Apoptosis in vitro in PC-12 cells induced by an organometallic Ir(III) complex through a ROS-mediated mitochondrial pathway

Abstract

An Ir(III) organometallic complex, [Ir(ppy)2(paip)]PF6 (1), (ppy and paip denote 2-phenylpyridine and 2-(4-aminophenyl) imidazo [4,5-f] [1,10] phenanthroline, respectively) was synthesized and characterized by elemental analysis, ESI-MS, 1H and 13C NMR. The cytotoxic activity in vitro of the complex was evaluated by MTT (MTT = (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)) method. The complex shows higher cytotoxic activity against PC-12 cells than cisplatin. The intracellular ROS generation and mitochondrial membrane potential (MMP) changes were determined by fluorescent microscope and flow cytometry. The cellular uptake and location of complex 1, as well as cell cycle distribution and matrigel invasion in PC-12 cells treated with the complex were investigated. Meanwhile, Bcl-2 family proteins expression was also explored by western blot. The results indicate that the complex shows efficient cellular uptake and cumulates in nucleus as well as in mitochondria, and inhibits both the growth at G0/G1 phase and the invasion in extracellular matrix. It is rationally concluded that complex 1 induces apoptosis in PC-12 cell through a ROS-mediated mitochondrial dysfunction pathway with an increase in ROS level and a decrease in MMP.