Modulation of the K+ Channels Encoded by the Human Ether-a-Gogo-Related Gene-1 (hERG1) by Nitric Oxide
- Section of Pharmacology, Department of Neuroscience, School of Medicine, University of Naples Federico II, Naples, Italy
Abstract
The inhibition of nitric oxide synthase byN-nitro-l-arginine methyl ester (0.03–3 mM) dose-dependently reduced nitric oxide (NO⋅) levels and enhanced the outward currents carried by human ether-a-gogo-related gene-1 (hERG1) K+ channels expressed inXenopus laevis oocytes, whereas the increase in NO⋅ levels achieved by exposure to l-arginine (0.03–10 mM) inhibited these currents. Furthermore, four NO⋅donors belonging to such different chemical classes as sodium nitroprusside (1–1000 μM), 3-morpholino-sydnonimine (100–1000 μM), (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (NOC-18; 1–300 μM), and S-nitrosoN-acetylpenicillamine (1–300 μM) dose-dependently inhibited hERG1 outward K+ currents. By contrast, the NO⋅ donor NOC-18 (0.3 mM) did not affect other cloned K+ channels such as rat neuroblastoma-glioma K+ channel 2, rat delayed rectifier K+ channel 1, bovine ether-a-gogo gene, rat ether-a-gogo-related gene-2, and rat ether-a-gogo-related gene-3. The inhibitory effect of NO⋅ donors on hERG1 K+ channels was prevented by the NO⋅ scavengers 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide and hemoglobin. The membrane permeable analog of cGMP, 8-bromo-cGMP (1 mM), failed to reproduce the inhibitory action of NO⋅ donors onhERG1 outward currents; furthermore, the specific inhibitor of the NO⋅-dependent guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (50 μM), neither interfered with outward hERG1K+ currents nor prevented their inhibition by 0.3 mM NOC-18. Both l-arginine (10 mM) and NOC-18 (0.3 mM) counteracted the stimulatory effect on hERG1 outward currents induced by the radical oxygen species-generating system FeSO4 (25 μM)/ascorbic acid (50 μM; Fe/Asc). Finally,l-arginine (10 mM) and NOC-18 (0.3 mM) inhibited both basal and Fe/Asc (0.1 mM/0.2 mM)-stimulated lipid peroxidation in X. laevis oocytes. Collectively, the present results suggest that NO⋅, both endogenously produced and pharmacologically delivered, may exert in a cGMP-independent way an inhibitory effect onhERG1 outward K+ currents via an interaction with radical oxygen species either generated under resting conditions or triggered by Fe/Asc.
Footnotes
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Send reprint requests to: Dr. Maurizio Taglialatela, Section of Pharmacology, Department of Neuroscience, School of Medicine, Via. S. Pansini 5, 80131 Naples, Italy. E-mail:mtaglial{at}unina.it
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The study was supported by Telethon Grant 1058 (to M.T.); National Research Council (CNR) Grants 97.04512.CT04, 97.01230.PF49, and 98.03149.CT04 (to M.T.) and CNR Grants 95.02857.CT04, 98.01048.CT04, and 98.00062.PF31 (PS Biotecnologie 5%) (to L.A.); MURST 60% and 40% (to L.A.); and grants from the Regione Campania (P.O.P. and Legge 41) (to L.A.).
- Abbreviations:
- NO⋅
- nitric oxide
- ROS
- radical oxygen species
- RNS
- radical nitrogen species
- O2⋅−
- superoxide anion
- ONOO−
- peroxynitrite
- rNGK2
- rat neuroblastoma-glioma K+ channel 2
- rDRK1
- rat delayed rectifier K+ channel 1
- bEAG
- bovine ether-a-gogo gene
- rERG2 and rERG3
- rat ether-a-gogo-related gene-2 and -3
- hERG1
- human ether-a-gogo related gene-1
- NO2−
- nitrite
- MDA
- malondialdehyde
- NOS
- NO⋅ synthase
- L-NAME
- N-nitro-l-arginine methyl ester
- NOC-18
- (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate
- SNAP
- S-nitroso N-acetylpenicillamine
- SNP
- sodium nitroprusside
- SIN-1
- 3-morpholino-sydnonimine
- PTIO
- 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide
- Hb
- hemoglobin
- ODQ
- 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one
- Fe/Asc
- iron- and ascorbate-containing solution
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- Received July 26, 1999.
- Accepted September 8, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
