Noble gas xenon is a novel adenosine triphosphate-sensitive potassium channel opener.
BACKGROUND
Adenosine triphosphate-sensitive potassium (KATP) channels in brain are involved in neuroprotective mechanisms. Pharmacologic activation of these channels is seen as beneficial, but clinical exploitation by using classic K channel openers is hampered by their inability to cross the blood-brain barrier. This is different with the inhalational anesthetic xenon, which recently has been suggested to activate KATP channels; it partitions freely into the brain.


METHODS
To evaluate the type and mechanism of interaction of xenon with neuronal-type KATP channels, these channels, consisting of Kir6.2 pore-forming subunits and sulfonylurea receptor-1 regulatory subunits, were expressed in HEK293 cells and whole cell, and excised patch-clamp recordings were performed.


RESULTS
Xenon, in contrast to classic KATP channel openers, acted directly on the Kir6.2 subunit of the channel. It had no effect on the closely related, adenosine triphosphate (ATP)-regulated Kir1.1 channel and failed to activate an ATP-insensitive mutant version of Kir6.2. Furthermore, concentration-inhibition curves for ATP obtained from inside-out patches in the absence or presence of 80% xenon revealed that xenon reduced the sensitivity of the KATP channel to ATP. This was reflected in an approximately fourfold shift of the concentration causing half-maximal inhibition (IC50) from 26 +/- 4 to 96 +/- 6 microm.


CONCLUSIONS
Xenon represents a novel KATP channel opener that increases KATP currents independently of the sulfonylurea receptor-1 subunit by reducing ATP inhibition of the channel. Through this action and by its ability to readily partition across the blood-brain barrier, xenon has considerable potential in clinical settings of neuronal injury, including stroke.
Bantel
Carsten
C
Department of Surgery and Cancer, Anaesthetics, Pain Medicine and Intensive Care Section, Blackett Laboratory, Imperial College London. London SW7 2AZ, United Kingdom.
Maze
Mervyn
M
Trapp
Stefan
S
D018528:ATP-Binding Cassette Transporters / Q000819:agonists / Q000235:genetics; D000465:Algorithms; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D004594:Electrophysiology; D006801:Humans; D054086:KATP Channels / Q000819:agonists* / Q000235:genetics; D051379:Mice; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000819:agonists / Q000235:genetics; D011955:Receptors, Drug / Q000819:agonists / Q000235:genetics; D064233:Sulfonylurea Receptors; D014162:Transfection; D014978:Xenon / Q000494:pharmacology*; D000099161:Kcnj11 Channel
D018528:ATP-Binding Cassette Transporters; D018685:Anesthetics, Inhalation; D054086:KATP Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D014978:Xenon; D000099161:Kcnj11 Channel