Three-Way Effect of Cyanine Dye on the Structure and Function of Mitochondria

Previously, we found that the cationic cyanine dye tri-S-C4(5) uncoupled mitochondrial oxidative phosphorylation by acting as an inducer of the mitochondrial permeability transition (PT). In the present study, the actions of cyanine dyes such as tri-S-C4(5) and tri-S-C7(5) on the mitochondrial structures and functions were further characterized. In the presence of inorganic phosphate (Pi), cyanine dyes were found to accelerate mitochondrial oxygen consumption that was partially sensitive to the PT inhibitor cyclosporin A (CsA). However, not only the CsA-sensitive but also CsA-insensitive acceleration of mitochondrial respiration was induced by cyanine dyes; and both of them were found to be associated with the release of mitochondrial cytochrome c. On the contrary, in the absence of Pi, moderate acceleration of respiration was induced by cyanine dyes, but this respiratory effect was not associated with the induction of swelling or the release of mitochondrial cytochrome c. Thus, cyanine dyes were concluded to have 3 different effects on the mitochondrial functions depending on the Pi status.