Effects of octogen and its intermediate product on apoptosis and oxidative stress of Chinese hamster lung cells

Background Octogen (HMX) is the best comprehensive explosive compound at present. Studies have found that HMX can affect the neurobehavioral function and peripheral nerve conduction velocity of occupational exposure groups. 3, 7-dinitro-1, 3, 5, 7-tetraazabicyclo3,3,1nonane (DPT) is the main intermediate of HMX synthesis, but the toxicities of DPT have been rarely reported across the world.

Objective This experiment investigates the effects of HMX and DPT on apoptosis and oxidative stress of Chinese hamster lung cells (CHL).

Methods Degsined doses (0, 31.25, 62.50, 125, 250, and 500 mg·L^-1) of HMX and DPT were applied to treat CHL cultured in vitro for 24 h. CCK-8 method was used to detect cell viability, Annexin V-FITC/PI double staining assay for cell apoptosis, and DCFH-DA fluorescent probe for intracellular reactive oxygen species (ROS). Furthermore, having been pretreated with 2.5 mmol·L^-1 N-acetyl cysteine (NAC) for 4h and administered with 120 mg·L^-1 DPT for 24h, the cell viability and apoptosis of CHL were detected.

Results The results of cell viability assay showed that the half inhibitory concentration of DPT on CHL was 119.55 mg·L^-1. DPT at 250 mg·L^-1 decreased the cell viability to (17.95±2.18)%, and 500 mg·L^-1 HMX decreased it to (83.34±3.03)%. Compared with corresponding control groups, the apoptosis rates of the exposure groups increased gradually with the exposure dose rising (P < 0.05). The apoptosis rate of the 62.50-500 mg·L^-1 HMX exposure groups increased moderately from (15.63±0.58)% to (37.00±1.25)%, while that of the 62.50-500 mg·L^-1 DPT exposure groups increased drastically from (33.75±0.57)% to (96.57±0.53)%. Both HMX and DPT increased intracellular ROS levels. However, HMX caused a smaller change of ROS levels than DPT did. The ROS intensity were 103.96±5.59 and 119.61±4.42 at 250 and 500 mg·L^-1 HMX, and 238.52±7.15 and 451.02±13.02 at 250 and 500 mg·L^-1 DPT, respectively (P < 0.05). In addition, the NAC intervention effectively alleviated the cell viability inhibition and apoptosis caused by the DPT exposure. The cell viability and apoptosis rate of the NAC pretreatment+DPT group were (76.41±4.91)% and (16.85±0.12)%, while those of the DPT group were (48.02±2.63)% and (62.67±8.49)%, respectively (P < 0.05).

Conclusion The toxicity of DPT to CHL is higher than that of HMX at the same dose. DPT at a high concentration could increase cell apoptosis of CHL via elevating intracellular ROS.