INVESTIGATION OF SOME MOLECULAR MECHANISMS OF CYTOTOXIC 1,5-DIARYL-3-OXO-1,4-PENTADIENES

Abstract

Glutathione S-transferase GSTπ has been one of the significant targets for cancer treatment in the past several years. The reason behind that is 1) its overexpression in some cancer cells compared to normal ones 2) its ability to cause resistance against cancer chemotherapeutics and 3) its protective role against reactive oxygen species (ROS). We have synthesized a large number of compounds which have strong potency against different cancer cell lines. These compounds possess a 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore. In the present study some investigations as to the way in which cytotoxicity is mediated was undertaken. Our results have demonstrated that the analogs NC 2067 and NC 2081 behaved as substrates for GSTπ and reduced the level of GSH. This was apparent by the decrease in the concentrations of both compounds after the addition of GSTπ and GSH. In addition, both agents caused about 3-7 folds increase in ROS levels. The dichlorodihydrofluorescein dye was used for this purpose due to its fluorescence characteristic after being oxidized by ROS. High levels of these species cause a drop in the mitochondrial membrane potential. This phenomenon was detected when the monomeric form of JC-1 levels were increased after treatment. The reduction of 2-3 folds was seen when the cells were treated with the IC₅₀ values of both compounds. In addition, both agents inhibited oxygen consumption implicating their ability to inhibit oxidative phosphorylation. We also evaluated the effect of both agents on mitochondrial swelling. NC 2081 caused swelling using concentrations of 10 μM and 50 μM. This was apparent when the absorption of an isolated rat liver mitochondrial solution decreased after the addition of the compound. The addition of the higher concentration caused about 2 fold greater effect than the lower one. On the other hand, compound NC 2067 produced minimal swelling only at a concentration of 50 μM.