Porphyrin photosensitization and Reactive Oxygen Species scavengers protection

FUKUDA H, ; TEIJO MJ,; BATLLE A.

Dusseldorf

Congreso; - International Congress on Porphyrins and Porphyrias 2015; 2015

Porphyrin photosensitization and Reactive Oxygen Species scavengers protectionPhotosensitization of endogenously synthesized porphyrins after administration of 5- aminolevulinic acid (ALA), are used in Photodynamic Therapy (ALA-PDT) of tumours and microorganisms infections. Irradiation with appropriate wavelength light triggers photochemical reactions inducing the production of ROS, ultimately leading to cell death. Several ROS scavengers agents, were assayed to know their ability to modulate ALA-PDT performed on A549 human lung adenocarcinoma cells by incubating 3h with 1mM ALA, followed by irradiation with or without 1 h preincubation with the modulators. The ratio between cell survival after ALA-PDT in the presence and in the absence of the scavenger agent (protection grade: PG) was determined, and the concentration showing no cytotoxicity/ photoactivity and providing the highest PG was used in the subsequent experiments. ALA-PDT alone induced a high percentage of apoptotic cell death (98.4 ± 3.5 %). Pre-incubation with the modulators at their highest PG concentration significantly reduced apoptotic cells to 48.3 ± 2.7 % (ascorbate), 58.8 ± 4.2 % (trolox), 78.5 ± 3.1 % (GSH), 64.3 ± 1.6 % (mannitol), and 74.6 ± 2.3 % (l-tryptophan). ROS involvement in early cell death induction after ALA-PDT was tested by flow cytometry. ROS production increased after ALA-PDT (H2-DCFDA + cells: control: 1.1 ± 0.1 %; 10 min-PDT: 69.3 ± 5.6%; MVP positive cells: control: 0.65 ± 0.35 %; 10 min-PDT: 83.5 ± 1.9 %). Ascorbate prevented peroxide formation and singlet oxygen increase it, whereas trolox limited peroxides generation, but did not affect significantly singlet oxygen production These results suggest that undesired photodamage to normal tissue might be attenuated by administration of antioxidant agents, showing a strong correlation between porphyrins, ROS production, scavengers and cell death, reinforcing the photodynamic properties of endogenously synthesized porphyrins, which are of high relevance in the photosensitization of the porphyrias