S, Khoury J, Le Seac'h E, Mabrouk K, De Pomyers H, Tricoire-Leignel H, Mattei C, Henrion D, Fajloun Z, De Waard M, Legendre C, Legros C. Pharmacological Dissection of the Crosstalk between Na V and Ca V Channels in GH3b6 Cells. Int J Mol Sci 2022; 23:827. [PMID: 35055012 DOI: 10.3390/ijms23020827] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/07/2022] [Accepted: 01/09/2022] [Indexed: 02/01/2023] Open
Abstract
Thanks to the crosstalk between Na+ and Ca2+ channels, Na+ and Ca2+ homeostasis interplay in so-called excitable cells enables the generation of action potential in response to electrical stimulation. Here, we investigated the impact of persistent activation of voltage-gated Na+ (NaV) channels by neurotoxins, such as veratridine (VTD), on intracellular Ca2+ concentration ([Ca2+]i) in a model of excitable cells, the rat pituitary GH3b6 cells, in order to identify the molecular actors involved in Na+-Ca2+ homeostasis crosstalk. By combining RT-qPCR, immunoblotting, immunocytochemistry, and patch-clamp techniques, we showed that GH3b6 cells predominantly express the NaV1.3 channel subtype, which likely endorses their voltage-activated Na+ currents. Notably, these Na+ currents were blocked by ICA-121431 and activated by the β-scorpion toxin Tf2, two selective NaV1.3 channel ligands. Using Fura-2, we showed that VTD induced a [Ca2+]i increase. This effect was suppressed by the selective NaV channel blocker tetrodotoxin, as well by the selective L-type CaV channel (LTCC) blocker nifedipine. We also evidenced that crobenetine, a NaV channel blocker, abolished VTD-induced [Ca2+]i elevation, while it had no effects on LTCC. Altogether, our findings highlight a crosstalk between NaV and LTCC in GH3b6 cells, providing a new insight into the mode of action of neurotoxins.
Collapse
|
3
|
Abstract
Voltage-gated sodium ion channels (NaVs) are integral to both neuronal and muscular signaling and are a primary target for a number of proteinaceous and small molecule toxins. Included among these neurotoxins is veratridine (VTD), a C-nor-D homosteroidal alkaloid from the seeds of members of the Veratrum genus. VTD binds to NaV within the pore region, causing a hyperpolarizing shift in the activation threshold in addition to reducing peak current. We have characterized the activity of VTD against heterologously expressed rat NaV1.4 and have demonstrated that VTD acts on the channel as either an agonist or antagonist depending on the nature of the electrophysiological stimulation protocol. Structure-activity studies with VTD and VTD derivatives against NaV mutants show that the functional duality of VTD can be decoupled. These findings suggest that the dichotomous activity of VTD may derive from two distinct, use-dependent binding orientations of the toxin.
Collapse
Affiliation(s)
- Robert A. Craig
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Catherine E. Garrison
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Phuong T. Nguyen
- Department of Physiology and Membrane Biology, University of California, Davis, California 95616, United States
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, California 95616, United States
| | - J. Du Bois
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| |
Collapse
|
4
|
Zhang XY, Bi RY, Zhang P, Gan YH. Veratridine modifies the gating of human voltage-gated sodium channel Nav1.7. Acta Pharmacol Sin 2018; 39:1716-1724. [PMID: 29950616 DOI: 10.1038/s41401-018-0065-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 06/05/2018] [Indexed: 01/22/2023] Open
Abstract
Veratridine is a lipid-soluble neurotoxin derived from plants in the family Liliaceae. It has been broadly investigated for its action as a sodium channel agonist. However, the effects of veratridine on subtypes of sodium channels, especially Nav1.7, remain to be studied. Here, we investigated the effects of veratridine on human Nav1.7 ectopically expressed in HEK293A cells and recorded Nav1.7 currents from the cells using whole-cell patch clamp technique. We found that veratridine exerted a dose-dependent inhibitory effect on the peak current of Nav1.7, with the half-maximal inhibition concentration (IC50) of 18.39 µM. Meanwhile, veratridine also elicited tail current (linearly) and sustained current [half-maximal concentration (EC50): 9.53 µM], also in a dose-dependent manner. Veratridine (75 µM) shifted the half-maximal activation voltage of the Nav1.7 activation curve in the hyperpolarized direction, from -21.64 ± 0.75 mV to -28.14 ± 0.66 mV, and shifted the half-inactivation voltage of the steady-state inactivation curve from -59.39 ± 0.39 mV to -73.78 ± 0.5 mV. An increased frequency of stimulation decreased the peak and tail currents of Nav1.7 for each pulse along with pulse number, and increased the accumulated tail current at the end of train stimulation. These findings reveal the different modulatory effects of veratridine on the Nav1.7 peak current and tail current.
