Abstract:

Objective To discuss the inhibitory effect of gallic acid-lecithin complex （GA-LC） on the proliferation of the lung cancer A549 cells induced by X-ray irradiation， and to clarify its possible mechanism. Methods The A549 cells were divided into different concentrations（0， 0.05， 0.10， 0.15， 0.20， 0.25， 0.30， and 0.35 g·L^－1）of GA-LC groups.CCK-8 assay was used to detect the proliferation activities of A549 cells in various groups， and the half-inhibitory concentration （IC₅₀） value of GA-LC was determined. The A549 cells were divided into control group， GA-LC group， 4 Gy X-ray irradiation group， and GA-LC+4 Gy X-ray irradiation group. CCK-8 assay was used to detect the proliferation activities of cells in various groups； flow cytometry was used to detect the reactive oxygen species （ROS） levels，mitochondrial membrane potential （MMP） levels and apoptotic rates of cells in various groups； the mitochondrial green fluorescence probe Mito-tracker was used to detect the permeability of mitochondrial membrane. Results Compared with 0 g·L^－1 GA-LC group， the proliferation activities of the cells in 0.15， 0.20， 0.25， 0.30 and 0.35 g·L^－1 GA-LC groups were significantly decreased （P<0.05）， and the IC₅₀ value of GA-LC to the A549 cells was 0.171 1 g·L^－1. Compared with control group， the proliferation activities and MMP levels of the cells in GA-LC group， 4 Gy X-ray irradiation group， and GA-LC+4 Gy X-ray irradiation group were significantly decreased （P<0.05 or P<0.01）， while the ROS levels and apoptotic rates of the cells in GA-LC group and GA-LC+4 Gy X-ray irradiation group were significantly increased （P<0.05 or P<0.01）. Compared with GA-LC group， the MMP level of the cells in GA-LC+4 Gy X-ray irradiation group was decreased（P<0.01）， while the ROS level and apoptotic rate of the cells in GA-LC+4 Gy X-ray irradiation group were significantly increased （P<0.05）； compared with 4 Gy X-ray irradiation group， the proliferation activity and MMP level of the cells in GA-LC+4 Gy X-ray irradiation group were decreased （P<0.05）， while the ROS level and apoptotic rate of the cells in GA-LC+4 Gy X-ray irradiation group were significantly increased （P<0.05 or P<0.01）. The mitochondrial fluorescence probe Mito-tracker staining results showed that the green fluorescence could be observed under fluorescence microscope； compared with control group， the green fluorescence intensities in the cells in GA-LC group， 4 Gy X-ray irradiation group， and GA-LC+4 Gy X irradiation group were increased，and the green fluorescence intensity in the cells in GA-LC+4 Gy X-ray irradiation group was the most obvious，demonstrating that the mitochondrial membrane permeability was increased. Conclusion GA-LC can enhance the inhibitory effect of X-ray irradiation on the proliferation activity of the lung cancer A549 cells， and its mechanism is related to the induction of oxidative stress，thereby increasing the mitochondrial permeability， decreasing the MMP and inducing the apoptosis.

Key words: Gallic acid-lecithin complex, X-ray, Oxidative stress, Apoptosis, Mitochondrial membrane potential