title: Mediation of the effect of nicotine on Kir6.1 channels by superoxide anion production.
abstract: KATP channels are a complex of regulatory sulfonylurea receptor subunits and the pore-forming inward rectifiers such as Kir6.1. Using the whole-cell patch-clamp technique, we investigated the interaction of nicotine with the Kir6.1 subunit as well as the underlying mechanism. Stable expression of Kir6.1 in HEK-293 cells yielded a detectable inward rectifier KATP current. This inward current was significantly inhibited by PNU-37883A and by a specific anti-Kir6.1 antibody. Nicotine at 30 and 100 microM increased Kir6.1 currents by 42 +/- 11.8% and 26.2 +/- 14.6%, respectively (n = 4-6, P < 0.05). In contrast, nicotine at 1-3 mM inhibited Kir6.1 currents (P < 0.05). Nicotine at 100 microM increased the production of superoxide anion (O2) by 20.3 +/- 5.7%, whereas at 1 mM it significantly decreased the production of O2 by 37.7 +/- 4.3%. Coapplication of hypoxanthine (HX) and xanthine oxidase (XO) to the transfected HEK-293 cells resulted in a significant and reproducible increase in Kir6.1 currents (P < 0.05). The stimulatory effect of HX/XO on Kir6.1 current was abolished by tempol, a scavenger of O2. Tempol also abolished the stimulatory effect of 30 muM nicotine on Kir6.1 currents. In conclusion, nicotine stimulates Kir6.1 channel at least in part through the production of O2.
authors.affiliation: Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Salma Toma
authors.initials: ST
authors.lastname: Hanna
authors.forename: Kun
authors.initials: K
authors.lastname: Cao
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Sun
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D019271:Hypoxanthine / Q000494:pharmacology; D054086:KATP Channels; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors; D013113:Spin Labels; D013481:Superoxides / Q000032:analysis / Q000378:metabolism*; D014162:Transfection; D019820:Xanthine / Q000494:pharmacology
chemical_list: D018528:ATP-Binding Cassette Transporters; D003497:Cyclic N-Oxides; D054086:KATP Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D017382:Reactive Oxygen Species; D013113:Spin Labels; C092520:uK-ATP-1 potassium channel; D013481:Superoxides; D019820:Xanthine; D019271:Hypoxanthine; D009538:Nicotine; C001803:tempol