Collapse
|
5
|
Sane S, Hafner A, Srinivasan R, Masood D, Slunecka JL, Noldner CJ, Hanson AD, Kruisselbrink T, Wang X, Wang Y, Yin J, Rezvani K. UBXN2A enhances CHIP-mediated proteasomal degradation of oncoprotein mortalin-2 in cancer cells. Mol Oncol 2018; 12:1753-1777. [PMID: 30107089 PMCID: PMC6166003 DOI: 10.1002/1878-0261.12372] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 07/12/2018] [Accepted: 08/02/2018] [Indexed: 01/07/2023] Open
Abstract
Overexpression of oncoproteins is a major cause of treatment failure using current chemotherapeutic drugs. Drug-induced degradation of oncoproteins is feasible and can improve clinical outcomes in diverse types of cancers. Mortalin-2 (mot-2) is a dominant oncoprotein in several tumors, including colorectal cancer (CRC). In addition to inactivating the p53 tumor suppressor protein, mot-2 enhances tumor cell invasion and migration. Thus, mot-2 is considered a potential therapeutic target in several cancer types. The current study investigated the biological role of a ubiquitin-like protein called UBXN2A in the regulation of mot-2 turnover. An orthogonal ubiquitin transfer technology followed by immunoprecipitation, in vitro ubiquitination, and Magnetic Beads TUBE2 pull-down experiments revealed that UBXN2A promotes carboxyl terminus of the HSP70-interacting protein (CHIP)-dependent ubiquitination of mot-2. We subsequently showed that UBXN2A increases proteasomal degradation of mot-2. A subcellular compartmentalization experiment revealed that induced UBXN2A decreases the level of mot-2 and its chaperone partner, HSP60. Pharmacological upregulation of UBXN2A using a small molecule, veratridine (VTD), decreases the level of mot-2 in cancer cells. Consistent with the in vitro results, UBXN2A+/- mice exhibited selective elevation of mot-2 in colon tissues. An in vitro Anti-K48 TUBE isolation approach showed that recombinant UBXN2A enhances proteasomal degradation of mot-2 in mouse colon tissues. Finally, we observed enhanced association of CHIP with the UBXN2A-mot-2 complex in tumors in an azoxymethane/dextran sulfate sodium-induced mouse CRC model. The existence of a multiprotein complex containing UBXN2A, CHIP, and mot-2 suggests a synergistic tumor suppressor activity of UBXN2A and CHIP in mot-2-enriched tumors. This finding validates the UBXN2A-CHIP axis as a novel and potential therapeutic target in CRC.
Collapse
Affiliation(s)
- Sanam Sane
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Andre Hafner
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Rekha Srinivasan
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Daniall Masood
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - John l. Slunecka
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Collin J. Noldner
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Alex D. Hanson
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Taylor Kruisselbrink
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Xuejun Wang
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| | - Yiyang Wang
- Department of ChemistryCenter for Diagnostics & TherapeuticsGeorgia State UniversityAtlantaGAUSA
| | - Jun Yin
- Department of ChemistryCenter for Diagnostics & TherapeuticsGeorgia State UniversityAtlantaGAUSA
| | - Khosrow Rezvani
- Division of Basic Biomedical SciencesSanford School of MedicineThe University of South DakotaVermillionSDUSA
| |
Collapse
|
6
|
Vanden Daele L, Boydens C, Devoldere J, Remaut K, Van de Voorde J. Search for the Source of the Retinal Relaxing Factor. Curr Eye Res 2018; 43:1383-1388. [PMID: 29966443 DOI: 10.1080/02713683.2018.1496267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Purpose/Aim of the study: the retinal relaxing factor (RRF) is an unidentified paracrine factor, which is continuously released from retinal tissue and causes smooth muscle cell relaxation. This study tried to identify the cellular source of the RRF. Furthermore, the possible RRF release by voltage-dependent sodium channel activation and the calcium-dependency of the RRF release were investigated. MATERIALS AND METHODS mouse femoral arteries were mounted in myograph baths for in vitro isometric tension measurements. The vasorelaxing effect of chicken retinas, which contain no vascular cells, and of solutions incubated with MIO-M1 or primary Müller cell cultures were evaluated. The RRF release of other retinal cells was investigated by using cell type inhibitors. Concentration-response curves of veratridine, a voltage-dependent sodium channel activator, were constructed in the presence or absence of mouse retinal tissue to evaluate the RRF release. The calcium-dependency of the RRF release was investigated by evaluating the vasorelaxing effect of RRF-containing solutions made out of chicken retinas in the absence or presence of calcium. RESULTS Chicken retinas induced vasorelaxation, whereas solutions incubated with Müller cell cultures did not. Moreover, the gliotoxin DL-α-aminoadipic acid, the microglia inhibitor minocycline, and the tetrodotoxin-resistant voltage-dependent sodium channel 1.8 inhibitor A-803467 could not reduce the RRF-induced relaxation. Concentration-response curves of veratridine were not enlarged in the presence of retinal tissue, and RRF-containing solutions made in the absence of calcium induced a substantial, but reduced vasorelaxation. CONCLUSIONS the RRF is not released from vascular cells and probably neither from glial cells. The retinal cell type that does release the RRF remains unclear. Veratridine does not stimulate the RRF release in mice, and the RRF release in chickens is calcium-dependent as well as calcium-independent.
Collapse
Affiliation(s)
| | | | - Joke Devoldere
- b Laboratory of General Biochemistry and Physical Pharmacy , Ghent University , Ghent , Belgium
| | - Katrien Remaut
- b Laboratory of General Biochemistry and Physical Pharmacy , Ghent University , Ghent , Belgium
| | | |
Collapse
|
7
|
Chernov-Rogan T, Li T, Lu G, Verschoof H, Khakh K, Jones SW, Beresini MH, Liu C, Ortwine DF, McKerrall SJ, Hackos DH, Sutherlin D, Cohen CJ, Chen J. Mechanism-specific assay design facilitates the discovery of Nav1.7-selective inhibitors. Proc Natl Acad Sci U S A 2018; 115:E792-801. [PMID: 29311306 DOI: 10.1073/pnas.1713701115] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Subtype-selective modulation of ion channels is often important, but extremely difficult to achieve for drug development. Using Nav1.7 as an example, we show that this challenge could be attributed to poor design in ion channel assays, which fail to detect most potent and selective compounds and are biased toward nonselective mechanisms. By exploiting different drug binding sites and modes of channel gating, we successfully direct a membrane potential assay toward non–pore-blocking mechanisms and identify Nav1.7-selective compounds. Our mechanistic approach to assay design addresses a significant hurdle in Nav1.7 drug discovery and is applicable to many other ion channels. Many ion channels, including Nav1.7, Cav1.3, and Kv1.3, are linked to human pathologies and are important therapeutic targets. To develop efficacious and safe drugs, subtype-selective modulation is essential, but has been extremely difficult to achieve. We postulate that this challenge is caused by the poor assay design, and investigate the Nav1.7 membrane potential assay, one of the most extensively employed screening assays in modern drug discovery. The assay uses veratridine to activate channels, and compounds are identified based on the inhibition of veratridine-evoked activities. We show that this assay is biased toward nonselective pore blockers and fails to detect the most potent, selective voltage-sensing domain 4 (VSD4) blockers, including PF-05089771 (PF-771) and GX-936. By eliminating a key binding site for pore blockers and replacing veratridine with a VSD-4 binding activator, we directed the assay toward non–pore-blocking mechanisms and discovered Nav1.7-selective chemical scaffolds. Hence, we address a major hurdle in Nav1.7 drug discovery, and this mechanistic approach to assay design is applicable to Cav3.1, Kv1.3, and many other ion channels to facilitate drug discovery.
