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Reddy P, Rochfort S, Read E, Deseo M, Jaehne E, Van Den Buuse M, Guthridge K, Combs M, Spangenberg G, Quinn J. Tremorgenic effects and functional metabolomics analysis of lolitrem B and its biosynthetic intermediates. Sci Rep 2019; 9:9364. [PMID: 31249318 PMCID: PMC6597573 DOI: 10.1038/s41598-019-45170-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 05/30/2019] [Indexed: 01/02/2023] Open
Abstract
The neuroactive mycotoxin lolitrem B causes a neurological syndrome in grazing livestock resulting in hyperexcitability, muscle tremors, ataxia and, in severe cases, clonic seizures and death. To define the effects of the major toxin lolitrem B in the brain, a functional metabolomic study was undertaken in which motor coordination and tremor were quantified and metabolomic profiling undertaken to determine relative abundance of both toxin and key neurotransmitters in various brain regions in male mice. Marked differences were observed in the duration of tremor and coordination between lolitrem B pathway members, with some showing protracted effects and others none at all. Lolitrem B was identified in liver, kidney, cerebral cortex and thalamus but not in brainstem or cerebellum which were hypothesised previously to be the primary site of action. Metabolomic profiling showed significant variation in specific neurotransmitter and amino acid profiles over time. This study demonstrates accumulation of lolitrem B in the brain, with non-detectable levels of toxin in the brainstem and cerebellum, inducing alterations in metabolites such as tyrosine, suggesting a dynamic catecholaminergic response over time. Temporal characterisation of key pathways in the pathophysiological response of lolitrem B in the brain were also identified.
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Affiliation(s)
- Priyanka Reddy
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, Victoria, 3083, Australia
- School of Applied Systems Biology, La Trobe University, Bundoora, Victoria, 3083, Australia
| | - Simone Rochfort
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, Victoria, 3083, Australia.
- School of Applied Systems Biology, La Trobe University, Bundoora, Victoria, 3083, Australia.
| | - Elizabeth Read
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, Victoria, 3083, Australia
- School of Applied Systems Biology, La Trobe University, Bundoora, Victoria, 3083, Australia
| | - Myrna Deseo
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, Victoria, 3083, Australia
| | - Emily Jaehne
- School of Psychology and Public Health, La Trobe University, Bundoora, Victoria, 3083, Australia
| | - Maarten Van Den Buuse
- School of Psychology and Public Health, La Trobe University, Bundoora, Victoria, 3083, Australia
| | - Kathryn Guthridge
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, Victoria, 3083, Australia
| | - Martin Combs
- School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia
- Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia
| | - German Spangenberg
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, Victoria, 3083, Australia
- School of Applied Systems Biology, La Trobe University, Bundoora, Victoria, 3083, Australia
| | - Jane Quinn
- School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia
- Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia
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Combs MD, Hamlin A, Quinn JC. A single exposure to the tremorgenic mycotoxin lolitrem B inhibits voluntary motor activity and spatial orientation but not spatial learning or memory in mice. Toxicon 2019; 168:58-66. [PMID: 31254599 DOI: 10.1016/j.toxicon.2019.06.228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 06/19/2019] [Accepted: 06/25/2019] [Indexed: 10/26/2022]
Abstract
The indole diterpenoid toxin lolitrem B is a tremorgenic agent found in the common grass species, perennial ryegrass (Lolium perenne). The toxin is produced by a symbiotic fungus Epichloë festucae (var. lolii) and ingestion of infested grass with sufficient toxin levels causes a movement disorder in grazing herbivores known as 'ryegrass staggers'. Beside ataxia, lolitrem B intoxicated animals frequently show indicators of cognitive dysfunction or exhibition of erratic and unpredictable behaviours during handling. Evidence from field cases in livestock and controlled feeding studies in horses have indicated that intoxication with lolitrem B may affect higher cortical or subcortical functioning. In order to define the role of lolitrem B in voluntary motor control, spatial learning and memory under controlled conditions, mice were exposed to a known dose of purified lolitrem B toxin and tremor, coordination, voluntary motor activity and spatial learning and memory assessed. Motor activity, coordination and spatial memory were compared to tremor intensity using a novel quantitative piezo-electronic tremor analysis. Peak tremor was observed as frequencies between 15 and 25Hz compared to normal movement at approximately 1.4-10Hz. A single exposure to a known tremorgenic dose of lolitrem B (2 mg/kg IP) induced measureable tremor for up to 72 h in some animals. Initially, intoxication with lolitrem B significantly decreased voluntary movement. By 25 h post exposure a return to normal voluntary movement was observed in this group, despite continuing evidence of tremor. This effect was not observed in animals exposed to the short-acting tremorgenic toxin paxilline. Lolitrem B intoxicated mice demonstrated a random search pattern and delayed latency to escape a 3 h post intoxication, however by 27 h post exposure latency to escape matched controls and mice had returned to normal searching behavior indicating normal spatial learning and memory. Together these data indicate that the tremor exhibited by lolitrem B intoxicated mice does not directly impair spatial learning and memory but that exposure does reduce voluntary motor activity in intoxicated animals. Management of acutely affected livestock suffering toxicosis should be considered in the context of their ability to spatially orientate with severe toxicity.
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Affiliation(s)
- M D Combs
- School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, 2560, Australia; Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), Wagga Wagga, New South Wales, 2560, Australia
| | - A Hamlin
- School of Science and Technology, University of New England, Armidale, NSW, 2351, Australia
| | - J C Quinn
- School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, 2560, Australia; Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), Wagga Wagga, New South Wales, 2560, Australia.
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Tremorgenic Mycotoxins: Structure Diversity and Biological Activity. Toxins (Basel) 2019; 11:toxins11050302. [PMID: 31137882 PMCID: PMC6563255 DOI: 10.3390/toxins11050302] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 05/22/2019] [Accepted: 05/22/2019] [Indexed: 11/23/2022] Open
Abstract
Indole-diterpenes are an important class of chemical compounds which can be unique to different fungal species. The highly complex lolitrem compounds are confined to Epichloë species, whilst penitrem production is confined to Penicillium spp. and Aspergillus spp. These fungal species are often present in association with pasture grasses, and the indole-diterpenes produced may cause toxicity in grazing animals. In this review, we highlight the unique structural variations of indole-diterpenes that are characterised into subgroups, including paspaline, paxilline, shearinines, paspalitrems, terpendoles, penitrems, lolitrems, janthitrems, and sulpinines. A detailed description of the unique biological activities has been documented where even structurally related compounds have displayed unique biological activities. Indole-diterpene production has been reported in two classes of ascomycete fungi, namely Eurotiomycetes (e.g., Aspergillus and Penicillium) and Sordariomycetes (e.g., Claviceps and Epichloë). These compounds all have a common structural core comprised of a cyclic diterpene skeleton derived from geranylgeranyl diphosphate (GGPP) and an indole moiety derived from tryptophan. Structure diversity is generated from the enzymatic conversion of different sites on the basic indole-diterpene structure. This review highlights the wide-ranging biological versatility presented by the indole-diterpene group of compounds and their role in an agricultural and pharmaceutical setting.
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Schatz DJ, Li W, Pronin SV. Catalytic enantioselective conjugate addition en route to paxilline indoloterpenoids. Tetrahedron 2019; 75:3361-3365. [PMID: 33071366 DOI: 10.1016/j.tet.2019.04.076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Development of enantioselective synthesis of precursor en route to paxilline indoloterpenoids is described. Evaluation of 25 diphosphine-based ligands has led to identification of JosiPhos derivative that allows for asymmetric conjugate addition of homoprenyl Grignard reagent to 2-methylcyclopent-2-en-1-one in excellent yield and with appreciable levels of enantioinduction. Application to the conjugate addition of other Grignard reagents is demonstrated.
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Affiliation(s)
- Devon J Schatz
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Wenqin Li
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Sergey V Pronin
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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Wulff H, Christophersen P, Colussi P, Chandy KG, Yarov-Yarovoy V. Antibodies and venom peptides: new modalities for ion channels. Nat Rev Drug Discov 2019; 18:339-357. [PMID: 30728472 PMCID: PMC6499689 DOI: 10.1038/s41573-019-0013-8] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Ion channels play fundamental roles in both excitable and non-excitable tissues and therefore constitute attractive drug targets for myriad neurological, cardiovascular and metabolic diseases as well as for cancer and immunomodulation. However, achieving selectivity for specific ion channel subtypes with small-molecule drugs has been challenging, and there currently is a growing trend to target ion channels with biologics. One approach is to improve the pharmacokinetics of existing or novel venom-derived peptides. In parallel, after initial studies with polyclonal antibodies demonstrated the technical feasibility of inhibiting channel function with antibodies, multiple preclinical programmes are now using the full spectrum of available technologies to generate conventional monoclonal and engineered antibodies or nanobodies against extracellular loops of ion channels. After a summary of the current state of ion channel drug discovery, this Review discusses recent developments using the purinergic receptor channel P2X purinoceptor 7 (P2X7), the voltage-gated potassium channel KV1.3 and the voltage-gated sodium channel NaV1.7 as examples of targeting ion channels with biologics.
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Affiliation(s)
- Heike Wulff
- Department of Pharmacology, University of California Davis, Davis, CA, USA.
| | | | | | - K George Chandy
- Molecular Physiology Laboratory, Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Vladimir Yarov-Yarovoy
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
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Alonso-Carbajo L, Alpizar YA, Startek JB, López-López JR, Pérez-García MT, Talavera K. Activation of the cation channel TRPM3 in perivascular nerves induces vasodilation of resistance arteries. J Mol Cell Cardiol 2019; 129:219-230. [PMID: 30853321 DOI: 10.1016/j.yjmcc.2019.03.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 03/01/2019] [Accepted: 03/06/2019] [Indexed: 10/27/2022]
Abstract
The Transient Receptor Potential Melastatin 3 (TRPM3) is a Ca2+-permeable non-selective cation channel activated by the neurosteroid pregnenolone sulfate (PS). This compound was previously shown to contract mouse aorta by activating TRPM3 in vascular smooth muscle cells (VSMC), and proposed as therapeutic modulator of vascular functions. However, PS effects and the role of TRPM3 in resistance arteries remain unknown. Thus, we aimed at determining the localization and physiological role of TRPM3 in mouse mesenteric arteries. Real-time qPCR experiments, anatomical localization using immunofluorescence microscopy and patch-clamp recordings in isolated VSMC showed that TRPM3 expression in mesenteric arteries is restricted to perivascular nerves. Pressure myography experiments in wild type (WT) mouse arteries showed that PS vasodilates with a concentration-dependence that was best fit by two Hill components (effective concentrations, EC50, of 14 and 100 μM). The low EC50 component was absent in preparations from Trpm3 knockout (KO) mice and in WT arteries in the presence of the CGRP receptor antagonist BIBN 4096. TRPM3-dependent vasodilation was partially inhibited by a cocktail of K+ channel blockers, and not mediated by β-adrenergic signaling. We conclude that, contrary to what was found in aorta, PS dilates mesenteric arteries, partly via an activation of TRPM3 that triggers CGRP release from perivascular nerve endings and a subsequent activation of K+ channels in VSMC. We propose that TRPM3 is implicated in the regulation of the tone of resistance arteries and that its activation by yet unidentified endogenous damage-associated molecules lead to protective vasodilation responses in mesenteric arteries.
