Melatonin can enhance the cell-killing effect of X-ray irradiation at low concentration. - GreenMedInfo Summary
Different Effects of Melatonin on X-Rays-Irradiated Cancer Cells in a Dose-Dependent Manner.
Dose Response. 2019 Jul-Sep;17(3):1559325819877271. Epub 2019 Sep 23. PMID: 31579126
The purpose of this study is to investigate the effects of melatonin on the radiosensitivity of HeLa cells. Concentration from 10 to 1000µM of melatonin was used on HeLa cells before X-rays irradiation (IR). The cellular inactivation effect was analyzed by clonogenic assay, and cell growth was measured by MTT assay at various concentrations. Ten micrometer melatonin promoted the cell-killing effects of IR, while 1000-µM melatonin prevented IR-induced cellular inactivation. Further analysis revealed that 1000-µM melatonin protected the cells from IR-induced reactive oxygen species damage, as the oxidative stress measured by fluorescent microscopy and fluorescence-activated cell sorting using 2,7-dichlorofluorescein diacetatestaining. This is further confirmed by melatonin receptor agonist, which has no antioxidant capacity. A 10-µM melatonin, on the contrary, enhanced the cell-killing effects of IR by activating c-Jun NH2-terminal kinase (JNK) signaling. c-Jun NH2-terminal kinase signaling activation was indicated byWestern blot of phosphorylated JNK. We used JNK inhibitor to further confirm the involvement of JNK signaling in the cell-killing enhancement of 10-µM melatonin administration. Our results suggest the importance of dose-dependent effects in melatonin application for radiotherapy.