title: Amiodarone sensitizes human glioma cells but not astrocytes to TRAIL-induced apoptosis via CHOP-mediated DR5 upregulation.
abstract: Amiodarone is a widely used anti-arrhythmic drug that inhibits diverse ion channels, including the Na(+)/Ca(2+) exchanger (NCX), L-type Ca(2+) channels, and Na(+) channels. Here, we report that subtoxic doses of amiodarone and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) synergistically induced apoptosis of various glioma cells. Treatment of U251MG glioma cells with amiodarone increased intracellular Ca(2+) levels and enhanced the expression of the endoplasmic reticulum (ER) stress-inducible transcription factor C/EBP homologous protein (CHOP). This upregulation of CHOP was followed by marked upregulation of the TRAIL receptor, DR5. Suppression of DR5 expression by small interfering (si) RNAs almost completely blocked amiodarone/TRAIL-induced apoptosis in U251MG glioma cells, demonstrating that DR5 is critical to this cell death. siRNA-mediated CHOP suppression reduced amiodarone-induced DR5 upregulation and attenuated the cell death induced by amiodarone plus TRAIL. In addition, omitting Ca(2+) from the external medium using ethylene glycol tetraacetic acid markedly inhibited this cell death, reducing the protein levels of CHOP and DR5. These results suggest that amiodarone-induced influx of Ca(2+) plays an important role in sensitizing U251MG cells to TRAIL-mediated apoptosis through CHOP-mediated DR5 upregulation. Furthermore, subtoxic doses of bepridil and cibenzoline, two other anti-arrhythmic drugs with NCX-inhibitor activity, also sensitized glioma cells to TRAIL-mediated apoptosis, via the upregulation of both CHOP and DR5. Notably, amiodarone/TRAIL cotreatment did not induce cell death in astrocytes, nor did it affect the expression of CHOP or DR5 in these cells. These results collectively suggest that a combined regimen of amiodarone plus TRAIL may offer an effective therapeutic strategy for safely and selectively treating resistant gliomas.
authors.affiliation: Department of Molecular Science & Technology Institute for Medical Sciences, Ajou University School of Medicine, Suwon 443-749, Korea.
authors.forename: In Young
authors.initials: IY
authors.lastname: Kim
authors.forename: You Jung
authors.initials: YJ
authors.lastname: Kang
authors.forename: Mi Jin
authors.initials: MJ
authors.lastname: Yoon
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Kim
authors.forename: Seung U
authors.initials: SU
authors.lastname: Kim
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
authors.forename: In Ah
authors.initials: IA
authors.lastname: Kim
authors.forename: Kyeong Sook
authors.initials: KS
authors.lastname: Choi
mesh_terms: D000638:Amiodarone / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005910:Glioma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: C497249:DDIT3 protein, human; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D014665:Vasodilator Agents; D051742:Transcription Factor CHOP; D008156:Luciferases; D000638:Amiodarone