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Affiliation(s)
- Lucía Alonso-Carbajo
- Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49, Campus Gasthuisberg, O&N1 Box 802, 3000 Leuven, Belgium; Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Universidad de Valladolid y CSIC, Sanz y Forés 3, 47003 Valladolid, Spain
| | - Yeranddy A Alpizar
- Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49, Campus Gasthuisberg, O&N1 Box 802, 3000 Leuven, Belgium
| | - Justyna B Startek
- Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49, Campus Gasthuisberg, O&N1 Box 802, 3000 Leuven, Belgium
| | - José Ramón López-López
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Universidad de Valladolid y CSIC, Sanz y Forés 3, 47003 Valladolid, Spain
| | - María Teresa Pérez-García
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Universidad de Valladolid y CSIC, Sanz y Forés 3, 47003 Valladolid, Spain
| | - Karel Talavera
- Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49, Campus Gasthuisberg, O&N1 Box 802, 3000 Leuven, Belgium.
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Kozák L, Szilágyi Z, Tóth L, Pócsi I, Molnár I. Tremorgenic and neurotoxic paspaline-derived indole-diterpenes: biosynthetic diversity, threats and applications. Appl Microbiol Biotechnol 2019; 103:1599-1616. [PMID: 30613899 DOI: 10.1007/s00253-018-09594-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 12/15/2018] [Accepted: 12/20/2018] [Indexed: 12/18/2022]
Abstract
Indole-diterpenes (IDTs) such as the aflatrems, janthitrems, lolitrems, paspalitrems, penitrems, shearinines, sulpinines, and terpendoles are biogenetically related but structurally varied tremorgenic and neurotoxic mycotoxins produced by fungi. All these metabolites derive from the biosynthetic intermediate paspaline, a frequently occurring IDT on its own right. In this comprehensive review, we highlight the similarities and differences of the IDT biosynthetic pathways that lead to the generation of the main paspaline-derived IDT subgroups. We survey the taxonomic distribution and the regulation of IDT production in various fungi and compare the organization of the known IDT biosynthetic gene clusters. A detailed assessment of the highly diverse biological activities of these mycotoxins leads us to emphasize the significant losses that paspaline-derived IDTs cause in agriculture, and compels us to warn about the various hazards they represent towards human and livestock health. Conversely, we also describe the potential utility of these versatile molecules as lead compounds for pharmaceutical drug discovery, and examine the prospects for their industrial scale manufacture in genetically manipulated IDT producers or domesticated host microorganisms in synthetic biological production systems.
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Affiliation(s)
- László Kozák
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
- Teva Pharmaceutical Works Ltd., Debrecen, Hungary
| | | | - László Tóth
- Teva Pharmaceutical Works Ltd., Debrecen, Hungary
| | - István Pócsi
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.
| | - István Molnár
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.
- Southwest Center for Natural Products Research, School of Natural Resources and the Environment, University of Arizona, Tucson, USA.
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58
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Thornbury KD, Hollywood MA, Sergeant GP. Ion Channels and Intracellular Calcium Signalling in Corpus Cavernosum. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:171-194. [PMID: 31183827 DOI: 10.1007/978-981-13-5895-1_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The corpus cavernosum smooth muscle is important for both erection of the penis and for maintaining penile flaccidity. Most of the time, the smooth muscle cells are in a contracted state, which limits filling of the corpus sinuses with blood. Occasionally, however, they relax in a co-ordinated manner, allowing filling to occur. This results in an erection. When contractions of the corpus cavernosum are measured, it can be deduced that the muscle cells work together in a syncytium, for not only do they spontaneously contract in a co-ordinated manner, but they also synchronously relax. It is challenging to understand how they achieve this.In this review we will attempt to explain the activity of the corpus cavernosum, firstly by summarising current knowledge regarding the role of ion channels and how they influence tone, and secondly by presenting data on the intracellular Ca2+ signals that interact with the ion channels. We propose that spontaneous Ca2+ waves act as a primary event, driving transient depolarisation by activating Ca2+-activated Cl- channels. Depolarisation then facilitates Ca2+ influx via L-type voltage-dependent Ca2+ channels. We propose that the spontaneous Ca2+ oscillations depend on Ca2+ release from both ryanodine- and inositol trisphosphate (IP3)-sensitive stores and that modulation by signalling molecules is achieved mainly by interactions with the IP3-sensitive mechanism. This pacemaker mechanism is inhibited by nitric oxide (acting through cyclic GMP) and enhanced by noradrenaline. By understanding these mechanisms better, it might be possible to design new treatments for erectile dysfunction.
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Affiliation(s)
- Keith D Thornbury
- Smooth Muscle Research Centre, Regional Development Centre, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland.
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Regional Development Centre, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Regional Development Centre, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland
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59
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Wang D, Neupane P, Ragnarsson L, Capon RJ, Lewis RJ. Synthesis of Pseudellone Analogs and Characterization as Novel T-type Calcium Channel Blockers. Mar Drugs 2018; 16:md16120475. [PMID: 30487473 PMCID: PMC6315694 DOI: 10.3390/md16120475] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 11/21/2018] [Accepted: 11/26/2018] [Indexed: 11/16/2022] Open
Abstract
T-type calcium channel (CaV3.x) blockers are receiving increasing attention as potential therapeutics for the treatment of pathophysiological disorders and diseases, including absence epilepsy, Parkinson's disease (PD), hypertension, cardiovascular diseases, cancers, and pain. However, few clinically approved CaV3.x blockers are available, and selective pharmacological tools are needed to further unravel the roles of individual CaV3.x subtypes. In this work, through an efficient synthetic route to the marine fungal product pseudellone C, we obtained bisindole alkaloid analogs of pseudellone C with a modified tryptophan moiety and identified two CaV3.2 (2, IC50 = 18.24 µM; 3, IC50 = 6.59 µM) and CaV3.3 (2, IC50 = 7.71 µM; 3, IC50 = 3.81 µM) selective blockers using a FLIPR cell-based assay measuring CaV3.x window currents. Further characterization by whole-cell patch-clamp revealed a preferential block of CaV3.1 activated current (2, IC50 = 5.60 µM; 3, IC50 = 9.91 µM), suggesting their state-dependent block is subtype specific.
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Affiliation(s)
- Dan Wang
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane, Qld 4072, Australia.
| | - Pratik Neupane
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane, Qld 4072, Australia.
| | - Lotten Ragnarsson
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane, Qld 4072, Australia.
| | - Robert J Capon
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane, Qld 4072, Australia.
| | - Richard J Lewis
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane, Qld 4072, Australia.
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60
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O'Donohoe PB, Huskens N, Turner PJ, Pandit JJ, Buckler KJ. A1899, PK-THPP, ML365, and Doxapram inhibit endogenous TASK channels and excite calcium signaling in carotid body type-1 cells. Physiol Rep 2018; 6:e13876. [PMID: 30284397 PMCID: PMC6170881 DOI: 10.14814/phy2.13876] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 08/24/2018] [Indexed: 01/10/2023] Open
Abstract
Sensing of hypoxia and acidosis in arterial chemoreceptors is thought to be mediated through the inhibition of TASK and possibly other (e.g., BKCa ) potassium channels which leads to membrane depolarization, voltage-gated Ca-entry, and neurosecretion. Here, we investigate the effects of pharmacological inhibitors on TASK channel activity and [Ca2+ ]i -signaling in isolated neonatal rat type-1 cells. PK-THPP inhibited TASK channel activity in cell attached patches by up to 90% (at 400 nmol/L). A1899 inhibited TASK channel activity by 35% at 400 nmol/L. PK-THPP, A1899 and Ml 365 all evoked a rapid increase in type-1 cell [Ca2+ ]i . These [Ca2+ ]i responses were abolished in Ca2+ -free solution and greatly attenuated by Ni2+ (2 mM) suggesting that depolarization and voltage-gated Ca2+ -entry mediated the rise in [Ca2+ ]i. Doxapram (50 μmol/L), a respiratory stimulant, also inhibited type-1 cell TASK channel activity and increased [Ca2+ ]i. . We also tested the effects of combined inhibition of BKCa and TASK channels. TEA (5 mmol/L) slightly increased [Ca2+ ]i in the presence of PK-THPP and A1899. Paxilline (300 nM) and iberiotoxin (50 nmol/L) also slightly increased [Ca2+ ]i in the presence of A1899 but not in the presence of PK-THPP. In general [Ca2+ ]i responses to TASK inhibitors, alone or in combination with BKCa inhibitors, were smaller than the [Ca2+ ]i responses evoked by hypoxia. These data confirm that TASK channel inhibition is capable of evoking membrane depolarization and robust voltage-gated Ca2+ -entry but suggest that this, even with concomitant inhibition of BKCa channels, may be insufficient to account fully for the [Ca2+ ]i -response to hypoxia.
