title: Large-conductance K+ channel openers NS1619 and NS004 as inhibitors of mitochondrial function in glioma cells.
abstract: Recently, it has been reported that large-conductance Ca(2+)-activated potassium channels, also known as BK(Ca)-type potassium channels, are present in the inner mitochondrial membrane of the human glioma LN229 cell line. Hence, in the present study, we have investigated whether BK(Ca)-channel openers (BK(Ca)COs), such as the benzimidazolone derivatives NS004 (5-trifluoromethyl-1-(5-chloro-2-hydroxyphenyl)-1,3-dihydro-2H-benzimidazole-2-one) and NS1619 (1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one), affect the functioning of LN229 glioma cell mitochondria in situ. We examined the effect of BK(Ca)COs on mitochondrial membrane potential, mitochondrial respiration and plasma membrane potassium current in human glioma cell line LN229. We found that BK(Ca)COs decrease the mitochondrial membrane potential with an EC(50) value of 3.6+/-0.4 microM for NS1619 and 5.4+/-0.8 microM for NS004. This mitochondrial depolarization was accompanied by an inhibition of the mitochondrial respiratory chain. Both BK(Ca)COs induced whole-cell potassium current blocked by charybdotoxin, as measured by the patch-clamp technique. The BK(Ca)COs had no effect on membrane bilayer conductance. Moreover, the inhibition of mitochondrial function by NS004 and NS1619 was without effect on cell survival, as measured by lactate dehydrogenase release from the cells.
authors.affiliation: Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-096 Warsaw, Poland.
authors.forename: Grazyna
authors.initials: G
authors.lastname: Debska
authors.forename: Anna
authors.initials: A
authors.lastname: Kicinska
authors.forename: Jerzy
authors.initials: J
authors.lastname: Dobrucki
authors.forename: Beata
authors.initials: B
authors.lastname: Dworakowska
authors.forename: Ewa
authors.initials: E
authors.lastname: Nurowska
authors.forename: Jolanta
authors.initials: J
authors.lastname: Skalska
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Dolowy
authors.forename: Adam
authors.initials: A
authors.lastname: Szewczyk
mesh_terms: D001562:Benzimidazoles / Q000494:pharmacology*; D018999:Charybdotoxin / Q000494:pharmacology; D002733:Chlorophenols / Q000494:pharmacology*; D005910:Glioma; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000819:agonists* / Q000502:physiology; D014407:Tumor Cells, Cultured
chemical_list: D001562:Benzimidazoles; D002733:Chlorophenols; D015221:Potassium Channels; D018999:Charybdotoxin; C086491:NS 1619; C083230:NS 004