Collapse
|
8
|
Kratholm NM, Jensen PS, Kringelholt S, Simonsen U, Bek T. Activation of Veratridine Sensitive Sodium Channels, But not Electrical Field Stimulation, Dilates Porcine Retinal Arterioles with Preserved Perivascular Tissue. Curr Eye Res 2017; 42:1497-1502. [PMID: 28910154 DOI: 10.1080/02713683.2017.1337156] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Disturbances in retinal blood flow are a prominent feature of vision threatening retinal diseases. The regulation of tone in retinal resistance vessels involves the perivascular retinal tissue, but it is unknown to what extent neurons or glial cells contribute to the effect. Therefore, the purpose of the present study was to study the contribution of neurons in the perivascular retina to vascular tone during activation of voltage-gated sodium channels with veratridine and electrical field stimulation (EFS). METHODS Porcine retinal arterioles with and without perivascular tissue were mounted in an isometric myograph system for studying the effects of the voltage-gated sodium channel opener veratridine and EFS on retinal vascular tone. RESULTS Veratridine induced concentration-dependent relaxation of retinal arterioles which was more pronounced in arterioles with preserved perivascular retinal tissue than in isolated vessels. In the presence of this tissue, veratridine-induced relaxation was inhibited by the voltage-gated sodium channel blocker tetrodotoxin and the nitric oxide synthase inhibitor, Nω-Nitro-L-arginine methyl ester (L-NAME), but was unaffected by the inhibition of the cyclo-oxygenase inbitior ibuprofen and by blocking of adenosine receptors with 8-(p-Sulfophenyl)theophylline hydrate (8-PSPT). Electrical field stimulation induced no changes in retinal vascular tone. CONCLUSIONS Sodium channels of neuronal origin are likely to be involved in the regulation of retinal vascular tone. The lack of effect of EFS on retinal vascular tone may be due to the lack of autonomic nerves in the retina.
Collapse
Affiliation(s)
- Nils M Kratholm
- a Department of Ophthalmology , Aarhus University Hospital , Aarhus C , Denmark
| | - Peter Skov Jensen
- a Department of Ophthalmology , Aarhus University Hospital , Aarhus C , Denmark
| | - Sidse Kringelholt
- a Department of Ophthalmology , Aarhus University Hospital , Aarhus C , Denmark
| | - Ulf Simonsen
- b Department of Biomedicine (Pharmacology) , University of Aarhus , Aarhus C , Denmark
| | - Toke Bek
- a Department of Ophthalmology , Aarhus University Hospital , Aarhus C , Denmark
| |
Collapse
|
9
|
Abdullah A, Sane S, Branick KA, Freeling JL, Wang H, Zhang D, Rezvani K. A plant alkaloid, veratridine, potentiates cancer chemosensitivity by UBXN2A-dependent inhibition of an oncoprotein, mortalin-2. Oncotarget 2015; 6:23561-81. [PMID: 26188124 DOI: 10.18632/oncotarget.4452] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 06/30/2015] [Indexed: 12/11/2022] Open
Abstract
Veratridine (VTD), an alkaloid derived from the Liliaceae plant shows anti-tumor effects; however, its molecular targets have not been thoroughly studied. Using a high-throughput drug screen, we found that VTD enhances transactivation of UBXN2A, resulting in upregulation of UBXN2A in the cytoplasm, where UBXN2A binds and inhibits the oncoprotein mortalin-2 (mot-2). VTD-treated cancer cells undergo cell death in UBXN2A- and mot-2-dependent manners. The cytotoxic function of VTD is grade-dependent, and the combined treatment with a sub-optimal dose of the standard chemotherapy, 5-Fluorouracil (5-FU) and etoposide, demonstrated a synergistic effect, resulting in higher therapeutic efficacy. VTD influences the CD44+ stem cells, possibly through UBXN2A-dependent inhibition of mot-2. The VTD-dependent expression of UBXN2A is a potential candidate for designing novel strategies for colon cancer treatment because: 1) In 50% of colon cancer patients, UBXN2A protein levels in tumor tissues are significantly lower than those in the adjacent normal tissues. 2) Cytoplasmic expression of the mot-2 protein is very low in non-cancerous cells; thus, VTD can produce tumor-specific toxicity while normal cells remain intact. 3) Finally, VTD or its modified analogs offer a valuable adjuvant chemotherapy strategy to improve the efficacy of 5-FU-based chemotherapy for colon cancer patients harboring WT-p53.
