Human leukemia cells photoinactivation employing an anthraquinone from Argentinean flora

MUGAS, L.; VALLECORSA, P.; DI VENOSA, G.; MARIONI, J.; SÁENZ, D.; CASAS, A.; CALVO G.; CÉSPEDES, MARIELA A.; NUÑEZ MONTOYA, S.

Barcelona

Congreso; 17th Congress of the International Union of Photobiology and 18th Congress of the European Society for Photobiology; 2019

International Union of Photobiology, European Society for Photobiology

Parietin (PTN), an anthraquinone (AQ) found in some vegetal species even lichens, has been shown to be a good photosensitizer with promising applications in bacterial photoinactivation1. The aim of this work was to evaluate the in vitro activity of PTN as photosensitizer on K562 human leukemic cells; in order to estimate its potential use in Photodynamic Cancer Therapy (PDT).PTN (1,8-dihydroxy-3-methoxy-6-methylanthraquinone) was isolated from the lichen Teoloschistes nodulifer (Nyl.) Hillman (Teloschistaceae) and it was purified by recrystallization from the acetone extract, and its purity was determined by HPLC. Employing human leukemic K562 cells, we determined: a) PTN maximum non-cytotoxic concentration (MNCC on darkness conditions)2; b) incorporation time (1 h-24 h); c) incorporation mechanism (passive or active transport); d) LD50: light dose inducing 50% of cell death after PDT treatment (MNCC of PTN, irradiation time ≤ 30 min) and e) cell cycle analysis after PDT in order to estimate the cell death mechanism. The results of experiments a) to d) were obtained by means of cellular viability measure, by employing the MTT colorimetric assay3, and experiment e) by flow cytometry analysis, using propidium iodide staining. K562 cells were used at semi confluency, PTN was prepared in RPMI medium with DMSO ≤ 1% and the irradiation doses were adjusted employing different times of exposition to a light system, which consisted in 2 blue compact fluorescent lamps (Sica, 15 W). PTN (purity of 91.2 ± 0.2%) presented a MNCC of 30 μM on K562 cells. Since little difference was observed between 1 h and 24 h incorporation, the optimal incubation time of PTN was set as 1 h. Passive transport seems to be the main mechanism involved in PTN entry to the cells, since not significant differences were observed between incorporation at 4 and 37°C. After illumination of K562 cells exposed to PTN, the LD50 was 1,39 J/cm2 (5 min), and cell cycle analysis suggested that apoptosis was involved in PTN-PDT treatment (55 %). Therefore, this natural AQ produced photo-destruction of leukemic cells, at non- cytotoxic concentrations employing visible light.The results of this work confirm the potential use of parietin in PDT, supporting the recommendations of the World Health Organization to revalue phytomedicine and consider the healing properties of the country´s flora. Currently, we are carrying out studies of PTN-PDT on cell lines of solid tumors, as well as in non-tumor cells.