INVESTIGADORES
MARINO Veronica Julieta
congresos y reuniones científicas
Título:
Photodynamic therapy with a a lipophilic Zn(II) phthalocyanine leads to apoptotic death through activation of caspase-8 and ER stress
Autor/es:
NICOLÁS A. CHIARANTE; JULIETA MARINO; GARCÍA VIOR M. CECILIA; OSVALDO REY; JOSEFINA AWRUCH; LEONOR P. ROGUIN
Lugar:
Buenos Aires
Reunión:
Congreso; International Congress in Translational Medicine; 2016
Institución organizadora:
International Master Program in Biomedical Sciences (Universidad de Buenos Aires) Albert-Ludwings University of Freiburg (Germany)
Resumen:
Phthalocyanines (Pcs) have been found to be useful photosensitizers for photodynamic therapy (PDT). The tendency of Pcs to form aggregates has promoted the use of nanocarriers that improve their solubility. The aim of this work was to study the phototoxic action of 2,9(10),16(17),23(24)-tetrakis[(2?dimethylamino)ethylsulfanyl] phthalocyaninatozinc(II) (Pc9) encapsulated into poloxamine polymeric micelles (T1107) in a murine colon carcinoma cell line (CT26). Pc9-T1107 was found to be cytotoxic after irradiation at 2.8 J.cm-2, being the IC50 value of 11 ± 1 nM. Using confocal microscopy we demonstrated that Pc9 localizes in lysosomes and endothelial reticulum (ER) but not in mitochondria. ER stress was revealed when different heat shot proteins were evaluated by western-blot. In addition, an increase in cytoplasmic calcium levels, which was partially inhibited by the antioxidant TROLOX, was evident after PDT. Consistently, a lower cytotoxic effect was obtained when cells were pretreated with the calcium chelator BAPTA. The importance of serine proteases and cathepsin B in this mechanism of cell death was clear after performing experiments with aprotinin and CA-074 Me. An apoptotic response was demonstrated by the increase of caspase-3, 8 and 9 activities, the decrease of Bcl-2 levels, the cleavage of PARP and apoptotic nuclei in cells stained with Hoechst 33258. The critical role of cathepsin D in the cleavage of procaspase-8 was evident when caspase-8 activity was evaluated in the presence of Pepstatin A. Finally, PDT provoked cell cycle arrest in the S and G2/M phases. These results encourage us to assess Pc9 in vivo phototoxic efficacy.