Avaliação da sinergia entre Curcuma longa e Piper nigrum na radiossensibilização de células neoplásicas da linhagem MDA-MB-231

Abstract

Curcuma longa and Piper nigrum are medicinal plants originated on Southeast Asia. For thousands of years, they are being used in this region, becoming popular worldwide in the last centuries. Curcumin and Piperine, active principles of these vegetals, attract growing scientific interest, as their therapeutic effects are elucidated. They have both shown properties as antibacterials, anti-inflammatories, antioxidants, antineoplastics, as well as radioprotectants and radiosensitizers. The use of these species in association is commonly observed, as Piperine enhances the bioavailability of Curcumin. The objective of this study was to evaluate the synergy of these two phytotherapics as radiosensitizing agents on the neoplastic and radioresistant MDA-MB-231 cell line. Secondarily, the radiosensitizing properties of Curcumin and Piperine, when used isolated, as well as their antineoplastic properties were evaluated. In parallel, it aimed on developing a nondestructive cell counting protocol. The phytotherapics properties were studied through an in vitro essay, with two analysis groups, each one with four MDA-MB-231 cell cultures. Each group was composed of one Control culture, a second culture exposed to isolated Curcumin, in 8μmol/L concentration, a third exposed to isolated Piperine, in 40μmol/L concentration, and a fourth culture exposed to the Curcumin+Piperine association, in 7μmol/L and 35μmol/L concentrations respectively. The cultures on the first group were irradiated with a Cobalt-60 source, with a 5Gy dose. The cultures on the second group were not exposed to radiation. All the eight cultures were followed up in time kinetics with digital microcopy images, using the software ImageJ to estimate the number of cells in each field. Curcumin and Piperine demonstrated radiosensitizing effects when used isolated, as well as in association. On the periods 6h, 12h and 24h post irradiation, isolated Curcumin led to cell counts 35,6%, 39,4% and 39,7% lower than Control. Isolated Piperine led to cell counts 10,3%, 21,9% and 8,9% lower than Control, but the last observation showed no statistic relevance. The Curcumin+Piperine association resulted in cell counts 10,4%, 7,4% and 42,6% lower than Control, but the second observation showed no statistic relevance. After 36h of evolution, there were no other measurements with statistic relevance in any of the study groups. No synergic effect between the compounds, as well as no antineoplastic properties, were observed in any of the study conditions. The cell counting protocol was efficient, being used throughout the whole experiment. However, even though promising, the protocol should be improved, since the analysis precision reduces as temporal kinetics advance. New essays using variable concentrations of Curcumin and Piperine will allow the improvement of the cell counting protocol, and the proper determination of the absence of synergy between Curcuma longa and Piper nigrum, also allowing the evaluation of a possible double inhibition effect of the phytotherapics.