Gamma irradiation of aloe-emodin induced structural modification and apoptosis through a ROS- and caspase-dependent mitochondrial pathway in stomach tumor cells

Abstract

Purpose: The changes in molecular structure and the physiological properties of a gamma-irradiated aloe-emodin were examined.

Materials and methods: Aloe-emodin was gamma-irradiated at doses ranging from 0 to 150 kGy, and the molecular structure was then analyzed using high-performance liquid chromatography (HPLC). AGS cells were cultured in RPMI medium and treated gamma irradiated aloe-emodin. Cell viability was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Apoptosis efficiency was investigated by cell cycle arrest, cell morphology, and signaling pathway. The structure of new radiolytic peak was identified by the hydrogen-nuclear magnetic resonance (¹H NMR).

Results: HPLC results showed that gamma irradiation induced new radiolytic peaks that were distinguishable from the aloe-emodin standard, and the area of new peaks was increased as the radiation dose increased. Gamma-irradiated aloe-emodin treatment significantly increased the cytotoxicity in AGS tumor cells. We also found that 150 kGy aloe-emodin increased the expression of Bax, cytosolic cytochrome c, PARP cleavage, and the activation of caspases-8, -9, -3, Bid, and Bcl-2. Treatment of 150 kGy aloe-emodin induced ROS production, DNA fragmentation, alterations of cell morphology, and the migration in AGS cells. Gamma-irradiated aloe-emodin induced an increase of sub-G1 phase and depolarization of mitochondrial membrane potential in AGS cells. We also confirmed that fractionated AEF1 (new radiolytic peak) induce the cell death, migration, an increase of sub-G1 phase and cytochrome c in a ROS-dependent manner.

Conclusions: The radiolysis product (AEF1) of aloe-emodin transformed by gamma-irradiation strongly induced apoptotic cell death in AGS cells, indicating AEF1 is a potential candidate drug for use in anti-cancer drug.

Keywords:

• Gamma irradiation
• aloe-emodin
• structural modification
• cytotoxicity
• apoptosis

Disclosure statement

The authors declare that there are no conflicts of interest.

Additional information

Funding

This study was supported by the Nuclear Research & Development Program of the National Research Foundation [NRF-2012M2A2A6011335] grant funded by the Government of the Republic of Korea. This project was supported by the Nuclear R&D Program of the Ministry of Science and ICT (MSIT), Republic of Korea.