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McCubbin S, Meade A, Harrison DA, Cooper RL. Acute lipopolysaccharide (LPS)-induced cell membrane hyperpolarization is independent of voltage gated and calcium activated potassium channels. Comp Biochem Physiol C Toxicol Pharmacol 2024; 285:110004. [PMID: 39154976 DOI: 10.1016/j.cbpc.2024.110004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Revised: 07/29/2024] [Accepted: 08/15/2024] [Indexed: 08/20/2024]
Abstract
The gram-negative toxin lipopolysaccharides (LPS) are known to trigger inflammatory cytokines in mammals, which can result in pathological responses. Upon treatment of bacterial sepsis with antibiotics, the lysing bacteria can present a surge in LPS, inducing a cytokine storm. However, LPS can also have direct cellular effects, including transient rapid hyperpolarizing of the membrane potential, blocking glutamate receptors and even promoting release of glutamate. The detailed mechanism of action for these immediate responses is still unresolved. In addressing the membrane hyperpolarization, voltage gated K+ channel blockers 4-aminopyridine (4-AP, 3 mM), quinidine hydrochloride monohydrate (0.1 mM) and tetraethylammonium (TEA, 20 mM) were examined along with RNAi knockdowns of potential calcium activated K+ channels. The immediate responses of LPS were not blocked. Even in the presence of glutamate, the membrane still hyperpolarizes with LPS. When the driving gradient for the ionotropic glutamate receptors is enhanced during hyperpolarization, spontaneous quantal responses are dampened in amplitude. Thus, glutamate receptors are blocked, and the mechanism of hyperpolarization remains unresolved. The larval Drosophila glutamatergic neuromuscular junction is used as a model synaptic preparation to address the direct rapid actions by LPS.
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Affiliation(s)
- Shelby McCubbin
- Department of Biology, University of Kentucky, Lexington, KY 40506-0025, USA.
| | - Alexis Meade
- Department of Biology, University of Kentucky, Lexington, KY 40506-0025, USA.
| | - Douglas A Harrison
- Department of Biology, University of Kentucky, Lexington, KY 40506-0025, USA.
| | - Robin L Cooper
- Department of Biology, University of Kentucky, Lexington, KY 40506-0025, USA.
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2
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Elliott ER, Brock KE, Vacassenno RM, Harrison DA, Cooper RL. The effects of doxapram and its potential interactions with K2P channels in experimental model preparations. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024:10.1007/s00359-024-01705-6. [PMID: 38802613 DOI: 10.1007/s00359-024-01705-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 05/15/2024] [Accepted: 05/18/2024] [Indexed: 05/29/2024]
Abstract
The channels commonly responsible for maintaining cell resting membrane potentials are referred to as K2P (two-P-domain K+ subunit) channels. These K+ ion channels generally remain open but can be modulated by their local environment. These channels are classified based on pharmacology, pH sensitivity, mechanical stretch, and ionic permeability. Little is known about the physiological nature of these K2P channels in invertebrates. Acidic conditions depolarize neurons and muscle fibers, which may be caused by K2P channels given that one subtype can be blocked by acidic conditions. Doxapram is used clinically as a respiratory aid known to block acid-sensitive K2P channels; thus, the effects of doxapram on the muscle fibers and synaptic transmission in larval Drosophila and crawfish were monitored. A dose-dependent response was observed via depolarization of the larval Drosophila muscle and an increase in evoked synaptic transmission, but doxapram blocked the production of action potentials in the crawfish motor neuron and had a minor effect on the resting membrane potential of the crawfish muscle. This indicates that the nerve and muscle tissues in larval Drosophila and crawfish likely express different K2P channel subtypes. Since these organisms serve as physiological models for neurobiology and physiology, it would be of interest to further investigate what types of K2P channel are expressed in these tissues. (212 words).
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Affiliation(s)
- Elizabeth R Elliott
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Kaitlyn E Brock
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | | | - Douglas A Harrison
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Robin L Cooper
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA.
