CONICET | Buscador de Institutos y Recursos Humanos

ROS ROS production by endogenously generated Protoporphyrin IX in murine leukemia cells Endogenous production of Protoporphyrin IX (PpIX) is successfully exploited for photodynamic therapy (PDT) on malignant cells, following 5-aminolevulinic acid (ALA) administration and light irradiation. It kills cancer cells by damaging organelles and impairing metabolic pathways via cellular reactive oxygen species (ROS) generation. PpIX is a very efficient photosensitizer having a high capacity of accumulating in the intracellular membrane organelles, like lysosomes and mitochondria. Interaction between the triplet excited state of the sensitizer and molecular oxygen leads to singlet oxygen production and other ROS, inducing cell death. We studied the efficiency of PpIX synthetized from ALA on ROS generation, in two murine leukemic cell lines: LBR- and LBR-V160, sensitive and resistant to the chemotherapeutic drug Vincristine, respectively. Cells were incubated 4 hours with 1 mM ALA and then irradiated during different times with fluorescent light (0.18 J/cm2). One hour later, production of ROS was asessed with the fluorescent probes hydroethidine (superoxide anion) and H2DCF-DA (peroxide hydrogen); mitochondrial damage was detected with DIOC6. In both cell lines we found that superoxide anion production increased with irradiation time (Table 1), whereas no peroxide hydrogen synthesis was detected (not shown). Mitochondrial damage also increased in an irradiation time dependent manner, and it was higher in the resistant line (Table 2). Previous studies have demonstrated that apoptotic cell death increased with irradiation time, which is consistent with ROS results. These data indicate that ROS are critical in ALA-PDT efficiency to kill malignant cells.