title: Large-conductance K+ channel openers induce death of human glioma cells.
abstract: Large-conductance Ca(2+)-activated K(+) channels (BKCa channels) are highly expressed in human glioma cells. It has been reported that BK(Ca) channels are present in the inner mitochondrial membrane of the human glioma cell line LN229. In the present study we investigated whether BK(Ca)-channel openers, such as CGS7181 (ethyl 2-hydroxy-1-[[(4-methylphenyl)amino]oxo]-6-trifluoromethyl-1H-indole-3-carboxylate) and CGS7184 (ethyl 1-[[(4-chlorophenyl)amino]oxo]-2-hydroxy-6-trifluoromethyl-1H-indole-3-carboxylate), affect the functioning of LN229 glioma cell mitochondria in situ. In the micromolar concentration range CGS7181 and CGS7184 induced glioma cell death. Morphological and cytometric analyses confirmed that both substances trigger the glioma cell death. This effect was not inhibited by the pan-caspase inhibitor z-VAD-fmk. Lack of DNA laddering, PARP cleavage, and caspase 3 activation suggested that glioma cell death was not of the apoptotic type. We examined the effect of CGS7184 on mitochondrial membrane potential and mitochondrial respiration. Potassium channel opener CGS7184 increased cell respiration and induced mitochondrial membrane depolarization. The latter was dependent on the presence of Ca(2+) in the external medium. It was shown that CGS7184 induced an increase of cytosolic Ca(2+) concentration due to endoplasmic reticulum store depletion. In conclusion, our results show that CGS7181 and CGS7184 induce glioma cell death by increasing the cytosolic calcium concentration followed by activation of calpains.
authors.affiliation: Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: G
authors.initials: G
authors.lastname: Debska-Vielhaber
authors.forename: M M
authors.initials: MM
authors.lastname: Godlewski
authors.forename: A
authors.initials: A
authors.lastname: Kicinska
authors.forename: J
authors.initials: J
authors.lastname: Skalska
authors.forename: B
authors.initials: B
authors.lastname: Kulawiak
authors.forename: M
authors.initials: M
authors.lastname: Piwonska
authors.forename: K
authors.initials: K
authors.lastname: Zablocki
authors.forename: W S
authors.initials: WS
authors.lastname: Kunz
authors.forename: A
authors.initials: A
authors.lastname: Szewczyk
authors.forename: T
authors.initials: T
authors.lastname: Motyl
mesh_terms: D020013:Calcium Signaling / Q000187:drug effects; D002154:Calpain / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects; D053144:Cell Nucleus Shape / Q000187:drug effects; D019069:Cell Respiration / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005910:Glioma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects*; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D010718:Phosphatidylserines / Q000378:metabolism; D013499:Surface Properties / Q000187:drug effects; D013997:Time Factors
chemical_list: C530927:CGS 7184; D007211:Indoles; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D010718:Phosphatidylserines; C548295:ethyl 2-hydroxy-1-(((4-methylphenyl)amino)oxo)-6-trifluoromethyl-1H-indole-3-carboxylate; D002154:Calpain