title: Microscopic photosensitization: a new tool to investigate the role of mitochondria in cell death.
abstract: Active involvement of mitochondria in cell death has been well-documented, but local apoptotic signaling between subsets of mitochondria has been poorly explored to date. Using mitochondrially localized CMXRos as a photosensitizer coupled to laser irradiation by confocal laser scanning microscopy, we demonstrate that partial irradiation of about half the mitochondria in human 143B TK- cells induces rapid loss of mitochondrial membrane potential (DeltaPsi(m)) in nonirradiated mitochondria. Cells so partially irradiated show apoptotic indications, including mobilization of cytochrome c and binding of annexin V within 2 h following irradiation. The loss of DeltaPsi(m) in nonirradiated mitochondria did not occur in cells photoirradiated in the absence of CMXRos. Increasing the proportion of irradiated mitochondria in each cell (up to about 50%) generated a correspondingly greater percentage of cells in which nonirradiated mitochondria lost DeltaPsi(m) and which also showed apoptotic indications. Only at the highest level of irradiation (global for all mitochondria in one cell) were signs of necrosis evident (judged by uptake of propidium iodide). Because laser irradiation is specific to the subpopulation of mitochondria targeted, the data imply that a signal emanating from irradiated mitochondria is processed by their nonirradiated counterparts. We conclude that intermitochondrial signaling occurs in the subcellular response to induction of apoptosis.
authors.affiliation: Department of Biochemistry and Molecular Biology, PO Box 13D, Monash University, Victoria 3800, Australia. Maggie.Lum@med.monash.edu.au
authors.forename: May-Ghee
authors.initials: MG
authors.lastname: Lum
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Minamikawa
authors.forename: Phillip
authors.initials: P
authors.lastname: Nagley
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*; D045744:Cell Line, Tumor; D003574:Cytochrome c Group / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology / Q000528:radiation effects; D006801:Humans; D007834:Lasers; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018613:Microscopy, Confocal / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D008928:Mitochondria / Q000737:chemistry / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*; D009930:Organic Chemicals; D012516:Osteosarcoma / Q000737:chemistry / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D010787:Photosensitivity Disorders; D017319:Photosensitizing Agents / Q000494:pharmacology; D011859:Radiography
chemical_list: D017304:Annexin A5; D003574:Cytochrome c Group; D005456:Fluorescent Dyes; D009930:Organic Chemicals; D017319:Photosensitizing Agents; C107472:red dye CMXRos; C076615:cytochrome c''