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Affiliation(s)
- Peadar B. O'Donohoe
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
- Nuffield Department of AnaestheticsOxford University HospitalsOxfordUnited Kingdom
| | - Nicky Huskens
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
| | - Philip J. Turner
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
| | - Jaideep J. Pandit
- Nuffield Department of AnaestheticsOxford University HospitalsOxfordUnited Kingdom
| | - Keith J. Buckler
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
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Cell Cycle Regulation by Ca 2+-Activated K⁺ (BK) Channels Modulators in SH-SY5Y Neuroblastoma Cells. Int J Mol Sci 2018; 19:ijms19082442. [PMID: 30126198 PMCID: PMC6121591 DOI: 10.3390/ijms19082442] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 08/02/2018] [Accepted: 08/13/2018] [Indexed: 12/28/2022] Open
Abstract
The effects of Ca2+-activated K+ (BK) channel modulation by Paxilline (PAX) (10−7–10−4 M), Iberiotoxin (IbTX) (0.1–1 × 10−6 M) and Resveratrol (RESV) (1–2 × 10−4 M) on cell cycle and proliferation, AKT1pSer473 phosphorylation, cell diameter, and BK currents were investigated in SH-SY5Y cells using Operetta-high-content-Imaging-System, ELISA-assay, impedentiometric counting method and patch-clamp technique, respectively. IbTX (4 × 10−7 M), PAX (5 × 10−5 M) and RESV (10−4 M) caused a maximal decrease of the outward K+ current at +30 mV (Vm) of −38.3 ± 10%, −31.9 ± 9% and −43 ± 8%, respectively, which was not reversible following washout and cell depolarization. After 6h of incubation, the drugs concentration dependently reduced proliferation. A maximal reduction of cell proliferation, respectively of −60 ± 8% for RESV (2 × 10−4 M) (IC50 = 1.50 × 10−4 M), −65 ± 6% for IbTX (10−6 M) (IC50 = 5 × 10−7 M), −97 ± 6% for PAX (1 × 10−4 M) (IC50 = 1.06 × 10−5 M) and AKT1pser473 dephosphorylation was observed. PAX induced a G1/G2 accumulation and contraction of the S-phase, reducing the nuclear area and cell diameter. IbTX induced G1 contraction and G2 accumulation reducing diameter. RESV induced G2 accumulation and S contraction reducing diameter. These drugs share common actions leading to a block of the surface membrane BK channels with cell depolarization and calcium influx, AKT1pser473 dephosphorylation by calcium-dependent phosphatase, accumulation in the G2 phase, and a reduction of diameter and proliferation. In addition, the PAX action against nuclear membrane BK channels potentiates its antiproliferative effects with early apoptosis.
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Putative neuromycotoxicoses in an adult male following ingestion of moldy walnuts. Mycotoxin Res 2018; 35:9-16. [PMID: 30088215 DOI: 10.1007/s12550-018-0326-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 07/19/2018] [Accepted: 08/02/2018] [Indexed: 01/21/2023]
Abstract
A tremorgenic syndrome occurs in dogs following ingestion of moldy walnuts, and Penicillium crustosum has been implicated as the offending fungus. This is the first report of suspected moldy walnut toxicosis in man. An adult male ingested approximately eight fungal-infected walnut kernels and after 12 h experienced tremors, generalized pain, incoordination, confusion, anxiety, and diaphoresis. Following symptomatic and supportive treatment at a local hospital, the man made an uneventful recovery. A batch of walnuts (approximately 20) was submitted for mycological culturing and identification as well as for mycotoxin analysis. Penicillium crustosum Thom was the most abundant fungus present on walnut samples, often occurring as monocultures on isolation plates. Identifications were confirmed with DNA sequences. The kernels and shells of the moldy walnuts as well as P. crustosum isolates plated on yeast extract sucrose (YES) and Czapek yeast autolysate (CYA) agars and incubated in the dark at 25 °C for 7 days were screened for tremorgenic mycotoxins and known P. crustosum metabolites using a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method. A relatively low penitrem A concentration of only 1.9 ng/g was detected on the walnut kernels when compared to roquefortine C concentrations of 21.7 μg/g. A similar result was obtained from P. crustosum isolates cultured on YES and CYA, with penitrem A concentrations much lower (0.6-6.4 μg per g mycelium/agar) compared to roquefortine C concentrations (172-1225 μg/g). The authors surmised that besides penitrem A, roquefortine C might also play an additive or synergistic role in intoxication of man.
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Goda AA, Siddique AB, Mohyeldin M, Ayoub NM, El Sayed KA. The Maxi-K (BK) Channel Antagonist Penitrem A as a Novel Breast Cancer-Targeted Therapeutic. Mar Drugs 2018; 16:md16050157. [PMID: 29751615 PMCID: PMC5983288 DOI: 10.3390/md16050157] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 05/06/2018] [Accepted: 05/09/2018] [Indexed: 12/24/2022] Open
Abstract
Breast cancer (BC) is a heterogeneous disease with different molecular subtypes. The high conductance calcium-activated potassium channels (BK, Maxi-K channels) play an important role in the survival of some BC phenotypes, via membrane hyperpolarization and regulation of cell cycle. BK channels have been implicated in BC cell proliferation and invasion. Penitrems are indole diterpene alkaloids produced by various terrestrial and marine Penicillium species. Penitrem A (1) is a selective BK channel antagonist with reported antiproliferative and anti-invasive activities against multiple malignancies, including BC. This study reports the high expression of BK channel in different BC subtypes. In silico BK channel binding affinity correlates with the antiproliferative activities of selected penitrem analogs. 1 showed the best binding fitting at multiple BK channel crystal structures, targeting the calcium-sensing aspartic acid moieties at the calcium bowel and calcium binding sites. Further, 1 reduced the levels of BK channel expression and increased expression of TNF-α in different BC cell types. Penitrem A (1) induced G1 cell cycle arrest of BC cells, and induced upregulation of the arrest protein p27. Combination treatment of 1 with targeted anti-HER drugs resulted in synergistic antiproliferative activity, which was associated with reduced EGFR and HER2 receptor activation, as well as reduced active forms of AKT and STAT3. Collectively, the BK channel antagonists represented by penitrem A can be novel sensitizing, chemotherapeutics synergizing, and therapeutic agents for targeted BC therapy.
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Affiliation(s)
- Amira A Goda
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
| | - Abu Bakar Siddique
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
| | - Mohamed Mohyeldin
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
- Department of Pharmacognosy, Faculty of Pharmacy, Alexandria University, Alexandria 21521, Egypt.
| | - Nehad M Ayoub
- Department of Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
| | - Khalid A El Sayed
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
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Bauer JI, Gross M, Hamscher G, Usleber E. A Rapid Screening Method for the Tremorgenic Indole-Diterpene Alkaloid Mycotoxin Paxilline in Beer. FOOD ANAL METHOD 2018. [DOI: 10.1007/s12161-017-1085-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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65
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Olver TD, Edwards JC, Ferguson BS, Hiemstra JA, Thorne PK, Hill MA, Laughlin MH, Emter CA. Chronic interval exercise training prevents BK Ca channel-mediated coronary vascular dysfunction in aortic-banded miniswine. J Appl Physiol (1985) 2018; 125:86-96. [PMID: 29596016 DOI: 10.1152/japplphysiol.01138.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Conventional treatments have failed to improve the prognosis of heart failure with preserved ejection fraction (HFpEF) patients. Thus, the purpose of this study was to determine the therapeutic efficacy of chronic interval exercise training (IT) on large-conductance Ca2+-activated K+ (BKCa) channel-mediated coronary vascular function in heart failure. We hypothesized that chronic interval exercise training would attenuate pressure overload-induced impairments to coronary BKCa channel-mediated function. A translational large-animal model with cardiac features of HFpEF was used to test this hypothesis. Specifically, male Yucatan miniswine were divided into three groups ( n = 7/group): control (CON), aortic banded (AB)-heart failure (HF), and AB-interval trained (HF-IT). Coronary blood flow, vascular conductance, and vasodilatory capacity were measured after administration of the BKCa channel agonist NS-1619 both in vivo and in vitro in the left anterior descending coronary artery and isolated coronary arterioles, respectively. Skeletal muscle citrate synthase activity was decreased and left ventricular brain natriuretic peptide levels increased in HF vs. CON and HF-IT animals. A parallel decrease in NS-1619-dependent coronary vasodilatory reserve in vivo and isolated coronary arteriole vasodilatory responsiveness in vitro were observed in HF animals compared with CON, which was prevented in the HF-IT group. Although exercise training prevented BKCa channel-mediated coronary vascular dysfunction, it did not change BKCa channel α-subunit mRNA, protein, or cellular location (i.e., membrane vs. cytoplasm). In conclusion, these results demonstrate the viability of chronic interval exercise training as a therapy for central and peripheral adaptations of experimental heart failure, including BKCa channel-mediated coronary vascular dysfunction. NEW & NOTEWORTHY Conventional treatments have failed to improve the prognosis of heart failure with preserved ejection fraction (HFpEF) patients. Our findings show that chronic interval exercise training can prevent BKCa channel-mediated coronary vascular dysfunction in a translational swine model of chronic pressure overload-induced heart failure with relevance to human HFpEF.
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Affiliation(s)
- T Dylan Olver
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri
| | - Jenna C Edwards
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri
| | - Brian S Ferguson
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri
| | - Jessica A Hiemstra
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri
| | - Pamela K Thorne
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri
| | - Michael A Hill
- Dalton Cardiovascular Research Center, University of Missouri-Columbia , Columbia, Missouri.,Department of Medical Pharmacology and Physiology, University of Missouri-Columbia , Columbia, Missouri
| | - M Harold Laughlin
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri-Columbia , Columbia, Missouri.,Department of Medical Pharmacology and Physiology, University of Missouri-Columbia , Columbia, Missouri
| | - Craig A Emter
- Department of Biomedical Sciences, University of Missouri-Columbia , Columbia, Missouri
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66
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Eid BG, Gurney AM. Zinc pyrithione activates K+ channels and hyperpolarizes the membrane of rat pulmonary artery smooth muscle cells. PLoS One 2018; 13:e0192699. [PMID: 29474372 PMCID: PMC5824988 DOI: 10.1371/journal.pone.0192699] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 01/29/2018] [Indexed: 01/09/2023] Open
Abstract
The membrane potential helps determine pulmonary artery smooth muscle cell (PASMC) contraction. The Kv7 channel activators, retigabine and flupirtine, are thought to dilate pulmonary arteries by hyperpolarising PASMC. Zinc pyrithione activates Kv7 channels by a mechanism distinct from retigabine and with different Kv7 subunit selectivity. This study aimed to determine if zinc pyrithione selectively activates Kv7 channels in rat PASMC to evoke pulmonary artery dilation. Zinc pyrithione relaxed pulmonary arteries with half-maximal effect at 4.3μM. At 10μM it activated pronounced voltage-dependent K+ current and hyperpolarized PASMCs by around 10mV. Tetraethylammonium ions (TEA, 10mM) and paxilline (1μM) abolished both the current and hyperpolarisation. XE991 (10μM) blocked the hyperpolarization and reduced the current by 30%. Iberiotoxin (50nM) had no effect on the hyperpolarisation, but reduced the current by 40%. The XE991-sensitive current activated with an exponential time course (time constant 17ms), whereas the iberiotoxin-sensitive current followed a bi-exponential time course (time constants 6 and 57ms), suggesting that the drugs blocked different components of the zinc pyrithione-induced current. Zinc pyrithione therefore appears to activate at least two types of K+ channel in PASMC; an XE991, TEA and paxilline-sensitive Kv7 channel and a TEA, paxilline and iberiotoxin-sensitive BKCa channel. Both could contribute to the relaxing effect of zinc pyrithione on pulmonary artery.