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3
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Chiliquinga AJ, Acosta B, Ogonaga-Borja I, Villarruel-Melquiades F, de la Garza J, Gariglio P, Ocádiz-Delgado R, Ramírez A, Sánchez-Pérez Y, García-Cuellar CM, Bañuelos C, Camacho J. Ion Channels as Potential Tools for the Diagnosis, Prognosis, and Treatment of HPV-Associated Cancers. Cells 2023; 12:1376. [PMID: 37408210 DOI: 10.3390/cells12101376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/19/2023] [Accepted: 05/05/2023] [Indexed: 07/07/2023] Open
Abstract
The human papilloma virus (HPV) group comprises approximately 200 genetic types that have a special affinity for epithelial tissues and can vary from producing benign symptoms to developing into complicated pathologies, such as cancer. The HPV replicative cycle affects various cellular and molecular processes, including DNA insertions and methylation and relevant pathways related to pRb and p53, as well as ion channel expression or function. Ion channels are responsible for the flow of ions across cell membranes and play very important roles in human physiology, including the regulation of ion homeostasis, electrical excitability, and cell signaling. However, when ion channel function or expression is altered, the channels can trigger a wide range of channelopathies, including cancer. In consequence, the up- or down-regulation of ion channels in cancer makes them attractive molecular markers for the diagnosis, prognosis, and treatment of the disease. Interestingly, the activity or expression of several ion channels is dysregulated in HPV-associated cancers. Here, we review the status of ion channels and their regulation in HPV-associated cancers and discuss the potential molecular mechanisms involved. Understanding the dynamics of ion channels in these cancers should help to improve early diagnosis, prognosis, and treatment in the benefit of HPV-associated cancer patients.
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Affiliation(s)
| | - Brenda Acosta
- Grupo de Investigación de Ciencias en Red, Universidad Técnica del Norte, Ibarra 100105, Ecuador
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
| | - Ingrid Ogonaga-Borja
- Grupo de Investigación de Ciencias en Red, Universidad Técnica del Norte, Ibarra 100105, Ecuador
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
| | - Fernanda Villarruel-Melquiades
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
| | - Jaime de la Garza
- Unidad de Oncología Torácica y Laboratorio de Medicina Personalizada, Instituto Nacional de Cancerología (INCan), Tlalpan, Ciudad de Mexico CP 14080, Mexico
| | - Patricio Gariglio
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
| | - Rodolfo Ocádiz-Delgado
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
| | - Ana Ramírez
- Facultad de Ciencias Químicas e Ingeniería, Universidad Autónoma de Baja California, Calzada Universidad 14418, Tijuana 22390, Mexico
| | - Yesennia Sánchez-Pérez
- Subdirección de Investigación Básica, Instituto Nacional de Cancerología (INCan), Tlalpan, Ciudad de Mexico CP 14080, Mexico
| | - Claudia M García-Cuellar
- Subdirección de Investigación Básica, Instituto Nacional de Cancerología (INCan), Tlalpan, Ciudad de Mexico CP 14080, Mexico
| | - Cecilia Bañuelos
- Programa Transdisciplinario en Desarrollo Científico y Tecnológico para la Sociedad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
| | - Javier Camacho
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Ciudad de Mexico CP 07360, Mexico
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Pinto FM, Odriozola A, Candenas L, Subirán N. The Role of Sperm Membrane Potential and Ion Channels in Regulating Sperm Function. Int J Mol Sci 2023; 24:6995. [PMID: 37108159 PMCID: PMC10138380 DOI: 10.3390/ijms24086995] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 04/02/2023] [Accepted: 04/05/2023] [Indexed: 04/29/2023] Open
Abstract
During the last seventy years, studies on mammalian sperm cells have demonstrated the essential role of capacitation, hyperactivation and the acrosome reaction in the acquisition of fertilization ability. These studies revealed the important biochemical and physiological changes that sperm undergo in their travel throughout the female genital tract, including changes in membrane fluidity, the activation of soluble adenylate cyclase, increases in intracellular pH and Ca2+ and the development of motility. Sperm are highly polarized cells, with a resting membrane potential of about -40 mV, which must rapidly adapt to the ionic changes occurring through the sperm membrane. This review summarizes the current knowledge about the relationship between variations in the sperm potential membrane, including depolarization and hyperpolarization, and their correlation with changes in sperm motility and capacitation to further lead to the acrosome reaction, a calcium-dependent exocytosis process. We also review the functionality of different ion channels that are present in spermatozoa in order to understand their association with human infertility.