Collapse
|
10
|
Jenson LJ, Bloomquist JR. ROLE OF SERUM AND ION CHANNEL BLOCK ON GROWTH AND HORMONALLY-INDUCED DIFFERENTIATION OF Spodoptera frugiperda (Sf21) INSECT CELLS. Arch Insect Biochem Physiol 2015; 90:131-139. [PMID: 26183110 DOI: 10.1002/arch.21249] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A neuronal morphological phenotype can be induced in cultured Spodoptera frugiperda insect cells (Sf21) by supplementing serum-containing media with 20-hydroxyecdysone (20-HE) and/or insulin. In this study, the primary objectives were to determine any role of ion channels in mediating the morphological change in cells treated with 20-HE and insulin, and whether serum was required to observe this effect. Results showed serum-free media also induced growth of processes in Sf21 cells, but at a lower percentage than that found previously in cells bathed in serum-containing media. Veratridine, a sodium channel activator, increased cell survival when applied in combination with 20-HE to Sf21 cells, and the effect was blocked by tetrodotoxin (1 μM) a known sodium channel blocker. Cobalt, a calcium channel blocker, showed significant inhibition of cell process growth when applied in combination with both 20-HE and 20-HE plus veratridine. Cobalt also showed significant inhibition of cell process growth when applied in combination with insulin. Thus, some type of sodium channel, as well as a mechanism for transmembrane calcium ion movement, are apparently expressed in Sf21 cells and are involved in the differentiation process. These cell lines may be used in a wide variety of endeavors, including the screening of insecticides, as well as foster basic studies of neurodevelopment and ecdysone action.
Collapse
Affiliation(s)
- Lacey J Jenson
- Neurotoxicology Laboratory, Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida, USA
| | - Jeffrey R Bloomquist
- Neurotoxicology Laboratory, Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida, USA
| |
Collapse
|
11
|
O'Malley D, Dinan TG, Cryan JF. Interleukin-6 modulates colonic transepithelial ion transport in the stress-sensitive wistar kyoto rat. Front Pharmacol 2012; 3:190. [PMID: 23162465 PMCID: PMC3491317 DOI: 10.3389/fphar.2012.00190] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 10/11/2012] [Indexed: 01/14/2023] Open
Abstract
Immunological challenge stimulates secretion of the pro-inflammatory cytokine interleukin (IL)-6, resulting in variety of biological responses. In the gastrointestinal tract, IL-6 modulates the excitability of submucosal neurons and stimulates secretion into the colonic lumen. When considered in the context of the functional bowel disorder, irritable bowel syndrome (IBS), where plasma levels of IL-6 are elevated, this may reflect an important molecular mechanism contributing to symptom flares, particularly in the diarrhea-predominant phenotype. In these studies, colonic ion transport, an indicator of absorption and secretion, was assessed in the stress-sensitive Wistar Kyoto (WKY) rat model of IBS. Mucosa-submucosal colonic preparations from WKY and control Sprague Dawley (SD) rats were mounted in Ussing chambers and the basal short circuit current (ISC) was electrophysiologically recorded and compared between the strains. Exposure to IL-6 (1 nM) stimulated a secretory current of greater amplitude in WKY as compared to SD samples. Furthermore, the observed IL-6-mediated potentiation of secretory currents evoked by veratridine and capsaicin in SD rats was blunted in WKY rats. Exposure to IL-6 also stimulated an increase in transepithelial resistance in both SD and WKY colonic tissue. These studies demonstrate that the neuroexcitatory effects of IL-6 on submucosal plexi have functional consequences with alterations in both colonic secretory activity and permeability. The IL-6-induced increase in colonic secretory activity appears to neurally mediated. Thus, local increases in IL-6 levels and subsequent activation of enteric neurons may underlie alterations in absorpto-secretory function in the WKY model of IBS.
Collapse
Affiliation(s)
- Dervla O'Malley
- Alimentary Pharmabiotic Centre, University College Cork Cork, Ireland ; Department of Physiology, University College Cork Cork, Ireland
| | | | | |
Collapse
|
12
|
Rocher A, Caceres AI, Obeso A, Gonzalez C. Tetrodotoxin as a tool to elucidate sensory transduction mechanisms: the case for the arterial chemoreceptors of the carotid body. Mar Drugs 2011; 9:2683-704. [PMID: 22363245 DOI: 10.3390/md9122683] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 11/22/2011] [Accepted: 12/01/2011] [Indexed: 12/17/2022] Open
Abstract
Carotid bodies (CBs) are secondary sensory receptors in which the sensing elements, chemoreceptor cells, are activated by decreases in arterial PO2 (hypoxic hypoxia). Upon activation, chemoreceptor cells (also known as Type I and glomus cells) increase their rate of release of neurotransmitters that drive the sensory activity in the carotid sinus nerve (CSN) which ends in the brain stem where reflex responses are coordinated. When challenged with hypoxic hypoxia, the physiopathologically most relevant stimulus to the CBs, they are activated and initiate ventilatory and cardiocirculatory reflexes. Reflex increase in minute volume ventilation promotes CO2 removal from alveoli and a decrease in alveolar PCO2 ensues. Reduced alveolar PCO2 makes possible alveolar and arterial PO2 to increase minimizing the intensity of hypoxia. The ventilatory effect, in conjunction the cardiocirculatory components of the CB chemoreflex, tend to maintain an adequate supply of oxygen to the tissues. The CB has been the focus of attention since the discovery of its nature as a sensory organ by de Castro (1928) and the discovery of its function as the origin of ventilatory reflexes by Heymans group (1930). A great deal of effort has been focused on the study of the mechanisms involved in O2 detection. This review is devoted to this topic, mechanisms of oxygen sensing. Starting from a summary of the main theories evolving through the years, we will emphasize the nature and significance of the findings obtained with veratridine and tetrodotoxin (TTX) in the genesis of current models of O2-sensing.
