Experimental studies for the personalized application of boron neutron capture therapy to the treatment of cutaneous melanoma

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Protection against radiation-induced damage of 6-propyl-2-thiouracil (PTU) in thyroid cells

Many epidemiologic studies have shown that the exposure to high external radiation doses increases thyroid neoplastic frequency, especially when given during childhood or adolescence. The use of radioprotective drugs may decrease the damage caused by radiation therapy and therefore could be useful to prevent the development of thyroid tumors. The aim of this study was to investigate the possible application of 6-propyl-2-thiouracil (PTU) as a radioprotector in the thyroid gland. Rat thyroid epithelial cells (FRTL-5) were exposed to different doses of g irradiation with or without the addition of PTU, methimazole (MMI), reduced glutathione (GSH) and perchlorate (KClO4). Radiation response was analyzed by clonogenic survival assay. Cyclic AMP (cAMP) levels were measured by radioimmunoassay (RIA). Apoptosis was quantified by nuclear cell morphology and caspase 3 activity assays. Intracellular reactive oxygen species (ROS) levels were measured using the fluorescent dye 20,70-dichlorofluorescein- diacetate. Catalase, superoxide dismutase and glutathione peroxidase activities were also determined. Pretreatment with PTU, MMI and GSH prior to irradiation significantly increased the surviving cell fraction (SF) at 2 Gy (P , 0.05), while no effect was observed with KClO4. An increase in extracellular levels of cAMP was found only in PTU treated cells in a dose and timedependent manner. Cells incubated with agents that stimulate cAMP (forskolin and dibutyril cAMP) mimicked the effect of PTU on SF. Moreover, pretreatment with the inhibitor of protein kinase A, H-89, abolished the radioprotective effect of PTU. PTU treatment diminished radiation-induced apoptosis and protected cells against radiation-induced ROS elevation and suppression of the antioxidant enzyme?s activity. PTU was found to radioprotect normal thyroid cells through cAMP elevation and reduction in both apoptosis and radiation-induced oxidative stress damage.Fil: Perona, Marina. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Radiobiología (centro Atómico Constituyentes); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dagrosa, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Radiobiología (Centro Atómico Constituyentes); ArgentinaFil: Pagotto, Romina María del Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Casal, Mariana. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncologí­a "Angel H. Roffo"; ArgentinaFil: Pignataro, Omar Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Pisarev, Mario Alberto. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Radiobiología (Centro Atómico Constituyentes); Argentina. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Juvenal, Guillermo Juan. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Radiobiología (centro Atómico Constituyentes); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Biochemical changes during goiter induction by methylmercaptoimidazol and inhibition by δ-iodolactone in rat

Background: We have demonstrated that the administration of δ-iodolactone (i.e., 5-iodo-delta lactone) of arachidonic acid (IL-δ), a mediator in thyroid autoregulation, prevents goiter induction by methylmercaptoimidazol (MMI) in rats. Other studies have shown that transforming growth factor beta-1 (TGF-β1) mimics some of the actions of excess iodide, but its participation in autoregulation is disputed. The present studies were performed to test the hypotheses that IL-δ decreases thyroid growth by inhibition of cell proliferation and/or by stimulation of apoptosis due to oxidative stress, that TGF-β is stimulated by an excess of iodide and by IL-δ, and that c-Myc and c-Fos expression are upregulated during goiter induction and downregulated during goiter inhibition. Methods: Rats were treated with MMI alone or together with iodide or IL-δ. Thyroid weight, cell number, cell proliferation, apoptosis, and oxidative stress were determined. Proliferating cell nuclear antigen (PCNA), TGF-β1, TGF-β3, c-Myc, and c-Fos were measured by Western blot. Results: MMI caused a progressive increase in thyroid weight accompanied by an increase in cell number, asymmetry of the ploidy histograms, and PCNA, c-Fos, and c-Myc expression. In addition, an early increase of apoptosis was observed. Peroxides as well as glutathione peroxidase and catalase activities were also increased in goitrous animals. The inhibitory action of IL-δ on goiter formation was accompanied by the inhibition of cell proliferation evidenced by a significant decrease in cell number, PCNA expression, and asymmetry of the ploidy histograms. A transient stimulation of apoptosis after 7 days of treatment was also observed. MMI administration stimulated TGF-β1 but not TGF-β3 synthesis. IL-δ alone caused a slight increase of TGF-β3 but not TGF-β1, whereas potassium iodide (KI) stimulated both isoforms and MMI reversed KI effect on TGF-β1 expression but not on TGF-β3. Conclusions: The goiter inhibitory action of IL-δ is due to the inhibition of cell proliferation and the transient stimulation of apoptosis. This latter action does not involve oxidative stress. TGF-β1 does not play a role in the autoregulatory pathway mediated by IL-δ. Iodide stimulates TGF-β3 without the need of being organified. These results suggest that there may be more than one pathway involved in the autoregulatory mechanism.Fil: Thomasz, Lisa. Comision Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. División Bioquímica Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Oglio, Andrea Romina. Comision Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. División Bioquímica Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Randi, Andrea Silvana. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fernandez, Marina Olga. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dagrosa, Maria Alejandra. Comision Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. División Bioquímica Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cabrini, Romulo L.. Comision Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. División Bioquímica Nuclear; ArgentinaFil: Juvenal, Guillermo Juan. Comision Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. División Bioquímica Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pisarev, Mario Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Comision Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. División Bioquímica Nuclear; Argentin