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Affiliation(s)
- Francisco M. Pinto
- Instituto de Investigaciones Químicas, CSIC-University of Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain;
| | - Ainize Odriozola
- Department of Physiology, Faculty of Medicine and Nursery, University of the Basque Country (UPV/EHU), 48940 Bizkaia, Spain; (A.O.); (N.S.)
- Biocruces-Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- MEPRO Medical Reproductive Solutions, 20009 San Sebastian, Spain
| | - Luz Candenas
- Instituto de Investigaciones Químicas, CSIC-University of Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain;
| | - Nerea Subirán
- Department of Physiology, Faculty of Medicine and Nursery, University of the Basque Country (UPV/EHU), 48940 Bizkaia, Spain; (A.O.); (N.S.)
- Biocruces-Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- MEPRO Medical Reproductive Solutions, 20009 San Sebastian, Spain
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Vacassenno RM, Haddad CN, Cooper RL. Bacterial lipopolysaccharide hyperpolarizes the membrane potential and is antagonized by the K2p channel blocker doxapram. Comp Biochem Physiol C Toxicol Pharmacol 2023; 266:109571. [PMID: 36740004 DOI: 10.1016/j.cbpc.2023.109571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 01/14/2023] [Accepted: 02/01/2023] [Indexed: 02/05/2023]
Abstract
Exposure of Drosophila skeletal muscle to bacterial lipopolysaccharides (LPS) rapidly and transiently hyperpolarizes membrane potential. However, the mechanism responsible for hyperpolarization remains unclear. The resting membrane potential of the cells is maintained through multiple mechanisms. This study investigated the possibility of LPS activating calcium-activated potassium channels (KCa) and/or K2p channels. 2-Aminoethyl diphenylborinate (2-APB), blocks uptake of Ca2+ into the endoplasmic reticulum (ER); thus, limiting release from ryanodine-sensitive internal stores to reduce the function of KCa channels. Exposure to 2-APB produces waves of hyperpolarization even during desensitization of the response to LPS and in the presence of doxapram. This finding in this study suggests that doxapram blocked the acid-sensitive K2p tandem-pore channel subtype known in mammals. Doxapram blocked LPS-induced hyperpolarization and depolarized the muscles as well as induced motor neurons to produce evoked excitatory junction potentials (EJPs). This was induced by depolarizing motor neurons, similar to the increase in extracellular K+ concentration. The hyperpolarizing effect of LPS was not blocked by decreased extracellular Ca2+or the presence of Cd2+. LPS appears to transiently activate doxapram sensitive K2p channels independently of KCa channels in hyperpolarizing the muscle. Septicemia induced by gram-negative bacteria results in an increase in inflammatory cytokines, primarily induced by bacterial LPS. Currently, blockers of LPS receptors in mammals are unknown; further research on doxapram and other K2p channels is warranted. (220 words).
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Affiliation(s)
- Rachael M Vacassenno
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA; Department of Biology, Eastern Kentucky University, Richmond, KY 40475, USA.
| | - Christine N Haddad
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA.
| | - Robin L Cooper
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA.
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6
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Vacassenno RM, Haddad CN, Cooper RL. The effects of doxapram (blocker of K2p channels) on resting membrane potential and synaptic transmission at the Drosophila neuromuscular junction. Comp Biochem Physiol C Toxicol Pharmacol 2023; 263:109497. [PMID: 36306997 DOI: 10.1016/j.cbpc.2022.109497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/26/2022] [Accepted: 10/23/2022] [Indexed: 11/03/2022]
Abstract
The resting membrane potential of most cells is maintained by potassium K2p channels. The pharmacological profile and distribution of various K2p channel subtypes in organisms are still being investigated. The Drosophila genome contains 11 subtypes; however, their function and expression profiles have not yet been determined. Doxapram is clinically used to enhance respiration in humans and blocks the acid-sensitive K2p TASK subtype in mammals. The resting membrane potential of larval Drosophila muscle and synaptic transmission at the neuromuscular junction are pH sensitive. The present study investigated the effects of doxapram on membrane potential and synaptic transmission using intracellular recordings of larval Drosophila muscles. Doxapram (1 mM and 10 mM) depolarizes the muscle and appears to depolarize motor neurons, causing an increase in the frequency of spontaneous quantal events and evoked excitatory junction potentials. Verapamil (1 and 10 mM) paralleled the action of doxapram. These changes were matched by an extracellular increase in KCl (50 mM) and blocked by Cd2+. It is assumed that the motor nerve depolarizes to open voltage-gated Ca2+ channels in presynaptic nerve terminals because of exposure to doxapram. These findings are significant for building models to better understand the function of pharmacological agents that affect K2p channels and how K2p channels contribute to the physiology of tissues. Drosophila offers a genetically amenable model that can alter the tissue-specific expression of K2p channel subtypes to simulate known human diseases related to this family of channels.
