Regulation of the human ether-a-gogo related gene (HERG) K+ channels by reactive oxygen species.
Human ether-a-gogo related gene (HERG) K+ channels are key elements in the control of cell excitability in both the cardiovascular and the central nervous systems. For this reason, the possible modulation by reactive oxygen species (ROS) of HERG and other cloned K+ channels expressed in Xenopus oocytes has been explored in the present study. Exposure of Xenopus oocytes to an extracellular solution containing FeSO4 (25-100 microM) and ascorbic acid (50-200 microM) (Fe/Asc) increased both malondialdehyde content and 2',7'-dichlorofluorescin fluorescence, two indexes of ROS production. Oocyte perfusion with Fe/Asc caused a 50% increase of the outward K+ currents carried by HERG channels, whereas inward currents were not modified. This ROS-induced increase in HERG outward K+ currents was due to a depolarizing shift of the voltage-dependence of channel inactivation, with no change in channel activation. No effect of Fe/Asc was observed on the expressed K+ currents carried by other K+ channels such as bEAG, rDRK1, and mIRK1. Fe/Asc-induced stimulation of HERG outward currents was completely prevented by perfusion of the oocytes with a ROS scavenger mixture (containing 1,000 units/ml catalase, 200 ng/ml superoxide dismutase, and 2 mM mannitol). Furthermore, the scavenger mixture also was able to reduce HERG outward currents in resting conditions by 30%, an effect mimicked by catalase alone. In conclusion, the present results seem to suggest that changes in ROS production can specifically influence K+ currents carried by the HERG channels.
Taglialatela
M
M
Section of Pharmacology, Department of Neurosciences, School of Medicine, University of Naples Federico II, Via. S. Pansini 5, 80131 Naples, Italy. mtaglial@unina.it
Castaldo
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P
Iossa
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S
Pannaccione
A
A
Fresi
A
A
Ficker
E
E
Annunziato
L
L
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D027682:Cation Transport Proteins; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D005290:Ferric Compounds / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008315:Malondialdehyde / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D017382:Reactive Oxygen Species / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000187:drug effects; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; D014981:Xenopus
D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D005290:Ferric Compounds; D016166:Free Radical Scavengers; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; C024823:ferric sulfate; D008315:Malondialdehyde; C061126:iron(III)-ascorbic acid complex; D001205:Ascorbic Acid