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Affiliation(s)
- Basma G. Eid
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Alison M. Gurney
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
- * E-mail:
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Abstract
The first enantioselective total synthesis of (-)-petromindole, an architecturally distinct congener of indole diterpene family, has been achieved. Key features of this synthetic route include the scalable and concise synthesis of tricyclic allylic alcohol from enantiopure Wieland-Mischer ketone derivative, and TMSOTf-mediated, highly efficient biomimetic C-4 cyclization of indole derivative for the rapid construction of a hexacyclic skeleton of petromindole.
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Affiliation(s)
- Dattatraya H Dethe
- Department of Chemistry, Indian Institute of Technology Kanpur , Kanpur-208016, India
| | - Susanta Kumar Sau
- Department of Chemistry, Indian Institute of Technology Kanpur , Kanpur-208016, India
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Mitochondrial BK Channel Openers CGS7181 and CGS7184 Exhibit Cytotoxic Properties. Int J Mol Sci 2018; 19:ijms19020353. [PMID: 29370072 PMCID: PMC5855575 DOI: 10.3390/ijms19020353] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 01/15/2018] [Accepted: 01/22/2018] [Indexed: 02/08/2023] Open
Abstract
Potassium channel openers (KCOs) have been shown to play a role in cytoprotection through the activation of mitochondrial potassium channels. Recently, in several reports, a number of data has been described as off-target actions for KCOs. In the present study, we investigated the effects of BKCa channel openers CGS7181, CGS7184, NS1619, and NS004 in neuronal cells. For the purpose of this research, we used a rat brain, the mouse hippocampal HT22 cells, and the human astrocytoma U-87 MG cell line. We showed that CGS7184 activated the mitochondrial BKCa (mitoBKCa) channel in single-channel recordings performed on astrocytoma mitoplasts. Moreover, when applied to the rat brain homogenate or isolated rat brain mitochondria, CGS7184 increased the oxygen consumption rate, and can thus be considered a potentially cytoprotective agent. However, experiments on intact neuronal HT22 cells revealed that both CGS7181 and CGS7184 induced HT22 cell death in a concentration- and time-dependent manner. By contrast, we did not observe cell death when NS1619 or NS004 was applied. CGS7184 toxicity was not abolished by BKCa channel inhibitors, suggesting that the observed effects were independent of a BKCa-type channel activity. CGS7184 treatment resulted in an increase of cytoplasmic Ca2+ concentration that likely involved efflux from internal calcium stores and the activation of calpains (calcium-dependent proteases). The cytotoxic effect of the channel opener was partially reversed by a calpain inhibitor. Our data show that KCOs under study not only activate mitoBKCa channels from brain tissue, but also induce cell death when used in cellular models.
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Van de Bittner KC, Nicholson MJ, Bustamante LY, Kessans SA, Ram A, van Dolleweerd CJ, Scott B, Parker EJ. Heterologous Biosynthesis of Nodulisporic Acid F. J Am Chem Soc 2018; 140:582-585. [DOI: 10.1021/jacs.7b10909] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Kyle C. Van de Bittner
- Ferrier
Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
- Biomolecular
Interaction Centre, University of Canterbury, 20 Kirkwood Avenue, Christchurch 8041, New Zealand
| | - Matthew J. Nicholson
- Ferrier
Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
- Biomolecular
Interaction Centre, University of Canterbury, 20 Kirkwood Avenue, Christchurch 8041, New Zealand
| | - Leyla Y. Bustamante
- Ferrier
Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
- Biomolecular
Interaction Centre, University of Canterbury, 20 Kirkwood Avenue, Christchurch 8041, New Zealand
| | - Sarah A. Kessans
- Biomolecular
Interaction Centre, University of Canterbury, 20 Kirkwood Avenue, Christchurch 8041, New Zealand
| | - Arvina Ram
- Institute
of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand
| | - Craig J. van Dolleweerd
- Protein Science & Engineering, Callaghan Innovation, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
| | - Barry Scott
- Institute
of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand
| | - Emily J. Parker
- Ferrier
Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
- Biomolecular
Interaction Centre, University of Canterbury, 20 Kirkwood Avenue, Christchurch 8041, New Zealand
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70
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BK K+ channel blockade inhibits radiation-induced migration/brain infiltration of glioblastoma cells. Oncotarget 2017; 7:14259-78. [PMID: 26893360 PMCID: PMC4924713 DOI: 10.18632/oncotarget.7423] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 01/29/2016] [Indexed: 12/14/2022] Open
Abstract
Infiltration of the brain by glioblastoma cells reportedly requires Ca2+ signals and BK K+ channels that program and drive glioblastoma cell migration, respectively. Ionizing radiation (IR) has been shown to induce expression of the chemokine SDF-1, to alter the Ca2+ signaling, and to stimulate cell migration of glioblastoma cells. Here, we quantified fractionated IR-induced migration/brain infiltration of human glioblastoma cells in vitro and in an orthotopic mouse model and analyzed the role of SDF-1/CXCR4 signaling and BK channels. To this end, the radiation-induced migratory phenotypes of human T98G and far-red fluorescent U-87MG-Katushka glioblastoma cells were characterized by mRNA and protein expression, fura-2 Ca2+ imaging, BK patch-clamp recording and transfilter migration assay. In addition, U-87MG-Katushka cells were grown to solid glioblastomas in the right hemispheres of immunocompromised mice, fractionated irradiated (6 MV photons) with 5 × 0 or 5 × 2 Gy, and SDF-1, CXCR4, and BK protein expression by the tumor as well as glioblastoma brain infiltration was analyzed in dependence on BK channel targeting by systemic paxilline application concomitant to IR. As a result, IR stimulated SDF-1 signaling and induced migration of glioblastoma cells in vitro and in vivo. Importantly, paxilline blocked IR-induced migration in vivo. Collectively, our data demonstrate that fractionated IR of glioblastoma stimulates and BK K+ channel targeting mitigates migration and brain infiltration of glioblastoma cells in vivo. This suggests that BK channel targeting might represent a novel approach to overcome radiation-induced spreading of malignant brain tumors during radiotherapy.
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Berntsen HF, Bogen IL, Wigestrand MB, Fonnum F, Walaas SI, Moldes-Anaya A. The fungal neurotoxin penitrem A induces the production of reactive oxygen species in human neutrophils at submicromolar concentrations. Toxicology 2017; 392:64-70. [PMID: 29037868 DOI: 10.1016/j.tox.2017.10.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 10/05/2017] [Accepted: 10/12/2017] [Indexed: 11/24/2022]
Abstract
Penitrem A is a fungal neurotoxin that recurrently causes intoxication in animals, and occasionally also in humans. We have previously reported that penitrem A induced the production of reactive oxygen species (ROS) in rat cerebellar granule cells, opening for a new mechanism of action for the neurotoxin. The aim of this study was to examine the potential of penitrem A to induce ROS production in isolated human neutrophil granulocytes, and to study possible mechanisms involved. Penitrem A significantly increased the production of ROS in human neutrophils at concentrations as low as 0.25μM (40% increase over basal levels), as measured with the DCF fluorescence assay. The EC50 determined for the production of ROS by penitrem A was 3.8μM. The maximal increase in ROS production was approximately 330% over basal levels at a concentration of 12.5μM. ROS formation was significantly inhibited by the antioxidant vitamin E (50μM), the intracellular Ca+2 chelator BAPTA-AM (5μM), the mitogen activated protein kinase kinase (MEK) 1/2 and 5 inhibitor U0126 (1 and 10μM), the p38 mitogen activated protein kinase (MAPK) inhibitor SB203580 (1μM), the c-Jun amino-terminal kinase (JNK) inhibitor SP600125 (10μM), and the calcineurin inhibitors FK-506 and cyclosporine A (1.5 and 0.5μM, respectively). These finding suggest that penitrem A is able to induce an increase in ROS production in neutrophils via the activation of several MAPK-signalling pathways. We suggest that this increase may partly explain the pathophysiology generated by penitrem A neuromycotoxicosis in both humans and animals.
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Affiliation(s)
- H F Berntsen
- Department of Administration, Lab Animal Unit, National Institute of Occupational Health, P.O. Box 8149 Dep, 0033 Oslo, Norway
| | - I L Bogen
- Oslo University Hospital, Department of Forensic Sciences, Section of Drug Abuse Research, P.O. Box 4950 Nydalen, N-0424 Oslo, Norway
| | - M B Wigestrand
- Institute of Basic Medical Sciences, Department of Biochemistry, University of Oslo, P.O. Box 1112 Blindern, N-0317 Oslo, Norway
| | - F Fonnum
- Institute of Basic Medical Sciences, Department of Biochemistry, University of Oslo, P.O. Box 1112 Blindern, N-0317 Oslo, Norway
| | - S I Walaas
- Institute of Basic Medical Sciences, Department of Biochemistry, University of Oslo, P.O. Box 1112 Blindern, N-0317 Oslo, Norway
| | - A Moldes-Anaya
- Section of Chemistry and Toxicology, Norwegian Veterinary Institute, P.O. Box 750 Sentrum, N-0106 Oslo, Norway; R&D Section, PET-center, University Hospital of North Norway (UNN), P.O. Box 100 Langnes, N-9038 Tromsø, Norway.
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Corsello MA, Kim J, Garg NK. Indole diterpenoid natural products as the inspiration for new synthetic methods and strategies. Chem Sci 2017; 8:5836-5844. [PMID: 28970940 PMCID: PMC5618777 DOI: 10.1039/c7sc01248a] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Accepted: 06/15/2017] [Indexed: 12/21/2022] Open
Abstract
Indole terpenoids comprise a large class of natural products with diverse structural topologies and a broad range of biological activities. Accordingly, indole terpenoids have and continue to serve as attractive targets for chemical synthesis. Many synthetic efforts over the past few years have focused on a subclass of this family, the indole diterpenoids. This minireview showcases the role indole diterpenoids have played in inspiring the recent development of clever synthetic strategies, and new chemical reactions.