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Affiliation(s)
- Rachael M Vacassenno
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA; Department of Biology, Eastern Kentucky University, Richmond, KY 40475, USA.
| | - Christine N Haddad
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA.
| | - Robin L Cooper
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA.
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7
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Cooper RL, Krall RM. Hyperpolarization Induced by Lipopolysaccharides but Not by Chloroform Is Inhibited by Doxapram, an Inhibitor of Two-P-Domain K + Channel (K2P). Int J Mol Sci 2022; 23:ijms232415787. [PMID: 36555429 PMCID: PMC9779748 DOI: 10.3390/ijms232415787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 11/20/2022] [Accepted: 11/24/2022] [Indexed: 12/15/2022] Open
Abstract
Bacterial septicemia is commonly induced by Gram-negative bacteria. The immune response is triggered in part by the secretion of bacterial endotoxin lipopolysaccharide (LPS). LPS induces the subsequent release of inflammatory cytokines which can result in pathological conditions. There is no known blocker to the receptors of LPS. The Drosophila larval muscle is an amendable model to rapidly screen various compounds that affect membrane potential and synaptic transmission such as LPS. LPS induces a rapid hyperpolarization in the body wall muscles and depolarization of motor neurons. These actions are blocked by the compound doxapram (10 mM), which is known to inhibit a subtype of the two-P-domain K+ channel (K2P channels). However, the K2P channel blocker PK-THPP had no effect on the Drosophila larval muscle at 1 and 10 mM. These channels are activated by chloroform, which also induces a rapid hyperpolarization of these muscles, but the channels are not blocked by doxapram. Likewise, chloroform does not block the depolarization induced by doxapram. LPS blocks the postsynaptic glutamate receptors on Drosophila muscle. Pre-exposure to doxapram reduces the LPS block of these ionotropic glutamate receptors. Given that the larval Drosophila body wall muscles are depolarized by doxapram and hyperpolarized by chloroform, they offer a model to begin pharmacological profiling of the K2P subtype channels with the potential of identifying blockers for the receptors to mitigate the actions of the Gram-negative endotoxin LPS.
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Affiliation(s)
- Robin L. Cooper
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA
- Correspondence:
| | - Rebecca M. Krall
- Department of STEM Education, University of Kentucky, Lexington, KY 40506-0001, USA
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The Effect of Doxapram on Proprioceptive Neurons: Invertebrate Model. NEUROSCI 2022. [DOI: 10.3390/neurosci3040041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The resting membrane potential enables neurons to rapidly initiate and conduct electrical signals. K2p channels are key in maintaining this membrane potential and electrical excitability. They direct the resting membrane potential toward the K+ equilibrium potential. Doxapram is a known blocker for a subset of K2p channels that are pH sensitive. We assessed the effects of 0.1 and 5 mM doxapram on the neural activity within the propodite-dactylopodite (PD) proprioceptive sensory organ in the walking legs of blue crabs (Callinectes sapidus). Results indicate that 0.1 mM doxapram enhances excitation, while the higher concentration 5 mM may over-excite the neurons and promote a sustained absolute refractory period until the compound is removed. The effect of 5 mM doxapram mimics the effect of 40 mM K+ exposure. Verapamil, another known K2p channel blocker as well as an L-type Ca2+ channel blocker, reduces neural activity at both 0.1 and 5 mM. Verapamil may block stretch activated channels in sensory endings, in addition to reducing the amplitude of the compound action potential with whole nerve preparations. These findings are notable as they demonstrate that doxapram has acute effects on neurons of crustaceans, suggesting a targeted K2p channel. The actions of verapamil are complex due to the potential of affecting multiple ion channels in this preparation. Crustacean neurons can aid in understanding the mechanisms of action of various pharmacological agents as more information is gained.
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