Visualization Of Mitochondria-targeted Photodynamic Effects Of Hpph-in Coupled With Visible Laser 637 Nm In Osteosarcoma 143b Cells

Abstract

Photosensitizer HPPH cooperated with metal complex containing In (III) (HPPH-In) produces much efficient singlet oxygen production and photodynamic effects (PDE) as compared to HPPH alone. With the application of mitochondrial fluorescent probes and laser scanning imaging microscopy, mitochondrial level of PDE induced by HPPH-In coupled with visible laser 637 nm were investigated in detail. PDE of HPPH-In significantly enhances depletion of a mitochondria specific fluorescent probe MitoTracker Green at very earlier time points suggesting its primary targeting on the mitochondrial membrane. Mitochondria soon swelled and followed by plasma membrane blebing and later apoptotic condensation of nuclei and cell death. These mitochondria-associated apoptotic events induced by PDE of HPPH-In can be partially inhibited by a mitochondria antioxidant, MitoQ, and by the removal of extracellular Ca2+ suggesting a mROS- and Ca2+-dependent mechanism is involved. When mitochondrial reactive oxygen species (ROS) formation and mitochondrial membrane potential depolarization (ΔΨ) were imaged simultaneously, PDE of HPPH-In significantly enhanced mROS formation and ΔΨ depolarization with small delay. PDE of HPPH-In-induced increase in mROS soon propagated to adjacent non-irradiated mitochondrial population as well as that in adjacent cells and caused depolarization ofΔΨ of these non-irradiated mitochondria. In addition to PDE of HPPH-In-enhanced mROS formation, we observed PDE of HPPH-In-induced sudden depolarization of ΔΨeffectively reduced mROS formation suggesting a possible protective preconditioning may exist. Finally, PDE of HPPH-In significantly altered mitochondrial dynamics by decreasing mitochondrial movement and enhancing fission of mitochondria. These observations suggest that multiple mitochondria-targeted devastating mechanisms provided by the PDE of HPPH-In coupled with 637 nm laser may be particularly useful in the eradication of malignant tumors for cancer therapy.