Detection of apoptosis in SK-N-MC neuroblastoma cells.

Detection of apoptosis in SK-N-MC neuroblastoma cells. Following a six-hour exposure to hydrogen peroxide, cells were labeled with Hoechst 33342 (Cat. no. H1399, H3570, H21492), tetramethylrhodamine ethyl ester (TMRE, Cat. no. T669) and rhodamine 110, bis-L-aspartic acid amide (Cat. no. R22122) for 15 minutes. Apoptotic cells show green cytosolic fluorescence resulting from cleavage of the rhodamine 110, bis-L-aspartic acid amide substrate by active caspase-3. The staining pattern of the Hoechst 33342 dye reveals that the majority of the rhodamine 110–positive cells also contain condensed or fragmented nuclei characteristic of apoptosis. Furthermore, the rhodamine 110–positive cells are also characterized by an absence of polarized mitochondria, as indicated by their failure to load the positively charged mitochondrial indicator TMRE. The image was contributed by A.K. Stout and J.T. Greenamyre, Emory University.