Collapse
|
13
|
Jordán J, Galindo MF, Tornero D, Benavides A, González C, Agapito MT, González-Garcia C, Ceña V. Superoxide anions mediate veratridine-induced cytochrome c release and caspase activity in bovine chromaffin cells. Br J Pharmacol 2002; 137:993-1000. [PMID: 12429571 PMCID: PMC1573576 DOI: 10.1038/sj.bjp.0704953] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2002] [Revised: 08/13/2002] [Accepted: 09/04/2002] [Indexed: 11/09/2022] Open
Abstract
1. Mitochondrial mechanisms involved in veratridine-induced chromaffin cell death have been explored. 2. Exposure to veratridine (30 micro M, 1 h) produces cytochrome c release to the cytoplasm that seems to be mediated by superoxide anions and that is blocked by cyclosporin A (10 micro M), MnTBAP (10 nM), catalase (100 IU ml(-1)) and vitamin E (50 micro M). 3. Following veratridine treatment, there is an increase in caspase-like activity, blocked by vitamin E (50 micro M) and the mitochondrial permeability transition pore blocker cyclosporin A (10 micro M). 4. Superoxide anions open the mitochondrial permeability transition pore in isolated mitochondria, an effect that is blocked by vitamin E (50 micro M) and cyclosporin A (10 micro M), but not by the Ca2+ uniporter blocker ruthenium red (5 micro M). 5. These results strongly suggest that under the stress situation caused by veratridine, superoxide anions become important regulators of mitochondrial function in chromaffin cells. 6. Exposure of isolated bovine chromaffin mitochondria to Ca2+ results in mitochondrial swelling. This effect was prevented by ruthenium red (5 micro M) and cyclosporin A (10 micro M), while it was not modified by vitamin E (50 micro M). 7. Veratridine (30 micro M, 1 h) markedly decreased total glutathione and GSH content in bovine chromaffin cells. 8. In conclusion, superoxide anions seem to mediate veratridine-induced cytochrome c release, decrease in total glutathione, caspase activation and cell death in bovine chromaffin cells.
Collapse
Affiliation(s)
- Joaquín Jordán
- Centro Regional de Investigaciones Biomédicas y Dpto. Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Albacete, Spain
| | - María F Galindo
- Centro Regional de Investigaciones Biomédicas y Dpto. Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Daniel Tornero
- Centro Regional de Investigaciones Biomédicas y Dpto. Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Amparo Benavides
- Centro Regional de Investigaciones Biomédicas y Dpto. Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Constancio González
- Departamento de Bioquímica, Biología Molecular y Fisiología, Facultad de Medicina, Valladolid, Spain
| | - María T Agapito
- Departamento de Bioquímica, Biología Molecular y Fisiología, Facultad de Medicina, Valladolid, Spain
| | - Carmen González-Garcia
- Centro Regional de Investigaciones Biomédicas y Dpto. Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Valentín Ceña
- Centro Regional de Investigaciones Biomédicas y Dpto. Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Albacete, Spain
| |
Collapse
|
14
|
Abstract
Tetrapentylammonium (TPeA) block of rat brain type IIA sodium channel alpha subunit was studied using whole cell patch clamp. Results indicate that TPeA blocks the inactivating brain sodium channel in a potential and use-dependent manner similar to that of the cardiac sodium channel. Removal of inactivation using chloramine-T (CT) unmasks a time-dependent block by TPeA consistent with slow blocking kinetics. On the other hand, no time dependence is observed when inactivation is abolished by modification with veratridine. TPeA does not bind in a potential-dependent fashion to veratridine-modified channels and does not significantly affect gating of veratridine-modified channels suggesting that high affinity binding of TPeA to the brain sodium channel is lost after veratridine modification.
Collapse
Affiliation(s)
- A S Ghatpande
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, Karnataka, India
| | - S Rao
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, Karnataka, India
| | - S K Sikdar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Author for correspondence:
| |
Collapse
|
15
|
Callaway JK, Beart PM, Jarrott B, Giardina SF. Incorporation of sodium channel blocking and free radical scavenging activities into a single drug, AM-36, results in profound inhibition of neuronal apoptosis. Br J Pharmacol 2001; 132:1691-8. [PMID: 11309240 PMCID: PMC1572735 DOI: 10.1038/sj.bjp.0704018] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
AM-36 is a novel neuroprotective agent incorporating both antioxidant and Na(+) channel blocking actions. In cerebral ischaemia, loss of cellular ion homeostasis due to Na(+) channel activation, together with increased reactive oxygen species (ROS) production, are thought to contribute to neuronal death. Since neuronal death in the penumbra of the ischaemic lesion is suggested to occur by apoptosis, we investigated the ability of AM-36, antioxidants and Na(+) channel antagonists to inhibit toxicity induced by the neurotoxin, veratridine in cultured cerebellar granule cells (CGC's). Veratridine (10 - 300 microM) concentration-dependently reduced cell viability of cultured CGC's. Under the experimental conditions employed, cell death induced by veratridine (100 microM) possessed the characteristics of apoptosis as assessed by morphology, TUNEL staining and DNA laddering on agarose gels. Neurotoxicity and apoptosis induced by veratridine (100 microM) were inhibited to a maximum of 50% by the antioxidants, U74500A (0.1 - 10 microM) and U83836E (0.03 - 10 microM), and to a maximum of 30% by the Na(+) channel blocker, dibucaine (0.1 - 100 microM). In contrast, AM-36 (0.01 - 10 microM) completely inhibited veratridine-induced toxicity ( IC(50) 1.7 (1.5 - 1.9) microM, 95% confidence intervals (CI) in parentheses) and concentration-dependently inhibited apoptosis. These findings suggest veratridine-induced toxicity and apoptosis are partially mediated by generation of ROS. AM-36, which combines both Na(+) channel blocking and antioxidant activity, provided superior neuroprotection compared with agents possessing only one of these actions. This bifunctional profile of activity may underlie the potent neuroprotective effects of AM-36 recently found in a stroke model in conscious rats.
