The induction of apoptosis in BEL-7402 cells by an iridium(III) complex through lysosome–mitochondria pathway

Abstract

A new iridium(III) polypyridyl complex [Ir(ppy)2(DPBD)](PF6) (ppy = 2-phenylpyridine, DPBD = 4-(dipyrido[3,2-a:2′,3′-c]phenazin-11-yl)benzene-1,2-diamine, Ir-1) was synthesized and characterized by element analysis, ESI-MS, IR, 1H NMR and 13C NMR. The cytotoxicity in vitro of the complex against cancer BEL-7402, A549, Eca-109 and normal LO2 cells was evaluated by 3-(4,5-dimethylthiazole)-2,5-diphenyltetraazolium bromide (MTT) method. The IC50 values of the complex toward BEL-7402, A549 and Eca-109 are 13.8 ± 0.7, 14.5 ± 0.6 and 15.2 ± 2.4 µM, respectively. The apoptosis was studied with acridine orange (AO) and ethidium bromide (EB) staining method and comet assay. The reactive oxygen species including superoxide anion and NO, the location of the complex at lysosomes, lysosomal membrane permeabilization, location of the complex at mitochondria and the change of mitochondrial membrane potential were assayed under a fluorescent microscope. The complex can enhance the intracellular Ca2+ levels and induce a release of cytochrome c. In addition, the complex can cause autophagy and upregulate the expression of LC-3 and Beclin-1 proteins. The complex inhibits the cell growth at S phase. The effects of the complex on the expression of caspase 3 and Bcl-2 family proteins were explored. The results show that the complex induces apoptosis in BEL-7402 cells through lysosome–mitochondrial dysfunction pathway, which was accompanied by the regulation of Bcl-2 family proteins.