Role of autophagy induced by anthocyanins in protection of DNA damages caused by UVB irradiation in HepG2 cells

DNA-protein cross-links and thymidine dimer are special types of DNA damages that formed when DNA exposed to many inducers as UV irradiations. Anthocyanins are members of phytochemicals found in many plants including Hibiscus sabdariffa. It was reported that anthocyanins protect DNA from UV-induced damages. Here we investigate the role of autophagy induced by anthocyanins in protection of UVB-induced DNA-protein cross-links and thymidine dimer in HepG2 cells . Cells were treated either with anthocyanins, Rapamycin, or combination of anthocyanins and Bafilomycin A1 or anthocyanins and 3-methyladenine for 24 h and then subjected to 0.36 J/cm 2 UVB irradiation. The results revealed that anthocyanins induce autophagy formation as detected by acridine orange pH dependent green to red (G/R) color shifting. To investigate the role of anthocyanins-induced autophagy on DNA-protein cross-links and thymidine dimer formation after UVB exposure, electrophoresis of protein covalently linked to DNA or thymidine dimer dot plot analysis of DNA were carried out. It was found that anthocyanins treated cells have reduced DNA-protein cross-links and thymidine dimer compared with the anthocyanins untreated cells. methyladenine together with anthocyanins significantly increased the DNA-protein cross-links and thymidine dimer formation compared with anthocyanins treated cells. Also, Rapamycin treatment alone protects cells from DNA-protein cross-links and thymidine dimer formation which confirm the role of autophagy in protection of cells from UVB-induced DNA-protein cross-links and thymidine dimer formation.