title: Critical role of mitochondrial reactive oxygen species formation in visible laser irradiation-induced apoptosis in rat brain astrocytes (RBA-1).
abstract: Laser irradiation-induced phototoxicity has been intensively applied in clinical photodynamic therapy for the treatment of a variety of tumors. However, the precise laser damage sites as well as the underlying mechanisms at the subcellular level are unknown. Using a mitochondrial fluorescent marker, MitoTracker Green, severe mitochondrial swelling was noted in laser-irradiated rat brain astrocytes. Nucleus condensation and fragmentation revealed by propidium iodide nucleic acid staining indicated that laser-irradiated cells died from apoptosis. Using an intracellular reactive oxygen species (ROS) fluorescent dye, 2',7'-dichlorofluorescin diacetate, heterogeneous distribution of ROS inside astrocytes was observed after laser irradiation. The level of ROS in the mitochondrial compartment was found to be higher than in other parts of the cell. With another ROS fluorescent dye, dihydrorhodamine-123, and time-lapse laser scanning confocal microscopy, a substantial increase in mitochondrial ROS (mROS) was visualized in visible laser-irradiated astrocytes. The antioxidants melatonin and vitamin E largely attenuated laser irradiation-induced mROS formation and prevented apoptosis. Cyclosporin A (CsA), a mitochondrial permeability transition (MPT) blocker, did not prevent visible laser irradiation-induced mROS formation and apoptosis. In conclusion, mROS formation contributes significantly to visible laser irradiation-induced apoptosis via an MPT-independent pathway.
authors.affiliation: Department of Physiology and Pharmacology, Chang Gung University, Tao-Yuan, Taiwan, ROC.
authors.forename: Mei-Jie
authors.initials: MJ
authors.lastname: Jou
authors.forename: Shuo-Bin
authors.initials: SB
authors.lastname: Jou
authors.forename: Hung-Ming
authors.initials: HM
authors.lastname: Chen
authors.forename: Chi-Hung
authors.initials: CH
authors.lastname: Lin
authors.forename: Tsung-I
authors.initials: TI
authors.lastname: Peng
mesh_terms: D000447:Aldehydes / Q000032:analysis; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D001921:Brain / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects; D002478:Cells, Cultured; D005452:Fluoresceins / Q000032:analysis / Q000378:metabolism; D007834:Lasers / Q000009:adverse effects*; D008550:Melatonin / Q000494:pharmacology; D018613:Microscopy, Confocal / Q000379:methods; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D011419:Propidium; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D000447:Aldehydes; D000975:Antioxidants; D005452:Fluoresceins; D017382:Reactive Oxygen Species; C111472:mitotracker green FM; D014810:Vitamin E; C029569:diacetyldichlorofluorescein; D011419:Propidium; D008550:Melatonin