Collapse
Affiliation(s)
- J K Callaway
- Department of Pharmacology, Monash University, Victoria, 3800, Australia.
| | | | | | | |
Collapse
|
16
|
Yokoo H, Shiraishi S, Kobayashi H, Yanagita T, Minami SI, Yamamoto R, Wada A. Short- and long-term differential effects of neuroprotective drug NS-7 on voltage-dependent sodium channels in adrenal chromaffin cells. Br J Pharmacol 2000; 131:779-87. [PMID: 11030728 PMCID: PMC1572381 DOI: 10.1038/sj.bjp.0703622] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In cultured bovine adrenal chromaffin cells, NS-7 [4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy) pyrimidine hydrochloride], a newly-synthesized neuroprotective drug, inhibited veratridine-induced (22)Na(+) influx via voltage-dependent Na(+) channels (IC(50)=11.4 microM). The inhibition by NS-7 occurred in the presence of ouabain, an inhibitor of Na(+),K(+) ATPase, but disappeared at higher concentration of veratridine, and upon the washout of NS-7. NS-7 attenuated veratridine-induced (45)Ca(2+) influx via voltage-dependent Ca(2+) channels (IC(50)=20.0 microM) and catecholamine secretion (IC(50)=25.8 microM). Chronic (>/=12 h) treatment of cells with NS-7 increased cell surface [(3)H]-STX binding by 86% (EC(50)=10.5 microM; t(1/2)=27 h), but did not alter the K(D) value; it was prevented by cycloheximide, an inhibitor of protein synthesis, or brefeldin A, an inhibitor of vesicular transport from the trans-Golgi network, but was not associated with increased levels of Na(+) channel alpha- and beta(1)-subunit mRNAs. In cells subjected to chronic NS-7 treatment, (22)Na(+) influx caused by veratridine (site 2 toxin), alpha-scorpion venom (site 3 toxin) or beta-scorpion venom (site 4 toxin) was suppressed even after the extensive washout of NS-7, and veratridine-induced (22)Na(+) influx remained depressed even at higher concentration of veratridine; however, either alpha- or beta-scorpion venom, or Ptychodiscus brevis toxin-3 (site 5 toxin) enhanced veratridine-induced (22)Na(+) influx as in nontreated cells. These results suggest that in the acute treatment, NS-7 binds to the site 2 and reversibly inhibits Na(+) channels, thereby reducing Ca(2+) channel gating and catecholamine secretion. Chronic treatment with NS-7 up-regulates cell surface Na(+) channels via translational and externalization events, but persistently inhibits Na(+) channel gating without impairing the cooperative interaction between the functional domains of Na(+) channels.
Collapse
Affiliation(s)
- Hiroki Yokoo
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
| | - Seiji Shiraishi
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
| | - Hideyuki Kobayashi
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
| | - Toshihiko Yanagita
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
| | - Shin-ichi Minami
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
| | - Ryuichi Yamamoto
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
| | - Akihiko Wada
- Department of Pharmacology, Miyazaki Medical College, Miyazaki 889-1692, Japan
- Author for correspondence:
| |
Collapse
|
17
|
Jordán J, Galindo MF, Calvo S, González-García C, Ceña V. Veratridine induces apoptotic death in bovine chromaffin cells through superoxide production. Br J Pharmacol 2000; 130:1496-504. [PMID: 10928950 PMCID: PMC1572211 DOI: 10.1038/sj.bjp.0703451] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2000] [Accepted: 05/03/2000] [Indexed: 12/31/2022] Open
Abstract
The molecular mechanisms involved in veratridine-induced chromaffin cell death have been explored. We have found that exposure to veratridine (30 microM, 1 h) produces a delayed cellular death that reaches 55% of the cells 24 h after veratridine exposure. This death has the features of apoptosis as DNA fragmentation can be observed. Calcium ions play an important role in veratridine-induced chromaffin cell death because the cell permeant Ca(2+) chelator BAPTA-AM and extracellular Ca(2+) removal completely prevented veratridine-induced toxicity. Following veratridine treatment, there is a decrease in mitochondrial function and an increase in superoxide anion production. Veratridine-induced increase in superoxide production was blocked by tetrodotoxin (TTX; 10 microM), extracellular Ca(2+) removal and the mitochondrial permeability transition pore blocker cyclosporine A (10 microM). Veratridine-induced death was prevented by different antioxidant treatments including catalase (100 IU ml(-1)), N-acetyl cysteine (100 microM), allopurinol (100 microM) or vitamin E (50 microM). Veratridine-induced DNA fragmentation was prevented by TTX (10 microM). Veratridine produced a time-dependent increase in caspase activity that was prevented by Ca(2+) removal and TTX (10 microM). In addition, calpain and caspases inhibitors partially prevented veratridine-induced death. These results indicate that chromaffin cells share with neurons the molecular machinery involved in apoptotic death and might be considered a good model to study neuronal death during neurodegeneration.