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Affiliation(s)
- Michael A Corsello
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095 , USA .
| | - Junyong Kim
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095 , USA .
| | - Neil K Garg
- Department of Chemistry and Biochemistry , University of California , Los Angeles , California 90095 , USA .
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Krabbendam IE, Honrath B, Culmsee C, Dolga AM. Mitochondrial Ca 2+-activated K + channels and their role in cell life and death pathways. Cell Calcium 2017; 69:101-111. [PMID: 28818302 DOI: 10.1016/j.ceca.2017.07.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Revised: 07/14/2017] [Accepted: 07/14/2017] [Indexed: 12/18/2022]
Abstract
Ca2+-activated K+ channels (KCa) are expressed at the plasma membrane and in cellular organelles. Expression of all KCa channel subtypes (BK, IK and SK) has been detected at the inner mitochondrial membrane of several cell types. Primary functions of these mitochondrial KCa channels include the regulation of mitochondrial ROS production, maintenance of the mitochondrial membrane potential and preservation of mitochondrial calcium homeostasis. These channels are therefore thought to contribute to cellular protection against oxidative stress through mitochondrial mechanisms of preconditioning. In this review, we summarize the current knowledge on mitochondrial KCa channels, and their role in mitochondrial function in relation to cell death and survival pathways. More specifically, we systematically discuss studies on the role of these mitochondrial KCa channels in pharmacological preconditioning, and according protective effects on ischemic insults to the brain and the heart.
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Affiliation(s)
- Inge E Krabbendam
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands.
| | - Birgit Honrath
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands; Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany.
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany.
| | - Amalia M Dolga
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands.
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Detection of the tremorgenic mycotoxin paxilline and its desoxy analog in ergot of rye and barley: a new class of mycotoxins added to an old problem. Anal Bioanal Chem 2017; 409:5101-5112. [DOI: 10.1007/s00216-017-0455-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/22/2017] [Accepted: 06/07/2017] [Indexed: 10/19/2022]
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Influence of Environmental Factors on the Production of Penitrems A-F by Penicillium crustosum. Toxins (Basel) 2017; 9:toxins9070210. [PMID: 28671569 PMCID: PMC5535157 DOI: 10.3390/toxins9070210] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 06/15/2017] [Accepted: 06/29/2017] [Indexed: 11/17/2022] Open
Abstract
Filamentous fungi produce a multitude of secondary metabolites, some of them known as mycotoxins, which are toxic to vertebrates and other animal groups in low concentrations. Among them, penitrems, which belong to the group of indole-diterpene mycotoxins, are synthesized by Penicillium and Aspergillus genera and exhibit potent tremorgenic effects. This is the first complex study of the penitrems A-F production under the influence of different abiotic factors, e.g., media, incubation time, temperature, pH, light, water activity, and carbon and nitrogen source as well as oxidative and salt stress. For this purpose, penitrems A-F were isolated from Penicillium crustosum cultures and used as analytical standards. Among the carbon sources, glucose supplemented to the media at the concentration of 50 g/L, showed the strongest inducing effect on the biosynthesis of penitrems. Among nitrogen sources, glutamate was found to be the most favorable supplement, significantly increasing production of these secondary metabolites. CuSO4-promoted oxidative stress was also shown to remarkably stimulate biosynthesis of all penitrems. In contrast, the salt stress, caused by the elevated concentrations of NaCl, showed an inhibitory effect on the penitrem biosynthesis. Finally, cheese model medium elicited exceptionally high production of all members of the penitrems family. Obtained results give insides into the biosynthesis of toxicologically relevant penitrems A-F under different environmental factors and can be utilized to prevent food contamination.
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Abstract
Over the past few years Penicillium brasilianum has been isolated from many different environmental sources as soil isolates, plant endophytes and onion pathogen. All investigated strains share a great ability to produce bioactive secondary metabolites. Different authors have investigated this great capability and here we summarize the metabolic potential and the biological activities related to P. brasilianum’s metabolites with diverse structures. They include secondary metabolites of an alkaloid nature, i.e., 2,5-diketopiperazines, cyclodepsipeptides, meroterpenoids and polyketides. Penicillium brasilianum is also described as a great source of enzymes with biotechnological application potential, which is also highlighted in this review. Additionally, this review will focus on several aspects of Penicillium brasilianum and interesting genomic insights.
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77
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Mullan B, Pettis J, Jackson WF. T-type voltage-gated Ca 2+ channels do not contribute to the negative feedback regulation of myogenic tone in murine superior epigastric arteries. Pharmacol Res Perspect 2017; 5:e00320. [PMID: 28603637 PMCID: PMC5464347 DOI: 10.1002/prp2.320] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 04/06/2017] [Accepted: 04/10/2017] [Indexed: 11/09/2022] Open
Abstract
T-type voltage-gated Ca2+ channels (CaV3.2 VGCC) have been hypothesized to control spontaneous transient outward currents (STOCs) through large-conductance Ca2+-activated K+ channels (BKCa), and contribute to the negative-feedback regulation of myogenic tone. We tested this hypothesis in superior epigastric arteries (SEAs) isolated from male C57BL/6 mice. SEAs were isolated and enzymatically dissociated to obtain single smooth muscle cells (SMCs) for whole-cell recording of paxilline-sensitive (PAX, 1 μmol/L) STOCs at -30 mV, or cannulated and studied by pressure myography (80 cm H2O, 37°C). The CaV3.2 blocker Ni2+ (30 μmol/L) had no effect on STOC amplitude (20.1 ± 1.7 pA vs. 20.6 ± 1.7 pA; n = 12, P = 0.6), but increased STOC frequency (0.79 ± 0.15 Hz vs. 1.21 ± 0.22 Hz; n = 12, P = 0.02). Although Ni2+ produced concentration-dependent constriction of isolated, pressurized SEAs (logEC50 = -5.8 ± 0.09; Emax = 72 ± 5% constriction), block of BKCa with PAX had no effect on vasoconstriction induced by 30 μmol/L Ni2+ (in the absence of PAX = 66 ± 4% constriction vs. in the presence of 1 μmol/L PAX = 65 ± 4% constriction; n = 7, P = 0.06). In contrast to Ni2+, the nonselective T-type blocker, mibefradil, produced only vasodilation (logEC50 = -6.9 ± 0.2; Emax = 74 ± 8% dilation), whereas the putative T-type blocker, ML218, had no significant effect on myogenic tone between 10 nmol/L and 10 μmol/L (n = 6-7, P = 0.59). Our data do not support a role for CaV3.2 VGCC in the negative-feedback regulation of myogenic tone in murine SEAs and suggest that Ni2+ may constrict SEAs by means other than block of CaV3.2 VGCC.
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Affiliation(s)
- Brendan Mullan
- Department of Pharmacology and ToxicologyMichigan State UniversityEast LansingMichigan48824
| | - Jessica Pettis
- Department of Pharmacology and ToxicologyMichigan State UniversityEast LansingMichigan48824
| | - William F. Jackson
- Department of Pharmacology and ToxicologyMichigan State UniversityEast LansingMichigan48824
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Hu XY, Meng LH, Li X, Yang SQ, Li XM, Wang BG. Three New Indole Diterpenoids from the Sea-Anemone-Derived Fungus Penicillium sp. AS-79. Mar Drugs 2017; 15:E137. [PMID: 28498358 PMCID: PMC5450543 DOI: 10.3390/md15050137] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 03/24/2017] [Accepted: 05/10/2017] [Indexed: 11/17/2022] Open
Abstract
Three new indolediterpenoids, namely, 22-hydroxylshearinine F (1), 6-hydroxylpaspalinine (2), and 7-O-acetylemindole SB (3), along with eight related known analogs (4-11), were isolated from the sea-anemone-derived fungus Penicillium sp. AS-79. The structures and relative configurations of these compounds were determined by a detailed interpretation of the spectroscopic data, and their absolute configurations were determined by ECD calculations (1 and 2) and single-crystal X-ray diffraction (3). Some of these compounds exhibited prominent activity against aquatic and human pathogenic microbes.
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Affiliation(s)
- Xue-Yi Hu
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road 7, Qingdao 266071, China.
- College of Earth Science, University of Chinese Academy of Sciences, Yuquan Road 19A, Beijing 100049, China.
| | - Ling-Hong Meng
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road 7, Qingdao 266071, China.
| | - Xin Li
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road 7, Qingdao 266071, China.
| | - Sui-Qun Yang
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road 7, Qingdao 266071, China.
- College of Earth Science, University of Chinese Academy of Sciences, Yuquan Road 19A, Beijing 100049, China.
| | - Xiao-Ming Li
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road 7, Qingdao 266071, China.
| | - Bin-Gui Wang
- Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road 7, Qingdao 266071, China.
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79
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Gebremedhin D, Zhang DX, Weihrauch D, Uche NN, Harder DR. Detection of TRPV4 channel current-like activity in Fawn Hooded hypertensive (FHH) rat cerebral arterial muscle cells. PLoS One 2017; 12:e0176796. [PMID: 28472069 PMCID: PMC5417564 DOI: 10.1371/journal.pone.0176796] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 04/17/2017] [Indexed: 11/18/2022] Open
Abstract
The transient receptor potential vallinoid type 4 (TRPV4) is a calcium entry channel known to modulate vascular function by mediating endothelium–dependent vasodilation. The present study investigated if isolated cerebral arterial myocytes of the Fawn Hooded hypertensive (FHH) rat, known to display exaggerated KCa channel current activity and impaired myogenic tone, express TRPV4 channels at the transcript and protein level and exhibit TRPV4-like single-channel cationic current activity. Reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunostaining analysis detected the expression of mRNA transcript and translated protein of TRPV4 channel in FHH rat cerebral arterial myocytes. Patch clamp recording of single-channel current activity identified the presence of a single-channel cationic current with unitary conductance of ~85 pS and ~96 pS at hyperpolarizing and depolarizing potentials, respectively, that was inhibited by the TRPV4 channel antagonist RN 1734 or HC 067074 and activated by the potent TRPV4 channel agonist GSK1016790A. Application of negative pressure via the interior of the patch pipette increased the NPo of the TRPV4-like single-channel cationic current recorded in cell-attached patches at a patch potential of 60 mV that was inhibited by prior application of the TRPV4 channel antagonist RN 1734 or HC 067047. Treatment with the TRPV4 channel agonist GSK1016790A caused concentration-dependent increase in the NPo of KCa single-channel current recorded in cell-attached patches of cerebral arterial myocytes at a patch potential of 40 mV, which was not influenced by pretreatment with the voltage-gated L-type Ca2+ channel blocker nifedipine or the T-type Ca2+ channel blocker Ni2+. These findings demonstrate that FHH rat cerebral arterial myocytes express mRNA transcript and translated protein for TRPV4 channel and display TRPV4-like single-channel cationic current activity that was stretch-sensitive and activation of which increased the open state probability of KCa single-channel current in these arterial myocytes.
