Radioprotective effects of asiaticoside and asiatic acid in neural stem cells derived from human stem cells from apical papilla through increasing dose-reduction factor and their lowering effects on SH-SY5Y cell viability.

OBJECTIVE: To investigate the effects of asiaticoside (AS) and asiatic acid (AA) against radiotherapy on neural stem cells induced from human stem cells from apical papilla (NSCs-hSCAPs) through dose-reduction factor (DRF) evaluation and their radiosensitization on human neuroblastoma SH-SY5Y cells. METHODS: NSCs-hSCAPs were treated with AS or AA (0-500 μM) and radiation (0-8 Gy). Isolated hSCAPs were verified mesenchymal stem cells (MSCs) properties according to standard protocol. Subsequently, NSCs-hSCAPs were characterized by Cresyl violet staining and immunocytochemistry. A culture plate containing the cells was embedded into the solid water and bolus phantom. After CT simulation and treatment planning, dose uniformity to the plate was evaluated. X-ray, AS, and AA toxicity were investigated using cell viability (MTT) assay. Finally, DRF50 was calculated from dose-response curves at 50% cell viability for both cell lines. RESULTS: hSCAPs presented MSCs markers. NSCs-hSCAPs were successfully generated due to the Nissl substance, Nestin, and SOX2 positively stained. Dose homogeneity was represented as isodose at 100% covered the cells in the phantom, suggesting that they were received according to prescribed doses. MTT results revealed that AA was more toxic than AS in both cells. X-ray reduced significantly in a number of tested cells and more radiosensitivity was observed in SH-SY5Y. However, the reduction affected by 4 Gy was diminished after AA or AS at 2 μM applied to NSCs-hSCAPs. Moreover, a significant increase of DRF50 was found at 2 μM of AA (6.72 ± 2.35) and AS (3.84 ± 1.41) in NSCs-hSCAPs whereas it did not show in SH-SY5Y. Interestingly, 20 μM AA could reduce SH-SY5Y cell viability (mean of the cell viability (%) was 25.22 ± 1.53 compared to 30.22 ± 1.46 in the control group), showing a very large in terms of its effect size (Cohen's d value = 1.37). CONCLUSION: AA and AS had a specific radioprotective effect on NSCs-hSCAPs without affecting SH-SY5Y. However, AA might be a better therapeutic agent due to expressing a lethal effect on the irradiated cancer cells.