Collapse
Affiliation(s)
- Joaquín Jordán
- Institute for Neurosciences University, Miguel Hernández, Alicante, Spain
| | - María F Galindo
- Institute for Neurosciences University, Miguel Hernández, Alicante, Spain
| | - Soledad Calvo
- Institute for Neurosciences University, Miguel Hernández, Alicante, Spain
| | | | - Valentín Ceña
- Institute for Neurosciences University, Miguel Hernández, Alicante, Spain
| |
Collapse
|
18
|
Dobrev D, Milde AS, Andreas K, Ravens U. The effects of verapamil and diltiazem on N-, P- and Q-type calcium channels mediating dopamine release in rat striatum. Br J Pharmacol 1999; 127:576-82. [PMID: 10385261 PMCID: PMC1566043 DOI: 10.1038/sj.bjp.0702574] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The putative inhibitory effects of verapamil and diltiazem on neuronal non-L-type Ca2+ channels were studied by investigating their effects on either K+- or veratridine-evoked [3H]-dopamine ([3H]-DA) release in rat striatal slices. Involvement of N-, P- and Q-type channels was identified by sensitivity of [3H]-DA release to omega-conotoxin GVIA (omega-CTx-GVIA), omega-agatoxin IVA (omega-Aga-IVA) and omega-conotoxin MVIIC (omega-CTx-MVIIC), respectively. 2. KCl (50 mM)-evoked [3H]-DA release was abolished in the absence of Ca2+, and was insensitive to dihydropyridines (up to 30 microM). It was significantly blocked by omega-CTx-GVIA (1 microM), omega-Aga-IVA (30 nM) and was confirmed to be abolished by omega-CTx-MVIIC (3 microM), indicating involvement of N-, P- and Q-type channel subtypes. 3. Verapamil and diltiazem inhibited K+-evoked [3H]-DA release in a concentration-dependent manner. The inhibitory effects of verapamil or diltiazem (each 30 microM) were fully additive to the effect of omega-CTx-GVIA (1 microM), whereas co-application with omega-Aga-IVA (30 nM) produced similar effects to those of omega-Aga-IVA alone. 4. As shown previously, veratridine-evoked [3H]-DA release in Ca2+ containing medium exclusively involves Q-type Ca2+ channels. Here, diltiazem (30 microM) did not inhibit veratridine-evoked [3H]-DA release, whereas verapamil (30 microM) partially inhibited it, indicating possible involvement of Q-type channels in verapamil-induced inhibition. However, verapamil (30 microM) inhibited this release even in the absence of extracellular Ca2+, suggesting that Na+ rather than Q-type Ca2+ channels are involved. 5. Taken together, our results suggest that verapamil can block P- and at higher concentrations possibly N- and Q-type Ca2+ channels linked to [3H]-DA release, whereas diltiazem appears to block P-type Ca2+ channels only.
Collapse
Affiliation(s)
- D Dobrev
- Institute of Pharmacology and Toxicology, Faculty of Medicine, University of Technology, Dresden, Germany.
| | | | | | | |
Collapse
|
19
|
Abstract
Intracellular calcium concentrations in individual rat motoneurones in enriched primary cultures were measured by Indo-1 fluorimetry. Motoneurones in the cultures were characterized morphometrically and by cholineacetyltransferase immunocytochemistry. Depolarization of the cells with glutamic acid or veratridine increased intracellular calcium levels, which returned to baseline only slowly after removal of the depolarizing agent. The use of selective agonists (N-methyl-D-aspartic acid, AMPA, kainic acid, quisqualic acid and 1R-3S-ACPD) and antagonists (MK 801 and CNQX) showed that the excitatory amino acid-evoked responses were mediated by AMPA/kainate receptors rather than by NMDA receptors. Depolarization-evoked calcium transients in motoneurones are blocked by the neuroprotective drug riluzole Calcium transients reflected entry of calcium from without the cell, and their blockade by nitrendipine and lanthanum chloride suggested that this entry took place primarily through voltage-dependent calcium channels. These findings may be relevant for understanding the selective vulnerability of motoneurones to excitotoxicity in amyotrophic lateral sclerosis, and the therapeutic activity of riluzole in the treatment of this disease.
Collapse
Affiliation(s)
- J P Hubert
- Pharmaceutical Research Department, Rhône-Poulenc Rorer SA, Vitry-sur-Seine, France
| | | | | | | | | |
Collapse
|
20
|
Cano-Abad MF, López MG, Hernández-Guijo JM, Zapater P, Gandía L, Sánchez-García P, García AG. Effects of the neuroprotectant lubeluzole on the cytotoxic actions of veratridine, barium, ouabain and 6-hydroxydopamine in chromaffin cells. Br J Pharmacol 1998; 124:1187-96. [PMID: 9720790 PMCID: PMC1565510 DOI: 10.1038/sj.bjp.0701955] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Incubation of bovine adrenal chromaffin cells with veratridine (10-100 microM) during 24 h, caused a concentration-dependent release of the cytosolic lactate dehydrogenase (LDH) into the bathing medium, an indicator of cell death. Lubeluzole or its R(-) enantiomer, R91154, did not enhance LDH release. Both lubeluzole and R91154 (0.3-10 microM) decreased the veratridine-induced LDH release. 2. Penfluridol did not increase LDH release at concentrations 0.003-1 microM; 3-10 microM increased LDH release to 50-60%, after 24 h exposure. Penfluridol (0.03-0.3 microM) did not protect against the cytotoxic effects of veratridine; at 1 microM, 15% protection was produced. Higher concentrations (3-10 microM) enhanced the cytotoxic effects of veratridine. 3. Ba2+ ions caused a concentration-dependent increase of LDH release. This cytotoxic effect was partially prevented by 3 microM lubeluzole and fully counteracted by 1 microM penfluridol. R91154 was less potent than lubeluzole and only protected against the lesion induced by 0.5 mM Ba2+. 4. Ouabain (10 microM during 24 h) increased LDH release to about 30%. Both lubeluzole (0.3-10 microM) and the lower concentrations of penfluridol (0.003-0.3 microM) prevented the ouabain cytotoxic effects. At higher concentrations (3 microM), penfluridol increased drastically the ouabain cytotoxic effects. 5. 6-Hydroxydopamine (6-OHDA) caused significant cytotoxic effects at 30 and 100 microM. Lubeluzole (3-10 microM) or penfluridol (0.03-0.3 microM) had no cytoprotective effects against 6-OHDA. 6. Lubeluzole (3 microM), R91154 (3 microM) and penfluridol (1 microM) blocked the current through Na+ channels in voltage-clamped chromaffin cells (I(Na)) by around 20-30%. Ca2+ current through Ca2+ channels (I(Ca)) was inhibited 57% by lubeluzole and R91154 and 50% by penfluridol. The effects of penfluridol were not washed out, but those of lubeluzole and R91154 were readily reversible. 7. Lubeluzole (3 microM) induced reversible blockade of the oscillations of the cytosolic Ca2+, [Ca2+]i, in fura-2-loaded cells exposed to 30 or 100 microM veratridine. Penfluridol (1 microM) inhibited those oscillations in an irreversible manner. 8. The results suggest that lubeluzole and its R-isomer caused cytoprotection against veratridine cell damage, by blocking the veratridine stimulated Na+ and Ca2+ entry, as well as the [Ca2+]i oscillations. The Ba2+ and ouabain cytotoxic effects were prevented more efficiently by penfluridol, likely by blocking the plasmalemmal Na+/Ca2+ exchanger. It remains dubious whether these findings are relevant to the reported neuroprotective action of lubeluzole in stroke; the doubt rests in the stereoselective protecting effects of lubeluzole in in vivo stroke models, as opposed to its lack of stereoselectivity in the in vitro model reported here.