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Affiliation(s)
- Debebe Gebremedhin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- * E-mail:
| | - David X. Zhang
- Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Medicine and, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Dorothee Weihrauch
- Department of Anesthesiology Medical College of Wisconsin, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Nnamdi N. Uche
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - David R. Harder
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement Zablocki VA Medical Center, Milwaukee, Wisconsin, United States of America
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80
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Liu T, Meyer SLF, Chitwood DJ, Chauhan KR, Dong D, Zhang T, Li J, Liu WC. New Nematotoxic Indoloditerpenoid Produced by Gymnoascus reessii za-130. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:3127-3132. [PMID: 28343383 DOI: 10.1021/acs.jafc.6b04353] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Chemical investigation of the fungal strain Gymnoascus reessii za-130, which was previously isolated from the rhizosphere of tomato plants infected by the root-knot nematode Meloidogyne incognita, led to the isolation and identification of a new indoloditerpenoid metabolite designated gymnoascole acetate. Its structure was established by spectroscopic methods including 1D- and 2D-NMR and MS analyses. Gymnoascole acetate demonstrated strong adverse effects on M. incognita second-stage juvenile (J2) viability; exposure to 36 μg/mL for 24 h induced 100% paralysis of J2 (EC50 = 47.5 μg/mL). Gymnoascole acetate suppressed M. incognita egg hatch relative to controls by >90% at 133 μg/mL after 7 days of exposure. The numbers of root galls and J2 in both soil and roots were significantly reduced (p = 0.05) by treatment with 2-200 μg/mL gymnoascole acetate/kg soil, compared to untreated control plants; nematode suppression increased with gymnoascole acetate concentration. This study demonstrated the nematotoxicity of gymnoascole acetate and indicates that it might be a potential biobased component in integrated management of M. incognita.
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Affiliation(s)
- Ting Liu
- Institute of Plant and Environmental Protection, Beijing Academy of Agricultural and Forestry Science , Beijing 100097, China
| | - Susan L F Meyer
- Mycology and Nematology Genetic Diversity and Biology Laboratory, Agricultural Research Service, U.S. Department of Agriculture , Building 010A, 10300 Baltimore Avenue, Beltsville, Maryland 20705, United States
| | - David J Chitwood
- Mycology and Nematology Genetic Diversity and Biology Laboratory, Agricultural Research Service, U.S. Department of Agriculture , Building 010A, 10300 Baltimore Avenue, Beltsville, Maryland 20705, United States
| | - Kamlesh R Chauhan
- Invasive Insect Biocontrol and Behavior Laboratory, Agricultural Research Service, U.S. Department of Agriculture , Building 007, 10300 Baltimore Avenue, Beltsville, Maryland 20705, United States
| | - Dan Dong
- Institute of Plant and Environmental Protection, Beijing Academy of Agricultural and Forestry Science , Beijing 100097, China
| | - TaoTao Zhang
- Institute of Plant and Environmental Protection, Beijing Academy of Agricultural and Forestry Science , Beijing 100097, China
| | - Jun Li
- Modern Research Center for Traditional Chinese Medicine, Beijing University of Chinese Medicine , Beijing 100029, China
| | - Wei-Cheng Liu
- Institute of Plant and Environmental Protection, Beijing Academy of Agricultural and Forestry Science , Beijing 100097, China
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81
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Nguyen HM, Blomster LV, Christophersen P, Wulff H. Potassium channel expression and function in microglia: Plasticity and possible species variations. Channels (Austin) 2017; 11:305-315. [PMID: 28277939 DOI: 10.1080/19336950.2017.1300738] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Potassium channels play important roles in microglia functions and thus constitute potential targets for the treatment of neurodegenerative diseases like Alzheimer, Parkinson and stroke. However, uncertainty still prevails as to which potassium channels are expressed and at what levels in different species, how the expression pattern changes upon activation with M1 or M2 polarizing stimuli compared with more complex exposure paradigms, and - most importantly - how these findings relate to the in vivo situation. In this mini-review we discuss the functional potassium channel expression pattern in cultured neonatal mouse microglia in the light of data obtained previously from animal disease models and immunohistochemical studies and compare it with a recent study of adult human microglia isolated from epilepsy patients. Overall, microglial potassium channel expression is very plastic and possibly shows species differences and therefore should be studied carefully in each disease setting and respective animal models.
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Affiliation(s)
- Hai M Nguyen
- a Department of Pharmacology , University of California , Davis, Davis , CA , USA
| | | | | | - Heike Wulff
- a Department of Pharmacology , University of California , Davis, Davis , CA , USA
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82
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Latorre R, Castillo K, Carrasquel-Ursulaez W, Sepulveda RV, Gonzalez-Nilo F, Gonzalez C, Alvarez O. Molecular Determinants of BK Channel Functional Diversity and Functioning. Physiol Rev 2017; 97:39-87. [DOI: 10.1152/physrev.00001.2016] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Large-conductance Ca2+- and voltage-activated K+ (BK) channels play many physiological roles ranging from the maintenance of smooth muscle tone to hearing and neurosecretion. BK channels are tetramers in which the pore-forming α subunit is coded by a single gene ( Slowpoke, KCNMA1). In this review, we first highlight the physiological importance of this ubiquitous channel, emphasizing the role that BK channels play in different channelopathies. We next discuss the modular nature of BK channel-forming protein, in which the different modules (the voltage sensor and the Ca2+ binding sites) communicate with the pore gates allosterically. In this regard, we review in detail the allosteric models proposed to explain channel activation and how the models are related to channel structure. Considering their extremely large conductance and unique selectivity to K+, we also offer an account of how these two apparently paradoxical characteristics can be understood consistently in unison, and what we have learned about the conduction system and the activation gates using ions, blockers, and toxins. Attention is paid here to the molecular nature of the voltage sensor and the Ca2+ binding sites that are located in a gating ring of known crystal structure and constituted by four COOH termini. Despite the fact that BK channels are coded by a single gene, diversity is obtained by means of alternative splicing and modulatory β and γ subunits. We finish this review by describing how the association of the α subunit with β or with γ subunits can change the BK channel phenotype and pharmacology.
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Affiliation(s)
- Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Romina V. Sepulveda
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Fernando Gonzalez-Nilo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Carlos Gonzalez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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83
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Augustynek B, Kunz WS, Szewczyk A. Guide to the Pharmacology of Mitochondrial Potassium Channels. Handb Exp Pharmacol 2017; 240:103-127. [PMID: 27838853 DOI: 10.1007/164_2016_79] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This chapter provides a critical overview of the available literature on the pharmacology of mitochondrial potassium channels. In the first part, the reader is introduced to the topic, and eight known protein contributors to the potassium permeability of the inner mitochondrial membrane are presented. The main part of this chapter describes the basic characteristics of each channel type mentioned in the introduction. However, the most important and valuable information included in this chapter concerns the pharmacology of mitochondrial potassium channels. Several available channel modulators are critically evaluated and rated by suitability for research use. The last figure of this chapter shows the results of this evaluation at a glance. Thus, this chapter can be very useful for beginners in this field. It is intended to be a time- and resource-saving guide for those searching for proper modulators of mitochondrial potassium channels.
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Affiliation(s)
- Bartłomiej Augustynek
- Laboratory of Intracellular Ion Channels, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland
| | - Wolfram S Kunz
- Department of Epileptology, University of Bonn, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland.
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84
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Huang ZG, Liu HW, Yan ZZ, Wang S, Wang LY, Ding JP. The glycosylation of the extracellular loop of β2 subunits diversifies functional phenotypes of BK Channels. Channels (Austin) 2016; 11:156-166. [PMID: 27690717 DOI: 10.1080/19336950.2016.1243631] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Large-conductance Ca2+- and voltage-activated potassium (MaxiK or BK) channels are composed of a pore-forming α subunit (Slo) and 4 types of auxiliary β subunits or just a pore-forming α subunit. Although multiple N-linked glycosylation sites in the extracellular loop of β subunits have been identified, very little is known about how glycosylation influences the structure and function of BK channels. Using a combination of site-directed mutagenesis, western blot and patch-clamp recordings, we demonstrated that 3 sites in the extracellular loop of β2 subunit are N-glycosylated (N-X-T/S at N88, N96 and N119). Glycosylation of these sites strongly and differentially regulate gating kinetics, outward rectification, toxin sensitivity and physical association between the α and β2 subunits. We constructed a model and used molecular dynamics (MD) to simulate how the glycosylation facilitates the association of α/β2 subunits and modulates the dimension of the extracellular cavum above the pore of the channel, ultimately to modify biophysical and pharmacological properties of BK channels. Our results suggest that N-glycosylation of β2 subunits plays crucial roles in imparting functional heterogeneity of BK channels, and is potentially involved in the pathological phenotypes of carbohydrate metabolic diseases.
