Study On The Effect And Mechanism Of Sinapine Thiocyanate In Protecting Skin Against Photoaging

The skin is at the surface of the body and is constantly threatened by external environmental factors.Ultraviolet rays are one kind of those negative factors,accelerating skin aging.Under the UV irradiation for a long time,our skins would become dry,rough and less elastic.Sinapine thiocyanate is one kind of alkaloid from cruciferous plants.It has been reported to be antioxidant and anti-inflammatory.It can also lower blood pressure and blood lipids.However,whether it could protect the skin against photoaging has not been reported.Therefore,in this study,we investigated the protective effects of sinapine thiocyanate against UV irradiation in skins.According to the different penetrability of UVA and UVB,we constructed cell injury models of two different types（fibroblasts irradiated by UVA and keratinocytes irradiated by UVB）.We assessed the cytotoxicity and photoprotective effect of sinapine thiocyanate by microscopy observation and MTS kit detection.The effects on apoptosis was investigated by flow cytometry analysis.Intracellular ROS generation was monitored to reflect the antioxidant activity of sinapine thiocyanate.Real-time quantitative PCR and Western blot were used to capture those changes in transcription and expression of genes related to inflammation,apoptosis,and extracellular matrix in cells.In the study of signal pathways,Western blot was also used to investigate the expression of related proteins.In addition,we designed an animal model of nude mice which was irradiated with UVA and UVB to verify the anti-photoaging effect of drugs in vivo.HaCaT cell growth inhibition induced by UVB was significantly suppressed by pre-treatment of cells with sinapine thiocyanate（75μM,150μM,and 300μM）in a concentration-dependent manner.Besides,drugs relieved UV-induced and H₂O₂-induced oxidative stress in HaCaT cells,which was evidenced by the reduction in ROS generation.The over-expression of COX-2,IL-6 and IL-8 induced by UVB was obviously inhibited by sinapine thiocyanate.It also led to recovery of the expression change of Bax and Bcl-2.Sinapine thiocyanate attenuated UVB-activated phosphorylation of JNK and p38 MAPK in HaCaT keratinocytes,as determined by Western blot.The results in 3T3 cells are basically consistent with HaCaT’s,except that the expression of MMPs was suppressed,and the reduction of TIMP-1 and procollagen was reversed by sinapine thiocyanate.In animal experiments,sinapine thiocyanate effectively alleviated the symptoms of swelling and peeling of the back skin stimulated by UV.Detection of the changes in transcription and expression of related genes verified the results of cell experiments.Sinapine thiocyanate could effectively protect the skin from UV irradiating damage by inhibiting apoptosis,inflammatory,intracellular ROS generation and maintaining the stability of extracellular matrix proteins.Moreover,it may exert its anti-photoaging effect by intervening ROS-MAPK signaling pathway.Considering that it is natural and with low toxicity,sinaloid thiocyanate is a good candidate to be addited to cosmetics for preventing and curing skin photoaging in the future.