Collapse
Affiliation(s)
- M F Cano-Abad
- Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain
| | | | | | | | | | | | | |
Collapse
|
21
|
Lichtshtein D, Kaback HR, Blume AJ. Use of a lipophilic cation for determination of membrane potential in neuroblastoma-glioma hybrid cell suspensions. Proc Natl Acad Sci U S A 1979; 76:650-4. [PMID: 284390 PMCID: PMC383006 DOI: 10.1073/pnas.76.2.650] [Citation(s) in RCA: 170] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Neuroblastoma-glioma hybrid cells (NG108-15) in suspension accumulate the permeant lipophilic cation [(3)H]tetraphenylphosphonium (TPP(+)) against a concentration gradient. The steady-state level of TPP(+) accumulation is about twice as great in physiological media of low K(+) concentration (i.e., 5 mM K(+)/135 mM Na(+)) than in a medium of high K(+) concentration (i.e., 121 mM K(+)/13.5 mM Na(+)). The latter manipulation depolarizes the NG108-15 plasma membrane and indicates that the resting membrane potential (DeltaPsi) is due primarily to a K(+) diffusion gradient (K(in) (+) --> K(out) (+)). TPP(+) accumulation is time and temperature dependent, achieving a steady state in 15-20 min at 37 degrees C, and is a linear function of cell number and TPP(+) concentration (i.e., the concentration gradient is constant). The difference in TPP(+) accumulation in low and high K(+) media under various conditions has been used to calculate mean (+/-SD) DeltaPsi values of -56 +/- 3, -63 +/- 4, and -66 +/- 5 mV at 26, 33, and 37 degrees C, respectively. Importantly, these values are virtually identical to those obtained by direct electrophysiological measurements made under the same conditions. TPP(+) accumulation is abolished by the protonophore carbonylcyanide-m-chlorophenylhydrazone, whereas the neurotoxic alkaloid veratridine diminishes uptake to the same level as that observed in high K(+) media. In addition, the effect of veratridine is dependent upon the presence of external Na(+) and is blocked by tetrodotoxin. The steady-state level of TPP(+) accumulation is enhanced by monensin, indicating that this ionophore induces hyperpolarization under appropriate conditions. Finally, ouabain has essentially no effect on the steady-state level of TPP(+) accumulation in short-term experiments, suggesting that Na(+),K(+)-ATPase activity makes little contribution to the resting potential in these cells. Because many of these observations are corroborated by intracellular recording techniques, it is concluded that TPP(+) distribution measurements can provide a biochemical method for determining membrane potentials in populations of cultured neuronal cells.
Collapse
|
22
|
Catterall WA, Nirenberg M. Sodium uptake associated with activation of action potential ionophores of cultured neuroblastoma and muscle cells. Proc Natl Acad Sci U S A 1973; 70:3759-63. [PMID: 4521201 PMCID: PMC427322 DOI: 10.1073/pnas.70.12.3759] [Citation(s) in RCA: 124] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Veratridine, an activator of action potential Na(+) ionophores, stimulated passive Na(+) uptake by electrically excitable neuroblastoma and muscle cells but had no effect on clonal cell lines defective in Na(+)-ionophore activity. Veratridine-dependent Na(+) uptake was completely inhibited by tetrodotoxin, a specific inhibitor of the action potential Na(+) ionophore. Half-maximal inhibition was obtained with 11 nM tetrodotoxin. Thus, veratridinedependent Na(+) uptake provides a specific and convenient means of assaying populations of cultured cells for action potential Na(+)-ionophore activity.
Collapse
|
23
|
Abstract
Potassium concentrations above 15-20 mM in the medium, or addition of 75 muM veratridine to medium that contains 5 mM K, stimulate calcium accumulation and Ca-dependent norepinephrine release by presynaptic nerve terminals (synaptosomes) incubated in vitro. The effects of veratridine, but not of K, are blocked by 0.2 muM tetrodotoxin. This association between Ca entry and norepinephrine release is consistent with the Calcium Hypothesis of transmitter release. These results add further evidence that synaptosomes may retain many functional properties of intact presynaptic endings.
Collapse
|