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Affiliation(s)
- Zhi-Gang Huang
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.,b Wuhan Foreign Languages School , Wuhan , Hubei , China
| | - Hao-Wen Liu
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
| | - Zhen-Zhen Yan
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
| | - Sheng Wang
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
| | - Lu-Yang Wang
- c Program in Neurosciences and Mental Health, SickKids Research Institute and Department of Physiology , University of Toronto , Toronto , Ontario , Canada
| | - Jiu-Ping Ding
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
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85
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Blomster LV, Strøbaek D, Hougaard C, Klein J, Pinborg LH, Mikkelsen JD, Christophersen P. Quantification of the functional expression of the Ca 2+ -activated K + channel K Ca 3.1 on microglia from adult human neocortical tissue. Glia 2016; 64:2065-2078. [PMID: 27470924 DOI: 10.1002/glia.23040] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 07/11/2016] [Indexed: 12/11/2022]
Abstract
The KCa 3.1 channel (KCNN4) is an important modulator of microglia responses in rodents, but no information exists on functional expression on microglia from human adults. We isolated and cultured microglia (max 1% astrocytes, no neurons or oligodendrocytes) from neocortex surgically removed from epilepsy patients and employed electrophysiological whole-cell measurements and selective pharmacological tools to elucidate functional expression of KCa 3.1. The channel expression was demonstrated as a significant increase in the voltage-independent current by NS309, a KCa 3.1/KCa 2 activator, followed by full inhibition upon co-application with NS6180, a highly selective KCa 3.1 inhibitor. A major fraction (79%) of unstimulated human microglia expressed KCa 3.1, and the difference in current between full activation and inhibition (ΔKCa 3.1) was estimated at 292 ± 48 pA at -40 mV (n = 75), which equals at least 585 channels per cell. Serial KCa 3.1 activation/inhibition significantly hyperpolarized/depolarized the membrane potential. The isolated human microglia were potently activated by lipopolysaccharide (LPS) shown as a prominent increase in TNF-α production. However, incubation with LPS neither changed the KCa 3.1 current nor the fraction of KCa 3.1 expressing cells. In contrast, the anti-inflammatory cytokine IL-4 slightly increased the KCa 3.1 current per cell, but as the membrane area also increased, there was no significant change in channel density. A large fraction of the microglia also expressed a voltage-dependent current sensitive to the KCa 1.1 modulators NS1619 and Paxilline and an inward-rectifying current with the characteristics of a Kir channel. The high functional expression of KCa 3.1 in microglia from epilepsy patients accentuates the need for further investigations of its role in neuropathological processes. GLIA 2016;64:2065-2078.
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Affiliation(s)
- Linda V Blomster
- Saniona A/S, Baltorpvej 154, 2750, Ballerup, Denmark.,Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | | | | | - Jessica Klein
- Saniona A/S, Baltorpvej 154, 2750, Ballerup, Denmark
| | - Lars H Pinborg
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.,Epilepsy Clinic, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Jens D Mikkelsen
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
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86
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Abstract
Large conductance Ca(2+)- and voltage-activated K(+) (BK) channels are widely distributed in the postnatal central nervous system (CNS). BK channels play a pleiotropic role in regulating the activity of brain and spinal cord neural circuits by providing a negative feedback mechanism for local increases in intracellular Ca(2+) concentrations. In neurons, they regulate the timing and duration of K(+) influx such that they can either increase or decrease firing depending on the cellular context, and they can suppress neurotransmitter release from presynaptic terminals. In addition, BK channels located in astrocytes and arterial myocytes modulate cerebral blood flow. Not surprisingly, both loss and gain of BK channel function have been associated with CNS disorders such as epilepsy, ataxia, mental retardation, and chronic pain. On the other hand, the neuroprotective role played by BK channels in a number of pathological situations could potentially be leveraged to correct neurological dysfunction.
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87
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Differential Regulation of Action Potential Shape and Burst-Frequency Firing by BK and Kv2 Channels in Substantia Nigra Dopaminergic Neurons. J Neurosci 2016; 35:16404-17. [PMID: 26674866 DOI: 10.1523/jneurosci.5291-14.2015] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
UNLABELLED Little is known about the voltage-dependent potassium currents underlying spike repolarization in midbrain dopaminergic neurons. Studying mouse substantia nigra pars compacta dopaminergic neurons both in brain slice and after acute dissociation, we found that BK calcium-activated potassium channels and Kv2 channels both make major contributions to the depolarization-activated potassium current. Inhibiting Kv2 or BK channels had very different effects on spike shape and evoked firing. Inhibiting Kv2 channels increased spike width and decreased the afterhyperpolarization, as expected for loss of an action potential-activated potassium conductance. BK inhibition also increased spike width but paradoxically increased the afterhyperpolarization. Kv2 channel inhibition steeply increased the slope of the frequency-current (f-I) relationship, whereas BK channel inhibition had little effect on the f-I slope or decreased it, sometimes resulting in slowed firing. Action potential clamp experiments showed that both BK and Kv2 current flow during spike repolarization but with very different kinetics, with Kv2 current activating later and deactivating more slowly. Further experiments revealed that inhibiting either BK or Kv2 alone leads to recruitment of additional current through the other channel type during the action potential as a consequence of changes in spike shape. Enhancement of slowly deactivating Kv2 current can account for the increased afterhyperpolarization produced by BK inhibition and likely underlies the very different effects on the f-I relationship. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. SIGNIFICANCE STATEMENT This work shows that BK calcium-activated potassium channels and Kv2 voltage-activated potassium channels both regulate action potentials in dopamine neurons of the substantia nigra pars compacta. Although both channel types participate in action potential repolarization about equally, they have contrasting and partially opposite effects in regulating neuronal firing at frequencies typical of bursting. Our analysis shows that this results from their different kinetic properties, with fast-activating BK channels serving to short-circuit activation of Kv2 channels, which tend to slow firing by producing a deep afterhyperpolarization. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell.
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88
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Philippe G. Lolitrem B and Indole Diterpene Alkaloids Produced by Endophytic Fungi of the Genus Epichloë and Their Toxic Effects in Livestock. Toxins (Basel) 2016; 8:47. [PMID: 26891327 PMCID: PMC4773800 DOI: 10.3390/toxins8020047] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 01/29/2016] [Accepted: 02/03/2016] [Indexed: 01/12/2023] Open
Abstract
Different group of alkaloids are produced during the symbiotic development of fungal endophytes of the genus Epichloë in grass. The structure and toxicity of the compounds vary considerably in mammalian herbivores and in crop pests. Alkaloids of the indole-diterpene group, of which lolitrem B is the most toxic, were first characterized in endophyte-infected perennial ryegrass, and are responsible for “ryegrass staggers.” Ergot alkaloids, of which ergovaline is the most abundant ergopeptide alkaloid produced, are also found in ryegrass, but generally at a lower rate than lolitrem B. Other alkaloids such as lolines and peramine are toxic for crop pests but have weak toxicological properties in mammals. The purpose of this review is to present indole-diterpene alkaloids produced in endophyte infected ryegrass from the first characterization of ryegrass staggers to the determination of the toxicokinetics of lolitrem B and of their mechanism of action in mammals, focusing on the different factors that could explain the worldwide distribution of the disease. Other indole diterpene alkaloids than lolitrem B that can be found in Epichloë infected ryegrass, and their tremorgenic properties, are presented in the last section of this review.
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Affiliation(s)
- Guerre Philippe
- Université de Toulouse, INP, ENVT, UR Mycotoxicologie, F-31076 Toulouse, France.
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89
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Rahman M, Mukherjee S, Sheng W, Nilius B, Janssen LJ. Electrophysiological characterization of voltage-dependent calcium currents and TRPV4 currents in human pulmonary fibroblasts. Am J Physiol Lung Cell Mol Physiol 2016; 310:L603-14. [PMID: 26851262 DOI: 10.1152/ajplung.00426.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 02/02/2016] [Indexed: 11/22/2022] Open
Abstract
We have presented indirect evidence of a key role for voltage-dependent Ca(2+) currents in TGFβ-induced synthetic function in human pulmonary fibroblast (HPF), as well as in bleomycin-induced pulmonary fibrosis in mice. Others, however, have provided indirect evidence for transient receptor potential vanilloid 4 (TRPV4) channels in both of those effects. Unfortunately, definitive electrophysiological descriptions of both currents in HPFs have been entirely lacking. In this study, we provide the first direct electrophysiological and pharmacological evidence of the currents in HPFs at rest and during overnight stimulation with TGFβ. These currents include a Ca(2+)-dependent K(+) current, a TRPV4 current, a chloride current, and an L-type voltage-dependent Ca(2+) current. Evidence for the TRPV4 current include activation of a large-conductance change by two putatively TRPV4-selective agonists (4α-phorbol-12,13-didecanoate; GSK1016790A), with a reversal potential near 0 mV, partial sensitivity to two different TRPV4-selective blockers (RN1734; HC067047), and partial reduction following removal of external Na(+) Substantial reduction of the evoked current was seen following the coapplication of RN1734, DIDS, and niflumic acid, suggesting that a chloride current is also involved. The voltage-dependent Ca(2+) current is found to be "L-type" in nature, as indicated by the voltage and time dependence of its activation, deactivation, and inactivation properties, and by its pharmacology (sensitivity to replacement with barium and inhibition by nifedipine, verapamil, or mibefradil). We also found that overnight treatment with TGFβ evoked a periodic current (inward at negative holding potentials, with reversal potential near 0 mV), which is sufficient to trigger the voltage-dependent Ca(2+) currents and, thereby, account for the rhythmic Ca(2+) oscillations, which we have described previously in these cells.
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Affiliation(s)
- Mozibur Rahman
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - Subhendu Mukherjee
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - Wei Sheng
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
| | - Bernd Nilius
- University of Leuven, Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, Leuven, Belgium
| | - Luke J Janssen
- Firestone Institute for Respiratory Health, St. Joseph's Hospital, Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and
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90
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91
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Yu M, Liu SL, Sun PB, Pan H, Tian CL, Zhang LH. Peptide toxins and small-molecule blockers of BK channels. Acta Pharmacol Sin 2016; 37:56-66. [PMID: 26725735 DOI: 10.1038/aps.2015.139] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 10/13/2015] [Indexed: 12/21/2022] Open
Abstract
Large conductance, Ca(2+)-activated potassium (BK) channels play important roles in the regulation of neuronal excitability and the control of smooth muscle contractions. BK channels can be activated by changes in both the membrane potential and intracellular Ca(2+) concentrations. Here, we provide an overview of the structural and pharmacological properties of BK channel blockers. First, the properties of different venom peptide toxins from scorpions and snakes are described, with a focus on their characteristic structural motifs, including their disulfide bond formation pattern, the binding interface between the toxin and BK channel, and the functional consequence of the blockage of BK channels by these toxins. Then, some representative non-peptide blockers of BK channels are also described, including their molecular formula and pharmacological effects on BK channels. The detailed categorization and descriptions of these BK channel blockers will provide mechanistic insights into the blockade of BK channels. The structures of peptide toxins and non-peptide compounds could provide templates for the design of new channel blockers, and facilitate the optimization of lead compounds for further therapeutic applications in neurological disorders or cardiovascular diseases.
