Chronology of cellular alterations during 7-ketocholesterol-induced cell death on A7R5 rat smooth muscle cells: analysis by time lapse-video microscopy and conventional fluorescence microscopy.
BACKGROUND
Time-lapse video microscopy was used to determine whether mitochondrial and nuclear changes (decrease in mitochondrial transmembrane potential, condensation, and/or fragmentation of the nuclei, morphologic features typical of apoptosis) occurring during 7-ketocholesterol-induced cell death on A7R5 rat smooth muscle cells took place before or after the loss of cell adhesion. In addition, changes in actin organization were followed by conventional fluorescence microscopy.


METHODS
Morphologic, functional, and spatial changes at the mitochondrial level were investigated with 3,3'-dihexyloxacarbocyanine iodide and/or MitoTracker Red, and nuclear morphology was characterized by staining with Hoechst 33342. Actin fibers, which are major components of the filament network of the cytoskeleton, were visualized with phalloidin linked to fluorescein. The numbers of adherent and nonadherent cells were determined by cell counting.


RESULTS
7-Ketocholesterol-induced cell death was associated with a rapid alteration of actin fibers, a loss of intercellular junctions, and cell shape modifications. Analysis of mitochondrial transmembrane potential showed successively a hyperpolarization and a more or less pronounced progressive decrease followed by a dramatic drop associated with an increase in Hoechst 33342 staining, reflecting chromatin condensation and morphologic changes in the nuclei.


CONCLUSIONS
During cell death induced by 7-ketocholesterol in A7R5 rat smooth muscle cells, the different methods of microscopy allowed us to establish that alterations of actin fibers and mitochondrial dysfunctions occurred before condensation and/or fragmentation of the nuclei, which preceded the loss of cell adhesion.
Zahm
Jean-Marie
JM
Institut National de la Santé et de la Recherche Médicale U514, Reims, France.
Baconnais
Sonia
S
Monier
Serge
S
Bonnet
Noël
N
Bessède
Ginette
G
Gambert
Philippe
P
Puchelle
Edith
E
Lizard
Gérard
G
D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002448:Cell Adhesion / Q000187:drug effects; D002452:Cell Count; D016923:Cell Death / Q000187:drug effects; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000633:toxicity*; D019044:Image Cytometry / Q000379:methods*; D007653:Ketocholesterols / Q000633:toxicity*; D008564:Membrane Potentials / Q000187:drug effects; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008928:Mitochondria / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D000199:Actins; D004791:Enzyme Inhibitors; D007653:Ketocholesterols; C003001:7-ketocholesterol