Cytoprotective effects of sinapic acid on human keratinocytes (HaCaT) against ultraviolet B

Abstract

Sinapic acid is a phenolic compound in various plants, including spices, berries, citrus fruits, vegetables, grains, and oil seeds. It has been studied mainly for the various pathological symptoms it induces related to its anticancer, antioxidant, and neuroprotective effects. However, little has been studied about sinapic acid in human keratinocytes (HaCaT). Therefore, this study examined its reactive oxygen species (ROS) scavenging capacity, protective effect against DNA damage, and DNA repair mechanism. To confirm the protective effects of sinapic acid on HaCaT irradiated by ultraviolet (UV) B, this study used the water-soluble tetrazolium salts (WST)-1 assay to determine the cytotoxicity of sinapic acid for verifying the cell survival rate and dichlorofluorescein diacetate (DCF-DA) to measure the changes in the concentration of ROS generated by UVB. This study also used the comet assay, cyclobutane pyrimidine dimer (CPD) formation, and malondialdehyde (MDA) assay to measure the degree of protection against cell damage. In addition, this study used quantitative real-time polymerase chain reaction (qRT-PCR) to measure the expression of repaired genes from cell damage. Sinapic acid protects cells from UVB-induced cytotoxicity and reduces ROS generation by UVB. This study showed that sinapic acid reduced the generation of tailed DNA, CPD, and lipid peroxidation, which are the indicators of DNA damage. Depending on the increase in the concentration of sinapic acid, the gene expressions of XPC and ERCC1 (repair factors for damaged DNA) increased. The findings of this study confirmed that sinapic acid is effective in removing ROS generated by UVB, reducing intracellular damage, and repairing damaged DNA in HaCaT. These results also showed that sinapic acid is effective in DNA damage repair, indicating its protective effect on HaCaT against UVB damage.