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92
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Kaczorowski G, Garcia M. Developing Molecular Pharmacology of BK Channels for Therapeutic Benefit. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:439-75. [DOI: 10.1016/bs.irn.2016.02.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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93
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Handforth A. Linking Essential Tremor to the Cerebellum—Animal Model Evidence. THE CEREBELLUM 2015; 15:285-98. [DOI: 10.1007/s12311-015-0750-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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94
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George DT, Kuenstner EJ, Pronin SV. A Concise Approach to Paxilline Indole Diterpenes. J Am Chem Soc 2015; 137:15410-3. [PMID: 26593869 DOI: 10.1021/jacs.5b11129] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A synthetic approach to paxilline indole diterpenes is described. The route to the pentacyclic core relies on a new regioselective alkenylation of ketones and a tandem radical addition-aldol reaction sequence to access vicinal quaternary stereocenters. Emindole SB, the simplest member of the family, is synthesized in 11 steps from commercially available material to demonstrate the application of this approach.
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Affiliation(s)
- David T George
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States
| | - Eric J Kuenstner
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States
| | - Sergey V Pronin
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States
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95
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Zemen BG, Lai MH, Whitt JP, Khan Z, Zhao G, Meredith AL. Generation of Kcnma1fl-tdTomato, a conditional deletion of the BK channel α subunit in mouse. Physiol Rep 2015; 3:e12612. [PMID: 26537348 PMCID: PMC4673641 DOI: 10.14814/phy2.12612] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 10/09/2015] [Accepted: 10/13/2015] [Indexed: 11/24/2022] Open
Abstract
BK large conductance calcium-activated K(+) channels (KC a1.1) are expressed widely across many tissues, contributing to systemic regulation of cardiovascular, neurological, and other specialized physiological functions. The pore-forming α subunit is encoded by the Kcnma1 gene, originally named mSlo1 in mouse and slowpoke in Drosophila. Global deletion in mouse (Kcnma1(-/-)) produces a plethora of defects in neuron and muscle excitability, as well as other phenotypes related to channel function in nonexcitable cells. While homozygous null mice are viable, the ubiquitous loss of BK function has complicated the interpretation of phenotypes involving the interaction of multiple cell types which independently express BK channels. Here, we report the generation of a targeted allele for conditional inactivation of Kcnma1 using the Cre-loxP system (Kcnma1(fl)-tdTomato). Cre-mediated recombination generates a null allele, and BK currents were not detectable in neurons and muscle cells from Nestin-Cre; Kcnma1(fl/fl) and SM22α-Cre; Kcnma1(fl/fl) mice, respectively. tdTomato expression was detected in Cre-expressing tissues, but not in Cre-negative controls. These data demonstrate the utility of Kcnma1(fl)-tdTomato for conditional deletion of the BK channel, facilitating the understanding of tissue-specific contributions to physiological function in vivo.
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Affiliation(s)
- Betsir G Zemen
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Michael H Lai
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Joshua P Whitt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Zulqarnain Khan
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Guiling Zhao
- Center of BioMedical Engineering and Technology and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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96
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2014 Conway review lecture, Royal Academy of Medicine in Ireland: “S6, drugs and RCK and Bowl”. Ir J Med Sci 2015; 185:1-10. [PMID: 26477033 DOI: 10.1007/s11845-015-1362-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 09/21/2015] [Indexed: 10/22/2022]
Abstract
BACKGROUND The Conway Review Lecture is held annually by the Royal Academy of Medicine in Ireland Biomedical Sciences Section, to remember the life and scientific work of a world class Irish scientist, Professor Edward J Conway. AIMS This years lecture will focus on large conductance Ca2+ activated K+ (BK) channels and aims to describe how a combination of techniques can be used to unravel drug effects on ion channels at a molecular level. METHODS Experiments were performed using a range of techniques including patch clamp electrophysiology, mutagenesis, structural biology and mathematical modeling. RESULTS Our data suggest that the novel BK channel opener GoSlo-SR-5-6 mediates its effects via an interaction with 2 residues on S6 (S317 and I326) and a residue on the S4/S5 linker (L227). CONCLUSIONS We hypothesize that this novel opener activates BK channels by altering an interaction between the S4/S5 linker and the pore-forming S6 transmembrane helix.
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97
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Crespo-Castrillo A, Punzón E, de Pascual R, Maroto M, Padín JF, García-Álvarez I, Nanclares C, Ruiz-Pascual L, Gandía L, Fernández-Mayoralas A, García AG. Novel synthetic sulfoglycolipid IG20 facilitates exocytosis in chromaffin cells through the regulation of sodium channels. J Neurochem 2015; 135:880-96. [DOI: 10.1111/jnc.13357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/03/2015] [Accepted: 08/19/2015] [Indexed: 11/27/2022]
Affiliation(s)
- Andrea Crespo-Castrillo
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Eva Punzón
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Ricardo de Pascual
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Marcos Maroto
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Juan Fernando Padín
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | | | - Carmen Nanclares
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Lucía Ruiz-Pascual
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Luis Gandía
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | | | - Antonio G. García
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Servicio de Farmacología Clínica; Instituto de Investigación Sanitaria; Hospital Universitario de La Princesa; Madrid Spain
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98
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Maragos CM. Development and Evaluation of Monoclonal Antibodies for Paxilline. Toxins (Basel) 2015; 7:3903-15. [PMID: 26426046 PMCID: PMC4626710 DOI: 10.3390/toxins7103903] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/08/2015] [Accepted: 09/22/2015] [Indexed: 11/16/2022] Open
Abstract
Paxilline (PAX) is a tremorgenic mycotoxin that has been found in perennial ryegrass infected with Acremonium lolii. To facilitate screening for this toxin, four murine monoclonal antibodies (mAbs) were developed. In competitive indirect enzyme-linked immunosorbent assays (CI-ELISAs) the concentrations of PAX required to inhibit signal development by 50% (IC50s) ranged from 1.2 to 2.5 ng/mL. One mAb (2-9) was applied to the detection of PAX in maize silage. The assay was sensitive to the effects of solvents, with 5% acetonitrile or 20% methanol causing a two-fold or greater increase in IC50. For analysis of silage samples, extracts were cleaned up by adsorbing potential matrix interferences onto a solid phase extraction column. The non-retained extract was then diluted with buffer to reduce solvent content prior to assay. Using this method, the limit of detection for PAX in dried silage was 15 µg/kg and the limit of quantification was 90 µg/kg. Recovery from samples spiked over the range of 100 to 1000 µg/kg averaged 106% ± 18%. The assay was applied to 86 maize silage samples, with many having detectable, but none having quantifiable, levels of PAX. The results suggest the CI-ELISA can be applied as a sensitive technique for the screening of PAX in maize silage.
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Affiliation(s)
- Chris M Maragos
- Bacterial Foodborne Pathogens and Mycology Research Unit, USDA-ARS-NCAUR, 1815 North University Street, Peoria, IL 61604, USA.
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99
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Sánchez-Carranza O, Torres-Rodríguez P, Darszon A, Treviño CL, López-González I. Pharmacology of hSlo3 channels and their contribution in the capacitation-associated hyperpolarization of human sperm. Biochem Biophys Res Commun 2015; 466:554-9. [PMID: 26381170 DOI: 10.1016/j.bbrc.2015.09.073] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 09/12/2015] [Indexed: 01/01/2023]
Abstract
Slo3 channels (mSlo3) primarily mediate mouse sperm K(+) currents and are essential for the capacitation-associated hyperpolarization (CAH). Whether Slo3 and/or Slo1, two Slo family K(+) channels are functionally expressed in human sperm is controversial. Our recent pharmacological studies of the human sperm CAH suggested the participation of both. Lack of a detailed pharmacology of heterologously expressed human Slo3 (hSlo3) prevented precisely identifying the K(+) channel(s) involved. In the present report, we compare the pharmacological profile of expressed hSlo3 in CHO cells with that of the CAH to advance this matter. Whole-cell patch-clamp recordings showed that hSlo3 currents are inhibited: significantly by progesterone, Ba(2+) and quinidine; partially by Penitrem A and Charybdotoxin; and poorly by Iberiotoxin and Slotoxin. Surprisingly, hSlo3 currents were resistant to Clofilium and 60 mM TEA(+) which inhibit mSlo3. Pharmacological comparison of the CAH and hSlo3 profiles indicates in addition to hSlo3, other K(+) channels, possibly Slo1, may participate in CAH. The pharmacological profile of heterologously expressed hSlo3 channels differs from that of mSlo3 K(+) channels, consistent with species-specific differences observed among other sperm ion channels. While the pharmacological correlation analysis of the hSlo3 currents and the CAH confirmed the participation of hSlo3 channels, it suggests that additional K(+) channels may be involved, in particular Slo1 channels.
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Affiliation(s)
- Oscar Sánchez-Carranza
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Paulina Torres-Rodríguez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Alberto Darszon
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Claudia L Treviño
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
| | - Ignacio López-González
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
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100
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BK Channels Localize to the Paranodal Junction and Regulate Action Potentials in Myelinated Axons of Cerebellar Purkinje Cells. J Neurosci 2015; 35:7082-94. [PMID: 25948259 DOI: 10.1523/jneurosci.3778-14.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In myelinated axons, K(+) channels are clustered in distinct membrane domains to regulate action potentials (APs). At nodes of Ranvier, Kv7 channels are expressed with Na(+) channels, whereas Kv1 channels flank nodes at juxtaparanodes. Regulation of axonal APs by K(+) channels would be particularly important in fast-spiking projection neurons such as cerebellar Purkinje cells. Here, we show that BK/Slo1 channels are clustered at the paranodal junctions of myelinated Purkinje cell axons of rat and mouse. The paranodal junction is formed by a set of cell-adhesion molecules, including Caspr, between the node and juxtaparanodes in which it separates nodal from internodal membrane domains. Remarkably, only Purkinje cell axons have detectable paranodal BK channels, whose clustering requires the formation of the paranodal junction via Caspr. Thus, BK channels occupy this unique domain in Purkinje cell axons along with the other K(+) channel complexes at nodes and juxtaparanodes. To investigate the physiological role of novel paranodal BK channels, we examined the effect of BK channel blockers on antidromic AP conduction. We found that local application of blockers to the axon resulted in a significant increase in antidromic AP failure at frequencies above 100 Hz. We also found that Ni(2+) elicited a similar effect on APs, indicating the involvement of Ni(2+)-sensitive Ca(2+) channels. Furthermore, axonal application of BK channel blockers decreased the inhibitory synaptic response in the deep cerebellar nuclei. Thus, paranodal BK channels uniquely support high-fidelity firing of APs in myelinated Purkinje cell axons, thereby underpinning the output of the cerebellar cortex.
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